JP4504040B2 - Endoscope device - Google Patents

Description

  The present invention relates to an endoscope apparatus that obtains an image using a solid-state imaging device capable of controlling sensitivity.

  An endoscope apparatus having a solid-state image sensor inserts an elongated insertion portion into a subject such as a body cavity, and irradiates a subject via a light guide built in the endoscope. This is a device that photoelectrically converts light reflected by light with a solid-state imaging device mounted at the distal end of an endoscope, then processes the output signal obtained by this photoelectric conversion and displays it on a monitor or the like.

  As such an endoscope apparatus, a plane sequential endoscope apparatus that performs normal observation using illumination light in the visible region, or a self emitted from a living body by irradiating a living tissue with excitation light. 2. Description of the Related Art Fluorescence diagnostic endoscope devices and the like for detecting early cancers by capturing fluorescence or fluorescence of a drug injected into a living body as a two-dimensional image and observing the fluorescence image are known. .

Since an imaging device used in an internal scope mirror device for fluorescence diagnosis requires high sensitivity for observing weak fluorescence, in recent years, for example, as disclosed in Patent Document 1, a charge multiplication mechanism is provided. Endoscopes equipped with a solid-state imaging device that can be varied in sensitivity have been developed, and it has become possible to obtain observation images with appropriate brightness even with weak fluorescence.
JP 2001-29313 A

  In an endoscope using the above-described variable sensitivity solid-state imaging device, the sensitivity can be varied by varying the number of pulses and the voltage value of the pulse signal applied to the charge multiplication mechanism of the solid-state imaging device. However, if the sensitivity of the pulse signal applied to the solid-state image sensor is varied to vary the sensitivity, and if you want to observe with weak light with higher sensitivity than before, a higher signal voltage than before will be required. May be limited by the upper limit voltage that can be used by the power supply.

  In this case, it can be dealt with by using a higher voltage and larger capacity power supply than before, but the driving voltage of the solid-state image sensor and the control voltage of the endoscope are low voltage from the viewpoint of measures against heat generation and energy saving. The new design and use of a high-voltage, large-capacity power supply not only impairs compatibility with conventional endoscope power supplies, but also increases the size, weight, and cost of the entire system. Invite rise.

  The present invention has been made in view of the above circumstances, and for an endoscope having a solid-state imaging device capable of varying the sensitivity by applying a voltage signal, avoiding the limitation of the sensitivity amplification factor due to the upper limit voltage of the power supply, and more An object of the present invention is to provide an endoscope apparatus that enables observation with high magnification sensitivity.

To achieve the above object, an endoscope apparatus according to the present invention includes an endoscope having a solid-state imaging device whose sensitivity can be changed by applying a voltage signal, and a power source that outputs a plurality of voltage values having different polarities. The positive polarity voltage and the negative polarity voltage output from the power supply are positive and negative with respect to a reference level in response to a signal based on a photometric result of an image captured by a solid-state imaging device. generating a control signal for the control signal generating means, said fixing the basal level of said positive and negative and the control signal is shifted to the high potential side while maintaining the amplitude due to the polarity of the control signal to the reference level solid Sensitivity control signal output means for outputting as a sensitivity control signal for controlling the sensitivity of the image sensor is provided.

  The endoscope apparatus of the present invention avoids the limitation of the sensitivity amplification factor due to the upper limit voltage of the power supply for the endoscope having a solid-state imaging device whose sensitivity is variable by applying a voltage signal, and at a higher magnification sensitivity. Observation becomes possible.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 17 relate to an embodiment of the present invention, FIG. 1 is a block diagram showing a schematic configuration of an endoscope apparatus, and FIG. 2 is a block diagram of a charge coupled device type solid-state imaging device (hereinafter abbreviated as CCD). FIG. 3, FIG. 3 is a timing chart of sensitivity control pulses and horizontal transfer pulses, FIG. 4 is an explanatory diagram showing the relationship between charge amplification unit applied voltage and sensitivity amplification factor relating to CCD sensitivity, and FIG. 5 is a block diagram of a CCD driving circuit. 6 is an equivalent circuit diagram of the driver, FIG. 7 is an explanatory diagram of the bias circuit, FIG. 8 is an explanatory diagram showing a change in signal level in the circuit of FIG. 7, FIG. 9 is a waveform diagram of sensitivity control pulses before and after clamping, and FIG. FIG. 11 is a timing chart of CCD driving in the special light mode, FIG. 12 is a timing chart of CCD driving in the normal light mode, and FIG. 14 is a graph showing the D sensitivity characteristic (monitor output signal), FIG. 14 is a graph showing the CCD sensitivity characteristic (S / N characteristic), FIG. 15 is a plan view showing the configuration of the RGB rotation filter, and FIG. FIG. 17 is a graph showing the spectral characteristics of fluorescence and reflected light in fluorescence observation.

  As shown in FIG. 1, an endoscope apparatus 1 according to the present embodiment is inserted into a body cavity and an electronic endoscope (hereinafter abbreviated as an endoscope) 2 for imaging the inside of the body cavity. 2 are detachably connected, and a processor 3 and a processor 3 include a signal processing device 4 that performs signal processing on an image signal captured by the endoscope 2 and a light source device 5 that supplies illumination light to the endoscope 2. And a monitor 6 that displays a video signal image-processed by the processor 3, the endoscope 2, and a power supply device 7 that supplies power to the processor 3. The light source device 5 may be provided separately from the processor 3.

  The endoscope 2 has an elongated insertion portion 11 to be inserted into a patient body cavity. The insertion part 11 is composed of a flexible part in the case of the digestive tract, bronchial, head and neck (for pharynx) and bladder, and is composed of a rigid part in the case of the abdominal cavity, thoracic cavity and uterus.

  A light guide 12 that transmits illumination light from the light source device 5 is inserted into the insertion portion 11, and the rear end side of the light guide 12 is detachably connected to the light source device 5 via a light guide connector. Illumination light supplied from the light source device 5 is transmitted by the light guide 12 and emitted from the illumination lens 16 disposed at the distal end portion 15 of the insertion portion 11 through the illumination window, and passes through the subject side such as an affected part in the body cavity. Illuminate.

  The distal end portion 15 of the endoscope 2 is provided with an observation window adjacent to the illumination window, and an objective lens 17 that forms an optical image of the subject inside the observation window and a specific wavelength band An excitation light cut filter 18 that transmits only the light, and a CCD 19 as a solid-state imaging device that is disposed at the imaging position of the objective lens 17 and photoelectrically converts an optical image of the subject are sequentially disposed. In FIG. 1, the CCD 19 is arranged in a direct view, but it may be configured to be arranged in a perspective view or a side view.

  Reflected light and autofluorescence from the subject are imaged on the light receiving surface of the CCD 19 via the objective lens 17 and the excitation light cut filter 18. In the present embodiment, the excitation light cut filter 18 has a spectral characteristic that transmits autofluorescence (wavelength of approximately 500 nm or more) generated from living tissue and does not transmit excitation light.

  In the present embodiment, as the CCD 19, for example, U.S. S. PAT. No. No. 5,337,340 No. 5,337,340 “Charge Multiplying Detector (CMD) suitable for small pixel CCD image sensors” uses a variable sensitivity CCD using impact ionization phenomenon, and passes through a plurality of CCD drive signal lines 13. The sensitivity is varied by a sensitivity control signal (sensitivity control pulse φCMD) output from the CCD drive circuit 31 (details will be described later).

  The subject image formed on the light receiving surface of the CCD 19 by the objective lens 17 and the excitation light cut filter 18 is transferred after photoelectric conversion in each pixel of the CCD 19 and output from the output amplifier. The output signal from the CCD 19 is supplied to the analog processing circuit 33 of the signal processing device 4 in the processor 3 via a plurality of CCD output signal lines 14.

  In addition, the endoscope 2 has a storage device 20 mounted on the proximal end side. The storage device 20 includes a CPU 21 and a memory 22. The CPU 21 controls data reading and writing to the memory 22 and controls data transmission / reception (communication) with the processor 3. The memory 22 uses, for example, a nonvolatile EEPROM or the like, and can hold data even when the power is turned off.

  The memory 22 stores an accumulation time (electronic shutter speed) of three wavelengths R, G, and B in the normal light mode, Ex1 (fluorescence), Ex2 (green reflected light), and Ex3 in the special light mode (fluorescence observation). Data such as accumulation time (electronic shutter speed) of three wavelengths of (red reflected light) is stored.

  Note that the memory 22 may store the charge clearing time, the R, G, B, and the three wavelength accumulation time ratios of Ex1, Ex2, and Ex3 instead of the accumulation time. In the memory 22, the fluorescence wavelength accumulation time is set to be longer than the two-wavelength accumulation time of the reflected light at the fluorescence wavelength and the reflected light two wavelengths.

  The storage time of the three wavelengths R, G, and B in the normal light mode stored in the memory 22 is set to be shorter than an endoscope in which a general CCD that is not a sensitivity variable CCD such as the CCD 19 is mounted. ing. As the three-wavelength accumulation time of the special light mode stored in the memory 22, the optimum accumulation time for each type of endoscope (bronchial, upper gastrointestinal tract, lower gastrointestinal tract, head and neck, bladder, etc.) Is set. This is because the fluorescence intensity and reflected light intensity obtained for each part are different, and the accumulation time is set between three wavelengths for each part so that they have the same level of intensity.

  Further, the memory 22 stores other data related to the endoscope in addition to the data other than the above-described accumulation time. As data related to the endoscope, for example, endoscope model (type) name, endoscope serial number, white balance setting value {for normal light, special light (fluorescence observation)}, and endoscope is a processor. And the number of times the power is turned on, endoscope forceps channel information, endoscope tip outer diameter data, endoscope insertion section outer diameter data, and the like.

  The storage time data of the normal light mode and the special light mode (fluorescence observation) may be stored in the memory on the processor 3 side, and accordingly, the capacity of the memory 22 of the endoscope 2 is reduced. be able to.

Next, the signal processing device 4 will be described.
The signal processing device 4 in the present embodiment includes a CPU 30, a CCD drive circuit 31, a CCD sensitivity control circuit 32, an analog processing circuit 33, and an analog / digital converter (hereinafter referred to as an A / D converter) 34. A digital processing circuit 35, a digital / analog converter (hereinafter referred to as a D / A converter) 36, and a photometric circuit 37.

  When the endoscope 2 is connected to the processor 3, the CPU 30 performs reading control of various data stored in the memory 22 via the CPU 21. In this case, various data stored in the memory 22 is output to the CPU 30 via the CPU 21, and various data is read out by the CPU 30.

  In addition, the CPU 30 outputs three-wavelength accumulation time data acquired from the memory 22 in the normal light mode and the special light mode (fluorescence observation) to the CCD drive circuit 31. Further, the CPU 30 displays the endoscope model name, serial number. And white balance setting values (for normal light and special light) are output to the digital processing circuit 35.

  The CCD drive circuit 31 outputs vertical transfer pulses φP1 and φP2, sensitivity control pulses φCMD, horizontal transfer pulses φS1 and φS2, and an electronic shutter pulse φOFD as drive signals to the CCD 19. Based on the drive signal from the CCD drive circuit 31, electronic shutter control, signal charge accumulation, sensitivity control and readout of the CCD 19 are performed.

  As described above, the CCD 19 of the present embodiment is a CCD with variable sensitivity using the impact ionization phenomenon. In such a CCD, a charge amplifying unit is provided between the horizontal transfer path in the CCD and the output amplifier or for each pixel. By applying a high electric field pulse to the charge amplifying unit, the signal charge is increased. Energy is obtained from the electric field and collides with electrons in the valence band, and new signal charges (secondary electrons) are generated by impact ionization. For example, when the avalanche effect is used, secondary electron generation occurs in a chain reaction when one pulse is applied. When collision ionization is used, one electron-positive pair is generated by applying a relatively low voltage pulse. Only hole pairs are generated.

  In a CCD with variable sensitivity using the impact ionization phenomenon, when the charge amplifier is provided in front of the output amplifier, the number of signal charges can be arbitrarily amplified by controlling the voltage value (amplitude) of the applied pulse. Is possible. On the other hand, when a charge amplifier is provided for each pixel, it is possible to arbitrarily amplify the number of signal charges by controlling the voltage value (amplitude) of the pulse to be applied or the number of pulses.

  In the present embodiment, as the CCD 19, as shown in FIG. 2, an FFT (Full Frame Transfer) type monochrome CCD in which a charge amplifier is mounted between the horizontal transfer path and the output amplifier is used. The CCD 19 includes an image area 60, an OB (Optical Black) unit 61, a horizontal transfer path 62, a dummy 63, a charge amplifying unit 64, and an output amplifier 65, and the charge amplifying unit 64 includes the number of cells in the horizontal transfer path 62. And approximately twice the number of cells.

  The signal charges generated in each pixel in the image area 60 are transferred to the horizontal transfer path 62 for each horizontal line by the vertical transfer pulses φP1 and φP2, and the dummy 63 and the charges are transferred from the horizontal transfer path 62 by the horizontal transfer pulses φS1 and φS2. It is transferred to the amplifying unit 64. Then, by applying a sensitivity control pulse φCMD to each cell of the charge amplifying unit 64 composed of a plurality of cells, charges are sequentially amplified one step at a time while being transferred to each cell, and sequentially transferred to the output amplifier unit 65. Is done. The output amplifier unit 65 converts the charge from the charge amplification unit 64 into a voltage and outputs the voltage.

  The sensitivity amplification factor obtained by the charge amplifier 64 is variable by changing the voltage value (amplitude) of the sensitivity control pulse φCMD applied from the CCD drive circuit 31 to the charge amplifier 64. As shown in FIG. 3, the CCD drive circuit 31 outputs a sensitivity control pulse φCMD in a phase relationship with the horizontal transfer pulses φS1 and φS2, and outputs the voltage value (amplitude) of the sensitivity control pulse φCMD in the CCD in the special light mode. By dynamically varying the signal based on the signal from the sensitivity control circuit 32, the voltage value (amplitude) of the sensitivity control pulse φCMD applied to the charge amplifier 64 is changed, and the CCD 19 can obtain a desired sensitivity amplification factor. To control.

  In this embodiment, the phases of the sensitivity control pulse φCMD and the horizontal transfer pulses φS1 and φS2 are such that φCMD rises before φS1 rises and φCMD falls before φS1 falls.

  As shown in FIG. 4, the sensitivity amplification factor obtained by the charge amplifying unit 64 starts to amplify when the voltage applied to the charge amplifying unit 64 exceeds a certain threshold Vth, and is amplified one step at each cell. The sensitivity is exponentially amplified. The CCD 19 according to the present embodiment can obtain a sensitivity amplification factor of 200 times when a threshold value Vth = 10 V and a sensitivity control pulse φCMD having a peak value +25 V is applied. When the sensitivity control pulse φCMD is at a reference level (0 V in this embodiment) to a threshold Vth (10 V in this embodiment), the signal charge is not amplified but transferred by the charge amplifier 64. Only.

  Here, the steepness of the sensitivity amplification factor with respect to the threshold at which charge amplification starts and the applied voltage depends on the CCD parameter, but the amplification factor based on the voltage value (amplitude) of the sensitivity control pulse φCMD depends on the maximum voltage output of the power supply device 7. Limited. For example, to obtain a 200 times sensitivity gain, a sensitivity control pulse φCMD having a peak value of +25 V is required. When the maximum output of the power supply device 7 is 25 V or less, the sensitivity gain of 200 times is obtained as it is. It is difficult.

  The power supply device 7 is supplied with power from an AC power supply, generates a plurality of DC power supplies having different polarities mainly by a PWM control switching circuit or the like, and supplies the CCD drive power supply and various control power supplies to the endoscope 2 and the processor 3. It is used as a power supply device used for an endoscope equipped with a CCD having a relatively small sensitivity amplification factor and a general endoscope not equipped with a variable sensitivity CCD.

  That is, the power supply device 7 is, for example, a power supply having a voltage output of + 5V, ± 8V, + 19V, −15V, + 12V. An existing power supply conforming to medical safety standards is used.

  For this reason, the CCD drive circuit 31 has a sensitivity control pulse φCMD having a peak value of +25 V that can obtain a sensitivity amplification factor of 200 times from +5 V, ± 8 V, +19 V, −15 V, and +12 V that are output voltages of the power supply device 7. Is provided.

  FIG. 5 shows the configuration of the CCD drive circuit 31. The CCD drive circuit 31 includes a timing generator 70 that generates a timing signal for driving the CCD 19 based on a signal from the CCD sensitivity control circuit 32, horizontal transfer pulses φS1 and φS2 based on the timing signal output from the timing generator, and sensitivity. Drivers 72, 73, and 74 for receiving horizontal transfer pulses φS1 and φS2 and sensitivity control pulse φCMD, respectively, in response to signals from timing adjustment circuit 71 and timing adjustment circuit 71 that adjust the phase difference with control pulse φCMD. In response to the timing signal from the timing generator 70, there are provided drivers 75, 76 and 77 for outputting vertical transfer pulses φP1 and φP2 and an electronic shutter pulse φOFD, respectively.

  As shown in FIG. 6, each of the drivers 72 to 77 includes a PNP transistor Q1 connected to the coupling capacitor C1 and the bias diode D1, and an NPN transistor Q2 connected to the coupling capacitor C2 and the bias diode D2. The buffer amplifier is push-pull connected by a collector, and each output terminal is connected to a CCD 19 via a CCD drive signal line 13.

  Among these drivers 72 to 77, the drivers excluding the driver 74 for outputting the sensitivity control pulse φCMD are supplied with positive and negative power sources set according to the voltage value (amplitude) and polarity of the pulse, and are fixed. A pulse having an output level and an amplitude of 1 is output. On the other hand, the driver 74 that outputs the sensitivity control pulse φCMD is supplied with power through voltage regulators 78 and 79 for adjusting the positive and negative voltages from the power supply device 7 to a predetermined voltage.

  As described above, when a sensitivity gain of 200 times is desired, a sensitivity control pulse φCMD of +25 V is required. When a newly designed power supply capable of outputting a voltage of about 30 V at the maximum is used, it is possible to obtain a sensitivity control pulse φCMD of +25 V by controlling the voltage regulator 78 with a signal from the CCD sensitivity control circuit 32. However, when the existing power supply device 7 of + 5V, ± 8V, + 19V, −15V, + 12V is used as in the present embodiment, the sensitivity control pulse φCMD of + 25V is simply adjusted by adjusting the power supply voltage supplied to the driver 74. Cannot be output.

  Therefore, in the present embodiment, the voltage regulator 78 is a variable regulator that varies the voltage of + 19V from the power supply device 7 to 0 to + 15V by a signal from the CCD sensitivity control circuit 32, and the voltage regulator 79 is the power supply device. By using a fixed regulator that adjusts and fixes the -15V voltage from 7 to a -10V voltage, a pulse having a positive / negative polarity having a maximum amplitude of 25V (voltage difference of -10V to + 15V) from the driver 74 is obtained. By enabling the output and shifting the base level of the positive and negative polarity pulses to the reference level (0 V) on the amplitude coordinate axis, a sensitivity control pulse φCMD having a peak value of +25 V is obtained.

  Both voltage regulators 78 and 79 may be variable regulators, or the voltage regulator 79 may be omitted and a negative voltage may be directly supplied from the power supply device 7. In short, the driver 74 may output a pulse having a voltage difference of 25V.

  Here, as a circuit for shifting the base level of a pulse having positive and negative polarities output from the driver 74 to a predetermined reference level (0 V), a bias circuit 80 for applying a DC bias is considered as illustrated in FIG. It is done. The bias circuit 80 AC-couples the output pulse signal from the driver 74 by the capacitor C3, and then applies a DC bias from the + 15V power source via the adjustment circuit VR, and sets the base level of the output pulse of the driver 74 to the reference level (0V). ).

  However, since the level shift by the bias circuit 80 only shifts the average of the integral value of the AC component through the capacitor C3, when the voltage supplied to the driver 74 is variably controlled, the bias must also be controlled in conjunction with it. The base level of the pulse output from the bias circuit 80 varies with respect to the reference level.

  For example, as shown in FIG. 8, the pulse (a ′ point waveform) output from the driver 74 is shifted so that the pulse becomes a pulse of 0 to +25 V amplitude (b ′ point waveform). Even if the bias is set, the base level of the pulse that has passed through the bias circuit 80 can be maintained at the reference level (0 V) when the output pulse from the driver 74 is variably controlled to an amplitude of −10 V to +15 V or less with the same bias. This is not possible and an offset δ occurs. This offset δ enlarges the control error of the sensitivity amplification factor particularly in the high magnification region, and obstructs endoscopic observation at a desired sensitivity amplification factor. In order to eliminate this offset δ, the bias must be linked to the variable voltage control of the driver 74, which is difficult in terms of control.

  Therefore, in the present embodiment, as shown in FIG. 5, the positive and negative pulses output from the driver 74 are shifted to the positive side while maintaining the amplitude and fixed to the reference level on the output side of the driver 74. A clamping circuit 90 is provided. The clamp circuit 90 may be configured using an active element such as an operational amplifier with high accuracy. However, from the viewpoint of cost effectiveness, the output from the driver 74 is AC-coupled to the capacitor C4 and then clamped by the diode D4. A diode clamp circuit is effective (where R1 is a discharge resistor).

  The clamp circuit 90 of FIG. 5 shows a basic configuration when the diode D4 is an ideal diode. In order to fix the base level of the input pulse to the reference level 0, the anode of the diode D4 is grounded. As shown in FIG. 9, for example, when a pulse (a waveform at point a) having an amplitude of −10 V to +15 V is input from the driver 74 to the clamp circuit 90, the diode D4 conducts on the negative side of this input pulse and the capacitor C3 is charged, and the output of the clamp circuit 90 is fixed to 0 level. Further, on the positive side of the input pulse, the difference between the voltage of the input pulse (+ 15V) and the charging voltage (−10V) of the capacitor C3 becomes the output of the clamp circuit 90, and has a peak value of + 25V (b-point waveform).

  In an actual clamp circuit, it is desirable to have a circuit configuration that cancels the influence of the forward characteristics of the diode D4.

  As a result, the output pulse of the driver 74 whose voltage is controlled by the signal from the CCD sensitivity control circuit 32 via the voltage regulator 78, for example, as shown in FIG. 10, -10V to 0V,... -10V to + 5V, ..., a pulse having an amplitude of -10V to + 15V is output as a pulse having a pulse amplitude of 0 to + 10V, ..., 0 to + 15V, ..., 0 to + 25V, exceeding the maximum voltage (+ 19V) of the power supply device 7 A sensitivity control pulse φCMD having a peak value (+25 V) and a base level fixed to 0 level can be obtained.

  In the clamp of the output pulse of the driver 74 by the clamp circuit 90, the DC offset voltage generated in the push-pull type driver 74 can be corrected, and the frequency characteristic of the CCD drive signal line 13 for transmitting the sensitivity control pulse φCMD to the CCD 19 is corrected. Variation of the bias due to variations in the number of pulses can be suppressed, stable pulse supply can be made, and image quality can be improved.

Next, the electronic shutter function of the CCD 19 will be described.
The operating principle of the electronic shutter is a substrate discharge type using the change in overflow characteristics due to the voltage value (amplitude) of a pulse applied to, for example, an overflow drain (Over Flow Drain), as in a general CCD.

  During the period when the electronic shutter pulse φOFD to be applied to the overflow drain is input to the CCD 19 (H level), the signal charge (noise-containing charge) in the pixel of the CCD 19 is discharged to the substrate, and the signal charge is supplied to the pixel of the CCD 19. Is not accumulated. In the period when the electronic shutter pulse φOFD is not input to the CCD 19, signal charges are accumulated in the pixels of the CCD 19.

  Since any value can be set as the pulse width and the number of pulses of the electronic shutter pulse φOFD, the signal charge accumulation time of the CCD 19 can be controlled at any time.

Next, the drive timing of the CCD 19 will be described.
FIG. 11 is a timing chart showing the drive signal and output signal of the CCD 19 for one wavelength among the three wavelengths in the special light mode. FIG. 11A shows the operation of the RGB rotation filter 43 in the special light mode. 11B shows vertical transfer pulses φP1 and φP2 in the special light mode, FIG. 11C shows sensitivity control pulse φCMD in the special light mode, and FIG. 11D shows horizontal transfer pulses φS1 in the special light mode. FIG. 11E shows the electronic shutter pulse φOFD in the special light mode, and FIG. 11F shows the output signal of the CCD 19 in the special light mode.

  12 shows a timing chart of the drive signal and output signal of the CCD 19 for one wavelength out of the three wavelengths in the normal light mode. FIG. 12A shows the operation of the RGB rotation filter 43 in the normal light mode. 12B shows vertical transfer pulses φP1 and φP2 in the normal light mode, FIG. 12C shows sensitivity control pulse φCMD in the normal light mode, and FIG. 12D shows horizontal transfer pulses φS1 and φS2 in the normal light mode. FIG. 12E shows the electronic shutter pulse φOFD in the normal light mode, and FIG. 12F shows the output signal of the CCD 19 in the normal light mode.

  Here, in FIG. 11 and FIG. 12, one cycle indicates a cycle corresponding to one of the three wavelengths, and indicates an operation corresponding to 1/3 rotation of the RGB rotation filter 43.

  Periods TE (special light mode) and TE ′ (normal light mode) are exposure periods. The CCD 19 can accumulate light incident from the subject on the light receiving surface of the CCD 19 during this exposure period as a signal charge by photoelectric conversion.

  In the periods TD (special light mode) and TD ′ (normal light mode), the signal charges accumulated in the image area 60 in the periods TE and TE ′ are horizontal by the vertical transfer pulses φP1 and φP2 for each horizontal line. This is a period in which the data is transferred to the transfer path 62, sequentially transferred to the dummy 63, the charge amplifier 64, and the output amplifier 65 by the horizontal transfer pulses φS 1 and φS 2, converted into charge voltage by the output amplifier 65 and output.

  In the special light mode, the RGB rotation filter 43 is set with an exposure period TE and a light shielding period TD shown in FIG.

  The electronic shutter pulse φOFD shown in FIG. 11 (e) becomes a high level pulse period TC for clearing the charge of the pixels of the CCD 19 at the beginning of the exposure period TE shown in FIG. 11 (a), and then falls to the low level. The charge accumulation period TA during which charges are accumulated in the pixels of the CCD 19 falls.

  In the light shielding period TD shown in FIG. 11A, that is, the readout period TD of the CCD 19, the CCD drive circuit 31 performs the vertical transfer pulses φP1 and φP2 shown in FIG. 11B and the sensitivity control pulse φCMD shown in FIG. 11D, the horizontal transfer pulses φS1 and φS2 shown in FIG. 11D are output, whereby the CCD 19 is read, and the output signal of the CCD 19 shown in FIG. 11F is obtained.

  Here, the CCD drive circuit 31 varies the voltage value (amplitude) based on the data supplied from the CCD sensitivity control circuit 32 with respect to the sensitivity control pulse φCMD shown in FIG. The CCD drive circuit 31 outputs the sensitivity control pulse φCMD shown in FIG. 11C to the CCD 19 in a phase relationship with the horizontal transfer pulses φS1 and φS2 shown in FIG.

  As a result, in the special light mode, the CCD drive circuit 31 changes the voltage value (amplitude) of the sensitivity control pulse φCMD applied to the charge amplifier 64 and controls the CCD 19 to obtain a desired sensitivity amplification factor.

  On the other hand, in the normal light mode, the RGB rotation filter 43 has an exposure period TE ′ and a light shielding period TD ′ shown in FIG.

  The electronic shutter pulse φOFD shown in FIG. 12E becomes a high level pulse period TC ′ for clearing the charge of the pixels of the CCD 19 at the beginning of the exposure period TE ′ shown in FIG. It falls and becomes a charge accumulation period TA ′ in which charges are accumulated in the pixels of the CCD 19.

  In the light shielding period TD ′ shown in FIG. 12A, that is, the readout period TD ′ of the CCD 19, the CCD drive circuit 31 performs the vertical transfer pulses φP1 and φP2 shown in FIG. 12B and the horizontal transfer shown in FIG. Pulses φS1 and φS2 are output, thereby reading out the CCD 19 and outputting the output signal of the CCD 19 shown in FIG.

  Here, in the normal light mode, the CCD drive circuit 31 outputs a sensitivity control pulse φCMD having a voltage value Vth or less as shown in FIG. As a result, in the normal light mode, the charge amplification unit 64 does not perform charge amplification, and the sensitivity amplification factor becomes 1.

  When a general endoscope not equipped with a variable sensitivity CCD such as that used for the CCD 19 is connected to the processor 3, the CCD drive circuit 31 performs the operation in the normal light mode shown in FIG. Do.

  The electronic shutter pulse φOFD shown in FIG. 11E and FIG. 12E is a pulse for discharging the charge accumulated in each pixel to the substrate, and is arbitrary from the exposure period start to the period end (light shielding period start). Output in pulse width or multiple pulses.

  The periods TE and TE ′ shown in FIGS. 11 and 12 are periods in which the subject image can be accumulated in the image area 60 of the CCD 19, and the electronic shutter pulse φOFD shown in FIGS. 11 (e) and 12 (e) is output. Signal charges are not accumulated during the periods TC and TC ′. Then, when the electronic shutter pulse φOFD shown in FIGS. 11 (e) and 12 (e) is not output, signal charge starts to be accumulated in each pixel of the CCD 19. The periods TA (= period TE−period TC) (special light mode) and TA ′ (= period TE′−period TC ′) (normal light mode) from the start of accumulation to the start of the light shielding period are substantial accumulation times. .

  As for the electronic shutter pulse φOFD of each wavelength, the pulse width or the number of pulses based on the accumulation time of each wavelength from the CPU 30 is output to the CCD 19.

  For example, assuming that the three wavelengths Ex1, Ex2, and Ex3 in the special light mode are stored, the accumulation time between the three wavelengths in the special light mode stored in the memory 22 is TA (Ex1) = TE, TA (Ex2) = 0.2 *. In the case of TE, TA (Ex3) = 0.1 * TE, these data are supplied to the CCD drive circuit 31 via the CPU 30, and the electronic shutter pulse φOFD for clearing the charge output from the CCD drive circuit 31 to the CCD 19 is supplied. The pulse widths are OFD (Ex1) = 0 * TE, OFD (Ex2) = 0.8 * TE, and OFD (Ex3) = 0.9 * TE.

  Further, the storage time between the three wavelengths in the normal light mode stored in the memory 22 is, for example, TA ′ (R) = 0.7 * TE ′, TA ′ (G) = 0.7 * TE ′, TA ′ (B ) = 0.7 * TE ′, these data are supplied to the CCD drive circuit 31 via the CPU 30, and the electronic shutter pulse φOFD is output from the CCD drive circuit 31 to the CCD 19 based on these data. The pulse width of the electronic shutter pulse φOFD for clearing the charge is OFD (R) = OFD (G) = OFD (B) = 0.3 * TE ′.

Next, a processing system for an output signal from the CCD 19 will be described.
The analog processing circuit 33 is provided with a preamplifier for amplifying the CCD output signal from the CCD 19 and a CDS circuit for performing correlated double sampling to reduce CCD noise. The signal subjected to CDS processing by the analog processing circuit 33 is output to the A / D converter 34 and converted into a digital signal. The output of the A / D converter 34 is output to the digital processing circuit 35.

  The digital processing circuit 35 performs signal processing such as clamp processing, white balance processing, color conversion processing, electronic zoom processing, gamma conversion processing, and image enhancement processing on the video signal input from the A / D converter 34. After that, a three-wavelength synchronization process is performed and the result is output to the D / A converter 36. The D / A converter 36 converts the digital video signal from the digital processing circuit 35 into an analog signal and outputs it.

  The analog video signal output from the D / A converter 36 is output to the monitor 6 to display various images. Further, the video signal output from the D / A converter 36 is also output to a display device or a recording device which is a peripheral device (not shown).

  Here, white balance processing and color conversion processing in the digital processing circuit 35 are different in each of the observation modes of the normal light mode and the special light mode (fluorescence observation), and the digital processing circuit 35 switches the mode from the mode switching circuit 50. Different processing is applied depending on the signal. The mode switching signal from the mode switching circuit 50 is output to the rotation filter switching mechanism 46, the RGB rotation filter control circuit 47, the photometry circuit 37, the CCD drive circuit 31, the CCD sensitivity control circuit 32, and the digital processing circuit 35.

  The mode switching circuit 50 is, for example, a switch that allows the operator to arbitrarily select one of the normal light mode and the special light mode (fluorescence observation), and is provided in the light source device 5 in FIG. However, it may be provided in the processor 3 or the endoscope 2, and may be provided in all of them.

  In the color conversion processing in the special light mode (fluorescence observation), a constant matrix coefficient is multiplied to the fluorescence wavelength and the reflected light 2 wavelength to construct a composite image of the fluorescence wavelength and the reflected light 2 wavelength. Further, in the white balance processing, setting values stored in the memory 22 are input to the digital processing circuit 35 via the CPU 30, so that different white balances are set in the normal light mode and the special light mode (fluorescence observation). .

  The photometry circuit 37 receives the video signal from the analog processing circuit 33, and calculates a screen average value of brightness of three wavelengths in the normal light mode and the special light mode (fluorescence observation).

  Here, according to the mode switching signal from the mode switching circuit 50, the photometry circuit 37 performs an operation in which the calculation method of the screen average value differs between the normal light mode and the special light mode (fluorescence observation).

  In the normal light mode, the photometry circuit 37 calculates a luminance signal from the screen average value for three wavelengths of R, G, and B, and outputs the luminance signal to the aperture control circuit 42 of the light source device 5. In the special light mode (fluorescence observation), the photometry circuit 37 calculates the screen average value for the three wavelengths Ex1, Ex2, and Ex3, and calculates the screen average value of the composite image composed of the fluorescence wavelength and the reflected light two wavelengths. And output to the CCD sensitivity control circuit 32 and the aperture control circuit 42.

  In the special light mode, the CCD sensitivity control circuit 32 controls the charge amplifying unit 64 provided in the CCD 19 via the CCD drive circuit 31 to perform AGC (Auto Gain Control). The CCD sensitivity control circuit 32 controls the sensitivity amplification factor of the charge amplifying unit 64 of the CCD 19 so that the average of the output signal level from the CCD 19 becomes a desired value corresponding to the intensity change of the subject incident on the light receiving surface of the CCD 19. I do.

  The CCD sensitivity control circuit 32 receives the screen average value of the combined image of the fluorescence image and the reflected light from the photometry circuit 37, and compares the screen average value with the monitor brightness value arbitrarily set by the operator. The surgeon can set a desired brightness target value on the monitor screen from a brightness setting switch (not shown) provided in the light source device 5 or the signal processing device 4.

  The CCD sensitivity control circuit 32 compares the screen average value with the brightness setting value (target value), and based on the comparison result (magnitude relationship), the sensitivity control pulse output from the CCD drive circuit 31 to the charge amplification unit 64 of the CCD 19. The voltage value (amplitude) of φCMD is calculated and output to the CCD drive circuit 31.

The AGC control method of the CCD sensitivity control circuit 32 will be described below.
The relationship between the voltage value of the sensitivity control pulse φCMD of the charge amplifier 64 shown in FIG. 4 and the sensitivity gain is approximated by the following equation.
M (V) = C · Exp {α (V−Vth)} (1)
However, M (V) is a sensitivity amplification factor when the voltage value (amplitude) of the sensitivity control pulse φCMD is V (v), Vth is a threshold voltage at which charge amplification is started, and C, α, and Vth are variable in design. Device-specific constants.

  When a subject having a certain intensity is imaged by the CCD, the CCD sensitivity control circuit 32 uses the fact that the average value of the screen of the image changes exponentially by increasing or decreasing the voltage value of the sensitivity control pulse φCMD. The voltage value (amplitude) of the sensitivity control pulse φCMD is changed (increased or decreased) so that the screen average value of the synthesized fluorescent image matches the monitor brightness set by the surgeon and the target value with respect to the change in the reflected light intensity. ) In addition, the CCD sensitivity control circuit 32 controls the CCD drive circuit 31 so that the applied voltage becomes 10 (V) when the voltage value of the sensitivity control pulse φCMD is equal to or less than the threshold value.

  FIGS. 13 and 14 show the signal with respect to the subject intensity displayed on the monitor 6 when the sensitivity gain is changed by changing the voltage value (amplitude) of the sensitivity control pulse φCMD input to the charge amplifier 64. The output and S / N characteristics are shown.

  As shown in these figures, in a faint light region (subject intensity is low), when the sensitivity amplification factor is 1 (no amplification), the brightness on the monitor is dark and the image quality (S / N) is low. As the gain is increased, the monitor is brighter and has higher image quality.

Next, the light source device 5 will be described.
The light source device 5 includes a lamp 40, a diaphragm 41, a diaphragm control circuit 42, an RGB rotation filter 43, a motor 44, a condenser lens 45, a rotation filter switching mechanism 46, an RGB rotation filter control circuit 47, The mode switching circuit 50 is included.

  The lamp 40 generates illumination light including a xenon lamp, a halogen lamp, an LED, an LD (semiconductor laser), and the like. The condensing lens 45 condenses the luminous flux of the illumination light guided from the lamp 40 through the diaphragm 41 and the RGB rotation filter 43 on the rear end surface of the light guide 12.

  The diaphragm 41 and the RGB rotation filter 43 are inserted between the lamp 40 and the condenser lens 45. The RGB rotation filter 43 is rotatably connected to the rotation shaft of the motor 44 and is rotationally controlled by the RGB rotation filter control circuit 47 at a predetermined speed.

  The RGB rotation filter control circuit 47 can control the rotation speed of the RGB rotation filter 43 (motor 44) to a predetermined rotation speed by a mode switching signal from the mode switching circuit 50. The RGB rotation filter control circuit 47 can extend the exposure time by making the rotation speed in the special light mode slower than that in the normal light mode.

  The aperture control circuit 42 receives the screen average value from the photometry circuit 37 and compares the screen average value with the monitor brightness target value arbitrarily set by the operator. The aperture control circuit 42 controls the opening / closing operation of the aperture 41 disposed between the lamp 40 and the RGB rotation filter 43 based on the comparison result (magnitude relationship), thereby reducing the light amount to the rear end surface of the light guide 12. Control.

  As shown in FIG. 15, the RGB rotation filter 43 has a double structure having two sets of filter sets 48 and 49 on the inner peripheral portion and the outer peripheral portion.

  As shown in FIG. 1, the rotary filter switching mechanism 46 has a first filter set 48 on the inner peripheral side of the RGB rotary filter 43 shown in FIG. 15 on the optical axis of the illumination light connecting the lamp 40 and the rear end surface of the light guide 12. And the second filter set 49 on the outer peripheral side are selectively moved, and the entire RGB rotation filter 43 is moved and arranged on the illumination optical path.

  In the normal light mode, the rotary filter switching mechanism 46 arranges the inner peripheral filter set 48 on the illumination optical path from the lamp 40 (the light beam P1 from the lamp 40 (solid line in FIG. 15) is the inner peripheral filter set. 48).

  In the special light mode, the rotary filter switching mechanism 46 arranges the outer peripheral filter set 49 on the illumination optical path from the lamp 40 (the light beam P2 from the lamp 40 (broken line in FIG. 15) is applied to the outer filter set 49. Incident).

  As shown in FIG. 15, the first filter set 48 in the inner peripheral portion of the RGB rotation filter 43 is three filters of R, G, and B for the normal light mode, which are red (R) and green (G). , Filters 48R, 48G, and 48B having spectral characteristics that transmit the blue (B) wavelength band.

  The second filter set 49 in the outer peripheral portion is provided with three filters 51, 52, and 53 of Ex1, Ex2, and Ex3 having spectral characteristics for special light mode (fluorescence observation). For example, in the present embodiment, the Ex1 filter 51 is a filter for excitation light that passes through the 390 to 470 nm region. The Ex2 filter 52 is a reflected light filter having a spectral characteristic of a narrow band with a center wavelength of about 550 nm, a half-value width of about 10 nm, and a transmittance of several percent. The Ex3 filter 53 is a reflected light filter having a spectral characteristic of a narrow band with a center wavelength of about 600 nm, a half width of about 10 nm, and a transmittance of about several percent.

  In the special light mode, the illumination light emitted from the illumination lens 16 of the endoscope 2 has a spectral characteristic as shown in FIG. 16, for example.

  The filters 48R, 48G, and 48B correspond to the exposure period of the CCD 19, and the light shielding portion provided between the filters 48R, 48G, and 48B corresponds to the light shielding period (readout period) of the CCD 19. The same applies to the second filter set 49. Each size of the second filter set 49 for special light observation is larger than that of the first filter set 48 for normal light observation. This is to make the exposure time longer during special light observation than during normal light observation.

  In FIG. 15, the filters 48R, 48G, and 48B for normal light are provided on the inner periphery and the filters 51, 52, and 53 for special light are provided on the outer periphery.

  Next, the usage method of the above endoscope apparatus 1 is demonstrated.

  In starting the endoscopy, the surgeon connects the type of endoscope 2 corresponding to the observation site from the plurality of types of endoscopes to the processor 3. As a result, the CPU 30 of the processor 3 reads various data related to the endoscope 2 stored in the memory 22 via the CPU 21 of the storage device 20 of the endoscope 2. The charge accumulation time in the CCD 19 having the three wavelengths in the normal light mode and the special light mode (fluorescence observation) corresponding to the type of endoscope, which is one of various data, is also read from the memory 22 to the CPU 30. This charge accumulation time data is output to the CCD drive circuit 31 according to the observation mode.

  Next, the operation of the normal light mode and the special light mode (fluorescence observation) will be described.

  The surgeon inserts the insertion portion 11 of the endoscope 2 into a patient's body cavity (bronchi, esophagus, stomach, large intestine, abdominal cavity, chest cavity, bladder, uterus, etc.) and performs observation.

  When normal light observation (normal light mode) is performed, the rotary filter 43 has the first filter set 48 arranged on the illumination optical path, and the sensitivity amplification factor of the CCD 19 is set to 1 (no sensitivity amplification). The illumination light emitted from the lamp 40 passes through the first filter set 48, so that R (red), G (green), and B (blue) surface-sequential illumination light is applied to the living tissue. The light is irradiated in time series from the illumination lens 16 through the guide 12.

  The CCD drive circuit 31 outputs an electronic shutter pulse φOFD to the CCD 19 for each exposure time of the reflected light of R, G, B based on the accumulation time data of R, G, B in the normal light mode input from the CPU 30. Then, a desired accumulation time control is performed by controlling the pulse period during which the charge is cleared.

  The accumulation time of the pixel charges in the CCD 19 is shorter than that of a general endoscope not equipped with a variable sensitivity CCD. Since the autofluorescence is weak, it is necessary to increase the amount of light incident on the light receiving surface of the CCD 19. For example, the number of light guides 12 is larger than that of a general endoscope, and the objective lens 17 is a general endoscope. Designed with a lens brighter than the mirror. For this reason, when normal light observation is performed, the incident intensity on the light receiving surface of the CCD 19 becomes larger than that of a general endoscope. Therefore, the amount of incident light can be adjusted by shortening the accumulation time. The accumulation time is set according to the type.

  The photometry circuit 37 calculates a luminance signal displayed on the monitor screen and outputs it to the aperture control circuit 42. The diaphragm control circuit 42 compares the luminance signal with the monitor brightness reference value (target value) set by the operator, and performs opening / closing control of the diaphragm 41 according to the comparison result (large or small).

  When the monitor screen (luminance signal) is brighter than the reference value, the diaphragm control circuit 42 is operated in a direction to close the diaphragm 41 (the irradiation intensity on the rear end surface of the light guide 12 is reduced). On the other hand, when the monitor screen is darker than the reference value, the monitor 41 is operated in the direction in which the aperture 41 is opened (the irradiation intensity on the rear end surface of the light guide 12 increases).

  As described above, the endoscope apparatus 1 automatically adjusts light by controlling the diaphragm 41 so that the brightness of the monitor 6 is maintained at the operator's set value by changing the irradiation intensity to the living tissue. Operation (dimming by light source device aperture opening / closing control) is performed.

  The R, G, B reflected light from the living tissue sequentially enters the CCD 19. CCD output signals corresponding to the reflected light of R, G, B from the CCD 19 are input to the signal processing device 4 and subjected to various signal processing by the analog processing circuit 33 and the digital processing circuit 35. Output to peripheral devices. As a result, the normal light image is displayed and recorded on the monitor 6 and peripheral devices. The monitor 6 can obtain an output signal and S / N characteristics corresponding to a sensitivity amplification factor of 1 as shown in FIGS.

  When performing fluorescence observation (special light mode), the surgeon selects the special light mode (fluorescence observation) with a mode switch provided in the endoscope 2 or the processor 3 constituting the mode switching circuit 50. . In accordance with this selection instruction, the rotary filter switching mechanism 46 arranges the second filter set 49 of the RGB rotary filter 43 on the illumination optical path. Further, the diaphragm control circuit 42 holds the diaphragm 41 in a substantially fully opened position because the incident light intensity to the CCD 19 is small.

  When the endoscope 2 is close to or enlarged from the living tissue, the incident intensity of the fluorescence to the CCD 19 increases, and the monitor screen may be saturated even when the sensitivity amplification factor of the charge amplification unit 64 is 1 (no amplification). is there. In that case, the aperture control circuit 42 controls the aperture 41 in the closing direction, thereby performing control to adjust the amount of light applied to the subject.

  The illumination light emitted from the lamp 40 of the light source device 5 is transmitted through the second filter set 49 of the RGB rotation filter 43, and the blue band that is the excitation light of the filter Ex1, the green narrow band light of the filter Ex2, The red narrow-band light of the filter Ex3 is incident on the rear end surface of the light guide 12 through the condenser lens 45, and enters the living tissue from the illumination lens 16 mounted on the distal end portion 15 of the endoscope 2, for example, FIG. Are sequentially irradiated as illumination light having spectral characteristics (spectrum, intensity) as shown in FIG.

  Based on the accumulation time data of fluorescence, green reflected light, and red reflected light in the special light mode (fluorescence observation) input from the CPU 30, the CCD drive circuit 31 causes the CCD 19 to transmit the fluorescence wavelength and the reflected light of the two wavelengths. The pulse width (period) for clearing the charge of the electronic shutter pulse φOFD at the time of imaging is controlled so as to achieve a desired accumulation time. Since the accumulation time of the fluorescence wavelength and the two wavelengths of the reflected light is longer for the fluorescence than the two wavelengths of the reflected light, the pulse width of the electronic shutter pulse φOFD is longer for the two wavelengths of the reflected light than for the fluorescence.

  The autofluorescence intensity is very weak with respect to the reflected light intensity, and the intensity ratio between the fluorescence wavelength and the two wavelengths of the reflected light differs from site to site. Therefore, for example, when normal living tissue as shown in FIG. 16 is irradiated onto a normal living tissue, the part on the light receiving surface of the CCD 19 (one kind of a plurality of endoscopes), for example, as shown in FIG. A spectrum of two wavelengths of fluorescence wavelength and reflected light is obtained.

  Here, it is assumed that the intensity ratio of each wavelength is, for example, approximately fluorescence: green reflected light (green narrow band): red reflected light (red narrow band) = 1: 5: 10.

  The storage time TA of each wavelength in the special light mode is, for example, fluorescence = TE, green reflected light is 0.2 * TE, and red reflected light is 0.1 * TE stored in the memory 22. When the two wavelengths of reflected light are imaged during this accumulation time, the average screen value at the same level is obtained at each wavelength. Thus, fluorescence is imaged with an accumulation time longer than two wavelengths of reflected light. Further, if the intensity ratio of the fluorescence and the reflected light is greatly different in other parts, the CPU 30 calculates the accumulation time of the fluorescence wavelength and the reflected light at the two wavelengths in consideration of the intensity ratio. The memory 22 stores optimal accumulation time data for each type of endoscope.

  The photometry circuit 37 calculates a screen average value of a combined image of fluorescence and reflected light related to the brightness of the monitor screen, and outputs the result to the CCD sensitivity control circuit 32 and the aperture control circuit 42.

  The CCD sensitivity control circuit 32 compares the screen average value with the monitor brightness reference value (target value) set by the operator, and determines the sensitivity amplification factor of the charge amplification unit 64 of the CCD 19 according to the comparison result (large or small). In order to perform control, the voltage value (amplitude) of the sensitivity control pulse φCMD output from the CCD drive circuit 31 to the CCD 19 is variably controlled.

  When the monitor screen is brighter than the reference value, the CCD sensitivity control circuit 32 reduces the sensitivity amplification factor by reducing the voltage value of the sensitivity control pulse φCMD. On the other hand, when the monitor screen is darker than the reference value, the CCD sensitivity control circuit 32 increases the sensitivity amplification factor by increasing the voltage value (amplitude) of the sensitivity control pulse φCMD.

  With these operations, the sensitivity amplification factor of the charge amplification unit 64 of the CCD 19 is automatically changed to maintain the brightness of the monitor 6 at the operator's set value (target value) for a subject whose brightness changes. A dimming operation (AGC by controlling the sensitivity amplification factor of the charge amplifier 64) is performed. Further, even if the sensitivity amplification factor changes due to the temperature change of the CCD, the sensitivity amplification factor of the charge amplification unit 64 of the CCD 19 is automatically changed so that the brightness of the monitor 6 can be maintained at the operator's set value (target value). Dimming control is performed.

  The objective lens 17 receives reflected light of the excitation light itself by irradiation of the excitation light to the living tissue and autofluorescence having a peak in the vicinity of approximately 520 nm emitted from the living tissue by the excitation light. As a result, the excitation light itself is cut, and only autofluorescence enters the light receiving surface of the CCD 19. Further, the reflected light with respect to the illumination light in the narrow green band and the narrow red band enters the objective lens 17, passes through the excitation light cut filter 18, and enters the light receiving surface of the CCD 19.

  Fluorescence, green reflected light, and red reflected light from the living tissue are sequentially incident on the CCD 19. A CCD output signal corresponding to each wavelength from the CCD 19 is input to the signal processing device 4 and subjected to various predetermined signal processing by the analog processing circuit 33 and the digital processing circuit 35, and fluorescence is emitted from peripheral devices such as the monitor 6 and a personal computer. Images are displayed and stored.

  Further, in the digital processing circuit 35, the white balance coefficient is switched to a setting value of a special light mode (fluorescence observation) different from the normal light mode stored in the memory 22 when fluorescent light, green reflected light, and red reflected light are imaged. It is done. In the color conversion process, for example, the output of each wavelength is subjected to color conversion so that fluorescence is output to the G channel, red reflected light is output to the B channel, and green reflected light is output to the R channel.

  Thereby, an output signal and an S / N characteristic corresponding to an arbitrary sensitivity amplification factor as shown in FIGS. 13 and 14 are obtained in the monitor 6. In particular, in the weak light region, by changing the voltage value (amplitude) of the sensitivity control pulse φCMD to the charge amplification unit 64 of the CCD 19 and increasing the sensitivity amplification factor, the monitor 6 outputs an output signal corresponding to the sensitivity amplification factor and S / N characteristics are obtained.

  In this case, the sensitivity amplification factor of the CCD 19 can be amplified to an arbitrary value by controlling the voltage value (amplitude) of the sensitivity control pulse φCMD as well as 3 times or 10 times. In the present embodiment, While using the power supply device 7 having a relatively low voltage, it is possible to generate a sensitivity control pulse φCMD having a high voltage (+25 V) exceeding the maximum output voltage (+19 V) of the power supply device 7 and a high sensitivity amplification factor of 200 times. Can be effectively observed.

  In fluorescence observation, for example, when the mucous membrane is irradiated with excitation light in a blue region, autofluorescence having a peak near 520 nm is obtained, and the intensity ratio of this autofluorescence uses a characteristic that a lesion site is smaller than a normal site. .

  In addition, it is obtained by imaging the site to be observed by using red reflected light as the influence of blood, that is, green reflected light capable of capturing the hemoglobin absorption band sensitively and reference light (wavelength band not affected by blood). The composite image is an image in which the presence or absence of a lesion excluding the influence of inflammation (blood) can be detected with high sensitivity. For example, by fluorescence observation, inflammation and hyperplasia are displayed in the same color as the normal tissue, and adenoma and cancer sites are displayed in a different color from the normal tissue. These make it easier to pick up neoplastic lesions compared to normal observation.

  As described above, according to the present embodiment, when the CCD is driven with high sensitivity, the limitation due to the upper limit voltage that can be used by the power supply is avoided, and the high-voltage sensitivity control pulse that exceeds the upper limit voltage of the power supply. Thus, an observation image with appropriate brightness can be obtained with a weaker light with good image quality. Therefore, it is possible to perform endoscopic observation with higher magnification sensitivity without increasing the size, weight, and cost of the entire system by using a new power source with high voltage and large capacity.

  In the present embodiment, as a solid-state imaging device capable of varying sensitivity, a CCD having a charge amplification unit mounted between a horizontal transfer path and an output amplifier has been described as an example. It may be a CCD mounted on the. In that case, the charge amplification can be performed by applying a sensitivity control pulse from the processor to the charge amplification section of the CCD, and the sensitivity amplification factor can be controlled by controlling the voltage value (amplitude) or the number of pulses of the sensitivity control pulse.

  In the present embodiment, an example is shown in which a single CCD, which is a solid-state imaging device, is mounted on the endoscope tip. However, two CCDs are mounted on the endoscope tip, and the first CCD is in the normal light mode. The second CCD may be used for the special light mode. In that case, a CCD drive signal consisting of a relay or the like, a CCD changeover switch for a readout signal, etc. are provided in the endoscope or in the cable connecting the endoscope and the processor, and according to the mode change signal from the mode change circuit. Then, the CCD corresponding to each observation mode may be driven and read out. Further, a CCD driving and reading circuit corresponding to two CCDs may be provided in the processor.

  Furthermore, in this embodiment, the CCD is mounted on the distal end portion of the endoscope. However, the CCD is mounted outside the fiberscope (image location other than the insertion portion) provided with an image fiber for transmitting an image in the endoscope. Alternatively, it may be configured as an integrated hybrid type, or may be configured as a detachable type instead of an integrated type.

Block diagram showing a schematic configuration of an endoscope apparatus Block diagram of charge coupled device solid-state imaging device Timing chart of sensitivity control pulse and horizontal transfer pulse Explanatory drawing which shows the relationship between charge amplification part applied voltage and sensitivity amplification factor regarding CCD sensitivity Block diagram of CCD drive circuit Driver equivalent circuit diagram Explanatory diagram of bias circuit Explanatory drawing which shows the change of the signal level in the circuit of FIG. Waveform diagram of sensitivity control pulse before and after clamping Explanatory diagram showing changes in amplitude of sensitivity control pulse by variable voltage control CCD drive timing chart in special light mode CCD drive timing chart in normal light mode Graph showing CCD sensitivity characteristics (monitor output signal) Graph showing CCD sensitivity characteristics (S / N characteristics) Plan view showing the configuration of the RGB rotation filter Graph showing spectral characteristics of light source device in fluorescence observation Graph showing spectral characteristics of fluorescence and reflected light in fluorescence observation

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Endoscope apparatus 2 ... Endoscope 3 ... Processor 4 ... Signal processing apparatus 5 ... Light source device 7 ... Power supply device 19 ... CCD
31 ... CCD drive circuit 32 ... Sensitivity control circuit 74 ... Driver 78, 79 ... Voltage regulator 90 ... Clamp circuit φCMD ... Sensitivity control pulse
Agent Patent Attorney Susumu Ito

Claims (5)

In an endoscope apparatus including a solid-state imaging device capable of changing sensitivity by applying a voltage signal, and a power source that outputs a plurality of voltage values having different polarities,
Receiving a signal based on the image of the result of photometry captured by the solid-state imaging device, the control signal for generating a control signal for the positive and negative polarity relative to the positive polarity side voltage and a negative polarity side reference level and a voltage output from the power supply Generating means;
And outputs as the sensitivity control signal for controlling the sensitivity of the basal level is fixed to the reference level the solid elements of the positive and negative and the control signal is shifted to the high potential side while maintaining the amplitude due to the polarity of the control signal An endoscope apparatus comprising: a sensitivity control signal output unit.   The endoscope apparatus according to claim 1, wherein the control signal generation unit includes a voltage regulator that varies at least one of the positive-side voltage and the polarity-side voltage.   The endoscope apparatus according to claim 2, wherein the voltage regulator varies an output voltage according to a signal based on the photometric result.   The endoscope apparatus according to claim 1, wherein the sensitivity control signal output unit includes a diode clamp circuit.   The endoscope apparatus according to claim 1, wherein the solid-state imaging device is a solid-state imaging device whose sensitivity can be varied by amplifying a charge generated by applying the voltage signal.

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