Patent Publication Number: US-2021168343-A1

Title: Control method for projector and projector

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-215066, filed Nov. 28, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a control method for a projector and the projector. 
     2. Related Art 
     JP-A-2008-250242 (Patent Literature 1) discloses a projector that detects the distance to an object with an object detection sensor and reduces the luminance of irradiated light when the detected distance is equal to or smaller than a shortest focal distance. 
     However, in the technique described in Patent Literature 1, it is likely that visibility of an image is unnecessarily deteriorated because the illuminance of the irradiate light is uniformly reduced irrespective of a type of the object when the distance to the object is equal to or smaller  than the shortest focal distance. 
     SUMMARY 
     An aspect is directed to a control method for a projector, including: projecting an image onto a projection surface; acquiring image data from an image sensor having a visual field including the image; specifying, based on the image data, a type of an object included in the visual field; determining, according to the type, a region where the object overlaps the image in the image data; and selectively reducing luminance of the image in a range corresponding to the region. 
     Another aspect is directed to a projector including: a projection device configured to project an image onto a projection surface; an image sensor having a visual field including the image; a type specifying section configured to specify, based on image data acquired from the image sensor, a type of an object included in the visual field; a region determining section configured to determine, according to the type, a region where the object overlaps the image in the image data; and a control section configured to control the projection device to selectively reduce luminance of the image in a range corresponding to the region.  
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram for explaining a projector according to an embodiment. 
         FIG. 2  is a block diagram for explaining a basic configuration of the projector according to the embodiment. 
         FIG. 3  is a diagram for explaining processing for detecting an object region. 
         FIG. 4  is a diagram for explaining processing for determining a superimposition region. 
         FIG. 5  is a diagram for explaining processing for specifying types of a plurality of objects. 
         FIG. 6  is a diagram for explaining processing for specifying a face as a type of an object. 
         FIG. 7  is a diagram for explaining processing for specifying eyes as a type of an object. 
         FIG. 8  is a flowchart for explaining the operation of the projector according to the embodiment. 
         FIG. 9  is a block diagram for explaining a basic configuration of a projector according to another embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An embodiment of the present disclosure is explained below with reference to the drawings. As shown in  FIG. 1 , a  projector  10  according to the embodiment includes a projection device  20  that projects an image P onto a projection surface C, an image sensor  30  having a visual field F including the image P, and a control circuit  40  that controls each of the projection device  20  and the image sensor  30 . As the projection surface C, for example, various screens such as a roll screen, a whiteboard, and a wail surface can be adopted. In an example shown in  FIG. 1 , an object Q, which is a human, is located in a projection range of the image P. 
     The projection device  20  includes, for example, a light source such as a discharge lamp or a solid-state light source, a display element such as a liquid crystal light valve including a plurality of pixels, and an optical system including a mirror and a lens. The display element modulates, according to the control by the control circuit  40 , light emitted from the light source. The projection device  20  projects the light modulated by the display element onto the projection surface C as the image P using the optical system. Besides, as a scheme of the projection device  20 , a scheme for using a mirror device that scans the projection surface C with the modulated light and a scheme for using a digital micro mirror device that controls reflection of the light in each of the pixels can be adopted. 
     The image sensor  30  includes a solid-state imaging element and an optical system that introduces light in the visual field F into the solid-state imaging element. That is, the position and the orientation of the image sensor  30  are adjusted such that a projection range of the image P is included in the visual field F. More specifically, the visual field F is determined as a range wider than the image P on the projection surface C. Accordingly, the position and the orientation of the image sensor  30  with respect to the projection device  20  can be easily adjusted. The image sensor  30  successively generates image data representing an image corresponding to the visual field F with the solid-state imaging element and outputs the image data to the control circuit  40 . In the example shown in  FIG. 1 , the projection device  20 , the image sensor  30 , and the control circuit  40  are disposed on the inner side of a housing  11  of the projector  10 . However, for example, the image sensor  30  may be disposed on the outer side of the housing  11 . 
     As shown in  FIG. 2 , the projector  10  further includes an interface (I/F)  12  and an image processing circuit  15 . For example, a video signal is input to the I/F  12  from an external device  50  via a communication link between the I/F  12  and the external device  50 . The external device  50  is any device having a function of outputting a video signal to the projector  10 . The communication link between the I/F  12  and the external device   50  may be either a wired communication link or a wireless communication link and may be a combination of the wired and. wireless communication links. The I/F  12  can include, for example, an antenna that transmits and receives radio signals, a receptacle into which a plug for a communication cable is inserted, and a communication circuit that processes a signal transmitted in the communication link. 
     The image processing circuit  15  generates, according to the control by the control circuit  40 , an image signal representing the image P projected from the projection surface C. Specifically, the image processing circuit  15  generates an image signal based on a video signal input to the I/F  12  from the external device  50  and outputs the image signal to the projection device  20 . The image processing circuit  15  may generate, based on computer graphics generated by a control program of the control circuit  40 , the image signal representing the image P. The image processing circuit  15  outputs successively generated image signals to the projection device  20 . The image processing, circuit  15  includes a rendering, engine and a graphics memory. The image processing circuit  15  may function as a circuit configuring a part of the control circuit  40 . 
     The control circuit  40  includes a type specifying  section  41 , a region determining section  42 , a control section  43 , and a storing section  44  as logical structure. The control circuit  40  is configured by, for example, a single or a plurality of processors. As an example, the control circuit  40  is configured by a single or a plurality of central processing units (CPUs). A part or all of functions of the control circuit  40  may be configured by a circuit such as a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The control circuit  40  configures a computer system that processes an arithmetic operation necessary for the operation of the projector  10 . For example, the control circuit  40  executes a preinstalled control program to thereby realize functions described in the embodiment besides the type specifying section  41 , the region determining section  42 , the control section  43 , and the storing section  44 . 
     The storing section  44  is, for example, a computer-readable storage medium that stores a control program, various data, and the like necessary for the operation of the control circuit  40 . The storing section  44  includes, for example, a semiconductor memory. The storing section  44  can include a nonvolatile auxiliary storage device, a volatile main storage device such as a register or a cash memory incorporated in the  CPU. The control circuit  40  may be configured from integral hardware or may be configured from a separate plurality of kinds of hardware. 
     As shown in  FIG. 3 , the type specifying section  41  successively specifies, based on image data acquired from the image sensor  30 , a type of the object Q included in the visual field F. For example, the type specifying section  41  specifies a type of the object Q using a learned model generated by machine learning. As the learned model, various object detection algorithms such as an SSD (Single Shot MultiBox Detector) and a YOLO (You Only Look Once) can be adopted. The type of the object Q specified by the type specifying section  41  is at least one type selected out of, for example, a human, a part of the body of the human, an animal, and a vehicle. The type specifying section  41  can highly accurately specify a type of the object Q by using the learned model. By changing the learned model, the type specifying section  41  can select a type of the object Q to be specified. 
     In an example shown in  FIG. 3 , the type specifying section  41  specifies a type of the object Q present outside the image P in image data of the visual field F as a human and successively detects an object region PR, which is a region where the object Q is present in the image data. The object region  PR is detected as a region corresponding to the position and the size of the object Q in the image data. The object region PR is, for example, a rectangular region occupied by the object Q in the image data. The type specifying section  41  racks the object Q in the image data to thereby cause the object region PR to follow the object Q. By selectively specifying a type of the object Q present outside the image P the image data and tracking the object Q, it is easy to distinguish an actual object Q present in the visual field a from an object projected as the image P. 
     As shown in  FIG. 4 , the region determining section  42  successively determines, according to the type of the object Q specified by the type specifying section  41 , a superimposition region R, which is a region where the object Q overlaps the image P in the image data. The superimposition region R is, for example, a rectangular region occupied by the object Q in the image P in the image data A region of the image P in the image data can be defined advance by a projection range or the like by the projection device  20 . Accordingly, the image P does not need to be actually projected at a point in time when the region determining section  42  determines the superimposition region R. Alternatively, the region determining section  42  may recognize the region of the image P in the image data based on a pattern  image projected by the projection device  20 . The region determining section  42  calculates a region where the object region PR overlaps the image P in the image data and determines the region as the superimposition region R. 
     The control section  43  indirectly controls the projection device  20  via the image processing circuit  15  to selectively reduce the luminance of the image P in a range corresponding to the superimposition region R. Specifically, the control section  43  converts the superimposition region R in the image data into a corresponding region in an image signal and outputs the image signal to the image processing circuit  15 . For example, the image processing circuit  15  changes a color tone of the corresponding region with respect to an image signal generated based on a video signal of the external device  50  and then outputs the image signal to the projection device  20 . The projection device  20  projects the image P onto the projection surface C according to the image signal input from the image processing circuit  15 . Consequently, the control section  43  selectively reduces the intensity of light projected by the projection device  20  in a range corresponding to the object Q of a predetermined type. Therefore, it is possible to suppress visibility of the image P from being unnecessarily deteriorated. 
     As shown in  FIG. 5 , the type specifying section  41  may  specify a type of each of a plurality of objects Q 1  and Q 2  included in the visual field F. In an example shown in  FIG. 5 , the type specifying section  41  specifies types of two objects Q 1  and Q 2  respectively as humans based on image data corresponding to the visual field F. The region determining section  42  determines a superimposition region R 1  where the object Q 1  overlaps the image P in the image data and a super imposition region R 2  where the object Q 2  overlaps the image P in the image data. The control section  43  controls the projection device  20  to selectively reduce the luminance of the image P in regions corresponding to the two superimposition regions R 1  and R 2 . 
     As shown in  FIG. 6 , the type specifying section  41  may specify a face of a human as a type of an object Q 3  in image data. In this case, as the learned model of the type specifying section  41 , face recognition algorithms such as DenseBox and UnitBox can be adopted. The region determining section  42  determines a super imposition region R 3 , which is a region where a rectangular region occupied by the face of the human overlaps the image P in the image data. The control section  43  controls the projection device  20  to selectively reduce the luminance of the image P in a range corresponding to the superimposition region R 3 . 
     Alternatively, as shown in  FIG. 7 , the type specifying  section  41  may specify eyes of a human as a type of an object Q 4  in image data. For example, the type specifying section  41  detects an object region including the eyes of the human in the image data. The region determining section  42  determine a super imposition region R 4  where the object region overlaps the image P in the image data. The control section  43  controls the projection device  20  to selectively reduce the luminance of the image P in a range corresponding to the superimposition region R 4 . Consequently, a range in which the luminance of the image P is reduced on the projection surface C can be further limited. Therefore, it is possible to further suppress deterioration in the visibility of the image P. Since the type specifying section  41  specifies the face or the eyes of the human as the type of the object Q, it is possible to suppress glare from being given to a human located between the projection device  20  and the projection surface C. 
     An example of the operation of the projector  10  is explained below as a control method for the projector  10  according to the embodiment with reference to a flowchart of  FIG. 8 . For example, the projector  10  acquires a video signal from the external device  50  to thereby project the image P onto the projection surface C. A series of processing shown in  FIG. 8  is repeatedly executed at a predetermined sampling period.  
     In step S 1 , the type specifying section  41  acquires image data of the visual field F from the image sensor  30  having the visual field F. In step S 2 , the type specifying section  41  specifies, based on the image data acquired in step S 1 , a type of the object Q present in the field F. The type specifying section  41  detects the object region PR, which is a region where the object Q is present in the image data. In step S 3 , the type specifying section  41  determines whether the type of the object Q specified in step S 2  is a predetermined type, that is, whether the object Q of the predetermined type is detected in the image data. The predetermined type is at least one type selected out of, for example, a human, a part of the body of the human, an animal, and a vehicle, when the type of the object Q is the predetermined type, the type specifying section  41  advances the processing to step S 4 . When the type of the object Q is not the predetermined type, the type specifying section  41  advances the processing to step S 6 . 
     In step S 4 , the region determining section  42  determines, according to the type of the object Q specified in step S 2 , the superimposition region R where the object region PR overlaps the image P in the image data. In step S 5 , the control section  43  controls the projection device  20  via the image processing circuit  15  to selectively reduce the luminance of the  image P in a range corresponding to the superimposition region R determined in step S 4 . That is, the image processing circuit  15  changes, according to the control by the control section  43 , an image signal such that the luminance of the image P in the range corresponding to the superimposition region R is selectively reduced and outputs the image signal to the projection device  20 . In step S 6 , the projection device  20  projects the image P onto the projection surface C according to the image signal input from the image processing circuit  15 . Consequently, the luminance of the image P on the projection surface C is selectively reduced in the range corresponding to the superimposition region R, that is, the region where the object Q is present. 
     With the projector  10  according to the embodiment, the projection device  20  is controlled according to the type of the object Q to selectively reduce the luminance of the image P in the range corresponding to the object Q. Therefore, it is possible to suppress visibility of the image P from being unnecessarily deteriorated. 
     The embodiment is explained above. However, the present disclosure is not limited to the disclosure of the embodiment. The components of the sections may be replaced with any components having the same functions. Any components in the  embodiment may be omitted or added within the technical scope of the present disclosure. In this way, various alternative embodiments are made clear for those skilled in the art from the disclosure of the embodiment. 
     For example, in the embodiment explained above, the type specifying section  41  may update the learned model with information acquired from the outside of the projector  10 . In this case, the control circuit  40  can include a programmable logic device (PLD) such as a field programmable gate array (FPGA) When the type specifying section  41  is realized by the PLD, the storing section  44  can function as a memory element such as a memory block included in a part of a logical block configuring the PLD. The PLD may have a configuration in which software processing and hardware processing are mixed. 
     For example, as shown in  FIG. 9 , the I/F  12  establishes a communication link between the I/F  12  and an external server  60  via a network  10  such as the Internet and acquires information for updating the learned model of the type specifying section  41 . The control circuit  40  updates the learned model of the type specifying section  41  with the information acquired from the server  60  via the network  70 . Consequently, the type specifying section  41  is capable of, for example, changing the learned model according to a use and using the latest learned model. The  control section  43  may change, according to a type of the object Q, a degree of reducing the luminance of the image P. 
     Besides, it goes without saying that the present disclosure includes various embodiments not described above such as a configuration in which the components described above are applied to one another. The technical scope of the present disclosure is decided only by the matters to define the invention relating the claims reasonable from the above explanation.