光栅尺基础知识 Basics of Linear Encoders

​随着数控技术的普及，现代机床在加工速度、精度和可靠性方面都有了巨大的进步。

With the popularization of numerical control technology, modern machine tools have achieved tremendous improvements in processing speed, precision and reliability.

作为数控机床核心技术之一的光栅测量技术对保障设备的各项性能指标起着决定性的作用。

As one of the core technologies of CNC machine tools, grating measurement technology plays a decisive role in ensuring the various performance indicators of the equipment.

一、光栅尺的概念与原理Concept and Principle of Linear Encoders

 概念：光栅尺是光栅尺位移传感器的简称，是根据莫尔条纹原理，通过光电转换，以数字方式将动态的测量数据以编码方式输出的长度测量仪器。

Concept: A linear encoder is the short name for linear displacement sensor with grating scales. Based on the principle of Moiré fringes, it is a dimensional measuring instrument that converts dynamic measurement data into digital coded output through photoelectric conversion.

 原理：当指示光栅（副光栅）与标尺光栅（主光栅）成一角度来放置两光栅尺进行相对位移时，会造成两光栅尺上的线纹互相交叉。在光源的照射下，距交叉点较远的区域，两光栅尺不透明的黑色线纹的重叠部分减少，遮光面积增大，只有较少的光线能通过这个区域透过光栅，使这个区域出现暗带，这些暗带就是莫尔条纹。

Principle: When the index grating (slave grating) is placed at an angle relative to the scale grating (master grating) and the two gratings undergo relative displacement, the grating lines on both scales intersect each other. Under illumination from a light source, in regions far from the intersection points, the overlapping area of the opaque dark lines on the two gratings decreases while the light-blocking area increases. Only a small amount of light can pass through this area, forming dark bands—these dark bands are known as Moiré fringes.

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图为摩尔条纹简单示意

The figure shows a simplified schematic of Moiré fringes

接着，光电器件转换莫尔条纹成正弦波变化的电信号，经过放大器放大，整形电路整形后，得到两路相差为90°的正弦波或方波，送入光栅数显表计数显示，得出测量数据。 

Subsequently, photoelectric devices convert the Moiré fringes into sinusoidal electrical signals. After being amplified by an amplifier and shaped by a shaping circuit, two sinusoidal or square wave signals with a 90° phase difference are obtained. These signals are sent to a grating digital readout for counting and display to derive the measurement data.

二、光栅尺的组成 Composition of the Grating Ruler

 标尺光栅一般固定在机床固定部件上，光栅读数头装在机床活动部件上，指示光栅装在光栅读数头中。

The scale grating is generally fixed to the stationary parts of the machine tool, the grating reading head is mounted on the moving parts, and the index grating is installed inside the grating reading head.

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图为光栅尺构成分解

Figure shows the exploded structure of the grating scale

光栅检测装置的关键部分是光栅读数头，它由光源、会聚透镜、指示光栅及光电元件等组成。

The key component of the grating detection device is the grating reading head, which consists of a light source, a converging lens, an index grating and photoelectric elements.