JP2623084B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus for forming a luminance signal and a color difference signal from a plurality of horizontal lines.

[Conventional technology]

 FIG. 8 is a layout view of a conventional color separation filter.

In the figure, n ₁ , n ₂ , n ₃ ... Mean each horizontal line, and 01, 02, 03... Mean each horizontal scan line in an odd field. The luminance signal and the chrominance signal of each horizontal scanning line are formed using the vertical correlation of two horizontal scanning lines.

First, when the pixel signals for two horizontal scan lines added respectively, W + G = R + 2G + B, and _{Y e + C Y = R +} 2G + B next, R + 2G + B next Both, simplified manner luminance signal Y so.

Then Taking the difference of two horizontal scanning lines of the signal W-G is R + B, It Y _e -C _Y is R when adding both because it is R-B are also to obtain Subtracting B Can be.

As described above, in the above method, the luminance signal Y and the color signals R and B can be obtained by addition and subtraction, so that the signal processing is simple, the resolution is good, and the false color signal is obtained despite the use of the complementary color filter. Occurrence is low.

[Problems to be solved by the invention]

In the conventional signal processing method using a color separation filter, a low-frequency luminance signal is obtained from two horizontal lines, so that the vertical resolution is not very good. Second, the complementary color subtraction processing is performed in that the repetition of the horizontal pixels is performed every four pixels, so that the sampling frequency is increased to reduce the sampling frequency and line crawl occurs in the image band. In addition, there is a problem that a large false signal is generated.

In the conventional imaging device as described above, the IL-CCD and the MOS
In the case of a type sensor, in the case of interlaced reading, the vertical correlation distance is long, so the number of moiré and false signals increases, and the 1H delay line is frequently used, so the scale of the peripheral circuit increases, which increases the cost There were problems such as.

Further, when the field accumulation mode is set to reduce the frame afterimage in the IL-CCD, since the imaging system is a modulation system, the color reproducibility is deteriorated, and two horizontal lines are added and read. Because the vertical resolution is worse, and the color difference signal is obtained only line-sequentially,
When the color difference signals are synchronized, there is a problem that a false signal is generated due to a difference between a low frequency component of the color difference signal and a low frequency component of the luminance signal.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems, and to provide an image pickup apparatus which has high horizontal and vertical resolution, has few false signals, and has good color reproduction.

[Means for solving the problem]

According to the present invention, a solid-state imaging device including a plurality of pixels, a first color separation filter arranged in a checkered pattern on the pixels of the solid-state imaging device, a second color separation filter, and a third color separation filter Color filters arranged line-sequentially between the first color separation filters, a signal of a main horizontal line and a signal of a sub-horizontal line of the solid-state imaging device are simultaneously read out for each horizontal scan, and Reading means for interlacing by shifting the reading position of each horizontal scan every time, and forming a color signal for forming a color difference signal from the signal of the main horizontal line, and a low-frequency signal for forming the color difference signal. And a signal processing means for forming a luminance signal from the main horizontal line and forming a high-frequency luminance signal from both the main horizontal line and the sub-horizontal line.

[Action]

According to the present invention, since the main horizontal line and the sub-horizontal line are simultaneously read and interlaced by shifting the read position of each horizontal scan for each field, high image quality can be obtained without using a 1H delay line or the like. Can be obtained. Also, when forming the color difference signal, since the color signal is formed from the signal of the main horizontal line, the generation of the false color signal is extremely small, while the high frequency luminance signal is generated by the main horizontal line and the sub horizontal line. Since it is formed from signals, high resolution can be obtained.

〔Example〕

FIG. 1 is a diagram showing an arrangement of a color separation filter according to an embodiment of the present invention, in which n ₁ , n ₂ ,... Indicate horizontal lines, and odd fields 01, 02,. Each horizontal scanning line in an odd field is shown. For example, in a horizontal scanning line 01, horizontal lines n1 and n2 are processed simultaneously to obtain a luminance signal and a chrominance signal. Similarly, the even fields e1, e2,... Also mean each horizontal scanning line in the even field. Here, the horizontal scanning line means one horizontal scanning line of the television, and the horizontal line means one horizontal line of pixels arranged in a matrix.

The color filter in this embodiment is an all-color transmission filter (W).
Are arranged in a checkered pattern, and a red transmission filter (R) and a blue transmission filter (B) are line-sequentially arranged every two pixels. That is, R filters and B filters are alternately arranged for each horizontal line.

By the above-described simultaneous processing of each horizontal line and the color filter arrangement, a luminance signal is formed from W signals of two horizontal lines, and a color difference signal is formed from a color signal and W signals of each horizontal line.

Furthermore, the low-frequency luminance components of the luminance signal and the color difference signal are shifted from the odd horizontal line as the main horizontal line in the odd field,
In the even field, the main horizontal line is formed from the even horizontal lines. Note that another horizontal line read at the same time is defined as a sub-horizontal line.

FIG. 2 is a schematic diagram of the driving of the sensor, where R, B, and W represent each pixel and a color filter on the pixel, V / SR is a vertical shift register, H / SR is a horizontal shift register, φV・ R
S and φH · RS indicate the charge refresh pulse for each vertical and each bit, respectively.

In the signal wiring method of this embodiment, two horizontal lines are simultaneously read out, and the R and B color signals are alternately read out from the output S2 for each pixel, and the W signal is continuously read out from S1 one pixel at a time.

FIG. 3 is a sampling timing chart of a signal read by the sensor of FIG. The R, B point sequential signal of S2 is separated into R and B at the timing shown in the figure, and the W, W point sequential signal of S1 is separated from the W signal from the horizontal line where R exists in the odd field, and in the even field, The W signal from the horizontal line where B is present is separated into low-frequency luminance components of a luminance signal and a color difference signal.

FIG. 4 is a signal processing block diagram.
Is a nondestructive readable image sensor (hereinafter referred to as SIT), 20
Is a clock generator, 40, 70a, 70b are sample-and-hold circuits (S / H), and 50, 80a, 80b are low-pass filters (LP
F) and 60 are bandpass filters (BPF), 90a and 90b are white balance circuits, 100 is a process circuit, and 110 is an adder.

In the device configured as described above, the neighboring 2
If the horizontal lines are read simultaneously, 2 is output from the output line S1 of SIT10.
The W signal of the horizontal line is alternately and dot-sequentially read, and the R and B dot-sequential signals are alternately read from the output line S2. The luminance signal is formed from the above-mentioned SIT output S1. First, the high-frequency luminance signal uses the SIT output S1 as it is, so that a high-resolution band is secured.

That is, the repetition frequency of the W signal from S1 is, for example, SIT10
If the number of horizontal pixels is 510 pixels, the readout frequency is about 9.5 MHZ, and if that is the Nyquist frequency, about 4.7 MHZ is the luminance band. In this case, the band of the BPF 60 has a band pass characteristic of about 1 MHz to 4.7 MHz.

Next, the low-frequency component for luminance, the low-frequency component for color difference, and the color signal are sampled and held by the sample and hold circuits 40, 70a, and 70b.
1, separated from S2. With reference to FIG. 1, in the 01 horizontal scanning line of the odd field, the W signal and the R signal corresponding to the horizontal line n1 are separated and the horizontal line n2
Are separated from the W signal and the B signal. Further, the low frequency luminance signal is formed from W signals n ₁ line. Then the 02 horizontal scan lines are separated W signal and B signal corresponding to the line n4 together with W and R signals corresponding to the horizontal line n3 are separated, yet low-frequency luminance signal from the W signal n ₃ lines It is formed. In the odd field, a low-frequency luminance signal is formed from an odd horizontal line of each horizontal line, and in the even field, a low-frequency luminance signal is formed from an even horizontal line of each horizontal line. Therefore, the vertical resolution does not deteriorate.

The low-frequency luminance signal and the chrominance signal obtained as described above are band-limited to about 1 MHz by the LPFs 50, 80a, and 80b at the next stage.
The color signal is further subjected to white balance operation by a control voltage (not shown) which is controlled line-sequentially by white balance circuits 90a and 90b at the next stage. The white-balanced R, the line sequential color signal B low frequency luminance signal Y _L is γ treatment in the process circuit 100 is performed, the low frequency luminance signal ▲ Y _^'L ▼
Line sequential color difference signals _{^{R'- ▲ Y 'L ▼, B'-}} ▲ Y' L ▼ is output. The low-frequency luminance signal ▲ Y _^'L ▼ is input to the encoder 200 becomes Y signal are added by the adder 110 and the high band luminance signal Y _H.

By performing the signal processing as described above, since the color signal is obtained from a pure color filter, the color reproducibility is good, and the error of one vertical pixel of R and B is not a problem in view of the band of the color signal.

Further, the band of the luminance signal is wide because W of two horizontal lines is used.

Further, since the luminance component of the color difference signal and the low frequency component of the luminance signal are the same signal, when returning to the original primary color signal, no false color signal due to the luminance signal is generated.

Also, since the low-frequency component of the luminance signal is formed from one horizontal line, the vertical resolution does not deteriorate.

And the like.

FIG. 5 is a layout diagram of a color separation filter according to a second embodiment of the present invention.

Niyotsute B signal is obtained when subtracting the Y _e signal from Figure 5 (a) the W signal and obtain Yotsute R signal by subtracting the C _Y signal from the W signal. The signal processing circuit block diagram at that time has a circuit configuration as shown in FIGS. 6 (a), (b) and (c) in which subtracters 190a and 190b are added to the signal processing circuit block diagram of FIG. That is, in FIG.
Connexion high frequency luminance signal to the W signal from the output line S1 of 0 Y _Y, but the point of obtaining a low-frequency luminance signal Y _L is the same as that of FIG. 4, R,
And B color signals are obtained by subtracting from W signal from Y _e, a line sequential color signal C _Y S1.

FIG. 6B is different from FIG. 6A in that the luminance signal Y is formed by directly outputting the output of the output line S1 through the low-pass filter 210.

Yotsute R signal is obtained by subtracting the G signal from the FIG. 5 (b) in Y _e signal, also obtain Yotsute B signal by subtracting the G signal from the C _Y signal. The block diagram of the signal processing circuit at that time is as shown in FIG. 6B, for example, and the above-described subtraction processing is performed by the subtracters 190c and 190d. For the luminance signal, the output S1 of the SIT 10 is used as it is as a luminance signal. That is, S1 Y _e, C _Y are output in a dot sequential output element Y _e S1 since G signals to S2 is output at point sequential, Y ≒ by passing the C _Y into LPF210 _{Y e} + C Y = R + 2G + B is formed.
In FIG. 6 (c), the SIT output S1 and the output S2 signal are added to generate a luminance signal.

FIG. 7 shows a luminance signal in which the output S1 of SIT10 is directly used as a luminance signal, and R, B
A point-sequential signal is obtained. Other processes are the same as those in FIG.

By performing the signal processing as described above, the present invention makes the low-frequency components of the chrominance signal and the luminance signal the same signal, so that when returning to the original primary color signal, the false color signal caused by the luminance error is reduced. Does not occur.

In another invention of this application, the band of the high-frequency luminance signal is wide because the W of two horizontal lines is synthesized, and the color signal is obtained from a filter for obtaining a pure color, so that the color reproducibility is low. good. It should be noted that the error of one pixel in the vertical direction between R and B is not a problem in view of the color signal band and can be ignored.

〔The invention's effect〕

According to the present invention, the main horizontal line and the sub-horizontal line are simultaneously read and interlaced by shifting the read position of each horizontal scan for each field, so that high image quality can be obtained without using a 1H delay line or the like. Can be obtained. Also, when forming the color difference signal, since the color signal is formed from the signal of the main horizontal line, the generation of the false color signal is extremely small, while the high frequency luminance signal is generated by the main horizontal line and the sub horizontal line. Since it is formed from signals, high resolution can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement of a color separation filter according to one embodiment of the present invention, FIG. 2 is a schematic diagram of driving of a sensor, FIG. 3 is a waveform diagram showing an output signal and a sample timing of the sensor of FIG. 4 is a signal processing block diagram of FIG. 2, FIG. 5 is a layout diagram of a color separation filter according to a second embodiment of the present invention, FIG. 6 is a block diagram of signal processing of a main part in the embodiment, and FIG. FIG. 5 is a block diagram of another signal processing circuit of FIG. 5, and FIG. 8 is a layout diagram of a conventional color separation filter. In the figure, 10 is the SIT, 20 is the clock generator, 40,
70a and 70b are sample-and-hold circuits, 50, 80a, 80b, and 210 are low-pass filters (LPF), and 60 is a band-pass filter (BP
F), 90a and 90b are white balance circuits, 100 is a process circuit, 110 and 120 are adders, 190a, 190b, 190c, 190d, 190e, and 19
0f is a subtractor, and 200 is an encoder.

Claims (1)

(57) [Claims] 1. A solid-state image pickup device comprising a plurality of pixels, and first color separation filters arranged in a checkered pattern on the pixels of the solid-state image pickup device, wherein a second color separation filter and a third color separation filter are arranged. A color filter arranged line-sequentially between the first color separation filters; a signal of a main horizontal line and a signal of a sub-horizontal line of the solid-state imaging device are simultaneously read out for each horizontal scan; Reading means for interlacing by shifting the reading position of each horizontal scan, and forming a color signal for forming a color difference signal from the signal of the main horizontal line, and a low-frequency luminance for forming the color difference signal. A signal processing means for forming a signal from the main horizontal line and forming a high-frequency luminance signal from both the main horizontal line and the sub-horizontal line.