JP2786251B2 - Video signal correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a video signal correction apparatus for performing a correction process for improving reproducibility on a video signal composed of a luminance signal and two types of color difference signals. About.

[Prior Art] At present, color video cameras are being reduced in size and weight, and are becoming widely popular in general. These color video cameras are, for example, CCD (Charge Coupled)
The device is configured to obtain a color video signal using an image sensor such as a device.

[Problems to be Solved by the Invention] However, in the above-described color video camera, depending on the imaging method, when obtaining a color video signal, a red signal, a green signal, and a blue signal are mixed at a mixing ratio different from a normal ratio. Are mixed, and the color video signal obtained in this case shows color reproducibility different from the original color video.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a video signal correction device which can solve the above problems and can improve the reproducibility of a video signal composed of a luminance signal and two types of color difference signals.

[Means for Solving the Problems] A video signal correction device of the present invention is a device that performs correction processing for improving reproducibility on a video signal composed of a luminance signal and two types of color difference signals. First analog-to-digital conversion means for converting an input luminance signal into a digital luminance signal in accordance with a first clock signal and outputting the digital luminance signal, and converting the input first color difference signal to be lower than the first clock signal A second digital chrominance signal which is converted and output according to a second clock signal having a frequency
Analog-to-digital converting means, third analog-to-digital converting means for converting an input second color difference signal into a second digital color difference signal in accordance with the second clock signal, and outputting the second digital color difference signal; Band limiting means for limiting the digital luminance signal output from the digital conversion means to the same frequency band as the first digital color difference signal or the second digital color difference signal, and outputting the signal from the band limiting means The digital luminance signal, the first digital color difference signal output from the second analog-to-digital conversion means, and the second digital color difference signal output from the third analog-to-digital conversion means are used as addresses. Correction data memory means for outputting correction data corresponding to the data, and the correction data memory Using the correction data output from the stage, a digital luminance signal output from the first analog / digital conversion means, a first digital color difference signal output from the second analog / digital conversion means, and the third A second digital color difference signal output from the analog-to-digital conversion means, and a correction means for correcting and outputting the digital luminance signal output from the correction means, and converting the digital luminance signal output from the correction means into an analog luminance signal in accordance with the first clock signal. First digital / analog converting means for outputting, and a second digital / analog converting means for converting the first digital chrominance signal output from the correcting means into a first analog chrominance signal in accordance with the second clock signal, and outputting the signal. Converting means for converting the second digital color difference signal output from the correction means into the second Into a second analog color difference signals in accordance click signal is obtained by comprising a third digital-to-analog conversion means for outputting.

[Operation] According to the above-described configuration, it is possible to perform correction processing appropriately corresponding to the characteristics of each of the luminance signal and the two types of color difference signals that constitute the input video signal, and the video signal having excellent reproducibility. Can be obtained.

EXAMPLES Hereinafter, the present invention will be described in detail using examples of the present invention.

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention.

In FIG. 11, 11 is an input terminal of a luminance signal from a video camera or the like, 12 is an input terminal of a color difference signal RY from the video camera or the like, 13 is an input terminal of a color difference signal BY,
Reference numeral 21 denotes a luminance signal input from the input terminal 11, for example, 14 MHz.
A / D (analog / digital) at sampling frequency of
A / D converters for conversion, 22A and 22B are converters for A / D conversion of the color difference signals input from the input terminals 12 and 13 at a sampling frequency of, for example, 3.58 MHz, and 3 is 3.58 MHz.
ROM (Read) that operates in synchronization with the clock signal of
Lookup tables 4A, 4B, and 4C, each of which is a delay circuit configured to delay an input signal by a predetermined time.

Reference numeral 51 denotes a digital low-pass filter having a pass frequency band of about 1.79 MHz that operates in synchronization with a clock signal having a frequency of 14 MHz, and 52 represents a digital filter having a pass frequency band of about 7 MHz that operates in synchronization with a clock signal having a frequency of 14 MHz. A low-pass filter 6 is a latch circuit that operates in synchronization with a clock signal having a frequency of 3.58 MHz. 7A, 7B, and 7C are digital signals that are converted into digital signals and delayed by delay circuits 4A, 4B, and 4C for a predetermined time. , An addition circuit for adding the data output from the look-up table 3,
A D / A converter that operates in synchronization with a clock signal with a frequency of MHz, 82 is a D / A converter that operates in synchronization with a clock signal with a frequency of 3.58 MHz, and 91 is the output of a corrected luminance signal. A terminal 92 is an output terminal of the color difference signal RY subjected to the correction processing, and a reference numeral 93 is an output terminal of the color difference signal BY subjected to the correction processing.

In the configuration described above, the luminance signal input from the luminance signal input terminal 11 is converted into a digital signal by the A / D converter 21 and supplied to the delay circuit 4A and the digital low-pass filter 51. The luminance signal input to the digital filter 51 is limited to a frequency band less than 1.79 MHz,
It is input to a latch circuit 6 that operates in synchronization with a clock signal having a frequency of 3.58 MHz. The latch circuit 6 holds the input signal in synchronization with the 3.58 MHz clock signal. Then, the signal output from the latch circuit 6 is supplied to the look-up table 3 together with the color difference signal converted into a digital signal by the A / D converters 22A and 22B.

For example, when a luminance signal and a color difference signal when a blue object is captured by a video camera are input to the apparatus from input terminals 11, 12, and 13, the input signals are output by A / D converters 21, 22A and 22B. The digital signal is input through a digital low-pass filter 51 and a latch circuit 6. Here, for example, the luminance signal supplied from the latch circuit 6 indicates a level shifted from a prescribed level and is converted into a digital signal. When the vectors of the color difference signals RY and BY are in the vicinity of the region indicating blue, the luminance signal correction data is stored in the lookup table 3 so that the correction data corresponding to the level of the luminance signal is output. ing. Also,
Similarly, the color difference signal correction data for correcting the vector indicated by the color difference signals RY and BY is stored in the lookup table 3 for the color difference signals.

As described above, the luminance signal correction data output from the look-up table 3 in response to the digital luminance signal supplied from the latch circuit 6 has a pass frequency band of about 7 MHz that operates in synchronization with a clock signal having a frequency of 14 MHz. , And after being subjected to band limitation in the digital filter 52, is input to the addition circuit 7A. In addition, correction data is supplied to the adder circuits 7B and 7C for the color difference signals output from the look-up table 3 in accordance with the digital color difference signals supplied from the A / D converters 22A and 22B.

Then, the adders 7A, 7B, and 7C are stored in the look-up table 3
In order to perform time adjustment by the delay circuits 4A, 4B, and 4C, the delayed digital luminance signal and digital color difference signal are added, respectively, and the output signals are output from the D / A converters 81 and 82A. , 82B. By adding the correction data as described above, the luminance signal and the color difference signal input from the input terminals 11, 12, and 13 are appropriately corrected with respect to the color reproducibility.

The digital luminance signal output from the adder circuit 7A is 14 MHz.
D / A converter that operates in synchronization with a clock of z frequency
The corrected digital luminance signal is converted into an analog signal by 81 and output from a luminance signal output terminal 91. Also,
The digital color difference signals output from the adders 7B and 7C are 3.5
The digital color difference signal R− corrected by the D / A converters 82A and 82B operating in synchronization with a clock having a frequency of 8 MHz.
Y, BY are converted to analog signals, and color difference signal output terminal 9
Output from 2,93.

As described above, the clock frequency for A / D and D / A conversion of the luminance signal is set to 14 MHz, and when forming the correction data of the luminance signal, the band is limited to the Nyquist frequency of the operation clock frequency of the lookup table by the digital filter when forming the correction data. The correction data stored in the look-up table is read out by the read digital luminance signal, the read correction data is converted into the band of the digital luminance signal after the A / D conversion, and then the digital data after the A / D conversion is converted. By adding to the luminance signal, without deterioration of the luminance signal,
In addition, the correction process can be performed in a state where the read frequency of the look-up table is low, and the optimum correction process can be performed without using a large-capacity memory in the look-up table.

[Effects of the Invention] As described above, according to the present invention, with a simple configuration, a correction process appropriately corresponding to the characteristics of a luminance signal and two types of color difference signals constituting an input video signal can be performed. The present invention can provide a video signal correction device capable of performing the above-described processing and improving the reproducibility of a video signal composed of a luminance signal and two types of color difference signals.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of one embodiment of the present invention. 11 luminance signal input terminal, 12 RY signal input terminal, 13 BY signal input terminal, 21, 22A, 22B A / D converter, 3 lookup table, 4A, 4B , 4C delay circuit, 51, 52 digital low-pass filter, 6 latch circuit, 7A, 7B, 7C addition circuit, 81, 82A, 82B D / A converter, 91 luminance signal correction Output terminal, 92: RY signal correction output terminal, 93: BY signal correction output terminal.

Continuation of the front page (56) References JP-A-61-88663 (JP, A) JP-A-60-240282 (JP, A) JP-A-58-1391 (JP, A) JP-A-63-242091 (JP) JP-A-61-222388 (JP, A) JP-A-58-3391 (JP, A) JP-A-58-3492 (JP, A) JP-A-62-21393 (JP, A) 57-41091 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 5/14-5/217 H04N 9/44-9/78

Claims (1)

(57) [Claims] An apparatus for performing a correction process for improving a reproducibility of a video signal composed of a luminance signal and two types of color difference signals, wherein the input luminance signal is corrected in accordance with a first clock signal. First analog-to-digital conversion means for converting and outputting a digital luminance signal, and a first digital color difference signal according to a second clock signal having a lower frequency than the first clock signal. A second analog / digital conversion means for converting and outputting the second color difference signal into a second digital color difference signal according to the second clock signal, and outputting the second digital color difference signal.
Analog-to-digital conversion means; and limiting the digital luminance signal output from the first analog-to-digital conversion means to the same frequency band as the frequency band of the first digital color difference signal or the second digital color difference signal; Band limiting means for outputting, a digital luminance signal output from the band limiting means,
A first digital color-difference signal output from the second analog / digital conversion means and the third analog / digital conversion signal;
Correction data memory means for outputting correction data corresponding to each signal with the second digital color difference signal output from the digital conversion means as an address; and using the correction data output from the correction data memory means, A digital luminance signal output from the first analog / digital conversion means;
Correction means for correcting and outputting the first digital color difference signal output from the digital conversion means and the second digital color difference signal output from the third analog / digital conversion means, respectively, and digital output from the correction means. First digital / analog converting means for converting a luminance signal into an analog luminance signal in accordance with the first clock signal, and outputting the analog digital signal; and converting a first digital color difference signal output from the correcting means into a second digital clock signal in accordance with the second clock signal. Second digital / analog conversion means for converting and outputting one analog color difference signal; and converting the second digital color difference signal output from the correction means into a second analog color difference signal according to the second clock signal. Video signal correction device comprising third digital / analog conversion means for performing .