JPS61287396A - Color image pickup device - Google Patents

Abstract

PURPOSE:To image pick up all color components with fidelity b respectively gamma correcting a chrominance signal and a luminance signal produced from an output color difference signal of a solid-state image pickup element. CONSTITUTION:In an adding circuit 40 for operating color difference signals 2R-G, 2B-G obtained in a demodulating circuit 22 and a narrow band luminance signal generates chrominance signals R, B and the obtained chrominance signals R, B are respectively supplied to gamma correcting circuits 46, 48. Luminance signal extracted in LPFs 12, 14 are respectively supplied to gamma correcting circuits 18, 54. From these corrected chrominance signals R, B and the luminance signals, the color difference signals R-Y, B-Y are produced and a composite video signal is obtained. Thereby, similarly to any color component of R, G, B the gamma correction is applied, so that the fidelity to a hue is good and a color reproduction is satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a color imaging device, and particularly to a single-chip color imaging device using a solid-state imaging device having a color mosaic filter of complementary colors.

[Prior Art] In order to configure a single-chip color imaging device using one solid-state imaging device, a color separation filter in which filter elements of different color components are arranged in a mosaic pattern is installed on the imaging surface of the solid-state imaging device. The zero color separation filter that needs to be provided is red (R
), green (G), blue CB), and yellow (Ye: transmits R and G), cyan (
Complementary colors such as Cy: transmits B and G) and transparent/white (W:
There are complementary colors that transmit all of R, G, and B, or a combination of G. The latter has higher light transmittance and is superior in terms of sensitivity and resolution. As a conventional example of a single-chip color imaging device using this complementary color separation filter, see Journal of the Society of Television Engineers, vol. 37, No. LO (1
983) (7) r7. r-rudo accumulation mode CCD
``Single plate coloring method'' (Sone).

Ishikawa, Hashimoto, Kuroda, Okubo).

Here, Cy, Ye, magenta (
A color separation filter including Mg (transmits R and B) and G is also used. The field accumulation mode is a readout mode in which the signal charges of two adjacent pixels that are different in the vertical direction are mixed in the A field and the B field, and has the advantage that there is less afterimage compared to the frame accumulation mode. Then, even if two vertical pixels are mixed and read out, the color separation filter is used so that the luminance signal is equal in each field and each line, and at least two types of color signals are obtained in two horizontal lines. The color arrangement has been determined. Furthermore, the number of pixels in the horizontal direction is repeated in two rows to ensure the frequency bandwidth of the luminance signal. From these, the color array of the color separation filter is a repeating array of 2 columns and 4 rows.

A conventional example of a video signal processing circuit for a COD camera having such a color separation filter will be described with reference to FIG. An optical image of a subject entered through an imaging lens 6 is entered into an imaging plane of a solid-state imaging device (C0D in this case) 10 via a color separation filter 8 as shown in FIG. 2, and is imaged. The output signal of C0D10 is passed through a low pass filter (LPF
) 12.14 and is supplied to a bandpass filter (BPF) 16. The passband of LPF12.14 is 3M each.
Hz, 0.5MHz. The center frequency of the BPF 16 is 3.58 MHz and the bandwidth is about 1 MHz.The color arrangement of the color separation filter 8 is as shown in Fig. 2, so for each line (Cy+Ye)+(Mg+G)= (
B+G+R+G)+ (R+B+G)=2R+3G+2
A luminance signal of the B component is obtained. A high band luminance signal Y and a narrow band luminance signal H'YL are obtained from the LPFs 12 and 14, respectively. The high-band luminance signal output from the LPF 12 is input to the composite video signal circuit 20 via a gamma (γ) correction circuit. The output of BPF16 is sent to demodulation circuit 2
2. It is input to the addition/subtraction circuit 26 via the LPF 24.

The demodulation circuit 22 subtracts the outputs of the odd columns from the outputs of the even columns and alternately outputs the following color difference signals. Here, the color difference signal is (Cy +Mg) - (y e +c) on one line, which is represented as n line in Figure 2.
=(B+G+R+B)-(R+G+G)=28-G
On the other line where the signal is obtained and is denoted as line n+1, (Y e +Mg)-(Cy+G)=(R+G+
R+B)-(B+G+G)=2RG signal is obtained. The narrowband luminance signal output from the LPF 14 is also input to the addition/subtraction circuit 26 . Since the color difference signals necessary to obtain a composite video signal are the R-Y and B-Y signals, the addition/subtraction circuit 26 multiplies the color difference signal and the narrowband luminance signal by an appropriate coefficient, adds them together, and generates the color difference signal. Output R-Y and B-Y. Here, the demodulation circuit 22 outputs two color difference signals for each l line.
Since R-Y and 2B-Y are outputted alternately, the color difference signals R-Y and B-Y are also outputted alternately from the addition/subtraction circuit 26 every l line. Therefore, the output signal of the addition/subtraction circuit 26 is transferred to the IH (one horizontal scanning period) delay circuit 28. Synchronization is performed using a line switching circuit 30. That is, the color difference signal of each line is delayed by the IH period and output from the line switching circuit 30 together with the color difference signal of the primary line. Color difference signals R-Y, B output from this line switching circuit 30
-Y is modulated (3.58 MHz) by the modulation circuit 32 to generate a color subcarrier signal, and this color subcarrier signal is supplied to the composite video signal circuit 20. Composite video signal circuit 20
generates a composite video signal based on this color subcarrier signal, the high band luminance signal output from the γ correction circuit 18, and the synchronization signal.

[Problem to be Solved by the Invention 1] However, in this conventional example, gamma correction is performed only on high-band luminance signals. Since the luminance signal has a correlation with the G signal, when looking at the R, G, and B components separately, gamma correction is performed only on the G component, and no gamma correction is performed on the R and B components. Therefore, such a color imaging device has poor fidelity with respect to hue, and it has been impossible to faithfully capture images with respect to all color components.

This invention was made with attention to such a problem, and it is possible to perform gamma correction equally for all color components in a single-chip color imaging device using a solid-state imaging device having a complementary color separation filter. An object of the present invention is to provide a color imaging device that can faithfully reproduce hue.

[Means for solving the problem] This device includes means for extracting a luminance signal and a first predetermined color difference signal from an output signal of a single-chip solid-state image sensor having a complementary color mosaic filter, and a means for extracting a luminance signal and a first predetermined color difference signal. means for generating a predetermined color signal from the first predetermined color difference signal; means for gamma correcting the luminance signal and the color signal; and generating a second predetermined color difference signal from the gamma-corrected luminance signal and color signal. It is equipped with a means for generating.

[Operation] In this device, a color signal is generated from the output color difference signal of the solid-state image sensor, and each of the color signal and luminance signal is gamma-corrected, so that all color components are faithfully imaged.

[Embodiment] An embodiment of a color imaging device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the first embodiment. The same parts as in the conventional example shown in FIG. 3 are given the same reference numerals, and detailed explanation will be omitted. An optical image formed by the imaging lens 6 is incident on the CCD 10. A color separation filter 8 as shown in FIG. 2 is provided between the imaging lens 6 and the CCD 10. COD l
The output of O is supplied to LPF L2.14 and BPF18.

From LPF L 2.14, each high band luminance signal Y
A narrowband luminance signal YL is obtained. Both the high band brightness signal and the narrow band brightness signal are 2R+3G+2B. The high band luminance signal output from the LPF 12 is input to the composite video signal circuit 20 via the γ correction circuit 18. The output of the BPF 16 is input to the addition/subtraction circuit 40 via the demodulation circuit 22 and the LPF 24. 1 from the demodulation circuit 22
Color difference signals 2R-G and 2B-G are alternately output for each line.

The narrowband luminance signal output from the LPF 14 is also input to the addition/subtraction circuit 40 . This addition/subtraction circuit 40 multiplies the color difference signal and the narrowband luminance signal by a coefficient different from the conventional example, adds them, and outputs color signals R and B instead of the color difference signal. Here, the demodulation circuit 22 generates a color difference signal 2R- for each line.
G, 2B-G are output alternately, so the addition/subtraction circuit 4
The output of 0 also becomes color signals R and B for each line. Therefore, the outputs of the adder/subtracter circuit 40 are synchronized using an IH (one horizontal scanning period) delay circuit 42 and a line switching circuit 44. The color signals R and B output from the line switching circuit 44 are sent to the addition/subtraction circuit 50 via the γ correction circuits 46 and 48, respectively.
．． 52. The narrowband luminance signal output from the LPF 14 is also sent to the addition/subtraction circuit 50.5 via the γ correction circuit 54.
2. Addition/subtraction circuits 50 and 52 subtract the narrowband luminance signal from the gamma-corrected color signal to obtain a color difference signal R.
-Y, B-Y are generated. The color difference signals R-Y and B-Y are converted into color subcarrier signals by the modulation circuit 32 and supplied to the composite video signal circuit 20. The composite video signal circuit 20 generates a composite video signal from this color subcarrier signal, the high band luminance signal output from the γ correction circuit 18, and the synchronization signal.

According to this embodiment, the addition/subtraction circuit 40 that calculates the color difference signals 2R-G, 2B-G obtained by the demodulation circuit 22 and the narrowband luminance signal generates the color difference signals RY, B-Y as in the conventional case. Instead, it generates color signals (primary color signals) R and B. The R and B color signals thus obtained are respectively supplied to γ correction circuits 46 and 48. The luminance signals extracted by the LPFs 12.14 are also supplied to the γ correction circuits 18.54, respectively. Color difference signals R-Y and B-Y are generated from these γ-corrected color signals R and B and the luminance signal, and a composite video signal is obtained as in the conventional example. For this reason, R
, G, and H, gamma correction is applied in the same way, so fidelity to hue is good and color reproducibility is good.

The present invention is not limited to the above-described embodiments and can be modified in various ways, and the configuration of the color separation filter may be arranged in other ways as long as it has complementary color components. In this case, it is sufficient to obtain a color signal once from the color difference signal output from the BPF and the demodulation circuit, perform gamma correction on this signal, and then generate the color difference signals RY and BY.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a single-chip color imaging device using a solid-state imaging device having a complementary color separation filter with good color reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a color imaging device according to the present invention, FIG. 2 is a diagram showing an example of a complementary color separation filter, and FIG. 3 is a solid state having a complementary color separation filter. 1 is a block diagram of a conventional example of a color imaging device using an image sensor. 8...Color separation filter lO...Solid-state imaging device 12.14...Low pass filter 16...Band pass filter 18.46.4B, 54...Gamma correction circuit 20...
・Composite video signal circuit 32...Modulation circuit 40.50.52...Addition/subtraction circuit 42...IH delay circuit Applicant's agent Patent attorney Atsushi Tsuboi Procedural amendment Showa 1961/3/4 Patent Office Director General Ubuya Michibu 1, Indication of the case, Patent Application No. 1988-128990 2, Title of the invention Color WM device 3, Person making the amendment Relationship to the case Patent applicant (037) 7I Rimbus Optical Industry Co., Ltd. 4, Agent No. 17 Mori Building 6, 1-26-5 Toranomon, Minato-ku, Tokyo;
Specification to be amended 7, Statement of contents of amendment IB, page 4, line 9, page 6, line 3, page 6, line 7, page 8, page 8 "High band" written in line 5, line 6, line 8, and line 15 on page 9 is corrected to "broad band." Procedural amendment 615.31 1936/1935 Director General of the Patent Office Ubuya Michibe 1, Indication of the case Japanese Patent Application No. 1988-128990 2, Name of the invention Color Ii Yu device 3, Person making the amendment Relationship to the case Patent Applicant (037) Olympus Optical Industry Co., Ltd. 4, Agent No. 17 Mori Building 6, 1-26-5 Toranomon, Minato-ku, Tokyo.
Target of amendment 7, contents of amendment (1) [2R-
Correct Y, 2B-YJ to r2R-G, 2B-GJ.

Claims (1)

[Claims] A single-chip solid-state imaging device having a complementary color mosaic filter, means for extracting a luminance signal and a first predetermined color difference signal from an output signal of the solid-state imaging device, and gamma of the luminance signal output from the extraction means. a first correction means for correcting the characteristics; and a first correction means for correcting the luminance signal outputted from the extraction means;
means for obtaining a predetermined color signal from a predetermined color difference signal; a second correction means for correcting gamma characteristics of the color signal; and a luminance signal output from the first correction means and a luminance signal output from the second correction means. and means for obtaining a second predetermined color difference signal from the color signal.