Optics: measuring and testing – Angle measuring or angular axial alignment – Apex of angle at observing or detecting station
Patent
1990-10-09
1993-03-23
Buczinski, Stephen C.
Optics: measuring and testing
Angle measuring or angular axial alignment
Apex of angle at observing or detecting station
356 1, 356152, 356375, 356376, G01B 1126, G01B 1124, G01C 100
Patent
active
051969009
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an opto-electronic angle measurement device, methods for calibration of said device for two-dimensional (spatial) angle measurements, and use of said device in position and geometry measurement systems, as well as an opto-electronic system for simultaneous measurements of the three dimensional coordinates of a plurality of points on a surface.
More specifically the invention relates to an opto-electronic sensor for measuring directions in two dimensions to point sized active light sources or to points illuminated by light sources. Said opto-electronic angle measurement device is calibrated once and for all for angle measurements in two dimensions (spatial direction) towards light sources or light reflecting points illuminated by one or more light sources, using a high precision angle reference.
Furthermore, the invention relates to a general opto-electronic system for spatial coordinate measurements for one or more light sources or light reflecting points illuminated by one or more light sources, including at least two angle sensors. Said system is applied for noncontact measurements of object position, orientation, and/or surface geometry.
The invention includes a method to determine the location of the rotational axes of the lens-system of said opto-electronic sensor, as well as methods for calibrating said opto-electronic sensor for measuring the angular direction in two dimensions to a light source or to a point illuminated by a light source.
Furthermore, the invention relates to an opto-electronic system for simultaneous measurement of the coordinates of a plurality of points on a surface, comprising a device designed to project a plurality of light spots on a surface in combination with angle sensors. This device consists of one or two gratings, dividing a collimated light beam into multiple beams which are focused to a pattern of point sized light spots on the surface, e.g. as described in Applied Optics, Vol. 23, No. 2, Jan. 15, 1984, pages 330-332.
DESCRIPTION OF THE RELATED ART
Non contact angle measurements are conventionally done by using a theodolite which is aimed manually at the target. The state of the art in this field is fully automatic, serve controlled theodolites as manufactured by Kern and Wild Leitz. Such devices can be automatically aimed at targets of known shape if the approximate positions of the targets are known. Thereby angles in two dimensions can be read automatically. The fact that the theodolite is physically directed towards each target using a servomotor system, means that the system has a very limited measurement frequency.
Non-contact, automatic geometry measurements are in great demand for surface profile surveying, e.g. in automotive industry. Today, mechanical coordinate measurement machines (CMM's) are used for these applications. CMM's are expensive, complex, inflexible and most of them are in direct contact with the surface. These limitations make them unapplicable in production line setups, hence, present quality control is based on spot testing by templates.
Present opto-electronic systems can be divided in three categories according to their measurement principle: structured light, range measurements (optical radar) and triangulation techniques.
Structured light techniques are based on projection of light spots or lines onto a surface to measure its shape, e.g. Moire-techniques. Common characteristics of these techniques are that the image of the projected pattern is registered using video cameras or conventional photography, and that a reference surface or an image of a reference pattern is needed to calibrate the system in its actual setup.
Range measuring techniques, usually based on measuring the time of flight of a laser pulse, have a very high depth resolution, but low lateral resolution and a limited measurement field.
Several companies manufacture opto-electronic systems based on triangulation, e.g. Seatex in Norway or Sagem in France. Their systems use a single opto-electronic sensor, and inc
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Machida et al., "High-efficiency fiber grating for producing multiple beams of uniform intensity", Applied Optics, vol. 23, No. 2, Jan. 15, 1984.
Buczinski Stephen C.
Metronor A.S.
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