JP2015085097A - Light source device for endoscope and endoscope system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device for an endoscope and an endoscope system allowing for linearization of relationship between an emission light quantity after APC (Auto Power Control) and light quantity setting value.SOLUTION: The light source device for an endoscope comprises an LED, an LED drive part, a light source control part, an APC part, and a correction part. The LED drive part supplies drive current to the LED to make the LED emit light. The light source control part inputs a light quantity setting value to the LED drive part to make the LED drive part generate drive current corresponding to the light quantity setting value. The APC part receives, by its light reception part, a part of light emitted from the LED to generate light reception voltage, and adjusts drive current by comparing the light reception voltage with a reference signal corresponding to the light quantity setting value. The correction part corrects the light quantity setting value used by the APC part so as to linearize relationship between the light quantity setting value and an emission light quantity of light from the LED after adjustment of the drive current.

Description

  The present invention relates to an endoscope light source device and an endoscope system for supplying illumination light to an endoscope.

  In recent medical treatments, diagnosis and the like using an endoscope system including an endoscope light source device, an electronic endoscope, and a processor device are widely performed. The endoscope light source device generates illumination light and irradiates the sample. The electronic endoscope is irradiated with illumination light, and the inside of the specimen is imaged by an image sensor to generate an image signal. The processor device performs image processing on the imaging signal generated by the electronic endoscope and generates an observation image for display on the monitor.

  Conventionally, in an endoscope light source device, a lamp light source such as a xenon lamp or a halogen lamp that emits white light as illumination light has been used, but recently, a light of a specific color is emitted instead of the lamp light source. Semiconductor light sources such as laser diodes (LDs) and light emitting diodes (LEDs) are being used (see, for example, Patent Document 1).

  In the endoscope light source device described in Patent Document 1, a first LED that emits red light, a second LED that emits green light, and a third LED that emits blue light are provided as the semiconductor light source for endoscope. The three colors of light emitted from the first to third LEDs are combined to generate white light. In an endoscope light source device including a lamp light source, the ratio of each color component in illumination light cannot be changed. However, in an endoscope light source device including a plurality of semiconductor light sources, the light amount of each semiconductor light source is independently controlled. Thus, the ratio of each color component in the illumination light can be changed, and the color temperature of the illumination light can be easily adjusted.

  However, since the semiconductor light source used in the endoscope light source device has high output and large self-heating, a temperature change or the like occurs in the semiconductor light source, and the amount of emitted light fluctuates. For this reason, in patent document 1, in order to stabilize the emitted light quantity of a semiconductor light source, the automatic power control (APC: Auto Power Control) part is provided. The APC unit includes a light receiving unit, a current-voltage conversion unit, a reference voltage generation unit, and a comparator (differential amplifier).

  The light receiving unit is formed of a photodiode, receives a part of the illumination light emitted from the semiconductor light source, and outputs a current (light receiving current). The current-voltage converter converts the received light current into a voltage (light received voltage) and inputs it to the inverting input terminal of the comparator. The reference voltage generation unit generates a reference voltage corresponding to the light amount setting value of the semiconductor light source and inputs the reference voltage to the non-inverting input terminal of the comparator. The comparator outputs a signal (APC signal) corresponding to the difference between the received light voltage and the reference voltage. A light amount setting value and an APC signal are input to the driving circuit of the semiconductor light source. This drive circuit adjusts the drive current of the semiconductor light source corresponding to the light amount setting value based on the APC signal. As a result, the received light voltage approaches the reference voltage, and the amount of light emitted from the semiconductor light source is stabilized with fluctuations suppressed.

JP 2010-158413 A

  However, since the light reception voltage is proportional to the product of the amount of illumination light emitted from the semiconductor light source proportional to the light amount setting value and the spectral sensitivity of the light receiving unit, the relationship between the light amount setting value and the light reception voltage is linear. There is a problem of non-linearity depending on spectral sensitivity characteristics.

  Specifically, the intensity spectrum of the illumination light changes in shape according to the amount of emitted light, and in particular, the peak wavelength position varies. If the wavelength dependence of the spectral sensitivity of the light receiving unit is small enough to be ignored, the relationship between the light intensity setting value and the light receiving voltage is almost linear, but the spectral sensitivity of the light receiving unit cannot be ignored. Since it has wavelength dependency (for example, the spectral sensitivity changes by about 20% with respect to the wavelength in the red wavelength region), the relationship between the light amount setting value and the light reception voltage is nonlinear.

  For this reason, for example, if the light amount setting value is changed to α times the current setting value, the emitted light amount and the reference voltage of the semiconductor light source are α times, whereas the received light voltage is β (≠ α) times. Become. In APC, the amount of light emitted from the semiconductor light source is controlled so that the light reception voltage that has been multiplied by β matches the reference voltage that has been multiplied by α. Therefore, the amount of emitted light after APC is from α times that is the original change magnification. It will shift.

  As described above, when the relationship between the emission light amount of the emission light amount after APC and the light amount setting value is nonlinear, the illumination light from the plurality of semiconductor light sources is combined to generate illumination light such as white light. The ratio of each color component in the light shifts, the spectral characteristics of the illumination light change, and the color of the observation image changes.

  An object of the present invention is to provide an endoscope light source device capable of linearizing the relationship between an emitted light amount after APC and a light amount setting value, and an endoscope system using the same.

  In order to achieve the above object, an endoscope light source device according to the present invention includes a light source that emits light, a light source drive unit that emits light by supplying a drive signal to the light source, and a light amount setting value for the light source drive unit. And a light source control unit that generates a drive signal according to the light amount setting value and a light receiving unit that receives a part of the light emitted from the light source and generates a light reception signal. A light amount control unit that compares the reference signal according to the set value and adjusts the drive signal, and a light amount set value that is used in the light amount control unit so that the relationship between the light amount set value and the light emission amount is linearized Or a correction unit that corrects the received light signal.

  Preferably, the correction unit corrects the light amount setting value based on the lookup table, and inputs the corrected light amount setting value to the light amount control unit. This look-up table is preferably determined based on the spectral intensity characteristic of light emitted from the light source and the spectral sensitivity characteristic of the light receiving unit.

  It is preferable that a plurality of light sources are provided, a light source driving unit and a light amount control unit are provided for each light source, and the correction unit is provided corresponding to at least one light source. It is preferable to provide an optical path integrating unit that integrates optical paths of light emitted from a plurality of light sources.

  It is preferable that at least one of the plurality of light quantity control units is provided with a wavelength band filter on the light incident side of the light receiving unit. This wavelength band filter preferably limits the wavelength so that the wavelength band of the light received by the light receiving unit matches the wavelength band of the corresponding light component emitted from the optical path integrating unit.

  The plurality of light sources preferably include three semiconductor light sources that emit red, green, and blue light. The semiconductor light source is preferably an LED.

  The light receiving part is preferably a photodiode.

  An endoscope system according to the present invention is an endoscope system including an endoscope having a light guide that guides light and an endoscope light source device that supplies light to the light guide. A light source device for emitting light, a light source driving unit for supplying a driving signal to the light source to emit light, and a light amount setting value input to the light source driving unit, and a driving signal corresponding to the light amount setting value The light source control unit that generates the light and a part of the light emitted from the light source is received by the light receiving unit to generate a light reception signal, and this light reception signal is compared with the reference signal according to the light amount setting value, and driven A light amount control unit that adjusts the signal, and a correction unit that corrects the light amount setting value or the received light signal used in the light amount control unit so that the relationship between the light amount setting value and the light emission amount of light is linearized.

  According to the present invention, the correction unit that corrects the light amount setting value or the received light signal used in the light amount control unit that performs APC is provided, so that the relationship between the emitted light amount after APC and the light amount setting value can be linearized.

It is an external view of an endoscope system. It is a front view of the front-end | tip part of an endoscope. It is a block diagram which shows the electric constitution of an endoscope system. It is a graph which shows the intensity spectrum of red light, green light, blue light, and purple light. It is a graph which shows the intensity spectrum of white light. It is a figure which shows the structure of an optical path integration part. It is a graph which shows the spectral reflection characteristic of a 1st dichroic mirror. It is a graph which shows the spectral reflection characteristic of a 2nd dichroic mirror. It is a graph which shows the spectral reflection characteristic of a 3rd dichroic mirror. It is a graph which shows the spectral transmission characteristic of a 1st wavelength limiting filter. It is a graph which shows the spectral transmission characteristic of a 2nd wavelength limiting filter. It is a block diagram which shows the structure of a drive part. It is a block diagram which shows the structure of a 1st APC part. It is a graph which shows the relationship between the light quantity setting value after correction | amendment, and light reception voltage. It is a graph which shows LUT used for correction | amendment of light quantity setting value. It is a graph which shows the spectral intensity characteristic of the red light inject | emitted from 1st LED. It is a graph which shows the spectral sensitivity characteristic of a 1st light-receiving part. It is a graph which shows the relationship between a light quantity setting value and a light reception voltage. It is a graph which shows the relationship between a light quantity setting value and an emitted light quantity. It is a graph which shows the relationship between the light quantity setting value and the error rate of the emitted light quantity.

  In FIG. 1, an endoscope system 10 includes an endoscope 11 that images an observation site in a living body, a processor device 12 that generates a display image of the observation site based on an image signal obtained by imaging, and an observation site. Is provided with an endoscope light source device (hereinafter simply referred to as a light source device) 13 and a monitor 14 for displaying a display image. An operation input unit 15 such as a keyboard or a mouse is connected to the processor device 12.

  The endoscope system 10 can execute a normal observation mode for observing an observation site and a blood vessel enhancement observation mode for observing a blood vessel existing inside the mucous membrane of the observation site. The blood vessel enhancement observation mode is a mode for visualizing a blood vessel pattern as blood vessel information and performing a diagnosis such as tumor quality discrimination. In this blood vessel enhancement observation mode, the observation site is irradiated with illumination light containing a large amount of light components in a specific wavelength band having a high absorbance with respect to blood hemoglobin.

  In the normal observation mode, a normal observation image suitable for observing the entire observation site is generated as a display image. In the blood vessel enhancement observation mode, a blood vessel enhancement observation image suitable for observation of a blood vessel pattern is generated as a display image.

  The endoscope 11 connects the insertion unit 16 inserted into the digestive tract of a living body, the operation unit 17 provided at the proximal end portion of the insertion unit 16, and the endoscope 11 to the processor device 12 and the light source device 13. And a universal cord 18 for the purpose. The insertion portion 16 includes a distal end portion 19, a bending portion 20, and a flexible tube portion 21, and is connected in this order from the distal end side.

  In FIG. 2, an illumination window 22 that irradiates the observation region with illumination light, an observation window 23 for capturing an image of the observation region, and air / water supply for cleaning the observation window 23 are provided on the distal end surface of the distal end portion 19. An air supply / water supply nozzle 24 for performing the above and a forceps outlet 25 for performing various treatments by projecting a treatment tool such as forceps and an electric knife are provided. An imaging device 36 and an objective optical system 45 (see FIG. 3) are built in the back of the observation window 23.

  The bending portion 20 is composed of a plurality of connected bending pieces, and bends in the vertical and horizontal directions according to the operation of the angle knob 26 of the operation portion 17. By curving the bending portion 20, the distal end portion 19 is directed in a desired direction. The flexible tube portion 21 has flexibility and can be inserted into a tortuous duct such as the esophagus or the intestine. The insertion unit 16 includes a communication cable that communicates a drive signal for driving the image sensor 36 and an image signal output from the image sensor 36, and a light guide 35 that guides illumination light supplied from the light source device 13 to the illumination window 22. (See FIG. 3) is inserted.

  In addition to the angle knob 26, the operation unit 17 includes a forceps port 27 for inserting a treatment instrument, an air / water supply button 28 that is operated when air / water is supplied from the air / water supply nozzle 24, a still image. A freeze button (not shown) or the like is provided for photographing the image.

  A communication cable and a light guide 35 extending from the insertion portion 16 are inserted into the universal cord 18, and a connector 29 is attached to one end of the processor device 12 and the light source device 13. The connector 29 is a composite type connector composed of a communication connector 29a and a light source connector 29b. The communication connector 29a and the light source connector 29b are detachably connected to the processor device 12 and the light source device 13, respectively. One end of a communication cable is disposed on the communication connector 29a. An incident end 35a (see FIG. 3) of the light guide 35 is disposed on the light source connector 29b.

  In FIG. 3, the light source device 13 includes a light source unit 30, an optical path integration unit 31, a drive unit 32, and a light source control unit 33. The light source unit 30 includes a first LED 30a that emits red light LR, a second LED 30b that emits green light LG, a third LED 30c that emits blue light LB, and a fourth LED 30d that emits purple light LV. The optical path integration unit 31 integrates the optical paths of the lights emitted from the first to fourth LEDs 30a to 30d. The drive unit 32 drives the first to fourth LEDs 30a to 30d. The light source control unit 33 controls driving of the first to fourth LEDs 30 a to 30 d by the driving unit 32.

  As shown in FIG. 4, for example, the red light LR has a wavelength band of 615 nm to 635 nm and a center wavelength of 620 ± 10 nm. For example, the green light LG has a wavelength band of 500 nm to 600 nm and a center wavelength of 520 ± 10 nm. For example, the blue light LB has a wavelength band of 440 nm to 470 nm and a center wavelength of 455 ± 10 nm. The purple light LV has, for example, a wavelength band of 395 nm to 415 nm and a center wavelength of 405 ± 10 nm.

  In the normal observation mode, the light source control unit 33 turns on the first to third LEDs 30a to 30c and turns off the fourth LED 30d. On the other hand, in the blood vessel enhancement observation mode, the light source control unit 33 turns on all the first to fourth LEDs 30a to 30d.

  As will be described in detail later, in the normal observation mode, the optical path integration unit 31 combines the red light LR, the green light LG, and the blue light LB to generate broadband white light LW as shown in FIG. On the other hand, in the blood vessel enhancement observation mode, mixed light is generated by mixing white light LW with purple light LV having a high absorbance with respect to blood hemoglobin. In the blood vessel enhancement observation mode, the light source control unit 33 reduces the ratio of the light amount of the blue light LB so that the violet light LV is more dominant than the blue light LB.

  The light emitting part of the optical path integrating part 31 is disposed in the vicinity of the receptacle connector 34 to which the light source connector 29b is connected. The optical path integrating unit 31 emits the light incident from the light source unit 30 to the incident end 35 a of the light guide 35 of the endoscope 11.

  The endoscope 11 includes a light guide 35, an imaging device 36, an analog processing circuit (AFE: Analog Front End) 37, and an imaging control unit 38. The light guide 35 is a fiber bundle obtained by bundling a plurality of optical fibers. When the light source connector 29 b is connected to the light source device 13, the incident end 35 a of the light guide 35 disposed on the light source connector 29 b faces the emission end of the optical path integrating unit 31. The exit end of the light guide 35 located at the distal end portion 19 branches into two at the front stage of the illumination window 22 so that light is guided to the two illumination windows 22 respectively.

  An irradiation lens 39 is disposed in the back of the illumination window 22. The illumination light supplied from the light source device 13 is guided to the irradiation lens 39 by the light guide 35 and irradiated from the illumination window 22 toward the observation site. The irradiation lens 39 is a concave lens, and irradiates the illumination light emitted from the light guide 35 to a wide range of the observation site.

  In the back of the observation window 23, an objective optical system 45 and an image sensor 36 are arranged. The image of the observation site enters the objective optical system 45 through the observation window 23 and is formed on the imaging surface 36 a of the image sensor 36 by the objective optical system 45.

  The imaging element 36 is a CCD image sensor, a CMOS image sensor, or the like, and a plurality of photoelectric conversion elements (photodiodes) constituting pixels are arranged in a matrix on the imaging surface 36a. The image pickup device 36 is a color image pickup device, and micro color filters of three colors B, G, and R are arranged on the incident side of the photoelectric conversion device for each pixel on the image pickup surface 36a. The arrangement of the micro color filter is, for example, a Bayer arrangement.

  The imaging element 36 photoelectrically converts the light received by the imaging surface 36a and accumulates signal charges corresponding to the amount of received light for each pixel. The signal charge is converted into a voltage signal and read from the image sensor 36. The voltage signal read from the image sensor 36 is input to the AFE 37 as an image signal.

  The image sensor 36 performs an accumulation operation for accumulating signal charges in the pixels and a read operation for reading the accumulated signal charges within an acquisition period of one frame. The light source device 13 generates illumination light according to the timing of the accumulation operation of the image sensor 36 and makes it incident on the light guide 35.

  The AFE 57 includes a correlated double sampling (CDS) circuit, an automatic gain control (AGC) circuit, an analog / digital (A / D) converter, and the like. The CDS circuit performs correlated double sampling processing on the image signal input from the image sensor 36 to remove noise. The AGC circuit amplifies the image signal from which noise has been removed by the CDS circuit. The A / D converter converts the image signal amplified by the AGC circuit into a digital signal having a predetermined number of bits and inputs the digital signal to the processor device 12.

  The imaging control unit 38 is connected to the controller 40 in the processor device 12 and inputs a drive signal to the imaging device 36 in synchronization with a reference clock signal input from the controller 40. The imaging element 36 inputs an image signal to the AFE 37 at a predetermined frame rate based on the drive signal from the imaging control unit 38. This image signal is a signal in which pixel values of R, G, and B pixels are mixed (hereinafter referred to as RGB signals).

  In addition to the controller 40, the processor device 12 includes a DSP (Digital Signal Processor) 41, an image processing unit 42, a frame memory 43, and a display control circuit 44. The controller 40 includes a CPU, a ROM that stores control programs and setting data necessary for control, a RAM that loads a program and functions as a working memory, and the CPU executes the control program. Control each part.

  The DSP 41 performs signal processing such as pixel interpolation processing, gamma correction, and white balance correction on an image signal (RGB signal) input from the AFE 57 in units of frames. In the pixel interpolation process, the image signal is separated into R, G, and B image signals, and the pixel interpolation process is performed on the image signals of the respective colors. The DSP 41 stores the image signal subjected to signal processing for each frame in the frame memory 43 as image data.

  Further, the DSP 41 has a luminance calculation unit that calculates the brightness (average luminance value) of the observation region based on the image signal input from the AFE 57, and inputs the calculated average luminance value to the controller 40. The controller 40 generates a dimming signal that is a difference between the average luminance value input from the luminance calculation unit and the reference brightness (target dimming value), and uses the dimming signal to control the light source of the light source device 13. Input to the unit 33.

  The light source control unit 33 adjusts the light amount setting value input to the drive unit 32 based on the dimming signal. Specifically, when the brightness of the observation site is insufficient (underexposure), the light intensity setting value is increased to increase the amount of illumination light, and when the observation site is too bright (overexposure), the light intensity Decrease the setting value.

  The image processing unit 42 performs predetermined image processing on the image data stored in the frame memory 43. Specifically, in the normal observation mode, a normal observation image is generated based on the image data. On the other hand, in the blood vessel enhancement observation mode, a blood vessel enhancement observation image is generated based on the image data. In order to enhance the surface blood vessels, for example, the region of the surface blood vessels in the image is extracted based on the B signal in the image data. Then, an edge enhancement process or the like is performed on the extracted surface blood vessel region. Then, the B signal that has been subjected to the contour enhancement process is combined with a full-color image generated based on the RGB signal. The same processing may be performed on the middle- and deep-layer blood vessels in addition to the surface blood vessels. In the case of emphasizing the intermediate deep blood vessel, the region of the intermediate deep blood vessel is extracted from the G signal containing a lot of information on the intermediate deep blood vessel, and the contour enhancement processing is performed on the extracted region of the intermediate deep blood vessel.

  The display control circuit 44 reads the image processed image data from the frame memory 43, converts it into a video signal such as a composite signal or a component signal, and outputs it to the monitor 14.

  In the blood vessel enhancement observation mode, a blood vessel enhancement observation image is generated using only the BG signal without using the R signal, the B signal is assigned to the B channel and the G channel of the monitor 14, and the G signal is assigned to the R channel of the monitor 14. Also good.

  In FIG. 6, the optical path integrating unit 31 includes first to fourth collimator lenses (CL) 50 a to 50 d, first to third dichroic mirrors (DM) 51 to 53, and a condenser lens 54. . The first to fourth CLs 50a to 50d are provided corresponding to the first to fourth LEDs 30a to 30d, respectively, and collimate each light emitted from the first to fourth LEDs 30a to 30d. 1st-3rd DM51-53 is an optical member which formed the dichroic filter which has a predetermined permeation | transmission characteristic in the transparent glass plate, permeate | transmits the light of a specific wavelength range, and reflects the light of a specific wavelength range. The condensing lens 54 condenses the light emitted from the optical path integrating unit 31 on the incident end 35 a of the light guide 35.

  The second LED 30 b is arranged at a position where the optical axis thereof coincides with the optical axis of the light guide 35. The first LED 30a is arranged so that its optical axis is orthogonal to the optical axis of the second LED 30b. The first DM 51 is disposed at a position where the optical axes of the first LED 30a and the second LED 30b are orthogonal to each other so as to form an angle of 45 ° with each optical axis. Similarly, the third LED 30c and the fourth LED 30d are arranged so that their optical axes are orthogonal to each other. The second DM 52 is arranged at an angle of 45 ° with each optical axis at a position where the optical axes of the third LED 30c and the fourth LED 30d are orthogonal to each other.

  The optical axis of the third LED 30c is orthogonal to the optical axis of the second LED 30b. The third DM 53 is arranged at an angle of 45 ° with each optical axis at a position where the optical axes of the third LED 30c and the second LED 30b are orthogonal to each other. The condenser lens 54 is disposed at a position where the optical axis thereof coincides with the optical axis of the second LED 30 b and faces the incident end 35 a of the light guide 35.

  As shown in FIG. 7, the first DM 51 has a spectral reflection characteristic that reflects light in the wavelength band equal to or greater than the first threshold λ1 (about 610 nm) and transmits light in the wavelength band less than the first threshold λ1. . Most of the red light LR emitted from the first LED 30a has a wavelength band equal to or greater than the first threshold λ1. Most of the green light LG emitted from the second LED 30b has a wavelength band less than the first threshold λ1. Accordingly, the first DM 51 reflects the red light LR and transmits the green light LG. As a result, the red light LR reflected by the first DM 51 and the green light LG transmitted through the first DM 51 are combined.

  As shown in FIG. 8, the second DM 52 has a spectral reflection characteristic that reflects light in a wavelength band less than the second threshold λ2 (about 430 nm) and transmits light in a wavelength band greater than or equal to the second threshold λ2. . Most of the blue light LB emitted from the third LED 30c has a wavelength band equal to or greater than the second threshold λ2. Most of the purple light LV emitted from the fourth LED 30d has a wavelength band less than the second threshold λ2. Accordingly, the second DM 52 reflects the violet light LV and transmits the blue light LB. Thereby, the purple light LV reflected by the second DM 52 and the blue light LB transmitted through the second DM 52 are combined.

  As shown in FIG. 9, the third DM 53 has a spectral reflection characteristic that reflects light in a wavelength band less than the third threshold λ3 (about 490 nm) and transmits light in a wavelength band greater than or equal to the second threshold λ2. . Most of the combination of the red light LR and the green light LG (hereinafter referred to as the first combination) by the first DM 51 is a wavelength band equal to or greater than the third threshold λ3. Most of the multiplex of the violet light LV and the blue light LB (hereinafter referred to as second multiplex) by the second DM 52 is a wavelength band less than the third threshold λ3. Accordingly, the third DM 53 reflects the second combined wave and transmits the first combined wave. As a result, the second combined wave reflected by the third DM 53 and the first combined wave transmitted through the third DM 53 are combined and enter the condenser lens 54.

  That is, in the blood vessel enhancement observation mode, the red light LR, the green light LG, the blue light LB, and the purple light LV emitted from the first to fourth LEDs 30a to 30d are all combined and enter the condenser lens 54. In the normal observation mode, since the fourth LED 30d is not lit, the red light LR, the green light LG, and the blue light LB, excluding the purple light LV, are combined and enter the condenser lens 54.

  Moreover, in the optical path integration part 31, the 1st-4th glass plates 55a-55d used for the automatic power control (APC: Auto Power Control) mentioned later corresponding to 1st-4th LED30a-30d are provided. ing. The first glass plate 55a is disposed between the first CL 50a and the first DM 51. The second glass plate 55b is disposed between the second CL 50b and the first DM 51. The third glass plate 55c is disposed between the third CL 50c and the second DM 52. The fourth glass plate 55d is disposed between the fourth CL 50d and the second DM 52.

  The first to fourth glass plates 55a to 55d have predetermined angles with respect to the optical axes of the first to fourth LEDs 30a to 30d, respectively, so that the reflectance by Fresnel reflection becomes a predetermined value (about 4% to 8%). They are arranged at an angle (for example, 35 °). The first to fourth glass plates 55a to 55d respectively reflect part of the red light LR, the green light LG, the blue light LB, and the violet light LV emitted from the first to fourth LEDs 30a to 30d by Fresnel reflection. To the fourth light receiving parts 56a to 56d.

  The 1st-4th light-receiving parts 56a-56d are sensors for measuring the emitted light quantity from 1st-4th LED30a-30d, and are comprised by the photodiode in which the color filter is not arrange | positioned. The first to fourth light receiving parts 56a to 56d receive light and output a current (light receiving current) corresponding to the amount of received light.

  A first wavelength limiting filter 57a is provided on the light incident side of the first light receiving unit 56a. The first wavelength limiting filter 57a has a long path for adjusting the wavelength band of the red light LR incident on the first light receiving unit 56a to the wavelength band of the component of the red light LR in the illumination light emitted from the optical path integrating unit 31. It is a filter. The spectral characteristics of the first wavelength limiting filter 57a are determined depending on the spectral characteristics of the first DM 51 and the third DM 53. Specifically, as shown in FIG. 10, the wavelength band is equal to or greater than the first threshold λ1 (about 610 nm). It has a spectral transmission characteristic that transmits only the light. By the first wavelength limiting filter 57a, the first light receiving unit 56a outputs a light receiving current that is accurately proportional to the light amount of the red light LR in the light amount emitted from the light source device 13.

  A second wavelength limiting filter 57b is provided on the light incident side of the second light receiving unit 56b. The second wavelength limiting filter 57b is a band for adjusting the wavelength band of the green light LG incident on the second light receiving unit 56b to the wavelength band of the component of the green light LG in the illumination light emitted from the optical path integrating unit 31. It is a path filter. The spectral characteristic of the second wavelength limiting filter 57b is determined depending on the spectral characteristics of the first DM 51 and the third DM 53, and specifically, as shown in FIG. 11, the first threshold value λ3 (about 490 nm) or more, It has a spectral transmission characteristic that transmits only light in a wavelength band less than the threshold λ1 (about 610 nm). By the second wavelength limiting filter 57b, the second light receiving unit 56b outputs a light receiving current that is accurately proportional to the amount of green light LG in the amount of light emitted from the light source device 13.

  A wavelength limiting filter is not provided on the light incident side of the third light receiving unit 56c and the fourth light receiving unit 56d. The third light receiving unit 56c measures the amount of blue light LB in the amount of light emitted from the light source device 13. The fourth light receiving unit 56d measures the amount of violet light LV in the amount of light emitted from the light source device 13. A wavelength limiting filter similar to the first and second wavelength limiting filters 57a and 57b may be provided on the light incident side of the third light receiving unit 56c and the fourth light receiving unit 56d.

  In FIG. 12, the drive unit 32 includes first to fourth LED drive units 60a to 60d, first to fourth correction units 61a to 61d, and first to fourth APC units 62a to 62d. The 1st-4th LED drive parts 60a-60d light the 1st-4th LED30a-30d by giving a drive current to 1st-4th LED30a-30d continuously, respectively.

  The 1st-4th correction | amendment parts 61a-61d each correct | amend 1st-4th light quantity setting value S1-S4 input from the light source control part 33, respectively, and input into 1st-4th APC part 62a-62d. The first to fourth light amount setting values S1 to S4 are values corresponding to the emitted light amounts emitted from the first to fourth LEDs 30a to 30d, respectively. As will be described in detail later, in the first to fourth correction units 61a to 61d, the relationship between the first to fourth light amount setting values S1 to S4 and the emitted light amount of the first to fourth LEDs 30a to 30d after APC is linear. The first to fourth light quantity set values S1 to S4 are corrected so as to be

  The first to fourth APC units 62a to 62d include the first to fourth light quantity setting values S1 ′ to S4 ′ and the first to fourth light receiving units 56a to 56d after correction by the first to fourth correction units 61a to 61d. The first to fourth APC signals A1 to A4 for adjusting the amount of emitted light are generated on the basis of the received light current from. The first to fourth LED drive units 60a to 60d generate drive currents for the first to fourth LEDs 30a to 30d based on the first to fourth light amount setting values S1 to S4 input from the light source control unit 33, respectively. The drive currents are adjusted based on the first to fourth APC signals A1 to A4.

  In FIG. 13, the first APC unit 62 a includes the first light receiving unit 56 a described above, a current / voltage (I / V) conversion unit 70, a reference voltage generation unit 71, and a comparator (differential amplifier) 72. ing. The first light receiving unit 56a outputs a light receiving current I corresponding to the amount of received red light LR. The I / V conversion unit 70 linearly converts the light reception current I into a voltage (light reception voltage) V. This received light voltage V is input to the inverting input terminal of the comparator 72.

  As illustrated in FIG. 14, the reference voltage generation unit 71 stores a lookup table (LUT) that represents the relationship “V = f (S1 ′)” between the corrected first light amount setting value S1 ′ and the received light voltage V. Based on this relationship, a voltage value corresponding to the first light amount setting value S1 ′ input from the first correction unit 61a is generated as the reference voltage Vs. The reference voltage Vs is input to the non-inverting input terminal of the comparator 72. V = f (S1 ') is a linear function.

  The comparator 72 compares the light reception voltage V input to the inverting input terminal with the reference voltage Vs input to the non-inverting input terminal, and generates the first APC signal A1. The first APC signal A1 is a 1-bit signal, and is at a high level when V> Vs and at a low level when V <Vs.

  The first LED drive unit 60a generates a drive current based on the first light quantity setting value S1, and adjusts the drive current based on the first APC signal A1. Specifically, when the first APC signal A1 is at a high level, the first LED driving unit 60a decreases the amount of drive current supplied to the first LED 30a to reduce the amount of light emitted from the first LED 30a, and when the first APC signal A1 is at a low level. Increases the amount of drive current supplied to the first LED 30a to increase the amount of light emitted from the first LED 30a.

  When a temperature change or the like occurs in the first LED 30a and the amount of emitted light varies, the light reception current I output from the first light receiving unit 56a varies, and the light reception voltage V deviates from the reference voltage Vs as the light reception current I varies. As described above, the comparator 72 generates the first APC signal A1 corresponding to the difference between the received light voltage V and the reference voltage Vs, and the first LED driving unit 60a adjusts the amount of light emitted from the first LED 30a based on the first APC signal A1. By doing so, the fluctuation | variation of the emitted light quantity is suppressed and it stabilizes.

  Since the second to fourth APC units 62b to 62d have the same configuration as the first APC unit 62a, description thereof is omitted.

  Next, details of the first correction unit 61a will be described. The first correction unit 61a converts the first light amount setting value S1 input from the light source control unit 33 into the first light amount setting value S1 'using the LUT illustrated in FIG. This LUT is created based on Formula (1) which is a nonlinear formula.

S1 ′ = g ⁻¹ (S1) (1)

The function g ⁻¹ (S1) in the formula (1) is an inverse function of the function g (S1) represented by the formula (2).

  g (S1) = S1 × (1 + Δ (S1)) (2)

  Here, Δ (S1) is an error rate obtained from the spectral intensity characteristic of the red light LR emitted from the first LED 30a and the spectral sensitivity characteristic of the first light receiving unit 56a, and is expressed by Expression (3). γ is a constant.

Δ (S1) = γ × (1-S1 / S1 _max ) (3)

  FIG. 16 shows the spectral intensity characteristics of the red light LR emitted from the first LED 30a. In this way, the peak position of the intensity spectrum of the red light LR varies with the change in the amount of emitted light. Specifically, the peak position of the intensity spectrum of the red light LR shifts to the lower wavelength side as the emitted light quantity decreases from the maximum light quantity. The relationship between the shift amount of the peak position and the amount of emitted light is almost linear.

  FIG. 17 shows the spectral sensitivity characteristics of the first light receiving unit 56a. The sensitivity of the first light receiving unit 56a changes substantially linearly with respect to the wavelength in the visible light wavelength band. Specifically, the sensitivity of the first light receiver 56a changes substantially linearly in the wavelength region where the peak position of the intensity spectrum of the red light LR changes, and the sensitivity decreases as the wavelength decreases.

  While the first light quantity setting value S1 is proportional to the emitted light quantity of the red light LR, the received light current I and the received light voltage V output from the first light receiving unit 56a are the emitted light quantity of the red light LR and the first received light quantity. Since it is proportional to the product of the sensitivity of the part 56a to the red light LR, the relationship between the first light quantity setting value S1 and the light reception voltage V is non-linear.

  Specifically, as shown in FIG. 18, the light reception voltage V1 when the first LED 30a is driven with the first light quantity setting value S1 is the original amount by the amount due to the wavelength dependence of the sensitivity of the first light receiving unit 56a. The light reception voltage (light reception voltage in the case where there is no wavelength dependency of sensitivity) is lower than V0.

  If the first light quantity setting value S1 is not corrected by the first correction unit 61a, the first APC unit 62a uses the light reception voltage V0 as the reference voltage Vs, and the light reception voltage V1 becomes the reference voltage Vs. An APC signal for adjusting the amount of light emitted from the first LED 30a is generated. As a result, the light emission amount W ′ (S1) of the red light LR after the adjustment based on the APC signal is performed by the first LED driving unit 60a, as shown in FIG. 19, is larger than the original light emission amount W (S1). It increases by h (S1).

The ratio (h (S1) / W (S1)) of the increased amount h (S1) to the original emitted light amount W (S1) is the above-described error rate Δ (S1). Since this error rate Δ (S1) is inversely proportional to the sensitivity change of the first light receiving portion 56a, as the first light quantity set value S1 decreases and the light reception voltage V decreases as shown in FIG. (For example, if the first light quantity setting value S1 is 1/20 times the maximum value S1 _max , the error rate Δ (S1) is about 1.8%). Then, the value of the error rate Δ (0) obtained by the extrapolation calculation is the above-described constant γ. Therefore, the amount of emitted light W ′ (S1) after APC is expressed by Expression (4).

  W ′ (S1) = W (S1) × (1 + Δ (S1)) (4)

  From this equation (4), in order to linearize the emitted light amount W ′ (S1) after APC and the first light amount setting value S1, the first light amount setting value S1 is corrected based on the equation (1). I know it ’s good.

  Specifically, when the first correction unit 61a performs the correction based on the formula (1), the corrected first light amount setting value S1 'is input to the first APC unit 62a. As a result, as shown in FIG. 18, the light reception voltage V1 when the first LED 30a is driven with the first light quantity setting value S1 is set to the reference voltage Vs, and fluctuations from the original emitted light quantity W (S1) are suppressed. That is, the amount of emitted light W ′ (S1) after APC becomes the original amount of emitted light W (S1), and the relationship with the first light amount set value S1 is linearized.

  Since the 2nd-4th correction | amendment parts 61b-61d are the structures similar to the 1st correction | amendment part 61a, description is abbreviate | omitted.

  Next, the operation of the endoscope system 10 will be described. When performing an endoscopic diagnosis, the endoscope 11 is connected to the processor device 12 and the light source device 13, the processor device 12 and the light source device 13 are turned on, and the endoscope system 10 is activated.

  The insertion part 16 of the endoscope 11 is inserted into the subject's digestive tract, and observation in the digestive tract is started. In the normal observation mode, the first to third LEDs 30a to 30c except the fourth LED 30d are turned on simultaneously. Red light LR, green light LG, and blue light LB are emitted from the first to third LEDs 30a to 30c, respectively, and enter the optical path integration unit 31. The optical path integrating unit 31 combines the red light LR, the green light LG, and the blue light LB to generate white light LW. The white light LW is emitted from the optical path integration unit 31 and supplied to the light guide 35 of the endoscope 11.

  In the endoscope 11, the white light LW is guided to the illumination window 22 through the light guide 35 and is irradiated from the illumination window 22 to the observation site. The reflected light of the white light LW reflected at the observation site enters the image sensor 36 from the observation window 23. The image sensor 36 photoelectrically converts the reflected light to generate an image signal. This image signal is subjected to processing such as CDS, AGC, A / D conversion and the like by the AFE 37 and is input to the DSP 41 of the processor device 12 as a digital signal.

  The DSP 41 performs signal processing such as pixel interpolation processing, gamma correction, and white balance correction on the digital imaging signal input from the endoscope 11 in units of frames to obtain image data, and this image data is stored in the frame memory. 43 is stored. The image processing unit 42 performs predetermined image processing on the image data stored in the frame memory 43 to generate a normal observation image. This normal observation image is displayed on the monitor 14 via the display control circuit 44. This normal observation image is updated according to the frame rate of the image sensor 36.

  Further, the DSP 41 calculates the brightness (average luminance value) of the observation region based on the image signal input from the endoscope 11 and inputs it to the controller 40. The controller 40 generates a dimming signal that is a difference between the input average luminance value and the target value, and inputs the dimming signal to the light source control unit 33 of the light source device 13.

  The light source control unit 33 adjusts the light amount setting value based on the dimming signal and inputs the light amount setting value to the drive unit 32. In the normal observation mode, the first to third light amount setting values S1 to S3 for setting the emitted light amounts of the first to third LEDs 30a to 30c are input from the light source control unit 33 to the drive unit 32. In the drive unit 32, the first to third correction units 61a to 61c correct the first to third light amount setting values S1 to S3 based on the LUT. For example, the first light amount setting value S1 is corrected by the LUT created based on the above equation (1). The same applies to the second and third light quantity setting values S2 and S3.

  The corrected first to third light quantity setting values S1 'to S3' corrected by the first to third correction units 61a to 61c are input to the first to third APC units 62a to 62c, respectively. In the first APC unit 62a, the reference voltage generation unit 71 generates the reference voltage Vs based on the corrected first light amount setting value S1 '. Further, the first light receiving unit 56a receives a part of the red light LR emitted from the first LED 30a, and outputs a light receiving current I. This received light current I is converted into a received light voltage V by the I / V converter 70. The received light voltage V and the reference voltage Vs are input to the comparator 72, and a first APC signal A1 representing the magnitude relationship between the received light voltage V and the reference voltage Vs is generated.

  The first LED drive unit 60a generates a drive current based on the first light intensity setting value S1, adjusts the drive current based on the first APC signal A1, supplies the adjusted drive current to the first LED 30a, and turns red An optical LR is generated.

  As shown in FIG. 16, the peak position of the intensity spectrum of the red light LR varies with a change in the amount of emitted light, and the sensitivity of the first light receiving unit 56a has a wavelength dependency as shown in FIG. As shown in FIG. 18, the light reception voltage V1 obtained when the first LED 30a is driven with the first light quantity setting value S1 is lower than the original light reception voltage V0. When the first light amount set value S1 is not corrected, the amount of light emitted from the first LED 30a is adjusted so that the light reception voltage V0 becomes the reference voltage Vs and the light reception voltage V1 becomes the reference voltage Vs. As described above, the emitted light amount W ′ (S1) increases more than the original emitted light amount W (S1). However, since the light reception voltage V1 becomes the reference voltage Vs by using the first light quantity setting value S1 ′ after correction by the first correction unit 61a, the emission light quantity W ′ (S1) after APC is the original emission light quantity W. (S1) and the relationship with the first light quantity setting value S1 is linearized.

  The second and third APC units 62b and 62c and the second and third LED driving units 60b and 60c perform the same operations as the first APC unit 62a and the first LED driving unit 60a. Therefore, the relationship between the emitted light amount of the first to third LEDs 30a to 30c after APC and the first to third light amount setting values S1 to S3 is linearized. Thereby, even if it changes 1st-3rd light quantity setting value S1-S3 by light control etc., the ratio of the emitted light quantity of red light LR in the white light LW which is illumination light, green light LG, and blue light LB Is kept constant, and a change in the color of the normal observation image is prevented.

  Next, when a lesion and a suspicious observation site are found in the normal observation mode, the normal observation mode is switched to the blood vessel enhancement observation mode. In this blood vessel enhancement observation mode, the first to fourth LEDs 30a to 30d are all turned on simultaneously. In this case, the light path integration unit 31 generates mixed light in which the violet light LV is mixed with the white light LW and is supplied to the light guide 35 of the endoscope 11.

  In the endoscope 11, the reflected light of the mixed light applied to the observation site is imaged in the same manner as in the normal observation mode, and an image signal is input to the processor device 12. In the processor device 12, the same operation as in the normal observation mode is performed except that the image processing unit 42 generates a blood vessel emphasized observation image and the display control circuit 44 displays the blood vessel emphasized observation image on the monitor 14.

  In the light source device 13, in addition to the first to third light amount setting values S <b> 1 to S <b> 3, a fourth light amount setting value S <b> 4 for setting the emitted light amount of the fourth LED 30 d is input to the driving unit 32 from the light source control unit 33. The In the drive unit 32, in the normal observation mode except that all of the first to fourth LED drive units 60a to 60d, the first to fourth correction units 61a to 61d, and the first to fourth APC units 62a to 62d operate. It is the same.

  In the above embodiment, the LUT used for correction by the first to fourth correction units 61a to 61d is created based on the function represented by the equation (1) or the like. The LUT may be created by actually measuring the relationship between the values S1 to S4 and the emitted light amounts of the first to fourth LEDs 30a to 30d. It is also possible to create an LUT by actually measuring the relationship between the first to fourth light quantity setting values S1 to S4 and the light reception current I and the light reception voltage V of the first to fourth APC units 62a to 62d.

  Moreover, in the said embodiment, although 1st-4th light quantity setting value S1-S4 is correct | amended, it replaces with this, and the light reception signal (light reception current or light reception voltage) of 1st-4th light-receiving part 56a-56d. By correcting the above, the relationship between the first to fourth light quantity setting values S1 to S4 and the emitted light quantity of the first to fourth LEDs 30a to 30d after APC may be linearized. In this case, for example, the light reception voltage V shown in FIG. 18 is corrected so as to be linear with respect to the light amount setting value.

  In the above embodiment, the correction units are provided in all of the first to fourth APC units 62a to 62d. However, the correction units may be provided only in some APC units (for example, only the first APC unit 62a). good.

  Moreover, in the said embodiment, in order to light-guide a part of emitted light from 1st-4th LED30a-30d to 1st-4th light-receiving part 56a-56d, respectively, 1st-4th glass plate 55a-55d is carried out. Although provided, other light guide members such as optical fibers may be used instead of these glass plates.

  Moreover, in the said embodiment, although the light-receiving part is provided with respect to all the 1st-4th LED30a-30d, a light-receiving part is provided with respect to some LED among 1st-4th LED30a-30d, and APC May be performed.

  Moreover, in the said embodiment, although 4th LED30d which emits purple light LV is provided as a blood-vessel information acquisition semiconductor light source for acquiring the vascular information of a biological tissue, it replaces with 4th LED30d or in addition to 4th LED30d. Other blood vessel information acquisition semiconductor light sources may be provided. For example, in order to acquire the oxygen saturation of blood hemoglobin as blood vessel information, a semiconductor light source that emits narrow-band blue light having a center wavelength of 473 ± 10 nm may be provided. Of course, when blood vessel information observation is not performed, the blood vessel information acquisition semiconductor light source may not be provided and only the blue, green, and red semiconductor light sources may be provided.

  Moreover, in the said embodiment, although LED is used as a light source, it may replace with LED and may use semiconductor light sources, such as LD (Laser Diode).

  In the above-described embodiment, in the blood vessel enhancement observation mode, the observation site is irradiated with the mixed light of the white light LW and the purple light LV. However, purple light and green light, or blue light and green light are applied to the observation site. The blood vessel enhancement observation image may be acquired by irradiation.

  Moreover, in the said embodiment, although the light of several colors is simultaneously irradiated to the observation site | part, you may irradiate these sequentially and may image the light of each color separately. In this case, it is preferable to use a monochrome image sensor as the image sensor 36.

  Moreover, in the said embodiment, although the light source device and the processor apparatus are made into the separate structure, you may comprise with a light source device and a processor apparatus and one apparatus. The present invention also relates to an endoscope system using a fiberscope that guides reflected light of an observation site of illumination light with an image guide, and an ultrasonic endoscope in which an image pickup element and an ultrasonic transducer are built in a tip portion. And an endoscope light source device used therefor.

  Note that “light source drive unit” and “light quantity control unit” in the claims correspond to “LED drive unit” and “APC unit” in the embodiments, respectively. Further, “drive signal”, “light reception signal”, and “reference signal” in the claims correspond to “drive current”, “light reception current or light reception voltage”, and “reference voltage” in the embodiments, respectively.

DESCRIPTION OF SYMBOLS 10 Endoscope system 11 Endoscope 13 Light source device 30 Light source part 30a-30d 1st-4th LED
31 optical path integration unit 32 drive unit 33 light source control unit 56a to 56d first to fourth light receiving unit 57a first wavelength limiting filter 57b second wavelength limiting filter 60a to 60d first to fourth LED driving unit 61a to 61d first to first 4 correction unit 62a to 62d 1st to 4th APC unit 70 current voltage conversion unit 71 reference voltage generation unit 72 comparator

Claims (11)

A light source that emits light;
A light source driving unit for supplying a driving signal to the light source and emitting the light;
A light source control unit that inputs a light amount setting value to the light source driving unit and generates the drive signal according to the light amount setting value;
A light amount for adjusting the drive signal by receiving a part of the light emitted from the light source by a light receiving unit and generating a light reception signal and comparing the light reception signal with a reference signal according to the light amount setting value A control unit;
A correction unit that corrects the light amount setting value or the light reception signal used in the light amount control unit so that the relationship between the light amount setting value and the light emission amount of the light is linearized;
An endoscope light source device comprising:   The endoscope light source device according to claim 1, wherein the correction unit corrects the light amount setting value based on a lookup table, and inputs the corrected light amount setting value to the light amount control unit. .   The endoscope light source according to claim 2, wherein the look-up table is determined based on a spectral intensity characteristic of light emitted from the light source and a spectral sensitivity characteristic of the light receiving unit. apparatus.   A plurality of the light sources, the light source drive unit and the light amount control unit are provided for each of the light sources, and the correction unit is provided corresponding to at least one of the light sources. The light source device for endoscopes according to any one of claims 1 to 3.   The light source device for an endoscope according to claim 4, further comprising an optical path integrating unit that integrates optical paths of light emitted from the plurality of light sources.   6. The endoscope light source device according to claim 5, wherein a wavelength band filter is provided on at least one of the plurality of light quantity control units on a light incident side of the light receiving unit.   The wavelength band filter performs wavelength limitation so that a wavelength band of light received by the light receiving unit matches a wavelength band of a corresponding light component emitted from the optical path integrating unit. The light source device for endoscopes described in 1.   The endoscope light source device according to claim 4, wherein the plurality of light sources include three semiconductor light sources that emit red, green, and blue light.   The endoscope light source device according to claim 8, wherein the semiconductor light source is an LED.   The endoscope light source device according to claim 1, wherein the light receiving unit is a photodiode. An endoscope having a light guide for guiding light;
An endoscope system comprising an endoscope light source device that supplies the light to the light guide,
The endoscope light source device is:
A light source that emits light;
A light source driving unit for supplying a driving signal to the light source and emitting the light;
A light source control unit that inputs a light amount setting value to the light source driving unit and generates the drive signal according to the light amount setting value;
A light amount for adjusting the drive signal by receiving a part of the light emitted from the light source by a light receiving unit and generating a light reception signal and comparing the light reception signal with a reference signal according to the light amount setting value A control unit;
A correction unit that corrects the light amount setting value or the light reception signal used in the light amount control unit so that the relationship between the light amount setting value and the light emission amount of the light is linearized;
An endoscope system comprising:

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