Galvanometer Mirror Scanning Microscope for Rapid Axial Imaging
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Solution Overview
Problem
Current scanning microscopes face limitations in quickly examining thick live biological specimens with minimal optical array impact on the specimen image, particularly due to mechanical disturbances and limited axial actuating speed, which hampers rapid three-dimensional imaging and precise neuronal stimulation in brain research.
Innovation Solution
A scanning microscope design that images any plane in a chromatically diffraction-limited and corrected manner using a movable mirror in an aberrant image space, canceling out aberrations through polarization optics, allowing for quick, interaction-free 3D imaging over axial stacking depths without creating a sharp mirror image for focal plane selection, and enabling objective changes without compromising image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If piezomechanical objective adjustment is used to change focal planes, then the microscope can examine different specimen planes, but the axial actuating speed is limited to a few tens of hertz due to the considerable mass of the objective
Solution Approach 1:
The patent replaces the piezomechanical objective adjustment system with a galvanometer-based mirror system. Instead of moving the heavy objective lens mechanically, the invention uses lightweight mirrors that can be rapidly positioned by galvanometers to change the focal plane. This substitution of mechanical movement with optical redirection enables axial scanning speeds exceeding 1000 Hz, dramatically improving the speed parameter while eliminating the constraint imposed by objective mass.
2Ease of operation
If piezomechanical objective adjustment is used, then focal plane switching is possible, but mechanical waves are transferred onto the specimen through the immersion medium causing disturbances
Solution Approach 1:
The invention eliminates mechanical disturbances by replacing the piezomechanical objective adjustment with an optical switching mechanism using galvanometer-controlled mirrors. The mirrors redirect the laser beam to different focal planes without any physical contact with the specimen or immersion medium, thereby completely avoiding the transfer of mechanical waves and vibrations to the sensitive biological specimen.
Solution Approach 2:
The patent introduces galvanometer-controlled mirrors as intermediary elements between the laser source and the specimen. These mirrors serve as mediators that enable focal plane switching through optical redirection rather than mechanical movement, allowing the system to change examination planes without the harmful mechanical coupling that would otherwise directly affect the specimen.
3Illumination intensity
If multiphoton excitation is used for deep penetration imaging, then excitation can be achieved at high power density via multiphoton processes, but the fluorescence is subject to larger scattering cross-section leading to loss of spatial information
Solution Approach 1:
The patent implements a confocal detection system with a pinhole aperture that provides optical sectioning capability. This feedback mechanism selectively transmits only the in-focus fluorescence photons while blocking out-of-focus scattered light. By combining multiphoton excitation with confocal detection, the system maintains high power density for deep penetration while the pinhole aperture restores spatial information by filtering scattered fluorescence, thereby resolving the contradiction between deep imaging capability and spatial resolution.
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
Enables rapid, high-resolution, and artifact-free three-dimensional imaging of thick live specimens with minimal mechanical interference, allowing for precise targeting and illumination of neurons, thus enhancing the capability for neuronal stimulation and imaging over extended depths without compromising image quality.
Implementation Method 1
A mirror in an aberrant image plane determined by an adapted optical system reflects the light back onto itself
Implementation Method 2
canceling out aberrations through polarization optics
Implementation Method 3
Multiphoton excitation microscopy is the preferred method for microscopy of thick specimens of a few hundred microns
Implementation Method 4
employes excitation light in the near infrared range and is thus much less prone to elastic scattering
Implementation Method 5
the exciting laser is focused into the specimen via a microscope objective
Implementation Method 6
all the photons that are collected through the objective opening are imaged on a detector located on a plane that is conjugated towards the pupil of the objective
Data Source
AI summary
A laser scanning microscope having a laser source for fluorescence excitation; a scanning mirror arrangement for scanning a specimen and scanning optics for generating a diffraction-limited reference image plane as a first intermediate image plane; an optical system for demagnified imaging of the reference plane in a second intermediate image plane; an axially slideable mirror in the second intermediate image plane; a beam splitter arrangement between the reference image plane and the optical system; and a tube lens and a first microscope objective for imaging of the reference image plane into a specimen. The imaging of the image is effected with a magnification of M≠n/n′ and/or a magnification of the second intermediate image plane into the specimen according to the equationM=y′y=nn′ξ,with |ξ|≠1, and/or the focal plane of the laser deviates from the axial position of the axially movable mirror across its scanning area in the second intermediate image plane.