Continuous optical self-alignment for light curtains and optical presence sensors for simplification and maintenance of alignment

• US 7,508,512 B1
• Filed: 02/23/2006
• Issued: 03/24/2009
• Est. Priority Date: 02/23/2006
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Inventors: Nair, Suresh, Schuster, George, Delcher, Ray, Rollins, George E., Jones, Derek W., Galera, Richard, Dogul, James E.
• Primary Examiner(s): Chowdhury; Tarifur
• Assistant Examiner(s): GOMEZ, TARA S PAJOOHI
• Application Number:
  US11/360,176
• Time in Patent Office: 1,125 Days
• Field of Search: 250/221, 250/229, 250/232, 250/559.12, 250621-622, 349 61- 65, 349/123, 349/193, 356/121, 356/153, 356/213, 356218-222, 356399-401, 356/616, 359/237
• US Class Current: 356/399
• CPC Class Codes: G01B 11/272 using photoelectric detection means
• CPC Class Codes: G01V 8/12 using one transmitter and one receiver

Abstract

Systems and methods are disclosed that facilitate tolerating and/or correcting light beam misalignment in a light-emitting device, such as a light curtain. Attributes of the light beam can be assessed and compared to predetermined threshold values to evaluate whether the light beam is misaligned, and corrective feedback can be generated to adjust the position of one or more transmissive apertures generated on an LCD, through which light is permitted to pass, in order to re-align the light beam.

Claims

1. A system that facilitates correcting misalignment in a light curtain, comprising:

a back-lit LCD that selectively permits light from an emitter to pass through transmissive apertures generated on the LCD;

a first lens that focuses light that has passed through the transmissive apertures on the back-lit LCD to generate the light beam that traverses a monitored area;

a second LCD that selectively permits a light beam that has traversed the monitored area to pass through transmissive apertures generated on the second LCD to a receiver;

a second lens that re-focuses the light beam at an opposite side of the monitored area prior to passing through the transmissive apertures on the second LCD; and

a control component that provides feedback information to at least one of the LCDs to adjust a position of the transmissive apertures generated thereon when the light beam is determined to be misaligned.

2. The system of claim 1, further comprising an analysis component that determines a position of the light beam as it passes through at least one of the back-lit LCD and the second LCD.

3. The system of claim 2, wherein the position of the light beam is quantified by an x-coordinate and a y-coordinate.

4. The system of claim 3, wherein the analysis component determines whether the x-coordinate and y-coordinate are within a predetermined threshold range, respectively, wherein the light beam is misaligned if at least one of the x-coordinate and the y-coordinate is outside a respective predetermined threshold range.

5. The system of claim 4, wherein the control component generates a feedback signal to one or both of the LCDs to adjust a position of the transmissive apertures generated thereon to re-align the light beam.

6. A method of correcting misalignment of a light beam in a light curtain, comprising:

employing a first LCD between an emitter and a monitored area on a first side of the monitored area;

employing a first lens to focus the light beam at the first side of the monitored area after the light beam has traversed the transmissive apertures on the first LCD;

employing a second LCD between the monitored area and a receiver on a second side of the monitored area;

employing a second lens to re-focus the light beam on the second side of the monitored area before passing the light beam through the transmissive apertures on the second LCD; and

selectively generating transmissive apertures on the first and second LCDs to control a position of a light beam.

7. The method of claim 6, further comprising determining Cartesian coordinates of the light beam as it passes through the transmissive apertures on at least one of the first and second LCDs to evaluate a path of the light beam.

8. The method of claim 7, further comprising comparing the Cartesian coordinates to a predetermined threshold range of coordinates to determine whether the Cartesian coordinates are within the threshold range.

9. The method of claim 8, further comprising re-aligning the light beam if the Cartesian coordinates are not within the threshold range.

10. The method of claim 9, wherein re-aligning the light beam comprises generating a feedback signal that is transmitted to at least one of the first and second LCDs to adjust a position of the transmissive apertures thereon.

11. The method of claim 10, further comprising regenerating transmissive apertures in a new position on at least one of the first and second LCDs to alter the path of the light beam and re-align the light beam, wherein the transmissive apertures are regenerated by manipulating the LCDs, such that the LCDs can be made opaque at all points where light is not to be transmitted through the LCD and clear or translucent at points corresponding the transmissive apertures.

12. The method of claim 6, further comprising determining an angle of transmission of the light beam across the monitored area.

13. The method of claim 12, further comprising comparing the angle of transmission to a predetermined threshold range of angles of transmission and evaluating whether the angle of transmission is within the threshold range.

14. The method of claim 13, further comprising regenerating transmissive apertures in a new position on one or both of the first and second LCDs to adjust the light beam if the angle of transmission is not within the predetermined threshold range, wherein the transmissive apertures are regenerated by manipulating the LCDs, such that the LCDs can be made opaque at all points where light is not to be transmitted through the LCD and clear or translucent at points corresponding the transmissive apertures.