JPS6251891A - Shading correcting circuit for color camera - Google Patents

Abstract

PURPOSE:To correct shading in 4 corners independently by taking out one horizontal saw tooth waveform and one vertical saw tooth waveform from 4 waveforms,. namely, horizontal and vertical saw tooth waveforms and waveforms obtained by inverting them to generate a correcting waveform of each of 4 corners. CONSTITUTION:Horizontal and vertical saw tooth wave signals generated from a horizontal saw tooth wave generating circuit 11 and a vertical saw tooth wave generating circuit 13 are applied to inverting circuits 12 and 14, and the horizontal saw tooth wave signal is supplied to correcting waveform generating circuits 15 and 16, and the vertical saw tooth wave signal is supplied to correcting waveform generating circuits 15 and 17. Outputs of inverting circuits 12 and 14 are supplied to correcting waveform generating circuits 17 and 18 and correcting waveform generating circuits 16 and 18 respectively. AS the result, one horizontal waveform and one vertical waveform are applied to each of correcting waveform generating circuits 15, 16, 17, and 18, and the correcting waveform for correction of the left upper corner, that of the the left lower corner, that of the right upper corner, and that of the right lower corner are generated from circuits 15, 16, 17, and 18 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a shading correction circuit in a color camera.

2. Description of the Related Art Conventionally, this type of shading correction circuit generates a sawtooth waveform and a parabolic waveform, which are combined to form a shading correction circuit.

FIG. 2 shows its configuration, where 1 is a horizontal sawtooth wave generation section, 2 is a parabolic waveform generation section, 3 is a vertical sawtooth wave generation section, and 4 is its parabolic waveform generation section. 5 to 7 are mix amplifiers that mix these four waveforms; the corrected waveform obtained from mix amplifier 5 is used as an R signal, that from mix amplifier 6 is used as a B signal, and that from mix amplifier 7 is used as a dynamic focus. , is supplied to a focus electrode of an image pickup tube (not shown).

The problem to be solved by the present invention, however, is that the conventional shading correction circuit described above cannot independently correct shading that occurs locally at the four corners of the screen. The present invention solves these conventional problems.

Means to Solve the Problems' In order to achieve the above object, the present invention provides horizontal and vertical sawtooth wave generation circuits similar to the conventional ones, as well as an inverting amplifier for the generated waveforms. Out of the four waveforms, one from the horizontal waveform and one from the vertical waveform were taken and combined to correspond to the four corners, allowing the differential amplifier to generate correction waveforms for the four corners. It is something.

Therefore, it is particularly advantageous for improving the image quality of high-band cameras where local corner shading is likely to occur.

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, 11 is a horizontal sawtooth wave generating circuit, 12 is its inverting amplifier, 13 is a vertical sawtooth wave generating circuit, and 14 is its inverting amplifier. 15 to 18 are correction waveform generation circuits that obtain one horizontal waveform and one vertical waveform from 11 to 14, mix them, and have a built-in differential amplifier.
The correction position can be varied at 42, the amount of correction for the R signal can be varied by variable resistors 43-46, and the amount of correction for the B signal can be varied by variable resistors 47-50.

On the other hand, the amount of correction to the focus voltage of the image pickup tube (not shown) can be varied by variable resistors 21 to 24, forming a dynamic focus circuit. In this way, the correction waveform generation circuits 15 to 18 can obtain waveforms necessary for each corner of the screen. That is, a horizontal sawtooth wave generation circuit 11 fed with a horizontal synchronizing signal (hereinafter referred to as Hs) generates a sawtooth wave (this is referred to as HL), and an inverting amplifier 12 generates a sawtooth wave that is an inversion of HL. (Hereinafter, the sawtooth wave obtained by inverting HL will be referred to as HR), vertical synchronization signal (hereinafter Vs
) is applied to the vertical sawtooth wave generation circuit 13 to obtain a sawtooth wave (hereinafter referred to as VT) synchronized with Vs, which is inverted by the inverter amplifier 14 to produce a sawtooth wave (hereinafter referred to as vB) which is the inversion of VT. get. Therefore, the correction waveform generation circuits 15 to 18 mix the waveforms shown in FIG. 1 from among HLl, HRl, VT%, and VB, and use the differential amplifier to obtain the correction waveforms necessary for each corner. . In this case, among the correction waveform generation circuits 15 to 18, 15 is in the upper left corner, I6 is in the lower left corner, 17 is in the lower right corner, 18
The waveform at the lower right corner is corrected, and the generation point of the corrected waveform at the corner can be arbitrarily set using variable resistors 39 to 42 and can be changed depending on the appearance of shading. The correction waveform obtained here is the variable resistor 43 to 4
6, the correction amount is set and added to the R signal. Similarly, it is added to the B signal through variable resistors 47-50.

On the other hand, apart from these, the waveforms mixed by the variable resistors 21 to 24 are sent to the focus electrode of the image pickup tube to function as a dynamic focus and reduce shading.

Effects of the Invention As explained above with reference to the embodiments, according to the present invention, each of the four corners of the screen can be independently corrected for shaving, so it is possible to correct single-tube color that is particularly prone to high band and local corner shading. It is extremely effective in improving camera image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a shading correction circuit in a color camera according to an embodiment of the present invention;
FIG. 2 is a block diagram of a conventional example. 11...Horizontal sawtooth wave generation circuit, 12.14...Inverting amplifier, 13...Vertical sawtooth wave generation circuit, 15-1
8...Correction waveform generation circuit. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure QF Figure 2

Claims (3)

[Claims] (1) Four correction waveform generation circuits are provided, each using a combination of inverted and non-inverted sawtooth waves generated from horizontal and vertical inputs, each with a different input, and the output of each circuit is A shading correction circuit in a color camera that is provided with means for mixing and extracting R, B signals and focus voltage. (2) A shading correction circuit in a color camera according to claim 1, wherein the correction waveform generation circuit is provided with a circuit for adjusting a correction position. (3) A shading correction circuit in a color camera according to claim 1, wherein a correction circuit is provided in each of the R, B and focus voltage output systems of the correction waveform generation circuit.