JPH0795819B2 - Contour corrector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour corrector for improving the image quality obtained by a television signal or the like.

2. Description of the Related Art As a contour correction device of the first conventional example, there is a configuration as shown in FIG. 9, for example. In FIG. 9, 1 is an input terminal to which a luminance signal is input, 2 is a contour signal forming circuit for producing horizontal and vertical luminance signals, and 3 is a level depender for adjusting the amplitude of the contour signal according to the level of the input luminance signal. Dent gate circuit, 4 noise slicing circuit, 5 adder for adding luminance signal and contour signal, 6 and 7 delay line for timing adjustment, 8
Is an output terminal.

The operation of the contour corrector configured as described above is shown in FIGS.
This will be described with reference to FIG.

FIG. 10 shows 1 of the internal configuration of the contour signal forming circuit 2 of FIG.
In the figure showing an example, 9 is a 1H (1 horizontal scanning time) delay circuit, 10
Is a t-time delay circuit, 11 is an amplifier that is a multiple of the number in a circle, and 12 is an adder. Explaining the operation of each part, assuming that the luminance signal shown in FIG. 11 (a) is input in the 1V (1 field) period in the vertical contour signal part, the output of the first H delay circuit 9 is shown in FIG. 11 (b). ), (C) becomes the signal, each amplifier
By adding the 11 output signals, the vertical contour signal shown in FIG. 11 (d) is obtained. Similarly, if the luminance signal shown in FIG. 11 (e) is input in the 1H period in the horizontal contour signal section, the output of each t time delay circuit 10 is shown in FIG. 11 (f), (g).
The output signal from each amplifier 11 is added to obtain the horizontal contour signal shown in FIG. 11 (h). Therefore, a two-dimensional contour signal (hereinafter referred to as DTL) can be obtained by adding the output signals of the water contour signal section and the vertical contour signal section. The frequency characteristics of the horizontal and vertical contour signal parts are
It becomes like Fig. 12 (a) and (b). Hereinafter, for the sake of simplification of the description, only the horizontal contour signal will be considered as the contour signal.

In order to widen the dynamic range, the high level part of the input signal is compressed by the highlight compression circuit, but the circuit part for expressing this signal more sharply is the near aperture signal part. The operating point for compression here is the knee point. The operation of this knee aperture signal section will be described with reference to FIG. In FIG. 13 (a), the peak level PL staircase wave in the input luminance signal is compressed from the knee point NP to the peak point PP at a constant rate. At this time, when an aperture signal is generated from the uncompressed staircase of the original signal, it becomes as shown in FIG. 13 (b). On the other hand, the thirteenth
A signal obtained by further γ-correcting the signal subjected to the highlight compression shown in FIG. 13A becomes a signal as shown in FIG. 13C, and when an aperture signal is created using this signal, it is shown in FIG. 13D. As shown. Only the aperture correction shown in FIG. 13 (e) can be made from this aperture signal, and the contour signal is small and lacks sharpness in the high-level compressed portion. Therefore, in the knee aperture signal section, of the luminance signals before the highlight compression and γ correction, although not shown in FIG. 10, a signal of an arbitrary level (threshold level) or higher is used by the circuit shown in FIG. Is making an aperture signal. The aperture signal generating operation is similar to that of the horizontal and vertical contour signal portions described above. If you set the arbitrary level (threshold level) to the knee point NP position and add the knee aperture signal to the signal that has been subjected to highlight compression and γ correction, the result will be as shown in Fig. 13 (f), and the contour emphasis will be applied only to the compressed part. It becomes the signal which was done.

When this signal is added to the luminance signal shown in FIG. 13 (c), which is input to the vertical contour signal section and the horizontal contour signal section described above and the contour signal DTL is generated, the contour correction shown in FIG. 13 (g) is performed. Signal is obtained. As shown in the figure, the knee aperture + DTL contour signal is above the threshold level, and only the DTL contour signal is below the threshold level, and the highlight-compressed portion is also reproduced sharply.

The contour signal generated by the contour signal forming circuit 2 described above is input to the level dependent gate circuit 3 in FIG. The operation of this circuit will be described with reference to FIG. 15th
FIG. 9A shows an output signal of the delay line 6 in FIG. 9, which is a 1H delay luminance signal which has been subjected to highlight compression, γ correction, and knee aperture correction, and is delayed by an appropriate time for timing adjustment. At any level of this signal
The contour signal output from the contour signal forming circuit 2 shown in FIG. 15B is gated. As a result, there is no contour signal on the low level side of the luminance signal, and the luminance signal becomes as shown in FIG.
When this signal is added to the luminance signal, a contour-corrected signal as shown in FIG. 15 (d) is obtained. Therefore, the level dependent gate circuit 3 corrects the contour to prevent deterioration of the S / N ratio on the low level side of the luminance signal and discomfort.
The output signal of the level dependent gate circuit 3 is further input to the noise slice circuit 4 of FIG.
Slice and remove the high frequency noise in the flat signal part that is generated by creating the contour signal as shown in
The contour signal shown in FIG. 16 (b) is output. This noise-sliced contour signal and the 1H delay luminance signal that has been timing-matched by the delay line 7 and that has been subjected to highlight compression, γ correction, and knee aperture correction are added by the adder 5 and are shown in FIG. Figure (d)
A contour-corrected luminance signal as shown in (1) is obtained from the output terminal 8.

In the above, the contour signal is made from the luminance signal, but as another method, the contour signal is made only from the green signal, and this signal is
There is a so-called “OUT OF GREEN” method in which (red), G (green), and B (blue) process amplifiers are mixed. (For example, Hiroshi Marubayashi et al., "Contour compensator for planvicon color cameras", Sho 44,6,26, 14th Television system circuit research committee material) This "OUT OF GREEN" system is registration, circuit scale Therefore, it is often used in cameras using an image pickup tube.

However, the above configuration has the following drawbacks.

One is that a circuit (a knee aperture signal portion in the conventional example) for producing a contour signal (knee aperture signal portion) of a compressed luminance signal other than the horizontal and vertical contour signal portions is required separately, and the level to which the knee aperture signal is applied is required. , Since it is controlled by an arbitrary threshold level of the analog circuit as shown in Fig. 14, it is not stable due to temperature changes,
In addition, since the level dependent action also gates the contour signal on and off at an arbitrary level,
There was a drawback that the boundary between the place where the contour signal was not attached and the place where the contour signal was attached was conspicuous and made me feel uncomfortable.

In contrast to the above drawbacks, the compressed luminance signal can be reproduced sharply and the level-dependent effect is not on / off smooth without separately providing a circuit for generating the contour signal for the compressed luminance signal. A contour corrector having various functions has been applied for a patent by the present applicant. The contour corrector will be described below as a second conventional example with reference to FIGS.

In FIG. 17, 1 is an input terminal to which a luminance signal is input, 2 is a contour signal forming circuit that creates only horizontal and vertical contour signals, 13 is a RAM table that nonlinearly converts the input luminance signal, and 14 is a RAM
A microcomputer that rewrites the characteristics of the table in various ways, 15 is a gain control circuit that changes the gain of an adjacent signal by the output signal of the RAM table 14, 4 is a noise slice circuit, 5 is a luminance signal and gain adjustment, and a noise sliced luminance signal Are added, 16 is a delay line for timing adjustment, 8 is an output terminal, and each circuit is composed of a digital circuit. 1,2,4,5,8,16 are similar in operation and action to the first conventional example.

The operation of the second conventional contour corrector having the above-described configuration will be described with reference to FIGS. 18 and 19.

FIG. 18 (a) is a diagram showing the γ characteristic and the highlight compression characteristic. As with the first conventional example, the signal of the peak level M is as shown by the solid line, and the signal of the peak level m is as shown by the dotted line. Compressed from point NP to peak point PP. Due to this characteristic, for example, the luminance signal of the staircase wave of equal level change shown in FIG. 18 (b) has a peak level up to m as shown by the solid line in FIG. 18 (c) when the peak level is up to M. If it is a staircase wave, it will be compressed as shown by the dotted line in Fig. 18 (c). This luminance signal is input to the contour signal forming circuit 2 from the input terminal 1 of FIG. 17, and the contour signal shown in FIG. 18 (d) is formed in the same manner as in the first conventional example. The size of the contour signal differs depending on the compression ratio, as shown by the dotted line and the solid line, but in both cases, the contour signal becomes small in the portion subjected to highlight compression. However, in the second conventional example, by setting the input / output characteristics of the RAM table 13 to the characteristics shown in FIG. 19, the output signal is increased with respect to the input signal relatively above the knee point and the gain of the contour signal is increased. Can be increased. Furthermore, by varying the output signal value of the highlight part of the input luminance signal according to the peak level of the input luminance signal, and having a characteristic of setting a large output signal value when the peak level is large and a small output signal value when the peak level is small. , It is possible to make the size of the contour signal approximately the same due to the difference in the compression ratio of the highlight compression. In addition, the low-level side (dark part) of the input luminance signal has a smooth input / output characteristic, so that the gain of the contour signal can be gradually changed, and the level-dependent effect can be operated smoothly. You can RA with the above characteristics
By writing the M table by the microcomputer 14 of FIG. 17, for example, the contour signal in the case of the luminance signal of the peak level M is output from the gain control circuit 15 to the 18th signal.
The signal is output as shown in FIG. This contour signal is passed through the noise slicing circuit 4 to remove high-frequency noise in the flat portion of the signal, and then delayed by the adder 5 by the delay line 16 for an appropriate time, as shown in FIG. 18 (c). It is added with the luminance signal. By this
A luminance signal as shown in 18 (f) is obtained from the output terminal 8. As can be seen from FIG. 18 (f), the contour signal on the low level side (dark portion) does not exist at an arbitrary level or higher as in the first conventional example, and the low level side (dark portion) does not exist. Gradually change and increase, smooth level-dependent action, and no visual discomfort. Further, the contour signal suitable for the compressed highlight portion does not lack sharpness.

As described above, the second conventional example eliminates the drawbacks of the first conventional example and is advantageous in that the performance of the contour corrector is significantly improved.

SUMMARY OF THE INVENTION However, even if the luminance signal portion compressed by the configuration of the second conventional example is reproduced sharply and the level dependent can be operated without a sense of incongruity, other than the contour corrector, for example, Γ circuit, which has the dynamic characteristics of other TV cameras,
When trying to operate the characteristics of the auto knee circuit, etc. with a microcomputer using a RAM table, the time for rewriting the characteristics of each RAM table is limited, and if it cannot be rewritten in the vertical blanking period of several V which does not hinder the image. For example, since there are two or more microcomputers and each operation is performed, there is a problem that the circuit scale increases. This leads to an increase in the number of gates, which is not preferable in terms of cost and IC.

In view of such a point, the present invention suppresses the increase in circuit scale to a minimum, reproduces a compressed luminance signal portion sharply, and operates level dependency smoothly instead of on / off. An object is to provide a contour corrector suitable for a digital camera.

Means for Solving the Problems To solve the above problems, the present invention provides a contour signal forming circuit that forms a contour signal from a luminance signal or a signal similar to the luminance signal, and a gain control circuit that adjusts the gain of the contour signal. And the luminance signal or a signal similar to the luminance signal is input as an address signal, a RAM table for outputting a control signal to the gain control circuit, a ROM table having various conversion characteristics, and the luminance signal or the luminance signal A table selection circuit for arithmetically processing similar signals, selecting an arbitrary characteristic in the ROM table according to the arithmetic result, and transferring the selected characteristic to the RAM table is provided.

Action The present invention has the above-described configuration, and the ROM control table prepared in advance by the table selection circuit is stored in the RAM table without rewriting the RAM table by calculating the gain control value of the contour signal required each time according to the input luminance level. The desired contour signal characteristics can be obtained simply by transferring it to the table.
This can prevent an increase in RAM rewrite time and an increase in the number of gates.

First Embodiment FIG. 1 is a block diagram showing the arrangement of a contour corrector according to the first embodiment of the present invention.

In FIG. 1, 1 is an input terminal to which a luminance signal is input, 2 is a contour signal forming circuit for producing only horizontal and vertical contour signals, 15 is a gain control circuit for adjusting the gain of the contour signal, 13
Is a RAM table for outputting a control signal to the gain control circuit 15, 17 is a ROM table having various characteristics,
18 processes the input luminance signal and performs RO based on the calculation result.
A table selection circuit for selecting an arbitrary characteristic of the M table 17 and transferring it to the RAM table 13, 4 is a noise slicing circuit, 5 is an adder for adding a luminance signal and gain adjustment, and a noise sliced contour signal, 16 is for timing adjustment Is a delay line, and 8 is an output terminal. Also in this embodiment, each circuit is composed of a digital circuit, and the same parts are designated by the same reference numerals.

The operation of the contour corrector of the present embodiment configured as described above will be described with reference to FIGS.

The contour corrector of the present embodiment performs almost the same operation and action as the second conventional example except for the ROM table 17 and the table selection circuit 18. Therefore, if the operation in the middle of the process is omitted for the sake of simplification of description, the second operation is omitted as in the case of the relationship between FIGS.
When the luminance signal shown in FIG. 2 (a) is input to the input terminal 1, the compressed high luminance portion as shown in FIG. The acquired luminance signal is output from the output terminal 8.

Below table selection circuit 18, RAM table 13, ROM table 1
The relationship of 7 will be described.

3 (a) and 3 (b) are diagrams showing the input / output relationship of the RAM table 13 and have the same characteristics as in FIG. Third
FIG. 6A shows the characteristics of the aperture gain with respect to changes in the high-luminance portion, that is, the gain characteristics of the knee aperture.
SA is the input luminance signal level at which the level dependent effect is turned off and the gain of the contour signal is standard, NPA is the input luminance signal level at the Ni-Apertia starting point, and IM is the maximum level of the input luminance signal. STD and MAX are the gain control values of the contour signal when the input luminance signal is standard time (peak A) and maximum respectively, and b, c, d, e and f are the contours when the input luminance signal is peak B to peak F. This is the gain control value of the signal. As can be seen from FIG. 3 (a), the gain control value of the contour signal is rewritten to various characteristics from NPA to IM according to the peak of the input luminance signal. This has achieved the purpose of Niapertia. Further, FIG. 3B shows the characteristic of the aperture gain with respect to the change in the low luminance portion, that is, the level dependent characteristic. In the figure
Like SA, SB and SC are input luminance signal levels at which the level-dependent effect is off. The three types of characteristics shown in FIG. 3 show the characteristics with respect to the gain up of the luminance signals of 0 dB 9bB and 18 dB, respectively, and by rewriting to such characteristics, the deterioration of the S / N ratio with the gain up is prevented. In this way, the table from NPA to IM is always used for the high-brightness area, and the SA or S
The tables up to B and SC are rewritten.

In the present embodiment, the rewriting of the RAM table 13 is performed by the RO prepared in advance as shown in FIGS. 4 (a) to (i).
This is done by simply selecting the M table 17 and transferring it to RAM. 4 (a) to (f) show peaks A to FIG. 3 (a).
The ROM table has the same characteristics as the RAM table from the input NPA to IM of the peak F characteristic, and (g) to (i) are 0 dB, 9 dB, and 18 dB gain increase 0 to SA, SB in FIG. 3 (b). , SC
It is a ROM table with the same characteristics as the RAM table up to.

The transfer of the ROM table 17 to the RAM table 13 is performed by the table selection circuit 18. An example is shown in FIG.

In FIG. 5, the table selection circuit 18 comprises a maximum value detection circuit and an address and control signal generation circuit.
If the input luminance signal is input with a peak C during an arbitrary period, the maximum value detection circuit detects the value of the peak C, and the address and control signal generation circuit generates the table c of the ROM table 17 based on the detection signal.
Address of RAM table 13 and rewrite address of RAM table 13 are specified, and transfer command signal is output and RAM table 1
The ROM table c is transferred to 3. As a result, the RAM table 13 is rewritten. Similarly, each peak (A ~
When the luminance signal of F) or the gain-up signal is input, a table suitable for each is selected and transferred.

As described above, the RAM table 13 is rewritten by a simple operation of selecting and transferring the ROM table 17, and for example, each circuit is comprehensively controlled by the microcomputer including the circuit section having the dynamic characteristics of another TV camera. When controlling the RAM table or the like, there is no consumption of calculation time in the contour correction unit, and control is possible with at least one microcomputer, so an increase in circuit scale can be avoided.

Needless to say, the transfer of the ROM table 17 by the table selection circuit 18 may be performed within the vertical blanking period of 1 V to several V which does not hinder the image. Further, it goes without saying that the maximum value detection circuit, the address and control signal generation circuit, etc. of the table selection circuit 18 are simply configured by digital circuits. The number of ROM tables should be prepared to the extent that it does not hinder the characteristics of knee aperture, etc.For example, the characteristics for peaks between arbitrary peaks should be taken to correspond to either peak table. Good.

FIG. 6 is a diagram showing the configuration of the second embodiment of the present invention.

In FIG. 6, 1 is an input terminal, 2 is a contour signal forming circuit, 15 is a gain control circuit, 4 is a noise slice circuit, 5 is an adder, 16 is a delay line, 8 is an output terminal, and 13 is a RAM.
Table, 17 ROM table, 19 ROM table 17 RAM
It is a microcomputer for transferring to the table 13. Also in this embodiment, each circuit is composed of digital circuits, and is exactly the same as that of the first embodiment except 19 microcomputers.

The operation of the present embodiment configured as described above will be described with reference to FIGS.
It will be described with reference to the drawings.

Similar to the first embodiment, the formation of the contour signal is omitted for simplification of description, and the RAM table 13 and the ROM table 1 are omitted.
7. The relationship between the microcomputer 19 will be described.
In this embodiment, the table selection circuit is a microcomputer.
It is composed of 19 and is shown as in FIG. Therefore, the microcomputer 19 detects the maximum value and generates the address signal, the control signal and the like, and the RAM table 13 is rewritten by selecting and transferring the ROM table 17 as in the first embodiment. The processing time for simple operations such as table selection and transfer is RA
It is much smaller than the calculation and rewriting of the characteristic curve of the M table, and the same effect as that of the first embodiment can be obtained.
Further, the effect peculiar to this embodiment will be described with reference to FIG. In FIG. 8 (a), a and b are the characteristics of the ROM tables C and D, respectively. In order to make the Niapertia effect work without any trouble, RO
When a luminance signal that requires intermediate characteristics between the M table C and the ROM table D (FIG. 7C) is input, the microcomputer simply takes the average of the two tables, and the RAM table 13
It can be achieved with the simple operation of transferring to.
In other words, the number of ROM tables required can be kept to a minimum. Further, as shown by d and e in FIG. 8 (b), the characteristics obtained by weighting the two tables can be easily obtained and can be effectively used for the knee aperture effect.

In the above description, the table average and weighting calculation are
Compared with the case where the knee aperture characteristic curve is calculated as a characteristic curve of, for example, a square or a fourth power, the calculation time is short, and therefore this embodiment is more effective than calculating the characteristic curve and directly rewriting the RAM table. Needless to say.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to eliminate the arithmetic processing of the microcomputer in the contour correction unit by the simple operation of simply selecting the ROM table prepared in advance and transferring it to the RAM table. Alternatively, the processing time can be reduced. Therefore, it is possible to control the RAM table and the like by the microcomputer in a comprehensive manner, including circuits having various other dynamic characteristics of the television camera, and prevent an increase in the circuit scale. Therefore, it contributes to the automation by the microcomputer and further to the IC, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a contour corrector according to a first embodiment of the present invention, and FIG. 2 is a waveform showing an input luminance signal subjected to γ correction and highlight compression and an output luminance signal subjected to contour correction. Figures 3, 3 and 19 are RAM
Input / output characteristic diagram of table, FIGS. 4 and 8 are input / output characteristic diagram of ROM table, FIGS. 5 and 7 are relationship diagrams of table selection circuit and RAM table, ROM table, and FIG. 2 is a block diagram of the contour corrector of the second embodiment in FIG.
FIG. 9 is a block diagram of a first conventional contour corrector, and FIG.
9 is a block diagram showing an example of the internal configuration of the contour signal forming circuit of FIG. 9, FIG. 11 is a waveform diagram of the contour signal forming circuit, and FIG.
Figure is a frequency characteristic diagram of the horizontal and vertical contour signal section, Figure 13 is a waveform diagram showing the operation of the knee aperture signal section, Figure 14 is a block diagram showing the same configuration, and Figure 15 is the operation of the level-dependent gate circuit. 16 is a waveform diagram showing the operation of the noise slicing circuit, FIG. 17 is a block diagram of the contour corrector of the second conventional example, and FIG. 18 is gamma correction and highlight compression, gamma correction and FIG. 18 is a waveform diagram showing a luminance signal before a highlight compression is applied and a luminance signal after the compression and a signal waveform of each part of FIG. 17. 1 ... input terminal, 2 ... contour signal forming circuit, 4 ... noise slicing circuit, 5 ... adder, 8 ... output terminal, 13 ...
… RAM table, 15… Gain control circuit, 16…
… Delay line, 17 …… ROM table, 18 …… Table selection circuit.

Claims (1)

[Claims] 1. A contour signal forming circuit that forms a contour signal from a luminance signal or a signal similar to the luminance signal, a gain control circuit that adjusts the gain of the contour signal, and a signal that is similar to the luminance signal or the luminance signal. A RAM table which is input as an address signal and outputs a control signal to the gain control circuit, a ROM table having various conversion characteristics, and the brightness signal or a signal similar to the brightness signal is arithmetically processed, and the RO result is calculated as the RO table.
A contour corrector comprising: a table selection circuit for selecting an arbitrary characteristic of the M table and transferring it to the RAM table.