Eye Tester Alignment Using Non-Telecentric Corneal Target Imaging
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Solution Overview
Problem
Existing ophthalmic apparatuses fail to accurately align an examinee's eye with an eye tester in the working distance direction due to the use of telecentric target photographing optical systems, which do not account for variations in corneal curvature and distance, leading to inaccuracies in test results.
Innovation Solution
An ophthalmic apparatus with a non-telecentric target photographing optical system that projects first and second targets under different conditions, coupled with a correction mechanism to adjust the positional relationship between the eye and the tester based on association information, correcting errors caused by corneal curvature and non-telecentricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a telecentric target photographing optical system is used, then the alignment in the working distance direction can be simplified, but the measurement precision deteriorates due to inability to account for corneal curvature variations
Solution Approach 1:
The patent changes the optical system parameter from telecentric to non-telecentric configuration. This enables the system to capture parallax information that correlates with corneal curvature variations, allowing the corrector to calculate accurate working distance measurements by processing the positional relationships between multiple target images under different projection conditions.
2Measurement precision
If alignment targets are projected under different projection conditions, then the measurement precision can be improved by accounting for corneal curvature, but the device complexity increases due to multiple targets and correction mechanisms
Solution Approach 1:
The non-telecentric target photographing optical system serves multiple functions: it photographs alignment targets for basic alignment, captures parallax information for corneal curvature estimation, and provides positional data for working distance calculation. This multi-functionality reduces the need for separate systems for each measurement task.
Solution Approach 2:
The system uses virtual images created by reflecting alignment targets off the cornea as copies to infer corneal curvature and working distance. By analyzing the positional relationships between these virtual target images and the actual targets, the corrector can calculate measurement parameters without direct physical measurement of the cornea.
3Measurement precision
If a non-telecentric target photographing optical system is used, then the measurement precision can be improved by accounting for corneal curvature and distance variations, but the ease of operation worsens due to the need for complex correction calculations
Solution Approach 1:
The system performs self-correction by automatically calculating the working distance error based on the positional relationships between targets and their virtual images. The corrector processes the captured image data and generates correction values without requiring manual intervention, making the complex correction process transparent to the user.
Solution Approach 2:
The system uses the positional information from the non-telecentric photographing to generate feedback about the actual working distance and corneal curvature. This feedback is processed by the corrector to determine correction values, which are then applied to achieve accurate alignment. The feedback loop enables automatic compensation for individual anatomical variations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for precise alignment and accurate test results by correcting errors in the working distance, reducing the need for re-adjustment and shortening alignment time, even when deviations occur.
Implementation Method 1
a first target image as an image of the first target reflected by the cornea and a second target image as an image of the second target reflected by the cornea
Data Source
AI summary
An ophthalmic apparatus includes a tester having a target projecting optical system and a target photographing optical system. with a configuration on an examinee's eye side being non-telecentric, an alignment adjuster that adjusts at least a positional relationship between an examinee's eye and the tester in the direction of a working distance between the examinee's eye and the tester, and a corrector that acquires an actual error from a proper working distance based on association information indicating the association of position information on the positions of first and second target images on an observation image with an error in the working distance with respect to the proper working distance due to the corneal curvature radius of the examinee's eye and the non-telecentricity of the target photographing optical system and the position information on the tester at the current position thereof in the working distance direction, correcting the actual error.