英语翻译INTRODUCTIONPiston is widely used in both fluid and air

英语翻译
INTRODUCTION
Piston is widely used in both fluid and air pressure drive system.The size and structure of its diameter have great influence on the piston’s effective work area,the slide fit between the cylinder and the piston,the minimum star-up pressure and the mechanical efficiency.Therefore,it is a key and important technology to measure the external diameter of the piston exactly.
There are many ways to measure the external diameter.Inductive transducer is not suitable for online detection because of its low automation level.Laser scanning method cannot reach the demand for its accuracy is affected by vibration,scanning speed and many other factors.In this paper we will introduce the parallel light projection method,which is to project the workpiece on the photosensitive units using parallel light through illumination path.In order to make it convenient for photoelectric conversion and circuit processing,charge-coupled device (CCD) is chosen for signal acquisition.CCD is favorable for high-speed online automatic measurement,position and industrial control,for the benefits of its low power consumption,fine frequency response,wide dynamic range,high resolution,and fine reproducibility.
The specific design on the optical paths,the signal processing circuits,the mechanical structure and the software for the measuring system will be introduced in detail.

引言
活塞广泛应用于两流体驱动系统和空气压力.的规模和结构,其直径对活塞的有效工作面积很大的影响,两者的气缸和活塞滑动配合,最低明星了压力和机械效率.因此,它是一个关键和重要的技术来测量活塞外径准确.
有很多方法来测量外径.感应式传感器是不是因为它的自动化程度低的在线检测的要求.激光扫描方法不能达到其精度要求是由振动的影响,扫描速度和许多其他因素.本文将介绍平行光投影法,即项目通过使用平行光照明路径光敏单元的工件.为了使方便光电转换和处理电路,电荷耦合器件（CCD）是信号采集选择.CCD是高速在线自动测量,位置和工业控制良好,为它的低功耗,优良的频率响应,动态范围宽,分辨率高的好处,重现性好.
关于具体的光路设计,信号处理电路,机械结构和测量系统的软件将详细介绍.