Fundus Camera Focusing Lens Reference Position Control
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Solution Overview
Problem
Differences in spherical diopter power among individuals lead to variations in fundus image sizes and angles of view during photography, causing inaccuracies in measurement and examination results due to changes in the incidence angle of examination targets.
Innovation Solution
A fundus photographing apparatus with a focusing lens that moves along the optical axis, setting a reference position where the distance from the diaphragm to the fundus is equal to the distance from the image of the diaphragm to the fundus image, ensuring a constant incidence angle and suppressing changes in the angle of view, regardless of individual diopter power differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focusing lens is moved to focus on the fundus based on individual diopter power, then the fundus can be photographed in focus, but the angle of view and image size vary causing measurement inaccuracies
Solution Approach 1:
The patent changes the reference position parameter of the focusing lens from being diopter-dependent to being fixed at the optical axis. This parameter change ensures that the distance relationship between the diaphragm and fundus remains constant, thereby maintaining a consistent angle of view and image size across different diopter powers, which resolves the measurement accuracy issue.
Solution Approach 2:
The patent creates a reference position model where the focusing lens is positioned at a fixed location on the optical axis. This reference position serves as a standardized copy that can be applied universally regardless of individual diopter variations, ensuring consistent examination conditions and improving reliability.
2Manufacturing precision
If the focusing lens position is adjusted for each individual's diopter power, then clear focus is achieved, but the incidence angle of examination targets changes affecting examination results
Solution Approach 1:
The patent changes the reference position parameter of the focusing lens from being diopter-dependent to being fixed at the optical axis. This parameter change ensures that the distance relationship between the diaphragm and fundus remains constant, thereby maintaining a consistent angle of view and image size across different diopter powers, which resolves the measurement accuracy issue.
3Adaptability or versatility
If the focusing lens moves along the optical axis to accommodate different diopter powers, then individual focusing requirements are met, but the angle of view changes causing variations in fundus image size
Solution Approach 1:
The patent changes the reference position parameter of the focusing lens from being diopter-dependent to being fixed at the optical axis. This parameter change ensures that the distance relationship between the diaphragm and fundus remains constant, thereby maintaining a consistent angle of view and image size across different diopter powers, which resolves the measurement accuracy issue.
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 approach allows for accurate fundus photography and examination across varying diopter powers, maintaining a consistent angle of view and improving measurement accuracy by setting the reference position of the focusing lens to minimize changes in image height due to diopter power variations.
Implementation Method 1
a photographing element for photographing the fundus to obtain a fundus image and detect the focus target
Implementation Method 2
a focusing lens that is moved along an optical axis to focus on the fundus
Implementation Method 3
a diaphragm arranged in a position substantially conjugate with a pupil of the examinee's eye
Data Source
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AI summary
A fundus photographing apparatus includes: an illuminating optical system for illuminating a fundus of an examinee's eye; a focus target presenting unit for projecting a focus target for focusing to the fundus via an objective lens; a photographing element for photographing the fundus to obtain a fundus image and detect the focus target; a diaphragm in a position substantially conjugate with a pupil of the examinee's eye with the objective lens therebetween; a focusing lens moved along an optical axis to focus on the fundus; and a controlling device for moving the focusing lens along the optical axis based on a result of detection of the focus target by the photographing element with a position where a first distance from the diaphragm to the fundus is substantially equal to a second distance from an image of the diaphragm to the fundus image as a reference position of the focusing lens.