Making the simple mono DIY HMD - OPTICS questions [REQ]

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cypher9000
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Making the simple mono DIY HMD - OPTICS questions [REQ]

Post by cypher9000 »

Hi all,

I finaly decided to make mine first beginners HMD. I have studied the topic a bit, but I am still not sure about the OPTICS.
I chose to make just a mono HDM - so I will use just one approx. 3,5"-6,5" LCD (maybe LED backlight) monitor. There are many types available and cheap - so this is no problem.

But the question is, what OPTICS should I use?
a) can be the OPTIC system just very simple? - I mean only 1 magnificating lens and nothing more is needed for a low-end diy project optics?

b) can I use just 1 long (probably 4" long rectangular fresnel) magnificating glass for booth eyes or better 2 separate lenses (1 for each eye - maybe aspheric - "fish eye type")? The longer rectangular sheet magnificient glass is usually widely available and cheap fresnel type (used for reading small book text, etc.) with zooming 2-3x. Is it usable in mine case?

c) what are the necessary parameters of the lenses in mine case? I mean zooming (3x, 5x), diameter, focal lenght. It is necessary to calculate these parameters exactly in some way or just dont need to be very precise (just keep some basic ranges and try)? The problem is, that the typical cheap consumer magnif. glasses do not have ussually listed all these optical parameters.

d) I think the lens zoom should be approx 3x-5x and focal length about 8-10 cm. are these guess parameters correct?

e) I normally wear a glases for long distances, I have approx. 3 dioptres. I hope, that I will be able to watch the HMD ok without my glasses, right? ;-)

thanks a lot for the coments. greetings
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cybereality
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Re: Making the simple mono DIY HMD - OPTICS questions [REQ]

Post by cybereality »

You can look into "LEEP on the cheap", those are supposed to be some of the best. I had the idea of using fresnel lenses in a DIY HMD, it could possibly work.

Also, good luck.
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Okta
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Re: Making the simple mono DIY HMD - OPTICS questions [REQ]

Post by Okta »

I used a couple of cheap 5 inch Fresnel lenses in 2 layers a few inches apart. This gave me a massive FOV and comfortable eyes but some visual quality loss.

http://www.mtbs3d.com/phpBB/viewtopic.p ... 237#p38237" onclick="window.open(this.href);return false;
Last edited by Okta on Sat Jan 07, 2012 9:10 pm, edited 1 time in total.
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Tone
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Re: Making the simple mono DIY HMD - OPTICS questions [REQ]

Post by Tone »

The other issue with 2 eyes and one screen is that your eyes must turn inward in a most uncomfortable way in order to converge the image. With an 80mm focal length, the screen is going to be about 2-3" from your face. Hold your finger 3" in front of your nose and converge your eyes on your finger. Now hold that position for 5 min. You will be in pain!

You need to insert some sort of prismatic element into the optics to allow your eyes to view more naturally (fairly parallel lines of sight.) LEEP used 3M Press-On fresnels as prisms, but you could also use narrow wedge glass or plastic prisms. Probably looking at 5-10 prismatic diopters. Thin wedges are usually made to use in pairs for anamorphic camera and projection lenses. Sometimes you can pick them up at Surplus Shed or some other optics outlet. In the end, Press-Ons are the path of least resistance.
Converge.jpg
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Okta
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Re: Making the simple mono DIY HMD - OPTICS questions [REQ]

Post by Okta »

Tone, just a normal cheap plastic fresnel or 2 will do the job of diverging the eyes.

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