JPS6089187A - Color solid-state image pickup device - Google Patents

Abstract

PURPOSE:To obtain excellent picture quality by constituting the titled device with color filter element array where each filter element is arranged in the order of transparent, yellow, transparent, cyan and with the color filter element array where the element is arranged in the order of magenta, cyan, magenta, yellow. CONSTITUTION:Signal electric charges of two photodiodes in vertical direction are mixed and read in the field storage drive. Thus, the repetitive signal of W+ Ye and Mg+Cy is obtained as the n-th line output of the field A and an output corresponding to W+Cy and Mg+Ye is obtained repetitively in the (n+1)-th line. Similarly, a repetitive signal of Ye+W and Cy+MG is obtained as the n-th line output in the field B and an output corresponding to Cy+W and Ye+Mg is obtained repetitively in the (n+1)-th line. The horizontal repetition of Ye+W and Cy+Mg is obtained in the n-th line and the repetition of W+Cy and Ye+ Mg is obtained in the (n+1)-th line in both the fields A and B.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a color solid-state imaging device V.

(Conventional configuration and its problems) Interline transfer type CCD (hereinafter referred to as T-CCD
(abbreviated as ), there is a frame accumulation drive in which charge is accumulated and read out for one frame in one photodiode as an element driving method, and this frame accumulation drive has been commonly used in single-chip color cameras. In this frame accumulation driving method, the charge accumulation time is one frame (1730
Problems include equivalent afterimages that occur due to the high resolution (seconds) and flicker in vertical high-resolution areas of reproduced images when frame accumulation driving is used. For this reason, a single-chip color camera using a field accumulation drive in which charges are accumulated and read out for one field has been proposed.

Figure 1 shows the IT-C using field storage drive.
This figure shows the configuration of a color filter for a CD single-plate color camera.

In FIG. 1, the portions indicated by dotted lines represent photodiodes corresponding to each filter element. In addition, G is a green transmission filter, Ye is a yellow (green and red) transmission filter, Cy is a cyan (green and blue) transmission filter,
Mg indicates magenta (red and blue) transmission filters, respectively, and has a comb-backed configuration of basic color filters arranged in circles and circles, 2 columns and 4 rows.

In field accumulation driving, the signal charges of two vertical photodiodes are mixed and read out. That is, in the nth line of the A field in FIG. 1, the signal charges of the photodiodes corresponding to the Cy and G filters are mixed, and the signal charges of the photodiodes corresponding to the Ye and Mg filters are mixed and read out. Also, the nth +
In one line, signal charges corresponding to the cy and Mg filters are mixed, and signal charges corresponding to Ye and G are mixed and read out. As a result, the signal output corresponding to (cy+G) and (Y
The signal output corresponding to e+Mg) is repeated and output.

Moreover, in the n-1-1 line, (Cy -t-Mg
) and (Ye+G) are inverted and read out.

Similarly, in the B field, repeated signals of (Mg + Ye) and (c+Cy) are obtained as the nth line output, and (G→-Ye) r on the n+1th line.
A signal output corresponding to (Mg-+Cy) is repeatedly obtained.

In this way, in both fields A and B, on the nth line (
Ye 1 Mg) and (G+G) in the horizontal direction, and on the n+1st line, (Ye-1-G) and (cy
+Mg) is repeated.

Here, if the element signal outputs of the n-th line and the n+1-th line are Sn and Sn+1, it is expressed by the following equation.

S = (Ye to Mg) + (Cy to G) + ((Ye + Mg
)−(Cy+G))s stone ωt...(1) Sn+1=(
Ye1G)+(Cy1Mg)+((Cy+Mg) (Y
e+G)) s-stone ωt-(2) Therefore Sn and Sn+
1 DC component (Ye - 1 - Mg + Cy + G) is used as the luminance signal, and as the chromatic signal (ye + Mg) -
(Cy+G)=2R-a −= (3)(Cy+Mg)
−(Ye+G)=28−G −(4) is used.

By using the above-mentioned color filter, it is possible to create a single-chip color camera using field storage drive, and it also reduces flicker in vertical high-resolution areas, which has traditionally been considered a drawback with frame storage drive, and eliminates equivalent afterimages. A stable color image is obtained, with no blemishes. However, when using the color filter array shown in Figure 1, when capturing an image of a subject with a high degree of color saturation, the resolution will be lower than that of a subject with a low degree of color saturation, and in particular diagonal lines will appear as broken lines. It has the disadvantage of becoming Figure 2 shows the state of the spatial frequency response of the color filter array in Figure 1 to R light (red light, LB light (blue light)). As shown in (a) and (b), the positional arrangement that responds to R and B lights is not uniform, and the so-called arrangement has a lower spatial frequency response to R and 13 lights in diagonal directions. Therefore, the resolution decreases for R light and B light with high saturation, and this is particularly noticeable in oblique directions.

(Objective of the Invention) The present invention provides a high-performance color solid-state imaging device that eliminates the above-mentioned drawbacks.

(Structure of the Invention) The color separation filter of the present invention is composed of a unit array of 2 columns and 4 rows in a color filter element group in which a large number of color filter elements are two-dimensionally arranged in m rows and n columns. The unit array is
A first color filter element column in which the column color filter elements are arranged in the order transparent, yellow, transparent, cyan, and a second color column color filter element column arranged in the order camagenta, cyan, magenta, yellow. It consists of a filter element sequence,
This is applied to a field storage driven solid-state image sensor.

As a result, flicker in the high-resolution portion in the vertical direction can be reduced, equivalent afterimages can be removed, and a stable color image with no reduction in resolution can be obtained even for objects with high color saturation.

(Description of Examples) The configuration of the color filter of the present invention is shown in FIG. The color filters include Ye (yellow), Cy (cyan), Mg (magenta), and W (transparent) filters.

In field accumulation 1 driving, signal charges of two vertical photodiodes are mixed and read out. Therefore, in the nth line of the A field, the signal charges of the two photodiodes corresponding to W and Ye are mixed, and
The photodiode signals corresponding to the Mg and cy filters are mixed and read out. Moreover, in the n-1-1th line, the signal charges corresponding to W and the cy filter are mixed,
The photodiode signal charges corresponding to Ye and Mg are mixed and read out. As a result, in the nth line of the A field, (W −1
−Ye ) and a signal output corresponding to (Mg+cy )
The signal output corresponding to 0 is inverted and output. Also, in the n+1th line, (w 1 cy).

The signal output corresponding to (Mg + Ye) is repeatedly output.

Similarly, in the B field, the repeating signals of (Ye +W) and (Cy+Mg) are obtained as the +1st line output, and in the n + 1st line, (Cy+W)
.

The output corresponding to (Ye 1 Mg) is obtained repeatedly.

In this way, in both fields A and B, on the nth line (
Horizontal repetition of (Ye +W) and (Cy0Mg), (W+Cy), (Ye
10 Mg) repeatedly.

Here, if the element signal outputs of the n-th line and the n + 1-th line are Sn and Sn+1, it is expressed by the following equation.

Sn=(Ye+W)+(Cy+Mg)+((Ye+W
) (Cy0Mg)) sinωt ・−(5)Sn+1
=(Cy+w)+(Ye-+Mg)+((Cy+W)
(Ye+Mg)) sin (dt ·- · (6) Therefore, when using the color filter shown in Fig. 3, Sn, Sn
+1 DC component (Ye +w+ cy +Mg) is used as the luminance signal Y, and as the color left signal, Cn -
Ye1W-(Cy1Mg)=R+G-B ・-(7)C
n+, = (Cg 10W) - (Ye 10Mg) = G + B, -R
,... (8) is used.

When using a true color filter, the R light is treated as shown in Figure 4 (a).
) and B light, the spatial frequency response is significantly improved compared to FIG. 2, as shown in FIG. 4(b).

This means that even for objects with high R and B color saturation, there is little reduction in resolution, and in particular, jagged edges of lines in diagonal and vertical directions of the object are improved. Furthermore, since the amount of light transmitted by the color filter for each color is proportional to the increase in spatial frequency, camera sensitivity will be improved.

Hereinafter, one embodiment of the present invention will be described using FIG. 5. FIG. 5 shows the circuit configuration of a single-chip color camera using the color filter of the present invention.

Light P from the subject is passed through lens L1 infrared cut filter G
1 After passing through a crystal low-gust filter Q, an interline transfer type CCD (IT-C
CD).

The wideband luminance signal YH (=Ye1W10y1Mg) is C
The CD signal output is obtained by directly passing it through a wideband low-pass filter 1. The color difference signal is obtained by passing the CCD (i-minute output K) through a bandpass filter 2 and a detection circuit 3. After passing through a white balance circuit 4 for color temperature correction, this color difference signal is Two types of color difference signals Cn and Cn+1 are generated by a sequential-to-simultaneous conversion circuit using a line 5 and an IH switching circuit 6. These color difference signals are balanced modulated by a color subcarrier in a balanced modulator 7, and then a mixing circuit 8
There, it is added to the broadband luminance signal YH that has passed through the process circuit 9, and a burst and composite synchronization signal is added to obtain an NTSC signal output. Further, as a signal for white balance, a wideband luminance signal Y1 (and a low-band luminance signal YL that has passed through a separate narrowband low-pass filter 1o and a process circuit 11) is used.

Furthermore, camera synchronization signals, pulses for driving the image sensor, etc. are obtained from a logic circuit with a master clock frequency of 14.31.818 MHz.

The IT-CCD used in this example has 384 pixels horizontally and 488 pixels vertically, and can use a %'' optical system.

(Effects of the Invention) A single-plate color camera using the color filter of the present invention has a resolution of 240 TV lines (horizontal direction) and 350 TV lines (vertical direction), and a lens aperture of 9 values F = 1. ,4. , ′
$.

Photography illuminance 200tX (color temperature 3200K) f s
7'N=55 dB was obtained, and compared to the case where conventional color filters were used, the effect of improving camera sensitivity by about 30% (3 dB) was obtained. In addition, even for subjects with high color saturation, there was almost no decrease in resolution, and in particular, the jaggedness of diagonal or vertical lines in the subject was significantly reduced, resulting in good image quality.

[Brief explanation of drawings]

Figure 1 is a block diagram of a color filter for a single-chip color camera using conventional field storage drive; Figure 2 (a);
(b) is a diagram for explaining the spatial frequencies of the color filter of FIG. 1 for R light and B light, respectively. FIG. 3 is a block diagram of the color filter of the present invention, and FIG. 4 (,)
, (b) are the R light of the color filter of the present invention, respectively.
FIG. 5, which is a diagram for explaining the spatial frequency of B light, is a circuit configuration diagram of an interline type COD single-chip color camera driven by field accumulation, using the color filter of the present invention. F...Color filter, 1...Broadband low-pass filter, 2
...Band filter, 3...Detection circuit, 4...White balance circuit, 5...IH delay line, 6...IH
Switching circuit, 7... Balanced modulator, 8... Mixing circuit, 9
, 11... Process circuit, 10... Narrowband low-pass filter. Figure 1 (B77-・Rudo poetry play) (A74-Rudo story play) Figure 2 (0) □□□-吋(b) (B 74. Ludo Ayami play) (A field read ↓ f/ly pause) Figure 3 (B fee I read titt) (A field accent removed)
Figure 4 (0) (b)

Claims (1)

[Claims] A color filter, which is applied to a field storage driven solid-state image sensor and is made up of a large number of color filter elements arranged in a matrix of 111 rows and 1 columns, is composed of a unit array of 2 columns and 4 rows, and the unit array is , a first color filter element row in which the color filter elements are arranged in the order of transparent, yellow, transparent, and cyan, and a second color in which the color filter elements are arranged in the order of magenta, cyan, magenta, and yellow. A color solid-state imaging device comprising a filter element array.