JPH10305004A - Fluorescent observation device for living body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a distance between an endoscope and a living body proper and to miniaturize an image pickup part by introducing a wavelength selecting optical element to the endoscope, taking prescribed wavelength light out of fluorescent light led from the living body, picking up its image and amplifying the image pickup output with an amplification factor corresponding to that output. SOLUTION: The top end of endoscope 10 is arranged near a fluorescent observation part in the living body, and the tissue of living body is irradiated with white light from a light source lamp 21. Thus, the observed image of living body is formed through an observation window 18 by an objective optical system 15 and led into an image pickup part 30. This image is displayed through a CCD camera 31 and a video switcher 40 onto a monitor 50. Next, a filter 22 for exciting light is set, the tissue of living body is irradiated with exciting light and the fluorescent light from the tissue of living body at that time is captured by a CCD camera 41, amplified and outputted through the video switcher 40 onto the monitor 50. The amplification factor inside the CCD camera 41 at such a time is controlled corresponding to the image pickup output so that the proper fluorescent observation of living body tissue is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for observing fluorescence of a living body, and more particularly, to irradiating excitation light from the end of an endoscope to capture a fluorescence observation image of the living body incident from the end of the endoscope. The present invention relates to a fluorescent observation apparatus for a living body, which displays on a display device.

[0002]

2. Description of the Related Art When a living tissue is irradiated with light having a wavelength of 420 to 480 nm, a fluorescent substance (for example, NA) in the living tissue is irradiated.
DH, FMN, etc.). In recent years, the correlation between fluorescence generated from living tissue and disease has been clarified. That is, the normal part of the living tissue emits green (G) fluorescence which is considerably stronger than the fluorescence of the red (R) region, and the tumor part (abnormal part) of the living tissue has G fluorescence relative to the normal part. It has been found that the strength decreases. Based on these facts, medical examinations are often performed to determine the presence or absence of a disease by performing fluorescence observation of a living tissue using a fluorescence observation device including an endoscope, a light source unit, and an imaging unit.

In fluorescence observation of a living tissue, a distal end of an endoscope is inserted into a living body, and excitation light is applied to the living tissue from the distal end. Then, the image of the living body at that time is
An image is formed by an objective optical system provided at the distal end of the endoscope, introduced into an imaging unit connected to an eyepiece, and only G fluorescent components are extracted by a filter. The image is taken and displayed on the screen of the monitor.

However, in such a configuration of the fluorescence observation apparatus, when the distance (observation distance) between the end of the endoscope and the living body changes, the intensity of the fluorescence from the living body incident on the objective optical system changes. Therefore, it is difficult to properly determine the presence or absence of a disease based on the intensity of the fluorescence.

[0005] Therefore, a fluorescence observation apparatus having the configuration shown in FIG. 10 has been proposed. In FIG. 10, a first CCD camera 31 for normal observation is provided on the optical axis of the eyepiece 16 in the imaging unit 30 of the fluorescence observation apparatus.
A second C for fluorescence observation is arranged alongside the first CCD camera 31.
A CD camera 5 and a third CCD camera 6 are provided. A reflection mirror 32 is provided between the eyepiece 16 and the first CCD camera 31 so as to be freely inserted into and removed from the optical axis of the eyepiece 16. This reflecting mirror 32
At the time of fluorescence observation, the light intersects the optical axis of the eyepiece 16 at an angle of 45 ° and reflects the light from the eyepiece 16 at an angle of 90 °.

On the optical axis of the light reflected by the reflecting mirror 32, the dichroic mirror 1 is installed at an angle of 45 ° with respect to the optical axis. The dichroic mirror 1 reflects only green light (G light) and transmits light of other wavelengths. A dichroic mirror 2 is provided on an optical path of light transmitted through the dichroic mirror 1. The dichroic mirror 2 reflects only red light (R light) and transmits light of other wavelengths.

[0007] The light reflected by the dichroic mirror 1 is transmitted to the dichroic mirror 1 and the second CCD camera 5.
Amplified by an image intensifier (hereinafter, referred to as “II”) 34a installed between
It is introduced into the CCD camera 5. On the other hand, the light reflected by the dichroic mirror 2 is an I.I.34 set between the dichroic mirror 2 and the third CCD camera 6.
b, and is introduced into the third CCD camera 6. Accordingly, the second CCD camera 5 captures the G light component of the fluorescence observation image, and the third CCD camera 6 captures the R light component of the fluorescence observation image.
The light component is imaged.

The second CCD camera 5 and the third CCD camera 6 are connected to an R / G ratio processor 7 via a cable, and the R / G ratio processor 7 is connected to a monitor 50 via a video switching device 40. It is connected. Each pixel of the second CCD camera 5 and each pixel of the third CCD camera 6 are associated with each other. The second CCD camera 5 and the third CCD camera 6 input the output of each pixel to the R / G ratio processing device 7.

The R / G ratio processor 7 corrects the distance of the fluorescent image data based on the output of the second CCD camera 5 and the output of the third CCD camera 6 by the following method. Here, FIG. 11 is a graph showing the distribution of each wavelength component included in the fluorescence observation image (however, the vertical axis in FIG. 11 shows the output of the CCD corresponding to the intensity of each wavelength component). FIG. 11 shows an example of a fluorescence distribution included in a fluorescence observation image of a normal portion of a living tissue and a fluorescence distribution included in a fluorescence observation image of an abnormal portion of the living tissue. Both the fluorescence distribution of the normal region and the fluorescence distribution of the abnormal distribution have a characteristic that the intensity in the G light band is larger than the intensity in the R light band. However, the ratio of the intensity in the G light band to the intensity in the R light band is larger in the normal part than in the abnormal part. For example, in FIG. 11, the ratio between the intensity at an arbitrary wavelength α in the G light band and the intensity at an arbitrary wavelength β in the R light band is shown for a normal part and an abnormal part, respectively. For the site, α: β = 4:
On the other hand, for an abnormal site, α: β =
It is about 2: 1. On the other hand, the magnitude relationship of the ratio does not change depending on the distance between the distal end portion of the endoscope 10 and the living tissue. Considering these points, when the ratio between the intensity of the G light (band) and the intensity of the R light (band) is large, it is determined that the region is normal, and when the ratio is small, it is determined that the region is abnormal. It is possible.

In view of the above, the R / G ratio processing device 7 outputs the pixel output (G light component) of the second CCD camera 5 and the pixel output of the third CCD camera 6 corresponding to the output of this pixel.
(R light component), the ratio between them (G / R ratio) is calculated. When the G / R ratio is large, the display color of the pixel of the monitor 50 corresponding to these pixels is determined to be green (G). On the other hand, when the G / R ratio is small, the display color of the pixel of the monitor 50 corresponding to these pixels is determined to be red (R). In this way, the R / G ratio processing device 7
G for each pixel of the D camera 5 and the third CCD camera 6
The image data is generated based on these determination results, converted into a video signal, and input to the monitor 50 via the video switching device 40. Thereby, the fluorescence observation image of the living body whose distance has been corrected is displayed on the screen of the monitor 50.

[0011]

However, the conventional fluorescence observation apparatus has the following problems. In other words, the conventional fluorescence observation apparatus installs two II.34a and II.34b in the imaging unit 30 for fluorescence observation, and
The configuration in which the CCD camera 5 and the third CCD camera 6 are installed is adopted. For this reason, there has been a problem that the imaging unit 30 is increased in size and weight, and the operability of the endoscope 10 is reduced. In addition, there is a problem that the cost of the fluorescence observation apparatus increases due to an increase in the number of components of the fluorescence observation apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and enables fluorescence observation of a living tissue to be performed properly regardless of the distance between the distal end of an endoscope and a living body. It is an object of the present invention to provide a fluorescence observation apparatus for a living body that can reduce the size of an imaging unit.

[0013]

The present invention employs the following configuration to solve the above-mentioned problems. That is, the invention according to claim 1 is an endoscope that irradiates excitation light from a distal end portion and introduces fluorescence from a living body excited by the excitation light from the distal end portion, and the endoscope introduced to the endoscope. A wavelength selection optical element that extracts only a light component of a predetermined wavelength from the fluorescence, an imaging element that captures an image of the living body including the light component of the predetermined wavelength that is extracted by the wavelength selection optical element, and an imaging element of the imaging element A fluorescent light of a living body, comprising: an amplifier for amplifying an output; and an auto gain controller for controlling an output of the amplifier by operating an amplification factor of the amplifier according to a magnitude of an output of the imaging device. Observation device.

According to the first aspect of the present invention, the fluorescence observation image of the living body is obtained by extracting only a light component of a predetermined frequency by the wavelength selection optical element and imaging by the imaging element. Subsequently, the output of the image sensor is amplified by the amplifier. At this time, the auto gain controller operates the amplification factor of the amplifier in accordance with the output of the imaging device, and sets the output of the amplification factor, that is, the output of the imaging device amplified by the amplifier, to a predetermined appropriate value. To control. Thus, the output signal of the image sensor amplified to an appropriate value is output from the amplifier.

Here, the wavelength selection optical element includes an optical filter such as a dichroic mirror or a band-pass filter. According to a second aspect of the present invention, the auto gain controller according to the first aspect increases the amplification factor of the amplifier when the output of the image sensor is small, and increases the amplification factor of the amplifier when the output of the image sensor is small. Is specified by reducing

According to a third aspect of the present invention, the automatic gain controller according to the first aspect specifies the gain by operating the amplification factor of the amplifier in a plurality of stages. This claim 3
According to the invention, the amplification factor of the amplifier can be linearly operated according to the output of the image sensor.

According to a fourth aspect of the present invention, the automatic gain controller according to the first aspect operates the amplification factor of the amplifier when a peak value of an output of the image pickup device becomes larger than a reference peak value, thereby specifying the gain. It was done.

According to a fifth aspect of the present invention, the automatic gain controller according to the first aspect of the present invention specifies the gain by operating the amplification factor of the amplifier for each output of one frame of the image sensor.

According to a sixth aspect of the present invention, there is provided an endoscope for irradiating excitation light from a distal end portion and introducing fluorescence from a living body excited by the excitation light from the distal end portion, and the endoscope is introduced into the endoscope. A wavelength selection optical element that extracts only a light component of a predetermined wavelength from the fluorescence, an image intensifier that amplifies the light component of a predetermined wavelength that is extracted by the wavelength selection optical element, and an image intensifier that is amplified by the image intensifier An image sensor for capturing an image of a living body composed of light components having a predetermined wavelength, and a voltage applied to the image intensifier in accordance with the magnitude of the output of the image sensor. And a control device for controlling the amplification factor of the living body.

According to the sixth aspect of the present invention, the control device controls the voltage applied to the image intensifier, whereby the amplification factor of the image intensifier is controlled. Therefore, the output of the image intensifier changes, and the output of the image sensor changes. At this time, the control device controls the voltage applied to the image intensifier so that the output of the image sensor falls within an appropriate range where the distance correction has been performed.

According to a seventh aspect of the present invention, the control device according to the sixth aspect specifies the voltage applied to the image intensifier by reducing the voltage applied to the image intensifier when the output of the image sensor is large. .

According to an eighth aspect of the present invention, the control device according to the sixth aspect specifies the voltage applied to the image intensifier by increasing the voltage when the output of the image sensor is small. .

According to a ninth aspect of the present invention, the light having the predetermined wavelength according to the first or sixth aspect is a light having a wavelength of 500 nm to 570 nm.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

[0025]

Embodiment 1 [Configuration of Fluorescence Observation Apparatus] FIG. 1 is a diagram showing the internal configuration of a fluorescence observation apparatus according to Embodiment 1 of the present invention. In FIG. 1, a fluorescence observation apparatus generally includes an endoscope 10 and a light source unit 20 that supplies the endoscope 10 with light for subject irradiation.
And an imaging unit 30 that captures an image captured by the endoscope 10. A monitor 50 that displays the captured image is connected to the imaging unit 30 via the video switching device 40.

The endoscope 10 includes a cord-shaped insertion section 11 having a distal end forming the distal end of the endoscope 10, an operation section 12 having one end connected to the base end of the insertion section 11, and an operation section 12 having And a cord-shaped light guide connecting pipe 13 extending from an outer peripheral surface of the light guide connecting pipe 13. An eyepiece 12 is provided at the other end of the operation unit 12.
The endoscope 10 and the imaging unit 30 are detachably connected by the eyepiece unit 12a. A connector 13a is provided at the end of the light guide connecting pipe 13.
The endoscope 10 and the light source unit 20 are detachably connected by the connector 13a.

An image guide fiber bundle 14 is disposed inside the endoscope 10 from the distal end of the insertion section 11 to the other end of the operation section 12. The end face of the image guide fiber bundle 14 on the insertion section 11 side is an incident end face, and the end face on the operation section 12 side is an emission end face. An objective optical system 1 for forming an image of a subject on the incident end face of the image guide fiber bundle 14 is provided at the tip of the insertion section 11.
5, and an observation window 18 are built in. On the other hand, eyepiece 1
2a, an eyepiece 16 for observing an image emitted from the exit end face of the image guide fiber bundle 14 is provided.
Is built-in. However, the eyepiece 16 moves to the position of 0 diopters when the imaging unit 30 is connected to the eyepiece 12a. As described above, one end of the insertion portion 11
Light from a subject located in front of (the end of the endoscope 10) enters the endoscope through the observation window 18 and enters the objective optical system 15
Image guide fiber bundle 1
The light is transmitted to the eyepiece section 12 a by 4 and is introduced into the imaging section 30 through the eyepiece lens 16.

The connector 1 is provided inside the endoscope 10.
A light guide fiber bundle 17 is provided from the end of 3a to the tip of the insertion portion 11. The end face on the connector 13a side of the light guide fiber bundle 17 is an incident end face, and the end face on the insertion section 11 side is an emission end face. And this light guide fiber bundle 17
When the connector 13 a is connected to the light source unit 20, the incident end face is disposed toward the inside of the light source unit 20. On the other hand, the exit end face of the light guide fiber bundle 17 is arranged in parallel with the objective optical system 15 described above, and an illumination window 19 is provided in front of the exit end face.

Inside the light source unit 20, a light source lamp 21 using a xenon lamp is disposed at a position facing the incident end face of the light guide fiber bundle 17. Thus, when the illumination light is emitted from the light source lamp 21, the illumination light is converged and incident on the incident end face of the light guide fiber bundle 17. Then, the illumination light passes through the inside of the light guide fiber bundle 17 and is radiated from the exit end face thereof to the outside via the illumination window 19.

The illumination light path between the light source lamp 21 and the incident end face of the light guide fiber bundle 17 is
An excitation light filter 22 that transmits only light in the wavelength range of 20 nm to 480 nm (excitation light: B light) is disposed so as to be freely inserted into and removed from the illumination light path by a solenoid (not shown).
That is, the excitation light filter 22 is retracted outside the illumination light path during normal observation, and inserted into the illumination light path during fluorescence observation. Thus, only the B light transmitted through the excitation light filter 22 is incident on the incident end face of the light guide fiber bundle 17 during the fluorescence observation. And
When the B light is applied to a living tissue as a subject, a normal portion of the living tissue emits fluorescence (green light: G light) in a wavelength region of about 500 nm to 570 nm. The fluorescence emitted at this time is transmitted to the observation window 18 and the objective optical system 15.
Is incident on the incident end face of the image guide fiber bundle 14 through the optical fiber.

An imaging optical system 30a, which constitutes a relay optical system together with the eyepiece lens 16, is disposed inside the image pickup section 30, and a light beam from the imaging optical system 30a forms an image for normal observation at a position where an image is formed. CCD camera 31 is disposed. Further, a CCD camera 41 for fluorescence observation is arranged in parallel with the CCD camera 31. The CCD camera 31 and the CCD camera 41 are connected to a video switching device 40 connected to a monitor 50, respectively.
One of the video signal output from the CD camera 31 and the video signal output from the CCD camera 41 is supplied to the monitor 50 by the video switching device 40. The CCD camera 31 and the CCD camera 41 have the same configuration.

Between the CCD camera 31 for normal observation and the eyepiece 16, a reflecting mirror 32 which is inserted on the optical axis of the eyepiece 16 to bend the optical axis of the eyepiece 16 is detachably inserted. is set up. The reflection mirror 32 is retracted from the optical path between the eyepiece lens 16 and the imaging optical system 30a during normal observation, and is centered on a rotation axis provided at the edge on the eyepiece lens 16 side during fluorescence observation. It rotates by a predetermined angle and intersects the optical axis of the eyepiece 16 at an angle of 45 °, and the optical axis of the eyepiece 16
Bend at an angle of ゜.

On the optical axis bent by the reflecting mirror 32, a dichroic mirror 33 is arranged at an angle of 45 ° with respect to the optical axis.
The dichroic mirror 33 constitutes the wavelength selection optical element of the present invention, and reflects only light (G light) in a wavelength region of about 500 nm to 570 nm and transmits light in other wavelength regions.

An image forming optical system 33a is arranged on the optical path of the light reflected by the dichroic mirror 33, and an image intensifier (hereinafter referred to as an image intensifier) is provided at a position where the light beam is converged by the image forming optical system 33a. , "I.
I. ") 34 is installed. This II.34
Is to greatly amplify the light reflected by the dichroic mirror 33. The optical path length from the eyepiece 16 to the CCD camera 31 and the optical path length from the eyepiece 16 to II.34 are set to the same length.

FIG. 2 is a block diagram of the II.34. FIG.
In the first embodiment, II.34 includes a first fiber plate 35 having a photocathode 35a and a microchannel plate.
(Hereinafter, referred to as “MCP”) 36 and a second fiber plate 37 having a fluorescent screen 37a. This I.
According to I.34, when an image of a living body is formed on the surface of the first fiber plate 35 by the imaging optical system 33a,
The first fiber plate 35 decomposes this image into pixels and transmits it to the photocathode 35a. The photoelectric surface 35a converts the transmitted image, that is, the optical image into an electronic image. Electrodes (not shown) are provided on both end surfaces of the MCP 36, and a predetermined voltage is applied between the electrodes. Thereby, the photocathode 35
The electronic image converted at a is amplified when passing through the MCP 36, hits the fluorescent screen 37a, and is again converted to an optical image. Then, this optical image is displayed on the second fiber plate 3.
7 to the opposite side. In this way, II.34
The fluorescence observation image amplified by the I.I.34 is subjected to a fluorescence observation CC by an imaging optical system 39 arranged on the exit side of II.34.
It is relayed to the D camera 41.

[Configuration of CCD Camera] FIG. 3 is a functional block diagram of the CCD camera 41. In FIG. 3, CC
The D camera 41 includes a CCD (corresponding to an image sensor) 51 and a CC
An amplifier 53 for amplifying the output from D51;
Auto gain controller that controls the amplification factor
AGC 54), and a video signal conversion circuit 55 for converting the output of the amplifier 53 into a video signal.

The CCD 51 is an area sensor for picking up an image of the exit end face of the image guide fiber bundle 14, and is arranged substantially perpendicular to the optical axis of the imaging optical system 39. Thus, the imaging optical system 39 allows C
The light that forms an optical image formed on the imaging surface of the CD camera 41 is
The light enters each pixel (image pickup pixel) and is stored as a charge.
Subsequently, the electric charge accumulated in each pixel is appropriately transferred in a horizontal direction or a vertical direction, output as an output signal of the CCD 51, and input to the amplifier 53. As shown in FIG. 5A, the output signal of the CCD 51 has such a characteristic that it becomes lower in accordance with the amount of received light with reference to the power supply voltage + Vcc.

The amplifier 53 amplifies the input from the CCD 51 at a predetermined amplification rate and inputs the amplified signal to the video signal conversion circuit 55. The AGC 54 controls the amplification factor of the amplifier 53 in accordance with the magnitude of the output signal of the CCD 51 to make the output level of the amplifier 53 constant. That is, the AGC 54
When the input level from the CD 51 is larger than a predetermined reference value (when the distance between the tip of the endoscope 10 and the living tissue to be observed is shorter than an appropriate distance, or the amount of excitation light applied to the living tissue) Is larger than the appropriate amount), the amplifier 53
To reduce the amplification factor. On the other hand, when the input level from the CCD 51 is smaller than a predetermined reference value (when the distance between the distal end portion of the endoscope 10 and the living tissue to be observed is longer than an appropriate distance, or when the excitation light is applied to the living tissue). Is smaller than the appropriate amount), the amplification factor of the amplifier 53 is increased.

The video signal conversion circuit 55 receives the output of the amplifier 53 and converts the output to a video signal (NTSC signal).
And transfer it to the video switching device 40. FIG. 4 is a circuit diagram showing a specific circuit configuration of the amplifier 53 and the AGC 54 described above. As shown in FIG. 4, the amplifier 53 includes a pair of operational amplifiers U1B and U2B and an output control circuit 53.
a, an output control circuit 53b, and other circuit elements.

The output voltage from the CCD 51 is applied to the inverting input terminal of the operational amplifier U1B via the resistor R10. On the other hand, a reference voltage _Vref1 generated by dividing the power supply voltage + Vcc by the variable resistor R17 is supplied to a non-inverting input terminal of the operational amplifier U1B.
It is applied via a resistor R14. Further, a feedback resistor R9 is connected between the output terminal and the inverting input terminal of the operational amplifier U1B. The inverting amplifier configured as described above outputs an output voltage Vz having a relationship represented by the following equation (1) with respect to an input voltage Vin from the CCD 51:
Output to the output terminal of the operational amplifier U1B.

Vz = V _ref1 (1 + R9 / R10) −R9 / R10 · Vin (1) A connection point Z between the output terminal of the operational amplifier U1B and the feedback resistor R9.
Are grounded via a CR series circuit of the capacitor C1 and the discharging resistor R16. This CR series circuit differentiates the output voltage Vz of the operational amplifier U1B and outputs a signal voltage Vx whose center of amplitude is shifted to 0 V to a discharge resistor R1.
6 at the connection point X.

The connection point X generating the signal voltage Vx is:
The operational amplifier U2B is connected to the inverting input terminal of the operational amplifier U2B via the resistor R11, and is connected to the inverting input terminal of the operational amplifier U1A constituting the output control circuit 53a via the resistor R4, and constitutes the output control circuit 53b.
It is connected to the inverting input terminal of A via a resistor R12. The connection point X is further connected to a positive input terminal of a buffer U3B forming a positive circuit of the AGC 54, and a buffer U5 forming a negative circuit of the AGC 54.
A is connected to the positive input terminal of A.

The inverting input terminal of the above-described operational amplifier U2B has an output control circuit 5 in addition to the resistor R11 connected to the connection point X.
A resistor R6 forming 3a and a resistor R20 forming an output control circuit 53b are connected. Also, this operational amplifier U
The ground resistor R15 is connected to the non-inverting input terminal 2B. Further, a feedback resistor R7 is connected between the output terminal and the inverting input terminal of the operational amplifier U2B. The connection point C between the output terminal of the operational amplifier U2B and the feedback resistor R7 is connected to the video signal conversion circuit 55.

Since the non-inverting input terminal of the operational amplifier U2B is grounded, a voltage is generated at the output terminal of the operational amplifier U2B such that the potential of the inverting input terminal, which has an imaginary short circuit with the non-inverting input terminal, becomes 0V.

Therefore, when both output control circuits 53a and 53b are inactive (that is, output control circuit 5 via resistor R6).
3a, the current Iα flowing into the output control circuit 53b via the resistor 20 is zero, and the potential difference between the connection point X and the inverting input terminal of the operational amplifier U2B is considered. Current caused by
Iγ is represented by the following equation (2).

Iγ = Vx / R11 = I _R7 γ = −V _C2 / R7 (2) where I _R7 γ is a current flowing through the feedback resistor R7 due to Vx, and V _C2 is a current due to Vx. This is a voltage generated at the output terminal of the operational amplifier U2B. Incidentally, i?, The polarity of I _R7 gamma, when flowing from the left of FIG. 4 to the right (when Vx positive) is positive is, when flowing from right to left (if Vx is negative) is negative.

Therefore, the potential of the connection point C (input voltage to the video signal conversion circuit 55) V _C at this point is obtained by inverting and amplifying Vx as shown in the following equation (3). V _C = V _C2 = −R7 / R11 · Vx (3) On the other hand, when the output control circuit 53a attempts to lower the potential at the connection point C beyond a predetermined negative reference value, the output control circuit 53a determines the decrease. This is a circuit for suppressing the rate (lowering the amplification rate of the amplifier 53). The output control circuit 53a includes the resistor R4 and the operational amplifier U1A, the ground resistor R8 connected to the non-inverting input terminal of the operational amplifier U1A, and the operational amplifier U1.
Inverting one end to the input terminal is connected resistors 1A R2, supplies a reference voltage -V _R2 to the other end of the resistor R2 to the power supply voltage -Vcc divide variable resistor R1, the inverting input terminal of the operational amplifier U1A and an output terminal And a feedback resistor R3 connected in series with a diode D2 for rectification (that is, the direction of the current flowing through the feedback resistor R3 is regulated in a direction from the inverting input terminal to the output terminal). A resistor R5 connected in series between the anodes of the diodes D1 and D2 for rectification (that is, a current flows only in the direction from the output terminal to the inverting input terminal) and the inverting input terminal of the operational amplifier U2B are connected in parallel. And a resistor R6 and a bypass FET Q1 whose source and drain are connected in parallel to the resistor R5. Note that the resistance values of the resistors R2 and R4 are the same.

Here, a voltage is applied to the inverting input terminal of the operational amplifier.
Since no current flows, the current Iδ flowing through the resistor R4 and the resistance R
2, the current Iε flowing through the diode D1,
The sum of the currents Iθ flowing through the resistor R3 is zero. Therefore,
If the potential Vx at the connection point X is + V_{R Two}, The current Iδ
And the current Iε are in opposite directions and have the same amount, the current Iε
Both η and the current Iθ become zero. Therefore, the operational amplifier
The potential V of the output terminal of U1A _Y1Is grounded, non-inverted
Inversion that has an imaginary short relation to the input terminal
It becomes 0V which is the same as the potential of the input terminal. In addition, the power
Vx is + V_R2At lower levels, the absolute value of the current Iδ becomes
is smaller than the absolute value of ε.
So that the current Iη flows out of the output terminal of the operational amplifier U1A
become. However, even in this case, the forward
A voltage drop occurs in the connected diode D1.
Because there is no, the potential V of the output terminal of the operational amplifier U1A_Y1Is 0
V. As described above, the output of the operational amplifier U1A
Input terminal potential V_Y1Is 0V, the voltage flowing through the resistor R6
The current Iα remains at zero, affecting the potential at node C.
I do not.

[0049] On the contrary, if larger than the connection point X of the potential Vx is + V _R2, the absolute value of the current Iδ is greater than the absolute value of the current Aiipushiron, current Iθ represented by the following formula (4) The current flows into the output terminal of the operational amplifier U1A via the resistor R3 and the diode D2.

[0050] Iθ = Iδ-Iε = Vx / R4-V R2 / R2 ... (4) Therefore, as shown in the following formula (5), only the voltage drop V _R3 at the potential 0V of the inverting input terminal resistor R3 A reduced voltage V _Y1 is generated at the output terminal of the operational amplifier U1A.

[0051] _{V Y1 = -V R3 = - (} Vx / R4-V R2 / R2) · R3 ... (5) connection point of the thus with diode D2 and the resistor R5 Y
When the potential V _{Y1 of} 1 becomes lower than 0 V, the resistance R6
As long as the bypass FET Q1 is OFF, the following equation (6)
4 flows from the right side to the left side in FIG.

Iα = V _Y1 / (R5 + R6) = − (Vx / R4− _VR2 / R2) · R3 / (R5 + R6) (6) At this point, the polarity of Vx is positive, and the connection point X and the operational amplifier U2B Of the resistor R7 due to the potential difference between the
The current I _R7 gamma flowing, flows from the left side of FIG. 4 at the value represented by the above formula (3) to the right. This current I
The current I _R7 α having the same amount as the current I α flows from the right side to the left side of the resistor R7 in a form superimposed on _R7 γ. To maintain the potential of the operational amplifier U2B at 0 V by compensating for the voltage drop at the resistor R7 due to the current I _R7 α, the voltage V _{C1 represented} by the following equation (7) is superimposed on the output terminal of the operational amplifier U2B. Must be generated.

[0053] _{V C1 = -R7 / (R5 +} R6) · V Y1 = (Vx / R4-V R2 / R2) · R3 · R7 / (R5 + R6) ... (7) After all, the potential of the connection point C at this point (video The input voltage to the signal conversion circuit 55) V _C is obtained by superimposing the voltage V _C1 on the voltage V _C2 as shown in the following equation (8).

[0054] _{V C = V C1 + V C2} = -R7 / (R5 + R6) · V Y1 -R7 / R11 · Vx = (Vx / R4-V R2 / R2) · R3 · R7 / (R5 + R6) -R7 / R11 · Vx ... 8 this equation (8), when Vx exceeds + V _R2, the output control circuit 53a reduces the amplification factor of the amplifier 53, to the negative side of the input voltage to the video signal conversion circuit 55 It means to suppress the increase.

In this output control circuit 53a, the variable
Reference voltage + V by adjusting resistor R1 _R2Some freedom
Since it can be set, the operation start point (A
The voltage V at which the amplification factor of the amplifier 53 changes_C) To some extent
Can be set.

On the other hand, the output control circuit 53b suppresses the rate of increase (decreases the amplification rate of the amplifier 53) when the potential of the connection point C exceeds the predetermined positive reference value. Circuit. This output control circuit 53b
The resistor R12 and the operational amplifier U2A described above, and the ground resistor R2 connected to the non-inverting input terminal of the operational amplifier U2A.
2, reversing resistance R18 having one end connected to the input terminal, the power supply voltage + Vcc to divide supplies a reference voltage + V _R2 to the other end of the resistor R18 variable resistor R21 of the operational amplifier U2A, an inverting input terminal of the operational amplifier U2A A feedback resistor R13 connected in series with the output terminal and a rectifier (that is, feedback resistor R13)
The direction of the current flowing through the feedback resistor R is regulated in the direction from the output terminal to the inverting input terminal.
13 and a diode D3 for rectification (that is, a current flows from the inverting input terminal to the output terminal) connected in parallel with the diode D4 and connected in series between the cathode of the diode D4 and the inverting input terminal of the operational amplifier U2B. Resistor R19 and resistor R20, and a bypass FET Q2 whose source and drain are connected in parallel to the resistor R19.
Is composed of Note that the resistance values of the resistors R12 and R18 are the same.

[0057] Here, as in the case of the output control circuit 53a, if the potential Vx of the node X is -V _R2, potential V _Y2 of the output terminal of the operational amplifier U2A becomes 0V. Further, when the potential Vx of the node X is exceeds the -V _R2, a current flows to the diode D3, so no voltage drop in the diode D1, the potential V _Y2 of the output terminal of the operational amplifier U2A is 0
V. As described above, when the potential _VY2 of the output terminal of the operational amplifier U1A is 0 V, the current Iβ flowing through the resistor R20 remains zero, and the potential of the connection point C is not affected.

On the other hand, the potential Vx at the connection point X is -V _R2
, A current flows from the output terminal of the operational amplifier U1A to the connection point X via the diodes D4 and R13, and as shown in the following equation (9), the potential of the inverting input terminal becomes 0 V and the resistance R13 voltage drop V _R3 higher by the value of the voltage V _Y2 in is at the output terminal of the operational amplifier U2A.

V _Y2 = V _R3 = (Vx / R12−V _R2 / R18) · R13 (9) In this way, when the potential V _{Y2 at} the connection point Y2 between the diode D4 and the resistor R19 becomes higher than 0V, As long as the bypass FET Q2 is OFF, the current Iβ shown in the following equation (10) flows through the resistor R20 from the left side to the right side in FIG.

[0060] polar _{Iβ = V Y2 / (R19 +} R20) = (Vx / R12-V R2 / R18) · R13 / (R19 + R20) ... (10) Vx at this time is negative, the connection point X and the operational amplifier U2B Due to the potential difference between the inverting input terminal and the resistor R7
The current I _R7 gamma flowing, flows from the right side of FIG. 4 at the value represented by the above formula (3) to the left. This current I
A current I _R7 β of the same amount as the current I β flows from the left side to the right side of the resistor R7 in a form superimposed on _R7 γ. To compensate for the voltage drop of the resistor R7 due to the current I _R7 β and maintain the potential of the inverting input terminal of the operational amplifier U2B at 0 V,
The voltage V _{C3 represented} by the following equation (11) must be generated in a superimposed manner at the output terminal of the operational amplifier U2B.

[0061] _{V C3 = -R7 / (R19 +} R20) · V Y2 = - (Vx / R12-V R2 / R18) · R13 · R7 / (R19 + R20) ... (11) Finally, the potential of the connection point C at this point ( The input voltage to the video signal conversion circuit 55) V _C is obtained by superimposing the voltage V _C1 on the voltage V _C3 as shown in the following equation (12).

[0062] _{V C = V C2 + V C3} = -R7 / (R19 + R20) · V Y2 -R7 / R11 · Vx = - (Vx / R12-V R2 / R18) · R13 · R7 / (R19 + R20) -R7 / R11 · Vx ... (12) equation (12), when Vx falls below -V _R2 is an output control circuit 53b reduces the amplification factor of the amplifier 53, the input voltage to the video signal conversion circuit 55 to the positive side Means to suppress the increase in

In this output control circuit 53b, a variable
Reference voltage -V by adjusting resistance R1 _R2Some freedom
Since it can be set, the operation start point (A
The voltage V at which the amplification factor of the amplifier 53 changes_CSome freedom)
Can be set to

The positive side circuit of the AGC 54 is configured so that the output voltage of the amplifier 53 (potential at the connection point C), that is, the peak value of the input voltage to the video signal conversion circuit 55 is a predetermined reference value (when the operational amplifier U1A operates). This is a circuit for further lowering the amplification factor of the amplifier 53 by turning on the bypass FET Q1 of the output control circuit 53a when the voltage falls below the voltage value of the output control circuit 53a. Similarly, the negative circuit of the AGC 54 includes an output voltage of the amplifier 53 (potential of the connection point C),
That is, when the peak value of the input voltage to the video signal conversion circuit 55 exceeds a predetermined reference value (a value higher than the voltage value when the operational amplifier U2A operates), the bypass FET Q2 of the output control circuit 53b is turned off. This is a circuit for further reducing the amplification factor of the amplifier 53 by turning it on. Since the positive side circuit and the negative side circuit have almost the same configuration, the positive side circuit will be described as an example, and the difference between the negative side circuit and the positive side circuit will be described.

As described above, the positive input terminal of the buffer U3B of the positive circuit is connected to the connection point X, and the output terminal of the buffer U3B is connected to the anode of the diode D5. The cathode of the diode D5 is connected to the positive input terminal of the buffer U3A via a signal line, and one end of a time constant circuit composed of a grounded capacitor C2 and a resistor R25 is connected to a signal line connecting them. Have been. The negative input terminal of the buffer U3B, the negative input terminal of the buffer U3A, and the output terminal of the buffer U3A are connected to each other by a signal line. Further, an output terminal of the buffer U3A is connected to a negative input terminal of a comparator (for example, a junction FET) U4A via a resistor R23. The positive input terminal of the comparator U4A is connected to a constant voltage source via a resistor R24 and a variable resistor R26, and the output terminal of the comparator U4A is connected to the gate of the bypass FET Q1.

According to such a positive side circuit, when the polarity of the potential Vx at the connection point X is positive, the potential Vx
When the voltage is input to 3B, the capacitor C2 starts accumulating a positive charge, and finally holds a positive peak value of the potential Vx at the connection point X. Accordingly, the positive peak value of the potential Vx at the connection point X is input to the comparator U4A via the buffer U3A and the resistor 23. On the other hand, a constant voltage source, a variable resistor R26, and a resistor 2 are connected to the positive input terminal of the comparator U4A.
4, a positive reference voltage is input. As a result, the comparator U4A outputs Hi only when the positive peak value of the potential Vx at the connection point X is larger than the positive reference voltage.
Output gh signal.

The above-described bypass FET Q1 is connected to the comparator U
When the High signal from 4A is applied to the gate, the gate is turned on, and the both ends of the resistor R5 are short-circuited. As a result, R5 disappears from the above equation (6) and the current Iα flowing through the resistor R5
Increases as shown by the following equation (6 ′).

Iα = V _Y1 / R6 = − (Vx / R4− _VR2 / R2) · R3 / R6 (6 ′) Under the influence, the above-described voltage V _C1 is represented by the following equation (7 ′). To change. _{V C1 = -R7 / R6 · V} Y1 = (Vx / R4-V R2 / R2) · R3 · R7 / R6 ... (7 ') after all, the connection point C at this point potential (to video signal conversion circuit 55 input voltage) V _C, as shown in the following formula (8 '), appear to decrease than during OFF of the bypass FET Q1.

[0069] _{V C = V C1 + V C2} = -R7 / R6 · V Y1 -R7 / R11 · Vx = (Vx / R4-V R2 / R2) · R3 · R7 / R6-R7 / R11 · Vx ... (8 ') As a result, the amplification factor of the amplifier 53 further decreases, and the increase of the input voltage to the video signal conversion circuit 55 on the negative side is further suppressed.

The resistor R25 forming the time constant circuit discharges the electric charge accumulated in the capacitor C2.
The time constant for holding the peak value of the positive potential Vx at the connection point X is determined by the resistor R25 and the capacitor C2. In the present embodiment, the time constant is one frame time (1/30 second)
Is set to However, the time constant can be freely set by a combination of the capacitor C2 and the resistor 25. For example, the time constant may correspond to one line output time. The reference voltage of the positive side circuit is the variable resistor R2
6 can be set freely to some extent. Thus, the point at which the bypass FET Q1 is turned on can be set freely.

In the negative circuit of the AGC 54, the cathode and the anode of the diode D6 corresponding to the diode D5 of the positive circuit are reversed. Further, a negative reference voltage is input to the negative input terminal of the comparator U4B corresponding to the comparator U4A of the positive circuit via a constant voltage source, a variable resistor R30, and a resistor R27. On the other hand, the negative peak value of the potential Vx held by the capacitor C3 is input to the positive input terminal of the comparator U4B. Then, the comparator U4B outputs a High signal only when the negative peak value of the potential Vx is larger than the negative voltage peak value.

The above-described bypass FET Q2 is connected to the comparator U
When the High signal from 4B is applied to the gate, the gate is turned on, and the both ends of the resistor R19 are short-circuited. As a result, R19 disappears from the above equation (10), and the current Iβ flowing through the resistor R20 increases as shown by the following equation (10 ′).

[0073] _{Iβ = V Y2 / R20 = (} Vx / R12-V R2 / R18) · R13 / R20 ... (10 ') in this influence, the voltage V _C3 described above, the following formula (11', as indicated by) Changes to

[0074] _{V C3 = -R7 / R20 · V} Y2 = - (Vx / R12-V R2 / R18) · R13 · R7 / R20 ... (11 ') eventually, the potential of the connection point C at this point (video signal conversion The input voltage to the circuit 55) V _C appears to be smaller than when the bypass FET Q2 is OFF, as shown in the following equation (12 ′).

V _C = V _C2 + V _C3 = −R7 / + R20 · V _Y2 −R7 / R11 · Vx = − (Vx / R12−V _R2 / R18) · R13 · R7 / R20−R7 / R11 · Vx 12 ') As a result, the amplification factor of the amplifier 53 further decreases, and the increase of the input voltage to the video signal conversion circuit 55 on the positive side is further suppressed.

Note that the capacitor C3 and the resistor R in the negative side circuit
The time constant determined by 29 is set to one frame time described above. This time constant can also be set freely. The point where the bypass FET Q2 is turned on is
By adjusting the negative reference voltage by adjusting the variable resistor R30, the voltage can be set to some extent freely.

FIG. 6 is a graph showing characteristics of an input signal (input voltage) from the CCD 51 and an output signal (output voltage) of the operational amplifier U2B. As shown in FIG. 6, the slope on the positive side of the graph becomes smaller in a range where the input signal is larger than the operation start point of the operational amplifier U2A, and further becomes smaller by turning on the bypass FET Q2. The slope on the negative side of the graph also becomes smaller in a range where the input signal is larger on the negative side than the operation start point of the operational amplifier U1A, and further becomes smaller by turning on the bypass FET Q2. That is, the sensitivity of the CCD 51 decreases in two steps on each of the positive side and the negative side.

In this embodiment, the output signal of the CCD 51 is 10 times up to the operation start point of the operational amplifier U1A or U2A, 5 times after the operation starts, and the bypass FET is used.
It is set to be amplified three times by turning on Q1 or Q2. Further, in the present embodiment, the amplification factor of the operational amplifier U2B is controlled in three steps on each of the positive side and the negative side, but may be two or four or more. In particular, it is preferable to use four or more stages because the amplification factor can be linearly controlled according to the output signal of the CCD 51.

The above-mentioned operational amplifier U1A, operational amplifier U2A, and operational amplifier U2B correspond to an amplifier for amplifying the output of the image pickup device of the present invention, and the output control circuit 53
a, the output control circuit 53b, and the AGC 54 correspond to an auto gain controller that controls the output of the amplifier by manipulating the amplification factor of the amplifier according to the magnitude of the output of the image sensor of the present invention.

[Operation of Fluorescence Observation Apparatus] Next, the operation of the fluorescence observation apparatus will be described. As a premise, the distal end of the endoscope 10
(The distal end of the insertion section) is inserted into the living body, is disposed in the vicinity of the living tissue to be subjected to fluorescence observation, and has a light source section 20, an imaging section 30, a video switching apparatus 40, and a monitor 50 of the fluorescence observation apparatus. Is turned on.

First, the operation during normal observation will be described. When normal observation is performed, the excitation light filter 22 of the light source unit 20 is retracted outside the illumination light path of the light source lamp 21. In addition, the reflection mirror 32 of the imaging unit 30 is retracted from the optical path of the light emitted from the eyepiece 16 and incident on the CCD camera 31. And the light source lamp 21
The illumination light (white light) emitted from the light source irradiates the living tissue via the light guide fiber bundle 17 and the illumination window 19. Then, an image of the living body (a normal observation image) is formed by the objective optical system 15 through the observation window 18, and is formed through the image guide fiber bundle 14 and the eyepiece 16.
Introduced in 0. Then, the normal observation image relayed by the eyepiece 16 and the imaging optical system 30a is captured by the normal observation CCD camera 31, converted into a video signal, and transmitted to the monitor 50 via the video switching device 40. Then, the normal observation image is displayed on the screen of the monitor 50.

Next, the operation at the time of fluorescence observation will be described. When performing fluorescence observation, the excitation light filter 2 of the light source unit 20 is used.
2 is inserted into the illumination light path of the light source lamp 21. In addition, the reflection mirror 32 of the imaging unit 30 is set to intersect with the optical axis of the eyepiece 16 at an angle of 45 °. When the light source lamp 21 of the light source unit 20 emits illumination light, the illumination light is applied to the excitation light filter 22. Then, the excitation light filter 22 transmits only the B light (excitation light) of the illumination light. The B light is applied to the living tissue through the light guide fiber bundle 13 and the illumination window 19. As a result, fluorescence is emitted from the living tissue. The fluorescence image (fluorescence observation image) of the living tissue at this time is formed by the objective optical system 15 through the observation window 18 and transmitted to the eyepiece 12a through the image guide fiber bundle 14. Then, the light emitted from each point of the emission end face of the image guide fiber bundle 14 is
It is introduced into the imaging unit 30 via the eyepiece 16. In the imaging unit 30, light emitted from the eyepiece 16 is
The light is reflected by the reflection mirror 32 and travels toward the dichroic mirror 33. The dichroic mirror 33 is
Of the incident light, only the G light component is reflected toward II.34. Then, I.I.3 is performed by the imaging optical system 33a.
A fluorescence observation image consisting of only the G light component is formed on the incident end face of No. 4. The I.I.34 amplifies the fluorescence observation image of the G light component and transmits it to the CCD camera 41 via the imaging optical system 39. In the CCD camera 41, the fluorescence observation image of the G light component is converted into an electric signal by each imaging pixel of the CCD 51, and this electric signal is output as a voltage value in a state where dark current compensation has been performed. The output signal (output voltage) of the CCD 51 is inverted and amplified at a predetermined amplification rate in each of an operational amplifier U1B and an operational amplifier U2B, and is input to a video signal conversion circuit 55.

[0083] At this time, when the potential Vx of the node X obtained by inverting amplifying the output voltage by the operational amplifier U1B of CCD51 is greater than the reference voltage + V _R2 because corresponding to the bright part, the output control The operational amplifier U1 of the circuit 53a
A starts its operation, and suppresses an increase in the output voltage of the operational amplifier U2B to the negative side by reducing the amplification factor of the operational amplifier U2B. On the other hand, when the potential Vx of the node X which is obtained by inverting amplified by the operational amplifier U1B output voltage of the CCD51 is increased to the negative side than the reference voltage -V _R2 because corresponding to the dark portion, the output control circuit 53b Of the operational amplifier U2A starts operating, and the amplification factor of the operational amplifier U2B is reduced, thereby suppressing an increase in the output voltage of the operational amplifier U2B to the positive side.

Further, the potential at the connection point X obtained by inverting and amplifying the output voltage of the CCD 51 by the operational amplifier U1B is obtained.
If the peak value of Vx is higher than the positive reference voltage, A
The positive circuit of the GC 54 turns on the FET Q1. This further reduces the amplification factor of the operational amplifier U2B, and further suppresses the increase in the output voltage of the operational amplifier U2B to the negative side. On the other hand, the output voltage of the CCD 51 is
When the peak value of the potential Vx at the connection point X obtained by the inversion amplification is lower than the negative reference voltage, the negative circuit of the AGC 54 turns on the FET Q2. As a result, the amplification factor of the operational amplifier U2B further decreases, and the operational amplifier U2B
The increase of the output voltage of 2B to the positive side is further suppressed.

That is, the output voltage of the operational amplifier U2B
(Output signal of CCD 51 amplified by amplifier 53)
Is lower than the original value when the distance between the distal end of the endoscope 10 and the living tissue is shorter than an appropriate distance, or when the amount of excitation light applied to the living tissue is larger than the appropriate amount. It will be. The output of the operational amplifier U2B is output from the endoscope 1
If the distance between the leading end of the zero and the living tissue is longer than the proper distance, or if the amount of B light applied to the living tissue is smaller than the proper amount, the value will be higher than the original value.

The output voltage of the operational amplifier U2B controlled as described above (the output voltage of the amplifier 53) is
The video signal is input to the video signal conversion circuit 55. Then, the video signal conversion circuit 55 converts the output voltage of the operational amplifier U2B into a video signal, and inputs the video signal to the video signal switching device 40. The video signal switching device 40 inputs the input video signal to the monitor 50. Then, the monitor 50 displays a fluorescence observation image of the living tissue on the screen based on the input video signal. Then, by observing the fluorescence observation image displayed on the monitor 50, the observer can determine whether or not there is a disease in the living tissue.

According to the fluorescence observation apparatus for a living body according to the first embodiment, the CCD is controlled according to the distance between the distal end of the endoscope 10 and the living tissue to be observed or the amount of light applied to the living tissue.
The output control circuit 53a, the output control circuit 53b, and the AGC 54 incorporated in the camera 41 operate the amplification factor of the operational amplifier U2B so that the output voltage of the operational amplifier U2B (the amplified output signal of the CCD 51) falls within an appropriate range. To control. For this reason, it is possible to avoid a problem caused by the distance correction not being performed in the conventional fluorescence observation device. Therefore, the observer can observe an appropriate fluorescence observation image of the living tissue, and can avoid erroneous determination of the presence or absence of a disease.

The fluorescence observation apparatus for a living body according to the first embodiment employs a configuration in which only the G light component is extracted from the fluorescence observation image. Therefore, the fluorescence observation apparatus installed in the conventional fluorescence observation apparatus (see FIG. 10) is used. Dichroic mirror 2, II.34b, CCD camera 6, and R for extracting R light component of the image
-The G ratio processing device 7 can be omitted. That is, the imaging unit 30
Can be reduced in size and weight, and the operability of the endoscope 10 can be improved. Further, the cost of the fluorescence observation device can be reduced.

[0089]

Second Embodiment Next, a fluorescence observation apparatus according to a second embodiment will be described. FIG. 7 is a diagram illustrating an internal configuration of the fluorescence observation device according to the second embodiment. The fluorescence observation apparatus according to the second embodiment is the same as that according to the first embodiment except that the configuration of the II 70 and the CCD camera 71 is slightly different, and that an applied voltage control unit 75 of the II 70 is added. It has the same configuration as the fluorescence observation device. Therefore, the description of the common points will be omitted, and the differences will be described.

FIG. 8 shows a CCD camera 7 according to the second embodiment.
FIG. 2 is a diagram showing an internal configuration of the first embodiment. In FIG. 7, II.7
0 has substantially the same configuration as the II.34 in the first embodiment, but the voltage applied between both electrodes (not shown) provided on both end surfaces of the MCP 36 is applied to the II. And an applied voltage control unit 75. The CCD camera 71 includes a CCD 51 that captures a fluorescence observation image of a living body, an I.I. control circuit 72 that amplifies an output signal (output voltage) of the CCD 51, and generates a control signal to an applied voltage control unit 75. , II control circuit 7
And a video signal conversion circuit 55 for converting the output signal of the CCD 51 amplified by 2 into a video signal.

FIG. 9 is a circuit diagram of the II control circuit 72. As shown in FIG. As shown in FIG. 9, the II control circuit 72
Is obtained by removing the output control unit 53a, the output control unit 53b, and the negative circuit of the AGC 54 from the circuit configuration shown in FIG.
A differential amplifier 73 is provided in place of the comparator U4A of the positive side circuit of the AGC 54, and an A / D converter 74 is connected to an output terminal of the differential amplifier 73.

The differential amplifier 73 has the potential appearing at the connection point X.
The difference between the positive-side peak value of Vx and the positive reference voltage is obtained, and the difference is amplified at a predetermined amplification factor to obtain an A / D converter 74.
To enter. At this time, if the distance between the distal end portion of the endoscope 10 and the living tissue to be observed is appropriate, and the amount of light applied to the living tissue is appropriate, the negative input terminal of the differential amplifier 73 is connected to the negative input terminal. Since the positive peak value of the potential Vx of the input node X coincides with the positive reference voltage, the output of the differential amplifier 73 becomes zero. On the other hand, if the distance between the distal end of the endoscope 10 and the living tissue to be observed is shorter than the appropriate distance, or if the amount of light applied to the living tissue is larger than the appropriate value, the connection point X Since the positive peak value of the potential Vx becomes larger than the positive reference voltage, the output of the differential amplifier 73 becomes a negative voltage. On the other hand, when the distance between the distal end portion of the endoscope 10 and the living tissue is longer than an appropriate distance, or when the amount of light applied to the living tissue is smaller than an appropriate value, the positive side of the potential Vx of the connection point X Is smaller than the negative reference voltage, the output of the differential amplifier 73 becomes a positive voltage.

The A / D converter 74 includes a differential amplifier 73
Is A / D converted and input to the applied voltage control unit 75. The applied voltage control unit 75 includes the MCP 36 of II.70.
Is a device for applying a voltage between both electrodes. The applied voltage control unit 75 converts the input voltage according to the input from the A / D converter 74, that is, the applied voltage according to the output of the differential amplifier 73, into an I.I.
70 MCP. In other words, while the differential amplifier 73 outputs a positive voltage, the voltage applied between the two electrodes of the MCP 36 of II 70 continues to increase, and while the differential amplifier 73 outputs a negative voltage, The voltage applied between both electrodes of the MCP 36 of I.70 is continuously decreased, and when the input from the differential amplifier 73 becomes zero, the voltage value at that time is maintained.

Therefore, when the output of the differential amplifier 73 is a negative voltage, the amplification factor of the MCP 36 decreases, and the I.I.
Is in a state where the sensitivity is lowered. As a result, the output level of the CCD 51 decreases, and the potential Vx at the connection point X approaches the positive-side reference voltage. On the other hand, when the output of the differential amplifier 73 is a positive voltage, the amplification factor of the MCP 36 increases and the I.I.
Is in a state where the sensitivity is increased. As a result, the CCD 51
And the potential Vx at the connection point X approaches the positive-side reference voltage. As described above, by changing the sensitivity of the I.I. 70 (the amplification factor of the MCP 36) according to the output of the differential amplifier 73, the output level of the CCD 51 is controlled so as to be within an appropriate range.

The above-described II control circuit 72 and applied voltage control unit 75 correspond to the control device of the present invention. Next, the operation of the fluorescence observation device according to the second embodiment will be described.
That is, the fluorescence observation image transmitted to the CCD camera 71 via the II 70 and the imaging optical system 39 is captured by the CCD 51, and the output signal (output voltage) of the CCD 51 is set to I.
I. Input to the control circuit 72. In the II control circuit 72, the output signal of the CCD 51 is amplified and input to the video signal conversion circuit 55. On the other hand, in the II control circuit 72, the peak value of the output signal of the CCD 51 (the potential V of the connection point X)
The difference between the positive voltage (the peak value on the positive side of x) and the reference voltage is obtained, and the applied voltage control unit 75 sets the applied voltage according to this difference to I.I.
70 MCP. This raises or lowers the sensitivity of the II.70 to fall within the proper range. As a result, the fluorescence observation image amplified with the appropriate range of sensitivity by the II 70 is captured by the CCD 51, and the video signal conversion circuit 55 supplies the output voltage (amplification) of the operational amplifier U2B within the appropriate range. The output signal of the CCD 51 is input. Then, a video signal is input from the video signal conversion circuit 55 to the video switching device 70. Therefore, an appropriate fluorescence observation image of the living tissue is displayed on the monitor 50.

The effect of the fluorescence observation device according to the second embodiment is as follows.
This is the same as the effect of the fluorescence observation device according to the first embodiment.

[0097]

According to the fluorescence observation apparatus for a living body according to the present invention, a fluorescence observation image of a living tissue can be properly observed regardless of the distance between the distal end portion of the endoscope and the living tissue to be observed. Further, the size of the imaging unit of the fluorescence observation device can be reduced as compared with the related art.

[Brief description of the drawings]

FIG. 1 is an internal configuration diagram of a biological fluorescence observation apparatus according to a first embodiment of the present invention;

FIG. 2 shows a diagram of the I.F. in the biological fluorescence observation apparatus shown in FIG.
Configuration diagram of I.

FIG. 3 is a functional block diagram of the CCD camera shown in FIG. 1;

FIG. 4 is a circuit configuration diagram of the CCD camera shown in FIG. 3;

5 is a diagram showing output signals (output voltages) of the CCD shown in FIG.

6 is a graph showing characteristics of an input signal from the CCD shown in FIG. 3 and an output signal of an amplifier.

FIG. 7 is an internal configuration diagram of a biological fluorescence observation apparatus according to a second embodiment of the present invention;

FIG. 8 is a configuration diagram of the CCD camera shown in FIG. 7;

FIG. 9 is a circuit configuration diagram of the II control circuit shown in FIG. 8;

FIG. 10 is an internal configuration diagram of a conventional biological fluorescence observation apparatus.

FIG. 11 is a graph showing the fluorescence distribution of a normal part of a living tissue and the fluorescence distribution of an abnormal part of a living tissue.

[Explanation of symbols]

U1A, U2A, U2B Operational amplifier (amplifier) 10 Endoscope 11 Insertion unit 20 Light source unit 30 Imaging unit 33 Dichroic mirror (wavelength selection optical element) 34, 70 Image intensifier 41, 71 CCD camera 51 CCD (Imaging element) 53 Amplifier (amplifier) 53a, 53b Output control circuit (auto gain controller) 54 auto gain controller 72 II control unit (control device) 75 applied voltage control unit (control device)

Claims (9)

[Claims] An endoscope for irradiating excitation light from a distal end portion and introducing fluorescent light from a living body excited by the excitation light from the distal end portion, and a predetermined wavelength from the fluorescent light introduced to the endoscope. A wavelength selection optical element that extracts only the light component of the light, an imaging element that captures the image of the living body including the light component of the predetermined wavelength that is extracted by the wavelength selection optical element, and amplifies an output of the imaging element. A fluorescence observation apparatus for a living body, comprising: an amplifier; and an auto gain controller that controls an output of the amplifier by operating an amplification factor of the amplifier according to a magnitude of an output of the imaging element. 2. The automatic gain controller increases the amplification factor of the amplifier when the output of the image sensor is smaller than a reference value, and increases the amplification factor of the amplifier when the output of the image sensor is larger than a reference value. 2. The fluorescence observation apparatus for a living body according to claim 1, wherein: 3. The biological fluorescence observation apparatus according to claim 1, wherein the auto gain controller operates the amplification factor of the amplifier in a plurality of stages. 4. The fluorescence of a living body according to claim 1, wherein the auto gain controller operates the amplification factor of the amplifier when a peak value of an output of the image sensor becomes larger than a reference peak value. Observation device. 5. The fluorescence observation apparatus for a living body according to claim 1, wherein the auto gain controller operates an amplification factor of the amplifier for each output of one frame of the image sensor. 6. An endoscope for irradiating excitation light from a distal end portion and introducing fluorescence from a living body excited by the excitation light from the distal end portion, a predetermined wavelength from the fluorescence introduced to the endoscope. A wavelength selecting optical element for extracting only the light component of the light, an image intensifier for amplifying a light component of a predetermined wavelength extracted by the wavelength selecting optical element, and a light of a predetermined wavelength amplified by the image intensifier An imaging element that captures an image of a living body composed of the following components: and a voltage applied to the image intensifier is operated in accordance with the magnitude of an output of the imaging element to control an amplification factor of the image intensifier. A biological fluorescence observation apparatus, comprising: 7. The fluorescence observation apparatus for a living body according to claim 6, wherein the control device reduces the voltage applied to the image intensifier when the output of the imaging device is large. 8. An apparatus according to claim 6, wherein said controller increases the voltage applied to said image intensifier when the output of said image sensor is small. 9. The light of the predetermined frequency is 500 nm to 57 nm.
7. The living body fluorescence observation apparatus according to claim 1, wherein the light has a wavelength of 0 nm.