{'fraction_non_alphanumeric': 0.014729950900163666, 'fraction_numerical': 0.004909983633387889, 'mean_word_length': 4.965853658536585, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Form measurement of small cylindrical objects using two-wavelength interferometry

Form measurements of cylindrical objects are commonly done by mechanical sensing of the rotated specimen by a stylus. The needed probing force could cause a deformation or an abrasion of the specimen. A new interferometric measurement technique for form measurements of cylindrical objects with diameters between 0.1 and 2.5 mm is presented. In this technique the specimen is measured contactless and no rotary table is needed. The specimen is placed in the centre of an inverse conic mirror and is illuminated by an iodine-stabilized diode laser. The reflected light is superposed under a slight angle with a reference beam and imaged on a CCD camera. The surface topography of the specimen can be derived from the reconstructed spatial phase distribution, which is calculated by a spatial phase shifting algorithm. In order to enhance the measurement range a second laser can be used to generate a synthetic wavelength. This will allow the quantification of surface variations in the micrometer range with an aimed uncertainty of less than 0.1 &mgr;m. First results on phase measurements of different samples are presented and discussed.