Ocular Depth Measurement Using Segmented Light Interference
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Solution Overview
Problem
Existing ocular depth dimension measurement apparatuses face challenges in achieving accurate non-contact measurements due to low signal-to-noise ratios in interference signals, primarily because the light reflected from the cornea and fundus have different reflectance levels, leading to increased measurement errors and a burden on the eye from strong light projection.
Innovation Solution
The apparatus employs a measurement light projecting system that separates light into corneal and fundus measurement lights, using a reference light to interfere with both, allowing for accurate interference signal detection and calculation of ocular depth dimension, while reducing the optical path length to enhance signal quality and minimize eye burden.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strong light is projected onto the eye to increase the S/N ratio of the interference signal, then measurement precision is improved, but the eye burden increases
Solution Approach 1:
The patent segments the measurement light into two separate beams: one for corneal measurement and one for fundus measurement. Each beam is optimized for its specific target, allowing the system to achieve high S/N ratios without requiring excessively strong light overall. The corneal measurement light interacts with the high-reflectance cornea, while the fundus measurement light interacts with the low-reflectance fundus, enabling precise measurements with reduced eye burden.
2Ease of operation
If light from cornea and fundus is made to interfere with each other, then measurement can be performed, but measurement precision deteriorates due to low S/N ratio
Solution Approach 1:
The patent divides the interference measurement into two independent channels: one for corneal measurement and one for fundus measurement. Each channel uses dedicated light beams optimized for its specific measurement target, preventing the S/N ratio degradation that occurs when mixing corneal and fundus light. The corneal measurement light is optimized for high reflectance interaction, while the fundus measurement light is optimized for low reflectance interaction, ensuring high precision in both measurements.
Solution Approach 2:
The patent introduces a reference light beam as an intermediary that interferes with both the corneal measurement light and the fundus measurement light separately. This reference light serves as a common baseline that enables precise measurement of both high-reflectance (cornea) and low-reflectance (fundus) surfaces without requiring the corneal and fundus lights to interfere with each other directly.
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 enables accurate ocular depth dimension measurement with improved signal-to-noise ratios and reduced eye burden by optimizing the interference signal detection and calculation, allowing for precise axial length determination.
Implementation Method 1
a light source emitting low coherent light
Implementation Method 2
synthesizing and making the light reflected from a fundus and the light reflected from a cornea interfere with each other
Implementation Method 3
an optical path length changing member, which obtains the axial length based on the obtained interference signal and the position of the optical path length changing member
Data Source
AI summary
An ocular depth dimension measurement apparatus capable of accurately obtaining an ocular depth dimension. The apparatus has a measurement light projecting optical system with a light source which is arranged to make a part of the light from the light source into first and second measurement light and collect the respective measurement light on first and second measurement surfaces of the eye, an interference optical system with a separation unit arranged to make the light into reference light and an optical path length changing unit which is arranged to synthesize the first and second measurement light respectively with the reference light to make them interfere with each other so as to photo-receive and obtain interference signals of the respective interference light, and a calculation part arranged to calculate the ocular depth dimension based on the interference signals and a driving result of the changing unit.