Vehicle electronic display device

Abstract

The vehicle electronic display device (1) includes an imaging section (2) that captures an image of at least the rear of the vehicle, a control unit (4) that acquires the image captured by the imaging section (2) and performs image processing to generate a display image having a smaller diopter value than the image captured by the imaging section (2) by changing the luminance histogram included in the image information, and a display section (5) that displays the display image generated by the control unit (4).

Description

[Technical Field]

[0001] The present disclosure relates to an electronic display device for a vehicle, for example, mounted on an automobile or the like. [Background technology]

[0002] For example, as disclosed in Patent Documents 1 to 3, electronic display devices are sometimes used as inner mirrors installed inside the cabin of automobiles. This type of electronic display device includes an imaging unit that captures images of the rear and sides of the vehicle, and a display unit that displays the images captured by the imaging unit. The display unit is installed diagonally above and in front of the driver, similar to conventional inner mirrors.

[0003] Furthermore, Patent Documents 4 and 5 disclose a display device mounted on a vehicle that uses a projection unit to project a virtual image onto a screen in front of the vehicle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-176131 [Patent Document 2] Japanese Patent Publication No. 2021-136463 [Patent Document 3] Japanese Patent Publication No. 2020-79025 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-329768 [Patent Document 5] Patent Publication No. 2021-35807 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional vehicle inner mirrors consist of mirrors. When a driver uses a mirror to check an object behind or to the side, he or she looks at the object reflected in the mirror and focuses his or her eyes on the object reflected in the mirror.

[0006] In contrast, when an electronic display device is used as an inner mirror, the image captured by the imaging unit is displayed on a display unit such as a liquid crystal display (LCD) or organic light-emitting diode (OLED).In this case, the driver recognizes objects by focusing their eyes on the image displayed on the display unit (display surface).

[0007] On the other hand, when driving a vehicle, the driver typically looks several tens of meters ahead of the vehicle. When a driver needs to check the rearview mirror, they shift their gaze from the forward position to the rearview mirror installed diagonally above. As mentioned above, in the case of a mirror, the driver focuses on the object reflected in the mirror itself, whereas in the case of an electronic display device, the driver must focus on the display surface. In particular, in the case of a rearview mirror, the driver is installed at the top center of the front windshield, so the distance between the driver and the rearview mirror is short. Given such a short distance, the driver can quickly and easily focus on the object reflected in the mirror itself, but in the case of an electronic display device, the driver must shift their focus from several tens of meters ahead to the display surface directly in front of them, which takes time. This time is particularly significant when the driver's ability to shift focus when viewing objects declines with age. As a result, the driver's ability to see the rearview mirror is delayed.

[0008] To facilitate such focusing, methods have been proposed in which a projection unit is used instead of a display to project a virtual image onto a screen in front of the vehicle, as disclosed in Patent Documents 4 and 5, for example. By projecting a virtual image, the driver can focus on the virtual image, eliminating the delay in focusing. However, it can be difficult to install such a projection device and a screen for displaying the virtual image in the interior space of a vehicle.

[0009] The present disclosure has been made in consideration of the above points, and its purpose is to enable a driver to quickly check behind them without using a large display device such as a projection unit and a screen. [Means for solving the problem]

[0010] To achieve the above object, one aspect of the present disclosure can be based on a vehicle electronic display device mounted on a vehicle, the vehicle electronic display device including: an imaging unit that captures an image of at least a rear area of ​​the vehicle; an image processing unit that acquires the image captured by the imaging unit and performs image processing to generate a display image having a smaller diopter value than the image captured by the imaging unit by changing a luminance histogram included in information about the image; and a display unit that displays the display image generated by the image processing unit.

[0011] According to this configuration, when the display unit is installed at the upper center of the front of the windshield in a manner similar to a conventional rearview mirror, the distance between the display unit and the driver of the vehicle will be closer. The image displayed on the display unit has a smaller diopter value than the image captured by the imaging unit, due to image processing performed by the image processing unit on the image captured by the imaging unit. The diopter value is a numerical value defined as the reciprocal of the visual distance. When focusing from a distant object to a near object, the diopter value decreases as the depth of focus increases. Therefore, an image with a smaller diopter value is easier to focus on than an image with a larger diopter value. Therefore, when the driver is looking several tens of meters ahead of the vehicle and then focuses their gaze on the display unit to check the rear, the display image displayed on the display unit is more easily focused, allowing for quick rearward check.

[0012] The vehicle electronic display device may further include an illuminance acquisition unit that acquires environmental illuminance around the vehicle. In this case, the image processing unit can generate the display image by changing a luminance histogram based on the environmental illuminance acquired by the illuminance acquisition unit.

[0013] The image processing unit can generate the display image by performing contrast conversion, gamma value conversion, and sharpness conversion as the image processing. The image processing unit can generate a display image with good color reproducibility and a natural appearance by not performing local flattening processing in the image processing.

[0014] The image processing unit determines whether the vehicle is in a bright place or a dark place based on the ambient illuminance acquired by the illuminance acquisition unit, and can change parameters of the image processing depending on whether the vehicle is in a bright place or a dark place. A dark place is a place with low ambient illuminance, such as when driving at night or in a tunnel. A bright place is a place with high ambient illuminance, such as when driving at night or in a tunnel.

[0015] When the vehicle is in a bright place, the image processing unit can set the contrast conversion parameter to 0.80 or more and 0.93 or less, the gamma value conversion parameter to 0.70 or more and 0.90 or less, and the sharpness conversion parameter to 0.66 or more and 1.00 or less.

[0016] When the vehicle is in a dark place, the image processing unit can set the contrast conversion parameter to 0.80 or more and 1.06 or less, the gamma value conversion parameter to 0.50 or more and 0.90 or less, and the sharpness conversion parameter to 0.33 or more and 1.00 or less.

[0017] The image processing unit may execute, as the image processing, a process of multiplying the luminance histogram of the image captured by the imaging unit by a parameter of the contrast conversion, and a process of raising the luminance histogram of the image captured by the imaging unit to the power of a parameter of the gamma value conversion. [Effects of the Invention]

[0018] As described above, it is possible to display on the display unit an image for display that has a smaller diopter value than the image captured by the imaging unit, which makes it easier for the driver to focus when checking behind the vehicle and enables the driver to check behind the vehicle quickly without using a large-scale display device such as a projection unit and screen. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing a part of a vehicle equipped with an electronic display device for a vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the configuration of the vehicle electronic display device. [Figure 3] FIG. 3 is a functional block diagram of the control unit. [Figure 4] FIG. 4 is a diagram showing an example of an image and a brightness histogram. [Figure 5] FIG. 5 is a plan view that schematically shows a test device for verifying the effect of each parameter related to image processing on focusing. [Figure 6] FIG. 6 is a side view of the test device. [Figure 7] FIG. 7 is a graph showing the distribution of diopter values ​​when the luminance, γ value, and contrast are changed. [Figure 8] FIG. 8 is a graph showing shaded areas where the diopter value decreases when the γ value, contrast, and brightness are changed. [Figure 9] FIG. 9 is a graph showing shaded areas where the diopter value decreases when the γ value, contrast, and local flattening are changed. [Figure 10] FIG. 10 is a graph showing shaded areas where the diopter value decreases when the γ value, sharpness, and brightness are changed. [Figure 11] FIG. 11 is a graph showing the distribution of diopter values ​​when contrast, sharpness, and local flattening are changed. [Figure 12]FIG. 12 is a graph showing the distribution of diopter values ​​when contrast, sharpness, and brightness are changed. [Figure 13] FIG. 13 is a graph showing the relationship between the gamma value, sharpness, local flattening, and diopter value. [Figure 14] FIG. 14 is a graph showing the relationship between the gamma value, sharpness, contrast and diopter value. [Figure 15] FIG. 15 is a graph showing the relationship between the gamma value, contrast, local flattening, and diopter value. [Figure 16] FIG. 16 is a graph showing the relationship between the distance from the display unit and the focusing time. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0021] FIG. 1 is a schematic diagram showing a part of a vehicle 100 equipped with a vehicle electronic display device 1 according to an embodiment of the present invention. The type of vehicle 100 is not particularly limited, and may be, for example, a passenger car or a freight vehicle (such as a truck). The vehicle 100 includes a front windshield 101, a roof 102, a rear windshield 103, a dashboard 104, and a driver's seat 105. A driver 200 is seated in the driver's seat 105. In this embodiment, a case will be described in which the vehicle electronic display device 1 is used as an electronic display device for an inner mirror, but the present invention is not limited to this, and the vehicle electronic display device 1 can also be used as an electronic display device for an outer mirror disposed outside the vehicle 100.

[0022] 2, the vehicle electronic display device 1 mounted on the vehicle 100 includes an imaging unit 2, an ambient light sensor 3, a control unit 4, and a display unit 5. The power supply 6 is for supplying power to the vehicle electronic display device 1 and is configured, for example, by an on-board battery. The power supply 6 may or may not be included in the vehicle electronic display device 1.

[0023] The imaging unit 2 is configured with a camera for capturing images of at least the rear of the vehicle 100, and is capable of capturing video. Although not shown, the imaging unit 2 includes an imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). The imaging element generates an image based on the intensity of light received via an optical system (not shown) that the imaging unit 2 has. The images are generated at a predetermined frame rate (e.g., 30 fps or more) and output from the imaging unit 2. The images output from the imaging unit 2 are input to the control unit 4. The images output from the imaging unit 2 may be input to a vehicle control device (not shown) and then input to the control unit 4. Power is supplied to the imaging unit 2 via the control unit 4.

[0024] As shown in FIG. 1, the imaging unit 2 is installed inside the rear windshield 103 of the vehicle 100. This allows the imaging unit 2 to continuously capture images of at least the area behind the vehicle 100 through the rear windshield 103. The field of view of the imaging unit 2 may include not only the area behind the vehicle 100 but also the sides. The imaging unit 2 may be installed outside the passenger compartment. The imaging unit 2 can continue capturing images not only while the vehicle 100 is moving, but also when the vehicle is stopped. The imaging unit 2 may be configured, for example, as a camera for a drive recorder or a camera for a backup monitor.

[0025] The ambient light sensor 3 is an illuminance acquisition unit that acquires the ambient illuminance around the vehicle 100 and includes a light-receiving element such as a photodiode. In this embodiment, the ambient light sensor 3 is mounted on the upper surface of the dashboard 104 and receives light that has passed through the windshield 101 and reached the interior of the vehicle. The ambient illuminance around the vehicle 100 can be acquired based on the intensity of the received light. When acquiring the ambient illuminance around the vehicle 100, the ambient illuminance can be calculated taking into account the light transmittance of the windshield 101. If the vehicle 100 is equipped with an automatic light system, the illuminance sensor of the automatic light system may be used as the ambient light sensor 3. Furthermore, since the image sensor 2 is a component that can receive light from outside and acquire the intensity of the external light (corresponding to the ambient illuminance), the image sensor 2 may also be used as the ambient light sensor 3. The ambient illuminance is acquired by the ambient light sensor 3 in approximately real time. A signal output from the ambient light sensor 3 is input to the control unit 4. The ambient light sensor 3 may be installed outside the vehicle interior.

[0026] The display unit 5 is a display device configured, for example, by a liquid crystal display (LCD) or an organic light-emitting diode (OLED) display. The display unit 5 is configured by a high-brightness display, and the brightness of the display unit 5 is 500 Cd / m 2 The above is the case. The shape of the display unit 5 is not particularly limited, but may be elongated in the vehicle width direction and have a shape similar to that of a conventional inner mirror. The front portion of the display unit 5 is attached to the upper front center of the windshield 101 via a stay 5a so that the angle can be adjusted. The display unit 5 may be attached to the interior surface of the roof 102. In addition, the surface of the display unit 5 has a half mirror structure, so that when an image is not displayed on the display unit 5, it can be used as an inner mirror. Power is supplied to the display unit 5 via the control unit 4.

[0027] 3 is a functional block diagram of the control unit 4, and as shown in this diagram, the control unit 4 includes an input unit 4a, an image processing unit 4b, a display panel control unit 4c, and a storage unit 4d. The input unit 4a, the image processing unit 4b, and the display panel control unit 4c may be configured as hardware of the control unit 4, or may be configured as a combination of hardware and software.

[0028] A typical example of the configuration of the control unit 4 is a configuration including a microcomputer having a central processing unit, ROM, RAM, etc. For example, a storage unit 4d can be configured with a ROM, and in addition to the operating program, various data, control parameters, image processing parameters (described later), etc. are pre-stored in this storage unit 4d.

[0029] The control unit 4 may be provided with a processing device such as an FPGA (Field Programmable Gate Array) or an ISP (Image Signal Processor). A processor integrating processing devices such as FPGA and DSP may be provided in each of the input unit 4a, the image processing unit 4b, and the display panel control unit 4c. Some of the input unit 4a, the image processing unit 4b, and the display panel control unit 4c may be configured by the first processing device, and the rest may be configured by the second processing device.

[0030] The input unit 4a includes a connection interface to which the imaging unit 2 and the ambient light sensor 3 are connected, for example, and accepts input of image data captured by the imaging unit 2, as well as input of a signal related to ambient illuminance output from the ambient light sensor 3. The image data and the signal related to ambient illuminance received by the input unit 4a are output to the image processing unit 4b.

[0031] The image processing unit 4b acquires the image captured by the imaging unit 2 and performs image processing to generate a display image having a smaller diopter value than the image captured by the imaging unit 2 by changing a luminance histogram included in the information of the image captured by the imaging unit 2. When performing image processing, the image processing unit 4b also acquires a signal related to the ambient illuminance output from the ambient light sensor 3. The image processing unit 4b then changes the luminance histogram based on the ambient illuminance acquired by the ambient light sensor 3 to generate a display image to be displayed on the display unit 5.

[0032] 4 is a diagram showing an example of an image acquired by the image processing unit 4b and an example of a luminance histogram of the image acquired by the image processing unit 4b. In the case of a color image, the luminance histogram is shown for each of R, G, and B. The characteristics of the image acquired by the image processing unit 4b can be shown by the luminance histogram.

[0033] The display panel control unit 4c is a unit that controls the display unit 5. The display image data generated by the image processing unit 4b is output to the display panel control unit 4c. The display panel control unit 4c generates a signal for controlling the display unit 5 based on the acquired display image data and transmits the signal to the display unit 5. As a result, the display image generated by the image processing unit 4b is displayed on the display unit 5.

[0034] The diopter value is a numerical value defined as the reciprocal of the visual distance, and when focusing from a distant object to a near object, the diopter value decreases as the depth of focus increases. The depth of focus is an index that indicates the range in which an object can be seen in focus, and a larger depth of focus indicates that it is easier to focus (the range in which an object can be seen in focus is wider). Easier focusing means that the eye movement places less strain on the eyes. Therefore, by generating a display image with a smaller diopter value than the image captured by the imaging unit 2 and displaying it on the display unit 5, the driver can easily focus when checking behind the vehicle and quickly check the vehicle behind the vehicle without using a large display device such as a projection unit and screen.

[0035] Parameters that affect the focal depth include brightness, contrast, γ value (gamma value), sharpness, local flattening, etc. of the image for display, but in this embodiment, the image processing unit 4b generates the image for display by performing contrast conversion, γ value conversion, and sharpness conversion on the image captured by the imaging unit 2 as image processing for generating the image for display on the display unit 5. The image processing unit 4b may perform all of the contrast conversion, γ value conversion, and sharpness conversion, or may perform any one or any two of the contrast conversion, γ value conversion, and sharpness conversion as necessary.

[0036] Here, we will explain how to convert the brightness histogram, which shows the characteristics of an image, using the above parameters and consider the parameters related to the depth of focus. First, we will explain how to apply each parameter to change the brightness histogram.

[0037] For brightness conversion, we use the sliding method (average brightness change), which adds a constant brightness to the brightness histogram of the original image.

[0038] (Output)=(Input)+(brightness value)

[0039] The contrast conversion is performed by multiplying the brightness histogram of the original image by a certain constant value. That is, the image processing unit 4b performs image processing by multiplying the brightness histogram of the image captured by the imaging unit 2 by a contrast conversion parameter.

[0040] (Output) = (Input) × (Scale value)

[0041] The gamma conversion is a method of raising the brightness histogram of the original image by a certain constant value. That is, the image processing unit 4b executes a process of raising the brightness histogram of the image captured by the imaging unit 2 by a parameter of the gamma conversion as image processing.

[0042] (Output)=(Input)^γ

[0043] Sharpness transformation converts the pixel value of a pixel of interest by performing a convolution process using the pixel values ​​of the center pixel and eight surrounding pixels. Convolution processing involves using the output value of a product-sum operation between each pixel of the image and a filter as the pixel value of the center pixel. A filter is made up of nine coefficient values ​​that are set for the center pixel and the eight adjacent pixels. The filter used for sharpness transformation is expressed as follows:

[0044]

number

[0045] The multiply-and-accumulate operation involves calculating the product of each coefficient value of the filter and the corresponding pixel value of the original image, and then adding them up.

[0046] Local flattening is a process of dividing an image into small tiles and flattening the histogram in each area. In this embodiment, local flattening reduces color reproducibility and creates an unnatural image. Therefore, the image processing unit 4b does not perform local flattening in the image processing for generating a display image to be displayed on the display unit 5.

[0047] Before executing the image processing, the image processing unit 4b executes a determination process to determine whether the vehicle 100 is in a bright place or a dark place based on the ambient illuminance acquired by the ambient light sensor 3. For example, when the vehicle 100 is traveling at night or in a tunnel, the ambient illuminance around the vehicle 100 is, for example, about 50 lx. When the ambient illuminance acquired by the ambient light sensor 3 is input to the image processing unit 4b, if the input ambient illuminance is 50 lx or less, the image processing unit 4b determines that the vehicle 100 is in a dark place. On the other hand, if the ambient illuminance input from the ambient light sensor 3 exceeds 50 lx, the image processing unit 4b determines that the vehicle 100 is in a bright place. The determination threshold "50 lx" used in the determination process by the image processing unit 4b is an example, and the determination threshold is not limited to 50 lx. Any determination threshold that is generally recognized as a dark place when the vehicle 100 is traveling can be used. The determination threshold can be set, for example, in the range of 40 to 100 lx. Furthermore, for example, the environmental illuminance when the headlights of the vehicle 100 are turned on in an automatic light system may be used as the determination threshold value.

[0048] The image processing unit 4b changes the image processing parameters depending on whether the vehicle 100 is determined to be in a bright place or a dark place in the above determination process. Specifically, when the image processing unit 4b determines that the vehicle 100 is in a bright place in the above determination process, the image processing unit 4b sets the contrast conversion parameter to 0.80 or more and 0.93 or less, the gamma value conversion parameter to 0.70 or more and 0.90 or less, and the sharpness conversion parameter to 0.66 or more and 1.00 or less. On the other hand, when the image processing unit 4b determines that the vehicle 100 is in a dark place in the above determination process, the image processing unit 4b sets the contrast conversion parameter to 0.80 or more and 1.06 or less, the gamma value conversion parameter to 0.50 or more and 0.90 or less, and the sharpness conversion parameter to 0.33 or more and 1.00 or less. Each parameter is pre-stored in, for example, the storage unit 4d, and the image processing unit 4b determines which parameter to apply based on the above determination process.

[0049] (Test example) Next, a test to verify the focusing effect of each parameter applied during image processing by the image processing unit 4b will be described. Figures 5 and 6 are diagrams that schematically show a test device 300 for verifying the focusing effect of each parameter related to image processing by the image processing unit 4b. This test device 300 simulates a situation in which a model driver 200A shifts his or her gaze from a forward-viewing state to an inner mirror while driving on a highway.

[0050] The main display 301 is placed 6 m in front of the simulated driver 200A to simulate a forward field of view. The sub-display 302 is placed 450 mm in front of the simulated driver 200A and diagonally above it to simulate an inner mirror. The relationship between the installation position of the sub-display 302 and the simulated driver 200A is approximately the same as the positional relationship between the driver 200 and the display unit 5 in the actual vehicle 100, as shown in FIG. 1. As shown in FIG. 6, the height of the eyes of the simulated driver 200A is 1150 mm. The display surface of the sub-display 302 is inclined by 5° with respect to a vertical line 303. Furthermore, assuming a horizontal plane 304 passing through the eyes of the simulated driver 200A, a line 305 connecting the eyes of the simulated driver 200A and the vertical center of the sub-display 302 is at an angle of 10° with respect to the horizontal plane 304. 5, the horizontal center of the main display 301 is located directly in front of the eyes of the simulated driver 200A. A line 306 connecting the eyes of the simulated driver 200A and the horizontal center of the sub-display 302 is at an angle of 20° with a line 307 connecting the eyes of the simulated driver 200A and the horizontal center of the main display 301.

[0051] Alphabetical characters or numbers were displayed on the main display 301 and the sub-display 302, alternating every 2.5 seconds. Numbers were displayed approximately once every 6 to 8 times (15 to 20 seconds). The head of the simulated driver 200A was fixed by the chin rest 310.

[0052] The simulated driver 200A visually recognizes the symbols displayed on the main display 301 and determines whether to continue looking at the main display 301 or to move his / her gaze to the sub-display 302 according to the type of symbol. If the symbols displayed on the main display 301 are alphabetic characters, the simulated driver 200A is made to continue gazing at the main display 301. If the symbols displayed on the main display 301 are numbers, the gaze is moved from the main display 301 to the sub-display 302.

[0053] When the simulated driver 200A moved his / her viewpoint to the sub-display 302, the simulated driver 200A was made to determine whether the numbers displayed on the main display 301 and the sub-display 302 were the same and to operate a button. If the numbers displayed on the main display 301 and the sub-display 302 were the same, the simulated driver 200A was made to press the button with his / her right hand, and if the numbers on the main display 301 and the sub-display 302 were different, the simulated driver 200A was made to press the button with his / her left hand.

[0054] In the above test, the diopter change of the viewpoint of the simulated driver 200A was measured. The diopter value was calculated from the depth coordinate of the focus using an eye tracking device. The diopter value and reaction time related to the depth of focus were evaluated, and the conditions under which the diopter value became smaller were analyzed.

[0055] The image displayed on the sub-display 302 was processed by the image processing unit 4b, and the change in the diopter value related to the focal depth and the time required for the simulated driver 200A to press the button after the image was displayed on the sub-display 302 (the reaction time of the simulated driver 200A) were evaluated.

[0056] The parameters used for image processing by image processing unit 4b were brightness between 0 and 60, contrast between 0.8 and 1.2, gamma value between 0.5 and 1.1, sharpness between 0 and 1.3, and local flattening between 4 and 32. Image processing unit 4b performed image processing by randomly changing two or three of these parameters to generate the image to be displayed on sub-display 302.

[0057] The reaction time of the simulated driver 200A was plotted in three dimensions for each combination of parameters that were changed, and the conditions under which the diopter value would become smaller were examined. That is, for each parameter, the diopter value was classified into three ranges: a 10% range with a high diopter value, a 10% range with a low diopter value, and the remaining median range. The three-dimensional plot was then used to verify what image transformation conditions would affect the diopter value. To facilitate focusing, conditions under which the diopter value becomes small are preferable.

[0058] The graph shown in FIG. 7 shows the distribution of diopter values ​​when the brightness, γ value, and contrast are changed as parameters used in image processing by the image processing unit 4b. The diopter values ​​were classified into three types as described above. The range of large diopter values ​​is 10% (shown by black squares). (shown in black), the small 10% range (shown in black circles), and the median of the remaining range (shown in black triangles). and plotted on a graph.

[0059] To make it easier to see the correlation between each of the changed parameters, the processing shown in Figure 8 was performed. The points in Figure 8 indicate the parameters resulting from the experiment. All of the experimental points are plotted on the graph in Figure 8. Of the three types of classification based on diopter value mentioned above, the parameters that indicate the area where the depth of focus is large, i.e., the small diopter value, are indicated by diagonal lines to make them easier to see. As a result, it was found that the area with small diopter values ​​is distributed (indicated by diagonal lines in Figure 8) in the area where the gamma value is between 0.5 and 0.9, and where the contrast is between 0.8 and 1.066.

[0060] Figure 9 shows the distribution of diopter values ​​when the gamma value, contrast, and local flattening are changed. The same analysis was performed as above, and the areas with low diopter values ​​are indicated by diagonal lines. The areas with low diopter values ​​are distributed near the midpoint between contrasts of 0.933 and 1.066. On the other hand, it can be seen that local flattening has almost no effect. The results of Figures 8 and 9 show that contrast has a large effect as a parameter that reduces the diopter value, that is, increases the depth of focus.

[0061] Figure 10 shows the distribution of diopter values ​​when the gamma value, sharpness, and brightness are changed. The area with small diopter values ​​is distributed in the sharpness range between 0 and 0.33. However, this graph shows that the gamma value and brightness have almost no effect on the diopter value.

[0062] Figures 11 and 12 show the distribution of diopter values ​​when contrast, sharpness, and local flattening are changed, and contrast, sharpness, and brightness are changed, respectively. The diopter values ​​are classified into the 10% range with the highest value (shown by black squares), the 10% range with the lowest value (shown by black circles), and the remaining median value (shown by black triangles), and plotted on a graph. With this parameter conversion, it was found that the "black circles" plot with low diopter values ​​are uniformly distributed, and no correlation is observed.

[0063] To examine the optimum parameters in more detail, the scatter plots showing trends in the small diopter value range were divided into grids and analyzed.

[0064] Figure 13 shows the relationship between sharpness, gamma value, local flattening, and diopter value. Figure 14 shows the relationship between gamma value, contrast, sharpness, and diopter value. Figure 15 shows the relationship between gamma value, contrast, local flattening, and diopter value.

[0065] In Figures 13 to 15, the areas where the diopter value decreases are indicated by black areas. From Figures 13 to 15, we derived that the optimal image transformation parameters for decreasing the diopter value are a contrast transformation parameter of 0.80 to 0.93, a gamma value transformation parameter of 0.70 to 0.90, and a sharpness transformation parameter of 0.66 to 1.00. By setting the image transformation parameters within these ranges, the diopter value becomes 2.02 to 2.93. Previous test results have shown that luminance has almost no effect on the diopter value. By applying parameters within this range to image processing by the image processing unit 4b, a display image with a reduced diopter value, i.e., a greater depth of field, can be obtained. As a result, a display image that is easy to focus on can be provided at a distance of 200 to 450 mm from the driver.

[0066] Note that an image that has undergone local flattening has poor color reproducibility compared to an actual image, resulting in an unnatural-looking image. Therefore, the image processing unit 4b does not perform local flattening, and generates a display image under the conditions for a natural look, with the contrast conversion parameter set to 0.80 or more and 0.93 or less, the gamma value conversion parameter set to 0.70 or more and 0.90 or less, and the sharpness conversion parameter set to 0.66 or more and 1.00 or less, and displays the image on the display unit 5.

[0067] The vehicle 100 equipped with the display unit 5 on which the display image according to the embodiment of the present invention is displayed was tested by 12 subjects (4 in their 60s, 2 in their 50s, 2 in their 40s, 2 in their 30s, and 2 in their 20s). After that, a questionnaire was given regarding the visibility of the display unit 5. The vehicle 100 was driven in the daytime under clear skies with an ambient illuminance of 10,000 lx. The results are shown below.

[0068] Easy to focus and see 5 people 3 people who are less likely to get tired 3 people who don't feel anything in particular Out of focus and blurred 1 person

[0069] As described above, when the display image processed according to the embodiment of the present invention was displayed on the display unit 5, three people felt nothing in particular, and five people said that it was easy to focus. Three people also said that the display image processed according to the embodiment of the present invention was not glaring and did not cause fatigue. Younger generations have a high ability to focus and are less likely to experience focusing delays. However, as people age, this ability declines, resulting in focusing delays. The results of this survey show that optimizing image processing parameters can make it easier to focus, making it appear as if the object was in focus, a phenomenon that occurs when the ability to change focus declines with age.

[0070] A similar experiment was conducted under dark conditions of 40 lx. Similar analysis was performed, and the following image conversion parameters were derived to reduce the diopter value: contrast conversion parameter between 0.80 and 1.06, gamma value conversion parameter between 0.50 and 0.90, and sharpness conversion parameter between 0.33 and 1.00.

[0071] As with the results of the study under bright conditions, the image with local flattening had poor color reproducibility, so the image processing unit 4b did not perform local flattening.When the subject described above performed a test drive at night (ambient illuminance: 50 lx), the results showed that it was easy to focus, just like under bright conditions.

[0072] FIG. 16 shows the relationship between the distance from the display unit 5 and the time required to focus. The time is shown as a relative time. It can be seen that the time required to focus decreases as the distance from the display unit 5 increases. This indicates that focusing becomes easier as the distance between the display unit 5 and the eye increases. Focusing at close range requires a greater change in the crystalline lens, which increases the time required to focus. In this test, the ease of focusing at a relatively short distance of 450 mm from the sub-display 302 (corresponding to the display unit 5) was verified. This effect is effective regardless of the distance from the display unit 5, and the effect of this embodiment remains unchanged regardless of the distance. However, the effect of image processing by the image processing unit 4b is particularly noticeable when the distance from the sub-display 302 is within a relatively short range of 400 mm to 550 mm.

[0073] From the above test results, when the vehicle 100 is in a bright place, the diopter value of the driver 200 can be reduced by setting the contrast conversion parameter to 0.80 or more and 0.93 or less, the gamma value conversion parameter to 0.70 or more and 0.90 or less, and the sharpness conversion parameter to 0.66 or more and 1.00 or less. Also, when the vehicle 100 is in a dark place, the diopter value of the driver 200 can be reduced by setting the contrast conversion parameter to 0.80 or more and 1.06 or less, the gamma value conversion parameter to 0.50 or more and 0.90 or less, and the sharpness conversion parameter to 0.33 or more and 1.00 or less.

[0074] The above-described embodiments are merely examples in all respects and should not be construed as limiting. Furthermore, all modifications and variations within the scope of the claims are within the scope of the present invention. [Industrial Applicability]

[0075] As described above, the electronic display device for a vehicle according to the present disclosure can be used as, for example, an inner mirror of a vehicle, and can also be applied to an electronic display device for an outer mirror. [Explanation of symbols]

[0076] 1. Electronic display device for vehicle 2. Imaging unit 3. Ambient light sensor (illuminance acquisition unit) 4. Control Unit 4b Image processing section 100 vehicles

Claims

1. An electronic display device for vehicles that is installed in a vehicle, An image processing unit acquires an image captured by an imaging unit that images at least the rear of the vehicle, and performs image processing to generate a display image in which the diopter value is smaller than that of the image captured by the imaging unit by changing the luminance histogram included in the information of the image. An electronic display device for a vehicle, comprising: a display unit that displays the display image generated by the image processing unit; and a display unit that displays the display image generated by the image processing unit.

2. In the vehicle electronic display device according to claim 1, The vehicle further comprises an illuminance acquisition unit that acquires the ambient illuminance around the vehicle, The image processing unit generates the display image by changing the luminance histogram based on the ambient illuminance acquired by the illuminance acquisition unit, in an electronic display device for a vehicle.

3. In the vehicle electronic display device according to claim 2, The image processing unit generates the display image by performing contrast conversion, gamma value conversion, and sharpness conversion as image processing, in an electronic display device for a vehicle.

4. In the vehicle electronic display device according to claim 2, The image processing unit is an electronic display device for a vehicle that does not perform local flattening processing in the image processing.

5. In the vehicle electronic display device according to claim 3, The image processing unit determines whether the vehicle is in a bright or dark place based on the ambient illuminance acquired by the illuminance acquisition unit, and changes the parameters of the image processing depending on whether the vehicle is in a bright or dark place, in this vehicle electronic display device.

6. In the vehicle electronic display device according to claim 5, The image processing unit, when the vehicle is in a bright place, sets the contrast conversion parameter to 0.80 or more and 0.93 or less, the gamma value conversion parameter to 0.70 or more and 0.90 or less, and the sharpness conversion parameter to 0.66 or more and 1.00 or less, in an electronic display device for a vehicle.

7. In the vehicle electronic display device according to claim 5, The image processing unit, when the vehicle is in a dark place, sets the contrast conversion parameter to 0.80 or more and 1.06 or less, the gamma value conversion parameter to 0.50 or more and 0.90 or less, and the sharpness conversion parameter to 0.33 or more and 1.00 or less, in an electronic display device for a vehicle.

8. In the vehicle electronic display device according to claim 3, The image processing unit performs the process of multiplying the luminance histogram of the image captured by the imaging unit by the contrast conversion parameters as the image processing, in an electronic display device for a vehicle.

9. In the vehicle electronic display device according to claim 3, The image processing unit performs the process of raising the luminance histogram of the image captured by the imaging unit to the power of the gamma value conversion parameter as the image processing, in an electronic display device for a vehicle.

10. In the vehicle electronic display device according to claim 1, The brightness of the display unit is 500 Cd / m². ２ That concludes the description of the vehicle electronic display device.

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