EP3652579A1

EP3652579A1 - Method for calibrating a projection device for a head-mounted display, and projection device for a head-mounted display for carrying out the method

Info

Publication number: EP3652579A1
Application number: EP18734175.5A
Authority: EP
Inventors: Andreas Petersen; Tobias Graf
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-07-12
Filing date: 2018-06-21
Publication date: 2020-05-20
Also published as: WO2019011615A1; DE102017211914A1; CN110832380A; US20200218075A1; US11487126B2; CN110832380B

Abstract

The invention relates to a method for calibrating a projection device (100) for a head-mounted display. The method has the following steps: scanning a light beam (106) emitted by a light source (104) over a scanning angle range by means of a reflection element (112) such that the light beam (106) deflected by the reflection element (112) passes over a head-mounted display (400) surface region of a deflection element arranged on a lens (402) of the head-mounted display (400), said surface region having at least two adjustment markings (132) arranged on the head-mounted display (400), wherein each adjustment marking (132) is arranged at a specified position relative to the surface of the deflection element arranged on a lens (402) of the head-mounted display (400), and determining (520) in which scan setting of the reflection element (112) the at least two adjustment markings (132) are struck by the light beam (106). The invention further relates to a projection device (100) for a head-mounted display, to a head-mounted display, and to a deflection element.

Description

description

Method for calibrating a projection device for a data goggle and projection device for a data goggle for carrying out a method.

The present invention relates to a method for calibrating a

Projection device for a data glasses, a projection device for a data glasses for performing a method, a data glasses, a

Deflection element, a computer program, a machine-readable

Storage medium and an electronic control unit.

State of the art

One expected trend in the future is the wearing of data glasses, which can display virtual image information in the field of view of a user. For example, while current data glasses are not transparent and thus hide the environment, newer concepts follow the approach of overlaying virtual image content with the environment. The superimposition of virtual image content with the still perceived environment is referred to as augmented reality. For example, an application is fading in

Information in the exercise of professional activities. So could one

Mechanics see a technical drawing or the data glasses could colorize certain areas of a machine. However, the concept also finds in the field of computer games or others

Leisure activities application.

Clear Head-Mounted Displays (HMD), e.g. for applications in the field of augmented reality (AR), are an active topic in research and

Development. In particular, interest in the development of low cost, lighter, more economical small form factor systems is of great interest, both for industrial applications and for the end user. One possible technical approach for such a display is based on the concept of a flying-spot laser projector, with the aid of which the image information is written directly onto the retina of the user. Therefore, such HMDs are also referred to as retina scanners. The concept is based on the fact that a single light beam, in particular a laser beam, by means of an electronically controlled scanner optics, such. B. an M EMS (Micro-Electro-Mechanical System) level, over a

Angle range is scanned. For example, the beam can be scanned across the lens in this way. To ensure that the scanned beam then reaches the eye of the observer or his pupil, a deflection of the incident beam is usually necessary. In this case, for geometric reasons, in general, the law of reflection, according to which

Angle of incidence is equal to the angle of reflection, be injured. Technically this can be realized for example by the application of a holographic optical element (HOE) on the spectacle lens. The HOE will be here

typically realized by a photopolymer layer.

DE 10 2015 213 376 A1 discloses a projection device for data glasses, data glasses and a method for operating a

Projection device for a data glasses. The projection device comprises at least one light source for emitting a light beam and at least one arranged on a spectacle lens of the data glasses or can be arranged

A holographic element for projecting an image on a retina of a user of the data glasses by redirecting and / or focusing the light beam on an eye lens of the user.

Disclosure of the invention

The method is used to calibrate a projection device for data glasses. The projection device has a scanner optics and a

Deflecting element on. An existing in the scanner optics light source is scanned by a reflection element on the deflecting element, from where the light beam falls into an eye lens of a user. The aim of the calibration is to determine the relative orientation of the scanner optics and deflection element. For this purpose, it is determined at which scan setting of the reflection element on the data glasses arranged alignment marks are taken, the position of the adjustment marks is known relative to the deflection. In a first step of the method becomes one of a light source

emitted light beam by means of a reflection element via a

Scan angle range scanned so that the deflected by the reflection element light beam sweeps over a surface area of the data glasses, which has at least two of the data glasses arranged alignment marks, each alignment mark is disposed at a predetermined position relative to the surface of a arranged on a lens of the data glasses deflection. Here, each alignment mark on the deflection or on a

Eyeglass frame of the data glasses to be arranged.

A light source may be understood to mean a light-emitting element such as a light-emitting diode, in particular an organic light-emitting diode, a laser diode or an arrangement of a plurality of such light-emitting elements. In particular, the light source can be designed to emit light of different wavelengths. The light beam can for

Serving a plurality of pixels on the retina are used, wherein the light beam can scan the retina, for example in rows and columns or in the form of Lissajous patterns and can be pulsed accordingly. Under a

Eyeglass lens may be understood as a disc member made of a transparent material such as glass or plastic. Depending on

Embodiment, the spectacle lens may be formed approximately as a correction glass or a tint for filtering light of certain wavelengths such as UV light.

A light beam can be understood in the paraxial approximation to be a Gaussian beam. By a reflection element, for example, a mirror, in particular a micromirror or an array of micromirrors, or a hologram can be understood. By means of the reflection element, a beam path of the light beam can be adapted to given spatial conditions. For example, the reflection element can be realized as a micromirror. The micromirror can be designed to be movable, such as a tiltable about at least one axis Have mirror surface. Such a reflection element offers the advantage of a particularly compact design. It is also advantageous if the

Reflection element is formed to change an angle of incidence and, additionally or alternatively, a point of incidence of the light beam on the holographic element. As a result, the holographic element can be scanned flat, in particular approximately in rows and columns, with the light beam.

A scan angle range is understood to mean a solid angle over which the light beam is scanned. The projection of the solid angle onto the surface of the data glasses yields the surface area swept by the scanned light beam.

Each alignment mark is arranged at a predetermined position relative to the surface of the deflecting element. As a result, a geometric relationship between the scan setting of the reflection element and the point of impact of the scanned beam on the data glasses, for example the deflection element or the spectacle frame, can advantageously be produced. The deflecting element may be a holographic element or a freeform mirror. A holographic element may, for example, be understood to mean a holographic-optical component, HOE for short, which can fulfill the function of a lens, a mirror or a prism. Depending on

Embodiment, the holographic element for certain colors and angles of incidence can be selective. In particular, the holographic element can fulfill optical functions that can be imprinted into the holographic element with simple point light sources. As a result, the holographic element can be produced very inexpensively.

The holographic element can be transparent. As a result, virtual image information generated by the projection device can be overlaid with image information from the environment.

By means of a holographic element arranged on a spectacle lens of a data goggle, a light beam can thus be applied to a retina of a wearer of the

Data goggles are steered that the wearer a sharp virtual image perceives. For example, the image may be projected directly onto the retina by scanning a laser beam through a micromirror and the holographic element.

Such a projection device can be built in a small space

be realized comparatively inexpensive and makes it possible to bring a picture content in a sufficient apparent distance from the carrier.

This allows the overlay of the image content with the environment. The fact that the image can be written directly to the retina by means of the holographic element, can be dispensed with a DLP chip (DLP = digital light processing). Furthermore, a particularly large depth of focus can be achieved thereby.

In general, the reflection behavior on the surface of the holographic element is different at each point. As already mentioned above, it is generally not the case that the angle of incidence equals the angle of reflection. The portion of the surface of the holographic element which serves to redirect the light beam to the eye of a user is referred to as a functional region. In principle, the same applies to a free-form mirror as to a holographic element. Each alignment mark has a predetermined and known reference to the functional region of the deflection element.

In general, two adjustment marks suffice to achieve calibration for both deflection directions of the reflection element. However, it is preferred that in the method at least two adjustment marks, in particular at least four adjustment marks are used. It is particularly preferred that four alignment marks be used in the process. This has the advantage that the calibration accuracy is increased compared to the case with only two adjustment marks.

The Justagemarken are preferably arranged outside or at the edge of the primary field of view on the deflector. This has the advantage that adjustment marks do not affect the user and thus the calibration can also take place while the user is using the data glasses. Because of the bigger one Distance of the adjustment marks with each other, however, advantageously a greater accuracy is achieved.

The deflecting element preferably has a primary region which serves to operate the data glasses normally, and an externally adjoining one

Secondary region used only for adjustment purposes. The primary region corresponds to the above-mentioned functional region.

According to a further embodiment, the adjustment marks are arranged on the spectacle frame of the data glasses. This has the advantage that the light beams required for the adjustment run separately from the light rays striking the deflecting element and thus can also be evaluated separately.

In a further step of the method it is determined, at each scan setting of the reflection element, the at least two adjustment marks are struck by the light beam. The term scan setting is understood to mean an adjustment of the reflection element which deflects the light beam by a specific angle. In this case, the angle is to be understood as meaning an angle in space which, starting from the surface of the planar reflection element, requires two angles in order to be clearly defined. Alternatively, the scan setting may also be called angle adjustment.

According to one embodiment, between the scan setting of

Reflection element and the point of impact of the light beam on the surface of the data glasses determines a clear functional relationship. This has the advantage that, for each scan adjustment of the reflection element, the point of impact of the light beam on the surface of the data glasses, i. on the deflecting element or on the spectacle frame, is known. If light beam strikes the deflection element, due to the knowledge of the properties of the

Deflection element also known for each point of impact of the light beam on the surface of the deflecting element, where the light beam is reflected.

According to yet another embodiment, the determination is carried out at each of which scan setting of the reflection element, the at least two Justagemarken be hit by the light beam by the light beam is detected in each case by arranged on the Justagemarken detectors. This arrangement of detectors on the alignment marks has the advantage that it can be detected very reliably when an alignment mark is hit by a light beam.

Alternatively, the determination may be made at each scan setting of the

Reflection element which are hit by the light beam at least two Justagemarken done by the light beam in each case by holographic or diffractive adjustment elements, which are respectively arranged on the Justagemarken, is deflected in each case a predetermined direction and detected after the respective deflection. This has the advantage that on the

Justagemarken, that is on the surface of the deflector, no detectors must be attached. This will be the

Projection device or the data glasses lighter and free of electronic components. The use of holographic or diffractive adjustment elements has the advantage that they are light, resulting in a reduced weight of the projection device or the data glasses. In the event that the deflection element is designed as a holographic element, there is an advantage in that the adjustment marks can be manufactured homogeneously with the deflection element. In this embodiment, the adjustment marks and the deflection element are arranged in the same layer, which is designed as a holographic element.

The respective predetermined direction, in which the light beam is deflected by the holographic or diffractive adjustment elements, may be the same for each holographic or diffractive adjustment element. According to another

Embodiment, however, the respective predetermined direction as well

be different. In this case, it is also possible that the light beam from each holographic or diffractive adjustment element is deflected to one and the same point.

According to one embodiment, the light beam from the holographic or diffractive adjustment elements is in each case directed to a common point, which can be called a puncture point, for example. In this Embodiment, the position of the puncture point must not be known, it is only important that all four holographic adjustment elements deflect the respective light beams to the puncture point. According to a further embodiment, the light beam is deflected in each case by the holographic or diffractive adjustment elements parallel to the respective surface normal. It should be noted that when the holographic element is a curved surface, the respective ones

Surface normals do not run parallel to each other.

According to a further embodiment, the light beam is deflected in each case by the holographic or diffractive adjustment elements in the same direction, which can deviate locally from the surface normal. For the detection of the light rays, those of the holographic or diffractive

Adjusting elements are reflected, a flat detector can be mounted in a plane, wherein the plane is preferably arranged in the surface of the holographic element in the event that the holographic element is flat. In this embodiment, the light beams need only be detected on the detector arranged in the detection plane, which

Positions where the light rays strike the detector need not be known.

According to a further embodiment, the light beam in each case by the holographic or diffractive adjustment elements in the direction of

Reflection element reflected back. In this case, advantageously, the detection via an integrated in the scanner module or in the light source

Detection unit, for example, a photodiode made. Here, the scanner module is understood to be the unit which controls the reflection element. According to this embodiment, it is further preferred if the

Light beam is reflected back into itself. In this case, the light beam is reflected back into the light source, where, in the event that a laser is used as the light source, it can advantageously be detected by interference with the laser generated radiation, the so-called self-mixing interference (SMI). According to a further embodiment, the light beam can be deflected in each case by the holographic or diffractive adjustment elements in the direction of an eye lens of a user. This has the advantage that a camera or a user can detect the light beam. In this case, a known illumination pattern is preferably used if the scanned beam hits the test region, ie an alignment mark.

According to a development, the light source which is used for the present method for calibration, also for the image formation

used. This has the advantage that there is no additional calibration

Light source must be used.

Preferably, a wavelength of the light beam lies in a wavelength range not visible to humans. For the advantage that a calibration is not noticed by a user of the data glasses. Thus, a

Calibration can also be performed while using the data glasses. Here, the calibration can be done by a laser integrated in the projection device. It is also possible to use a light source of an existing eye tracking system. When

Wavelength of the changed laser beam, the range of the near infrared (NI R), in particular the range between about 700 nm to 1400 nm, are selected. Infrared radiation has the advantage that it is invisible to the human eye and therefore does not disturb the sensory perception of the eye. Furthermore, it is not harmful to the eye at a correspondingly low intensity. In addition, there are suitable laser sources that can be used advantageously. In this case the alignment marks could also be seen in the field of view, i. be installed in the primary region. According to a preferred embodiment, the light beam of the light source is coupled via an interface from outside the data glasses. In this case, a light source used for the image formation is not with the

Calibration used the same light source. In this case, the coupling of the light beam can preferably take place from an external test stand via a defined interface. This has the advantage that a test bench for calibration can be used, which checks a variety of data glasses and is set up in the long term. Such a test bench can therefore such

Calibrate data glasses with high accuracy and high reliability.

The scanning of the light beam emitted by the light source by means of the reflection element over the scanning angle range can be automated or manual.

In one embodiment, the calibration is automated by a controller reading and processing the detector signals and controlling the scanner optics to obtain the position for a maximum signal. This has the advantage that the calibration does not have to be performed by a user.

According to yet another embodiment, the calibration is performed manually, wherein the detector signal is communicated to the user via an optical or acoustic signal. This has the advantage that a possibly interference-prone

automated calibration is avoided.

Another aspect of the invention relates to the projection device for the data glasses for carrying out the above-described method for

Calibration of the projection device. The projection device has at least one light source for emitting a light beam and at least one arranged on a spectacle lens of the data glasses or can be arranged

Deflection element for projecting an image on a retina of a user of the data glasses by deflecting and / or focusing the light beam on an eye lens of the user. The projection device is thereby

characterized in that the projection device at least two

Justagemarken and that each alignment mark is disposed at a predetermined position relative to the surface of the deflecting element. The

Projection device has the advantage that it is easy to calibrate. Further advantages have already been mentioned above in connection with the procedure

described.

The invention further comprises a deflecting element for a

Projection device for a data glasses. The deflecting element has at least two Justagemarken, each alignment mark is disposed at a predetermined position relative to the surface of the deflecting element. The deflecting element can be arranged on the basis of the

Adjustment marks are advantageously calibrated by the method described above. The deflection element has the advantage that it is easy to calibrate. Further advantages have already been described above in connection with the method.

The invention further comprises a computer program which is set up to carry out the described steps of the method in order to be able to carry out a calibration of the projection device with this computer program. Furthermore, the invention comprises a machine-readable

Storage medium on which such a computer program is stored, as well as an electronic control unit that is set up a

Projection device for a data glasses or a data glasses by means of the described steps of the method to operate. Such an electronic control unit, for example, as a microcontroller in a

Projection device or data glasses to be integrated.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.

FIG. 1 shows a schematic representation of a projection apparatus according to an embodiment;

FIG. 2 schematically shows a flow diagram of a method according to an embodiment.

FIG. 3 shows a schematic representation of a deflecting element according to an embodiment;

FIGS. 4 to 6 each schematically illustrate a course of light beams in a method according to an embodiment; and Figure 7 shows schematically a data glasses according to an embodiment in isometric view.

Embodiments of the invention

FIG. 1 shows the basic mode of operation of the projection device 100. A light beam 106 emitted by a laser diode as the light source 104 is collimated by means of a lens as a collimation element 114 and in the direction of a

Micro mirror guided as a reflection element 112. The reflection element 112 deflects the light in the direction of the holographic element 103

Deflecting element. The holographic element 103 is applied to a spectacle lens 402. The light beam 106 deflected by the holographic element 103 then strikes an eye lens 108, from where the light beam 106 is focused on the retina 110 of an eyeball 107 of a user.

The light source 104 is arranged in a housing 105 attached to the eyeglass frame 120. At the output of the housing 105, the collimating element 114 is arranged. The light source 104, the collimating element 114 and the

Reflection element 112 may be housed in a common housing, not shown, wherein the reflected from the reflection element 112

Light beam 106 is coupled out by a arranged on one side of the housing window. This housing can on the temple 118 or on

Eyeglass frame 120 to be attached. The projection direction 100 also has two adjustment marks 132, which are applied to the holographic element 103.

FIG. 2 shows a flowchart of the method 500 for calibrating a projection device 100 for smart glasses. In a first step 510 of the method 500, a light beam 106 emitted by a light source 104 is scanned over a scanning angle range by means of a reflection element 112, so that the light beam 106 deflected by the reflection element 112 has a surface area of a spectacle lens 402 of the data glasses

arranged deflecting element, which is designed as a holographic element 103, passes over which at least two adjustment marks 132nd wherein each alignment mark 132 is disposed at a predetermined position on the surface of the holographic element 103. In a second step 520, the method 500 is determined, in each case which

Scan setting of the reflection element 112, the at least two

Adjustment marks 132 are hit by the light beam 106.

FIG. 3 shows a deflection element for a projection device 100 for a data goggle 400. The deflection element is presently a holographic element 103. The holographic element 103 embodied as a layer is applied to a spectacle lens 402. The holographic element 103 has a

Rectangular shape. An adjustment mark 132 is arranged on each of the four corners of the holographic element 103. The spectacle lens 402 is of a

Spectacle frame 120 taken. FIG. 4 shows the deflecting element of the holographic element 103

Figure 3, wherein in addition to the four Justagemarken 132 each have a detector 136 is arranged. According to one embodiment of the method, a light beam 106 emitted by the light source 104 is scanned over the surface of the holographic element 103, the light beam 106 also sweeping over the four detectors 136. The light source 104 and the light beam 106 are here only schematically drawn to illustrate the scanning of the light beam 106. The reflection element 112 is not shown here. Since the positions of the detectors 136 on the holographic element 103 are known, it can be determined at which scan setting of the

Reflection element 112, the detectors 136 are met. From this, a functional relationship between the point of impact of the light beam 106 on the surface of the holographic element 103 and the scan setting of the reflection element 112 can be determined. FIG. 5 shows a similar embodiment to FIG

Embodiment of Figure 4 four holographic adjustment elements 134 are here instead of the four detectors 136 on the four Justagemarken 132 arranged. In the present embodiment, the four direct holographic

Justageelemente 134 each falling on them light beam 106 to a common point, the puncture point 146. At the puncture point 146 is a detector 136 is arranged, which detects the light beam 106, which are deflected by the four holographic adjustment elements 134. In this embodiment, the position of the piercing point 146 need not be known, it is only important that all four holographic adjustment elements 134 redirect the respective light rays 106 to the piercing point 146. Then, analogous to the embodiment of FIG. 3, a functional relationship between the point of impact of the light beam on the surface of the

holographic element 103 and the scan setting of the reflection element 112.

FIG. 6 shows a similar embodiment to FIG. 5. In contrast to the embodiment of FIG. 5, the four holographic adjustment elements 134 direct the light rays 106 incident on them parallel to the respective one

Surface normal 142 from. It should be noted that if that

holographic element 103 is a curved surface, the respective

Surface normal 142 not parallel to each other. For detection of the four light beams 106, which are reflected by the four holographic adjustment elements 134, a flat detector can be mounted in a detection plane 144. If the four illustrated surface normals 142 are each equal in length, and the holographic element 103 is planar, the

Detection plane 144 parallel to the plane of the holographic element 103. In this embodiment, the four light beams 106 must be detected only on the detector arranged in the detection plane 144, the

Positions where the light rays strike the detector need not be known. Then, analogously to the embodiment of Figure 4 a

functional relationship between the point of impact of the light beam on the surface of the holographic element 103 and the scan setting of the reflection element 112 are determined. Figure 7 shows a schematic representation of a data glasses 400 with a

Projection device 100 according to an embodiment. The

Projection device 100 in this case has a scanner optics 152 and the holographic element 103. The scanner optics 152 is arranged in the housing 105 and transmits a light beam 106, not shown, through the appearance window 148 to the holographic element 103. The data glasses 400 are facing a spectacle lens 402 on which the holographic element 103 is disposed. For example, the holographic element 103 is realized as part of the spectacle lens 402. Alternatively, the holographic element 103 is realized as a separate element and connected to the spectacle lens 402 by means of a suitable joining method.

Claims

claims

A method (500) for calibrating a projection apparatus (100) for smart glasses (400), the method (500) comprising the steps of:

Scanning (510) a light beam (106) emitted by a light source (104) by means of a reflection element (112) over a scan angle range such that the light beam (106) deflected by the reflection element (112) passes over a surface area of the data glasses (400) at least two alignment marks (132) arranged on the data glasses (400), each alignment mark (132) being arranged at a predetermined position relative to the surface of a spectacle lens (402) of the data glasses (400)

Deflecting element is arranged; and

Determining (520) at each scan setting of the

Reflection element (112) the at least two adjustment marks (132) are hit by the light beam (106).

2. Method (500) according to claim 1, characterized in that

between the scan setting of the reflection element (112) and the point of impact of the light beam (106) on the surface of the data glasses (400) a clear functional relationship is determined.

3. Method (500) according to claim 1, wherein determining (520), at each scan setting of the reflection element (112), the at least two alignment marks (132) are struck by the light beam (106) takes place by the light beam (106) is respectively detected by detectors (136) arranged on the adjustment marks (132).

4. Method (500) according to claim 1, characterized in that the determination (520) of the at least two adjustment marks (132) being hit by the light beam (106) at each scan setting of the reflection element (112) is effected by the light beam (106) each of holographic or diffractive adjustment elements (134), each on the Justagemarken (132) are arranged, is deflected in each case a predetermined direction and is detected after the respective deflection.

Method (500) according to claim 4, characterized in that the light beam (106) in each case from the holographic or diffractive adjustment elements (134) in the direction of the reflection element (112) is reflected back.

Method (500) according to claim 4, characterized in that the light beam (106) is deflected in each case by the holographic or diffractive adjustment elements (134) in the direction of an eye lens (108) of a user.

Method (500) according to one of the preceding claims, characterized in that the light source (104) is also used for image formation.

Projection device (100) for data glasses (400) for carrying out a method (500) according to one of claims 1 to 7, wherein the projection device (100) has the following features:

at least one light source (104) for emitting a

Light beam (106); and

at least one deflection element arranged on or disposable on a spectacle lens (402) of the data glasses (400) for projecting an image onto a retina (110) of a user of the data glasses (400) by deflecting and / or focusing the light beam (106) on an eye lens (108 ) of the user,

characterized in that

the projection device (100) has at least two alignment marks (132), and

in that each alignment mark (132) is arranged at a predetermined position relative to the surface of the deflection element.

Data glasses (400) with the following features:

a spectacle lens (402); and a projection device (100) according to claim 8, wherein the deflecting element is arranged on the spectacle lens (402).

10. deflecting element for a projection device (100) for a data goggles (400) comprising:

at least two alignment marks (132), each alignment mark (132) at a predetermined position relative to the surface of the

Deflection element is arranged.

11. Computer program which is set up every step of the

Method (500) according to one of Claims 1 to 7.

12. Machine-readable storage medium on which a

Computer program according to the preceding claim is stored.

13. Electronic control device, which is set up, a

Projection device (100) for data glasses (400) or data glasses (400) by means of a method (500) according to one of claims 1 to 7 to calibrate.