JP2638148B2 - Signal correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal correction device used for an imaging device or the like.

2. Description of the Related Art As a conventional signal correction device, for example, JP-A-63-7727
No. 2 discloses this. FIG. 6 shows a block diagram of this conventional signal correction apparatus, where 1 is an adder, 2
Is a linear conversion device, 3 is a subtraction device, and 4 is a microcomputer. FIG. 7 is a diagram for explaining the operation of the conventional signal correction device, wherein the non-linear characteristics are represented by Y = f (X).

In the conventional signal correction device configured as described above, when the maximum value of the amplitude level of the input video signal increases, the microcomputer controls the required signals 1 and 2 input to the addition device 1 and the subtraction device 3. Then, the maximum value of the amplitude level of the output of the subtraction device 3 is made constant.

That is, in FIG. 7, when the maximum value of the amplitude level of the input video signal changes from ▲ ▼ to ▲ ▼, the value ▲ ▼ of the required signal 1 is changed to the input video signal ▲ ▼ ′ = ▲
Set so that it becomes ▼ '. The value of the required signal 2 is
▲ ▼

However, in the above configuration, the required signal 1
(▲ ▼) and 2 (▲ ▼ ') had to be obtained by calculation from the following formula.

f (▲ ▼) = f (▲ ▼) -f (▲ ▼) ▲ ▼ '= f (▲ ▼) This operation uses the function f. Or have to approximate function f, the calculation is complicated, and
I needed to have memory for the table. As a non-linear process, it is a general solution to correct gamma. However, it is necessary to determine a non-linear characteristic in consideration of an overall gamma characteristic, and it is difficult to determine the characteristic.

Means for Solving the Problems The present invention provides a first non-linear conversion device for non-linearly converting a video signal with gamma correction processing or compression processing of a dynamic range of the video signal or input / output characteristics equivalent thereto, and the first non-linear conversion apparatus. And an adder for adding the output of the non-linear converter and the first required signal so that the dynamic range of the final output signal is constant. The output of the adder is used as an input, and the input / output characteristics of the adder have a plurality of gains. A second non-linear conversion device which is defined in a polygonal line by different knitting conversions and non-linearly compresses and converts the dynamic range of the input signal; and the maximum value of the amplitude level of the final output signal is fixed to the output of the second non-linear conversion device. A signal correction device comprising a signal processing device for adding and subtracting a second required signal.

According to the present invention, when the maximum value of the amplitude of the input video signal becomes larger than a predetermined value due to the above-described configuration, the maximum value of the amplitude of the output of the signal processing device is converted into the first required signal and the second required signal. When determining to be constant, the first non-linear processing such as gamma correction is performed by the first non-linear conversion device in order to reduce the amount of calculation and facilitate the calculation, and the second non-linear conversion device and the adding device are used. The operation of the signal processing device for making the maximum value of the amplitude of the output signal constant is realized.

Embodiment FIG. 1 shows a configuration diagram of a signal correction device according to a first embodiment of the present invention. In FIG. 1, 1 is an adder, 4 is a microcomputer, 5 is a non-linear converter A, 6 is a non-linear converter B, and 7 is a signal processor.

The operation of the signal correction device of the present embodiment configured as described above will be described below.

First, the input video signal is input to the non-linear conversion difference A5. Here, FIG. 2 shows the input / output characteristics of the nonlinear conversion device A5. This is so-called gamma correction. The gamma-corrected video signal is added to the required signal A by the adder 1, passes through the non-linear converter B6, and is subtracted by the signal processor 7 from the required signal B. Here, FIG. 3 shows the input / output characteristics of the nonlinear conversion device B6. At the input of the adder 1, if the maximum value of the amplitude of the input video signal is not more than ▲, the microcomputer 4 sets the required signals A and B to 0. Therefore, the input video signal is subjected to only the gamma correction processing by the non-linear converter A5, and the magnitude of the output is ▲
▼ '.

Next, when the input video signal is input to the adder 1,
If it is larger than ▲ ▼ and ▲ ▼, if the video signal is output as it is, the output of the signal processing device 7 will be ▲
▼ ′, and the maximum value of the amplitude of the output signal ▲
▼ 'will be exceeded. Therefore, the required signal A (▲) is added in the adder 1, and the amplitude of the video signal at the input of the nonlinear converter B6 is set as ▼. At this time, the output of the non-linear converter B6 becomes ▲ ', and the signal processor 7 outputs the required signal B, here the offset ▲.
Subtract ▼ '. Here, the maximum value of the amplitude of the video signal at the output can be made constant by setting ▼ ′ ′ to ▲ ′ ′. From the above, the required signals A and B given by the microcomputer can be expressed by the following equations.

Required signal A (▲) = (a ・ -b- ・ -c) / (bc) Required signal B (▲ ') = a ・It is not necessary to introduce a complicated function such as gamma correction into the calculation, a simple calculation is required, and the microcomputer does not need to have the characteristics of the nonlinear conversion device B. Further, by adjusting the value of the required signal B (（), the pedestal level of the output video signal can be adjusted.

When the required signal B is expressed by the following equation, when the maximum value of the signal amplitude at the input of the adder 1 becomes larger than ▼, the output signal is offset according to the magnitude of the input signal.

Required signal B (▲ ′ ′) = (a · −−k1 · ▲ /／) where k1 is a constant for adjusting the magnitude of the offset.

In recent television receivers, a portion having a low luminance level is often darkened in black. By doing so, a portion having a low luminance level can be prevented from being blackened. Further, the required signal B may be obtained only by addition and subtraction as in the following equation.

Required signal B (▲ ′ ′) = (a ・ ▲ -k2 ・ (▲ -−)) where k2 is a constant for adjusting the magnitude of the offset.

As described above, according to the present embodiment, the gamma correction is realized by the non-linear converter A5, the required signal A is added by the adder, the signal is passed through the non-linear converter B6, and the required signal B is subtracted by the signal processor 7. As a result, it is possible to keep the output of the signal processing device 7 constant by simple calculation of the required signals A and B, and it is not necessary to have a gamma correction characteristic for calculating the required signals A and B in the memory. .

FIG. 4 is a configuration diagram of a signal correction device showing a second embodiment of the present invention. In the figure, 1 is an adder, 4 is a microcomputer, 5 is a first non-linear converter A, 6 is a second non-linear converter B, and 7 is a signal processor. The above is the same as the configuration in FIG. 1 in that a required signal B is obtained by providing a clamp device 8.

The operation of the signal correction device of the second embodiment configured as described above will be described below.

The clamp device 8 captures the clan data portion of the video signal at the output of the nonlinear conversion device B6, and sets the required signal B as the signal of the clamp data portion. Other operations are
This is the same as the first embodiment of the present invention. By doing so, the maximum value of the amplitude of the output of the signal processing device 7 can be made constant, and the video signal can be clamped at the same time.

FIG. 5 is a block diagram of a signal correction device according to a third embodiment of the present invention. In FIG. 5, reference numeral 1 denotes an addition device, 4 denotes a microcomputer, 5 denotes a first nonlinear conversion device A6 denotes a second nonlinear conversion device.
Are the signal processing devices. The above is the same as the configuration in FIG. A different point is that a shading correction data generator 9 having a different configuration is provided, and when an input video signal is obtained from an image sensor, a shading component of the image sensor is corrected.

The shading correction data generator 9 has shading data of an image sensor in a memory, and generates a required signal B according to the data as in the following equation.

Required signal B = a · ▲ + shading data Other operations are the same as those in the first embodiment of the present invention. In this case, the shading data may be pixel-by-pixel or block-by-pixel, and indicates a local offset change of the video signal at the output of the image sensor. By doing so, it is possible to correct shading by the image sensor while keeping the maximum width of the amplitude of the output of the signal processing device 7 substantially constant.

In the above embodiment, the characteristic of the nonlinear conversion device B6 is 2
Although a straight line is used, a plurality of straight lines may be used.

As described above, according to the present invention, the first required signal is added to the signal after the nonlinear conversion by the adding device, the signal is passed through the second nonlinear conversion device, and the second required signal is converted by the signal processing device. By subtraction, the output of the signal processing device can be kept constant, and there is no need to have in the memory non-linear characteristics for calculating the first and second required signals, such as gamma correction characteristics. This has an excellent effect that the system configuration can be easily performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a signal correction device according to a first embodiment of the present invention, FIG. 2 is an input / output characteristic diagram of a nonlinear conversion device A5 of the embodiment, and FIG. 3 is a nonlinear conversion device B6 of the embodiment. FIG. 4 is a block diagram of the signal correction device of the second embodiment of the present invention, FIG. 5 is a block diagram of the signal correction device of the third embodiment of the present invention, and FIG. FIG. 7 is a configuration diagram of a conventional signal correction device, and FIG. 7 is an input / output characteristic diagram of a nonlinear conversion device of the conventional signal correction device. Reference Signs List 1 addition device, 2 nonlinear conversion device, 3 subtraction device, 4 microcomputer, 5 nonlinear conversion device A, 6 nonlinear conversion device B, 7 signal processing device
8 ... clamping device, 9 ... shading correction data generator.

Claims (5)

(57) [Claims] A first nonlinear conversion device for performing a gamma correction process or a compression process on a dynamic range of the video signal or a nonlinear conversion process based on input / output characteristics equivalent thereto, and an output of the first nonlinear conversion device. And an adder for adding the first required signal and the final output signal so that the dynamic range of the final output signal is constant. An output of the adder is used as an input, and its input / output characteristics are linearly transformed by a plurality of linear transformations having different gains. And a second non-linear conversion device for non-linearly compressing and converting the dynamic range of the input signal into a non-linear signal, and a second non-linear conversion device for outputting the maximum amplitude level of the final output signal to the output of the second non-linear conversion device. A signal correction device comprising signal processing for adding and subtracting a required signal. 2. The signal processing device according to claim 1, wherein the second required signal is an addition / subtraction device for subtracting or adding a second required signal from an output of the second nonlinear conversion device. 2. The signal correction device according to claim 1, wherein the clamp data is determined to be a black level at the output of the signal processing device. 3. The signal processing device is an addition / subtraction device for subtracting or adding a second required signal from an output of a second non-linear converter, and adjusts a pedestal level according to a value of the second required signal. The signal correction device according to claim 1, wherein: 4. The signal processing device is an addition / subtraction device for subtracting or adding a second required signal from an output of a second nonlinear conversion device, wherein the second required signal cancels a shading component of an input video signal. 3. The signal correction device according to claim 1, wherein the signal is a signal obtained by adding such data and the second required signal according to claim 1. 5. The signal processing device is an addition / subtraction device for subtracting or adding a second required signal from an output of a second non-linear conversion device, wherein the second required signal is the amplitude of the signal at the input of the adding device. 2. The signal correction apparatus according to claim 1, wherein when the maximum value is larger than a certain reference, the value is made smaller than the value of the second required signal in claim 1 according to the magnitude.