Corneal Reflection Optics With Dual Pattern Projection
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Solution Overview
Problem
Existing ophthalmic apparatuses face a challenge in maintaining measurement accuracy of the corneal shape due to reduced light intensity of the pattern index projected from the examination window, which is attenuated by the optical path coupling unit, when the objective lens and examination window are enlarged.
Innovation Solution
The apparatus employs a dual projection system using visible and infrared light for pattern indices, coupled by an optical element with lower attenuation for visible light, allowing efficient capture of corneal reflections through an optical paths coupler like a dichroic mirror, and image processing to enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the objective lens and examination window are enlarged to expand measurement range, then the measurement range is improved, but the light intensity of the pattern index reaching the imaging optical system is attenuated
Solution Approach 1:
The patent divides the pattern index projection into two separate optical systems: a first pattern index projection optical system positioned outside the examination window and a second pattern index projection optical system positioned inside the examination window. This segmentation allows each system to be optimized independently for its specific function, with the first system providing strong illumination for overall corneal shape measurement and the second system providing complementary illumination to compensate for attenuation in the enlarged optical path.
Solution Approach 2:
The patent introduces an optical paths coupler as an intermediary component that couples the optical paths of the imaging optical system and the second pattern index projection optical system. This coupler mediates the light transmission, ensuring that the pattern index light from the second optical system reaches the imaging element with sufficient intensity despite the enlarged examination window and objective lens.
2Measurement precision
If the pattern index is projected from inside the examination window to maintain measurement accuracy, then the measurement accuracy is improved, but the light intensity is attenuated due to optical path coupling unit
Solution Approach 1:
The patent segments the pattern index projection function into two independent optical systems positioned at different locations (outside and inside the examination window). This allows the first system to provide strong illumination for accurate measurement while the second system compensates for attenuation, with each system optimized for its specific positioning and illumination requirements.
Solution Approach 2:
The patent employs different optical characteristics for the two pattern index projection systems, with the first system using optical parameters optimized for strong illumination from outside the examination window and the second system using parameters optimized for compensation of attenuation when projected from inside the examination window. The optical paths coupler is specifically designed with transmission characteristics that preserve light intensity for the second system.
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 approach ensures sufficient light intensity for accurate corneal shape measurement, particularly of the central portion, by optimizing light projection and reception, reducing the impact of iris color variation, and enhancing measurement precision.
Implementation Method 1
the optical paths coupler is an optical element having a characteristic in which a ratio of attenuation of the visible light is smaller than a ratio of attenuation of the infrared light in an optical path from a cornea of the subject eye toward the imaging element
Implementation Method 2
the first index projection optical system projects the first pattern index with visible light
Implementation Method 3
the second index projection optical system projects the second pattern index with infrared light
Implementation Method 4
an imaging optical system including an imaging element configured to receive a first cornea reflection image caused by the first pattern index
Implementation Method 5
an imaging optical system including an imaging element configured to receive a second cornea reflection image caused by the second pattern index
Data Source
AI summary
An ophthalmic apparatus has an examination window, a first optical system which projects a first pattern index with visible light onto a subject eye from an outside of the examination window, a second optical system which projects a second pattern index with infrared light onto the subject eye from an inside of the examination window, an imaging optical system including an imaging element which receives a first cornea reflection image caused by the first pattern index and a second cornea reflection image caused by the second pattern index via an objective lens, and a coupler which couples optical paths of the imaging optical system and the second optical system. The coupler is an optical element having a characteristic in which an attenuation ratio of the visible light is smaller than that of the infrared light in an optical path from a cornea of the subject eye toward the imaging element.