Optics: measuring and testing – Angle measuring or angular axial alignment – Apex of angle at observing or detecting station
Reexamination Certificate
2000-03-21
2003-10-07
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Angle measuring or angular axial alignment
Apex of angle at observing or detecting station
C356S141500
Reexamination Certificate
active
06630993
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to the field of precise position measurement in a three-dimensional workspace and more particularly to an improved apparatus and method of providing position-related information.
2. Description of Related Art
A variety of endeavors require or are greatly aided by the ability to make a precise determination of position within a three-dimensional workspace. For example, laying out a construction site according to a blueprint requires the identification at the actual construction site of a number of actual positions that correspond to features of the building on the blueprint.
Despite the many applications which require or are advanced by the ability to make precise determinations of position, it has historically been relatively difficult or expensive to precisely fix the position of any given point relative to an origin in an actual three-dimensional workspace.
A variety of techniques are known in the art to measure position, including land surveying techniques and global positioning satellite (“GPS”) system techniques. However, these techniques generally are not precise or require expensive devices which are complex and difficult to manufacture with high precision and accuracy. Additionally, many of these techniques required extensive training, and therefore cannot be practiced by those not trained in the art. Land surveying techniques, for example, fix position using a precision instrument known as a theodolite. The theodolite is both an expensive piece of equipment and requires substantial training to use. GPS equipment is relatively easy to use, but can be expensive and has limited accuracy on a small scale due to a certain amount of intentional error that is introduced by the military operators of GPS satellites.
Consequently, there has long been a need in the art for a method and device that can quickly and accurately fix positions in a three-dimensional workspace. There is a further need in the art for such a method and device which is easy to use and does not require extensive training.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and device that can quickly and accurately fix positions in a three-dimensional workspace. It is a further object of the present invention to provide such a method and device that is easy to operate and does not require extensive training.
Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims.
To achieve these stated and other objects, the present invention may be embodied and described as a position fixing system that includes, at a high level, several transmitters and a receiving instrument. The transmitters are preferably optical transmitters that transmit laser beams that have been fanned into a plane. The transmitters transmit signals from stationary locations and the receivers receive these signals. Consequently, the receiving instrument incorporates sensors, e.g., light detectors, that detect the signals from the transmitters. The receiving instrument then determines a coordinate system and calculates its position and assorted other information of interest from these received signals. The receiving instrument then displays this information through a user interface. The information may be, for example, the location of the receiving instrument or its distance relative to another location.
Various Figs. are included throughout this disclosure to illustrate a variety of concepts, components of several subsystems, manufacturing processes, and assembly of several subsystems.
1. Transmitter
The transmitter of the present invention includes a rotating head which sweeps one or more, preferably two, fanned laser beams continually through the three-dimensional workspace in which the receiver will be used to make position determinations based on the optical signals received from the transmitter. In this way, the signals from the transmitter cover the entire three-dimensional workspace. The present invention can be used in conjunction with the techniques and apparatus described in previous patent application U.S. Ser. No. 99/23615 to Pratt, also assigned to the present assignee, filed on Oct. 13, 1999, and incorporated herein by reference.
A. Simplified Optical Path
The receiver preferably has a clear optical path to each transmitter in the system during position fixing operation. One of the key advantages of the transmitters according to the present invention is the simplification of the optical paths as exemplified by the lasers rotating with the head. Additionally, there is no window in the preferred transmitter. Therefore, there is no distortion introduced by the movement of the laser beam across a window. As described in detail below, the preferred embodiment utilizes a lens or other device which rotates with the laser. Thus, there is no distortion caused, for example, by variable window characteristics or angles of incidence or between a rotating lens and a fixed laser. The absence of a fixed window also simplifies manufacture, maintenance, and operation. The absence of a fixed window does make it preferable that a rotating seal be added to the transmitter.
B. Speed of Rotation and Storage of Parameters
The rotating head of the transmitter of the present invention, and the lasers within it, rotate through a full 360 degrees at a constant, although configurable, velocity. As will be explained below, each transmitter in the system needs to rotate at a different velocity. Therefore, each transmitter has a velocity that can be controlled by the user. Additionally, each transmitter has an easily quantifiable center of rotation which simplifies the algorithms for determining position and can simplify the set-up of the system. A separate synchronization signal, also preferably an optical signal, fires in the preferred embodiment once per every other revolution of the rotating head to assist the receiver in using the information received from the transmitter.
The velocity of the rotating head is configurable through the use of, in the preferred embodiment, a field programmable gate array (“FPGA”). Such configurable speed control allows transmitters to be differentiated by a receiver based on their differing speeds of rotation. The use of multiple transmitters, as is appreciated by those of ordinary skill in the art, enhances position detection. Other advantages are obtained through the use of programmable electronics (FPGAs, flash memory, etc). Not only can the desired speed be set by changing the clock to the phase locked loop that controls the speed of rotation of the optical head, but the overall gain of the control loop can be programmed to maximize performance at the velocity of interest.
C. Beam Type and Number
As described in the incorporated provisional and known in the art, position detection is also enhanced by using multiple beams and controlling the shape of those beams. These beams may be in the same rotating head assembly or in separate rotating head assemblies.
Two beams is the preferred number per rotating head assembly, however, more beams can be used. In particular, another embodiment uses four beams, two for short range and two for long range. The two short-range beams have fan angles as large as possible. This allows the user to operate near the transmitters, such as in a room. For long-range, the user would normally be operating away from the transmitters. Therefore, in that circumstance the vertical extent of the beams is reduced to maximize the range of the system. The beams are, preferably, generated by Class III lasers. However, the rotation of the beams reduces their average intensity to the fixed observer such that the transmitters can be classified as Class I laser devices. Safety features are integrated into the device to
Casteel Scott C.
Dornbusch Andrew
Gaff Doug
Hedges Thomas M.
Pendleton Edmund S.
Arc Second Inc.
Buczinski Stephen C.
Fish Paul W.
Nichols Steven L.
Rader Fishman & Grauer
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