IR Microscope Beam Limiting Element for Stray Light Control
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Solution Overview
Problem
Infrared (IR) microscopes with multi-element detectors face issues of vignetting and stray radiation due to the limitations in the size and position of the detector stop, which affects the quality of measurements by allowing ambient light and reducing the dynamic range of the detector.
Innovation Solution
The effectively beam-limiting element is placed in the collimated IR input beam before the first optical device, ensuring that the detector stop opening is optimally sized and positioned to prevent ambient light from entering, thereby ensuring all sensor elements receive only modulated IR radiation from a defined region of the sample plane without vignetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the detector stop is enlarged to reduce vignetting, then all sensor elements are illuminated without vignetting, but stray light from uncooled surroundings reaches the sensor and corrupts measurements
Solution Approach 1:
The patent introduces a new spatial dimension by placing a beam-limiting element in the collimated input beam path before the interferometer, rather than only relying on the detector stop in the image space. This dual-location approach creates a two-dimensional beam control system that simultaneously prevents vignetting and blocks stray light.
Solution Approach 2:
The beam-limiting element acts as an intermediary component between the light source and the interferometer, filtering the input beam before it enters the measurement system. This intermediary structure prevents stray light from entering the system while maintaining proper illumination of all sensor elements.
2Object-affected harmful factors
If the detector stop is positioned to block stray light, then ambient light is prevented from entering the detector, but vignetting occurs at edge regions of the sensor
Solution Approach 1:
The patent adds a beam-limiting element in the collimated input beam path, creating a two-dimensional beam control system. This allows the detector stop to maintain its light-blocking function while the additional beam-limiting element ensures uniform illumination by preventing vignetting at sensor edges.
Solution Approach 2:
The beam control function is segmented into two separate locations: the beam-limiting element in the input beam path and the detector stop in the image space. Each element performs a specific function - the beam-limiting element controls illumination uniformity while the detector stop blocks stray light, resolving the contradiction between these two requirements.
3Manufacturing precision
If a single beam-limiting element is used in the input beam, then all sensor elements receive equal illumination without vignetting, but the system becomes more complex
Solution Approach 1:
The beam-limiting element in the input beam path serves multiple functions simultaneously: it defines the input beam geometry, prevents vignetting at sensor edges, and blocks stray light from entering the interferometer. This multi-functional design achieves illumination uniformity without proportionally increasing system complexity.
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 configuration maximizes luminous efficiency, minimizes stray radiation, and maintains high signal quality by ensuring that all pixels are illuminated equally, preventing saturation and maintaining a high signal-to-noise ratio.
Implementation Method 1
the IR light passes through an interferometer, in which the lengths of the interferometer arms are varied with respect to one another by moving one or more mirrors and, as a result, the infrared light is modulated depending on its wavelength
Implementation Method 2
a first optical device configured to focus the collimated IR input beam emerging from the IR light source onto the sample position
Implementation Method 3
a second optical device configured to image the sample position onto the IR sensor
Implementation Method 4
In order to suppress radiation from the surroundings as much as possible, the detector contains a detector stop
Implementation Method 5
The detector is therefore generally cooled in order to minimize undesired signals that can be caused by thermal excitations in the sensor material
Data Source
AI summary
An IR microscope includes an IR light source/interferometer (1) generating a collimated IR beam (26), an effectively beam-limiting element (8) in a stop plane (27), a sample position (15), a detector (19) having an IR sensor (19a), a detector stop (19b), a first optical device focusing the collimated IR beam onto the sample position, and a second optical device imaging the sample position onto the IR sensor. The effectively beam-limiting element is situated in the collimated IR beam. The first and second optical devices image the detector stop opening into an input beam plane. For the area A1 of the image of the detector stop opening in the input beam plane and the area A2 of the cross section of the collimated IR beam in the input beam plane: 0<A1/A2≤1. Thereby, only collimated IR radiation is picked up, while vignetting and stray radiation are avoided.