Position Of Optical Center Research Articles

Optimizing correction of coma aberration in keratoconus with a novel soft contact lens

PurposeTo report on a second-generation prototype contact lens (modified lens) with enhanced optics to correct coma aberration and compare its performance with that of the prototype contact lens (conventional lens) used to optimise correction of coma aberration in keratoconus (KC). MethodsBoth lenses were designed as a set of standardised soft contact lenses (SCLs) with asymmetric powers along the posterior surface. The modified lens differs from the conventional lens in that the optical zone is decentred superiorly by 0.7 mm. The on-eye performance was compared between the SCLs and no-lens wearing in terms of manifest refraction, corrected distance visual acuity (CDVA), ocular aberrations, subjective quality of vision, and on-eye lens position relative to the pupil. ResultsThirty-four KC eyes were included. SCLs significantly decreased coma aberration compared to no-lens wear (none, 0.68 ± 0.27 μm; conventional lens, 0.37 ± 0.28 μm; modified lens, 0.19 ± 0.15 μm; P < 0.001), with the reduction in coma aberration being significantly greater with the modified lens than with the conventional lens (P = 0.018). No significant difference in manifest refraction or CDVA was found among the three conditions. Quality of vision was significantly better with the modified lens than with no SCL wear (P < 0.05) but no differences were found between the SCLs. The on-eye optical center position relative to the pupil was closer to the pupil centre using the modified lens than the conventional lens (P < 0.001). ConclusionOptimisation of the location of the optical zone in a standardised asymmetric SCL improves correction of coma aberrations and on-eye optical centration.

PLANAR POLYGONS DETECTION IN LIDAR SCANS BASED ON SENSOR TOPOLOGY ENHANCED RANSAC

Abstract. Detecting planar structures in point clouds is a very central step of the point cloud processing pipeline as many Lidar scans, in particular in anthropic environments, present such planar structures. Many improvements have been proposed to RANSAC and the Hough transform, the two major types of plane detection methods. An important limitation however is that these methods detect planes running across the whole scene instead of more localized planar patches. Moreover, they do not exploit the sensor information that often comes with Lidar point cloud (sensor topology and optical center position in particular). In this paper we address both issues: we aim at detecting planar polygons that have a limited spatial extent, and we exploit sensor topology. The latter is used to enhance a RANSAC framework on two aspects: to make seed points selection more local and to define more compact sets of inliers through sensor space region growing.

Three-element optical system with a given fixed position of optical center.

Our paper presents a detailed theoretical analysis of the three-element optical system with zero separation of principal planes and approximately corrected Petzval sum, which has the required value of the axial position of its optical center for a given value of focal length and a given value of axial distance of the image focal point from the last element of the system. Formulas that make it possible to calculate paraxial parameters of such types of optical systems are derived, and the application of the derived formulas is presented in several examples. Such optical systems represent a subset of the new family of optical systems with the constant position of the optical center. The optical center of such an optical system is at a given required axial position, and this position does not change with the object distance, which could be advantageous for certain applications.

Three-component zoom lens with fixed position of optical center.

A method is proposed for calculation of initial parameters of a three-element zoom lens with an identical position of object and image principal planes of the optical system and approximately zero Petzval sum. Such an optical system has a fixed position of its optical center, which does not depend on object distance. The proposed method makes it possible to determine focal length values of individual elements and trajectories of their movements during zooming. The analysis is presented on examples of the calculation of parameters of such optical systems. These systems could be useful in optical measuring methods, photogrammetry, and machine vision techniques.

Paraxial design of four-component zoom lens with fixed position of optical center composed of members with variable focal length

The paper presents paraxial analysis of special types of zoom lenses, which are composed of four members with variable focal length. The position of optical center of these systems is required to be fixed for a given value of focal length (i.e., the position of the optical center does not depend on object distance for given value of focal length of the zoom). The formulas that enable the calculation of the optical powers of individual members of such a zoom lens are derived from--and the practical application of the derived formulas is demonstrated with--an example. Such optical systems represent a completely new family of zoom optical systems with applications in measuring systems in photogrammetry, computer vision, triangulation sensors, fringe projection techniques, surveying, machine vision, and so forth.

Analysis of the optical center position of an optical system of a camera lens.

A theory of an optical center of a camera lens is described. The concept of an optical center (a camera center) is used widely in various methods dedicated to the calibration of optical imaging and measuring systems in photogrammetry, computer vision, triangulation sensors, fringe projection techniques, surveying, and machine vision, where the so-called pinhole camera model is used as the camera's basic model. It is shown that the optical center of the optical system with a fixed position does not exist generally, even for an ideal optical system. The optical center can be defined unambiguously for an ideal lens only for one specific object distance in general. Moreover, equations are derived for the calculation of initial design parameters of the three-element optical system composed of thin lens elements having the identical position of object and image principal planes. Such optical systems will have a fixed-position optical center, which does not depend on the object distance. The analysis was presented on several examples of the calculation of parameters of these optical systems.

Phase-locked optical metrology I: identification of intrinsic camera parameters from multiple grid views.

Camera-based optical metrology crucially relies on a proper identification of intrinsic (optical center position) and extrinsic (camera position) parameters of the used camera. A novel approach for processing phase data from multiple views of a target grid is presented, allowing these identifications within a pinhole camera model. First, the homography associated with the perspective distortion of each grid image is accurately identified using a phase-locking loop. Then, the affine transform for each view is determined, with the constraint of an identical set of intrinsic camera parameters. This requires slightly adjusting each homography. As there are highly redundant data, a criterion has to be chosen to optimize the result. The chosen criterion is the simultaneous minimization of the standard deviation between in-plane grid line displacements between the acquired grid images and the reconstructed ones. Experimental results demonstrate the efficiency of the method.