JPH06217159A - Pincushon distortion correcting circuit - Google Patents

Abstract

PURPOSE:To extremely suitably correct picture distortion by applying this circuit to the picture distortion correcting system of a TV receiver by correcting the picture distortion by forming a pincushon distortion correcting signal in the shape of a parabolic wave from a vertical deflecting signal corresponding to a valid picture displayed on a CRT. CONSTITUTION:A vertical oscillation circuit 12 is driven by a vertical synchronizing signal supplied to a terminal 11, and a swa-tooth-shaped vertical signal is outputted and supplied to a vertical deflecting circuit 13. The output of the circuit 13 is impressed through a capacitor 14 for S-shaped correction to a vertical deflection coil VDY15, a vertical deflecting signal Sa flows to the coil 15, vertical deflection is performed and as the result of vertical deflection, a raster picture LS is provided. The signal Sa is further gated by a gate circuit 16 with a signal Sg, and the signal Sa is gated only inside the valid picture VS. Concerning the gated signal Sa', a parabolic wave correction signal Sb' is generated inside an integrator 18, and the horizontal deflecting signal is modulated by this pincushon distortion correcting signal Sb'. Afterwards, the signal is modulated by the signal Sb' and right and left pincushon distortion is dynamically corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pincushion distortion correction circuit suitable for correcting a pincushion-shaped screen distortion of a television receiver.

[0002]

2. Description of the Related Art A cathode ray tube (CR) for a television receiver
In T), if no special correction means is applied to this, FIG.
Screen distortion as shown by the solid line occurs. This is because the screen should originally have a rectangular shape as shown by the chain line. This screen distortion is called left and right pincushion distortion due to its shape.

In order to correct the left and right pincushion distortions, conventionally, a parabola-shaped pincushion distortion correction signal as described below is used. This will be described with reference to FIG.

FIG. 4A shows a vertical deflection signal Sa output from a vertical deflection circuit (described later) and flowing to a vertical deflection coil. By the vertical deflection signal Sa, a raster screen LS as shown in FIG. 9B is displayed on the CRT display screen.

The raster screen LS should originally have a quadrangular shape as shown in the figure, but in reality, it is subjected to left and right pincushion distortions as shown in FIG. This is omitted in the figure. Although the vertical deflection signal Sa is converted into the parabola-shaped signal Sb as shown in FIG. 7C, the parabola wave is not actually generated in the vertical blanking period VBLK, so the blanking signal Sg ′ shown in FIG. It is converted into a parabolic wave signal based on the blanked vertical deflection signal Sa.

Then, a parabola-shaped pincushion distortion correction signal Sb 'corresponding to the raster screen shown in FIG. 6E is obtained, and if the horizontal deflection signal is modulated by this, the pincushion screen distortion is corrected, and then in FIG. A correct deflection screen as shown in is obtained.

[0007]

By the way, the effective screen VS on which the image actually projected on the raster screen LS can be seen is a screen area smaller than the raster screen LS. Since ringing occurs at the beginning of the raster screen LS, the lower part of the raster screen LS excluding the upper part is used as the actual effective screen VS in consideration of screen stability. That is, as shown in FIG. 4B, the center p of the raster screen LS does not match the center q of the effective screen VS, and the effective screen center q is located below the raster screen center p.

On the other hand, since the pincushion distortion correction signal Sb 'is generated with reference to the raster screen LS, the center p'of the pincushion distortion correction signal Sb' is the raster screen L.
It coincides with the center p of S and does not coincide with the center q of the actual effective screen VS. As a result, the pincushion distortion correction signal Sb 'cannot correct the pincushion distortion occurring on the display screen.

Of course, since the dynamic focus adjustment is also performed using the same waveform as the pincushion distortion correction signal Sb ', the dynamic focus is not performed correctly.

Therefore, the present invention solves the above-mentioned conventional problems, and proposes a pincushion distortion correction circuit capable of correctly correcting a pincushion distortion in consideration of the position of the effective screen.

[0011]

In order to solve the above problems, according to the present invention, there is provided a pincushion distortion correction circuit for correcting pincushion distortion, which forms a vertical deflection signal corresponding to an effective screen displayed on a CRT. Then, the parabolic wave-shaped pincushion distortion correction signal is formed from this vertical deflection signal, so that the pincushion distortion is corrected in a state where the center of the effective screen and the center of the pincushion distortion correction signal coincide with each other. It is characterized by that.

[0012]

As shown in FIG. 2, the gate signal Sg corresponding to the actual effective screen VS is generated, the vertical deflection signal Sa is gated based on this gate signal Sg, and the gated vertical deflection signal Sa is integrated. A parabola-shaped pincushion distortion correction signal Sb 'is generated.

The pincushion distortion correction signal Sb 'is the effective screen V
Since it corresponds to S, the pincushion distortion correction signal Sb '
The center q'of is substantially completely coincident with the center q of the effective screen VS. This completely corrects the left and right pincushion distortion.

Since the same waveform as the pincushion distortion correction signal Sb 'is used to perform the dynamic focus adjustment,
Dynamic focus is also done correctly.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a case where an example of the pincushion distortion correction circuit according to the present invention is applied to the left and right pincushion distortion correction in the above-mentioned television receiver will be described in detail with reference to the drawings.

FIG. 1 is a system diagram of an essential part showing an example of a left and right pincushion distortion correction circuit 10 according to the present invention. The vertical oscillation circuit 12 is driven by a vertical synchronizing signal supplied to a terminal 11 to form a sawtooth wave. A vertical signal is output and supplied to the vertical deflection circuit 13.

The output of the vertical deflection circuit 13 is applied to the vertical deflection coil (VDY) 15 through the S-correction capacitor 14 so that the vertical deflection signal Sa as shown in FIG. A vertical deflection is carried out. As a result of the vertical deflection, the raster screen LS shown in FIG. 2B is obtained.

The vertical deflection signal Sa is further supplied to the gate circuit 16
And is gated by the gate signal Sg as shown in FIG. 2D. This gate signal Sg supplied to the terminal 17 is a signal corresponding to the effective screen VS, as is apparent from FIG. 2, and the vertical deflection signal Sa only within the effective screen VS.
Is gated.

This gated vertical deflection signal Sa '(not shown) is supplied to the integrator 18 to generate a parabolic correction signal (pincushion distortion correction signal) Sb' shown in FIG. 2E. The horizontal deflection signal is modulated by the pincushion distortion correction signal Sb '.

Since the above-mentioned gate signal Sg can be generated based on the vertical synchronizing signal or the vertical blanking signal, detailed description thereof will be omitted.

Reference numeral 20 denotes a horizontal deflection circuit. A horizontal deflection signal obtained from this circuit flows through a horizontal deflection coil (HDY) 22 to perform a horizontal deflection operation. A horizontal drive signal (pulse signal) having a horizontal cycle is supplied to the terminal 21, which drives the horizontal output transistor Qa.

Da and Db are damper diodes connected in series, Ca and Cb are charging and discharging capacitors connected in series, and a control transistor Qb is located at the connection midpoint between them.
Are connected. The above-described pincushion distortion correction signal S is applied to the control transistor Qb functioning as a variable impedance element.
b'is supplied.

As a result, the horizontal deflection signal is modulated by the pincushion distortion correction signal Sb 'having a vertical cycle, and the pincushion distortion on the left and right is dynamically corrected.

Reference numeral 23 is a flyback transformer (FBT), the horizontal deflection coil 22 is connected to the primary coil 23a side thereof, and a pulsed high voltage is generated on the secondary coil 23b side thereof. Is rectified to obtain a predetermined high voltage HV.

Now, as shown in FIG. 2, the actual effective screen V
The vertical deflection signal S based on the gate signal Sg corresponding to S
a is gated and the gated vertical deflection signal Sa 'is integrated to generate a parabolic wave pincushion distortion correction signal Sb'.

The pincushion distortion correction signal Sb 'is the effective screen V
Since it corresponds to S, the pincushion distortion correction signal Sb '
The center q'of is substantially completely coincident with the center q of the effective screen VS. With this, the left and right pincushion distortions can be almost completely corrected.

Since the same waveform as the pincushion distortion correction signal Sb 'is used to perform the dynamic focus adjustment,
Dynamic focus will also be performed correctly.

The present invention can be applied not only to the screen distortion correction system of a television receiver, but also to other screen distortion correction systems using a CRT. The correction of the pincushion distortion may be either left or right or top and bottom pincushion distortion.

[0029]

As described above, the pincushion distortion correction circuit according to the present invention corrects the screen distortion by forming a parabolic wave pincushion distortion correction signal from the vertical deflection signal corresponding to the effective screen displayed on the CRT. It was done like this.

According to this, since the pincushion distortion can be corrected in the state where the center of the effective screen and the center of the pincushion distortion correction signal coincide with each other, the pincushion distortion can be correctly corrected.

Of course, since the dynamic focus adjustment is also performed using the same waveform as the pincushion distortion correction signal, the dynamic focus can be correctly adjusted. Therefore, the present invention is extremely suitable when applied to a screen distortion correction system of a television receiver.

[Brief description of drawings]

FIG. 1 is a system diagram of essential parts showing an example of a pincushion distortion correction circuit according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation.

FIG. 3 is an explanatory diagram of pincushion distortion.

FIG. 4 is a waveform diagram for explaining a conventional pincushion distortion correction operation.

[Explanation of symbols]

 10 Left and right pincushion distortion correction circuit 13 Vertical deflection circuit 15 Vertical deflection coil 16 Gate circuit 18 Integrator 20 Horizontal deflection circuit 22 Horizontal deflection coil Qb Control transistor

Claims (3)

[Claims] 1. A pincushion distortion correction circuit for correcting pincushion distortion, wherein a vertical deflection signal corresponding to an effective screen displayed on a CRT is formed, and a parabolic wave-shaped pincushion distortion correction signal is formed from the vertical deflection signal. Accordingly, the pincushion distortion correction circuit is configured to correct the pincushion distortion in a state where the center of the effective screen and the center of the pincushion distortion correction signal coincide with each other. 2. The pincushion distortion correction circuit according to claim 1, wherein the pincushion distortion correction is left and right pincushion distortion correction. 3. The pincushion distortion correction circuit according to claim 1, wherein a parabola-shaped pincushion distortion correction signal is generated based on a vertical deflection signal in which a screen other than the effective screen is blanked.