JP2605289B2 - Focus switching adjustment circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus switching adjustment circuit that contributes to simplification of lens focus adjustment and white balance adjustment when a projection type color receiver is installed.

2. Description of the Related Art Projection tubes (CRs) generally used in projection color receivers
As shown in FIG. 2, the drive voltage vs. light emission characteristics of each of the phosphors of T) are, as shown in FIG. Therefore, there is a restriction that the white color temperature must be lowered by adjusting the white balance of the receiver.

In order to alleviate the luminance saturation of the blue phosphor as much as possible and to increase the color temperature of white, the focus adjustment of the blue CRT is usually performed in a slightly overfocus state 21 which is advantageous in terms of luminance saturation characteristics.
Is set to

However, in this state, it is difficult to optimally adjust the focus of the projection lens mainly because the display video information is defocused and the luminosity of the blue emission color is lower than the other two colors. Therefore, it has two modes for just focus setting for projection lens focus adjustment and overfocus adjustment for white balance adjustment.

Hereinafter, an embodiment of a conventional focus switching adjustment circuit (in the case of an electromagnetic focusing CRT) will be described with reference to FIG.

1 is an internal cross hatch signal terminal, 2 is a video signal terminal,
Reference numeral 3 denotes a video process circuit for controlling brightness, contrast, etc., 5 denotes a focus adjustment volume for blue just focus setting (mode A), 6 denotes a focus adjustment volume for blue overfocus adjustment (mode B), 7
Is a vertical parabolic wave voltage input terminal, 8 is an impedance conversion transistor, 9 is a differential amplifier, 10 is a drive transistor, 11 is a blue focus output transistor, 12 is a blue static focus coil, 13 is a green focus adjustment volume, and 14 is a red focus. An adjustment volume, 15 is a green focus constant current stabilizing circuit, 16 is a red focus constant current stabilizing circuit, 17 is a green static focus coil, 18 is a red static focus coil, 23 is a signal changeover switch, and 24 is a mode changeover switch.

In this static circuit, a vertical parabolic wave current is applied to a static focus coil using an electromagnetic focusing method by using a vertical parabolic wave voltage, and focus control is performed.

First, when the receiver is installed, the internal crosshatch signal is projected by the signal changeover switch 23, the mode changeover switch 24 is set to the mode A, the electric focus volume 5 is adjusted, and the base voltage of the transistor of the differential amplifier 9 is changed. By changing the current flowing through the blue static focus coil 12, the electric focus of the blue CRT is set to the just focus state. In this state, the blue CRT projection lens is turned to optimize the lens focus.

Next, the signal is switched to a video signal by the signal changeover switch 23, the mode changeover switch 24 is set to the mode B, the electric focus volume 6 is adjusted and set to a little overfocus, and the white balance is optimized.

Problems to be Solved by the Invention However, in the above configuration, there is a problem that the signal changeover switch and the mode changeover switch must be switched every time the focus is adjusted, resulting in poor operability.

The present invention has been made in view of the above problems, and provides an apparatus with good operability at the time of focus adjustment.

Means for Solving the Problems In view of the above problems, the present invention makes the two-mode changeover switch for focus adjustment and the signal changeover switch interlock.

Operation The present invention realizes simplification of focus adjustment in each of the projection lens focus adjustment and the white balance adjustment by the above configuration.

An embodiment of the present invention (in the case of an electromagnetic focusing CRT) will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a focus switching adjustment circuit according to the present invention. 1 is an internal cross hatch signal terminal, 2 is a video signal terminal, 4 is a signal and mode switch, and 5 and 6 are blue CRT electric focus volumes.

First, when the internal crosshatch signal is projected by the signal changeover switch 4, the focus changeover adjustment circuit is in the A mode at the same time, so that the electric focus volume 5 is adjusted and set to the just focus state. Then, in this state, the blue CRT projection lens is turned to optimally adjust the lens focus.

Next, in order to adjust the white balance, when the signal changeover switch 4 is switched to the video signal side, at the same time, the focus switch adjustment circuit is in the B mode, so that the electric focus volume 6 is adjusted to optimize the white balance. Aim. As a result, at the time of re-installation, the projection lens focus adjustment only needs to switch the video signal to the internal cross hatch signal to adjust the lens focus, and the focus adjustment is easy.

Effects of the Invention As described above, the present invention makes it possible to simplify the focus adjustment at the time of installation of a projection type color receiver by interlocking a signal switch and a mode switch for focus adjustment as one switch. Can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a focus switching adjustment circuit according to an embodiment of the present invention, FIG. 2 is a diagram showing drive voltage vs. light emission characteristics of a projection tube (CRT), and FIG. 3 is a circuit diagram of a conventional focus circuit. 1 internal crosshatch signal terminal, 2 video signal terminal, 3 video processing circuit, 4 signal switch in conjunction with focus mode switching, 5 blue mode A focus adjustment volume, 6 Blue mode B focus adjustment volume, 7: Vertical parabolic wave voltage input terminal, 8: Impedance conversion transistor, 9:
… Differential amplifier, 10… Drive transistor, 11… Blue focus output transistor, 12… Blue static focus coil, 13… Green focus adjustment volume,
14… Red focus adjustment volume, 15… Green focus constant current stabilization circuit, 16 …… Red focus constant current stabilization circuit, 17 …… Green static focus coil, 18 …… Red static focus coil.

Claims (1)

(57) [Claims] 1. A just focus mode necessary for adjusting the lens focus of a projection type color receiver, and an over focus required for correcting a light emission saturation of a blue phosphor in a high luminance region and realizing a proper white balance. A focus switching adjustment circuit in which means for separately setting two modes of a focus mode, a switch for switching between the two modes, and a switch for switching between a built-in crosshatch signal and an external video signal used for convergence adjustment are linked. .