Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1987-12-22
1989-04-11
McGraw, Vincent P.
Optics: measuring and testing
By particle light scattering
With photocell detection
G01B 902
Patent
active
048200476
ABSTRACT:
A detection system is provided which has a very wide linear dynamic range (for a typical laser, fifteen orders of magnitude), as well as a high sensitivity (shot noise limited), high angular resolution (diffraction limited), and which is also polarization resolving. The apparatus is used for measuring optical power, and includes a system for producing two optical beams such that at some point and thereafter along an optical path of the beams, a frequency difference exists between the two beams, with one of the two beams having a known or constant optical power, and the other of the two beams being the beam whose power is to be measured. Also included is a combining element for coherently combining the two optical beams. An optical detection system receives the combined two optical beams, and in response thereto provides an electrical signal that is modulated at the difference frequency of the optical fields of the two optical beams, the electrical signal being functionally related to the heterodyne product of the two fields. An electrical power detector is then used for measuring the electrical power of the electrical signal. Several embodiments are described which use the basic power measuring system to characterize optical filters, to measure optical density of photographic plates, to measure BRDF and BTDF, and to provide a well calibrated laser radiation source which is particularly well suited for very low power applications.
REFERENCES:
patent: 3857636 (1974-12-01), Angelbeck
McGraw Vincent P.
Smith Joseph H.
Turner S. A.
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