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Thread: Look MA! No Glasses! Autostereoscopic 3D on a computer monitor

  1. #1
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    Default Look MA! No Glasses! Autostereoscopic 3D on a computer monitor

    Autosteroscopic 3d is becoming the "Next Big Thing" for digital displays. Several new computer monitors have been announced in the recent past that can display 3D images without the need for any viewing aids. THEY ARE EXPENSIVE. I am interested in anything optical and have been fiddling around with this technology. It relies on the same technology that has been around for a long time for making 3D images on post cards etc. A lenticular lens is placed in front of the image and the image is processed to contain the left and right eye views as alternating stripes. The lens depends on the parallax effect to display two different views to the viewer's eyes depending on the small difference in angle which with each eye sees the image.

    I decided to see if I could produce a lenticular lens with sufficient accuracy and suitable focal length to make my own stereographic display. This is an ongoing project but this is the first attempt out of half a dozen that actually works. I ran into a number of issues not the least of which is that the dot pitch of my monitor isn't exactly as advertised. The lens elements must line up all the way across the display or the image will not appear correctly.

    This image shows my first success. This may be a first of some sort as I have taken a stereo image of a stereo image on a display that isn't manufactured to be capable of displaying stereo images. It is intended for crossed eye viewing and clearly shows the 3D effect in the garden scene at bottom.



    The original images are processed with masking screens to produce an interlaced set of lines from the left and right images. The lens must be correctly aligned so the the interlaced lines are presented only to the intended eye when viewed from the correct angle.



    Drivers are now available for recent model video cards that will produce this type of display automatically from any software that uses 3D graphics such as a CAD program.

    The lens was made on my milling machine by dragging a concave ground carbide cutter with enough pressure to deform the Lexan to the correct lens shape. This produces a perfectly clear surface that can't be accomplished by machining.



    I am working on doubling the horizontal resolution as this current image is made with double pixel line pairs. To reduce that to single pixel lines will require accurate lens elements with a frequency of 93.1 lines per inch.

    This is the tool. There is obviously room for improvement. I will have to build a custom grinding jig to polish the carbide. I use 1500 grit diamond dust on a brass rod of the correct dimension to produce the spherical curve of the lens element.

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  2. #2
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    Quote Originally Posted by Evan
    The lens was made on my milling machine by dragging a concave ground carbide cutter with enough pressure to deform the Lexan to the correct lens shape. This produces a perfectly clear surface that can't be accomplished by machining.
    The accuracy, that is quite impressive. But your technique for forming the lenticular screen without degrading transparency is ingenious. Has anybody tried that before?
    Allan

  3. #3
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    I don't know if it has been done before. I don't usually don't do much research on machining techniques of any sort with the exception of tooling properties for items such as inserts.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  4. #4
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    Quote Originally Posted by Evan
    I don't know if it has been done before.
    The entry on lenticular screens in the Focal Encyclopedia of Photography (1969 edition) mentions that the ridges are of cylindrical shape, embossed in plastic "by a suitably-machined heated roller." By forming each lens strip directly you have bypassed the process of making a mold for the embossing.

    You may have heard that Fuji has announced an autostereoscopic camera, the FinePix REAL 3D W1 http://www.fujifilm.com/products/3d/...epix_real3dw1/ and a photoframe viewer. Interest in stereo photography is heating up.
    Allan

  5. #5
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    I have done a lot of experimentation with polycarbonate. It's a very versatile material and very easy to machine. The embossing technique was something I developed when exploring ways to make very even illumination diffusers for backlit transparencies. I am still working on that and all of this experimentation is leading toward a common goal. I was asked some time ago by the local art society director if I would be interested in doing a one man show of my astrophotography at the local gallery.

    Toward that end I am developing methods to display my astrophotos. They just don't look good as prints since they represent objects that are luminous rather than illuminated. I have in mind to do a few images in 3D using LED backlighting where I manipulate actual photos of objects such as the Pleiades to show the proper relationships in space of the stars that make up the cluster. This would involve looking up the distances for the individual stars and then calculating the offsets to produce the correct 3D image by manually adjusting the spacing in the photographs.
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  6. #6
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    ??

    "Lenticular lens" just means "lens-shaped lens".

    It looks like the description here is of an array of cylindrical lenses.

  7. #7
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    I didn't make up the jargon. The phrase "lenticular lens" gathers 52000 hits for that pair of words used together. It's in encyclopedias, product descriptions and domain names. BTW, a single lens element in the array is called a lenticule.
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  8. #8
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    Rather than dragging the tool, why not make a negative form mold and then cast the lens out of acrylic or polyester?

    I forget what variety of acrylic we used, but I'm pretty sure everyone cast pennies or whatever in dixie cups in shop class.

  9. #9
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    That is part of the plan. It takes a long time to make one of these screens using the mill. My half gallon of UV inhibited optical quality polyurethane casting resin should be here today.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  10. #10
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    Evan, Very interesting technology. The thought of micro lenses created by pressing dimples from a formed tool comes to mind but your Z axis would probably suffer infant mortality The left and right could then be halftone screens, each picked up by the lens group with the proper "aim"

    Another method might be to roll the pattern in with a formed roller, polished to the required finish, with built in pitch for N lines at once. It would take more pressure, though, maybe more than you'd like on the Z. Den

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