Optical: systems and elements – Diffraction – From grating
Patent
1992-09-08
1995-07-18
Ben, Loha
Optical: systems and elements
Diffraction
From grating
359569, 359573, 359576, 359571, 369112, G02B 518, G02B 2744, G11B 700
Patent
active
054347084
ABSTRACT:
Optical reproducing apparatus utilizes a dual diffraction grating having first and second diffraction gratings with the diffraction gratings oriented at an angle with respect to one another to polarize an incident return beam into TM and TE components. TM and TE components emerge from the dual diffraction grating at a slight angle with respect to one another and are focused on a photodetector chip by an objective lens. In accordance with a first specific embodiment of the apparatus, the TM and TE polarized components are focused directly on a photoelectric chip, with the TE component focused on a spot size focus detector comprised of three rectangular photoelectric elements. One photoelectric element is disposed between the other two with a pair of parallel interfaces. Disturbances introduced into the TE beam are in the direction of the parallel interfaces, rendering the spot size focus detector wavelength-insensitive. In a second embodiment of the invention, the TE and TM beams are split into four sub-beams by a quad prism prior to impinging on a photodetector chip.
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Gupta Mool C.
Kay David B.
Ben Loha
Collins Darryl J.
Eastman Kodak Company
Owens Raymond L.
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