JP2007082023A - Imaging apparatus and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus and an imaging method for acquiring satisfactory image quality in a multi-CCD (Charge-Coupled Device) imaging apparatus. <P>SOLUTION: A Y signal generating circuit 13 is made to generate a luminance signal from an RGB (Red, Green and Blue) signal after gain adjustment by a gain adjustment circuit 12. An AE exposure time control circuit 15 is made to calculate the exposure time tg of a CCD 4 for G corresponding to the luminance signal. An RGB integration circuit 14 is made to integrate the value of the image pickup signal of each RGB. An exposure time control circuit 16 is made to calculate an exposure time tr of a CCD 3 for R and an exposure time tb of a CCD 5 for B for matching the level of the luminance signal for each RGB based on the rates of the integration values ΣR, ΣG and ΣB and the exposure time tg. Driving circuits 6, 7 and 8 are made to drive the respective CCD 3, 4 and 5 according to driving signals corresponding to the calculated exposure time tr, tg and tb. Thus, it is possible to adjust a white balance without generating the deterioration of specific color components under the control of the exposure time of each RGB corresponding to the level rate of the image pickup signal of each RGB. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-plate imaging apparatus and an imaging method.

Conventionally, an imaging apparatus such as a digital camera or a digital video camera is generally provided with an auto white balance function (AWB) that automatically adjusts the white balance of a captured image. White balance adjustment in a digital camera or the like is performed for each RGB after separating an imaging signal output from a solid-state imaging device such as a CCD or a CMOS sensor into RGB color components, as described in Patent Document 1 below, for example. In general, the gain of the provided amplifier is generally controlled by gain control that individually adjusts the ratio of each color component to be the same. In addition, the method is not limited to a single-plate type imaging device that acquires color information using a single solid-state imaging device, but is also applicable to a multi-plate type (three-plate type) imaging device that uses a plurality of solid-state imaging devices. It is.
JP-A-11-289547

  However, in the above-described white balance adjustment by gain control, for example, when the light source at the time of photographing is a fluorescent lamp or in the shade of daylight, since the imaging signal has a small R component, the gain of the R component is set to G. It will be larger than the gain of the component and B component. This means that the S / N ratio of the R component in the image picked up under the photographing light is deteriorated, and noise such as red and skin color portions in the image is increased. Such a problem is also the same in a multi-plate imaging apparatus having advantages such as excellent sensitivity, resolution, and color tone, wide dynamic range, and high color resolution as compared with a single-plate type.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an imaging apparatus and an imaging method that can obtain better image quality in a multi-plate imaging apparatus.

  In order to solve the above-mentioned problem, in the invention of claim 1, in an imaging apparatus including a plurality of solid-state imaging elements for converting the dispersed light into charges for each color, the light is output from the plurality of solid-state imaging elements. A control means for adjusting the level ratio of the image signal for each color by controlling the ratio of the charge accumulation time between the plurality of solid-state image sensors based on the level ratio of the image signal for each color It was.

  In such a configuration, the level ratio of the image signal for each color is adjusted by controlling the ratio of the charge accumulation time in the plurality of solid-state imaging devices based on the color signal, thereby reducing the S / N ratio of a specific color component. The color of the image can be adjusted without any problem.

  According to a second aspect of the present invention, the control means controls a ratio of charge accumulation time between the plurality of solid-state imaging devices when adjusting the white balance of the image based on the image signal for each color. It was supposed to be.

  In such a configuration, the level ratio of the image signal for each color is adjusted by controlling the ratio of the charge accumulation time in a plurality of solid-state imaging devices based on the level ratio, thereby reducing the S / N ratio of a specific color component. The white balance of the image can be adjusted.

  According to a third aspect of the present invention, the plurality of solid-state imaging devices include solid-state imaging devices that convert light of each color of RGB into electric charges, and the control means is configured to display G color according to the brightness of the subject. Including an exposure control means for controlling the charge accumulation time of the solid-state image pickup device for the image, and using the charge accumulation time of the solid-state image pickup device for G color controlled by the exposure control means as a reference. The charge accumulation time of the device was controlled.

  According to a fourth aspect of the present invention, a plurality of amplifying means for individually amplifying the color-specific image signals and a gain ratio between the plurality of amplifying means are controlled by the control means. Gain control means for adjusting a level ratio of image signals for each color after amplification by the plurality of amplification means by controlling to a predetermined ratio according to a ratio of charge accumulation time between the plurality of solid-state imaging elements And provided.

  In such a configuration, the level ratio of the image signal for each color is controlled by controlling both the ratio of the charge accumulation time in the plurality of solid-state imaging devices based on the color ratio and the ratio of the gain of the amplification unit for each color corresponding to them By adjusting, it is possible to adjust the color of the image while suppressing the S / N ratio of the specific color component to a very slight decrease.

  In the invention of claim 5, between the plurality of light amount adjusting means for individually adjusting the amount of incident light to the plurality of solid-state image sensors and the amount of incident light adjusted by the plurality of light amount adjusting means. Incident that adjusts the level ratio of the image signal for each color by controlling the ratio to a predetermined ratio according to the ratio of the charge accumulation time between the plurality of solid-state imaging devices controlled by the control means And a light amount control means.

  In such a configuration, the level ratio of the image signal for each color is adjusted by controlling both the ratio of the charge accumulation time in the plurality of solid-state imaging devices based on the color signal and the ratio of the incident light amount for each color corresponding thereto. As a result, the color of the image can be adjusted without reducing the S / N ratio of the specific color component.

  According to a sixth aspect of the present invention, in the imaging apparatus including a plurality of solid-state imaging elements that convert the dispersed light into charges for each color, the amount of incident light to the plurality of solid-state imaging elements is individually adjusted. Controlling a ratio between the incident light amounts adjusted by the plurality of light amount adjusting units based on a level ratio of the image signals for each color output from the plurality of solid state image sensors. And a control means for adjusting the level ratio of the image signal for each color.

  In such a configuration, the level ratio of the image signal for each color is adjusted by controlling the ratio of the incident light amounts adjusted by the plurality of light amount adjustment units based on the level ratio, so that the S / Color adjustment of an image can be performed without reducing the N ratio.

  The invention according to claim 7 is an image pickup method in an image pickup apparatus including a plurality of solid-state image pickup devices for converting the dispersed light into charges for each color, and is output from each of the plurality of solid-state image pickup devices. Determining the charge accumulation time of each of the plurality of solid-state image sensors based on the level ratio of the image signal for each color, and setting the charge accumulation time of the plurality of solid-state image sensors to the determined charge accumulation time And a step of adjusting the level ratio of the image signal for each color by controlling.

According to this method, the level ratio of the image signal for each color is adjusted by controlling the ratio of the charge accumulation time in a plurality of solid-state imaging devices based on the ratio, thereby reducing the S / N ratio of a specific color component. It is possible to adjust the color of the image without causing it.
Can do.

  As described above, in the present invention, it is possible to perform image color adjustment without reducing the S / N ratio of a specific color component. Therefore, it is possible to perform white balance adjustment that can obtain better image quality in a multi-plate imaging apparatus.

  In addition, the white balance adjustment of an image can be performed without reducing the S / N ratio of a specific color component. Therefore, it is possible to perform white balance adjustment that can obtain better image quality in a multi-plate imaging apparatus.

  In addition, the color adjustment of the image can be performed while suppressing a decrease in the S / N ratio of a specific color component to a very small amount. Therefore, it is possible to perform white balance adjustment that can obtain better image quality in a multi-plate imaging apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main part of an image pickup apparatus 1 including a white balance adjusting device according to the present invention.

  That is, the imaging apparatus 1 converts the incident light from the imaging lens and the dichroic prism that decomposes incident light from the imaging lens into RGB (three primary colors) light and the like, and converts the separated color-specific light into electric charges for imaging. An R CCD (CCD-R) 3, a G CCD (CCD-G) 4, and a B CCD (CCD-B) 5 that output signals as signals are provided. The CCDs 3, 4, and 5 are connected to the R drive circuit 6, the G drive circuit 7, and the B drive circuit 8, respectively, and are driven by the drive circuits 6, 7, and 8.

  The imaging signals output from the CCDs 3, 4, and 5 are individually converted into digital signals by CDS (Correlated Double Sampling) / ADC (analog-to-digital conversion) circuits 9, 10, and 11 for each color component. And output to the gain adjustment circuit 12. The gain adjustment circuit 12 includes an R amplifier 12a, a G amplifier 12b, and a B amplifier 12c for each color component, and adjusts the gain of the imaging signal for each color component in accordance with a set value of sensitivity (ISO sensitivity, etc.) The signals are output to the Y signal generation circuit 13 and the RGB integration circuit 14, respectively. The image pickup signal for each color component after gain adjustment is also output to other signal processing circuits not shown.

  The Y signal generation circuit 13 generates a luminance (Y) signal from the R, G, and B imaging signals and outputs it to the AE exposure time control circuit 15. The AE exposure time control circuit 15 constitutes the control means of the present invention together with the exposure time control circuit 16 described later, and functions as the exposure control means of the present invention. The AE exposure time control circuit 15 is a value of a luminance signal (here, 0 to 255). ) Is calculated to obtain a charge accumulation time (exposure time) tg of the G CCD 4 necessary for setting the value to an appropriate value (for example, 110), and the result is sent to the exposure time control circuit 16 and a control signal indicating it is sent. This is sent to the G drive circuit 7.

The RGB integration circuit 14 integrates the values of the imaging signals from the R, G, and B imaging signals, and outputs the integration values ΣR, ΣG, and ΣB to the exposure time control circuit 16. The exposure time control circuit 16 uses the following formula tr = tg × ΣG / ΣR based on the integrated values ΣR, ΣG, ΣB of the imaging signals for each color component and the charge accumulation time tg of the G CCD 4.
tb = tg × ΣG / ΣB
Then, the charge accumulation time tr of the R CCD 3 and the charge accumulation time tb of the B CCD 5 are calculated, and control signals indicating them are sent to the R drive circuit 6 and the B drive circuit 8, respectively.

  The G drive circuit 7 drives the G CCD 4 based on the control signal sent from the AE exposure time control circuit 15, and the R drive circuit 6 and the B drive circuit 8 control the exposure time. Based on the control signal sent from the circuit 16, the R CCD 3 and the B CCD 5 are driven.

  Specifically, as shown in FIG. 2, each of the drive circuits 6, 7, and 8 has a SUB (sweep pulse) corresponding to the control signal (charge accumulation time tr, tg, tb) every frame (30 ms) as shown in FIG. ) Signal and SG (readout pulse) signal are supplied to the CCDs 3, 4, 5. Then, by being driven by the drive signal, the charge accumulation times tr, tg, and tb of the CCDs 3, 4, 5 are integrated values of the imaging signals for each color component after gain adjustment output from the gain adjustment circuit 12. The time is controlled to make ΣR, ΣG, and ΣB coincide.

For example, the integrated values ΣR, ΣG, and ΣB of the imaging signals for each color component output from the RGB integrating circuit 14 are respectively ΣR = 100.
ΣG = 200
ΣB = 80
In this case, when the charge accumulation time tg of the G CCD 4 obtained by the AE exposure time control circuit 15 is 10 ms, the charge accumulation times tr and tb of the R CCD 3 and the B CCD 5 are tr = 20 ms, respectively.
tb = 25ms
Controlled.

  In other words, for example, in the case of a digital camera, when capturing an image that displays a through image, when capturing a still image for recording according to a user's operation, or when capturing a moving image on a digital camera or digital video camera. At the time of capturing a frame image, the ratio between the charge accumulation times of the CCDs 3, 4, and 5 is controlled based on the level ratio of the image signal for each color component after gain adjustment output from the gain adjustment circuit 12. As a result, the white balance of the image generated through other signal processing is ensured.

  As described above, in the present embodiment, each CCD 3, 4 is based on the ratio (level ratio) of the integrated values ΣR, ΣG, ΣB of the imaging signals for each color component after gain adjustment output from the gain adjustment circuit 12. , 5 are controlled (feedback control) so that the accumulated values ΣR, ΣG, ΣB coincide with each other, so that the white balance of the captured image is ensured. Therefore, when white balance adjustment is performed, a decrease in the S / N ratio of a specific color component that occurs when gain control is performed by adjusting the amplification factor of each amplifier 12a, 12b, 12c of the gain adjustment circuit 12, for example, the light source is a fluorescent lamp. In addition, there is no decrease in the S / N ratio of the R component in the shade of daylight, and an image with better image quality can be obtained.

  In the present embodiment, the case where each of the R, G, and B drive circuits 6, 7, and 8 outputs the SG signal next to the SUB signal as the drive signal has been described. 6, 7 and 8 may output the SUB signal after the SG signal.

  In this embodiment, the AE exposure time control circuit 15 determines and controls the charge accumulation time of the G CCD 4 based on the luminance signal generated by the Y signal generation circuit 13, and the exposure time control circuit 16 The charge storage times tr and tb of the R CCD 3 and the B CCD 5 are determined and controlled based on the charge storage time (tg). However, the present invention is not limited to this, and the following configuration is also possible. Good.

  For example, based on the luminance signal, integration of R, G, and B imaging signals integrated by the RGB integration circuit 14 and a first circuit that calculates a charge accumulation time serving as a reference for all the CCDs 3, 4, and 5 Based on the values ΣR, ΣG, ΣB, a second circuit for calculating the charge storage time ratio of the CCDs 3, 4 and 5 for matching them, the charge storage time calculated by the first circuit, A third circuit for individually determining and controlling the charge accumulation time of each of the CCDs 3, 4, and 5 based on the ratio calculated by the two circuits may be provided.

  In any case, if the imaging device is configured to separately detect the brightness of the subject using an optical sensor or the like, the AE exposure time control circuit 15 or the first first sensor based on the detection result of the optical sensor or the like. You may make it make a circuit perform the calculation mentioned above.

  Furthermore, in the present embodiment, it is only necessary to control the ratio between the charge accumulation times of the CCDs 3, 4, 5 from the image signal for each color component after gain adjustment output from the gain adjustment circuit 12. In the above description, the method for ensuring the white balance of the image generated through the signal processing has been described. However, the following configuration may be employed.

  For example, in addition to the configuration shown in FIG. 1, a gain adjustment circuit that individually adjusts the amplification factor of each amplifier 12a, 12b, 12c of the gain adjustment circuit 12 is provided, and the charge accumulation time of each CCD 3, 4, 5 is adjusted. By performing the ratio control and the gain control by adjusting the amplification factors of the amplifiers 12a, 12b, and 12c of the gain adjustment circuit 12 in the conventional manner, the color after gain adjustment output from the gain adjustment circuit 12 is performed. The integrated values ΣR, ΣG, and ΣB of the imaging signal for each component may be matched. In that case, the amplification factor of each amplifier 12a, 12b, 12c is controlled based on the charge accumulation time in each CCD 3, 4, 5, or conversely, the amplification factor of each amplifier 12a, 12b, 12c is used as a reference. The charge storage time may be controlled.

  Even in such a configuration, as compared with the case where white balance adjustment is performed only by gain control, image quality deterioration due to the adjustment can be negligible, and an image with better image quality can be obtained. In particular, in the case of controlling the amplification factor of each amplifier 12a, 12b, 12c on the basis of the charge accumulation time, when the charge accumulation time of each CCD 3, 4, 5 is determined in advance, an upper limit is set for the maximum time difference between them. In this case, it is possible to prevent a deterioration in image quality due to a positional shift between an image of a specific color component and an image of another color component, which is expected when capturing a fast-moving subject.

  Further, different from the above, for example, in addition to the configuration shown in FIG. 1, the optical system 2 is located between the optical system 2 and the CCDs 3, 4 and 5 for R, G and B, respectively. A light amount adjusting means (a diaphragm or the like) for adjusting the amount of incident light of each separated color, and an incident light amount control circuit for controlling the incident light amount to each of the CCDs 3, 4, and 5 adjusted by each light amount adjusting means; Instead of the charge accumulation time ratio control in each of the CCDs 3, 4, 5, the incident light amount control circuit uses the level ratio of the imaging signal for each color component after gain adjustment output from the gain adjustment circuit 12. Based on this, the ratio of the amount of light incident on each of the CCDs 3, 4, 5 may be controlled.

  Even in such a case, as in the present embodiment, when white balance adjustment is performed, the S / of specific color components generated when gain control is performed by adjusting the amplification factors of the amplifiers 12a, 12b, and 12c of the gain adjustment circuit 12. There is no decrease in the N ratio, and an image with better image quality can be obtained.

  Further, based on the level ratio of the image pickup signal for each color component after gain adjustment output from the gain adjustment circuit 12, in parallel with the charge accumulation time ratio control in each CCD 3, 4, 5, each CCD 3, 4, It is good also as what controls the ratio of the incident light quantity to 5. That is, the gain output from the gain adjustment circuit 12 is controlled by controlling the charge accumulation time in each CCD 3, 4, 5 and the exposure amount for each color determined by the amount of light incident on each CCD 3, 4, 5 by the light amount adjusting means. The integrated values ΣR, ΣG, and ΣB of the imaging signals for each color component after adjustment may be made to coincide. In this case, the amount of incident light on each CCD 3, 4, 5 is controlled based on the charge accumulation time in each CCD 3, 4, 5, or conversely, the amount of charge accumulated on the basis of the incident light amount on each CCD 3, 4, 5 is used. What is necessary is just to set it as the structure which controls time.

  Even in such a configuration, at the time of white balance adjustment, a decrease in the S / N ratio of a specific color component that occurs when gain control is performed by adjusting the amplification factor of each amplifier 12a, 12b, 12c of the gain adjustment circuit 12, for example, a light source In the case where is a fluorescent lamp or in the shade of daylight, there is no reduction in the S / N ratio of the R component, and an image with better image quality can be obtained. In particular, in the case of controlling the amount of incident light on each CCD 3, 4, 5 on the basis of the charge accumulation time, when determining the charge accumulation time of each CCD 3, 4, 5 in advance, an upper limit is set for the maximum time difference between them. If this is the case, it is possible to prevent deterioration in image quality due to a positional shift between an image of a specific color component and an image of another color component, which is expected when capturing a fast-moving subject.

  Further, in the above description, the present invention is described in the case where the present invention is applied to a three-plate type image pickup apparatus that separates incident light into RGB light and picks up a color image of a subject with three CCDs 3, 4, and 5. However, the present invention can also be applied to an image sensor using a CMOS sensor. Further, the present invention is not limited to a three-plate type imaging device, and for example, in addition to R, G, B, a W (white) CCD or two G CCDs (R, G, B) G1, G2, B), and a four-plate type image pickup apparatus that further includes CCDs for Ye, Mg, G, and Cy.

  Further, the case where the present invention is applied to an image pickup apparatus that separates incident light into RGB light by a dichroic prism or the like and obtains an image pickup signal for each color component has been described. The present invention can also be applied to an imaging apparatus configured to obtain an imaging signal for each color component by providing a color filter on each CCD 3, 4, 5.

  Here, in the above description, the case where the present invention is applied mainly to white balance adjustment at the time of imaging has been described, but the present invention is not limited to this, and the present invention emphasizes a specific color component of an image captured by the imaging apparatus. In this case, for example, the present invention can also be applied when a color filter effect is applied to a captured image. For example, if the charge accumulation time of the R CCD 3 shown in FIG. 2 is increased to 30 ms instead of 20 ms, red can be emphasized and a red filter effect can be obtained. In that case, an image with better image quality can be obtained without reducing the S / N ratio of the specific color component to be emphasized.

  Further, when emphasizing a specific color component of an image as described above, instead of controlling the charge accumulation time of each of the CCDs 3, 4, 5 as described above, gain control for each color of the imaging signal and each CCD 3 , 4 and 5 may be controlled, or the incident light amount may be controlled in parallel with the charge accumulation time control.

It is a block diagram which shows the principal part of the imaging device which concerns on this invention. It is a timing chart which shows the drive signal supplied to each CCD for R, G, B.

Explanation of symbols

1 Imaging device 2 Optical system 3 R CCD
4 G CCD
5 B CCD
6 R drive circuit 7 G drive circuit 8 B drive circuit 9, 10, 11 CDS / ADC circuit 12 gain adjustment circuit 12a R amplifier 12b G amplifier 12c B amplifier 13 Y signal generation circuit 14 RGB integration circuit 15 AE exposure time Control circuit 16 Exposure time control circuit

Claims (7)

In an imaging device including a plurality of solid-state imaging elements that convert the dispersed light into charges for each color,
Based on the level ratio of the image signals for each color output from the plurality of solid-state image sensors, the level of the image signal for each color is controlled by controlling the ratio of the charge accumulation time between the plurality of solid-state image sensors. An imaging apparatus comprising control means for adjusting a ratio.   The image pickup apparatus according to claim 1, wherein the control unit controls a ratio of charge accumulation time between the plurality of solid-state image pickup elements when adjusting white balance of an image based on the image signal for each color. . The plurality of solid-state imaging devices include solid-state imaging devices that convert light of each color of RGB into electric charges,
The control means includes an exposure control means for controlling a charge accumulation time of the G color solid-state imaging device according to the brightness of the subject, and a charge accumulation time of the G color solid-state imaging element controlled by the exposure control means. 3. The white balance adjustment device according to claim 1, wherein the charge accumulation time of the solid-state image sensor for R color and B color is controlled with reference to. A plurality of amplifying means for individually amplifying the color-specific image signals;
By controlling the gain ratio between the plurality of amplifying means to a predetermined ratio according to the ratio of the charge accumulation time between the plurality of solid-state imaging devices controlled by the control means, 4. The imaging apparatus according to claim 1, further comprising: gain control means for adjusting a level ratio of the image signal for each color after amplification by the amplification means. A plurality of light amount adjusting means for individually adjusting the amount of incident light to the plurality of solid-state image sensors;
The ratio of the incident light amounts adjusted by the plurality of light amount adjusting means is controlled to a predetermined ratio corresponding to the ratio of the charge accumulation time between the plurality of solid-state imaging devices controlled by the control means. The imaging apparatus according to claim 1, further comprising: an incident light amount control unit that adjusts a level ratio of the image signal for each color. In an imaging device including a plurality of solid-state imaging elements that convert the dispersed light into charges for each color,
A plurality of light amount adjusting means for individually adjusting the amount of incident light to the plurality of solid-state image sensors;
Based on the level ratio of the image signals for each color output from the plurality of solid-state image sensors, the image signal for each color is controlled by controlling the ratio of the incident light amounts adjusted by the plurality of light amount adjusting means. And a control means for adjusting the level ratio. An imaging method in an imaging apparatus including a plurality of solid-state imaging elements that convert split light into charges for each color,
Determining a charge accumulation time of each of the plurality of solid-state imaging devices based on the level ratio of the image signals for each color output from the plurality of solid-state imaging devices;
Adjusting the level ratio of the image signal for each color by controlling the charge accumulation times of the plurality of solid-state imaging devices to the determined charge accumulation times.

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