JP2000078594A - Dynamic range widening process method for single-plate type color camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic range widening process method for a single- plate type color camera which can decrease the circuit scale. SOLUTION: Images of a light and a dark area are picked up by switching a shutter time or a stop at intervals of a specific number of fields and the obtained image data are synthesized. By this dynamic range widening process method for the single-plate type color camera, the synthesis 7 is performed before color separation 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for widening the dynamic range of a single-chip color camera.

[0002]

2. Description of the Related Art As shown in FIG. 7, when a single-panel color camera captures a scene in which a bright area E1 and a dark area E2 coexist, blackout or overexposure occurs due to the sensitivity of the single-panel color camera. There is a problem that occurs.

In order to solve this problem, the information on the bright area and the information on the dark area are separately captured by changing the shutter time for each field, and the obtained information is combined into one image. A method has already been developed (see JP-A-6-141229). However, in the conventional method, synthesis is performed after color separation, and there is a problem that the circuit scale is large.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a processing method for widening the dynamic range of a single-chip color camera which can reduce the circuit scale.

[0005]

According to the present invention, there is provided a single-panel color camera having a wide dynamic range processing method, wherein a shutter time or an aperture is switched every predetermined number of fields to separately image a bright area and a dark area. In a wide dynamic range processing method for a single-chip color camera that combines the obtained image data into one image, the combining is performed at a stage before performing color separation.

When performing color separation based on a composite image,
It is preferable that color separation is performed on a bright area in the composite image using data of only the bright area, and that on a dark area, color separation is performed using data of only the dark area.

It is preferable to provide a false color suppression circuit for suppressing the color at the boundary between the bright area and the dark area in the composite image.

The timing for switching the shutter time or the aperture may be changed depending on whether the movement of the input image is large or small. For example, when the movement of the image of the input image is large, the shutter time or the aperture is switched every one field, and when the movement of the image of the input image is small, the shutter time or the aperture is switched every two fields.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a processing device for widening the dynamic range of a single-chip color camera. The single-chip color camera includes a CCD 1 having a color filter array.

FIG. 2 shows a part of a color filter array provided on the light receiving surface side of the CCD 1.

In this example, in the odd-numbered rows, cyan (Cy) color filters and yellow (Ye) color filters are alternately arranged in the horizontal direction. In the even-numbered rows, magenta (Mg) color filters and green (G) color filters are alternately arranged in the horizontal direction.

Here, in the mixing of light colors, a so-called additive method is established, so that the three primary colors R (red) and G
(Green), B (blue), complementary colors Mg, Y
The following equation 1 is established between e and Cy.

[0014]

(Equation 1)

A CC having such a color filter array
A method of reading a signal from D1 will be described.

In the odd (ODD) field, the pixel value of the odd-numbered row in the vertical direction and the pixel value of the even-numbered row below it are added and output. That is, in the n-th scanning line, D1 (= Cy + Mg) and D2 (= Ye +
G), D1, D2,..., D3 (= Cy + G), D4 (= Ye + Mg), D3, D
Signals are output in the order of 4..

In an even (EVEN) field,
The pixel value of the even-numbered row in the vertical direction and the pixel value of the odd-numbered row below it are added and output. That is, in the m-th scanning line, D1 (= Mg + Cy), D2 (= G + Y
e), D1, D2,..., D3 (= G + Cy), D4 (= Mg + Ye), D3, D
Signals are output in the order of 4..

Signals D1 to D4 output from CCD1
Are AGC and CDS (Corr) in the CDS / AGC circuit 2.
A / D after the processing of elated Double Sampling)
The signal is sent to the converter 3 and converted into a digital signal.

In this embodiment, the timing control circuit 5 controls switching of the shutter time (charge accumulation period) for each field. The switching mode includes a first mode and a second mode. This mode switching is performed based on the magnitude of the motion of the image detected by the motion detection circuit 4. As the motion detection circuit 4, for example, a circuit that detects a motion vector is used.

When the motion of the image detected by the motion detection circuit 4 is large, the switching mode is set to the first mode, and when the motion of the image detected by the motion detection circuit 4 is small, the switching mode is set to the first mode. The second mode is set.

The electronic shutter time includes a long first shutter time and a short second shutter time. In the first mode, the shutter time is switched between the first shutter time and the second shutter time for each field. Second
In the mode, the shutter time is switched between the first shutter time and the second shutter time every two fields.

First, the operation in the first mode will be described. Here, it is assumed that the shutter time for odd fields is set to the first shutter time, and the shutter time for even fields is set to the second shutter time (<first shutter time).

The broken line A in FIG. 3 indicates the brightness and the CCD 1 when the shutter time is the first shutter time which is relatively long.
3 shows the relationship with the output signal level. Straight line B in FIG.
Shows the relationship between the brightness and the output signal level of the CCD 1 when the shutter time is the relatively short second shutter time.

In this embodiment, a bright area is synthesized by synthesizing an image captured during the first shutter time with a relatively long shutter time and an image captured during the second shutter time with a relatively short shutter time. When capturing a scene in which both a dark area and a dark area are captured, blackout and whiteout are prevented from occurring.

Image data D1 to D for each field
4 is temporarily stored in the memory 6 and the synthesizing circuit 7
And sent to the motion detection circuit 4. In the first mode, the memory 6 stores data for one field.

In the synthesizing circuit 7, as shown in FIG.
And the data D1 to D4 of the current field sent directly from the A / D converter 3 to the combining circuit 7. FIG.
O in Li (O) and Si (E) which are CCD outputs of
Indicates an odd field, E indicates an even field, L indicates that the shutter time is the first shutter time, and S indicates that the shutter time is the second shutter time.

Data D1 of two fields to be synthesized
3 to D4, a pixel whose data signal level of a field (odd field in this example) captured at the first shutter time is equal to or lower than the predetermined level Q shown in FIG. 3 was captured at the first shutter time. Outputs the data of the field (odd field). For a pixel whose signal level of the data of the field (odd field) captured in the first shutter time exceeds the predetermined level Q shown in FIG. 3, the data of the field (even field) captured in the second shutter time Output the data after the gain adjustment as shown by the broken line C in FIG. This pixel switching is performed in units of two pixels in order to suppress the generation of false colors. For example, if D1 is equal to or greater than Q, D2 is also the second
Data captured during the shutter time is output.

Each pixel data of the composite image is either odd field data (data for a dark area) or even field data (data for a bright area).
Is added to the area identification data of 1 bit (0 or 1) indicating whether the area identification data is

The synthesizing circuit 7 outputs synthesized image data D1 to D1.
D4 and an edge signal indicating a boundary between a dark area in which the data of the odd field in the composite image is adopted and a bright area in which the data of the even field is adopted. The composite image data D1 to D4 are sent to the color separation circuit 8, and the edge signal is sent to the false color suppression circuit 15.

In the color separation circuit 8, first, based on the following equation 2, the luminance signal Y, the color difference signal Cb, and the color difference signal Cr
Is required.

[0031]

(Equation 2)

In practice, as D1 to D4 in Equation 2, not the data of D1 to D4 of one pixel but the data of the target pixel and the data before and after the target pixel are used.

For example, in FIG. 5, when the data of the target pixel is D1 _n and D2 _n , D1 _{n + 1} , D1 _n ,
The weighted average of D1 _n-1 is D1, and D2 _{n + 1} , D2 _n , D
_{Assuming that} the weighted average of 2 _{n− 1} is D2, Y or Cb is obtained.

The color separation is performed by using only the data of the same area among the dark area (the area where the data of the odd field is used) and the bright area (the area where the data of the even field is used). .

For example, if the data of the pixel of interest is D1_nAnd D
2_nD1_{n + 1}And D1 _nIn dark areas
Yes, D1_n-1Is a bright area, D1
_n-1To D_nAfter replacing D1,_{n + 1}, D1_n, D1
_n-1Is calculated and set as D1. That is,
D1_{n + 1}, D1_n, D1_nIs set to D1.

The luminance signal Y obtained by the color separation circuit 8
Is sent to the bit compression circuit 10 via the filter 9,
Bitwise compression is performed. This is because the gain of the original data of the even field is increased in a bright area where the data of the even field is adopted in the composite image. The luminance signal Y that has been compressed in the bit direction by the bit compression circuit 10 is converted to a γ correction circuit 11
After the γ correction process is performed, the synchronization and blanking addition circuit 17 adds the synchronization signal and the blanking signal, and then outputs the result through the delay circuit 18.

The luminance signal Y, the color difference signal Cb and the color difference signal Cr obtained by the color separation circuit 8 are sent to the RGB matrix circuit 12. In the RGB matrix circuit 12, the R, G, and B signals, which are three primary color signals, are obtained from the luminance signal Y, the color difference signal Cb, and the color difference signal Cr in accordance with the following equation (3).

[0038]

(Equation 3)

In Equation 3, K _{YG to} K _BB are predetermined coefficients. R, G, obtained by Equation 3
The B signal is sent to the bit compression circuit 13, where compression in the bit direction is performed. The R, G, and B signals that have been compressed in the bit direction by the bit compression circuit 13 are converted to a γ correction circuit 14.
After the gamma correction process is performed, the signal is sent to the false color suppression circuit 15.

The false color suppression circuit 15 suppresses (reduces) the R, G, and B signals at the boundary between the dark area where the data of the odd field is adopted and the bright area where the data of the even field are adopted in the composite image. Is done. The R, G, B signals output from the false color suppression circuit 15 are sent to a color difference matrix circuit 16.

In the color difference matrix circuit 16, the following equation (4) is used.
The color difference signal (RY) and the color difference signal (BY) are obtained in accordance with the conversion formula.

[0042]

(Equation 4)

In Equation 4, K _RRY , K _BRY ,
_KRBY and _KBBY are predetermined coefficients.

The chrominance signals (RY) and (BY) obtained by the chrominance matrix circuit 16 are added to the synchronizing / blanking signal by a synchronizing / blanking circuit 17 and then an encoding circuit 19 is added. Sent to

As is well known, the encoding circuit 19 converts two chrominance subcarriers (3.58 MHz) having a phase difference of 90 ° into color difference signals (RY) and (B).
−Y) are combined, and the carrier chrominance signal C is generated and output.

Next, the second mode set when the motion of the image detected by the motion detection circuit 4 is small will be described. In the second mode, the shutter time is switched between the first shutter time and the second shutter time every two fields. Image data D1 for each field
D4 is temporarily stored in the memory 6 and sent to the synthesizing circuit 7 and the motion detecting circuit 4. In the second mode, the memory 6 stores data for two fields.

In the synthesizing circuit 7, as shown in FIG.
And the data D1 to D4 of the current field sent directly from the A / D converter 3 to the combining circuit 7. That is, as shown in FIG. 6, the data of the two fields to be combined are data D1 to D4 between odd fields or data D1 to D4 between even fields.

Li (O) and Li which are the CCD outputs of FIG.
In (E), Si (O) and Si (E), O indicates an odd field, E indicates an even field, L indicates that the shutter time is the first shutter time, and S indicates the shutter time is the second shutter time. It indicates that there is.

Data D1 of two fields to be synthesized
Among the pixels D4 to D4, the data of the field data captured in the first shutter time is output to the pixels whose signal level is equal to or lower than the predetermined level Q shown in FIG. For a pixel whose signal level of the data of the field captured at the first shutter time exceeds the predetermined level Q shown in FIG. 3, the data of the field captured at the second shutter time is indicated by a broken line C in FIG. As shown, the data after the gain adjustment is output. Subsequent processing is the same as in the first mode, and a description thereof will be omitted.

In the above embodiment, the electronic shutter time is switched every field or every two fields. However, the aperture may be switched.

[0051]

According to the present invention, a processing method for widening the dynamic range of a single-chip color camera which can reduce the circuit scale is realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a processing device for increasing a dynamic range of a single-chip color camera.

FIG. 2 is a schematic diagram showing a part of a color filter array provided on a light receiving surface side of a CCD 1;

FIG. 3 shows the relationship between the brightness and the output signal level of the CCD1 when the shutter time is a relatively long first shutter time, and the brightness and the output signal level of the CCD1 when the shutter time is a relatively short second shutter time. 6 is a graph showing a relationship with the graph.

FIG. 4 is a time chart showing combinations of fields synthesized by a synthesis circuit in a first mode.

FIG. 5 is a schematic diagram for explaining the operation of the color separation circuit.

FIG. 6 is a time chart illustrating a combination of fields synthesized by a synthesis circuit in a second mode.

FIG. 7 shows a different shutter time for each field, and separately captures information of a bright area and information of a dark area;
It is a schematic diagram which shows the concept of the method of synthesize | combining each obtained information with one image.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CCD 4 Motion detection circuit 5 Timing control circuit 6 Memory 7 Synthesis circuit 8 Color separation circuit 15 False color suppression circuit

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yukio Mori 2-5-1-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Naohiro Takebishi 1-1-1, Sanyocho, Daito-shi, Osaka No. SANYO ELECTRONIC PARTS CO., LTD. F term (reference) 5C022 AB17 AC42 5C065 AA01 BB12 BB13 BB15 BB48 CC01 DD02 DD17 EE05 EE07 EE08 GG02 GG12 GG17 GG18 GG30 GG50

Claims (5)

[Claims] 1. A single-chip color camera that switches a shutter time or an aperture for each predetermined number of fields, separately captures a bright area and a dark area, and combines the obtained image data into one image. A method for widening the dynamic range of a single-chip color camera, wherein the synthesis is performed before color separation is performed. 2. When performing color separation on the basis of a composite image, color separation is performed using data of only bright areas in a bright area of the composite image, and dark areas are determined using dark area data. 2. The processing method for widening the dynamic range of a single-chip color camera according to claim 1, wherein color separation is performed using only data. 3. The single-plate color according to claim 1, further comprising a false color suppression circuit for suppressing a color at a boundary between a bright area and a dark area in the composite image. A wide dynamic range processing method for cameras. 4. The single-plate color as claimed in claim 1, wherein the timing of switching the shutter time or the aperture is changed depending on whether the movement of the input image is large or small. A wide dynamic range processing method for cameras. 5. The shutter time or aperture is switched every field when the motion of the input image is large, and the shutter time or aperture is switched every two fields when the motion of the input image is small. 5. The processing method for widening the dynamic range of a single-chip color camera according to claim 4, wherein