JP2776849B2 - Solid color camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state color camera, and more particularly to a solid-state color camera provided with a color separation filter on an image sensor to obtain a color video signal.

[Conventional technology]

Solid-state color cameras using a solid-state image sensor in an image pickup unit include a three-chip type using three image sensors and a single-chip type using one image sensor. The single-panel type is the mainstream for solid color cameras for home use that require small size, light weight, and a fixed price.

In a single-chip color camera, a mosaic or striped color separation filter is provided on an image sensor, and a color signal corresponding to each of these separation filters is calculated to obtain a luminance signal and a color difference signal. In such a single-plate system, the sampling density of each color signal is inevitably low, and a false signal, that is, a moire generated by shifting a high frequency component of an input to a low frequency band is large, thereby deteriorating image quality.

As a method of suppressing the moiré generated in the luminance signal, it is known that the luminance moiré can be minimized by adding the respective color signals to obtain a luminance signal and setting an addition ratio (luminance matrix) to the reciprocal of the sensitivity ratio of each color signal. ing. But it is impossible to moire minimize simultaneously to the input of the sensitivity of any color because it depends on the input light color (spectral distribution) color signals. For this reason, a method of setting a luminance matrix that minimizes moire at a certain color temperature with respect to achromatic input light is used. This method is described in detail in “Review of Moire of High-Resolution MOS Single-chip Color Camera”, pp. 89-90, Proceedings of the National Conference of the Institute of Television Engineers, July 1984.

However, as described above, moire has the property of being dependent on the color of the input light and of being particularly noticeable in a portion where the color saturation is high. Therefore, in the conventional method of setting a luminance matrix in which moire is minimized with respect to achromatic input light, large moiré that changes depending on the color of the input light and occurs with high saturation of input is sufficiently suppressed. I couldn't.

[Problems to be solved by the invention]

The object of the present invention is to eliminate the disadvantages of the prior art described above,
An object of the present invention is to provide a solid color camera capable of sufficiently suppressing moiré even for a subject having a high degree of color saturation.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, a solid-state color including a plurality of color separation filters in an imaging unit, and a luminance signal generation circuit for generating a luminance signal by adding a plurality of color signals corresponding to the color separation filters. The camera is characterized in that means for controlling the addition ratio of each color signal is provided so that the product of the addition ratio of each color signal and each color signal level or the temporal average level of each color signal is substantially constant.

〔Example〕

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram showing an example of a solid-state color camera according to the present invention, wherein 1 is an image sensor, 2 ₁ , 2 ₂ , 2 ₃ are amplification circuits, 3 is a luminance signal generation circuit, and 4 is a color signal matrix circuit. 5, a process circuit; 6, a color encoder; and 7, a control circuit.

In the figure, an image sensor 1 has a color separation filter
As shown in the figure, it has a light receiving surface on which each color separation filter is arranged, and outputs a W signal Ye signal and a Cy signal to different signal lines. These signals are respectively amplified by amplifier circuits 2 ₁ , 2 ₂ , 2 ₃
The signal is amplified and supplied to the luminance signal generation circuit 3 and the chrominance signal matrix circuit 4.

W signal in the addition ratio luminance signal generating circuit 3 to be described later, by adding the Ye signal and Cy signal, the luminance signal (i.e. Y ₁ signal)
Generate On the other hand the color matrix circuit 4 calculates the W signal, Ye signal and Cy signal, the luminance signal (i.e. Y ₂ signal) and the R signal for generating a color difference signal to produce a B signal. The generated Y ₁ signal, Y ₂ signal, R signal, and B signal are subjected to known signal processing such as gamma correction in the process circuit 5, and the Y ₁ signal, the (Y ₂ -R) signal, and the (Y ₂ -B) signal are processed. Two color chain signals of the signal are generated. These signals are supplied to a color encoder 6 to form, for example, an NTSC color video signal, which is supplied to an output terminal 8 as a camera output signal.

Figure 2 is a block diagram showing the configuration of a luminance signal generation circuit 3 of FIG. 1, 3 _1, 3 _2, 3 ₃ is the amplification factor variable amplifier circuit, 3 ₄ are additive circuit.

Amplifier circuit 2 ₁ to 2 ₃ In the drawing (FIG. 1) W which is output from, Cy, Ye signal, the control circuit 7 amplification degree variable amplifier which is controlled in amplification degree to be described later by (Figure 1) after being amplified by the circuit 3 ₁ to 3 ₃ are added are supplied to the adding circuit 3 _4, Y ₁ signal is generated.

Incidentally, now W signal, and addition ratio of the adding circuit 3 ₄ For Ye signal and Cy signal, alpha respectively the product of the level ratio of each signal, beta, when the gamma, generated with the difference in the sensitivity ratio of the light-receiving element The intensity M of the moire is expressed by the following equation.

From equation (1), α = β = γ, that is, the W signal, Ye
By making the product of the signal and the addition ratio of the Cy signal and the signal level substantially equal to each other, in other words, by making the addition ratio of the respective signals substantially equal to the reciprocal of the respective signal level ratios. Moire can be suppressed almost completely.

Therefore amplification factor variable amplifier 3 ₁ to 3 ₃ illustrates the amplification of characteristic of the amplifier to 3 ₃ to have the amplification degree of the reciprocal of the signal level as described above. In the figure, the horizontal axis indicates the relative value of the control signal to the reference signal, and the vertical axis indicates the amplification. By using the signal levels of the W, Cy, and Ye signals with respect to a certain reference signal as the control signal, the above-described moiré suppression condition is satisfied. The reference signal may be one of the W signal, the Cy signal, and the Ye signal, for example, a Ye signal, or may be an average value of each signal.

FIG. 5 is a block diagram showing an example of the configuration of the control circuit 7 shown in FIG. 1, 7 _{1-7 3} low-pass filter, 7 ₄
The reference signal generating circuit, 7 _{5-7 7} is a division circuit.

Reference signal generating circuit 7 ₄ W at the output from the low pass filter 7 ₁ to _7-3, Ye, from Cy signal, and outputs the average value. This as a reference signal, the division circuit 7 ₅ to _7-7, W,
Ye, detects a relative value to the reference signal of Cy signal, this amplification factor variable amplifier 3 ₁ to 3 ₃ 4 amplification degree as shown in the figure as a control signal for controlling the amplification degree of the (Figure 2) Control.

By reducing the time constant of the low pass filter 7 _{1-7 3,} it is also possible to correspond to the instantaneous change in the color of the object also by increasing the time constant, may correspond to slowly change in color It is possible.

FIG. 6 shows the moiré suppression effect when the addition ratio of the W, Ye, and Cy signals is controlled as described above. FIG. 6 shows the intensity of the moiré with respect to the color of the input light. The moiré intensity when the moiré is suppressed according to the present invention is 12b, and the addition of each color signal is minimized with respect to the white light input. 12a shows the moire intensity when the ratio is fixed. According to the present invention, it can be seen that the moire intensity can be almost completely suppressed for input light of any color.

FIG. 7 is a block diagram showing an embodiment of the present invention. Reference numeral 8 denotes a color detection circuit, parts corresponding to those in FIG.

In this embodiment, the W signal, the Ye signal,
An average signal level of each of the Cy signals over the entire subject is detected. The control circuit 7 according to this signal level
, A control signal for the W, Cy, and Ye signals is generated, and control is performed so that each signal is amplified with an amplification degree of a reciprocal of the average level of each color signal over the entire subject.

In this embodiment, the perfect moire cannot be suppressed as in the above-described embodiment, but since a luminance signal is generated at a constant addition ratio over the entire screen, a stable image can be obtained.

In the above-described embodiment, the case of W, Ye, Cy shown in FIG. 3 has been described as the color filter of the image sensor, but the present invention can be applied to other color filter arrangements.

FIG. 8 is a block diagram showing an embodiment to which the present invention is applied when the color filter of the image sensor has a four-color complementary picture element configuration. It has the same configuration as the embodiment shown in FIG.
2 ′ _{1 to} 2 ′ ₄ are amplification circuits, 3 ′ is a luminance signal generation circuit,
Reference numeral 7 'denotes a control circuit which can suppress moire by the same operation as in the above-described embodiment.

FIG. 9 (a) shows the configuration of this complementary color 4 picture element filter. Also, in the case of the primary color filter shown in FIG. 9B, the W, Cy, and Ye signals shown in FIG. 1 may be replaced with R, G, and B as they are, and the moire may be suppressed in the same manner. it can.

〔The invention's effect〕

According to the present invention, moire generated in principle in a solid-state imaging device provided with a color separation filter can be significantly reduced, and moire generated in a subject of any color can be sufficiently suppressed. An excellent solid color camera can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of a luminance signal generating circuit of FIG. 1, and FIG. 3 is a configuration of a color separation filter of a solid-state imaging device of the embodiment. FIG. 4, FIG. 4 is a graph showing the characteristics of the amplifier circuit, FIG. 5 is a block diagram showing the configuration of the control circuit, FIG. 6 is a graph showing the moire suppressing effect, and FIGS. FIG. 9 is a block diagram showing one embodiment, and FIG. 9 is a configuration diagram of a color separation filter. 1 ... solid-state imaging device, 3, 3 '... luminance signal generation circuit, 3 ₁ ,
3 ₃ …… Amplification degree variable amplification circuit, 3 ₄ …… Addition circuit, 7,7 ′
... A control circuit, 7 _{1 to} 7 _{3, a} low-pass filter, 7 _{4, a} reference signal generation circuit, 7 _{5 to} 7 _{7, a} division circuit, 8, a color detection sensor.

Claims (1)

(57) [Claims] An image pickup section having a plurality of color separation filters; and an addition ratio of each color signal level and each color signal based on a level of each color signal obtained from each color signal output from the image pickup section. Means for controlling an addition ratio of the respective color signals so that the product of the color signals becomes substantially equal to each other, and a luminance signal is generated by adding the respective color signals output from the imaging unit by the addition ratio controlled by the control means. A solid-state color camera, comprising: