Chromatic point sensor optical pen with adjustable range and adjustable stand-off distance
A chromatic point sensor (CPS) optical pen provides a signal usable to measure a distance to a surface, and includes an axial chromatic aberration portion arranged to receive source radiation from an aperture, output it toward the surface as a focused measurement beam having axial chromatic dispersion, receive reflected radiation from the surface and focus it proximate to the aperture. The axial chromatic aberration portion includes a first axially dispersive focusing element that receives the source radiation and focuses it at a first focal region, a second axially dispersive focusing element that receives the radiation from the first focal region and focuses it at a second focal region, and a third axially dispersive focusing element that receives the radiation from the second focal region and outputs the measurement beam. Lengths between the first, second and third axially dispersive focusing elements are adjustable (i.e., resulting in an adjustable range).
1. A chromatic point sensor (CPS) optical pen operable to provide a signal usable to measure a distance to a surface, the CPS optical pen comprising:
a housing;
an aperture that outputs source radiation and receives reflected radiation; and
an axial chromatic aberration portion arranged along an optical axis of the CPS optical pen to receive the source radiation from the aperture, output it toward the surface as a focused measurement beam having axial chromatic dispersion, receive reflected radiation from the surface and focus the reflected radiation proximate to the aperture with axial chromatic dispersion, wherein:
the axial chromatic aberration portion is formed of a plurality of axially dispersive focusing elements including: a first axially dispersive focusing element that receives the source radiation and focuses that radiation at a first focal region internal to the axial chromatic aberration portion, a second axially dispersive focusing element that receives the radiation from the first focal region and focuses that radiation at a second focal region internal to the axial chromatic aberration portion, and a third axially dispersive focusing element that receives the radiation from the second focal region and outputs the measurement beam; wherein
a first length between the first and second axially dispersive focusing elements is configured to be adjustable, and a second length between the second and third axially dispersive focusing elements is configured to be adjustable.
2. The CPS optical pen of claim 1 , wherein the first length and the second length are adjustable during manufacturing of the CPS optical pen.
3. The CPS optical pen of claim 1 , comprising:
an actuator configured to adjust the first length and the second length, the actuator operable by a user of the CPS optical pen.
4. The CPS optical pen of claim 3 , wherein the actuator comprises one or more linear actuators to slide at least one of the first, second, and third axially dispersive focusing elements relative to each other to change the first length and the second length.
5. The CPS optical pen of claim 1 , which is configurable in a plurality of configurations, wherein the plurality of configurations are defined by respective values of the first length and respective values of the second length.
6. The CPS optical pen of claim 5 , wherein the plurality of configurations are associated with respective values of a stand-off distance of the CPS optical pen, and respective values of a range of the CPS optical pen.
7. The CPS optical pen of claim 6 , wherein the values of a range of the CPS optical pen range between 3 mm and 30 mm and the values of a stand-off distance of the CPS optical pen range between 2 mm and 7 mm.
8. The CPS optical pen of claim 6 , wherein the plurality of configurations are associated with respective values of a spot size of the measurement beam at the stand-off distance, and respective values of a spot size of the measurement beam at the range added to the stand-off distance.
9. The CPS optical pen of claim 8 , wherein the plurality of configurations includes:
a first configuration associated with the stand-off distance of 2 mm, the range of 4 mm, the spot size at the stand-off distance of 14 um, and the spot size at the stand-off distance plus the range of 31 um;
a second configuration associated with the stand-off distance of 2 mm, the range of 8 mm, the spot size at the stand-off distance of 22 um, and the spot size at the stand-off distance plus the range of 98 um;
a third configuration associated with the stand-off distance of 3 mm, the range of 8 mm, the spot size at the stand-off distance of 21 um, and the spot size at the stand-off distance plus the range of 62 um;
a fourth configuration associated with the stand-off distance of 4 mm, the range of 7 mm, the spot size at the stand-off distance of 20 um, and the spot size at the stand-off distance plus the range of 35 um; and
a fifth configuration associated with the stand-off distance of 4 mm, the range of 10 mm, the spot size at the stand-off distance of 20 um, and the spot size at the stand-off distance plus the range of 60 um.
10. The CPS optical pen of claim 1 , wherein the second axially dispersive focusing element is formed of at least two intermediate axially dispersive focusing elements including a first intermediate axially dispersive focusing element and a last intermediate axially dispersive focusing element, the first intermediate axially dispersive focusing element receives the radiation from the first focal region and focuses that radiation at a first intermediate focal region, and the last intermediate axially dispersive focusing element receives radiation from a last intermediate focal region and focuses that radiation at the second focal region.
11. The CPS optical pen of claim 1 , wherein each of the plurality of axially dispersive focusing elements comprises at least one optical component which is identical among the plurality of axially dispersive focusing elements.
12. The CPS optical pen of claim 11 , wherein the plurality of axially dispersive focusing elements are identical to each other.
13. The CPS optical pen of claim 1 , wherein each of the plurality of axially dispersive focusing elements comprises one or more aspheric lenses.
14. The CPS optical pen of claim 1 , further comprising an electronics portion with a signal processor, wherein an adjustment of the first and second lengths achieves a stand-off distance and range sufficient for measuring the workpieces of certain dimensions, and the electronics portion is configured to be operated to determine measurements of the workpieces.
15. The CPS optical pen of claim 14 , wherein the determined measurements are included in a first set of measurements which are taken with the first and second lengths having been adjusted to first values as part of a first configuration, and after the electronics portion is operated to take the first set of measurements, the first and second lengths are configured to be adjustable to second values as part of a second configuration and the electronics portion is configured to be operated to determine measurements of workpieces as part of a second set of measurements.
16. A method of adjusting a range and a stand-off distance of a chromatic point sensor (CPS) optical pen operable to provide a signal usable to measure a distance to a target surface, the method comprising:
providing a CPS optical pen including:
a housing;
an aperture that outputs source radiation and receives reflected radiation; and
an axial chromatic aberration portion arranged along an optical axis of the CPS optical pen to receive the source radiation from the aperture, output it toward the surface as a focused measurement beam having axial chromatic dispersion, receive reflected radiation from the surface and focus the reflected radiation proximate to the aperture with axial chromatic dispersion, wherein:
the axial chromatic aberration portion is formed of a plurality of axially dispersive focusing elements including: a first axially dispersive focusing element that receives the source radiation and focuses that radiation at a first focal region internal to the axial chromatic aberration portion, a second axially dispersive focusing element that receives the radiation from the first focal region and focuses that radiation at a second focal region internal to the axial chromatic aberration portion, and a third axially dispersive focusing element that receives the radiation from the second focal region and outputs the measurement beam; and
adjusting a first length between the first and second axially dispersive focusing elements and a second length between the second and third axially dispersive focusing elements.
17. The method of claim 16 , wherein the step of adjusting the first length and the second length is performed during manufacturing of the CPS optical pen.
18. The method of claim 16 , wherein the CPS optical pen includes an actuator configured to adjust the first length and the second length, and the step of adjusting the first length and the second length is performed by a user of the CPS optical pen.
19. The method of claim 16 , wherein the CPS optical pen is configurable in a plurality of configurations, the plurality of configurations are defined by respective values of the first length and respective values of the second length, and the step of adjusting the first length and the second length includes selecting one of the plurality of configurations.
20. The method of claim 19 , wherein the plurality of configurations are associated with respective values of a stand-off distance of the CPS optical pen and respective values of a range of the CPS optical pen, and the step of adjusting the first length and the second length includes selecting desired values of the stand-off distance and the range.
21. The method of claim 20 , wherein the plurality of configurations are associated with respective values of a spot size of the measurement beam at the stand-off distance, and respective values of a spot size of the measurement beam at the range added to the stand-off distance.
22. The method of claim 20 , comprising stitching of multiple ranges including:
for measuring a first range, selecting a first configuration out of the plurality of configurations, the first configuration associated with a first stand-off distance and the first range, wherein the adjusting of the first and second lengths is to achieve the first configuration for measuring the first range, and
for measuring a second range different from the first range, selecting a second configuration out of the plurality of configurations, the second configuration associated with a second stand-off distance and the second range, and adjusting the first and second lengths to achieve the second configuration for measuring the second range.
23. The method of claim 16 , further comprising:
initially determining dimensions of workpieces to be measured, wherein the adjustment of the first and second lengths achieves a stand-off distance and range sufficient for measuring the workpieces; and
after the adjustment, operating the CPS optical pen to take measurements of the workpieces.
24. The method of claim 23 , wherein the measurements of the workpieces are included in a first set of measurements which are taken with the first and second lengths having been adjusted to first values as part of a first configuration, and after the CPS optical pen is operated to take the first set of measurements, the method further comprises adjusting the first and second lengths to second values as part of a second configuration and operating the CPS optical pen to take a second set of measurements of workpieces.
25. The method of claim 16 , wherein the adjustment of the first and second lengths is to first values as part of a first configuration that achieves a first range, the method further comprising:
operating the CPS optical pen with the first configuration to take a first set of measurements of a workpiece;
adjusting the first and second lengths to second values as part of a second configuration that achieves a second range that is smaller than the first range; and
operating the CPS optical pen with the second configuration to take a second set of measurements of the workpiece, wherein the second set of measurements correspond to at least one of higher resolution or smaller spot sizes than the first set of measurements.