Electromagnetic position transducer having active transmitting stylus
First Claim
1. A position transducer comprising:
- (a) a helical electrically conductive tablet coil having a plurality of coil turns and first and second end extremities, and a plurality of coil tap nodes thereon, the coil tap nodes being spaced between the end extremities;
(b) selector means for sequentially addressing selected ones of the coil tap nodes;
(c) a transducer body movable in a first transducer direction relative to the tablet coil and having a stylus coil fixedly mounted thereto; and
(d) oscillator means for producing a coil drive current in one of the tablet coil and the stylus coil, the oscillator means being connected to the tablet coil, the coil drive current flowing in opposite directions on opposite sides of each selected tap node;
(e) circuit means connected to the selector means and responsive to the stylus coil for providing a first position signal, the first position signal representing the position of the transducer body relative to a first position reference, the first position reference being perpendicular to the first direction.
3 Assignments
0 Petitions
Accused Products
Abstract
Disclosed is electromagnetic transducer (10) that does not require complex analog to digital, digital to analog converters, microprocessors or large memory circuitry. The transducer has a helical tablet coil (22) with tap nodes (24) spaced between its end extremities (26). In one configuration, an oscillator (42) drives the tablet coil for simultaneously producing oppositely directed currents on opposite sides of selected taps, creating a moving fringing field (34) that is compatible with modern graphic display tablet technology. A control circuit (40) of the transducer has a closed-loop integrator (82, 106) for detecting the centroid of a received stylus signal (AC) from a stylus coil (36). Analog and digital versions of the integrator are disclosed. In another configuration, the oscillator (174, 175, 176, 177) drives the stylus coil (162) for variably coupling magnetic flux to the tablet coil, a receiver signal (190) that is coupled from the end extremities being responsive to the position of the stylus coil and the taps selected. A preferred configuration of the tablet coil has separate oppositely wound coil components ( 22a, 22b).
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Citations
26 Claims
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1. A position transducer comprising:
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(a) a helical electrically conductive tablet coil having a plurality of coil turns and first and second end extremities, and a plurality of coil tap nodes thereon, the coil tap nodes being spaced between the end extremities; (b) selector means for sequentially addressing selected ones of the coil tap nodes; (c) a transducer body movable in a first transducer direction relative to the tablet coil and having a stylus coil fixedly mounted thereto; and (d) oscillator means for producing a coil drive current in one of the tablet coil and the stylus coil, the oscillator means being connected to the tablet coil, the coil drive current flowing in opposite directions on opposite sides of each selected tap node; (e) circuit means connected to the selector means and responsive to the stylus coil for providing a first position signal, the first position signal representing the position of the transducer body relative to a first position reference, the first position reference being perpendicular to the first direction. - View Dependent Claims (2, 3, 4, 5)
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6. A position transducer comprising:
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(a) a helical electrically conductive tablet coil having a plurality of coil turns and first and second end extremities, and a plurality of coil tap nodes thereon, the coil tap nodes being spaced between the end extremities; (b) selector means for sequentially addressing selected ones of the coil tap nodes; (c) a transducer body movable in a first transducer direction relative to the tablet coil and having a stylus coil fixedly mounted thereto; (d) oscillator means for producing a coil drive current in one of the tablet coil and the stylus coil, the oscillator means being connected to the stylus coil for magnetically coupling a stylus field to the tablet coil; (e) circuit means connected to the selector means and responsive to the stylus coil for providing a first position signal, the first position signal representing the position of the transducer body relative to a first position reference, the first position reference being perpendicular to the first direction, the circuit means comprising a receiver node electrically coupled to the end extremities of the tablet coil, a receiver signal at the receiver node being responsive to the magnitude of the stylus field at the tablet coil; (f) an auxiliary coil fixably located relative to the tablet coil for providing an auxiliary signal in response to magnetic coupling from the stylus field; and (g) a substantially planar conductive shield member for blocking electrical field interference between the transducer and external devices, the shield member being fixably located opposite the tablet coil from the body, and a planar tablet surface capable of slidably supporting the body proximate the tablet coil, and wherein the auxiliary coil is located between the shield member and the tablet surface, the auxiliary coil having a plurality of serially-connected turns including; (i) a first turn extending in an x-direction parallel to the first transducer direction, and in an orthogonally oriented y-direction parallel to the shield member, the first turn substantially enclosing the tablet coil; (ii) a second turn extending in the x-direction to proximate congruence with opposite ends of the first turn, the second turn extending a substantially reduced distance in the y-direction between opposite sides of the first turn; and (iii) a third turn extending in the y-direction to proximate congruence with the opposite sides of the first turn, the third turn extending a substantially reduced distance in the x-direction between the opposite ends of the first turn. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A position transducer comprising:
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(a) a tablet circuit in association with a tablet domain; (b) a stylus that is wirelessly coupled to the tablet circuit; (c) timer means in the stylus for generating timer signals; and (d) means for synchronizing the tablet circuit in response to the timer signals, whereby the tablet circuit is responsive to movement of the stylus relative thereto, the tablet circuit being operative for generating respective X and Y coordinate measurements of the position of the stylus in corresponding scan intervals, the scan intervals being sequentially initiated in response to the timer signal. - View Dependent Claims (23, 24, 25)
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26. A position transducer comprising:
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(a) a tablet circuit in association with a tablet domain; (b) a stylus that is wirelessly coupled to the tablet circuit, the stylus comprising auxiliary control circuit means; (c) timer means in the stylus for generating timer signals, the timer being responsive to the auxiliary control circuit means, the tablet circuit including means for generating at least one auxiliary output in response to the timer means, the auxiliary output corresponding to operation of the auxiliary control circuit means, the timer signals being operative for activating an oscillator within the stylus during a scan interval, the oscillator being inactive during a first timer interval, the first timer interval being responsive to the auxiliary control circuit means; and (d) means for synchronizing the tablet circuit in response to the timer signals, whereby the tablet circuit is responsive to movement of the stylus relative thereto.
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Specification