JPH065480B2 - Sharpness correction device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sharpness correction device for correcting the sharpness of an RGB logical input signal of a television receiver having an RGB logical signal input terminal such as a personal computer. is there.

Conventional example configuration and its problems Except for some RGB character display monitors, the display monitor of RGB logic signals of a personal computer (hereinafter referred to as a personal computer) is generally a television set as shown in FIG. It is constructed so that it can also receive video signals.

In FIG. 1, in the input switching circuits 1R, 1G, 1B,
The analog input signal of RGB demodulated from the television video signal and the RGB signal of the logical input signal of a personal computer or the like are switched, and the switched signals are RGB output amplifier circuits 2R, 2
It is amplified by G and 2B and drives the color picture tube 3.

However, a logic input signal from a personal computer or the like is generally 2000 although it depends on the number of characters displayed on the personal computer.
In the case of the character display type or the like, the pulse width of the electric signal expressing the thinnest character is 50 to 70 ns, which is a considerably high speed pulse signal. Therefore, the frequency characteristics of the receiver circuit,
As shown in FIG. 2, the signal S1 having a wide pulse width and the signal S having a minimum pulse width are subject to the restrictions such as the mask pitch of the picture tube.
There is a defect that a level difference occurs between the two and appears as a difference in brightness level on the picture tube surface (that is, a high brightness level L1 and a low brightness level L2 occur).

An object of the present invention is to solve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a sharpness correction device capable of making the brightness substantially the same regardless of the width of the pulse width. is there.

According to the present invention, only the signal having the minimum pulse width is separated from the input logic signal, and the input logic signal is added to this signal so that the amplitude of the signal having the minimum pulse width becomes larger than the amplitudes of other pulse widths. This makes it possible to improve the luminance of the signal having the minimum pulse width and to obtain an easy-to-see screen.

Description of Embodiments FIG. 3 is a circuit block diagram of a sharpness correction apparatus for RGB logic input signals in one embodiment of the present invention, and FIG. 4 is a diagram showing operation waveforms of respective portions in FIG.

The operation of this embodiment will be described below with reference to FIGS. 3 and 4.

The circuit block diagram of FIG. 3 boosts a signal having a minimum pulse width for each of the RGB logic input signals. First, the input signal (waveform a) applied to the input stage of the delay circuit 11 is set to the minimum pulse width T by the delay circuit 11.
_It receives a delay slightly longer than _min (waveform b). Then, the logical differentiation circuit 12 extracts only the rising component (waveform c) and applies it to one input end of the AND gate 14. An output pulse (waveform d) of a monostable multivibrator (hereinafter referred to as monomulti) 13 triggered by the falling edge of the pulse of the input signal is applied to the other input terminal of the AND gate 14 to output the output of the AND gate 14. In the (waveform e), of the rising components (waveform c) of the logical differentiating circuit 12, only the logical differential signal of the signal with the minimum pulse width is extracted. This output triggers a monostable multivibrator (hereinafter referred to as monomulti) 15 to take out an output (waveform f), and gates of outputs b and f are performed by an AND gate 16 to obtain an output g and then an output b. The output g is added by the adder circuit 17. A controller 18 for controlling the amount of addition between the outputs b and g is connected to the adder circuit 17. By controlling this, the relative level between the outputs b and g can be varied. ,
At the output h of the adder circuit 17, a signal in which the level of the minimum pulse width is emphasized and varied is obtained. This signal h is amplified by an analog amplifier circuit (not shown), passed through an output amplifier circuit, and the luminance level of the signal with the minimum pulse width, which is originally reduced by driving the picture tube, is changed to the luminance level of the signal with another pulse width. Can be controlled close to.

If the pulse width of the input signal is different from the minimum pulse width, the output g of the AND gate 16 does not occur because the output c of the logic differentiating circuit 12 and the output pulse d of the monomulti 13 differ. The amplitude does not increase and the input signal is output as it is.

As described above, according to the present invention, the original input logic signal is added to the minimum pulse width signal of the input logic signals to make the amplitude larger than the amplitudes of the signals having other pulse widths. As a result, the brightness can be improved, and a screen that is easy to see can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a television receiver capable of inputting an input logic signal, FIG. 2 is a diagram showing a relationship between a pulse width and a luminance level, and FIG. 3 is a sharp view in one embodiment of the present invention. 3 is a circuit block diagram of the degree correction device, and FIG. 4 is a waveform diagram of each part for explaining the operation of FIG. 11 ... Delay circuit, 12 ... Differentiation circuit, 13, 14 ...
Monostable multivibrator, 14, 16 ... AN
D gate, 17 ... Addition circuit, 18 ... Controller.

Claims (1)

[Claims] 1. A delay circuit for delaying a logical input signal input from an RGB signal input terminal of a television receiver, a differentiating circuit for extracting only a rising component of the delayed signal delayed by the delay circuit, and the logical input. The first mono-multivibrator triggered by the trailing edge of the signal pulse, and the logical product of the rising component of the delayed signal and the output of the first mono-multivibrator are calculated to minimize the rising component of the differentiating circuit. A first AND gate that extracts only the differential signal of the pulse width signal, a second mono-multivibrator that is triggered by the output of the first AND gate, and the logic of the delay signal and the second mono-multivibrator output A second AND gate that calculates a product and outputs only the minimum pulse width signal of the logical input signal; A pulse width signal and the delay signal are added, the amplitude of the minimum pulse width signal of the logic input signal is made larger than the amplitude of a signal having a pulse width wider than the minimum pulse width, A sharpness correction device for a television receiver, characterized in that the sharpness is corrected.