JPH03201681A - Line correlation detector - Google Patents

Abstract

PURPOSE:To obtain a simple line correlation detector at low cost by composing the detector of a low-priced average value detecting means or a sample/hold means without using a 1H delay circuit using the CCD of a complicated circuit. CONSTITUTION:An average value detecting means 6 is provided to detect an average value for the luminance of an (n)th horizontal scanning line, and first and second holding means 7 and 8 are provided to hold the detected value until the scanning periods of the (n+1)th and (n-1)th horizontal scanning lines. Then, a rising edge detecting means 14 is provided to output a rising detection signal based on a result to compare the hold values of those holding means. A falling edge detecting means 15 is provided to output a falling detection signal, and a hold switching means 9 is provided. Further, a comparing means 16 is provided to compare the switching output with an input luminance signal and to output a compared result as a comparing pulse, and correlation detection pulse output means 20-22 are provided to control the comparing pulse by the output signals of the edge detecting means 14 and 15 and to output the pulse as a correlation detection signal. Thus, without using the 1H delay circuit of complicated structure, line correlation detection can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a line correlation detection device that can be used to control a cyclic noise reduction circuit for video luminance signals used in television receivers, video tape recorders, etc. It is.

2. Description of the Related Art In recent years, as color television receivers have become larger, noise reduction circuits have been used in luminance signal and color signal circuits to reduce noise contained in images and make the images appear clearer.

Although cyclic noise reduction circuits can be constructed at low cost and are often used, they have the disadvantage of causing so-called trailing of signals in the vertical direction of the image. In order to reduce this tailing, we detect the vertical correlation of the video signal,
Line correlation detection circuits have been used that act to stop the cycle if there is no correlation. A conventional line correlation detection circuit will be described below with reference to the drawings.

FIG. 3 is a block diagram of a conventional line correlation detection circuit. In FIG. 3, 1 uses a CCD (charge imaging device) to delay the human luminance signal a by IH, resulting in a delayed luminance signal I.
) is an IH delay circuit that outputs. 2 is human brightness signal a
This is a subtraction circuit that subtracts the delayed luminance signal S from the subtraction circuit and outputs a non-correlation detection signal C.

3 is a full-wave rectifier circuit which performs full-wave rectification of the J1 correlation detection signal C and outputs a rectified non-correlation detection signal d. 4 is a comparison circuit that compares the rectified non-correlation detection signal d with a comparison voltage e set externally and outputs a noise reduction control signal f.

A cyclic noise reduction circuit 5 circulates the human luminance signal g, reduces noise, and obtains an output luminance signal, and is turned on/off by the noise reduction control signal f.

Regarding the line correlation detection circuit configured as above,
The operation will be explained below.

FIG. 4 shows signals of various parts in the conventional example. First, the human-powered luminance signal a ((a) in the same figure) is manually input to the 1H delay circuit l,
A delayed luminance signal b ((L+) in the same figure) is obtained.

Human brightness signal a and i! The I extended luminance signal S is subtracted by a subtracting circuit 2, and a non-correlation detection signal C (FIG. 4(C)) is obtained. This non-correlation detection signal C is full-wave rectified by the full-wave rectifier circuit 3 to obtain a rectified non-correlation detection signal d (FIG. 3(d)). Next, the rectified non-correlation detection signal d is compared with a comparison voltage e ((d) in the same figure) in a comparison circuit rJ4, and a noise reduction control signal r ((f) in the same figure) is obtained. 0) The signal causes the cyclic noise reduction circuit ``'' IN 5,
'Cycling ((g), (n') in the same figure) is turned on/off,
Color tailing is improved.

Problems to be Solved by the Invention In the above configuration, since an IH delay circuit using CCI is used in addition to the noise reduction circuit, not only the COD but also the driving This requires a drive circuit, which complicates the entire circuit and increases costs considerably.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a line correlation detection device that can detect line correlation without using a separate IH delay circuit.

Means for Solving the Problems The present invention provides average value detection means for detecting the average brightness value of the n-th horizontal scanning line, and holding the detected value until scanning 171 of the (n11)-th horizontal scanning line. a first hold means holding the average luminance value of the (n-1)th horizontal scanning line, and comparing the bold values of the first and second hold means, A rising edge detection means outputs a rising-L detection signal based on the comparison results, and compares the hold values indicated in in,
a falling edge detection means for outputting a falling detection signal based on the comparison results; a hold switching means for switching the outputs of the first halt means and the second hold means; and a brightness switching output and a human brightness signal. and a correlation detection pulse output stage for controlling the comparison pulse by the output signal of the edge detection means and outputting it as a correlation detection signal. This is a line correlation detection device that detects vertical correlation of luminance signals.

Effect of the present invention With this configuration, the I of a CCD with a complicated structure is
Line correlation detection can be performed without using an H delay circuit by comparing the average luminance level for each line obtained by the sample and hold means using the comparing means.

EXAMPLES The present invention will be described below with reference to drawings showing examples thereof.

FIG. 1 is a block diagram of a line interference detection device in one embodiment of the present invention.

In FIG. 1, the average value detection means 6 is means for detecting the average luminance level of the human-powered luminance signal every n (first
, the second sample and hold means 7.8
This is means for sampling and bolding the output of the Iq detecting means 6. Switches 9.17.18 are means for selecting one of the two human input signals. History 10, Ill 2.1
3 is a resistor, l 4.15.16 is a comparator, 19.20 is an inversion circuit, 21.22 is a switch that is turned on/off by a control signal, and 23 is a control pulse generation circuit that generates control pulses necessary for each circuit. It is.

Regarding the line correlation detection circuit configured as above,
The operation will be explained below. Figure 2 shows the waveforms of each part.

First, the human-powered luminance signal a ((a) in the same figure) is manually inputted to the average value detection means 6, and the average value reset pulse 2 ((2) in the same figure) is input manually to the average value detection means 6.
) detects the average luminance level for each line and outputs it as an average luminance signal J ((j) in the figure). The next signal ζ, 1, is input to sample and hold means 7 and 8. These means 7.8 are the same circuit, but the sample/hold pulse l(m) ((m) in the same figure) or
Each circuit is controlled by the sample/hold pulse 2 (II) (01 in the same figure), and each circuit repeats its operation alternately at intervals of lH.

The hold voltage 1(k) ((k) in the same figure) and the hold voltage 2(1) ((1) in the same figure), which are the respective outputs from the sample/hold means 7.8, are output from the comparator n4 or the comparator 215. is input. Further, signals r) and q ((p) and (q) in the figure) obtained by dividing the hold voltage by resistors RIIO and R2n or resistors R312 and R414 are input to the remaining terminals of the comparator n/L. Here, R1 and R3
The voltage drops are equal, and this voltage is set at a level that will prevent the comparator from malfunctioning due to noise. As a result, the outputs of comparators 1 and 2 have a comparison output 1(r) (0 and 2 in the figure).
)) and 2(s) ((S) in the same figure) are obtained. These outputs r and s detect the uncorrelated portion of the image in the vertical direction. Next, the comparison outputs l and 2 are switched by switches 2 and 3 controlled by the hold voltage switching pulse (0) ((0) in the same figure), and the rising detection signal (1) ((t) in the same figure) is switched. Falling detection signal (tJ
) ((U) in the same figure). In other words, when the sample and hold circuit 1 holds the signal, if the comparison output 2 becomes "HIGH", it is a rising edge, and if the comparison output 1 becomes "°'J(I(,)r"), it is a falling edge. , conversely, when held in sample-and-hold circuit 2, each is the opposite, so rising and falling can be detected. Hold voltage switching pulse (0
) is controlled by

The voltage switched in this manner is input to the comparator 3 as a switched hold voltage (V) ((V) in the figure).

The other input terminal of the comparator 3 receives a human luminance signal (a
) are manually generated, and these are compared to obtain the uncorrelated detection signal (W).
((W) in the same figure) is output. This uncorrelated detection signal is
When it is 'HIGH', it is the part where the human brightness signal a is larger than the average brightness level, and when it is 'LOW', it is the part where it is small. The inverted non-correlation detection signal is switched to switch 4.
is input. - If there is a correlation in the vertical direction of the image, both the rising and falling detection signals (T) and (U) are "LOW" and the noise reduction control signal ("
) ((()) in the same figure becomes "LOW".However, if the signal is large in the non-correlated part of the scanning line, it becomes "LOW"). is “HIG”
H", the switch 5 is turned on, and W is output as the noise reduction control signal r. Also, vice versa,
If the signal is small, X ((X) in the same figure) is output as a noise reduction control signal. The control pulse generation circuits 2 and 3 generate respective control pulses based on the horizontal pulse human input signal (y) ((y) in the figure).

As described above, according to this embodiment, the correlation in the vertical direction of an image can be detected using a circuit that detects the average level of a scanning line, a sample-and-hold circuit, and a comparison circuit without using a delay circuit. It is possible to reduce the cost, which is a drawback of the conventional method.

In this embodiment, the human input signal (a) is a luminance signal, but it may also be a color signal. Furthermore, although the manual signal of the cyclic noise reduction circuit is a luminance signal, it may also be a color signal. In addition, the noise reduction control signal (f
Although the circuit controlled by ) is a noise reduction circuit, it may also be a notch filter or a bandpass filter.

Effects of the Invention As described above, the present invention allows the line correlation detection device to be constructed using inexpensive average value detection means and sample/hold means without using an IH delay circuit using a complicated CCD circuit. This method has the advantage of providing a simple and low-cost line correlation detection device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a line correlation detection device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of various parts in the same embodiment, and FIG. 3 is a block diagram of a conventional line correlation detection circuit.
FIG. 4 is a waveform diagram of each part of a conventional line correlation detection circuit. 6... Average nσ detection means, 7.8... Sample bold means, l 4.15.16... Comparison means.

Claims (1)

[Claims] average value detection means for detecting the luminance average value of the nth horizontal scanning line; first holding means for holding the detected value until the scanning period of the (n+1)th horizontal scanning line;
1) Compare the hold values of the second hold means that holds the average luminance value of the horizontal scanning line with the first and second hold means, and output a rising detection signal based on the comparison result. a rising edge detection means, a falling edge detection means for comparing the hold values and outputting a falling detection signal based on the comparison result; and outputs of the first hold means and the second hold means. A hold switching means for switching, a comparison means for comparing the switching output with the input luminance signal and outputting the comparison result as a comparison pulse, and controlling the comparison pulse by the output signal of the edge detection means and outputting it as a correlation detection signal. What is claimed is: 1. A line correlation detection device comprising: correlation detection pulse output means for detecting correlation in a vertical direction of a video luminance signal.