Spatial Three-Mirror Off-Axis Freeform Optical System without Any Symmetry

Tan, Yilin; Zhu, Jun

doi:10.3390/photonics9050326

Cited by 5 publications

(1 citation statement)

References 32 publications

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“…Therefore, this paper adopts the X-Y polynomials for the characterization of the freeform surfaces in the telescope system and the spectral imaging system. The expression of the X-Y polynomial is as follows [29]:…”

Section: Freeform Surface Aberration Correction Methodsmentioning

confidence: 99%

Design of a Spaceborne, Compact, Off-Axis, Multi-Mirror Optical System Based on Freeform Surfaces

Wang,

Jiang

et al. 2024

Photonics

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Based on the application requirements of high spectral resolutions, high spatial resolutions and wide swatches, a new-generation, high-performance, spaceborne, hyperspectral imaging spectrometer (NGHSI) with a spatial resolution of 15 m and a swatch of 90 km is proposed. The optical system of the NGHSI has a focal length of 1128 mm, an F-number of three, a field of view (FOV) of 7.32° and a slit length of 144 mm. A new off-axis, multi-mirror telescope structure with intermediate images is put forward, which solves the design problem that realizes secondary imaging and good telecentricity at the same time. And a new off-axis lens-compensation Offner configuration is adopted to address the challenge of the high-fidelity design of spectral imaging systems with long slit lengths. The relationship between X-Y polynomials and aberration coefficients is analyzed, and the X-Y polynomial freeform surfaces are used to correct the off-axis aberrations. The design results show that the image quality of the telescope system is close to the diffraction limit. The smile, known as the spectral distortion along the line, and keystone, which is the magnification difference for different wavelengths, of the spectral imaging system are less than 1/10 pixel size. The complete optical system of the NGHSI, including the telescope system and the spectral imaging system, has excellent imaging quality and the layout is compact and reasonable, which realizes the miniaturization design.

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Section: Freeform Surface Aberration Correction Methodsmentioning

confidence: 99%

Design of a Spaceborne, Compact, Off-Axis, Multi-Mirror Optical System Based on Freeform Surfaces

Wang,

Jiang

et al. 2024

Photonics

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Steep freeform measurement method based on a normal transverse differential confocal

Wang¹,

Zheng²,

Liu³

et al. 2022

Opt. Express

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A normal transverse laser differential confocal freeform measurement (NTDCFM) method was proposed to address the high-precision measurement difficulty of steep freeform surfaces with large variations in inclination, scattering, and reflectance. Using D-shaped diaphragm technology, the freeform surface under test (FSUT) axial variation transformed into a spot transverse movement on the detection focal plane. Meanwhile, a 2D position sensitive detector (PSD) was used to obtain the normal vector of the sampling points so that the measuring sensor’s optical axis could track the FSUT normal direction. The focus tracking method extended the sensor measurement range. Theoretical analysis and experimental results showed that the axial resolution of the NTDCFM was better than 0.5 nm, the direction resolution of the normal vector was 0.1°, the maximum surface inclination could be measured up to 90°, the sensor range was 5 mm, and the measurement repeatability of the FSUT was better than 9 nm. It provides an effective new anti-inclination, anti-scattering, and anti-reflectivity method for accurately measuring steep freeform surfaces.

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Multi-field cosine condition in the design of wide-field freeform microscope objectives

Wang,

Zhu

2023

Opt. Express

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To break through the limitations of the classical sine condition, a multi-field cosine condition (MCC) is proposed in this paper. Building on this condition, a design method for wide field-of-view (FOV) freeform aplanatic systems is also proposed. This design method ensures that the optical system meets the MCC by correcting the mapping relationships of rays that originate from different apertures on both the object and image sides of the optical system. Using this method, we have successfully designed a chromatic-aberration-free and unobstructed freeform off-axis reflective microscope objective that is characterized by a wide FOV, an extensive spectral working range, and an extended working distance. The objective, which comprises only three freeform mirrors, has a numerical aperture (NA) of 0.4, magnification of 20×, an FOV of 2 mm × 2 mm, and an extended working distance of up to 60 mm. The objective demonstrates imaging quality close to the diffraction limit across the visible band to the short-wave infrared band (0.4–3 µm). When compared with a transmission-type wide-field microscope objective with identical NA and magnification properties, the reflective microscope objective nearly triples the FOV.

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Spatial Three-Mirror Off-Axis Freeform Optical System without Any Symmetry

Cited by 5 publications

References 32 publications

Design of a Spaceborne, Compact, Off-Axis, Multi-Mirror Optical System Based on Freeform Surfaces

Design of a Spaceborne, Compact, Off-Axis, Multi-Mirror Optical System Based on Freeform Surfaces

Steep freeform measurement method based on a normal transverse differential confocal

Multi-field cosine condition in the design of wide-field freeform microscope objectives

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