Ophthalmic Camera Automatic Focus via Luminance Analysis
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Solution Overview
Problem
Conventional ophthalmic photographing apparatuses, such as OCT and SLO, require manual focus adjustment, which is time-consuming and complex, and fundus cameras with target projection systems complicate the structure, making automatic focus adjustment difficult.
Innovation Solution
An ophthalmic photographing apparatus with a movable focusing optical element driven by a mechanism, controlled by a unit that calculates luminance frequency distribution changes to detect focus positions, allowing for automatic focus adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a target projection optical system is included in the optical system of OCT or SLO to enable automatic focus adjustment, then automatic focus adjustment capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the target projection function from a separate optical system and integrates it into the existing photographing optical system by placing a target plate at a specific position in the optical path. This eliminates the need for a dedicated target projection system while maintaining automatic focus adjustment capability.
Solution Approach 2:
The patent merges the target projection function with the existing photographing optical system. The target plate is positioned in the optical path such that the same optical system used for imaging also projects the target onto the fundus, combining two functions into one system.
2Device complexity
If manual focus adjustment is performed in OCT or SLO, then device structure remains simple, but operation time and complexity increase
Solution Approach 1:
The system performs self-service focus adjustment by automatically detecting the focus state through the photodetector and control unit, which analyze the reflected light from the target plate and autonomously adjust the focusing optical element without examiner intervention.
Solution Approach 2:
The patent implements a feedback mechanism where the photodetector continuously monitors the reflected light from the target plate, and the control unit uses this information to automatically adjust the focusing optical element, creating a closed-loop system that eliminates manual focus adjustment time.
3Measurement precision
If a target projection optical system is added to fundus camera, then automatic focus detection is enabled, but structure complexity increases
Solution Approach 1:
The patent makes the photographing optical system universal by enabling it to perform both target projection and fundus imaging functions. The same optical components are used for both purposes, eliminating the need for separate target projection and imaging systems.
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 simplifies the structure and enables efficient automatic focus adjustment, improving the speed and accuracy of image capture for both OCT and SLO systems.
Implementation Method 1
a photodetector arranged to photo-receive reflection light from the given region
Implementation Method 2
a focusing optical element provided movable in a direction of an optical axis by a driving mechanism
Data Source
AI summary
An ophthalmic photographing apparatus comprising a photographing optical system for obtaining a regional image of an examinee's eye, comprising a light source, a focusing optical element movable in an optical-axis direction by a driving mechanism, and a photodetector, and a control unit controlling driving of the mechanism and obtain the image based on a signal from the photodetector, wherein the control unit further moves the optical element in predetermined steps/continuously to obtain the image at each position, calculates frequency distribution of luminance of each of the images to detect a change characteristic of luminance values having frequencies equal or exceeding a threshold value in the frequency distribution with respect to the optical element position, and detects a focus position of the optical element based on the change characteristics to move the optical element to a position corresponding to the detected focus position.