[Tfug] Yet another optics question

[johngalt1]

----- Original Message ----- 
From: "Bexley Hall" <bexley401 at yahoo.com>
To: "Tucson Free Unix Group" <tfug at tfug.org>
Sent: Monday, December 21, 2009 9:36 PM
Subject: Re: [Tfug] Yet another optics question


>> With my totally unqualified opinion, I would go with what 
>> the
>> guy in the climate change business, (ostensibly) said...
>>
>> Just go with the 1460X six volt lamp as B&L designed.
>> It's really common and easy to get by mail order. Its 
>> color
>> characteristics are probably consistent. Kind of looks 
>> like
>> an automotive lamp base with a flange...
>
> The lamps run anywhere from $5 to $??? (some fools trying
> to peddle them for $20!).  The old lamp was an "S1460" --  
> I
> have not been able to get any clarification as to the
> differences between the S1460 and 1460X... perhaps just
> differences in manufacturer's part numbering schemes?

X indicates a long life version.

> The kicker with mail order is the $8 - $10 they want to 
> ship
> the 1 ounce bulb!

That's why I buy three. (As long the shipping doesn't 
multiply also.) If so, I look for another supplier.

> And, *using* the 20W device throws off a fair bit of heat
> (the lamp is sited just below/in front of your forehead)
> which makes it quite uncomfortable.
>
>> Having said that, the lens assembly is probably like that
>> of a photo enlarger condenser. As I understand it, it 
>> takes
>> a point source and gives light focused at infinity. Good 
>> as
>> an illuminator.
>
> Yes.  My question is:  how critical is the location of
> that point source?

I don't believe they would go to the trouble of fabricating 
a lamp with prefocused base unless there was a good reason 
for it. If a convex side of the lens is toward the lamp, 
that cinches it for me. Nevertheless it will stlll work, but 
be less optimal.

>> If you wanted to play around have money to blow you could
>> get a cheap high power LED emitter from a place like Deal
>> Extreme. Place it at the focus where the lamp filament 
>> is.
>> Give it an appropriate heat sink. The microscope power
>> supply might work too.
>>
>> Have fun!
>
> I suspect I don't even have to go to the extreme of a 
> fancy
> emitter.  I tried an LED flashlight and it seemed to work 
> OK.
> Granted, more light would be nicer but I don't really see 
> the
> advantage of TONS of light (?).  The brochure explains 
> that
> it "helps cast shadows" (?)  OK, maybe that helps with 
> depth
> cues??

Wasting a handy flashlight might be considered extreme... 
However, what might push me over the edge to commit 
flashlighticide is the idea of waiting three weeks for the 
$5-$7 emitter (shipped) to arrive from China.

www.dealextreme.com/products.dx/category.917

It's a tradeoff... Money for a known thing, or spending 
money and time to tinker with something else.

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