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 Source of inexpensive high power meniscus lenses 
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Sharp Eyed Eagle!

Joined: Thu May 22, 2008 9:13 pm
Posts: 380
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Hi,

I have found a lens product which may be suitable for adaptation to virtual reality displays like the Oculus Rift.

They are generically described as a MACRO CLOSE UP LENS FILTER set.

They are a stackable series of meniscus lenses of progressive powers, in a low profile modular filter ring format, and are interchangeable so the overall magnification power can be varied at will.

Best of all, they are readily available, of photographic optical quality and are quite cheap at $20 or so a set.

They usually come in a set of 4 lenses, with digital powers of +10, +4, +2 and +1. The diameters are quite generous too at around 60mm depending on the filter thread size they are made for.

The +10 lens alone will bring the focal length down to 100mm, which I believe is the minimum optical power needed to obtain a decent virtual reality experience for side-by-side format viewing.

Thanks


Sun Mar 17, 2013 8:44 am
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Petrif-Eyed
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Joined: Sat Jan 09, 2010 2:06 pm
Posts: 2255
Location: Perpignan, France
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Do you have a link for these ?


Sun Mar 17, 2013 9:08 am
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Sharp Eyed Eagle!

Joined: Thu May 22, 2008 9:13 pm
Posts: 380
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Hi,

I just whacked 'MACRO CLOSE UP LENS FILTER ' into ebay and over 1000 items came up.

:lol:

Thanks.


Sun Mar 17, 2013 9:13 am
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Petrif-Eyed
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Joined: Sat Sep 01, 2012 10:47 pm
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Thanks. I just ordered a set for my Canon EOS 550D for $10 (free shipping). If they work for VR I will order another set (or two).

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Sun Mar 17, 2013 11:45 am
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Cross Eyed!
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Joined: Wed Feb 06, 2008 9:10 pm
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budda wrote:
Hi,

I have found a lens product which may be suitable for adaptation to virtual reality displays like the Oculus Rift.

They are generically described as a MACRO CLOSE UP LENS FILTER set.

They are a stackable series of meniscus lenses of progressive powers, in a low profile modular filter ring format, and are interchangeable so the overall magnification power can be varied at will.

Best of all, they are readily available, of photographic optical quality and are quite cheap at $20 or so a set.

They usually come in a set of 4 lenses, with digital powers of +10, +4, +2 and +1. The diameters are quite generous too at around 60mm depending on the filter thread size they are made for.

The +10 lens alone will bring the focal length down to 100mm, which I believe is the minimum optical power needed to obtain a decent virtual reality experience for side-by-side format viewing.

Thanks



Budda - Yep, I can absolutely confirm this to be true. :)

Almost all of my original HMD prototypes all made use of these 'Macro' lenses. :)

They can be left in their mounts for simplicity as long as the lens diameter is small enough. Once you start going w/ larger lenses the rings will start cutting into your nose, etc.

For a couple of my earlier prototypes I went w/ the 75mm DIA 100mm FL and ran them through a wet tile saw to make room for the nose. They're heavy but make an excellent DIY HMD lenses when working with 5"+ LCDs. ;)

Note: You can pickup a spanner wrench on ebay pretty cheaply to remove the lenses from their mounts...but I've found that sometimes they were so tight it was easier to just cut the mounts off w/ a dremel.

Good job realizing their potential as cost effective high quality HMD lenses. :)

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Mon Mar 18, 2013 3:00 pm
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Golden Eyed Wiseman! (or woman!)

Joined: Fri Aug 21, 2009 9:06 pm
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Are they really Meniscus lenses, though? I was under the impression that they were generally not.


Mon Mar 18, 2013 8:47 pm
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Sharp Eyed Eagle!

Joined: Thu May 22, 2008 9:13 pm
Posts: 380
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Hi,

Thanks TheLostBrain for your information.

It seems there are now four common sources of lenses for VR applications.

Magnifying loupes, spectacle lenses, camera macro lenses and fresnel lenses.

One of the least appreciated aspects of VR is fitting the 'standard' VR display to a 'non-standard' face and eyes.

I see the Oculus Rift uses circular lenses too, so it will be interesting to see how it avoids the potential nose and face interference problems.

If the lenses could be appropriately decentred in the filter ring and offset accordingly with respect to the face, then some adjustment flexibility could be made for the eye centres.

One thing I would like to try with the larger circular lenses is to put a standoff spacer between the lens and the eye, so it can help clear the nose and face.

The spacer would be a thick acrylic window that would funnel the light to the eye whilst being contoured at the sides to the face of the user. This would assist in getting a wrap-around immersive VR experience.

In any case, having more design options available means the less practical design approaches can be thrown out.

Thanks.


Mon Mar 18, 2013 9:04 pm
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Sharp Eyed Eagle!

Joined: Thu May 22, 2008 9:13 pm
Posts: 380
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Hi,

Quote:
Are they really Meniscus lenses, though? I was under the impression that they were generally not.


Generally speaking, the supplementary lenses or close-up lenses used in these camera filter rings are positive meniscus lenses.

Apparently they are nothing new, and these macro lens attachments have been around in photography for years.


There are a few caveats with the use of them.


1. The quality is variable depending on the source of manufacture.


2. Most lenses are described as 'simple' and are single element, spherical curvature, positive meniscus lenses.


3. It is recommended that no more than two lenses be used in a stack because of cumulative aberations.


4. The stackable lens set is designed so the lenses can be stacked in any order.

If making your own lens stack with regular low profile filter rings, care must be taken to ensure lens clearances, because of the pronounced bow of the lenses.

Some commentators suggest the lenses need to be ordered progressively in the lens stack, with the highest power lens nearest to the eye, for a better image.


5. The range of powers available from even two stacked meniscus lenses is sufficient for prototyping work. You can get +10, +11, +12 and +14 powers with a single or dual lens combination.


6. For more advanced work I suggest obtaining a single aspheric prescription lens of the required overall power, with or without the filter ring mount.

Someone has developed a DIY macro lens using a custom aspheric lens in a filter ring as shown here.

http://www.instructables.com/id/High-Quality-Aspherical-Close-Up-Lens/


Thanks.


Tue Mar 19, 2013 8:18 pm
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