SU1739381A1 - Device for monitor information track of optical carrier - Google Patents

Abstract

The invention relates to the field of accumulation of information by optical means, in particular, to devices for tracking the information track of optical disk information carriers, and can be used in computing. To reduce the size of the device and increase its functional reliability in the radiation beam, -resolved from the information carrier 2, the separation element 6 of the angular spectrum of the radiation is installed. The separation element 6 is made in the form of a trihedral total internal reflection prism, which is installed between the beam splitter 5 and the photoreceivers 7 and 8 in the rear focal plane of the matching lens. When the track is shifted relative to the radiation beam, the differential amplifier 9 generates a correction signal to control the position of the mirror 3. 7 Il.

Description

The invention relates to the accumulation of information by optical means, in particular, to devices for tracking information track of optical disk information carriers, and can be used in computing.

The purpose of the invention is to reduce the size of the device while increasing its functional reliability.

FIG. 1 shows a diagram of the device; in fig. 2 - a fragment of the information track; in fig. 3 - the course of the beam of rays reflected from the information carrier; in fig. 4 shows the dependence of the reflection coefficients R and transmission T on the angle of incidence of the radiation on the element separating the angular spectrum of the radiation; in fig. 5 — angular reflection spectra; in fig. 6 — reproduction signal spectra; in fig. 7 is a prism of total internal reflection as an element of separation of the angular spectrum, radiation.

The device contains a lens 1 (Fig. 1), an information carrier 2, a movable mirror 3 with a drive 4 tracking the information track, a beam splitter 5, a separation element 6 for the angular emission spectrum, photodetectors 7 and 8, a differential amplifier 9, an information track 10 (Fig. 2), the spot 11 of the focused radiation 11, the edges 12 and 13 of which are outside the information track 10, the prism 14 (Fig. 7) of the total internal reflection and the beams 15 and 16 of the radiation arriving at the photodetectors 7 and 8.

The device works as follows.

When the amplitude of the information track is illuminated with 10 spotted focused laser radiation (in Fig. 1, the laser is not

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shown), a portion of the radiation, proportional to the reflection coefficient, is reflected from the information carrier 2 (Fig. 1). Since the reflection coefficient of the information track 10 (Fig. 2) is minimal, a part of the radiation power reflected from the track can be neglected. With the highest intensity, the radiation will be reflected from the areas of carriers 12 and 13 (Fig. 2). Due to the spatial separation in the focal plane of the micro-lens, these radiation beams will slightly diverge, as shown in FIG. 3. The radiation beams are transmitted (Fig. 1) through the lens 1 (micro lens), the movable mirror 3 reflects them to the beam splitter 5 and further to the separation element 6 of the angular emission spectrum, having reflection and transmission coefficients varying from the angle of incidence like graphs on FIG. four.

Since the angular spectrum separation element 6 is located in the rear focal plane of the matching lens (not shown), the intensity of the transmitted and reflected radiation depends on the mutual arrangement of the angular spectra of the information track image (Fig. 5) and the arrangement of the angular spectrum separation element 6 having the characteristic shown in FIG. 4. Consider their relative positions, shown in FIG. 4 and 5.

For the case of symmetrical arrangement of the information track relative to the reproduction radiation, we have a spectrum (Fig. 56), characterized by the same intensity distribution from regions 12 and 13 (Fig. 2). After the passage of the radiation and its reflection from the separation element 6 of the angular spectrum of the radiation, there is an intensity distribution spectrum shown in FIG. 66. Photodetectors 7 and 8 (Fig. 1) are lit in the same way. The differential amplifier 9 generates a zero control signal. When the reproduction radiation is shifted up (Fig. 2), the intensity distribution spectrum will have the form shown in

FIG. 5a. At the output of the separation element 6, there is a spectrum of radiation reflected and transmitted to the photoreceiver, the signal of which is shown in FIG. 6a. Intensity

the transmitted radiation will be greater than the intensity of the reflected radiation. At the output of the differential amplifier 9, a voltage appears that corrects the departure of the reproduction radiation from the track

by rotating the mirror 3 by driving the track of the information track 4 (Fig. 1).

A similar picture of the spectrum when the beam is shifted relative to the information track in the other direction - the graphs of FIG. 5c and bv

Fig. 7 shows an example of using a full prism 14 as an element of dividing the angular spectrum of the radiation of a prism 14.

internal reflection. The spectra (beams 15 and 16 of radiation) emanating from the edges 12 and 13 of the beam are spatially separated by the reflecting face of the prism 14 and are fed to photodetectors 7 and 8.

Claims (1)

Invention Formula A device for tracking an optical medium information track, comprising a sequentially installed beam splitter, a mirror with a tracking track for the information track, and a micro lens, as well as two photoreceivers optically connected to the beam splitter, the outputs of which are connected to the inputs of the differential amplifier, the output of which associated with the control input of the drive tracking the information track, characterized in that, in order to reduce the size of the device while increasing its functional reliability; entered into it an element for dividing the angular spectrum of radiation in a plane perpendicular to the image of the information track, installed between the beam splitter and photodetectors and made in the form of a trihedral total internal reflection prism; four 1U 12 x "five / l and and FL.2 Riga.1 ,, h g Fm.d (Rig 5 15 r h h FIG. 6 (Rig 7