Archive for category application notes
Radiometry explained by NIST
Posted by Michael Beach in application notes, books we like, tech notes, technical articles on September 14th, 2009
The measurement of light is complicated by a variety of units and concepts that are not used in other fields. For example, the ‘light level’ could be measured in units appropriate to the sensitivity of our eyes (lux), or by the power level (Watts) – but that’s confounded by the wavelength (nano-meters, but sometimes Angstroms) and you need to think in steradians, etendue must be conserved … you get the idea.
We’ve written about some of these issues in earlier posts, but this is one big, complete reference manual – a kind of ‘everything you wanted to know about light, but were afraid to ask’ – and it’s from NIST. They call it a ‘Self-Study Manual’ and it’s a clearly written tutorial on optical radiometry.
And it’s a free download. Enjoy. The test is Tuesday.
link to NIST Self Study Manual on Optical Radiation
The official title is The Self-Study Manual on Optical Radiation Measurements, edited by Fred Nicodemus
Radiometric Measurements
Posted by Michael Beach in application notes, books we like, how-to, metrology, optics, tech notes on July 6th, 2009
It’s easy to confuse the units of LED light output. Steradians, luminous intensity, etc.
Here’s a link to an application note that explains these well, written by C. Richard Duda of UDT (now part of OSI Inc.). Apertures, intentional and otherwise, are discussed, along with typical test configurations.
Link to pdf of application note titled Radiometripdf of Radiometric and
Please tell us if the link gets broken!
CCD Cameras, eyes, and physics
Posted by Michael Beach in application notes, how-to, math, metrology, optics, tech notes, technical articles on March 14th, 2009
This tech note was motivated by the question – how does the response of our eyes
differ from the response of a CCD camera sensor.
Using the data of a particular Hammamatsu CCD camera as an example,
we compared how silicon ’sees’ to the photopic eye response
and compared both to a Planck black-body curve of a light at a particular
color temperature.
We don’t know what those lumps are in that CCD response curve – maybe some
strange reflection interference??
If you know – tell us!
Vision response vs. Planck’s Black Body Curve
Posted by Michael Beach in application notes, how-to, math, metrology, optics, tech notes, technical articles on March 14th, 2009
Color temperature is based upon the idea of a Planck black-body radiator.
Here’s a Tech Note that shows how our eyes respond to the Planck Black-Body radiator.
For a lamp filament at a certain ‘color temperature’ there’s a curve of how our eyes
respond to the lamp. Pete put this into a MathCAD model, and there’s a pdf here
that shows off a few nice graphs.
Silicon Photodetector Units
Posted by Michael Beach in application notes, tech notes, technical articles on March 9th, 2009
Our eyes and silicon light detectors see things differently.
AND the units of photometrics differ from units used by normal MKS systems
here’s an Actinica tech note that tries to sort this out, click link for pdf file
Actinica Book List
Posted by Michael Beach in application notes, books we like, how-to, math, metrology, optics, research papers, tech notes on May 31st, 2008
Ok, we have a book problem.
Both of us waay like good engineering books. A good explanation, or a great
graph that sums up why that camera ’sees’ differently than my eyes, etc.
Since we’re always stumbling on more good books, this list will grow.
Drop by later see what’s new.
Here’s some of the books we like, as a pdf file here,
and here’s some more books we like:
- the Feynman Lectures on Physics, a 3 volume set. Here’s a guy who can explain anything well. Like how sine, cosine and the magic number e all relate to the imaginary number i (square root of -1). He also has a great description of how a ‘50 Ohm’ transmission line acts like ‘50 Ohms’ no matter how long it is. For a really great puzzle – read his description of how charging a capacitor really involves magnetic fields outside the cap’s plates.