JPS61126886A - Solid-state color photographing device - Google Patents

Abstract

PURPOSE:To get a high quality colored image by calculating mutually >=two output signals of the 1st, 2nd, 3rd and 4th synchronous detection circuits which applies synchronous detection to a modulation signal R and a modulation signal B both are separated in color by two carrier waves whose phase are shifted by pi/2. CONSTITUTION:Bm(t), Rm(t) are detected by three synchronous detection circuits composed of a multiplication circuits 41-43, LPFs 44-46 of 500kHz cut-off frequency and a transfer circuit 47. A carrier wave to be put in a multiplication circuit 43 is phiB0, and carrier wave to be put in the multiplication circuit 42 is phiR0. A carrier wave phiR90 to be put in a multiplication circuit 43 shifted by pi/2 in phase from phiR0. Therefore, B(t)0, R(t)0 which are originally the same in phase and the same in synchronous detection output can be obtained from LPFs 44, 45. A D/C synchronous detection output R(t) by a carrier wave which shifts by pi/2 in phase with the carrier wave of the modulated R signal can be obtained from an LPF46. After controlled in gain on the basis of the fixed level by a gain control circuit 48, R(t)90 is added to addition circuit 50 to get B(t). MTF is improved and B detection wave in which moire is decreased, can be obtained because R(t)90 of good resolution is added to B(t).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a single-carrier frequency separation type solid-state color imaging device that reduces moiré in color signals obtained by addition.

[Technical background of the invention and its problems]

A solid-state color imaging device using a single-carrier frequency separation type that uses one solid-state imaging device can produce red (
Taking advantage of the frequency interleaving relationship between the blue (hereinafter referred to as R) signal and the blue (B) signal, a comb-shaped filter is used to separate RlB. FIG. 6 shows an example of the arrangement of color filters mounted on the front surface of the solid-state image sensor in such an image sensor. Figure 6 shows full color light transmission (
It consists of four colors: a green (hereinafter referred to as "W") filter, a green (hereinafter referred to as "G") filter, a cyan ("Cy") filter, and a yellow (lifflYe) filter. The unit of one color filter corresponds to one pixel of the solid-state GII sensor, and two pixels in the vertical direction have the same color due to the interlacing of the television screen. Furthermore, Fig. 7 shows a configuration diagram of a comb filter for color separation.The output signal from the solid-state image sensor is passed through a predetermined band pass filter (hereinafter referred to as BPF).
After the modulated color signal components are extracted in step (3), they are applied to a comb filter consisting of a delay line α for one horizontal scanning period (hereinafter referred to as IH) and an addition circuit t13% subtraction circuit I, and are color-separated. That is, the B signal is obtained from the addition output, and the R signal is obtained from the subtraction output. This is because, in the color filter array of FIG. 6, the B component is in phase between two scanning lines within one field, and the ordinary component is in opposite phase, so that they are in a frequency interleaved relationship with each other.

In this way, in the case of a uniform object, the R component can substantially double the horizontal frequency of spatial sampling due to the vertical correlation between scanning lines, and becomes equivalent to the G component that exists over the entire surface. However, since the B component is in phase between the scanning lines, the spatial sampling frequency in the horizontal direction is 1/2 that of the G and F. Therefore, the B component has a large level of aliasing distortion due to spatial sampling, and the G ,
The balance between the resolution and the R component was also poor, and in the reproduced image, phenomena called moiré and false signals, which were major causes of image quality deterioration, occurred.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid-state color imaging device that eliminates the above-mentioned drawbacks of the prior art, reduces the moiré component of the B signal, and provides a high-quality color image with less false signals and moiré.

[Summary of the invention]

The present invention provides a single carrier frequency separation type solid-state imaging device including first and second synchronous detection circuits that synchronously detect a color-separated modulated R signal using two carrier waves whose phases are shifted by "/2" from each other; The phase of the separated modulated B signals is “
Comprising @3 and 4th synchronous detection circuits that perform synchronous detection using two carrier waves shifted by /2, and an arithmetic circuit that mutually calculates at least two or more output signals among the output signals of the four synchronous detection circuits. By doing so, the above objectives are achieved.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a circuit configuration diagram of a single-carrier frequency separation type solid-state image pickup device using one solid-state image pickup device of the present invention.

The optical image incident through the imaging lens Q1) passes through a color filter @ and is imaged on the photosensitive surface of a solid-state imaging device, such as a charge-coupled imaging device (hereinafter referred to as a CCD imaging device) (c). For example, the CCD image sensor (c)
0 pixels and 400 pixels in the horizontal direction are arranged.

Further, the color filters (A) are arranged, for example, as shown in FIG. That is, in the n-th scanning line, the W filter and the G filter are arranged alternately in the horizontal direction at a 2-pixel period, and the
In the scanning line, the ay filter and the YC filter are arranged alternately in the horizontal direction at a two-pixel period, and in the subsequent horizontal scanning lines, the two horizontal lines are alternately repeated. In addition, for the interlacing of TV Gillan,
In odd fields, scanning lines n, n+1,... are read out, and in even fields, scanning lines n+263 are read out.
.

It is read out with a shift such as n+264.

The light that has been spatially modulated through such a color filter (to) is electrically converted to a CCDC image sensor by driving the CCDC image sensor with a drive pulse converted through a pulse signal drive circuit (b) obtained from a pulse generation circuit (to). The modulated electrical signal is then amplified to a predetermined level via an amplifier. Since the color filter (c) is a frequency-separated array,
The output signal of the amplifier @ is a combination of a luminance signal, which is a DC component, and R and B modulated color signal components, which are in a frequency interleaved relationship with each other. horizontal direction is 40
In the case of 0 pixel, the center frequency of the modulated color signal is 3.58MH
It is z.

The output of this amplifier Q4 has a fast-cutting frequency of 3.01, respectively.
1i [Hz, 0.5 MHz first low-pass filter (hereinafter referred to as LPF) No. *E (C) and second LPF@, respectively, to become a luminance signal Y and a low-frequency chrominance signal YL.

The low frequency color signal YL is applied to a second subtraction circuit (to).

On the other hand, the passband of a part of the output signal of increase@a@ is 3.58
MHz±0.5 MHz BPF @ through-modulation color signal C
becomes. This modulated color signal C has R and B in a frequency interleaved relationship, so the IH delay line (end), adder circuit -
and a first subtraction circuit (30), the signal is separated into a modulated R signal and a modulated B signal. In this case, the modulated B signal is obtained from the adder circuit (2) and the modulated R signal is obtained from the first subtractor circuit (30) due to the arrangement of color filters (22).These modulated R1B signals are The signal is detected by the reduction circuit Gυ, and the seven elements are reduced to become R and B signals.A part of these R and B signals is used together with the low frequency color signal YL to generate the G signal in the second subtraction circuit GSD. The luminance signals Y and G and the 8.Light signal obtained as above are added to the color encoder (to) K, and the NT8C signal, which is one of the standard television signals, is obtained from the output terminal (to). The structure is such that

Here, the detection and moiré reduction circuit 01 which is the main point of the present invention
) will be explained in detail with reference to the drawings. FIG. 2 shows an internal configuration diagram of the detection and moiré reduction circuit C31). 1st
The color-separated modulation B, which is the output of the comb filter in the figure,
Let the R signal be the narrow 0Rm(t) in FIG. These Bm(t) and Rm(1) are multiplier circuits ha to (43
Detected by three synchronous detection circuits consisting of LPF (44 to -1 phase shift circuit circuits) with fast-acting frequency 2>E 500KHz.Here, the general transmission wave that enters the multiplier circuit (41) K is the modulated B signal and the frequency φB0 has the same phase as the multiplier circuit (
The carrier wave entering c) is φ8° with the same frequency and phase as the modulated R signal, and the carrier wave φ1. . Is it phase shift circuit 4? ) The phase is shifted by '/2 from K and φ.

O Therefore, from LPFf44 and (c), the original in-phase synchronous detection outputs B(00 and R(t)) are obtained, respectively, and from Lppt4, the phase is shifted by f/2 from the carrier wave of the modulated and harmonic B signal. Quadrature synchronous detection output R(t) by carrier wave,
o is obtained.

When the circuit operates in an ideal state, B(t). , R(t)9
0, the output signal is O, but in reality the multiplier circuit (6
), an output similar to the differential waveform of the in-phase synchronous detection output is obtained as the orthogonal synchronous detection output.

The situation will be explained using FIGS. 3 and 4.

FIG. 3 shows an example of a multiplication circuit, which is a so-called double-balanced differential amplifier. Taking the iR times signal example, the modulated R(t) signal is input from the terminal (64), and the carrier wave φ8. . is input from the terminal (63). Dan Q is the 4th
In the case of the waveform shown in Figure (a), the waveform of the collector current of transistors (61) and (62) in Figure 3 is
) and (C), there is a small time difference Δt between them.
occurs. This is a delay corresponding to the delay time from the base to the emitter of the transistor (61). Due to this minute time difference and variations in the frequency characteristics of the transistors themselves, the original in-phase synchronous detection output section). is shown in FIG. 4(d), the orthogonal synchronous detection output Fat
)9o provides an output similar to the differential waveform shown in <e) of the same figure. However, the fast-acting frequency is 500K.
Since the signal passes through the Hz LPF f43, mu and o are also responses within that band.

After the gain of R+(t) and o is controlled to a predetermined level by the gain control circuit 6υ, the in-phase synchronous detection output B(
It is added to the adder Q together with t)o, and the final detection output B(t) is obtained. This B(t) is R(t) with good resolution.

is added, the contour is emphasized in the low frequency part, and the level is enhanced in the part relatively close to 500 KHz. and as a result MTFQldodulati
On Transfer Function) is improved, and a B detection signal with reduced noise can be obtained. In order to maintain white balance as a whole by correcting the detection signal, R(t)so is gain controlled to a predetermined level by the second gain control circuit 531C. Enters the adder circuit (incorporated) and becomes the final 8-detection signal &
0 is obtained.

Although the seven-array reduction and detection circuit has been described with reference to FIG. 2, the circuit configuration is not limited to this. For example, if the color filter array is as shown in FIG. 8, the R component will be in phase and the B component will be in opposite phase between two scanning lines within one field. Therefore, the moiré reduction and detection circuit is constructed as shown in FIG. In FIG. 5, the same parts as in FIG. 2 are given the same numbers.

That is, a multiplication circuit (6
1) is provided, and the carrier wave φBo is transferred by a phase shift circuit (63).
/2 phase shifted carrier wave φB90 multiplication circuit (61)
added to. The output of the multiplication circuit (61) is L P F
(62) becomes the detected signal B(0,.), which is level-adjusted by the gain control circuit (c) 1 and then added to the adder circuit fi, 5m to form the detected signal B(t). ,
R(t). Correct.

Although the number of horizontal pixels of the CCD image sensor is described as 400 as an example, it is not limited to this. Also, as an image sensor, CC
Although the D image sensor is taken as an example, the present invention is not limited to this, and other image sensors such as an MO8 type image sensor may be used. Furthermore, the charge storage method of the CCD image sensor may be field storage instead of the frame storage described in the embodiment.

In any case, the present invention can be implemented with a single carrier frequency separation type color camera. As described above, the present invention can be modified in various ways without departing from the spirit thereof.

〔Effect of the invention〕

According to the present invention, the detection J
Conventionally, the resolution of the B component, which is in phase between adjacent scanning lines in the same field, is poorer than that of G, and is one of the major causes of moiré and false signals in reproduced images.
It had become. However, by adding an ordinary orthogonal synchronous detection signal with good resolution and characteristics similar to the differential characteristics, the contour is emphasized on the low frequency side and the amplitude is enhanced at frequencies close to 500 KHz, so the detection B The response of the signal can be compensated for.

This feature greatly reduces moiré and false signals, which are one of the main causes of image quality deterioration. In the case of this achromatic image, which is often the case, the orthogonal synchronous detection output waveform becomes natural, and the effect of the present invention is even greater. Furthermore, since it is a synchronous detection method, the linearity of the detection characteristics is good from dark to bright areas of the subject, that is, from low to high signal levels, and it has the advantage that faithful color reproduction images can be obtained. Furthermore, the double-balanced differential amplifier constituting the multiplier circuit is also required to have high performance (it has the manufacturing advantage of being able to achieve the conventional performance of 1).

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a solid-state color imaging device according to the present invention, FIG. 2 is a block diagram showing the main part of FIG. 1 in detail, and FIG. 3 is an example of the main part of FIG. A circuit diagram showing
4 is a waveform diagram for explaining the operation of FIG. 3, FIG. 5 is a circuit configuration diagram showing another example of the main part of FIG. 2, and FIG. 6 is a configuration diagram showing an example of a color filter arrangement. , FIG. 7 is a circuit configuration diagram of a comb filter, and FIG. 8 is a configuration diagram showing another example of a color filter arrangement. Ru...P solid-state image sensor, Line...1 horizontal scanning period delay line, Fourth...addition circuit, Blade...subtraction circuit. 41-43, 61...Multiplication circuit, 44-46, 62...Low pass filter, 4
7, 63...Phase shift circuit, 48.49...Gain control circuit, 51...Addition circuit. Figure 1 Figure 2 Figure 38 Figure 4 Figure 512!

Claims (1)

[Claims] Optical information imaged on a solid-state image sensor in which pixels are arranged two-dimensionally through a color filter array is converted into an electrical signal by the solid-state image sensor and sequentially read out. In the single carrier frequency separation type color solid-state imaging device, the signal is added to a signal delayed by one horizontal scanning period to separate the first modulated color signal and subtracted to separate the second modulated color signal. a first detection circuit that synchronously detects a first modulated color signal with a first carrier wave; a second detection circuit that synchronously detects the second modulated color signal with a second carrier wave; and the second modulation circuit. The phase of the color signal and the second carrier wave is π/
a third detection circuit that performs synchronous detection using two different third carrier waves; and means for adding the output of the third detection circuit to the output of the first and second detection circuit to obtain a first and second color signal. A solid-state color imaging device comprising: