Optics: measuring and testing – Lamp beam direction or pattern
Patent
1990-04-26
1992-01-07
Rosenberger, Richard A.
Optics: measuring and testing
Lamp beam direction or pattern
G01J 100
Patent
active
050784919
ABSTRACT:
A method and apparatus for determining the quality of a multimode laser beam (10). In the preferred embodiment, the apparatus includes a lens (32) for creating a transformed or imaged waist from the input beam. The location of the transformed beam waist and its diameter are then determined. These steps can be carried out by chopping the beam using a rotating hub (34) having apertures (36,38) for selectively passing the beam. Preferably, one of the apertures has a pair of 45.degree. knife edges (40,42). The transmission of the beam past the knife edge is monitored by a detector (30). In operation, the lens focal position is varied while the transmission of the beam past the knife edge is monitored in order to locate and measure the diameter of the transformed waist. The diameter of the beam at one other known location is measured. A processor then calculates beam quality by fitting these measurements to a mathematical model. Once the quality of the beam is calculated, the location of the original beam waist and its diameter can be derived. Once all of the beam parameters are derived, the propagation characteristics of the beam can be predicted. In one embodiment of the subject invention, the device includes a blocking member (602) having a knife edge (604) disposed perpendicularly to one of the knife edges of the apertures carried on the hub. The blocking member is translated in discrete steps for each revolution of the hub. The measurement of the power transmitted past the knife edge and blocking member can be used to generate a two-dimensional pixel map of beam intensity.
REFERENCES:
patent: 4828384 (1989-05-01), Plankenhorn et al.
Fleischer et al., "Gaussian Beam Profiling: How and Why", Lasers & Optronics (May 1987) pp. 61-64.
Coherent Inc.
Rosenberger Richard A.
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