Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Patent
1995-11-08
1998-04-21
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
25055924, 250236, 356380, G01N 2186
Patent
active
057420688
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an apparatus for measuring the distance to one or more areas of an object in order to determine one or more dimensions of said object, comprising means for directing a light beam towards the object, means for registering the light beams that are reflected from the object, means for calculating the time it takes for the beams to travel to and from the object, and means causing the light beam to sweep over the object perpendicular in relation to a fixed reference plane during the entire sweeping operation, and with relative movement between the apparatus and the object to be measured, the light that is reflected by the object being transmitted back to the light registration means via said light beam sweeping means, and said light beam sweeping means including a stationary mirror which is arced in its longitudinal direction, and also means, e.g. a rotatable mirror, which causes the light beam to move over the stationary mirror.
PROBLEMS OF THE RELATED TECHNOLOGY AND OBJECTS OF THE INVENTION
An apparatus of this kind is known from U.S. Pat. 4,996,440. This known solution includes a pitch in the scanning arc which corresponds to the radius of curvature of the stationary mirror. This means that the measuring apparatus must move over an unduly long distance which corresponds to the length of the object plus twice the length of said radius of curvature.
It is therefore an objective of the present invention to reduce the radius of curvature and thereby make the measuring apparatus as compact as possible.
In the known solutions, it is intended that the distance be measured from the measuring apparatus and down towards the underlying support along parallel, vertical light paths. However, in is not always easy to obtain such vertical and parallel paths of measurement. This makes great demands on the measuring optics. With the present invention, it is thus intended to obtain parallel paths of measurement of this kind, and also to ensure that it is possible to continuously calibrate the distance measuring apparatus while in operation.
One objective of measuring by means of parallel, vertical lines is, inter alia, that the position of the point of measurement will not be dependent upon the vertical distance of movement of the light. In addition, it is desirable that a reflecting component in the surface of the object will at one point at least, namely the highest point, reflect the light back to the measuring apparatus. Furthermore, a principal objective of the present invention is to avoid fields of shadow.
One of the known problems with distance reading apparatus is to be able to shield a light detector in such a way that one prevents or compensates for unwanted reflected rays or so-called scattered light in such a way that light of this kind does not reach the detector. The present invention provides a solution which enables this problem to be overcome.
Moreover, to be able to finely adjust the position and/or focus of a lens unit of a diode laser in a simple way is known to be a problem. The present invention aims also to provide a means to enable this to be accomplished.
BRIEF DESCRIPTION OF THE DRAWING
The characteristic features of the invention will become apparent in the patent claims hereinbelow and also in the specification with reference to the enclosed drawings.
FIG. 1 illustrates one use of the invention in a typical working situation.
FIG. 2 illustrates the problems linked with "fields of shadow".
FIG. 3 illustrates the measuring principle of a laser distance reader.
FIGS. 4A and 4B show the pitch and gauge length in connection with the prior art, e.g., as disclosed in U.S. Pat. 4,996,440, and FIGS. 5A and 5B show the pitch of the scanning arc and the gauge length, according to the invention.
FIGS. 6, 7, 8, 9 and 10 show in perspective view, in side view, plan view, side view and from above, respectively, details of the measuring principle according to the invention.
FIGS. 11 and 12 illustrate in detail a polygonal mirror unit seen from below a
REFERENCES:
patent: 3529884 (1970-09-01), Ives et al.
patent: 3943361 (1976-03-01), Miller
patent: 4433894 (1984-02-01), Hanson et al.
patent: 4684252 (1987-08-01), Makiguchi et al.
patent: 4692629 (1987-09-01), Nakamura
patent: 4996440 (1991-02-01), Nordbryhn
patent: 5005928 (1991-04-01), Suzuki et al.
patent: 5416630 (1995-05-01), Ito et al.
Dybdahl Stig
Holte Stian
L.o slashed.ken Morten
S.o slashed.rensen Einar
Slettemoen Gudmunn
Cargoscan A/S
Pyo Kevin
Westin Edward P.
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