1、.,1,檢測技術,.,2,光電開關,.,3,光電開關,.,4,光電開關-工作原理,光電開關（光電傳感器）是利用被檢測物體對光束的遮光或反射，由同步回路選通而檢測物體的有無，所檢測的物體不限于金屬，對所有能反射光線的物體均可檢測。,.,5,光電開關-工作原理,.,6,Principle of Photoelectric Sensor,.,7,Principle of Photoelectric Sensor,Emitting method Pulse-modulated Most of the photoelectric sensors emit a beam which is pulse-mo

2、dulated. 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.,.,8,Principle of Photoelectric Sensor,.,9,Principle of Photoelectric Sensor,Unmodulated Th

3、e 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

4、 a modulated beam.,.,10,Principle of Photoelectric Sensor,.,11,光電開關-漫反射式光電開關,漫反射光電開關是一種集發射器和接收器于一體的傳感器，當有被檢測物體經過時，將光電開關發射器發射的足夠量的光線反射到接收器，于是光電開關就產生了開關信號。當被檢測物體的表面光亮或其反光率極高時，漫反射式的光電開關是首選的檢測模式。,.,12,光電開關-漫反射式光電開關,漫反射式光電開關,引起理想漫反射的光度分布,局部較強漫反射時的光度分布,.,13,Reflective type,.,14,光電開關-對射式光電開關,對射式光電開關的發射器和接收

5、器是分離的，發射器發出的光線直接進入接收器。當被檢測物體經過發射器和接收器之間且阻斷光線時，光電開關就產生了開關信號。當檢測物體是不透明時，對射式光電開關是最可靠的檢測模式。,.,15,Thru-beam type,.,16,General use,.,17,光電開關-槽式光電開關,槽式光電開關通常是標準的U字型結構，其發射器和接收器分別位于U型槽的兩邊，并形成一光軸，當被檢測物體經過U型槽且阻斷光軸時，光電開關就產生了檢測到的開關量信號。槽式光電開關比較安全可靠，適合檢測高速變化，分辨透明與半透明物體。,.,18,U-shaped,.,19,光電開關-鏡反射式光電開關,鏡反射式光電開關是集發

6、射器與接收器于一體，光電開關發射器發出的光線經過反射鏡，反射回接收器，當被檢測物體經過且完全阻斷光線時，光電開關就產生了檢測開關信號。,.,20,Retroreflective type,.,21,General use,.,22,With polarizing filters,.,23,With polarizing filters,.,24,With polarizing filters,.,25,With polarizing filters,Opposite types of polarizing filters are placed in front of the emitting

7、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 o

8、bjects can be reliably detected.,.,26,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

9、 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.,.,27,However, a specular object does not destroy the polarization. The reflected beam o

10、scillates horizontally, as before, and cannot pass through the vertical polarizing filter.,.,28,With polarizing filters,.,29,光電開關-光纖式光電開關,光纖式光電開關采用塑料或玻璃光纖傳感器來引導光線，以實現被檢測物體不在相近區域的檢測。通常光纖傳感器分為對射式和漫反射式。 優點：體積小。,.,30,Principle of optical fiber,.,31,Principle of optical fiber,When light is incident on th

11、e 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.,.,32,Fiber cable structure,.,33,Fiber cable structure,Fib

12、er 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.,.,34,光電開關的接線方式,三線式,.,35,光電開關的接線方式,二線式,.,36,光電開關的使用注意事項,紅外線光電開關在環境照度高的情況下能穩定工作，但原則上應回避將傳感器光軸正對太陽光等強光源。 2. 當使用感性負載（如燈、電動機等）時，其瞬態沖擊電流較大，可能劣化或損壞交流二線的光電開關，在這種情況下，請經過交流繼電器作為負載來轉換使用。 3. 紅外線光電開關的透鏡可用擦鏡紙擦拭，禁用稀釋溶劑等化學品，以免永久損壞塑料鏡。,.,37,光電