CN100451577C - Hartmann wavefront sensor based on micro-prism array for pulse light beam quality detection - Google Patents

Abstract

The present invention relates to a pulse light beam quality detecting Hartmann wavefront sensor based on micro prism arrays, which comprises a data acquisition device, a micro prism array, a Fourier lens and a photodetector, wherein the data acquisition device can receive and send synchronous pulse signals. The present invention is characterized in that the present invention is composed of the micro prism array in a variable period two-dimensional sawtooth-shaped phase grating structure and the Fourier lens and the photodetector which are appressed with the micro prism array, wherein the micro prism array in the two-dimension sawtooth-shaped phase grating array structure can be in a single surface photoetching centrosymmetrical annular structure and in a double surface photoetching double surface grating structure, and the micro prism array can be processed by adopting not only micro optical techniques, but also binary optics techniques. The present invention has the advantages of simple and stable structure and easily realized processing technology; compared with the existing micro lens techniques, the present invention can simplify the installation and the adjustment of Hartmann wavefront sensors and can realize bulk production.

Description

Light pulse beam quality testing Hartmann wave front sensor based on microprism array

Technical field

The present invention relates to a kind of Hartmann wave front sensor that is used for the light pulse beam quality testing, particularly a kind of microprism Hartmann wave front sensor.

Background technology

The beam quality of laser is determining the transport property of laser and the converging property in far field, usually with M ²The factor, Strehl ratio, wave front aberration RMS value wait the quantitative description that provides beam quality.In fact, just can determine its transport property and converging property of far field by the intensity distributions and the PHASE DISTRIBUTION of laser beam.Hartmann wave front sensor can detect the intensity distributions and the PHASE DISTRIBUTION of light beam simultaneously in a two field picture of laser beam, be a highly effective instrument for laser beam especially light pulse beam quality testing therefore.The existing Hartmann wave front sensor that is used to detect the light pulse beam quality, usually adopt microlens array to cut apart light beam aperture, and incident light is focused on the photosensitive target surface of photodetector (being generally CCD), perhaps lenticular focal plane hot spot image is imaged in the photodetector photosensitive target surface by a relay system, see patent " Apparatus and method for characterizing pulsedlight beams ", Neal et al.Patent No.6,052,180, Apr.18,2000.The deficiency of this class Hartmann sensor is the coupling technique more complicated of microlens array and CCD, the focus error of the lenticule unit of microlens array is inconsistent to cause influencing sensor accuracy, requirement to the microlens array manufacturing technology is very high, installation, debug difficulties are not suitable for manufacturing in enormous quantities.

Jiang Wenhan etc. once proposed and made the mirror of cutting apart that a kind of prism (referring to wedge or wedge) that has different angles of wedge forms and cut apart light beam aperture (" 37 unit self-adapting optical system ", Jiang Wenhan, Wu Xubin, Ling Ning, photoelectric project, 22 volumes, 1 phase 38-45 page or leaf, nineteen ninety-five), and, can overcome the difficulty that aperture segmentation element and CCD are coupled with the Hartmann sensor of object lens focusing in the CCD photosensitive target surface.But the manufacturing technology that is assembled into the aperture segmentation element with single sub-prism is complicated and expensive, also is unwell to batch process.

Propose among the embodiment 1 of Chinese patent application number " 01108433.2 ": the aperture segmentation element 1 ' of Hartmann wave front sensor can be the integrated form binary Fresnel microprism array that adopts micro-optic technology or binary optical technique to make, the focal plane of condenser lens 2 ' overlaps with the photosensitive target surface of CCD3 ' 4 ', as shown in Figure 1.The present invention patented claim has proposed a kind of Hartmann wave front sensor structure of simple and stable, but to wherein key components-light beam aperture cutting element, does not provide definite structure and production program.Therefore, the present invention is the continuation to above-mentioned patented claim.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome that the focus error of lenticule unit of coupling technique more complicated, microlens array of microlens array and photodetector in the prior art is inconsistent to cause influencing sensor accuracy; And sub-wedge assembling technique complex process and costliness, be not suitable for deficiencies such as batch process, a kind of microprism Hartmann wave front sensor that is used for the light pulse beam quality testing that is suitable for industrialized mass production is provided.

Technical solution of the present invention is: the microprism Hartmann wave front sensor that is used for the light pulse beam quality testing, comprise data acquisition equipment, microprism array, fourier transform lens and the photodetector CCD that can receive and send synchronization pulse, it is characterized in that: described microprism array is a variable period two dimension sawtooth shaped phase grating array structure, with the aperture segmentation of fourier transform lens combination realization light beam.

The variable period two dimension sawtooth shaped phase grating array of serration depth such as the microprism array of described variable period two dimension sawtooth shaped phase optical grating construction is, promptly each grating is same serration depth in the array, and just x, y director space cycle have nothing in common with each other.

Described variable period two dimension sawtooth shaped phase optical grating construction microprism array two kinds of implementations can be arranged: the two-sided optical grating construction of centrosymmetric annular layout structure of single face photoetching and two sides photoetching.The centrosymmetric annular layout structure of single face photoetching is single face photoetching on substrate, with the center is basic point, the circle-shaped outside expansion that is centrosymmetric, and each sub-aperture x, y director space period T x and Ty outwards are 1 by the center simultaneously in the array, 1/2,1/3...1/n progression multiplying power alternation.The two-sided optical grating construction of two sides photoetching is for being benchmark in substrate one side with the x coordinate axis, and etching produces and is arranged in parallel, the grating cycle, its grating cycle outwards was 1,1/2 by the center, 1/3...1/n progression multiplying power alternation along the sawtooth shaped phase grating of x direction; Is benchmark at the substrate another side with the y coordinate axis, and etching produces and to be arranged in parallel, the grating cycle, its grating cycle outwards was 1,1/2 by the center, 1/3...1/n progression multiplying power alternation along the sawtooth shaped phase grating of y direction.

The microprism array of described variable period two dimension sawtooth shaped phase optical grating construction can adopt micro-optic technology or binary optical technique processing.

Principle of the present invention is: the microprism array of variable period two dimension sawtooth shaped phase optical grating construction is to adopt micro-optic or binary optical technique, etching forms variable period two dimension sawtooth shaped phase grating array on a sheet base, its serration depth remains unchanged and cycle alternation between sub-aperture, realize evenly arranging of spot array by setting serration depth, grating in parameters such as the space periodic of pairwise orthogonal direction and fourier transform lens focal lengths, two kinds of implementations of two-sided optical grating construction of centrosymmetric annular layout structure of single face photoetching and two sides photoetching can be arranged; The sawtooth shaped phase structure of grating adopts the binary optical technique etching to form; Fourier transform lens is according to the anaberration lens of focal length, the processing of f number parameter requests such as (lenticular focal length/bores), does not receive by photodetector CCD like this and can produce distortion.

The present invention compared with prior art has following advantage:

1. microprism Hartmann wave front sensor disclosed in this invention, its light beam aperture cutting element-microprism array is made of variable period two dimension sawtooth shaped phase grating array, only need and a fourier transform lens combination, just can realize that light beam aperture cuts apart, converge to the photodetector photosensitive target surface by public fourier transform lens before all wavelets, overcome the inconsistent influence that the Hartmann wave front sensor precision is produced of the lenticule unit focal length of microlens array in the prior art.

2. microprism array disclosed in this invention is to utilize directly etching on a slice base of micro-optic or binary optical technique, has avoided a work sheet prism respectively, carries out the complexity of sub-prism assembly unit, loaded down with trivial details, expensive technology then.

3. microprism array disclosed in this invention is adding man-hour, only need to change the space periodic of each sawtooth shaped phase grating in the array and serration depth remains unchanged, and broached-tooth design adopts micro-optic or binary optical technique etching to form, it is simple in structure, processing technology easily realizes, is easy to realize mass production.

4. the installation adjustment of Hartmann wave front sensor will be simplified.Existing lenticule Hartmann sensor needs a relay system usually, the focus of microlens array is coupled to the photosensitive target surface of CCD, as shown in Figure 2, except that the collimation adjustment that must finish microlens array 21, relay system 22 and CCD 23, also must finish between the photosensitive target surface 24 of the focal spot array of microlens array 21 and CCD 23 object-image conjugate adjustment with respect to relay system 22, the whole link of debuging is more and difficulty is big, is unfavorable for producing in batches.And microprism array 41 that this patent proposed and fourier transform lens 42 combinations, direct imaging is in CCD photosensitive target surface 44, as shown in Figure 4, and except that necessary collimation adjustment, only CCD photosensitive target surface 44 need be focused with respect to fourier transform lens 42, simplify the work of debuging of sensor.

Description of drawings

Fig. 1 is the Hartmann wave front sensor structural representation that Chinese invention patent application " 01108433.2 " proposes in embodiment 1;

Fig. 2 is the structural representation of lenticule Hartmann wave front sensor in the prior art;

Fig. 3 detects pulsed light light beam quality device synoptic diagram for the Hartmann sensor based on microprism array among the present invention;

Fig. 4 among the present invention based on the Hartmann wave front sensor structure and the principle of work synoptic diagram of microprism array;

Fig. 5 adopts the centrosymmetric annular layout structural representation of single face photoetching for the microprism array 41 of variable period two dimension sawtooth shaped phase optical grating construction among the present invention;

Fig. 6 is the schematic perspective view of Fig. 5;

Fig. 7 adopts the two-sided optical grating construction synoptic diagram of two sides photoetching for the microprism array 41 of variable period two dimension sawtooth shaped phase optical grating construction among the present invention;

Fig. 8 is the left view of Fig. 7;

Fig. 9 is the right view of Fig. 7.

Embodiment

As shown in Figure 3, the laser beam irradiation that LASER Light Source 1 is sent is to microprism array 41, and by fourier transform lens 42 imagings, the overall optical beam orifice is evenly cut apart and form spot array on the photosensitive target surface of CCD 43; LASER Light Source provides synchronizing signal simultaneously to data acquisition equipment 5, data acquisition equipment 5 sends synchronizing signal 51 to CCD 43, make it begin the exposure of certain hour length, after exposure is finished, CCD 43 exports to data acquisition equipment 5 with the data message gathered (simulation or numeral) by data cable 52, send information to computing machine 6 by data acquisition equipment 5, handle, can obtain the relevant parameter of laser beam by 6 pairs of resulting information of computing machine.

As shown in Figure 4, the microprism Hartmann wave front sensor is by the microprism array 41 of variable period two dimension sawtooth shaped phase optical grating construction, fourier transform lens 42 and CCD 43 form, fourier transform lens 42 is close to the microprism array 41 of variable period two dimension sawtooth shaped phase optical grating construction, the photosensitive target surface 44 of CCD 43 is positioned on fourier transform lens 42 focal planes, the microprism array 41 of variable period two dimension sawtooth shaped phase optical grating construction is for adopting micro-optic or the binary optical technique two-dimentional sawtooth shaped phase grating array that etching produces on same substrate, and the variable period two dimension sawtooth shaped phase grating array of serration depth such as be, be that each grating is same serration depth in the array, be x, the y director space cycle has nothing in common with each other, it can have two kinds of implementations: the two-sided optical grating construction of centrosymmetric annular layout structure of single face photoetching and two sides photoetching, respectively as Fig. 5, Fig. 6 and Fig. 7, Fig. 8, shown in Figure 9.

Its concrete enforcement of structure shown in Figure 4 can be: microprism array 41 and fourier transform lens 42 adopt the mechanical parts that has three-dimensional adjustment function to fix respectively, and CCD thereafter needs the axial translation adjustment.When debuging, respectively to microprism array 41, fourier transform lens 42 and CCD 43 adjustment that collimates; Directional light incident then, CCD 43 axially adjusts, and its photosensitive target surface is positioned on the focal plane of fourier transform lens 42, and the whole process of debuging is finished.

The present invention is when work, as shown in Figure 4, incident beam is behind the microprism array 41 of two-dimentional serrate variable period phase grating structure, the light beam in each sub-aperture has produced the respective phase variation respectively, via the fourier transform lens of being close to thereafter 42, survey its light distribution with the CCD 43 that is positioned on the fourier transform lens focal plane, this light distribution is comprising the phase information that two-dimentional sawtooth shaped phase grating array 41 is produced, the phase change difference that each sub-aperture produced, thereby on fourier transform lens 42 focal planes, forming a spot array, the overall optical beam orifice is evenly cut apart.The spot array that the incident of standard flat ripple produces has been saved in advance and has been used as nominal data.When having the wavefront incident of certain aberration, each local dip plane wave produces new additive phase to two-dimentional sawtooth shaped phase grating in its sub-aperture, and this phase change will be reflected in the facula position skew of fourier transform lens 42 focal planes.

The hot spot signal that CCD 43 receives can be handled by computing machine, adopts centroid algorithm: the position (x that is 1. calculated hot spot by formula _i, y _i), the corrugated control information of detection full aperture:

$x_i=\frac{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{x}_{\mathrm{nm}}{I}_{\mathrm{nm}}}{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{I}_{\mathrm{nm}}},$ $y_i=\frac{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{y}_{\mathrm{nm}}{I}_{\mathrm{nm}}}{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{I}_{\mathrm{<figure-callout\; id="1"\; label="nm"\; filenames="C20031010016800101.png,C20031010016800103.png"\; state="\{\{state\}\}">nm</figure-callout>}}}$ ①

In the formula, m=1～M, n=1～N are that sub-aperture is mapped to pixel region corresponding on CCD 43 photosensitive target surfaces 44, I _NmBe (n, the m) signal received of individual pixel-by-pixel basis, x on CCD 43 photosensitive target surfaces 44 _Nm, y _NmBe respectively (n, m) the x coordinate of individual pixel and y coordinate.

2. calculate the wavefront slope g of incident wavefront again according to formula _Xi, g _Yi:

$g_{\mathrm{xi}}=\frac{\mathrm{\&Delta;x}}{\mathrm{\&lambda;f}}=\frac{x_i-{\mathrm{<figure-callout\; id="0"\; label="x"\; filenames="C20031010016800112.png"\; state="\{\{state\}\}">x</figure-callout>}}_0}{\mathrm{\&lambda;f}},$ $g_{\mathrm{yi}}=\frac{\mathrm{\&Delta;y}}{\mathrm{\&lambda;f}}=\frac{y_i-{\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="C20031010016800112.png"\; state="\{\{state\}\}">y</figure-callout>}}_0}{\mathrm{\&lambda;<figure-callout\; id="2"\; label="f"\; filenames="C20031010016800101.png,C20031010016800112.png"\; state="\{\{state\}\}">f</figure-callout>}}$ ②

In the formula, (x ₀, y ₀) demarcate the spot center reference position that Hartmann sensor obtains for the standard flat ripple; During Hartmann sensor probing wave front-distortion, spot center is displaced to (x _i, y _i), finish the detection of Hartmann wave front sensor to signal.

As shown in Figure 5, microprism array can have the centrosymmetric annular layout structure of single face photoetching: the cycle of each grating and groove direction form annular layout, i.e. single face photoetching on substrate, with central point o is basic point, circle-shaped outside expansion is centrosymmetric, each sub-aperture x, y director space period T x and Ty outwards are 1,1/2 by the center, 1/3...1/n progression multiplying power alternation simultaneously in the array.

Fig. 6 is the schematic perspective view of structure shown in Figure 5.

As Fig. 7, Fig. 8 and shown in Figure 9, microprism array can also have the two-sided optical grating construction of two sides photoetching: the branch two sides is determined the X of each grating in the array and the grating cycle of Y direction respectively, produce the directions X cycle at groove of substrate, another side then groove produces the Y direction cycle, two-sided groove forms the different cycles of grating array jointly, be benchmark with the x coordinate axis promptly in the substrate one side, etching produces and to be arranged in parallel, the grating cycle is along the sawtooth shaped phase grating of x direction, its grating cycle outwards is 1 by the center, 1/2,1/3...1/n progression multiplying power alternation; Is benchmark at the substrate another side with the y coordinate axis, and etching produces and to be arranged in parallel, the grating cycle, its grating cycle outwards was 1,1/2 by the center, 1/3...1/n progression multiplying power alternation along the sawtooth shaped phase grating of y direction.

Claims (5)

1, based on the light pulse beam quality testing Hartmann wave front sensor of microprism array, comprise data acquisition equipment, microprism array, fourier transform lens and the photodetector that can receive and send synchronization pulse, it is characterized in that: by same serration depth, the aperture segmentation of microprism array and the fourier transform lens combination realization light beam of the variable period two dimension sawtooth shaped phase optical grating construction that has nothing in common with each other of x, y director space cycle just.

2, the light pulse beam quality testing Hartmann wave front sensor based on microprism array according to claim 1, it is characterized in that: the microprism array of described variable period two dimension sawtooth shaped phase optical grating construction adopts the micro-optic technology, or adopts binary optical technique processing.

3, the light pulse beam quality testing Hartmann wave front sensor based on microprism array according to claim 1 is characterized in that: the microprism array of described variable period two dimension sawtooth shaped phase optical grating construction adopts the two-sided optical grating construction of centrosymmetric annular layout structure of single face photoetching or two sides photoetching.

4, the light pulse beam quality testing Hartmann wave front sensor based on microprism array according to claim 3, it is characterized in that: the centrosymmetric annular layout structure of described single face photoetching is single face photoetching on substrate, with the center is basic point, circle-shaped outside expansion is centrosymmetric, each sub-aperture x, y director space period T x and Ty outwards are 1 by the center simultaneously in the array, 1/2,1/3...1/n progression multiplying power alternation.

5, the light pulse beam quality testing Hartmann wave front sensor based on microprism array according to claim 3, it is characterized in that: the two-sided optical grating construction of described two sides photoetching is for being benchmark in substrate one side with the x coordinate axis, etching produces and to be arranged in parallel, the grating cycle is along the sawtooth shaped phase grating of x direction, its grating cycle outwards is 1 by the center, 1/2,1/3...1/n progression multiplying power alternation; Is benchmark at the substrate another side with the y coordinate axis, and etching produces and to be arranged in parallel, the grating cycle, its grating cycle outwards was 1,1/2 by the center, 1/3...1/n progression multiplying power alternation along the sawtooth shaped phase grating of y direction.

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