Heterodyne moiré interferometry for measuring corneal surface profile

Chang, Wei Yao; Chen, Kun Huang; Chen, Der Chin; Tseng, Jung-Kai; Chen, Shyan Tarng; Sun, Han; Chen, Jing Heng; Hsu, Ken Yuh

doi:10.1016/j.optlaseng.2013.07.013

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…In 1995, referring to Kawara’s design shown in Figure 7 , Maastricht Shape Topographer shown in Figure 8 was developed to measure the corneal surface elevation point-by-point based on the projection of two sinusoidal gratings and the analysis of the distortion of the gratings caused by the corneal-scleral shape [ 65 , 66 ]. More recently, in 2013, a method for reconstructing the corneal surface profile based on the Moiré method and heterodyne interferometry using a simple optical setup was described in Figure 9 [ 67 , 68 ].…”

Section: Approaches In Measuring the Anterior Segmentmentioning

confidence: 99%

Biometric Measurement of Anterior Segment: A Review

Liu

Kang

2020

Sensors

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Biometric measurement of the anterior segment is of great importance for the ophthalmology, human eye modeling, contact lens fitting, intraocular lens design, etc. This paper serves as a comprehensive review on the historical development and basic principles of the technologies for measuring the geometric profiles of the anterior segment. Both the advantages and drawbacks of the current technologies are illustrated. For in vivo measurement of the anterior segment, there are two main challenges that need to be addressed to achieve high speed, fine resolution, and large range imaging. One is the motion artefacts caused by the inevitable and random human eye movement. The other is the serious multiple scattering effects in intraocular turbid media. The future research perspectives are also outlined in this paper.

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Section: Approaches In Measuring the Anterior Segmentmentioning

confidence: 99%

Biometric Measurement of Anterior Segment: A Review

Liu

Kang

2020

Sensors

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“…A variety of optical interferometric techniques and instruments have been developed to conduct surface topography measurements. Table 2 summarizes the stateof-the-art research [89][90][91][92][93][94][95] on various interferometric techniques and corresponding specifications and applications. Recently, some novel interferometric techniques, such as diffraction phase microscopy [96,97] and quantitative phase imaging [98], have been proposed for nanoscale surface topography measurement.…”

Section: Heterodyne Interferometrymentioning

confidence: 99%

“…The central fringe nearest to the centroid position can be identified from its adjacent fringes [114]. If the function [87]; corneal surface profile [95] Abbreviations. PSI: Phase-shifting interferometry; OPD: Optical path difference; RMS: Root mean square; CSI: Coherence scanning interferometry; WSI: Wavelength scanning interferometry; HI: Heterodyne interferometry; PZT: Piezoelectric transducer.…”

Section: Centroid Approachmentioning

confidence: 99%

Development of surface reconstruction algorithms for optical interferometric measurement

2020

Front. Mech. Eng.

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Optical interferometry is a powerful tool for measuring and characterizing areal surface topography in precision manufacturing. A variety of instruments based on optical interferometry have been developed to meet the measurement needs in various applications, but the existing techniques are simply not enough to meet the ever-increasing requirements in terms of accuracy, speed, robustness, and dynamic range, especially in on-line or on-machine conditions. This paper provides an in-depth perspective of surface topography reconstruction for optical interferometric measurements. Principles, configurations, and applications of typical optical interferometers with different capabilities and limitations are presented. Theoretical background and recent advances of fringe analysis algorithms, including coherence peak sensing and phase-shifting algorithm, are summarized. The new developments in measurement accuracy and repeatability, noise resistance, self-calibration ability, and computational efficiency are discussed. This paper also presents the new challenges that optical interferometry techniques are facing in surface topography measurement. To address these challenges, advanced techniques in image stitching, on-machine measurement, intelligent sampling, parallel computing, and deep learning are explored to improve the functional performance of optical interferometry in future manufacturing metrology.

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“…There are two common forms of projection-based systems: raster-stereography [29][30][31] and moiré-deflectometry. 32,33 Surface height resolution for these types of systems have been demonstrated to be in the order of microns; however, the introduction of a foreign substance alters the behavior of the tear film making them undesirable to study the tear film. 34 Furthermore, it could be argued that topographic resolution is limited by the fact that the introduction of a foreign substance alters the shape and behavior of the tear film structure.…”

Section: Introductionmentioning

confidence: 99%

Dual interferometer for dynamic measurement of corneal topography

Micali

Greivenkamp

2016

J. Biomed. Opt

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Abstract. The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface, where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. A dual interferometer system for measuring the dynamic corneal topography is designed, built, verified, and qualified by testing on human subjects. The system consists of two coaligned simultaneous phase-shifting polarization-splitting Twyman-Green interferometers. The primary interferometer measures the surface of the tear film while the secondary interferometer tracks the absolute position of the cornea, which provides enough information to reconstruct the absolute shape of the cornea. The results are high-resolution and high-accuracy surface topography measurements of the in vivo tear film and cornea that are captured at standard camera frame rates.

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Heterodyne moiré interferometry for measuring corneal surface profile

Cited by 6 publications

References 8 publications

Biometric Measurement of Anterior Segment: A Review

Biometric Measurement of Anterior Segment: A Review

Development of surface reconstruction algorithms for optical interferometric measurement

Dual interferometer for dynamic measurement of corneal topography

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