Digital pen using speckle tracking

#1. Field of the Invention

#The present invention relates generally to handwriting data entry, and more particularly to methods and systems for facilitating data entry using a pen input device.

#2. Description of the Related Art

#FIG. 1 is a schematic view of the pen input system of the present invention;

#FIG. 2 is a schematic view of a program storage device;

#FIG. 3 is a flow chart showing the overall logic by which pen position signals are generated based on movement of a pen across the substrate;

#Referring initially to FIG. 1, a pen input device is shown, generally designated 10, which includes a substrate 12 and at least one lightweight elongated hollow plastic or metal pen body 14. The preferred embodiment set forth herein contemplates a pen body 14 that can be manipulated by a writer to write ink or graphite or other substance onto a substrate 12 such as paper, while digitally recording strokes across the substrate 12. It is to be understood, however, that the principles advanced herein can be used with a pen body 14 that is a stylus-type device that does not necessarily deposit ink or other substance onto a substrate.

#A contact sensor 16 can be supported on the pen body 14, for purposes to be shortly disclosed. The contact sensor can include, e.g., force sensing resistors or other force sensors. The contact sensor is energized by a dc power supply 18, preferably a type AAA Nickel Metal Hydride rechargeable battery with voltage step-up electronics, with the signals from the contact sensor 16 being sent to an analog to digital converter (ADC) 20. Or, the power supply 18 could be an alkaline battery or other equivalent source. Digitized signals from the ADC 20 are sent to a digital processor 22, which selectively stores pen position information in a digital memory 24. Signals stored in the memory 24 indicate the position of the tip 28, such that the signals can be transferred to a PC-based handwriting recognition engine for correlation of the position signals to alpha-numeric characters. The handwriting recognition engine can be any suitable handwriting recognition system, such as those disclosed in U.S. Pat. Nos. 5,644,652, 5,343,537, or 5,550,931, all owned by the present assignee and all incorporated herein by reference. The power supply 18, ADC 20, processor 22, and memory 24 are all mounted on the pen body 14 as shown.

#In accordance with the present invention, the power supply 18 also energizes a laser 26 that is mounted on the body 14. Preferably, the laser 26 is an infrared (IR) laser. As can be appreciated in reference to FIG. 1, the laser 26 is oriented on the body 14 such that it directs a laser beam toward the vicinity of a distal writing tip 28 of the pen body 14, such that a three dimensional interference pattern is generated when the coherent laser light reflects off the texture of the substrate 12. The interference pattern is referred to herein as “speckles”. As contemplated hereunder, the speckles are detected by a detector 30, also mounted, in the preferred embodiment, on the body 14. In the preferred embodiment the detector 30 is a lensless CMOS imaging sensor array or CCD. The signal from the detector 30 is digitized by the ADC 20 or by a separate ADC (not shown), with the digitized signal then being sent to the processor 22.