|
|
|
Proximity Switches - Retro Reflective
The retro-reflective light barrier combines transmitter and receiver all in one housing. The light emitted by the transmitter is reflected by a reflector (target). The receiver evaluates the reflected light. The small size of the reflector is advantageous for accurate detection. In addition, it is easy to install being a passive element, thus not requiring connection.
As through-beam sensors, retro-reflective light barriers are often selected according to their scanning range. As the light has to travel the distance between sensor and reflector twice, it is often called two-way light barrier. The reflector causes additional dispersions, which has an unfavourable effect on the scanning range. In simplified terms, the transmitter sends out a cone of light. This means, that the diameter of the light cone increases at larger scanning ranges. This is the reason why for large scanning ranges a larger reflector is used than for small scanning ranges. Therefore the data sheet indicates the scanning range referring to the reflector type.
By means of suitable constructional measures the beam angle can be influenced. Laser sensors produce a nearly parallel light beam which is extremely small and parallel across the whole detection area. This advantage is particularly useful for the reliable detection of very small objects inside the whole working range.
| |
| Regardless of their physical principle, all SensoPart retroreflective sensors possess a polarizing filter:
Polarizing filters are optical filters which are comparable with a line grid, Incoming light, which oscillates in all directions, is filtered. Only light beams which oscillate parallel to the grid plane are let through. By use of polarizing filters in combination with triple reflectors, retro-reflective light barriers can detect even mirror-like objects securely.
| |
|