JP4757932B2 - Exposure control device and exposure control method for vehicle imaging device - Google Patents

Description

The present invention relates to an exposure control device and an exposure control method for an imaging device for a vehicle, and more particularly to an exposure control technique when traveling in a tunnel.

  2. Description of the Related Art Conventionally, a technique is known in which a digital camera is mounted on a traveling vehicle, and an image in front of the vehicle captured by this camera (a so-called vehicle imaging device) is processed to control the traveling of the vehicle. For example, a white line drawn on the road is recognized based on the captured image, and the vehicle is automatically driven along the white line on the road by controlling the engine, brake, steering, etc. based on the recognition result. Or by processing the captured image in front of the vehicle, recognizing the distance to the preceding vehicle, and controlling the engine, brake, etc. based on the recognition result, so that the distance from the preceding vehicle is kept constant. The technology to run is known.

  Some vehicle imaging devices have an exposure auto function that detects ambient illuminance by a built-in optical sensor and automatically controls the exposure of the camera in accordance with the illuminance. Normally, when performing exposure control, the brightness of a captured image is measured and digitized to obtain an evaluation value of brightness. Then, the evaluation value is compared with a reference value (exposure target value) of brightness set from the outside, and the speed of the electronic shutter and the gain of the amplifier of the imaging apparatus are controlled so that the two values substantially coincide.

  However, in general, in an imaging apparatus for a vehicle having an exposure auto function, when the illuminance around the vehicle changes suddenly when the vehicle enters and exits a tunnel or the like, exposure control is performed after the illuminance around the vehicle changes. Therefore, the exposure of the in-vehicle surveillance camera cannot follow a sudden change in illuminance in the surrounding area, and a clear image necessary for image processing cannot be acquired for a certain period of time. There was a problem of being accurate. As shown in FIG. 9, the illuminance rapidly decreases at the entrance of the tunnel, and the illuminance increases rapidly at the exit of the tunnel. At this time, if there is a response delay in the exposure control of the imaging device with respect to the decrease and increase in illuminance, the gradation that serves as an indicator of the amount of light received at the entrance of the tunnel is saturated, and the dark image is gradation at the entrance of the tunnel. There will be no black crushing, and a bright whiteout with no gradation will appear in the bright image at the exit of the tunnel.

  Therefore, a technology is disclosed that detects the tunnel entrance in advance before the traveling vehicle reaches the tunnel entrance, and quickly controls the exposure in the vicinity of the tunnel entrance so that there is no response delay in response to a sudden change in ambient illuminance. Has been.

  For example, an upper light sensor that is mounted upward on a vehicle and detects a wide range of illuminance around the vehicle, and a front light sensor that is mounted on the front of the vehicle and detects a illuminance in a narrow range in front of the vehicle. The illuminance change in the vehicle traveling direction is predicted from the illuminance of the two optical sensors, and when the ambient illuminance changes abruptly as in the entrance and exit of the tunnel, the exposure of the imaging unit for in-vehicle monitoring is changed in advance immediately before that. An exposure control device is known (see, for example, Patent Document 1).

JP 2005-167842 A

  However, according to the exposure control device described in Patent Document 1, the illuminance in a wide range around the vehicle and the illuminance in a narrow range in front of the vehicle are detected, and the illuminance change in the vehicle traveling direction is predicted from the comparison of the illuminance between the two. However, when the ambient illuminance changes abruptly, such as at the entrance and exit of the tunnel, the exposure of the imaging unit for in-vehicle monitoring is changed in advance immediately before that, so the tunnel is not necessarily observed in its entirety. However, there is room for further improvement in the exposure control in the tunnel running, because the tunnel detection is not necessarily obtained with high accuracy. For example, when the tunnel is short and the scenery after the exit is visible at the entrance of the tunnel, it may be difficult to accurately detect the entrance / exit of the tunnel.

  Moreover, according to the exposure control apparatus described in Patent Document 1, in addition to the optical sensor provided in the in-vehicle camera, two sensors, an upper light sensor with a wide light receiving angle and a front light sensor with a narrow light receiving angle, are required. Therefore, there is a problem that an increase in the number of parts, an associated increase in cost, and complicated control are caused.

  Therefore, the present invention has a simple configuration and accurately detects the entrance / exit of the tunnel using the photographed image, and even if there is a sudden change in the brightness in front of the vehicle, such as the entrance / exit of the tunnel, the It is an object of the present invention to provide an exposure control device and an exposure control method for a vehicular imaging device that can quickly control the exposure of a camera without delaying response in response to changes.

The invention according to claim 1, which is made to achieve the above object, is an exposure control device for a vehicle imaging device that is mounted on a vehicle and controls an exposure amount for imaging a vehicle traveling direction according to a target value. In the imaging apparatus, a plurality of photoelectric conversion elements are arranged in a matrix, and an optical signal is photoelectrically converted to generate an electric signal corresponding to the amount of received light for each of the photoelectric conversion elements, and the electric signal is converted into a digital signal. The exposure control apparatus includes an imaging unit that quantizes and outputs, and the exposure control device includes a luminance generation unit that generates a luminance signal from the digital signal output from the imaging unit, and a screen that is defined in a grid pattern. Tunnel evaluation value generating means for totalizing the luminance signal for each of a plurality of blocks and generating the total value as an evaluation value for tunnel detection; and the evaluation generated by the tunnel evaluation value generating means Based on the above, a tunnel detection means for detecting presence / absence of tunnel imaging in the optical image, and exposure control switching for switching the exposure amount control in association with presence / absence of tunnel imaging obtained via the tunnel detection means A plurality of continuous images as time elapses via the imaging means, and the tunnel evaluation value generating means extends radially from the center of the captured image in the outer direction. The evaluation value is generated for each of the plurality of blocks along each of the plurality of lines to be output, and the tunnel detection unit is configured to generate the evaluation value for each of the blocks generated along each of the plurality of radial lines . based on the evaluation value, a contour detecting means for detecting the contour position of the tunnel entrance per each of the plurality of lines of each of the radial in the image, of a plurality of lines of the radial Every people, and contour distance detecting means for detecting a contour distance from the detected contour position through the contour detecting unit and the center of the image, a plurality of each respective to a line of the radial, the passage of time In response, the change rate detection means for detecting the change rate of the contour distance detected via the contour distance detection means and the change rate detected by the change rate detection means are compared between the plurality of radial lines. Te, a synchronization determination means, wherein the rate of change to determine whether the synchronization between the line of said plurality of, based on the detected contour distance the contour distance means, the area of該輪Kakunai for the entire screen A trigger determination unit that detects a ratio of the occupancy and compares the detected ratio with a predetermined value to determine the effectiveness of tunnel detection; and a determination result of the synchronization determination unit is determined to be synchronized; and the trigger determination unit In the judgment result And a tunnel determining means for determining that the tunnel entrance is in the vicinity of the vehicle traveling direction when it is determined that the tunnel detection is effective, and the exposure control switching means is the tunnel determining means. When it is determined that the entrance / exit is in the vicinity, the convergence speed of the control with respect to the target value of exposure in the travel range near the tunnel entrance / exit is faster than the convergence speed in the travel range excluding the vicinity of the tunnel entrance / exit. It is comprised so that it may switch, It is characterized by the above-mentioned.

According to the exposure control apparatus for an imaging device for a vehicle according to claim 1, the luminance signal is totaled for each of a plurality of blocks each having a screen defined in a grid shape, and the total value is used for tunnel detection. A tunnel evaluation value generating unit that generates as an evaluation value of the tunnel, a tunnel detection unit that detects presence / absence of tunnel imaging in the optical image based on the evaluation value generated by the tunnel evaluation value generation unit, and a tunnel detection unit Since it has exposure control switching means that switches the exposure amount control in correspondence with the presence or absence of the obtained tunnel imaging, it is possible to accurately detect the entrance and exit of the tunnel using the photographed image, in the vicinity of the entrance and exit of the tunnel Even if there is an abrupt change in luminance, the exposure of the imaging device can be quickly controlled without delay in response according to the change. In addition, since a plurality of optical sensors disclosed in Patent Document 1 are not required and a tunnel can be detected based on a photographed image, the exposure control device can have a simple configuration.

According to the exposure control device for an imaging device for a vehicle according to claim 1, a plurality of continuous images are acquired according to the passage of time via the imaging unit, and the tunnel evaluation value generating unit is captured. An evaluation value is generated for each of the plurality of blocks along each of the plurality of lines extending radially from the center of the image to the outer shape direction, and the tunnel detection means is arranged along each of the plurality of radial lines. The contour detection means for detecting the contour position of the tunnel entrance / exit in the image for each of the plurality of radial lines based on the evaluation value for each block generated in the step, and the contour for each of the plurality of radial lines a contour distance detecting means for detecting a contour distance from the detected contour position through the detection means to the center of the image, a plurality of each respective to a line of parabolic, via the contour distance detecting means in accordance with the lapse of time Detected A change rate detecting means for detecting a rate of change of Guo distance, by comparing the detected change rate change rate detecting means among the plurality of lines of parabolic, whether the rate of change is synchronized between the line of said plurality of Based on the contour distance detected by the synchronization determination means and the contour distance means, the ratio of the area in the contour to the entire screen is detected, and the detected ratio is compared with a predetermined value. When the determination result of the trigger determination means that determines the effectiveness of the tunnel detection and the determination result of the synchronization determination means is determined to be synchronized, and the determination result of the trigger determination means determines that the tunnel detection is valid, the tunnel entrance and exit is the vehicle running Since it is configured by the tunnel determination means that determines that the vehicle is in the vicinity of the direction, the reliability of detecting the tunnel entrance / exit in the exposure control in the tunnel traveling can be improved.

According to the exposure control device for an imaging device for a vehicle according to claim 1, when the tunnel determination means determines that the tunnel entrance is in the vicinity, the control for the exposure target value in the traveling range in the vicinity of the tunnel entrance is provided. It is configured to switch the convergence speed of the vehicle so that it is faster than the convergence speed in the travel range excluding the vicinity of the tunnel entrance and exit, so that it can quickly respond to the sudden light and dark changes that occur in the vicinity of the tunnel entrance and exit. There is no response delay, and exposure control can be performed appropriately.

Then, the serial mounting of the invention in claim 2, near the exposure control device for a vehicular image pickup device according to claim 1, wherein the exposure control switching means, the tunnel entrance in the tunnel determination means of the vehicle running direction When it is determined that the exposure control image range is switched so that the central portion of the exposure control image range in the travel range near the tunnel entrance is located at the tunnel entrance.

According to the exposure control apparatus for an imaging device for a vehicle according to claim 2, when the tunnel determination means determines that the tunnel entrance is in the vicinity of the vehicle traveling direction, the image of exposure control in the traveling range near the tunnel entrance. By switching the image range of exposure control so that the center of the range is located at the tunnel entrance / exit, it is possible to perform exposure control with a weight on the existence of the tunnel in the vicinity of the tunnel entrance / exit, and perform exposure control appropriately. be able to.

According to a third aspect of the present invention, there is provided an exposure control method for a vehicular imaging apparatus that is mounted on a vehicle and controls an exposure amount for imaging a vehicle traveling direction in accordance with a target value. Elements are arranged, photoelectrically converting an optical image to generate an electrical signal corresponding to the amount of received light for each of the photoelectric conversion elements, and using an imaging unit that quantizes the electrical signal into a digital signal and outputs it.
A luminance generation step for generating a luminance signal from the digital signal output from the imaging means; and the luminance signal is aggregated for each of a plurality of blocks each having a screen defined in a lattice shape, and the aggregated value is tunneled A tunnel evaluation value generating step for generating as an evaluation value for detection, and a tunnel detection step for detecting presence or absence of tunnel imaging in the optical image based on the evaluation value generated in the tunnel evaluation value generating step; The exposure control switching step for switching the control of the exposure amount in association with the presence or absence of tunnel imaging obtained through the tunnel detection step, and using the imaging means, continuous over time acquiring a plurality of images, the tunnel evaluation value generating step, extending radially to the outer direction from the center of the captured image double The line along the respective generates the evaluation value for each each of the plurality of blocks, the tunnel detection step, the evaluation value for each of the blocks generated along each of a plurality of lines of the radial Based on the contour detection step for detecting the contour position of the tunnel entrance / exit in the image for each of the plurality of radial lines, and detecting the contour position for each of the plurality of radial lines through the contour detection step the contour distance detection step of detecting a contour distance to the center of the image from the contour position, the plurality of each respective to a line of radial, is detected through the contour distance detection step as time passes a rate of change detection step of detecting a rate of change in contour distance, the detected rate of change in the change rate detecting step by comparing among a plurality of lines of the radial, said change There a synchronization determining step of determining whether or not to synchronize between lines of the plurality based on said contour distance detected contour distance detecting step, detecting a ratio of the area of該輪Kakunai for the entire screen In the trigger determination step for determining the effectiveness of tunnel detection by comparing the detected ratio with a predetermined value and the determination result in the synchronization determination step, and in the determination result in the trigger determination step A tunnel determination step that determines that the tunnel entrance is in the vicinity of the vehicle traveling direction when it is determined that tunnel detection is valid, and the exposure control switching step includes the step of determining whether the tunnel entrance is in the tunnel determination step. When it is determined that the vehicle is in the vicinity, the exposure target value in the travel range near the tunnel entrance The control convergence speed is switched so as to be faster than the convergence speed in the travel range excluding the vicinity of the tunnel entrance.

According to the exposure control method for an imaging apparatus for a vehicle according to claim 3, the luminance signal is totaled for each of a plurality of blocks each having a screen defined in a grid pattern, and the total value is used for tunnel detection. A tunnel evaluation value generation step that is generated as an evaluation value, a tunnel detection step that detects presence / absence of tunnel imaging in the optical image based on the evaluation value generated in the tunnel evaluation value generation step, and a tunnel detection step An exposure control switching step for switching the control of the exposure amount in association with the presence or absence of the obtained tunnel imaging, so that the entrance of the tunnel can be opened using the photographed image as in the first aspect of the invention. Even if there is a sudden change in brightness near the entrance of the tunnel, the exposure of the imaging device can be accelerated quickly without delay in response. It can be controlled. In addition, a tunnel can be detected based on a captured image without requiring a plurality of optical sensors disclosed in Patent Document 1.

According to the exposure control method for an imaging apparatus for a vehicle according to claim 3, the tunnel detection step is performed in the image based on the evaluation value for each block generated along each of the plurality of radial lines . A contour detecting step for detecting the contour position of the tunnel entrance for each of the plurality of radial lines, and the center of the image from the contour position detected through the contour detecting step for each of the plurality of radial lines. A contour distance detecting step for detecting the contour distance up to and a rate of change for detecting a change rate of the contour distance detected through the contour distance detecting step according to the passage of time for each of the plurality of radial lines. synchronization determining step of determining a detection step, by comparing the detected change rate change rate detecting step among the plurality of lines of parabolic, whether the rate of change is synchronized between a plurality of lines Based on the contour distance detected in the contour distance detection step, the ratio of the area in the contour to the entire screen is detected, and the detected ratio is compared with a predetermined value to confirm the effectiveness of tunnel detection. When it is determined that synchronization is determined in the determination result of the trigger determination step and the determination step of the synchronization determination, and tunnel detection is determined to be valid in the determination result of the trigger determination step, the tunnel doorway is in the vicinity of the vehicle traveling direction. Since it comprises the tunnel determination step for determining, it is possible to improve the reliability of detecting the tunnel entrance / exit in the exposure control in the tunnel traveling.

According to the exposure control method for an imaging apparatus for a vehicle according to claim 3, when the tunnel determination means determines that the tunnel entrance is in the vicinity, the control for the exposure target value in the travel range in the vicinity of the tunnel entrance is performed. By switching the convergence speed of the vehicle so that it is faster than the convergence speed in the travel range excluding the vicinity of the tunnel entrance and exit, it responds quickly to sudden changes in brightness near the entrance and exit of the tunnel, and there is no response delay , Exposure control can be performed appropriately.

Next, according to a fourth aspect of the present invention, in the exposure control method for an imaging device for a vehicle according to the third aspect, the exposure control switching step is the tunnel determination step, and the tunnel entrance is in the vicinity of the vehicle traveling direction. When it is determined that there is an image, the image range for exposure control is switched so that the center of the image range for exposure control in the travel range near the tunnel entrance is located at the tunnel entrance .

According to the exposure control method for an imaging device for a vehicle according to claim 4, when it is determined in the tunnel determination step that the tunnel entrance is in the vicinity of the vehicle traveling direction, the image of the exposure control in the traveling range in the vicinity of the tunnel entrance. By switching the exposure control image range so that the center of the range is located at the tunnel entrance / exit, exposure control is performed with a weight applied to the presence of the tunnel in the vicinity of the tunnel entrance as in the invention of claim 2. Exposure control can be performed appropriately.

Further, the exposure control device and the exposure control method for an imaging device for a vehicle according to the present invention obtains a plurality of continuous images according to the passage of time via the imaging means, and detects the center of the image when detecting a tunnel. Evaluation values for tunnel detection are detected along each of the plurality of lines extending radially from the outer shape to the outer contour direction, and then based on the evaluation values for each block generated along the plurality of radial lines Then, the contour position of the tunnel in the image is detected for each of the plurality of radial lines, and then the distance from the detected contour position to the center of the image is detected for each of the plurality of radial lines. Then, for each of the plurality of radial lines, the change rate of the contour distance is detected as time passes, and then the change rate is compared between the plurality of radial lines . to determine whether synchronization between the line It allows accurately detected tunnel. Also, at this time, through the trigger determination, the ratio of the area in the contour to the entire screen is detected to determine the effectiveness of the tunnel detection, and based on the determination result of the synchronization determination and the determination result of the trigger determination, The reliability of tunnel detection can be increased by making a prior decision on entry / exit.

Further, according to the exposure control device and the exposure control method for an imaging device for a vehicle of the present invention, when a tunnel is detected, the central part of the image range (photometry frame) of the exposure control in the traveling range in the vicinity of the tunnel entrance is the entrance to the tunnel. By switching the image range of the exposure control so as to be positioned at the position, it is possible to perform exposure control in which the presence of the tunnel is weighted in the vicinity of the tunnel entrance, and to appropriately perform the exposure control.

  Further, according to the exposure control device and the exposure control method for a vehicle imaging device of the present invention, when a tunnel is detected, the convergence speed in the traveling range near the tunnel entrance is faster than the convergence speed outside the traveling range. By switching in this way, it is possible to quickly cope with a sudden change in brightness that appears in the vicinity of the entrance and exit of the tunnel, there is no response delay, and exposure control can be appropriately performed.

It is a block diagram showing the structure of the exposure control apparatus of the imaging device for vehicles of one Example of this invention. It is the block diagram showing the structure of the tunnel detection means in the exposure control apparatus of the imaging device for vehicles of the Example. It is explanatory drawing showing the operation | movement of a tunnel detection in the exposure control apparatus of the imaging device for vehicles of the Example. It is explanatory drawing of the contour position detection of a tunnel in the exposure control apparatus of the imaging device for vehicles of the Example. It is explanatory drawing of the synchronous determination of a tunnel outline coordinate in the exposure control apparatus of the imaging device for vehicles of the Example. It is explanatory drawing of the photometry frame position switching in the exposure control apparatus of the imaging device for vehicles of the Example. It is explanatory drawing of convergence speed switching in the exposure control apparatus of the imaging device for vehicles of the Example. It is a flowchart showing the procedure of the exposure control method of the imaging device for vehicles of one Example of this invention. It is a figure showing the delay of the exposure control which tends to generate | occur | produce at the time of tunnel travel.

  As shown in FIG. 1, the vehicular imaging apparatus 100 uses an imaging unit 200 that captures an image of the vehicle periphery and outputs a digital image signal (image data), and a digital image signal input from the imaging unit 200. And an exposure control device 300 that controls exposure so that an image with appropriate brightness can be obtained.

  The imaging means 200 photoelectrically converts and amplifies the optical image formed through the imaging optical system 1 and converts it into a digital signal and outputs it. An image sensor 2 is used.

The imaging optical system 1 includes an imaging lens 1a that condenses subject light and guides it to an image sensor, and an iris 1b that adjusts the amount of incident light that has entered through the imaging lens 1a. , Etc.

The image sensor 2 has an imaging element 2a that converts an optical image formed through the imaging optical system 1 into an analog electric signal in association with the amount of received light, and a variable gain that amplifies the analog electric signal output from the imaging element 2a. An amplifier (AGC: Automatic Gain Control) 2b, an AD converter (ADC: Analog Digital Converter ) 2c that converts an analog electric signal output from the variable gain amplifier 2b into a digital signal, and the like are configured. The imaging element 2a has a plurality of photoelectric conversion elements arranged in a matrix and generates an electrical signal corresponding to the amount of received light for each photoelectric conversion element.

Next, the exposure control device 300 processes the digital signal input via the imaging unit 200 and outputs data necessary for exposure control, and stores the data obtained by the signal processing device 3. A SDRAM (Synchronous Dynamic Access Memory) 4, a CPU (Central Processing Unit) 5 that obtains data necessary for exposure control obtained by the signal processing device 3 via the SDRAM 4 and generates a command signal for exposure control, etc. I have. Further, the CPU 5 controls each function of the imaging unit 200 and the exposure control device 300.

  The signal processing device 3 includes a luminance generation unit 3a that generates a luminance signal (hereinafter referred to as a luminance value) having a predetermined number of pixels as a unit based on the digital signal output from the imaging unit 200, and the luminance generation unit 3a. A tunnel evaluation value generating means 3b for extracting the luminance along the radial shape from the center of the image based on the luminance signal generated via the image, and an exposure evaluation value based on the luminance signal generated via the luminance generating means 3a. And an exposure evaluation value generating means 3c for generating

As shown in FIG. 3A, the luminance generation unit 3a sequentially generates a luminance signal for each captured image as time passes .

As shown in FIG. 4A, the tunnel evaluation value generation unit 3b totalizes the luminance signal for each block configured by defining the screen in a grid pattern for each captured image. The value is an evaluation value for tunnel detection described later. Further, as shown in FIG. 4A, the tunnel evaluation value generating unit 3b includes a plurality of pieces arranged along each line (W0, W1, W2) extending radially from the center of the screen in the outer shape direction. Luminance signals are aggregated for each block .

  The exposure evaluation value generation means 3c integrates luminance signals within a predetermined photometry frame (photometry frame in FIG. 6) on the screen, compares the integrated value with a reference value, and displays data representing the comparison result as an exposure evaluation value. Generate as

  The SDRAM 4 includes a tunnel evaluation value storage unit 4a that stores the tunnel evaluation value obtained by the tunnel evaluation value generation unit 3b, and an exposure evaluation value storage unit 4b that stores the exposure evaluation value obtained by the exposure evaluation value generation unit 3c. It is constituted by.

  The CPU 5 associates the function of the tunnel detection means 5a for detecting the presence / absence of tunnel imaging based on the tunnel evaluation value generated by the tunnel evaluation generation means 3b with the presence / absence of tunnel imaging obtained by the tunnel detection means 5a. And the function of the exposure control means 5b for switching the control of the exposure amount of the exposure control device 300.

As shown in FIG. 2, the tunnel detection means 5a detects the contour position of the tunnel in the image, and detects the contour distance from the contour position detected via the contour detection means 51 to the center of the image. A contour distance detecting means 52 that detects the change rate of the contour distance detected via the contour distance detecting means 52 according to the passage of time for each of the plurality of radial lines. The change rate detected by the change rate detection means 53 is compared between a plurality of radial lines, and a synchronization determination means 54 for determining whether or not the change rate is synchronized between the plurality of lines, and a contour distance detection Based on the contour distance detected by the means 52, the trigger determination means 55 for determining the effectiveness of the tunnel detection, and the entry to the tunnel based on the determination result of the synchronization determination means 54 and the determination result of the trigger determination means 55. It is formed by performing a pre-determined tunnel determination unit 56 and the like.

  Specifically, as shown in FIGS. 4 (a) and 4 (b), the contour detection means 51 is a luminance generated by the tunnel evaluation value generation means 3b along the radiation (W0, W1, W2). Based on the total value of the signal, the position of the evaluation frame where the total value greatly changes is detected as the contour position.

  Next, as shown in FIGS. 3B and 3C, the contour distance detecting unit 52 detects the contour position detected by the contour detecting unit 51 along the radiation (W0, W1, W2). The distances (D0, D1) from the coordinates to the center of the screen are calculated in association with the distances (L0 to L3) to the entrance / exit of the tunnel.

  Next, the change rate detection means 53 detects the change rate of the contour position for each radial line in association with the distance to the tunnel entrance. For example, as shown in FIG. 3, the change rate of the contour distance D0 and the change rate of the contour distance D1 from the distance L0 to the tunnel L3 are calculated.

Next, as shown in FIG. 5A and FIG. 5B, the synchronization determination unit 54 determines a predetermined ratio with respect to the change rate of the contour distance Dn according to the passage of time (t0 to t4). Compared with the value, it is determined whether to synchronize between the radial lines (W0 to W2).

  Next, using the contour distance detected by the contour distance detection means, the trigger determination means 55 detects the proportion of the area in the contour relative to the entire screen, and compares this detected proportion with a predetermined value. To determine the effectiveness of tunnel detection.

  Next, when it is determined that there is tunnel detection in the determination result of the synchronization determination unit 54 and the tunnel determination unit 55 determines that the tunnel detection is effective, the tunnel determination unit 56 On the other hand, when it is different from the determination result in at least one of the synchronization determination means and the trigger determination means, “the tunnel doorway is not in the vicinity of the vehicle traveling direction”. Is determined. The tunnel determination is continued even when the vehicle enters the tunnel and travels in the tunnel. When at least one of the synchronization determination unit 54 and the trigger determination unit 55 changes after the vehicle enters the tunnel, the tunnel determination is switched according to the change.

  Next, when it is determined that “the entrance / exit of the tunnel is in the vicinity of the vehicle traveling direction”, the exposure control means 5b, as shown in FIG. 6, sets the photometric frame (exposure control image range). From a normal setting including a wide field of view in front of the vehicle (FIG. 6 (a)), a position where the tunnel is weighted (for example, a position where a tunnel doorway exists at the center of the photometric frame as shown in FIG. 6 (b)). Switch to. On the other hand, when it is determined that “the entrance / exit of the tunnel is not in the vicinity of the vehicle traveling direction”, the position of the photometric frame is set to the normal setting including the wide field of view in front of the vehicle (FIG. 6A).

  Further, the exposure control means 5b calculates an input value of the exposure (BV) to the imaging device so as to obtain appropriate luminance based on the exposure evaluation value obtained by the exposure evaluation value generation means 3c, and the input The exposure (BV) is switched via the IRIS (aperture) 1b, the exposure time of the image sensor 2a, and the gain of the variable gain amplifier 2c so as to approach the value, and the convergence speed of the exposure switching control is switched according to the tunnel determination result. .

  Specifically, as shown in FIG. 7, the normal driving mode is set in the traveling range in which it is determined that “the entrance of the tunnel is not in the vicinity of the vehicle traveling direction”, and the “entrance of the tunnel is in the vicinity of the vehicle traveling direction”. In the travel range determined to be “in”, the convergence speed control is set to the tunnel entrance / exit mode.

  In FIG. 7, (a) and (c) represent exposure control curves in the normal travel mode, and (b) and (d) represent exposure control curves in the tunnel entrance / exit mode. Also. The inputs described in (a) to (d) represent a transition curve of an appropriate exposure (target value) on the photographing screen, and the output represents a transition curve of an output value when approaching the appropriate exposure. Further, (a) and (b) represent examples of step responses, and (c) and (d) represent examples of frequency responses.

  As shown in FIG. 7, in the travel range in which it is determined that “the entrance of the tunnel is not in the vicinity of the vehicle travel direction”, the output value (the output for approaching the input) with respect to the input value (exposure target value) In the traveling range where it is determined that “the entrance of the tunnel is in the vicinity of the vehicle traveling direction”, the output value (to be close to the input) with respect to the input value (exposure target value) Change the output signal) quickly to bring it closer to the correct exposure.

  Next, the procedure of the exposure control method in the vehicle imaging device 100 will be described with reference to FIG. This procedure is executed by the CPU 5 giving a command signal to each functional unit based on a program stored in a ROM (not shown). Further, S in FIG. 8 represents a step.

  First, this procedure starts when a start signal is input to the vehicle imaging device 100 by the user.

  Next, in S100, the luminance generation unit 3a is used to generate a luminance signal (hereinafter referred to as a luminance value) having a predetermined number of pixels as a unit based on the digital signal output from the imaging unit 200, and then S200. And go to S220.

Next, in S200, the exposure evaluation value generating means 3c is used to integrate the luminance signal in a predetermined photometric frame (photometric frame in FIG. 6) on the screen based on the luminance signal generated in S100, and this integrated value. Is compared with a reference value to generate data representing the comparison result as an exposure evaluation value, and then the process proceeds to S300.

On the other hand, in S220, using the tunnel evaluation value generation means 3b, the luminance signals for each block constituted by the screen being defined in a grid pattern for each photographed image are totaled, and this total value is detected by tunnel detection. The evaluation value is generated, and then the process proceeds to S240.

Next, in S240, the presence or absence of a tunnel in the photographed image is detected using the tunnel detection means 5a. Specifically, the contour position of the tunnel in the image is detected along each of the plurality of radial lines using the contour detector 51, and then the image center is determined from the contour position using the contour distance detector 52. detecting the contour distance to, then, by using the change rate detecting means 53, a plurality of each respective to a line of parabolic, detects the rate of change of the contour distance in accordance with the elapse of time, then the synchronization determination means 54, the detected rate of change is compared between the plurality of radial lines to determine whether the rate of change is synchronized between the plurality of lines , and the trigger determining means 55 is used to The ratio of the area in the contour to the whole is detected, and the detected ratio is compared with a predetermined value to determine the effectiveness of the tunnel detection. Near the direction of travel Luke carried out as to whether or not the decision.

  In S240, when it is determined that “there is no tunnel”, the process returns to S220 and repeats S220 to S240 until it is determined that “there is a tunnel”, and when it is determined that “the tunnel is present” in S240, the process proceeds to S260. Move.

  Next, in S260, the exposure control means 5b is used to switch the exposure control convergence speed and the position of the photometric frame to the tunnel entrance / exit mode, and then the process proceeds to S300 and S400.

Next, in S300, an exposure error with respect to the exposure target value is detected based on the exposure evaluation value generated in S200, and thereafter, the process proceeds to S400. Further, when the position of the photometric frame is switched to the tunnel entrance / exit mode in S260, the exposure evaluation value in the switched photometric frame is replaced with the exposure evaluation value to detect the exposure target value, and then the process proceeds to S400. .

  Next, in S400, an exposure movement amount (change amount) for each step that determines the convergence speed of the exposure control is determined based on the tunnel determination result in S240, and then the process proceeds to S500.

  Next, in S500, using a predetermined exposure program, the shutter speed (Tv), aperture value (Av), and ISO sensitivity (Sv) are obtained in association with the movement amount of exposure obtained in S400, and then in S600. Move.

  Next, in S600, the operation of each device constituting the imaging unit 200 is controlled in association with the shutter speed Tv, the aperture value Av, and the ISO sensitivity Sv, and then the processing procedure of the main exposure control is terminated.

  As described above, according to the exposure control device 300 of the vehicle imaging device 100 of the present embodiment, the luminance is adjusted along the radial shape from the center of the image based on the luminance signal generated through the luminance generation unit 3a. Tunnel extraction value generation means 3b to be extracted, tunnel detection means 5a for detecting the presence or absence of tunnel imaging in the optical image based on the luminance extracted along the radial pattern, and the tunnel detection means 5a. Exposure control switching means 5b that switches exposure control in association with the presence or absence of tunnel imaging, so that the entrance / exit of the tunnel can be detected with high accuracy using the photographed image, and brightness is increased in the vicinity of the entrance / exit of the tunnel. Even if there is an abrupt change, the exposure of the imaging means 200 can be quickly controlled without delay in response according to the change.

Further, according to the exposure control apparatus 300 of the vehicle imaging apparatus 100 of the present embodiment, the tunnel detection means 5a is based on the sum of the luminance signals for each value frame along each of the plurality of radial lines. The contour detecting means 51 for detecting the contour position of the tunnel in the image, and the contour for detecting the distance from the contour position detected via the contour detecting means 51 to the center of the image along each of a plurality of radial lines The distance detection means 52, the change rate detection means 53 for detecting the change rate of the contour distance as time passes, and the change rate detected by the change rate detection means 53 for each of the plurality of radial lines. A comparison is made between the plurality of radial lines , and the screen is based on the synchronization determination means 54 for determining whether the change rate is synchronized between the plurality of lines and the contour distance detected by the contour distance detection means 52. Contoured against the whole A trigger determination unit 55 that detects a ratio occupied by the area and compares the detected ratio with a predetermined value to determine the effectiveness of tunnel detection. The determination result of the synchronization determination unit 54 and the determination of the trigger determination unit 55 Based on the result, it is possible to improve the reliability of tunnel detection by making a prior determination of entering and exiting the tunnel.

  As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, Various aspects can be taken.

The exposure control device and the exposure control method for a vehicle imaging device according to the present invention are suitable for a vehicle imaging device that is mounted on a vehicle traveling on a tunnel road and images the surroundings of the vehicle .

  DESCRIPTION OF SYMBOLS 1 ... Imaging optical system, 1a ... Imaging lens, 1b ... Iris (diaphragm), 2 ... Image sensor, 2a ... Imaging element, 2b ... Variable gain amplifier (AGC: Automatic Gain Control), 2c ... A / D converter, DESCRIPTION OF SYMBOLS 3 ... Signal processing apparatus, 3a ... Luminance production | generation means, 3b ... Tunnel evaluation value production | generation means, 3c ... Exposure evaluation value production | generation means, 4 ... SDRAM (Synchronous DRAM), 4a ... Tunnel evaluation value storage means, 4b ... Exposure evaluation value storage Means, 5 ... CPU (Central Processing Unit), 5a ... Tunnel detection means, 5b ... Exposure control means, 51 ... Contour detection means, 52 ... Contour distance detection means, 53 ... Change rate detection means, 54 ... Synchronization determination means, 55 ... Trigger determination means, 56 ... Tunnel determination means, 100 ... Vehicle imaging device, 200 ... Imaging hand Stage, 300 ... exposure control device.

Claims (4)

In an exposure control device for a vehicle imaging device that is mounted on a vehicle and controls an exposure amount for imaging a vehicle traveling direction according to a target value.
The imaging device includes a plurality of photoelectric conversion elements arranged in a matrix, photoelectrically converts an optical image to generate an electrical signal corresponding to the amount of received light for each of the photoelectric conversion elements, and converts the electrical signal into a digital signal. An image pickup means for quantizing and outputting the output,
In the exposure control device,
Luminance generation means for generating a luminance signal from the digital signal output from the imaging means;
A tunnel evaluation value generating means for totalizing the luminance signal for each of a plurality of blocks each having a screen defined in a grid and generating the total value as an evaluation value for tunnel detection;
Based on the evaluation value generated by the tunnel evaluation value generation means, tunnel detection means for detecting the presence or absence of tunnel imaging in the optical image,
Exposure control switching means for switching the control of the exposure amount in association with the presence or absence of tunnel imaging obtained through the tunnel detection means;
With
Via the imaging means to obtain a plurality of continuous images over time,
The tunnel evaluation value generating means generates the evaluation value for each of the plurality of blocks along each of a plurality of lines extending radially from the center of the captured image in the outer shape direction ,
The tunnel detection means is
Based on the evaluation value for each of the blocks generated along each of a plurality of lines of the radial contour detecting means for detecting the contour position of the tunnel entrance in the image for each of each of the plurality of lines of each of the radial When,
Contour distance detecting means for detecting the contour distance from the contour position detected via the contour detecting means to the center of the image for each of the plurality of radial lines ;
A plurality of each respective to a line of the radial, and the rate of change detecting means for detecting a rate of change of the detected contour distance through the contour distance detecting means in accordance with the elapse of time,
A synchronization determination unit that compares the change rate detected by the change rate detection unit between the plurality of radial lines and determines whether the change rate is synchronized between the plurality of lines ;
Based on the contour distance detected by the contour distance means, the ratio of the area in the contour to the entire screen is detected, and the detected ratio is compared with a predetermined value to determine the effectiveness of tunnel detection. Trigger determination means to perform,
Tunnel determination for determining that the tunnel entrance is in the vicinity of the vehicle traveling direction when it is determined that the synchronization is determined in the determination result of the synchronization determination unit and the tunnel detection is determined to be valid in the determination result of the trigger determination unit. Means,
Composed by
When the exposure control switching means determines that the tunnel entrance / exit is in the vicinity by the tunnel determination means, the control convergence speed for the exposure target value in the travel range in the vicinity of the tunnel entrance / exit is determined in the vicinity of the tunnel entrance / exit. It is configured to switch so as to be faster than the convergence speed in the travel range excluding,
An exposure control device for an imaging device for vehicles. When the exposure control switching means determines that the tunnel entrance is in the vicinity of the vehicle traveling direction by the tunnel determining means, the central part of the image range of the exposure control in the travel range near the tunnel entrance is the tunnel entrance Switch the image range of exposure control so that it is located at
The exposure control apparatus of the imaging device for vehicles of Claim 1 characterized by the above-mentioned. In an exposure control method for a vehicle imaging device that is mounted on a vehicle and controls an exposure amount for imaging a vehicle traveling direction according to a target value.
A plurality of photoelectric conversion elements are arranged in a matrix, and an optical image is photoelectrically converted to generate an electrical signal corresponding to the amount of received light for each of the photoelectric conversion elements, and the electrical signal is quantized into a digital signal and output. Using imaging means,
A luminance generation step of generating a luminance signal from the digital signal output from the imaging means;
A tunnel evaluation value generating step for totalizing the luminance signal for each of a plurality of blocks configured by defining a screen in a grid pattern and generating the total value as an evaluation value for tunnel detection;
Based on the evaluation value generated in the tunnel evaluation value generation step, a tunnel detection step of detecting the presence or absence of tunnel imaging in the optical image,
An exposure control switching step of switching the control of the exposure amount in association with the presence or absence of tunnel imaging obtained through the tunnel detection step;
Use
Via the imaging means to obtain a plurality of continuous images over time,
The tunnel evaluation value generation step generates the evaluation value for each of the plurality of blocks along each of a plurality of lines extending radially from the center of the captured image in the outer shape direction ,
The tunnel detection step comprises:
Based on the evaluation value for each of the blocks generated along each of a plurality of lines of the radial contour detection step of detecting the contour position of the tunnel entrance in the image for each of a plurality of lines of each of the radial When,
A contour distance detecting step for detecting a contour distance from the contour position detected through the contour detecting step to the center of the image for each of the plurality of radial lines ;
A change rate detection step for detecting a change rate of the contour distance detected through the contour distance detection step according to the passage of time for each of the plurality of radial lines ;
A synchronization determination step for comparing the change rate detected in the change rate detection step between the plurality of radial lines and determining whether the change rate is synchronized between the plurality of lines ;
Based on the contour distance detected in the contour distance detection step, the ratio of the area in the contour to the entire screen is detected, and the detected ratio is compared with a predetermined value to confirm the effectiveness of tunnel detection. A trigger determination step for determining;
Tunnel determination for determining that the tunnel entrance is in the vicinity of the vehicle traveling direction when it is determined that the synchronization is determined in the determination result of the synchronization determination step and the tunnel detection is determined to be valid in the determination result of the trigger determination step. Steps,
Composed by
When the exposure control switching step determines that the tunnel doorway is in the vicinity in the tunnel determination step, the convergence speed of the control for the exposure target value in the travel range in the vicinity of the tunnel doorway is determined in the vicinity of the tunnel doorway. Switch to a speed that is faster than the convergence speed in the driving range except
An exposure control method for a vehicular imaging device. When the exposure control switching step is determined in the tunnel determination step that the tunnel entrance is in the vicinity of the vehicle traveling direction, the central portion of the image range of the exposure control in the travel range near the tunnel entrance is the tunnel entrance Switch the image range of exposure control so that it is located at
The exposure control method of the imaging device for vehicles according to claim 3 characterized by things.

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