JP2012143398A - Endoscope system and image generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely correct differences among light distributions, which are caused in application of a plurality of kinds of irradiation light beams different in wavelength, even when observation conditions such as a subject distance are changed during endoscopic diagnosis.SOLUTION: A wavelength-variable element makes reflected light and the like from a subject separated into narrowband light beams with a wavelength making an extinction coefficient of oxygenated hemoglobin (HbO2) and that of reduced hemoglobin (Hb) different from each other, and makes the reflected light and the like from the subject separated into narrowband light beams with a wavelength making the extinction coefficient of oxygenated hemoglobin (HbO2) and that of reduced hemoglobin (Hb) equal to each other. Three or more image signals are obtained by taking an image of each separated light beam by an image sensor. The image signal, which is used for generation of an oxygen saturation image, among the image signals is corrected to eliminate differences among signal distributions, which are caused by the differences among the light distributions of the narrowband light beams. Since correction is performed by using correction data obtained from the image signal with the wavelength making the extinction coefficient of oxygenated hemoglobin and that of reduced hemoglobin equal to each other, oxygen saturation information borne by the image signal is not erased.

Description

  The present invention relates to an endoscope system and an image generation method for imaging information related to oxygen saturation of blood hemoglobin.

  In recent medical treatments, diagnosis using an endoscope apparatus is widely performed. For observation of the inside of the subject using an endoscope device, in addition to normal light observation using broadband white light as illumination light, blood vessels in the subject are highlighted using narrowband light with a narrowed wavelength. Special light observation is also being carried out.

  In addition to special light observation, functional information of the subject such as oxygen saturation of blood hemoglobin is also imaged. For example, in Patent Document 1, a subject is irradiated with light having a wavelength whose light absorption changes according to the oxygen saturation of blood hemoglobin, and the simulated light is simulated based on image signals obtained by imaging reflected light of each light. Oxygen saturation is displayed in color. In Patent Document 1, in addition to light having a wavelength whose light absorption changes depending on the oxygen saturation, light of a plurality of wavelengths including light having a wavelength whose light absorption does not change is irradiated into the subject sequentially in time series. (Sequential method).

  By sequentially irradiating the subject with light having different wavelengths in this manner, for example, the distribution of light distribution when light having a wavelength that changes light absorption depending on the degree of oxygen saturation and the wavelength at which light absorption does not change. There may be a difference in the light distribution when irradiated with light. This difference in light distribution hinders accurate display of oxygen saturation, and in particular, there is a high possibility that the display of oxygen saturation at the edge of the image will be inappropriate.

  As a method for correcting the difference in the light distribution, Patent Document 2 discloses the distribution of light distribution when irradiated with white light of broadband light and the distribution of light distribution when irradiated with excitation light having a wavelength range different from that of the white light. A method for correcting the difference is shown. The method of Patent Document 2 can be applied to the case of correcting the difference between the light distribution of light having a wavelength that changes light absorption due to oxygen saturation and the light distribution of light having a wavelength that does not change as described above. Conceivable.

Japanese Patent No. 2648494 JP 2005-349007 A

  In Patent Document 2, when obtaining correction data used to correct a difference in light distribution between white light and excitation light, a cap having a standard subject on the inner surface is attached to the distal end portion of the endoscope. A white light image of a standard subject when white light is irradiated and imaged and an excitation light image when excitation light is irradiated and imaged are acquired, and correction data is obtained from the acquired image. Then, at the time of actual endoscopic diagnosis (at the time of autofluorescence observation), the image is corrected using the correction data calculated in advance.

  Therefore, the correction data is obtained based on the difference in the light distribution in the case of the positional relationship between the light distribution optical system when the cap is attached and the standard object on the inner surface of the cap. When the positional relationship between the scope and the subject tissue varies with distance and angle as in the case of observing the tissue, there is a possibility that the difference in the light distribution cannot be corrected correctly with the correction data obtained in advance.

  The present invention provides light distribution that occurs when a plurality of types of illumination light having different wavelengths are irradiated even if the observation conditions such as the distance and angle of the positional relationship between the scope and the subject tissue change during endoscopic diagnosis. An object of the present invention is to provide an endoscope system and an image generation method capable of reliably correcting a difference in distribution.

  In order to achieve the above object, the endoscope system of the present invention captures the image light of the subject including the narrow band light of a specific wavelength, and thereby selects a wavelength having a difference in the extinction coefficient between oxyhemoglobin and reduced hemoglobin. Image signal acquisition means for acquiring a total of three or more second image signals corresponding to narrow band light having a wavelength having the same absorption coefficient of oxyhemoglobin and reduced hemoglobin, and a first image signal corresponding to the narrow band light having Based on the correction data obtained by using the second image signal, the first or second image signal is corrected so that the difference in signal distribution due to the difference in light distribution between the narrowband lights is eliminated. A signal correcting unit; and an oxygen saturation image generating unit configured to generate an oxygen saturation image indicating a distribution of oxygen saturation of blood hemoglobin based on the corrected first and second image signals. And wherein the door.

  The signal correction unit is configured to generate an image signal other than the intermediate image signal corresponding to the narrowband light having a middle wavelength among the narrowband lights among the three or more image signals, as a signal distribution of the intermediate image signal. Correct to match.

  The image signal acquisition means includes, as the first image signal, an image signal S440 corresponding to narrowband light having a center wavelength of 440 nm, an image signal S475 corresponding to narrowband light having a center wavelength of 475 nm, and a narrowness having a center wavelength of 540 nm. An image signal S540 corresponding to band light is acquired, and an image signal S450 corresponding to narrowband light having a center wavelength of 450 nm and an image signal S500 corresponding to narrowband light having a center wavelength of 500 nm are used as the second image signal. The signal correcting means acquires and corrects the image signal S440 based on the correction data C440 obtained using the image signal S500 and the image signal S450, and the correction obtained using the image signal S500 and the image signal S540. On the basis of the data C540, the image signal S540 is corrected, and the oxygen saturation generation means generates the corrected image signal. '440 may generate oxygen saturation level image based on S'540 the image signal S475.

  The image signal acquisition means includes, as the first image signal, an image signal S440 corresponding to narrowband light having a center wavelength of 440 nm, an image signal S475 corresponding to narrowband light having a center wavelength of 475 nm, and a narrowness having a center wavelength of 560 nm. An image signal S560 corresponding to band light is acquired, and as the second image signal, an image signal S450 corresponding to narrowband light having a center wavelength of 450 nm, and an image signal S500 corresponding to narrowband light having a center wavelength of 500 nm, The image signal S570 corresponding to the narrowband light having the center wavelength of 570 nm is acquired, and the signal correction unit corrects the image signal S440 based on the correction data C440 obtained by using the image signal S500 and the image signal S450. Based on the correction data C560 obtained using the image signal S570 and the image signal S500, the image signal S 60 corrected, the oxygen saturation level image generating means, image signal S'440 corrected, may generate the oxygen saturation level image based on S'560 the image signal S475.

  The correction data is obtained using a low frequency component of the second image signal. The signal correction means may not correct the image center of the image signal. Each narrow band light may be generated by spectrally dividing the broadband light from the subject with a wavelength variable element. Each narrowband light may be generated using a rotary filter having a plurality of transmission parts that transmit only each narrowband light from the broadband light. The image signal acquisition unit performs imaging with a monochrome imaging device.

  The image generation method of the present invention is compatible with narrowband light having a wavelength that has a difference in absorption coefficient between oxyhemoglobin and reduced hemoglobin by capturing image light of a subject including narrowband light of a specific wavelength on the imaging surface. Three or more second image signals corresponding to narrow-band light having wavelengths having the same extinction coefficients of oxyhemoglobin and reduced hemoglobin are obtained, and obtained using the second image signal. Based on the correction data to be corrected, the first or second image signal is corrected so as to eliminate the difference in signal distribution due to the difference in light distribution between the narrowband lights, and the corrected first and second images are corrected. Based on the signal, an oxygen saturation image indicating a distribution of oxygen saturation of blood hemoglobin is generated.

  According to the present invention, the first and second image signals used for generating the oxygen saturation image are sequentially acquired by the imaging device, and the oxygen saturation information is obtained for the acquired first or second image signal. While maintaining the riding signal, it is corrected so that the difference in signal distribution due to the difference in light distribution between each narrowband light is eliminated, so in the actual endoscopic diagnosis, the scope and subject tissue Real-time correction is possible regardless of observation conditions such as the positional relationship. In addition, the oxygen saturation image generated based on the image signal corrected in this way does not cause false color display due to a difference in light distribution, so that the diagnostic ability is improved.

1 is an external view of an endoscope system according to a first embodiment. It is a block diagram showing the internal structure of an endoscope system. It is a graph showing the emission spectrum of white light. It is the schematic of a wavelength variable element. It is explanatory drawing for demonstrating drive control of the wavelength variable element and imaging element in 1st Embodiment. It is a graph which shows the extinction coefficient of hemoglobin. It is a flowchart which shows the effect | action of this invention. It is explanatory drawing for demonstrating drive control of the wavelength variable element and image pick-up element in 2nd Embodiment. It is a block diagram showing the internal structure of the endoscope system of 3rd Embodiment. It is a front view of a rotary filter. It is a front view of the rotation filter in which the transmission characteristic in each transmission part differs from the rotation filter of FIG. It is a block diagram showing the internal structure of the endoscope system of 4th Embodiment.

  As shown in FIGS. 1 and 2, the endoscope system 10 according to the first embodiment includes a light source device 11 that generates illumination light to the subject, and light emitted from the light source device 11 to guide the subject. An endoscope apparatus 12 that irradiates an observation area with illumination light and picks up reflected light and the like, a processor apparatus 13 that performs image processing on an image signal obtained by the endoscope apparatus 12, and an image processing A display device 14 for displaying an endoscopic image and the like, and an input device 15 including a keyboard and the like are provided.

  The light source device 11 includes a xenon lamp 18 that emits white light as light having a broad wavelength from blue to red as shown in FIG. White light emitted from the xenon lamp 18 enters the optical fiber 24 through a condenser lens (not shown). In addition to a xenon lamp, a halogen lamp or a white LED (Light Emitting Diode) may be used. Further, a light quantity control unit may be connected to the xenon lamp, and the light quantity of the white light may be controlled by the light quantity control unit.

  The combiner 21 multiplexes the light from the optical fiber 24. The combined light is demultiplexed into two systems of light by a coupler 22 which is a demultiplexer. The demultiplexed two systems of light are transmitted by the light guides 28 and 29. The light guides 28 and 29 are composed of bundle fibers obtained by bundling a large number of optical fibers. In addition, it is good also as a structure which puts the white light from the xenon lamp 18 directly in the light guides 28 and 29, without using the combiner 21 and the coupler 22. FIG.

  The endoscope apparatus 12 includes an electronic endoscope, and includes an endoscope scope 32, an illumination unit 33 that emits two systems (two lights) of light transmitted by light guides 28 and 29, and an observation area. An imaging unit 34 for imaging, an operation unit 35 for performing an operation for bending and observing the distal end portion of the endoscope scope 32, and the endoscope scope 32, the light source device 11, and the processor device 13 are attached and detached. A connector portion 36 that is freely connected is provided.

  The endoscope scope 32 is provided with a flexible portion 38, a bending portion 39, and a scope distal end portion 40 in this order from the operation portion 35 side. Since the flexible portion 38 has flexibility, it can be bent in the subject when the endoscope is inserted. The bending portion 39 is configured to be freely bent by a turning operation of an angle knob 35 a disposed in the operation portion 35. Since the bending portion 39 can be bent in an arbitrary direction and an arbitrary angle according to the region of the subject, the scope distal end portion 40 can be directed to a desired observation region.

  The scope tip 40 is provided with an illumination unit 33 and an imaging unit 34. The imaging unit 34 includes a single observation window 42 that captures reflected light from the subject region at a substantially central position of the scope distal end 40. The illumination unit 33 includes two illumination windows 43 and 44 provided on both sides of the imaging unit 34, and each illumination window 43 and 44 emits white light toward the observation region.

  In the back of the observation window 42, an objective lens 48 is provided for capturing image light of the observation region of the subject. Further behind that, a wavelength tunable element 50 capable of selectively transmitting light in a specific wavelength band out of light passing through the objective lens 48 and changing the wavelength band of the transmitted light, and the wavelength tunable element 50. And an image sensor 60 that receives the light passing through and images the observation area.

  The wavelength tunable element 50 is composed of an etalon, and as shown in FIG. 4, two high reflection light filters 51 and 52 provided on the optical path L between the objective lens 48 and the imaging element 60, and one of the high reflection light. And a piezoelectric actuator 53 that moves the filter 52 along the optical path L. The wavelength tunable element 50 disperses narrowband light having a specific wavelength among white light by changing a surface interval (air gap) d between the two high reflection light filters 51 and 52 by the piezoelectric actuator 53.

  The image pickup device 60 is composed of a monochrome image pickup device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor), and receives light from the wavelength tunable device on a light receiving surface (image pickup surface). It converts and outputs an imaging signal (analog signal). An imaging signal (analog signal) output from the imaging device 60 is input to the A / D converter 68 through the scope cable 67. The A / D converter 68 converts the imaging signal (analog signal) into an image signal (digital signal) corresponding to the voltage level. The converted image signal is input to the image processing unit 73 of the processor device 13 via the connector unit 36.

  The scope control unit 70 controls the wavelength variable element 50 and the image sensor 60. In the first embodiment, as shown in FIG. 5, the wavelength tunable element 50 is controlled by the drive of the scope control unit 70 so that the narrowband light having the center wavelength of 440 nm, the narrowband light having the center wavelength of 450 nm, and the center wavelength of 475 nm. The narrow-band light, the narrow-band light having a center wavelength of 500 nm, and the narrow-band light having a center wavelength of 540 nm are sequentially separated every frame period. Each time each narrowband light is split, the image sensor 60 accumulates charges obtained by photoelectrically converting each narrowband light and reads out the accumulated charges under the drive control of the scope control unit 70. The drive control for these five frames is repeatedly performed.

  Here, S440 is an image signal obtained when imaging narrow-band light having a center wavelength of 440 nm, S450 is an image signal obtained when imaging narrow-band light having a center wavelength of 450 nm, and narrow-band light having a center wavelength of 475 nm. S475 is an image signal obtained when an image is captured, S500 is an image signal obtained when an image of narrowband light having a center wavelength of 500 nm is imaged, and an image signal obtained when an image of narrowband light having a center wavelength of 540 nm is imaged. Let S540.

  Although not shown, a forceps channel for inserting a tissue collection treatment tool or the like, an air supply / water supply channel, or the like inside the operation unit 35 and the endoscope scope 32 in the endoscope apparatus 12. Various channels are provided.

  The processor device 13 includes a control unit 72, an image processing unit 73, and a storage unit 74, and the display device 14 and the input device 15 are connected to the control unit 72. The control unit 72 controls operations of the image processing unit 73, the scope control unit 70 of the endoscope apparatus 12, and the display device 14. The image processing unit 73 corrects an image signal input from the endoscope apparatus 12, and an oxygen saturation image that images oxygen saturation of blood hemoglobin based on the corrected image signal. And a generation unit 81.

  The signal correction unit 80 corrects the image signal so that the difference in signal distribution due to the difference in light distribution between frames is eliminated. The difference in the light distribution is caused by the irradiation of narrow-band light with different wavelengths in each frame. Due to the effects of illumination and the imaging optical system, the center of the image is the least, and as it moves toward the periphery of the image It turns out to grow gradually. Therefore, if the oxygen saturation image is generated without correcting the difference in signal distribution due to the difference in light distribution, the accuracy of oxygen saturation displayed in the oxygen saturation image may be reduced. Is expensive.

Accordingly, in the first embodiment, among the image signals S440, S475, and S540 used for generating the oxygen saturation image, the intermediate frequency signal S440 and S540 are maintained in a state where the low frequency component signal carrying the oxygen saturation information is maintained. Correction is made to match the signal distribution of wavelength S475. For the correction of S440, the low frequency components L (S450) and L (S500) of the image signals S450 and S500 having a wavelength close to that of S440 are used. Based on these L (S450) and L (S500), correction data C440 is generated by the following equation.
C440 = L (S500) −L (S450) + F440 (d)
In this equation, F440 (d) is a value depending on the distance d from the image center, and is an offset value for setting C440 to “0” at the image center. Note that L (S500) and L (S450) are obtained by multiplying the image signals S500 and S450 by an average value filter of a predetermined size.

When the correction data C440 is obtained, the correction signal S′440 is obtained by adding the correction data C440 to S440 according to the following equation.
S'440 = S440 + C440
In this equation, the correction data C440 itself added to S440 is an image signal of wavelengths 450 nm and 500 nm (iso-absorption wavelength (see FIG. 6)) in which the absorption coefficients of oxyhemoglobin (HbO 2) and reduced hemoglobin (Hb) are the same. Since S450 is created based on S450 and S500, S′440 after correction does not erase the low-frequency oxygen saturation signal that may be on S440, and the signal distribution of S475 at the intermediate wavelength. The signal is close to.

On the other hand, for the correction of S540, the low frequency component L (S540) of S540 and the low frequency component L (S500) of the image signal S500 having a wavelength close to S540 are used. Based on L (S540) and L (S500), correction data C540 is generated by the following equation.
C540 = L (S500) -L (S540) + F540 (d)
In this equation, F540 (d) is the same offset value as F440 (d).

When the correction data C540 is obtained, the correction signal S′540 is obtained by adding the correction data C540 to S540 according to the following equation.
S'540 = S540 + C540
This S′540 is a signal that is close to the signal distribution of the intermediate wavelength S475. In the above equation, the correction data C540 is generated based on the image signal of the isosbestic wavelength, and S540 itself is an image of the isosbestic wavelength, so that the signal value of S′540 changes due to the change in oxygen saturation. Does not occur.

  The oxygen saturation image generation unit generates an oxygen saturation image based on the corrected S′440, S′540, and S475. The oxygen saturation image is a video signal composed of RGB channels, and S′440, S475, and S′540 are assigned to each of the RGB channels. The generated oxygen saturation image is displayed on the display device 14. The color saturation of the oxygen saturation image displayed on the display device 14 changes according to the oxygen saturation.

  As described above, in the present invention, S ′ 440 and S ′ 540 among the image signals used for generating the oxygen saturation image maintain the signal carrying the oxygen saturation information and the signal distribution of S 475. Therefore, even if there is a difference in the light distribution between the frames, the oxygen saturation information (color information that changes according to the oxygen saturation) is displayed incorrectly. 14 is not displayed.

  Next, the operation of the present invention will be described with reference to the flowchart of FIG. First, the wavelength tunable element 50 separates narrowband light having a center wavelength of 440 nm from reflected light from a subject. The spectrally narrowband light having a center wavelength of 440 nm is imaged by the monochrome image sensor 60. Thereby, an image signal S440 is obtained.

  Similarly, the wavelength variable element 50 spectrally separates narrowband light having a center wavelength of 450 nm, narrowband light having a center wavelength of 475 nm, narrowband light having a center wavelength of 500 nm, and narrowband light having a center wavelength of 540 nm, and imaging is performed every time the spectrum is split. Imaging is performed with the element 60. Thereby, an image signal S450, an image signal S475, an image signal S500, and an image signal S540 are obtained.

  When the five types of image signals are obtained, correction data C440 is generated using the image signals S500 and S450 of the equal absorption wavelength in order to perform the signal correction of S440. By adding the correction data C440 to the image signal S440, an image signal S′440 is obtained. S′440 is a signal approaching the signal distribution of S475 while maintaining a low-frequency oxygen saturation signal that may be on S440.

  Further, in order to perform the signal correction in S540, correction data C540 is generated using the image signals S540 and S500 having the equal absorption wavelength. By adding the correction data C540 to the image signal S540, an image signal S′540 is obtained. S′540 is a signal approaching the signal distribution of S475.

  Then, an oxygen saturation image is generated from the corrected image signals S ′ 440 and S ′ 540 and the image signal S 475, and the generated oxygen saturation image is displayed on the display device 14. The color saturation of the oxygen saturation image displayed on the display device 14 changes according to the change in oxygen saturation.

  In the second embodiment, for the generation of the oxygen saturation image, a narrowband light image signal S440 having a center wavelength of 440 nm, a narrowband light image signal S475 having a center wavelength of 475 nm, and a narrowband light image signal having a center wavelength of 560 nm are used. The image signal is corrected using a narrowband light image signal S450 having a center wavelength of 450 nm, a narrowband light image signal having a center wavelength of 500 nm, and a narrowband light image signal S570 having a center wavelength of 570 nm.

  The second embodiment is the same as the first embodiment except that the number of image signals used for generating an oxygen saturation image and correcting an image signal is increased to six. Therefore, as shown in FIG. 8, each narrowband light is generated by splitting the reflected light or the like from the subject with the wavelength variable element 50 for each frame period, and splits each narrowband light. Imaging is performed by the imaging device 60 every time.

  The correction of the image signal is performed on S440 and S570 among the image signals S440, S475, and S570 used for generating the oxygen saturation image. In S440 and S570, correction is performed so as to match the signal distribution of the image signal S475 of the intermediate wavelength while maintaining the signal of the low frequency component carrying the oxygen saturation information. Here, since the signal correction in S440 is the same as that in the first embodiment, the description thereof is omitted.

On the other hand, the low frequency components L (S570) and L (S500) of the image signals S570 and S500 having a wavelength close to that of S440 are used for the correction of S570. Based on these L (S570) and L (S500), correction data C570 is generated by the following equation.
C570 = L (S500) -L (S570) + F570 (d)
In this equation, F570 (d) is the same offset value as F440 (d) and F540 (d) shown in the first embodiment. Note that L (S500) and L (S570) are obtained by multiplying the image signals S500 and S570 by an average value filter of a predetermined size.

When the correction data C570 is obtained, the correction signal S′570 is obtained by adding the correction data C570 to S570 according to the following equation.
S'570 = S570 + C570
In this equation, the correction data C570 itself added to S570 is created based on the image signals S500 and S570 having the equal absorption wavelengths of 500 nm and 570 nm (see FIG. 6). The signal is close to the signal distribution of S475 of the intermediate wavelength without erasing the low frequency oxygen saturation signal that may be on S570.

  When the corrections in S440 and S570 are completed, an oxygen saturation image is generated using the corrected S′440 and S′570 and S475, and the generated oxygen saturation image is displayed on the display device 14.

  In the third embodiment, instead of the wavelength tunable element used for generating the narrow band light in the first and second embodiments, as shown in FIG. 9, the narrow band light is generated using the rotary filter 110. The rotary filter 110 is provided between the xenon lamp 18 and the optical fiber 24 in the light source device 11 in the endoscope system 100. The rotary filter 110 is provided with a plurality of transmission parts that transmit narrowband light of a specific wavelength in the white light from the xenon lamp 18 along the circumferential direction. Each transmission part has a different transmission wavelength range. Therefore, when the rotary filter rotates, narrowband light having different wavelengths is sequentially transmitted. The transmitted narrow band light is irradiated into the subject through the light guides 28 and 29. And every time each narrow-band light is irradiated, imaging is performed by the image sensor 60.

  As in the first embodiment, when five types of narrowband light (440 nm, 450 nm, 475 nm, 500 nm, and 540 nm) are required, only the narrowband light is transmitted to the rotary filter 110 as shown in FIG. First to fifth transmission parts 111 to 115 to be provided are provided. Further, as in the second embodiment, when six types of narrow band light (440 nm, 450 nm, 475 nm, 500 nm, 560 nm, 570 nm) are required, instead of the rotary filter 110, as shown in FIG. A rotary filter 120 provided with first to sixth transmission parts 121 to 126 that transmit only each narrow band light is used.

  In the fourth embodiment, unlike the first and second embodiments in which the wavelength variable element is provided in front of the imaging element, as shown in FIG. 12, between the xenon lamp 18 in the light source device 11 and the optical fiber 24, The wavelength variable element 50 is installed. Therefore, in the endoscope system 200 of the fourth embodiment, the white light from the xenon lamp 18 is dispersed by the wavelength variable element 50, and narrow band light obtained by the spectroscopy is irradiated into the subject. And every time each narrow-band light is disperse | distributed, it images with the image pick-up element 60. FIG. In addition, 4th Embodiment is the same as that of 1st Embodiment except performing spectroscopy on the light source device 11 side.

  In the above embodiment, an etalon is used as the wavelength tunable element, but a liquid crystal tunable filter may be used instead. The liquid crystal tunable filter is configured by sandwiching a birefringence filter and a nematic liquid crystal cell between polarizing filters, and controls a wavelength band of transmitted light by changing a voltage applied to the liquid crystal cell.

10, 100, 200 Endoscope system 14 Display device 50 Wavelength variable element 60 Imaging element 73 Image processing unit 80 Signal correction unit 81 Oxygen saturation image generation unit

Claims (10)

A first image signal corresponding to narrowband light having a wavelength having a difference in absorption coefficient between oxyhemoglobin and reduced hemoglobin, and oxyhemoglobin and reduced by imaging image light of a subject including narrowband light of a specific wavelength. Image signal acquisition means for acquiring a total of three or more second image signals corresponding to narrow-band light having wavelengths with the same absorption coefficient of hemoglobin;
Based on correction data obtained using the second image signal, a signal for correcting the first or second image signal so that a difference in signal distribution due to a difference in light distribution between the narrowband lights is eliminated. Correction means;
An endoscope comprising: an oxygen saturation image generating means for generating an oxygen saturation image indicating a distribution of oxygen saturation of blood hemoglobin based on the corrected first and second image signals system. The signal correction means includes
Among the three or more image signals, the image signals other than the intermediate image signal corresponding to the narrowband light having an intermediate wavelength in each narrowband light are corrected so as to match the signal distribution of the intermediate image signal. The endoscope system according to claim 1. The image signal acquisition means includes
As the first image signal, an image signal S440 corresponding to narrowband light having a center wavelength of 440 nm, an image signal S475 corresponding to narrowband light having a center wavelength of 475 nm, and an image signal corresponding to narrowband light having a center wavelength of 540 nm. While acquiring S540
As the second image signal, an image signal S450 corresponding to narrowband light having a center wavelength of 450 nm and an image signal S500 corresponding to narrowband light having a center wavelength of 500 nm are acquired,
The signal correction means includes
Based on the correction data C440 obtained using the image signal S500 and the image signal S450, the image signal S440 is corrected,
Based on the correction data C540 obtained using the image signal S500 and the image signal S540, the image signal S540 is corrected,
The endoscope system according to claim 1 or 2, wherein the oxygen saturation generation unit generates an oxygen saturation image based on the corrected image signals S'440, S'540 and the image signal S475. . The image signal acquisition means includes
As the first image signal, an image signal S440 corresponding to narrowband light having a center wavelength of 440 nm, an image signal S475 corresponding to narrowband light having a center wavelength of 475 nm, and an image signal corresponding to narrowband light having a center wavelength of 560 nm. While acquiring S560,
As the second image signal, an image signal S450 corresponding to narrowband light having a center wavelength of 450 nm, an image signal S500 corresponding to narrowband light having a center wavelength of 500 nm, and an image signal corresponding to narrowband light having a center wavelength of 570 nm. Get S570,
The signal correction means includes
Based on the correction data C440 obtained using the image signal S500 and the image signal S450, the image signal S440 is corrected,
Based on the correction data C560 obtained using the image signal S570 and the image signal S500, the image signal S560 is corrected,
The endoscope according to claim 1 or 2, wherein the oxygen saturation image generation means generates an oxygen saturation image based on the corrected image signals S'440, S'560 and the image signal S475. system.   The endoscope system according to claim 3 or 4, wherein the correction data is obtained using a low-frequency component of the second image signal.   The endoscope system according to any one of claims 1 to 5, wherein the signal correction unit does not correct an image center in the image signal.   The endoscope system according to claim 1, wherein each narrowband light is obtained by spectrally dividing broadband light from a subject with a wavelength variable element.   The endoscope system according to claim 1, wherein each narrowband light is obtained by using a rotary filter having a plurality of transmission parts that transmit only each narrowband light from the broadband light.   The endoscope system according to any one of claims 1 to 8, wherein the image signal acquisition unit performs imaging with a monochrome imaging device. A first image signal corresponding to narrowband light having a wavelength having a difference in absorption coefficient between oxyhemoglobin and reduced hemoglobin and oxidation by imaging image light of a subject including narrowband light of a specific wavelength on the imaging surface Obtaining a total of three or more second image signals corresponding to narrow-band light having wavelengths with the same absorption coefficient of hemoglobin and reduced hemoglobin,
Based on the correction data obtained using the second image signal, the first or second image signal is corrected so that there is no difference in signal distribution due to the difference in light distribution between each narrowband light,
An image generation method characterized by generating an oxygen saturation image showing a distribution of oxygen saturation of blood hemoglobin based on the corrected first and second image signals.

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