JPS6319973A - Generating circuit for correcting waveform - Google Patents

Abstract

PURPOSE:To obtain plural desired waveforms at a time in response to different synchronizing frequencies by storing the amplitude value of a single cycle of a correcting waveform in time division and with multiplexing. CONSTITUTION:The two types of signals of an up-down pincushion distortion correcting waveform and a vertical convergence correcting waveform are divided into (n) equal parts, e.g., 32 parts of a correcting waveform and stored previously in a waveform data ROM 2. An address generator 1 supplies a synchronizing signal S1 and produces clock pulses S2 and S3 having 1/n cycle of the signal S1. Then the generator 1 produces an address of the waveform data synchronously with generation of pulses S2 and S3. The latch circuits 31 and 32 latch the waveform data D1 and D2 delivered from the ROM 2. These data are delivered via the D/A converters 41 and 42 and low-pass filter (LPF) 51 and 52 in the form of the up-down pincushion distortion correcting waveform and the vertical convergence correcting waveform respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a correction waveform generation circuit for correcting screen distortion such as convergence correction of a video projector using a variable scan display, CRT display, and pincushion distortion correction.

[Conventional technology]

Conventionally, this type of correction waveform generation circuit generates sawtooth waves, parabolic waves, etc. from horizontal and vertical synchronization pulses, etc.
Changes in amplitude due to changes in the synchronization frequency in a variable scan display have been adjusted to a constant level by an AGC circuit or the like.

[Problem that the invention seeks to solve]

Conventional correction waveform generation circuits have the disadvantage that the phase of the generated waveform changes depending on the synchronization frequency, causing the waveform to change.

[Means for solving problems]

The correction waveform generation circuit of the present invention generates a plurality of correction waveform signals used for correcting screen distortion of a variable scan display that can correspond to different synchronization frequencies at each time and point where one cycle of the correction waveform is equally divided by a predetermined integer. Waveform data consisting of the amplitude at this time is time-division multiplexed and stored.
When the address corresponding to the time is input, a waveform data ROM that outputs each waveform data and a synchronization signal are input, and a clock pulse is generated at a cycle equal to one integer fraction of the synchronization signal. an address generator that generates an address for the waveform data ROM in synchronization with a clock pulse; and a plurality of address generators that latch waveform data of each waveform output from the waveform data ROM using the clock pulse output from the address generator. a latch circuit, a D/A converter that converts the waveform data latched in each of the latch circuits into an analog signal, and a low frequency band that removes harmonic noise components from the analog signal output from the D/A converter. It has a filter.

[Effect]

Instead of generating a correction waveform signal by oscillating from a synchronization pulse etc. as in the case of Saki, the correction waveform signal is generated from waveform data that is time-division multiplexed and stored in the waveform data ROM, so different synchronization frequencies can be generated. It is possible to simultaneously generate a plurality of correction waveform signals for screen distortion correction in which a desired waveform is maintained correspondingly and the phase of this waveform does not change.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the correction waveform generating circuit of the present invention, and FIGS. 2 and 3 are diagrams showing 1 m periods of waveform data stored in the waveform data ROM 2.

The waveform data ROM2 contains convergence correction for variable scanning displays that can accommodate different synchronization frequencies, vertical pincushion distortion correction waveforms used for screen distortion correction such as pincushion distortion correction, and vertical convergence correction waveforms (sawtooth waves and parabolic waves are superimposed). Two types of correction waveform signals (waveform) are stored in advance by dividing one cycle of the correction waveform into 32 equal parts. In other words, the upper and lower pincushion distortion correction waveforms are
As shown in the figure and Table 1, the time and amplitude (tIl
l + al+l ) r (Ll, 2 + a
l+2 ) + ”' +(tl+32 + al+
32) as the waveform data DI consisting of the time tl+
Address 1.3 corresponding to l + tl+2 +...+ tl+32. ..., 83, the vertical convergence correction waveform is determined by the time and amplitude (tz,+, a2.+) as shown in FIG. 3 and Table 1.
).

(h, 2. 62+2) ,...+ (t2+3
As waveform data D2 consisting of □+82,32),
Addresses 2, 4°..., 64 corresponding to time t2+l +h+2 +..., tz, 32, in the order of time t
1.凰 + h+l *EI+2 *t2+
2 +...tl+32 + t2+32 in the order of time division multiplexing and stored in the waveform data ROM2.

The address generator 1 in Table 1 inputs the synchronization signal St, and generates a clock pulse S2.5 having a period of 1/32 times the synchronization signal S1.
3, and this clock pulse S2. The address of waveform data DI+o2 is generated in synchronization with S3. Latch circuit 3. , 32 are the clock pulses S2 . . . , 32 outputted from the address generator l, respectively. Waveform data D,, D, outputted from the waveform data ROM2 by S3.
Latch. D/A converter4. , 42 convert the waveform data DI, D2 loaded into the launch circuits 31+32, respectively, into analog signals. Low-pass filter 5.
, 52 remove harmonic noise components from the analog signals output from the D/A converters 41+'2, respectively, and output them to output circuits (not shown).

The waveform data Dl is generated by the latch circuit 31 from the address signal generator 1 at the time tl+l +kl+;'
+...+ When the clock pulse S3 output to tI+32 is input, it is latched by the latch circuit 31,
The signal is converted into an analog signal by the D/A converter 41, harmonic noise components are removed by the low-pass filter 51, and the signal is output to the output circuit. The waveform data D2 is generated by the latch circuit 32 from the address generator 1 at times t2, 1+t2+2+ of each one cycle.
...i Clock pulse S output to t2+32
When 2 is input, it is latched by the latch circuit 32. The operation after the waveform signal D2 is output from the latch circuit 32 is based on the waveform data D.

The same is true for .

In this way, the vertical pincushion distortion correction waveform and the vertical convergence correction waveform are simultaneously output to their respective output circuits.

There are times when it is necessary to adjust the phase of the waveform stored in the waveform data ROM 2 by a desired value and output a signal of this phase-adjusted waveform for correcting screen distortion. At this time, an additional address that corresponds to the phase to be changed (this is called an offset address) is added to the address generated from the address generator 1 to obtain waveform data whose phase has changed by the desired value. waveform data RO
What is necessary is to output it from M2.

The type of waveform is a left and right pincushion distortion correction waveform.

Similarly, in the case of waveforms such as horizontal convergence correction waveforms, signals of each waveform are simultaneously output to respective output circuits.

〔Effect of the invention〕

As explained above, in the present invention, a correction waveform signal is time-division multiplexed and stored in a waveform data ROM, and an address generator generates a clock pulse and an address for the waveform data ROM in synchronization with the clock pulse. A plurality of latch circuits each latch waveform data in response to a clock pulse from an address generator, a D/A converter converts the latched waveform data into an analog signal, and a low-pass filter converts the latched waveform data into an analog signal. By removing harmonic noise components from , a desired waveform can be maintained corresponding to different synchronization frequencies, and a plurality of correction waveform signals for correcting screen distortion without changing the phase of this waveform can be generated simultaneously.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the correction waveform generating circuit of the present invention, and FIGS. 2 and 3 are diagrams showing one cycle of waveform data stored in the waveform data ROM 2. l...Address generator. 2... Waveform data ROM. 31.3□...Latch circuit, 4,,42...D/A converter. 5, 52...low-pass filter. D,, Dl...Waveform data. Sl...Synchronization signal, S2. S3...Clock pulse. Patent issuer: NEC Home Electronics Co., Ltd. Agent: Wakabayashi To the output ri JM- To the output 1 Raku M1 Figure c (t, ri Figure 2

Claims (1)

[Claims] A plurality of correction waveform signals used for correcting screen distortion of a variable scan display that can accommodate different synchronization frequencies are obtained by dividing one period of the correction waveform into equal parts by a predetermined integer, and at each time. Waveform data RO that is time-division multiplexed and stored as waveform data consisting of amplitudes, and outputs each waveform data when an address corresponding to the time is input.
M; an address generator that receives a synchronization signal, generates a clock pulse at a cycle equal to one integer fraction of the synchronization signal, and generates an address for the waveform data ROM in synchronization with the clock pulse; A plurality of latch circuits that latch the waveform data of each waveform output from the waveform data ROM according to the clock pulse output from the address generator, and convert the waveform data latched in each of the latch circuits into analog signals. A correction waveform generation circuit comprising: a D/A converter for converting; and a low-pass filter for removing harmonic noise components from an analog signal output from the D/A converter.