A chromatic point sensor (CPS) optical pen operable to provide a signal usable to measure a distance (MD) to a surface , the CPS optical pen comprising: an aperture configured to output source radiation and to receive 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 configured to receive the source radiation and to focus that radiation at a first focal region (FR 1) internal to the axial chromatic aberration portion , a second axially dispersive focusing element configured to receive the radiation from the first focal region (FR 1) and to focus that radiation at a second focal region (FR 2) internal to the axial chromatic aberration portion , and a third axially dispersive focusing element configured to receive the radiation from the second focal region (FR 2) and to output the measurement beam ; wherein a first length (L1) between the first and second axially dispersive focusing elements is configured to be adjustable, and a second length (L2) between the second and third axially dispersive focusing elements is configured to be adjustable. an aperture configured to output source radiation and to receive 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 configured to receive the source radiation and to focus that radiation at a first focal region (FR 1) internal to the axial chromatic aberration portion , a second axially dispersive focusing element configured to receive the radiation from the first focal region (FR 1) and to focus that radiation at a second focal region (FR 2) internal to the axial chromatic aberration portion , and a third axially dispersive focusing element configured to receive the radiation from the second focal region (FR 2) and to output the measurement beam ; wherein a first length (L1) between the first and second axially dispersive focusing elements is configured to be adjustable, and a second length (L2) between the second and third axially dispersive focusing elements is configured to be adjustable. the axial chromatic aberration portion is formed of a plurality of axially dispersive focusing elements including: a first axially dispersive focusing element configured to receive the source radiation and to focus that radiation at a first focal region (FR 1) internal to the axial chromatic aberration portion , a second axially dispersive focusing element configured to receive the radiation from the first focal region (FR 1) and to focus that radiation at a second focal region (FR 2) internal to the axial chromatic aberration portion , and a third axially dispersive focusing element configured to receive the radiation from the second focal region (FR 2) and to output the measurement beam ; wherein a first length (L1) between the first and second axially dispersive focusing elements is configured to be adjustable, and a second length (L2) between the second and third axially dispersive focusing elements is configured to be adjustable. <EOS>