Patent Publication Number: US-2018049631-A1

Title: Light source apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a light source apparatus for irradiating a subject with light. 
     BACKGROUND ART 
     Endoscope systems that can capture special images are known. A specific configuration of this type of endoscope system is disclosed in WO 2012/108420 pamphlet (called “Patent Document 1” hereinafter), for example. 
     The endoscope system disclosed in Patent Document 1 includes a light source apparatus that is provided with a rotating filter. The rotating filter is an optical filter that allows only light in a specific wavelength region to pass, and rather than having a simple disk shape, has a special shape in which a portion of the outer circumferential region is cut away. A controller drives the rotating filter to rotate at a constant rotation period such that the optical filter portion and the cutaway portion successively enter the light path of irradiation light, and an image of biological tissue formed by irradiation light that passed through the optical filter portion and an image of biological tissue formed by irradiation light that passed through the cutaway portion (i.e., unfiltered irradiation light) are successively captured. The controller generates one observation image based on captured image data regarding the biological tissue irradiated by irradiation light that passed through the optical filter portion, generates another observation image based on captured image data regarding biological tissue illuminated with unfiltered irradiation light, and displays these two types of generated observation images side-by-side on the display screen of a monitor. 
     SUMMARY OF INVENTION 
     Silk lines for detecting the rotation position of the rotating filter are printed on the central portion of the rotating filter disclosed in Patent Document 1. However, the silk lines are extremely small, and therefore there is a problem in that the rotation position of the rotating filter cannot be precisely detected if there is even a slight error in the silk lines. 
     The present invention was achieved in light of the above-described circumstances, and an object of the present invention is to provide a light source apparatus that is suited to irradiating a subject with two types of irradiation light that have different wavelength regions. 
     A light source apparatus according to an embodiment of the present invention includes: a light source; a switching means for switching a light path of irradiation light emitted by the light source between a first light path and a second light path; and an optical filter that. is fixedly arranged in the first light path and filters irradiation light propagating along the first light path into light in a specific wavelength region. 
     Also, in the embodiment, of the present invention, a configuration is possible in which the switching means alternatingly switches the light path of irradiation light between the first light path and the second light path in accordance with a timing synchronized with a predetermined imaging cycle. 
     Also, in the embodiment of the present invention, a configuration is possible in which the switching means has a light path changing means capable of being inserted into the light path of irradiation light. In this configuration, the irradiation light enters the second light path when the light path changing means is inserted into the light path of irradiation light, and the irradiation light enters the first light path when the light path changing means is removed from the light path of irradiation light. 
     Also, in the embodiment of the present invention, the light path changing means is a reflecting member that bends the light path of irradiation light, for example. 
     Also, in the embodiment of the present invention, a configuration is possible in which the switching means inserts the light path changing means into the light path of irradiation light or removes the light path changing means from the light path of irradiation light by shifting the light path changing means in a direction orthogonal to the light path of irradiation light. 
     Also, in the embodiment of the present invention, a configuration is possible in which the switching means inserts the light path changing means into the light path of irradiation light or removes the light path changing means from the light path of irradiation light by rotating the light path changing means about a predetermined shaft on which the light path changing means is supported. 
     Also, a light source apparatus according to an embodiment of the present invention may include a plurality of light sources. A first light source that emits first irradiation light and a second light source that emits second irradiation light, for example, are included among the plurality of light sources. In this case, when the light path of irradiation light is switched between the first light path and the second light path by the switching means, the second light source is accordingly switched between on and off states. 
     According to the embodiment of the present invention, a light source apparatus that is suited to irradiating a subject with two types of irradiation light that have different wavelength regions is provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram showing a configuration of an electronic endoscope system according to an embodiment of the present invention. 
         FIG. 2  is a diagram showing a spectral intensity distribution of LEDs included in the electronic endoscope system of the embodiment of the present invention. 
         FIG. 3  is a perspective view of a movable unit included in the electronic endoscope system of the embodiment of the present invention. 
         FIG. 4  is a diagram showing spectral characteristics of a narrow-band light filter included in the electronic endoscope system of the embodiment of the present invention. 
         FIG. 5  is a diagram for assisting a description of operations of the electronic endoscope system in various observation modes. 
         FIG. 6  is a diagram schematically showing a configuration of a movable unit according to a variation of the embodiment of the present invention. 
         FIG. 7  is a perspective diagram showing a configuration of a mirror and an actuator included in the movable unit according to a variation of the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that an electronic endoscope system is taken as an example of an embodiment of the present invention in the following description. 
       FIG. 1  is a block diagram showing the configuration of an electronic endoscope system  1  according to an embodiment of the present invention. As shown in  FIG. 1 , the electronic endoscope system  1  is a system specialized for medical use, and includes an electronic endoscope  100 , a processor  200 , and a monitor  300 . 
     The processor  200  includes a system controller  202  and a timing controller  204 . The system controller  202  executes various programs stored in a memory  222  and performs overall control of the electronic endoscope system  1 . Also. the system controller  202  is connected to an operation panel  221 . The system controller  202  changes operations of the electronic encloscope system  1  and parameters for various operation in accordance with instructions from an operator that are input using the operation panel  224 . One example of an instruction input by an operator is an instruction for switching the observation mode of the electronic endoscope system  1 . Examples of observation modes include a normal observation mode, a special observation mode, and a twin observation mode. The timing controller  204  outputs a clock pulse, which is for adjustment of the timing of the operations of portions, to circuits in the electronic endoscope system  1 . 
     The processor  200  includes multiple LEDs (Light Emitting Diodes) as examples of light sources. Specifically, the processor  200  includes a white LED  206 .  FIG. 2( a )  shows an example of the spectral intensity distribution of the white LED  206 . As shown in  FIG. 2( a ) , the white LED  206  is a so-called pseudo white light source that has an uneven emission spectrum. White light emitted by the white LED  206  passes through a collimator lens  208  and a dichroic mirror  210  in this order, and then enters a movable unit  212 . 
     The processor  200  also includes an ultraviolet LED  216 .  FIG. 2( b )  shows an example of the spectral intensity distribution of the ultraviolet LED  216 . As shown in  FIG. 2( b ) , the ultraviolet LED  216  is a light source that. emits only light in the ultraviolet region. Ultraviolet light emitted by the ultraviolet LED  216  passes through a collimator lens  218 , is reflected by the dichroic mirror  210 , and enters the movable unit  212 . 
     The movable unit  212  operates as a switching means for switching the light path of light emitted by the light sources, and as shown in  FIG. 1 , includes a movable mount  212   a , a linear shaft  212   b , linear bushes  212   c , a first mirror  212   d , a second mirror  212   e , a third mirror  212   f , a fourth mirror  212   g , and an actuator  212   h . The mirrors inside the movable unit  212  function as light path changing means that can enter and exit the light path of light emitted by the light sources. 
       FIG. 3  shows a perspective view of the movable unit  212 . Note that for the sake of convenience in  FIG. 3 , support members that support the various constituent elements of the movable unit  212  have been omitted from the illustration as appropriate, and the actuator  212   h  has also been omitted from the illustration. 
     As shown in  FIG. 3 , the linear bushes  212   c  are attached to the upper surface of the movable mount  212   a . The linear shafts  212   b , which are fixed to the case of the processor  200 , guide the linear bushes  212   c  in a straight line, and thus the movable mount  212   a  shifts in the vertical direction (the lengthwise direction of the linear shafts  212   b ) inside the case. Note that the lengthwise direction of the linear shafts  212   b  is orthogonal to the light path of white light that passed through the dichroic mirror  210  (or ultraviolet light reflected by the dichroic mirror  212 ). 
     The first mirror  212   d  and the fourth mirror  212   g  are attached to the movable mount  212   a , and shift in the vertical direction integrally with the movable mount  212   a  inside the case of the processor  200 . In contrast., the second mirror  212   e  and the third mirror  212   f  are attached to the case, and have fixed positions in the case. Also, a narrow-band light filter  220 , which is an example of an optical filter, is also attached to the case, and has a fixed position in the case. The narrow-band light filter  220  is shaped as a simple disk, for example. 
     When the movable mount  212   a  is shifted upward by the actuator  212   h , the first mirror  212   d  is inserted into the light path of white light (or ultraviolet light) (see the first mirror  212   d  indicated by solid lines in  FIG. 1 , and see  FIG. 3( a ) ). Hereinafter, for the sake of convenience in the description, the state in which the first mirror  212   d  has been inserted into the light path will be referred to as the “entered light path state”. 
     In the entered light path state, in order to circumvent the narrow-band light filter  220  located between the first mirror  212   d  and the fourth mirror  212   g , white light (or ultraviolet light) that is incident on the first mirror  212   d  is reflected by the first mirror  212   d , passes through a hole  212   aa  formed in the movable mount  212   a , is reflected by the second mirror  212   e  and the third mirror  212   f  in this order, passes through a hole  212   ab  formed in the movable mount  212   a , is reflected by the fourth mirror  212   g , and then enters the condensing lens  214  arranged in the stage after the movable unit  212 . 
     On the other hand, when the movable mount  212   a  is shifted downward by the actuator  212   h , the first mirror  212   d  and the fourth mirror  212   g  are removed from the light path of white light (or ultraviolet light) (see the first mirror  212   d  indicated by dashed lines in  FIG. 1 , and see  FIG. 3( b ) ). Hereinafter, for the sake of convenience in the description, the state in which the first mirror  212   d  has been removed from the light path will be referred to as the “exited light path state”. 
     In the exited light path state, white light emitted by the white LED  206  (or ultraviolet light emitted by the ultraviolet LED  216 ) passes through the narrow-band light filter  220  and enters the condensing lens  214 . 
     In this way, in the entered light path state, unfiltered light (light that substantially has the same spectral intensity distribution as when emitted from the LED) enters the condensing lens  214 , whereas in the exited light path state, light filtered by the narrow-band light filter  220  enters the condensing lens  214 . Hereinafter, for the sake of convenience in the description, the light path that circumvents the narrow-band light filter  220  shown in  FIG. 3( a )  will be referred to as the “circumvent light path”, and the light path that passes through the narrowband light filter  220  shown in  FIG. 3( b )  will be referred to as the “filtering light path”. In other words, the movable unit  212  switches the light path of white light emitted by the white LED  206  (or ultraviolet light emitted by the ultraviolet LED  216 ) between the circumvent light path and the filtering light path. 
       FIG. 4( a )  shows an example of the spectral characteristics of the narrow-band light filter  220 . Also,  FIG. 4( b )  shows a different example of spectral characteristics from  FIG. 4( a )  for the narrow-band light filter  220 . As shown in  FIGS. 4( a ) and 4( b ) , the narrow-band light filter  220  has a spectral characteristic of allowing only light in a specific wavelength region to pass. 
     The light that entered the condensing lens  214  is condensed on the entrance surface of an LCB (Light Carrying Bundle)  102  by a condensing lens  214 , and enters the LCB  102 . 
     The light that entered the LCB  102  propagates inside the LCB  102 . The light that propagated inside the LCB  102  exits from the exit surface of the LCB  102  arranged at the distal end of the electronic endoscope  100 , passes through a light distribution lens  104 , and irradiates the subject. Returning light from the subject irradiated by the light from the light distribution lens  101  passes through the objective lens  106  and forms an optical image on the light receiving surface of the solid-state image sensor  108 . 
     The solid-state image sensor  108  is a single-plate color CCD (Charge Coupled Device) image sensor that has a Bayer pixel arrangement. The solid-state image sensor  108  accumulates charge according to the light quantity of an optical image formed on pixels on the light receiving surface, generates R (Red), G (Green), and B (Blue) image signals, and outputs the image signals. Note that the solid-state image sensor  108  is not limited to being a CCD image sensor, and may be replaced with a CMOS (Complementary Metal Oxide Semiconductor) image sensor or another type of imaging apparatus. The solid-state image sensor  108  may be an element that includes a complementary color filter. 
     A driver signal processing circuit  110  is provided in the connection portion of the electronic endoscope  100 . Image signals of the subject irradiated by light from the light distribution lens  104  are input by the solid-state image sensor  108  to the driver signal processing circuit  110  at a frame cycle. Note that the terms “frame” and “field” may be switched in the following description. In the present embodiment, the frame cycle and the field cycle are respectively 1/30 seconds and 1/60 seconds. The image signals input from the solid-state image sensor  108  are subjected to predetermined processing by the driver signal processing circuit  110  and output to a pre-stage signal processing circuit  226  of the processor  200 . 
     The driver signal processing circuit  110  also accesses a memory  112  and reads out unique information regarding the electronic endoscope  100 . The unique information regarding the electronic endoscope  100  recorded in the memory  112  includes, for example, the pixel count, sensitivity, operable frame rate, and model number of the solid-state image sensor  108 . The unique information read out from the memory  112  is output by the driver signal processing circuit  110  to the system controller  202 . 
     The system controller  202  generates control signals by performing various computation based on the unique information regarding the electronic endoscope  100 . The system controller  202  uses the generated control signals to control the operations of and the timing of various circuits in the processor  200  so as to perform processing suited to the electronic endoscope that is connected to the processor  200 . 
     A timing controller  204  supplies a clock pulse to the driver signal processing circuit  110  in accordance with timing control performed by the system controller  202 . In accordance with the clock pulse supplied from the timing controller  204 , the driver signal processing circuit  110  controls the driving of the solid-state image sensor  108  according to a timing synchronized with the frame rate of the images processed by the processor  200 . 
     The pre-stage signal processing circuit  226  performs predetermined signal processing such as demosaicing processing, matrix computation, and Y/C separation on the image signal received in one frame cycle from the driver signal processing circuit  110 , and outputs the result to an image memory  228 . 
     The image memory  228  buffers image signals received from the pre-stage signal processing circuit  226 , and outputs the image signals to a post-stage signal processing circuit  230  in accordance with timing control performed by the timing controller  204 . 
     The post-stage signal processing circuit  230  performs processing on the image signals received from the image memory  228  to generate screen data for monitor display, and converts the generated monitor display screen data into a predetermined video format signal. The converted video format signal is output to the monitor  300 . Accordingly, subject images are displayed on the display screen of the monitor  300 . 
       FIG. 5  is a diagram for assisting a description of operations of the electronic endoscope system  1  in various observation modes. Specifically,  FIG. 5  shows the ON/OFF states of the LEDs, the operation state of the movable unit  212 , the filtering state of the narrow-band light filter  220 , and a schematic illustration of various constituent elements (the LEDs, the movable unit  212 , and the narrow-band light filter  220 ) in the various observation modes. 
     Normal Observation Mode 
     The following describes operations of the electronic endoscope system  1  in the normal observation mode. 
     As shown in  FIG. 5 , in the normal observation mode, the white LED  206  is on at all times, and the ultraviolet LED  216  is off at all times. Also, the movable unit  212  is set to the entered light path state (see  FIG. 3( a ) ). In this case, white light emitted by the white LED  206  travels along the circumvent light path, enters the condensing lens  214 , and irradiates the subject. In other words, the subject is irradiated by white light that has the spectral intensity distribution shown in  FIG. 2( a ) . 
     The solid-state image sensor  108  images the subject irradiated by white light, and outputs the image signal to the pre-stage signal processing circuit  226  via the driver signal processing circuit  110 . The image signal is processed by the pre-stage signal processing circuit  226 , the image memory  228 , and the post-stage signal processing, circuit  230  and then output to the monitor  300 , and thus a normal color image of the subject is displayed on the display screen of the monitor  300 . 
     Special Observation Mode 
     The following describes operations of the electronic endoscope system  1  in the special observation mode. 
     As shown in  FIG. 5 , in the special observation mode, the white LED  206  and the ultraviolet LED  216  are on at all times. Also, the movable unit  212  is set to the exited light path state (see  FIG. 3( b ) ). In this case, white light emitted by the white LED  206  and ultraviolet light emitted by the ultraviolet LED  216  travel along the filtering light path, enter the condensing lens  214 , and irradiate the subject. In other words, the subject is irradiated by light that is a combination of white light and ultraviolet light (light having the spectral intensity distribution shown in  FIG. 2( c ) ) and has been filtered by the narrow-band light filter  220 . Hereinafter, for the sake of convenience in the description, this light that is a combination of white light and ultraviolet light will be referred to as “superimposed light”, and the light filtered by the narrow-band light filter  220  will be referred to as “special light”. 
     The solid-state image sensor  108  images the subject irradiated by special light, and outputs the image signal to the pre-stage signal processing circuit  226  via the driver signal processing circuit  110 . Here, this special light is light that is highly absorbed by a specific biological structure. For this reason, the image signal is processed by the pre-stage signal processing circuit  226 , the image memory  228 , and the post-stage signal processing circuit  230  and then output to the monitor  300 , and thus a spectral image in which a specific biological structure is enhanced is displayed on the display screen of the monitor  300 . 
     Twin Observation Mode 
     The following describes operations of the electronic endoscope system  1  in the twin observation mode. 
     In the twin observation mode, the white LED  206  is on at all times. On the other hand, the ultraviolet LED  216  is alternatingly switched on and off (one frame at a time) in accordance with a timing synchronized with the frame cycle. Also, in accordance with a timing synchronized with the frame cycle (one frame at a time), the movable unit  212  is set to the entered light path state when the ultraviolet LED  216  is turned off, and is set to the exited light path state when the ultraviolet LED  216  is turned on. In other words, the light path of irradiation light is alternatingly switched between the circumvent light path and the filtering light path in accordance with a timing synchronized with the frame cycle, which is the imaging cycle, (one frame at a time). In this case, the subject is alternatingly irradiated by white light and special light in accordance with a timing synchronized with the frame cycle (one frame at a time). 
     In one frame, the solid-state image sensor  108  images the subject irradiated by white light and outputs the image signal to the pre-stage signal processing circuit  226  via the driver signal processing circuit  110 , and then in the next frame, images the subject irradiated by special light and outputs the image signal to the pre-stage signal processing circuit  226  via the driver signal processing circuit  110 . In other words, the solid-state image sensor  108  alternatingly outputs an image signal of the subject irradiated by white light and an image signal of the subject irradiated by special light to the pre-stage signal processing circuit  226  via the driver signal processing circuit  110 . The former and latter image signals are processed by the pre-stage signal processing circuit  226 , the image memory  228 , and the post-stage signal processing circuit  230  and then output to the monitor  300 . 
     Two regions for displaying observation images are arranged side-by-side in the display screen of the monitor  300 . A normal color image of the subject irradiated by white light is displayed in one of the regions, and a spectral image in which the subject irradiated by special light (specific biological structure) is enhanced is displayed in the other region. In other words, a normal color image and a spectral image of the subject are displayed side-by-side on the display screen of the monitor  300 . 
     In this way, according to the present embodiment, the narrow-band light filter  220  is not a moved member, but rather is a member that is fixed inside the case of the processor  200 , and therefore there is no need for indicators for detecting the rotation position such as silk lines. Also, because the narrow-band light filter  220  is not a moved member, there are few constraints in terms of its shape, and it may have a simple disk shape for example. In other words, according to the present embodiment, there is no need for indicators required to have strict tolerance management, and there are few constraints on the shape of the narrow-band light filter  220 , thereby achieving advantages in terms of manufacturing (e.g., the yield is easily improved). 
     An illustrative embodiment of the present invention has been described above. The embodiments of the present invention are not limited to the embodiment described above, and various changes can be made without departing from the scope of the technical idea of the present invention. For example, appropriate combinations of embodiments and the like explicitly given as examples in this specification and obvious embodiments and the like are also encompassed in embodiments of the present invention. 
     The light source apparatus is provided inside the processor  200  in the above embodiment, but in another embodiment, a configuration is possible in which the processor  200  and the light source apparatus are separate. In this case, a wired or wireless communication means for exchanging timing signals is provided between the processor  200  and the light source apparatus. 
     Also, although the ultraviolet LED  216  is off at all times in the normal observation mode in the above embodiment, the present invention is not limited to this. The ultraviolet LED  216  may be on at all times in the normal observation mode in order to improve color rendering. 
     Also, although the ultraviolet LED  216  is switched on and off one frame at a time in the twin observation mode in the above embodiment, the present invention is not limited to this. The ultraviolet LED  216  may be on at all times in the twin observation mode in order to improve color rendering. 
       FIG. 6  schematically shows the configuration of a movable unit  2120  according to a variation of the present embodiment. As shown in  FIG. 6 , the movable unit  2120  includes a first mirror  2120   d , a second mirror  2120   e , a third mirror  2120   f , a fourth mirror  2120   g , and actuators  2120   h   1  and  2120   h   2 . 
       FIG. 7  shows a perspective view of the first mirror  2120   d  and the actuator  2120   h   1 . As shown in  FIG. 7 , the first mirror  2120   d  includes a mirror body  2120   da  and a mirror holding member  2120   db  that holds the mirror body  2120   da  by screw fastening, bonding, or the like. The actuator  2120   h   1  is a servo motor or a stepping motor, and a drive shaft thereof is press-fitted into a shaft bearing of the mirror holding member  2120   db . The first mirror  2120   d  is rotated about the drive shaft by the actuator  2120   h   1 . Note that the fourth mirror  2120   g  and the actuator  2120   h   2  have the same configuration as the first mirror  2120   d  and the actuator  2120   h   1 , and operate in the same manner. 
     In the state where the first mirror  2120   d  and the fourth mirror  2120   g  have been inserted into the light path (see the first mirror  2120   d  and the fourth mirror  2120   g  indicated by dashed lines in  FIG. 6 . and see  FIG. 7( a ) ), white light (or ultraviolet light) that was incident on the first mirror  2120   d   1  is reflected by the first mirror  2120   d , the second mirror  2120   e , the third mirror  2120   f , and the fourth mirror  2120   g  in this order so as to circumvent the narrow-band light filter  220  located between the first mirror  2120   d   1  and the fourth mirror  2120   g , and then enters the condensing lens  214 . 
     On the other hand, in the state where the first mirror  2120   d  and the fourth mirror  2120   g  have been removed from the light path (see the first mirror  2120   d  and the fourth mirror  2120   g  indicated by solid lines in  FIG. 6 . and see  FIG. 7( b ) ), white light emitted by the white LED  206  (or ultraviolet light emitted by the ultraviolet LED  216 ) passes through the narrow-band light filter  220  and then enters the condensing lens  214 . 
     In this way, in the present variation as well, in the former state (see  FIG. 7( a )  etc.), unfiltered light (light that substantially has the same spectral intensity distribution as when emitted from the LED) enters the condensing lens  214 , whereas in the latter state (see  FIG. 7( b )  etc.), light filtered by the narrow-band light filter  220  enters the condensing lens  214 . In the present variation, there is no need for a movable mount or shafts, and the configuration of the moved portions can be suppressed to a small size.