Ophthalmic OCT Path-Length Control for Wide-Range Fundus Scanning
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Solution Overview
Problem
Existing ophthalmic devices face challenges in producing satisfactory three-dimensional data of a fundus due to deviations in fundus tomographic images within B-scan images, particularly when the scanning range of measurement light is wide, leading to reversed or folded images and reduced accuracy in auto-Z and Z-lock processing.
Innovation Solution
The ophthalmic device incorporates an interference optical system with an optical path length changing unit, optical scanner, pre-scan controlling unit, cross-sectional shape acquiring unit, main scan controlling unit, and three-dimensional data producing unit to adjust the optical path length to an optimum position, ensuring accurate alignment of tomographic images within B-scan images during three-dimensional OCT scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the scanning range of measurement light is set wide, then the coverage area of the fundus tomographic image is improved, but the image may not fit within the B-scan image frame and may produce reversed or folded images
Solution Approach 1:
The system performs a pre-scan before the main three-dimensional OCT photographing to acquire preliminary information about the fundus cross-sectional shape. Based on this pre-scan data, the system predicts the cross-sectional shape and calculates the optimum optical path length in advance, allowing the main scan to proceed with pre-determined optimal settings that prevent image reversal and folding while maintaining wide scanning coverage
Solution Approach 2:
The system uses the pre-scan results as feedback to adjust and determine the optimum optical path length for the main scan. The cross-sectional shape acquiring unit analyzes the pre-scan B-scan image to detect the fundus cross-sectional shape, and this detected shape feeds back into the optical path length determination process, creating a closed-loop control system that optimizes image positioning based on actual fundus geometry
2Area of stationary object
If the scanning range of measurement light is set wide, then the coverage area is improved, but the sharpness of fundus tomographic image is reduced
Solution Approach 1:
The pre-scan is executed before the main wide-range scan to gather preliminary data about the fundus structure. This preliminary action allows the system to optimize scanning parameters and determine optimal optical path lengths specifically tailored to the patient's anatomy, enabling the main scan to achieve both wide coverage and high image sharpness through pre-optimized settings
Solution Approach 2:
The system dynamically changes scanning parameters based on the detected cross-sectional shape. The optical path length is adjusted as a key parameter to optimize image quality for each specific scanning position and fundus geometry, allowing the system to maintain sharp images across wide scanning ranges by adapting parameters to local anatomical conditions
3Stability of the object's composition
If auto-Z and Z-lock functions are used to maintain reference position, then the position stability of fundus tomographic image is improved, but the accuracy of position detection is reduced when scanning range is wide
Solution Approach 1:
The system performs preliminary detection of the fundus cross-sectional shape through pre-scan before executing the main scan with auto-Z and Z-lock functions. This preliminary action provides accurate reference data about the fundus geometry, enabling the position detection algorithms to operate with higher accuracy even when wide scanning ranges are used, thereby maintaining both stability and precision
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 easy production of high-accuracy three-dimensional data by maintaining the position of fundus tomographic images within B-scan images, even with wide scanning ranges, thereby improving the accuracy and completeness of the three-dimensional data.
Implementation Method 1
an interference optical system that splits light from a light source into measurement light and reference light, irradiates a subject eye with the measurement light, and detects interference light between return light from the subject eye and the reference light
Data Source
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AI summary
There are provided an ophthalmic device and a control method for the ophthalmic device capable of easily producing satisfactory three-dimensional data of a site to be observed of a subject eye. The ophthalmic device includes a pre-scan controlling unit (216) configured to execute a pre-scan on a site to be observed (a fundus (Ef)), a cross-sectional shape acquiring unit (218) configured to detect or predict a cross-sectional shape of the site to be observed, a main scan controlling unit (220) configured to control an optical scanner and execute a main scan on the site to be observed, an optical path length acquiring unit (214) configured to acquire an optimum optical path length at a particular scanning position of the main scan at least before the main scan, an optical path length adjustment controlling unit (224) configured to, during execution of the main scan, control an optical path length changing unit to adjust an optical path length to the optimum optical path length, and a three-dimensional data producing unit (226) configured to produce three-dimensional data (404) of the site to be observed.