JP2587410B2 - Digital image processing equipment - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a digital image processing apparatus for improving image quality by digitally processing a television signal obtained by taking a very dark subject with a camera using a high-sensitivity photographing tube. About.

[Conventional technology]

In order to capture very dark subjects, the shooting unit uses a high-sensitivity SIT (Silicon Intensifier Target) tube camera or a CCD camera II (Imare Intensifi).
Use a camera with es,) added. Cameras with high sensitivity using SIT or II will add extra noise due to SIT or II, and the screen will be grainy. Also, for example, when shooting the night sky, the part of the night sky that should be uniformly dark is SIT or II
Does not uniformly darken due to an extra signal such as a dark current generated by. Therefore, in order to improve the image quality of such a camera video signal with a digital image processing device, the video signal from the camera is integrated by a specified number of frames, random noise is reduced, and then the light incident on the camera is cut. By outputting only the fixed pattern noise and subtracting the same number of frames from the previously integrated signal, the image quality is improved by removing components due to characteristic unevenness of the photographing unit and interference from electronic circuits.

[Problems to be solved by the present invention]

In the above-described conventional image processing method, the integration is started and the screen level gradually rises. However, in normal control, to determine how much to integrate, (A) the process of integration is always performed. It is necessary to employ a method of monitoring and stopping when the level reaches an appropriate level, (B) designating a time for integration and integrating for a fixed time.

However, it is inconvenient since it is not possible to determine whether the level of the integration result is good unless integration is performed by any of the above methods.

[Means for solving the problem]

The present invention provides an A / D conversion circuit for converting a video signal from a television camera into a digital signal, a sensitivity switching circuit for controlling a coefficient of A / D converted data, an addition / subtraction circuit for adding / subtracting two input signals, A one-frame memory circuit for delaying or storing the output signal of the addition / subtraction circuit for one frame;
A D / A conversion circuit for D / A converting a frame memory circuit output signal, wherein two input signals of the addition / subtraction circuit are achieved such that an output of the sensitivity switching circuit and an output of the one frame memory circuit are input. You. By controlling the coefficient of the sensitivity switching circuit according to the case where the image quality of the video signal is improved and the case where the level after integration is checked, the image processing operation is facilitated because the sensitivity can be checked quickly.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of one embodiment of the present invention. A video signal from a television camera is input to an input signal terminal 1 and an A / D conversion circuit 2
Is converted into a digital signal. The coefficient of the A / D converted data is controlled by the sensitivity switching circuit 3. The addition / subtraction circuit 4 adds or subtracts the output signal of the sensitivity switching circuit 3 and the output signal of the one-frame memory circuit 5 to generate a D / A conversion circuit 6.
And D / A converted to output to the output signal terminal 7.

In order to improve the image quality, the addition and subtraction circuit 4 adds a fixed number of frames, and the integrated one-frame signal is stored in the one-frame memory circuit 5. This reduces random noise in the video signal of the camera. The setting of the coefficient of the sensitivity switching circuit can be easily performed by a bit shift. When the number of images to be added with a small coefficient is increased, the improvement rate of the random noise is increased.

Next, light incidence is cut, only fixed pattern noise is output, and a certain number of frames are subtracted by the addition / subtraction circuit 4,
One frame signal obtained by subtracting the same number of frames from the previously integrated signal is stored. As a result, components due to unevenness in the characteristics of the photographing unit and interference from the electronic circuit are removed, and the image quality is improved.

At this time, assuming that a video signal of a predetermined level that is G times larger than the input is obtained in the frame memory, and the coefficient of the sensitivity switching circuit 3 is 1/256 times, NTSC adds 30 frames per second, so the necessary integration is required. Time T is Becomes

In this manner, it takes too much time to determine how much integration should be performed after the integration time T [seconds] has elapsed. Therefore, when determining the coefficient, the coefficient of the sensitivity switching circuit 3 is set to 1 and the digital gain is set to G. Then the integration time T becomes And can be determined in a short time.

Thus, for example, by setting the coefficient of the sensitivity switching circuit 3 to 1,
After confirming that an appropriate predetermined level is obtained at G / 30 seconds, and then setting the coefficient of the sensitivity switching circuit 3 to 1/256 to improve image quality, the integration time for obtaining the same level is determined by the sensitivity switching circuit 3.
Since the coefficient is inversely proportional to the coefficient of, it can be calculated as 256 times G / 30 seconds, and the image quality can be immediately improved in this time.

〔The invention's effect〕

As described above, the present invention performs A / D conversion of a video signal from a television camera and adds or subtracts a fixed frame video signal to improve the image quality of the video signal. By controlling the switching circuit, there is an effect that the image processing time is shortened and the operation is facilitated.

[Brief description of the drawings]

FIG. 1 is a system diagram of one embodiment of the present invention. 1 ... input signal terminal, 2 ... A / D conversion circuit, 3 ... sensitivity switching circuit, 4 ... addition / subtraction circuit, 5 ... 1 frame memory circuit, 6 ... D / A conversion circuit, 7 ... output Signal terminal.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Minoru Harada, Inventor 5-33-1, Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-55-39493 (JP, A) −19669 (JP, U)

Claims (1)

(57) [Claims] An apparatus for improving the image quality of a television camera signal obtained by photographing a dark place, comprising: an A / D conversion circuit for converting a video signal from the television camera into a digital signal; and a gain for the A / D converted data. A sensitivity switching circuit for controlling; an addition / subtraction circuit for adding / subtracting two input signals; a one-frame memory circuit for delaying or storing the output signal of the addition / subtraction circuit for one frame;
And a D / A conversion circuit for performing D / A conversion. The output of the sensitivity switching circuit and the output of the one-frame memory circuit are input to the addition / subtraction circuit, and the television camera signal is input to the one-frame memory by the addition / subtraction circuit. In a configuration in which integration is performed by adding an output of a circuit and storing the result in the one-frame memory circuit, an integration time corresponding to the number of additions by the addition / subtraction circuit and the sensitivity switching circuit are performed so that the output becomes a predetermined level. The digital image processing apparatus is set to be inversely proportional to the gain of the digital image processing apparatus.