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- Changchun Rongde Optics
- Co.,Ltd.
- Add：No.1666 Yaan Road,
- North Lake Development District,
- Changchun 130102,China
- Tel：86-431-81881745
- Fax：86-0431-85256892
- E-mail：rongdecui@roundss.net
- Skype：adacui_roundss
Optical encoders！
Changchun Rongde Optics Co.,Ltd. Release time：2016/7/23 Browse：613The optical encoder was the earliest of the non-contact devices developed to eliminate the wear problems inherent with contact incremental encoders. Present day optical encoders provide the highest resolution and encoding accuracy and can be operated efficiently at high speeds.
Optical encoder discs have opaque and transparent segments (see Figure 3-3). The discs can be produced by exposing a photographic emulsion to light, by plating metal on the substrate or by etching segments into a metal substrate. Each type has characteristics that may make it preferable in certain applications.
Readout is effected by an array of carefully aligned photoelectric sensors positioned on one side of the disc. A light source on the other side provides excitation. As the disc rotates in response to an input variable, the opaque area on the disc passes between the light beam modulating the sensor output in accordance with the selected code. Optical systems focus the light on the sensors. Light columnating LED’s, mirrors, prisms, lenses, fiber optics, laser diodes, and optical slits or diffraction gratings perform this function.
light detection can be performed by one of several devices.material for all types of light detecting devices are selecte from groups III,IV,V of the periodic table and lie haftway in the spetrum between metals and non-metals.As such they are semiconductors.Each device responds to light in a dfferent manner,Sillion or selenium based photovoltaic cells generate an electric current when exposed to light devices is usually cadmium sulfide or cadmium selenide, depending on the desired response of the device or the portion of the light spectrum for which sensitivity is desired. Current capabilities varies with the intensity of light. Photodiodes are similar to photoconductive cells. Photodiodes are used because their very small surface areas allow very high frequency response. They are generally run with back bias and
the reverse leakage current is modulated with the light.
Phototransistors are photodiodes with built-in transistor amplification. Photodiodes have better frequencyresponse and are less sensitive to temperature than phototransistors. In phototransistors, silicon controlled rectifiers (SCR’s) act as sensitive high current switches when exposed to light.
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