Most of the commercial available sub-aperture stitching interferometers measure the surface with a standard lens that produces a reference wavefront, and the precision of the interferometer is generally limited by the standard lens. The test accuracy can be achieved by removing the error of reference surface by the absolute testing method. When the testing accuracy (repeatability and reproducibility) is close to 1nm, in addition to the reference surface, other factors will also affect the measuring accuracy such as environment, zoom magnification, stitching precision, tooling and fixture, the characteristics of optical materials and so on. We establish a stitching system in the thousand level cleanroom. The stitching system is including the Zygo interferometer, the motion system with Bilz active isolation system at level VC-F. We review the traditional absolute flat testing methods and emphasize the method of rotation-shift functions. According to the rotation-shift method we get the profile of the reference lens and the testing lens. The problem of the rotation-shift method is the tilt error. In the motion system, we control the tilt error no more than 4 second to reduce the error. In order to obtain higher testing accuracy, we analyze the influence surface shape measurement accuracy by recording the environment error with the fluke testing equipment.
In the optical processing, ion beam processing has been used widely for the advantages of highly-precision, less pollution
and no stress and distortion. In order to analysis the preferential sputtering phenomenon, that Ar ion processing SiO2
mirror is considered as an example, which is commonly done in ion beam processing. In order to improve the processing
precision, the influence of Ar ion incident angle and incident energy on SiO2 sputtering yield is analyzed in the case of
considering the preferential sputtering phenomenon. By using the TRIM 2008 software, the sputtering situation of two
elements of Si and O are simulated. The sputtering yield rate of the two elements is always a certain proportion, and the
ratio is not related with the incident angle and it almost stays the same in a certain energy range. So, the SiO2 can be
thought as a whole when considering its sputtering yield, which equals to the sum of Si and O sputtering yield.
The ion beam figuring machine is a kind of high precise machining facility for optical components. In the field of optical
fabrication, the machining precision is always an important capability for the machining facility. The basic structures and
working principles of the ion beam figuring system are primarily introduced. And then, various errors which may reduce
the final machining precision have been analyzed through theories analysis and computer simulations. The errors
include: the approximate error from the discrete compute model to the actual continuum machining model; the system
error and random error of the high precision 3-axis motion stage which drives the ion source; the system error and
random error of the material removal rate of the ion source. A set of potential error parameters has been given for each
part of the ion beam figuring system. By using this set of parameters, it is possible to reach the nano-level machining.
The precision analysis in the paper will be a reference for ion beam figuring.
The process of Ion Beam Figuring (IBF) can be described by a two-dimensional convolution equation which including
dwell time. Solving the dwell time is a key problem in IBF. Theoretically, the dwell time can be solved from a
two-dimensional deconvolution. However, it is often ill-posed]; the suitable solution of that is hard to get. In this article, a
dwell time algorithm is proposed, depending on the characters of IBF. Usually, the Beam Removal Function (BRF) in
IBF is Gaussian, which can be regarded as a headstand Gaussian filter. In its stop-band, the filter has various filtering
abilities for various frequencies. The dwell time algorithm proposed in this article is just based on this concept. The
Curved Surface Smooth Extension (CSSE) method and Fast Fourier Transform (FFT) algorithm are also used. The
simulation results show that this algorithm is high precision, effective, and suitable for actual application.
Recently most of modern absolute measurement rotation the flats or spheres in the interferometer. We review traditional
absolute testing of flats methods and emphasize the method of even and odd functions. The rotation of the lens can lead
to some errors such as angle rotation error, center excursion error and other coordinate system motion error. We analyze
the errors by using Zernike polynomial. The flat or sphere can be expressed as Zernike polynomial which can also be
divided into even-odd, odd-even, even-even and odd-odd functions. We can use 36 Zernike polynomials to generate 3
plats A, B, C. Then the six measurements can be generated from the three plats. For the angle rotation error, we can
simulate the angle error distribution and substitute in the systems. According the error distribution we can change the
arithmetic to improve the measurement accuracy. The results of errors analyzed by means of Matlab are shown that we
can change the arithmetic according the coordinate direction motion errors which can be detected to improve the accuracy. The analysis results can also be used in other interferometer systems which have the motion of the coordinate system.