Rear-Projection Yarn Detection with UV Photodiode
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Solution Overview
Problem
Existing yarn clearing methods, particularly photodetection methods, are unable to detect hetero fibre and homogeneous heterochromous fibre effectively, and combined photodetection and capacitive detection methods are complex and costly.
Innovation Solution
A rear-projection photodetection yarn clearing apparatus using an ultraviolet enhanced silicon photodiode, with a light emitting diode and detector arranged behind the yarn, a reflector in front, and a light filter capturing light rays between 330 nm to 470 nm, along with a two-stage annealing process for the photodiode, enhancing its sensitivity and response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photodetection method is used to detect yarn quality, then detection of sectional area variations (slubs, neps) is achieved, but detection of hetero fibre and homogeneous heterochromous fibre is impossible
Solution Approach 1:
The patent transitions from front-projection to rear-projection geometry, fundamentally changing the optical path arrangement. The light source and detector are positioned on the same side of the yarn, with light passing through the yarn and being reflected back to the detector, enabling detection of hetero fibre and homogeneous heterochromous fibre that were previously undetectable
Solution Approach 2:
The patent employs a composite optical system combining ultraviolet light source (380-405nm), blue light source (430-470nm), and a specialized silicon photodiode detector with specific spectral response characteristics. This composite approach enables simultaneous detection of different fibre types by utilizing their distinct optical absorption and reflection properties across multiple wavelength ranges
2Measurement precision
If combined photodetection and capacitive detection method is used, then detection of hetero fibre and homochromatic fibre is achieved, but device complexity and cost increase
Solution Approach 1:
The patent makes the photodetection system universally capable of detecting all types of yarn defects including hetero fibre, homogeneous heterochromous fibre, slubs, and neps by using a single integrated optical system with dual-wavelength illumination and a specially designed silicon photodiode, eliminating the need for separate capacitive detection subsystems
Solution Approach 2:
The patent changes the operational parameters of the photodetection system by using ultraviolet and blue light wavelengths (380-470nm) that interact differently with various fibre materials, and by employing a silicon photodiode with optimized spectral response. This parameter optimization enables the single system to achieve detection capabilities previously requiring multiple different detection methods
3Device complexity
If light source and detector are arranged in front-projection configuration, then simple structure is maintained, but stray light directly enters detector reducing signal-to-noise ratio
Solution Approach 1:
The patent rearranges the optical components from a linear front-projection sequence to a rear-projection configuration where the light source and detector share the same side. The light passes through the yarn and is reflected back to the detector, creating a folded optical path that naturally separates the direct light path from the detection path, preventing stray light contamination while maintaining structural simplicity
Solution Approach 2:
The patent introduces a reflector as an intermediary component that redirects the light passing through the yarn back toward the detector. This reflector acts as a mediator that separates the illumination function from the detection function, ensuring that direct light from the source does not enter the detector while still enabling the detection of light-modulated signals from the yarn
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 the detection of homochromatic hetero fibre and homogeneous heterochromous fibre with improved signal-to-noise ratio and photocurrent conversion, reducing stray light impact and enhancing light uniformity across the yarn.
Implementation Method 1
The light emitting diode includes an ultraviolet light emitting diode, and the detector includes an ultraviolet enhanced silicon photodiode... a light filter for capturing light rays having a waveband from 330 nm to 470 nm
Implementation Method 2
a light filter for capturing light rays having a waveband from 330 nm to 470 nm
Implementation Method 3
a reflector arranged in front of the to-be-detected yarn... a light-reflecting surface of the reflector is in parallel with the photosurface of the detector
Data Source
AI summary
A rear-projection photodetection yarn clearing apparatus includes a light emitting diode and a detector arranged behind a to-be-detected yarn, and further includes a reflector arranged in front of the to-be-detected yarn. A front end face of the light emitting diode is flush with a photosurface of the detector, a light filter for capturing light rays having a waveband from 330 nm to 470 nm is also arranged in front of the light emitting diode and the detector, and a light-reflecting surface of the reflector is in parallel with the photosurface of the detector. The light emitting diode includes an ultraviolet light emitting diode, and the detector includes an ultraviolet enhanced silicon photodiode. The ultraviolet enhanced silicon photodiode is made from a high-resistivity N-type (111) silicon wafer having a resistivity of 3,000 Ω·cm and a field oxide thickness of 1,000 nm.