Abstract Refractive elements typically have ground glass edges in areas where the perly-transmitted laser beam does not impinge. Defects on either incident optical surface or the exit optical will produce wide-angle scattering. Some of this scattered radiation will impinge directly upon the ground glass; other scattered radiation will reach it after one or more internal reflections in the optical element: An optical fiber abutted to an edge transfers scattered light to a detector. If a threshold is exceeded, a visual or auditory signal may be generated to alert the operator and/or an interlock may be activated to disable the laser. One photodetector is used to detect returns from several elements. Fibers of different lengths are used to couple the different components into the detector. In this way, a pulsed laser with a pulse length short compared with the delay difference between fibers may be used to identify the individual element which contains the defect. The time taken between the laser pulse and a threshold exceedence can be used to identify the optical element which is the source of the stray light scattering. The surface of other optical elements, such as front-surfaced mirrors and stops, may also be monitored by locating the fiber off the main beam path at a point where stray light from the surface will be coupled into its numerical aperture.
A system for detecting degradation of an optical element comprising an optical detector for detecting optical emission in an area of said optical element where optical emissions are normally not present except under conditions of degradation of the optical element, and first coupling means coupling optical emissions from said area to said optical detector.
Claim 2
Independent Claim
54 words
A system for detecting degradation of an optical element comprising an optical detector for detecting optical emission in an area of said optical element where optical emissions are normally not present except under conditions of degradation of the optical element, and first coupling means coupling optical emissions from said area to said optical detector.
Claim 3
Dependent Claim
34 words
A system as set forth in claim 1 wherein said optical element has ground edges and said first coupling means couples the emission from at least one of the edges to said optical detector.
Claim 4
Dependent Claim
29 words
A system as set forth in claim 2 wherein said first coupling means is a fiber optics device which has one end that abuts one of said ground edges.
Claim 5
Dependent Claim
43 words
A system as set forth in claim 1 wherein a plurality of optical elements are present each having an area normally not emitting optical signals, and a plurality of coupling means coupling optical emissions from each of these areas to said optical detector.
Claim 6
Dependent Claim
78 words
A system as set forth in claim 4 wherein said plurality of coupling means are of different predetermined lengths such that upon the emission of a pulse of electromagnetic energy through the optical elements, the time the optical emissions from said areas are transmitted to said optical detector are each spaced apart a predetermined amount of time whereby a particular emission being received by said optical detector can be identified as to which optical element it originated from.
Claim 7
Dependent Claim
15 words
A system as set forth in claim 5 wherein said coupling means are fiber optics.