JPH10178648A - Solid-state color camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the variation of practical sensitivity in every other horizontal period which is caused by the mixture of pixels and to perform moire suppression by changing the addition ratio of a luminance signal in every other horizontal period. SOLUTION: Two adjacent lines among vertical gate lines 101 to 104 are selected and read during a certain horizontal period. Entire pixel element scan is finished during one field by repeating this scan. Although two adjacent lines are simultaneously selected in the next one field in the same way, a combination of the two selected lines is shifted from the preceding combination by one line to be a combination of the two adjacent lines, and a signal of the two lines is simultaneously read. In such cases, because each vertical signal line 111 to 116 are connected to different output terminals 131 and 132 every other row through horizontal switches 121 to 126, each mixed signal, i.e., W and Cy, and G and Cy from the terminal 131 and G and Ye, and W and Ye from the terminal 132 are alternately outputted in every other horizontal period. Though this signal is added by prescribed addition ratio inside a luminance signal generating circuit after amplifying it so that a luminance signal can be generated, the addition ratio is changed in every other horizontal period in such cases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to suppression of a false signal of a solid-state color camera.

[0002]

2. Description of the Related Art In a color video camera using a solid-state imaging device, that is, a solid-state color camera, a high-frequency component of a spatial frequency component of a subject is turned to a low-frequency component because a light receiving portion of the imaging device is a sampling system. A false signal (moiré) occurs, and particularly a single-panel solid-state color camera using a single image sensor generates a large moiré, which causes deterioration in image quality.

A video camera that suppresses such moiré is described in Japanese Patent Application Laid-Open No. 60-81992.

[0004]

However, in the above prior art, a luminance signal is added by adding a plurality of color signals output from the image sensor corresponding to a plurality of color separation filters provided on the light receiving surface of the image sensor. When obtaining the image sensor, the addition ratio of each color signal is optimized to suppress the moiré generated in the luminance signal. When used, there is a problem that the moire cannot be suppressed by the above-described conventional technology. Japanese Patent Application Laid-Open No. 57-39 discloses an image sensor of the type in which color signals are mixed and output inside the image sensor.
684. (Hereinafter, such a method is referred to as a mixed reading method.) An object of the present invention is to eliminate the above-mentioned problems of the prior art and to provide a solid color camera with less moire.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to set a luminance signal addition ratio in a solid-state color camera that generates a luminance signal by adding signals obtained from different color separation filters output from an image sensor. This is achieved by providing a means for performing the operation and changing the addition ratio every horizontal period.

Means for setting an addition ratio of the luminance signal is provided,
By switching this for each horizontal period, it is possible to correct the effective sensitivity variation for each horizontal period caused by the mixture of pixels as in the mixed readout method. Can be suppressed.

[0007]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing one embodiment of a solid-state color camera according to the present invention.
Is a preamplifier circuit, 3 is a luminance signal generation circuit, 31 to 34 are amplification circuits, 35 is a line switch, 36 is an addition circuit,
Denotes a signal processing circuit, 5 denotes a color signal generation circuit, and 6 denotes a color encoder.

In FIG. 1, the output of the image sensor 1 is amplified by preamplifier circuits 21 and 22 and then supplied to a luminance signal generation circuit 3 and a chrominance signal generation circuit 5. The luminance signal generation circuit generates the luminance signal Yh by adding the signals supplied from the preamplifier circuits 21 and 22 at an addition ratio described later. At this time, the addition ratio is changed every horizontal period. The color signal generation circuit 5 calculates the signals supplied from the preamplifier circuits 21 and 22 to generate the red signal R, the blue signal B, and the low-frequency component Ye of the luminance signal, and supplies them to the signal processing circuit 4. . In the signal processing circuit 4, after performing signal processing such as white balance adjustment and gamma processing, the luminance signal Y and the color difference signal R are output.
−Y and BY are supplied to the color encoder 6, which forms, for example, a color video signal of the NTSC system from these signals and outputs it from the output terminal 7.

FIG. 2 is a block diagram showing an example of the image pickup device 1 in FIG. 1, wherein 8 is a horizontal shift register, 9 is a vertical shift register, 14 is a picture element, 101 to 104 are vertical gate lines, 111 to 111. 116 is a vertical signal line, 121 to 12
Reference numeral 6 denotes a horizontal switch, and 131 and 132 denote signal output terminals. The signals output from 131 and 132 correspond to the signals supplied to the preamplifier circuits 21 and 22 in FIG. 1, respectively.

The image sensor shown in FIG.
The operation will be described below with reference to an S type.

When a certain row is selected by the vertical register 9 and a high-level voltage is applied to a vertical gate line of the selected row, a signal stored in each picture element of the selected row is read out to a vertical signal line. Thereafter, during the horizontal scanning period, the horizontal switches 121 to 126 are operated by the horizontal shift register 8.
Are sequentially turned on, a video signal corresponding to one horizontal scan is output.

In the present image pickup device, pseudo interlaced reading as described below is performed in accordance with interlaced scanning. In one horizontal period, two adjacent rows are read simultaneously. For example, vertical gate lines 101 and 102
At the same time, and in the next horizontal period, the vertical gate line 10
3, 104 are selected simultaneously. In FIG. 2, for convenience,
Only 4 picture elements in the vertical direction and 6 picture elements in the horizontal direction are shown.
In the same manner, reading of two rows adjacent to each other in one horizontal period is repeated, and scanning of all picture elements of the image sensor is completed during one field. In the next one field, similarly, two adjacent rows are selected at the same time, but the combination of the selected two rows is shifted by one row. On the other hand, a combination of the vertical gate lines 102, 103 and 104 and the vertical gate lines of the next row is selected to simultaneously read signals of two adjacent rows.

When reading signals in this manner, each of the vertical signal lines 111 to 116 is connected to the horizontal switch 121.
Through 126, different signal output terminals 131 for each row,
132, the output terminal 131
A mixed signal of W and Cy and a mixed signal of G and Cy are output alternately every horizontal period. From the output terminal 132, a mixed signal of G and Ye and a mixed signal of W and Ye are alternately output every horizontal period. Where W, G,
Cy and Ye indicate signals obtained from picture elements provided with transparent, green, cyan, and yellow color separation filters, respectively.

FIG. 3 is a diagram schematically showing signal waveforms output from the output terminals 131 and 132.
52 indicates signals output from the output terminals 131 and 132 during one horizontal period, and signals 153 and 154 indicate signals output from the output terminals 131 and 132 during the next one horizontal period. From 131 and 132, two types of signals of different combinations are mixed and output every one horizontal period.

Thus, the output terminals 131 and 13 of the image pickup device
2 are amplified by preamplifier circuits 21 and 22 (FIG. 1) and then added at a predetermined addition ratio in luminance signal generating circuit 3 to generate a luminance signal. In the present invention, the addition ratio is changed every horizontal period.
The luminance signal Y is generated by the following operation alternately for each horizontal period. When each of them is represented by Y1 and Y2, Y1 = α (W + Cy) + β (G + Ye)-(1) Y2 = α (G + Cy) + β ( W + Ye)-(2) Here, α and β indicate the addition ratio (addition coefficient) of each signal. By changing α and β according to the formulas (1) and (2) according to the present invention, the luminance signal is changed as described later. Moire generated in the area can be suppressed.

In FIG. 1, reference numerals 31 to 33 denote amplification circuits, 35 denotes a line switch, and the preamplification circuit 2
The signals respectively output from 1 and 22 are alternately amplified by the amplifying circuits 31 and 33 and the amplifying circuits 32 and 34 every one horizontal period, and then added and generated by the adding circuit 36. At this time, if the amplification factors of the amplification circuits 31 and 33 and the amplification factors of the amplification circuits 32 and 34 are set to be different from each other, the addition ratio for each horizontal period can be changed.

FIG. 4 shows another embodiment of the luminance signal generation circuit, which functions similarly to the luminance signal generation circuit 3 in FIG. 31 'and 32' amplification degree variable amplification circuits,
A different voltage is applied to the control terminals 34 ', 35' every horizontal period to change the amplification degree.

FIG. 5 shows moire generated when an image pickup device as shown in FIG. 2 is used. In FIG. 6, 161, 16
Reference numeral 2163 denotes a spatial frequency of an input signal at which a main moiré causing image quality deterioration occurs is shown on a two-dimensional spatial frequency axis. The moire intensities M1, M2, M3 occurring at the spatial frequencies of 161, 162, 163 are respectively

[0019]

(Equation 1)

## EQU2 ## Where α1, β1
And α2, β2 indicate the addition ratios α, β in equations (1) and (2) with subscripts to distinguish between equations (1) and (2). The strength of the moiré shown here is described in "Review of Moiré of High-Resolution MOS Single-Plate Color Camera", pp. 89-90, Proceedings of the National Institute of Television Engineers of Japan (July 1984).

In the equations (3) and (5), the second item in the route on the right side indicates a component whose polarity is inverted for each field, and is visual when a still image is captured. Inconspicuous. Therefore, in order to suppress these moirés, α1, α2, β are set so that the first term in the route on the right side of the equations (3) and (5) and the value of the equation (4) become 0.
The values of 1, β2 may be determined. When the addition coefficient is not changed every horizontal period, that is, when α1 = α2, β1 = β2, the moiré of the equations (4) and (5) cannot be suppressed in general. For example, α1 = K / W, α2 = K /
G, β1 = 1 / G, β2 = 1 / W, K = (2 + Ye / G
By selecting an addition coefficient such as + Ye / W) / (2 + Cy / G + Cy / W), it is possible to suppress all the moiré in the expressions (3) to (5).

In setting the addition coefficient, W, Cy,
Usually, the values of the Ye and G signals may be set to the signal amounts of the respective signals when an achromatic subject is imaged. However, since the optimal addition coefficient changes depending on conditions such as the picture, hue, and color temperature of the subject, various settings can be made according to these conditions.

FIG. 6 shows another embodiment of the present invention, and 17 is a color separation circuit. The image sensor 1 'is shown in FIG.
Is a CCD type image pickup device having a structure as shown in FIG. FIG. 8 shows the signals output at this time. G + Ye, W for each horizontal period
A + Cy dot sequential signal 191 and W + Ye, G + Cy dot sequential signals 192 are output alternately. Therefore, in order to change the addition ratio when generating the luminance signal, the output signal must be set to 1
Sampling is performed for each pixel, and the signals W + Cy and G + Ye and the signals G + Cy and W + Ye
You need to separate the signals. The color separation circuit 17 (FIG. 6) is a circuit for this purpose. After a signal similar to that of FIG. 3 is obtained, moiré can be suppressed in exactly the same manner as in the embodiment of FIG.

In the above embodiment, the color filter arrangement shown in FIG. 2 has been described as an example. However, the present invention can be applied to a similar filter arrangement as shown in FIG. The color filter array a in FIG. 9 is different from the color filter array shown in FIG. 2 or 7 in that the horizontal positions of W and G are inverted for each row, whereas the horizontal positions of Cy and Ye are changed for each row. It has been inverted. The addition coefficient of the luminance signal when such a filter array is used may be obtained by replacing W and Cy and Ye and G in equations (3) to (5).

The filter arrangement shown in FIG. 9B is different from the filter arrangement shown in FIG. 2 or FIG.
The g (magenta) filter is used. In this case, W may be replaced with Mg in the equations (3) to (5) to determine the addition coefficient.

FIG. 10 is an embodiment showing the configuration of the luminance signal generating circuit 3 in FIG. In FIG.
To 104 are resistors, 105 and 106 are analog switches,
107 is an inverter. In this embodiment, the resistance 101
１０４104 are used to set an addition coefficient by resistance division. Resistors 101, 102 and 103, 10
The luminance signals generated by the combination of the four are switched by the analog switches 105 and 106 every one horizontal period. A pulse whose polarity switches every horizontal period is applied to the pulse input terminal 108 to operate the analog switches 105 and 106.

In this embodiment, since an addition coefficient can be set by resistance division without using an amplifier circuit, the circuit configuration can be simplified.

[0028]

According to the present invention, even in a solid-state color camera of the mixed readout type, it is possible to optimize the addition ratio when a luminance signal is obtained by adding output signals of an image sensor.
A solid color camera with good image quality with little moiré can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a configuration diagram of an image sensor.

FIG. 3 is an output waveform diagram of an image sensor.

FIG. 4 is a block diagram of a luminance signal generation circuit.

FIG. 5 is a graph showing the occurrence frequency of moiré.

FIG. 6 is a block diagram showing one embodiment.

FIG. 7 is a configuration diagram of an image sensor.

FIG. 8 is a signal waveform diagram.

FIG. 9 is a schematic diagram illustrating an example of a color filter array.

FIG. 10 is a configuration diagram of a luminance signal generation circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image sensor 3 Luminance signal generation circuit 31-34 Amplification circuit 35 Line switch 36 Addition circuit 4 Signal processing circuit 5 Color signal generation circuit 6 Color encoder 3 'Luminance signal generation circuit

Claims (1)

[Claims] 1. A CCD type image pickup device having a filter in which different types of color separation filters are arranged in adjacent rows, a reading means for mixing and reading two adjacent rows of image pickup devices, and a mixed read color. In a solid-state color camera including a color separation unit that separates a signal and a luminance signal generation unit that obtains a luminance signal by adding the read color signals, the luminance signal generation unit includes a horizontal scanning period and a next horizontal scanning period. A solid-state color camera which adds color signals at different addition ratios in a horizontal scanning period.