Infrared and Laser Engineering, Volume. 54, Issue 2, 20240488(2025)

Design of freeform uncooled infrared off-axis three-mirror optical system

Xing LI1,2, Bin WANG3, Jinpeng LI4, Rong GAO4, and Xianglong MAO2,4、*
Author Affiliations
  • 1State Key Laboratory of Ultrafast Optical Science and Technology, Xi′an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi′an 710119, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China
  • 3Norinco Group Testing and Research Institute, Xi′an 710086, China
  • 4The Spectral Imaging Technique Laboratory, Xi'an Institute of Optics and Precision Mechanics, Xi'an 710119, China
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    Figures & Tables(12)
    Obscuration constraints of the optical system
    3D layout of the optical system
    The 3D diagrams of residual sag distribution of M1-M3 after removing the best-fit sphere
    Spot diagram of the optical system
    Full field geometric spot radius distribution
    Full field RMS wavefront error distribution
    MTF curves of the optical system
    Distortion grid of the optical system
    • Table 1. Overall technical specification requirements

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      Table 1. Overall technical specification requirements

      ParameterSpecification
      Working wavelength/µm8-12
      Target size/mΦ2
      Field of view7.5°×5.6°
      Resolution800 pixel×600 pixel
      Resolution @10 km/m≤2
      Physical size of system(X-Y-Z)≤250 mm×350 mm×200 mm
    • Table 2. Detector parameters

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      Table 2. Detector parameters

      ParameterSpecification
      TypeNon-refrigerated vanadium oxide
      Pixel size/μm17
      Wavelength/μm8-14
      NETD/mK≤40 @f/1.0
      MRTD/mK≤400 @f/1.0
      Resolution800 pixel×600 pixel
      Frame rate/Hz25
      Operating temperature/℃−40-65
      Boot-up time/s≤15
    • Table 3. XY polynomial coefficients of M1-M3

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      Table 3. XY polynomial coefficients of M1-M3

      TermM1M2M3TermM1M2M3TermM1M2M3
      c0.00240.00520.0047X4 Y0−2.50 E-09−1.55 E-07−3.99 E-08X4 Y21.46 E-14−7.15 E-11−2.53 E-12
      k000X2 Y2−5.12 E-09−3.14 E-07−7.89 E-08X2 Y4−7.53 E-15−8.19 E-11−2.49 E-12
      X0 Y1−3.63 E-03−2.02 E-021.83 E-02X0 Y4−2.46 E-09−1.59 E-07−3.82 E-08X0 Y62.13 E-16−3.16 E-11−7.92 E-13
      X2 Y0−1.81 E-03−6.60 E-04−5.23 E-03X4 Y19.67 E-128.17 E-10−2.37 E-11X6 Y1−1.55 E-154.91 E-13−7.60 E-16
      X0 Y2−1.85 E-03−3.98 E-04−5.12 E-03X2 Y36.63 E-122.44 E-09−3.47 E-11X4 Y3−2.25 E-151.08 E-12−4.22 E-15
      X2 Y1−5.58 E-075.23 E-06−8.39 E-07X0 Y5−2.81 E-121.53 E-09−1.41 E-11X2 Y5−1.13 E-151.30 E-12−3.53 E-15
      X0 Y31.95 E-071.01 E-05−4.44 E-07X6 Y0−4.28 E-14−2.30 E-11−8.42 E-13X0 Y74.74 E-164.53 E-13−7.32 E-16
    • Table 4. Assembly tolerance allocation table of M1-M3 mirrors

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      Table 4. Assembly tolerance allocation table of M1-M3 mirrors

      TermValue
      Distance between M1 and M2/μm±50
      Distance between M2 and M3/μm±50
      X-decenter of M1-M3/μm±25
      Y-decenter of M1-M3/μm±25
      X-tilt of M1-M3/(°)±0.017
      Y-tilt of M1-M3/(°)±0.017
      Z-tilt of M1-M3/(°)±0.05
      Surface figure accuracy of M1-M3/nm150 (RMS)
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    Xing LI, Bin WANG, Jinpeng LI, Rong GAO, Xianglong MAO. Design of freeform uncooled infrared off-axis three-mirror optical system[J]. Infrared and Laser Engineering, 2025, 54(2): 20240488

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    Paper Information

    Category: Optical design and fabrication

    Received: Nov. 9, 2024

    Accepted: --

    Published Online: Mar. 14, 2025

    The Author Email: Xianglong MAO (maoxianglong@opt.ac.cn)

    DOI:10.3788/IRLA20240488

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