JPH03205966A - Brightness correction circuit - Google Patents

Abstract

PURPOSE: To make the luminance distribution on a whole screen uniform by correcting a grid voltage supplied to the first grid of a cathod ray tube for the periods of horizontal deflected signals and vertical deflected signals. CONSTITUTION: Vertical and horizontal signals respectively impressed through vertical and horizontal signal input terminals 20 and 30 are supplied to the first grid terminal of a cathode ray tube 90 after the signals are synthesized to one parabolic signal through a parabolic signal generating section 40 and amplified by means of an amplifying section 60. For the starting sections of horizontal and vertical periods, for example, for the left- and top-side peripheral sections of a screen, a grid correcting voltage is made higher, and, for the central part of the screen, the grid correcting voltage is made lower. For the terminating section of the horizontal and vertical periods, namely, for the right- and bottom-side peripheral section of the screen, the grid correcting voltage is made higher. Therefore, the quality of pictures displayed on the screen of a cathod ray tube can be improved, because the luminance on the whole screen of the cathod ray tube becomes uniform and a noise phenomenon which is caused by a luminance difference in the peripheral section can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brightness correction circuit, and particularly relates to a brightness correction circuit that corrects the first grid voltage and the gain of a video signal so that the entire screen of a color brown tube has the same brightness. It is related to.

In general, as the resolution of color brown tubes becomes higher and the screen size of brown tubes becomes larger, color brown tubes are used to remove the difference in color purity that occurs between the center and the periphery of the screen and correct the brightness. As you go to the periphery, R. G
．． B. %lThe black matrix (blac) between the light bodies
k matrix) has a structure in which the part gradually expands.

Therefore, the color brown tube cathode
) to drive the color brown tube, the gain of the video signal has a constant value that does not fluctuate within any period of the horizontal deflection signal and the vertical deflection signal, so it is as described above. When a white raster is displayed on the entire screen of a color brown tube having a screen structure using the same beam current, the brightness at the periphery of the screen is lower than the brightness at the center of the screen.

As shown in Figure 1, as the brightness of the peripheral part of the color brown screen decreases compared to the central part, a phenomenon appears in which the peripheral part becomes darker and a part of the screen appears blurred, resulting in a decrease in image quality. It had some disadvantages.

The present invention was devised to solve the above-mentioned conventional problems, and in driving the color brown tube, the color brown tube is moved from the center of the screen to the periphery in the vertical and horizontal directions. The purpose of the present invention is to provide a brightness correction circuit that solves the phenomenon in which the brightness of the screen gradually decreases and makes the brightness distribution of the entire screen of a brown screen uniform.

As a technical means to achieve the above object, the present invention corrects the grid voltage provided to the first grid of the Brownian tube according to the period of the horizontal deflection signal and the vertical deflection signal, so as to correct the grid voltage provided to the first grid of the Brownian tube at the beginning of the horizontal and vertical periods. For example, the grid correction voltage is set high at the left and upper periphery of the screen, and at the same time, the grid correction voltage is set at a low value at the center of the screen. The part is characterized by a brightness correction circuit that increases the grid correction voltage.

As another technical means to achieve the above object, the present invention corrects the gain of the video signal provided to the color brown tube according to the period of the horizontal deflection signal and the vertical deflection signal, so that For example, the left side and upper periphery of the screen have a high gain of the video signal, while the center of the screen has a low gain of the video signal, and the final parts of the horizontal and vertical periods, such as the right side and bottom of the screen, have a high gain of the video signal. The side peripheral portion features a brightness correction circuit that increases the gain of the video signal.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIGS. 2A and 2B are circuit block diagrams showing one embodiment and other embodiments of the luminance correction circuit according to the present invention,
A synchronization circuit amplifies the color composite video signal (including brightness signal, chromaticity signal, synchronization signal, and color burst signal) output from the receiver's video detector (not shown) to the required size. The video signal provided by the video amplifier circuit (not shown) that distributes the signal to the band amplifier circuit, corrects the delay time due to the difference in the bandwidth of the color signal and the luminance signal, regenerates the DC component, and compensates for the Takagi characteristic. It is provided to the cathode of the brown tube through the brown tube driver and the video output section.

As shown in FIG. 2A above, the vertical signal and horizontal signal applied through the vertical/horizontal signal input terminals (21) and (30) are converted into one parabolic signal via the parabolic signal generator (40). After being combined into a signal, the signal is amplified by the amplifier (60) and provided to the first grid terminal of the Brown tube (9o).

The vertical signal input terminal (21) and the horizontal signal input terminal (30) are connected by a conventional Brownian vertical deflection circuit and horizontal deflection circuit, respectively. As shown in FIG. 2B, the video signal is passed through the video signal input terminal (10), the gain is corrected in the video signal gain correction section (50), and then amplified by the amplifier section (60). Driver (7
0).

The means for gain correcting the video signal in the gain correction section (50) includes a parabolic signal generation section (4o) which receives the vertical signal applied through the terminal (21) and the horizontal signal applied through the terminal (30). ), this vanipolar signal generation section (40) transforms each vertical and horizontal signal into a parabolic waveform signal, synthesizes it into one parabolic signal, and sends the synthesized parabolic signal to the video signal gain correction section (50). Provided to.

In FIG. 3A, which is a detailed circuit diagram of one embodiment of the present invention having such a configuration, in the parabolic signal generating section (4o), a signal according to the vertical deflection period inputted through the terminal (21) is transmitted to the vertical deflection coil. (L1), then applied to the amplifier (GO) through the blocking diode (D1), and the horizontal signal according to the horizontal deflection period input through the terminal (30) is passed through the horizontal deflection coil (L2) to the resistor ( R2)
It can be seen that the voltage is applied to the amplification section (60) through the blocking diode P (D2).

In addition, the vertical deflection coil (L1) and the diode (D1
) is connected to a series-connected capacitor (C1) and a grounded resistor (R1), so the vertical signal is converted into a parabolic waveform as shown in Figure 4(a), and the horizontal deflection coil Since the connection point between (L2) and the resistor (R) is connected to a grounded capacitor (C2), the horizontal signal is converted into a parabolic waveform like 4v4(b), and the vertical or The horizontal deflection parabolic signal coincides with the deflection period. The synthesized parabolic signal is passed through a capacitor (C3) and a bias resistor (R5) to an amplification transistor (Q) as shown in FIG. 3A.
1) is applied to the base of this transistor (Q1)
The phase of the signal is inverted and applied to the collector of the transistor (Q2), and the amplified signal having the same phase as the signal applied to the base is applied to the emitter of the transistor (Q2). It is outputted and provided to the first grid of the Brown tube (90) through the capacitor (C4). Here, the resistors (R6) to (R8) are bias resistors, and the resistors (R3, R4) are used as voltage dividing resistors.

That is, as the synthesized parabolic signal is applied to the base of the transistor (Q1), the collector-emitter bias pressure of the transistor (Q1) is converted, and at the same time, the synthesized parabolic signal applied to the base of the transistor (Q2) is amplified and the bias voltage of the transistor (Q1) is amplified. (Q2), this signal is provided to the first grid of the Brown tube together with the voltage (VG1) provided to the first grid.

Moreover, if we look at FIG. 3B, which is a detailed circuit diagram of another embodiment of the present invention having the above-mentioned configuration, we can see that the parabolic signal generation 1
In 1B (40), a vertical signal based on the vertical deflection period inputted through the terminal (21) passes through the vertical deflection coil (L1), is applied to the integrating circuit via the blocking diode (D1), and is applied to the integrating circuit through the terminal (30). After the horizontal signal according to the input horizontal deflection period passes through the horizontal deflection coil (L2), it is connected to a variable resistor (VR) and a blocking diode (D
It can be seen that the voltage is applied to the integrating circuit through 2).

The video signal gain correction unit (50), which allows the video signal input through the terminal (IO) to be gain-corrected to the synthetic parabolic signal, is configured to include a video signal gain correction control transistor (50) to which the synthetic parabolic signal is applied. Q4) and a transistor (Q4) that corrects the gain of the video signal by changing the collector-emitter voltage by a synthesized parabolic signal applied to the base of this transistor (Q4).
3) and bias resistors (R10) to (R14).

Therefore, the integrating circuit of the parabolic signal generating section (40) synthesizes the two parabolic signals of vertical and horizontal deflection as shown in the waveform of FIG. 4(C), and applies the synthesized signal to the video signal gain correcting section (50).

That is, as the synthesized parabolic signal is applied to the base of the transistor (Q4), the collector-emitter bias voltage of the transistor (Q4) is changed, and at the same time, the gain of the video signal applied to the base of the transistor (Q3) is corrected. Since the gain-corrected video signal is output to the collector of (Q3), this signal (Fig. 4 (D)) is a composite parabolic signal (Fig. 4 (C)
)) with inverted phase.

That is, instead of making the gain of the video signal have a constant value without fluctuation within any period of the vertical and horizontal deflection signals, the gain of the video signal and the grid voltage are corrected according to the period of the vertical and horizontal deflection signals. In this way, the periphery, which is the beginning and end of a horizontal or vertical period, is largely compensated,
The central portion of the horizontal or vertical period is compensated low.

In this way, the gain-corrected video signal is amplified in three stages by the amplifier section (60) in which transistors (Q5), (Q6), and (Q7) are successively connected. The amplified gain-corrected video signal is passed through a Brownian dryer (70
The light is supplied to the cathode of the brown tube (90) through the L video output section (80), so that the entire screen has the same brightness.

In addition, in the first grid voltage (VG1) adjustment method described above, the grid voltage (VG1) increases in the peripheral part of the brown tube to increase the brightness, and the grid voltage (VG1) increases in the central part of the brown tube.
Since G1) is low and the brightness is lowered, the entire screen of the large brown tube should have the same brightness.

As described above, according to the present invention, the image quality can be improved because the entire brown screen screen has the same brightness and the noise phenomenon caused by the difference in brightness in the peripheral area is removed.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention, and is a diagram illustrating that when displaying raster, the brightness is lower at the periphery than at the center of the screen, and FIG. 2A is an example of an embodiment according to the present invention. FIG. 2B is a block diagram of a brightness correction circuit according to another embodiment of the present invention, FIG. 3A is a detailed circuit diagram according to FIG. 2A, and FIG. 3B is a block diagram of a brightness correction circuit according to another embodiment of the present invention.
The figure is a detailed circuit diagram according to FIG. 2B, and FIG. 4 is a waveform diagram of important parts of the output signal in FIG. 3. IO...Video signal input terminal 21)...Vertical signal input terminal 30...Horizontal signal input terminal 40...Parabolic signal generation section 50...Video signal gain correction section 60...Amplification section 21) ...Brown Suga driver 80...Video output section 90...Brown Suga et al. Procedural amendment (method) (Patent Office examiner 1. Display of case 1999 2. Name of invention Patent 270135 Luminance Correction circuit 3. 4. Name of the person making the correction in relation to the case

Claims (6)

[Claims] (1) The video signal provided by the video amplifier circuit is provided to the cathode of the Brown tube (90) via the Brown tube driver (70) and the video output section (80). a parabolic signal generator (40) that converts the signal and the horizontal deflection signal into respective parabolic signals and then combines them into one parabolic signal; and a brown tube (90) that amplifies the combined parabolic signal in stages. A brightness correction circuit characterized by comprising an amplifier section (60) provided to a first grid of. (2) In the parabolic signal generator (40), the vertical deflection signal provided from the vertical deflection coil (L1) flows through a capacitor (C1) and a grounded resistor (R1), which also passes through a blocking diode (D1). The horizontal deflection signal provided from the horizontal deflection coil (L2) flows to the grounded capacitor (C2), then to the resistor (R2), and then to the blocking diode, so that the horizontal deflection signal provided from the horizontal deflection coil (L2) flows through the two diodes (D1). ) and (D2), the brightness correction circuit is characterized in that the two parabolic signals output from (D2) are provided to the amplifier (60). (3) In the amplification section (60), the synthesized parabolic signal is provided to the base of the amplification transistor (Q1) via a capacitor (C3) and a bias resistor (R5), and is provided to the collector of the transistor (Q1). The phase of the signal appears inverted, and the secondary amplification transistor (Q2)
An amplified signal whose phase is synchronized with the parabolic signal applied to the base of the transistor (Q2) is outputted from the emitter of the transistor (Q2), and is sent to the Brownian tube (
90).
Term brightness correction circuit. (4) The video signal provided from the video amplification circuit is supplied to the cathode of the Brown tube (90) via the Brown tube driver (70) and the video output section (80). and a parabolic signal generating unit (40) that converts the horizontal deflection signals into respective parabolic signals and then combines them into one parabolic signal, and a gain control signal based on the combined parabolic signal that causes the video signal to correspond to the scanning period. a video signal gain correction unit (50) that performs gain correction and outputs the video signal, and a stepwise amplification of the gain-corrected video signal output from the gain correction unit (50) and outputs the video signal to the Brown tube driver (70). an amplification unit (60) provided to
A brightness correction circuit characterized by comprising: (5) In the parabolic signal generator (40), a vertical deflection signal provided from a vertical deflection coil (L1) flows through a capacitor (C1), a grounded resistor (R1), and then a blocking diode (D1). Then, the horizontal deflection signal provided from the horizontal deflection coil (L2) flows to the grounded capacitor (C2), then to the variable resistor (VR), and then to the blocking diode (D2), thereby achieving the above two conditions. two diodes (D1) and (D2
4. The brightness correction circuit according to item 4, characterized in that the two parabolic signals output from the circuit (2) are synthesized by an integrating circuit composed of a resistor (R21) and a capacitor (C5). (6) The video signal gain correction section (50) includes a transistor (Q4) whose bias voltage is changed according to the combined parabolic signal level and outputs a gain correction control signal, and a transistor (Q4) whose bias voltage is changed according to the combined parabolic signal level and which outputs a gain correction control signal. A transistor (Q
3) and bias resistors (R10) to (R14).