JPS60182527A - Optical head - Google Patents

Abstract

PURPOSE:To facilitate control for positioning of an erasion beam by providing a diffraction grating at the output side of a collimator on the optical axis of an erasion optical system and enlarging laser light in an oval shape. CONSTITUTION:The laser beams delivered from a semiconductor laser 11 form pots to a memory thin film 43 on a disk 40 via a record/reproduction optical system 10, a polarized beam splitter PBS15, lambda/4 plate 16 and an aperture lens 30. Thus recording is carried out. In a reproduction mode the weak reflected light of the light spot goes back and is made incident on a photosensor 19 via the PBS15, a lambda/4 plate 17 and a BPF18. While the output light of a semiconductor laser 21 is turned into an oval luminous flux by a diffraction grating 23 via a collimator lens 22 together with the 90 deg. deflection given to the S wave component through the PBS15 and then forms an oval erasion spot on the thin film 43 via the plate 16 and the lens 30. This facilitates control for positioning of an erasion beam.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates to a recording/reproducing and erasable optical head used in an optical disk memory system.

BACKGROUND ART There are systems for recording and reproducing various types of information that use mechanical methods, magnetic methods, optical methods, and the like. Among these, original disk memory systems that use optical disks as memory media are capable of high-density recording several tens to hundreds of times higher than systems that use conventional magnetic media, and are also capable of high-density recording without contact. It has the excellent feature of being able to obtain high-quality reproduced signals, and has been actively researched and developed in recent years, with some devices already being put into practical use.

Recently, a thin film of Te0x (thirium oxide), which is a chalcogenide-based glass semiconductor, has been used as a memory thin film to enable erasing, and by applying the reversible phase transition phenomenon between the crystalline state and the amorphous state, recorded signals can be erased. An optical system that enables real-time recording and erasure of information signals, which enables so-called overwriting, in which information signals are rewritten with new signals, is now at a practical level. This system changes the erased state of the memory thin film to a crystallized state,
This is a method in which recording, reproduction, and erasing are performed by making the recording state amorphous.

Generally, the crystallization temperature gradient is smaller than the vitrification (amorphization) temperature gradient, so in the above system, recording, reproduction 9 and erasing are performed as follows.

The memory thin film 43 of the disk medium rotating at high speed is irradiated with a high-output laser beam R corresponding to the information signal at high speed, and as shown in FIG. 1, the memory thin film is rapidly heated and cooled by increasing the temperature gradient. A phase transition occurs from a crystalline state to an amorphous state. Information bits are recorded by changes in reflectance associated with the phase transition (from high to low to morning).

Reproduction is performed by lowering the output of the same laser beam, scanning the recorded bits, and reading the changes in the intensity of the reflected light.

For erasing, a low-power laser beam E is irradiated to the recording focus of the information trunk, and as shown in Figure 1, the temperature gradient is reduced and the memory is gradually cooled, thereby changing the memory thin film from an amorphous state to a crystallized state. It is done by transferring. Therefore, the erasing laser beam is formed into an oval shape as shown in FIG.

In optical systems such as those mentioned above, the power of
Two semiconductor lasers with an oscillation wavelength of An optical head is used that uses a single aperture lens to focus and irradiate the disk. In order to obtain this light, it is necessary to form the spot of the laser beam for erasing from a circular shape to an elliptical shape, and for this purpose, conventionally, the erasing optical system has been configured with a cylindrical lens system. However, according to this, the diameter of the two beam spots that irradiate and converge on the disk is extremely small, 1 ptng degree. This minute spot is guided and converged onto the TiSF surface by a separate optical system, so two optical systems are required to correctly position the two beam spots for recording/reproducing and erasing on the recording l/rank. The optical axis of the lens must be aligned accurately. Second, each component, especially the cylindrical lens that makes up the erasing optical system, must be picked up and aligned and adjusted with respect to the optical axis with high precision at an extremely minute level of within about 0.1 μm.

For example, if the cylindrical lens is not aligned correctly with respect to the optical axis, it may get kicked out even if it is slightly misaligned, or if there is a slight deviation in the cylindrical lens. However, if this occurs, the strength of the bending power may cause the erasing beam slot I-E to shift from the recording trunk as shown in Figures 2 (a) and (b).
1) distortion or (d) distortion may occur and it may not be possible to form the oval shape correctly.As a result, a good erasing operation cannot be performed.Therefore, the cylindrical shape may not be properly formed.・Make sure to adjust the position very carefully and carefully move the center line, and place the January arm on the trunk.
, <Q 1i'? Adjustment 1']: The work is extremely troublesome and requires a lot of manual labor 3. Disclosure of the invention This scream ζ; 11. In the above-mentioned erasing optical system,
Correctly place the 16 oval hem for erasing on the iiL' JJ l rank. The purpose is to make it easier.

) Purpose of writing? [↓rIn order to achieve this, in this invention, the collimator output I (11) on Y, 1+III is converted to t'
. . , q+4 < laser beam is expanded into an elliptical shape through a diffraction grating.

According to the optical head according to the present invention, by using a diffraction grating as a means for forming an elliptical beam for erasing, its attachment and position adjustment can be easily performed with rough precision. Therefore, the adjustment work for correctly positioning the elliptical beam on the recording track becomes easier. Moreover,
It is easy to form an elliptical beam, and the IE can be accurately focused on the recording trunk by constantly aligning the position correctly.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a preferred embodiment of the present invention will be described in detail at N111 with reference to FIG. 3 and FIG. 1m.

FIG. 3 shows a light nozzle according to the present invention.

The optical head has an optical system 10 for recording and an optical system 20 for erasing, which are integrated into the optical head. ( ], 20 are provided with semiconductor lasers il, 21. The semiconductor lasers 11, 21 are composed of, for example, laser diodes. The oscillation wavelength of the semiconductor laser il, 21 of the recording horn optical system 10 is (λ -830 nm).The emission wavelength of the semiconductor laser 21 of the erasing optical system 20 is set to (λ-780~79 (,1n r
n) has been established.

In J and M raw yarn 10, semiconductor laser 11
The Rayleigh beam coming out from/out is collimated by the collimator lens 12.
'I'J)', then the circular 1x concave lens 13, the circularly convex/sl 4 kj]jl and the interplane beam splitter 15 1, '5 also JL, S wave component power 900111
Directed to Ij. 90' iJ=The directed laser beam is transformed into a circle by the quarter-wave plate 16 and then transformed into a diameter R of approximately 0.8 μm (I'z) by the 1/4 wavelength plate 16. The laser output of the half-eleven-body laser 11 is as high as about 8 mW for J, and for endogenous It is emitted with a low power of about 10 IW.

Note *7: IL) Nin J1, the power of hitting the unit score that was inserted in JiI Namikai Amane + 'I; 1 skin high i'',
, "j output laser beam R or 1';:+:dk I
irradiated with ul. As a result, the diameter of the disk 4° is 1' as shown in figure ε4A4.
The coldness of the delivery note and the Amorno Earth with low reflectivity from the surface caused a sharp blow in the morning. The information bits are now recorded in the memory space 43.

The reflected light from the TiSF 40 bends through the above-mentioned path Ilη, reaches the -direction beam splinter 15, and passes through the l/4 wave plate 17.
830n with bandpass filter 18.
Only m light is extracted and enters the original sensor 19 (l).

This band-pass filter 18 blocks the erasing light from the erasing optical system 20 so that it does not leak into the sensor 19 and disturb the focusing or tracking servo. The light received and emitted by the original sensor 19 is transmitted to
] Converted to your issue. With this, a part of the information signal is extracted at the time of internal transmission 4. A part of the signal collected by the optical sensor 19 is used to focus and track the aperture lens 30.
This serves as a drive signal for a servo actuator (not shown) that performs a groovy motion.

In the erasing optical system 20, the laser beam output point of the collimator lens 22] light: iQb t, with a diffraction grating 23 above
is installed. In this optical system 20, the laser beam emitted from the semiconductor laser 21 is made into parallel light by the collimator lens 22, and the laser beam is collimated by the collimator lens 22, and by the diffraction and interference effect of the light, it is converted into a spectrum I and a ram as shown in FIG. No J<
0°, ±1, which is emitted at a slight angle in every direction.
Next, ±2nd order, etc. are divided into multiple beanos. By taking the envelope of the diffracted light of this diffraction grating 23, the laser beam is formed into an elliptical shape. The S-wave component is 9 in this number of anti-nodes beams 1 and 15.
It is deflected by 0° and then deflected by a 1/47 skin plate 16 to form a deflection lens 30, J< ill and t, -
The ratio to the axis is approximately (I
The disc 40 is shaped like a bush 1 (thin 1.
1. S'! 4. ．． 3 i・-])・, 111. At the time of erasing, the output power of the semiconductor laser 'r21'zJ is set to about 10 mW.

To erase the information hint written on the film 13 (・, 1, times i: +1−+□”r −1” 2 i
Diffraction of 3 - [P○'Mi 1-1□1.
j1ul 'I-',j l↓I・)L<The prisoner's laser blast E goes to Teru・+t-s member), tsu, 2tshi:, 2 more meshirisubu 1maku・1:3 is the 4th The figure shows small 1-, -1・
), the eelgrass is kept cold with a crystallinity gradient of 1.
I-,,2,i,! ,,Tiger:Halp' Village/4-1
Blasphemy 4 Yoshiaki 4 is forced to transfer 1 no.

As described above, the record of the 1゛tj report 1t; issue, i'' + student - soil fc&shi is erased.Then, the above 1
(According to 4-sei, ■ To erase the 400 pieces of i4B that should be erased in one meal, and to immediately erase the signal. ■ To erase the recorded signal by preceding the erasing bee 1 and spot i. "It's 1 loaf," I wrote on No. 1d, so to speak.
- Become a writing skill. That is, erasure 11
: Kikyoe [Koni r'rib: becomes.

It is written that the α medium Tisfu 40 V,'L (ig 6 /J\ is made up of 11"4.
0], ←Plate 4] ('j1, laser incidence surface is 113'
I was kicked out once. Mirror (11), integrally molded with acrylic resin, treated with A4 resin, old 1
Anti, 11 no 1sho bow (sada) VCI right side 7 o o X
(No. Tuxt 1''-mu), 1:'MQ, 8μTl
l1:lj! , 11J's milky white tofunoku, 42 is a constant binona, and the concentric ma/ko is formed in a spiral shape. ) Nisaka 41 no 1. ) - Memory consisting of T e Ox on the arch side / i'i'IIQ 43 layers (recording h\j)
and the Ray@J absorption layer 44 are laminated on this one layer by the vapor deposition method 1/ζ sputtering method. Furthermore, a first layer 45 of resin is coated on top of this, and a two-layer structure is formed with this layer 45 placed inside.

The guide track 42 has a guide trunk function for the laser beam, and the depth of the groove is set to a depth corresponding to, for example, 1/8 wavelength of the laser beam, and the width of the groove is set to the width of the focus recorded by the laser beam. is set to the corresponding size.

With the above configuration, the diffraction signal from the guide trunk 42 is detected, the laser beam spot is tracked and servoed, and the reflectance change after recording is recorded.
It becomes possible to die.

The original head configured as described above is linearly driven in the disk radial direction by a drive mechanism consisting of a linear motor, a linear slide mechanism, etc., and accesses a desired recording trunk.

[Brief explanation of drawings]

The figure is a graph showing a heating-cooling model of a mechari thin film using a recording laser spot and an erasing laser spot irradiated onto the disk surface. The deviation of the laser spot for erasing the light beam from the recording track due to the configuration, 11:1' (Plan view to explain the state, Figure 3 is 1 system) Y:, Implementation of the head A block diagram showing an example, Fig. 4 is a graph showing the additive one-sea cooling model using a laser spot of a memory thin film at Hongen Akira, and Fig. 5 is an erasing laser obtained using a diffraction grating at Hontsuirocho. FIG. 6 is a sectional view of the original disk to which the present invention is applicable. 20...Erasing optical system, L...Optical axis, 23...Diffraction grating, 21...Semiconductor laser, 10...Recording and reproduction Optical system for use, 11...Semiconductor laser, 30...Aperture lens, 40...Disc, 43...Memory thin pattern, R... ... Laser spot for recording and reproduction, E... Laser spot for erasing. Patent applicant: NEC Home Electronics Figure 1 1 Min Figure 2 (a) (b) 3

Claims (1)

[Claims] (1) An optical system for recording/reproducing and erasing is formed by two semiconductor lasers, and the laser beam from the semiconductor V-laser is irradiated and focused on the disk surface by a single aperture lens to record/reproduce data.
In the original head for reproducing and erasing, a diffraction grating is disposed on the collimator output side on the optical axis of the erasing optical system, and the laser light from the semiconductor laser is expanded into an elliptical shape through the diffraction grating. An optical head characterized by: