Image-Based Scanning for Fixation Measurement
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Solution Overview
Problem
Existing optometry devices face challenges with mechanical scanning methods, including vibrations, short motor lifespan, high production costs, and signal-to-noise ratio issues with polarization techniques, which affect accuracy and safety.
Innovation Solution
An image-based scanning method using a beam splitter, projection system, and image sensing devices to capture fixation information without mechanical movement or polarization, allowing for fixed components and improved signal-to-noise ratio through pulsed laser illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical scanning methods are used with rotating mirrors, then fixation measurements can be performed, but vibrations occur that impact measurement accuracy
Solution Approach 1:
The patent replaces the mechanical rotating mirror scanning system with a fixed mirror configuration combined with a moving image sensor array. The scanning function is achieved by moving the sensor array across the retinal image plane rather than mechanically scanning the light path, thereby eliminating vibrations associated with high-speed rotating components while maintaining measurement capability.
Solution Approach 2:
Instead of moving the optical path to scan the retinal image (traditional approach), the patent inverts the approach by keeping the optics fixed and moving the image sensor array to achieve the same scanning effect. This reversal eliminates the need for high-speed rotating mirrors and their associated vibrations.
2Measurement precision
If high-speed rotating mirrors are used for scanning, then fixation measurements can be performed, but the motor lifespan is reduced
Solution Approach 1:
The patent eliminates the high-speed rotating mirror and its drive motor by substituting with a fixed optical system combined with a moving image sensor array. This replacement removes the short-lived motor component entirely, achieving the same measurement function through a different mechanical approach that does not require high-speed rotation.
Solution Approach 2:
The patent extracts and removes the problematic high-speed motor from the system by replacing the active scanning mirror mechanism with a passive fixed mirror system. The scanning function is achieved through sensor array movement rather than motor-driven mirror rotation, eliminating the component with short lifespan.
3Measurement precision
If mechanical scanning components are used, then fixation measurements can be performed, but production costs increase due to tight tolerances and skilled assembly
Solution Approach 1:
The patent replaces the complex mechanical scanning system requiring tight tolerances and skilled assembly with a fixed optical system and moving sensor array. This substitution eliminates the need for precision-balanced rotating mirrors and complex motor assemblies, significantly simplifying manufacturing and reducing costs.
Solution Approach 2:
The patent segments the scanning function from the optical system, placing the scanning capability in the movable sensor array rather than in the fixed optical components. This segmentation allows the optical system to be simpler and easier to manufacture, while the scanning function is achieved through a separate, more manufacturable mechanism.
4Measurement precision
If polarization techniques are used for fixation measurement, then measurements can be obtained, but the signal-to-noise ratio is reduced in environments with background light
Solution Approach 1:
The patent changes the measurement parameter from polarization state detection to direct intensity detection of the retinal image. By using an image sensor array to capture the retinal image directly and track its movement, the system avoids the signal-to-noise ratio problems of polarization measurements in environments with background light.
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 image-based method reduces vibration-related issues, increases device lifespan, and enhances signal quality, enabling accurate fixation measurement and potential for refraction error analysis with reduced instrument complexity and cost.
Implementation Method 1
illuminating an eye with light from a light source so as to cause a first image of the light source to be formed on a retina of the eye
Implementation Method 2
capturing the light returning from the retina with a sensor so as to receive at least a portion of a second image of the first image on the sensor
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A method and apparatus for fixation measurement includes projecting, by an image projector, a stimulus onto one or more eyes of a patient via a beam splitter, and capturing, by one or more image sensing devices disposed conjugate to the one or more eyes, a reflected image including light reflected from the one or more eyes in response to the stimulus, the reflected image including information indicating the fixation of the one or more eyes.