JPS6057789B2 - Keystone distortion correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a projection type television system in which a large-screen television image is obtained by projecting an image from a projection tube onto a directional reflective screen. , automatically improves the difference in the skewness of the trapezoidal raster when changing the screen tilt,
The purpose is to make it possible to freely select the desired screen angle.

In general, a projection television system projects the image of a projection CRT onto a screen with reflective directionality for viewing.The system shown in Figure 1 integrates the projector and screen and uses a folding reflective mirror. In the integrated type,
The principal axis 6 of light normally has an angle θ with respect to the normal line of the screen 5, and the raster shape of the image projected on the screen 5 appears distorted into an inverted trapezoid as shown in 7a when viewed from the direction of the principal axis 6. .

Therefore, it is necessary to correct the deflection raster generated in the projection tube 2 into a trapezoid so that the raster appears as a normal rectangle, that is, in the shape of 7b on the screen. Light emitted from a projection tube 2 built into a projector body 1 is reflected by a plane mirror 4 and is incident on a screen 5 located at the rear.

Projection television systems are sometimes viewed by a large number of people, taking advantage of their large screens. Normally, in order to improve screen brightness, the screen 5 is provided with reflective directivity, whose main axis is at the height of the human eye, or 1.27T.
Most are around L to 1.5wL. As shown in Figure 2, the disadvantage of such a case is that when viewing a projection television in a place such as a classroom with stairs, in order to show a brighter image equally to a large number of people, the main axis of the light must be from normal 6a to 6b
There are many things I want to focus on. In order to do this, the main body 1 should be tilted entirely with respect to the floor, but this would be unstable to support nine out of ten main bodies, and adjustment would be difficult. In order to obtain the principal axis direction of the light shown at 6b in FIG. 2, it is easiest to change the angle of only the screen 5.
Changing the slope of θ means that the angle of incidence θ in Figure 1 changes, and the raster shape also changes, so the trapezoidal distortion correction that was initially adjusted becomes more difficult as the angle changes. The problem is that it gradually becomes inappropriate. With conventional equipment, it is not impossible to eliminate raster distortion by readjusting the correction circuit in the projector 1, but it is difficult to see the image on the screen 5 from the chassis side, so adjustment requires two people. It is difficult for general users to readjust the keystone correction according to the purpose when moving from classroom or room. It cannot be said that this is preferable from a safety point of view. The present invention detects the inclination of the screen and automatically adjusts the amount of correction for trapezoidal distortion, and one embodiment thereof is shown in FIG.

Here, the same members as in the conventional example are denoted by the same numbers. 8 is a potentiometer to which a DC voltage is applied between fixed terminals V1 and 3, and an output control voltage is taken out from a movable terminal V2; 9 is a control section for a trapezoidal distortion correction circuit provided in the horizontal deflection output circuit.

The movable terminal 2 of the potentiometer 8 is linked to the rotation of the screen 5 (from 5a to 5b or from 5a to 5c). That is, when the screen 5 is rotated to obtain the desired optical axis 6a, 6b or 6c of the reflected light, the potentiometer 8
The output control voltage output from the movable terminal V2 changes,
This signal is input to the control unit 9 to optimally adjust the correction amount of the trapezoidal distortion correction circuit. FIG. 4 shows an example of a potentiometer 10 whose position can be detected.

This potentiometer 10. The rotation of the screen 5 is detected by the displacement of the end portion of the screen 5, and the RARIDE shaft serving as the detection portion is interlocked with the movable terminal. The above embodiment shows a configuration in which the trapezoidal distortion correction circuit is controlled by a DC voltage, but this is a case where the trapezoidal distortion correction circuit is controlled by a DC voltage. This is because it is necessary to pull out the yometer 8 from inside the projector body 1 to the screen 5, and electrical stability is taken into consideration.

When performing trapezoidal distortion correction using a power modulation type horizontal deflection output circuit, the power supply is modulated with a vertical frequency sawtooth wave voltage, so a variable resistor for adjusting the gain of this sawtooth wave is used. It is clear that the potentiometer 8 can be used in the same manner as the potentiometer 8 and linked to the screen 5. Fifth
The figure shows an example of a more specific configuration of the embodiment of FIG. 3. This shows the horizontal deflection output circuit for the 3-projection tube system, which separates the upper and lower two windings of each horizontal deflection coil, and corrects raster trapezoidal distortion by flowing horizontal sawtooth wave currents of different sizes. It is a correction device. Although it is possible to correct the trapezoidal raster by distorting the magnetic field of the deflection coils by inserting an inductance into one side of the upper and lower windings of each horizontal deflection coil, this is somewhat unsuitable for application of the present invention.
This is because drawing out the above inductance to the outside as a means of converting the mechanical movement of the screen may cause instability because the horizontal deflection current has a large power and high frequency.Therefore, this implementation In the example, control is performed via a saturable reactor.11 is a horizontal oscillation drive circuit, whose output pulse drives a switching transistor 12, and the collector of this transistor 12 is connected to a diode 13 connected in parallel. A capacitor 14 is connected.

The collector is also connected to +B via a horizontal output transformer 15, and horizontal deflection coils 16, 17, 18.
is used as a load, and is grounded via a linearity coil 20 and an S-shaped capacitor 21. Each of the above deflection coils 16,
17 and 18 are separated into upper and lower parts, respectively, and windings 16a and 1
A saturable reactor 2 is connected to the point where one end of 7a and 18a are connected.
The two secondary windings 23 and 24 are inserted in a connected manner and join the connection point between the linearity coil 20 and the windings 16b, 17b, and 18b. On the other hand, a direct current from a constant current circuit whose current magnitude can be arbitrarily varied is passed through the control winding 25 of the saturable reactor 22. control transistor 29
One end of the control winding 25 is connected to the emitter of the control winding 25, and the other end is grounded by a detection resistor 26. The detected voltage of the resistor 26 is applied to the base of the comparison transistor 27 and compared with the reference voltage V2 voltage of the variable resistor 33, and that signal controls the base of the control transistor 29 via the resistors 28 and 30. be. The reference voltage is generated by the resistor 31 and the Zener diode 32, and the voltage of the variable resistor 33 is
added in between. This reference voltage and variable resistor
In the potentiometer shown in FIGS. 2 and 2, the movable shaft (terminal V2) is linked to the mechanical displacement of the screen 5. When the screen 5 is rotated from the standard position 5a as shown in 5b, the V2 voltage increases, the emitter potential of the comparison transistor 27 decreases, the current 1c of the control winding 25 decreases, and the inductance increases, so that the winding a The current difference between the side and the b side increases, and the amount of trapezoidal correction is increased. In this embodiment, keystone distortion correction is performed by the difference in current flowing through the divided deflection coils, and the amount of correction is controlled by direct current generated in conjunction with the displacement of the screen.
It is possible to correct raster distortion due to changes in screen angle (direction of reflected optical axis) with very stable operation.
Therefore, even if you change the installation location of the projection television device or change the projection direction, it is possible to always make the raster in the correct shape in the direction with the best reflection conditions, reducing the hassle of adjustment work and improving service accuracy. The above was also a big improvement. As described above, the present invention provides a convenient trapezoidal distortion correction device that can correct raster trapezoidal distortion in conjunction with changes in the screen angle, making it easy and convenient to change the screen angle depending on the situation. be.

[Brief Description of the Drawings] Figure 1 is a side view and front view for explaining the projection television device and its raster shape, Figure 2 is a side view of the installation location, and Figure 3 is the trapezoidal distortion of the present invention. A configuration diagram of one embodiment of the correction device, FIG. 4 is a main part circuit diagram of another embodiment, and FIG.
FIG. 3 is a circuit diagram of the illustrated embodiment; 1... Projector body, 2... Projection tube, 4
...Flat mirror, 5...Screen,
8, 10... Potentiometer, 9...
- Control unit of trapezoidal distortion correction circuit, 11... Horizontal oscillation drive circuit, 12... Switching transistor, 13... Diode, 14... Capacitor, 15... ...Horizontal output transformer, 16,1
7, 18...Horizontal deflection coil, 22...
・Saturable reactor, 26...Detection resistor, 27.
... Comparison transistor, 29 ... Control transistor, 33 ... Variable resistor.

Claims (1)

[Scope of Claims] 1. A trapezoidal distortion correction device used in a projection television device that integrally includes a projection picture tube and a directional reflective screen that reflects the image projected from the projection picture tube forward. a detection mechanism for detecting the tilt angle of the directional screen; a circuit means for obtaining an electrical output in conjunction with the detection mechanism; and an automatic raster keystone distortion correction circuit using the output of the circuit means as input. 1. A trapezoidal distortion correction device, comprising: a control means for controlling. 2. The trapezoidal distortion correction circuit connects a deflection yoke whose winding is divided into parts to the output end of the horizontal deflection output circuit, and connects the secondary winding of the saturable reactor to one of the divided windings. A detection mechanism that is configured and linked to a unidirectional screen,
The trapezoidal distortion correction device according to claim 1, wherein the circuit means and the control means constitute a DC control circuit that controls the control winding of the saturable reactor by using the output of the potentiometer as an input. .