Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1998-06-25
2000-09-12
Le, Que T.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356305, H01J 314
Patent
active
061181196
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to spectral analysis of electromagnetic radiation and, in particular, devices for simultaneously determining the direction and wavelength of an incident monochromatic light beam.
It is known to use dispersive techniques for analyzing electromagnetic radiation. In the context of modern weapons systems, the use of lasers has become widespread. The need to warn vehicle operators and the like of the presence and origin of incident laser radiation has lead to the development of various devices intended to use dispersive techniques to identify incident laser radiation.
U.S. Pat. No. 4,682,888 to Welner discloses a spectral analyzer and direction indicator. The device uses a non-diffracted beam and two detector arrays to determine the direction of incidence of the radiation, and two reflection gratings with a further three detector arrays to provide information for spectral analysis.
U.S. Pat. No. 4,674,871 to Shifrin discloses a spectral analyzer and direction indicator. The device uses two reflection gratings arranged at 90.degree., each having a lens with a detector array at the focal plane. In order to provide full directional information, a double apparatus with four gratings with their associated optical systems and detector arrays is required. The field of view (FOV) of the device appears to be about 30.degree. wide.
U.S. Pat. No. 5,043,726 to Shifrin discloses a spectral analyzer and direction indicator. The device uses two orthogonally mounted optical channels each having a reflector partially ruled with a diffraction grating. Each channel is provided with an optical system having a detector array at its focal plane. The FOV of the device is about 10.degree.-20.degree. wide.
All of the devices disclosed in these patents share a number of shortcomings. Firstly, each of the devices includes a large number of optical elements which must be maintained in precise geometrical and angular alignment to ensure correct operation. This makes them expensive to produce, oversized, and susceptible to inaccuracies and malfunctioning due to misalignments. Secondly, the design of each of the devices imposes severe geometrical limits on its operative field of view.
There is therefore a need for a spectral analyzer and direction indicator for simultaneously determining the direction and wavelength of an incident light beam which is structurally simple, compact and inexpensive, and which has a wide operational field of view.
SUMMARY OF THE INVENTION
The present invention is of devices for simultaneously determining the direction and wavelength of an incident light beam.
According to the teachings of the present invention there is provided, a device for simultaneously determining the direction and wavelength of an incident light beam, the device comprising: (a) a transparent block having a first face and a second face; (b) a diffraction grating associated with the first face for diffracting the incident light beam to produce a plurality of diffracted beams within the transparent block; (c) a detector array associated with the second face, the detector array generating an output indicative of positions of intersection of the diffracted beams with the second face; and (d) a processor for processing the output to determine the direction and wavelength of the incident light beam.
According to a further feature of the present invention, the transparent block is cuboid, the first face being opposite to the second face.
According to a further feature of the present invention, the detector array is a two-dimensional array, the output being indicative of the positions measured in two-dimensions.
According to a further feature of the present invention, in the case of a two-dimensional array, the diffraction grating includes lines ruled in two directions.
In another form of the present invention, the transparent block has a first dimension parallel to lines of the diffraction grating and a second dimension perpendicular to the lines and parallel to the second face,
REFERENCES:
patent: 4674871 (1987-06-01), Shifrin
patent: 4682888 (1987-07-01), Welner
patent: 4971442 (1990-11-01), Okutani et al.
patent: 5043726 (1991-08-01), Shifrin
Friedman Mark M.
Le Que T.
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