JPH04172082A - Digital electronic still camera - Google Patents

Abstract

PURPOSE:To make the S/N of the output signals (G, Mg) of a small level excellent by amplifying the output signals Cy, G, Ye and Mg of a charge coupled type image sensor (CCD) to the full scale of an A/d converter by each amplifier respectively. CONSTITUTION:A charge coupled type image sensor 1, amplifiers 23-26 amplifying the output signal of the image sensor, and an A/D converter 3 converting the amplified signal into digital data are provided. And the amplifiers 23-26 are constructed so as to amplify the output signals Cy, G, Ye and Mg of the CCD 1 respectively and separately. Therefore, it is possible to amplify the output signals Cy, G, Ye and Mg of the CCD to the full scale of the A/D converter respectively. Thus, the influence of a quantization. noise is reduced, and the S/N is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a digital electronic still camera that is less affected by quantization noise and has a good LS/N.

(Prior Art) FIG. 4 is a block diagram showing the configuration of a digital electronic still camera to which the present invention is implemented.

To give an overview of this operation, the output signal from a complementary color checkerboard charge-coupled image sensor (hereinafter simply referred to as COD) is amplified by an amplifier 2 and converted to digital data by an A/D converter 3. .

The digital data is stored in a frame memory 4 whose addresses and the like are controlled by a memory control circuit 6. The digital data stored in the frame memory 4 is subjected to arithmetic processing in the processing unit 5, then encoded in the encoder 7, and converted into an analog signal (NTSC signal) in the D/A converter 8.

In this case, the data is stored in the frame memory 4 in a one-to-one correspondence with the pixels of the CCD 1, and a frame image is output based on the data.

(Problem to be Solved by the Invention) In the digital electronic still camera having the above configuration, the CCD
1 output signals Cy (cyan), G (green),
Ye (yellow) and Mg (magenta) have different output levels depending on the spectral sensitivity characteristics of COD.

When amplifying this with one amplifier 2 as in the past, A
Since the input level to the A/D converter 3 is fixed, the amplification factor is determined so that the output signals (Cy, Ye) with high levels become the full scale of the A/D converter 3. As a result, low-level output signals (G, Mg) cannot be amplified to the full scale of the A/D converter 3 and are more affected by quantization noise, so G
, there was a problem that the S/N of Mg deteriorated.

On the other hand, contrary to the above, low level output signals (G, Mg
) is the full scale of A/D converter 3, the output signal (Cy, Ye) with a high level
If the level becomes excessive and exceeds a predetermined level, colors cannot be reproduced and the colors will be the same, so the amplification factor will be determined based on the output signal (Cy, Ye) with a large level. . The present invention solves these problems by extracting the COD output signals Cy, G, Ye, and Mg separately and amplifying each to the full scale of the A/D converter 3, thereby producing a low-level output. Signal (G,
The purpose is to improve the S/N of Mg).

(Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention includes a charge-coupled image sensor, an amplifier that amplifies the output signal of the image sensor, and a charge-coupled image sensor that amplifies the output signal of the image sensor. An A/D converter that converts a signal into digital data, and the A/D
a frame memory that stores digital data converted by the converter; a memory control circuit that performs address control of the frame memory; a process unit that performs arithmetic processing on the digital data stored in the frame memory; It is composed of an encoder that encodes digital data after arithmetic processing, and a D/A converter that converts the digital data from the encoder into an analog signal, and is connected one-to-one with the pixels of the charge-coupled image sensor. In a digital electronic still camera that stores data in the frame memory in a corresponding form and outputs a frame image based on the stored data, the output signal G of the charge-coupled image sensor
, Cy, Ye, and Mg, respectively.

(Function) The present invention amplifies the output signals Cy, G, Ye, and Mg of the COD by each amplifier up to the full scale of the A/D converter. N can be made good.

(Embodiment) FIG. 1 shows a circuit configuration diagram of an amplifier 2 according to an embodiment of the present invention. In the figure, 21.22 is a switch whose switching contacts 21a and 22a switch at 1/2H (horizontal synchronization frequency), and 23.24.25.26 are amplification factors A, B, and C, respectively.

each amplifier of the output signal Cy, Q, Ye, Mg with D;
27.28 is 2f, (subcarrier frequency) switching contacts 27a and 28a are changeover switches, 29 is l/2
V.

The switching contact 29a is a changeover switch that changes at the vertical synchronization frequency.

The above-mentioned changeover switches 21, 22, 27, 28 and 29 are all electronic switches whose switching operations are performed synchronously,
The drawings are shown schematically for ease of understanding.

Figure 2 is a diagram for explaining the reading method from the CGDI, and the figure ( ]) is a CCD color filter array diagram.
A section indicates one pixel. In addition, (2) in the same figure shows the output signal of the even field (A), which is the output signal in (1) in the same figure, the signal (Cy),
S, signal (Ye) and odd field (A) S, signal (Mg, G), S, signal CG, Mg) are shown.

FIG. 3 is a diagram showing the storage arrangement of the frame memory 4,
(1) in the same figure shows the even field memory (Cy, Ye), and (2) in the same figure shows the odd field memory (Mg, G). During storage, the data is sequentially stored in the odd and even field memories in chronological order, and the data is read out. Odd and even field memories are read simultaneously.

Next, to explain the operation, even field (A) S I I
The S3 signal is sent to the Cy amplifier 23. A each with Ye amplifier 25
The signal is amplified to the full scale of the A/D converter 3 and output to the A/D converter 3 via the changeover switches 27 and 29.

On the other hand, the odd field S, , S, signals are sent to the Mg amplifier 26 . G amplifier 24, then G amplifier 24. By repeating these steps, the Mg amplifier 26 amplifies the signal up to the full scale of the A/D converter 3, and outputs it to the A/D converter 3 via the changeover switches 28 and 29.

Then, the digital data converted by the A/D converter 3 is sent to the odd-even field memories (2) and (1) of the frame memory 4 by the memory control circuit 6 shown in FIG. 4 in the memory storage arrangement shown in FIG. Store in chronological order.

The processing section 5 reads out the digital data stored in the frame memory 4 in a different order from the above-mentioned storage time, that is, the odd-even field memory simultaneously, and sends a signal Cy to the processing section 5.
, G, Ye, and Mg. These 4 pixels worth of data are read out for the first time (1st field) and 2
In the second readout (second field), different pixels are read out.

In this way, the overlapping pixel shift carried out within the CCD is carried out by the memory address control of the memory control circuit 6. Based on the signals Cy, G, Ye, and Mg, the processing section 5 performs the following calculations.

However, A, B, C, and D are the amplification factors of amplifiers 23 to 26, and α and β are coefficients.

γ conversion to R, G, and B obtained by the above formulas (1) and (2).

Perform matrix calculation and white balance calculation, Y.

Calculate RY and BY. And this Y, R-Y
, B-Y are digitally converted into composite digital data by an encoder 7, and converted into an analog signal (NTSC signal) by a D/A converter 8 and output.

(Effects of the Invention) As explained above, the present invention provides the COD output signal Cy,
Since G, Ye, and Mg are each amplified to the full scale of the A/D converter, the influence of quantization noise is reduced and the S/N is
gets better.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a circuit diagram of an amplifier according to an embodiment of the present invention;
FIG. 2 is an explanatory diagram of a reading method from the CCD 1, FIG. 3 is a diagram showing a memory storage column of a frame memory, and FIG. 4 is a block diagram showing the configuration of a digital electronic still camera to which the present invention is implemented. be. l...charge-coupled image sensor (CCD),
2...Amplifier, 3...A/D converter, 4.
...Frame memory, 5.Process section, 6.
...Memory control circuit, 7...Encoder, 8.
...D/A converter, 21, 22.27.28.29...
・Selector switch, 23...Cy amplifier, 24...G
Amplifier, 25...Ye amplifier, 26...Mg amplifier. Patent applicant Rico Co., Ltd. → Fig. 4 Fig. 2 3 4 West field mail life) Even field S+ , Cy, Cy, Cy, Cy;---...c
y, cy, cy, cy...52,,, Ye, Y
e, Ye, Ye,------,・Ye, Ve, Ve
,Ye,-...I) Strong field S+,,, Mg, Mg, Mg, Mg,-,-G
, G, G, G -52-G, G, G, G-...M
g, Mg, Mg, Mg-...Figure t field memory

Claims (1)

[Scope of Claims] A charge-coupled image sensor, an amplifier that amplifies the output signal of the image sensor, an A/D converter that converts the signal amplified by the amplifier into digital data, and the A/D converter. a frame memory that stores digital data converted by the frame memory; a memory control circuit that performs address control of the frame memory; and a process unit that performs arithmetic processing on the digital data stored in the frame memory;
The processing unit includes an encoder that encodes digital data after arithmetic processing, and a D/A converter that converts the digital data from the encoder into an analog signal, and is connected to the pixels of the charge-coupled image sensor. In a digital electronic still camera that stores data in the frame memory in a pair-to-one correspondence and outputs a frame image based on the stored data, output signals Cy, G, and
A digital electronic still camera characterized in that the amplifier is configured to amplify Ye and Mg separately.