JPH06315463A - Electronic endoscope device - Google Patents

Abstract

PURPOSE:To provide a high quality and equal white balance over the full screen. CONSTITUTION:Added color signal sampled at sampling circuits 10 and 11 is sent to multiplexers 12 and 13 and to a WB compensation control circuit 14. The WB compensation control circuit 14 detects the ratio between a specified color component of the added color signal and other color components when a white object is exposed and calculates a WB coefficient to be multiplied with an added color signal so that the ratio becomes equal over the full screen. The multiplexer 12 and 13 multiply a WB coefficient with an added color signal to adjust the white balance of the screen. This results in a high quality and equal white balance to the full screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope apparatus, and more particularly to a simultaneous type electronic endoscope apparatus provided with a color filter array.

[0002]

2. Description of the Related Art In recent years, by inserting an elongated insertion portion into a body cavity, it is possible to observe internal organs in the body cavity and, if necessary, perform various therapeutic treatments using a treatment instrument inserted into a treatment instrument channel. Endoscopes (also called scopes or fiberscopes) are widely used.

Various electronic scopes using a solid-state image pickup device such as a charge coupled device (CCD) as an image pickup means have been proposed. This electronic scope has a higher resolution than the fiber scope and is easy to record and reproduce images.
Further, there is an advantage that image processing such as image enlargement and comparison of two images is easy.

[0004] As the image pickup method of the color image of the electronic scope, a frame sequential type in which illumination light is sequentially switched to R (red), G (green), B (blue), etc. R, G, B
There is also a simultaneous type in which a filter array in which color filters that transmit color lights of the same type are arranged in a mosaic pattern is provided. The frame-sequential method has an advantage that the number of pixels can be reduced as compared with the simultaneous method, while the simultaneous method has an advantage that no color shift occurs.

By the way, the color filter array is a CCD
In the electronic endoscope provided on the front face of the CCD, the video signal from the CCD is color-separated to extract the R and B signals and output line-sequentially. The levels of the color signals R and B vary depending on the color temperature of the light source. Therefore, the present application proposes a device for adjusting the white balance by generating a white balance adjustment signal synchronized with the R, B line sequential signal in Japanese Patent Application Laid-Open No. 2-63428 filed earlier. Further, in this proposal, a color difference signal is obtained from the separated R and B line sequential signals and the luminance signal Y, and the level of the Y signal is adjusted so that the difference between the average levels of the color difference signals when white is captured is zero. Therefore, a device for automatically adjusting the white balance is also disclosed.

[0006]

The color filter array arranged in front of the CCD has, for example, an array of magenta (Mg), cyan (Cy), yellow (Ye), and green (G) filter elements. It is arranged in. The color video signal is created by calculating the signals based on the light that has passed through the filter element. That is, when the constituent elements of the color filter array vary, the white balance cannot be perfectly adjusted by simply correcting the level of the color signal.

The present invention has been made in view of the above problems, and provides an electronic endoscope apparatus capable of obtaining accurate color reproducibility regardless of variations in constituent elements of a color filter array. With the goal.

[0008]

In the electronic endoscope apparatus according to the present invention, an extracting means for extracting each color component from an output of a solid-state image pickup device provided with a color filter array, and a white image by the solid-state image pickup device. An average value calculating means for obtaining an average of one screen of each color component extracted by the extracting means when an image is captured, and an average of one screen of a predetermined color component and an average of each other color component from the calculation result of the average value calculating means. And a weighting means for weighting each color component from the extracting means so that each of the ratios has a predetermined value.

[0009]

In the present invention, each color component based on the color filter array is extracted from the output of the solid-state image pickup device by the extraction means. The average value calculating means calculates the average of one screen of each color component when white is imaged, and the ratio calculating means calculates the ratio of the average of one screen of the predetermined color component to the average of each of the other color components. The weighting means weights the respective color components from the extraction means so that this ratio becomes a predetermined value, so that the white balance is uniformly made good in the ratio calculation unit over the entire screen.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 relate to a first embodiment of the present invention, FIG. 1 is a configuration diagram showing a configuration of an electronic endoscope apparatus of the first embodiment, FIG. 2 is an explanatory diagram showing a configuration of a color filter, and FIG.
Is an explanatory diagram for explaining the output of the CCD, FIG. 4 is a block diagram showing a specific configuration of the WB correction control circuit in FIG. 1,
FIG. 5 is an explanatory diagram for explaining the white balance correction control of the present embodiment, and FIG. 6 is a timing chart for explaining the operation of the sampling circuits 10 and 11.

A light guide 2 for transmitting illumination light is inserted into the scope 1, and the light guide 2 transmits the illumination light from the light source 3 to the emission end face side. The illumination light transmitted by the light guide 2 is emitted from the distal end portion 4 of the insertion portion of the scope 1 to illuminate the front observation object 5 side.

In addition, a C is provided at the tip 4 of the insertion portion of the scope 1.
A CD 6 is provided, and reflected light from the observation object 5 is made incident on the incident surface of the CCD 6 via an imaging objective lens (not shown). CCD drive circuit 8 is C
The clock signal for driving the CD is supplied to the CCD 6, and the CCD 6
Operates in response to a CCD driving clock signal to convert the optical image formed on the image pickup surface into an electric signal and outputs the electric signal to a correlated double sampling circuit (hereinafter referred to as a CDS circuit) 7. A color filter is formed on the front surface of the CCD 6. FIG. 2 is an explanatory diagram for explaining the arrangement of the color filters.

As shown in FIG. 2, the magenta element Mg and the green element G are alternately and repeatedly arranged in the odd rows of the color filter, and the cyan element Cy and the yellow element Ye are alternately arranged in the even row. Are repeated. In addition, the elements Cy and Ye in the even-numbered rows that are adjacent to each other are arranged one column apart. The CCD 6 photoelectrically converts the light passing through each of the elements Mg, G, Cy, and Ye to generate signals Mg, G, Cy, Y.
get e. The CCD 6 performs two-line simultaneous reading in which signals of two adjacent lines are added and read. That is, CCD6
From FIG. 3, as shown in FIG. 3, the addition color signal (Mg + Cy) and the addition color signal (G + Ye) are alternately repeated and output, and the addition color signal (Mg + Ye) and the addition color signal ( G + Cy) are alternately repeated and output.

The CDS circuit 7 performs double sampling in order to remove 1 / f and reset noise contained in the CCD output signal, removes noise components, and makes a signal with improved S / N, and an A / D converter. Give to 9. The A / D converter 9 converts the input line-sequential video signal into a digital signal and supplies it to the sampling circuits 10 and 11.

The sampling circuits 10 and 11 are supplied with sample pulses 1 and 2 having a period corresponding to the number of horizontal pixels, respectively. The phases of the sample pulses 1 and 2 are 180 degrees out of phase, and the signal (Mg + Cy) is sampled by the sampling circuit 10 on the odd line,
The signal (G + Ye) is sampled by 11. Similarly, in the even lines, the sampling circuit 10 samples the signal (Mg + Ye), and the sampling circuit 11 samples the signal (G + Cy).
The sampling outputs of the sampling circuits 10 and 11 are given to the multipliers 12 and 13, respectively.

The sampling output is also given to the WB correction control circuit 14. FIG. 4 shows a specific configuration of the WB correction control circuit in FIG.

The sampling output of the sampling circuit 10 is supplied to the average value circuits 31 and 32 of the WB correction control circuit 14,
The sampling output of the sampling circuit 11 is supplied to the average value circuits 33 and 34. The average value circuits 31 to 34 respectively include a signal (Mg + Cy), a signal (Mg + Ye), and a signal (G + Y).
e), the average of the signal (G + Cy) for one screen is obtained. The averages for one screen obtained by the average value circuits 31, 32, 34 are given to the division circuits 35, 36, 37, respectively. Also, the division circuits 35 to 37
Also, the average of the signal (G + Ye) for one screen is given to the average value circuit 33.

2 × 2 pixel added color signal (Mg + Cy),
White can be reproduced by appropriately setting the ratios of (Mg + Ye), (G + Ye), and (G + Cy).
In this case, the division circuits 35 to 37 have the signals (G + Y
signals (Mg + Cy), (Mg + Ye),
The ratios A, B, and C of (G + Cy) are held as reference ratios. Due to variations in the color filter array, added color signals (Mg + Cy), (Mg + Ye), (G + Y)
Even if e) and (G + Cy) are mixed based on the reference ratio, uniform white cannot be obtained. Therefore, in this embodiment, white is imaged during the white balance adjustment, and the signal (G +
Signals (Mg + Cy), (Mg + Y) for Ye)
e), the ratio a, b, c of (G + Cy) is calculated, and the ratio a,
By controlling the level of the added color signal so that b and c match the reference ratios A, B and C, a uniform white balance is obtained over the entire screen.

That is, the dividing circuits 35 to 37 are (Mg + Cy), (Mg + Ye), and (G + C) with respect to the average value of (G + Ye) for one screen during white balance adjustment.
The ratios a, b, and c of the average values for one screen of y) are obtained. Then, the division circuits 35 to 37 have the reference ratios A, B, C.
And the ratios a, b, and c are obtained by, for example, division, and the WB coefficient is obtained and held and output to the selectors 38 and 39. Selector 38
During normal shooting, the WB coefficient of the division circuit 35 is selected and given to the multiplier 12 at the timing when the signal (Mg + Cy) is input to the multiplier 12, and the division is performed at the timing when the signal (Mg + Ye) is input to the multiplier 12. The WB coefficient of circuit 36 is selected and provided to multiplier 12. Similarly, during normal shooting, the selector 39 selects the coefficient 1 at the timing when the signal (G + Ye) is input to the multiplier 13 and gives it to the multiplier 13 to output the signal (G +
Cy) is input to the multiplier 13 at the timing of division circuit 37
The WB coefficient of is selected and given to the multiplier 13.

The multipliers 12 and 13 are sampling circuits 10 and 10, respectively.
By multiplying the output of 11 by the WB coefficient of the selectors 38 and 39, the white balance of the line-sequential video signal is adjusted and output to the adder 15 and the subtracter 16. Adder 15 is a multiplier
The white balance adjusted data from 12 and 13 are added to be converted into a luminance signal and given to the Y processing circuit 17. The subtractor 16 subtracts the outputs of the white balance-adjusted multipliers 12 and 13 to obtain a color difference line sequential signal and outputs the color difference line sequential signal to the color processing circuit 18.

The Y processing circuit 17 performs processing such as contour compensation on the input luminance signal and supplies it to the Y color difference RGB conversion circuit 19. Further, the color processing circuit 18 performs processing such as synchronization and color correction on the input color difference line sequential signal to obtain a color difference signal and supplies it to the Y color difference RGB conversion circuit 19. Y color difference R
The GB conversion circuit 19 obtains an RGB signal from the input luminance signal and color difference signal using, for example, the conversion formula shown in the following formula (1).

R = 7.3 (RY) 2Y- (BY) G = 2Y-2 (RY) -1.5 (BY) B = 4 (BY) +0.52 {2Y- (RY)} (1) The RGB signal obtained based on the equation (1) is supplied to the γ correction circuit 20, and the γ correction circuit 20 performs predetermined nonlinear processing on the RGB signal. Gamma-corrected and output to the D / A converter 21. The D / A converter 21 converts the gamma-corrected RGB signal into an analog signal and outputs it.

Next, the operation of the embodiment thus constructed will be described with reference to the explanatory view of FIG. 5 and the timing chart of FIG.

Illumination light from the light source 3 is emitted from the tip of the tip 4 of the insertion portion of the scope 1 via the light guide 2 to illuminate the observation object 5. The reflected light from the observation object 5 is C
The light enters the image pickup surface of the CD 6, and the CCD 6 is a CCD drive circuit 8
It operates in accordance with the CCD driving clock signal from, to convert the optical image formed on the imaging surface into an electrical signal and output it to the CDS circuit 7. In this case, 2-line simultaneous reading shown in FIG. 3 is performed. As shown in FIG. 3, signals of two lines and two columns (Mg + C
2 × 2 of (y), (Mg + Ye), (G + Ye), and (G + Cy) constitutes one unit. CCDS output is CDS
The reset noise is removed by the circuit 7, converted into a digital signal in the A / D converter 9, and supplied to the sampling circuits 10 and 11.

The output of the A / D converter 9 in the odd line is as shown in FIG.
The output of the / D converter 9 is as shown in FIG. 6 (d). In the odd line, the sampling circuit 10 samples the signal (Mg + Cy) by the sample pulse 1 shown in FIG. 6B, and the sampling circuit 11 samples the signal (Mg + Ye) by the sample pulse 1 shown in FIG. 6E. . Similarly, on even-numbered lines, signals (G + Ye), (G
+ Cy) is sampled.

The signals sampled by the sampling circuits 10 and 11 are given to the WB correction control circuit 14. W
The B correction control circuit 14 controls the signals (Mg + Cy), (Mg + Ye), (G + Y) during white balance adjustment.
e) and (G + Cy) for one screen are calculated, and the signal (G + Ye) and the signals (Mg + Cy), (Mg + Ye),
Ratios a, b, and c with (G + Cy) are obtained. The WB correction control circuit 14 holds the reference ratios A, B, and C at the time of white image pickup, and it is 2 from the ratio of the ratios a, b, and c and the reference ratios A, B, and C.
The WB coefficient is calculated and held in units of × 2 pixels.

During normal shooting, the sampling circuit 1
Signals (Mg + Cy), (G +) from 0, 11 to the multipliers 12, 13
When (Ye), (Mg + Ye), and (G + Cy) are input, the multipliers 12 and 13 are provided with corresponding WB coefficients from the WB correction control circuit 14 at the timing when these signals are input, and the input signal and WB Multiplies with a coefficient. This allows
In any part of the screen, the ratio of the added color signal is based on the reference ratio. That is, since the multipliers 12 and 13 adjust the white balance in units of 2 × 2 pixels using the WB coefficient, the white balance is uniformly adjusted over the entire screen regardless of the filter variation.

The white balance-adjusted data is added by the adder 15 and converted into a luminance signal, and then the Y processing circuit 17 performs contour compensation and the like. Meanwhile, the subtractor
16 converts white balance adjusted data into color difference line-sequential signals, and color processing circuit 18 performs line-sequential signal synchronization and color correction. The luminance signal from the Y processing circuit 17 and the color difference signal from the color processing circuit 18 are supplied to the Y color difference RGB conversion circuit 19 and converted into RGB signals. Furthermore, the RGB signal is γ
D / A converter after gamma correction by the correction circuit 20
It is converted into an analog signal by 21 and output.

Thus, in this embodiment, 2 × 2
Since the white balance adjustment is performed on a pixel-by-pixel basis, it is possible to perform uniform and good white balance adjustment over the entire screen regardless of filter variations.

In the above embodiment, the WB coefficient is obtained by simply dividing the reference ratios A, B, C and the ratios a, b, c, but the calculation using a predetermined constant should be performed. The color-corrected WB coefficient may be obtained by. Further, although the ratio is calculated based on the signal (G + Ye), the ratio may be calculated based on other color components.

Further, the ratios a, b, c are the reference ratios A, B,
If the difference is significantly different from C, it may be detected that the deviation from the predetermined range has occurred, and a warning indicating that the white balance adjustment is impossible may be issued. For example, if you accidentally turn on the white balance switch during diagnosis, incorrect white balance adjustment will be performed,
Must be a preset value. In this case, it is possible to prevent the white balance from becoming defective by determining whether or not the white balance adjustment is possible depending on whether or not the ratio of the color components is within a predetermined range, and prohibiting the white balance adjustment. it can. Further, by constantly observing the ratio not only during white balance adjustment but also during normal imaging, it is possible to detect that an abnormality has occurred in the light source or the like by a sudden change in the ratio.

FIG. 7 is a block diagram showing the structure of the electronic endoscope apparatus according to the second embodiment of the present invention. 7, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The present embodiment is provided with a reference voltage control circuit 42 for applying the output of the CDS circuit 7 to the A / D converter 41 and controlling the reference voltage of the A / D converter 41, and a reference external setting section 43. Different from the first embodiment.

In the first embodiment, digital processing is adopted, and the dynamic range of the signal is limited by the dynamic range of the A / D converter 41. Therefore, when the observed image is bright, the level of the added color signal may be saturated relatively easily beyond the dynamic range of the A / D converter 41, and the observation may be impossible. Therefore, in this embodiment, by controlling the reference voltage of the A / D converter 41, the dynamic range can be widened and a relatively bright observation image can be observed.

That is, the reference voltage of the A / D converter 41 can be controlled by the reference voltage control circuit 42. The reference external setting unit 43 is composed of, for example, a variable resistor or a switch, and controls the reference voltage control circuit 42 based on a user operation. The reference voltage control circuit 42 generates a reference voltage of a level based on the operation of the reference external setting section 43 and supplies it to the A / D converter 41.

In the embodiment thus constructed,
The reference voltage level of the A / D converter 41 is set to a predetermined level in advance. As a result, the video signal from the CCD 6 is converted into a digital signal with a predetermined dynamic range.

Here, it is assumed that the portion of the observed image to be observed is too bright and the level of the added color signal exceeds the dynamic range of the A / D converter 41. In this case, the user operates the reference external setting unit 43 to control the reference voltage control circuit 42. As a result, the reference voltage control circuit 42 changes the reference voltage of the A / D converter 41 to expand the dynamic range. Then, the level of the added color signal falls within the dynamic range, and a faithful image corresponding to the brightness of the observed image is reproduced.

The reference voltage control circuit 42 may not only widen the dynamic range by changing the reference voltage but also shift the conversion range. In addition, when the observation region is too dark, the dynamic range of the A / D converter 41 can be narrowed by controlling the reference voltage by operating the reference external setting unit 43. As a result, the added color signal is digitally amplified and can be easily observed.

As described above, in this embodiment, the user can freely control the reference voltage of the A / D converter 41 to facilitate the observation of the observation image regardless of the brightness of the observation region. be able to.

FIG. 8 is a block diagram showing the configuration of the electronic endoscope apparatus according to the third embodiment of the present invention. 8, the same components as those in FIG. 7 are designated by the same reference numerals and the description thereof will be omitted.

This embodiment differs from the second embodiment in that an image detection circuit 45 for detecting the output of the A / D converter 41 and controlling the reference voltage control circuit 42 based on the detected output is provided. That is, the video detection circuit 45 detects the peak value of the video signal from the output of the A / D converter 41. The video detection circuit 45 controls the reference voltage control circuit 42 based on the detected peak value to make the peak value of the video signal equal to the full range of the A / D converter 41.

In the embodiment thus constructed,
The reference voltage control of the A / D converter 41 is automatically performed according to the peak value of the video signal. That is, A / D converter
The output of 41 is video-detected by the video detection circuit 45, and the peak of the video signal is detected. Now, it is assumed that the peak value of the video signal is relatively high. In this case, the video detection circuit
Reference numeral 45 controls the reference voltage control circuit 42 to change the reference voltage and increase the dynamic range of the A / D converter 41. As a result, the dynamic range of the A / D converter 41 extends to the peak value of the video signal. vice versa,
When the peak value of the video signal is relatively low, the video detection circuit 45 controls the A / D converter 41 so as to reduce the dynamic range. Also in this case, the dynamic range of the A / D converter 41 is narrowed to the peak value of the video signal. Thus, the dynamic range of the A / D converter 41 is effectively used by matching the full range of the A / D converter 41 with the peak value of the video signal.

FIG. 9 is a block diagram showing the arrangement of an electronic endoscope apparatus according to the fourth embodiment of the present invention. 9, the same components as those of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

This embodiment differs from the first embodiment in that it has an adder 51 for adding the outputs of the A / D converter 9, a motion detection circuit 52, and a dimming circuit 53. The motion detection circuit 52 is A /
The motion of the image is detected from the output of the D converter 9, and the adder 51 and the dimming circuit 53 are controlled according to the detection result. The adder 51 adds the outputs of the A / D converter 9 and outputs it to the sampling circuits 10 and 11. The dimming circuit 53 is controlled by the motion detecting circuit 52 to adjust the amount of light emitted from the light source 3.

In the embodiment constructed as described above,
Light control and addition of images are controlled according to the movement of the images. That is, the motion detection circuit 52 detects the motion of the image by detecting the difference in the image between the fields from the digital video signal of the A / D converter 9. The motion detection circuit 52 gives the detection result to the adder 51 and the dimming circuit 53.

Now, it is assumed that the image has a motion. In this case, normal control is performed. That is, the motion detection circuit
According to the detection result of 52, the adder 51 outputs the output of the A / D converter 9 as it is to the sampling circuit 10, without performing addition.
11, the dimming circuit 53 controls the light source 3 by normal dimming.

Here, it is assumed that there is no motion in the image, for example, when observing a specific part. In this case, the dimming circuit 53 diminishes the illumination by reducing the amount of light emitted from the light source 3 based on the detection result of the motion detection circuit 52. As a result, the amount of reflected light from the observation object 5 decreases. Further, the adder 51 adds images based on the detection result and outputs the images to the sampling circuits 10 and 11. A sufficient signal level can be obtained by performing addition. By these controls, the halation portion can be eliminated, random noise can be reduced, and the image quality can be improved.

FIG. 10 is a block diagram showing the arrangement of an electronic endoscope apparatus according to the fifth embodiment of the present invention. 10, the same components as those in FIG. 8 are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, the CCD driving circuit 8 is replaced by a CC
The third embodiment differs from the third embodiment in that the D drive circuit 46 is adopted and an adder 51, a switching control circuit 47, and a switching instruction section 48 are provided. The CCD 6 operates according to the CCD driving clock signal from the CCD driving circuit 46. CCD drive circuit 46 is CC
It is possible to generate a clock signal for reading D6 once in one field and a clock signal for reading it a plurality of times, and the switching control signal from the switching control circuit 47 causes the CCD to operate.
The clock signal given to 6 is switched.
The switching control circuit 47 generates a switching control signal based on the operation of the switching instructing section 48 and supplies it to the CCD drive circuit 46, and
It is also given to the adder 51 and the reference voltage control circuit 42.

The output of the A / D converter 41 is given to the sampling circuits 10 and 11 via the adder 51. The adder 51 adds the output of the A / D converter 41 a plurality of times to increase the signal level when the switching control signal indicates that the CCD 6 has read out a plurality of times in one field. The output is expanded from the dynamic range of the A / D converter 41. The adder 51 outputs the output of the A / D converter 41 as it is to the sampling circuits 10 and 11 when the CCD 6 reads out once per field.

When the switching control signal indicates that the CCD 6 has read out a plurality of times in one field, the reference voltage control circuit 42 supplies the reference voltage to the A / D converter 41 to a predetermined constant voltage. When the reading is performed once in one field, the reference voltage is controlled based on the output of the video detection circuit 45.

In the embodiment thus constructed,
For example, when the number of images on the CCD 6 is large and reading is performed only once in one field, the user instructs the switching instruction section 48 to read once. Then C
The CD drive circuit 46 generates a clock signal for one read operation and gives it to the CCD 6. Further, the adding operation of the adder 51 is stopped, and the reference voltage control circuit 42 controls the reference voltage based on the detection result of the video detection circuit 45 to bring the peak value of the video signal to the full range of the A / D converter 41. Match. That is, in this case, the same operation as in the third embodiment is performed.

Here, it is assumed that the CCD 6 has a small number of pixels and can read out a plurality of times in one field. In this case, the user uses the switching instructing section 48 to instruct reading multiple times. The switching control circuit 47 generates a switching control signal, and the CCD drive circuit 46 supplies the CCD 6 with a clock signal that enables multiple readings. A / D converter 41
Converts the output of the CDS circuit 7 into a digital signal with a fixed reference voltage. In this case, the adder 51 adds the outputs of the A / D converter 41 multiple times. As a result, the video signal level input to the sampling circuits 10 and 11 is increased, and a signal having a level wider than the dynamic range of the A / D converter 41 is obtained.

As described above, in this embodiment, the CCD
Since the driving of the CCD, the addition of the video signal and the reference voltage are controlled by the number of pixels, the image with a wide dynamic range can be obtained regardless of the number of pixels.

In the present embodiment, the instruction is given to generate the switching control signal according to the number of pixels, but the switching control signal is automatically generated by detecting the type of scope by the scope ID or the like. You may do it.

11 to 13 relate to a sixth embodiment of the present invention, FIG. 11 is a block diagram showing the configuration of an electronic endoscope apparatus of the sixth embodiment, and FIG. 12 is a gamma correction circuit in FIG. FIG. 13 is a block diagram showing a specific configuration, and FIG. 13 is a graph for explaining the γ conversion memory.

In FIG. 11, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. This embodiment is different from the embodiment of FIG. 1 in that a γ correction circuit 55 is used instead of the γ correction circuit 20 and an α conversion value selection circuit 56 is used.

When the gamma correction circuit is composed of a gamma conversion ROM, the capacity of the gamma conversion ROM is RG.
It is determined by the number of quantization bits of the B signal. For example,
If the RGB signal is represented by 10 bits, the capacity of the gamma conversion ROM is 2 10 bits. Furthermore, if a plurality of gamma characteristics can be set, the required capacity becomes large. For example, when four types of gamma conversion are possible, a capacity of (2 to the 10th power) × 4 bits is required.
However, such a large-capacity ROM is extremely expensive and relatively slow. Therefore, in this embodiment, the gamma correction circuit is configured using a high-speed and inexpensive ROM.

That is, as shown in FIG. 12, the γ correction circuit 55 is composed of (2 8) × 4 bit γ conversion memories 61 to 64 and a selector 65. It is assumed that the RGB signal input to the γ correction circuit 55 is quantized with 10 bits. The lower 8 bits of this RGB signal are γ
It is given as an address to the conversion memories 61 to 64. The upper 2 bits are used as a select signal for the selector 65 described later.

As shown in FIG. 13, the γ conversion memory 61 stores gamma correction values corresponding to 0 to 255 of the input data, and the γ conversion memory 62 stores 256 to 5 of the input data.
The gamma correction value corresponding to 11 is stored. Similarly,
The γ conversion memories 63 and 64 are 512 to 76 of input data, respectively.
Gamma correction values corresponding to Nos. 7 and 768 to 1023 are stored. The γ conversion memories 61 to 64 are designed so that their addresses are designated by 8-bit input data and the stored gamma correction values are output to the selector 65.
Further, the γ conversion memories 61 to 64 store gamma correction values of four types of gamma characteristics A, B, C, D, and these characteristics are selected by specifying an address by a γ value selection signal. To be done. Note that the γ conversion memories 61 to 64
The γ-value selection signal supplied to is generated by the gamma-converted value selection circuit 56.

The selector 65 is supplied with the upper 2 bits of the RGB signal and selects one of the outputs of the γ conversion memories 61 to 64 and outputs it. The upper 2 bits of the RGB signal are 0 to 255, 256 to 511, 51 to 767,
768 to 1023, the gamma correction value corresponding to the RGB signal is selected by selecting the γ conversion memories 61 to 64 by the upper 2 bits.

In the embodiment constructed as described above,
The RGB signal from the Y color difference RGB conversion circuit 19 is a γ correction circuit.
Supplied to 55. γ conversion memories 61 to 64 of the γ correction circuit 55
Is designated by the lower 8 bits of the RGB signal. Further, the upper 2 bits of the RGB signal are given to the selector 65, and one of the outputs of the γ conversion memories 61 to 64 is selected. For example, when the RGB signal has any value from 256 to 511, the output of the γ conversion memory 62 is selected by the selector 65, and 256 addresses of the γ conversion memory 62 are designated by the lower 8 bits of the RGB signal. Done, R
A gamma correction value corresponding to the GB signal is output.

Further, the γ conversion value selection circuit 56 outputs a γ value selection signal for selecting the characteristics A, B, C and D of FIG. 13, and this γ value selection signal is used as an address in the γ conversion memory 61. 13 to 64, the characteristics A, B, C, and D of FIG. 13 are selected, and the selected gamma correction value is output. The gamma-corrected RGB signal is converted into an analog signal by the D / A converter 21 and output.

In the present embodiment, the γ value selection signal is used as a signal for controlling the addresses of the γ conversion memories 61 to 64. The selected gamma conversion data may be loaded.

As described above, the γ conversion memory is divided, and one of the γ conversion memories is selected according to the upper bits of the input signal. Therefore, it is possible to use a conversion ROM having a small capacity, a low cost and a high speed. it can. In addition, the data can be loaded at high speed.

[0066]

As described above, according to the present invention, there is an effect that accurate color reproducibility can be obtained regardless of variations in constituent elements of the color filter array.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an electronic endoscope apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a color filter.

FIG. 3 is an explanatory diagram for explaining an output of a CCD.

4 is a block diagram showing a specific configuration of a WB correction control circuit in FIG.

FIG. 5 is an explanatory diagram for explaining white balance correction control of the present embodiment.

6 is a timing chart for explaining the operation of sampling circuits 10 and 11 in FIG.

FIG. 7 is a configuration diagram showing an example of an electronic endoscope apparatus according to a second example of the present invention.

FIG. 8 is a configuration diagram showing an example of an electronic endoscope apparatus according to a third example of the present invention.

FIG. 9 is a configuration diagram showing an example of an electronic endoscope apparatus according to a fourth example of the present invention.

FIG. 10 is a configuration diagram showing an example of an electronic endoscope apparatus according to a fifth example of the present invention.

FIG. 11 is a configuration diagram showing an example of an electronic endoscope apparatus according to a sixth example of the present invention.

12 is a block diagram showing a specific configuration of a γ correction circuit in FIG.

FIG. 13 is an explanatory diagram for explaining the γ conversion memory in FIG. 12.

[Explanation of symbols]

10, 11 ... Sampling circuit, 12, 13 ... Multiplier, 14 ... WB
Correction control circuit

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[Procedure amendment]

[Submission date] September 2, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0057

[Correction method] Change

[Correction content]

In FIG. 11, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. This embodiment differs from the embodiment of FIG. 1 in that a γ correction circuit 55 is used instead of the γ correction circuit 20, and a γ conversion value selection circuit 56 is used.

Claims (1)

[Claims] 1. Extraction means for extracting each color component from the output of a solid-state image pickup element provided with a color filter array, and one screen of each color component extracted by the extraction means when white is picked up by the solid-state image pickup element. An average value calculating means for obtaining the average of the above, and a ratio calculating means for respectively obtaining each ratio between the average of one screen of a predetermined color component and the average of each of the other color components from the calculation result of this average value calculating means; And a weighting unit that weights each color component from the extraction unit so that each becomes a predetermined value.