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WO1992003698A1 - Dispositif servant a detecter la position de faisceaux laser - Google Patents

Dispositif servant a detecter la position de faisceaux laser Download PDF

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Publication number
WO1992003698A1
WO1992003698A1 PCT/DE1991/000654 DE9100654W WO9203698A1 WO 1992003698 A1 WO1992003698 A1 WO 1992003698A1 DE 9100654 W DE9100654 W DE 9100654W WO 9203698 A1 WO9203698 A1 WO 9203698A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser
reference beam
mirror system
sensitive
measuring
Prior art date
Application number
PCT/DE1991/000654
Other languages
German (de)
English (en)
Inventor
Jürgen THIEL
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.
Publication of WO1992003698A1 publication Critical patent/WO1992003698A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
    • G01B11/306—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces for measuring evenness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
    • G01B5/0018—Measuring arrangements characterised by the use of mechanical techniques for measuring key-ways

Definitions

  • the invention relates to a device for detecting the beam position of laser beams, for example for straightness measurements with a laser, in which the laser beam impinges on a position-sensitive sensor, the output signal of which is applied to an evaluation unit that determines positional deviations with respect to the laser beam
  • the aim is to detect fluctuations in the beam position of the laser source in order to eliminate errors that arise due to beam position fluctuations.
  • Devices for straightness measurement which are also referred to as straightness measuring systems, are used, for example, in production measurement technology, where they are used to check the straightness of guides, traversing slides, movements of machine slides, robot movements etc. or for alignment measurements.
  • a known device for straightness measurement is the laser straightness meter from Vialog, Hanover.
  • the laser beam from a HeNe laser is used as a straightness reference, that is to say as an "optical ruler", and the offset to this beam is measured with the aid of a position-sensitive photodiode.
  • the photodiode is shifted in the laser beam direction and the point of impact of the beam on the photodiode is measured in one or two dimensions.
  • the outlay on equipment is great in order to reduce the deviations of the laser beam from the “straight line” below a value of a few micrometers / meters (um / m) hold.
  • the known device for straightness measurement is therefore comparatively complex and therefore expensive to manufacture.
  • a device for detecting the beam position is also known, for example, from the dissertation by E. Trapet "A contribution to reducing the measurement uncertainty of laser-based alignment measuring systems". Trapet describes in connection with possibilities of a beam position correction, among other things, a device for straightness measurement, in which the laser beam emanating from a position-stabilized laser head and aligned parallel to the direction of movement is first passed through a fixed beam splitter arranged at the beginning of the measuring section, to which a first reference detector is assigned. The beam entering the measuring section hits another beam splitter on the movable machine part, to which the measuring detector for the straightness measurement is assigned. The beam part running straight through the beam control of the movable machine part strikes a third detector at the end of the measuring section, namely the second reference detector.
  • a device for beam detection is known from the patent publication DE 34 00 151.
  • a device is described in which a partially transparent triple reflector is used on parts of the beam splitter on the movable machine part, with which the beam is positioned on the one hand at a position at the beginning of the measuring section Reference detector is reflected back, on the other hand runs through the partially transparent triple reflector and strikes a second reference detector attached to the end of the measuring section.
  • This arrangement has the advantage over the Trapet solution that pitching, yawing and rolling movements leave the measurement result unaffected by the use of the triple reflector, and in addition straightness deviations are displayed with a double parallel offset.
  • the invention is based on the object of specifying a device for beam position control, for measuring tasks which use a laser beam as a reference line, which detects beam position fluctuations of a laser beam and which are largely independent of disruptive influences caused by air turbulence and refractive index gradients
  • a device for beam position control for measuring tasks which use a laser beam as a reference line, which detects beam position fluctuations of a laser beam and which are largely independent of disruptive influences caused by air turbulence and refractive index gradients
  • the laser beam is split into two partial beams by a beam splitter, namely the actual useful laser beam and a reference beam.
  • two position-sensitive sensors which can be position-sensitive diodes, for example, measure the point at which the beam strikes at two different distances from the laser, so that beam position fluctuations are recognized and their size and direction determined can.
  • the reference branch should be as long as possible in order to obtain the largest possible correction signal. It is particularly preferred if the length of the reference beam path is in the order of the length of the useful beam path, which can be, for example, several meters. For this reason, the beam path is folded several times and shielded from external influences, so that changes in the point at which the laser beam strikes the position-sensitive sensors, which are not caused by beam position fluctuations, are small compared to the changes caused by beam position fluctuations.
  • the object of the invention can be achieved in that a beam splitter is arranged in the beam path of the laser beam, which splits the laser beam into the actual useful laser beam and a reference beam, and that another beam in the beam path of the reference beam or the useful beam
  • a beam splitter is provided with an associated first reference detector, which detects the beam position at the beginning of the reference path, and which has a mirror system in the beam path of the reference beam that folds the reference beam several times and a second position-sensitive sensor is provided after the mirror system, which the reference beam strikes; From the output signals of both position-sensitive sensors, the evaluation unit determines changes in position of the laser beam in space, with the knowledge of which the beam position in the useful branch can be corrected.
  • each laser beam is subject to parallel shifts on the one hand and changes in direction on the other hand, the latter being in the range of typically 10 ⁇ rad.
  • the position of the laser beam at a distance of one meter in a plane perpendicular to the beam direction can already fluctuate by ⁇ 10 ⁇ m relative to the ideal reference.
  • Beam position fluctuations taking into account the distance between laser and position-sensitive sensor in the useful branch, the position of the laser beam in the room can be corrected by calculation.
  • the design according to the invention makes it possible to keep the (corrected) beam position fluctuation of the laser in the order of magnitude of 1 ⁇ m / m even with commercially available lasers and even with semiconductor lasers.
  • an arrangement according to claim 1 has the disadvantage that beam position correction is only sensibly possible if the stability of the reference path is guaranteed, in particular the stability of the mirror path with respect to tilting of the mirrors with respect to one another.
  • a further optical element is provided in the reference beam path, which The reference beam is split into two beams, with the original reference beam remaining unchanged in its direction, for example, and the second reference beam striking the mirror system at an angle different from the original reference beam, and a third position-sensitive reference detector is provided after the mirror system, the output signal of which is used to tilt the Mirror to each other.
  • the mirror system is largely independent of mechanical or thermal influences.
  • a further embodiment, in which the mirror system is attached to a base part, which can also carry the laser, and which consists of a material with a small coefficient of thermal expansion - for example Zerodur, Invar or a fiber composite material - has the advantage that changes in the impact of the Laser beam on the position sensitive sensor that is not from
  • the modulation of the laser light significantly reduces interference from light, particularly when working with light in the visible range, which can also be emitted by semiconductor lasers, for example.
  • the mirror system can have two mirrors, each of which the reference beam strikes several times.
  • This design not only provides a simple structure, but also a structure that is largely free of interferences, such as those caused by thermal expansion, shocks, etc.
  • the laser / position-sensitive sensor distance in addition to the (known) laser / position-sensitive reference sensor distances, it is also necessary to know the laser / position-sensitive sensor distance in the measuring branch, which is generally variable. Therefore, in a further development, a distance measuring system is provided, which measures the distance between the laser and the position-sensitive (measuring) sensor, and whose output signal is applied to the evaluation unit, which determines the beam position fluctuations occurring at the respective location of the position-sensitive sensor.
  • This distance measuring system can in particular be an ultrasonic measuring system in which the ultrasonic transmitter is connected to the base part, for example, and the ultrasonic receiver is connected to the position-sensitive (measuring) sensor.
  • Fig. 1 shows the structure of a device for detecting the
  • Fig. 2 is a block diagram of an evaluation unit. Description of an embodiment
  • FIG. 1 shows the structure of a device according to the invention for detecting the beam position of laser beams, in which the laser beam is split into a reference beam R and a measuring beam M with the aid of a beam splitter BS1.
  • the reference beam R is with the help of a
  • Beam splitter BS2 split into the reference beams R1 and R2.
  • the reference beam R1 strikes a position- sensitive photodiode PSD Ref1 .
  • the reference beam R2 (dashed) is folded several times by two mirrors S1 and S2 and strikes a position- sensitive photodiode PSD Ref2 , which, like PSD Ref1, registers the deviation of the beam beam from the central position, so that beam position fluctuations of the laser beam in the reference beam branch can be detected.
  • the virtual position of the two reference photodiodes is shown in dashed lines in FIG.
  • the penetration points of the laser beam on these fixed reference detectors define the position of the straight lines spanned by the laser beam in space and can be described by the following formula, where x p , y p for the
  • the measuring beam M strikes a measuring photodiode PSD measuring which on the one hand registers the straightness deviation to be measured and on the other hand also the beam position fluctuations.
  • a measuring photodiode PSD measuring which on the one hand registers the straightness deviation to be measured and on the other hand also the beam position fluctuations.
  • y o ⁇ y 2 ⁇ z M -z 1 ) + y 1 (z 2 -z M ) ⁇ / (z 2 -z 1 )
  • the distance of the measuring detector from this zero point must also be known, since a change in direction of the beam has a greater effect at a greater distance than at a smaller one.
  • the reference branch R with the mirrors S1 and S2 is housed in a stable, closed housing G, which preferably a mounting plate made of a material with a low coefficient of thermal expansion, such as. B. Zerodur, Invar or fiber composite material.
  • the reference beam R2 can be used, for example, with the aid of a beam splitter BS3 (Fig. 1) are divided such that the original reference beam R2 remains unchanged in its direction (dashed beam) and the other beam is reflected perpendicular to the plane of the drawing and deflected with a prism or mirror so that it is at a different angle to R2 strikes the mirror system (solid beam) so that fewer reflections take place.
  • the planes of both beams are (not necessary) preferably parallel.
  • This beam strikes a third position- sensitive reference detector PSD Ref3 , which registers the point of impact of the beam.
  • the ultrasound signal and the signals of the reference diodes and the measuring diode are simultaneously recorded, amplified and, after A / D conversion by an A / D converter, processed digitally by means of a computer, which can be, for example, a commercially available microcomputer.
  • the computer determines the correction value, determines the straightness deviation in the usual way and creates a measurement report etc.
  • the invention has the advantage, on the one hand, that with the correction of the beam position of the laser described above, it is possible to advance into the accuracy class of 1 ⁇ m, while known devices working with lasers have beam direction deviations of 10 ⁇ rad, ie 10 ⁇ m / m. Beam position fluctuations are thereby corrected, so that the accuracy of the measuring system only depends on the accuracy of the position-sensitive photodiode or the electronic circuit and additionally is independent of the measuring distance.
  • the device according to the invention is significantly cheaper, more compact and more robust than current measuring systems.

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

Abstract

Il est décrit un dispositif pour la détection de la position de faisceaux laser, par exemple pour la mesure de la rectitude au moyen d'un laser dont le faisceau atteint un détecteur de position dont le signal de sortie est appliqué à une unité d'analyse déterminant les déviations de la position par rapport au faisceau laser. La présente invention est caractérisée par le fait que dans la trajectoire du faisceau laser est disposé un séparateur de faisceau (RS1) lequel sépare le faisceau laser en un faisceau laser de mesure (M) proprement dit et en un faisceau de référence (R), que, dans la trajectoire du faisceau de référence, un système à miroirs (S1, S2) réfléchit plusieurs fois le faisceau de référence et qu'après le système à miroirs est prévu un second détecteur de position (PSD) atteint par le faisceau de référence et dont le signal de sortie permet à l'unité d'analyse de déterminer les changements de direction du faisceau laser dans l'espace, grâce à la connaissance desquelles la position du faisceau est corrigée dans la branche utile.
PCT/DE1991/000654 1990-08-15 1991-08-15 Dispositif servant a detecter la position de faisceaux laser WO1992003698A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DEP4026164.6 1990-08-15
DE4026164 1990-08-15

Publications (1)

Publication Number Publication Date
WO1992003698A1 true WO1992003698A1 (fr) 1992-03-05

Family

ID=6412469

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE1991/000654 WO1992003698A1 (fr) 1990-08-15 1991-08-15 Dispositif servant a detecter la position de faisceaux laser

Country Status (3)

Country Link
AU (1) AU8322791A (fr)
DE (1) DE4126948C2 (fr)
WO (1) WO1992003698A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4341227A1 (de) * 1993-12-03 1995-06-08 Gernot Baur Optisch-analytisches Detektionssystem zur Einfallswinkelbestimmung eines Lichtstrahls
DE19827786C2 (de) * 1998-06-23 2000-11-02 Gernot Baur Optisch-analtytisches Detektionssystem zur Richtungs- und Lagebestimmung eines Lichtstrahles

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19614183C2 (de) * 1996-04-11 2000-08-31 Ulrich Wimmer Verfahren zur Schwerkraftwellendetektion

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3942894A (en) * 1974-11-20 1976-03-09 The United States Of America As Represented By The Secretary Of The Air Force Self referencing retransmitting alignment sensor for a collimated light beam
DD220393A1 (de) * 1983-08-30 1985-03-27 Zeiss Jena Veb Carl Vorrichtung fuer gleichzeitige fluchtungs- und richtungsmessung mit optischem ausgang
US4627725A (en) * 1983-04-18 1986-12-09 Pioneer Electronic Corporation Optical axis monitoring system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH676289A5 (fr) * 1987-03-24 1990-12-28 Wild Leitz Ag
DE3814466A1 (de) * 1988-04-28 1989-11-09 Busch Dieter & Co Prueftech Verfahren und vorrichtung zum feststellen der relativen lage einer bezugsachse eines objekts bezueglich eines referenzstrahls, insbesondere eines laserstrahls

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3942894A (en) * 1974-11-20 1976-03-09 The United States Of America As Represented By The Secretary Of The Air Force Self referencing retransmitting alignment sensor for a collimated light beam
US4627725A (en) * 1983-04-18 1986-12-09 Pioneer Electronic Corporation Optical axis monitoring system
DD220393A1 (de) * 1983-08-30 1985-03-27 Zeiss Jena Veb Carl Vorrichtung fuer gleichzeitige fluchtungs- und richtungsmessung mit optischem ausgang

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4341227A1 (de) * 1993-12-03 1995-06-08 Gernot Baur Optisch-analytisches Detektionssystem zur Einfallswinkelbestimmung eines Lichtstrahls
DE19827786C2 (de) * 1998-06-23 2000-11-02 Gernot Baur Optisch-analtytisches Detektionssystem zur Richtungs- und Lagebestimmung eines Lichtstrahles

Also Published As

Publication number Publication date
DE4126948C2 (de) 1996-03-07
DE4126948A1 (de) 1992-02-20
AU8322791A (en) 1992-03-17

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