JP2003010114A - Electronic endoscope system and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intracorporeal tissue image with superior color reproducibility in an electronic endoscope system. SOLUTION: An optical filter for attenuating a red light component is used for the emitting light from a white light source having a wave length-reflectance characteristic L1, to become a wave length-reflectance characteristic L2. Intracorporeal tissues each having the dominance in a red component are irradiated with the light having the wave length reflectance characteristic L2, and the red components in the images of those intracorporeal tissues are restrained to obtain the images of the intracorporeal tissues each with superior color reproducibility.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electronic endoscope apparatus and a control method thereof.

[0002]

2. Description of the Related Art An electronic endoscope apparatus is a device for imaging a body tissue such as an esophagus, a stomach wall, and an intestinal wall in color, and detecting a lesion based on the color, shape, etc. of the obtained color body tissue image. is there. The in-vivo tissue image obtained by the electronic endoscope apparatus is used for lesion detection, and therefore relatively high color reproducibility and image quality are required.

Further, there are also problems that the SN ratio of the obtained in-vivo tissue image is poor and the gradation is insufficient.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to improve the image quality of an in-vivo tissue image obtained by imaging, and it is an object of the present invention to improve color reproducibility, SN ratio and gradation.

An electronic endoscope apparatus according to the present invention includes an illumination optical system including a light source for illuminating internal tissue, a solid-state electronic image pickup device for capturing internal tissue illuminated by the light source of the illumination optical system, and has a color internal body. A color imaging means for outputting a plurality of color component data representing a tissue image, and an image of a body tissue (including a normal body tissue, a body tissue of a lesion, and a body tissue which can be regarded as a body tissue) before the examination by the color imaging means When this is done, it is characterized by comprising adjustment means for setting the level of each of the color component data output from the color image pickup means to a predetermined ratio.

The present invention also provides a control method suitable for the electronic endoscope apparatus. That is, this method illuminates body tissue using a light source, images the body tissue illuminated by the light source using a solid-state electronic imaging device, and obtains a plurality of color component data representing color body tissue, The level of each of the color component data obtained when the internal tissue is imaged before the examination is set to a predetermined ratio.

According to the present invention, the body tissue is illuminated by the light source before the examination using the electronic endoscope apparatus. Illuminated body tissue is imaged by the solid-state electronic image pickup device, and a plurality of color component data representing the body tissue image (data of each independent element constituting the color image. For example, RGB three primary color image) Each image data of R, G and B in the data, cyan Cy, magenta Mg, yellow Y
e, each image data of cyan, magenta, yellow, and green in complementary color image data of green G) is obtained. The plurality of color component data are adjusted so that their levels have a predetermined ratio. When the adjustment before the examination is performed, the examination (imaging of the body tissue to be inspected) using the electronic endoscope device in the adjusted state is performed.

As described above, since the internal tissues are the esophagus, the stomach wall, the intestinal wall, etc. in which blood vessels are stretched, the internal tissue image obtained by imaging is affected by blood passing through the blood vessels. Since blood is red due to hemoglobin, red is predominant in the body tissue image as well, and saturation of the signal representing red is likely to occur, resulting in poor color reproducibility as described above.

According to the present invention, when the internal tissue is imaged before the examination, the levels of the plurality of color component data output from the solid-state electronic image pickup device have a predetermined ratio (for example, a ratio such that the levels are substantially equal to each other, proximity to each other). Of the color components output from the image sensor even when the internal tissue in which red is dominant is imaged. -It can be prevented that only data (color signal) is easily saturated. An in-vivo tissue image with good color reproducibility can be obtained.

For example, the adjusting means may be arranged such that, when the color image pickup means picks up an image of a body tissue, the level of each color component data output from the color image pickup means becomes a predetermined ratio. It is a first optical filter that attenuates the red component of the light emitted from the light source of the illumination optical system.

Since the red component of the light emitted from the light source can be attenuated, when the internal tissue is imaged before the examination, each color
The level of component data becomes a predetermined ratio.
It is possible to prevent only one of the color component data output from the image sensor from being easily saturated,
An in-vivo tissue image with good color reproducibility can be obtained.

The electronic endoscope apparatus includes a so-called simultaneous type and a frame sequential type. In the simultaneous electronic endoscope apparatus, a color filter is provided on the light receiving surface of the solid-state electronic image pickup device. In this case, the adjusting means adjusts the color component data so that the levels of the respective color component data output from the color image capturing means become substantially equal when the color image capturing means images the internal tissue. The spectral characteristics of the filter are defined.

The color filter may be of the three primary colors of RGB, or may be of the complementary colors of cyan, magenta, yellow and green.

Further, the color image pickup means is provided with a third optical filter for color-converting the light emitted from the light source of the illumination optical system into a plurality of color lights as in the case of a frame sequential electronic endoscope apparatus. Alternatively, the plurality of color component data may be obtained by imaging the body tissue illuminated by the plurality of color lights with the individual electronic image pickup device.

In this case, the adjusting means sets the color component data levels output from the color image pickup means to be substantially equal to each other when the color image pickup means picks up an image of a body tissue. The spectral characteristics of the third optical filter will be defined.

Before the examination, the adjusting means emits light that makes the levels of the respective color component data output from the color imaging means substantially equal when the color imaging means images the internal tissue. It may be a light source of the illumination optical system that emits light.

A second optical filter for attenuating the blue component and the green component of the light emitted from the light source of the illumination optical system with an attenuation amount smaller than the attenuation amount of the red component may be further provided.

This is because depending on the characteristics of the color image pickup means, the levels of the color component data output from the color image pickup means may become more equal by attenuating the blue and green colors.

The first, second and third optical filters may be used alone or in combination.

[0020]

Description of Embodiments First, the principle of the electronic endoscope according to this embodiment will be described.

The electronic endoscope, for example, when imaging the inside of the stomach as a body tissue, uses a video scope (video scope).
insert) from the mouth. The video scope is
It reaches the inside of the stomach through the esophagus.

Light emitted from the light source is guided to the tip of the video scope by a light guide inside the video scope. Light is emitted from the tip of the light guide,
Illuminate the stomach wall. The light reflected from the stomach wall is imaged on the light receiving surface of the CCD provided at the tip of the video scope. C
Color image data representing an image of the stomach wall is output from the CD.

A color image represented by the output color image data is displayed on the display screen of the display device. The doctor determines the presence or absence of a lesion by looking at the color image displayed on the display screen of the display device.

FIG. 1 shows a white light source (xenon lamp, halogen lamp, etc.) used for illumination light of an electronic endoscope.
Is a wavelength-light intensity characteristic (shown by a solid line L1). The horizontal axis represents wavelength and the vertical axis represents relative intensity.

The wavelengths are distributed over the entire range from about 400 nm to about 700 nm. The broken line L2 indicates the wavelength-light intensity characteristic when the output light from the white light source is filtered by the optical filter, as described later.

FIG. 2 shows the wavelength-reflectance characteristic of normal body tissue. The horizontal axis is the wavelength and the vertical axis is the reflectance.

Since blood vessels extend around the surface of body tissues, blood passing through the blood vessels affects the reflectance.
Blood is red due to the effect of hemoglobin. As a result, the reflectance of body tissues is red (6
(14 nm or more) is higher.

FIG. 3 shows an R provided on the light receiving surface of the CCD.
7 shows wavelength-transmittance characteristics of a GB three-primary color filter. The horizontal axis is the wavelength and the vertical axis is the transmittance.

Blue wavelengths (eg 465 nm), green wavelengths (eg 539 nm) and red wavelengths (eg 614n)
m) The transmittance of light of wavelengths in the vicinity is high.

When a body tissue is illuminated by using a light source having such wavelength-transmittance characteristics and a CCD and the body tissue is imaged, the spectral characteristics of the light source, the reflectance characteristic of the body tissue, and the spectral intensity of the CCD. The amount of signal charge depending on the product of C
Stored on CD. Therefore, as shown in FIG. 4, the closer the color is to the red component, the larger the amount of signal charges accumulated. That is, the amount of the signal charge showing the red component is the largest, the amount of the signal charge showing the green component is the next largest, and the amount of the signal charge showing the blue component is the smallest.

The blue component and the green component have a smaller amount of signal charges accumulated as compared with the red component, so that the SN ratio is relatively worse than that of the red component. As a result, the SN ratio of the obtained in-vivo tissue image also deteriorates. Since the red component signal is large, saturation tends to occur and accurate color reproduction cannot be achieved.

Further, since the amount of signal charge showing the red component is the largest, the amount of signal charge showing the green component is the next largest, and the amount of signal charge showing the blue component is the smallest, therefore, for example, 1024 When the gradation can be expressed, the red component can be expressed using the 1024 gradations.
It is not possible to use all 1024 gradations for the blue component, and it is possible to express only 100 to 200 gradations. In this way, the gradation expression also deteriorates.

What has been described above is that the RGB on the light receiving surface of the CCD is
However, the same applies to the case where complementary color filters of cyan, magenta, yellow and green are provided on the light receiving surface of the CCD.

FIG. 5 shows the spectral characteristics of the complementary color filter provided on the light receiving surface of the CCD. The horizontal axis is the wavelength and the vertical axis is the transmittance.

Cyan wavelengths (eg 495 nm), green wavelengths (eg 539 nm), magenta wavelengths (eg 455 nm and 610 nm) and yellow wavelengths (eg
The transmittance of light of 545 nm) is high.

Even if the internal tissue is imaged using the complementary color filter having such characteristics, the amount of signal charges accumulated in the CCD increases as the color component has a wavelength closer to the wavelength of the red component. That is, the amount of signal charges accumulated in the CCD increases as the color components of yellow and magenta increase, and the amount of signal charges accumulated in the CCD decreases as the color components having wavelengths farther from the wavelength of the red component increase. That is, the cyan and green color components have a smaller amount of signal charges accumulated in the CCD.

Even if complementary colors are used for the color filters, accurate color reproduction is difficult. It is also difficult to obtain a good SN.

In this embodiment, as shown by the broken line in FIG. 1, the spectral characteristic of the light emitted from the light source is adjusted so that the light intensity of the red component becomes weaker (the portion of the wavelength higher than the solid line A). . Further, preferably, as shown by the solid line B, the spectral characteristic of the emitted light of the light source is adjusted before the actual inspection so that the reflectance of the blue component is slightly weakened. Therefore, the light emitted from the light source has a spectral characteristic represented by the wavy line L2. The examination is performed using a calibrated electronic endoscope.

When the reflectance characteristics of the light emitted from the light source are adjusted in this way and an actual experiment is performed, as shown in FIG.
The difference in the amount of signal charges accumulated corresponding to each of the green color component, the cyan color component, the magenta color component, and the yellow color component was reduced. When taking images of living tissue,
It can be seen that the saturation of yellow and magenta was alleviated and the color reproduction rate was improved. Not only for complementary color filters, but for RGB three primary color filters as well,
It can be understood that the color reproducibility is improved.

FIG. 8 is a block diagram showing the electrical construction of an electronic endoscope apparatus capable of adjusting the spectral characteristics of the light emitted from the light source. This electronic endoscope apparatus is a so-called simultaneous endoscope, in which RGB primary color filters are arranged on the light receiving surface of the CCD.
Of course, complementary color filters of cyan, magenta, yellow and green may be arranged.

The electronic endoscope system comprises a secondary circuit 1, a patient circuit (primary circuit) 20, and a slender and flexible video scope 30. The secondary circuit 1 has a display device.
40 are connected. The secondary circuit 1 and the patient circuit 20 are
It is placed on a table and operated by a doctor.
When the patient lies on the bed, for example, when imaging the stomach wall, the doctor inserts the videoscope 30 through the mouth. The video scope 30 passes through the esophagus, and the tip of the video scope 30 reaches the inside of the stomach. Video scope 30
As will be described later, a CCD 33 is provided at the tip of the, and the CCD 33 captures an image of the stomach wall as a body tissue Ob.

The operation of the secondary circuit 1 is controlled by the CPU 7.

The secondary circuit 1 is provided with an illumination light source 2 for illuminating internal tissues. The light emitted from the illumination light source 2 is condensed by the condenser lens 3. A diaphragm 4 whose diaphragm value is set by a diaphragm motor 5 is provided on the front surface of the condenser lens 3. The light condensed by the condenser lens 3 passes through the diaphragm 4 and is given to the optical filter 6.

As described with reference to FIG. 1, the optical filter 6 outputs the light emitted from the light source 2 having the wavelength-light intensity characteristic indicated by the solid line L1 and the wavelength-light intensity characteristic indicated by the broken line L2. It has an attenuation characteristic that makes it have light. As a result, when the internal tissue is illuminated using the transmitted light of the optical filter 6, the image data of each of R, G and B (color component
(Data) becomes almost the same level when the internal tissue Ob is normal. An image having good color reproducibility and sufficient gradation expression can be obtained. The optical filter 6 may be either a reflection type or an absorption type.

The light transmitted through the optical filter 6 is the patient circuit.
It is guided to the rear end surface (the surface on the secondary circuit 1 side) of the light guide 11 arranged in the video scope 20 and the video scope 30.
The illumination light propagates in the light guide 11 and is emitted from the front end surface of the light guide 11. An illumination lens 31 is arranged in front of the front end face of the light guide 11. Light
The light emitted from the guide 11 illuminates the internal tissue Ob by the illumination lens 31.

The reflected light of the internal tissue Ob is condensed by the objective lens 32. As a result, an image representing the internal tissue Ob is formed on the light receiving surface of the CCD 33. As described above, the RGB three primary color filters are arranged on the light receiving surface of the CCD 33, and the RGB representing the image of the internal tissue Ob is displayed.
A color video signal is output.

The RGB color video signal output from the CCD 33 is amplified by the amplifier circuit 21 provided in the patient circuit 20, and is subjected to CDS (correlated double sampling) / AGC.
(Auto gain control) Input to circuit 22.
The CDS / AGC circuit 22 performs correlated double sampling processing and gain adjustment processing, and inputs the analog / digital conversion circuit 23.

The RGB color image data converted in the analog / digital conversion circuit 23 is passed through the insulating element 10 provided between the patient circuit 20 and the secondary circuit 1 to the signal processing circuit 9 of the secondary circuit 1. To enter. Signal processing circuit 9
In the above, predetermined signal processing such as gamma correction, generation of luminance data Y and color difference data BY and RY, digital / analog conversion, etc. is executed, and analog luminance signal Y and analog color difference signals BY and RY are executed. Is output. The analog luminance signal Y and the analog color difference signals BY and RY output from the signal processing circuit 9 are given to the display device 40, and an image representing the body tissue Ob is displayed on the display screen.

As described above, since the wavelength characteristics of the light emitted from the light source 2 are changed by the optical filter 6, the display device
The image of the internal tissue Ob displayed on the 40 display screen has good color reproducibility and gradation. It is possible to accurately detect a lesion.

Further, in the above-mentioned embodiment, the wavelength-light intensity characteristic of the output light from the light source 2 is changed by using the optical filter 6, but the wavelength-light intensity characteristic shown by the broken line L2 in FIG. You may use the light source which it has. In that case, needless to say, the optical filter 6 becomes unnecessary.

Furthermore, by changing the spectral sensitivity characteristics of the CCD 33, the levels of the RGB image data obtained when the normal body tissue Ob is imaged may be made substantially equal. For example, the wavelength-light intensity characteristic of the light source 2, the wavelength-reflectance characteristic of the body tissue Ob, and the CCD
The product of the spectral sensitivity characteristics of 33 is calculated, and actual simulation is performed so that the RGB image data are at substantially the same level, and the characteristics of the CCD 33 (the transmission characteristics of the color filter arranged on the light receiving surface of the CCD 33). ) Will be decided. As an example, if the color filter arranged on the CCD 33 is as shown in FIG. 3, it will be as shown by the broken line L3. If the color filter arranged on the CCD 33 is as shown in FIG. 5, it will be as shown by the broken line L4.

FIG. 9 shows another embodiment, and is a block diagram showing the electrical construction of a so-called frame-sequential type electronic endoscope. In this figure, the same components as those shown in FIG. 8 are designated by the same reference numerals and the description thereof will be omitted.

In the frame-sequential type electronic endoscope, the secondary circuit 1A filters the light that has passed through the diaphragm 4 and is rotatable by the drive motor 19 so as to be rotatable.
Is provided. This color filter plate 12 is shown in FIG.
As shown in Fig. 5, the region is circular and has the characteristic of transmitting the red component light every 120 degrees (R region), the region having the characteristic of transmitting the green component light (G region) and the blue component. It is divided into three regions, a region (B region) having a property of transmitting light. Every 1/60 second, the drive motor 19 rotates the color filter plate 12 so that light passes through the next region. From the color filter plate 12, light having a red component, light having a green component, and light having a blue component are transmitted at a cycle of 1/60 second.

FIG. 11 shows the transmitted light intensity of the color filter plate 12. In the color filter plate 12, the transmittance of the R region is set so that the light intensity of the transmitted red component becomes smaller than the light intensity of each of the blue component and the green component. As a result, the red component in the image showing the internal tissue Ob is weakened. Since the signal saturation of the red component is relaxed, the color reproducibility of the image of the internal tissue Ob is improved.

The light transmitted through the color filter plate 12 propagates through the light guide 11 and illuminates the internal tissue Ob by the illumination lens 31 as described above. The reflected light from the body tissue Ob is condensed by the objective lens 32, and the image of the body tissue Ob is formed on the light receiving surface of the CCD 33A. CCD33A is
Unlike the CCD 33 which is an image pickup device for black and white and is used in a simultaneous electronic endoscope system, a color filter is not attached on the light receiving surface. However, as described above, by using the color filter plate 12, 1 /
Every 60 seconds, video signals representing the red component image, the green component image, and the blue component image of the image of the internal tissue Ob are sequentially output from the CCD 33A.

As described above, the video signal sequentially output from the CCD 33A has the amplifier circuit 21, the CDS / ADC circuit 22,
It is input to the synchronization circuit 17 included in the secondary circuit 1A via the analog / digital conversion circuit 23 and the insulating element 10.

The synchronizing circuit 17 includes a changeover switch 13 capable of changing over the r terminal, the g terminal and the b terminal. The r terminal is connected to the R data memory 14, the g terminal is connected to the G data memory 15, and the b terminal is connected to the B data memory 16.

When the image data representing the red color component of the body tissue Ob is input to the synchronization circuit 17, the changeover switch 13 is switched so that the r terminal is connected. Similarly,
The changeover switch 13 is switched such that the g terminal is connected when image data representing the green component of the body tissue Ob is input, and the b terminal is connected when image data representing the blue component of the body tissue is inputted. As a result, the R data memory 14 stores the image data representing the red color component of the body tissue Ob, and the G data memory 15 stores the body tissue O.
Image data representing the green color component of b is stored, and B data
The memory 16 stores image data representing the blue color component of the body tissue Ob.

Image data representing the red component of the body tissue Ob stored in the R data memory 14, G data memory 15
The image data representing the green color component of the body tissue Ob stored in the memory and the image data representing the blue color component of the body tissue Ob stored in the B data memory 16 are read out and input to the signal processing circuit 18A. As described above, the signal processing circuit 18A performs signal processing such as gamma correction, generation of luminance data Y and color difference data BY and RY, and digital / analog conversion.

The luminance signal Y and the color difference signals BY and RY output from the signal processing circuit 18A are applied to the display device 40. On the display screen of the display device 40, the body tissue O
The image of b will be displayed.

Since the characteristics of the color filter plate 12 are determined so that the transmitted red light component is attenuated, the displayed image has good color reproduction.

In the above-described embodiment, the transmittance of the R region of the color filter plate 12 is set so that the red light component is attenuated, but the size of the R region can be set to G without changing the transmittance. It may be smaller than the size of the region and the size of the B region. Further, the time for irradiating the R region may be shorter than the time for irradiating the G region and the B region. Further, the light source 2 may be adjusted so that the intensity of light transmitted through the R region is lower than that of light transmitted through the G region and the B region. In short, the levels of the R image data, G image data, and B image data output from the CCD 33A when a normal body tissue Ob is imaged are expressed in color so that each image data can express a desired gradation. The level of component data may be set to a predetermined ratio.

Preferably, the red component (red component or magenta and yellow component) is reduced (the red component is reduced from the component ratio of each color for obtaining a normal color image).
More preferably, of the light incident on the charge conversion surface of the CCD, the incidence of light of 610 nm or more should be reduced.

[Brief description of drawings]

FIG. 1 shows a wavelength-light intensity characteristic of a white illumination light source.

FIG. 2 shows wavelength-reflectance characteristics of internal tissues.

FIG. 3 shows wavelength-transmittance characteristics of RGB primary color filters.

FIG. 4 shows accumulated amounts of signal charges corresponding to R color component, G color component, and B color component.

FIG. 5 shows wavelength-transmittance characteristics of a complementary color filter.

FIG. 6 shows accumulated amounts of signal charges corresponding to cyan color component, green color component, magenta color component, and yellow color component.

FIG. 7 shows accumulated amounts of signal charges corresponding to cyan color component, green color component, magenta color component, and yellow color component.

FIG. 8 is a block diagram showing an electrical configuration of a simultaneous electronic endoscope.

FIG. 9 is a block diagram showing an electrical configuration of a frame sequential electronic endoscope.

FIG. 10 is an example of a color filter plate.

FIG. 11 shows light intensities of R color component, G color component, and B color component.

[Explanation of symbols]

1,1A secondary circuit 2 light sources 6 Optical filter (first optical filter) 7 CPU 11 Light guide 12 Color filter plate (third optical filter) 17 Synchronization circuit 18 Drive motor 20 patient circuit 30,30A video scope 33, 33A CCD Wavelength-light intensity characteristics of L1 white light source L2 wavelength-light intensity characteristics after adjusting the light emitted from the white light source Ob body tissue

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 9/04 H04N 9/04 Z F term (reference) 2H040 GA03 GA06 GA11 2H048 CA01 CA14 CA18 FA01 FA09 FA15 4C061 CC06 LL02 MM03 MM05 NN01 TT03 5C054 AA05 CA04 CC03 EB05 ED02 ED04 ED13 EF02 FB03 HA12 5C065 AA05 BB01 BB12 CC02 CC03 DD02 EE06 EE07 GG12 GG15 GG18 GG26 GG32 GG44

Claims (7)

[Claims] 1. An illumination optical system including a light source for illuminating a body tissue, a plurality of colors representing a color body tissue image including a solid-state electronic image pickup device for imaging the body tissue illuminated by the light source of the illumination optical system. A color image pickup means for outputting component data, and a level of each of the color component data outputted from the color image pickup means when the color image pickup means picks up an image of a body tissue before the examination. An electronic endoscopic device having an adjusting means for setting to. 2. The adjusting means is configured such that, when the color imaging means images an internal tissue, the level of each color component data output from the color imaging means has a predetermined ratio. The electronic endoscope apparatus according to claim 1, wherein the electronic endoscope apparatus is a first optical filter that attenuates a red component of light emitted from a light source of the illumination optical system. 3. The second optical filter according to claim 2, further comprising a second optical filter that attenuates the blue component and the green component of the light emitted from the light source of the illumination optical system with an attenuation amount smaller than that of the red component. The described electronic endoscope apparatus. 4. A color filter is provided on the light-receiving surface of the solid-state electronic image pickup device, and the adjusting means outputs each from the color image pickup means when the color image pickup means picks up an image of a body tissue. So that the level of the color component data of above becomes a predetermined ratio,
The electronic endoscope apparatus according to claim 1, wherein the spectral characteristics of the color filter are defined. 5. The color image pickup means color-converts light emitted from a light source of the illumination optical system into a plurality of color lights.
Is to obtain the plurality of color component data by imaging the body tissue illuminated by the plurality of color lights with the solid-state electronic image pickup device, and the adjusting means includes the color image pickup device. The spectral characteristic of the third optical filter is determined so that the levels of the respective color component data output from the color imaging means have a predetermined ratio when the means images the body tissue. The electronic endoscope apparatus according to claim 1, wherein 6. The adjusting means emits light such that the level of each color component data output from the color image pickup means when the color image pickup means picks up an image of a body tissue is a predetermined ratio. The electronic endoscope apparatus according to claim 1, which is a light source of the illumination optical system that emits light. 7. A light source is used to illuminate body tissue, and the body tissue illuminated by the light source is imaged using a solid-state electronic image pickup device to obtain a plurality of color component data representing the body tissue in color for inspection. A method of controlling an electronic endoscopic apparatus, wherein the level of each of the color image data obtained when the internal tissue is imaged is set to a predetermined ratio.