Deflectometric profilometers are used to precisely measure the form of beam shaping optics of synchrotrons and X-ray free-electron lasers. They often utilize autocollimators which measure slope by evaluating the displacement of a reticle image on a detector. Based on our privileged access to the raw image data of an autocollimator, novel strategies to reduce the systematic measurement errors by using a set of overlapping images of the reticle obtained at different positions on the detector are discussed. It is demonstrated that imaging properties such as, for example, geometrical distortions and vignetting, can be extracted from this redundant set of images without recourse to external calibration facilities. This approach is based on the fact that the properties of the reticle itself do not change - all changes in the reticle image are due to the imaging process. Firstly, by combining interpolation and correlation, it is possible to determine the shift of a reticle image relative to a reference image with minimal error propagation. Secondly, the intensity of the reticle image is analysed as a function of its position on the CCD and a vignetting correction is calculated. Thirdly, the size of the reticle image is analysed as a function of its position and an imaging distortion correction is derived. It is demonstrated that, for different measurement ranges and aperture diameters of the autocollimator, reductions in the systematic errors of up to a factor of four to five can be achieved without recourse to external measurements.

We report on recent work towards improving interference microscopy metrology of variable-line-spacing (VLS) x-ray diffraction gratings through a combination of techniques: image reconstruction to correct for distortion and blurring, multi-image super-resolution data acquisition to increase resolution beyond the single-image limit, and image stitching to increase the measurement area. Here, we concentrate on precision characterization and correction for lens distortion (aka geometrical distortion) and provide precise measurements of the effective image pixel distribution. We present and analyze the results of geometrical distortion measurements performed with test samples, including traditional checkerboard test artifacts and binary pseudo-random array (BPRA) standards patterned with two-dimensional uniformly redundant arrays (URA). The URA BPRA standards are also useful for measurement of the instrument transfer function (ITF), a measure of the optical aberrations and limited lateral resolution of the instrument. We also outline other essential elements and the next steps of the project on development of so-called super-resolution interference microscopy, enabling more precise measurements of VLS groove density than previously possible. The global aim of this project is to integrate our metrology technique into the manufacture of high-resolution x-ray gratings.

The thorough realization of the advantages of the new generation x-ray light sources, such as the Upgraded Advanced Light Source (ALS-U) under construction, requires near-perfect x-ray optics, capable of delivering light without significant degradation of brightness and coherence. The stringent requirements of beamline optics drive the state of the art in ex situ optical metrology. Here, we present the results of the ongoing efforts at the ALS X-Ray Optics Laboratory to develop a new generation long trace profiler, LTP-2020. We discuss the system design that incorporates different types of surface slope sensors. In addition to the classical pencil beam interferometry (PBI) sensor with an improved optical design, we develop a deflectometry sensor based on a customized electronic autocollimator (AC). By applying a new data processing algorithm to the AC raw image data available from the customized AC, we significantly reduce the quasi-periodic systematic error of the AC equipped with a small size aperture. We also treat the possibility to use the AC as a PBI sensor with external light beam sources based on super-luminescent emitting diode (SLED) and single-mode laser diode (SMLD). Operation modes with stationary and/or translated sensors are possible due to the two-carriage gantry system with adjustable vertical position. The variety of the available operation modes allows optimization of the LTP-2020 experimental arrangement for providing the best possible performance in measurements with state-of-the-art aspherical x-ray optics, variable-line-spacing diffraction gratings, and multi-element optical systems.

We describe details of a recent deep upgrade of the MicroMap-570 interferometric microscope available at the Advanced Light Source X-Ray Optics Laboratory. The upgrade has included an improvement of the microscope optical sensor and data acquisition software, design and implementation of automated optic alignment and microscope translation systems, and development of a specialized software for data processing in the spatial frequency domain. With the upgraded microscope, we are now capable for automated (remoted) measurements with large x-ray optics and optical systems. The results of experimental evaluation of the upgraded microscope performance and calibration of its instrument transfer function are also discussed. Because the same already obsolete MicroMap-570 microscopes have been used for years at other metrology laboratories at the x-ray facilities around the globe, we believe that our experience on upgrade of the microscope describe in detail in the present paper is broadly interesting and useful.