JPS63256060A - Contour compensation circuit - Google Patents

Abstract

PURPOSE:To switch properly the adjusting state in response to the change in the pickup condition by providing plural adjusting circuits to a contour signal generating circuit and using a 2nd changeover circuit in interlocking with a 1st changeover circuit so as to switch the adjusting state of at least one of the plural adjusting circuits. CONSTITUTION:While an object suitable for the adjustment of a contour signal generating circuit 40 is being picked up in advance, each adjusting circuit is adjusted manually under each pickup condition so as to obtain a proper pickup condition, and a value of each control parameter is written in 1st-4th memories 41-44 for each pickup condition. In applying actual pickup, switches 33B, 33R and 45A-45N are switched interlockingly depending on the pickup condition at that time and a proper set of control parameter is read out of one of the four memories 41-44 as a control parameter file so as to switch instantly the adjusting state of the contour signal generating circuit 40.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a contour compensation circuit for video signals.

[Summary of the invention]

The present invention switches the combination of primary color signals for generating contour components of an image according to various photographing conditions, and
Appropriate values for various control parameters stored in memory are read out in advance, and the adjustment state of the circuit for generating contour components is switched to perform appropriate contour compensation in immediate response to changes in imaging conditions. This is what I did.

[Conventional technology]

Imaging devices and image receiving devices are provided with contour compensation circuits to compensate for resolution degradation due to insufficient characteristics in high spatial frequency regions, so-called aperture distortion, and to increase image sharpness.

As such a contour compensation circuit, each primary color video signal R
, G, and B, take its −th order and second derivative to obtain the contour component,
That is, a circuit is known that extracts contour signals and individually compensates for contours.

As another contour compensation circuit, three primary color video signals R1G, B
A contour signal is extracted from the luminance signal Y or the green video signal G, which is a mixture of the two primary color video signals R,
A compensation circuit configured to add to G and B is known.

Note that the above-mentioned contour signal can also be generated by combining the original signal and a delayed signal using a delay circuit, as is well known. Further, the level of such a contour signal is set so as to provide appropriate sharpness when viewed on, for example, an accurately adjusted color monitor.

[Problem that the invention seeks to solve]

However, when performing contour compensation for the three primary color signals R, G, and B individually, three systems of contour signal extraction circuits are required, resulting in a problem that the configuration becomes complicated.

On the other hand, in a contour compensation circuit that focuses on the luminance signal Y or the green signal G, the contour signal is extracted based only on the luminance signal Y or the green signal G in which the mixing ratio of the three primary color signals R, G, and B is fixed. Therefore, when the background of the screen changes and exhibits various colors, there is a problem in that it is difficult to perform sufficient contour compensation of the image.

For example, in the case of underwater photography, the background is bluish, so the sharpness of swimming objects such as fish in the sea cannot be sufficiently improved.

In order to solve this problem, the applicant has filed a patent application filed in 1983.
No. 1-235638 discloses a "contour compensation circuit" in which the composition of a three-primary color mixture signal for extracting a contour signal is variable.
has already been proposed.

First, a previously proposed contour compensation circuit will be described with reference to FIG.

The configuration of the previously proposed contour compensation circuit using analog processing is
As shown in the figure.

In Fig. 2, input terminals (lr), (Ig),
The three primary color video signals R, G, and B from (ib) are output terminal (2r).

(2g) and (2b), respectively, and the gain control amplifier (
llr), (l1g) (llb) (llb) and the averaging circuit (12).

In this averaging circuit (12), the three primary color video signals R,
G and B are each averaged over a range of several fields to several tens of fields to obtain average color signals Ra, Ga, and Ba.
is supplied to the control signal forming circuit (13).

In the control signal forming circuit (13), a level control signal K r + K g + K b is formed from the average color signals Ra, Ga, and Ba according to the following equation (11).

Note that, as is clear from equation (1), the sum of each control signal is 1.

These control signals Kr, Kg, Kb are supplied to the amplifier (
The gains of each amplifier (Llr), (l1g), (llb) are controlled, and the gains of each amplifier (Llr), (l1g), (llb) are controlled.
The output of llb) has a level ratio of Kr :Kg
:Kb and supplied to the adder (14), and the contour component extraction circuit (20
), the contour signal is extracted, and this contour signal is added to the primary color video signals R, G, and B in each adder (3r), (3g), and (3b), respectively, to have preshoot, overshoot, etc. , contour-compensated three primary color video signals Rc, Gc, Bc are output terminals (2r),
(2g) and (2b) are derived, respectively.

Level control signals Kr, Kg, Kb are updated every several fields to several tens of fields, and contour compensation is further performed based on this. Since such signal processing cycles are repeated successively, appropriate contour compensation can be performed successively for the subject even if the screen background exhibits various colors.

However, depending on the composition of the three primary color mixture signal output from the matrix circuit (10), the values of the control parameters of the contour component extraction circuit (20) may be reset to perform appropriate contour compensation. This is necessary.

The control parameters of the contour component extraction circuit (20) are as follows:
There are a crispening level Lc and an amplitude limiting level L1 of the input/output characteristics as shown in FIG. 3, a gain (gradient of the human output characteristic, tanθ), a boost frequency, etc. not shown in the figure.

In the proposed circuit, the various control parameters described above are manually controlled in response to various changing shooting conditions, such as changes in lighting on a stage, outdoors and indoors at sunset, or underwater shooting. However, there are problems in that setting takes time and it is difficult to obtain optimal settings.

In view of this, an object of the present invention is to provide a contour compensation circuit that can appropriately set control parameters for contour signal generation in response to variously changing imaging conditions.

[Means for solving problems]

The present invention provides a matrix circuit in which a combination of a plurality of input primary color signals can be switched by a first switching circuit;
A contour signal generation circuit is supplied with the output of this matrix circuit and generates contour components of an image corresponding to a plurality of primary color signals, and an addition circuit is provided that adds the output of this contour signal generation circuit to each of the plurality of primary color signals. , the contour signal generation circuit has a plurality of adjustment circuits, and at least one of the plurality of adjustment circuits is a contour compensation circuit whose adjustment state can be switched by a second switching circuit interlocking with the first switching circuit. It is.

[Effect]

With this configuration, the adjustment state of the contour signal generation circuit can be appropriately switched in response to changes in imaging conditions.

〔Example〕

An embodiment of the contour compensation circuit according to the present invention will be described below with reference to FIG.

FIG. 1 shows the configuration of an embodiment of the present invention.

In Fig. 1, input terminals (lr), (Ig),
The three primary color video signals R, G, and B from (lb) are sent to an adder (3r).

(3g) and (3b), respectively, and
Buffer amplifier (31r) of matrix circuit (30),
(31g) and (31b), respectively, and the output of each amplifier (31r), (31g), and (31b) is supplied to an adder (32). The connection middle point P of the amplifier (31r) and adder (32) is a 4-contact changeover switch (
33R), and the connection midpoint Q of the amplifier (31b) and adder (32) is connected to the first and third fixed contacts of the four-contact changeover switch (33B). Ru. The movable contacts of switches (331'l) and (33B) are both grounded.

(40) is a contour signal generation circuit, to which the output of the adder (32) of the matrix circuit (30) is supplied, and the contour signal output from the contour signal generation circuit (40) is supplied to the adder (32).
r), (3g), and (3b), and the contour-compensated three primary color video signals Rc, Gc, and Bc from each adder (3r), (3g), and (3b) are output to the output terminal (2r ), (2g).

(2b), respectively.

The RAMs (41) to (44) store control parameter values for n types of control items for each imaging mode.

The n outputs of RAM (41) are connected to a 4-contact changeover switch (
45A), (45B) and -(45N), and the n outputs of RAM (42) are supplied to the second fixed contacts of the four-contact changeover switches (45A) to (45N), respectively. n of RAM (43)
output is 4 contact changeover switch (45A) ~ (45N)
RAM (44
) n outputs are 4 contact changeover switches (45A) to (4
5N) are supplied to the respective fourth fixed contacts.

n switches (45A) to (45N) are switches (
33B) and (33R), each output of the switches (45^) to (45N) is supplied to the contour signal generation circuit (40), and the state of the adjustment circuit for each control item is determined. controlled.

Next, the operation of this embodiment will be explained.

In this embodiment, four photographing conditions as shown in Table 1 below are targeted, and each photographing condition is set using a switch (33B).
, (33R), (45^) ~ (45N) each first
~Assign to the fourth connection state.

In general, there are relatively few objects with high chroma, and in many cases it can be considered that the green signal G is proportional to the brightness.

Also, in the case of subjects with highly saturated costumes or rapidly changing lighting such as red and blue, such as in popular music programs,
Contour components are extracted using all three primary color signals R, G, and B, and contour compensation is also possible for folds, patterns, etc. of costumes in red and blue hues.

Third. In the fourth photographing condition, since contour compensation using only the green signal G is insufficient, the red signal R1 and the blue signal B are respectively added.

Table 1 Table 2 The control parameters of the contour signal generation circuit (40) are set as shown in Table 2, corresponding to the photographing conditions as described above.

The green signal G used in the first photographing condition has an S/N of
is relatively high, and noise is rarely emphasized by contour compensation, so the crispening level is set low. Further, the boost frequency is appropriately set depending on the fineness of the subject.

Third. Under the fourth photographing condition, the illuminance of the subject is often low, and the S/N of each primary color signal R, G, and B is low. In this case, since the gain of the camera itself is often increased, the noise level of each primary color signal becomes high, and the crispening level is set high.

In addition, since there are many videos with little brightness difference overall, the limit/t level is set low to limit the amplitude of contour signals extracted from areas where there is a certain degree of brightness difference. For the partial contour signal, the gain is set high to enhance the compensation effect. Note that the boost frequency is set low so as not to degrade the S/N.

In this example, under each photographing condition shown in Table 1, a subject (
For example, while photographing a test chart that consists of multiple types of vertical stripes and a multiburst with a frequency of Mllz units, each adjustment circuit is manually adjusted to obtain appropriate contour compensation, and each control parameter is adjusted. The values are written in the first to fourth memories (41) to (44) for each photographing condition.

During actual shooting, switches (33B), (33R), and (33B), (33R), (
45^) to (45N) are switched in conjunction, and four memories (41) to (4
4), the adjustment state of the contour signal generation circuit (40) can be immediately switched by reading out a suitable set of control parameters.

In addition, in the above-mentioned embodiment, the switches (45A) to (45N
) are all linked to switches (33B) and (33R), but at least one of switches (45A) to (45N) is linked to switches (33B) and (33R).
It may be made to be linked with.

〔Effect of the invention〕

As described in detail above, according to the present invention, the combination of primary color signals for generating the contour components of an image is switched according to various shooting conditions, and various control parameters stored in advance in memory are Since the adjustment state of the circuit for generating the contour component is switched by reading out an appropriate value of the contour component, it is possible to obtain a contour compensation circuit that can perform appropriate contour compensation in immediate response to changes in photographing conditions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a contour compensation circuit according to the present invention, FIG. 2 is a block diagram showing a configuration example of a contour compensation circuit according to an existing proposal, and FIG. It is a route map of input/output characteristics. (30) is a matrix circuit, (33B), (33R
), (45A). (45B)-(45N) are switching circuits, (40) are contour signal generation circuits, (41), (42), (43)
, (44) is a memory (control parameter file).

Claims (1)

[Scope of Claims] A matrix circuit whose combination of a plurality of input primary color signals can be switched by a first switching circuit; and an output of the matrix circuit is supplied, and an image corresponding to the plurality of primary color signals is The contour signal generation circuit includes a contour signal generation circuit that generates contour components, and an addition circuit that adds the output of the contour signal generation circuit to each of the plurality of primary color signals, the contour signal generation circuit having a plurality of adjustment circuits, and the plurality of adjustment circuits. A contour compensation circuit characterized in that the adjustment state of at least one of the adjustment circuits can be switched by a second switching circuit interlocking with the first switching circuit.