Patent Publication Number: US-2023147711-A1

Title: Methods for generating stereoscopic views in multicamera systems, and associated devices and systems

Description:
TECHNICAL FIELD 
     The present technology generally relates to methods for selecting pairs of cameras in a multicamera array configured to image a scene, such as a surgical scene, to generate stereoscopic views, and associated systems and devices. 
     BACKGROUND 
     In a mediated reality system, an image processing system adds, subtracts, and/or modifies visual information representing an environment. The visual information can be captured using an array of multiple cameras. For surgical applications, a mediated reality system can enable a surgeon to view a surgical site from a desired perspective together with contextual information that assists the surgeon in more efficiently and precisely performing surgical tasks. In some implementations, to reconstruct an image of the environment, mediated reality systems can utilize (i) image data from multiple ones of the cameras positioned at different angles and orientations relative to the environment and (ii) depth information about the environment. However, such reconstructed images can be complex to compute and/or can be of relatively poor image quality if the reconstruction is based on sparse image data from relatively few cameras. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on clearly illustrating the principles of the present disclosure. 
         FIG.  1    is a schematic view of an imaging system in accordance with embodiments of the present technology. 
         FIG.  2    is a perspective view of a surgical environment employing the imaging system of  FIG.  1    for a surgical application in accordance with embodiments of the present technology. 
         FIG.  3    is an isometric view of a portion of the imaging system of  FIG.  1    illustrating four cameras of the imaging system in accordance with embodiments of the present technology. 
         FIG.  4    is a flow diagram of a process or method for generating stereoscopic views using the imaging system of  FIG.  1    in accordance with embodiments of the present technology. 
         FIG.  5    is a schematic illustration of a portion of the imaging system of  FIG.  1    including a selected pair of the cameras in accordance with embodiments of the present technology. 
         FIG.  6    is a schematic illustration of a first source image received from a first one of the selected pair of the cameras of  FIG.  5    and a second source image received from a second one of the selected pair of the cameras of  FIG.  5    in accordance with embodiments of the present technology. 
         FIG.  7    is a flow diagram of a process or method for generating magnified stereoscopic views using the imaging system of  FIG.  1    in accordance with embodiments of the present technology. 
         FIGS.  8 A and  8 B  are schematic illustrations of the first source image and the second source image of  FIG.  6    in accordance with additional embodiments of the present technology. 
         FIG.  9    is a flow diagram of a process or method for generating a view of a scene using the imaging system of  FIG.  1    in accordance with additional embodiments of the present technology. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present technology are directed generally to methods for generating stereoscopic views of a scene, such as a surgical scene, based on images from a multicamera array, and associated systems and devices. In several of the embodiments described below, for example, a representative method includes selecting a pair of cameras from the multicamera array from which to generate a stereoscopic view. In some embodiments, the selection is dynamically based on the tracked position of a display device (e.g., a head-mounted display device) and/or an instrument within the scene. The method can further include receiving images of the scene from the selected pair of cameras, and cropping the images based on a known calibration of the cameras and a desired disparity. The desired disparity can correspond to an interpupillary distance of a user (e.g., a surgeon wearing the head-mounted display device). The method can further include displaying the cropped images on the display device to generate the stereoscopic view. 
     In some embodiments, the stereoscopic view can be a magnified view of the scene. In such embodiments, the method can further include determining a region of interest in the cropped images, and further cropping each of the cropped images to the region of interest. In some embodiments, the regions of interest are dynamically selected based on the tracked position of the display device and/or an instrument within the scene. Then, the regions of interest can be displayed on the display device to generate the magnified stereoscopic view. 
     In some embodiments, a generated stereoscopic view can be combined/merged with a three-dimensional (3D) reconstructed view of the scene. The 3D reconstructed view can be a computational reconstruction of image data (e.g., light field image data) captured by multiple ones of the cameras in the array. The combined 3D reconstructed view and stereoscopic view of the scene can be displayed on the display device. 
     Specific details of several embodiments of the present technology are described herein with reference to  FIGS.  1 - 9   . The present technology, however, can be practiced without some of these specific details. In some instances, well-known structures and techniques often associated with camera arrays, light field cameras, image reconstruction, registration processes, user interfaces, optical tracking, camera calibration, stereoscopic imaging, and the like have not been shown in detail so as not to obscure the present technology. Moreover, although frequently described in the context of tracking surgical instruments relative to a surgical scene (e.g., a spinal surgical scene), the methods and systems of the present technology can be used to track other types of objects relative to other scenes. 
     The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the disclosure. Certain terms can even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section. 
     The accompanying Figures depict embodiments of the present technology and are not intended to be limiting of its scope. Depicted elements are not necessarily drawn to scale, and various elements can be arbitrarily enlarged to improve legibility. Component details can be abstracted in the figures to exclude details as such details are unnecessary for a complete understanding of how to make and use the present technology. Many of the details, dimensions, angles, and other features shown in the Figures are merely illustrative of particular embodiments of the disclosure. Accordingly, other embodiments can have other dimensions, angles, and features without departing from the spirit or scope of the present technology. 
     The headings provided herein are for convenience only and should not be construed as limiting the subject matter disclosed. 
     To the extent any materials incorporated herein by reference conflict with the present disclosure, the present disclosure controls. 
     I. Selected Embodiments of Imaging Systems 
       FIG.  1    is a schematic view of an imaging system  100  (“system  100 ”) in accordance with embodiments of the present technology. In some embodiments, the system  100  can be a synthetic augmented reality system, a virtual-reality imaging system, an augmented-reality imaging system, a mediated-reality imaging system, and/or a non-immersive computational imaging system. In the illustrated embodiment, the system  100  includes a processing device  102  that is communicatively coupled to one or more display devices  104 , one or more input controllers  106 , and a camera array  110 . In other embodiments, the system  100  can comprise additional, fewer, or different components. In some embodiments, the system  100  includes some features that are generally similar or identical to those of the mediated-reality imaging systems disclosed in (i) U.S. patent application Ser. No. 16/586,375, titled “CAMERA ARRAY FOR A MEDIATED-REALITY SYSTEM,” and filed Sep. 27, 2019 and/or (ii) U.S. patent application Ser. No. 15/930,305, titled “METHODS AND SYSTEMS FOR IMAGING A SCENE, SUCH AS A MEDICAL SCENE, AND TRACKING OBJECTS WITHIN THE SCENE,” and filed May 12, 2020, each of which is incorporated herein by reference in its entirety. 
     In the illustrated embodiment, the camera array  110  includes a plurality of cameras  112  (identified individually as cameras  112   a - 112   n ; which can also be referred to as first cameras) that can each capture images of a scene  108  (e.g., first image data) from a different perspective. The scene  108  can include for example, a patient undergoing surgery (e.g., spinal surgery) and/or another medical procedure. In other embodiments, the scene  108  can be another type of scene. The camera array  110  can further include dedicated object tracking hardware  113  (e.g., including individually identified trackers  113   a - 113   n ) that captures positional data of one more objects, such as an instrument  101  (e.g., a surgical instrument or tool) having a tip  109 , to track the movement and/or orientation of the objects through/in the scene  108 . In some embodiments, the cameras  112  and the trackers  113  are positioned at fixed locations and orientations (e.g., poses) relative to one another. For example, the cameras  112  and the trackers  113  can be structurally secured by/to a mounting structure (e.g., a frame) at predefined fixed locations and orientations. In some embodiments, the cameras  112  are positioned such that neighboring cameras  112  share overlapping views of the scene  108 . In general, the position of the cameras  112  can be selected to maximize clear and accurate capture of all or a selected portion of the scene  108 . Likewise, the trackers  113  can be positioned such that neighboring trackers  113  share overlapping views of the scene  108 . Therefore, all or a subset of the cameras  112  and the trackers  113  can have different extrinsic parameters, such as position and orientation. 
     In some embodiments, the cameras  112  in the camera array  110  are synchronized to capture images of the scene  108  simultaneously (within a threshold temporal error). In some embodiments, all or a subset of the cameras  112  are light field/plenoptic/RGB cameras that capture information about the light field emanating from the scene  108  (e.g., information about the intensity of light rays in the scene  108  and also information about a direction the light rays are traveling through space). Therefore, in some embodiments the images captured by the cameras  112  encode depth information representing a surface geometry of the scene  108 . In some embodiments, the cameras  112  are substantially identical. In other embodiments, the cameras  112  include multiple cameras of different types. For example, different subsets of the cameras  112  can have different intrinsic parameters such as focal length, sensor type, optical components, and the like. The cameras  112  can have charge-coupled device (CCD) and/or complementary metal-oxide semiconductor (CMOS) image sensors and associated optics. Such optics can include a variety of configurations including lensed or bare individual image sensors in combination with larger macro lenses, micro-lens arrays, prisms, and/or negative lenses. For example, the cameras  112  can be separate light field cameras each having their own image sensors and optics. In other embodiments, some or all of the cameras  112  can comprise separate microlenslets (e.g., lenslets, lenses, microlenses) of a microlens array (MLA) that share a common image sensor. 
     In some embodiments, the trackers  113  are imaging devices, such as infrared (IR) cameras that can capture images of the scene  108  from a different perspective compared to other ones of the trackers  113 . Accordingly, the trackers  113  and the cameras  112  can have different spectral sensitives (e.g., infrared vs. visible wavelength). In some embodiments, the trackers  113  capture image data of a plurality of optical markers (e.g., fiducial markers, marker balls) in the scene  108 , such as markers  111  coupled to the instrument  101 . 
     In the illustrated embodiment, the camera array  110  further includes a depth sensor  114 . In some embodiments, the depth sensor  114  includes (i) one or more projectors  116  that project a structured light pattern onto/into the scene  108  and (ii) one or more depth cameras  118  (which can also be referred to as second cameras) that capture second image data of the scene  108  including the structured light projected onto the scene  108  by the projector  116 . The projector  116  and the depth cameras  118  can operate in the same wavelength and, in some embodiments, can operate in a wavelength different than the cameras  112 . For example, the cameras  112  can capture the first image data in the visible spectrum, while the depth cameras  118  capture the second image data in the infrared spectrum. In some embodiments, the depth cameras  118  have a resolution that is less than a resolution of the cameras  112 . For example, the depth cameras  118  can have a resolution that is less than 70%, 60%, 50%, 40%, 30%, or 20% of the resolution of the cameras  112 . In other embodiments, the depth sensor  114  can include other types of dedicated depth detection hardware (e.g., a LiDAR detector) for determining the surface geometry of the scene  108 . In other embodiments, the camera array  110  can omit the projector  116  and/or the depth cameras  118 . 
     In the illustrated embodiment, the processing device  102  includes an image processing device  103  (e.g., an image processor, an image processing module, an image processing unit), a registration processing device  105  (e.g., a registration processor, a registration processing module, a registration processing unit), and a tracking processing device  107  (e.g., a tracking processor, a tracking processing module, a tracking processing unit). The image processing device  103  can (i) receive the first image data captured by the cameras  112  (e.g., light field images, light field image data, RGB images) and depth information from the depth sensor  114  (e.g., the second image data captured by the depth cameras  118 ), and (ii) process the image data and depth information to synthesize (e.g., generate, reconstruct, render) a three-dimensional (3D) output image of the scene  108  corresponding to a virtual camera perspective. The output image can correspond to an approximation of an image of the scene  108  that would be captured by a camera placed at an arbitrary position and orientation corresponding to the virtual camera perspective. In some embodiments, the image processing device  103  can further receive and/or store calibration data for the cameras  112  and/or the depth cameras  118  and synthesize the output image based on the image data, the depth information, and/or the calibration data. More specifically, the depth information and the calibration data can be used/combined with the images from the cameras  112  to synthesize the output image as a 3D (or stereoscopic 2D) rendering of the scene  108  as viewed from the virtual camera perspective. In some embodiments, the image processing device  103  can synthesize the output image using any of the methods disclosed in U.S. patent application Ser. No. 16/457,780, titled “SYNTHESIZING AN IMAGE FROM A VIRTUAL PERSPECTIVE USING PIXELS FROM A PHYSICAL IMAGER ARRAY WEIGHTED BASED ON DEPTH ERROR SENSITIVITY,” and filed Jun. 28, 2019, which is incorporated herein by reference in its entirety. In other embodiments, the image processing device  103  can generate the virtual camera perspective based only on the images captured by the cameras  112 —without utilizing depth information from the depth sensor  114 . For example, the image processing device  103  can generate the virtual camera perspective by interpolating between the different images captured by one or more of the cameras  112 . 
     The image processing device  103  can synthesize the output image from images captured by a subset (e.g., two or more) of the cameras  112  in the camera array  110 , and does not necessarily utilize images from all of the cameras  112 . For example, for a given virtual camera perspective, the processing device  102  can select a stereoscopic pair of images from two of the cameras  112 , as described in greater detail below with reference to  FIGS.  4 - 9   . In some embodiments, such a stereoscopic pair can be selected to be positioned and oriented to most closely match the virtual camera perspective. In some embodiments, the image processing device  103  (and/or the depth sensor  114 ) estimates a depth for each surface point of the scene  108  relative to a common origin to generate a point cloud and/or a 3D mesh that represents the surface geometry of the scene  108 . For example, in some embodiments the depth cameras  118  of the depth sensor  114  detect the structured light projected onto the scene  108  by the projector  116  to estimate depth information of the scene  108 . In some embodiments, the image processing device  103  estimates depth from multiview image data from the cameras  112  using techniques such as light field correspondence, stereo block matching, photometric symmetry, correspondence, defocus, block matching, texture-assisted block matching, structured light, and the like, with or without utilizing information collected by the depth sensor  114 . In other embodiments, depth may be acquired by a specialized set of the cameras  112  performing the aforementioned methods in another wavelength. 
     In some embodiments, the registration processing device  105  receives and/or stores previously-captured image data, such as image data of a three-dimensional volume of a patient (3D image data). The image data can include, for example, computerized tomography (CT) scan data, magnetic resonance imaging (MRI) scan data, ultrasound images, fluoroscope images, and/or other medical or other image data. The registration processing device  105  can register the preoperative image data to the real-time images captured by the cameras  112  and/or the depth sensor  114  by, for example, determining one or more transforms/transformations/mappings between the two. The processing device  102  (e.g., the image processing device  103 ) can then apply the one or more transforms to the preoperative image data such that the preoperative image data can be aligned with (e.g., overlaid on) the output image of the scene  108  in real-time or near real time on a frame-by-frame basis, even as the virtual perspective changes. That is, the image processing device  103  can fuse the preoperative image data with the real-time output image of the scene  108  to present a mediated-reality view that enables, for example, a surgeon to simultaneously view a surgical site in the scene  108  and the underlying 3D anatomy of a patient undergoing an operation. In some embodiments, the registration processing device  105  can register the previously-captured image data to the real-time images by using any of the methods disclosed in U.S. patent application Ser. No. 17/140,885, titled “METHODS AND SYSTEMS FOR REGISTERING PREOPERATIVE IMAGE DATA TO INTRAOPERATIVE IMAGE DATA OF A SCENE, SUCH AS A SURGICAL SCENE,” and filed Jan. 4, 2021, which is incorporated herein by reference in its entirety. 
     In some embodiments, the tracking processing device  107  processes positional data captured by the trackers  113  to track objects (e.g., the instrument  101 ) within the vicinity of the scene  108 . For example, the tracking processing device  107  can determine the position of the markers  111  in the 2D images captured by two or more of the trackers  113 , and can compute the 3D position of the markers  111  via triangulation of the 2D positional data. More specifically, in some embodiments the trackers  113  include dedicated processing hardware for determining positional data from captured images, such as a centroid of the markers  111  in the captured images. The trackers  113  can then transmit the positional data to the tracking processing device  107  for determining the 3D position of the markers  111 . In other embodiments, the tracking processing device  107  can receive the raw image data from the trackers  113 . In a surgical application, for example, the tracked object can comprise a surgical instrument, an implant, a hand or arm of a physician or assistant, and/or another object having the markers  111  mounted thereto. In some embodiments, the processing device  102  can recognize the tracked object as being separate from the scene  108 , and can apply a visual effect to the 3D output image to distinguish the tracked object by, for example, highlighting the object, labeling the object, and/or applying a transparency to the object. 
     In some embodiments, functions attributed to the processing device  102 , the image processing device  103 , the registration processing device  105 , and/or the tracking processing device  107  can be practically implemented by two or more physical devices. For example, in some embodiments a synchronization controller (not shown) controls images displayed by the projector  116  and sends synchronization signals to the cameras  112  to ensure synchronization between the cameras  112  and the projector  116  to enable fast, multi-frame, multicamera structured light scans. Additionally, such a synchronization controller can operate as a parameter server that stores hardware specific configurations such as parameters of the structured light scan, camera settings, and camera calibration data specific to the camera configuration of the camera array  110 . The synchronization controller can be implemented in a separate physical device from a display controller that controls the display device  104 , or the devices can be integrated together. 
     The processing device  102  can comprise a processor and a non-transitory computer-readable storage medium that stores instructions that when executed by the processor, carry out the functions attributed to the processing device  102  as described herein. Although not required, aspects and embodiments of the present technology can be described in the general context of computer-executable instructions, such as routines executed by a general-purpose computer, e.g., a server or personal computer. Those skilled in the relevant art will appreciate that the present technology can be practiced with other computer system configurations, including Internet appliances, hand-held devices, wearable computers, cellular or mobile phones, multi-processor systems, microprocessor-based or programmable consumer electronics, set-top boxes, network PCs, mini-computers, mainframe computers and the like. The present technology can be embodied in a special purpose computer or data processor that is specifically programmed, configured or constructed to perform one or more of the computer-executable instructions explained in detail below. Indeed, the term “computer” (and like terms), as used generally herein, refers to any of the above devices, as well as any data processor or any device capable of communicating with a network, including consumer electronic goods such as game devices, cameras, or other electronic devices having a processor and other components, e.g., network communication circuitry. 
     The present technology can also be practiced in distributed computing environments, where tasks or modules are performed by remote processing devices, which are linked through a communications network, such as a Local Area Network (“LAN”), Wide Area Network (“WAN”), or the Internet. In a distributed computing environment, program modules or sub-routines can be located in both local and remote memory storage devices. Aspects of the present technology described below can be stored or distributed on computer-readable media, including magnetic and optically readable and removable computer discs, stored as in chips (e.g., EEPROM or flash memory chips). Alternatively, aspects of the present technology can be distributed electronically over the Internet or over other networks (including wireless networks). Those skilled in the relevant art will recognize that portions of the present technology can reside on a server computer, while corresponding portions reside on a client computer. Data structures and transmission of data particular to aspects of the present technology are also encompassed within the scope of the present technology. 
     The virtual camera perspective is controlled by an input controller  106  that can update the virtual camera perspective based on user driven changes to the camera&#39;s position and rotation. The output images corresponding to the virtual camera perspective can be outputted to the display device  104 . In some embodiments, the image processing device  103  can vary the perspective, the depth of field (e.g., aperture), the focus plane, and/or another parameter of the virtual camera (e.g., based on an input from the input controller) to generate different 3D output images without physically moving the camera array  110 . The display device  104  can receive output images (e.g., the synthesized 3D rendering of the scene  108 ) and display the output images for viewing by one or more viewers. In some embodiments, the processing device  102  receives and processes inputs from the input controller  106  and processes the captured images from the camera array  110  to generate output images corresponding to the virtual perspective in substantially real-time or near real-time as perceived by a viewer of the display device  104  (e.g., at least as fast as the frame rate of the camera array  110 ). 
     Additionally, the display device  104  can display a graphical representation on/in the image of the virtual perspective of any (i) tracked objects within the scene  108  (e.g., a surgical instrument) and/or (ii) registered or unregistered preoperative image data. That is, for example, the system  100  (e.g., via the display device  104 ) can blend augmented data into the scene  108  by overlaying and aligning information on top of “passthrough” images of the scene  108  captured by the cameras  112 . Moreover, the system  100  can create a mediated reality experience where the scene  108  is reconstructed using light field image date of the scene  108  captured by the cameras  112 , and where instruments are virtually represented in the reconstructed scene via information from the trackers  113 . Additionally or alternatively, the system  100  can remove the original scene  108  and completely replace it with a registered and representative arrangement of the preoperatively captured image data, thereby removing information in the scene  108  that is not pertinent to a user&#39;s task. 
     The display device  104  can comprise, for example, a head-mounted display device, a monitor, a computer display, and/or another display device. In some embodiments, the input controller  106  and the display device  104  are integrated into a head-mounted display device and the input controller  106  comprises a motion sensor that detects position and orientation of the head-mounted display device. In some embodiments, the system  100  can further include a separate tracking system (not shown), such an optical tracking system, for tracking the display device  104 , the instrument  101 , and/or other components within the scene  108 . Such a tracking system can detect a position of the head-mounted display device  104  and input the position to the input controller  106 . The virtual camera perspective can then be derived to correspond to the position and orientation of the head-mounted display device  104  in the same reference frame and at the calculated depth (e.g., as calculated by the depth sensor  114 ) such that the virtual perspective corresponds to a perspective that would be seen by a viewer wearing the head-mounted display device  104 . Thus, in such embodiments the head-mounted display device  104  can provide a real-time rendering of the scene  108  as it would be seen by an observer without the head-mounted display device  104 . Alternatively, the input controller  106  can comprise a user-controlled control device (e.g., a mouse, pointing device, handheld controller, gesture recognition controller) that enables a viewer to manually control the virtual perspective displayed by the display device  104 . 
       FIG.  2    is a perspective view of a surgical environment employing the system  100  for a surgical application in accordance with embodiments of the present technology. In the illustrated embodiment, the camera array  110  is positioned over the scene  108  (e.g., a surgical site) and supported/positioned via a movable arm  222  that is operably coupled to a workstation  224 . In some embodiments, the arm  222  is manually movable to position the camera array  110  while, in other embodiments, the arm  222  is robotically controlled in response to the input controller  106  ( FIG.  1   ) and/or another controller. In the illustrated embodiment, the display device  104  is a head-mounted display device (e.g., a virtual reality headset, augmented reality headset). The workstation  224  can include a computer to control various functions of the processing device  102 , the display device  104 , the input controller  106 , the camera array  110 , and/or other components of the system  100  shown in  FIG.  1   . Accordingly, in some embodiments the processing device  102  and the input controller  106  are each integrated in the workstation  224 . In some embodiments, the workstation  224  includes a secondary display  226  that can display a user interface for performing various configuration functions, a mirrored image of the display on the display device  104 , and/or other useful visual images/indications. In other embodiments, the system  100  can include more or fewer display devices. For example, in addition to the display device  104  and the secondary display  226 , the system  100  can include another display (e.g., a medical grade computer monitor) visible to the user wearing the display device  104 . 
       FIG.  3    is an isometric view of a portion of the system  100  illustrating four of the cameras  112  in accordance with embodiments of the present technology. Other components of the system  100  (e.g., other portions of the camera array  110 , the processing device  102 , etc.) are not shown in  FIG.  3    for the sake of clarity. In the illustrated embodiment, each of the cameras  112  has a field of view  330  and a focal axis  332 . The cameras  112  can be oriented such that the fields of view  330  are aligned with a portion of the scene  108  and at least partially overlap one another to together define an imaging volume. For example, in the illustrated embodiment the fields of view  330  of the cameras  112  converge toward a common measurement volume including a portion of a spine  309  of a patient (e.g., a human patient) located in/at the scene  108 . In some embodiments, the cameras  112  are further oriented such that the focal axes  332  converge to a common point in the scene  108 . In some aspects of the present technology, the convergence/alignment of the focal axes  332  can generally maximize disparity measurements between the cameras  112 . In some embodiments, the cameras  112  are fixedly positioned relative to one another (e.g., rigidly mounted to a common frame) such that a relative positioning of the cameras  112  relative to one another is known and/or can be readily determined via a calibration process. In other embodiments, the system  100  can include a different number of the cameras  112  and/or the cameras  112  can be positioned differently relative to another. 
     II. Selected Embodiments of Generating Stereoscopic Views from a Multicamera Array 
     Referring to  FIGS.  1 - 3   , in some embodiments the system  100  can generate stereoscopic views of the scene  108  from images captured by one or more pairs of the cameras  112  in the camera array  110 . For example, the system  100  can (i) receive an image from a first one of the cameras  112 , (ii) receive an image from a second ones of the cameras  112 , and (iii) display the images on the display device  104  to generate a stereoscopic view of the scene  108 . In some aspects of the present technology, such stereoscopic views can be computationally easier to generate and/or of higher image quality than views generated via computational (e.g., image synthesis) processes, as described in detail above. 
     More specifically,  FIG.  4    is a flow diagram of a process or method  440  for generating stereoscopic views from a multicamera system (e.g., the camera array  110  including the cameras  112 ) in accordance with embodiments of the present technology. Although some features of the method  440  are described in the context of the embodiments shown in  FIGS.  1 - 3    for illustration, one skilled in the art will readily understand that the method  440  can be carried out using other suitable systems and/or devices described herein. 
     At block  441 , the method  440  can include selecting a pair of the cameras  112  (e.g., a stereoscopic pair) in the camera array  110  from which to generate a stereoscopic view. In some embodiments, the selection of the pair of the cameras  112  is dynamic. For example, the system  100  can track the location of the head-mounted display device  104  (e.g., using the trackers  113  and/or an auxiliary tracking system) and select a pair of the cameras  112  that is nearest to the head-mounted display device  104  or that best correspond to a viewpoint of the head-mounted display device  104 . Similarly, the system  100  can track the location of the instrument  101  and select a pair of the cameras  112  that is nearest the instrument  101  or that have a best view of the instrument  101 . In other embodiments, the pair of the cameras  112  can be manually selected by a user. For example, a user can select a pair of the cameras  112  that provide the least obstructed view of an object of interest in the scene  108 . 
     At block  442 , the method  440  can include receiving images (e.g., “source images”) from the selected pair of the cameras  112 . The images can have a first resolution that is relatively high, such as a resolution of greater than 5 megapixels, greater than 9 megapixels, greater than 12 megapixels, greater than 15 megapixels, or greater. In some embodiments, the images can be rectangular having a resolution of, for example 3008 pixels×3008 pixels. 
       FIG.  5    is a schematic illustration of a portion of the system  100  including a selected pair of the cameras  112  (identified individually as a first camera  112   a  and a second camera  112   b ) from the camera array  110  in accordance with embodiments of the present technology. In the illustrated embodiment, the cameras  112   a - b  are separated by a fixed baseline distance B. The baseline distance B can be determined from a process used to manufacture the camera array  110  and/or, during a calibration process for the camera array  110 . The baseline distance B can correspond to a disparity between the source images captured by the cameras  112   a - b  (block  442 ). In some embodiments, the disparity is greater than the interpupillary distance (IPD) of a user (e.g., greater than about 62 millimeters, greater than 50 millimeters, two times greater than the IPD or an average IPD). Accordingly, if the source images were presented to a user via the display device  104 , the relatively large disparity between the images could cause the user to be unable to perceive the source images as a stereoscopic 3D view of the scene  108 . 
     Accordingly, at block  443  the method can include cropping the source images from the selected pair of the cameras  112  based on a known calibration (e.g., including a geometry and/or other extrinsic parameters) of the cameras  112  and a desired disparity (e.g., a horizontal disparity along an axis X in  FIG.  5   ). In some embodiments, the source images are initially aligned vertically (e.g., along an axis Y in  FIG.  5   ) using the known calibration including the baseline distance B. Alternatively or additionally, the source images can be vertically aligned using an optical flow process which can help account for any errors in the calibration. Then, a horizontal disparity between the source images can be calculated based on the calibration of the pair of the cameras  112  and a viewing plane corresponding to the desired disparity. The desired disparity can correspond to an IPD of a particular user or an average IPD (e.g., about 62 millimeters, between about 54-74 millimeters). In some embodiments, the desired disparity can be greater than or less than the IPD of the user or an average IPD based on a desired viewing characteristic for the subsequently generated stereoscopic view, as described in greater detail below. 
     More specifically, as shown in  FIG.  5   , there is some viewing plane P (e.g., a horizontal plane extending along the axis X) at which the focal axes  332  of the cameras  112   a - b  are separated by the desired disparity (identified as desired disparity D) because the focal axes  332  converge. Accordingly, the source images from the cameras  112   a - b  can each be cropped based on the calibration of the cameras  112   a - b  (e.g., the baseline distance B, a distance at which the focal axes  332  converge, and/or other extrinsic parameters) to a cropped region corresponding to the viewing plane P. Therefore, the resulting cropped images of the scene  108  can have the desired disparity. 
       FIG.  6   , for example, is a schematic illustration of a first source image  650   a  received from the first camera  112   a  and a second source image  650   b  received from the second camera  112   b  in accordance with embodiments of the present technology. In the illustrated embodiment, the first source image  650   a  can be cropped to a first cropped region  652   a  corresponding to the viewing plane P ( FIG.  5   ), and the second source image  650   b  can likewise be cropped to a second cropped region  652   b  corresponding to the view plane P. As such, the cropped regions  652   a - b  can provide a view of the scene  108  at the desired disparity. 
     At block  444 , the method  440  can include presenting the cropped images on a display device to generate a stereoscopic view (e.g., three-dimensional (3D) view) of the scene  108 . For example, with reference to  FIG.  6   , the first cropped region  652   a  and the second cropped region  652   b  can be presented on the head-mounted display device  104  and/or another display device to provide the stereoscopic view to the viewer. Because the images are cropped, they have a second resolution less than the first resolution of the cameras  112   a - b  and the corresponding source images  650   a - b . In some embodiments, the display device  104  can have a resolution that matches the resolution of the cropped images, or the cropped images can be scaled (e.g., scaled down) in resolution for display on the display device  104 . 
     In some embodiments, the desired disparity can be selected (block  443 ) to provide a desired viewing characteristic of the stereoscopic view (e.g., to enhance the sense of “depth” in the scene  108 ). For example, the desired disparity can correspond to the IPD of the user or an average IPD such that the stereoscopic view provides a realistic 3D view of the scene  108 . In some embodiments, the desired disparity can be greater than the IPD of the user or an average IPD such that the source images and the cropped images overlap less and the stereoscopic view provides a view of the scene  108  with a greater depth of field—providing the user with a more accurate sense depth. In other embodiments, the desired disparity can be less than the IPD of the user or an average IPD such that the source images and the cropped images overlap more and the stereoscopic view provides a view of the scene  108  with a smaller depth of field—magnifying the depth perceived by the user (e.g., such that objects at different depths vary as shallow changes). 
     After block  444 , the method can return to block  441  and/or block  442 . For example, the method  440  can return to block  441  to select a new pair of the cameras  112 , or can return to block  442  to receive another set of images from the previously-selected pair of the cameras  112 . In some embodiments, the method  440  can operate in real-time or near real-time to continuously receive images from a selected pair of the cameras  112  (block  442 ), crop the images based on a desired disparity ( 443 ), and present the cropped images on the display device  104  to provide a stereoscopic video view. 
     In some embodiments, the system  100  can generate magnified stereoscopic views of the scene  108  from images captured by one or more pairs of the cameras  112  in the camera array  110 . More specifically,  FIG.  7    is a flow diagram of a process or method  760  for generating a magnified stereoscopic view from a multicamera system (e.g., the camera array  110  including the cameras  112 ) in accordance with embodiments of the present technology. Although some features of the method  760  are described in the context of the embodiments shown in  FIGS.  1 - 3    for illustration, one skilled in the art will readily understand that the method  760  can be carried out using other suitable systems and/or devices described herein. 
     At block  761 , the method  760  can include selecting a pair of the cameras  112  in the camera array  110  (e.g., a stereoscopic pair of the cameras  112 ) from which to generate a magnified stereoscopic view. At block  762 , the method  760  can include receiving images (e.g., “source images”) from the selected pair of the cameras  112 . In some embodiments, blocks  761  and  762  of the method  760  can be generally similar or identical to blocks  441  and  442  of the method  440  described in detail above with reference to  FIG.  4   . 
     At block  763 , the method  760  can optionally include scaling up the images received from the pair of the cameras  112  to increase their resolution. The images can be scaled up using an interpolation, super-resolution, and/or other suitable method. In some embodiments, the images are scaled up using a super-resolution method, which can effectively increase resolution while minimizing image artifacts because the images from the cameras  112  at least partially overlap (e.g., due to the overlapping fields of view  330  shown in  FIG.  3   ). 
     At block  764 , the method  760  can include cropping the source images from the selected pair of the cameras  112  based on a known calibration of the cameras  112  and a desired disparity, such as a disparity corresponding to an IPD of the user. In some embodiments, block  764  of the method  760  can be generally similar or identical to block  463  of the method  440  described in detail above with reference to  FIGS.  4 - 6   . 
     At block  765 , the method  760  can include determining a region of interest (e.g., which can also be referred to as a magnification region) in each of the cropped regions of the images.  FIGS.  8 A and  8 B , for example, are schematic illustrations of the first source image  650   a  including the first cropped region  652   a  and the second source image  650   b  including the second cropped region  652   b  in accordance with embodiments of the present technology. In  FIG.  8 A , first regions of interest  854   a  have been selected in the cropped regions  652   a - b . In  FIG.  8 B , different second regions of interest  854   b  have been selected in the cropped regions  652   a - b . Referring to  FIGS.  8 A and  8 B  together, the regions of interest  854   a - b  can have different sizes and/or positions relative to the cropped regions  652   a - b . In some embodiments, the regions of interest  854   a - b  are selected to have the same relative position and size within the cropped regions  652   a - b . For example, in the embodiment illustrated in  FIG.  8 A , the first regions of interest  854   a  each have the same size and are positioned in a lower right corner of the cropped regions  652   a - b . Likewise, in the embodiment illustrated in  FIG.  8 B , the second regions of interest  854   b  each have the same size (smaller than the first regions of interest  854   b ) and are positioned in an upper left portion of the cropped regions  652   a - b . In some aspects of the present technology, selecting the regions of interest to have the same relative size and position relative to the cropped regions of the source images can ensure that a disparity between the selected regions of interest is the same as the disparity between the cropped regions. For example, the cropped regions can be selected to have a disparity generally corresponding to an IPD of the user such that the regions of interest also have a disparity corresponding to the IPD. 
     The size and/or position of the regions of interest can be selected by a user, such as a surgeon or surgical technician, viewing one or more of (i) the cropped regions  652   a - b  and/or (ii) the source images  650   a - b . For example, the user can manually select the rectangular first regions of interest  854   a  based on an object in the source images  650   a - b  to be viewed with greater magnification. In other embodiments, the regions of interest can be automatically selected as a predetermined portion of the cropped regions  652   a - b —such as a center, top left, bottom right, etc., of the cropped regions  652   a - b . In  FIG.  8 A , for example, the first regions of interest  854   a  correspond to a lower right portion of the cropped regions  652   a - b . In other embodiments, the regions of interest can be dynamically selected. For example, the system  100  can track the location of the head-mounted display device  104  (e.g., using the trackers  113  and/or an auxiliary tracking system) to determine a gaze direction of the user, and determine the regions of interest to correspond to the gaze direction of the user. Similarly, the system  100  can track the location of the instrument  101  and/or another instrument and determine the regions of interest to best match the location of the instrument  101 . In yet other embodiments, the regions of interest are determined by tracking the direction of the user&#39;s eyes via, for example, an eye tracker mounted in the head-mounted display device  104 . 
     At block  766 , the method  760  can include further cropping the cropped images to the regions of interest. And, at block  767 , the method  760  can include presenting the regions of interest on a display device to generate a magnified stereoscopic view (e.g., three-dimensional (3D) view) of the scene  108 . For example, with reference to  FIGS.  8 A and  8 B , the first regions of interest  854   a  or the second regions of interest  854   b  can be presented on the head-mounted display device  104  and/or another display device to provide a stereoscopic view to the viewer. Because the images are cropped, they have a second resolution less than the resolution of the cameras  112   a - b  and the corresponding source images  650   a - b . In some embodiments, the display device  104  can have a resolution that matches the resolution of the regions of interest, or the cropped images can be scaled (e.g., scaled down) in resolution for display on the display device  104 . By presenting the regions of interest to the user at a resolution sufficient to match the resolution of the display device  104 , the regions of interest provide a digitally magnified view of the scene  108 . In some embodiments, scaling up the resolution of the source images (block  763 ) can allow for greater magnification by providing a greater difference in resolution between the source images and the display device  104  (and the images to be presented thereon). Additionally, as described in detail above, the disparity between the regions of interest can match the disparity of the cropped images such that magnified view has disparity corresponding to the desired disparity to provide a selected depth of field. 
     After block  767 , the method can return to blocks  761 ,  762 , and/or  765 . For example, the method  760  can return to block  761  to select a new stereoscopic pair of the cameras  112  (e.g., based on a changing view point and/or position of the user), or can return to block  762  to receive another set of images from the previously-select pair of the cameras  112 . In some embodiments, the method  760  can return to block  765  to update the position of the regions of interest in the cropped images. For example, referring to  FIG.  8 B , the position of the second regions of interest  854   b  can be moved (e.g., panned and/or dollied) within the cropped regions  652   a - b  as indicated in phantom lines based on, for example, the tracked position of the head-mounted display device  104 , the tracked position of the instrument  101 , and so on. Therefore, the positioning of the regions of interest can be updated in real-time or near real-time to provide a desired viewpoint to the user. That is, for example, the regions of interest can be panned in the direction of the user&#39;s head motion as the user moves their head within the scene  108 . In some aspects of the present technology, if there is sufficient overlap between the cameras  112 , the method  760  can operate to provide a magnified stereoscopic view of the scene  108  that is continuously updated to match the viewpoint of the head-mounted display device  104  as it moves through the scene  108  by updating (i) the pair of the cameras  112  selected to provide the stereoscopic view and (ii) the position of the regions of interest within the source images received from a selected pair of the cameras  112 . 
     III. Selected Embodiments of Generating Combined Stereoscopic and Reconstructed Three-Dimensional (3D) Views from a Multicamera Array 
     As described in detail above, the system  100  can (i) generate/reconstruct a synthetic view of the scene  108  corresponding to a desired viewpoint by combining image data (e.g., light field image data) from multiple ones of the cameras and (ii) generate stereoscopic views of the scene  108  based on images received from selected pairs of the cameras  112  and cropped to match a desired disparity to provide a desired depth of field. In some embodiments, such synthetic/combined views can be more computationally complex to generate and/or of poorer image quality than such stereoscopic views. However, stereoscopic views can be limited by the positioning of the cameras  112  and their overlap, and the views from any selected pair of the cameras  112  are limited in how they can be viewed (e.g., by panning, dollying, or otherwise moving cropped regions within the source images from the cameras). Moreover, stereoscopic views are not true 3D views as they are perspective locked. 
     Accordingly, in some embodiments the system  100  can merge/combine a 3D reconstructed view of the scene  108  with stereoscopic images from a selected pair of the cameras  112  to provide a merged view that leverages the benefits of both 3D reconstruction and stereoscopic viewing. For example,  FIG.  9    is a flow diagram of a process or method  970  for generating a view of a scene from a multicamera system (e.g., the camera array  110  including the cameras  112 ) in accordance with embodiments of the present technology. Although some features of the method  970  are described in the context of the embodiments shown in  FIGS.  1 - 8 B  for illustration, one skilled in the art will readily understand that the method  970  can be carried out using other suitable systems and/or devices described herein. 
     At block  971 , the method  970  can include reconstructing a 3D view of the scene  108  from a desired viewpoint based on image data from multiple ones of the cameras  112 . For example, as described in detail above, the image processing device  103  can (i) receive first image data captured by the cameras  112  (e.g., light field images, light field image data, RGB images) and depth information from the depth sensor  114 , and (ii) process the image data and the depth information to synthesize (e.g., generate, reconstruct, render) a three-dimensional (3D) view of the scene  108  corresponding to a virtual camera perspective from the desired viewpoint. In some embodiments, the desired viewpoint corresponds to a position and/or orientation of the head-mounted display device  104  within the scene  108 . 
     At block  972 , the method  970  can include generating a stereoscopic view of the scene  108  based on image data from a pair of the cameras  112 . The stereoscopic view can be generated via, for example, the method  440  and/or the method  760  described in detail above with reference to  FIGS.  4 - 8 B . In some embodiments, the stereoscopic view is from at or near the same viewpoint as the reconstructed 3D view of the scene  108 . For example, a pair of the cameras  112  and/or a region of interest within the images from the cameras  112  can be selected based on the position of the head-mounted display device  104  within the scene  108 . 
     At block  973 , the method can include combining the reconstructed 3D view of the scene  108  (block  971 ) and the stereoscopic view of the scene  108  (block  972 ) to generate an output image of the scene  108 . In some embodiments, the stereoscopic view images can be inserted into the 3D view as inserts. For example, each stereoscopic view image can be shown in its own panel (e.g., in a picture-in-picture manner) in the 3D reconstructed view. In some embodiments, the stereoscopic view images can be toggled (e.g., by a user) to selectively replace the 3D reconstructed view. In some embodiments, the stereoscopic view images can be projected onto the 3D topology of the 3D reconstructed view. In some such embodiments, constraints can be set for the motion of the head-mounted display device  104  to reduce motion artifacts in the combined output image. 
     At block  974 , the method  970  can present the output image on the display device  104 . In some embodiments, the method  970  can return to block  971  to continuously update the 3D reconstructed view, the stereoscopic view, and/or the combination thereof to provide a real-time or near real-time video view of the scene  108 . 
     IV. Additional Examples 
     The following examples are illustrative of several embodiments of the present technology: 
     1. A method for generating a stereoscopic view of a scene, the method comprising:
         selecting a pair of cameras from a plurality of cameras from which to generate the stereoscopic view;   receiving images of the scene from the pair of the cameras;   cropping the images based on a known calibration of the cameras and a desired disparity; and displaying the cropped images on a display device to generate the stereoscopic view.       

     2. The method of example 1 wherein the display device is a head-mounted display device, and wherein selecting the pair of the cameras includes selecting the pair of the cameras based on a position of the head-mounted display device within the scene. 
     3. The method of example 2 wherein the method further comprises tracking the position of the head-mounted display device within the scene. 
     4. The method of any one of examples 1-3 wherein the desired disparity corresponds to an interpupillary distance of a user. 
     5. The method of any one of examples 1˜4 wherein the desired disparity is between about between about 54-74 millimeters. 
     6. The method of any one of examples 1-5 wherein the images received from the pair of the cameras have a higher resolution than a resolution of the display device. 
     7. The method of any one of examples 1-6 wherein the cameras are mounted to a common frame. 
     8. The method of example 7 wherein the known calibration includes a relative position and orientation of the cameras relative to one another. 
     9. The method of example 7 or example 8 wherein the cameras each include a focal axis, and wherein the focal axes of the cameras converge. 
     10. The method of any one of examples 7-9 wherein the plurality of cameras includes four or more cameras. 
     11. A method of generating a magnified stereoscopic view of a scene, the method comprising:
         selecting a pair of cameras from a plurality of cameras from which to generate the stereoscopic view;   receiving images of the scene from the pair of the cameras;   cropping the images based on a known calibration of the cameras and a desired disparity;   determining a region of interest in the cropped images;   cropping each of the cropped images to the region of interest; and   displaying the regions of interest on a display device to generate the magnified stereoscopic view.       

     12. The method of example 11 wherein the display device is a head-mounted display device, and wherein determining the region of interest in the cropped includes determining the region of interest based on the position of the head-mounted display device within the scene. 
     13. The method of example 11 or example 12 wherein the desired disparity corresponds to an interpupillary distance of a user. 
     14. The method of any one of examples 11-13 wherein the method further comprises scaling up a resolution of the images received from the pair of the cameras. 
     15. The method of any one of examples 11-14 wherein scaling up the resolution of the images includes scaling up the resolution using a super-resolution process. 
     16. The method of any one of examples 11-15 wherein the known calibration includes a relative position and orientation of the cameras relative to one another, wherein the plurality of cameras includes four or more cameras, wherein the cameras each include a focal axis, and wherein the focal axes of the cameras converge. 
     17. The method of example 16 wherein the desired disparity corresponds to an interpupillary distance of a user. 
     18. A method of generating a view of a scene, the method comprising:
         receiving image data from a plurality of cameras;   reconstructing a three-dimensional (3D) view of the scene from a desired viewpoint based on the image data;   selecting a pair of the cameras;   receiving images from the selected pair of the cameras;   generating a stereoscopic view of the scene based on the received images;   combining the 3D view of the scene and the stereoscopic view of the scene to generate an output image of the scene; and   displaying the output image on a display device.       

     19. The method of example 18 wherein the display device is a head-mounted display device, wherein the viewpoint is from a position and orientation of the head-mounted display device within the scene, and wherein selecting the pair of the cameras is based on the position of the head-mounted display device within the scene. 
     20. The method of example 18 or example 19 wherein the method further comprises cropping the images received from the selected pair of the cameras based on a known calibration of the cameras and a desired disparity, wherein the desired disparity corresponds to an interpupillary distance of a user, and wherein generating the stereoscopic view of the scene is based on the cropped images. 
     V. CONCLUSION 
     The above detailed description of embodiments of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology as those skilled in the relevant art will recognize. For example, although steps are presented in a given order, alternative embodiments may perform steps in a different order. The various embodiments described herein may also be combined to provide further embodiments. 
     From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the technology. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. 
     Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term “comprising” is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. It will also be appreciated that specific embodiments have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Further, while advantages associated with some embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein.