{'fraction_non_alphanumeric': 0.011976047904191617, 'fraction_numerical': 0.0011976047904191617, 'mean_word_length': 4.5364238410596025, '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}}
Accurate Measurement of Lens Thickness by Using White-Light Fringes

An interferometer for the measurement of thickness of a lens by the aid of white-light fringes to an accuracy of 1 µm was designed. The two end mirrors of the dispersion compensated Michelson interferometer were replaced by a lens L to be tested and a reference plane parallel plate R of the same kind of glass and of the same thickness. The interferometer was adjusted to give rise to the white-light Newton rings over the front surfaces of L and R, and then either of L or R was made to move until another white-light fringes appear at the rear surfaces. The translation relates directly to the thickness difference between L and R. Experimental results confirmed that the method is capable of being applied to the thickness measurement of precision single lenses.