JPH1132344A - Crt projection type receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make deterioration in a phosphor screen due to a video signal inconspicuous. SOLUTION: A convergence output circuit 17, a convergence yoke 18 and a convergence correction current sensing resistor R1 configure a vertical scanning line position control means to control a position of a scanning line in a vertical direction, and a triangle wave generating circuit 14, a convergence correction waveform generating circuit 15 and an adder circuit 16 move a position of the scanning line vertically in a triangle wave, a stepwise wave or a random waveform whose frequency is 1/10 or below of a vertical deflection frequency. Thus, a movement control circuit controls the vertical scanning line position control means so that the maximum movement amount in the vertical direction is equal to a multiple of (n) (n is a natural number) of a scanning line interval.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CRT projection type receiver, and more particularly to a CRT capable of reducing phosphor screen deterioration.
The present invention relates to an RT projection type receiver.

[0002]

2. Description of the Related Art Conventionally, a cathode ray tube projection type receiver (hereinafter, referred to as a CRT projection type receiver) called a projection television uses a projection lens to project an image on a 7 to 9-inch projection CRT screen to a screen. Enlarged projection. In this case, in order to obtain a high-luminance image on the screen, it is necessary to increase the image luminance on the projection tube surface. Therefore, the amount of energy per unit area of the phosphor screen is larger than that of a CRT direct-view TV receiver. Fluorescent surface degradation (decrease in emission efficiency), which is generally called burn-in, tends to progress quickly,
It is not suitable for displaying a video signal that becomes a still image at least partially for a long time. For this reason, warning texts are attached to projection televisions for general households, so as not to use them for playing back home games in which the background video becomes a still image.

FIG. 6 is an explanatory view showing a state of phosphor screen deterioration due to a still image. FIG. 6 (a) shows a still image, and FIG.
(B) shows uneven light emission.

As shown in FIG. 6A, when an input signal is a still image, a high-luminance portion 92 of the screen 91 has a greater degree of deterioration of the phosphor screen than a low-luminance portion 93 indicated by oblique lines. As shown in FIG. 6B, when light emission unevenness occurs in a portion corresponding to the scanning line on the screen 91 and a portion 94 in which the light emission efficiency is deteriorated indicated by oblique lines displays an image different from that in FIG. It stands out as a video. In such a deteriorated projection tube, for example, when an all-white signal is input, the entire screen does not become white, and traces of phosphor screen deterioration can be seen.

[0005] Such deterioration of the phosphor screen mainly occurs in the case of a still image. However, even when a moving image such as a normal television broadcast is received, the portion irradiated with the electron beam does not deteriorate. It has occurred.

FIGS. 7A and 7B are explanatory diagrams showing the influence of the phosphor screen degradation due to the moving image. FIG. 7A shows the phosphor screen degradation due to the moving picture, and FIG. Is shown.

In FIG. 7, although a moving image does not deteriorate as in a still image, a portion irradiated with an electron beam is irradiated with a beam as shown in FIG. The scanning line portion 96 of the screen 95 is gradually and uniformly degraded as compared with the other portions. Even if such deterioration occurs, there is no problem if the signal of the same format is continuously received, since the deterioration of the phosphor screen at the place where the electron beam scans progresses uniformly. However, C corresponding to a plurality of input signals called a multi-scan receiver
In the case of the RT projection type receiver, for example, after a certain input frequency signal (signal A) has been used for a while and the phosphor screen has deteriorated at the scanning line interval of the signal A, a signal having a different number of scanning lines (signal When B) is input, as shown in FIG. 7B, the interval between the phosphor screen degradation 97 due to the signal A and the scanning line interval due to the signal B do not match, so that the phosphor screen luminous efficiency differs depending on the location of the scanning line. This causes inconveniences such as flickering of a reproduced image called flicker and interference fringes called moiré.

[0008]

The above-mentioned conventional CRT
Projection-type receivers tend to have a large amount of energy per unit area of the phosphor screen, and the phosphor screen tends to deteriorate rapidly, because at least a part of the phosphor screen needs to be long, since it is necessary to increase the image brightness on the projection tube surface. It is not suitable for displaying video signals or multi-scans that become still images over time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a CRT projection type receiver which eliminates the above-mentioned problems and makes the phosphor screen deterioration caused by a video signal inconspicuous.

[0010]

A CRT projection type receiver according to the present invention irradiates a phosphor with a beam from an electron gun and scans the beam in horizontal and vertical directions to display an image. A vertical scanning line position control means for controlling the position of the scanning line in the vertical direction of the beam, and raising and lowering the position of the scanning line with a signal waveform having a frequency of 1/10 or less of the vertical deflection frequency. And a movement control circuit for controlling the vertical scanning line position control means so that the maximum movement amount in the vertical direction is equal to n times the scanning line interval (n is a natural number). It is characterized by the following.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a main part showing an embodiment of a CRT projection type receiver according to the present invention.

In FIG. 1, according to an embodiment of the present invention, a phosphor is irradiated with a beam from an electron gun, and the beam is scanned in the horizontal and vertical directions to display a CR.
It is used for a T-projection type receiver. Input terminal 1
1, 12, and 13, a horizontal synchronizing signal a1H and a vertical synchronizing signal a1V created from the composite video signal, and a DC voltage Vsize proportional to the vertical amplitude, respectively, are led. The horizontal synchronizing signal a1H, the vertical synchronizing signal a1V, and the DC voltage Vsize guided to the input terminals 11, 12, and 13 are supplied to a triangular wave generation circuit 14. The triangular wave generation circuit 14 supplies the supplied horizontal synchronization signal a1H, vertical synchronization signal a1V, and DC voltage V
A triangular wave signal b1 is created based on the size,
To one input terminal. The convergence correction waveform generation circuit 15 creates a convergence correction waveform signal c1 and supplies it to the addition circuit 16. The addition circuit 16 adds the triangular wave signal b1 to the convergence correction waveform signal c1 to generate a convergence reference waveform voltage Vin, and supplies the convergence reference waveform voltage Vin to a non-inverting input terminal (+) to a convergence output circuit 17 constituted by a differential amplifier. .

The convergence output circuit 17 subtracts a current detection voltage V1 from a convergence correction current detection resistor R1 to be described later from the reference waveform voltage Vin, and uses the resulting output voltage as a convergence output signal d1 as a convergence coil L1 of the convergence yoke 18. To one end. The other end of the convergence coil L1 is connected to a reference potential point via a convergence correction current detection resistor R1.

The connection point between the convergence coil L1 and the convergence correction current detection resistor R1 is connected to the inverting input terminal (-) of the convergence output circuit 17. As a result, the current detection voltage V1 from the convergence correction current detection resistor R1 is supplied to the inverting input terminal (-) of the convergence output circuit 17.

With this configuration, the current Icy flows through the convergence coil L1.

Next, the convergence output circuit 17 will be described in detail.

The convergence reference waveform voltage Vin from the adder circuit 16 is input to the non-inverting input terminal (+) of the convergence output circuit 17, and the current flowing through the convergence coil L1 is input to the inverting input terminal (-). The waveform converted to the voltage V1 by the resistor R1 is fed back. The convergence output circuit 17 drives the convergence coil L1 so that the non-inverting input terminal (+) and the inverting input terminal (-) have the same shape.
in and Icy are proportional, and the following equation is established.

Icy = Vin / R (1) Next, the triangular wave generating circuit 14 will be described in detail.

The triangular wave generating circuit 14 has a horizontal synchronizing signal a
1H, a vertical synchronizing signal a1V, and a DC voltage Vsize are input. Here, the horizontal frequency of the horizontal synchronization signal a1H is fh
(Hz), and the vertical frequency of the vertical synchronization signal a1V is represented by fv (H
z), the convergence sensitivity in the vertical direction is S (m / A),
Assuming that the vertical screen size is Hs (m) and the vertical raster size of the electron beam is Hr (m), the pp value A (V) of the output waveform of the triangular wave generation circuit 14 is expressed by the following equation. Can be.

A = n × (R × fv × Hr) / (S × fh) (2) where n is a natural number.

At this time, the maximum displacement Ypp of the scanning line on the screen can be expressed by the following equation from equation (1).

Ypp = Icy × S = (A / R) × S (3) When Expression (2) is substituted into Expression (3), Ypp = n × Hr / (fh / fv) (4) Expression ( In 4), Hr of the numerator is the raster dimension in the vertical direction, and fh / fv of the denominator is the number of scanning lines per field. Therefore, Ypp is n times the interval between adjacent scanning lines.

As an example, a case where n = 1 will be described.

FIG. 2 is an explanatory diagram for explaining how the scanning line moves in the vertical direction with time when n = 1. FIG. 2A shows the triangular wave signal b1, and FIG. The position of the line on the screen is shown.

The triangular wave signal b1 shown in FIG. 2A has an amplitude with the maximum displacement Ypp. The scanning line is shown in FIG.
As shown in (b), the scanning line moves with time by an interval between vertically adjacent scanning lines. Further, even when the raster size in the vertical direction, the horizontal frequency, or the vertical frequency is changed and the scanning line interval on the screen is changed, the value of Ypp is automatically corrected by Expression (4).
The maximum vertical displacement Ypp is always the value of the currently input scanning line interval. Here, the cycle of the triangular wave signal b1 output from the triangular wave generating circuit 14 is set to a sufficiently low frequency of 1/10 or less of the vertical deflection frequency in order to avoid beat interference with the vertical deflection frequency.

With such a setting, the convergence output circuit 17, the convergence yoke 18, and the convergence correction current detection resistor R1 constitute vertical scanning line position control means for controlling the position of the scanning line in the vertical direction. 14. The convergence correction waveform generation circuit 15 and the addition circuit 16 move the position of the scanning line up and down with a triangular wave, staircase wave or random waveform having a frequency of 1/10 or less of the vertical deflection frequency, and Is a movement control circuit for controlling the vertical scanning line position control means so that the maximum movement amount is equal to n times (n is a natural number) the scanning line interval.

According to the embodiment of the present invention, by moving the scanning line up and down, the deterioration of the phosphor screen can be made to progress uniformly over the entire screen, and the deterioration of the phosphor screen caused by the video signal is not noticeable. can do. Thus, even in the case of multi-scan display in which a still image is displayed or a plurality of video signals are used while being switched, it is possible to prevent the occurrence of inconvenience due to the deterioration of the phosphor screen.

In the embodiment of the invention shown in FIG. 1, the description has been made assuming that the value of Ypp is changed by using three parameters of the raster size in the vertical direction, the horizontal frequency, and the vertical frequency as parameters. If the raster size is always the same, the value of Ypp is set using two items of the horizontal frequency and the vertical frequency as parameters, and Ypp is set using one of the two items or one item as a parameter. You may.

The signal supplied to one input terminal of the adder circuit 16 moves the position of the scanning line up and down at a frequency of 1/10 or less of the vertical deflection frequency, in addition to the triangular wave shown in FIG. In addition, if the maximum vertical movement amount is equal to n times the scanning line interval (n is a natural number), a staircase wave shown in FIG. 4 or a random waveform shown in FIG. 5 may be used.

In the case of a staircase wave or a random waveform, the maximum movement amount of the scanning line in the vertical direction is multiplied by (n-1) + [(N + 1) / N] times the scanning line interval (n is a natural number, N May be configured to be equal to the number of steps of a staircase wave or a random waveform). In this case, in the staircase wave of FIG.
= 1, N = 3.

A convergence correction waveform generation circuit 1
Reference numeral 5 denotes a configuration that can be controlled by a microcomputer. If the microcomputer changes the static convergence value output from the convergence correction waveform generation circuit 15 periodically, the triangular wave generation circuit 14 is omitted. be able to.

Also, instead of the convergence output circuit,
The same effect can be obtained even if the position of the scanning line is periodically moved in the vertical direction by the vertical phase circuit or the vertical centering circuit.

[0034]

According to the present invention, the deterioration of the phosphor screen due to the video signal can be made inconspicuous. Therefore, in the case of multi-scan display in which a still image is displayed or a plurality of video signals are used while being switched. However, it is possible to prevent inconvenience caused by deterioration of the phosphor screen.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part showing an embodiment of a CRT projection type receiver according to the present invention.

FIG. 2 is an explanatory diagram illustrating a manner in which a scanning line moves up and down with time.

FIG. 3 is a triangular wave used in the CRT projection type receiver of FIG.

FIG. 4 is a staircase wave usable for the CRT projection type receiver of FIG. 1;

FIG. 5 is a random waveform usable in the CRT projection type receiver of FIG. 1;

FIG. 6 is an explanatory diagram showing a phosphor screen deterioration due to a still image of a conventional CRT projection type receiver.

FIG. 7 is an explanatory diagram showing the influence of phosphor screen deterioration due to a moving image of a conventional CRT projection type receiver.

[Explanation of symbols]

 14 Triangular wave generation circuit 15 Convergence correction waveform generation circuit 16 Addition circuit 17 Convergence output circuit 18 Convergence yoke R1 Convergence correction current detection resistor

Claims (5)

[Claims] Irradiating a phosphor with a beam from an electron gun;
A CRT projection type receiver for displaying an image by scanning the beam in the horizontal and vertical directions, comprising: a vertical scanning line position control means for controlling a position of a vertical scanning line of the beam; The position of the scanning line is moved up and down with a signal waveform having a frequency of 1/10 or less of the frequency, and the maximum movement amount in the up and down direction is equal to n times the scanning line interval (n is a natural number). And a movement control circuit for controlling the vertical scanning line position control means. 2. A method of irradiating a phosphor with a beam from an electron gun,
A CRT projection type receiver for displaying an image by scanning the beam in the horizontal and vertical directions, comprising: a vertical scanning line position control means for controlling a position of a vertical scanning line of the beam; The position of the scanning line is moved up and down by a signal waveform having a frequency of 1/10 or less of the frequency and changing at a predetermined step interval, and the maximum movement amount in the up and down direction is (n) of the scanning line interval. -1) + [(N + 1) /
N] times (n is a natural number, N is the number of steps of the signal waveform)
And a movement control circuit for controlling the vertical scanning line position control means so as to be equal to: CRT projection type receiver. 3. The CRT projection type according to claim 1, wherein the movement control circuit is configured such that a maximum movement amount of the scanning line in a vertical direction is proportional to a vertical raster dimension. Receiver. 4. The CRT projection type according to claim 1, wherein said movement control circuit is configured such that a maximum movement amount of said scanning line in a vertical direction is proportional to a vertical deflection frequency. Receiver. 5. The CRT projection type according to claim 1, wherein the movement control circuit is configured such that a maximum movement amount of the scanning line in a vertical direction is proportional to a horizontal deflection frequency. Receiver.