Optics: measuring and testing – Range or remote distance finding – With photodetection
Reexamination Certificate
2003-01-17
2004-05-11
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
With photodetection
C356S141100, C356S141500
Reexamination Certificate
active
06734952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to surveying and geodetic measurements, and relates more particularly to a process and device for the automatic location of a reference marker, a receiver unit, a geodetic measuring device, and geodetic measurement systems.
2. Description of the Relevant Art
For a long time, there has existed the need, in connection with geodetic measurements, for automatically recognizing geodetic reference markers to be measured and located in the field, and, if possible, at the same time, obtaining a rough measurement. This necessity is even greater as a result of the tendency toward fully automatic integrated measuring systems.
Optical-electronic devices for the automatic location of geodetic reference markers or a retro reflector or a reflection foil are corresponding already used in various embodiments. Devices of this type thereby supplement the usual sensory measuring means usually employed in geodetic measuring work. The combination of a motorized theodolite with automatic marker detection provides substantial advantages.
Devices for finding markers and, therefore, also the present invention involve all measuring devices that are optically pointed to measuring points through directing means handled by humans.
The concept “geodetic measuring device” in this connection should generally be understood to be a measuring instrument that has devices for measuring or checking data with spatial references or also for pointing. Especially, this involves the measurement of distances and/or directions or the angles to a reference or measuring point. In addition, however, additional devices, for example, components for satellite-supported location determination (for example, GPS or GLONASS) may be present, which can be used for measurements in accordance with the invention. Here, geodetic measuring devices should be understood to mean theodolites, level or total stations, tachymeters with electronic angle measurements, and electronic optical distance measuring devices. Similarly, the device is suitable for use in specialized devices with similar functionality, for example, in military aiming circles or in industrial construction or process monitoring. These systems are thereby also included under the concept “geodetic measuring device.”
Automated theodolites commonly used today, as an example of a geodetic measuring device, are not only equipped with angle and distance sensors, but also with an optical-electronic marker seeking positioning and marker point measuring device, hereinafter called automatic marker locating unit (AZE). Such theodolites are capable of moving directly to the marking point and measuring the spatial coordinates. When operating perfectly, the time saved with such automated instruments is substantial. If, in addition, the system can be operated through remote control, for example, from the marking point as a one-man station, then the work efficiency and the savings in cost achieved thereby is even greater.
An essential component of these automated measuring instruments is AZE. Various solutions are known, such as CCD or CMOS cameras with image processing, optical-electronic position-sensitive semiconductor detectors (PSD); 4-quadrant diodes, acoustical-optical beam scanners, etc.
The primary function of this AZE includes the exact measurement of a reference mark or a reflector precise to the millimeter, over short and long distances, where distances in excess of 1000 m can also be measured. In order to achieve this mm precision, the seeking devices have the disadvantage of a limited sensor site view field. Only in the case of small to medium view fields of a few degrees can point precisions of <5 mm be achieved at 1000 m.
A substantial disadvantage of a small sensor view field is that the search for the marker is rendered more difficult, since the reference mark to be measured is often outside the view field at the beginning of a measurement. In many applications, especially in the short distance range, which does with a broad angle working field, an expanded sensor view field is advantageous.
Today, two methods are used in searching for markers. In one method, the sensor seeks the marker independently following a programmed algorithm or procedure; however, this takes time, due to the small field of view. In the second method, the search field is defined by the user, so that marker search proceeds in a more directed manner and takes less time; however, this has the disadvantage that the search field configuration must be reprogrammed every time the position changes.
A further disadvantage exists in following moved markers. In the case of tangential movements that are too rapid or jerky for the marker guidance of the automatic theodolite, it can occur that the marker leaves the view field of the marker detection device. Even a loss of the marker for a short time can then interfere with an efficient following process.
Further deficiencies in the case of devices with AZE in the state of technology are also the lack of robustness in the recognition of markers in the case of reflections by foreign markers. Foreign markers are those with a high degree of reflectivity, such as traffic signs. In marker recognition, the identification of the marker to be measured has not to date been satisfactorily solved, since especially the lack of robustness in solar reflections on objects with shiny surfaces has a disadvantageous effect.
While solar reflections on objects can be recognized with modern equipment, nevertheless the analysis necessary for this takes time, as a result of which the search process comes to a halt at every reflection.
In the case of rough-search sensors of the state of technology, due to the small sensor view field, the rough marker search requires too much time. The small view field, therefore, has effects that are out of proportion. In the first place, it has a smaller area of coverage of the environment, so that examining the search range requires a longer period of time. Secondly, the coverage must be done with a slower scan speed due to the shorter time that the object remains in the view field. A fan shape for the detection area of the sensors is, in this regard, more suitable, however the view fields, made up of fan angles of typically 1 to 5 degrees, is still much to small.
From the patent CH 676 042, a device is known with a fan-shaped transmitter and receiver, which is housed in a rotating measuring head. Light pulses are transmitted in a light fan from the transmitter unit; the reflected impulses are correspondingly evaluated with respect to angular information. However, this device has a substantial disadvantage of selecting not only the markers to be measured, but also outside interference objects. Such objects are, among other things, optically reflecting objects such as plate glass windows or traffic signs, and even sunlight reflected from motor vehicles.
An extension of the above marker search device for the rough determination of the marker coordinates is described in CH 676 041. In this case, a combination with an optical-electronic device is made for fine measurement. The actual marker search device sets up two fans that are perpendicular to each other, with which the location of the marker point is measured roughly. The subsequent fine measurement can then be carried out with the second device without the marker search procedure. The disadvantage of this combination is also the lack of robustness with respect to an erroneous locking in on foreign objects.
A further device is known from U.S. Pat. No. 6,046,800. A motorized theodolite, which is equipped with a sensor to detect the marker point coordinates, is revealed, consisting of one or two fan-shaped transmission bundles and two optical receiver channels. A special characteristic of this device consists of the fact that the optical axes of the transmitting channel and the two receivers lie triaxially in a single plane. This makes it possible to differentiate between normal reflecting and retro reflecting objec
Bayer Gerhard
Benz Paul
Buerki Marcel
Geser Markus
Graf Roland
Buczinski Stephen C.
Leica Geosystems AG
Stallman & Pollock LLP
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