Lens for projection and detection of light, MEMS projector, augmented reality glasses and camera

Abstract

Lens for projection and detection of light, comprising a microscanner (1) for variable deflection of at least one light beam (2) by means of a scanner mirror (11) capable of vibration in at least one dimension, which has an optical axis (O) referenced to a rest position of the scanner mirror (11) and an opening (12) around the optical axis (O) for collinear transmission of the light beam (2), a convex mirror (3) arranged on the optical axis (O) and designed to reflect the light beam (2) transmitted through the opening (12) of the scanner mirror (11) along the optical axis (O) onto the scanner mirror (11), and a lens arrangement (4) arranged between the convex mirror (3) and the microscanner (1) on the optical axis (O) to influence a divergence of the light beam (2) such that the light beam deflected by the scanner mirror (11) is collimated.

Description

The invention relates to an objective for the projection and detection of light, which can be used in particular in augmented reality glasses (AR glasses for short), in head-up displays or sensor and camera applications.In the mentioned applications, an objective with a micro scanner (also micro-electro-mechanical system, MEMS for short) can be used for projecting or collecting light. For projection, a light beam is directed onto the microscanner, which light beam is generated by a light source arranged, for example, in a bow of a pair of spectacles and is subsequently shaped. The microscanner can then scan the light beam, producing an image on an observation field. Such an imaging system with a microscanner requires comparatively few optical elements, as a result of which small and cost-effective projectors can be realized.A micro scanner is described, for example, in DE 10 2021 116 151 B3. The microscanner disclosed therein can simultaneously execute rotational oscillations about two resonant axes of oscillation in order to bring about a nonlinear Lissajous projection into an observation field by deflecting a light beam incident on a deflection element during the oscillations.The oscillations scan a field of view (FOV) at high frequencies in a scan pattern similar to a Lissajous figure. In contrast to conventional raster scanning methods, which periodically scan the FOV from top to bottom at maximum resolution, hundreds of partial images can thus be processed simultaneously and a more liquid motion representation can be made possible. Moreover, artifacts in the three-dimensional perception of fast-moving objects are greatly reduced.W. Davis et al., "MEMS-based pico project display", published in IEEE / LEOS International Conference on Optical MEMs and Nanophotonics Vol. 2008, pp. 31-32, published in 2008, describes a MEMS projector in which light beams in an illumination beam path are reflected via a beam splitter onto a microscanner. The projection beam path is transmitted through the same beam splitter. The illumination beam path and the projection beam path thus have only a slight overlap with one another and the light source is arranged independently of the other components of the projector. This requires separate beam guidance for each of the light beams.Objectives are frequently integrated into optics or beam paths in such a way that at least one light beam is incident on the microscanner obliquely, i.e. not perpendicularly to the microscanner in its rest position. This is disadvantageous, among other things, because an angle of field in a projection plane, which runs parallel to a mirror plane of the microscanner in the rest position, is limited as a result. Moreover, distortion is generated by the oblique incidence of the light beam. This distortion must subsequently be corrected. Furthermore, the oblique incidence of light limits the available installation space for further components, such as diaphragms, since the microscanner has to be deflected further in the event of oblique incidence of light in order to scan the same space.The object of the invention is therefore to provide a novel objective for the projection and detection of light, which lens requires a very small installation space and can be produced very cost-effectively by means of a wafer-based design. It is furthermore the object of the invention to provide a MEMS projection device, augmented reality eyeglasses and a camera, each containing an objective according to the invention.The object is achieved by an objective for the projection and detection of light, comprising a microscanner for the variable deflection of at least one light bundle by means of a scanner mirror which can oscillate at least in one dimension and which has an optical axis related to a rest position of the scanner mirror and an opening about the optical axis for collinear passage of the light bundle, a convex mirror which is arranged on the optical axis and is designed to reflect the light bundle passed through the opening of the scanner mirror along the optical axis onto the scanner mirror, and a lens arrangement which is arranged between the convex mirror and the microscanner on the optical axis in order to influence a divergence of the light bundle such that the light bundle deflected by the scanner mirror is collimated.Because the micro scanner, the convex mirror and the lens arrangement are arranged on the optical axis, the objective lens takes up very little installation space and can be manufactured very cost-effectively by means of wafer-based design.Wafer-level assembly (wafer-level assembly) refers to a technology in which components are directly mounted on a wafer. A wafer is a wafer of semiconductor material such as silicon. Wafer level mounting offers several advantages over conventional chip mounting. By performing the mounting process at the wafer level, time and costs can be significantly reduced during production.A system is referred to as being capable of vibration within the meaning of the invention when it is capable of carrying out a periodic movement about a rest position. Thus, any system capable of periodic movement about a rest position in multiple dimensions is oscillatory in multiple dimensions.The scanner mirror preferably has a diameter of 0.5 mm to 10 mm and is preferably round. The opening advantageously has a diameter of 20 μm to 1,000 μm and is advantageously round. The convex mirror preferably has a diameter of 0.5 mm to 10 mm or the same diameter as the scanner mirror or a diameter only slightly larger than the scanner mirror and is preferably round. The lens arrangement preferably has a thickness of 0.5 mm to 10 mm and a diameter of 3 mm to 20 mm.Preferably, the scanner mirror and / or the aperture have a diameter between 0.1 mm and 5 mm. Particularly preferably, the scanner mirror 11 and / or the aperture have a diameter between 1 mm and 2 mm. The distance between the scanner mirror and the aperture is preferably less than 1 mm, particularly preferably the distance between the scanner mirror 11 and the aperture 7 is less than 0.5 mm and more than 0.1 mm. The angle by which the scanner mirror can be tilted with respect to its rest position is preferably between 3° and 15°, particularly preferably between 5° and 10°.Additional optical elements such as lenses or diffractive optical elements can be arranged between the lens arrangement and the convex mirror or between the lens arrangement and the microscanner in order to influence the divergence of the at least one light beam and / or in order to minimize or eliminate aberrations.Preferably, at least one aperture for limiting the light beam is provided in the beam path of the light beam, which aperture is mounted in a defined position relative to the microscanner as a function of a direction of incidence of the light beam.An optical aperture is a mechanical component that controls the amount of incident light in an optical system and / or spatially limits a light beam. This is a round, oval or polygonal opening, for example, which is let into a diaphragm material. The diaphragm material can be metal or plastic, for example. The diaphragm can be introduced into the objective in particular by wafer-level mounting. The aperture may also be formed by a structured coating comprising an absorbent material or an absorbent surface structure on a transparent substrate.Advantageously, at least the scanner mirror is arranged within an encapsulation which hermetically encloses the scanner mirror and the encapsulation has an interior space with a gas pressure which is reduced compared to normal conditions.The encapsulation of the microscanner is provided for protecting the movable mechanical and optical components of the microscanner and for protecting it from external influences and dirt. Placing the microscanner in a vacuum serves to reduce friction, avoid particles contained in the air, and reduce thermal effects such as convection heat input.The microscanner can be designed in particular as a micro-electro-mechanical system (MEMS) and / or designed to bring about a non-linear Lissajous projection into an observation field. The microscanner is designed to scan the light beam over the observation field, thereby producing an image on the observation field. Scanning the at least one light beam along a Lissajous figure enables hundreds of partial images to be processed simultaneously and enables a more liquid movement display. Moreover, the perception of artifacts in the three-dimensional representation of rapidly moving objects is greatly reduced for the user.The lens arrangement preferably comprises one or more planar optical elements with diffractive effect. Likewise preferably, the lens arrangement can contain one or more elements consisting of optical metamaterial. The lens arrangement can alternatively or additionally have one or more meta lenses or one or more refractive optical lenses.The objective advantageously comprises at least one light source for emitting the at least one light beam along the optical axis in the direction of the microscanner, and the at least one light source is arranged on the side of the microscanner facing away from the convex mirror. If the objective comprises a light source, it can be used in particular as a projection device in order to effect a projection into an observation field.Preferably, the at least one light source is equipped with collimating or converging beam forming. The divergence with which the light beam is emitted specifies how the remaining components of the objective, in particular the microscanner, the opening of the microscanner and the convex mirrors, are dimensioned and arranged. Therefore, it is advantageous if the divergence of the light beam after it has been emitted by the light source is adjustable.The at least one light source is advantageously a laser diode, which is designed as an edge emitter, surface emitter, or a fiber-coupled laser light source and is equipped with beam shaping and focusing. Surface emitters and fiber-coupled light sources have the advantage that the light beams emitted by these light sources are generally less divergent than the light beams emitted by edge emitters. For this purpose, the initial costs of surface emitters and fiber-coupled light sources are generally significantly higher than those of edge emitters.The objective can preferably comprise at least one sensor for detecting the at least one light bundle and the at least one sensor can be arranged on the side of the microscanner facing away from the convex mirror. If the objective comprises a sensor, it can be used with different types of detectors, such as cameras (CCD, CMOS), position sensitive or conventional photodiodes, quadrant photodiodes or photodiode arrays.The object is furthermore achieved by a MEMS projection device containing an objective according to one of the described embodiments.The object is also achieved by augmented reality glasses containing an objective for generating and displaying images according to one of the described embodiments, wherein the at least one light source for emitting the at least one light bundle is integrated in the objective or in the augmented reality glasses.The object is furthermore achieved by a camera containing an objective according to one of the described embodiments and at least one sensor for detecting the at least one light bundle.The invention will be described in more detail below by way of exemplary embodiments with reference to drawings. The following are shown in this connection: FIG. 1 a shows a view of a first embodiment of the objective with a light source, a microscanner, a lens arrangement comprising a lens and a convex mirror and a first section of an optical path, FIG. 1 b is a view of the first embodiment of the objective and of a second section of the beam path, FIG. 1 cshows a view of the first embodiment of the objective and a third section of the beam path, FIG. 2 is a side view of a section through a second embodiment of the objective, wherein the lens arrangement contains only one meta-lens, FIG. 3 is a side view of a section through a third embodiment of the objective, showing two different optical paths of the light beam after it has been deflected by the microscanner, and the lens arrangement contains a converging lens and a diverging lens, FIG. 4 is a side view of a section through a fourth embodiment of the objective, wherein a diaphragm is arranged directly above the microscanner, and FIG. 5 shows a side view of a section through a fifth embodiment of the objective, wherein a diaphragm is arranged directly above the microscanner and the scanner mirror is completely enclosed by an encapsulation.FIG. 1 ashows a first embodiment of an objective for the projection and detection of light. The objective lens comprises a microscanner 1 for the variable deflection of a light beam 2. the microscanner 1 comprises a scanner mirror 11 capable of oscillating in one dimension for the deflection of the light beam. the scanner mirror 11 has an optical axis O related to a rest position of the scanner mirror 11 and an opening 12 around the optical axis O for the collinear passage of the light beam 2.The objective lens further comprises a convex mirror 3. The convex mirror 3 is arranged on the optical axis O and is designed to reflect the light beam 2 transmitted through the opening 12 of the scanner mirror 11 along the optical axis O onto the scanner mirror 11.The objective also comprises a lens arrangement 4. the lens arrangement is arranged between the convex mirror 3 and the microscanner 1 on the optical axis O and is designed to influence a divergence of the light beam 2 such that the light beam deflected by the scanning mirror 11 is collimated.FIG. 1 ashows a first section of an optical path of the light bundle 2. The light beam 2 is emitted by a light source 6 in the direction of the micro scanner 1 and transmitted through the opening 12 of the micro scanner 1. Between the micro scanner 1 and the convex mirror 3, the light beam 2 merges at a focus and is transmitted through the lens arrangement 4, whereby the divergence of the light beam 2 decreases before it strikes the convex mirror 3. The distances and dimensioning of scanner mirror 11, opening 12, convex mirror 3 and lens arrangement 4 must be matched to one another in such a way that a diameter of light beam 2 at convex mirror 3 is not greater than the diameter of convex mirror 3, since otherwise a portion of the light beam would be lost during the reflection at the convex mirror.FIG. 1 b shows the first embodiment of the objective and a second section of an optical path of the light bundle 2. The light beam 2 is reflected by the convex mirror 3 in the direction of the micro scanner 1. Before the light beam 2 impinges on the microscanner 1, it is again transmitted through the lens arrangement 4, as a result of which the divergence of the light beam 2 decreases further. Subsequently, the light beam 2 impinges on the microscanner 1.The microscanner 1 deflects the light beam 2 in the direction of the optical axis O, as shown in FIG. 1c. In this case, a first portion of the light beam 2 is always lost at the microscanner 1 on account of the opening 12. After being deflected by the microscanner 1, the light beam 2 is transmitted a third time through the lens arrangement 4 and thereby collimated. Depending on the dimensioning and arrangement of the convex mirror 3 and depending on the direction in which the light beam 2 has been deflected by the microscanner 1, a second portion of the light beam 2 is additionally lost at the convex mirror 3.A lens arrangement 4 which contains only one meta-lens is shown in FIG. 2. in the second embodiment of the objective shown in FIG. 2, the meta-lens of the lens arrangement 4 is arranged in the same plane as the convex mirror 3. FIG. 2 shows the entire beam path of the light beam 2 from the light source 6 until the light beam 2 passes through the meta-lens. In the second embodiment, the light beam 2 is transmitted only once through the lens arrangement 4 and is thereby collimated.The lens array 4 may also be composed of a plurality of lenses, for example, a condenser lens 41 and a condenser lens 42 as in the second embodiment shown in Fig. 3. By the cooperation of the converging lens 41 and the diverging lens 42, the deflected light beam 2 is collimated. In the configuration shown in FIG. 3, the scanner mirror 11 of the micro scanner 1 is deflected in a configuration and the deflected light beam 2 does not run along the optical axis O. This configuration is illustrated in FIG. 3 by dashed lines.FIG. 4 shows a fourth embodiment of the objective. The fourth embodiment of the objective comprises a sensor 5. the sensor 5 is arranged below the microscanner 1, as seen from the direction of incidence of the light beam 2. The incident light beam 2 is reflected or deflected by the micro scanner 1 onto the convex mirror 3 and reflected by the convex mirror 3 by the micro scanner 1 onto the sensor 5.In addition, the fourth embodiment has a diaphragm 7 located between the microscanner 1 and the lens arrangement 4 for limiting the light beam 2. The diaphragm 7 must be dimensioned and arranged in such a way that the scanner mirror 11 does not come into contact with the diaphragm 7 during its deflection.Preferably, the scanner mirror 11 and / or the aperture 7 have a diameter between 0.1 mm and 5 mm. Particularly preferably, the scanner mirror 11 and / or the aperture have a diameter between 1 mm and 2 mm. The distance between the scanner mirror 11 and the aperture 7 is preferably less than 1 mm, particularly preferably the distance between the scanner mirror 11 and the aperture 7 is less than 0.5 mm and more than 0.1 mm. The angle by which the scanner mirror 11 can be tilted with respect to its rest position is preferably between 3° and 15°, particularly preferably between 5° and 10°.FIG. 5 shows a side view of a section through a fifth embodiment of the objective. A shutter 7 is arranged directly above the microscanner 1, and the microscanner 1 is completely enclosed by an encapsulation 8. Furthermore, the scanner mirror 11 is arranged within an encapsulation 8 which hermetically encloses the scanner mirror 11 together with the micro scanner 1. An interior of the encapsulation 8 has a gas pressure that is reduced compared to normal conditions.List of reference characters1 Microscanner 11 Scanner mirror 12 Opening 2 Light bundle 3 Convex mirror 4 Lens arrangement 41 First lens 42 Second lens 5 Sensor 6 Light source 7 Aperture 8 Encapsulation O Optical axisReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2021 116 151 B3

[0003] Cited Non-Patent LiteratureW. Davis et al., "MEMS-based pico project display", published in IEEE / LEOS International Conference on Optical MEMs and Nanophotonics Vol. 2008, pp. 31-32, published in 2008

[0005]

Claims

Objective for the projection and detection of light, comprising - a microscanner (1) for the variable deflection of at least one light beam (2) by means of a scanner mirror (11) which can oscillate at least in one dimension and which has an optical axis (O) related to a rest position of the scanner mirror (11) and an opening (12) about the optical axis (O) for the collinear passage of the light beam (2), - a convex mirror (3) which is arranged on the optical axis (O) and is designed to reflect the light beam (2) transmitted through the opening (12) of the scanner mirror (11) onto the scanner mirror (11) along the optical axis (O), and - a lens arrangement (4) which is arranged between the convex mirror (3) and the microscanner (1) on the optical axis (O), to influence a divergence of the light beam (2) such that the light beam deflected by the scanner mirror (11) is collimated.Objective according to Claim 1, wherein in the beam path of the light beam (2) at least one aperture (7) for delimiting the light beam (2) is present, which aperture is mounted in a defined position relative to the microscanner (1) as a function of a direction of incidence of the light beam (2).Objective according to one of claims 1 to 2, wherein at least the scanner mirror (11) is arranged within an encapsulation (8) which hermetically encloses the scanner mirror (11) and has an interior space with a gas pressure which is reduced compared to normal conditions.Objective according to one of Claims 1 to 3, wherein the microscanner (1) is designed as a microelectromechanical system (MEMS).The objective according to any one of claims 1 to 4, wherein the microscanner (1) is configured to effect a non-linear Lissajous projection into an observation field.The objective according to any one of claims 1 to 5, wherein the lens arrangement (4) comprises one or more composite optical lenses.Objective according to one of claims 1 to 5, wherein the lens arrangement (4) comprises one or more planar optical elements with diffractive effect.The objective according to any one of claims 1 to 5, wherein the lens arrangement (4) contains one or more elements consisting of optical metamaterial.Objective according to one of Claims 1 to 8, wherein the objective comprises at least one light source (6) for emitting the at least one light bundle (2) along the optical axis (O) in the direction of the microscanner (3), and the at least one light source (6) is arranged on the side of the microscanner (1) facing away from the convex mirror (3).Objective according to claim 9, wherein the at least one light source (6) is provided with collimating or converging beam forming.Objective according to claim 9, wherein the at least one light source (6) is designed as an edge emitter, surface emitter or as a fiber-coupled light source.Objective according to one of Claims 1 to 8, wherein the objective comprises at least one sensor (5) for detecting the at least one light bundle (2), and the at least one sensor (5) is arranged on the side of the microscanner (1) facing away from the convex mirror (3).MEMS projector comprising an objective according to one of claims 1 to 12.Augmented reality spectacles comprising an objective for generating and displaying images according to one of claims 1 to 11, wherein the at least one light source (6) for emitting the at least one light bundle (2) is integrated in the objective or in the augmented reality spectacles.Camera, comprising an objective according to one of Claims 1 to 8 and at least one sensor (5) according to Claim 12 for detecting the at least one light bundle (2).

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