JP2002158927A - Video signal synthesizer - Google Patents

Abstract

(57) [Problem] To provide a video signal synthesizing device capable of realizing a wide dynamic range while maintaining a high S / N. SOLUTION: A long-exposure video signal having a long exposure time and a short-exposure video signal having a short exposure time are input signals, and each exposure video signal is separated into a high-frequency component and a low-frequency component. Means for individually controlling the gain of each high-frequency component and each low-frequency component and adding them,
This is a video signal synthesizing apparatus that has means for adaptively adding these to generate a synthesized signal and generates a wide dynamic range video signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device for expanding a dynamic range of a video signal.

[0002]

2. Description of the Related Art In the camera system, various proposals have conventionally been made as a method for expanding a dynamic range. One of the prominent methods is a signal having a long exposure time (long exposure signal) and a signal having a long exposure time. Short signal (short exposure signal)
Are adaptively combined to realize a wide dynamic range. Here, signals of different exposure times are
This can be realized by switching the storage time of the imaging unit. Many CCDs having such a function have been announced. A long exposure signal having a long accumulation time has a sufficient contrast in a low level part (dark part) of the signal, and has a high S / N (amount of signal with respect to noise) (good), but a high level part of the signal. (Light part) is saturated, and the detailed information is lost. A so-called underexposure occurs, resulting in a narrow dynamic range. On the other hand, a short exposure signal having a short accumulation time has a high saturation level and a wide dynamic range. However, since the accumulation time is short, the contrast in a dark part is insufficient, and the S / N is low. Not available. This is a so-called black crush. The simplest method of expanding the dynamic range is the simple addition method. That is, this is a method in which a long exposure signal and a short exposure signal are simply added to generate a composite signal. Since the synthesized signal includes a short exposure signal, a wide dynamic range can be obtained. Further, since a long exposure signal is included, contrast in a dark portion can be obtained. Therefore,
Video information over a wide area from dark to bright can be obtained,
A wide dynamic range can be realized.

[0003]

A wide dynamic range can be realized by the simple addition method. However, as described above, the short exposure signal has a short accumulation time, so that the S / S in the dark part is small.
N is low, and if this is simply added to the long exposure signal, the S / N in the dark portion of the composite signal is reduced, which is a practical problem. When a wide dynamic range video signal is generated, important information in the video signal is detailed information, that is, a high-frequency component in both a dark portion and a bright portion. Even if a signal with only a low-frequency component is used to achieve a wide dynamic range, the picture will be blurred and unclear, and will be meaningless. It is important how to save the high frequency components of the original image in a state of good S / N. On the other hand, in the conventional method, since the long exposure signal and the short exposure signal are added without distinguishing the high frequency component and the low frequency component, the above-described problem occurs. In a recent camera system, a simple process such as gain control is performed on a signal output from a CCD in an analog unit, and then A / D conversion is performed immediately, and a main process is generally performed digitally. It is. Since the digital processing is performed in synchronization with the sampling clock, the noise generated by the digital section also includes many high-frequency components synchronized with the sampling clock.
This noise wraps around to the CCD or A / D converter, and is a main cause of S / N reduction. Here, again, considering the characteristics of the long exposure signal and the short exposure signal, in the long exposure signal, the high frequency component in the bright part is lost by saturation, and in the short exposure signal, the high frequency component in the dark part is lost buried in noise and lost. I will. An object of the present invention is to provide a video signal synthesizing apparatus capable of eliminating these drawbacks and achieving a wide dynamic range while maintaining a high S / N.

[0004]

According to the present invention, a long exposure video signal having a long exposure time and a short exposure video signal having a short exposure time are used as input signals. Means for separating into a component and a low-frequency component; means for individually controlling the gain and adding each of the separated high-frequency and low-frequency components; and adaptively adding these to generate a composite signal. Means for generating a video signal with a wide dynamic range. Further, the means for individually controlling the gain and adding the weights may be a means for weighting and adding the short-exposure video signal and the long-exposure video signal with a weight corresponding to the input signal level for the high-frequency component, and for the low-frequency component. Are means for performing gain control and addition with gain characteristics that provide equivalent input / output characteristics. Further, the means for individually controlling and adding the gain does not limit the amount of the high frequency component for the long exposure video signal, and reduces and adds the amount of the high frequency component to the short exposure video signal. It is what it was. Further, the means for individually controlling and adding the gain is such that the high-frequency component of the high-level part signal of the long exposure video signal is reduced, and the high-frequency component of the low-level part signal of the short exposure video signal is reduced. It is what it was. In addition, a long-exposure video signal with a long exposure time and a short-exposure video signal with a short exposure time are used as input signals, and each of the exposure video signals is separated into a luminance signal component and a color signal component. Means for separating into frequency components, means for controlling and adding high-frequency and low-frequency component amounts independently for each of the separated luminance signal components and chrominance signal components, and adaptively adding these to form a composite signal The video signal synthesizing device has a generating means and generates a wide dynamic range video signal.
As described above, for the high-frequency component, the weighted addition of the dark part of the long exposure signal and the bright part of the short exposure signal is used,
The above-mentioned problems can be solved, wide dynamic range and high S
/ N can be achieved.

[0005]

FIG. 1 shows the configuration of an embodiment of a video signal synthesizing apparatus according to the present invention, which will be described below. A low-pass filter (LPF) is obtained from two types of input signals, a short exposure signal and a long exposure signal, output from a CCD (not shown).
Low frequency components are extracted by 1 and LPF2, respectively, and high frequency components are separated by subtraction circuits 3 and 4, respectively. The extracted low frequency components are output from multipliers 5 and 7 to fixed coefficient generating circuits 6 and 8.
Are multiplied by the respective coefficients, and are combined by the adder 9. The separated high-frequency components are weighted by the weighting control circuits 11 and 12 according to the coefficient characteristics generated by the level-dependent weighting coefficient generation circuit 10, and then combined by the adder 13. Finally, the adder 14 adds the low-frequency component and the high-frequency component to generate a final composite signal. Thereby, a wide dynamic range can be realized. Here, regarding the characteristics of the weighting coefficient, as shown in FIG. 2, "1" in the dark portion for the long exposure signal, "0" in the bright portion, "0" in the dark portion for the short exposure signal, and "0" in the bright portion for the short exposure signal. In the overlap area, the state is continuously switched from "1" to "0" and from "0" to "1", respectively. This characteristic is given only to the high frequency component to generate a composite signal. In FIG. 1, the synthesis of the low-frequency components is simply an addition multiplied by a fixed coefficient. However, as shown in FIG. 3, a gain characteristic depending on the input signal level is added to each of the long / short exposure signals. In addition, the difference in the level of the output signal is eliminated, and the problem of unnaturalness in the composition is solved. According to the above method, S / N for high frequency components important as detailed information
Can be increased, and both a wide dynamic range and a high S / N can be achieved.

Next, a second embodiment of the present invention will be described. Usually, in a television camera system, the color 3
In addition to the three-plate system that supports and processes three primary CCDs and has three CCDs, one CCD can be used by using a color filter.
There is a single-panel system that generates a color signal from a single panel. This second
In the embodiment, a single-plate configuration is shown. This single-plate system is a frequency modulation system, which demodulates a modulation signal of a CCD output and returns it to a standard luminance (Y) signal and color (C) signal. At the stage of modulation, considering the frequency component, the luminance component spreads from a low band to a high band, but the color component is a modulated carrier and has a component in a high band. Therefore, high-frequency noise tends to jump into color components. As a result, the demodulated signal appears as color noise. If the video input was a monochrome image, this color noise would be very noticeable,
This is a practical problem. In this embodiment, similarly to the first embodiment, a means is provided for separating each of the long / short exposure signals into a high frequency component and a low frequency component. Eliminate noise problems. The configuration of the present embodiment is the same as that of the first embodiment (FIG. 1), and will not be described. In this embodiment, the high-frequency component contains a large amount of a color signal component. Therefore, weighting control depending on the input signal level is performed for this. In particular, for a short exposure signal having a poor S / N, the gain of the dark part (low-level area) is reduced and added. As a result, color noise can be reduced, and both a wide dynamic range and a high S / N can be achieved.

[0007]

According to the present invention, the S / N ratio can be improved for high frequency components which are important as detailed information by removing the dark portion component of the short exposure signal which causes S / N deterioration. Therefore, it is possible to achieve both a wide dynamic range and a high S / N.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a characteristic explanatory diagram for explaining a weighted addition operation according to one embodiment of the present invention;

FIG. 3 is a characteristic explanatory diagram for explaining a weighted addition operation according to one embodiment of the present invention;

[Explanation of symbols]

1: 2, LPF, 3,4: subtraction circuit, 5,7: multiplier,
6, 8: fixed constant generation circuit, 9, 13, 14: adder,
10: Level-dependent weighting coefficient generation circuit, 11, 12:
Weight control circuit.

Continued on the front page F-term (reference) 5C021 PA17 PA66 PA67 RB03 XB02 5C022 AB19 AB37 AB51 AC42 5C024 AX01 CX47 DX01 DX04 GY01 HX18 HX28 HX29 HX30 5C065 AA03 BB22 BB48 CC01 CC08 DD02 DD17 EE06 GG02 AGG11 GG02 AGG03A EA03 EC01 EE01 GA01 GA05 GB01 KA12 KC02 KE02 KE03 KM02 LA02

Claims (5)

[Claims] 1. A means for taking a long exposure video signal having a long exposure time and a short exposure video signal having a short exposure time as input signals, and separating each exposure video signal into a high frequency component and a low frequency component. Means for individually controlling the gain of each high-frequency component and each low-frequency component, and adding
A video signal synthesizing apparatus, comprising means for adaptively adding these to generate a synthesized signal, and generating a wide dynamic range video signal. 2. The method according to claim 1, wherein the means for individually controlling and adding the gain is weighted addition of the short-exposure video signal and the long-exposure video signal with respect to the high-frequency component by weighting according to an input signal level. A video signal synthesizing device, wherein the low frequency component is gain controlled and added with a gain characteristic so that the input and output characteristics are equivalent to each other. 3. The apparatus according to claim 1, wherein the means for individually controlling and adding the gain does not limit a high-frequency component amount for the long-exposure video signal and a high-frequency component for the short-exposure video signal. A video signal synthesizing apparatus characterized in that component amounts are subtracted and added. 4. The high-frequency part of the short-exposure video signal according to claim 1, wherein the means for individually controlling and adding the gain comprises reducing a high-frequency component amount of a high-level part signal of the long-exposure video signal, A video signal synthesizing apparatus characterized in that component amounts are subtracted and added. 5. A format in which a long-exposure video signal having a long exposure time and a short-exposure video signal having a short exposure time are input signals, and each of the exposure video signals is separated into a luminance signal component and a chrominance signal component. Means for separating the component and the low frequency component, means for controlling and adding the high frequency component and the low frequency component amount independently for each of the separated luminance signal component and color signal component, and adaptively adding these, An image signal synthesizing apparatus, comprising: means for generating a synthesized signal, and generating a wide dynamic range image signal.