DE102008062458A1 - Laser-based measuring device for use during manufacturing process in machine and equipment construction, has polarizing filter provided in radiation, where adjustment of plane corresponds to direction of linear polarization of radiation - Google Patents

Abstract

The device has a laser (1) utilized as a light source and an optical sensor e.g. charge couple device (CCD) matrix sensor (2), where an object (4) to be measured is provided in laser radiation (3) of the laser. A polarizing filter (5) is provided in the radiation, where adjustment of a polarization plane corresponds to a direction of linear polarization of the radiation, against which a polarization filter (6) is provided so that a polarization plane of a polarizing filter (6) is rotated opposite to the filter (5). A color filter (7) is provided in the radiation.

Description

The The invention relates to a device for laser-based measurement of Workpieces, assemblies and tools during Manufacturing processes in mechanical and plant engineering.

The obtained measurement data can be used for compensation in particular the dimensional trends or the dimensional drift due thermally induced deformations and / or as a result of tool wear. Depending on the version of the device for laser-based measurement of workpieces, assemblies and tools Dimensions and shapes as well as the location of geometric features to measure each other.

Currently tactile, inductive and optical measuring systems are used for workpiece measurement.

tactile and inductive measuring systems are for the process-accompanying Measurement of workpieces and tools less well suited, because they either have a high mechanical and wear sensitivity or unsatisfactory in the case of inductive measuring systems Have accuracies.

The better suited optical systems work either as incident light or backlight systems, with only the backlight systems being somewhat reasonably achieve satisfactory measurement accuracy.

The basic concept of a backlight system is based on a diffuse light source (eg halogen lamp, fluorescent tube, flash lamp, etc.) and a high-resolution camera, between which the measurement object is located and its recorded by the camera silhouette is computer-aided evaluation, for. B. to determine the target-actual deviation of a measured object. Such solutions are for. B. in the measuring systems of Omron and Zoller ( Pfeifer, T. et al., Optoelectronic Methods for Measuring Geometric Quantities in Manufacturing, Kontakt & Studium, Volume 405, expert-Verlag, Ehningen at Böblingen, 1993, p. 166 ff. ).

According to another concept - the laser scanner - a laser beam is deflected by means of a mostly rotating mirror system in order to scan an object to be measured. Photodiode-triggered the respective actual measurement of an object is calculated with the aid of the simultaneously detected mirror deflection. Such solutions can be found below www.betalasermike.com , The main disadvantage of the aforementioned optical surveying solutions is the high cost that the very expensive camera or scanner-based systems cause in their implementation. An additional disadvantage is the fault influence, which can cause incident extraneous light.

Devices for laser-based measurement of workpieces outside of machines are z. B. after DE 37 13 109 C2 known, however, the laser beam is moved here with a separate complex device and determined from the context of measured interruption time of the laser beam through the workpiece whose dimension. Such a method is inconvenient for the detection of workpiece geometries in operational machining processes because of its complicated and expensive implementation.

According to the DE 40 30 994 A1 For example, a geometric inspection of rotationally symmetrical workpieces can be carried out by combining a laser measuring head with a mechanical probe. Again, the field of application is limited to the non-operational area. The implementation effort is disproportionately large, since even with this solution laser measuring head and button must be moved and controlled separately.

at all mentioned optical systems for the measurement of workpieces, Assemblies and tools are also required a dense positioning of the optical sensor on the object to be measured, in order to limit external light influences.

The Disadvantages of the prior art can be achieved in high implementation costs, often unsatisfactory measurement reliability, lack of robustness during the application in the manufacturing process and ultimately limited Summarize application area.

Around to avoid the disadvantages of the prior art solutions the object is a device for laser-based measurement of workpieces, assemblies and tools, which consists of simple and robust components, a high measuring accuracy also has under unfavorable lighting conditions and can be produced at a reduced cost. Furthermore is a small size of the device in general desirable.

According to the invention this object by a device for laser-based measurement solved by workpieces, assemblies and tools, the having the features of the first claim. The requirements 2 to 12 contain particularly advantageous embodiments of the invention.

The essence of the invention is that in the combination of a laser as Mess light source emitting linearly polarized light, and an optical sensor in the form of a CCD or CMOS matrix sensor as a measuring signal receiver filters are included, which ensure optimum exposure of the sensor. By introducing a polarization filter adapted to the polarization direction of the linearly polarized laser radiation into the laser beam, a considerable part of the extraneous light can be masked out and kept away from the optical sensor.

It especially in unfavorable lighting conditions be expedient to provide two polarizing filters, one of which is oriented so that its polarization plane the polarization direction of the laser radiation corresponds, whereas the second polarizing filter is arranged so that its polarization plane is rotated relative to the first polarizing filter. In such an arrangement, the first polarizing filter a significant portion of the extraneous light withheld during the laser radiation almost undamped by the polarization filter passes. Through the second polarization filter is the remaining Part of the extraneous light almost completely retained and attenuated the laser radiation. An optimization can doing so by changing the direction of the polarization plane of the second polarizing filter can be achieved.

It may still be appropriate, in addition to provide a color filter for one or two polarizing filters, whose transmission wavelength is the wavelength of the usually corresponds to monochrome laser light. As a result, the external light influence on the optical sensor can be further reduced.

The Filters should be as close to the optical as possible Sensor be arranged. It is advantageous to the sensor as well the filters in a predominantly opaque Housing with a filter as an inlet window for to accommodate the laser radiation.

The Resolution and thus possible measurement accuracy of Device for laser-based measurement of workpieces, Assemblies and tools are primarily based on the line spacing of the sensor matrix dependent. Therefore, an increase in resolution by tilting the matrix with respect to the direction of the laser radiation possible. Another way, the resolution To increase, the laser radiation is cone-shaped fanning.

A Significant improvement in measurement accuracy can be about it out through one opposite the main edges of the to be measured Workpiece rotated arrangement of the measuring signal receiver, d. H. of the CCD or CMOS matrix sensor, namely such that the orientation of the rows of the matrix sensor is opposite the main edges of the object to be measured are larger by one angle 0 ° and less than 45 °, preferably at an angle between 4 ° and 10 °, are rotated. Is preferred the measuring signal receiver to one approximately in the direction of Beam path of the laser radiation facing axis arranged rotated. By facing the main edges of the to be measured Workpiece rotated arrangement of the measuring signal receiver is a line-parallel impact of the at the main edge of the measurement object avoiding passing laser light on the matrix sensor, whereby a very significant improvement of the measurement accuracy is achieved.

A Further improvement of the measuring accuracy can be achieved by signal processing of the sensor signal by means of a regression calculation according to known mathematical methods are achieved. This allows the measurement accuracy over increased the resolution of the CCD or CMOS matrix sensor become. In the simplest case, this can improve edge detection be a linear regression calculation.

The following advantages are associated with the inventive, surprisingly simple solution of a device for laser-based measurement of workpieces, assemblies and tools:
The structure is in relation to previous camera and scanner solutions very simple with small dimensions. Instead of elaborate optical systems or complicated movement mechanisms, only one or two polarization filters and possibly a color filter are required in addition to the robust components laser light source and optical matrix sensor.

by virtue of a high realizable light intensity of the laser radiation Compared to extraneous light, this is already the case for a large number of applications significantly attenuated by the first polarizing filter Extraneous light for the subsequent image evaluation of the sensor image often without appreciable influence, so that the invention in its simple design, d. H. with only one polarizing filter, a large number of practical applications.

For the measurement of workpieces, assemblies and tools with a preferred major edge for the survey it has proven to be useful to the laser and of course with at least one polarization filter align so that the polarization direction of the linearly polarized Laser radiation corresponds to the direction of this main edge.

The inventive device for laser-based measurement of workpieces, assemblies and tools thus offers the opportunity at low effort, ie with simple and robust assemblies to achieve a high quality measurement. A complex lens optics, as used on camera systems, is not required.

The Invention is intended below to an embodiment be explained in more detail.

there shows the accompanying drawing a schematic diagram the device according to the invention for laser-based Measurement of workpieces, assemblies and tools with two polarizing filters and one color filter.

According to the drawing, the device for laser-based measurement of workpieces, assemblies and tools consists of a laser 1 and a CCD matrix sensor 2 , In the beam path of the laser radiation 3 the laser 1 is the measuring object four while two polarizing filters 5 and 6 as well as a color filter 7 between the measuring object four and the CCD matrix sensor 2 in the beam path of the laser radiation 3 are arranged. The measurement object four is so in the beam path of the laser radiation 3 positioned that it is the laser radiation 3 not completely obscured. The CCD matrix sensor 2 and the polarizing filter 6 as well as the color filter 7 are in an opaque housing 8th with the polarization filter 5 as an inlet window for the laser radiation 3 accommodated.

The polarization filter 5 is oriented so that the orientation of its polarization plane of the orientation of the linearly polarized laser radiation 3 corresponds during the polarization filter 6 oriented in a different orientation of the polarization plane. In this way, the quasi-series polarizing filter 5 and 6 diffuse foreign light components to a proportion of at least 50% and usually retained more than 80%. A further filtering of extraneous light takes place through the color filter 7 , whose transmission curve is wavelength-wise designed so that the color filter 7 the wavelength of the laser light of the laser 1 optimal passage and light of different wavelength is maximally damped.

The filter series from polarizing filters 5 and 6 as well as color filters 7 continuous laser radiation 3 then partially hits the target four and is reflected or absorbed there, leaving only the contour of the measured object four unlocked part of the laser radiation 3 on the CCD matrix sensor 2 meets. Depending on whether a sensor point of the CCD matrix of a laser beam 3 is lit or not, creates a corresponding pixel signal. From the totality of the signals of the individual sensor points is then in a known manner, the geometric detection and metrological evaluation of the measurement object four possible.

The fineness of the evaluation, ie the measurement accuracy, is dependent on the resolution of the CCD matrix sensor 2 ie the size, number and spacing of the sensor points within the matrix. Therefore, an improved resolution and thus higher measurement accuracy can already be achieved by the fact that the CCD matrix sensor 2 against the beam path of the laser beams 3 is inclined. To further improve the measurement result, a regression calculation is performed.

1

laser

2

CCD matrix sensor

3

laser beams

4

measurement object

5

polarizing filter

6

polarizing filter

7

color filter

8th

casing

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3713109 C2 [0008]
• - DE 4030994 A1 [0009]

Cited non-patent literature

• Pfeifer, T. et al., Optoelectronic Methods for Measuring Geometrical Quantities in Manufacturing, Kontakt & Studium, Volume 405, expert-Verlag, Ehningen bei Böblingen, 1993, p. 166 et seq. [0006]
• - www.betalasermike.com [0007]

Claims (12)

Device for the laser-based measurement of workpieces, assemblies and tools, a laser ( 1 ) as a light source and an optical sensor ( 2 ) in the form of a CCD or CMOS matrix sensor, wherein the object to be measured in the beam path ( 3 ) of the laser ( 1 ), characterized in that in the beam path ( 3 ) of the laser ( 1 ) at least one polarizing filter ( 5 ) whose orientation of the polarization plane of the direction of the linear polarization of the laser radiation ( 3 ) corresponds. Device for laser-based measurement according to claim 1, characterized in that in the beam path ( 3 ) of the laser ( 1 ) another polarizing filter ( 6 ) whose orientation of the polarization plane with respect to the orientation of the polarization plane of the first polarization filter ( 5 ) is twisted. Device for laser-based measurement according to one of claims 1 or 2, characterized in that a color filter ( 7 ) with the passband of the wavelength of the laser radiation ( 3 ) in the beam path ( 3 ) of the laser ( 1 ) is arranged. Laser-based measuring device according to one of the preceding claims, characterized in that the optical sensor ( 2 ) in the form of a CCD or CMOS matrix sensor with respect to the main edges of the measurement object ( four ) is arranged rotated. Laser-based measuring device according to claim 4, characterized in that the optical sensor ( 2 ) in the form of a CCD or CMOS matrix sensor about in the direction of the beam path ( 3 ) of the laser radiation ( 3 ) facing axis is arranged rotated. Laser-based measuring device according to claim 4 or 5, characterized in that the optical sensor ( 2 ) in the form of a CCD or CMOS matrix sensor with respect to the main edges of the measurement object ( four ) is arranged at an angle greater than 0 ° and less than 45 °, preferably at an angle between 4 ° and 10 °, rotated. Laser-based measuring device according to one of the preceding claims, characterized in that the optical sensor ( 2 ) in the form of a CCD or CMOS matrix sensor with respect to the beam axis of the laser ( 1 ) is inclined. Device for laser-based measurement according to one of the preceding claims, characterized in that in the beam path ( 3 ) of the laser ( 1 ) Means for cone-shaped fanning of the laser radiation ( 3 ) are arranged. Device for laser-based measurement according to one of the preceding claims, characterized in that in the beam path ( 3 ) of the laser ( 1 ) arranged filters ( 5 . 6 . 7 ) immediately in front of the optical sensor ( 2 ) are arranged in the form of a CCD or CMOS matrix sensor. Laser-based measuring device according to claim 6, characterized in that the optical sensor ( 2 ) in the form of a CCD or CMOS matrix sensor and in the beam path ( 3 ) of the laser ( 1 ) arranged filters ( 5 . 6 . 7 ) in a housing ( 8th ) are arranged, wherein a filter ( 5 ) the inlet window for the laser radiation ( 3 ) in the housing ( 8th ). Device for laser-based measurement according to one of the preceding claims, characterized in that the orientation of the linearly polarized laser radiation ( 3 ) and at least one polarizing filter ( 5 ) is carried out so that they in the direction of a significant for the measurement of the main edge of the workpiece to be measured ( four ), which are to be measured assembly or the tool to be measured. Laser-based measuring device according to one of the preceding claims, characterized in that the optical sensor ( 2 ) in the form of a CCD or CMOS matrix sensor for signal processing, a device for regression calculation is connected downstream.