Focal Length Measurement Based on Hartmann-Shack Principle

The measurement of the diopters of spectacle lenses using an artificial neural network is proposed in this paper. A diopter is measured by obtaining the distances between the spots imaged by a charge-coupled device (CCD) during a Hartmann test. Backpropagation (BP) and a radial basis function (RBF) algorithm are applied to train the BP and RBF neural networks, respectively. A set of − 20 D to 20 D spectacle lenses is used to test the proposed method. When comparing the diopter measurement results of the RBF neural network with those of the BP neural network, the former exhibited higher stability and lower errors. In addition, the errors of diopter measurement are not against the system error measured by an auto-focimeter due to the increase of curvature of spectacle lenses. These results indicated that RBF neural network has better performance in diopter detection, and it can overcome the system error caused by the change of lens curvature in auto-focimeter measurement.

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Measurement of Wafer Focus by Grating Shearing Interferometry

Wang

Zhu

2020

Applied Sciences

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A method applied for improving the measurement precision and efficiency of wafer focusing in an optical lithography instrument (OLI) is introduced. Based on grating shearing interferometry, the defocus and tilt of the wafer are measured by testing the phase difference in the interference pattern. To validate the feasibility, an experiment is implemented, of which the measurement precision is indicated as 30 nm due to the high precision of phase-resolving arithmetic after analyzing the measurement uncertainty and indicating the precision by interferometer.

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Focal Length Measurement Based on Hartmann-Shack Principle

Cited by 4 publications

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Full-aperture diopter distribution measurement method for single vision and progressive addition lenses

Full-aperture diopter distribution measurement method for single vision and progressive addition lenses

Diopter measurement based on an artificial neural network

Measurement of Wafer Focus by Grating Shearing Interferometry

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