US 5,317,502 A · High resolution system for sensing spatial coordinates

Abstract

An improved high resolution method and apparatus are described for sensing and determining the spatial coordinates of a movable object with respect to a energized conductive surface. The coordinates of the object are precisely measured with respect to a two-dimensional coordinate system independent of the third orthogonal dimension, thereby avoiding significant measurement errors due to variations of the object position in the third orthogonal dimension. The system also ascertains the coordinate position of the object in this third dimension, which can then be utilized as an independent control variable in the system. Further, the system can accommodate a number of energized conductive surfaces over which the object may be positioned and can determine the spatial coordinates of the object with respect to any such surface. In general, the system of the present invention can ascertain the generalized n-tuple position vector of the object with respect to each of a plurality of generalized, energized conductive surfaces. In any of the foregoing forms, the energized conductive surfaces can be transparent. The system described improves the precision and accuracy of the location of the selected point and hence the precision and accuracy of the spatial coordinates calculated by the system for display. The improvement in system performance is the result of innovations in fundamental design concepts utilized throughout the system.

Claims19

Dependent claims

An apparatus for determining the spatial position of a probe with respect to a surface, comprising:

drive means connected to the surface for providing alternating electrical current in the surface in predetermined directions and at predetermined intervals of time;
means for detecting and amplifying alternating electrical signals produced in the surface, the detected and amplified signals varying depending upon the position of the probe with respect to the surface;
rectifying means connected to the detect and amplify means for controllably rectifying the detected and amplified alternating electrical signals and for providing rectified electrical output signals, wherein the rectifying means during periodic intervals does not provide rectified electrical output signals;
integrating means for periodically integrating the rectified electrical output signals output form the rectifying means and for producing output signals in response to the rectified electrical output signals;
analog-to-digital converter means for producing digital signals in response to the output signals of the integrating means;
processing means connected to the analog-to-digital converter means for calculating the spatial position of the probe with respect to the surface based on the digital signals produced by the analog-to-digital converter means;
and
control means for generating control signals for controlling the drive means, rectifying means, integrating means and processing means, wherein the integrating means is reset in a periodic interval during which the rectifying means is not providing rectified electrical output signals.

5 more elements

A method for determining the spatial position of a probe with respect to a surface, comprising the steps of:

providing alternating electrical current int he surface in predetermined directions and at predetermined intervals of time;
detecting alternating electrical signals, the detected alternating electrical signals varying depending upon the position of the probe with respect to the surface;
rectifying the detected alternating electrical signals to produce rectified electrical output signals, wherein rectified electrical output signals are not produced during periodic intervals;
periodically integrating the rectified electrical output signals with an integrator and producing integrated output signals in response to the rectified electrical output signals;
resetting the integrator during intervals in which rectified electrical output signals are not produced;
producing digital signals tin response to the integrated output signals;
and
calculating the spatial position of the probe with respect to the surface in response to the digital signals.

5 more elements

Dependencies are inferred from the claim text.

High resolution system for sensing spatial coordinates

Life of this patent

High resolution system for sensing spatial coordinates

Life of this patent

Abstract

Claims19