JP5639522B2 - Electronic endoscope system - Google Patents

Description

  The present invention relates to an electronic endoscope system that performs magnified observation.

  In the medical field, many diagnoses and treatments using an electronic endoscope are performed. An electronic endoscope has an observation optical system for capturing image light in a subject at the distal end of an insertion portion that is inserted into the subject, and an image sensor on which the image light captured by the observation optical system is imaged And an illumination optical system for irradiating the observation light of the observation optical system with the illumination light guided by the light guide. The illumination optical system is generally arranged at a position close to the observation optical system.

  Conventionally, there is an electronic endoscope provided with a mechanism for changing the focal length of an observation optical system (for example, Patent Document 1). In such an electronic endoscope, since the focal length can be switched between normal observation and magnified observation, first, normal observation is performed, and when an abnormal site such as a lesion is found, switching to magnified observation is clear. An observation image can be obtained.

  When magnifying observation with an electronic endoscope, the depth of field of the observation optical system becomes narrower than normal observation. Therefore, the surface of the subject cannot be focused unless the distance between the surface of the subject and the tip of the observation optical system (referred to as working distance) is a predetermined distance. When the insertion unit is moved and the observation optical system is moved closer to the subject in order to make the focus on the surface of the subject, the illumination optical system also approaches the subject, so that the illumination is specularly reflected on the surface of the subject. Light easily enters the observation optical system. In a portion where the light intensity of the illumination light is high, the amount of light received by the image sensor may be saturated, and overexposure may occur in the observation image.

  Some electronic endoscopes control the light intensity of illumination light in order to prevent unclear observation images such as overexposure. The electronic endoscope system described in Patent Document 2 has a configuration for switching the light intensity of the light source, and changes the light intensity of the illumination optical system by switching the light intensity of the light source when performing magnified observation. The electronic endoscope described in Patent Document 3 includes two sets of illumination optical systems having different irradiation angles and light intensities, and switches to one of the illumination optical systems in conjunction with the viewing angle switching of the observation optical system. Further, in the endoscope illumination device described in Patent Document 4, the relative position of the light guide with respect to the condensing lens that condenses the light emitted from the light source is moved in a direction orthogonal to the optical axis of the condensing lens. Thereby, when the light guide approaches the position of the optical axis of the condenser lens, the light intensity increases. When the light guide moves away from the position of the optical axis of the condenser lens, the light intensity decreases.

  Furthermore, the electronic endoscope described in Patent Document 5 includes a light modulation device such as a liquid crystal panel, and controls the pattern of the light modulation device according to the luminance distribution of the observation image captured by the observation optical system. The brightness is controlled. Alternatively, in the electronic endoscope system described in Patent Document 6, two light sources, a condensing lens, a diaphragm disposed on an optical path from the light source to the condensing lens, a light guide, and an illumination optical system are provided. The illumination light emitted from the two illumination optical systems is changed by varying the diaphragm positioned on the optical path.

Japanese Patent Laid-Open No. 2002-253489 JP-A-2005-34491 JP-A-5-297288 JP 2000-199864 A JP 2001-275916 A Japanese Patent Laid-Open No. 10-165357

  In an electronic endoscope, light emitted from a light source is collected by a mirror and a condenser lens and is incident on a light guide. The light incident on the light guide has a high light intensity near the optical axis of the condenser lens and a low light intensity in the vicinity. In the illumination optical system of the electronic endoscope, the illumination light is irradiated according to the light intensity distribution guided by the light guide. Therefore, the light intensity of the illumination light guided from the vicinity of the optical axis of the condenser lens is increased. As described above, when magnifying observation is performed, in the portion where the light intensity of the illumination light is high, reflection is likely to occur on the lens surface of the observation optical system, so the luminance in the range corresponding to the vicinity of the optical axis of the condensing lens increases. The observation image will be overexposed.

  However, in the electronic endoscope and the electronic endoscope system described in Patent Documents 2 and 3, when performing magnified observation, even if the intensity of the light source or the illumination optical system is switched, the vicinity of the optical axis and its surroundings are changed. Since there is a difference in light intensity between the two, there is no change in that only the range corresponding to the vicinity of the optical axis of the condenser lens is brightened, and the light intensity of the light source is reduced to reduce the light intensity near the optical axis. The periphery is too dark to obtain a clear observation image. Further, in the endoscope illumination device described in Patent Document 4, even when magnification observation is performed, even if the position of the optical axis of the condenser lens and the light guide are separated and the light intensity is reduced, the light in the vicinity of the optical axis Since the intensity is larger than that of the surrounding area, the luminance distribution within the observation range is biased.

  Further, in the electronic endoscope described in Patent Document 5, the brightness of the illumination light is controlled by controlling the pattern of the light modulation device according to the luminance distribution of the observation image. Therefore, when magnification observation is performed, the light intensity corresponding to the vicinity of the optical axis of the condenser lens increases, and the luminance distribution within the observation range is likely to be biased. Furthermore, in the electronic endoscope described in Patent Document 6, the light intensity is varied with different aperture amounts for the two illumination optical systems, and the light intensity difference between the illumination lights irradiated from the two illumination optical systems is different. If there is, the brightness with the higher light intensity becomes higher and overexposure tends to occur.

  The present invention has been made in view of the above circumstances, and provides an electronic endoscope system capable of obtaining a clear observation image by suppressing a deviation in luminance distribution within an observation range when performing magnified observation. With the goal.

An electronic endoscope system according to the present invention includes an observation optical system that is provided at a distal end portion of an insertion portion that is inserted into a subject, takes in image light within the subject, and performs observation. Focus variable means for changing the focal length between normal observation and magnified observation, an illumination optical system for irradiating illumination light toward the observation range by the observation optical system, and the illumination optical system are aligned with each other is, an endoscope light guide and for guiding the illumination light to the illumination optical system is provided, a light source for emitting light, a condensing means to be incident on the light guide by condensing light from the light source, the When the observation optical system is normally observable, retract from the light path from the light source to the light guide, and when the observation optical system is switched from the normal observable state to the magnified observable state, the optical path from the light source Of the light incident on the light guide, only the light attenuation region located at the center is partially dimmed, and the light transmitted through the light transmission region located around the light attenuation region is not dimmed. And the illumination optical system irradiates illumination light according to the distribution of the light intensity incident on the light guide.

  The partial dimming means is a partial dimming plate in which a light attenuating filter having a low light transmittance is formed in a portion matched with the light reducing region, and a light transmittance of a portion matched with the transmissive region is high. And a partial dimming plate provided movably between a dimming position for aligning the center position of the neutral density filter with the optical axis of the condenser lens and a retreat position for retreating from the optical path; When the observation optical system is in a normally observable state, the neutral density filter is in the retracted position, and when the observation optical system is switched from a state in which normal observation is possible to a state in which magnified observation is possible, the neutral density filter is It is preferable to include a moving means for moving from the retracted position to the dimming position.

  The partial dimming plate is preferably disposed between the light guide and the condenser lens. Alternatively, it is preferable that the partial dimming plate is disposed between the light source and the condenser lens.

  It is preferable to include a light source device provided with the light source, the condensing means, and the partial dimming means.

According to the present invention, when the observation optical system is normally observable, the partial dimming means is retracted from the optical path from the light source to the light guide, and the observation optical system is normally observable and can be magnified. When switching to the state, the light that enters the light guide is partially dimmed only in the light-reducing area located in the center, and light is not dimmed in the transmission area located around the light-reducing area. Illumination light is irradiated to the observation range according to the distribution of the light intensity incident on the light guide, so that when magnifying observation is performed, the bias in the luminance distribution within the observation range is suppressed and a clear observation image is obtained Can be obtained.

It is an external appearance perspective view of an electronic endoscope system. It is a perspective view which shows the structure of the front-end | tip part of an electronic endoscope. It is sectional drawing of the front-end | tip part cut | disconnected along the observation optical system. It is a block diagram which shows the outline | summary of the electric constitution of an electronic endoscope system. It is a top view of a partial dimming plate. It is explanatory drawing which shows the structure of a light source part. It is a graph which shows each light intensity distribution of the illumination light irradiated from an illumination lens, when performing normal observation (A) and expansion observation (B) with an observation optical system. It is explanatory drawing of the partial dimming part which shows 2nd Embodiment of this invention. It is explanatory drawing of the partial dimming part which shows 3rd Embodiment of this invention.

  As shown in FIG. 1, the electronic endoscope system 10 includes an electronic endoscope 11, a processor device 12, a light source device 13, an air / water supply device 14, and the like. The air / water supply device 14 is built in the light source device 13 and is a well-known air supply device (pump or the like) 14a for supplying air, and a washing water tank that is provided outside the light source device 13 and stores washing water. 14b. The electronic endoscope 11 includes an insertion portion 16 to be inserted into a subject, a hand operation portion 17 connected to a proximal end portion of the insertion portion 16, and a connector 18 connected to the processor device 12 and the light source device 13. And a universal cord 19 that connects between the hand operating section 17 and the connector 18.

  The insertion portion 16 is provided at the distal end thereof, and includes a distal end portion 16a having a built-in CCD image sensor (see FIG. 3; hereinafter referred to as CCD) 38 as an imaging element for in-subject imaging, and a distal end portion 16a. It comprises a bendable bending portion 16b provided continuously at the base end, and a flexible flexible tube portion 16c provided continuously at the base end of the bending portion 16b.

  The connector 18 is a composite type connector to which the processor device 12, the light source device 13, and the air / water supply device 14 are connected. The hand operating section 17 includes an angle knob 21 for bending the bending section 16b vertically and horizontally, and an air / water supply button 22 for ejecting air and water from an air / water supply nozzle 30 (see FIG. 2). An operating member is provided. The hand operating section 17 is provided with a forceps inlet 23 for inserting a treatment instrument such as an electric knife into a forceps channel (not shown).

  The processor device 12 is electrically connected to the light source device 13 and comprehensively controls the operation of the electronic endoscope system 10. The processor device 12 supplies power to the electronic endoscope 11 via the universal cord 19 and a transmission cable inserted into the insertion portion 16 and controls driving of the CCD 38 described later. Further, the processor device 12 acquires an imaging signal output from the CCD 38 via a transmission cable, and performs various image processing to generate image data. The image data generated by the processor device 12 is displayed as an observation image on a monitor 24 connected to the processor device 12 by a cable.

  2 and 3, the distal end portion 16a includes a distal end portion main body 25, a distal end protective cap 26 fixed to the distal end side of the distal end portion main body 25, an observation lens 27 that constitutes an observation optical system 36 described later, Illumination lenses 28a and 28b as illumination optical systems, a forceps outlet 29, and an air / water supply nozzle 30 are provided. The rear end of the distal end portion main body 25 is connected to a bending piece (not shown) on the distal end side that constitutes the bending portion 16b.

  The tip protection cap 26 includes a tip plate portion 26 a that covers the tip side of the tip portion main body 25 and a cylindrical portion 26 b that covers the outer peripheral surface of the tip portion main body 25. An outer skin layer 31 covering the outer peripheral surface of the curved portion 16b extends to the distal end portion body 25, the distal end of the outer skin layer 31 and the rear end of the cylindrical portion 26b are brought into contact with each other, and the end portions are fixed with an adhesive or the like. . The distal end plate portion 26 a is formed with a distal end surface 26 c that is flat and orthogonal to the axial direction (insertion direction) of the insertion portion 16 and is located on the distal end side. Through-holes 26d to 26g and a forceps outlet 29 are formed in the distal end plate portion 26a.

  The observation lens 27 has an optical axis arranged along a direct viewing direction F parallel to the insertion direction of the insertion portion 16. The observation lens 27 is attached at a position exposed from the through-hole 26d, and the surface to be a light incident surface is located on the same plane as the distal end surface 26c, and takes in the image light from the direct viewing direction F.

  The illumination lenses 28a and 28b are attached to positions exposed from the through holes 26e and 26f, and the surfaces thereof are located on the same plane as the tip surface 26c. The exit ends of the light guides 32a and 32b face the back of the illumination lenses 28a and 28b. The illumination lenses 28a and 28b irradiate the illumination light guided by the light guides 32a and 32b toward the observation range where the observation optical system 36 takes in the image light.

  The light guides 32a and 32b are formed by bundling a large number of optical fibers (for example, made of quartz) and covering the outer peripheral surface with a tube. The light guides 32a and 32b are held by the distal end body 25 and pass illumination light from the light source device 13 to the illumination lenses 28a and 28b through the insertion portion 16, the hand operating portion 17, the universal cord 19, and the connector 18. Guide each one.

  The forceps outlet 29 communicates with the forceps inlet 23 of the hand operation unit 17 via a forceps conduit (not shown). Various treatment tools inserted from the forceps inlet 23 are guided to the forceps conduit and can be treated by protruding the tip from the forceps outlet 29. The air / water supply nozzle 30 is provided so as to be exposed from the through-hole 26g, and jets air and washing water supplied from the air / water supply device 14 toward the observation lens 27 and adheres to the direct-view observation lens 27. It is possible to wash away dirty dirt.

  An imaging unit 35 is incorporated in the distal end portion 16a. The imaging unit 35 includes an observation optical system 36, a lens moving mechanism 37, and a CCD 38. The observation optical system 36 includes an observation lens 27 and a zoom lens 39.

  The CCD 38 is located on the extension of the optical axis of the observation lens 27. The zoom lens 39 is located between the observation lens 27 and the CCD 38, and is arranged with the position of the optical axis aligned with the observation lens 27 and the CCD 38. Incident light from the observation lens 27 passes through the zoom lens 39, forms an image on a light receiving surface (not shown) of the CCD 38, and is converted into an imaging signal.

  The zoom lens 39 and the lens moving mechanism 37 constitute a focal point changing unit, and the focal distance of the observation optical system 36 is changed by the lens moving mechanism 37 moving the zoom lens 39 forward and backward along the optical axis direction. The lens moving mechanism 37 includes a moving cylinder 41 as a lens holding member that holds the zoom lens 39, a fixed cylinder 42 as a guide member that guides the moving cylinder 41, and an actuator 43. The fixed cylinder 42 is fixed inside the distal end portion body 25, and the axial direction is arranged in parallel with the optical axis of the zoom lens 39. A CCD 38 is fixed to the rear end portion of the fixed cylinder 42.

  The outer peripheral surface of the movable cylinder 41 is slidably fitted to the inner peripheral surface of the fixed cylinder 42. Thereby, the zoom lens 39 is guided in the optical axis direction. The moving tube 41 is integrally provided with a connecting portion 44. The connecting portion 44 protrudes outside the fixed cylinder 42 through a slit 45 formed in the fixed cylinder 42. The actuator 43 is connected to the moving cylinder 41 via the connection portion 44. For example, a solenoid is used as the actuator 43. By driving the actuator 43, the zoom lens 39 can be moved forward and backward together with the moving cylinder 41.

  The lens moving mechanism 37 varies the focal length of the observation optical system 36 between the normal observation and the enlarged observation having a longer focal length than the normal observation by moving the zoom lens 39 forward and backward by driving the actuator 43. be able to. In the following, the position of the zoom lens 39 during normal observation is the normal observation position (position indicated by the two-dot chain line in FIG. 3), and the position of the zoom lens 39 during magnification observation is the enlarged observation position (position indicated by the solid line in FIG. 3). Called.

  FIG. 5 schematically shows the electrical configuration of the electronic endoscope system 10. The electronic endoscope 11 includes an AFE 51 and an imaging control unit 52 in addition to the imaging unit 35. The CCD 38 photoelectrically converts the image in the subject imaged on the light receiving surface as described above, accumulates signal charges, and outputs the accumulated signal charges as an imaging signal. The output imaging signal is sent to the AFE 51. The AFE 51 includes a correlated double sampling (CDS) circuit, an automatic gain adjustment (AGC) circuit, an A / D converter, and the like (all not shown). The CDS performs correlated double sampling processing on the imaging signal output from the CCD 38 to remove noise generated by driving the CCD 38. The AGC amplifies the imaging signal from which noise has been removed by CDS.

  The imaging control unit 52 is connected to the controller 57 in the processor device 12 when the electronic endoscope 11 and the processor device 12 are connected, and sends a drive signal to the CCD 38 when an instruction is issued from the controller 57. . The CCD 38 outputs an imaging signal to the AFE 51 at a predetermined frame rate based on the drive signal from the imaging control unit 52.

  The processor device 12 includes a digital signal processing circuit (DSP) 53, a digital image processing circuit (DIP) 54, a display control circuit 55, a VRAM 56, a controller 57, an operation unit 58, and the like.

  The controller 57 controls the overall operation of the processor device 12. The DSP 53 performs various signal processing such as color separation, color interpolation, gain correction, white balance adjustment, and gamma correction on the imaging signal output from the AFE 51 of the electronic endoscope 11 to generate image data. The image data generated by the DSP 53 is input to the working memory of the DIP 54. Further, the DSP 53 generates ALC control data necessary for automatic control (ALC control) of the amount of illumination light, such as an average luminance value obtained by averaging the luminance of each pixel of the generated image data, and inputs the data to the controller 57.

  The DIP 54 performs various types of image processing such as electronic scaling, color enhancement processing, and edge enhancement processing on the image data generated by the DSP 53. Image data that has been subjected to various image processing by the DIP 54 is temporarily stored as an observation image in the VRAM 56 and then input to the display control circuit 55. The display control circuit 55 selects and acquires an observation image from the VRAM 56 and displays it on the monitor 24.

  The operation unit 58 includes a known input device such as an operation panel, a mouse, and a keyboard provided in the housing of the processor device 12. The controller 57 operates each unit of the electronic endoscope system 10 in accordance with operation signals from the operation unit 58 and the hand operation unit 17 of the electronic endoscope 11.

  The lens moving mechanism 37 moves the zoom lens 39 to the normal observation position or the magnified observation position by driving the actuator 43 when an instruction to move the zoom lens 39 is given from the controller 57.

  The light source device 13 includes a light source unit 61, a light source control unit 62, and the like. The light source unit 61 includes a light source 63, a mirror 64, a condenser lens 65, an optical fiber 66, a partial dimming unit 67, and the like.

  The light source 63 is a white light source such as a xenon tube. The mirror 64 is a parabolic mirror formed in a bowl shape, and a mirror surface is formed on the inner peripheral surface. The mirror 64 has a light source 63 disposed near the center of the inner peripheral surface, and reflects light emitted from the light source 63 forward. The condensing lens 65 is in a position facing the inner peripheral surfaces of the light source 63 and the mirror 64, condenses the light emitted from the light source 63 and the light reflected by the mirror 64, and guides it to the optical fiber 66.

  The optical fiber 66 is arranged with its center position aligned with the position of the optical axis L1 (see FIG. 6) of the condenser lens 65, and is connected to the light guides 32a and 32b of the electronic endoscope 11 via the connector 18. The Light enters the light guides 32 a and 32 b from the condenser lens 65 through the optical fiber 66. The illumination lenses 28a and 28b irradiate illumination light according to the distribution of light intensity incident on the light guides 32a and 32b. It should be noted that at the connection portion between the optical fiber 66 and the light guides 32a and 32b, the distribution of the light intensity incident on the optical fiber 66 from the condenser lens 65 is equally distributed to the light guides 32a and 32b, respectively. The optical fiber 66 is divided into two areas that pass through the center at the exit end, the incident end of the light guide 32a faces the exit end of one area, and the entrance end of the light guide 32b faces the exit end of the other area. .

  The light emitted from the light source 63 is guided to the light guides 32a and 32b and enters the illumination lenses 28a and 28b. Since the center positions of the light guides 32a and 32b are attached in accordance with the optical axes of the illumination lenses 28a and 28b, the illumination lenses 28a and 28b are covered according to the distribution of the light intensity incident on the light guides 32a and 32b. Illuminate the sample with illumination light. The light source control unit 62 adjusts the lighting / extinguishing timing of the light source 63 according to the adjustment signal and the synchronization signal input from the controller 57 of the processor device 12.

  The partial dimming unit 67 includes a partial dimming plate 68 and a slide mechanism 69. The partial dimming plate 68 is located between the condenser lens 65 and the optical fiber 66. As shown in FIG. 5, the partial dimming plate 68 has a disc shape, and a circular dimming filter 68a is formed in the central portion. The partial light attenuating plate 68 has a low light transmittance of the dark filter 68a, and a portion from the periphery to the outside of the dark filter 68a has a high light transmittance.

  The partial dimming plate 68 is positioned on the optical path where light enters the optical fiber 66 from the condensing lens 65, and the center position of the neutral density filter 68a is aligned with the optical axis L1 (see FIG. 6) of the condensing lens 65. It is movable between the dimming position (the position indicated by the solid line in FIGS. 4 and 6) and the dimming position, that is, the retracted position (the position indicated by the two-dot chain line in FIGS. 4 and 6). Is provided.

  The slide mechanism 69 includes a guide member that guides the movement of the partial dimming plate 68 and an actuator that moves the partial dimming plate 68. As the actuator, for example, a solenoid is used. When an instruction is given to the light source control unit 62 by the controller 57, the slide mechanism 69 slides the partial dimming plate 68 between the retracted position and the dimming position by driving an actuator that receives a control signal from the light source control unit 62. Let

  The controller 57 operates the slide mechanism 69 when the focal length of the observation optical system 36 is switched between normal observation and magnified observation, that is, when the zoom lens 39 moves between the normal observation position and magnified observation position. Thus, the partial dimming plate 68 is moved between the retracted position and the dimming position. When the zoom lens 39 is in the normal observation position, the partial dimming plate 68 is in the retracted position, and when the zoom lens 39 is in the enlarged observation position, the partial dimming plate 68 is in the dimming position.

  As shown in FIG. 6, the neutral density filter 68 a formed on the partial darkening plate 68 reduces the light out of the light incident on the optical fiber 66 from the condenser lens 65 when the partial darkening plate 68 is in the darkening position. It is formed in accordance with the area A1. Since the light intensity in the vicinity of the optical axis L1 of the light condensed by the condenser lens 65 is large, the central circular area including the optical axis L1 is set as the light reducing area A1. A transmission area A2 is set around the light attenuation area A1. As a result, when the partial dimming plate 68 is in the dimming position, the partial dimming plate 68 partially diminishes only the dimming area A1 located in the center of the light incident on the optical fiber 66 from the condensing lens 65, thereby transmitting the transmissive area. In A2, light is transmitted without being dimmed. The dimming area A1 is appropriately changed according to the light intensity of the light emitted from the light source 63, the performance of the condensing lens 65, the diameters of the light guides 32a and 32b, and the optical axis L1 by experiment or simulation. The light intensity in the vicinity is measured, and from this measurement result, the range where the light intensity is high is defined as the light attenuation area A1, and the light attenuation filter 68a is formed in accordance with the light attenuation area A1.

  The operation of the above configuration will be described. When the insertion unit 16 is inserted into the subject and observation is performed with the electronic endoscope 11, the imaging unit 35 is normally observable (the zoom lens 39 is the normal observation position) and the light source unit 61 is in the initial state. The light reducing plate 68 is in the retracted position. Normal observation is performed in this state, and an observation image obtained by imaging the inside of the subject is displayed on the monitor 24.

  During normal observation, in the light source unit 61, since the partial dimming plate 68 is in the retracted position, the light condensed by the condensing lens 65 is incident on the light guides 32a and 32b without being dimmed. The illumination lenses 28 a and 28 b irradiate the observation light of the observation optical system 36 with the illumination light guided by the light guides 32 a and 32 b without being partially dimmed.

  When an operator wants to see a more detailed observation image of the abnormal part, the operator performs an operation of switching from normal observation to magnified observation using the operation unit 58. The controller 57 moves the zoom lens 39 from the normal observation position to the magnified observation position in accordance with the operation of the operation unit 58 and controls the light source control unit 62 to operate the slide mechanism 69 to retract the partial dimming plate 68. Move from position to dimming position. Thereby, in the light source part 61, only the light-reduction area | region A1 is partially dimmed out of the light condensed by the condensing lens 65, and injects into the light guides 32a and 32b. The illumination lenses 28a and 28b are partially dimmed by the partial dimming plate 68 and irradiate the observation range of the observation optical system 36 with illumination light according to the distribution of the light intensity incident on the light guides 32a and 32b.

  FIG. 7 shows an example of the light intensity distribution of illumination light emitted from the illumination lenses 28a and 28b when normal observation and magnified observation are performed using the imaging unit 35. FIG. As shown in FIG. 7A, when normal observation is performed using the imaging unit 35, the illumination light guided by the light guides 32a and 32b without being dimmed by the light source unit 61 is emitted from the illumination lens 28a. , 28b, the light intensity in the vicinity of the optical axis, that is, the light intensity at the position where the light distribution angle is 0 ° is large. On the other hand, as shown in FIG. 7B, when performing magnified observation using the imaging unit 35, the illumination light according to the light intensity distribution in which only the dimming region A1 is partially dimmed in the light source unit 61. Is irradiated from the illumination lenses 28a and 28b, the light intensity in the range including the optical axis, that is, in the range of the light distribution angle of −50 ° to 50 ° is reduced.

  As described above, when the imaging unit 35 performs magnified observation, the illumination light partially dimmed by the partial dimming plate 68 is irradiated. Therefore, when performing magnified observation with the imaging unit 35, the light intensity of the dimming area A1 is lowered even when the observation optical system 36 is brought close to the surface of the subject so that the subject is in focus. Can be suppressed. Since the unevenness of the luminance distribution is suppressed, it is possible to obtain a clear image while preventing overexposure.

  In the first embodiment, the slide mechanism 69 that slides the partial dimming plate 68 is used as the moving means for moving the partial dimming plate 68 between the retracted position and the dimming position. However, the present invention is not limited to this, and any moving means that moves the partial dimming plate 68 between the retracted position and the dimming position, such as a rotating mechanism that rotates the partial dimming plate 68 by a motor or the like, may be used.

  In the first embodiment, the dark filter 68a having a low light transmittance is formed as a partial light reducing unit that partially reduces light incident on the optical fiber 66 from the condenser lens 65 when the imaging unit 35 is magnified. The partial dimming plate 68 and the partial dimming unit 67 including the slide mechanism 69 that moves the partial dimming plate 68 are used. However, the present invention is not limited to this, and as in the second embodiment shown in FIG. A partial light reduction unit 70 including a liquid crystal panel 71 on which a light reduction pattern 71a having a low light transmittance is formed and a liquid crystal driver 72 for driving and controlling the liquid crystal panel 71 may be used. The configuration other than the partial dimming unit 70 is the same as that of the electronic endoscope system 10 of the first embodiment.

  In the case of the second embodiment, the liquid crystal panel 71 is located between the condensing lens 65 and the optical fiber 66 in the same manner as the partial dimming plate 68 of the first embodiment. The dimming pattern 71a formed on the liquid crystal panel 71 is set in a substantially circular shape in accordance with the dimming area A1. In addition, the liquid crystal panel 71 transmits no light at a high light transmittance without forming a pattern in a portion corresponding to the transmission region A2. The liquid crystal panel 71 is controlled by the light source control unit 62 via the liquid crystal driver 72, and when the zoom lens 39 is in the normal observation position, the dimming pattern 71a is not formed, and the entire surface is in a transmissive state. When 39 is in the magnified observation position, a dimming pattern 71a is formed. Thereby, when the imaging unit 35 performs normal observation, the entire surface of the liquid crystal panel 71 is in a transmissive state, and thus the light collected by the condenser lens 65 is not dimmed, and the illumination lenses 28a and 28b. Irradiated from. On the other hand, when magnifying observation is performed with the imaging unit 35, a dimming pattern 71 a is formed, and only the dimming region A <b> 1 of the light incident on the optical fiber 66 from the condenser lens 65 is partially dimmed. As described above, when the imaging unit 35 performs magnified observation, the illumination light partially dimmed by the liquid crystal panel 71 is irradiated.

  In the first and second embodiments, the partial dimming plate 68 and the liquid crystal panel 71 constituting the partial dimming units 67 and 70 are disposed between the condenser lens 65 and the optical fiber 66. The present invention is not limited to this, and may be located at any position on the optical path from the light source 63 to the light guides 32a and 32b. For example, the light guide 63 and the condenser lens 65 may be disposed. .

  In the first and second embodiments, the partial dimming plate 68 and the slide mechanism are used as the partial dimming unit for partially dimming the light incident on the optical fiber 66 from the condensing lens 65 during the magnification observation of the imaging unit 35. 69, and the partial dimming unit 70 including the liquid crystal panel 71 and the liquid crystal driver 72 on which the dimming pattern 71a is formed are used. As in the third embodiment, an initial position orthogonal to the optical axis L1 of the condenser lens 65 (position shown in FIG. 9A) and a dimming position obliquely intersecting with the optical axis of the condenser lens 65 (FIG. 9). (Part (B)) is provided with a parallel plate 81 that can be rotated between the rotary plate 82 and a rotating mechanism 82 that rotates the parallel plate 81 between an initial position and a dimming position. May be used. The configuration other than the partial dimming unit 80 is the same as that of the electronic endoscope system 10 of the first embodiment.

  In the case of the third embodiment, the parallel plate 81 is an optical member that transmits light, the light incident surface and the light emission surface are formed in parallel to each other, and the partial light reduction plate 68 of the first and second embodiments, Similar to the liquid crystal panel 71, it is located between the condenser lens 65 and the optical fiber 66. The rotation mechanism 82 includes a motor that rotates the parallel plate 81, a motor driver, and the like. The rotation mechanism 82 is controlled by the light source control unit 62. When the zoom lens 39 is in the normal observation position, the parallel plate 81 is set to the initial position. When switching from the normal observation position to the magnified observation position, the parallel plate 81 is rotated from the initial position to the dimming position.

  When the imaging unit 35 performs normal observation, as shown in FIG. 9A, since the parallel plate 81 is in the initial position orthogonal to the optical axis L1, the light condensed by the condenser lens 65 is parallel plate. The light near the optical axis L <b> 1 having a large light intensity enters the optical fiber 66 through 81. Therefore, the light condensed by the condenser lens 65 is emitted from the illumination lenses 28a and 28b without being attenuated by the partial dimming unit 80. On the other hand, when the imaging unit 35 performs magnified observation, as shown in FIG. 9B, the light collected by the condensing lens 65 because the parallel plate 81 is at a dimming position that crosses the optical axis L1. The optical path is refracted by the parallel plate 81, and light in the vicinity of the optical axis L1 having a high light intensity in the light intensity distribution centered on the optical axis L1 does not enter the optical fiber 66, and the peripheral portion having a low light intensity. Only enters the optical fiber 66. Therefore, the light condensed by the condensing lens 65 is attenuated by the partial dimming unit 80 and irradiated from the illumination lenses 28a and 28b.

  In each of the above-described embodiments, a CCD is used as an image pickup element that picks up image light in a subject.

DESCRIPTION OF SYMBOLS 10 Electronic endoscope system 11 Electronic endoscope 16 Insertion part 16a Tip part 27 Observation lens 32a, 32b Light guide 36 Observation optical system 63 Light source 65 Condensing lens 67, 70, 80 Partial light reduction part 68 Partial light reduction board 68a Reduction Optical filter 69 Slide mechanism 71 Liquid crystal panel 71a Dimming pattern 72 Liquid crystal driver 81 Parallel plate 82 Rotating mechanism

Claims (5)

An observation optical system that is provided at the distal end of the insertion portion that is inserted into the subject and that captures the image light in the subject for observation, and the focal length of the observation optical system during normal observation and magnification observation Variable focus means, an image sensor on which image light in the observation range captured by the observation optical system is formed, an illumination optical system for irradiating illumination light toward the observation range, and the illumination optics An electronic endoscope provided in alignment with the system and provided with a light guide for guiding illumination light to the illumination optical system;
A light source that emits light;
Condensing means for condensing the light from the light source and entering the light guide;
When the observation optical system is in a normally observable state, retracted from the light path from the light source to the light guide, and when the observation optical system is switched from a normally observable state to a state capable of magnifying observation, Of the light incident on the light guide that is located on the optical path, only a light-reducing area located at the center is partially dimmed, and light is not reduced in a transmission area located around the light-reducing area. And a partial dimming means for transmitting light to
The electronic endoscope system according to claim 1, wherein the illumination optical system emits illumination light in accordance with a distribution of light intensity incident on the light guide. The partial dimming means is
A light-reducing filter having a low light transmittance is formed in a portion matched with the light-reducing region, a partial light-reducing plate having a high light transmittance in a portion matched with the light-transmitting region, located on the light path, and the light collecting plate. A partial dimming plate movably provided between a dimming position for aligning the center position of the neutral density filter with the optical axis of the optical lens, and a retreat position for retreating from the optical path;
When the observation optical system is in a normally observable state, the neutral density filter is in the retracted position, and when the observation optical system is switched from a state in which normal observation is possible to a state in which magnified observation is possible, the neutral density filter is The electronic endoscope system according to claim 1, further comprising a moving unit that moves the retracted position to the dimming position.   The electronic endoscope system according to claim 2, wherein the partial dimming plate is disposed between the light guide and the condenser lens.   The electronic endoscope system according to claim 2, wherein the partial dimming plate is disposed between the light source and the condenser lens.   The electronic endoscope system according to any one of claims 1 to 4, further comprising a light source device provided with the light source, the condensing unit, and the partial dimming unit.

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