CN104062004A - Extremely weak optical signal detecting device and method - Google Patents
Extremely weak optical signal detecting device and method Download PDFInfo
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- CN104062004A CN104062004A CN201410264268.6A CN201410264268A CN104062004A CN 104062004 A CN104062004 A CN 104062004A CN 201410264268 A CN201410264268 A CN 201410264268A CN 104062004 A CN104062004 A CN 104062004A
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Abstract
The invention belongs to the field of signal detection, and particularly relates to a high-precision extremely weak optical signal detecting device and method based on a DSP. The device comprises a mechanical shutter, a photomultiplier, a low-noise preamplifier, a high-pass filter circuit, a high-resolution A/D conversion circuit, a DSP processing circuit, a shutter drive circuit and a computer. Processing of modulation, background noise elimination and digital sampling integration is carried out on extremely weak optical signals through the device, and precise detection on extremely weak incident light is achieved. Meanwhile, the extremely weak optical signal detecting device is low in production cost, simple in structure and convenient to use.
Description
Technical field
The invention belongs to optical signal detection field, relate to a kind of utmost point low light level signal detecting device and method, relate in particular to a kind of high precision utmost point low light level signal detecting device and method based on digital signal processor (DSP).
Background technology
In utmost point low light level signal measurement, usually there will be ground unrest or disturb very large and measured signal situation very faint, that even fallen into oblivion by noise.In this case, convert low light level signal to ultra-weak electronic signal by photodetector, then measured signal cannot be extracted and recover to the classic method of ultra-weak electronic signal being amplified by low-noise preamplifier from noise.Conventional method is to realize detection and the extraction to utmost point low light level signal by lock-in amplifier or Sampling Integral device at present.
Lock-in amplifier utilizes the frequency of noise and signal characteristic uncorrelated with phase place, has realized the significantly inhibition to noise by compressed detected channel bandwidth, thereby improves the signal to noise ratio (S/N ratio) of signal.Sampling Integral device is to utilize a reference signal consistent with signal repetition frequency, to sampling processing containing noisy signal, through repeatedly repeated sampling extraction, the statistical average of noise is gone to zero, and realizes the extraction to signal.
These two kinds of methods exist the shortcoming of the following aspects in the time that reality is used:
1), while utilizing lock-in amplifier to survey low light level signal, need to install a chopper additional in detector front end.The effect of chopper be incident optical signal is modulated into sinusoidal ac signal and export one with modulation signal with the reference signal of homophase frequently to lock-in amplifier.This has proposed very high requirement to chopper, light signal can be modulated in time domain to sinusoidal signal, and the reference signal of output and the same homophase frequently of modulation signal, also requires reference signal to possess very high frequency stability in order to avoid beyond the arrowband that drifts about out.Conventionally, a chopper that can meet above-mentioned requirements is very expensive, has increased development task cost.
2), because lock-in amplifier and chopper are two equipment that work alone, reference signal is may cause because of the impact of cable distribution parameter the phase shift of signal during to lock-in amplifier reference edge by cable transmission.In addition, if reference signal is subject to electromagnetic interference (EMI) in transmitting procedure, its frequency and phase place can disturbed signal modulation.This can cause the inaccurate of final test undoubtedly, and particularly in long Distance Transmission or electromagnetic environment when poor, these impacts are very obvious.
3) Sampling Integral device is a kind of instrument of measuring cycle repeating signal faint in noise, therefore in the time measuring utmost point low light level signal, need to, to periodically being modulated by photometry, have similar problem with lock-in amplifier equally.
4) core of Sampling Integral device is sampling simulation switch and RC integrating circuit, wherein sampling simulation switch under the control of gate pulse by faint simulating signal is carried out to interval sampling, and RC integrating circuit is, in the time of connecting at analog switch, the analog signal values of sampling is carried out to integration, then output after final stage is amplified.Analog switch belongs to semiconductor devices, has leakage current, can not realize shutoff truly, can introduce extra noise.RC integrating circuit has determined integration time constant τ, conventionally the capacitance of capacitor C is determined, resistance by regulating resistance R has just realized the adjusting to τ, but because the resistance of R can not be measured accurately, therefore can not realize fine adjustment to integration time constant τ.
5) lock-in amplifier and Sampling Integral device all need detector output signal more extremely weak useful signal to be extracted after amplify on the road of discharging before low noise.Conventionally require detector output as far as possible close with prime amplifier input end, and shorten the transmission range between prime amplifier output and lock-in amplifier or Sampling Integral device input end as far as possible.On the one hand, signal attenuation can be reduced, long Distance Transmission can be reduced on the other hand and be subject to the interference of external electromagnetic environment.But can limit like this application of some special occasions, particularly, in the time that detector riding position is far away apart from prime amplifier or when prime amplifier is far away apart from testing tool, the interference of signal attenuation and external electromagnetic environment can have a strong impact on test result.
6) conventionally in the time using lock-in amplifier or Sampling Integral device, often can not determine the noise of signal preamplifier self, because this part noise is not by modulation, uncorrelated with measured signal, belong to the background noise of circuit.
Summary of the invention
For the existing deficiency of common method and limitation in technical solution background, the present invention proposes a kind of cost low, simple to operate, can realize utmost point low light level signal detecting device and method that the carrying out of utmost point low light level signal accurately surveyed.
Concrete technical scheme of the present invention is:
A kind of utmost point low light level signal detecting device, is characterized in that: comprise mechanical shutter, photomultiplier, low-noise preamplifier, high-pass filtering circuit, high resolution A/D change-over circuit, DSP treatment circuit, fast gate drive circuit and computing machine;
Photomultiplier and enter between the emitter-base bandgap grading low light level to be provided with mechanical shutter, the output terminal of photomultiplier is connected with the input end of low-noise preamplifier, the output terminal of low-noise preamplifier is connected with the input end of high-pass filtering circuit, the output terminal of high-pass filtering circuit is connected with the input end of high resolution A/D change-over circuit, the output terminal of high resolution A/D change-over circuit is connected with the input end of DSP treatment circuit, and DSP treatment circuit and computing machine interconnect; Between described mechanical shutter and DSP treatment circuit, be provided with fast gate drive circuit.
Above-mentioned low-noise preamplifier is that low current turns voltage-type prime amplifier; The bias current of described low-noise preamplifier is less than 2pA, 10
6noise≤2mV when I/V conversion gain
p-p; ; Described high-pass filtering circuit filtering can meet the low-frequency component that filtering is less than 100Hz; The resolution grade of described high resolution A/D change-over circuit is 16bit.
Between above-mentioned computing machine and DSP treatment circuit, interconnect by shield type netting twine.
According to above-mentioned sniffer, a detection method of this device is now proposed, it is characterized in that, comprise the following steps:
1) parameter such as the modulation period to utmost point low light level signal, sampling time, sampling interval and sampling number is set on computers;
2) computing machine is by step 1) set parameter transfer to DSP treatment circuit;
3) DSP treatment circuit makes mechanical shutter modulate utmost point low light level signal according to controlling fast gate drive circuit the modulation period of setting;
4) low current signal is surveyed and exported to photomultiplier to the utmost point low light level signal after modulating;
5) (bias current is less than 2pA to low noise pre-amplification circuit, 10
6noise≤2mV when I/V conversion
p-
p; ) receive photomultiplier output low current signal and convert voltage signal to and amplify, then by the voltage signal output of this amplification;
6) high-pass filtering circuit receives the voltage signal amplifying and this signal is carried out to high-pass filtering, and the low-frequency component below filtering 100Hz, then by the voltage signal output after filtering;
7) voltage signal of high resolution A/D change-over circuit after accepting filter converts 16bit digital signal to and this signal transferred to DSP treatment circuit;
8) DSP treatment circuit gathers, goes background noise, digital sampling, bandpass filtering and digital integration to obtain the signal data of the ultimate low light level to digital signal, then sends data to computing machine by shield type netting twine;
Wherein, described in, removing background noise is to remove low noise pre-amplification circuit noise.
Above-mentioned steps 8) in the step of removing background noise as follows:
8.1) mechanical shutter, in closed condition, does not have light signal input;
8.2) low noise pre-amplification circuit amplifies the weak voltage signals of body and exports high-pass filtering circuit to; Weak voltage signals after amplification, through high-pass filtering circuit filtering low-frequency component, transfers to high resolution A/D change-over circuit by the voltage signal after filtering; High resolution A/D change-over circuit by filter after voltage signal convert to digital signal and by this digital data transmission to DSP treatment circuit;
8.3) background noise that data recording when DSP treatment circuit is closed by mechanical shutter is pre-amplification circuit;
8.4) digital signal of DSP treatment circuit when having light signal incident deducts the background noise of pre-amplification circuit.
The invention has the advantages that:
1, the present invention modulates the low light level of incident by mechanical shutter, and all working carries out sequential control by DSP treatment circuit, makes between modulation circuit and Acquisition Circuit sequential relationship clear and definite, has correlativity, and modulation system is simple and with low cost;
2, the present invention can determine the background noise of low-noise preamplifier under mechanical shutter CLOSE state, and can deduct by DSP treatment circuit the impact of background noise, makes result truer, credible;
3, the present invention adopts high-resolution A/D change-over circuit, makes sampled result more approach actual value;
4, the present invention uses DSP treatment circuit to carry out determining of sampling time and sampling interval to data, has avoided the noise of sampling simulation switch self introducing and the inaccuracy that RC integrating circuit brings;
5, the present invention adopts high-pass filtering circuit to carry out digital filtering to data, has reduced the noise of being introduced by circuit hardware filtering;
6, the data after the present invention adopts DSP treatment circuit to sampling are carried out digital integration, and processing speed is fast;
7, the DSP treatment circuit in the present invention is connected by shield type netting twine with computing machine, and output data are numeric type, and antijamming capability is strong, can realize the data transmission distance of the longest 90m by shield type netting twine;
8, to realize cost low, reproducible, easy and simple to handle in the present invention, is convenient to the integrated of system.
Brief description of the drawings
Fig. 1 is structure diagram of the present invention.
1-mechanical shutter, 2-high-voltage power supply, 3-photomultiplier, 4-low-noise preamplifier, 5-high-pass filtering circuit, 6-high resolution A/D change-over circuit, 7-DSP treatment circuit, the fast gate drive circuit of 8-, 9-computing machine.
Embodiment
The present invention proposes and a kind ofly can carry out the sniffer precisely surveyed and the detection method of this device to utmost point low light level signal.
Below in conjunction with Fig. 1, the structure of this device is described:
This sniffer comprises mechanical shutter 1, photomultiplier 3, and low-noise preamplifier 4, high-pass filtering circuit 5, high resolution A/D change-over circuit 6, DSP processes electric 7 tunnels, fast gate drive circuit 8 and computing machine 9;
Photomultiplier 3 and enter to be provided with mechanical shutter 1 between the emitter-base bandgap grading low light level, the output terminal of photomultiplier 3 is connected with the input end of low-noise preamplifier 4, the output terminal of low-noise preamplifier 4 is connected with the input end of high-pass filtering circuit 5, the output terminal of high-pass filtering circuit 5 is connected with the input end of high resolution A/D change-over circuit 6, the output terminal of high resolution A/D change-over circuit 6 is connected with the input end of DSP treatment circuit 7, and DSP treatment circuit 7 interconnects with computing machine 9; Between mechanical shutter 1 and DSP treatment circuit 7, be provided with fast gate drive circuit 8.
Wherein, those skilled in the art know, in using photomultiplier, connect a high-voltage power supply 2 must to photomultiplier 3 and could meet it and normally work.
Low-noise preamplifier 4 turns voltage-type prime amplifier for low current; The bias current of low-noise preamplifier is less than 2pA, 10
6noise≤2mV when I/V conversion gain
p-
p; High-pass filtering circuit 5 filterings can meet the low-frequency component that filtering is less than 100Hz; The resolution grade of high resolution A/D change-over circuit 6 is 16bit.
In addition, when this device work, for fear of external interference, between computing machine 9 and DSP treatment circuit 7, connect by shield type netting twine, and shield type netting twine can realize the data transmission distance of the longest 90m, realize the data transmission of noiseless, long distance.
By the above-mentioned description to apparatus structure, the specific works process of this device is to comprise the following steps:
Step 1) on computers the parameter such as the modulation period to utmost point low light level signal, sampling time, sampling interval and sampling number set;
Step 2) computing machine is step 1) parameter set transfers to DSP treatment circuit;
Step 3) DSP treatment circuit is according to controlling fast gate drive circuit mechanical shutter is modulated the utmost point low light level signal modulation period of setting;
Step 4) photomultiplier to modulation after utmost point low light level signal survey and export low current signal;
Step 5) (bias current is less than 2pA to low noise pre-amplification circuit, 10
6noise≤2mV when I/V conversion
p-p) receive photomultiplier output low current signal and convert voltage signal to and amplify, then by the voltage signal output of this amplification;
Step 6) high-pass filtering circuit receives the voltage signal amplifying and this signal carried out to high-pass filtering, and filtering low-frequency component, then by the voltage signal output after filtering; (note: the high-pass filtering circuit that we adopt under normal circumstances filters out the low-frequency component below 100Hz, guarantees that like this sampled result is more accurate)
Step 7) voltage signal conversion digital signal after high resolution A/D change-over circuit accepts filter this signal is transferred to DSP treatment circuit;
Step 8) DSP treatment circuit gathers, goes background noise, digital sampling, bandpass filtering and digital integration to obtain the signal data of the ultimate low light level to digital signal, then send data to computing machine by shield type netting twine;
Wherein, described in, removing background noise is to remove low noise pre-amplification circuit noise.
Step 8) in specifically go the step of background noise as follows:
Step 8.1) mechanical shutter is in closed condition, there is no light signal input;
Step 8.2) low noise pre-amplification circuit amplifies the weak voltage signals of body and exports high-pass filtering circuit to; Weak voltage signals after amplification, through high-pass filtering circuit filtering low-frequency component, transfers to high resolution A/D change-over circuit by the voltage signal after filtering; High resolution A/D change-over circuit by filter after voltage signal convert to digital signal and by this digital data transmission to DSP treatment circuit;
(note: the high-pass filtering circuit that we adopt under normal circumstances filters out the low-frequency component below 100Hz, guarantees that like this sampled result is more accurate)
Step 8.3) data recording of DSP treatment circuit when mechanical shutter is the closed background noise that is pre-amplification circuit;
Step 8.4) DSP treatment circuit deducts the digital signal that enters the emitter-base bandgap grading low light level receiving the digital signal of this bulk noise of low noise pre-amplification circuit that DSP treatment circuit receives.
Claims (5)
1. a utmost point low light level signal detecting device, is characterized in that: comprise mechanical shutter, photomultiplier, low-noise preamplifier, high-pass filtering circuit, high resolution A/D change-over circuit, DSP treatment circuit, fast gate drive circuit and computing machine;
Photomultiplier and enter between the emitter-base bandgap grading low light level to be provided with mechanical shutter, the output terminal of photomultiplier is connected with the input end of low-noise preamplifier, the output terminal of low-noise preamplifier is connected with the input end of high-pass filtering circuit, the output terminal of high-pass filtering circuit is connected with the input end of high resolution A/D change-over circuit, the output terminal of high resolution A/D change-over circuit is connected with the input end of DSP treatment circuit, and DSP treatment circuit and computing machine interconnect; Between described mechanical shutter and DSP treatment circuit, be provided with fast gate drive circuit.
2. utmost point low light level signal detecting device according to claim 1, is characterized in that: described low-noise preamplifier is that low current turns voltage-type prime amplifier; The bias current of described low-noise preamplifier is less than 2pA, 10
6noise≤2mV when I/V conversion gain
p-p; Described high-pass filtering circuit filtering can meet the low-frequency component that filtering is less than 100Hz; The resolution grade of described high resolution A/D change-over circuit is 16bit.
3. utmost point low light level signal detecting device according to claim 1 and 2, is characterized in that: between described computing machine and DSP treatment circuit, interconnect by shield type netting twine.
4. a detection method for sniffer claimed in claim 3, is characterized in that, comprises the following steps:
1) parameter such as the modulation period to utmost point low light level signal, sampling time, sampling interval and sampling number is set on computers;
2) computing machine is by step 1) set parameter transfer to DSP treatment circuit;
3) DSP treatment circuit makes mechanical shutter modulate utmost point low light level signal according to controlling fast gate drive circuit the modulation period of setting;
4) low current signal is surveyed and exported to photomultiplier to the utmost point low light level signal after modulating;
5) (bias current is less than 2pA to low noise pre-amplification circuit, 10
6noise≤2mV when I/V conversion gain
p-p) receive photomultiplier output low current signal and convert voltage signal to and amplify, then by the voltage signal output of this amplification;
6) high-pass filtering circuit receives the voltage signal amplifying and this signal is carried out to high-pass filtering, and the low-frequency component below filtering 100Hz, then by the voltage signal output after filtering;
7) voltage signal of high resolution A/D change-over circuit after accepting filter converts 16bit digital signal to and this signal transferred to DSP treatment circuit;
8) DSP treatment circuit gathers, goes background noise, digital sampling, bandpass filtering and digital integration to obtain the signal data of the ultimate low light level to digital signal, then sends data to computing machine by shield type netting twine;
Wherein, described in, removing background noise is to remove low noise pre-amplification circuit noise.
5. the detection method of sniffer according to claim 4, is characterized in that, described step 8) in the step of removing background noise as follows:
8.1) mechanical shutter, in closed condition, does not have light signal input;
8.2) low noise pre-amplification circuit amplifies the weak voltage signals of body and exports high-pass filtering circuit to; Weak voltage signals after amplification, through high-pass filtering circuit filtering low-frequency component, transfers to high resolution A/D change-over circuit by the voltage signal after filtering; High resolution A/D change-over circuit by filter after voltage signal convert to digital signal and by this digital data transmission to DSP treatment circuit;
8.3) background noise that data recording when DSP treatment circuit is closed by mechanical shutter is pre-amplification circuit;
8.4) digital signal of DSP treatment circuit when having light signal incident deducts the background noise of pre-amplification circuit.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105445549A (en) * | 2015-12-11 | 2016-03-30 | 中国电子科技集团公司第四十一研究所 | Weak electromagnetic signal frequency spectrum measuring method |
| CN108363445A (en) * | 2018-01-12 | 2018-08-03 | 中国科学院合肥物质科学研究院 | A kind of signal drift dynamic correcting method and device |
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| CN1851403A (en) * | 2006-05-24 | 2006-10-25 | 北京航空航天大学 | Looped optical-frequency detection apparatus of resonance type micro-light electromechanical gyro |
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Cited By (3)
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| CN108363445A (en) * | 2018-01-12 | 2018-08-03 | 中国科学院合肥物质科学研究院 | A kind of signal drift dynamic correcting method and device |
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