Summagraphics Corporation

Thomas C Zalenski

Jamie L Barbetti

Henry G Matthews

Al Mletzko

Alexander M Purcell

Robert M McDermott

A digitizer tablet providing hysteresis compensation in which the X and Y coordinates of a pointing device are measured at different times. In order to enable the tablet to report X and Y coordinates that when displayed will more accurately reflect the pointing device movements, a correction algorithm, built, for example, into the controlling software, estimates and reports what the first measured coordinate would have been, measured when the second coordinate is measured, based upon the calculated velocity and acceleration of the pointing device. A similar technique can be used to correct the reported value of the second coordinate. In a preferred embodiment, constant coefficients of a linear equation having as variables three consecutive coordinate values or three consecutive preprocessed coordinate values are predetermined and used in the correction algorithm. The preferred embodiment integrates the velocity and acceleration hysteresis compensation into a three point recursive noise filter.

Hysteresis compensation for a digitizer tablet

An electromagnetic digitizer tablet comprising an array of conductors having plural, spaced, similar active portions regularly and uniformly distributed throughout the active tablet region, together with additional structure to distinguish pointing device positions over the similar active portions. This arrangement reduces the number of individual conductors required. In a preferred arrangement, the active portions have a block S shape. As a further feature, novel algorithms are used to calculate the fine location of the pointing device.

Digitizer tablet with fixed incremented grid portions

A method for storing a k-bit output value for each of a plurality of m-bit input values in a memory having an n-bit word stored at each of 2.sup.n n-bit addresses, wherein m, n and k are positive integers, m&gt;n&gt;k and m-n.gtoreq.k, the method comprising the steps of storing a first k-bit output value corresponding to a first m-bit input value at a first n-bit address in the memory, and storing the 2n-m most significant bits of the first n-bit address at a second n-bit address, the stored 2n-m most significant bits of the first n-bit address occupying the 2n-m most significant bits at the second n-bit address, the first and second n-bit addresses being selected such that the n most significant bits of the first m-bit input value correspond to the n bits making up the second n-bit address and the m-n least significant bits of the first m-bit input value correspond to the m-n least significant bits making up the first n-bit address.

Method for retrieving compressed data from a memory storing a look-up

A digitizer tablet consuming less power than is required of current tablets comprises short duration fast rise time energizing pulses, and a resonant circuit in the induced signal detector tuned to the frequency of the pulse repetition rate or preferably a higher frequency. Peak detector or timed sample and hold circuits are connected to the resonant circuit to improve resolution and reduce noise.

Low power sensing apparatus for digitizer tablets

An electromagnetic digitizer system employing an interleaved array of individual conductors each in a W configuration bent into plural sections to define plural parallel portions distributed in different segments of a tablet such that each section comprises a center conductor portion connected in series with outer parallel portions such that the current in the center conductor portion splits or divides among the outer conductors and also flows in the opposite direction. Each of the plural sections defines two tablet coarse positions for a pointing device. Interpolation is employed to determine a fine position.

Digitizer tablet with split-current conductor array

A low-power electromagnetic digitizer table employing triangular-shaped electrodes arrayed in a single plane. A pointing device coil when energized induces signal voltages in the electrodes underneath. The electrodes are scanned in timed relation, and the induced voltages digitized and compared to determine the X/Y coordinates of the pointing device with respect to the electrode array.

Low-power electromagnetic digitizer tablet

An electro-optical mouse has a four-quadrant photodetector, each quadrant producing a voltage proportional to the amount of light impinging thereon. The mouse slides over a surface having optically contrasting, i.e. reflecting and nonreflecting, indicia thereon. The position of the mouse relative to a coordinate system in the plane of the surface is determined by projecting light onto the surface and then detecting the amount of light reflected from the surface onto the respective quadrants. The mouse is able to detect within which of four ranges the amount of light impinging on each quadrant lies. A two-bit code indicating the range is generated for each quadrant, thereby forming an eight-bit detector code. In the case where the eight-bit detector code is the same, i.e., ambiguous, for two different positions of the mouse relative to an indicium being optically detected, the true position at a current instant in time is identified by interpolating between the position at a previous instant in time and the position at a subsequent instant in time. This look-ahead routine is performed after the predetermined ambiguous detector code has been recognized and after a determination has been made that the position at the previous instant in time was not at or in the vicinity of one of the two positions corresponding to the ambiguous detector code.

Electro-optical mouse with improved resolution for compensation of

A conventional three-electrode wedge-and-strip pattern in a digitizer tablet surface is used with a conventional cursor or stylus. A phantom cursor electrode is located at predetermined coordinates of the active area of the digitizer tablet beneath the X, Y and balance (B) electrodes and separated therefrom by a layer of dielectric material, preferably an air gap. Prior to use of the digitizer apparatus, the phantom cursor electrode is electrostatically coupled to the X, Y and B electrodes in order to obtain data signals representing the phantom cursor's measured coordinates without compensation for resolution distortion. A microprocessor produces a correction factor using the data signals and the predefined coordinates of the phantom cursor electrode, which correction factor is applied in normal use to compensate for resolution distortion resulting from the unavoidable gaps between the X, Y and B electrodes. Also raw measured data obtained from the electrostatically coupled electrodes is adjusted to compensate for environmental and inherent noise and an offset corresponding to the difference in the reference potentials of the integrator and comparator.

Method and apparatus for calibration of a charge ratio digitizer

A method and apparatus for calibrating an electro-optical mouse during the detection of light reflected from a surface with optically contrasting indicia. The voltage output from the light detector is compared with stepped ramped sequences of reference voltage signals representing a count, the ramped sequence being stopped in response to each transition of the comparator between a first state where the amplitude of one of the input signals is less than that of the other and a second state where the amplitude of the one of the input signals is equal to or greater than the other. A processor determines the highest and lowest numbers at which any of the ramped sequences are stopped; and calculates at least one threshold value in dependence on the difference between the highest and lowest numbers.

Method and apparatus for calibrating an electro-optical mouse

A charge ratio tablet having three patterned electrodes for determining the position coordinates of a stylus relative to a first area on the tablet is provided with a menu in a second area. The menu includes first and second pluralities of menu electrodes, the three menu electrodes of the first pluralilty having a first geometric pattern and the three menu electrodes of the second pluralilty having a second geometric pattern. The patterned electrodes and menu electrodes are driven in accordance with a predetermined sequence. The processing circuitry determines the position coordinates of the stylus if the signal induced in the stylus in response to driving of the three patterned electrodes simultaneously has at least a predetermined magnitude. The processing circuitry carries out operations other than position coordinate determination if instead the stylus is capacitively coupled to a driven menu electrode. The processing circuitry discriminates which menu electrode is capacitively coupled to the stylus.

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Killingworth, CT, United States of America

Thomas C Zalenski