Variable Focal Length Lens Aberrometer with Calibration Feedback
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Solution Overview
Problem
Existing optical measurement systems, particularly wavefront aberrometers, face challenges in determining the current focal length of a variable focal length lens, leading to poor repeatability in measurements, especially when temperature stability is compromised.
Innovation Solution
Incorporating a switchable calibration light source and signal processing techniques to determine the adjusted focal length of the variable focal length lens, allowing for accurate refraction measurements by processing image data from both probe light and calibration light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a variable focal length lens is used to correct lower order aberrations, then the ability to correct aberrations is improved, but the repeatability of focal length setting deteriorates due to temperature instability
Solution Approach 1:
The system uses a feedback mechanism where the wavefront sensor measures the actual focal length setting by analyzing the wavefront of light returning from the variable focal length lens. This measured focal length is then fed back to the control system, which adjusts the control signal to achieve the desired focal length setting, thereby compensating for temperature-induced drift and improving repeatability.
Solution Approach 2:
The patent replaces direct mechanical positioning mechanisms with an optical measurement and feedback control system. Instead of relying solely on mechanical precision to maintain focal length settings, the system uses optical wavefront sensing to detect and correct focal length deviations, substituting mechanical stability requirements with optical measurement and electronic control.
2Ease of manufacture
If commercially available variable focal length devices are used, then device availability is improved, but measurement repeatability deteriorates under temperature changes
Solution Approach 1:
The system implements a feedback control loop that continuously monitors the actual focal length setting using wavefront sensing and adjusts the control signal accordingly. This feedback mechanism compensates for temperature-induced focal length drift, enabling commercially available devices to achieve repeatable measurements despite environmental temperature changes.
3Measurement precision
If the wavefront sensor is used to measure eye refraction, then measurement capability is improved, but the system cannot determine the current focal length setting without additional techniques
Solution Approach 1:
The system uses an intermediary measurement approach where the wavefront sensor measures the wavefront of light that has passed through the variable focal length lens. By analyzing this wavefront, the system indirectly determines the actual focal length setting of the lens, recovering information that would otherwise be lost due to the lack of direct sensing capability.
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 enhances the repeatability and accuracy of wavefront aberrometry measurements by accounting for the focal length variations, even under changing temperature conditions, thereby improving the reliability of aberration determination in eye measurements.
Implementation Method 1
a variable focal length lens configured to provide a pre-correction system which compensates the probe light beam to be injected into a subject's eye for aberrations in the subject's eye
Implementation Method 2
a wavefront sensor configured to measure a wavefront of light returned from the subject's eye
Implementation Method 3
provides a pre-correction system which compensates the probe light beam to be injected into a subject's eye for aberrations in the subject's eye
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
An optical measurement system: passes a probe light beam through a variable focal length lens to the retina of an eye, and returns light from the retina through the variable focal length lens to a wavefront sensor; adjusts the focal length of the variable focal length lens to provide a desired characteristic to at least one of: the probe light beam, and the light returned by the retina to the wavefront sensor; passes a calibration light through the variable focal length lens to the wavefront sensor while the variable focal length lens is at the adjusted focal length to ascertain the adjusted focal length; and makes a wavefront measurement of the eye from the light returned from the retina of the eye through the variable focal length lens to the wavefront sensor, and from the adjusted focal length ascertained from the calibration light received by the wavefront sensor.