JPH06205300A - Shading correction device - Google Patents

Abstract

PURPOSE:To obtain optimum shading correction data and to attain superior shading correction. CONSTITUTION:First shading correction data are formed in a state that light is not made incident on an image pickup surface of image pickup elements 1R, 1G, 1B, and 2nd shading correction data are obtained by the 1st shading correction data from an image pickup output signal subject to shading correction, the 1st and 2nd shading correction data are added, 3rd shading correction data with the 1st and 2nd shading correction data added stored in a storage means 21 and the 3rd shading correction data are fed to a shading correction means 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CCD (Change Coupled Deuic) in which a plurality of pixels are arranged in a matrix.
e) The present invention relates to a shading correction device that corrects a shading component of an image pickup output signal of an image pickup device.

[0002]

2. Description of the Related Art Generally, an image pickup output signal obtained from an image pickup device is accompanied by shading which is caused by various causes such as sensitivity unevenness of the image pickup device and an influence of dark current, that is, a light and dark distortion over a relatively wide range of a screen. Are known.

For example, the signal charges of a plurality of pixels arranged in a matrix of a CCD image pickup device are vertically transferred and sequentially read out one horizontal line at a time during one horizontal scanning period via a horizontal transfer register. Since the image pickup output signal is obtained by reading out the signal charges of all pixels for one screen in the period, a dark current proportional to the time of transfer to the horizontal transfer register is added to the signal charges, This dark current causes a sawtooth-like luminance change in one vertical scanning period, that is, causes shading in the vertical direction.

Further, the dark current in the horizontal transfer register causes a sawtooth-like luminance change in one horizontal scanning period, that is, horizontal shading.

This shading includes white shading in which the output signal is small in the peripheral portion of the screen and black shading in which the black level is not uniform over the entire screen.

As a conventional shading correction device, one shown in FIG. 2 has been proposed. In FIG. 2, reference numerals 1R, 1G and 1B denote image pickup elements for red (R), green (G) and blue (B) color signals, respectively.
The image pickup output signals E _R , E _G , and E _B of RGB channels obtained by R, 1G, and 1B are converted into preamplifiers 2R and 2
It is supplied to the shading correction processing circuit 3 via G and 2B.

The image pickup devices 1R, 1G and 1B form an image pickup portion of a three-plate color image pickup device, and are provided in an image pickup optical system 7 including an image pickup lens 4, an iris mechanism 5, a color separation prism 6 and the like. There is.

Further, the image pickup devices 1R, 1G and 1B
Is a CCD image sensor in which M pixels in the horizontal direction and M pixels in the vertical direction, M × N pixels S _{11 to} S _MN are arranged in a matrix as shown in FIG. It is driven by a CCD driving unit (not shown) so that the signal charges of all the pixels S _{11 to} S _MN for one screen are read out.

The image pickup device 1R picks up an image pickup output signal E of the red component of the subject image color-separated by the color separation prism 6.
_R is supplied as an R channel signal to the shading correction processing circuit 3 via the preamplifier 2R.

Further, the image pickup device 1G uses the image pickup output signal E _G of the green component of the subject image color-separated by the color separation prism 6 as a G channel signal in the preamplifier 2G.
Is supplied to the shading correction processing circuit 3 via.

Further, the image pickup device 1B uses the image pickup output signal E _B of the blue color component of the subject image color-separated by the color separation prism 6 as a B channel signal through the preamplifier 2B to generate the shading correction processing circuit 3. Supply to.

The shading correction processing circuit 3
The image pickup device 1R, be one that performs black shading correction processing and white shading correction processing on 1G and imaging output signals of each RGB channel E _R obtained from 1B, E _G and E _B, the imaging output signals E _R, E _G and E
Subtractors 8R and 8G for each RGB channel to which _B is supplied
And 8B, and the subtraction output signals from the subtractors 8R, 8G, and 8B are respectively supplied via the amplifiers 9R, 9G, and 9B, and the dividers 10R, R, G, and B for the respective channels.
And 10G and 10B.

RG of the shading correction processing circuit 3
The signal of each channel B is supplied to the signal processing circuit 11 for making a color video signal for display or recording.

The shading correction processing circuit 3
R, G, and B channel signals are supplied to the selector circuit 12 and selected by the selector circuit 12 to obtain R / G / B dot-sequential data D, and this data D is calculated in advance from the input signal. This data D is decimated to ⅛ through the DC subtraction circuit 13 that subtracts the DC component,
8 thinning circuit 14 is supplied.

The output signal of the 1/8 decimation circuit 14 is supplied to one input terminal of the selector circuit 15, and the output signal of the 1/8 decimation circuit 14 is supplied to the other input terminal of the selector circuit 15 via the absolute value circuit 16. Supply to the input terminal.

As shown in FIG. 3, signals in the positive direction only selected by the selector circuit 15 are output in the row direction (horizontal direction) 1.
The signal obtained at the output side of the selector circuit 15 is supplied to the row integration circuit 17 that performs synchronous addition during the video period of the horizontal period, and the signal is synchronized during the video period of one vertical period in the column direction (vertical direction) as shown in FIG. It is supplied to the column integration circuit 18 for addition.

In this case, the DC subtraction circuit 13, the row integration circuit 17, the column integration circuit 18, etc. form shading correction data.

Row-side and column-side shading correction data obtained at the output sides of the row integration circuit 17 and the column integration circuit 18 are supplied to a selector circuit 19, respectively, and an output signal of the selector circuit 19 is written / read switching circuit. A random access memory (RAM) 21 is supplied via 20.

In this case, the write / read switching circuit 2
With 0 as the write state, the row synchronous addition data from the row integration circuit 17 is stored in the RAM 21 during the blanking period of the horizontal period.
The column synchronous addition data from the column integration circuit 18 is written in the RAM 21 during the blanking period of the vertical period.

In the conventional example, when the black shading correction data is obtained, the iris driving device 22 closes the iris mechanism 5 so that no light is incident on the image pickup surfaces of the image pickup devices 1R, 1G and 1B. 2R, 2
G, 2B, shading correction processing circuit 3, selector circuits 12, 15, 19, DC subtraction circuit 13, 1/8 decimation circuit 14, absolute value circuit 16, row integration circuit 17, and column integration circuit 18 are set as operating states, and black shading is performed. After obtaining the correction data, the black shading correction data is stored in the RAM 21.
I will remember it.

Further, in the conventional example, when the white shading correction data is obtained, the iris driving device 22 opens the iris mechanism 5 to photograph a white board or the like to obtain a uniform luminance level on the image pickup surfaces of the image pickup elements 1R, 1G and 1B. Of the preamplifier 2R, 2G, 2
B, shading correction processing circuit 3, selector circuit 1
2, 15, 19, the DC subtraction circuit 13, the 1/8 decimation circuit 14, the absolute value circuit 16, the row integration circuit 17, and the column integration circuit 18 are operated to obtain white shading correction data, and the white shading correction data is obtained. It is stored in the RAM 21.

Based on the shading correction data written in the RAM 21, the shading correction of the image pickup output signal is performed.

When performing the shading correction of the image pickup output signal, the writing / reading switching circuit 20 is set to the reading state, and the shading correction data is read from the RAM 21.

The shading correction data read from the RAM 21 is supplied to the row / column shading correction data separation circuit 23. The row black shading correction data separated by the row / column shading correction data separating circuit 23 is supplied to the adder 24B and the row white shading correction data is supplied to the adder 24W.

The column shading correction data separated by the row / column shading correction data separating circuit 23 is
8 is supplied to a data interpolation and black / white separation circuit 25 which interpolates 8 into 1/4 and separates into black and white shading correction data.

The column black shading correction data interpolated by the data interpolation / black and white separation circuit 25 is supplied to the adder 24B, and the data interpolated column white shading correction data is supplied to the adder 24W.

The output signals of the adders 24B and 24W are supplied to the latch circuits 26B and 26W, respectively. The output signals of the latch circuits 26B and 26W are interpolated to 1/4 → 1 through the series circuits of the noise removing circuits 27B and 27W and the clipping circuits 28B and 28W, respectively, and the shading correction data is converted into R, G, and Data interpolation and RGB separation circuits 29B and 29 for separating into B
Supply to W respectively.

This data interpolation and RGB separation circuit 29B
The black R shading correction data, the black G shading correction data, and the black B shading correction data obtained on the output side of 1 are supplied to the subtractors 8R, 8G, and 8B of the shading correction processing circuit 3, respectively, to perform the black shading correction.

Further, this data interpolation and RGB separation circuit 2
White R shading correction data, white G shading correction data, and white B shading correction data obtained on the output side of 9 W are supplied to the dividers 10R, 10G, and 10B of the shading correction processing circuit 3 to perform white shading correction. .

[0030]

However, in such a conventional shading correction apparatus, the shading correction data is obtained only once in a state in which the iris mechanism 5 is closed and a state in which light is uniformly incident before image pickup. Since this is stored in the RAM 21 and the shading correction is performed by this, the optimum shading correction data cannot be obtained depending on the shading state, the noise state, etc., and thus the good shading correction cannot be performed. was there.

In view of the above point, the present invention has an object to obtain optimum shading correction data and to enable good shading correction.

[0032]

SUMMARY OF THE INVENTION
The positive device has a plurality of pixels S as shown in FIG.₁₁~ S _MN
Image sensors 1R, 1G, 1 arranged in a matrix
B and the image pickup of each pixel of the image pickup elements 1R, 1G, 1B
Shading component by integrating the level data of force signal
Shade that forms shading correction data according to
Swing correction data forming means 17 and 18, and this shade
Storage means 21 for storing the swing correction data, and
Shading correction read from the storage unit 21
Output from this image sensor 1R, 1G, 1B by data
A shading correction means 3 for correcting the signal.
In the fading correction device, the first shading
The correction data is displayed on the image pickup surfaces of the image pickup elements 1R, 1G, 1B.
No light is incident, or the brightness level is evenly distributed on this imaging surface.
It is formed in the state that a simple light is incident and the second shell is formed.
The shading correction data is used for this first shading correction.
The imaging output signal that is shading-corrected by the data
The first and second shading compensation
Positive data is added so that the first and second she
Third shading to which the boarding correction data is added
The correction data is stored in the storage means 21 and
The third shading correction data is used for this shading.
It is adapted to be supplied to the correction means 3.

[0033]

According to the present invention, the second shading correction data for the second time is obtained while performing the shading correction with the first shading correction data obtained for the first time, and the second shading correction data is obtained by the second shading correction data. Since the shading correction data of is added, the optimum shading correction data can be obtained.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the shading correction apparatus of the present invention will be described below with reference to FIG. 1, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 1, similar to FIG. 2, the image pickup output signals E _R , E _G , and E _B of RGB channels obtained by the image pickup devices 1R, 1G, and 1B are converted into preamplifiers 2R,
It is supplied to the shading correction processing circuit 3 via 2G and 2B.

The image pickup devices 1R, 1G and 1B form an image pickup portion of a three-plate color image pickup device, and are provided in an image pickup optical system 7 including an image pickup lens 4, an iris mechanism 5, a color separation prism 6 and the like. There is.

Further, the image pickup devices 1R, 1G and 1B
Is a CCD image sensor in which M × N pixels S _{11 to} S _MN of M in the horizontal direction and N in the vertical direction are arranged in a matrix as shown in FIG. It is driven by a CCD driving unit (not shown) so that the signal charges of all the pixels S _{11 to} S _MN for one screen are read out.

The image pickup device 1R outputs an image pickup output signal E of the red component of the subject image color-separated by the color separation prism 6.
_R is supplied as an R channel signal to the shading correction processing circuit 3 via the preamplifier 2R.

Further, the image pickup device 1G uses the image pickup output signal E _G of the green component of the subject image color-separated by the color separation prism 6 as a G channel signal in the preamplifier 2G.
Is supplied to the shading correction processing circuit 3 via.

Further, the image pickup device 1B uses the image pickup output signal E _B of the blue component of the subject image color-separated by the color separation prism 6 as a B channel signal via the preamplifier 2B to generate the shading correction processing circuit 3. Supply to.

The shading correction processing circuit 3
The image pickup device 1R, be one that performs black shading correction processing and white shading correction processing on 1G and imaging output signals of each RGB channel E _R obtained from 1B, E _G and E _B, the imaging output signals E _R, E _G and E
Subtractors 8R and 8G for each RGB channel to which _B is supplied
And 8B, and the subtraction output signals from the subtractors 8R, 8G, and 8B, or the dividers 10R for the RGB channels supplied via the amplifiers 9R, 9G, and 9B, respectively.
And 10G and 10B.

RG of this shading correction processing circuit 3
The signal of each channel B is supplied to the signal processing circuit 11 for making a color image pickup signal for display or recording.

Further, the shading correction processing circuit 3
R, G, and B channel signals are supplied to the selector circuit 12 and selected by the selector circuit 12 to obtain R / G / B dot-sequential data D, and this data D is calculated in advance from the input signal. This data D is decimated to ⅛ through the DC subtraction circuit 13 that subtracts the DC component,
8 thinning circuit 14 is supplied.

The output signal of the 1/8 decimation circuit 14 is supplied to one input terminal of the selector circuit 15 and the output signal of the 1/8 decimation circuit 14 is supplied to the other input terminal of the selector circuit 15 via the absolute value circuit 16. Supply to the input terminal.

The signal in the positive direction selected by the selector circuit 15 is set to 1 in the row direction (horizontal direction) as shown in FIG.
The signal obtained at the output side of the selector circuit 15 is supplied to the row integration circuit 17 that performs synchronous addition during the video period of the horizontal period, and the signal is synchronized during the video period of one vertical period in the column direction (vertical direction) as shown in FIG. It is supplied to the column integration circuit 18 for addition.

In this case, the DC subtraction circuit 13, the row integration circuit 17, the column integration circuit 18, etc. form shading correction data.

Row-side and column-side shading correction data obtained at the outputs of the row integration circuit 17 and the column integration circuit 18 are supplied to a selector circuit 19, respectively, and the output signal of the selector circuit 19 is supplied to an adder 30. And this adder 3
An output signal of 0 is supplied to the RAM 21 via the write / read switching circuit 20.

In this case, the write / read switching circuit 2
0 is set to the write state, and the row synchronous addition data from the row integration circuit 17 is stored in the RAM 2 during the blanking period of the horizontal period.
The column synchronous addition data from the column integration circuit 18 is written into the RAM 21 during the blanking period of the vertical period.

In this embodiment, the shading correction data read from the RAM 21 is supplied to the row / column shading correction data separation circuit 23 and the shading correction data is supplied to the stock circuit 31 which stocks the shading correction data. The output signal of the circuit 31 is supplied to the adder 30.

In FIG. 1, the other parts are configured in the same manner as in FIG.

To obtain the black shading correction data in this example, first, the iris mechanism 5 is closed by the iris driving device 22 so that no light is incident on the image pickup surfaces of the image pickup devices 1R, 1G and 1B. 2R, 2
G, 2B, shading correction processing circuit 3, selector circuits 12, 15, 19, DC subtraction circuit 13, 1/8 decimation circuit 14, absolute value circuit 16, row integration circuit 17, and column integration circuit 18 are set as operating states, and black shading is performed. After obtaining the correction data, the black shading correction data is stored in the RAM 21.
I will remember it.

Next, the write / read switching circuit 20 is set to the read state with the iris mechanism 5 left open, and this R
The shading correction of the image pickup output signal is performed using the black shading correction data written in the AM 21, and the first black shading correction data read from the RAM 21 at this time is stocked in the stock circuit 31, and the stocked first black shading correction is performed. The correction data and the next black shading correction data obtained from the image pickup output signal that has been shading corrected by the first black shading correction data are added by the adder 30, and the added black shading correction data is stored in the RAM in the same manner as described above.
As written in 21.

The above is repeated a predetermined number of times to optimize the black shading correction data, and the optimized black shading correction data written in the RAM 21 is used to perform the shading correction of the image pickup output signal thereafter.

To obtain white shading correction data in this example, first, the iris driving device 22 opens the iris mechanism 5 to pick up an image of a white board or the like to obtain uniform brightness on the image pickup surfaces of the image pickup devices 1R, 1G and 1B. With the level of light incident, the preamplifiers 2R, 2G, 2
B, shading correction processing circuit 3, selector circuit 1
2, 15, 19, the DC subtraction circuit 13, the 1/8 decimation circuit 14, the absolute value circuit 16, the row integration circuit 17, and the column integration circuit 18 are operated to obtain white shading correction data, and the white shading correction data is obtained. It is stored in the RAM 21.

Next, the write / read switching circuit 20 is set to the read state with the iris mechanism 5 left open, and this R
Shading correction of the imaging output signal is performed using the white shading correction data written in the AM 21, and at this time, the first white shading correction data read from the RAM 21 is stocked in the stock circuit 31, and the stocked first white shading is stored. The correction data and the next white shading correction data obtained from the image pickup output signal that has been subjected to the shading correction by the first white shading correction data are added by the adder 30, and the added white shading correction data is stored in the RAM in the same manner as described above.
As written in 21.

The above operation is repeated a predetermined number of times to optimize the white shading correction data, and the optimized white shading correction data written in the RAM 21 is used to perform the shading correction of the image pickup output signal thereafter.

As described above, according to this example, while the shading correction is performed using the first shading correction data obtained first, the following second shading correction data is obtained, and the first shading correction data is converted into the first shading correction data. Since the shading correction data of 2 is added,
There is an advantage that optimum shading correction data can be obtained and good shading correction can be performed.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0058]

According to the present invention, there is an advantage that optimum shading correction data can be obtained and good shading correction can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a shading correction device of the present invention.

FIG. 2 is a configuration diagram showing an example of a conventional shading correction device.

FIG. 3 is a diagram used for explanation.

[Explanation of symbols]

 1R, 1G, 1B Image sensor 3 Shading correction processing circuit 17 Row integration circuit 18 Column integration circuit 20 Write / read switching circuit 21 RAM 30 Adder 31 Stock circuit

Claims (4)

[Claims] 1. An image sensor having a plurality of pixels arranged in a matrix, and shading correction that integrates level data of an image output signal of each pixel of the image sensor to form shading correction data according to a shading component. A shading correction device comprising: a data forming unit; a storage unit that stores the shading correction data; and a shading correction unit that corrects an output signal from the image sensor based on the shading correction data read from the storage unit at the time of shooting. , The first shading correction data is formed in a state where no light is incident on the image pickup surface of the image pickup device, or in a state where light having a uniform brightness level is incident on the image pickup surface, and the second shading correction data is formed as described above. Shading compensation by the first shading correction data The first shading correction data is added to the first and second shading correction data, and the third shading correction data to which the first and second shading correction data are added is stored in the storage means. And the third
Shading correction data is supplied to the shading correction means. 2. The shading correction apparatus according to claim 1, wherein the shading correction data forming means integrates level data of an image pickup output signal of each pixel of the image pickup element in a horizontal direction and a vertical direction, A shading correction device, which is configured to form shading correction data according to a shading component in a vertical direction. 3. The shading correction apparatus according to claim 1, wherein white shading is corrected. 4. The shading correction apparatus according to claim 1, wherein the black shading is corrected.