SU1254549A1 - Device for reproducing-recording information on medium with magnetooptic recording layer - Google Patents

Description

Wash sequentially at intervals of time set by delay line 17, allows for the accumulation of heat in the area of the carrier 5, leading to a change in direction. The invention relates to the accumulation of information, in particular, optical recording information reproduction devices.

The purpose of the invention is to increase the reliability of reproduction of recording information.

FIG. Figure 1 shows the optical layout of the device; in fig. 2 - depolarization curves of linearly polarized light by a focusing lens and a correction element, as well as the resulting compensation curve.

The device contains source 1

ft

light, collimating lens 2, light beam prism - polarizer 3 lens 4, carrier 5 with a magneto-optical recording layer, correction element 6, beam splitter prism analyzer 7, beam splitter 8, photodetector 9 of the playback, first, second and third lenses 10, 11 and 12 photodetector 13, four-element photodetector 14, buffer storage unit 15, birefringent compensator 16 and line

17. Delays.

I. ..The device works as follows.

 When recording information, the low-power radiation of the light source 1, collected by the collimator 2, passes the beam-splitting prism-polarizer and is focused by the lens 4 on the recording layer of the moving magneto-optical medium 5. When the focused spot of light hits the illuminated surface of the carrier, then due to the small reflection coefficient of such a surface (, 002) there is practically no radiation in the reproduction path. The photodetector 13 produces a zero signal of its magnetization in an external magnetic field and recording information. An embodiment of the correction element I. 6 is provided. f-ly, 2 ill.

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cash When, due to carrier movement, light falls on one of the elements of the magneto-optical recording layer (reflection coefficient R "0.5), 5 photocurrent pulses appear at the output of the photoreceiver 13, which are used as sync pulses for the buffer unit 15. Buffer unit

1 performs conversion functions

 About incoming information to the pulses of control of the light source.

Consequently, when recording information in the form O, the power of the light source decreases and the temperature of the irradiated section of the magneto-optical information carrier 5 practically does not change, since the recording layer of the carrier is made in the form of equal-sized sections of small size separated by equal intervals.

At such temperatures, the magnetization reversal of this region does not occur. When recording information in the form of 1, under the action of a control signal, the radiation power of the light source is greatly increased, which leads to a significant increase in the temperature of the magneto-optical section

30 of the carrier 5 and the change in the direction of its magnetization vector in the external magnetic field on the opposite. As a result, information will be recorded on a mobile medium.

35 8 as the oppositely directed magnetic moments of individual elements (O or 1).

This constructive implementation of the magneto-optical recording

The 40-layer in the form of separate sections allows a significant reduction in the radiation power of the light source necessary to achieve the magnetization reversal temperature T0, as compared to a continuous layer of the same thickness. For

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31254549

diameter of a separate section d, ravat le ri from 5 di okla

foot diameter of the focused light spot,

d.

 4x.

R".

(one)

where P is the radiation power required to heat the continuous layer in the center of the focused spot to TQ; Xp is the thermal diffusivity of the layer; - pulse duration. From (1) it follows that with typical data dc, 1 μm, 2 cm / s, we obtain for ns -P, 0.1 Pp; for NS R. 0.025 P.

For the magneto-optical layer in the form of separate sections the increase in the duration of the recording impulse does not drive, and to increase the size of the recorded information bit in contrast to the case of a continuous magneto-optical layer. Such an embodiment of the layer reduces the requirements for the form of distribution of the focused light, i.e. allows the use of multimode laser beams, which also increases the reliability of the device. When reproducing information, the light source (laser) operates in a continuous mode with a constant output power of radiation, which is much less than the power required for recording. When the focused spot of light hits the luminous layer of the movable carrier 5, the reflected light signal on the photoreceiver 9 is almost zero. When a focused radiation hits a section with a magneto-optical layer, the power of the reflected radiation transmitted to the photodetector 9 of reproduction through the light-prism analyzer 7 and the first lens 10 grows more than three orders of magnitude and at the same time its plane of field is rotated by the magneto-optical Kerr effect. customization.

Depending on the state of magnetization of the region, i.e. from the recorded information O or 1, the angle of the angle is - c) i or -cC. The reflected light passes through the lens and with the help of a beam-splitting prism-polarizer 3 is directed to the light-splitting prism analyzer 7. When

As a result, the polarization selectivity in the reflection of the prism-polarizer 3 (the light of one polarization is reflected completely, and during the porpolarisation, 5 diacular polarization reflects about 6%) an increase in the angle "6" occurs. After the prism-polarizer 3, the light enters the prism-analyzer 7 through the correction element 6 from

10 two cylindrical concave lenses made of right- and left-handed crystalline quartz, the main optical axis of which is perpendicular to the flat surface of the lenses, and the concave five-sided surfaces are connected to the convex surfaces of the positive lenses of the same glass aperture made of glass, the refractive index of which is light frequency

The 20 emission of light source 1 is

refractive index for an ordinary ray in crystalline quartz.

The forming cylindrical surfaces of the lenses are mutually perpendicular and coincide with the directions on which the light is not depolarized by the focusing lens 4, i.e. with the direction parallel and Q perpendicular to the plane of oscillation of light after the prism-polarizer 3. When a beam of plane-polarized light passes through such lenses in the beam, the same decrease occurs in magnitude of the degree of linearity 5.

the polarization of light, as in object 4, but opposite in sign.

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The angle of rotation of the plane of oscillations in each of the four quadrants of the field is determined by the expression

D (p, her) k (TJr -p sinV - cos cf).

(2)

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where r p is the distance from the axis of the optical system to the point

observation;

g is the radius of curvature of the lenses; f running azimuth

angle of the observation point; k is the coefficient of optical rotation of the material. By selecting the radius of curvature of the lenses h for a selected type of focusing lens g, you can increase the degree of polarization in the radiation that passes through the lens twice for one

Of the two types of information (for example, for O), almost 100%.

FIG. Figure 2 shows the dependences of the maximum depolarization angle on the azimuthal angle c for one quadrant of a focusing five-lens lens with a focal length of 35 mm (curve q), the dependence of the depolarization by the cylindrical lenses of the correction element in mm, degree / mm (curve 5) and the resulting depolarization compensation curve (curve E).

It can be seen that while without a correction element, the background light signal Rd is 5 5 x 10 P on the order of the information signal, and with the introduction of a correction element it is possible to reduce it by almost three orders P, 5 X 10 P. The corrected reflected light beam goes further to the beam-splitting prism analyzer 7, which is set in such a way that its transmission plane is perpendicular to the plane of polarization of light when reflected from the section where the information is recorded as O. Therefore, when the information is recorded, The reproduction signal is equal to zero, and since the sync pulse from the photodetector 13 arrives in the bu. Fern block 15, indicates that the information signal must follow, then the buffer block generates a signal corresponding to 0. When the individual section is oppositely magnetized, a light signal of sin 2 ct arrives at the reproduction photo detector 9 and a signal corresponding to 1 is generated in the buffer block.

Both during recording and during reproduction, part of the reflected light radiation after the prism analyzer 7 hits the beam-splitting prism 8 and, after passing through the second lens 11, hits the four-element photo receiver 14, and through the third lens 12 - onto the photodetector 13. the four-element photodetector 14 enters the servo system for focusing and tracking the track (not shown).

The introduction of the photodetector 13 into the device and the proposed implementation of the information carrier make it possible to combine the information and sync path, as well as reduce the requirements for the stability of the linear speed of the carrier: relative to lens 4. Located between the squirrel prism analyzer 7 and the corrective element 6, the birefringent compensator 16 reduces elliptical polarization of light radiation, arising due to dichroism in reflection from magnetic films, to linear -. Since the dichroism effect for magnetic films can be comparable to the magneto-optical Kerr effect, the use of the compensator 16 nullifies the background illumination of the reproduction sensor 9 when playing the recorded information in the form O, and also increases the luminous flux incident on

this photodetector when playing back information recorded 1

When recording information, the introduction into the device of the delay line 17 and the execution of the light source in the form of a line of point sources (semiconductor lasers), which turn on sequentially at intervals specified by the delay line 17, determined by the time of movement of a separate section of the recording magneto-optical layer of the carrier 5 from the focus point of the light radiation one point source to another., allow to obtain the accumulation of heat in the area of the carrier, irradiated by the first, second, ..., and -m point sources light, which reduces the power requirement of a single light source. When playing information in this case, one point light source works.

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F o rmu l invention

Claims (3)

1. A device for reproducing the recording of information on a carrier with a magneto-optical recording layer containing an optically coupled light source, a collimating lens, a beam-splitting prism-polarizer, a lens, a beam-splitting prism analyzer, the first and second lenses, a photoreceiver of information reproduction and a four-element photodetector, and also a buffer memory, the first input of which is connected to the output of the photodetector of the information, and the output - to the input of the light source, characterized in that A record of information recording reliability, optically coupled corrective element and a birefringent compensator for transforming elliptic polarization into linear, as well as between the beam-distributing prism analyzer and the second lens optically interconnected with each other and the beam-splitting prism analyzer a splitter, a third lens and a photodetector, the output of which is connected to the second input of the buffer storage unit, a correction element and a birefringent compensator The op are located between the beam-splitting prism-floor by the p-isator and the prism-analyzer, while the recording layer of the information carrier is made in the form of equal-sized sections separated by equal intervals. 2. A device according to claim 1, characterized in that the correction element is made of two perpendicularly oriented cylindrical flat-concave lenses made of right- and left-rotating crystalline quartz, the main optical axis of which is perpendicular to the flat surface of the lenses, the concave surfaces of these lenses are connected to convex surfaces of positive lenses of the same geometric aperture, while the positive lenses are made of glass, the refractive index of which at the frequency of light emitted by the light source is equal to azatelyu prelo.mleni for ordinary ray in crystalline kvatse. ; 3. The device according to claim 1, l and - by the fact that, for the purpose of reduce energy costs when recording information, the light source is made in the form of a line of emitters, controlling the inputs of which are connected to the buffer storage unit through a delay line. d f, f.zpod Editor M. Petrov Compiled by S. Ilchuk Tehred L. Serdyukova Proofreader V. But ha Order 4727/56 Circulation 543 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushskal nab. 4/5 Production and printing company, Uzhgorod, st. Project, 4 Fi, 2