JP2520435B2 - Automatic hue adjustment circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic hue adjustment circuit installed in a standard television receiver such as NTSC.

(Prior Art) In a standard television receiver such as NTSC, a color difference signal (R
A hue adjustment circuit that adjusts the hue by rotating -Y) and (BY) by a predetermined angle in the hue space is installed. The predetermined rotation angle in the hue space is manually set by the viewer of this television receiver.

(Problems to be Solved by the Invention) In the above-described conventional hue adjustment circuit, since the adjustment of the hue depends on the manual operation of the viewer, there is a problem that the adjustment operation becomes complicated. In particular, there is a problem that the fluctuation of the hue due to the change of the characteristic of the color demodulation circuit cannot be dealt with by the manual operation and the deterioration of the image quality cannot be avoided.

(Means for Solving Problems) The automatic hue adjustment circuit of the present invention rotates the color difference signals (RY) and (BY) demodulated from the standard television video signal by a predetermined angle in the hue space. By doing so, a hue adjustment unit that performs hue adjustment, a burst gate that passes the color difference signal (RY) output from this hue adjustment unit in synchronization with a signal that notifies the appearance of a color burst, and a burst gate that passes this burst gate It is provided with an adjustment control unit that changes a predetermined rotation angle in the hue adjustment unit in a direction to reduce the low-frequency component of the color difference signal, and is configured to automate the hue adjustment with a simple configuration. .

 Hereinafter, the operation of the present invention will be described in detail with reference to Examples.

(Embodiment) FIG. 1 is a block diagram showing a configuration of an automatic hue adjustment circuit according to an embodiment of the present invention. 1 is a hue adjustment unit, 2 is a burst gate, 3 is an adjustment control unit, and 4 is demultiplexing. The circuit 5 is a multiplexing circuit.

The input terminal I1 is converted to a digital video signal by an A / D conversion circuit (not shown) in the preceding stage, Y / C separated from the luminance signal, ACC (Automatic Color Control) is applied, and color demodulated NTSC The color difference signal of the video signal is input. This color difference signal is in a state in which (RY) and (BY) are time-division multiplexed. The multiplexed color difference signal is supplied to the hue adjusting unit 1 while being separated into the color difference signals (RY) and (BY) in the demultiplexing circuit 4 in synchronization with the clock signal CLK supplied to the input terminal I2. To be done.

As shown in the hue space of FIG. 2, the hue adjustment unit 1 receives the color difference signals (BY) and (R) input to the hue adjustment unit 1.
The hue is adjusted by performing the following conversion on -Y) to give a rotation of a predetermined angle ζ.

(BY) '= cos? (BY) -sin? (RY) (RY)' = sin? (BY) + cos? (RY) The hue adjustment unit 1 uses the coefficient as described above. In order to perform conversion by the combination of multiplication and addition / subtraction of, multipliers 11, 12, 13, 14 and
It is provided with adders 15 and 16, coefficient ROMs 17 and 18, a delay device 19, and a polarity inverter 20. The rotation angle ζ in this hue space is
The read addresses for the coefficient ROMs 17 and 18 are given from the adjustment control unit 3 to the hue adjustment unit 1.

That is, the coefficient sin ζ is stored in the address ζ of the coefficient ROM 17, which is read out in synchronization with the clock signal and supplied to the multiplier 13 and the polarity inverter 20 to the multiplier 12. Similarly, address ζ of coefficient ROM18
Stores a coefficient cos ζ, which is read in synchronization with the clock signal and supplied to the multipliers 11 and 14.

The hue-adjusted color difference signals (BY) 'and (RY)' output from the hue adjuster 1 are time-division multiplexed in the multiplexing circuit 5 and supplied to the output terminal O.

FIG. 3 is a timing chart for explaining the operations of the demultiplexing circuit 4, the hue adjusting unit 1 and the multiplexing circuit 5 of FIG.

In FIG. 3, A is a clock signal CLK supplied to the input terminal I2, B is a multiplexed color difference signal supplied to the input terminal I1, C is a demultiplexed color difference signal (R) output from the demultiplexing circuit 4. -Y) and D are demultiplexed color difference signals (R-
Y) and E are demultiplexed color difference signals (BY) output from the demultiplexing circuit 4. Further, F, G, H, I are multipliers 11,
12, 13 and 14 are outputs, J and K are outputs from adders 15 and 16, and L is a hue-adjusted multiplexed color difference signal output from the multiplexing circuit 5.

The burst gate 2 receives the adjusted color difference signal (R-
Y) 'is passed in synchronization with the signal notifying the appearance of the color burst supplied from the input terminal I3. The low-pass filter 21 in the adjustment control circuit 3 extracts the low-frequency component from the adjusted color difference signal (RY) 'which has passed through the burst gate 2 and outputs it to one input terminal of the adder 22. Supply to.
The other input terminal of the adder 22 has one line or one field before the adder 22 held in the sample and hold circuit 23.
The output of is supplied. Therefore, the adder 22 outputs a new output ζ obtained by adding the output of the low-pass filter 21 to the output of one line or one field before, and is held in the sample and hold circuit 23. This sample and hold circuit
The output of 23 is supplied to the hue adjusting unit 1 as a read address of the coefficient ROMs 17 and 18.

As shown in the hue space in FIG. 4, if the hue adjustment by the hue adjusting unit 1 is complete, the color burst signal appears as the color difference signal C on the color difference axis − (BY) and the color difference axis (R -Y) The above component becomes 0. Actually, due to the incompleteness of the hue adjustment, the color burst signal is not
It is assumed that the color difference signal C ′ rotated from (BY) by Δζ appears, and the component c on the color difference axis (RY) appears accordingly. The polarity and amplitude of this component c are detected by the low-pass filter 21, and the output ζ of the adder 22 is corrected in the increasing direction. As a result, the rotation angle is readjusted by the color difference adjusting unit 1 in the direction in which the color difference signal C ′ approaches the − (BY) axis.

As described above, the color difference signals (RY) and (B-
Since Y) is time-division multiplexed, a configuration in which the demultiplexing circuit and the multiplexing circuit are arranged before and after the hue adjustment unit 1 is illustrated. However, in order to simplify the configuration of the hue adjustment unit, the time division multiplexed signal may be directly multiplied and added without performing demultiplexing.

Further, the case where the color difference signals are digitized has been illustrated, but the present invention can be similarly applied even if the color difference signals are analog signals.

(Effects of the Invention) As described in detail above, the automatic hue adjustment circuit according to the present invention notifies the appearance of the color burst by the hue adjustment unit and the color difference signal (RY) output from the hue adjustment unit. The hue adjustment unit is configured to change the predetermined rotation angle in the direction of decreasing the low-frequency component, so that the automatic hue adjustment can be realized with a simple configuration. There is an effect that the complexity is removed and the image quality is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an automatic hue adjustment circuit according to an embodiment of the present invention, FIG. 2 is a conceptual diagram for explaining the principle of hue adjustment by the hue adjustment unit 1 in FIG. 1, and FIG. Is the first
FIG. 4 is a timing chart for explaining the operation of the figure, and FIG. 4 is a conceptual diagram for explaining the operation principle of the above embodiment. I1 …… Adjustment target color difference signal input terminal, I3 …… Signal input terminal for notifying the appearance of color burst, O …… Adjusted color difference signal output terminal, 1 …… Hue adjuster, 2 …… Burst gate 3 ... adjustment control unit, 4 ... demultiplexing circuit,
5 ... Multiplexing circuit, 11-14 ... Multiplier, 15,16 ... Adder, 17,18 ... Coefficient ROM, 21 ... Low-pass filter, 22 ...
Adder, 23 ... delay device.

Claims (1)

(57) [Claims] 1. A hue adjustment unit for performing hue adjustment by rotating a color difference signal (RY) and (BY) color-demodulated from a standard television image signal in a hue space by a predetermined angle, and a hue adjustment unit. A burst gate that allows the color difference signal (RY) output from the adjusting unit to pass in synchronism with a signal that notifies the appearance of a color burst; and a burst gate that reduces the low-frequency component of the color difference signal that has passed through the burst gate. An automatic hue adjustment circuit, comprising: an adjustment control section for changing the predetermined angle in the hue adjustment section.