microscanner

Common chip dimensions are 4 mm × 5 mm for mirror diameters between 1 and 3 mm.[http://www.ipms.fraunhofer.de/content/dam/ipms/common/products/AMS/varios-e.pdf VarioS Mikroscanner Construction Kit]. Fraunhofer Institute for Photonic Microsystems IPMS (Product Description). Larger mirror apertures with side measurements of up to approx. 10 mm × 3 mm can also be produced.{{cite journal

| last1 = Sandner | first1 = T.

| last2 = Grasshoff | first2 = T.

| last3 = Wildenhain | first3 = M.

| last4 = Schenk | first4 = H.

| title = Synchronized micro scanner array for large aperture receiver optics of LIDAR systems

| journal = Proc. SPIE

| volume = 7594 – MOEMS and Miniaturized Systems IX

| year = 2010

| pages = 75940C

| doi = 10.1117/12.844923 | series = MOEMS and Miniaturized Systems IX

| bibcode = 2010SPIE.7594E..0CS

| s2cid = 108647803

| editor1-last = Schenk

| editor1-first = Harald

| editor2-last = Piyawattanametha

| editor2-first = Wibool

}} The scan frequencies depend upon the design and mirror size and range between 0.1 and 50 kHz. The deflection movement is either resonant or quasi-static.{{cite journal

|last1 = Holmstrom | first1 = S.T.S.

|last2 = Baran | first2 = U.

|last3 = Urey | first3 = H.

|title = MEMS Laser Scanners: A Review

|journal = Journal of Microelectromechanical System

|year = 2014

|volume = 23

|issue = 2

|pages = 259–275

|doi = 10.1109/JMEMS.2013.2295470

| s2cid = 23257771

}} With microscanners that are capable of tilting movement, light can be directed over a projection plane.

Many applications requires that a surface is addressed instead of only a single line. For these applications, actuation using a Lissajous pattern can accomplish sinusoidal scan motion, or double resonant operation. Mechanical deflection angles of micro scanning devices reach up to ±30°.{{cite journal

| last1 = Drabe | first1 = C.

| last2 = James | first2 = R.

| last3 = Schenk | first3 = H.

| last4 = Sandner | first4 = T.

| title = MEMS-Devices for Laser Camera Systems for Endoscopic Applications

| journal = Proc. SPIE

| volume = 7594 – MOEMS and Miniaturized Systems IX

| year = 2010

| pages = 759404

| doi = 10.1117/12.846855 | series = MOEMS and Miniaturized Systems IX

| bibcode = 2010SPIE.7594E..04D

| s2cid = 111072386

| editor1-last = Schenk

| editor1-first = Harald

| editor2-last = Piyawattanametha

| editor2-first = Wibool

}} Translational (piston type) microscanners, can attain a mechanical stroke of up to approx. ±500 μm.{{cite journal

| last1 = Sandner | first1 = T.

| last2 = Grasshoff | first2 = T.

| last3 = Schenk | first3 = H.

| last4 = Kenda | first4 = A.

| title = Out-Of-Plane Translatory MEMS actuator with extraordinary large stroke for optical path length modulation

| journal = Proc. SPIE

| volume = 7930 – MOEMS and Miniaturized Systems X

| year = 2011

| pages = 79300I

| doi = 10.1117/12.879069 | series = MOEMS and Miniaturized Systems X

| citeseerx = 10.1.1.1001.2433

| bibcode = 2011SPIE.7930E..0IS

| s2cid = 42065927

| editor1-last = Schenk

| editor1-first = Harald

| editor2-last = Piyawattanametha

| editor2-first = Wibool

}} This configuration is energy efficient, but requires complicated control electronics. For high end display applications the common choice is raster scanning, where a resonant scanner (for the longer display dimension) is paired with quasi-static scanner (for the shorter dimension).

The required drive forces for the mirror movement can be provided by various physical principles. In practice, the relevant principles for driving such a mirror are the electromagnetic, electrostatic, thermoelectric, and piezoelectric effects. Because the physical principles differ in their advantages and disadvantages, the driving principle is chosen according to the application. Specifically, the mechanical solutions required for resonant scanning are very different for those of quasi-static scanning. Thermoelectric actuators are not applicable for high-frequency resonant scanners, but the other three principles can be applied to the full spectrum of applications.

For resonant scanners, one often employed configuration is the indirect drive. In an indirect drive, a small motion in a larger mass is coupled to a large motion in a smaller mass (the mirror) through mechanical amplification at a favorable mode shape. This is in contrast to the more common direct drive, where the actuator mechanism moves the mirror directly. Indirect drives have been implemented for electromagnetic,{{cite journal

| last1 = Yalcinkaya | first1 = A.D.

| last2 = Urey | first2 = H.

| last3 = Brown | first3 = D.

| last4 = Montague | first4 = T.

| last5 = Sprague | first5 = R.

| title = Two-Axis Electromagnetic Microscanner for High Resolution Displays

| journal = Journal of Microelectromechanical Systems

| volume = 15

| issue = 4

| year = 2006

| pages = 786–794

| doi = 10.1109/JMEMS.2006.879380 | s2cid = 43694721

}} electrostatic,{{cite journal

|last1 = Arslan | first1 = A.

|last2 = Brown | first2 = D.

|last3 = Davis | first3 = W.O.

|last4 = Holmstrom | first4 = S.

|last5 = Gokce | first5 = S.K.

|last6 = Urey | first6 = H.

|title = Comb-Actuated Resonant Torsional Microscanner With Mechanical Amplification

|journal = Journal of Microelectromechanical System

|year = 2010

|volume = 19

|issue = 4

|pages = 936–943

|doi = 10.1109/JMEMS.2010.2048095| s2cid = 9521896

}} as well as piezoelectric actuators.{{cite journal

|last1 = Baran | first1 = U.

|last2 = Brown | first2 = D.

|last3 = Holmstrom | first3 = S.

|last4 = Balma | first4 = D.

|last5 = Davis | first5 = W.O.

|last6 = Muralt | first6 = P.

|last7 = Urey | first7 = H.

|title = Resonant PZT MEMS Scanner for High-resolution Displays

|journal = Journal of Microelectromechanical System

|year = 2012

|volume = 21

|issue = 6

|pages = 1303–1310

|doi = 10.1109/JMEMS.2012.2209405 | s2cid = 19273731

|citeseerx = 10.1.1.710.550

}}{{cite conference

| title = Piezoelectric resonant micromirror with high frequency and large deflection applying mechanical leverage amplification

| last1 = Gu-Stoppel| first1 = S.

| last2 = Janes| first2 = J.

| last3 = Kaden| first3 = D.

| last4 = Quenzer| first4 = H.

| last5 = Hofmann| first5 = U.

| last6 = Benecke| first6 = W.

| year = 2013

| conference = Proc. SPIE Micromachining and Microfabrication Process Technology XVIII

| pages = 86120I–1–86120I–8

| location = San Francisco, CA, USA

| doi = 10.1117/12.2001620

}} Existing piezoelectric scanners are more efficient using direct drive.

Electrostatic actuators offer high power similar to electromagnetic drives. In contrast to an electromagnetic drive, the resulting drive force between the drive structures cannot be reversed in polarity. For the realization of quasi-static components with positive and negative effective direction, two drives with positive and negative polarity are required.{{citation|surname1=D. Jung|surname2=T. Sandner|surname3=D. Kallweit|surname4=T. Grasshoff|surname5=H. Schenk|periodical=MOEMS and Miniaturized Systems XI|title=Vertical comb drive microscanners for beam steering, linear scanning and laser projection applications |volume=8252|pages=82520U–1–10|date= 2012|language=German|bibcode=2012SPIE.8252E..0UJ|doi=10.1117/12.906690|url=https://zenodo.org/record/3437462|series=MOEMS and Miniaturized Systems XI|s2cid=109410879 |editor1-last=Schenk|editor1-first=Harald|editor2-last=Piyawattanametha|editor2-first=Wibool|editor3-last=Noell|editor3-first=Wilfried}} As a rule of thumb, vertical comb drives are utilized here. Nevertheless, the highly non-linear drive characteristics in some parts of the deflection area can be hindering for controlling the mirror properly. For that reason many highly developed microscanners today utilize a resonant mode of operation, where an eigenmode is activated. Resonant operation is the most energy-efficient. For beam positioning and applications which are to be static-actuated or linearized-scanned, quasi-static drives are required and therefore of great interest.

Magnetic actuators offer very good linearity of the tilt angle versus the applied signal amplitude, both in static and dynamic operation. The working principle is that a metallic coil is placed on the moving MEMS mirror itself and as the mirror is placed in a magnetic field, the alternating current flowing in the coil generates Lorentz force that tilts the mirror. Magnetic actuation can either be used for actuating 1D or 2D MEMS mirrors. Another characteristic of the magnetically actuated MEMS mirror is the fact that low voltage is required (below 5V) making this actuation compatible with standard CMOS voltage. An advantage of such an actuation type is that MEMS behaviour does not present hysteresis, as opposed to electrostatic actuated MEMS mirrors, which make it very simple to control. Power consumption of magnetically actuated MEMS mirrors can be as low as 0.04 mW.{{cite web |url=http://www.lemoptix.com/technology/products/lscanmicromirror |title=Lemoptix - LSCAN Micromirror |accessdate=2012-02-07 |url-status=dead|archiveurl=https://web.archive.org/web/20120206023758/http://www.lemoptix.com/technology/products/lscanmicromirror |archivedate=2012-02-06 }}

Thermoelectric drives produce high driving forces, but they present a few technical drawbacks inherent to their fundamental principle. The actuator has to be thermally well insulated from the environment, as well as being preheated in order to prevent thermal drift due to environmental influences. That is why the necessary heat output and power consumption for a thermal bimorph actuator is relatively high. One further disadvantage is the comparably low displacement which needs to be leveraged to reach usable mechanical deflections. Also thermal actuators are not suitable for high frequency operation due to significant low pass behaviour.

Piezoelectric drives produce high force, but as with electrothermal actuators the stroke length is short. Piezoelectric drives are, however, less susceptible to thermal environmental influences and can also transmit high-frequency drive signals well. To achieve the desired angle some mechanism utilizing mechanical amplification will be required for most applications. This has proven to be difficult for quasi-static scanners, although there are promising approaches in the literature using long meandering flexures for deflection amplification.{{cite conference

| title = A two Axis Piezoelectric Tilting Micromirror with a Newly Developed PZTmeandering Actuator

| last1 = Tani| first1 = M.

| last2 = Akamatsu| first2 = M.

| last3 = Yasuda| first3 = Y.

| last4 = Toshiyoshi| first4 = H.

| year = 2007

| conference = Proc. IEEE 20th Int. Conf. MEMS

| pages = 699–702

| location = Kobe, Japan

| doi = 10.1109/MEMSYS.2007.4432994

}}{{cite journal

|last1 = Kobayashi | first1 = T.

|last2 = Maeda | first2 = R.

|last3 = Itoh | first3 = T.

|title = Low Speed Piezoelectric Optical Microscanner Actuated by Piezoelectric Microcantilevers Using LaNiO3 Buffered Pb(Zr, Ti)O3 Thin Film

|journal = Smart Materials and Structures

|year = 2009

|volume = 18

|issue = 6

|pages = 065008–1–065008–6

|doi = 10.1109/JMEMS.2012.2209405| bibcode = 2009SMaS...18f5008K

| s2cid = 19273731

|citeseerx = 10.1.1.710.550

}} For resonant rotational scanners, on the other hand, scanners using piezoelectric actuation combined with an indirect drive are the highest performer in terms of scan angle and working frequency.{{cite conference

|last1 = Baran | first1 = U.

|last2 = Holmstrom | first2 = S.

|last3 = Brown | first3 = D.

|last4 = Davis | first4 = W.O.

|last5 = Cakmak | first5 = O.

|last6 = Urey | first6 = H.

|title = Resonant PZT MEMS Scanners with Integrated Angle Sensors

|journal = Journal of Microelectromechanical System

|year = 2014

|conference = 2014 International Conference on Optical MEMS and Nanophotonics (OMN)

|pages = 99–100

|location = Glasgow, Scotland

|doi = 10.1109/OMN.2014.6924612}} However, the technology is newer than electrostatic and electromagnetic drives and remains to be implemented in commercial products.

Applications for tilting microscanners are numerous and include:

• Projection displays{{cite journal

| last1 = Scholles | first1 = Michael

| last2 = Bräuer | first2 = Andreas

| last3 = Frommhagen | first3 = Klaus

| last4 = Gerwig | first4 = Christian

| last5 = Lakner | first5 = Hubert

| last6 = Schenk | first6 = Harald

| last7 = Schwarzenberg | first7 = Markus

| title = Ultracompact laser projection systems based on two-dimensional resonant microscanning mirrors

| journal = Journal of Micro/Nanolithography, MEMS, and MOEMS

| volume = 7

| issue = 2

| year = 2008

| pages = 021001

| doi = 10.1117/1.2911643 }}

• Image recording, e.g. for technical and medical endoscopes
• Bar code scanning{{cite journal

| last1 = Wolter | first1 = A.

| last2 = Schenk | first2 = H.

| last3 = Gaumont | first3 = E.

| last4 = Lakner | first4 = H.

| title = MEMS microscanning mirror for barcode reading: from development to production

| journal = Proc. SPIE

| volume = 5348 – MOEMS Display and Imaging Systems II

| year = 2004

| pages = 32–39

| doi = 10.1117/12.530795 | series = MOEMS Display and Imaging Systems II

| bibcode = 2004SPIE.5348...32W

| s2cid = 120908834

| editor1-last = Urey

| editor1-first = Hakan

| editor2-last = Dickensheets

| editor2-first = David L

}}

• Spectroscopy
• Laser marking and material processing
• Object measurement / triangulation
• 3D cameras
• Object recognition
• 1D and 2D light grid
• Confocal microscopy / OCT
• Fluorescence microscopy
• Laser wavelength modulation

Some of the applications for piston type microscanners are:

• Fourier transform infrared spectrometer
• Confocal microscopy
• Focus variation

Microscanners are usually manufactured with surface or bulk micromechanic processes. As a rule, silicon or BSOI (bonded silicon on insulator) are used.

Microscanners are smaller, lower mass, and consume smaller amounts of power compared to macroscopic light modulators such as galvanometer scanners. Additionally, microscanners can be integrated with other electronic components such as position sensors.{{cite journal

| last1 = Grahmann | first1 = J.

| last2 = Grasshoff | first2 = T.

| last3 = Conrad | first3 = H.

| last4 = Sandner | first4 = T.

| last5 = Schenk | first5 = H.

| title = Integrated piezoresistive position detection for electrostatic driven micro scanning mirrors

| journal = Proc. SPIE

| volume = 7930 – MOEMS and Miniaturized Systems X

| year = 2011

| pages = 79300V

| doi = 10.1117/12.874979 | series = MOEMS and Miniaturized Systems X

| bibcode = 2011SPIE.7930E..0VG

| s2cid = 109599620

| url = https://zenodo.org/record/3437424

| editor1-last = Schenk

| editor1-first = Harald

| editor2-last = Piyawattanametha

| editor2-first = Wibool

}} Microscanners are resistant to environmental influences, and can tolerate humidity, dust, physical shocks in some models up to 2500g, and can operate in temperatures from -20 °C to +80 °C.

With current manufacturing technology microscanners can suffer from high costs and long lead times to delivery. This is an active area of process improvement

{{Reflist}}

{{Commons category}}

• [https://www.mirrorcletech.com/wp/products/mems-mirrors/ Scanning Micromirrors]. Mirrorcle Technologies Gimbal-less, Two-axis scanning micromirrors
• [http://www.ipms.fraunhofer.de/en/applications/mems-scanners.html MEMS Scanners]. Fraunhofer Institute for Photonic Microsystems
• [http://www.adriaticresearch.org/demos.htm ARI MEMS Micromirror Demonstration Devices]. Adriatic Research Institute
• [http://focus.ti.com/analog/docs/memstoplevel.tsp?sectionId=623&tabId=2458&familyId=1744 Getting Started with Analog Mirrors]. Texas Instruments (Product Page)
• [http://www.lemoptix.com/technology/innovation/scanning-micromirror.html Magnetic MEMS micromirrors]{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}. Lemoptix (Technology description Page)
• [http://maradin.co.il MEMS Laser Scanning Mirrors]. Maradin Ltd

Category:Microtechnology

Category:Microelectronic and microelectromechanical systems