JPH0433477A - Gamma correction system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gamma compensation method for television signals.

[Summary of the invention]

When implementing a gamma compensation circuit digitally, it would be easy to use a conversion memory, but since it requires a large amount of power, the present invention does not use a memory.

In addition, as a method for easily changing the characteristics, three pieces of information that determine the gamma characteristics are externally set in the processing circuit, and arithmetic processing is performed based on the information to provide the output characteristics.

[Conventional technology]

In order to realize the gamma characteristics shown in Figure 4.

The conventional concept required a conversion memory as shown in FIG. The conventional system will be explained below based on FIGS. 4 and 5.

First, the output level relative to the input level is calculated. For example, gamma characteristics.

If y=X0°45 (x two-person power, y: output), input x
The value of output y at =50% is.

0.5×100=73%. If the input data is an 8-bit hexadecimal representation, two pieces of data are required.

Next, the calculated data is written to memory. This corresponds the input level to a memory address and writes the output value to that address.

In this way, write 2, for example, 28 pieces of data, connect the 8-bit data to the address line of the memory,
If the data output of the memory is used as output data, the necessary input/output characteristics can be obtained.

[Problem to be solved by the invention]

When using the above-mentioned conventional technology, a large amount of power is required due to the use of a conversion memory, and the maximum processing speed is lower than that of digital circuits such as LSI.

Also, when changing the gamma characteristics, calculate the data again.

It required writing to memory, which was time-consuming.

It is an object of the present invention to eliminate these drawbacks and realize a gamma compensation method that reduces power consumption and allows easy changes in gamma characteristics.

[Means to solve the problem]

In order to achieve the above object, the present invention realizes optimal gamma compensation characteristics through arithmetic processing entirely in digital circuits without using a conversion memory.

FIG. 1 is a graph showing the main points of the present invention. As shown in the figure, the gamma curve is approximated by a polygonal line.
Approximate with five polygonal lines at 0%), and set the parameter for the number of polygonal lines in each section from the outside.

Based on this, a polygonal line characteristic is given to the output signal for each section, and the level of the input signal is detected.

It is determined which section this is in, and the polygonal line characteristic is selected based on the result.

FIGS. 2 and 3 schematically show the hardware configuration of the present invention.

[Effect]

By using the above-mentioned means, no memory is required.

In addition, when changing the gamma characteristics, each function parameter (in Figure 1, V1 + V2t y3s '/4
Alternatively, □*lc2+k3y k4t k5) can be recalculated and set again. This allows the characteristics to be easily changed.

〔Example〕

An embodiment of the present invention is shown in FIGS. 2 and 3.

In FIG. 2, 1 to 4 are parameter setting registers, and the input levels of FIG. 1 are 20% and 40%.

Set the output signal level at 60% and 80%.

Reference numeral 7 denotes a function parameter calculation circuit, which calculates straight line parameters in each polygonal line section based on the data set in registers 1 to 4. For example, the function for the input level range of 20% to 40% is:

2-yl y" 20 X 1y□-(yl-yl) (x
: input, y: output, 100% is 100).

Reference numeral 6 denotes an input level detection circuit that determines in which section the input level is located and provides this information to the selectors 8 and 9. With selector 8.9.

The selected parameters are squaring circuit 1o and addition circuit 1
1, thereby providing the necessary gamma characteristics to the input. for example.

When the input level is between 20% and 40%.

2-yl The selector 8 selects y, -(yl-y,), and the selector 9 selects y, -(yl-y,), and the multiplier 1
0. and is given to the adder 11. This allows input
The output y for is.

yl-3'1 ''20 χ1y, -(yl-y,), and a desired gamma characteristic can be provided.

However, this is the parameter y yl t yl t y3
Instead of giving p y4 as the setting data for registers 1 to 4.

The slope of the straight line in each section is □, k2. k, k4.
k5 is given to registers 1-5.

〔Effect of the invention〕

According to the present invention, gamma characteristics can be provided without using memory, resulting in a reduction in power consumption. Furthermore, since it is composed only of digital circuits, high-speed processing can be achieved. Furthermore, since the gamma characteristics are determined by parameter settings, the characteristics can be easily changed, and can be applied to characteristics different from the gamma characteristics, making it extensible.

[Brief explanation of drawings]

FIG. 1 is a graph showing the gist of the present invention, and FIG. 2 is a graph showing the gist of the present invention. FIG. 3 is a block diagram showing an embodiment of the present invention, FIG. 4 is a gamma characteristic diagram, and FIG. 5 is a block diagram of a conventional example. 1 to 5: Parameter setting register, 6: Kugata level detection circuit, 7: Function parameter calculation circuit. The example shown in Figure 3 is similar to the example shown in Figure 2, lol! Input record 1

Claims (1)

[Claims] 1. In a circuit system that performs gamma compensation in television signals, the gamma characteristic curve is approximated by a polygonal line,
Gamma compensation characterized in that information determining the characteristics of each divided (broken line) section is externally set, and based on this information, the characteristics sought for each divided section are given to the output signal by digital calculation processing. method.