Variable-Width Slit Illumination for Wide-Angle Fundus Imaging
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Solution Overview
Problem
Existing ophthalmic apparatuses face challenges in capturing high-quality, wide-angle images of the fundus due to illumination unevenness in peripheral regions, leading to reduced image quality.
Innovation Solution
The apparatus employs an illumination optical system with a slit-shaped aperture whose width in the shorter direction varies along the longitudinal direction, coupled with a photographic optical system using curved mirrors to receive returning light, thereby eliminating illumination unevenness and enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional aperture is used in the illumination optical system, then the device configuration is simple, but illumination unevenness occurs in peripheral regions leading to reduced image quality
Solution Approach 1:
The aperture is designed with non-uniform width where the width in the shorter direction varies depending on the position in the longitudinal direction. Specifically, the aperture is wider in the peripheral regions and narrower at the central region, creating local variations in light transmission that compensate for the natural fall-off of illumination intensity in wide-angle imaging systems. This local quality adjustment ensures uniform illumination across the entire field of view.
2Area of stationary object
If a wide scanning angle is used to capture the entire fundus in a single shot, then the field of view is increased, but optical distortions and contrast decrease occur
Solution Approach 1:
The aperture width parameter is changed along the longitudinal direction to compensate for optical distortions. By making the aperture wider at the periphery and narrower at the center, the system adjusts the light distribution to maintain consistent illumination intensity across the wide field of view, thereby preserving image quality and contrast even when capturing the entire fundus in a single shot.
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 the acquisition of high-quality, wide-angle images by correcting optical distortions and suppressing contrast decrease, enabling precise measurement of the eye's optical characteristics.
Implementation Method 1
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
Implementation Method 2
a slit with an aperture configured to be disposed at a fundus conjugate position and configured to irradiate slit-shaped illumination light, that is generated by irradiating light from a light source onto the slit
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An ophthalmic apparatus includes two or more curved mirrors, an illumination optical system ,and a photographic optical system. The illumination optical system includes a slit with an aperture configured to be disposed at a fundus conjugate position, the fundus conjugate position being substantially conjugate optically to a fundus of an eye to be examined, and 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 photographic optical system includes an image sensor configured to be disposed at the fundus conjugate position and to receive returning light from the eye to be examined through the two or more curved mirrors. The aperture is formed so that a width in a shorter direction differs depending on a position in a longitudinal direction.