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Randomly-coded hybrid grating based on light flux constraint

A technology of random coding and hybrid grating, applied in the field of random coding hybrid grating, can solve the problems of unfavorable instrument adjustment, interference effect, complex system structure, etc., and achieve the effects of improving system stability, improving detection accuracy, and simplifying system structure.

Active Publication Date: 2015-05-27
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The crossed grating transverse shearing interferometer can directly obtain the shearing interferogram in two orthogonal directions by using a two-dimensional crossed grating, and realize the real-time detection of the transient wavefront, but the existence of the order selection window makes the system structure complicated, which is not conducive to the instrument adjustment
[0004] Now the common four-wave transverse shearing interferometer uses the improved Hartmann template MHM as the spectroscopic element, which can obtain the phase information of the wavefront to be detected without order selection window, wherein the Hartmann template MHM is composed of two Composed of stepped phase grating and amplitude grating, the duty ratio of the amplitude grating is 2 / 3, and the period of the phase grating is twice the period of the amplitude grating. Ideally, there are only even-order secondary light and ±3 orders in the diffracted light field of MHM and ±3 order diffracted light are eliminated, so strictly speaking, MHM also includes other order diffracted light, which affects the interference between ±1 order light in the x and y directions

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  • Randomly-coded hybrid grating based on light flux constraint
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  • Randomly-coded hybrid grating based on light flux constraint

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Embodiment 1

[0032] The present invention can be made into a randomly coded hybrid grating based on luminous flux constraint with an incident light wavelength λ of 632.8nm and a grating distance d of 120um. The grating uses quartz as a substrate, its refractive index n is about 1.46, and a chrome film is used as a mask. image 3 It is the transmittance distribution diagram of the grating within the size range of 300um*300um, where the white area is the light-transmitting area without mask coverage, the black area is the opaque area covered by the mask, and the mask covers part of the area on the substrate So that the luminous flux in each area of ​​9 square microns satisfies distribution, and in each area of ​​9 square microns, the mask is randomly arranged in small squares of 1 square micron; Figure 4 It is the etching depth distribution map of the grating in the corresponding area of ​​300um*300um, where the white area is the area that does not need to be etched, and the black area is ...

Embodiment 2

[0034] An example of the four-wave transverse shear interference wavefront detection applied to continuous wavefronts by the present invention is described as follows:

[0035] Figure 5 It is a system structure diagram of four-wave transverse shear interference continuous wavefront detection based on random coded hybrid grating based on luminous flux constraint. The distorted wavefront to be measured in this embodiment is a continuous wavefront with an aperture of Φ=8mm and a wavelength of 632.8nm. After the wavefront to be measured passes through the random-coded hybrid grating, it will be divided into four wavefronts of ±1 level in two orthogonal directions. Using the computer to control the CCD to collect the overlapping parts of the four beam spots can obtain the four-wave transverse shear interferogram, such as Figure 6 .

[0036] After obtaining the cross-grating transverse shear interferogram, the wavefront to be measured needs to be reconstructed by differential Z...

Embodiment 3

[0052] The real-time detection of the four-wave transverse shear interference wavefront applied to the transient wavefront by the present invention is described as follows:

[0053] Figure 9 It is a system structure diagram of a random-coded hybrid grating based on luminous flux constraints for four-wave transverse shear interference transient wavefront detection. The system is composed of pulsed laser, laser driver, synchronous trigger control system, collimated beam expander system, random code hybrid grating, CCD and computer. After the laser is output by the pulse laser, it is expanded into a wide beam of Φ=25mm by the collimator beam expander system. After the beam passes through the disturbance field, it will carry the inhomogeneous information of the refractive index in the disturbance field to the wavefront distortion. The disturbance here The field generally refers to the high-speed air flow field or other disturbance fields in the wind tunnel. After the wavefront ...

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Abstract

The invention discloses a randomly-coded hybrid grating based on a light flux constraint. The randomly-coded hybrid grating comprises a non-transparent mask S2 and a transparent substrate S1, wherein the mask S2 covers a partial region of the substrate S1, so that the light flux of each square region with the area of S on the grating meets distribution as shown in a FORMULA, in which d is the grating distance of the randomly-coded hybrid grating, and mask blocks in each square region with the area of S are randomly distributed; the region, within the range as shown in a FORMULA and not covered by the mask, of the substrate S1 is etched, so that at the etching depth, light wave penetrating through a light-transmittable part of the etched region is advanced by phi phase relative to light wave penetrating through a light-transmittable part of the non-etched substrate. On one hand, the randomly-coded hybrid grating omits a level selection window in four-wavefront lateral shearing interference of a conventional cross grating, simplifies the structure of a system and improves the stability of the system; on the other hand, interference from other diffraction levels in a formed four-wavefront lateral shearing interference pattern is reduced and the detection precision of a wavefront to be detected is improved.

Description

technical field [0001] The invention belongs to the field of light beam wavefront detection, in particular to a randomly coded hybrid grating based on luminous flux constraint used in a four-wave transverse shearing interferometer. Background technique [0002] Transverse shearing interference technology utilizes the wavefront to be measured for dislocation interference, so as to realize the direct measurement of the phase of the wavefront. Since it adopts a common path system and does not need a reference beam, the interference fringes are stable, the anti-interference ability is strong, and the environmental requirements are low. , the instrument structure is simple. Based on the above advantages, transverse shearing interferometry is often used in the inspection and measurement of optical materials and components, the detection of beam properties and parameters, optical system calibration, inspection and evaluation, etc. [0003] The traditional transverse shearing inter...

Claims

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Application Information

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IPC IPC(8): G02B5/18G01J9/02
CPCG01J9/02G02B5/18G02B5/1857
Inventor 杨甬英凌曈岳秀梅刘东
Owner ZHEJIANG UNIV
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