JPS60253376A - Signal processing method of video camera - Google Patents

Abstract

PURPOSE:To improve equivalently both the S/N and the image resolution of a picture by emphasizing the aperture correction signal at a bright part of a picture then reducing the level of the aperture correction signal to a degree that gives no deterioration to the S/N at a dark part of the picture. CONSTITUTION:The aperture correction signal is supplied to an adder cicuit 15 through an AGC circuit 14 and synthesized with the luminance signal underwent the gamma correction. This synthetic signal is supplied to an encoder 9. Thus the amplification factor of the circuit 14 increases when the photographing is carried out in a bright place. Therefore, the aperture correction signal is emphasized. While the amplification factor of the circuit 14 is reduced when the photographing is carried out in a dark place. Thus the aperture correction signal is reduced. The aperture correction signal has a lower level than a conventional case by an amount obtained with no gamma correction in a place of the brightness between black and gray. As a result, the S/N is improved at a part of the brightness between black and gray.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a video camera, and relates to a video camera signal processing method for obtaining an image with an excellent signal-to-1% signal-to-noise ratio and resolution. Regarding 〇〇　My brother's backstory〕 For example, when shooting with a home video camera, it is often used in a dark place such as indoors.

When shooting under such low illumination, the level of the image signal obtained by the video camera is reduced, so
The image of δ cold becomes extremely poor.

Therefore, it is desired that high-quality images can be obtained even when photographing is performed indoors or the like.

Hereinafter, a conventional signal processing method for a video camera will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an example of a signal processing system of a conventional frequency separation single-tube color camera, in which 1 indicates an image pickup tube;
2 is a preamplifier, and 3 is an automatic gain control circuit (hereinafter referred to as AGC).
4. 5 is a t-band filter, 6 is a bandpass filter, 7 is a gamma correction circuit, 8 is an aperture correction circuit, 9
is an encoder, 10 is a color separation circuit, 11 is a fixture circuit, 1
2 is an output terminal.

FIG. 2 is a characteristic diagram that combines the input and output characteristics of the comma correction circuit 70 shown in FIG. 1.

In FIG. 1, the image value -@ received from the camera tube 1 is
Signal processing by preamplifier 2 [! N1' to the level
% and supplied to the AGC circuit 3. AGC episode lol! I3
Now, the supplied image signal.

Even if there is a level of KIIIJ due to shooting in a dark jajtfjr + bright place, -additional hair A/c
v BI level so that the N T S C signal is obtained.
AIi or row rl.

In this way, the transposed signal is subjected to level BI4u.

A low-pass filter 4.5 and a bandpass filter 6 [respectively provided.

The low-pass filter 4 separates the luminance signal, and since the comma of the turpentine blind receiver is approximately z2, this luminance signal is converted to L[
! In order to comply with the 11 law, the signal is processed by a gamma correction circuit 7 having an input/output characteristic of a comma coefficient of 0.45, as shown in FIG. 2, and is supplied with an aperture correction circuit w68ic.

The aperture correction circuit 8 corrects the aperture effect that occurs due to the finite beam diameter of the image tube and the receiver, processes to obtain an image with good resolution, and supplies the processed image to the encoder 9. Ru.

On the other hand, the color signal modulated by the ^7IIO frequency is separated by the bandpass filter 6, and this color signal is separated into a red signal and a blue signal by the one-color separation circuit 10, and then supplied to the subtraction circuit 11. Then, the image i#! from the AGC circuit 6 is transmitted by the low-pass filter 5 with a cutoff J@ wave number of 06Ml1z! The luminance signal separated from the J@ signal, the red signal and the blue signal are supplied to the subtraction circuit #j66 to form the next color difference signal g, and these color difference signals are supplied to the encoder 9.

The encoder 9 processes the corrected luminance signal from the aperture correction circuit 8 and the color difference signal to convert the NTSC
A signal line is formed and attached to the output terminal 12.

By the way, the image signal superior to the 3D M tube 1 is as follows.

The SA of the image that is served with the ``Ukekushin'' depends on the ``Ukeku violet'', and the ``Ukekushin'' is different depending on the ``@ij# place'' and the bright place.
A run occurs in ratio. The 5lIV ratio of the video camera does not generate noise in the image tube 1.

It is determined by the level of noise generated by the preamplifier 2 itself and the level of the ll1I7 signal obtained from the combustion tube 1.

As mentioned above, 7. -Yo5KAGC episode #j66.

- In order to obtain the desired level of NTSC multiplication, the amplification factor is changed according to the signal level from the preamplifier 2. Therefore, even if the brightness appears to be the same with the Uke-117R aircraft, the shading ratio will be different when photographed at the feeder.

It's much more labor intensive than when shooting in a bright place.

As is well known, the main noise produced by video cameras is frequency dependent, and is small at low frequencies.

? It becomes larger in j671fl. The so-called triangular pyramid Shin is Ruru.

By the way, the aperture correction time W68 is liJIIgi
! This has the effect of emphasizing the edge part 1, that is, the high-frequency vibration part, and the resolution difference of ρ and ke, which greatly aggravates this correction violet, is the same as above, but along with it, triangular noise As rx increases, in addition to the deterioration of the syy ratio due to the AGC circuit 3, the 5lIf ratio also deteriorates.

Therefore, conventionally, a laborious method of suppressing s7y has been adopted by clipping the low level portion of the aperture correction signal in the portion where the difference in level of the j11 signal is small.

However, when the aperture correction is performed using the clicked aperture correction signal t5, there are parts where the aperture correction has been made and parts where the aperture correction has not been made in the luminance signal.
! There are mainly parts where aperture correction has been applied to i1# and parts where aperture correction has not been made, and a large k will occur in the appearance of these parts, resulting in an unnatural-looking image [rL]. In addition, since the aperture correction signal is created from the 'R degree signal 9, which has been comma corrected or bc to emphasize the low level part, 841 this poor low level part, that is, the dark a
Since the aperture correction signal in the $ portion becomes excessively large and the luminance signal is aperture-corrected using this aperture correction signal, the image quality of the IC is further deteriorated.

[Purpose of the invention]

The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art.

The object of the present invention is to provide a signal processing method for a video camera that can obtain a natural-looking image with an excellent image/width ratio and resolution.

[Summary of the invention]

In order to achieve this objective, the present invention &'@ is based on the characteristic power of the human eye (resolution is high in bright areas of an image).

Considering that the resolution decreases in dark areas, the aperture correction signal is emphasized in the bright areas of the image, and in the dark areas, the level of the aperture correction signal is suppressed to the extent that the SIN ratio does not deteriorate. There is a % imitation in that the ψ ratio and resolution are the same as above.

[Great example of invention]

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 3 is a block diagram showing a signal processing system of a video camera according to the invention, in which 16 is an aperture circuit, 14 is an AGC circuit, 15 is an addition circuit, and 16 is a control signal.
The same parts as in Figure 1 are given the same symbols.

The 1iIll image signal obtained from the image pickup tube 1 passes through the preamplifier 2, and is always converted to a defined level NTS by the AGC circuit 3.
Processing is performed to obtain the C signal.

It is supplied to the low-pass filter 4.5 and the bandpass filter O.

The low-pass filter 4 separates the luminance signal and supplies it to the gamma correction circuit 7 and the aperture circuit 1stc 11&, and the luminance signal processed by the comma correction circuit 7 is supplied to the addition circuit 15. - In the aperture circuit 13, an aperture correction signal is formed.

This aperture correction signal is supplied to the booster circuit 15 after passing through the AGC circuit 14, and is combined with the comma-corrected luminance signal and supplied to the encoder 9. And, as explained in FIG. 1 above.

The *i-times signal separated by the low-pass filter 5 passes through the bandpass filter 6 and the color signal formed by the color separation circuit 10 is converted into a color difference signal whose shape is distorted by the subtraction circuit 11 or the encoder 9
In addition, encoder 9 output terminal 12ttcNTs
c'@ number is output.

For example, comma correction circuit 7 and aperture circuit 1
3, when a luminance signal as shown in FIG. 4 (C1) is supplied, the aperture circuit 16 forms an aperture correction signal as shown in FIG. Since the aperture correction signal is combined with the luminance signal from the circuit 7, a luminance signal that has been subjected to gamma correction and aperture correction is formed as shown in FIG. 4 (C1).

Furthermore, the amplification factor of the VC and AGC circuit 14 is controlled by a control signal 16 from the AGC circuit 6. This control signal 1
6 is the level A? of the image signal supplied from 1 ring 2 to the AGC circuit 6? As the image signal level increases, the amplification factor of the AGC circuit 14 increases, and as the level of the image signal decreases, the amplification factor of the AGC circuit decreases.5tKmJ
I am in control.

Therefore, when filming takes place at 81 points,
Since the %A rate of the AGC circuit 14 becomes large, the aperture correction signal is strengthened. Conversely, when imaging in a dark place, the amplification factor of the AGC circuit 14 becomes small and the aperture correction signal becomes small.

In this way, since the aperture correction signal is formed from the luminance signal before gamma correction, when the level of the image signal is low, the aperture correction signal for the brightness area from black to gray is comma. 1 for the amount not corrected
1! , the level is lower than that of the aperture correction signal according to the conventional example shown in FIG. Therefore, the SIN ratio in the brightness range from black to gray is improved.

When the 10,000, 1ili image signal level is large, that is,
The level of the aperture correction signal for areas with brightness close to white is approximately the same level as conventional technology.

It is possible to obtain a pattern with good resolution.

Furthermore, the level of the aperture correction signal is ACrC times wr
Since the AGC circuit 14 is set up based on the control signal 16 from S.
I have a bad l ratio! When photographing in a dark place where a li image is obtained, the level of the aperture correction signal is smaller than when it is bright, and deterioration of the sAV ratio is suppressed.

With this, it is no longer necessary to perform aperture correction (Kurilag No. II) as in the conventional magic, and a natural i# image can be obtained from the dark part to the bright part l of one image.

[Effect of dawn]

As explained above, according to one aspect of the present invention, an aperture correction signal is formed using a roVs luminance signal called gamma correction, and the level of this aperture correction signal is set to 5! , [,
111 things you can get from Renkakan! This is because the signal changes as the signal level changes.

As the Si ratio in the low luminance signal level area is adjusted, an aperture correction that meets the resolution characteristics of the human eye can be made, and the 116 southern matter's distortion is superior, excluding the drawbacks of the conventional technology. It is possible to provide a signal processing method for a steering video camera.

[Brief explanation of the drawing]

Figure 1 shows an example of a conventional video camera signal processing method, Figure 2 shows the input/output characteristics of the comma correction circuit, and Figure 3 shows the signal processing method of the video camera according to the present invention. A block diagram showing an example of the processing method, Figure 4 is an explanatory diagram explaining the aperture correction production at the *V processing pressure shown in Figure 3. 1゜1... Image pickup tube 7... Comma correction Circuit 13... Aperture circuit 14... AGC circuit cost Shioiri Benshiroshi? t
bal Akira Major 1 Diagram■? Diagram Input No. 37 Story 4El

Claims (1)

[Claims] In a signal processing method for a video camera that aims to improve image quality by applying gamma correction and aperture correction to a luminance signal from an image pickup tube, an aperture correction signal is formed from a luminance signal before the gamma correction is performed, and the aperture correction signal is A signal processing circuit for a video camera, characterized in that an aperture correction signal level is controlled according to a change in a luminance signal level from a KK image pickup tube.