JPH0779442B2 - Noise reduction circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for effectively reducing grain noise when a photographic film is picked up by a TV camera.

[Prior Art] As a signal source in a TV broadcasting station, there are an image pickup signal from a camera and one obtained by applying photographic film to an image pickup device. The latter is a so-called film program, and it is a TV together with the program by VTR.
It occupies most of the programs. And when shooting and transmitting programs made with photographic film, especially positive film,
Since the graininess of the film is not good, it causes image deterioration on the image receiving side. Therefore, it is necessary to reduce the granular noise in the positive film, but conventionally, a normal noise reducing circuit as shown in FIG. 4 was used instead of a dedicated circuit for that purpose. In FIG. 4, reference numeral 1 is a terminal for separating and inputting only the luminance signal of the output signal of the film imager, 2 is a high-pass filter, 3 is a low-pass filter, 4
Is a slice circuit, 5 is an overlay circuit, and 6 is a luminance signal output terminal. In FIG. 4, only the luminance signal is input and the high frequency signal and the low frequency signal are separated by the filters 2 and 3.
What is noticeable as noise concentrates in the low level part of the high frequency signal, so it is removed by the slice circuit 4.
Next, after level matching, the output signal of the low-pass filter 3 and the superimposing circuit 5 superimpose them, and a signal from which noise has been removed is output from the terminal 6.

[Problems to be Solved by the Invention] With the noise reduction circuit shown in FIG. 4, a sufficient effect can be obtained for an image picked up by a TV camera, but it is not sufficient for an image signal picked up on a film. It was This is because the circuit of FIG. 4 performs amplitude processing in the time axis direction, and high frequency information is lost due to image blurring of the image pickup device. Therefore, the circuit shown in FIG. 4 can only obtain an image having a reduced resolution, which is a drawback especially when high fidelity is required recently.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a noise reduction circuit which solves the above-mentioned drawbacks and processes a signal obtained by imaging a positive film so that a good signal can be transmitted without degrading the resolution.

[Means for Solving the Problems] FIG. 1 is a diagram showing a principle configuration of the present invention. In FIG. 1, 1 is a luminance signal input terminal, 6 is a luminance signal output terminal,
Reference numeral 7 is a band-pass filter in an oblique midrange, 8 is a subtracting circuit, 9 is a time direction averaging circuit, and 10 is an adding circuit.

The present invention has the following configuration. That is, a diagonal mid-range band pass filter 7 to which a luminance signal obtained from a photographic film imager serving as a TV signal source is applied, and a subtraction circuit 8 for subtracting the output signal of the band pass filter 7 from the luminance signal. A time direction averaging circuit 9 to which the output signal of the band pass filter 7 is applied, and the subtracting circuit 8
Is added to the output of the averaging circuit 9 in the time direction, and a luminance signal with reduced granular noise is obtained at the output of the adding circuit 10.

[Operation] With respect to one frame of the film to be imaged, the state of the granular noise is measured by an image signal measuring device (for example, an oscilloscope). In the frequency domain diagram shown in FIG. 2, normally, the noise is most noticeable in the horizontal frequency (H) and vertical frequency (V) in the intermediate band (the part without hatching), and that band is in the diagonal middle band. Say. In order to take out only the band signal, the center frequency of the band pass filter 7 is selected as that frequency, and then the luminance signal of the film image pickup signal is input from the terminal 1. Since the output signal that has passed through the band-pass filter 7 is the unhatched portion of the input luminance signal, the output signal is applied to the subtraction circuit 8 so as to be subtracted from the input luminance signal. Therefore, the subtraction circuit 8
The output signal of is the signal of the hatched portion.
The I and Q signals other than the luminance signal need only be given a predetermined delay such as 1H time. The output signal of the bandpass filter is also applied to the time direction averaging circuit 9. Here, for example, since a signal obtained by averaging the signal state of one frame before and the current signal is obtained, a signal in which the granular noise is reduced is obtained with respect to the unhatched portion of the signal shown in FIG. Next, in the adder circuit 10, the output signal of the subtraction circuit 8 and the output of the time direction averaging circuit 9 are added, and a luminance signal with reduced noise is obtained at the output terminal 6 in the unhatched portion of FIG. You can

[Embodiment] FIG. 3 is a block diagram showing an embodiment of the present invention. In FIG. 3, 71 is a vertical band pass filter, 72 is a horizontal band pass filter, and 71 and 72 are combined to form an oblique mid-range band pass filter. And 7-1, 7-2
Is a 1H delay circuit, 7-3 is a signal multiplication circuit, and 7-4 is a delay circuit having a time substantially equal to the delay time of the horizontal band pass filter. In the time direction averaging circuit 9, 9-1, 9-
Reference numeral 4 indicates an adder circuit, 9-2 indicates a coefficient unit, and 9-3 indicates a frame memory. Reference numeral 11 is a delay circuit, and its delay time is set to be substantially equal to the delay time in the time direction averaging circuit 9.

In FIG. 3, the vertical band pass filter 71 includes an original signal, a signal passed through the 1H delay circuit 7-1, and a 1H delay circuit 7
It is configured by applying the signal that has passed through -1, 7-2 to the multiplication circuit 7-3 and performing arithmetic operation. At this time, 1H delay circuit 7-
The signal passed through 1 is multiplied by the signals of the three scanning lines above and below it. The center frequency of the obtained bandpass filter is set to 525/4 CPH for a 16 mm positive film, for example.
Here, CPH indicates the number of cycles in which a black-and-white pattern is repeatedly present within the vertical size (height H) of the screen. Young
When changing the center frequency of the filter 71, two signals above and below the horizontal scanning line one field before may be added to the signal multiplication circuit 7-3 and the multiplier may be changed.

Next, the center frequency of the horizontal band pass filter 72 is, for example,
For 16mm positive film, select 1.5MHz. The signal passing condition at the output of the horizontal band pass filter 72 is as shown in the vicinity of the filter, which is the frequency region where the non-hatched portion is passing. That is, since the band-pass filters 71 and 72 are provided in the vertical and horizontal directions, the signal in the non-hatched portion passes. Next, in the subtraction circuit 8,
The passing signals of the filters 71 and 72 are subtracted from the original luminance signal from the terminal 1. Therefore, the signal that has passed through the subtraction circuit 8 has lost the intermediate band, and is a signal in which the hatched portion is missing as shown in the vicinity thereof.

Next, the signals that have passed through the filters 71 and 72 are applied to the time direction averaging circuit 9 to obtain, for example, a signal obtained by averaging the state of the signal one frame before. That is, the signal is delayed by one frame by the frame memory 9-3, and the addition circuit (actually operates as a subtraction circuit) 9-4
Calculate with the current signal. The signal is multiplied by a predetermined coefficient by the coefficient unit 9-2, the subtraction processing is performed by the addition circuit 9-1, and then input to the next addition circuit 10. Then, addition processing is performed on the output of the subtraction circuit 8 with some correction. The noise of the signal passing through the time direction averaging circuit 9 is reduced within the band.

Although the example in which the band-pass filters are cascaded in the vertical direction and the horizontal direction has been described, the same effect can be obtained even if the order is changed.

[Effects of the Invention] According to the present invention, in particular, when a film is imaged and used as a TV signal source, granular noise that is conspicuous depending on the type of film is reduced by the band-pass filter means. There is little deterioration, and a good signal can be sent on the image sending side. Since the processing is performed by the band pass filter means, it is possible to easily cope with the case where the type of film used is different.

[Brief description of drawings]

 FIG. 1 is a diagram showing a principle configuration of the present invention, FIG. 2 is an operation explanatory diagram of FIG. 1, FIG. 3 is a diagram showing a configuration of an embodiment of the present invention, and FIG. 4 is a conventional noise reduction circuit. FIG. 1 ... Luminance signal input terminal 6 ... Luminance signal output terminal 7 ... Diagonal mid-pass filter 8 ... Subtraction circuit 9 ... Time direction averaging circuit 10 ... Addition circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeharu Urano 14-2 Nibancho, Chiyoda-ku, Tokyo Nippon Television Broadcasting Network Co., Ltd. (72) Toshiya Ito 14-14 Nibancho, Chiyoda-ku, Tokyo Nippon Television Broadcasting Network Within the corporation

Claims (1)

[Claims] 1. A vertical band-pass filter and a horizontal direction to which a luminance signal obtained from an imager of a photographic film serving as a TV signal source is applied to pass an intermediate frequency band of horizontal and vertical frequency regions of the luminance signal. A diagonal mid-range bandpass filter in which bandpass filters are cascade-connected, a subtraction circuit that subtracts the output signal of the bandpass filter from the luminance signal, and the output signal of the bandpass filter is applied to change the previous signal state. The output of the stored memory is calculated and multiplied by a predetermined coefficient, and the output is added to the time-direction averaging circuit that performs calculation processing in the addition circuit, the output of the subtraction circuit, and the output of the time-direction average circuit. A noise reduction circuit comprising another addition circuit, wherein a luminance signal with reduced granular noise is obtained in the other addition circuit.