JPH02181591A - Color balance correction system for color picture - Google Patents

Abstract

PURPOSE:To obtain a picture having satisfactory color reproducibility by correcting deviation amount for a signal output level deciding element according to the stop quantity of elements to decide the output levels of respective red(R), green(G), and blue(B) picture signals. CONSTITUTION:In order to correct the deviation of color balance to occur dependently on the stop quantity by a light quantity stop plat 33 in illuminating means 30, 30a, and 30b, the elements to decide the output levels of the respective R, G, and B picture signals are changed according to the stop quantity. Further, these color picture signal level deciding element, for example, light source light quantity, signal amplification gain, etc., are corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention is for solid-state imaging, such as in an electronic endoscope, by sequentially irradiating R, G, and B color wavelength light toward an observation target. In a color image capturing system that captures each color image using an element, performs signal processing on this color image signal, and displays it on a display device, there is a system that corrects changes in color balance that change depending on the aperture amount of illumination light. The present invention relates to a color balance correction method for color images.

[Prior Art] For example, in an endoscope, an insertion section connected to a main body operation section is inserted into a patient's body, etc., and an image of the observation target area is generated by irradiating illumination light toward the observation target area. The observation system of this endoscope uses a solid-state image sensor such as a CCD to perform photoelectric conversion, and performs predetermined signal processing by a processor. There is an electronic endoscope that displays an image of the object to be observed at °C using a display device such as a cathode ray tube. This electronic endoscope allows multiple people to observe at the same time, and also allows for image processing and recordability.

It has become widely popular in recent years due to its excellent storage stability.

In such electronic endoscopes, one image sensor is used in order to reduce the diameter of the insertion section, and red (R) is used in order to improve the resolution of images.

An image pickup device is used in which the image pickup device is driven in a so-called field-sequential method in which green (G) and blue (B) color images are formed for each field, and the images are displayed by superimposing them.

In this way, in order to perform imaging using the field sequential method, the illumination light directed toward the observation target is separated into the three colors of R, Cr, and B by passing through a filter. Illumination light using wavelength light of each color must be time-divided and sequentially irradiated.

For this purpose, an illumination means is used in which a rotating color filter having a filter area that transmits light in the wavelength range of each color of R, G, and B is used, and this rotating color filter is interposed in the optical path of the illumination light from the light source. It is being

For example, when observing a position close to the tip of the insertion tube of an endoscope, if the illumination is too strong, it may cause halation, making it difficult to observe well. I need to narrow it down. On the other hand, when observing a position away from the distal end of the insertion section, it is difficult to accurately detect the WA unless a certain amount of strong illumination light is irradiated. That is, it is necessary to adjust the amount of illumination light depending on the region to be observed.

For this purpose, as shown in FIG. 1, the illumination means used in the electronic endoscope described above includes a condenser lens l that condenses the illumination light from the light source, and a condenser lens 1 that condenses the illumination light from the light source. A light guide 2 for transmitting illumination light without attenuating it, and the light guide 2
The illumination lens 3 is connected to the output end of the illumination lens 3 for illuminating a predetermined range of the observation target. Furthermore, a light quantity diaphragm plate 4 is interposed on the light source side of the condenser lens 1, and a rotating color filter 5 is provided between the condenser lens 1 and the light guide 2. The amount of illumination light incident on the light guide 2 is adjusted by moving the diaphragm plate 4 forward and backward in the optical path of the illumination light passing through the condenser lens 1 by a drive mechanism (not shown).

The illumination means sequentially illuminates with R, G, and B color wavelength light to sequentially capture images of each color, and this imaging system is constructed as shown in FIG. 2.

That is, as shown in the figure, a solid-state image sensor for capturing an image includes a CCD 10, for example, and the CC
A CCD drive circuit 11 is connected to D10.

This CCD drive circuit 11 includes a timing pulse generator 1.
2 is connected, and the CCD 10 is driven based on the timing pulse inputted from the timing pulse generator 12 to the CCD driving circuit 11. , B (7)
Image signals for each color are read out. The image signal thus read out from the CCD 10 is input to the preprocessor 13. This briprocessor 13 is
It is composed of a correlated double sampling circuit, a low-pass filter, etc., and performs processing such as removing noise components in the image.

The output signal from this preprocessor 13 is amplified by a gain control amplifier 14, and the output signal from the processor 15 is amplified by a gain control amplifier .
It is now entered into The processor 15 is
It includes a γ correction circuit, an enhancer circuit, etc., and performs processing such as image quality correction of input image signals. The output signal of the processor 15 is digitally converted by the A/D converter 16 and stored in the R, G, and B field memories 17R, 17G, and 17B that constitute the image memory 17. Then, when each of the R, G, and B image data is stored in the image memory 17, the R, G, and B image data are simultaneously read out and sent to the D converters 18R, 18G, and 18B.
The signal is converted into an analog signal and output via an encoder 19.

By the way, depending on the filter characteristics in each filter area of the rotating color filter 5 and the sensitivity characteristics of the C:CD 10,
Since there is a difference in the amplitude of each R, G, and B color image signal, in order to improve color reproducibility, the gain value of the gain control amplifier 14 must be changed for each R, G, and B color image signal. It is necessary to do so. For this purpose, as shown in FIG. 3, an auto white balance mechanism equipped with an auto color controller 20 is provided to send R, G, and B gain control signals to the gain control amplifier 14.
By inputting C, the color balance between each color image is maintained.

Here, the adjustment of the gain control signal described above is to change the gain values of the R and B fields using the gain value of the G field as a reference, and for this purpose, first, the output signal from the gain control amplifier 14 is Starting from the 0th part in FIG. 2, area integration is performed by the integrating circuit 21.

Here, the output signal from the integrating circuit 21 is the reference G
If it is a field image signal, this signal is held by the sample and hold circuit 22, and R,
When the image signal of each field of B is captured, it is input to the gain value calculation circuit 23 together with the reference signal held in the sample hold circuit 22.
Ratio of gain value of R field to G field R/
G and the ratio of gain values in the B field B/G are calculated. Then, the results of each of these calculations are output as digital signals, which are latched by latch circuits 24R and 24B, respectively, and D/A converters 25R and 25B.
When the R, G, and B color image signals are input to the gain control amplifier 14, the respective gain controls are performed.

[Problem to be Solved by the Invention 1] By the way, in the prior art method described above, each color image signal of R2O and B is amplified in the gain control amplifier 14 according to the filter characteristics of the rotating color filter 5 and the sensitivity characteristics of the CCD 10. Even if such correction is performed, the color balance may not necessarily be achieved, and the colors in the image of the observation target may not be accurately reproduced.

That is, when the aperture plate 4 as described above is used as the aperture mechanism in the illumination means, although there is an advantage that the configuration of the aperture mechanism is simplified, it is difficult to change the aperture from a fully closed state to a fully closed state. As shown in Figure 4, due to the influence of chromatic dispersion in the condenser lens l, the attenuation rate of the amount of illumination light for each wavelength of R, G, and B is not equal; When the wavelength component of changes as shown by the solid line in the same figure, the wavelength light component of B, which has a shorter wavelength, has a higher attenuation rate than the wavelength component of G, as shown by the dotted line, and also has a longer wavelength. As shown by the dashed line, the attenuation rate of the light component of the average wavelength tends to be smaller than that of the light of the G wavelength component. Therefore, accurate color reproducibility cannot be obtained unless the variation in the attenuation rate of each wavelength light component caused by C based on the aperture amount by the aperture plate 4 is corrected.

The present invention has been made in view of the above points, and its purpose is to make it possible to obtain images with accurate color reproducibility even when the aperture amount is changed. An object of the present invention is to provide a color balance correction method for color images.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention has a light amount diaphragm plate that can move forward and backward with respect to the illumination optical path from the light source, and has R, G , B, a solid-state image sensor that captures R, G, and B color images, and a processor that processes color image signals output from the solid-state image sensor. In order to correct the color balance according to the difference in attenuation rate of each wavelength light of R, G, and H that occurs when changing the aperture amount of illumination light, each color image of R, G, and B is provided. The deviation according to the aperture amount of the element that determines the signal output level is measured in advance, and during actual shooting, the deviation is corrected for the element that determines the signal output level. Its characteristics are:

Here, the signal output level determining factor is the gain value of the amplification means in the processor. Therefore, when changing the gain value of this amplifying means, the R, G, and
The gain and correction value of the amplification means for each B color image signal are measured in advance and stored in the memory means, and at the time of imaging,
The gain correction value data is read out and the amplification amount in each color image signal is corrected according to the aperture amount.

Further, the brightness of the illumination lamp in the illumination means, that is, the amount of illumination light can be used as the signal output level determining factor. In this case, the amount of illumination light corresponding to the aperture amount when forming image signals of each color of R, G, and B is measured in advance and stored in a memory means, and when capturing an image, the amount of illumination data is read out from the memory means. , correcting the amount of light from the light source according to the aperture amount.

[Function] In this way, by changing the signal output level determining factors consisting of the amplification amount of each color image signal, the amount of illumination light, etc. in accordance with the change in the aperture amount of the illumination means, even if the aperture plate is used to change the optical path of the illumination light, Even if a light amount diaphragm mechanism having an extremely simple structure of advancing and retracting is used, the color balance of each color image signal is improved, and the color reproducibility of a color image displayed on a display screen is significantly improved.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

5 to 8 show a first embodiment of the present invention, and FIG. 5 first shows the structure of the illumination means.

As shown in the figure, the illumination light has a light source section 30 composed of an illumination lamp 30a and a concave mirror 30b for converting the illumination light from the illumination lamp 30a into parallel light.
Illumination light irradiated from 0 is condensed through a condenser lens 31 and is made incident on a light guide 32. Then, the light source section 3 of the condenser lens 31
A light quantity diaphragm plate 33 is provided at the 0 side position, and a rotating color filter 34 is interposed between the condenser lens 31 and the light guide 32. In these respects, there is no particular difference from the prior art described above.

[The rotating color filter 34 is rotatably driven by a motor 35, and the rotating color filter 34 is provided with a rotational phase detector 36 for detecting its rotational phase. This rotational phase detector 36
Detection is made as to which wavelength light of R, G, or B is being used for illumination, and the imaging system described later is controlled as R2O and B enable signals.

Further, the aperture plate 33 is moved forward and backward into the optical path of the illumination light by a rack-pinion mechanism 37 consisting of a rack 37a and a pinion 37b. In order to detect the angle of this pinion 37b, a rotation angle detector 38 consisting of a potentiometer or the like is provided. It is now output as follows.

While the above-mentioned illumination means is illuminating, the CCD captures R, G, and B color images of the observation target area, and predetermined image processing is performed.This imaging system itself is based on the above-mentioned conventional technology. Since there is no particular difference from that shown in FIG.

However, the auto white balance mechanism connected to the 0 section on the output side of the gain control amplifier 14 in FIG. 2 described above is configured as shown in FIG. 6.

That is, the output signal from the gain control amplifier 14 is subjected to area integration by the integrating circuit 40, the image signal of the G field is held by the sample hold circuit 41, and the image signals of each of the R and G fields are captured. Sometimes, by inputting the reference signal held in the sample and hold circuit 41 to the gain value calculation circuit 42, the ratio of the gain value of the R field to the G field, R/G, and the ratio of the gain value of the B field, B/ There is no particular difference from the prior art described above in that G is calculated, the result of the calculation is output as a digital signal, and this is latched by the latch circuits 43R and 43B, respectively. Further, it is similar to the prior art in that an auto color controller 44 is provided to control the signal processing described above.

However, after the output signals from the latch circuits 43R and 43B described above are converted into analog signals by the D/A converters 45R and 45B, the multiplier type D/A converter 46R946B
By using this signal as a reference signal and multiplying it by the gain correction values for the R field and B field, respectively, the gain control signals of the R field and B field corrected according to the light aperture value are sent to the gain control amplifier. It has been made so that it can be done manually. That is, using the gain value of the G field as a reference, the deviation of the gain values of the R field and the B field with respect to this reference gain value is determined. The gain correction value based on the deviation of the R field and the B field is recorded in advance in each memory 47R, 47B, and the position signal of the aperture plate 33 is taken in by the rotation angle detector 38 via the buffer circuit 48. A gain correction value corresponding to the position of the aperture plate 33 can be read out to the multiplication type D/A converters 46R and 46B via the I10 port 49.

Here, the gain correction values for the R field and the B field are determined by changing the aperture position by the aperture plate 33 so that the white balance can be achieved based on the signal level of the G field at each aperture position.
Gain correction value based on B field signal level, R/G
and calculate B/G. For example, as shown in FIG. 7, the aperture amount by the aperture plate 33 is 4/4 and 3/4.
, 2/4, 1/4 gain correction value R/
By calculating G and B/G and performing interpolation from these data, as shown by the dotted line in Fig. 7, using the G data as a reference, as shown by the dashed line in the same figure,
Draw R/G correction data and /G correction data as shown by dotted lines, and store these in memories 47R and 47, respectively.
All you have to do is write it to B. Data for this gain correction value can be created by operations as shown in FIG.

Then, the gain correction value data created in this way is stored in, for example, a battery backup RAM.

If you record it in a nonvolatile memory such as an EEPROM or memory card, you can simply create -degree data and use it repeatedly.
It is possible to reduce the burden of white balance adjustment operations during actual observation.

As a result, when actually observing the observation target part,
A well-known automatic light amount adjustment means operates according to the distance to the observation target area, so that the area is illuminated with the optimal amount of illumination light.
The aperture plate 33 automatically moves forward and backward into the optical path. The signal at the position of the aperture plate 33 is input to the buffer circuit 48 as an aperture amount signal. At the same time, the rotational phase of the rotational color filter 34 is detected by the rotational phase detector 36, and the rotational phase of the rotational color filter 34 is detected by the rotational phase detector 36.

The B enable signals are sequentially input to the auto color controller 44.

Therefore, from the auto color controller 44, R, G
, B, and the amplification gain values of the R field and B field with reference to the G field so that the normal auto white balance can be performed, that is, the balance of each color image signal according to the filter characteristics and COD sensitivity characteristics. The calculation results are input to multiplication type D/A converters 46R and 46B, respectively. Further, when the aforementioned aperture amount signal is taken in from the buffer circuit 48, the R field and B field are stored from the memories 47R and 47B.
A gain correction value signal corresponding to the aperture amount in the field is input to multiplication type D/A converters 46R and 45B,
A signal gain value corrected according to the aperture amount is calculated, and R and G corrected in this way.

The gain control signal of each field of B is outputted to the gain control amplifier 14 (see FIG. 2).

Therefore, the R, G, and B field images No. 4g have accurate color balance, and when a composite video signal is formed based on this signal and reproduced by a display device, its color reproducibility is It becomes extremely good.

Next, FIG. 9 shows a second embodiment of the present invention. In this embodiment, a microprocessor system with computing power is used as the auto color controller 50, and this auto color controller 50 controls the amount of light. R, G with the light amount corrected according to the aperture amount by the aperture coffin.
, B is shown in which gain control signals for each color image signal can be input to a gain control amplifier 51.

As is clear from the figure, the output signal of the gain control amplifier 51 is integrated by the integrating circuit 52.
The G field signal is held in the sample hold circuit 53 to be used as a reference signal, and this reference signal and the R and B field signals are input to the gain value calculation circuit 54 to calculate R/G and B/G. Calculate the gain value. Then, this calculation result is sent to the auto color controller 5.
I am trying to input it to 0.

On the other hand, the memory 55 stores R/G correction data and B/G correction data obtained using the same method as in the first embodiment, and includes R, G, and B enable signals. When the aperture amount signal is input from the buffer circuit 56 to the I10 port 57, this R/G and B/G correction data is accessed from the memory 55, and the R, B/G correction data is input from the D/A converter 58.
A gain control signal for the image signal of each field in G and B is calculated. Then, it becomes possible to input the corrected state according to the aperture amount to the gain control amplifier 51, and it becomes possible to significantly improve the color reproducibility of the image displayed on the display device.

Next, FIGS. 10 to 13 show a third embodiment of the present invention, and in this embodiment, R, G.

In order to mutually adjust the image signal levels of each color of B, the brightness of the illumination light irradiated toward the observation target area, that is, the amount of illumination light is controlled.

As is clear from FIG. 10, the illumination lamp 30a constituting the light source section 30 is connected to a light source light amount adjustment circuit 50 for adjusting its light amount. By controlling the output voltage or output current of this light source light amount adjustment circuit 60, the brightness of the illumination lamp 30a can be changed. Therefore, the brightness of the illumination lamp 30a is adjusted according to the aperture amount by the aperture plate 33.
The brightness of the illumination light in each of the R, G, and B wavelength regions can be changed.

Here, as is clear from FIG. 11, the auto white balance mechanism used is similar to that of the prior art shown in FIG. 3. Therefore, in the following description, regarding the same or equivalent components as 3U:A,
The same reference numerals are given and the explanation thereof will be omitted. However, depending on the aperture position output from the gain value calculation circuit 23, the G
R/G and B/G based on field signal level
A signal regarding the output ratio of is input to the arithmetic processing unit 62 via the I10 boat 61, and the arithmetic processing unit 62 calculates R and B light amount correction values so as to maintain white balance.
This light amount correction value data is written into the memory 63.

The procedure for sampling the light amount correction value data and interpolating the sampled data described above is essentially the same as in the first embodiment, so a flowchart is shown in FIG. Explanation will be omitted. In this way, brightness correction value data is created, and this data becomes as shown in FIG. 13.

With this configuration, when actually observing the image of the observation target area, each enable signal of R, G, and B that is output in five by the rotation of the rotating color filter 34 and the aperture amount by the aperture plate 33 are used. The signals are directly transmitted to the memory 63 via the buffer circuit 64, and the R and G signals at the aperture amount are transmitted directly from the memory 63 to the memory 63.

Data regarding the brightness of the illumination lamp 30a in each field of B is read out, and this data is sent to the D/A converter 6.
5 converts it into an analog signal, and sends it to the light source light adjustment circuit 6.
By inputting 0, the brightness of the illumination lamp 30a can be corrected so that the levels of the R, G, and B color image signals match.

■Effects of the Invention] As explained above, the present invention provides a method for adjusting the image signals of R, G, and B according to the aperture amount in order to correct the shift in color balance that occurs depending on the aperture amount in the illumination means. R,G,
The elements that determine the output level of each color image signal of B are changed in accordance with the aperture amount, and the elements that determine the color image signal level, such as the light source light amount and signal amplification gain, are corrected, so that the light amount The aperture plate is moved forward and backward with respect to the optical path of illumination light. Even when a light aperture mechanism with a simple structure is used, the white balance of the image can be maintained, and an image with extremely good color reproducibility can be formed.

[Brief explanation of the drawing]

Figures 1 to 3 show the prior art, in which Figure 1 is an explanatory diagram of the configuration of the illumination means, Figure 2 is a block diagram showing the configuration of the imaging system, and Figure 3 is the configuration of the auto white balance mechanism. The block diagram shown in FIG. 4 shows the aperture amount of illumination light and R
, G, B diagram showing the relationship with the attenuation rate of each wavelength light, 5th
8 to 8 show the first embodiment of the present invention, FIG. 5 is an explanatory diagram of the configuration of the illumination means, FIG. 6 is a block diagram showing the configuration of the auto white balance mechanism, and FIG. Line segments showing gain correction value data, FIG. 8 is a flowchart showing the procedure for creating gain value correction data, FIG. 9 is a block diagram of an auto white balance mechanism showing a second embodiment of the present invention, and FIG. 10 Figures 13 to 13 show a third embodiment of the present invention, in which Figure 10 is an explanatory diagram of the configuration of the illumination means, Figure 11 is a block diagram showing the configuration of the auto white balance mechanism, and Figure 12 is a diagram illustrating the configuration of the auto white balance mechanism. FIG. 13 is a flowchart showing the procedure for creating correction data, and a line diagram showing gain correction value data. 30: light source section, 30a: illumination lamp, 30b: concave mirror,
31: Condenser lens, 32 Ni-light guide, 33:
Light amount diaphragm plate, 34: Rotating color filter, 35: Motor, 36: Rotating phase detector, 37: Rack-binion mechanism, 38: Rotating angle detector, 40.52: Integrating circuit, 41
．． 53 + sample hold circuit, 42.54 gain value calculation circuit, 43R, 43B: latch circuit, 44°50
: Auto color controller, 46R, 46B : Multiplying type D/A converter, 47R, /17B, 55.6
3: Memory, 60: Light source light amount adjustment circuit, 62: Arithmetic processing unit.

Claims (4)

[Claims] (1) An illumination means having a light amount diaphragm plate that can move forward and backward with respect to the illumination optical path from the light source, and configured to sequentially repeat illumination of the observation target area with light in each of the R, G, and B wavelength regions; R
, G, and B color images, and a processor that processes the color image signals output from the solid-state image sensor. In order to correct the color balance according to the difference in the attenuation rate of each wavelength light of B, the deviation according to the aperture setting of the elements that determine the output level of the R, G, and B color image signals is measured in advance. A color balance correction method for a color image, characterized in that, during actual photographing, a deviation amount is corrected for this signal output level determining element. (2) An illumination means having a light quantity diaphragm plate that can move forward and backward with respect to the illumination optical path from the light source, and configured to sequentially illuminate the observation target area with light in each of the R, G, and B wavelength regions;
, G, and B color images, and a processor that processes color image signals output from the solid-state image sensor. In order to correct this, the gain correction value of the amplifying means for each color image signal of R, G, and B in the processor is measured in advance according to the aperture amount and stored in the memory means, and the gain correction value is stored in the memory means at the time of imaging. A color balance correction method for a color image, characterized in that value data is read out and the amount of amplification in each color image signal is corrected according to the amount of aperture. (3) An illumination means having a light quantity diaphragm plate that can move forward and backward with respect to the illumination optical path from the light source, and configured to sequentially illuminate the observation target area with light in each of the R, G, and B wavelength regions;
, G, and B multicolor images, and a processor that processes color image signals output from the solid-state image sensor, and a color balance shift that occurs depending on the aperture amount by the light aperture plate. In order to correct this, the amount of illumination light corresponding to the aperture amount when forming image signals for each color of R, G, and B is measured in advance and stored in a memory means, and when capturing an image, data on the amount of illumination light is read from the memory means. A color balance correction method for a color image, characterized in that the amount of light from the light source is corrected according to an aperture amount. (4) The color balance correction method for a color image according to any one of claims (1) to (3), characterized in that a non-volatile memory is used as the memory means.