JPH0223075B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a registration correction circuit in a color television camera that combines image signals from a plurality of image pickup tubes.

Color television cameras have conventionally used multiple image pickup tubes with different spectral sensitivity characteristics, and synthesized the video signals from these tubes to obtain a color video signal. is often used.

Therefore, in such a color television camera, it is necessary to ensure that the respective images obtained from the video signals obtained from each of the plurality of image pickup tubes are accurately superimposed.

This type of superimposition of images is called registration, and it is divided into various forms based on various causes.Among them, there is a method for correcting registration deviation due to non-uniformity of deflection distortion in the deflection system of the image pickup tube. Conventionally, a method has been widely adopted in which a correction signal is generated according to horizontal and vertical deflection components, and this correction signal is superimposed on a sawtooth wave signal for deflection to perform registration correction.

An example of a conventional vertical deflection circuit to which such a correction method is applied is shown in FIG.

In the figure, 1 is a vertical deflection signal generation circuit, 2 is a vertical deflection drive circuit, 3 is a vertical deflection coil, 4 is a registration correction signal (hereinafter simply referred to as correction signal) generation circuit, 5 and 6 are synchronization signal inputs, 7~
11 is a resistor, and 12 is a capacitor.

The vertical deflection signal generation circuit 1 generates a sawtooth wave signal a for deflection from the synchronization signal and supplies it to the vertical deflection drive circuit 2.

The vertical deflection drive circuit 2 includes feedback resistors 10 and 11.
It has a differential input including a capacitor 12 and a capacitor 12, and causes a deflection current b to flow through a deflection coil 3 to perform a deflection operation of an image pickup tube (not shown).

The correction signal generation circuit 4 generates a correction signal c based on the horizontal and vertical synchronization signals from the input 6, superimposes it on the output of the vertical deflection signal generation circuit 1 via the resistor 7, and supplies it to the input of the vertical deflection drive circuit 2. supply

As a result, as shown in the figure, the waveform of the deflection current b supplied to the deflection coil 3 becomes one in which the correction signal c is superimposed on the sawtooth wave component for deflection. Correction of the deviation will be performed. It goes without saying that registration correction requires correction for each of the R, G, and B image pickup tubes.

Incidentally, in such a correction circuit, in order to perform the correction operation with high precision, the correction signal c needs to contain a considerable amount of harmonic components. In order to amplify signals containing many harmonic components with sufficiently low distortion, an amplifier with sufficiently good frequency characteristics must be used.

Further, in general, in such a correction circuit, it is necessary to use a low impedance deflection coil 3 in order to obtain a good correction effect, and therefore,
The vertical deflection drive circuit 2 needs to have a high gain and a wide band.

Therefore, the above-mentioned conventional circuit has the disadvantage that the cost increases significantly, and furthermore, the correction signal is susceptible to distortion due to the high gain vertical deflection drive circuit 2, making it difficult to perform high-precision registration correction. The disadvantage was that it was difficult to

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-cost correction circuit capable of performing registration correction with sufficient accuracy without using a high-gain, wide-band vertical deflection drive circuit, while eliminating the drawbacks of the prior art described above. It is in.

In order to achieve this object, the present invention is characterized in that a correction signal current drive circuit is provided independent of the vertical deflection drive circuit, and a correction current is supplied directly to the deflection coil.

Embodiments of the correction circuit according to the present invention will be described below.

FIG. 2 shows an embodiment of the present invention, in which the same or equivalent parts as in the conventional example shown in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 2, 20 is a correction signal current drive circuit, 21 is a vertical deflection current drive circuit, and 22 to 25 are resistors.

The correction signal current drive circuit 20 forms a constant current amplification circuit with resistors 23, 24, etc., outputs a correction signal current according to the correction signal c applied from the correction signal generation circuit 4, and supplies it to the deflection coil 3.

On the other hand, the vertical deflection current drive circuit 21 also has a resistor 10,
22 and the like form a constant current amplifying circuit, outputting a current according to the sawtooth wave signal a applied from the vertical deflection signal generating circuit 1, and supplying a deflection current to the deflection coil 3.

Therefore, a current having a waveform in which the correction signal c is superimposed on the sawtooth signal a for vertical deflection flows through the deflection coil 3, and the geometric distortion caused by the non-uniformity of the deflection magnetic field due to the deflection coil 3 is eliminated. Correct deflection operation will be performed after correction. At this time, since only the sawtooth wave signal a for vertical deflection is applied to the vertical deflection drive circuit 21, there is no need to use an amplifier with broadband characteristics.

On the other hand, since the correction signal current drive circuit 20 also targets a correction signal c with a relatively small amplitude, there is almost no risk of increasing costs even if a wideband amplifier is used, and the correction current with the correct waveform with little distortion is transmitted to the deflection coil. 3, it is possible to perform highly accurate correction.

Moreover, in the above embodiment, after using a constant current amplifier circuit for the vertical deflection current drive circuit 21 and the correction signal current drive circuit 20, the vertical deflection current is Since the correction current can be supplied, even more accurate correction can be easily performed.

It goes without saying that in this embodiment as well, registration correction requires correction for a plurality of image pickup tubes for each color such as R, G, and B.

Further, in the above embodiments, the present invention is applied to a vertical deflection system, but it goes without saying that the present invention can also be applied to a horizontal deflection system at the same time.

As explained above, according to the present invention, the shortcomings of the prior art can be eliminated with a simple configuration in which the correction signal current is supplied to the deflection coil from a supply system independent of the deflection current supply system, and the cost is low. A correction circuit capable of highly accurate correction can be provided. Furthermore, according to the present invention, since the correction signal current supply system is independent, it is possible to use a higher order correction signal for more accurate correction, and it is possible to expect better correction results. .

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example of a registration correction circuit, and FIG. 2 is a circuit diagram showing an embodiment of a registration correction circuit according to the present invention. DESCRIPTION OF SYMBOLS 1... Vertical deflection signal generation circuit, 3... Vertical deflection coil, 4... Registration correction signal generation circuit, 20... Registration correction signal current drive circuit, 21... Vertical deflection current drive circuit.

Claims (1)

[Scope of Claims] 1. In a television camera that is equipped with a plurality of image pickup tubes and that supplies each deflection coil with a deflection current superimposed with a registration correction signal, a deflection device that supplies the deflection current to the deflection coil. A registration correction circuit that generates a registration correction current independent of a drive circuit is provided, and the registration correction is performed by supplying the registration correction current directly to the deflection coil. Features a registration correction circuit for color television cameras. 2. The registration correction circuit for a color television camera according to claim 1, wherein the deflection drive circuit and the registration correction circuit are each constituted by a constant current amplifier circuit.