JPH05145940A - Signal processor for color image pickup device - Google Patents

Abstract

(57) [Summary] [Object] In a color image pickup device having an image pickup device having a color separation filter, it is possible to suppress a luminance reproduction error generated under a light source of a low color temperature and a high color temperature or a luminance reproduction error based on gamma processing. , Which makes it possible to obtain a luminance signal faithful to the subject [Configuration] The output signal of the image pickup device 1 is processed by the signal processing circuit 2, the color signal generation circuit 9, and the white balance processing circuit 10, and white balance processing is performed. The R, G, B signals are obtained, and the luminance signal Yrgb is formed by the adder circuit 11 from these R, G, B signals. The high-frequency component Y of the luminance signal is output from the output signal of the signal processing circuit 2 to the luminance signal generation circuit 3.
The H and low frequency components YL are generated, and the subtraction circuit 4 forms a correction signal from the luminance signal Yrgb and the low frequency components YL. This correction signal is subjected to coring processing in the core circuit 5, is multiplied by the coefficient K2 in the multiplication circuit 6, and is added to the low frequency component Y in the addition circuit 7.
L and the high frequency component YH are further added by the adder circuit 8 to obtain a luminance signal Y.

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 apparatus, and more particularly to a color image pickup apparatus which uses a single image pickup element and which is provided with a color separation filter to obtain a color video signal. The present invention relates to a signal processing device.

[0002]

2. Description of the Related Art Conventional color image pickup apparatuses include one using one image pickup element and one using a plurality of image pickup elements in an image pickup section.

A color image pickup device using a plurality of image pickup elements,
For example, a three-plate color solid-state image pickup device is provided with a solid-state image pickup device for each light of red, green, and blue, and white balance processing is performed on red, green, and blue signals (primary color signals) obtained from these image pickup devices. Then, gamma processing is performed, and a luminance signal is generated from the primary color signal subjected to the processing (three-channel process). According to this, there is no luminance reproduction error due to gamma processing or the color temperature of the light source, and a luminance signal that is faithful to the subject can always be obtained.

On the other hand, a single-plate type color solid-state image pickup device which obtains a color image signal using one solid-state image pickup device is smaller and cheaper than a three-plate type color solid-state image pickup device. Since this solid-state image sensor is provided with a plurality of color separation filters having different spectral sensitivities to generate color signals, it is not possible to generate a luminance signal from the color signals subjected to white balance processing in view of poor resolution. Therefore, as described in, for example, Japanese Patent Application Laid-Open No. 60-62290, the output signal of the solid-state image sensor is gamma processed,
This gamma-processed signal was used as the luminance signal.

[0005]

In the above-mentioned conventional single-plate color solid-state image pickup device, since the luminance signal is not subjected to white balance processing, when a chromatic subject is imaged under a light source of low color temperature and high color temperature. However, there is a problem that a luminance signal different from the actual one is generated.

In addition, as described above, the gamma processing is applied to the output signal of the solid-state image pickup device in which the red, green and blue signals are mixed to obtain the luminance signal. , Which is essentially different from generating a luminance signal by subjecting each of the blue signals to gamma processing. Therefore, even when the gamma processing is performed on the output signal of the solid-state image sensor as described above, this luminance signal is also used. Is not true to the subject.

In order to solve such a problem, a first object of the present invention is to suppress a luminance reproduction error and obtain a luminance signal faithful to a subject even when an image is picked up under a light source of a low color temperature and a high color temperature. It is an object of the present invention to provide a signal processing device of a color image pickup device using a single image pickup device capable of performing the above.

A second object of the present invention is to perform signal processing of a color image pickup device with a single image pickup device capable of obtaining a luminance signal faithful to a subject by suppressing a luminance reproduction error based on gamma processing. To provide a device.

[0009]

In order to achieve the first object, the present invention generates a low frequency component of a luminance signal from a white balance-corrected color signal.

In order to achieve the second object, the present invention generates a low frequency component of a luminance signal from a gamma-processed color signal.

[0011]

Since the low-frequency component of the luminance signal is generated from the white-balance-corrected color signal, even if a chromatic subject is imaged under light sources of low color temperature and high color temperature,
Brightness reproduction error does not occur. Further, since the high frequency component of the luminance signal is not replaced with anything, the resolution is not deteriorated.

Further, by generating the replacement signal from the gamma-processed color signal, it is possible to suppress the luminance reproduction error based on the non-linear processing (gamma processing), which is close to the luminance reproduction of the three-channel process and is faithful to the object. A luminance signal can be obtained.

[0013]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of a signal processing device of a color image pickup device according to the present invention, in which 1 is an image sensor, 2 is a signal processing circuit, 3 is a luminance signal generation circuit, 4 is a subtraction circuit, and 5 is a subtraction circuit. Core circuit, 6 is a multiplication circuit, 7 and 8 are addition circuits, 9 is a color signal generation circuit, 10 is a white balance processing circuit, 11 is an addition circuit, 12 is a color difference matrix circuit,
Reference numeral 13 is an encoding circuit.

In the figure, an output signal of the image pickup device 1 obtained by photoelectric conversion is processed by a signal processing circuit 2 to obtain 2
Two signals S1 and S2 are generated, and each of them is a color signal generation circuit 9
And the luminance signal generation circuit 3. Here, a specific example of the signal processing circuit 2 will be described with reference to FIG.
However, 14 is an amplifier, 15 is an A / D converter, 16,
Reference numeral 17 is a coefficient circuit, 18 and 19 are 1H delay circuits, and 20 is an addition circuit.

In the figure, the output signal of the image pickup device 1 is
After being amplified by the amplifier 14, it is converted into a digital signal by the A / D converter 15. This digital signal (hereinafter referred to as the current signal) is 1H by the 1H delay circuits 18 and 19.
(However, 1H is one horizontal scanning period). The current signal is also multiplied by a coefficient of 1/2 in the coefficient circuit 16,
The output signal of the 1H delay circuit 19 is also multiplied by a coefficient of 1/2 in the coefficient circuit 17. The output signals of the coefficient circuits 16 and 17 are added by the adder circuit 20, and the output signal of the adder circuit 20 is the signal S1. In addition, the 1H delay circuit 18
Is the signal S2 described above. That is, the signal S1 is an average signal of the current signal and a signal delayed by 2H from this,
The signal S2 is a signal delayed by 1H from the current signal.

Returning to FIG. 1, in the color signal generation circuit 9, the output signals S1 and S2 of the signal processing circuit 2 are separated for each color component of the color separation filter provided in the image sensor 1, and the color components are calculated. Processed into red, green and blue primary color signals (r, g,
b) is generated. These three primary color signals are subjected to white balance correction processing by the white balance processing circuit 10,
Red and blue signals with white balance correction (hereinafter,
The R signal and the B signal are supplied to the addition circuit 11 and the color difference matrix circuit 12, and the green signal of which the white balance is corrected (hereinafter referred to as the G signal) is supplied to the addition circuit 11. The adder circuit 11 adds the R, G, and B signals to generate a white balance-corrected luminance signal (Yrgb). The luminance signal (Yrgb) is supplied to the color difference matrix circuit 12 and the subtraction circuit 4. The color difference matrix circuit 12 generates two color difference signals (R-Yrgb, B-Yrgb) from the R and B signals and the luminance signal (Yrgb), and supplies them to the encoder circuit 13, respectively.

On the other hand, in the luminance signal generating circuit 3, a composite signal (YH) of the high frequency component and the vertical edge component of the luminance signal from the output signals S1 and S2 of the signal processing circuit 2 and the low frequency component (YL) of this luminance signal. And are generated. The low frequency component (YL) of the luminance signal is supplied to the subtraction circuit 4 and the addition circuit 7, and the combined signal (YH) is supplied to the addition circuit 8. Here, a specific example of the luminance signal generation circuit 3 will be described with reference to FIG. However, 21 is an addition circuit, 22 is an LPF (low pass filter), 23 is a horizontal aperture correction circuit, and 24 is a vertical aperture correction circuit.

In the figure, the output signal S1 of the signal processing circuit 2 is supplied to the LPF 22 and band-limited. This L
The output signal of the PF 22 is the low frequency component (Y
L). Further, the output signal S1 of the signal processing circuit 2 is supplied to the horizontal aperture correction circuit 23, and the high frequency component of the luminance signal is extracted. Further, the output signals S1 and S2 of the signal processing circuit 2 are supplied to the vertical aperture correction circuit 24, and the vertical edge component in the luminance signal is extracted. The output signal of the horizontal aperture correction circuit 23 and the output signal of the vertical aperture correction circuit 24 are added by the adder circuit 21, and the output signal of the adder circuit 21 is the above-mentioned combined signal (YH).

Returning to FIG. 1 again, the subtraction circuit 4 subtracts the low frequency component (YL) of the luminance signal from the luminance signal (Yrgb) output from the addition circuit 11 to obtain the correction signal (Yrgb).
-YL) is generated, and the signal component having a level equal to or lower than the level determined by the coefficient K1 preset in the core circuit 5 is deleted (coring processing is performed), and then the coefficient K2 is multiplied by the multiplication circuit 6 to obtain a correction signal. Is added to the low frequency component (YL) of the luminance signal from the luminance signal generation circuit 3 in the addition circuit 7.

The low frequency component of the corrected luminance signal from the adding circuit 7 is added to the combined signal (YH) from the luminance signal generating circuit 3 in the adding circuit 8 and supplied to the encoder circuit 13 as the luminance signal Y. In the encoder circuit 13, a color video signal is generated from the luminance signal Y and the color difference signals (R-Yrgb, B-Yrgb) from the color difference matrix circuit 12.

As described above, in this embodiment, the luminance signal Yrgb generated from the color signal subjected to the white balance correction.
Since the low-frequency component YL of the luminance signal generated from the output of the image sensor that has not been subjected to white balance correction is replaced with, the level of the luminance signal does not change due to the color temperature of the light source.

Further, the coefficient K1 of the core circuit 5 is subtracted from the subtraction circuit 4
If the correction signal (Yrgb-YL) from the above is set to a level at which coring processing is not performed, the output signal of the multiplication circuit 6 is (Yrgb-YL) × K2, and the luminance signal Y output from the addition circuit 8 is Y = Yrgb × K2 + YL × (1-K2) + YH, and when K2 = 1, Y = Yrgb + YH, K2 = 0
In this case, Y = YL + YH (note that the low-frequency component of the luminance signal Y when K2 = 1 has been replaced by the luminance signal Yrgb from the adder circuit 11). Therefore,
By changing K2, it is possible to smoothly switch between the luminance signal (YL + YH) generated from the output signal of the image sensor 1 and the luminance signal (Yrgb + YH) subjected to the white balance correction, and the output signal of the addition circuit 11 Yrg
By making the frequency bands of b and the low frequency component YL substantially coincide with each other, the frequency band of the luminance signal does not change even if the coefficient K2 changes.

Further, by setting the coefficient K1 to an appropriate value, only when the difference between the level of the luminance signal generated from the output signal of the image pickup device 1 and the actual luminance level of the subject becomes a certain amount or more. It is also possible to smoothly switch the brightness signal to the brightness signal subjected to the white balance correction. By doing so, when the brightness level of the color imaging device is close to the brightness level of the actual subject, the brightness signal is not replaced as described above. Therefore, especially when imaging an achromatic subject or the like, S / N Deterioration can be suppressed.

FIG. 3 is a block diagram showing an embodiment of a color image pickup device according to the present invention, in which 25 is an adder circuit and 26 is an adder circuit.
Is a white balance control circuit, 27 is a color temperature detection circuit,
Reference numeral 28 is a coefficient circuit, and the portions corresponding to those in FIG.

In FIG. 3, the color difference matrix circuit 12
The color difference signals (R-Yrgb, B-Yrgb) generated in (1) are supplied to the encoder circuit 13 and the white balance control circuit 26. The white balance control circuit 26 uses the color difference signals (R-Yrgb, BY).
The gain of the primary color signal (r, b) in the white balance processing circuit 10 is calculated from rgb), and the calculated gain values are supplied to the white balance processing circuit 10 and the color temperature detection circuit 27. The color temperature detection circuit 27 detects the color temperature of the light source from the gains of the r and b signals, and the coefficient circuit 28 calculates the coefficient K2 of the multiplication circuit 6 according to the detection result. Therefore, the coefficient K2 of the multiplication circuit 6 depends on the color temperature of the light source that illuminates the imaged subject.

The following is the same as the embodiment shown in FIG.
On the other hand, in the luminance signal generation circuit 3, the high frequency component YH and the low frequency component YL of the luminance signal are generated, the low frequency component YL is supplied to the subtraction circuit 4 and the addition circuit 25, and the high frequency component Y is generated.
H is supplied to the adding circuit 25. The correction signal (Yrgb-YL) generated in the subtraction circuit 4 is subjected to coring processing in the core circuit 5 at a level determined by the coefficient K1, the multiplication circuit 6 multiplies the coefficient K2 from the coefficient circuit 28, and the addition circuit 7
Thus, the high frequency component YH and the low frequency component YL are added.

In this embodiment, the coefficient K2 is generated in real time according to the color temperature of the light source in the embodiment shown in FIG. 1, and the luminance signal (from the output of the image sensor 1 ( YL + YH) and the white balance correction processed luminance signal (Yrgb + YH) can be smoothly switched according to the color temperature of the light source. Therefore, substantially the same effect as that of the embodiment shown in FIG. 1 can be obtained except that the composition of the low-frequency component of the luminance signal automatically changes according to the color temperature of the light source. The color temperature detection circuit 2
7 and the coefficient circuit 28 may be realized by a microcomputer.

FIG. 4 is a block diagram showing still another embodiment of the signal processing device of the color image pickup device according to the present invention, in which 29 is a lens, 30 is an aperture, 31 is an aperture control circuit,
Reference numeral 32 is a coefficient circuit, and the portions corresponding to those in FIG.

In FIG. 4, light from a subject (not shown) that has passed through the lens 29 and the diaphragm 30 is applied to the image pickup device 1, and a signal is generated by photoelectric conversion as in each of the previous embodiments, and a signal is generated. It is supplied to the processing circuit 2. This aperture 30
Is controlled by the aperture control circuit 31. Coefficient circuit 32
Forms the coefficient K2 of the multiplication circuit 6 in accordance with a signal representing the aperture value of the aperture 31 from the aperture control circuit 31. Therefore, the coefficient K2 changes in real time according to the aperture value of the aperture 30.

As described above, in this embodiment, the luminance signal (YL + YH) generated by the luminance signal generation circuit 3 and the luminance signal (the low-frequency component are subjected to the white balance correction processing in real time according to the aperture value. Yrgb + YH) can be switched smoothly. Other than that,
The effect is essentially the same as that of the embodiment shown in FIG. 1 and the same effect can be obtained. The aperture control circuit 31 and the coefficient circuit 32 may be realized by a microcomputer.

FIG. 5 is a block diagram showing still another embodiment of the signal processing apparatus of the color image pickup apparatus according to the present invention, in which 33 and 34 are gamma circuits, and the portions corresponding to those in FIG. A duplicate description will be omitted.

In FIG. 5, the high frequency component YH and the low frequency component YL of the luminance signal from the luminance signal generation circuit 3 are gamma-processed by the gamma circuit 33, respectively, and the high frequency component YH is supplied to the adder circuit 8 and the low frequency component YL is processed. It is supplied to the subtraction circuit 4 and the addition circuit 7, respectively. Also, the white balance processing circuit 1
The R, G, and B signals output from 0 are the gamma circuit 34, respectively.
These gamma-processed R'and B'gamma-processed
The signals are sent to the color difference matrix circuit 12 and the addition circuit 11,
The gamma-processed G ′ signals are supplied to the adder circuit 11, respectively. Therefore, in the adder circuit 11, the gamma-processed R
A luminance signal Yrgb 'is generated from the', G ', and B'signals.

The subtraction circuit 4 produces a difference component between the luminance signal Yrgb 'and the gamma-processed low frequency component YL' and a correction signal (Yrgb'-YL '), which is the core circuit 5.
Is subjected to coring processing with the coefficient K1, the multiplication circuit 6 multiplies the coefficient K2, and the addition circuit 7 adds the low frequency component YL '.

As described above, in this embodiment, since the low frequency component of the luminance signal is replaced after the gamma processing, the luminance reproduction error based on the gamma processing can be suppressed. When the coefficient K1 of the core circuit 5 is set to a level at which the coring processing is not performed on the correction signal to set the coefficient K2 = 1, the input luminance signal Y ′ of the encoding circuit 13 is Y ′ = α · R ′ + β · G '+ γ ・ B' + YH '(However,
α, β, and γ are constants, and some errors occur in the high-frequency component YH ′, but since these errors are sufficiently negligible, it is possible to obtain faithful luminance reproduction for the subject.

Further, by changing the coefficient K2,
It is also possible to smoothly switch between the luminance signal gamma-processed in a state where the R, G, and B signals are mixed and the luminance signal generated by gamma-processing the R, G, and B signals, respectively.
Since white balance correction is performed on the gamma-processed R, G, and B signals, the same effect as that of the embodiment shown in FIG. 1 can be obtained.

The embodiment shown in FIG. 6 is obtained by adding the gamma circuits 33 and 34 shown in FIG. 5 to the embodiment shown in FIG. Therefore, the difference between the luminance signal Yrgb ′ generated by the adder circuit 11 from the gamma-processed R ′, G ′, and B ′ signals and the low-frequency component YL ′ of the gamma-processed luminance signal is used as a correction signal, and this correction is performed. The core circuit 5 correlates the signal, the multiplication circuit 6 multiplies the coefficient K2 according to the color temperature of the light source, and the addition circuit 25 gamma-processes the high-frequency component YH 'and the low-frequency component YL of the luminance signal. ´ is added.

As described above, in this embodiment, since the gamma-processed luminance signal is replaced, the luminance reproduction error based on the gamma processing can be suppressed as in the embodiment shown in FIG. The coefficient K2 depends on the color temperature of the light source, and the gamma-processed R ′, G ′, and B ′ signals are white-balance corrected, so that the same effect as that of the embodiment shown in FIG. 3 can be obtained.

The embodiment shown in FIG. 7 is obtained by adding the gamma circuits 33 and 34 shown in FIG. 5 to the embodiment shown in FIG. Therefore, the difference between the luminance signal Yrgb ′ generated by the adder circuit 11 from the gamma-processed R ′, G ′, and B ′ signals and the low-frequency component YL ′ of the gamma-processed luminance signal is used as a correction signal, and this correction is performed. After the signal is subjected to coring processing in the core circuit 5, the multiplication circuit 6 calculates a coefficient K according to the aperture value of the aperture 30.
It is multiplied by 2 and added to the high frequency component YH ′ and the low frequency component YL ′ of the luminance signal which has been gamma processed by the addition circuit 25.

As described above, in this embodiment, since the gamma-processed luminance signal is replaced, the luminance reproduction error based on the gamma processing can be suppressed as in the embodiment shown in FIG. The coefficient K2 depends on the aperture value of the aperture, and the gamma-processed R ', G', and B'signals are white-balance corrected, so that the same effect as that of the embodiment shown in FIG. 4 can be obtained.

FIG. 8 is a block diagram showing an embodiment of the signal processing device of the color image pickup device according to the present invention.
Reference numeral 36 is an adder circuit, and 37 is an LPF (low-pass filter) circuit. Parts corresponding to those in FIG.

In FIG. 8, the high frequency component YH and the low frequency component YL of the luminance signal output from the luminance signal generation circuit 3 are added by the addition circuit 35. The luminance signal output from the adding circuit 35 is supplied to the subtracting circuit 4 and the adding circuit 36. In the subtraction circuit 4, R, G, and
A difference between the luminance signal Yrgb formed from the B signal and the luminance signal from the adder circuit 35 is formed, and this difference is supplied to the LPF circuit 37 to remove the high frequency component. This LP
The output signal of the F circuit 37 is subjected to coring processing in the core circuit 5 as a correction signal as in the embodiment shown in FIG.
The multiplication circuit 6 multiplies the coefficient K2 and the addition circuit 36 adds the multiplication result with the luminance signal from the addition circuit 35.

According to this embodiment, by making the pass band of the LPF circuit 37 substantially equal to the frequency band of the luminance signal Yrgb, the correction signal output from the LPF circuit 37 produces the luminance signal Yrgb and the luminance signal of the same frequency band. Since it is formed from the low frequency component of the luminance signal output from the circuit 3, the replacement with the luminance signal Y obtained by the adder circuit 36 is more accurate as compared with the embodiment shown in FIG. Become.

Of course, as in the embodiment shown in FIG. 1, in the addition circuit 36, the correction signal from the multiplication circuit 6 is added to the low frequency component YL, and then the high frequency component YH is added to this addition signal. You may make it add.

The embodiment shown in FIG. 9 is obtained by adding the gamma circuits 33 and 34 to the embodiment shown in FIG. 8 as shown in FIG. 5, and the effect of the embodiment shown in FIG. In addition to
The same effect as the embodiment shown in FIG. 5 can be obtained.

In the embodiment shown in FIGS. 8 and 9, the coefficient K2 of the multiplication circuit 6 is changed according to the color temperature and aperture value of the light source, as in the embodiment shown in FIGS. You may do it.

[0046]

As described above, according to the present invention,
Even in a color solid-state image pickup device having a single image pickup element, it is possible to obtain the same luminance reproduction as that of a color solid-state image pickup device of a three-channel process, and it is possible to obtain a luminance reproduction faithful to a subject.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a signal processing device of a color imaging device according to the present invention.

FIG. 2 is a block diagram showing a specific example of a signal processing circuit and a luminance signal generation circuit in FIG.

FIG. 3 is a block diagram showing another embodiment of the signal processing device of the color image pickup device according to the present invention.

FIG. 4 is a block diagram showing still another embodiment of the signal processing device of the color imaging device according to the present invention.

FIG. 5 is a block diagram showing still another embodiment of the signal processing device of the color imaging device according to the present invention.

FIG. 6 is a block diagram showing still another embodiment of the signal processing device of the color imaging device according to the present invention.

FIG. 7 is a block diagram showing still another embodiment of the signal processing device of the color image pickup device according to the present invention.

FIG. 8 is a block diagram showing still another embodiment of the signal processing device of the color imaging device according to the present invention.

FIG. 9 is a block diagram showing still another embodiment of the signal processing device of the color imaging device according to the present invention.

[Description of Codes] 1 Image sensor 2 Signal processing circuit 3 Luminance signal generation circuit 4 Subtraction circuit 5 Core circuit 6 Multiplication circuit 7, 8 Addition circuit 9 Color signal generation circuit 10 White balance processing circuit 11 Addition circuit 12 Color difference matrix circuit 13 Encoding Circuit 25 Addition circuit 26 White balance control circuit 27 Color temperature detection circuit 28 Coefficient circuit 30 Aperture 31 Aperture control circuit 32 Coefficient circuit 33, 34 Gamma circuit 35, 36 Addition circuit 37 LPF circuit

Claims (5)

[Claims] 1. An image pickup section having a plurality of color separation filters having different spectral sensitivities, a color signal processing circuit for generating a color signal from each signal corresponding to the color separation filter output from the image pickup section, and the color. In a color image pickup apparatus including a white balance processing circuit for performing a white balance correction process on a signal and a luminance signal processing circuit for generating a luminance signal from each signal corresponding to the color separation filter output from the image pickup unit, a white balance First means for generating a luminance signal from the corrected color signal, and luminance generated by the first means for a low frequency component of the luminance signal output from the luminance signal processing circuit at a predetermined ratio. A signal processing device for a color image pickup device, comprising: a second means for replacing a signal. 2. A third means for detecting a color temperature of a light source for irradiating an object to be photographed according to claim 1, wherein the predetermined ratio set by the second means is set to the third ratio.
The signal processing device of the color imaging device, wherein the ratio is in accordance with the detection result of the means. 3. A third means for detecting an aperture value of a lens according to claim 1, wherein the predetermined ratio set by the second means is the third ratio.
The signal processing device of the color imaging device, wherein the ratio is in accordance with the detection result of the means. 4. The fourth means according to claim 1, further comprising: fourth means for generating a difference signal between the luminance signal generated by the first means and a low frequency component of the luminance signal generated by the luminance signal processing circuit. , The predetermined ratio set by the second means is
The signal processing device of the color imaging device, wherein the ratio is in accordance with the detection result of the means. 5. The color signal according to claim 1, 2, 3 or 4, wherein the color signal supplied to the first means is gamma processed, and the luminance signal supplied to the second means is low. A signal processing device for a color image pickup device, wherein frequency components are also gamma processed.