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WO2003021237A2 - Procede et dispositif de mesure de mouvements de translation entre une surface et un dispositif de mesure - Google Patents

Procede et dispositif de mesure de mouvements de translation entre une surface et un dispositif de mesure Download PDF

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Publication number
WO2003021237A2
WO2003021237A2 PCT/DE2002/002982 DE0202982W WO03021237A2 WO 2003021237 A2 WO2003021237 A2 WO 2003021237A2 DE 0202982 W DE0202982 W DE 0202982W WO 03021237 A2 WO03021237 A2 WO 03021237A2
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WO
WIPO (PCT)
Prior art keywords
light
reflected
diffraction grating
detector
propagation component
Prior art date
Application number
PCT/DE2002/002982
Other languages
German (de)
English (en)
Other versions
WO2003021237A3 (fr
Inventor
Andreas BRÄUER
Herbert Brunner
Peter Dannberg
Peter Schreiber
Ulrich STEEGMÜLLER
Uwe Zeitner
Original Assignee
Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. filed Critical Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority to AU2002328784A priority Critical patent/AU2002328784A1/en
Priority to EP02764547A priority patent/EP1417459A2/fr
Publication of WO2003021237A2 publication Critical patent/WO2003021237A2/fr
Publication of WO2003021237A3 publication Critical patent/WO2003021237A3/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses
    • G01D5/38—Forming the light into pulses by diffraction gratings

Definitions

  • the present invention relates to a method and a device for high-resolution contactless measurement of one- and / or two-dimensional translation movements between a rough or diffusely scattering surface of an object and a measuring device with detection of the amount and the direction of the translation movement according to patent claims 1 and 6.
  • optical measurement methods and systems for measuring relative movements between a device and an object. These can be roughly divided into interferometric measurement methods, autocorrelation measurements, aser-Doppler anemometry, run-time measurements of pulses and encoders.
  • two spatially separated, coherent partial beams, the measurement beam and the reference beam are generated by means of beam splitting, which are brought together again after passing through a predetermined optical path and overlap in an interfering manner.
  • Conclusions regarding the optical and thus also the geometrical path differences of the two partial beams can be drawn from the intensity distributions resulting from the interference.
  • a path or speed can be determined. The highest accuracies are currently achieved with such interferometric measurement methods.
  • the moving surface of an object is illuminated by a light source and the reflected light with a flat, spatially resolving detector. gate added. It is possible to draw conclusions about the direction of movement and the speed from the evaluation of several images of the reflected light taken in succession by means of an autocorrelation analysis of the intensity patterns.
  • a texture of the moving surface is generally necessary in order to achieve a sufficiently high contrast in the reflected light pattern.
  • speckle patterns resulting from the reflection on surface roughness can be used for evaluation.
  • a laser beam is split up and the two partial beams are brought to interference at a certain position. If a scattering object, such as a rough surface, passes the area of the resulting interference fringes, part of the light is scattered onto a detector.
  • the signal measured at the detector varies with the intensity of the interference pattern at the position of the scattering object.
  • the frequency of the signal variation caused by a moving object is therefore proportional to the speed of the scattering object and can therefore be used to measure the distance.
  • a further possibility for optically determining a path or a change in path is the running time measurement of light pulses which are reflected on the surface of the moving object. If this run time measurement is carried out repeatedly over a certain period of time, the relative movement of the object towards or away from the detector can be determined.
  • encoder is understood to mean angle coding or length coding devices in which the mapping of a moving stripe pattern onto detector elements is used to determine the angle or the path.
  • the moving object ject connected code strip or connected code wheel, which has narrow light column, illuminated.
  • the movement of the light-shadow pattern generates a periodic current-time profile with a suitable, usually multiple photodiode arrangement, which can be evaluated by electronic counter.
  • encoders based on reflection as well as transmission, which are suitable for low to high resolution applications.
  • the surface of a moving object is irradiated with a coherent light source and a partially reflecting optical element, such as in particular a, between the light source and the surface in the vicinity of the surface parallel to the latter
  • the grating is positioned so that part of the incident light is reflected from the grating to a detector (reference beam), while the other part of the incident light passes through the grating to the surface of the moving object and is reflected on it (measuring beam) in order to deal with it overlay the reference beam.
  • the detector detects a periodic measurement signal, from the frequency of which the amount of the relative movement between the measuring device and the object can be determined parallel to the surface of the object.
  • a phase shift is additionally generated between the two partial beams, from the sign of which one can infer the direction of the relative movement.
  • the detector module has a beam splitting grating and two detectors for detecting the two partial beams generated in this way.
  • Two polarizers are arranged in front of the detectors, the polarization vectors of which are rotated by 90 ° to one another, so that the measurement signals detected by the detectors have a phase difference of -90 ° or + 90 ° depending on the direction of the relative movement.
  • a circular polarizer is provided in the vicinity of the surface of the moving object, ie adjacent to the partially reflecting grating, so that finally the linearly polarized reference light which is reflected on the grating is combined with the circularly polarized scattered light which is reflected on the object surface. superimposed before it is divided in the detector module as described above.
  • an object of the present invention to further develop an interferometric measuring method or a measuring device of the type described above, with which simple, high-resolution measurement of both the amount and the direction of a translational movement between the measuring device and an object surface in a compact measuring arrangement.
  • translational movements between a measuring arrangement and a surface that extends in the x-y plane of an orthogonal reference system are measured by a light source having a coherent one
  • Light beam with a main propagation component in the z direction of the orthogonal reference system in the direction of itself is oriented relative to the measuring arrangement in the y-direction and a partially reflecting diffraction grating is positioned in front of the surface, which is designed such that the light reflected thereon diffraction orders with a propagation component in the -y direction and diffraction orders with a propagation component in the + y direction which are equally strong, and that it passes through another part of the coherent light beam in order to be scattered on the surface and then to overlap with the light reflected on the diffraction grating.
  • the light scattered on the surface is also circularly polarized.
  • a first detector arrangement receives the light reflected on the diffraction grating with a propagation component in -y - direction, which is superimposed on the light scattered on the surface
  • a second detector arrangement receives the light reflected on the diffraction grating with a propagation component in -iy - Direction that is superimposed on the light scattered on the surface
  • the detector arrangement having a beam splitter and a first and a second detector for detecting a first and a second measurement signal, and a device for generating a phase difference between the beam splitter and the first and second detector is provided between the first and the second measurement signal.
  • first and the second measurement signal are fed to an evaluation circuit to determine the direction of movement in the y direction from the sign of the phase difference between the first and the second measurement signal and the amount of movement in the y direction from the frequency of the change in amplitude of the first and the second Determine measurement signal.
  • the frequency of the amplitude changes of the interference signals is determined by the superimposition of the reference beam (of the light reflected on the diffraction grating) and the measuring beam (of the light scattered on the surface) ) result ben determined or counted the zero crossings or maxima of the waveforms.
  • the invention uses the coherent superimposition of circularly polarized scattered light with linearly polarized reference light, the phase shift generated in the detector arrangement acting only on the circularly polarized scattered light, but not influencing the linearly polarized reference light, so that the sign of the phase difference between the two Measurement signals on the direction of movement can be concluded.
  • the accuracy of the measurement can be increased.
  • the partially reflecting diffraction grating is designed such that the light reflected thereon diffraction orders with a propagation component in the -y direction, diffraction orders with a propagation component in the + y direction, diffraction orders with a propagation component in the x direction and diffraction orders with a
  • the measuring device further comprises a third detector arrangement for receiving the light reflected on the diffraction grating with a propagation component in the -x direction, which is superimposed on the light scattered on the surface, and / or a fourth detector arrangement for receiving the light reflected on the diffraction grating with a propagation component in the + x direction, which is superimposed on the light scattered on the surface.
  • the third and / or the fourth detector arrangement are with one
  • Beam splitter and a third and a fourth detector for detecting a third or fourth measurement signal wherein a device for generating a phase difference between the third and the fourth measurement signal is provided between the beam splitter and the third and fourth detector.
  • the third and the fourth measurement signal supplied to the evaluation circuit in order to determine the direction of movement in the x-direction from the sign of the phase difference between the third and fourth measurement signals and the amount of movement in the x-direction from the frequency of the change in amplitude of the third and fourth measurement signals.
  • the device for generating a phase difference preferably has a first polarization filter with a first polarization vector between the beam splitter and the first or third detector and / or a second polarization filter with a second polarization vector different from the first polarization vector between the beam splitter and the second or fourth detector or alternatively between the beam splitter and the first or third detector a first phase delay layer with a first phase delay preferred axis parallel to the direction of polarization of the reflected light and / or between the beam splitter and the second or fourth detector a second phase delay layer with a second phase delay Preferred axis perpendicular to the direction of polarization of the reflected light.
  • the first and third detectors and the second and fourth detectors can each be arranged in a row and have a common device for generating a phase difference.
  • a collimation lens is provided between the light source and the diffraction grating, which has a flat side facing the diffraction grating, which is inclined at an angle to the xy plane, so that the coherent light beam is inclined at an angle to the z direction becomes.
  • the diffraction grating is advantageously a periodic surface profile in the x- and y-directions on a substrate on which a partially reflecting layer, for example in the form of a dielectric interference layer, is provided.
  • the formation of the surface profile as a binary height profile with a height difference between upper surfaces and lower surfaces the upper and lower surfaces being essentially square and the sides of the square upper and lower surfaces opposite the x-axis and the y-axis are rotated by 45 °.
  • FIG. 1 shows a schematic representation of a measuring arrangement in section of the x-z plane to explain the measuring method according to the invention
  • FIG. 2 shows a schematic illustration of a measuring arrangement in the section of the y-z plane to explain the measuring method according to the invention
  • FIG. 3 shows a schematic illustration of a measuring device according to the present invention in section
  • 4A and 4B are schematic representations of a diffraction grating and a circular polarizer of the measuring device of FIG. 3 in section and in plan view;
  • 5A and 5B are schematic representations of two different exemplary embodiments of detectors and devices for generating a phase difference of the measuring device of FIG. 3; and 6 shows a schematic illustration of detectors and devices for generating a phase difference according to a further exemplary embodiment.
  • FIGS. 1 and 2 show schematic sectional representations which are perpendicular to one another, so that when the two views are viewed together, the spatial structure of the measuring arrangement is obtained.
  • a monochromatic light source 2 such as a laser diode
  • a main propagation component in the positive z direction downward in FIGS. 1 and 2
  • the direction of polarization in the xy plane is parallel to the x axis.
  • This light c is first collimated with a collimation lens 3. 1 and 2, an aspherical plano-convex lens is used as the collimation lens 3, the plane side 3a of which lies on the side facing away from the light source 2.
  • the plane side 3a of the collimation lens 3 is inclined by an angle ⁇ with respect to the xy plane in order to implement a slight deflection of the collimated light beam c by an angle ⁇ with respect to the z direction.
  • This deflection can be used to increase the distance between the light source 2 and the detector arrangements 9 mentioned below in the xy plane.
  • the overall length of the measuring arrangement 1 in the z direction can be shortened by this measure.
  • the diffraction grating 4 is partially reflective, so that part of the incident light c is reflected and the reflected portion r is split up into diffraction orders due to the grating effect of the diffraction grating 4.
  • the reflected diffraction orders have a propagation component in the -y direction (to the left in FIG. 2), in the + y direction (to the right in FIG. 2) and in the -x direction (to the left in FIG. 1) and in the + x direction (to the right in FIG. 1), the latter being not shown in the figures, since it is not used in the exemplary embodiment shown for measuring the translational movement.
  • the non-reflected portion t of the light c falling on the diffraction grating 4 is transmitted without a grating effect being intended to occur. This means that the transmitted light t is not split into different diffraction orders.
  • Adjacent to the diffraction grating 4 is a circular polarizer, which is composed of a device 5 for phase delay and a linear polarizer 6.
  • the device 5 for phase delay is a so-called ⁇ / 4 phase plate and the linear polarizer 6 is a polarization filter, the transmission direction of the polarization filter 6 being rotated through 45 ° to the optical axis of the ⁇ / 4 phase plate 5.
  • the light t After passing through the circular polarizer 5, 6, the light t hits the surface 7, the movement of which relative to the measuring arrangement 1 is to be determined.
  • the light t is on the
  • the light s scattered back and transmitted by the system of circular polarizers 5, 6 and diffraction grating 4 is superimposed on the light r reflected in different diffraction orders at the diffraction grating 4.
  • This interference signal resulting from the superimposition is received by a plurality of detector arrangements 9, a detector arrangement 9 -y , 9 + y , 9_ x being provided for each diffraction order.
  • the detector arrangements 9 each have a focusing lens 10, with the aid of which the interference signal r + s is focused on the detectors 12, 13.
  • a beam splitter grating 11 is provided, which splits the focused light beam generated by the focusing lenses into two light beams which hit a total of six detectors. More specifically, the beam splitter grating 11 of the first detector arrangement 9.
  • a fourth detector arrangement 9 + x which would receive the reference beam of the reflected light r + x with a propagation component in the + x direction and the scattered light s and would split the interference beam into a third light beam i 3 and a fourth light beam i 4 for a third and fourth detector 12, 13, respectively not provided in this embodiment of FIGS. 1 and 2.
  • the electrical measurement signals generated by the detectors 12, 13 are amplified by suitable electronic amplifiers in the evaluation circuit before they are evaluated further.
  • a device for generating a phase difference between the first or third light beam i 1 # i 3 and the second or fourth light beam i 2 , i is arranged in front of each pair of detectors 12, 13 and acts as an analyzer for the incident light.
  • the exact structure of this device 14, 15 for generating the phase difference and its mode of operation are explained in more detail below with reference to FIGS. 5 and 6.
  • the measuring arrangement described above enables the movement of a surface relative to the measuring arrangement in the x and y directions to be detected simultaneously in a particularly simple manner and by means of a compact measuring device.
  • the superimposition of the light r reflected directly on the diffraction grating 4 and the scattered light s from the surface 7 from the detectors 12, 13 generates an electrical measurement signal with changing amplitude.
  • the frequency with which the signal amplitude changes is directly proportional to the speed of the movement.
  • the maxima or the zero crossings of the measurement signals are above all dependent on the grating period of the diffraction grating 4.
  • the movement can therefore be measured exactly, the measurement signals being counted by a suitable electronic circuit being transformed, before they are specifically processed in the evaluation circuit.
  • the arrangement of the circular polarizer 5, 6 and the device 14, 15 for generating a phase difference enables the distinction between movements in the + x direction and - x direction or + y direction and -y direction.
  • the superimposition of the scattered light s from the surface 7, which is transformed into circularly polarized light by the arrangement of the circular polarizer 5, 6, and the linearly polarized light r reflected directly on the diffraction grating 4 between the two alternating signals of a pair of detectors 12 , 13, which are generated by the splitting on the partial beam grating 11 and the subsequent analysis by the device 14, 15 for generating a phase difference introduced a phase shift between the two measurement signals.
  • the direction of movement can be derived directly from the sign of this phase shift.
  • the measuring arrangement 1 of the present invention can be used to measure purely one-dimensional movements, for example only in y Direction, be simplified.
  • the two-dimensional diffraction grating 4 of the above exemplary embodiment is replaced by a one-dimensional line grating.
  • the two reference beams used r. y and r + y are focused by the focusing lenses 10 and the beam splitter grids 11 of the two detector arrangements 9 -y and 9 + y onto the total of four detectors 12, 13.
  • the measuring device is implemented, for example, as an optoelectronic sensor 20, as is illustrated schematically in FIG. 3.
  • the same reference numerals are used in the following for the same components as in FIGS. 1 and 2.
  • the housing substrate 16 of the sensor 20 consists of a conductor strip or a so-called lead frame 17, which is encapsulated with a plastic body 18.
  • the leadframe 17 is structured, for example, by etching or stamping processes and then provided with a suitable surface to fulfill its interface functions.
  • Suitable leadframe materials are, for example, Cu or NiFe alloys, and the end surface is usually applied galvanically.
  • the lead frame 17 has the following functions in particular. It provides electrical connections with suitable surfaces (e.g. SnPb, Au, NiPd, PdAu, Ag) for soldering, gluing or plugging. It is also used to attach the entire optoelectronic sensor 20 to a circuit board, a suitable substrate or a plug contact.
  • the leadframe 17 has connection areas made of, for example, Ag, Pd or Au for the laser light source 2 and the detectors 12, 13. It is also used for heat dissipation and as an optical or mechanical reference for subsequent assembly.
  • the overmolded plastic 18 embeds the leadframe for mechanical stabilization and is used for insulation.
  • the plastic body 18 can be designed such that it has mounting interfaces suitable for the optical module to be mounted.
  • a laser diode or an edge emitter with beam deflection is preferably used as the coherent light source 2.
  • the laser diode 2 is glued to the housing substrate 16 and electrically connected to the leadframe 17 using a connecting wire made of aluminum or gold.
  • a single-mode VCSEL Very Cavity Surface Emitting Laser
  • the direction of polarization of the emitted light is oriented according to the definitions of FIGS. 1 and 2 at 0 ° to the x-axis.
  • the full beam angle of the VCSEL is usually around 10 ° and its optical power in the single mode range is around 1 mW.
  • the use of a VCSEL has the advantage that no redirection and circularization optics are required and that standard methods such as for the assembly of LEDs can be used.
  • photodiodes are preferably used as detectors 12, 13.
  • the resulting photocurrents can basically be processed in analog or digital form in the evaluation circuit.
  • the photodiodes 12, 13 are also glued to the housing substrate 16 and electrically connected to the leadframe 17 with a connecting wire.
  • the devices 14, 15 for generating a phase difference are attached above the photodiodes 12, 13 in order to be able to determine the sign of the direction of movement.
  • Polarization-sensitive applications typically use external, discrete and glass-laminated polarization elements built into the detection beam path based on absorbent film linear polarizers.
  • Conventional, inexpensive film polarizers show a high temperature sensitivity, which on the one hand requires complex protective measures and, moreover, cannot be integrated on the detector chip because of the usual soldering temperatures.
  • stable polarizers based on Polarcor or light-crosslinking polymers are preferably used, with which the polar effect can be achieved directly on the semiconductor chip.
  • the high temperature resistance of these materials also allows the use of standard soldering processes.
  • the orientation of the phase delay preferred axis is for one Photodiode 12 oriented parallel and for the other photodiode 13 perpendicular to the polarization direction of the reference light r.
  • the polarization state of the linearly polarized reference light r is not influenced by the phase delay layers 31, while the circularly polarized scattered light s is converted into linearly polarized light, the polarization vector of which is + 45 ° in one photodiode and -45 ° in the other photodiode Polarization vector of the reference light are twisted.
  • the cholesteric layer 30 acts as a circular polarizer, which generates circularly polarized light from the linearly polarized reference light and the linearly polarized scattered light.
  • linear polarizers based on glass polarizers such as Polarcor can be used to generate the phase difference.
  • the one photodiodes 12 are covered with a first linear polarizer 14, the preferred axis 32 of which is at + 45 ° is inclined to the polarization vector 34 of the reference light r.
  • the other photodiodes 13 are provided with a second linear polarizer 15, the preferred axis 33 of which is inclined at -45 ° to the polarization vector 34 of the reference light.
  • the exemplary embodiments of the polarization components described with reference to FIGS. 5A and 5B each cause a phase difference between the electrical measurement signals generated in the photodiodes 12 and 13, which are + 90 ° or -90 ° depending on the direction of movement of the surface 7 relative to the measurement arrangement is.
  • the sign of the phase shift generated in this way can therefore be used to draw direct conclusions about the direction of movement.
  • the phase shift between the measurement signals generated in the photodiodes 12, 13 is only + 45 ° or -45 °.
  • This embodiment is less expensive due to the lower assembly effort and the smaller amounts of material for polarization components, but on the other hand the evaluation circuit must be able to ensure an adequate differentiation of the sign even with smaller phase shifts.
  • This arrangement is made possible by the off-axis focusing lenses 10, which are explained in detail below and which focus the light beams onto these two rows.
  • the advantage of this arrangement compared to, for example, a triangular arrangement, in which the focusing lenses are also arranged, lies in the homogeneous design of the photodiode area 12, 13 on an integrated circuit and the possibility of covering the rows of photo diodes together with the polarization components 14, 15.
  • the photodiodes themselves are preferably hexagonal in order to be able to save chip area taking into account the tolerance requirements, and have a diameter of approximately 500 ⁇ m.
  • the integrated circuit or evaluation circuit provided on the substrate 35 contains various analog and digital assemblies, such as amplification, filter and logic functions, in order to convert digital output signals (voltage-time) from the electrical current-time measurement signals proportional to the movement of the surface. Signals). This includes in particular DC voltage suppression, high and low frequency filters, maximum or zero crossing detection and
  • the driver stage for the laser light source 2 can also be arranged on the integrated circuit.
  • Circuit either be quadrature signals for movement in the x and y directions or digital output signals that are provided in parallel or in series via a bus system.
  • a quadrature output for example, the movement in the x direction is represented by two output signals which have a phase shift of ⁇ 90 °.
  • a one-dimensional measuring system will therefore have two output channels and a two-dimensional measuring system will have four output channels.
  • an evaluation circuit can achieve four times the resolution of the actual resolution of the measuring arrangement.
  • an optical module 19 is connected to the housing substrate 16.
  • the optics module 19 has in particular the collimation lens 3 for the coherent light c, the focusing lenses 10, the beam splitter grating 11 and a layered structure 21, which essentially contains the diffraction grating 4 and the circular polarizer 5, 6.
  • the optics module 19 can be manufactured, for example, by injection molding from PC, PMMA, COC or COP and can also be provided with an opening (not shown) for ventilation purposes.
  • the collimation and focusing components 3, 10, 11 can be produced together with the necessary connection structures for the layer structure 21 (so-called “sandwich”) and the housing substrate 16 as a single component. It is particularly important to ensure that the material used and the
  • Process control in injection molding should be selected so that there is as little stress birefringence as possible in the optically effective parts.
  • the optics module 19 can already contain the assembly interfaces to the housing substrate 16, in addition to the shaping of the optical elements, the shaping of an optomechanical support frame 22 is also carried out in an injection mold.
  • the optics module 19 can also be inserted into a separately manufactured optomechanical support frame 22.
  • the optomechanical support frame 22 can be made light-tight and weakly reflective, as a result of which the stray light component is reduced by external light radiation and internal reflections.
  • the optomechanical support frame 22 has interfaces (not shown) to the housing substrate 16, to the optics module 19 (if manufactured separately), to the sandwich 21 and to the optional external installation location in the application.
  • the support structure 22 can be provided with a groove or an opening for the purpose of ventilation.
  • the optics module can also consist of two separate parts.
  • beam splitter 11 and imaging optics 3 and 10 or beam splitter 11 and a combination of diffraction grating 4 and imaging optics can be manufactured as independent parts and then assembled.
  • a circumferential groove in the plastic jacket 18 of the housing substrate 16 which is filled with a suitable adhesive, and a corresponding connection geometry on the support frame 22 can be provided.
  • the groove is interrupted at certain points and is designed as a ventilation opening with a dust barrier, the support structure being provided with corresponding counterparts at these points.
  • the housing substrate 16 can also have centering aids and openings to the rear, into which corresponding pins of the optomechanical support frame 22 can be inserted and optionally riveted to the rear of the housing substrate 16 or the like can be fixed.
  • the support structure 22 has, for example, a circumferential recess or depression 23 into which the layer structure 22 can be inserted. Additional recesses or the like for receiving an adhesive are formed in the recess 23. Furthermore, this interface can also have ventilation with a dust barrier at certain points.
  • the optomechanical support frame 22 has, for example, protrusions and flats which are part of a snap connection with corresponding counter elements at the installation site.
  • a circumferential groove with a counterpart at the installation location can be provided as ESD protection, so that the airway for a possible rollover is significantly increased without enlarging the optoelectronic sensor 20 itself in a corresponding manner.
  • all of the interfaces of the support structure 22 described above can have special construction features, such as dust barriers, ventilation openings to avoid Fertilization of microclimate, ESD protection devices and anti-rotation protection included.
  • the fixed connection between the support frame 22 and the housing substrate 16 and the layer structure 21 is preferably carried out by means of UV adhesive technology.
  • the collimation lens 3 integrated in the optical module 19 is preferably an aspherical plano-convex lens, the plane side 3a of the plano-convex lens 3 facing the layer structure 21 being able to be inclined by an angle ⁇ with respect to the x-y plane in order to achieve an additional beam deflection, as already explained above.
  • the material of the collimation lens 3 is, for example, polycarbonate with a refractive index of 1.57 and the aperture of the collimation lens is square with an extension of 0.8 mm ⁇ 0.8 mm.
  • the already mentioned layer structure 21 of the optical module 19 consists of several layers and essentially has the partially reflecting optical diffraction grating 4, the circular polarizer 5, 6 and a mechanically permanent coating to protect the optical module 19 against mechanical damage.
  • the entire layer structure 21 is produced, for example, over a large area by means of DVD / CD injection molding / injection molding technology or by roller embossing, and is subsequently divided into smaller parts which are inserted into the optomechanical support frame 22.
  • the layer structure 21 has, on the one hand, the task of generating the reference beams r required for the interferometric measurement by reflection, and on the other hand it has to reflect the state of polarization of the scattered back from the surface 7 Effectively influence light s to enable the determination of the direction of movement.
  • the structure of the layer structure 21 is shown schematically in an enlarged illustration in FIGS. 4A and 4B.
  • the partially reflecting diffraction grating 4 of the layer structure 21 essentially consists of a surface profile periodic in the x-direction and in the y-direction on a substrate 24 on which a partially reflecting layer 27 is provided in order to reflect part of the incident light c and in several diffraction orders split. Since the grating effect of the diffraction grating 4 for the transmitted light t is to be canceled, the partially reflective coated surface profile is leveled with a material 28 whose optical refractive index is matched to that of the grating material. This material 28 also serves as an adhesive to the adjacent circular polarizer 5, 6. The period can be different in the x and y directions.
  • the substrate 24 of the diffraction grating 4 is positioned at a distance of approximately 11 mm from the laser diode 2 and has a layer thickness of approximately 0.6 mm.
  • the surface profile of the diffraction grating 4 is designed such that the light r reflected thereon is preferably deflected into the diffraction orders described above, which serve as reference beams for the interferometric measurement, while avoiding light in other diffraction orders for energetic reasons and for suppressing disturbing scattered light shall be.
  • the generated diffraction orders each have a propagation component in the -y direction, in the + y direction, in the -x direction and in the + x direction.
  • a binary height profile is formed in the substrate 24 from square surfaces 25, 26 with two height levels, which are arranged like a checkerboard are, as can be seen in the top view of FIG. 4B.
  • the optically effective height difference between the upper surfaces 25 shown dark in FIG. 4B and the lower surfaces 26 shown light in FIG. 4B is preferably ⁇ / 4 of the wavelength of the laser light source 2 used.
  • the orientation of the square surfaces 25, 26 is 45 ° to the x-axis or to the y-axis and the size of the surfaces is determined by the desired deflection angle of the diffraction orders.
  • Such a grating structure generates four equally strong diffraction orders with an angle of approximately 6.9 ° to the reflection Direction of direct reflection (0th diffraction order).
  • the diffraction order with the propagation component in the + x direction is no longer used.
  • the reference beams of the diffraction orders in the - y direction and in the - y direction on the one hand and in the - x direction and in the + x direction on the other hand generate the same measurement signals in the detector arrangements 9, so that a diffraction order of such a pair of reference beams can basically be dispensed with. If both reference beams, such as the diffraction orders in the - y direction and in the + y direction, are evaluated, the measurement accuracy can be further increased by averaging the two measurement signals thus obtained.
  • the molding process available is the molding of an original structure using so-called injection molding or roller embossing.
  • the original structure required for this can be produced, for example, by means of electroplating from a lithographically realized surface profile or by means of precision milling of a metal stamp.
  • the surface profile 25, 26 is coated with a partially reflective layer 27, which has a reflectivity of approximately 10%.
  • a thin metal layer for example made of gold or silicon, can be applied to produce the partially reflecting layer 27.
  • a metal layer is part of the transmitted
  • the partially reflective layer 27 is preferably realized with a dielectric interference layer.
  • the surface profile with the partially reflecting layer 27 is then leveled with a material 28 which has the same refractive index as the substrate 24. In this way, the transmitted part of the light does not experience a grating effect through the diffraction grating 4.
  • the layer structure 21 In addition to generating the reference rays by reflection at the diffraction grating 4, the layer structure 21 also has the task of circularly polarizing the light scattered back from the surface, in order later to enable directional detection of the movement of the surface.
  • the layer structure 21 has a circular polarizer adjacent to the diffraction grating 4.
  • the circular polarizer consists of a ⁇ / 4 phase retardation layer 5 and a linear polarizer layer 6.
  • the preferred axes of both layers 5, 6 are rotated by 45 ° to one another.
  • the orientation of the circular polarizer to the polarization axis of the transmitted light is, however, as long as the ⁇ / 4 phase delay layer 5 is matched to the wavelength ⁇ of the laser light source 2.
  • the total thickness of the circular polarizer 5, 6 is approximately 0.5-1.0 mm.
  • the portion t of the collimated light beam c transmitted through the diffraction grating 4 passes through the ⁇ / 4 plate 5 and the linear polaristor 6 before it strikes the moving surface 7 after a further approximately 1.5 mm.
  • the light is diffusely scattered back from this surface 7.
  • a portion of the backscattered light s first passes through the linear polarizer 6, which again establishes a linear polarization state, provided that the scattering takes place under non-polarization-maintaining conditions, and then again through the ⁇ / 4 plate 5, the optical axis of which is 45 ° against the transmission direction of the linear polarizer 6 is rotated.
  • the linearly polarized light is converted into circularly polarized scattered light s, which then passes through the partially reflecting diffraction grating 4 without diffraction effects and interferes with the light r reflected at the diffraction grating 4.
  • Phase delay and linear polarizer films based on mechanically stretched organic polymers are preferably used as materials for the circular polarizer 5, 6.
  • cholesteric polymer layers or polar cor layers can also be used.
  • a coating 29 made of a transparent, mechanically insensitive material is provided on the side facing the surface 7.
  • the focusing lenses 10 are arranged directly next to the collimation lens 3 and are preferably designed as spherical off-axis plano-convex lenses.
  • the aperture centers of these focusing lenses 10 are shifted along the x-axis or the y-axis with respect to the collimation lens 3 such that the reference rays r and the scattered light s running parallel to them collide completely with these lenses.
  • a preferred arrival The order of the three focusing lenses 10 is given in the following table:
  • the flat surface of the focusing lenses 10 facing the light source 2 is at a distance of approximately 3 mm from the x-y plane in which the light source 2 lies.
  • a beam splitter grating 11 On the plane side of the focusing lenses 10, which faces the detectors 12, 13, a beam splitter grating 11 is attached, which causes the focal points of the focusing lenses to be split into two foci, which correspond to the respective pair of detectors 12, 13.
  • the beam splitter grating 11 can be designed, for example, as a binary height profile with a profile depth of preferably ⁇ / (2 (nl)), where ⁇ is the wavelength of those used Light source 2 and n is the refractive index of the lattice material.
  • ⁇ is the wavelength of those used Light source 2
  • n is the refractive index of the lattice material.
  • a linear, binary grid is used in which the grid lines run in the y direction.
  • the split light beams are additionally provided with a phase difference, as described above.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Optical Transform (AREA)

Abstract

On mesure des mouvements de translation entre un dispositif de mesure (1) et une surface (7) en dirigeant le faisceau lumineux cohérent (c), ayant une composante de propagation principale, d'une source lumineuse (2) dans la direction z sur la surface (7) qui se déplace par rapport au dispositif de mesure dans le plan x-y et en plaçant en face de la surface un réseau de diffraction (4) partiellement réfléchissant. Ce réseau de diffraction est conçu de telle manière que la lumière réfléchie par lui a plusieurs ordres de diffraction (r-y, r+y, r-x), des composantes de propagation dans la direction y, la direction +y, la direction -x et la direction +x de même intensité et qu'il laisse passer une autre partie du faisceau lumineux cohérent (t) qui est dispersée sur la surface (7) et se superpose à la lumière réfléchie sur le réseau de diffraction. La lumière dispersée sur la surface étant également à polarisation circulaire. Plusieurs dispositifs détecteurs (9-y, 9+y, 9-x) reçoivent la lumière qui est réfléchie par le réseau de diffraction et qui se superpose à la lumière (s) dispersée sur la surface. Les dispositifs détecteurs ont respectivement un séparateur de faisceaux (11) et deux détecteurs (12, 13) pour détecter un premier ou un deuxième signal de mesure. Un dispositif (14, 15) de production d'une différence de phase entre le premier et le deuxième signal de mesure est placé entre les séparateurs de faisceaux (11) et les détecteurs (12, 13). Finalement, le premier et le deuxième signal de mesure sont cédés à un circuit d'évaluation pour déterminer le sens de déplacement dans la direction y et la direction x à partir du signe de la différence de phase entre le premier et le deuxième signal de mesure et l'importance de déplacement dans la direction y et la direction x à partir de la fréquence de l'amplitude de variation du premier et du deuxième signal de mesure.
PCT/DE2002/002982 2001-08-14 2002-08-14 Procede et dispositif de mesure de mouvements de translation entre une surface et un dispositif de mesure WO2003021237A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2002328784A AU2002328784A1 (en) 2001-08-14 2002-08-14 Method and device for measuring translational movements between a surface and a measuring device
EP02764547A EP1417459A2 (fr) 2001-08-14 2002-08-14 Procede et dispositif de mesure de mouvements de translation entre une surface et un dispositif de mesure

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2001139796 DE10139796A1 (de) 2001-08-14 2001-08-14 Verfahren und Vorrichtung zum Messen von Translationsbewegungen zwischen einer Oberfläche und einer Messvorrichtung
DE10139796.8 2001-08-14

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WO2003021237A2 true WO2003021237A2 (fr) 2003-03-13
WO2003021237A3 WO2003021237A3 (fr) 2003-09-04

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AU (1) AU2002328784A1 (fr)
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DE10351560A1 (de) * 2003-11-03 2005-06-02 Metronic Ag Impulsgeber
DE102004047679B4 (de) * 2004-09-30 2017-05-04 Osram Opto Semiconductors Gmbh Optisches Sensormodul
JP4607080B2 (ja) 2005-09-27 2011-01-05 オムロン株式会社 プログラマブル・コントローラ・システム
DE202006005978U1 (de) * 2006-03-10 2007-07-19 Pepperl + Fuchs Gmbh Optoelektronischer Sensor
DE102006030810B4 (de) * 2006-06-30 2010-06-10 Siemens Ag Anordnung zur Erfassung der Bewegung von flachen Sendungen

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0481356A2 (fr) * 1990-10-18 1992-04-22 Dr. Johannes Heidenhain GmbH Système optique utilisant polarisation
WO1999046603A1 (fr) * 1998-03-09 1999-09-16 Otm Technologies, Ltd. Mesure de translation optique

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0481356A2 (fr) * 1990-10-18 1992-04-22 Dr. Johannes Heidenhain GmbH Système optique utilisant polarisation
WO1999046603A1 (fr) * 1998-03-09 1999-09-16 Otm Technologies, Ltd. Mesure de translation optique

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WO2003021237A3 (fr) 2003-09-04
AU2002328784A1 (en) 2003-03-18
EP1417459A2 (fr) 2004-05-12
DE10139796A1 (de) 2003-03-13

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