基于线阵CCD的精密尺寸测量系统

Precise dimension measurement system based on linear CCD

现有尺寸测量方式精度低,测量费时费力。为了提高尺寸测量的精度,使测量系统便携化,操作简单,文中实现了一种基于线阵CCD的精密尺寸测量系统。文中提出新的象元细分方法,将2个像元间距为8μm的线阵CCD等距错排并以60°斜放,可突破像元间距对测量精度的限制,将最大测量误差减小为2μm,在此基础上采用浮动阈值方法进行数据处理,实现高精度尺寸测量。利用FPGA进行硬件描述实现线阵CCD的驱动,对CCD的输出信号进行差分放大,采用硬件滤波方法消除曝光积分和转移过程中的电子学噪声,采用10位模数转换器实现数字量的并行输出,FPGA内部FIFO存储数字量结果。系统充分利用FPGA的可编程资源,有效降低了硬件设计复杂度,无需上位机或者ARM,节约成本,系统小型化便携化。实验表明,该系统有效克服光源及电子学噪声影响,可对1 mm-29 mm的中型尺寸物体进行测量,误差小于2μm。

The existing size measurement methods have low accuracy and time-consuming and laborious measurement.In order to improve the accuracy of dimension measurement,make the measurement system portable and easy to operate,a precise dimension measurement system based on linear CCD is realized in this paper.A new method of subdivision of pixels is proposed in this paper.By staggering two linear CCDs with 8 um pixel spacing equally and placing them obliquely at 60 degrees,it can break through the limitation of pixel spacing on measurement accuracy and reduce the maximum measurement error to 2 μm.On this basis,the floating threshold method is used for data processing to achieve high-precision size measurement.The drive of linear CCD is realized by hardware description in FPGA,the output signal of CCD is amplified differently,the electronic noise in the process of exposure integration and transfer is eliminated by hardware filtering method,the parallel output of digital quantity is realized by 10-bit analog-to-digital converter,and the digital result is stored in FIFO in FPGA.The system makes full use of the programmable resources of the FPGA,effectively reduces the complexity of hardware design,does not need the upper computer or ARM,saves costs,and makes the system miniaturized and portable.Experiments show that the system can effectively overcome the influence of light source and electronic noise.It can measure medium-sized objects of 1 mm-29 mm,and the error is less than 2 μm.