Normal tracing deflectometry using a secondary light source

Abstract

Scanning deflectometric profilers based on an f-θ system are typical optical tools used to measure mirror profiles at many synchrotron facilities. Unlike these profilers, which are based on a pencil beam, here a secondary light source and a pinhole are used to construct a system that automatically selects a beam that will always pass through the pinhole and propagate along the normal direction of the measured area on the surface under test. By measuring the angle variation of the selected beam, slope variations of the surface under test can be measured. Systematic errors introduced by manufacturing defects or aberrations of an optical element, which greatly degrade the performance of traditional profilers, could be minimized by using the developed method. Simulation values of the proposed method and a conventional method are compared.

Angle measurement system based on Risley prisms and normal tracing method

“…Since the system uses ordinary lenses for f-θ angle conversion, it can be seen from Fig. 8a that in the range, with the change of measurement distance, the measurement error of the TAC system reaches (PV) and has obvious rotational symmetry with respect to the origin (aberration error characteristic 12 ). This is consistent with the phenomenon described in literature 14, and the systematic error in Fig.…”

“…In order to eliminate the influence of many errors in the system and realize the simultaneous improvement of angle measurement range, accuracy and working distance, based on Risley prisms(RPs) and normal tracing method [12][13][14] , we propose the Normal Tracing -Risley prisms (NTRP) 14 angle measurement system. The core of NTRP system to eliminate the systematic error is the "normal tracing method".…”

X-ray optics development and metrology at Shanghai synchrotron radiation facility

“…For example, the accuracy of mirror slope error has been pushed into tens of nano-radian 2 . Ex-situ metrology instruments such as the Nanometer Optical Measuring system (NOM) and the Long Trace Profiler (LTP) demonstrate high accuracy and have become indispensable tools for any metrology labs at synchrotron facilities 3,4 . They improved to reach an accuracy of a few nm PV.…”

Research on achromatic Risley prism in normal tracing angle measurement system

“…Due to the influence of aberrations, process defects, response consistency errors in various areas of the CCD, it is difficult to improve the measurement range and measurement accuracy at the same time. Our team introduced the Risley prisms (RPs) into the traditional autocollimator system and used the normal tracing method 3 , 5 to measure the angle with a large range and high precision. In the measurement of the new system, by rotating the RPs, the measurement beam direction can be precisely adjusted 6 – 9 and the measuring beam can be reflected near the normal direction of the tested mirror to realize the paraxial propagation of the measuring beam.…”