CN1047272C

CN1047272C - Gamma correction circuit for video camera

Info

Publication number: CN1047272C
Application number: CN94119538A
Authority: CN
Inventors: 金成勋
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1993-12-29
Filing date: 1994-12-20
Publication date: 1999-12-08
Anticipated expiration: 2014-12-20
Also published as: CN1132975A

Abstract

The present invention relates to a gamma correcting device used for single-board type television cameras, which comprises a brightness signal detector, a first gamma corrector, a second gamma corrector, a color difference signal detector and a mixer. The television camera is provided with a relevant secondary sampling device which can receive a signal output by a complementary filter type charge-coupled device (CCD) to generate a colored row order signal. Thus, a gamma correcting circuit can carry out gamma correction to the colored row order signal output by the relevant secondary sampling device in order to simplify the circuit.

Description

The gamma correction circuit of television camera

The present invention relates to a kind of gamma correction circuit that is used for the one-board television camera, described television camera has the charge-coupled device (CCD) camera head that adopts the complementary color filtering method.Specifically, the present invention relates to a kind of checking gamma circuit between relevant secondary sampling unit and chrominance separation circuit.

During picture tube representation color, light beam not with the proportional variation of picture signal.The television camera that produces picture signal should be considered this characteristic of picture tube, and the reverse nonlinear distortion of image signal correction reproduction in colour correspondingly, and this is called γ and proofreaies and correct.The non-linear color representation is called the γ characteristic of television camera.

Conventional one-board television camera utilizes the color separation circuit that the color lines sequential signal that is produced by the CCD imaging apparatus is divided into primary colours, then the primary colour signal of separating is like this carried out γ and proofreaies and correct.In other words, each primary colour signal (red, green, blue) and luminance signal need be carried out the γ correction respectively.Entire circuit becomes complicated like this.

Especially, the resolution of the components and parts of the formation checking gamma circuit of the television camera of employing Digital Signal Processing need be higher than other circuit.

Here the γ property list is shown:

Output=(input) ^γ(1)

By equation (1) as can be known, the output of checking gamma circuit is the exponential function to the exponent gamma of its input.In other words, if the resolution of output signal constitutes by eight, then the resolution of input signal should have ten or multidigit more.Therefore, in the existing-quality television video camera, it is ten or the element of multidigit more that checking gamma circuit should have resolution, and this makes that just the manufacturing cost of product is higher.

Thereby, for addressing the above problem, be exactly total purpose of the present invention will provide a kind of checking gamma circuit that is used to simplify the circuit structure of television camera system.Described television camera system has the CCD imaging apparatus that adopts the complementary color filtering method.

For achieving the above object, the invention provides a kind of checking gamma circuit, it comprises a luminance signal separator, is used for isolating luminance signal from the color lines sequential signal of CCD imaging apparatus output; One first gamma corrector is used for that the luminance signal of separating from the luminance signal separator is carried out γ and proofreaies and correct; One second gamma corrector is used for the color lines sequential signal of CCD imaging apparatus output is carried out the γ correction, and a color difference signal separator is used for isolating the color difference signal that γ proofreaies and correct from the color lines sequential signal of being proofreaied and correct by the second gamma corrector γ; A blender is used for mixing luminance signal of being proofreaied and correct by first gamma corrector and the color difference signal of being proofreaied and correct by the isolated γ of aberration separator.

According to checking gamma circuit of the present invention the carrier chrominance signal of relevant secondary sampling unit output is divided into luminance signal and color difference signal, then luminance signal and color difference signal are carried out the γ correction, again these two signals are mixed to produce the carrier chrominance signal that a γ proofreaies and correct.

When combining, from following detailed of the present invention, will see these and other purpose of the present invention, feature, mode and advantage more significantly with accompanying drawing.In the accompanying drawing:

Fig. 1 is that the characteristic figure of a γ releases;

Fig. 2 A and 2B provide relevant secondary sampling unit respectively before γ proofreaies and correct and the oscillogram of the color lines sequential signal exported of back;

Fig. 3 is the block diagram of the television camera of employing checking gamma circuit of the present invention;

Fig. 4 is a most preferred embodiment of gamma correction circuit shown in Figure 3;

Fig. 5 is the detailed diagram of gamma correction circuit shown in Figure 4;

Fig. 6 A-6G is the oscillogram that figure disengages the signal of present device difference shown in Figure 5.

Fig. 1 provides a γ characteristic curve that is expressed in the equation 1, and γ is general in the equation 1 adopts about 0.45.

Fig. 2 A shows a color lines sequential signal by CCD output.With reference to figure 2A, the color lines sequential signal be a continuous signal string S1 (S11, S12 ...) and S2 (S21, S22 ...).Wherein, the value of S1 can be described as following composition.

S1=Mg+Ye or S1=Ye+Cy ... (2) similarly, the value of S2 can be described as these compositions:

S2=G+Cy or S2=Cy+Mg ... (3) wherein Mg, Ye, G and Cy are the corresponding signal components of each chromatic filter with compensating filter.

Then, use following definite luminance signal of value (equation 4) and the color difference signal (equation 5) of S1 and S2:

S1+S2=(Mg+Ye)+(G+Cy)

=(Ye+G)+(Cy+Mg)

=2R+2B+3G …(4)

S1-S2=(Mg+Ye)-(G+Cy)

=2R-G

S1-S2=(Ye+G)-(Cy+Mg)

=-(2B-G) …(5)

Shown in equation (4) and (5); YUV can by S1 and S2 and or difference open.

The variation of the capable sequential signal average level of Fig. 2 B display color, the i.e. level of luminance signal under the situation of color lines sequential signal shown in Fig. 2 A being carried out direct compensation according to γ characteristic shown in Figure 1.As what seen from equation (1), the γ characteristic is the form of a nonlinear exponent function, so that the ratio of the high and low level of relative its average level of input signal is different from output signal.In other words, when the color lines sequential signal by the direct timing of γ circuit, the color lines sequential signal of correction has the level of a variation, thus the luminance signal that equation (4) provides has the level of a variation.

Therefore, checking gamma circuit of the present invention is separated luminance signal and color difference signal from the color lines sequential signal, each signal is carried out γ proofread and correct.

Fig. 3 is the block diagram of an employing according to the television camera of checking gamma circuit of the present invention.Device shown in Figure 3 comprises a relevant secondary sampling unit 100, is used for receiving Mg, Ye, G and the Cy signal component of CCD (not providing) output, produces a color lines sequential signal thus; A modulus (A/D) transducer 200 is used for converting the output signal of relevant secondary sampling unit 100 to digital form; An automatic gain controller 300 is used for controlling automatically the gain of 200 output signals of A/D converter; One gamma corrector 400 is used for the signal of automatic gain controller 300 outputs is carried out the γ correction; A 1H delayer 500, it postpones the output signal of gamma corrector 400 in a horizontal scanning period (1H), thereby produces the delay output of a 1H; A delayer 600, its output signal with 1H delayer 500 postpones the 1H time again; A luminance signal processor 700, of signal who is used for receiving the output signal of gamma corrector 400 and 1H delayer 500,600 is to produce the luminance signal of a contour correction; Handle 800 with carrier chrominance signal, it receives in the output signal of gamma corrector 400 and 1H delayer 500,600 signals one, is about to those signal combination to produce carrier chrominance signal corresponding to each horizontal sweep.

Fig. 4 is the block diagram of the embodiment of gamma corrector 400 shown in Figure 3.Circuit shown in Figure 4 comprises one first gamma corrector 410, and it receives the color lines sequential signal of automatic gain controller 300 outputs and wants output signal according to γ characteristic correction shown in Figure 1 thus; A color difference signal wave detector 420, it detects color difference signal from 410 output signals of first gamma corrector; A luminance detector 430 is used for detecting the luminance signal of 300 output signals of automatic gain controller; One second gamma corrector 440 is proofreaied and correct the signal that will export according to γ characteristic shown in Figure 1 by the mode identical with first gamma corrector 410 thereby be used to receive luminance signal that luminance detector 430 exported; A blender 450 is used for the output signal of secondary colour difference signal wave detector and the output signal of second gamma corrector 440 and also produces the color lines sequential signal that a γ proofreaies and correct thus.

Fig. 5 is the block diagram of the detailed circuit of device shown in Figure 4.With reference to figure 5, color difference signal wave detector 420 comprises first timer 421 and a subtracter 422.First timer 421 is used for controlling the signal S1 of the first gamma corrector 410 color lines sequential signal of exporting and the timing of S2 (Fig. 2), and the level of signal S1 and S2 should compare mutually.Subtracter 422 is used for the signal of comparison first timer 421 outputs to produce the relatively output as color difference signal thus.

First timer 421 has the first and the

3rd sampling holder

4211 and 4213 that S1 level signal sampling among Fig. 2 is kept, and signal S1 is exported according to preset clock signal CLK1 and CLK2 respectively by first gamma corrector 410.First timer also has one second sampling holder 4212, is used for according to preset clock signal CLK2 sampling and keeps the S2 level signal of Fig. 2.

Luminance detector 430 shown in Figure 4 comprises a second timer 431,

adder

432 and 1/2 multiplier 433.Second timer 431 carries out timing controlled by the mode identical with first timer 421 to the signal of first gamma corrector, 410 outputs.Adder 432 and 1/2 multiplier 433 are used for detecting the mean value of 431 output signals of second timer.

Second timer 431 comprises the 4th and the 6th sampling holder spare 4311 and 4313 and one the 5th sampling holder spares 4312.The the 4th and the 6th sampling keeper 4311 with 4313 respectively according to preset clock signal CLK1 and CLK2, the S1 level signal in the capable sequential signal of input color sampled and keep by the mode identical with the first and the 3rd sampling holder spare 4211 of first timer 421 and 4213.4312 pairs of S2 level signals of the 5th sampling holder spare are sampled by predetermined clock CKL2 and are kept.

Fig. 6 A is the oscillogram of the signal that presents of circuit difference shown in Figure 5 to 6G.Wherein, Fig. 6 A is the sequential chart of 410 output signals of first gamma corrector, and Fig. 6 B is the sequential chart of 4211 output signals of the first sampling holder spare; Fig. 6 C is the sequential chart of 4213 output signals of the 3rd sampling keeper; Fig. 6 D is the sequential chart of 4212 output signals of the second sampling holder spare; Fig. 6 E is the sequential chart of 4221 output signals of subtracter; Fig. 6 F is the oscillogram of first clock signal (CLK1); Fig. 6 G is the oscillogram of second clock signal (CLK2).

Here, will operation principle of the present invention be described referring to figs. 3 to Fig. 6.

The color lines sequential signal of automatic gain controller 300 outputs is input in first gamma corrector 410 (Fig. 4) and the luminance detector 430 (Fig. 4).First gamma corrector 410 carries out γ by γ characteristic shown in Figure 1 to the color lines sequential signal of importing to be proofreaied and correct, thereby output γ correction signal is to color difference signal wave detector 420.The color difference signal wave detector is isolated color difference signal (as Fig. 6 E) from the color lines sequential signal that first gamma corrector 410 provides, with its output.

The first and second sampling holder spares 4211,4212 of first timer 421 receive the color lines sequential signal that the γ shown in Fig. 6 A proofreaies and correct.The first sampling holder spare 4211 and clock signal clk shown in Fig. 6 F 1 with the S1 part of the signal of sample graph 6A, produce the sampled signal S1 shown in Fig. 6 B synchronously.The second sampling holder spare 4212 is synchronous with clock signal clk 2 shown in Fig. 6 G, thereby the S2 of the signal of sample graph 6A part is to produce the sampled signal S2 shown in Fig. 6 D.

The signal of the first sampling holder spare 4211 (Fig. 6 B) is input to the 3rd sampling holder spare 4213.The 3rd sampling holder spare 4213 is synchronous with the clock signal clk 2 that is added to the second sampling holder spare 4212, thereby pins signal among Fig. 6 B of the first sampling holder spare, 4211 outputs to produce the inhibit signal S1 shown in Fig. 6 C.

The signal of the second and the 3rd sampling holder spare 4212 and 4213 outputs is input to subtracter 422, subtracter 422 deducts the output signal of the 3rd sampling holder spare 4213 from the output signal of the second sampling holder spare 4212, thereby produces the color difference signal shown in Fig. 6 E.At this moment, also produced a sign bit that causes by subtraction, so that the figure place of output is total up to 9.

On the other hand, if luminance detector 430 has received automatic gain controller 300 output λ signals, it will be by obtaining the arithmetic mean sensed luminance signal of S1 and S2.

In other words, if luminance detector receives the signal by automatic gain controller 300 outputs shown in Fig. 6 A, timing just by the 4th, the 5th with the 6th sampling holder spare 4311,4312 and 4313 second timer 431, control by the mode identical with first timer 421, is shown in the inhibit signal S1 of Fig. 6 C and 6D and the signal S2 of sampling respectively thereby produce.The the 5th and the 6th sampling holder spare 4312 and 4313 output signal are sent to adder 432.

The accumulation result of adder 432 outputs to 1/2 multiplier 433 that is positioned at next unit.Here, the carry of overflowing of front accumulation result generation also is sent to 1/2 multiplier 433.1/2 multiplier 433 is with the signal of its attenuated input signal 3dB and output attenuatoin in addition.

The output signal of 1/2 multiplier 433 is sent to second gamma corrector 440.Luminance signal is proofreaied and correct and exported thus to second gamma corrector 440 by with the same mode of first gamma corrector 410 luminance signal being carried out γ.Here,, so it also comprises more than " 0 " (low level), represent a positive number, thereby equate, output to blender 450 thus with the figure place of color difference signal wave detector 420 as sign bit because output signal is based on eight.

The output signal of the blender 450 hybrid subtraction devices 422 and second gamma corrector 440 is therefrom removed sign bit, and produces " the signal that pure γ proofreaies and correct thus.Therefore, the output of blender 450 becomes eight outputs.

As mentioned above, the present invention carries out the γ correction to the color lines sequential signal of relevant secondary sampling unit output, so that checking gamma circuit can be based upon in the better simply structure.

In addition, checking gamma circuit of the present invention reduces the cost of product by avoiding the unnecessary high-resolution of color separated circuit by this checking gamma circuit.

The present invention is described in detail and when describing in the contrast embodiment, those skilled in the art will understand that, can carry out the various variations of form and details to these embodiment, but not break away from the spirit and scope of the present invention of claims definition.

Claims

1. gamma correction circuit.It is used to comprise that the signal of a compensation filter type charge-coupled device (CCD) and a reception CCD generation produces the television camera of the relevant secondary sampling unit of color lines sequential signal, and it comprises:

-luminance detector is used for detecting the luminance signal of described color lines sequential signal;

One first gamma corrector is used for proofreading and correct carry out γ from the detected luminance signal of described luminance detector;

One second gamma corrector is used for that described color lines sequential signal is carried out γ and proofreaies and correct;

A color difference signal wave detector is used for detecting color difference signal from the color lines sequential signal, and described color lines sequential signal carries out γ by second gamma corrector and proofreaies and correct; With

A blender is used for mixing the color difference signal of the γ correction that luminance signal that the described first gamma corrector γ proofreaies and correct and described color difference signal wave detector detect.