Fundus Imaging Optics Using Curved Mirrors and a Displaced Slit
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Solution Overview
Problem
Existing fundus imaging technologies face challenges in achieving high-quality images at wide angles without requiring expensive high-speed scanners, advanced optical designs, and suffer from issues like contrast reduction, flare, and ghosting due to unnecessary light reception.
Innovation Solution
A fundus imaging apparatus using two or more curved mirrors to scan the fundus with slit-shaped illumination light and receive returning light with an image sensor, where the slit opening is displaced to minimize aberrations and unnecessary light capture, allowing for higher-quality images without complex designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a high speed scanner such as a polygon mirror is used to scan the fundus at a wide angle, then the imaging angle of view is improved, but the cost of the apparatus increases significantly
Solution Approach 1:
The patent employs curved mirrors (specifically ellipsoidal mirrors) instead of flat mirrors or polygon mirrors to achieve wide-angle fundus imaging. The curved surface geometry enables broad field of view without requiring high-speed mechanical scanning components, thereby resolving the contradiction between imaging angle and apparatus cost.
2Area of stationary object
If the slit opening is made wider to illuminate a broader range of the fundus, then the imaging coverage is improved, but unnecessary light is received causing contrast reduction and flare
Solution Approach 1:
The patent applies asymmetric displacement to the slit opening, where only specific portions (one or both ends in the longitudinal direction) are displaced in the shorter direction. This localized modification allows the slit to maintain appropriate illumination coverage while preventing excessive light reception that causes flare and contrast loss.
Solution Approach 2:
The slit opening is designed with asymmetric geometry by displacing ends relative to the center longitudinal direction. This asymmetric configuration optimizes the balance between illumination coverage and suppression of unwanted light, eliminating the need for symmetric rectangular or circular openings.
3Device complexity
If ellipsoidal concave mirrors are used to achieve wide-angle imaging with simple configuration, then the apparatus complexity is reduced, but optical aberrations increase requiring advanced optical design
Solution Approach 1:
The patent modifies the slit opening parameters by displacing its ends in the shorter direction relative to the longitudinal center line. This parameter change compensates for optical aberrations introduced by the ellipsoidal mirrors, maintaining image quality without requiring complex optical design or additional corrective elements.
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 apparatus achieves higher-quality fundus images at low cost and with a simple configuration by minimizing aberrations and reducing unnecessary light reception, improving contrast and reducing flare and ghosting.
Implementation Method 1
an illumination optical system configured to irradiate slit-shaped illumination light, that is generated by irradiating light from a light source onto a slit, onto the fundus... two or more curved mirrors; an illumination optical system... configured to irradiate slit-shaped illumination light
Implementation Method 2
at least one of both ends of the opening in a longitudinal direction is displaced in a shorter direction of the opening with reference to the longitudinal direction passing through a center of the opening
Data Source
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AI summary
A fundus imaging apparatus includes two or more curved mirrors, an illumination optical system, and an image sensor. The illumination optical system includes a slit with an opening configured to be disposed at a fundus conjugate position. Here, the fundus conjugate position is substantially conjugate optically to a fundus of an eye to be examined. The illumination optical system is configured to irradiate slit-shaped illumination light, that is generated by irradiating light from a light source onto the slit, onto the fundus through the two or more curved mirrors. The image sensor is configured to be disposed at the fundus conjugate position and to receive returning light from the eye to be examined. At least one of both ends of the opening in a longitudinal direction is displaced in a shorter direction of the opening with reference to the longitudinal direction passing through a center of the opening.