JPS5935553B2 - convergence circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses the same convergence circuit in a projection type color television device that obtains a color image by projecting three primary color images on a CRT surface and superimposing them on a screen surface. The present invention aims to make it possible to correct both the raster distortion caused by projection onto a reflective screen and the raster distortion caused by projection onto a transmissive screen, and to provide a simple correction circuit. be.

Conventionally, in a projection type color television device that obtains a color image by projecting three primary color images onto a screen surface and superimposing them on the screen surface, for example, when a projector device as shown in Fig. 1 is used. , raster distortion as shown in FIG. 2 will occur on the projection screen surface.

Here, FIG. 1A is a side view of the projection state, and FIG. 1B is a plan view.

In the figure, 1 indicates a projection screen surface, 2 indicates a red projector, 3 indicates a green projector, and 4 indicates a blue projector. (Note that the positional relationship of each primary color projector does not have to be as shown.) Also, Figure 2 shows the shape of the projected raster, where 1 is the projection screen surface, 5, 6, and T are If R, G, and B are arranged as shown in Figure 1, R, G, and B
The projected raster shape is shown.

Therefore, in order to obtain a satisfactory color image, it is necessary to correct this distortion by some method.

As can be seen from FIG. 2, when attempting to superimpose three primary color images, static correction and dynamic correction are required.

In conventional three-primary color projectors, static correction was sometimes performed by changing the mechanical position of the projector itself, but this resulted in a very large-scale device and high cost. Generally, this is done using an electrical method. In addition, dynamic correction is performed in the vertical direction,
This was done by superimposing a correction current on the horizontal deflection coil, but when using a directional aluminum spherical screen as the screen surface to obtain a high-brightness projected image, the screen If the surface is flat, the relative distortion becomes more complicated, and the number of types of correction current increases, and it becomes extremely difficult to superimpose all of these correction currents on the deflection current. Therefore, generally, a convergence correction core as shown in FIG. 3 is separately provided to perform raster correction regardless of deflection. Figure 3A (shows the neck part of the CRT for each primary color; 8 in the figure is the CRT cone, 9 is the deflection coil,
10 and 11 indicate the static convergence score of 1 and the dynamic convergence score of 1, respectively.
12 indicates a coil bobbin, and 13 indicates a CRT neck.

Figure 3B shows the relationship between the static and dynamic convergence scores and the CRT network. Correction is performed by flowing a correction current of . As for the type of correction current, for example, if the projector is arranged as shown in Figure 1, and a spherical screen is used as the projection screen surface, the projection raster distortion of the R projector will be as shown in Figure 4. become.

In the figure, 14 is the desired raster shape, and 15 is the actual projected raster shape.If the horizontal amplitude and horizontal linearity are adjusted on the deflection coil side, the correction waveform that must be sent to the dynamic convergence coil is The vertical correction coil has the following:
It is necessary to flow a vertically periodic sawtooth wave, a parabolic wave, a horizontally periodic parabolic wave, and a trapezoidal distortion correction current. Further, it is necessary to send a vertically periodic sawtooth wave, parabolic wave, and trapezoidal distortion correction waveform to the horizontal direction correction coil. When trying to pass these waveforms, it is extremely difficult to pass the waveforms obtained from the deflection circuit through transformer coupling or the like. Therefore, it is generally performed by a combination of a waveform generation circuit that generates the necessary correction waveform and an output circuit that synthesizes those waveforms and sends a correction current to the dynamic convergence coil. . FIG. 5 shows an example of such a conventional configuration. In the figure, 16 is a deflection circuit, 1
7, 18, 19 are waveform generators for obtaining the necessary correction waveforms, 20 is an R vertical output circuit, 21 is also a horizontal output circuit, 22 is a G vertical output circuit, and 23 is also a horizontal output circuit. direction output circuit, 24 is a vertical direction output circuit of B, 25 (also shows the horizontal force direction output circuit), 26 is a vertical direction dynamic correction coil of R, 27 is a horizontal direction correction coil of R, 28 Reference numeral 29 indicates a G vertical correction coil, 29 a G horizontal correction coil, 30 a B vertical correction coil, and 31 a B horizontal correction coil.

In this way, the various outputs of the waveform generators 17, 18, and 19 must be combined and supplied to the correction coils for each color, requiring a very complex dynamic convergence correction circuit. Furthermore, as the convergence output circuits shown at 20 to 25 in FIG. 5, the one shown in FIG. 6 has conventionally been used.

In the figure, Al and a2 are human power terminals, Rl and R2 are resistors for applying bias to the bases of transistors Ql and Q2,
R5 is a resistor that prevents the terminal A2 from being grounded AC and the amount of negative feedback becoming zero when negative feedback is applied to the base of Q1 through the resistor R1, and R4 is a dynamic resistor. This is the damping resistance of the convergence coil L1.

In such a circuit, since it is a resistive load, if the input is constant, the current flowing through the dynamic convergence coil can be kept at a constant amount almost regardless of the frequency; Since negative feedback is also applied to the dynamitsuta convergence coil L1, there is no possibility that a direct current will flow through the dynamitsuta convergence coil L1 due to a change in ambient temperature or the like.
Therefore, such a circuit has a very large advantage as a dynamic convergence output circuit. In addition, it has two input terminals a1 and A2 as input terminals, and even when applying the same manual waveform, a current in the opposite direction can flow through the dynamic convergence coil L1 depending on whether it is applied to terminal a1 or A2. It is possible to select the input terminal according to the direction of distortion appearing on the projection screen. However, if you use a projection device arranged as shown in Figure 1, with the direction of the current flowing through the deflection coil and the direction of the current flowing through the dynamic convergence coil set, you can use the projection device as shown in Figure 7. Let's consider projecting onto a transparent screen. In this case, the direction of the vertical deflection coil current may be the same as that shown in Figure 1, but since the direction of the horizontal deflection coil current C is obviously reversed left and right, the direction of the deflection coil current is reversed. It is necessary to In that case, the direction of the image is corrected, but since the direction of the deflection current and the direction of the dynamic convergence coil current are independent, if the horizontal deflection current is reversed, the dynamic convergence in the horizontal direction will be corrected. All correction directions are reversed, and the trapezoidal distortion correction direction applied in the vertical direction is also reversed. This situation will be explained using FIG. 8. For simplicity, let's consider correcting the trapezoidal distortion in the left and right directions. In this case, a correction current waveform as shown in FIG. 8B is required to be applied to the vertical dynamic convergence coil. Furthermore, C
indicates the direction of the vertical deflection current. When the correction current shown in B is passed through the vertical convergence coil, the vertical amplitude is corrected in the positive direction in the first half of the horizontal period and in the negative direction in the second half, and the vertical amplitude is corrected in the first half of the vertical period. In the latter half of the period, the opposite is true, and the correction is made as shown by the dotted line in FIG. 8A. However, if the direction of the horizontal deflection is reversed here, the raster distortion remains the same and only the scanning direction is reversed. Therefore, in the first half of the vertical period, the vertical amplitude is corrected in the positive direction in the first half of the horizontal period and in the negative direction in the second half, and vice versa, resulting in the distortion shown in Figure 8A. The direction will be to further emphasize the The same thing can be said about trapezoidal distortion that occurs in the vertical direction. Therefore, if a projector that is set to correct the distortion that occurs when projecting under the conditions shown in Figure 1 projects under the conditions shown in Figure 7, the direction of the horizontal deflection coil current will change. In addition to reversing the waveforms applied to the vertical dynamic convergence coil, only the left and right trapezoidal distortion correction currents are reversed, and all waveforms applied to the horizontal dynamic convergence coil are also reversed. There is a need.

Further, the positional relationship between the projector and the screen surface is not limited to that shown in FIGS. 1 and 7, and various other conditions may be considered. In that case, the direction of the waveform applied to the dynamic convergence circuit must be switched to suit each case, making the adjustment extremely complicated. One way to avoid this is to convert the waveforms generated by the waveform generation circuits 17, 18, and 19 in FIG. It may be possible to change the size and direction depending on the position, but
For all the waveforms performed for each primary color, the 9th
Adding a circuit like the one shown in the figure increases the number of circuit components and also increases the cost. The present invention is intended to enable convergence correction in all types and positional relationships between the projector and the projection screen using a very simple circuit. The configuration of an embodiment of the present invention will be explained below using FIG. 10.

Except that both ends of a variable resistor VRl are connected between both bases of transistors Q1 and Q2 forming a differential amplifier, and input is applied to the sliding terminal of the variable resistor VRl through a high resistance R6. Since it is similar to the circuit shown in FIG. 6, its explanation will be omitted. If the value of the variable resistor VRl is selected to be larger than the values of Rl and R2 and smaller than R6, the dynamic resistance will be reduced when the sliding part is located approximately at the center of the variable resistor VR. Convergence coil L
1, and when the sliding part is located on the base side of transistor Q1, a current flows in coil L1 in the opposite direction to the input waveform. Conversely, when the sliding part is located on the base side of transistor Q2 When it is located at , it is possible to flow a correction current in the same direction as the input waveform. Regarding another type of correction waveform, as shown in FIG.
Just add R2, VR3... in parallel, connect resistors R7, R8... in series to the sliding terminals of each variable resistor, and add their respective correction waveforms. .
By adopting this configuration, correction can be made in only one direction, regardless of whether the projection screen surface is reflective or transmissive, or even in a configuration where the projection optical path is turned back by a mirror midway. By simply generating a waveform in a waveform generator, dynamic convergence correction can be performed using exactly the same circuit without the need for any other switching. Also, among primary color projectors, if the projection raster distortion is in a positional relationship that is opposite in the horizontal or vertical direction, for example, if the projection arrangement is as shown in Figure 1, R and G For something like a projector, the projection distortion in the left and right direction appears in completely opposite forms, as shown in FIG.

Therefore, in order to correct the vertical distortion among the distortions in the opposite direction, the R and G vertical correction coils are connected in parallel so that their polarities are reversed, as shown in FIG. That is, in FIG. 13, R4 is a damping resistor, L1 is an R vertical correction coil, and L2 is a G vertical correction coil. Moreover, the method of connecting the coils is not limited to parallel connection, but may also be connected in series so that currents of opposite polarity flow. FIG. 14 shows a state in which the distortion in the opposite direction appearing in the vertical direction from FIG. 12 is corrected in this way. With this configuration, one R and G vertical convergence circuit can be omitted without any reduction in convergence correction ability. Regarding correction in the horizontal direction, overall there is a trapezoidal distortion in which the upper part of the raster spreads, but this can be commonly removed by the deflection circuit.
Further, if horizontal linearity correction and static convergence correction are performed, a projected raster as shown in FIG. 15 will be obtained.

In this case as well, the distortions are in opposite directions in the horizontal direction, so correction can be made by connecting the horizontal correction coils in parallel or in series so that currents of opposite polarity flow in the same way as the vertical correction coils. It is possible. If the screen surface is flat, the R and G rasters can be matched by the above correction, but if a spherical screen or the like is used as the screen surface, the result will be as shown in Figure 16. Curved vertical and horizontal lines occur.

In this case, the curvature of the horizontal lines can be commonly corrected by the vertical deflection circuit, but the curvatures of the vertical lines are in opposite directions. Therefore, if the correction coil in the horizontal direction is also connected so that a current of opposite polarity flows through it, correction is possible. As described above, even if the correction coils are connected so that the polarities of the currents flowing in both the horizontal and vertical directions are opposite to each other, projection distortion can be completely corrected.

Also, regarding projector B, both vertical and horizontal directions are R.
, G can be corrected independently, it is possible to superimpose the three primary colors. Furthermore, by adopting the above-mentioned method of connecting the correction coil, it is possible to reduce the number of adjustment points and convergence output circuit components to i' without reducing the correction ability in any way. Furthermore, in the present invention, the signal input to the movable terminal of the variable resistor does not have to be a large signal current but a small signal voltage, and a special circuit for obtaining an input signal is not required, and a complex correction input signal can be used. Even if such a problem occurs, it can easily occur, and any projection type color television device can be corrected as desired.

Although the embodiments of the present invention have been described using SEPP circuits as output circuits, it is of course possible to obtain similar effects by using other circuits.

Furthermore, even if a circuit with two differential input terminals is used as a manual circuit, and its output signal drives separate output circuits, two colors can be corrected at the same time at one adjustment point. It is possible to reduce

[Brief explanation of the drawing]

FIG. 1A is a side view showing an example of the arrangement of the projector of a projection type color television apparatus, FIG. 1B is a plan view of the same, and FIG.
Figure 3A is a side view of the projection cathode ray tube's neck, Figure 3B is a wiring diagram showing the connection of the convergence correction coil, and Figure 4 is a diagram showing the connection of the convergence correction coil. Figure 5 is a block diagram of a conventional convergence circuit, Figure 6 is an electrical wiring diagram showing an example of a conventional convergence output circuit, and Figure 7 is a diagram showing the shape of a raster when a transmission screen is used. FIG. 8A is a diagram showing the raster shape in the case of FIG. 7, FIG. 8B is a waveform diagram of the necessary correction current, and FIG. 8C is a waveform diagram of the vertical deflection current in that case. Fig. 9 is an electrical wiring diagram showing an example of a circuit for changing the waveform applied to the convergence circuit, Figs. 10 and 11 are electrical wiring diagrams of the convergence circuit in an embodiment of the present invention, and Fig. 12 is a raster diagram. A diagram showing the shape of distortion, Figure 13 is an electrical wiring diagram showing an example of the connection of the correction coil in that case, Figure 14 is a diagram showing the raster shape corrected from the state in Figure 12, and Figure 15 is a diagram showing the corrected shape. FIG. 16 is a diagram showing the shape of the raster when a spherical screen is used. Ql, Q2...transistor, VRl...
...Variable resistor, L1...Dynamic convergence coil.

Claims (1)

[Claims] 1 A convergence circuit for a projection type color television receiver, in which the input side is composed of a differential amplifier, and both ends of one or more variable resistors are connected between the two input terminals of the differential amplifier. , inputting a correction signal from the movable terminal of the variable resistor, connecting a convergence coil to the output side of the differential amplifier, and connecting a detection resistor in series with the convergence coil to detect the current flowing through the convergence coil. . A convergence circuit, characterized in that a voltage generated across the detection resistor is fed back to an input terminal on a negative feedback side of two input terminals of the differential amplifier.