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Relative Position Error Sensor with Critical Angle Prism for Optical Drive

IP.com Disclosure Number: IPCOM000117910D
Original Publication Date: 1996-Jul-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Hirasaka, Y: AUTHOR [+2]

Abstract

Disclosed is a method for obtaining the relative error signal of a galvano mirror angle by using a differential signal created by the optical spots which are projected to the two detectors through an auto-collimator type package of detectors.

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This is the abbreviated version, containing approximately 100% of the total text.

Relative Position Error Sensor with Critical Angle Prism for Optical
Drive

      Disclosed is a method for obtaining the relative error signal
of a galvano mirror angle by using a differential signal created by
the optical spots which are projected to the two detectors through an
auto-collimator type package of detectors.

      The Figure shows an example of this apparatus.  The optical
beam (1) from the light source is reflected by a galvano mirror (2)
which is used for tracking to the data area on the optical disk (3).
Then the beam (1) is divided into two directions by the prism (4).
One beam (5) is bent to the objective lens (6) and is used for
reading the data signal or obtaining the focus and tracking error
signal.  The angle of the corner of this prism (4) is designed near
the critical angle (9).  Then another beam (13) goes though the prism
(4).  The beam angle is amplified by this prism (4).  The beam (13)
goes to the auto-collimator type detector (7).  By the
auto-collimator type package, the beam is focused on the detectors
(10,11).  The angle of  the galvano mirror is obtained by the
differential signal (12) from these detectors (10,11).

      The signal gain can be greater than that without the critical
angle prism system (9).