JP6058108B2 - Photodetectors, microscopes and endoscopes - Google Patents

Description

  The present invention relates to a light detection device, a light detection method, a microscope, and an endoscope.

  In various systems that use light such as body observation, sensors, security, and laser radar, the technology that detects the desired signal light (detected light) is a fundamental and important factor that greatly affects its performance. . In particular, the need for high-speed and high-sensitivity detection technology is high.

  For example, when viewing a living body, since the state and shape of the living body change every moment, it is necessary to perform light detection at high speed in order to perform accurate observation. Moreover, since a living body is easily damaged by light irradiation, there is an upper limit to the amount of illumination light and excitation light that can be irradiated to a biological sample. Therefore, the optical signal obtained from a living body is usually weak. For these reasons, there is a strong demand for high-speed and high-sensitivity light detection technology in living body observation using light.

  Typical photodetection elements currently used include PMT (Photo Multiplier Tube), APD (Avalanche Photo Diode), and PD (Photo Diode). Since PMT and APD perform electron multiplication in the detection element, highly sensitive light detection can be realized. On the other hand, although a PD can realize a very high response speed, it does not have an electron multiplication function in the detection element, and therefore, a signal is usually amplified using an electric amplifier. In other words, the PMT, APD, and PD all perform signal amplification electrically to improve sensitivity.

  Typical two-dimensional photodetectors include a CCD (Charge Coupled device), a CMOS (Complementary Metal Oxide Semiconductor), an EM-CCD (Electron Multiple-CCD), and an EB-CCD (Electron IMD CCD). (Intensified-CCD). When weak light is detected using a CCD or CMOS, it is necessary to arrange an electric amplifier in the subsequent stage in the same manner as in the case of PD in order to improve sensitivity. As in the case of APD, EM-CCD and EB-CCD have an electron multiplication function in the detection element and realize high sensitivity. The I-CCD is connected to the I.C. I. (Image Intensifier) is arranged. I.I. temporarily converts an incident light signal into an electrical signal, performs electron multiplication in an MCP (Micro Channel Plate) built in I.I., and then transfers the multiplied electrons to a fluorescent plate. The multiplied electron signal is converted into light again by colliding with. The output light from I.I. is converted into an electrical signal by the CCD. That is, the I-CCD also realizes highly sensitive light detection by performing signal amplification at the electrical stage.

  A photodetection method using the above-described photodetector and converting light intensity into current is widely used. This light detection method is called a direct detection method. In this direct detection method, thermal noise, electron multiplication noise, or excess noise becomes the dominant noise factor. Since these noises are larger than shot noises due to the quantum nature of light, ultimate high-sensitivity light detection is very difficult with the direct detection method.

  Optical heterodyne detection technology is also widely used as one of the technologies that enable high-speed and high-sensitivity light detection. Conventional optical heterodyne detection technology is a light detection method that uses the interference effect between detected light and local oscillation, which has a slightly different optical frequency than the optical frequency of the detected light. By doing so, the detected light is detected with high sensitivity. When local light is sufficiently high in intensity, ideal light detection with a shot noise limit is possible even with a high-speed electronic circuit, so that both high-speed detection and high sensitivity can be realized. However, at this time, light that stabilizes the mutual interference state both in time and space is usually used for the signal light and the local light.

  As a method for stabilizing the interference state in terms of time, the following two methods are mainly used. The first method is a method of demultiplexing outputs from the same light source and using them as signal light and local light. At this time, since the same light source output is demultiplexed, the relative delay time until the signal light and the local light are combined is used so as to be shorter than the coherence time of the light source. By doing so, the interference state between the signal light and the local light is temporally stabilized. Note that the optical frequencies of the signal light and the local light are set to be slightly different using an optical frequency shifter or the like. This method has been used for a long time since it can realize a stable interference state relatively easily (see, for example, Patent Document 1).

  The second method is a method using two independent light sources having a very narrow optical spectral line width (very high optical spectral purity) and stable oscillation optical frequency with high accuracy. . Here, it is assumed that the optical spectrum line width is narrower than the operation band of the electric circuit portion including the photoelectric conversion portion. These two independent light sources are used as signal light or local light, respectively. At this time, the oscillation light frequencies of the signal light and the local light are set to be slightly different. This method has heretofore been very difficult to implement due to technical limitations. However, due to recent technological progress, a laser with an optical spectral line width of about kHz and a very high optical spectral purity and a stable oscillation optical frequency has become available. Even if this method is used, a relatively stable interference state can be obtained.

  On the other hand, in order to stabilize the interference state spatially, it is necessary to use light with high spatial coherence for signal light and local light, and to make the spatial mode distributions coincide with each other. Therefore, a spatial mode filter such as a confocal optical system or an optical fiber is used on the signal light side. By doing so, it is possible to extract only the signal light component that keeps the local light emission and the spatial interference state stable. As a result, the interference state can be spatially stabilized.

Japanese Patent No. 2890309

  However, the signal light detected by biological observation, sensors, security, laser radar, etc. is not high in temporal coherence like laser light, but low in temporal coherence such as lamp light or fluorescence, that is, optical spectrum lines. Very often it is wide. Even when laser light is used in spectroscopic measurement or the like, in particular, when measuring a scattering medium, in order to avoid the influence of speckle, a device for intentionally widening the optical spectrum line width is made. That is, in spectroscopic measurement or the like, laser light having an optical spectral line width that can ensure the accuracy of the optical frequency to some extent and at the same time avoid the influence of speckle is used.

  Therefore, according to the conventional method as described above, in order to heterodyne detect such signal light with low temporal coherence, the signal light and the local light source are made the same, and the signal light and the local light are generated. It is necessary to perform detection in a situation where the relative delay time of light emission is shorter than the coherence time.

For example, in the case of light having a center optical frequency of 600 THz (wavelength 500 nm) and an optical spectral line width of 120 THz (wavelength width of about 100 nm), the coherence time is about 1.0 × 10 ⁻¹⁴ seconds (at a spatial distance in a vacuum). Corresponding to about 3.0 × 10 ⁻⁶ m), and the allowable delay time between the signal light and the local light is very short.

Further, for example, considering the case of laser light whose line width is intentionally widened with a center optical frequency of 600 THz and an optical spectral line width of 120 GHz (wavelength width of about 100 pm), the coherence time is about 1.0 × 10 ^−11. Second (corresponding to about 3.0 × 10 ⁻³ m in space distance in a vacuum), the allowable relative delay time is also short.

  Thus, in a situation where the allowable relative delay time is short, the temporal and distance tolerances are small, so that the application of heterodyne detection is very severely limited.

  Further, when the signal light (detected light) is newly generated temporally low-coherence light such as fluorescence, local light emission suitable for high-sensitivity optical heterodyne detection cannot be prepared.

  For the above-described reason, when heterodyne detection is performed on a temporally low-coherent optical signal, a stable interference state cannot be maintained, and it is difficult to realize high-speed and high-sensitivity optical detection.

  Accordingly, an object of the present invention made in view of such a point is to provide a photodetection device and a photodetection method capable of heterodyne detection of desired detection light with high sensitivity and high SN (Signal to Noise) ratio, and a microscope and an endoscope. To provide a mirror.

  Another object of the present invention is to provide a photodetection device and photodetection method capable of heterodyne detection with high sensitivity and a high SN (Signal to Noise) ratio even for light to be detected having a wide wavelength band, and a microscope and It is to provide an endoscope.

  Furthermore, another object of the present invention is to achieve a high sensitivity and a high signal-to-noise (SN) ratio even if the interference between the signal light and the local light is temporally or spatially unstable. An object of the present invention is to provide a light detection apparatus and a light detection method capable of detecting heterodyne, a microscope, and an endoscope.

  The invention of the photodetecting device according to the first aspect to achieve the above object comprises a local light generating light source for generating local light and an irradiation light different from the local light generating light source for generating irradiation light for irradiating a subject. A beat signal of the local light and the detected light by photoelectrically converting the detected light and the local light generated by the generated light source and the irradiation light reflected, transmitted, refracted, and diffracted by the subject And a heterodyne detection means for heterodyne detecting the detected light based on the output of the photoelectric conversion means, and the optical spectrum line width of the local light emitted by the local light generation light source is It is characterized in that it is wider than the operating band of the heterodyne detection means.

  Here, the meaning of “local light whose state of interference with detected light is not stable over time” will be described. Here, the case where local light is generated from the same light source as the detected light and the case where local light and detected light are generated from independent light sources will be described separately.

ここでｃは光の速度、λ₀は光源にて生成される光の中心波長、Δλは光源にて生成される光の光スペクトルの波長線幅を表す。 First, the case where local light is generated from the same light source as the detected light will be described. In this case, the output from the same light source is demultiplexed, and each light is used as light irradiated to the sample or the like and local light. Light generated by reflection, transmission, scattering, refraction, diffraction, or the like on a sample or the like is detected signal light, and this detected light and local light are recombined to detect heterodyne. At this time, the local light emission under the condition that the relative delay time until the light is demultiplexed from the light source and recombined is longer than the coherence time τ _{c of the} light source, Is not stable. " Here, the coherence time τ _c is a time defined by the equation (1).

Here, c is the speed of light, λ ₀ is the center wavelength of the light generated by the light source, and Δλ is the wavelength line width of the light spectrum of the light generated by the light source.

  Next, a case where local light and detected light are generated from independent light sources will be described. In this case, during heterodyne detection, local light whose optical spectrum line width is wider than the operating band of the electric circuit part including the photoelectric conversion part is “local light whose interference state with the detected light is not stable”. It is said. Here, wavelength drift and the like are also included in the optical spectrum line width.

  The invention according to a second aspect is characterized in that, in the photodetecting device according to the first aspect, the photoelectric conversion means performs balanced detection.

  The invention according to a third aspect is characterized in that, in the photodetecting device according to the first or second aspect, the local light generation light source comprises a plurality of light generation sources.

  The invention according to a fourth aspect is characterized in that, in the photodetecting device according to the first or second aspect, the local light generation light source has optical filter means for selecting a predetermined optical frequency component. is there.

  The invention according to a fifth aspect is characterized in that, in the photodetecting device according to the first or second aspect, the local light generation source has an optical spectrum shaping means for shaping an optical spectrum into a desired shape. Is.

  The invention according to a sixth aspect is characterized in that, in the photodetecting device according to the first or second aspect, the local light generation light source has a fluorescence generation means.

  The invention according to a seventh aspect is characterized in that, in the photodetecting device according to the first or second aspect, spatial light filter means for selecting only light having a desired spatial distribution is provided in the preceding stage of the photoelectric conversion means. It is what.

  The invention according to an eighth aspect is characterized in that, in the photodetecting device according to the first or second aspect, spatial light homogenizer means for equalizing a spatial light intensity distribution is provided upstream of the photoelectric conversion means. To do.

  The invention according to a ninth aspect is characterized in that, in the photodetector according to any one of the first to eighth aspects, further comprises an envelope detection means for detecting an envelope of the output of the photoelectric conversion means. To do.

  The invention as a reference example of the present invention according to a tenth aspect is the photodetection device according to the first aspect, wherein the detected light and the local light are used by branching the output of the same light source, and the photoelectric The relative delay time between the light to be detected and the local light when the conversion means is incident is not within a coherence time.

  The invention as a reference example of the present invention according to the eleventh aspect is that, in the photodetector according to the first aspect, the optical spectrum line width of the local light is wider than the signal processing band after the photoelectric conversion means. It is characterized by.

  Furthermore, the invention of the light detection method as a reference example of the present invention according to the twelfth aspect for achieving the above object has an optical spectral line width wider than the operating frequency band of the detection system, and the detected light and time Output of the photoelectric conversion step, including a local light generation step for generating local light whose interference state is not stable, and a photoelectric conversion step for generating a beat signal between the local light and the detected light by photoelectric conversion Based on the above, the detected light is heterodyne detected.

  Furthermore, the invention of the photodetection method as a reference example of the present invention according to the thirteenth aspect for achieving the above object is characterized in that balanced detection is performed in the photoelectric conversion step.

  Furthermore, the invention of a microscope according to a fourteenth aspect for achieving the above object is a microscope for detecting light to be detected from an observation sample, comprising the photodetection device according to any one of the first to eleventh aspects. The light to be detected from the observation sample is heterodyne detected by the light detection device.

  Furthermore, an invention of an endoscope according to a fifteenth aspect for achieving the above object is an endoscope that detects light to be detected from inside a body cavity and observes the inside of the body cavity. The light detection device according to any one of the aspects is provided, and the detection light from the body cavity is heterodyne-detected by the light detection device.

  Furthermore, the invention of an endoscope according to a sixteenth aspect for achieving the above object is an endoscope for detecting the detected light from inside the body cavity and observing the inside of the body cavity, wherein the irradiation light is sampled Scanning means for scanning above, a light transmission optical system for transmitting light transmitted, reflected, scattered, refracted or diffracted from the sample, and a light detection device according to any one of the first to eleventh aspects, The detection light from the body cavity is heterodyne detected by the light detection device.

  According to the light detection device and the light detection method according to the present invention, a plurality of beat signals are generated from the local light and the detected light whose interference state is not stable with respect to the detected light, and these are added together, Because detection light is heterodyne-detected, for example, even if the target light is scattered by a scatterer such as a living body or the detection light is significantly reduced due to the influence of absorption, etc. Can be detected with high sensitivity and a high S / N ratio. In addition, not only for scatterers, but also for test light from test substances that exist in the deep or distant area of the detection target, and test substances that exist in environments where other light-absorbing substances are present, It becomes possible to detect with high sensitivity and high S / N ratio.

Further, according to the light detection apparatus and the light detection method according to the present invention, when the light irradiated to the sample and the local light are generated from the same light source, unlike the conventional case, the detected signal light and the local light are Since the relative delay time between them need not be shorter than the coherence time τ _{c of the} light source, it is freed from the adjustment of the relative delay time of the light detection. In addition, when the light to be detected and the local light are generated from different light sources, there is no problem even if the optical spectrum of the local light is wide, so the conditions required for local light compared to the conventional heterodyne detection method are It is greatly eased. That is, an inexpensive light source such as an LED (Light Emitting Diode) or an SLD (Super Luminescent Diode) can be used as the local light source. These effects are highly industrially significant.

  Further, according to the microscope according to the present invention, the light detection device detects the beat signal of the detected light from the observation sample and the local light whose interference state is not stable with the detected light in time. An observation sample can be observed with high sensitivity and a high S / N ratio.

  Further, according to the endoscope of the present invention, the detected light from the body cavity is detected by the above-described light detection device as a beat signal with the detected light and the local light whose interference state is not stable over time. Therefore, it becomes possible to observe the inside of the body cavity with high sensitivity and high SN ratio.

It is a block diagram which shows the basic composition of the photon detection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the basic composition of the photon detection apparatus which concerns on 2nd Embodiment of this invention. It is a schematic diagram explaining the operation | movement of the photon detection apparatus shown in FIG. It is a schematic diagram explaining the operation | movement of the photon detection apparatus shown in FIG. It is a block diagram which shows the structure of the principal part of the photon detection apparatus which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the structure of the principal part of the photon detection apparatus which concerns on 1st reference embodiment of invention as a reference example of this invention. It is a block diagram which shows the structure of the principal part of the photon detection apparatus which concerns on 2nd reference embodiment of invention as a reference example of this invention. It is a block diagram which shows the structure of the principal part of the photon detection apparatus which concerns on 4th Embodiment of this invention. It is a block diagram which shows the structure of the principal part of the endoscope which concerns on 5th Embodiment of this invention. It is a block diagram which shows the structure of the principal part of the photon detection apparatus which concerns on 6th Embodiment of this invention.

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

(First embodiment)
FIG. 1 is a block diagram showing a basic configuration of the photodetecting device according to the first embodiment of the present invention. This photodetection device uses local light generation means 10 that generates local light whose state of interference with detected light is not stable over time, and the local light from this local light generation means 10 and the detected light are converted into photoelectric conversion means 20. To convert it to an electrical signal. The photoelectric conversion means 20 obtains a signal obtained by adding a plurality of beat signals based on local light and detected light, and performs heterodyne detection on the input signal light.

  The local light generation means 10 is configured using, for example, a device that emits spontaneous emission light, fluorescence, or the like, such as an LED, SLD, or SOA (Semiconductor Optical Amplifier). The local light generation means 10 can be composed of a light source different from the light to be detected. The local light generation means 10 can also be configured by using a part of the illumination light as described below. When the light that has been transmitted, reflected, and scattered by the object is used as the detected light, the relative time longer than the coherence time of the illumination light between a part of the illumination light used as the local light and the detected light It is possible to detect by inserting a delay. The photoelectric conversion means 20 is comprised using PMT, APD, PD, CCD, CMOS, EM-CCD, EB-CCD, etc., for example. When the light to be detected and the local light are incident on the photoelectric conversion means 20, an optical element such as a beam splitter or an optical fiber coupler is arranged immediately before the photoelectric conversion means 20 to combine the light to be detected and the local light. The beat signal may be obtained by being incident on the photoelectric conversion means 20, or the light to be detected and the local light may be incident on the light receiving surface of the photoelectric conversion means 20.

  The signal light that is the light to be detected is detected using, in particular, amplitude information and intensity information among the electrical signals output from the photoelectric conversion means 20. Such information is acquired by envelope detection, square detection, or the like. Filter means for removing a DC component may be added after the photoelectric conversion means 20. Further, the intensity of the beat signal can be adjusted by adjusting the intensity of the local light.

(Second Embodiment)
FIG. 2 shows a balanced detection configuration. The signal light is bifurcated by the optical multiplexing / demultiplexing means 30. One of the branched lights is incident on the photoelectric conversion means (A) 21, and the other light is incident on the photoelectric conversion means (B) 22. For example, a beam splitter or an optical fiber coupler can be used as the optical multiplexing / demultiplexing means. Further, the local light emitted from the local light generation means 10 is also bifurcated by the optical multiplexing / demultiplexing means 30, and one light is incident on the photoelectric conversion means (A) 21 and the other light is incident on the photoelectric conversion means (B) 22. Is done. The electric signals output from the photoelectric conversion means (A) 21 and the photoelectric conversion means (B) 22 are input to the subtraction means 40. For the subtracting means 40, for example, an analog differential amplifier circuit, a digital differential amplifier circuit, signal processing by software, or the like can be used. In the photoelectric conversion means (A) 21 and the photoelectric conversion means (B) 22, beat signals between signal lights (hereinafter referred to as signal light-signal light beat signals) and beat signals between local lights (hereinafter referred to as local light-local light beats). Signal) and beat signals of signal light and local light (hereinafter, signal light-local light beat signal) are detected. With respect to the signal light-signal light beat signal and the local light-local light beat signal, the beat signal having the same phase is detected by the photoelectric conversion means (A) 21 and the photoelectric conversion means (B) 22, so the subtraction means 40 Offset. On the other hand, the signal light-local light beat signal output from the photoelectric conversion means (A) 21 and the signal output from the photoelectric conversion means (B) 22 are in opposite phases. It is added by the subtracting means 40. That is, by using the balanced detection configuration as shown in FIG. 2, the signal light-signal light beat signal and the local light-local light beat signal that are background signals at the time of light detection can be removed, and a high S / N ratio can be obtained. Light detection can be performed. Further, by using the balanced detection configuration of FIG. 2, it becomes possible to reduce relative intensity noise (RIN) possessed by the local light itself.

FIG. 3 is a schematic diagram for explaining the operation of the photodetector shown in FIG. 2 on the frequency axis. 3A, 3B, 3C, and 3D respectively show the optical spectrum of the signal light, the optical spectrum when the signal light and the local light overlap, the optical spectrum of the local light, and the electrical spectrum after photoelectric conversion. Indicates. Here, the optical spectrum line width of the local light is Δf _Lo , and the operation band of the electric circuit after the photoelectric conversion means 20 is B. Wider than the optical spectrum width of FIG. 3 Delta] f _Lo signal light, Delta] f _Lo indicates a broader example than B. Further, the light spectrum of the local light has an overlap with the optical spectrum of the signal light on the optical frequency axis, and the local light has a sufficiently higher intensity than the signal light.

  In the example of FIG. 3, since both signal light and local light have a plurality of optical frequency components, the signal light-local light beat signal by any combination of optical frequencies is detected within the operating band B of the electric circuit. . A large number of the same signal light-local light beat signals by combinations of different optical frequencies are also detected, but these signal light-local light beat signals are uncorrelated with each other, and are added incoherently.

On the other hand, FIG. 4 is a schematic diagram for explaining the operation of the photodetector shown in FIG. 2 on the time axis. 4A, 4 </ b> B, 4 </ b> C, and 4 </ b> D are respectively the time waveform of the signal light electric field, the time waveform when the signal light electric field and the local light emission field overlap, the time waveform of the local light emission electric field, and photoelectric conversion. The later time waveform is shown. As in the example of FIG. 3, Δf _Lo is wider than B, the light spectrum of the local light has an overlap with the optical spectrum of the signal light on the optical frequency axis, and the local light has a sufficiently higher intensity than the signal light. It is said. When the signal light electric field and the local light emission electric field overlap in time and space, a signal as shown in FIG. 4D is obtained. Since the signal light and the local light are uncorrelated with each other, the time waveform of the signal detected as illustrated in FIG. Envelope detection or square detection may be used to detect this noise-like signal.

(Third embodiment)
FIG. 5 is a block diagram showing a configuration of a main part of the in-vivo internal observation device according to the third embodiment of the present invention. In this in-vivo internal observation device, an illumination light source having a semiconductor laser (Laser diode: LD) 51 that emits light at a central wavelength of 940 nm was used. The light emitted from the LD 51 was coupled to the optical fiber 52 and irradiated onto the living tissue 100 via the lens 53. And the light which permeate | transmitted the biological tissue 100 was made into the to-be-detected signal light. The light transmitted through the living tissue 100 was collected by the lens 54 and input to a single mode fiber (SMF) 56. The lens 54 used was held on a movable base 55. Here, the movable base 55 is set so as to be movable on a plane parallel to the surface of the living tissue 100. The output light from the SMF 56 was connected to one of the input ports of the optical fiber coupler 31 having a 2-input 2-output port. Local light was input to the other input port of the optical fiber coupler 31. An SLD 11 having a wavelength of 940 nm was used as a local light generation source. A band-pass filter (BPF) 12 having a center wavelength of 940 nm and a transmission bandwidth of 2 nm is disposed at the subsequent stage of the SLD 11, and light output from the BPF 12 is used as local light. At this time, the transmission center wavelength of the BPF 12 was adjusted so that the detected signal light wavelength was included in the local light emission wavelength band. Two output ports of the optical fiber coupler 31 were connected to a dual balanced detector (DBD) 23. The DBD 23 is composed of two InGaAs photodiodes as the photoelectric conversion means (A) 21 and the photoelectric conversion means (B) 22 and an analog differential amplification electronic circuit as the calculation means 40, and has an operation band of 200 MHz. Using. The output of the DBD 23 was input to a 16-bit analog-to-digital converter (ADC) 57, and the analog input signal was converted into a digital signal. The digital signal output from the ADC 57 was input to the computer 58. In the computer 58, an envelope of the input signal from the ADC 57 is calculated, and an integrated value for a certain time with respect to the envelope waveform is calculated. The control unit 60 controls the strength of the SLD 11 and the position of the movable base 55 according to the signal from the computer 58. The movable table 55 stays at the same position for a certain time T, and the computer 58 stores the integrated value of the envelope waveform for the position of the movable table 55 and displays it on the monitor 59 as a two-dimensional image.

  By doing so, the inside of the living body that strongly scatters light could be observed at high speed and with a high SN ratio.

(First embodiment)
FIG. 6 is a block diagram showing a configuration of a main part of the endoscope according to the first reference embodiment of the invention as a reference example of the present invention. This endoscope is for observing the inside of a body cavity, and has the configuration of the light detection apparatus shown in FIG. 2 as a detection system for light to be detected. In FIG. 6, the illumination light source 61 includes an Xe lamp and is driven by a control unit 71 controlled by a computer 58. Light emitted from the illumination light source 61 was input to a light guide fiber (LGF) 63 via a lens 62.

  The LGF 63 is disposed so as to pass through the endoscope housing 64. The light propagating through the LGF 63 was emitted into the space via the lens optical system 65 installed in the endoscope housing 64. The emitted light is branched into two by a beam splitter 66 similarly installed in the endoscope housing 64, one is irradiated to the living tissue 100 via the lens optical system 67, and the other is input to the half mirror 32. Is done. The light input to the half mirror 32 was used as local light when detecting light. Reflected light or scattered light from the living tissue 100 was collected by the lens optical system 68 and used as detected signal light. At this time, the optical path length difference between the optical path (beam splitter 66-lens optical system 67-biological tissue 100-lens optical system 68-half mirror 32) and the optical path (beam splitter 66-half mirror 32) It was set to be longer than the coherence length.

  The half mirror 32 functions in the same manner as the optical fiber coupler 31 in FIG. 5, that is, plays a role of a 2-input / 2-output optical multiplexer / demultiplexer. The half mirror 32 has a light input from the beam splitter 66 serving as local light and a light input from the lens optical system 68 serving as signal light to be detected. A) A CCD (A) 24 as 21 and a CCD (B) 25 as photoelectric conversion means (B) 22 are inputted and converted into analog electric signals. Output signals from the CCD (A) 24 and the CCD (B) 25 are amplified by an amplifier 69 and an amplifier 70, respectively, and converted into digital signals by a 2-input ADC 57, respectively.

  The output signal from the ADC 57 is input to the computer 58, and the computer 58 calculates signal envelopes for subtracting the outputs from the CCD (A) 24 and the CCD (B) 25, calculates an envelope after the subtraction, and performs integration for a certain period of time. The signal processing to be performed is performed. This subtraction signal processing, envelope calculation, and integration processing correspond to the subtraction means 40 in FIG.

  By doing so, it is possible to obtain a bright endoscopic image while keeping the illumination light intensity low. Since it is possible to obtain a bright image while suppressing the heat generation at the distal end portion of the endoscope due to the increase in illumination light intensity, it is possible to provide a safer endoscopic image for the patient. become. Further, in the present embodiment, since the light source for local light emission is unnecessary, there is an advantage that the configuration is simplified.

  Further, narrow band imaging (NBI) can be performed by arranging a wavelength band filter that transmits blue, green, and red after the Xe lamp in the illumination light source 61 in FIG. . In the conventional NBI, a decrease in image brightness due to the use of a wavelength band filter is inevitable, but according to the first reference embodiment shown in FIG. 6, NBI can be performed without sacrificing image brightness. It becomes possible.

  In the first embodiment, an example using a CCD as a two-dimensional photodetector has been described. However, other two-dimensional photodetections such as CMOS, EM-CCD, EB-CCD, and I-CCD are used. The instrument may be used for imaging.

(Second embodiment)
FIG. 7 is a block diagram showing a configuration of a main part of a fluorescence endoscope according to a second reference embodiment of the invention as a reference example of the present invention. This fluorescence endoscope is for observing the inside of a body cavity, and has the configuration of the photodetection device shown in FIG. 2 as a detection system for detected light. FIG. 7 is similar to the configuration of FIG. 6, but in FIG. 7, the fluorescence excitation light source 72 includes a Xe lamp and a wavelength band filter that transmits only light having a wavelength of 450 nm, and is controlled by a computer 58. It is driven by 73. Further, the fluorescent plate 13 and the optical spectrum shaping filter 14 are disposed between the beam splitter 66 and the half mirror 32, and the excitation light removal filter 26 is disposed between the lens optical system 68 and the half mirror 32 as shown in FIG. Is different. Since other configurations are the same as those in FIG. 6, the same components are denoted by the same reference numerals and description thereof is omitted.

  As the fluorescent plate 13, a fluorescent plate that emits fluorescence in the same wavelength band as that of fluorescence from a living tissue, for example, a wavelength of 530 nm band, when the fluorescence excitation light source 72 is excitation light is used. The optical spectrum shaping filter 14 used to remove the excitation light from the fluorescence excitation light source 72 and simultaneously shape the shape of the light spectrum emitted from the fluorescent plate.

  As the excitation light removal filter 26, a filter that removes light emitted from the fluorescence excitation light source 72 and transmits only light having a wavelength of interest emitted from the living tissue 100, for example, light having a wavelength of 530 nm, is used.

  By using such a configuration, it is possible to brightly detect even weak fluorescence emitted from a living body. In the present embodiment, the optical spectrum shaping filter 14 is used. However, by adjusting the optical spectrum shape of the local light in this way, it is possible to adjust the wavelength dependence in the light detection. Moreover, it is possible to adjust the central wavelength and wavelength band of local light by changing the fluorescent plate 13. For example, even if the wavelength band of light emitted from the fluorescence excitation light source 72 is a narrow band, it is possible to generate local light corresponding to a wide wavelength band by using the fluorescent plate 13 having a wide emission wavelength band. Become. In addition, when it is desired to detect only light in a specific wavelength band, it is effective to use the fluorescent plate 13 having a narrow emission wavelength band.

(Fourth embodiment)
FIG. 8A is a block diagram showing a configuration of a main part of an optical fiber scan endoscope according to the fourth embodiment of the present invention. This endoscope is for observing the inside of a body cavity, and has the configuration of the light detection apparatus shown in FIG. 2 as a detection system for light to be detected.

  The signal light source unit 74 includes an LD having an oscillation wavelength of 480 nm, a diode pumped solid state (DPSS) laser having an oscillation wavelength of 532 nm, and an LD having a wavelength of 633 nm. The output from each laser is combined by a dichroic mirror. , And output from the signal light source unit 74. The controller 81 controls the wavelength and intensity of the light output from the signal light source unit 74.

  Output light from the signal light source unit 74 was input to the optical fiber 75. The optical fiber 75 was connected to a multi-core optical fiber 77 via an optical fiber type splitter 76. A cross-sectional shape of the multi-core optical fiber 77 is shown in FIG. The multi-core optical fiber 77 is composed of one illumination core 77A, a plurality of light receiving cores 77B, and a clad 77C. The optical fiber type demultiplexer 76 couples the light propagating through the optical fiber 75 to the illumination core 77A of the multicore optical fiber 77, and multiplies the light propagating through the plurality of light receiving cores 77B in the multicore optical fiber 77. Coupled to mode optical fiber 80.

  The light output from the signal light source unit 74 is propagated through the optical fiber 75 and is coupled to the illumination core 77 A of the multi-core optical fiber 77 by the optical fiber type splitter 76. The tip of the multi-core optical fiber 77 is held by a drive mechanism 78. The drive mechanism 78 is composed of a piezo element or the like, and is driven so as to control the direction of light emitted from the tip of the multi-core optical fiber 77 in accordance with a signal from the control unit 81. The light emitted from the illumination core 77A of the multicore optical fiber 77 was irradiated to the living tissue 100 via a lens optical system 79 such as a gradient refractive index (GRIN) lens.

  The light reflected or scattered by the living tissue 100 was coupled to the light receiving core 77 </ b> B of the plurality of multi-core optical fibers 77 via the lens optical system 79. The reflected / scattered light from the living tissue 100 propagating through the core 77B of the light receiving fiber of the multi-core optical fiber 77 was used as detected signal light. The detected signal light propagating through the light receiving core 77 </ b> B of the multicore optical fiber 77 is coupled to the multimode optical fiber 80 by the optical fiber type splitter 76.

  The light output from the LED unit 15 was used as local light. The LED unit 15 includes LEDs having wavelengths of 480 nm band, 532 nm band, and 633 nm band, and output light from each LED is multiplexed by a dichroic mirror. The controller 81 controls the wavelength and intensity of light output from the LED unit 15.

  The detected light output from the multimode optical fiber 80 and the local light output from the LED unit 15 were multiplexed / demultiplexed by the half mirror 32 as in the fourth embodiment. The light multiplexed / demultiplexed by the half mirror 32 was input to the DBD 26 via the mirror 33 or the mirror 34, respectively. The DBD 26 is composed of two Si photodiodes as the photoelectric conversion means (A) 21 and photoelectric conversion means (B) 22 and an analog differential amplification electronic circuit as the calculation means 40, and uses an operation band of 200 MHz. The operations of the ADC 57, the computer 58, and the monitor 59 are the same as those in FIG.

  Since this embodiment uses a plurality of light sources for local light emission having different wavelengths, the configuration is advantageous for detecting light in various wavelength bands. In addition, by using a plurality of local light sources having different wavelengths as in this embodiment, highly sensitive detection is possible even when the wavelength band of the detected light is wide.

(Fifth embodiment)
FIG. 9 is a block diagram showing a configuration of a main part of a capsule endoscope according to the fifth embodiment of the present invention. This endoscope is for observing the inside of a body cavity, and has the configuration of the light detection apparatus shown in FIG. 2 as a detection system for light to be detected.

  The LED 83 for illumination, the condensing lens optical system 84, the half mirror 32, the CCD (A) 24, the CCD (B) 25, the LED 16 for local oscillation, the homogenizer 17, the signal processing unit 85, and the signal transmission unit 86 are a capsule-type casing 82. It has a configuration that fits inside.

  As the lighting LED 83, one that emits white light is used. Output light from the illumination LED 83 is irradiated to the living tissue 100 outside the capsule-type housing 82. Illumination light reflected or scattered by the living tissue 100 was condensed using the condensing lens optical system 84 in the capsule housing 82 and used as detected signal light.

  As the local light source, a local LED 16 that emits white light was used. The light emitted from the local LED 16 was input to the homogenizer 17. From the homogenizer 17, the spatial pattern of the local LED 16 is made uniform and output. The light output from the homogenizer 17 is used as local light.

  The detected signal light collected by the condensing lens optical system 84 and the local light output from the homogenizer 17 are input to the half mirror 32. The operations of the half mirror 32, the CCD (A) 24, and the CCD (B) 25 are the same as those in the fourth embodiment shown in FIG.

  Analog output signals from the CCD (A) 24 and the CCD (B) 25 are input to the signal processing unit 85 and converted into digital signals. Thereafter, envelope detection is performed in the signal processing unit 85, and a digital signal is output from the signal processing unit 85. Next, the output of the signal processing unit 85 is input to the signal transmission unit 86. The signal transmission unit 86 transmits information to the outside of the capsule casing 82 by wireless transmission of the input digital signal.

  In the present embodiment, a homogenizer 17 is used in the subsequent stage of the local LED 16. Usually, the spatial output pattern of the LEDs is very non-uniform, and the heterodyne detection sensitivity depends on the spatial position. That is, image unevenness occurs. Therefore, the spatial output dependence of the heterodyne detection sensitivity is made uniform by making the spatial output pattern of the local light emission uniform by the homogenizer 17 disposed at the subsequent stage of the local LED 16.

  In the seventh embodiment, the example in which the CCD is used as the two-dimensional photodetector has been described. However, other two-dimensional photodetectors such as CMOS, EM-CCD, EB-CCD, and I-CCD are described. May be used for imaging.

(Sixth embodiment)
FIG. 10 is a block diagram showing a configuration of a main part of a laser scanning fluorescence microscope according to the sixth embodiment of the present invention. The laser scanning fluorescence microscope 87 has an Ar laser 88 that continuously oscillates at a wavelength of 488 nm as an excitation light source. In FIG. 10, the laser light emitted from the Ar laser 88 is adjusted by a light intensity adjuster 89 such as an acousto-optic modulator (AOM), for example, and an XY galvanometer mirror 90, Through the pupil projection lens 91, the imaging lens 92, the dichroic mirror 93, and the objective lens 94, the living cell sample 101 to be examined was condensed and irradiated. Therefore, in this laser scanning fluorescence microscope, the light intensity adjuster 89, the XY galvanometer mirror 90, the pupil projection lens 91, the imaging lens 92, the dichroic mirror 93, and the objective lens 94 use the excitation light from the excitation light source as a sample. The light irradiation means to irradiate is comprised. Further, the XY galvanometer mirror 90 constitutes an optical scanning unit.

  As the live cell sample 101, an inspection object stained with a fluorescent dye or an inspection object expressing a fluorescent protein was used. Here, it is assumed that a substance to be examined in which fluorescent protein Enhanced green fluorescence protein (eGFP) is expressed is used. Therefore, when the live cell sample 101 was irradiated with laser light from the Ar laser 88, eGFP was excited and fluorescence having a wavelength of about 500 nm to 600 nm was generated.

  The fluorescence generated from the living cell sample 101 is guided to the dichroic mirror 93 through the objective lens 94. The dichroic mirror 93 is configured to transmit light having a wavelength of 488 nm and reflect light having a wavelength longer than 500 nm. Thereby, the fluorescence having a wavelength of about 500 nm to 600 nm generated in the living cell sample 101 was reflected by the dichroic mirror 93.

  The fluorescence reflected by the dichroic mirror 93 was condensed by a lens 95, and a pinhole 96 was disposed at the position of the condensing point. The fluorescence transmitted through the pinhole 96 becomes parallel light through the lens 97. This was detected signal light and input to the half mirror 32.

  As the light source for local light emission, a light output from the LED (A) 18 that emits light in the wavelength 530 nm band and the LED (B) 19 that emits light in the wavelength 630 nm band is combined by the dichroic mirror 98. The light combined by the dichroic mirror 98 is input to the half mirror 32 via the homogenizer 17.

  Since the half mirror 32, the mirror 33, the mirror 34, the DBD 26, the ADC 57, and the computer 58 have the same functions as those of the sixth embodiment shown in FIG. However, the computer 58 performs control in addition to controlling the entire laser scanning fluorescent microscope 87. As a result, the laser beam from the Ar laser 88 is deflected by the XY galvanometer mirror 90, and the living cell sample 101 is two-dimensionally scanned in a plane orthogonal to the optical axis of the objective lens 94. The output obtained from the ADC 57 is processed to display a fluorescent image on the monitor 59.

  As described above, the laser scanning fluorescence microscope according to the present embodiment detects heterodyne fluorescence generated from the living cell sample 101 by irradiation with the laser light from the Ar laser 88. Therefore, even if the fluorescence, which is the signal light obtained from the live cell sample 101, is weak, the live cell sample 101 can be raised without increasing the intensity of the laser light applied to the live cell sample 101 or increasing the light reception integration time. The fluorescence can be observed with high sensitivity and high S / N ratio. Note that the number of LEDs constituting the local light generation means is not limited to two, but may be three or more according to the wavelength band of the input signal light to be detected.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, the detected signal light is not limited to reflected light, scattered light, and fluorescence from the sample, but the light detection apparatus according to the present invention can be effectively applied to transmitted light and phosphorescence. In the above-described embodiment, the case where a biological sample such as a living tissue or living cell is a scatterer has been described. However, the present invention can be applied to various test substances existing in a scatterer other than a biological sample. . In addition to analytes other than the analyte in the scatterer, analytes that exist in the deep or distant area of the detection target (radar detection targets, astronomical substances, seabed, deep-sea creatures, etc.) and other light-absorbing substances are present. It is possible to detect with high sensitivity and a high S / N ratio even for light to be detected from a test substance existing in such an environment.

  The present invention can be applied to light detection from ultraviolet light having a wavelength of about 180 nm to infrared light having a wavelength of about 50 μm, and is not limited to the detection of visible light described in the above embodiment. For example, when detecting ultraviolet rays, the local light generation means can use, for example, ultraviolet lamp light as local light for ultraviolet detection. The optical multiplexing means can be configured using, for example, a multilayer mirror, and the photoelectric conversion means can be configured using, for example, a PMT.

  Moreover, when detecting infrared rays, an infrared lamp can be used as the local light generation means, for example. The optical multiplexing means can be configured using, for example, a CsI substrate type beam splitter, and the photoelectric conversion means can be configured using, for example, a photoconductive element using Ge: Zn.

10 Local light emission means 11 SLD
12 BPF
13 Fluorescent plate 14 Spectrum shaping filter 15 LED unit 16 Local LED
17 Homogenizer 18 LED (A)
19 LED (B)
20 Photoelectric conversion means 21 Photoelectric conversion means (A)
22 Photoelectric conversion means (B)
23 DBD
24 CCD (A)
25 CCD (B)
26 DBD
30 Optical multiplexing / demultiplexing means 31 Optical fiber coupler 32 Half mirror 33 Mirror 34 Mirror 40 Subtracting means 51 LD
52 Optical fiber 53 Lens 54 Lens 55 Movable base 56 SMF
57 ADC
58 Computer 59 Monitor 60 Control Unit 61 Illumination Light Source 62 Lens 63 LGF
64 Endoscope housing 65 Lens optical system 66 Beam splitter 67 Lens optical system 68 Lens optical system 69 Amplifier 70 Amplifier 71 Control unit 72 Light source for fluorescence excitation 73 Control unit 74 Signal light source unit 75 Optical fiber 76 Optical fiber type splitter 77 Multi-core optical fiber 77A Illumination core 77B Light-receiving core 77C Clad 78 Drive mechanism 79 Lens optical system 80 Multimode optical fiber 81 Control unit 82 Capsule type housing 83 Illumination LED
84 Condensing Lens Optical System 85 Signal Processing Unit 86 Signal Transmitting Unit 87 Laser Scanning Fluorescence Microscope 88 Ar Laser 89 Light Intensity Adjuster 90 XY Galvano Mirror 91 Pupil Projection Lens 92 Imaging Lens 93 Dichroic Mirror 94 Objective Lens 95 Lens 96 pinhole 97 lens 98 dichroic mirror 100 biological tissue 101 living cell sample

Claims (12)

A local light source that generates local light,
An irradiation light generating light source different from the local light generating light source for generating irradiation light to be irradiated to the subject;
A photoelectric that generates a beat signal of the local light and the detected light by photoelectrically converting the detected light and the local light generated when the irradiation light is reflected, transmitted, refracted, or diffracted by the subject. Conversion means;
Heterodyne detection means for heterodyne detection of the detected light based on the output of the photoelectric conversion means,
An optical detection device, wherein an optical spectrum line width of the local light emitted from the local light generation light source is wider than an operating band of the heterodyne detection means.   The photodetection device according to claim 1, wherein the photoelectric conversion unit performs balanced detection.   The light detection device according to claim 1, wherein the local light generation light source includes a plurality of light generation sources.   The light detection apparatus according to claim 1, wherein the local light generation light source includes an optical filter unit that selects a predetermined optical frequency component.   The light detection apparatus according to claim 1, wherein the local light generation light source includes a light spectrum shaping unit that shapes a light spectrum into a desired shape.   The light detection apparatus according to claim 1, wherein the local light generation light source includes fluorescence generation means.   3. The photodetecting device according to claim 1, further comprising a spatial light filter unit that selects only light having a desired spatial distribution in a stage preceding the photoelectric conversion unit.   3. The photodetecting device according to claim 1, further comprising a spatial light homogenizer unit that makes a spatial light intensity distribution uniform before the photoelectric conversion unit.   The photodetector according to claim 1, further comprising an envelope detection unit that detects an envelope of an output of the photoelectric conversion unit. A microscope for detecting light to be detected from an observation sample,
It has the photon detection device according to any one of claims 1 to 9,
A microscope configured to detect heterodyne the detected light from the observation sample by the light detection device. An endoscope for detecting light to be detected from inside a body cavity and observing the inside of the body cavity,
It has the photon detection device according to any one of claims 1 to 9,
An endoscope characterized in that the detected light from the body cavity is heterodyne detected by the light detection device. An endoscope for detecting light to be detected from inside a body cavity and observing the inside of the body cavity,
Scanning means for scanning the irradiation light on the sample;
An optical transmission optical system for transmitting light transmitted, reflected, scattered, refracted or diffracted from the sample;
A light detection device according to any one of claims 1 to 9, comprising:
An endoscope characterized in that the detected light from the body cavity is heterodyne detected by the light detection device.

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