Imaging apparatus with simplified optical design

• US 10,507,088 B2
• Filed: 02/26/2019
• Issued: 12/17/2019
• Est. Priority Date: 08/15/2014
• Status: Active Grant

• Current Assignee: Align Technology Incorporated
• Original Assignee: Align Technology Incorporated
• Inventors: Verker, Tal, Levin, Adi, Saphier, Ofer, Moshe, Maayan
• Primary Examiner(s): Akanbi, Isiaka O
• Application Number:
  US16/286,437
• Publication Number:
  US 20190192263A1
• Time in Patent Office: 294 Days
• Field of Search: 356601, 356445, 356603
• CPC Class Codes: A61C 9/0066 Depth determination through adaptive focusing
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G02B 21/006 focusing arrangements; selection of the plane to be imaged
• CPC Class Codes: G02B 23/2446 of the image relay G02B23/26 takes precedence
• CPC Class Codes: G02B 23/2461 Illumination
• CPC Class Codes: G02B 23/26 using light guides for illumination G02B23/2469
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration

Abstract

Embodiments are directed to an imaging apparatus, which in an embodiment includes a light source to provide light, optics, a translation mechanism and a detector. The optics include focusing optics to perform focusing of the light onto a non-flat focal surface and to direct the light toward a three dimensional object. The translation mechanism adjusts a location of at least one lens of the focusing optics to displace the non-flat focal surface. The detector measures intensities of returning light that is reflected off of the three dimensional object, wherein the intensities of the returning light are measured for a plurality of locations of the at least one lens for determination of positions of a plurality of points of the three dimensional object. Detected positions of one or more of the plurality of points are adjusted to compensate for the non-flat focal surface.

Claims

1. An imaging apparatus for performing intraoral scans, comprising:

a light source to provide light;

an optical system comprising a plurality of lenses disposed along an optical path of the light, wherein the optical system comprises a non-flat focal surface, and wherein the optical system comprises focusing optics to perform focusing of the light onto the non-flat focal surface and to direct the light toward a three dimensional object to be imaged in an oral cavity;

a translation mechanism to adjust a location of at least one lens of the plurality of lenses to thereby adjust a focusing setting of the optical system and displace the non-flat focal surface along an imaging axis defined by the optical path, wherein the at least one lens is a lens of the focusing optics, and wherein at least one of a shape or a magnification of the non-flat focal surface changes with changes in the focusing setting; and

a detector to measure intensities of returning light that is reflected off of the three dimensional object and directed back through the focusing optics, wherein the intensities of the returning light are to be measured for a plurality of locations of the at least one lens for determination of positions on the imaging axis of a plurality of points of the three dimensional object, wherein detected positions of one or more of the plurality of points are to be adjusted to compensate for the non-flat focal surface using one or more compensation models that provide different adjustments for different focusing settings of the optical system.

2. The imaging apparatus of claim 1, wherein the non-flat focal surface comprises a curved focal plane and the detected positions for the one or more of the plurality of points are to be adjusted to compensate for a curvature of the curved focal plane.

3. The imaging apparatus of claim 1, further comprising:

a beam splitter disposed along the optical path between the light source and the focusing optics, wherein the beam splitter directs the light from the light source towards the focusing optics and directs the returning light from the focusing optics to the detector;

wherein the imaging apparatus is characterized in having an absence of a field lens between the beam splitter and the light source.

4. The imaging apparatus of claim 3, wherein the imaging apparatus is further characterized in having an absence of a field lens between the beam splitter and the detector.

5. The imaging apparatus of claim 3, wherein the light source comprises an illumination module configured to generate an array of light in an x-y plane.

6. The imaging apparatus of claim 1, further comprising:

a folding prism along the optical path of the light after the focusing optics, wherein the folding prism is to direct the light onto the three dimensional object to be imaged;

wherein the plurality of lenses comprise;

a first lens group;

a second lens group disposed proximate to the folding prism, the second lens group having a fixed location relative to the first lens group; and

a third lens group disposed between the first lens group and the second lens group, the third lens group having a variable location that is adjustable by the translation mechanism, wherein the focusing optics comprises the third lens group.

7. The imaging apparatus of claim 1, wherein a radius of a largest lens of the plurality of lenses is less than 13 millimeters.

8. The imaging apparatus of claim 1, wherein the imaging apparatus is a confocal imaging apparatus, and wherein the optical system is a confocal optical system, the imaging apparatus further comprising a processor to:

determine a location of the at least one lens that yields a maximum measured intensity for a portion of the returning light;

determine a position on the imaging axis of a point of the three dimensional object illuminated by the portion of the returning light that corresponds to the determined location of the at least one lens; and

adjust the position on the imaging axis of the point of the three dimensional object based on applying the determined location of the at least one lens to a field curvature model that is calibrated to the imaging apparatus to compensate for the non-flat focal surface.

9. The imaging apparatus of claim 1, wherein the optical system is a non-telecentric optical system.

10. The imaging apparatus of claim 8, further comprising:

one or more elements near or along the optical path, the one or more elements having a fixed distance from a first lens of the plurality of lenses, wherein the fixed distance changes with changes in temperature, wherein the processor is further to;

determine a current distance between the one or more elements and the first lens; and

apply an adjustment factor to the field curvature model based on the current distance.

11. An imaging apparatus for performing intraoral scans, comprising:

a light source to provide light comprising a plurality of light beams;

optics comprising a plurality of lenses disposed along an optical path of the light, wherein the optics comprises focusing optics to perform focusing of the light onto a focal surface and to direct the light toward a three dimensional object to be imaged in an oral cavity, and wherein the optics are characterized by an absence of a field lens, wherein the field lens is a diverging lens that opens rays of the plurality of light beams;

a translation mechanism to adjust a location of at least one lens of the plurality of lenses to displace the focal surface along an imaging axis defined by the optical path, wherein the at least one lens is a lens of the focusing optics; and

a detector to measure intensities of returning light that is reflected off of the three dimensional object and directed back through the focusing optics, wherein the intensities of the returning light are to be measured for a plurality of locations of the at least one lens for determination of positions on the imaging axis of a plurality of points of the three dimensional object, wherein detected positions of one or more of the plurality of points are to be adjusted to compensate for the absence of the field lens.

12. The imaging apparatus of claim 11, wherein the absence of the field lens causes the focusing optics to perform the focusing of the light onto a non-flat focal surface.

13. The imaging apparatus of claim 12, wherein the non-flat focal surface comprises a curved focal plane, wherein the detected positions for the one or more of the plurality of points are to be adjusted to compensate for a curvature of the curved focal plane, and wherein a shape of the non-flat focal surface changes with changes in the location of the at least one lens.

14. The imaging apparatus of claim 11, further comprising:

a beam splitter disposed along the optical path between the light source and the focusing optics, wherein the beam splitter directs the light from the light source towards the focusing optics and directs the returning light from the focusing optics to the detector.

15. The imaging apparatus of claim 14, wherein the light source comprises an illumination module configured to generate an array of light in an x-y plane.

16. The imaging apparatus of claim 12, further comprising:

a folding prism along the optical path of the light after the focusing optics, wherein the folding prism is to direct the light onto the three dimensional object to be imaged;

wherein the plurality of lenses comprise;

a first lens group;

a second lens group disposed proximate to the folding prism, the second lens group having a fixed location relative to the first lens group; and

a third lens group disposed between the first lens group and the second lens group, the third lens group having a variable location that is adjustable by the translation mechanism, wherein the focusing optics comprises the third lens group.

17. The imaging apparatus of claim 11, wherein a radius of a largest lens of the plurality of lenses is less than 13 millimeters.

18. The imaging apparatus of claim 11, wherein the imaging apparatus is a confocal imaging apparatus, and wherein the optics are confocal optics, the imaging apparatus further comprising a processor to:

determine locations of the at least one lens that yields yield a maximum measured intensity for portions of the returning light;

determine positions on the imaging axis of points of the three dimensional object illuminated by the portions of the returning light that corresponds correspond to the determined locations of the at least one lens; and

adjust the positions on the imaging axis of the points of the three dimensional object based on applying the determined locations of the at least one lens to one or more field curvature models that are calibrated to the imaging apparatus to compensate for the absence of the field lens, wherein the one or more field curvature models provide different adjustments for different locations of the at least one lens.

19. An imaging apparatus for performing intraoral scans, comprising:

a light source to provide light;

a non-telecentric optical system comprising a plurality of lenses disposed along an optical path of the light, wherein the non-telecentric optical system comprises focusing optics to perform focusing of the light onto a focal surface and to direct the light toward a three dimensional object to be imaged in an oral cavity, the focusing optics comprising at least one lens of the plurality of lenses;

a translation mechanism to adjust a location of the at least one lens to displace the focal surface along an imaging axis defined by the optical path, wherein adjustments to the location of the at least one lens cause a change in magnification of the focal surface; and

a detector to measure intensities of returning light that is reflected off of the three dimensional object and directed back through the focusing optics, wherein the intensities of the returning light are to be measured for a plurality of locations of the at least one lens for determination of positions on the imaging axis of a plurality of points of the three dimensional object, wherein detected positions of one or more of the plurality of points are to be adjusted to compensate for respective magnifications of the focal surface associated with respective locations of the plurality of locations of the at least one lens.

20. The imaging apparatus of claim 19, wherein the focusing optics perform the focusing of the light onto a non-flat focal surface.

21. The imaging apparatus of claim 20, wherein the non-flat focal surface comprises a curved focal plane, wherein the detected positions for the one or more of the plurality of points are to be adjusted to compensate for a curvature of the curved focal plane, and wherein a shape of the non-flat focal surface changes with changes in the location of the at least one lens.

22. The imaging apparatus of claim 19, further comprising:

a beam splitter disposed along the optical path between the light source and the focusing optics, wherein the beam splitter directs the light from the light source towards the focusing optics and directs the returning light from the focusing optics to the detector;

wherein the imaging apparatus is characterized in having an absence of a field lens between the beam splitter and the light source, and is further characterized in having an absence of a field lens between the beam splitter and the detector.

23. The imaging apparatus of claim 22, wherein the light source comprises an illumination module configured to generate an array of light beams in an x-y plane, wherein the imaging apparatus is a confocal imaging apparatus, and wherein the non-telecentric optical system is a confocal optical system.

24. The imaging apparatus of claim 19, wherein the light source comprises a semiconductor laser unit.

25. The imaging apparatus of claim 19, further comprising:

a folding prism along the optical path of the light after the focusing optics, wherein the folding prism is to direct the light onto the three dimensional object to be imaged;

wherein the plurality of lenses comprise;

a first lens group;

a second lens group disposed proximate to the folding prism, the second lens group having a fixed location relative to the first lens group; and

a third lens group disposed between the first lens group and the second lens group, the third lens group having a variable location that is adjustable by the translation mechanism, wherein the focusing optics comprises the third lens group.

26. The imaging apparatus of claim 19, wherein a radius of a largest lens of the plurality of lenses is less than 13 millimeters.

27. A method of performing an intraoral scan, comprising:

providing light;

directing, via an optical system comprising a non-flat focal surface, the light toward a three dimensional object to be imaged in an oral cavity;

performing focusing of the light onto the non-flat focal surface using focusing optics comprising a plurality of lenses disposed along an optical path of the light;

adjusting a location of at least one lens of the plurality of lenses to displace the non-flat focal surface along an imaging axis defined by the optical path using a translation mechanism;

measuring intensities of returning light that is reflected off of the three dimensional object and directed back through the focusing optics, wherein the intensities of the returning light are measured for a plurality of locations of the at least one lens for determination of positions on the imaging axis of a plurality of points of the three dimensional object; and

adjusting detected positions of one or more of the plurality of points to compensate for the non-flat focal surface using one or more compensation models that provide different adjustments for different focusing settings of the focusing optics.

28. The method of claim 27, wherein the focusing comprises confocal focusing, the method further comprising:

determining a location of the at least one lens that yields a maximum measured intensity for a portion of the returning light;

determining a position on the imaging axis of a point of the three dimensional object illuminated by the portion of the returning light that corresponds to the determined location of the at least one lens; and

adjusting the position on the imaging axis of the point of the three dimensional object based on applying the determined location of the at least one lens to a field curvature model that is calibrated to compensate for the non-flat focal surface.

29. The method of claim 28, wherein the field curvature model comprises a three dimensional polynomial function.

30. The method of claim 27, wherein the non-flat focal surface comprises a curved focal plane and the detected positions for the one or more of the plurality of points are adjusted to compensate for a curvature of the curved focal plane.