Abstract
This paper proposes a new method for the measurement of spherical coordinates by using capacitive sensors as a non-contact probe solution of measurement of aspheric surfaces. The measurement of the average effect of the capacitive probe and the influence of capacitive probe tilting were studied with respect to an eccentric spherical surface. Based on the tested characteristic curve of the average effect of the sphere and probe, it was found that nonlinear and linear compensation resulted in high measurement accuracy. The capacitance probe was found to be trying to fulfill a need for performing nm-level precision measurement of aspheric electromagnetic surfaces.
Highlights
Aspherics are optical components whose surfaces deviate from those of spherics [1]
Aspherics are used in the optical field to correct aberrations effectively and reduce the number of optical components in optical systems [2,3]
Capacitive probes can measure the radial distance with accuracy in in thethe nanometer range when thethe asphericity is less than thethe measuring range
Summary
Aspherics are optical components whose surfaces deviate from those of spherics [1]. Compared to spherical optics, they are more flexible, have a larger degree of freedom, and exhibit more diversity. Null correction is normally required for accurate interferometric measurements of large departure aspheres [6] This method typically requires a specially designed and customized compensator, computer generated hologram (CGH), or other auxiliary components [7]. Another approach used to measure aspheres is that of profilometry [8]. As traditional non-contact probes, capacitive probes have many advantages such as non-contact, high accuracy, short responding delay, and good dynamic adaptability [13] Their resolution is at the sub-nanometer level; they can achieve measurements on a nanometer scale. By comparing the measurement results from a roundness measuring instrument and capacitive probe, validity of the error compensation method were verified
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