A kind of formation method and device based on laser array induced surface thermal deformation effect
The present invention relates to photo-thermal detection technique field, specifically is a kind of formation method and device based on laser array induced surface thermal deformation effect.
The ultimate principle of utilizing induced with laser surface heat deformation effect to detect is based on material and raises because of the absorbing light energy causes local temperature at the effect lower surface of light (to call pump light in the following text), thereby deformation takes place.The space distribution of this thermal deformation and being closely related with pump light parameter and material behavior over time.And because this surface heat deformation, the propagation characteristic of the light that reflects out from material surface can change, and produces and assembles or effect weakening, just as having increased lens newly.Therefore, this surface heat deformation effect is called the surface thermal lens effect again.
The most common method of utilizing the surface heat deformation effect to carry out material behavior detection and analysis is to utilize a branch of amplitude to produce thermal deformation through the pump light irradiation sample spatial induction of ovennodulation, utilizes another bundle detection light process sample surfaces thermal deformation zone to survey the surface heat deformation that pump light causes simultaneously.During measurement, in the detection light light path that reflects, add a spatial filter, can be through the detection luminous energy that arrives photodetector behind the spatial filter because surface heat deformation changes the convergence of surveying light or effect weakening.In the actual measurement,, need utilize phaselock technique usually for improving response.Two-dimensional imaging to sample then is to obtain through sample is carried out point by point scanning.This two-dimensional scan formation method can obtain higher resolution, under the far-field measurement condition, is similar to and is subject to pump light/detection diffraction of light limit, than being easier to reach sub-micrometer scale.
But this two-dimensional scan formation method is very limited in practical application.Main cause is that image taking speed is too slow.On the one hand since signal a little less than, all to carry out the lock phase integral of certain hour to each sample spot; On the other hand, sample moves at every turn and all need spend certain moving and the stand-by period, and the latter is in order to make total system from the mechanical shock to the local temperature, can both reach new balance.The image that obtains 500 microns of 500 microns x of 5 microns lateral resolutions so generally speaking needs nearly one hour time.If absorption of sample is faint, then to increase integral time, imaging time will be longer.This shortcoming has greatly limited this The Application of Technology.
Summary of the invention
The technical matters that the present invention will solve provides a kind of formation method and device based on laser array induced surface thermal deformation effect, solves to utilize the surface thermal lens effect to carry out needing point by point scanning in the two-dimensional imaging process, thus long problem consuming time.
Technical scheme of the present invention is:
A kind of formation method based on laser array induced surface thermal deformation effect may further comprise the steps:
(1), the pump light that pump light source is sent is divided into aplanatic, as to be equidistant array distribution pump beam group; The pump beam group is shone the sample surface after assembling, each bundle pump light of pump beam group has caused corresponding local surfaces deformation at the sample irradiation area;
(2), the detection light that probe source is sent is divided into aplanatic, as to be equidistant array distribution detecting light beam group; The detecting light beam group is shone sample surface after assembling, and each bundle of detecting light beam group is surveyed light and restrainted with each of pump beam group all that pump light is corresponding spatially to be overlapped;
The variation of the detecting light beam propagation characteristic that (3), get into photodetector by the detecting light beam group of sample outgoing, causes through the surface measurements thermal deformation obtains the two dimensional image of material surface characteristic.
After the pump beam group that obtains behind the pump light diffraction light-dividing device was passed through modulator again, the modulating frequency of each bundle pump beam had nothing in common with each other in the described step 1, and this pump beam group is irradiation sample surface after assembling again; It is described that to be used to detect the photodetector of surveying light be photodetector array or a photodetector.
Detection to through the detecting light beam of spatial filter can have two kinds of diverse ways, specifically describes as follows:
Method one: the detecting light beam group to through spatial filter detects with a photodetector.Like this on single photodetector or signal be the stack of whole detecting light beam group signal, be the mixing of a plurality of area informations simultaneously tested on the sample.Want to utilize a photodetector to realize two-dimensional imaging, the signal that needs each bundle to survey the light generation is distinguishable on detector.。This can be through applying the modulation of different frequency to each bundle pump light; Again in end of probe; Utilize lock to detect mutually and frequency-scan technique; Just can restraint the surface heat deformation signal (pixel) that pump light causes to each and differentiate, thereby just can not obtain two-dimensional surface thermal deformation signal pattern through point by point scanning.
Method two: the detecting light beam array to from the outgoing of spatial filter array detects with photodetector array, and promptly each bundle is surveyed photodetector of the corresponding respectively entering of light.Every bit on the signal counter sample on each photodetector so just can obtain two-dimensional surface thermal deformation signal pattern thereby need not sample scanned.The modulating frequency of pump light can be identical in this case, also can be different.Surveying the terminal, utilize parallel processing circuit to handle, just can restraint surface heat deformation signal (pixel) resolution that pump light causes to each and come out.
Described pump light source emission light path is different with the radiative path of probe source; Described pump beam group is all exported through the dichronic mirror output terminal after another input end input of dichronic mirror with described detecting light beam group after dichronic mirror one input end is imported, and after same focal imaging lens are assembled, shines in sample surperficial.
Shone in the described step 3 detecting light beam group behind the sample reflex to survey behind the light condenser lens again through spatial filter with survey the light optical filter, get into photodetector at last.
A kind of imaging device based on laser array induced surface thermal deformation effect includes pump light source and probe source, is positioned at the sample stage of pump light source and probe source rear end and the spatial filter that is provided with in order, surveys light optical filter and photodetector; From being provided with pump light diffraction light-dividing device, dichronic mirror and focal imaging lens between described pump light source to the sample stage in order; Survey optical diffraction light-dividing device, polarization spectroscope, quarter-wave plate, dichronic mirror and focal imaging lens from being provided with in order between described probe source to the sample stage; Described quarter-wave plate is arranged at the rear end of polarization spectroscope one output terminal; Described spatial filter is arranged at the rear end of another output terminal of polarization spectroscope; Described photodetector is a photodetector array.
Be provided with the array photomodulator between described pump light diffraction light-dividing device and the dichronic mirror, described photodetector is photodetector array or a photodetector.
Described imaging device based on laser array induced surface thermal deformation effect also includes surveys the light condenser lens, and described detection light condenser lens is arranged between polarization spectroscope and the spatial filter or is arranged at the rear end of spatial filter.
Advantage of the present invention:
The present invention carries out the point by point scanning method to sample and can improve a lot than traditional on image taking speed; In addition owing to need not to carry out point by point scanning; Concrete detect and the Image-forming instrument design can avoid the use of moving-member, help improving instrument stability, reduce cost, further miniaturization and widen application.
Description of drawings
The structural representation of the embodiment of the invention.
See Fig. 1; A kind of imaging device based on laser array induced surface thermal deformation effect; Include pump light source 1 and probe source 2; Be positioned at the sample stage 3 of pump light source 1 and probe source 2 rear ends; Be arranged at pump light diffraction light-dividing device 4, array photomodulator 5, dichronic mirror 6 and focal imaging lens 7 between pump light source 1 to the sample stage 3 in order; Be arranged at detection optical diffraction light-dividing device 8, polarization spectroscope 9, quarter-wave plate 10, dichronic mirror 6 and focal imaging lens 7 between probe source 2 to the sample stage 3 in order, be arranged at detection light condenser lens 11, spatial filter 12, detection light optical filter 13 and the photodetector 14 of the rear end of polarization dichronic mirror 9 in order; Wherein, quarter-wave plate 10 is arranged at the rear end of polarization dichronic mirror 9 transmission output terminals; Survey the rear end that light condenser lens 11 is arranged at polarization spectroscope 9 reflection output terminals.Survey acting as of light optical filter 13 and block parasitic light, have only the light of detection to pass through in theory.
See Fig. 1, a kind of formation method: may further comprise the steps based on laser array induced surface thermal deformation effect:
(1), with sample 15 as on the sample stage 3;
(2), the pump light that sends of pump light source 1 is divided into aplanatic, as to be equidistant array distribution pump beam group through pump light diffraction light-dividing device 4; The pump beam group maybe must be modulated behind array photomodulator 5 again; The modulating frequency of each Shu Guang can be looked the concrete condition of surveying the terminal and confirmed: if use single electrooptic modulator, then the modulating frequency of each Shu Guang has nothing in common with each other; If the use photodetector array, then the modulating frequency of each Shu Guang can be identical; This pump beam group is again through dichronic mirror 6 reflections, and through irradiation sample 15 surfaces behind focal imaging lens 7 post-concentrations, each bundle pump light of pump beam group has caused corresponding local surfaces distortion at sample 15 irradiation areas;
(3), the detection light that sends of probe source 2 is divided into aplanatic, as to be equidistant array distribution detecting light beam group through surveying optical diffraction light-dividing device 8; The detecting light beam group is successively through polarization spectroscope 9, quarter-wave plate 10, dichronic mirror 6; Assemble irradiation sample 15 surfaces, back by focal imaging lens 7 then, and each bundle detection light of detecting light beam group overlaps spatially with each bundle pump light of pump beam group all;
The detecting light beam group of (4), coming out by sample 15 reflections; Pass through focal imaging lens 7, dichronic mirror 6, quarter-wave plate 10 again, assemble adjustment by polarization spectroscope 9 reflection and through surveying light condenser lens 11 then, through spatial filter 12, survey that light optical filter 13 is laggard goes into photodetector 14 and record and survey light two-dimensional surface thermal deformation signal pattern.The output signal utilization lock phase detection technique of photodetector 14 is surveyed.At this moment; The reference signal that detects mutually as lock with the AC signal identical with the modulating frequency of a certain modulated pump beam; Have only this pump beam to induce the surface heat deformation signal of generation to be measured by lock-in amplifier like this, other pump beam induces the signal of generation all to be filtered.Change the frequency of reference signal successively, just can obtain corresponding pump beam excited surface thermal deformation signal.According to the numbering and the corresponding signal that records of pump beam, obtain the two dimensional image of spatial discrimination again.
Also can utilize a plurality of analog to digital converters or lock-in amplifier that each bundle is surveyed light in actual the use and carry out parallel measurement, change the time that reference signal is measured successively, further improve image taking speed to save.