please dont rip this site

Light Sensors

Cameras@ LED@ Wearables@ Infra-Red I/O@ Fiber optics

Richard Ottoson says:

...a quick rule of thumb about opto's:

These times assume a "reasonable" resistor value. There are amplified optocouplers that are in the 100ns range as well.

Application notes on photodiodes ( A Primer on Photodiode Technology has some simple circuits for photodiodes, and tons of nit-picky detail on how they work. Offline as of 2009-06-13 -- has it moved elsewhere?  Perhaps to

Brian Kraut says:

Go to your local disco and theatrical lighting supply store and ask for for a gell sample book. Voila, about 100 different color plastic filters in 1 X 3" size. Some of them even have spectral response graphs for each sheet.

James Newton Says: " For optical interruption sensors, don't forget your standard super low cost "mechanical" mouse! " +

Phototransistors +


Dark Current
A small value current that flows in a photodiode while reversed biased, due to thermal generation of carriers and surface leakage with no incident light (also called leakage current).
Range: a few pA to 10 m A
Photo Current
Flow of current generated by a photodiode in response to an incident optical power. The absorbed photons generate free charge carriers that are collected within the
Photo Voltaic Mode
Unbiased mode of operation of a photodiode, preferred in low frequency (up to 350 MHz) as well as ultra low light level applications.
Photo Conductive Mode
Reverse biased mode of operation of a photodiode, in which lower capacitance and faster rise time are obtained. Generates more noise (dark current).
Shot Noise
Noise related to the statistical fluctuation in both the photocurrent and the dark current. It is the dominant noise in the photoconductive mode.
Shunt Resistance
Defined as the current flow in the dark of a photodiode when reverse biased at 10mV. More current flow reduces the effect of noise.
Thermal Noise
All devices have a thermal (or Johnson) noise associated with them, due to thermal generation of carriers
Noise Equivalent Power
Optical power necessary to create a photocurrent equal to the noise, to obtain a signal-to-noise ratio of 1. It depends on the noise current and the responsivity.
Responsivity (or Sensitivity)
The ratio of output current (in Amperes) to input light power (in Watts). It is a constant in the dynamic range, at a given wavelength.
A drift in output for a detector submitted to a constant input optical power for a long period of time.

See also:

file: /Techref/io/sensor/light.htm, 9KB, , updated: 2011/9/6 12:34, local time: 2024/7/23 23:50,

 ©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE!

<A HREF=""> Light Sensors</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type a nice message (short messages are blocked as spam) in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.

Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

  PICList 2024 contributors:
o List host: MIT, Site host, Top posters @none found
- Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.

Welcome to!