Laser beam horizontal trueness testing device and corresponding method

Patent metadata

Field	Value
Publication number	US-9644960-B2
Application number	US-201314649861-A
Country	US
Kind code	B2
Filing date	Dec 3, 2013
Priority date	Dec 5, 2012
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

The invention relates to a laser beam horizontal trueness testing device for a laser beam projection device for construction and/or interior design work. The laser beam projection device is equipped with a beam self-leveling functionality. The laser beam horizontal trueness testing device has a telescope with an attenuating filter, a magnifying objective, and a flat image sensor for capturing an image of a laser beam incident on the objective. Components of the laser beam horizontal trueness testing device further include a natural inclination compensator and an analyzing unit which is designed to automatically ascertain an image position of the laser beam captured in the image by processing the image. According to the invention, the flat image sensor is arranged on an image plane of the objective, and the analyzing unit is additionally designed to quantify the laser beam horizontal trueness.

First claim

What is claimed is:

1. A laser beam horizontal trueness testing device for a laser beam projection apparatus having a beam leveling functionality, wherein the laser beam horizontal trueness testing device comprises:
a telescope having
an aperture,
an attenuation filter,
an objective having a magnifying effect and defining an optical axis, and
a planar image sensor arranged in an image plane of the objective and serving for capturing an image from a laser beam incident in the objective, wherein a focus is set or settable in such a way that beams running parallel to one another and incident in the objective coincide and are imaged over the entire aperture of the objective at the same point on the image plane and are thus detectable by the image sensor in a single, identical pixel,

an inherent inclination compensator, and
an evaluation unit designed for automatically carrying out
a determination of an image position of the laser beam captured in the image on the basis of image processing and
a quantification of the laser beam horizontal trueness with a translation of the determined image position into a laser beam inclination value on the basis of a translation rule related to calibration parameters dependent on a position of the image sensor in the telescope.

2. The laser beam horizontal trueness testing device as claimed in claim 1 , wherein:
the attenuation filter is designed in such a way that a multiplicity of different degrees of attenuation are provided, from which
a respective degree of attenuation is selectable and settable on the part of the user, or
a degree of attenuation is automatically selected and caused to be set by evaluation of a test image captured from the laser beam incident in the objective,
wherein
the attenuation filter is designed in such a way that a respective degree of attenuation is selectable and settable continuously variably in a wide degree-of-attenuation range, wherein the attenuation filter has at least one rotatably arranged linear polarizer, specifically two or more linear polarizers arranged rotatably relative to one another,
and/or
the attenuation filter extends substantially uniformly over an entire objective cross-sectional area as aperture.

3. The laser beam horizontal trueness testing device as claimed in claim 1 , wherein:
the telescope is designed in a diaphragm-free fashion, and the image sensor and the objective are arranged in a cooperating fashion in the telescope, in such a way that an incident laser beam is detectable by the image sensor over at least a wide part of the objective cross-sectional area as aperture.

4. The laser beam horizontal trueness testing device as claimed in claim 1 , wherein:
the telescope is designed in a diaphragm-free fashion, and the image sensor and the objective are arranged in a cooperating fashion in the telescope, in such a way that an incident laser beam is detectable by the image sensor over substantially over the entire objective cross-sectional area.

5. The laser beam horizontal trueness testing device as claimed in claim 1 , wherein:
the telescope furthermore has a focusing element disposed downstream of the objective in the beam path,
and/or
the inherent inclination compensator is designed
as an optomechanical self-leveler having an optomechanical element for the self-leveling of the optical axis of the telescope, said optomechanical element being arranged between the objective and the image sensor in the beam path of the telescope,
or
as an electronic inclination considerer having a high-precision inclination sensor for ascertaining a telescope inclination value dependent on a current inclination position of the telescope, wherein the telescope inclination value is automatically taken into consideration by the evaluation unit in the automatically conducted translation of the image position into the laser beam inclination value.

6. The laser beam horizontal trueness testing device as claimed in claim 1 , wherein the stored calibration parameters represent at least one of:
an imaging position of the optical axis in the image and, which represents an offset direction brought about hypothetically by a pure horizontality error of a laser beam impingement position on the image sensor,
a zero inclination line running substantially horizontally over the entire image region in the image in the image, and
a look-up table, from which an assigned laser beam inclination value is stored directly for respective image positions.

7. The laser beam horizontal trueness testing device as claimed in claim 6 , wherein:
for the translation
a distance is ascertained which is present in the image between the image position and the imaging position in that direction which is assumed as direction or is stored in the calibration parameters and which represents an offset direction brought about hypothetically by a pure horizontality error of a laser beam impingement position on the image sensor,
and said distance in accordance with a translation factor defined by the objective imaging ratio is translated into the laser beam inclination value, and/or
a distance is ascertained which is present in the image between the image position and the zero inclination line,
and said distance in accordance with a translation factor defined by the objective imaging ratio is translated into the laser beam inclination value, and/or
the laser beam inclination value assigned to the determined image position in the look-up table is read out,
wherein the laser beam inclination value is output as inclination angle of the laser beam.

8. The laser beam horizontal trueness testing device as claimed in claim 1 , wherein:
a pattern is in each case stored for different laser beam cross-sectional shapes in a memory retrievably for the evaluation unit,
a pattern corresponding to the laser beam cross-sectional shape of the incident laser beam is selectable on the part of the user or is automatically selected by image processing with feature recognition,
and by means of the evaluation unit when determining the image position
the selected pattern is matched on the basis of a best fit method in the image with the captured laser beam, and
on the basis of the matched position of the pattern in the image, the image position of the laser beam captured in the image is ascertained,
wherein information is concomitantly stored for each stored pattern, which information allows the derivation of a pattern-internally defined pattern position to be used for the ultimate determination of the image position within the pattern, specifically wherein the information is the pattern-internally defined pattern position itself or a defined pattern position ascertaining algorithm such as a pattern centroid ascertaining algorithm.

9. The laser beam horizontal trueness testing device as claimed in claim 8 , wherein
the selected pattern is matched with subpixel accuracy; and/or
the pattern comprises a stencil.

10. The laser beam horizontal trueness testing device as claimed in claim 1 , wherein:
the telescope furthermore has a beam splitter arranged in the beam path and serving for splitting the beam path into a first channel and a second channel in such a way that a first image plane of the objective is produced in the first channel and a second image plane of the objective is produced in the second channel, wherein
the image sensor is arranged in the first image plane, and
an optical unit carrying an indicator for the optical axis and an eyepiece disposed downstream of said optical unit and serving for a user's eye to view the intermediate image generated in the second image plane are arranged in the second image plane.

11. The

Assignees

• Leica Geosystems Ag

Inventors

• Dumoulin Charles Leopold Elisabeth
• Petermann Marco

Classifications

• G01C15/006

  Detectors therefor · CPC title

• G01C9/06

  Electric or photoelectric indication or reading means · CPC title

• G01C15/008 Primary

  combined with inclination sensor · CPC title