Linear systems formulation of scattering theory for rough surfaces with arbitrary incident and scattering angles

Krywonos, Andrey; Harvey, James E.; Choi, Narak

doi:10.1364/josaa.28.001121

Cited by 116 publications

(87 citation statements)

References 57 publications

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“…Active optics cannot correct or compensate for high and MSFR in the optics train. While high spatial frequency finish errors scatter energy out of the image core into a broad scattering halo, again without significantly broadening the image core, the mid-spatial frequency surface irregularities produce smallangle scatter which has the effect of smearing out the image core, thus reducing the resolution drastically [11].…”

Section: Mid-spatial Frequency Error and Surface Microroughnessmentioning

confidence: 99%

Ultra-smooth finishing of aspheric surfaces using CAST technology

Kong¹,

Young²

2014

Advanced Optical Technologies

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Abstract:Growing applications for astronomical groundbased adaptive systems and air-born telescope systems demand complex optical surface designs combined with ultra-smooth finishing. The use of more sophisticated and accurate optics, especially aspheric ones, allows for shorter optical trains with smaller sizes and a reduced number of components. This in turn reduces fabrication and alignment time and costs. These aspheric components include the following: steep surfaces with large aspheric departures; more complex surface feature designs like stand-alone off-axis-parabola (OAP) and free form optics that combine surface complexity with a requirement for ultra-high smoothness, as well as special optic materials such as lightweight silicon carbide (SiC) for air-born systems. Various fabrication technologies for finishing ultra-smooth aspheric surfaces are progressing to meet these growing and demanding challenges, especially Magnetorheological Finishing (MRF) and ion-milling. These methods have demonstrated some good success as well as a certain level of limitations. Amongst them, computer-controlled asphere surface-finishing technology (CAST), developed by Precision Asphere Inc. (PAI), plays an important role in a cost effective manufacturing environment and has successfully delivered numerous products for the applications mentioned above. One of the most recent successes is the Gemini Planet Imager (GPI), the world's most powerful planet-hunting instrument, with critical aspheric components (seven OAPs and free form optics) made using CAST technology. GPI showed off its first images in a press release on January 7, 2014 . This paper reviews features of today's technologies in handling the ultra-smooth aspheric optics, especially the capabilities of CAST on these challenging products. As examples, three groups of aspheres deployed in astronomical optics systems, both polished and finished using CAST, will be discussed in detail.

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Section: Mid-spatial Frequency Error and Surface Microroughnessmentioning

confidence: 99%

Ultra-smooth finishing of aspheric surfaces using CAST technology

Kong¹,

Young²

2014

Advanced Optical Technologies

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“…The Generalised Harvey Shack (GHS) method or model was recently reported [3] and has been applied in the visible, infrared and ultraviolet, demonstrating a good fit to experimental data for surfaces which are both smooth and rough. This method, which is based on diffraction, uses a family of transfer functions based on the autocovariance function of the surface, the incidence angle, the scattering angle and the refractive index and we have applied this method to THz scattering.…”

Section: Scattering Modelsmentioning

confidence: 99%

“…H is related to the surface properties as shown in equation 1 where n 1 and n 2 are the refractive index of the first and second medium and ) , (ŷ x C s is the surface autocovariance function and s is the RMS roughness and rel is the band limited RMS roughness [3].…”

Section: The Bidirectional Reflectance Distribution Function (Brdf) Imentioning

confidence: 99%

Scattering in the THz region, measurement prediction and extrapolation

Appleby¹,

Saenz

Wylde

et al. 2014

The 8th European Conference on Antennas and Propagation (EuCAP 2014)

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An instrument has been designed which is capable of measuring scattering from 0.075-0.5 THz. This will enable a more accurate determination of the optical properties of materials by correcting for scatter and also the characterisation of the mechanical properties of the surface. Models have been investigated to help in experimental design and in reducing the number of required measurements by extrapolation. The Generalized Harvey Shack (GHS) method has been evaluated for this purpose. Predictions for 40 grit gold coated sandpaper at 37 degrees incidence angle and 0.8 THz are made showing the surface to be almost completely diffuse. The GHS method was compared to the Integral Equation Model (IEM).

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“…A new linear systems formulation of non-paraxial scalar diffraction theory [13,14] applied to surface scatter phenomena eventually resulted in a generalized Harvey-Shack (GHS) surface scatter theory that produces accurate results for rougher surfaces than the Rayleigh-Rice theory and for larger incident and scattered angles than the classical Beckmann-Kirchhoff theory [15,16].…”

Section: Historical Background Of Surface Scatter Theorymentioning

confidence: 99%

Effect of surface scatter upon the MTF of the solar ultra violet imager (SUVI) telescope

Harvey¹,

Choi

2013

Solar Physics and Space Weather Instrumentation V

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The solar UV imager (SUVI) is an extreme ultraviolet instrument that will fly on the Geostationary Operational Environmental Satellite (GOES)-R and-S platforms, as part of NOAA's space weather monitoring fleet. It will provide important information on solar activity and the effects of the Sun on the earth and the near-earth environment. This instrument will image the full solar disc in 6 EUV wavebands between 303.8 Å and 93.9 Å. A generalized Cassegrain telescope configuration is employed where six mirror sectors utilize multilayer coatings optimized for the six wavelengths of interest. An aperture shutter is used to select the appropriate sector for observations at a particular wavelength. A thinned, back-illuminated CCD sensor with 21m (2.5 arcsec) pixels resides in the telescope focal plane. The modulation transfer function (MTF) is usually considered to be the image quality criterion of choice for applications where fine detail in extended images needs to be specified or evaluated. However, the contractual image quality requirement was specified in terms of fractional ensquared energy for a variety of different wavelengths and square sizes. In this paper we will calculate and present MTF plots (as degraded by diffraction, geometrical aberrations, surface scatter effects and detector effects) for each of the SUVI wavelengths of interest. Surface scatter due to residual optical fabrication errors is a major factor limiting the performance at the shorter wavelengths, and the large detector size severely limits the performance at all SUVI wavelengths.

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Linear systems formulation of scattering theory for rough surfaces with arbitrary incident and scattering angles

Cited by 116 publications

References 57 publications

Ultra-smooth finishing of aspheric surfaces using CAST technology

Ultra-smooth finishing of aspheric surfaces using CAST technology

Scattering in the THz region, measurement prediction and extrapolation

Effect of surface scatter upon the MTF of the solar ultra violet imager (SUVI) telescope

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