WO2010094474A1

WO2010094474A1 - Device and method for distance measurement

Info

Publication number: WO2010094474A1
Application number: PCT/EP2010/001005
Authority: WO
Inventors: Cristina Alvarez Diez; Bernd Spruck
Original assignee: Carl Zeiss Ag
Priority date: 2009-02-23
Filing date: 2010-02-18
Publication date: 2010-08-26
Also published as: DE102009010159B4; DE102009010159A1

Abstract

A device for the distance measurement of an object (2) is designed to emit a measurement light beam (11) along a beam path (13) in the direction of the object (2). The device (1) comprises a reflector (4), which is designed to receive the measurement light beam reflected from the object (2) and to direct said light beam in the direction of the object (2), so that the measurement light beam propagates from the device (1) to the object (2) several times, thus increasing the path length travelled by the measurement light beam (11). In order to determine the distance, the path length travelled by the measurement light beam is recorded.

Description

Device and method for distance measurement

The invention relates to a device and a method for distance measurement. In particular, the invention relates to a device and a method for distance measurement using optical methods.

The measurement of distances has numerous applications, for example, in industrial manufacturing or quality control in industrial manufacturing, must be determined in the dimensions of manufacturing products. Numerous measuring devices, such as micrometers or slides, are available for measuring small distances. However, in many such measuring devices, the maximum measurable length range is coupled to the resolution such that length measurements with high accuracy are possible at small lengths, for example using a micrometer However, such mechanical measuring means are often not designed for the measurement of lengths in the range of a few meters. Conventional U-turn flow meters and laser rangefinders are suitable for measuring larger distances, but have a length resolution that often does not fall below the millimeter range in the case of inexpensive devices. The scope of conventional laser rangefinders is also limited by the fact that many devices are not designed to measure very short distances in the range of a few centimeters or a few meters.

Especially in industrial applications, such as in mechanical engineering, however, an accurate measurement of parts with dimensions in the range of a few centimeters to a few meters with high resolution is often required. However, the devices typically used for these purposes, such as those based on tactile sensing, often have large dimensions and are permanently installed so that they can not be used flexibly at different locations.

DE 41 32 113 A1 describes a sensor for changes in length or distance, in which a light beam in an elastic light guide is repeatedly guided back and forth between two groups of mirrors. Although the strain gauge of DE 41 32 113 A1 allows the determination of changes in length, but must be attached to the object on which the change in length is to be determined. Since the light beam is guided in the elastic substrate, the strain gauge is designed to determine the change in length on objects in which the relevant distances do not exceed the size of the strain gauge.

The invention has for its object to provide an apparatus and a method for optical distance measurement, can be determined with the or with the distances with high accuracy. In particular, the invention has for its object to provide such a device and such a method that uses the transportable devices that can be used at different locations.

According to the invention the object is achieved by a device and a method as indicated in the independent claims. The dependent claims define advantageous or preferred embodiments.

According to one aspect of the invention, an apparatus for optical distance measurement of an object, which is set up to radiate a measuring light beam along a beam path in the direction of the object, comprises a reflector. The reflector is set up in such a way that, during operation of the device, it receives a measuring light beam reflected by the object and redirects it toward the object along a further radiation path offset to the beam path.

In this device, the measuring light beam is guided along a beam path, on which it is directed several times on staggered beam paths to the object. By using the reflector, the beam path is folded so that the measuring light beam covers the distance between the measuring device and the object more than twice. For a given resolution of a laser rangefinder, extending the path length to be traveled by the measurement light beam allows an increase in the accuracy of the distance measurement.

The reflector may be arranged to direct the measuring light beam reflected at the object into the further beam path, wherein the further beam path is substantially parallel and offset from the measuring light beam reflected at the object. The further beam path is also advantageous parallel to the beam path. If the measurement light beam successively has several parallel beam paths gene passes through between the device and the object, the distance of the object can be determined in a simple manner from the path length traveled by the measuring light beam. This guidance of the measuring light beam furthermore makes it possible to use an arrangement of reflectors on the measuring device, which can be selected independently of the distance between the measuring device and the object.

The device may comprise at least one further reflector which is set up to receive a measurement light beam reflected again on the object and to direct it in the direction of the object. By using a plurality of reflectors, which redirect the measuring light beam in the direction of the object, the distance covered by the measuring light beam is further increased for a given distance between the object and the measuring device. This embodiment of the beam path allows an increase in the accuracy with which the distance can be determined.

The reflector and another reflector can be set up such that the measuring light beam directed by the further reflector in the direction of the object lies outside a plane which is defined by the beam path and the further beam path. The plurality of reflectors of the device may be arranged so that the different beam paths on which the measuring light beam passes between the device and the object do not lie in a single plane. For example, the reflector and the at least one further reflector can be set up such that the measuring light beam is guided back and forth between the device and the object on a mantle surface of a virtual three-dimensional body. This allows the reflector and the other reflectors of the device to be positioned in a two-dimensional array to accommodate a large number of reflectors in an area of predetermined dimensions.

One of the further reflectors can be designed as a retroreflector in order to further increase the path length to be covered by the measurement light beam by the retroreflection of the measurement light beam in itself.

In use of the device, at least one object reflector is provided on the object in order to receive the measuring beam of light emitted by the device along the beam path and to direct it to the reflector. The object reflector may be configured to offset the measurement light beam emitted by the device and to direct it to the reflector in a direction substantially parallel to the beam path. in the Using the device, a plurality of object reflectors can be provided on the object, the arrangement of which can be selected depending on the arrangement of reflectors of the device so that the measuring light beam reciprocates on a plurality of mutually parallel and offset beam paths between the measuring device and the object.

The reflector or the plurality of reflectors of the device can be attached to a carrier. An actuator may be provided to adjust the carrier. With the actuator, an orientation of the carrier can be controlled, for example, to set a parallel orientation of the carrier to a surface of the object on which the object reflectors are provided.

The device may include a sensor for detecting the orientation of the carrier, which may be coupled to the actuator. A part of the measuring light beam can be directed to the sensor. This makes it possible to use the measurement light beam both for distance measurement and to control the orientation of the carrier.

The measuring light beam may have light components of two different wavelengths, one of which is directed to the sensor coupled to the actuator to be used to control the alignment. The other of the light components can be fed to another detector for distance measurement.

To regulate the orientation of the carrier, a separate light source can also be provided which transmits a light beam independent of the measuring light beam from the device to the object in order to determine an instantaneous orientation of the carrier.

The sensor may include a four-quadrant sensor. Output signals of the four-quadrant sensor make it possible to control tilting of the carrier along two independent tilt axes.

The deflection of the measuring light beam in such a way that it is guided back and forth repeatedly between the measuring device and the object on mutually offset beam paths can be used in combination with conventional laser range finders, which measure distance, for example based on transit time measurements or interferometric methods. By extension the path length traveled by the measuring light beam can increase the accuracy of the distance determination and reduce a minimum measurable distance.

The device may also include a light source for generating the measurement light beam, which in operation generates a sequence of light pulses at a repetition rate. The light source may be a short pulse laser that generates an optical frequency comb. The use of a sequence of light pulses in the measuring light beam allows a determination of the path length traveled by the measuring light beam on the basis of phase positions of the sequence of light pulses. The device may comprise an evaluation device for detecting the sequence of light pulses and for determining the path length covered by the measurement light beam, which determines a phase shift of a signal component of the detected sequence of light pulses for determining the path length, the signal component having a frequency that is a multiple corresponds to the repetition rate. By using a harmonic of the detected signal, the path length traveled by the measuring light beam can be determined with high accuracy.

The evaluation device can be set up to generate a further signal for determining the phase difference, which essentially has the phase shift of the signal component and a lower frequency than the signal component. For this purpose, the signal component can be fed to a frequency mixer whose output signal is band-pass filtered. The generation of the further signal with the lower frequency facilitates the measurement of the phase difference.

The device according to the various embodiments can be used in various applications. For example, it may be integrated with a caliper to determine a position or a distance of a movable element of the caliper. In this case, reflectors of the measuring device may be provided on the leg of the caliper fixed relative to a guide, while corresponding object reflectors may be attached to the movable leg of the caliper.

According to a further aspect of the invention is in a method for optical

Distance measurement of an object, a measuring light beam directed such that it is repeatedly fed back and forth between the object and a measuring device, so that it is the distance from the measuring device to the object and the distance from the object runs through to the measuring device several times. Based on the distance traveled by the measuring light beam, the distance of the object is determined.

Since the measuring light beam passes through the distance from the measuring device to the object and the distance from the object to the measuring device several times, the path length covered by the measuring light beam is lengthened. For a given resolution of a laser rangefinder, extending the path length traveled by the measuring light beam allows an increase in the accuracy of the distance measurement.

The measuring light beam can successively pass through a plurality of mutually parallel first beam paths from the measuring device to the object and mutually parallel second beam paths from the object to the measuring device. In this case, the first beam paths and the second beam paths can be parallel to one another. The first beam paths and the second beam paths may be offset from each other. The parallelism of the beam paths makes it possible to easily determine the distance of the object from the path length traveled by the measuring light beam.

At least one first ray path of the plurality of first ray paths may be arranged to extend outside the plane defined by another first ray path of the plurality of first ray paths and a second ray path of the plurality of second ray paths. The first beam paths and the second beam paths can in particular run on a mantle surface of a virtual three-dimensional body. If the beam paths are not within one plane, the reflectors required for deflecting the measurement light beam can be provided in a surface area on the measuring device or on the object which has smaller length dimensions than when arranged along a line.

The measuring light beam may be retroreflected so as to pass through the plurality of first beam paths twice and the plurality of second beam paths twice. In this way, the path length covered by the measuring light beam can be further increased.

In order to direct the measuring light beam so that it is guided back and forth several times between the measuring device and the object, at least one measuring device can be used. Direction provided reflector and attached to the object object reflector can be used. An orientation of the reflector of the measuring device relative to the object reflector may be actively adjusted so that the plurality of first beam paths are parallel to the plurality of second beam paths.

In order to control the orientation of the reflector, a position of the measurement light beam which is guided back and forth repeatedly between the measuring device and the object can be detected. The measurement light beam can thus be used both for determining the distance and for controlling the orientation of the reflector.

In the method, a conventional laser rangefinder can be used to generate the measurement light beam and to determine the path length traveled by the measurement light beam.

However, the measurement light beam can also comprise a sequence of light pulses which are generated at a repetition rate, for example an optical frequency comb generated by a short-pulse laser. In order to determine the path length traveled by the measuring light beam, a light intensity of the measuring light beam can be detected after the measuring light beam has been repeatedly guided back and forth between the object and the measuring device. The path length may be determined based on a phase shift of a signal component of the measurement light beam having a frequency that is a multiple of the repetition rate. By using a harmonic of the detected sequence of light pulses, the traveled path length can be determined with high accuracy.

The signal component may be applied to a frequency mixer, the output of which is filtered to produce a further signal having substantially the phase shift of the signal component and a lower frequency than the signal component.

The method according to the various embodiments can be carried out with a device according to an embodiment.

The devices and methods according to various embodiments of the invention can be used generally for distance measurement. exemplary

Areas of application include distance or length measurement in the production or quality control of machine parts or in other industrial processes. sen. However, the embodiments of the invention are not limited to these applications.

The invention will be explained in more detail by means of exemplary embodiments with reference to the attached drawings.

Fig. 1 is a schematic representation of a device according to an embodiment, wherein in Fig. 1A and 1B different object distances are shown.

Fig. 2 is a schematic representation of a device according to another embodiment.

Fig. 3 is a schematic perspective view of a device according to another embodiment.

FIGS. 4 and 5 illustrate beam paths of a measuring light beam.

Fig. 6 is a schematic perspective view of an apparatus according to an embodiment having an actuator for adjusting a reflector.

Fig. 7 is a schematic perspective view of a device according to another embodiment having an actuator for adjusting a reflector.

Fig. 8 is a schematic representation of a device according to another embodiment having an actuator for adjusting a reflector.

9A shows, by way of example, a sequence of light pulses as a function of time, and FIG. 9B schematically shows a Fourier spectrum of the sequence of light pulses of FIG. 9A.

FIG. 10 is a schematic representation of a light source and a detector that may be used in the devices of various embodiments. FIG.

11 is a schematic block diagram of an evaluation device that may be used with the devices according to various embodiments. Fig. 12A shows exemplary input signals of the evaluation device of Fig. 11, and Fig. 12B shows a signal component of the input signals.

Hereinafter, embodiments of the invention are explained in detail. The features of the various embodiments may be combined with each other unless expressly excluded in the following description. Although individual embodiments are described with respect to specific applications, for example in the context of an industrial plant, the present invention is not limited to these applications.

FIG. 1 is a schematic representation of a distance measuring device 1, FIGS. 1A and 1B showing the device at different distances of an object 2.

The device 1 comprises a light source and detector device 3, a reflector 4 and a retroreflector 5. The light source and detector device 3 may, for example, be a conventional laser range finder which determines the path length traveled by a measuring light beam. To determine the path length, for example, a transit time measurement, an interferometric method or the determination of a phase position of a pulsed signal can be used.

The light source and detector device 3 is set up so that it emits a measuring light beam 11 along a beam path 13 in the direction of the object 2 whose distance is to be determined. The reflector 4 is set up in such a way that it receives the measuring light beam reflected by the object 2 and deflects it in such a way that the measuring light beam is redirected to the object 2 along a beam path 14 offset and parallel to the beam path 13. The retroreflector 5 is arranged to receive the measuring light beam reflected on the object 2 and to reflect in itself.

On the object 2, a plurality of reflectors 6, 7 are provided, each of which is adapted to receive the measuring light beam directed by the measuring device 1 in the direction of the object 2 and offset and parallel to the received measuring light beam back towards the measuring device 1. For reasons of clarity, the reflectors 6, 7 attached to the object are referred to below as object reflectors. During operation of the measuring device 1, the measuring light beam 11 is radiated by the light source and detector device 3 of the measuring device 1 along the beam path 13 in the direction of the object 2. The object reflector 6 receives the measuring light beam 11 and deflects it in such a way that it is directed to the reflector 4 along a ray path 16 that is parallel and offset from the ray path 13. The reflector 4 of the measuring device receives and deflects the measuring light beam 11 in such a way that it is directed to the object reflector 7 along the beam path 14 that is parallel and offset from the beam paths 13 and 16. The object reflector 7 receives the measuring light beam 11 and deflects it in such a way that it is directed to the retroreflector 5 along a beam path 17 that runs parallel and offset from the beam paths 13, 16 and 14. The retroreflector 5 reflects the measuring light beam in itself, so that the measuring light beam passes through the beam paths 17, 14, 16 and 13 in the reverse direction back to the light source and detector device 3.

In the measuring device 1, the reflectors 4, 5 of the measuring device and the object reflectors 6, 7 attached to the object fold the beam path of the measuring light beam, so that the measuring light beam is repeatedly guided back and forth between the measuring device 1 and the object 2. In the case of the measuring device 1 shown in FIG. 1, the measuring light beam traverses the distance between measuring device and object eight times, so that the path length covered by the measuring light beam is lengthened by a factor of four in comparison to the beam guidance in a conventional laser distance measurement.

The light source and detector device 3 determines the path length traveled by the measuring light beam. Proportions of the path length traveled by the measuring light beam, which result from a beam path transverse to the beam paths 13, 14, 16 and 17, as occurs, for example, at the reflector 4 and the object reflectors 6, 7, or from a beam path within the beam Measuring device 1 are caused by the system geometry and can be assumed to be known. Alternatively, the measuring device 1 can be calibrated in a simple manner by positioning the object 2 at the position xθ in contact with the measuring device 1 in order to determine a path length which is determined only by the system geometry. In this way, the path length which corresponds to the sum of the parallel beam paths 13, 14, 16 and 17 between the measuring device 1 and the object 2 can be determined from the path length covered by the measuring light beam. Thus, can starting from the distance determined by the light source and detector device 3 distance of the object 2 can be determined.

When the object is displaced by a distance d from the position x1 to a position x2, as shown schematically in FIG. 1B, the length of each of the beam paths 13 ^' , 14 ^' , 16 ^' and 17 ^{' changes} between the measuring device 1 and the object 2 by the length d, so that the total traversed by the measuring light beam path length increased by 8-d.

The beam guidance of the measuring light beam in the apparatus of FIG. 1 leads to an increase in the resolution or accuracy with which the distance of the object 2 can be measured, since the resolution of the distance measurement is determined by the resolution with which the light source and detector device 3 determines the optical path length of the measuring light beam, divided by the number of beam paths between the measuring device and the object, which passes through the measuring light beam.

For example, if a conventional laser range finder is used as the light source and detector 3 which can measure a minimum optical path length of 1 m and has a resolution of the path length measurement of ± 20 mm, in a conventional beam guide, a minimum object distance of 50 cm can be measured, and the resolution of the distance measurement is ± 10 mm. If the beam path of the measurement light beam is folded using the apparatus 1, a minimum object distance of 12.5 cm can be measured with the laser rangefinder, and the resolution of the distance measurement is ± 2.5 mm.

As a reflector 4 of the measuring device and as object reflectors 6, 7, for example, mutually tilted mirrors, a triple mirror, a triple prism or the like can be used in the device 1.

The embodiment of the device can be modified in further embodiments. The number of reflectors and object reflectors may be selected depending on the particular field of application of the measuring device and the properties of the light source and detector device 3. For example, more than two reflectors can be provided on the measuring device and the object. In a further embodiment, a retroreflector may be provided on the object to reflect the measuring light beam in itself. In a further embodiment, the measuring light beam is not reflected in itself, but the The light source and the detector can be spatially spaced so provided that the detector detects the measuring light beam. With reference to FIG. 1, for example, instead of the retroreflector 5, a detector may be provided which detects the measuring light beam after it has been repeatedly reciprocated on offset beam paths between the measuring device and the object.

FIG. 2 shows the use of a device for distance measurement according to an exemplary embodiment in a caliper 20. A first measuring jaw 22 is provided fixedly on a guide 21 of the caliper 20, while a movable second measuring jaw 30 is displaceable along the guide 21, as schematically indicated by the arrow 31. On the first measuring jaws 22, the device for distance measurement is provided, which has a light source and detector device 23, a plurality of reflectors 24-26 and a retroreflector 27. On the movable measuring jaws 30 a plurality of object reflectors 33-36 are provided.

For example, the reflectors 24-26 and the object reflectors 33-36 may each comprise a pair of mutually tilted mirrors, a triple mirror, a triple prism, or the like. Each of the reflectors 24-26 is configured to receive a measuring light beam guided by an object reflector 33-36 in the direction of the corresponding reflector and to direct it back in the direction of the movable measuring jaw 30 parallel to the received measuring light beam. Each of the object reflectors 33-36 is set up to receive a measuring light beam guided by the measuring device in the direction of the movable measuring jaw 30 and to guide it back in the direction of the first measuring jaw 22 parallel to the received measuring light beam. The retroreflector 27 is arranged to receive the measurement light beam from the object reflector 36 and to refract it.

During operation of the device, the light source and detector device 3 radiates the measuring light beam along a beam path 37 to the object reflector 33. The object reflector directs the measuring light beam along a beam path 38, which runs parallel and offset to the beam path 37, to the reflector 24. The reflector 24 directs the measuring light beam along a beam path 39, which runs parallel and offset to the beam path 38, to the object reflector 34 The measuring light beam is guided via the object reflector 34, the reflector 25, the object reflector 35, the reflector 26 and the object reflector 36 to the retroreflector 27, where it is irradiated along a ray path. 40 is reflected in itself and on the object reflectors 33-36 and the reflectors 24-26 back to the light source and detector device 23 is guided.

The light source and detector device 23 determines the path length traveled by the measurement light beam, from which the distance of the movable measurement jaw 31 from the fixed measurement jaw 22 can be determined. In the caliper 20, the operation of the device for determining the distance of the movable measuring jaw 31 is identical to the operation of the device described in FIG. 1. Since the measuring light beam is guided back and forth eight times between the two measuring jaws, the spatial resolution and the smallest measurable distance can be correspondingly reduced by a factor of eight compared to a conventional beam guidance in distance measurement.

In the devices described with reference to Figures 1 and 2, the measuring light beam is reciprocated in a plane several times between the measuring device and the object. However, the measurement light beam can also be guided so that the beam paths between object and measuring device are not all in one plane.

3 shows a schematic representation of a device 50 for distance measurement according to a further exemplary embodiment, in which the reflectors and the object reflectors are arranged such that the measuring light beam is guided along a mantle surface of a virtual cuboid.

The device 50 has on a carrier 51 a light source 52 for generating a measuring light beam, reflectors 53-55 and a detector 56 for detecting the measuring light beam. The detectors 53-55 are each arranged to receive a measurement light beam reflected on the object and to redirect it to the object with an offset parallel to the received measurement light beam. For each of the reflectors 53-55, the direction of the respective offset of the measuring light beam is shown schematically in Fig. 3 by the longitudinal axis of the reflector 53-55. The reflectors 53-55 are not collinear, but arranged rotated against each other. As a result, the measurement light beam is reciprocated along a non-planar mantle surface of a three-dimensional body between the device 50 and the object. Object reflectors 62-65 are arranged on an object 61. Each of the object reflectors 62-65 is configured to receive the measuring light beam from the measuring device 50 and to redirect it toward the measuring device 50 with an offset parallel to the received measuring light beam. Depending on the arrangement of the reflectors 53-55, the arrangement of the object reflectors 62-65 is selected such that the measurement light beam alternately passes between the object 50 and the object 61 via one of the object reflectors 62-65 and one of the reflectors 53-55. and is guided and thus guided by the light source 52 to the detector 56. In particular, the object reflectors are arranged so that at least two of the object reflectors are provided rotated relative to each other.

The reflectors 53-55 and the object reflectors 62-65 may be formed as a pair of mutually inclined mirrors, a triple mirror, a triple prism, or the like.

During operation of the device, the measuring light beam is emitted from the light source 52 along the beam path 71 to the object reflector 62. The object reflector 62 directs the measuring light beam along a beam path 72 to the reflector 53. The reflector 53 directs the measuring light beam along a ray path 73 to the object reflector 63. The object reflector 63 is arranged such that it displaces the measuring light beam along the ray path 74 to the reflector 54, which is rotated relative to the reflector 53 by 90 °. Accordingly, the object reflector 63 is arranged such that the beam path 74 lies outside the plane in which the beam paths 71, 72 and 73 lie. The reflector 54 directs the measuring light beam along the beam path 75 to the object reflector 64. The object reflector 64 directs the measuring light beam along the beam path 76 to the reflector 55. The reflector 55 directs the measuring light beam along the beam path 77 to the object reflector 65. The object reflector 65 directs the Measuring light beam along the beam path 78 to the detector 56th

In the arrangement shown in Fig. 3 of reflectors 53-55 and object reflectors 62-65, in which the reflectors are arranged rotated by 90 ° to each other and the object reflectors are rotated by 90 ° from each other, the measuring light beam along a plurality of Beam paths 71-78 repeatedly between the device 50 and the object 61 and led back. The ray paths 71-78 are parallel and staggered but not all in one plane. For example, that of the object reflector 63 is too the beam 53 leading to the reflector 53 and the beam path 75 leading from the reflector 54 to the object reflector 64 not in the plane defined by the beam path 71 and the beam path 72 or the beam path 73.

In such a beam path of the measuring light beam, the reflectors and the object reflectors are not provided in a linear arrangement. This makes it possible to position the reflectors of the measuring device or the object reflectors in a two-dimensional arrangement. For example, the reflectors may be arranged along a peripheral edge of a base surface of a virtual three-dimensional body, and the object reflectors may be arranged along a peripheral edge of an opposite ceiling surface of the virtual three-dimensional body. As a virtual three-dimensional body while a non-existing real body is called, on the mantle surface of the beam path of the measuring light beam is located.

An array of reflectors, as described with reference to FIG. 3, allows a larger number of reflectors to be accommodated in an area of limited dimensions than when arranged along a line. In this way, the ratio of the distance traveled by the measuring light beam path length to the object distance can be further increased.

The determination of the object distance may be as described with reference to the devices of FIGS. 1 and 2. In order to determine the path length covered by the measuring light beam, it is possible with the light source 52 and the detector 56 to carry out a propagation time measurement, an interferometric method or a measuring method using a pulse sequence. The portion of the path length traveled by the measuring light beam, which is not caused by the repeated propagation of the measuring light beam between measuring device 50 and object 61, can be determined, for example, based on the device geometry or by means of a calibration of the measuring device 50.

In the device explained with reference to FIG. 3, the light source 62 and the detector 56 are provided separately. In a modification, instead of the detector 56, a retroreflector may be provided to reflect the measuring light beam within it, and instead of the light source 52 may be provided an integrated light source and detector, for example a conventional laser rangefinder. The number and arrangement of reflectors and object reflectors may also be used in a measuring device in which the beam path of the measuring light beam is guided along a mantle surface of a three-dimensional body, depending on the characteristics of the light source and the detector device as well as a desired range of distances with the Distance measuring device to be measured can be selected.

4 shows an example of a beam path of a measuring light beam 85 in a further exemplary embodiment. The measuring light beam 85 is reciprocated on a mantle surface of a virtual cuboid 80 several times between a measuring device and an object. Reflectors of the measuring device, which are not shown in FIG. 4, are arranged along an edge of a base 81 of the virtual cuboid 80, and object reflectors, which are not shown in FIG. 4, are along an edge of a ceiling surface 82 opposite the base 81 Cuboid 80 disposed on the object whose distance is to be determined. A light source and detector device 83 generates the measurement light beam 85, which is repeatedly guided back and forth on the mantle surface of the cuboid 80 between the base surface 81 and the ceiling surface 82. A retroreflector 84 reflects the measuring beam of light 85 back into itself, so that it propagates back to the light source and detector device 83.

5 shows an example of a beam path of a measuring light beam 95 in a further exemplary embodiment. The measuring light beam 95 is reciprocated on a mantle surface of a virtual cylinder 90 several times between a measuring device and an object. Reflectors of the measuring device, which are not shown in Fig. 5, are arranged along an edge of a base 91 of the virtual cylinder 90, and object reflectors, which are not shown in Fig. 5, along an edge of the base 91 opposite ceiling surface 92 of Cylinder 90 disposed on the object, whose distance is to be determined. A light source and detector device 93 generates the measuring light beam 95, which is repeatedly guided back and forth on the mantle surface of the cylinder 90 between the base surface 81 and the ceiling surface 82. A retroreflector 94 reflects the measuring light beam 95 back into itself so that it propagates back to the light source and detector device 93. For accurate distance measurement, the reflectors of the measuring device should have a well-defined orientation to the object reflectors mounted on the object. If the reflectors of the measuring device are mounted on a flat support and the object reflectors are mounted on a planar support, the support and support arrangement can be chosen so that a parallel arrangement of the two supports can be set and an existing residual tilt the measured distance not heavily influenced.

For this, the support of the reflectors and / or the support of the object reflectors may be located at a point located on a connecting line between the array of reflectors and the array of object reflectors and advantageously through a connecting line of a center of the array of reflectors with a center of the array of object reflectors , Alternatively, the support of the reflectors and / or the support of the object reflectors may be mounted along a line which intersects said connecting line. For example, the carrier of the reflectors and / or the carrier of the object reflectors may be mounted on a line connecting the centers of the carriers. As a result, the influence of tilting of the two carriers relative to one another on the measured distance can be reduced.

The orientation of the support for the reflectors and the support for the object reflectors to each other can also be actively set, as will be explained below with reference to FIG. 6-8.

FIG. 6 is a schematic illustration of a distance measuring device 100 with a carrier 103 on which a reflector assembly 104 is mounted. For example, the reflector assembly may comprise a linear array of reflectors as discussed with reference to FIGS. 1 and 2, or a two-dimensional array of reflectors as discussed with reference to FIGS. 3-5. An arrangement of object reflectors (not shown) is provided on a carrier 119. The carrier 119 may be formed, for example, as a movable measuring jaws of a caliper.

The carrier 103 is mounted on a plate 102 so that the carrier 103 is tiltable about an axis 112 extending through the center of the carrier 103 relative to the plate 102. For tilting the carrier 103 relative to the plate 102, a pair of piezo elements 107, 108 is provided, via which the carrier 103 is supported on the plate 102. The plate 102 is supported on a plate 101 such that the plate 102 is tiltable relative to the plate 101 about an axis 111 passing through the center of the plate 102, which is orthogonal to the axis 112. For tilting the plate 102 relative to the plate 101, a pair of piezo elements 105, 106 is provided, via which the plate 102 is supported on the plate 101. The plate 101 is fixedly mounted in use of the device 100.

The carrier 103 can be tilted by actuation of the piezo elements 105, 106 and / or the piezo elements 107, 108 about the orthogonal axes 11 and / or 112 so that the carrier 104 is aligned with the object reflectors as parallel as possible to the carrier 119. For this purpose, the pairs of piezo elements 107, 108 and 105, 106 can be controlled by a control device 118 depending on an orientation of the carrier 103 relative to the carrier 119 with the object reflectors. In one embodiment, the control device 118 can control the piezoelectric elements 105 and 106 in antiphase such that one of the piezoelectric elements expands by a certain distance while the other of the piezoelectric elements shrinks by the same distance in order to achieve tilting of the carrier 103 about the axis 111. Similarly, the control device 118, the piezo elements 107 and 108 in anti-phase drive such that one of the piezoelectric elements expands by a certain distance, while the other of the piezoelectric elements shrinks the same distance in order to achieve a tilt about the axis 112.

The controller 118 may be fed in a closed loop input signals representing the orientation of the carrier 103 relative to the plane of the carrier 119. The orientation of the carrier 103 can be optically determined.

In the device shown in FIG. 6, light sources 113, 114 are provided for determining the orientation of the carrier 103 on the carrier 103, wherein the light source 113 transmits a light beam (not shown) to a sensor 115 and the light source 114 a (not shown) ) Emits light beam to a sensor 116. The sensors 115, 116 are arranged on the support 119 for the object reflectors. The sensor 115 detects a position of the light beam irradiated thereon along a first direction, for example a vertical direction of the carrier 119. In an orthogonal direction, for example, the horizontal direction of the carrier 119, the sensor 115 has a width which is sufficient that for expected tilting of the carrier 103 relative to the carrier 119 around the vertical axis of the light beam emitted by the light source 113 still strikes the sensor 115. However, the sensor 115 may be insensitive to the position of the light beam in the second direction, for example, the horizontal direction of the carrier 119. The sensor 116 detects a position of the light beam irradiated thereon along the second direction, for example, the horizontal direction of the carrier 119. In a direction orthogonal thereto, for example, the vertical direction of the carrier 119, the sensor 116 has a width sufficient is that for expected tilting of the carrier 103 relative to the carrier 119 around its horizontal axis, the light beam emitted by the light source 114 still strikes the sensor 116. However, the sensor 16 may be insensitive to the position of the light beam in the first direction, for example, the vertical direction of the carrier 119.

The output signals of the sensors 115 and 116 indicating the orientation of the carrier 103 are fed to the control device 118, which generates signals for driving the piezoelements 105-108. To generate the signals for the piezoelectric elements, the control device 118 can amplify and optionally invert the output signals of the sensors 115, 16 in order to achieve the desired control of the orientation of the carrier 103. The control gain is determined by the product of a beam optical amplification factor, which indicates the deflection of the light beam emitted by the light source 113 or 114 per tilt angle, the conversion factor of the sensor 115 or 116, the gain of the control circuit 118 and the conversion characteristic of the piezo elements 105-16. 108th

In further embodiments, modifications of the adjustment mechanism for the carrier 103 or the sensor for detecting the orientation of the carrier 103 may be used. For example, instead of the pairs of piezo elements, in each case a single piezoelement can be used in order to tilt the carrier 103 about the axis 111 or the axis 112. Instead of piezoelectric elements, other suitable actuators can be used.

For detecting the orientation of the carrier 103, a single light source and a single sensor can also be used, as described in more detail with reference to FIG. 7.

FIG. 7 is a schematic illustration of a device 120 for distance measurement. Elements or devices, their function and design of those 6 correspond to elements or devices of the device 100 described with reference to FIG. 6, are denoted by the same reference numerals and will not be described again.

In the device 120, a light source 113 provided at the intersection of the tilt axes 111 and 112 of the carrier 103 and a four-quadrant sensor 117 attached to the carrier 1 19 are used to adjust the orientation of the carrier 103 relative to the carrier 119 for the object reflectors to determine. The four-quadrant sensor 117 is provided on the carrier 119 at a position opposite to the intersection of the tilting axes 111 and 112. The output signals of the four-quadrant sensor 117 indicate the coordinates of the light beam emitted from the light source 113 on the four-quadrant sensor 117 and are processed by the evaluation device 118 as described with reference to FIG relative to the carrier 119 to regulate.

While in the device 120 the four-quadrant sensor 117 is provided on the carrier 119 for the object reflectors, in another embodiment, the four-quadrant sensor may be attached to the carrier 103 for the reflectors of the measuring device. An additional reflector for reflecting the light beam from the light source 113 to the four-quadrant sensor may then be provided on the object reflector support 119.

In one embodiment, the orientation of the carrier for the reflectors in the measuring device is determined on the basis of the measuring light beam used for distance measurement. For this purpose, a beam splitter can be provided in the beam path of the measuring light beam, which decouples a part of the light energy of the measuring light beam to a sensor, for example a four-quadrant sensor, in order to determine the orientation of the carrier.

FIG. 8 is a schematic illustration of a device 130 for distance measurement. On a carrier 131 of the measuring device 130, a light source and detector device 23, reflectors 23-26 and a retroreflector 27 are provided, the design and operation of which corresponds to that of the corresponding elements described with reference to FIG. On a carrier 132, which can form a part of the object whose distance is to be determined, or which is to be attached to this object, object reflectors 33-36 are provided, the design and mode of operation of which is described with reference to FIG. corresponds to corresponding corresponding elements. The reflectors 24-27 and the object reflectors 33-36 direct the measuring light beam in such a way that it repeatedly traverses the distance between the support 131 of the measuring device and the support 132 with the object reflectors in each direction.

In the beam path of the measuring light beam, a beam splitter 133 is arranged. In operation of the device, the beam splitter 133 decouples a portion of the measuring light beam from the beam path and directs it to a four-quadrant sensor 134. The position of the measuring light beam on the four-quadrant sensor 134 represents a tilt of the carrier 131 relative to the carrier 132. The output of the four-quadrant sensor 134 indicative of the position of the measuring light beam on the four-quadrant sensor 134 is fed to a controller 135 which controls the orientation of the carrier 131 via an actuator 136 such that the carrier 131 is substantially parallel is aligned with the carrier 132.

While in Fig. 8, the decoupling of a portion of the measuring light beam for controlling the orientation of the support is shown for a reflector assembly in which the reflectors 24-27 are provided along a line, a decoupled part of the measuring light beam can also be advantageous in measuring devices for controlling the off - Direction of reflectors are used in which the measuring light beam is not performed in a single plane. Such measuring devices have been explained with reference to Figs. 3-5. For example, an array of reflectors 53-55, as shown in FIG. 3, can be mounted on the actuator-adjustable carrier 103 of the device 100 of FIG. 6 or the device 120 of FIG. A portion of the measuring light beam may be coupled out to a four-quadrant sensor to control the orientation of the carrier 103.

If a part of the measuring light beam is coupled out in order to regulate an orientation of the carrier for the reflectors in the distance measuring device, the control gain is increased since the multiple propagation of the measuring light beam between the measuring device and the object causes a positional deviation of the measuring beam caused by tilting of the carrier Measuring light beam from the desired beam path can increase.

In one embodiment, a measurement light beam may be generated having light components of at least two different wavelengths. It can be provided a light-wave sensitive beam splitter, the light of a wavelength decouples the measuring light beam used to determine the orientation. The undocked portion of the measuring light beam can be used for distance determination.

In the devices explained with reference to FIGS. 1 to 8, the measurement light beam for distance measurement is repeatedly guided back and forth between the measuring device and the object. The resulting lengthening of the path length traveled by the measuring light beam makes it possible to reduce a smallest measurable distance and to achieve a higher measuring accuracy when using a conventional laser rangefinder.

Instead of a conventional laser range finder, in the measurement devices described with reference to Figs. 1-8, a short pulse laser may also be used as a light source which generates a train of light pulses at a repetition rate. The sequence of light pulses is detected with a photodetector after being passed back and forth several times between the measuring device and the object. The transit time of the light pulses and thus the path length traveled by them can be determined from the phase shift of a signal component of the detected signal whose frequency is essentially a multiple of the repetition rate, as will be explained in more detail with reference to FIGS. 9-12.

9A shows by way of example a sequence of short light pulses 141, the output power P of a light source being shown as a function of the time t. The time interval TO between successive pulses is indicated by the reference numeral 142, while the duration of each light pulse is indicated by the reference numeral 143. The duration of each light pulse can be very small compared to the time interval TO between successive light pulses, for example of the order of MO ^'5. The repetition rate f.theta and the time duration of each pulse can be appropriately selected depending on a desired measurement accuracy in determining a distance traveled by the measuring light beam If the n-th harmonic of fθ is to be used to determine the phase difference, the duration of each light pulse and the time interval TO between successive light pulses are chosen so that the The sequence of light pulses emitted by the light source still has a sufficient spectral weight at the frequency n f0. Although a sequence of rectangular coils is shown in FIG. sen, other suitable pulse shapes may also be selected, for example the square of a hyperbolic secant or a Gaussian function.

Fig. 9B exemplifies a frequency spectrum 145 of a sequence of light pulses generated at a repetition rate fθ, the duration of each light pulse being short compared to TO = 1 / f0. The frequency spectrum 145 has a number of peaks with a constant frequency spacing fθ, which is schematically indicated at reference numeral 146. The spectral weight of the individual peaks decreases towards higher frequencies, the strength of the drop being determined by the ratio of the time interval between successive light pulses and the duration of the light pulse. These magnitudes are chosen such that the spectral weight of the frequency component 147 with frequency n f0, which is used in the path length measurement for the determination of phase angles, in the sequence of light pulses is sufficiently high for carrying out phase measurements.

A sequence of light pulses, as shown schematically in FIG. 9, may be generated by various lasers adapted to generate short pulses of light. In particular, optical frequency synthesizers can be used. For example, an electrically pumped diode laser, e.g. a Q-switched laser, a gain switched laser, an active or passive mode locked laser or a hybrid mode-locked laser, or a mode-locked vertical cavity surface emitting laser (VCSEL) may be used as the light source. Also, an optically pumped laser such as a passive mode-coupled external external cavity (VECSEL) surface emitting laser or a photonic-crystal-fiber laser may be used as the light source , Exemplary pulse durations of the light source are in a range of 100 fs and 100 ps. Exemplary repetition rates range from 50 MHz to 50 GHz. Exemplary average powers are in a range of 1 mW to 10 W. Exemplary values for the pulse jitter are between 10 fs and 1 ps effective value (root mean square).

10 shows a light source and detector arrangement 150 with a light source 151, photodetectors 153, 154 and 156 and an evaluation device 157. The light source and detector arrangement 150 can be used, for example, in the devices described with reference to FIGS. 1-8 were. As shown in FIG. 10, a partial beam of the sequence of light pulses output by the light source 151 is directed via the beam splitter 152 as a reference signal 158 to the reference signal detectors 153, 154. If necessary, in the beam path from the beam splitter 152 to the reference signal detectors 153, 154, an optical element for beam splitting, in particular a beam splitter may be provided to ensure that the sub-beam 158 hits both the reference signal detector 153 and the reference signal detector 154. Another partial beam 160 is emitted as a measuring light beam in the direction of the object whose distance is to be determined. As explained with reference to Figs. 1-8, the measuring light beam is repeatedly reciprocated between the measuring device and the object. For purposes of explanation, it will be assumed that one of the reflectors of the measuring device is a retroreflector. The measuring light beam which is guided back and forth repeatedly between the measuring device and the object is directed onto a photodetector 156 via a semitransparent mirror 155. From the phase angle of the signal detected by the photodetector 156, the path length traveled by the measuring light beam can be determined.

Both the photodetector 156 and the reference signal detectors 153, 154, which are likewise configured as photodetectors, detect a light energy incident on them as a function of time. Due to the light pulses generated with a well-defined repetition rate, the signal component resulting from the sequence of light pulses can be determined during signal processing by the evaluation circuit 157 by suitable filtering, so that in the following other signal components detected by the photodetectors 154, 154 and 156 will not be further discussed become.

The different optical path length of a light pulse, on the one hand to get to one of the reference signal detectors 153, 154 and on the other hand after passing through the folded beam path for the measuring light beam to the photodetector 156, leads to a time shift τ between the arrival of one and the same light pulse to the detector 156th and at the reference signal detectors 153, 154 which is equal to the path length difference divided by the speed of light c. By measuring the time shifts τ between the light signal detected by the photodetector 156 and the reference signal detected by the reference signal detectors 153, 154, the optical path length traveled by the light pulse between the beam splitter 152 and the photodetector 156 can be determined. The photodetector 156 and the reference signal detectors 153, 154 are coupled to the evaluation circuit 157, which determines a phase difference between the detected light intensity of the measuring light beam and the reference signal. As will be explained in detail, the evaluation circuit 157 of the arrangement 150 may be configured to determine the phase difference between the light signal detected by the photodetector 156 and the reference signal detected by the reference signal detectors 153, 154 for a signal component whose frequency is substantially is a multiple of the repetition rate.

The sequence of light pulses received at the photodetector 156, as explained with reference to FIG. 9 for the sequence of light pulses generated by the light source, has a plurality of harmonics whose frequencies are multiples of the repetition rate fθ:

fj = i -fo. (1)

where i is a natural number and fθ is the repetition rate of the light source 151. A characteristic quantity for frequencies which still have a significant spectral weight in a Fourier representation of the light energy received by the photodetector 156 as a function of time is given by the quotient of the time period TO between successive light pulses and the characteristic duration of a light pulse ,

The temporal shift τ between the signals detected by the photodetector 156 and the reference signal detectors 153, 154 results in a signal component of the signal 159 received at the photodetector 156 having a frequency fj relative to a reference signal component of the reference signal detector 153 154 received reference signal 158, which has a frequency fj, a phase shift of

Δφj = 2-π-fj-τ = 2-πΨfO-τ (2a)

= 2-π-i-fO- (d / c) (2b)

Has. D denotes the path length difference between a light path of a light pulse which is emitted by the beam splitter 152 in the direction of the object and is guided back and forth several times between the object and the measuring device, and a light path of a light pulse which emerges from the beam splitter 152 to the reference. signal detectors 153, 154 is directed. It is assumed that the length of the light path of a light pulse, which is directed from the beam splitter 152 to the reference signal detectors 153, 154, is known, since it depends only on the device geometry.

If an estimated value dS for the path length difference d is already known, which approximates this with an accuracy of c / (i-fθ), so that

I d - dS | <c / fj = c / (i fθ), (3)

For example, on the basis of dS, the amount of phase shift on the right side of Equation (2a) which is an integer multiple of 2-π can be determined. Based on dS, an integer m is determined so that

d = d ¹ + rn-c / fj, where | d '| <c / fj. (4)

Consequently, it is

= 2-π-i-fO- (d '/ c) (5)

a variable lying in the interval of 0 to 2-π, which can be determined by measuring the phase angle between an output signal of the photodetector 156 and an output signal of one of the reference signal detectors 153, 154. The size d ', then according to

d ¹ = c-Δφj7 (2-π-i-fO) (6)

can be determined leads according to equation (4) to an improved value for the path length difference d. Since the two quantities Δφj 'and Δφj differ only by an integer multiple of 2-π irrelevant for the determination of the phase difference, both quantities are referred to below as the phase difference and are not further distinguished.

In the apparatus and method of embodiments of the invention, i> 1, typically i »1, is chosen to determine the phase difference. Therefore, given a given measurement accuracy for a phase difference, below referred to as phase resolution, the measurement accuracy for the path length difference and thus the axial resolution can be increased.

By way of illustration, it is assumed that the phase resolution is 2-π / 1000 and fθ = 100 MHz. Then, the axial resolution is 3 mm / i and decreases as the frequency of the signal component, i, increases. For i = 700, for example, an axial resolution of about 4.1 μm is achieved. Thus, the axial resolution can be increased by determining the phase difference based on a signal component of the signal 159 corresponding to a high frequency harmonic of the sequence of light pulses, i. whose frequency is the repetition rate multiplied by a factor i »1. The signal component, on the basis of which the phase difference is determined, is chosen such that it has the highest possible frequency at which the sequence of light pulses still has a sufficient spectral weight and allows signal processing by the evaluation circuit 157 designed as a high-frequency circuit.

The evaluation circuit 157 can determine the phase difference by mixing several O berwellen together. By appropriately selecting the harmonics and mixing a signal component of the light signal received at the photodetector 156 with a reference signal component of the reference signal received from the reference signal detectors 153, 154, a mixed product may be generated which is relatively low frequency but contains the phase difference of the harmonic. As a result, instead of the original requirement to measure short propagation times, it is possible to perform a phase measurement at low frequencies.

11 shows a schematic block diagram of a detector arrangement and evaluation circuit according to an exemplary embodiment. The evaluation device 157 of the arrangement 150 of FIG. 10 can be designed as shown in FIG. 11.

The evaluation circuit 170 includes a signal processing path for an electrical signal output from the photodetector 156 representing the light signal detected by the photodetector 156, an input side amplifier 171 and a bandpass filter 172. The evaluation circuit 170 further includes a signal processing path for one of the first reference signal detector 153 output electric signal representing the reference signal detected by the first reference signal detector 153, having an input side amplifier 173 and a band pass filter 174, and a signal processing path for one of second reference signal detector 154 outputs electrical signal representative of the reference signal detected by the second reference signal detector 154 with an input side amplifier 176 and a bandpass filter 177. Since the signals output from the detectors represent the optical signals incident thereto and the light intensity as a function reflecting the time, the signals output by the detectors or reference signal detectors are denoted as well as the detected optical signals, ie as a detected "light signal" or "reference signal", wherein the signals processed by the evaluation circuit are electrical signals.

The band-pass filter 172 is arranged to pass a signal component of the light signal detected by the photodetector 156 at a frequency of n-fθ, where n is a natural number greater than one. As described above, n is advantageously chosen as large as possible in order to improve the axial resolution. Advantageously, the bandpass filter 172 has a passband selected such that transmission of signal components having frequencies of (n + 1) -fθ and (n-1) -fθ is significant as compared to transmission of the signal component of frequency n-fθ is weakened. For this, the band-pass filter 172 may have a passband having a width smaller than fθ.

The band-pass filter 174 is arranged to pass a reference signal component of the reference signal detected by the first reference signal detector 153 at a frequency of k-fθ, where k is a natural number. For example, k = n-1 can be chosen so that the bandpass filter 174 passes a reference signal component with the frequency (n-1) -f0. Advantageously, the bandpass filter 174 has a passband selected such that the transmission of reference signal components having frequencies of (k + 1) -fθ and (k-1) -fθ is significant as compared to the transmission of the reference signal component of frequency k-fθ is weakened. For this, the band-pass filter 174 may have a passband having a width smaller than fθ.

A mixer 175 is input-coupled to the band-pass filters 172 and 174 to receive the signal component 181 of the light signal and the reference signal component 182 of the reference signal. The result of the frequency mixing,

cos (nf ^(M + Δφn) -cos ((n-1) -fθ-t) = [cos (f o t + Δφ _n) + cos ((2-n-1) -f o-t + Δφ _n) ] / 2

(7) has a low-frequency component with the frequency fθ, which corresponds to the fundamental frequency or repetition rate of the signal generated by the light source 151, and a high-frequency component.

Although the first term on the right side of equation (7) has the fundamental frequency fθ, the phase Δφ _n in the argument of the low frequency component in equation (7) is determined by equation (2), thus corresponding to the phase difference for the signal component of the light signal the frequency n-fθ. The low-frequency component is provided as a signal 183 to a phase evaluator 178 whose second input is coupled to the bandpass filter 177.

The band-pass filter 177 is arranged to pass a reference signal component of the reference signal detected by the second reference signal detector 153 at a frequency of fθ. Advantageously, the bandpass filter 177 has a passband which is chosen so that the transmission of reference signal components with frequencies of 0-f0 and 2-f0 is significantly attenuated compared to the transmission of the reference signal component with the frequency f0. For this, the band-pass filter 177 may have a passband having a width smaller than fθ. The resulting reference signal component at frequency fθ is provided as signal 184 to phase evaluator 178.

The phase evaluator 178 determines the phase difference Δφ _n between the signal 183 and the signal 184. Since mixing produces a signal of frequency fθ and the phase difference Δφ _n , the phase measurement can be performed at low frequencies.

Since the signal 184 is optically picked up by the second reference signal detector 153 and is not generated from the signal received by the first reference signal detector 154, the amplifiers 173 and 176 can be selectively selected in the signal processing paths for the two reference signal detectors 153, 154. For example, the amplifier 176 may be selected to have a good power characteristic at the frequency fθ, while the amplifier 173 may be selected to have a good power characteristic at the frequency (n-1) -fθ. From the determined with the evaluation circuit 170 phase difference Δφ _n can be determined according to the equations (4) - (6) covered by the measuring light beam path length from which the distance of the object can be calculated. The high resolution of the path length measurement which can be achieved using the optical frequency comb, in conjunction with the convolution of the beam path effected by the reflectors of the measuring device, allows an accurate distance measurement.

Devices and methods for distance measurement according to various exemplary embodiments have been described with which, due to the beam guidance between measuring device and object, distances in a length range corresponding to typical dimensions of machine parts can be determined with high accuracy using optical methods. Because the devices and methods can combine conventional laser rangefinders of small dimensions with a reflector arrangement, the distance measuring device can be designed to be easily transported and installed in different locations.

Exemplary fields of application of the devices and methods according to the various embodiments include length or distance determination in industrial manufacturing or industrial quality control, for example in machine components. However, the devices and methods according to the various embodiments are not limited to these fields of application.

Claims

An apparatus for optical distance measurement of an object (2; 30; 61; 132) which is set up to move a measuring light beam (11; 85; 95) along a beam path (13; 37; 71) in the direction of the object (2; , 61, 132), the apparatus comprising a reflector (4; 24; 53) arranged to receive a measuring light beam (16; 38; 72) reflected from the object (2; 30; 61; 132) and directing them along a further beam path (14; 39; 73) offset to the beam path (13; 37; 71) in the direction of the object (2; 30; 61; 132).

Apparatus according to claim 1, wherein the reflector (4; 24; 53) is arranged to transmit the measuring light beam (16; 38; 72) reflected at the object (2; 30; 61; 132) into the further beam path (14; 39; 73) which is substantially parallel and offset from the measuring light beam (16; 38; 72) reflected at the object (2; 30; 61; 132).

Device according to claim 1 or 2, comprising at least one further reflector (5; 25-27; 54, 55) arranged to detect a measuring light beam (17.) Reflected on the object (2; 30; 61; 40, 74, 76) and to guide them towards the object (2; 30; 61; 132).

4. Device according to claim 3, wherein a further reflector (54, 55) of the at least one further reflector (54, 55) is set up such that the measuring light beam guided by the further reflector (54, 55) in the direction of the object (61) (75, 77) lies outside a plane defined by the beam path (71) and the further beam path (73).

5. Apparatus according to claim 3 or 4, wherein the reflector (53) and the at least one further reflector (54, 55) are arranged such that the measuring light beam (85; 95) on a mantle surface of a virtual three-dimensional body (80; 90) between the device and the object.

6. Device according to one of claims 3-5, wherein the reflector or another reflector of the at least one further reflector is designed as a retroreflector (5; 27; 84; 94) in order to reflect the measurement light beam in on itself.

Apparatus according to any one of the preceding claims, comprising an object reflector (6; 33; 62) to be mounted on the object (2; 30; 61; 132) adapted to receive and to which the measuring light beam radiated from the apparatus To direct the reflector (4; 24; 53).

Apparatus according to claim 7, wherein the object reflector (6; 33; 62) is arranged to offset the measuring light beam radiated from the apparatus along the beam path (13; 37; 71) and substantially parallel to the beam path (13; 71) to the reflector (4; 24; 53).

A device according to any one of the preceding claims, wherein the reflector (24; 53) is mounted on a support (51; 104; 131) and the device comprises an actuator (105-108; 136) for displacing the support (51; 104; 131).

The apparatus of claim 9, including a sensor (115, 116; 1 17; 134) coupled to the actuator (105-108; 136) for detecting an orientation of the carrier (104; 131).

11. The apparatus of claim 10, which comprises a provided in the beam path of the measuring light beam beam splitter (133) which is adapted to direct a portion of the measuring light beam to the sensor (134).

The apparatus of claim 11, wherein the measurement light beam has light components of two different wavelengths, the beam splitter (133) being arranged to direct light having one of the wavelengths to the sensor (134).

The apparatus of any of claims 10-12, wherein the sensor (117; 134) comprises a four-quadrant sensor.

14. Apparatus as claimed in any one of the preceding claims including a light source (151) for generating the measurement light beam configured to generate a train of light pulses at a repetition rate.

15. The apparatus of claim 14, wherein the light source is a short pulse laser (151).

16. Device according to claim 14, which comprises an evaluation device for determining a path length covered by the measuring light beam, which is set up to determine a phase shift of a signal component of a detector for determining the path length. detected sequence of light pulses, wherein the signal component (181) has a frequency which corresponds to a multiple of the repetition rate.

17. Device according to claim 16, wherein the evaluation device (157) is set up to generate, for determining the phase difference, a further signal (183) which essentially has the phase shift of the signal component and a lower frequency than the signal component.

18. caliper, comprising a guide (21), on the guide (21) movably mounted element (30), and a device according to one of the preceding claims for determining the position of the movably mounted element (30) on the guide (21).

19. caliper according to claim 18, wherein the device is designed as a device according to claim 7 or 8 and the object reflector (33) on the movably mounted element (30) is provided.

20. A method for optical distance measurement of an object (2; 30; 61; 132), in which the distance of the object (2; 30; 61; 132) is determined as a function of a path length covered by a measuring light beam (11; 85; 95) in that the measurement light beam (11; 85; 95) is steered such that it is guided back and forth several times between the object (2; 30; 61; 132) and a measuring device (1; 22; 51; 131).

21. The method of claim 20, wherein the measuring light beam sequentially receives a plurality of first ray paths (13, 14; 37, 39; 71, 73, 75, 77) parallel to each other from the measuring device to the object (2; 30; 61; 132 ) and mutually parallel second beam paths (16, 17; 38, 40; 72, 74, 76, 78) from the object (2; 30; 61; 132) to the measuring device.

22. Method according to claim 21, wherein the first ray paths (13, 14; 37, 39; 71, 73, 75, 77) and the second ray paths (16, 17; 38, 40; 72, 74, 76 78) are parallel to each other.

23. A method according to claim 21 or 22, wherein the first beam paths (13, 14; 37, 39; 71, 73, 75, 77) and the second beam paths (16, 17; 38, 40; 72, 74, 76, 78) offset from each other.

24. The method of claim 21, wherein at least one first ray path (75, 77) of said plurality of first ray paths is outside that of another first ray path (71) of said plurality of first ray paths and a second ray path (72) of said plurality plane defined by second ray paths.

The method of any one of claims 21-24, wherein the first beam paths (71, 73, 75, 77) and the second beam paths (72, 74, 76, 78) extend on a mantle surface of a virtual three-dimensional body (80, 90).

26. A method according to any one of claims 21 to 25, wherein the measuring light beam (85; 95) is retroreflected so as to pass twice through the plurality of first beam paths and the plurality of second beam paths.

27. Method according to one of claims 21-26, wherein at least one reflector (4, 5, 24-27, 53-56) provided on the measuring device and one on the object (2; 30; 61; 132) are provided for directing the measuring light beam. Object Reflector (6, 7, 33-36, 62-65) are provided, wherein an orientation of the reflector (4, 5, 24-27, 53-56) relative to the object reflector (6, 7, 33-36 62-65) is adjusted so that the first beam paths (13, 14; 37, 39; 71, 73, 75, 77) and the second beam paths (16, 17, 38, 40, 72, 74, 76, 78) are parallel to each other.

28. The method according to claim 27, wherein a position of the measuring light beam reciprocated repeatedly between the measuring device and the object (132) is detected and the orientation of the reflector (24-27) is controlled based on the detected position.

29. The method of claim 20, wherein the measuring light beam comprises a sequence of light pulses (191) generated at a repetition rate.

30. A method according to claim 29, wherein a light intensity of the measuring light beam (160) is detected after the measuring light beam has been repeatedly reciprocated between the object (2; 30; 61; 132) and the measuring device, and one of the measuring light beam passed through Path length is determined based on a phase shift of a signal component (181) of the measuring light beam having a frequency corresponding to a multiple of the repetition rate.

The method of claim 30, wherein the signal component (181; 196) is applied to a frequency mixer (175) to produce a further signal (183) that substantially matches the phase shift of the signal component (181) and a lower frequency than the sig - Nalkomponente (181, 196).

32. The method according to any one of claims 20-31, for measuring a distance in industrial production.

33. The method according to any one of claims 20-32, for measuring a distance between legs (22, 30) of a caliper (20).

34. The method according to any one of claims 20-33, which is carried out with the device according to any one of claims 1-17.