Distance Sensors - Optical
- Basic Description
-
Optical distance sensors work by transmitting a pulse of light (usually red or infrared) and
waiting for the reflected signal. The delay associated with reception of the reflected signal
can be correlated to the distance of the reflecting object. Optical signals are very good at
detecting objects that strongly reflect light (e.g. clean, bright objects).
Because they operate at wavelengths on the order of a few nanometers, optical systems are
pretty good at detecting objects of any visible size. However, the range of optical systems
can be severely limited by smoke or dense fog.
Two basic methods for detecting distance (or proximity) using optical
signals that are currently used.
- Direct Method: This method sends the optical signal and then waits
for the signal to be reflected and received again. The signal's trip is timed and the
time correlates with the distance. The main disadvantage of this type of system is
that the system must include a sophisticated timing device capable of the precision
necessary when dealing with the speed of light.
- Triangulation Method: This method utilizes an led or laser as a
emitter and a photodiode as a receiver. The emitter's beam is directed onto
the surface it is detecting and then diffusely reflects. This reflected beam
will be directed towards the photodiode if the object is within the measurement
range. The beam will strike the photodiode at a different place depending on the
distance of the object. The photodiode then produces a different electric
current based on where the light falls on its surface and this signal can be
processed to obtain the object's distance.
- Manufacturers
- Acuity,
Avago,
Balluff,
Bosch,
Continental, Dimetix,
Electrotap,
Keyence,
Moduloc,
NFM
- For More Information
- [1]
Distance sensors (range finders) comparison, Jean-Christophe Zufferey, Oct. 9, 2007.
- [2] Fundamentals of Photoelectric Sensors, Gary Frigyes et al., Automation.com.
- [3] Laser Rangefinder, Wikipedia.
- [4] Photodiode, Wikipedia.
- [5] Tech Talk: Rangefinders, Bushnell website.
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