Low coherence interferometry for central thickness measurement of rigid and soft contact lenses

Abstract

Abstract:In this paper we propose contact lens central thickness measurement with a low coherence interferometry technique using either a SLED source or a broadband continuum generated in air-silica Microstructured Optical Fiber (MOF) pumped with a picosecond microchip laser. Each of these sources associated with the interferometer provides, at the same time, good measurement resolution and quick signal recording without moving any optical elements and without need of a Fourier Transform operation. Signal improvement is performed afterwards by a numerical treatment for optimal correlation peaks detection leading to central thickness value of several contact lenses.

Interfaces detection after corneal refractive surgery by low coherence optical interferometry

“…The experimental set-up is nearly similar to the one described in reference [27]. The light of a supercontinuum source generated in an air-silica Microstructured Optical Fiber (MOF) pumped by a picoseconds microchip laser [28] is injected in a Mach-Zehnder interferometer, which is followed by a SISAM (Spectromètre Interférentiel à Sélection par l’Amplitude de Modulation) optical correlator (Fig.…”

“…Like other OCT, the method presented in this paper [26] is also based on low coherence interferometry and has been already applied to measurement of central thickness of contact lenses [27]. Our technique has been now adapted to be devoted to a very specific application, namely the interfaces detection of corneas after LASIK during corneal storage in Eye banks.…”

New method for lens thickness measurement by the frequency-shifted confocal feedback

“…Contact measurement can only be utilized when machining and assembling the lenses, which has lower accuracy and even causes damage to the coated lens. The non-contact measurement methods mainly include machine vision method [9], chromatic confocal microscopy [10,11], low coherence interferometry [12], and laser differential confocal technique [13,14]. Machine vision method has advantages of continuous measurement and flexible in production line with an accuracy of less than 0.005 mm.…”

Low-coherence interferometer for contact lens surface metrology

“…10,11 It uses a low-coherence TwymanGreen interferometer along with a Mach-Zehnder interferometer in transmission to measure the phase and group indices of refraction to an accuracy of 0.0001. The thickness is also required for a full description of a contact lens and has been characterized in several ways, 12,13 but it will also be determined by the interferometer described in this paper. The main purpose of the interferometer described in this paper is to provide surface measurements of a submerged contact lens in order to perform a whole lens reconstruction.…”