Optical force sensor

• US 7,657,128 B2
• Filed: 07/31/2006
• Issued: 02/02/2010
• Est. Priority Date: 05/23/2000
• Status: Expired due to Term

• Current Assignee: Livescribe Incorporated (Anoto Group AB)
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Lapstun, Paul
• Primary Examiner(s): Dang, Duy M
• Application Number:
  US11/495,822
• Publication Number:
  US 20070014490A1
• Time in Patent Office: 1,282 Days
• Field of Search: 382312-315, 345/179, 235/375, 358473-474, 738/18, 178 18- 20
• US Class Current: 382/313
• CPC Class Codes: B41J 13/103 for the sheet feeding section
• CPC Class Codes: B41J 13/106 for the sheet output section
• CPC Class Codes: B41J 2/17503 Ink cartridges
• CPC Class Codes: B41J 2/17513 Inner structure
• CPC Class Codes: B41J 2/1752 Mounting within the printer
• CPC Class Codes: B41J 2/17523 Ink connection
• CPC Class Codes: B41J 2/17546 electronically
• CPC Class Codes: B41J 2/17553 Outer structure
• CPC Class Codes: B41J 2/17556 Means for regulating the pressure in the cartridge
• CPC Class Codes: B41J 2/17563 Ink filters
• CPC Class Codes: B41J 2/2114 Ejecting transparent or white coloured liquids, e.g. processing liquids B41J2/211 takes precedence
• CPC Class Codes: B42C 19/02 starting with single sheets
• CPC Class Codes: B42C 9/0006 by applying adhesive to a stack of sheets
• CPC Class Codes: B42C 9/0081 applying adhesive to individual sheets for binding them together by fusing, welding B42C9/0093
• CPC Class Codes: B65H 29/34 from supports slid from under the articles
• CPC Class Codes: B65H 37/04 for securing together articles or webs, e.g. by adhesive, stitching or stapling adhering replacement to expiring web during change of web roll B65H19/18
• CPC Class Codes: G01L 1/25 using wave or particle radiation, e.g. X-rays , microwaves, neutrons G01L1/24 takes precedence
• CPC Class Codes: G06F 3/016 Input arrangements with force or tactile feedback as computer generated output to the user
• CPC Class Codes: G06F 3/0321 by optically sensing the absolute position with respect to a regularly patterned surface forming a passive digitiser, e.g. pen optically detecting position indicative tags printed on a paper sheet constructional details of pen-shaped pointing devices G06F3/03545, G06F3/03542, G06F3/037
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06V 10/17 : using hand-held instruments
• CPC Class Codes: G06V 10/19 : by sensing codes defining pattern positions
• CPC Class Codes: G06V 10/22 : by selection of a specific region containing or referencing a pattern; Locating or processing of specific regions to guide the detection or recognition
• CPC Class Codes: G06V 10/225 : based on a marking or identifier characterising the area
• CPC Class Codes: G06V 30/1423 : the instrument generating sequences of position coordinates corresponding to handwriting preprocessing or recognising digital ink G06V30/32
• CPC Class Codes: H04N 1/00127 : Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture
• CPC Class Codes: H04N 1/00204 : with a digital computer or a digital computer system, e.g. an internet server programmed control between transmitter and receiver or between image input and image output device H04N1/32561
• CPC Class Codes: H04N 1/00244 : with a server, e.g. an internet server fax-servers or the like for store and forward H04N1/324
• CPC Class Codes: H04N 1/00326 : with a data reading, recognizing or recording apparatus, e.g. with a bar-code apparatus arrangements for the associated working of recording or reproducing apparatus with related apparatus G11B31/00
• CPC Class Codes: H04N 1/00358 : Type of the scanned marks
• CPC Class Codes: H04N 1/00376 : Means for identifying a mark sheet or area
• CPC Class Codes: H04N 1/00567 : Handling of original or reproduction media, e.g. cutting, separating, stacking
• CPC Class Codes: H04N 1/00968 : by scanning marks on a sheet mark-sheet input means H04N1/00355; sensing record carriers G06K7/00
• CPC Class Codes: H04N 1/32101 : Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
• CPC Class Codes: H04N 1/32122 : in a separate device, e.g. in a memory or on a display separate from image data
• CPC Class Codes: H04N 1/32128 : attached to the image data, e.g. file header, transmitted message header, information on the same page or in the same computer file as the image for information embedded in the image H04N1/32144
• CPC Class Codes: H04N 1/32771 : in response to a request, e.g. for a particular document
• CPC Class Codes: H04N 1/32778 : using a mark-sheet or machine-readable code request
• CPC Class Codes: H04N 2201/0082 : Image hardcopy reproducer H04N2201/0091 - H04N2201/0094 take precedence
• CPC Class Codes: H04N 2201/3243 : of type information, e.g. handwritten or text document
• CPC Class Codes: H04N 2201/3269 : of machine readable codes or marks, e.g. bar codes or glyphs
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes

Abstract

A force sensor particularly suited for use in an electronic stylus that senses the contact force on its nib for recording pen strokes and handwriting recognition. The sensor has a housing for a load bearing member for receiving an input force to be sensed and associated circuitry for converting the input force into an output signal indicative of the input force. The bearing member is movably mounted within the elongate body (up to 100 microns). The input force acting on the load bearing member is caused by contact on the nib. The load bearing member is biased against the direction of the input force.

The force sensor also has a light source and photo-detector for sensing levels of illumination from the light source. Associated circuitry converts a range of illumination levels sensed by the photo-detector into a range of output signals, so that the illumination level sensed by the photo-detector varies with movement of the load bearing member within the elongate body such that the output signal from the circuitry is indicative of the input force. Using an optical sensor avoids the need to use a delicate piezo-resistive sensor that requires careful tolerancing during production.

Claims

1. A force sensor assembly comprising:

a housing;

a load bearing member movably mounted in the housing for receiving an input force to be sensed, the load bearing member being biased against the direction of the input force;

a light source;

a photo-detector for sensing levels of illumination from the light source; and

,

circuitry for converting a range of illumination levels sensed by the photo-detector into a range of output signals;

wherein,

the illumination level sensed by the photo-detector varies with movement of the load bearing member within the housing such that the output signal from the circuitry is indicative of the input force.

2. A force sensor assembly according to claim 1 wherein the light source is fixed to the housing for illuminating at least part of the load bearing member.

3. A force sensor assembly according to claim 2 wherein the photo-detector is mounted to the housing such that the load bearing member moves between the light source and the photo-detector.

4. A force sensor assembly according to claim 1 wherein the load bearing member has an aperture through which light from the light source can illuminate the photo-detector, the aperture being positioned between the light source and the photo-detector at part of the load bearing member'"'"'s travel within the housing.

5. A force sensor assembly according to claim 4 wherein the load bearing member is biased with a spring, the spring having a spring constant equal to the maximum force the sensor is to sense, divided by the length in the direction of travel within the housing of the aperture.

6. A force sensor assembly according to claim 5 wherein the aperture is aligned with the light source and the photo-detector when the input force is the maximum force, and the load bearing member fully obscures the light source from the photo-detector when the input force is zero.

7. A force sensor assembly according to claim 1 wherein the light source is a LED.

8. A force sensor assembly according to claim 1 wherein the load bearing member has a maximum travel of 100 microns within the housing.

9. A force sensor assembly according to claim 1 wherein the force sensor is configured to sense a maximum force of 5 Newtons.

13. An electronic stylus according to claim 1 wherein the load bearing member has an aperture through which light from the light source can illuminate the photo-detector, the aperture being positioned between the light source and the photo-detector at part of the load bearing member'"'"'s travel within the elongate body.

14. An electronic stylus according to claim 13 wherein the load bearing member is biased with a spring, the spring having a spring constant equal to the maximum force the sensor is to sense, divided by the length in the direction of travel within the elongate body of the aperture.

15. An electronic stylus according to claim 14 wherein the aperture is aligned with the light source and the photo-detector when the input force is the maximum force, and the load bearing member fully obscures the light source from the photo-detector when the input force is zero.

10. An electronic stylus comprising:

an elongate body;

a nib extending from one end of the elongate body;

a load bearing member movably mounted to the elongate body for receiving an input force caused by contact on the nib, the load bearing member being biased against the direction of the input force;

a light source;

a photo-detector for sensing levels of illumination from the light source; and

,

circuitry for converting a range of illumination levels sensed by the photo-detector into a range of output signals;

wherein,

the illumination level sensed by the photo-detector varies with movement of the load bearing member within the elongate body such that the output signal from the circuitry is indicative of the input force.

11. An electronic stylus according to claim 10 wherein the light source is fixed to the elongate body for illuminating at least part of the load bearing member.

12. An electronic stylus according to claim 11 wherein the photo-detector is mounted to the elongate body such that the load bearing member moves between the light source and the photo-detector.

16. An electronic stylus according to claim 10 wherein the load bearing member has a maximum travel of 100 microns within the elongate body.

17. An electronic stylus according to claim 10 wherein the nib of the electronic stylus is a ball point writing nib with a tubular ink cartridge extending from the nib toward the load bearing member such that the coupling is a detachable boot that fits over the end of the cartridge opposite the nib.

18. An electronic stylus according to claim 10 wherein the force sensor is configured to sense a maximum force of 5 Newtons.

19. An electronic stylus according to claim 10 wherein the output signal from the circuitry support a hand writing recognition facility.

20. An electronic stylus according to claim 10 wherein the light source is a LED.