WO2013110665A1

WO2013110665A1 - Scanning device

Info

Publication number: WO2013110665A1
Application number: PCT/EP2013/051251
Authority: WO
Inventors: Jan Grahmann; Ian Wallhead; Michael Wildenhain; Alexander Wolter
Original assignee: Jan Grahmann; Ian Wallhead; Michael Wildenhain; Alexander Wolter
Priority date: 2012-01-24
Filing date: 2013-01-23
Publication date: 2013-08-01
Also published as: GB201222370D0

Abstract

A scanning device (10) for scanning a two-dimensional area is disclosed. The scanning device (10) comprises a light source (40), a first deflection mirror (20), and a second deflection mirror (30). The light source (40) generates a light beam (50) and directs it onto the first deflection mirror (20). By reflection from the first deflection mirror (20) the light beam (50) is directed onto the second deflection mirror (20). By reflection from the second deflection mirror (30) the light beam (50) is directed onto a projection surface (60). When the first deflection mirror (20) is being pivoted the light beam (50) reflected by the first deflection mirror (20) scans a first dimension of the two-dimensional area. When the second deflection mirror (30) is being pivoted the light beam (50) reflected by the first deflection mirror (20) scans a second dimension of the two-dimensional area. The scanning device (10) may comprise an optical element (45). A method for scanning the two-dimensional area is also disclosed.

Description

Title: Scanning Device

Cross-Reference to Related Applications

[0001] This application claims priority to and benefit of German Patent Application Serial No. DE 10 2012 001 378.7 "Optische Anordnung fur einen Projektor", filed on 24 January 2012, and of the British Patent Application Serial No. GB 1222370.7 "Scanning Device", filed on 12 December 2012.

[0002] The entire contents of the application are incorporated herein by reference.

Field of the Invention

[0003] The field of the invention relates to a scanning device.

Background of the invention

[0004] The deflection of light beams, with a radiation frequency in the visible or non-visible spectrum, in order to scan a two-dimensional area on surfaces with the help of deflection mirrors is known in several areas of application, such as but not limited to treatment of materials, laser marking, image acquisition, image projection, microscopy, or spectroscopy. The deflection mirrors move while deflecting the light beam from a stationary light source impinging on the deflection mirrors, and thus scan the two-dimensional area. Scanning devices using one single deflection mirror pivotable around two axes of rotation and scanning devices using two deflection mirrors pivotable around one single axis of rotation are known in the art.

[0005] In the case of using one single deflection mirror, a gimbal mount provides two axes of rotation through the center of the deflection mirror, allowing the reflected light beam to scan the two-dimensional are. [0006] In the case of using two deflection mirrors, each one of the deflection mirrors is pivotable around one axis of rotation. The two axes of rotation are arranged such that the light beam is first deflected by a first deflection mirror and subsequently by a second deflection mirror, thereby scanning the two-dimensional area.

[0007] The scanning of the two-dimensional area by deflecting the light beam with the help of deflection mirrors inevitably results in distortion of the two-dimensional area. In the case of using one single deflection mirror pivotable around two axes of rotation, the resulting distortion of the two-dimensional area is comparably strong, and the only way of reducing the distortion is by adjusting the angle of incidence of the light beam onto the deflection mirror. When using two deflection mirrors pivotable around their respective one single axis of rotation there is more freedom of arranging the deflection mirrors in such a way so as to reduce distortion.

[0008] The geometrical configuration of the light beam impinging on the first deflection mirror orthogonally to a first axis of rotation of the first deflection mirror and being reflected towards a second deflection mirror with a second axis of rotation arranged orthogonally to the first axis of rotation is known in the art. In this configuration, the two-dimensional image is free of distortion in the one dimension scanned by the first deflection mirror. US patent No. 4135902 discloses such a configuration using galvanometers in its Fig.l. US patent No. 5550346 discloses such a configuration using galvanometers in its Fig. l. However, both US '902 and US '346 are completely silent about the issue of distortion. [0009] In an article with the title "Beam deflection and scanning by two-mirror and two-axis systems of different architectures: a unified approach", Applied Optics, 47 (32), 5976-5985, (10 Nov 2008) the author Y. Li discloses a geometrical configuration of the two deflection mirrors and the light beam, in which the light beam and the second axis of rotation lie in a plane, in which the first axis of rotation forms a normal to the plane, and in which the first axis of rotation and the second axis of rotation are orthogonal to each other. In the course of the article, Li further discusses geometrical properties of the scan pattern, e.g. pincushion distortion, and ways to influence the geometrical properties. [0010] Recent years have seen an advance in the development of micro mirrors. Micro mirrors integrated with MEMS (Mircoelectromechanical Systems) devices result in so-called MOEMS (Micro-Opto-Electro-Mechanical Systems) devices and are produced using MEMS packaging techniques. MOEMS devices are suitable for industrial cost-effective mass- fabrication.

[0011] US Patent Application Publication No. US 2011/0304828A1 discloses the use of micro-optical modules or components, among them micro mirrors, that have parallelepiped shapes for ease of assembly and improved quality of alignment in order to reduce efficiency losses and deviations of the light from the optical path. These parallelepiped shaped have flat contact faces and can easily be stacked.

[0012] Winter et al. (Micro-Beamer Based on MEMS Micro-Mirrors and Laser Light Source, Proceedings of the Eurosensors XXIII conference, p. 1311-1314 (2009),

doi: 10.1016/j.proche.2009.07.327) publish a micro-beamer using micro mirrors. The micro mirrors are pivoted in the same way as conventional galvanometers. A current flowing through a coil in a magnetic field results in a magnetic force that pivots the micro mirror (s. Fig. 1 in Winter et al.). The light beam emitted by the laser diode first impinges on the first micro mirror at angle of nearly 45° and then impinges on the second micro mirror at an angle of nearly 45°.

[0013] International Patent Application No. WO 2012/000556A1 discloses a device using two micro mirrors pivotable around an axis of rotation whereby the axis of rotation of one mirror is orthogonal to the axis of rotation of the other. The two micro mirrors are arranged in a single package.

[0014] Micro mirrors to date have diameters that range between a few tenths of a millimeter and a few millimeters. The use of the micro mirrors in scanning applications in combination with MEMS technology paves the way to miniaturization of optical devices. Etching technology provides MOEMS scanner chips of a chip size of a few tens of square millimeters and chip thickness of less than one hundred micrometers.

[0015] The micro mirrors comprised in the MOEMS scanner chips can be suspended by springs and thus be driven to move. There are different ways of driving the micro mirrors in the MOEMS scanner chips based on electromagnetic or electrostatic interactions. The use of torsional springs, for example, makes the micro mirrors suitable to be driven such that the micro mirrors oscillate resonantly around an axis of rotation at high frequencies. The resonant oscillations of the micro mirrors reduce the wearing of the suspensions of the micro mirror leading to long-lasting and reliable devices (Sandner et al., Application specific Micro Scanning Mirrors, Proceedings SENSOR 2011, p. 337 - 342 (2011), doi: 10.5162/sensorl l/b7.4).

[0016] The scanning frequencies of the micro mirrors comprised in MOEMS scanner chips can be very high as compared to conventional mirrors. Higher scanning frequencies result in higher scanning resolution. The scanning frequencies depend on the size of the micro mirror and lie in a range of 0.1 to 50 kHz in the fast scanning dimension and in a range of 0.1 to 12 kHz in the slow scanning dimension. Depending on the scanning frequency optical scan ranges of about 20° to 100° can be achieved.

[0017] The integration of the scanning device into a mobile phone or other portable device requires the construction of small ones of the scanning devices, such as MOEMS devices. Not only do the size and number of components used in the construction of the MOEMS devices matter, but the optical path along which the light beam propagates is also to be carefully taken into consideration. The components of the MOEMS device, apart from the optical components, i.e. transmissive components and/or reflective components, should not obstruct the optical path and thus interfere with the light beam.

[0018] In the scanning device using two deflection mirrors both pivotable around their respective one single axis of rotation, the distance between the first deflection mirror and the second deflection mirror impacts on the size of the scanning device. The larger the distance between the first deflection mirror and the second deflection mirror the bigger is the size of the second deflection mirror. The size of the second deflection mirror in turn impacts on the size of the scanning component as a whole. For example, an outlet window of the scanning device needs to be designed according to the size of the second deflection mirror. Placing the first deflection mirror and the second deflection mirror as close as possible reduces the size of the scanning device. Summary of the Invention

[0019] The present disclosure relates to a scanning device. The disclosure further relates to a scanning device with a geometrical configuration of the light beam, the first deflection mirror and the second deflection mirror reducing the distortion of the scanned two-dimensional area. The disclosure further relates to a MOEMS scanning device using micro mirrors and the industrial fabrication thereof. The disclosure relates to a compact MOEMS scanning device comprising a beam deflecting and/or beam shaping optical element. The disclosure discloses a MOEMS scanning device suitable for production at a high numbers and reasonable costs.

[0020] More particularly, a scanning device scanning a two-dimensional area is taught in this disclosure. The scanning device has a light source, a first deflection mirror pivotable around a first axis of rotation, a second deflection mirror pivotable around a second axis of rotation. The light source generates a light beam and directs it onto the first deflection mirror. By reflection from the first deflection mirror the light beam is directed onto the second deflection mirror. By reflection from the second deflection mirror the light beam is directed onto a projection surface. When the first deflection mirror is being pivoted the light beam reflected by the first deflection mirror scans a first dimension of the two-dimensional area. When the second deflection mirror is being pivoted the light beam reflected by the first deflection mirror scans a second dimension of the two-dimensional area. [0021] In one aspect, the light beam impinges on the first deflection mirror substantially perpendicularly to the first axis of rotation. Upon reflection from the first deflection mirror the light beam then impinges on the second deflection mirror nearly perpendicularly to the second axis of rotation. [0022] In a further aspect, the first deflection mirror and the second deflection mirror are micro mirrors.

[0023] In another aspect, the light beam is deflected and/or shaped before impinging on the first deflection mirror. Light of certain wavelengths may be dampened or filtered. [0024] In another aspect, the scanning device is constructed by assembling parts in a process suitable for industrial fabrication without the need for optical alignment. This scanning device can be produced in high numbers at reasonable costs. This scanning device may be custom- designed according to the needs of the customer.

[0025] A method for scanning the two-dimensional area is also disclosed in this document. This method comprises the steps of generating a light beam, a step of deflecting and/or shaping the light beam, a step of directing the light beam onto the first deflection mirror, a step of scanning the light beam in a first dimension of the two-dimensional area and directing the light beam onto the second deflection mirror, a step of scanning the light beam in a second dimension of the two-dimensional area and directing the light beam onto the projection surface.

Description of the Figures

[0026] Fig. 1 shows an outline of the scanning device according to this disclosure.

[0027] Fig. 2a shows a side view of a scan head according to this disclosure.

[0028] Fig. 2b shows an oblique view of the scan head according to this disclosure.

[0029] Fig. 3a shows the first deflection mirror comprised in a first MOEMS scanner chip carried by a first carrier prism and put into a first MOEMS frame.

[0030] Fig. 3b shows the second deflection mirror comprised in a second MOEMS scanner chip carried by a second carrier prism and put into a second MOEMS frame.

[0031] Fig. 4a shows how the first MOEMS frame and the second MOEMS frame are assembled to a scan head according to this disclosure.

[0032] Fig. 4b shows the assembled scan head according to this disclosure.

[0033] Fig. 5 shows a method for scanning the two-dimensional area 66.

Detailed Description of the Invention

[0034] The invention will now be described on the basis of the drawings. It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects and/or embodiments of the invention. [0035] As shown in figure 1, the scanning device 10 comprises a first deflection mirror 20, a second deflection mirror 30, and a light source 40. The light source 40 generates a light beam 50 and is oriented such that the light beam 50 is directed towards the first deflection mirror 20. The light beam 50 impinges on the first deflection mirror 20 and is thereby reflected by the first deflection mirror 20 such that the light beam 50 is directed towards the second deflection mirror 30. The light beam 50 then impinges on the second deflection mirror 30 and is thereby reflected by the second deflection mirror 30 such that the light beam 50 is directed towards the projection surface 60. The light beam 50 impinges on the projection surface 60 and thereby produces a first spot 61 on the projection surface 60 visible to an observer. [0036] The light beam 50 may be visible light, infra-red light or X-ray radiation, but is not limited to these wavelenghs.

[0037] The scanning device 10 may direct the light beam 50 onto a surface other than a projection surface 60 for displaying an image. The projection surface 60 may be a bar code on a surface, a light sensitive surface or a probe surface of a probe, but is not limited to these examples.

[0038] As shown in figure 1, the first deflection mirror 20 is pivotable in a first degree of freedom defined by a first axis of rotation 70. Pivoting the first deflection mirror 20 around the first axis of rotation 70 to an altered position alters the orientation of the light beam 50 with respect to the first deflection mirror 20. The light beam 50 is reflected in the altered direction from the first deflection mirror 20. The orientation of the light beam 50 with respect to the second deflection mirror 30 is altered. The light beam 50 is reflected in an altered direction from the second deflection mirror 30. The orientation of the light beam 50 with respect to the projection surface 60 is altered. The light beam 50 impinges on the projection surface 60 at an altered location compared to the first spot 61, due to the privoting of the first deflection mirror 20 and the second deflection mirror 30, and thereby produces a second spot 63. [0039] Pivoting the first deflection mirror 20 around the first axis of rotation 70 in a continuous manner from one position to another and holding the second deflection mirror 30 in a fixed position results in a first trajectory or trace on the projection surface 60. If the continuous pivoting of the first deflection mirror 20 around the first axis of rotation 70 occurs fast enough the first trajectory on the projection surface 60 will appear to be a first continuous line. The first continuous line may be a horizontal line, and the projection surface 60 may be oriented vertically. [0040] As shown in figure 1, the second deflection mirror 30 is pivotable in a second degree of freedom defined by a second axis of rotation 80. Pivoting the second deflection mirror 30 around the second axis of rotation 80 to an altered position alters the orientation of the light beam 50 with respect to the second deflection mirror 30. Consequently, the light beam 50 is reflected in an altered direction from the second deflection mirror 30 upon impinging thereon. Thereby the orientation of the light beam 50 with respect to the projection surface 60 is altered. Consequently, the light beam 50 impinges on the projection surface 60 at an altered location compared to the first spot 61 and thereby produces a third spot 65.

[0041] The pivoting of the second deflection mirror 30 around the second axis of rotation 80 in a continuous manner from one position to another position and holding the first deflection mirror 20 in a fixed position results in a second trajectory or trace on the projection surface 60. If the continuous pivoting of the second deflection mirror 30 around the second axis of rotation 80 occurs fast enough the second trajectory on the projection surface 60 will appear to be a second continuous line. The second continuous line may be a substantially vertical line, and the projection surface 60 may be oriented vertically.

[0042] The pivoting of both the first deflection mirror 20 and the second deflection mirror 30 simultaneously and in a continuous manner results in a third trajectory or trace on the projection surface 60. If the simultaneous pivoting of both the first deflection mirror 20 and the second deflection mirror 30 occurs fast enough and in a cooperative manner, the third trajectory on the projection surface 60 will appear to be a continuous two-dimensional area 66. [0043] In one aspect, the third trajectories are Lissajous trajectories that are the result of the first deflection mirror 20 oscillating at a first frequency around the first axis of rotation 70 and the second deflection mirror 30 oscillating at a second frequency around the second axis of rotation 80.

[0044] In a further aspect, one of or both of the first deflection mirror 20 and/or the second deflection mirror 30 move in a piecewise linear fashion.

[0045] Distortion of the two-dimensional area 66 as a result of scanning the two- dimensional area 66 on the projection surface 60 is a known issue in the art. The distortion is inherent to a geometrical configuration of the first deflection mirror 20, the second deflection mirror 30, and the light beam 50. The distortion is the result of the first deflection mirror 20 and the second deflection mirror 30 being pivoted and the light beam 50 being oriented non- perpendicularly to one of or both of the first axis of rotation 70 and/or the second axis of rotation 80. The geometrical configuration may be arranged such that the distortion is reduced.

[0046] In one aspect, the light beam 50 impinges on the first deflection mirror 20 substantially perpendicularly to the first axis of rotation 70. Upon reflection from the first deflection mirror 20, the light beam 50 impinges on the second deflection mirror 30 substantially perpendicularly to the second axis of rotation 80. The angle of incidence of the light beam 50 onto the second deflection mirror 30 depends on the momentary position of the first deflection mirror 20. [0047] In this aspect, the light beam 50 marks a straight line on the second deflection mirror 30 when the first deflection mirror 20 is being pivoted. If the light beam 50 impinges on the second deflection mirror 30 non-perpendicularly to the second axis of rotation 80 the light beam 50 marks a curved line on the projection surface 60 after reflection from the second deflection mirror 30 when the first deflection mirror 20 is fixed and the second deflection mirror 30 is being pivoted.

[0048] In a further aspect, the light beam 50 impinges on the first deflection mirror 20 substantially perpendicularly to the first axis of rotation 70 and on the second deflection mirror 30 substantially perpendicularly to the second axis of rotation 80. Furthermore in this aspect, the light beam 50 is directed substantially horizontally towards the projection surface 60 and the projection surface 60 is oriented substantially vertically. If the first deflection mirror 20 is being pivoted and the second deflection mirror 30 is fixed, the light beam 50 marks a horizontal line on the projection surface 60. If the first deflection mirror 20 is fixed and the second deflection mirror 30 is being pivoted, the light beam 50 marks a nearly vertical curved, i.e. distorted, line on the projection surface 60. In this aspect, , the scanned two- dimensional area 66 is undistorted in the horizontal direction and distorted in the vertical direction. [0049] In a further aspect, one of or both the first deflection mirror 20 is a micro mirror comprising a ID torsional suspension and the second deflection mirror 30 is a micro mirror comprising a ID torsional suspension. A micro mirror comprising a ID torsional suspension is pivotable around the ID torsional suspension. The use of micro mirrors and MOEMS technology enables the fabrication of miniaturized optical devices. Miniaturized optical devices may, for example, be designed to be integrated into mobile phones or other portable devices.

[0050] Figs. 2a shows a side view of a scan head 11 using the micro mirrors. Fig. 2b shows an oblique view of the scan head 11. The light beam 50 impinges on the first deflection mirror 20 and is thereupon reflected towards the second deflection mirror 30. The light beam 50 impinges on second deflection mirror 30 and is thereupon reflected towards the projection surface 60 (not shown in Figs. 2a and 2b).

[0051] The first deflection mirror 20 is a micro mirror with a ID torsional suspension providing the first axis of rotation 70. The second deflection mirror 30 is a micro mirror with a ID torsional suspension providing the first axis of rotation 70.

[0052] The micro mirrors according to Sandner et al. (Application specific Micro Scanning Mirrors, Proceedings SENSOR 2011, p. 337 - 342 (2011), doi: 10.5162/sensorl l/b7.4) are pivoted around the ID torsional suspensions by exerting electrostatic forces using driving comb electrodes. Voltages applied to the driving comb electrodes result in the electrostatic forces. The driving comb electrodes achieve large deflection angles at low voltages (Grahmann et al., Integrated position sensing for 2D microscanning mirrors using the SOI device layer as the piezoresistive mechanical-elastic transformer, Proc. SPIE, 720808 (2009), doi: 10.1117/12.808151).

[0053] Pulsed voltages applied to the driving comb electrodes in a manner synchronized with the movement of the micro mirrors result in electrostatic forces leading to resonant oscillations of the micro mirrors. Such resonant oscillations lead to highly stable, shock- resistant, and accurate operation of the micro mirrors. The micro mirrors intended to be solely operated in resonant mode ensure a mature fabrication process and render the quality testing more cost-efficient.

[0054] It is conceivable that one of or both the first deflection mirror 20 and the second deflection mirror 30 are micro mirrors that are pivoted either electrostatically, electromagnetically, or piezoelectrically. One of or both the first deflection mirror 20 and the second deflection mirror 30 may be pivoted in resonant mode.

[0055] As shown in Figs. 2a and 2b the first deflection mirror 20 is located in a first MOEMS scanner chip 90 and the second deflection mirror 30 is located in a second MOEMS scanner chip 100. The MOEMS scanner chips with the micro mirrors are produced in a series of etching, oxidizing, and depositing steps from a single crystalline silicon layer, as disclosed in Sandner et al..

[0056] The MOEMS scanner chips comprising the micro mirrors with a ID torsional suspension are suitable for custom design. Such custom designed MOEMS scanner chips are deliverable to customers within a few weeks. Some key parameters of the micro mirrors may be set according to the desire of the customer. The diameter (open aperture) of the micro mirror with the ID torsional suspension ranges between 0.5 millimeters and 4 millimeters. The angles of deflection (scan range) of the micro mirror lie in a range of 20° to 120°. The oscillation frequency (scanning speed) of the micro mirror can be as low as 0.1kHz and as high as 50kHz.

[0057] As shown in Figs. 2a and 2b, the first MOEMS scanner chip 90 is mounted on a first MOEMS carrier 110 in the form of a first carrier prism 110. The first carrier prism 110 is mounted on a first MOEMS substrate 130. The second MOEMS scanner chip 100 is mounted on a second MOEMS carrier 120 in the form of a second carrier prism 120. The second carrier prism 120 is mounted on a second MOEMS substrate 140.

[0058] The first MOEMS scanner chip 90 is mounted on a first slope 111 of the first carrier prism 110 so as to bias the first deflection mirror 20 comprised in the first MOEMS scanner chip 90 to a desired orientation with respect to light beam 50. The second MOEMS scanner chip 100 is mounted on a second slope 121 of the first carrier prism 110 so as to bias the second deflection mirror 30 comprised in the second MOEMS scanner chip 100 to a desired orientation with respect to light beam 50.

[0059] It is conceivable to devise the first slope 111 of the first carrier prism 110 and the second slope 121 of the second carrier prism 120 in Figs. 2a and 2b and to position the first deflection mirror 20 and the second deflection mirror 30 such that the scan head 11 as shown in Figs. 2a and 2b occupies as little as possible space resulting in a substantially flat design limited in the vertical direction by the first MOEMS substrate 130 and the second MOEMS substrate 140.

[0060] In one aspect the first MOEMS scanner chip 90 has a size of approximately 6.5 millimeters by 4.5 millimeters and the second MOEMS scanner chip 100 has a size of approximately 7.4 millimeters by 3.3 millimeters. The first deflection mirror 20 has an approximate distance of 5 millimeters to the second deflection mirror 30.

[0061] It is conceivable that the scan head 11 further comprises an optical element 45 deflecting the light beam 50. The light source 40 (not shown in Figs. 2a and 2b) directs the light beam 50 onto the optical element 45. The optical element 45 deflects the light beam 50 and directs the light beam 50 onto the first deflection mirror 20. The deflection of the light beam 50 by the optical element 45 reduces the angle of incidence of the light beam 50 onto the first deflection mirror 20. [0062] In one aspect the light beam 50 impinges on the first deflection mirror 20 at an angle of incidence ranging between 24° and 34°.

[0063] The deflecting of the light beam 50 with the help of the optical element 45 permits reducing the size of the first deflection mirror 20 while keeping the design of the scan head 11 flat (with respect to the vertical direction of Figs. 2a and 2b). The size of the first deflection mirror 20 depends on the angle of incidence of the light beam 50 onto the first deflection mirror 20. The smaller the angle of incidence of the light beam 50 onto the first deflection mirror 20, the smaller the required size of the first deflection mirror 20 in order to completely reflect the light beam 50 without losing part of the light beam 50.

[0064] It is conceivable that the optical element 45 shapes the light beam 50, i.e. that the optical element 45 alters the profile of the light beam 50.

[0065] It is furthermore conceivable that optical element 45 both deflects and shapes the light beam 50. In one aspect, the optical element 45 is an optical wedge prism. The wedge prism 45 deflects and shapes the light beam 50.

[0066] In one aspect, the light beam 50 with an elliptical beam profile before impinging on the optical wedge prism 45 has a circular beam profile after passing through optical element 45. The light beam 50 with the circular beam profile permits the first deflection mirror 20 to be smaller without losing part of the light beam 50 when reflecting the light beam 50.

[0067] It is furthermore conceivable that optical prism 45 dampens or filters light of certain wavelengths.

[0068] A further aspect of the disclosure is shown in Figs. 3a and 3b. The first carrier prism 110 carrying the first deflection mirror 20 is mounted on a first MOEMS frame 135. The second carrier prism 120 carrying the second deflection mirror 30 is mounted on a second MOEMS frame 145. The first MOEMS frame 135 and the second MOEMS frame 145 are designed in a way such that they are easily put together to form a scan head 11, as shown in Fig. 4b. The first MOEMS frame 135 and the second MOEMS frame 145 cooperate to form a housing of the scan head 11, as shown in Fig. 4b.

[0069] As shown in Figs. 3b, 4a, and 4b the second MOEMS frame 145 comprises an inlet 150. The light beam 50 is directed through the inlet 150 onto the first deflection mirror 20. It is conceivable that the inlet 150 accommodates the optical element 45.

[0070] As shown in Fig. 4b the housing of the scan head 11 built from the first MOEMS frame 135 and the second MOEMS frame 145 comprises an outlet 160. The light beam 50 reflected from the second deflection mirror 30 is directed through the outlet 160 towards the projection surface 60 (not shown in Fig. 4b).

[0071] In one aspect, the inlet 150 accommodates the optical element 45 and the outlet 160 accommodates a window such that the scan head 11 is completely sealed off. The sealing off of the scan head 11 protects the first deflection mirror 20 and the second deflection mirror 30 against dust and moisture.

[0072] It is conceivable to orient a window accommodated by the outlet 160 such that it is non-perpendicular to the light beam 50 directed towards the projection surface 60 upon reflection from the second deflection mirror 30. This orientation of the window accommodated by the outlet 160 avoids back reflections of the light beam 50.

[0073] The scan head as shown in Figs. 3a, 3b, 4a, and 4b enables the alignment of the first carrier prism 110, the second carrier prism 120, the first MOEMS frame 135, and the second MOEMS frame 145 such that optical element 45, the first deflection mirror 20 and the third deflection mirror 30 during the assembling of the scan head 11. This also enables industrial- scale manufacture to be carried out of a complete assembly. [0074] It is conceivable to pre-fabricate all of the components according to the design as desired by a customer and to put the components together in an assembling step.

[0075] Fig. 5 shows a method for scanning the two-dimensional area 66 on the projection surface 60.

[0076] A step 300 comprises generating the light beam 50 in the light source 40.

[0077] A step 310 comprises deflecting and/or shaping the light beam 50. The light beam 50 generated by the light source 40 is directed onto the optical element 45. It is conceivable that the optical element 45 deflects the light beam 50 and directs the light beam 50 onto the first deflection mirror 20. The deflection of the light beam 50 by the optical element 45 reduces the angle of incidence of the light beam 50 onto the first deflection mirror 20. [0078] The deflecting of the light beam 50 with the help of optical element 45 permits reducing the size of the first deflection mirror 20 while keeping the design of the scan head 11 flat (with respect to the vertical direction of Figs. 2a and 2b). [0079] It is further conceivable that the optical element 45 shapes the light beam 50, i.e. that the optical element 45 alters the profile of the light beam 50. Likewise it is conceivable that optical element 45 both deflects and shapes the light beam 50. In one aspect, the optical element 45 is an optical wedge prism. The wedge prism 45 deflects and shapes the light beam 50.

[0080] It is further conceivable that the optical element 45 dampens or filters light of certain wavelengths.

[0081] A step 320 comprises directing the light beam 50 onto the first deflection mirror 20. In one aspect, the light beam 50 impinges on the first deflection mirror 20 perpendicularly to the first axis of rotation 70. Additionally, the light beam 50 may impinge on the first deflection mirror 20 at an angle of incidence ranging between 24° and 34°.

[0082] A step 330 comprises scanning the light beam 50 in a first dimension of the two- dimensional area 66 and directing the light beam 50 onto the second deflection mirror 30. When the first deflection mirror 20 is being pivoted, the light beam 50 reflected from the first deflection mirror 20 and directed onto to the second deflection mirror 30 marks a continuous line on the second deflection mirror 30. If the light beam 50 impinges on the first deflection mirror 20 substantially perpendicularly to the first axis of rotation 70, the continuous line is a straight line. In one aspect, the continuous line is a horizontal line.

[0083] A step 340 comprises scanning the light beam 50 in a second dimension of the two- dimensional area 66 and directing the light beam 50 onto the projection surface 60. When the second deflection mirror 30 is being pivoted and the first deflection mirror 20 is fixed the light beam 50 reflected from the second deflection mirror 30 and directed onto the projection surface 60 marks a continuous line on the projection surface 60. If the light beam 50 impinges on the second deflection mirror 30 nearly perpendicularly to the second axis of rotation 80 and the projection surface 60 is planar the continuous line is a nearly straight line. In one aspect, the continuous line is a nearly vertical line.

List of reference numbers

Scanning device

Scan head

First deflection mirror

Second deflection mirror

Light source

Optical element

Light beam

Projection surface

First spot

Second spot

Third spot

Two-dimensional area

First axis of rotation

Second axis of rotation

First MOEMS scanner chip

Second MOEMS scanner chip

First MOEMS carrier

First slope

Second MOEMS carrier

Second slope

First MOEMS substrate

First MOEMS frame

Second MOEMS substrate

Second MOEMS frame

Inlet

Outlet

Claims

A scanning device (10) for projecting an image on a projection surface (60) using at least one light beam (50) comprising: at least one light source (40) for producing the at least one light beam (50);

a first deflection mirror (20) pivotable around a first axis of rotation (70);

a second deflection mirror (30) pivotable around a second axis of rotation (80), wherein the at least one light beam (50) and the second axis of rotation (80) span a plane;

wherein the first axis of rotation (70) forms a normal to the spanned plane and intersects with the at least one light beam (50);

wherein the first deflection mirror (20) and the second deflection mirror (30) are micro mirrors, and

wherein the first deflection mirror (20) and the second deflection mirror (30) are adapted to cooperate and direct the at least one light beam (50) onto the projection surface (60).

The scanning device (10) according to claim 1, wherein the at least one laser beam (50) is adapted to pass an optical element (45) before impinging on the first deflection mirror (20).

The scanning device (10) according to claim 2, wherein the optical element (45) adapted to deflect the light beam (50).

4. A scanning device (10) according to claim 2 or 3, wherein the at least one light beam (50) impinges on the first deflection mirror (20) at an angle ranging between 24° and 34°.

5. The scanning device (10) according to any one of claims 2 to 4, wherein the optical element (45) is adapted to shapen the light beam (50).

6. The scanning device (10) according to any one of claims 2 to 5, wherein the optical element (45) is adapted to filter or dampen light of certain wavelengths.

7. The scanning device (10) according to any one of the above claims, wherein the first deflection mirror (20) is mounted onto a first MOEMS carrier (110) and/or the second deflection mirror (30) is mounted onto a second MOEMS carrier (120).

8. The scanning device (10) according to claim 7, wherein the first MOEMS carrier (110) is a carrier prism (110) and/or the second MOEMS carrier (120) is a carrier prism (120).

9. The scanning device (10) according to any one of the above claims, wherein the first deflection mirror (20) is comprised in a MOEMS frame (135) and the second deflection mirror (30) is comprised in a MOEMS frame (145).

10. The scanning device (10) according to claim 9, wherein the first MOEMS frame (135) and the second MOEMS frame (145) are adapted to cooperate to form a housing of the first deflection mirror (20) and the second deflection mirror (30).

11. The scanning device (10) according to claim 10, wherein an inlet (150) of the housing accommodates the optical element (45).

12. The scanning device (10) according to claim 10 or 11, wherein an outlet (160) of the housing accommodates a window.

13. The scanning device (10) according to claim 12, wherein the window is non- perpendicular to the at least one light beam (50) reflected from the second deflection mirror (30).

14. The scanning device (10) according to any one of the above claims, wherein the at least one light source (40) is a diode laser.

15. The scanning device (10) according to any one of the above claims, wherein one of or both the first deflection mirror (20) and the second deflection mirror (30) oscillate resonantly or move in a piecewise linear fashion.

16. A method for projection of an image on a projection surface (60) using at least one light beam (50) comprising the steps of: generating the at least one light beam (50) in the at least one light source (40), directing the light beam (50) onto the first deflection mirror (20),

scanning the light beam (50) in a first dimension of the two-dimensional area (66) and directing the light beam onto the second deflection mirror (30),

scanning the light beam (50) in a second dimension of the two-dimensional area (66) and directing the light beam (50) onto the projection surface (60).

17. The method according to claim 16 comprising passing the at least one light beam (50) through the optical element (45) deflecting the light beam (50) before directing light beam (50) onto deflection mirror (20).

18. The method according to claim 17 comprising passing the at least one light beam (50) through the optical element (45) and thereby modifying the profile of the at least one light beam (50) before directing light beam (50) onto deflection mirror (20).

19. The method according to claim 17 or 18 comprising passing the at least one light beam (50) through the optical element (45) and thereby dampening or filtering light of certain wavelenghts before directing light beam (50) onto deflection mirror (20).

20. The use of the scanning device (10) according to any one of the claims 1 to 15 for projecting a two-dimensional area (66) on a projection surface (60).