Infrared Microscope Micro-Source Imaging Near the Diffraction Limit
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Solution Overview
Problem
Conventional infrared microscopes struggle to achieve spatial resolutions beyond the diffraction limit due to the use of large light sources and limitations in forming smaller spot regions, leading to deteriorated measurement accuracy when measuring smaller microregions.
Innovation Solution
Employing a nanocarbon light source with a micrometer-scale light-emitting surface and a configuration that includes a light source side collecting element, irradiating side objective element, and a spectroscopic portion that performs lock-in detection to form an image of the light source directly on the sample, while using a light source with pulsed lighting to minimize background radiation interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a large light source is used to ensure sufficient light intensity, then the light intensity is adequate, but the spatial resolution cannot reach the diffraction limit
Solution Approach 1:
The optical system is segmented into multiple functional components: a micro light source, a light source side collecting element, and an irradiating side objective element. This segmentation allows each component to be optimized independently - the light source for intensity and the optical elements for spatial resolution control.
Solution Approach 2:
A light source side collecting element is introduced as an intermediary between the micro light source and the sample. This collecting element captures light from the small source and directs it through the objective element, enabling the system to achieve both sufficient light intensity and high spatial resolution that would be impossible with a single large light source.
2Area of stationary object
If a mask is used to limit the spot region to achieve smaller measurement area, then the spot size is reduced, but measurement accuracy significantly deteriorates
Solution Approach 1:
The mechanical mask system is replaced with an optical system consisting of a micro light source and objective element. Instead of using a mask to mechanically limit the spot region, the patent uses optical elements to focus light from a micro light source directly onto the sample, achieving smaller spot sizes without the measurement accuracy deterioration associated with mask-based approaches.
3Manufacturing precision
If the light-emitting surface size is reduced to micrometer order to improve spatial resolution, then spatial resolution approaches diffraction limit, but the source light becomes extremely weak and is affected by background radiation
Solution Approach 1:
The patent employs periodic modulation of the micro light source emission intensity. By pulsing the light source at a specific frequency and using synchronous detection, the system can distinguish the weak signal from the micro light source against the background radiation, enabling both high spatial resolution and adequate signal detection.
Solution Approach 2:
A synchronous detection system provides feedback to distinguish the modulated light signal from background radiation. The detection system uses the reference signal from the modulated light source to selectively amplify the desired signal while rejecting background noise, enabling detection of extremely weak light from micrometer-scale sources.
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 infrared microscope achieves high spatial resolution close to the diffraction limit with reduced stray light and improved measurement accuracy by effectively collecting and processing the infrared light from a micro light-emitting source, allowing for selective switching between high and low spatial resolution measurements.
Implementation Method 1
A black-body radiation light source such as a halogen lamp or a high luminance ceramic light source is used in conventional infrared light sources
Implementation Method 2
Rayleigh criterion is a representative idea of spatial resolution. According to this criterion, diffraction-limited spatial resolution (Δd) is defined by the equation of Δd=1.22λ/2n sin θ
Implementation Method 3
A signal processing portion such as a computer performs Fourier transform on a detection signal from the detector to acquire an absorption spectrum of the measurement portion
Implementation Method 4
a detector (40) that detects the infrared light that is spectrally processed
Data Source
AI summary
An infrared microscope including a light source that emits infrared light of which intensity increases and decreases repetitively, a collecting element that collects the infrared light from the light source, an irradiating side objective element that irradiates the sample with infrared light, a collecting side objective element that collects the infrared light transmitted through the sample, a spectroscopic portion that spectrally processes the collected infrared light, a detector of the infrared light; and a signal processing portion that performs lock-in detection to a detection signal by using a reference signal that synchronizes with an intensity of the infrared light to acquire an infrared spectrum of the sample. The light source has a light-emitting surface having a size of 0.1 μm or greater and 20 μm or less. Light-emitting surface's image is formed on the sample by the collecting element and the irradiating side objective element.