大动态范围高速光子相关器研究

发布时间：2019-03-20 12:28

【摘要】：光子相关光谱技术作为测量纳米颗粒粒径及其分布的主要方法,在纳米颗粒测量领域得到了广泛应用。光子相关器是光子相关光谱测量系统的核心装置,通过对光子脉冲计数,并进行实时自相关运算得到散射光强的时间自相关函数。目前国内使用的光子相关器多为进口产品,因此,设计开发具有自主知识产权的大动态范围高速光子相关器具有重要的经济和社会效益。 本文围绕扩大相关器动态范围、提高相关器运算速度及相关函数的归一化精度,进行了以下研究工作： (1)基于光子相关光谱理论,研究了线性光子相关器、比例光子相关器及多采样时间光子相关器的结构和优缺点。 (2)采用FPGA设计了双光子计数器对光子脉冲信号进行交替计数,实现了无缝隙光子计数；利用DSP片内大容量存储器设计了环形移位寄存器,实现了大动态范围比例相关器；PC机和DSP之间通过USB接口进行数据传递；提出了比例相关器中通道延迟时间的计算公式；分析了相关函数的归一化方法。 (3)分析了多采样时间相关器的工作原理；采用FPGA设计实现了高速多采样时间相关器,其核心模块为相关运算模块,由移位寄存器、乘法器、累加器以及数据类型转换器组成,各部分均采用Verilog语言编程实现；研究了相关函数的三角平均影响及相关函数的归一化方法。 (4)基于DSP的比例相关器扩展了动态范围,基于FPGA设计了相关器的高速相关运算通道,提高了相关运算速度,采用DSP+FPGA相结合的结构实现了大动态范围高速光子相关器。 (5)采用本文设计的大动态范围高速光子相关器组成光子相关光谱颗粒测量装置,在25℃温度下,分别对60、150、200、300及450nm五种标准聚苯乙烯颗粒进行了实测。测量结果表明,本文设计的相关器能够提高测量结果的准确性,选择合适的采样间隔和动态范围可使测量结果的相对误差小于5%,重复性误差小于3%,完全满足纳米颗粒测量的需要。 本文在研究光子相关光谱理论、光子相关器结构和相关函数的归一化方法基础上,采用DSP+FPGA相结合的结构实现了大动态范围高速光子相关器,最小采样间隔为100ns,实现的动态范围可达1010。
[Abstract]:As the main method to measure the particle size and its distribution, photon correlation spectroscopy has been widely used in the field of nano-particle measurement. Photon correlator is the core device of photon correlation spectrum measurement system. The time autocorrelation function of scattered light intensity is obtained by counting photon pulses and performing real-time autocorrelation operation. At present, most of the photon correlators used in China are imported products. Therefore, the design and development of large dynamic range high-speed photon correlators with independent intellectual property rights has important economic and social benefits. In this paper, we focus on expanding the dynamic range of correlator and improving the speed of correlator operation and the normalization precision of correlation function. The following work has been done: (1) based on the theory of photon correlation spectrum, the linear photon correlator is studied, and the linear photon correlator is studied. The structure, advantages and disadvantages of proportional photon correlator and multisampling time photon correlator. (2) the two-photon counter is designed with FPGA to count the photon pulse signal alternately, and the gap-free photon count is realized, the loop shift register is designed by using the large-capacity memory in DSP chip, and the proportional correlator with large dynamic range is realized. The data transfer between PC and DSP is carried out through USB interface, the formula of channel delay time in proportional correlator is proposed, and the normalization method of correlation function is analyzed. (3) the working principle of multi-sampling time correlator is analyzed. The high-speed multi-sampling time correlator is designed and implemented with FPGA. The core module of the correlator is the correlation operation module, which consists of shift register, multiplier, accumulator and data type converter. Each part is programmed in Verilog language. The influence of trigonometric mean of correlation function and the normalization method of correlation function are studied. (4) the proportional correlator based on DSP extends the dynamic range, designs the high-speed correlation channel of the correlator based on FPGA, improves the speed of correlation operation, and realizes the high-speed photon correlator with large dynamic range by using the structure of DSP FPGA. (5) using the high-speed photon correlator designed in this paper, five kinds of standard polystyrene particles (60150 200300 and 450 nm) were measured at 25 鈩，

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