JP6082108B2 - Optical signal detection circuit and measurement device - Google Patents

Description

  The present invention relates to an optical signal detection circuit, and more particularly to an optical signal detection circuit that detects optical signals of a plurality of channels.

  In recent years, gene analysis devices and various diagnostic devices applying optical measurement technology have been actively developed. For example, Patent Document 1 discloses an apparatus that detects genetic polymorphism, particularly SNP (single nucleotide polymorphism), and diagnoses disease morbidity and diagnoses the relationship between the type of drug administered, effects, and side effects. Here, there is shown a method of irradiating a measurement sample with two types of excitation light and detecting fluorescence generated from the sample as a result.

  FIG. 1 is a diagram for explaining a configuration of a fluorescence detection unit disclosed in Patent Document 1. In FIG. The fluorescence detection unit 64 shown in FIG. 1 includes two optical units 90A and 90B each having an excitation light irradiating unit and a fluorescence light receiving unit, and these two optical units have the wavelength of excitation light and the fluorescence received. The wavelengths are set to be different from each other. The optical unit 90A includes an LED 92a as an excitation light source, and includes a pair of lenses 94a and 96a and a dichroic mirror 98a that collects and emits the emitted light as excitation light to the bottom surface of the reaction vessel 41 containing the measurement sample. The optical unit 90B includes an LED 92b as an excitation light source, and includes a pair of lenses 94b and 96b and a dichroic mirror 98b that collects and emits the emitted light as excitation light on the bottom surface of the reaction vessel 41. The dichroic mirrors 98a and 98b have wavelength characteristics so as to reflect excitation light and transmit fluorescence generated from the sample. The fluorescence transmitted through the dichroic mirrors 98 a and 98 b is incident on the optical fibers 103 a and 103 b by the condenser lenses 102 a and 102 b and guided to the common photodetector 105. In the fluorescence detection unit 64, the LEDs 92a and 92b are alternately turned on, and the light detection by the photodetector 105 is performed while the LEDs 92a or 92b are turned on.

  Patent Document 2 discloses a method of measuring relative changes in cerebral blood flow information, that is, blood hemoglobin concentration, by detecting transmitted light of light irradiated on the head of a living body. 2 and 3 are diagrams for explaining the configuration of the biological light measurement device disclosed in Patent Document 2. FIG. This biological light measurement apparatus includes a first set of irradiation probes 11a and detection probes 11b shown in FIG. 2, and a second set of irradiation probes and detection probes (not shown). In FIG. 2, the signal modulation circuit and the signal detection circuit related to the first set of irradiation probes 11a and detection probes 11b are shown, but similar circuits are also provided for the second set of irradiation probes and detection probes.

  This biological light measurement apparatus uses a semiconductor laser 2 as a light source. The semiconductor laser 2 emits light whose intensity has been modulated into a rectangular wave by the laser driving circuit 3. A modulation frequency is applied to the laser driving circuit 3 by an oscillator 4. The emitted light is irradiated to the head of the subject 5 through the irradiation optical fiber 18a and the irradiation probe 11a, and the light transmitted through the subject 5 is sent to the detector 6 through the detection probe 11b and the detection fiber 18b. Sent. The detection signal converted into current by the detector 6 is sent to the lock-in processing unit 7 (see FIG. 3). The lock-in processing unit 7 includes an amplifier 13, an analog switch 14, a low-frequency cut filter unit 15, an AD converter 16, and a lock-in calculation unit 17.

  The pulse generator 19 generates a pulse signal for alternately turning on and off the first set of light sources and the second set of light sources. The pulse signal and the modulation signal from the oscillator 4 are input to the AND gate 20, and the output from the AND gate 20 is input to the laser driving circuit 3. As a result, the laser drive circuit 3 turns the semiconductor laser 2 on and off in synchronization with the pulse generated by the pulse generator 19. The pulse signal from the pulse generator 19 is also input to the analog switch 14. As a result, the analog switch 14 turns on / off the signal input to the low-frequency cut filter unit 15 in synchronization with the pulse generated by the pulse generator 19.

  As shown in FIG. 3, the signal that has passed through the low-frequency cut filter unit 15 is converted into a digital signal by the AD converter 16 and input to the lock-in calculation unit 17. The lock-in calculation unit 17 detects a signal synchronized with the reference signal using the same frequency as the modulation frequency of the light source as a reference signal. By the above operation, the first set and the second set of optical signals transmitted through the head of the subject 5 can be detected alternately.

  In the above two examples, two sets of optical signals having different wavelengths are detected, but both sets of optical signals are detected alternately (in a time division manner). That is, in the example shown in FIG. 1, since the photodetector 105 is common, a time-division detection method is used to distinguish the fluorescence signals from the two optical units 90A and 90B. In the example shown in FIG. 2, the detectors 6 are separate for the first set and the second set, but one set of detection probes detects transmitted light from the irradiation light from the other set of irradiation probes. Therefore, a time-division detection method is used as in the example shown in FIG.

JP 2006-271347 A JP 2009-424 A

  FIG. 4 is a diagram for explaining a problem of the biological light measurement device according to the related art. In the biological light measurement apparatus according to Patent Document 2, as shown in FIG. 4, the first set of light sources is turned on / off at regular intervals while being modulated at the modulation frequency f1, and the second set of light sources is modulated at the modulation frequency f2. Is turned on / off at the opposite timing to the first set of light sources.

  The optical signals received by the first set and the second set of detectors 6 are finally processed by the lock-in calculation unit 17 and converted into DC voltage signals, which are output. This detection signal is output only when each light source is on as shown in FIG. 4 (since normalization is performed in the normal lock-in calculation, the rise and fall of the detection signal are as shown in FIG. Is usually an exponential change). Therefore, as shown in FIG. 4, the detection signals of the first set and the second set are discontinuous, and there is a time lag between the detection timings of the first set and the second set. This is a problem caused by taking a time-division detection method in which the first set and the second set of detection operations are alternately performed. When the number of sets to be detected is larger, the period in which each set is not detected (period in which the light source is off) and the time lag in detection timing are further increased. In particular, a shift in detection timing may cause a problem that not all sets of detection signals can be obtained simultaneously when it is important to observe temporal changes in detection signals.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an optical signal detection circuit for detecting optical signals of a plurality of channels, which can continuously obtain detection signals of each channel and all channels. It is an object of the present invention to provide a technique capable of simultaneously obtaining the detection signals.

  In order to solve the above problems, an optical signal detection circuit according to an aspect of the present invention is an optical signal detection circuit that detects optical signals of a plurality of channels, and includes a light source provided for each channel and a plurality of light sources. In contrast, a pulse generation circuit that sequentially supplies blinking pulses one by one, a photodetector that photoelectrically converts a response light signal from the light source, and a switch provided for each channel, synchronized with the blinking pulse And a switch that extracts a signal corresponding to each channel from the output signal of the photodetector by being switched, and a DC conversion circuit that is provided for each channel and converts the output signal of each switch into a DC signal. .

  An external light component detection circuit for detecting an external light component and a subtracting circuit for subtracting the external light component from the output signal of the photodetector may be further provided between the light detector and the switch.

  The pulse generation circuit generates an external light detection pulse at a timing different from the blinking pulse, and the external light component detection circuit includes a sample and hold circuit that detects the external light component using the external light detection pulse. Good.

  The external light component detection circuit may further include a low-pass filter that removes shot noise of the photodetector.

  The DC converter circuit converts the output signal of the high-pass filter to DC by switching between an inverting amplification operation and a non-inverting amplification operation in accordance with the on / off timing of the blinking pulse, and a high-pass filter that removes the DC component from the switch output signal. And an inverting / non-inverting amplifier that converts the signal into a signal.

  The pulse generation circuit may provide a time interval between blinking pulses.

  Another aspect of the present invention is a measurement device. This measuring apparatus includes the above-described optical signal detection circuit, and a probe that irradiates an optical signal from a light source onto an object to be detected, and detects a response optical signal from the object to be detected and outputs it to the optical detector.

  The probe may be common for multiple channels. Alternatively, a separate probe may be provided for each channel.

  A first optical fiber that guides an optical signal from the light source to the probe and a second optical fiber that guides a response optical signal from the probe to the photodetector may be provided for each channel. The photodetector may be common for multiple channels.

  Yet another embodiment of the present invention is also a measurement device. This measuring apparatus includes the above-described optical signal detection circuit, an irradiation probe that irradiates an object with an optical signal from a light source, and a detection probe that detects a response optical signal from the object to be detected and outputs it to a photodetector. May be provided.

  According to the present invention, in an optical signal detection circuit that detects optical signals of a plurality of channels, detection signals for each channel can be obtained continuously, and detection signals for all channels can be obtained simultaneously.

It is a figure for demonstrating the structure of the fluorescence detection part disclosed by patent document 1. FIG. It is a figure for demonstrating the structure of the biological light measuring device disclosed by patent document 2. FIG. It is a figure for demonstrating the structure of the biological light measuring device disclosed by patent document 2. FIG. It is a figure for demonstrating the subject of the biological light measuring device which concerns on a prior art. It is a figure for demonstrating the fluorescence detection apparatus to which the optical signal detection circuit which concerns on this embodiment is applied. It is a figure for demonstrating the structure of a signal detection circuit. It is a figure which shows the light emission timing of the light source of each channel, and the waveform of the output signal which generate | occur | produces in 1st IV amplifier of a 1st channel by them. It is a figure which shows the mode of the signal processing after the fluorescence signal extraction of the 1st channel. It is a figure which shows the fluorescence detection apparatus to which the optical signal detection circuit based on 1st Example of this invention is applied. It is a figure which shows the waveform of the blinking pulse and external light detection pulse in 1st Example. It is a figure which shows a step response waveform when using said pigment | dye liquid mixture as a measurement sample. It is a figure for demonstrating the fluorescence detection apparatus which concerns on a modification. It is a figure for demonstrating the fluorescence detection apparatus which concerns on another modification. It is a figure which shows the fluorescence detection apparatus to which the optical signal detection circuit based on 2nd Example of this invention is applied.

  Hereinafter, an optical signal detection circuit according to an embodiment of the present invention will be described. The optical signal detection circuit according to the present embodiment can be used for detecting optical signals of a plurality of channels. Here, a case where an optical signal of three channels is detected will be described as an example. The optical signal detection circuit of the present embodiment can be used for various optical signal detections that require a time-division detection method, and is not limited to a specific optical system, Here, a case where an optical signal detection circuit is applied to the fluorescence detection device will be described.

  FIG. 5 is a diagram for explaining a fluorescence detection apparatus 500 to which the optical signal detection circuit 530 according to the present embodiment is applied. The fluorescence detection apparatus 500 irradiates a sample 501 as an object to be detected with excitation light and detects fluorescence generated from the sample 501 by the irradiation.

  As shown in FIG. 5, the fluorescence detection apparatus 500 includes three fluorescence detection optical units (a first fluorescence detection optical unit CH1 for the first channel, a second fluorescence detection optical unit CH2 for the second channel, and A third fluorescence detecting optical unit CH3 for the third channel; a pulse generating circuit 520; and a probe 522.

  The first fluorescence detection optical unit CH1 includes a first light source 502a, a first light source drive circuit 503a, a first optical multiplexer / demultiplexer 504a, a first photodetector 505a, a first signal detection circuit 506a, The optical fiber 512a for 1st excitation light, the optical fiber 513a for 1st light guide, and the optical fiber 514a for 1st fluorescence are provided. The first signal detection circuit 506a includes a first IV amplifier (current-voltage conversion amplifier) 507a, a first external light detection circuit 508a, a first subtraction circuit 509a, a first analog switch 510a, and a first DC conversion circuit 511a. With.

  The second fluorescence detection optical unit CH2 includes a second light source 502b, a second light source drive circuit 503b, a second optical multiplexer / demultiplexer 504b, a second photodetector 505b, a second signal detection circuit 506b, The optical fiber 512b for 2 excitation light, the optical fiber 513b for 2nd light guide, and the optical fiber 514b for 2nd fluorescence are provided. The second signal detection circuit 506b includes a second IV amplifier 507b, a second external light detection circuit 508b, a second subtraction circuit 509b, a second analog switch 510b, and a second DC conversion circuit 511b.

  The third fluorescence detection optical unit CH3 includes a third light source 502c, a third light source drive circuit 503c, a third optical multiplexer / demultiplexer 504c, a third photodetector 505c, a third signal detection circuit 506c, The optical fiber 512c for 3 excitation light, the optical fiber 513c for 3rd light guide, and the optical fiber 514c for 3rd fluorescence are provided. The third signal detection circuit 506c includes a third IV amplifier 507c, a third external light detection circuit 508c, a third subtraction circuit 509c, a third analog switch 510c, and a third DC conversion circuit 511c.

  The optical signal detection circuit 530 according to the present embodiment includes a light source for each channel, a light source driving circuit, a photodetector and a signal detection circuit, and a pulse generation circuit 520.

  Since the first to third fluorescence detection optical units CH1 to CH3 have the same configuration, the configuration of the first fluorescence detection optical unit CH1 will be described as a representative here. The first light source 502a and the first light source driving circuit 503a constitute a light source part of the first fluorescence detection optical unit CH1. The first light source driving circuit 503a receives the first blinking pulse CL1 from the pulse generation circuit 520 at a constant cycle, and uses the first light source 502a to drive the first light source 502a based on the first blinking pulse. Output to. The first light source 502a emits the first excitation light having the main wavelength λ1a based on the drive pulse from the first light source drive circuit 503a. For the first light source 502a, an LED, a semiconductor laser, or the like can be used.

  The first pumping light emitted from the first light source 502a is guided to the first optical multiplexer / demultiplexer 504a through the first pumping light optical fiber 512a. As the 1st optical multiplexer / demultiplexer 504a, what was described in Unexamined-Japanese-Patent No. 2005-30830 can be used, for example. The first excitation light incident on the first optical multiplexer / demultiplexer 504a is guided to the first light guiding optical fiber 513a in the first optical multiplexer / demultiplexer 504a, and probed through the first light guiding optical fiber 513a. 522.

  The probe 522 includes a condensing lens that condenses the first excitation light emitted from the distal end portion of the first light guiding optical fiber 513a. As the condenser lens, for example, a rod lens can be used. The first excitation light is applied to the sample 501 through this condenser lens. Fluorescence (referred to as “first fluorescence”) having a dominant wavelength λ1b (λ1b> λ1a) generated from the sample 501 by irradiation with the first excitation light is collected by the condenser lens, and the first light guiding optical fiber 513a. Is propagated in the direction opposite to that of the first excitation light and is incident on the first optical multiplexer / demultiplexer 504a. The first fluorescence incident on the first optical multiplexer / demultiplexer 504a is guided to the first fluorescence optical fiber 514a in the first optical multiplexer / demultiplexer 504a, and the first optical detection is performed via the first fluorescence optical fiber 514a. Is incident on the container 505a.

  The first photodetector 505a converts the incident fluorescence into a current (photoelectric conversion), and outputs the current signal to the first signal detection circuit 506a. As the first photodetector 505a, a photodiode (PD), an avalanche photodiode (APD), a photomultiplier tube, or the like can be used. The first signal detection circuit 506a extracts only a signal corresponding to the first fluorescence from the input signal, converts the signal into a DC signal, and outputs the DC signal. The detailed configuration of the first signal detection circuit 506a will be described later.

  In the fluorescence detection apparatus 500, the first excitation light having the dominant wavelength λ1a is emitted from the first light source 502a of the first fluorescence detection optical unit CH1, and the dominant wavelength is emitted from the second light source 502b of the second fluorescence detection optical unit CH2. The second excitation light of λ2a is emitted, and the third excitation light of the main wavelength λ3a is emitted from the third light source 502c of the third fluorescence detection optical unit CH3. The main wavelengths λ1a, λ2a, and λ3a are different from each other. The first light guiding optical fiber 513a that propagates the first excitation light, the second light guiding optical fiber 513b that propagates the second excitation light, and the third light guiding optical fiber 513c that propagates the third excitation light, The sample 501 is irradiated to the sample 501 through the common condenser lens provided in the probe 522. As the structure of such a fluorescence detection probe, for example, the one described in JP-A-2009-36538 can be used.

  The sample 501 generates fluorescence corresponding to each of the three colors of excitation light. That is, the sample 501 receives the first excitation light having the main wavelength λ1a to generate the first fluorescence having the main wavelength λ1b (λ1b> λ1a), and receives the second excitation light having the main wavelength λ2a. The second fluorescence of λ2b (λ2b> λ2a) is generated, and the third fluorescence of the main wavelength λ3b (λ3b> λ3a) is generated by receiving the third excitation light of the main wavelength λ3a. Examples of such a sample that generates multiple colors of fluorescence include a DNA composition labeled with a plurality of fluorescent dyes.

  In the fluorescence detection apparatus 500, the first optical multiplexer / demultiplexer 504a is configured to guide the first fluorescence having the main wavelength λ1b to the first optical fiber 514a for fluorescence, and the second optical multiplexer / demultiplexer 504b is the first optical multiplexer / demultiplexer 504b having the first wavelength λ2b. The second fluorescence is configured to guide the second fluorescence optical fiber 514b, and the third optical multiplexer / demultiplexer 504c is configured to guide the third fluorescence having the main wavelength λ3b to the third fluorescence optical fiber 514c. Accordingly, fluorescences having λ1b, λ2b, and λ3b as main wavelengths are incident on the first to third photodetectors 505a to 505c, respectively.

  Here, when there is at least a partial overlap between the wavelength band of the excitation light of one channel and the wavelength band of the fluorescence of the other channel, there is a possibility that the excitation light of the other channel enters the photodetector of one channel. . For example, when there is at least partial overlap between the wavelength band of the second excitation light of the second channel and the wavelength band of the first fluorescence of the first channel, a part of the surface of the condensing lens of the probe 522, the surface of the sample 501, etc. The reflected second excitation light of the second channel may be incident on the first photodetector 505a of the first channel. Therefore, it is necessary to separate fluorescence that should be detected from unnecessary excitation light.

  FIG. 6 is a diagram for explaining the configuration of the signal detection circuit. Here, the first signal detection circuit 506a of the first channel is shown, but the signal detection circuits of the other two channels basically have the same configuration.

  As described above, the first signal detection circuit 506a includes the first IV amplifier 507a, the first external light detection circuit 508a, the first subtraction circuit 509a, the first analog switch 510a, and the first DC conversion circuit 511a. Prepare.

  As shown in FIG. 6, the first external light detection circuit 508 a includes a resistor R and a sample and hold circuit 600. The sample and hold circuit 600 includes a switch 601, a capacitor 602, and a buffer amplifier 603. One terminal of the resistor R is connected to the output terminal of the first IV amplifier 507a, and the other terminal is connected to one terminal of the switch 601. The other terminal of the switch 601 is connected to one terminal of a capacitor 602, and the other terminal of the capacitor 602 is grounded. The other terminal of the switch 601 is connected to the input terminal of the buffer amplifier 603. The switch 601 is controlled to be turned on / off by an external light detection pulse CL4 from a pulse generation circuit 520 (see FIG. 5).

  The first subtraction circuit 509a is composed of an operational amplifier. The two input terminals of the first subtracting circuit 509a are connected to the output terminal of the first IV amplifier 507a and the output of the sample & hold circuit 600, that is, the output terminal of the buffer amplifier 603. From the output signal of the first IV amplifier 507a, The output signal of the sample and hold circuit 600 is subtracted.

  The output terminal of the first subtraction circuit 509a is connected to one input terminal A of the first analog switch 510a. The other input terminal B of the first analog switch 510a is grounded. The first analog switch 510a switches between the input terminals A and B in synchronization with the first blinking pulse CL1 from the pulse generation circuit 520.

  As shown in FIG. 6, the first DC conversion circuit 511a includes a high-pass filter (HPF) 604, an inverting / non-inverting amplifier (an amplifier capable of switching between inverting amplification operation and non-inverting amplification operation) 605, and a low-pass filter (LPF). 609). The inverting / non-inverting amplifier 605 includes an inverting amplifier 606, a non-inverting amplifier 607, and a switch 608. The output terminal of the first analog switch 510 a is connected to the input terminal of the high pass filter 604. The output terminal of the high pass filter 604 is connected to the input terminal of the inverting amplifier 606 and the input terminal of the non-inverting amplifier 607. The output terminal of the inverting amplifier 606 is connected to one input terminal of the switch 608, and the output terminal of the non-inverting amplifier 607 is connected to the other input terminal of the switch 608. The output terminal of the switch 608 is connected to the low pass filter 609. The switch 608 is controlled to be turned on / off in synchronization with the first blinking pulse CL1 from the pulse generation circuit 520. The output signal of the first signal detection circuit 506a is output from the output terminal of the low-pass filter 609.

  FIG. 7 shows the light emission timing of the light source of each channel and the waveform of the output signal generated by the first IV amplifier of the first channel. In the present embodiment, the pulse generation circuit 520 causes the three light sources to blink (on / off) sequentially one pulse at a time by sequentially supplying blinking pulses to the three light sources one by one. That is, first, the first blinking pulse CL1 is supplied to the first light source 502a to emit one pulse of the first excitation light, and then the second blinking pulse CL2 is supplied to the second light source 502b to supply the second excitation light. Is emitted, and then the third blinking pulse CL3 is supplied to the third light source 502c to emit one pulse of the third excitation light.

  The external light detection pulse CL4 is used to detect an external light component included in the optical signal received by each photodetector and the output signal of each IV amplifier. Here, although expressed as an external light component, this includes components that cause a so-called baseline, such as a dark current of a photodetector and an offset signal of an IV amplifier. The external light detection pulse CL4 is generated at a timing different from that of the first flashing pulse CL1, the second flashing pulse CL2, and the third flashing pulse CL3. That is, the external light detection pulse CL4 is turned on during a period in which the first blinking pulse CL1, the second blinking pulse CL2, and the third blinking pulse CL3 are all off. The first flashing pulse CL1, the second flashing pulse CL2, the third flashing pulse CL3, and the external light detection pulse CL4 have the same cycle.

  As shown in FIG. 7, the output signal of the first channel first IV amplifier 507a includes first fluorescence generated by the first excitation light, reflected light of the second excitation light, reflected light of the third excitation light, and external light. The ingredients are synthesized. However, since the reflected light of the excitation light is cut by the first optical multiplexer / demultiplexer 504a when there is no portion overlapping the wavelength band of the first fluorescence, the reflected light of the second excitation light and the third excitation light is not necessarily reflected. Both do not always appear.

  As shown in FIG. 6, the output signal of the first IV amplifier 507a is divided into two, and one is sent to the sample and hold circuit 600 to detect the external light component. In the sample and hold circuit 600, the charge of the signal is stored in the capacitor C (sample) while the external light detection pulse CL4 is on, and the charge is held (held) while the external light detection pulse CL4 is off. The The signal during the period when the external light detection pulse CL4 is on is only the external light component because all the light sources are extinguished. Therefore, the signal from which the external light component is extracted appears at the output of the sample and hold circuit 600. become. The external light component can be detected not only when the intensity is constant, but also when the external light component fluctuates at a sufficiently slow period as compared with the blinking period of the light source. Normally, the output of the first photodetector 505a that has received external light includes shot noise (a type of white noise) corresponding to the intensity of external light, but the capacitor C of the sample & hold circuit 600 and the sample & By removing noise with a low-pass filter including the resistor R immediately before the hold circuit 600, it is possible to detect the average behavior of the external light component. If R = 0Ω and noise removal is not performed, the noise voltage appears as it is at both ends of the capacitor C. Therefore, the held voltage level (the voltage level at the moment when the external light detection pulse CL4 is switched from on to off) is set. The external light detection pulse CL4 may vary greatly every period, and the external light component detected as a result may include large noise.

  The external light component detected by the sample and hold circuit 600 is subtracted from the output signal of the original first IV amplifier 507a in the next first subtraction circuit 509a. The subsequent first analog switch 510a extracts only the first fluorescence corresponding to the first channel from the output signal of the first subtracting circuit 509a by switching in synchronization with the first blinking pulse CL1 of the first light source 502a. To do. That is, during the period when the first blinking pulse CL1 is on, the first analog switch 510a is switched to the input terminal A, and the first fluorescence is extracted and output to the subsequent circuit. On the other hand, since the first analog switch 510a is switched to the input terminal B and grounded while the first blinking pulse CL1 is off, the ground potential is output to the subsequent circuit. With the operation so far, the external light component is removed and separated from the signals of other channels without losing the amplitude information of the fluorescence signal.

  The external light component is not the method performed here, for example, when the output signal of the first IV amplifier 507a is passed through the high-pass filter as it is or when the signal separation between the channels is performed first, and then When the high-pass filter is used for removal, the amplitude information of the fluorescence signal is lost at that time, and thus correct signal detection cannot be performed.

  FIG. 8 shows a state of signal processing after extraction of the fluorescence signal of the first channel. The pulse signal extracted by the first analog switch 510a is converted into a DC signal by the first DC conversion circuit 511a. As described above, the first DC conversion circuit 511a includes the high-pass filter (HPF) 604, the inverting / non-inverting amplifier 605, and the low-pass filter (LPF) 609.

  The output signal from the first analog switch 510a is subjected to signal amplification in accordance with the ON / OFF timing of the first blinking pulse CL1 in the inverting / non-inverting amplifier 605 after the DC component is removed by the high-pass filter 604. As shown in FIG. 8, when the duty ratio x of the first blinking pulse CL1 is expressed by x = a / (a + b), when the first blinking pulse CL1 is on, the non-inverting amplifier 607 increases it to +1 times. When one blinking pulse CL1 is off, it is amplified-(1-x) / x times (-3 times when the duty ratio is 25%) by the inverting amplifier 606, and as a result, the signal is converted to DC. Become. Here, in order to make the explanation easy to understand, the inverting / non-inverting amplifier 605 is composed of two amplifiers of an inverting amplifier 606 and a non-inverting amplifier 607 and a switch 608, but a circuit having the same function. Can be configured with only one operational amplifier and switch. In this case, the operation of one operational amplifier is switched to the non-inverting amplification operation or the inverting amplification operation by turning on / off the switch with the first blinking pulse CL1 (the connection position of the switch in this case is shown in FIG. 6). (This is slightly different from the connection position of the switch 608, but the description is omitted here.)

  The signal converted into direct current by the inverting / non-inverting amplifier 605 is subjected to noise removal by the low-pass filter 609, and a final output is obtained.

  The above is the description of the operation of the first signal detection circuit 506a of the first channel. The basic operation of the second signal detection circuit 506b of the second channel and the third signal detection circuit 506c of the third channel is the same as that of the first signal detection circuit 506a of the first channel. The latter-stage analog switch and inverting / non-inverting amplifier changeover switch operate in synchronization with the flashing pulse of each channel (second flashing pulse CL2, third flashing pulse CL3), that is, the flashing pulse of each channel is turned on / off. It is only a point that operates at timing. The detection of the external light component is performed simultaneously on all the channels during the period when the light sources of all the channels are turned off.

  Since the signal detection circuit of the present embodiment can be configured only with an analog circuit, an inexpensive optical signal detection circuit 530 and, in turn, a fluorescence detection device 500 can be realized.

  In the optical signal detection circuit 530 according to the present embodiment, the response time of the output signal is determined by the response time of the low-pass filter 609 at the final stage of the detection circuit, that is, the signal averaging time. Usually, averaging is performed for a time corresponding to the number of pulses of several tens of blinking pulses or more. As shown in FIG. 4, this averaging process is the same for the optical measurement device of Patent Document 2 described above. However, in the optical measurement device of Patent Document 2, since the averaging process for one channel is performed after the averaging process for one channel is completed, there are several tens of pulses or more between the output signals of each channel. A time difference corresponding to the number of pulses is generated. On the other hand, in this embodiment, since the light emission timing of each channel has a shift of only one pulse, only a time difference of one pulse occurs between the output signals of each channel, and substantially all channels have the same time. It can be considered that the output signals are output at the same time (measurement results are shown in the examples described later). As described above, since signal processing is simultaneously performed in all channels, the detection time can be shortened as compared with the optical measurement device disclosed in Patent Document 2. Further, since the detection of the external light component is simultaneously performed in all channels, the detection time can be further shortened.

  Furthermore, in the optical signal detection circuit 530 according to the present embodiment, since the output signals of each channel are continuously output, the output signals of each channel are discontinuous as in the conventional example shown in FIG. No.

  Further, the conventional example shown in FIG. 4 has the following problems. When the number of groups to be detected in this conventional example is N, the time required to detect all the groups once each is N times that when only one group is detected. In particular, the rise time and fall time that occur each time the detection of each set is switched on and off is wasted time. Or, conversely, in order to make the total time required to detect all the sets one at a time to be the same as the detection time when only one set is detected, the detection time of each set is set to 1 / N. In this case, the detection accuracy generally decreases.

  In order to solve such a problem, in the optical signal detection circuit 530 according to the present embodiment, the cycle of the blinking pulse of each channel is set to be the same as the cycle of the blinking pulse when only one channel is detected. The response time of the low-pass filter at the final stage of the detection circuit is made the same as when only one channel is detected. Further, the peak value of the output power of the light source (excitation light) is increased by the amount by which the duty ratio of the blinking pulse is reduced. For example, if the duty ratio of the blinking pulse when detecting three channels is 25%, the duty ratio of the blinking pulse is usually 50% when only one channel is detected, so the duty ratio of the blinking pulse is 25%. In this case, the peak value of the output power of the light source (excitation light) can be increased as compared with the case where the duty ratio of the blinking pulse is 50% (in this case, the peak value of the output power is typically 2). But can be slightly different depending on the light source used).

  This is due to the following reason. The period of the blinking pulse of each channel is the same as the period of the blinking pulse when only one channel is detected, and the response time of the low-pass filter at the final stage of the detection circuit is the same as when only one channel is detected. If they are the same, the response time of the output signal is the same for both. On the other hand, when the duty ratio of the blinking pulse decreases, the detection accuracy usually decreases, but the peak value of the output power of the light source (excitation light) can be increased by the amount of decrease in the duty ratio of the blinking pulse. Detection can be performed with the same detection accuracy as when only one channel is used, or a decrease in detection accuracy can be minimized.

  Next, examples of the present invention will be described. FIG. 9 shows a fluorescence detection apparatus to which the optical signal detection circuit according to the first embodiment of the present invention is applied. In the first example shown in FIG. 9, the same or corresponding components as those in the embodiment shown in FIG. 5 are denoted by the same reference numerals, and the corresponding descriptions are omitted as appropriate.

  The fluorescence detection apparatus 500 shown in FIG. 9 is a three-channel fluorescence detection apparatus, and the overall configuration is basically the same as that of the embodiment shown in FIG. The first light source 502a of the first channel is a blue LED, and the main wavelength of the first excitation light is 470 nm. The second light source 502b of the second channel is a green LED, and the main wavelength of the second excitation light is 530 nm. The third light source 502c of the third channel is a red LED, and the main wavelength of the third excitation light is 630 nm. The dominant wavelength of the first fluorescence is 530 nm, the dominant wavelength of the second fluorescence is 630 nm, and the dominant wavelength of the third fluorescence is 680 nm. PD (photodiode) was used for the photodetector of each channel.

  The signal detection circuits 506a, 506b, and 506c for each channel have the same configuration as that shown in FIGS. Although a low noise type operational amplifier is used as the IV amplifier, any amplifier can be used as necessary. As elements constituting the sample and hold circuit of the external light component detection circuit, a general-purpose analog switch and capacitor C, and a general-purpose operational amplifier as a buffer amplifier were used. Although any amplifier can be used as the buffer amplifier, an operational amplifier having a low offset voltage and a low offset current is desirable. The time constant τ (= R × C) of the low-pass filter constituted by the capacitor C of the sample and hold circuit and the resistor R immediately before the circuit was set to 10 ms.

  Although a general-purpose operational amplifier is used for the subtraction circuit, it is desirable to use a low offset voltage and low offset current type operational amplifier. The analog switch used was a general-purpose type. The high-pass filter is composed of a resistor R and a capacitor C, and the time constant τ (= R × C) is set to 15 ms. A general-purpose operational amplifier is used as the inverting / non-inverting amplifier of the DC conversion circuit, but it is desirable to use a low offset voltage and low offset current type operational amplifier. The last low-pass filter was a fourth-order Bessel type low-pass filter composed of a general-purpose operational amplifier, a resistor R, and a capacitor C. This low-pass filter determines the response time of the signal detection circuit. The response time in the step response (here, the time from when the step-like input signal is added until the output signal reaches the level of 90% of the final value) ) Is about 0.18 s.

  FIG. 10 shows waveforms of the blinking pulse and the external light detection pulse in the first embodiment. The period of each pulse is about 9.09 ms (frequency 110 Hz), and the duty ratio is about 15%. The on / off timing of each pulse is as shown in FIG. A time interval as shown in the figure is provided between the pulses, in order to avoid an overlap between signals of each channel due to a time delay of the response of the IV amplifier. The pulse interval can be determined experimentally by observing the output signal waveform of the IV amplifier. The pulse period needs to be set to the same value for all the blinking pulses and the external light detection pulse, but the pulse ON time (or duty ratio) and the pulse interval do not necessarily have to be the same value. The output power of each LED was determined according to the specifications of the element used, and specifically, was set to about 1.7 times that in the case of a duty ratio of 50% (duty ratio at the time of detecting one channel).

  The signal detection performance of the three-channel fluorescence detection apparatus 500 according to the first embodiment will be described below. Here, a mixed liquid in which three kinds of fluorescent dyes, FITC (for blue excitation), Resorufin (for green excitation) and Cy5 (for red excitation) were mixed at an arbitrary concentration was used as a measurement sample.

  FIG. 11 shows a step response waveform when the above three-dye mixed solution is used as a measurement sample. This is obtained by measuring the change in the output signal of each channel from the time when the pulse shown in FIG. As shown in the figure, it can be seen that the detection signals of all the channels are output simultaneously and continuously with a response time of about 0.18 s.

  Next, the detection accuracy was compared when detecting only one channel and when detecting three channels simultaneously. When detecting only one channel, in the fluorescence detection apparatus 500 of FIG. 9, the duty ratio of the blinking pulse CL1 of the first channel is 50%, and the LED output power is about 1 / 1.7 when three channels are detected. Measurement was performed with the LED blinking pulses CL2 and CL3 turned off so that the second channel and the third channel would not operate. As a result, when the same sample was measured, the signal-to-noise ratio of the output signal at the time of simultaneous detection of 3 channels was only about 12% lower than that at the time of detection of 1 channel, indicating substantially the same detection performance.

  As described above, the first embodiment has the advantage that the detection signals for each channel can be obtained continuously and the detection signals for all channels can be obtained simultaneously. In addition, the detection accuracy when detecting three channels simultaneously can be made substantially equal to the detection accuracy when only one channel is detected in the same detection time.

  In the first embodiment described above, an LED is used as the light source of each channel, but a semiconductor laser or the like may be used instead of the LED. In the first embodiment, the PD is used as the photodetector for each channel, but an avalanche photodiode (APD), a photomultiplier tube (PMT), or the like may be used instead of the PD.

  In the first embodiment, the IV amplifier is provided after the photodetector (PD). However, when the IV amplifier is incorporated in the photodetector, it is not necessary to separately provide the IV amplifier.

  In the first embodiment, a circuit including a sample and hold circuit and a low-pass filter is shown as the external light component detection circuit. However, a sampling circuit such as an AD converter may be used.

  In the case where measurement is performed in an environment where external light components can be ignored, such as in a dark room, the external light component detection circuit and the subtraction circuit can be omitted.

  In the first embodiment, the case of detecting optical signals of three channels has been described, but the number of detected channels is not particularly limited.

  FIG. 12 is a diagram for explaining a fluorescence detection apparatus 500 according to a modification. In FIG. 12, the signal detection circuit and the like are not shown. Although the three-channel probe 522 is common in the first embodiment shown in FIG. 9, a separate probe may be provided for each channel as shown in this modification of FIG. That is, the first channel may include the first probe 522a, the second channel may include the second probe 522b, and the third channel may include the third probe 522c. It should be noted that excitation of each channel is possible not only when the points measured by the first probe 522a, the second probe 522b, and the third probe 522c are the same point on the sample as shown in FIG. When light influences each other, the optical signal detection circuit of this embodiment is effective.

  FIG. 13 is a diagram for explaining a fluorescence detection apparatus 500 according to another modification. In FIG. 13, the signal detection circuit and the like are not shown. In FIG. 13, only a single-channel fluorescence detection optical unit is shown. In the first embodiment shown in FIG. 9, each channel guides excitation light and fluorescence using a single optical fiber, but it may be configured to guide excitation light and fluorescence using separate optical fibers. . That is, in this modification, excitation light is guided from the light source 502 to the probe 522 by the excitation light guiding optical fiber 513_1, and fluorescence is guided from the probe 522 to the photodetector 505 by the fluorescence guiding optical fiber 513_2. Yes. In this case, it is preferable to provide the excitation light filter 504_1 between the light source 502 and the excitation light guiding optical fiber 513_1, and to provide the fluorescence filter 504_2 between the fluorescence guiding optical fiber 513_2 and the photodetector 505. .

  The optical signal detection circuit 530 according to the first embodiment is not limited to the fluorescence detection device as long as it is an optical measurement device that irradiates the detection target with the optical signal and detects the response optical signal from the detection target. It can be applied to various devices. For example, the optical signal detection circuit 530 according to the first embodiment can also be used in a device that detects transmitted light of light irradiated on the head of a living body as shown in FIG. Furthermore, the optical signal detection circuit 530 according to the first embodiment is not limited to a living body related measuring device such as a gene analyzer, and can be applied to various multichannel optical measuring devices.

  In the optical measurement device that detects transmitted light, an irradiation probe that irradiates a detection object with an optical signal from a light source, a detection probe that detects a response light signal from the detection object and outputs the response light signal to the photodetector, May be provided separately.

  FIG. 14 shows a fluorescence detection apparatus to which the optical signal detection circuit according to the second embodiment of the present invention is applied. In the second example illustrated in FIG. 14, the same or corresponding components as those in the embodiment illustrated in FIG. 5 are denoted by the same reference numerals, and the corresponding description is omitted as appropriate.

  Similarly to the first embodiment shown in FIG. 9, the fluorescence detection apparatus 500 shown in FIG. 14 is also a three-channel fluorescence detection apparatus. In the second embodiment, the probes (first probe 522a, second probe 522b, and third probe 522c) of each channel are independent, and a photodetector 505 (here, PMT (photomultiplier tube) is used). ) Is common to all channels.

  When the sample to be measured is different for each channel (the first sample 501a, the second sample 501b, the third sample 501c), or even when they are the same, there is a distance between the probes and the reflection of the excitation light does not affect each other. Can share a photodetector 505 that detects fluorescence. In the signal detection circuit 506, the IV amplifier 507 to the subtraction circuit 509 can be shared by all channels.

  The main wavelengths of excitation light and fluorescence of each channel and the configuration of the signal detection circuit are the same as those in the first embodiment shown in FIG. The waveforms of the blinking pulse and the external light detection pulse are the same as those of the first embodiment shown in FIG. Furthermore, the output power of the LED of each channel was also made the same as in the first embodiment.

  With such a configuration, the step response was measured in the same manner as in the first example. As a result, the same result as the measurement result in the first example (see FIG. 11) was obtained.

  Similarly to the first embodiment, as a result of comparing the detection accuracy when detecting only one channel and when detecting three channels at the same time, as in the first embodiment, the output signal at the time of simultaneous detection of three channels. The S / N ratio was almost the same as when one channel was detected.

  The second embodiment has the following advantages in addition to the advantages described in the first embodiment. In the second embodiment, a part of the photodetector 505 and the signal detection circuit 506 is shared by all channels. Accordingly, the cost and size of the fluorescence detection device 500 can be reduced. In particular, when an expensive photodetector such as a PMT (photomultiplier tube) is used, the cost can be greatly reduced.

  A modification similar to that of the first embodiment can be applied to the second embodiment. Here, only differences from the first embodiment will be described. As the common photodetector 505, a photodiode (PD), an avalanche photodiode (APD), or the like may be used instead of the PMT.

  Further, the main wavelengths of excitation light and fluorescence may be the same for all channels. Further, as the fluorescence detection optical unit of each channel, a type in which the excitation light guiding optical fiber and the fluorescence guiding optical fiber are separated as shown in FIG. 13 may be used.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  CH1 first fluorescence detection optical unit, CH2 second fluorescence detection optical unit, CH3 third fluorescence detection optical unit, 500 fluorescence detection device, 501 sample, 505 photodetector, 506a first signal detection circuit, 506b second Signal detection circuit, 506c third signal detection circuit, 520 pulse generation circuit, 522 probe, 530 optical signal detection circuit, 600 sample & hold circuit, 603 buffer amplifier, 604 high-pass filter, 605 inverting / non-inverting amplifier, 609 low-pass filter.

  The present invention can be used for an optical measuring device such as a gene analyzer.

Claims (11)

An optical signal detection circuit for detecting an optical signal of a plurality of channels,
A light source provided for each channel;
A pulse generation circuit for sequentially supplying blinking pulses one by one to the plurality of light sources;
A photodetector that photoelectrically converts a response optical signal to the optical signal from the light source;
A switch provided for each channel, wherein the switch extracts the signal corresponding to each channel from the output signal of the photodetector by switching in synchronization with the blinking pulse;
DC conversion circuit that is provided for each channel and converts the output signal of each switch into a DC signal;
Equipped with a,
The DC conversion circuit includes a high-pass filter that removes a DC component from the output signal of the switch, and an output of the high-pass filter by switching between an inverting amplification operation and a non-inverting amplification operation in accordance with the on / off timing of the blinking pulse. optical signal detecting circuit according to claim Rukoto includes inverting and non-inverting amplifier that converts a signal into a DC signal. An external light component detection circuit for detecting an external light component provided between the photodetector and the switch;
A subtracting circuit for subtracting the external light component from the output signal of the photodetector;
The optical signal detection circuit according to claim 1, further comprising: The pulse generation circuit generates an external light detection pulse at a timing different from the blinking pulse,
The optical signal detection circuit according to claim 2, wherein the external light component detection circuit includes a sample and hold circuit that detects the external light component using the external light detection pulse.   The optical signal detection circuit according to claim 3, wherein the external light component detection circuit further includes a low-pass filter that removes shot noise of the photodetector. Said pulse generating circuit, the optical signal detecting circuit according to any one of claims 1 to 4, characterized in that providing a time interval between the flashing pulses. An optical signal detection circuit according to any one of claims 1 to 5 ,
A probe that irradiates a detection object with a light signal from the light source, detects a response light signal from the detection object, and outputs the response light signal to the light detector;
A measuring device comprising: The measurement apparatus according to claim 6 , wherein the probe is common to a plurality of channels. The measurement apparatus according to claim 6 , wherein the probe is provided separately for each channel. Each channel includes a first optical fiber that guides an optical signal from the light source to the probe, and a second optical fiber that guides a response optical signal from the probe to the photodetector. The measuring device according to claim 8 . The photodetector, the measurement apparatus according to claim 8 or 9, characterized in that a common for multiple channels. An optical signal detection circuit according to any one of claims 1 to 5 ,
An irradiation probe for irradiating an object with an optical signal from the light source;
A detection probe for detecting a response light signal from the object to be detected and outputting it to the photodetector;
A measuring device comprising:

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