Optical head in a recording and reading device for a data carrier
AssigneeThomson-CSF
InventorsDominique Leterme, Jean-Pierre Le Merer
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Abstract
The optical head in a data carrier recording-reading device comprises a semiconductor laser source. A lens makes it possible to focus the beam from this source. A polarization beam splitter makes it possible to deflect the beam reflected by this carrier towards a group of photodetectors. According to the invention the splitter is an isosceles prism, which serves as an anamorphotic-splitting means. A quarter-wave plate is bonded to one of the faces of the prism. A planoconvex lens can also be bonded to the other face of the prism upstream of the photodetector.
Claims21
A device for optically sensing data at a reference surface of a data carrier, said device comprising:
- a semi-conductor laser source emitting rectilinearly polarized optical energy;
- collimator means for gathering said optical energy and forming therefrom a bundle of parallel rays of predetermined cross section;
- polarization beam splitter means having a polarization splitting planar face receiving said bundle of parallel rays at oblique incidence from an external medium of low refractive index to which said polarization splitting planar face is exposed, whereby the portion of said bundle of parallel rays selectively transmitted by said planar face travels in a contiguous material of high refractive index for modifying the shape of said cross section;
- photodetector means arranged downstream of said planar face;
- optical means for causing said transmitted bundle of parallel rays to locally interact in said reference surface and for collecting from the area of interaction optical energy of crossed polarization, which being selectively reflected by said planar face is fed to said photodetector means for sensing said data.
Dependencies are inferred from the claim text.