Auxiliary-Lens Mach-Zehnder Interferometer for Lens Power Measurement
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Solution Overview
Problem
Existing interferometers struggle to accurately measure the lens power of high-power transparent test objects, such as intraocular lenses, due to the close spacing of fringes in transmitted wavefront measurements.
Innovation Solution
A Mach-Zehnder interferometer is configured with auxiliary lenses in the test arm to collimate the test beam, allowing for varying relative distances between the test object and auxiliary lenses, capturing multiple interference patterns to determine lens power through interferometric measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Mach-Zehnder interferometer is used to measure transparent test objects, then the transmitted wavefront can be measured, but the fringe spacing becomes too close for accurate measurement of lens power
Solution Approach 1:
An auxiliary lens is introduced as an intermediary element in the test arm of the interferometer. This auxiliary lens modifies the wavefront before it reaches the test object, creating a virtual image that effectively increases the fringe spacing. The auxiliary lens acts as a mediator that transforms the measurement problem into a solvable form by making fringes detectable and measurable.
Solution Approach 2:
The system changes the optical parameters by introducing the auxiliary lens with a specific focal length. This parameter change modifies the wavefront curvature and spacing characteristics, transforming the fringe pattern from too-close-to-measure to appropriately spaced for accurate lens power measurement. The focal length of the auxiliary lens is specifically chosen to achieve the desired fringe spacing.
2Measurement precision
If auxiliary lenses are added to collimate the test beam, then lens power can be accurately measured, but the device complexity increases
Solution Approach 1:
The auxiliary lens serves as a simple intermediary element that adds minimal complexity while solving the measurement problem. Rather than redesigning the entire interferometer system, a single auxiliary lens is introduced into the test arm to collimate the beam and create measurable fringes, thereby achieving accurate lens power measurement with minimal added complexity.
3Measurement precision
If multiple images are captured at different relative distances, then lens characteristics can be determined, but the measurement process becomes more complex
Solution Approach 1:
The system employs dynamic positioning of the test object or auxiliary lens to create multiple images at different relative distances. By moving either component along the optical axis, the system captures interferometric images at varying object distances, enabling determination of multiple lens characteristics including power and aberrations through analysis of the fringe pattern changes.
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
Accurately measures the lens power of high-power transparent objects by minimizing fringe spacing and enabling precise determination of lens characteristics, including aberrations, using auxiliary lenses to collimate and recombine beams.
Implementation Method 1
One or more auxiliary lenses are located in the test arm so that the test beam is transmitted through the test object and one or more auxiliary lenses. The configuration and respective positions of the test object and one or more auxiliary lenses are configured to approximately collimate the test beam.
Implementation Method 2
The interferometer splits an illumination beam into a reference beam directed to a reference arm and test beam directed to a test arm.
Implementation Method 3
The reference beam and test beam are combined after a single transmission of the test beam through the test object. The recombined beams generate an interference patterns.
Data Source
AI summary
A Mach-Zehnder interferometer is configured for measuring a transparent test object, such as measuring the power of a lens. The test object, for example, may be an interocular lens. The interferometer splits an illumination beam into a reference beam and test beam. The test beam is transmitted through the test object and one or more auxiliary lenses. The configuration and respective positions of the test object and one or more auxiliary lenses are configured to collimate the test beam. The one or more auxiliary lenses and/or test object may be positioned at different relative distances. The reference beam and test beam are recombined and the interference patterns imaged for different relative distances between the test object and one or more auxiliary lenses. A lens power may be determined based on the interferometric power measurements from the images and the change in the relative distances used for the images.