Focus and tracking detection apparatus for optical head employin

Details Focus and tracking detection apparatus for optical head employin Focus and tracking detection apparatus for optical head employin

1986-11-26

1988-11-08

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

369 45, G11B 509, 250, 250, 250, 250

Patent

active

047835893

ABSTRACT:
In an optical head, a laser beam L emitted from a semiconductor laser is collimated by a collimator lens and is incident on a beam splitter. The laser beam passing through the beam splitter is and a quarter wave plate converged by an objective lens onto an optical disk and reflected by the optical disk. The reflected laser beam passing through the objective lens and the quarter wave plate is returned to the beam splitter and is reflected from a polarizing surface of the splitter. The reflected laser beam is guided to a beam emerging surface of the prism, the surface being defined by a flat surface and a semicylindrical concave surface. The laser beam is separated at the surfaces and converged by a projection lens onto a photodetector.

REFERENCES:
patent: 4079248 (1978-03-01), Lehureau et al.
patent: 4612437 (1986-09-01), Ohsato
patent: 4654519 (1987-03-01), Ando
patent: 4687917 (1987-08-01), Kusaka et al.

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