Method for determining the position of a first moving component relative to a second component and device for applying said method

• US 20090147271A1
• Filed: 12/05/2008
• Published: 06/11/2009
• Est. Priority Date: 12/23/2005
• Status: Active Grant

• Current Assignee: Wright C. David
• Original Assignee: Wright C. David
• Inventors: Wright, C. David
• Granted Patent: US 7,842,913 B2
• Time in Patent Office: Days
• US Class Current: 356/614
• CPC Class Codes: G01D 5/347 using displacement encoding scales

Abstract

A method for determining the position of one of two components in relative motion with respect to each other, using optical means, comprises:

• • directing at least one light beam emitted by a light source attached to one component towards a diffractive support attached to the second component, calculated and manufactured for generating an optical signal indicative of the positioning of said support, the optical signal being produced by the diffractive support in transmission and/or in reflection, and the optical signal including information indicative of its quality;
  • detecting and reading at least one optical code formed by said signal, which corresponds to a unique position of the diffractive support relatively to the beam; and
  • assigning a position to each detected optical code.

Claims

1. A diffractive support for applying the method according to claim 1, comprising:

mounting means on a first component in relative motion with respect to a second component; and

at least one diffractive track;

wherein said diffractive track has means diffracting the light beam emitted by at least one light source fixed relatively to the second component;

wherein said diffractive track contains information indicative of its quality.

2. The diffractive support according to claim 1, wherein the diffractive track has an etched relief in the constituent material of said support capable of diffracting the incident beam(s) and of generating an optical signal, the reading of which allowing the position of the first component relatively to the second component to be identified, by identifying the code formed by the signal.

3. The diffractive support according to claim 1, wherein the diffractive track is obtained by modulating the transparency of the support, for example by applying an opaque material at certain locations on a transparent support, in order to diffract the incident beam(s) and to generate an optical signal, the reading of which allows the position of the first component relatively to the second component to be identified by identifying the code formed by the signal.

4. The diffractive support according to claim 2, wherein the modulation of the reliefs or of the transparency of the support, the distribution and geometry of which are calculated by a computer, generates a particular diffracted optical signal under the action of at least one light beam, said signal forming an optical code consisting of optical structures defining a unique position of the support at any time.

5. The diffractive support according to claim 1, wherein each track is divided into areas of individualized diffractive structures generating a code corresponding to a position of the support, each area including a plurality of elementary shapes with a parallelogrammic aspect, positioned as a periodic or aperiodic grid.

6. The diffractive support according to claim 1, further comprising:

a rigid disk;

a means for mounting said disk to a rotary shaft; and

at least one ring-shaped diffractive track.

7. The diffractive support according claim 5, wherein each track is divided into angular sectors with equal surfaces forming the individualized diffractive structures.

8. The diffractive support according to claim 7, wherein the angular sectors have dimensions of the order of 10 μ

m to 100 μ

m.

9. The diffractive support according to claim 7, wherein at least one track comprises 4,096 angular sectors.

10. The diffractive support according to claim 6, wherein the disk includes at its periphery, a tapered portion, one of the tilted surfaces of which includes at least one diffractive track.

11. The diffractive support according to claim 1, wherein the diffractive track is positioned on a flexible support which may be adhered to a rigid component.

12. A device for measuring the position of a first component in relative motion with respect to a second component, with a diffractive support according to claim 1, further comprising:

at least one fixed light source, emitting at least one light beam onto at least one mobile diffractive support;

means for detecting and reading an optical signal obtained by diffraction of the light beam(s) by transmission or reflection from the diffractive support(s), wherein said optical signal contains information indicative of its quality; and

means for processing the optical code resulting from the detected signal allowing the position of the diffractive support(s) relatively to the beam(s) and the reliability of the position information to be determined.

13. The measuring device according to claim 12, further comprising means for assessing the reliability of the position information.

14. The measuring device according to claim 12, further comprising means for correcting the position information.

15. The measuring device according to claim 14, wherein the coherent light source is a laser diode.

16. The measuring device according to claim 12, wherein the light beam is sent towards the diffractive support via at least one optical relay component of the lens, prism, diffractive component, reflective component, refractive component type and/or via at least one optical guiding component of the optical fiber or waveguide type.

17. The measuring device according to claim 12, wherein the beam is towards the diffractive support via at least one unit exerting a collimation, focusing or astigmatism function.

18. The measuring device according to claim 12, wherein the light beam is towards the diffractive support via at least one conformation diaphragm.

19. The device according to any of claim 12, wherein the means for detecting and reading diffracted optical codes consist of photodetectors of the type, array strips or pixel matrices, CCD sensors, photodiodes, or even photoelectric or photovoltaic cells positioned on the trajectory of the rays diffracted by the diffractive support.

20. The measuring device according to claim 19, wherein the photodetectors are positioned so that each diffracted optical structure obtained at the location where a diffracted ray encounters a pixel array, covers at least 3 pixels.

21. The device according to claim 19, wherein the number of pixels between two adjacent spots is set to at least 3 pixels.

22. The device according to claim 12, wherein the light beam is directed at an incidence normal to the diffractive support.

23. The device according to claim 12, wherein the light ray is tilted towards the diffractive support, by an angle between 0°

and 17°

, relatively to the normal to the diffractive support.

24. The device according to claim 12, further comprising synchronization means for detecting and reading an optical code generated by an individualized diffractive structure when the beam emitted by the light source is centered on said structure.

25. The measuring device according to claim 24, characterized in that the synchronization means include specific photodetectors dedicated to detecting optical structures obtained independently of those forming the code of the position to be measured, for example light spots positioned on at least one diffractive track specifically dedicated to synchronization.

26. The measuring device according to claim 12, wherein the device is configured to facilitate measurement of the rotary movement applied to at least one diffractive support permanently attached to a rotary shaft.

27. The measuring device according to claim 26, comprising two superimposed diffractive rotary disks, one including the measurement of angular positions on one revolution and the other, rotating N times less rapidly, allowing the number of accomplished revolutions to be measured within the limit of N revolutions.

28. The measuring device according to claim 12, wherein a single component forming an optical guide simultaneously acts as a diaphragm, a collimating lens, mirror(s), a protective housing for the laser diode and the photodetectors.

30. A steering column of a vehicle comprising a position-measuring device according to claim 12.

29. A method for calculating the position of a component with respect to another one from an optical code formed by a photon signal generated by a diffractive support, said signal generating a code consisting of optical structures with variable intensity, distributed over detection means, comprising:

detecting the status of each optical structure and assigning it an electronic state corresponding to its intensity;

calculating the value of the code of the measured position;

assessing the quality or reliability of said value

and converting said code into a distance