JPS5823336A - Recording information reproducing device - Google Patents

Abstract

PURPOSE:To prevent damage to be inflicted to a recording medium, by focusing reflected light from a recording medium to a photodetector via a lens and beam splitter provided between an emitted end of scanning spot and the recording medium and reproducing the image contactlessly. CONSTITUTION:A spot S polarized from an end plane 8 of a spot scanning element 1 is scanned between J1-K1 of the end plane and also scanned between J2-K2 of a recording medium 14 via a polarizer 11, a beam splitter 12 and a lens 13 and reflected. The reflected light is focused to K3-J3 at a conjugation point J through the lens 13 and the beam splitter 12 with Kerr rotation and further, focused as J4-K4 on a photodetector 17 via a photodetector 15 and a lens 16. The photodetector 15 passes through a specific polarized component only and discriminates recording information, i.e., direction of magnetic domain to conduct luminous flux. Thus, the magnetic storage information on a recording medium 14 can contactlessly be read out, allowing to prevent damage to be inflicted to the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recorded information reproducing apparatus for reproducing information from a recording medium on which information is recorded using a thin film waveguide type scanning element.

The present applicant has already proposed several recorded information reproducing devices using thin film waveguide type bright spot scanning elements. These proposals mainly employ a mechanism for reproducing information by bringing an information recording medium into contact with the end face of a bright spot scanning element. However, with these methods, there is a high risk of damage to the bright spot scanning element and the recording medium due to mechanical friction caused by the running of the recording medium.

SUMMARY OF THE INVENTION An object of the present invention is to provide a recorded information reproducing apparatus which reproduces information from a recording medium using a non-contact method and which causes no damage to the members. , in an apparatus that deflects and scans a light flux incident on a thin film waveguide, irradiates a recording medium having a magneto-optic effect with light emitted from a scanning element emitted from an end face of the thin film waveguide, and reproduces recorded information from the reflected light. a beam splitter disposed between the scanning element and the recording medium to split the light; an optical system for focusing the emitted light from the scanning element onto the recording medium; The present invention is characterized by comprising a light detection unit that receives the reflected light split by the beam splitter while distinguishing the polarization angles.

Conventionally, as a bright spot scanning device, a device is known in which a laser beam is deflected by a polygon rotating mirror, a galver mirror, or the like, and the beam is condensed by an f-θ lens. These devices have drawbacks such as an increase in the size of the device because each member is independent and requires a constant optical path spacing from each other.

A bright spot scanning device using a thin film waveguide was filed by applicant 1 as Japanese Patent Application No. 1983-92939, and compared to a scanning device using a conventional bulk-type Mul deflector, It is capable of high-speed scanning, wide deflection angle, and high-resolution scanning, and is also excellent in its small size and low cost.

FIG. 1 shows an embodiment of a bright spot scanning element 1, in which a thin film waveguide 3 with a high refractive index is formed on a piezoelectric substrate 2 made of, for example, L1NbO, lithium opate, placed on the X2 plane. ,
The light beam emitted from the semiconductor laser 4 installed at the end face of the waveguide 6 is guided directly into the waveguide 6. On the piezoelectric substrate 1, first and second thin film lenses 5.6 and a comb-teeth electrode 7 (hereinafter referred to as IDT) as a surface acoustic wave transducer are provided. The light beam L1 directly coupled from the semiconductor laser 4 to the thin film waveguide Sζ is converted into a parallel light beam by the first thin film lens 5. A beam of light that intersects with the surface acoustic wave W, which is generated by the piezoelectric effect of the IDT 7 and which is applied with a so-called Charbut signal whose frequency changes continuously, and which travels in the X direction, undergoes Bragg diffraction. The diffraction angle, that is, the deflection angle, changes depending on the pips of the surface acoustic wave W, or the frequency of the signal applied to the IDT 7. The diffracted light is a second thin film lens 6 arranged to form a bright spot S on the end surface 8 of the thin film waveguide 6.
The light is focused and bright spot scanning is performed on the end face 8.

The substrate 1 has a piezoelectric effect and is made of Li from the point of view of ultrasonic propagation efficiency.
Nb01 (7) Others 1: LITaO, (lithium tantalate), ZnO (zinc oxide), etc. can be considered. The waveguide 6 is made of LiNb0. For base 2, the TI is approximately 10
Diffusion at a high temperature of 00°C to form a substrate 2 to a thickness of 2 cm.

In addition, in the case of a 1iTaOs substrate, Nb or TI is similarly obtained (=diffused).The first and second thin film lenses 5
and 6 and 1. -C is l1li Quntsa* El
ect vol Q) 2-16, P129.1977
(by D, W, Vajcey &■an E, Wo
The mode index lens (
Mode 1ndex 1ens), ILt*Plug VVs (Luneburg 1ens), 'Geode 4') Klemme (geodesic 1ens), etc. are suitable. In particular, the latter two types of lenses 1 and 2 have a performance closer to the limit of rotation.

On the other hand, many materials have been known as information recording bodies to date. For example, materials such as photoresists and thermoplastics that record information through surface irregularities, and Li
There are materials such as NbOH crystal that record information by changes in internal refractive index, and so-called heat mode recording materials that are coated with a metal thin film and evaporate the thin film with the heat of a laser beam.

To reproduce information from these recording bodies, light is irradiated onto the recording body,
This is done by using a photodetector to detect changes in the amount of reflected or transmitted light due to interference or differences in reflectance.

Furthermore, research on information recording and reproduction using amorphous magnetic thin films has recently been actively conducted. This recording material is Gd
C0%GdF@, TbF, GdTbFe, etc. are well known, and are produced by sputtering on substrates, sheets, tapes, etc. The recording method is to first align the magnetic domains of the magnetic material in the same direction in the thickness direction, apply heat with a focused spot such as a laser beam to achieve an equilibrium state, and then reverse the direction of the magnetic domains using the surrounding magnetic field. This is done by

Reproduction utilizes rotation of the plane of polarization of reflected or transmitted light, which is well known as the magneto-optical effect, and utilizes changes in the amount of light caused by passing through an analyzer. The reproducing apparatus according to the present invention (the second uses the amorphous magnetic thin film described above as a recording medium will be explained below, but it is also effective for reproducing the other recording bodies described above).

FIG. 2 shows a basic configuration diagram of an information reproducing apparatus according to the present invention, and the configuration of the bright spot scanning element 1 is the same as that in FIG. 1. I
The light beam deflected by the surface acoustic wave W generated by the alternating current electric field applied to the DT 7 passes through the second thin film lens 6.
As a result, the light is focused as a bright spot S on the exit end face 8 of the scanning element 1. On the exit side of the exit end surface 8, a polarizer 11, a beam splitter 12, a first lens system 16, and a recording medium 14 running like a tape are arranged along the optical path. is the bright spot S of scanning element 1
has a geometrical positional relationship such that an image is formed on the recording medium 14 at a magnification of M1. Further, an analyzer 15, a second lens system 16, and a photodetector 17 are arranged on the reflective surface side of the beam splitter 12, that is, in a direction perpendicular to the optical path. A conjugate point T of the bright spot S formed by the first lens system 16 exists within this reflected optical path, and the second lens system 16 forms a point image M at the conjugate point T.

The image is formed on the photodetector 17 at twice the magnification.

Now, let J2 be the positions at both ends of the scanning width of the bright spot 8 scanned by the surface acoustic wave W, and let the interval be J2. As shown by the dotted line in FIG.
An image is formed as a bright spot Jh dog on the recording material 14 at twice the magnification,
The scanning width at this time, the interval between the bright spots J, is MIl
It is expressed as

The light flux emitted from the scanning element 1 as a bright spot S is linearly polarized by a polarizer 11, and then passes straight through a beam splitter 12.
The recording medium 14 is irradiated by the first lens system 13 .

The light reflected by the recording medium 14 is
As is well known as an effect, the plane of polarization is rotated by +θk or −θ with respect to the plane of polarization of the incident light beam, depending on the orientation of the magnetic domain recorded as information. Normally, if the thin film waveguide 6 is made as a TM or TI single mode waveguide, the light beam emitted from the waveguide 6 is considered to be linearly polarized light. Since the polarization state may be disturbed due to imperfections in the wave path 6, it is preferable to arrange a polarizer 11 immediately after the exit end face 8 of the scanning element 1 as shown in FIG. The reflected light that has undergone Kerr rotation passes through the first lens 13 again, is separated from the incident optical path by the beam splitter 12, and is reflected, passes through the analyzer 15, and is reflected at the conjugate point T by the second lens system 16. The point images J1, K, which are generated by the bright spot photodetector 17 are formed at a magnification of M8. By positioning the analyzer 15 at a predetermined position, which will be described later, it allows only a specific polarized light component to pass through, distinguishes the direction of the recorded information, or magnetic domain, and transmits a light beam to the photodetector 17.

Now, - set the information track length recorded on the recording body 14 to 1.
1. The scanning width at the exit end surface 8 of the bright spot scanning element 1 is l, the first
When the magnification of the lens system 1S is M, the following equation is satisfied.

Right=MIl ・・・・・・・・・・・・・・・・・・
...... (1) Reflected by the recording body 14,
The light beam separated by the beam splitter 12 forms a point image J, , K, which is the same size as the bright spot J, , K, at the conjugate point T in front of the second lens system 16 . The magnification of the first lens system 13 can be selected from an enlargement system and a reduction system depending on the scanning width of the recording area to be recorded on the recording medium 14 and the bright spot size. The length of the light receiving part of the photodetector 17 is 6, and the second lens system 16
Let M be the magnification for forming the point images J5, K as bright spots Ja, Ka on the light receiving section, then the following relationship is satisfied.

6≧341 ・・・・・・・・・・・・・・・・・・
・・・・・・・・・ (2) Normally, high-speed response photodetectors have a small light-receiving area like bin photodiodes, so
The bright spot scanning width j is often larger than that, and it is often effective that M, <1 satisfies equation (2). Of course, the scanning width j and the length l of the light receiving section! If l≦6, the second lens system 16 can be omitted without any problem as long as an image can be formed on the photodetector 17. The first lens system 13 is a double magnification system when the light beam is directed toward the recording medium 14,
Point images J,,K reflected from the recording medium 14.

If it forms, it is a reduced system. Therefore, in the above explanation, if M1≧1, the lens systems 16 and 16 can be considered to be combined to form a reduction system.

In the configuration shown in FIG. 2, the bright spot scanning element 1 has a TE0 mode type waveguide structure, and the polarization plane of the light beam emitted from such a waveguide 3 is P with respect to the beam splitter 12.
It enters as polarized light. The beam splitter 12 has polarization characteristics, has a high transmittance for incident P-polarized light, and therefore has a low reflectance for P-polarized light components.

Further, the reflectance of incident S-polarized light is high, and therefore the transmittance of 8 polarized light components is small. Figure 6 (
As shown in a), when the incident light beam is reflected by the recording body 14, it is rotated by +θK or −0 according to the direction of magnetization of the recording body 14. The light beam reflected from the recording medium 14 is
In Fig. 6, vectors are shown as vectors, and the polarization planes are rotated to +θK or -θ, respectively, and the beam splitter 1
The P-polarized light amplitude component a of the luminous flux for 2 is, assuming the amplitude of the reflected luminous flux as a, Town = Heat cOs (±θIL) ・・・・・・・・・・・・・・・
・・・・・・・・・(2) becomes 8 polarization amplitude components 1
．． is, a, = m 5ti (±θk)...... Song interval (4)
It is.

If the 8-component amplitude reflectance of the beam splitter 12 is 'as1 and the P component amplitude reflectance is r, the reflected light beam can be shown as shown in FIG. 3(b), and the amplitude of the P component is 'as1'.
The amplitude of P"Ps8 component is r, Jl. Therefore, the rotation angle ±9 from the incident polarization plane is -(±9) = 's "g/rv "P = (r
s/rp)m(±θK)・・・・・・・・・・・・・・・
......(5). As mentioned above; 2r, <
Since r, −(±ψ) > 1−(±θK) ・
・・・・・・・・・・・・Song...Song...(6), and the angle becomes larger due to θ. Generally, θ is about 0.4 degrees, and the analyzer 15 can detect such small differences in polarization angle.
In order to perform the separation, a high-performance and expensive analyzer with an extinction ratio of about 10-4 to 10-6 is required. Here r, = 9
5%, r = 5%, and θ = 0.4 degrees, from equation 6), ψ becomes 7.6 degrees, which yields an angular amplification of approximately 19 times, and the performance imposed on the analyzer 15 is relaxed. Ru. Therefore, the angle of the analyzer 15 can be set with sufficient accuracy.

FIG. 4 shows a modification of the configuration shown in FIG. 2, in which a polarizing element 20 such as a Glan Tiller, Glan Thomson, or polarizing beam splitter is installed between the scanning element 1 and the lens system 13, YIG, rare earth, doped glass, etc. A Faraday rotation element 21 for optical rotation is arranged. A photodetector 17 is arranged at the conjugate point T of the exit end surface 8 of the lens system 13 on the reflective surface side of the polarizing element 20.

The polarization direction of the light beam emitted from the scanning element 1 is shown in Fig. 5(a).
The transmission axis of the polarizing element 20 is arranged in the direction of A. Faraday rotation element 21 (: When a magnetic field is applied so that the plane of polarization rotates by /2 to θ, and a light beam passes through it, the plane of polarization rotates by /2 to θ as shown in the opening of (a). Recording body 14
As shown in FIG. 5(b), the plane of polarization of the light beam reflected from the mouth is further rotated from the state of the mouth to +θK or -θ,
There are eight or two states.

When the reflected light passes through the Faraday rotation element 21 again, the polarization plane of 2 and C is further rotated by θ/2, as shown in FIG.
C). In this case, it is clear that 2 is the same polarization direction as the incident polarization plane.

Of the light beams that have returned to the polarizing element 20 again, the light beam with the second polarization direction passes in the direction of the scanning element 1, as shown in FIG. Only the polarized light component E in the direction is reflected and directed toward the photodetector 17. Here, the second lens system 16 shown in FIG. 2 is not required when the scanning width l is smaller than the light receiving section of the photodetector 17.

Therefore, the photodetector 17 in FIG.
When the polarizing element 20 is rotated to +θK, there is a light beam that is reflected and separated from the polarizing element 20, and in other cases it becomes 0. According to this principle, magnetically recorded information can be reproduced.

The embodiment shown in FIG. 6 uses the scanning element 1 in which the second thin film lens 6 for imaging the bright spot S is removed from the embodiment shown in FIG. is arranged. In this case, the spread of the light beam emitted from the scanning element 1 is in the plane direction and in the vertical direction: ;If considered separately, the spread in the vertical direction (: Since the thickness of the waveguide 3 is approximately a number of am, , due to the influence of diffraction of the exit end face 8, the number of
It has a divergence angle of degrees. Furthermore, since the light beam is almost parallel in the horizontal direction, the focal point of the first lens system 13 is different in the horizontal and vertical directions. The reflected light beam, which is made into a parallel light beam in the overlapping direction by using the (/9) optical lens 60, is taken out by the beam splitter 12, and then sent to the analyzer 15 and the reduction lens system 16.
The light is guided to a photodetector 17 via a.

In this embodiment, by disposing the cylindrical lens 30, it is possible to omit the thin film lens 6 for focusing light in the scanning element 1. This advantage is small, for example 2~
The manufacturing technology of the thin film lens 6 for imaging a bright spot S of about 1 μm is quite difficult at the current stage, and it is possible to manufacture an inexpensive scanning element 1 by removing this thin film lens 6. is now possible.

As explained above, it has been explained that in the information reproducing apparatus according to the present invention, information can be reproduced by a combination of a thin film waveguide type scanning element and a normal lens system. This effect has the advantage that by employing the above arrangement, it is possible to avoid mechanical contact between the recording medium and the scanning element, and there is no damage to the members.

5

[Brief explanation of the drawing]

The drawings show an embodiment of the information reproducing device according to the present invention, and the first embodiment
The figure is a perspective view of the bright spot scanning element, FIG. 2 is a configuration diagram of the reproducing device, FIG. Configuration diagram, Figure 5(a)
, (b), (C), and (d) are explanatory diagrams of optical reading of the recorded state, FIG. 6(a) is another planar configuration diagram of the reproducing apparatus, and Φ) is a side configuration diagram. 1 is a scanning element, 2 is a substrate, 3 is a thin film waveguide, 4 is a semiconductor laser, 5.6 is a thin film lens, 7 is a comb-shaped electrode, 8 is an exit end face, 11 is a polarizer, and 12 is a beam splitter. , 13 and 16 are lens systems, 14 is a recording medium, 15 is an analyzer, 17 is a photodetector, 20 is a polarizing element, 21 is a Faraday rotation element, and 30 is a cylindrical lens. Patent applicant Canon Co., Ltd. No. 31!1 (C1) No. 41!1 (b) 15all

Claims (1)

[Claims] 1. The light flux incident on the film waveguide is deflected and scanned, and the light emitted from the scanning element is emitted from the end face of the waveguide, and the light emitted from the scanning element is irradiated onto a recording medium having a magnetic and optical effect, and recorded information is obtained from the reflected light. In an apparatus for reproducing a file, a beam splitter arranged between the scanning element and the recording medium splits the light, an optical system focuses the emitted light from the scanning element on the recording medium, and a beam splitter is arranged between the scanning element and the recording medium to form an image on the recording medium. 1. A recorded information reproducing apparatus, comprising: a light detection section that receives reflected light split by the beam splitter, with the information i being a polarization angle, while distinguishing the polarization angles. 2. The recorded information reproducing apparatus according to claim 1, wherein the optical system is a magnifying lens system. & The recorded information □ reproducing device according to claim 2, wherein a C2 reduction lens system is disposed between the beam splitter and the photodetector. 4. The recorded information reproducing apparatus according to claim 1, wherein an optical rotation mechanism is inserted between the beam splitter and the recording medium.