JP5554288B2 - ENDOSCOPE SYSTEM, PROCESSOR DEVICE, AND IMAGE CORRECTION METHOD - Google Patents

Description

  The present invention relates to an endoscope system for observing the inside of a subject, a processor device used therefor, and an image correction method.

  In the medical field, diagnosis inside a subject using an endoscope is widely performed. The endoscope includes an insertion portion that is inserted into the subject, and an illumination window that irradiates illumination light toward the observation portion in the subject and an observation portion are imaged at the distal end portion of the insertion portion. And an observation window. An imaging element such as a CCD or CMOS is provided in the back of the observation window, and the illuminated observation region is imaged by the imaging element, and an image signal representing the observation image is output. The observation image is displayed on the monitor.

  As a light source of illumination light, a white light source such as a xenon lamp, a halogen lamp, or a metal halide lamp is often used. However, as shown in Patent Documents 1 and 2, a semiconductor light source such as an LED or a laser light source is also used. It has become to.

  Patent Document 1 discloses an endoscope system that generates white light by combining three-color LEDs by combining three-color LEDs of B (blue), G (green), and R (red). Patent Document 2 combines an LED that emits blue excitation light with a phosphor that absorbs part of the blue excitation light to excite yellow fluorescence and transmits the remaining excitation light. An endoscope system that generates white light by mixing blue and yellow light in a complementary color relationship is disclosed.

  The semiconductor light source is advantageous in that it is smaller than a white light source such as a xenon lamp, has low power consumption, and can easily control the light emission amount. There are also problems that should be improved. Specifically, the color distribution of white light such as a xenon lamp is a color distribution with a relatively flat light intensity over the entire range from blue to red, whereas white light generated by three-color LEDs. The color distribution is a biased color distribution having a peak of light intensity in each of the B, G, and R wavelength ranges. Such a difference in color distribution appears as a uniform change in color tone over the entire observation image. In the endoscope system of Patent Document 1, the observation image is corrected by image processing so that the color distribution with the bias of white light by the three color LEDs approaches a flat color distribution such as a xenon lamp.

JP 2010-45615 A Japanese Patent Laid-Open No. 10-216085

  The present applicant has developed an endoscope system that generates white light by a combination of a semiconductor light source that emits excitation light and a phosphor as described in Patent Document 2. In the course of development, in addition to the problem of the semiconductor light source pointed out in Patent Document 1, a new color unevenness occurs in the observation image due to the difference in the light distribution of excitation light and fluorescence (spatial light intensity distribution). It has become clear that there is a problem.

  As shown in FIG. 5, the light distribution of the excitation light (blue laser light) N1 and the light distribution of the fluorescence FL both have the maximum light intensity at the irradiation center OI in the irradiation area where the light distribution angle is 0 °. It becomes a mountain-shaped light distribution in which the light intensity decreases as the absolute value of the light distribution angle increases toward the periphery. In FIG. 5, the light distributions of both are represented by relative intensities normalized by matching the light intensities at the irradiation center OI. The difference ΔI between the two light intensities is not constant from the irradiation center OI to the periphery, and becomes larger toward the periphery.

  The light distribution distribution of excitation light and fluorescence changes because the wavelength range of excitation light and fluorescence is different. In addition to the difference in refractive index that occurs in optical members such as illumination windows, excitation light passes through the phosphor. Fluorescence is thought to be caused by the highly diffusible light that the phosphor emits and emits light, whereas the light is highly directional (which goes straight without diffusing). The influence by the difference in the diffusibility of fluorescence is large.

  The difference in the light distribution between the excitation light and the fluorescence appears as uneven color whose color tone changes depending on the region in the observation image. In diagnosis, since it is determined whether or not the lesion is a lesion based on a subtle change in color of the observation image, it is not preferable that the color tone changes depending on the region in the observation image.

  Moreover, as a measure for preventing such color unevenness, it is conceivable to make the light distributions of the two coincide with each other by improving the illumination optical system. However, if the illumination optical system is improved, the component configuration such as optical members is complicated. There is a concern that

  Neither Patent Document 1 nor 2 discloses or suggests the above problem and its solution. In Patent Document 1, in contrast to the color distribution of white light such as a xenon lamp, the color distribution of the white light of the semiconductor light source is caused by the deviation of the color distribution, and uniform color tone change in the entire observation image is a problem. Is caused by a difference in light distribution between excitation light and fluorescence, and is clearly different from the problem of color unevenness in which the color tone changes depending on the region in the observed image.

  The present invention has been made in view of the above-described background, and an object of the present invention is to distribute excitation light and fluorescence without complicating the configuration of the illumination optical system when white light is generated by excitation light and fluorescence. The object is to reduce color unevenness in the observed image caused by the difference in light distribution.

  In order to achieve the above object, an endoscope system according to the present invention has an insertion portion to be inserted into a subject, and irradiates illumination light to an observation site in the subject at a distal end portion of the insertion portion. An endoscope having an illuminating window, an observation window for photographing the observation site, a first semiconductor light source that emits excitation light, and a phosphor that emits fluorescence when excited by the excitation light Irradiating means for irradiating, as the illumination light, a mixture of a part of the excitation light that passes through the phosphor and the fluorescence from the illumination window, and the reflected from the observation site through the observation window An imaging unit that receives illumination light and images an observation image of the observation site, and stores correction data for correcting color unevenness in the observation image caused by a difference in light distribution between the excitation light and the fluorescence Storage means for storing the correction data Zui it, characterized in that it includes a color unevenness correction means for correcting the color unevenness by performing image processing on the observation image.

  The first semiconductor light source is, for example, a laser light source.

  Two illumination windows are provided, and it is preferable that the color unevenness correction unit corrects the color unevenness in accordance with how the irradiation areas of the two illumination windows overlap each other.

  An observation distance measuring unit that measures an observation distance that is a distance between the distal end portion and the observation site; and the color unevenness correction unit overlaps the two irradiation areas based on the measured observation distance. It is preferable to determine the direction.

  The correction data is partial data corresponding to a light distribution of a part of the irradiation area, and the color unevenness correction unit converts the light distribution over the entire irradiation area based on the partial data. It is preferable to generate corresponding global data.

  For example, in the excitation light and the fluorescence, each irradiation area is substantially circular, and the difference in light intensity in each light distribution varies depending on the radial distance from the irradiation center, and the partial data is One-dimensional data corresponding to a light distribution in a one-dimensional direction extending in a radial direction from the irradiation center, and the color unevenness correction unit generates the whole area data by expanding the one-dimensional data in a circumferential direction. To do.

  The storage means is preferably provided in the endoscope.

  Preferably, the excitation light is blue light, the fluorescence is green to red light, and the white illumination light is generated by mixing the excitation light and the fluorescence.

  The irradiation unit includes a second semiconductor light source that emits light having a wavelength range different from that of the excitation light, and transmits the light emitted from the second semiconductor light source through the phosphor through the illumination window. It may be irradiated.

  The correction data includes first correction data when only the excitation light and the fluorescence are irradiated, and second correction when the light from the second semiconductor light source is irradiated in addition to the excitation light and the fluorescence. The data has two types of correction data, and the color unevenness correction unit selects either the first correction data or the second correction data in accordance with the presence or absence of light irradiation from the second semiconductor light source. It is preferable.

  For example, the first semiconductor light source emits narrow band light having a central wavelength of 445 nm, and the second semiconductor light source emits narrow band light having a central wavelength of 405 nm, for example.

  The processor device of the present invention includes a first semiconductor light source that emits excitation light, and a phosphor that emits fluorescence when excited by the excitation light, and transmits the phosphor from an illumination window of an endoscope. In a processor device used in an endoscope system having irradiation means for irradiating light mixed with a part of the excitation light and the fluorescence as illumination light, in the observation image photographed by the endoscope, the excitation Means for reading out from the storage means correction data for correcting color unevenness caused by a difference in light distribution between light and the fluorescence; and based on the correction data, the observed image is subjected to image processing to produce the color unevenness. And color unevenness correcting means for correcting the above.

  The image correction method of the present invention includes a first semiconductor light source that emits excitation light and a phosphor that emits fluorescence when excited by the excitation light, and the phosphor is emitted from an illumination window of an endoscope. In an image correction method used in an endoscope system having an irradiation unit that irradiates light that is a mixture of a part of the excitation light that is transmitted and the fluorescence as illumination light, in an observation image captured by the endoscope, Reading correction data for correcting color unevenness caused by a difference in light distribution between the excitation light and the fluorescence from the storage means, and performing image processing on the observation image based on the correction data, A color unevenness correcting step for correcting the color unevenness.

It is a figure shown in an endoscope system. It is a figure which shows the front end surface of the front-end | tip part of an electronic endoscope. It is a figure which shows the cross section of the front-end | tip part of an electronic endoscope. It is a graph which shows the spectrum of a light projection unit. It is a graph which shows the light distribution of a light projection unit. It is explanatory drawing which shows the relationship between an irradiation area and an imaging | photography area. It is explanatory drawing which shows the mode of how the irradiation area and imaging | photography area overlap when an observation distance is long. It is explanatory drawing which shows the mode of how the irradiation area and imaging | photography area overlap when an observation distance is short. It is a block diagram which shows the outline of the electric constitution of an endoscope system. It is a block diagram of an image processing part. It is a flowchart which shows a color nonuniformity correction procedure. It is a block diagram of the light projection unit which has two laser light sources. It is a graph which shows the spectrum of the light projection unit of FIG. It is a graph which shows the light distribution of the light projection unit of FIG. It is explanatory drawing of the expansion | deployment process of one-dimensional correction data. It is explanatory drawing of the example which provided the correction data memory | storage part in the electronic endoscope.

[First Embodiment]
As shown in FIG. 1, the endoscope system 2 according to the first embodiment includes an insertion unit 20 that is inserted into a subject, an electronic endoscope 10 that images an observation site in the subject, and an electronic A processor device 12 that performs image processing on an imaging signal representing an observation image captured by the endoscope 10; a light source device 13 that is provided in the processor device 12 and irradiates illumination light to an observation site; A monitor 14 for displaying an observation image and a water supply tank 16 for storing water to be sent into the subject are provided.

  The electronic endoscope 10 includes an insertion unit 20 that is inserted into a body cavity of a patient, an operation unit 22 that is connected to a proximal end portion of the insertion unit 20 and that is operated by an operator such as a doctor or a technician, and an operation unit. And a universal cord 24 extending from 22. The insertion portion 20 includes a distal end portion 26, a bending portion 27, and a flexible tube portion 28 in order from the distal end. The tip portion 26 is formed of a hard resin material. The flexible tube portion 28 is a long tubular member having flexibility, and connects the operation portion 22 and the bending portion 27.

  The operation unit 22 includes an angle knob 30 for changing the direction of the distal end portion 26 by pushing and pulling the operation wire inserted through the insertion unit 20 to bend the bending unit 27 in the vertical and horizontal directions, and air / water supply In addition to the air / water feed button 31 for ejecting air and water from the nozzle 44 (see FIG. 2), operation members such as a release button for recording an observation image are provided.

  Further, a forceps port 32 through which a treatment tool such as an electric knife is inserted is provided at the distal end side of the operation unit 22. The forceps port communicates with a forceps outlet 43 (see FIG. 2) provided at the distal end portion 26 through a forceps channel in the insertion portion 20.

  The universal cord 24 includes a light guide 24 a made of an optical fiber and a signal cable for transmitting an electrical signal between the electronic endoscope 10 and the processor device 12. One end of the universal cord 24 is provided with a connector 36 for detachably connecting to the processor device 12. One end of the light guide 24 a and the signal cable is inserted through the operation portion 22 and the insertion portion 20 and extends to the distal end portion 26.

  The processor device 12 comprehensively controls the operation of the endoscope system 2. The processor device 12 supplies power to the electronic endoscope 10 via a signal cable, and controls the driving of the image sensor 66 (see FIG. 8) mounted on the distal end portion 26. In addition, the processor device 12 receives an imaging signal output from the imaging device 66 via a signal cable, and performs various processes on the received imaging signal to generate image data. The image data generated by the processor device 12 is output to the monitor 14 connected to the processor device 12 with a cable, and displayed on the monitor 14 as an observation image.

  The light source device 13 includes a laser light source 15 that emits blue laser light having a center wavelength of 445 nm. The blue laser light enters the ride guide 24a from the laser light source 15, and is guided to the distal end portion 26 of the electronic endoscope by the light guide 24a. The blue laser light is excitation light that causes the phosphor 50 provided at the distal end portion 26 to excite and emit light, and generates white light by mixing with yellow fluorescence emitted from the phosphor 50 (see FIG. 2). White light is irradiated to the observation site as illumination light. An irradiation apparatus that emits white light by combining the laser light source 15 and the phosphor 50 as in this example is commercialized under a name such as Micro White (registered trademark). In this example, the light source device 13 is described as being built in the processor device 12, but the light source device 13 and the processor device 12 may be configured separately.

  In FIG. 2, an observation window 41, two illumination windows 42, a forceps outlet 43, and an air / water supply nozzle 44 are provided on the distal end surface 26 a of the distal end portion 26. The observation window 41 is located substantially at the center in the left-right direction of the distal end surface 26a, and is arranged slightly above the center in the vertical direction. The two illumination windows 42 are arranged at symmetrical positions with the observation window 41 in between.

  As illustrated in FIG. 3, an imaging unit 46 that images an observation site is disposed behind the observation window 41. The imaging unit 46 includes an objective optical system 67 (see FIG. 8) and an image sensor 66 that captures image light imaged by the objective optical system 67 (see FIG. 8). The objective optical system 67 includes, for example, a fixed focus type lens group capable of photographing within an observation distance range of about 2 mm to 10 cm, and a prism. The prism is fixed to the rear end of the lens barrel in which the lens group is accommodated, and refracts the image of the observation region by 90 ° and guides it to the imaging surface of the image sensor 66.

  Behind each illumination window 42, the phosphor 50 and the tip of the light guide 24a, which together with the illumination window 42 constitute a light projection unit 47, are arranged. The light projecting unit 47 and the laser light source 15 constitute an irradiation unit. The phosphor 50 absorbs part of the blue laser light from the laser light source 15 guided by the light guide 24a and transmits the remaining unabsorbed blue laser light. The phosphor 50 contains a fluorescent substance that emits green to red fluorescence when excited with blue laser light in a base material such as inorganic glass, and emits yellow fluorescence as a whole. In FIG. 4, as shown in the spectral spectrum of the light projecting unit 47, white light illumination light is generated by mixing the blue laser light N <b> 1 and the yellow (green to red) fluorescence FL in a complementary color relationship.

  In addition, laser light is generally characterized by high monochromaticity (narrow band light with a very narrow spectral width) and high directivity (going straight without diffusing). N1 also has these characteristics. Since the blue laser light N1 has high directivity, the phosphor 50 is mixed with a filler that diffuses the blue laser light N1 that is not absorbed by the fluorescent material. Furthermore, the illumination window 42 is configured by a concave lens, and expands the light distribution angle of illumination light emitted from the phosphor 50. The illumination light spreads in a conical shape from the illumination window 42 and is irradiated to the observation site.

  The light projecting unit 47 has a ferrule 55 and a sleeve 60. The ferrule 55 holds the phosphor 50 and the light guide 24a in an optically connected state. The ferrule 55 has a small-diameter through hole 55a extending in the axial direction and a tip storage portion 55b having a diameter larger than that of the through hole 55a. The light guide 24a is inserted into the through hole 55a, and the phosphor 50 is accommodated in the tip storage portion 55b. The phosphor 50 is fixed to the tip storage portion 55 b by an adhesive 56, and the light guide 24 a is fixed at a position where the tip contacts the rear end of the phosphor 50.

  The sleeve 60 is a cylindrical member that is slightly larger in diameter than the ferrule 55, holds the illumination window 42 at the tip, and holds the ferrule 55 so that the phosphor 50 is positioned behind the illumination window 42.

  As shown in FIG. 5, the light distribution of illumination light (blue laser light and fluorescence) emitted from one illumination window 42 is light at the irradiation center OI corresponding to the illumination optical axis with a light distribution angle of “0”. As the intensity becomes maximum and the light distribution angle becomes wider (away from the irradiation center OI), the light intensity decreases. In the illumination light irradiation area AI, the irradiation center OI is the brightest and becomes darker toward the periphery.

  In FIG. 5, the light intensities of the blue laser light N1 and the fluorescence FL are expressed as relative intensities normalized by matching the light intensities at the irradiation center OI. The light distribution of the blue laser light N1 and the light distribution of the fluorescence FL do not completely match. Compared to each other, the light distribution of the blue laser light N1 is light from the irradiation center OI toward the periphery. The rate of decrease in strength is large. Therefore, the differences ΔI1, ΔI, ΔI3 between the light intensities at the positions P1, P2, P3 at which the radial distance from the irradiation center OI increases in order are also increased in that order. In the region outside the position of P3, the light intensity of the blue laser light N1 is close to 0, and only the fluorescent light FL is irradiated.

  Due to such a difference in light distribution, in the irradiation area AI, the mixing ratio, which is the ratio of the blue laser light N1 and the fluorescence FL, changes from the irradiation center OI toward the periphery, and color unevenness of the illumination light occurs. The color unevenness of the illumination light also appears as color unevenness whose color tone changes depending on the region in the observation image.

  The reason why the light distributions of the blue laser light N1 and the fluorescent light FL are different is that the wavelength range of the blue laser light N1 and the fluorescent light FL is different, so that a difference in refractive index occurs in the illumination window 42 formed of a concave lens. The blue laser light N1 is highly directional light, whereas the fluorescent FL is considered to be caused by highly diffusible light that is excited by the phosphor.

  As shown in FIG. 6, the illumination light emitted from the left and right illumination windows 42 spreads in a conical shape with the illumination window 42 as a base point. Therefore, when the observation distance L between the observation site S and the distal end surface of the distal end portion 26 changes, the way in which the irradiation areas AI of the left and right illumination windows 42 overlap also changes. As shown in FIG. 7, specifically, when the observation distance L is L1, the imaging area AP is AP1, and the irradiation area AI of the left and right illumination windows 42 is AI1. The symbol OP indicates the center of the photographing area AP corresponding to the photographing optical axis PA. On the other hand, when the observation distance L is L2 shorter than L1, the imaging area AP is AP2 smaller than AP1, and the irradiation areas AI of the left and right illumination windows 42 are AI2 smaller than AI1.

  In FIG. 7, circles indicated by dotted lines in each irradiation area AI correspond to the positions P1, P2, and P3 shown in FIG. As described above, in one irradiation area AI, since the mixing ratio of the blue laser light and the fluorescence changes from P1 close to the irradiation center OI toward the peripheral position P3, uneven illumination occurs. Since the illumination light spreads in a conical shape, when the size of the irradiation area AI changes due to the change in the observation distance L, the sizes of the circles corresponding to P1, P2, and P3 also change according to the ratio.

  Since most of the imaging area AP is an area where the left and right irradiation areas AI overlap, the color unevenness generated in the observation image is a combination of the illumination unevenness of each irradiation area AI. FIG. 7A showing how the irradiation areas AI overlap in the imaging area AP1 when the observation distance L is L1, and the irradiation areas AI in the imaging area AP2 when the observation distance is L2 shorter than L1. As is apparent from FIG. 7B showing the state of the direction, when the observation distance L changes, the overlapping manner of the respective irradiation areas AI changes, so that the mode of color unevenness appearing in the observation image corresponding to the imaging area AP is also the observation distance. It changes with L.

  In FIG. 8, the image sensor 66 is arranged so that an image of an observation site in the subject via the observation window 41 and the objective optical system 67 is incident on the imaging surface. On the imaging surface, a color filter composed of a plurality of color segments, for example, a primary color (RGB) color filter in a Bayer array is formed. The imaging element 66 is electrically connected to the circuit board, and an imaging signal is transmitted to a subsequent processing circuit via a transmission cable.

  In the electronic endoscope 10, for example, an analog signal processing circuit (hereinafter abbreviated as AFE) 76, a drive circuit 77, and a CPU 78 are provided in the operation unit 22. The AFE 76 includes a correlated double sampling circuit (hereinafter abbreviated as CDS), an automatic gain control circuit (hereinafter abbreviated as AGC), and an analog / digital converter (hereinafter abbreviated as A / D). The CDS performs correlated double sampling processing on the image signal output from the image sensor 66 and removes reset noise and amplifier noise generated in the image sensor 66. The AGC amplifies the image signal from which noise has been removed by CDS with a gain (amplification factor) designated by the processor device 12. The A / D converts the imaging signal amplified by the AGC into a digital signal having a predetermined number of bits. The imaging signal digitized by A / D is input to the image processing unit 84 of the processor device 12 via a transmission cable.

  The drive circuit 77 generates a drive pulse (vertical / horizontal scanning pulse, electronic shutter pulse, readout pulse, reset pulse, etc.) of the image sensor 66 and a synchronization pulse for the AFE 76. The imaging element 66 performs an imaging operation in accordance with the drive pulse from the drive circuit 77 and outputs an imaging signal. Each part of the AFE 76 operates based on a synchronization pulse from the drive circuit 77.

  After the electronic endoscope 10 and the processor device 12 are connected, the CPU 78 drives the drive circuit 77 based on an operation start instruction from the CPU 80 of the processor device 12, and the AGC of the AFE 76 via the drive circuit 77. Adjust the gain.

  The CPU 80 controls the overall operation of the processor device 12. The CPU 80 is connected to each unit via a data bus, an address bus, and a control line (not shown). The ROM 81 stores various programs (OS, application programs, etc.) and data (graphic data, etc.) for controlling the operation of the processor device 12. The CPU 80 reads out necessary programs and data from the ROM 81, develops them in the RAM 82 which is a working memory, and sequentially processes the read programs. Further, the CPU 80 obtains information that changes for each examination, such as examination date and time, character information such as patient and surgeon information, from the operation panel of the processor device 12 and a network such as a LAN (Local Area Network) and stores the information in the RAM 82. .

  The operation unit 83 is an operation panel provided on the housing of the processor device 12 or a known input device such as a mouse or a keyboard. The CPU 80 operates each unit according to operation signals from the operation unit 83 and a release button or the like in the operation unit 22 of the electronic endoscope 10.

  The image processing unit 84 performs various image processing such as color interpolation, white balance adjustment, gamma correction, image enhancement, image noise reduction, color conversion, and the like on the imaging signal input from the electronic endoscope 10 for observation. Generate an image. In addition, as will be described later, the image processing unit 84 performs image processing on the observation image to correct color unevenness caused by a difference in light distribution between the blue laser light and the fluorescence.

  The display control unit 85 receives graphic data in the ROM 81 and the RAM 82 from the CPU 80. The graphic data includes a display mask that hides the invalid pixel area of the observation image and displays only the effective pixel area, examination date and time, character information such as the patient, the operator, and the currently selected observation mode, a graphical user interface ( GUI; Graphical User Interface). The display control unit 85 performs various display control processes such as a display mask, character information, GUI superimposition processing, and drawing processing on the display screen of the monitor 14 on the image from the image processing unit 84.

  The display control unit 85 has a frame memory that temporarily stores the image from the image processing unit 84. The display control unit 85 reads an image from the frame memory, and converts the read image into a video signal (component signal, composite signal, etc.) corresponding to the display format of the monitor 14. Thereby, an observation image is displayed on the monitor 14.

  In addition to the above, the processor device 12 includes a compression processing circuit that compresses an image in a predetermined compression format (for example, JPEG format), and the compressed image is transferred to a CF card, a magneto-optical disk (MO), a CD- A media I / F for recording on removable media such as R, and a network I / F for controlling transmission of various data with a network such as a LAN are provided. These are connected to the CPU 80 via a data bus or the like.

  In addition to the laser light source 15, the light source device 13 includes a light source driver 92 that drives the laser light source 15, a condenser lens 93, and a CPU 96. The light source driver 92 controls lighting and light quantity of the laser light source 15. The condensing lens 93 condenses each light emitted from the laser light source 15 and guides it to the incident end of the light guide 24a. The CPU 96 communicates with the CPU 80 of the processor device 12 and controls the operation of the light source driver 92.

  As shown in FIG. 9, the image processing unit 84 is provided with an observation distance measurement unit 84a, a color unevenness correction unit 84b, and a correction data storage unit 84c. The observation distance measuring unit 84a measures the observation distance L based on observation image data generated based on the imaging signal. Specifically, the average exposure amount is obtained from the pixel value of the observation image, and the observation distance L is calculated from the average exposure amount. If the amount of illumination light is constant, the amount of reflected light from the observation site is small when the observation distance L is long, and increases when the observation distance L is short. The amount of exposure also changes.

  The observation distance measuring unit 84a measures the observation distance L according to the average exposure amount using the correlation between the observation distance L and the average exposure amount. Note that the average exposure amount may be an average value of all pixels of the observation image, or may be an average value of pixels near the center.

  The correction data storage unit 84c is composed of, for example, a ROM, and stores correction data for correcting color unevenness caused by a difference in light distribution between the blue laser light N1 and the fluorescence FL (see FIG. 5). As described above, the difference ΔI in the light intensity between the blue laser beam N1 and the fluorescence FL changes according to the radial distance from the irradiation center OI of the irradiation area AI. In this example, the light intensity difference ΔI gradually increases from the irradiation center OI toward the periphery.

  The correction data is a collection of a plurality of correction coefficients for correcting color unevenness according to the light intensity differences ΔI at a plurality of positions in the radial direction of the irradiation area AI. The correction coefficient is, for example, a coefficient for correcting the blue component corresponding to the blue laser light N1 in the pixel value of the observation image. In this case, since the difference ΔI is larger at the position P2 than at the position P1 shown in FIG. 5, the value of the correction coefficient corresponding to the position P2 is larger than the value of the correction coefficient corresponding to the position P1.

  The correction data is prepared for each of the left and right irradiation areas AI. The correction data is created based on the light distribution of the illumination light of the left and right illumination windows 42 measured during manufacturing and maintenance. The correction data may be in the form of an LUT (Look Up Table) or a function.

  As shown in the flowchart of FIG. 10, when the observation distance measurement unit 84a calculates the observation distance L (step (S) 101), the observation distance L is input to the color unevenness correction unit 84b. Then, the color unevenness correction unit 84b obtains how the left and right irradiation areas AI overlap based on the input observation distance L (S102). Specifically, first, the positions of the irradiation centers OI of the left and right irradiation areas AI in the observation image corresponding to the imaging area AP shown in FIG. 7 are obtained. Then, based on the size of the left and right irradiation areas AI and the imaging area AP at the calculated observation distance L, the radial direction of the irradiation area AI, such as the positions P1, P2, and P3 (see FIG. 5) of each irradiation area AI. It is determined which pixel in the observation image corresponds to each position.

  The parameters that determine how the left and right irradiation areas AI overlap are excluded from the observation distance L, and the electronic endoscope 10 such as the relative positional relationship between the observation window 41 and the illumination window 42, and their viewing angle and light distribution angle. It is determined in advance as a unique value. These parameters are stored in advance in the memory in the color unevenness correction unit 84b, the ROM 81, or the like.

  Then, the color unevenness correction unit 84b corrects the color unevenness of the observation image according to how the left and right irradiation areas AI overlap (S103). Specifically, the color unevenness correction unit 84b reads the correction data from the correction data storage unit 84c, and corrects the pixel value of the corresponding pixel in the observation image based on the correction coefficient prepared for each position. Since the correction data is prepared for each of the left and right irradiation areas AI, the color unevenness correction unit 84b corrects the pixel value of the observation image based on the left and right correction data.

  The timing for executing such color unevenness correction may be always performed while the endoscope system 2 is activated and observation is performed with the electronic endoscope 10, or may be performed manually without being performed constantly. You may go only when. Manual operation instructions are provided by the operation unit 22 of the electronic endoscope 10 or the operation unit 83 of the processor device 12 with operation buttons such as a color unevenness correction button, and the CPU 80 of the processor device 12 inputs the operation button by pressing the operation button. Accept. The CPU 80 performs color unevenness correction when receiving an operation instruction input.

  Color unevenness caused by the difference in light distribution between the blue laser light N1 and the fluorescence FL takes a long observation distance L and observes the entire state of the observation site in the duct (esophagus, stomach, intestine, etc.) from a distant view. However, there is often a problem when the observation distance L is shortened and the properties of the observation site such as the inner wall of the duct are closely observed. Therefore, there is no practical problem even if color unevenness correction is performed only when instructed by manual operation. From the viewpoint of the processing load in the image processing unit 84, the color unevenness correction is performed only when instructed, so that the load can be reduced as compared with the case where the color unevenness correction is always performed.

  In the present invention, by performing image processing on the observation image, color unevenness in the observation image caused by the difference in light distribution between the blue laser light N1 and the fluorescence FL is corrected, so that color unevenness can be reduced. . In addition, since the color unevenness is corrected by image processing, it is not necessary to improve the illumination optical system so that the light distribution of the blue laser light N1 and the fluorescence FL coincide with each other, so that the structure is not complicated.

  In the above-described embodiment, the observation distance L is measured by the observation distance measurement unit 84a and the method of overlapping the two irradiation areas AI according to the observation distance L is obtained, but when the observation distance L is constant, The observation distance measurement unit 84a may not be provided. As a method of making the observation distance L constant, there is a method of using a cylindrical hood that is detachably attached to the distal end portion 26 of the insertion portion 20. If observation is performed with the tip of the hood in contact with the observation site, the observation distance L is fixed to the length of the hood. As described above, color unevenness is particularly problematic in the case of near-field observation, so a method of fixing the observation distance L with a hood is also effective.

  In this case, the observation distance L corresponding to the length of the hood is stored in advance in the memory in the image processing unit 84. The color unevenness correction unit 84b determines how the two irradiation areas AI overlap according to the observation distance L, and corrects the color unevenness.

[Second Embodiment]
In the endoscope system 2 of the first embodiment described above, an example in which only white illumination light is irradiated by one laser light source and a phosphor has been described. However, the present invention is applied to an endoscope system capable of irradiating special light other than white. The invention may be applied. In endoscopic diagnosis, special light observation using special light is performed in addition to normal observation in which an observation site is observed under white light. Special light observation includes, for example, narrow-band light observation that uses narrow-band light with a narrow wavelength band to highlight blood vessels on the surface of the mucosa.

  As an example of an endoscope system for performing narrow-band light observation, as shown in FIGS. 11 and 12, in addition to the laser light source 15 that emits the blue laser light N1 of the first embodiment, the center wavelength is 405 nm. A laser light source 98 that emits blue laser light N2 having a shorter wavelength than the blue laser light N1 is provided. Since hemoglobin in the blood shows high absorbance for blue light having a wavelength of around 405 nm, irradiation with blue laser light N2 improves the contrast of the surface blood vessels and highlights the surface blood vessels in the observed image. The The difference between the second embodiment and the first embodiment is only the presence or absence of the laser light source 98, and the other configurations are the same. Description of common parts is omitted, and only differences will be described below.

  Similarly to the blue laser light N1, the blue laser light N2 emitted from the laser light source 98 is guided to the light projecting unit 47 by the light guide 24a and irradiated from the irradiation window 42. The blue laser light N2 also causes the phosphor 50 to excite and emit light. However, the excitation efficiency is lower than that of the blue laser light N1 (the proportion absorbed by the phosphor 50 is small), and most of the blue laser light N2 causes the phosphor 50 to emit light. To Penetrate. The blue laser beam N2 is not irradiated during normal observation, but is irradiated in addition to the blue laser beam N1 only when performing narrow-band light observation.

  As shown in FIG. 13, when the blue laser light N2 is irradiated, the illumination light irradiated from the irradiation window 42 includes light in three wavelength ranges of the blue laser light N1, the blue laser light N2, and the fluorescence FL. It is. The light distribution of the blue laser light N2 differs from the light distribution of the fluorescent light FL for the same reason as the blue laser light N1. Further, since the wavelength is different from that of the blue laser light N1, the light distribution of the blue laser light N1 is also different. As described above, since the three light distributions of the blue laser beams N1 and N2 and the fluorescence FL are different from each other, color unevenness occurs in the observation image due to the difference of the respective light distributions.

  In this example using the two laser light sources 15 and 98, the correction data storage unit 84c performs observation without irradiating the blue laser light N2, and performs observation by irradiating the blue laser light N2. Two types of correction data for narrowband light observation are stored. The correction data for normal observation is the same as that in the first embodiment, and the correction data for narrow-band light observation is corrected in consideration of the light distribution of the blue laser light N2 based on the correction data for normal observation. What is given is used. The color unevenness correction unit 84b selects either normal observation correction data or narrowband light observation correction data depending on whether or not the laser light source 98 is irradiated.

  In this example, two laser light sources are used, but the number of laser light sources may be three or more. In addition, as the special light observation, the narrow band light observation that highlights the blood vessel is exemplified, but the fluorescence observation is performed by irradiating the fluorescent substance in the living body or the fluorescent substance administered as the medicine with the excitation light. Other special light observations may be used.

  Furthermore, the endoscope system according to the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

  In the above-described embodiment, an example in which color unevenness correction is performed according to how two irradiation areas overlap is described. However, when a zoom lens capable of zooming is provided in an electronic endoscope, zoom magnification is also provided. It is preferable to perform color unevenness correction according to the above. If the observation distance L is constant, there is no change in the way in which the two irradiation areas AI overlap, but when the zoom magnification changes, the size of the shooting area AP in the irradiation area AI changes. The mode of color unevenness in the image also changes. Therefore, it is necessary to correct color unevenness in accordance with the zoom magnification.

  In the above embodiment, the laser light source is described as an example of the semiconductor light source, but the semiconductor light source may be an LED light source. However, since the laser light emitted from the laser light source generally has higher directivity than the LED light emitted from the LED light source, a difference in light distribution is likely to occur. This is because, as described above, the main cause of the difference in the light distribution is the difference in diffusivity between the fluorescence emitted from the phosphor and the excitation light transmitted through the phosphor. This is because laser light has high directivity compared to LED light and has a large difference in diffusibility with fluorescence, and therefore, color unevenness becomes conspicuous as compared with the case where excitation light is LED light. Therefore, the present invention is more effective when a laser light source is used than an LED light source.

  As correction data for correcting color unevenness, correction data (entire area data) corresponding to the light distribution over the entire area of the irradiation area AI may not be stored in the correction data storage unit 84c. Correction data (partial data) corresponding to a part of the area may be stored. The partial data is, for example, one-dimensional data D corresponding to a light distribution in a one-dimensional direction extending radially from the irradiation center OI toward the periphery in the irradiation area AI as shown in FIG.

  The irradiation area AI is substantially circular, and the light distribution changes concentrically from the irradiation center OI toward the periphery. Therefore, if the one-dimensional data D is stored in the correction data storage unit 84c, the color unevenness correction unit 84b develops the one-dimensional data D in the circumferential direction and corresponds to the light distribution over the entire irradiation area AI. The whole area data to be generated can be generated. Since the one-dimensional data D is smaller in data size than the entire area data, the memory capacity of the correction data storage unit 84c can be reduced.

  Instead of the one-dimensional data, partial data of the semicircular area of the irradiation area AI or partial data of the 1/4 circular area may be used. Even in this case, since the data size is smaller than the entire area data of the irradiation area AI, there is an effect of suppressing the memory capacity of the correction data storage unit 99.

  In particular, as shown in FIG. 15, when the correction data storage unit 99 such as a ROM is provided in the electronic endoscope 10, the capacity of the ROM cannot be increased due to the limitation of the arrangement space of the electronic endoscope 10. There is a case. In such a case, storing the correction data as partial data is effective.

  Since the correction data changes depending on the model of the electronic endoscope 10 and individual differences, the correction data storage unit 99 of the electronic endoscope 10 stores correction data corresponding to the model and individual differences, and the processor device 12. However, the correction data may be acquired from the connected electronic endoscope 10.

  In addition, a plurality of types of correction data corresponding to the plurality of types of electronic endoscope 10 are stored in the correction data storage unit in the processor device, and the CPU of the processor device is set to the model of the connected electronic endoscope 10. Correction data may be selected accordingly. Thus, even when the correction data storage unit is provided in the processor device, it is necessary to store a plurality of types of correction data in the correction data storage unit, and it is necessary to reduce the memory capacity. Therefore, storing the correction data as partial data is effective even when the correction data storage unit is provided in the processor device. Further, a correction data storage unit may be provided in an external data server connected to the processor device via a network so that the processor device reads the correction data via the network.

  In the above embodiment, a two-lamp electronic endoscope provided with two illumination windows has been described as an example, but the number of illumination windows is not limited to a two-lamp type. The present invention may be applied to an electronic endoscope such as a 4-lamp type in which two illumination windows are provided on the left and right sides of the observation window, or a single-lamp type in which only one illumination window is provided.

  The present invention can also be applied to other types of endoscopes such as an ultrasonic endoscope in which an image pickup element and an ultrasonic transducer are built in the distal end portion. Moreover, you may apply to the endoscope utilized not only for medical use but in an industrial field. However, color unevenness becomes more problematic in the medical field where precise diagnosis is required with respect to the properties of the observation site, and thus the present invention is more necessary in medical endoscope systems.

2 Endoscope system 10 Electronic endoscope 12 Processor device 13 Light source device 15, 98 Laser light source 26 Tip 41 Observation window 42 Illumination window 46 Imaging unit 47 Projection unit 50 Phosphor 84 Image processing unit 84a Observation distance measurement unit 84b Color unevenness correction unit 84c, 99 correction data storage unit

Claims (13)

An illumination window for illuminating the observation site in the subject with illumination light, and an observation window for imaging the observation site; An endoscope having;
A first semiconductor light source that emits excitation light; and a phosphor that emits fluorescence when excited by the excitation light, and a part of the excitation light that passes through the phosphor from the illumination window and the fluorescence Irradiating means for irradiating mixed light as the illumination light;
Imaging means for receiving the illumination light reflected by the observation site through the observation window and capturing an observation image of the observation site;
Storage means for storing correction data for correcting color unevenness between regions in the observation image caused by a difference in light distribution between the excitation light and the fluorescence;
An endoscope system comprising: color unevenness correcting means for performing image processing on the observed image based on the correction data to correct the color unevenness.   The endoscope system according to claim 1, wherein the first semiconductor light source is a laser light source. There are two lighting windows,
The endoscope system according to claim 1, wherein the color unevenness correcting unit corrects the color unevenness according to a method of overlapping each irradiation area of the two illumination windows. An observation distance measuring means for measuring an observation distance which is a distance between the tip and the observation site;
The endoscope system according to claim 3, wherein the color unevenness correction unit obtains how the two irradiation areas overlap based on the measured observation distance. The correction data is partial data corresponding to a light distribution in a part of the irradiation area, and the color unevenness correction unit calculates a light distribution in the entire irradiation area based on the partial data. 5. The endoscope system according to claim 3, wherein corresponding whole area data is generated. In the excitation light and the fluorescence, each irradiation area is substantially circular, and the difference in light intensity in each light distribution varies depending on the radial distance from the irradiation center,
The partial data is one-dimensional data corresponding to a light distribution in a one-dimensional direction extending in a radial direction from the irradiation center,
The endoscope system according to claim 5, wherein the color unevenness correcting unit generates the whole area data by expanding the one-dimensional data in a circumferential direction.   The endoscope system according to claim 1, wherein the storage unit is provided in the endoscope.   8. The illumination light according to claim 1, wherein the excitation light is blue light, the fluorescence is green to red light, and the excitation light and the fluorescence are mixed to generate the white illumination light. The endoscope system according to any one of the above.   The irradiation unit includes a second semiconductor light source that emits light having a wavelength range different from that of the excitation light, and transmits the light emitted from the second semiconductor light source through the phosphor through the illumination window. The endoscope system according to any one of claims 1 to 8, wherein irradiation is performed. The correction data includes first correction data when only the excitation light and the fluorescence are irradiated, and second correction when the light from the second semiconductor light source is irradiated in addition to the excitation light and the fluorescence. There are two types of correction data,
10. The endoscope according to claim 9, wherein the color unevenness correction unit selects one of the first correction data and the second correction data in accordance with presence / absence of light irradiation from the second semiconductor light source. Mirror system.   11. The first semiconductor light source emits narrow band light having a central wavelength of 445 nm, and the second semiconductor light source emits narrow band light having a central wavelength of 405 nm. Endoscope system. A part of the excitation light that has a first semiconductor light source that emits excitation light and a phosphor that emits fluorescence when excited by the excitation light and passes through the phosphor from an illumination window of an endoscope In a processor device used in an endoscope system having irradiation means for irradiating light mixed with fluorescence as illumination light,
In the observation image captured by the endoscope, means for reading caused by the difference of light distribution of the fluorescence and the excitation light, the correction data for correcting color non-uniformity between the regions from the storage means,
A processor apparatus comprising: color unevenness correcting means for performing image processing on the observed image based on the correction data to correct the color unevenness . A part of the excitation light that has a first semiconductor light source that emits excitation light and a phosphor that emits fluorescence when excited by the excitation light and passes through the phosphor from an illumination window of an endoscope In an image correction method performed by a processor device used in an endoscope system having irradiation means for irradiating light mixed with fluorescent light as illumination light,
In the observation image captured by the endoscope, a step of reading caused by the difference of light distribution of the fluorescence and the excitation light, the correction data for correcting color non-uniformity between the regions from the storage means,
An image correction method comprising: a color unevenness correction step of performing image processing on the observed image based on the correction data to correct the color unevenness.

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