Tacheometer telescope

Details Tacheometer telescope Tacheometer telescope

2000-08-25

2003-01-07

Buczinski, Stephen C. (Department: 3662)

Optics: measuring and testing

Range or remote distance finding

With photodetection

C356S004010, C356S141100

Reexamination Certificate

active

06504602

ABSTRACT:

The invention relates to a tacheometer telescope according to the precharacterizing clause of claim
1
. Such a telescope system is disclosed in the patent application of the present Applicant, submitted to the German Patent Office on 2.9.1998.
Tacheometers are defined as theodolites with integrated distance meters. For distance measurement, either a reflector is mounted on the target object (cooperative target object) and sighted either manually or with the aid of automatic target recognition or a natural target object without such target marking (noncooperative target object) is sighted manually. In spite of the rapid development of electrooptical distance meters (EDM) during the past twenty years, however, very few tacheometers measuring without reflectors are commercially available today. Where there was a need for these, virtually all apparatuses measuring without reflectors and developed for the geodetics sector were in fact realized as add-on distance meters for technical reasons, such add-on instruments being mounted on the respective theodolites by means of a mechanical or electromechanical adapter.
As a result of the design according to the above-mentioned patent application submitted on 2.9.1998, both cooperative and noncooperative target objects can be recognized. It is true that tacheometers having integrated electrooptical distance meters measuring without reflectors are already known per se (ZEISS REC Eita-RL). Such apparatuses are also used both for surveying cooperative target objects and for measuring distances to objects having natural rough surfaces, for example for surveying poorly accessible surfaces, as in quarries, tunnel profiles, road profiles, building facades, etc.
Distance meters measuring without reflectors are as a rule based on the principle of measurement of the transit time of an emitted optical radiation pulse. Compact apparatuses with economical energy consumption always use a pulsed laser diode with a peak output power of about 1 watt to more than 100 watt. In these apparatuses, pulsed infrared semiconductor laser diodes having large emitting surfaces are used as a radiation source. A disadvantage arises from the relatively large dimensions of the emitting surfaces of these lasers, of the order of magnitude of 100 &mgr;m or more. This results in a radiation slope of this apparatus of about 1.5 mrad or more, with the result that a beam cross-section of as much as 15 cm is present at a distance of 100 m. Distances to structures which are smaller than 15 cm therefore cannot be measured. The physical reason for the large beam diameter is that the radiation sources used to date emit non-diffraction-limited radiation. On the other hand, one disadvantage of a radiation beam having a large cross-section is that, in the case of measurements to inclined or structured surfaces of the objects, it is not the true distance which is measured but a distance value intensity-weighted over the irradiated area, and hence the result of the measurement is falsified.
Another disadvantage of electrooptical distance meters measuring without reflectors is that, owing to the infrared or extensive measuring radiation, the object point actually sighted is not detectable. However, in order nevertheless to visualize the target location, it is necessary to use an additional beam, in particular a laser beam, with visible and diffraction-limited emission, whose beam axis must also be adjusted relative to the transmitted beam axis.
In addition to all these difficulties, it is also generally necessary, apart from the distance between the points, also to determine associated angles with geodetic accuracy, and to do so in a distance range from 0.1 m to about 2000 m or more. In general, it is desired to implement surveying tasks as ergonomically as possible. To meet this requirement, it was necessary to date to mark target points with reflection-supported means. Such cooperative target points can be sighted, for example, very rapidly by automatic target recognition (ATR) and surveyed using the conventional infrared distance meter. However, it is not always possible to mount a reflection-supporting means on the target object. Owing to obstacles which cannot be overcome, such as building heights, rivers, lack of authorization for access to plots, etc., certain target objects are not accessible and therefore cannot be marked by reflection means. Consequently, both target points having a natural surface and those which reflect have to be sighted in one and the same surveying task. This was not possible at all using known tacheometers. Apart from the disadvantage of not being able to provide simultaneously in a single instrument all sensors necessary in geodetic surveying tasks, which in any case complicates the surveying task, existing electronic theodolites have the additional deficiency of not complying with the required accuracy of measurement of 1 mm, in particular in distance measurement without reflectors.
A further complicating factor is a desirable miniaturization of a theodolite, i.e. housing a plurality of measuring components in a very small space. This is because even the theodolites equipped with few sensors, in particular theodolite telescopes, which are available at present have relatively large outer dimensions and are therefore heavy, impeding ergonomic use in the field. These are tacheometers with automatic target recognition (ATR) or theodolites having only one EDM measuring to targets without reflectors. In the past, this was certainly one of the reasons why no attempt was made to completely equip a single theodolite, and, where necessary, different measuring tasks were performed using different instruments. It is particularly difficult to miniaturize telescopes of those theodolites which are to have automatic target recognition, since the accuracy of measurement required in geodetic applications is typically 3 to 5 cc (=8 &mgr;rad) or 1 mm point resolution. Such accuracies are achievable only with long focal distances, which, in spite of additional optical components, results in a great constructional length of the optical system. However, shortening may impair the accuracy of angular measurement, in particular if the automatic target recognition is performed by means of a separate, for example biaxial, beam path separated from the visual channel (PCT-SE90-00233).
It is therefore the object of the invention to provide a telescope for an electronic—in particular motorized, preferably with respect to both axes—theodolite, by means of which the geodetic needs can be better covered. In particular, it is the object of the present invention, in addition to a visual telescope and a distance meter measuring only to reflecting target objects, for example an infrared distance meter, to design a diffraction-limited, reflectorless distance meter together with a miniaturized sensor unit for automatic target point recognition and to integrate it in a theodolite telescope.
The telescope equipped with sensors should have as small outer dimensions as possible in order to meet the requirements for convenience during field measurements. Furthermore, the energy consumption should be so low that battery operation is at least possible.
The special challenge of the object according to the invention is in particular to nest four optical channels of 4 independent sensors in one another in such a way that their function individually and in mutual cooperation is ensured. On the one hand, a sensor must operate satisfactorily by itself; on the other hand, the channels may not interfere with one another when functioning simultaneously.
According to the invention, the extension of the object for a telescope according to the precharacterizing clause of claim
1
is possible through the characterizing features of this Claim. This permits not only distance measurement to cooperative and noncooperative target objects but additionally angle determination, in particular cases alternatively with manual or automatic sighting. Thus, natural objects, such as rocks or trees, and buildings, churc

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