Non-contact Tonometer Optical Alignment for Corneal Imaging
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Solution Overview
Problem
Existing tonometers fail to accurately measure corneal thickness and correct intraocular pressure due to focus issues on peripheral and posterior corneal surfaces, leading to inaccurate measurements.
Innovation Solution
A non-contact tonometer with a projecting optical system that includes a light restriction unit and an imaging optical system aligned to intersect on one axis, allowing for precise imaging of the anterior segment's cross-sectional image, and a fluid blowing unit to deform the cornea, enabling accurate corneal thickness measurement and intraocular pressure correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical system is used to image the cornea, then the center of the corneal anterior surface can be imaged in focus, but the peripheral part of the corneal anterior surface and corneal posterior surface cannot be imaged in focus
Solution Approach 1:
The patent applies the Scheimpflug principle to tilt the imaging plane relative to the object plane, creating a three-dimensional imaging geometry. This allows the imaging plane to be perpendicular to the optical axis while the object plane (corneal surface) is tilted, enabling simultaneous sharp focus across the entire corneal surface including peripheral and posterior regions, thereby resolving the focus issue that limited conventional optical systems
2Illumination intensity
If light is projected onto the anterior segment without restriction, then more light reaches the cornea, but light passes through outside the nozzle causing measurement errors
Solution Approach 1:
The patent introduces a light restriction unit (aperture) that selectively allows light to pass through only the nozzle region while blocking light from other areas. This creates localized illumination precisely where needed (through the nozzle onto the cornea) while preventing stray light from interfering with the measurement, thereby simultaneously maintaining sufficient illumination intensity and 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
The solution provides clear, focused cross-sectional images of the cornea, allowing for precise calculation of corneal thickness and accurate correction of intraocular pressure, overcoming previous focus issues and ensuring reliable measurements.
Implementation Method 1
a projecting optical system for projecting light onto an anterior segment of the examinee's eye through the nozzle
Implementation Method 2
an imaging optical system for imaging a cross-sectional image of the anterior segment, the system including an imaging lens and an imaging element
Implementation Method 3
a fluid blowing unit for blowing a fluid at a cornea of the examinee's eye through a nozzle
Data Source
Figure 1
Figure 2
Figure 3~5(c)
AI summary
A tonometer for measuring intraocular pressure of an examinee's eye in a non-contact manner, comprises: an arithmetic part (20) for calculating the intraocular pressure; a fluid blowing unit (1-7, 9) for blowing a fluid at a cornea of the examinee's eye through a nozzle (6); a projecting optical system (90a) for projecting light onto an anterior segment of the examinee's eye through the nozzle, the system including a light source (91) and a condensing lens (34, 47, 92); and an imaging optical system (90b) for imaging a cross-sectional image of the anterior segment, the system including an imaging lens (96) and an imaging element (97). The imaging optical system is placed so that extended planes of a cross section of the light projected onto the anterior segment by the projecting optical system, a principal plane of the imaging lens, and an imaging plane of the imaging element intersect one another on one axis, and the projecting optical system includes a light restriction unit (7) that allows the light from the light source to pass through inside of the nozzle but not to pass through outside of the nozzle.