JPH0243877A - Gradation converter - Google Patents

Abstract

PURPOSE:To improve the S/N without losing effective information of a video signal by applying gradation conversion in the state of an analog signal. CONSTITUTION:An A/D converter circuit 12 is digitized a video signal S10, a digital signal S12 is inputted to a conversion table memory circuit 13, where it is converted into a magnification signal S11. The magnification signal S11 is a multiple of the video signal S10 at an analog multiplication circuit 11 and it is stored in advance in a conversion table memory circuit 13 in advance as a multiple for gradation conversion in response to the value of the digital signal S12. Then the gradation conversion multiple read from the memory is converted into an analog signal at the conversion table memory circuit 13 and the result is outputted as the multiple signal S11, the analog multiplication circuit 11 multiplies the video signal S10 with the multiple signal S11 and the result is outputted as the gradation conversion signal S13. Thus, the S/N of the signal after gradation conversion is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gradation conversion device, and particularly to a gradation conversion device that performs gradation conversion of a video output signal of a television camera.

[Conventional technology]

As a conventional gradation conversion device, there is one that uses a gradation conversion table memory.

Next, a conventional gradation conversion device will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing a conventional example.

The gradation conversion device shown in FIG. 2 includes an A-D conversion circuit 21,
A conversion table memory circuit 22 that outputs a gradation conversion signal S22 from the digital signal S21 of the A-D conversion circuit 21
, A-D conversion circuit 21 , and conversion table memory circuit 2
2 and a timing control circuit 23 that outputs an A-D conversion and table memory read timing control signal S23.

Here, the video signal is converted into an 8-bit digital signal S21 by the A-D conversion circuit 21 and output to the conversion table memory circuit 22.

The conversion table memory circuit 22 is a memory circuit whose address is the digital signal S21, and stores the value of the gradation conversion signal S22 output according to the magnitude of the digital signal. The conversion table memory circuit 22 receives the digital signal S.
By storing conversion values corresponding to 21 gradations and sequentially reading them in accordance with input signals, gradation conversion can be performed.

[Problem to be solved by the invention]

The conventional gradation conversion device described above performs gradation conversion after digitizing the video signal, so the signal-to-noise level ratio (hereinafter referred to as S/N) of the signal after gradation conversion does not improve. There were drawbacks.

[Means to solve the problem]

The gradation conversion device of the present invention includes: an A-D conversion circuit that digitizes a video signal and outputs the digital signal; a conversion table memory circuit that outputs a magnification signal based on the digital signal; The device includes an analog multiplier circuit that outputs a gradation conversion signal based on the video signal, and a timing control circuit that outputs a timing signal to the A-D conversion circuit and conversion table memory circuit based on the video signal.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

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

The operation will be explained in detail below.

The video signal S10 is input to an analog multiplication circuit 11, an A-D conversion circuit 12, and a timing control circuit 14.

The A/D conversion circuit 12 digitizes the video signal S10 into 8 bits and outputs a digital signal S12. The digital signal S12 is input to the conversion table memory circuit 13 and converted into a magnification signal Sll. Here, the magnification signal S
ll is an analog multiplication circuit 11 that serves as a multiplier for the video signal SIO;
This is stored in advance as a gradation conversion multiplier corresponding to the value of the digital signal S12.

Then, the conversion table memory circuit 13 converts the gradation conversion multiplier read from the memory into an analog signal and outputs it as a magnification signal Sll.

The analog multiplication circuit 12 multiplies the video signal S10 and the magnification signal Sll, and outputs the result as a gradation conversion signal 813.

The timing control circuit 14 is connected to the A-D converter circuit 12.
It outputs a timing signal S14 for D conversion timing and memory access and reading of the conversion table memory circuit 13.

〔Effect of the invention〕

The gradation conversion device of the present invention performs gradation conversion in the analog signal state instead of converting the gradation after digitization.
It has an excellent effect of improving /N.

DESCRIPTION OF SYMBOLS 11... Analog multiplication circuit, 12... AD conversion circuit, 13... Conversion table memory circuit, 14... Timing control circuit, 21... AD conversion circuit, 22.
...Conversion table memory circuit, 23...Timing control circuit, SIO...Video signal, Sll...Magnification signal, S12
... Digital signal, 313 ... Gradation conversion signal, S
14... Timing control signal, S21... Digital signal, S22... Gradation conversion signal, 32B... Timing control signal.

Claims (1)

[Claims] A that digitizes the video signal and outputs the digital signal
- a D conversion circuit, a conversion table memory circuit that outputs a magnification signal based on the digital signal, an analog multiplication circuit that outputs a gradation conversion signal based on the magnification signal and the video signal, and an analog multiplication circuit that outputs a gradation conversion signal based on the video signal; The above A
- A gradation conversion device comprising: a D conversion circuit; and a timing control circuit that outputs a timing signal to a conversion table memory circuit.