Background technology
Laser-induced Breakdown Spectroscopy (Laser Induced Breakdown Spectroscopy, be called for short LIBS) be a kind of novel elemental analysis technology, it pulse laser beam is focused on sample surfaces ablation form plasma and launch spectrum, analyzes composition and the content thereof of its element by gathering plasma spectrometry.Compared with traditional analytical instrument, LIBS technology has significant technical advantage, such as, without the need to sample preparation, analyzes rapidly, can detect that multiple element, detection limit are low, low cost and other advantages simultaneously, can be used for detecting solid, liquids and gases material etc.
But existing LIBS system also comes with some shortcomings part:
First, traditional LIBS system adopts Nd:YAG solid state laser on optical table, build complicated light path system mostly, and equipment volume is huge, and the environmental requirement of placing equipment is high, as needed special optical table etc. (such as, South China Science & Engineering University, Li Runhua etc., photoelectric double-pulse laser induced breakdown spectrograph and spectroscopic analysis methods, [P], China, 200910041442,20100106; Tsing-Hua University, horse Xiao Hong etc., detection time and position controlled Laser-induced Breakdown Spectroscopy pick-up unit, [P], China, 201010569401,20110720).Some laser instrument needs constant temperature, dry environment etc., therefore cannot move huge instrument to field extreme environment or industry spot carries out determination and analysis; Meanwhile, because the fluctuation of Nd:YAG energy of lasers is general larger, causes measuring result error larger, have impact on detection accuracy and the stability of LIBS system.
Secondly; some current LIBS system is in order to strengthen plasma light spectral intensity; often adopt some ancillary methods; such as fill protection gas, be evacuated, electric spark or microwave heating etc., adding of these servicing units; often need to do a special sample chamber; the size of sample chamber makes the size of target sample be very limited, and particularly cannot complete the constituent analysis of large dimension specimen, also cannot carry out Real-Time Monitoring in industry spot.
Summary of the invention
In order to overcome some defects that existing LIBS technology exists and in order to adapt to the needs that field work and industry spot detect in real time, the invention provides a kind of portable LIBS analyser based on fiber laser, this portable LIBS analyser volume is little, lightweight, easy to carry, simple to operate, analyze rapidly, can be used for field environment or industry spot detects in real time, do not need vacuum environment, without the need to carrying out pre-service to sample; To the size of analyzed sample and electric conductivity unrestricted, analysis efficiency is high.
A kind of portable laser probe analytical instrument provided by the invention, it is characterized in that, it comprises laser acquisition head and host computer system two parts, wherein, detecting head comprises Laser output head, diaphragm, catoptron, dichroic mirror, lens, the first miniature displacement platform, the second miniature displacement platform and light collector; Host computer system comprises spectrometer, microcontroller, portable PC and fiber laser main frame;
First miniature displacement platform, the second miniature displacement platform are installed in the housing of laser acquisition head, and lens are arranged on the first miniature displacement platform, and light collector is arranged on the second miniature displacement platform; Laser output head, diaphragm and catoptron are all positioned in same light path, and the optical axis of catoptron and Laser output head in angle of 45 degrees; Dichroic mirror is arranged on the reflected light path of catoptron, and principal plane is parallel with the principal plane of catoptron; The light-emitting window of light collector, two-phase look mirror, lens and detecting head is successively in another light path, and parallel with the light path at catoptron place with Laser output head, diaphragm; Light collector is connected by optical fiber with spectrometer;
Described first miniature displacement platform is all connected with microcontroller electric signal with the second miniature displacement platform, and microcontroller is connected with portable PC dynamoelectric signal, makes the motion that can realize the miniature displacement platform of control first and the second miniature displacement platform on portable PC; Portable PC respectively with spectrometer and fiber laser control card electrical signal, for controlling the work of spectrometer and laser instrument, and make the data of spectrometer synchronous acquisition be sent to portable PC.
Another kind of portable laser probe analytical instrument provided by the invention, it is characterized in that, it comprises laser acquisition head and host computer system two parts, wherein, laser acquisition head comprises Laser output head, diaphragm, lens, light collector and the first to the 3rd miniature displacement platform, host computer system comprise spectrometer, microcontroller, portable PC and and fiber laser main frame;
First miniature displacement platform and the 3rd miniature displacement platform are arranged in the housing of laser acquisition head, and lens are arranged on the first miniature displacement platform; The light-emitting window of Laser output head, diaphragm, lens and detecting head is positioned in same light path, Laser output head is arranged on the 3rd miniature displacement platform, light collector is arranged on the second miniature displacement platform, and is paraxonic collection, and light collector is connected with spectrometer by optical fiber;
Described first miniature displacement platform is all connected with microcontroller electric signal to the 3rd miniature displacement platform, and microcontroller is connected with portable PC dynamoelectric signal, makes to realize the motion of control first to the 3rd miniature displacement platform on portable PC; Portable PC respectively with spectrometer and fiber laser control card electrical signal, for controlling spectrometer and work with laser instrument simultaneously, and make the data of spectrometer synchronous acquisition be sent to portable PC.
As the improvement of above-mentioned two technical schemes, this portable laser probe analytical instrument can also arrange polarizer and Miniature turntable.
The present invention adopts fiber laser as LASER Light Source, and provides a kind of new spectra collection mode, improves detection sensitivity and reduces detection limit.There is due to novel fiber laser the advantages such as cost is low, miniaturization, conversion efficiency is high, power is high, good beam quality, loss is low, rapid heat dissipation, laser threshold are low, high stability, severe working environment can be competent at, to dust, concussion, impact, humidity, temperature, there is very high tolerance, do not need thermoelectric cooling and water-cooled, only need simply air-cooled, be particularly suitable for being portable LIBS.Meanwhile, the present invention passes through structural design cleverly, makes structure of the present invention convenient and practical, small and exquisite convenient, reliable and stable.
When the present invention sets up polarizer, the interference of the continuous background in plasma spectrometry can also be suppressed, improve detection sensitivity further and reduce detection limit.
In a word, portable laser probe machine provided by the invention analysis is rapid, detection limit is low, highly sensitive, or rugged surroundings and industry spot Real-Time Monitoring, can well make up the shortcoming and defect of existing LIBS scheme in the wild.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described further.It should be noted that at this, the explanation for these embodiments understands the present invention for helping, but does not form limitation of the invention.In addition, if below in described each embodiment of the present invention involved technical characteristic do not form conflict each other and just can mutually combine.
As shown in Figure 1, the portable LIBS analyser of the one that the embodiment of the present invention provides, comprises laser acquisition head A and host computer system B two parts, wherein, detecting head A comprises: Laser output head 1, diaphragm 2, catoptron 3, dichroic mirror 10, lens 5, first, second miniature displacement platform 9,13, polarizer 24, Miniature turntable 25, and light collector 12 etc.Host computer system B comprises spectrometer 19, fiber laser control card 20, microcontroller 21, and portable PC 22, host computer system B can carry or outer luminous intensity distribution fibre laser main frame 23 etc.
In detecting head A, Laser output head 1, diaphragm 2 and catoptron 3 are installed on the same line, and catoptron 3 and laser beam are in angle of 45 degrees; Dichroic mirror 10 is arranged on immediately below catoptron 3, and principal plane is parallel with the principal plane of catoptron 3; Light collector 12, polarizer 24, two-phase look mirror 10, lens 5 and detecting head light-emitting window 6 successively on another straight line, and with the straight line parallel at Laser output head 1, diaphragm 2 and catoptron 3 place; Light collector 12 is connected by optical fiber 16 with spectrometer 19, and Laser output head 1 is connected with fiber laser main frame 23 by optical fiber.
The first miniature displacement platform 13 of miniature displacement platform 9, second and Miniature turntable 25 are installed in the housing 4 of detecting head A, wherein, lens 5 are arranged on miniature displacement platform 9, and polarizer 24 is arranged on Miniature turntable 25, and light collector 12 is arranged on miniature displacement platform 13.Miniature turntable 25, miniature displacement platform 9 are all connected with microcontroller 21 by control signal wire with 13.
In host computer system B, microcontroller 21 is connected by data line with portable PC 22, for the communication between PC 22 and microcontroller 21, thus on PC, controls the motion of Miniature turntable 25, miniature displacement platform 9 and 13.Be connected by data line between spectrometer 19 with portable PC 22, for communicating between spectrometer 19 with PC 22, the data that spectrometer 19 gathers be sent on PC 22 and show.
Fiber laser main frame 23 is configured with fiber laser control card 20, and portable PC 22 is connected with fiber laser control card 20 electric signal, and portable PC 22 can control fiber laser main frame 23 and spectrometer 19 synchronous working.
Miniature displacement platform used in the present invention is the micro two-dimensional displacement platform that volume is little, can to x-axis and the motion of y-axis both direction, and preferred orientation precision can reach 10 μm, and straigheness can reach the Two-dimensional Position moving stage of 10 μm.
Miniature turntable used in the present invention is the electric rotary table that volume is little, and rotation angle range is 0 to 360 degree, and preferred repetitive positioning accuracy can reach the miniature electric universal stage of less than 0.1 degree.
Miniature displacement platform 9 can be controlled by microcontroller 21 by the software on PC, to regulate the locus of lens 5, realize high-precision focusing, precision can reach 10 μm, that avoids manual focusing to bring wastes time and energy and the situation such as error is large, general by the 2-4mm place of focal adjustments outside probe light-emitting window 6, to ensure that laser spot and sample surfaces have a defocusing amount, plasma spectrometry laser being got to sample produces is the strongest.When defocusing amount needs conversion, accurate adjustment can be carried out by miniature displacement platform 9.
Miniature turntable 25 can be controlled by the software on PC by microcontroller 21, to regulate the angle of polarizer 24, reach the object suppressing the continuous background in plasma spectrometry and improve detection limit.Structure shown in Fig. 1 can not arrange polarizer 24 and Miniature turntable 25.
Can control miniature displacement platform 13 by the software on PC by microcontroller 21, to adjust the locus of light collector 12, make it just in time aim at the plasma plume of wish collection, control accuracy reaches 10 μm.
Light collector 12 is used for collecting plasma spectrometry, is then transferred to spectrometer 19 by optical fiber 16.
The adjustment of lens 5, polarizer 24 and light collector 12 can be regulated by software control, also can manual adjustments.
Said diaphragm 2 is that internal diameter is adjustable, and its diameter is generally adjusted to 1-10mm.
Catoptron 3 is the plane mirror for specific wavelength of surface coating, and reflectivity reaches more than 98%.
Dichroic mirror 10 is medium total reflection films that surface is coated with that one deck corresponds to operation wavelength, and to the only reflection of specific wavelength, and reflectivity reaches more than 98%, be then transmission, and percent of pass reaches more than 98% to the light of other wavelength.
Detecting head light-emitting window 6 is detecting head and sample contacts part, adopt resistant to elevated temperatures alloy material to make, the diameter of its top round mouth is 2-5mm, emits from this mouth for laser, meanwhile, the plasma spectrometry that laser excitation goes out also is enter light collector 12 from this round mouth.
Said laser instrument is the wavelength of small size is the fiber laser of 1064nm, preferred power is 20w, and single pulse energy is about 0.5mJ, and pulse repetition rate is that 10-400kHz is adjustable, pulsewidth is the adjustable Miniature optical fiber laser instrument of 10-200ns, can meet different detection demands.
Optical path adjusting method:
Laser instrument red-emitting pilot light, be irradiated to the relevant position on sample, the motion of miniature displacement platform 9 and 13 is controlled by upper computer software, by adjusting the position of lens 5, pilot light is made to focus on the relevant position of sample surfaces, by automatically adjusting the position of light collector 12, make spectrometer collection arrive this pilot light, then illustrate that light path system is adjusted.
Spectra collection method:
Differently with traditional LIBS system be, it not the continuous background removed by the method for time delays in plasma spectrometry, but the continuous background in plasma spectrometry is suppressed by polarizer, also reduce detection limit simultaneously and enhance detection sensitivity.So the spectra collection method of this portable LIBS analyser is, software arranges integral time and average time that times of collection and spectrometer once gather, software design patterns laser instrument and spectrometer work simultaneously, between each collection of spectrometer 19 and each laser pulse, delay time is not set, in an integral time of spectrometer (such as 20ms), what collect is the result of multiple pulse accumulation effect.
As shown in Figure 2, specific works process of the present invention is as follows:
1. initialization
Miniature displacement platform, fiber laser, the connection of spectrometer and the setting of correlation parameter default value is completed during initialization, then laser instrument glows pilot light, be irradiated to the relevant position on sample, PC is utilized to control miniature displacement platform, the position of adjustment lens and light collector, make pilot light focus on sample surfaces, make spectrometer collection arrive this pilot light simultaneously, then illustrate that light path system is adjusted.
2. spectra collection
Laser output head 1 launch laser beam after diaphragm 2 shaping, incide catoptron 3, and with catoptron 3 in angle of 45 degrees; After catoptron 3 reflects, again after the reflection of two-phase look mirror 10, incide on lens 5, focus on through lens 5, then the surface being irradiated to sample 8 produces plasma plume, the light that plasma resonance goes out enters detecting head A from light-emitting window 6, directional light is become after lens 5, again transmitted through after dichroic mirror 10, gathered by light collector 12, then be transferred to spectrometer 19 li by optical fiber 16, the light signal collected is converted to electric signal by spectrometer 19, is then transferred to portable PC 22 by USB interface.
3. data analysis
PC receiving spectrum signal, pre-service (comprise denoising, go background, overlap peak be separated and self-absorption compensation etc.) is carried out to it, spectral information in the spectroscopic data obtained and database is analyzed, determines element kind contained by sample and content thereof and be shown to user.
The present invention also can adopt the second embodiment as shown in Figure 3, with the first embodiment unlike: the second embodiment adopts paraxonic to gather the mode of plasma spectrometry.Laser output head 1 is arranged on the 3rd miniature displacement platform 26, lens 5 are arranged on the first miniature displacement platform 9, Laser output head 1, diaphragm 2, lens 5 and light-emitting window 6 are point-blank, light collector 12 is arranged on miniature displacement platform 13,, polarizer 24 is arranged on Miniature turntable 25, and is just in time positioned at the dead ahead of light collector 12, for paraxonic acquisition mode, gather spectrum of laser plasma from the side of plasma plume.Adopt paraxonic acquisition mode, miniature displacement platform 13 and Miniature turntable 25 can be arranged on outside housing 4, if space allows, also can be arranged in housing 4.
For easy to operate, on housing 4, two handles 11,14 can be installed.Sleeve pipe 18 can also be adopted optical fiber 16,17, and the various circuit cover such as control signal wire 15 inside.
Equally, structure shown in Fig. 3 also can not arrange polarizer 24 and Miniature turntable 25.
The above is preferred embodiment of the present invention, but the present invention should not be confined to the content disclosed in this embodiment and accompanying drawing.So, every not departing from the equivalence or amendment that complete under spirit disclosed in this invention, all fall into the scope of protection of the invention.