[Laser] Re: Fresnel lenses

[Paul Cianciolo]

Hey Tim,
 
Thanks a bunch for the time to answer my email.
I was never sure if the answer came out in mR or in degrees.
 
Where does the constant 57.3 come from?  I have seen formulas  that state FOV = detector dia/ focal length.
 
I have a 1 watt laser diode that I want to collimate a single 5" lens.  The diode has a fiber output angle that closely matches a 5" lens I have.
 
I have been doing some experiments with an 808nm at 150 mw if you want to see a pix of cloud bounce at straight up I have that I can send you. Also Have a clear sky night trace of signal return as well.
 
Both are graphs showing noise floor and the 1 Khz square wave.  Boy does the signal pic up when you follow the light column up and finally hit the dot on the clouds.

hi pau\
i'm using a short focal length mirror for some NLOS
experiments and it has a FOV of about 0.7 degrees or
so. (247mm focal length and 3x3mm detector)

here's a formula for calculating field of view:

F = (57.3/FL) x D

where:
F= field size in degrees
FL = focal length of lens or mirror in millimeters
D = detector or film dimension in millimeters

for your example:
57.3 / 400mm = 0.14325
0.14325 x 2.5mm = 0.358 degrees FOV

in milliradians:
milliradians = degrees x 17.45
0.358 x 17.45 = 6.247 mR FOV


>
>From: "Paul Cianciolo" 

>Subject: [Laser] Fresnel lenses
>
>Folks,
>
>I wonder if anyone has used a 10" or so diameter for
>a receive antenna?
>
>The problem I see is the relatively short focal
>lengths. This combined with the a 2.5 mm dia.
>detector makes for a pretty wide FOV.
>The fresnel's have tried have not been the most well
>focused lens's.
>Just curios.
>3DLEN.COM perhaps?
>What are you guys using as a FOV for NLOS receivers?
>W1VLF
>PauLC
>



Tim Toast
http://www.aladal.net/toast/exp.html



__________________________________ 
Discover Yahoo! 
Get on-the-go sports scores, stock quotes, news and more. Check it out! 
http://discover.yahoo.com/mobile.html
_______________________________________________
Laser mailing list
Laser at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/laser