Non-Contact Tonometer Dual Alignment Reference Switching
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Solution Overview
Problem
Conventional non-contact tonometers face challenges in accurately measuring corneal thickness due to the small reflection from the corneal rear surface, which results in decreased measurement accuracy when the alignment reference is set with the corneal front surface, leading to a decrease in the peak of the reflected light from the rear surface.
Innovation Solution
A non-contact tonometer with a moving mechanism and alignment detection system that switches between two alignment references, one for eye pressure measurement on the corneal front surface and another closer to the corneal rear surface for corneal thickness measurement, using a shared detector to differentiate between reflection signals from both surfaces and adjust the measurement unit accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the alignment reference is set on the corneal front surface for eye pressure measurement, then the eye pressure measurement can be performed, but the measurement accuracy of corneal thickness decreases due to small reflection from the corneal rear surface
Solution Approach 1:
The patent applies dynamics by making the alignment reference position changeable between two states: a first alignment reference on the corneal front surface for eye pressure measurement, and a second alignment reference closer to the corneal rear surface for corneal thickness measurement. This dynamic adjustment of the alignment reference position allows the system to optimize signal detection for different measurement modes, resolving the contradiction between maintaining eye pressure measurement capability and improving corneal thickness measurement accuracy.
Solution Approach 2:
The patent changes the parameter of alignment reference position based on the measurement mode. By switching between two distinct alignment reference positions (first on front surface, second near rear surface), the system optimizes the detection conditions for each type of measurement. This parameter change enables the reflected light signal from the corneal rear surface to be sufficiently strong for accurate corneal thickness measurement while preserving eye pressure measurement functionality.
2Device complexity
If a single alignment reference is used for both eye pressure and corneal thickness measurement, then the device structure is simplified, but measurement accuracy for corneal thickness decreases
Solution Approach 1:
The patent implements multi-functionality by enabling a single alignment detection system to serve dual purposes through switching between two alignment reference positions. The same detection device can align with either the first alignment reference (corneal front surface) for eye pressure measurement or the second alignment reference (near corneal rear surface) for corneal thickness measurement. This universal design achieves accurate measurements for both functions without requiring separate alignment systems, thus maintaining device simplicity while improving measurement precision.
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 accurate measurement of corneal thickness and correction of eye pressure values by ensuring optimal alignment and signal detection, enhancing the precision of both measurements.
Implementation Method 1
Reflected light from the cornea is received by a light receiving device, such as a line sensor. The apparatus measures the corneal thickness based on a peak value of a light receiving signal for reflected light from front and rear surfaces of the cornea.
Data Source
AI summary
A non-contact type tonometer includes: a measurement unit including a first measuring unit for measuring an eye pressure of an examinee's eye in a non-contact manner and a second measuring unit for measuring a corneal thickness of the examinee's eye in a non-contact manner; a moving mechanism for causing relative movement of the measurement unit with respect to the examinee's eye; a drive controller for driving the moving mechanism for aligning the measurement unit; and a setting switch controller for switching an alignment reference on the cornea used for aligning the measurement unit between first and second alignment references. The first alignment reference is a reference for measuring the eye pressure with the first measuring unit and the second alignment reference is a reference for measuring the corneal thickness with the second measuring unit and set closer to a corneal rear surface than the first alignment reference.