Acta Optica Sinica, Volume. 38, Issue 2, 0205001(2018)

Experimental Study on Spatial Filtering Imaging Method of Diffraction Gratings

Xu Gao1、*, Renjie Wang2, Jinhuan Li2, Yuting Wang2, and Jipeng Huang2
Author Affiliations
  • 1 School of Optoelectronic Engineering, Changchun University of Science and Technology, Changchun, Jilin 130022, China
  • 2 School of Physics, Northeast Normal University, Changchun, Jilin 130024, China
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    Figures & Tables(22)
    Diffraction principle of photographic encoder grating signal. (a) Schematic of the head of an encoder; (b) propagation of light diffraction
    Fraunhofer diffraction intensity distribution of rectangular grating
    Optical design principle of sine holographic grating
    Diffraction pattern of holographic grating and spatial frequency detection
    Fraunhofer diffraction pattern of holographic grating
    Spatial filtering principle of grating
    Fraunhofer diffraction pattern of filtered holographic gratings
    Optical system principle of grating test using parallel light
    Optical system for testing grating using point light
    Fringe images of multi-beam interferometry holographic grating with spatial frequency of 100 lp/mm before and after filtering imaging processing. (a) Before filtering; (b) after filtering
    Transmittance functions of multi-beam interferometry holographic grating with spatial frequency of 100 lp/mm before and after filtering imaging processing. (a) Before filtering; (b) after filtering
    Frequency spectra of multi-beam interferometry holographic grating with spatial frequency of 100 lp/mm before and after filtering imaging processing. (a) Before filtering; (b) after filtering
    Diffraction light intensity distributions of multi-beam interferometry holographic grating with spatial frequency of 100 lp/mm before and after filtering imaging processing. (a) Before filtering; (b) after filtering
    Frequency spectra of rectangular grating with spatial frequency of 100 lp/mm before and after filtering. (a) Before filtering; (b) after filtering
    Diffraction light intensity distribution of rectangular grating with spatial frequency of 100 lp/mm
    Diffraction light intensity distributions of rectangular grating with spatial frequency of 100 lp/mm after spatial filtering imaging processing. (a) Light intensity of -1 level and 0 level; (b) light intensity of 0 level and +1 level
    • Table 1. Advantages and disadvantages of sine grating fabrication method

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      Table 1. Advantages and disadvantages of sine grating fabrication method

      MethodAdvantageDisadvantage
      Fresnel double sided mirror and biprism1) Fewer components;2) Symmetrical optical system and the optical path difference is almost zero;3) The range of the grating constant is wide1) The light spot of interference area is small when using collimating lens;2) Two light beams are non-parallel without collimating lens
      Lloyd mirror method1) Fewer components and no secondary images;2) Simple operation and convenient adjustment1) Relatively high requirements for the reflectivity of the reflector, collimation property of two light beams and the intensity ratio;2) Only suitable for the fabrication of gratings with larger constant and smaller spatial frequency;3) The interferential light beams are not strictly parallel
      Michelson interferometry method1) Larger size of the grating fabricated;2) Two-dimensional grating fabricated by one exposure1) More transmissive components, so that the wave surface of the plane wave will be deformed and deviate from the plane wave;2) Only suitable for the fabrication of gratings with larger constant
      Mach-Zehnder interferometry method1) Symmetrical optical system and convenient to set up;2) The optical path difference of two light beams is small and the interference effect is good;3) The adjustment is convenient and the spatial frequency of gratings can be changed with the adjustment of one beam splitter angle1) More optical components and the fringe is uneven and the symmetry property is decreased;2) The angle between the reflected light and the transmissive light is small and the grating constant is not accurate;3) The angle of two light beams is restricted by the area of beam splitter and this method is not suitable for the fabrication of gratings with small constant
    • Table 2. Relationship between d0 and f0

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      Table 2. Relationship between d0 and f0

      f0 /(lp·mm-1)50100120150
      d0 /cm0.7911.5821.8982.373
    • Table 3. Relationship between f″0 and p

      View table

      Table 3. Relationship between f″0 and p

      f″0 /(lp·mm-1)50100120150
      p /cm1.2652.5313.0373.797
    • Table 4. Relationship among f″0, f″1, and p

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      Table 4. Relationship among f″0, f″1, and p

      f″0 /(lp·mm-1)50100120150
      p /cm2.5305.0656.0757.600
      f″1 /(lp·mm-1)100200240300
    • Table 5. Light intensity ratio of ±2 level to ±1 level of grating with spatial frequency of 100 lp/mm

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      Table 5. Light intensity ratio of ±2 level to ±1 level of grating with spatial frequency of 100 lp/mm

      y100±1y100±2p100p¯100
      1005.38500.0539
      1105.66170.0515
      1206.36000.0530
      1306.84190.0526
      1407.32620.0523
      1507.38000.04920.0527
      1608.22400.0514
      1708.83150.0520
      1809.64260.0536
      1909.87050.0520
      20011.68000.0584
    • Table 6. Light intensity ratio of ±2 level to ±1 level of each grating

      View table

      Table 6. Light intensity ratio of ±2 level to ±1 level of each grating

      Spatial frequency /(lp·mm-1)50100120150
      Light intensity ratio /%8.595.273.502.48
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    Xu Gao, Renjie Wang, Jinhuan Li, Yuting Wang, Jipeng Huang. Experimental Study on Spatial Filtering Imaging Method of Diffraction Gratings[J]. Acta Optica Sinica, 2018, 38(2): 0205001

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    Paper Information

    Category: Diffraction and Gratings

    Received: Aug. 23, 2017

    Accepted: --

    Published Online: Aug. 30, 2018

    The Author Email: Gao Xu (gaox19870513@163.com)

    DOI:10.3788/AOS201838.0205001

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