WO1990002969A1

WO1990002969A1 - Device for deflecting a light beam

Info

Publication number: WO1990002969A1
Application number: PCT/EP1989/001032
Authority: WO
Inventors: Klaus Kinzinger
Original assignee: Klaus Kinzinger
Priority date: 1988-09-08
Filing date: 1989-09-05
Publication date: 1990-03-22
Also published as: DE3830455C2; DE3830455A1

Abstract

The source of light of a large-area laser display panel is a laser (16). A deflecting unit (14) is connected downstream of said laser and is controlled by a process control computer (42) using signals of the type normally used to produce vector graphics on monitors. The deflecting unit (14) contains acousto-optical deflector units (26x, 26y), each comprising two deflector crystals, in which opposing refringence fields depending on the external deflection control signal are generated. A lens (30) is also provided in the deflecting unit (14), which enlarges the beam deflection before the laser beam impinges on a screen (10).

Description

Device for deflecting a light beam

description

=============== The invention relates to a device for deflecting a light beam, in particular for use in a large-area display device according to the preamble of claim 1. Known large-area display devices are e.g. used in discotheques for projecting geometric patterns on walls, ceilings or free-standing screens. The deflection device contains deflectors in the form of mirrors for the two beam deflection directions, which can in principle be adjusted according to the moving coil. With such

Display devices are not dependent on accuracy and very high speed of the display; the information content of the projected patterns is small. Monitors, LCD displays and plasma displays are also known for the representation of letters, numbers and drawings, which can also display rapidly changing information with a high information content, e.g. continuous texts or complex technical drawings.

However, these display devices can only be realized with a small display area.

Large-scale display panels are also known which operate in a similar manner to the monitors and displays just described. Only in these display panels are the individual display elements formed by individual lamps or mechanically adjustable flaps. Such large-scale display boards can be found, for example, in football stadiums. These scoreboards have the disadvantage that they work slowly compared to monitors not suitable for displaying rapidly changing information. In addition, these large-scale display boards are very expensive, which excludes their use in purely technical applications, for example in control rooms and the like.

Serade for use in the control room area, in traffic monitoring, in process control, etc., it would be advantageous to have a large display device available, which enables the display of rapidly changing information with high resolution at low cost. The present invention is intended to develop a deflection device in accordance with the preamble of claim 1 in such a way that it is suitable for such operating conditions.

For this purpose, a deflection unit with the features specified in claim 1 is proposed according to the invention.

Advantageous developments of the invention are specified in the subclaims.

With the development of the invention according to claim 2, the maximum deflection angle for the different Kogrdinatenrichtung is increased.

Deflector crystals, such as acousto-optical deflector crystals, which can be controlled locally in terms of their optical refractive power by means of electrical signals, bring with them a side effect of dynamic distortion of the light beam, as would also be produced by a weak cylindrical lens. This effect is due to the fact that in the deflector crystal the wavelength of the refractive power fields is not the same throughout, but rather varies locally since the working frequency has to be varied in order to deflect the light beam. With the development of the invention according to claim 3 it is achieved that this disturbing cylindrical lens effect is eliminated, since a corresponding positive effect in the first deflector crystal is offset against an opposite effect in the second deflector crystal.

The development of the invention according to claim 4 also serves to increase the deflection angle.

The development of the invention according to claim 5 is advantageous in terms of producing the smallest possible light spots when the light beam strikes a screen.

With the development of the invention according to claim 6 it is achieved that the deflection device or the light source is automatically switched off or in a standby state when a person is in a place where they could be hit directly by the light beam emitted by the deflection device.

This monitoring of the space possibly traversed by the light beam can be carried out according to claim 7 simply by using known monitoring devices, such as are used for theft protection and burglar protection.

A monitoring device, as specified in claim 8, is characterized by a particularly simple and cost-effective design: the space to be monitored is scanned by the light beam which is also used for display purposes together with a light guide running at the edge of a screen, in that the light beam is inside a test cycle is moved along the light guide arrangement. With this test movement there is only a slight risk of injury to one to be monitored Person in the room because the light beam is moved quickly here. If desired, the light source power can also be reduced for the test cycle (cf.

Claim 9).

The monitoring device specified in claim 8 can also be used to calibrate the deflection device: if it is known that there is no obstacle in front of the light guide arrangement, the lack of an output signal on the light-sensitive detector C when the detector is working properly can only mean that the light beam passes through the deflection unit , whose control unit or a computer controlling it is not correctly guided over the light guide arrangement. If the control of the deflection device is then modified so that the light beam runs correctly over the light guide arrangement, the deflection device is also correctly adjusted overall.

The development of the invention according to claim 10 brings the advantage of a sharp and angular mapping of

Light beam on the screen according to the electrical signals applied to the deflection device even when it strikes the screen at an angle. If you look at laser light with the eye, it always appears scintillating (speckle effect). With the development of the invention according to claim 11, this speckle effect is eliminated, so that one obtains a uniform, still image.

This equalization of the generated image is obtained in a mechanically particularly simple manner. A continuously rotating disc-shaped equalizing element also runs quietly. The arrangement of the equalization element within the optics in front of the last lens of the latter (cf. claim 13) is advantageous in terms of avoiding a pixel widening.

With the development of the invention according to claim 14, the refractive power fields in the deflector crystals can be electrically inclined so that the end faces of the deflector crystal can be placed perpendicular to the incident light beam. This is advantageous with regard to undesired reflections from the end face of the deflector crystals.

With the development of the invention according to claim 15, a further increase in the deflection angle is obtained, since both the wavelength of the refractive power field and

Angle of attack to the incident light beam is changed according to the deflection control signal.

With the development of the invention according to claim 16 it is achieved that the incident conditions for the light beam on the power fields arranged one behind the other deflector elements are the same, although the

Orientation of the deflector elements in space is always the same. With the same orientation of the different deflector elements, the adjustment of the entire deflection device is particularly simple; the deflection device is also compact. With the development of the invention according to claim 16, the constant

Incidence conditions at the various deflector elements by rotating the refractive power fields generated in them, which can be accomplished simply by phase shifting the signals with which the various ultrasonic generators of a deflector element are applied. With the development of the invention according to claim 17 it is achieved that only the light beams diffracted in a predetermined order by the deflectors are used in the generation of the image on the screen. This diffraction order is usually the first order. Since the materials that can be used for deflector crystals are usually optically anisotropic anyway, the diffraction of the light beams at the refractive power fields also results in a rotation of the polarization with respect to the incident light beam, so that the undesired orders of the diffracted can be obtained in a very simple manner Hide light beam or at least weaken it strongly.

The development of the invention according to claim 18 enables the masking of light beams of undesired order using a diaphragm and thus without any weakening of the beam of desired order and 100% suppression of the beams of undesired order. In a deflection device according to claim 19, the position of the diaphragm body in the axial direction is not critical. With this arrangement, both deflector elements can also be placed equally on the axis of the deflection unit, which is advantageous with regard to compact dimensions and simple adjustment to the direction of the incident light beam.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In this show:

Figure 1: a schematic representation of a large area

Laser scoreboard; Figure 2: a plan view of a modified screen for the laser display panel of Figure 1;

Figure 3 is a schematic representation of one of the deflector units of a laser display panel;

Figure 4 is a schematic representation of a modified deflector unit for a laser display panel;

Figure 5 is a schematic representation of a further modified deflector unit for a laser display panel, which comprises a three-lens zoom lens;

FIG. 6: a view similar to FIG. 5, with an additional polarizer for blanking out the zero and second orders of the diffracted laser beam;

FIGS. 7a and 7b: a modified arrangement for generating the refractive power fields in the deflector crystals with different angles of attack; and

Figure 8 is a schematic representation of a modified

Defector unit with several defector crystals arranged one behind the other.

In FIG. 1, 10 denotes a screen on which rapidly changing information is to be displayed with high resolution. The screen is usually rectangular and can e.g. are 4 m wide in the x-direction and 3 m high in the y-direction (room dividers as control room display boards) or larger (projection on house wall). The specified

Directions refer to the coordinate systems shown in Figures 1 and 2. Information is displayed on the screen 10 by moving a laser beam 12 according to the information to be displayed on the screen 10. A corresponding deflection unit is identified by a total of 14 in the drawing. It receives the laser beam from a laser 16, which generates light in the visible range.

Do you look for a white on black representation of conditions such as When projecting texts or technical drawings, a laser 16 with a power of 40 watts is enough to illuminate one

Umbrella 10 from 4 m to 3 m.

Behind the laser 16 is a widening optic 17, which in practice consists of two lenses and will be described in more detail below.

The laser light emerging from the widening optics 17 reaches a deflector unit, designated overall by 26, which comprises a κ deflector unit 26κ and a y deflector unit 26y. These deflect the laser beam by a predetermined angle in the x-direction or y-direction from the optical axis of the laser 16 denoted by 28. The deflector units 2όx and 26y contain acousto-optical deflector crystals as active elements, for example TeO ₂ single crystals. The

The structure and the mode of operation of such deflector units will be explained in more detail later with reference to FIGS. 3 to 8. The maximum deflection angle that can be achieved with them is approximately 2.5 degrees.

The light emitted by the deflection unit deflector unit 26 passes through an equalizing disc 18 which rotates about an axis parallel to the beam direction and whose local refractive power (refractive index integrated via the

Slice thickness) slightly in the circumferential direction slowly changes, e.g. B. due to streaks or due to surface contouring (eg according to a sine law). The shaft carrying the equalization disk 18 also carries a pinion 20 which meshes with a large gear wheel 22. The latter is driven by a synchronous motor 24.

The exact arrangement of the equalization disk 18 in the beam path will be discussed later with reference to FIG. 5.

In order to be able to choose the distance between the deflector unit 14 and the screen 10 to be smaller than the maximum deflection angle per se would allow, an objective 30 is provided which increases the beam deflection.

The information to be displayed on the screen is provided by a computer 32. This information can be entered via a terminal 34 if such a direct information display is desired. The

Computer 32 can, however, also cooperate with other signal sources, e.g. with a computer for which the display panel represents an output unit, or with sensors 36, 33, 40, which are used, for example, to monitor a chemical reactor or to monitor a production line or the like. The computer 32 can then process the output signals of these sensors, compare them with target values and issue warnings in the event of deviations from the target values according to predetermined criteria, or also provide the sensor output signals or variables derived from these in the form of graphics for the user.

A process computer 42 cooperates with the computer 32 and controls voltage-controlled oscillators 44x, 44y on the output side. Their outputs are via power amplifiers 46x, 46y with the control terminals of the deflector units 26x and 26y vsrbunden. The oscillators 44x, 44y are voltage-controlled oscillators with a center frequency of the order of 100 MHz and a frequency swing of about 50 MHz. The oscillator output voltages amplified by the power amplifiers 46x, 46y generate sound waves of corresponding frequency in the deflector crystals of the deflector units 26x and 26y, at which the laser beam is diffracted for the purpose of deflection, as will be described in more detail.

The process computer 42 works together with a read-only memory 48, in which the most important corrector and work values are stored. These are, in particular, factors v _x and v _y for converting the desired coordinate deflections in the x and y directions on the screen 10 into associated deflection angles of the laser beam 12. Furthermore, the parameters P _x and P _y specifying the point size are stored in the read-only memory 48. Taking this into account

Parameters which indicate in the exemplary embodiment according to FIG. 1 by how much a pixel has to be enlarged at a specific coordinate x or y so that it is the one in the

The edge of the screen area, due to the oblique impingement of the laser beam, which inevitably has to accept a dot size, the process computer 42 additionally modulates the control voltages for the oscillators 44x and 44y.

This widening of the image point in the middle areas of the screen results in a constant resolution over the entire area of the screen 10, which is perceived by the viewer as pleasant.

The entire control unit, which is inserted between the computer 32 and the deflection unit 14, bears the reference number 50 in the drawing. For some applications it is necessary that the laser beam 12 is moved for a long time within a small portion of the screen 10. If there were a person in the area between the projection unit 14 and the screen 10, there could be a risk of injury. For this reason, this area is monitored by an ultrasonic sensor 54, as is otherwise used for room monitoring in burglar alarms. It is connected to a detector circuit 56, which then generates an output signal when the ultrasonic sensor 54 detects the presence of a person in the space between the projection unit 14 and the screen 10.

When the process computer 42 receives an output signal from the detector circuit 56, it controls the deflection unit 14 independently of the information received from the computer 32 and to be displayed in such a way that the laser beam 12 is guided along the edge of the screen 10 at high speed. This means that only a very small fraction of the laser power hits a person standing in the area to be monitored. Alternatively, the output signal of the

Also use the detector circuit 56 to turn the laser 16 off or to decrease its power or to control a shutter or beam attenuator provided in the deflection unit 14.

In normal work for displaying information, the process computer 42 operates in a manner similar to that which is known per se from the control of graphics terminals. Only characteristic points of the overall pattern to be generated are input to the process computer 42. It then calculates any desired connecting lines according to predetermined interpolation formulas and / or generates certain, often recurring patterns at the selected points, for example letters or frequently required graphic symbols, which are also stored in the read-only memory 48. It can be seen that characters, drawings, graphics and other information can be displayed very quickly, very variably and over a large area in the manner described above.

FIG. 2 shows an alternative for monitoring the space between the deflection unit 14 and the screen 10.

A light guide 58 is provided along the edge of the screen 10. A photodetector 60 faces the mutually adjacent ends of the light guide 58 which extend beyond the screen 10 on the same side. This thus responds when one end or the other of the

Light guide 58 light emerges. Such a light emission is obtained when the laser beam 12 is guided exactly along the light guide 58 by appropriate control of the deflection unit 26. If there is an obstacle in the volume of space to be monitored, which the laser beam 12 can also sweep as far as possible when information is displayed, a signal drop is observed at the output of the photodetector 60. This falling signal edge is passed via an inverter 62 to the set terminal of a bistable multivibrator 64. The latter is reset by the process computer 42 via a line 66 at the beginning of a test cycle, within which the laser beam is guided via the light guide 58, and the state of the bistable flip-flop 64 is queried by the process computer via a line 68 at the end of the test cycle. If the process computer 42 receives a signal from the "1" output of the flip-flop 64, the normal display is interrupted and switched to the ready position in the manner described above. The process computer 42 is programmed in such a way that it carries out such test cycles at regular intervals, for example every second, the interval between the test cycles being higher with a small laser power and with a larger laser power is chosen smaller.

If there is no obstacle between the deflection unit 14 and the screen 10, an output signal from the bistable multivibrator 64 indicates that the laser beam 12 is not correctly guided along the light guide 58. By adjusting the control signals for the deflection unit such that no output signal from the bistable flip-flop 64 is obtained in a test cycle without obstacle between it and the screen 10, the beam deflection can be calibrated in the x and y directions.

FIG. 3 shows details of the deflector unit 26y. The

Deflector unit 26x is constructed analogously. The incident

Laser beam 12 is first deflected by a prism 96 from the optical axis 28. The deflected laser beam strikes an acousto-optical deflector crystal 1 98, which can, for example, be a plane-parallel cut piece of a TeO ₂ single crystal. A piezoelectric ultrasound generator 100 or an ultrasound absorber 102 is applied to the end faces of the deflector crystal 98. The ultrasonic generator 100 is excited by the power amplifier 46y, as explained above with reference to FIG. 1.

If the deflector crystal 1 98 is not subjected to ultrasound waves, it behaves like a plane-parallel transparent disc, the laser beam 12 passes through it

Deflector crystal 98 essentially rectilinear (apart from a small parallel offset, which is not shown here for the sake of clarity). If the ultrasonic generator 100 is excited by the power amplifier 46y, a sound wave field 104 is obtained in the volume of the deflector crystal 98. The optical refractive index in the detector crystal 98 is periodically modulated by this, and a large number of optical reflection planes are thus obtained. If the Bragg condition is fulfilled, the partial waves reflected at the individual refractive index extreme value planes like one another, while the partial waves passing through largely cancel themselves out, and overall a reflected laser beam is obtained, which is denoted in FIG. 3 by 12 '. By changing the frequency at which the voltage-controlled oscillators 44x, 44y operate, the distance between the maxima and minima of the optical refractive index generated by the sound wave field 104 can be varied, and hence the angle of reflection between the reflected laser beam 12 ′ and the incident laser beam 12.

To double the deflection angle, a second deflector crystal 106 is arranged in the beam path behind the deflector crystal 98. The deflector crystal 106 again carries an ultrasonic generator 108 on its one end face, which is connected to the output of the power amplifier 46y. The other end face of the deflector crystal 106 carries an ultrasound absorber 110. In this way, a sound wave field 112 is generated in the deflector crystal 106, which, however, runs in the opposite direction with respect to the laser beam as the sound wave field 104. In this way, interference effects are associated with the reflection of the laser beam at a refractive index field generated by a wave field for the two

Deflector crystals 98 and 106 averaged out overall.

These effects are due to the fact that a certain amount of time elapses before the frequency changes

Has formed a completely uniform sound wave field inside a deflector crystal. Such non-uniformities in the scarf wave field mean that a deflector crystal also acts like a weak cylindrical lens.

Depending on the special conditions of the sound field, this can be a convex or concave cylindrical lens, but this is not considered in detail here are needed because the two effects in the deflector crystal 98 and in the deflector crystal 106 are just the opposite in size and stand out overall. To ensure this, the deflector crystals le 98 and 106 are identical in terms of their beam deflecting effect. The deflector crystal 106 is rotated through 180 ° with respect to the laser beam and its axis encloses an angle with the axis of the deflector crystal 98. With the deflector unit shown in FIG. 3, the deflection angle of the laser beam is thus doubled overall. This deflection angle is typically about 2.5 ° for a single deflecting crystal. The inclination of the laser beams and the tilting of the deflector crystals relative to one another are thus greatly exaggerated in FIG. 3 compared to the actual conditions. It is understood that the beam deflection can be increased even further by attaching further deflector crystals behind the deflector crystal 106, preferably again in pairs, the sound wave fields running in the opposite direction in each pair of these deflector crystals. Thus, the cross section of the laser beam 12 remains th behind the deflector. FIG. 4 shows a deflector unit 26x or 26y, which is similar to that according to FIG. 3. Only to increase the beam deflection angle beyond that angle that a single deflector crystal can achieve, instead of one or more further deflector crystals le, the objective 30, which is preferably a zoom lens, is provided. In this way, doubling or even greater multiplication of the beam deflection can easily be achieved. FIG. 5 shows a section of the one shown in FIG Deflection unit for the special case that the lens 30 consists of three lenses 116, 118, 120, the lens 116 by the distance 1 ₁ from the center of the deflector crystal

98 is removed, the lens 118 the distance 1 ₂ from the

Lens 116 is removed and lens 120 is the distance ₁₃ from lens 118. The focal lengths of these lenses are f ₁ , f ₂ and f ₃ .

Furthermore, FIG. 5 shows that the equalizing disc 18 is interleaved with the lenses 116, 118, 120 of the objective 30, specifically in such a way that the lens 120 forms a sharp image of the beam passage point through the equalizing disc on the screen 10. If the screen is at a large distance from the deflection unit 14, this corresponds to

Distance between the equalizing disk 18 and lens 120 of focal length f ₃ .

For the sake of clarity, FIGS. 5 and 6 show only a single deflector crystal; in reality you have to take the overall arrangement of everyone in its place

Deflector crystals of the deflector units 26x and 26y think, the central plane of the overall arrangement then at the

Central plane of the deflector crystal shown in FIGS. 5 and 6 lies.

The two-lens expansion optics 17 is arranged in front of the deflector crystal 98. The distance from the deflector crystal 98 is denoted by 1 ₀ and is selected such that at the center of the detector crystal 98 (in the case of a plurality of detector crystals and a plurality of deflector units arranged one behind the other: at the center plane of the deflection unit) a waist of the

Laser beam lies. The widening optics 17 is also set so that its focal point also coincides with the center plane of the detector crystal arrangement. In this way, a minimal cross section of the laser beam is obtained overall behind the lens 30.

Figure 6 corresponds to the main optical parts of

FIG. 5, wherein at the output of the deflector crystal 98, in addition to the laser beam 12 'diffracted in the zero order and the laser beam 12' 'diffracted in the first order, a laser beam 12' '' diffracted in the second order is also reproduced. Of these laser beams, only the laser beam 12 ″ is to be used to generate the image on the screen 10. A prism 124 is provided to mask out the beams 12 'and 12' '' that are not used, which preferably is a

Polarizer with end faces perpendicular to the longitudinal axis, e.g. after Glan-Thompson. Since the different laser beams 12 ′, 12 ″ and 12 ″ ″ are polarized differently, but the polarizer 124 is set to the polarization direction of the laser beam 12 ″, only the laser beam 12 ″ with a higher level is obtained at the output of the polarizer 124 Intensity. In the above description, ultrasonic piezoelectric generators have been considered as one for simplicity

only component addressed. In practice, such ultrasonic generators are expediently constructed from a plurality of oscillators arranged next to one another, so that the sound field inside the deflecting crystal receives a certain rotation. In this way it is achieved that the laser light always finds a partial wave of the sound field, at which it is reflected. The rotation of the sound field can be e.g. via the phase shift between the signals to excite the various ultrasonic transducers.

Generate the phase shift between the signals to excite the various ultrasonic vibrators with electrically controllable phase shifter circuits, and control these phase shifter circuits in accordance with the deflection Unit 14 given deflection control signals, you get an additional tilt of the laser beam, which is added to the Bragg tilt. FIG. 7 shows a corresponding excitation of the refractive power fields in the deflector crystal 98. Instead of the single ultrasonic generator 100 mentioned above, two ultrasonic generators 100a and 100b are provided at a distance from the lower end face of the deflector crystal 98, one of which directly with the output signal of the assigned power amplifier 46 is connected while the other this signal via a controllable

Phase shifter 126 receives. Due to the resulting phase shift between the sound waves generated by the ultrasonic generators 100a and 100b, the wavefronts in the deflector crystal 98 are tilted, as shown schematically in FIG. 11a with the simplified assumption of flat wavefronts (in the near field of the ultrasonic generators 100a and 100b one has in reality, of course, more complicated forms of the wave fronts).

The phase shifter 126 contains a computing circuit 128 which, taking into account the respective deflection angle (and thus the wavelength of the sound wave generators generated by the ultrasound generators 100a and 100b), calculates the necessary angle of attack of the sound wave fields for the direction of the incident laser beam and determines the phase shift with which the Ultrasonic generator 100b must be excited. Since the deflection angles can change very rapidly in the large-area laser display panel under consideration here, an analog arithmetic circuit or a read-only memory is preferably used as arithmetic circuit 128, in which the various arithmetic results have previously been stored for all control signals that can be considered, similar to the above in a different context

(Compensation of non-linearities in the deflection characteristic). FIG. 7a shows the conditions for a first control signal output by the process computer 42, which is equally applied to the frequency-controllable oscillator 44 and the electrically controllable phase shifter 126. With this first control signal, a sound wave field 104 and a corresponding refractive power field having wave fronts are obtained in the deflector crystal 98, the wavelength of which is relatively large and the angle of incidence relative to the horizontal direction of incidence of the laser beam is relatively small.

Figure 7b shows the situation with another of

Process computer 42 emitted control signal, by means of which in the deflector crystal 98 a refractive power field with a shorter one

Wavelength and steeper angle of attack to the direction of the incident laser beam is generated.

As explained above with reference to FIG. 3, the deflection angle can be multiplied by connecting equivalent deflector crystals in series. In the embodiment according to FIG. 3, geometrically identical diffraction ratios of the laser beam in the deflector crystals 98 and 106 were ensured by tilting the rear deflector crystal 106 accordingly. As an alternative to this, the deflector crystals 98 and 106 can also be set up in the same orientation and by appropriate ones

Signal application of several ultrasonic generators, which generate the refractive power fields in the deflector crystals, additionally twist the refractive power field in the second deflector crystal. A corresponding embodiment shows

Figure 8. There are parts of the deflector unit that are above standing with reference to Figures 3 and 7 already

have been explained, again provided with the same reference symbols,

A lens 130 is arranged behind the first deflector crystal 1 98 in such a way that its focal point is in the central plane of the lens

Deflector crystal les 98 falls. The lens 130 thus converts the laser beams 12-0, 12-1 and 12-2 found behind the deflector crystal 98 into axially parallel beams. A

second lens 132 is arranged in front of the second deflector crystal 106 so that its center falls in the crystal center plane. The laser beam thus intersects the optical axis at the center of the deflector crystal 106 at an angle which corresponds to the amount at which it is deflected away from the optical axis in the deflector crystal 98. If one designates this angle with w, the fronts of the sound wave field 104 run underneath one

Angle 0.5 w inclined to the optical axis, as indicated in FIG. 8. To in the deflector crystal 106 with respect to the

To have the laser beam reflected by the changes in refractive power caused by the sound wave field 112 comparable to those in the deflector crystal 98, the wave fronts of the sound wave field 112 must be inclined by an angle of minus 1.5 w to the optical axis. As shown in Figure 8, the deflector crystals are

98 and 106 are both arranged so that their end faces are perpendicular to the optical axis (direction of the incident

Laser beam). The oblique positioning of the refractive power fields 104 and 112 takes place through a phase shift between the electrical signals with which the ultrasound generators 100a, 100b or 100a 'and 100b' are excited. These different phase shifts for the ultrasonic generators 100b and 100b 'generate the computing circuits 128 and 128', respectively, which belong to the controllable phase shifters 126. The laser beam leaving the deflector crystal 106 is thus tilted in total by the angle 2 w against the starting direction. The lenses 130 and 132 rotate the beam a total of 180 ° about its axis, which has no serious consequences for the purpose of information display even if the beam cross-section deviates from the exact circular shape.

As already explained above with reference to FIG. 6, the incident laser beam in the deflector crystals 98 and 106 at the refractive power field 104 or 112 is not only diffracted in the first order, but rather also in the second and higher order

Order. For this you have the beam that continues to penetrate the crystal (zero order).

Since the beams of different orders are tilted by different angles by a given control signal in the deflector crystals, but only one point of impact of the laser beam is desired on the screen 10 for each control signal, the beams must not be of the desired order (here: zero order and second order) be eliminated. In the exemplary embodiment under consideration, this is done by an aperture plate 134 which is arranged in the middle between the lenses 130 and 132. The aperture plate 134 has an opening 136, the inner edge of which is still above the optical axis, so that the zero-order beam is retained. The upper edge of the opening 136 is selected such that the second-order beam with a minimum deflection angle occurring during operation for the first-order beam (this must be from

Be selected differently) is still retained by the aperture plate 134: the one shown in FIG

Beam path, which represents the angle ratios much exaggerated in practice, was assumed, for example, that the beam of the first order behind the deflector crystal 98 is tilted a maximum of 20 ° away from the optical axis. To prevent the second order beam from passing through the

Breakthrough 136 can pass, the deflection angle must obviously not be less than the angle of 20 °. Simplifying a linear relationship between the

Assuming first and second order diffraction, this would result in a minimum deflection angle of 10 ° for the first order beam, thus providing a useful working range for deflection w of the first order beam from 10 to 20 °.

Fig. 8 shows one for the sake of clarity

Deflector unit for one coordinate. The deflector unit for the second coordinate can be easily integrated into the deflection unit shown, that the first

Deflector crystal of this unit in front of the deflector crystal 98, the second deflector crystal symmetrically

Aperture plate 134 behind the deflector crystal 106

Deflection direction of these deflector crystals lies in

Drawing plane of Figure 8 vertical direction. The opening 136 is given a similar contour in the direction perpendicular to the plane of the drawing as in the plane of the drawing and thus has the overall shape of a rectangle. The lenses 130 and 132 shown in FIG. 8 can be made of

Glass or other medium made conventional

Be lenses, preferably aspherical lenses. One can

use holographic lenses or diffraction gratings instead, the latter changing the distance of the bitter lines from the center axis to the outside, as is necessary to correct the chromatic aberation.

In the above description, a laser 16 is provided as the light source for the display panel. It goes without saying that a conventional white light source can also be used in Can use connection with a color filter, such as a xenon high pressure lamp.

To simplify the illustration, the above description also describes only a monochrome, large-area laser display panel together with its control electronics. It goes without saying that it is also possible to produce large-area color laser display panels, whereby the light source used is either a laser that provides multiple wavelengths (e.g. white light crypton ion laser, argon ion laser), or pump lasers in conjunction with a dye cell . The different color laser beams can then be deflected simultaneously by associated deflection units and then meet to form mixed colors on the screen. Alternatively, it is also possible to provide only a single deflector unit which is used in the time-division multiplex method for the laser beams of different wavelengths. In the exemplary embodiments described above, the space between the laser and the screen was monitored using one at the edge of the

Shielded light guide, at the ends of which light-sensitive detectors were arranged. It goes without saying that a large number of light-sensitive detectors can be used instead, which are arranged at a distance in succession along the edge of the screen and are connected in an OR circuit to a common signal line. For many applications, ss is also sufficient if the security check for the presence of people in front of the screen is only carried out at the lower edge of the screen.

Claims

Claims ===============

1. Device (14, 50) for deflecting a light beam

(12) as a function of an external deflection control signal, in particular for use in a large-area display device, with a deflection unit (14) for deflecting the light beam (12) and with a control unit (50) assigned to this, which is equipped with a deflection control signal generator (32) .connectable, characterized in that the deflection unit (14) at least one controllable in its refractive power, for example Has acousto-optical, electro-optical or magneto-optical deflector unit (26x, 26y) and means (42 to 46, 102, 108) for generating a periodic refractive field (104, 112) are provided in the deflector material, the periodicity of the refractive field and the angle of attack of the wave fronts of the refractive field (104, 112) for the direction of the falling light beam are selected so that the Bragg condition is fulfilled.

2. Deflection device according to claim 1, characterized in that the controllable optical deflector units

(26κ, 26y) each have two or more deflectable crystal crystals (98, 106) which are arranged one behind the other and tilted in terms of their refractive power.

3. Deflection device according to claim 2, characterized in that the refractive power fields (104, 112) len in the two deflector crystals (98, 106) have the same amplitude and the same frequency, but run in the opposite direction.

4. deflection device according to one of claims 1 to 3,

characterized in that the deflection unit (14) has optics (30) which enlarge the beam deflection angle.

5. Deflection device according to claim 4, characterized in that the optics (30) several, preferably three

Has lenses (116, 118, 120), the focal point of the first lens (116) preferably coinciding with the central plane of the deflector units (26x, 26y), and an expansion optics (17) being arranged in front of the controllable optical deflector units (26x, 26y) which gives the light beam (12) a waist at the center plane of these units.

6. deflection device according to one of claims 1 to 5,

characterized by a device (54, 56; 12, 58 to 64) which monitors the space traversed by the deflected light beam for the presence of persons and whose output signal can be used to switch off a light source (16) providing the light beam (12) or in to reduce the power, switch off the deflection unit (14) or operate it independently of the one to be displayed

Controlling information in such a way that the light beam (12) is placed in an edge region of a screen (10) catching it or is moved at high speed over an area, preferably a side area, of such a screen (10), or the light beam (12) is closed by a shutter or to completely or partially hide its modulator.

7. Deflection device according to claim 6, characterized in that the monitoring unit is an ultrasound or infrared room space monitoring device (54, 56) known per se for intrusion detection.

8. deflection device according to claim 6, characterized in that the monitoring device comprises a light guide arrangement (58) arranged at the edge of a screen (10); that a process computer (42) acts on the deflection unit (14) at regular intervals with control signals that the light beam (12) is guided along the light guide arrangement (58); and that a light-sensitive detector (60) is arranged at the end of the light guide arrangement (58), the output signal of which is given to a detector circuit (62, 64) which responds to falling signal edges.

9. Deflection device according to claim 8, characterized in that the speed of movement of the light beam (12) along the light guide arrangement (58) is large and / or the power of the light source (16) is reduced when guiding along the light guide arrangement (58) .

10. Display device according to claim 4 to 9, characterized in that the last lens (120) of the optics (30) is offset downwards with respect to the lens axis, this lens being preferably an f-theta lens.

11. Deflection device according to one of claims 1 to 10, characterized by a flat continuous refractive power profile having a transparent equalization element (18) which is arranged in the beam path and is moved at a frequency which is so great that a frequency of the changes in the refractive power receives which exceeds the temporal resolving power of the human eye and is preferably about 70 to 100 Hz.

12. Deflection device according to claim 11, characterized in that the equalizing element is a circular disc (18) in which the refractive power profile is provided in the circumferential direction and which is preferably driven by a motor (24) at a constant speed.

13. Deflection device according to claim 11 or 12 in conjunction fertilizer with claim 4, characterized in that the equalizing element (18) through the last lens

(120) of the multi-lens optics (30) is imaged sharply on the screen (10).

14. deflection device according to one of claims 1 to 13,

characterized in that the deflector units (26x,

26y) contain optically anisotropic deflector crystals (98, 106) and the means for generating the refractive power fields in the deflector crystals (98, 106) a plurality of spaced apart

Include benerators (100a, 100b), at least one of which is excited via a phase shifter (126).

15. Deflection device according to claim 14, characterized in that the phase shifter (126) is electrical

are controllable phase shifters and their control terminal are acted upon by a signal derived from the external deflection control signal.

16. Deflection device according to claim 14, characterized in that the phase shifter (126) computing circuits

(128), which each generate a phase control signal from the external deflection control signal such that the

Light beam with respect to the wave fronts of the refractive power fields (104, 112) in both deflector crystals (98, 106) each fulfills the Bragg condition.

17. deflection device according to one of claims 1 to 15,

characterized in that the deflector units (26x, 26y) contain optically anisotropic deflector crystals (98, 106) and polarisers (124) are arranged behind them

are whose transmission direction is set to the direction of polarization of the light beam diffracted in a predetermined order, preferably the light beam diffracted in the first order.

18. Deflection device according to one of claims 1 to 16, characterized in that behind the first

Deflector crystal (9B) of a deflector unit (26x, 26y) a diaphragm body (134) is set up, which of the light beams diffracted in different order behind the first deflector crystal (98) only allows the beam diffracted in a predetermined order, but intercepts the other beams.

19. Deflection device according to claim 16, characterized in that between the diaphragm body (134) and the two deflector crystals (98, 106), an optical system (130, 132) is arranged, the focal point in the central plane of the adjacent deflector crystal les (98, 106 ) falls.