Method and apparatus for optically sensing the position and velocity of piano keys
US5567902A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 6, 1995 |
| Grant date | Oct 22, 1996 |
| Priority date | — |
| Expiry date | Jan 6, 2015 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S84/07
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
An electronic keyboard musical instrument is provided having optical emitters and detectors both positioned beneath each of the instrument's keys, whereby optical energy is emitted upon the bottom reflective surface of the key and the reflected light is detected. The distance between the optoelectronic sensor and the bottom of the key is detected by the light detector which produces an analog output signal and, by measuring the time between a first and second threshold crossing, the key's velocity can be determined. The two thresholds are preferably chosen to measure a rising voltage as the key is depressed, and the threshold values are preferably chosen at 50% of key travel and 75% of key travel. By use of these thresholds, a relatively clean and useful waveform is available at both threshold crossings, particularly since the mechanical movement of the key has nearly reached its terminal velocity. Electronics in the keyboard instrument sequentially scan each of the output voltages produced by their corresponding light detectors so that a single microprocessor can measure all of the key position values. A single set of threshold voltages can be utilized for all of the keys of the k…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.