Scanning Microscopy Pupil Centering to Reduce Vignetting
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Solution Overview
Problem
Current optical beam scanning microscopy devices face limitations in the accessible field width due to vignetting, resulting in reduced spatial resolution and lower quality Raman spectrometry measurements, with the extent of scanning being significantly less than the optical field of the microscope objective.
Innovation Solution
The solution involves pivoting the laser beam around the center of the entrance pupil of the microscope objective, using two mirrors for each scanning axis to maintain the beam's centering on the pupil, thereby reducing vignetting and increasing the accessible field width without compromising spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the laser beam is angularly displaced to scan a larger area, then the accessible field width increases, but vignetting occurs causing reduced spatial resolution and lower measurement quality
Solution Approach 1:
The scanning system is divided into two separate mirror assemblies: a first mirror assembly for angular displacement of the laser beam, and a second mirror assembly for recentering the beam on the pupil. This segmentation allows independent control of beam positioning and beam centering, resolving the contradiction by enabling large angular displacements without vignetting.
Solution Approach 2:
The second mirror assembly acts as an intermediary between the first mirror assembly and the microscope objective. It receives the angularly displaced beam from the first mirror and recenters it on the pupil before entering the objective, thereby eliminating vignetting while preserving the expanded field of view.
2Productivity
If the laser beam is angularly displaced to cover more sample area, then productivity increases, but the signal-to-noise ratio decreases due to vignetting
Solution Approach 1:
By separating the angular displacement function (first mirror) from the beam centering function (second mirror), the system maintains full beam intensity at the pupil regardless of scan position. This eliminates the signal loss from vignetting, preserving high signal-to-noise ratio while enabling fast scanning across large areas.
Solution Approach 2:
The system changes the angular parameters of the beam by using the first mirror to rotate the beam direction for area coverage, while the second mirror adjusts the beam's position parameter relative to the pupil to maintain centering. This parameter control allows high-speed scanning without sacrificing measurement quality.
3Device complexity
If a single mirror is used for beam scanning, then device complexity is reduced, but the accessible field width is limited by vignetting
Solution Approach 1:
The scanning function is segmented into two independent mirror assemblies with distinct roles: the first mirror provides angular displacement for field expansion, while the second mirror provides beam recentering to eliminate vignetting. This segmentation resolves the contradiction by showing that increased component count enables dramatically expanded accessible field width.
Solution Approach 2:
The second mirror assembly serves multiple functions: it recenters the beam on the pupil, compensates for angular displacement artifacts, and maintains optimal beam coupling into the microscope objective. This multi-functionality justifies the additional component by delivering superior field coverage and image quality.
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 allows for a larger scanning area to be covered while maintaining high spatial resolution and improving the signal-to-noise ratio, enabling more precise and efficient Raman microspectrometry measurements.
Implementation Method 1
using two mirrors for each scanning axis to maintain the beam's centering on the pupil
Implementation Method 2
microscope objective, having an entrance pupil... pivoting the laser beam around the center of the entrance pupil
Implementation Method 3
collect a Raman backscatter beam and transmit it towards a detection system
Data Source
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AI summary
The invention relates to an optical beam scanning microscopy apparatus comprising a light source adapted for emitting an optical beam (2) and a microscope objective (1) adapted for focusing said optical beam (2) in an object plane (11). According to the invention, the microscopy apparatus comprises first and second reflecting optical means (M‑X1, M‑X2) disposed in series over the optical path of the optical beam (2) between the light source and the microscope objective (1), first means of angular tilting (21, 25) adapted for tilting said first reflecting optical means (M‑X1, M‑XY1) according to a first predetermined angle of rotation (RX1), and second means of angular tilting (22, 26) adapted for tilting said second reflecting optical means (M‑X2, M‑XY2) according to a second angle of rotation (RX2), in such a way as to angularly tilt the axis (12) of the optical beam (2) by pivoting about the centre (O) of the pupil of the microscope objective (1).