Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1988-08-12
1990-03-06
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356369, G02F 101
Patent
active
049068440
ABSTRACT:
The thickness of growing thin film layer is monitored by directing a beam of circularly polarized monochromatic monitoring light into the layer and detecting the portion of the monitoring light reflected from the layer. The difference in phase between the s and p polarized components of the reflected light is measured and those thicknesses of the layer at which the difference in phase between the s and p components is zero are related to thicknesses which are an integral multiple of one fourth of the wavelength of the monitoring light in the layer. An apparatus for monitoring the thickness of a growing layer during the fabrication of an optical thin film includes a source of light for directing a beam of light at the growing layer and a polarizer between the source and the layer for converting the light beam to a linearly polarized beam. A quarterwave plate between the polarizer and the layer converts the linearly polarized beam to a circularly polarized beam, while a polarizing beam splitter receives the portion of the beam reflected from the layer and divides the portion into a +45.degree. polarized component and a -45.degree. polarized component. A first detector detects the intensity of the +45.degree. polarized component and a second detector detects the intensity of the -45.degree. polarized component.
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Deinken John J.
Hamann H. Frederick
Nelms David C.
Rockwell International Corporation
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