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.
Real-time measurement of the thickness and group refractive index is crucial for semiconductor devices. In this paper, we proposed a fast synchronous method for measuring the thickness and group refractive index distribution of solid plates based on line-field dispersive interferometry. The proposed method measured the line-field distribution in an illuminated region through a single step. A low-cost spectrometer calibration method using an eight-channel dense wavelength division multiplexer was developed for verification. The line-field distribution of a three-step silicon wafer was successfully measured within 3.3 ms. The combined uncertainties for the geometrical thickness and group refractive index were <50 nm and 4 × 10−4, respectively.
Structured-light vision methods are widely employed for three-dimensional reconstruction. As a typical structured light pattern, grid pattern is extensively applied in single-shot three-dimensional reconstruction. The uniqueness of the grid feature retrieval is critical to the reconstruction. Most methods using grid pattern utilize the epipolar constraint to retrieve the correspondence. However, the low calibration accuracy of the camera–projector stereo system may impact the correspondence retrieval. An approach using grid pattern-based structured-light vision method is proposed. The grid pattern-based structured-light model was combined with the camera model and the multiple light plane equations. An effective extraction method of the grid stripe features was investigated. The system calibration strategy, based on coplanar constraint, is presented. The experimental setup consisted of a camera and an LED projector. Experiments were carried out to verify the accuracy of the proposed method.
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