JPH067680B2 - Matrix circuit - Google Patents

Description

The present invention relates to a matrix circuit for forming a luminance signal and a color difference signal in a signal processing system of an electronic camera such as an electronic still camera or a color video camera.

(Prior art example) Generally, in such an electronic camera, a signal for each pixel obtained by read-out scanning from an image pickup device such as a solid-state image pickup device is color-separated by a color separation circuit, and R (red) generated by this color separation is generated. , G (green), B (blue), and the like, the matrix circuit forms a luminance signal and a color difference signal, and the encoder circuit forms a composite color video signal based on these signals. .

(Problems to be Solved by the Invention) However, in the matrix circuit incorporated in such a signal processing system, the circuit network is complicated, and the circuit network for forming the luminance signal and the color difference signal are formed. There is a problem in that there is a difference in processing time from the circuit network for this purpose, which causes a phase shift between the luminance signal and the color difference signal, which causes deterioration in image quality due to color shift.

(Means for Solving Problems) The present invention has been made in view of the above problems, and a sample and hold circuit for sampling the formed luminance signal and color difference signal in accordance with a predetermined synchronization timing. It is an object of the present invention to provide a matrix circuit that corrects the phase shift of each signal by including.

Embodiment An embodiment of the matrix circuit according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall structure of an electronic still camera according to the present invention. First, the configuration will be described. An imaging optical system including a taking lens 1 and a diaphragm and an optical shutter (not shown) is provided, and the imaging lens 1 can be moved back and forth along an optical axis C by an optical system drive circuit 2. it can. That is, a drive motor or the like in the optical system drive circuit 2 operates in a predetermined direction in accordance with a control signal from the central control circuit 4, and the driving force causes the taking lens 1 to move forward of the camera, rearward of the camera, or a predetermined direction. Stop at a position.

A solid-state image pickup device 5 having a two-dimensional image pickup cell array such as a CCD forming a pixel is arranged on the focal plane of the image pickup optical system. Output as a serial signal in synchronization with the clock signal. In the cell array of the solid-state image sensor 5, as shown in FIGS. 2 (a) and 2 (b), a green (G) portion and a red (G) portion are provided.
A color filter having a ratio of (R) and blue (B) of 2: 1: 1 is provided to form a pixel, and horizontal scanning readout is performed for each row to output the serial signal. It

The signal from the fixed image pickup device 5 is amplified by the preamplifier 7, then separated into R, G, and B color signals by the color separation circuit 8 and supplied to the matrix circuit 9 according to the present invention.

The matrix circuit 9 converts the color signals R, G, B from the color difference signal R-
Y, to form a B-Y and luminance signal Y _C, to magnetically recorded on the magnetic recording medium through the magnetic head 11 of the recording unit 10.

Reference numeral 12 is a synchronization signal generation circuit that generates a synchronization signal S _C that is added to the luminance signal Y _C in the matrix circuit 9, 13 is a shutter release, and when the central control circuit 4 detects that the shutter release 13 is pressed, A command signal is transmitted to the optical system drive circuit 2 to set the diaphragm and / or the exposure, the signal output from the solid-state image sensor 5 is signal-processed, and the subject image is recorded via the recording unit 10.

Next, the configurations of the matrix circuit 9 and the recording unit 10 will be described in detail with reference to FIG.

Color signals R, G, B output from the color separation circuit 8 in FIG.
Are supplied to the process circuits 15 and 16, respectively. The color signals R and B generated by the color filter shown in FIG. 2A or 2B are line-sequential signals.

In the process circuits 15 and 16, color signal processing such as γ correction is performed, and the processed color signals R ₀ , B ₀ and G ₀ are output. Further, the color signal from the process circuits 15 and 16 is 1
The H delay circuits 17 and 18 delay the image signals by one horizontal scanning period (1H), and output the color signals R ₁ , B ₁ and G ₁ .

Here, the color signals R ₀ , G ₀ , and B ₀ are color signals from the pixel at which the horizontal scanning reading is currently performed, and the color signals R ₁ ,
G ₁ and B ₁ are color signals output from the pixels in the previous row by the horizontal scanning read-out in the previous horizontal scanning period. That is, the subscript "0" means the present, the subscript "1" means the color signal obtained by the horizontal scanning reading 1H before, and the same applies hereinafter.

In addition, the color signal R output from the process circuits 15 and 16
₀ , G ₀ , B ₀ are supplied to the subtractor 19 where the subtraction process is performed to form the signals R ₀ -G ₀ and B ₀ -G ₀ . Similarly, from the subtractor 20, the color signals R ₁ , G ₁ ,
By subtraction processing based on B _1, signals _R 1 -G ₁ and _{B 1} -
G ₁ is output.

These signals R ₀ -G ₀ , B ₀ -G ₀ , R ₁ -G ₁ , B
_1- G ₁ is selectively supplied to the chroma matrix circuit 22 and the Y _L matrix circuit 23 via the multiplexer 21.

The chroma matrix circuit 22 outputs signals R ₀ -G ₀ and B ₁
By calculating the following equation (1) based on −G ₁ ,
Thereby generating the color difference signals R-Y, to generate a color difference signal B-Y by performing the calculation of the following equation (2) based on the signals _R 1 -G ₁ and _B 0 -G _0.

_{R-Y = 0.7 (R 0} -G 0) -0.11 (B 1 -G 1) ... (1) B-Y = 0.89 (B 0 -G 0) -0.30 (R 1 -G 1) ...
(2) The calculation of the above formulas (1) and (2) is alternately performed according to the color signal currently read out in the horizontal scanning from the pixel corresponding to the color filter shown in FIG. 2 (a) and (b). Therefore, the color difference signal R-
Y and BY are line sequential signals. Also, the color difference signals RY,
The BY frequency band is limited to 0 to 0.7 MHz by an internal low-pass filter. The band characteristic is shown in FIG. 4 (a).

On the other hand, the Y _L matrix circuit 23 includes the multiplexer 21
And a color signal G ₀ from the process circuit 15 are supplied to form a low-frequency luminance signal Y _L. Low range luminance signal Y _L
Is, as shown in FIG. 4 (b), the color difference signals R-Y and B-Y.
Similarly, is a signal in the frequency band (0 to 0.7 MHz) limited by the internal low-pass filter, and is formed by arithmetic processing based on the following equations (3) and (4).

_{Y L = 0.11 (B 0 -G} 0) +0.30 (R 1 -G 1) + G 0 ... (3) Y L = 0.11 (B 1 -G 1) +0.30 (R 0 -G 0) + G 0 (4) When the output signals from the solid-state image sensor 5 in the current horizontal scanning read out are the blue signal B ₀ and the green signal G ₀ , the above formula is obtained.
The arithmetic processing of (3) is performed, and when the output signals from the solid-state image sensor 5 in the current horizontal scanning read out are the red signal R ₀ and the green signal G ₀ , the arithmetic processing of the above formula (4) is performed.

Further, the process circuits 15, 16 and the 1H delay circuit 17,
18 color signals R ₀ , B ₀ , R ₁ , B ₁ , G ₀ , G ₁
Is supplied to the multiplexer 24 and the adder 25, and a color signal selected by the switching operation of the multiplexer 24,
The signal G ₀ + G ₁ generated by the adder 25 is supplied to the Y _H matrix circuit 26.

The Y _H matrix circuit 26 performs arithmetic processing of the following equations (5) and (6) on the basis of these input signals to obtain a high-frequency luminance signal Y
Form _H.

_{Y H = 0.25 (R 1 +} B 0) +0.25 (G 0 + G 1) ... (5) Y H = 0.25 (R 0 + B 1) +0.25 (G 0 + G 1) ... (6) where the current When the output signals from the solid-state image sensor 5 for which horizontal scanning reading is performed are the blue signal B ₀ and the green signal G ₀ , the arithmetic processing of the above formula (5) is performed, and the output signals are the red signal R ₀ and the green signal. When the signal is G ₀ , the arithmetic processing of the above equation (6) is performed. The high-band luminance signal _YHi has a color signal ratio of R: B: G = 1: 1: 2, and the frequency band thereof is limited to 0.7 MHz to 4.2 MHx by an internal high-pass filter.

The high-frequency luminance signal Y _H is supplied to one input terminal of the adder 28 via the sample and hold circuit 27, and is added together with the low-frequency luminance signal Y _L to form a signal Y _L −Y _H. That is, as shown in FIG. 4 (d), Figure 4 signal by the signal Y _L and the fourth view of the band of the (b) a signal Y _H of the (c) adding a reverse polarity Y _L -Y _H Is formed. Signal _Y L -Y
_H is passed through the low-pass filter 30 via the sample and hold circuit 29, and after being limited to a signal in the frequency band of 0.7 MHz or less, is supplied to one input terminal of the adder 31 and the band from the sample and hold circuit 27. The addition processing is performed together with the luminance signal Y _H , and the band (0 to 4.2 MH) shown in FIG.
The luminance signal Y of z) is formed. That is, as shown in the figure, the luminance signal Y is composed of a low-frequency luminance signal Y _{L at} a frequency of 0.7 MHz or less and a combined luminance signal Y _H at a frequency of 0.7 MHz to 4.2 MHz. Has become. Then, in the adder 32, the luminance signal Y _C to which the synchronizing signal S _C from the synchronizing signal generating circuit 12 is added is formed.

In this way, the sample and hold circuits 27, 29, 33,
The respective signals R-Y, B-Y, and Y _C that have passed through 34 are
Frequency modulation circuits 36 and 37 corresponding to the recording unit 10 in the figure,
The signal is converted into a magnetically recordable signal by the adder 38 and the buffer amplifier 39, and recorded on the magnetic recording medium via the magnetic head 11.

Here, the conventional matrix circuit is not provided with the sample and hold circuits 27, 29, 33, and 34, so that the signals between the matrix circuits 22, 23, and 26 based on the difference in signal processing speed between them are not provided. The signals R-Y, B-Y, Y _L , and Y _H are added to the adder 31 and the adder 31, while there is a phase shift.
32 and the multiplexer 35,
It was causing color misregistration. However, in this embodiment, the sample and hold circuits 27, 29, 33 and 34 are provided, and the sample and hold operation is performed based on the synchronizing signals φ _{1 to} φ ₄ at the predetermined timing, so that each signal R-
_{Y, B-Y, Y L} , Y H is the phase shift is corrected, degradation of image quality due to color shift or the like is prevented.

Further, by the addition processing in the adders 28 and 31, the components in the frequency band of 0 to 0.7 MHz in the luminance signal Y are changed to 0 to
Since the color signals R and B having a band of 0.7 MHz are formed, the resolutions of the luminance signal Y _L and the color signals R and B in this band are kept equal, and the deterioration of the image quality due to color moire is prevented. You can do it.

(Effects of the Invention) As described above, according to the present invention, a sample and hold circuit for sampling the formed luminance signal and color difference signal in accordance with a predetermined synchronization timing is provided, and each of the signals is sampled at the timing. Since the phase shift is corrected, it is possible to prevent the occurrence of color shift in the reproduced image and provide a high quality image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a case where an embodiment of a matrix circuit according to the present invention is incorporated in an electronic still camera,
2 is an explanatory view showing an example of a color filter provided in the solid-state image pickup device shown in FIG. 1, FIG. 3 is a block diagram showing in detail the configuration of the matrix circuit shown in FIG. 1, and FIG.
FIG. 6 is a frequency characteristic diagram showing a process of forming a luminance signal. 9: Matrix circuit, 15, 16; Process circuit 17, 18; 1H delay circuit, 19, 20; Subtraction circuit 21, 24, 35; Multiplexer 25, 28, 31, 32, 38; Adder 22; Chroma matrix circuit 23 Y _L matrix circuit 26; Y _H matrix circuit 27, 29, 33, 34; sample and hold circuit 30; low pass filter 36, 37; frequency modulation circuit 39; buffer amplifier

Claims (1)

[Claims] 1. A matrix circuit for forming a luminance signal and a color difference signal on the basis of a color signal generated by an image sensor, comprising a sample and hold circuit for sampling the luminance signal and the color difference signal in accordance with a predetermined synchronization timing. A matrix circuit characterized by the above.