JP2016063352A - On-vehicle display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle display device that has suppressed incorrect recognition of a sense of distance between an object of interest and a vehicle that occurs due to the difference in size of the object of interest between camera images caused by a difference in installation position of cameras.SOLUTION: A similarity calculation part 9 calculates the similarity between camera images photographed by a rear camera 2, side camera 3, and side camera 4 on the basis of the sizes in the camera images of an object of interest that is photographed in common by the cameras. A control part 6 determines a form of a display image to be displayed on a liquid crystal display 5 on the basis of the similarity calculated by the similarity calculation part 9 and outputs the form to an image processing part 10. The image processing part 10 creates an image to be displayed on the liquid crystal display 5 according to the form of the display image determined by the control part 6.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vehicle-mounted display device that presents a driver with images taken by a plurality of cameras mounted on a vehicle.

  As an in-vehicle display device that presents to a driver images captured by a plurality of cameras mounted on a conventional vehicle, a camera image captured by a rear camera installed at the rear of the vehicle and two side cameras installed at the left and right of the front of the vehicle There is known a technique in which photographed camera images are combined and presented to a driver as one image (see, for example, Patent Document 1).

  Other in-vehicle display devices are known that display a camera image captured by a rear camera installed at the rear of the vehicle and a camera image captured by two side cameras installed at the left and right of the front of the vehicle (for example, Patent Document 2).

JP 2013-141120 A Japanese Patent Laid-Open No. 2003-081014

  In general, when images taken by cameras with different mounting positions and orientations are combined to generate a single image, the scale conversion of the camera image is performed based on the matching portions in each camera image so that the combined images are smooth. Done.

  In the in-vehicle display device described in Patent Document 1, the scale conversion of the camera image is performed so that the road surface reflected in the combined camera image is smooth.

  Depending on the scale conversion of the camera image, the size of the object at the same distance from the host vehicle may be different in the synthesized image. When recognizing an object with a combined camera image, there may be a case where a misrecognition occurs in the sense of distance between the host vehicle and the object photographed by the camera. In particular, when the object is in the vicinity of the rear of the vehicle, there is a high possibility that the sense of distance between the subject vehicle and the object photographed by the camera is erroneously recognized by scale conversion.

  In the in-vehicle display device described in Patent Document 2, camera images taken by cameras installed at different positions are displayed side by side. In camera images taken by cameras installed at different positions, the same object has a different size in each camera image due to the difference in camera installation positions.

  When such camera images are displayed side by side, there may be a case where misrecognition occurs in the sense of distance between the host vehicle and the object photographed by the camera. In particular, when the object is in the vicinity of the rear of the vehicle, there is a high possibility of misrecognizing a sense of distance between the host vehicle and the object photographed by the camera due to a difference in the installation position of the camera.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an in-vehicle display device that solves the above-described problems and suppresses misrecognition of a sense of distance between the host vehicle and an object photographed by a camera.

  In order to solve the above problem, an in-vehicle display device according to the present invention includes a camera image of a rear camera that is installed at the rear of the vehicle and photographs the rear of the vehicle, and a side camera that is disposed at the front left and right of the vehicle and photographs the rear of the vehicle. The calculation result of the video display unit that displays the camera image, the similarity calculation unit that calculates the similarity between the camera image captured by the rear camera and the camera image captured by the side camera, and the calculation result of the similarity calculation unit And a control unit that determines the form of the display image displayed by the video display unit. The video display unit is configured to display the camera image according to the form of the display image determined by the control unit.

  According to the present invention, the similarity calculation unit calculates the similarity between the camera image captured by the rear camera and the camera image captured by the side camera, and the control unit displays the image displayed by the video display unit based on the camera image similarity. Determine the form of the image.

  That is, the vehicle-mounted display device of the present invention displays camera images in different forms depending on the similarity of camera images. Thereby, the vehicle-mounted display apparatus which suppressed the misrecognition of the distance feeling of the own vehicle and the object image | photographed with the camera can be provided.

Schematic diagram of a vehicle equipped with an in-vehicle display device in Embodiment 1 of the present invention Same as above, control block diagram of in-vehicle display device Flow chart showing an example of the operation of the in-vehicle display device The figure which shows the relationship between the position of an attention object, and the form of a display image similarly The flowchart which shows an example of operation | movement of the vehicle-mounted display apparatus in Embodiment 2 of this invention. The figure which shows the relationship between the position of an attention object, and the form of a display image similarly

  Hereinafter, an example in which an in-vehicle display device according to an embodiment of the present invention is mounted on a vehicle will be described with reference to the accompanying drawings.

(Embodiment 1)
As shown in FIG. 1, a rear camera 2 that captures the rear of the vehicle is installed at the rear center of the vehicle 1. A side camera 3 and a side camera 4 for photographing the rear side of the vehicle are installed on the left and right of the front part of the vehicle. The side camera 3 installed on the right side of the vehicle captures the right rear of the vehicle, and the side camera 4 installed on the left side of the vehicle captures the left rear of the vehicle.

  The angles of view of the rear camera 2 and the side camera 3, and the rear camera 2 and the side camera 4 are installed so as to overlap in the vicinity of the rear of the vehicle. Objects existing within a common angle of view between the cameras are photographed in common by the cameras.

  A liquid crystal display 5 which is a video display unit constituting an in-vehicle display device is installed in the front part of the vehicle interior and in the vicinity of instruments such as a speedometer.

  The liquid crystal display 5 displays camera images taken by the rear camera 2, the side camera 3, and the side camera 4. From the camera images taken by the rear camera 2, the side camera 3, and the side camera 4, the driver can check the rear of the vehicle 1 over a wider area than the rear mirror.

  The liquid crystal display 5 is connected to a control unit 6 that controls the entire in-vehicle display device 100 as shown in FIG. A storage unit 7, an operation unit 8, a similarity calculation unit 9, and an image processing unit 10 are connected to the control unit 6.

  The storage unit 7 stores a control program for the control unit 6 to control the in-vehicle display device 100, temporarily held data, control data, and the like.

  The operation unit 8 is for a driver to perform various operations of the in-vehicle display device 100 such as ON / OFF of the in-vehicle display device 100, change of the display image form of the liquid crystal display 5, and the like. Is done.

  The similarity calculation unit 9 calculates the similarity between the camera image captured by the rear camera 2 and the camera images captured by the side camera 3 and the side camera 4. The similarity calculation unit 9 calculates the similarity for each fixed time interval and outputs it to the control unit 6. The similarity will be described in detail in the description of the operation of the in-vehicle display device 100.

  The image processing unit 10 generates a display image to be displayed on the liquid crystal display 5 from camera images taken by the rear camera 2, the side camera 3, and the side camera 4.

  An example of main operations in the first embodiment of the vehicle-mounted display device 100 in the first embodiment of the present invention configured as described above will be described.

  FIG. 3 is a flowchart showing an example of main operations related to the first embodiment of the in-vehicle display device 100.

  When the processing is started, the control unit 6 displays, on the liquid crystal display 5, one image obtained by combining the camera images taken by the rear camera 2, the side camera 3, and the side camera 4 as the display image form of the liquid crystal display 5. The composite display is output to the image processing unit 10.

  The image processing unit 10 synthesizes camera images taken by the cameras with reference to, for example, a road surface, and generates one image and outputs the image to the liquid crystal display 5. The liquid crystal display 5 displays the image generated by the image processing unit 10 (step S301).

  The similarity calculation unit 9 is a similarity between the rear camera image captured by the rear camera 2 and the side camera 3 image captured by the side camera 3, and the rear camera image captured by the rear camera 2 and the side camera captured by the side camera 4. The degree of similarity with the four images is calculated (step S302).

  In the first embodiment, the similarity between camera images is the size in each camera image of an object of interest that a driver pays attention in a driving operation, such as a vehicle traveling behind a host vehicle that is photographed in common between camera images. The difference. The size of the object of interest in each camera image is calculated from the ratio of the area occupied by the object of interest in each camera image and the occupation rate.

  The similarity calculation unit 9 specifies, for example, a target object that is captured in common between camera images based on a time-series change in each camera image of the object captured by each camera, and calculates the similarity of the target object. To do.

  The control unit 6 acquires the similarity calculated by the similarity calculation unit 9, and determines the similarity of the camera image based on the acquired similarity. The control unit 6 determines whether or not the similarity is a predetermined value, for example, the difference in occupation ratio is 1% or more (step S303).

For example, when the rear camera 2 and the side camera 3 are shooting a common target object, the difference between the target object occupancy in the rear camera image and the target object occupancy in the side camera 3 image is 1% or more. In this case, the control unit 6 determines that the similarity between the rear camera image and the side camera 3 image is equal to or greater than a predetermined value.

  The control unit 6 repeats the determination of the degree of similarity until the degree of similarity reaches a predetermined value, for example, an occupation ratio difference of 1% or more (step S303, NO).

  When the control unit 6 determines that the similarity of the camera image is equal to or greater than a predetermined value (step S303, YES), the control unit 6 divides the display area of the liquid crystal display 5 into three as the display image form, and displays the divided display. A parallel display that displays the camera images taken by the rear camera 2, the side camera 3, and the side camera 4 side by side in the region is output to the image processing unit 10.

  The image processing unit 10 captures the camera image captured by each camera, for example, the rear camera image captured by the side camera 3 on the right side of the rear camera image around the rear camera image captured by the rear camera. An image is generated in which the side camera 4 image captured by the side camera 4 on the left side is arranged with a boundary between the camera images. The liquid crystal display 5 displays the image generated by the image processing unit 10 (step S304).

  The similarity calculator 9 calculates the similarity (step S305), and the controller 6 acquires the similarity from the similarity calculator 9 and determines the similarity of the camera image (step S306). When the control unit 6 determines that the similarity is a predetermined value, for example, less than 1% difference in occupation ratio (step S306, YES), the control unit 6 proceeds to the process of step S301.

  The controller 6 repeats the similarity determination until it is determined that the similarity is less than the predetermined value (step S306, NO). The control unit 6 performs the process shown in FIG. 3 while the in-vehicle display device is activated.

  FIG. 4 is a diagram showing the relationship between the position of the object of interest and the form of the display image in Embodiment 1 of the present invention.

  FIG. 4A shows a display image on the liquid crystal display 5 when the object of interest is located behind the vehicle 1 that is the host vehicle. In FIG. 4, view angles 2 a, 3 a, and 4 a indicate the view angles of the rear camera 2, the side camera 3, and the side camera 4, respectively.

  When the vehicles 41, 42, and 43 that are traveling behind the vehicle 1 that is the object of interest are located far from the vehicle 1, the images of the object of interest that are captured in common between the camera images captured by the cameras The size is small and the similarity of camera images is low.

  When the target object is far behind the vehicle 1, the change in the size of the target object due to the image composition is small with respect to the entire synthesized image. There is little possibility of misrecognizing the sense of distance between the vehicle 1 and the vehicles 41, 42, and 43 that are the object of interest by image composition. The in-vehicle display device 100 displays the combined image in the form of a display image and displays on the liquid crystal display 5 one image 4A obtained by combining the camera images.

  FIG. 4B shows a display image on the liquid crystal display 5 when the vehicles 41, 42, and 43, which are objects of interest, are near the rear of the vehicle 1. When the target object is in the vicinity of the vehicle 1, the size of the target object captured in common among the camera images captured by the cameras is large in each image, and the similarity between the camera images is high.

When the target object is near the rear of the vehicle 1, the change in the size of the target object due to image synthesis is larger than that when the target object is far from the host vehicle with respect to the entire synthesized image. The possibility of misrecognizing the sense of distance between the vehicle 1 and the vehicles 41, 42, and 43, which are the object of interest, by image synthesis increases. The in-vehicle display device 100 uses parallel display as a form of display image, and displays an image 4B on the liquid crystal display 5 in which a boundary is provided between the camera images and the side camera 4 image, the acamera image, and the side camera 3 image are displayed side by side.

  By providing a boundary between camera images and displaying the camera images side by side, the driver recognizes that each image is a camera image of a different scale taken by a different camera installed at a different position, and the size of the object of interest It is possible to suppress misrecognition of a sense of distance due to the difference between the two.

  The image 4C in FIG. 4B is a side mirror type display area of the camera image of the side camera. By changing the shape of the display area, it is possible to make it easier to recognize that the left and right images are camera images of different scales taken by different cameras installed at different positions.

  As described above, in the in-vehicle display device 100 according to Embodiment 1 of the present invention, the similarity calculation unit 9 is similar to the camera image captured by the rear camera 2 and the camera image captured by the side camera 3 and the side camera 4. The control unit 6 determines the display image form displayed on the liquid crystal display 5 based on the similarity of the camera images.

  The control unit 6 displays on the liquid crystal display 5 one image obtained by combining the camera images when the similarity between the camera image captured by the rear camera and the camera images captured by the side camera 3 and the side camera 4 is lower than a predetermined value. The composite display to be performed is a display image form. When the similarity is equal to or higher than a predetermined value, a parallel display in which a boundary is provided between the camera images and the camera images are displayed side by side is taken as a display image form.

  By determining the form of the display image according to the similarity of the camera image and changing the form of the display image according to the similarity, an error in the sense of distance between the host vehicle and the target object due to a change in the size of the target object due to image composition A vehicle-mounted display device in which recognition is suppressed can be provided.

  In the first embodiment, the divided area is described as fixed, but the boundary width may be changed according to the similarity.

  For example, by increasing the width of the boundary as the degree of similarity increases, it becomes easier to recognize the effect of the difference in installation position on the difference in the size of the target object due to the width of the boundary. It becomes possible to suppress misrecognition of a sense of distance.

  Moreover, you may comprise so that the shape of a display area may change according to similarity. By making the side camera image display area a side mirror type as the similarity increases, it becomes easier to recognize the installation position of each camera image, and misrecognition of the sense of distance due to the difference in the size of the object of interest It becomes possible to suppress.

  Further, as the similarity, the difference in size in each camera image of the object of interest photographed in common between the camera images was used, but each object of interest photographed in the camera image as the similarity and the own vehicle May be used.

  For example, the distance calculation unit 9 measures the distance between each object of interest and the host vehicle using a laser radar and outputs the distance to the control unit 6. When the distance between the object of interest captured by the rear camera 2 and the host vehicle is equal to or greater than a predetermined distance, the control unit 6 displays the form of the display image as a composite display.

The distance between the target object captured by the rear camera 2 and the host vehicle is equal to or less than a predetermined distance, the distance between the target object captured by the side camera 3 or the side camera 4 and the host vehicle, and the target object captured by the rear camera 2 The controller 6 may be configured to determine that the camera images are similar when the difference in distance from the host vehicle is a certain value or less.

(Embodiment 2)
Hereinafter, the in-vehicle display device according to Embodiment 2 of the present invention will be described. The difference from the first embodiment is that the in-vehicle display device in the second embodiment displays the camera images side by side without synthesizing the camera images, and reduces the display area of the camera image taken by the side camera according to the similarity. This is the point to display.

  Hereinafter, an in-vehicle display device according to a second embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected about the structure similar to Embodiment 1, and the detailed description is abbreviate | omitted.

  A schematic diagram of a vehicle equipped with a vehicle-mounted display device according to a second embodiment of the present invention and a control block diagram of the vehicle-mounted display device are the same as those in FIGS. 1 and 2 in the first embodiment. What is different from the first embodiment is the operation flow of the control unit 6 shown in FIG. 5 and the form of a display image displayed on the liquid crystal display 5 shown in FIG.

  FIG. 5 is a flowchart showing an example of the operation of the in-vehicle display device according to Embodiment 2 of the present invention. As shown in FIG. 5, when the control unit 6 starts processing, the control unit 6 outputs, to the image processing unit 10, a form in which each camera image is displayed side by side in a display area having the same area as a display image form on the liquid crystal display 5. .

  The image processing unit 10 includes a side camera captured by the side camera 3 on the right side of the rear camera image centered on the rear camera image, in three display areas having the same display area provided between the camera images. The three images are generated by arranging the side camera 4 images taken by the side camera 4 on the left side of the rear camera image. The liquid crystal display 5 displays the image generated by the image processing unit 10 (step S501).

  The similarity calculation unit 9 uses the similarity between the rear camera image captured by the rear camera 2 and the side camera 3 image captured by the side camera 3, and the side camera captured by the rear camera 2 and captured by the rear camera image and the side camera 4. The degree of similarity with the four images is calculated (step S502).

  The control unit 6 acquires the similarity calculated by the similarity calculation unit 9, and determines the similarity of the camera image based on the acquired similarity as in the first embodiment (step S503). The control unit 6 repeats the determination of the degree of similarity until the degree of similarity reaches a predetermined value, for example, an occupation ratio difference of 1% or more (step S503, NO).

  When the control unit 6 determines that the similarity of the camera image is equal to or greater than the predetermined value (step S503, YES), the control unit 6 uses a form in which the display area of the side camera is reduced as the form of the display image. Output to. The control unit 6 determines the size of the display area of the side camera based on the difference in the size of the object that exists in common in the camera image, which is the similarity of the camera image, and outputs it to the image processing unit 10.

  For example, when the occupation ratio of the target object in the camera image captured by the rear camera 2 is 1.2 times the occupation ratio of the target object in the camera image captured by the side camera 3, the control unit 6 The display area is determined to be 0.83 times the display area of the rear camera.

  By changing the display area of the camera image without changing the scale of the camera image of the side camera, the image appears on the camera with the same angle of view when the camera is at the same position.

  Since the size of the object to be photographed with respect to the display area matches in the video of each camera, it is possible to suppress misrecognition of a sense of distance due to a difference in camera installation position.

  The image processing unit 10 generates an image in which the camera image of the side camera is arranged in the reduced display area without changing the scale of the camera image. The liquid crystal display 5 displays the image generated by the image processing unit 10 (step S504).

  The similarity calculation unit 9 calculates the similarity (step S505), and the control unit 6 acquires the similarity from the similarity calculation unit 9 and determines the similarity of the camera image (step S506). When the control unit 6 determines that the similarity is a predetermined value, for example, the difference in occupation ratio is less than 1% (step S506, YES), the control unit 6 proceeds to the process of step S501.

  The control unit 6 determines the size of the display area of the side camera according to the similarity and outputs it to the image processing unit 10 until it is determined that the similarity is less than a predetermined value (step S506, NO). The control unit 6 performs the process shown in FIG. 5 while the in-vehicle display device 100 is activated.

  FIG. 6 is a diagram showing the relationship between the position of the object of interest and the form of the display image in Embodiment 2 of the present invention.

  FIG. 6A shows a display image on the liquid crystal display 5 when the object of interest is located behind the vehicle 1 that is the host vehicle. In FIG. 6, view angles 2 a, 3 a, and 4 a indicate the view angles of the rear camera 2, the side camera 3, and the side camera 4, respectively. When the vehicles 61, 62, and 63 that are traveling behind the vehicle 1 that is the object of interest are in the distance, the size of the object of interest captured in common among the camera images captured by the cameras is Small and low similarity.

  When the object of interest is far behind the vehicle 1, the difference in size between the images of the object of interest resulting from the difference in the installation positions of the rear camera 2, the side camera 3, and the side camera 4 is small. By displaying each camera image in a display area of the same size, there is little possibility of erroneously recognizing a sense of distance between the vehicle 1 and the vehicles 61, 62, 63 that are the object of interest.

  The in-vehicle display device 100 includes an image 6A in which a side camera 3 image, a rear camera image, and a side camera 4 image are arranged in this order in three display areas having the same display area provided between camera images. Is displayed on the liquid crystal display 5.

  FIG. 6B shows a display image on the liquid crystal display 5 when the vehicles 61, 62, and 63, which are objects of interest, are near the rear of the vehicle 1. When the target object is in the vicinity of the vehicle 1, the size of the target object captured in common among the images captured by the cameras is larger in each image than in the case where the target object is far from the vehicle 1. The similarity is high.

  When the target object is near the rear of the vehicle 1, the difference in size between the images of the target object resulting from the difference in the installation positions of the rear camera and the side camera is also large. Displaying each camera image in a display area of the same size also increases the possibility of misrecognizing the sense of distance between the vehicle 1 and the vehicles 61, 62, 63 that are the object of interest.

  The in-vehicle display device 100 displays the side camera with a display area narrowed according to the similarity between the camera images.

6 and 6B, when the occupation rate of the target object in the camera image captured by the rear camera 2 is 1.2 times the occupation rate of the target object in the camera image captured by the side camera 3,
It is a display image of a liquid crystal display in which the display area of the side camera is 0.83 times the display area of the rear camera.

  This is an image reflected on a camera with the same angle of view when the rear camera and side camera are at the same position. Since the size of the object to be photographed with respect to the display area matches in each camera image, erroneous recognition of the sense of distance between the vehicle 1 and the vehicles 61, 62, and 63 that are the object of interest due to the difference in the camera installation position is suppressed. be able to.

  FIG. 6 and image 6C are image examples in the form of a display image in which the display area of the rear camera is emphasized. By emphasizing the display area of the rear camera image, erroneous recognition of a sense of distance can be further suppressed.

  As described above, in-vehicle display device 100 according to Embodiment 2 of the present invention displays camera images side by side. The control unit 6 reduces the area of the display part of the camera image taken by the side camera based on the similarity of the camera image calculated by the similarity calculation unit 9.

  By reducing the display area of the camera image based on the similarity according to the similarity, the camera images taken by the rear camera and the side camera installed at different positions have the same angle of view when they are at the same position. Will be reflected in the video.

  In each camera image, the distance to the object of interest and the size of the object to be photographed with respect to the display area are always the same, which prevents misrecognition of the sense of distance between the vehicle and the object of interest due to the difference in the camera installation position An in-vehicle display device that can be provided can be provided.

  In order to prevent misrecognition of the sense of distance between the host vehicle and the object of interest due to the difference in the camera installation position, the image of one camera is scaled based on the difference in the size of the object existing in the common area of each camera. There is a way to convert. In this method, when the scale conversion base existing in the common area suddenly disappears, the scale is suddenly changed in accordance with the next object, resulting in an annoying image for the driver.

  In the in-vehicle display device 100 according to the second embodiment, this troublesomeness can be eliminated.

  Further, as the similarity, the difference in size in each camera image of the object of interest photographed in common between the camera images was used, but each object of interest photographed in the camera image as the similarity and the own vehicle May be used.

  For example, the distance calculation unit 9 measures the distance between each object of interest and the host vehicle using a laser radar and outputs the distance to the control unit 6. When the distance between the object of interest photographed by the rear camera 2 and the host vehicle is equal to or greater than a predetermined distance, the control unit 6 displays the form of displaying the camera images of the cameras side by side in the display area of the same size. To do.

  The distance between the target object captured by the rear camera 2 and the host vehicle is equal to or less than a predetermined distance, the distance between the target object captured by the side camera 3 or the side camera 4 and the host vehicle, and the target object captured by the rear camera 2 When the difference in distance from the host vehicle is equal to or less than a certain value, the control unit 6 may be configured to determine the display image form so that the display area of the side mirror is reduced according to the difference in distance. Good.

  The vehicle-mounted display device of the present invention is useful as a vehicle-mounted monitoring device such as an electronic mirror.

1, 41, 42, 43, 61, 62, 63 Vehicle 2 Rear camera 3 Side camera 4 Side camera 5 Liquid crystal display 6 Control unit 7 Storage unit 8 Operation unit 9 Similarity calculation unit 10 Image processing unit 100 In-vehicle display device

Claims (6)

A video display unit that displays a camera image of a rear camera that is installed at the rear of the vehicle and shoots the rear of the vehicle and a camera image of a side camera that is installed at the front left and right of the vehicle and shoots the rear of the vehicle;
A similarity calculation unit that calculates the similarity between the camera image captured by the rear camera and the camera image captured by the side camera;
A control unit that determines a form of a display image displayed by the video display unit based on a calculation result of the similarity calculation unit;
The video display unit is a vehicle-mounted display device that displays the camera image in a display image form determined by the control unit.   The control unit is configured to display a combined image for displaying an image obtained by combining the camera images when the similarity of the camera images is lower than a predetermined value, and between the camera images when the similarity of the camera images is equal to or higher than the predetermined value. The in-vehicle display device according to claim 1, wherein a boundary display is provided to form a parallel display in which camera images are displayed side by side.   The in-vehicle display device according to claim 2, wherein the control unit is configured to change a width of a boundary between camera images according to the similarity.   The in-vehicle apparatus according to claim 1, wherein the control unit is configured to display the camera images side by side, and display a display image in which the display area of the camera image captured by the side camera is reduced according to the similarity. Display device.   When the distance between the object of interest photographed by the rear camera and the host vehicle is shorter than a predetermined distance, the similarity calculation unit calculates the distance between the object of interest photographed by the side camera and the host vehicle and the rear camera. 5. The system according to claim 1, wherein the similarity between the camera image captured by the rear camera and the camera image captured by the side camera is calculated based on a difference in distance between the captured object of interest and the host vehicle. The on-vehicle display device according to item 1.   5. The structure according to claim 1, wherein the similarity calculation unit is configured to calculate the similarity of the camera image based on a size in the camera image of the target object that is captured in common between the camera images. The vehicle-mounted display device according to item.