Write test method for use in recording process for recording information by modulating the power of a laser light thereby forming a high-temperature state and a low-temperature state on a recording medium

• US 5,815,477 A
• Filed: 01/30/1996
• Issued: 09/29/1998
• Est. Priority Date: 01/31/1995
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Miyashita, Akira, Shiratori, Tsutomu, Kimura, Shunpei, Ashinuma, Takaaki
• Primary Examiner(s): Young, W. R.
• Application Number:
  US08/594,300
• Time in Patent Office: 973 Days
• Field of Search: 369/50, 369/54, 369/116
• US Class Current: 369/47.53
• CPC Class Codes: G11B 11/1053 to compensate for the magnetic domain drift or time shift
• CPC Class Codes: G11B 11/10595 Control of operating function
• CPC Class Codes: G11B 7/0045 Recording G11B7/006, G11B7/0065 take precedence
• CPC Class Codes: G11B 7/126 Circuits, methods or arrangements for laser control or stabilisation

Abstract

A write test method for use in a recording process for recording information is effected by such that the power of a laser light is modulated to form a high-temperature state and a low-temperature state on a recording medium. First, a predetermined signal is recorded on the recording medium while varying the power level of the laser light. The information recorded on the recording medium is reproduced to detect the power level of the laser light, immediately before formation of the high-temperature state, based on the amplitude of a reproduced signal. The power levels of the laser light for forming the low-temperature state and for forming the high-temperature state are determined on the basis of the detected power level.

Claims

1. A write test method for use in a recording process for recording information by modulating the power of a laser light thereby forming a high-temperature state and a low-temperature state on a recording medium, comprising:

a step of recording a predetermined signal on the medium;

a first step of reproducing the recorded information;

steps of repeating the recording step with a variation in the power level of the laser light and repeating said first reproducing step;

a step of detecting the power level of the laser light which occurs immediately before the formation of the high-temperature state, based on amplitudes of reproduced signals obtained in said first reproducing step; and

a step of determining the power level of the laser light for forming the low-temperature state and the power level of the laser light for forming the high-temperature state, based on the detected power level,

wherein said determining step includes;

a step of recording record marks of different sizes on the medium, with a variation of the power level of the laser light, taking the detected power level as a reference;

a second step of reproducing the recorded information; and

a step of detecting middle values of the peak and bottom values of the reproduced signals, obtained in said second reproducing step and corresponding to the record marks, and detecting the difference between the middle values,

wherein the power level of said laser light for forming the high-temperature state is determined according to said difference.

2. A write test method according to claim 1, wherein the power level of the laser light for forming said low-temperature state is determined by multiplying said detected power level with a predetermined coefficient.

3. A method according to claim 1, wherein said recording step performs an optical modulation overwriting process, and when a power level of the laser light for formation of the low-temperature state is PL and power levels of the laser light for formation of the high-temperature state are PH1 and PH2, in order to set the power levels PL, PH1, and PH2 of the laser light, wherein said determining step further includes the steps of:

determining the recording power level PL by multiplying the detected power level by a predetermined constant;

obtaining a ratio of the recording power level PH1 and the recording power level PH2; and

recording recording marks having different lengths with a variation of the recording power levels PH1 and PH2 while keeping the ratio constant, and reproducing the respective recording marks, detecting a middle value between a peak value and a bottom value of the reproduction signals corresponding to each of the recording marks, detecting a difference between the middle values, and determining the recording power levels PH1 and PH2 at which the difference becomes substantially zero.

4. A method according to claim 3, wherein said step for obtaining the ratio of said recording power levels PH1 and PH2 includes the steps of:

recording recording marks having different lengths with a variation of the recording power level PH1 while fixing the recording power level PH2, reproducing the respective recording marks, detecting a middle value between a peak value and a bottom value of the reproduction signals corresponding to each of the recording marks, detecting a difference between the middle values, determining the recording power level PH1 at which the difference becomes substantially zero, and storing the recording power level PH1;

recording recording marks having different lengths with a variation of the recording power level PH2 while fixing the power level PH1 to the stored value, reproducing the respective recording marks, detecting a middle value between a peak value and a bottom value of the reproduction signals corresponding to each of the recording marks, detecting a difference between the middle values, and determining the recording power level PH2 at which the difference becomes substantially zero; and

calculating the ratio of the recording power level PH1 and the recording power level PH2 on the basis of the stored recording power level PH1 and the determined recording power level PH2.

5. A method according to claim 3, wherein said step for obtaining the ratio of said recording power levels PH1 and PH2 includes the steps of:

recording recording marks having different lengths with a variation of the recording power level PH1 while fixing the recording power level PH2, reproducing the respective recording marks, detecting a middle value between a peak value and a bottom value of the reproduction signals corresponding to each of the recording marks, detecting a difference between the middle values, determining the recording power level PH1 at which the difference becomes substantially zero, and storing the recording power level PH1;

recording recording marks having different lengths with a variation of the recording power levels PH1 and PH2 while taking the determined recording power level PH1 as a reference and keeping the ratio of the recording power level PH1 and PH2 constant, reproducing the respective recording marks, detecting an amplitude value of the reproduction signal corresponding to each of the recording marks, and detecting a difference between the amplitude values, and determining the recording power level PH2 at which the difference first occurs; and

calculating the ratio of the recording power levels PH1 and PH2 on the basis of the stored recording power level PH1 and the determined recording power level PH2.

6. A method according to claim 1, wherein said determining step is performed at plural positions on the recording medium.