Apparatus for varying a focal point of an optical system in a dental 3D-scanner and dental 3D-scanner

Patent metadata

Field	Value
Publication number	US-12066686-B2
Application number	US-201917279148-A
Country	US
Kind code	B2
Filing date	Sep 27, 2019
Priority date	Sep 27, 2018
Publication date	Aug 20, 2024
Grant date	Aug 20, 2024

Abstract

The present invention relates to an apparatus for varying a focal point of an optical system in a dental 3D-scanner, comprising: a lens unit with a lens being movable between a front reversal position and a rear reversal position to vary a position of a focal point with respect to a scan object; a guide unit for guiding a movement of the lens unit between the front reversal position and the rear reversal position along a guide axis being parallel to an optical axis of the lens; and a drive unit for driving the movement of the lens unit, said drive unit including a linear motor with an anchor and a stator, said anchor being movable along a drive axis of the drive unit that is parallel to the guide axis, said stator being affixed to the guide unit. The present invention further relates to a dental 3D-scanner for scanning a three-dimensional scan object.

First claim

The invention claimed is:

1. Apparatus for varying a focal point of an optical system in a dental 3D-scanner, comprising:
a lens unit with a lens being movable between a front reversal position and a rear reversal position to vary a position of a focal point with respect to a scan object;
a guide unit for guiding a movement of the lens unit between the front reversal position and the rear reversal position along a guide axis being parallel to an optical axis of the lens; and
a drive unit for driving the movement of the lens unit, said drive unit including a linear motor with an anchor and a stator, said anchor being movable along a drive axis of the drive unit that is parallel to the guide axis, said stator being affixed to the guide unit
wherein the drive unit includes a coupling arrangement for coupling a movement of the anchor and the lens unit so that a movement of the anchor in a first direction is transferred to a movement of the lens in a second direction opposite to the first direction.

2. Apparatus as claimed in claim 1 , wherein
the coupling arrangement includes a flexible connection element for connecting the anchor and the lens unit to transfer a force from the anchor to the lens unit.

3. Apparatus as claimed in claim 2 , wherein
the coupling arrangement includes a tension element for tensioning the flexible connection element.

4. Apparatus of claim 1 , wherein
the coupling arrangement includes an inverting element for inverting the movement of the anchor.

5. Apparatus as claimed in claim 1 , wherein
the guide unit includes a position sensor for determining a position of the lens unit between the front reversal position and the rear reversal position.

6. Apparatus as claimed in claim 5 , wherein the drive unit is configured to control the movement of the lens unit based on a sensor signal of the position sensor.

7. Apparatus as claimed in claim 1 , wherein
the guide unit includes a linear recirculating ball bearing guide; and
the lens unit includes an engaging element for engaging into said linear recirculating ball bearing guide.

8. Apparatus as claimed in claim 1 , wherein a mass of the lens unit is equal to a mass of the anchor to compensate reaction forces resulting from accelerations of the lens and the anchor.

9. Apparatus as claimed in claim 1 , wherein a centerline of mass of the lens unit parallel to the guide axis corresponds to a centerline of mass of the anchor parallel to the guide axis.

10. Apparatus as claimed in claim 1 , wherein
the linear motor is a brushless 3-phase linear servomotor; and
the linear motor preferably includes a hall sensor for measuring a position of the anchor with respect to the stator.

11. Apparatus as claimed in claim 1 , wherein a maximum displacement of the anchor is equal to a distance between the front reversal position and the rear reversal position.

12. Apparatus as claimed in claim 1 , wherein the drive unit is configured to drive the movement of the lens unit to oscillate between a selectable front oscillation position and a selectable rear oscillation position at an oscillation frequency of 2 to 20 Hz.

13. Dental 3D-scanner for scanning a three-dimensional scan object, comprising:
an apparatus as claimed in claim 1 ;
a detector for detecting a light signal from the scan object passing through the lens; and
a handheld housing for manually guiding the 3D-scanner around the scan object.

14. Dental 3D-scanner as claimed in claim 13 , comprising a control unit for controlling the drive unit.

15. Apparatus of claim 2 , wherein said connection element includes a steel strip.

16. Apparatus of claim 3 , wherein said tension element includes a spring.

17. Apparatus of claim 4 , wherein said inverting element includes a ball bearing.

18. Apparatus of claim 5 , wherein the position sensor includes an optical distance measurement sensor.

Assignees

• Dentsply Sirona Inc

Inventors

• Berner Markus
• Seib Martin
• Confalonieri Fabrizio

Classifications

• G02B27/646

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title

• A61B5/0088

  for oral or dental tissue · CPC title

• A61B5/0062

  Arrangements for scanning · CPC title

• A61B2018/20353

  Scanning in three dimensions [3D] · CPC title

• G02B7/08

  adapted to co-operate with a remote control mechanism · CPC title