A new in situ method for testing the optical thickness of removed transparent elements

Abstract

ABSTRACT A new remote method for a fast inspection of optical thickness oftransparent elements is developed. The methodis based on use of an high order interference of white light reflected from sample's sides. Method gives apossibility for in situ measuring optical thickness of sample with accuracy to 0.5 nm on aperture beforeI 00 mm and distance as far as some meters. Keywords: optics, interferometry, optical thickness, removed control, in situ measurements 1. INTRODUCTION A development ofnon-contact precise methods for estimating optical elements parameters was connected withgrowing needs both of precise optical measurements and high-performance optics providing this experiments. Aproblem for checking optical elements is satisfactory solved when a sample is studied directly on workingtable ofthe testing device. However there are reasons to develop methods for remote checking. First of all to perform a number of fundamental tasks it is not enough to know preliminary characteristics of optical scheme. When precisemeasurements are running optical element parameters of scheme can be changed in consequence of differentfactors: temperature, pressure, radiation influence. In this case continuous checking of optical parameters isnecessary without withdrawal elements from scheme. The other reason is connected with technologies of aproduction ofthe high-precision optical elements. To achieve required accuracy testing ofthe optic elements hasto carry out in real time and in situ i.e. on the technological table.In present paper we describe a novel remote method and set-up for inspection of optical thickness ofoptical elements, removed from testing device.