Test system for optical disks

Details

Inventors: Mikuriya, Kenta; Ohya, Akira; Nakagawara, Minoru; Hirukawa, Hideo; Uehara, Shoji;
Assignee: Yokogawa Electric Corporation (Tokyo, JP)
Primary Examiner: McGraw; Vincent P.
Assistant Examiner: Turner; S. A.
Attorney, Agent or Firm: Kojima; Moonray

A test system for optical disks, comprising a spindle motor for clamping and rotating an optical disk at a constant speed; an encoder for generating a pulse output corresponding to the angle of rotation of the motor; a measuring head comprising focus and tracking servo mechanisms for causing the focal point of a laser beam irradiating the disk to follow the guide groove thereof, and a displacement detector for optically detecting the displacement of a focusing lens driven by the servo mechanisms; the measuring head being operative to generate an output signal proportional to the displacement of the focusing lens; a feed mechanism for moving the measuring head in the radial direction of the disk; a control circuit for controlling the operations of the motor, the servo mechanisms and the feed mechanism; an analog to digital converter for converting the output of the measuring head at a timing according to the pulse output of the encoder; and a computer for commanding the control circuit and for computing the output of the analog to digital converter to determine the shape of the disk, whereby displacement of the focusing lens is directly detected by the displacement detector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG.
2, the components which are similar to those of FIG.
1 bear the same reference numerals.
The system comprises an encoder 21 for generating a pulse output according to the angle of rotation of spindle motor 2; and a measuring head 3 comprising focusing lens 31, a laser beam source 32, a lens actuator 33, a beam splitter 34, a quarter wave (.
lambda.
/4) plate 35, a light receiving element 36 and a displacement detector 37.
In measuring head 3, the focal state on disk 1 is detected by element 36 to generate feedback signals for the focusing and tracking servo mechanisms.
The displacement of focusing lens 31 is detected by detector 37 to generate an output signal proportional to the displacement of focusing lens 31.
Detector 37 is of the optical type for converting the displacement of focusing lens 31 into changes in the amount of light.
The system further comprises a controller 5 for driving lens actuator 33, in accordance with the output of light receiving element 36, to operate the focus servo mechanism and the tracking servo mechanism and controls the operations of spindle motor 2 and feed mechanism 4, an analog to digital converter 6 (also referred to as "A/D converter") for analog to digital converting the output signal from measuring head 3 at a timing according to the pulse output of encoder 21; and a computer 7 for commanding controller 5 and for computing the output of A/D converter 6 to determine the shape of disk 1.
The operation sequence of the individual portions are selected in response to the commands of computer 7, and a variety of mechanical characteristics of disk 1, such as the axial runout or concentricity, are measured on the basis of these displacements.
In FIG.
3, the parts similar to those in FIG.
2 bear the same numerals.
The displacement detector of FIG.
3 comprises a shielding plate 371 having a rectangular aperture 372 and fixed on focusing lens 31; a light source 373 for irradiating shielding plate 371 with a parallel beam having a spot diameter larger than the moving range of aperture 372; and a multi-divided sensor 374 made receptive of a beam spot 375 having passed through aperture 372 of plate 371 for locating the position thereof

Related patents

0.044
Archive: All patents - Links Copyright (c)2006 Eipa-patents.org - All rights reserved