Optical Thickness Measurement Using Fluorescent Fiber Illumination
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Solution Overview
Problem
Existing measuring apparatuses face challenges in achieving sufficient light irradiation for accurate measurement due to the large spot diameter of light sources like white LEDs or halogen lamps, leading to insufficient measurement accuracy and resolution, while high-power light sources like super continuum light sources are expensive and bulky.
Innovation Solution
The apparatus employs a light source unit with an excitation light source, a fluorescent body, and a dichroic mirror to generate fluorescence with a wider wavelength band, allowing efficient irradiation of the measurement-target object using a monochromatic light source with a small spot diameter, eliminating the need for expensive, large-size light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a white LED or halogen lamp is used as the light source, then the light source has a wide wavelength band suitable for measurement, but the spot diameter is large making it difficult to focus on the optical fiber end, resulting in insufficient light amount and poor measurement accuracy
Solution Approach 1:
The patent introduces a fluorescent body as an intermediary between the blue LED excitation source and the optical fiber. The fluorescent body converts the blue light into wide-spectrum fluorescence that can be efficiently coupled into the optical fiber, thereby achieving both wide wavelength coverage and sufficient light concentration at the fiber end.
Solution Approach 2:
The patent changes the wavelength parameter of light through the fluorescent conversion process. The blue LED (narrow wavelength) excites the fluorescent body which emits wide-spectrum fluorescence, effectively transforming the spectral characteristics while maintaining spatial concentration suitable for optical fiber coupling.
2Measurement precision
If a super continuum light source is used to provide sufficient light amount, then the measurement accuracy improves, but the light source becomes expensive and increases in size
Solution Approach 1:
The patent replaces the expensive super continuum light source with a much cheaper blue LED combined with a fluorescent body. This substitution achieves comparable or superior measurement performance while dramatically reducing both cost and device size, making the system more practical for industrial applications.
Solution Approach 2:
The patent fundamentally changes the approach to generating wide-spectrum light by using fluorescent conversion from a narrow-band LED source, rather than using a complex super continuum source. This parameter change in the light generation mechanism achieves the same spectral width requirement with a much simpler and cheaper system.
3Productivity
If the excitation light is focused too strongly on the fluorescent body, then the fluorescence generation efficiency increases, but the fluorescent body temperature rises causing characteristic changes
Solution Approach 1:
The patent incorporates a cooling mechanism that actively removes heat from the fluorescent body before the temperature can cause significant characteristic changes. This preliminary cooling action maintains the fluorescent body at a stable temperature, ensuring consistent fluorescence emission characteristics during continuous operation.
Solution Approach 2:
The patent implements temperature control through a cooling mechanism that monitors and adjusts the thermal state of the fluorescent body. This feedback control ensures that the fluorescent body operates within an optimal temperature range, maintaining stable fluorescence characteristics while preventing thermal degradation.
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 enables high-efficiency light irradiation with a sufficient light amount, improving measurement accuracy and resolution without the costs and size issues associated with high-power light sources.
Implementation Method 1
a fluorescent body that emits fluorescence with a wavelength different from that of excitation light when receiving the excitation light emitted by the excitation light source
Implementation Method 2
a first collecting lens that focuses the excitation light emitted by the excitation light source on the fluorescent body
Implementation Method 3
a light collector that focuses the light guided by the optical fiber on the measurement-target object held by the holding table
Data Source
AI summary
A measuring apparatus includes a holding table that holds a measurement-target object and a measuring unit that measures a height or a thickness of the measurement-target object held by the holding table. The measuring unit includes a light source unit, an optical fiber that guides light emitted by the light source unit, and a light collector that focuses the light guided by the optical fiber on the measurement-target object held by the holding table. The light source unit includes an excitation light source, a fluorescent body that emits fluorescence when receiving excitation light emitted by the excitation light source, and a collecting lens that focuses the excitation light emitted by the excitation light source on the fluorescent body.