Optical pick-up apparatus capable of reading data irrespective of disc type

• US 6,026,065 A
• Filed: 12/04/1995
• Issued: 02/15/2000
• Est. Priority Date: 03/04/1995
• Status: Expired due to Term

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Song, In-Sang, Kim, Jin-Yong, Park, Song-Chan, Kim, Dae-Young, Lee, Man-Hyung
• Primary Examiner(s): Tran, Thang V.
• Application Number:
  US08/567,041
• Time in Patent Office: 1,534 Days
• Field of Search: 369/94, 369/93, 369/118, 369/112, 369/44.23, 369/58, 369/190, 369/44.25, 369/53, 369/110, 369/50, 369/54
• US Class Current: 369/44.27
• CPC Class Codes: G11B 19/12 by sensing distinguishing features of or on records, e.g. diameter end mark
• CPC Class Codes: G11B 2007/0006 adapted for scanning different types of carrier, e.g. CD & DVD
• CPC Class Codes: G11B 7/0037 with discs
• CPC Class Codes: G11B 7/0933 Details of stationary parts
• CPC Class Codes: G11B 7/0935 Details of the moving parts
• CPC Class Codes: G11B 7/094 Methods and circuits for servo offset compensation
• CPC Class Codes: G11B 7/0945 Methods for initialising servos, start-up sequences
• CPC Class Codes: G11B 7/123 Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
• CPC Class Codes: G11B 7/1369 Active plates, e.g. liquid crystal panels or electrostrictive elements
• CPC Class Codes: G11B 7/139 Numerical aperture control means
• CPC Class Codes: G11B 7/22 Apparatus or processes for the manufacture of optical heads, e.g. assembly

Abstract

An improved optical pick-up apparatus capable of reading data irrespective of disc type capable of reading various kinds of discs having different thicknesses and writing densities using only one pick-up apparatus, which includes a light source; a beam splitter for passing through or splitting a beam from the light source; an objective lens for condensing the beam onto corresponding disc among discs having different thicknesses and different densities; a numerical aperture control unit for controlling an effective numerical aperture of the objective lens so as to execute a focussing operation with respect to a certain disc; and a photodetector for receiving the beam reflected by the disc and transmitted from the beam splitter.

Claims

1. An optical disc data pick-up apparatus for reading data from an optical disc, comprising:

a light source constructed and arranged to emit a beam of light;

an objective lens for condensing said beam onto the optical disc;

numerical aperture control means for controlling an effective numerical aperture value of said objective lens by controlling a size of said beam reaching said objective lens, so as to execute a focusing operation with respect to the optical disc;

a photo-detector constructed and arranged to receive light corresponding to said beam reflected by the optical disc, and to generate a first signal in response to said reflected light;

a beam splitter constructed and arranged to transmit said beam from said light source towards said objective lens, and to reflect said reflected light towards said photo-detector; and

a tracking control unit;

a focus control unit;

reproducing signal processing means for generating and transmitting a second signal to said tracking control unit and said focus control unit corresponding to said first signal outputted from said photo-detector;

disc identifying means for identifying an optical disc having a particular thickness and generating a corresponding third signal, based on said second signal from said reproducing signal processing means;

a numerical aperture control means driving apparatus for driving said numerical aperture control means according to a thickness of the optical disc identified by said disc identifying means;

a spindle motor;

a motor control unit for controlling said spindle motor in accordance with the identified optical disc;

a digital signal processing unit connected to said reproducing signal processing means and to said motor control unit; and

a microcomputer constructed and arranged to selectively control at least one of said numerical aperture control means driving apparatus, said focus control unit, said tracking control unit, and said motor control unit in accordance with said third signal from said disc identifying means.

2. The apparatus of claim 1, wherein said reproducing signal processing means includes:

an RF signal computation unit for processing said first signal output by said photo-detector,

a tracking error computation unit, and

a focus error computation unit.

3. The apparatus of claim 1, wherein said tracking control unit connected to said reproducing signal processing means includes a voltage amplifier for amplifying a predetermined voltage in response to a tracking error signal output by said reproducing signal processing means, and a power voltage amplifier.

4. The apparatus of claim 1, wherein said focus control unit of said reproducing signal processing means includes a voltage amplifier for amplifying a voltage in response to a focus error signal output by said reproducing signal processing means, and a power voltage amplifier.

5. An optical disc data pick-up apparatus for reading data from an optical disc, comprising:

a light source constructed and arranged to emit a beam of light;

a collimating lens constructed and arranged to collimate said light beam so as to be parallel;

a diffraction grating arranged between said light source and said collimating lens;

an objective lens for condensing said light beam onto the optical disc;

numerical aperture control means for controlling an effective numerical aperture of said objective lens by controlling a size of said light beam reaching said objective lens;

a photo-detector assembly constructed and arranged to receive the light reflected by the optical disc corresponding to said light beam incident thereupon, and to generate a first signal in response to said light reflected by the optical disc;

a beam splitter constructed and arranged to transmit said beam from said light source towards said objective lens and to reflect said light reflected by the optical disc towards said photo-detector;

a tracking control unit;

a focusing control unit;

reproducing signal processing means for generating and transmitting a second signal to said tracking control unit and said focusing control unit, respectively, in response to said first signal from said photo-detector assembly;

disc identifying means for identifying an optical disc according to a thickness of the optical disc, and for generating a corresponding third signal, based on said second signal from said reproducing signal processing means;

a numerical aperture driving unit for driving said numerical aperture control means in response to said identification of the optical disc according its thickness by said disc identifying means;

a spindle motor;

a motor control apparatus for controlling said spindle motor in accordance said identification of the optical disc; and

a microcomputer constructed and arranged to selectively control at least one of said numerical aperture control driving unit, said focus control unit, said tracking control unit, and said motor control unit, in accordance with said third signal from said disc identifying means.

6. In an apparatus for reading data from an optical disc, the apparatus including:

a light source constructed and arranged to emit a beam of light;

an objective lens for condensing the beam onto an optical disc;

numerical aperture control means for controlling an effective numerical aperture value of the objective lens by controlling a size of the beam reaching the objective lens, so as to execute a focusing operation with respect to the optical disc;

a photo-detector constructed and arranged to receive light corresponding to the beam reflected by the optical disc and to generate a first signal in response to the reflected light;

a beam splitter constructed and arranged to transmit the beam from the light source towards the objective lens, and to reflect the reflected light towards the photo-detector;

a tracking control unit;

a focus control unit;

reproducing signal processing means for generating and transmitting a second signal to the tracking control unit and the focus control unit corresponding to the first signal received from the photo-detector;

disc identifying means for identifying an optical disc having a particular thickness and generating a corresponding third signal, based on the second signal from the reproducing signal processing means;

a numerical aperture control means driving apparatus for driving the numerical aperture control means according to a thickness of the optical disc identified by the disc identifying means;

a spindle motor;

a motor control unit for controlling the spindle motor in accordance with the identified optical disc;

a digital signal processing unit connected to the reproducing signal processing means and to the motor control unit; and

a microcomputer constructed and arranged to selectively control at least one of the numerical aperture control means driving apparatus, the focus control unit, the tracking control unit, and the motor control unit in accordance with the third signal from the disc identifying means;

a control method comprising the steps of;

an initialization step, including;

rotating the optical disc at a normal speed;

moving the actuator to the optical disc in accordance with a signal from the microcomputer to judge an optical disc type; and

decreasing the effective numerical aperture of the objective lens;

generating a characteristic signal if the optical disc is a first type optical disc, whereby the optical disc is distinguishable between the first type optical disc and a second type optical disc;

wherein for the first type optical disc, the method further comprises the steps of;

rotating the first type at a constant linear velocity;

applying feedback control for focus and tracking; and

reading data from the first type optical disc;

wherein for the second type optical disc, the method further comprises the steps of;

moving the actuator away from the second type optical disc;

increasing an effective numerical aperture of the objective lens;

moving the actuator back to the second type optical disc;

checking for generation of said characteristic signal;

generating an error signal if said checking step does not detect said characteristic signal;

rotating the second type optical disc at a constant linear velocity;

applying feedback control for focus and tracking; and

reading data from the second type optical disc.

7. In an apparatus for reading data from an optical disc, the apparatus including:

a light source constructed and arranged to emit a beam of light;

a collimating lens constructed and arranged to collimate the beam of the light;

a diffraction grating arranged between the light source and the collimating lens;

an objective lens for condensing the beam onto the optical disc;

numerical aperture control means for controlling an effective numerical aperture value of the objective lens by controlling a size of the beam reaching the objective lens, so as to execute a focusing operation with respect to the optical disc;

a photo-detector assembly constructed and arranged to receive light corresponding to the beam reflected by the optical disc and to generate a first signal in response to the reflected light;

a beam splitter constructed and arranged to transmit the beam from the light source towards the objective lens, and to reflect the reflected light towards the photo-detector;

a tracking control unit;

a focus control unit;

reproducing signal processing means for generating and transmitting a second signal to the tracking control unit and the focus control unit corresponding to the first signal received from the photo-detector;

disc identifying means for identifying an optical disc having a particular thickness and generating a corresponding third signal, based on the second signal from the reproducing signal processing means;

a numerical aperture control driving unit for driving the numerical aperture control means according to a thickness of the optical disc identified by the disc identifying means;

a spindle motor;

a motor control unit for controlling the spindle motor in accordance with the identified optical disc; and

a microcomputer constructed and arranged to selectively control at least one of the numerical aperture control driving unit, the focus control unit, the tracking control unit, and the motor control unit in accordance with the third signal from the disc identifying means;

a control method comprising the steps of;

an initialization step, including;

rotating the optical disc at a normal speed;

moving the actuator to the optical disc in accordance with a signal from the microcomputer to judge an optical disc type; and

decreasing the effective numerical aperture of the objective lens;

generating a characteristic signal if the optical disc is a first type optical disc, whereby the optical disc is distinguishable between the first type optical disc and a second type optical disc;

wherein for the first type optical disc, the method further comprises the steps of;

rotating the first type at a constant linear velocity;

applying feedback control for focus and tracking; and

reading data from the first type optical disc;

wherein for the second type optical disc, the method further comprises the steps of;

moving the actuator away from the second type optical disc;

increasing an effective numerical aperture of the objective lens;

moving the actuator back to the second type optical disc;

checking for generation of said characteristic signal;

generating an error signal if said checking step does not detect said characteristic signal;

rotating the second type optical disc at a constant linear velocity;

applying feedback control for focus and tracking; and

reading data from the second type optical disc.