JPH01220162A - optical disc device - Google Patents

Abstract

PURPOSE:To radiate laser power over a whole track and to completely erase information by enlarging the spot diameter of an optical head at the time of erasing to be larger than the spot diameter at the time of recording and reproducing. CONSTITUTION:A reflected light from an optical disk is received by optical detectors 14 and 14 and focus dislocation between an optical spot and the optical disk is detected by a subtracting amplifier 17. Then, a signal 31 is obtained to correct dislocation quantity. The signal 31 is inputted through a phase compensating circuit 18 to a direct current off-set circuit 19. The circuit 19 inputs a signal which gives an off-set at the time of the erasing to an automatic focus coil driving circuit 20 and an automatic focus coil 21 is driven. Then, the spot diameter is enlarged.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a rewritable optical disc device, and particularly to a method for recording and erasing information suitable for reproducing information recorded on a recording medium with high reliability. .

[Conventional technology]

The method of reproducing, recording, and erasing information in conventional devices is to position the optical spot at the center of the track using a tracking servo system and reproduce information, and when recording information, the reproducing power is approximately 7.
Recording was performed by emitting pulsed laser power ~8 times as much. Furthermore, during erasing, the information recording area was erased in a DC manner using the same power as during recording. A related device of this type is JP-A-61-190741.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into consideration the possibility of unerased areas when the optical spot is recorded with a deviation from the center of the track.
There was a problem with media compatibility.

That is, if information is recorded with the light spot positioned offset from the track center, the recorded information (domain) will be formed offset from the track center as shown in FIG. If this recording medium is erased using another device in which the entire spot is centered on the track, unerased areas will be generated on both sides of the track (one side in this example) as shown in Figure 6, and noise will be generated when information is recorded next time. This results in a reduction in the S/N of the reproduction system.

An object of the present invention is to completely erase all information even if the optical spot is recorded with a deviation from the center of the track (and to improve reliability during reproduction).

[Means to resolve the issue]

The above object is achieved by making the spot width of the optical head larger during erasing than during recording and reproducing, so that the entire track can be irradiated with laser power and information can be completely erased.

[Effect]

A larger optical focus can be achieved by applying a DC offset to the automatic focus control system during erasing and defocusing it from when recording or reproducing. As a result, the irradiation energy of the laser power decreases, but by adding a function to increase the laser power during erasing, the irradiation energy is equal to or higher than that during recording, and information can be completely erased, which prevents malfunctions. Never.

〔Example〕

Below is an example of the present invention! 1-(8) will be explained.

FIG. 1 shows a functional block diagram of the automatic focus control system.

A photodetector 14.15 that receives reflected light from the optical disk detects a total of 17 focal deviations between the optical spot and the optical disk using a subtraction amplifier, and a signal 51 corrects the deviation itt.
get. This signal passes through the entire phase compensation circuit 18 for the optical head and reaches the 1α flow offset circuit 19. The DC offset circuit is added according to the present invention, and does not operate during recording/reproducing, but provides a DC offset during erasing, and can be specifically configured as a circuit as shown in FIG. This circuit defocuses the light spot during erasing to widen the spot diameter and eliminate unerased areas during erasing. The output signal 32 of the DC offset circuit passes through the autofocus coil drive circuit 20 and drives the autofocus coil 21 .

Furthermore, a power-up circuit 50 during erasing as shown in FIG. 2 is added as a supplementary circuit for the irradiation energy of the semiconductor laser which has decreased due to defocusing.

FIG. 2 shows a functional block diagram of the automatic power control system. A photodetector 22 that monitors the power output of the semiconductor laser, a power error detection circuit 24, an analog switch 25, and a sample hold circuit that records the laser power during playback to open the automatic power control system 23 during recording. 2
6. Consists of a semiconductor laser drive circuit 27 and a semiconductor laser 28.

It also includes a circuit 29 for obtaining power to be superimposed on the reproducing power during writing, and a circuit 30 for increasing the laser power during erasing, which is added according to the present invention.

The circuit 50 can be easily constructed by turning a constant current circuit on and off during erasing and other times, as shown in FIG.

〔Effect of the invention〕

According to the present invention, even when information is recorded with the optical spot of the optical head being shifted, the spot length is expanded during erasing compared to during recording/reproducing to eliminate any unerased information. Reliability can be improved.

[Brief explanation of the drawing]

1st. FIG. 2 is a block diagram showing one embodiment of the present invention; Figure 4 is the same circuit diagram, Figure 5 is a diagram of the state of domain formation when the optical head spot is recorded with an offset from the track center, and Figure 6 is an optical spot of a medium where the optical head spot is recorded with an offset from the track center. FIG. 4 is an explanatory diagram showing the unerased area when erased when is located at the center of the track. DESCRIPTION OF SYMBOLS 1... Optical disc, 2... Guide groove, 3... Track, 4... Light spot when located at the center of the track, 5...
Objective lens, 6...Zj information, 7...10' information, 8...Track center line, 9...Unerased area, 10...Spot when expanding the light spot) 71. 1
1...Objective lens at defocus, 14.15...
・Automatic focus detector, 16...Automatic focus control system, 17...Subtraction amplifier, 18...Phase compensation circuit, 19...DC offset circuit, 20...AP coil drive circuit, 21... - Auto focus drive coil, 22... Monitor, 25... Automatic power control system, 24... Power error detection circuit, 25... Analog switch, 26... Sample hold circuit, 27... Semiconductor laser drive circuit, 28... semiconductor laser. Figure 1 L4. l5--Nine moxibustion pottery Z2--1,000 conductors 1 inch thick 16--- Vigilante Shi\'7-7! °Isa (1,4-123-, own FJ,!, beggar jiiηp,
<・, zl--1 vigilante r) $, 4. Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] 1. In a rewritable optical disk device using magneto-optical recording, a means for obtaining a higher output semiconductor laser power when erasing information than when recording information, and a means for applying a DC offset to an automatic focus control system when erasing information. An optical disc device comprising: