JP6115967B2 - Endoscope system - Google Patents

Description

The present invention relates to an endoscope system that supplies illumination light including fluorescence emitted from a phosphor to an endoscope.

  As illumination light for normal observation in an endoscope, in addition to broadband light such as a xenon lamp, white light including fluorescence excited and emitted by a phosphor with excitation light has been used. In recent years, in order to perform special light observation such as highlighting of superficial microvessels, in addition to white light containing fluorescence, narrow-band light of a specific wavelength is also mixed and simultaneously irradiated into the body. .

In this way, in the case of illumination using the fluorescence of the phosphor, it is possible to increase the brightness, and since installation space is not required as in the case of illumination such as a xenon lamp, the entire apparatus can be made compact. it can. On the other hand, some new problems that did not exist when using a xenon lamp or the like have also appeared. For example, when blue excitation light is also included as white light used during normal observation, the amount of green and red fluorescent light is determined by the amount of blue excitation light. In this case, since the amount of fluorescent light cannot be controlled independently regardless of the amount of excitation light, it may be difficult to match the color tone of white light. Further, when special light observation using an RGB imaging device is used, when blue excitation light is used and blue narrowband light is used as other narrowband light for special observation, it is fixed by simultaneous irradiation of these lights. When the light amount thus exceeded, B pixels in the RGB imaging device was sometimes caused a problem that is saturated.

  In order to deal with these problems, Patent Document 1 uses ultraviolet excitation light as phosphor excitation light. Since the excitation light in the ultraviolet region is invisible light, even if the excitation light in the ultraviolet region is included in the illumination light, the color tone of the illumination light is not affected. In addition, since the excitation light in the ultraviolet region is completely shielded by the RGB imaging device, it is saturated even when a narrow band light for special observation with a relatively high light amount enters a special observation pixel such as a B pixel. There is no fear.

JP 2009-297311 A

Besides the above Symbol of problems, when using the semiconductor light emitting devices such as semiconductor lasers and light emitting diodes disclosed in Patent Document 1 as a light source, a problem is that the emission wavelength is varied depending on the amount of light is there. When the emission wavelength varies, the color tone of the illumination light may become unstable. In addition, since the luminous efficiency of the phosphor depends on the excitation wavelength, when the phosphor is excited to emit light using the excitation light emitted from the semiconductor light emitting element, the phosphor is subjected to the fluctuation in the emission wavelength. The luminous efficiency may vary. Thus, even when the luminous efficiency of the phosphor varies, the color tone of the illumination light may become unstable.

When the color tone of the illumination light is unstable as described above, it is difficult to stabilize the display of the surface layer fine blood vessels or the like in the special light observation. In particular, in the case of performing special light observation in which pseudo-color display is performed on the superficial fine blood vessels and the mid-depth blood vessels, it is difficult to stabilize the color tone of the superficial fine blood vessels and the mid-depth blood vessels. Therefore, it has been required to stabilize the color tone of the illumination light by controlling the light amount of the light source .

An object of the present invention is to provide an endoscope system capable of stabilizing the color tone of illumination light including fluorescence emitted from a phosphor by performing light amount control of a light source .

In order to achieve the above object, an endoscope system of the present invention includes a first semiconductor light source that emits blue light having a blue band and a second semiconductor light source that emits excitation light having a wavelength range different from the blue band. A wavelength converter that converts the wavelength of the excitation light into broadband light that includes at least the green band and is wider than the blue band; and green that reflects blue light and has a green band of the broadband light Imaging that outputs blue light and green light by transmitting light and images the subject under illumination with blue light and green light combined by the dichroic mirror and outputs an image signal An endoscope having a means, an image generating section for generating a pseudo color image representing a subject in a pseudo color based on an imaging signal, and a charge accumulation period in one frame by the imaging means. By performing the scan modulation control, a control that Ru to light the first semiconductor light source and the second semiconductor light source when the pulse is launched within the charge accumulation period, if there is no rise of the pulse in the charge accumulation period And a light source controller that performs control to turn off the first semiconductor light source and the second semiconductor light source.

The blue band is preferably narrower than the green band .

The broadband light includes a red band in addition to the green band, and the dichroic mirror preferably has characteristics of reflecting blue light and light having the red band of the broadband light and transmitting green light. .

IMAGING means, and B pixels provided B filter for transmitting blue light, and at least comprises a color image sensor and a G pixel G filter is provided which transmits green light, as an imaging signal, B pixel The blue signal is output from the G pixel, the green signal is output from the G pixel, and the image generation unit, when generating the pseudo color image, the monitor display channel to which the blue signal is assigned and the monitor display channel to which the green signal is assigned. by causing different such et mutually bets, it is preferable to pseudocolor of surface blood vessels of a subject represented in the image tone patterns and the middle of different each other and color pattern of the deep layer blood vessel al.

  A third semiconductor light source that emits red light, and the light source control unit controls lighting of the first semiconductor light source, the second semiconductor light source, and the third semiconductor light source within the charge accumulation period; The first semiconductor light source, the second semiconductor light source, and the third semiconductor light source are controlled to be turned off, and the dichroic mirror reflects blue light and red light and transmits green light. When the blue light, the green light, and the red light are combined, and the blue light, the green light, and the red light are combined by the dichroic mirror, the image generation unit replaces the pseudo color image with the surface blood vessel. It is preferable to generate an image for emphasizing the superficial blood vessel. The first semiconductor light source and the third semiconductor light source are preferably provided on a common light source substrate.

It is preferable to provide monitoring means for monitoring the amount of blue light and the amount of green light. The endoscope is supplied with a part of the blue light and a part of the green light via the dichroic mirror, and the monitoring means is supplied with the remaining part of the blue light and the remaining part of the green light via the dichroic mirror. The light source controller preferably controls the first semiconductor light source and the second semiconductor light source based on the monitoring result.

According to the present invention, by performing pulse modulation control during the charge accumulation period, even if the emission wavelength varies according to the amount of light in a semiconductor light emitting device such as a semiconductor laser or a light emitting diode, the variation in the color tone of the illumination light is minimized. Can be suppressed.

Moreover, although the luminous efficiency of the phosphor is also dependent on the excitation wavelength, the fluctuation of the luminous efficiency can be further suppressed by the pulse modulation control in the charge accumulation period.

Further, when generating the pseudo color image, the color tone of the surface blood vessel included in the blue signal and the color tone of the middle-deep blood vessel included in the green signal can be stabilized.

It is a figure which shows the outline of an endoscope system. It is a figure which shows the internal structure of a light source device and a processor apparatus. It is a figure for demonstrating the incident angle of the excitation light which injects diagonally with respect to the fluorescent substance without an AR film. It is a figure for demonstrating the incident angle of the excitation light which injects diagonally with respect to the fluorescent substance with AR film | membrane. It is a graph which shows the spectral transmission factor of the excitation light with respect to fluorescent substance. It is a graph which shows the spectral transmittance of a dichroic mirror, and the emitted light intensity of 1st blue light, 2nd blue light, green fluorescence, and red light. It is a graph which shows the light emission pattern and light emission intensity in normal light observation mode. 5 is a graph showing a light emission pattern and light emission intensity in a first special light observation mode. It is a graph which shows the light emission pattern and light emission intensity in 2nd special light observation mode. It is a graph which shows the light emission pattern and light emission intensity in oxygen saturation observation mode. It is a figure for demonstrating PNM, PDM, and PWM. It is a graph which shows the spectral transmittance of a color image sensor. It is a figure for demonstrating the production | generation method of a normal light image. It is a figure for demonstrating the production | generation method of a 1st special light image. It is a figure for demonstrating the production | generation method of a 2nd special light image. It is a figure for demonstrating the production | generation method of an oxygen saturation image. It is a graph which shows the temperature characteristic of fluorescent substance.

  As shown in FIG. 1, an endoscope system 10 according to a first embodiment includes an electronic endoscope 11 that images an inside of a subject, a light source device 12 that generates light that illuminates the subject, and an electronic endoscope. The image processing apparatus 13 includes a processor device 13 that generates an image based on an image pickup signal from the image sensor and performs various image processing, and a monitor 14 that displays an endoscopic image.

  In this endoscope system 10, a normal light observation mode in which a normal light image in a subject illuminated with white light is displayed on the monitor 14, the fine blood vessels and fine structures on the surface layer are highlighted on the normal light image. A first special light observation mode for displaying a first special light image on the monitor 14; a second special light observation mode for displaying a second special light image in which surface microvessels and middle-deep blood vessels are represented in pseudo color on the monitor 14; There are provided four modes of an oxygen saturation observation mode in which an oxygen saturation image obtained by imaging the oxygen saturation of blood hemoglobin is displayed on the monitor 14. These modes are appropriately switched by mode switching SW15.

  The electronic endoscope 11 includes a flexible insertion portion 16 to be inserted into a body cavity, an operation portion 17 provided at a proximal end portion of the insertion portion 16, an operation portion 17, a light source device 12, and a processor device 13. And a universal cord 18 for connecting the two. A bending portion 19 in which a plurality of bending pieces are connected is formed at the distal end of the insertion portion 16. The bending portion 19 is bent in the vertical and horizontal directions by operating the angle knob 21 of the operation portion. At the distal end of the bending portion 19, a distal end portion 16 a incorporating a color imaging element 20 (for example, a color CCD or a color CMOS) that captures the inside of a body cavity is provided. The distal end portion 16 a is directed in a desired direction within the body cavity by the bending operation of the bending portion 19.

  A connector 24 is attached to the universal cord 18 on the light source device 12 and the processor device 13 side. The connector 24 is a composite type connector including a communication connector and a light source connector, and the electronic endoscope 11 is detachably connected to the light source device 12 and the processor device 13 through the connector 24.

  A light guide 25 and a signal cable 26 are provided inside the electronic endoscope 11. The light guide 25 is a bundle optical fiber capable of guiding a plurality of types of light having different wavelengths, and guides the light from the light source device 12 to the distal end portion 16a. The guided light is emitted from the distal end portion 16a toward the body cavity. The signal cable 26 transmits the image signal from the color image sensor 20 to the processor device 13.

  As shown in FIG. 2, the light source device 12 includes an excitation light source 30 that emits excitation light having a wavelength range in the ultraviolet region, a first light emitting unit 31 that emits green fluorescence by excitation light from the excitation light source 30, and a center. A second light emitting unit 32 emitting a first blue light having a wavelength of 405 nm, a second blue light having a center wavelength of 470 nm, and a red light having a center wavelength of 625 nm; the green fluorescence from the first light emitting unit 31; A multiplexing unit 35 that multiplexes one blue light, second blue light, or red light, and a light source control unit 37 that controls the emission intensity and emission timing of green fluorescence, first blue light, second blue light, and red light. And a condensing lens 39 that condenses the light combined by the combining unit 35 toward the incident surface of the light guide 25.

  The excitation light source 30 is composed of a semiconductor light source such as a laser diode or a light emitting diode. In the excitation light source 30, excitation light for exciting and emitting green fluorescence is emitted from the phosphor 42 of the first light emitting unit 31. This excitation light has a peak wavelength at 365 nm, 380 nm, or 395 nm within the wavelength range of the ultraviolet region which is a non-visible light region. The excitation light is irradiated toward the phosphor 42 of the first light emitting unit 31 through the irradiation lens 30a.

The first light emitting unit 31 is emitted by a phosphor 42 that excites and emits green fluorescence with excitation light, a high reflection unit 44 that is made of a highly reflective material such as silver, aluminum, or an alloy thereof, and the phosphor. And a heat dissipating part 46 for dissipating heat. As the phosphor 42, a phosphor that has high light absorption characteristics for excitation light in the ultraviolet region and emits green fluorescence with high emission intensity and emission efficiency is used. In the present embodiment, “BaMgAl ₁₀ O ₁₇ : Eu, Mn” is used as the phosphor 42. “BaMgAl ₁₀ O ₁₇ : Eu, Mn” has an absorption rate of “66.8%” for the excitation light when the peak wavelength of the excitation light is “378 nm”, and the luminous efficiency is “55.8%”. Is. The light absorption rate and the light emission efficiency are higher than “Li _0.6 Na _0.4 W ₂ O ₈ ”, and the light emission intensity is higher than “Li _0.6 Na _0.4 W ₂ O ₈ ”.

  The phosphor 42 is formed by being hardened with a glass resin or the like and a binder, and has a substantially rectangular parallelepiped shape. One surface of the phosphor 42 is an entrance / exit surface 42a through which excitation light from the excitation light source enters and green fluorescence is emitted, and the other surface receives excitation light and green fluorescence at the high reflection portion 44. The reflection surface 42b is reflected on the surface. Further, a convex lens 48 is provided on the incident / exit surface 42 a, and the convex lens 48 condenses the excitation light on the phosphor 42 and emits the excited green fluorescent light toward the multiplexing unit 35. Therefore, the excitation light source 40 and the multiplexing unit 35 are provided on the incident / exit surface 42 a side of the phosphor 42.

  In this way, by using a reflection type in which the incident surface of the excitation light and the emission surface of green fluorescence are the same surface, the heat generated by the phosphor 42 is radiated to the reflection surface 42b opposite to the incidence / emission surface 42a. A heat dissipating means or the like can be provided directly. On the other hand, as in Patent Document 1, in the case of a transmission type in which the incident surface for excitation light and the emission surface for fluorescence are separate surfaces, a space for directly dissipating heat dissipation means on the phosphor 42 is provided. It cannot be secured. Further, in the reflection type, in order to make the excitation light incident on the phosphor 42 from an oblique direction, an installation space for installing the excitation light source 30 spatially separated from the phosphor 42 is necessary. In terms of the point, the light source device 12 is easier to secure the installation space than the distal end portion 16a of the electronic endoscope.

  In addition, among the illumination light that illuminates the inside of the subject, green fluorescence is used as green light instead of a semiconductor light source such as an LED for the following reason. As the ride guide 25 of the endoscope, one having a small diameter is used from the viewpoint of reducing the diameter of the insertion portion, so that the light incident portion is small. Therefore, it is necessary to make illumination light with high luminance enter the light guide 25. That is, a light source having a large output per unit area is required. At present, it is known that blue light and red light of illumination light can be emitted with high brightness by a semiconductor light source such as LED and LD. On the other hand, for green light, green LED, green semiconductor laser, and green phosphor emitting means are conceivable.

  As for the green LED, there is only an LED element whose luminous efficiency is drastically decreased from blue to red like the current gallium nitride LED. Moreover, even if a high-brightness LED can be manufactured, it is conceivable that the half-value width is narrower than that of the laser diode. Therefore, when it is used as illumination for an endoscope, the light emission half-value width becomes too narrow, so that the color rendering property may be inferior. On the other hand, although the green semiconductor laser is a high-intensity light source, the emission half-value width is too narrow. Therefore, when used as illumination light, it is difficult to obtain a reflection signal such as an object having steep light absorption or reflection (for example, a dye used in an endoscope). At present, the green semiconductor laser has problems in terms of output and life.

  On the other hand, the green phosphor does not have a problem like the green LED and the green semiconductor laser. Therefore, green phosphor is most suitable as the light emitting means used for endoscope illumination.

  When excitation light is incident on the phosphor 42, it is preferable that the excitation light is not reflected by the incident / exit surface 42a. If the excitation light reflected by the incident / exiting surface 42a is irradiated into the body through the multiplexing unit 35 and the light guide 25, several problems may occur. As one of the problems, since the excitation light can also be an excitation light for an autofluorescent substance in a living tissue, unnecessary autofluorescence may be excited and emitted from the body. Since this unnecessary autofluorescence is noise for the observation image, it is preferable that excitation light does not enter the body.

For example, as shown in FIG. 3A, when an AR (Anti Reflection) film is not provided on the incident / exit surface 42a, the polarization plane of the excitation light is p-polarized, and the incident angle θ of the excitation light is the Brewster angle. “56 °” is preferable (θ = ArcTan (n2 / n1) (n1: refractive index of air, n2 (1.5): refractive index of phosphor-containing glass))). As shown in FIG. 3B, when the AR film 50 is provided on the incident / exit surface 42a, it is preferable that the polarization plane of the excitation light is p-polarized and the incident angle θ of the excitation light is “50 °”. (Θ = ArcTan (n2 / n1) (n1: refractive index of air, n2 (1.5): refractive index of phosphor-containing glass))). Here, the AR film 50 includes a magnesium fluoride MgF ₂ (refractive index n3, approximately 1.38) film 50a and alumina Al ₂ O ₃ (refractive index n4, approximately 2.1 to 2.4. Under film formation conditions. When changed, it is preferable to form the film 50b of 2.3). With regard to magnesium fluoride MgF ₂ and alumina Al ₂ O ₃ , it is preferable that the thickness is ½λ when the design wavelength λ is 405 nm. Therefore, the refractive index is preferably in the relationship of n1 <n3 <n2 <n4.

  In either case of FIG. 3A and FIG. 3B, as shown in the transmission distribution T (p) shown in FIG. 4, the transmittance to the phosphor around the peak wavelength of “365 nm, 380 nm, or 395 nm” of the excitation light. Is close to “99.98%”. Therefore, the excitation light reliably enters the phosphor 42 without being reflected by the incident / exit surface 42a. When the polarization plane of the excitation light is s-polarized light, the transmittance around “365 nm, 380 nm, or 395 nm” is “90%” as shown in the transmission distribution T (s). About 10% of the excitation light to be reflected is reflected by the entrance / exit surface 42a.

  As shown in FIG. 2, the heat dissipation part 46 is provided with a Peltier element 52, a heat sink 54, and a fan 56 in order from the phosphor 42 side. The Peltier element 52 includes a cooling plate 52a provided on the phosphor 42 and the high reflection portion 44 side, and a heat radiating plate 52b provided on the heat sink 54 side. By driving the Peltier element 52 by an element driving unit (not shown), the heat generated in the phosphor 42 moves to the heat radiating plate 52b via the cooling plate 52a. The heat sink 54 is provided with a plurality of metal square pillars so that heat generated from the heat radiating plate 52b is easily diffused. Wind from the fan 56 is blown against the heat sink 54. Thereby, the heat accumulated in the heat sink 54 is dissipated to the outside of the light source device 12.

  The second light emitting unit 32 includes a first blue light source 60 that emits first blue light having a center wavelength of 405 nm, a second blue light source 61 that emits second blue light having a center wavelength of 470 nm, and red that emits red light having a center wavelength of 625 nm. A light source 62, a light source substrate 65 provided with these light sources 60 to 62, and a heat radiating portion 67 that radiates heat generated by each of the light sources 60 to 62 are provided. Similar to the excitation light source 30, the first blue light source 60, the second blue light source 61, and the red light source 62 are constituted by semiconductor light sources such as a laser diode and a light emitting diode. The light sources 60 to 62 are controlled in light emission timing and light quantity by the light source control unit 37 via a common light source substrate 65. The first blue light, the second blue light, and the red light emitted from each of the light sources 60 to 62 are irradiated toward the multiplexing unit 35 through the irradiation lens 69.

  The heat dissipating part 67 includes the same Peltier element 52 as the heat dissipating part 46, a heat sink 54, and a fan 56. The cooling plate 52a of the Peltier element 52 and the light source substrate 65 are bonded to each other with a silicon grease 70 having a low thermal resistance. Since other than that is the same as the said heat radiating part 46, description is abbreviate | omitted.

  The combining unit 35 includes a dichroic mirror 72 that combines the green fluorescence from the first light emitting unit and the first blue light, the second blue light, and the red light from the second light emitting unit, and a first blue light PD ( Photo Detector) 74a, a second blue light PD 74b, a green fluorescence PD 74c, and a red light PD 74d.

  The dichroic mirror 72 has a transmission distribution Ta as shown in FIG. Therefore, when green fluorescence is incident on the dichroic mirror, most of the incident green fluorescence is transmitted and only a small amount of light is reflected. The transmitted light is incident on the condenser lens 39, while the reflected light is detected by the green fluorescent PD 74c. On the other hand, when the first blue light, the second blue light, and the red light are incident on the dichroic mirror 72, most of the light is reflected and only a small amount of light is transmitted. The reflected light enters the condenser lens 39, while the transmitted light is detected by the first blue light PD 74a, the second blue light PD 74b, and the red light PD 74d.

  The first blue light PD 74a, the second blue light PD 74b, the green fluorescence PD 74c, and the red light PD 74d constantly monitor the light amounts of the first blue light, the second blue light, the green fluorescence, and the red light, and the monitoring results. Is transmitted to the light source control unit 37.

  The light source control unit 37 controls the excitation light source, the first blue light source, the second blue light source, and the red light source so that the light quantity ratio among the first blue light, the second blue light, the green fluorescence, and the red light is constant. To do. As shown in FIG. 2, the light amount control of the excitation light source 30 is performed by the excitation light control unit 37a, the light amount control of the first blue light source 60 is performed by the first blue light control unit 37b, and the light amount control of the second blue light source 61 is performed. Is performed by the second blue light control unit 37c, and the light amount control of the red light source 62 is performed by the red light control unit 37d. These control units 37a to 37d enable independent light quantity control of the first blue light, the second blue light, the green fluorescence, and the red light. Further, while each light is emitted, the light amount is kept constant by the light amount feedback control based on the monitoring results of the PDs 74a to 74d.

  The light emission timing and the light amount ratio of the first blue light, the second blue light, the green fluorescence, and the red light are predetermined for each mode. When the normal light observation mode is set, as shown in FIG. 6A, first blue light, green fluorescence, and red light are emitted. At this time, light is emitted so that the peak intensities are the same. Therefore, the inside of the body is irradiated as white light in which the first blue light, green fluorescence, and red light are mixed.

  Here, since the first blue light, green fluorescence, and red light can be independently controlled in light quantity, their light quantity ratios can be kept constant. In addition, since the excitation light is outside the visible light region, even if the excitation light enters the body, the color of white light is not affected. From the above, the color of the white light irradiated into the body is kept constant without changing.

  When the first special light observation mode is set, as shown in FIG. 6B, first blue light, green fluorescence, and red light are emitted. At this time, the first blue light is emitted so that the peak intensity of the first blue light is higher than the peak intensity of the other green fluorescence and red light, and the contrast ratio between the blood vessel and the mucous membrane in the body becomes “1.6” or more. Light is emitted at a first light quantity ratio (light quantity ratio of first blue light, green fluorescence, and red light). As described above, the first blue light, the green fluorescence, and the red light can be independently controlled in light quantity, so that the first light quantity ratio can be kept constant.

  When the second special light observation mode is set, as shown in FIG. 6C, first blue light and green fluorescence are emitted. At this time, light is emitted with a second light amount ratio (first blue light and green fluorescent light amount ratio) in which the contrast ratio between the blood vessel and the mucous membrane in the body is “1.6” or more. As described above, since the first blue light and the green fluorescence can be controlled independently, the second light quantity ratio can be kept constant.

  When the oxygen saturation observation mode is set, as shown in FIG. 6D, the emission of only the second blue light and the emission of green fluorescence and red light are alternately repeated every frame. At this time, light is emitted so that the third light quantity ratio of the second blue light, green fluorescence, and red light is constant. As described above, the amount of light of the second blue light, green fluorescence, and red light can be controlled independently, so that the third light amount ratio can be kept constant.

  The light amount control by the light source control unit 37 is preferably performed by pulse modulation control based on a predetermined driving pulse for the light emission amounts of the light sources 30 and 60 to 62. The pulse modulation control is performed by pulse number control (PNM), pulse density control (PDM: Pulse Density Modulation), and pulse width control (PWM: Pulse Width Modulation).

  Specifically, as shown in FIG. 7, the light amount control is performed by performing pulse modulation of any one of PNM, PDM, and PWM during the charge accumulation period of the color image sensor 20 in one frame. Here, in FIG. 7, the light sources 30, 60 to 62 are turned on when the pulse rises, and the light sources 30, 60 to 62 are turned off at other times. Note that one frame period is 33 ms and the shutter speed is 1/60 s. At the maximum light amount, as shown in the drive pulse [1], it is assumed that 2000 pulses are included in the charge accumulation period of the color imaging device (frequency is 120 kHz).

  When reducing the light amount between the maximum light amount and the minimum light amount, first the number of pulses is reduced by PNM control, then the pulse density is reduced by thinning out the pulses by PDM control, and finally the pulse width by PWM control. The amount of light is gradually reduced by narrowing.

  In the PNM control, as shown in the drive pulse [2], the number of pulses is decreased within the charge accumulation period to shorten the lighting period. As the number of pulses decreases, the amount of light also decreases. Then, as shown in drive pulse [3], after shortening to a predetermined lighting period Wmin by PNM control, a process of thinning drive pulses by PDM control is performed. In this PDM control, the pulse density in the lighting period is reduced by thinning out drive pulses at predetermined intervals with respect to the lighting period shortened to the predetermined lighting period Wmin.

  Then, as shown in the drive pulse [4], PDM control is performed until the pulse interval of the drive pulse reaches the thinning limit, that is, until the drive pulse reaches a predetermined minimum pulse density. Next, as shown in drive pulse [5], after the drive pulse reaches a predetermined minimum number of pulses, the pulse width of the drive pulse is reduced by PWM control. Then, as shown in drive pulse [6], PWM control is performed until the pulse width of the drive pulse reaches a certain limit width (PWM control limit).

  By using the pulse modulation method, even if the light emission wavelength varies in accordance with the amount of light in a semiconductor light emitting device such as a semiconductor laser or a light emitting diode, the variation in the color tone of the illumination light can be minimized. Moreover, although the luminous efficiency of the phosphor 42 is also dependent on the excitation wavelength, fluctuations in the luminous efficiency can be further suppressed by the pulse modulation.

  As illustrated in FIG. 2, the processor device 13 generates an observation image in the subject based on the reception unit 80 that receives the imaging signal from the electronic endoscope 11 and the imaging signal received by the reception unit 80. In addition to the image generating unit 81, the receiving unit 80 and the image generating unit 81, the light source control unit 37 in the light source device 12, the mode switching SW 15 of the electronic endoscope 11, the monitor 14 and the like are electrically connected to the processor device. 13 is provided with a controller 82 that controls the entire system 13.

  The receiving unit 80 receives an imaging signal output from the color imaging element 20 of the electronic endoscope 11. The color image pickup device 20 includes a large number of B pixels, G pixels, and R pixels provided with B filters, G filters, and R filters having spectral transmittances as shown in FIG. Therefore, when the color imaging device images the inside of the subject, a blue signal is output from the B pixel, a green signal is output from the G pixel, and a red signal is output from the R pixel for each frame.

  The image generation unit 81 generates an observation image corresponding to the set mode. When the normal light observation mode is set, as shown in FIG. 9A, a normal light image is generated based on the blue signal Bc, the green signal Gc, and the red signal Rc from the reception unit. In the normal light observation mode, white light having substantially the same peak intensity of each color (blue, green, red) is irradiated into the body, so that each signal Bc, Gc, Rc has substantially the same signal value. Yes. Accordingly, a bright normal light image is displayed on the monitor 14 as a whole.

  When the first special light observation mode is set, as shown in FIG. 9B, the first special light image is generated based on the blue signal Bm, the green signal Gm, and the red signal Rm from the receiving unit. To do. In the first special light observation mode, white light whose blue peak intensity is higher than other colors (green, red) is irradiated into the body, so that the blue signal Bm has a higher signal value than the green signal Gm and the red signal Rm. have. That is, the blue signal Bm contains a large amount of information of blue components such as microvessels and microstructures on the surface layer. Therefore, the monitor 14 displays the first special light image in which the fine blood vessels and the fine structure of the surface layer are clearly displayed on the normal light image that is bright overall.

  When the second special light observation mode is set, as shown in FIG. 9C, a second special light image is generated based on the blue signal Be and the green signal Ge from the reception unit. When generating the second special light image, the blue signal Be is assigned to the B and G channels for monitor display, and the green signal Ge is assigned to the R channel for monitor display. Therefore, the monitor 14 has a second special light image in which the information on the surface blood vessels included in the blue signal Be is a brown tone pattern and the information on the middle and deep blood vessels included in the green signal Ge is expressed in a cyan tone pattern. Is displayed.

  When the oxygen saturation observation mode is set, as shown in FIG. 9D, a blue signal B1 obtained when the second blue light is emitted, a green signal G2 obtained when the green fluorescence and the red light are emitted, An oxygen saturation image is generated based on the red signal R2. At the center wavelength 470 nm of the second blue light, the absorption coefficients of oxyhemoglobin and reduced hemoglobin are greatly different, so the blue signal B1 contains a lot of information on the oxygen saturation. Therefore, it is possible to visually grasp the change in oxygen saturation from the oxygen saturation image displayed on the monitor 14.

  In the above embodiment, blue light (first and second blue light) and red light are emitted from the semiconductor light source, and green fluorescence is excited and emitted from the phosphor. Instead, blue light is emitted from the semiconductor light source. Light and green light may be emitted, and red fluorescence may be excited and emitted from a red phosphor.

  In the above embodiment, in order to prevent excitation light in the ultraviolet region from entering the subject, the excitation light is cut or dimmed on the optical path from the phosphor to the tip of the electronic endoscope. It is preferable to provide an excitation light cut filter. Further, by using a light guide having extremely low transmission characteristics in the ultraviolet region, the excitation light may be cut or dimmed by the ride guide.

DESCRIPTION OF SYMBOLS 12 Light source device 30 Excitation light source 37 Light source control part 42 Phosphor 44 High reflection part 46 Heat radiation part 50 AR film 60 1st blue light source 61 2nd blue light source 62 Red light source

Claims (8)

A first semiconductor light source emitting blue light having a blue band ;
A second semiconductor light source that emits excitation light having a wavelength range different from the blue band ;
A wavelength converter that converts the wavelength of the excitation light into broadband light that includes at least a green band and is wider than the blue band ;
A dichroic mirror that combines the blue light and the green light by reflecting the blue light and transmitting the green light having the green band of the broadband light ;
An endoscope having imaging means for imaging an object under illumination with the blue light and the green light combined by the dichroic mirror and outputting an imaging signal;
An image generation unit that generates a pseudo color image representing the subject in a pseudo color based on the imaging signal;
By performing pulse modulation control in the charge accumulation period of the one frame according to previous SL imaging means, said first semiconductor light source and the second semiconductor light source when the pulse is launched in the charge accumulation period the endoscope system comprising a control Ru is lit, a light source control unit that performs a control to turn off the first semiconductor light source and the second semiconductor light source in the absence rise of the pulse in the charge accumulation period . The endoscope system according to claim 1, wherein the blue band is narrower than the green band. The broadband light includes a red band in addition to the green band,
The endoscope system according to claim 1, wherein the dichroic mirror reflects the blue light and the light having the red band out of the broadband light and transmits the green light. . Before SL imaging means, and B pixels B filter transmitting the blue light is provided, and at least comprises a color image sensor and a G pixel G filter is provided which transmits the green light,
As the imaging signal, a blue signal is output from the B pixel, a green signal is output from the G pixel,
The image generating unit, when generating the pseudo color image, a channel for monitor display to assign the blue signal, by causing the channel and the mutually different for al for monitor display to assign the green signal, the pseudo the endoscope system according to any one of claims 1 to 3 to mutually different as al and color pattern of the color patterns and the middle depth layer vessels of surface blood vessels of the subject represented in the color image. A third semiconductor light source that emits red light;
The light source control unit controls lighting of the first semiconductor light source, the second semiconductor light source, and the third semiconductor light source within the charge accumulation period, and the first semiconductor within the charge accumulation period. Performing a control to turn off the light source, the second semiconductor light source, and the third semiconductor light source,
The dichroic mirror combines the blue light, the green light, and the red light by reflecting the blue light and the red light and transmitting the green light,
When the blue light, the green light, and the red light are combined by the dichroic mirror, the image generating unit replaces the pseudo color image and emphasizes the surface blood vessels. The endoscope system according to claim 4 , wherein the image is generated. The endoscope system according to claim 5 , wherein the first semiconductor light source and the third semiconductor light source are provided on a common light source substrate. The endoscope system according to any one of claims 1 to 6 , further comprising a monitoring unit that monitors the amount of blue light and the amount of green light. The endoscope is supplied with a part of the blue light and a part of the green light through the dichroic mirror,
The monitoring means is supplied with the remaining part of the blue light and the remaining part of the green light via the dichroic mirror,
The endoscope system according to claim 7 , wherein the light source control unit controls the first semiconductor light source and the second semiconductor light source based on the monitoring result.

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