[Laser] (OT) Uses for a 35-60 zoom lens

[John Randall]

Hi, Just one though on using a zoom lens. The back focus would need to be set 
with a neutral density filter, if the background and foreground are to be in 
focus.

John




________________________________
From: "n5gui at cox.net" <n5gui at cox.net>
To: Free Space LASER Communications <laser at mailman.qth.net>
Sent: Wed, 29 December, 2010 1:34:10
Subject: Re: [Laser] (OT) Uses for a 35-60 zoom lens

I am not sure of a value for that particular camera lens for optical 
communication experimentation.  I think from the description that you gave that 
the lens diameter ( clear aperture ) is less than 10 mm.

Your inquiry did remind me of a lens that I have on a back shelf.  I cannot 
recall where I got it, probably from a garage sale.  It is a 12.5 mm to 75 mm 
zoom and is about 42 mm diameter.  Since it has a 6:1 zoom ratio, I thought that 
if used with a photo sensor, it should have a 6:1 field of view range.  In the 
wide field mode, if could be used to detect a station, although there is a large 
potential of picking up a lot of noise as well.  Then you could "swing" the 
optics to find where the limits of the field of view are, return to that 
approximate center.  Then by zooming in on the desired signal, you can reduce 
the likelyhood of noise sources in the restricted field of view.

You could repeat the swinging of the optics, this time in smaller steps, and 
slower, to re-center, and zoom in further.  The idea is to have a broad field of 
view for detecting the desired station, then narrow the field of view to limit 
noise sources.  The parallel activity on radio is to tune the frequency with a 
broad filter, then use narrow filters to improve the signal to noise ratio.

I am not sure that it has much of an application.  Perhaps if you are trying to 
set up a temporary link among a lot of city lights.  It certainly does not sound 
cost effective to me to try to obtain a zoom lens for this purpose.  But I 
already have the unused lens, like you have the camera from which to get the 
parts.


Best wishes to all for the new year.


James
n5gui


---- Paolo Cravero <pcravero at as2594.net> wrote: 
> Sirs,
> I couldn't find any idea through a search engine, so I ask to the 
> largest community of "optical builders" I know of. Please reply directly 
> since my request is off-topic. Thank you for you patience.
> 
> 
> After few days in the hands of my daughter, a point and shoot 35mm 
> camera plastic has started to break apart... time to put it aside and 
> start opening it up.
> 
> The viewfinder lens is good for a macro addition to my cameraphone 
> (instead of a much smaller DVD laser head lens!). Then there are 
> electronics, motors, flashes, and ... the motorized 35-60 mm (f/4,3 to 
> f/6,3) zoom.
> 
> Is there any useful re-use of that piece of optics? Not necessarily in 
> front of my never-finished light receiver... I know the focus area is 
> pretty wide, 35mm in fact :-), way larger than any photosensor, so an 
> opto-RX might not find that zoom too useful.
> 
> Any idea is welcome, also for reusing other parts I will find inside the 
> camera.
> 
> 
> I wish you all a Bright 2011,
> Paolo IK1ZYW
> 
> ______________________________________________________________
> Laser mailing list
> Home: http://mailman.qth.net/mailman/listinfo/laser
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Laser at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Laser mailing list
Home: http://mailman.qth.net/mailman/listinfo/laser
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Laser at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html