JP2001157221A - Convergence device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a convergence device that can correct convergence corresponding to fluctuation in an anode voltage without the need for a high voltage stabilizing device in a rear projection type projector where three projection tubes are placed with an offset. SOLUTION: In the projector where an R tube and a B tube are placed at both sides of a G tube as a center tube at a prescribed angular distance and images projected from the projection tubes are composited on a screen, a convergence control means of the convergence device corrects an offset of the convergence of the images projected onto the screen, produces a correction signal that relatively corrects the position of the image projected from the R, B tubes around the projected image from the G tube depending on the fluctuation of the anode voltage applied to each projection tube, adds this correction signal to convergence adjustment signals for the R, B tubes, and supplies the sum to a convergence yoke so as to attain the convergence correction on the screen without the need for a high voltage stabilizing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a convergence device applied to a projection display device (hereinafter, referred to as a projector) using a plurality of projection tubes.

[0002]

2. Description of the Related Art While the size of color television receivers has been increased, the weight of a type of receiver that directly looks at a cathode ray tube or a cathode ray tube (hereinafter referred to as a CRT) increases rapidly due to the increase in the size of the CRT. Therefore, the size of the CRT is naturally limited. For this reason, a projector that uses a projection type CRT (hereinafter, referred to as a projection tube) to enlarge and project an image on the projection tube surface with a lens has been developed, and a large-screen TV receiver of a direct-view type, which is difficult to realize, has been put into practical use. Have been.

The above-mentioned projector is generally a three-tube type projector using three projection tubes of three primary colors of R (red), G (green) and B (blue) for expressing a color television image.

In this three-tube projector, as described above, three projection tubes for projecting image light of different colors of R, G, and B are housed and arranged in the same cabinet, and the three projection tubes are arranged on the respective projection tube surfaces. The image light is enlarged and projected by a lens, and the images of the three primary colors are superimposed on a screen to display a color image. Therefore, it is necessary to completely match the images projected from each projection tube on the screen surface.

Hereinafter, the configuration of a conventional projector will be specifically described. 2A and 2B show a projector on which an image is projected on the back of the screen. FIG. 2A is an explanatory diagram viewed from the front, and FIG. 2B is an explanatory diagram viewed from the side. A screen 2 is arranged on the front upper portion of the cabinet 1, and the screen 2 is disposed below the screen 2 via a reflection mirror 3 provided on the rear surface of the cabinet 1.
Are provided with projection tubes 4R, 4G, and 4B for projecting R (red), G (green), and B (blue) image lights, respectively. The video light projected from the R, G, and B projection tubes forms an image on a screen so that a G projection tube (hereinafter, referred to as a G tube).
Centering on the left, R projection tube (hereinafter referred to as R tube)
, A projection tube for B (hereinafter, referred to as a B tube) is arranged in a C-shape on the right side in the figure. An enlarged projection lens 5 is arranged in front of each of the R, G, and B tubes. The size of the image magnified and projected on the screen is set by the magnification of the magnifying projection lens and the projection distance from the R, G, G tubes to the screen via the reflection mirror.

Assuming that the projection distance from the R, G, and B tubes to the screen surface is infinite, the mounting angles of the R, G, and B tubes in the cabinet are the same with respect to the screen, and three tubes are provided. Are arranged in parallel. However, since the projection distance is actually short, the three tubes must be mounted at different angles, and the R tube and the B tube are located on both sides of the screen surface with respect to the G surface as shown in FIG. Mounted at an angle.

Further, in a rear projection type projector comprising a relatively large screen and a cabinet, an R tube, a G
Although it is possible to arrange the tubes (B, B) at a relatively small mounting angle so that the center (optical axis) of the projected light intersects the center of the screen, if the size of the cabinet is made compact by a rear projection type projector, Since the projection distance is shortened by using a short focus projection lens, the center of the projection light of the R tube, the G tube, and the B tube cannot be matched at the center of the screen.

The reason for this will be described with reference to FIGS. In order to shorten the projection distance by using a short focus projection lens and to make the center of the projection light coincide with the center of the screen surface, as shown in FIG. The inclination mounting angle θ1 needs to be large. However, when the inclination angle θ1 between the R tube and the B tube increases, the quality of the image displayed on the screen deteriorates. This is shown in FIG.
This will be described with reference to FIG.

[0009] Center (optical axis) of light projected from R, G, B tubes
Is matched at the center of the screen, an image as shown in FIG. 3B is displayed on the screen. This figure 3
(B) assumes that a rectangular image is displayed without performing distortion correction in the horizontal deflection circuit and vertical deflection circuit and convergence correction in the convergence circuit.
The image of the G tube is indicated by a solid line, the image of the R tube is indicated by a dashed line, and the image of the B tube is indicated by a dotted line.

That is, in this case, as shown in FIG. 3 (a), since the light projected from the R tube and the B tube is deviated from the center of the projection lens, the light passing through the periphery of the lens is projected as compared with the G tube. Will be. Generally, light transmitted not only in the projection lens but also in the periphery of the lens causes an increase in aberration, a decrease in resolution, an increase in distortion, and the like, resulting in deterioration of performance. Also, on the tube surface of the projection tube, the images of the R tube and the B tube are offset from the center, and the image displayed on one end of the projection tube is projected as compared to the G tube, and the projection tube also has a lens. Similarly, the quality of the image is lower in the periphery than in the vicinity of the center due to an increase in aberration with respect to the shape of the electron beam and a decrease in focus quality.
In addition, an image displayed on a half surface near the G tube from the center of the R tube and the B tube displays half of the screen in a small area due to the relationship between the tube surface and the screen. As a result, the resolution on the screen decreases.

In order to eliminate such deterioration of image quality, the center (optical axis) of light projected from the R, G and B tubes is set on the screen as shown in FIG. Instead of making them coincide, they are deliberately shifted in the horizontal direction, and the inclination mounting angle θ2 between the R pipe and the B pipe centered on the G pipe is set small,
A method of offsetting the centers of the projection light of the R tube and the B tube so as to project on the screen is usually used. When the projection light of the R tube and the B tube is offset in this way, FIG.
Is displayed on the screen. FIG. 4B shows an example in which an image under the same conditions as those in FIG. 3B is displayed.

When the projection light of the R tube and the B tube is offset in this way, an image is displayed at the center of the tube surface of the R tube and the B tube,
The light to be projected also passes through the center of the projection lens, which can eliminate the above-mentioned increase in aberrations around the lens, a decrease in resolution and an increase in distortion, and a deviation of images displayed on the R and B tube surfaces. It is possible to eliminate an increase in aberration and a decrease in focus quality due to the projection tube and a decrease in resolution due to an electron beam density.

When the optical axes of the R tube and the B tube are offset from the optical axis of the G tube, the R and B images are shifted left and right. Is corrected so as to overlap. Generally, a deflection yoke of a projector is a main yoke for largely deflecting an electron beam in the horizontal and vertical directions from corner to corner of a projection tube, similarly to a direct-view television, and corrects image distortion and three-color misalignment. For the purpose of convergence correction, a convergence yoke which slightly deflects the electron beam is integrally assembled. Therefore, the deviation of the center of the image can be easily matched by superimposing a DC current on the main yoke using a horizontal centering circuit provided in the horizontal deflection circuit or correcting the current flowing through the convergence yoke. . Also, as compared with the image shown in FIG.
In the image shown in (b), the trapezoidal distortion of the images of the R tube and the B tube is small, and the horizontal centering, image distortion correction, and convergence correction can be easily performed.

Therefore, in a rear projection type projector in which the cabinet is compact, the centers of the projection light of the R tube and the B tube are mounted offset from the G tube, and the image shift caused by this is deflected by electromagnetic deflection of the G tube. I try to match the image.

However, in such a projector, there is a new problem that the convergence of the image displayed on the screen is shifted in the horizontal direction due to a change in the anode voltage of the projection tube.

Therefore, in the conventional projector, a high voltage stabilizer is provided to suppress the fluctuation of the anode voltage, and a circuit of a type in which the high voltage generating means and the deflecting means are separated is employed. A conventional projector provided with this high-pressure stabilizer will be described with reference to FIG. In this figure, only a circuit for one projection tube is shown, but a similar circuit is applied to other projection tubes.

In FIG. 5, a high-frequency television signal (RF signal) induced by an antenna 51 is supplied to a tuner 52. The tuner 52 is controlled by a tuning circuit 53 to tune a predetermined channel, and to output an intermediate frequency signal. (IF signal) and output to the detection / amplification circuit 54. Detection
The amplification circuit 54 detects the IF signal, amplifies it, and outputs it to the signal processing IC 55.

The signal processing IC 55 performs video processing, chroma processing and synchronous deflection processing on the input baseband video signal, and converts the baseband video signal into R (red), G
The signals are converted into (green) and B (blue) signals and supplied to the projection tube drive circuit 56. Also, signal processing IC
55 supplies a horizontal pulse H separated from the video signal to the horizontal drive circuit 57 and the high voltage drive circuit 58, and supplies a vertical pulse V to the vertical output circuit 59.

Horizontal drive circuit 57, horizontal output circuit 6
1. The horizontal output transformer 62 and the vertical output circuit 59 constitute a deflection circuit 60. Horizontal drive circuit 5
Reference numeral 7 denotes a horizontal output circuit 61 which outputs a horizontal drive pulse having a horizontal period.
The horizontal output circuit 61 generates a horizontal period saw-tooth wave current and supplies it to the horizontal deflection coil 63. This sawtooth wave current is also supplied to the horizontal output transformer 62. Also,
The horizontal output transformer 62 also outputs a horizontal pulse HD having a horizontal cycle and supplies the horizontal pulse HD to the convergence correction circuit 75. The vertical output circuit 59 generates a vertical period sawtooth current based on the vertical pulse and supplies the current to the vertical deflection coil 64. The vertical output circuit 59 generates a pulse VD having a vertical cycle and outputs the pulse VD to the convergence correction circuit 75.

On the other hand, the projection tube drive circuit 56 drives the projection tube 68 based on the primary color signal. The projection tube 68 is horizontal,
It has vertical deflection coils 63 and 64 and a convergence correction coil 71. Horizontal and vertical deflection coils 6
Reference numerals 3 and 64 denote a horizontal output circuit 61 and a vertical output circuit 59, respectively.
Controls the horizontal and vertical deflection of the projection tube 68 based on the sawtooth current from The convergence correction coil 71 is supplied with a convergence correction current from a convergence correction circuit 75 described later, and corrects the convergence of the projection tube 68. The horizontal and vertical deflections of the projection tube 68 are controlled by the horizontal and vertical deflection coils 63 and 64 and the convergence correction coil 71, and an image based on any of the RGB signals is emitted from the tube surface.

The high pressure generated by the high pressure generator 67 is supplied to the anode 69 to the projection tube 68. The high-voltage generator 67 includes a high-voltage drive circuit 5
8, a high-voltage output circuit 65 and a flyback transformer 66. The high voltage drive circuit 58 supplies a pulse having a horizontal period to the high voltage output circuit 65. The high voltage output circuit 65 supplies a current of a horizontal cycle to the flyback transformer 66. The flyback transformer 66 has a primary winding and a secondary winding, and controls the voltage of the primary winding by the high-voltage control device 72 to stabilize the high-voltage output obtained from the secondary winding. The output is supplied to the anode 69 of the projection tube 68.

The high voltage output from the high voltage generator 67 is detected by a high voltage fluctuation detecting section 76, and the high voltage controller 72 is controlled in accordance with the high voltage fluctuation. The high-voltage fluctuation detecting unit 76 includes resistors R1 and R2 and a comparator 77.
1 and R2. The voltage at the connection point between the resistors R1 and R2 is
7, the comparator 77 compares the voltage at the connection point of the resistors R1 and R2 with the reference voltage, and outputs a control voltage according to the high-voltage fluctuation to the high-voltage control device 72.
The high-voltage control device 72 includes, for example, a control transistor and a saturable reactor, and controls the voltage of the primary winding of the flyback transformer 66 in accordance with the high-voltage fluctuation to make the high-voltage fluctuation zero. Works like that. These high-voltage fluctuation detecting section 76 and high-voltage control device 72
The high-pressure stabilizing device 73 is constituted by these.

Next, an example of the high voltage fluctuation detecting section 76 and the high voltage stabilizing device 73 will be described with reference to FIG.

The high voltage fluctuation detecting section 76 includes resistors R1 to R7.
, Capacitors C1 and C2, Zener diode Dz
1, a voltage follower 81 and a comparator 82. A comparator 77 is configured by the voltage follower 81 and the comparator 82. Zener diode Dz1, resistors R5 to R7, and capacitor C
2 generates a predetermined reference voltage and supplies it to the positive input terminal of the comparator 82. Resistance R1
, R2 and the reference potential point, a parallel circuit of a resistor R3 and a capacitor C1 is connected to a resistor R1,.
The voltage appearing at the connection point of R2 is smoothed and applied to the voltage follower 81 via the resistor R4. This voltage is supplied to the comparator 8 via the voltage follower 81.
2 is supplied to the negative input terminal. The comparator 82 is connected to the reference voltage input to the positive input terminal and the voltage follower 8.
The difference from the output of 1 is output to the high-pressure control device 72.

The high voltage control device 72 includes resistors R8 and R9, a transistor Q1, and a saturable reactor 83. The power supply terminal 84 is connected to the reference potential point via the collector-emitter path of the transistor Q1, the primary winding of the saturable reactor 83, and the resistor R9. Also,
One end of the secondary winding of the saturable reactor 83 is connected to a power supply terminal 85 that supplies 120 V, and the other end is connected to the primary winding of the flyback transformer 66. The inductance of the wire varies inversely with the current flowing through the primary winding.

The high-pressure stabilizing device 73 thus constructed
Outputs the output of the high-voltage fluctuation detector 76 provided on the secondary side of the flyback transformer 66 to the flyback transformer 6.
The output of the comparator 82 of the high-voltage fluctuation detecting unit 76 increases and the saturable reactor 83, for example, when the high voltage suddenly becomes high luminance and the high voltage decreases, is returned. The current flowing through the primary winding is increased. As a result, the inductance of the secondary winding is reduced, the voltage drop due to the saturable reactor 83 is reduced, and the voltage supplied from the power supply terminal 85 to the primary winding of the flyback transformer 66 is increased. Is controlled so as to increase the high voltage appearing in the secondary winding, thereby stabilizing the high voltage. However, it is difficult to completely convert the high voltage to a constant voltage, and the high voltage fluctuates slightly. Then, the screen is distorted into a trapezoid by the high-voltage fluctuation.

Incidentally, such a high-pressure stabilizing device 73
However, as can be seen from FIG. 6, the circuit configuration becomes complicated and the cost rises. Therefore, even if an attempt was made to provide a small and popular projector by simplifying the circuit configuration, it was difficult to significantly reduce the cost because the high-voltage stabilizing device was required.

If this high-pressure stabilizing device is reduced,
There is a new problem that the convergence at the center of the screen is shifted in the horizontal direction in accordance with a change in the brightness of the image displayed on each projection tube. Generally, the amount of movement of the electron beam of the projection tube due to electromagnetic deflection is proportional to the strength of the magnetic field generated by the deflection yoke, and inversely proportional to the half power of the anode voltage.
Assuming a rear projection type projector having a screen size of about 50 inches, a convergence deviation due to a change in anode voltage is calculated.

The offset amount of a projector of about 50 inches is generally about 30 mm on a screen surface. The anode voltage of each of the R, G, and B tubes of the projector set to this offset amount is about 30 kV when the anode current is the maximum, and the magnitude of the fluctuation is about 2 kV. The displacement of the center of the image having an offset amount of 30 mm is electromagnetically deflected by the current flowing through the deflection yoke or convergence yoke. When the voltage increases by 2 kV, the correction amount decreases. That is, 30 mm × (30 kV / 3
2 kV) ^1/2 = 29 mm, and the image (convergence) of the R tube and the B tube at the center of the screen is shifted by 1 mm from the G tube depending on the magnitude of the anode current, that is, the brightness of the screen. If this deviation cannot be tolerated, the high-voltage stabilizing device will be employed. However, the saturable reactance connected to the primary side of the flyback transformer 66 is considerably large, and the cost of winding components is high. Will be. In addition, a direct current is applied to control the inductance of the saturable reactance.
Power is also consumed.

It has also been proposed to perform convergence correction by detecting a change in the anode voltage of the projection tube.
For example, Japanese Patent Application Laid-Open No. 8-102965 discloses that a high voltage detected by resistors R1 and R2 is supplied to a convergence correction circuit 75 via an inverter 78 and a low-pass filter 74 as shown in FIG. An example is shown in which correction is made in accordance with a change in high pressure.

In the case of Japanese Patent Application Laid-Open No. 8-102965, the amount of convergence correction is controlled in accordance with the change in the anode voltage of the projection tube. In the central part, so that it becomes a mouth
Correction is applied to all of the R, G, and B tubes, the correction method and circuit configuration are complicated, and it has been difficult to apply the correction to a small projector.

[0032]

The conventional three-tube projector has a drawback that the convergence at the center of the screen is deviated due to the fluctuation of the anode voltage of the projection tube. It was necessary to suppress fluctuations.

There is also a method of controlling the convergence correction amount in accordance with the high voltage fluctuation. However, the circuit configuration is complicated for application to a small and inexpensive projector, and further improvement is required to simplify the circuit. Was.

An object of the present invention is to provide a convergence device which enables convergence correction of three projection tubes without requiring a high-pressure stabilization device and which can easily correct a deviation of convergence due to a change in anode voltage of the projection tubes. With the goal.

[0035]

According to the present invention, a second projection tube and a third projection tube are arranged on both sides of a first projection tube at a predetermined angle, and an image projected from each projection tube is arranged. And a high-voltage generating circuit for supplying a high voltage to the anode of each of the projection tubes, and a convergence for correcting a deviation of convergence of the image projected on the screen. Convergence control means for generating an adjustment signal, convergence yokes attached to the first, second, and third projection tubes, a detection circuit for detecting a change in an anode voltage of each projection tube, and the detection circuit Is supplied to the second, third, and third detectors according to the amount of change in the anode voltage.
And generating a correction signal for relatively correcting the screen position of the image projected from the projection tube relative to the projection image from the first projection tube, and using the correction signal to generate a correction signal for the second and third projection tubes. A screen position correcting means for correcting the convergence adjusting signal, and a first convergence adjusting signal supplied from the convergence control means to a convergence yoke of the first projection tube, and a convergence of the second and third projection tubes. Means for supplying to the yoke the second and third convergence adjusting signals corrected from the screen position correcting means, respectively, and the convergence on the screen is eliminated without the need for a device for stabilizing the high voltage. A convergence device characterized in that correction is possible.

According to the convergence device of the present invention, a change in the anode voltage of the projection tube is detected, and the screen positions of the images projected from the second and third projection tubes are corrected in accordance with the amount of change in the anode voltage. A correction signal is generated, and the correction direction is relatively corrected with respect to the projected image from the first projection tube. This enables convergence correction without the need for a high-pressure stabilizer.

[0037]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of a convergence device according to the present invention.

In the projector of the present invention, as shown in FIG. 4, the center (optical axis) of the light projected from the G tube and the R
The center of the light projected from the tube and the tube B (optical axis) does not coincide at the center on the screen, and is a short-focus projector that is arranged offset in the left-right direction in the figure. Description will be given as a convergence device in the projector.

In FIG. 1, reference numeral 11 denotes a horizontal period pulse input terminal supplied from a horizontal output circuit, and reference numeral 12 denotes a vertical period pulse input terminal supplied from a vertical output circuit. The horizontal and vertical periodic pulses supplied to the input terminals 11 and 12 are supplied to the digital conversion control circuit 1.
3 to generate convergence adjustment data for each of the R, G, and B tubes in correspondence with a plurality of adjustment points set in the horizontal direction and the vertical direction, and the convergence between the adjustment points described above. Based on the correction data, interpolation processing is performed in the horizontal and vertical directions to generate correction data, and a digital convergence adjustment signal is generated and output for each portion on the screen. As the digital convergence adjustment signal generated by the digital converter control circuit 13, a static convergence adjustment signal and a dynamic convergence adjustment signal are generated.

This digital convergence control circuit 13
Of the digital convergence adjustment signals generated in
The convergence adjustment signal for the G tube is converted into an analog signal by a digital / analog converter 14G, and the analog signal is converted to a low-pass filter 15G and an amplifier 16G.
Horizontal convergence yoke 1 of G tube 17G through G
8G.

The digital convergence control signal for the R tube and the B tube output from the digital convergence control circuit 13 is supplied to an addition circuit 20 of a screen position correction device 19 described later. The adding circuit 20 creates screen position correction data corresponding to the high-voltage fluctuations of the R tube and the B tube, adds the data to the static digital convergence adjustment signal, and adjusts the digital convergence adjustment corrected for the R tube and the B tube respectively. For supplying the application signal. The outputs of the adder circuit 20 are digital-to-analog converters 14R and 14B and low-pass filters 15R and 15B, respectively.
And R tube and B tube 17R via amplifiers 16R and 16B,
It is supplied to horizontal convergence yokes 18R and 18B of 17B.

On the other hand, a driving voltage having a horizontal period is supplied to the base electrode of the horizontal output transistor 23. The damper diode 24, the resonance capacitor 25, and the horizontal deflection coil 26 are connected in parallel with the collector-emitter path of the transistor 23. A series circuit of the character correction capacitor 27 is connected. The horizontal deflection coil 26 is a horizontal output transistor 2
3, a horizontal sawtooth current is supplied with the on / off of 3,
The pulse voltage generated during the flyback period of the horizontal sawtooth current is boosted by the flyback transformer 28.
The flyback transformer 28 includes a primary winding 28a,
A DC voltage Vcc is supplied to the primary winding 28a, one end of the secondary winding 28b is grounded via a capacitor 28d, and a resistor 28c is connected to the primary winding 28b by a secondary winding 28b. It is connected between the next windings. Then, the pulse generated in the secondary winding 28b is rectified by the rectifier 29 so that a high DC voltage can be obtained. This high voltage is supplied to the anode electrodes of the R, G, B tubes 17R, 17G, 17B.

The voltage rectified by the rectifier 29 is divided by a voltage detector 30 composed of a voltage dividing resistor of resistors 30a and 30b, and a voltage that changes from the voltage dividing point according to a change in the anode voltage is detected. Like that. The voltage detected by the voltage detector 30 is supplied to an analog / digital converter 22 to convert the voltage into a digital signal of a plurality of bits, and to supply the digital signal to a screen position correction circuit 21. The screen position correction circuit 21 generates a position correction signal for correcting a positional deviation of the projected images of the R tube and the B tube caused by a change in the anode voltage.

The convergence position correction signal generated by the screen position correction circuit 21 is supplied to an addition circuit 20 and added to the convergence correction signal for the R tube and the B tube generated by the digital convergence control circuit 13. A convergence signal for position correction is generated.
The position correction convergence signals of the R tube 17R and the B tube 17B are respectively converted into digital / analog converters 14R and 14B and low-pass filters 15R and 15B.
And supplied to the horizontal convergence yokes 18R and 18B via the amplifiers 16R and 16B.
The convergence correction and the position correction of the projection light of R and 17B are performed.

Next, the convergence correcting operation of the projector according to the present invention when the anode voltage of the projection tube fluctuates will be described.

As shown in FIG. 4, the optical axis of the R tube is shifted to the left from the center of the projected light of the G tube, and the projected image having the highest anode voltage generally tends to shift to the left in the figure. is there. For this reason, when the anode voltage is the highest, the screen position correction circuit 21 generates a correction signal for largely correcting the position of the projection light of the R tube to the right in the drawing, and according to the decrease in the variation of the anode voltage, the correction signal for the right. , A correction signal for reducing the position correction amount is generated. Conversely, the projection light of the B tube tends to shift to the right in the figure as a whole when the anode voltage becomes the highest. For this reason, when the anode voltage is the highest, a correction signal for largely correcting the position of the projected image of the B tube in the left direction in the drawing is generated, and the position correction amount in the left direction is reduced according to the decrease in the amount of change in the anode voltage. A correction signal is generated.

That is, a position correction signal shown below is generated in response to a change in the anode voltage.

[0048] Thus, the image projected from each of the cathode ray tubes 17R, 17G, and 17B and synthesized on the screen has a screen position corresponding to the change in the anode voltage detected by the voltage detector 31 even if the screen position is shifted due to a change in luminance or the like. A correction signal can be generated by the screen position correction circuit 21, and the screen position correction signal is added to the convergence correction signals for the R tube and the B tube generated by the digital convergence control circuit 13, so that the R tubes 17 R and B The position of the projected image of the tube 17B can be corrected, and the movement can be corrected in the direction of the projected image of the G tube. Moreover, there is no need to use a high-pressure stabilizer.

In the above description of the present invention, digital convergence correction has been described as an example, but an analog convergence correction circuit can be used. When an analog convergence circuit is used, the R tube 17R
And an analog convergence correction signal supplied to the horizontal convergence yokes 18R and 18B of the B tube 17B, superimposed with a screen position correction signal generated by a screen position correction circuit also formed of an analog circuit, and the R tube 17R due to a change in anode voltage. The position of the B tube 17B can be corrected. When the analog convergence circuit is used, the analog / digital converter 22 shown in FIG. 1 is not required.

The position correction signal generated by the screen position correction circuit 21 uses the anode voltage detected by the voltage detector 31. However, in order to limit the anode current supplied from the flyback transformer 28, It is also possible to use the voltage (ABL voltage) of the automatic luminance limiting circuit (ABL circuit) provided in the back transformer 28. That is, by using a voltage that correlates with the change in the anode voltage of the projection tube, it is possible to correct the convergence and to correct the screen position of the displayed image without using a high-voltage stabilizing circuit.

[0051]

As described above, the present invention relates to a projector in which an R tube and a B tube are arranged on both sides of a G tube with respect to a screen and each projection tube is offset. Even if the position of the projected image from the R tube and the B tube changes due to the fluctuation of the anode voltage, the displacement of the screen at the center of the screen can be corrected without using a high-voltage stabilizing circuit, and the convergence is shifted. This makes it possible to display an image having no image, which has the effect of reducing the size of the projector and reducing power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a convergence device according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a conventional rear projection type projector.

FIG. 3 shows an example of a conventional rear projection type projector;
(A) is an explanatory view showing the relationship between the arrangement of the projection tube and the projection light,
(B) is an explanatory view showing a projected image projected on a screen.

4A and 4B show another example of a conventional rear projection type projector, wherein FIG. 4A is an explanatory diagram showing the relationship between the arrangement of projection tubes and projected light, and FIG. 4B is an explanatory diagram showing a projected image projected on a screen. In the figure.

FIG. 5 is a block diagram showing a circuit configuration of a conventional projector.

FIG. 6 is a block diagram showing a high-pressure stabilizer in a conventional projector.

[Explanation of symbols]

11: horizontal cycle pulse input terminal, 12: vertical cycle pulse input terminal, 13: digital convergence control circuit, 1
4 Digital-to-analog converter, 15 Low-pass filter, 16 Amplifier, 17 Projected cathode ray, 18 Horizontal convergence yoke, 19 Screen position correction device, 20
... Addition circuit, 21 ... Screen position correction circuit, 22 ... Analog to digital converter, 23 ... Horizontal output transistor, 2
4: Damper diode, 25: capacitor, 26: deflection coil, 27: capacitor, 28: flyback transformer, 31: anode voltage detector

Claims (7)

[Claims] A second projection tube is arranged on both sides of a first projection tube at a predetermined angle at a predetermined angle, and images projected from the respective projection tubes are combined on a screen. In the projector, a high-voltage generating circuit for supplying a high voltage to the anode of each projection tube, and convergence control means for generating a convergence adjustment signal for correcting a convergence deviation of an image projected on the screen A convergence yoke attached to the first, second, and third projection tubes, a detection circuit for detecting a change in anode voltage of each of the projection tubes, and a detection output from the detection circuit, The screen positions of the images projected from the second and third projection tubes are relatively corrected centering on the image projected from the first projection tube according to the amount of voltage fluctuation. A screen position correcting means for generating a positive signal and correcting the convergence adjusting signal for the second and third projection tubes by the correction signal; and a convergence yoke of the first projection tube to the first convergence yoke. Is supplied, and the convergence of the second and third projection tubes is supplied.
The second and third corrections made by the screen position correction means
Means for supplying the convergence adjustment signals of the above, respectively, and the convergence correction on the screen can be performed without the need for a device for stabilizing the high voltage. 2. The projector according to claim 1, wherein each of the projection tubes is offset from the optical axis of the first projection tube in the left-right direction without intersecting the optical axes of the second and third projection tubes on the screen. 2. The convergence device according to claim 1, wherein 3. The screen position correcting means generates a correction signal for largely correcting a screen position of an image projected from the second and third projection tubes when the anode voltage fluctuates in a higher direction. And a correction signal for correcting a screen position of an image projected from the second and third projection tubes to be smaller when the anode voltage fluctuates in a lower direction. A convergence device as described. 4. The convergence adjustment signal from the convergence control circuit and the correction signal for correcting the screen position of the image projected from the second and third projection tubes are added by the screen position correction means. The convergence device according to claim 1, further comprising an adder circuit. 5. The convergence control means according to claim 1, wherein said convergence control means comprises a digital convergence correction circuit for generating convergence adjustment data corresponding to a plurality of adjustment points of an image displayed on said screen. A convergence device as described. 6. The detecting means includes a voltage dividing circuit for dividing a high voltage output from the high voltage generating circuit, and a comparing circuit for comparing the voltage divided by the voltage dividing circuit with a predetermined reference voltage. The convergence device according to claim 1, wherein the convergence device is provided. 7. The convergence device according to claim 1, wherein said detecting means detects an ABL voltage for automatically limiting an anode current of said projection tube.