Reflective piano keyboard scanner
First Claim
1. An apparatus for measuring each distance from a plurality of sensors to a related movable surface associated with each said sensor, the apparatus having:
- a key decoder having a plurality of analog inputs and one or more control signals associated with each said analog input;
a reader having a plurality of n-way multiplexers, each said n-way multiplexer having n said sensors, each said sensor comprising an optical emitter oriented towards one of said movable surfaces and a photo-sensor oriented to receive reflected optical energy from the same said surface, each said optical emitter of said n-way multiplexer operative to a unique said key decoder control signal such that each said n-way multiplexer has only one said optical emitter and an associated said photo-transistor enabled during a particular interval of time;
said key decoder causing a particular said n-way multiplexer optical emitter to be enabled for a first duration T2 sufficient to measure from an associated said photo-sensor a LghtCmp plus ambient value for a particular movable surface, after which interval particular said n-way multiplexer optical emitter is disabled for a second duration T3 sufficient to measure an ambient value from same said photo-sensor, thereafter subtracting said ambient value to form said LghtCmp value, said key decoder deriving said distance from said LghtCmp value.
2 Assignments
0 Petitions
Accused Products
Abstract
A scanner for a keyboard device having a reflective surface for each key has a sensor associated with each key that includes an LED and a photo-transistor. The LED is turned ON for a first measurement, followed by a second measurement with the LED turned off, and a subtraction of the second measurement from the first yields an illumination value for a key x. The LEDs and associated photo-transistors are sequentially enabled in groups of n, thereby eliminating optical interference. Each key x has associated correction parameters of LinRest(x) associated with illumination value with the key in the rest (up) position, LinDown(x) associated with illumination value with the key in the down position, TrebErr(x) associated with the reflectivity effect of one adjacent key(x+1), and BassErr(x) associated with the reflectivity effect of another adjacent key(x−1). By reading a single illumination value in combination with these correction parameters, the key position may be accurately extracted and the effect of ambient light and surrounding key interference removed.
30 Citations
19 Claims
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1. An apparatus for measuring each distance from a plurality of sensors to a related movable surface associated with each said sensor, the apparatus having:
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a key decoder having a plurality of analog inputs and one or more control signals associated with each said analog input; a reader having a plurality of n-way multiplexers, each said n-way multiplexer having n said sensors, each said sensor comprising an optical emitter oriented towards one of said movable surfaces and a photo-sensor oriented to receive reflected optical energy from the same said surface, each said optical emitter of said n-way multiplexer operative to a unique said key decoder control signal such that each said n-way multiplexer has only one said optical emitter and an associated said photo-transistor enabled during a particular interval of time; said key decoder causing a particular said n-way multiplexer optical emitter to be enabled for a first duration T2 sufficient to measure from an associated said photo-sensor a LghtCmp plus ambient value for a particular movable surface, after which interval particular said n-way multiplexer optical emitter is disabled for a second duration T3 sufficient to measure an ambient value from same said photo-sensor, thereafter subtracting said ambient value to form said LghtCmp value, said key decoder deriving said distance from said LghtCmp value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for measuring each distance from a plurality of sensors to a related movable surface associated with each said sensor, the apparatus having:
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each sensor of said plurality of sensors related to a movable surface associated with said sensor, each sensor having an optical emitter part and a photo-sensor part, the photo-sensor part oriented to receive optical energy originating from said optical emitter part and directed to said movable surface, thereafter reflecting from said associated movable surface and to said photo-sensor, said photo-sensor also receiving optical energy reflected from adjacent movable surfaces and also receiving ambient light; whereby a range R of adjacent photo-sensors are commonly connected in parallel to form a single sensor responsive to optical energy reflected from said movable surfaces, and where only one of said optical emitters over said range R is enabled; and where a distance measurement from a photo-sensor to a particular movable surface is formed by; turning on a particular one of said optical emitters in said range R for a duration T2 and taking a first measurement over said range R of photo-sensors; turning off said particular optical emitter for a duration T3 and taking a second measurement over said range R of photo-sensors; forming a distance measurement for said particular measurement by subtracting said second measurement from said first measurement. - View Dependent Claims (14, 15, 16, 17, 18)
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19. An apparatus for the measurement of each distance from a plurality of sensors to a movable surface associated with a particular sensor, each sensor having an optical emitter part and an optical detector part;
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said optical detectors receiving and summing reflected optical energy over a range of R said sensors; each said optical emitter exclusively active during an interval when other adjacent optical emitters are not active; each said optical detector receiving optical energy reflected from an associated said movable surface and also optical energy reflected from adjacent movable surfaces; a rest measurement and a down measurement associated with each movable surface and associated optical detector; a distance computer for computing a distance measurement using the optical detector measurement from a particular key and correcting said measurement using optical detector measurements from said R adjacent sensors.
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Specification