Picking up holography again after many years.

JohnFP · Post by **JohnFP** » Mon Aug 31, 2009 1:23 pm

Set the angle of the reference beam to 54 degrees off the normal. Also, put a piece of black electrical tape over the leading edge of the plate during exposure to keep light from entering into the edge of the plate and causing noise on that end of the hologram.

The_Stranger · Post by **The_Stranger** » Mon Aug 31, 2009 1:45 pm

JohnFP wrote:Set the angle of the reference beam to 54 degrees off the normal. Also, put a piece of black electrical tape over the leading edge of the plate during exposure to keep light from entering into the edge of the plate and causing noise on that end of the hologram.

Just to be sure, since English is not my native language, with 54 degrees of the normal, would that, for instance, be 54 degrees measured up from the horizontal?

(btw would like to applaud you for your website, nice photos and nice pieces about DCG holograms, allthough that is miles away from my level)

JohnFP · Post by **JohnFP** » Mon Aug 31, 2009 3:09 pm

: 56degreesOffNormal.JPG (9.26 KiB) Viewed 2862 times

JohnFP · Post by **JohnFP** » Mon Aug 31, 2009 3:11 pm

Thank you you for the compliments.

Whoops, it should be 56 not 54, sorry about that misprint.

Check this site out.
http://en.wikipedia.org/wiki/Brewster's_angle

The_Stranger · Post by **The_Stranger** » Mon Aug 31, 2009 4:08 pm

JohnFP wrote:Thank you you for the compliments.

Whoops, it should be 56 not 54, sorry about that misprint.

Check this site out.
http://en.wikipedia.org/wiki/Brewster's_angle

I knew there was a name to that angle (obviously), couldn't remember it though.
Assuming by your remark that it should be 56 instead of 54, is really comes down to one or two degree(s). Mmm, I need to make my makeshift setup a little more accurate

But that's half the fun....

JohnFP · Post by **JohnFP** » Mon Aug 31, 2009 4:13 pm

A degree or two does not matter but the closer you are the better.

Ed Wesly · Post by **Ed Wesly** » Mon Aug 31, 2009 8:59 pm

To find the Brewster angle empirically, rotate the glass in the spread beam until the reflection from the glass surface is gone or at least minimized.

JohnFP · Post by **JohnFP** » Tue Sep 01, 2009 10:41 am

It just so happens 56 degrees is a very nice number.
90 degrees in half is 45.
45 degrees in half is 22.5
22.5 degrees in half is 11.25

11.25 degrees + 45 degrees is 56.25 degrees....darn close.

Where am i going with this. See below.

How to make a home made Brewsters Protractor.

: BrewsterProtractor.JPG (37.36 KiB) Viewed 2846 times

The_Stranger · Post by **The_Stranger** » Tue Sep 01, 2009 10:47 am

JohnFP wrote:It just so happens 56 degrees is a very nice number.
90 degrees in half is 45.
45 degrees in half is 22.5
22.5 degrees in half is 11.25

11.25 degrees + 45 degrees is 56.25 degrees....darn close.

Where am i going with this. See below.

How to make a home made Brewsters Protractor.

nice, nice... and I was thinking a had to get the toolbox out of the shed to get the, whatever it is named in English, tool out which measures up angles, but this is even better.

JohnFP · Post by **JohnFP** » Tue Sep 01, 2009 11:09 am

LOL, I have used this, a table saw mitre, a plastic protractor, the reflection statement made by Ed....

But while we are on the subject, I would really play with Ed's statememt. This is all mute if your laser is not polarized in the correct direction.