1. Field of the Invention
The present invention relates to the technical field of contactless detection or measurement, respectively, of three-dimensional objects. In particular, the present invention relates to the technical sub-field of scanners for detecting a surface relief by means of optical scanning.
2. Description of the Related Art
Known scanners for short object distances mainly use the method of triangulation, as it is illustrated in
Depending on the application, different light sources are used, like for example traditional projectors having shadow masks for structuring (e.g. DE 000010149750 A1, US 00006501554 B1) or laser light sources corresponding for example to DE 000019721688 A1. Also light sources having attachment optics for generating light figures according to DE 000019615685 A1 or ones having DMD members (DMD=Digital Micro Device) may be used for generating electronically controllable light figures, for example according to EP 000000927334 B1, US 000006611343 B1, DE 000019810495 A1. Any known devices of those classes use laminar (DE 000010149750 A1 or DE 000019615685 A1) or at least line-shaped image sensors (at it is for example disclosed in US 000006501554 B1) as image receivers, however, on the basis of CCD or CMOS technology (CCD=Charge Coupled Device=sensor type that accumulates electrical charges under light incidence that are fed to suitably controlled electrodes of a read-out electronic; CMOS=Complementary Metal Oxide Semiconductor=widely used circuit technology and manufacturing technology for integrated solid circuitries on a silicon basis).
Recently, with the so-called micro-scanner mirrors new elastically suspended micro optical members electrostatically excited close to their natural resonance and the associated control electronics are available, as it is for example explained in more detail in the following documents:
A New Driving Principle for Micromechanical Torsional Actuators
H. Schenk, P. Dürr, D. Kunze, H. Kück; Micro-Electro-Mechanical System, MEMS-Vol. 1, Conf.: 1999 int. Mech. Eng. Congr. & Exh., 14-19 Nov. 1999, Nashville, p. 333-338, 1999
A Novel Electrostatically Driven Torsional Actuator
H. Schenk, P. Dürr, H. Kück
Proc. 3rd Int. Conf. On Micro Opto Electro Mechanical Systems, Mainz, 30. August-1. September 1999, page 3-10, 1999
Micromirror Spatial Light Modulators
P. Dürr, A. Gehner, U. Dauderstädt, 3rd International Conference on Micro Opto Electro Mechanical Systems (Optical MEMS) Proc. MEMS 1999, Mainz, 1999, S. 60-65
A Resonantly Excited 2D-Micro-Scanning-Mirror with Large Deflection
H. Schenk, P. Dürr, D. Kunze, H. Lakner, H. Kück
Sensors & Actuators, 2001 Sensors & Actuators, A 89 (2001), Nr. 1-2, ISSN 0924-4247, S. 104-111
Large Deflection Micromechanical Scanning Mirrors for Linear Scans and Pattern Generation
H. Schenk, P. Dürr, T. Haase, D. Kunze, U. Sobe, H. Lakner, H. Kück
Journal of Selected Topics of Quantum Electronics 6, (2000), Nr. 5 ISSN 1077-260×, S. 715-722
An Electrostatically Excited 2D-Micro-Scanning-Mirror with an In-Plane Configuration of the Driving Electrodes
H. Schenk, P. Dürr, D. Kunze, H. Lakner, H. Kück
Proc. MEMS 2000, 13th Int. Micro Electro Mechanical Systems Conf, Miyazaki, Japan, page 473-478, 2000
Mechanical and Electrical Failures and Reliability of Micro Scanning Mirrors
E. Gaumont, A. Wolter, H. Schenk, G. Georgelin, M. Schmoger 9th Int. Symposium on the physical and failure analysis of integrated circuits (IPFA 9), 8-12 Jul. 2002, raffles City Convention Centre, Singapore, Proc. New York, IEEE Press, 2002, ISBN 0-7803-7416-9, S. 212-217
Improved Layout for a Resonant 2D Micro Scanning Mirror with Low Operation Voltages
A. Wolter, H. Schenk, E. Gaumont, H. Lakner, SPIE Conference on MOEMS Display and Imaging Systems (mf07), 28-29 January 2003, San Jose, Calif., USA, Proceedings, Bellingham, Wash.: SPIE, 2003 (SPIE Proceedings Series 4985) ISBN 0-8194-4785-4, S. 72-74
US020040183149A1
Micromechanical device
WO002003010545A1
Mikromechanisches Bauelement (Micro-mechanical device)
WO002000025170A1, Mikromechanisches Bauelement Mit Schwingkörper (Micro-mechanical Device With Vibrating Body)
EP000001123526B1, US000006595055B1
WO002004092745A1
Mikromechanisches Bauelement Mit Einstellbarer Resonanzfrequenz (Micro-mechanical Device With Settable Resonance Frequency)
Driver ASIC for Synchronized Excitation of Resonant Micro-Mirror
K.-U. Roscher, U. Fakesch, H. Schenk, H. Lakner, D. Schlebusch, SPIE Confernece on MOEMS Display and Imaging Systems (mf07), 28-29 January 2003, San Jose, Calif., USA, Proceedings, Bellingham, Wash.: SPIE, 2003 (SPIE Proceedings Series 4985) ISBN 0-8194-4785-4, S. 121-130
The class of MOEMS (MOEMS=Micro Opto Electromechanical Systems) allow to deflect light beams in an electronically controlled way one- or two-dimensional so that using points-shaped light sources or detector elements, respectively, an area or a solid angle may sequentially be scanned or sweeped (scanning).
For projection purposes the use of resonant micromirrors already represents a known solution, which may for example be seen from the following documents:
DE 000019615685 A1
Low Cost Projection Device with a 2-Dimensional Resonant Micro Scanning Mirror
K.-U. Roscher, H. Grätz, H. Schenk, A. Wolter, H. Lakner MEMS/MOEMS display and imaging systems II (2004), pp. 22-31
WO002003032046A1, Projektionsvorrichtung
US020040218155A1,
Also the projection purposes mirrors are used in another way, for example moved in a rotating way according to DE 000010304187A1, DE000010304188A1 and WO002004068211A1 or be already mentioned DMD members according to EP 000000927334B1, US00000661134B1 or DE 000019810495A1 for generating light patterns.
One possibility for a one-dimensional detection of a position of a light beam was presented in “Torsional stress, fatigue and fracture strength in silicon hinges of a micro scanning mirror” of A. Wolter, H. Schenk, H. Korth and H. Lackner (SPIE Bellingham Wash. 2004; Proceedings of SPIE Vol. 5343). This one-dimensional detection of a position of a light beam only offers a coarse and delayed possibility for a determination of the position of the light beam, as the described method requires a complete pass of the light beam between two oscillation amplitude maxima of a travel path of the light beam.
Further, for the application area of the following invention, still the further documents are relevant:
EP000000999429A1 Messinstrument für 3D Form mit Laser Scanner und Digitalkamera (Measurement Instrument for 3D-form with laser scanner and digital camera
US020030202691A1 Calibration of multiple cameras for a turntable-based 3D scanner
US000006486963B1 Precision 3D scanner base and method for measuring manufactured parts
DE000019846145A1 Verfahren und Anordnung zur 3D-Aufnahme (Method and Arrangement for 3D-Recording)
DE000019613978A1 Verfahren zum Zusammenfugen der Messdaten unterschiedlicher Ansichten und Objektbereiche bei der optischen 3D-Koordinatenmeβtechnik mittels flachenhaft und auf der Basis von Musterprojekten arbeitenden Triangulationssensoren (Method for joining the measurement data of different views and object areas in the optical 3D-coordinate measurement technology by means of triangulation sensors operating in a laminar way and on the basis of sample projection)
DE000019536287A1 Verfahren zur geometrischen Kalibrierung von optischen 3D-Sensoren zur dreidimensionalen Vermessung von Objekten und Vorrichtung hierzu (Method for a geometric calibration of optical 3D sensors for a 3-dimensional measurement of objects and devices for the same)
DE000019536294A1 Verfahren zur geometrischen Navigation von optischen 3D-Sensoren zum dreidimensionalen Vermessen von Objekten (Method for a geomectrical navigation of optical 3D sensors for a 3-dimensional measurement of objects)
EP000001371969A1 Ausrichtungsverfahren zum Positionieren von Sensoren für 3D-Meβsysteme (Alignment method for positioning sensors for 3D measurement systems)
WO002000077471A1 Vorrichtung zur Berüthrungslosen Dreidimensionalen Vermessung von Körpern und Verfahren zur Bestimmung eines Koordinatensystems für Messpunktkoordinaten (Device for a contactless 3 dimensional measurement of bodies and methods for determining a coordinate system for measurement point coordinates)
EP000000916071B1 Triangulation-Based 3D Imaging And Processing Method And System
US000005546189A Triangulation-based 3D imaging and processing method and system
US000005654800A Triangulation-based 3D imaging and processing method and system
WO001998005923A1 Triangulation-Based 3D Imaging And Processing Method And System
CA000002365323A1 Method Of Measuring 3D Object And Rendering 3D Object Acquired By A Scanner
DE000019721903C1 Verfahren und Anlage zur meβtechnischen räumlichen 3D-Lageerfassung von Oberflächenpunkten (Method and apparatus for a measurement-technical spatial 3D position detection of surface points)
CA000002376103A1 Active Structural Scanner For Scanning In 3D Mode Data Of Unknown Structures
All of those approaches known in the prior art have the same disadvantage, however, that the detection of the position of the light beam or the position of a location on the surface relief to be sampled by controlling is very expensive and therefore very cost-intensive. Apart from the already mentioned mechanical problems in micro-mirror guiding it is to be noted, however, that also an evaluation electronics in the prior art is to be implemented very expensively. In particular, it is often required to determine the position of the light beam or the location to be sampled using signals of electro-mechanical sensors with regard to a positioning of the control motors of the micro-mirror, whereby, apart from the provisioning of further electromechanical sensors, also a susceptibility of such a system with regard to shock and vibration results.
It is therefore the object of the present invention to provide an improved possibility for the detection of the position of a light beam or a position of a location on the surface relief to be scanned providing an improvement with regard to the prior art in relation to a mechanical robustness, an ability to evaluate, a complexity of signal processing and a reduction of manufacturing costs.
In accordance with a first aspect, the present invention provides a device for determining a position of a light beam within an illumination line, having a light source for providing the light beam, wherein the light source is configured to move the light beam with a predefined movement in a movement area; a shutter with a shutter edge defining the illumination line, wherein the illumination line is a subarea of the movement area and wherein an optical sensor is disposed within the movement area on the shutter edge on the shutter such that detecting of a light beam from the light source by the optical sensor is possible, and wherein the optical sensor is configured to output a sensor signal when detecting the light beam of the light source; and a signal processing unit configured to determine the position of the light beam within the illumination line based on the predefined movement, the position of the optical sensor and the sensor signal.
In accordance with a second aspect, the present invention provides a method for operating a device for determining a position of a light beam within an illumination line, wherein the device includes a light source for providing the light beam, wherein the light source is configured to move the light beam with a predefined movement in a movement area, wherein the device further includes a shutter with a shutter edge defining the illumination line, wherein the illumination line is a subarea of the movement area and wherein an optical sensor is disposed within the movement area on the shutter edge on the shutter such that detecting of a light beam from the light source by the optical sensor is possible, and wherein the optical sensor is configured to output a sensor signal when detecting the light beam of the light source, and wherein the device further includes a signal processing unit configured to determine the position of the light beam within the illumination line based on the predefined movement, the position of the optical sensor and the sensor signal, and wherein the method has the steps of providing of a light beam by the light source and taking the light beam across a movement area; detecting of a light beam from the light source by the optical sensor and outputting a sensor signal; and determining a position of the light beam in the illumination line on the basis of the predefined movement, the position of the optical sensor and the sensor signal.
In accordance with a third aspect, the present invention provides a computer program with program code for performing the method according to the above-mentioned method for operating a device for determining a position of a light beam within an illumination line, when the computer program runs on a computer.
In accordance with a forth aspect, the present invention provides a device for determining a scan position within a detection area, having a light detector configured to scan a scan area with a predefined movement, a shutter with a shutter edge defining a detection area, wherein the detection area is a subarea of the scan area and wherein a reference light source is disposed within the scan area on the shutter edge on the shutter, wherein the light detector is configured to allow detecting a light beam from the reference light source by the light detector to output a sensor signal when detecting a light beam of the reference light source; and a signal processing unit configured to determine the position of the scan position within the detection area based on the predefined movement, the position of the reference light source on the shutter and the sensor signal.
In accordance with a fifth aspect, the present invention provides a method for operating a device for determining a scan position of the light detector within a detection area, wherein the device includes a light detector configured to scan a scan area with a predefined movement, wherein the device further includes a shutter with a shutter edge defining a detection area, wherein the detection area is a subarea of the scan area and wherein a reference light source is disposed within the scan area on the shutter edge on the shutter, wherein the light detector is configured to allow detecting a light beam from the reference light source by the light detector to output a sensor signal when detecting a light beam of the reference light source, and wherein the device further includes a signal processing unit configured to determine the position of the scan position within the detection area based on the predefined movement, the position of the reference light source on the shutter and the sensor signal, wherein the method further has the steps of providing of a light beam by the reference light source and taking the light beam from the reference light source across a movement area; detecting of a light beam from the reference light source by the light detector and outputting a sensor signal; and determining the scan position of the light detector within a detection area on the basis of the predefined movement, the position of the reference light source and the sensor signal.
In accordance with a sixth aspect, the present invention provides a computer program for performing the method according to the above-mentioned method for operating a device for determining a scan position of the light detector within a detection area, when the computer program runs on a computer.
In accordance with a seventh aspect, the present invention provides a device for determining a position of a light beam within an illumination line, having a light source for providing the light beam, wherein the light source is configured to move the light beam with a predefined movement in a movement area; a shutter with a shutter edge with two opposing shutter edge sides defining the illumination line, wherein the illumination line is a subarea of the movement area and wherein two optical sensors are disposed within the movement area on the opposing shutter edge sides on the shutter such that detecting of a light beam from the light source by the optical sensors is possible, and wherein the optical sensors are configured to output a sensor signal each when detecting the light beam of the light source; and a signal processing unit configured to determine the position of the light beam within the illumination line based on the predefined movement, the position of the optical sensors and the sensor signal.
In accordance with an eighth aspect, the present invention provides a method for operating a device for determining a position of a light beam within an illumination line, wherein the device includes a light source for providing the light beam, wherein the light source is configured to move the light beam with a predefined movement in a movement area, wherein the device for determining further includes a shutter with a shutter edge with two opposing shutter edge sides defining the illumination line, wherein the illumination line is a subarea of the movement area and wherein two optical sensors are disposed within the movement area on the opposing shutter edge sides on the shutter such that detecting of a light beam from the light source by the optical sensors is possible, and wherein the optical sensors are configured to output a sensor signal each when detecting the light beam of the light source, and wherein the device for determining further includes a signal processing unit configured to determine the position of the light beam within the illumination line based on the predefined movement, the position of the optical sensors and the sensor signal and wherein the method has the steps of providing of a light beam by the light source and taking the light beam across a movement area; detecting of a light beam from the light source by the optical sensors and outputting of a sensor signal by each of the optical sensors; and determining a position of the light beam in the illumination line on the basis of the predefined movement, the position of the optical sensors and the sensor signal.
In accordance with a ninth aspect, the present invention provides a computer program with program code for performing the method according to the above-mentioned method for operating a device for determining a position of a light beam within an illumination line, when the computer program runs on a computer.
In accordance with a tenth aspect, the present invention provides a device for determining a scan position within a detection area, having a light detector configured to scan a scan area with a predefined movement in a first scan direction and a second scan direction differing from the first scan direction; a shutter with a shutter edge defining a detection area, wherein the detection area is a subarea of the scan area and wherein a first reference light source is disposed within the scan area on the shutter edge in the first scan direction and a second reference light source is disposed within the scan area on the shutter edge in the second scan direction on the shutter, wherein the light detector is configured to allow detecting a light beam from the first or second reference light source by the light detector to output a sensor signal when detecting a light beam of the first or second reference light source; and a signal processing unit configured to determine the scan position within the detection area based on the predefined movement, the position of the first and second reference light sources on the shutter and the sensor signal.
In accordance with an eleventh aspect, the present invention provides a method for operating a device for determining a scan position of the light detector within a detection area, wherein the device includes a light detector configured to scan a scan area with a predefined movement in a first scan direction and second scan direction differing from the first scan direction, wherein the device further includes a shutter with a shutter edge defining a detection area, wherein the detection area is a subarea of the scan area and wherein a first reference light source is disposed within the scan area on the shutter edge in the first scan direction and a second reference light source is disposed within the scan area on the shutter edge in the second scan direction on the shutter, wherein the light detector is configured to allow detecting a light beam from the first or second reference light source by the light detector to output a sensor signal when detecting a light beam of the first or second reference light source, and wherein the device further includes a signal processing unit configured to determine the scan position within the detection area based on the predefined movement, the position of the first and second reference light sources on the shutter and the sensor signal, wherein the method further has the steps of providing of a light beam by the first and second reference light sources and taking the light beam from the reference light source across a movement area; detecting of a light beam from the first or second reference light source by the light detector and outputting a sensor signal; and determining the scan position of the light detector within a detection area on the basis of the predefined movement, the position of the first or second reference light source and the sensor signal.
In accordance with a twelfth aspect, the present invention provides a computer program for performing the method according to the above-mentioned method for operating a device for determining a scan position of the light detector within a detection area, when the computer program runs on a computer.
The present invention is based on the finding, that by use of a shutter a reference position in the form of a reference light source or an optical sensor may be detected when guiding a light beam over the optical sensor or a scanning position, respectively, over the reference light source, in order to detect a position of the light beam in the illumination line or the scanning position in the scanning area by this. This may in particular be performed as a predefined movement is known and that by detecting a point of time of overwriting or detecting, respectively, the known reference position on the shutter, the direction and location of the light beam and/or the “direction of view” of the light detector may be determined.
This provides the advantage of a substantially improved possibility for detecting the position of a light beam or the position of a location on the surface relief to be sampled, offering an improvement with regard to the prior art relating to a mechanical robustness, a capability to evaluate, a complexity of signal processing and a reduction of manufacturing costs.
In the following, some embodiments of the present invention are explained in more detail with reference to the accompanying drawings, in which:
a shows a schematic illustration of an embodiment for a shutter of the collector;
b shows a diagram for illustrating received signals of a photo diode when using the shutter illustrated in
a shows a plan view of a further embodiment of the inventive scanner using the shutters illustrated in
b shows a sectional illustration of the further embodiment corresponding to a section at the intersection line AA′;
c shows a flowchart of an embodiment of the inventive method for operating a scanner; and
In the Figures, same or similar elements are designated by same or similar reference numerals, wherein a repeated description for those elements is omitted.
The first embodiment of the inventive scanner is schematically illustrated in
According to the first embodiment of the present invention, micro-mirrors may thus be used, when applying the known triangulation method, as a scanner for the 3D detection of objects. Micro-scanner mirrors find application according to the first embodiment both for a projection of a structured illumination onto the object and within the light receiver (i.e. the collector 16) for the detection of the back-scattered light.
What is new, in particular, is that, for the image acquisition in the collector, a point-shaped light detector 18 (or also light sensor) is used in combination with a two-dimensional oscillating micro mirror which defines the respective “viewing direction” of the detector via its momentary displacement. Corresponding to
In order to detect the surface relief of the object to be scanned, there will further be used a procedure as explained in more detail in the following. When using micro mirrors, for example for the illumination of the object and for the detection of the backscattered light, what must basically be taken into consideration is that each of the oscillating mirrors is only directed to exactly one point (spot) of the object at any time. Therefore, it is preferred that both mirrors are controlled such that the detector may detect the spot generated by the projector on the surface relief of the object.
In order to detect this generated spot (i.e. the illuminated place marked with the reference numerals 22 or 22′, respectively, in
The principle of scanning with preferably two mirrors parallel to the triangulation plane may thus be represented as follows, wherein the term “triangulation plane” means the plane defined by the centers of the image field in the reference plane and both mirrors and/or by the triangulation angle:
At the collector, a framelike shutter provided with LEDs according to
A similar shutter is attached to the projector which, however, carries two opposing photodiodes instead of the LEDs, which, when illuminated by the spot, provide a signal serving to calculate amplitude and phase of the y oscillation of the projector micro mirror and, at the same time, limiting the displacement of the spot.
A second step 112 involves outputting a projection signal from which the position of the light beam in the illumination line may be derived.
Subsequently, a third step 114 involves detecting an illuminated place of the surface relief using a micro mirror in the collector stimulated to oscillations.
A fourth step 116 involves outputting a detection signal from which a position of the illuminated place on the surface relief may be derived. A final step 118 of the embodiment of the inventive method involves processing the projection signal and the detection signal to acquire the surface relief therefrom.
In summary, it may be said that a novel 3D scanner is disclosed herein provided with a projector (preferably with a point-shaped light source and a micro scanner mirror) and a collector, wherein the collector includes a micro scanner mirror and a point-shaped light detector on which a reflection of a light point from a surface relief of an object to be detected may be projected by the micro scanner mirror. Further, a corresponding electronic circuit with an interface to a host computer for controlling and further processing of the obtained data may be provided. Furthermore, a method for stimulating the two micro scanner mirrors of the 3D scanner is disclosed herein such that the spot generated by the projector micro scanner mirror may actually be found in the detection area via the collector micro scanner mirror and the light detector, by way of the projector mirror oscillating only in a direction perpendicular to the triangulation plane with a defined frequency and amplitude, the collector micro mirror being stimulated preferably synchronously and with the same amplitude preferably also perpendicular to the triangulation plane, and the collector mirror furthermore performing a second oscillation in the triangulation plane at the same time to detect the displacement of the spot caused by the measuring principle.
Furthermore, a device, for example for the 3D scanner, is disclosed herein, preferably allowing a synchronization of the oscillations of both mirrors in the direction perpendicular to the triangulation plane according to the stimulation method, consisting of a shutter with photodiodes in the optical train of the projector and/or a shutter designed analogously but provided with LEDs in the optical train of the collector by which signals on the momentary amplitudes and phases of one or both oscillations of the micro scanner mirrors may be obtained. Furthermore, an electronic circuit is disclosed which may influence the control of the mirrors in a regulating way, for example to influence control of the frequency, phase or amplitude of a stimulation of a micro mirror, for example to increase a line density of the Lissajous figure and thereby increase the probability of finding the reflection of the light point.
The invention described herein therefore has the advantage of being able to operate without area or line camera so that no area or line image sensors and no corresponding associated complex mapping optics are required. Furthermore, a micro scanner mirror is small, mechanically robust and may be manufactured at a low price, whereby the central advantages of the present invention present themselves in a reduction of the space requirements and the manufacturing costs as well as an increase in mechanical robustness. The described circuit for processing a faint light signal further allows an increase in resolving power. Thus, the described 3D scanner may continue to be constructed in a spatially very compact way. The required signal processing, for example the detection of the laser spot in the sensor data stream, may, at least in part, be realised in hardware and may, for example, be integrated in the scanner, whereby the corresponding computational effort for processing the obtained data to a controlling host computer may be significantly reduced and thus the detection of the surface relief of the corresponding object may be significantly accelerated and the complexity of corresponding algorithms to be performed in the host computer becomes possible. Thus, image processing operations for the extraction of areas of interest from a 2D image are not necessary.
Furthermore, the inventive method for operating a device for determining a position of a light beam within an illumination line or the method for operating a device for determining a scan position of the light detector within a detection area may be implemented in hardware or software, depending on the circumstances. The implementation may be carried out on a digital storage medium, particularly a disk or CD with control signals that may be read out electronically, which may cooperate with a programmable computer system so that the corresponding method is performed. Generally, the invention thus also consists in a computer program product with a program code stored on a machine readable carrier for performing the inventive method, when the computer program product runs on a computer. In other words, the invention may thus be realised as a computer program with a program code for performing the method, when the computer program runs on a computer.
While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.
This application claims the priority, under 35 U.S.C. § 119, of German patent application No. ______, filed Jan. 17, 2005; the entire disclosure of the prior application is herewith incorporated by reference.
Number | Date | Country | Kind |
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10 2005 002 189.1 | Jan 2005 | DE | national |