US 8,013,234 B1 · Reflective piano keyboard scanner

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.

Claims20

Dependent claims

A method for reducing crosstalk from an adjacent movable bass surface and an adjacent movable treble surface to a movable current surface, the movable bass, movable treble, and movable current surfaces a subset of an array of movable surfaces, the method comprising:

associating with each said movable bass, treble, and current surface:
a BassErr value;
a TrebErr value;
a linearized and normalized measurement NormLinPos for each said current, said bass, and said treble movable surface, each said measurement NormLinPos derived from the output of each optical detector principally coupled to light reflected from a corresponding said current, said bass, and said treble movable surfaces;
computing a bass key crosstalk correction value by multiplying said current movable surface BassErr value by the difference between said bass movable surface NormLinPos and said current movable surface NormLinPos;
computing a treble key crosstalk correction value by multiplying said current movable surface TrebErr value by the difference between said movable treble surface NormLinPos and said movable current surface NormLinPos;
forming a corrected position value by subtracting said bass key crosstalk correction value and said treble key crosstalk correction value from said current movable surface NormLinPos value.

4 more elements

A method for making a distance measurement to a current movable surface and removing crosstalk from a bass movable surface and a treble movable surface, said current movable surface adjacent to said bass movable surface and also said treble movable surface, each said current movable surface, said bass movable surface, and said treble movable surface having an associated optical source and optical detector for receiving said optical source energy reflected primarily from each said associated movable surface, the method comprising:

associating which each current movable surface a LinRest value, a LinDown value, a TrebErr value, and a BassErr value;
for each said current movable surface, a calibration step which includes:
a rest position step where a photodetector response associated with a current key is linearized and saved as said LinRest value when said current movable surface, said treble movable surface, and said bass movable surface are in a rest position;
a key down step where the photodetector response associated with a current key is linearized and saved as said LinDown value when said current movable surface is in a down position and said treble movable surface and said bass movable surface are in a rest position, and during said single key down step also measuring the photodetector response associated with said bass movable surface, linearizing said response, and saving said value as a bass movable surface TrebErr value, also measuring the photodetector response associated with said treble movable surface and saving said value as a treble movable surface BassErr value;
performing said calibration step for said adjacent keys where said adjacent key is used as a current movable surface in a subsequent said calibration step;
a subsequent operational step where a current movable surface photodetector response is corrected for crosstalk by subtracting a treble photodetector response and also a bass photodetector response from said current movable surface photodetector response.

3 more elements

A method for removing crosstalk from a plurality of movable surfaces, said plurality of movable surfaces being divisible into a subgroup comprising:

a bass movable surface, a current movable surface, and a treble movable surface;
each said bass movable surface, said current movable surface, and said treble movable surface having:
a LinRest value associated with a movable surface rest position photodetector response;
a LinDown value associated with a movable surface down position photodetector response;
a TrebErr value associated with the crosstalk contribution of a first adjacent movable surface to a current movable surface;
a BassErr value associated with the crosstalk contribution of a second adjacent movable surface to a current movable surface;
where an estimate of position for one key of said movable surfaces may be made by identifying one of said subgroups where said key is a current movable surface, and thereafter measuring a photodetector response from said current movable surface using said current movable surface LinRest value and said current movable surface LinDown value, and thereafter subtracting a Treble Crosstalk Error value derived from said TrebErr value and said movable surface photodetector responses and also subtracting a Bass Crosstalk Error value derived from said BassErr value and said movable surface photodetector responses.

4 more elements

Dependencies are inferred from the claim text.

Reflective piano keyboard scanner

Life of this patent

Reflective piano keyboard scanner

Life of this patent

Abstract

Claims20