Surface sensing device with optical sensor

• US 20110043827A1
• Filed: 10/26/2010
• Published: 02/24/2011
• Est. Priority Date: 04/26/2005
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: McFarland, Geoffrey, Jonas, Kevyn Barry
• Granted Patent: US 8,144,340 B2
• Time in Patent Office: Days
• US Class Current: 356/614
• CPC Class Codes: G01B 11/007 feeler heads therefor
• CPC Class Codes: G01B 5/012 Contact-making feeler heads therefor

Abstract

A surface sensing device for use in position determining apparatus has an elongate stylus with a tip for scanning the surface of a workpiece to be measured. Lateral displacements of the stylus tip are detected by a light beam which passes along the stylus from a light source to a retroreflector. This reflects the beam back via a beamsplitter to a position sensitive detector. The stylus is mounted for longitudinal displacement on a carriage. The longitudinal displacement is measured by another light beam projected by the beamsplitter onto a second position sensitive detector.

Claims

1. A surface sensing device for use in position determining apparatus, comprising:

an elongate stylus having a workpiece-sensing stylus tip;

the stylus having a relatively flexible portion permitting bending and a portion which is stiffer than the relatively flexible portion, the stiffer portion being closer to the tip than the relatively flexible portion;

said tip being subjected to lateral displacements caused by said bending;

a transducer system which measures lateral displacements of the tip, including those caused by said bending.

2. A surface sensing device according to claim 1, wherein the transducer system is optical.

3. A surface sensing device according to claim 2, wherein the transducer system includes an optical element at or near or connected to the tip so as to be subjected to the lateral displacements of the tip, and a detector, and wherein the transducer system projects a light beam between the optical element and the detector.

4. A surface sensing device according to claim 1, comprising:

a mounting for the stylus in the surface sensing device which enables longitudinal displacement of the stylus; and

a displacement measurement transducer arranged to measure said longitudinal displacement of the stylus.

5. A surface sensing device according to claim 1, comprising a probe, wherein the stylus is exchangeably attached to the probe.

6. A surface sensing device according to claim 4, comprising a probe, wherein the probe comprises a longitudinally movable carriage, to which the stylus is exchangeably attached, and wherein said displacement measurement transducer is arranged to measure longitudinal displacement of the carriage.

7. A surface sensing device according to claim 5, wherein the exchangeable stylus adjusts the gain of the transducer system which measures the lateral displacements of the stylus tip.

8. A surface sensing device for use in position determining apparatus, comprising:

an elongate stylus having a workpiece-sensing stylus tip;

the stylus having a relatively weakened portion permitting bending and a portion which is stiffer than the relatively weakened portion, the stiffer portion being closer to the tip than the relatively weakened portion;

said tip being subjected to lateral displacements caused by said bending;

a transducer system which measures lateral displacements of the tip, including those caused by said bending.

9. A surface sensing device according to claim 8, wherein the relatively weakened portion comprises local perforations of the stylus.

10. A surface sensing device according to claim 8, wherein the transducer system is optical.

11. A surface sensing device according to claim 10, wherein the transducer system includes an optical element connected to the tip so as to be subjected to the lateral displacements of the tip, and a detector, and wherein the transducer system projects a light beam between the optical element and the detector.

12. A surface sensing device according to claim 8, comprising:

a mounting for the stylus in the surface sensing device which enables longitudinal displacement of the stylus; and

a displacement measurement transducer arranged to measure said longitudinal displacement of the stylus.

13. A surface sensing device according to claim 8, comprising a probe, wherein the stylus is exchangeably attached to the probe.

14. A surface sensing device according to claim 12, comprising a probe, wherein the probe comprises a longitudinally movable carriage, to which the stylus is exchangeably attached, and wherein said displacement measurement transducer is arranged to measure longitudinal displacement of the carriage.

15. A surface sensing device according to claim 13, wherein the exchangeable stylus adjusts the gain of the transducer system which measures the lateral displacements of the stylus tip.