Laser touch panel reflective surface aberration cancelling

• US 5,196,835 A
• Filed: 05/02/1991
• Issued: 03/23/1993
• Est. Priority Date: 09/30/1988
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: MacInnis, Alexander G., Gonzalez-Heres, Jose F., Freedman, Bruce T., Blue, Larry A.
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): FATAHI YAR, MAHMOUD
• Application Number:
  US07/697,493
• Time in Patent Office: 691 Days
• Field of Search: 340/706, 340/712, 341/20, 341/31, 178/18, 178/19, 250/221, 364/520, 364/521
• US Class Current: 345/175
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/0423 using sweeping light beams, e.g. using rotating or vibrating mirror

Abstract

A method and apparatus that distinguish a valid touch from an optical aberration caused by unwanted objects and/or scratches in the light plane of an optical touch panel device is disclosed. During a training mode the device learns the relative position of "aberration dropouts" caused by the unwanted objects. During normal operating mode the relative positions of "touch and aberration dropouts" are generated and compared with the relative position of aberration dropouts to distinguish between aberration dropout signals and touch dropout signals. The touch dropout signals are subjected to further processing to determine the precise location of a touch while the aberration dropout signals are discarded.

Claims

1. In an apparatus which determines the location of a pointer relative to a surface area by triangulation where the apparatus includes a light source, means for causing light beams from said source to form a light plane relative to the surface area, one or more reflective surfaces positioned at the periphery of said light plane and means for detecting the absence of light reflected from those surfaces, a method for compensating for aberrations in the reflective surfaces which may otherwise be interpreted as indicating the presence of a pointer, said method comprising the steps of:

(a) activating the light beams to form the light plane relative to said surface area;

(b) determining each beam position whereat an aberration indicating beam interruption occurs during a sequence while no pointer is in use;

(c) determining each beam position whereat beam interruptions occur while a pointer is in use;

(d) comparing the beam positions at interruptions occurring during no pointer use with beam positions at interruptions occurring during pointer use; and

discarding beam positions only if the offset between their respective displacements e fall within a range of predetermined values, otherwise performing further tests to distinguish aberration-cause signals from valid pointer signals.

2. The method set forth in claim 1 wherein the determining beam position steps of (b) and (c) above further include the steps of

(e) generating a digital electronic image with pulses representing the position of beam interruption;

(f) identifying a leading and a corresponding trailing edge for each pulse on said digital electronic image; and

(g) correlating each pulse with a source of interruption in said light plane.

3. The method set forth in step (d) of claim 1 wherein the range of values includes zero.

4. The method set forth in step (d) of claim 1 wherein the further tests include determining the respective displacements for pairs of beam positions whereat interruptions occur with a beam position in a pair occurring with no pointer in use and another beam position in the pair occurring with pointer in use.

5. The method set forth in claim 4 further including the steps of identifying an interrupted beam position as a pointer position if the displacements for the interrupted beam position which occurs during pointer use and the interrupted beam position which occurs during no pointer use are not coincident.

12. The method set forth in claim 4 further including the steps of identifying an interrupted beam position as a pointer position if the displacement for the interrupted beam position occurring during pointer use in not coincident and straddles the displacement for the interrupted beam position occurring during no pointer use.

13. The method set forth in claim 4 further including the steps of identifying an interrupted beam position as a pointer position if the displacement for the interrupted beam position occurring during pointer use is partially coincident and overlaps the displacement for a beam position which occurs during no pointer use.

6. In an apparatus which determines the location of a stylus relative to a surface area by triangulation where the apparatus includes a light source, means for causing light beams from said source to form a light plane relative to the surface area, one or more reflective surfaces positioned at the periphery of said light plane and means for detecting the absence of light reflected from those surfaces, a method for compensating for aberrations in the reflective surfaces which may otherwise be interpreted as indicating the presence of a stylus, said method comprising the steps of:

(a) activating the light plane;

(b) determining beam positions whereat interruption occurs within the light plane;

(c) comparing the beam positions in step (b) with a predetermined value and discarding all beam positions that are less than the predetermined value;

(d) determining each beam position whereat an aberration indicating beam interruption occurs during a sequence while no stylus is in use;

(e) determining each beam position whereat stylus beam interruptions occur while a stylus is in use;

(f) comparing the beam positions at interruptions occurring during no stylus use with beam positions at interruptions occurring during stylus use; and

(g) distinguishing between a valid stylus signal and an aberration-caused signal only if compared positions partially coincide.

7. The method of claim 6 wherein step (d) further includes the step of recording each beam position whereat an aberration indicating beam interruption occurs.

8. The method set forth in claim 7 further including the steps of periodically adjusting recorded information by adding new beam positions whereat new aberrations indicating beam interruptions occur and removing old beam positions whereat old aberration indicating interruptions occurred.

9. In an apparatus which determines the location of a pointer relative to a surface area by triangulation where the apparatus includes a light source, means for causing light beams from said source to form a light plane relative to the surface area, one or more reflective surfaces positioned at the periphery of said light plane and means for detecting the absence of light reflected from those surfaces, a method for compensating for aberrations in the reflective surfaces which may be otherwise be interrupted as indicating the presence of a pointer, said method comprising the steps of:

(a) generating a light plane image with interruptions caused by a pointer intersecting said surface area and debris and/or scratches located in said surface area;

(b) processing the light plane images and generating therefrom electronic images with pulses representing pointers interruptions and pulses representing debris and/or scratch interruptions;

(c) filtering the pulses representing debris and/or scratches; and

(d) performing further processing on the pulses representing pointers interruptions to identify a precise location at which the pointers intersect the surface area.

10. In a touch panel device having a light source, means for causing light beams from said source to form a light plane relative to a viewing surface, one or more reflective surfaces disposed at the periphery of the display screen, means for detecting the absence of light reflected from those surfaces and a triangulation method for determining the location of a stylus relative to the display screen, an apparatus for compensating for aberrations in the reflective surfaces which may otherwise be interpreted as indicating the presence of a stylus, said apparatus comprising:

means for generating light plane images with interruptions caused by the stylus intersecting said display screen and debris and/or scratches located on said reflective surfaces;

means for receiving the light plane images and generating therefrom electronic images with pulses representative of styli interruptions and pulses representative of debris and/or scratches interruptions;

means for analyzing the electronic images and filtering all pulses which represent debris and/or scratches interruptions; and

means for processing the pulses representative of styli interruptions to determine the precise location whereat the styli intersect the display screen.

11. For use with an interface apparatus which determine the location of a stylus relative to a surface area by triangulation where the apparatus includes a light source, means for causing a light beam from the source to scan across the surface area, one or more reflective surfaces and means for detecting the presence or absence of light reflected from those surfaces, a method for compensating for aberrations in the reflective surfaces which might otherwise be interpreted as indicating the presence of a stylus, said method comprising the steps of:

causing the light beam to scan the surface area during a power-up sequence while no stylus is in use;

recording each beam position at which an aberration-indicating beam interruption occurs;

comparing the beam positions at interruptions which occur during normal apparatus operation with the recorded beam positions; and

distinguishing an aberration-caused signal from a valid stylus signal if the compared positions fall within a range of predetermined values.

14. In an apparatus which determines the location of a pointer relative to a surface area by triangulation where the apparatus includes a light source, means for causing light beams from said source to form a light plane relative to the surface area, one or more reflective surfaces positioned at the periphery of said light plane and means for detecting the absence of light reflected from those surfaces, a method for compensating for aberrations in the reflective surfaces which may otherwise be interpreted as indicating the presence of a pointer, said method comprising the steps of:

(a) activating the light beams to form the light plane relative to said surface area;

(b) determining aberration locations within said surface area whereat beam interruptions occur when no pointer is used to touch locations in said surface area;

(c) determining pointer locations within said surface whereat beam interruptions occur when a pointer is used, to touch locations within the surface area;

(d) comparing selected ones of the aberration locations with selected ones of the pointer locations; and

(e) discarding those aberration locations positioned a predetermined distance from pointer locations.

15. In an apparatus which determines the location of a pointer relative to a surface area by triangulation where the apparatus includes a light source, means for causing light beams from said source to form a light plane relative to the surface area, one or more reflective surfaces positioned at the periphery of said light plane and means for detecting the absence of light reflected from those surfaces, a device for compensating for aberrations in the reflective surfaces which may otherwise be interpreted as indicating the presence of a pointer, said device comprising:

(a) means for activating the light beams to form the light plane relative to said surface area;

(b) means for determining aberration locations within said surface area whereat beam interruptions occur when no pointer is used to touch locations in said surface area;

(c) means for determining pointer locations within said surface whereat beam interruptions occur when a pointer is used, to touch locations within the surface area;

(d) means for comparing selected ones of the aberration locations with selected ones of the pointer locations; and

(e) means for discarding those aberration locations positioned a predetermined distance from pointer locations. i