Digital correlator for photon correlated nanometer zetasizer

Abstract

The invention provides a digital correlator for a photon correlated nanometer zetasizer, which is a digital correlator for acquiring an autocorrelation function and a cross correlation function of a scattering signal in the technology for testing granularity of nanometer and sub-micron particles on the basis of a dynamic light scattering principle. The digital correlator comprises a sampling time set module, a photon counting module, a correlation operation module, a universal serial bus (USB) communication module and a synchronous reset module which are solidified in a field programmable gate array (FPGA), wherein the photon counting module is connected with the sampling time set module, and is connected with the signal input end of the correlation operation module; and the signal output end of the correlation operation module is connected with the USB communication module. The digital correlator realizes the functions of photon pulse counting, self-correlation operation, cross correlation operation and computer communication, has the characteristics of high sampling speed, wide delay time range and more correlation channels, and completely meets the requirement of high difficulty on acquiring the autocorrelation function and the cross correlation function of the high-speed changing dynamic scattering signal in the nanometer particle granularity test.

Description

(1) Technical field [0001] The invention relates to a device for acquiring the autocorrelation function and cross-correlation function of scattered light signals in hardware in the measurement technology of nanoparticle particle size based on the principle of dynamic light scattering (photon correlation spectroscopy (PCS) and photon cross-correlation spectroscopy (PCCS), specifically Said to be a digital correlator based on Field Programmable Gate Array (FPGA) technology. (2) Technical background [0002] The key technology of the nanoparticle size analyzer based on the principle of dynamic light scattering (photon correlation spectroscopy PCS and photon cross-correlation spectroscopy PCCS) is to extract the autocorrelation function or cross-correlation function of the scattered light of the nanoparticles suspended in the solution, and calculate the Diffusion coefficient, thus analyzing the particle size. The digital correlator is a device for extracting the autocorrelation...

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Problems solved by technology

At present, such devices are widely used in China, mainly imported from American Brookhaven company BI-9000AT, BI-9010AT and Turbocorr digital correlators, these devices can only complete autocorrelation calculations but not cross-correlation calculations, so they are only applicable to PCS method Test the particle size of nanoparticles, but it is not suitable for PCCS method to test the particle size of nanoparticles, so it has great limitations on the test environment, the concentration of the sample to be measured, and the stability of the test. make up for the shortcomings of the law

In addition, these devices are all based on customized ASICs, or DSP technology, or multi-chip and interconnected components, which not only have great limitations, but also are expensive.

In addition, some people in China try to realize the digital correlator by means of software, that is, first use the photon counter to count the scattered light photons and store them in the memory, and then read the data from the memory according to the computer software to perform correlation calculations. The correlation function of the scattered light intensity is calculated, but since the processing time required by the software is much longer than the processing time required by the hardware, the photon measurement is suspended during such a long processing time (ie, the photon is lost during the processing time), The deviation of the calculated correlation function is relatively large. Therefore, the digital correlator using software has poor real-time performance and cannot meet the requirements of particle size analysis.

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