Developing a laser diffraction particle size analyzer for current customer requirements

A combined reverse Fourier set-up was presented on Fresnel diffraction theory. The set-up was used to measure particle size distribution with laser. A particle sample is set back of a lens. A first detector array is set in the focus plane of the lens. A second lens and a second detector array are set behind the first detector and the combined focus plane of the two lenses in turn. Thus the measurable size range at on sampling is enlarged. Experimental results on some latex samples by the prototype show that the relative errors are less than 6%.

A Combined Reverse Fourier Set-Up for Laser Particle Size Measurement

In laser particle size measurement, it is preferable to enhance the performance of measuring widely distributed particle size. Based on diffraction theory, a laser particle size measurement scheme is proposed to extend the measurable size range at one time. In this project, two lenses are set coaxially and signals are detected on the back focal plane of the first lens and the combined back focal plane of the two lenses at the same time. Particle size distribution is obtained when signals are integrated and inverted with an independent model algorithm. Simulation result shows that particles in the range of 1~2000 μm can be measured simultaneously, and the measuring dynamic range is 2000:1when the focal lengths of the two lenses are both 100 mm and the two sets of detectors have both 32 rings. The presented method can be applied to measure particle size distribution with large range. Meanwhile, it is unnecessary to change lens or move detectors.

Laser particle size measurement by detecting signals on two coaxial focal planes

In laser particle size measurement, the instrument based on traditional Fourier transform structure is disadvantaged in the
narrow measurable dynamic size range. So it is hardly to be used to measure broadly distributed particle. The presented
technology is based on Fresnel diffraction theory. The formula of combined spectrum technology by detecting signals on
coaxial focal planes is educed. In the proposed method, the two lenses are set coaxially and signals are detected on the
back focal plane of the first lens and the combined back focal plane of the two lenses. The detected signals are then
combined. The data are processed with a no-model algorithm. Thus, the measurable dynamic range can be broadened as
no component of the sizer is changed. Experimental results of some samples show that the particulate in the size range of
5 ~ 3500 µm can be measured simultaneously.

Study on broadening the size range in laser particle size measurement by combined spectrum technology

In this study, a surface plasmon resonance sensor for detecting haemoglobin concentration based on a D-type optical fibre with a graphene-gold surface architecture is proposed. The graphene-gold surface architecture included a 50 nm thick gold film and monolayer graphene film, which were decorated on a 10 mm long D-type sensing region. The proposed sensor worked in wavelength interrogation mode, with the light wavelength ranging from 400 to 1100 nm. The authors realised the D-type optical fibre surface polishing process, the gold film vacuum coating process, and the chemical-vapour-deposited graphene's wet transfer process. Furthermore, the fabricated sensors were used to detect the refractive index (RI) of haemoglobin samples, which varied from 1.331 to 1.346. Experiment results show that the fitted RI sensitivity of the sensor decorated with gold and graphene reaches 1874.41 nm/RIU, 4.995% higher than that of the sensor decorated only with gold. The concentration sensitivity of the sensor coated with gold and graphene film is 4.96 nm/(g/dL), and the proposed sensor can provide a resolution of 20.2 mg/dL for haemoglobin concentration detection. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1049/ote2.12092

Wen-Chao Li

Papers

Study on broadening the size range in laser particle size measurement by combined spectrum technology

A surface plasmon resonance haemoglobin concentration sensor based on D‐type optical fibre with a graphene‐gold surface architecture