Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1996-12-19
1998-06-23
Evans, F. L.
Optics: measuring and testing
By polarized light examination
With light attenuation
33293, G01B 1100, G01C 1502
Patent
active
057710996
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The invention relates to an optical device for determining the location of a reflective target, having a spotlight for illuminating the target, an imaging system for imaging the target onto a position-resolving detector device and an evaluation device for determining the position coordinates of the target image.
U.S. Pat. No. 3,188,739 discloses a target which is a transparent sphere having a marked center. The marking is carried out by means of a drilling along a radial line of the sphere as far as the center of the sphere. In addition, the marking of the center of the sphere can be reinforced by illuminating the drilled hole. Another possibility for marking results from the use of luminescent materials which are melted into the center of the sphere. Using spheres marked in this way, a determination of the distance between two points in space is possible in a known way by means of triangulation with the aid of theodolites.
German Publication DE 40 13 576 Al discloses an opaque glass sphere which is used as a target for determining measurement points using optical sights. As a result of the translucent, light-scattering material of the sphere, a homogeneous lightness of the sphere surface is achieved, which makes sighting from a large angular range possible.
U.S. Pat. No. 5,207,003 describes a target having at least four conventional retroreflectors and a spherical reflector, with which the three-dimensional position and the angular location of the target is measured. For this purpose, the target is illuminated by a light source via a semitransparent scattering mirror. The light reflected from the spherical reflector and the four retroreflectors passes via some optics to a photographic detector. In this case, the center of curvature of the spherical reflector and the retroreflectors are imaged as spots of light. From the coordinates of these spots of light on the detector, the three-dimensional position and the angular location of the target and the object connected to it are determined by computation.
Further optical devices of the said type are known and extensively represented in the publication Technische Rundschau No. 39, 1988, pp. 14-18 under the title "Theodolitsysteme fur industrielle und geodatische by W. Huep, O. Katowski, and in the publication Opticus No. 1/94, pp. 8-9 from Leica AG in an article under the title "Theodolite-Sensoren fur die
The theodolite systems which are described in these publications are employed for the non-contacting surveying of surfaces such as, for example, the panels of aircraft or car body parts. The theodolite systems used have a compact structure with a theodolite telescope as an imaging system, a spotlight arranged coaxially therewith for illuminating the target, a video camera with a CCD array and an electronic evaluation device, which may also contain an image processing computer and appropriate software. In addition, the theodolite system may also be equipped with a distance measuring device.
The theodolite systems are equipped with electronic circular taps and motorized drives for the horizontal and vertical adjustments of the telescope, with the result that an automatic, remotely controlled measurement sequence is possible. The horizontal and vertical angles indicate the directions to the targets in a given coordinate system.
In order to achieve an objective and precise measurement of direction, the video camera is used with the inclusion of image processing algorithms. The target image produced on the CCD array of the camera is evaluated with the aid of suitable algorithms and the center of the target image is determined. The coordinates of this center on the CCD array are then converted by means of software into displacement angles which, together with electronic circle read-outs yield the direction to the target.
Using the measurements of direction, the three-dimensional target coordinates are in turn determined if there is additional information. In the case of the polar method, a distance measurement is undertaken in addition to the angular m
REFERENCES:
patent: 3188739 (1965-06-01), Olsen et al.
patent: 5207003 (1993-05-01), Yamada et al.
Huep et al., "Theodolite Systems For Industrial And Geodatic Measurements", Technische Rundschau, No. 39:14-18, (1988).
"Theodolites-Sensors For Industrial Surveying", Opticus No. 1/94, pp. 8-9 from Leica AG.
Evans F. L.
Leica AG
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