[simpits-tech] More Projector questions, Flat Mirrors

[Marv De Beque]

I don't think that Mylar will give you a satisfactory image.  The sheet will
probably have too many aberrations.

The place to get optical grade flat mirrors is from amateur telescope
makers.

They use them as secondaries for Newtonian telescopes.  However, there are
not very large (a few inches).

If you need bigger, get raw glass primary mirrors (available from 12"
diameters and up) that have not been ground (parabolic).  You can surface
grind these flat very easily and send the ground mirror out for mirroring
and get back just what you need.


-- 


> From: "D E" <d_p_e@hotmail.com>
> Reply-To: simpits-tech@simpits.org
> Date: Fri, 18 Oct 2002 13:51:12 +0000
> To: simpits-tech@simpits.org
> Subject: Re: [simpits-tech] More Projector questions,
> 
> Hey all,
> 
> Part of my 'flight sim' project, although further off in the future for now,
> is to build an off axis rear projected type of visual system (similar to the
> ones used in commercial flight sims).
> 
> For the collimating mirror, I thought this looks like the way to go ..
> 
> http://www.nielsensenterprises.com/snomo/mylar.htm
> 
> seems quite reasonable in price ..
> 
> I am designing a curved frame (which is a lower section of a sphere), the
> mylar will be attached to this frame at the edges and then a vacuum applied
> to it which will bring the sheet to the right tension.
> 
> Does a vacuum have to be appplied to it all the time? (is the mylar
> permeable?)
> 
> I am still working out the angles on CAD .. seems like it is do-able.
> 
> As i mentioned before .. I am a fair way off from making this .. but even if
> it doesn't work, I don't think i will have lost much (Apart from hours of
> dreaming).
> 
> Derek
> 
> 
> 
> 
> 
> 
> 
>> From: Allen Buffington <allen@simworld.biz>
>> Reply-To: simpits-tech@simpits.org
>> To: simpits-tech@simpits.org
>> Subject: Re: [simpits-tech] More Projector questions,
>> Date: Thu, 17 Oct 2002 18:05:51 -0600
>> 
>> Yes, this is an option however you should use a "first surface" optical
>> grade mirror.
>> A first surface mirror has the reflective coating on the surface of the
>> glass,
>> whereas regular mirrors have the reflective surface on the back of the
>> glass.
>> Rear projection TV's use a first surface mirror. This might be a source
>> of finding
>> a usable mirror that could work for you. You could check with some TV
>> repair shops
>> and see if any have a unrepairable TV cabinet and convert it to your
>> use.
>> Using a regular mirror you will get an unwanted ghost image reflected
>> off the glass
>> surface as well as the silver reflecting surface.
>> 
>> ~~Allen
>> 
>> Johan Nauwelaertz de Agé wrote:
>> 
>>> Thanks for the info Sean, Is it possible to use a setup as on the
>>> picture? I have lack of distance in front of the cockpit and thought
>>> it might work with a mirror to double the distance, but what happens
>>> with the picture / quality? Damn I'm to tired to figure it out
>>> myself. Johan
>> 
>> 
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> 
> 
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