Analog Compensation For Scanned Beam Intensity

R. L. Trantow

doi:10.1117/12.932548

26 April 1982 Analog Compensation For Scanned Beam Intensity

R. L. Trantow

Proceedings Volume 0299, Advances in Laser Scanning Technology; (1982) https://doi.org/10.1117/12.932548
Event: 25th Annual Technical Symposium, 1981, San Diego, United States

Abstract

An analog method was developed for compensating surface reflected light intensity data for predictable and unpredictable variations in incident beam intensity. The compensation is performed in real time by dividing the reflected light intensity by a reference beam intensity which is split from the incident beam. The compensated signal is then a function of surface reflectance which is insensitive to the spatially-dependent beam intensity modulations encountered with acousto-optic scanners, as well as to unexpected modulations introduced by laser instability, spatial filter vibration, and dust accumulations in the optical path. Analog circuitry, described as a "Reference Compensated Photodiode Amplifer," was developed to implement this compensation method in rapid beam scanning applications. The amplifier has a frequency response which is flat within + 0.5 db from dc to .5 MHz, and is capable of correcting the reflected light intensity data for variations in incident light intensity of over 30%. The compensation scheme and circuitry are presently employed in an optical surface flaw inspection system being developed at the Hanford Engineering Development Laboratory (HEDL).

Citation Download Citation

R. L. Trantow "Analog Compensation For Scanned Beam Intensity", Proc. SPIE 0299, Advances in Laser Scanning Technology, (26 April 1982); https://doi.org/10.1117/12.932548

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