JP5411086B2 - Electronic endoscope system - Google Patents

Description

  The present invention relates to an electronic endoscope system that captures an image of a subject with an electronic endoscope having an image sensor at the tip of an insertion portion to be inserted into the subject.

  Conventionally, examinations using an electronic endoscope system have been widely used in the medical field. The electronic endoscope system includes an electronic endoscope having an insertion portion that is inserted into the body of a subject (patient), a processor device connected to the electronic endoscope, a light source device, and the like.

  The electronic endoscope has an illumination window that irradiates illumination light into the subject and an image sensor that images the inside of the subject at the distal end of the insertion portion (hereinafter referred to as the distal end portion). The processor device performs various processes on the imaging signal output from the imaging device, and generates an observation image for diagnosis. The observation image is displayed on a monitor connected to the processor device. The light source device has a white light source capable of adjusting the amount of light, and supplies illumination light to the electronic endoscope. Illumination light is guided to the tip through a light guide inserted into the electronic endoscope, and is irradiated from the illumination window into the subject through an illumination optical system including a lens and the like.

  When an electronic endoscope is used, the tip portion rises in temperature due to heat generation due to transmission loss of the light guide, heat generation of the image sensor, or the like. When the temperature of the tip increases, dark current noise of the image sensor increases, and white conspicuous pixels (so-called white scratches) become conspicuous, and the observed image deteriorates. Further, there is a problem that the lifetime of the image sensor is shortened when exposed to a high temperature state. Furthermore, when the temperature of the tip portion rises, there is a risk of causing burns in the subject.

  In order to solve the problem of the temperature rise of the tip part, in recent years, a temperature sensor that monitors the temperature of the tip part is provided, and an electronic device that controls the amount of illumination light so that the temperature of the tip part does not rise above a predetermined temperature. Endoscope systems are known (Patent Documents 1 and 2).

  Moreover, although an electronic endoscope provided with an LED that emits illumination light at the tip is also known, since the LED generates heat when emitting illumination light, the problem of heat generation at the tip is the same as described above. An electronic endoscope that limits the upper limit of the amount of illumination light according to the temperature of the tip measured by a temperature sensor is known (Patent Documents 3 and 4).

JP 63-071233 A JP 2007-117538 A JP 2007-252516 A JP 2008-035883 A

  As described above, in the electronic endoscope system, it is preferable to suppress an increase in the temperature of the tip by adjusting the amount of illumination light according to the temperature of the temperature of the tip. However, in Patent Documents 1-4, the most advanced surface of the tip (hereinafter referred to as the tip surface), the LED that emits illumination light, and the temperature measured by one temperature sensor provided in the image sensor are used as the temperature of the tip. However, since the temperature distribution corresponding to the arrangement of the heat factors of the light guide (or LED for illumination light) and the image sensor and the amount of generated heat is generated in the actual tip, for example, the temperature of the tip surface and the image sensor There is a problem that it is impossible to accurately measure each of them simultaneously.

For example, the temperature of the distal end surface may change abruptly when it comes into contact with the subject or when the imaging observation window is washed by spraying water from the water supply port. For this reason, when a temperature sensor is arranged on the front end surface and the temperature of the front end surface is measured as the temperature of the front end portion, even if the image pickup device is in a high temperature state, it reflects that the temperature of the front end surface has dropped rapidly. The amount of light is increased and the observed image is deteriorated.

  On the other hand, if a temperature sensor is placed on the image sensor and the temperature of the image sensor is measured as the temperature of the tip, illumination will continue until the temperature of the image sensor is sufficiently cooled without reflecting this even if the temperature of the tip surface decreases. The state in which the amount of light is excessively reduced continues, and the period during which a dark observation image is continuously captured may become unnecessarily long.

  Therefore, not only simply measure the temperature of the tip and adjust the amount of illumination light according to the temperature of the tip, but also measure the temperature at multiple locations such as the tip surface and image sensor, and the temperature at each of these locations. Accordingly, it is desired to adjust the amount of illumination light more finely and appropriately.

  However, if temperature sensors are provided at a plurality of locations in order to measure the temperature at a plurality of locations at the tip, the insertion portion (and the tip) may be installed depending on the installation space of each temperature sensor, wiring for reading signals from each temperature sensor, etc. However, there is a problem that the diameter of the tube increases and the load on the subject increases.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to accurately measure the temperatures of the imaging element and the front end surface with one temperature sensor.

An electronic endoscope system according to the present invention includes an electronic endoscope having an imaging element that images the inside of the subject at the distal end of an insertion portion that is inserted into the subject, and illumination from the distal end of the insertion portion into the subject. Illuminating means for irradiating light; a temperature sensor for outputting a signal corresponding to the temperature of the image sensor; a measuring means for measuring the temperature of the image sensor based on a signal output from the temperature sensor; Based on the thermal circuit model at the tip of the insertion section, the measured temperature of the imaging device and the known heat, the storage means for storing the heat generation amount of the imaging device, the thermal characteristic data around the imaging device, Based on the characteristic data, the tip surface temperature estimating means for estimating the temperature of the tip surface of the insertion portion, and based on at least the temperature of the tip surface, an upper limit value of the amount of illumination light is set, and the temperature of the image sensor Based on The illumination light is within a range that is lower than the lower upper limit of the upper limit value of the light amount of the illumination light and the upper limit value of the light amount of the illumination light set based on the temperature of the tip surface. And a light amount adjusting means for adjusting the amount of light .

It is preferable that the thermal characteristic data includes a thermal resistance and a thermal capacity at the distal end of the insertion portion. Further, the temperature sensor is, for example, the image sensor itself, and the measurement unit may measure the temperature of the image sensor based on a dark output value output from a pixel that does not receive light in the image sensor. Good. When the illumination unit includes a light source that generates the illumination light and a diaphragm unit that adjusts the light amount of the illumination light, the light amount adjustment unit controls the diaphragm unit to adjust the light amount of the illumination light. . When the diaphragm means includes a diaphragm opening of a predetermined size and a diaphragm blade that adjusts the opening amount of the diaphragm opening, the light amount adjusting means controls the diaphragm blade to adjust the light amount of the illumination light.

Another electronic endoscope system according to the present invention includes an electronic endoscope having an imaging element that images the inside of the subject at the tip of an insertion portion to be inserted into the subject, and the inside of the subject from the tip of the insertion portion. Illuminating means for irradiating illumination light, a temperature sensor for outputting a signal corresponding to the temperature of the image sensor, and a temperature T1 of the image sensor for each time interval Δt based on a signal output from the temperature sensor. Measuring means for measuring and measuring a change amount ΔT1 of the temperature T1 of the imaging device during the time interval Δt, a temperature Ta in the subject, a calorific value Q of the imaging device, the imaging device and the subject, Storage means for storing thermal characteristic data including a thermal resistance R1, a thermal resistance R2 between the imaging element and the distal end surface of the insertion part, and a thermal capacity C in the vicinity of the imaging element; Based on the following equation representing the thermal network model There are, and a tip surface temperature estimating means for calculating an estimated value of the temperature T2 of the front end surface and a temperature and known the thermal property data of the measured image pickup device.
Formula: (T1-Ta) / R1 + (T1-T2) / R2 + CΔT1 / Δt = Q

  It is preferable that the temperature sensor is the image pickup device itself, and the measurement unit measures the temperature of the image pickup device based on a dark output value output from a pixel that does not receive light in the image pickup device.

Moreover, it is preferable to provide a light amount adjusting means for adjusting the light amount of the illumination light based on at least the temperature of the tip surface. The illumination unit includes a light source that generates the illumination light and a diaphragm unit that adjusts a light amount of the illumination light, and the light amount adjustment unit controls the diaphragm unit to adjust the light amount of the illumination light. It is preferable.

  The diaphragm means includes a diaphragm opening of a predetermined size and a diaphragm blade that adjusts the aperture amount of the diaphragm opening, and the light amount adjusting means controls the diaphragm blade to adjust the light amount of the illumination light. preferable.

  According to the present invention, it is possible to accurately measure the temperatures of the imaging device and the tip surface with one temperature sensor.

It is an external view which shows the structure of an electronic endoscope system. It is a block diagram which shows the structure of an electronic endoscope system. It is a block diagram which shows the electrical constitution of a CMOS sensor. It is explanatory drawing which shows the structure of an aperture mechanism. It is a figure which shows the thermal network model of a front-end | tip part. It is a flowchart which shows the aspect which identifies thermal resistance R1, R2. It is a flowchart which shows the aspect which identifies the heat capacity C. It is a flowchart which shows the operation | movement aspect of an electronic endoscope system. It is explanatory drawing which shows the aspect which switches a light quantity upper limit according to CMOS temperature T1 and front end surface temperature T2. It is explanatory drawing which shows the aspect which switches a light quantity upper limit according to CMOS temperature T1 and front end surface temperature T2. It is a block diagram which shows the structure which provides a temperature sensor in a front end surface. It is a figure which shows the thermal network model in the case of providing a temperature sensor in a front end surface. It is a figure which shows the other example of a thermal network model.

  As shown in FIG. 1, the electronic endoscope system 11 includes an electronic endoscope 12, a processor device 13, and a light source device 14. The electronic endoscope 12 includes a flexible insertion portion 16 that is inserted into the body of the subject, an operation portion 17 that is connected to a proximal end portion of the insertion portion 16, a processor device 13, and a light source device 14. A connector 18 to be connected and a universal cord 19 connecting the operation unit 17 and the connector 18 are provided. A CMOS image sensor (refer to FIG. 2; hereinafter referred to as a CMOS sensor) 21 for in-subject imaging is provided at the distal end (hereinafter referred to as a distal end portion) 20 of the insertion portion 16.

  The operation unit 17 has an angle knob for bending the distal end 20 in the vertical and horizontal directions, an air / water feed button for ejecting air and water from the distal end of the insertion unit 16, and a still image recording image. Operation members such as a release button and a zoom button for instructing enlargement / reduction of the observation image displayed on the monitor 22 are provided. A forceps port through which a treatment tool such as an electric knife is inserted is provided on the distal end side of the operation unit 17. The forceps port communicates with a forceps outlet provided at the distal end portion 20 through a forceps channel in the insertion portion 16.

  The processor device 13 is electrically connected to the light source device 14 and comprehensively controls the operation of the electronic endoscope system 11. The processor device 13 supplies power to the electronic endoscope 12 via the universal cord 19 and a transmission cable inserted into the insertion portion 16 and controls the driving of the CMOS sensor 21. Further, the processor device 13 acquires an imaging signal output from the CMOS sensor 21 via a transmission cable, and performs various image processing to generate image data. The image data generated by the processor device 13 is displayed as an observation image on a monitor 22 connected to the processor device 13 by a cable.

  As shown in FIG. 2, the distal end portion 20 is provided with an observation window 23, an illumination window 24, a timing generator (hereinafter referred to as TG) 26, a CPU 27, a temperature sensor 30, and the like. A CMOS sensor 21 is arranged behind the observation window 23 so that an image in the subject is formed in the imaging region 51 (see FIG. 3) by an objective optical system 25 including a lens group and a prism. Illumination light is emitted from the illumination window 24 into the subject. Illumination light is supplied from the light source device 14 to the electronic endoscope 12, guided by the light guide 28 inserted through the universal cord 19 and the insertion portion 16, and illuminated by the illumination lens 29 disposed at the exit end. It is irradiated into the subject through

  The CMOS sensor 21 photoelectrically converts an image in the subject formed in the imaging region 51 by the objective optical system 25 and outputs it as an imaging signal. The CMOS sensor 21 has an imaging region 51 made up of a plurality of pixels in a predetermined arrangement on the front surface (imaging surface) on which an object image is formed by the objective optical system 25. The imaging region 51 is composed of a central light receiving portion and an optical black (OB) portion provided so as to surround the light receiving portion. The light receiving unit is an area in which apertured pixels used for imaging in a subject are arranged, and each pixel has a color filter composed of a plurality of color segments, for example, a primary color (RGB) or a complementary color (CMY or CMYG) in a Bayer array. ) A color filter is formed. The OB portion is a region composed of light-shielded pixels, and outputs data (pixel values) corresponding to dark current noise. The imaging signal output from the CMOS sensor 21 includes data output from the OB unit together with data output from the light receiving unit. An imaging signal output from the CMOS sensor 21 is input to the processor device 13 via the universal code 19 and the connector 18 and temporarily stored in a working memory of a DSP 32 (described later). Thereafter, various types of signal processing are performed on the imaging signal, and an observation image is generated.

  The temperature sensor 30 is a thermistor, for example, and is attached to the CMOS sensor 21. When the temperature of the CMOS sensor 21 increases, the resistance value of the temperature sensor 30 increases accordingly. When the temperature of the CMOS sensor 21 decreases, the resistance value of the temperature sensor decreases accordingly. A signal indicating the resistance value of the temperature sensor 30 is input to the DSP 32 as a temperature signal and converted into the temperature of the CMOS sensor 21. Although an example in which a thermistor is used as the temperature sensor 30 will be described here, another temperature sensor such as a thermocouple may be used.

  A clock signal is given to the CMOS sensor 21 to the TG 26. The CMOS sensor 21 performs an imaging operation according to the clock signal input from the TG 26 and outputs an imaging signal. The TG 26 may be provided in the CMOS sensor 21. After the electronic endoscope 12 and the processor device 13 are connected, the CPU 27 drives the TG 26 based on an operation start signal from the CPU 31 of the processor device 13.

  The processor device 13 includes a CPU 31, a digital signal processing circuit (hereinafter referred to as DSP) 32, a digital image processing circuit (hereinafter referred to as DIP) 33, a display control circuit 34, an operation unit 35, and the like.

  The CPU 31 is connected to each unit via a data bus, an address bus, and a control line (not shown), and comprehensively controls the operation of the entire processor device 13. The ROM 36 stores various programs (OS, application programs, etc.) and data (graphic data, characteristic data of the temperature sensor 30, thermal characteristic data (described later) of the tip 20 and the like) for controlling the operation of the processor device 13. Is done. The CPU 31 reads out necessary programs and data from the ROM 36, develops them in the RAM 37, which is a working memory, and sequentially processes the read programs. Further, the CPU 31 obtains information that changes for each examination such as examination date and time, character information such as information on the subject and the operator from a network such as an operation unit 35 or a LAN described later, and stores the information in the RAM 37.

  The DSP 32 performs various signal processing such as color separation, color interpolation, gain correction, white balance adjustment, and gamma correction on the image pickup signal input from the CMOS sensor 21 to generate image data. The image data generated by the DSP 32 is input to the working memory of the DIP 33. Further, the DSP 32 generates ALC control data necessary for ALC control (described later) such as an average luminance value obtained by averaging the luminance of each pixel of the generated image data, and inputs the generated data to the CPU 31.

  Furthermore, the DSP 32 measures the temperature of the CMOS sensor 21, and the tip surface temperature estimation unit estimates the temperature of the tip surface 42 (hereinafter referred to as the tip surface) 42 of the tip part 20 based on the temperature of the CMOS sensor 21. 43.

  The measurement unit 41 receives a temperature signal (thermistor resistance value) input from the temperature sensor 30. The measurement unit 41 measures the temperature T1 of the CMOS sensor 21 (hereinafter referred to as the CMOS temperature) by converting the temperature signal into a temperature based on the known characteristic data of the temperature sensor 30. The measurement of the CMOS temperature T1 by the measurement unit 41 is performed every predetermined time interval Δt, and the measurement unit 41 subtracts the previously measured CMOS temperature T1 from the measured CMOS temperature T1 to thereby determine the CMOS temperature T1 during the time interval Δt. A change amount ΔT1 is calculated. The CMOS temperature T1 measured by the measurement unit 41 is used for calculation of an estimated value of the tip surface temperature in the tip surface temperature estimation unit 43 and ALC control. Further, the CMOS temperature T1 and the change amount ΔT1 are used for calculating the estimated value of the tip surface temperature.

  The tip surface temperature estimation unit 43 calculates (estimates) the temperature T2 of the tip surface 42 (hereinafter referred to as tip surface temperature) T2 based on the temperature of the CMOS sensor 21 and the thermal characteristic data 44 input from the measurement unit 41. In the thermal characteristic data 44, the thermal capacity C in the vicinity of the CMOS sensor 21, the thermal resistance R1 from the CMOS sensor 21 to the endoscope atmosphere A (for example, the temperature Ta = 37 ° C. atmosphere, see FIG. 5), the CMOS sensor The thermal resistance R1 from 21 to the tip surface 42, the calorific value Q of the CMOS sensor 21 according to the driving state, and the like are included, and each value is measured in advance and stored in the ROM 36. The tip surface temperature T2 estimated by the tip surface temperature estimation unit 43 is used for ALC control.

  The DIP 33 performs various types of image processing such as electronic scaling, color enhancement processing, and edge enhancement processing on the image data generated by the DSP 32. Image data that has been subjected to various types of image processing by the DIP 33 is input to the display control circuit 34 as an observation image.

  The display control circuit 34 has a VRAM that stores an observation image input from the DIP 33. Further, the display control circuit 34 receives graphic data of the ROM 36 and the RAM 37 from the CPU 31. Examples of the graphic data include a display mask for displaying only an effective pixel region in which an object is photographed in an observation image, character information such as examination date and time, information on a subject and an operator, and GUI. The display control circuit 34 superimposes graphic data or the like on the observation image stored in the VRAM and converts the observation image into a video signal (component signal, composite signal, etc.) according to the display format of the monitor 22. Output to. Thereby, an observation image is displayed on the monitor 22.

  The operation unit 35 is a well-known input device such as an operation panel, a mouse, or a keyboard provided in the casing of the processor device 13, and includes a button and the like on the operation unit 17 of the electronic endoscope 12. The CPU 31 operates each unit of the electronic endoscope system 11 in accordance with an operation signal from the operation unit 35.

  In addition to the above, the processor device 13 includes a compression processing circuit that compresses the image data in a predetermined compression format (for example, JPEG format), and the compressed image as a removable medium in conjunction with the operation of the release button. A network I / F for controlling transmission of various data to and from a network such as a media I / F and a LAN to be recorded is provided. These are connected to the CPU 31 via a data bus or the like.

  The light source device 14 includes a light source 45, a diaphragm mechanism 46, a wavelength selection filter 47, and a CPU 48.

  The light source 45 generates light having a broad wavelength from red to blue (for example, light mainly in a wavelength band of 400 nm to 800 nm, hereinafter referred to as normal light). The light source 45 is composed of, for example, a xenon lamp, and emits normal light having a constant light amount. The amount of normal light generated by the light source 45 is adjusted by the diaphragm mechanism 46. Further, the normal light generated by the light source 45 may be irradiated into the subject by being limited to light having a specific narrow wavelength band (hereinafter referred to as special light) by the wavelength selection filter 47. Thus, the illumination light (normal light or special light) emitted from the light source 45 is condensed by the condenser lens 49 and guided to the incident end of the light guide 28.

  As will be described later, the diaphragm mechanism 46 includes a diaphragm opening 64 (see FIG. 4), a diaphragm blade 65 (see FIG. 4) that opens and closes the diaphragm opening 64, and adjusts the amount of illumination light. The diaphragm mechanism 46 is automatically controlled by the CPU 48 in accordance with the shooting mode, the CMOS temperature T1, the tip surface temperature T2, and the like.

  The wavelength selection filter 47 is a filter that limits normal light emitted from the light source 45 to special light. The wavelength selection filter 47 has, for example, a semicircular shape in which half of a disk is cut out, and is rotated by a motor so as to cross between the light source 45 and the condenser lens 49. Further, the wavelength selection filter 47 is provided with a sensor for detecting the rotational position. While the wavelength selection filter 47 crosses between the light source 45 and the condenser lens 49, special light is irradiated, and while the notch portion of the wavelength selection filter 47 crosses between the light source 45 and the condenser lens 49. Normal light is irradiated into the subject as illumination light. As the special light, for example, light having a wavelength in the vicinity of 450 nm, 500 nm, 550 nm, 600 nm, and 780 nm is raised.

  Imaging with special light in the vicinity of 450 nm is suitable for observing the fine structure of the surface to be observed, such as blood vessels and pit patterns on the surface layer. With illumination light in the vicinity of 500 nm, it is possible to observe a macro uneven structure such as a depression or a bulge in the observation site. Illumination light in the vicinity of 550 nm has a high absorption rate by hemoglobin, and is suitable for observation of fine blood vessels and redness, and illumination light in the vicinity of 600 nm is suitable for observation of thickening. For observation of deep blood vessels, a fluorescent substance such as indocyanine green (ICG) is injected intravenously and can be clearly observed by using illumination light in the vicinity of 780 nm.

  Here, the wavelength selection filter 47 is used. However, instead of the wavelength selection filter 47 or in addition to the wavelength selection filter 47, a plurality of LEDs, LDs, and the like that emit light having different wavelength bands are provided as 41. Normal light and special light may be switched by controlling lighting and extinguishing. Alternatively, normal light may be generated using a blue laser light source and a phosphor that emits green to red excitation light when irradiated with blue laser light, and special light may be generated using a wavelength selection filter.

  The CPU 48 communicates with the CPU 31 of the processor device 13 and controls the operation of the diaphragm mechanism 46 and the wavelength selection filter 47. The control of the diaphragm mechanism 46 by the CPU 48 is ALC (Auto Light Control) control that automatically adjusts the amount of illumination light in accordance with the shooting mode and the like. The ALC control performed by the CPU 48 is performed based on the ALC control data generated by the DSP 32. Further, when performing ALC control, the CPU 48 acquires the CMOS temperature T1 and the tip surface temperature T2 at a predetermined timing via the CPU 31 of the processor device 13. Then, the upper limit of the illumination light quantity is limited to a predetermined value in accordance with the CMOS temperature T1 and the tip surface temperature T2, and ALC control is performed within a range where the light quantity is less than or equal to this upper limit.

In the electronic endoscope system 11, threshold values T _A1 and T _A2 (T _A1 > T _A2 ) are preset for the CMOS temperature T1, and threshold values T _B1 and T _B2 (T _B1 > T are set for the tip surface temperature T2. _B2 ) is preset. Further, an upper limit value of illumination light quantity (hereinafter referred to as upper limit of light quantity) Lmin1 is predetermined with respect to the CMOS temperature T1, and the upper limit of light quantity is limited to Lmin1 depending on the magnitude relationship between the CMOS temperature T1 and the thresholds T _A1 and T _A2. Sometimes. Similarly, a light amount upper limit Lmin2 is predetermined with respect to the tip surface temperature T2, and the light amount upper limit may be limited to Lmin2 depending on the magnitude relationship between the tip surface temperature T2 and the thresholds T _B1 and T _B2 . The light quantity upper limits Lmin1 and Lmin2 can be set arbitrarily, but here the light quantity upper limit Lmin2 is smaller than the light quantity upper limit Lmin1 (Lmin1> Lmin2). Then, it is necessary to limit the upper limit of the light amount to Lmin1 based on the magnitude relationship between the CMOS temperature T1 and the threshold values T _A1 and T _A2 , and at the same time, based on the magnitude relationship between the tip surface temperature T2 and the threshold values T _B1 and T _B2. When it becomes necessary to limit the light amount upper limit to Lmin2, the electronic endoscope system 11 employs a smaller light amount upper limit Lmin2.

The high temperature threshold T _{A1 with} respect to the CMOS temperature T1 is 60 ° C., for example, and if the CMOS temperature T1 exceeds this, white scratches become conspicuous in the observed image, and the diagnosis is likely to be hindered. Further, the low temperature threshold T _{A2 with} respect to the CMOS temperature T1 is 50 ° C., for example, and is used as a reference for determining that the temperature of the CMOS sensor 21 has sufficiently decreased.

The high temperature threshold T _{B1 with} respect to the tip surface temperature T2 is 60 ° C., for example, and if the tip surface temperature T2 rises beyond this, there is a risk of causing the subject to feel uncomfortable or causing burns in the subject. Increase. Cold threshold T _B2 against the distal end surface temperature T2 is, for example, 37 ° C., is used as a reference for determining that the tip surface temperature T2 has fallen sufficiently.

As will be described later, the upper limit of the amount of illumination light is illumination that is ALC-controlled according to the magnitude relationship between the CMOS temperature T1 and the threshold values T _A1 and T _{A2 and} the magnitude relationship between the tip surface temperature T2 and the threshold values T _B1 and T _B2. It defines the upper limit of the amount of light. When no upper limit is set for the amount of illumination light in ALC control, the size of the aperture 64 is the maximum amount of illumination light Lmax.

For example, when the CMOS temperature T1 is lower than the threshold T _A1 and the tip surface temperature T2 is lower than the threshold T _B1 , the CPU 48 opens the upper limit of the amount of illumination light and performs ALC control within the range of the maximum light amount Lmax or less. Do. For example, when the CMOS temperature T1 exceeds a threshold value _{T A1,} or when the distal end surface temperature T2 exceeds the threshold value _{T B1,} CPU 48 limits the upper limit of the amount of illumination light to the light quantity upper limit Lmin1 or Lmin2, which following ALC control is performed within the range to suppress the heat generation at the tip 20. Further, CPU 48 is, when the upper limit of the amount of illumination light to the light quantity upper limit Lmin1 or Lmin2, CMOS temperature T1 is below the threshold value _{T A2,} and, when the tip surface temperature T2 is below the threshold value _{T B2,} the upper limit of the amount of illumination light To the maximum light quantity Lmax.

  For example, the light guide 28 is formed by bundling a plurality of quartz optical fibers with a wound tape or the like. The illumination light guided to the exit end of the light guide 28 is irradiated into the subject diffused by the illumination lens 29.

  As shown in FIG. 3, the CMOS sensor 21 includes a vertical scanning circuit 56, a correlated double sampling (CDS) circuit 57, a column selection transistor 58, a horizontal scanning circuit 59, and an output circuit 61.

  In the imaging region 51, the pixels 62 are arranged in a matrix. The pixel 62 includes a photodiode D1, an amplification transistor M1, a pixel selection transistor M2, and a reset transistor M3. The photodiode D1 generates and accumulates signal charges corresponding to the amount of incident light through photoelectric conversion. The signal charge accumulated in the photodiode D1 is amplified as an imaging signal by the amplifying transistor M1, and is output to the outside of the pixel 62 at a predetermined timing by the pixel selecting transistor M2. The signal charge accumulated in the photodiode D1 is discharged to the drain through the reset transistor M3 at a predetermined timing. The pixel selecting transistor M2 and the resetting transistor M3 are N-channel transistors, which are turned on when a high level “1” is applied to the gate and turned off when a low level “0” is applied.

  In the imaging region 51, a row selection line L1 and a row reset line L2 are wired from the vertical scanning circuit 56 in the horizontal direction (X direction), and the column signal line L3 from the CDS circuit 57 in the vertical direction (Y direction). Is wired. The row selection line L1 is connected to the gate of the pixel selection transistor M2, and the row reset line L2 is connected to the gate of the reset transistor M3. The column signal line L3 is connected to the source of the pixel selection transistor M2, and is connected to the column selection transistor 58 of the corresponding column via the CDS circuit 57.

  The CDS circuit 57 holds the imaging signal of the pixel 62 connected to the row selection line L1 selected by the vertical scanning circuit 56 based on the clock signal input from the TG 26, and performs noise removal. The horizontal scanning circuit 59 generates a horizontal scanning signal based on the clock signal input from the TG 26, and performs on / off control of the column selection transistor 58.

  The column selection transistor 58 is provided between the output bus line 63 connected to the output circuit 61 and the CDS circuit 57, and selects a pixel for transferring an imaging signal to the output bus line 63 according to a horizontal scanning signal. To do.

  The output circuit 61 amplifies the imaging signal sequentially transferred from the CDS circuit 57 to the output bus line 63, performs A / D conversion, and outputs the amplified signal. The gain of the image pickup signal by the output circuit 61 is adjusted by inputting a gain adjustment signal from the CPU 27 to the output circuit 61. Thereafter, the output circuit 61 performs A / D conversion on the imaging signal and outputs the converted signal to the DSP 32.

  As shown in FIG. 4, the aperture mechanism 46 includes an aperture blade 65 that opens and closes the aperture opening 64 and a spring 66 that biases the aperture blade 65 to a position where the aperture opening 87 is closed. The diaphragm blade 65 rotates in a direction (clockwise) in which the opening amount of the diaphragm opening 64 increases against the urging force of the spring 66 by the torque applied from the motor 67, and the magnitude of the torque and the urging force of the spring 66 are balanced. Stop at position. When the torque is large, the force against the urging force of the spring 66 is also large, so that the opening amount of the aperture opening 64 is also large. If the torque is small, the force against the urging force of the spring 66 is small, so the opening amount of the aperture opening 64 is small. The torque of the motor 67 increases as the PWM value (described later) increases, and decreases as the PWM value decreases.

  The CPU 48 of the light source device 14 controls the aperture adjustment mechanism 68 including the aperture blade 65 and the spring 66 based on the ALC control data calculated by the DSP 32. The CPU 48 calculates a PWM (pulse width modulation) value that determines the torque of the motor 67 in accordance with the ALC control data, and generates a drive pulse corresponding to the PWM value by a motor driver (not shown). To drive. The PWM value determines the duty ratio of the drive pulse of the motor 67 (a value obtained by dividing the pulse width by the pulse period), and determines the torque of the motor 67. When the ALC control data is a signal requesting an increase, the CPU 48 increases the PWM value according to the increase, and when the ALC control data is a signal requesting a decrease, the CPU 48 decreases the PWM value according to the decrease. Thus, the CPU 48 performs ALC control.

  As shown in FIG. 5, the state in which heat is transferred in the distal end portion 20 is that the CMOS sensor 21 is connected to the endoscope atmosphere A (inside the subject; hereinafter, the temperature Ta is constant) through the thermal resistance R1 and the heat capacity C in parallel. It can be modeled as being thermally connected to the distal end surface 42 via the thermal resistance R 2. The tip surface temperature estimation unit 43 calculates an estimated value of the tip surface temperature T2 from the CMOS temperature T1 and the thermal characteristic data 44 according to the thermal circuit network model 71.

  The thermal network model 71 is expressed by the following equation (1). In Equation 1, the CMOS temperature T1 is a variable input to the tip surface temperature estimation unit 43 when the tip surface temperature T2 is estimated, and the heat resistance R1 and R2, the heat capacity C, and the heat generation amount Q of the CMOS sensor 21 are known amounts. As obtained from the thermal characteristic data 44. Since the thermal resistances R1 and R2 and the heat capacity C are determined by the arrangement and materials of the objects (the CMOS sensor 21 and the light guide 29) in the distal end portion 20, they are measured (or calculated) before using the electronic endoscope system 11. Is done. The calorific value Q of the CMOS sensor 21 is an amount of heat generated from the CMOS sensor 21 itself by driving the CMOS sensor 21, and is measured in advance for each specific driving state such as a driving voltage and a frame rate. In the thermal circuit network model 71, the heat generation amount Q 'from the illumination system such as the light guide 28 and the illumination lens 29 is directly reflected in the estimated tip surface temperature T2.

Number 1:
(T1-Ta) / R1 + (T1-T2) / R2 + CdT1 / dt = Q

  Equation 1 formulates the thermal circuit network model 71 based on Kirchhoff's law, based on the fact that the amount of heat released from the CMOS sensor 21 that can directly measure the temperature (left side) is equal to the calorific value Q. . The heat outflow from the CMOS sensor 21 is stored in the path around the CMOS sensor 21 through the path through the front end face 42 for estimating the temperature and the path not passing through the front end face 42 (heat outflow from the side surface of the front end portion 20). There is a route. The first term is a term representing the amount of heat q1 flowing out from the CMOS sensor 21 to the endoscope atmosphere A without passing through the tip surface 42, and is proportional to the difference between the CMOS temperature T1 and the endoscope atmosphere temperature Ta. 21 is inversely proportional to the thermal resistance R1 between the endoscope atmosphere A. The second term is a term representing the amount of heat q2 flowing out from the CMOS sensor 21 to the front end surface 42, which is proportional to the difference between the CMOS temperature T1 and the front end surface temperature T2, and to the thermal resistance R2 between the CMOS sensor 21 and the front end surface 42. Inversely proportional. The third term is a term representing the amount of heat q3 stored transiently around the CMOS sensor 21 and is the product of the time derivative of the CMOS temperature T1 and the heat capacity C, assuming that the endoscope ambient temperature Ta does not change with time. expressed.

  Equation 1 is used as a change amount ΔT1 of the CMOS temperature T1 between the predetermined time intervals Δt and Δt, the differential term (dT1 / dt) is approximated by a difference, and the estimated tip surface temperature T2 is set as the input CMOS temperature T1 and If it arranges so that it may represent with known quantity R1, R2, C, Q, it can write as T2 = T1 + R2 * (T1-Ta) / R1 + C * R2 * (DELTA) T1 / (DELTA) t-R2 * Q. Therefore, by measuring the CMOS temperature T1 every predetermined time interval Δt, an estimated value of the tip surface temperature T2 is calculated from the change amount ΔT1 of the CMOS temperature between the CMOS temperature T1 and the time interval Δt.

  The thermal resistances R1 and R2 are identified in advance as shown in FIG. First, the electronic endoscope 12 is placed in a first predetermined temperature ta (for example, 37 ° C. assuming the inside of the subject) such as a thermostatic bath, and waits for at least the entire distal end portion 20 to be in a thermal equilibrium state. (Step S11). At this time, the CMOS sensor 21 and the light source 45 are turned off.

  When the tip 20 is in a thermal equilibrium state at the first predetermined temperature ta, a heat source at the second predetermined temperature t2 is brought into contact with the tip surface 42 (step S12). The heat source is, for example, a block-like high heat conduction member made of aluminum or the like, and has a volume with a heat capacity sufficiently larger than that of the tip portion 20, and substantially ignores the temperature change of the heat source itself due to contact with the tip surface 42. Use what you can. Further, the temperature t2 of the heat source is preferably set to a temperature (for example, about +5 to 10 ° C.) that has an appropriate difference with respect to the first predetermined temperature ta (37 ° C.) in which the tip portion 20 is first brought into a thermal equilibrium state. . The heat source is preferably one that can freely adjust the temperature t2.

  Thereafter, when the tip 20 is in a thermal equilibrium state with the heat source having the second predetermined temperature in contact with the tip surface 42 in the first predetermined temperature ta atmosphere, the CMOS temperature T1 is measured (step S13). At this time, the measured CMOS temperature T1 is set to t1. Further, since the CMOS sensor 21 is not supplied with power, the calorific value Q = 0, and is in thermal equilibrium, dT1 / dt (≈ΔT1 / Δt) = 0. Further, the first predetermined temperature Ta is equal to the first predetermined temperature ta, and the tip surface temperature T2 is the second predetermined temperature t2 and is known. From these, the thermal resistance ratio R2 / R1 = (t2−t1) / (t1−ta) is calculated from the equation (1) (step S14).

  Next, the CMOS sensor 21 is driven under a predetermined condition (step S21), waits for a thermal equilibrium state again, and the CMOS temperature T1 is measured (step S22). The measured CMOS temperature T1 is assumed to be t1 '. In addition, since the differential term is 0 and the tip temperature T2 = t2 because it is in a thermal equilibrium state, the CMOS sensor 21 is driven under a predetermined condition, so that the CMOS sensor 21 generates heat with a heat generation amount Q ≠ 0. Therefore, R1, R2, t1 ', t2, ta, and Q satisfy the relationship of (t1'-t2) / R2 + (t1'-ta) / R1) = Q according to the equation (1). Thermal resistances R1 and R2 are calculated from this equation and the value of the thermal resistance ratio R2 / R1 calculated in step S14 (step S23).

  The heat capacity C is identified as shown in FIG. 7 on the assumption that the thermal resistances R1 and R2 are calculated as described above and are known amounts. First, the electronic endoscope 12 is arranged in a first predetermined temperature ta atmosphere such as a thermostatic bath, and waits for at least the entire tip portion 20 to be in a thermal equilibrium state (step S31). At this time, the CMOS sensor 21 and the light source 45 are turned off. And if the front-end | tip part 20 will be in a thermal equilibrium state with 1st predetermined temperature ta, the heat source of 2nd predetermined temperature t2 will be made to contact the front end surface 42 (step S32). Thereafter, the CMOS temperature T1 is measured while changing the temperature t2 of the heat source stepwise (or changing the heat source stepwise) (step S33).

  From the equation (1), the temperature change of the CMOS temperature T1 (T1-Ta temperature change) indicates a first-order lag response, and the time constant τ is τ = C · R1 · R2 / (R1 + R2). Therefore, the time constant τ is calculated from the change state of the CMOS temperature T1 measured while changing the temperature t2 (= tip surface temperature T2) of the heat source stepwise in step S33 (step S34). Then, the heat capacity C = τ · (1 / R1 + 1 / R2) is calculated using the calculated time constant τ of the first-order lag response (step S35).

  The operation of the electronic endoscope system 11 configured as described above will be described. When observing the inside of the subject with the electronic endoscope 12, the operator connects the electronic endoscope 12, the processor device 13, and the light source device 14, and turns on the power of the processor device 13 and the light source device 14. Then, the operation unit 35 is operated to input information about the subject, and the insertion unit 16 is inserted into the subject to start the examination. When the examination is started, the electronic endoscope system 11 images the inside of the subject with the CMOS sensor 21 while irradiating illumination light (for example, normal light) from the illumination window 24 of the distal end portion 20. An observation image generated based on the output imaging signal is displayed on the monitor 22.

  As shown in FIG. 8, when the electronic endoscope 12 is used to illuminate the subject with a predetermined amount of illumination light (step S51), the temperature sensor 30 changes the temperature of the CMOS sensor 21 at every predetermined time interval Δt. In response, the temperature signal is output, and the measurement unit 41 converts the temperature signal into a temperature based on the characteristic data of the temperature sensor 30 to obtain the CMOS temperature T1 and the change amount ΔT1 of the CMOS temperature T1 during the predetermined time interval Δt. Measurement is performed (step S52).

  The tip surface temperature estimation unit 43 acquires the measured variation ΔT1 of the CMOS temperature T1, CMOS temperature T1, and thermal characteristic data 44, and calculates the estimated value of the tip surface temperature T2 based on the above-described equation (1). (Step S53).

Thereafter, the CPU 48 of the light source device 14 acquires the CMOS temperature T1 and the tip surface temperature T2 via the CPU 31 of the processor device 13, and the magnitude relationship between these values and the threshold values T _A1 , T _A2 , T _B1 , T _B2. Based on this, an upper limit of the amount of illumination light in ALC control is determined (step S54). The upper limit of the illumination light amount in the ALC control is set to either the maximum light amount Lmax determined by the size of the aperture of the diaphragm opening 64 or the predetermined light amount upper limits Lmin1 and Lmin2.

  Then, the CPU 48 acquires ALC control data calculated by the DSP 32 at the time of shooting, and controls the aperture mechanism 46 based on the ALC control data so that the amount of illumination light falls within the set upper limit of the light amount. Thus, ALC control is performed (step S55). The above-described operation is repeated until the inspection (observation) is completed (step S56).

As shown in FIG. 9, the relationship of the upper limit of the amount of illumination light determined by the CMOS temperature T1 differs between when the CMOS temperature T1 rises and when it falls. When the CMOS temperature T1 rises immediately after the start of the inspection or the like, the CPU 48 sets the upper limit of the light amount to the maximum light amount Lmax, and maintains this upper limit of the light amount until the CMOS temperature T1 reaches T _A1 (high temperature threshold). When the CMOS temperature T1 exceeds _{T A1,} to limit the amount upper limit to the quantity limit Lmin1. On the other hand, when the CMOS temperature T1 decreases after the light intensity upper limit L1 is once limited to the light intensity upper limit Lmin1, the light intensity upper limit L1 becomes the light intensity upper limit Lmin1 until the CMOS temperature T1 sufficiently decreases to T _A2 (low temperature threshold). Limited. When the CMOS temperature T1 is below the _{T A2,} the light quantity upper limit is opened to the maximum amount Lmax.

As shown in FIG. 10, the relationship of the upper limit of the amount of illumination light determined by the tip surface temperature T2 differs between when the tip surface temperature T2 rises and when it falls. When the tip surface temperature T2 rises immediately after the start of the inspection or the like, the CPU 48 sets the light amount upper limit L2 to the maximum light amount Lmax, and maintains this light amount upper limit until the tip surface temperature T2 reaches T _B1 (high temperature threshold). The tip surface temperature T2 is more than _{T B1,} to limit the amount upper limit to the quantity limit Lmin2. On the other hand, when the tip surface temperature T2 decreases after the light amount upper limit L2 is once limited to the light amount upper limit Lmin2, the light amount upper limit L2 is the light amount upper limit until the tip surface temperature T2 is sufficiently lowered to T _B2 (low temperature threshold). Limited to Lmin2. When the distal end surface temperature T2 is below the _{T B2,} the light quantity upper limit is opened to the maximum amount Lmax.

  As the upper limit of the amount of illumination light in ALC control, the lower one of the upper limit of the amount of light determined by the CMOS temperature T1 and the upper limit of the amount of light determined by the tip surface temperature T2 is adopted.

  Furthermore, since the electronic endoscope system 11 adjusts the amount of illumination light by ALC control based on both the CMOS temperature T1 and the tip surface temperature T2, the temperature of the tip portion 20 represents the CMOS temperature T1 or the tip surface temperature T2. The amount of illumination light can be adjusted more favorably compared to the case where it is used.

For example, when water is ejected from the front end surface 42 to clean the observation window 23 and the illumination window 24, the front end surface temperature T2 immediately decreases, but depending on the amount of water ejected, the CMOS temperature T1 does not decrease or the CMOS temperature Even if T1 decreases, a time lag may occur from the decrease timing of the tip surface temperature T2. In this case, if the ALC control using the tip surface temperature T2 as a representative temperature of the tip portion 20 is performed, the amount of illumination light is increased in conjunction with a decrease in the tip surface temperature T2, so the CMOS temperature T1. However, it tends to exceed the temperature (threshold value T _A1 ) at which white scratches are noticeable. However, the electronic endoscope system 11 accurately obtains the CMOS temperature T1 and the tip surface temperature T2 at the same time and sets the upper limit of the amount of illumination light with reference to both of them, so that only the tip surface temperature T2 is set as described above. Even when the temperature drops, appropriate ALC control can be performed so that the CMOS temperature T1 does not rise too much.

Further, when the ALC control is performed using the CMOS temperature T1 as the temperature of the tip portion 20, if the CMOS temperature T1 is low enough to make white scratches inconspicuous (for example, a temperature equal to or lower than the threshold T _A1 ), There is a risk that the tip surface temperature T2 rises to a high temperature causing burns or the like in the subject. However, the electronic endoscope system 11 accurately acquires the CMOS temperature T1 and the tip surface temperature T2 at the same time and sets the upper limit of the amount of illumination light with reference to both of them, so that the CMOS temperature T1 is used to acquire the observation image. The amount of illumination light can be automatically adjusted so that it is within an appropriate range and the tip surface temperature T2 is within a range that does not cause burns or the like in the subject.

  In the above-described embodiment, the example in which the temperature sensor 30 is provided in the CMOS sensor 21 has been described. However, the temperature sensor 30 may be provided on the distal end surface 42 of the electronic endoscope system 72 as illustrated in FIG. The thermal network model 73 in the case where the temperature sensor 30 is provided on the distal end surface 42 in this way includes a thermal resistance R3 between the distal end surface 42 and the endoscope atmosphere A, a heat capacity C ′ near the distal end surface 42, and a heat generation amount Q on the distal end surface 42 It can be expressed as shown in FIG. Therefore, the amount of heat generated Q ′ at the distal end surface 42, the amount of heat q2 flowing out from the distal end surface 42 to the CMOS sensor 21 via the thermal resistance R2, and the amount of heat flowing out from the distal end surface 42 into the endoscope atmosphere A via the thermal resistance R3. If it is formulated that the sum of the amount of heat q5 flowing out to the endoscope atmosphere A via q4 and the heat capacity C ′ is balanced, the thermal circuit network model 73 can be expressed almost the same as the equation (1). Therefore, the heat resistance R2 and R3, the heat capacity C ′, and the heat generation amount Q ′ on the tip surface 42 corresponding to the amount of illumination light are obtained in advance as the thermal characteristic data 44, so that the time of the tip surface temperature T2 and the tip surface temperature T2 is obtained. An estimated value of the CMOS temperature T1 can be calculated based on the change ΔT2. However, the distal end surface 42 may be cooled by spraying water for cleaning the observation window 23 and the illumination window 24 even during use of the electronic endoscope 12. The amount of heat taken away from the surface 42 is different. For this reason, even if the temperature sensor 30 is provided on the tip surface 42, it is difficult to always accurately measure the tip surface temperature T2 that reflects only the amount of heat generation Q ′ at the tip surface 42 that directly affects the CMOS temperature T1. Therefore, as in the above-described embodiment, it is preferable to provide the temperature sensor 30 in the CMOS sensor 21, measure the CMOS temperature T1 and the time change ΔT1, and calculate the estimated value of the tip surface temperature T2 based on these.

  In the above-described embodiment, the example in which the CMOS temperature T1 and the tip surface temperature T2 are measured (calculated) has been described, but the present invention is not limited thereto. For example, an estimated value of the emission end temperature of the light guide 28 may be calculated by measuring the CMOS temperature T1. Alternatively, the CMOS temperature T1 may be measured to calculate an estimated value of the temperature on the side surface of the tip portion 20. Even in such a case, the thermal circuit network in each case can be modeled and formulated almost in the same manner as the thermal network model 71 of the above-described embodiment.

  In the above-described embodiment, the example of measuring (calculating) two temperatures of the CMOS temperature T1 and the tip surface temperature T2 has been described. However, even if three or more temperatures of the tip 20 are measured (calculated). good. In such a case, a more complicated thermal network model than that in the above-described embodiment is required, but it can be modeled and formulated in substantially the same manner as the thermal network model 71 described in the above-described embodiment. .

  In the above-described embodiment, the example in which the configuration of the distal end portion 20 is modeled by the thermal network model 71 (see FIG. 5) has been described. However, the thermal network model is not limited to this example. For example, as shown in FIG. 13, the thermal resistance R1 between the CMOS sensor 21 and the endoscope atmosphere A, the thermal capacity C in the vicinity of the CMOS sensor 21, the thermal resistance R2 between the CMOS sensor 21 and the tip surface 42, and the inside of the tip surface 42- A thermal circuit network model 74 using the thermal resistance R3 between the endoscope atmosphere A, the heat capacity C ′ near the tip surface 42, the heat generation amount Q of the CMOS sensor 21, and the heat generation amount Q ′ at the tip surface 42 may be used. Even when this thermal circuit network model 74 is used, the calorific value Q and the calorific values q1, q2, and q3 flowing out from the CMOS sensor 21 are balanced, and the calorific value Q ′ and the tip are the same as in equation (1). Formulation is made so that the amounts of heat q2, q4, and q5 flowing out from the surface 42 are balanced, and an estimated value of the tip surface temperature T2 can be calculated from the CMOS temperature T1 and the time variation ΔT1. However, the thermal circuit network model 71 described in the above-described embodiment requires less thermal characteristic data 44 and has a higher accuracy of the estimated tip surface temperature T2.

  In the above-described embodiment, the configuration of the distal end portion 20 is modeled by the thermal network model 71 (see FIG. 5), and the example in which the thermal resistance and the heat capacity at the distal end of the endoscope insertion portion are used as thermal characteristic data has been described. However, a simpler thermal network model may be used. For example, a thermal network model that ignores the heat capacity in FIG. 5 may be used. In this case, R1 and R2 are identified in advance as the thermal characteristic data, and C may be calculated by estimating the tip end surface temperature based on Equation 1 using zero. In this case, the tip surface temperature T2 can be estimated by simpler and faster calculation.

  In the above-described embodiment, ALC control is performed by providing two threshold values for the CMOS temperature T1 and the tip surface temperature T2, respectively, and the illumination light amount is limited to either the open (maximum light amount Lmax) or the light amount upper limit L. However, the present invention is not limited to this. For example, you may make it perform ALC control which provided the threshold value 3 or more with respect to CMOS temperature T1 and front end surface temperature T2. In addition, the upper limit of the light amount is not a two-stage limit of the opening and the upper limit of the light amount, but an upper limit of two or more light amounts is set, and the upper limit of three or more light amounts including the opening is used. You may make it switch the upper limit of the illumination light quantity in order. By setting a plurality of light amount upper limits in this way, the illumination light amount can be adjusted more smoothly, hunting can be prevented, and the visibility of the observation image can be improved.

  In the above-described embodiment, an example of a method for identifying the thermal characteristic data 44 (thermal resistance R1, R2, thermal capacity C in the thermal network model 71) has been described. Characteristic data 44 can be identified. For example, in the above-described embodiment, a heat source is brought into contact with the tip surface 42 as necessary. However, a temperature sensor is installed on the tip surface 42 from the outside only when the thermal characteristic data 44 is identified, and thereby the tip surface temperature T2 is directly measured. It may be possible to measure. In the above-described embodiment, the CMOS sensor 21 is turned off when the thermal resistances R1 and R2 are identified. Even if the CMOS sensor 21 is driven, the thermal resistances R1 and R2 are repeatedly measured under different driving conditions. R2 can be identified. The same applies to the illumination light.

  In the above-described embodiment, the example in which the thermal characteristic data 44 is identified in advance for the electronic endoscope 12 has been described. However, the thermal characteristic data 44 is used for the same type of electronic endoscope 12 having the same parts and materials. Therefore, it is not always necessary to individually identify the thermal characteristic data 44 for each electronic endoscope 12, and the thermal characteristic data 44 may be identified for each model.

  In the above-described embodiment, the example in which the thermal characteristic data 44 is stored in advance and the estimated value of the tip surface temperature T2 is calculated based on the thermal characteristic data 44 has been described. However, the present invention is not limited thereto. For example, instead of the thermal characteristic data 44, data of the tip surface temperature T2 corresponding to the CMOS temperature T1 may be stored in advance in a table format or the like, and the measured CMOS temperature T1 may be directly converted into the tip surface temperature T2. . Further, if the data of the tip surface temperature T2 corresponding to the CMOS temperature T1 is held in advance in this way, the tip surface temperature T2 corresponding to the measured CMOS temperature T1 may not be included in the data held in advance. In such a case, it is preferable to calculate the tip surface temperature T2 corresponding to the measured CMOS temperature T1 by storing the data in the table.

  In the above-described embodiment, an example in which the CMOS image sensor 21 is used as the image sensor (image sensor) has been described. However, other well-known image sensors such as a CCD image sensor can be used.

  In the above-described embodiment, the example in which the temperature sensor 30 is installed in the CMOS sensor 21 has been described. However, the present invention is not limited to this. The CMOS sensor 21 has a pixel group (so-called optical black) that is shielded from light in order to perform dark current correction. The data output from the optical black reflects the dark current, and the dark current becomes more prominent as the temperature of the CMOS sensor 21 increases. Therefore, if the data output from the optical black from the CMOS sensor 21 is acquired and converted into the temperature of the CMOS sensor 21, the CMOS sensor 21 itself can be used as a temperature sensor. When the CMOS sensor 21 is used as a temperature sensor in this way, it is not necessary to provide the temperature sensor 30 for measuring the temperature of the CMOS sensor 21, so that the CMOS temperature T1 is reduced while the insertion portion 16 (tip portion 20) is further reduced in diameter. And the tip surface temperature T2 can be accurately measured simultaneously. The same applies when another image sensor such as a CCD type image sensor is used instead of the CMOS sensor 21.

  In the above-described embodiment, an example in which an RGB color filter is provided in each pixel 62 and a method of obtaining a color imaging signal (a so-called simultaneous method) is used has been described. It is also possible to employ a method (so-called frame sequential method) in which the color of light is switched in order to RGB to obtain an image signal of each color for each frame.

  In the above-described embodiment, an example in which a xenon lamp is used as the light source 45 has been described. However, as the light source 45, another known light source such as an LD or an LED can be suitably used. In the above-described embodiment, the example in which the illumination light amount is adjusted by the diaphragm mechanism 46 has been described. However, when a light source that can easily adjust the light amount, such as an LD or LED, is used, the illumination light amount is adjusted by adjusting the output of the LD or LED. You may make it adjust. Moreover, when using LD and LED as a light source of illumination light, you may provide this in the front-end | tip part 20. FIG.

  In the above-described embodiment, the example in which the amount of illumination light is adjusted to reduce the heat generation at the distal end portion 20 is described, but the present invention is not limited to this. For example, the amount of illumination light by ALC control may be indirectly adjusted by changing the amplification factor of the imaging signal in accordance with the CMOS temperature T1 and the tip temperature T2 and adjusting the content of the ALC control data.

In the above-described embodiment, the example in which the upper limit of the amount of illumination light is set according to the CMOS temperature T1 and the tip temperature T2 has been described. However, the CMOS temperature T1 exceeded the threshold T _A1 (or a predetermined threshold set separately). In such a case, it is preferable to perform dark current correction on the imaging signal to suppress the occurrence of white scratches. Further, the CMOS temperature T1 may be used exclusively for on / off switching of dark current correction.

  In the above-described embodiment, the example in which the CMOS temperature T1 is measured at every predetermined time interval Δt has been described. However, the time interval Δt at which the CMOS temperature T1 is measured is also every frame (for example, 30 fps or 60 fps) of the CMOS sensor 21. Good, or every few frames.

DESCRIPTION OF SYMBOLS 11,72 Electronic endoscope system 12 Electronic endoscope 13 Processor apparatus 14 Light source device 16 Insertion part 17 Operation part 18 Connector 19 Universal code 20 Tip part 21 CMOS sensor 22 Monitor 23 Observation window 24 Illumination window 25 Objective optical system 26 TG
27 CPU
28 Light Guide 29 Illumination Lens 30 Temperature Sensor 31 CPU
32 DSP
33 DIP
34 Display Control Circuit 35 Operation Unit 36 ROM
37 RAM
41 Measurement Unit 42 Tip Surface 43 Tip Surface Temperature Estimator 44 Thermal Characteristic Data 45 Light Source 46 Aperture Mechanism 47 Wavelength Selection Filter 48 CPU
49 Condensing Lens 51 Imaging Area 56 Vertical Scan Circuit 57 CDS Circuit 58 Column Selection Transistor 59 Horizontal Scan Circuit 61 Output Circuit 62 Pixel 63 Output Bus Line 64 Aperture Opening 65 Diaphragm Blade 66 Spring 67 Motor 68 Aperture Adjustment Mechanism 71, 73, 74 Thermal network model

Claims (12)

An electronic endoscope having an imaging element for imaging the inside of the subject at the tip of an insertion portion to be inserted into the subject;
Illuminating means for irradiating illumination light into the subject from the distal end of the insertion portion;
A temperature sensor that outputs a signal corresponding to the temperature of the image sensor;
Measuring means for measuring the temperature of the image sensor based on a signal output from the temperature sensor;
Storage means for storing the calorific value of the image sensor measured in advance and thermal characteristic data around the image sensor;
Based on a thermal network model at the tip of the insertion portion, tip surface temperature estimating means for estimating the temperature of the tip surface of the insertion portion from the measured temperature of the imaging device and the known thermal characteristic data;
An upper limit value of the amount of illumination light is set based on at least the temperature of the tip surface, and an upper limit value of the amount of illumination light set based on the temperature of the imaging element and the temperature of the tip surface A light amount adjusting means for adjusting the light amount of the illumination light within a range that is lower than the lower upper limit value of the upper limit value of the light amount of the illumination light set by
An electronic endoscope system comprising:   The electronic endoscope system according to claim 1, wherein the thermal characteristic data includes a thermal resistance and a thermal capacity at a distal end of the insertion portion. The temperature sensor is the image sensor itself,
3. The electronic endoscope according to claim 1 , wherein the measurement unit measures the temperature of the imaging device based on a dark output value output from a pixel that does not receive light in the imaging device. 4. system. The illumination unit includes a light source that generates the illumination light, and a diaphragm unit that adjusts the amount of the illumination light.
The electronic endoscope system according to any one of claims 1 to 3 , wherein the light amount adjusting unit controls the diaphragm unit to adjust the light amount of the illumination light. The diaphragm means comprises a diaphragm opening of a predetermined size, and diaphragm blades for adjusting the aperture amount of the diaphragm opening,
The electronic endoscope system according to claim 4 , wherein the light amount adjusting unit adjusts the light amount of the illumination light by controlling the diaphragm blades. An electronic endoscope having an imaging element for imaging the inside of the subject at the tip of an insertion portion to be inserted into the subject;
Illuminating means for irradiating illumination light into the subject from the distal end of the insertion portion;
A temperature sensor that outputs a signal corresponding to the temperature of the image sensor;
Measuring means for measuring the temperature T1 of the image sensor at each time interval Δt based on a signal output from the temperature sensor, and measuring a change amount ΔT1 of the temperature T1 of the image sensor during the time interval Δt ;
Temperature Ta in the subject, calorific value Q of the imaging device, thermal resistance R1 between the imaging device and the subject, thermal resistance R2 between the imaging device and the distal end surface of the insertion portion, Storage means for storing thermal characteristic data including the heat capacity C in the vicinity of the image sensor ;
Tip surface temperature estimation for calculating an estimated value of the tip surface temperature T2 from the measured temperature of the imaging device and the known thermal characteristic data based on the following equation representing a thermal network model at the tip of the insertion portion Means,
An electronic endoscope system comprising:
Formula: (T1-Ta) / R1 + (T1-T2) / R2 + CΔT1 / Δt = Q The temperature sensor is the image sensor itself,
The electronic endoscope system according to claim 6 , wherein the measuring unit measures the temperature of the imaging device based on a dark output value output from a pixel that does not receive light in the imaging device. The electronic endoscope system according to claim 6 or 7 , further comprising a light amount adjusting unit that adjusts a light amount of the illumination light based on at least a temperature of the distal end surface. The light amount adjusting means sets an upper limit value of the light amount of the illumination light based on at least a temperature of the tip surface, and adjusts the light amount of the illumination light within a range equal to or less than the upper limit value. Item 9. The electronic endoscope system according to Item 8 . The light amount adjusting means is either an upper limit value of the light amount of the illumination light set based on the temperature of the imaging element or an upper limit value of the light amount of the illumination light set based on the temperature of the tip surface. The electronic endoscope system according to claim 9 , wherein the light amount of the illumination light is adjusted within a range equal to or lower than the lower upper limit value. The illumination unit includes a light source that generates the illumination light, and a diaphragm unit that adjusts the amount of the illumination light.
The electronic endoscope system according to any one of claims 8 to 10 , wherein the light amount adjusting unit controls the diaphragm unit to adjust the light amount of the illumination light. The diaphragm means comprises a diaphragm opening of a predetermined size, and diaphragm blades for adjusting the aperture amount of the diaphragm opening,
The electronic endoscope system according to claim 11 , wherein the light amount adjusting unit adjusts the light amount of the illumination light by controlling the diaphragm blades.

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