JPH0467326A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of light transmission efficiency by means of the diameter eclipse of an objective lens in a multibeam optical head and to improve performance by giving a multibeam laser light source, the objective lens and a beam splitter and providing a light source/convergence control optical system moving part which can be moved to the track access direction of an optical recording and reproducing medium. CONSTITUTION:The multibeam laser light source 101 which independently emits plural light beams and the objective lens 107 converging the light beams by the multibeam laser light source 101 on the optical recording and reproducing medium DK are provided. Furthermore, the beam splitter 103 guiding reflected reproduced light from the optical recording and reproducing medium DK in a direction different from the optical path of an outgoing beam by the multibeam laser light source 101 is provided and the light source/convergence control optical system moving part 100 which can be moved to the track access direction of the optical recording and reproducing medium DK is provided. Thus, the length of the optical path from the light source 101 to the objective lens 107 can be set constant and short and the deterioration of light transmission efficiency by the diameter eclipse of the objective lens 107 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording and reproducing apparatus that performs recording and reproducing operations in parallel on tracks on an optical recording and reproducing medium using a multi-beam laser.

(Prior Art) Conventionally, in an optical disk recording/reproducing device, when information is simultaneously recorded on multiple tracks on an optical disk medium,
This is performed by using a so-called multi-beam laser (hereinafter abbreviated as MBL) in which a plurality of semiconductor lasers are integrally formed into an array. The recording optical system in this case may basically have the same configuration as in the case of a single beam laser.

FIG. 2 is a block diagram of a conventional optical disc recording/reproducing apparatus using MBL. In FIG. 2, reference numeral 1 denotes a light source and signal detection optical system fixing part, which includes an MBL light source 2, a collimator lens 3, a polarizing beam splitter 4, a 1/4 wavelength plate 5, a roof-shaped prism 6, and a rotation mechanism 7 for the roof-shaped prism 6. , condenser lens 8, beam splitter 9, cylindrical lens 10
, a focus detection photodiode 11, and a reproduction signal and track detection photodiode, and is fixed to a base (not shown) of the optical disk recording/reproducing apparatus. Note that the roof-shaped prism 6 has an image rotation function that adjusts the azimuth angle with respect to a track (not shown) on the optical disc medium DK.

20 is a movable part of the condensing control optical system, and an optical path changing prism 21
, an objective lens 22, and a positioning control mechanism 23 for the objective lens 22, and is mounted on a positioner (not shown) that allows a light beam to access a track on the optical disk medium DK, so that it can move in the track access direction.

Further, IA indicates the optical axis of incidence on the optical disk medium DK, RA indicates the optical axis of reflection from the optical disk medium DK, FA indicates the optical axis of the focus detection optical system, and TA indicates the optical axis of the reproduction and track detection optical system. ing.

The focus detection optical system on the optical axis FA is for detecting focus errors, and uses an astigmatism method using a condenser lens 8 and a cylindrical lens 10. In addition, the optical axis TA
The reproduction and track detection optical system is for detecting track errors and reproduction signals, and a bush-pull method is used for track detection.

In such a configuration, the linearly polarized light beam emitted from the MBL light source 2 is converted into a plane wave beam by the collimator lens 3, transmitted through the polarization beam splitter 4, and then incident on the quarter-wave plate 5. . The light beam is 1/4
The wave plate 5 converts the light into circularly polarized light, and the roof prism 6 adjusts the position.
The optical path is changed by the optical path changing prism 21 of 0. The light beam whose optical path has been changed is passed through the objective lens 22 and the control mechanism 23.
The light is focused onto the optical disk medium DK while being tracked by the light beam. In this way, information is recorded and reproduced.

The reflected reproduction light from the optical disk medium DX is transmitted through the objective lens 2.
2. The light enters the quarter-wave plate 5 via the optical path changing prism 21 and the roof-shaped prism 6.

The reflected reproduction light that has passed through the quarter-wave plate 5 becomes linearly polarized light whose polarization direction is perpendicular to the incident light beam, is reflected by the polarizing beam splitter 4, and is condensed by the condenser lens 8.

The condensed reflected reproduction light is split by the beam splitter 9 into a focus detection optical system on the optical axis FA and a reproduction and track detection optical system on the optical axis TA, and is received by photodiodes 11 and 12, respectively.

In the conventional optical disk recording and reproducing apparatus having the above-mentioned functions, as described above, the light source detection optical system fixed part 1 and the condensing control optical system movable part 2o are separated into separate units, so the positioner It has the advantage of reducing movable weight, speeding up access, and reducing power consumption of the positioner.

(Problem to be Solved by the Invention) However, in the above conventional device, the MBL light source 2
Since the distance between the BL and the objective lens 22 is longer than when the optical radar is integrated, the beam outside the MBL, which propagates at an angle with respect to the optical axis of the optical system, is affected by the vignetting of the objective lens. There was a problem that the transmission efficiency decreased.

This problem will be explained in more detail.

FIG. 3 is an explanatory diagram of the inclination of the propagation optical path with respect to the optical axis of the multi-beam optical system, and in the figure, PK is MBL.
In the package of light source 2, cp is an MBL semiconductor laser chip, Lt, L2, and L3 are laser emission points, CL is a collimator lens, OL is an objective lens, DK is an optical disk medium, and SL + 82 + 83 is a convergence on the optical disk medium DK. This is a multi-beam spot.

In the configuration shown in FIG. 3, each laser light emitting point LLtL2. L
3 is placed at the focal point of the collimator lens CL, and the light beams emitted from these are converted into plane waves by the collimator lens CL, and a spot S2 is connected to the focal point of the objective lens OL.

At this time, the front focal length of the collimator lens CL is fl
+If the rear focal length is f2, the front focal length of the objective lens OL is f3, the distance between the collimator lens CL and the objective lens OL is (g+f2), and the distance between the light emitting points of the MBL is dl, then the spot interval on the optical disc medium DK is d is given by the following equation (1).

d3=d・f3/f・・・・(1)
Further, the deviation d2 of the center position of the luminous flux of both multi-beams from the optical axis at the entrance aperture of the objective lens OL is given by the following equation (2).

d2=Il'' d1/f2...(2
) In Figure 4, the focal length f2 is set to 9 among the parameters in Figure 3.
mm, the interval d1 is 150 μm, and the aperture of the objective lens OL is 70% of the 1/e2 diameter of the beam luminous flux with Gaussian intensity distribution.
12 is a graph showing the results of calculations when the laser beams on both sides are subjected to vignetting by the objective lens OL, normalized by the optical transmission rate of the central beam of the multi-beam.

As can be seen from FIG. 4, when the optical path length ρ exceeds 130 degrees, the loss becomes more than 10%, and the decrease in laser power required for recording cannot be ignored.

In particular, in a separate type device like the conventional device, the optical path length changes as the track of the optical disk medium DK is accessed, and the transmitted power also changes.

The present invention has been made in view of the above circumstances, and its purpose is to provide an optical recording and reproducing device that can prevent a decrease in light transmission efficiency due to vignetting of the objective lens of a multi-beam optical head and realize high performance. It is about providing.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an optical recording and reproducing apparatus that performs recording and reproducing operations by collectively irradiating a plurality of tracks on an optical recording and reproducing medium with a light beam. ,
A multi-beam laser light source that independently emits a plurality of light beams, an objective lens that focuses the light beam from the multi-beam laser light source onto the optical recording and reproducing medium, and a reflected reproducing light from the optical recording and reproducing medium. a beam splitter that guides the light beam in a direction different from the optical path of the light beam emitted by the multi-beam laser light source, a light source and a light collection control optical system movable part that is movable in a track access direction of the optical recording and reproducing medium; and the beam splitter. It has an optical system that detects a reproduction signal and a servo system signal by receiving reflected reproduction light transmitted through the optical system, and includes a reproduction and servo system signal detection optical system fixing part fixed at a predetermined position.

(Function) According to the present invention, the multi-beams emitted from the multi-beam laser light source are focused onto the optical recording/reproducing medium by the objective lens. Further, at the time of access, the multi-beam laser light source and the objective lens are moved together to access the track.

Further, the reflected reproduction light from the optical recording/reproduction medium is guided by a beam splitter to an optical path different from the optical path of the output light beam, and is incident on the reproduction and servo system signal detection optical system fixed part. Thereby, the reproduction signal and the servo system signal are detected.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of an optical disk recording/reproducing apparatus according to the present invention.

In FIG. 1, reference numeral 100 denotes a movable part of the light source and condensing control optical system, which includes an MBL (multi-beam laser) light source 101 that independently emits a plurality of linearly polarized light beams, and a light beam emitted from the MBL light source 101. a collimator lens 102 that converts the plane wave into a plane wave, a polarizing beam splitter 103 that transmits the plane wave produced by the collimator lens 102 and reflects the reflected reproduction light from the optical disk medium DK in a direction different from the incident direction of the plane wave, and a polarizing beam splitter 103 that converts the linearly polarized light into a circular A quarter-wave plate 104 for converting into polarized light; a roof-shaped prism 105 having an image rotation function for adjusting the azimuth angle of a track (not shown) on a multi-beam optical disc medium DK; and a rotation mechanism 106 for the roof-shaped prism 104. , roof prism 1
an objective lens 107 that focuses the light beam whose position has been adjusted by 05 on the optical disk medium DK, and an objective lens 10
7 control mechanisms 108.

The light source and condensing control optical system movable unit 100 is mounted on a positioner (not shown) that allows the light beam to access a track (not shown) of the optical disc medium DK, and is movable in the track access direction (radial direction). ing.

Reference numeral 200 denotes a fixed part of the reproduction and servo system signal detection system, which includes a condenser lens 201 that condenses the reflected reproduction light reflected by the polarization beam splitter 103 of the light source and condensing control optical system movable part 100; a beam splitter 202 that splits the reflected reproduction light through the beam splitter 20;
A cylindrical lens 203 for imparting astigmatism to the divided light of 2, a photodiode 204 for receiving the reflected reproduction light through the cylindrical lens 203 and obtaining a focus error signal, and other divisions of the beam splitter 202. It is composed of a photodiode 205 for receiving light and obtaining a reproduction signal and a servo/error signal for track detection.

The reproduction and servo signal detection system fixing section 200 is fixed to a base section (not shown) of the optical disk recording/reproducing apparatus.

Further, IA indicates the optical axis of incidence on the optical disk medium DK, RA indicates the optical axis of reflection from the optical disk medium DK, FA indicates the optical axis of the focus detection optical system, and TA indicates the optical axis of the reproduction and track detection optical system. ing.

Next, the operation of the above configuration will be explained.

The linearly polarized multi-beam emitted from the MBL light source 101 is converted into a plane wave beam by the collimator lens 102, and after passing through the polarization beam splitter 103, the linearly polarized multi-beam is
The light is incident on the four-wavelength plate 104.

The multi-beam is converted into circularly polarized light by a quarter-wave plate 104, and the azimuth angle is adjusted by a roof prism 105, that is, the position with respect to the track is adjusted. After this position adjustment, the light is focused onto the optical disc medium DK while being tracked by the objective lens 107 and the control mechanism 108.

In this way, information is recorded and reproduced.

The reflected reproduction light from the optical disk medium DK is transmitted through the objective lens 1.
07, 1/4 wavelength plate 10 via roof prism 105
4. The reflected reproduction light that has passed through the quarter-wave plate 104 becomes linearly polarized light whose polarization direction is perpendicular to the light beam incident on the optical disk medium DK.

Next, this reflected reproduction light is transmitted to the polarizing beam splitter 103
and is reflected by the reproduction and servo system signal detection optical system fixed part 2
00 is input.

The reflected reproduction light incident on the reproduction and servo system signal detection optical system fixed part 2 (10 is condensed by a condenser lens 201, and then
The beam is split into two by a beam splitter 202.

The - split light by the beam splitter 202 is received by the photodiode 204 via the cylindrical lens 203. The other split light is transmitted through the photodiode 20
The light is received by 5.

Focus error detection is performed by a processing circuit (not shown) based on the electrical signal from the photodiode 204,
Based on the electric signal from the photodiode 205, a reproduction signal and a tracking error (servo error) are detected.

In this embodiment, explanations of the operations of the actuator system, focus/track servo system, positioner system, and command processing system necessary for the optical disk recording/reproducing apparatus are omitted because they are not directly related to the present invention. .

As explained above, according to this embodiment, the MBL light source 1
01, the objective lens 107 as a condensing control system, and the control mechanism 108 are made to move integrally, so the optical path length from the MBL light source 101 to the objective lens 107 can be kept constant.
Moreover, it can be shortened, and a decrease in light transmission efficiency due to vignetting of the objective lens 107 can be prevented.

In addition, since the reproduction and servo signal detection optical system is separated from the movable part 100 for access, the movable weight of the positioner on which the movable part 100 is mounted can be reduced, making access faster and reducing the power consumption of the positioner. .

Note that the roof-shaped prism 105 used in this example is for positioning each multi-beam spot on the track by adjusting the azimuth angle between the imaging spot array and the track on the multi-beam optical disk medium DK. However, this is a so-called image rotation optical system, and it is of course possible to use not only the roof-shaped prism 105 but also an optical system having the same functional effect, such as a combination of mirrors or a combination of prisms.

In addition, although this embodiment has been explained using the optical disk medium DK as an example, it is not limited to this (it goes without saying that the present invention can be applied to any optical recording/reproducing medium such as an optical tape medium or an optical card medium). Nor.

Further, the present invention is applicable regardless of the recording/reproducing principle such as magneto-optical or phase change.

Furthermore, an image rotation mechanism such as a roof-shaped prism is used for multi-beam tracking when the curvature of the disk track or the access direction is not toward the center of curvature of the track, or when the track pitch is variable. is placed perpendicular to the track and the access direction is toward the center of track curvature, etc.
Needless to say, this image rotation mechanism is not mounted on a movable part.

Further, in this embodiment, the astigmatism method is used as the focus detection method, but other Foucault method or spot size detection method may of course be used.

(Effects of the Invention) As described above, according to the present invention, there is provided a multi-beam laser light source that independently emits a plurality of light beams, and a light beam from the multi-beam laser light source that is focused on the optical recording/reproducing medium. an objective lens that emits light, and a beam splitter that guides the reflected reproduction light from the optical recording and reproducing medium in a direction different from the optical path of the light beam emitted by the multi-beam laser light source, the beam splitter directing the reflected reproduction light from the optical recording and reproducing medium in a track access direction of the optical recording and reproducing medium. Since a movable light source and a movable part of the condensing control optical system are provided, the optical path length from the light source to the objective lens can be kept constant and short, and a decrease in light transmission efficiency due to vignetting of the objective lens can be prevented. .

In addition, it has an optical system that is separated from the movable part and receives reflected reproduction light via a beam splitter to detect reproduction signals and servo system signals, and a reproduction and servo system signal detection optical system fixed at a predetermined position. Since a portion is provided, the movable weight of a positioner such as an optical disk recording/reproducing device can be reduced, and access speed can be increased and power consumption of the positioner can be reduced.

As a result, the optical transmission rate of the laser increases, high-speed recording and reproduction becomes possible, and there are advantages in that access time is shortened and data transfer speed is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an optical disk recording/reproducing apparatus according to the present invention, FIG. 2 is a block diagram of a conventional optical disk recording/reproducing apparatus, and FIG. 3 is a propagation of multi-beams along the optical axis of the optical system. FIG. 4, which is an explanatory diagram of the inclination of the optical path, is a graph showing the calculation results of vignetting caused by the objective lens. In the figure, 100... light source and condensing control optical system movable part, 1
01... MBL light R11 (12... Collimator lens, 103... Polarizing beam splitter, 104...
1/4 wavelength plate, 105... Roof prism, 107.
...Objective lens, 200...Reproduction and servo system signal detection optical system fixed part, 201...Condensing lens, 202...
- Beam splitter, 203...Cylindrical lens, 204.205...Photodiode. Optical path length, l, (mm) Graph showing calculation results of vignetting due to objective lens Figure 4

Claims (1)

[Scope of Claims] In an optical recording and reproducing device that performs recording and reproducing operations by collectively irradiating a plurality of tracks on an optical recording and reproducing medium with a light beam, there is provided a multi-beam laser that independently emits a plurality of light beams. a light source; an objective lens for condensing a light beam from the multi-beam laser light source onto the optical recording/reproducing medium; a light source and a condensing control optical system movable part that is movable in the track access direction of the optical recording and reproducing medium; What is claimed is: 1. An optical recording and reproducing apparatus, comprising: an optical system for detecting system signals; and a reproducing and servo system signal detection optical system fixing section fixed at a predetermined position.