Abstract In order to protect a delicate photo-detector from high-intensity optical radiation such as from a laser, a device for limiting power to the detector is interposed between the radiation and detector. This device has two embodiments and is made such that high-intensity radiation is totally reflected. In the absence of high-intensity radiation, total reflection is frustrated, and desired radiation passes to the detector. Both embodiments use two prisms with parallel surfaces skewed to incident radiation and with a slightly absorbant optical material between the surfaces. Desired radiation normally passes through the prisms and the material to the detector. In one embodiment, the material is a liquid which vaporizes in response to high-intensity radiation, and in the other embodiment, the material expands and pushes the prisms apart. In either case, transmission of radiation halts, and the radiation is totally reflected by a prism skewed surface.
A device for protecting a photo-detector for relatively low-power light radiation from high-intensity light radiation, wherein the device is positioned on an optical axis between said detector and incident radiation, and the device includes: a pair of optical prisms having a first pair of parallel sides normal to said optical axis, and a second pair of parallel sides adjacent to each other and skewed with respect to said optical axis; and an optical material between said second pair of sides responsive to the intensity of the radiation on said optical axis to cause diversion of said axis for high-intensity radiation.
Claim 2
Independent Claim
100 words
A device for protecting a photo-detector for relatively low-power light radiation from high-intensity light radiation, wherein the device is positioned on an optical axis between said detector and incident radiation, and the device includes: a pair of optical prisms having a first pair of parallel sides normal to said optical axis, and a second pair of parallel sides adjacent to each other and skewed with respect to said optical axis; and an optical material between said second pair of sides responsive to the intensity of the radiation on said optical axis to cause diversion of said axis for high-intensity radiation.
Claim 3
Dependent Claim
24 words
The device as set forth in claim 1 wherein the skewed sides of the prisms are at an angle greater than the critical angle.
Claim 4
Dependent Claim
18 words
The device as set forth in claim 2 wherein said material is partially absorbent to said incident radiation.
Claim 5
Dependent Claim
32 words
The device as set forth in claim 3 wherein the thickness of said material is normally less than the wavelength of said incident radiation such that evanescent coupling occurs between said prisms.
Claim 6
Dependent Claim
30 words
The device as set forth in claim 3 wherein said optical material has substantially the same index of refraction as said prisms and provides a transmission path between said prisms.
Claim 7
Dependent Claim
35 words
The device as set forth in claim 4 wherein said material is a gas which expands in response to high-intensity light radiation, whereby said evanescent coupling is defeated, and total reflection of said radiation occurs.
Claim 8
Dependent Claim
39 words
The device as set forth in claim 5 wherein said material is a liquid which vaporizes in the region of and responsive to high-intensity light radiation, whereby said transmission path is interrupted, and total reflection of said radiation occurs.