DE2228292C3 - Method and device for storing data on a light-sensitive flat recording medium - Google Patents

Description

35

generate a discrete output beam each recording pass, the output beams to recover the recorded data through photo-electrical conversion are acquired sequentially.

4. The method according to any one of claims 1 to 3, characterized in that the readout light beam is successively directed at the recording medium at such angles that each

The invention relates to a method of the type mentioned in the preamble of claim 1 above. Such a method has already been proposed (DT-PS 20 56 025), in which on the photosensitive flat recording medium in itself

The carrier runs over this, in order to extend for 40 in the direction of movement of the record carrier continuous one-dimensional hologram is recorded. The radiation beam and the reference beams are derived from a pulsed source of coherent light to produce a partial beam to avoid smearing of the interference pattern exposed by them on the recording medium. The duration of the pulses must be so short that the recording medium and the interference field during the pulse duration by at most a small amount

wcils the 50 fractions of the smallest occurring interference used in the storage of a beam successively changed angles move past each other. at correspond. the proposed method is, in particular

5. The method according to any one of claims 1 to 3, in a tape-shaped recording medium for characterized in that each of the one dis- the handling and mechanical movement of the The required width of the output 55 recording medium corresponding to the corresponding output grid frequency is not radiated given to a separate detector, so that the storage density with respect to the and the electrical output signals of the surface of the recording medium is low. Despite the Detectors in recovering the pulsation of the two beams is the bandwidth that recorded data are commutated. can be used for recording, vcr-

6. Device for carrying out the comparatively small; the PuIsfahrcns, which cannot be increased at will according to one of claims 1 to 5, with frequency must be twice as large as the upper one a source of coherent light, a beam cut-off frequency of the data to be recorded. Also divider for dividing one emitted from the source - the signal-to-noise ratio is likely to be worse. th light beam in the exposure beam and further is a method for generating at least one reference beam, a modula- 65 two-dimensional single hologramnias, the one-gate are assigned to modulate one of the beams in dependent images of a film, known (DT-ability of the data to be recorded, means OS 20 84 122), in which with the help of an exposure to Aligning the beams on the recording light beam and a reference beam coherent

3 4

Be light on a tape-shaped recording medium ble sound recording. When playing Color-coded phases corresponding to the individual images - the partial holograms are exposed on the Fraunhofer-type recording holograms are also completely illuminated in strips, while the record carrier is moving step by step because of the discontinuous movements of the record will. Reading out the two-dimensional 5 information carrier is a complicated and precise pre-individual hologram takes place by means of a corresponding push mechanism. The storage density on clearing. the recording medium is small. Neither with the

From US-PS 35 60 071 a method for recording is still running during playback

Storing data on a photosensitive beam in one direction across the recording

Record carrier known, in which for storage 10 carriers which are transverse to the direction of movement of the recorder

of different holographic images two-drawing carrier extends.

or three-dimensional objects of the reference Furthermore, it is known from DT-AS 12 80 581, beam at different angles with respect to the one onto a photosensitive flat recording exposure beam light beam incident on the recording medium as a function of the is steered so that the individual holograms can be modulated from the data to be recorded, building interference fields with different grating frequencies exhibit. During exposure, the light emitted from the source is attached to physical bar recording media not moved. It is possible to diffract gratings with different grating frequencies, that there are several holograms on the record. The different bit positions are used as bits cover funding carriers completely; on the other hand it is used and 20 of these different diffraction gratings but it is also possible that the diffraction images of these diffraction gratings are used between the individual diffraction patterns exposures of the holograms of the two- or three- readout of the information when illuminating the two-dimensional Objects of the recording media. It step by step is moved, so that the individual delt here is not a holographic VerHologram partially overlap. Go to save 25.

of digital data on a light-sensitive Finally, from DT-PS 8 64 924 a flattening recording medium is known as two-way punch cards for photographic recording and re-dimensional objects for the reproduction of sound processes, in which a recording medium is also used when the recording medium is stationary Record used light beam on a warning beam and reference beam exposed. In order to avoid a light-sensitive recording medium with a loss of information from the overlapping component transversely to its direction of movement on holograms of different punched cards, there is an extremely complicated adjustment device that is used depending on the intensity of the one precise adjustment of the punch cards sound processes modulated lights on partial circular paths before exposure. Here, too, it is a question of a movement that moves radially with respect to the wheel, always leading completely or partially over the light-sensitive recording medium. Since the lapping of two-dimensional delts produced by individual exposure while the record carrier is not moving is a holographic process, the record carrier is moved along the partial holograms, so that the known process does not orbit depending on the fluctuations for recording digital data with a higher 40 blackened by the light source.
Bandwidth is suitable. It is the object of the present invention,

From DT-OS 14 97 922 a method for a method for storing data on a

Recording and playback of moving two-dimensional, light-sensitive, flat recording media from

sional pictures known, in which the pictures in the form of the type mentioned above, in which

of holograms of the individual images on a recording 45 analog or digital data with higher bandwidths

signatures are saved; the holograms and high storage density at much lower

mechanical requirements and high noise

stripe spacing during playback can be recorded,

shaped contiguous two-dimensional This task is carried out by the in the characteristic of the

Nalen partial holograms composed, wherein the 50 preceding claim 1 listed features

Strip width is so small that solved between the front. The recording medium is saved when it is saved

and the trailing edge of the strip only one of the data is not incremented at each time

negligible perspective shift occurs. to record a single hologram while the carrier is at rest

Between the exposures of the individual partial but with constant relative movement of the rays unc

holograms the recording medium is relative to 55 of the recording medium, the rays run into one

the rays advanced discontinuously so that backward direction over the recording medium, which quci

other then completely identical partial holograms to the direction of movement of the recording medium

on one of the individual images to be recorded. It will diminish with each pass

corresponding image length are strung together. sional hologram instead of focussed points

There is no exposure during the shift. 60 generated on the recording medium. After everyone

It is also possible that the holograms will pass the angle that one of the beams

several individual images are superimposed when included with the plane of the recording medium

the recording changed a different one for each hologram, so that in the following pass on

The position of the reference beam and the exposure beam for drawing the hologram has a different filter frequency

is selected and has the position of 65 during playback. The signal to noise ratio of the saved file

Playback beam changed in a corresponding manner is therefore increased significantly.

will. The recording medium for the holograms There is no need to worry about who

can at the same time bear a continuously diminishing effect that the individual holograms do not overlap

2% 28 292

cover; rather it is even preferably provided that the playback is disturbed by noise,
that the successively recorded holograms

partially overlap, since then on a particularly special embodiment of the device for the transmitted length of the recording medium in implementation of the method according to the invention,
Seen in the direction of travel, even more information is available. The following are exemplary embodiments of Speig. A crosstalk between the read-out and read-out devices can be described in more detail using the drawing of the individual one-dimensional holograms. It shows
not done because because of the different grid F i g. 1 a schematic representation of the storage frequencies of the individual runs in the re-process with one exposure beam and several would give the io reference rays assigned to the individual runs,

Information can be securely separated. Since the F i g. Figure 2 is a side view of the record carrier

Individuals to be considered as a Fourier transformation for the representation of two overlapping one-dimensional holograms are spatially invariant dimensional holograms, which are assigned to different and thus the position of the to be reconciled during reading,
perturbing light field regardless of the hori- 15 F i g. 3 a schematic representation of the readout mounting position of the holograms on the recording process,

is carrier, can in this way possibly during the F i g. 4 is a side view of a device for

Recording of lateral displacements that occur Storage is carried out,
the one-dimensional holograms are compensated for

the. Such shifts can in particular 20 Fig. 4,

due to erratic F i g that cannot always be prevented. 6 is a schematic representation of various

Changes in the movement of the recording medium reference beams,

caused, but also by disturbances F i g. 7 a representation of the positions of with

HoIowie recorded at the device for carrying out the method, different grid frequencies it is described below. 35 grams and the reading light beam,

Dust or scratches the size of a resolution F i g. 8 shows a side view of a first point of execution on the recording medium, not in the form of a read-out device;
to a destruction of information. F i g. 9 a plan view of the readout device

Further sub-claims relate to particular F ig. Sund

other embodiments of the invention. FIG. 10 shows a second embodiment of an extension. reading device.

However, the invention also relates to a device in FIG. 1 is shown schematically how

to carry out the method, with a source different reference beams 1, 2 and 3 with an in coherent light, a beam splitter for splitting depending on the data to be stored modueines from the source radiated light beam in the 35 lated exposure beam 26 can interact. Exposure light beam and at least one reference beam. The reference beams and the exposure beam

strahl, a modulator for modulating one of the light-sensitive flat recording rays as a function of the voltage carrier 20 to be recorded, the data from an unwinding reel 22, Means for directing the beams onto and onto a reel spool 24. The one-record carrier and a device for individual reference beams 1, 2 and 3 in FIG. 1 across movement of the recording medium. to the direction of movement of the recording medium 20

According to the invention it is provided that in the radiation over the same, ie perpendicular to the plane of the drawing. In the case of a rotary body with several discrete under each pass, a one-dimensional hoop of different angles with respect to the axis of rotation and grams arises, as shown in FIG. 2 is shown schematically with axial positions that differ from one another. The hologram assigned to pass 1 is incorporated, and it has a lower grating frequency than the HoIo recording medium so with respect to the rotating body of pass 2, which can be moved relative to the hoopers by the movement device, grams of pass 1 slightly offset arranged that one after the other the holograms are different, but still parts of the grating frequency associated with pass 1 are generated or read out over 50 neten holograms. Upon closer inspection. The reflection formed on the rotating body must be due to the constant relative movement of the surfaces of the rotating body, in their angle between the rays and the recording medium with respect to the axis of rotation of the rotating body, a slight inclination of the one-dimensional covering a certain tolerance range, since the holograms result as they are in the enlarged illustration of these angular deviations in accordance with FIG. 7 has been taken into account. Due to the peculiarity of the holographic information grams during the recording and when reading out and the different grating frequencies of the reading in because of the aforementioned spatial individual passes, the partial overlap does not lead to errors. Even small ones due to the individual holograms no crosstalk,
the bearing play of the rotating body caused 60 With reference to FIGS. 3, the reading out of the ge errors should now be possible for this reason in the case of the stored data according to the principle shown. In Fig.3 is the exposed and developed. Although the requirements for the mechanical recording medium with the reference number 30 are indicative of precision in the case of the Vernet according to the invention. If a coherent read-out light travel is not very large when reading out, it is possible to repeatedly use the 65 beam 27 essentially transversely to the method according to the invention and the device direction of movement of the recording medium 30 over data in analog or digital form with one of these, for each recording -Record bandwidth up to 400 MHz without running under different reference beam angles

ei h-

rs i- π

Output liaisons 32, 34 and 36, respectively, are generated, each The beam passes through a lens 38 and on the side of the lens 38 facing away from the recording medium falls on a pholodiector 40, 42 and 44, respectively. the Output voltages of the photodetectors are provided by a suitable commutator, not shown sequentially queried, whereby the stored data can be reconstructed.

A device for storing data on the light-sensitive recording medium 20 is now shown in FIGS. A laser beam 50 is directed onto a beam splitter 51 , which splits the laser beam 50 into a reference beam 52 and the exposure beam 26. A modulator 56 is switched into the path of the exposure beam 26 in order to modulate the exposure beam 26 with the data to be stored. The modulator 56 can use a transverse field, preferably KD 'p. The exposure beam 26 is switched on for each digital pulse or is continuously modulated for an analog signal. The reference beam 52 and the exposure beam 26 are guided through suitable lens-reflector arrangements 60 and onto a rotating body 62 (polygon mirror) with several discrete reflective surfaces a, />, c arranged at different angles with respect to the axis of rotation A and with mutually softening axial angles. . . steered. The rotating body 62 is divided into two parts by a plane extending perpendicular to its axis of rotation A , on one part the surfaces a, b, c arranged at different angles with respect to the axis of rotation. . . for reflecting the reference beam 52 and on the other part reflecting surfaces 64 are arranged at the same angles with respect to the axis of rotation A for reflecting the exposure beam 26, in FIG. 4 the surfaces a, b, c are arranged on the upper part and the surfaces 64 on the lower part. Accordingly, when the rotating body 62 rotates, the reference beam 52 strikes the upper surfaces a, b, c in a different axial position and is reflected in this position. The lower reflective surfaces 64 always reflect the exposure beam 26 at the same angle, as shown in FIGS. 4 and 6 can be seen.

The angles of the reflective striking surfaces are set in such a way that they direct the reference beam 52 onto the exposure beam 26 on the recording medium 20 at different angular positions 1, 2 and 3, respectively. Since the reference beam assumes different angles with respect to the recording medium 30 and the light beam 26, a one-dimensional hologram with a different grating frequency is created for each pair of the associated reflective surfaces on the upper part and the lower part of the rotating body with each passage of the beams over the recording medium generated. The reference beam 52 and the exposure beam 26 are reflected by the rotating rotating body 62 and pass through a converging lens 70 and a cylindrical lens 72 so that they are focused on the recording medium 20 at 74 (see FIG. 5). The cylinder lens 72 focuses the cooperating rays into narrow, horizontally extending lines. The vertical sharpness of these lines determines the storage density in the direction of movement of the recording medium 20. When a data bit is present, a one-dimensional hologram is recorded in a grid shape with a narrow grid line spacing on the recording medium. If no signal is present, the reference beam 52 exposes the recording medium uniformly. With each revolution of the rotating body 62, the sequence of the Gitlerfrequcnzen determined by the different pairings of the reflective surfaces on the rotating body 62 is repeated. The feed speed of the recording medium? ίο 20 is set so that a predetermined distance is maintained in the longitudinal direction of the recording medium for the holograms with one and the same grating frequency, as shown in FIG. 7 is shown.

In FIG. 6 the different angular positions 1, 2 and 3 of the reference beam 52 are shown, the different reflecting surfaces from <. associated with the rotating body 62; the exposure beam 26 is reflected at one of the surfaces 64 of the lower part, which always occupy the same angle with respect to the axis of rotation A , and is directed onto the recording medium 20.

In FIG. 7 are the corresponding positions of the individual reflective surfaces a. b, c and thus the one-dimensional holograms assigned to the various grating frequencies are shown, and FIG. 7 shows the repetition frequency or the above-mentioned distance with which the holograms assigned to a grating frequency occur in the direction of movement of the recording medium 20. The readout light beam 27 has a width which is somewhat greater than the width of the holograms, but not significantly greater than the hologram spacing. Because of the overlap of the holograms having different grating frequencies, the readout light beam 27 is adjusted approximately to a hologram, regardless of the positional relationship between the position of the recording medium and the angle of the rotating body 62. Adjacent holograms are also illuminated, but with a lower light component than the hologram on which the readout light beam 27 has been centered.

One embodiment of a device for reading out the stored data is shown schematically in FIG. 8 is shown in side view, while FIG. 9 shows a view from below. The readout device is comparable to the storage device in that a rotating body 82 is used, which corresponds to the rotating body 62 in its structure. However, since the storage device and the read-out device do not necessarily have to be one and the same device, the rotating body is given the reference number 82 for the read-out. In the readout arrangement according to FIGS . 8 and 9, the readout light beam 27 is incident on the reflecting surfaces of the lower part of the rotating body 82 and is guided through a collecting lens 86 and a cylindrical lens 88 onto the exposed and developed recording medium 30. Behind

A transforming lens 90 is arranged on the recording medium 30, which transforms the direct beam, i.e. H. the undiffracted beam focused to a point 92 and that diffracted by the individual holograms Light at separate points in their focal plane

^Fi 5 focussed, on which the aforementioned photodetectors 40, 42 and 44 are arranged (cf. FIG. 9), namely one photodetector for each grating frequency. The horizontal position of the focusing

609 651/225

points in the focal plane of the transformicr lens regardless of the position of the recording medium 30.

From the in the F ι g. 9 can be seen that the transforming lens 90 causes the rays to fall on the photodetectors. Since the axis of rotation of the Rotary body with the front in the direction of the passage When the focal point of the cylindrical lens 88 coincides, the central location is the recording medium 30 penetrating light beam always horizontal when it runs over the film. Therefore, the transform lens focuses 90 these parallel beams in the FIG. 9 (lying on one axis), so that a single fixed bank of detectors is sufficient to reproduce the entire signal wave train, i.e. H. to capture all one-dimensional holograms with different grating frequencies.

To reconstruct the data used to modulate the modulator 56, the output voltages of the photodetectors 40, 42 and 44 ... in the context of FIG. 3 described Way to be commutated. Each photodetector is dated for one pass Commutator queried and switched to the input of a playback device, not shown. At the At the end of the cycle, the adjacent detector is connected to the input of the playback device. The selection of the detector to be queried. is achieved by integrating the total energy in determined for each channel. On average, the most centrally located hologram becomes the lattice form provide most of the energy detected by the detectors. Appropriate logic circles indicate the commutator to ask the detector which of the Gitlerfrequencies assigned. which carries the highest average current. The communication switch is controlled by a sync pulse derived from the readout light beam 27 and z. B. from the photo detector 42 is removed. Shortly before each readout light beam illuminates the first data bit, the beam sweeps over a slit, not shown, and the photodetector star, which in turn has the Synchronization Inpiils generated. This synchronization pulse wild to control the servo system for the recording medium! rubbed or the playback used. On average, with each of these impulses the film moves the width of one of the one-dimensional ones Hoiorramuic. d. H. the width of the data track on the recording medium.

10 shows a readout device in which no commutator is required Areas of the upper part of the polygon mirror 80 which are arranged at different angles with respect to the axis of rotation A , as has already been done in connection with the polygon mirror 62 according to FIG. 4 has been described. As with saving, a different angular direction is assigned to each pass. Therefore, when recording medium 30 and rotating body

ίο 82 are in suitable positional relation to one another, the complete signal appears on a single readout scanner 102. This photodetector is aligned so that it would just capture the exposure beam if it were present. When loading

-> 5 illumination of the holograms on the recording medium with reference beams at different angular directions, the exposure beam is then always the one reconstructed. It is then necessary to match the horizontal position of the recording medium 30 with the Synchronize position of the reference beam mirror. Otherwise, the reading out corresponds to the embodiment according to FIG. 10, the reading out, as has been described with reference to FIGS. 8 and 9. When the recording medium is appropriately aligned relative to the angle of rotation of the rotating body 82. the readout detector 102 generates averaged signals with maximum energy, the time sequence of average signals corresponds to the time sequence of the holograms on the recording medium. the The holograms that are adjacent to the hologram that has just been read can have different filter frequencies for the purpose of coarse tracking with the help of further Folodelcktorcn 104, as they are in of Fig. K) are shown. If one of these auxiliary detectors 104 generates a larger output energy on average than the actual read-out detector 102. the speed of the recording tractor drive is changed in a suitable manner.

It should be summarized here again-

4 "be directed that a through the modulator 56 time-modulated data signal is recorded in the form of one-dimensional holograms, which differs from a two-dimensional hologram of a two- or three-dimensional object clearly distinguish. In a corresponding manner, a time-sequential sequence is used when reading out electrical signals generated.

As is apparent from the above description, both in the device for The same polygon mirrors and partly comparable ones are saved as well as with the device for reading out optical devices used. It is therefore quite conceivable that storing and reading out with Can be done using the same device.

For this purpose 3 sheets of drawings

Claims (1)

Patent claims: 1. Method for storing data on a light-sensitive flat recording medium, in which an exposure beam and a reference beam of coherent light onto the recording medium are directed, one of the beams is modulated as a function of the data to be recorded, the beams and the record carrier are moved relative to each other in such a way that a one-dimensional hologram is recorded, and in which the stored Data read out with the aid of a readout light beam directed onto the recording medium after its modulation by the hologram on a light-sensitive detector is guided, characterized in that with constant relative movement of the beams and the record carrier unidirectional beams across the record carrier run which extends transversely to the direction of movement of the recording medium, with each Run a one-dimensional hologram is recorded, and that after each run the angle which one of the rays forms with the plane of the record carrier is changed to record a hologram during each pass that is one of the grating frequency grating frequency that differs from the hologram recorded during the previous run having. 2. The method according to claim 1, characterized in that the successively recorded Holograms partially overlap. 3. The method according to claim 1 «of 2, characterized in that when reading out a coherent readout light beam successively substantially transversely to the direction of movement of the recording medium and a device for moving the recording medium, characterized in that a rotating body (62; 82 groove several) in the beam path discreet under different winds no reflective surfaces (a, b, c ... ) arranged with respect to the axis of rotation (A) and with diverging axial positions (a, b, c ...) has collapsed and the recording medium (20) is in such a way Z ¹ UgIiCh of the rotary body by the movement device ( 22, 24) is movable so that one after the other the holograms with different filter frequencies can be generated or read out. 7. Apparatus according to claim 6, characterized in that the rotating body (62; 82) is divided into two parts by a plane extending perpendicularly to its axis of rotation (A ) and both parts are provided with discrete reflective surfaces, on one part the surfaces (a, b, c ) arranged at different angles with respect to the rotating rises for reflecting one beam (52) and surfaces (64) reflecting on the other part at the same angles with respect to the axis of rotation (A ) for reflecting the other Beam (26) are arranged.