JPH0767129A - Image pickup device - Google Patents

Abstract

(57) [Summary] [Object] To provide an imaging device capable of reducing the amount of hardware and simplifying the tuning of coefficient determination. A Y / C separator 105 separates a video signal output from an image pickup device 101 into a luminance signal and a chrominance signal, and these signals are synchronized by a synchronization circuit 114 to generate signals YL ', CR', and CB. When it is input as ', the matrix operation circuit 116 once outputs RG based on the signals YL', CR ', CB', not via the RGB signals.
B signal is generated, and the color difference signal R is generated based on the RGB signal.
-Y, BY without generating signals YL ', CR',
The color difference signals RY and BY are directly generated based on CB '.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus which processes a video signal from an image pickup device to obtain a video output.

[0002]

2. Description of the Related Art In a conventional image pickup apparatus, as shown in FIG. 8, an analog video signal from an image pickup device 601 is subjected to correlation double sampling by a correlation double sampling circuit 602, and an automatic gain adjustment circuit 603 automatically performs the sampling. The gain is adjusted and AD-converted by the A / D converter 604 to become a digital signal. Then, the Y / C separator 605 separates the luminance signal Y and the color signal C, and the low-pass filter 6
At 06, carrier removal and correction of optical filter characteristics are performed.

Then, the band of the luminance signal Y is narrowed by the low-pass filter 607 to generate the luminance signal Ys used for high luminance color suppression. Further, the contour detection circuit 608 detects a contour signal from the luminance signal Y from the low-pass filter 606, and the adder 609 adds the contour signal to the luminance signal Y to perform edge enhancement. The edge-enhanced luminance signal Y is gamma-corrected by the gamma correction circuit 610, the high-saturation portion luminance suppression circuit 611 suppresses the luminance of the high-saturation portion, and the blanking addition circuit 612 performs blanking processing. . Then, DA conversion is performed by the DA converter 613, and an analog output luminance signal is obtained.

On the other hand, for the color signal C, the signal components Wr and G read out from the image sensor in the order shown in FIG.
b, Gr, and Wb are synchronized by the synchronization circuit 614,

## EQU1 ## YL = Wr + Gb = Gr + Wb CR = Wr-Gb CB = Wb-Gr. These signals YL, CR, and CB suppress the carrier generated by the later point-sequentialization by the low-pass filter 615.

Next, by the matrix operation circuit 616,

[Equation 2] The following matrix calculation is performed to generate a dot-sequential RGB signal. Further, in the multiplier 617, R '= G1R, G' =
The calculation of G2G, B '= G3B is performed in a time-sharing manner to obtain white balance.

Next, a gamma correction circuit 618 performs gamma correction, a low pass filter 619 performs interpolation processing and RGB simultaneous processing, and a matrix calculation circuit 620 produces color difference signals RY, B-.
Y is generated. At this time, in the matrix calculation circuit 620,

EQUATION 3 RY = R- (0.3R + 0.59G + 0.11B) BY = B- (0.3R + 0.59G + 0.11B) is calculated. For these color difference signals R-Y and B-Y, the hue correction circuit 621 calculates a linear matrix.

[Equation 4] The hue is corrected by. Then, for the hue-corrected color difference signals RY and BY, the high-luminance color suppression circuit 622 is used.
High-luminance color suppression is performed by, and modulation and burst addition are performed by the modulation circuit 623. Then, it is converted into an analog signal by the DA converter 624 and output as the output color signal C.

[0007]

However, in such a conventional method, a dot-sequential RGB signal is temporarily generated during color signal processing, and gamma correction is performed on the dot-sequential RGB signal. Therefore, many processes such as matrix calculation and multiplication before and after the gamma correction are required. As a result, there is a problem in that the amount of hardware is increased and the number of parameters is large, so that tuning when determining the coefficient of the multiplier becomes complicated.

Since the three types of RGB color signals are dot-sequential, the sampling rate for each color component is 1
/ 3. For this reason, as shown in FIG. 9, the carrier stands on a frequency ⅓ times that of the carrier in the previous method (see FIG. 9A) (see FIG. 9B). In order to remove and prevent aliasing, bandwidth MCL
There is a problem that a sharp filter is required in a narrow band of K / 6, which increases the hardware amount of the filter.

The present invention has been made under such circumstances, and an object thereof is to provide an image pickup apparatus capable of reducing the amount of hardware and simplifying the tuning of coefficient determination.

[0010]

In order to achieve the above object, the present invention provides a separation means for separating a video signal output from an image pickup device into a luminance signal and a plurality of color signals, and the separation means. In an imaging device having a luminance signal and a synchronizing means for synchronizing a plurality of color signals, a matrix for directly generating a color difference signal based on the signals synchronized by the synchronizing means without using RGB signals A matrix calculation means for performing calculation is provided.

[0011]

The separating means separates the video signal output from the image pickup device into a luminance signal and a plurality of color signals, and the synchronizing means synchronizes the luminance signal and the plurality of color signals separated by the separating means.

The matrix calculating means directly generates the color difference signals based on the signals synchronized by the synchronizing means without passing through the RGB signals, that is, once based on the signals synchronized by the synchronizing means. Without generating a RGB signal and a color difference signal based on the RGB signal,
By performing a matrix operation for directly generating color difference signals based on the signals synchronized by the synchronizing means, RGB
The number of matrix operations in the entire system is reduced by eliminating the matrix operation for signal generation and generating the color difference signal by one matrix operation, which in turn reduces the amount of hardware and simplifies tuning of coefficient determination. So that it can be realized.

[0013]

Embodiments of the present invention will be described in detail below with reference to FIGS.

[First Embodiment] FIG. 1 is a block diagram showing the schematic arrangement of an image pickup apparatus according to the first embodiment of the present invention.
The image pickup apparatus includes an image pickup element 101, a correlated double sampling circuit 102, an automatic gain adjustment circuit 103, and an A / D converter 1.
04, Y / C separator 105, low-pass filter 106,
107, 115, 119, contour detection circuit 108, adder 109, gamma correction circuits 110, 117, high-saturation part luminance suppression circuit 111, blanking addition circuit 112, D / A
The converters 113 and 121, the synchronization circuit 114, the matrix calculation circuit 116, the hue correction circuit 119, and the high-luminance color suppression circuit 11
8 and the modulation circuit 120.

The analog video signal output from the image pickup device 101 is subjected to correlation double sampling by the correlation double sampling circuit 102, whereby random noise of the image pickup device 101 is reduced. Then, the automatic gain adjustment circuit 103 performs automatic gain adjustment, and the A / D converter 10
4 is AD-converted into a digital signal, which is separated into a luminance signal Y and a color signal C by a Y / C separator 105.

Of the luminance signal Y, the low pass filter 106 removes carriers and corrects the optical filter characteristics. The luminance signal Y from which the carrier has been removed and the optical filter characteristic has been corrected is supplied to the low-pass filter 107, the contour detection circuit 108, and the adder 109. The low-pass filter 107 narrows the band of the supplied luminance signal Y to generate a luminance signal Ys used for high luminance color suppression, and supplies it to the gamma correction circuit 117 and the high luminance color suppression circuit 118.

The contour detection circuit 108 detects the contour of the subject based on the supplied luminance signal Y and supplies the contour signal to the adder 109. Then, the adder 109 performs edge enhancement by adding the luminance signal Y and the contour signal. The edge-enhanced luminance signal Y is gamma-corrected by the gamma correction circuit 110, the high-saturation portion luminance suppression circuit 111 suppresses the luminance of the high-saturation portion, and the blanking addition circuit 112 performs a blanking process on the D / A. It is converted into an analog signal by the converter 113 and output as the final luminance signal Y.

On the other hand, for the color signal C, the signal components Wr, Gb, Gr, Wb arranged as shown in FIG. 2 are synchronized by the synchronizing circuit 114, and the matrix of the formula 1 described in the conventional example. The calculation is performed to generate the signals YL, CR, CB.
With respect to these signals YL, CR and CB, the low pass filter 115 suppresses the carriers generated by the subsequent dot-sequentialization and becomes signals YL ', CR' and CB '.

Next, the matrix calculation circuit 116 generates dot-sequential color difference signals RY and BY by matrix calculation. Here, when the color separation in the matrix calculation circuit 616 and the white balance in the multiplier 617 in the conventional example are expressed in matrix,

[Equation 5] Becomes

Further, the matrix operation circuit 620 outputs the color difference signal R
The operation for generating −Y, BY is

## EQU6 ## RY = R- (0.3R + 0.59G + 0.11B) = (0.7G1-0.59G2-0.11G3) YL '+ (0.7a1G1-0.59a2G2-0.11a3G3) CR '+ (0.7b1G1-0.59b2G2-0.11b3G3) CB'. This is generally

## EQU7 ## It can be written that RY = m0YL '+ m1CR' + m2CB '. Similarly,

## EQU8 ## It can be written as BY = n0YL '+ n1CR' + n2CB '.

When the expressions 7 and 8 are expressed in matrix,

[Equation 9] Becomes

Further, the linear matrix of the hue correction in the hue correction circuit 621 of the conventional example is expressed by Equation 4 as described above.
Therefore, from Equation 4 and Equation 9 above,

[Equation 10] Becomes This equation 10 is generally

[Equation 11] Can be written. Therefore, in the matrix calculation circuit 116,
Is performed, and color separation, white balance, color difference signal generation, and hue correction are performed at the same time.

That is, the detailed configurations of the matrix operation circuit 116 and the gamma correction circuit 117 are as shown in FIG. 3, and the multipliers 202, 203, and 204 of the matrix operation circuit 116 have the multiplication coefficient p0 and the multiplication coefficient p0 in Expression 11, respectively. q0, p1
And q1 and p2 and q2 are set by time division. Then, the signals YL ', CR', and CB 'are multiplied by the multiplication coefficient by the multipliers 205 and 206, and the signals are added to each other to generate dot-sequential color difference signals RY and BY. To do.

As described above, the RGB signals are once generated based on the signals YL ', CR', and CB ', and the color difference signals RY and BY are not generated based on the RGB signals, and they are synchronized. Since the color difference signals R-Y and B-Y are directly generated based on the signals YL ', CR', and CB ', the matrix operation circuit for generating the RGB signals becomes unnecessary, and accordingly,
The number of matrix operation circuits will be reduced.

The gamma correction circuit 117 performs gamma correction on these color difference signals RY and BY. That is,
As shown in FIG. 3, the gamma correction circuit 117 includes a differential characteristic generation circuit 208, a clip circuit 209, and a multiplier 210.
And the narrow band luminance signal Ys used for high luminance color suppression is given to the input X by the differential characteristic generating circuit 208.

[Equation 12] Process to obtain the output of. Note that the differential characteristic generation circuit 208 may obtain the output as in Expression 12 by either the ROM table or the hardware processing.

Then, the clipping circuit 209 causes the clipping circuit 209 shown in FIG.
As shown in (4), the output signal expressed by the equation 12 output from the differential characteristic generation circuit 208 is clipped by the upper limit a and the lower limit b. Then, the multiplier 210 applies dot-sequential color difference signals RY or B-to the clipped signals.
Multiply Y. As a result, the color difference signals RY and BY are
A full range input d and a full range output c such as y = f (x) in FIG. 4 are subjected to gamma correction.

Returning to the explanation of FIG. 1, the color difference signals RY and BY which have been gamma-corrected by the gamma correction circuit 117.
The high-luminance color suppression circuit 118 performs high-luminance color suppression based on the luminance signal Ys. Then, the low-pass filter 119 performs pixel interpolation and synchronization, the modulation circuit 120 performs modulation and burst addition, and D
The converted signal is converted into an analog signal by the / A converter 121 and output as an output color signal C.

As described above, after the signal components from the image pickup device 101 are synchronized, the color difference signal R-
Y, BY, and these color difference signals RY,
By performing gamma correction on BY, the calculation amount and parameters are reduced, the hardware amount is reduced, and the tuning of coefficient determination is simplified.

Since the two color difference signals R-Y and B-Y are dot-sequentially set, the carrier stands at a half of the system clock MCLK as shown in FIG. It may be removed, and the band becomes MCLK / 4 even if folding is considered. As a result, the band of the carrier suppression filter becomes 3/2 of that of the conventional one, which does not require a steeper filter than the conventional one, and the hardware amount of the carrier suppression filter
It is also possible to reduce the complexity of the design of the filter.

[Second Embodiment] Next, a second embodiment will be described with reference to FIGS.
It will be described based on 7. The second embodiment and the first embodiment are synchronized with each other in the first embodiment to generate signals YL, CR, CB.
However, the second embodiment is different in that the "four-color processing" for synchronizing the signal components Wr, Gb, Gr, and Wb is performed.

That is, the synchronization circuit 414 shown in FIG.
Is the signal component Wr output from the Y / C separator 105,
Gb, Gr, and Wb are synchronized as they are. These synchronized signal components Wr, Gb, Gr, and Wb suppress the carrier generated by the point-sequentialization in the low pass filter 415, and the matrix calculation circuit 416 suppresses the carrier-suppressed signal component Wr ′. , Gb ', Gr', Wb 'are used to perform matrix calculation for color difference signal generation and the like.

Here, when the RGB generation and the white balance in the conventional four-color processing are represented by a matrix,

[Equation 13] Becomes

The operation for generating the color difference signals RY and BY is

## EQU14 ## RY = R- (0.3R + 0.59G + 0.11B) = (0.7G1a11-0.59G2a21-0.11G3a31) Wr '+ (0.7G1a12-0.59G2a22-0.11G3a32) Gb It can be written as' + (0.7G1a13-0.59G2a23-0.11G3a33) Gr '+ (0.7G1a14-0.59G2a24-0.11G3a34) Gb'. this is,

It can be written that RY = m0Wr '+ m1Gb' + m2Gr '+ m3Wb'. Similarly,

## EQU16 ## It can be written that BY = n0Wr '+ n1Gb' + n2Gr '+ n3Wb'. Mathematical expressions 15 and 16 are expressed in matrix form,

[Equation 17] Becomes

[Mathematical formula-see original document] When this equation 17 and the linear matrix for hue correction explained in the conventional example are combined,

[Equation 18] Becomes This equation 18 is generally

[Formula 19] Can be written.

Therefore, in the matrix operation circuit 416,
By performing the processing for realizing 8, the color separation, the white balance, the color difference signal generation, and the hue correction are simultaneously performed.

FIG. 7 is a diagram showing a detailed configuration of the matrix operation circuit 416, in which the multipliers 502,
In 503, 504, and 505, the multiplication coefficients p0 and q0, p1 and q1, p2 and q2, and p3 and q3 in Equation 18 are set in time division. Then, the multipliers 502, 503,
Signals Wr ', Gb', Gr ', Wb' by 504 and 505
The signals obtained by multiplying the
6, 507 and 508 are added to generate dot-sequential color difference signals RY and BY.

The other constituent elements of the second embodiment shown in FIG. 6 have exactly the same functions as those of the first embodiment shown in FIG. 1, so the description thereof will be omitted, but the second embodiment will be omitted. It goes without saying that the same effects as those of the first embodiment can be obtained in the above.

[0038]

According to the present invention, the color difference signals RY and B which are dot-sequentially converted from the synchronized signals by one matrix operation.
-Y is generated, and gamma correction is applied to these color difference signals RY and BY, so that the amount of hardware required for arithmetic processing is reduced, the tuning of coefficient determination is simplified, and further point-sequential generation occurs. It is possible to reduce the amount of hardware of the carrier suppressing filter to be used and the complexity of its design.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image pickup apparatus according to a first embodiment of the present invention.

FIG. 2 is a layout diagram of signals to be synchronized.

FIG. 3 is a block diagram showing a matrix operation circuit in the first embodiment.

FIG. 4 is an explanatory diagram for explaining gamma correction.

FIG. 5 is an explanatory diagram for explaining carrier generation and suppression.

FIG. 6 is a block diagram showing a schematic configuration of an image pickup apparatus according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a matrix operation circuit according to a second embodiment.

FIG. 8 is a block diagram showing a schematic configuration of a conventional imaging device.

FIG. 9 is an explanatory diagram for explaining problems with conventional carrier generation and suppression.

[Explanation of symbols]

 101 ... Image sensor 114,414 ... Simultaneous circuit 115,415 ... Low pass filter 117 ... Gamma correction circuit 116, 416 ... Matrix operation circuit 117 ... Gamma correction circuit 202-204, 502-505 ... Multipliers 206-207, 506 to 507 ... Adder 208 ... Differential characteristic generation circuit 209 ... Clip circuit MCLK ... System clock

Claims (2)

[Claims] 1. A separating means for separating a video signal output from an image pickup device into a luminance signal and a plurality of color signals, and a synchronizing means for synchronizing the luminance signal and the plurality of color signals separated by the separating means. In the image pickup apparatus having: R, based on the signals synchronized by the synchronization means, R
An image pickup apparatus comprising a matrix calculation means for performing a matrix calculation for directly generating a color difference signal without using a GB signal. 2. The image pickup apparatus according to claim 1, further comprising gamma correction means for performing gamma correction on the color difference signals generated by the matrix calculation means.