《光电开关检测技术》PPT课件.ppt

检测技术,光电开关,光电开关,光电开关-工作原理,光电开关（光电传感器）是利用被检测物体对光束的遮光或反射，由同步回路选通而检测物体的有无，所检测的物体不限于金属，对所有能反射光线的物体均可检测。,光电开关-工作原理,Principle of Photoelectric Sensor,Principle of Photoelectric Sensor,Emitting method Pulse-modulated Most of the photoelectric sensors emit a beam which is pulse-modulated. In this method, a strong optical signal of fixed width is emitted at a fixed time interval. This helps the receiver to distinguish the signal from extraneous light and to achieve a long sensing range.,Principle of Photoelectric Sensor,Principle of Photoelectric Sensor,Unmodulated The high-speed fiber sensor FX2-A3R and the color mark sensor LX-12N series use an unmodulated beam. In this method, the beam is emitted constantly at a fixed intensity. This enables high-speed response, although the sensors are a little susceptible to extraneous light as compared to the sensors using a modulated beam.,Principle of Photoelectric Sensor,光电开关-漫反射式光电开关,漫反射光电开关是一种集发射器和接收器于一体的传感器，当有被检测物体经过时，将光电开关发射器发射的足够量的光线反射到接收器，于是光电开关就产生了开关信号。当被检测物体的表面光亮或其反光率极高时，漫反射式的光电开关是首选的检测模式。,光电开关-漫反射式光电开关,漫反射式光电开关,引起理想漫反射的光度分布,局部较强漫反射时的光度分布,Reflective type,光电开关-对射式光电开关,对射式光电开关的发射器和接收器是分离的，发射器发出的光线直接进入接收器。当被检测物体经过发射器和接收器之间且阻断光线时，光电开关就产生了开关信号。当检测物体是不透明时，对射式光电开关是最可靠的检测模式。,Thru-beam type,General use,光电开关-槽式光电开关,槽式光电开关通常是标准的U字型结构，其发射器和接收器分别位于U型槽的两边，并形成一光轴，当被检测物体经过U型槽且阻断光轴时，光电开关就产生了检测到的开关量信号。槽式光电开关比较安全可靠，适合检测高速变化，分辨透明与半透明物体。,U-shaped,光电开关-镜反射式光电开关,镜反射式光电开关是集发射器与接收器于一体，光电开关发射器发出的光线经过反射镜，反射回接收器，当被检测物体经过且完全阻断光线时，光电开关就产生了检测开关信号。,Retroreflective type,General use,With polarizing filters,With polarizing filters,With polarizing filters,With polarizing filters,Opposite types of polarizing filters are placed in front of the emitting and receiving elements. A horizontal polarizing filter placed in front of the emitting element passes only horizontally polarized light and a vertical polarizing filter placed in front of the receiver ensures that only vertically polarized light is received. Using this configuration, even specular objects can be reliably detected.,With polarizing filters,1 Normal unpolarized beam emitted from the LED oscillates in a random manner. As it passes through the horizontal polarizing filter, the oscillation is aligned horizontally and the beam is horizontally polarized. 2 When the polarized beam falls on the reflector, its polarization is destroyed and the reflected beam oscillates in a random manner. So, the reflected beam can pass through the vertical polarizing filter and reach the receiving element.,However, a specular object does not destroy the polarization. The reflected beam oscillates horizontally, as before, and cannot pass through the vertical polarizing filter.,With polarizing filters,光电开关-光纤式光电开关,光纤式光电开关采用塑料或玻璃光纤传感器来引导光线，以实现被检测物体不在相近区域的检测。通常光纤传感器分为对射式和漫反射式。 优点：体积小。,Principle of optical fiber,Principle of optical fiber,When light is incident on the core, it propagates in the core by being totally reflected at the boundary between the core and the cladding. After traveling through the fiber, light spreads at an angle of approx. 60 at the cable end and is directed on the sensing object.,Fiber cable structure,Fiber cable structure,Fiber sensors are classified broadly into two groups thru beam type and reflective type. The thru-beam type has two fiber cables: the emitting cable and the receiving cable. The reflective type has one fiber cable that contains, both, the emitting part and the receiving part.,光电开关的接线方式,三线式,光电开关的接线方式,二线式,光电开关的使用注意事项,红外线光电开关在环境照度高的情况下能稳定工作，但原则上应回避将传感器光轴正对太阳光等强光源。 2. 当使用感性负载（如灯、电动机等）时，其瞬态冲击电流较大，可能劣化或损坏交流二线的光电开关，在这种情况下，请经过交流继电器作为负载来转换使用。 3. 红外线光电开关的透镜可用擦