JP2006339994A - Onboard camera controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a delicate contrast of an image even when a high-luminance part is included. <P>SOLUTION: When an image photographed by a camera 1 includes high-luminance parts of headlights of an oncoming vehicle, high-luminance parts of tail lamps, brake lamps, etc., of a vehicle traveling before, etc., an onboard controller lowers sensitivity of variation in pixel value to lightness as pixel value and lightness characteristics that the camera 1 has and also performs variation to pixel value and lightness characteristics which have smaller rate of variation in pixel value as the level of lightness is higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an in-vehicle camera control device.

Conventionally, for example, according to the technique described in Patent Document 1, image signals from a TV camera are converted into image data to detect lanes, and the coordinates of a predetermined range of image data for performing next lane detection from the current vehicle speed are calculated. Extract. Then, by calculating the luminance (brightness) of the road surface portion of the coordinates, the next received light amount is determined and the aperture (exposure amount) of the TV camera is controlled.
JP-A-6-253208

  FIG. 5A shows pixel value / brightness characteristics indicating the relationship between the level of brightness (luminance) of an image and the pixel value corresponding to the intensity of light incident on the pixel of the camera. As shown in FIG. 9A, in normal shooting, the pixel value and the brightness are linear or the sensitivity of the change of the pixel value with respect to the brightness is high so that a fine contrast of the image can be detected. It also rests on the camera.

  By the way, when photographing the front of the vehicle using a camera (vehicle camera) mounted on the vehicle, the photographed image includes high-luminance portions such as headlights of oncoming vehicles, tail lamps and brake lamps of preceding vehicles. Sometimes. When there is such a high-luminance part, as shown in FIG. 5B, by reducing the shutter speed of the in-vehicle camera and the gain of the image signal, the sensitivity of the change in the pixel value with respect to the brightness is low. This can be changed to reduce the overall brightness of the image.

  However, in order to provide the pixel value / brightness characteristics shown in FIG. 5B, it is impossible to detect the delicate contrast of the image simply by reducing the shutter speed or the gain of the image signal.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an in-vehicle camera control device capable of detecting a fine contrast of an image even when a high-luminance portion exists. .

In order to achieve the above object, an in-vehicle camera control device according to claim 1,
An in-vehicle camera that is mounted on a vehicle and that captures an image of the surroundings of the vehicle, and that repeatedly outputs a pixel value according to the intensity of light incident on each pixel constituting the image sensor as an image signal;
A determination means for determining whether or not a pixel having a pixel value equal to or greater than a predetermined threshold exists adjacent to or close to a predetermined number of pixels in the image signal;
A pixel value indicating the relationship between the brightness level of the imaging range of the in-vehicle camera and the pixel value, when the determination unit determines that the pixels are adjacent to or close to each other by a predetermined number of pixels. -As the brightness characteristics, the sensitivity of the change in the pixel value relative to the brightness is low, and the higher the brightness level, the smaller the pixel value change rate. And a changing means.

  In this way, the determination means determines whether or not there is a high luminance part such as the headlight of the oncoming vehicle, the tail lamp or the brake lamp of the preceding vehicle, and if this high luminance part exists, As the pixel value / brightness characteristic, the sensitivity of the change of the pixel value with respect to the brightness is lowered, and the pixel value / brightness characteristic is changed so that the change rate of the pixel value is smaller as the brightness level is higher.

  As a result, as shown in FIG. 3A, since the original linear characteristic is changed to the pixel value / brightness characteristic taking into consideration the logarithmic characteristic, the in-vehicle camera having the changed pixel value / brightness characteristic is Therefore, it is possible to output an image signal capable of detecting a delicate contrast while suppressing the brightness of the entire image.

The in-vehicle camera control device according to claim 2 includes a control unit that controls at least one of a gain applied to the image signal and a shutter speed of the in-vehicle camera,
The pixel value / brightness characteristic changing means performs at least one of control for reducing the gain applied to the image signal by the control means and control for increasing the shutter speed, so that the sensitivity of the change in the pixel value with respect to the brightness is controlled. Is changed to a low pixel value / brightness characteristic.

  As described above, when using an in-vehicle camera capable of controlling the gain and shutter speed applied to the image signal, the pixel value / brightness characteristic changing unit is configured to display the original pixel value as shown in FIG. -Change to a characteristic that reduces the rate of change of the pixel value as the brightness level increases (tone curve correction) with respect to the brightness characteristic, along with reducing the gain applied to the image signal, and shutter By increasing the speed, it is possible to change to a pixel value / brightness characteristic that is less sensitive to changes in pixel value with respect to brightness.

  According to the on-vehicle camera control device according to claim 3, the pixel value / brightness characteristic changing means increases the brightness level as the number of pixels existing adjacent to or close to each other by a predetermined number of pixels increases. It is characterized in that the pixel value / brightness characteristic is changed so that the rate of change of the pixel value with respect to the brightness is further decreased as the value of is higher.

  Thereby, the degree of change in the pixel value with respect to the brightness level can be changed according to the range of the range of the high-luminance portion described above.

The on-vehicle camera control device according to claim 4 is mounted on a vehicle and captures an image around the vehicle, and a pixel value corresponding to the intensity of light incident on each pixel constituting the image sensor. An in-vehicle camera that repeatedly outputs as an image signal,
A determination means for determining whether or not a pixel having a pixel value equal to or greater than a predetermined threshold exists adjacent to or close to a predetermined number of pixels in the image signal;
When it is determined by the determination means that the pixels are adjacent to or close to each other by a predetermined number of pixels, the image signal of the large pixel value region including at least a predetermined number of pixels that are adjacent or close to each other Control means for performing control for reducing the gain.

  For example, as shown in FIG. 4A, when there is a high luminance part such as a headlight of an oncoming vehicle or a tail lamp or a brake lamp of a preceding vehicle, the brightness of the high luminance part is saturated and the saturation causes bleeding. Contrasts other than the light source that is projected on are not detected.

  Therefore, when using an in-vehicle camera that can control the gain of the image signal for each pixel, the gain of the image signal in the large pixel value region corresponding to the high luminance portion is reduced to reduce the large pixel value region. The brightness of the image can be suppressed. As a result, since the image shown in FIG. 4B is obtained, the background contrast of the light source can be detected.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an image signal processing apparatus according to an embodiment. As shown in FIG. 1, the image signal processing apparatus includes a camera 1 and a control unit 2. The camera 1 is installed at a predetermined position in the vehicle interior, for example, on the back side of a room mirror, and images the front in the traveling direction of the vehicle.

  The camera 1 includes an amplification unit and an A / D conversion unit in addition to a known CCD image sensor or CMOS image sensor. When an image is picked up by an image sensor, the amplifying unit and the A / D converting unit amplify an analog signal indicating the brightness of each pixel of the image with a predetermined gain, and convert the amplified analog value into a digital value. To do. Then, the camera 1 outputs the signal (pixel value) converted into the digital value as an image signal to the control unit 2 for each line of the image.

  As shown in FIG. 3A, the camera 1 has a pixel value / brightness characteristic indicating the relationship between the brightness level of the imaging range of the in-vehicle camera and the pixel value, and this pixel value / brightness. The characteristic is configured such that the characteristic can be changed based on the camera control value from the control unit 2.

  The control unit 2 performs predetermined processing on the image signal output from the camera 1 and outputs the image signal subjected to the processing to various in-vehicle application systems (forward obstacle detection, white line detection, etc.).

  Further, the control unit 2 controls the exposure of the camera 1 so that the contrast of the processed image becomes appropriate. That is, the control unit 2 outputs camera control values including these adjustment instruction values to the camera 1 in order to adjust the shutter speed and frame rate of the camera 1 and the gain of the amplification unit. The control unit 2 corresponds to the brightness level (a1, a2,..., An) and the respective brightness levels in order to change the pixel value / brightness characteristics to be given to the camera 1. A camera control value including pixel values (b1, b2,..., Bn) is output to the camera 1.

  The control unit 2 includes an image interface (I / F) 3, a CPU 4, a memory 5, and a communication I / F 6. The image I / F 3 receives a pixel value output from the camera 1 and a horizontal / vertical synchronization signal.

  The CPU 4 recognizes to which pixel position the pixel value output for each horizontal line of the image corresponds to the horizontal / vertical synchronization signal input to the image I / F 3. Then, the pixel value output from the camera 1 is stored in the memory 5 so as to correspond to the recognized pixel position. In this way, the image signal output from the camera 1 is stored in the memory 5. The communication I / F 6 adjusts communication between the CPU 4 and various in-vehicle application systems.

  FIG. 2 is a flowchart showing image signal processing executed in the control unit 2. In FIG. 2, first, in step S110, an image signal output from the camera 1 is captured. That is, as described above, the pixel values constituting the image signal are stored in the memory 5 based on the horizontal / vertical synchronization signal output from the camera 1.

  In step S120, the pixel values of each pixel stored in the memory 5 are sequentially extracted. In step S130, a saturated pixel (a pixel that has reached the saturation level) is determined. As described above, the camera 1 includes the amplifying unit and the A / D conversion unit, and an analog value indicating the brightness of each pixel amplified by the amplifying unit is set to, for example, 0 to 0 by the A / D conversion unit. It is converted into a 255-stage digital value and output. In this step S130, a pixel showing a pixel value equal to or higher than a predetermined pixel threshold (for example, about 200, which differs depending on the in-vehicle application system that uses the image) is determined as a saturated pixel.

  In step S140, whether or not the saturated pixels determined in step S130 are adjacent (adjacent) by a predetermined number of pixels, or saturated pixels are close to each other by a predetermined number of pixels (a few pixels apart). ) Determine if it exists. That is, it is determined whether or not a high-luminance portion exists in the image. If the determination is affirmative, the process proceeds to step S150. If the determination is negative, the process proceeds to step S170.

  In step S150, as shown in FIG. 3A, the pixel value / brightness characteristic of the camera 1 when the camera 1 captures the next image is changed to a direction in which the high luminance portion is suppressed. That is, the original linear pixel value / brightness characteristic of the camera 1 is changed to a pixel value / brightness characteristic in consideration of logarithmic characteristics.

  Specifically, as shown in FIG. 5A, as the pixel value / brightness characteristics of the camera 1, the sensitivity of the change of the pixel value with respect to the brightness is lowered, and the pixel value is increased as the brightness level is higher. Change to a pixel value / brightness characteristic with a small change rate. In this way, by changing the pixel value / brightness characteristics, the camera 1 can output an image signal that can detect a delicate contrast while suppressing the overall brightness of an image to be captured next time. it can.

  Since the camera 1 can adjust the shutter speed, the frame rate, and the gain of the amplifying unit, as shown in FIG. 3B, the brightness with respect to the original pixel value / brightness characteristics. The brightness level is changed by decreasing the gain applied to the image signal or increasing the shutter speed. The pixel value / brightness characteristics may be changed so that the sensitivity of the change of the pixel value with respect to is low.

  Further, in step S150, as shown in FIG. 3A, the brighter the more the number of pixels adjacent to or close to each other than the predetermined number of pixels (the wider the range of the high luminance portion), the brighter It is preferable to change to a pixel value / brightness characteristic in which the rate of change of the pixel value with respect to the brightness is further decreased as the level is higher. Thus, the degree of change in the pixel value with respect to the brightness level can be changed according to the range of the high-luminance portion.

  In step S150, brightness levels (a1, a2,..., An) indicating the pixel value / brightness characteristics to be changed, and pixel values (b1, b2) corresponding to the respective brightness levels are displayed. The camera control values including b2,..., bn) are output to the camera 1.

  In step S160, since there is no high-luminance portion in the image, as shown in FIG. 3A, the pixel value / brightness characteristics of the camera 1 when the camera 1 captures the next image are changed to the original linear pixel value / Change the direction back to the brightness characteristic. That is, the pixel value / brightness characteristics taking into account the logarithmic characteristics shown in FIG. 3A can suppress a high luminance portion, but the higher the brightness level, the smaller the rate of change of the pixel value with respect to the brightness. For this reason, it is not possible to detect a delicate contrast in a high luminance part. Therefore, when there is no high-luminance part, the camera 1 detects the contrast of the bright part of the image to be captured next time by changing the pixel value / brightness characteristic in the direction to return to the original linear characteristic. An image signal that can be output can be output.

  Then, step S160 corresponds to the brightness level (a1, a2,..., An) indicating the pixel value / brightness characteristics to be changed and the respective brightness levels, as in step S150. The camera control values including the pixel values (b1, b2,..., Bn) to be output are output to the camera 1.

  In step S170, the image signal output from the camera 1 is subjected to image signal processing for use in various in-vehicle application systems. Finally, in step S180, the image signal of the image subjected to image signal processing is output to various in-vehicle application systems.

  Thereafter, the processing from step S110 to step S180 is repeated. In addition, about the change of the pixel value and brightness characteristic in step S150 and step S160, the characteristic is changed with respect to the characteristic changed last time. That is, in step S150, even if it is not possible to suppress the brightness of the high-intensity portion using the characteristic changed in one process, the characteristic is changed with respect to the previously changed characteristic in the next process. By repeating the process several times, it is possible to finally suppress the brightness of the high-luminance portion.

  Also in step S160, if the original linear pixel value / brightness characteristics are changed in one process, the possibility that the camera 1 captures an image with a high-luminance portion in the next process increases. . Therefore, by repeating the process several times, the sensitivity of the change of the pixel value with respect to the brightness is gradually increased so as to gradually approach the linear characteristic, and the brightness of the pixel value increases as the brightness level increases. It is better to gradually increase the rate of change with respect to.

  As described above, the image signal processing apparatus according to the present embodiment has a pixel value of the camera 1 when the image captured by the camera 1 includes a high-luminance portion such as a headlight of an oncoming vehicle, a tail lamp or a brake lamp of a preceding vehicle. As the brightness characteristic, the sensitivity of the change of the pixel value with respect to the brightness is lowered, and the pixel value / brightness characteristic is changed so that the rate of change of the pixel value is smaller as the brightness level is higher.

  As a result, as shown in FIG. 3 (a), the original linear characteristic is changed to the pixel value / brightness characteristic taking the logarithmic characteristic into consideration, so that the camera 1 having the changed pixel value / brightness characteristic is Therefore, it is possible to output an image signal capable of detecting a delicate contrast while suppressing the brightness of the entire image.

(Modification)
In the exposure control for controlling the exposure of the camera 1 in the present embodiment, when adjusting the gain of the amplification unit of the camera 1, all the image signals output from the camera 1 are adjusted to have the same gain. When the camera 1 in which the gain of the image signal can be adjusted for each pixel is adopted, only the gain of the image signal of each pixel in the high brightness portion described above is adjusted to suppress the brightness of the high brightness portion. Also good.

  That is, for example, as shown in FIG. 4A, when there is a high-luminance portion such as a headlight of an oncoming vehicle, a tail lamp or a brake lamp of a preceding vehicle, the brightness of the high-luminance portion is saturated. As a result, contrast other than the light source that is blurred and projected is not detected.

  Therefore, when the camera 1 in which the gain of the image signal can be adjusted for each pixel is used, a camera control value for reducing the gain of the image signal of each pixel in the high-luminance portion is given to the camera 1 in step S150 in FIG. Output. Thus, by reducing the gain of the image signal of each pixel in the high luminance portion, the brightness of the image in the high luminance portion can be suppressed. As a result, since the image shown in FIG. 4B is obtained, the background contrast of the light source can be detected.

It is a block diagram which shows the structure of the image signal processing apparatus in embodiment. 4 is a flowchart illustrating image signal processing executed in a control unit 2. (A), (b) is a figure for demonstrating the change of a pixel value and a brightness characteristic. It is a figure for demonstrating the modification 1 of embodiment. (A) is a diagram showing the pixel value / brightness characteristics in the normal state, and (b) shows the pixel value / brightness characteristics when it is impossible to detect a delicate contrast in the image. FIG.

Explanation of symbols

1 Camera 2 Control unit 3 Image I / F
4 CPU
5 Memory 6 Communication I / F

Claims (4)

An in-vehicle camera mounted on a vehicle for taking an image of the surroundings of the vehicle, and repeatedly outputting a pixel value corresponding to the intensity of light incident on each pixel constituting the image sensor as an image signal;
In the image signal, a determination unit that determines whether or not pixels indicating a pixel value equal to or greater than a predetermined threshold are present adjacent to or close to a predetermined number of pixels;
When it is determined by the determination means that the pixels are adjacent to or close to each other by a predetermined number of pixels, the brightness level of the imaging range of the in-vehicle camera and the pixel value of the in-vehicle camera As the pixel value / brightness characteristic indicating the relationship, the pixel value / brightness characteristic is such that the sensitivity of the change of the pixel value with respect to the brightness is low, and the higher the brightness level, the smaller the change rate of the pixel value. An in-vehicle camera control device comprising: a pixel value / brightness characteristic changing means for changing to Control means for controlling at least one of a gain applied to the image signal and a shutter speed of the in-vehicle camera;
The pixel value / brightness characteristic changing means performs at least one of control for reducing the gain applied to the image signal by the control means and control for increasing the shutter speed, so that the brightness with respect to the brightness is controlled. 2. The in-vehicle camera control device according to claim 1, wherein the on-vehicle camera control device is changed to a pixel value / brightness characteristic with low sensitivity of change in pixel value.   The pixel value / brightness characteristic changing unit is configured to change the pixel value with respect to the brightness as the number of pixels adjacent to or close to the predetermined number of pixels increases or as the brightness level increases. The in-vehicle camera control device according to claim 1, wherein the ratio is changed to a pixel value / brightness characteristic in which the ratio is further reduced. An in-vehicle camera mounted on a vehicle for taking an image of the surroundings of the vehicle, and repeatedly outputting a pixel value corresponding to the intensity of light incident on each pixel constituting the image sensor as an image signal;
In the image signal, a determination unit that determines whether or not pixels indicating a pixel value equal to or greater than a predetermined threshold are present adjacent to or close to a predetermined number of pixels;
When the determination means determines that the pixels are present adjacent to or close to a predetermined number of pixels, a large pixel value region including at least pixels equal to or greater than the predetermined number of pixels present adjacent or close to each other. An in-vehicle camera control device comprising: control means for performing control for reducing the gain of the image signal.

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