Particulate contamination scatter is often modeled using Bidirectional Scatter Distribution Functions (BSDFs) based
upon Mie scattering by a distribution of spherical particles. Starting with the basic model described in P. R. Spyak and
W. L. Wolfe [1,2,3,4], we improve upon it by adding multiplicative geometrical form factors. These factors prevent the
Total Integrated Scatter (TIS) from exceeding unity and ensure that reciprocity is always obeyed. Preventing the TIS
from exceeding unity is necessary for energy to be conserved in the raytrace, and obeying reciprocity is necessary to
obtain consistent results between forward and backwards raytraces. As will be shown, this improved model fits
measured data better than the previous model.
This paper presents a theoretical (closed-form) solution for the z-axis surface deformations of a linear, homogeneous, unconstrained and isotropic paraboloidal surface subjected to a 3-dimensional linear thermal temperature gradient and soak temperature change. Previously, an equation for the component of the nodal surface displacement in the z direction has been published. Attaching the z-axis component of the nodal surface displacement to the original surface does not accurately describe the final surface. This work extends the previous analysis and presents a polynomial equation for the corrected surface deformation along the z-axis, as well as, the coefficients for the standard Zernike polynomial describing the corrected surface deformation. Also included is a discussion about z-axis temperature gradients across the paraboloidal surface and how to calculate an equivalent soak temperature change.
We present a method for designing and testing a null corrector for use with scatterplate interferometry on a large conic mirror. The null corrector in a scatterplate interferometer must maintain OPD of less than 1/2 wave over a finite field size for optimal fringe visibility. Our design uses an aspheric diamond-turned mirror (DTM) to exactly cancel out the spherical aberration of the surface under test. The DTM has the additional benefit of being useable in other types of interferometers for testing of the conic surface in a null condition. Low power refractive elements correct field aberrations over the finite aperture of the scatterplate. The null corrector can be certified using another smaller DTM or a computer generated hologram (CGH). This design has the advantages of being small in size, less expensive than designs using spherical surfaces (due to the small size of the null-correcting mirror), useable with other interferometers, and easy to align.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.