Speckle interference in space was monitored by using a newly developed transparent thin-film photodiode, which was fabricated by micromachining techniques. Since the sensitive region of the developed photodiode was thinner than one-half of the wavelength, an optical standing wave generated by the interference between two waves propagating in opposite directions was detected. This photodiode was used in a short-range displacement measurement in a speckle field. Using the sinusoidal phase modulation technique, object displacement was sensed with an accuracy of about 30 nm in a speckle granular structure.
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