Coarse position digitizer

Claim 2

Apparatus for determining the distance of a point on a surface from an axis on said surface comprising a cursor having a magnetisable element adapted to be energized by an alternating voltage, a grid of substantially parallel spaced conductors, said cursor being movable thereover and inductively coupled thereto, means for sequentially enabling only one of said conductors to conduct a current induced by said alternating voltage at any one time, means for comparing percentages of the amplitudes of currents induced in successively enabled conductors, means for sensing a change in the phase of said induced current, and means responsive to said comparing means and said sensing means for counting the number of conductors which have been enabled at the time a phase change is sensed.

Claim 3

Apparatus for determining the distance of a point on a surface from an axis on said surface comprising a grid adjacent said surface and including a plurality of substantially parallel spaced conductors, a cursor moveable over said surface and having an element adapted to generate a multidirectional magnetic field thereabout, said magnetic field having adjacent first and second regions with oppositely directed components of said magnetic field for inducing electric currents in proximate ones of said conductors, the currents induced in conductors closest to said first region having one phase and the current induced in conductors closest to said second region having a different phase, a phase shift detector having an input and an output, a plurality of normally open switching devices, one in circuit with each respective conductor and said phase shift detector input, each switching device completing a circuit between its respective conductor and said phase shift detector input when closed and interrupting said circuit when open, switch actuation means for closing and then opening each of the switching devices sequentially in one recurring switching cycle so that current can flow in only one of said conductors at any given time, means for comparing percentages of the amplitudes of successive currents induced in said conductors upon the closing of said switching devices, and a counter responsive to the commencement of each switching cycle for beginning to count and to the output of said phase shift detector for storing said count when the current applied to the input of said phase shift detector changes phase, the stored count being proportional to the distance of said cursor from said axis, said stored count also being dependent on the output of said comparing means.

Claim 4

Apparatus for determining the distance of a point on a surface from an axis on said surface comprising a grid adjacent said surface and including a plurality of substantially parallel spaced conductors, a cursor moveable over said surface and having an element adapted to generate a multidirectional magnetic field thereabout, said magnetic field having adjacent first and second regions with oppositely directed components of said magnetic field for inducing electric currents in proximate ones of said conductors, the currents induced in conductors closest to said first region having one phase and the current induced in conductors closest to said second region having a different phase, a phase shift detector having an input and an output, a plurality of normally open switching devices, one in circuit with each respective conductor and said phase shift detector input, each switching device completing a circuit between its respective conductor and said phase shift detector input when closed and interrupting said circuit when open, switch actuation means for closing and then opening each of the switching devices sequentially in one recurring switching cycle so that current can flow in only one of said conductors at any given time, means for comparing percentages of the amplitudes of successive currents induced in said conductors upon the closing of said switching devices, and a counter responsive to the commencement of each switching cycle for beginning to count and to the output of said phase shift detector for storing said count when the current applied to the input of said phase shift detector changes phase, the stored count being proportional to the distance of said cursor from said axis, said stored count also being dependent on the output of said comparing means.

Claim 5

Apparatus according to claim 2 wherein said conductors are substantially equally spaced and parallel to said axis.

Claim 6

Apparatus according to claim 2 wherein said cursor has a circular core about which there is wound a coil adapted to be excited by an alternating voltage.

Claim 7

Apparatus according to claim 4 wherein said switching devices are actuated at a frequency proportional to the frequency of said alternating voltage.

Claim 8

Apparatus according to claim 5 wherein said actuating means is responsive to said alternating voltage for sequentially actuating said switching devices.

Claim 9

Apparatus according to any of claims 2 through 6 wherein said one current phase and said different current phase are substantially 180° apart.

Claim 10

In apparatus for determing the distance of a point on a surface from an axis on said surface wherein there is a first planar grid structure having pairs of spaced parallel elements defining adjacent cycles of said grid, a cursor moveable over said surface, and fine measurement means responsive to signals transmitted between said cursor and said grid for determining the penetration distance of said cursor into said grid cycle in which said cursor is disposed the improvement comprising means for determining the grid cycle in which said cursor is disposed including a second planar grid adjacent said first grid, said second grid including a plurality of substantially parallel conductors adjacent ones of which are spaced apart a distance equal to the distance of one of said first grid cycles and defining cycles of said second grid in substantial alignment with said first grid cycles, a phase shift detector having an input and an output, a plurality of normally open switching devices, one in circuit with each respective conductor of said second grid and said phase shift detector, each switching device completing a circuit between its respective conductor and said phase shift detector when closed and interrupting said circuit when open, switch actuator means for closing and then opening each of the switching devices sequentially in one recurring switching cycle so that current can flow in only one of said conductors at any given time, and a counter responsive to the commencement of each switching cycle for beginning to count and to said phase shift detector for storing said count in response to the current applied to the input of said phase shift detector changing phase, the stored count being proportional to the distance of said cursor from said axis.

Claim 11

In apparatus for determing the distance of a point on a surface from an axis on said surface wherein there is a first planar grid structure having pairs of spaced parallel elements defining adjacent cycles of said grid, a cursor moveable over said surface, and fine measurement means responsive to signals transmitted between said cursor and said grid for determining the penetration distance of said cursor into said grid cycle in which said cursor is disposed the improvement comprising means for determining the grid cycle in which said cursor is disposed including a second planar grid adjacent said first grid, said second grid including a plurality of substantially parallel conductors adjacent ones of which are spaced apart a distance equal to the distance of one of said first grid cycles and defining cycles of said second grid in substantial alignment with said first grid cycles, a phase shift detector having an input and an output, a plurality of normally open switching devices, one in circuit with each respective conductor of said second grid and said phase shift detector, each switching device completing a circuit between its respective conductor and said phase shift detector when closed and interrupting said circuit when open, switch actuator means for closing and then opening each of the switching devices sequentially in one recurring switching cycle so that current can flow in only one of said conductors at any given time, and a counter responsive to the commencement of each switching cycle for beginning to count and to said phase shift detector for storing said count in response to the current applied to the input of said phase shift detector changing phase, the stored count being proportional to the distance of said cursor from said axis.

Claim 12

Apparatus according to claim 8 further comprising means for determining the one of two adjacent cycles of said second grid over which said cursor is disposed when said cursor is proximate an element of said second grid separating said adjacent grid cycles comprising first means for determining which of said grid elements conducted said current which said phase shift detector detected as changing phase, second means responsive to said penetration distance determining means for indicating that the cursor is in the one of said two adjacent grid cycles nearest said axis when the grid cycle penetration distance is more than one half the distance of a cycle of said first grid and for indicating that the cursor is in the one of said two adjacent grid cycles farthest from said axis when the grid cycle penetration distance is less than one half the distance of a cycle of said first grid, third means for decrementing said stored count when said next adjacent element conducted said phase shift detected current, and said cursor is in said nearest cycle, and fourth means for incrementing said stored count when said grid element conducted said phase shift detected current and said cursor is in said farthest grid cycle.

Claim 13

Apparatus according to claim 9 wherein said first means comprises means for comparing a percentage of the peak amplitude of a cycle of said current with the amplitude of the next succeeding cycle of said current and having an output signal of one magnitude when said peak amplitude is exceeded and another value when said peak amplitude is not exceeded, and means for determining the value of said comparator output signal at the time said count is stored, said value being indicative of the grid element conducting the current in which a phase shift was detected by said phase shift detector.