WO1998033093A1

WO1998033093A1 - Process and device for directing a beam onto different positions of a surface and use of the device

Info

Publication number: WO1998033093A1
Application number: PCT/EP1998/000321
Authority: WO
Inventors: Keming Du; Peter Loosen; Reinhart Poprawe
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 1997-01-24
Filing date: 1998-01-21
Publication date: 1998-07-30

Abstract

A process is disclosed for directing a beam onto different positions of a surface. The direction of the beam is altered by a defined force that acts upon it so that the beam may be associated to a defined position on the surface. The process is characterised in that the beam propagating in the axial or z direction runs through a region in the z direction and in that a force acts upon the beam in defined zones in the z direction within said region, altering the direction of a defined part of the beam in the defined zone by a defined amount. Also disclosed are a device for directing a beam onto different positions of a surface, and the use of the device.

Description

P A T E N T A N M E L D U N G

"Method and device for directing a beam onto different positions of a surface and use of the device"

The present invention relates to a method and a device for directing a beam onto different positions of a surface, the beam experiencing a change in direction by acting on it in such a way that a defined portion of this beam can be assigned to a defined position on the surface.

Mechanical scanning devices, such as rotating polygon mirrors, galvanic scanning devices, vibrating micromirrors and acoustic reflectors, are used in many applications of image reproduction or scanning. With respect to image display technology, cathode ray tubes and LCD arrangements (liquid crystal displays) are still used today. However, image reproduction techniques using laser beams are also becoming increasingly popular. These reproduction techniques using laser beams are characterized by their good transmission quality and the practically unlimited image size that can be generated.

According to one procedure, the laser beam or beams are scanned or scanned over a line by means of a rotating polygon mirror. The scanning or scanning from line to line is carried out by a galvanic mirror. The rotational frequency of the polygon mirror is a maximum of a few kHz. The mechanical load caused by the high rotational frequency is a limiting factor for this process. Another possibility is that instead of the polygon mirror, as mentioned above, the scanning from pixel to pixel is realized by an A / O deflector (acoustic optics deflector). The method has the advantage of higher speed compared to the method in which the polygon mirror is used; however, the applications are severely limited due to the small angular range of the deflection, typically up to 3 °, which can be achieved by an A / O deflector.

According to another procedure, scanning from point to point is carried out by means of an acousto-optical modulator and by means of a pulsed laser. This method uses pulsed lasers with pulse durations of a few nanoseconds. The pulsed laser beams are transformed into a line and radiated into an acousto-optical cell. A sound wave modulated in amplitude or a wave of a refractive index change that is generated in such a material runs across the beam. The amplitude modulation is coded depending on the application. If the laser pulse duration is shorter than the propagation time of the sound wave from pixel to pixel, a line with corresponding intensity modulation can be generated by a laser pulse. The problem with this method is that only pulsed lasers with a powder duration in the nanosecond range or shorter can be used.

Starting from the prior art specified above, the present invention has for its object to provide a method and an apparatus with which the disadvantages listed above can be avoided.

This object is achieved in accordance with the method according to the invention, starting from a prior art as stated at the outset, in that the beam traverses an area in the z direction with a propagation direction in the axial or z direction and that defines the beam Zones in the z direction are acted on within this area in such a way that a defined beam component in the defined zone undergoes a change in direction by a defined amount. According to the device, the object is achieved in that the beam with a direction of propagation in the axial or z direction has an area in the z direction traverses and that acts on the beam at defined zones in the z direction within this area in such a way that a defined portion of the beam in the defined zone undergoes a change in direction by a defined amount.

On the basis of these measures, pixels can be generated at defined points, for example on an imaging surface, with a structurally simple and maintenance-free structure. Only one laser beam is required for each line on a screen, which is then deflected at the respective corresponding image points or image zones from its propagation in the z-direction onto the imaging surface, without the need for moving parts. The respective beam components for a line are preferably deflected at substantially the same angles or are bent from the z direction and therefore run approximately parallel to one another towards an imaging surface.

Electron beams and in particular laser beams are suitable for the beam which is deflected in a defined manner from its direction of propagation. In order to define defined deflection areas, the zone in which the beam is acted on is changed over time. The zones along the z direction, i.e. along the direction of propagation of the laser beam should also be actively addressable.

Naturally, each beam (and ultimately also a laser beam) has a certain divergence. On the other hand, the interaction zone in which the beam is deflected is limited by the available driver power. For technical reasons, axial scanning or scanning can become impractical where the incident beam is freely propagated into the medium and a scanning device dimension is required that is large in size and difficult to master technically. In order to avoid such a problem, the cross dimensions of the beam are limited by a medium in a preferred development. Depending on the area of application, optical fibers, self-focusing media, or a medium that is equipped with a refractive index distribution that leads across the z-direction are suitable for this. With regard to an optical waveguide, a planar optical waveguide should preferably be used. This has the advantage that it is technically easy to implement Another preferred structure is achieved when the medium is an acousto-optical medium and is in contact with an acousto-optical material. Such an acousto-optical medium then has an interaction zone for the incident beam, which essentially moves along the direction of propagation of the beam (continuously or discontinuously). This interaction zone has the function of deflecting the beam propagated through it. As the interaction zone continues, the incident beam is deflected at different axial positions, as indicated above, and possibly sucked out at different times due to a kind of diffraction on the grating and directed onto the imaging surface. The interaction zone can be segmented for the simultaneous decoupling of radiation.

In order to achieve the change of direction in connection with an acousto-optical material as the medium through which the beam propagates, a simple measure is used to arrange at least one piezoelectric sound exciter on the acousto-optical material. TeO ₂ , Ge, GaP, InP or SiO ₂ is preferably used as the acousto-optical material. A moving, acousto-optical wave train is obtained in the medium by pulsing the driver power of the acoustic exciter. As a result, the incident beam can be deflected from the direction of propagation at different axial positions (along the z direction) and possibly at different times. In addition to acousto-optical effects, electro-optical and thermo-optical effects can also be used to deflect the beam from a direction of propagation.

In order to achieve the required driver power, the sound waves emanating from the piezoelectric sound exciter are reflected back to the medium by the reflector on the opposite side. Then a pulsed sound oscillator is created, so that the necessary driver power is reduced by the factor of the sound oscillator quality.

In order to be able to control defined zones, it can be advantageous to assign a respective piezoelectric sound exciter to each zone in the z direction. In order to take advantage of the electro-optical effects for the defined deflection of beam components, electro-optical media are used in the field. LiNbO ₃ , KNbO ₃ or electro-optical polymers are preferably used for such a medium.

If the limiting medium is an optical waveguide, there is the possibility of mechanically deforming the optical waveguide in the respective zone, in order then to cancel the beam-guiding conditions in this zone due to the deformation. Such a deformation can be carried out by a movable element which engages in the optical waveguide. Another embodiment results from a deformation by means of a capacitive actuator or by means of a piezo-electric actuator. Finally, the deformation is possible by means of an actuator which has a mirror, which lies against the optical waveguide at defined zones in order to cancel the beam-guiding conditions there. The possibility of deformation by means of fluid or the deformation by means of acoustic waves should also be emphasized.

Another procedural measure, which is to be preferred in connection with an optical waveguide, is such that the optical waveguide has a defined deformation corresponding to the zones and is partially surrounded by a transmissive medium. The refractive index of such a transmissive medium is changed by external influences, so that the beam-guiding conditions at the respective zones are canceled by the defined change in the refractive index and thus the totally reflecting conditions. Such a transmissive medium is preferably a liquid crystal. Furthermore, the optical waveguide can be deformed in a wave shape, so that a zone for coupling out the beam is defined with each wave section. Such an optical waveguide comprises a core region and a cladding region, the cladding region having a lower refractive index than the core region and the core region being left free from the cladding region at turning points of the optical waveguide in order to define the zones at these free regions where the beam can be coupled out . With the measures according to the method and the structures as described above, imaging units with n zones and m rows can be built up by stacking a corresponding number of zones through which the beam is guided, running parallel to one another, so that with each Zone, a defined image line can be generated by decoupling the beam at defined locations on a surface. In order to achieve a relatively simple, two-dimensional structure, a plurality of optical waveguides can be arranged with their axes running essentially parallel to one another. Furthermore, the individual waveguide sections can be connected at their ends to form an endless optical waveguide, so that it is sufficient to generate a two-dimensional image with a beam, for example a laser beam, without a line scanner. With such an arrangement, image projection systems or arrangements for information transmission can be set up, and read / write heads or scanning devices can also be set up with it.

A continuously operated (cw) laser or a pulsed laser can be used as the laser.

The laser beam modulated in terms of power is coupled into the light-guiding channel, preferably an optical waveguide, located in the movement device. For scanning, the acousto-optical effects, which are explained above, are brought about by applying a high-frequency (HF) pulse, the duration of which is defined such that the product of the pulse duration and the speed of propagation in the acousto-optical Medium smaller or approximately equal to a defined pixel distance on the surface is correlated. This measure ensures a non-blurred projection on the imaging surface.

In order to deflect or decouple radiation components from the axial guidance of the beam using laser pulses in the nanosecond range, an acousto-optical medium is controlled with an associated radio-frequency (HF) voltage and the amplitude of the HF voltage is modulated in time so that a Line image with a defined intensity curve along the line of the imaging surface is produced. This has the advantage that only a low sound intensity is required for the deflection, which corresponds to a typical deflection efficiency of less than 1%.

The arrangements according to the invention, as described above, can be integrated within a laser resonator, which, in addition to a compact and simple construction, enables a further reduction in the driver power or voltage. The waveguide lasers are particularly suitable for this.

On the basis of the principle according to the invention, the beams deflected from corresponding zones along the axial or z-direction can first be fed to a line scanning device in order to then deflect or scan them to defined locations on the imaging surface with a single channel. In this way, for example, a field can be generated from pixel signals on an imaging surface. The respective rows or columns are generated with a single channel or optical waveguide guiding the beam, from which the radiation components are coupled out, which are then preferably deflected in a direction perpendicular to it in order to achieve a corresponding two-dimensional pixel field on the imaging surface.

Preferred uses of the arrangement according to the invention, also with further training for carrying out the various features according to the method, are those for an image generation system, for information transmission, for forming a read / write head and as a scanning device.

Exemplary embodiments are described below with reference to the drawings. In the drawing shows

FIG. 1 shows a schematic representation of a basic structure according to the invention, which serves to explain the principle according to the invention,

FIG. 2 shows an arrangement in which, compared to the arrangement in FIG. 1, a waveguide is used for beam guidance, FIG. 3A shows a further arrangement, which shows a structure in which the beam is deflected by means of an acousto-optically induced refractive index grating,

FIGS. 3B and 3C are pulse diagrams of the driver power of the sound exciter on the one hand and the position of the acousto-optical wave train in the propagation medium as a function of time on the other hand.

4A and an arrangement corresponding to FIG. 3A, but with an additional reflector, FIG. 4B again showing the driver power of the pulsed acoustic exciter,

5A shows a further arrangement in which, compared to the arrangement in FIGS. 3A and 4A, the input beam is pulsed with a pulse duration in the nanosecond range or shorter, FIG. 5B representing the correspondingly modulated driver power of the piezoelectric sound exciter.

FIG. 6 shows an arrangement in which a plurality of discrete interaction channels are provided along the medium through which the beam traverses;

FIG. 7 shows an arrangement in which electro-optical effects for beam deflection are carried out along discrete interaction zones along the medium,

FIGS. 8A and 8B show an arrangement in which the beam is deflected by mechanical devices

FIGS. 9A and 9B show an arrangement in which a beam component can be decoupled by the surface deformation caused by the pulsed acoustic wave at certain, local positions,

FIGS. 10A and 10B show an arrangement in which an optical waveguide is acted on by means of piezoelectric actuators,

FIGS. 11A and 11B arrangements in which the optical waveguide is acted on by means of micro-nozzles, FIG. 12 shows an arrangement in which the refractive index of a waveguide is changed by external action, for example by an electric field in the case of a liquid crystal, in order to couple out a beam component,

FIG. 13 shows an arrangement modified compared to FIG. 14,

FIG. 14 shows an arrangement with an optical waveguide for constructing a two-dimensional imaging arrangement, and

Figure 15 shows the basic structure of a projection device with an additional line scanner.

The principle of directing an input beam 1 with a direction of propagation, which is indicated by the arrow 2, to different positions of a surface indicated by a dash-dotted line 3 is shown in FIG. 1. The beam 1 traverses a defined area 4, which can be defined by a medium, as will be explained in the further embodiments. Along the direction of propagation, also marked as z-direction in FIG. 1, an interaction zone is moved to defined coordinate points in the z-direction or a plurality of interaction zones are arranged along the direction of propagation in order to act on the input beam, for example a laser beam or an electron beam, in such a way that a Defined beam portion 6 is deflected towards surface 3, scattered or bent out, ie this beam component 6 undergoes a change in direction by a defined amount. Depending on the position of the interaction zone 5 is deflected at the different axial positions (possibly at different times), so that defined pixels can be generated on the surface 3. As FIG. 1 shows, the amount of change in direction of the respective beam components 6 along the z-direction is preferably selected such that the beam components 6 run essentially parallel to one another.

Each beam has a divergence transverse to the direction of propagation, as is also indicated in FIG. 1 on the basis of the beam course of the input beam 1. This also applies to laser beams, even if the beam divergence is low in relation to laser beams. On the other hand, the interaction zone 5 that can be achieved limited by the available power that is coupled into this zone 5 in order to couple out a beam portion 6. Therefore, the free spreading of the input beam 1 in the area or a medium 4 can become impractical, since with the free spreading of the input beam 1 in the area 4 dimensions are required which are difficult to master technically. For this reason, in a further embodiment, as shown in FIG. 2, the input beam 1 is coupled into an optical waveguide 8. This creates beam portions 6 which emerge from the optical waveguide 8 towards the surface 3 at different axial positions and possibly at different times. Since the input beam is limited to a defined cross section by the optical waveguide, the interaction zone 5 and thus the power required to decouple the beam components 6 can be kept low. The achievable interaction length in the z direction can be chosen to be as large as possible in order to achieve a large number of pixels.

Instead of the optical waveguide 8 which is used in FIG. 2, a medium with a suitable refractive index distribution or a self-focusing medium can be used in order to keep the lateral dimensions of the beam small over a long propagation distance (z direction).

Different mechanisms, each with their specific advantages, as will be explained below, can be used to deflect a beam from its direction of propagation or propagation. This includes acousto-optical effects and electro-optical effects. The two effects are based on the change in the refractive indices of a medium through an acoustic wave or an electric wave or an electric field.

Figure 3 shows a basic structure in which the deflection of the beam components 6 of an input beam 1 is caused by acousto-optical effects. In this construction, a piezoelectric sound exciter is attached to an acousto-optical medium 9, via which sound waves are coupled into the medium 9 in the direction of arrow 11. The driving power of this piezo-electric sound exciter is pulsed, so that a moving, acousto-optical is moving in the medium 9 Wave train, designated by the reference number 12 in FIG. 3A, arises. Since the input beam 1 is irradiated at an angle from the side opposite the sound exciter 10, the wave train strikes the input beam 1 at different axial positions at different times, so that defined beam components 6 are deflected out by the interaction of the wave train with the beam . The radiation components 6 thus produce a radiation field which corresponds to an axial scanning of the input beam 1. In FIG. 3B, in relation to FIG. 3A, the time spread of the wave train 12 as a function of A (t) (amplitude of the sound wave) is indicated. In addition, the pulsed driver voltage U (t) is shown in FIG. 3C, the two pulse sequences corresponding to the wave trains 12.

In the embodiment of FIG. 3A, the acousto-optical medium is designed in such a way that the side 13 opposite the acoustic exciter 10 is sound-absorbing. This embodiment results in a relatively simple structure, but requires a high drive voltage U (t). In order to reduce the driver voltage U (t), according to the schematic arrangement of FIG. 4A, the acousto-optical medium 9 corresponding to an acoustic oscillator is used, the coupling surface 14 assigned to the piezoelectric sound exciter and the side 13 opposite this coupling surface 14 aligned in parallel and sound-reflecting. The driver power under the resonance condition can be considerably reduced by suitably matching the driver frequency of the sound exciter 10 and the dimensions of the acousto-optical medium.

FIG. 5A shows a basic structure of an acousto-optical scanning device according to the invention using a light-guiding medium, the driver voltage U (t) of the sound exciter 10 being modulated in time, as shown in FIG. 5B. The arrangement essentially consists of an acousto-optical material 9, into which an optical waveguide 8 is inserted as a radiation-guiding channel. This optical waveguide 8 can be embedded in the acousto-optical material, but is preferably placed, for example in the form of an optical waveguide with a flattened cross-sectional profile, on a corresponding surface of the acousto-optical material 9 or embedded therein. On one side surface 14 The piezoelectric sound exciter 10 is attached to the acousto-optical material 9, which can be, for example, TeO ₂ , Ge, GaP, InP or SiO ₂ . A laser beam 1 with the intensity l ₀ is coupled into one end of the optical waveguide 8 by means of coupling optics (not shown in more detail). By applying a high-frequency voltage (HF-U (t)) to the piezoelectric sound exciter 10, a continuous sound wave is modulated in time in the acousto-optical material 9 and in the light waveguide 8, corresponding to FIG. 5B, and thus a refractive index grating in the direction of the Arrow 11 generated. The sound wave is set at an angle Θ _B to the light waveguide 8. The direction of propagation of the acousto-optical wave has a component which is preferably anti-parallel to the direction of light propagation. If the amplitude of the acousto-optical wave is modulated accordingly, the short-pulsed (ns) laser beam 1, which leads through the light waveguide 8, can be deflected from different axial positions due to a kind of diffraction on the grating, so that deflected at the different axial positions Rays I ,, l ₂ , l ₃ , l ₄ .... I _n ... I _N arise. As can be seen, image or pixel points can be generated at different positions on an imaging screen without moving devices.

In order to produce a two-dimensional pixel field on an imaging surface, several arrangements, as shown in FIG. 5A, can be stacked on top of one another, so that individual lines can be formed from pixel points with the respective arrangements. However, there is also the possibility of deflecting the individual beams \ _v l ₂ , l ₃ , l ₄ .... I _n ... I _N by means of a deflection device in order to form a pixel field.

In contrast, FIG. 6 now shows an embodiment in which a plurality of discrete interaction channels 18, each with a sound exciter 10 (for example acousto-optic or electro-optical interaction zones), are used, which are arranged one behind the other essentially along the beam propagation direction 2 of the beam 1 . The respective driver voltages U (t) for the sound exciter 10 are indicated with U1 (t), U2 (t), U8 (t). Through a suitable, temporal control of the interaction strength of the respective interaction channels 18 the beam 1, which in turn can be limited by an optical waveguide 8, is directed in order to decouple the respective beam components 6 from the beam 1.

Corresponding to acousto-optical effects, as already mentioned, electrical-optical effects can also be used. For this purpose, an arrangement is shown in FIG. 7 in which the beam 1 is guided through an optical waveguide 8. Along the optical fiber 8 along the z direction, i.e. An array of multiplexers is arranged along the axis of the optical waveguide 8 by means of an electro-optical effect. This principle of operation uses the multiplexing technique as is known in the field of information technology. By applying a suitable electrical voltage, a defined beam component 6 is coupled from the waveguide 8 into the respective optical waveguide 8 '; each beam component 6 arises in the respective light waveguide 8 '. In this way, the intensities of the respective beam components can be modulated in time by changing the designed voltages in order to generate the respective pixels on a surface (not shown).

FIGS. 8A and 8B now show an example in which the beam deflection from an optical waveguide 8 takes place largely mechanically. Micromirrors 20 (shown schematically in FIGS. 8A and 8B) are arranged one after the other in the z-direction along the direction of propagation of an input beam 1 in a waveguide 8. These respective micromirrors 10 essentially comprise a capacitive arrangement 21 in which a mirror 22 is accommodated. The cladding 24 of the optical waveguide 8 lies against the mirror 22. By applying a suitable voltage to the respective capacitive arrangement 21, the mirror carriers 22 can change their position, as is shown on the pivoted-up mirror carrier 22 at the fourth position, seen from the left in FIG. 8B. In this position, in which the optical waveguide 8 is deflected from its straight orientation running in the z direction, the angle of the beam will exceed the acceptance angle of the optical waveguide 8, so that a beam component 6 is coupled out.

An arrangement comparable to the arrangement according to FIGS. 8A and 8B is shown in FIGS. 9A and 9B, FIG. 9A representing a plan view of the arrangement of FIG. 9B from the direction of the arrow IXA of FIG. 9B. In this In one embodiment, the light waveguide 8, again with a core 25 and a jacket 24 for guiding the input beam 1, is applied to an acoustic material 26. A suitable excitation mechanism, for example a sound exciter 10, generates an acoustic wave, a Scherer wave or a pseudo-Rayleigh wave 27 which is suitably pulsed. A common principle here is that a traveling wave 29, which is exaggerated in FIG. 9B, is generated on the surface 28 on which the light waveguide 8 rests with its jacket 24. On the flank 30 of this height wave 29, on which the optical waveguide 8 is deflected from the z direction, the light-guiding function within the optical waveguide 8 is at least partially canceled, so that the beam portion 6 emerges. The incidence beam is coupled out at different positions along the direction of propagation of the input beam 1 due to the movement of the height wave.

FIGS. 10A and 10B now show an embodiment whose basic structure is comparable to the embodiment shown in FIGS. 8A and 8B. In contrast to the capacitive arrangements 21, the respective micromirrors 20 or their mirror supports or Mirror 23 actuators, preferably piezo-electric actuators 31, assigned. The change in the electrical voltage supplied to the piezoelectric actuators changes their position and thus the position of the mirrors 23, as shown in the middle of FIG. 10B, so that, in the deflected state, the mirrors 23 attached to the jacket 24 of Light waveguide 8 abut, the light-guiding function of the optical waveguide cancels, so that a beam portion 6 can be deflected at defined positions along the z direction by actuating the respective actuator 31. It will be understood that different application of voltage to the actuators 31, or else to the capacitive arrangements 21 in FIGS. 8A and 8B, can result in a different coupling-out direction of the beam portion 6.

In FIGS. 11A and 11B, an optical waveguide 8 is guided over a carrier 32. The carrier 32 has a cavity 33 which is filled with a fluid, preferably a suitable liquid, along the optical waveguide 8 Micro nozzles 34 positioned at different positions in the z direction. Each individual micro nozzle 34 can be controlled by arrangements, not shown, similar to the nozzles of an ink jet printer, so that a liquid jet 35 can be emitted from defined micro nozzles 34. As a result, the optical waveguide 8 rises, so that the setting angle of the optical waveguide 8 is varied. The underside, ie the side that rests on the carrier 32, is configured such that a steel portion 6 is coupled out at the respective position on the rising flank 30 of the optical waveguide 8 raised by the liquid jet 35.

A further arrangement for implementing the principle according to the invention is shown in FIG. In this arrangement, a light-transmitting coating, for example in the form of an optical waveguide 8, is applied to a substrate carrier 36, the surface 37 of which has a sawtooth-shaped or undulating structure. A medium 38, for example a liquid crystal, is arranged above the surface 37 of the substrate carrier, the refractive index of which can be influenced by external influences. The medium is divided into individual zones, so that the refractive index in the respective zone can be actively varied so that the wave-guiding function of the light waveguide 8 is canceled locally and a beam portion 6 emerges from the upper cover 39. Through a sequential variation of the refractive index of the medium (liquid crystal) 38, a defined coupling of the beam components 6 in the area of the respective flanks 30 of the sawtooth-like structure of the surface 37 of the optical waveguide 8 can be coupled out.

An embodiment modified from the arrangement in FIG. 12 is shown in FIG. 13, with the difference that the light waveguide 8 is provided with a structured jacket 24. The jacket 24 of the optical waveguide 8 is interrupted at defined points, designated by the reference numeral 40, so that the core 25 is exposed in each case. At these exposed points, a beam portion 6 is coupled out again by changing the refractive index of the liquid crystal 35. In the above arrangements explained with reference to the figures, an optical waveguide 8 with a flat, rectangular cross section is preferably used, which has the advantage that the underside is flat and defined on a carrier, for example on the substrate carrier 36 of FIGS. 12 and 13, can be hung up.

The above-described embodiments for axial scanning devices can be modified for various applications, for example for image reproduction techniques, for information technology and for use in the field of computer technology. For this purpose, it may be necessary to supply the beam components 6, which are coupled out, to downstream optical systems for beam shaping and to scanning devices, such as, for example, line scanning devices.

In addition, embodiments for a single scanning channel were explained above, so that linear scanning devices can be formed therewith. FIG. 14 now shows an embodiment in which the optical waveguide is folded in order thereby to arrange a plurality of channels essentially parallel to one another, so that a two-dimensional arrangement is produced. The respective optical waveguides can each be supplied by a single input beam 1, but it is also possible to use a continuous optical waveguide 8, so that the individual sections, as can be seen in FIG. 14, each have their ends with the dash-dotted connecting lines 41 designated, are interconnected.

If arrangements, as also shown in FIG. 14, are built on very small chips with typical dimensions of 10 mm x 10 mm, a very compact image display unit can be realized, which moreover has a simple construction, is robust and reliable with one high flexibility, which in principle allows an unlimited number of resolution points.

FIG. 15 shows, using the arrangement as shown in FIG. 5A, a basic structure of a projection device with a laser pulsed in the nanosecond range. The laser 41 is coupled into the optical waveguide 8 using coupling optics, for example a focusing lens 42. about the piezoelectric sound exciter 10, continuous and amplitude-modulated sound waves are generated in the acousto-optical material and optical waveguide, as explained with reference to FIG. 5A, and a line is bent out using an imaging optics 43 and an additional line scanner 44 on an imaging screen 45 is shown.

The drive voltage U (t), which is generated in the driver device 46 and with which the piezoelectric sound exciter 10 is driven, is derived from a video signal of a video signal processing device 47, which is compressed in a compressor 48. The individual components are controlled by a central processor unit 49.

As can be seen from the above description, two-dimensional scanning devices can be constructed using the method according to the invention and the corresponding devices; a transfer of the arrangements to a 4π space scanning angle is also possible, i.e. a three-dimensional space can be scanned in all directions.

Insofar as corresponding reference numerals are used for corresponding components in the individual figures, the description sections for the respective figures can also be transferred analogously to the other figures. In addition, the features specific to the individual embodiments according to the individual figures can be combined with one another to build up arrangements as shown in FIG.

In all of the performances discussed above, the interaction areas are outside the laser source. It is also possible for the interaction area to be placed within the laser resonator. A significantly lower extraction efficiency from the respective interaction zones is sufficient. In this case, a ring laser, for example a ring fiber laser, is preferred.

Claims

PATENT CLAIMS

1. A method for directing a beam at different positions of a surface, the beam undergoing a change in direction by acting on it in such a way that this beam can be assigned to a defined position on the surface, characterized in that the beam has a direction of propagation in the axial or z Direction traverses an area in the z direction and that the beam is acted on at defined zones in the z direction within this area in such a way that a defined portion of the beam in the defined zone undergoes a change in direction by a defined amount.

2. The method according to claim 1, characterized in that the respective amount of changes in direction at the respective zones is set substantially to the same size.

3. The method according to claim 1 or 2, characterized in that the beam is an electron beam.

4. The method according to claim 1 or 2, characterized in that the beam is a laser beam

5. The method according to claim 4, characterized in that the region is arranged within the laser sonator.

6. The method according to claim 4 or 5, characterized in that a fiber laser with a ring resonator is used as the laser.

7. The method according to any one of claims 1 to 6, characterized in that the zone in which the beam is acted on is changed over time.

8. The method according to any one of claims 1 to 7, characterized in that the zones are actively addressable along the z-direction.

9. The method according to any one of claims 4 to 8, characterized in that the area in the z direction through which the beam traverses is limited by a medium.

10. The method according to claim 9, characterized in that an optical waveguide is used as the medium.

11. The method according to claim 9, characterized in that a self-focusing medium is used as the medium.

12. The method according to claim 9, characterized in that such a medium is used with a transverse to the z-direction of the refractive index distribution.

13. The method according to any one of claims 10 to 12, characterized in that a planar optical waveguide is used.

14. The method according to any one of claims 1 to 13, characterized in that the changes in direction are brought about by acousto-optical effects.

15. The method according to claim 14, characterized in that the medium consists of an acousto-optical material and is in contact with an acousto-optical material and at least one piezoelectric sound exciter is arranged on the acousto-optical material.

16. The method according to claim 15, characterized in that TeO ₂ , Ge, GaP, InP or SiO _{2 is} used as the acousto-optical material.

17. The method according to claim 15, characterized in that the sound waves emanating from the piezoelectric sound exciter are reflected on the opposite side of the medium.

18. The method according to claim 15, characterized in that a respective piezoelectric sound exciter is assigned in the z direction of each zone.

19. The method according to any one of claims 1 to 13, characterized in that the change in direction is brought about by electro-optical effects.

20. The method according to claim 19, characterized in that LiNbO ₃ , KNbO ₃ or an electro-optical polymer is used as the electro-optical medium.

21. The method according to any one of claims 9 to 13, characterized in that the optical waveguide is mechanically deformed at the respective zone in such a way that the beam-guiding conditions at the zone are eliminated.

22. The method according to claim 21, characterized in that the deformation takes place in each case by means of a movable element which engages in the optical waveguide.

23. The method according to claim 21, characterized in that the deformation takes place by means of a capacitive actuator

24. The method according to claim 21, characterized in that the deformation takes place by means of piezo-electric actuator.

25. The method according to any one of claims 21 to 24, characterized in that the shaping is carried out by means of an actuator which has a mirror which bears against the optical waveguide.

26. The method according to claim 21, characterized in that the deformation takes place by means of a fluid.

27. The method according to claim 21, characterized in that the deformation takes place by means of acoustic waves.

28. The method according to claim 9 to 13, characterized in that the light waveguide has a defined deformation corresponding to the zones and is partially surrounded by a transmissive medium, the refractive index of which can be changed by external influences, the beam-guiding conditions at the zone being defined by Change in the refractive index is canceled.

29. The method according to claim 28, characterized in that the transmissive medium is a liquid crystal.

30. The method according to claim 28 or 29, characterized in that the optical waveguide is deformed in a wave shape, and in that the optical waveguide has a core region and a cladding region, the core region being left free from the cladding region at turning points of the optical waveguide, in order to avoid the free regions at these To define decoupling points.

31. A method for building an imaging unit with n zones and m rows, characterized in that a plurality of arrangements according to one of claims 1 to 30, each forming a row with n zones, are arranged offset in a direction substantially perpendicular to the z direction, to form m rows.

32. A method for building an imaging unit with n zones and m rows, characterized in that a light waveguide according to one of claims 9 to 13 is arranged in each row, the individual light waveguides being connected to one another at one end or the other to form a continuous light waveguide are.

33. Device for directing a beam onto different positions of a surface, the beam experiencing a change in direction through defined action on it in such a way that this beam can be assigned to a defined position on the surface, characterized in that the beam with a Direction of propagation in the axial or z direction traverses a region in the z direction and that the beam is acted on at defined zones in the z direction within this region in such a way that a defined portion of the beam in the defined zone undergoes a change in direction by a defined amount .

34. Use of the device according to claim 33 for an image generation system.

35. Use of the device according to claim 34 for information transmission.

36. Use of the device according to claim 35 for forming a read / write head.

37. Use of the device according to claim 36 as a scanning device.