CN101576483A - Optical system and method for improving spatial resolution of laser film absorption measurement - Google Patents
Optical system and method for improving spatial resolution of laser film absorption measurement Download PDFInfo
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- CN101576483A CN101576483A CNA2009100523751A CN200910052375A CN101576483A CN 101576483 A CN101576483 A CN 101576483A CN A2009100523751 A CNA2009100523751 A CN A2009100523751A CN 200910052375 A CN200910052375 A CN 200910052375A CN 101576483 A CN101576483 A CN 101576483A
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- 238000003384 imaging method Methods 0.000 claims abstract description 9
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Abstract
An optical system and method for improving the spatial resolution of laser film absorption measurement, the optical system is based on the surface thermal lens principle, and is composed of a detection light path and a pumping light path; the pumping light is irradiated on the surface of the sample after being focused by the lens, and the detection light spot is superposed with the pumping light spot; the light spot of the detection light on the surface of the sample is equal to or larger than that of the pump light; the detection light and the pump light are respectively modulated by the chopper at the same frequency, and the phases of the two rows of modulated waves are controllable; the detection light reflected by the sample is received by an area array CCD camera after passing through an imaging lens; and obtaining an image phase locking signal corresponding to the film absorption according to the image phase locking principle. The invention has the characteristics of high sensitivity, simple and convenient adjustment, visual measurement result and high measured spatial resolution.
Description
Technical field
The present invention is relevant with the absorptiometry of laser film, is a kind of optical system and method that improves laser film absorptiometry spatial resolution.
Technical background
During the laser irradiation optical thin film, film produces laser and absorbs and scattering.Absorption and scattering not only can cause the decline of film performance, and cause the photic damage of film easily.The absorption of light is meant that incident optical energy is converted into the other forms of energy such as heat energy of film sample.Absorptiometry and thermal defect thereof to laser film detect, and have become the affirmation product quality, review the important technical in sample defects source.Based thin film absorbs the relation with damage threshold, can demarcate effective processing region for the film pre-service to the face distribution measuring of film absorption, thereby greatly improve treatment effeciency.
Photothermal technique is widely used in the film absorption measurement as a kind of non-contacting non-destructive measuring method.Wherein, the surface thermal lens technology is stable owing to its measuring system, easy being widely used of adjusting, can realize spot measurement, two-dimensional surface scanning survey to film absorption, measures sensitivity and reaches the 0.1ppm magnitude.The surface scanning and measuring spatial resolution of this method depends primarily on the size of pump spot radius and stepping platform step pitch in the measurement except the limitation of theoretical model.In actual face absorptiometry, for the radius that improves the efficiency of measurement pump spot can not infinitely reduce, this has just inevitably produced the contradiction of efficiency of measurement and measurement space resolution.
Nowadays, because the application of large-aperture optical device more and more widely, the face absorptiometry of sample and thermal defect be detected as be important research project.It is significant to improving the device detection technique to improve measurement spatial resolution under the prerequisite that guarantees efficiency of measurement.
Summary of the invention
The purpose of this invention is to provide a kind of optical system and method that improves laser film absorptiometry spatial resolution, under the prerequisite that guarantees measuring speed, improve the spatial resolution of absorptiometry.
Technical solution of the present invention is as follows:
A kind of optical system that improves laser film absorptiometry spatial resolution, its characteristics are that this system is made of pumping light path, detection light path, imaging optical path and computing machine:
Described pump light route pump light and second attenuator that sets gradually along this pump light, second modulator and second lens constitute, and this pump light is radiated on the film sample to be measured after second lens are assembled and forms pump spot;
Described detection optical routing surveys light and first attenuator that sets gradually along this detection light, first modulator, first catoptron and first lens constitute, described detection light carries out phase modulation (PM) and described first lens accumulate on the film sample to be measured through described first modulator, makes this detection hot spot cover described pump spot;
Described imaging optical path is included in second catoptron, extender lens and the area array CCD of described detection reflection of light light direction;
Described computing machine links to each other with described area array CCD, first modulator and second modulator respectively.
The two-sided plating anti-reflection film of described first lens and second lens.
Described first modulator and second modulator are mechanical chopper, acousto-optic modulator or other modulation device.
Described pump light is infrared basic frequency laser, two double-frequency lasers or frequency tripled laser.
Described detection light is basic mode He-Ne laser.
Described first catoptron and second catoptron are 45 ° of total reflective mirrors of 632.8nm.
Described area array CCD has the pixel more than 1,000,000 or 1,000,000.
Utilize the optical system of above-mentioned raising laser film absorptiometry spatial resolution to carry out the method for film absorption measurement, comprise the following steps:
1. adjust second lens and make pump light on the film sample surface, obtain suitable pump spot, adjust second attenuator control pump light, make and measure in the range of linearity at the lip-deep power of film sample;
2. adjust first lens, make described detection light cover described pump spot, adjust first attenuator control and survey light intensity, make the area array CCD can supersaturation at the lip-deep hot spot of film sample;
3. adjust extender lens, make detection photoimaging from the film sample surface reflection in the CCD receiving plane and be full of whole receiving plane;
4. pass through the modulating frequency and the initial phase of described first modulator of computing machine synchro control and second modulator, the relative first phase place value that light and pump light are surveyed in modulation is followed successively by 0, pi/2, π and 3 pi/2s, and the described area array CCD of described computer drives writes down four reflections under the phase place successively and surveys light signal S simultaneously
1, S
2, S
3And S
4, computing machine (17) receives the signal of described area array CCD (16) input, and according to formula
Calculate the amplitude signal value S that absorbs the light intensity variation that causes.
The present invention has the following advantages:
1, the present invention utilizes the surface thermal lens principle, and is highly sensitive, regulates easy.
2, because the present invention has adopted area array CCD camera with the 1000000 above pixels signal receiver spare as film absorption information, improve 1,000,000 times of measurement spatial resolution thus, method is simple.
Description of drawings
Fig. 1 is the surface thermal lens principle schematic
Fig. 2 is the light path synoptic diagram that the present invention improves the optical system embodiment of laser film absorptiometry spatial resolution
Embodiment
The invention will be further described below in conjunction with embodiment and accompanying drawing, but should not limit protection scope of the present invention with this.
See also Fig. 1 earlier, Fig. 1 is the surface thermal lens principle schematic, method of the present invention is based on film surface thermal lens principle, pump light after lens focus irradiation in film sample 2 surfaces, surveying hot spot overlaps with pump spot, the hot spot of surveying light 3 on the film sample is equivalent to or greater than the hot spot of pump light 1, surveying light 3 and pump light 1 is modulated with frequency by chopper respectively, the relative phase of two light modulated is set at 0, pi/2, π and 3 pi/2s, film sample 2 detection light reflected write down four width of cloth successively corresponding to above-mentioned four phase state area array CCD cameras 4 and survey light image S through being received by area array CCD camera 4 behind the extender lens
1, S
2, S
3And S
4, obtain the amplitude of the light intensity variable signal of film absorption correspondence according to the phase-locked principle of image
This detection mode is called image model.
What spatial resolution r described is the minor increment of discernmible two the different absorption points of measuring system.Distinguishable two absorption points adopt Rayleigh criterion to define.For image model, the resolution of object space characterizes with image space resolution.In the image space, CCD needs two pixels to differentiate a pair of line at least, and therefore the ultimate resolution that can reach is R=2 * Pixel, and Pixel is the picture dot size.If the imaging magnification of system is M, the maximum space resolution of object space satisfies equation so:
r＝R/M＝2×Pixel/M (1)
Generalized case obtains the image lockin signal of film absorption correspondence according to the phase-locked principle of image.The object space signal is for surveying diffraction pattern, and the image space signal is the image of CCD record.Because object space signal amplification imaging is in the image space, the object space signal is characterized by all face battle array picture dots, thereby has improved measurement spatial resolution.Power of a lens is big more, and the pixel count of area array CCD is high more, and picture dot is more little, and then spatial resolution is high more.
Fig. 2 is the light path synoptic diagram that the present invention improves the optical system embodiment of laser film absorptiometry spatial resolution, as seen from the figure, the present invention improves the optical system of laser film absorptiometry spatial resolution, and this system is made of pumping light path, detection light path, imaging optical path and computing machine 17:
Described pump light route pump light 10 and second attenuator 11 that sets gradually along this pump light 10, second modulator 12 and second lens 13 constitute, and this pump light 10 is radiated on the film sample to be measured 2 after second lens 13 are assembled and forms pump spot;
Described detection optical routing surveys light 5 and first attenuator 6 that sets gradually along this detection light 5, first modulator 7, first catoptron 8 and first lens 9 constitute, described detection light 5 carries out phase modulation (PM) and described first lens 9 accumulate on the film sample to be measured 2 through described first modulator 7, makes this detection hot spot cover described pump spot;
Described imaging optical path is included in second catoptron 14, extender lens 15 and the area array CCD 16 of described detection reflection of light light direction;
Described computing machine 17 links to each other with second modulator 12 with described area array CCD 16, first modulator 7 respectively.
In the present embodiment:
Described pump light 10 can be infrared basic frequency laser, its two frequencys multiplication or frequency tripled laser; Described detection light 5 is basic mode He-Ne laser.
Above-mentioned pump light 10 focuses on film sample 2 surfaces through second lens 13, survey light 5 and can be focus on also directly irradiation on the film sample surface; Survey the radius of the radius of hot spot on the film sample greater than pump spot.
Described area array CCD 16 has the pixel more than 1,000,000 or 1,000,000.Above-mentioned modulator is a mechanical chopper.Described extender lens 15 can be single negative lens or compound lens, and its magnification M requires to satisfy M＞1, and lens combination needs double-sided coating and aplanasia and distortion.
Above-mentioned image phaselock technique, it is applied to phase-locked principle to handle all picture dots of a row consecutive image.The net result that obtains is one or two width of cloth images, one or two direct current output that their corresponding respectively traditional lock-in amplifier obtains.
Film absorption causes that the subtle change of surveying light intensity obtained by the image phaselock technique.Utilize first modulator, 7, the second modulators 14 to apply with modulation frequently respectively to surveying light 5 and pump light 10, the relative first phase place value of the two-beam of modulation is set at 0 successively, pi/2, π, 3 pi/2s, and write down four reflections under the phase place successively by CCD 16 and survey light signal S
1, S
2, S
3, S
4According to formula
The amplitude signal value S that the light intensity that causes of being absorbed changes.The modulating frequency and the initial phase of computing machine 17 described first modulators 7 of control and second modulator 14, and receive and handle the signal of importing by CCD 16.
After 15 pairs of sample detection light reflected of extender lens expand bundle, make it to image in the CCD receiving plane and be full of whole bin.Signal distributions is when whole induction bin, and the signal of less search coverage is characterized by bigger face battle array picture dot, thereby improves measurement spatial resolution.
In an embodiment, 6 pairs of first attenuators are surveyed optical attenuation and are made that CCD can supersaturation, and second attenuator, 11 control pump lights make and measure in the range of linearity at sample 2 lip-deep power.
In an embodiment, first lens 9 and second lens 13 focus on detection light 5 and pump light 10 respectively, thus control spot size and power density.Require first lens 9 and second lens, 13 two-sided plating anti-reflection films.
In an embodiment, first catoptron 8 and second catoptron 13 are 632.8nm45 ° of total reflective mirror.
Utilize the optical system of described raising laser film absorptiometry spatial resolution to carry out the method for film absorption measurement, comprise the following steps:
1. adjust second lens 13 and make pump light on film sample 2 surfaces, obtain suitable pump spot, adjust second attenuator, 11 control pump lights, make and measure in the range of linearity at film sample 2 lip-deep power;
2. adjust first lens 9, make described detection light cover described pump spot, adjust the intensity that light 5 are surveyed in the control of first attenuator 6, make the area array CCD 16 can supersaturation at film sample 2 lip-deep hot spots;
3. adjust extender lens 15, make detection photoimaging from film sample 2 surface reflections in the CCD receiving plane and be full of whole receiving plane;
4. pass through the modulating frequency and the initial phase of described first modulator 7 of computing machine 17 synchro control and second modulator 12, the relative first phase place value that light 5 and pump light 10 are surveyed in modulation is followed successively by 0, pi/2, π and 3 pi/2s, and simultaneously described computing machine 17 drives described area array CCD 16 and writes down four reflections under the phase place successively and survey light signal S
1, S
2, S
3And S
4, computing machine (17) receives the signal of described area array CCD 16 inputs, and according to formula
Calculate the amplitude signal value S that absorbs the light intensity variation that causes.
Our experiments show that the present invention has improved the spatial resolution of film absorption measurement significantly under the prerequisite that guarantees measuring speed.The present invention has highly sensitive, regulate easy, intuitive measurement results, the characteristics that measurement spatial resolution is high.
Claims (8)
1, a kind of optical system that improves laser film absorptiometry spatial resolution is characterized in that this system is made of pumping light path, detection light path, imaging optical path and computing machine (17):
Described pump light route pump light (10) and second attenuator (11) that sets gradually along this pump light (10), second modulator (12) and second lens (13) constitute, and this pump light (10) is radiated at film sample to be measured (2) and goes up the formation pump spot after second lens (13) are assembled;
Described detection optical routing surveys light (5) and first attenuator (6) that sets gradually along this detection light (5), first modulator (7), first catoptron (8) and first lens (9) constitute, described detection light (5) carries out phase modulation (PM) and described first lens (9) accumulate on the film sample to be measured (2) through described first modulator (7), makes this detection hot spot cover described pump spot;
Described imaging optical path is included in second catoptron (14), extender lens (15) and the area array CCD (16) of described detection reflection of light light direction;
Described computing machine (17) links to each other with described area array CCD (16), first modulator (7) and second modulator (12) respectively.
2, the optical system of raising laser film absorptiometry spatial resolution according to claim 1 is characterized in that the two-sided plating anti-reflection film of described first lens (9) and second lens (13).
3, the optical system of raising laser film absorptiometry spatial resolution according to claim 1 is characterized in that described first modulator (7) and second modulator (12) are mechanical chopper, acousto-optic modulator or other modulation device.
4, the optical system of raising laser film absorptiometry spatial resolution according to claim 1 is characterized in that described pump light is infrared basic frequency laser, two double-frequency lasers or frequency tripled laser.
5, the optical system of raising laser film absorptiometry spatial resolution according to claim 1 is characterized in that described detection light is basic mode He-Ne laser.
6, the optical system of raising laser film absorptiometry spatial resolution according to claim 1 is characterized in that described first catoptron (8) and second catoptron (14) are 632.8nm45 ° of total reflective mirror.
7, the optical system of raising laser film absorptiometry spatial resolution according to claim 1 is characterized in that described area array CCD (16) has the pixel more than 1,000,000.
8, utilize the optical system of the described raising laser film of claim 1 absorptiometry spatial resolution to carry out the method for film absorption measurement, it is characterized in that comprising the following steps:
1. adjust second lens (13) and make pump light on film sample (2) surface, obtain suitable pump spot, adjust second attenuator (11) control pump light, make and measure in the range of linearity at the lip-deep power of film sample (2);
2. adjust first lens (9), make described detection light cover described pump spot, adjust the intensity that light (5) is surveyed in first attenuator (6) control, make the area array CCD (16) can supersaturation at the lip-deep hot spot of film sample (2);
3. adjust extender lens (15), make detection photoimaging from film sample (2) surface reflection in the CCD receiving plane and be full of whole receiving plane;
4. pass through the modulating frequency and the initial phase of computing machine (17) described first modulator of synchro control (7) and second modulator (12), the relative first phase place value that light (5) and pump light (10) are surveyed in modulation is followed successively by 0, pi/2, π and 3 pi/2s, and described computing machine (17) drives described area array CCD (16) and writes down four reflections detection light signal S under the phase place successively simultaneously
1, S
2, S
3And S
4, computing machine (17) receives the signal of described area array CCD (16) input, and according to formula
Calculate the amplitude signal value S that absorbs the light intensity variation that causes.
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| CNA2009100523751A CN101576483A (en) | 2009-06-02 | 2009-06-02 | Optical system and method for improving spatial resolution of laser film absorption measurement |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104458216A (en) * | 2014-12-30 | 2015-03-25 | 工业和信息化部电子第五研究所 | Device and method for detecting weak absorption of optical element |
| CN106442335A (en) * | 2016-12-16 | 2017-02-22 | 中国科学院工程热物理研究所 | Microscopic visual pump-probe heat reflection system |
| CN109444166A (en) * | 2018-12-04 | 2019-03-08 | 电子科技大学 | A kind of method of optical elements of large caliber Surface absorption type defect distribution fast imaging |
| CN112730262A (en) * | 2020-12-18 | 2021-04-30 | 中国科学院上海光学精密机械研究所 | Device and method for improving femtosecond laser induced damage threshold of KDP (Potassium dihydrogen phosphate) crystal |
| CN113203680A (en) * | 2021-04-09 | 2021-08-03 | 中国科学院上海光学精密机械研究所 | Device and method for measuring thermal diffusivity of thin film element and bulk material based on surface thermal lens technology |
-
2009
- 2009-06-02 CN CNA2009100523751A patent/CN101576483A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104458216A (en) * | 2014-12-30 | 2015-03-25 | 工业和信息化部电子第五研究所 | Device and method for detecting weak absorption of optical element |
| CN106442335A (en) * | 2016-12-16 | 2017-02-22 | 中国科学院工程热物理研究所 | Microscopic visual pump-probe heat reflection system |
| CN106442335B (en) * | 2016-12-16 | 2024-04-09 | 中国科学院工程热物理研究所 | Microscopic visual pumping detection heat reflection system |
| CN109444166A (en) * | 2018-12-04 | 2019-03-08 | 电子科技大学 | A kind of method of optical elements of large caliber Surface absorption type defect distribution fast imaging |
| CN109444166B (en) * | 2018-12-04 | 2021-07-23 | 电子科技大学 | Method for quickly imaging surface absorption type defect distribution of large-caliber optical element |
| CN112730262A (en) * | 2020-12-18 | 2021-04-30 | 中国科学院上海光学精密机械研究所 | Device and method for improving femtosecond laser induced damage threshold of KDP (Potassium dihydrogen phosphate) crystal |
| CN113203680A (en) * | 2021-04-09 | 2021-08-03 | 中国科学院上海光学精密机械研究所 | Device and method for measuring thermal diffusivity of thin film element and bulk material based on surface thermal lens technology |
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