Optics: measuring and testing – Angle measuring or angular axial alignment – Apex of angle at observing or detecting station
Reexamination Certificate
2002-11-22
2003-11-04
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Angle measuring or angular axial alignment
Apex of angle at observing or detecting station
C356S004010, C356S004080, C356S141100, C356S152200
Reexamination Certificate
active
06643004
ABSTRACT:
This invention relates to field-deployable spatial positioning or measurement systems. Specifically, the present invention provides spatial positioning or measurement systems that use novel system hardware, calibration methods and transmission/detection modes to provide increased ease-of-use, better reliability, increased system longevity, easier calibration methods, wider usable range and improved versatility. As such, the spatial positioning or measurement systems according to the various embodiments of the present invention are capable of providing high resolution, reproducible and accurate spatial or position measurements in two or three dimensions thus allowing enhanced accuracy and utility for use in surveying and construction and manufacturing layout. The present invention may also be used for applications including spatial data generation for design of vehicular systems or vector and tensor mapping such as accumulating data relating to temperature, wind shear, electric fields, radiation flux, etc.
Present uses for field-deployable spatial positioning systems include construction layout such as setting reference points or setting control lines, asymptotes and similar geometric boundaries or guide lines; laying out parallel or perpendicular lines; measuring linear distances between points; navigating to specific points entered by a user; and establishing working planes. Such uses may include generation of level or sloped plane references for earthwork and site preparation; generation of vertical (plumb) plane references for tilt-up wall placement; and XY (2-D) or XYZ (3-D) coordinate measurement for positioning concrete forms, footers, and anchor bolts.
Additional uses for field-deployable spatial positioning systems include machine control or robotic applications, and transfer of measurement or spatial positioning data to and from CAD systems or databases.
Prior art field-deployable spatial positioning and measurement systems include those described in U.S. Pat. Nos. 4,874,238; 5,100,229; 5,110,202; 5,579,102; 5,461,473; 5,294,970; and 5,247,487, all of which are hereby incorporated by reference in their entirety. Spatial positioning systems described in these patent references usually comprise a single “laser transmitter” and a single “laser receiver”. The transmitter is placed at a fixed location and serves as a measurement reference or beacon for the receiver. The handheld receiver is carried by the user and displays in real-time the location of the receiver relative to the transmitter. Because of mathematical constraints, such a single-transmitter system is only capable of measuring the horizontal (azimuth) and vertical (elevation) angular location of the receiver; that is, no direct measurement of the range from the transmitter to receiver is possible. A more advanced system consists of two or more transmitters and a single receiver. The transmitters are again placed at fixed locations, and serve the same purpose as before. The receiver calculates its azimuth and elevation location relative to each transmitter. If the transmitters are at known locations, the receiver can then calculate its position in 3-D space using known methods and algorithms, e.g., see U.S. Pat. No. 5,100,229 as cited above. In either the single or multi-transmitter systems, multiple receivers may be used simultaneously with the same transmitter(s). This is possible since the transmitters only serve as a reference or beacon, in the same way that GPS satellites serve as a reference for many users. Calculations to determine the location of a given receiver take place in that receiver, not the transmitter(s).
As will be described more fully below, the primary components of a transmitter can include the following: a rotary laser head containing two laser assemblies; a spindle assembly including a motor and encoder for spinning the rotary laser head; an optical strobe assembly that functions as an azimuth reference to establish a “zero” angle for the azimuth angle; a gimbal assembly including level sensors and motors for leveling the rotary laser head; and control electronics needed to perform various functions including sensing, balancing, monitoring, position determination, user interfacing and data output. The rotary laser head contains two laser assemblies that produce two fanned infrared laser beams perpendicular to the spin axis of the head as described in the above-reference U.S. patents. The radial axes of the fan beams can be chosen to be separated by approximately 90 degrees (or other angle) around the head. The fan beams are also rotated approximately 30 degrees in opposite directions about their respective radial axes.
The rotating laser head is attached to the top end of a shaft through the spindle assembly. The lower end of the shaft is attached to a motor and rotary encoder. The motor spins the shaft, and thus the head at a known constant speed. The rotary encoder is used to sense the rotation speed of the shaft and provides feedback to the motor drive circuit in the control electronics.
As is described in the above-reference U.S. patents, an optical strobe assembly can be used to synchronize, or set a rotation datum for, the azimuthal angle swept by the fanned beams. This can be implemented as a ring of outward-facing IREDs (infrared emitting diodes) located just below the rotating laser head. The strobe is stationary, and mounted to the outside of the spindle assembly. Using feedback from the rotary encoder on the shaft, the control electronics cause the strobe to emit a very short flash of infrared light once per revolution of the head, or any other set interval. This flash is detected by the mobile receiver and used as a zero azimuth angle reference.
The gimbal assembly is attached to the outside of the spindle assembly, and connects it to the outer housing of the transmitter. The purpose of the gimbal assembly is to allow a tilt (in two axes) in a known manner of the rotary head spin axis relative to the outer housing. In most applications it is desirable, for reasons to be explained below, to plumb the spin axis of the head with respect to gravity (or to some other desired axis). If this is done, the radial axes of the fan lasers, which are perpendicular to the spin axis, will sweep through a plane that is level with respect to gravity. In order to plumb the spin axis, the control electronics reads the output of the level sensors, which are attached to the outside of the spindle assembly, and drives the motors of the gimbal assembly until the sensor outputs indicate that the spin axis is plumb. Well known electrolytic vials can be used as monitors in assisting this feedback function.
Control electronics govern the overall operation of the laser transmitter. As mentioned above, the electronics control the rotation speed of the head by using the rotary encoder output as feedback. The electronics further trigger the optical strobe once per revolution of the head and plumbs the spin axis by moving the gimbal assembly based on feedback from the level sensors.
The primary components of the receiver generally include the following: a detector such as a (photodiode) assembly for sensing the optical strobe and fan lasers from the transmitter(s); timing electronics for measuring the time between received pulses; a processor, such as a microprocessor, for calculating the location of the receiver; and a user interface such as a display and keypad. The detector or photodiode assembly produces an electrical output in response to the optical strobe signal from the transmitter(s). The detector or photodiode assembly also produces an output pulse whenever crossed by one of the rotating fan beams from a transmitter. For example, when the detector is in the vicinity of a single transmitter, the output for one complete rotation of the transmitter head can include times T
1
, T
2
, and Trev measured by timing electronics, where T
1
is the time between a (received) strobe light pulse and a first fanned laser beam; T
2
is the time between a strobe light pulse and a second fanned laser beam; and Tre
Corey Nathan A.
Denney James E.
Detweiler Philip L.
Douglas Frank B.
Jackson Jonathan A.
Buczinski Stephen C.
Killworth, Gottman Hagan & Schaeff LLP
Trimble Navigation Limited
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