CN102539330B - Off-resonance dual-cavity photoacoustic cell used in noninvasive blood glucose measurement and detection method - Google Patents
Off-resonance dual-cavity photoacoustic cell used in noninvasive blood glucose measurement and detection method Download PDFInfo
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Abstract
The invention discloses an off-resonance dual-cavity photoacoustic cell used in noninvasive blood glucose measurement and a detection method. The off-resonance dual-cavity photoacoustic cell includes a sample cell, an incidence window, a laser, a communicating pipe, an inspection room, an adjusting plate and a microphone, wherein a to-be-detected sample is placed in the sample cell; a gas cavity is formed by the space from the upper surface of the to-be-detected sample to the incidence window; the incidence window is installed at the top of the sample cell; the laser is arranged on the incidence window; the communicating pipe is arranged on the lateral surface of the sample cell and faces to the gas cavity; the inspection room is placed at the rear end of the communicating pipe and forms a detection cavity together with the adjusting plate; and the detection cavity is mutually communicated with the gas cavity through the communicating pipe. As the position of the adjusting plate in the inspection room is adjustable, the volume of the detection cavity can be changed to adapt to different modulating frequencies; and the microphone installed on the adjusting plate is used for detecting the intensity of the optical and acoustic signals. The off-resonance dual-cavity photoacoustic cell and the method solve the disadvantages that the traditional resonance type photoacoustic cell has big volume, is difficult to process and manufacture and is only suitable for single stationary modulating frequency, and can meet the requirement of blood glucose monitoring.
Description
Technical field
The present invention relates to a kind of Woundless blood sugar detection photoacoustic cell, particularly, is a kind ofly can be used for the off-resonance two-chamber photoacoustic cell that Woundless blood sugar detects and utilize this photoacoustic cell to carry out the method for Woundless blood sugar detection.
Background technology
Noninvasive Blood Glucose Detection Methods due to patient's misery less, infect that probability is low, Monitoring Blood Glucose variation continuously, thereby become the development trend in blood sugar test field.At present main blood sugar mainly contains near infrared spectroscopy, fluorescent spectrometry, photocaustic spectroscopy etc. without wound detection method.Wherein photocaustic spectroscopy, specificity good become highly sensitive owing to having is hopeful one of method for clinic diagnosis most.
Optoacoustic spectroscopy is an important branch of spectroscopy, is a kind of spectral analysis new method that combines the principle technology such as light, heat, sound, electricity.By light source or the light-pulse generator of certain frequency modulation, irradiate material, when material is subject to irradiation, material is stimulated because absorbing luminous energy, and the process then exciting by non-radiative elimination makes the luminous energy (all or part of) absorbing change heat into.The cyclical variation that this part material and contiguous medium thereof is expanded with heat and contract with cold and produce stress (or pressure) is modulated in the illumination in cycle, thereby produces acoustical signal, and this kind of signal claims photoacoustic signal.The frequency of photoacoustic signal is identical with light modulation frequency, and its intensity and phase place are decided by the characteristic of optics, calorifics, elasticity and the geometry of material.
Typical photocaustic spectroscopy is mainly comprised of light source, chopper, photoacoustic cell, acoustic sensor (microphone), amplifier, signal processing system and register system, and wherein the generation of photoacoustic signal depends on again this particularly important carrier of photoacoustic cell and conversion environment.In the method for utilizing optoacoustic spectroscopy, carry out in the research field of Woundless blood sugar detection, photoacoustic cell is being brought into play vital effect, is mainly manifested in the effect that how a superior optoacoustic conversion environment is provided and strengthens photoacoustic signal.
Along with the further investigation to laser and photoacoustic technique, for the research of the core component photoacoustic cell of photo-acoustic spectrometer, more and more cause people's concern.Different detected objects has different requirements to photoacoustic cell, and photoacoustic cell directly affects again its detection sensitivity, and the photoacoustic cell of different structure has different characteristics.Photoacoustic cell can be divided into gas photoacoustic cell, solid photoacoustic cell and liquid photoacoustic cell function, mainly needs liquid photoacoustic cell (measured target is D/W) for blood sugar monitoring.Photoacoustic cell can be divided into two kinds of single chamber and multi-cavities structure.In multi-cavity photoacoustic cell, comparatively common with two-chamber photoacoustic cell, it is advantageous that and can and utilize helmholtz resonance theory to strengthen photoacoustic signal with differential principle.Such as " for the longitudinal resonance photoacoustic cell (201010251483.4) of gas optoacoustic spectroscopy monitoring " etc.
But existing resonance type photoacoustic cell is mostly gas photoacoustic cell, and blood sugar monitoring needs solid (sample is glucose powder) or liquid (sample is D/W) photoacoustic cell.And, helmholtz resonance frequency by the volume of two cavitys be connected cavity and determined, so very large drawback of helmholtz resonance type photoacoustic cell, when modulating frequency changes, the size of communicating pipe can not be adjusted again exactly, and helmholtz resonance type photoacoustic cell is applicable to single changeless modulating frequency.When modulating frequency changes, its resonance effect is also just had a greatly reduced quality, thereby loses meaning.In addition, when modulating frequency is lower (blood sugar monitoring requires so), the volume of communicating pipe must be enough large, and it is very little to connect the gas pipeline diameter of two communicating pipes, has not so good realization in processing technology.Therefore, traditional helmholtz resonance type photoacoustic cell is not too applicable to the requirement of blood sugar monitoring.
Summary of the invention
The present invention is directed to and lack the present situation that the design that detects required photoacoustic cell, traditional resonance type photoacoustic cell for Woundless blood sugar lacks enough data and parameter design criterias, propose a kind ofly can be used for the off-resonance two-chamber photoacoustic cell that Woundless blood sugar detects and utilize this photoacoustic cell to carry out the method for Woundless blood sugar detection, can be simultaneously for the detection of solid glucose powder and D/W concentration, thereby can meet the requirement of Woundless blood sugar monitoring.
The present invention is achieved by the following technical solutions:
Described photoacoustic cell, is to take RG theory as basis, with reference to the physical property of various related materials, usings air as carrier, and comprehensive theory designs with the consideration of putting into practice two aspects.
Theoretical according to RG: signal depends on generation and the disturbance of acoustic pressure disturbance in sample-gas interface and by gas, arrives the transmission of microphone, and the generation of surface pressing disturbance depends on again the cyclical variation of temperature in sample-gas interface.In gas, depend on the temperature component of time along with leaving the very fast decay of increase of solid surface distance.Due to the periodicity heating in boundary layer, the expansion in this gas blanket cycle and contraction, thereby can be similar to regard a piston as, this piston action is in other gas parts, the sound pressure signal of generation is by whole gas column, and can be detected by microphone.
Photoacoustic cell of the present invention is comprised of sample cell, incidence window, laser instrument, communicating pipe, sensing chamber, adjustable plate and microphone etc.Testing sample is placed in sample cell, and its upper surface is until the space self-assembling formation air chamber of incidence window.Incidence window is installed on the top of sample cell, and laser instrument is installed on incidence window, can have to sample projection the laser beam of certain modulating frequency.Be arranged on the side of sample cell communicating pipe, over against air chamber.Sensing chamber is placed in communicating pipe rear end, and sensing chamber and adjustable plate form test chamber jointly, and test chamber interconnects by communicating pipe and air chamber.Adjustable plate is adjustable in the position of sensing chamber, can change thus the volume size of test chamber, to adapt to different modulating frequencies.High performance microphone is installed on adjustable plate, in order to detect the power of photoacoustic signal.
Described sample cell adopts the larger material of thermal diffusivity to make, to reduce issuable undesired signal.The preferential aluminum alloy materials that adopts is made sample cell, secondly can adopt brass material to make sample cell, and the thermal diffusivity of other materials should not be less than the thermal diffusivity of brass.
Described sample cell has enough thick and heavy housing, to form good acoustic shielding and defening effect.The selection of its thickness, should guarantee the sound transmission loss of 500Hz acoustical signal to be greater than 35dB.Meanwhile, for fear of photoacoustic cell generation coincidence effect, the wall thickness of photoacoustic cell should guarantee that its identical threshold frequency is greater than the more than 10 times of laser modulation frequency.
Described sample cell inside surface is smooth, to avoid acoustical signal to produce excessive decay before being transferred to microphone.Can adopt the processes such as conventional polishing or plated film to process to realize.
The shape of described sample cell adopts various feasible regular shapes, such as cylindrical etc., to be conducive to processing and to reach desirable surface requirements.The concrete size of sample cell depends on the number of sample size and radial dimension and the position of communicating pipe, particularly should guarantee that sample upper surface equals 1.8 times of thermal diffusion length of air in air chamber apart from the height of incidence window, the diameter of sample cell should be greater than 12 times of air thermal diffusion length.
Described incidence window is selected transparent material, is convenient to observe.Because needs are processed various apertures on incidence window, be used for installing laser instrument and gib screw, so pond of the present invention adopts organic glass as incident light window.
Described incidence window has enough thickness, to form good acoustic shielding and defening effect.The thickness of incidence window is selected to select according to identical according to the thickness with sample cell.It is smooth that the inside surface of incidence window should keep.
Between described incidence window and sample cell, lay rubber seal, by screw, reliably connect and realize sealing.
The advantages such as described laser instrument adopts semiconductor laser, and it has, and volume is little, lightweight, instantaneous power is stable.The power of laser instrument is large as far as possible, is conducive to improve the signal to noise ratio (S/N ratio) of photoacoustic signal.The output beam of laser instrument is that frequency is adjustable, to form different modulating frequencies, meets the requirement of blood sugar monitoring.The frequency modulation (PFM) of laser instrument can adopt well-known method to realize.Between laser instrument and incidence window, need flexible encapsulant, to guarantee reliable acoustic shielding and sealing.
The described larger material of communicating pipe same employing thermal diffusivity, to reduce issuable undesired signal.The preferential aluminum alloy materials that adopts is made communicating pipe, secondly can adopt brass material to make communicating pipe, and the thermal diffusivity of other materials should not be less than the thermal diffusivity of brass.The inside surface of communicating pipe is smooth (can polishing or coating film treatment), to avoid acoustical signal to produce excessive attenuation before being transferred to microphone.The shape of communicating pipe can adopt various regular shapes, such as cylindrical etc., is conducive to processing and reaches desirable surface requirements.In order to guarantee signal to noise ratio (S/N ratio) and the detection sensitivity of signal, should adopt as far as possible little radial dimension and longer axial dimension communicating pipe, its smallest radial size depends on processing technology and condition.Between communicating pipe and sample cell and sensing chamber, by conventional method, be reliably connected and seal, for example gluing, weld or be threaded.
Described sensing chamber adopts the material that thermal diffusivity is larger equally, to reduce issuable undesired signal.The preferential aluminum alloy materials that adopts is made sensing chamber, secondly can adopt brass material to make sensing chamber, and the thermal diffusivity of other materials should not be less than the thermal diffusivity of brass.The inside surface of sensing chamber is smooth (can polishing or coating film treatment), to avoid acoustical signal to produce excessive attenuation before being transferred to microphone.The shape of sensing chamber can adopt various regular shapes, such as cylindrical etc., is conducive to processing and reaches desirable surface requirements.In order to guarantee signal to noise ratio (S/N ratio) and the detection sensitivity of signal, sensing chamber should adopt large as far as possible radial dimension and shorter axial dimension.
Described adjustable plate adopts the material that thermal diffusivity is larger equally, to reduce issuable undesired signal.The preferential aluminum alloy materials that adopts is made adjustable plate, secondly can adopt brass material to make adjustable plate, and the thermal diffusivity of other materials should not be less than the thermal diffusivity of brass.The inner surface of adjustable plate is smooth (can polishing or coating film treatment), to avoid acoustical signal to produce excessive attenuation before being transferred to microphone.Adjustable plate is adjustable in the position of sensing chamber, can regulate thus the volume size of test chamber, for meeting the requirement of different modulating frequency.The position adjustments of adjustable plate can adopt well-known method to realize, for example, be threaded.On adjustable plate, be processed with mounting hole, in order to microphone to be installed.Between microphone and adjustable plate, be provided with O-ring seal, to guarantee reliable acoustic shielding and defening effect.
Described microphone adopts the sensor of low noise, highly sensitive, low cutoff frequency.Described is minimum by frequency, should determine according to the requirement of blood sugar monitoring.
The invention provides a kind of method that adopts above-mentioned photoacoustic cell to carry out Woundless blood sugar detection, detecting step is as follows:
(1) first incidence window is taken off from sample cell, with graduated cylinder, measure glucose powder or D/W, pour in sample cell.
(2) by the entrance window lid with laser instrument at sample cell top, between the two, put into O-ring seal, and use screw-driving.
(3) whole photoacoustic cell is placed on crash roll, opens laser power supply, start microphonic output signal to sample.
(4) finally the data that sample are carried out to fast Flourier (FFT) conversion, obtain the spectral characteristic of signal, can be adjusted the photoacoustic spectrum under frequency.
Compared with prior art, the beneficial effect of photoacoustic cell of the present invention is: photoacoustic cell of the present invention adopts unique adjustable, off-resonance two-chamber photoacoustic cell structure, avoided traditional resonance type photoacoustic cell volume large, be difficult to processing and fabricating, be only applicable to the drawback of single fixed modulation frequency, can meet the requirement of blood sugar monitoring.
Accompanying drawing explanation
Fig. 1 is that off-resonance two-chamber photoacoustic cell structure forms schematic diagram;
Fig. 2 is off-resonance two-chamber photoacoustic cell structural parameters schematic diagram;
In figure, 1-sample cell, 2-incidence window, 3-laser instrument, 4-sample, 5-air chamber, 6-communicating pipe, 7-sensing chamber, 8-test chamber, 9-adjustable plate, 10-microphone, d
1-sample cell internal diameter, l
1-air chamber length, V
1-air chamber volume, d
2-communicating pipe internal diameter, l
2-communicating pipe length, V
2-communicating pipe volume, d
3-test chamber internal diameter, l
3-test chamber length, V
3-test chamber volume.
Embodiment
Below in conjunction with accompanying drawing, embodiments of the invention are elaborated, the present embodiment be take technical solution of the present invention and is implemented as prerequisite, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.
As shown in Figure 1, the photoacoustic cell of the present embodiment is comprised of sample cell 1, incidence window 2, laser instrument 3, communicating pipe 6, sensing chamber 7, adjustable plate 9 and microphone 10 etc.Testing sample 4 is placed in sample cell 1, and its top is until the space self-assembling formation air chamber 5 of incidence window 2.Incidence window 2 is installed on the top of sample cell 1, and laser instrument 3 is installed on incidence window 2, can have to sample 4 projections the laser beam of certain modulating frequency.Communicating pipe 6 is arranged on the side of sample cell 1, over against air chamber 5.Sensing chamber 7 is placed in communicating pipes 6 rear end, sensing chamber 7 and the common test chamber 8 that forms of adjustable plate 9, and test chamber 8 interconnects by communicating pipe 6 and air chamber 5.Adjustable plate 9 is adjustable in the position of sensing chamber 7, can change thus the volume size of test chamber 8, to adapt to different modulating frequencies.High performance microphone 10 is installed on adjustable plate 9, in order to detect the power of photoacoustic signal.
Described sample cell 1 adopts the larger aluminum alloy materials of thermal diffusivity, to reduce issuable undesired signal.Sample cell 1 has enough thick and heavy housing, and the about 10mm～20mm of thickness is advisable, and to form good acoustic shielding and defening effect, avoids coincidence effect simultaneously.The inside surface of sample cell 1 is smooth, adopts polishing process method to realize, to avoid acoustical signal being transferred to the excessive decay of the front generation of microphone 10.The shape of sample cell 1 adopts cylindrical, to be conducive to processing and to reach desirable surface requirements.The concrete size of sample cell 1 depends on the number of sample 4 amounts and size and the position of communicating pipe 6, particularly: sample 4 upper surfaces are apart from the height h of incidence window 2
1equal 1.8 times of thermal diffusion length μ of air chamber 5 interior air, that is:
h
1＝1.8μ (1)
The inner diameter d of sample cell 1
1should be greater than 12 times of air thermal diffusion length μ, that is:
d
1≥12μ (2)
The thermal diffusion length peace of air chamber 5 interior air is calculated according to following formula:
In formula, k is air pyroconductivity, and c is air specific heat, and ω=2 π f is Laser Modulation angular frequency (f modulating frequency), and ρ is atmospheric density.
According to the requirement of blood sugar monitoring, modulating frequency is low as far as possible.Considering general microphonic is 3Hz left and right by frequency, and desirable lowest modulation frequency is f thus
min=3Hz.Can calculate thus maximum heat diffusion length is μ
max=1.42mm.Therefore, the diameter of desirable sample cell is d
1=22mm, sample 4 upper surfaces are h apart from the height (being the length of air chamber 5) of incidence window 2
1=3mm.
Described incidence window 2 selects organic glass to make, and is convenient to observe and process various apertures, is used for installing laser instrument and gib screw.About 10mm～the 20mm of thickness of incidence window 2 is advisable, and to form good acoustic shielding and defening effect, avoids coincidence effect simultaneously.It is smooth that the inside surface of incidence window should keep.Between incidence window 2 and sample cell 1, lay rubber seal, by screw, reliably connect and realize sealing.
The advantages such as described laser instrument 3 adopts semiconductor laser, and it has, and volume is little, lightweight, instantaneous power is stable.The power of laser instrument 3 is large as far as possible, and the present embodiment adopts the semiconductor laser of wavelength 650nm, power 50mW, is conducive to improve the signal to noise ratio (S/N ratio) of photoacoustic signal.The output beam of laser instrument 3 is that frequency is adjustable, to form different modulating frequencies, meets the requirement of blood sugar monitoring.The modulating frequency requiring due to blood sugar monitoring is not high, minimum about 3Hz, and the highest about 40Hz, so the frequency modulation (PFM) of laser instrument 3 can adopt simple square-wave frequency modulation method to realize.Between laser instrument 3 and incidence window 2, increase the encapsulant that elasticity is moderate, be generally rubber ring, to guarantee reliable acoustic shielding and sealing.
The described larger material of communicating pipe 6 same employing thermal diffusivity, this example adopts aluminium alloy to make, to reduce issuable undesired signal.Communicating pipe 6 has enough thick and heavy housing, and wall thickness is 5mm, to form good acoustic shielding and defening effect.The inside surface of communicating pipe 6 is smooth, and this example adopts the method for polishing to realize, to avoid acoustical signal to produce excessive attenuation before being transferred to microphone.The shape of communicating pipe 6 adopts cylindrical, is conducive to processing and reaches desirable surface requirements.In order to guarantee signal to noise ratio (S/N ratio) and the detection sensitivity of signal, should adopt as far as possible little radial dimension and longer axial dimension communicating pipe, its smallest radial size depends on processing technology and condition, the communicating pipe 6 of the present embodiment is taken as inner diameter d
2=1mm, length l
2=50mm.Between communicating pipe 6 and sample cell 1 and sensing chamber 7, by conventional method, be reliably connected and sealed, the present embodiment adopts excessively and coordinates and be connected with bonding method.
The same larger materials of aluminum alloy of thermal diffusivity that adopts of described sensing chamber 7, to reduce issuable undesired signal.Sensing chamber 7 has enough thick and heavy housing, and the about 10mm of thickness, to form good acoustic shielding and defening effect.The inside surface of sensing chamber 7 is smooth, realizes, to avoid acoustical signal being transferred to the front generation excessive attenuation of microphone 10 by polishing.The shape of sensing chamber 7 adopts cylindrical, is conducive to processing and reaches desirable surface requirements.In order to guarantee signal to noise ratio (S/N ratio) and the detection sensitivity of signal, sensing chamber 7 should adopt large as far as possible radial dimension and shorter axial dimension, and the present embodiment is taken as inner diameter d
3=50mm, length 40mm.
The same larger materials of aluminum alloy of thermal diffusivity that adopts of described adjustable plate 9, to reduce issuable undesired signal.Adjustable plate 9 has enough thick and heavy housing, and the about 10mm of thickness, to form good acoustic shielding and defening effect.The inner surface of adjustable plate 9 is smooth, realizes, to avoid acoustical signal being transferred to the front generation excessive attenuation of microphone 10 by polishing.Adjustable plate 9 is adjustable in the position of sensing chamber 7, can regulate thus the volume size of test chamber 8, for meeting the requirement of different modulating frequency.The position adjustments of adjustable plate can adopt well-known method to realize, for example, be threaded.On adjustable plate, be processed with mounting hole, in order to microphone to be installed.Between microphone and adjustable plate, be provided with O-ring seal, to guarantee reliable acoustic shielding and defening effect.
Modulating frequency computing formula under different parameters is:
γ＝4πη/ρs (7)
In formula, ω is modulating frequency, ω
0for resonant frequency, S is communicating pipe cross-sectional area, the length that L is communicating pipe, and resonance angular frequency, f is chopper frequencies (namely modulating frequency), C=340m/s is the velocity of sound, η=1.29kg/m
3for the gas coefficient of viscosity.Desirable L=0.05m, S=3.14 * 10
-6m
2, the length of the test chamber 8 under different modulating frequency (being the position of adjustable plate 9) is:
| f(Hz) | 1 | 5 | 10 | 15 | 20 |
| L1(cm) | 21.6298 | 11.4716 | 4.6488 | 2.3346 | 1.3758 |
Described microphone 10 adopts the sensor of low noises, highly sensitive, low cutoff frequency.Described is minimum by frequency, the requirement of blood sugar monitoring should be installed and determine, minimum is 3Hz.
The present embodiment utilizes above-mentioned photoacoustic cell to carry out Woundless blood sugar detection, and concrete testing process is as follows:
(1) first incidence window 2 is taken off from sample cell 1, with graduated cylinder, measure glucose powder or D/W, pour in sample cell.
(2) incidence window with laser instrument 32 is covered at sample cell 1 top, between the two, put into O-ring seal, and use screw-driving.
(3) whole photoacoustic cell is placed on crash roll, opens the power supply of laser instrument 3, start the output signal of microphone 10 to sample.
(4) finally the data that sample are carried out to fast Flourier (FFT) conversion, obtain the spectral characteristic of signal,
Can be adjusted the photoacoustic spectrum under frequency.
The above-mentioned resonance type two-chamber photoacoustic cell based on RG theory of the present invention, can, simultaneously for the detection of solid glucose powder and D/W concentration, can meet the requirement that blood sugar detects without wound.The present invention avoided traditional resonance type photoacoustic cell volume large, be difficult to processing and fabricating, be only applicable to the drawback of single fixed modulation frequency, can meet the requirement of blood sugar monitoring.
Although content of the present invention has been done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to limitation of the present invention.Those skilled in the art, read after foregoing, for multiple modification of the present invention with to substitute will be all apparent.Therefore, protection scope of the present invention should be limited to the appended claims.
Claims (10)
1. can be used for the off-resonance two-chamber photoacoustic cell that Woundless blood sugar detects, it is characterized in that: this photoacoustic cell is comprised of sample cell, incidence window, laser instrument, communicating pipe, sensing chamber, adjustable plate and microphone; Testing sample is placed in sample cell, and its upper surface is until the space self-assembling formation air chamber of incidence window; Described incidence window is installed on the top of sample cell, and laser instrument is installed on incidence window, and laser instrument can have the laser beam of setting modulating frequency to sample projection; Described communicating pipe is arranged on the side of sample cell, over against described air chamber; Described sensing chamber is placed in communicating pipe rear end, and sensing chamber and adjustable plate form test chamber jointly, and test chamber interconnects by communicating pipe and air chamber; Described adjustable plate is adjustable in the position of sensing chamber, changes thus the volume size of test chamber, to adapt to different modulating frequencies; On described adjustable plate, be provided with to detect the strong and weak microphone of photoacoustic signal.
2. off-resonance two-chamber photoacoustic cell according to claim 1, it is characterized in that: described sample cell adopts thermal diffusivity to be not less than the material of brass, sample cell has enough thick and heavy housing, and the inside surface of sample cell is smooth, described thickness of shell should guarantee the sound transmission loss of 500Hz acoustical signal to be greater than 35dB, and identical threshold frequency is greater than the more than 10 times of laser modulation frequency.
3. off-resonance two-chamber photoacoustic cell according to claim 1, it is characterized in that: described adjustable plate adopts thermal diffusivity to be not less than the material of brass, adjustable plate has enough thick and heavy housing, and the inner surface of adjustable plate is smooth, described thickness of shell should guarantee the sound transmission loss of 500Hz acoustical signal to be greater than 35dB, and identical threshold frequency is greater than the more than 10 times of laser modulation frequency.
4. according to the off-resonance two-chamber photoacoustic cell described in claim 2 or 3, it is characterized in that: described sample cell, adjustable plate adopt aluminium or brass to make.
5. according to the off-resonance two-chamber photoacoustic cell described in claim 1-3 any one, it is characterized in that: the concrete size of described sample cell, guarantee that sample upper surface equals 1.8 times of thermal diffusion length of air in air chamber apart from the height of incidence window, the diameter of sample cell is greater than 12 times of air thermal diffusion length.
6. according to the off-resonance two-chamber photoacoustic cell described in claim 1-3 any one, it is characterized in that: between described incidence window and sample cell, lay rubber seal, be connected by screw and realize sealing.
7. off-resonance two-chamber photoacoustic cell according to claim 6, is characterized in that: described incidence window is selected the transparent material that is easy to processing.
8. according to the off-resonance two-chamber photoacoustic cell described in claim 1 or 3, it is characterized in that: between described microphone and adjustable plate, be provided with O-ring seal, between described communicating pipe and sample cell and sensing chamber, be tightly connected.
9. off-resonance two-chamber photoacoustic cell according to claim 1, is characterized in that: adopt thermal diffusivity to be not less than the material of brass described communicating pipe.
10. adopt the method that off-resonance two-chamber photoacoustic cell carries out Woundless blood sugar detection described in claim 1-3 any one, it is characterized in that described detecting step is as follows:
1. first incidence window is taken off from sample cell, with graduated cylinder, measure glucose powder or D/W, pour in sample cell;
2. by the entrance window lid with laser instrument at sample cell top, between the two, put into O-ring seal, and with screw-driving;
3. whole photoacoustic cell is placed on crash roll, opens laser power supply, start microphonic output signal to sample;
4. finally the data that sample are carried out to fast fourier transform, obtain the spectral characteristic of signal, be adjusted the photoacoustic spectrum under frequency.
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| CN108872087A (en) * | 2018-07-10 | 2018-11-23 | 昆山和智电气设备有限公司 | A kind of sound pressure signal channel design |
| CN111380805B (en) * | 2020-01-02 | 2021-04-06 | 华中科技大学 | Photoacoustic cell with adjustable resonant frequency and adjusting method |
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