Investigation on lateral resolution of surface slope profilers

Abstract

We investigate and compare the spatial (lateral) resolution, or more generally, the instrument's transfer function (ITF) of surface slope measuring profilometers of two different types that are commonly used for high accuracy characterization of x-ray optics at the long-spatial-wavelength range. These are an autocollimator based profiler, Optical Surface Measuring System (OSMS), and a long trace profiler, LTP-II, both available at the Advanced Light Source (ALS) X˗Ray Optics Lab (XROL). In the OSMS, an ELCOMAT-3000 electronic auto-collimator, vertically mounted to the translation carriage and equipped with an aperture of 2.5 mm diameter, is scanned along the surface under test. The LTP˗II ITF has been measured for two different configurations, a classical two-beam pencil-beam-interferometry and a single-Gaussian-beam deflectometry. For the ITF calibration, we apply a recently developed method based on test surfaces with one-dimensional (1D) linear chirped height profiles of constant slope amplitude. Analytical expressions for the ITFs, empirically deduced based on the experimental results, are presented. We also discuss the application of the results of the ITF measurements and modeling to improve the surface slope metrology with state-of-the-art x-ray mirrors. This work was supported by the U. S. Department of Energy under contract number DE-AC02-05CH11231.

Characterization of groove density variation of VLS gratings with ALS XROL LTP-II in different operation modes

“…The smaller variation corresponds to the operation modes with lower spatial resolution, the SGB/GMF and PBI/SOPF, correspondingly (compere with the results of the resolution measurement in Ref. [10]).…”

“…The major observation from the LTP-II measurements with the grating is the strong correlation between the LTP-II mode of operation and the residual (after subtraction of the best-fit 1 st -or 3 rd -order polynomial functions) groove density variation. The smaller residual variation corresponds to the operation modes the SGB/GMF and PBI/SOPF with lower spatial resolution [3,10].…”

“…4a). We have recently demonstrated that the LTP spatial resolution of surface slope measurements in these two modes is significantly different [10]. Additionally, these modes of operation can have different sensitivity to the LTP-II systematic errors [3,11].…”

Reliability investigation of the instrument transfer function calibration technique based on binary pseudo-random array standards

“…This can be thought of as an illustration of how the application of metrology data deconvolution based on the experimentally measured ITF, can advance the confidence of surface topography metrology with state-of-the-art x-ray optics. Note that this point has been experimentally justified in application to surface slope metrology with super high quality x-ray optics [37,38].…”

Binary pseudorandom array test standard optimized for characterization of large field-of-view optical interferometers

“…This is principally important for usage of the measured 2D MTF for sub-resolution reconstruction of 2D data from the interferometers, analogous to the 1D surface slope data reconstruction demonstrated in Ref. [23]. The work on 2D data reconstruction is in progress.…”