JP2003047015A - Color photographing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the variation in the S/N ratio of respective colors, in a multi-CCD color photographing apparatus. SOLUTION: The color photographing apparatus has a plurality of solid-state photographing elements capable of obtaining individually the color signals of a plurality of colors, at least one driving-signal generating circuits for generating the driving signals for driving individually the plurality of solid photographing elements, exposure-term adjusting means capable of adjusting in a predetermined unit term individually the exposure terms of the respective ones of the plurality of solid-state photographing elements, a signal processing circuit for performing the signal processing for obtaining a picture-data signal by receiving the signals outputted from the plurality of solid photographing elements, and an exposure- term calculating circuit for so calculating the new exposure terms of the respective ones of the plurality of solid-state photographing elements as to output them to the exposure-term adjusting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image pickup device, and more particularly, to a noise reduction technique for a color image pickup device of a type in which a plurality of solid-state image pickup elements having different color sensitivities are combined to obtain a color image.

In this specification, a color image pickup device means
It includes a digital still camera mainly for shooting still images and a digital video camera mainly for shooting moving images, and further includes an imaging device having both functions. In the present specification, each solid-state image sensor basically generates an image signal for only one color. Here, the color signal is individually generated for each solid-state image sensor, and
An image pickup device that generates an image using the image signal data obtained from the above solid-state image pickup device is referred to as a double-plate image pickup device.

The solid-state image pickup device for each color includes an area sensor and a line sensor. At least one photoelectric conversion element may be provided in each solid-state image pickup element.

[0004]

2. Description of the Related Art When an image pickup device having individual color components, for example, an image pickup device for forming image data by using a CCD solid image pickup device of RGB3 plate type is used, the CCD solid image pickup device of each color outputs RGB three colors. Any of these color signals can be obtained independently.

The three-plate type image pickup device is excellent in sensitivity, resolution and color tone. Furthermore, it has the advantages of a wide dynamic range and high color resolution. Since the dichroic prism transmits or reflects the incident light ray to perform color separation, there is little loss such as absorption of light, and light utilization efficiency is good.

Therefore, it is suitable for realizing a color image pickup device having high sensitivity. Further, since the data of all pixels is provided for each color, basically, interpolation processing is unnecessary and high resolution can be obtained.

[0007]

In the above-described three-plate type image pickup device, when a plurality of color components such as RGB are obtained from, for example, individual CCD solid-state image pickup devices, adjustment of the color components is output for each color component. Is done by converting to. Since the noise of the signal obtained from the CCD solid-state imaging device having a color component with low sensitivity among the CCD solid-state imaging devices of the respective colors is likely to be relatively larger than the noise of the signals from other CCD solid-state imaging devices, the image quality is deteriorated. There is a problem that is likely to occur.

For example, in a primary color image pickup device having a CCD solid-state image pickup device of three colors of RGB, sensor sensitivity (signal / noise ratio: G (green)) of R (red) and B (blue) is lower than that of R (red) and B (blue). (S / N ratio)) is high. this is,
In the natural world (under sunlight), G has a larger spectral irradiance (incident light amount) than R and B (abbreviated as RB below), and noise of a certain level that does not substantially depend on the incident light amount among noise components. Is predominant.

An object of the present invention is to reduce the difference in S / N ratio for each color and keep the noise level constant in a multi-plate type image pickup device.

[0010]

According to one aspect of the present invention, a plurality of solid-state image pickup devices capable of individually obtaining color signals of a plurality of colors and a plurality of solid-state image pickup devices are individually driven. At least one drive signal generation circuit for generating the drive signal, an exposure period adjusting unit capable of individually adjusting an exposure period within a predetermined unit for each of the plurality of solid-state image pickup devices, and the plurality of solid-state image pickup devices. A signal processing circuit for receiving an output signal from the image processing device to perform a signal processing to obtain an image data signal, and calculating a new exposure period for each of the solid-state imaging devices based on the output signal or the image data signal, There is provided a color image pickup device including an exposure period calculation circuit which outputs a new exposure period to the exposure period adjusting means.

In the above-mentioned color image pickup device, since the exposure period can be adjusted for each color, S depending on the color can be adjusted.
The influence of variations in the / N ratio can be reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A three-plate type solid-state image pickup device is described, for example, on page 107 of Introduction to CCD Camera Technology (Hiroo Takemura, Corona Publishing Co.). FIG. 8 shows a schematic configuration diagram of a three-plate CCD solid-state imaging device which is also described in the above document.

As shown in FIG. 8, a three-plate CCD solid-state image pickup device 400 includes an image pickup lens 401, a solid-state image pickup device 411 for R, a solid-state image pickup device 415 for G, and a solid-state image pickup device 417 for B. It has and. In addition, a dichroic prism 403 is provided between the imaging lens 401 and each solid-state imaging device 411, 415 and 417.
The dichroic prism 403 includes three prism blocks 403a, 403b and 403, first to third prism blocks 403a, 403b and 403.
It is composed of c. A multilayer interference film is deposited on the bonding surfaces 405a and 405b of each prism block.
An interference film that reflects, for example, the B ray and transmits the RG ray is formed between the third prism block 403c closest to the imaging lens 401 side and the first prism block 403a. First prism block 403a
Between the second prism block 403b and the second prism block 403b, for example, R
An interference film that reflects light rays and transmits G rays is formed.

By using the above structure, RGB3
The primary color ray L is a green ray Lg, a red ray Lr, and a blue ray L.
It can be decomposed into b and. Each decomposed light ray Lg,
Lr and Lb enter the corresponding CCD solid-state imaging devices 411, 415, and 417, respectively.

For example, an image pickup device using a three-plate CCD solid-state image pickup device of RGB primary colors has different sensitivities for each RGB color. Therefore, if the exposure time is made equal for each of the three color solid-state image pickup devices, the signal level becomes three.
Colors cannot be the same. If this is supplemented by signal processing or the like, the S / N of the low-sensitivity color deteriorates. Therefore, the exposure time can be controlled independently for each color. By adjusting the exposure time for each color, the signal level of each color of GRB can be made uniform.

FIG. 1 shows an example of a flowchart of signal processing capable of equalizing signal levels. As shown in FIG. 1, in step S1, signals of each color for each frame are integrated. In step S2, a ratio Rx (Rx = Sm / Sx) between the largest integral value Sm of each color and the integral value Sx of the other colors is calculated. Step S3
In step 1, the initial reference exposure time ts set as the initial value is multiplied by the ratio Rx relating to each color obtained in step S2, and a new exposure time tx (= ts × Rx) is obtained for each color.
Ask for. Exposure is performed for each color based on the new exposure time tx for each color obtained in step S3. As indicated by the symbol F, the new exposure time tx may be updated by returning from step S3 to step S1 again.

The color image pickup apparatus according to the first embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

FIG. 2 is a block diagram of the color image pickup device according to the present embodiment, FIG. 3 is a partial cross-sectional view of each CCD solid-state image pickup device constituting the color image pickup device, and FIG.
FIG. 6 is a timing chart diagram for explaining the operation of the color imaging device.

As shown in FIG. 2, the color image pickup apparatus A is
For example, a three-plate CCD solid-state image sensor 1, 3 for RGB
And 5. The "CCD solid-state image pickup device" is an example of the image pickup device, and other image pickup devices such as a CMO.
An S-type solid-state image sensor and the like are also included.

Further, the color image pickup apparatus A includes a drive circuit section 7 for driving the CCD solid-state image pickup elements 1, 3 and 5.
And a control unit 11 that controls the drive circuit unit 7 and the like.

The structure of each CCD solid-state image pickup device 1, 3 and 5 will be described later with reference to FIG. 3, but each CCD solid-state image pickup device has at least one or more for converting an optical signal into an electric signal. A photoelectric conversion element, an output section for outputting the obtained electric signal to a signal processing circuit, and an overflow drain OFD for discharging unnecessary charges out of the charges accumulated in the photoelectric conversion element are provided. ing. The overflow drain OFD includes an OFD1 for G, an OFD2 for B, and an OFD3 for R.
Each is configured to be able to operate independently.

The drive circuit section 7 includes a drive signal generation circuit 15 for G, a drive signal generation circuit 17 for B, a drive signal generation circuit 21 for R, and a common drive circuit 23.
The control unit 11 includes an image signal processing circuit 25, an exposure amount determination circuit (AE) 27, and a color balance determination circuit (AWB) 31.
It has and.

The common drive circuit 23 operates in synchronization with a signal from a clock signal generator that generates a reference clock signal that serves as a reference for the operation of the entire circuit. Common drive circuit 23
Is a common drive signal necessary for driving the CCD solid-state image pickup elements 1, 3 and 5 of each color, for example, reading out signal charges from the photoelectric conversion elements, and transferring signal charges in the vertical charge transfer channel or the horizontal charge transfer channel. Is generated and supplies a common drive signal S1 to the CCD solid-state image pickup devices 1, 3 and 5, and outputs the drive signal S1 to the (individual) drive signal generation circuits 15, 17 and 21 for each color of RGB. is there.

(Individual) drive signal generation circuit for each of RGB colors
15, 17 and 21 are outputs from the common drive circuit 23
The signal S1 and the output signal Tex from the exposure amount determination circuit 27
p (G) and R drive signal from the color balance determination circuit 31
Signal g / r entering the generation circuit 17 and B drive signal generation times
G / b entering the path 21 (in the drive signal generation circuit 15 for G
No signal)), based on the CCD solid-state image sensor
Separate OFD1, OFD2, and OFD3 of 1, 3 and 5
The OFD drive signal for driving the
It outputs to the body image pickup devices 1, 3 and 5. Configuration above
The drive circuit section 7 having the CCD solid-state image sensor 1,
It is possible to drive 3 and 5 independently.
It The common drive signal S1 is, for example, a vertical synchronization signal.
No.Φ_VSYNC, Horizontal sync signal Φ_HSYNC, Vertical charge transfer signal Φ
_VCCDAnd horizontal charge transfer channel Φ_{HCC D}Including etc. image
The signal processing circuit 25 includes CCD solid-state image pickup devices 1 and 3 for each color.
And receiving the image signals from 5 to form an image
The image data signals of the respective colors are combined. Image data signal for each color
Reproduce or process the image of the subject by combining the numbers
You can

The amount of light incident on the CCD is represented by the product of the intensity of the incident light beam and the integration time. The exposure amount determination circuit 27 is C
A circuit for optimizing the amount of light incident on the CD solid-state imaging devices 1, 3 and 5, and a CCD for obtaining the optimum conditions.
The magnitude of the output signal from the solid-state image sensor is detected. More specifically, based on the magnitude of the output signal, the amount of light can be controlled by combining the operation of the electronic shutter and the diaphragm of the imaging lens, the gain adjustment of the amplifier, and the gain adjustment of the signal processing. .

Color balance (Auto White Ba
(Lance: AWB) determination circuit is a circuit that detects a deviation of a color balance of an image obtained from a signal output from a CCD solid-state image sensor from a reference value. Is a circuit for obtaining an output signal ratio suitable for the CCD solid-state image pickup device. Note that color balance is also called auto white balance. For example, a CCD solid-state image sensor is used as a sensor, and RGB signals are balanced by an output signal from the CCD solid-state image sensor, or simply, it is included in one screen for image capturing. The processing is performed based on the assumption that the total color components are almost zero, that is, they are close to achromatic colors.

The display circuit 33 is a circuit for performing signal processing for data format for displaying an image on a liquid crystal monitor or the like, based on the processed image signal. The storage circuit 35 is a circuit for performing signal processing for data format for storing image data in an external memory card, for example.

FIG. 3 shows a structural sectional view of the CCD solid-state image pickup device. As shown in FIG. 3, the p-type semiconductor layer 55 is formed on the semiconductor substrate 51. A photoelectric conversion element (photodiode) on the p-type semiconductor layer 55 together with the p-type semiconductor layer 55.
Forming the n-type semiconductor layer 57. A vertical charge transfer channel 61 is formed in proximity to the n-type semiconductor layer 57 by the n-type semiconductor layer. Read gate 57 between the two
a is formed. On the outside of the n-type semiconductor layer 57 and the vertical charge transfer channel 61, a channel stopper layer 63 is formed of a p-type semiconductor layer having a high impurity concentration.

A gate oxide film 65 is formed on the p-type semiconductor layer 55. A charge transfer electrode 67a is formed in a region on the gate oxide film 65 and above the vertical charge transfer channel layer 61.
67b is formed of, for example, polycrystalline silicon. An insulating film 65a is formed on the charge transfer electrodes 67a and 67b,
An n-type semiconductor layer 5 forming a part of the photoelectric conversion element thereon
A light shielding film 71 having an opening exposing the insulating film 65 on the surface of 7 and covering the charge transfer electrodes 67a and 67b and the vertical charge transfer channel layer 61 is formed. A planarization film 70 is formed so as to cover the above structure. A color filter, for example, a green color filter 73, is formed on the entire surface of the solid-state image pickup element on a region of the flattening film 70 corresponding to each photoelectric conversion element. On the other solid-state imaging device, either a blue color filter or a red color filter is formed on one surface.

A flattening film 70 is formed on the color filter 73 to reduce surface irregularities. A microlens 81 for focusing light on the opening of the photoelectric conversion element is formed on a region of the flattening film 70 corresponding to each photoelectric conversion element. The p-type semiconductor layer 55 is grounded (GND), for example. The output of the voltage supply circuit 90 is connected to the n-type semiconductor layer 51 so that a desired voltage can be applied as the substrate potential Vsub. When a high positive voltage is applied from the voltage supply circuit 90 as the substrate potential Vsub, the charges accumulated in the photoelectric conversion element can be collectively extracted from the substrate side to the outside. Such a structure is referred to as a vertical overdrain (VOF).
D) called structure. Solid-state image pickup devices of other colors have the same structure. Other structures may be used as long as they can extract charges.

The operation of the image pickup apparatus according to this embodiment will be described with reference to FIGS. 2 to 4. Figure 4 shows R
FIG. 6 is a timing chart of a GB 3-plate type image pickup device. For simplification, description will be made assuming that the 1V period (one frame period or one field period) in FIG. 4 is equal to the 8H period. In FIG. 4, (a) shows a vertical charge transfer channel synchronization and signal read period. (B)
Is a charge discharging pulse signal for G, and (c) is R
And (d) is a charge discharging pulse signal for B. (E) shows the count value of the G subtraction counter and the G charge accumulation amount, and (f) shows the count value of the R subtraction counter and the R charge accumulation amount.
(G) shows the count value of the B subtraction counter and the B charge accumulation amount.

For example, from time t1 to time t2 in (e), the count value of the subtraction counter decrements as time advances. The charge accumulation amount during this period is
0 "is maintained. When the count value of the subtraction counter reaches" 0 "at time t2, OFD1 (FIG. 2) is turned off and exposure is started. During the exposure period from time t2 to time t3, G The amount of electric charges accumulated in the image pickup element (photoelectric conversion element) is increased, and the exposure is stopped at time t3.

Again using the subtraction counter, the count value is decremented by the subtraction counter from time t3 to time t4 based on the maximum value of the G charge amount accumulated from time t2 to time t3. The charge storage amount at this time also maintains "0". The count value and charge accumulation amount of R shown in (f) and the count value and charge accumulation amount of B shown in (g) are the same as G. More detailed operation will be described later. The exposure period during which the reference exposure amount is obtained is a 1 / 2V period, that is, a 4H period.

Although the exposure amount is determined by the value of the luminance component Y, it can be substituted by, for example, the G signal value that most contributes to the luminance component Y. The color balance can be determined based on the color difference components Cb and Cr.

The operation will be described in more detail. As for the value of the color balance from the color judgment circuit, the signal g / b is supplied to the B drive signal generation circuit and the signal g / r is supplied to the R drive signal generation circuit. It is output to. The exposure amount determination circuit outputs the individual reference exposure amounts for the respective colors of RGB to the drive signal generation circuits for the respective colors of RGB. At this time, a new reference exposure time is calculated for R and B. Regarding G, the original reference exposure time: Texp (G) is used as it is.

That is, the exposure time of the new R is Tex.
p (R) = Texp (G) × g / r. The exposure time of the new B is Texp (B) = Texp
It is used by using the formula of (G) × g / b.

Therefore, the CCD solid-state image pickup devices 1, 3 and 5
Each of the OFD drive periods can be calculated by the following formula.

T _OFDG = T1V-Texp (G) T _OFDR = T1V-Texp (R) T _OFDR = T1V-Texp (B) 1V (vertical) period (one field period or one frame) shown in (a) of FIG. Period), as shown in FIGS. 4B to 4D, with respect to the CCD solid-state imaging device for each color of GRB, a period of the same length starting from time t1, for example, a 1/2 V period, that is, The substrate voltage supply circuit 90 for VOFD shown in FIG.
(This circuit may be included in each color drive signal generation circuit 15, 17 and 21 shown in FIG. 2, for example)
OFD1 to OF provided in each CCD solid-state image sensor of
All of the signals up to D3 are turned on, and the RGB signal charges are continuously discharged.

In the example of FIG. 3, each color drive signal generation circuit 1
A time counter is included in each of 5, 17 and 21, and the count value is decremented (subtracted) over time. Finally, at the time when the count value of the subtraction counter becomes "0", that is, at time t2 after the ½ V period (t2-t1 period) in FIG. 4, the OFD drive circuit (each color drive signal generation circuit (Included) turns off OFD1 to OFD3 to start the actual exposure. In the example of FIG. 4, the initial value of the counter is set to "4".

During a 1/2 V period from time t2 to time t3, signal charges are accumulated in the CCD solid-state image sensor of each color of RGB. The amount of charge read at time t3 when 1V period has elapsed from time t1 is the output signal value (integrated value of signal)
Corresponding to.

During the constant period from t3 to t5, the above 1
A new exposure time (exposure period) is calculated based on the information of the V period (t2-t3). As shown in FIG. 3, the discharge of charges and the exposure by VOFD may be continued during the period from t3 to t5. A new reference exposure amount is determined before time t5. For example, the exposure amount determination circuit
When it is determined that the luminance component Y does not need to be changed (it is the optimal value as it is), the new G reference exposure period is maintained at 1 / 2V. Of course, if it is determined that the new reference exposure period for G should be changed from 1 / 2V, a value different from 1 / 2V may be set. The case where it is determined that the new G exposure time can be maintained at 1/2 V will be described below.

In this case, the color balance determination circuit calculates the exposure time (period) of R and B based on the following calculation formula.

Texp (R) _i = Vg / Vr × Texp (R) _i−1 = (1.5 / 1.2) × (1 / 2V) = 5 / 8V Texp (B) _i = Vg / Vb × Texp (B) _i-1 = (1.5 / 1.0) × (1 / 2V) = 3 / 4V However, i shows the present field period, and i-1 is one field period or more before the present. Shows the field period of. As can be seen in FIG. 4, the G exposure time is 4 /
8V, R exposure time to 5 / 8V, B exposure time to 6
When set to / 8 V, the accumulated signal charge amounts (signal integration values) are almost the same in R, G and B.

Based on these signal integration values, the exposure amount determination circuit 27 and the color balance determination circuit 31 (FIG. 2) are set to G
CC for each of the drive signal generation circuit 15 for B, the drive signal generation circuit 17 for B, and the drive signal generation circuit 21 for R
A drive signal for driving the D solid-state image pickup devices 1, 3 and 5 is generated. CCD of each color based on this drive signal
The solid-state image sensor is driven.

For the B charge that requires the longest exposure time, the OFD3 is turned on only during the period from time t5 to time t6 (the period corresponding to "2" in the count value).
After that, the OFD 3 is turned off. The effective exposure period in one field period is 3/4 V, and the accumulated signal amount Vb in 1 V is 1.5 times the first period (initial value).

For the R signal, the OFD is applied only during the period from time t5 to t7 (the period corresponding to the count value "3").
2 is turned on and then OFD2 is turned off. The effective exposure time in one field period is 5 / 8V,
The accumulated signal amount Vb in 1 V has the same value as B.

Regarding the G signal, the OFD1 is turned on during the period from the time t5 to the time t8 (the period when the count value is "4"), and then the OFD1 is turned off. Exposure time is 1 / 2V
The stored signal amount Vg in 1 V is 1.5, which is the same as R and B.

As a result, in the period from t5 to t9, the accumulated signal amounts (signal integrated values) of R, G and B are almost the same. Therefore, the signal level of GRB can be made uniform. By repeating the above operation, the color balance of the image signal obtained from the image sensor A can be maintained in an optimum state.

In the above example, it is assumed that the luminance Y = G, but the reference exposure amount may be obtained using the accurate luminance Y obtained based on all the values of RGB.

The image pickup device according to this embodiment can be applied to a digital still camera using a three-plate CCD solid-state image pickup device. In addition, it can be applied to a digital video camera using a three-plate CCD solid-state image sensor. When applied to a digital video camera, it is sufficient to feed back the color balance information with a delay of 1 V (or more) as shown by the symbol F in FIG. 1 and continue to obtain the optimum exposure time (period).

Next, an image pickup apparatus according to a first modification of the first embodiment of the present invention will be described with reference to FIG.

The image pickup apparatus B shown in FIG. 5 is basically the same as that shown in FIG.
The image pickup apparatus A shown in FIG. Figure 2
For components similar to those in FIG.
00 is added, and the detailed description thereof is omitted.

As described above, in the image pickup apparatus according to the first embodiment, the reference exposure amount for G is output from the exposure amount determination circuit to each of the RGB drive signal generation circuits and the color balance determination circuit is also output. Thus, the color balance signal g / b is output to the B drive signal generation circuit and the color balance signal g / r is output to the R drive signal generation circuit.
Based on these signals, from the RGB drive signal generation circuits, OFD1 to O
A predetermined drive signal for driving the OFD is output to each of up to FD3.

By the way, at least one specific color of RGB (usually G having the maximum sensitivity) is saturated (the maximum charge amount that can be stored in the photoelectric conversion element exceeds the predetermined exposure time). In such a case, if the image pickup apparatus according to the first embodiment is used, the RGB exposure time cannot be corrected accurately. Therefore, in the imaging device according to the present modification, the value of the reference exposure period Texp obtained by the exposure amount determination circuit 127 is set to the drive signal generation circuit 114, more specifically, the drive signal generation circuit 1 for each of the RGB colors included therein.
The reference exposure amount is output to each of 15, 117, and 121, and the RGB signals are also output from the color balance determination circuit.
Color balance signals g / g ₀ , b / b ₀ , r / r ₀ for each color
Are output to the drive signal generation circuits for the respective colors of GBR. Here, g ₀ , b ₀ , and r ₀ are values set in advance in the signal processing system, for example, and are target values of the signal amount of each color of GBR to be determined as “white”.
For example, the target value is 9 of the saturated charge accumulation amount of the CCD.
A value of about 0% may be set. These signals (g / g
₀ , b / b ₀ , r / r ₀ ) from the respective RGB drive signal generation circuits to OFD1 to O of the CCD solid-state image sensor for each RGB color.
It is output for each of up to FD3.

More specifically, the charge of the 1V in FIG.
As the accumulated amount, when B is 100, R is 120,
It is assumed that G has a value of 255. Most of these
An example of the charge storage amount of G having a large charge storage amount of 255
90% is the target value. g ₀If you set 220 to 25,
Since it is about 86% of 5, G is close to the target value.
Therefore, it is highly possible that a value below the saturation value will be obtained. From G
Also for R and B with small charge accumulation amount, target value b₀When
Target value r₀As target value g₀Use 220 which is the same value as
If so, it is unlikely that saturation will be reached within the exposure time. Goal
Value g₀Based on the 2V exposure period that does not exceed
Exposure is performed. For example, the charge storage amount of G is 240, B
Assuming that the charge accumulation amounts of R and R are both 220, G
Is still above the target value of 220, 1V
It is thought that it was saturated. In this case, 220 again
If the exposure period is determined with the goal of
Normally, G is also likely to fall within the target value. Of course with R
B is within the target value of 220 at the second voltage. that's all
For example, the G signal is saturated due to the above process.
Even if the exposure period is adjusted within the period in which G is not saturated,
Then, you can add the optimum correction for R and B.
It

On the other hand, the signals from the color balance determination circuit 131 are the drive signal generation circuits 115 (for G) 117 of each color.
It is output to (for B) and 121 (for R). More specifically, each color drive signal generation circuit 115 (for G), 117
Overflow drains OFD1 and OFD provided in the CCD solid-state image pickup devices 101, 103, and 105 of corresponding colors from (for B) and 121 (for R), respectively.
2 and OFD3 are individually output with signals for operating them.

As in the image pickup apparatus according to the first embodiment, two CCD solid-state image pickup elements of RGB, such as G, are used.
When the exposure time is obtained based on only the two color signals R and B from the color balance determination circuit using the color signal from the reference signal as the reference signal, for example, within the initial exposure period initially designated as the reference exposure period. When the signal voltage of G is saturated, the estimation of the incident light includes an error and is not appropriate (the value of the g signal is estimated to be smaller than the actual value). If the exposure period for R and B is calculated based on the g signal including an error, it is difficult to make the signal level uniform even if the corrected exposure period is used. On the other hand, in the image pickup apparatus B according to the first modified example, the ratio r ₀ /
r, g ₀ / g and b ₀ / b are calculated, and the reference exposure period Texp
Is multiplied by these color signal ratios to obtain the exposure period for each color. Even if g is saturated, optimal correction is added to r and b. Saturation is close to "white", so its effect is small. Therefore, although the processing becomes slightly complicated as compared with the image pickup apparatus according to the first embodiment, the exposure period for each color can be corrected more accurately.

Next, an image pickup apparatus according to the second modification of the first embodiment of the present invention will be described with reference to FIG. The imaging device C shown in FIG. 6 has basically the same configuration as the imaging device B shown in FIG. Constituent elements similar to those in FIG. 5 are denoted by reference numerals obtained by adding 100 to the reference numerals in FIG. 5, and detailed description thereof will be omitted.

The image pickup device C shown in FIG. 6 is newly provided with a drive circuit control device 241. Drive circuit control device 241
Is a color balance determination circuit 231 and an exposure amount determination circuit 227.
Drive signal generating circuits 215 for RGB based on the output signals relating to the luminance signal Y and the color signals Cb and Cr from
An exposure time control signal is output to 217 and 221. The common drive circuit 223 is used for the CCD solid-state image sensor 20.
Control signals S2 ′ (OFD) for 1, 203 and 205
Output signals other than drive signals).

RGB drive signal generation circuits 215, 21
Reference numerals 7 and 221 output exposure time control signals for individually driving the OFDs 1, 2 and 3 to the CCD solid-state image pickup devices 201, 203 and 205 of the corresponding colors.

In this image pickup device C, the new exposure amounts obtained by the exposure amount determination circuit 227 and the color balance determination circuit 231 are collectively output to the drive circuit control device 241. The drive circuit control device uses the common drive circuit 2 as well as the drive signal generation circuits 215, 217 and 221 for RGB colors.
23 and 23. The common drive circuit 223 uses CC of each color.
A control signal is output to the OFD of the D solid-state image sensor.

The image pickup device C according to the second modification is different from the image pickup device A according to the first embodiment or the image pickup device B which is a modification thereof, in a drive circuit control device for calculating a signal for each drive signal generating circuit. 241 is provided. Therefore, the individual drive signal generation circuits 215, 217, and 221 do not need to calculate the respective exposure times or charge discharge periods, and the circuit can be simplified. In addition, it becomes possible to adjust the exposure period in consideration of the limitation of the exposure time (the longest period or the shortest period as the limit).

Next, an image pickup apparatus according to the second embodiment of the present invention will be described with reference to FIG.

The image pickup device D shown in FIG. 7 has a central processing unit (CPU) in addition to the image pickup device B shown in FIG. Control unit 311, CPU 351 and storage circuit 335
And a RAM 355, a ROM 357, and a non-volatile memory 361.

Signals can be exchanged between these devices via the system bus 353.
A drive setting communication unit 351a is provided in the CPU 351.

The CPU 351 is a drive setting communication means 351.
a. The drive setting communication unit 351a is a CPU
Drive signal generation circuit 31 for each color
5, 317 and 321 are output as signals for individually driving the CCD solid-state image pickup devices 301, 303 and 305 of the respective colors.

The operation of the image pickup device D will be described.

CCD solid-state image pickup devices 301 and 30 for respective colors
The output signals S _G , S _B, and S _R from the reference numerals 3 and 305 are the signal processing circuit 325 and the exposure amount determination circuit 3 in the control unit 311.
27 and the color balance determination circuit 331 based on the timing of the common drive signal (horizontal / vertical drive signal and reference clock). Here, the determination values of the exposure amount and the color balance value are generated. The CPU 351 normally reads the determination value at a timing of each 1V (vertical scanning) period and determines whether the exposure amount and the color balance are appropriate. Based on the judgment values of the color balance and the exposure amount, the optimum set value in the actual shooting is calculated. Drive setting communication means 351a
Is used to output the value obtained by the calculation to the drive signal generation circuit for each color. The above process may be performed only once, but may be performed twice or more or continuously depending on the case. The final condition may be obtained by repeating the process several times. The calculation by the CPU is, for example, the same calculation as the calculation described in the first embodiment.

When the CPU 351 determines that the final condition is obtained, the signal after the next 1V period is used as the main image, and this image data is displayed and stored.

The above processing is started by the shutter operation in the still image shooting mode of the digital still camera, for example. On the other hand, when applying to digital movies,
It may be performed constantly or periodically while the continuous moving image is displayed.

Alternatively, by providing a color balance correction switch or the like, the exposure period may be corrected as many times as necessary only when called by the operation of turning on the switch.

When a moving picture for a monitor can be displayed on a digital still camera, an optimum exposure amount is obtained during display on a moving picture monitor so that a still picture can be taken under optimized exposure conditions. good. Although the embodiments of the present invention have been illustrated above, the above examples do not have a restrictive meaning. In addition to the RGB primary color image pickup device, a complementary color image pickup device is also included. In addition, it will be apparent to those skilled in the art that various modifications, improvements, and combinations can be made.

[0073]

EFFECTS OF THE INVENTION In a multi-plate color image pickup device of a type in which the exposure amount can be adjusted for each color, it is possible to reduce the difference in S / N ratio between the colors and keep the noise level constant.
It is possible to reduce the level difference between signal outputs and reduce the overall noise level.

[Brief description of drawings]

FIG. 1 is a flowchart showing the principle of an image pickup apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image pickup apparatus according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a schematic structure of one solid-state image pickup element included in the image pickup apparatus according to the first embodiment of the present invention.

FIG. 4 is a block diagram of an image pickup apparatus according to a first modification of the first embodiment of the present invention.

FIG. 5 is a block diagram of an image pickup device according to a second modification of the first embodiment of the present invention.

FIG. 6 is a block diagram of an image pickup apparatus according to a third modification of the first embodiment of the present invention.

FIG. 7 is a block diagram of an image pickup apparatus according to a second embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a three-plate CCD solid-state imaging device.

[Explanation of symbols]

A, B, C, D color imaging device 1G CCD solid-state image sensor 3B CCD solid-state image sensor 5R CCD solid-state image sensor 7 Drive circuit section 11 Control unit 15 G drive signal generation circuit 17 B drive signal generation circuit 21 R drive signal generation circuit 25 Signal processing circuit 27 Exposure amount determination circuit 31 color balance judgment circuit 33 Display circuit 35 memory circuit 351 Central processing unit (CPU)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5C024 BX01 CX54 EX43 EX52 GX03                       GY01 GZ03 GZ36 HX32                 5C065 AA01 AA03 BB22 BB48 DD02                       DD11 DD19 EE03

Claims (6)

[Claims] 1. A plurality of solid-state image pickup devices capable of individually obtaining a plurality of color signals, and at least one drive signal generation circuit for generating a drive signal for individually driving the plurality of solid-state image pickup devices. An exposure period adjusting means capable of individually adjusting an exposure period within a predetermined unit for each of the plurality of solid-state image pickup devices, and obtaining an image data signal by receiving output signals from the plurality of solid-state image pickup devices A signal processing circuit for performing signal processing, and calculates a new exposure period for each of the solid-state imaging devices based on the output signal or the image data signal, and outputs the new exposure period to the exposure period adjusting means. A color imaging device including an exposure period calculation circuit. 2. The exposure period calculation circuit obtains an integral value of an image data signal for each color obtained within a fixed exposure period, and a new value for each color is determined so that the integral value of the image data signal becomes equal. The color image pickup apparatus according to claim 1, further comprising a circuit that calculates a different exposure period. 3. The exposure period calculation circuit, the exposure amount determination circuit for adjusting the exposure period of the solid-state imaging device for generating a color signal contributing to the luminance component to the optimized first exposure period, and the color difference component. A color balance determination circuit for calculating a new exposure time for each color, which is determined so that the integrated value of the color signal is equal in each solid-state image sensor Claim 1 including
The color imaging device according to. 4. The exposure period adjusting means is a means capable of collectively discharging the signals accumulated in the plurality of solid-state image pickup devices for each color to the outside. The color imaging device according to any one of items. 5. The exposure period calculation circuit calculates a new exposure period for each of the solid-state image pickup devices based on an image data signal obtained at least one unit period before, and the new exposure period is calculated as the new exposure period. 5. The color image pickup apparatus according to claim 1, wherein the color image pickup apparatus is a circuit that performs an operation of outputting to an exposure period adjusting unit for each photographing. 6. The exposure period calculation circuit calculates a new exposure period for each of the solid-state image pickup devices based on an image data signal obtained at least one unit period before, and the new exposure period is calculated as the new exposure period. The color image pickup apparatus according to claim 1, wherein the color image pickup apparatus is a circuit that continuously performs an operation of outputting to the exposure period adjusting means.