Patent Publication Number: US-2020296306-A1

Title: Imaging apparatus and moveable body

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to and the benefit of Japanese Patent Application No. 2017-187197 filed Sep. 27, 2017, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an imaging apparatus and a moveable body. 
     BACKGROUND 
     A technique for mounting a complementary metal oxide semiconductor (CMOS) image sensor in a vehicle and capturing images of the outside of the vehicle during driving is known. For example, see patent literature (PTL) 1. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP2002-209173A 
     SUMMARY 
     An imaging apparatus according to an embodiment of the present disclosure includes an imaging optical system and an image sensor to be mounted in a moveable body that moves along a movement surface. The imaging optical system is configured to form an image of a subject located around the moveable body. The image sensor includes an imaging surface having pixels arranged thereon, the pixels capturing the image of the subject formed by the imaging optical system. The pixels belong to pixel groups, each pixel group including pixels arranged in a first direction that intersects the movement surface. The pixel groups are arranged in a second direction intersecting the first direction. The image sensor is configured to read imaging data of the image from each pixel group in order of arrangement of the pixel groups in the second direction. 
     A moveable body according to an embodiment of the present disclosure moves along a movement surface. The moveable body includes an imaging apparatus mounted thereon. The imaging apparatus includes an imaging optical system and an image sensor. The imaging optical system is configured to form an image of a subject located around the moveable body. The image sensor includes an imaging surface having pixels arranged thereon, the pixels capturing the image of the subject formed by the imaging optical system. The pixels belong to pixel groups, each pixel group including pixels arranged in a first direction that intersects the movement surface. The pixel groups are arranged in a second direction intersecting the first direction. The image sensor is configured to read imaging data of the image of the subject from each pixel group in order of arrangement of the pixel groups in the second direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a block diagram illustrating an example configuration of an imaging apparatus according to an embodiment; 
         FIG. 2  is a plan view illustrating an example arrangement of pixels on an imaging surface; 
         FIG. 3  is a plan view illustrating an example arrangement of pixels on an imaging surface; 
         FIG. 4  is a plan view illustrating an example arrangement of pixels on an imaging surface; 
         FIG. 5A  illustrates an example of the relationship between movement of an object and readout pixels; 
         FIG. 5B  illustrates an example of the relationship between movement of an object and readout pixels; 
         FIG. 5C  illustrates an example of the relationship between movement of an object and readout pixels; 
         FIG. 6A  illustrates a captured image based on imaging data read in the example in  FIG. 5A ; 
         FIG. 6B  illustrates a captured image based on imaging data read in the example in  FIG. 5B ; 
         FIG. 6C  illustrates a captured image based on imaging data read in the example in  FIG. 5C ; 
         FIG. 7A  illustrates an example of the relationship between movement of an object and readout pixels; 
         FIG. 7B  illustrates an example of the relationship between movement of an object and readout pixels; 
         FIG. 7C  illustrates an example of the relationship between movement of an object and readout pixels; 
         FIG. 8A  illustrates a captured image based on imaging data read in the example in  FIG. 7A ; 
         FIG. 8B  illustrates a captured image based on imaging data read in the example in  FIG. 7B ; 
         FIG. 8C  illustrates a captured image based on imaging data read in the example in  FIG. 7C ; 
         FIG. 9  is a side view illustrating an example configuration of a moveable body with an on-board camera; 
         FIG. 10  illustrates an example configuration of the interior of a moveable body with an on-board camera; 
         FIG. 11  illustrates an example of a captured image when a first direction intersects a movement surface; 
         FIG. 12  illustrates an example of a captured image when the first direction is parallel to the movement surface; 
         FIG. 13  illustrates an example of the positional relationship between the moveable body and subjects; 
         FIG. 14A  illustrates an example image yielded by capturing an image of the subjects in  FIG. 13 ; 
         FIG. 14B  illustrates an example image yielded by capturing an image of the subjects in  FIG. 13 ; 
         FIG. 14C  illustrates an example image yielded by capturing an image of the subjects in  FIG. 13 ; and 
         FIG. 15  is a plan view illustrating an example configuration of an imaging apparatus according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     When a complementary metal oxide semiconductor (CMOS) captures an image of a moving body, focal plane distortion may occur, diagonally distorting the shape of the object in the captured image. For example, when a CMOS image sensor is mounted in a vehicle and used as an electronic mirror, the distortion of the shape of an object appearing in the image may cause the person driving the vehicle to misidentify the object. 
     The frame rate of imaging by the CMOS image sensor may be raised to reduce the focal plane distortion. This may lead to problems, however, such as increased power consumption or reduced image brightness due to insufficient exposure time. 
     The image captured by the CMOS image sensor may be corrected to reduce focal plane distortion. This may lead to problems, however, such as enlargement of the image processing circuitry or increased power consumption in the image processing circuitry. 
     A charge coupled device (CCD) may be used to reduce focal plane distortion. CMOS image sensors are mainly used, however, as image sensors mounted in automobiles. It is not realistic to use CCDs for only some image sensors. 
     A global shutter function may be used to reduce focal plane distortion, but this may cause problems such as increased costs and an increase in the area occupied by parts. 
     Various problems thus occur when the above-described methods are adopted to reduce focal plane distortion. As described below, an imaging apparatus  1  according to the present embodiment can reduce focal plane distortion of a captured image without incurring the above-described problems. 
     As illustrated in  FIG. 1 , an imaging apparatus  1  according to an embodiment includes a processor  10 , a storage  12 , and a camera  20 . The imaging apparatus  1  connects to a display  30 . The camera  20  includes an image sensor  22  and an imaging optical system  24 . The imaging optical system  24  may include optical elements such as a lens or mirror. The camera  20  uses the image sensor  22  to capture a subject image formed by the imaging optical system  24 . The image captured by the camera  20  is also referred to as a captured image. The image sensor  22  may be a device, such as a CMOS image sensor, in which focal plane distortion may, in principle, occur. 
     The processor  10  outputs control information to the camera  20  and acquires a captured image from the camera  20 . The processor  10  may output the captured image to the display  30  and cause the display  30  to display the captured image. 
     The processor  10  may execute general processing in accordance with a program or may execute specific processing. The processor  10  may include an application specific integrated circuit (ASIC). The processor  10  may include a programmable logic device (PLD). The PLD may include a field-programmable gate array (FPGA). The processor  10  may be either a system-on-a-chip (SoC) or a system in a package (SiP) with one or a plurality of ICs, devices, or the like that work together. 
     The storage  12  may store various information or parameters related to operation of the imaging apparatus  1 . The storage  12  may store programs executed by the processor  10 . The storage  12  may, for example, be a semiconductor memory. The storage  12  may function as a working memory of the processor  10 . The storage  12  may store captured images. The storage  12  may be included in the processor  10 . 
     The display  30  may display captured images acquired from the processor  10 . The display  30  may, for example, include a liquid crystal, organic electro-luminescence (EL), inorganic EL, or light emission diode (LED) display device. 
     The processor  10 , camera  20 , and display  30  may include a communication device for communicating with each other. The communication device may, for example, be a communication interface for a local area network (LAN), control area network (CAN), or the like. The communication device may communicate in a wired or wireless manner. 
     As illustrated in  FIG. 2 , the image sensor  22  includes an imaging surface  23  on which a plurality of pixel cells  26  are arranged. The subject image is an image formed on the imaging surface  23  by the imaging optical system  24 . The image sensor  22  receives light of the subject image on each pixel cell  26  and generates a captured image based on a voltage or current signal outputted by each pixel cell  26 . The voltage or current signal outputted by each pixel cell  26  is also referred to as imaging data. The pixel cells  26  may be arranged on the imaging surface  23  in a first direction indicated by u and a second direction indicated by v. The first direction is from top to bottom but may instead be a different direction. The second direction is from left to right but may instead be a different direction. The first direction and the second direction intersect each other. The first direction and the second direction may be orthogonal. A vector representing the second direction can be considered at least to have a component orthogonal to the first direction. 
     The image sensor  22  may include pixel groups  28  each having a plurality of pixel cells  26  as elements. The pixel group  28  may include pixel cells  26  arranged in the first direction as elements. In other words, a set of pixel cells  26  arranged in the first direction may belong to a pixel group  28 . The pixel group  28  may include pixel cells  26  arranged in a straight line along the first direction. The pixel group  28  may include one column of pixel cells  26  as elements or two or more columns of pixel cells  26  as elements. 
     As illustrated in  FIG. 3 , for example, the pixel cells  26  may be arranged on the imaging surface  23  along the first direction while being shifted in the second direction. The pixel group  28  may include pixel cells  26  arranged in the first direction and shifted by a predetermined distance or less in the second direction. The predetermined distance may be a value equal or close to the length of a pixel cell  26  in the second direction or may be another value. 
     The pixel groups  28  each including pixel cells  26  arranged in the first direction are arranged in the second direction. Even when the second direction is not orthogonal to the first direction, at least a portion of the pixel cells  26  in the pixel groups  28  are arranged in a direction orthogonal to the first direction. The pixel cells  26  arranged in a direction orthogonal to the first direction may be in a straight line or may be shifted in the first direction. At least a portion of the pixel cells  26  belonging to a pixel group  28  may, when viewed in a direction orthogonal to the first direction, overlap with the pixel cells  26  belonging to at least one other pixel group  28 . 
     For example, as illustrated in  FIG. 4 , the pixel cells  26  included in the pixel groups  28  arranged in the second direction may be shifted in the first direction. In other words, the pixel cells  26  included in the pixel groups  28  arranged in the second direction need not be aligned directly in the second direction. 
     The image sensor  22  reads the imaging data of each pixel group  28  in order of arrangement in the second direction. Even when the second direction is not orthogonal to the first direction, the image sensor  22  can be considered to read imaging data from at least a portion of the pixel cells  26  of the pixel groups  28  in order in a direction orthogonal to the first direction. The image sensor  22  may read imaging data from each pixel cell  26  in order of arrangement in the first direction within the pixel group  28 . After reading the imaging data from each pixel cell  26  in the pixel group  28 , the image sensor  22  may start to read from the next pixel group  28 . The image sensor  22  may be a device such as a CMOS image sensor that reads imaging data in each group of pixel cells  26  arranged in a column. The image sensor  22  is not limited to being a CMOS image sensor and may be another device that reads imaging data from the pixel groups  28  in the order of arrangement in the second direction. 
     The pixel groups  28  may be identified by hardware or by software. Based on control information from the processor  10 , the image sensor  22  may change the first direction to a different orientation by software. In other words, the image sensor  22  may change the combinations of pixel cells  26  included in the pixel groups  28 . The image sensor  22  may change the second direction to a different orientation by software. 
     If the image sensor  22  reads the imaging data at once from all of the pixel cells  26 , as with a CCD, then the subject image  210  in the captured image is unlikely to be distorted, even if the subject image  210  is moving (see  FIG. 5A  and the like). When imaging data is read in order from a portion of the pixel cells  26 , as with a CMOS image sensor, the subject image  210  in the captured image may be distorted if the subject image  210  moves while the imaging data is being read. 
     For example, when the first direction indicated by u is the direction from top to bottom, and the second direction indicated by v is the direction from left to right, as illustrated in  FIGS. 5A, 5B, and 5C , then the imaging apparatus  1  can capture the subject image  210  moving in the second direction together with the passage of time.  FIGS. 5A, 5B, and 5C  respectively illustrate the pixel cells  26  in which the subject image  210  is formed at times represented by T 1 , T 2 , and T 3 . The pixel group  28  from which imaging data is read at each time is illustrated in  FIGS. 5A, 5B, and 5C . The pixel group  28  includes six pixel cells  26  arranged in the first direction.  FIGS. 6A, 6B, and 6C  represent the captured image generated based on the imaging data read at each time illustrated in  FIGS. 5A, 5B, and 5C  respectively. 
     As illustrated in  FIG. 5A , the subject image  210  at time T 1  is formed on the pixel cells  26  in the third column to the fourth column from the left. The pixel group  28  from which imaging data is read at time T 1  is the group in the third column from the left. Among the pixel cells  26  included in the pixel group  28  from which imaging data is read, the subject image  210  is formed in the third to the fifth pixel cells  26  from the top. Consequently, the subject image  210  appears in the third column from the left of the captured image, in the third to the fifth pixels from the top, as illustrated in  FIG. 6A . 
     As illustrated in  FIG. 5B , the subject image  210  at time T 2  is formed on the pixel cells  26  in the right half of the third column to the left half of the fifth column from the left. The pixel group  28  from which imaging data is read at time T 2  is the group in the fourth column from the left. Among the pixel cells  26  included in the pixel group  28  from which imaging data is read, the subject image  210  is formed in the third to the fifth pixel cells  26  from the top. Consequently, the subject image  210  further appears in the fourth column from the left of the captured image, in the third to the fifth pixels from the top, as illustrated in  FIG. 6B . 
     As illustrated in  FIG. 5C , the subject image  210  at time T 3  is formed on the pixel cells  26  in the fourth column to the fifth column from the left. The pixel group  28  from which imaging data is read at time T 3  is the group in the fifth column from the left. Among the pixel cells  26  included in the pixel group  28  from which imaging data is read, the subject image  210  is formed in the third to the fifth pixel cells  26  from the top. Consequently, the subject image  210  further appears in the fifth column from the left of the captured image, in the third to the fifth pixels from the top, as illustrated in  FIG. 6C . 
     The size, in the left-right direction, of the subject image  210  appearing in the captured image corresponds to the size of three pixels, as illustrated in  FIG. 6C . On the other hand, the actual size of the subject image  210  in the left-right direction corresponds to the size of two pixels, as illustrated in FIGS.  5 A,  5 B, and  5 C. That is, as a result of the subject image  210  moving in the second direction while the imaging data is being read in order in the second direction, the shape of the subject image  210  appearing in the captured image may be expanded in the left-right direction as compared to the actual shape of the subject image  210 . 
     If the imaging apparatus  1  captures a subject image  210  moving in the opposite direction from the second direction as time passes in the example illustrated in  FIGS. 5A, 5B, 5C  and  FIGS. 6A, 6B, 6C , the shape of the subject image  210  appearing in the captured image may be smaller in the left-right direction than the actual shape of the subject image  210 . In other words, when the imaging apparatus  1  captures a subject image  210  moving in the same direction as the second direction or in the opposite direction, the shape of the subject image  210  appearing in the captured image may be deformed in the left-right direction at a predetermined magnification as compared to the actual shape of the subject image  210 . The predetermined magnification may be greater than or less than one. 
     The pixel cells  26  are arranged in a 6 by 6 grid in the example illustrated in  FIGS. 5A, 5B, 5C  and  FIGS. 6A, 6B, 6C , but this arrangement is not limiting. The pixel cells  26  may be arranged in any number of rows or columns or in a diagonal grid. The pixel cells  26  may be arranged without being aligned in rows or columns. The pixel cells  26  may be arranged in various ways. 
     As a comparative example differing from the example in  FIGS. 5A, 5B, 5C  and  FIGS. 6A, 6B, 6C , the imaging apparatus  1  may capture a subject image  210  moving in the first direction as time passes, as illustrated in  FIGS. 7A, 7B, and 7C . The first direction in  FIGS. 7A, 7B, and 7C  is the direction from left to right, which differs from the first direction in  FIGS. 5A, 5B, and 5C . The second direction is the direction from top to bottom.  FIGS. 7A, 7B , and  7 C respectively illustrate the pixel cells  26  in which the subject image  210  is formed at times represented by T 1 , T 2 , and T 3  and the pixel group  28  from which imaging data is read. The pixel group  28  includes six pixel cells  26  arranged in the first direction.  FIGS. 8A, 8B, and 8C  represent the captured image generated by the imaging data read from the pixel group  28  illustrated in  FIGS. 7A, 7B, and 7C  respectively. 
     As illustrated in  FIG. 7A , the subject image  210  at time T 1  is formed on the pixel cells  26  that are in the third column to the fourth column from the left and the third row to the fifth row from the top. The pixel group  28  from which imaging data is read at time T 1  is the group in the third row from the top. Among the pixel cells  26  included in the pixel group  28  from which imaging data is read, the subject image  210  is formed in the third and the fourth pixel cells  26  from the left. Consequently, the subject image  210  appears in the pixels that are in the third row from the top and the third and fourth columns from the left in the captured image, as illustrated in  FIG. 8A . 
     As illustrated in  FIG. 7B , the subject image  210  at time T 2  is formed on the pixel cells  26  that are in the right half of the third column to the left half of the fifth column from the left and the third row to the fifth row from the top. The pixel group  28  from which imaging data is read at time T 2  is the group in the fourth row from the top. Among the pixel cells  26  included in the pixel group  28  from which imaging data is read, the subject image  210  is formed in the right half of the pixel cells  26  in the third column, the pixel cells  26  in the fourth column, and the left half of the pixel cells  26  in the fifth column from the left. Consequently, the subject image  210  further appears in the fourth row from the top of the captured image, in the right half of the pixel in the third column, the pixel in the fourth column, and the left half of the pixel in the fifth column from the left, as illustrated in  FIG. 8B . 
     As illustrated in  FIG. 7C , the subject image  210  at time T 3  is formed on the pixel cells  26  that are in the fourth column to the fifth column from the left and the third row to the fifth row from the top. The pixel group  28  from which imaging data is read at time T 3  is the group in the fifth row from the top. Among the pixel cells  26  included in the pixel group  28  from which imaging data is read, the subject image  210  is formed in the fourth and the fifth pixels from the left. Consequently, the subject image  210  further appears in the fifth row from the top of the captured image, in the pixels in the fourth and fifth columns from the left, as illustrated in  FIG. 8C . 
     As illustrated in  FIG. 8C , the shape of the subject image  210  appearing in the captured image is a parallelogram. By contrast, the actual shape of the subject image  210  is a rectangle, as illustrated in  FIGS. 7A, 7B, and 7C . That is, as a result of the subject image  210  moving in the first direction, which intersects the second direction, while the imaging data is being read in order in the second direction, the shape of the subject image  210  appearing in the captured image may be deformed by being distorted diagonally as compared to the actual shape of the subject image  210 . 
     A person viewing the captured image is less likely to feel uncomfortable with the shape of the subject image  210  that appears deformed by expanding or shrinking in the left-right direction, as illustrated in  FIG. 6C , than with the shape of the subject image  210  that appears deformed by being distorted diagonally as illustrated in  FIG. 8C . In other words, when the first direction intersects the movement direction of the subject image  210 , as illustrated in  FIGS. 5A, 5B, 5C  and  FIGS. 6A, 6B, 6C , a person may feel more comfortable with the shape of the subject image  210  in the captured image than when the first direction is parallel to the movement direction of the subject image  210 . 
     The imaging apparatus  1  may be configured so that the first direction is orthogonal to the movement direction of the subject image  210 . In other words, a vector representing the first direction need not have a component in the same direction as the movement direction of the subject image  210 . When the vector representing the first direction does not have a component in the same direction as the movement direction of the subject image  210 , the subject image  210  appearing in the captured image is less likely to be distorted diagonally than when the vector representing the first direction does have such a component. Consequently, a person may feel more comfortable with the shape of the subject image  210  in the captured image. 
     As illustrated in  FIG. 9  and  FIG. 10 , cameras  20   a ,  20   b ,  20   c  of the imaging apparatus  1  may be mounted in a moveable body  100  that moves along a movement surface  200 . The cameras  20   a ,  20   b ,  20   c  are collectively referred to as the camera  20 . The movement surface  200  may be flat or curved. The movement surface  200  may be formed by a plurality of connected surfaces. The movement surface  200  illustrated in  FIG. 9  is the ground and is the XY plane, but the movement surface  200  may be a variety of other surfaces. The moveable body  100  is a passenger car but may instead be another vehicle, airplane, or the like that runs on the ground, or a boat that moves on the ocean. The forward direction of the moveable body  100  is assumed to be the positive direction of the x-axis. In other words, the forward direction of the moveable body  100  in  FIG. 9  is the direction from right to left. The forward direction of the moveable body  100  in  FIG. 10  is the direction from the front of the drawing towards the back. A driver  110 , indicated by a virtual dashed double-dotted line, is riding in the moveable body  100 . A display  30  for displaying the captured image may also be mounted in the moveable body  100 . The combination of the imaging apparatus  1  and the display  30  may function as an electronic mirror, a surrounding view monitor, or the like by displaying, on the display  30 , images of the surroundings of the moveable body  100  captured by the imaging apparatus  1 . The display  30  may be located near the center of the center console of the vehicle or may be located at the right and left sides inside the vehicle in place of side view mirrors. 
     The camera  20   a  is positioned on the left side surface of the moveable body  100  in place of the sideview mirror on the left side in the forward direction of the moveable body  100 . The camera  20   a  captures images towards the left rear, or the diagonal left rear, of the moveable body  100 . The left side in the forward direction of the moveable body  100  corresponds to the side in the positive direction of the y-axis. The camera  20   b  is positioned on the right side surface of the moveable body  100  in place of the sideview mirror on the right side in the forward direction of the moveable body  100 . The camera  20   b  captures images towards the right rear, or the diagonal right rear, of the moveable body  100 . The right side in the forward direction of the moveable body  100  corresponds to the side in the negative direction of the y-axis. The range captured by the cameras  20   a ,  20   b  includes the range that the driver  110  can confirm with sideview mirrors when the moveable body  100  includes sideview mirrors. 
     At least the imaging optical system  24  in the camera  20  may be located on the side surface of the moveable body  100 . At least a portion of the imaging optical system  24  located on the subject image  210  side may be located on the side surface of the moveable body  100 . The image sensor  22  may be located away from the side surface of the moveable body  100 . For example, the image sensor  22  may be located inside the body of the vehicle. In this case, the subject image  210  incident on a portion of the imaging optical system  24  located on the subject image  210  side can be formed on the imaging surface  23  of the image sensor  22  via the other portion of the imaging optical system  24 . In other words, the imaging apparatus  1  may include an image sensor  22  corresponding to the imaging optical system  24  located on the subject image  210  side. 
     The camera  20   a  may capture not only images towards the left rear or diagonal left rear of the moveable body  100 , but also images towards the left or diagonal left front of the moveable body  100 . The camera  20   b  may capture not only images towards the right rear or diagonal right rear of the moveable body  100 , but also images towards the right or diagonal right front of the moveable body  100 . 
     The camera  20   c  is positioned at the rear of the moveable body  100  as a rear camera that captures images in a direction corresponding to the rear relative to the forward direction of the moveable body  100 . The rear relative to the forward direction of the moveable body  100  is the negative direction of the x-axis. The camera  20   c  may be positioned to replace the rear view mirror of the vehicle. When the camera  20   c  is positioned to replace the rear view mirror, the range captured by the camera  20   c  includes the range that the driver  110  can confirm with a rear view mirror. 
     The moveable body  100  moves along the movement surface  200 . In other words, the movement direction of the moveable body  100  is along the movement surface  200 . When the movement surface  200  corresponds to the xy plane, the movement direction of the moveable body  100  can be expressed as a vector in the xy plane. When the imaging apparatus  1  is mounted in the moveable body  100  so that the first direction representing the array of pixel cells  26  of the image sensor  22  intersects the movement surface  200 , the first direction may intersect the movement direction of the moveable body  100 . 
     It is assumed that the subject image  210  located on the movement surface  200  is captured by the imaging apparatus  1  mounted in the moveable body  100 . The shape of the subject image  210  as viewed from the camera  20  of the imaging apparatus  1  is assumed to be the rectangular subject shape  212   a  indicated by the dashed lines in  FIGS. 11 and 12 . In other words, when the imaging apparatus  1  captures a still subject image  210  while the moveable body  100  is still, the subject image  210  can appear in the captured image with the same shape as the subject shape  212   a  indicated by the dashed lines in  FIGS. 11 and 12 . 
     The camera  20  is assumed to read image data in order in the second direction represented by v from the pixel group  28  that includes pixel cells  26  arranged in the first direction represented by u. The first direction may be from top to bottom in the drawings. The second direction may be from left to right in the drawings. Due to movement of the moveable body  100 , the subject image  210  moves relatively from the perspective of the camera  20 . When the subject image  210  moves from the perspective of the camera  20 , the subject image  210  in the captured image may be deformed. 
     When the second direction is from left to right, the movement direction of the subject image  210  may be the same as the second direction. In this case, the subject image  210  may appear in the captured image with a shape expanded in the left-right direction as compared to the actual subject shape  212   a , as illustrated by the subject shape  212   b  indicated by solid lines in  FIG. 11 . The subject shape  212   b  in the captured image is expanded in the left-right direction relative to the actual subject shape  212   a  for the same reason that the subject image  210  is deformed in the captured image in the example illustrated in  FIGS. 5A, 5B, 5C  and  FIGS. 6A, 6B, 6C . 
     As a comparative example, the camera  20  may read the imaging data from the pixel group  28  in order from top to bottom. This case is illustrated in  FIG. 12 . In other words, the second direction represented by v may be from top to bottom. When the second direction is from top to bottom, the movement direction of the subject image  210  may intersect the second direction. In this case, the subject image  210  may appear in the captured image with a shape distorted diagonally as compared to the actual subject shape  212   a , as illustrated by the subject shape  212   b  indicated by solid lines. The subject shape  212   b  in the captured image is distorted diagonally relative to the actual subject shape  212   a  for the same reason that the subject image  210  is deformed in the captured image in the example illustrated in  FIGS. 7A, 7B, 7C  and  FIGS. 8A, 8B, 8C . 
     A person viewing the captured image is less likely to feel uncomfortable with the subject shape  212   b  that appears expanded in the left-right direction, as illustrated in  FIG. 11 , than with the subject shape  212   b  that appears distorted diagonally as illustrated in  FIG. 12 . In other words, a person may feel more comfortable with the shape of the subject image  210  appearing in the captured image when the second direction is the same as the movement direction of the subject image  210  than when the second direction is orthogonal to the movement direction of the subject image  210 . 
     When the second direction intersects the movement direction of the subject image  210 , the second direction has a component in the same direction as the movement direction of the subject image  210 . As a result of the second direction having a component in the same direction as the movement direction of the subject image  210 , a person may feel more comfortable with the shape of the subject image appearing in the captured image than when the second direction is orthogonal to the movement direction of the subject image  210 . The driver  110  of the moveable body  100  may feel more comfortable with the captured image when the captured image is used as the display image of an electronic mirror or the like in the moveable body  100 . Consequently, the driver  110  is less likely to misidentify the surrounding conditions. 
     As illustrated in  FIG. 13 , the camera  20  mounted in the moveable body  100  can capture subjects  214   a  to  214   g  located around the moveable body  100  on the movement surface  200 . The subjects  214   a  to  214   g  are collectively referred to as a subject  214 . The camera  20  is assumed to be mounted in the moveable body  100  so that the imaging surface  23  lies in the yz plane. The imaging surface  23  is not limited to the yz plane and may be a different plane. In the imaging surface  23 , the first direction represented by u is assumed to be the negative direction of the z-axis, and the second direction represented by v is assumed to be the positive direction of the y-axis (see  FIG. 14A  and the like). 
     The camera  20   a  mounted on the left side of the moveable body  100  can capture subject images  210   a ,  210   b , located at the left rear of the moveable body  100 , on the imaging surface  23   a . The subject image  210   a  corresponds to the subject  214   a , and the subject image  210   b  corresponds to the subject  214   b . From the perspective of the imaging surface  23   a , the subject image  210   a  is located in the opposite direction from the forward direction of the moveable body  100 . The subject image  210   b  is assumed to be located in a direction having a predetermined angle, represented by a, with respect to the direction in which the subject image  210   a  is located on a surface along the xy plane. An image like the one illustrated in  FIG. 14A  may be formed on the imaging surface  23   a . In the images illustrated in  FIGS. 14A, 14B, and 14C , the direction from left to right corresponds to the positive direction of the y-axis. The direction from the back to the front corresponds to the positive direction of the x-axis. The subject image  210   b  is formed further in the positive direction of the y-axis than the subject image  210   a . When the moveable body  100  is moving forward in the positive direction of the x-axis, the direction of the subject image  210   a  from the perspective of the imaging surface  23   a  tends not to change. Accordingly, the position where the subject image  210   a  is formed on the imaging surface  23   a  tends not to move. When the moveable body  100  is moving forward in the positive direction of the x-axis, the angle (α) representing the direction of the subject image  210   b  from the perspective of the imaging surface  23   a  may decrease. Accordingly, the position where the subject image  210   b  is formed on the imaging surface  23   a  may move in the direction represented as L in  FIG. 14A . The direction represented as L is a direction from right to left in the drawing. As the angle (α) representing the direction of the subject image  210   b  from the perspective of the imaging surface  23   a  is greater, the position where the subject image  210   b  is formed in the imaging surface  23   a  may move faster. 
     The camera  20   b  mounted on the right side of the moveable body  100  can capture subject images  210   c ,  210   d , located at the right rear of the moveable body  100 , on the imaging surface  23   b . The subject image  210   c  corresponds to the subject  214   c , and the subject image  210   d  corresponds to the subject  214   d . From the perspective of the imaging surface  23   b , the subject image  210   c  is located in the opposite direction from the forward direction of the moveable body  100 . The subject image  210   d  is assumed to be located in a direction having a predetermined angle, represented by β, with respect to the direction in which the subject image  210   c  is located on a surface along the xy plane. An image like the one illustrated in  FIG. 14B  may be formed on the imaging surface  23   b . The subject image  210   d  is formed further in the negative direction of the y-axis than the subject image  210   c . When the moveable body  100  is moving forward in the positive direction of the x-axis, the direction of the subject image  210   c  from the perspective of the imaging surface  23   b  tends not to change. Accordingly, the position where the subject image  210   c  is formed on the imaging surface  23   b  tends not to move. When the moveable body  100  is moving forward in the positive direction of the x-axis, the angle (β) representing the direction of the subject image  210   d  from the perspective of the imaging surface  23   b  may decrease. Accordingly, the position where the subject image  210   d  is formed on the imaging surface  23   b  may move in the direction represented as R in  FIG. 14B . The direction represented as R is a direction from left to right in the drawing. As the angle (β) representing the direction of the subject image  210   d  from the perspective of the imaging surface  23   b  is greater, the position where the subject image  210   d  is formed in the imaging surface  23   b  may move faster. 
     As illustrated in  FIGS. 14A and 14B , the position where the subject image  210   b  is formed on the imaging surface  23   a  and the position where the subject image  210   d  is formed on the imaging surface  23   b  may move in opposite directions due to forward movement of the moveable body  100 . The subject images  210   b  and  210   d  appearing in the captured image may expand or shrink in the y-axis direction at a predetermined magnification. 
     If, on the imaging surface  23   a , the first direction intersects the xy plane, which is the movement surface  200 , and the second direction is the positive direction of the y-axis, then the shape of the subject image  210   b  in the captured image may be shrunken in the y-axis direction, since the subject image  210   b  moves in the negative direction of the y-axis. If, on the imaging surface  23   b , the first direction intersects the xy plane, which is the movement surface  200 , and the second direction is the positive direction of the y-axis, then the shape of the subject image  210   d  in the captured image is expanded in the y-axis direction, since the subject image  210   d  moves in the positive direction of the y-axis. In other words, when the second direction is the same direction on the imaging surfaces  23   a  and  23   b  located on the opposite side surfaces of the moveable body  100 , the subject images  210  appearing in the captured image may deform differently from each other. 
     When the second direction of the imaging surface  23   b  is the negative direction of the y-axis, i.e. opposite the second direction of the imaging surface  23   a , then the shape of the subject image  210   d  appearing in the captured image is shrunken in the y-axis direction. By the second direction of the imaging surface  23   a  and the second direction of the imaging surface  23   b  being opposite directions, the subject images  210   b  and  210   d  appearing in the captured images can deform in the same way. In other words, when the second directions are opposite each other on the imaging surfaces  23  located on opposite side surfaces of the moveable body  100 , the shapes of the subject images  210  appearing in the images captured at the imaging surfaces  23  can deform in the same way with respect to the actual shapes of the subject images  210 . Consequently, the driver  110  of the moveable body  100  is less likely to be uncomfortable with the difference between the left and right captured images. 
     The camera  20   c  mounted at the rear of the moveable body  100  can capture subject images  210   e ,  210   f ,  210   g , located at the rear of the moveable body  100 , on the imaging surface  23   c . The subject images  210   e ,  210   f ,  210   g  correspond respectively to the subjects  214   e ,  214   f ,  214   g . From the perspective of the imaging surface  23   c , the subject image  210   e  is located in the opposite direction from the forward direction of the moveable body  100 . The subject images  210   f ,  210   g  are each assumed to be located in a direction having a predetermined angle with respect to the direction in which the subject image  210   e  is located on a surface along the xy plane. An image like the one illustrated in  FIG. 14C  may be formed on the imaging surface  23   c . The subject image  210   f  is formed further in the positive direction of the y-axis than the subject image  210   e . The subject image  210   g  is formed further in the negative direction of the y-axis than the subject image  210   e . When the moveable body  100  is moving forward in the positive direction of the x-axis, the direction of the subject image  210   e  from the perspective of the imaging surface  23   c  tends not to change. Accordingly, the position where the subject image  210   e  is formed on the imaging surface  23   c  tends not to move. When the moveable body  100  is moving forward in the positive direction of the x-axis, the positions where the subject images  210   f  and  210   g  are formed on the imaging surface  23   c  may move respectively in the directions represented by L and R. The positions where the subject images  210   f  and  210   g  are formed move because the predetermined angle between the direction in which the subject images  210   f  and  210   g  are located and the direction in which the subject image  210   e  is located decreases due to forward movement of the moveable body  100 . 
     Suppose that the second direction is the positive direction of the y-axis on the imaging surface  23   c . The subject image  210   f  moves in the negative direction of the y-axis, and the subject image  210   g  moves in the positive direction of the y-axis. The shape of the subject image  210   f  in the captured image may therefore be shrunken in the y-axis direction, and the shape of the subject image  210   g  in the captured image may be expanded in the y-axis direction. If the second direction is the negative direction of the y-axis on the imaging surface  23   c , the shape of the subject image  210   f  in the captured image may be expanded in the y-axis direction, and the shape of the subject image  210   g  in the captured image may be shrunken in the y-axis direction. In other words, depending on the position at which the subject image  210  is formed on the imaging surface  23 , the subject image  210  appearing in the captured image may deform into a different shape. 
     The processor  10  may correct the shape of the subject image  210  appearing in the captured image. The processor  10  may correct the shape of the subject image  210  in the captured image based on the second direction of the imaging surface  23  and the position at which the subject image  210  appears in the captured image. With this approach, the driver  110  is even less likely to feel uncomfortable with the captured image. 
     In the example illustrated in  FIG. 14A , for example, the processor  10  may correct the shape of the subject image  210   b  in the captured image by expanding the shape in the y-axis direction. The processor  10  may progressively increase the magnification for expanding the shape of the subject image  210   b  in the captured image in the y-axis direction as the position at which the subject image  210   b  formed on the imaging surface  23   a  is farther in the positive direction of the y-axis than the position at which the subject image  210   a  is formed. 
     In the example illustrated in  FIG. 14B , for example, the processor  10  may correct the shape of the subject image  210   d  in the captured image by shrinking the shape in the y-axis direction. The processor  10  may progressively decrease the magnification for shrinking the shape of the subject image  210   d  in the captured image in the y-axis direction as the position at which the subject image  210   d  formed on the imaging surface  23   b  is farther in the negative direction of the y-axis than the position at which the subject image  210   c  is formed. 
     In the example illustrated in  FIG. 14C , for example, the processor  10  may correct the shape of the subject image  210   f  in the captured image by expanding the shape in the y-axis direction. The processor  10  may progressively increase the magnification for expanding the shape of the subject image  210   f  in the captured image in the y-axis direction as the position at which the subject image  210   f  formed on the imaging surface  23   c  is farther in the positive direction of the y-axis than the position at which the subject image  210   e  is formed. The processor  10  may correct the shape of the subject image  210   g  in the captured image by shrinking the shape in the y-axis direction. The processor  10  may progressively decrease the magnification for shrinking the shape of the subject image  210   g  in the captured image in the y-axis direction as the position at which the subject image  210   g  formed on the imaging surface  23   c  is farther in the negative direction of the y-axis than the position at which the subject image  210   e  is formed. 
     The processor  10  may correct the shape of the subject image  210  in the captured image based also on the speed of the moveable body  100 . For example, the processor  10  may increase the magnification for expanding the shape of the subject image  210  in the y-axis direction, or decrease the magnification for shrinking the shape of the subject image  210  in the y-axis direction, progressively as the moveable body  100  moves forward at a faster speed. With this approach, the driver  110  is even less likely to feel uncomfortable with the captured image. The processor  10  may correct the shape of the subject image  210  in the captured image based on the moving speed of the position where the subject image  210  is formed on the imaging surface  23 . The processor  10  may calculate the moving speed of the position where the subject image  210  is formed on the imaging surface  23  based on the speed of the moveable body  100 . 
     The moving speed of the moveable body  100  may be less when moving in reverse than when moving forward. The deformation of the shape of the subject image  210  in the captured image may be considered negligible when the moveable body  100  moves in reverse. In this case, the processor  10  may be configured not to correct the captured image. This configuration can reduce the load of the processor  10 . 
     When the moveable body  100  moves along a narrow road or is in a traffic jam, the moving speed of the moveable body  100  may be less than when the moveable body  100  is moving normally on a highway, a main road, or the like. The deformation of the shape of the subject image  210  in the captured image may be considered negligible when the moving speed of the moveable body  100  is less than a predetermined speed. In this case, the processor  10  may be configured not to correct the captured image. This configuration can reduce the load of the processor  10 . The predetermined speed may be determined based on a variety of information such as the position of the moveable body  100  and the surrounding conditions of the moveable body  100 . 
     When the imaging apparatus  1  is mounted in the moveable body  100 , the relationship between the movement surface  200  and the first and second directions that specify the order in which the image sensor  22  reads imaging data from the pixel cells  26  can be adjusted. The imaging apparatus  1  may be mounted in the moveable body  100  so that the first direction intersects the movement surface  200 . The imaging apparatus  1  may, for example, include a substrate  14  on which the image sensor  22  is mounted, as illustrated in  FIG. 15 . The processor  10  may be further mounted on the substrate  14 . The image sensor  22  may be mounted so that the first direction becomes the positive direction of the z-axis and the second direction becomes the negative direction of the y-axis. The imaging optical system  24  indicated by a virtual dashed double-dotted line may be positioned so that the optical axis thereof matches the center of the imaging surface  23  of the image sensor  22 . 
     The imaging apparatus  1  may include a housing  50 . The housing  50  may include an attachment portion  52  for attaching the imaging apparatus  1  to the moveable body  100 . The attachment portion  52  may include a hole through which a screw or the like passes. The housing  50  may include at least two attachment portions  52 . The attachment portion  52  may be positioned around the housing  50 . The attachment portion  52  may be positioned on the opposite surface of the housing  50  from the imaging optical system  24 . 
     The attachment portion  52  may be positioned so as not to be point-symmetric with respect to any point of the housing  50 . This configuration allows the attachment portion  52  to specify the relationship between the first direction on the imaging surface  23  and the movement surface  200 . The imaging apparatus  1  can be mounted in the moveable body  100  so that the first direction intersects the movement surface  200 . When the first direction can be changed based on control information from the processor  10 , the processor  10  can control the relationship between the first direction and the movement surface  200  in conjunction with the actual attachment state as a result of the attachment direction of the imaging apparatus  1  being specified by the attachment portion  52 . 
     The imaging apparatus  1  may include a mark or the like on the housing  50  to represent the first direction or the second direction of the image sensor  22 . When the attachment portion  52  is not point-symmetric with respect to any point of the housing  50 , the position of the attachment portion  52  can be considered a mark representing the first direction or the second direction of the image sensor  22 . The provision of a mark on the imaging apparatus  1  to represent the first direction or the second direction reduces the likelihood of mistakes when the imaging apparatus  1  is attached to the moveable body  100 . 
     The camera  20   a  may be mounted on the left side and the camera  20   b  on the right side of the moveable body  100 , as in the example in  FIG. 13 . In this case, the attachment portion  52  of the camera  20   a  and the attachment portion  52  of the camera  20   b  may have different positional relationships. This configuration reduces the probability that cameras  20  with different second directions will be mounted in reverse on the moveable body  100 . 
     The moveable body  100  according to the present disclosure may encompass vehicles, ships, and the like. The term “vehicle” in the present disclosure includes, but is not limited to, automobiles and industrial vehicles and may also include railway vehicles, vehicles for daily life, and aircraft that run on a runway. Automobiles include, but are not limited to, passenger vehicles, trucks, buses, motorcycles, and trolley buses, and may include other vehicles that travel on the road. Industrial vehicles include industrial vehicles for agriculture and for construction. Industrial vehicles include, but are not limited to, forklifts and golf carts. Industrial vehicles for agriculture include, but are not limited to, tractors, cultivators, transplanters, binders, combines, and lawnmowers. Industrial vehicles for construction include, but are not limited to, bulldozers, scrapers, backhoes, cranes, dump cars, and road rollers. The term “vehicle” includes human-powered vehicles. The vehicle is not limited to the above-listed types. For example, automobiles may include industrial vehicles that can be driven on the road. The same vehicle may also be included in multiple categories. The term “ship” in the present disclosure includes marine jets, boats, and tankers. 
     Although embodiments of the present disclosure have been described through drawings and examples, it is to be noted that various changes and modifications will be apparent to those skilled in the art on the basis of the present disclosure. Therefore, such changes and modifications are to be understood as included within the scope of the present disclosure. For example, the functions and the like included in the various components may be reordered in any logically consistent way. Furthermore, components may be combined into one or divided. While embodiments of the present disclosure have been described focusing on apparatuses, the present disclosure may also be embodied as a method that includes steps performed by the components of an apparatus. The present disclosure may also be embodied as a method executed by a processor provided in an apparatus, as a program, or as a recording medium having a program recorded thereon. Such embodiments are also to be understood as falling within the scope of the present disclosure. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  Imaging apparatus 
               10  Processor 
               12  Storage 
               14  Substrate 
               20  ( 20   a ,  20   b ,  20   c ) Camera 
               22  Image sensor 
               23  ( 23   a ,  23   b ,  23   c ) Imaging surface 
               24  Imaging optical system 
               26  Pixel cell 
               28  Pixel group 
               30  Display 
               50  Housing 
               52  Attachment portion 
               100  Moveable body 
               110  Driver 
               200  Movement surface 
               210  ( 210   a  to  210   g ) Subject image 
               212   a ,  212   b  Subject shape