Patent Publication Number: US-11394860-B2

Title: Multiple optical path imaging techniques and shared emitter for active depth sensing techniques

Description:
RELATED APPLICATIONS 
     This patent application claims priority to U.S. provisional patent application No. 63/004,970 entitled “MULTIPLE OPTICAL PATH IMAGING TECHNIQUES AND SHARED EMITTER FOR ACTIVE DEPTH SENSING TECHNIQUES” and filed on Apr. 3, 2020, which is assigned to the assignee hereof. This patent application also claims priority to U.S. provisional patent application No. 63/010,447 entitled “MULTIPLE OPTICAL PATH IMAGING TECHNIQUES AND SHARED EMITTER FOR ACTIVE DEPTH SENSING TECHNIQUES” and filed on Apr. 15, 2020, which is assigned to the assignee hereof. The disclosures of the prior applications are considered part of and are incorporated by reference in this patent application. 
     This patent application is related to co-pending United States utility patent application entitled “MULTIPLE OPTICAL PATH IMAGING TECHNIQUES AND SHARED EMITTER FOR ACTIVE DEPTH SENSING TECHNIQUES” and filed on the same day as this patent application. The co-pending United States utility patent application is assigned to the assignee hereof. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to image capture systems and devices, such as an apparatus including multiple image sensors sharing optical paths for imaging. This disclosure also relates generally to active depth sensing systems and devices, such as an apparatus including an emitter for active depth sensing shared by multiple apertures. 
     BACKGROUND 
     Many devices may include multiple cameras. For example, a smartphone may include one or more rear facing cameras and one or more front facing cameras. Each camera includes an image sensor and associated components for capturing an image. For example, if a device includes two or more cameras, the device includes two or more image sensors, and each image sensor is associated with its own dedicated optical path for imaging. 
     Many devices may also include multiple active depth sensing systems. For example, a smartphone may include a front facing active depth sensing transmitter (such as for face unlock or other applications using depth information) and a rear facing active depth sensing transmitter (such as for generating a depth map, to assist with auto-focus for one or more rear facing cameras, and so on). Each active depth sensing transmitter is associated with its own dedicated optical path for emitting light for active depth sensing. 
     SUMMARY 
     This Summary is provided to introduce in a simplified form a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. 
     Some aspects of the present disclosure relate to a shared optical path between image sensors. An example device for digital imaging includes a first aperture, a first image sensor, a second image sensor, and an optical element. A first optical path is formed between the second image sensor and the first aperture. The optical element is configured to direct light from the first optical path towards the first image sensor in a first optical element (OE) mode. The second image sensor receives light from the first optical path in a second OE mode. 
     In some implementations, the device also includes a second aperture. A second optical path is formed between the first image sensor and the second aperture. The optical element is further configured to direct light from the second optical path towards the second image sensor in the first OE mode. The first image sensor receives light from the second optical path in the second OE mode. The optical element may be configured to direct the light from the first optical path towards the first image sensor in the first OE mode, and allow the light from the first optical path to pass through the optical element in the second OE mode. The optical element may be further configured to direct the light from the second optical path towards the second image sensor in the first OE mode and allow the light from the second optical path to pass through the optical element in the second OE mode. 
     The device may include an actuator configured to move the optical element between a first position associated with the first OE mode and a second position associated with the second OE mode. In some implementations, the actuator is configured to rotate the optical element between a first orientation and a second orientation with reference to a direction of the light from the first optical path, and a transparency and a reflectiveness of the optical element may be based on an orientation of the optical element with reference to the first optical path. The device may include an electrical current source configured to apply an electrical current to the optical element, and a transparency and a reflectiveness of the optical element may be based on an amount of electrical current applied to the optical element. In some implementations, the first image sensor includes a color image sensor and the second image sensor includes one of a monochrome image sensor, an infrared image sensor, or an image sensor with a different resolution than the first image sensor. In some implementations, the first image sensor includes a lower power image sensor, and the second image sensor includes a higher power image sensor. The lower power image sensor consumes less power than the higher power image sensor over a same amount of time. 
     The first aperture and the second aperture may be positioned on a first side of the device. Alternatively, the first aperture may be positioned on a first side of the device, and the second aperture may be positioned on a second side of the device. In some implementations, the first aperture is positioned on a first side including a display, and the second aperture is positioned on a second side of the device different than the first side. Whether the optical element is in the first OE mode or the second OE mode may be based on an orientation of the device. The device may include a lens configured to focus light toward the first image sensor or the second image sensor and an actuator configured to adjust a position of the lens with reference to a position of the first image sensor or a position of the second image sensor. The device may also include an image signal processor configured to process images received from the first image sensor and the second image sensor, an application processor configured to provide instructions to the image signal processor, and a memory configured to store the processed images. 
     In another example, a method for digital imaging by a device including a first aperture, a first image sensor, a second image sensor, and an optical element is disclosed. The example method includes identifying whether the device is to be in a first device mode or a second device mode and controlling the optical element based on the identified device mode. The optical element directs light from the first aperture to the first image sensor in a first OE mode. Light from the first aperture is directed to the second image sensor when the optical element is in the second OE mode. Controlling the optical element may include identifying whether the optical element is to be in the first OE mode or the second OE mode based on the identified device mode and adjusting the optical element based on the identified OE mode. Identifying whether the optical element is to be in the first OE mode or the second OE mode may be further based on an orientation of the device. Adjusting the optical element may include one or more of rotating the optical element, translationally moving the optical element, or applying an electrical current to the optical element. In some implementations, identifying whether the device is to be in the first device mode or the second device mode is based on a user input indicating a device mode. In some other implementations, identifying whether the device is to be in the first device mode or the second device mode is based on one or more of: a field of view for image capture; a zoom factor for image capture; a depth of field for image capture; or a device orientation (such as a landscape or portrait orientation). The first image sensor may be associated with a first field of view, and the second image sensor may be associated with a second field of view. The first image sensor may be associated with a first zoom factor, and the second image sensor may be associated with a second zoom factor. The first image sensor may be associated with a first depth of field, and the second image sensor may be associated with a second depth of field. In some implementations, the device is in a first device mode based on the device having a first orientation. The device may be in a second device mode based on the device having a second orientation different than the first orientation. 
     Identifying whether the device is to be in the first device mode or the second device mode may include comparing one or more of: the field of view for image capture to a threshold field of view between the first field of view and the second field of view; the zoom factor for image capture to a threshold zoom factor between the first zoom factor and the second zoom factor; or the depth of field for image capture to a threshold depth of field between the first depth of field and the second depth of field. Identifying whether the device is to be in the first device mode or the second device mode may include detecting the orientation of the device. Identifying whether the device is to be in the first device mode or the second device mode may also include selecting the first device mode or the second device mode based on the comparison or the detection. 
     The method may further include directing, by the optical element, one or more of: light from the first aperture to the first image sensor in the first OE mode; or light from the first aperture to the second image sensor in the second OE mode. The method may also include capturing one or more of: a first image from the light directed to the first image sensor during the first device mode; or a second image from the light directed to the second image sensor during the second device mode. The method may also include capturing a second image from the light directed to the second image sensor during the second device mode. The method may further include directing, by the optical element, one or more of: light from a second aperture of the device to the second image sensor in the first OE mode; or light from the second aperture to the first image sensor in the second OE mode. 
     In a further example, a computer-readable medium is disclosed. The computer-readable medium may store instructions that, when executed by one or more processors of a device comprising a first aperture, a first image sensor, a second image sensor, and an optical element, cause the device to identify whether the device is to be in a first device mode or a second device mode and control the optical element based on the identified device mode. The optical element directs light from the first aperture to the first image sensor in a first OE mode. Light from the first aperture is directed to the second image sensor when the optical element is in the second OE mode. In some implementations, execution of the instructions to control the optical element causes the device to identify whether the optical element is to be in the first OE mode or the second OE mode based on the identified device mode and adjust the optical element based on the identified OE mode. Identifying whether the optical element is to be in the first OE mode or the second OE mode may be further based on an orientation of the device. Adjusting the optical element may include one or more of rotating the optical element, translationally moving the optical element, or applying an electrical current to the optical element. 
     In some implementations, identifying whether the device is to be in the first device mode or the second device mode is based on a user input indicating a device mode. In some other implementations, identifying whether the device is to be in the first device mode or the second device mode is based on one or more of: a field of view for image capture; a zoom factor for image capture; a depth of field for image capture; or a device orientation such as landscape or portrait. The first image sensor may be associated with a first field of view, and the second image sensor may be associated with a second field of view. The first image sensor may be associated with a first zoom factor, and the second image sensor may be associated with a second zoom factor. The first image sensor may be associated with a first depth of field, and the second image sensor may be associated with a second depth of field. In some implementations, the device is in a first device mode based on the device having a first orientation. The device may be in a second device mode based on the device having a second orientation different than the first orientation. Execution of instructions to identify whether the device is to be in the first device mode or the second device mode may cause the device to compare one or more of: the field of view for image capture to a threshold field of view between the first field of view and the second field of view; the zoom factor for image capture to a threshold zoom factor between the first zoom factor and the second zoom factor; or the depth of field for image capture to a threshold depth of field between the first depth of field and the second depth of field. Execution of instructions to identify whether the device is to be in the first device mode or the second device mode may cause the device to alternatively detect the orientation in which it is positioned. Execution of the instructions to identify whether the device is to be in the first device mode or the second device mode may also cause the device to select the first device mode or the second device mode based on the comparison or the detection. 
     Execution of the instructions may further cause the device to direct, by the optical element, one or more of: light from the first aperture to the first image sensor in the first OE mode; or light from the first aperture to the second image sensor in the second OE mode. Execution of the instructions may also cause the device to capture one or more of: a first image from the light directed to the first image sensor during the first device mode; or a second image from the light directed to the second image sensor during the second device mode. Execution of the instructions may further cause the device to direct, by the optical element, one or more of: light from a second aperture of the device to the second image sensor in the first OE mode; or light from the second aperture to the first image sensor in the second OE mode. 
     In another example, a device for digital imaging is disclosed. The device includes means for identifying whether the device is to be in a first device mode or a second device mode and means for controlling the optical element based on the identified device mode. The optical element directs light from the first aperture to the first image sensor in a first OE mode. Light from the first aperture is directed to the second image sensor when the optical element is in the second OE mode. Controlling the optical element may include identifying whether the optical element is to be in the first OE mode or the second OE mode based on the identified device mode and adjusting the optical element based on the identified OE mode. Adjusting the optical element may include one or more of rotating the optical element, translationally moving the optical element, or applying an electrical current to the optical element. In some implementations, identifying whether the device is to be in the first device mode or the second device mode is based on a user input indicating a device mode. In some other implementations, identifying whether the device is to be in the first device mode or the second device mode is based on one or more of: a field of view for image capture; a zoom factor for image capture; a depth of field for image capture; or a device orientation such as landscape or portrait. The first image sensor may be associated with a first field of view, and the second image sensor may be associated with a second field of view. The first image sensor may be associated with a first zoom factor, and the second image sensor may be associated with a second zoom factor. The first image sensor may be associated with a first depth of field, and the second image sensor may be associated with a second depth of field. The first image sensor may be associated with a first orientation of the device, and the second image sensor may be associated with a second orientation of the device different than the first orientation. 
     Some aspects of the present disclosure relate to a shared emitter between apertures. An example device for active depth sensing includes a first aperture configured to receive light propagated along a first optical path, a second aperture configured to receive light propagated along a second optical path, a first emitter configured to emit a first light, and an optical element configured to direct the first light from the first emitter towards the first optical path in a first optical element (OE) mode. The first light from the first emitter is directed towards the second optical path in a second OE mode. 
     The device may include an actuator configured to move the optical element between a first position associated with the first OE mode and a second position associated with the second OE mode. The device may include an actuator configured to rotate the optical element between a first orientation associated with the first OE mode and a second orientation associated with the second OE mode. In some implementations, a transparency and a reflectiveness of the optical element are based on an orientation of the optical element with reference to the first optical path. The device may include an electrical current source configured to apply an electrical current to the optical element. A transparency and a reflectiveness of the optical element may be based on an amount of electrical current applied to the optical element. 
     In some implementations, the device includes a second emitter configured to emit a second light. The optical element may direct the second light from the second emitter towards the second optical path in the first OE mode. The second light may be directed from the second emitter towards the first optical path in the second OE mode. The first emitter may be configured to emit a first distribution of light for structured light depth sensing, and the second emitter may be configured to emit one of: a periodic pulsed light for time-of-flight depth sensing; a second distribution of light for structured light depth sensing; or a diffuse light for flood illumination. The device may include one or more receivers configured to receive a reflection of the first light for active depth sensing. 
     In some implementations, the device includes an image sensor configured to capture one or more images. The image sensor may be a lower power image sensor. A lower power image sensor consumes less power than other image sensors over a same amount of time. In some implementations, the first emitter is configured to emit light for active depth sensing, and the image sensor includes a lower power image sensor configured to capture one or more images for object detection. The optical element may direct light from the second aperture towards the image sensor in the first OE mode. Light from the first aperture may be directed towards the image sensor in the second OE mode. In some implementations, the device includes a signal processor configured to process the one or more images, an application processor configured to provide instructions to the signal processor, and a memory configured to store the processed images. 
     The device may also include a controller to control the optical element. The controller may control the optical element based on an orientation of the device. 
     In another example, a method for active depth sensing by a device including a first aperture, a second aperture, a first emitter, and an optical element is disclosed. The example method includes identifying whether the optical element is to be in a first OE mode or a second OE mode, and controlling the optical element based on the identified OE mode. The optical element directs light from the first emitter towards the first aperture in the first OE mode. Light from the first emitter is directed towards the second aperture in the second OE mode. 
     Controlling the optical element may include adjusting the optical element. Adjusting the optical element may include one or more of rotating the optical element, translationally moving the optical element, or applying an electrical current to the optical element. 
     Identifying whether the optical element is to be in the first OE mode or the second OE mode may be based on a device mode of the device, and the device may include a second emitter or an image sensor. A first device mode is associated with the first emitter, and a second device mode is associated with the second emitter or the image sensor. Identifying whether the optical element is to be in the first OE mode or the second OE mode may be based on a user input 
     In some implementations, the method includes emitting light by the first emitter, directing, by the optical element, the light from the first emitter towards the first aperture in the first OE mode, and directing the light from the first emitter towards the second aperture in the second OE mode. The method may also include emitting light by a second emitter when the device is in a second device mode, directing, by the optical element, the light from the second emitter towards the second aperture in the first OE mode, and directing the light from the second emitter towards the first aperture in the second OE mode. The first emitter emits light when the device is in a first device mode. The method may further include receiving, by one or more receivers, a reflection of the light from the first emitter when the device is in the first device mode, and receiving, by the one or more receivers, a reflection of the light from the second emitter when the device is in the second device mode. 
     In some implementations the method includes capturing images by an image sensor when the device is in a second device mode, directing, by the optical element, light from the second aperture towards the image sensor in the first OE mode, and directing light from the first aperture towards the image sensor in the second OE mode. The first emitter emits light when the device is in a first device mode. Identifying whether the optical element is to be in the first OE mode or the second OE mode may be based on an orientation of the device. In some implementations, the image sensor is a lower power image sensor, and the images captured by the image sensor in the second device mode are for object detection. The lower power image sensor consumes less power than other image sensors over a same amount of time. 
     In a further example, a computer-readable medium is disclosed. The computer-readable medium may store instructions that, when executed by one or more processors of a device for active depth sensing including a first aperture, a second aperture, a first emitter, and an optical element, cause the device to identify whether the optical element is to be in a first OE mode or a second OE mode, and control the optical element based on the identified OE mode. The optical element directs light from the first emitter towards the first aperture in the first OE mode. Light from the first emitter is directed towards the second aperture in the second OE mode. 
     Execution of the instructions to control the optical element may cause the device to adjust the optical element. Adjusting the optical element may include one or more of rotating the optical element, translationally moving the optical element, or applying an electrical current to the optical element. 
     Identifying whether the optical element is to be in the first OE mode or the second OE mode may be based on a device mode of the device. The device may include a second emitter or an image sensor. A first device mode may be associated with the first emitter, and a second device mode may be associated with the second emitter or the image sensor. Identifying whether the optical element is to be in the first OE mode or the second OE mode may be based on a user input. 
     Execution of the instructions may further cause the device to emit light by the first emitter, direct, by the optical element, the light from the first emitter towards the first aperture in the first OE mode, and direct the light from the first emitter towards the second aperture in the second OE mode. In some implementations, execution of the instructions causes the device to emit light by a second emitter when the device is in a second device mode, direct, by the optical element, the light from the second emitter towards the second aperture in the first OE mode, and direct the light from the second emitter towards the first aperture in the second OE mode. The first emitter emits light when the device is in a first device mode. Execution of the instructions may also cause the device to receive, by one or more receivers, a reflection of the light from the first emitter when the device is in the first device mode, and receive, by the one or more receivers, a reflection of the light from the second emitter when the device is in the second device mode. 
     In some implementations, execution of the instructions causes the device to capture images by an image sensor when the device is in a second device mode, direct, by the optical element, light from the second aperture towards the image sensor in the first OE mode, and direct light from the first aperture towards the image sensor in the second OE mode. The first emitter emits light when the device is in a first device mode. Identifying whether the optical element is to be in the first OE mode or the second OE mode may be based on an orientation of the device. In some implementations, the image sensor is a lower power image sensor, and the images captured by the image sensor in the second device mode are for object detection. The lower power image sensor consumes less power than other image sensors over a same amount of time. 
     In another example, a device for active depth sensing including a first aperture, a second aperture, a first emitter, and an optical element is disclosed. The device includes means for identifying whether the optical element is to be in a first OE mode or a second OE mode, and means for controlling the optical element based on the identified OE mode. The optical element directs light from the first emitter towards the first aperture in the first OE mode. Light is directed from the first emitter towards the second aperture in the second OE mode. The device may include means for adjusting the optical element. 
     In another example, another device for active depth sensing is disclosed. The device includes means for emitting a first light, means for directing the first light towards a first optical path in a first OE mode, and means for directing the first light propagated along the first optical path to outside of the device in the first OE mode. The device also includes means for directing the first light towards a second optical path in a second OE mode, and means for directing the first light propagated along the second optical path to outside of the device in the second OE mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements. 
         FIG. 1  shows a cross-section of a device portion illustrating a first image sensor associated with a first optical path and a second image sensor associated with a second optical path. 
         FIG. 2  shows a cross-section of a device portion illustrating a first emitter for active depth sensing associated with a first optical path and a second emitter for active depth sensing associated with a second optical path. 
         FIG. 3A  shows a block diagram of an example device including a first image sensor and a second image sensor sharing a first optical path. 
         FIG. 3B  shows a depiction of a device having a first aperture on a first side and a second aperture on a second side. 
         FIG. 3C  shows a depiction of a device having a first aperture and a second aperture on a side including a display. 
         FIG. 3D  shows a depiction of a device having a first aperture and a second aperture on a side opposite a display. 
         FIG. 3E  shows a depiction of a device switching between image capture from a first side of a device and from a second side of the device. 
         FIG. 3F  shows a depiction of a device adjusting a FOV or zoom factor for images captured by the device. 
         FIG. 3G  shows a depiction of a device having a first aperture and a third aperture on a side including a display and a second aperture and a fourth aperture on a side opposite the display. 
         FIG. 4A  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path. 
         FIG. 4B  shows the cross-section of the example device portion in  FIG. 4A  illustrating a second image sensor associated with the first optical path. 
         FIG. 4C  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path. 
         FIG. 4D  shows the cross-section of the example device portion in  FIG. 4C  illustrating a second image sensor associated with the first optical path. 
         FIG. 4E  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path and a third image sensor associated with a third optical path. 
         FIG. 4F  shows a cross-section of the example device portion in  FIG. 4E  illustrating a second image sensor associated with the first optical path and a fourth image sensor associated with the third optical path. 
         FIG. 5A  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path when the device is in a first OE mode. 
         FIG. 5B  shows the cross-section of the example device portion in  FIG. 5A  illustrating a second image sensor associated with the first optical path when the device is in a second OE mode. 
         FIG. 5C  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path. 
         FIG. 5D  shows the cross-section of the example device portion in  FIG. 5C  illustrating a second image sensor associated with the first optical path. 
         FIG. 6A  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path. 
         FIG. 6B  shows the cross-section of the example device portion in  FIG. 6A  illustrating a second image sensor associated with the first optical path. 
         FIG. 6C  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path. 
         FIG. 6D  shows the cross-section of the example device portion in  FIG. 6C  illustrating a second image sensor associated with the first optical path. 
         FIG. 6E  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path. 
         FIG. 6F  shows the cross-section of the example device portion in  FIG. 6E  illustrating the first image sensor associated with a second optical path. 
         FIG. 6G  shows a cross-section of an example device portion illustrating a first image sensor associated with a first optical path. 
         FIG. 6H  shows the cross-section of the example device portion in  FIG. 6G  illustrating the first image sensor associated with a second optical path. 
         FIG. 7A  shows a cross-section of an example device portion illustrating a first image sensor and a second image sensor associated with one or more lenses to adjust a field of view (FOV) for image capture. 
         FIG. 7B  shows a cross-section of an example device portion illustrating a second image sensor associated with a moveable lens. 
         FIG. 7C  shows a cross-section of an example device portion illustrating a second image sensor that is moveable. 
         FIG. 7D  shows a cross-section of an example device portion illustrating a first image sensor and a second image sensor associated with one or more lenses to adjust a field of view (FOV) for image capture. 
         FIG. 7E  shows a cross-section of an example device portion illustrating a second image sensor associated with a moveable lens. 
         FIG. 7F  shows a cross-section of an example device portion illustrating a second image sensor that is moveable. 
         FIG. 8A  shows an illustrative flow chart depicting an example operation for a first image sensor and a second image sensor to share a first optical path. 
         FIG. 8B  shows an illustrative flow chart depicting an example operation for the first image sensor and the second image sensor in  FIG. 8  to share a second optical path. 
         FIG. 9A  shows an illustrative flow chart depicting an example operation for image capture. 
         FIG. 9B  shows an illustrative flow chart depicting an example operation for controlling an optical element. 
         FIG. 9C  shows an illustrative flow chart depicting an example operation for controlling an optical element based on a device orientation. 
         FIG. 10  shows a block diagram of an example device including a first emitter for active depth sensing coupled to a first optical path when the device is in a first mode and a second optical path when the device is in a second mode. 
         FIG. 11  shows a depiction of an example active depth sensing system including an emitter for emitting a distribution of light. 
         FIG. 12  shows a depiction of a direct time-of-flight (TOF) active depth sensing system including an emitter. 
         FIG. 13  shows a depiction of an indirect TOF active depth sensing system including an emitter. 
         FIG. 14A  shows a cross-section of an example device portion illustrating a first emitter associated with a first optical path. 
         FIG. 14B  shows the cross-section of the example device portion in  FIG. 14A  illustrating the first emitter associated with a second optical path. 
         FIG. 14C  shows a cross-section of an example device portion illustrating a first emitter associated with a first optical path and a first image sensor associated with a third optical path. 
         FIG. 14D  shows a cross-section of the example device portion in  FIG. 14C  illustrating a second emitter associated with the first optical path and a second image sensor associated with the third optical path. 
         FIG. 15A  shows a cross-section of an example device portion illustrating a first emitter associated with a first optical path. 
         FIG. 15B  shows the cross-section of the example device portion in  FIG. 15A  illustrating the first emitter associated with a second optical path. 
         FIG. 16A  shows a cross-section of an example device portion illustrating a first emitter associated with a first optical path. 
         FIG. 16B  shows the cross-section of the example device portion in  FIG. 16A  illustrating the first emitter associated with a second optical path. 
         FIG. 16C  shows a cross-section of an example device portion illustrating a first emitter associated with a first optical path. 
         FIG. 16D  shows the cross-section of the example device portion in  FIG. 16C  illustrating the first emitter associated with a second optical path. 
         FIG. 16E  shows a cross-section of an example device portion illustrating a first emitter associated with a first optical path. 
         FIG. 16F  shows the cross-section of the example device portion in  FIG. 16E  illustrating the first emitter associated with a second optical path. 
         FIG. 17A  shows an illustrative flow chart depicting an example operation for active depth sensing by a device. 
         FIG. 17B  shows an illustrative flow chart depicting an example operation for active depth sensing by a device configured for multiple device modes. 
         FIG. 18  shows an illustrative flow chart depicting an example operation of controlling an optical element for active depth sensing. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present disclosure may be used for image capture systems and devices or active depth sensing systems and devices. Some aspects may include a device having a shared optical path between multiple image sensors. Some other aspects may include a device having an emitter for active depth sensing shared between multiple optical paths. 
     Referring to aspects including a device having a shared optical path between multiple image sensors, many devices have multiple cameras. For a device having multiple cameras, each camera includes an image sensor, a lens, and other camera components (such as a shutter, imaging front end, color filter, and so on). For example, a smartphone may have a plurality of rear facing cameras (opposite a side including the display), and each rear facing camera includes dedicated camera components. Each rear facing camera may be configured to capture a different field of view (FOV) of a scene based on the image sensor and one or more lenses directing light to the image sensor. When an image is to be captured, the associated camera is used to capture the image while the other cameras are generally unused. In another example, one rear facing camera may be a primary camera for color imaging, and another rear facing camera may be an auxiliary camera for black and white imaging. If a black and white image is to be captured, the auxiliary camera may be used while the primary camera is unused. 
     The smartphone may also have one or more front facing cameras (such as located at a punch hole in the display, a notch on a side of the display, or under a display), and each front facing camera may be associated with a different FOV. For example, if a smartphone includes one front facing camera, the front facing camera may be configured to capture images with a FOV for portrait images. If the smartphone includes a second front facing camera, the second front facing camera may be configured to capture images with a FOV for landscape images or group selfie images. Based on the FOV to be used for capturing a front facing image (such as a selfie image), the associated front facing camera is used while the other front facing camera is unused. 
       FIG. 1  shows a cross-section of a device  100  portion illustrating a first image sensor  102  associated with a first optical path  106  and a second image sensor  104  associated with a second optical path  108 . The first image sensor  102  is associated with a front facing camera configured to receive light  114  via a first aperture  110  through a display  118  of the device  100  (such as via a notch, punch hole, and so on). The second image sensor  104  is associated with a rear facing camera configured to receive light  116  via a second aperture  112  through a rear panel of the device  100 . The first image sensor  102  is associated with dedicated imaging components for capturing images by the front facing camera, and the second image sensor  104  is associated with dedicated imaging components for capturing images by the rear facing camera. When a front facing image is to be captured, the rear facing camera is unused. When a rear facing image is to be captured, the rear facing camera is unused. 
     Each image sensor being coupled to a dedicated optical path requires space and additional camera components within the device. As the number of image sensors increases, the space required increases and the number of camera components increases. Additionally, since each image sensor is associated with an aperture to allow light into the device, the number of apertures visible on an exterior of a device increases as the number of image sensors increases. For example, as the number of front facing cameras increases in a smartphone, a notch size, a punch hole size, or number of punch holes through the smartphone display increases to accommodate the additional apertures, effecting design and manufacturing complexity and/or design aesthetic. Furthermore, while one image sensor may not be used when another image sensor is used for imaging, the unused image sensor and camera components may be enabled and consuming power. As the number of image sensors (and their dedicated camera components) increase, the amount of power consumed increases. 
     The device may include fewer image sensors (and dedicated camera components) to reduce the space required, number of components required, number of apertures required, and power consumption for the device. However, reducing the number of image sensors may reduce the capabilities of the device. For example, if a smartphone includes only one front facing camera configured with a portrait FOV, the smartphone is not capable of capturing landscape or group FOV selfie images (even if the smartphone includes a landscape FOV configured rear facing camera). 
     In some implementations, a device may include a first image sensor and a second image sensor that are configured to share at least one optical path (and associated aperture). For example, a first image sensor may be configured to capture images with a first FOV, and a second image sensor may be configured to capture images with a second FOV. The device includes an optical element configured to switch between directing light from the shared optical path to the first image sensor and directing light from the shared optical path to the second image sensor. In this manner, the device may require a reduced space and number of camera components for the multiple image sensors. Additionally, an image sensor may be used for front facing imaging and rear facing imaging such that multiple dedicated image sensors for a specific FOV are not required for multiple sides of the device. For example, one image sensor with a first FOV may be used for front facing images and rear facing images from a smartphone or other device. Other benefits of implementations are described herein with reference to the figures and examples. 
     Referring to aspects including a device having an active depth sensing emitter shared by multiple optical paths in the device (and their associated apertures on the device), a device may be configured for active depth sensing to assist with various operations of the device. For example, a smartphone may include a rear facing active depth sensing system for auto focus of one or more rear facing cameras, for depth mapping, for range finding, or for other suitable operations. In another example, a smartphone may include a front facing active depth sensing system for facial recognition, for depth mapping, or for other suitable operations. Each active depth sensing system includes a dedicated emitter and components for active depth sensing. Each active depth sensing system also includes one or more dedicated apertures. 
       FIG. 2  shows a cross-section of a device  200  portion illustrating a first emitter  220  for active depth sensing associated with a first optical path  222  and a second emitter  230  for active depth sensing associated with a second optical path  232 . The first emitter  220  is configured to emit light  224  through the first optical path  222  and out a front of the device  200  via a first aperture  226  through a device display  218 . The second emitter  230  is configured to emit light  234  through the second optical path  232  and out a rear of the device  200  via a second aperture  236  through a rear side of the device  200 . The device  200  also includes a sensor  202  configured to receive light  214  via a third aperture  210  through the display  218  and via the third optical path  206 . The light  214  includes reflections of the light  224  for active depth sensing. The device  200  also includes a sensor  204  configured to receive light  216  via a fourth aperture  212  through a rear side of the device  200  and via the fourth optical path  208 . The light  216  includes reflections of the light  234  for active depth sensing. 
     As shown, a front facing active depth sensing system (including the emitter  220 ) is associated with dedicated components for active depth sensing, and a rear facing active depth sensing system (including the emitter  230 ) is associated with different dedicated components for active depth sensing. When only one of the active depth sensing systems is in use, the components of the other active depth sensing system may be unused. For example, when the first emitter  220  is in use, the second emitter  230  may not be in use. Additionally, a number of similar components are required when the device includes multiple active depth sensing systems (such as multiple emitters and components for driving and controlling the emitters). As the number of active depth sensing systems increases in a device, the number of emitters, components, and space required in the device increases. 
     A device may include fewer active depth sensing systems (and dedicated emitters) to reduce the space required, number of components required, and number of apertures required in the device. However, reducing the number of active depth sensing systems may reduce the capabilities of the device. For example, if a smartphone includes only a front facing active depth sensing system (and no rear facing active depth sensing system), the smartphone may be capable of performing facial recognition for screen unlock, but the smartphone is not capable of performing laser autofocus for the rear facing cameras. 
     In some implementations, a device may include a first aperture and optical path and a second aperture and optical path that are configured to share an emitter for active depth sensing. For example, the first aperture (coupled to a first optical path in the device) may be a front facing aperture, and the second aperture (coupled to a second optical path in the device) may be a rear facing aperture. The device includes an optical element configured to switch between coupling the emitter to the first optical path and coupling the emitter to the second optical path. In this manner, the emitter may be configured to emit light out of the device via the first aperture or via the second aperture (such as a front facing aperture for front facing active depth sensing or a rear facing aperture for rear facing active depth sensing). The device may require a reduced space and number of components for the shared emitter for active depth sensing. Other benefits of implementations are described herein with reference to the figures and examples. 
     In the following description, numerous specific details are set forth, such as examples of specific components, circuits, and processes to provide a thorough understanding of the present disclosure. The term “coupled” as used herein means connected directly to or connected through one or more intervening components or circuits. Also, in the following description and for purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details may not be required to practice the teachings disclosed herein. In other instances, well known circuits and devices are shown in block diagram form to avoid obscuring teachings of the present disclosure. Some portions of the detailed descriptions which follow are presented in terms of procedures, logic blocks, processing and other symbolic representations of operations on data bits within a computer memory. In the present disclosure, a procedure, logic block, process, or the like, is conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, although not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present application, discussions utilizing the terms such as “accessing,” “receiving,” “sending,” “using,” “selecting,” “determining,” “normalizing,” “multiplying,” “averaging,” “monitoring,” “comparing,” “applying,” “updating,” “measuring,” “deriving,” “settling” or the like, refer to the actions and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
     In the figures, a single block may be described as performing a function or functions; however, in actual practice, the function or functions performed by that block may be performed in a single component or across multiple components, and/or may be performed using hardware, using software, or using a combination of hardware and software. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are described below generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Also, the example devices may include components other than those shown, including well-known components such as a processor, memory and the like. 
     Aspects of the present disclosure are applicable to any suitable electronic device including an image sensor configured to capture images or video or an emitter configured for active depth sensing (such as security systems, smartphones, tablets, laptop computers, digital video and/or still cameras, web cameras, and so on). While many examples described herein depict a device including two image sensors sharing one or two optical paths, aspects of the present disclosure are applicable to devices having any number of optical paths and any number of shared image sensors. Although the image sensors are also depicted as being oriented for different sides of a device, each image sensor may be oriented in any suitable manner (such as for a same side of a device). Additionally, while many examples described herein depict a device including one emitter sharing two optical paths and apertures for active depth sensing, aspects of the present disclosure are applicable to devices having any number of emitters and any number of shared optical paths. Therefore, the present disclosure is not limited to devices having a specific number of image sensors, active depth sensing emitters, components, orientation of components, apertures, optical paths, and so on. 
     The term “device” is not limited to one or a specific number of physical objects (such as one smartphone, one camera controller, one processing system and so on). As used herein, a device may be any electronic device with one or more parts that may implement at least some portions of the disclosure. While the below description and examples use the term “device” to describe various aspects of the disclosure, the term “device” is not limited to a specific configuration, type, or number of objects. 
       FIG. 3A  shows a block diagram of an example device  300 . The example device  300  may include a first aperture  320  to direct light to a first optical path  301 , a first image sensor  302 , a second image sensor  303 , and an optical element  304 . The example device  300  also includes a processor  305 , a memory  306  storing instructions  308 , and an image signal processor  312 . The device  300  optionally may include (or be coupled to) a display  314 , a number of input/output (I/O) components  316 , and a number of sensors  326 . The device  300  may include additional features or components not shown. In one example, a wireless interface, which may include a number of transceivers and a baseband processor, may be included for a wireless communication device. The device  300  also may include a power supply  318 , which may be coupled to or integrated into the device  300 . 
     The device  300  is configured to use the first image sensor  302  for capturing images when the device is in a first device mode (or first mode). The device  300  is also configured to use the second image sensor  303  for capturing images when the device is in a second device mode (or second mode). When the device  300  is in the first mode, the first image sensor  302  may be configured to receive light propagating along the first optical path  301  based on the optical element  304 . The optical element  304  is configured to direct light propagating along the first optical path to the first image sensor  302  when in a first optical element (OE) mode. When the device  300  is in the second mode, the second image sensor  303  may be configured to receive light propagating along the first optical path  301  based on the optical element  304 . For example, the optical element  304  is configured to allow the second image sensor  303  to receive light propagating along the first optical path  301  when the optical element  304  is in a second OE mode. 
     In some implementations, the device  300  includes a second aperture  322  to direct light along a second optical path  324 . The first image sensor  302  and the second image sensor  303  may also share the second optical path  324 . The optical element  304  may be configured to direct light along the second optical path  324  to the second image sensor  303  when the optical element  304  is in the first OE mode, and the device  300  may be configured to direct light along the second optical path  324  to the first image sensor  302  when the optical element  304  is in the second OE mode. As noted above, switching between a first device mode and a second device mode may refer to switching between image sensors for capturing images. In some implementations, the first image sensor  302  receives light propagated along the first optical path  301  during a first portion of the first device mode, and the first image sensor  302  receives light propagated along the second optical path  324  during a second portion of the first device mode. Similarly, the second image sensor  303  may receive light propagated along the first optical path  301  during a first portion of the second device mode, and the second image sensor  303  receives light propagated along the second optical path  324  during a second portion of the second device mode. The first portion and the second portion may be based on whether the optical element  304  is in a first OE mode or a second OE mode, and the device  300  is configured to switch the optical element  304  between OE modes. In some implementations, the first portion of the first device mode is the same as the first portion of the second device mode, and the second portion of the first device mode is the same as the second portion of the second device mode. For example, when the optical element  304  is configured to direct light propagating along the first optical path  301  to the first image sensor  302 , the optical element  304  allows light propagating along the second optical path  324  to reach the second image sensor  303 . 
     The device modes may be based on one or more image capture characteristics. For example, a first mode may be for capturing images having a first FOV and a second mode may be for capturing images having a second FOV. In one example, a first FOV may be a telephoto FOV, and a second FOV may be a wide FOV. A telephoto FOV may refer to a FOV associated with a telephoto lens or a suitable FOV for capturing telephoto FOV images. A wide FOV may refer to a wide FOV, an ultra-wide FOV, or any other FOV greater than the telephoto FOV. In another example, a first mode may be for capturing color images, and a second mode may be for capturing black and white images. In a further example, a first mode may be associated with a first zoom factor, and a second mode may be associated with a second zoom factor (such as based on an optical zoom caused by lenses directing light to the associated image sensor). 
     In some other implementations, switching between a first device mode and a second device mode may refer to switching between an image sensor for image capture and an image sensor for active depth sensing. A first image sensor may be used for visual photography (such as capturing selfies, capturing portrait images, capturing group images, and so on). A second image sensor may be used for active depth sensing (such as capturing reflections of light for time of flight depth sensing or structured light depth sensing). For example, the first mode is for capturing images using a first image sensor  302 , and the second mode is for capturing light reflections from an emitter using a second image sensor  303  for active depth sensing. 
     In some implementations, switching between a first device mode and a second device mode may be based on information captured by an image sensor during one device mode to cause the device  300  to switch to the other device mode. For example, a device  300  may include a lower power image sensor and a higher power image sensor. As used herein, a lower power image sensor refers to an image sensor that consumes less power than one or more other image sensors (such as conventional image sensors used in devices). A higher power image sensor may refer to an image sensor that consumes more power over a same amount of time than the lower power image sensor. In this manner, a lower power image sensor may refer to an image sensor that consumes less power over a same amount of time than the higher power image sensor. In some implementations, differing power consumptions may be based on a difference in resolution. For example, a lower power image sensor may be a lower resolution image sensor and a higher power image sensor may be a higher resolution image sensor with reference to each other. Since less sensor pixels are readout for a frame for the lower resolution image sensor, the lower resolution image sensor may consume less power during a common period of time of operation than the higher resolution image sensor. Different power consumption rates may alternatively or additionally be based on different frame rates (a lower power image sensor may have a lower frame rate), different sampling frequencies (a lower power image sensor may have a lower sampling frequency), different exposure window sizes per frame (a lower power image sensor may have a smaller exposure window size), or different pixel sizes (a lower power image sensor may have larger pixels). 
     In some implementations, the lower power image sensor may include an always on (AO) image sensor. As used herein, an AO image sensor refers to an image sensor that may continuously operate for different operating states and device power states of a device. For example, an AO image sensor may be active while a device is in a low power state (such as a sleep state), an active state (such as when the device is in use by a user), or another suitable state while the device is powered on. A lower power image sensor that is an AO image sensor may differ from another image sensor in that the other image sensor may be active or operate only during select times of device operation. For example, when the device is in a low power state (such as in an inactive state or sleep state), the AO image sensor may continue to capture images while the other image sensor may be inactive. For example, a higher power image sensor may be inactive when the device is in an inactive state or sleep state. The higher power image sensor may include an image sensor with better signal to noise ratio for output, better pixel density, more dynamic range of light frequency response, or another quantifiable measure that is better than the lower power image sensor. 
     In some implementations, the lower power image sensor may include a lower frame rate or lower sampling frequency than other image sensors (such as a higher power image sensor). Since the lower power image sensor is readout less times than another image sensor over a same amount time (with each readout requiring a defined amount of power consumption), the lower power image sensor may consume less power over the same amount of time than another image sensor. 
     In some implementations, the lower power image sensor may include larger pixels than the higher power image sensor. As used herein, a size of a pixel refers to the photosensitive area for receiving photons to be measured by a photodetector of the pixel. Increasing the pixel size means increasing the photosensitive area. In this manner, a larger size pixel receives more photons than a smaller size pixel from a same ambient lighting during a same size exposure window. In some implementations, an exposure window size for a larger pixel may be decreased to conserve power. When the exposure window size decreases, the image sensor may consume less power per frame. If the frame rate is the same between the lower power image sensor with larger pixels and another image sensor, the lower power image sensor may consume less power over a same amount of time than the other image sensor. In some implementations, a frame rate of the pixel may be increased when the exposure window size is decreased. With a faster frame rate, a device may more quickly detect changes in light intensity. 
     In some implementations, the lower power image sensor may include a lower resolution than another image sensor. Since less pixels are readout per frame for the lower power image sensor than for the other image sensor, the lower power image sensor may consume less power over a frame than the other image sensor. If the frame rate is the same for the lower power image sensor (with a lower resolution) and the other image sensor with a higher resolution, the lower power image sensor may consume less power over a same amount of time than the other image sensor. While the lower power image sensor may have a lower resolution, the resolution may be suitable for measuring changes in light intensity for different regions in a scene. If the light intensities change across the entire (or a large portion of the) lower power image sensor for a frame, the device may determine that the change is a result of a global motion (moving the camera) instead of local motion (an object entering the scene). If changes in light intensities is only in a portion of the field of view of the lower power image sensor, the device may determine that the change is a result of local motion (an object moving in the scene). For example, outer pixels of the lower power image sensor (such as edge pixels) may first measure a different light intensity for an object entering the lower power image sensor&#39;s field of view. Neighboring pixels may then measure a different light intensity as the object approaches the middle of the lower power image sensor&#39;s field of view. Additional pixels may measure a different light intensity until the object moves to the center of the lower power image sensor&#39;s field of view. At such point, the center pixels of the lower power image sensor may measure a different light intensity. In another example, neighboring pixels may measure different light intensities across frames as an object moves across the scene during the frames. For example, a user moving his hand across the field of view causes a sequence of pixels from one side to the other in the lower power image sensor to measure different light intensities across frames. In this manner, a device may track an object moving in the scene. Measuring a different light intensity refers to measuring a light intensity in a subsequent frame that is different than the light intensity in a previous frame. In some implementations, a different light intensity may refer to the difference in light intensities measured by a pixel (or region of pixels) being greater than a threshold between frames (to filter variations in light intensity attributed to noise). 
     While the lower power image sensor may have sufficient resolution to detect objects entering a scene, the lower power image sensor may not have sufficient resolution for an operation to be performed by the device. For example, a lower power image sensor may have sufficient resolution to be used for object detection to determine if a possible face moves towards the center of the image sensor&#39;s field of view, but the lower power image sensor&#39;s resolution may not be sufficient for facial recognition. In one example, the lower power image sensor may be used to detect if a face is present in the scene (such as based on changes in light intensities), but the lower power image sensor may not include a sufficient resolution to be used for identifying the face in the scene (such as identifying the eyes, nose, or mouth, the space between the eyes, nose, or mouth, or whether the eyes are open). The higher power image sensor may be used for facial recognition in identifying the face. In another example, the lower power image sensor may be used to identify a user gesture (such as waving an arm left, right, up, or down) for gesture commands to the device. The device may perform an operation associated with the gesture (such as powering a flash for a flashlight operation, adjust a volume, adjust a display brightness, and so on). If the device operation to be performed is a camera operation, the higher power image sensor may be used for imaging based on the user gesture. If the device operation is active depth sensing, the higher power image sensor may be an image sensor configured for receiving reflections of light for active depth sensing. 
     In a further example other than object detection, the lower power image sensor may capture light information used for image analysis or video content analysis to determine temporal or spatial events in a scene. For example, the lower power image sensor&#39;s measurements may be used to determine an amount of global motion or local motion in the scene, an overall light intensity in the scene, a change in overall light intensity over time, a range of light intensities across different portions of the scene, and so on. The information may then be used to configure the higher power image sensor for capturing one or more image frames (such as for still images or for video). For example, the information may be used to set an initial exposure setting or otherwise be used in configuring the higher power image sensor for image capture. 
     For a lower power image sensor (such as an AO image sensor), a first device mode may be a low power mode (for which the lower power image sensor is used), and a second device mode may be an active mode (for which the higher power image sensor is used). In one example, the low power mode may include using an AO image sensor to capture light information from a front side of a smartphone (the side including the display) to detect when a face may be in front of the display. If the smartphone detects a face in the low power mode, the smartphone may switch to the active mode. The active mode may include using the higher power image sensor for facial recognition. Switching device modes may include switching OE modes so that both image sensors use the same aperture from the front of the smartphone. In this manner, the device may perform face unlock or other facial recognition operations without prompt (such as not requiring a user to swipe on a touch-sensitive device display, power on the device display, or otherwise indicate to the device to perform facial unlock). A lower power image sensor (such as an AO image sensor) may also be used by the device to determine when to wake up or otherwise remove itself from a lower power mode (such as based on a user gesture or a user face in the scene). 
     Referring back to  FIG. 3A , the first aperture  320  may be configured to receive light incident to any side of the device  300 . For example, if the device  300  is a smartphone, the first aperture  320  may be positioned on any side of the smartphone. If the device  300  includes a second aperture  322 , the second aperture  322  may also be configured to receive light incident to any side of the device  300 . For example, the second aperture  322  may be positioned on any side of the smartphone. In some implementations, the apertures  320  and  322  are positioned on different sides (such as one rear facing (on a side opposite a side including the display  314 ) and one forward facing (on the side including the display  314 )). In some other implementations, the apertures  320  and  322  may be positioned on the same side (such as both being rear facing or both being front facing). 
     The first image sensor  302  and the second image sensor  303  may be any suitable image sensor and may be configured in any suitable manner. As noted above, the first image sensor  302  may be a lower power image sensor, and the second image sensor  303  may be a higher power image sensor. The first image sensor  302  may active during a first device mode (such as a lower power mode) while the second image sensor  303  may be active during a second device mode (such as an active mode). In some other implementations, the first image sensor  302  is configured to capture images with a first FOV (such as a telephoto FOV), and the second image sensor  303  is configured to capture images with a second FOV (such as a wide FOV or an ultra-wide FOV). The FOV may be based on one or more lenses configured to direct light toward the image sensor for image capture or may be based on the size of the image sensor. 
     In some other implementations, the first image sensor  302  is associated with a first zoom factor, and the second image sensor  303  is associated with a second zoom factor. For example, one or more lenses may be configured to magnify a scene for a first image sensor  302 , and the scene may not be magnified for the second image sensor  303 . In this manner, the first image sensor  302  is associated with a greater zoom factor than a zoom factor associated with the second image sensor  303 . 
     In some other implementations, the first image sensor  302  is associated with a first depth of field, and the second image sensor  303  is associated with a second zoom factor. For example, one or more lenses may be configured to place a portion of a scene at a first range of depths in focus for images captured by the first image sensor  302 . A different portion of the scene at a second range of depth may be in focus for images captured by the second image sensor  303 . In this manner, the first image sensor  302  may be used to capture images of objects in a first depth of field, and the second image sensor  303  may be used to capture images of objects in a second depth of field. 
     In some further implementations, the first image sensor  302  may be coupled to a color filter array (such as an RGB color filter array (CFA)), and the second image sensor  303  may be coupled to a different type of filter or may not be coupled to a filter. Example filters include a bandpass filter for a specific wavelength range of light (such as for a specific color, for infrared light, and so on). As used herein, an image sensor may refer to the image sensor itself or the image sensor and one or more components coupled to the image sensor. For example, a color image sensor may refer to an image sensor and an associated color CFA. In another example, an infrared (IR) image sensor may refer to an image sensor not associated with a CFA or an image sensor and an associated bandpass filter for filtering at least a portion of light outside of IR light. In a further example, a monochrome image sensor may refer to an image sensor not associated with a CFA. 
     An IR image sensor is configured to receive IR light. In some implementations, the IR image sensor is configured to receive light in a range of frequencies greater than IR. For example, an image sensor not coupled to a color filter array may be capable of measuring light intensities for light from a large range of frequencies (such as both color frequencies and IR frequencies). In some other implementations, the IR image sensor is configured to receive light specific to IR light frequencies. For example, the IR image sensor may include or be coupled to a bandpass filter to filter light outside of a range of frequencies not associated with IR light. As used herein, IR light may include portions of the visible light spectrum and/or portions of the light spectrum that is not visible to the naked eye. In one example, IR light may include near infrared (NIR) light, which may or may not include light within the visible light spectrum, and/or IR light (such as far infrared (FIR) light) which is outside the visible light spectrum. The term IR light should not be limited to light having a specific wavelength in or near the wavelength range of IR light. Further, IR light is provided as an example emission for active depth sensing. In the following description, other suitable wavelengths of light may be captured by an image sensor or used for active depth sensing, and an IR image sensor or active depth sensing is not limited to IR light or a specific frequency of IR light. 
     The memory  306  may be a non-transient or non-transitory computer readable medium storing computer-executable instructions  308  to perform all or a portion of one or more operations described in this disclosure (such as for adjusting a position of an optical element). The processor  305  may be one or more suitable processors (such as general purpose processors) capable of executing scripts or instructions of one or more software programs (such as instructions  308 ) stored within the memory  306 . For example, the processor  305  may be an applications processor and execute an imaging application. In additional or alternative aspects, the processor  305  may include integrated circuits or other hardware to perform functions or operations described in this disclosure without the use of software for processor  305 . 
     The processor  305  includes a controller  310  for selecting the image sensor to be used (such as selecting a first device mode or a second device mode) and for controlling the optical element  304  (such as switching between a first OE mode and a second OE mode). In some implementations, the controller  310  may be configured to adjust the position of the optical element  304  (such as by rotating or translationally moving the optical element  304 ). For example, the controller  310  may instruct an actuator to translationally move the optical element  304  when switching between OE modes. In another example, the controller  310  may instruct an actuator to rotate the optical element  304  when switching between OE modes. 
     In some other implementations, the controller  310  may be configured to adjust a state of the optical element  304  (such as by applying an electrical current or other stimulus). The optical element&#39;s state may include a reflectiveness or transparency (or refractive index) of the optical element  304  based on the stimulus. For example, the controller  310  may cause electrical current to not be applied to the optical element  304  for a first OE mode and cause electrical current to be applied to the optical element  304  for a second OE mode. 
     In some implementations, the controller  310  also determines or otherwise controls which image sensor is to be used for image capture. For example, the controller  310  selects whether the stream of images captured by the first image sensor or the stream of images captured by the second image sensor are processed by the image signal processor  312  for generating an image or video. In another example, the image signal processor  312  processes both streams of images, and the controller  310  selects one of the processed streams for generating an image of video. In a further example, the controller  310  uses the first image sensor (as a lower power image sensor) to capture images during a first mode, and the controller  310  initializes the second image sensor (as a higher power image sensor) to capture images during a second mode. For example, during a low power mode, a smartphone is inactive (such as with the display off). The smartphone may be in a lower power mode for which the controller  310  receives images from the lower power image sensor. The controller  310  (or the image signal processor  312 ) may determine a difference in light intensity for one or more pixels across the received image frames. The controller  310  may determine changes in light intensity associated with a user gesture to wake up the smartphone or with a face being positioned in front of the display of the smartphone. The controller  310  may then wake up the display. If facial recognition is to be performed (such as by detecting a face approaching a center of the field of view of the lower power image sensor), the controller  310  may switch device modes to an active mode. In some implementations, the controller  310  switches OE modes so that the higher power image sensor may be used for facial recognition using the same device aperture. In this manner, switching between device modes may also include adjusting the state of the optical element  304 . While some example uses of lower power image sensors (such as AO image sensors) are described, any suitable use may be implemented, and the present disclosure is not limited to the provided examples. 
     Referring back to  FIG. 3A , while shown to be coupled to each other via the processor  305  in the example device  300 , the processor  305 , the memory  306 , the image signal processor  312 , the optional display  314 , and the optional I/O components  316  may be coupled to one another in various arrangements. For example, the processor  305 , the memory  306 , the image signal processor  312 , the optional display  314 , and the optional I/O components  316  may be coupled to each other via one or more local buses (not shown for simplicity). 
     The display  314  may include any suitable display or screen allowing for user interaction and/or to present items (such as captured images, video, or preview images from the first image sensor  302  or the second image sensor  303 ). In some aspects, the display  314  may include a touch-sensitive display. The I/O components  316  may include any suitable mechanism, interface, or device to receive input (such as commands) from a user and to provide output to the user. For example, the I/O components  316  may include a graphical user interface, keyboard, mouse, microphone and speakers, and so on. The sensors  326  may include any suitable sensors, such as motion and orientation sensors, positioning sensors, temperature sensors, and so on. Motion and orientation sensors may include an accelerometer, a gyroscope, or a magnetometer. Positioning sensors may include a global positioning system (GPS) receiver. 
     In some implementations, the device mode or the OE mode may be based on an orientation or motion of the device  300 . The device orientation or motion may be determined based on one or more measurements from the number of sensors  326  (such as an orientation determined from measurements from a magnetometer). In addition or to the alternative, an orientation or motion of the device may be determined from differences in light information captured by an image sensor across multiple image frames. 
     In an example use case, the device  300  may be a smartphone in a low power state, locked, or otherwise with a screen lock. The device  300  may include a first aperture  320  on a front side of the device  300  (collocated with the display  314 ), and the device  300  may include a second aperture  322  on a back side of the device  300  (on a side opposite the front side with the display  314 ). The device  300  may be configured to perform contactless screen unlock based on facial recognition of a user. The first image sensor  302  may be a lower power image sensor used to detect whether a face approaches a center of the field of view of the first image sensor  302 . The second image sensor  303  may be a higher power image sensor used in performing facial recognition. In this manner, a first device mode may include an object detection mode based on images captured by the first image sensor  302 , and a second device mode may include a facial recognition mode based on images captured by the second image sensor  303 . 
     Which aperture is to be used for facial recognition (and thus the OE mode of the device  300 ) may be based on an orientation of the device  300 . If the device  300  is placed front side up on a table, chair, or other surface, the second aperture  322  may be directed toward the surface. As a result, the first aperture  320  may be desired for contactless screen unlock based on facial recognition. The device  300  may receive periodic measurements from one or more sensors while the screen is locked. For example, the device  300  may receive periodic measurements from a magnetometer. The controller  310  may determine an orientation of the device  300  with reference to the azimuth based on the magnetometer measurements. 
     If the determined orientation of the device  300  is with a front side up and approximately horizontal to the azimuth, the controller  310  may determine that the first aperture  320  is to be used for the first device mode (object detection using the lower power image sensor) and for the second device mode (facial recognition using the higher power image sensor). In this manner, the controller  310  may set the device mode to the first device mode while waiting for a face to be in the field of view, and the controller  310  may control the optical element  304  so that light from the first aperture  320  is directed towards the first image sensor  302 . When the controller  310  detects a face (or other object) in the scene towards the center of the field of view of the first image sensor  302 , the controller  310  may switch device modes to begin using the second image sensor  303  for image capture. In switching device modes, the controller  310  may initialize the second image sensor  303  or remove the second image sensor  303  from an inactive state. The controller  310  may also switch the OE mode so that light from the first aperture  320  is directed towards the second image sensor  303 . Facial recognition may then be performed using the images from the second image sensor  303 . 
     If the device  300  is oriented front side down towards the surface, the first aperture  320  is directed towards the surface. The orientation may be determined from magnetometer measurements, light intensity information from the first image sensor  302  or the second image sensor  303 , or measurements from other suitable orientation sensors. In this example, it may be desired to use the second aperture  322  for object detection during a first device mode and facial recognition during a second device mode. The controller  310  may control the optical element  304  to direct light from the second aperture  322  towards the first image sensor  302  during the first device mode and to direct light from the second aperture  322  towards the second image sensor  303  during the second device mode. 
     The image signal processor  312  may be configured to process captured images from the first image sensor  302  and the second image sensor  303 . In some implementations, the image signal processor  312  includes one or more filters of an image processing pipeline, and the filters may be configured based on instructions from the processor  305 . For example, an image signal processor  312  may include a noise reduction filter, edge enhancement filter, image stabilization filter, color correction filter, and other filters applied to an image or video during processing. 
     In some aspects, the image signal processor  312  may execute instructions from a memory (such as instructions  308  from the memory  306  or instructions stored in a separate memory coupled to or included in the image signal processor  312 ). In some other aspects, the image signal processor  312  may include specific hardware to perform one or more operations described in the present disclosure. In some further aspects, the image signal processor  312  may include a combination of specific hardware and the ability to execute software instructions. 
     The optical element  304  may be adjusted in some manner to switch between OE modes. For example, the optical element  304  may include a reflective surface (such as a mirror) or a refractive element (such as a pentaprism) to direct light from the first optical path  301  to a first image sensor  302  during a first OE mode. When switching to a second OE mode, the optical element  304  may be translationally moved, may be rotated, or otherwise may be adjusted to not cause the light from the first optical path  301  to be directed to the first image sensor  302 . For example, the light from the first optical path  301  may be directed to the second image sensor  303  during a second OE mode. 
     If the device  300  includes a second aperture  322  and second optical path  324 , the optical element  304  may be configured to direct light from the second optical path  324  to a second image sensor  303  during the first OE mode. For example, the optical element  304  may include a second reflective surface or a second refractive element to direct light from the second optical path  324  to a second image sensor  303  during the first OE mode. When switching to the second OE mode, the optical element  304  may be translationally moved, may be rotated, or otherwise may be adjusted to not cause the light from the second optical path  324  to be directed to the second image sensor  303 . For example, the light from the second optical path  324  may be directed to the first image sensor  302  during a second mode of the device  300 . 
     In this manner, a light along a first optical path  301  may be directed to a first image sensor  302  when in a first OE mode, and the light along the first optical path  301  may be directed to a second image sensor  303  when in a second OE mode. Example operations and configurations of an optical element is described in more detail with reference to  FIGS. 4A-6H . 
     As noted herein, the one or more apertures  320  and  324  may be oriented in any suitable manner, and the image sensors  302  and  303  may be configured for any suitable purpose. A first aperture  320  may be on any side of the device  300 . For example, the first aperture  320  may be collocated with a display on a smartphone (a front of the device), or the first aperture  320  may be located on a side of the smartphone opposite the display (a rear of the device). If the device  300  includes both apertures  320  and  324 , the apertures may be on any suitable side and may be on the same side or on different sides depending on the operations to be performed using the image sensors  302  and  303 .  FIGS. 3B-3G  illustrate some example configurations of apertures and some example operations and use cases for the multiple image sensors. While the example devices in  FIGS. 3B-3G  are illustrated as a smartphone, any suitable device or configuration of components may be used to perform aspects of the present disclosure. The example devices in the FIGS. are example implementations of the device  300  in  FIG. 3A , but any suitable device or configuration may be used. 
       FIG. 3B  shows a depiction of a device  330  having a first aperture  332  on a first side and a second aperture  334  on a second side. In the example, the first aperture  332  is on a side of the smartphone including the display  331 . The second aperture  334  is on a side of the smartphone opposite the display  331 . The first aperture  332  may be for front facing image capture (such as for capturing selfie images, capturing images for object detection and facial recognition, and so on), and the second aperture  334  may be for rear facing image capture (such as to capture group images, images of landscapes, and so on). 
     The device  330  is configured to switch between a first image sensor  302  and a second image sensor  303  to receive light from a first aperture  332 . In one example, if the first image sensor  302  is a lower power image sensor and the second image sensor  303  is a higher power image sensor, the device mode may be based on whether the device  300  is in a low power mode. In another example, if the first image sensor  302  is configured for capturing images with a telephoto FOV (such as based on one or more lenses configured to direct light on to the first image sensor  302  or the size of the first image sensor  302 ) and the second image sensor  303  is configured for capturing images with a wide FOV (such as based on one or more lenses configured to direct light on to the second image sensor  303  or the size of the second image sensor  303 ), selecting a device mode may be based on a desired FOV for an image or video. As a result, the device  330  is configured to adjust a FOV for image capture (between telephoto FOV and wide FOV) based on which image sensor is selected. In one example, the FOV for selfie images to be captured (from the first aperture  332 ) may be adjusted based on switching between modes. In another example, if the first image sensor  302  is configured for capturing images with a first optical zoom or a first depth of field (such as based on one or more lenses coupled to the first image sensor  302 ) and the second image sensor  303  is configured for capturing images with a second optical zoom or a second depth of field (such as based on one or more lenses coupled to the second image sensor  303 ), the device  330  is configured to adjust an optical zoom or a depth of field for image capture based on the device mode. In this manner, the optical zoom or the depth of field for selfie images to be captured (from the first aperture  332 ) may be adjusted based on switching between device modes. When to switch between device modes may be based on a user input or the device  330  automatically determining when to switch (such as based on object tracking within different FOVs, changes to a zoom factor when performing a zoom function for image capture, and so on). 
     The second aperture  334  on the rear of the device  330  may be coupled to the second image sensor  303  when the first aperture  332  is coupled to the first image sensor  302  (such as during a first OE mode). Conversely, the second aperture  334  may be coupled to the first image sensor  302  when the first aperture  332  is coupled to the second image sensor  303  (such as during a second OE mode). In this manner, if the device  330  switches OE modes in adjusting a FOV, optical zoom, or depth of field, the device  330  may adjust the FOV, optical zoom, or depth of field for image capture from the rear of the device  330 . For example, a depth of field for image capture using the second aperture  334  may be adjusted by switching OE modes based on a depth of a target object to be captured in the image. In another example, a FOV for image capture using the second aperture  334  may be adjusted by switching OE modes based on the type of images to be captured (such as a telephoto FOV for image capture of a person and a wide FOV for image capture of a landscape). When to switch between device modes or OE modes may be based on a user input or the device  330  automatically determining when to switch (such as based on automatically detecting an object or scene to be captured and its depth, size with reference to the FOV, and so on). In this manner, both forward facing images (captured using the first aperture  332 ) and rear facing images (captured using the second aperture  334 ) may have adjustable FOVs, optical zooms, depths of field, and so on based on the mode of the device  330 . 
     In some other implementations, the first aperture and the second aperture may be on the same side of the device.  FIG. 3C  shows a depiction of a device  335  having a first aperture  337  and a second aperture  338  on a side including a display  336 .  FIG. 3D  shows a depiction of a device  340  having a first aperture  341  and a second aperture  342  on a side opposite a display. The first image sensor  302  may receive light from the first aperture  337  or  341  during a first OE mode, and the second image sensor  303  may receive light from the first aperture  337  or  341  during a second OE mode. Conversely, the first image sensor  302  may receive light from the second aperture  338  or  342  during the second OE mode, and the second image sensor  303  may receive light from the second aperture  338  or  342  during the first OE mode. In  FIG. 3C , the first aperture  337  is separated from the second aperture  338  by a distance  339 . In  FIG. 3D , the first aperture  341  is separated from the second aperture  342  by a distance  343 . 
     If the first aperture  337  or  341  and the second aperture  338  or  342  are configured to receive light from the same (or overlapping) portion of a scene, the first aperture  337  or  341  and the second aperture  338  or  342  may be used by an image sensor to capture images of the scene portion from different perspectives. For example, if the first aperture  337  is coupled to the first image sensor  302  during a first OE mode, and the second aperture  338  is coupled to the first image sensor  302  during a second OE mode, the perspective for image capture using the first image sensor  302  may be adjusted based on switching OE modes. Similarly, the perspective for image capture using the second image sensor  303  may be adjusted based on switching OE modes. 
     The OE mode may be switched during a device mode. In this manner, the device in a first device mode uses the first image sensor  302  to capture images or video, and the first image sensor  302  may capture images from different perspectives based on the OE mode during the first device mode. 
     The device may be configured to use the difference in perspectives for image capture by the first image sensor  302  and/or the second image sensor  303  for stereoscopic imaging or vision. For example, the device may alternate between a first OE mode and a second OE mode, and thus the first image sensor  302  alternates between capturing one or more images from a first perspective and one or more images from a second perspective. An image captured during the first OE mode may be paired with an image captured during the second OE mode, and a parallax between the images may be used to generate a three dimensional image. If the device alternates at a sufficient rate (such as 10 to 60 times per second), a stream of three dimensional images may be generated for three dimensional video. 
     In some implementations when the first image sensor  302  is a lower power image sensor and the second image sensor  303  is a higher power image sensor, the first image sensor  302  may be used for scene analysis during a first device mode, and the second image sensor  303  may be used for image capture after scene analysis during a second device mode. For example, the lower power image sensor&#39;s images may be used to determine an exposure setting or other suitable capture setting for the second image sensor  303 . The device may switch to the second device mode with the second image sensor  303  configured using the determined capture settings. The apertures on the same side of the device may be associated with different perspectives, different FOVs, different depths of field, or other differing characteristics. In this manner, the controller  310  may determine the OE mode based on which perspective, FOV, depth of field, or other characteristic is desired for image capture. In the first device mode, light from the desired aperture is directed towards the first image sensor  302 . In the second device mode, the controller  310  may switch the OE mode so that light from the desired aperture is directed towards the second image sensor  303 . 
     When the first image sensor  302  is configured to receive light from the first aperture  337  or  341 , the second image sensor  303  may be configured to receive light from the second aperture  338  or  342 . In this manner, the first image sensor  302  and the second image sensor  303  concurrently capture images of overlapping portions (or the same portion) of the scene. In some implementations, a first image sensor  302  may be configured to capture images for three dimensional imaging, and a second image sensor  303  may be configured for assisting in one or more operations for configuring the first image sensor  302  and its image processing pipeline. For example, the device performs one or more of autofocus, autoexposure, or automatic white balance (AWB) operations (3A operations) to determine a focus setting, exposure setting, or AWB setting. Captures from the second image sensor  303  may be used to determine the autofocus, autoexposure, or AWB settings for the first image sensor  302  (and its associated image processing pipeline). 
     In some other implementations, the first image sensor  302  may be associated with three dimensional imaging having a first FOV, first optical zoom, or first depth of field, and the second image sensor  303  may be associated with three dimensional imaging having a second FOV, second optical zoom or second depth of field. The device  330  may concurrently generate three dimensional images having different FOVs, zoom factors, or depth of fields. In some implementations of generating a three dimensional video (including a succession of three dimensional images), the device may switch between device modes. In this manner, the device may switch between using three dimensional images generated from images from the first image sensor  302  and three dimensional images generated from images from the second image sensor  303  to generate the video. In this manner, the device may adjust the FOV, zoom, or depth of field for the scene in the video. 
     Alternative to the first aperture  337  or  341  being configured to receive light from the same portion of the scene as the second aperture  338  or  342 , the first aperture  337  or  341  and the second aperture  338  or  342  may be configured to receive light from different portions of a scene. For example, a first aperture  341  may be configured to receive light from a top portion of a scene and the second aperture may be configured to receive light from a bottom portion of the scene when the device  340  is in a portrait orientation. The differing portions of the scenes in complementary images may be stitched together to generate a wider FOV image. For stitching purposes, the top portion and the bottom portion may have some overlap. 
     In a first OE mode, the first image sensor  302  is configured to capture one or more images of the top portion of the scene. In a second OE mode, the first image sensor  302  is configured to capture one or more images of the bottom portion of the scene. An image captured by the first image sensor  302  during the first OE mode may be paired with an image captured by the first image sensor  302  during the second OE mode, and the paired images may be combined (such as stitched together) to increase the FOV of an image generated using the first image sensor  302 . In this manner, the device  340  may be configured to generate panorama images without requiring a user to move the device  340 . In some implementations, captures from the second image sensor  303  may be used to determine the autofocus, autoexposure, or AWB settings for the first image sensor  302  (and its associated image processing pipeline). In some other implementations, the second image sensor  303  is configured to capture images with a different zoom factor or depth of field than the first image sensor  302 . In this manner, the device  340  may be configured to generate panorama images with different zoom factors or depths of field. Adjusting the zoom factor or the depth of field may be based on the device  340  switching device modes (and thus which image sensor is to be used). Similar to the example of three dimensional video with adjustable zoom factors or depths of field, video with a larger FOV may include an adjustable zoom factor or depth of field based on switching between images generated using the first image sensor  302  and the second image sensor  303 . 
     Referring back to  FIG. 3B , if apertures  332  and  334  are on different sides of the device  330 , the device  330  may be configured for concurrent image capture from the different device sides (such as selfie image capture using the first aperture  332  and image capture of landscapes using the second aperture  334 ). As such, a graphical user interface (GUI) on the display  331  may be configured for a user to indicate from which side image capture is desired and one or more characteristics of image capture, such as a FOV, zoom factor, or depth of field (which may affect which device mode is to be selected). 
       FIG. 3E  shows a depiction of a device  345  switching between image capture from a first side of the device  345  and from a second side of the device  345 . The device  345  may be an example implementation of the device  330  in  FIG. 3B . Based on the device  345  executing a camera application, the display  346  may display a GUI for the camera application. The GUI may include a shutter button  347  to be used by the user to indicate when the device  345  is to capture an image or a video (such as from the stream of image frames captured by the first image sensor  302  or from the stream of image frames captured by the second image sensor  303 ). In a first OE mode, the first image sensor  302  may capture images from a front of the device  345  (such as using the first aperture  332  in  FIG. 3B ), and the second image sensor  303  may capture images from a rear of the device  345  (such as using the second aperture  334  in  FIG. 3B ). In switching OE modes, the front image sensor  302  captures images from the rear of the device  345 , and the second image sensor  303  captures images from the front of the device  345 . 
     The first image sensor  302  and the second image sensor  303  may concurrently capture images from the front and rear of the device  345 . With both image sensors  302  and  303  concurrently capturing a stream of image frames, the user may determine from which side to capture an image or video. For example, the display  346  may display a preview of the image frames from the first image sensor  302  or the second image sensor  303  based on the direction the user intends for the device  345  to generate an image. On the left side of  FIG. 3E , the device  345  displays a preview of a selfie image that may be captured by the first image sensor  302 . If the user intends for an image to be captured from the rear of the device  345 , the user may select the camera switch  348 . The camera switch  348  in the GUI may be a button (as illustrated), scroll wheel, slider, or other interactive object and may be configured to receive any suitable user input (such as a tap on the display  346 , swipe on the display  346 , shake of the device  345 , audible commands, and so on). When the user presses the camera switch  348 , the device  345  may display a preview from the stream of image captures from the second image sensor  303 . 
     The first image sensor  302  may be associated with capturing images having a first FOV, a first zoom factor, or a first depth of field, and the image sensor  303  may be associated with capturing images having a second FOV, a second zoom factor, or a second depth of field. The user may indicate a preferred FOV, zoom factor, or depth of field. For example, the user may use the selection tool  349  to indicate a zoom factor for an image to be captured (such as pressing the − to zoom out and pressing the + to zoom in). The device mode may then be determined based on the zoom factor. For example, if the first image sensor  302  is associated with a 0× optical zoom (lenses do not magnify the scene for image capture by the image sensor  302 ) and the second image sensor  303  is associated with a 5× optical zoom (one or more lenses magnify the scene to appear five times larger in images captured by the image sensor  303 ), the first image sensor  302  may be used for image capture for a user selected zoom factor less than a threshold between 0× and 5×. If the device  345  is to capture a selfie image and the zoom factor is less than the threshold, the device  345  is in the first device mode for the selfie image capture. The second image sensor  303  may be used for image capture for a user selected zoom factor greater than the threshold. If the device  345  to capture a selfie image receives an indication of a zoom factor greater than the threshold, the device  345  is in the second device mode for the selfie image capture. In some other implementations, the user may explicitly indicate the mode (or the image sensor to be used) for image capture. 
     Basing the device mode on the FOV, zoom factor, or depth of field may also apply to the device  335  in  FIG. 3C  or the device  340  in  FIG. 3D  with both apertures on the same side of the device. For example, a user may indicate a desired FOV, zoom factor, or depth of field, and the image sensor for image capture may be based on the user indication.  FIG. 3F  shows a depiction of a device  350  adjusting a FOV or zoom factor for images captured by the device  350 . The device  350  may be an example implementation of the device  340  in  FIG. 3D , thus including two apertures on a rear of the device  350 . The display  351  displays a GUI for a camera application, and the GUI may include a shutter button  352  to indicate when the device  350  is to capture an image or video. The GUI may also include a selection tool  353  to indicate a FOV or zoom factor. For a zoom factor example, a first image sensor  302  may be associated with a 0× zoom factor, and a second image sensor  303  may be associated with a 5× zoom factor. The user may zoom in for an image to be captured by pressing the T on the selection tool  353 , moving the slider in the middle of the selection tool  353  toward T, swiping right on the selection tool  353 , providing a haptic or audible instruction, or other suitable input. For a FOV example, the first image sensor  302  may be associated with a larger FOV than the second image sensor  303 . The user may increase the FOV for an image to be captured by pressing the W (such as for wide angle) on the selection tool  353 , moving the slider in the middle of the selection tool  353  toward W, swiping left on the selection tool  353 , providing a haptic or audible instruction, or other suitable input. The display  351  also displays a preview of an image to be captured based on the zoom factor or FOV indicated by the user. 
     Referring to the optical zoom example, whether the first image sensor  302  (associated with, e.g., a 0× optical zoom) or the second image sensor  303  (associated with, e.g., a 5× optical zoom) is to capture the image is based on the indicated zoom factor. For example, the first image sensor  302  may be used if the indicated zoom factor is less than a threshold, and the second image sensor  303  may be used if the indicated zoom factor is greater than the threshold. As noted herein, a first device mode refers to using the first image sensor  302  for image capture, and a second device mode refers to using the second image sensor  303  for image capture. In this manner, a first mode may refer to using the first image sensor  302  for three dimensional imaging, wider FOV imaging, and so on (with the device  350  switching between using the different apertures to capture associated image frames), and a second mode may refer to using the second image sensor  303  for three dimensional imaging, wider FOV imaging, and so on (with the device  350  switching between using the different apertures to capture associated image frames). Thus, a first image sensor  302  may be associated with a first aperture for a first portion of the first mode and may be associated with a second aperture for a second portion of the first mode for three dimensional imaging and wider FOV imaging. Conversely, a second image sensor  303  may be associated with the second aperture for a first portion of a second mode and may be associated with the second aperture for a second portion of the second mode for three dimensional imaging and wider FOV imaging. 
     As described for  FIG. 3E  and  FIG. 3F , the device may adjust an FOV, zoom factor, depth of field, or another suitable characteristic based on a device mode. In some other implementations, the first image sensor and the second image sensor may be used for bokeh effects or other effects based on depth of field. For example, referring back to  FIG. 3C , if the device  335  is configured for three dimensional imaging, the first image sensor  302  is associated with a first depth of field, and the second image sensor  303  is associated with a second depth of field, the device  335  may use the difference in depths of field to apply a bokeh effect (such as blurring or otherwise adjusting a background of a person) for a three dimensional or wider FOV selfie image. 
     The different image capture characteristics between device modes may be based on the difference between image sensors and components coupled to the image sensors. In this manner, characteristics other than FOV, zoom factor, and depth of field may be based on the device mode. For example, if a first image sensor  302  is coupled to a color CFA and a second image sensor  303  is not coupled to a filter, a first mode may be associated with color imaging (using the first image sensor  302 ) and a second mode may be associated with grayscale imaging (using the second image sensor  303 ). 
     While two image sensors sharing one or two apertures and optical paths are described above, a device may include any number of image sensors sharing any number of apertures and optical paths. For example, the device  300  may include a third optical path shared by the first image sensor  302  and the second image sensor  303 . In another example, the device  300  may include a third image sensor to share the first optical path  301 . In some further examples, multiple systems of two image sensors sharing an optical path may be included in a device. For example, the device  300  may include four image sensors. The first image sensor  302  and the second image sensor  303  share a first optical path  301 . A third image sensor and a fourth image sensor may share a third optical path (similar to the first and second image sensors sharing an optical path). In this manner, the device  300  may have four apertures (including the first aperture  320  and the second aperture  322 ). 
       FIG. 3G  shows a depiction of a device  360  having a first aperture  364  and a third aperture  368  on a side including a display  362  and a second aperture  366  and a fourth aperture  370  on a side opposite the display  362 . The first aperture  364  and the second aperture  366  may be shared by a first image sensor and a second image sensor (similar to  FIG. 3B ). In addition, the third aperture  368  and the fourth aperture  370  may be shared by a third image sensor and a fourth image sensor. The first image sensor and the second image sensor may be associated with a first optical element, and the second third image sensor and the fourth image sensor may be associated with a second optical element. In some implementations, a first OE mode of the first optical element corresponds to a first OE mode of the second optical element. In this manner, the optical elements may switch OE modes at the same time. 
     In some implementations, the third image sensor may be complementary to the first image sensor (such as to assist in performing the 3A operations for the first image sensor), and the fourth image sensor may be complementary to the second image sensor. For example, the first image sensor and the third image sensor may be associated with the same FOV, zoom factor, or depth of field, and the second image sensor may be associated with a different FOV, zoom factor, or depth of field. The fourth image sensor may be associated with the same FOV, zoom factor or depth of field as the second image sensor. The third image sensor and the fourth image sensor may be configured to capture images from the same device side as the first image sensor and the second image sensor, respectively, based on switching OE modes of the optical elements at the same time. In this manner, the complementary image sensor may be used for one or more 3A operations for the first image sensor or the second image sensor. 
     In some further implementations, the first image sensor and the third image sensor&#39;s capture of images may be aligned, and the aligned images may be used for stereoscopic imaging. Similarly, the second image sensor and the fourth image sensor&#39;s capture of images may be aligned, and the aligned images may be used for stereoscopic imaging. In this manner, the device  360  may be configured to perform stereoscopic imaging from the front or the rear of the device  360 . 
     In some other implementations, each image sensor may be used for image or video capture. For example, the device  360  may include four device modes. At least a subset of the first image sensor through the fourth image sensor may be associated with a different combination of FOV, zoom factor, depth of field, color image capture, grayscale image capture, or other image capture characteristics. In this manner, a device mode of the four device modes may refer to using one of the image sensors associated with the desired FOV, zoom factor, depth of field, or other capture characteristics. 
     In some other implementations, the first aperture  364  and the third aperture  368  may be shared by a first image sensor and a second image sensor (similar to  FIG. 3C ). In addition, the second aperture  366  and the fourth aperture  370  may be shared by a third image sensor and a fourth image sensor (similar to  FIG. 3D ). In this manner, the device  360  may be configured for three dimensional imaging or wider FOV imaging (as described with reference to  FIG. 3D ) from both sides of the device  360 . 
     For any of the device configurations in  FIG. 3B - FIG. 3G , a zoom factor or a depth of field may be adjustable for a specific image sensor. For example, a first image sensor may be coupled to one or more lenses, and the lens position may be adjusted to change the distance between the first image sensor and the one or more lenses. In another example, the first image sensor may be configured to move with reference to the one or more lenses to adjust the distance. In this manner, a focal length for the first image sensor may be adjustable to adjust the depth of field. Adjusting a lens position is described with reference to  FIGS. 7B, 7C, 7E, and 7F  below. 
     As noted herein, which aperture is associated with which image sensor at a specific point in time may be based on an OE mode of the optical element. Switching between OE modes may be based on adjusting the optical element (such as rotating the optical element between different orientations, moving the optical element between different positions, or applying an electrical current or other stimulus to the optical element). 
     When switching OE modes includes rotating the optical element, the optical element may have a first orientation with reference to light approaching the optical element from a first optical path during a first OE mode, and the optical element may have a second orientation with reference to the light from the first optical path during a second OE mode. A device controller (such as controller  310 ) is configured to cause the orientation of the optical element to be adjusted when switching between OE modes. 
       FIG. 4A  shows a cross-section of an example device  400  portion illustrating a first image sensor  402  associated with a first optical path  406  during a first OE mode. The first image sensor  402  is associated with the first optical path  406  based on the optical element  414  having a first orientation.  FIG. 4B  shows the cross-section of the device  400  portion illustrating the second image sensor  404  associated with the first optical path  406  during a second OE mode. The second image sensor  404  is associated with the first optical path  406  based on the optical element  414  having a second orientation. 
     Referring to  FIG. 4A , the optical element  414  is configured to direct light from the first optical path  406  (received via the first aperture  410 ) to the first image sensor  402 . The optical element  414  may refract and/or reflect light in order to direct the light from the first optical path  406  to the first image sensor  402 . For example, the optical element  414  may include a reflective surface to reflect light from the first optical path  406  to the first image sensor  402 . In another example, the optical element  414  may include a prism of a suitable shape and refractive index to refract light from the first optical path  406  to the first image sensor  402 . The first optical path may be coupled to one or more components  418  also configured to direct the light from the first optical path  406 . For example, the component  418  may include a reflective surface to direct the light from the first optical path  406  to the optical element  414 . The optical element  414  (and any components  418 ) may be in any suitable orientation and configuration to direct light from the first optical path  406  to the first image sensor  402  during a first OE mode. The device  400  also includes a second image sensor  404 . When in a first OE mode, the second image sensor  404  does not receive light from the first optical path  406 . In the illustrated example device  400 , the optical element  414  blocks the light from the first optical path  406  from reaching the second image sensor  404  (with the light instead being directed to the first image sensor  402 ). 
     In some implementations, the device  400  further includes a second aperture  412  coupled to a second optical path  408 . The second aperture  412  is illustrated as being on an opposite side of device  400  than the first aperture  410 , but the second aperture  412  may be positioned on any suitable side of the device  400 . While not shown, the second optical path  408  may be coupled to one or more components configured to direct light from the second optical path  408  to the optical element  414  (such as similar to component  418 ). The optical element  414  may be configured to refract and/or reflect light in order to direct the light from the second optical path  408  to the second image sensor  404 . For example, the optical element  414  may include a second reflective surface to direct the light from the second optical path  408  to the second image sensor  404 . In another example, a prism of the optical element  414  may be configured to direct light from the second optical path  408  to the second image sensor  404  based on a shape of the prism and the prism&#39;s refractive index. 
     The optical element  414  may include or be coupled to an actuator  416  to control rotation of the optical element  414 . In some implementations, the actuator  416  includes or is coupled to a rotatory motor or other means to move the optical element  414 , and the actuator  416  is controlled by a controller (such as controller  310  in  FIG. 3A ). For example, the controller  310  instructs the actuator  416  to rotate the optical element  414  from a first orientation (such as illustrated in  FIG. 4A ) to a second orientation when switching from a first OE mode to a second OE mode. The examples in  FIGS. 4A and 4B  (and later figures) may refer to the orientation of the optical element with reference to a first optical path. While the examples in  FIGS. 4A and 4B  (and later figures) may refer to the orientation of the optical element with reference to a first optical path, the orientation of the optical element may be with reference to any suitable device component or suitable reference within the device. For example, the orientation may be with reference to an orientation of an image sensor, with reference to an orientation of an emitter, with reference to a direction of light approaching the optical element from an optical path, and so on. 
       FIG. 4B  shows the cross-section of the device  400  portion in  FIG. 4A  with the optical element  414  having an example second orientation for a second OE mode. During the second OE mode, the device  400  is configured to direct light from the first optical path  406  to the second image sensor  404 . If the device  400  includes a second aperture  412  coupled to a second optical path  408 , the device  400  is also configured to direct light from the second optical path  408  to the first image sensor  402 . 
     In some implementations, the optical element  414  may be perpendicular with reference to light received from the first optical path  406  (within a tolerance) during the second OE mode. While  FIG. 4B  illustrates one example orientation of the optical element  414  for the second OE mode, any suitable orientation may be used. For example, in some other implementations, the second orientation causes the optical element  414  to be perpendicular to light from the second optical path  408 . In some other implementations, the second orientation causes the optical element  414  to be oriented such that light from the first optical path  406  and light from the second optical path  408  are not directed to the optical element  414 . For example, the second orientation may be on the opposite side of the actuator  416  with reference to the first orientation. In this manner, the actuator may rotate the optical element  414  180 degrees when switching between the first OE mode and the second OE mode. 
     In some implementations, the optical element  414  may include a refractive index, reflectiveness, or transparency that is based on the orientation of the optical element  414  with reference to light approaching the optical element  414  (such as from the first optical path  406 ). For example, the optical element  414  may be reflective for light that approaches the optical element  414  in the first orientation, and the optical element  414  may be transparent for light that approaches the optical element  414  in the second orientation. For example, the optical element  414  is transparent to light approaching the optical element  414  at a zero angle of incidence (as illustrated in  FIG. 4B ), and the optical element  414  is reflective to light approaching the optical element  414  at a non-zero angle of incidence (such as a 45 degree angle of incidence as illustrated in  FIG. 4A ). 
     In some implementations, the optical element  414  is a transparent material or substrate (such as glass, transparent plastic, and so on) coated on at least one side to create a reflective surface. The coating (also referred to as an optical coating) may include a film causing a different angle of refraction based on the angle of incidence of light approaching the film. For example, the film may be associated with a critical angle for refraction of light from the first optical path  406  when the optical element  414  is in a first orientation with reference to the first optical path  406 , and the film may be associated with a zero angle of refraction for light from the first optical path  406  when the optical element  414  is in a second orientation with reference to the first optical path  406 . The optical coatings may be any suitable material. In some implementations, the optical coatings may include a combination of thin layers of materials (such as oxides, metals, and so on). The performance of an optical coating (such as reflectiveness, transparency, critical angle, and so on) may be based on the number of layers, the thickness of each layer, and the refractive index difference between layers. For example, an optical coating may be created by depositing thin films of dielectric and metallic materials on a transparent substrate (such as glass) in an alternating manner. The materials may alternate between a higher refraction index and a lower refraction index. Example thin films may include magnesium fluoride (MgF 2 ), tantalum pentoxide (Ta 2 O 5 ), and aluminum oxide (Al 2 O 3 ). 
     Based on the variable refractive indexes of the coatings and based on an angle of incidence of incoming light, the optical element  414  may be configured to direct light from the first optical path  406  to the first image sensor  402  (as illustrated in  FIG. 4A ), and the optical element  414  may be configured to allow light from the first optical path  406  to pass through it to the second image sensor  404  (as illustrated in  FIG. 4B ). If the device  400  includes the second aperture  412  coupled to the second optical path  408 , the optical element  414  may include a similar coating on a second side. In this manner, the optical element  414  may be configured to direct light from the second optical path  408  to the second image sensor  404  (as illustrated in  FIG. 4A ), and the optical element  414  may be configured to allow light from the first optical path  406  to pass through it to the second image sensor  404  (as illustrated in  FIG. 4B ). 
       FIGS. 4A and 4B  illustrate the first aperture  410  and the second aperture  412  being on different sides of the device  400 . In some implementations, the apertures may be on the same side of the device, such as illustrated in  FIG. 4C  and  FIG. 4D .  FIG. 4C  shows a cross-section of an example device portion illustrating a first image sensor  422  associated with a first optical path  426 .  FIG. 4D  shows the cross-section of the example device portion illustrating a second image sensor  424  associated with the first optical path  426 . The device  420  may be similar to the device  400  other than the first aperture  430  being on the same side of the device  420  as the second aperture  432 . In this manner, the first image sensor  422  may be similar to the first image sensor  402 , the second image sensor  424  may be similar to the second image sensor  404 , the first optical path  426  may be similar to the first optical path  406 , the second optical path  428  may be similar to the second optical path  408 , the optical element  434  may be similar to the optical element  414 , and the actuator  436  may be similar to the actuator  416 . The device  420  may include one or more suitable components  438  for directing light in the device  420 .  FIGS. 4A and 4B  may illustrate example component configurations for device  330  in  FIG. 3B , and  FIGS. 4C and 4D  may illustrate example component configurations for device  335  in  FIG. 3C  or for device  340  in  FIG. 3D . 
     As noted herein, a device may include multiple systems for image sensors to share an optical path. For example, a device may include multiple instances of the components in  FIG. 4A  (or multiple instances of the components in  FIG. 4C ).  FIG. 4E  shows a cross-section of an example device portion illustrating a first image sensor  442  associated with a first optical path  446  and a third image sensor  462  associated with a third optical path  466 . The optical element  454  may direct light from the first optical path  446  to the first image sensor  442  based on the optical element  454  being in a first orientation with reference to the first optical path  446 . The optical element  474  may direct light from the third optical path  466  to the third image sensor  462  based on the optical element  474  being in a first orientation with reference to the third optical path  466 . In some implementations, the optical element  454  may also direct light from the second optical path  448  to the second image sensor  444  based on the optical element  454  being in the first orientation, and the optical element  474  may direct light from the third optical path  466  to the third image sensor  462  based on the optical element  474  being in the first orientation. Comparing  FIG. 4E  to  FIG. 4A , the components  458  and  478  may be similar to component  418 , the optical elements  454  and  474  may be similar to optical element  414 , and the actuators  456  and  476  may be similar to actuator  416 . 
       FIG. 4F  shows the cross-section of the example device portion illustrating the second image sensor  444  associated with the first optical path  446  and the third image sensor  462  associated with the third optical path  466 . The optical element  454  (in a second orientation with reference to the first optical path  446 ) may allow light from the first optical path  446  to reach the second image sensor  444 , and the optical element  474  (in a second orientation with reference to the third optical path  466 ) may allow light from the third optical path  466  to reach the fourth image sensor  464 . In some implementations, the optical element  454  may also allow light from the second optical path  448  to reach the first image sensor  442 , and the optical element  474  may allow light from the fourth optical path  468  to reach the third image sensor  462 . Comparing  FIG. 4F  to  FIG. 4B , the components  458  and  478  may be similar to component  418 , the optical elements  454  and  474  may be similar to optical element  414 , and the actuators  456  and  476  may be similar to actuator  416 . 
     In some implementations, one optical element may be shared by the image sensors  442 ,  444 ,  462 , and  464 . For example, the image sensors may be positioned such that one larger optical element may be rotated to direct light as shown in  FIG. 4E  or  FIG. 4F . In some other implementations, the first aperture  450  and the second aperture  452  may be on the same side of the device  440 , and/or the third aperture  470  and the fourth aperture  472  may be on the same side of the device  440 . 
       FIGS. 5A-7F  depict a device including a second aperture and a second optical path. However, the depictions are for clarity in explaining aspects of the disclosure. As shown in  FIGS. 3A-4B , a device is not required to include the second aperture and the second optical path. Additionally, while one instance of a shared optical path between image sensors is shown in  FIGS. 5A-7F , any number of instance may be included in a device (such as illustrated in  FIGS. 4E and 4F ). For example, instead of rotating the multiple optical elements in  FIG. 4E , the multiple optical elements may both be translationally moved, have an electrical current applied, or adjusted in another manner. How the different optical elements in the different instances change states may be different or the same (such as one being rotated and one being translationally moved). As such, the disclosure (including the examples depicted in  FIGS. 5A-7B ) is not limited to requiring a second aperture and second optical path or to only one instance of multiple image sensors sharing an optical path. 
     In some implementations, the optical element may be at a first position in the device during a first OE mode, and the optical element may be at a second position in the device during a second OE mode. A device controller (such as controller  310  in  FIG. 3A ) is configured to cause the optical element to be translationally moved between the first position and the second position when switching between OE modes.  FIG. 5A  shows a cross-section of an example device  500  portion illustrating a first image sensor  502  associated with a first optical path  506  when the device is in a first mode. The first image sensor  502  is associated with the first optical path  506  based on the optical element  514  being at a first position in the device  500 .  FIG. 5B  shows the cross-section of the example device  500  portion illustrating the second image sensor  504  associated with the first optical path  506  when the device  500  is in a second mode. The second image sensor  504  is associated with the first optical path  506  based on the optical element  514  being at a second position in the device  500 . 
     Referring to  FIG. 5A , the optical element  514  is configured to direct light from the first optical path  506  (received via the first aperture  510 ) to the first image sensor  502  during a first OE mode. If the device  500  includes a second aperture  512  configured to direct light along a second optical path  508 , the optical element  514  may be configured to direct light from the second optical path  508  to the second image sensor  504  during the first OE mode. In some implementations, the optical element  514  may be constructed similar to the optical element  414  in  FIGS. 4A and 4B . For example, the optical element  514  may include a transparent substrate coated on one or more sides with a film to direct light. In some other implementations, the optical element  514  may include a one sided mirror or a two sided mirror, a prism, or other suitable object for directing light. Similar to  FIGS. 4A and 4B , the device  500  may include one or more components  518  configured to direct light from the first optical path  506  (or the second optical path  508 ) to the optical element  514 . 
     The optical element  514  may include or be coupled to an actuator  516  to move the optical element  514  from the first position to a second position when switching device modes. In some implementations, the actuator  516  includes or is coupled to a motor (such as a magnetic motor or stepper motor) to move the optical element  514 , and the actuator  516  is controlled by a controller (such as controller  310  in  FIG. 3A ). For example, the controller  310  controls the actuator  516  to cause the optical element  514  to be moved from a first position (such as illustrated in  FIG. 5A ) to a second position when switching from a first OE mode to a second OE mode. In some implementations, the optical element  514  may be magnetic, and the actuator  516  include or be coupled to one or more magnets for which a magnetic force is adjusted to attract or repel the optical element  514 . In some other implementations, the actuator  516  may include or be coupled to a spring system, a pulley system, or other mechanical means to move the optical element  514  between positions in the device  500 . 
       FIG. 5B  shows the cross-section of the device  500  portion in  FIG. 5A  with the optical element  514  at an example second position in the device  500 . During the second OE mode, the device  500  is configured to direct light from the first optical path  506  to the second image sensor  504 . If the device  500  includes a second aperture  512  coupled to a second optical path  508 , the device  500  is also configured to direct light from the second optical path  508  to the first image sensor  502 . For example, the second position of the optical element  514  may be configured such that the optical element  514  is not in the path of light from the first aperture  510  and is not in the path of light received from the second aperture  512 . 
       FIGS. 5A and 5B  illustrate the first aperture  510  and the second aperture  512  being on different sides of the device  500 . Similar to  FIGS. 4C and 4D , the apertures may be on the same side of the device, such as illustrated in  FIG. 5C  and  FIG. 5D .  FIG. 5C  shows a cross-section of an example device portion illustrating a first image sensor  522  associated with a first optical path  526 .  FIG. 5D  shows the cross-section of the example device portion illustrating a second image sensor  524  associated with the first optical path  526 . The device  520  may be similar to the device  500  other than the first aperture  530  being on the same side of the device  520  as the second aperture  532 . In this manner, the first image sensor  522  may be similar to the first image sensor  502 , the second image sensor  524  may be similar to the second image sensor  504 , the first optical path  526  may be similar to the first optical path  506 , the second optical path  528  may be similar to the second optical path  508 , the optical element  534  may be similar to the optical element  514 , and the actuator  536  may be similar to the actuator  516 . The device  520  may include one or more suitable components  538  for directing light in the device  520 .  FIGS. 5A and 5B  may illustrate example component configurations for device  330  in  FIG. 3B , and  FIGS. 5C and 5D  may illustrate example component configurations for device  335  in  FIG. 3C  or for device  340  in  FIG. 3D . 
     In some implementations, a transparency and a reflectiveness (or a refractive index) of the optical element is based on an electrical current applied to the optical element. For example, the optical element may be transparent when an electrical current is not applied to the optical element, and the optical element may be reflective and/or refractive when an electrical current is applied to the optical element. In this manner, the optical element may be coupled to an electrical current source (such as a power rail), and the electrical current source or means for directing electrical current from the electrical current source to the optical element (such as a switch) may be controlled by a device controller (such as controller  310  in  FIG. 3A ).  FIG. 6A  shows a cross-section of an example device  600  portion illustrating a first image sensor  602  associated with a first optical path  606 . The first image sensor  602  is associated with the first optical path  606  based on whether an electrical current is applied to the optical element  614 .  FIG. 6B  shows the cross-section of the example device  600  portion illustrating the second image sensor  604  associated with the first optical path  606 . The second image sensor  604  is associated with the first optical path  606  based on whether an electrical current is applied to the optical element  614 . 
     Referring to  FIG. 6A , the optical element  614  is configured to direct light from the first optical path  606  (received via the first aperture  610 ) to the first image sensor  602  during a first OE mode. The device  600  may also include one or more components  618  configured to direct light to/from/along the first optical path  606 . If the device  600  includes a second aperture  612  configured to direct light along a second optical path  608 , the optical element  614  may be configured to direct light from the second optical path  608  to the second image sensor  604  during the first OE mode. The optical element  614  may be constructed such that a transparency and a reflectiveness (or a refractive index) of the optical element  614  is based on whether an electrical current is applied to the optical element  614  (such as via electrical contacts  616  that may be controlled by a device controller (such as controller  310  in  FIG. 3A )). 
     In some implementations, the optical element  614  may include a switchable mirror that switches between transparency and reflectiveness based on an electrical current applied (referred to herein as a variable transmittance glass). An example implementation of a variable transmittance glass includes a magnesium nickel (Mg—Ni) alloy encasing a hydrogen (H 2 ) gas. When an electrical current is applied to the Mg—Ni alloy, the alloy absorbs the hydrogen gas and becomes transparent. When the electrical current is removed from the Mg—Ni alloy, the alloy dispels the hydrogen gas and becomes reflective. Another example variable transmittance glass includes a suspended particle device (SPD). An SPD may include nanometer scale particles suspended in a liquid. When an electrical current is applied to the SPD, the particles arrange in a similar orientation/align to allow light to pass through the SPD. When the electrical current is removed from the SPD, the particles unalign (such as return to their previous orientations), and the SPD becomes reflective. For example, the particles may be reflective and in a random orientation in a transparent liquid when an electrical current is not applied so as to be reflective. When an electrical current is applied, the particles may align such that a surface area of each particle is reduced or minimized from the perspective of light reaching the SPD (allowing the light to pass through the transparent liquid). The SPD may include a thin film applied to a transparent substrate (such as glass). Some other implementations of a variable transmittance glass include an electrochromic mirror. An electrochromic mirror changes states between transparent and opaque (such as reflective) when a burst of electrical current is applied to the mirror. For example, an electrochromic mirror may include lithium ions that change orientations each time a burst of electrical current is applied to the mirror. 
     While the optical element  614  is illustrated as changing states based on an electrical current applied to the optical element  614 , other example optical elements may switch states based on other stimuli. For example, state changes of the optical element may be based on a change in temperature (such as applying heat), a change in magnetism, a change in pressure, and so on. Therefore, the stimulus to cause a state change in the optical element is not limited to electrical current. 
     The optical element  614  may include or be coupled to electrical contacts  616  to apply electrical current to the optical element  614  (either to maintain the optical element  614  in a specific state or to cause the optical element  614  to change states). In some implementations, the electrical contacts  616  are coupled to a power rail or other electrical current source, and application of the electrical current may be controlled by a switch between the source and the electrical contacts  616 . The switch may be controlled by a controller (such as controller  310  in  FIG. 3A ). In some examples, the controller  310  may control switching the optical element  614  between being reflective for a first OE mode and transparent for a second OE mode. 
       FIG. 6B  shows the cross-section of the device  600  portion in  FIG. 6A  with the optical element  614  in a transparent state. During the second OE mode, the device  600  is configured to direct light from the first optical path  606 , through the optical element  614 , and to the second image sensor  604 . If the device  600  includes a second aperture  612  configured to direct light along a second optical path  608 , the device  600  is also configured to direct light from the second optical path  608 , through the optical element  614 , and to the first image sensor  602 . 
       FIGS. 6A and 6B  illustrate the first aperture  610  and the second aperture  612  being on different sides of the device  600 . Similar to  FIGS. 4C and 4D , the apertures may be on the same side of the device, such as illustrated in  FIG. 6C  and  FIG. 6D .  FIG. 6C  shows a cross-section of an example device portion illustrating a first image sensor  603  associated with a first optical path  607 .  FIG. 6D  shows the cross-section of the example device portion illustrating a second image sensor  605  associated with the first optical path  607 . The device  601  may be similar to the device  600  other than the first aperture  611  being on the same side of the device  601  as the second aperture  613 . In this manner, the first image sensor  603  may be similar to the first image sensor  602 , the second image sensor  605  may be similar to the second image sensor  604 , the first optical path  607  may be similar to the first optical path  606 , the second optical path  609  may be similar to the second optical path  608 , the optical element  615  may be similar to the optical element  614 , and the electrical contacts  617  may be similar to the electrical contacts  616 . The device  601  may include one or more suitable components  619  for directing light in the device  601 .  FIGS. 6A and 6B  may illustrate example component configurations for device  330  in  FIG. 3B , and  FIGS. 6C  and  6 D may illustrate example component configurations for device  335  in  FIG. 3C  or for device  340  in  FIG. 3D . 
       FIGS. 6E-6H  show other example implementations of an optical element for switching between OE modes. In some implementations, the cross-sections may be from a top of a device. For example, the cross-section may be from a top of a smartphone in a portrait mode. In this manner, the one or more image sensors may be perpendicular to a front and rear of the device (such as a front and rear of a smartphone). However, the one or more image sensors may be positioned on any suitable plane with reference to the device. For example, the cross-section may be from a side of the device (such as a side of a smartphone in a portrait mode), and the one or more image sensors may be parallel to a top and a bottom of the device. In another example, the cross-section may be from a front of the device (such as a front of a smartphone including a display), and the one or more image sensors may be parallel to a top of the device, parallel to a side of the device bordering the top, or oriented along plane between the plane for the top of the device and the plane for the side of the device. The present disclosure is not limited to a specific orientation of the one or more image sensors in the device. Similarly for  FIGS. 4A-7F , the present disclosure is not limited to a specific orientation of the one or more image sensors in a device. 
       FIG. 6E  shows a cross-section of an example device portion illustrating a first image sensor  652  associated with a first optical path  656 . A first aperture  660  is configured to direct light along a first optical path  656 , and a second aperture  662  may be configured to direct light along a second optical path  658 . The optical element  664 , in a first orientation with reference to the first optical path  656  for a first OE mode, directs light from the first optical path  656  to the first image sensor  652 . 
     In some implementations, the example device  650  includes a first image sensor  652  shared by at least two apertures  660  and  662 . In some other implementations, the first image sensor  652  and an optional second image sensor  654  may share one or more apertures (such as the aperture  660  and an optional aperture  662 ). For an example device including both image sensors  652  and  654  and both apertures  660  and  662 , the optical element  664  may direct light from the second optical path  658  to the second image sensor  654  for the first OE mode. The optical element  664  may be similar to the optical element  414  in  FIG. 4A . 
     In switching between a first OE mode and a second OE mode, the actuator  666  may rotate the optical element  664  to a second orientation with reference to the first optical path  656 . The actuator  666  may be similar to the actuator  416  in  FIG. 4A , except the actuator  666  rotates the optical element  664  along an axis towards a center of the optical element  664  (instead of an axis towards one end of the optical element).  FIG. 6F  shows the cross-section of the example device portion illustrating the first image sensor  652  associated with the second optical path  658 . If the device  650  includes a second aperture  662 , the optical element  664 , in the second orientation for a second OE mode, is configured to direct light from the second optical path  658  to the first image sensor  652 . If the device  650  includes a second image sensor  654 , the optical element  664 , in the second orientation for a second OE mode, may be configured to direct light from the first optical path  656  to the second image sensor  654 . In some other implementations, the optical element may be a prism or other object that is moved or rotated to switch between OE modes. 
     In some implementations, instead of rotating the optical element, the optical element may be a prism or other structure configured to direct light based on a stimulus applied to the optical element.  FIG. 6G  shows a cross-section of an example device portion illustrating a first image sensor  672  associated with a first optical path  676 . The device  670  may be similar to the device  650  in  FIG. 6E  other than the type of optical element used. In this manner, the first image sensor  672  may be similar to the first image sensor  652 , the optional second image sensor  674  may be similar to the optional second image sensor  654 , the first optical path  676  may be similar to the first optical path  656 , the optional second optical path  678  may be similar to the optional second optical path  658 , the first aperture  680  may be similar to the first aperture  660 , and the optional second aperture  682  may be similar to the optional second aperture  662 . 
     While the optical element  686  is illustrated as changing states based on application of an electrical current via electrical contacts  688  and electrical contacts  690 , any suitable stimulus may be used and may be applied in any manner. In some implementations, a first portion of the optical element  686  includes a first set of molecules having a first orientation when an electrical current is applied via the electrical contacts  688 , and a second portion of the optical element  686  includes a second set of molecules having a first orientation when an electrical current is applied via the electrical contacts  690 . While two electrical contacts are illustrated, any suitable number may be used (such as one or more electrical contacts). When the first set of molecules and the second set of molecules are in the first orientation, the optical element  686  may be configured to direct light as shown in  FIG. 6G . The first set of molecules and the second set of molecules may also have a second orientation when no electrical current is applied. In this manner, when the first set of molecules and the second set of molecules are in the second orientation, the optical element  686  may be configured to direct light as shown in  FIG. 6H .  FIG. 6H  shows the cross-section of the example device portion in  FIG. 6G  illustrating a second image sensor  674  associated with the first optical path  676 . 
     In some other implementations, the optical element  686  may include separate components of two or more optical elements combined together. For example, a first portion of the optical element  686  may be similar to the optical element  614  in  FIG. 6A . The first portion may be controlled based on an electrical current applied via the electrical contacts  688 . A second portion of the optical element  686  may be similar to the optical element  614  rotated by 90 degrees. The second portion may be controlled based on an electrical current applied via the electrical contacts  690 . In this manner, switching between OE modes may include switching between providing an electrical current via contacts  688  and not providing an electrical current via contacts  690  for a first OE mode and not providing an electrical current via contacts  688  and providing an electrical current via contacts  690  for a second OE mode. 
     While adjustment of the optical element is shown in the examples of rotating the optical element, moving the optical element, or applying an electrical current (or other stimulus) to the optical element, any combination of the example adjustments (or other suitable means for adjusting the optical element, such as applying heat) may be performed. For example, the device may be configured to translationally move and rotate the optical element as appropriate. In another example, the device may be configured to rotate the optical element and apply an electrical current to the optical element. In some implementations, the optical element may be configured to service more than two optical paths or two image sensors based on a combination of adjustment means for the optical element. 
     As noted herein, a first image sensor may be coupled to a first group of one or more lenses, or a second image sensor may be coupled to a second group of one or more lenses. The first group or the second group may be configured such that the first image sensor is associated with a different FOV, optical factor, or depth of field than the second image sensor. The first image sensor or the second image sensor associated with one or more lenses is depicted in the examples shown in  FIGS. 7A-7F . The following examples depicted in  FIGS. 7A-7F  illustrate the optical element as rotating (similar to  FIGS. 4A and 4B ). However, the adjustment of the optical element being a rotation of the optical element is for clarity purposes in explaining aspects of the disclosure. If an optical element is to be adjusted, the optical element may be adjusted in any suitable manner (including being rotated, being moved, or changing states based on a stimulus). 
     As noted herein, a first image sensor may be associated with a first FOV, a first optical zoom, or a first depth of field, and a second image sensor may be associated with a second FOV, a second optical zoom, or a second depth of field. In some implementations, the first image sensor may be disposed to receive light that propagates through one or more lenses to enable the associated FOV, optical zoom, or depth of field. In some implementations, the second image sensor may be disposed to receive light that propagates through one or more lenses to enable the associated FOV, optical zoom, or depth of field. In some other implementations, the second image sensor may be configured for the associated FOV, optical zoom, or depth of field without the use of one or more lenses. 
       FIG. 7A  shows a cross-section of an example device  700  portion illustrating a first image sensor  702  associated with one or more lenses  720 . The one or more lenses  720  may direct light toward the first image sensor  702  and adjust a FOV, zoom factor, or depth of field for image capture. In some implementations, the device  700  may also include one or more lenses  718  associated with the second image sensor  704 . The one or more lenses  722  may direct light toward the second image sensor  704  and adjust a FOV, zoom factor, or depth of field for image capture. The one or more lenses  720  (and, optionally, one or more lenses  718 ) may be configured in any suitable manner to direct light received to the first image sensor  702  (or to the second image sensor  704 ). If the device  700  is a smartphone and the first aperture  710  is front facing (such as coinciding with a display of the smartphone), the smartphone may be configured to capture selfie images with differing characteristics (such as differing FOVs, zoom factors, or depths of fields) based on the device mode. If the smartphone includes the second aperture  712  as a rear facing aperture, the smartphone may be configured to capture images (such as group images, images of landscape scenes, and so on) with differing characteristics (such as differing FOVs, zoom factors, or depths of field) based on the device mode. The other components of the device  700  (including the first optical path  706 , the second optical path  708 , and the component  718 ) may be similar to like components illustrated in  FIGS. 4A-4B . 
     In some implementations, one or more lenses associated with the image sensor may be movable with reference to the image sensor. In this manner, a FOV, zoom factor, or depth of field may be adjusted based on moving the one or more lenses.  FIG. 7B  shows a cross-section of an example device  730  portion illustrating a second image sensor  734  associated with a moveable lens  749 . In some implementations, the movable lens includes one or more lenses. The one or more lenses may be for focus or zoom purposes, or for other suitable purposes (such as adjusting a FOV). If the device  730  is a smartphone (or a device having similar proportion), a smartphone may enable a longer distance between the first aperture  740  and the second image sensor  734  if at least a portion of the distance is parallel to the smartphone&#39;s display. In this manner, the device  730  may include an optical system to move one or more lenses with reference to the second image sensor  734  (or with reference to another lens of the one or more lenses). While the example depicted in  FIG. 7B  shows one lens  749 , the lens  749  may include any number of lenses and means to move the lenses with reference to one another or the second image sensor  734 . 
     The device  730  includes an actuator  747  to move the lens  749 . Moving the lens  749  may be for a focus operation for the second image sensor  734  or to adjust a zoom factor for the second image sensor  734 . While not shown, the first image sensor  732  may also be associated with one or more moveable lenses. As illustrated, a position of the lens  749  may be adjusted with reference to the second image sensor  734  when the device  730  is configured to use the second image sensor  734  for image capture for light received from the second aperture  742  (such as in a first OE mode). Adjustment of the position of the lens  749  may also occur when the device  730  is configured to use the second image sensor  734  for image capture for light received from the first aperture  740  (such as in a second OE mode). In some implementations, a device controller (such as controller  310  in  FIG. 3A ) is configured to control the actuator  747 . The actuator  747  may move the lens  749  based on a mechanical force, electrical force, magnetic force, or other suitable force. For example, the actuator  747  may move the lens  749  along a guide with different positions away from the second image sensor  734 . In this manner, the controller  310  may control a position of the lens  749 . 
     In some implementations, the second image sensor may move with reference to one or more lenses.  FIG. 7C  shows a cross-section of an example device  750  portion illustrating a second image sensor  754  that is moveable with reference to the lens  769 . While the lens  769  is shown as not moving with reference to the device  750 , the lens  769  may also be moveable. The device  750  may be similar to the device  730  in  FIG. 7B  other than the second image sensor  754  being movable. In some implementations, the second image sensor  754  may be moved similar to how the lens  749  ( FIG. 7B ) is moved. For example, the second image sensor  754  may be coupled to an actuator  767 , and the actuator may be configured to move the second image sensor  754  (such as via a mechanical force, an electrical force, a magnetic force, or other suitable force). In this manner, an FOV, zoom factor, or depth of field associated with the second image sensor  754  may be adjusted. 
       FIGS. 7A-7C  illustrate a first aperture and a second aperture being on different sides of the device. However, the apertures may be on the same side of the device, such as illustrated in  FIGS. 7D-7F , respectively.  FIG. 7D  shows a cross-section of an example device  701  portion illustrating a first image sensor  703  associated with a first optical path  707 . The device  701  may be similar to the device  700  in  FIG. 7A , other than the apertures  711  and  713  being on the same side of the device.  FIG. 7E  shows a cross-section of an example device  731  portion illustrating a first image sensor  733  associated with a first optical path  737 . The device  731  may be similar to the device  730  in  FIG. 7B , other than the apertures  741  and  743  being on the same side of the device.  FIG. 7F  shows a cross-section of an example device  770  portion illustrating a first image sensor  772  associated with a first optical path  776 . The device  770  may be similar to the device  750  in  FIG. 7C , other than the apertures  780  and  782  being on the same side of the device.  FIGS. 7A-7C  may illustrate example component configurations for device  330  in  FIG. 3B , and  FIGS. 7D-7F  may illustrate example component configurations for device  335  in  FIG. 3C  or for device  340  in  FIG. 3D . 
     Referring back to  FIGS. 3E and 3F , whether the device is in a first mode or a second mode may be based on a threshold zoom factor or a threshold FOV. If the device is configured to move one or more lenses or an image sensor (such as depicted in  FIGS. 7B, 7C, 7E, and 7F ) the device may adjust an optical zoom or FOV in an incremental manner by moving one or more lenses or an image sensor. When the one or more lenses or the image sensor reaches a maximum movement, the device may switch modes to use the other image sensor. For example, referring back to  FIG. 7F , the second image sensor  774  may be associated with an optical zoom from 1× to 5× based on moving the image sensor, and the first image sensor  772  may be associated with a 0× optical zoom. If the current zoom factor is set to 5× (such as the slider being all the way to the right in selection tool  353  in  FIG. 3F ), the device  770  may be configured to use the second image sensor  774  for image capture. The user may decrease the zoom factor (such as by pressing the W or moving the slider to the left). As the zoom factor decreases, the device  770  moves the second image sensor  774  until the second image sensor  774  reaches a limit (associated with a 1× optical zoom). If the user continues to decrease the zoom factor to less than 1×, the device  770  may switch device modes and use the first image sensor  772  associated with 0× optical zoom. In some implementations, digital processing of the images from the first image sensor  772  may be performed to simulate the zoom factor being decreased. If the device shows a preview (such as from the preview on the bottom in  FIG. 3F  to the preview on the top of  FIG. 3F  in decreasing the zoom factor), the preview may show the zoom factor gradually decreasing. 
     If the device mode is based on a threshold FOV, zoom factor, or depth of field, the threshold may be based on the physical limitations of moving the one or more lenses and/or the image sensor. In the above example, the threshold zoom factor may be 1×, with the second image sensor  774  used for a zoom factor greater than the threshold and the first image sensor  772  used for a zoom factor less than the threshold. If the one or more lenses and the image sensors are fixed, a threshold may be based on a digital processing requirement of images from the image sensors, a resolution of the image sensors, or other image capture characteristics. 
     As described, a device may be configured to use a single aperture for different FOV based images, for different zoom based images, for different depth of field based images, or for other suitable differences in image capture between device modes. In the examples, two or more image sensors may share a first optical path (and associated aperture) in the device. In some examples, the two or more image sensors may share a second optical path (and associated aperture) in the device. How the optical path is shared may be based on an optical element (such as whether the optical element is in a first OE mode or a second OE mode). 
       FIG. 8A  shows an illustrative flow chart depicting an example operation  800  for a first image sensor and a second image sensor to share a first optical path. The first image sensor, the second image sensor, and the first optical path may be as depicted in  FIGS. 3A-7F  (or as otherwise described). The operation  800  and other operations (such as operation  900  in  FIG. 9 ) are described as being performed by the device  300  in  FIG. 3A  for clarity, but may apply to any suitable device or device configuration. 
     At  802 , a first aperture  320  directs light to a first optical path  301  in the device  300 . At decision block  804 , if the optical element  304  of the device  300  is in a first OE mode, the operation  800  proceeds to step  806 . For example, the optical element  304  may be in a first orientation, a first position, have an electrical current or other stimulus applied, and so on. If the optical element  304  is not in a first OE mode (such as the optical element  304  being in a second orientation, a second position, have no electrical current or other stimulus applied, and so on), the operation  800  proceeds to step  810 . Referring to step  806 , an optical element  304  directs light from the first optical path  301  to a first image sensor  302 . For example, the optical element  304  may reflect or refract light from the first optical path  301  to the first image sensor  302  based on an orientation of the optical element  304 , a position of the optical element  304 , a state of the optical element  304  (based on electrical current to be applied to the optical element  304 ), and so on. At  808 , the first image sensor  302  captures a first image from the light received from the first optical path  301 . 
     Referring to step  810 , the device  300  directs light from the first optical path  301  to a second image sensor  303 . For example, the optical element  304  may not block light from the first optical path  301  to allow the light to reach the second image sensor  303 . In another example, the optical element  304  may have an orientation or be in a state based on a stimulus (such as electrical current) to allow light from the first optical path  301  to pass through the optical element  304  and to the second image sensor  303 . At  812 , the second image sensor  303  captures a second image from the light received from the first optical path  301 . As noted herein, the controller  310  may be configured to adjust the optical element  304  to switch between OE modes for the example operation  800 . 
     The device  300  may also include additional apertures coupled to additional optical paths. For example, as shown in  FIG. 3A , the device  300  may include a second aperture  322  configured to direct light along a second optical path  324 . The optical element  304  may be configured to direct light from the second optical path  324  to the first image sensor  302  or to the second image sensor  303  for image capture. 
       FIG. 8B  shows an illustrative flow chart depicting an example operation  820  for the first image sensor  302  and the second image sensor  303  to also share a second optical path  324 . Example operation  820  may be complementary to (such as being performed concurrently with) the example operation  800  in  FIG. 8A . At  822 , a second aperture  322  directs light to a second optical path  324  in the device  300 . At decision block  824 , if the optical element  304  is in a first OE mode, the operation  820  proceeds to step  826 . If the optical element  304  is not in a first OE mode (such as the optical element  304  being in a second orientation, a second position, and so on), the operation  820  proceeds to step  830 . Referring to step  826 , an optical element  304  directs light from the second optical path  324  to the second image sensor  303 . For example, the optical element  304  may reflect light from the second optical path  324  to the second image sensor  303  based on an orientation of the optical element  304 , a position of the optical element  304 , a state of the optical element  304  (based on electrical current to be applied to the optical element  304 ), and so on. At  828 , the second image sensor  303  captures a third image from the light received from the second optical path  324 . 
     Referring to step  830 , the device  300  directs light from the second optical path  324  to the first image sensor  302 . For example, the optical element  304  may be in a position to not block light from the second optical path  324  to allow the light to reach the first image sensor  302 . In another example, the optical element  304  have an orientation or be in a state based on a stimulus (such as electrical current) to allow light from the second optical path  324  to pass through the optical element  304  and to the first image sensor  302 . At  832 , the first image sensor  302  captures a fourth image from the light received from the second optical path  324 . As noted herein, the controller  310  may be configured to adjust the optical element  304  to switch between OE modes for the example operation  820 . 
       FIG. 9A  shows an illustrative flow chart depicting an example operation  900  for image capture. At  902 , the device  300  identifies whether the device is to be in a first device mode or a second device mode. For example, the controller  310  determines whether the first image sensor  302  or the second image sensor  303  is to be used for image capture. In some implementations, the controller  310  may determine the device mode based on a user input ( 904 ). For example, the user may use a GUI via the display  314  to indicate that the device  300  is to be in a second device mode (such as indicating that the second image sensor is to be used). In some other implementations, the controller  310  may determine the device mode based on one or more of a FOV ( 906 ), a zoom factor ( 908 ), or a depth of field ( 910 ). For example, a user may indicate a desired FOV, zoom factor, or depth of field, and the device  300  may compare the desired FOV, zoom factor or depth of field to the FOV, zoom factor, or depth of field associated with the first image sensor and to the FOV, zoom factor, or depth of field associated with the second image sensor. The device  300  may then select the first image sensor or the second image sensor based on the comparison. For example, a threshold zoom factor may be used to determine whether the device  300  is to be in a first device mode or a second device mode. If the image to be captured is associated with a zoom factor less than the threshold, the device  300  may determine that the device  300  is to be in the first device mode. If the image to be captured is associated with a zoom factor greater than the threshold, the device  300  may determine that the device  300  is to be in the second device mode. 
     In some implementations, the controller  310  may determine the device mode based on a state of the device  300  ( 911 ). For example, the first image sensor  302  may be a lower power image sensor, and the second image sensor  303  may be a higher power image sensor. When the device  300  has a locked (or off) display  314  (such as in a low power state, locked state, and so on), the device  300  may be configured to perform object detection using the first image sensor  302  to determine if a face may be entering a field of view for facial recognition using the second image sensor  303 . In this manner, the controller  310  may determine that the device  300  is in a first device mode when in a low power state (to detect objects entering the field of view). When an object is detected, the controller  310  may switch the device  300  to the second device mode to perform facial recognition using the second image sensor  303 . 
     At  912 , the device  300  may control the optical element  304  based on the identified device mode. For example, the controller  310  may determine whether the optical element  304  is to be adjusted so that the optical element  304  directs light from a shared optical path to the image sensor associated with the identified device mode. If the optical element  304  is to be adjusted, the controller  310  may instruct one or more components to adjust the optical element  304 . In some implementations, the optical element  304  directs light from the first aperture  320  (which may propagate along the first optical path  301 ) to the first image sensor  302  in a first OE mode ( 914 ). In addition, or to the alternative, the optical element  304  may direct light from the first aperture  320  to the second image sensor  303  in a second OE mode ( 916 ). If the device  300  includes a second aperture  322  to direct light to a second optical path  324  shared by the first image sensor  302  and the second image sensor  303 , the optical element  304  may direct light from the second aperture  322  to the second image sensor  303  in the first OE mode, and the optical element  304  may direct light from the second aperture  322  to the first image sensor  302  in the second OE mode. 
     In some implementations, the OE mode may be based on light information from an image sensor. If the first image sensor  302  is a lower power image sensor for object detection and the second image sensor  303  is a higher power image sensor for facial recognition, the controller  310  may first control the OE mode to direct light from the desired aperture to the first image sensor  302  for object detection (during a first device mode). When the controller  310  determines from the images from the first image sensor  302  that a face may have entered the field of view, the controller  310  may switch the OE mode to direct light from the desired aperture to the second image sensor  303  for facial recognition (during a second device mode). In some implementations, the OE mode may also be based on measurements from one or more sensors  326  (such as orientation measurements from a magnetometer or other suitable measurements from other sensors). 
       FIG. 9B  shows an illustrative flow chart depicting an example operation  920  for controlling an optical element  304 . The operation  920  may be an example implementation of  912  in  FIG. 9A . At  922 , the device  300  identifies whether the optical element  304  is to be in the first OE mode or the second OE mode based on the identified device mode. For example, the controller  310  may determine whether the optical element  304  is to direct light from the first optical path  301  to the first image sensor  302  or to the second image sensor  303  based on which image sensor is to be used for image capture. In some implementations, the controller  310  identifies the OE mode based on which aperture is to be used ( 924 ). For example, if a first aperture  320  is on a front side of a smartphone, a second aperture  322  is on a back side (opposite the front side) of the smartphone, and the smartphone is on a table front side up, the controller  310  may determine that the first aperture  320  is to be used (such as based on light information from images captured by the first image sensor  302  or the second image sensor  303 , based on orientation measurements from one or more sensors  326 , and so on). 
     In addition or to the alternative, the controller  310  may identify the OE mode based on the imaging application ( 926 ). For example, if the device  300  is in a low power mode with a locked screen, the imaging application may be object detection (during a first device mode) using a lower power image sensor and facial recognition (during a second device mode) using a higher power image sensor. The OE mode may thus be based on directing light from the desired aperture to the first image sensor  302  during object detection and directing light from the desired aperture to the second image sensor  303  during facial recognition. In another example, the OE mode may change while the device  300  is in a single device mode. For example, the OE mode may switch (such as alternate) while using a first image sensor  302  for three dimensional imaging. In this manner, operation  920  may be performed multiple times while the device  300  is in a specific device mode. Identifying the OE mode (including whether the OE mode is to change during the device mode) may thus be based on the imaging application. For the determined OE mode, the controller  310  may determine in which state the optical element  304  is to be. For example, the controller  310  may determine if the optical element  304  is to be in a first or second orientation (via rotation), a first or second position (via a translational movement), or a first or second material state (via application of a stimulus, such as an electrical current, heat, and so on). 
     In some implementations, the controller  310  may receive feedback from one or more components moving, rotating, or applying a stimulus to the optical element  304  to determine the current state of the optical element  304 . In some other implementations, the controller  310  may determine the current OE mode based on previous instructions or controls for the optical element  304  to place the optical element  304  into a specific OE mode. For example, the controller  310  or another suitable component may store the current OE mode based on the controller&#39;s instructions to or control of the optical element  304 . In this manner, the controller  310  may compare the current OE mode to the identified OE mode to determine if the optical element  304  is to change OE modes or otherwise be adjusted. 
     At  928 , the device  300  may adjust the optical element  304  based on the identified OE mode. In some implementations, if the controller  310  determines that a difference exists between the current OE mode and the identified OE mode, the controller  310  may control the optical element  304  to place the optical element  304  in the identified OE mode. For example, the device  300  may rotate the optical element  304  ( 930 ). In this manner, the controller  310  may instruct or control an actuator to rotate the optical element  304 . In another example, the device  300  may translationally move the optical element ( 932 ). In this manner, the controller  310  may instruct or control an actuator to apply a physical force, a magnetic force, or other suitable force to the optical element  304  to translationally move the optical element  304  into another position. In a further example, the device  300  may apply (which may include removing or adjusting a level of) a stimulus to the optical element  304  ( 934 ). One stimulus may be an electrical current applied to the optical element  304  ( 936 ). For example, the controller  310  may control a switch to deliver or remove an electrical current from a power rail to the optical element. In another example, the controller  310  may control an electrical current level applied to the optical element, and one or more properties of the optical element  304  may be based on the electrical current level. For example, a refractive index, a reflectiveness, or a transparency may vary based on a change in electrical current applied to the optical element  304 . 
     When the device  300  is in the first device mode, the first image sensor  302  may capture one or more images (such as a succession of images for video) for processing. When the device  300  is in the second device mode, the second image sensor  303  may capture one or more images (such as a succession of images for video) for processing. The image signal processor  312  or other portions of the image processing pipeline in the device  300  may process the one or more images to generate a final image or video (such as applying one or more image processing filters, encoding a sequence of images for video, and so on). As noted herein, the device mode may change during video capture (such as when adjusting a FOV, zoom factor, or depth of field for the video). In this manner, the image signal processor  312  (and other components) may process a first group of images from the first image sensor  302  and process a second group of images from the second image sensor  303 . The first group of images and the second group of images may be encoded together to generate the video. 
     As noted above, the optical element may be controlled based on information from one or more device sensors. For example, the controller  310  may control an OE mode based on an orientation of the device  300  (such as determined from orientation measurements from a magnetometer, light intensity measurements from a first image sensor  302 , and/or other suitable measurements).  FIG. 9C  shows an illustrative flow chart depicting an example operation  950  for controlling an optical element  304  based on a device orientation. The device orientation may be determined using one or more device sensors. The device sensors for device  300  may include one or more sensors  326  (such as an orientation sensor, which may include a gyroscope or a magnetometer), the first image sensor  302 , the second image sensor  303 , or any other suitable sensor of the device  300 . Operation  950  may be an example implementation of step  924  in  FIG. 9B . For step  924  ( FIG. 9B ), the controller  310  may identify the OE mode based on which aperture is to be used for image capture. 
     At  952  in  FIG. 9C , the controller  310  determines the orientation of the device  300 . In some implementations, the controller  310  determines the device orientation based on light intensity information from one or more images from an image sensor ( 954 ). For example, if the device  300  is in a first OE mode such that light from the first aperture  320  is directed to the first image sensor  302  and the device  300  is set on a surface or is otherwise oriented such that the first aperture  320  is blocked from receiving light from the scene, the controller  310  may determine that the orientation of the device  300  is such that the first aperture  320  is directed down towards a surface. If the second aperture  322  is on a different side of the device  300  than the first aperture  320 , the second aperture  322  may be the desired aperture based on the light intensity information. In addition or to the alternative, the controller  310  may determine the device orientation based on measurements from one or more orientation sensors ( 956 ). For example, a magnetometer or gyroscope may provide measurements indicating an orientation of the device  300  to the controller  310 . The orientation may indicate that a first aperture  320  is directed down (such as towards a surface on which the device  300  is resting). If the second aperture  322  is on a different side of the device  300  than the first aperture  320 , the second aperture  322  may be the desired aperture based on the orientation measurements. 
     At  958 , the controller  310  determines which aperture to use based on the orientation of the device  300 . For example, if the device  300  is a smartphone with a first aperture  320  on a front side and a second aperture  322  on a back side, which aperture is to be used may be based on which side is facing up when the smartphone is resting on a surface (such as a table or chair). If the device  300  is oriented with the front side down/towards the surface, the controller  310  may identify the second aperture  322  as the aperture to use (with the first aperture  320  directed towards the surface). If the device  300  is oriented with the back side down/towards the surface, the controller  310  may identify the first aperture  320  as the aperture to use (with the second aperture  322  directed towards the surface). 
     At  960 , the controller  310  identifies the OE mode based on the identified aperture. For example, if the display  314  is locked, the device  300  may perform object detection using the first image sensor  302  (which may be a lower power image sensor, such as an AO image sensor). If the device  300  is identified as being oriented front side up, the device  300  may determine that the first aperture  320  is to be used. Since the first aperture  320  and the first image sensor  302  are to be used, the controller  310  may identify the first OE mode for the first aperture  320  to direct light towards the first image sensor  302 . When the device  300  is to perform facial recognition using the second image sensor  303 , the device  300  may identify the second OE mode for the first aperture  320  to direct light towards the second image sensor  303 . In this manner, the device  300  may control the optical element  304  for image capture during different device modes. 
     Aspects of an adjustable optical element may also be used for emitters. In some implementations, the device may be configured for active depth sensing. For example, the device may include one or more emitters to emit light for active depth sensing. Active depth sensing may be used for operations including laser auto focus for a camera, facial recognition for screen unlock, range finding, depth mapping (such as for virtual reality or augmented reality applications), and so on. In some implementations, an emitter may be shared by multiple apertures. In this manner, emissions from the emitter may be directed by an optical element out of a first aperture or out of a second aperture. Conversely, an aperture may be shared by a first emitter and a second emitter (such as for different active depth sensing techniques), or the aperture may be shared by an emitter for active depth sensing or a receiver (such as an image sensor). For example, the device may be configured to perform different active depth sensing techniques (including structured light depth sensing or time of flight depth sensing) or the device may be configured to perform a combination of active depth sensing and image capture using a shared aperture.  FIGS. 10-17  depict example device configurations and operations for a device configured to perform one or more active depth sensing techniques. 
       FIG. 10  shows a block diagram of an example device  1000  including a first emitter  1002  for active depth sensing. At least a portion of the components in the example device  1000  may be similar to the components in the example device  300  in  FIG. 3A . For example, the example device  1000  may include a processor  1005  (which may include a controller  1010  configured to control the optical element  1004 ). The device  1000  may also include a memory  1006  storing instructions  1008 , an optional display  1014 , one or more optional I/O components  1016 , and a power supply  1018 . The processor  1005 , memory  1006 , controller  1010 , display  1014 , I/O components  1016 , and power supply  1018  may be similar to the processor  305 , memory  306 , controller  310 , display  314 , I/O components  316 , and power supply  318  depicted in  FIG. 3A . The device  1000  may also include other components not shown in  FIG. 10 , similar to the device  300  in  FIG. 3A . For example, the device  1000  may include one or more sensors (such as orientation or motion sensors, positioning sensors, temperature sensors, and so on). 
     The device  1000  may include a first aperture  1020  that directs light along a first optical path  1001  or receives light from the first optical path  1001 . The device  1000  may also include a second aperture  1022  that directs light along a second optical path  1024  or receives light from the second optical path  1024 . In some implementations, the first emitter  1002  is shared by the first aperture  1020  and the second aperture  1022 . For example, the device  1000  includes an optical element  1004 . The optical element  1004  is configured to direct light from the first emitter  1002  to the first optical path  1001  when the optical element  1004  is in a first OE mode. When the optical element  1004  is in a second OE mode, light from the first emitter  1002  is propagated along the second optical path  1024 . 
     In some implementations, the device  1000  includes an image sensor or a second emitter  1003 . With an image sensor or second emitter  1003 , the device  1000  may be configured to be in a first device mode (using the first emitter  1002 ) or a second device mode (using the image sensor or second emitter  1003 ). For example, if the device  1000  includes an image sensor, a first device mode may be an active depth sensing mode using the first emitter  1002 , and a second device mode may be an image capture mode using the image sensor. 
     In some implementations, the image sensor may be a lower power image sensor (such as described above with reference to  FIG. 3A ). For example, the lower power image sensor may be an AO image sensor to be used in different operating states of the device (such as for object detection). For example, the device  1000  may be configured to perform active depth sensing for facial recognition (such as for screen unlock). The first emitter  1002  may emit a distribution of light for the active depth sensing, and facial recognition may be performed during a first device mode. The lower power image sensor may measure light intensities in different regions of a scene for object detection (such as to detect whether a possible face moves into a center of the field of view of the image sensor). Object detection may be performed during a second device mode. In this manner, a single aperture may be used during the second device mode for object detection using the image sensor and may be used during the first device mode for facial recognition based on active depth sensing using the first emitter  1002 . As described above with reference to  FIGS. 3A and 9C , the aperture to be used may be based on an orientation of the device  1000 , which may be determined from measurements from one or more sensors or light intensity information captured by the image sensor. 
     In another example, if the device  1000  includes a second emitter, a first device mode may be a first active depth sensing mode using the first emitter  1002 , and a second device mode may be a second active depth sensing mode using the second emitter  1003 . In another example, one of the device modes may be a flashlight mode if the second (or first) emitter is a flood illuminator. The first emitter  1002  (and, optionally, a second emitter  1003 ) may be configured to emit a determined wavelength of light (such as IR light or light at another suitable wavelength). In some other implementations, light having a range of wavelengths may be emitted. 
     For an image sensor, when the optical element  1004  is in a first OE mode, the optical element  1004  may direct light propagated along the second optical path  1024  to the image sensor. When the optical element  1004  is in a second OE mode, the optical element  1004  may direct light propagated along the first optical path  1001  to the image sensor. For a second emitter, when the optical element  1004  is in a first OE mode, the optical element  1004  may direct light from the second emitter to the second optical path  1024 . When the optical element  1004  is in a second OE mode, the optical element  1004  may direct light from the second emitter to the first optical path  1001 . 
     While not shown, the device  1000  may include one or more receivers for active depth sensing. In some implementations, the device  1000  may include one or more receivers configured to receive reflections of the light emitted by the first emitter  1002  during a first device mode. The one or more receivers may also be configured to receive reflections of the light emitted by a second emitter  1003  during a second device mode. For example, the one or more receivers may include an IR image sensor (or other suitable image sensor) to capture reflections of the IR light (or at another suitable wavelength) emitted by the first emitter  1002 . In some other implementations, the one or more receivers for active depth sensing may be outside of the device  1000 . In this manner, the device  1000  may act as the emitter for an active depth sensing system. 
     The memory  1006  may be a non-transient or non-transitory computer readable medium storing computer-executable instructions  1008  to perform all or a portion of one or more operations described in this disclosure (such as for adjusting a position of an optical element). If active depth sensing includes structured light depth sensing, the memory  1006  may also include a library of codewords used to process images from an active depth sensing receiver in order to determine one or more depths of objects in a scene. 
     The processor  1005  may be one or more suitable processors (such as general purpose processors) capable of executing scripts or instructions of one or more software programs (such as instructions  1008 ) stored within the memory  1006 . For example, the processor  1005  may be an applications processor and execute an active depth sensing application (such as for screen unlock, laser auto focus, and so on). In additional or alternative aspects, the processor  1005  may include integrated circuits or other hardware to perform functions or operations described in this disclosure. 
     The processor  1005  includes a controller  1010 . If the device  1000  includes an image sensor or second emitter  1003 , the controller  1010  may be configured to select the emitter (or image sensor) to be used. The controller  1010  is also configured to control the optical element  1004  (such as switching between a first OE mode and a second OE mode). In some implementations, the controller  1010  may be configured to adjust the position of the optical element  304  (such as by rotating or translationally moving the optical element  1004 ). For example, the controller  1010  may instruct an actuator to translationally move the optical element  1004  when switching between OE modes. In another example, the controller  1010  may instruct an actuator to rotate the optical element  1004  when switching between OE modes. 
     In some other implementations, the controller  1010  may be configured to adjust a state of the optical element  1004  (such as by applying an electrical current or other stimulus). The optical element&#39;s state may include a reflectiveness or transparency (or refractive index) of the optical element  1004  based on the stimulus. For example, the controller  1010  may cause electrical current to not be applied to the optical element  1004  for a first OE mode and cause electrical current to be applied to the optical element  1004  for a second OE mode. 
     Similar to the controller  310  in  FIG. 3A , the controller  1010  may determine an orientation of the device  1000  from measurements from one or more orientation sensors or light intensity measurements from the image sensor (such as from a lower power image sensor when the display  1014  is locked or the device  1000  is in a low power or inactive state). The controller  1010  determining the device mode or the OE mode may be based on the orientation of the device  1000 . The device mode or the OE mode may also be based on the device state. 
     The controller  1010  may be embodied in software (such as in instructions  1008  stored in memory  1006 ), hardware (such as one or more integrated circuits), or a combination of both. In some other device implementations, the controller  1010  may be embodied in a separate processor from the processor  1005  or dedicated hardware. For example, a discrete processor may include the controller  1010  and the image signal processor  1012 . The discrete processor may include one or more application specific integrated circuits (ASICs) and/or a one or more general purpose processors. The discrete processor may be configured to perform operations associated with image capture, active depth sensing, computer vision (such as virtual reality (VR), augmented reality (AR), or stereoscopic vision), and so on for which the first emitter  1002  or the image sensor or second emitter  1003  are used. 
     While shown to be coupled to each other via the processor  1005  in the example device  1000 , the processor  1005 , the memory  1006 , the image signal processor  1012 , the optional display  1014 , and the optional I/O components  1016  may be coupled to one another in various arrangements. For example, the processor  1005 , the memory  1006 , the image signal processor  1012 , the optional display  1014 , and the optional I/O components  1016  may be coupled to each other via one or more local buses (not shown for simplicity). 
     The image signal processor  1012  may be configured to process captured images from the image sensor  1003 . In some implementations, the image signal processor  1012  includes one or more filters of an image processing pipeline, and the filters may be configured based on instructions from the processor  1005 . If the images from the image sensor  1003  or for depth mapping, the image signal processor  1012  may be configured for processing the images to determine one or more depths. For example, the image signal processor  1012  may use a library of codewords to identify codewords in an image for structured light depth sensing. 
     In some aspects, the image signal processor  1012  may execute instructions from a memory (such as instructions  1008  from the memory  1006  or instructions stored in a separate memory coupled to or included in the image signal processor  1012 ). In some other aspects, the image signal processor  1012  may include specific hardware to perform one or more operations described in the present disclosure. In some further aspects, the image signal processor  1012  may include a combination of specific hardware and the ability to execute software instructions. In some implementations, if the device  1000  does not include an image sensor  1003  (such as instead including a second emitter  1003 ), the device  1000  may not include the image signal processor  1012 . 
     Similar to optical element  304  depicted in  FIG. 3A , the optical element  1004  may be adjusted in some manner to switch between modes of the device  1000 . For example, the optical element  1004  may include a reflective surface (such as a mirror) or a refractive element (such as a pentaprism) to direct light from the first emitter  1002  to the first optical path  1001  during a first OE mode. When the optical element  1004  switches to a second OE mode, the optical element  1004  may be translationally moved, may be rotated, or otherwise may be adjusted to not cause the light from the first emitter  1002  to be directed to the first optical path  1001 . 
     If the device  1000  includes an image sensor or second emitter  1003 , the optical element  1004  may also be configured to direct light from/to the second optical path  1024  to/from the image sensor or second emitter  1003  in the first OE mode. For example, the optical element  1004  may include a second reflective surface or a second refractive element to direct light from/to the second optical path  1024  to/from the image sensor or second emitter  1003  during the first mode. When switching to the second OE mode, the optical element  1004  may be moved, may be rotated, or otherwise may be adjusted to not cause the light to/from the image sensor or second emitter  1003  to be directed from/to the second optical path  1024 . For example, for an image sensor, the light from the first optical path  1001  may be directed to the image sensor  1003 . For a second emitter, the light from the second emitter  1003  may be directed to the first optical path  1001 . Example operations and configurations of an optical element  1004  are described in more detail with reference to  FIGS. 14A-16F , and may be similar to operations and configurations of an optical element depicted in  FIGS. 4A-6H . 
     Any suitable active depth sensing system or technique may be used by or included in the device  1000 . In this manner, the first emitter  1002  (and, optionally, the second emitter  1003 ) is configured to emit a light configured for the type of active depth sensing system. In some implementations, the first emitter  1002  is configured to emit a flood illumination of light (such as IR light), and a depth of an object may be based on an intensity of a reflection of the light as measured at an active depth sensing receiver (such as at an IR image sensor). In some other implementations, the active depth sensing system may be based on emitting a known distribution of light (which may be referred to as a structured light depth sensing system, and is described in more detail with reference to  FIG. 11 ). In some further implementations, the active depth sensing system may be a direct TOF active depth sensing system (described in more detail with reference to  FIG. 12 ). In some other implementations, the active depth sensing system may be an indirect TOF active depth sensing system (described in more detail with reference to  FIG. 13 ). The first emitter  1002  (and, optionally, the second emitter  1003 ) may include an emitter configured for one or more of the example active depth sensing systems described herein (or another suitable active depth sensing system). 
       FIG. 11  shows a depiction of an example active depth sensing system  1100  including an emitter  1102  for emitting a distribution of light (such as distribution  1104 ). The active depth sensing system  1100  (which herein also may be referred to as a structured light system) may be used to generate a depth map (not pictured) of a scene  1106  or may be used in the performance of one or more operations based on depths of objects in the scene  1106 . For example, the scene  1106  may include a face, and the active depth sensing system  1100  may be used for identifying or authenticating the face for screen unlock or security purposes. The active depth sensing system  1100  may include an emitter  1102  and a receiver  1108 . The emitter  1102  may be referred to as a “transmitter,” “projector,” and so on, and should not be limited to a specific transmission component. Throughout the following disclosure, the terms projector and emitter may be used interchangeably. The receiver  1108  may be referred to as a “detector,” “sensor,” “sensing element,” “photodetector,” and so on, and should not be limited to a specific receiving component. 
     While the disclosure refers to the distribution as a light distribution, any suitable wireless signals at other frequencies may be used (such as radio frequency waves, sound waves, etc.), and the device may be configured to direct such wireless signals in the device. Further, while the disclosure refers to the distribution as including a plurality of light points, the light may be focused into any suitable size and dimensions. For example, the light may be projected in lines, squares, or any other suitable dimension. In addition, the disclosure may refer to the distribution as a codeword distribution, where a defined portion of the distribution (such as a predefined patch of light points) is referred to as a codeword. If the distribution of the light points is known, the codewords of the distribution may be known. In some implementations, the memory  1006  may include a library of codewords for the codewords included in the distribution emitted by the first emitter  1002  (and, optionally, a second emitter  1003 ). The library of codewords may then be used to identify codewords in reflections of the light emitted by the first emitter  1002  (or second emitter  1003 ) as received by a receiver, and the location of the codewords on the receiver&#39;s sensor may be used to determine one or more depths in the scene. In another implementation, an image sensor  1003  may be configured to capture images including reflections of a codeword distribution emitted by an associated emitter. The memory  1006  may store a library of codewords for the associated emitter, and the image signal processor  1012  may use the library of codewords in processing the images from the image sensor  1003 . The distribution may be organized and used in any way, and the present disclosure should not be limited to a specific type of distribution or type of wireless signal. 
     The emitter  1102  may be configured to project a distribution  1104  of light points onto the scene  1106 . Black circles in the distribution  1104  may indicate where no light is projected for a possible point location, and white circles in the distribution  1104  may indicate where light is projected for a possible point location. In some example implementations, the emitter  1102  may include one or more light sources  1124  (such as one or more lasers), a lens  1126 , and a light modulator  1128 . The light source  1124  may include any suitable light source. In some example implementations, the light source  1124  may include one or more distributed feedback (DFB) lasers. In some other example implementations, the light source  1124  may include one or more vertical cavity surface-emitting lasers (VCSELs). In some examples, the one or more light sources  1124  include a VCSEL array, DFB laser array, or other suitable laser array. 
     The emitter  1102  also may be coupled to an aperture  1122  from which the emitted light escapes the emitter  1102  onto the scene. In some implementations, the aperture  1122  may be the first aperture  1020  or the second aperture  1022  in  FIG. 10 . While not shown in  FIG. 11  for simplicity in explanation, the emitter  1102  may be coupled to an optical element  1004  to direct the light to the first aperture  1020  or the second aperture  1022 . In some implementations, the emitter  1102  may further include a diffractive optical element (DOE) to diffract the emissions from one or more light sources  1124  into additional emissions. In some aspects, the light modulator  1128  (to adjust the intensity of the emission) may comprise a DOE. A DOE may include a material situated in the projection path of the light from the light source  1124 . The DOE may be configured to split a light point into multiple light points. For example, the material of the DOE may be a translucent or a transparent polymer with a known refractive index. The surface of the DOE may include peaks and valleys (varying the depth of the DOE) so that a light point splits into multiple light points when the light passes through the DOE. For example, the DOE may be configured to receive one or more lights points from one or more lasers and project an intended distribution with a greater number of light points than emitted by the one or more lasers. 
     In projecting the distribution  1104  of light points onto the scene  1106 , the emitter  1102  may output one or more light points from the light source  1124  through the lens  1126  (and/or through a DOE or light modulator  1128 ) and onto the scene  1106 . In some implementations, the emitter  1102  may be positioned on the same reference plane as the receiver  1108 , and the emitter  1102  and the receiver  1108  may be separated by a distance called the baseline ( 1112 ). In some other implementations, the emitter  1102  and the receiver  1108  may be positioned on different reference planes. The emitter  1102  may be positioned on a first reference plane, and the receiver  1108  may be positioned on a second reference plane. The first reference plane and the second reference plane may be the same reference plane, may be parallel reference planes separated from each other, or may be reference planes that intersect at a non-zero angle. The angle and location of the intersection on the reference planes is based on the locations and orientations of the reference planes with reference to each other. The reference planes may be oriented to be associated with a common side of the device. For example, both reference planes (whether parallel or intersecting) may be oriented to receive light from a common side of the device (such as from a back side of the device, a front side of the device, a top side of the device, and so on). 
     In device production, minor differences or errors in manufacturing may cause differences in orientation or positioning of the first reference plane or the second reference plane. In one example, mounting the emitter  1102  or the receiver  1108  on a printed circuit board (PCB) may include an error (within a tolerance) that the orientation of the emitter  1102  or the receiver  1108  differs from the orientation of the PCB. In another example, orientations of different PCB s including the emitter  1102  and the receiver  1108  may differ slightly than as designed (such as a slight variation in orientations when the PCBs are designed to be along a same reference plane or parallel to one another). A first reference plane and a second reference plane of a device may be referred to as being the same reference plane, parallel reference planes, or intersecting reference planes as intended through device design without regard to variations in the orientations of the reference planes as a result of manufacturing, calibration, and so on in producing the device. 
     In some example implementations, the light projected by the emitter  1102  may be IR light. IR light is provided as an example emission from the emitter  1102 . In the following description, other suitable wavelengths of light may be used. For example, light in portions of the visible light spectrum outside the IR light wavelength range or ultraviolet light may be output by the emitter  1102 . Alternatively, other signals with different wavelengths may be used, such as microwaves, radio frequency signals, and other suitable signals. 
     The scene  1106  may include objects at different depths from the structured light system (such as from the emitter  1102  and the receiver  1108 ). For example, objects  1106 A and  1106 B in the scene  1106  may be at different depths. The receiver  1108  may be configured to receive, from the scene  1106 , reflections  1110  of the transmitted distribution  1104  of light points. To receive the reflections  1110 , the receiver  1108  may capture an image. When capturing the image, the receiver  1108  may receive the reflections  1110 , as well as (i) other reflections of the distribution  1104  of light points from other portions of the scene  1106  at different depths and (ii) ambient light. Noise may also exist in the captured image. The active depth sensing system  1100  may be configured to filter or reduce the ambient light interference and noise to isolate the reflections of the distribution  1104  in the captured image. 
     In some example implementations, the receiver  1108  may include a lens  1130  to focus or direct the received light (including the reflections  1110  from the objects  1106 A and  1106 B) on to the sensor  1132  of the receiver  1108 . The receiver  1108  also may include or be coupled to an aperture  1120 . In some implementations, the aperture  1120  may be the first aperture  1020  or the second aperture  1022  in  FIG. 10 . Assuming for the example that only the reflections  1110  are received, depths of the objects  1106 A and  1106 B may be determined based on the baseline  1112 , displacement and distortion of the light distribution  1104  (such as in codewords) in the reflections  1110 , and intensities of the reflections  1110 . For example, the distance  1134  along the sensor  1132  from location  1116  to the center  1114  may be used in determining a depth of the object  1106 B in the scene  1106 . Similarly, the distance  1136  along the sensor  1132  from location  1118  to the center  1114  may be used in determining a depth of the object  1106 A in the scene  1106 . The distance along the sensor  1132  may be measured in terms of number of pixels of the sensor  1132  or a distance (such as millimeters). 
     In some example implementations, the sensor  1132  (such as an IR image sensor) may include an array of photodiodes (such as avalanche photodiodes) for capturing an image. To capture the image, each photodiode in the array may capture the light that hits the photodiode and may provide a value indicating the intensity of the light (a capture value). The image therefore may be the capture values provided by the array of photodiodes. 
     In addition or alternative to the sensor  1132  including an array of photodiodes, the sensor  1132  may include a complementary metal-oxide semiconductor (CMOS) sensor. To capture the image by a photosensitive CMOS sensor, each pixel of the sensor may capture the light that hits the pixel and may provide a value indicating the intensity of the light. In some example implementations, an array of photodiodes may be coupled to the CMOS sensor. In this manner, the electrical impulses generated by the array of photodiodes may trigger the corresponding pixels of the CMOS sensor to provide capture values. 
     The sensor  1132  may include at least a number of pixels equal to the number of possible light points in the distribution  1104 . For example, the array of photodiodes or the CMOS sensor may include a number of photodiodes or a number of pixels, respectively, corresponding to the number of possible light points in the distribution  1104 . The sensor  1132  logically may be divided into groups of pixels or photodiodes (such as 4×4 groups) that correspond to a size of a bit of a codeword. The group of pixels or photodiodes also may be referred to as a bit, and the portion of the captured image from a bit of the sensor  1132  also may be referred to as a bit. In some example implementations, the sensor  1132  may include the same number of bits as the distribution  1104 . 
     If the light source  1124  transmits IR light (such as NIR light at a wavelength of, e.g., 940 nm), the sensor  1132  may be an IR sensor to receive the reflections of the NIR light. The sensor  1132  also may be configured to capture an image using a flood illuminator (not illustrated). In some implementations, the sensor  1132  may be an example of an image sensor  1003  in  FIG. 10 , an image sensor  302  in  FIG. 3A , or an image sensor  303  in  FIG. 3A . While not shown for simplicity, an optical element  1004  may be configured to direct light from the aperture  1120  to the sensor  1132 . For example, when the sensor  1132  is an example implementation of the image sensor  1003 , the optical element  1004  may direct light from a first aperture  1020  or from a second aperture  1022  to the sensor  1132  in different OE modes. In this manner, the sensor  1132  may be shared by multiple apertures. 
     As illustrated, the distance  1134  (corresponding to the reflections  1110  from the object  1106 B) is less than the distance  1136  (corresponding to the reflections  1110  from the object  1106 A). Using triangulation based on the baseline  1112  and the distances  1134  and  1136 , the differing depths of objects  1106 A and  1106 B in the scene  1106  may be determined in generating a depth map of the scene  1106 . Determining the depths may further include determining a displacement or a distortion of the distribution  1104  (such as a distortion of a codeword) in the reflections  1110 . 
     Although a number of separate components are illustrated in  FIG. 11 , one or more of the components may be implemented together or include additional functionality. All described components may not be required for an active depth sensing system  1100 , or the functionality of components may be separated into separate components. Additional components not illustrated also may exist (such as an optical element and additional apertures). For example, the receiver  1108  may include a bandpass filter to allow signals having a determined range of wavelengths to pass onto the sensor  1132  (thus filtering out signals with a wavelength outside of the range). In this manner, some incidental signals (such as ambient light) may be prevented from interfering with the captures by the sensor  1132 . The range of the bandpass filter may be centered at the transmission wavelength for the emitter  1102 . For example, if the emitter  1102  is configured to transmit NIR light with a wavelength of 940 nm, the receiver  1108  may include a bandpass filter configured to allow NIR light having wavelengths within a range of, e.g., 920 nm to 960 nm. Therefore, the examples described with reference to  FIG. 11  are for illustrative purposes, and the present disclosure is not limited to the example structured light system  1100  for active depth sensing. 
     Other active depth sensing systems may include TOF active depth sensing systems. An example TOF active depth sensing system includes a direct TOF active depth sensing system (such as depicted in  FIG. 12 ). A direct TOF system emits pulses, senses the pulses, and determines a difference in time between emitting a pulse and sensing a reflection of the pulse. The direct TOF system uses the time difference to determine a round trip time, and thus a depth of an object from the TOF system. Another example TOF active depth sensing system includes an indirect TOF active depth sensing system (such as depicted in  FIG. 13 ). An indirect TOF system may also be referred to as a Frequency Modulated Continuous Wave (FMCW) TOF system. An indirect TOF system emits a periodic signal (such as a continuous wave sinusoidal signal or periodic pulsed light), senses a reflection of the signal, and determines a phase difference between the emitted signal and the sensed reflection of the signal. The indirect TOF system uses the phase difference to determine a depth of an object from the TOF system. 
       FIG. 12  shows a depiction of a direct TOF active depth sensing system  1200  including an emitter  1202 . The emitter  1202  may be an example implementation of the first emitter  1002  depicted in  FIG. 10 . The emitter  1202  may be configured to emit signals (such as light  1204 ) toward a scene including surface  1206 . While the emitted light  1204  is illustrated as being directed to surface  1206 , the field of the emission by the emitter  1202  may extend beyond the size of the surface  1206 . For example, a TOF system emitter may have a fixed focal length lens that defines the field of the emission for the emitter. The emitter  1202  may be an example implementation of the first emitter  1002  or the second emitter  1003 . While not shown for simplicity, an optical element may be configured to direct light from the emitter  1202  to one of multiple apertures (such as apertures  1020  and  1022  in  FIG. 10 ). 
     The emitted light  1204  includes light pulses  1214  at known time intervals (such as a defined period). The receiver  1208  includes an image sensor  1210  to sense the reflections  1212  of the emitted light  1204 . The reflections  1212  include the reflected light pulses  1216 , and the round trip time  1222  is determined for the light by comparing the timing  1218  of the emitted light pulses  1214  to the timing  1220  of the reflected light pulses  1216 . The distance of the surface  1206  from the TOF system  1200  may be calculated to be half the round trip time multiplied by the speed of the emissions (such as the speed of light for light emissions). The depth may be determined using equation (1) below: 
                   D   =       TOF   *   c     2             (   1   )               
where D is the depth of the surface  1206  from the direct TOF system  1200  and c is the speed of light (based on the emitter  1202  emitting light  1204 ).
 
     The image sensor  1210  may include an array of photodiodes and components to sense the reflections and produce an array of currents or voltages corresponding to the intensities of the light received. Each entry in the array may be referred to as a pixel or cell. The voltages (or currents) from a pixel may be compared over time to detect reflections  1212  of the emitted light  1204 . For example, the signal from a pixel may be compared to a threshold (corresponding to noise or ambient light interference), and peaks greater than the threshold may be identified as reflected light pulses  1216  sensed by the image sensor  1210 . The threshold may be based on ambient light, noise, or other interference. For example, an amount of ambient light may exist (without the emitted light  1204 ), and the threshold may be based on the magnitude of ambient light (such as measured by the image sensor  1210  when the emitter  1202  is not emitting). The upper limit of the effective range of a TOF system  1200  may be the distance where the noise or the degradation of the signal before sensing the reflections cause the signal-to-noise ratio (SNR) to be too great for the image sensor  1210  to accurately sense the reflected light pulses  1216 . To reduce interference (and thus increase range or improve the signal to noise ratio), the receiver  1208  may include a bandpass filter before the image sensor  1210  to filter incoming light outside of a wavelength range centered at the wavelength of the emitted light  1204 . 
     In some implementations, each pixel of an image sensor  1210  of a direct TOF system  1200  may include a single-photon avalanche diode (SPAD) due to its sensitivity and responsivity to enable identifying pulses in the reflections and resolving the arrival time of pulsed light reflections. Each SPAD may be coupled to a readout circuit, a time-correlated time-to-digital converter (TDC) and one or more memory cells of the image sensor  1210  to enable the image sensor  1210  to capture images. An alternative to a direct TOF system is an indirect TOF system. The image sensor  1210  may be an example implementation of the image sensor  1003  in  FIG. 10  or the image sensor  302  or  303  in  FIG. 3A . While not shown for simplicity, an optical element may be configured to direct light from a first aperture or a second aperture (such as apertures  1020  and  1022  in  FIG. 10 ) to the image sensor  1210 . 
       FIG. 13  shows a depiction of an indirect TOF active depth sensing system  1300  including an emitter  1302 . The emitter  1302  may be an example implementation of the first emitter  1002  depicted in  FIG. 10 . The emitter  1302  may be configured to emit signals (such as light  1304 ) toward a scene including surface  1306 . While not shown for simplicity, an optical element may direct light from the emitter  1302  to one or multiple apertures based on an OE mode. While the emitted light  1304  is illustrated as being directed to surface  1306 , the field of the emission by the emitter  1302  may extend beyond the size of the surface  1306 . For example, a TOF system emitter may have a fixed focal length lens that defines the field of the emission for the transmitter. 
     The emitted light  1304  includes a sinusoidal signal  1314  (or other suitable periodic signal) of a defined frequency. The receiver  1308  includes an image sensor  1310  to sense the reflections  1312  of the emitted light  1304 . The image sensor  1310  may be an example implementation of the image sensor  1003  in  FIG. 10  or the image sensor  302  or  303  in  FIG. 3A . While not shown for simplicity, an optical element may be configured to direct light from a first aperture or a second aperture (such as apertures  1020  and  1022  in  FIG. 10 ) to the image sensor  1310 . The reflections  1312  include the reflected sinusoidal signal  1316 . A phase difference  1322  between the emitted sinusoidal signal  1314  and the reflected sinusoidal signal  1316  (as illustrated by emitted sinusoid timing  1318  and reflected sinusoid timing  1320 ) is determined. The phase difference  1322  may indicate a round trip time and thus may be used to determine the distance of the surface  1306  from the indirect TOF system  1300 . To produce the sinusoidal signal  1314 , the TOF system  1300  may be configured to modulate a carrier signal to produce the sinusoid wave. For example, a 940 nanometer wavelength light may be modulated to create the sinusoidal signal  1314 . The frequency of the wave may be referred to herein as a modulation frequency. In comparing the relationship of TOF and phase difference, the TOF may be defined in terms of the measured phase difference (PD) and the modulation frequency (f mod ), as depicted in equation (2) below: 
                   TOF   =     PD     2   ⁢   π   ⁢     f   mod                 (   2   )               
In a simplified example, if the PD is π and f mod  is approximately 250 kilohertz (kHz), the TOF is 2 microseconds (1 divided by 500 kHz). Referring back to equation (1), the depth D based on the TOF equaling 2 microseconds is approximately 300 meters.
 
     While  FIG. 13  illustrates the emitted light  1304  as having a sinusoidal waveform (illustrated by sinusoid  1314 ), any suitable waveform may be used. For example, the TOF system  1300  may be configured to stepwise increase and decrease the intensity of the emitted light in a periodic pattern. In this manner, the waveform of the emitted light may approximate a square wave (such as for a periodic pulsed signal). Other waveforms may be used, including a saw waveform and so on. As used herein, a sinusoid waveform or wave may refer to any suitable waveform for the signals (including an approximated square wave). 
     In some implementations, the indirect TOF system  1300  may include a demodulation circuit for each pixel of the image sensor  1310  (referred to herein as a demodulation pixel or a lock-in pixel). Each demodulation pixel may include a demodulation photodetector and be configured to generate and store one or more voltages corresponding to a phase or phase difference of the reflected sinusoidal signal received at the photodiode of the array and the emitted sinusoidal signal. The phase difference may be determined from the one or more stored voltages. For example, a demodulation pixel may generate a voltage signal (such as using a current from a photodiode to determine whether to send a pixel voltage (such as a rail voltage) or a low voltage as the voltage signal). An example image sensor  1310 , using the demodulation pixels, may generate an array of voltages for a single capture by the image sensor  1310 . The array of voltages may be processed to generate a PD for each pixel, and the PDs are processed to generate one or more depths of objects in the scene. 
     While some example active depth sensing systems are described in the present disclosure, any suitable active depth sensing system may be used. The first emitter  1002  (or the second emitter  1003 ) of the device  1000  in  FIG. 10  is not limited to a specific type of emitter for active depth sensing or a specific type or configuration of active depth sensing. As such, a device mode of the device  1000  may be configured for any suitable configuration of active depth sensing. 
     As noted herein, an optical element  1004  may be configured to switch between two or more OE modes for active depth sensing. For example, if the first aperture  1020  is positioned on a first side of the device  1000  and the second aperture  1022  is positioned on a second side of the device  1000 , a first OE mode may be associated with active depth sensing for light emitted from the first side of the device  1000 , and a second OE mode may be associated with active depth sensing for light emitted from the second side of the device  1000 . Also as noted herein, the device  1000  may be configured to switch between two or more device modes. For example, if the device  1000  includes a second emitter  1003 , a first device mode may be associated with a first type or configuration of active depth sensing using the first emitter  1002 , and a second device mode may be associated with a second type or configuration of active depth sensing using the second emitter  1003 . For example, the first emitter  1002  may be configured to emit a first distribution of light, and the second emitter  1003  may be configured to emit a second distribution of light (such as a distribution of light having different size or distribution of codewords than the first distribution of light). In another example, the first emitter  1002  may be configured to emit a distribution of light for structured light depth sensing, and the second emitter  1003  may be configured to emit pulsed light for TOF depth sensing. In some other implementations, the device  1000  may be configured to switch between one or more active depth sensing modes and one or more image capture modes. For example, if the device  1000  includes an image sensor  1003 , the device  1000  may be configured to switch between an active depth sensing mode using the first emitter  1002  and an image capture mode using the image sensor  1003 . If the device  1000  includes an image sensor or second emitter  1003 , an OE mode of the optical element  1004  may depend on a device mode of the device  1000 . In some implementations, the device  1000  may not include an image sensor or a second emitter  1003 , and the device  1000  may not have different device modes. The OE mode of the optical element  1004  may depend from other criteria, such as an intended direction of emission for active depth sensing. 
     In switching between OE modes, the device  1000  (such as the controller  1010 ) may adjust the optical element  1004 . For example, the device  1000  may rotate the optical element  1004  (such as depicted in  FIGS. 14A and 14B  and similar to as depicted in  FIGS. 4A and 4B ), adjust a position of the optical element  1004  (such as depicted in  FIGS. 15A and 15B  and similar to as depicted in  FIGS. 5A and 5B ), or adjust a state of the optical element  1004  based on a stimuli (such as an electrical current) applied to the optical element (such as depicted in  FIGS. 16A and 16B  and similar to as depicted in  FIGS. 6A and 6B ). The optical element and adjusting the optical element depicted in  FIGS. 16C-16F  may be similar to as depicted in  FIGS. 6E-6H . 
       FIG. 14A  shows a cross-section of an example device  1400  portion illustrating a first emitter  1402  associated with a first optical path  1406  when the device  1400  is in a first mode. The optical element  1414  is configured to direct light from the first emitter  1402  to the first optical path  1406  (and on to the first aperture  1410 ) during a first OE mode. The optical element  1414  is similar to the optical element  414  in  FIGS. 4A and 4B . Light may propagate along the first optical path  1406 , and the light may be from the first aperture  1410  or the optical element  1414 . One or more components  1418  may direct the light between the first optical path  1406  and the optical element  1414 . The device  1400  includes a second aperture  1412  configured to direct light along a second optical path  1408  or receive light propagated along the second optical path  1408  in the device  1400 . While the apertures  1410  and  1412  are shown on different sides of the device  1400 , the apertures  1410  and  1412  may be on a same side of the device  1400 . The optical element  1414  (and any components  1418 ) may be in any suitable orientation and configuration to direct light between the first optical path  1406  and the first emitter  1402  during a first device mode. If the first aperture  1410  is positioned on the left side of device  1400  illustrated in  FIG. 14A  (similar to  FIG. 4C ), the component  1418  may direct light received from the optical element  1414  to the first aperture  1410  (or vice versa). In the second OE mode, the first emitter  1402  may emit light that is emitted outside of the device  1400  via the second aperture  1412  (such as depicted in  FIG. 14B ). In the illustrated example device  1400 , the optical element  1414  may block the light from the first emitter  1402  from reaching the second aperture  1412  (with the light instead being reflected to the first aperture  1410 ). 
     If the device  1400  includes an image sensor  1404 , the optical element  1414  may be configured to direct the light from the second optical path  1408  to the image sensor  1404  in the first OE mode. If the device  1400  includes a second emitter  1404 , the optical element  1414  may be configured to direct the light from the emitter  1404  to the second optical path  1408 . 
     An actuator  1416  may rotate the optical element  1414  to switch between OE modes. The actuator  1416  may be similar to the actuator  416  in  FIG. 4A  and  FIG. 4B . For example, the actuator  1416  may include or be coupled to a rotatory motor or other means to rotate the optical element  1414  between a first orientation and a second orientation, and the actuator  1416  is controlled by a controller (such as controller  1010  in  FIG. 10 ). As noted above in describing  FIGS. 4A and 4B , the examples in  FIGS. 14A and 14B  (and later figures) may refer to the orientation of the optical element with reference to a first optical path. While the examples in  FIGS. 14A and 14B  (and later figures) may refer to the orientation of the optical element with reference to a first optical path, the orientation of the optical element may be with reference to any suitable device component or suitable reference within the device. For example, the orientation may be with reference to an orientation of an image sensor, with reference to an orientation of an emitter, with reference to a direction of light approaching the optical element from an optical path, and so on. 
       FIG. 14B  shows the cross-section of the device  1400  portion in  FIG. 14A  with the optical element  1414  at an example second orientation with reference to the first optical path  1406  for a second OE mode. In the second OE mode, the device  1400  is configured to direct light from the first emitter  1402  to the second optical path  1408 . If the device  1400  includes an image sensor or second emitter  1404 , the device  1400  is also configured to direct light from/to the first optical path  1406  to/from the image sensor or second emitter  1404  during the second device mode. 
     As noted above for optical element  414  ( FIGS. 4A and 4B ), a reflectiveness and transparency or a refractive index of the optical element  1414  may be based on an angle of incidence of light received at the optical element  1414 . In this manner, the reflectiveness and transparency of the optical element  1414  may be based on the orientation of the optical element  1414  with reference to the first optical path  1406 . The optical element  1414  may be composed of materials as described above for optical element  414 . 
     If the apertures  1410  and  1412  are on different sides of the device, an OE mode may be based on an intended direction to emit light from the device  1400  (or for capturing an image for an image sensor  1404 ). If the apertures  1410  and  1412  are on the same side of the device, for a second device mode including an image sensor  1404 , the image sensor  1404  may be used for wider FOV imaging or three dimensional imaging (such as described above with reference to  FIGS. 3C, 3D and 3F ). For a first device mode (or a second device mode including a second emitter  1404 ), the apertures on a same side of the device may be oriented and configured to direct light from the emitter on to different portions of a scene (such as described herein with reference to wider FOV imaging). In this manner, the light from the emitter may be emitted onto a larger portion of the scene than if only one aperture is used. 
     Referring back to  FIGS. 4E and 4F , multiple instances of the image capture system may coexist in a device. In some implementations, multiple instances of the active depth sensing system may exist in the device  1000 . In addition, or to the alternative, one or more instances of the active depth sensing system may exist with one or more instances of the image capture system in a device. For example, referring back to  FIG. 3G , a first aperture  364  and a second aperture  366  may be associated with an active depth sensing system (similar to as illustrated in  FIG. 14A ). A third aperture  368  and a fourth aperture  370  may be associated with a second active depth sensing system (similar to as illustrated in  FIG. 14A ) or an image capture system (similar to as illustrated in  FIG. 4A ). If two emitters  1002  and  1003  share a first aperture  364  and a second aperture  366 , and two image sensors  302  and  303  share a third aperture  368  and a fourth aperture  370 , a first image sensor may be associated with a first emitter, and a second image sensor may be associated with a second emitter. In this manner, the device may include multiple active depth sensing systems. In another example, the device may include one emitter and three image sensors (with the emitter and one image sensor sharing two apertures). While  FIGS. 14C and 14D  show an example of a combination of image sensors and emitters, any combination, number, and configuration of emitters, image sensors, optical elements, and so on may be included in a device. 
       FIG. 14C  shows a cross-section of an example device  1440  portion illustrating a first emitter  1442  associated with a first optical path  1446  and a first image sensor  1462  associated with a third optical path  1466 . The optical element  1454  may direct light from the first emitter  1442  to the first optical path  1446  based on the optical element  1454  being in a first orientation. The optical element  1474  may direct light from the third optical path  1466  to the first image sensor  1462  based on the optical element  1474  being in a first orientation. In some implementations, the optical element  1454  may also direct light from the second emitter  1444  to the second optical path  1448  based on the optical element  1454  being in a first orientation, and the optical element  1474  may direct light from the third optical path  1466  to the second image sensor  1464  based on the optical element  1474  being in a first orientation. Comparing  FIG. 14C  to  FIG. 4A  and  FIG. 14A , the components  458  and  478  may be similar to components  418  or  1418 , the optical elements  454  and  474  may be similar to optical elements  414  or  1414 , and the actuators  456  and  476  may be similar to actuators  416  or  1416 . 
     If the first image sensor  1462  is the receiver for the first emitter  1442 , active depth sensing may be performed using the emitter/sensor pair. If the second image sensor  1464  is the receiver for the second emitter  1444 , active depth sensing may also be performed using the emitter/sensor pair. The two pairs may be configured for different types of active depth sensing or a different configuration of a same type of active depth sensing. While  FIGS. 14C and 14D  show emitters sharing apertures and image sensors sharing apertures, a first emitter  1442  may share apertures with a second image sensor  1464 , and a second emitter  1444  may share apertures with a first image sensor  1462 . For example, in  FIG. 14C  the second emitter  1444  and the second image sensor  1464  may be switched. In some other implementations, the apertures may be arranged on any side. For example, apertures  1450  and  1452  may be arranged on a side of the device with aperture  1472 , and aperture  1470  may be on a different side of the device  1440 . In this manner, active depth sensing may be desired in a specific direction from the device (such as from a rear of a smartphone), but image capture may be desired from multiple sides of the device (such as also from a front of a smartphone for selfie imaging). If the apertures for active depth sensing are configured to allow light to be emitted on a wider portion of the scene (and the image sensor is configured to capture images for the wider FOV of the scene), an OE mode for optical element  1454  may alternate to allow depth sensing for a wider portion of the scene (similar to operations for wider FOV imaging described herein). While a few example configurations are described, any suitable configuration of components may be used. 
       FIG. 14D  shows a cross-section of the example device  1440  portion illustrating the second emitter  1444  associated with the first optical path  1446  and the second image sensor  1464  associated with the third optical path  1466 . The optical element  1454  (in a second orientation) may allow light from the second emitter  1444  to reach the first aperture  1450 , and the optical element  1474  (in a second orientation) may allow light from the third optical path  1466  to reach the second image sensor  1464 . The optical element  1454  may also allow light from the first emitter  1442  to reach the second aperture  1452 , and the optical element  1474  may allow light from the fourth optical path  1468  to reach the first image sensor  1462 . Comparing  FIG. 14D  to  FIG. 4B  and  FIG. 14B , the components  1458  and  1478  may be similar to components  418  or  1418 , the optical elements  1454  and  1474  may be similar to optical elements  414  or  1414 , and the actuators  1456  and  1476  may be similar to actuators  416  or  1416 . In some implementations, one optical element may be shared by the emitters or image sensor  1442 ,  1444 ,  1462 , and  1464 . For example, the emitters and image sensors may be positioned such that one larger optical element may be rotated to direct light as shown in  FIG. 14C  or  FIG. 14D . In some other implementations, the optical elements  1454  and  1474  may have different OE modes from one another or switch modes at different times. In some further implementations, the optical element  1454  and  1474  may be moved or have a stimulus applied to be adjusted. Other configurations may exist, and the disclosure is not limited to the above examples. 
       FIGS. 15A-16F  depict a device including an image sensor or second emitter associated with the optical element. However, the depictions are for clarity in explaining aspects of the disclosure. As shown in  FIGS. 10, 14A, and 14B , a device is not required to include the image sensor or second emitter associated with the optical element. As such, the disclosure (including the examples depicted in  FIGS. 15A-16F ) is not limited to requiring an image sensor or second emitter associated with the optical element. 
       FIG. 15A  shows a cross-section of an example device  1500  portion illustrating a first emitter  1502  associated with a first optical path  1506 . The optical element  1514  is configured to direct light from the first emitter  1502  to the first optical path  1506  in a first OE mode. If the device  1500  includes an image sensor or second emitter  1504 , the optical element  1514  is also configured to direct light from/to the optical path  1508  to/from the image sensor or second emitter  1504 . The light along the first optical path  1506  may exit the device  1500  via the first aperture  1510 . If the device  1500  includes an image sensor  1504 , light along the second optical path  1508  may enter the device via the second aperture  1512 . If the device  1500  includes a second emitter  1504 , light from the second emitter  1504  along the second optical path  1508  may exit the device  1500  via the second aperture  1512 . Similar to  FIGS. 14A and 14B , the device  1500  may include one or more components  1540  configured to direct light between the first optical path  1506  (or the second optical path  1508 ) and the optical element  1514 . 
     The optical element  1514  may be configured similar to the optical element  514  depicted in  FIGS. 5A and 5B . For example, the optical element  1514  may include a one sided mirror or a double sided mirror, a prism, or other suitable element for directing light. An actuator  1516  may be configured to move the optical element  1514  between a first position (such as illustrated in  FIG. 15A ) and a second position (such as illustrated in  FIG. 15B ). The actuator  1516  may be controlled by a device controller (such as controller  1010  in  FIG. 10 ). The actuator  1516  may be configured similar to the actuator  516  in  FIGS. 5A and 5B . 
       FIG. 15B  shows the cross-section of the device  1500  portion in  FIG. 15A  with the optical element  1514  at an example second position in the device  1500  in a second OE mode. The device  1500  is configured to direct light from the first emitter  1502  to the second optical path  1508 . If the device  1500  includes an image sensor or second emitter  1504 , the device  1500  is also configured to direct light between the image sensor or second emitter  1504  and the first optical path  1506 . While not shown, the apertures  1510  and  1512  may be on the same side of the device (similar to as illustrated in  FIGS. 5C and 5D ). 
       FIG. 16A  shows a cross-section of an example device  1600  portion illustrating a first emitter  1602  associated with a first optical path  1606  for a first OE mode. The first emitter  1602  is associated with the first optical path  1606  based on whether an electrical current (or another suitable stimulus) is applied to the optical element  1614 .  FIG. 16B  shows the cross-section of the example device  1600  portion illustrating the first emitter  1602  associated with a second optical path  1608  for a second OE mode. The first emitter  1602  is associated with the second optical path  1608  based on whether an electrical current (or another suitable stimulus) is applied to the optical element  1614 . A transparency, reflectiveness, or refractive index of the optical element  1614  may be based on a level of stimulus applied to the optical element  1614  (such as an amount of electrical current applied). For example, the optical element  1614  may be transparent when an electrical current is applied, and the optical element  1614  may be reflective when an electrical current is not applied. The optical element  1614  may be configured similar to the optical element  614  depicted in  FIGS. 6A and 6B . For example, the material composition of the optical element  614  and the optical element  1614  may be the same. In this manner, the optical element  1614  may include or be coupled to electrical contacts  1616  for applying an electrical current to the optical element  1614 . The electrical contacts  1616  may be controlled by a device controller (such as the controller  1010  in  FIG. 10 ) to control a state of the optical element  1614 . Control of the optical element  1614  may be similar to control of the optical element  614  depicted in  FIG. 6A  and  FIG. 6B . For example, the controller  1010  may control a switch to cause electrical current to be applied to or removed from the electrical contacts  1616  in order to switch between OE modes. While not shown, the apertures  1610  and  1612  may be on the same side of the device (similar to as illustrated in  FIGS. 6C and 6D ). 
       FIGS. 16C-16F  show other example implementations of an optical element for switching between OE modes.  FIG. 16C  shows a cross-section of an example device  1650  portion illustrating a first emitter  1652  associated with a first optical path  1656 . A first aperture  1660  is configured to direct light along a first optical path  1656 , and a second aperture  1662  is configured to direct light along a second optical path  1658 . The optical element  1664 , in a first orientation for a first OE mode, directs light from the first emitter  1652  to the first optical path  1656 . The optical element  1664  may also direct light from/to the second optical path  1658  to/from the image sensor or second emitter  1654  for the first OE mode. The optical element  1664  may be similar to the optical element  664  in  FIG. 6E . 
     In switching between a first OE mode and a second OE mode, the actuator  1666  may rotate the optical element  1664  to a second orientation. The actuator  1666  may be similar to the actuator  1416  in  FIG. 14A , except the actuator  1666  rotates the optical element  1664  along an axis towards a center of the optical element  1664  (instead of an axis towards one end of the optical element).  FIG. 16D  shows the cross-section of the example device portion illustrating the first emitter  1652  associated with the second optical path  1658 . The optical element  1664 , in the second orientation for a second OE mode, is configured to direct light from the first emitter  1652  to the second optical path  1658 . The optical element  664  is also configured to direct light from/to the first optical path  1656  to/from the image sensor or second emitter  1654 . In some other implementations, the optical element may be a prism or other object that is moved or rotated to switch between OE modes. 
     In some implementations, instead of rotating the optical element, the optical element may be a prism or other structure configured to direct light based on a stimulus applied to the optical element.  FIG. 16E  shows a cross-section of an example device portion illustrating a first emitter  1672  associated with a first optical path  1676 . The device  1670  may be similar to the device  1650  in  FIG. 16C  other than the type of optical element used. For example, the optical element  1686  may be similar to the optical element  686  in  FIG. 6G . In this manner, the first emitter  1672  may be similar to the first emitter  1652 , the image sensor or second  1674  may be similar to the image sensor or second emitter  1654 , the first optical path  1676  may be similar to the first optical path  1656 , the second optical path  1678  may be similar to the second optical path  1658 , the first aperture  1680  may be similar to the first aperture  1660 , and the second aperture  1682  may be similar to the second aperture  1662 . 
     While the optical element  1686  is illustrated as changing states based on application of an electrical current via electrical contacts  1688  and electrical contacts  1690 , any suitable stimulus may be used and may be applied in any manner. In some implementations, a first portion of the optical element  1686  includes a first set of molecules having a first orientation when an electrical current is applied via the electrical contacts  1688 , and a second portion of the optical element  1686  includes a second set of molecules having a first orientation when an electrical current is applied via the electrical contacts  1690 . While two electrical contacts are illustrated, any suitable number may be used (such as one or more electrical contacts). When the first set of molecules and the second set of molecules are in the first orientation, the optical element  1686  may be configured to direct light as shown in  FIG. 16E  (and similar to as shown in  FIG. 6G ). The first set of molecules and the second set of molecules may also have a second orientation when no electrical current is applied. In this manner, when the first set of molecules and the second set of molecules are in the second orientation, the optical element  1686  may be configured to direct light as shown in  FIG. 16F  (and similar to as shown in  FIG. 6H ).  FIG. 16F  shows the cross-section of the example device portion in  FIG. 16E  illustrating the first emitter  1672  associated with the second optical path  1678 . 
     In some other implementations, the optical element  1686  may include separate components of two or more optical elements combined together. For example, a first portion of the optical element  1686  may be similar to the optical element  1614  in  FIG. 16A . The first portion may be controlled based on an electrical current applied via the electrical contacts  1688 . A second portion of the optical element  1686  may be similar to the optical element  1614  rotated by 90 degrees. The second portion may be controlled based on an electrical current applied via the electrical contacts  1690 . In this manner, switching between OE modes may include switching between providing an electrical current via contacts  1688  and not providing an electrical current via contacts  1690  for a first OE mode and not providing an electrical current via contacts  1688  and providing an electrical current via contacts  1690  for a second OE mode. 
     As depicted in  FIGS. 14A-16F , directing light by the optical element for an active depth sensing mode may be similar to directing light by the optical element for an image capture mode (such as depicted in  FIGS. 3A-6H ). In this manner, aspects of the disclosure described herein with reference to an image capture mode may be applied with reference to an active depth sensing mode (such as depicted in  FIGS. 10 and 14A-16H ). 
       FIG. 17A  shows an illustrative flow chart depicting an example operation  1700  for active depth sensing. The first emitter, the first aperture, and the second aperture may be as depicted in  FIGS. 10 and 14A-16B  (or as otherwise described).  FIG. 17A  is described as being performed by the device  1000  depicted in  FIG. 10  for clarity purposes. However, any suitable device or device configuration may be used to perform the example operation  1700 . 
     At  1702 , a first emitter  1002  of the device  1000  emits a first light for active depth sensing. For example, the first emitter  1002  may emit a first distribution of light, may emit a periodic pulsed light, or may emit a diffuse light (such as for flood illumination). At decision block  1704 , if the optical element  1004  is in a first OE mode, the operation  1700  proceeds to step  1706 . If the optical element  1004  is not in the first OE mode (such as being in a second OE mode), the operation  1700  proceeds to step  1710 . Referring to step  1706 , an optical element  1004  directs the first light emitted by the first emitter  1002  to a first optical path  1001 . For example, the optical element  1004  may reflect or refract light from the first emitter  1002  to the first optical path  1001  based on an orientation of the optical element  1004 , a position of the optical element  1004 , a state of the optical element  1004  (based on an electrical current to be applied to the optical element  1004 ), and so on. At  1708 , the first aperture  1020  directs the first light from the first optical path  1001  to outside of the device  1000 . 
     Referring to step  1710 , the device  1000  directs the first light from the first emitter  1002  to a second optical path  1024 . For example, the optical element  1004  may be in a position to not block light from the first emitter  1002  to reach the second optical path  1024  (and the second aperture  1022 ). In another example, the optical element  1004  may have an orientation or be in a state based on a stimulus (such as an electrical current applied or not applied) to allow light from the first emitter  1002  to pass through the optical element  1004  and to the second optical path  1024 . At  1712 , the second aperture  1022  directs the first light from the second optical path  1024  to outside of the device  1000 . As noted herein, the controller  1010  may be configured to adjust the optical element  1004  to switch between OE modes for the example operation  1700 . 
     If the device  1000  includes the image sensor or second emitter  1003 , the device  1000  may also have different device modes.  FIG. 17B  shows an illustrative flow chart depicting an example operation  1720  for active depth sensing by the device  1000  configured for different device modes. At decision block  1722 , if the device  1000  is in a first device mode, operation may proceed to step  1702  in  FIG. 17A . In this manner, the first emitter  1002  is to be used for active depth sensing. If the device  1000  is not in a first device mode (such as the device  1000  being in a second device mode), operation may proceed to decision block  1724 . If the device  1000  is in a second device mode, an image sensor may be used for image capture or a second emitter may be used for active depth sensing. 
     At decision block  1724 , if the device  1000  includes a second emitter, operation may proceed to  1726 . If the device  1000  includes an image sensor, operation may proceed to  1730 . Referring back to  1726 , the second emitter emits a second light when the device  1000  is in the second device mode. For example, the first device mode may be a first active depth sensing mode using the first emitter, and the second device mode may be a second active depth sensing mode using the second emitter. The two active depth sensing modes may be for different types of active depth sensing techniques (such as structured light versus time of flight). In another example, the two active depth sensing modes may be for emitting different distributions of light for structured light depth sensing or for emitting different pulsed frequencies or different wavelengths of light for time of flight depth sensing. For example, a first emitter may be configured to emit sub-1000 nm wavelength light, and a second emitter may be configured to emit light with a wavelength greater than 1000 nm. In this manner, time of flight depth sensing may use different frequency light based on the application. 
     At  1728 , the device  1000  directs the second light from the second emitter  1003  to a first optical path  1001  or a second optical path  1024  based on an OE mode. For example, if the optical element  1004  is in a first OE mode, the optical element  1004  may direct the second light toward the second aperture  1022 . If the optical element  1004  is in a second OE mode, the optical element  1004  may direct the second light toward the first aperture  1020 . The first OE mode may be associated with a first orientation of the optical element  1004 , a first position of the optical element  1004 , or a first state of the optical element  1004 . The second OE mode may be associated with a second orientation of the optical element  1004 , a second position of the optical element  1004 , or a second state of the optical element  1004 . In some implementations, the device  1000  is configured to adjust the optical element  1004  based on which OE mode is to be used. For example, the controller  1010  may instruct an actuator or otherwise control the optical element  1004  to rotate between orientations, move between positions, or apply a stimulus to the optical element  1004 . 
     Referring back to  1724 , if the device  1000  includes an image sensor, the device  1000  may direct light propagated along the first optical path or the second optical path to the image sensor based on the OE mode ( 1730 ). For example, if the optical element  1004  is in a first OE mode, the optical element  1004  may direct light from a second aperture  1022  (which propagates along the second optical path  1024 ) toward the image sensor  1003 . If the optical element  1004  is in a second OE mode, the optical element  1004  may direct light from a first aperture  1020  (which propagates along the first optical path  1001 ) toward the image sensor  1003 . In some implementations, the device  1000  is configured to adjust the optical element  1004  based on which OE mode is to be used. For example, the controller  1010  may instruct an actuator or otherwise control the optical element  1004  to rotate between orientations, move between positions, or apply a stimulus to the optical element  1004 . 
     The controller  1010  (or another suitable component of the device  1000 ) may control the optical element  1004  for the different OE modes (and, optionally, during different device modes).  FIG. 18  shows an illustrative flow chart depicting an example operation  1800  of controlling an optical element  1004  for active depth sensing. Operation  1800  may be performed by the controller  1010  or another suitable component of the device  1000 . 
     At  1802 , the device  1000  (such as the controller  1010 ) identifies whether the optical element  1004  is to be in a first OE mode or a second OE mode. In some implementations, the controller  1010  identifies the OE mode based on a device mode ( 1804 ). For example, if a first aperture  1020  is to be used for active depth sensing using a second emitter  1003  (which may correspond to a second device mode), the controller  1010  may identify that the optical element  1004  is to be in the second OE mode. In another example, is the first aperture  1020  is to be used for active depth sensing using the first emitter  1002  (which may correspond to a first device mode), the controller  1010  may identify that the optical element  1004  is to be in the first OE mode. In another example, if the device  1000  is to use both apertures to emit light across a wider portion of the scene for active depth sensing, the controller  1010  may determine that the first OE mode is to be used for a first portion of time and a second OE mode is to be used for a second portion of time (such as alternating OE modes). 
     In some implementations of basing the identification of OE modes on a device mode, the controller  1010  may identify the OE mode based on an efficiency of different active depth sensing systems. For example, a first emitter  1002  may emit a first distribution of light and the second emitter  1003  may emit a second distribution of light for structured light depth sensing. The first distribution of light may be sparser or have larger codewords than the second distribution of light. In this manner, a first depth map using the first distribution of light may have less resolution that a second depth map using the second distribution of light in the absence of interference (such as ambient light). However, the second distribution of light may be more susceptible to interference since light points may be more closely bunched and have a lower individual light intensity. For example, depth mapping using the second distribution of light may be more difficult in bright sunlight. In another example, depth mapping using the second distribution of light may be more difficult as the depths of objects increase. In this manner, the device  1000  may determine whether the current distribution of light being used is sufficient. For example, when the images including the reflections of the distribution of light are processed and depths are determined to generate a depth map, the depth map may include holes where a depth cannot be determined. If the number or sizes of holes reaches a threshold for the second distribution of light, the device  1000  may determine that the first emitter  1002  is to be used (with a sparser distribution of light emitted). In this manner, the device  1000  may determine to switch from a second device mode to a first device mode for active depth sensing. As a result, the controller  1010  may control the optical element to switch OE modes in order to switch from using the second distribution of light for active depth sensing to using the first distribution of light for active depth sensing. 
     In some other implementations, the controller  1010  identifies the OE mode based on an active depth sensing or imaging application ( 1806 ). For example, if the second aperture  1022  is a front facing aperture on a smartphone, and the smartphone is to perform active depth sensing using the first emitter  1002  for facial recognition, the controller  1010  may determine that the second aperture  1022  is to be used for active depth sensing. In this manner, the controller  1010  may identify that the optical element  1004  is to be in the second OE mode. In another example, if the smartphone is in a low power state or locked state, the device  1000  may be configured to perform an imaging application using a lower power image sensor for object detection (such as to detect if a possible face approaches the center of the field of view for the image sensor). If a possible face is detected, the controller  1010  may determine to switch OE modes in using the first emitter  1002  to emit a distribution of light for active depth sensing (such as for facial recognition). 
     In some further implementations, the controller  1010  identifies the OE mode based on a user input ( 1808 ). For example, if the apertures  1020  and  1022  are on different sides of the device  1000 , the user may indicate in which direction from the device to perform active depth sensing. For example, the user may explicitly select a direction or otherwise indicate the OE mode through one or more inputs (such as via a GUI, audible command, haptic command, and so on). 
     In some implementations, the controller  1010  identifies the OE mode based on an orientation of the device  1000  ( 1809 ). For example, the controller  1010  may determine (such as based on orientation measurements or measurements of light intensities in images from the image sensor) that the device  1000  is resting on a surface with the first aperture  1020  directed up and the second aperture  1022  directed down towards the surface. The controller  1010  may determine that the first aperture  1020  is to be used for object detection using the image sensor and active depth sensing for facial recognition using the first emitter  1002 . In this manner, the controller  1010  may identify a second OE mode for object detection (to direct light from the first aperture  1020  towards the image sensor), and the controller  1010  may identify a first OE mode for facial recognition (to direct light from the first emitter  1002  towards the first aperture  1020  for active depth sensing). 
     At  1810 , the device  1000  controls the optical element  1004  based on the identified OE mode. For example, the controller  1010  may determine whether the optical element  1004  is to be adjusted for the identified OE mode, and the controller  1010  may adjust the optical element  1004  based on the identified OE mode ( 1812 ). As noted herein, adjusting the optical element  1004  may include rotating the optical element  1004 , moving the optical element  1004 , or applying a stimulus (such as an electrical current) to the optical element  1004 . For example, the controller  1010  may compare the current OE mode to the identified OE mode and determine if a difference exists. If a difference exists, the controller  1010  may instruct (or otherwise control) an actuator to rotate or move the optical element  1004  or may control electrical contacts to apply or remove an electrical current to or from the optical element  1004 . As noted herein, the optical element  1004  may change modes during device operation (including during a device mode). As such, operation  1800  may be performed multiple times. 
     In some implementations, the first device mode and the second device mode may occur concurrently. For example, if the device  1000  includes a second emitter  1003 , active depth sensing may be performed using both emitters and both apertures of the device  1000 . In another example, if the device  300  includes a second aperture  322 , image capture may be performed using both image sensors and both apertures of the device  300 . For example, active depth sensing or image capture from a front of a smartphone may be performed concurrently with active depth sensing or image captured from a rear of a smartphone. In another example, both active depth sensing and image capture may be performed from a same side of a device  1000 . In some implementations, the active depth sensing may be a time of flight depth sensing for laser autofocus for the image sensor  1003  for image capture. 
     As noted herein, a device may include any suitable combination of image sensors, emitters, optical elements and so on, and the configuration of the components may be any suitable configuration. The device may perform any combination of the described methods herein. For example, a device may be configured for a plurality of active depth sensing modes and a plurality of image capture modes. 
     The techniques described herein may be implemented in hardware, software, firmware, or any combination thereof, unless specifically described as being implemented in a specific manner. Any features described as modules or components may also be implemented together in an integrated logic device or separately as discrete but interoperable logic devices. If implemented in software, the techniques may be realized at least in part by a non-transitory processor-readable storage medium (such as the memory  306  in the example device  300  of  FIG. 3A  or the memory  1006  in the example device  1000  of  FIG. 10 ) comprising instructions that, when executed by the processor (or a controller, a signal processor, or another suitable component), cause the device to perform one or more of the methods described above. The non-transitory processor-readable data storage medium may form part of a computer program product, which may include packaging materials. 
     The non-transitory processor-readable storage medium may comprise random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, other known storage media, and the like. The techniques additionally, or alternatively, may be realized at least in part by a processor-readable communication medium that carries or communicates code in the form of instructions or data structures and that can be accessed, read, and/or executed by a computer or other processor. 
     The various illustrative logical blocks, modules, circuits and instructions described in connection with the embodiments disclosed herein may be executed by one or more processors, such as the processor  305  or  1005  or the image signal processor  312  or  1012  in the example device  300  of  FIG. 3A  and example device  1000  of  FIG. 10 . Such processor(s) may include but are not limited to one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), application specific instruction set processors (ASIPs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. The term “processor,” as used herein may refer to any of the foregoing structures or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated software modules or hardware modules configured as described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     While the present disclosure shows illustrative aspects, it should be noted that various changes and modifications could be made herein without departing from the scope of the appended claims. For example, while specific orientations of an image sensor and an emitter are depicted, the orientations of such components may be other suitable orientations. For example, one or more emitters or one or more image sensors may be positioned on any suitable plane with reference to the device (such as a plane parallel to any side of the device, including a front, rear, top, bottom, and so on, or a plane between planes defined by two or more sides of the device). Therefore, the present disclosure is not limited to a specific orientation of an image sensor or a specific orientation of an emitter. In another example, while translational movement of the optical element is shown along one axis, translational movement may be along one or more suitable axes. In a further example, while rotation of the optical element is shown along one axis, rotation of the optical element may occur along any suitable number of axes. 
     Additionally, the functions, steps or actions of the method claims in accordance with aspects described herein need not be performed in any particular order unless expressly stated otherwise. For example, the steps of the described example operations, if performed by the device (such as by components including the controller  310  or  1010 , the processor  305  or  1005 , the signal processor  312  or  1012 , or the optical element  304  or  1004 ) may be performed in any order and at any frequency. Furthermore, although elements or components may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. For example, an optical element may be configured to support three or more image sensors or emitters.