JPS6132875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic color balance device for color signals generated by a color television camera, etc.
It automatically adjusts white balance and gamma balance.

The automatic color balance device automatically adjusts R, R,
This is to adjust the balance of G and B signals. Traditionally, typical devices of this type are the color camera R,
Determine the threshold using the G, B output signal or luminance signal, and if the R, G, B output signal or luminance signal is less than 10% of the specified level, or greater than 90%, the threshold is set at 45% to 55%. In the case between R,
The black, white, and gamma balances of G and B are automatically adjusted to maintain color balance. This device is particularly used built into a telecine color camera.

FIG. 1 shows a block diagram of a typical detector in a conventional device, which generates a control signal for automatically controlling gamma. In the figure, 1, 2, and 3 are R, G, and B signal input terminals, respectively, and receive R, G, and B output signals from a color television camera. These R, G, and B signals enter the level comparators 4, 5, and 6, and are compared with the gamma threshold value determined by the gamma threshold determination circuit 7. Usually, the R, G, and B signals are approximately 45 to 55% of the specified level. , G, and B signals, AND gate 8
A gate pulse is generated to open the gate circuits 11 and 12. On the other hand, the R, G, and B input signals are input to differential amplifiers 9 and 10.
A difference signal between the signals is taken out and sent to the gate circuit 11,1.
2, the difference signal is gated only when a gate pulse is generated, and the difference signal is converted into DC and held in the average value holding circuits 13 and 14. Furthermore, a gamma control signal output is sent to the R and B gamma control signal output terminals 16 and 17, and sent to the gamma balance control circuit of the color television camera body so as to form a feedback loop, and these control signals are used to adjust the relative gamma balance. I'm going. That is, the gamma of the R and B signals is corrected so as to eliminate the difference between the intermediate levels of the R and B signals compared to the intermediate level of the G signal.

When using a conventional telecine color camera using this type of device to capture images of a mixture of faded film that requires significant color balance correction and good film that does not require color balance correction, the faded film is fine. If you want to correct it, set the threshold hold to 35 for gamma, for example.
It will be necessary to set it deeper than usual, such as ~55%.
However, setting the threshold too deep often results in erroneous correction in which intermediate level colors are undesirably corrected in good films that do not require correction. Therefore, there is a drawback that the threshold must be constantly set at a shallow level, or the operator must switch from automatic to manual each time the film is of good quality. Further, these drawbacks also apply to automatic black balance and white balance adjustment.

The present invention aims to eliminate these drawbacks. Specifically, the present invention does not directly use the error signal as a color balance control signal, but rather controls the color balance via an arithmetic control unit equipped with a microprogram control circuit. The threshold value is controlled appropriately by sending a control signal to the threshold determination circuit, which eliminates over-correction and
The objective is to provide stable automatic color balance adjustment with very few erroneous corrections.

FIG. 2 is an embodiment to which the present invention is applied, and shows a block diagram of a detector that generates a control signal for automatically controlling gamma in an automatic color balance device. The details of the invention will be explained below. Components designated by numerals 1 to 6, 8 to 14, 16, and 17 correspond to the components having the same symbols in FIG. 1, respectively. 15 is an average value holding circuit 13, 14
7 is the calculation control unit 1 which calculates the output of
This is a gamma threshold determining circuit which receives the output of 7 and generates a level signal to be applied to level comparators 4-6.

Next, the operation of this embodiment will be explained. The R, G, and B output signals of the color television camera applied to input terminals 1, 2, and 3 are sent to level comparators 4, 5, and 6.
and is compared with the gamma threshold value by the gamma threshold determination circuit 7, and within the range of the gamma threshold value, e.g.
If the R, G, and B signal levels each exist between 45% and 55%, they are detected by 8 AND gates 11,
A gate pulse is generated which opens 12 gate circuits.

On the other hand, the R, G, and B input signals are handled by differential amplifiers 9 and 10.
The differential signals of the R and G, B and G signals, which are used as a reference, are taken out, and the gate circuits 11 and 12
The difference signal is gated only when a gate pulse is generated, and average value holding circuits 13 and 14 convert the difference signal into DC and hold it as R and B gamma error signals. These error signals are processed by an arithmetic control unit equipped with a microprogram control circuit 15 and sent to the R and B gamma control signal output terminals 1.
6 and 17, and is sent to the gamma balance circuit of the color television camera body to form a feedback loop, and relative gamma balance adjustment is performed by these control signals. On the other hand, the arithmetic control unit 15 performs arithmetic processing to determine the threshold value, sends a threshold control signal to the gamma threshold determination circuit, and adjusts the gamma balance threshold value appropriately depending on the material to be imaged. control and stable color balance adjustment.

Next, the arithmetic control section 15 equipped with the microprogram control circuit shown in FIG. 2 will be explained with reference to FIG. 3 showing a specific example thereof.

101 and 102 are R receiving gamma error signals
and B gamma error signal input terminals, and these error signals are selected by the multiplexer 103 and converted from analog signals to digital signals by the A/D converter 104. This digital signal is subjected to calculations and judgments in a microprogram control section 107 via a bus line 106, and a data signal is sent to a D/A converter 109 and an input/output port 105 at an appropriate time. D/A converter 109
The signals converted into analog signals are selected by a multiplexer 110 and sent to R and B gamma control signal output terminals 111 and 112 as gamma control signal outputs.

On the other hand, the data signal sent to the input/output port 105 is further sent to the gamma threshold control signal output terminal 113 and becomes a gamma threshold control signal. A/D converter 104, input/output port 105, and D/A converter 109 are all connected to memory 108 and microprogram control section 107 via bus line 106. Also, the memory 108 is the microprogram control unit 1
It maintains the control contents of 07 and data as necessary, and exchanges data.

All of the above controls are performed by the external synchronization signal input terminal 11.
It is executed in synchronization with the synchronization signal inputted at 4, and started and stopped by the start signal inputted to the start signal input terminal 115.

FIG. 4 shows a flowchart of one embodiment of the arithmetic control section.

Waits for a start signal with the external functions initialized, and starts with the start signal. Next, when a synchronization signal interrupt occurs, the data stored in the memory is output and used as a gamma control signal and a gamma threshold control signal. These processes are performed within the vertical retrace period, and the gamma error signal is read and calculated within the vertical blanking period. If the gamma balance is found as a result, a synchronization signal interrupt wait is performed. If the gamma balance is not maintained, the calculation is performed once again, compared with the data stored in the memory, and the gamma control data and gamma threshold data values are replaced at an appropriate time and used as an output signal.

All of the above operations are performed for each field. The detector that generates a control signal for automatically controlling gamma has been described above as an embodiment of the present invention using FIGS. 2 to 4. A detector that generates control signals for automatically controlling the level and white level can be implemented in exactly the same way.

As explained above, since the present invention is a system for automatically controlling the threshold value appropriately, the present invention is very effective when used in a telecine color camera or the like. For example, if you are taking an image of a faded film whose color balance has been significantly disrupted, you can increase the gamma threshold setting value from the normal 45 to 55% if it is gamma balanced, for example 35 to 55%, to obtain a good film whose color balance is not disrupted. In the case of , by making it shallow, for example, 50 to 55%, it can be used as an automatic color balance device that responds to deviations in the color balance of the imaged material with very few erroneous corrections, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional automatic color balance device that generates a gamma control signal, FIG. 2 is a block diagram of an automatic color balance device according to an embodiment of the present invention, and FIG. 3 is a block diagram of an arithmetic control section. Figure 4 is a flowchart. 4 to 6... Level comparator, 7... Gamma threshold determination circuit, 9, 10... Differential amplifier, 1
1, 12...gate circuit, 13, 14...average value holding circuit, 15...arithmetic control section.

Claims (1)

[Claims] 1 Compare the R, G, B signals or luminance signals of a color television camera, etc. and the threshold value output from the threshold determination circuit,
Gate when the R, G, B signal or the luminance signal is a black signal below a predetermined value determined by the threshold value, a white signal above a predetermined value, or a halftone signal within a predetermined range. a gate pulse generating means that generates a pulse; a gate circuit that gates a difference signal between the R signal and the G signal and a difference signal between the B signal and the G signal using the gate pulse;
In addition to calculating and outputting a color balance control signal according to each of the above difference signals, the output threshold value of the threshold determination circuit is set so as to widen the generation range of the gate pulse when the above difference signal is large. An automatic color balance device comprising: arithmetic control means for outputting a threshold control signal for automatic control.