Endoscope system and operating method thereof

An observation object is imaged under irradiation with oxygen saturation level measurement light to obtain a first image signal, and the observation object is imaged under irradiation with white light to obtain a second image signal. A normal light image is produced from the second image signal. An oxygen saturation level is calculated from the first and second image signals. The calculated oxygen saturation level is imaged in an oxygen saturation image. By superimposing the normal light image on the oxygen saturation image, an emphasized oxygen saturation image is produced. In the emphasized oxygen saturation image, an abnormal area in which a calculation result of the oxygen saturation level is likely to be abnormal is emphasized by its brightness. The produced emphasized oxygen saturation image is displayed on a display device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an endoscope system for producing a biological function information image, which images biological function information including the amount of hemoglobin in blood, an oxygen saturation level, and the like, and an operating method thereof.

2. Description Related to the Prior Art

In recent medical care, an endoscope system that is provided with a light source device, an endoscope device, and a processor device is widely used. In an endoscopic diagnosis using this endoscope system, not only normal light observation that uses white light being broad band light as illumination light, but also special light observation that emphasizes a blood vessel of an observation object in display by using narrow band light in a narrowed wavelength band has become widespread.

Besides the special light observation, it is performed to calculate biological function information, including the amount of hemoglobin, an oxygen saturation level, and the depth of a blood vessel, from an image signal obtained by the endoscope system with the use of a light absorption property of the blood vessel and a scattering property of living body tissue, and image the calculated biological function information. For example, a pseudo color oxygen saturation image, which is colored in accordance with the magnitude of the oxygen saturation level, is produced in Japanese Patent No. 2648494. This oxygen saturation image facilitates finding out a cancer being in a hypoxic state.

Since the biological function information is obtained by an arithmetic process based on the image signal, the correctness of the oxygen saturation level itself is reduced unless the image signal is obtained in an appropriate imaging condition. For example, when a pixel value of the image signal is abnormally high because of too high intensity of the illumination light applied to the observation object, the correctness of the oxygen saturation level obtained from that image signal is regarded to be low.

Against this problem, according to Japanese Patent No. 2768936 and U.S. Pat. No. 5,956,416 corresponding to Japanese Patent No. 3217343, an area in which the pixel value of the image signal is beyond a certain threshold value is detected as an abnormal area, and processing and control for differing display of this abnormal area from that of a normal area in which the pixel value is not beyond the threshold value (for example, by masking) are performed. This allows a user to easily distinguish an incorrect area from an area having the correct biological function information such as the oxygen saturation level.

According to the method of distinguishing the abnormal area from the normal area using the certain threshold value as a border, as described in the Japanese Patent No. 2768936 and the U.S. Pat. No. 5,956,416, if the pixel value of the abnormal area largely exceeds the threshold value, in other words, in the case of the occurrence of halation, the reliability of the oxygen saturation level is precisely reflected in display of the abnormal area on a screen. However, although an area is judged to be the abnormal area, if the pixel value of the abnormal area is just slightly above the threshold value and the actual reliability of the oxygen saturation level is not low, the reliability of the oxygen saturation level is not precisely reflected in display of the abnormal area on the screen. On the contrary, although an area is judged to be the normal area, if the pixel value of the normal area is just slightly below the threshold value and the actual reliability of the oxygen saturation level is low, the reliability of the oxygen saturation level is not precisely reflected in display of the normal area on the screen. Therefore, there is a demand for an endoscope system that can precisely display the reliability of the biological function information such as the oxygen saturation level.

SUMMARY OF THE INVENTION

The present invention aims to provide an endoscope system and an operating method thereof that can precisely display the reliability of the biological function information such as the oxygen saturation level.

To achieve the above object, an endoscope system according to the present invention includes an image information obtaining section, a biological function information calculating section, a first image generating section, an emphasized image generating section, and a display section. The image information obtaining section obtains image information by imaging an observation object. The biological function information calculating section calculates biological function information of the observation object based on the image information. The first image generating section produces a biological function information image that images the biological function information. The emphasized image generating section produces an emphasized image. In the emphasized image, a bright part within an abnormal area in which a calculation result of the biological function information calculating section is likely to be abnormal in the biological function information image is further brightened for emphasis. The display section displays the emphasized image.

It is preferable that the endoscope system further includes a second image generating section for producing based on the image information a normal light image that images the observation object irradiated with white light. The emphasized image generating section preferably produces the emphasized image by superimposing the biological function information image on the normal light image.

The biological function information image is preferably composed of luminance information and color difference information. It is preferable that the emphasized image generating section applies no information process to the color difference information of the biological function information image, and applies an information process to the luminance information of the biological function information image so as to further brighten a bright part. The emphasized image generating section preferably adjusts a pixel value of the biological function information image so as to further brighten the bright part.

It is preferable that the endoscope system further includes a halation detecting section and a display control section. The halation detecting section detects whether or not a halation area exists in the biological function information image. In the halation area, a pixel value exceeds a halation value being a certain value or more. In a case where the halation area is detected, the display control section displays the biological function information image on the display section. In a case where no halation area is detected, the display control section displays the emphasized image on the display section.

The biological function information preferably includes a blood volume being the amount of hemoglobin in blood and an oxygen saturation level of the hemoglobin in the blood. The biological function information calculating section preferably isolates information on the blood volume and information on the oxygen saturation level from a plurality of types of the biological function information included in the image information.

The image information preferably includes first image information and second image information. The first image information is obtained by imaging the observation object under irradiation with first illumination light having a first wavelength range in which a light absorption coefficient varies with a variation in the oxygen saturation level. The second image information is obtained by imaging the observation object under irradiation with second illumination light having a second wavelength range different from the first wavelength range.

An operating method of an endoscope system according to the present invention includes the steps of obtaining image information by an image information obtaining section by imaging an observation object; calculating biological function information of the observation object based on the image information by a biological function information calculating section; producing by a first image generating section a biological function information image that images the biological function information; producing an emphasized image by an emphasized image generating section, in said emphasized image, a bright part within an abnormal area in which a calculation result of the biological function information calculating section is likely to be abnormal in the biological function information image being further brightened for emphasis; and displaying the emphasized image on a display section.

According to the present invention, the emphasized image, in which the bright part of the abnormal area in which the calculation result of the biological function information calculating section is likely to be abnormal is further brightened for emphasis, is displayed on the display section. The abnormal area is displayed in the emphasized image so as to be just emphasized by the brightness to facilitate a grasp at sight, instead of determining a border with a normal area using a threshold value just as in the case of the Japanese Patent No. 2768936 and the U.S. Pat. No. 5,956,416. Therefore, it is possible to indicate the reliability of the biological function information, including the oxygen saturation level and the like, with high precision.

Note that, as for the biological function information image having the halation area that already exists, it is apparent that the calculation result of the halation area is abnormal. Thus, in the present invention, the biological function information image having the halation area is displayed on the display section as is, without producing the emphasized image. This eliminates time required for producing the emphasized image and improves the property of a moving image.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown inFIGS. 1 and 2, an endoscope system10according to a first embodiment is provided with a light source device11for emitting light in a predetermined wavelength band, an endoscope system12for imaging an area to be observed of an observation object while illuminating the observation object with the light from the light source device11, a processor device13for processing an image signal obtained by the endoscope device12, a display device14for displaying an image of the observation object based on the image signal processed by the processor device13, and an input device15including a keyboard for inputting various types of information to the processor device13and the like.

The endoscope system10has a normal observation mode and a biological information observation mode. In the normal observation mode, a normal light image, being an image of the observation object under visible light whose wavelength range extends from blue to red, is displayed on the display device14. In the biological information observation mode, a blood volume image, which images the amount of hemoglobin in blood in the observation object, and an oxygen saturation image, which images an oxygen saturation level of hemoglobin, are displayed on the display device14. The endoscope system10is switched between the observation modes by operation of a switch17of the endoscope device12or the input device15.

The light source device11is provided with two types of laser light sources LD1and LD2, a light source controller20, a combiner21, and a coupler22. The laser light source LD1emits narrow band light (oxygen saturation level measurement light) used for measuring an oxygen saturation level. The laser light source LD2emits excitation light for exciting a phosphor50disposed at a distal end portion of the endoscope device12. Fluorescence emitted from the excited phosphor50and the excitation light produce white light. The light emitted from the laser light sources LD1and LD2enter optical fibers24and25through condenser lenses (not shown), respectively. Note that, as the laser light sources LD1and LD2, a broad-area type InGaN laser diode, InGaNAs laser diode, GaNAs laser diode, or the like is available.

The light source controller20controls the laser light sources LD1and LD2so as to adjust emission timing of each laser source and a light amount ratio between the laser sources LD1and LD2. In this embodiment, in the normal observation mode, the laser light source LD1is turned off, while the laser light source LD2is turned on. In the biological information observation mode, on the other hand, the laser light sources LD1and LD2are turned on and off alternately.

The combiner21combines light from the optical fibers24and25. The combined light is separated into four beams of light by the coupler22being a branching filter. Out of the branched four beams of light, the light from the laser light source LD1is led through light guides26and27, and the light from the laser light source LD2is led through light guides28and29. These light guides26to29are composed of a bundle fiber, i.e. a bundle of a number of optical fibers, or the like. Note that, the light from the laser light sources LD1and LD2may directly enter the light guides26to29without through the combiner21and the coupler22.

The endoscope device12, being an electronic endoscope, is provided with an endoscope32, a lighting section33for applying the four beams of light led through the light guides26to29to the observation object, an imaging section34for imaging the area to be observed, a handling section35for bending the distal end portion of the endoscope32and performing another operation for observation, and a connector section36for detachably connecting the endoscope32to the light source device11and the processor device13.

The endoscope32is provided with a soft portion38, a bending portion39, and a distal end portion40in this order from the side of the handling section35. The soft portion38is flexible so as to be bendable in insertion of the endoscope32. The bending portion39is flexibly bent by a turning operation of an angle knob35adisposed in the handling section35. By bending the bending portion39in an arbitrary direction and an arbitrary angle according to a body part of the observation object and the like, the distal end portion40can be aimed at the desired part to be observed.

The distal end portion40has the lighting section33and the imaging section34. The imaging section34is provided with one imaging window42approximately at the center of the distal end portion40to receive light from the observed area. The lighting section33has two lighting windows43and44provided at both sides of the imaging section34. One of two types of light, i.e. the oxygen saturation level measurement light and the white light is applied to the area to be observed through each of the lighting windows43and44.

Two light projection units46and47are contained in the recess of the lighting window43. The light projection unit46applies the oxygen saturation level measurement light from the light guide26to the area to be observed through a lens48. In the other light projection unit47, the excitation light from the light guide28is applied to the phosphor50to emit the white light. The emitted white light is applied to the area to be observed through a lens51. Note that, other two light projection units, that is, a light projection unit53identical to the above light projection unit46and a light projection unit54identical to the above light projection unit47are contained in the recess of the other lighting window44.

As shown inFIG. 3, the lighting windows43and44are disposed at both sides of the imaging window42in the distal end portion40. The four light projection units46,47,53, and54are disposed in a staggered manner such that a straight line LA connecting light exit surfaces of the light projection units47and54having the phosphor50and a straight line LB connecting light exit surfaces of the light projection units46and53without having the phosphor50intersect at the center of the imaging window42. Such a disposition can prevent the occurrence of lighting unevenness.

The phosphor50contains a plurality of types of fluorescent substances (for example, a YAG-based fluorescent substance or a fluorescent material such as BAM (BaMgAl10O17)) that absorb apart of the excitation light from the laser light source LD2and emit green to red light. Applying the excitation light to the phosphor50produces the white light (pseudo white light) by mixing of the green to red light (fluorescence) emitted from the phosphor50and the excitation light passed through the phosphor50without being absorbed. The phosphor50preferably has an approximately rectangular parallelepiped shape. In this case, the phosphor50may be formed by compacting the fluorescent substances by a binder into the rectangular parallelepiped shape, or may be formed of a mixture of the fluorescent substances and a resin such as inorganic glass into the rectangular parallelepiped shape. Note that, the phosphor50is known under the trademark of Micro White (MW).

Therefore, as shown inFIG. 4, the white light emitted from the light projection units47and54having the phosphor50has an emission spectrum in a wavelength range (for example, 440 to 460 nm) of the excitation light whose center wavelength is 445 nm and a wavelength range of approximately 450 to 700 nm in which the fluorescence emitted by the application of the excitation light has high intensity. On the other hand, the oxygen saturation level measurement light emitted from the light projection units46and53without having the phosphor50has an emission spectrum in a wavelength range (for example, 460 to 480 nm) in the vicinity of a center wavelength of 473 nm.

Note that, in this specification, the white light does not necessarily contain every wavelength component of the visible light, as long as it contains light of specific wavelength bands of R (red), G (green), and B (blue) being primary colors, and the like, such as the pseudo white light described above. In other words, the white light includes, for example, light having a wavelength component from green to red, light having a wavelength component from blue to green, and the like in a broad sense.

An optical system such as an objective lens unit (not shown) is provided in the recess of the imaging window42to capture image light of the area to be observed of the observation object. In the recess of the objective lens unit, an imaging device60, e.g. a CCD (charge coupled device) imaging device or a CMOS (complementary metal-oxide semiconductor) imaging device, is disposed to receive the image light and image the area.

The imaging device60receives the image light from the objective lens unit at its light receiving surface (imaging surface), and performs photoelectric conversion of the received image light to output an imaging signal (analog signal). The imaging device60is a color CCD. In the light receiving surface of the imaging device60, a number of pixel groups each of which includes an R pixel having an R color filter, a G pixel having a G color filter, and a B pixel having a B color filter are arranged into a matrix. The B, G, and R color filters have spectral transmittance represented by curves63,64, and65ofFIG. 5, respectively.

The imaging signal (analog signal) from the imaging device60is inputted to an A/D converter68through a scope cable67. The A/D converter68converts the imaging signal (analog signal) into an image signal (digital signal) corresponding to its voltage level. The converted image signal is inputted to an image processing unit73of the processor device13through the connector section36.

An imaging controller70performs imaging control of the imaging device60. As shown inFIG. 6A, in the normal observation mode, a step of accumulating electric charge obtained by the photoelectric conversion of the white light (445 nm+fluorescence (represented in this manner because the white light is produced by applying the excitation light of 445 nm to the phosphor50in this embodiment)) and a step of reading out the accumulated electric charge, that is, the two steps in total are carried out in one frame period. This is repeated in a predetermined cycle during the normal observation mode. In the normal observation mode, a blue signal Bc outputted from the B pixels of the imaging device60, a green signal Gc outputted from the G pixels, and a red signal Rc outputted from the R pixels are obtained.

On the other hand, in the biological information observation mode, as shown inFIG. 6B, a step of accumulating electric charge obtained by photoelectric conversion of the oxygen saturation level measurement light (narrow band light of 473 nm) and a step of reading out the accumulated electric charge, that is, the two steps in total are carried out in one frame period (first frame period). Next, a step of accumulating electric charge obtained by photoelectric conversion of the white light (445 nm+MW) and a step of reading out the accumulated electric charge, that is, the two steps in total are carried out in one frame period (second frame period). The imaging control of the two frame periods in total is repeated in a predetermined cycle.

In the biological information observation mode, a blue signal B1outputted from the B pixels of the imaging device60, a green signal G1outputted from the G pixels, and a red signal R1outputted from the R pixels are obtained in the first frame period. A blue signal B2outputted from the B pixels, a green signal G2outputted from the G pixels, and a red signal R2outputted from the R pixels are obtained in the second frame period. Note that, the signals B2, G2, and R2obtained in the second frame period are the same as the signals Bc, Gc, and Rc obtained in the normal observation mode.

Note that, various channels, which include a forceps channel for inserting a tissue taking device, an air and water feeding channel, and the like, are provided in the handling section35and the endoscope32of the endoscope device12, though they are not illustrated.

As shown inFIG. 2, the processor device13is provided with a control unit72, the image processing unit73, and a storage unit74. To the control unit72, the display device14and the input device15are connected. The control unit72controls the operation of the image processing unit73, the light source controller20of the light source device11, the imaging controller70of the endoscope device12, and the display device14based on input information from the switch17of the endoscope device12and the input device15.

The image processing unit73is provided with a normal light image processor80, a function information image processor82, and an emphasized image processor90. The image processing unit73applies a predetermined image process to the image signal from the endoscope device12.

The normal light image processor80produces a normal light image by applying a predetermined image process to the image signal. The normal light image is produced by a video signal composed of a luminance Y and color difference signals Cb and Cr. The green signal Gc obtained in the normal observation mode or the green signal G2obtained in the biological information observation mode is assigned as the luminance Y. A difference value (Bc−Gc) between the blue signal Bc and the green signal Gc obtained in the normal observation mode, or a difference value (B2−G2) between the blue signal B2and the green signal G2obtained in the biological information observation mode is assigned as the color difference signal Cb. A difference value (Rc−Gc) between the red signal Rc and the green signal Gc obtained in the normal observation mode, or a difference value (R2−G2) between the red signal R2and the green signal G2obtained in the biological information observation mode is assigned as the color difference signal Cr.

The function information image processor82calculates information on a blood volume of the observation object and information on the oxygen saturation level of hemoglobin based on the image signals inputted from the endoscope device12. The function information image processor82also produces a blood volume image representing the blood volume and an oxygen saturation image representing the oxygen saturation level. The function information image processor82includes a signal ratio calculator84, a correlation memory85, a blood volume and oxygen saturation level calculator86, a blood volume image generator87, and an oxygen saturation image generator88.

The signal ratio calculator84calculates a ratio of intensity of each pixel between the image signal of the first frame period and the image signal of the second frame period obtained in the biological information observation mode. The signal ratio of every pixel of the entire screen is calculated. In this embodiment, the signal ratio calculator84calculates a signal ratio B1/G2between the blue signal B1of the first frame period and the green signal G2of the second frame period, and a signal ratio R2/G2between the green signal G2and the red signal R2of the second frame period. Note that, the signal ratio may be calculated with respect to the pixels within a blood vessel area, out of the image signal. In this case, the blood vessel area is determined based on the difference between the image signal of the blood vessel area and the image signal of the other area.

The correlation memory85stores the correlation among the signal ratios B1/G2and R2/G2, the blood volume, and the oxygen saturation level. As shown inFIG. 7, the correlation between the signal ratio and the blood volume is defined such that the blood volume is increased with increase in the signal ratio R2/G2. This correlation is stored in the form of a one-dimensional table. Note that, the signal ratio is represented in a log scale.

On the other hand, the correlation among the signal ratios and the oxygen saturation level is stored in the form of a two-dimensional table in which contour lines of the oxygen saturation level are defined in two-dimensional space as shown inFIG. 8. The position and shape of the contour lines are obtained by physical simulation of light scattering and varied in accordance with the blood volume. For example, variation in the blood volume widens or narrows the distance between the contour lines. Note that, the signal ratios B1/G2and R2/G2are depicted in a log scale.

Note that, the above correlation is closely related to a light absorbing property and a light scattering property of oxyhemoglobin and deoxyhemoglobin, as shown inFIG. 9. A line81represents a light absorption coefficient of oxyhemoglobin, and a line91represents a light absorption coefficient of deoxyhemoglobin. For example, the use of a wavelength of 473 nm at which the light absorption coefficient much differs between oxyhemoglobin and deoxyhemoglobin allows easy obtainment of information on the oxygen saturation level. However, a blue signal that includes a signal corresponding to light of 473 nm highly depends not only on the oxygen saturation level but also on the blood volume. Thus, the use of the signal ratios B1/G2and R2/G2, which are obtained by the red signal R2corresponding to light mainly depending on the blood volume and the green signal G2being a reference signal of the blue signal B1and the red signal R2, in addition to the blue signal B1, allows obtainment of the oxygen saturation level with high accuracy without depending on the blood volume.

The following three items hold true according to the dependence of the light absorption coefficient of hemoglobin on a wavelength:

(1) In the vicinity of a wavelength of 470 nm (for example, a blue wavelength range having a center wavelength of 470±10 nm), the light absorption coefficient largely varies in accordance with a variation in the oxygen saturation level.

(2) In a green wavelength range of 540 to 580 nm, the light absorption coefficient is averagely insusceptible to the oxygen saturation level.

(3) In a red wavelength range of 590 to 700 nm, the light absorption coefficient seems to vary largely in accordance with the oxygen saturation level, but in actual fact, is insusceptible to the oxygen saturation level because a value of the light absorption coefficient itself is very small.

The blood volume and oxygen saturation level calculator86calculates both the blood volume and the oxygen saturation level of each pixel by using the correlation stored in the correlation memory85and the signal ratios B1/G2and R2/G2obtained in the signal ratio calculator84. The blood volume is a value that corresponds to the signal ratio R2/G2obtained in the signal ratio calculator84in the one-dimensional table of the correlation memory85. As for the oxygen saturation level, on the other hand, as shown inFIG. 10, a point P that corresponds to signal ratios B1*/G2* and R2*/G2* obtained in the signal ratio calculator84is determined in the two-dimensional space.

If the corresponding point P is situated between a lower limit line130representing an oxygen saturation level of 0% and an upper limit line131representing an oxygen saturation level of 100%, the oxygen saturation level is determined according to a percentile of the contour line on which the corresponding point P is situated. TakingFIG. 10as an example, the point P is situated on the contour line of 60%, so the oxygen saturation level is 60%. Note that, if the corresponding point is situated above the lower limit line130, the oxygen saturation level is determined to be 0%. If the corresponding point is situated below the upper limit line131, the oxygen saturation level is determined to be 100%. Note that, in such cases, the oxygen saturation level may be judged to have low reliability and not be displayed.

The blood volume image generator87produces a blood volume image, which represents the blood volume obtained by the blood volume and oxygen saturation level calculator86with artificial colors. The blood volume image is composed of the video signal containing the luminance Y and the color difference signals Cb and Cr. The green signal G2, which includes information on reflected light in a wavelength band in which hemoglobin absorbs light at a relatively high rate, is assigned as the luminance Y. Since the luminance Y defines the total brightness of the artificial color image, assigning the green signal G2as the luminance Y improves visibility of projections and depressions of mucosa, a blood vessel, and the like.

On the other hand, signal values corresponding to the blood volume in accordance with a color table87aare assigned as the color difference signals Cb and Cr. The color table87ais defined such that a value of the color difference signal Cb decreases with increase in the blood volume, and a value of the color difference signal Cr increases with increase in the blood volume. Therefore, the blood volume image becomes reddish at a part of the large blood volume. With decrease in the blood volume, red chroma decreases and approaches monochrome.

The oxygen saturation image generator88produces the oxygen saturation image, which represents the oxygen saturation level obtained by the blood volume and oxygen saturation level calculator86with artificial colors. The oxygen saturation image is composed of a video signal containing the luminance Y and the color difference signals Cb and Cr, just as with the blood volume image. The green signal G2, which defines the total brightness and facilitates improving visibility of projections and depressions of mucosa, a blood vessel, and the like, is assigned as the luminance Y. Signal values corresponding to the oxygen saturation level in accordance with a color table88aare assigned as the color difference signals Cb and Cr.

According to the color table88a, the color difference signal Cr is defined to be a positive signal value and the color difference signal Cb is defined to be a negative signal value at a high oxygen saturation level, and on the contrary, the color difference signal Cr is defined to be a negative signal value and the color difference signal Cb is defined to be a positive signal value at a low oxygen saturation level. The magnitude relation between the signal value of the color difference signal Cr and the signal value of the color difference signal Cb is reversed at a middle oxygen saturation level. According to this definition, the color of the oxygen saturation image is changed from bluish, sky bluish, greenish, yellowish, orangish, to reddish as the oxygen saturation level increases.

As shown inFIG. 11, the emphasized image processor90includes a halation detector90aand an emphasized image generator90b. The halation detector90adetects whether or not a halation area in which a calculation result of the blood volume and oxygen saturation level calculator86becomes abnormal exists in the blood volume image or the oxygen saturation image. The emphasized image generator90bsuperimposes the normal light image on the blood volume image or the oxygen saturation image having no halation area to produce an emphasized image. In the emphasized image, a first abnormal area in which a calculation result of the blood volume and oxygen saturation level calculator86is likely to be abnormal is emphasized.

The halation detector90adetects whether or not the halation area that has a luminance Y of a halation value H or more, as shown inFIG. 12, exists in the blood volume image or the oxygen saturation image. Taking an oxygen saturation image92shown inFIG. 13as an example, an area93has a luminance Y1over the halation value H, and hence is detected as a halation area93. The oxygen saturation image92having the halation area93is displayed on the display device14as is. The halation area93is seen brightly in the display device14because of the extremely high luminance Y1. Therefore, an operator seeing the display device14can grasp at sight that the calculation result of the oxygen saturation level is abnormal i.e. unreliable in the halation area.

The emphasized image generator90bproduces an emphasized blood volume image by superimposing the normal light image on the blood volume image in which no halation area has detected, and produces an emphasized oxygen saturation image by superimposing the normal light image on the oxygen saturation image in which no halation area has detected. The emphasized blood volume image or the emphasized oxygen saturation image after being produced is displayed on the display device14. In superimposing the images, the luminance Y of the normal light image is added to the luminance Y of the blood volume image or the oxygen saturation image, while the color difference signals Cb and Cr of the normal light image are not added to the color difference signals Cb and Cr of the blood volume image or the oxygen saturation image. Thus, only brightness is varied in the blood volume image or the oxygen saturation image without changing its color. Note that, also in a case where there is a halation area detected, the emphasized blood volume image or the emphasized oxygen saturation image may be produced as with above.

For example, as shown inFIG. 14, in the case of superimposing a normal light image97having an area95having a luminance Y3slightly less than the halation value H on an oxygen saturation image96having an area94having a luminance Y2slightly less than the halation value H (the areas94and95are in approximately the same position), the luminance Y3of the normal light image97is added to the luminance Y2of the oxygen saturation image95to produce an emphasized oxygen saturation image98. In the emphasized oxygen saturation image98after being overlaid, an area99corresponding to the areas94and95is emphasized because its luminance Y4exceeds the halation value H.

The area99is seen as brightly as the halation area, or a little less brightly than the halation area. Thus, the area99is determined to be the first abnormal area99in which it is grasped at sight that the calculation result of the oxygen saturation level is abnormal or is likely to be abnormal, i.e. unreliable. Note that, the luminance Y4of the first abnormal area99is larger than the halation value H inFIG. 14, but the luminance Y after the superimposition does not necessarily exceed the halation value H. For example, the luminance Y may get close to the halation value H by the superimposition.

Next, the operation of the present invention will be described with referring to a flowchart ofFIG. 15. In the normal observation mode, the endoscope32is inserted into a human body, for example, a digestive canal. The distal end portion is aimed at the desired area to be observed by the operation of the angle knob35a, to perform normal observation. In the normal observation, the color normal light image of the observed area captured under irradiation with the white light is displayed on the display device14.

When the observed area seems to be a lesion, the endoscope system10is put into the biological information observation mode by the operation of the switch17of the endoscope device12. Thus, the oxygen saturation level measurement light, being the narrow band light having a center wavelength of 473 nm, is applied from the distal end portion40to the observation object. The imaging device60having the B pixels, the G pixels, and the R pixels performs the photoelectric conversion of the light reflected from the observation object. Thus, the image signal of the first frame including the blue signal B1, the green signal G1, and the red signal R1is obtained (frame1).

After the image signal of the first frame is obtained, the excitation light having a center wavelength of 445 nm is applied to the phosphor50of the distal end portion40. Accordingly, the white light is emitted from the phosphor50, and the emitted white light is applied to the observation object. The imaging device60captures the light reflected from the observation object, so the image signal of the second frame including the blue signal B2, the green signal G2, and the red signal R2is obtained (frame2).

Upon obtaining the image signal of the second frame, the normal light image is produced from the image signals B2, G2, and R2of the second frame. Also, the blood volume and the oxygen saturation level are calculated from the image signal B1of the first frame and the image signals G2and R2of the second frame. First, the signal ratios B1/G2and R2/G2are calculated with respect to a pixel in the same position between the image signal of the first frame and the image signal of the second frame. After the calculation of the signal ratios, the blood volume and the oxygen saturation level corresponding to the signal ratios B1/G2and R2/G2are obtained from the correlation stored in the correlation memory85. The blood volume and the oxygen saturation level are obtained with respect to every pixel in the screen.

Upon calculating the blood volume and the oxygen saturation level of every pixel, the color difference signals Cb and Cr corresponding to the blood volume are obtained with referring to the color table87aof the blood volume image generator87. Based on the obtained color difference signals Cb and Cr and the luminance Y as which the green signal G2is assigned, the blood volume image is produced in which the blood volume is represented with the artificial colors. As with the blood volume image, the oxygen saturation image in which the oxygen saturation level is represented with the artificial colors is produced using the color table88a.

Next, it is detected whether or not the halation area that has the luminance Y over the halation value H exists in the produced blood volume image and the oxygen saturation image. The blood volume image and the oxygen saturation image having the halation area are displayed on the display device14side by side. If no halation area has been detected, on the other hand, the emphasized blood volume image having the increased luminance Y is produced by superimposing the normal light image on the blood volume image, and the emphasized oxygen saturation image having the increased luminance Y is produced by superimposing the normal light image on the oxygen saturation image. Since these emphasized blood volume image and the emphasized oxygen saturation image have the increased luminance Y, the first abnormal area is produced in which the luminance Y exceeds or gets close to the halation value H.

As described above, the blood volume image and the oxygen saturation image having the halation area are displayed on the display device14as is without increasing its luminance Y. Thus, it is possible to notify the operator that the calculation result of the halation area is abnormal, while the calculation result of the other area is normal. On the other hand, as for the blood volume image and the oxygen saturation image having no halation area, the normal light image is overlaid thereon to produce the emphasized blood volume image and the emphasized oxygen saturation image. The produced emphasized blood volume image and the produced emphasized oxygen saturation image are displayed on the display device14. Therefore, it is possible to notify the operator that the calculation result of the first abnormal area in the emphasized blood volume image and the emphasized oxygen saturation image is abnormal or likely to be abnormal, while the calculation result of the other area is normal. An operation sequence described above is repeated as long as the endoscope system10is put in the biological information observation mode.

In a second embodiment of the present invention, a first abnormal area in which the calculation result of the blood volume and oxygen saturation level calculator86is likely to be abnormal because of too large luminance Y is brightened to emphasize the first abnormal area itself by its brightness, while a second abnormal area in which the calculation result of the blood volume and oxygen saturation level calculator86is likely to be abnormal because of too small luminance Y is darkened to emphasize the second abnormal area by its darkness. An emphasized image processor100as shown inFIG. 16, instead of the emphasized image processor90, performs an emphasizing process of the second embodiment. Note that, components other than the emphasized image processor100are identical to those of the first embodiment and therefore the description thereof will be omitted.

The emphasized image processor100includes a halation detector100a, which is identical to the halation detector90aof the first embodiment, and a luminance adjusting filter section100b. The luminance adjusting filter section100bapplies luminance adjusting filtering to the blood volume image and the oxygen saturation image in which the halation detector100ahas not detected the halation area. By the luminance adjusting filtering, the first abnormal area is further brightened and the second abnormal area is further darkened.

The luminance adjusting filter section100bhas a gain table as shown inFIG. 17. According to the luminance adjusting filtering using this gain table, when the luminance Y is more than a certain upper limit value U, the luminance Y increases with a gain of “1” or more. When the luminance Y is less than a certain lower limit value L, the luminance Y decreases with a gain of “1” or less. In the other cases, the luminance Y is maintained as is with a gain of “1”. An emphasized blood volume image that is obtained by applying the luminance adjusting filtering to the blood volume image and an emphasized oxygen saturation image that is obtained by applying the luminance adjusting filtering to the oxygen saturation image are displayed on the display device14.

For example, as shown inFIG. 18, when an oxygen saturation image102has a bright first abnormal area103having a luminance Ym more than the upper limit value U and a dark second abnormal area104having a luminance Yn less than the lower limit value L, the luminance adjusting filtering is applied to the oxygen saturation image102to obtain an emphasized oxygen saturation image105. In the emphasized oxygen saturation image105, the luminance Ym of the first abnormal area103is further increased, while the luminance Yn of the second abnormal area104is further decreased. In the emphasized oxygen saturation image105displayed on the display device14, the first abnormal area103is extremely bright, while the second abnormal area104is extremely dark. Emphasizing the first abnormal area103by its brightness and the second abnormal area104by its darkness makes it possible for the operator to grasp at sight that the oxygen saturation level of the first and second abnormal areas103and104is unreliable.

Note that in the above first embodiment, even in a case where the halation area is detected in the blood volume image and the oxygen saturation image, the first abnormal area may be emphasized by superimposing the normal light image on the blood volume image and the oxygen saturation image. Also, in the above second embodiment, even in a case where the halation area is detected in the blood volume image and the oxygen saturation image, the first and second abnormal area may be emphasized by luminance adjusting filtering.

In the above second embodiment, the first and second abnormal areas are emphasized by adjusting the luminance Y. However, a pixel value itself may be adjusted instead of the luminance Y. The first and second abnormal areas are emphasized by both the brightness and the darkness, but may be emphasized by only one of the brightness and the darkness.

In a third embodiment of the present invention, the illumination light needed for producing the blood volume image and the oxygen saturation image is produced using a white light source such as a xenon lamp and a rotating filter having a wavelength separation function. As shown inFIG. 19, an endoscope system120according to the third embodiment is provided with a broad band light source121, a rotating filter122, an optical fiber123, and a rotation controller124, instead of the laser light sources LD1and LD2, the light source controller20, and the combiner21of the first and second embodiments. The broad band light source121, such as a xenon light source, emits white light having spectral intensity as shown inFIG. 20. The rotating filter122transmits a wavelength component of the oxygen saturation level measurement light out of the white light, or transmits the entire white light. The light transmitted through the rotating filter122enters the optical fiber123. The rotation controller124controls rotation of the rotating filter122.

The light that has entered the optical fiber123is split in two beams of light by the coupler22. The split two beams of light are applied from the light projection units46and53to the observation object through the light guides26and27, respectively. Note that, the other components of the endoscope system120are identical to those of the endoscope system10, so the description thereof will be omitted.

As shown inFIG. 21, the rotating filter122has a band-pass filter125for transmitting the oxygen saturation level measurement light (seeFIG. 4) having a center wavelength of 473 nm out of the white light, and an opening126for transmitting the white light as is. Thus, by the rotation of the rotating filter122, the oxygen saturation level measurement light and the white light are alternately applied to the observation object. At this time, as with the first and second embodiments, the image signal of the first frame is obtained under irradiation with the oxygen saturation level measurement light, and the image signal of the second frame is obtained under irradiation with the white light. The normal light image is produced from the image signal of the second frame, and the blood volume image and the oxygen saturation image are produced from the image signals of the first and second frames, just as with the first and second embodiments. Note that, the band-pass filter125preferably transmits light in a wavelength range of 460 to 480 nm.

Just as with the first and second embodiments, the emphasized blood volume image in which an area whose calculation result of the blood volume is abnormal or likely to be abnormal is emphasized is produced by superimposing the normal light image on the blood volume image. In addition, the emphasized oxygen saturation image in which an area whose calculation result of the oxygen saturation level is abnormal or likely to be abnormal is emphasized is produced by superimposing the normal light image on the oxygen saturation image.

Note that, since the white light has a spectral intensity property as shown inFIG. 20, the blue signal B2contains a signal corresponding to light in a wavelength range of 400 to 530 nm. The green signal G2contains a signal corresponding to light in a wavelength range of 540 to 580 nm. The red signal R2contains a signal corresponding to light in a wavelength range of 590 to 700 nm.

Note that, out of the light of three wavelengths used in calculating the blood volume and the oxygen saturation level, part of the light may be light of a semiconductor light source just as with the first and second embodiments, while the other light may be light split from broad band light BB of the white light source such as the xenon lamp by wavelength separation.

In a fourth embodiment of the present invention, a light source device200as shown inFIG. 22is adopted. Light produced in the light source device200is applied to an endoscope device180. This endoscope device180has almost the same structure as the endoscope device12of the first and second embodiments, except that there is no phosphor50in the lighting section33at the distal end portion. Therefore, the light from the light source device200is applied to the observation object as is through the endoscope device180.

The structure of an imaging device180aand the operation of the imaging controller70in the endoscope device180differ from those of the first and second embodiments. In the processor device13, a method for producing the normal light image in the normal light image processor80is different from that of the first and second embodiments, and signals used in the function information image processor82are different from those used in the first and second embodiments. Only matters different from the above first and second embodiments will be hereinafter described, and the description of the others will be omitted.

The light source device200is provided with a white light source unit230for emitting broad band light BB (400 to 700 nm), a rotary filter234for color separating the broad band light BB from the white light source unit230into three colors of light of B, G, and R and sequentially applies the light of each color to the endoscope device180, a semiconductor light source unit236for emitting blue narrow band light BN, a light combining section238for merging an optical path L2of the blue narrow band light BN into an optical path L1of the broad band light BB, and a shutter plate240for blocking the optical path of the broad band light BB between the white light source230and the rotary filter234in predetermined timing.

The white light source unit230includes a white light source230afor radiating the broad band light BB and an aperture stop230bfor adjusting a light amount of the broad band light BB. The white light source230ais composed of a xenon lamp, a halogen lamp, a metal halide lamp, or the like. The degree of opening of the aperture stop230bis adjusted by a light amount controller (not shown).

As shown inFIG. 23, the rotary filter234is rotatable so that a B filter234a, a G filter234b, and an R filter234care selectively inserted in the optical path L1of the broad band light BB. The rotary filter234is in a disk shape and partitioned in a circumferential direction into three sectors each having a central angle of 120°. The B filter234a, the G filter234b, and the R filter234care provided in each of the sectors.

As shown inFIG. 24, the B filter234atransmits B light in a blue wavelength band out of the broad band light BB. The G filter234btransmits G light in a green wavelength band out of the broad band light BB. The R filter234ctransmits R light in a red wavelength band out of the broad band light BB. Therefore, by the rotation of the rotary filter234, the B light, the G light, and the R light are sequentially projected from the rotary filter234.

The semiconductor light source unit236has a laser light source236aand a light source controller236b. As shown inFIG. 24, the laser light source236aemits blue narrow band light BN having a center wavelength of 473 nm. The laser light source236aturns on and off under the control of the light source controller236b. The light source controller236bis controlled by the control unit72of the processor device13. The blue narrow band light BN emitted from the laser light source236ais projected to the light combining section238through a condenser lens236c.

The light combining section238, being a dichroic mirror, transmits light from the rotary filter234as is, while reflecting the blue narrow band light BN from the semiconductor light source unit236, so that the optical path L2of the blue narrow band light BN is merged into the optical path L1of the broad band light BB. The merged light exits from the light combining section238and is supplied to the endoscope device180through a condenser lens242.

As shown inFIG. 25, the shutter plate240includes a light shielding section240ahaving a central angle of 120° for blocking the broad band light BB, and a light transmitting section240bhaving a central angle of remaining 240° for transmitting the broad band light BB. The shutter plate240is rotatable. By the rotation of the shutter plate240, the light shielding section240aand the light transmitting section240bare alternately and selectively inserted in the optical path of the broad band light BB.

The shutter plate240is rotatable between a position inserted in the optical path L1of the broad band light BB and a position retracted from the optical path L1of the broad band light BB. In the normal observation mode, the shutter plate240is stopped in such a state that the light shielding section240ais retracted from the optical path L1of the broad band light BB and the light transmitting section240bis inserted into the optical path L1. Thus, the broad band light BB always enters the rotary filter234. Accordingly, the three colors of light, i.e. the B light, the G light, and the R light are sequentially produced by the B, G, and R filters234a,234b, and234cinserted in the optical path L1of the broadband light BB.

On the other hand, in the biological information observation mode, as shown inFIG. 26, the shutter plate240repeats intermittent operation between the inserted position and the retracted position. In an insertion period in which the shutter plate240is in the inserted position, the broad band light BB is not incident on the rotary filter234, so the B light, the G light, and the R light from the rotary filter234is not supplied to the endoscope device180. Instead of this, the laser light source236ais turned on and the blue narrow band light BN is supplied to the endoscope device180. This insertion period continues from the insertion of one color filter of the rotary filter234in the optical path L1of the broad band light BB to the retraction of the one color filter therefrom, in other words, for a duration of a one-third turn of the rotary filter234a.

After a lapse of the insertion period, the shutter plate240is rotated from the inserted position to the retracted position, to start a retraction period in which the shutter plate240is situated in the retracted position. This retraction period continues for a duration of one turn of the rotary filter234. The three colors of light, i.e. the B light, the G light, and the R light are supplied to the endoscope device180in the retraction period.

Taking the case ofFIG. 26as an example, in a first insertion period in which the R filter234cof the rotary filter234is inserted in the optical path L1of the broad band light BB, the broad band light BB is not incident on the R filter234c, and instead the blue narrow band light BN is supplied to the endoscope device180. Then, upon starting a next first retraction period, the broad band light BB is sequentially incident on the B filter234a, the G filter234b, and the R filter234c. Therefore, the B light, the G light, and the R light are supplied in this order to the endoscope device180.

In a next second insertion period, the B filter234aof the rotary filter234is inserted in the optical path L1, but the broad band light BB is not incident on the B filter234a. The blue narrow band light BN is supplied to the endoscope device180in this second insertion period. Then, in a next second retraction period, the broad band light BB is sequentially incident on the G filter234b, the R filter234c, and the B filter234aof the rotary filter234, so the G light, the R light, and the B light are supplied in this order to the endoscope device180.

The imaging device180aof the endoscope device180is a monochrome imaging device having no micro color filter in its imaging surface, in contrast to the imaging device60of the above first and second embodiments. The imaging controller70for controlling the imaging operation of the imaging device180aperforms operation different from that in the above first and second embodiments.

In the normal observation mode, as shown inFIG. 27A, three colors of image light of B, G, and R is sequentially captured and electric charge is accumulated. Based on the accumulated electric charge, surface sequential imaging signals B, G, and R are sequentially outputted. This operation sequence is repeated during the normal observation mode. In the biological information observation mode, on the other hand, as shown inFIG. 27B, four types of image light, including the blue narrow band light BN, the B light, the G light, and the R light is sequentially captured and electric charge is accumulated. Based on the accumulated electric charge, surface sequential imaging signals N, B, G, and R are sequentially outputted. This operation is repeated during the biological information observation mode.

The normal light image processor80of the processor device13produces the normal light image based on the surface sequential imaging signals B, G, and R. In this normal light image, the surface sequential imaging signal B approximately corresponds to the blue signal B2(Bc) of the first and second embodiments. The surface sequential imaging signal G approximately corresponds to the green signal G2(Gc) of the first and second embodiments. The surface sequential imaging signal R approximately corresponds to the red signal R2(Rc) of the first and second embodiments.

The function information image processor82of the processor device13calculates the blood volume and the oxygen saturation level based on the surface sequential imaging signals N, G, and R. N/G is used as a luminance ratio corresponding to the first luminance ratio B1/G2of the first and second embodiments, and RIG is used as a luminance ratio corresponding to the second luminance ratio R2/G2of the first and second embodiments. In accordance with it, the correlation memory85stores the correlation among the luminance ratios B1/G2and R2/G2, the blood volume, and the oxygen saturation level. The same procedure as the first and second embodiments is performed as for the others.

Note that, the blood volume and the oxygen saturation level are imaged as the biological function information in the above first to fourth embodiments, but instead or in addition to this, an oxyhemoglobin index calculated by “blood volume (the sum of oxyhemoglobin and deoxyhemoglobin)×oxygen saturation level (%)” or a deoxyhemoglobin index calculated by “blood volume×(100-oxygen saturation level) (%)” may be imaged.

Although the present invention has been fully described by the way of the preferred embodiment thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein.