JP2841753B2 - Magneto-optical recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing apparatus, and more particularly to a magneto-optical recording / reproducing apparatus which is useful when performing focus servo by a sample servo method.

[Summary of the Invention]

The magneto-optical recording / reproducing apparatus of the present invention detects an offset of a focus error signal of a laser spot at the time of reproduction in a head area of a sector and an offset of a focus error signal at the time of recording, and holds the respective values. A first sample-and-hold circuit; and a second sample-and-hold circuit. A value obtained by subtracting the output of the second sample-and-hold circuit from the output of the first sample-and-hold circuit in a data recording area is supplied to the focus servo circuit. It is configured to be injected.

For this reason, it is possible to eliminate defocusing that occurs when data is recorded on the magneto-optical disk by performing focus servo using the sample servo method.

[Conventional technology]

2. Description of the Related Art There is known an optical disk capable of recording data in response to light, in which servo pits are arranged concentrically at predetermined intervals so that concentric recording tracks are formed on a recording surface of the optical disk. ing.

FIG. 3 shows the recording surface of such a sample format optical disk, wherein S1 to S32 are, for example, three in the circumferential direction.
Indicates a sector divided into two.

The track of each sector S is an address (header) area AD
Is divided into the following 42 segments SG1 to SG42,
Each segment records 18 bytes of data.

In each segment SG, for example, as shown in FIG. 4, a 2-byte servo byte SB is arranged first, followed by 16-byte data bytes DB1 to DBn.

The servo byte SB has a pair of wobbling bits P1 and P2 shifted by 1/4 track pitch in the outer and inner circumferential directions around the track T, and a clock pit P3 arranged on the center line of the track T in advance. It is formed by processing or the like.

The middle between the wobbling pits P1 and P2 and the clock pit P3 is a mirror surface MR, and the laser light reflected from the mirror surface detects a focus servo signal and enables laser power control. ing.

In the case of such an optical disc, a tracking error signal can be formed by calculating the reflected light when the wobbling pits P1 and P2 are detected at the sample points t1 and t2, and the clock pit P3 can be formed. Sample point t3
The data read clock is formed by the signal detected at step (1).

The focus error signal detected in this sample pit area is held until the next sample pit area, and the focus servo is applied.

[Problems to be solved by the invention]

The laser beam irradiated to such a magneto-optical disk is generally used as a semiconductor laser light emitting source. However, this semiconductor laser light emitting source has a problem that the laser wavelength fluctuates when its temperature or output power changes. is there.

Therefore, in the recording mode for recording data on the magneto-optical disk, the laser power is controlled so as to increase, so that the laser wavelength generally fluctuates.

When the output wavelength of the semiconductor laser emission source changes, this output beam causes a change in the focal length of the objective lens irradiating the magneto-optical disk.

This change in focal length is mainly caused by the refractive index and chromatic aberration of the lens, and can usually be eliminated by a focus actuator controlled by a focus error signal of a focus servo circuit.

However, as described above, in a focus servo type device that detects a focus error signal in the sample servo pit area and holds the focus error signal in the data writing area, data is recorded in the hold period, that is, in the recording data area. If the laser power is increased during the recording, a slight change in the laser wavelength causes a change in the focus focal length, which may cause defocus when recording data during the focus hold period. Therefore, there is a problem that the resolution of the recording / reproducing data is deteriorated, and error data frequently occurs.

[Means for solving the problem]

The present invention has been made to solve such a problem, and when irradiating a laser beam in a test writing area provided in a part of a sector mark of a magneto-optical disk, a focus error signal is generated. A first sample-and-hold circuit for detecting the signal and a second sample-and-hold circuit for detecting an offset signal of a focus error signal output at the time of reproduction; A value obtained by subtracting the output of the second sample hold circuit from the output of the hold circuit is injected as an offset voltage of the focus servo circuit.

[Action]

The data recording area is set to the recording mode, and the difference signal between the offset voltage detected when the laser power is increased and the offset voltage detected in the reproduction mode is detected, and this difference signal is used as a focus error signal during reproduction. , The focus servo can be applied so that the focal point is in focus even during the period when the focus error signal is sampled and held, and the defocus generated at the time of recording can be eliminated.

〔Example〕

FIG. 1 shows an outline of a focus servo circuit in a magneto-optical recording / reproducing apparatus of the present invention, in which 10 is an optical detector for detecting a focus error, 11 is an arithmetic circuit for a focus error signal, and 12 is a sample. A sample and hold circuit for holding a discrete focus servo error signal obtained from a servo area. As is well known, the sample and hold circuit 12 opens and closes a switch S (not shown) by a clock CLK of an optical disk. The focus error signal sampled for each segment is held in the capacitor C.

Reference numeral 13 denotes an offset voltage addition circuit, and reference numeral 14 denotes a focus error signal phase compensation and drive circuit, the output of which is supplied to a focus coil L via a drive circuit 15.

Then, the distance between the objective lens R and the disk D is changed,
The focus is on.

Reference numeral 16 denotes a Bach amplifier for detecting the terminal voltage of a resistor r connected in series with the focus coil L. The output of the buffer amplifier 16 is supplied to a first sample-and-hold circuit 18 and a second It is supplied to the sample and hold circuit 19.

As shown in FIG. 2, the first sample and hold circuit 18 outputs a signal so that sampling is performed in an APLP area set in a header (address) area of the magneto-optical disk in which a sector mark is recorded. SAMPL (W) is supplied, and the second sample hold circuit 19 is also supplied with the signal SAMPPL (R) so that the offset signal is sampled in the reproduction area of the header.

Here, the offset signal is a direct current (voltage) supplied to the focus actuator when a focus servo is applied to the objective lens and the object lens is in a focused state.

20 is a subtractor for subtracting the output of the first sample and hold circuit 18 and the output of the second sample and hold circuit 19;
Reference numeral 21 denotes a switch for injecting the output signal of the subtracter 20 into the focus servo circuit in the data write area.

Reference numeral 22 denotes an APL circuit that switches the power of the semiconductor laser diode LED during reproduction and recording by the timing control unit 23. For example, the APL circuit is controlled so that the semiconductor laser power during recording is about 10 times higher than during reproduction.

The focus servo circuit of the magneto-optical recording / reproducing apparatus according to the present invention operates as described below by adopting the above-described configuration.

In the normal reproduction mode, the sample path S for detecting a focus error in the servo pit area of the optical disc is used.
_Fe is supplied, and focus servo in the data area is also performed by the focus error signal sampled and held.

In addition, in the header portion serving as a sector mark of the optical disk, as shown in FIG.
(R) and SAMPL (W) are supplied, and the focus offset signal ROF is recorded in the second sample-and-hold circuit 19 during the period of reproduction, and the test writing area ( The focus offset signal WOF at the in-focus position at the high output laser power applied to the APLP) is held in the first sample and hold circuit 18. Therefore, the first sample and hold circuit is used in the data area when the data recording mode is set.
18 the output of the difference output Dof output was subtracted of the second sample and hold circuit 19 is formed so as to supply via the switch 21, Fuo upon reproduction this difference signal D _of is held in the recording data area If the difference signal D _of is superimposed on the cas error signal and the offset signal is set so that an offset current to be focused at the time _of recording flows, the laser output is increased at the time of recording and the laser wavelength is increased. The lens can be brought to the focal point.

Generally, at the time of recording, the laser wavelength becomes longer and the focal length tends to become longer. Therefore, the offset signal supplied by the difference signal is controlled in a direction to move the objective lens away from the disk surface.

In the above embodiment has been configured such difference signal D _of is injected directly into Fuo Kas servo circuit, the value of comparison by comparison means the terminal voltage of the difference signal and the resistor r are injected into Fuo Kas servo circuit, It is also possible to employ a feedback circuit in which the signal output of the comparing means becomes zero so that the offset at the time of data recording is eliminated.

〔The invention's effect〕

As described above, the magneto-optical recording / reproducing apparatus of the present invention detects an offset signal from a focus error signal when performing test writing with a sector mark, and calculates the offset signal and the offset signal output during normal reproduction. Since the difference signal is supplied as an offset signal at the time of recording, it is possible to prevent the occurrence of defocusing even at the time of recording on an optical disk in which focus servo is performed by the sample servo pit. Therefore, especially in a magneto-optical recording / reproducing apparatus in which focus servo is performed by a discrete focus signal, it is possible to eliminate defocusing even at the time of recording when the laser power is increased, and to improve the resolution at the time of data recording / reproducing. And the probability of occurrence of data errors can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a focus offset circuit in a magneto-optical recording device of the present invention, FIG. 2 is a signal waveform diagram showing an operation of the present invention, and FIG. 3 is a description showing a recording format of a sample servo type magneto-optical disk. FIG. 4 is an explanatory diagram of a sample servo area and a data recording area. In the figure, 10 is an optical detector, 11 is a focus error calculation circuit, 12 is a sample and hold circuit, 16 is a buffer amplifier for detecting an offset signal, and 18 and 19 are first and second.
1 shows a sample hold circuit.

Claims (1)

(57) [Claims] 1. A magneto-optical recording / reproducing apparatus which samples and holds a discrete focus control signal detected in a reproduction area of an optical disk and performs focus servo based on the sampled / held focus error signal. Magneto-optical recording includes first and second sample-and-hold circuits for respectively sampling a laser spot test-written in a recording mode and a focus offset of a laser spot irradiated in a reading mode in a sector head area of an optical disc. When the reproducing apparatus is set to the recording mode in the data recording area, a signal obtained by subtracting the output of the second sample and hold circuit from the output of the first sample and hold circuit is added to the focus error signal as an offset signal. Light characterized by being constituted Gas-recording and reproducing apparatus.