JP2013135305A - Signal processor, imaging apparatus, and imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of obtaining an image free from discomfort which is similar to an actual appearance, in imaging at night.SOLUTION: A signal processor processes an image signal obtained by imaging means capable of changing imaging conditions, and comprises an extraction unit, a determination unit, and a change unit. The extraction unit extracts a chromaticity parameter from the image signal. The determination unit determines the change amount of the chromaticity parameter on the basis of the imaging conditions when the image signal is obtained. The change unit changes the chromaticity parameter extracted by the extraction unit, in accordance with the change amount.

Description

  The present invention relates to a signal processing device, an imaging device, and an imaging system.

  There are various types of imaging devices depending on the application. For example, an in-vehicle camera that captures an image of the surroundings of a vehicle and recognizes objects (vehicles, pedestrians, etc.) and road markings / signs (road surface paint such as lane markings, signs such as stops) in the captured image Are known.

  The vehicle-mounted camera captures an image of a subject while the vehicle is traveling, and acquires an image signal for displaying the imaging result in real time. Various image processing is performed on the acquired image signal.

  For example, a technique is known in which lightness determination and saturation determination are performed for each pixel, and a natural color is reproduced by performing chroma suppression processing (saturation correction processing) based on these determination results (hereinafter referred to as the following). Patent Document 1).

JP 2007-288573 A

  By the way, when shooting a front subject with a vehicle-mounted camera at night, if the brake light and tail light of the car in front are turned on, the image displayed on the display (monitor) will turn red, and what is the actual appearance? It becomes an image with a different sense of incongruity.

  Also, when shooting the back, your own brake lamp and tail lamp will reflect off the object behind, and the image displayed on the display (monitor) will be completely red. End up.

  In the prior art described above, correction processing is performed to reduce the saturation when the brightness of the pixel is low. However, it is difficult to perform a correction process for reducing (suppressing) saturation because the brightness around the lit brake lamp and tail lamp is high.

  The present invention solves the above-described problems, and an object thereof is to provide a technique capable of obtaining an image that is close to an actual appearance and has no sense of incongruity in night photography.

  In order to solve the above problem, the signal processing device according to claim 1 is a signal processing device that processes an image signal obtained by an imaging unit capable of changing a shooting condition, and includes an extraction unit, a determination unit, And a change unit. The extraction unit extracts a chromaticity parameter from the image signal. The determination unit determines a change amount of the chromaticity parameter based on the shooting condition when the image signal is obtained. The changing unit changes the chromaticity parameter extracted by the extracting unit based on the change amount.

  In order to solve the above problem, the signal processing device according to claim 2 is the signal processing device according to claim 1, wherein the imaging condition is a condition parameter that is changed according to the brightness of the imaging field of view. Including. The determination unit includes a storage unit that stores in advance first association information that associates the condition parameter and the color transmittance, and the value of the color transmittance associated with the value of the condition parameter when the image signal is obtained Is specified based on the first association information as the change amount.

  In order to solve the above problem, a signal processing device according to a third aspect is the signal processing device according to the second aspect, wherein the condition parameter includes a photographing sensitivity, an aperture value, and / or a shutter speed.

  In order to solve the above problem, a signal processing device according to claim 4 is the signal processing device according to claim 2 or 3, wherein the first association information is a condition parameter smaller than a predetermined threshold. A value smaller than the maximum value of the color transmittance is associated with the value.

  In order to solve the above problem, the signal processing device according to claim 5 is the signal processing device according to claims 2 to 4, wherein the storage unit includes a luminance value and a color transmittance of a pixel of the image signal. Is stored in advance, and the determination unit specifies, for each pixel of the image signal, the color transmittance value associated with the luminance value as a change amount based on the second association information. .

  In order to solve the above problem, the signal processing device according to claim 6 is the signal processing device according to claim 5, wherein the determination unit determines only the color transmittance for a specific color as the luminance value. The amount of change is determined so as to be smaller in accordance with.

  In order to solve the above problem, an imaging apparatus according to a seventh aspect includes an imaging unit and the signal processing apparatus according to any one of the first to sixth aspects.

  In order to solve the above problem, an imaging apparatus according to claim 8 is the imaging apparatus according to claim 7, wherein the imaging unit linearly converts incident light into an image signal, and It is a linear log sensor having a plurality of elements that can switch the second operation for logarithmically converting the linearly converted image signal according to the amount of incident light, and the changing unit is in a logarithmic region where the second operation is performed. The chromaticity parameter is changed based on the shooting conditions.

  In order to solve the above problem, an imaging system according to a ninth aspect includes an imaging means mounted on a vehicle, a detection unit that detects whether or not the brake of the vehicle is depressed, and any one of the first to sixth aspects. And a vehicle control unit that controls the changing unit and changes the chromaticity parameter based on the photographing condition when the depression of the brake is detected.

  Thus, according to the signal processing device (imaging device, imaging system) of the present invention, the imaging condition is acquired, and the change amount of the extracted chromaticity parameter is determined and extracted based on the imaging condition. The chromaticity parameter is changed based on the change amount.

  Accordingly, since the degree of brightness around the subject is determined based on the shooting conditions, for example, when the light emitted from the light source near the subject is monochromatic light (for example, red) in night shooting, the monochrome Is color-suppressed. For this reason, an image that is close to the actual appearance and has no sense of incongruity can be obtained.

It is a block diagram which shows the structure of an imaging device. It is a block diagram which shows the structure of a processing unit. It is a block diagram which shows the structure of an image process part. It is a block diagram which shows the structure of a color processing part. It is a block diagram which shows the structure of an extraction part. It is a flowchart explaining operation | movement of an imaging device. It is a flowchart explaining operation | movement of a color processing part. It is a schematic diagram for demonstrating a chromaticity suppression process. 10 is a schematic diagram for explaining chromaticity suppression processing in a color processing unit according to Modification 1. FIG. It is a graph explaining the chroma suppression process which concerns on the modification of 2nd Embodiment. It is a block diagram for demonstrating the imaging system which concerns on 3rd Embodiment.

<First Embodiment>
The imaging device 1 according to the embodiment will be described with reference to FIGS. The imaging device 1 can be used as an in-vehicle camera, a surveillance camera, or the like. Note that “image” and “image signal (video signal)” in the present embodiment correspond one-to-one.

[Overall configuration of imaging device]
As shown in FIG. 1, the imaging device 1 includes a lens unit 2, an imaging unit 3, an amplifier 4, an A / D conversion unit 5, a processing unit 6, and a main microcomputer (main control unit) 7. It consists of The processing unit 6 includes a sub-microcomputer (sub-control unit) (not shown) that performs processing for changing chromaticity parameters (Cb, Cr) described later.

  In the example of FIG. 1, the imaging unit 3, the amplifier 4, and the A / D conversion unit 5 are each configured independently, but are not limited thereto. For example, the imaging unit 3, the amplifier 4, and the A / D conversion unit 5 may be integrally configured with one chip.

  The lens unit 2 is composed of an optical system composed of a single lens or a plurality of lenses. The lens unit 2 captures the optical image of the subject and guides it to the imaging unit 3. The lens unit 2 may be provided with a diaphragm and a shutter (both not shown) for adjusting the amount of transmitted light.

  The imaging means 3 includes a plurality of elements. The plurality of elements photoelectrically convert the light image formed in the lens unit 2 and image of color components (for example, red (R), green (G), blue (B)) having a level corresponding to the amount of light. A signal (color signal: RGB signal) is generated. The generated image signal is output to the amplifier 4. The imaging means 3 in the present embodiment uses a sensor (so-called linear log sensor) having a plurality of elements that can switch an operation for linearly converting incident light into an image signal and an operation for logarithmic conversion according to the amount of incident light. Yes. For example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, or the like can be used as the imaging unit 3.

  The amplifier 4 amplifies the image signal output from the imaging unit 3. The amplifier 4 includes, for example, an AGC (Auto Gain Control) circuit that amplifies an image signal, a CDS (Correlated Double Sampling) circuit that removes a noise component included in the image signal, and the like. The amplified image signal is output to the A / D converter 5.

  The A / D converter 5 converts the image signal amplified by the amplifier 4 into a digital image signal. The A / D converted image signal is output to the processing unit 6.

  The processing unit 6 performs various processes described later on the input image signal. In the present embodiment, the processing unit 6 is an example of a “signal processing device”.

  The main microcomputer 7 controls the operation of the entire imaging apparatus 1 and acquires shooting conditions described later, and sends the shooting conditions to a processing unit 6 described later.

  As shown in FIG. 1, a display unit 10 is connected to the imaging device 1 in the present embodiment. Note that the imaging apparatus 1 may be configured including the display unit 10.

  The display unit 10 is configured by an arbitrary display device such as an LCD (Liquid Crystal Display). For example, when the imaging device 1 is an in-vehicle camera, a display device of a car navigation device installed in the vehicle can be used as the display unit 10. An image based on an image signal (NTSC signal (described later)) processed by the processing unit 6 is displayed on the display unit 10.

[Processing unit configuration]
As shown in FIG. 2, the processing unit 6 includes a logarithmic conversion processing unit 61, a compression unit 62, a linearization processing unit 63, an image processing unit 64, and an NTSC conversion unit 65.

  The logarithmic conversion processing unit 61 performs logarithmic conversion processing on the image signal input from the imaging unit 3. The logarithmic conversion processing unit 61 includes an adder, a multiplier, and an LUT (Lookup Table) not shown.

  The compression unit 62 compresses the dynamic range of the logarithmic conversion image signal. For the dynamic range compression method, see, for example, Konica Minolta Technology Report Vol. 4 (2007) can be used.

  Specifically, the compression unit 62 extracts an illumination component from the input image signal. Then, the compression unit 62 compresses the extracted illumination component according to a predetermined compression characteristic. Further, the compression unit 62 multiplies the compressed illumination component by a reflectance component obtained by dividing the image signal by the illumination component before compression. Thereby, an image signal with a compressed dynamic range is generated.

  The image signal subjected to the dynamic range compression is sent to a linearization processing unit 63 that performs linear conversion (linear conversion) processing. The image signal linearly converted by the linearization processing unit 63 is input to the image processing unit 64.

  The image processing unit 64 performs luminance processing, chromaticity processing, and the like on the image signal with the dynamic range compressed. Details will be described later. The image signal processed by the image processing unit 64 is sent to the NTSC conversion unit 65.

  The NTSC converter 65 converts the image signal processed by the image processor 64 into an NTSC signal (video signal). Specifically, the NTSC converter 65 converts a digital image signal into an analog NTSC signal by D / A conversion or the like. This NTSC signal is output to the display unit 10. Note that the NTSC converter 65 in this embodiment is an example of a unit that converts a digital image signal into an analog video signal. The video signal is not limited to the NTSC signal, and any format that can display an image on the display unit 10 may be used. For example, a PAL (Phase Alternating Line) signal or the like is also included in the “video signal”.

[Configuration of Image Processing Unit 64]
As shown in FIG. 3, the image processing unit 64 includes a color interpolation processing unit 81, an RGB conversion processing unit 82, a gradation conversion processing unit 83, and a color processing unit 84.

  The color interpolation processing unit 81 performs a process of interpolating the missing image signal at each position of the pixels arranged in a mosaic pattern.

  The RGB conversion processing unit 82 performs RGB conversion on the image signal interpolated by the color interpolation processing unit 81 by a 3 × 3 matrix calculation. As a result, color reproduction is improved.

  The gradation conversion processing unit 83 corrects the gradation of the image so that the screen brightness of the display unit is proportional to the image signal.

  The color processing unit 84 extracts a chromaticity parameter from the image signal that has been subjected to gradation correction by the gradation conversion processing unit 83, and changes the chromaticity parameter according to a change amount of the chromaticity parameter based on a shooting condition described later.

[Configuration of Color Processing Unit 84]
As shown in FIG. 4, the color processing unit 84 includes an extraction unit 90, a determination unit 91, and a change unit 92. The determining unit 91 and the changing unit 92 constitute the sub-microcomputer described above.

  The extraction unit 90 uses the Y value (luminance value) of the luminance signal Y indicating the luminance component of the pixels constituting the image from the image signal from the gradation conversion processing unit 83, and the chromaticity signal (color difference signal) Cb indicating the color difference component. , Cr Cb value, Cr value (chromaticity parameter) is extracted.

  As shown in FIG. 5, the extraction unit 90 includes a luminance generation unit 95 that generates a luminance signal Y and a chromaticity generation unit 96 that generates chromaticity signals Cb and Cr.

  The determination unit 91 determines a change amount of the chromaticity parameter (hereinafter referred to as “chromaticity change amount”) based on the shooting condition sent from the main microcomputer 7 and sends the change amount information. The shooting conditions include, for example, shooting sensitivity (ISO sensitivity), aperture value (F value), shutter speed, shooting sensitivity (ISO sensitivity), aperture value (F value), and subject speed acquired based on the shutter speed. Ambient brightness information (condition parameters) is included.

  The determining unit 91 also includes first association information (first table) in which the condition parameter and the color transmittance are associated with each other, and a brightness value of the pixel of the image signal and the color transmittance are associated with each other. Storage information (second table) stored therein (not shown). Note that there is a one-to-one correspondence between the luminance value and the color transmittance.

  Here, the color transmittance is a parameter for adjusting the color saturation (brightness). For example, when the color transmittance is equal (× 1), the color saturation is not changed. When the color transmittance is halved (× 0.5), the color saturation is also halved. When the color transmittance is zero, the color saturation is also zero. Note that saturation refers to the degree of vividness (color purity) of a saturation color, and is one of the three attributes of color (saturation, lightness, and hue).

  The changing unit 92 changes the chromaticity parameters Cb value and Cr value extracted by the extracting unit 90 based on the chromaticity change amount, and sends the changed chromaticity signals Cb ′ and Cr ′ to the display unit 10.

[Operation of Imaging Device 1]
With reference to FIG. 6, the operation of the imaging apparatus 1 will be described.

  When the imaging device 1 is driven, the imaging unit 3 photoelectrically converts the light image formed in the lens unit 2 to generate an image signal (S10). The main microcomputer 7 controls the image pickup means 3 and outputs the generated image signal to the amplifier 4.

  The amplifier 4 amplifies the image signal generated in S10 (S11). The main microcomputer 7 controls the amplifier 4 to output the amplified image signal to the A / D converter 5.

  The A / D converter 5 converts the image signal amplified in S11 into a digital image signal (S12). The main microcomputer 7 controls the A / D converter 5 and causes the logarithmic conversion processor 61 to output an A / D converted image signal.

  The logarithmic conversion processing unit 61 performs logarithmic conversion processing on the image signal digitally converted in S12 (S13). The main microcomputer 7 controls the logarithmic conversion processing unit 61 and causes the compression unit 62 to output the image signal that has undergone the logarithmic conversion processing.

  The compression unit 62 compresses the dynamic range of the image signal subjected to the logarithmic conversion process in S13 (S14). The main microcomputer 7 controls the compression unit 62 and causes the linearization processing unit 63 to output an image signal subjected to dynamic range compression.

  The linearization processing unit 63 performs linear conversion on the image signal that has been subjected to dynamic range compression in S14 (S15). The main microcomputer 7 controls the linearization processing unit 63 and causes the image processing unit 64 to output the linearized image signal.

  The image processing unit 64 performs luminance processing and chromaticity processing on the image signal linearly converted in S15 (S16). The main microcomputer 7 controls the image processing unit 64 and causes the NTSC conversion unit 65 to output an image signal that has been subjected to luminance processing and chromaticity processing.

  The NTSC conversion unit 65 converts the image signal subjected to the luminance processing and chromaticity processing in S16 into an NTSC signal (S17). The main microcomputer 7 controls the NTSC conversion unit 65 and causes the display unit 10 to output an NTSC signal. The NTSC signal is subjected to image processing (dynamic range compression or the like) so that the gradation of the subject falls within the input range of the display unit 10. Therefore, the display unit 10 can display an image based on the NTSC signal.

  The main microcomputer 7 is used as a processing device (not shown) such as a CPU (Central Processing Unit), a ROM (Read Only Memory) storing a control program executed by the CPU, and a working memory of the CPU. It is configured by a storage device (not shown) such as a RAM (Random Access Memory). The sub-microcomputer described above also has the same configuration as the main microcomputer. The storage device described above stores a control program and the like for executing the operation control performed in each step. A processing device such as a CPU executes the control program stored in the storage device, whereby the operation control of each step is executed.

[Operation of Color Processing Unit 84]
Hereinafter, the operation (S16) of the color processing unit 84 will be described with reference to FIG. 4, FIG. 7, and FIG.

  When an image signal is input to the color processing unit 84 (S20), the extraction unit 90 extracts Cb values and Cr values (chromaticity parameters) of chromaticity signals (chrominance signals) Cb and Cr indicating chrominance components (chromaticity parameter). S21). The determination unit 91 acquires imaging sensitivity (ISO sensitivity), aperture value (F value), shutter speed, and condition parameters based on imaging sensitivity, aperture value, and shutter speed. Then, the determination unit 91 refers to the first table stored in advance and determines (specifies) the color transmittance value corresponding to the acquired condition parameter value as the chromaticity parameter change amount (S22). .

  Here, the lower left graph of FIG. 8 is a graph showing the relationship between the condition parameter and the color transmittance. The graph on the upper left of FIG. 8 is a graph showing the relationship between pixel luminance and color transmittance. The upper right graph in FIG. 8 is a waveform of the chromaticity signal corresponding to the luminance value (luminance value) in the Nth column. The dotted waveform is a signal waveform based on the change amount of the condition parameter in the present embodiment. The solid line waveform is a signal waveform that is not based on the amount of change (a signal waveform that is color-suppressed based only on the second table).

  In the graph at the upper left of FIG. 8, the waveform drawn by a thin solid line (hereinafter referred to as “waveform A”) is suppressed in chromaticity based only on the second association information stored in the second table. It is a waveform which shows a mode. That is, the waveform A is a waveform when the first association information is not applied at all.

  For example, at point b in the lower left graph of FIG. 8, the color transmittance is the maximum value (transmittance 100%) (when the brightness around the subject is brighter than the predetermined brightness), so the first association information is applied. Instead, the chromaticity suppression process is performed based only on the normal second association information. Then, the chromaticity suppression process is performed, and chromaticity signals Cb ′ and Cr ′ (solid line waveform in the upper right of FIG. 8) are output from the changing unit 92.

  On the other hand, in the graph in the upper left of FIG. 8, the waveform drawn with a thick solid line (hereinafter referred to as “waveform B”) is changed from the first association information stored in the first table to the second association information. It is a waveform which shows a mode that chromaticity suppression is applied and applied.

  For example, at point a in the lower left graph of FIG. 8, the color transmittance is smaller than the maximum value (when the brightness around the subject is darker than the predetermined brightness), so the first association information is applied to the second association information. Then, chromaticity suppression processing (chromaticity parameter changing processing (S23)) is performed based on the chromaticity parameters after the application. The applied chromaticity parameter is obtained by multiplying the second association information by the first association information. In addition, the determination unit 91 determines whether or not the color transmittance is smaller than the maximum value. In the present embodiment, the above determination is made with the maximum value set to 100% transmittance, but the maximum value may not be set to 100% transmittance but may be set to an arbitrary transmittance.

  Then, the chromaticity suppression process is performed, and the chromaticity signals Cb ′ and Cr ′ (dotted line waveform in the upper right in FIG. 8) are output from the changing unit 92. As can be seen from the dotted line waveform in the upper right of FIG. 8, when the brightness around the subject is darker than the predetermined brightness, the chromaticity signals Cb and Cr are suppressed, and the suppressed chromaticity signals Cb ′ and Cr ′ are output. Is done.

  In the present embodiment, the determination unit 91 constituting the color processing unit 84 receives the shooting conditions sent from the main microcomputer 7 to acquire the condition parameters, and the color transmittance corresponding to the acquired value of the condition parameters. Although the value is determined as the change amount of the chromaticity parameter, the main microcomputer 7 may be configured to have the function of the determination unit 91.

Specifically, the main microcomputer 7 includes a determination unit including a storage unit that stores the first table and the second table, and the color processing unit 84 includes an extraction unit and a change unit. The functions of these determination unit, color processing unit, and extraction unit are the same as described above. That is, the determination unit that configures the main microcomputer 7 acquires the shooting conditions and the condition parameters based on the acquired shooting conditions. Then, the determination unit refers to the first table stored in advance, determines the color transmittance value corresponding to the acquired condition parameter value as the change amount of the chromaticity parameter, and sets information on the change amount. Send to change section. The subsequent processing of the changing unit 92 is the same as described above.
[effect]
Below, the effect of this Embodiment is demonstrated.

  The signal processing apparatus 1 according to the present embodiment is a signal processing apparatus that processes an image signal obtained by an imaging unit that can change imaging conditions, and includes an extraction unit 90, a determination unit 91, and a change unit 92. .

  The extraction unit 90 extracts chromaticity parameters from the image signal. The determination unit 91 determines a change amount of the chromaticity parameter based on the shooting condition when the image signal is obtained. The changing unit 92 changes the chromaticity parameter extracted by the extracting unit 90 based on the change amount.

  In addition, the shooting conditions include a condition parameter that is changed according to the brightness of the shooting field of view. The determination unit 91 includes a storage unit that stores in advance first association information (first table) that associates the condition parameter and color transmittance, and the condition parameter when the image signal is obtained is determined. The value of the color transmittance associated with the value is specified as the change amount based on the first table. Here, the condition parameter includes a photographing sensitivity, an aperture value, and / or a shutter speed.

  In the first table, a value smaller than the maximum value of the color transmittance is associated with the value of the condition parameter smaller than a predetermined threshold.

The storage unit stores in advance second association information (second table) in which the luminance value of the pixel of the image signal and the color transmittance are associated with each other. The determination unit 91 specifies the value of the color transmittance associated with the luminance value of each pixel of the image signal as the change amount based on the second table.
In addition, the imaging device 1 in the present embodiment includes the imaging unit 3 and the signal processing device.

  Thus, according to the signal processing device (imaging device 1) of the present invention, brightness information around the subject is detected as a condition parameter, and based on the association information that associates the condition parameter with the color transmittance, The chromaticity change amount of the chromaticity parameters Cb value and Cr value is changed.

Therefore, for example, when photographing a subject in front of the vehicle at night, even if the brake lamp and tail lamp of the vehicle in front are turned on, the imaging device determines that the periphery of the subject is dark according to the condition parameter. The light source color (red) of the tail lamp is transmitted through. For this reason, the image displayed on the display unit (monitor) is not red, and an image that is close to the actual appearance and has no sense of incongruity can be obtained.
Further, in night photography near a traffic light, the light source color (green) of the traffic light is transmitted through, so an image that is close to the actual appearance and has no sense of incongruity can be obtained.

<Modification>
In the first embodiment described above, the plus / minus regions of the chromaticity signals Cb and Cr of the pixel group in the Nth column of the pixel group configured in a matrix (for example, the gradation range is −128 bits to +127 bits (256 Bit)) The chromaticity suppression process was performed in the entire area.

  In the present modification, for example, when it is desired to suppress only red, only the plus region of the chromaticity signal Cr is suppressed as shown in FIG. For example, when only blue is desired to be suppressed, only the positive region of the chromaticity signal Cb may be suppressed.

  Thus, by suppressing only a specific color, it can suppress more appropriately according to the purpose of use. For example, when shooting a subject in front with an in-vehicle camera, only the red color is suppressed even if the brake light and tail light of the front car are lit, so the image displayed on the display unit (monitor) is more actual. The image is close to the appearance of the image, and the image is more comfortable.

<Second Embodiment>
In this embodiment, a linear log sensor having a plurality of elements that can switch between an operation for linearly converting incident light into an image signal and an operation for logarithmic conversion according to the amount of incident light is used as the image pickup means 3 in the image pickup apparatus 1. Is. Since this linear log sensor is publicly known (see, for example, International Publication WO2006-103881 etc.), the description thereof is omitted here.

  As described above, the dynamic range can be expanded by using a linear log sensor as the imaging unit 3. Therefore, a high-quality image can be displayed on the display unit 10.

  By the way, when a linear log sensor is used as the imaging means 3, noise is likely to occur in the image signal linearized (linear conversion processing) by the linearization processing unit 63 (see FIG. 2). This is because there is a difference between the gradation (resolution) of image data (image signal) captured in the linear region (linear region) and the gradation of image data (image signal) captured in the logarithmic region (log region). This is because when the image data captured in the logarithmic region is linearized, the image data is skipped.

  According to the present embodiment, the color suppression processing of the pixel in the logarithmic region is performed using the second table in which the luminance value of the pixel and the color transmittance are associated with each other. Noise generated during (linear conversion processing) can be suppressed.

<Modification>
By the way, the color transmittance with respect to the luminance value of the pixel when the linear log sensor is used changes the boundary position between the linear region and the logarithmic region at the time of imaging or signal processing as shown in FIG.
For example, when the boundary position in FIG. 10 changes from point A to point B, the color transmittance in the logarithmic region is as shown by a solid line A. Between point B and point A, the color transmittance is constant despite the logarithmic region, so that the original suppression process (change as shown by dotted line B) is not performed.

  Further, when the boundary position in FIG. 10 changes from the point A to the point C, the color transmittance is constant from the point A to the point C although it is a linear region. Processing (changes like dotted line C) is not performed, and natural color reproduction cannot be achieved.

  Therefore, in this modification, the following functions are added to the determination unit 91 and the change unit 92. The determination unit 91 receives the information on the boundary position at the time of imaging or signal processing, and when the boundary position changes, the change amount information so as to change the color transmittance from the boundary point after the change. Is sent to the changing unit 92. The change unit 92 changes the color transmittance (changes the chroma suppress area) according to the change amount.

  According to this modification, even if the boundary position between the linear region and the logarithmic region changes, the chroma suppress region is changed according to the change, so that natural color reproduction can be achieved.

<Third Embodiment>
[overall structure]
As shown in FIG. 11, the imaging system according to the present embodiment has a configuration in which a detection unit 102 and a vehicle control unit 101 are added to the imaging device 1 (see FIG. 1) according to the first embodiment described above. It has become. Note that the configuration of the imaging apparatus 1 is the same as described above, and thus the description thereof is omitted.

  Here, the imaging device 1 is an imaging device mounted on a vehicle. The detection unit 102 detects whether or not the brake of the vehicle is depressed, and sends a brake detection signal indicating whether or not the brake is depressed to the vehicle control unit 101. The vehicle control unit 101 is a so-called vehicle ECU (Engine Control Unit), and sends a change start signal to the change unit 92 that constitutes the color processing unit 84 when a brake depression by the driver is detected. To do.

[Operation]
When the change unit 92 receives a change start signal from the vehicle control unit 101, the change unit 92 changes the chromaticity parameter Cb value and the Cr value extracted by the extraction unit 90 based on the chromaticity change amount, and the changed color Degree signals Cb ′ and Cr ′ are sent to the display unit 10. Note that the change process based on the chromaticity change amount of the chromaticity parameters Cb value and Cr value is the same as the change process in the change unit 92 in the first embodiment described above, and thus the description thereof is omitted.

[effect]
According to the present embodiment, when the change start signal is received, the extracted chromaticity parameter Cb value and Cr value are changed based on the chromaticity change amount, and the changed chromaticity signals Cb ′ and Cr ′. Is sent out. Therefore, the chromaticity change amount of the chromaticity parameters Cb value and Cr value is changed in conjunction with the lighting of the brake lamp.

  Therefore, for example, when photographing a subject behind the vehicle at night, the imaging device that constitutes the imaging system can be automatically activated when its own brake lamp is reflected by a rear object (subject). .

  For this reason, simultaneously with the lighting of the brake lamp, it is determined that the surroundings of the subject are dark according to the acquired condition parameter, and the light source color (red) of the brake lamp is transmitted through, so an image that is close to the actual appearance and has no sense of incongruity is obtained. be able to.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Lens part 3 Imaging means 4 Amplifier 5 A / D conversion part 6 Processing unit 7 Main microcomputer 10 Display part 61 Logarithmic conversion processing part 62 Compression part 63 Linearization processing part 64 Image processing part 65 NTSC conversion part 81 Color interpolation Processing unit 82 RGB conversion processing unit 83 Gradation conversion processing unit 84 Color processing unit 90 Extraction unit 91 Determination unit 92 Change unit 95 Luminance generation unit 96 Chromaticity generation unit 101 Vehicle control unit 102 Detection unit

Claims (9)

A signal processing device for processing an image signal obtained by an imaging means capable of changing imaging conditions,
An extraction unit for extracting chromaticity parameters from the image signal;
A determination unit that determines a change amount of a chromaticity parameter based on the photographing condition when the image signal is obtained;
A signal processing apparatus comprising: a changing unit that changes the chromaticity parameter extracted by the extracting unit based on the change amount. The shooting condition includes a condition parameter that is changed according to the brightness of the shooting field of view,
The determination unit
A storage unit that stores in advance first association information in which the condition parameter and the color transmittance are associated;
2. The signal according to claim 1, wherein a value of color transmittance associated with a value of the condition parameter when the image signal is obtained is specified based on the first association information as the amount of change. Processing equipment.   The signal processing apparatus according to claim 2, wherein the condition parameter includes a photographing sensitivity, an aperture value, and / or a shutter speed.   The first association information associates a value smaller than a maximum value of color transmittance with a value of the condition parameter that is smaller than a predetermined threshold value. Signal processing device. The storage unit stores in advance second association information that associates the luminance value of the pixel of the image signal and the color transmittance,
The said determination part specifies the value of the color transmittance linked | related with the luminance value about each pixel of the said image signal as said change amount based on said 2nd correlation information. The Claim 2 characterized by the above-mentioned. Item 5. The signal processing device according to any one of Items 4 to 6. The signal processing apparatus according to claim 5, wherein the determination unit determines the change amount so that only a color transmittance for a specific color is reduced according to the luminance value. Imaging means;
A signal processing device according to any one of claims 1 to 6;
An imaging device comprising: The imaging unit includes a plurality of elements that can switch between a first operation for linearly converting incident light into an image signal and a second operation for logarithmically converting the linearly converted image signal according to the amount of incident light. Log sensor,
The imaging apparatus according to claim 7, wherein the changing unit changes the chromaticity parameter based on the shooting condition in a logarithmic region in which the second operation is performed. Imaging means mounted on the vehicle;
A detection unit for detecting presence or absence of depression of the brake of the vehicle;
A signal processing device according to any one of claims 1 to 6;
A vehicle control unit that controls the changing unit when the depression of the brake is detected, and changes the chromaticity parameter based on the shooting condition;
An imaging system comprising:

Images