JP5762344B2 - Image processing apparatus and endoscope system - Google Patents

Description

  The present invention relates to an image processing apparatus that processes an image captured by an endoscope, and an endoscope system including the image processing apparatus.

  In the medical field, endoscopic diagnosis using an endoscopic system is widespread. An endoscope system includes an endoscope having an insertion portion that is inserted into a living body and has an imaging element and an illumination window disposed at a distal end thereof, a light source device that supplies light to the endoscope, and an image signal output by the imaging element. And a processor device (image processing device) for processing. The endoscope has a built-in light guide composed of a plurality of optical fibers, and light supplied from the light source device is guided to the illumination window by the light guide and irradiated to the observation site.

  In recent endoscopic diagnosis, special observation using special light limited to a specific wavelength is used in addition to normal observation of observing the overall properties of the surface of living tissue under normal light, which is white light. Light observation is also performed. There are various types of special light observations. For example, by utilizing the optical characteristics of living tissue that the depth of penetration from the surface of the mucosa varies depending on the wavelength, the superficial blood vessels that exist near the mucosal surface and the surface blood vessels There is known blood vessel enhancement observation in which middle and deep blood vessels in the deep layer are highlighted and displayed (see, for example, Patent Document 1 and Patent Document 2). In abnormal tissues such as cancer that occurs in living tissue, the state of blood vessels is different from that in normal tissues, so that blood vessel enhancement observation has been found useful for early cancer detection.

  The extinction coefficient of blood hemoglobin has a wavelength dependence, and increases rapidly in the region where the wavelength is about 450 nm or less, and has a peak in the blue region near 405 nm. Moreover, although it is a low value compared with the wavelength of 450 nm or less, it has a peak even when the wavelength in the green region is about 530 nm to 560 nm. When the observation site is irradiated with light having a wavelength with a large extinction coefficient, the blood vessel has a large absorption, so that an image with high contrast between the blood vessel and the other portion can be obtained. Therefore, in the endoscope system of Patent Document 1, blue light in the wavelength region having a wavelength of about 390 to 445 nm is used for surface blood vessel enhancement, and green light in the wavelength region of about 530 to 550 nm is used for medium and deep blood vessel enhancement. Utilizing this, a blood vessel emphasizing image for emphasizing each of the superficial blood vessel and the middle-deep blood vessel is acquired.

  In the endoscope system described in Patent Document 1, a blue light and a green light are generated by combining a white light source such as a xenon lamp and a rotating filter having light transmittance in the blue and green wavelength regions. . Patent Document 1 discloses a technique for performing color tone calibration by photographing a color reference object with an endoscope and adjusting the gain of an image signal for each obtained color (paragraph 0035). , 0036). According to this, even when there is a difference in the transmission characteristics of the optical system depending on the endoscope model, an image with an appropriate color tone can be obtained regardless of the model.

  In the endoscope system described in Patent Document 2, a semiconductor light source such as a laser diode (LD) or an LED is used as a light source that emits blue light or green light. The greater the amount of blue light or green light, the higher the blood vessel contrast. If a semiconductor light source is used, a high output can be obtained as compared with the xenon lamp disclosed in Patent Document 1, so that a high-contrast image can be easily obtained.

JP-A-2005-131130 JP 2011-041758 A

  However, when the light transmission characteristics of the light guide of the existing endoscope were examined, as shown in FIG. 17, the light transmittance in the short wavelength region is lower than that in the long wavelength region, and in particular, the wavelength is about 430 nm or less. It was found that the light transmittance dropped drastically in the blue region. If the light guide has a low light transmittance, the amount of emitted light that is guided by the light guide and emitted to the observation site also decreases, making it difficult to utilize the performance of the semiconductor light source. Therefore, development of an improved endoscope having a light guide with improved light transmittance in the blue region is being studied.

  Even when developing an improved endoscope, considering the convenience of users who have existing endoscopes (operators performing endoscopy), the improved endoscope and existing endoscopes It is desirable to ensure the compatibility of both in the light source device so that both can be used.

  However, if the light transmission characteristics of the light guide are different, the amount of emitted light varies depending on the type of endoscope. In normal observation, there is little effect because the brightness of a part of the wide wavelength range from blue to red is reduced, but in the case of blood vessel enhancement observation, since monochromatic light such as blue light and green light is used, The decrease in the light transmittance of blue light has a great effect because it causes a decrease in the contrast of the superficial blood vessel that is the main observation target.

  Patent Documents 1 and 2 do not clearly indicate or suggest such problems or solutions. Patent Document 1 discloses a technique for performing color tone calibration by adjusting the gain of an image signal for each color in an image processing apparatus that acquires an image signal from an endoscope. For example, the above problem cannot be solved because it is a process of increasing the brightness of the entire screen including a bright portion and a dark portion in one screen with respect to a blue image signal.

  The present invention has been made in view of the above problems, and its purpose is to provide an observation image captured by each of the endoscopes even when blood vessel enhancement observation is performed using a plurality of types of endoscopes having different optical characteristics of the light guide. The purpose is to obtain similar blood vessel contrast.

  The image processing apparatus of the present invention is a first and second light guide for guiding illumination light that illuminates an observation site in a living body, and has a first difference in light transmittance with respect to light for blood vessel information observation. The first and second endoscopes each incorporating the first and second light guides in a replaceable manner, and the types of endoscopes connected to the connection parts are the first and second endoscopes. An endoscope identifying unit that identifies which one is a mirror, and an image processing unit that performs image processing on an image signal output from each of the first and second endoscopes. For image signals output from an endoscope having a relatively low light transmittance among the endoscopes of the above, the image processing for the image signal output from the endoscope having a higher light transmittance is performed. In addition, an image processing unit that performs contrast enhancement processing is provided.

  The contrast enhancement process is, for example, a gradation correction process.

  There are at least two types of light for observing blood vessel information, for example, first light and second light, and at least one of the two types has a difference in light transmittance.

  For example, the image processing unit performs contrast enhancement processing only on an image signal corresponding to light having a relatively large difference in light transmittance among the first and second lights.

  For example, the second light has a relatively large difference in light transmittance between the first light and the second light, and the second light is blue light having a wavelength of about 430 nm or less. Blue light has a wavelength of about 410 ± 10 nm, for example. The first light includes, for example, green light having a wavelength range of about 530 nm to 560 nm. The light for observing blood vessel information is output by, for example, a semiconductor light source.

  The light guide is, for example, a fiber bundle in which optical fibers are bundled. The contrast enhancement process is, for example, a gradation correction process.

  An endoscope system according to the present invention is an endoscope system including first and second endoscopes, and an image processing device to which the first and second endoscopes are interchangeably connected. The second endoscope is a first and second light guide for guiding illumination light for illuminating an observation site in a living body, and there is a difference in light transmittance with respect to light for blood vessel information observation. Each of the first and second light guides is built in, and the image processing apparatus includes a connection unit that connects the first and second endoscopes in a replaceable manner, and a type of endoscope that is connected to the connection unit. An endoscope identification unit that identifies which is the first or second endoscope, and first and second lights output from the first and second endoscopes, respectively. An image processing unit that performs image processing on a corresponding image signal, and the light transmittance of the first and second endoscopes is relatively An image processing unit that performs contrast enhancement processing on the image signal output from the endoscope having the higher light transmittance in addition to the image processing for the image signal output from the endoscope having the higher light transmittance. It is characterized by having.

  According to the present invention, when performing image processing on each image signal for observing blood vessel information output from a plurality of endoscopes, an endoscope with a relatively low light transmittance of the light guide outputs. For image signals, in addition to image processing for image signals output by endoscopes with high light transmittance, contrast enhancement processing is executed. Therefore, in the observation images taken with each endoscope, similar blood vessels are used. Contrast can be obtained.

It is an external view of the endoscope system of the present invention. It is a front view of the front-end | tip part of an endoscope. It is a block diagram which shows the electric constitution of an endoscope system. It is a graph which shows the spectrum of illumination light. It is a graph which shows the absorption spectrum of hemoglobin. It is a graph which shows the scattering coefficient of a biological tissue. It is a graph which shows the spectral characteristic of the color microfilter of an image pick-up element. It is explanatory drawing which shows the irradiation timing and imaging timing of illumination light. It is explanatory drawing of the structure which identifies the model of an endoscope. It is a graph which shows the light transmission characteristic of a light guide. It is a graph which shows the relationship between a drive current value and emitted light quantity. It is explanatory drawing which shows the image processing procedure in normal observation mode. It is explanatory drawing which shows the image processing procedure in blood-vessel emphasis observation mode. It is explanatory drawing of a contrast adjustment process. It is a flowchart which shows the image processing procedure in blood-vessel emphasis observation mode. It is explanatory drawing which shows another aspect of the light for blood vessel emphasis. It is a graph which shows the light transmission characteristic of the conventional light guide.

  As shown in FIG. 1, an endoscope system 10 according to a first embodiment of the present invention includes an endoscope 11 that images an observation site in a living body, and an observation image of the observation site based on a signal obtained by the imaging. , A light source device 13 that supplies light to irradiate the observation site to the endoscope 11, and a monitor 14 that displays an observation image. The processor device 12 is provided with a console 15 that is an operation input unit such as a keyboard and a mouse.

  The endoscope system 10 includes a normal observation mode for observing an observation site under white light, and a blood vessel enhancement observation mode for highlighting blood vessels existing in the observation site using special light. The blood vessel enhancement observation mode is a special light observation mode for diagnosing the quality of blood vessels, etc., and making a diagnosis such as tumor quality. Special light has a wavelength range with high absorbance to hemoglobin in the blood. Narrow band light is used.

  The endoscope 11 includes an insertion portion 16 to be inserted into a subject's digestive tract, an operation portion 17 provided at a proximal end portion of the insertion portion 16, an operation portion 17, a processor device 12, and a light source device 13. And a universal cord 18 for connecting the two.

  The insertion portion 16 includes a distal end portion 19, a bending portion 20, and a flexible tube portion 21 that are continuously provided from the distal end. As shown in FIG. 2, on the distal end surface of the distal end portion 19, the illumination window 22 that irradiates the observation site with illumination light, the observation window 23 that receives the image light reflected by the observation site, and the observation window 23 are washed. An air supply / water supply nozzle 24 for performing air supply / water supply, a forceps outlet 25 for projecting a treatment instrument such as forceps and an electric knife, and the like are provided. An imaging element 44 (see FIG. 3) and an imaging optical system are built in the back of the observation window 23.

  The bending portion 20 includes a plurality of connected bending pieces, and is bent in the vertical and horizontal directions by operating the angle knob 26 of the operation portion 17. By bending the bending portion 20, the direction of the distal end portion 19 is directed in a desired direction. The flexible tube portion 21 is flexible so that it can be inserted into a tortuous duct such as the esophagus or the intestine. The insertion unit 16 includes a communication cable that communicates a drive signal for driving the image sensor 44 and an image signal output from the image sensor 44, and a light guide 43 that guides illumination light supplied from the light source device 13 to the illumination window 22. (See FIG. 3) is inserted.

  In addition to the angle knob 26, the operation unit 17 is provided with a forceps port 27 for inserting a treatment instrument, an air / water supply button for performing air / water supply operation, a release button for photographing a still image, and the like. Yes.

  A communication cable and a light guide 43 extending from the insertion portion 16 are inserted into the universal cord 18, and a connector 28 is attached to one end of the processor unit 12 and the light source device 13. The connector 28 is a composite type connector composed of a communication connector 28a and a light source connector 28b. One end of a communication cable is disposed on the communication connector 28a, and the communication connector 28a is detachably connected to a receptacle connector 42a (see FIG. 3) of the processor device 12. The light source connector 28b is provided with an incident end of the light guide 43, and the light source connector 28b is detachably connected to the receptacle connector 42b (see FIG. 3) of the light source device 13.

  As shown in FIG. 3, the light source device 13 includes two types of first and second light source modules 31 and 32 having different emission wavelengths, and a light source control unit 34 that drives and controls them. The light source control unit 34 controls drive timing and synchronization timing of each unit of the light source device 13.

  The first and second light source modules 31 and 32 have laser diodes LD1 and LD2 that emit narrowband light in a specific wavelength range, respectively. As shown in FIG. 4, the laser diode LD1 emits narrowband light N1 having a wavelength region limited to 440 ± 10 nm and a center wavelength of 445 nm in the blue region. In the blue region, the laser diode LD2 emits narrowband light N2, which is a narrowband light whose wavelength range is limited to 410 ± 10 nm and whose center wavelength is 405 nm, for example. As the laser diodes LD1 and LD2, those of InGaN, InGaNAs, and GaNAs can be used. Further, as the laser diodes LD1 and LD2, a broad area type laser diode having a wide stripe width (waveguide width) capable of increasing output is preferable.

The first light source module 31 is a light source that emits white light for normal observation. The first light source module 31 includes a phosphor 36 in addition to the laser diode LD1. As shown in FIG. 4, the phosphor 36 is excited by the 445 nm blue-band narrow-band light N1 emitted from the laser diode LD1, and emits fluorescence FL in a wavelength region extending from the green region to the red region. The phosphor 36 absorbs a part of the narrowband light N1 to emit fluorescence FL and transmits the remaining narrowband light N1. The narrowband light N1 that passes through the phosphor 36 is diffused by the phosphor 36. White light is generated by the transmitted narrow-band light N1 and the excited fluorescence FL. As the phosphor 36, for example, a YAG-based or BAM (BgMgAl ₁₀ O ₁₇ ) -based phosphor is used. Two first light source modules 31 are provided so that the amount of white light increases.

  The second light source module 32 is a light source for surface blood vessel enhancement. In FIG. 5 showing the absorption spectrum of blood hemoglobin, the absorption coefficient μa of blood hemoglobin has a wavelength dependence, increases rapidly in the region where the wavelength is 450 nm or less, and has a peak in the vicinity of 405 nm. Yes. Moreover, although it is a low value compared with the wavelength of 450 nm or less, it also has a peak at wavelengths of 530 nm to 560 nm. When the observation site is irradiated with light having a wavelength having a large extinction coefficient μa, the blood vessel has a large absorption, so that an image having a large contrast between the blood vessel and the other portion is obtained. In FIG. 5, an absorption spectrum Hb indicates an absorption spectrum of reduced hemoglobin not bonded to oxygen, and an absorption spectrum HbO2 indicates an absorption spectrum of oxidized hemoglobin bonded to oxygen.

  Further, as shown in FIG. 6, the light scattering characteristics of the living tissue also have wavelength dependence, and the scattering coefficient μS increases as the wavelength becomes shorter. Scattering affects the depth of light penetration into living tissue. That is, the greater the scattering, the more light that is reflected near the mucosal surface layer of the biological tissue and the less light that reaches the mid-depth layer. Therefore, the shorter the wavelength, the lower the depth of penetration, and the longer the wavelength, the higher the depth of penetration. In view of such light absorption characteristics of hemoglobin and light scattering characteristics of living tissue, the wavelength of light for blood vessel enhancement is selected.

  The 405 nm narrow-band light N2 emitted from the second light source module 32 has a low depth of penetration, and is therefore absorbed by the surface blood vessels, and is therefore used as light for emphasizing the surface blood vessels. By using the narrowband light N2, the superficial blood vessel can be depicted with high contrast in the observation image. Further, the green component of white light emitted from the first light source module 31 is used as the light for emphasizing the middle deep blood vessel. In the absorption spectrum shown in FIG. 5, the absorption coefficient gradually changes in the green region of 530 nm to 560 nm as compared with the blue region of 450 nm or less. It is not required to be. Therefore, as described later, a green component color-separated from white light by the G-color micro color filter of the image sensor 44 is used.

  The light source control unit 34 controls turning on / off of the laser diodes LD <b> 1 and LD <b> 2 and the amount of light through the driver 37. Specifically, the light source control unit 34 turns on the laser diodes LD1 and LD2 by applying a drive pulse. Then, by performing PWM control for controlling the duty ratio of the drive pulse, the output (light emission amount) is controlled by changing the drive current value. The control of the drive current value may be PAM control for changing the amplitude of the drive pulse.

  A branched light guide 41 is provided on the downstream side of the optical path of the first and second light source modules 31 and 32. The branched light guide 41 is an optical path integration unit that integrates the optical paths of the first and second light source modules 31 and 32 into one optical path. Since the light guide 43 of the endoscope 11 has one incident end, each module is provided in a stage before the light from the first and second light source modules 31 and 32 is supplied to the endoscope 11 by the branched light guide 41. The optical paths 31 and 32 are integrated. The branched light guide 41 has branch portions 41a to 41c whose incident ends are branched into a plurality of portions, and emits light incident from the respective branch portions 41a to 41c from one output end 41e.

  The two first light source modules 31 are disposed so as to face the incident surfaces of the branch portions 41a and 41b of the branch light guide 41, respectively, and the second light source module 32 faces the incident surface of the branch portion 41c. Be placed.

  The exit end 41e of the branched light guide 41 is disposed near the receptacle connector 42b to which the connector 28b of the endoscope 11 is connected. The exit end 41e is provided with a homogenizer 50 for making the light quantity distribution in the cross section of the light beam uniform, and the light from the first and second light source modules 31 and 32 incident on the branched light guide 41 is the homogenizer 50. Is supplied to the light guide 43 of the endoscope 11 disposed in the connector 28b.

  The endoscope 11 includes a light guide 43, an imaging element 44, an analog processing circuit 45 (AFE: Analog Front End), and an imaging control unit 46. The light guide 43 is a fiber bundle in which a plurality of optical fibers are bundled. When the connector 28 is connected to the light source device 13, the incident end of the light guide 43 faces the emission end of the homogenizer 50 of the light source device 13. . The exit end of the light guide 43 branches into two at the front stage of the illumination window 22 so that light is guided to the two illumination windows 22.

  An irradiation lens 48 is disposed behind the illumination window 22. The light supplied from the light source device 13 is guided to the irradiation lens 48 by the light guide 43 and irradiated from the illumination window 22 toward the observation site. The irradiation lens 48 is a concave lens, and widens the divergence angle of the light emitted from the light guide 43. Thereby, illumination light is irradiated to the wide range of an observation site | part.

  In the back of the observation window 23, an objective optical system 51 and an image sensor 44 are arranged. The image light reflected by the observation site enters the objective optical system 51 through the observation window 23 and is imaged on the imaging surface 44 a of the imaging element 44 by the objective optical system 51.

  The imaging element 44 is composed of a CCD image sensor, a CMOS image sensor, or the like, and has an imaging surface 44a in which a plurality of photoelectric conversion elements constituting pixels such as photodiodes are arranged in a matrix. The image sensor 44 photoelectrically converts the light received by the imaging surface 44a and accumulates signal charges corresponding to the amount of received light in each pixel. The signal charge is converted into a voltage signal by an amplifier and read out. The voltage signal is output from the image sensor 44 as an image signal, and the image signal is sent to the AFE 45.

  The image pickup device 44 is a color image pickup device, and micro-color filters of three colors B, G, and R having spectral characteristics as shown in FIG. 7 are assigned to each pixel on the image pickup surface 44a. The white light emitted from the first light source module 31 is split into three colors B, G, and R by the micro color filter. The arrangement of the micro color filter is, for example, a Bayer arrangement.

  As shown in FIG. 8, in the normal observation mode, the image sensor 44 performs an accumulation operation for accumulating signal charges and a read operation for reading the accumulated signal charges within an acquisition period of one frame. As shown in FIG. 8A, in the normal observation mode, the laser diode LD1 is turned on in accordance with the accumulation timing, and the observation site is irradiated with white light composed of the narrowband light N1 and the fluorescence FL as illumination light. The reflected light enters the image sensor 44. In the image sensor 44, the white light is color-separated by a micro color filter, the B pixel receives reflected light corresponding to the narrowband light N1, the G pixel in the fluorescent FL, the G pixel in the fluorescent FL, The R pixel receives reflected light corresponding to the R component. The image sensor 44 sequentially outputs the image signals B, G, and R for one frame in which the pixel values of the B, G, and R pixels are mixed according to the frame rate in accordance with the readout timing. Such an imaging operation is repeated while the normal observation mode is set.

  In the blood vessel enhancement observation mode, as shown in FIG. 8B, the second light source module 32 is turned on in addition to the first light source module 31 in accordance with the accumulation timing. When the first light source module 31 is turned on, similarly to the normal observation mode, the observation site is irradiated with white light (N1 + FL) composed of the narrowband light N1 and the fluorescence FL as illumination light. When the second light source module 32 is turned on, the narrowband light N2 is added to the white light (N1 + FL), and these are irradiated to the observation site as illumination light.

  As in the normal observation mode, the illumination light in which the narrow-band light N2 is added to the white light is split by the B, G, and R micro color filters of the image sensor 44. In the image sensor 44, the B pixel receives the narrowband light N2 in addition to the narrowband light N1. The G pixel receives the G component of the fluorescence FL. The R pixel receives the R component of the fluorescence FL. Even in the blood vessel enhancement observation mode, the image sensor 44 sequentially outputs the image signals B, G, and R according to the frame rate in accordance with the readout timing. Such an imaging operation is repeated while the blood vessel enhancement observation mode is set.

  In FIG. 3, the AFE 45 includes a correlated double sampling circuit (CDS), an automatic gain control circuit (AGC), and an analog / digital converter (A / D) (all not shown). The CDS performs a correlated double sampling process on the analog image signal from the image sensor 44, and removes noise caused by resetting the signal charge. AGC amplifies an image signal from which noise has been removed by CDS. The A / D converts the image signal amplified by AGC into a digital image signal having a gradation value corresponding to a predetermined number of bits and inputs the digital image signal to the processor device 12.

  The imaging control unit 46 is connected to a controller 56 in the processor device 12 and inputs a drive signal to the imaging element 44 in synchronization with a base clock signal input from the controller 56. The imaging element 44 outputs an image signal to the AFE 45 at a predetermined frame rate based on the drive signal from the imaging control unit 46.

  The ID memory 47 is a storage unit that stores an endoscope ID that is identification information for identifying the model and the individual of the endoscope 11, and includes, for example, a nonvolatile memory such as an EEPROM or a flash memory. The endoscope ID is output to the processor device 12 through the connector 28a. Of course, as the ID memory 47, an RFID tag capable of wirelessly transmitting information may be used.

  As shown in FIG. 9, the endoscope system 10 can use a plurality of types of endoscopes 11A and 11B. The endoscope 11B is an existing endoscope having a light guide 43B, and the endoscope 11A is an improved endoscope having a light guide 43A with improved light transmission characteristics with respect to the light guide 43B. is there.

  As shown in FIG. 10, in the light transmission characteristic B of the light guide 43B, the light transmittance drops in the blue region having a wavelength of 430 nm or less, particularly in the vicinity of about 410 nm. On the other hand, the light transmission characteristic A of the light guide 43A has an improved light transmittance mainly in the blue region as compared with the light guide 43B.

  Comparing the light transmission characteristics A and B, the difference d2 between the light transmittances TA2 and TB2 in the blue region is large, and the difference d1 between the light transmittances TA1 and TB1 in the green region having a longer wavelength than the blue region is small. Therefore, the output of light supplied from the light source device 13 to the endoscopes 11A and 11B and the light guides 43A and 43B of the endoscopes 11A and 11B are guided and emitted from the respective illumination windows 22 to the observation site. The relationship with the emitted light quantity is as shown in FIG.

  In FIG. 11, the drive current value is a current value for driving the laser diodes LD1 and LD2, and corresponds to the light output of each of the first light source modules 31 and 32. Graphs GA and GB are the relationship between the output of the G component of the white light emitted by the first light source module 31 and the amount of emitted light when the endoscopes 11A and 11B are used. The graphs N2A and N2B are the second This is the relationship between the output of the light source module 32 and the amount of emitted light.

  As shown in the graphs GA and GB, for the G component of the white light emitted from the first light source module 31, the difference Δ1 between the light transmittances TA1 and TB1 of the light guides 43A and 43B corresponding thereto is small, so the first light source When the output of the module 31 is the same, the difference in the amount of emitted light is also small. On the other hand, as shown in the graphs N2A and N2B, for the narrowband light N2 emitted from the second light source module 32, the difference Δ1 between the light transmittances TA2 and TB2 of the light guides 43A and 43B is large. When the output of the module 32 is the same, the difference in emitted light quantity is also large. Since the light transmittance TB2 of the light guide 43B is about half of the light transmittance TA2 of the light guide 43A, the amount of emitted light also falls to about half.

  3 and 9, the processor device 12 includes a DSP (Digital Signal Processor) 57, an image processing unit 58, a frame memory 59, and a display control circuit 60 in addition to the controller 56. The controller 56 includes a CPU, a ROM that stores a control program and setting data necessary for control, a RAM that loads the program and functions as a work memory, and the like. To control.

  The ROM in the controller 56 stores a model table (TBL) 56a that stores a correspondence relationship between the endoscope ID and model information representing one of the endoscopes 11A and 11B. The controller 56 transmits the model information identified with reference to the model table 56 a to the image processing unit 58. Since the endoscopes 11A and 11B have different light transmission characteristics of the light guides 43A and 43B, the image processing unit 58 changes the contents of the image processing according to the model information as will be described later.

  The DSP 57 acquires an image signal output from the image sensor 44. The DSP 57 separates an image signal in which signals corresponding to B, G, and R pixels are mixed into B, G, and R image signals, and performs pixel interpolation processing on the image signals of the respective colors. In addition, the DSP 57 performs signal processing such as gamma correction and white balance correction on each of the B, G, and R image signals.

  Further, the DSP 57 calculates the exposure value based on the image signals B, G, and R, and the light amount is increased so that the light amount of the illumination light is increased when the light amount of the entire image is insufficient (underexposure). If it is too high (overexposure), an exposure control signal is transmitted to the light source device 13 via the controller 56 so as to reduce the amount of illumination light.

  The frame memory 59 stores image data output by the DSP 57 and processed data processed by the image processing unit 58. The display control circuit 60 reads the image processed image data from the frame memory 59, converts it into a video signal such as a composite signal or a component signal, and outputs it to the monitor 14.

  As shown in FIG. 12, in the normal observation mode, the image processing unit 58 displays the display image for normal observation based on the image signals B, G, and R separated into B, G, and R colors by the DSP 57. (Observation image P) is generated. The generated observation image P is output to the monitor 14. The image processing unit 58 updates the display image every time the image signals B, G, and R in the frame memory 59 are updated. In the observation image P, the entire properties of the observation site such as the mucous membrane, the superficial blood vessel 61, and the intermediate deep blood vessel 62 are displayed in full color.

  In the normal observation mode, white light (N1 + FL) output from the first light source module 31 is irradiated to the observation site and imaging is performed. Since there is no significant difference in the light transmission characteristics of the light guides 43A and 43B with respect to white light, the image processing unit 58 performs the same image processing on both of the image signals output from the endoscopes 11A and 11B. Do.

  As shown in FIG. 13, in the blood vessel enhancement observation mode, the image processing unit 58 generates a display image for blood vessel enhancement observation based on the image signals B, G, and R. The image signal B in the blood vessel enhancement observation mode includes information on the narrow band light N2 in addition to the B component of white light (including a part of the narrow band light N1 and the fluorescence FL). It is drawn with high contrast. In lesions such as cancer, there is a tendency to increase the density of superficial blood vessels compared to normal tissues, so there is a feature in the blood vessel pattern, so in blood vessel enhancement observation for the purpose of tumor discrimination, It is preferable that the superficial blood vessel is clearly depicted. Further, since the image signal G contains a lot of information on the middle-deep blood vessels, the image signal G is subjected to contour enhancement processing and the like to emphasize the middle-deep blood vessels.

  The display image for blood vessel enhancement observation is generated based on the three color image signals B, G, and R in the same way as for normal observation, so that the observation site can be displayed in full color. The image signal B in the mode has a higher blue density than the image signal B in the normal observation mode. For this reason, when a display image for blood vessel enhancement observation is generated, color correction is performed so that the same color as that of the display image for normal observation is obtained. The image processing unit 58 generates a display image (observation image PE) for blood vessel enhancement observation every time the image signals B, G, and R in the frame memory 59 are updated. In the observation image PE, the observation site is displayed in full color as in the observation image P. However, as compared with the observation image P, the superficial blood vessel 61 and the middle-deep blood vessel 62 are drawn with high contrast and highlighted.

  In the blood vessel enhancement observation mode, imaging is performed by irradiating the observation site with narrow-band light N2 output from the second light source module 32 in addition to white light. Since there is a large difference in the light transmission characteristics of the light guides 43A and 43B with respect to the narrowband light N2, the image processing unit 58 determines whether the output source of the image signal is the endoscope 11A or the endoscope. The content of the image processing is changed according to whether it is 11B.

  As shown in FIG. 12A, the above-described image processing is performed on the image signal output from the endoscope 11A having a high light transmittance with respect to the narrowband light N2. On the other hand, as shown in FIG. 12B, for the image signal output from the endoscope 11B having a low light transmittance with respect to the narrowband light N2, the image processing unit 58 uses the endoscope 11A. In addition to image processing, contrast enhancement processing is performed. Since the image signal corresponding to the narrow band light N2 is the blue image signal B, the contrast enhancement process is performed on the image signal B.

  As illustrated in FIG. 14, the image processing unit 58 obtains a density histogram for the image signal B when performing contrast adjustment processing. As is well known, the density histogram is a graph with pixel values (luminance values) on the horizontal axis and frequency on the vertical axis. In the image PB corresponding to the image signal B, the superficial blood vessel 61 and the intermediate deep blood vessel 62 are depicted.

  Since the narrowband light N2 has a wavelength region of 405 nm where the absorption coefficient of hemoglobin is high, the amount of reflected light is small and the pixel value is low in the region of the superficial blood vessel 61 and the mid-deep blood vessel 62. On the other hand, the region where the blood vessel does not exist is not absorbed by hemoglobin, and therefore the amount of reflected light is large and the pixel value is high. Therefore, in the image PB, the density of the superficial blood vessel 61 and the intermediate deep blood vessel 62 is higher than that of the region where the surrounding blood vessels do not exist.

  Further, since the narrowband light N2 has a blue wavelength region, it is highly scattered and has a low depth of penetration. Therefore, the amount of light reaching the middle-deep blood vessel 62 is small, and the surface blood vessel 61 absorbs a lot. In the image PB, the density of the superficial blood vessel 61 is rendered higher than that of the mid-deep blood vessel 62. The density histogram of the image PB has three peaks in descending order of density (lowest pixel value): a peak a of the superficial blood vessel 61, a peak b of the mid-deep blood vessel 62, and a peak c of the mucosa where no blood vessel exists.

  The image signal B output from the endoscope 11B has a smaller amount of narrowband light N2 than the endoscope 11A. This appears as a difference in the dynamic range DR which is the width of the maximum value (max) and the minimum value (min) of the pixel value in the density histogram. The dynamic range DR of the image PB obtained with the endoscope 11B is narrower than the dynamic range DR of the image PB obtained with the endoscope 11A.

  The image processing unit 58 has an internal memory such as a ROM, and a gradation correction table 58a is stored in the internal memory. The gradation correction table 58a has an input value on the horizontal axis and an output value on the vertical axis, and has a gradation correction curve indicating the correspondence between the input value and the output value. In order to increase the contrast, the low density portion of the original image before processing may be lower in density, and the higher density portion may be higher. Therefore, the image processing unit 58 performs the contrast enhancement processing as follows. Tone correction is performed based on the substantially S-shaped tone correction curve shown in FIG. 14 to widen the dynamic range DR of the image PB. As a result, the density difference between the blood vessel region and the region where no blood vessel exists increases, and the contrast of the blood vessel is improved. Since the image PB contains a lot of information on the superficial blood vessel 61, the contrast of the superficial blood vessel 61 is particularly improved.

  By performing such contrast enhancement processing, the contrast of the superficial blood vessel is improved in the image signal B output from the endoscope 11B. Thereby, the shortage of the narrow band light N2 in the endoscope 11B is compensated.

  In this example, as a method for generating a display image for blood vessel enhancement observation, a full-color image is generated using three color image signals B, G, and R. However, other methods may be used, for example, Instead of using the image signal R, the image signals B and G are generated in only two colors, the image signal B is set to the B channel and the G channel of the monitor 14, and the signal corresponding to the image signal G is set to the R channel of the monitor 14. A method of displaying the observation site in a pseudo color, such as an allocation method, may be employed.

  Hereinafter, the operation of the above configuration will be described with reference to the flowchart of FIG. When performing endoscopic diagnosis, the endoscope 11 is connected to the processor device 12 and the light source device 13 with the connector 28, the processor device 12 and the light source device 13 are turned on, and the electronic endoscope system 10 is activated. To do.

  The insertion part 16 of the endoscope 11 is inserted into the subject's digestive tract, and observation in the digestive tract is started. In the normal observation mode, the first light source module 31 is turned on as shown in FIG. White light in which narrowband light N1 emitted from the laser diode LD1 and fluorescence FL emitted from the phosphor 36 are mixed is supplied to the endoscope 11. The supplied light is guided to the illumination window 22 through the light guide 43 and irradiated to the observation site.

  As shown in FIGS. 8A and 12, the observation site is imaged by the imaging element 44 during the irradiation with white light (N1 + FL), and B, G, and R image signals are generated by the DSP 57. In the normal observation mode, the image processing unit 58 generates a display image for normal observation based on the B, G, and R image signals. The display control circuit 60 converts the generated display image into a video signal and displays the observation image P on the monitor 14. Such processing is repeated in the normal observation mode.

  In the normal observation mode, only white light emitted from the first light source module 31 is used as illumination light. Regarding the light transmittance of white light, the difference between the light guide 43A of the endoscope 11A and the light guide 43B of the endoscope 11B is small, so the image processing unit 58 does not distinguish the output source of the image signal. The same image processing is applied to both. A similar observation image can be obtained regardless of whether the endoscope 11A or the endoscope 11B is used. Therefore, the operator can use either the endoscope 11A or the endoscope 11B without any problem. it can.

  When performing blood vessel enhancement observation, a mode switching operation is performed by the console 15, and the processor device 12 is set to the blood vessel enhancement observation mode. As shown in FIG. 15, in the blood vessel enhancement observation mode, first, the light source control unit 34 acquires an endoscope ID from the ID memory 47 of the endoscope 11 via the processor device 12 (S101). Based on the acquired endoscope ID, the controller 56 identifies whether the connected endoscope 11 is the endoscope 11A or the endoscope 11B (S102), and performs image processing on the model information. It transmits to the part 58.

The image processing unit 58 changes the content of the image processing according to the model information (S103). When the model information is the endoscope 11A, a display image is generated by performing image processing based on the image signals B, G, and R, as shown in FIG. When the model information is the endoscope 11B, as shown in FIG. 13B, a contrast adjustment process is performed on the image signal B (S104). Then, a display image is generated based on the processed image signal B and the image signals G and R. Thereby, the same observation image PE is obtained regardless of which of the endoscopes 11A and 11B is used. Such a process is repeated until the blood vessel enhancement observation mode ends (S105).

  In the above embodiment, as a light source in the blood vessel enhancement observation mode, a light source (second light source module 32) that emits narrow-band light N2 having a wavelength of 405 nm and a white light source (first light source module 31) are used. However, as shown in FIG. 16, instead of or in addition to the white light source, the narrow-band light N2 is used for medium-deep layer blood vessel enhancement. A light source that emits narrowband light N3 (green narrowband light having a wavelength of about 530 to 560 nm) may be used.

  In addition, as a white light source, a light source composed of a light emitting element that emits blue excitation light and a phosphor that emits yellow fluorescence has been described as an example, but as a white light source, a light emitting element that emits blue excitation light and a red light emission The light emitting element may be composed of two light emitting elements and a phosphor emitting green fluorescence, or may be composed of light emitting elements of three colors of blue, green, and red without using the phosphor.

  In the above-described embodiment, blood vessel enhancement observation has been described as an example of blood vessel information observation. However, blood vessel information observation includes, in addition to blood vessel enhancement observation, oxygen saturation of blood, which is imaged and observed. There is saturation observation. The present invention can also be applied to oxygen saturation observation.

  Illumination light in oxygen saturation observation is, for example, light having a difference in extinction coefficient between oxyhemoglobin and reduced hemoglobin, such as light having a wavelength of 445 nm or 473 nm, and reduction from oxyhemoglobin, such as light having a wavelength of 405 nm. The light of the isosbestic point having the same extinction coefficient of hemoglobin is used. Then, an oxygen saturation is calculated by performing an operation between a plurality of images acquired at each wavelength. In the inter-image calculation, coefficients used for the calculation are set on the premise that the ratio of the emitted light amount of the light of each wavelength is maintained at a predetermined ratio. Therefore, it is not preferable that the ratio of the amount of emitted light changes depending on the endoscope model. Therefore, the accuracy of the inter-image calculation can be improved by performing contrast enhancement processing that compensates for the light amount reduction of the narrow-band light N2 (405 nm) in the endoscope 11B.

  In addition, in oxygen saturation observation, three or more types of light having different wavelengths are used as an example, but in blood vessel enhancement observation, in addition to blue light and green light, the wavelength is increased to emphasize deeper blood vessels. In some cases, three or more types of light are used, such as using long red light. The present invention may be applied when three or more types of light are used.

  In the above embodiment, as an example of a plurality of types of endoscopes, an existing endoscope and an improved endoscope with improved light transmission characteristics of the light guide in the blue region have been described as an example. The improved endoscope is an example. However, the present invention is not limited to this, and the endoscopes of a plurality of models are a plurality of endoscopes in which light guides having different light transmittances for at least one of two types of light for blood vessel information observation are incorporated. Good.

  In the above embodiment, the laser diode is described as an example of the semiconductor light source, but another semiconductor light source such as an LED may be used. In addition, the present invention combines a white light source that emits white light having a wide wavelength range from blue to red, such as a xenon lamp and a halogen lamp, and a rotating filter having transparency in a specific wavelength range such as narrow-band light N2. Thus, the present invention can also be applied to an endoscope system that generates light for blood vessel information observation.

  However, in the spectrum of white light emitted from a xenon lamp, a halogen lamp, or the like, the light intensity in the wavelength region close to the ultraviolet region, such as narrow-band light N2 (wavelength is about 405 nm), is often relatively low. Therefore, it is preferable to use a semiconductor light source when blood vessel information observation using the narrowband light N2 is performed, and the present invention is particularly effective when such a semiconductor light source is used.

  In the above-described embodiment, the contrast enhancement process is performed on the image signal B corresponding to the narrow-band light N2 in the blue region. However, the light guide has a light transmittance other than that in the blue region, such as the green region. In the case of a decrease in the region, contrast enhancement processing may be performed on the image signal for the wavelength region. In addition, regarding the light transmittance of the light guide, when there is a large difference in light transmittance in a plurality of wavelength regions such as a blue region and a green region, a contrast enhancement process is performed on the image signal corresponding to each wavelength region. May be executed.

  However, the present invention is particularly necessary when the narrow band light of the blue region is used as the blood vessel information observation light as shown in the above embodiment. The reason is as follows. As shown in FIG. 5, in the absorption spectrum of hemoglobin, the change in the extinction coefficient is sharper in the blue region than in the green region. Therefore, it is preferable that the light in the blue region for emphasizing the superficial blood vessels is narrowband light having a narrower wavelength range than the light in the green region for emphasizing the mid-deep blood vessels. If the wavelength range is narrow, the amount of light decreases accordingly. In addition, when the light transmittance is low in the blue region of the light guide, the amount of light further decreases. The greater the shortage of light quantity, the higher the need to compensate for the decrease in contrast by contrast enhancement processing as in the present invention. Therefore, the present invention is particularly effective when an endoscope having a light guide with a low light transmittance in the blue region is used to observe blood vessel information using narrow band light in the blue region.

  As contrast enhancement processing, instead of or in addition to gradation correction processing, edge enhancement processing for detecting and enhancing the edge of a blood vessel in an image may be used.

  In the above embodiment, the content of the image processing is changed based only on the model information of the endoscope. However, the content of the image processing is changed when the following conditions are satisfied in addition to the model information. May be. Even when the endoscope 11B is connected, if the output of the second light source module 32 that emits the narrowband light N2 can be increased as compared with the case where the endoscope 11A is connected, the narrowband light N2 by the light guide 43B can be increased. A decrease in the amount of emitted light can be compensated. Therefore, when the endoscope 11B is connected, first, in the light source device 13, the output of the second light source module 32 is increased so as to be the same as the amount of emitted light when the endoscope 11A is connected. Then, when the output of the second light source module 32 reaches the upper limit value and the output cannot be increased any more, the content of the image processing is changed.

  In the above-described embodiment, an example of a simultaneous method in which white light is color-separated by a micro color filter and a plurality of color images are simultaneously acquired using a color image sensor provided with B, G, and R micro color filters is described. However, the present invention may be applied to a frame sequential method in which images of respective colors are sequentially acquired using a monochrome imaging element not provided with a color filter.

  In the above-described embodiment, the example in which the light source device and the processor device that performs image processing are configured separately is described, but the two devices may be configured integrally. In addition, the present invention can be applied to other types of endoscope systems such as a system including an ultrasonic endoscope in which an imaging element and an ultrasonic transducer are built in a distal end portion and a processor device that performs image processing. it can.

DESCRIPTION OF SYMBOLS 10 Endoscope system 11, 11A, 11B Endoscope 12 Processor apparatus (image processing apparatus)
13 Light source device 28 Connector 31 1st light source module 32 2nd light source module 34 Light source control part 42a, 42b Receptacle connector (connection part)
43, 43A, 43B Light guides 47, 47A, 47B ID memory 56 Controller (endoscope identification unit)
58 Image processor 58a Gradation correction table LD1, LD2 Laser diode

Claims (10)

First and second light guides for guiding illumination light for illuminating an observation site in a living body, and first and second light guides having a difference in light transmittance with respect to light for observing blood vessel information are built in, respectively. A connecting portion for connecting the first and second endoscopes exchangeably,
An endoscope identification unit for identifying whether the type of endoscope connected to the connection unit is the first or second endoscope;
An image processing unit that performs image processing on an image signal output from each of the first and second endoscopes, and the light transmittance of the first and second endoscopes is relatively high. An image processing unit that performs contrast enhancement processing on the image signal output from the lower endoscope in addition to image processing on the image signal output from the endoscope having the higher light transmittance. An image processing apparatus comprising: The image processing apparatus according to claim 1 , wherein the contrast enhancement process is a gradation correction process.   The light for observing blood vessel information is at least two types of first light and second light, and at least one of the two types has a difference in the light transmittance. 2. The image processing apparatus according to 2.   The image processing unit performs the contrast enhancement process only on an image signal corresponding to light having a relatively large difference in the light transmittance among the first and second lights. 3. The image processing apparatus according to 3. It is the second light that has a relatively large difference in the light transmittance among the first and second lights,
5. The image processing apparatus according to claim 3, wherein the second light is blue light having a wavelength of about 430 nm or less.   The image processing apparatus according to claim 5, wherein the blue light has a wavelength of about 410 ± 10 nm.   The image processing apparatus according to claim 5, wherein the first light includes green light having a wavelength range of about 530 nm to 560 nm.   The image processing apparatus according to claim 1, wherein the blood vessel information observation light is light output from a semiconductor light source.   The image processing apparatus according to claim 1, wherein the light guide is a fiber bundle in which optical fibers are bundled. In an endoscope system including first and second endoscopes and an image processing device to which the first and second endoscopes are exchangeably connected,
The first and second endoscopes are:
First and second light guides for guiding illumination light for illuminating an observation site in a living body, and first and second light guides having a difference in light transmittance with respect to light for observing blood vessel information are built in, respectively. Has been
The image processing apparatus includes:
A connecting portion for connecting the first and second endoscopes in a replaceable manner;
An endoscope identification unit for identifying whether the type of endoscope connected to the connection unit is the first or second endoscope;
An image processing unit that performs image processing on image signals corresponding to the two types of light of the first and second lights output from the first and second endoscopes;
Of the first and second endoscopes, the image signal output from the endoscope having the relatively low light transmittance is received from the endoscope having the higher light transmittance. An endoscope system comprising: an image processing unit that performs contrast enhancement processing in addition to image processing on an output image signal.

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