DE2364143A1 - DEVICE FOR REPLAYING IMAGES AND SOUND SIGNALS - Google Patents

Description

The invention relates to an apparatus for reproducing picture content information acoustic information, which are recorded on an information storage track, which is on a disc-shaped information carriers and with "a light beam, for _e as a laser beam is scanned"

Devices have already been proposed which serve to transmit image content information or video signals and reproduce audio frequency information stored on an information carrier such as a disk or tape.

For example, the US, according to ₀ passing a light beam on the information carrier A. Patent 3 J81 086, and this light beam is reflected by two reflective surfaces. extend at an acute angle to each other, so that the light beam is divided into two light beams which are then directed to two photocells which generate signals by means of which a reproducing device is optically controlled along the recording track.

However, this known device is not suitable for ensuring the required accuracy in the control.

409828/0784

accomplish ^ since the position of the light beam 'opposite the on- ■ drawing trace determined by the movement of a housing a detector arrangement and the optical system are assigned O Furthermore, the usability is limited ' this known device on information carriers which are rotated during the playback process. '

Furthermore, in the year® ^ 972. . Japanese disclosed. Patent application 26 04-1 describes a device which has a grid "bai" box part and a light detector source to control the display device. In this device, a picture of some information memories is shown on the grid part ₉ and. then the light detector Selle is selected to be scanned recording track using -

Since one sue in this device control benqtigt a light spot ₉ of such a diameter that it is not only the abzutastend © track _s but also that their adjacent tracks covering ₉ is reproducible smallest wavelength considerably larger than 5 Mikrono Even if di © reproduced If track is selected, there is therefore a restriction regarding the smallest possible wavelength and therefore also the recording density _β

This is sure · gurücksuführeas that in the sea Vorriehtungen two reflective © mirrors are available ₃ bzvj _o that © is located in Haster in the beam path of the photo Selle, recognize & n to that track "Jeraer eigaea to di © ® @ Vorrichtongea Meht sua Playing Iafomationea .;, die ax hoti ©. ^ Density recorded 'sina ₅ S ₀ Bo on Spurea ax a width of 1 micron ₉ where the center distance is thus 2 microns so that a value γοη 3 results for the smallest wavelength of the recording Micron equals ο

Bi © disadvantages of this? let known devices decrease, if one considers the position of the light beam between the device generating the light beam and the

plate-shaped information carrier so precisely determined that the condensed light spot, which is caused by the light beam is generated, falls exactly on the reproduced track of the information carrier.

The invention is based on the object of creating a novel and improved playback device, which is suitable for reproducing information recorded with high density in which the light beam between the device for generating the light beam and the disc-shaped information carrier so precisely controlled is that the condensed light spot falls exactly on only one of the information storage tracks in which further Output signal in the form of a light beam contains a signal part which forms the puncture which the deviation between the position of the light spot and the information recording trace, without disturbing the recorded To effect information so that the light spot is exactly in the right position with respect to the recording track is brought to reproduce information recorded on the disc-shaped information carrier with high density are recorded with the output signal light beam also contains a signal for controlling the light spot, which is not an interference signal with the reproduced information is mixed, as well as a reproducing apparatus in which the light spot is secondarily controlled by vibration whose! frequency corresponds to the speed of the disc-shaped information carrier, so that the control area is further narrowed and the recording track is scanned with high fidelity.

The invention and advantageous details of the invention are described below with reference to schematic drawings explained in more detail using exemplary embodiments. It shows:

! "Fig. 1 shows a section through a plate-shaped Information carrier j

JFig. 2 is a perspective view of a plate-shaped Information carrier;

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Pig »3 an enlarged top view of a! '© ils von

M- a® side view of a device for reproducing B ^ Id- or Tonsignalenι

₀ 5 shows a perspective illustration of details of the optical system of a signal pickup;

6 is a schematic representation for illustrative purposes the movements of a light spot with respect to a recording track; , ·

FIG. 7 is a graph showing the waveform of the output signal of a first one shown in FIG Light detector element;

8 is a block diagram of an embodiment of an electrical circuit which constitutes the main controller for scanning a recording track with the help one. Forms a light spot?

9 shows a graphic representation of the intensity distribution in the case of a light beam or a laser beam;

Fig. 10 is a schematic representation of the relationship that exists between the. Angle of incidence with respect to a lens and the position of a light spot if the light beam is a parallel light beam.

11 shows a schematic illustration similar to FIG. 10, which applies in the event that the light beam is not directed parallel;

12 shows a perspective illustration of the beam path in a beam deflector to which an electrophotocrystal belongs, for example from ADP, KDP or the like exists;

1J shows a moving coil type beam deflector with a prism or mirror;

14 and 15 are circuit diagrams of integration circuits;

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16 shows the block diagram of an embodiment of a second main control device for the main light spot;

17 and 19 are graphical representations of the situation an auxiliary light spot opposite the information tracks;

Fig. 18 is a graph showing an output signal wave a second power detector element according to FIG. 5t

20 shows the block diagram of an auxiliary control device;

21 and 22 are graphic representations for illustration of the relative movements of a recording track and a light spot | and

23 shows an embodiment of an automatic focusing device.

In Fig. 1 to 5 is a disc-shaped information carrier 1 shown, on the image or sound information along concentrically arranged spiral Tracks 2 and 2 'are recorded.

The disc-shaped information carrier 1 has an upper side A and a lower side B _s, and information can be recorded on both sides. Side A also bears information, labeled B, about the content of the information recorded on side B. Correspondingly, side B bears details of the information recorded on side A, which are not shown. This information makes it easier for the user to arrange the information carrier in the correct way on a turntable that has yet to be written on, since, for example, the content of side B is indicated on side A. The information carrier 1 has a track 2 along which picture * · and / or {Pon information are recorded. According to FIG. 3, the information track 2 has a signal bit 5 to which a little reflective surface 3 and a highly reflective one

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Area 4 belong, ■ by means of which the 'desired information is recorded' «. The width 5a of the bit 5 is constant while the length ,, 5 "ö of the bits 5 and d @ _r% 5c distance between adjacent bits along the track 2 sindο variable Bit 5 preferably has a width of about 5 microns and a length iron at least 2 to 3 microns5 but could the length of bits 5 also be changed? the distance 5ά between adjacent track cut-offs is about 2 microns is driven, learner according Pig, 4 a light source 8 is provided, which eraeugt 9 ₉ which is passed through a first mirror 10 and a mirror 11 to a sweiten · pickup 12 a light beam "'. ■

The sensor 12 has a semitransparent mirror 17 (FIG. 5) which divides the light beam 9 into a main light beam 28 and - © in © η auxiliary si icht beam "29 according to Egg 5. First mirror 13 lets the main light beam 28 fall in a vertical direction onto the recording medium 1 here a first condenser 14 collects the main light beam 26 to form a main light spot 30 on the track 2 susaiamenj and a UaleBkeinriehtung 15 deflects the main light beam 29 within its limited angular range in order to the light spot 50 in the correct way gu leave the lane 2 fall? ein® automatically © lOkussiereinriehtiäng 16 serves the diameter of the light spot 30 to maintain a constant _s, and a second condenser 18 grasps the auxiliary light beam 29 so together ₉ that he generated an auxiliary light spot 31 further below the receiver includes 12, a first light detector 2M and a second light detector 25 _S, which serve to detect the first 3reflected light beam 22 and the second, respectively to convert the reflected light beam 23 into electrical signals \ a second main mirror 26 and an auxiliary mirror 27 guide the light beams 22 and 23 to the light detectors 24 and 25

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During operation, the pickup 12 is continuously moved in the correct manner in accordance with a division amount 5 & $ e rotation of the information carrier 1 according to FIG. The light beam 9 is fed to the sensor 12 in order to be divided into the two light beams 28 and 29 by the semi-transparent mirror 17. The main light beam 29 is reflected by the first mirror 13 and combined on the information carrier to form the main light spot 30 by the first condenser 14. The angle of incidence of the light beam 28 with respect to the condenser 14 can be changed with the aid of the deflection device connected upstream of the condenser 14. The auxiliary light beam 29 is combined by the second condenser 18 to form an auxiliary light spot 31 on the information carrier. The main light spot and the auxiliary light spot 31 are generated at such a distance from one another that they do not interfere with one another. The control of the main light spot 30 by the deflection device 15 is described below.

If the main light spot 30 is not exactly the right one "Lie on information lane 2 and take her moved back and forth opposite in the manner shown in FIG. 6, the output signal of the first light detector decreases 24 has the shape shown in FIG. 7 as a function of the reflected light beam 22. In Fig. 7 is the output signal 32 of the first light detector 24 shown, which is directed to the light beam 22, which from the highly reflective surface 4 of FIG is reflected, and also the output signal of the light detector 24 is shown, which is after the Directs light beam 22 which is reflected back from the weakly reflecting surface 3 * i.e. the bit 5j. the Image and dance information are expressed in a change of the output signal 32 along the time axis in FIGS do not appear in the output level along the output level axis in that appearing intermittently in FIG

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τ

Output signal 33 ° The level of output signal 33 is only varied by a deviation between different positions d @ s Liefetfleks 30 compared to information track 2 With the help of a filter it is broken down into an information part and the above-mentioned deviation part ₉ but this results in an unsatisfactory control effect

Figure "8 _s belonging guiding the main light spot along the information track 2 with auxiliary © the level of the output signal 33 ateuert * to the circuit of Fig. 8" shows the block diagram of an exemplary ■ form an electrical circuit for a first main control means includes first light detector circuit 34 - is a photodiode or the like. The output signal 33 is separated from the output signal of the first light detector circuit 34 - by a separating circuit 35 - in order then to be converted into the output signal corresponding to an envelope curve by a circuit 36 _9, for example an integration circuit, so that the tracking signal, which corresponds to the difference between the output signal given by the envelope curve and the basic output signal, which corresponds to a selected basic setting in which the main light spot 30 assumes the correct position on the information track 2; for this purpose a level setting circuit 37 is provided which this difference signal z is carried out.

The tracking signal obtained in this way is set is not an intermittent signal, and it plays an important part in stabilizing in a manner to be explained the deflection of the light spot.

According to FIG. 9, the distribution corresponds to the intensity of the Laj§er ray emerging from a round opening the Gaussian distribution curve, which theoretically

has an infinite length if a wavelength and a Overall output signal are constant.

If this laser beam is combined into a light spot, which falls on the information bit results the deviation value 1- at which the light spot differs from the Track deviates for a very small period of time as a function F of the value for the reflected beam as a tracking signal as follows:

- l (t) - ϊ

Herein v (t) "is a tracking signal at time t, and therefore can be a total deviation value L compared to the Express track 2 as follows?

L «Jl (t) dt
Hence L = Jf {v (t) j dt

Therefore, the light spot always falls on the. Trace if it is moved by the deflector according to the value of L.

If, according to Hg. 10, the angle of incidence of the light beam is changed so that it assumes the value θ, the light spot ^ & © r moves through the lens ©, which according to FIG. 10 has the focal length f, in the focal plane vm fe, if θ, is a very small angle.

If the light beam is not collimated, as shown in FIG. 11, the magnitude of the movement results of the light spot in the same manner as in Fig. 10, and the value (f + m) © is obtained. Thus the value for the movement of the light spot to the angle of incidence θ ' proportional when this angle is very small. Figs. 12 and 13 show the deflector 15 for effecting a Angular deflection. The device of Fig. 12 uses an electrophotocrystal 38 made, for example, of ADP, KDP, barium titanate, or potassium nitrate. In the deflection device of Fig. 13 is with a prism, a Mirror or the like worked.

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ΊΟ

In Figo 12 correspond to the arrows 8a ^ _s 38b and 38c to the X and Z ₉ T- ~ Aehsen the electrophotographic crystal 38o If a voltage V across the crystal in the direction of the Z-axis results in a ₉ applied to the lnd@ru.ng Refractive index corresponding to the following expression "

An «'n ₀ ³ r

Herein "n_ denotes the refractive index in the event that no spsnarag is applied, _s r an electro-optical constituent of the electropliotocrystals 58, and d the thickness of the crystal in the direction dsr Z

Thus mbm receives light beam la direction Werts.

daa Äbl @ akungswiak @ l ^ - des Sfoils 38a the following

dar 2L »Aelis © and Ii di @ Dick © in! the direction of the

Äfeleatengswiakel et. - ^ asiit ^ t proportional to the lnä. © r-iiBg of the created Spaanmago Bas? Electrophotocrystalline 3S sit down aas ar? @I prisaati @ n

© - aueii @ia

You TOllstiadig® "Gl®ictasg ffe the tension ¥ reads wi © follows:

f) 1 f @ S

- K L = k / f {v (t) J dt

Herein K 'is constant and equal to (h d) / (H η ^ r f)

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It should be noted that the voltage V ₃ which is applied to the crystal in order to obtain the movement value L of the light beam ^ is generated with the aid of the proximity signal v (t)

It is also useful to attach to the electrophotocrystal to apply a bias voltage Vo, the magnitude of which is given by the following Expression is given

F ^ v (t) J dt

Vo> J

This ensures that the crystal has a high sensitivity receives, and that a linear deflection is achieved, or that there is one connected to it Can simplify circuit.

It is appropriate to apply the bias in the direction in which the refractive index increases it is obvious to every person skilled in the art that one should use the function that applies to the tracking signal

through a proportional function with the form

Ko v (t)
or an approximation function of the shape

1 / (1 + v (t) ² )

replace and various computing circuits used for approximation can use.

These functions can be easily performed with the aid of the circuits shown schematically in FIGS integrate.

A second main control device is shown in block diagram form in FIG. 16; in this device the tracking signal v (t) is calculated by an arithmetic circuit 39 and then integrated by an I _n tegrationsschaltung 40th Then the tracking signal is fed to a proportional damping element 41, from which it is sent to the

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Electrophotocrystal 42 applied trirdo Fig »13 shows one Deflector with a prism or mirror 45 ° Die Task the correct angle of rotation of the prism or mirror 43 can be solved in different ways; in one case a change in the magnetic flux is used for this purpose, while in another arrangement piezoelectric components made of ceramic material are mechanically stressed «,"

FIG. 15 shows a deflection device 15 of the type indicated in FIG. 1 in the form of a Derhspmlsystem, which moves proportionally to changes in the current flowing through it. On the axis of rotation 44-44 · V a mirror or prism 43 is disposed ₉ that the reflecting surface or the incident surface is substantially parallel to the rotation axis "is placed a magnetic field at right angles to the axis of rotation by a magnet 45 to the effect , and when a current flows through the coil, the coil 46 generates a rotational force equal to the force of a spring 47. In the area of small angles of rotation, the angles of rotation are proportional to the changes in the current intensity and are given by the following expression!

cc '= P 1

Here <* - 'is the angle of rotation, which is half the angle of deflection is equivalent to; P is a constant in which the magnetic flux density, the number of turns of the coil, the spring constant and the like are taken into account. The angle of rotation can be expressed as follows?

; oc = (P / E) V

Here P denotes a constant, E the impedance of the Coil and V is the voltage applied to the coil.

Thus, the rotation angle can be easily converted into a voltage, and the light spot becomes the same Manner as described with reference to FIG. 12 with respect to the electrophotocrystal 38. In the present Case, however, corresponds to the deflection angle of the

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2364H3 " ¹⁵ ~

Laser beam twice the angle of rotation.

As with the electrophotocrystal, it is also necessary to apply a bias voltage, and in it Case, the bias is determined by the fact that Adjusts the angle of rotation against the force of the spring.

In the following, an auxiliary control device is described which is used to control the main light spot with the aid of the auxiliary light spot zn . If the second reflected light spot 31 falls on the second light detector element 25, this is obtained in FIG. ^{5 1 Xg;} 18, of which the eccentricity of the information track is 50 to 100 microns and the auxiliary light spot according to FIG. 17 moves over 50 to 100 tracks, of which? for the sake of simplicity only ten are shown. In FIG. 17, the reference number 48 designates a specific position of the auxiliary light spot 31 with respect to the information tracks 2. Here, the auxiliary light spot is fixed while the information tracks are moving. The distance between the points 49 and 49 'along the curve illustrated corresponds to one revolution of the information carrier. The information carrier swings outwards at 50 and inwards at 51, while at 52 it is on the curve,

FIG. 18 shows the output signal of the Xdchfcdetektorelement 25 for the case that the auxiliary light spot is in the position shown in FIG. evidently moved. If the speed of the information track in the circumferential _{belt is constant 3} the value differs from this along the time axis on the cable 50 or the part 51. In FIG. 18, the sections 53 and 54 correspond to the sections 50 and 52 in FIG Fig. 17..

To distinguish between them, © is used in frequency discriminator or a pulse width discriminator is used. With Using a discriminator of one kind or another one can easily distinguish between a part of 50 or 51 and one

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! 4143 "

Part of section 52 differentiate ₉ so aass can determine the PMase of the eccentricity of the information part,

Ia Figo 19 are the geometric locations of the auxiliary light spot al® curves _55 ^ ad 56 for a small Tbzvj _o a large value of the eccentricity shown Has the eccentricity @ in @ n large? / Ert ₉ takes the change in the output signal of the Liehtd @ tektor © l © ments along the time aehs © gu ₅ and toei a kl © in @ n W © 2? td © z · Escaentricity diminished see, di © lsd @ rung ₂ so that sas. dan Exentrisitätswer-t for di © 'XnfonaatAoiagspiÄE ¹ n with the help of the frequency- = discrisinat © ^ ® © ramittel- can «Maa © rhalt di® Phas © and.

whom the Ansgaagssigaal d @ ® Setektos © l © msnts d @ m Freguens

Mg ₉ 20 s @ igt the Blocksonaltibilä '© innr Hilf einriehtwng for the Hamptlicaffl © ek _o Bias © auxiliary © inrielitning regulates- di @ Seawingmagea the main light elements © ks

.der Söteiogiias @ a ait © ia @ i? .! ^ © qssns amgfiihrt, di © äas ¹ Uialaiifg © se & .windigk © it dos lafesaatiensteägers entspriekt «, ia ä, © ^ SieirfemBg 4 @@ - BadiB © d © s IsjföSHütionstEägers ait" Hilf® d @ g Aasgaagsüigaals LicKtd © t0kt @ r © lea © atis 25 © Ιβθγ liEirichtengg di® di® glei © ii @ a Sehwiagusgen- bei-

las Amsgaiigg © igaal & @ ii Mcatdstokto ^ elem ^ nts 2, ws © k üQn ! ^ © ^ «© asaislssiainator 57 saeä I ¹ Ig ₀ 20 and

60 ia. © in © ® OssillateQE ¹ 59 ₉

Beteiagmagsn ait siaos ¹ shs ¹ turn of the Infor ™

spiensonen Ereg.n®as C3i-a © ugt _o Ein Eoil

of the output signal of the frequency discriminator 5? a Ämplitudenregelsclialtung 61 sua Hegeln the amplitude of oscillator 59 ° sngef iia to A in Figure 5 pointed _o driver 62 "causes that _g d @ r condenser 14 mechanical Seh.wis |?. pmg © n together nit * of 15 Ablenlieinricktong i

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right angles to the track 2 ₉ ie in the direction of a radius, executes, corresponding to the output of the oscillator 59th

In addition, the driver 62 oscillates in accordance with the output signal of the first light detecting element 24. At of this oscillation, the amplitude and the phase are controlled by the oscillator 59 so that the oscillating movement of the main light spot corresponds to the movement of the information track 2 where the main light spot is located. Even if only the condenser 14 is set into mechanical vibrations, the driver 62 works properly, when the condenser 14 vibrates so that the light beam 28 falls through the condenser 14. This will also be achieved in that the output signal of the oscillator 59 is fed to the deflection device 15.

21 and 22, which are used to explain further details of the operation of the above-described Arrangement according to the invention, show the relevant movements in the direction of the vertical axis as well as the Movements in the circumferential direction along the horizontal axis.

The curve 63 applies to the movement of the information track in the direction of the radius of the information carrier, while curve 64 represents the movement of the main light spot controlled by the auxiliary control device will. If the auxiliary control device is not used, the control of the movement corresponding to the curve 64 must be effected by the deflection device 15. Therefore must the deflection device 15 the main light spot in comparison to change the distance between curves 63 and 64 within a range of 46 db to 52 db.

If the auxiliary control device is used, the control device for the main light spot, which is caused by the Deflector 15 is controlled to control the light spot within the distance between curves 63 and 64.

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3? Ig. 22 illustrates the distance between the curves and 64 “If the auxiliary control device is used, then the control device for the main light spot, which is controlled by the deflection device, the light spot control within the width of the information track so that this control can be carried out easily and accurately.

3? Ig. 23 shows an automatic focusing device, in which the driver 67 moves the condenser 14 in the direction of the optical axis with the aid of the output signal of a motion detector 66 actuated, which the movement of the information carrier in the vertical direction with the help of Detects change in the electrostatic capacity between the information carrier and a metal body 65.

In this way, the distance between the condenser 14 and the information carrier is kept constant.

Expectations;

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Claims (9)

2364H3 EXPECTATIONS "Device for reproducing picture or sound signals, characterized by a disc-shaped information carrier (1) with an information storage track (2, 2 '), on which an image or sound signal is recorded, means (16) for rotating the information carrier at a substantially constant speed, means (8) for generating and Emitting a light beam and a device (14) for focusing the light beam in the form of a light spot (30) on the information storage track, the means for focusing the light beam substantially is movable in the direction of a radius of the information carrier at a speed that per revolution of the Information carrier corresponds to the distance between two adjacent track sections, and wherein the light spot through a mechanical oscillation is controlled, the period of which corresponds to one revolution of the information carrier. 2. Device for reproducing video or audio signals, marked by a disc-shaped information carrier (1) with an information storage track (2, 2 ¹ ) on which a video or audio signal is recorded, a device (6) for rotating the information carrier at a substantially constant speed, a device (8) for generating and emitting a light beam, a device (14) for focusing the light beam which can be moved substantially in the direction of a radius of the information carrier at a speed, which corresponds to the distance between two adjacent sections of the information storage track with each revolution of the information carrier, wherein the focusing device focuses the light beam on the information 409828/0784 Focused storage track in the form of a light spot (30), the diameter of which is smaller than the distance between adjacent sections of the information storage track, wherein a light beam (22), which is reflected by the information carrier, intermittently, contains a signal "the deviation between the light spot and corresponds to the information storage track, a light detector element (24) 5 which converts the reflected light beam into an electrical signal, as well as a deflection device (15) for deflecting the light beam _$ which is actuated by the electrical signal * 3. Gate direction - for reproducing picture or «, ü'onsignalea, -marked by a plate-. shaped information carrier with an information storage track (2 ₉ 2 ') on which an image signal and a sound signal are recorded, a device (6 $ for rotating the information carrier at a substantially constant speed, a device (8) for generating , and emitting a light beam, a device (14) for focusing the light beam, which is movable essentially in the direction of a radius of the information carrier at a speed which corresponds to the distance between two adjacent sections of the information storage track for each revolution of the information carrier, wherein the focusing device focuses the light beam on the information storage track in the form of a light spot (30), the diameter of which is smaller than the distance between two adjacent sections of the information storage track, a light beam (22) reflected by the information carrier intermittently containing a signal indicating the deviation between de s light spot and the information storage track corresponds, a light detector element ^ (24-) for converting the reflected light beam into an electrical signal, a device (15) for deflecting the light beam, which is actuated by the electrical © signal, the light spot by a mechanical vibration is controlled, whose period each 409828/0784 corresponds to one revolution of the information carrier. 4. Apparatus according to claim 1, characterized g e k e η η ze ichnet that the mechanical vibration for controlling of the light spot (30) is generated with the aid of an auxiliary light beam (29, 23). 5 · Device according to claim 3 »characterized in that the mechanical vibration for controlling of the light spot (30) with. With the help of an auxiliary light beam (29, 23) is generated. 6. Apparatus according to claim 1, characterized in that the plate-shaped information carrier 1. Has a top and a bottom on which Allow information to be recorded that on the upper side an indication of the content of the recorded on the lower side Information is present and that on the bottom there is an indication of what is recorded on the top Information is available. 7. Apparatus according to claim 2, characterized in that the plate-shaped information carrier has a top and a bottom on which there is information let record that on "the upper side an indication of the content of the recorded on the lower side Information is present and that on the bottom there is an indication of what is recorded on the top Information is available. 8. Apparatus according to claim 3 * characterized in that the plate-shaped information carrier has an upper text and a lower side, on which information can be recorded, that on the upper side an indication of the content of the information recorded on the subpage is available and that on the On the bottom side there is an indication of the content of the information recorded on the top side. 409828/0784 2384143 9. Apparatus according to claim 4-, characterized in that g e k e η η draw t that the disc-shaped information carrier has a top and a bottom on which information can be recorded that on the top a Indication of the content of the information recorded on the subpage is present, and that on the subpage there is an indication of the content of the information recorded on the upper side. 10 _o Device according to claim 5, characterized in that the plate-shaped information carrier has a top and a bottom on which information can be recorded, that on the top there is an indication of the content of the information recorded on the bottom, and that on the On the bottom side there is an indication of the content of the information recorded on the top side. The patent attorney: 409828/078