JP2021113872A - Image display device - Google Patents

Abstract

To provide an image display device capable of improving visibility of an image captured in a dark or bright environment.SOLUTION: An image display device 100 comprises: a camera 10; a graphic IC 30 for correcting pixel values of pixels consisting of an image for one screen obtained by imaging with the camera 10 so that difference between the maximum value and the minimum value of the pixel values increases, for the image; and an LCD 40 displaying an image for one screen using the pixel values corrected by the graphic IC 30.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image display device that displays an image or the like behind a vehicle captured by a camera.

Conventionally, an in-vehicle display device as an electronic mirror that displays an image captured by a camera on a liquid crystal display instead of an optical rearview mirror has been known (see, for example, Patent Document 1). In this in-vehicle display device, when the brightness of the vehicle ceiling detected by the illuminance sensor is bright, the image of the display unit can be brightened by increasing the brightness of the display unit, and conversely, the brightness of the vehicle ceiling at night or the like. When it becomes dark, the image on the display unit can be darkened to prevent the image on the display unit from becoming unnecessarily bright.

Japanese Unexamined Patent Publication No. 2019-1293

Many electronic mirrors including the electronic mirror disclosed in Patent Document 1 described above have a problem that visibility deteriorates because the entire displayed image becomes dark at night when the surroundings of the vehicle are dark. .. Since the brightness of the entire image is determined by the sensitivity of the camera lens and the image sensor, even if a liquid crystal display having good gradation performance (high gradation) is used, the visibility cannot be improved by itself. It should be noted that such deterioration of visibility is caused not only when the pixel value of each pixel constituting the image is biased to the low gradation side as in the case where the entire image is dark, but also when the entire image is bright and each pixel value is high gradation. The same can happen when it is biased to the side.

The present invention has been created in view of these respects, and an object of the present invention is to provide an image display device capable of improving the visibility of an image captured in a dark or bright environment.

In order to solve the above-mentioned problems, the image display device of the present invention includes a camera and a maximum value and a minimum value of the pixel values of the pixels constituting the image in a predetermined range obtained by imaging with the camera. It is provided with a pixel value correction means for correcting these pixel values and a display means for displaying an image in a predetermined range using the pixel values corrected by the pixel value correction means so that the difference between the two is widened. ..

In particular, the pixel value correction means described above is detected by the maximum / minimum detection means for detecting the maximum value and the minimum value of the pixel value of each pixel constituting the image in a predetermined range obtained by imaging by the camera, and the maximum / minimum detection means. A predetermined range using a correction value determining means for determining a correction value for a pixel value of each pixel constituting an image in a predetermined range based on the determined maximum value and a minimum value, and a correction value determined by the correction value determining means. It is desirable to provide a correction execution means for correcting the pixel value of each pixel constituting the image.

As a result, even when the difference between the bright part and the dark part is small like an image captured in a dark or bright environment, these differences can be enlarged to obtain an image with clear light and darkness. Visibility can be improved.

Further, the correction value determining means described above sets a reference value between the maximum value and the minimum value, corrects the pixel value larger than the reference value to increase the pixel value, and values the value higher than the reference value. For pixel values with a small value, it is desirable to make corrections that reduce the pixel value. Further, as the above-mentioned reference value, it is desirable to use an intermediate value between the maximum value and the minimum value that can be taken as the pixel value. Alternatively, as the reference value described above, it is desirable to use an intermediate value between the maximum value and the minimum value detected by the maximum / minimum detection means. By setting a reference value and correcting the pixel value by comparing with the reference value, it is possible to correct each of the bright pixel value and the dark pixel value and surely create an image with clear contrast.

Further, as the pixel value described above, it is desirable that a value corresponding to each component of the RGB format is used. This makes it possible to improve the visibility of images in widely used formats.

It is a figure which shows the whole structure of the image display device of one Embodiment. It is a functional block diagram which shows the detail of a graphic IC. It is a flow chart which mainly shows the operation procedure of a graphic IC which takes in the captured image and performs the correction operation which makes the lightness and darkness of an image clear. It is a figure which shows the outline of the maximum value and the minimum value detection performed by the maximum / minimum detection unit. It is a figure which shows the outline of the correction operation which increases the pixel value with respect to the pixel value which the value is larger than a reference value. It is a figure which shows the outline of the correction operation which reduces a pixel value with respect to the pixel value which the value is smaller than a reference value.

Hereinafter, an image display device according to an embodiment to which the present invention is applied will be described with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration of an image display device according to an embodiment. As shown in FIG. 1, the image display device 100 of the present embodiment includes a camera 10, an image processing processor 20, a graphic IC 30, and an LCD (liquid crystal display) 40. The image display device 100 has a function as an electronic mirror that creates an image of the rear of the vehicle and replaces it with a mirror image of a rearview mirror to display the image.

The camera 10 is attached to a predetermined position behind the vehicle (for example, the upper part of the rear glass or the upper part of the license plate), and captures a range equal to or wider than the mirror image reflected on the rearview mirror. The camera 10 includes, for example, an image sensor such as a CCD or SMOS and a lens, and data (RAW data) output from the image sensor is input to the image processor 20.

The image processor 20 generates pixel values in pixel units after performing correction processing of an optical system such as a lens and scratch correction caused by variations in image sensors on the data input from the camera 10. Output. For example, for each pixel, RGB data having an 8-bit pixel value for each RGB is generated.

The graphic IC 30 captures RGB data output from the image processing processor 20 for one display screen and performs predetermined processing. In the present embodiment, as a predetermined process, gamma correction and the like, which are generally performed, and a process necessary for clarifying the brightness of the captured image are performed.

The LCD 40 is for displaying as an electronic mirror. Generally, the rearview mirror is mounted in the center of the driver's and passenger's seats of the vehicle and above the windshield. The rear-view mirror is provided with an LCD 40 on the back side, and when an image is displayed on the LCD 40, the displayed image is visible to the driver through the mirror surface. When the LCD 40 is in the non-display state, the driver can see the mirror image of the rear of the vehicle reflected by the surface (mirror surface) of the rearview mirror.

FIG. 2 is a functional block diagram showing details of the graphic IC 30. As shown in FIG. 2, the graphic IC 30 includes an image input unit 31, an image data conversion unit 32, a pre-correction image storage unit 33, a maximum / minimum detection unit 34, a correction value determination unit 35, a correction execution unit 36, and a corrected image storage unit. A unit 37 and an image output unit 38 are provided.

The image input unit 31 takes in the image data output from the camera 10. The image data conversion unit 32 converts the image data (RAW data) captured by the image input unit 31 into pixel-by-pixel RGB data. For example, each of RGB is converted into an 8-bit pixel value corresponding to one pixel. The pre-correction image storage unit 33 stores the pixel values (RGB data) of each pixel of the display 1 screen output from the image data conversion unit 32.

The maximum / minimum detection unit 34 detects the maximum value and the minimum value of the pixel values of each pixel for one screen stored in the pre-correction image storage unit 33. This detection is performed for each pixel value of RGB. Further, this detection may be performed by reading out the image data stored in the pre-correction image storage unit 33, but the operation is to store the image data output from the image data conversion unit 32 in the pre-correction image storage unit 33. By performing in parallel, the operation procedure can be simplified.

The correction value determination unit 35 is a correction value (correction parameter) for the pixel value (RGB data) of each pixel constituting the image for one screen based on the maximum value and the minimum value detected by the maximum / minimum detection unit 34. To determine.

In the present embodiment, a reference value is set between the detected maximum value and the minimum value, and a pixel value larger than the reference value is corrected to increase the pixel value, and a pixel having a value smaller than the reference value is corrected. The value is corrected to reduce the pixel value.

The correction execution unit 36 uses the correction value determined by the correction value determination unit 35 (specifically, equations (1) and (2) represented by the correction parameters p, q, s, and t described later). The pixel value of each pixel constituting the image for one screen is corrected. By this correction, the pixel value whose value is smaller than the reference value is corrected to a smaller value, and conversely, the pixel value whose value is larger than the reference value is changed to a larger value and corrected, so that the brightness is clear. You can get the image. The corrected image storage unit 37 stores the pixel values for one screen after correction output from the correction execution unit 36. The image output unit 38 reads out the pixel values stored in the corrected image storage unit 37 and outputs them to the LCD 40.

The graphic IC 30 described above is used as a pixel value correcting means, an LCD 40 is used as a display means, a maximum / minimum detecting unit 34 is used as a maximum / minimum detecting means, a correction value determining unit 35 is used as a correction value determining means, and a correction executing unit 36 is used as a correction executing means. Corresponds to each.

The image display device 100 of the present embodiment has such a configuration, and the operation thereof will be described next.

FIG. 3 is a flow chart mainly showing an operation procedure of the graphic IC 30 that captures an captured image and performs a correction operation for clarifying the brightness and darkness of the image.

When the image is taken by the camera 10 (step 100), the image data is taken in by the image input unit 31, and the image data is converted into RGB data for each pixel by the image data conversion unit 32 and stored in the pre-correction image storage unit 33. It is stored (step 102).

In parallel with the storage operation of the image data for one screen (or even after the storage operation is completed), the maximum / minimum detection unit 34 inputs the RGB data of each pixel constituting the one screen. The maximum value a and the minimum value b are detected in the target (step 104). Since there are three types (RGB) of pixel values for each pixel, assuming that the number of pixels included in one screen is n, there are 3n pixel values in the entire screen, and the maximum value a and the minimum value are among them. b is detected.

FIG. 4 is a diagram showing an outline of the maximum value and the minimum value detection performed by the maximum / minimum detection unit 34. Considering the case where the pixel value is represented by 8 bits for each of RGB, the gradation of the pixel value is 256 gradations for each of RGB, and the range that the pixel value can take is 0 to 255. In the example shown in FIG. 4, the maximum value of the pixel value of R is 215, the minimum value is 25, the maximum value of the pixel value of G is 235, the minimum value is 27, the maximum value of the pixel value of B is 205, and the minimum value is. It is 17.

The maximum / minimum detection unit 34 selects the largest value 235 from the three types of maximum values 215, 235, and 205 as the maximum value a for determining the correction value, and the three types of minimum values 25, 27, and 17 The smallest value 17 is selected as the minimum value b for determining the correction value.

Next, the correction value determination unit 35 sets a correction parameter as a correction value for correcting a pixel value larger or smaller than the reference value based on the detected maximum value a and minimum value b. Determine (step 106).

FIG. 5 is a diagram showing an outline of a correction operation for increasing a pixel value for a pixel value having a value larger than a reference value. In the correction of the pixel value, the maximum value a of the pixel value is converted to the maximum value 255 of the gradation, and the pixel value equal to the reference value k has the same value even after the correction, and is between the reference value k and the maximum value a. It is assumed that the pixel value m of is converted to the pixel value m'by the correction. When these pixel values m'and m are linearly combined,
m'= pm + q ・ ・ ・ (1)
Relationship is established. Here, p and q are correction parameters used for this correction. Since the pixel value a before correction is converted to the pixel value 255 and the pixel value k is maintained as it is,
p = (255-k) / (ak)
q = k × (a-255) / (ak)
Will be. The reference value k may be, for example, an intermediate value 128 of the gradation.

FIG. 6 is a diagram showing an outline of a correction operation for reducing a pixel value for a pixel value whose value is smaller than the reference value. In the correction of the pixel value, the minimum value b of the pixel value is converted to the minimum value 0 of the gradation, and the pixel value equal to the reference value k has the same value after the correction, and is between the reference value k and the minimum value b. It is assumed that the pixel value n of is converted to the pixel value n'by the correction. When these pixel values n'and n are linearly combined,
n'= sn + t ... (2)
Relationship is established. Here, s and t are correction parameters used for this correction. Since the pixel value b before correction is converted to the pixel value 0 and the pixel value k is maintained as it is,
s = k / (kb)
t = -kb / (kb)
Will be.

The correction execution unit 36 corrects the pixel value larger than the reference value by using the equation (1), and corrects the pixel value smaller than the reference value by using the equation (2) (step 108). This correction increases the difference between light and dark in the image. Actually, at the same time as these corrections, conventional corrections such as gamma correction are also performed. As for the pixel value corrected in this way, one screen portion is stored in the corrected image storage unit 37 (step 110).

As described above, in the image display device 100 of the present embodiment, by performing correction for increasing or decreasing the pixel value of each pixel constituting the image, a bright portion and a dark portion such as an image captured in a dark or bright environment can be obtained. Even when the difference between the two is small, these differences can be enlarged to make an image with clear brightness and darkness, and the visibility of the image can be improved. In addition, a reference value is set and the reference value is set. By correcting the pixel values by comparing the above, it is possible to correct each of the bright pixel value and the dark pixel value and surely create an image with clear light and dark. As the pixel value, the value corresponding to each component of the RGB format is used for correction, and it is possible to improve the visibility of an image in a widely used format.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in the above-described embodiment, the intermediate value 128 of the gradation is used as the reference value k when performing the correction, but other values may be used. For example, an intermediate value (average value) between the detected maximum value a and minimum value b may be used as a reference value. In this way, by using the intermediate value of the variable pixel values, it is possible to evenly correct the bright portion and the dark portion in the image.

Further, in the above-described embodiment, the case where the pixel value is represented by 8 bits for each of RGB has been described, but the case where the pixel value is other than 8 bits (for example, 6 bits) or the pixel value represented by YUV data or RGGB data has been described. The present invention can also be applied to.

Further, in the above-described embodiment, the case where the pixel value is corrected by the graphic IC 30 has been described, but the same correction is performed in the image processing processor 20, or a processing unit dedicated to correction between the image processing processor 20 and the graphic IC 30. (Dedicated IC or the like) may be provided.

Further, in the above-described embodiment, the pixel value of the image for one screen is corrected to change the brightness, but the correction may be performed only in a part of the area of one screen.

As described above, according to the present invention, even when the difference between the bright part and the dark part is small as in an image captured in a dark or bright environment, these differences are enlarged to make the light and dark clear. It can be an image, and the visibility of the image can be improved.

100 Image display device 10 Camera 20 Image processor 30 Graphic IC
31 Image input unit 32 Image data conversion unit 33 Image storage unit before correction 34 Maximum / minimum detection unit 35 Correction value determination unit 36 Correction execution unit 37 Image storage unit after correction 38 Image output unit 40 LCD (liquid crystal display device)

Claims (6)

With the camera
Pixel value correction means for correcting a predetermined range of images obtained by imaging with the camera so that the difference between the maximum value and the minimum value of the pixel values of each pixel constituting the image is widened. When,
A display means for displaying an image in the predetermined range using a pixel value corrected by the pixel value correction means, and a display means.
An image display device comprising. The pixel value correction means
A maximum / minimum detection means for detecting the maximum and minimum pixel values of each pixel constituting the image in the predetermined range obtained by imaging with the camera, and
A correction value determining means for determining a correction value for a pixel value of each pixel constituting the image in the predetermined range based on the maximum value and the minimum value detected by the maximum / minimum detecting means.
A correction executing means for correcting the pixel value of each pixel constituting the image in the predetermined range by using the correction value determined by the correction value determining means.
The image display device according to claim 1, further comprising. The correction value determining means sets a reference value between the maximum value and the minimum value, corrects the pixel value having a value larger than the reference value to increase the pixel value, and makes a correction from the reference value. The image display device according to claim 2, wherein the pixel value having a small value is corrected to reduce the pixel value. The image display device according to claim 3, wherein the reference value uses an intermediate value between a maximum value and a minimum value that can be taken as the pixel value. The image display device according to claim 3, wherein the reference value uses an intermediate value between the maximum value and the minimum value detected by the maximum / minimum detection means. The image display device according to any one of claims 1 to 5, wherein a value corresponding to each component of the RGB format is used as the pixel value.

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