Idle Diffractions

What if you could adjust the “filter” on your eyes?

For those in science, and particularly those in optics, we know that the eye responds to only a limited range of all possible wavelengths that are shooting past us.  We know short of deep blue there is the UV (and skin cancer).  The long of deep red is the infra-red, then eventually heat, and on to radio waves, extending eventually to the water waves on a lake, in a less abstract medium.  What if we had a button that allowed us to see other wavelengths?

Well, electronic detectors, like those on the Hubble Space Telescope (HST), let us do just that.  By encoding wavelength information we cannot see in a spectrum that we can, we can begin to learn what the world, and better yet the universe, looks like at other wavelengths, and in fact how much there is to learn.  In fact, one important point when it comes to the universe is that light arriving here from far away is also very old—billions of years.  Light travels fast enough to circle the earth at the equator about 7 times in a second, but, on the scale of the universe that is actually pretty slow.  This old light is red-shifted (I am not going to cover this today), meaning, even if it starts out blue, by the time it gets here, it is not even red—it is deep in the infra-red. 

Subsequently, the new James Webb Space Telescope (JWST) , designed to routinely look to and try to understand the edge of the universe, and therefore the edge of time (and no, I’m not going there today either), will have detectors that are designed to only see infrared light that we cannot ourselves “see”.  Starting at a large scale with the space-based telescopes of the last 20 years, we have been building a massive database of information in colors that we cannot ourselves see, including x-Ray (Chandra) and deep Infra-red (WISE).

That brings us to today’s “find”, which comes to us from ORA’s Mark Kahan.  It came to Mark from a friend, Art Ferruzzi, who is always on the lookout for interesting Internet articles in science.  There is now a web-link where you can call up regions of the sky/universe and dial in the wavelength bands you would like to “see”.

www.chromoscope.net

Somewhat reminiscent of recent photo reconstructions of space where they remove the “new” objects and leave only the really “old” ones, this view of our universe is truly inspiring.

It so reminds me of something I was once asked in high school, as I was labeled as the science kid in the group.  My friend from the age of 4 said to me, “I really hope I get to travel into outer space and go to another planet to see different colors”.  That was somewhat a confused view of the world, but, I will be forwarding this website to him next and let him know his wish has been granted, more or less.

Since we always like to have a graphic, this is one of my favorites, as I was not able to copy off of the live site successfully.  On the left, the darkest region in space over the format of the Hubble Space Telescope as seen from the ground in ultra-deep exposure mode (i.e., a region with the least number of objects).  On the right, the same region shot with the Hubble following the 1st repair mission.  Soon to be surpassed, I believe, by the new equipment.  If anyone happens to spot a new shot of this region, do let me know.

Wachendorf?

So, I am doing a little research on the history of aspherics.  I learned one thing.  The earliest written reference I found so far is a US patent by Abbe, US 697,959, filed in 1899.  Along the way, I came on the name of Fritz Wachendorf.  A new name for me, and interesting unto itself, but, even more interesting for the following, unrelated Google search experience.

Let’s say you are interested in finding out the most significant books specifically oriented to optical design.  Here is what to do:

1. Go to www.scholar.google
2. Type “F. Wachendorf” with the quotation marks

At least at the moment, where I am, the second item should look like:

[CITATION] Bestimmung der Bildfehler 5. Ordnung in zentrierten optischen …
F Wachendorf - Optik, 1949
Cited by 7 - Related articles

Now, click on Related articles and you should see, near the top,

[CITATION] Geometrical Optics
JG Baker - Fundamental formulas of physics, 1955 - Prentice-Hall
Related articles - All 2 versions

Now, click on Related articles again, and you now have pretty much the top 100 books in geometrical optics. 

I recognize the list, because I spent over 10 years, in the pre-Internet period, collecting old books in optics and this list parallels what was my collection.  That collection has since been donated to the College of Optical Sciences at the University of Arizona.  However, in a few months, the optics books in that collection that are dated before 1923 will be posted to the ORA website as they were recently scanned by Kirtas books using funding from ORA.  This will begin an exciting opportunity to get your own e-book, soft-cover, or, even hardcover version of the classics in optics, including, for example Coddington, from 1828 and Airy from 1850. There will be more on this, soon.  Try out the search series – the book list is really great.  And, there are a few articles that are interesting if you have missed them.  The one below for example. 

[CITATION] WHO? DISCOVERED CODDINGTON'S Equations?
R Kingslake - Optics and Photonics News, 1994 - opticsinfobase.org
In these formulae, s and t represent the distances from the point of incidence of the traced ray
to the sagittal and tangential object or image, measured along the traced principal ray, and r
is the radius of curvature of the refracting surface.

And, there appears to be a new book on photographic lenses out (don’t buy them all, I’m ordering mine tomorrow).  Looks good, especially if you happen to read German.