Projection device with a waveguide having a recess

Abstract

Projection device for generating and displaying an image in an observation field (1) provided for the display of information and images, comprising at least one light source (2) for emitting at least one light beam (3), a microscanner (4) for variably deflecting the at least one light beam (3) in the direction of the observation field (1), wherein the microscanner (4) has at least one axis of rotation for a rotary oscillation movement for deflecting the at least one light beam (3), a waveguide (5) arranged between the light source (2) and the microscanner (4) in a beam path of the at least one light beam (3), wherein the waveguide (5) has at least one recess (6) in the beam path of the light beam (3), the diameter of which is larger than a diameter of the light beam (3) at the location of the recess (6).

Description

[0001] The invention relates to a projection device for generating and displaying an image on an observation field intended for projecting augmented reality, which field of observation can in particular be a spectacle lens or a retina of a user of augmented reality glasses.

[0002] Augmented reality (AR) refers to the computer-assisted enhancement of reality perception that addresses at least one of the human sensory modalities. However, AR is often understood to refer only to the visual representation of information, namely the supplementation of images or videos with computer-generated additional information and / or virtual objects by means of overlay or superimposition. In particular, the visual representation or projection of images, user interfaces, or information, such as directions, weather information, or news, represents a common application of AR and is increasingly being used in so-called AR glasses, which can display images, user interfaces, or information directly on the user's lenses or retina.

[0003] A microscanner (also known as a micro-electro-mechanical system, or MEMS for short) can be used to project images or text information. A light beam, generated by a light source located, for example, in the temple of a pair of glasses and subsequently shaped, is deflected onto the MEMS scanner. The light beam can then be scanned by the MEMS scanner, generating an image in an observation field. Such an imaging system with a MEMS scanner requires comparatively few optical elements, allowing for small and cost-effective projectors. For AR applications, a projector must achieve very good optical resolution and consume very little power. Due to a lack of alternatives, edge emitters are often used as the light source. However, these emit a highly divergent, elliptically shaped light beam that must be collimated.

[0004] A MEMS scanner is described, for example, in DE 10 2021 116 151 B3. The MEMS scanner disclosed therein can perform simultaneous rotational oscillations around two resonant oscillation axes to create a nonlinear Lissajous projection into an observation field by deflecting a light beam incident on a deflection element during the oscillations.

[0005] The oscillations scan a field of view (FOV) at high frequencies in a scan pattern resembling a Lissajous figure. Unlike conventional raster scanning methods, which periodically scan the FOV from top to bottom at maximum resolution, this allows hundreds of partial images to be processed simultaneously, enabling smoother motion representation. Furthermore, artifacts in the three-dimensional perception of fast-moving objects are greatly reduced.

[0006] DE 10 2018 201 525 A1 discloses a projection device for data glasses with at least one temple piece, wherein the projection device comprises at least one light source for emitting at least one light beam; at least one first deflection element arranged or arrangeable on a lens of the data glasses for projecting an image onto a retina of a user of the data glasses by deflecting and / or focusing the at least one light beam onto a lens of the user's eye; and at least one reflection element for reflecting the light beam onto the first deflection element. The projection device further comprises a light guide arranged between the light source and the reflection element.

[0007] US 2021 / 0 278 669 A1 discloses a display device for data glasses with a laser-based light engine. Optical interference effects resulting from the coherent nature of a laser light source are mitigated in US 2021 / 0 278 669 A1 by shortening the coherence length of the laser light source. The shortening of the coherence length is achieved by providing a laser source with multiple longitudinal modes, pulsing the laser light source to achieve spectral broadening, or by providing laser light sources with multiple emitters whose emission wavelength varies from emitter to emitter.

[0008] Projection devices with a waveguide are known in practice. The waveguide is arranged in the beam path of a light beam between a microscanner and a light source to reduce the installation space required for the device. The light source is arranged such that a light beam emitted by the light source is transmitted through the waveguide or reflected in the waveguide toward the microscanner.

[0009] The transmission of the light beam through the waveguide degrades the image quality of the optical image of the projection device, as aberrations are induced by the transmission of the light beam through the waveguide. Furthermore, contamination and defects in the waveguide can cause the image quality to deteriorate even further.

[0010] The object of the invention is therefore to find a new possibility for image generation and image display on an observation field for AR information projection, which requires little installation space and has a very high image quality.

[0011] The object is achieved by a projection device for generating and displaying an image in an observation field provided for the display of information and images, comprising at least one light source for emitting at least one light beam, a microscanner for the variable deflection of the at least one light beam in the direction of the observation field, wherein the microscanner has at least one axis of rotation for a rotary oscillating movement for deflecting the at least one light beam, a waveguide arranged between the light source and the microscanner in a beam path of the at least one light beam, wherein the waveguide has at least one recess in the beam path of the light beam, the diameter of which recess is greater than a diameter of the light beam at the location of the recess.

[0012] The recess, within the meaning of the invention, is a continuous hollow or incision in the material or object of a functional object, here in particular the waveguide. It can have various shapes and sizes. The recess can create space for additional parts or components of the projection device for generating an image in an area of ​​the functional object and / or reduce the required installation space for the projection device. The position and size of the recesses are usually carefully planned to ensure that they do not impair the functionality of the object.

[0013] The generation and display of images, within the meaning of the invention, is to be understood as the generation and display of one image, multiple images, or a sequence of images. A device according to the invention can also be used to display user interfaces or information, such as directions, weather information, or news, on the observation field.

[0014] The observation field is advantageously at least one optically effective surface, for example at least one beam splitter or a holographic optical element (HOE), which is applied in a lens of AR glasses or on a windshield of a motor vehicle. Alternatively, the observation field can be the retina of at least one eye of a user.

[0015] The recess primarily improves the imaging quality of the projection device, since the light beam does not have to be transmitted through the waveguide.

[0016] Advantageously, the recess is a hole in the waveguide. The hole is to be understood as a special type of recess, which is usually rounded, circular, or elliptical and formed as a continuous opening through the material of the functional object (waveguide), which has a shape in the most general sense of a mathematical hollow cylinder.

[0017] Preferably, at least one optical component selected from a mirror, a collimator and / or a diffractive element is arranged in the recess.

[0018] It is advantageous if a deflecting mirror is arranged at the recess, designed to reflect the light beam toward the microscanner. The deflecting mirror allows the light source to be positioned as desired, thus providing greater flexibility in the design of the projection device.

[0019] Advantageously, the at least one light source is a laser diode designed as an edge emitter or surface emitter or a fiber-coupled laser light source.

[0020] Surface emitters and fiber-coupled light sources have the advantage that the light beams emitted by these light sources are generally less divergent than those emitted by edge emitters. However, the acquisition costs of surface emitters and fiber-coupled light sources are generally significantly higher than those of edge emitters.

[0021] The at least one light source can be designed to emit a plurality of light beams with pairwise different spectral compositions or wavelengths. Alternatively, the at least one light source can be supplemented by further similar light sources so that a plurality of light beams with the same spectral composition are emitted. The distance between the light beams emitted by the light source or light sources can preferably be adjusted using an additional optical element. The use of a light source that emits a plurality of light beams or of a plurality of light sources is particularly useful when the microscanner is designed to be rotatable about only one axis of rotation, since a two-dimensional image can then be generated by simultaneously controlling the line light source and the microscanner.

[0022] The microscanner can, in particular, be embodied as a micro-electro-mechanical system (MEMS) and configured to effect a nonlinear Lissajous projection into the observation field. The microscanner is configured to scan the light beam across the observation field, thereby generating an image on the observation field. By scanning the at least one light beam along a Lissajous figure, hundreds of partial images can be processed simultaneously, enabling a smoother representation of motion. Furthermore, artifacts in the user's three-dimensional perception of fast-moving objects are greatly reduced. A MEMS scanner is a small, integrated system used for optical scanning and imaging of objects. The system consists of a tiny movable mirror controlled by micro-electro-mechanical systems (MEMS).The MEMS mirror is typically only a few hundred micrometers or millimeters in size and can be moved very quickly and precisely to reflect the light beam from the light source. The movement of the MEMS mirror can be controlled by electrical signals sent to the microscanner from a computer or other control unit, which may also be part of the projection device. MEMS microscanners offer the advantages of high speed, accuracy, and reliability while maintaining low power consumption and a small footprint.

[0023] Particularly advantageously, the microscanner is designed for rotational oscillations around exactly two axes of rotation that are orthogonal to each other, and oscillates at its natural frequency around both axes of rotation. The microscanner can also be designed for rotational oscillations around only one axis of rotation; in the latter case, the light source is designed to emit several adjacent light beams in a line pattern.

[0024] The waveguide is not an optical fiber, but rather a substrate made of a material transparent to the light beam, through which the light beam can be guided. Advantageously, the waveguide is a lens for augmented reality glasses.

[0025] The object is further achieved by augmented reality glasses containing a device for generating and displaying images according to one of the described embodiments.

[0026] The invention will be described in more detail below by means of exemplary embodiments based on the drawings. These show: Fig. 1 A view of a first embodiment of a projection device with a recess, Fig. 2 a view of a second embodiment of the projection device with a hole made of recess, Fig. 3 a view of a third embodiment of the projection device with a hole as a recess, Fig. 4 a view of a fourth embodiment of the projection device with a deflecting mirror arranged at the recess, Fig. 5 is a further view of the fourth embodiment of the projection device, Fig. 6 a view of a fifth embodiment of the projection device with a hole as a recess and optical components arranged in the hole, Fig. 7 a view of a sixth embodiment of the projection device with a hole as a recess, a deflecting mirror arranged at the recess and optical components arranged in the hole, and Fig. 8 a seventh embodiment of the projection device with a hole as a recess and a parabolic mirror arranged at the recess.

[0027] In Fig. 1 shows a first embodiment of a projection device for generating and displaying an image in an observation field 1 provided for displaying information and images. The projection device comprises a light source 2 designed to emit a divergent light beam 3 in the direction of a microscanner 4. The microscanner 4 is configured to variably deflect the light beam 3 in the direction of the observation field 1. For this purpose, it has at least one axis of rotation for a rotational oscillating movement of a mirror element for deflecting the at least one light beam 3. A waveguide 5 is arranged in the beam path of the light beam 3. The waveguide 5 is provided with a recess 6 in the region of the beam path of the light beam 3. The recess 6 has a larger diameter than the light beam 3 so that the light beam 3 is not limited or clipped by the waveguide 5.Due to the recess 6, no or fewer imaging errors are induced by the waveguide 5, which can lead to a reduced imaging quality of the projection device.

[0028] In the beam path of the light beam 3, a collimator 8 for collimating the light beam 3 is also arranged between the light source 2 and the microscanner 4.

[0029] Furthermore, in the beam path of the light beam 3, downstream of the microscanner 4, there is a coupling window on the waveguide 5, which serves to couple the light beam 3 into the waveguide 5. The coupling window can be a grating, a prism, or beam splitter surfaces in the waveguide. Fig. 1 schematically shows several beam paths of the light beam 3 after the microscanner 4.

[0030] In the first embodiment of the projection device, the light source 2 is designed as an edge emitter.

[0031] Fig. Figure 2 shows a second embodiment of the projection device, in which the recess 6 is a circular cylindrical hole in the waveguide 5. The hole is designed such that the light beam 3 is transmitted completely through the hole and impinges on the microscanner 4. The recess 6 could also be designed in the form of an oblique elliptical hollow cylinder to reduce the restrictions on the functional surfaces of the waveguide 5.

[0032] In the second embodiment of the projection device, the microscanner 4 is designed as a micro-electromechanical system (MEMS) and is designed to effect a non-linear Lissajous projection into the observation field 1.

[0033] In Fig. 2 shows, by way of example, three beam paths of the light beam 3 after it has been deflected by the microscanner 4.

[0034] The waveguide 5 is essentially plate-shaped (with parallel opposite surfaces) and consists of a material through which the at least one light beam 3 emitted by the light source 2 can propagate.

[0035] The waveguide 5 can consist of multiple layers or a single layer. Preferably, the waveguide 5 is a glass plate. Particularly preferably, the waveguide 5 is a lens of augmented reality glasses or the windshield of a motor vehicle.

[0036] In Fig. Figure 3 shows a third embodiment of the projection device with a hole as a recess 6. A collimator 8 is arranged in front of the hole in the beam path of the light beam 3. The collimator 8 consists of a pair of lenses and is designed to collimate the light beam 3 before it strikes the microscanner 4. In the third embodiment, the light source 2 is designed as a surface emitter.

[0037] In a fourth embodiment, a deflecting mirror 7 can be arranged at the recess 6, which is designed to deflect the light beam 3 in the direction of the microscanner 4. This fourth embodiment of the projection device, which is equipped with a deflecting mirror 7 arranged at the recess 6, illustrates Fig. 4.

[0038] In Fig. 5 also shows a waveguide 5 with a recess 6, which, as a fifth embodiment of the projection device, shows the recess 6 as a depression (e.g. a blind hole) in the waveguide 5, on the bottom surface of which (on the back of the waveguide 5) the deflection mirror 7 is arranged.

[0039] In the recess 6, especially when the recess 6 is a through hole, optical components can be arranged, as in Fig. 6. The Fig. The sixth embodiment of the projection device shown in Figure 6 comprises a collimator 8 arranged in the recess 6. The collimator 8 can simultaneously act as a diffractive element to remove or reduce aberrations from the light beam 3 or to shape the light beam 3. This may be necessary in particular when the light source 2 emits a light beam 3 with a non-circular cross-section.

[0040] The described features of the different versions of the projection device can be combined with each other as desired. For example, a deflecting mirror 7 can be arranged at the recess 6 and additional optical components can be arranged in the recess 6, as in the Fig. 7 can be seen in the seventh embodiment of the projection device.

[0041] The deflecting mirror 7 arranged at the recess 6 can also be designed as a parabolic mirror 9. An eighth embodiment with the parabolic mirror 9 arranged at the recess 6 is shown in Fig.8 is shown schematically. The parabolic mirror 9 simultaneously serves to deflect the light beam 3 toward the microscanner 4 and to collimate the light beam 3. As a result, in contrast to the seventh embodiment of the projection device, only one optical component is required for deflection and collimation, further reducing the required installation space for the projection device. Reference symbol 1 observation field 2 light source 3 light beams 4 micro scanners 5 waveguides 6 Recess 7 deflecting mirrors 8 Collimator 9 parabolic mirrors

Claims

[1] Projection device for generating and displaying an image in an observation field (1) intended for displaying information and images, comprising: - at least one light source (2) for emitting at least one light beam (3), - a microscanner (4) for the variable deflection of the at least one light beam (3) in the direction of the observation field (1), wherein the microscanner (4) has at least one axis of rotation for a rotary oscillating movement for deflecting the at least one light beam (3), - a waveguide (5) arranged between the light source (2) and the microscanner (4) in a beam path of the at least one light beam (3), wherein - the waveguide (5) has at least one recess (6) in the beam path of the light beam (3), the diameter of which is larger than a diameter of the light beam (3) at the location of the recess (6). [2] Projection device according to claim 1, wherein the recess (6) is a hole in the waveguide (5). [3] Projection device according to claim 1 or 2, wherein at least one optical component selected from a mirror, a collimator (8) and / or a diffractive element is arranged in the recess (6). [4] Projection device according to one of claims 1 to 3, wherein a deflecting mirror (7) is arranged on the recess (6) and is designed to reflect the light beam (3) in the direction of the microscanner (4). [5] Projection device according to one of claims 1 to 4, wherein the at least one light source (2) is designed as an edge emitter, a surface emitter or a fiber-coupled light source. [6] Projection device according to one of claims 1 to 5, wherein the projection device comprises a plurality of light sources (2) and each light source (2) emits a respective light beam (3). [7] Projection device according to claim 6, wherein the light beams (3) have different wavelengths from one another. [8] Projection device according to one of claims 1 to 7, wherein the microscanner (4) is designed as a micro-electromechanical system (MEMS) and is designed to effect a non-linear Lissajous projection into the observation field (1). [9] Projection device according to one of claims 1 to 8, wherein the waveguide (5) is a spectacle lens of augmented reality glasses. [10] Augmented reality glasses containing a projection device for generating and displaying images according to one of claims 1 to 9.

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