Chromatic confocal microscopy using staircase diffractive surface

Area of Science:

• Optical Engineering
• Metrology
• Microscopy

Background:

• Chromatic confocal microscopy (CCM) is a noncontact distance measurement technique utilizing hyperchromatic lenses.
• Current CCMs often use refractive-based chromatic dispersion, limiting performance and application range.
• Improvements are needed for CCMs to compete with laser triangulation gauges and laser encoders.

Purpose of the Study:

• To demonstrate the potential of hybrid aspheric diffractive (HAD) lenses for CCMs.
• To improve CCM performance metrics including dynamic range, resolution, and optical head efficiency.
• To address manufacturing limitations of diffractive optical elements in CCMs.

Main Methods:

• Investigated the use of hybrid aspheric diffractive (HAD) lenses in CCM design.
• Analyzed the impact of HAD lenses on dynamic range, resolution, and light throughput.
• Conducted a theoretical study on manufacturing losses and diffraction efficiency of diffractive surfaces, focusing on staircase diffractive surfaces (SDS).

Main Results:

• HAD lenses increased CCM dynamic range by a factor of 2 and resolution by a factor of 5.
• HAD lenses passively athermize the optical head and increase light throughput efficiency.
• Staircase diffractive surfaces (SDS) offer the highest diffraction efficiency, potentially reducing manufacturing light losses by a factor of 5.

Conclusions:

• HAD lenses represent a significant advancement for chromatic confocal microscopy.
• SDS configurations within HAD lenses overcome manufacturing limitations, enabling diffraction-limited optical design.
• The improved CCM performance positions it as a viable alternative to existing laser measurement systems.