RU191298U1 - Glass Media Reader - Google Patents

Abstract

The invention relates to the field of reading information using optical means, in particular to a device for reading data recorded on a glass carrier by inducing an anisotropic refractive index. The device contains a laser radiation source, a quarter-wave plate, a focusing lens, and also after the Disk on the same optical axis: a confocal lens, a differential polarization analyzer, and a control unit, which makes it possible to control the focus of the reading laser beam, sequentially placed before the optical Glass Disc on the same optical axis . Between the laser radiation source of the reading beam and the quarter-wave plate, a three-link Wollaston prism is introduced, which divides the laser reading beam into eight beams along the angle. An eight-channel optoelectronic unit is used as a differential polarization analyzer. The information processing unit provides decoding of each of the eight reading beams in real time. The device allows to increase the speed of reading information. 3 ill.

Description

The invention relates to the field of reading information using optical means, in particular, to a device for reading data recorded on a glass carrier by inducing an anisotropic refractive index.

The problem of creating durable media that is resistant to various environmental influences: extreme climatic conditions, elevated temperature, strong electromagnetic fields, ultraviolet radiation, radiation, cosmic rays and not subject to natural aging, has become very urgent today in connection with the recent years the tendency to informatization of all spheres of human life and activity, mass transfer of various types of data, including archival funds, to digital media As a result, the rapid growth of digital information requiring long-term storage. Quartz and a number of other oxide glasses allow multilayer recording of information with multilevel coding, which can be stored indefinitely and is extremely resistant to these factors.

The method of optical recording and reading of data with multilevel coding is based on the formation of birefringent pits in the glass volume - nanogrids. Nano-gratings are a special type of modification in quartz and some other glasses, which is formed in the glass volume under the influence of femtosecond (PS) laser pulses and is optically characterized by the presence of birefringence of the shape, the parameters of which (phase shift arising between the components of the light passing through the nano-grating with different polarization, and the orientation of the slow birefringence axis) are determined by the parameters of the recording laser beam [Y. Shimotsuma, P.G. Kazansky, Q. Jiarong, and K. Hirao. Self-organized nanogratings in glass irradiated by ultrashort light pulses. Phys. Rev. Lett. 91, 247405 (2003)]. A feature of their use in optical memory technology is the ability to encode multiple bits into one nanogrid and high thermal stability up to 1100 ° C [J. Zhang, M. Gecevicius, M. Beresna, P.G. Kazansky. Seemingly unlimited lifetime data storage in nanostructured glass. Phys. Rev. Lett. 112, 033901 (2014)]. To read the information recorded in the nanogratings, birefringence analyzers are used, based on the measurement of the polarization of the radiation transmitted through the optical carrier.

Known schemes of the polarization analyzer with registration of transmitted radiation by a single photodetector, followed by processing and outputting information to a personal computer [Technical description for the polarization analyzer PAX5710 / PAX5720 from Thorlabs GmbH, 2008]. In such systems, an algorithm is implemented for sequentially measuring the polarization components of the intensity of the analyzed radiation, which determines the long duration of the measurement process, which prevents the reading of information in real time.

The main device for reading information encoded using nanogrids is an optical microscope with an attachment for the quantitative measurement of birefringence [J. Zhang, M. Gecevicius, M. Beresna, P.G. Kazansky. Seemingly unlimited lifetime data storage in nanostructured glass. Phys. Rev. Lett. 112, 033901 (2014)], which is taken as a prototype. The prototype consists of a universal phase compensator, including two variable moderators on liquid crystals, which are controlled by applying a given voltage, a linear polarizer and a CCD matrix, used as a registrar of transmitted radiation intensity, and allows you to accurately determine the values of the phase shift and the orientation angle of the slow axis [SB Mehta, M. Shribak, R. Oldenbourg. "Polarized light imaging of birefringence and diattenuation at high resolution and high sensitivity." Journal of Optics 2013, V.15, No.9, P. 094007]. The main disadvantages of the prototype are the high cost of manufacture due to the presence of liquid crystal phase compensators, a highly sensitive CCD matrix and the need for an optical microscope of the research class, as well as a low reading speed due to the fact that for the analysis of birefringence, several images of each section of the formed array of nanogrids are sequentially shot at several orientations of the phase compensator, and based on the obtained images birefringence parameters are calculated. Moreover, the size of the site is limited by the field of view of the microscope, and moving between adjacent sites is carried out in a step-by-step mode and requires the participation of the operator. Thus, it is impossible to talk about the reading process in real time, and the estimation of the reading speed when analyzing birefringence in 1 time from an array of pits in the field of view of a high-aperture lens (which allows you to confidently resolve recorded pits, for example, a 40x Olympus UplanFLN lens with numerical aperture 0.75), the size determined from the field number ratio (22 mm) / magnification (40 times), with a distance between pits of 1.5, gives an upper value of ~ 50 KB / s when recording 3 bits in 1 pit.

The objective of this utility model is to read information recorded in birefringent pits in real time, to achieve a read speed of 100 Mbit / s and higher while simplifying the design of the polarization analyzer.

The task is achieved by an information reading device, characterized in that for reading information recorded in the form of induced anisotropy of the refractive index in a multilayer optical disk made of glass (hereinafter referred to as the Disk), they are used sequentially placed up to the Disk on one optical axis: a laser radiation source with a wavelength AL, a quarter-wave plate, a focusing lens, and also after the Disk on the same optical axis: a confocal lens, a differential polarization analyzer, and a control unit providing the ability to control the focus of the reading laser beam, and a three-link Wollaston prism is introduced between the laser source of the reading beam and the quarter-wave plate, dividing the laser reading beam into eight rays by the angle, using an eight-channel optoelectronic unit as a polarization differential analyzer, and the information processing unit provides real-time decoding of each of the eight reading beams.

The present utility model is illustrated by figures 1-3.

FIG. 1. Schematic of an eight-channel reader.

FIG. 2. Arrangement of eight read rays in the information layer of a glass disk.

FIG. 3. The oscillogram of the actual output signals at the polarization photodetector.

Below are the designations of the positions in the figures.

1 - Semiconductor laser.

2 - Prism Wollaston: the first link.

3 - Prism Wollaston second and third links.

4 - Quarter wave plate.

5 - Focusing lens.

6 - Optical glass disk on a rotating platform.

7 - Collimating lens.

8 - Beam-splitting pentaprism.

9, 10 - photodetector lenses.

11, 12, 13, 14 — eight-channel polarization photodetectors.

15 - Information processing unit.

16 - The proportional-integral-differentiating (PID) controller for controlling the focusing lens of the track tracking system (focus).

In FIG. 1 is an optical diagram of an eight-channel reader. The collimated radiation of a semiconductor laser 1 with a wavelength of 650 ± 10 nm, which replaces the illuminator unit and the microscope condenser and simplifies the design of the device, passes through an eight-beam splitter unit, which consists of a combined Wollaston prism 2, 3, dividing the read beam by the polarization angle by eight rays, and a quarter-wave phase plate 4. Next, eight circularly polarized rays are focused by the lens 5 onto the information layer of the glass optical disk on a rotating platform 6, with each beam focusing is recorded on its recording track (Fig. 2). Lens 7 collects the transmitted radiation of eight rays that carry information in an altered polarization state, and sends it to the eight-channel block of a differential polarization analyzer, consisting of pentaprism 8, focusing lenses 9, 10 and eight-channel polarization photodetectors 11, 12, 13, 14. Information processing unit 15 decodes the information and extracts the analog track tracking error signal and controls the position of the focusing 5 and collimating 7 lenses through the PID controller 16.

Example 1

On the basis of the optical scheme shown in Fig. 1, a setup for reading information recorded in the volume of quartz glass along a spiral path at a depth of 600 μm with a distance between birefringent pits of 3 μm was created. Each pit contains 2 bits of information. In the process of reading, the speed of rotation of the optical disk made of glass is up to 15 r / s, tracking and retention of the track with birefringent pits is carried out, and the amplitudes of the output signals at the photodetectors for each pit in real time are analyzed. Using the waveform of the actual output signals at the polarization receiver (Fig. 3), the time required to read 1 pit and determined as ~ 150 ns was estimated. Thus, the created eight-channel reader provides the reading speed (V), determined from the ratio: eight channels are multiplied by two bits in a pit and multiplied by a factor equal to the ratio of one second to the reading duration of one pit of approximately one hundred and fifty nanoseconds, as a result we get

V = 8 * 2 * (1 / (~ 150 * 10 ^-9 )) = ~ 106.7 [Mbps].

The result of the installation for reading information according to example 1 confirmed the achievement of the speed of reading information set in the task of this utility model.

Claims (1)

An information reading device, characterized in that for reading information recorded in the form of induced anisotropy of the refractive index in a multilayer optical disc made of glass, hereinafter referred to as the Disc, one uses sequentially placed up to the Disc on one optical axis: a laser radiation source with a wavelength of λ1, a quarter-wave plate focusing lens, as well as after the Disk on the same optical axis: a confocal lens, a differential polarization analyzer and a control unit providing the ability to control the focus of the reading laser beam, and a three-link Wollaston prism is introduced between the laser source of the reading beam and the quarter-wave plate, dividing the laser reading beam into eight rays by the angle, using an eight-channel optoelectronic unit as a polarization differential analyzer, and the information processing unit provides decoding of each eight reading beams in real time.

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