Method for Improving the Playability of Non-Ideal Optical Carriers

• US 20080259769A1
• Filed: 08/30/2006
• Published: 10/23/2008
• Est. Priority Date: 09/09/2005
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Zhou, Yu, Tan, Kia Suan
• Application Number:
  US12/065,627
• Publication Number:
  US 20080259769A1
• Time in Patent Office: Days
• US Class Current: 369/112.22
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/10027 adjusting the signal strength during recording or reproduction, e.g. variable gain amplifiers optimum power control for optical discs G11B7/125
• CPC Class Codes: G11B 20/10046 filtering or equalising, e.g. setting the tap weights of an FIR filter
• CPC Class Codes: G11B 20/10481 optimisation methods

Abstract

The present invention relates to a method for improving the playability of non-ideal optical disks. Initially, an asymmetry (AsI) of the optical carrier is determined. If the asymmetry is above a pre-defined first threshold then a step of decreasing an upper cut-off frequency (HPF) to a first cut-off frequency (HPF1) of a high pass filtering (BPF) performed on a data channel (HF) in response to the asymmetry (AsI) is undertaken. Subsequently, a step of optimizing an amplification level of a radial error signal (RE) and/or a focus error signal (FE) of a servomechanism controlling the optical carrier is undertaken. Finally, a last step of determining a second indication of asymmetry (As2) of the data channel (HF) from the optical carrier is performed. The invention is advantageous because a better indication of the asymmetry is provided because the asymmetry is assessed two consecutive times interrupted by a high pass filter adjustment.

Claims

1. A method for improving the playability of information from a non-ideal optical carrier (1) during readout of information from the optical carrier, the method comprising the steps of:

a. determining a first indication of asymmetry (As1) of a data channel (HF) of the information from the optical carrier,

if said first indication of asymmetry is above a pre-defined first threshold then

b. decreasing an upper cut-off frequency (HPF) to a first cut-off frequency (HPF1) of a high pass filtering (BPF) performed on the data channel (HF) of the information on the carrier in response to said first indication of asymmetry (As1),

c. optimizing an amplification level of a radial error signal (RE) and/or a focus error signal (FE) of a servomechanism controlling the optical carrier, and

d. determining a second indication of asymmetry (As2) of the data channel (HF) from the optical carrier.

2. A method according to claim 1 comprising the step of e1) further decreasing the cut-off frequency to a second cut-off frequency (HPF2) of the high pass filtering performed on the data channel (HF) of the information on the carrier if said second indication of asymmetry (As2) is above a pre-defined second threshold.

3. A method according to claim 1 further comprising the step of e2) increasing a lower cut-off frequency (LPF1) of a low pass filtering performed on the data channel (HF) of the information on the carrier if said second indication of asymmetry (As2) is above a pre-defined second threshold.

4. A method according to claim 2, wherein the second cut-off frequency (HPF2) and/or the lower cut-off frequency (LPF1) is/are adjusted as a result of an optimization procedure for the asymmetry (As2).

5. A method according to claim 1 further comprising the steps of f) determining a third indication of asymmetry (As3) of the data channel (HF) from the optical carrier, and then g) applying an equalizer for amplifying a data channel portion comprising a relatively low integer of channel bits (3T) in a channel code (EFM+) of the data channel (HF) in response to said third indication of asymmetry (As3).

6. A method according to claim 5 further comprising the step h) of performing an optimization of the data channel jitter by variation of one or more adjustable parameters of the equalizer (a,b).

7. A method according to claim 5, wherein the said data channel portion comprises the lowest integer number of channel bits (3T) in the channel code (EFM+) of the data channel (HF).

8. A method according to claim 1, wherein the step c) of optimizing an amplification level of a radial error signal (RE) and/or a focus error signal (FE) of a servomechanism controlling the optical carrier is performed by application of automatic gain control (ATC).

9. A method according to claim 1, wherein one or more of the steps a, b, c, and d are repeated a plurality of times.

11. A computer program product being adapted to enable a computer system comprising at least one computer having data storage means associated therewith to improve the playability of information from a non-ideal optical carrier (1) during readout of information according to claim 1.

10. An optical drive for recording/reproducing information from a non-ideal optical carrier (1), said optical drive being adapted to improve the playability during readout of information from the optical carrier, the optical drive comprising:

a. measurement means (As?) adapted for determining a second indication of asymmetry (As2) of the data channel (HF) from the optical carrier. determining a first indication of asymmetry (As1) of a data channel (HF) of the information from the optical carrier,

b. high pass filtering (BPF) means for decreasing an upper cut-off frequency (HPF) to a first cut-off frequency (HPF1) of the data channel (HF) of the information on the carrier in response to said first indication of asymmetry (As1) if said first indication of asymmetry is above a pre-defined first threshold, and

c. amplification means (AGC) for optimizing an amplification level of a radial error signal (RE) and/or a focus error signal (FE) of a servomechanism controlling the optical carrier, and

d. measurement means (As?) adapted for determining a second indication of asymmetry (As2) of the data channel (HF) from the optical carrier.