Eye Chart Device Using Folded Optical Path for Compact Design
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Solution Overview
Problem
Conventional eye chart presentation devices are bulky due to the need for a long optical path length, increasing their height and depth dimensions, which is undesirable for placement on optometry tables.
Innovation Solution
The device incorporates a display that emits light flux laterally, a reflection mirror system with two mirrors to redirect light flux orthogonally, and a convex lens system with a focal length greater than 800 mm, allowing for a compact design by optimizing the optical path without compromising image presentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the light flux is reflected vertically upward by the reflection mirror and the convex lens system is disposed vertically above the reflection mirror, then the optical path length is secured, but the height dimension of the apparatus increases
Solution Approach 1:
The patent changes the arrangement from a vertical configuration to a lateral configuration. The display emits light flux in the lateral direction (width direction), the reflection mirror reflects light in the width direction, and the convex lens system is disposed in the width direction rather than height direction. This dimensional change allows the optical path to be secured while reducing the height dimension of the apparatus.
2Length of stationary object
If the distance from the reflection mirror to the convex lens system is increased to secure the optical path length, then the optical function is maintained, but the depth dimension of the apparatus increases
Solution Approach 1:
The patent redistributes the optical path in the width direction and height direction using multiple reflection mirrors instead of extending it in the depth direction. The first reflection mirror reflects light in the width direction, and the second reflection mirror reflects light in the height direction, allowing the optical path to be folded back on itself. This creates a compact optical path that achieves the necessary optical length without increasing the depth dimension.
3Volume of stationary object
If the apparatus is downsized in the height direction and depth direction, then the space efficiency is improved, but the optical path length necessary for the reflection mirror and convex lens system may be compromised
Solution Approach 1:
The patent implements a folded optical path where light flux is reflected back and forth within a compact space. The first reflection mirror and second reflection mirror create a nested optical path structure where the light path folds within the apparatus body. This allows the optical path length to be extended without proportionally increasing the apparatus volume, achieving compact downsizing while maintaining necessary optical path length.
Solution Approach 2:
The patent uses multiple reflection mirrors to redirect light flux in different directions (width direction and height direction), creating a three-dimensional folded optical path. This allows the optical path to utilize the available space more efficiently by extending in multiple dimensions rather than a single direction, achieving compact apparatus size while maintaining sufficient optical path length.
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 reduces the height and depth of the device by approximately half, enabling a more compact and space-efficient ophthalmologic apparatus while maintaining the necessary optical path length, thus downsizing the apparatus effectively.
Implementation Method 1
a reflection mirror to reflect light flux emitted from the display
Implementation Method 2
a convex lens system to form a virtual image of the eye chart image based on the light flux reflected by the reflection mirror
Implementation Method 3
an optical path bending mirror to bend an optical path of the reflected light passing through the convex lens system
Data Source
AI summary
An eye chart presentation device includes a display to display an eye chart image on a screen, a reflection mirror to reflect light flux emitted from the display, and a convex lens system to form a virtual image of the eye chart image from the light flux reflected by the reflection mirror, the focal length of the convex lens system being greater than 800 mm. The screen is positioned within the focal length of the convex lens system, and the display emits the light flux from a lateral direction with respect to sightline of the eye. The reflection mirror includes a first mirror to directly reflect the light flux from the display and a second mirror to reflect the light flux reflected by the first mirror to the convex lens system.