Catadioptric Scanning Microscope with Curved Mirror
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Solution Overview
Problem
Conventional scanning microscopes face challenges in achieving high resolution with a numerical aperture (NA) of 0.5 or more while providing a wide field of view (FOV) greater than 10 mm, which is limiting in applications like two-photon microscopy of live organisms.
Innovation Solution
A scanning microscope apparatus utilizing a catadioptric objective with a curved, partially transmissive mirror and a reflective polarizer, combined with beam expanders and polarization retarders, to enhance FOV up to 20 mm while maintaining high NA, using adaptations of pancake optics to minimize aberrations and maximize signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional lens systems are used to increase FOV, then FOV can be expanded, but optical aberrations increase and system complexity increases
Solution Approach 1:
The patent employs a curved, partially transmissive mirror surface with a center of curvature positioned at or near the scanner's axis of rotation. This spherical curvature allows the mirror to focus light across a wide angular range while maintaining optical quality, enabling FOV expansion to greater than 10 mm without requiring complex multi-element lens systems to correct aberrations.
Solution Approach 2:
The patent introduces a reflective polarizer as an intermediary element between the curved mirror and the sample. This polarizer, combined with polarization retarders in the optical path, enables the system to manage light polarization states to minimize aberrations while maintaining high transmission efficiency, thereby achieving wide FOV without proportional increases in system complexity.
2Area of stationary object
If conventional lens systems are used to increase FOV, then FOV can be expanded, but optical aberrations increase
Solution Approach 1:
The curved mirror surface with its center of curvature at the scanner's rotation axis inherently focuses light from wide angles with minimal spherical aberration. This geometric configuration naturally corrects for off-axis aberrations that would otherwise require complex corrective lens elements, thereby maintaining high optical precision across an expanded FOV of greater than 10 mm.
Solution Approach 2:
The patent utilizes polarization state manipulation through reflective polarizers and retarders to control light-matter interaction. By changing the polarization parameters of the excitation light and managing its state through the optical system, the patent minimizes polarization-induced aberrations and maintains high image quality across the expanded field of view.
3Measurement precision
If high NA is maintained for high resolution, then resolution is improved, but FOV is restricted to about 1-2 mm
Solution Approach 1:
The curved mirror surface provides angular focusing capability that maintains high numerical aperture (NA) across a wide range of scan angles. Unlike conventional planar mirrors or simple lens systems that require reducing NA to expand FOV, the spherical geometry of the curved mirror enables the system to maintain NA greater than 0.5 while achieving FOV of greater than 10 mm through its inherent focusing properties at multiple angles.
Solution Approach 2:
The patent transitions from a single-plane focusing approach to a three-dimensional focusing geometry using the curved mirror. The mirror's surface curvature in the vertical dimension, combined with the scanner's angular movement, creates a volumetric focusing capability that maintains high NA across a large FOV, effectively adding a spatial dimension to the focusing mechanism.
4Area of stationary object
If FOV is increased beyond conventional limits, then imaging capability is improved, but signal transmission efficiency decreases
Solution Approach 1:
The reflective polarizer serves as a high-efficiency intermediary that directs light with minimal loss. By utilizing the polarizer's reflective properties for one polarization state and the curved mirror's focusing for the other, the system maintains high transmission efficiency (>80%) across the expanded FOV, avoiding the signal losses typically associated with wide-angle optical systems.
Solution Approach 2:
The optical system employs a composite approach combining reflective and transmissive elements. The curved partially transmissive mirror and reflective polarizer work together as a composite optical train, where each component is optimized for its specific function. This composite design enables the system to maintain high signal transmission efficiency while achieving FOV of greater than 10 mm, as the combination of elements compensates for individual losses.
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 solution enables high-resolution imaging with an increased FOV of up to 20 mm, maintaining high NA and reducing signal loss, thus improving the capability for multiphoton and fluorescent microscopy applications.
Implementation Method 1
a curved, partially transmissive mirror surface that is symmetric about an optical axis and disposed to focus a portion of the received scanned collimated beam toward a focal plane at the sample
Implementation Method 2
a reflective polarizer that is disposed in the path of both collimated light of a first polarization state and focused light of an orthogonal polarization state
Implementation Method 3
a reflective polarizer that is disposed in the path of both collimated light of a first polarization state and focused light of an orthogonal polarization state, wherein the reflective polarizer is configured to cooperate with the curved mirror surface to direct the focused light toward the sample
Data Source
AI summary
A scanning microscope apparatus has a laser light to generate a beam at an excitation wavelength. A beam expander enlarges the beam width and forms a collimated beam, scanned in a raster pattern. A catadioptric objective has a curved partially transmissive mirror surface symmetric about an optical axis and disposed to focus a portion of the received scanned collimated beam toward a focal plane at the sample, wherein the mirror surface has a center of curvature either at an axis of rotation of the scanner or at an image of the axis of rotation. A reflective polarizer cooperates with the curved mirror to direct the focused light toward the sample. One or more polarization retarders condition excitation light conveyed toward and away from the curved mirror. A beam splitter separates the generated laser light from a signal and directs the signal toward a detector.