Positioning device comprising a light beam

• US 9,243,898 B2
• Filed: 04/14/2014
• Issued: 01/26/2016
• Est. Priority Date: 04/15/2013
• Status: Active Grant

• Current Assignee: CSEM Centre Suisse d'Electronique et de Microtechnique SA Recherche et Développement
• Original Assignee: CSEM Centre Suisse d'Electronique et de Microtechnique SA Recherche et Développement
• Inventors: Masa, Peter, Hasler, David, Grenet, Eric, Stanley, Ross
• Primary Examiner(s): STAFIRA, MICHAEL PATRICK
• Application Number:
  US14/251,812
• Publication Number:
  US 20140368836A1
• Time in Patent Office: 652 Days
• US Class Current: 1/1
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01J 1/0437 using masks, aperture plates, spatial light modulators, spatial filters, e.g. reflective filters
• CPC Class Codes: G01S 3/781 Details
• CPC Class Codes: G01S 3/7835 using coding masks
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

A position measurement system for determining 2D displacement or position of a mobile element with respect to a reference frame, including: a point light; an optical mask having transparent and opaque areas defining a repetitive pattern on at least one side of its surfaces; an imager, fixed to a mobile element, including integrated electronic circuits allowing detection, computing and analyzing of a shadow projected by the optical mask. The position measurement system includes an optical diffuser plate between the light source and the mask. The imager, mask and diffuser plate form an assembly so as to produce a light spot created by the scattering of the incident light beam emitted by the light source on the diffuser plate. The mask positioned between the diffuser plate and imager, produces a shadow on the imager, allowing to compute and provide 2D position of the mobile element relative to the fixed reference frame.

Claims

1. A position measurement system for determining 2D displacement or position of a mobile element with respect to a reference frame, comprising:

a point light source fixed to a reference frame, said point light source being arranged to emit a light beam;

an optical mask, comprising transparent and opaque areas on at least one side of its surfaces, said areas defining a repetitive pattern; and

an imager, fixed to a mobile element, comprising integrated electronic circuits allowing detection, computing and analyzing of a shadow projected by the optical mask,

wherein said position measurement system comprises an optical diffuser plate positioned between said point light source and the optical mask and wherein the imager, the optical mask and the optical diffuser plate form an assembly, said light beam producing a light spot created by the scattering of an incident light beam emitted by the point light source on said optical diffuser plate, and

wherein said optical mask, positioned in between said optical diffuser plate and said imager, produces a shadow on said imager, said imager being arranged to compute and provide 2D position of the mobile element relative to the fixed reference frame.

2. The position measurement system according to claim 1, wherein said repetitive pattern comprises a distinctive element.

3. The position measurement system according to claim 1, wherein the point light source is a super luminous LED or a Laser.

4. The position measurement system according to claim 1, wherein the point light source is positioned to a distance d2 greater than 10 times the distance d1, the distance d1 being the distance between the optical diffuser plate and the imager.

5. The position measurement system according to claim 4, wherein said distance d2 is between 0.2 meter and 2 meter, preferably between 0.5 meter and 1.5 meter.

6. The position measurement system according to claim 4, wherein said distance d2 is greater than 100 meter, preferably greater than 1 km.

7. The position measurement system according to claim 1, wherein at least one first mirror is inserted between the point light source and said assembly, and wherein the optical diffuser plate, the optical mask and the imager of said assembly may have any orientation angle relative to the incident laser beam on said first mirror and positioned so that anyone of said optical diffuser plate, said optical mask and said imager does not intersect the light beam between the point light source and said first mirror.

8. The position measurement system according to claim 7, arranged to measure the angular position of said first mirror, wherein said first mirror can be rotated in reference to a rotation axis located in the plane of said first mirror.

9. The position measurement system according to claim 1, arranged to determine the 2D cartesian position, or displacement of said mobile element, and at the same time determining the rotation of the point light source relative to the reference frame, comprising a second assembly comprising a second optical diffuser plate, a second optical mask and a second imager, and wherein an optical beam splitter is positioned in front of the point light source and deviates part of the emitted light beam on said second assembly.

10. The position measurement system according to claim 9, wherein a second mirror is positioned between the beam splitter and said second assembly.

11. The position measurement system according to claim 10, wherein said second mirror is positioned adjacent to the point light source, and wherein said second mirror is used to direct said deviated light beam on the optical diffuser plate of said second assembly and such that the reflected light beam provided by said second mirror does not intersect said beam splitter.

12. The position measurement system according to claim 11 wherein a third mirror is positioned adjacent to the beam splitter, allowing to realize multiple reflections of the light beam between said second and said third mirror, enhancing as such the sensitivity of the position or rotation detection of the second imager.

13. The position measurement system according to claim 9, wherein at least a fourth mirror and a fifth mirror are positioned between the point light source and the beam splitter, in order to realize multiple reflections of the light beam before said light beam intersects the beam splitter, and enhancing as such the sensitivity of the position or rotation detection of the two imagers.

14. The position measurement system according to claim 1 wherein the system comprises speckle reduction means.

15. The position measurement system, according to claim 14, wherein said speckle reduction means comprises a vibration system attached to the optical diffuser plat.

16. The position measurement system, according to claim 14, wherein said speckle reduction means comprises an acousto-optic system positioned in the emitted light beam.

17. The position measurement system according to claim 2, wherein the point light source is a super luminous LED or a Laser.