JPH0937102A - Crt focus voltage control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance of white balance tracking and to prevent dispersion between sets by controlling the blue focus of a projection television into the optimum value corresponding to a CRT. SOLUTION: A signal source 1 outputs the synthetic wave of an H parabolic wave and a V parabolic wave and a preamplifier 2 amplifies the output from the signal source 1 to the suitable level. Then, an amplifier circuit 3 amplifies the output from the preamplifier 2 to the level for inputting toe focus electrode of the CRT and a variable resistor 4 controls the output from the amplifier circuit 3. A test point 5 is the output part of the preamplifier 2. Thus, the dispersion of a CRT drive current and luminance characteristics is suppressed and the performance of picture quality is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CRT focus voltage adjusting circuit in a CRT three-tube type projection television receiver and the like. It is intended to improve the image quality performance.

[0002]

2. Description of the Related Art Conventionally, in a CRT three-tube projection television receiver, etc., the focus adjustment of the CRT is
A general method is to receive a predetermined evaluation pattern signal and adjust by visual evaluation so that the center of the screen has the best focus.

An example of the adjusting method is disclosed in Japanese Patent Laid-Open No. 62-62.
As described in JP-A-188568, a method of adjusting the focal length of the electrostatic lens and setting the electrostatic focus by setting the area of the electron beam spot on the phosphor screen to a required size. There is.

[0004]

However, in the above-mentioned conventional method, there is no particular problem in the focus adjustment of the red and green CRTs, but in the blue CRT, the characteristics of the CRT drive current and the brightness are adjusted by the focus adjustment points. Since the difference in focus is significantly different, the performance of white balance tracking deteriorates due to the variation in focus adjustment and the variation between sets occurs. Also, when the characteristics similar to the CRT drive current and brightness characteristics of the red and green CRTs are obtained with the blue CRT, the focus is determined by visual evaluation with the evaluation pattern signal in the same method as the red and green CRTs, depending on the type of CRT. In some cases, it may be better to set the focus voltage on the blooming side (higher voltage side) rather than the focus voltage adjusted to the optimum point.

The present invention sets the focus of a blue CRT to C
The purpose of the present invention is to improve the tracking performance of the white balance and prevent the variation between sets by adjusting the optimum point according to RT without variation between sets.

[0006]

In order to achieve the above object, a CRT focus voltage adjusting circuit of the present invention provides a signal source for outputting a composite wave of an H parabolic wave and a V parabolic wave, and an appropriate output from the signal source. A preamplifier that amplifies the size, an amplifier circuit that amplifies the output from the preamplifier to a level that is input to the focus electrode of the CRT, a variable resistor that adjusts the output level from the amplifier circuit to an optimum point for the CRT, and a preamplifier It has the test points of the output part of.

[0007]

According to the present invention, the test point of the output part of the preamplifier and GND are short-circuited at the time of set adjustment, the output from the preamplifier is set to 0 V, and the output of the amplifier circuit is set to the DC component only. By projecting a window signal in which the beam current flowing in the CRT is 8 mA or more, and adjusting the variable resistor so that the brightness of that part becomes the minimum value, the DC level at the optimum point in the normal state of the focus voltage is It is possible to set the DC level to a level that is higher by half the value of the AC component of the dynamic focus waveform. Therefore, if you return the test point at the output of the preamplifier and the GND short,
The output from the amplifier circuit does not vary between sets, and the AC of the dynamic focus waveform is higher than the optimum point in the normal state.
It can be set to a DC-high value by half the value of the component.
In addition, by selecting a point at which the window signal is displayed and adjusted, the focus voltage value is within a range of half the AC component of the dynamic focus waveform.
An arbitrary value can be set to a high value in terms of DC. As a result, it is possible to improve the tracking performance of white balance and suppress variations between sets.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A CRT focus voltage adjusting circuit in an embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram of a CRT focus voltage adjusting circuit according to a first embodiment of the present invention. As shown in FIG. 1, the CRT focus voltage adjusting circuit of the present invention includes a signal source 1 that outputs a composite wave of an H parabolic wave and a V parabolic wave, and a preamplifier 2 that amplifies the output from the signal source 1 to an appropriate size. And the output from the preamplifier 2 is C
An amplifier circuit 3 that amplifies to a level input to the focus electrode of the RT, a variable resistor 4 that adjusts the output level from the amplifier circuit 3 to an optimum point for the CRT, and a test point 5 at the output part of the preamplifier 2. To be done.

When the output from the signal source 1 is observed at the horizontal rate, the H parabolic waveform shown in FIG. 2 is observed. The output from the signal source 1 is amplified by the preamplifier 2 to an appropriate size, and is amplified by the amplifier circuit 3 to a level for controlling the focus electrode of the CRT. Observing the output of the amplifier circuit 3,
The H parabola waveform shown in FIG. 3 is observed.

The operation of the first embodiment will be described below. In addition,
The waveform in FIG. 3 is a waveform in the optimum state of the focus adjustment of the CRT in the normal state. At the time of set adjustment, the test point 5 of the output part of the preamplifier 2 and GND are short-circuited, the output from the preamplifier 2 is set to 0 V, and the output of the amplifier circuit 3 is set to only the DC component as shown in FIG. 4 (a). ,
As shown in FIG. 5, a window signal in which the beam current flowing in the CRT is 8 mA or more is projected on the left end of the screen, and the variable resistor 4 is adjusted so that the brightness of that portion becomes the minimum value. The DC level is set to a level that is higher than the DC level at the optimum point in (1) by half the value of the AC component of the dynamic focus waveform. Therefore, the test point 5 at the output of the preamplifier 2 and the GND
4B, it becomes possible to adjust as shown in FIG. 4B, the output from the amplifier circuit 3 does not vary between the sets, and the AC component of the dynamic focus waveform is less than the optimum point in the normal state. It can be set to a DC high value by only one-half the value. Further, by selecting the adjustment point shown in FIG. 5, it is possible to set a DC-high value by an arbitrary value within the range of the value of half the AC component of the dynamic focus waveform.

(Second Embodiment) FIG. 6 is a block diagram of a CRT focus voltage adjusting circuit according to the second embodiment of the present invention. As shown in FIG. 6, the circuit configuration shown in FIG. 1, the brightness sensor 6 installed on the screen frame, and the microcomputer 7 that controls the setting of the variable resistor 4 according to the output from the brightness sensor 6 are included. It The operation will be described below.

At the time of set adjustment, the test point 5 of the output part of the preamplifier 2 and GND (ground) are short-circuited, the output from the preamplifier 2 is set to 0 V, and the amplifier circuit 3
The output of is set to only the DC component as shown in FIG. 4, and as shown in FIG. 6, a window signal with a beam current of 8 mA or more flowing in the CRT is projected on the place where the brightness sensor of the screen frame is installed. The brightness sensor 6 detects the brightness, and the microcomputer 7 controls the setting of the variable resistor 4 so that the detected value becomes the minimum value. As a result, it is possible to set the DC level to a level that is higher than the DC level at the optimum point in the normal state shown in FIG. 3 by a half of the AC component of the dynamic focus waveform. Therefore, the test point 5 at the output of the preamplifier 2 and the GND
If the short circuit is restored, the output from the amplifier circuit 3 can be set to a DC value higher than the optimum point in the normal state by a half of the AC component of the dynamic focus waveform without variation between the sets.

(Embodiment 3) FIG. 7 is a block diagram of a CRT focus voltage adjusting circuit according to a third embodiment of the present invention. As shown in FIG. 7, the preamplifier 2 in the circuit configuration shown in FIG. 1 has a function of amplifying the output from the signal source 1 to an appropriate size, and the output from the signal source 1 is inverted by mode switching. In this configuration, the preamplifier 8 has a function of amplifying to an appropriate size. The operation will be described below. At the time of set adjustment, the operation mode of the preamplifier 8 is switched to the inverting amplifier, and the output of the amplifier circuit 3 is set to the waveform in which the AC component of FIG. 3 is inverted as shown in FIG.
As shown in FIG. 5, a window signal in which the beam current flowing in the CRT is 8 mA or more is projected on the left end of the screen, and the variable resistor 4 is adjusted so that the brightness of that portion becomes the minimum value. It is possible to set the DC level to a level higher than the DC level at the optimum point by the value of the AC component of the dynamic focus waveform.
Therefore, the test points 5 and G at the output of the preamplifier 2
By returning the short circuit of ND, the output from the amplifier circuit 3 can be set to a value higher in terms of DC than the optimum point in the normal state by the value of the AC component of the dynamic focus waveform without variation between the sets. Further, by selecting the adjustment point shown in FIG. 5, it is possible to set a high DC value by an arbitrary value within the range of the value of the AC component of the dynamic focus waveform.

[0015]

As described above, according to the present invention, the blue CR
By adjusting the focus of T to the optimum point according to the CRT without variation between sets, it is possible to improve the tracking performance of white balance and prevent variation between sets.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a CRT focus voltage adjusting circuit according to a first embodiment of the present invention.

2 is an output waveform diagram of the signal source 1 in FIG.

3 is an output waveform diagram of the amplifier 3 in FIG.

FIG. 4 is an output waveform diagram of the amplifier 3 during adjustment in FIG.

FIG. 5 is an explanatory diagram showing adjustment points in the embodiment of the present invention.

FIG. 6 is a circuit diagram of a CRT focus voltage adjustment circuit according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a CRT focus voltage adjusting circuit according to a third embodiment of the present invention.

8 is an output waveform diagram of the amplifier 3 at the time of adjustment in FIG.

[Explanation of symbols]

 1 Signal Source 2 Preamplifier 3 Amplifying Circuit 4 Variable Resistor 5 Test Point 6 Luminance Sensor 7 Microcomputer 8 Preamplifier

Claims (3)

[Claims] 1. A signal source for outputting a combined wave of H and V parabolic waves, a preamplifier for amplifying the output from the signal source to an appropriate size, and a CRT for the output from the preamplifier.
Of the preamplifier, a variable resistor for adjusting the output level from the amplifier circuit to an optimum point for the CRT, and a test point of the output part of the preamplifier. CRT focus voltage adjustment circuit. 2. A signal source for outputting a combined wave of H-parabola wave and V-parabola wave, a preamplifier for amplifying an output from the signal source to an appropriate size, and a CRT for an output from the preamplifier.
Installed on the screen frame, an amplifier circuit that amplifies to the level that is input to the focus electrode of, a variable resistor that adjusts the output level from the amplifier circuit to the optimum point for the CRT, the test point of the output part of the preamplifier, and An automatic CRT focus voltage adjusting circuit comprising a brightness sensor and a microcomputer that controls the setting of the variable resistor according to the output from the brightness sensor. 3. A signal source for outputting a combined wave of H-parabola wave and V-parabola wave, a function for amplifying the output from the signal source to an appropriate magnitude, and an output from the signal source is inverted by mode switching. , A preamplifier that also has the function of amplifying to an appropriate size, an amplifier circuit that amplifies the output from the preamplifier to the level that is input to the focus electrode of the CRT, and the output level from the amplifier circuit is the optimum point for the CRT. A CRT focus voltage adjustment circuit comprising a variable resistor for adjusting to and a test point of an output part of a preamplifier.