WO2025022247A1 - Headmounted display system for displaying a virtual image in the field of view of a user, comprising phase-and amplitude-synchronized beam splitter elements - Google Patents

Abstract

The invention relates to a headmounted display system (1) for displaying a virtual image in the field of view of a user, comprising a screen unit (2) for emitting a light (142), in the form of computer-generated image information, in an emission direction; and comprising a scanning/deflecting unit (3) for scanning the screen unit (2) and for deflecting the computer-generated image information emitted by the scanned screen unit (2) into an eye (15) of the user, wherein the scanning/deflecting unit (3) has at least two beam splitter elements (17, 17ʻ, 17ʻʻ, 17ʻʻʻ) which are arranged one behind the other in the emission direction of the light (142) and each of which comprises a partly translucent reflective surface (17a, 17aʻ, 17aʻʻ, 17aʻʻʻ, 17b, 17bʻ, 17bʻʻ, 17bʻʻʻ), and the beam splitter elements (17, 17ʻ, 17ʻʻ, 17ʻʻʻ) are movably mounted in a tiltable manner about a respective central position along a tilting axis (18, 18ʻ, 18ʻʻ, 18ʻʻʻ) between two reversing positions at which the tilting speed of the beam splitter elements (17, 17ʻ, 17ʻʻ, 17ʻʻʻ) is null when used as intended. The scanning/deflecting unit (3) has a coupling rod element (12), and each of the at least two beam splitter elements (17, 17ʻ, 17ʻʻ, 17ʻʻʻ) is mechanically coupled to the coupling rod element (12) via a respective spring element (11, 11ʻ, 11 ʻʻ, 11ʻʻʻ ) and via at least one respective filament element (43, 43ʻ) in order to achieve an image quality which is as high as possible for virtual images which are as large as possible when using a small-sized headmounted display system (1).

Description

title

Glasses display system for displaying a virtual image in a field of view of a user with phase and amplitude synchronized beam splitter elements

area of the invention

The disclosure relates to a glasses display system for displaying a virtual image in a field of vision of a user, with a screen unit for emitting a light as computer-generated image information in an emission direction; and with a scanning-deflection unit for scanning the screen unit and for deflecting the computer-generated image information emitted by the scanned screen unit into an eye of the user, wherein the scanning-deflection unit has at least two beam splitter elements arranged one behind the other in the emission direction of the light, each with a partially transparent reflection surface, wherein the beam splitter elements are movably mounted, namely tiltable around a respective center position along a tilt axis between two reversal positions at which a tilting speed of the beam splitter elements is zero when used as intended.

background

For a glasses display system for displaying a virtual image in a user's field of view, which is based on a cell-shaped screen unit (in short augmented reality "AR" glasses with line display), the missing image dimension for a two-dimensional virtual image must be created using time multiplexing, also referred to below as scanning. A single beam splitter or mirror can be used for this, but this must have a large dimension for a desirable large field of view. As an advantageous variant, it is possible to use several partially transparent

beam splitter elements. Such a system is known, for example, from DE 10 2021 206 209 B3.

Light or visible rays must be guided with great precision to avoid artifacts in the virtual image. The requirements are based on the resolution of the human eye at 1/60°, whereby a doubled angular accuracy of 1/120° is required for the parallelism of two reflecting beam splitter elements. The doubling results from the physical relationship between the angle of incidence and the angle of reflection, i.e. a movement of a reflecting beam splitter element by 1/120° results in an angular offset of 1/60° for the reflected light beam.

The technical challenge is therefore to achieve the highest possible image quality for the largest possible virtual images while keeping the size of the glasses display system small. overview

This object is achieved by the subject matter of the independent claims. Advantageous embodiments emerge from the dependent claims, the description and the figures.

One aspect relates to a glasses display system for displaying a virtual image in a user's field of vision, i.e. AR glasses. These have a line screen unit for emitting light as computer-generated image information in a direction of emission. The direction of emission is a vertical direction when used as intended. The direction of emission can be understood as the mean direction of an emitted parallel or essentially parallel light beam as emitted light. To parallelize the light generated, for example, in a cell-shaped display element, the screen unit can accordingly have one or more lens and/or mirror elements, in particular one or more free-form lens and/or mirror elements. The line screen unit can also be referred to as a cell-shaped screen unit, since at a given time it can only display one or a few lines of a two-dimensional (2D) image to be displayed. The second dimension of the image to be displayed is accessed by displaying further lines of the image to be displayed at other times (time multiplexing). In this case, a length as the main direction of extension of the display element of the cell-shaped screen unit can be at least one order of magnitude, i.e. a factor of 10, in particular at least 1.5 orders of magnitude, i.e. a factor of 50, greater than a width of the display element running transversely to the length. In particular, the width and/or length of the display element run transversely, i.e. essentially perpendicular (perpendicular or perpendicular up to a predetermined deviation) to the radiation direction.

The glasses display system also has a scanning-deflection unit for scanning the screen unit and for deflecting the computer-generated image information emitted by the scanned screen unit into a second direction that is different from the direction of emission into the user's eyes. The second direction can also be understood as a directional range that covers various possible positions of the eye when used as intended, i.e., positions of the eye in a so-called eyebox, as well as a target position for the line of the 2D image displayed by the line screen unit at a given time in the user's field of vision. The second direction can be understood as an essentially horizontal direction or an essentially horizontal directional range. The second direction or the second directional range is then oriented horizontally up to a predetermined deviation of, for example, a maximum of 55 or a maximum of 45 degrees when used as intended, i.e. the second directional range then only includes directions that deviate from the horizontal by less than the predetermined deviation. The specified deviation can also be less, for example 25 or 15 degrees, and individually for a deviation from the horizontal in the positive and negative vertical direction.

The scanning deflection unit has at least two, preferably more than two, for example four or five or six or seven or eight or nine or ten, in the Beam splitter elements arranged one behind the other in the direction of light emission, each with at least one reflection surface that is partially transparent to the light emitted by the screen unit. The reflection surface can also be referred to or understood as a mirror layer, ie a reflective layer. The reflection or mirroring of the surface can be achieved, for example, by a difference in the refractive index with or without a coating of a (for example glass) carrier.

The beam splitter elements can also be arranged one behind the other in the direction of radiation, offset in the horizontal direction. The beam splitter elements are mounted so that they can be moved, namely around a respective central position around or along a tilt axis running perpendicular to the direction of radiation and the second direction, between two reversal positions. At the reversal positions, the tilting speed of the beam splitter elements is zero when used as intended, in which the scanning of the screen unit or the redirection of the computer-generated image information to different positions in the user's eye is achieved by tilting back and forth between the two reversal positions.

The tilt axis runs along a main extension direction, a length of the beam splitter elements. Since the beam splitter elements only actively scan in one dimension, namely the dimension perpendicular to the tilt axis and thus perpendicular to the (main extension direction of the) line screen unit or the line display element, the scanning deflection unit can also be referred to as a one-dimensional (ID) scanning deflection unit.

The screen unit and scanning deflection unit can be arranged on a common frame unit, a glasses frame unit, by means of which the glasses display system can be worn by the user on his head. The glasses display system can have a control unit for controlling the scanning deflection unit and the screen unit, which synchronizes the angular position of the beam splitter elements based on sensor data from a sensor unit for detecting the respective angular positions of the beam splitter elements with the image contents of the line screen, i.e. the light emitted as computer-generated image information at a given time.

The scanning deflection unit has respective thread elements, each of which mechanically couples one (or more) beam splitter elements to a coupling rod element and is designed to hold the coupled beam splitter elements in a predetermined parallel position when the beam splitter elements coupled via thread elements and coupling rod element are moved around the tilt axis. The respective thread element thereby realizes a positive, tension-positive mechanical connection between the respectively assigned beam splitter element and coupling rod element. The thread element can be understood as a thread in the broader sense. Accordingly, the thread element can consist in particular of glass fiber, polyethylene, polyamide, nylon, steel, stainless steel, carbon fiber, aramid, natural fiber (such as silk or spider threads) or other fibers, or comprise one or more of the components mentioned. The thread element can also be chosen as a monofilament or as a filament bundle, as well as braided or twisted in some other way. A round cross-section does not have to be chosen for the thread element(s), the thread element can also be in the form of a Flat strip. Also referred to as thread elements are form-fitting mechanical connections which are implemented using thin and thus thread-like etched parts, for example using structures etched from silicon, glass or metal. This allows the mechanical coupling of the thread element in the form of a thin thread-like structure to the associated beam splitter elements to be integrated as a common etched part. As an alternative to this integration, the thread element can be connected to the beam splitter element in a form-fitting manner using adhesive, whereby alternatively or in addition other joining methods can be used such as welding and/or knotting and/or others.

The thread element is a thin structure compared to the beam splitter element and the coupling rod element, which creates a mechanical connection between each of the beam splitter elements and the coupling rod element, is positively connected to the respective beam splitter element and the coupling rod element and enables a relative movement of the beam splitter elements preferably exclusively by means of elastic deformation. Spring energy can also be absorbed by the thread element, which stores kinematic energy as a participating spring element during an oscillating movement of the beam splitter elements and thus influences the natural frequency of the coupled beam splitter elements.

The scanning deflection unit also has at least two spring elements, each of which additionally mechanically couples a beam splitter element to the coupling rod element and is designed to hold the beam splitter elements coupled by the coupling rod element in a predetermined parallel position when the beam splitter elements coupled by the coupling rod element are moved around the tilt axis. The spring element thereby creates a positive, force-locking mechanical connection between the respective beam splitter element and the coupling rod element and reduces the forces acting on the associated thread element. The spring element therefore refers to a structure that is thin compared to the beam splitter element and coupling rod element, but thick compared to the thread element. The thickness of the thread element and coupling rod element can be understood, for example, as a size of a cross-sectional area transverse to the radiation direction, the thickness of the beam splitter elements as a size of a cross-sectional area transverse to the tilt axis, and the thickness of the spring elements as a size of a cross-sectional area parallel to the plane spanned by the tilt axes.

Thus, each of the at least two beam splitter elements is mechanically coupled to the coupling rod element via a respective spring element and via at least one respective thread element. As a result, the phase of the beam splitter elements is synchronized at least substantially by means of a first force transmission through the respective spring element, via which the respective beam splitter element is mechanically coupled to the coupling rod element, and the amplitude of the beam splitter elements is synchronized at least substantially by means of a second force transmission through the respective thread element, via which the respective beam splitter element is mechanically coupled to the coupling rod element.

The present approach is based on the realization that the beam splitter elements for scanning are best designed as a spring-mass system, which Natural frequency that corresponds to the desired half refresh rate of the virtual AR image. Since two images can be displayed per oscillation when scanning up and down, the full refresh rate is achieved. The "mass" of the spring-mass system is essentially given by the mass moments of inertia of the beam splitter elements. In addition, a "spring" is necessary in the spring-mass system to absorb the forces. The spring proposed here comprises the spring elements and the coupling rod element. The thread element can be neglected when viewed as a spring-mass system due to the low elastic deformation compared to the spring element.

The phenomenon of weakly coupled systems and the phenomenon of isochronism are known from physics. For example, metronomes that are placed on a common table form a weakly coupled system. If the natural frequencies in such a system are sufficiently similar but not the same, the individual sub-systems oscillate in phase after an initial settling time. The proposed scanning-deflection unit also forms a coupled spring-mass system, but with a very high coupling in order to promote oscillation of the sub-systems, namely the individual beam splitter elements with their respective associated components, in phase. In this case, one can also speak of a strongly coupled system. However, here too, as a technical feature, an (individual) natural frequency of each individual beam splitter with spring element is best chosen so that it is identical to the (total) natural frequency of the entire system, i.e. the scanning-deflection unit. If the beam splitter elements are not identical, i.e. if they have different mass moments of inertia due to different geometric dimensions, for example, then the stiffness of the spring element can be individually adjusted in order to adapt the natural frequencies of the individual beam splitter elements to each other and/or to the overall natural frequency, i.e. to match them as precisely as possible. Preferably, the natural frequencies of the respective beam splitter elements are at least essentially the same as each other and/or a natural frequency of the scanning deflection unit. This minimizes the forces occurring in the system and which have to be absorbed by the thread element, spring element and coupling rod element, which is advantageous for the amplitude synchronization of the beam splitters.

The phenomenon of isochronism states that a spring-mass system can oscillate at the same natural frequency, independent of the amplitude, to a very good approximation. With regard to the requirement of the (parallel) alignment of the beam splitter elements or the reflection surfaces, it is therefore possible that even if the same natural frequency was selected for each individual system of the respective beam splitter elements, the entire system of the scanning deflection unit can oscillate at a natural frequency at which each spring element oscillates with its own amplitude. Thus, in addition to synchronizing the phase, synchronizing the amplitude is also necessary.

For the purpose of synchronizing the amplitude, a (preferably play-free pre-tensioned) thread kinematics is proposed, for which a round or elliptical or other shaped run-off surface is preferably present on the beam splitter elements, as described below. A thread element is attached to the coupling rod element as described and connects one or more beam splitter elements with the coupling rod element. In the sense of increased symmetry and thus For an advantageous distribution of the forces occurring, the mechanical coupling can also be bilateral:

An angular movement of the beam splitter elements results in a vertical, predominantly translational movement of the thread element because it is pulled up and down. In this way, the angular amplitude is also mechanically coupled to the coupling rod element, i.e. synchronized with the other beam splitter elements via the coupling rod element. The attachment to the coupling rod also allows the system to be pre-tensioned in order to achieve a play-free coupling. For this purpose, an upper and a lower thread connection is symmetrically present for each beam splitter element, i.e. each of the at least two beam splitter elements is mechanically coupled to the corresponding thread element in an area of the coupling rod element that is closer to the screen unit and in an area of the coupling rod element that is further away from the screen unit. The respective areas of the coupling in which the thread element(s) are attached to the coupling rod element are preferably located on a respective holding arm of the coupling rod element. Such a holding arm can be a projection of the coupling rod element in the second direction, which projects into the area between two adjacent beam splitter elements in a projection on a plane running perpendicular to the tilt axis, or can comprise such a projection. This has the advantage that the preload can be completely absorbed in the coupling rod element and in particular does not have to be absorbed via bearings.

The described approach with the double coupling of the beam splitter elements with both thread and spring elements thus creates the effect of optimal distribution of the forces occurring on different mechanical systems, which enables the separate and therefore long-term precise synchronization of phase and amplitude. This enables a particularly precise positioning of the different beam splitter elements relative to each other and thus a particularly good image quality with little space requirement.

In one embodiment, it is provided that the coupling rod element has a first coupling rod element part and a second coupling rod element part, the main extension directions of which each run transversely to the tilt axes along a vertical direction and at least substantially parallel to one another, wherein the respective tilt axes run through an area between the two coupling rod element parts. The first coupling rod element part is further away than the second coupling rod element part according to the user. The pair of first and second coupling rod element parts is preferably arranged laterally, i.e. in a beam splitter element end area, on the beam splitter elements. The mechanical coupling described for the coupling rod element via the corresponding thread and/or spring element is then designed for each coupling rod element part and thus multiple times. This has the advantage that the symmetry is increased again and the forces that occur are better distributed.

In particular, it is provided that the two coupling rod element parts are each anchored via a respective flexible anchor arm to at least one - preferably common - anchor element. The respective anchor element is relatively arranged in a fixed position relative to the screen unit, in particular with an anchor element arranged in the direction of radiation between the screen unit and the beam splitter elements and/or a further anchor element arranged behind the beam splitter elements in the direction of radiation from the screen unit. The anchor arms are preferably dimensioned such that the vertical movement of the coupling rod element and the inward movement of the coupling rod element corresponds to the movement of the anchor arms. The coupling rod element and anchor arms then form the kinematics of a parallelogram. The tilting forces of the entire system can thus be absorbed without play. This is particularly advantageous when the beam splitter elements are mounted with a torsion bar. A torsion bearing element with a torsion bar or a torsion thread cannot absorb radial forces, but can mount them without friction. This creates additional torsional spring moments in the torsion bar, which can be designed as a thin wire, for example, which must be taken into account when designing the natural frequency.

It can also be provided that a circle radius assigned to the anchor arms when the coupling rod element parts move along the direction of radiation is different from a corresponding spring arm of the respective spring elements when the coupling rod element parts move along the direction of radiation. The anchor arms can thus be longer or shorter than the corresponding components of the spring elements, i.e. spring arms extending from a receptacle on the beam splitter elements to the coupling rod element in order to minimize the effects of force on the coupling rod element parts when the coupling rod element parts are moved.

In a further embodiment, it is provided that the spring elements are each designed with at least one spring arm, preferably two spring arms, which in particular each form a spiral spring with the associated tilting axis as the spiral spring axis or are part of such a spiral spring. This has the advantage that the corresponding spring constants can be adapted favorably in terms of production technology.

In particular, it can be provided that spring elements, in particular spring arms, of different groups of beam splitter elements are designed with different thicknesses, each of which is an integer multiple of a unit thickness. The thickness is preferably measured in the direction of the tilt axis. This is advantageously combined with dimensions of the beam splitter elements, which are selected such that the mass moments of inertia of the beam splitter elements of different groups are, for each group, the integer multiple of a unit mass moment of inertia corresponding to the multiple of the unit thickness. This has the advantage that different dimensions can be selected for the beam splitter elements, and yet an essentially identical natural frequency can be achieved for the beam splitter elements and/or the beam splitter element groups. At the same time, only the relative difference in the manufacturing deviation between the respective spring elements is then relevant. For example, the respective spring elements can be composed of one or more base spring elements with a uniform thickness, for example glued or welded together. In another embodiment, a rolling surface for the at least one thread element is arranged on each of the beam splitter elements, the length of the rolling surface corresponding to the angular range between the two reversal positions. The rolling surface therefore has at least a length which, in terms of radians, corresponds to the maximum angular movement of the associated beam splitter. This prevents the thread element from buckling, which improves the longevity and accuracy of the mechanical coupling, in particular ensuring fatigue strength.

It can be provided that the respective rolling surface, viewed in the plane transverse to the respective tilt axis, has the shape of an ellipse or an ellipse segment. This has the advantage that the thread element always remains vertically aligned at least for a small angle range of, for example, +/-20° around the center position, since the elliptical shape compensates for an internal movement of the coupling rod element in the direction of the tilt axis during the tilting movement of the thread element. This not only prevents acoustic vibrations, but also increases the fatigue strength because buckling is avoided in a particularly gentle manner.

In particular, it can also be provided that the respective thread element is arranged on the rolling surface in a plane transverse to the respective tilt axis, circulating once around the tilt axis. This has manufacturing advantages and allows a one-piece thread coupling of the beam splitter elements to the coupling rod element, which leads to particularly high precision.

The corresponding thread element can run between the assigned beam splitter element and the area further away from the screen unit essentially parallel to the thread element between the assigned beam splitter element and the area closer to the screen unit, in particular along the direction of radiation. This allows the forces that occur to be diverted as best as possible and the respective thread element to be pre-tensioned without additional forces being introduced into a bearing element of the beam splitter elements. This again improves durability and precision.

It is particularly advantageous if each of the at least two beam splitter elements is mechanically coupled to the coupling rod element by means of two thread elements, with a thread element closer to the user being arranged essentially between a plane spanned by the tilting axes and the user, and a thread element further away from the user being arranged essentially behind the plane spanned by the tilting axes when viewed from the user. This also serves to distribute the forces that occur more symmetrically and thus contributes to increased longevity and precision. In addition, the tilting axis is fixed in its position, since neither rotation of the beam splitter is possible nor is vertical or horizontal movement possible without the system oscillating in the desired mode in which the coupling rod moves vertically and the beam splitters oscillate with a rotational movement. This is particularly advantageous when torsion bearings are used that cannot absorb radial forces or can only absorb them when there is a deflection from the central position.

In a further embodiment, it is provided that the beam splitter elements are movably mounted around the tilt axis by means of respective torsion bearing elements. The Torsion bearing elements can, for example, have a wire that functions as a torsion bar. This has the advantage that a very small, play-free bearing is created, which, in contrast to known systems, can easily be implemented as a miniaturized system. The play-free design avoids vibration noises and also improves the precision of the deflection of the beam splitter elements. In addition, friction plays no role in torsion bearing elements, which saves noise, vibrations and energy and also results in less wear. This also improves the precision of the deflection of the beam splitter elements.

A further aspect relates to a method for synchronizing the amplitude and phase of a scanning movement of beam splitter elements of a glasses display system for displaying a virtual image in a field of vision of a user. The glasses display system has a screen unit for emitting light as computer-generated image information in a radiation direction, and a scanning-deflection unit for scanning the screen unit and for deflecting the computer-generated image information emitted by the scanned screen unit into an eye of the user. The scanning-deflection unit has at least two beam splitter elements arranged one behind the other in the radiation direction of the light, each with a partially transparent reflection surface. The beam splitter elements are movably mounted and can be tilted around a respective center position along a tilt axis between two reversal positions at which a tilt speed of the beam splitter elements is zero when used as intended.

The method has the method steps of synchronizing the phase of the beam splitter elements at least substantially by means of a first force transmission through a respective spring element, via which the respective beam splitter element is mechanically coupled to a coupling rod element; and synchronizing the amplitude of the beam splitter elements at least substantially by means of a second force transmission through at least one respective thread element, via which the respective beam splitter element is mechanically coupled to the coupling rod element.

Advantages and advantageous embodiments of the latter aspect correspond to the advantages and advantageous embodiments described for the former aspect and vice versa.

The described features and feature combinations, including those in the general introduction, as well as the features and feature combinations disclosed in the description of the figures or the figures alone, can be used not only alone or in the combination described, but also with other features or without some of the disclosed features, without departing from the scope of the invention. Consequently, embodiments that are not explicitly shown and described in the figures, but that can be produced by separately combining the individual features disclosed in the figures, are also part of the invention. Therefore, embodiments and feature combinations that do not include all the features of an originally formulated independent claim are also to be regarded as disclosed. Furthermore, embodiments and feature combinations that deviate from the feature combinations or go beyond those described in the dependencies of the claims are to be regarded as disclosed. In the context of this disclosure, "transverse/along" can be understood as "at least substantially perpendicular/parallel", i.e. "vertical/parallel" or "substantially perpendicular/parallel", i.e. perpendicular/parallel up to a predetermined deviation. The predetermined deviation can be, for example, at most 15°, preferably at most 5°, particularly preferably at most 3°. Accordingly, "oppositely oriented" in the context of this disclosure can be understood as "at least substantially oppositely oriented", i.e. "at least substantially antiparallel oriented". The restriction "substantially" can also refer to a maximum permissible deviation specified as a percentage, for example at most 15%, preferably at most 5%, particularly preferably at most 3%.

Detailed description

Exemplary embodiments are described in more detail below using schematic drawings.

Fig. 1 shows an exemplary embodiment of a glasses display system for displaying a virtual image in a field of view of a user at two different times;

Fig. 2 shows an exemplary embodiment of a scanning deflection unit;

Fig. 3 further exemplary embodiments of a scanning deflection unit;

Fig. 4 shows yet another exemplary embodiment of a scanning deflection unit; and

Fig. 5 shows a part of another exemplary embodiment of a scanning deflection unit.

In the figures, identical or functionally equivalent features are provided with the same reference symbols.

In Fig. 1, an exemplary embodiment of a glasses display system for displaying a virtual image in a field of view of a user at two different times is shown.

The glasses display system 1 has a screen unit 2 for emitting light as computer-generated image information in a direction of emission, here the negative y-direction and, when used as intended, a vertical direction. The light is symbolized here with the light beam 142 as part of the light. In the example shown, the screen unit 2 comprises a cell-shaped display element 131 with pixels arranged in rows mainly in the z-direction, which emits a light 141 that is imaged to infinity, i.e. parallelized, by a lens and/or mirror element 132. The light beam 142 is a light beam of the parallelized light. The glasses display system 1 also has a scanning deflection unit 3 for scanning the screen unit 2 and for deflecting the computer-generated image information emitted by the scanned screen unit into an eye 15 of the user. The scanning deflection unit 3 has at least two, in this case four, beam splitter elements 17, 17', 17", 17'" arranged one behind the other in the direction of emission of the light with at least one (here two) respective partially transparent reflection surface 17a, 17a', 17a", 17a'", 17b, 17b', 17b", 17b'", in this case with one reflection surface 17a, 17a', 17a", 17a'" on a front side facing the screen unit 2 and with one reflection surface 17b, 17b', 17b", 17b'" on a rear side facing away from the screen unit 2. The beam splitter elements 17, 17', 17", 17'" are movably mounted, namely around a respective center position along a tilt axis 18, 18', 18", 18'" tiltable between two reversal positions at which a tilt speed of the beam splitter elements is zero when used as intended. The tilt axes 18, 18', 18", 18'" run in the z-direction in the Fig. 1 shown.

A two-dimensional virtual image becomes visible to the user by performing time multiplexing. For this purpose, when used as intended, the beam splitter elements 17, 17', 17", 17'" arranged parallel to the reflection surfaces 17a, 17a', 17a", 17a'" and 17b, 17b', 17b", 17b'" move with an angular range of, for example, +/-20° around the center position with, for example, a sinusoidal movement profile around their respective tilt axis 18, 18', 18", 18'". For a given point in time, i.e. for a fixed angular position of the beam splitter elements 17, 17', 17", 17'", the light beams 142 are deflected at each beam splitter element 17, 17', 17", 17'" such that corresponding subsequent light beams 143a, 143a', 143a", 143a'" and 143b, 143b', 143b", 143b'" are deflected in the direction of the user. The beam splitter elements 17, 17', 17", 17'" are arranged in such a way that a portion of these subsequent light rays 143a, 143a', 143a", 143a'" and 143b, 143b', 143b", 143b'" hit the pupil 151 of the eye 15. This creates virtual light rays 144a and 144b, which the eye 15 perceives under the assumption that light always propagates in a straight line.

In Fig. lb), the time multiplexing is shown for a different point in time, in which the beam splitter elements 17, 17', 17", 17'" have assumed a different angular deflection 171. In this case, the light is deflected in the direction of the subsequent light beam 18 and the observing eye sees a virtual light beam 181. For the time multiplexing, a scanning movement of the beam splitter elements 17, 17', 17", 17'", a scanning of the screen unit 2 and a deflection of the light beams 142 at changing angles is therefore necessary.

The beam splitter elements 17, 17', 17", 17'" and thus the scanning-deflection unit 3 are designed as a spring-mass system oscillating with a sinusoidal movement profile. This has the advantage that only a small amount of energy needs to be introduced to maintain the oscillation and the scanning-deflection unit 3 carries out a sinusoidal scanning movement without additional movement control. The mass of the mass-spring system to be considered is essentially given by the mass moment of inertia of the beam splitter elements 17, 17', 17", 17'". In the present case, a system of spring elements 11, 11', 11", 11'" serves as the spring, each of which mechanically couples an associated beam splitter element 17, 17', 17", 17'" to a coupling rod element 12. In the example shown, the coupling rod element 12 has a first coupling rod element part 12a and a second coupling rod element part 12b, the main extension directions of which each run transversely to the tilt axes 18, 18', 18", 18'" along the vertical direction -y and at least substantially parallel to one another, wherein the respective tilt axes 18, 18', 18", 18'" run through an area between the two coupling rod element parts 12a, 12b. In addition to the mechanical coupling of the beam splitter elements 17, 17', 17", 17'" to the coupling rod element 12 via the spring elements 11, 11', 11", 11'", the beam splitter elements 17, 17', 17", 17'" are also mechanically coupled to the coupling rod element 12 via at least one, preferably two respective thread elements 43, 43' (Fig. 4). The thread elements

An angular deflection such as the angular deflection 171 of the beam splitter elements 17, 17', 17", 17'" shown in Fig. lb results in a displacement of the coupling rod element parts 12a, 12b in a positive or negative vertical direction and thus a mechanical elastic deformation of the spring elements 11, 11', 11", 11'". Kinetic energy is stored in the spring elements 11, 11', 11", 11'", so that the spring-mass system oscillates at a designable natural frequency. The natural frequency is best designed as half the refresh rate because the image is scanned twice per oscillation.

An exemplary embodiment of a scanning deflection unit is shown in Fig. 2. The spring elements 11, 11', 11", 11'" can be made, for example, from spring steel, silicon, glass or from a combination of these or other, particularly hybrid materials. The spring elements 11, 11', 11", 11'" are comparatively thin so that spring energy can be stored in them in the form of elastic deformation. The material-dependent maximum permissible stress in the material must not be exceeded. The maximum stress is reached at the maximum angular deflection, which must be taken into account accordingly in the design.

Accordingly, within the scope of the design, the spring elements 11, 11', 11", 11'" can be enlarged in the z-direction, i.e. in their thickness, in order to set the necessary spring constant to achieve a desired natural frequency. In the present case, there are three groups A, B, C of beam splitter elements 17, 17', 17", 17'". In the example shown, the first group A and the second group B each comprise a beam splitter element 17, 17' and the third group C comprises two beam splitter elements 17", 17'".

The spring elements 11", 11'" of the third group C can, for example, be designed with the unit thickness, the spring elements 11' of the second group B with twice the unit thickness and the spring elements 11 of the first group A with three times the unit thickness. The respective spring elements 11, 11', 11", 11'" can consist of or include one (group C), two (group B) or three (group A) base spring elements with the corresponding unit thickness. The respective base spring elements can then be lined up along the tilt axes 18, 18', 18", 18'" in the z direction and couple the beam splitter elements 17, 17', 17", 17'" to the coupling rod element 12. The base spring elements of a beam splitter element 17, 17', 17", 17'" can be materially connected to one another, so that the corresponding spring element 11, 11' is a one-piece spring element 11, 11', or not be materially connected to one another, so the corresponding spring element 11, 11' can be a multi-part spring element 11, 11'.

In Fig. 2b) the forces F, G and moments M that arise when the beam splitter elements 17, 17', 17", 17'" are deflected are shown. Each beam splitter element 17, 17', 17", 17'" generates a moment M that causes the elastic deformation of the spring elements 11, 11', 11", 11'". This results in several resulting forces, which is why the spring elements 11, 11', 11", 11'" and coupling rod element 12 in the form shown tend to rotate in the x-y plane. The forces F, G can be absorbed by bearings on the tilt axes 18, 18', 18", 18'". Since these are oscillating forces, it is advantageous to design the bearings without play.

Accordingly, another exemplary embodiment of a scanning deflection unit is shown in Fig. 3. In order to reduce or completely avoid the lateral movements in the x-y plane resulting from the forces F shown in Fig. 2b), the two coupling rod element parts 12a, 12b are each anchored to at least one anchor element 32 or 32' via a respective flexible anchor arm 31, 31' or 31", 31'". The respective anchor element 32, 32' is arranged in a fixed position relative to the screen unit 2.

The first anchor element 32 is arranged here in the radiation direction between the screen unit 2 and the beam splitter elements 17, 17', 17", 17'", the second anchor element 32' is arranged behind the beam splitter elements 17, 17', 17", 17'" when viewed from the screen unit 2. The anchor elements 32, 32' thus limit the movement of the coupling rod element parts 12a, 12b according to parallel kinematics. Lateral forces F (Fig. 2b) are absorbed by the anchor elements 32, 32' and lateral movements in the x-direction are thus reduced or avoided. In Fig. 3a) the movement of the beam splitter elements 17, 17', 17", 17'" is shown for three angular positions 34, 34', 34". The coupling rod element parts 12a, 12b make a stroke of d.

In the exemplary embodiment of Fig. 2b), a circle radius assigned to the anchor arms 31, 31' when the coupling rod element parts 12a, 12b move along the radiation direction is different from a circle radius assigned to the spring arms 11a, 11b of the respective spring elements 11 when the coupling rod element parts 12a, 12b move along the radiation direction. The anchor arms 31, 31' are longer than the spring arms 11a, 11b in this case, corresponding to a larger circle radius.

The coupling rod element parts 12a, 12b essentially make a movement in the y-direction with stroke d, as shown in Fig. 3a). However, a (smaller) movement also occurs in the x-direction, since the spring elements 11 rotate around the tilt axis 18. The variant in Fig. 3b enables a design that allows the same movements of the coupling rod element parts 12a, 12b in the y- and x-direction as a function of the angular deflection caused by the spring elements 11 and the anchor arms 31, 31'. Under the mathematical assumption that the spring elements 11 and the anchor arms 31, 31', 31", 31'" undergo an elastic deformation, which is approximated as a circular arc with a constant radius, it can be shown that the movements cannot be perfectly synchronized, but the differences only diverge in the small single-digit micrometer range. A sufficiently precise design of identical movements is therefore possible and due to the flexible anchor arms 31, 31', 31", 31'" small deviations are compensated by means of elastic deformations. As a degree of freedom in the design, the length of the anchor arms 31, 31' is selected to be different from the length of the spring elements 11 or the spring arms 11a, 11b.

Fig. 4 shows yet another exemplary embodiment of a scanning deflection unit. Since the spring elements 11, 11', 11", 11'" shown in Figs. 1-3 can only achieve phase synchronization of the beam splitter elements 17, 17', 17", 17'", but not amplitude synchronization, at least one form-fitting thread element 43, 43' is used for additional coupling of the beam splitter elements 17, 17', 17", 17'" to the coupling rod element 12. The exemplary structure of the thread kinematics shown here is explained below.

A thread element 43, here (preferably symmetrically) two thread elements 43 and 43' are guided around a respective rolling surface 42, 42', 42", 42'" and attached to respective holding arms 41, 41', 41", 41'", ... on the coupling rod element 12. The holding arms 41, 41', 41", 41'", ... protrude in the selected representation, i.e. an orthogonal projection into the drawing plane running perpendicular to the tilt axes 18, 18', 18", 18'", into areas between the next adjacent beam splitter elements 17, 17', 17", 17'".

Each of the at least two beam splitter elements 17, 17', 17", 17'" is thus mechanically coupled to the coupling rod element 12 by means of two thread elements 43, 43'. A thread element 42 closer to the user is arranged essentially between a plane spanned by the tilt axes 18, 18', 18", 18'" and the user, and a thread element 43' further away from the user is arranged essentially behind the plane spanned by the tilt axes 18, 18', 18", 18'" when viewed from the user.

The respective rolling surface 42, 42', 42", 42'" has the shape of an ellipse or an ellipse segment when viewed in the plane transverse to the respective tilt axis 18, but can also have other shapes such as a circle. The rolling surfaces 42, 42', 42", 42'" are arranged on the associated beam splitter elements 17, 17', 17", 17'". The length of the rolling surfaces 42, 42', 42", 42'" corresponds at least to the angular range between the two reversal positions. In this case, the respective thread element 43, 43' is arranged on the rolling surface 42 in a plane transverse to the respective tilt axis 18, i.e. the plane of the drawing, so as to encircle the tilt axis 18 once.

The rolling surfaces 42, 42', 42", 42'" are thus designed in such a way that an angular deflection of the jet splitter elements 17, which is positively connected to the run-off surface 42, winds up as many of the thread elements 43, 43' as the coupling rod element 12 moves.

In the present case, each of the at least two beam splitter elements 17, 17', 17", 17'" is mechanically coupled to the coupling rod element 12 with the corresponding thread element 43, 43' in an area closer to the screen unit 2 and an area further away from the screen unit 2. The respective areas are located on the holding arms 41, 41', 41", 41'", ... The respective thread element 43, 43' runs between the associated beam splitter element 17 and the area further away from the screen unit 2 essentially parallel to the thread element 43, 43' between the associated beam splitter element 17 and the area closer to the screen unit. The holding arms 41 and 41" between the next adjacent beam splitter elements 17, 17', 17", 17"' allow a pre-tension to be given to the respective thread elements 43, 43' without this force having to be absorbed in the bearings of the tilting axes 18, 18', 18", 18'" or the anchor elements 32, 32', since the fastening leads to a balance of forces and the forces cancel each other out. For the purpose of simpler illustration, the thread 43 is shown in Fig. 4 with some distance around the run-off surface 42. Due to the advantageous freedom of play, however, a tight winding should be aimed for in the actual implementation, e.g. by giving a pre-tension to the respective thread elements 43, 43' during winding. A representation has been chosen for the thread element 43' which is designed tightly around the ellipses. Depending on the angle range used, only partial sections and thus segments of the ellipses are used as rolling surfaces 42, 42', 42", 42"'.

Figure 5 shows part of another exemplary embodiment of a scanning deflection unit. There, the spring elements 11, 11', 11", 11'" are each designed with at least one, here two spring arms 11a, 11b, which each form a spiral spring with the associated tilt axis 18 as a spiral spring axis or are part of such a spiral spring.

Accordingly, the spring elements 11, 11', 11", 11'" are not designed as a substantially straight structure, but as a spiral spring-like structure. This can be an advantageous variant if the spring stiffness of the spring elements 11, 11', 11", 11'" has to be further reduced due to the maximum permissible stresses in the material. This variant is also compatible with amplitude synchronization by means of run-off surfaces as shown in Fig. 4. The spring elements 11, 11', 11", 11'" are advantageously designed to be point-symmetrical about tilting axes 18, 18', 18", 18'", which prevents imbalances.

Claims

claims 1. Glasses display system (1) for displaying a virtual image in a field of view of a user, with - a screen unit (2) for emitting a light (142) as computer-generated image information in an emission direction; - a scanning-deflecting unit (3) for scanning the screen unit (2) and for deflecting the computer-generated image information emitted by the scanned screen unit (2) into an eye (15) of the user, wherein the scanning-deflecting unit (3) has at least two beam splitter elements (17, 17', 17", 17'") arranged one behind the other in the direction of emission of the light (142) with a respective partially transparent reflection surface (17a, 17a', 17a", 17a"', 17b, 17b', 17b", 17b'"), wherein the beam splitter elements (17, 17', 17", 17"') are movably mounted, tiltable around a respective center position along a tilt axis (18, 18 ', 18", 18 '") between two reversal positions, at which a tilting speed of the beam splitter elements (17, 17', 17", 17'") is zero when used as intended; characterized in that the scanning deflection unit (3) has a coupling rod element (12) and each of the at least two beam splitter elements (17, 17', 17", 17'") is mechanically coupled to the coupling rod element (12) via a respective spring element (11, 11', 11", 11'") and via at least one respective thread element (43, 43'). 2. Spectacle display system (1) according to claim 1, characterized in that the coupling rod element (12) has a first coupling rod element part (12a) and a second coupling rod element part (12b), the main extension directions of which each run transversely to the tilt axes (18, 18', 18", 18"') and at least substantially parallel to one another, wherein the respective tilt axes (18, 18', 18", 18'") run through a region between the two coupling rod element parts (12a, 12b). 3. Glasses display system (1) according to the preceding claim, characterized in that the two coupling rod element parts (12a, 12b) are each anchored to at least one anchor element (32, 32') via a respective flexible anchor arm (31, 31', 31", 31'"), wherein the respective anchor element (32, 32') is arranged in a stationary manner relative to the screen unit (2), in particular with an anchor element (32, 32') arranged in the radiation direction between the screen unit (2) and the beam splitter elements (17, 17', 17", 17'") and/or a further anchor element (32, 32') arranged behind the beam splitter elements (17, 17', 17", 17'") when viewed in the radiation direction from the screen unit (2). 4. Spectacle display system (1) according to the preceding claim, characterized in that a force acting on the anchor arms (31, 31', 31", 31'") during a movement of the coupling rod Element parts (12a, 12b) along the radiation direction associated circular radius is different from a corresponding spring arm (11a, 11b) of the respective spring elements (11, 11', 11", 11'") during the movement of the coupling rod element parts (12a, 12b) along the radiation direction associated circular radius. 5. Spectacle display system (1) according to one of the preceding claims, characterized in that the spring elements (11, 11', 11", 11'") are each designed with at least one spring arm (11a, 11b), preferably two spring arms (11a, 11b), which each form a spiral spring with the associated tilt axis (18, 18', 18", 18'") as a spiral spring axis or are part of such a spiral spring. 6. Spectacle display system (1) according to one of the preceding claims, characterized in that a rolling surface (42, 42', 42", 42'") for the at least one thread element (43, 43') is arranged on each of the beam splitter elements (17, 17', 17", 17'"), wherein the rolling surface (42, 42', 42", 42"') corresponds in its length to the angular range between the two reversal positions. 7. Spectacle display system (1) according to the preceding claim, characterized in that the respective rolling surface (42, 42', 42", 42'"), viewed in a plane transverse to the respective tilt axis (18, 18', 18", 18'"), has the shape of an ellipse or an ellipse segment. 8. Spectacle display system (1) according to one of the two preceding claims, characterized in that the respective thread element (43, 43 ') is arranged on the rolling surface (42, 42', 42", 42" ') in the plane transverse to the respective tilt axis (18, 18', 18", 18" ') so as to encircle the tilt axis (18, 18', 18", 18'") once. 9. Spectacle display system (1) according to one of the preceding claims, characterized in that Natural frequencies of the respective beam splitter elements (17, 17', 17", 17'") are at least substantially equal to a natural frequency of the scanning deflection unit (3). 10. Glasses display system (1) according to one of the preceding claims, characterized in that each of the at least two beam splitter elements (17, 17', 17", 17'") is mechanically coupled to the coupling rod element (12) with the corresponding thread element (43, 43') in a region of the coupling rod element (12) that is closer to the screen unit (2) and further away from the screen unit (2), wherein the respective regions are preferably located on a respective holding arm (41, 41', 41", 41'") of the coupling rod element (12). 11. Glasses display system (1) according to the preceding claim, characterized in that the thread element (43, 43') between the associated beam splitter element (17, 17', 17", 17'") and the area further away from the screen unit (2) runs essentially parallel to the thread element (43, 43') between the associated beam splitter element (17, 17', 17", 17'") and the area closer to the screen unit (2). 12. Glasses display system (1) according to one of the two preceding claims, characterized in that each of the at least two beam splitter elements (17, 17', 17", 17'") is mechanically coupled to the coupling rod element (12) by means of two thread elements (43, 43'), wherein a thread element (43, 43') closer to the user is arranged substantially between a plane spanned by the tilt axes (18, 18', 18", 18"') and the user, and a thread element (43, 43') further away from the user is arranged substantially behind the plane spanned by the tilt axes (18, 18', 18", 18'") when viewed from the user. 13. Spectacle display system (1) according to one of the preceding claims, characterized in that the beam splitter elements (17, 17', 17", 17'") are movably mounted about the tilt axis (18, 18', 18", 18'") by means of respective torsion bearing elements. 14. Method for synchronizing the amplitude and phase of a scanning movement of beam splitter elements of a glasses display system (1) for displaying a virtual image in a field of vision of a user, wherein the glasses display system (1) has a screen unit (2) for emitting a light (142) as computer-generated image information in a radiation direction, and a scanning-deflection unit (3) for scanning the screen unit (2) and for deflecting the computer-generated image information emitted by the scanned screen unit (2) into an eye (15) of the user, wherein the scanning-deflection unit (3) has at least two beam splitter elements (17, 17', 17", 17'") arranged one behind the other in the radiation direction of the light (142) with a respective partially transmissive reflection surface (17a, 17a', 17a", 17a"', 17b, 17b', 17b", 17b'"), wherein the beam splitter elements (17, 17', 17", 17'") are movably mounted, tiltable about a respective center position along a tilt axis (18, 18', 18", 18'") between two reversal positions, at which a tilting speed of the beam splitter elements (17, 17', 17", 17'") is zero when used as intended, with the method steps: - synchronizing the phase of the beam splitter elements (17, 17', 17", 17'") at least substantially by means of a first force transmission through a respective spring element (11, 11', 11", 11'"), via which the respective beam splitter element (17, 17', 17", 17"') is mechanically coupled to a coupling rod element (12); and - Synchronizing the amplitude of the beam splitter elements (17, 17', 17", 17'") at least substantially by means of a second force transmission through at least one respective thread element (43, 43'), via which the respective beam splitter element (17, 17', 17", 17'") is mechanically coupled to the coupling rod element (12).