JPS583141A - Optical head - Google Patents

Abstract

PURPOSE:To record information on a nonrecording track with one light spot, by using two laser light spots in which the polarized planes are mutually orthogonal, reproducing a recorded track with another light spot. CONSTITUTION:LD1 and LD2 are semiconductor lasers and the polarized planes are mutually orthogonal. The output of the semiconductor laser LD2 is smaller than that of the LD1 and is always illuminated and the output is set to an output causing no over-light at the reading of information. While tracking a track having the written information by the LD2, the information can be written in an arbitrary track within the range moving a polarized beam splitter PBS1 from this track in an accurate track pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical head capable of writing information at a highly accurate track pitch in an optical disk device.

Conventionally, when writing to an optical disk device, the optical head was mounted on a stage and the stage was moved according to the track pitch to perform writing, but in this case, no matter how accurately the stage was moved, the writing It is possible to know where the light beam is on the medium.If the optical system of the optical head, which is supported by a relatively low-rigidity member such as a plate spring, is moved by a stage, the track pitch is 1 to 2 (μ). Therefore, it is difficult to move the stage at an accurate pitch.

The present invention aims to solve the above-mentioned drawbacks, and uses two light sources to read information on a track on which information has already been written using one of the light sources, and from the obtained signal, information on the eccentricity of the track is obtained. , obtain vibration information of the recording surface, and write with the other light source while controlling the optical system so that the light spot on the recording surface accurately follows the track and focuses accurately on the medium. This provides an optical head that is not affected by external vibrations and can write while maintaining an accurate track pitch.

The present invention will be explained in detail below using figures.

FIG. 1 shows an embodiment of the present invention.

LDI and LD2 are semiconductor lasers whose polarization planes are perpendicular to each other. In this embodiment, the polarization plane of the semiconductor laser LDI is fixed to be parallel to the paper surface, and the polarization plane of the semiconductor laser LD2 is fixed to be perpendicular.

The light beam from the LDI passes through a collimator lens CL1, a polarization tracking optical deflector (rotating mirror) RM, an objective lens OL with a focusing drive mechanism OM, and reaches the recording medium, connecting the light points.

In this system, when the positional relationship between the objective lens OL and the medium is normal, the conjugate point of the light point p with respect to the objective lens OL is point P1 in FIG. 1.The collimator lens CL is the light emitting point of the semiconductor laser LDI. The focal length and arrangement are such that P coincides with P. Therefore, the light point X) on the medium
This is a map of the light emitting point of the semiconductor laser LDI. The light from the semiconductor laser LD2 is transmitted to the first polarizing beam splitter P.
Although it is reflected by BSL, the mirror image of the light emitting point of the semiconductor laser LD2 is the conjugate point P of the light point 1) with respect to the objective lens OL,
The semiconductor laser LD2 is arranged so that the second conjugate point P is located at a distance d in the vertical direction from the optical axis Z1. From now on, the light beam from the semiconductor laser LD2 is
A light spot P6 is connected on the medium using the same optical path as in the case of DI.

Therefore, the plane perpendicular to the optical axis Z and containing Pl + PM becomes a conjugate plane of the medium plane with respect to the objective lens OL. At this time,
If the magnification of the objective lens OL is α, and the angle θ is above the recording medium with respect to the radial direction of the recording medium, then d'
By setting d and 0 so that t = d'cos θ is a predetermined track pitch or an integer multiple thereof, one light point can read the track on which information has been written in advance, while the other light point can read the adjacent track. A track comb can write information to a new track that is an integer multiple of the track pitch. In this embodiment, when the semiconductor laser LDII is used as the writing light source, the semiconductor laser LDI is modulated according to the information to be written, but the semiconductor laser LD2 is the semiconductor laser LDI.
It always emits light with a smaller output than DI, and its output is set to a level that does not override when reading information. The light from the semiconductor laser LD2 is reflected by the medium surface, passes through the objective lens OL and the optical deflector RM, is reflected by the half mirror HM, and reaches the photodetector. This photodetector converts track eccentricity information and vibration information on the medium surface obtained from the light emitted from the LD2 and reflected from the medium surface into electrical signals, and sends them to the control system C0NT to ensure correct reading. The signal is fed back to the optical deflector RM and the objective lens drive mechanism OM to perform track servo and focus servo, and also reproduce recorded information. Further, here, the semiconductor lasers LDI and LD2 do not particularly need to have the same wavelength as long as their polarization planes are orthogonal. It goes without saying that a similar system can be constructed by using one or both of the semiconductor lasers 1LD1 and LD2 as gas lasers or the like.

In addition, in this embodiment, the semiconductor laser L which is the writing light source
If an optical system is provided between the DI and the first polarizing beam splitter PBSIO that can move the point P in or near the conjugate plane with respect to the objective lens OL facing the medium, it is possible to move the point P from the semiconductor laser LD2. This is done by moving the light point P≦, which the light ray connects on the medium, to the reference position and Q position.

The same thing can also be achieved by changing the optical path of the light beam from the semiconductor laser LD2 and changing the position of the light spot P≦ on the medium. An example in this case is shown in FIG.
Here, a drive system MB is added so that the first polarizing beam splitter PB81 can be moved in parallel along the Z1 axis. Note that 攬 is the reflective surface of the polarizing beam splitter PB81 before the polarizing beam splitter PBSI moves, R△ is the reflective surface B after the polarizing beam splitter PBSI has moved, and R is the reflective surface of the polarizing beam splitter PBS.
The optical path from the semiconductor laser LD2 before I moves, Bl
△ is the optical path after moving, P≦ is the deflection beam splitter P
P≦△ is a light spot on the medium caused by the semiconductor laser LD2 before B81 moves, and P≦△ is a light spot on the medium after B81 moves. Also, the same symbol parts as in FIG. 1 are shown.

Here, if the polarizing beam splitter PBSI is moved to the right in the figure, the optical path of the light beam from the semiconductor laser LD2 will move upward in parallel, but this is because the 22 points in Fig. 1 have moved upward. Similarly, the conjugate point P6 on the medium surface of P moves to the left.

During this time, the conjugate relationship between P and P remains unchanged, and only the relative positions between the two light spots p< and p≦ on the medium surface change. Therefore, while following the track on which information has been written, the semiconductor laser LD2 can write information at an accurate track pitch to any track within the range in which the polarizing beam splinter PBSI can be moved from this track.

As explained above, according to the present invention, since two light sources are used, the track servo is always in position even during writing, and highly stable writing is possible. In addition, since two linearly polarized light sources with orthogonal polarization planes are used, there is no interference between the two lights, and the light intensity on the medium remains constant, even when the optical disc is replaced. , 7n, it is possible to add information at a fine, constant track pitch.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the present invention, FIG. 2 is an explanatory diagram of the present invention,
FIG. 3 shows another embodiment of the invention. LDI, LD2...Semiconductor laser, CL...Collimator lens, PBSI, PBS2...Polarizing beam splitter, HM...Half mirror, RM...Light polarizer for tracking, OM...For fish gathering alignment Drive mechanism, O
L...Objective lens, D...Recording medium, MB...Drive system, C0NT...Control system, Ro...Reflection surface of PBSl before PBSl moves, R△...PBSl Reflection surface of PBSl after moving, B... optical path from LD2 before PBSl moves, B2△... optical path from LD2 after PBSl moves, P... before PBSl moves The light spot on the medium by LD2, PG△...
Light spot on the media by LD2 after PBSI has moved.

Claims (1)

[Claims] (1) In a recording/reproducing optical head of an optical disk device, it relates to a lens system such as an objective lens and a collimator lens. Two laser point light sources, which are separated perpendicularly to the optical axis and whose polarization planes are perpendicular to each other, are provided on the conjugate plane of the recording medium surface, and the radial direction of the light spots from the two point light sources mapped onto the recording medium is The recording medium is arranged so that the distance is equal to the track pitch or an integral multiple thereof, and a light spot on one of the recording media is used to reproduce information on a track on which information has already been written, using a reproduction signal. Then, the focus servo of the lens system and the track servo are performed using an optical deflector that can simultaneously move the light spots on the two recording media in the radial direction. When information is recorded by a light spot, (2) an optical system is provided that moves the optical axis of one of the laser point light sources in parallel, and the information is written by the light spot of the one laser point light source on the recording medium. According to the first aspect of the present invention, a light spot is created on an arbitrary track on the recording medium by the other laser point light source, and information can be added to the recording medium while following the track on the recording medium. Optical head described in section.