Comparison of three techniques in measuring progressive addition lenses

Area of Science:

• Optometry and Vision Science
• Optical Engineering
• Metrology

Background:

• Progressive addition lenses (PALs) are complex optical devices requiring precise manufacturing and measurement.
• Evaluating the accuracy and comparability of different measurement techniques for PALs is crucial for quality control and product development.

Purpose of the Study:

• To compare the measurement accuracy of three distinct techniques for progressive addition lenses (PALs).
• To assess the differences in spherical power, cylindrical power, and higher-order aberrations (HOAs) across measurement methods.

Main Methods:

• Five contemporary PALs were evaluated using a Hartmann-Shack wavefront sensor (HSWFS), a Rotlex lens analyzer (moiré interferometer), and a coordinate measuring machine (CMM).
• Measurements were taken under lateral displacement conditions, and data were analyzed to generate contour plots of optical properties.
• The CMM measured surface height data, which was converted to optical properties.

Main Results:

• The HSWFS, Rotlex, and CMM methods demonstrated minimal differences (near zero) for spherical and cylindrical power measurements across all tested PALs.
• Maximum differences of approximately 0.50 D were observed between the HSWFS/CMM and Rotlex methods in specific lens regions.
• Higher-order aberrations (HOAs) were highest in the progressive corridor and near zone; CMM measurements of HOAs were slightly lower than HSWFS.

Conclusions:

• The three evaluated methods (HSWFS, Rotlex, CMM) are comparable for measuring spherical and cylindrical power in PALs.
• The non-optical CMM method, utilizing surface height measurements, is a viable option for assessing PAL optical properties.
• While CMM provides comparable power measurements, its HOA estimates are lower than those obtained from the HSWFS.