3 ms·

Depends on size of occluded area? If I block the sun with my thumb, some light does go around, but it's still a decently effective mask.

by bobsil1 10y ago

mojomark 10y ago
If you hold out your thumb between your eye and the sun, such that your thumb appears to just block the edges of the sun, then you will be effectively blocking the entire set of overlapping wavefronts emanating from the sun (that would have formed multiple "pixels" forming the sun image on your retina), preventing their arrival at your cornea and ultimately entering your pupil. Notice that your thumb is about about 1.5ft from your eye. Could you emulate that with a transparent LCD display? Yes, but that display would need to be large and about 1.5ft from your eye. Not really practical for a near eye (head mounted display). If you try to accomplish this occlusion directly with an LCD microdiplay (such as those found in many projectors) in a near eye application, at best you end up with a blackish smudge with very fuzzy edges. To see this in action, look at Figure 11.D in the following paper: http://www.cs.unc.edu/~maimone/media/pinlights_siggraph_2014.pdf http://www.cs.unc.edu/~maimone/media/pinlights_siggraph_2014...
- bobsil1 10y ago
  Thanks for the paper link. Is there a plausible way to use destructive interference to create true black? I remember patents around this.
  - kelsolaar 10y ago
    Most of the light that is received by the retina in day to day life is highly incoherent thus it is unlikely that you can produce a destructive wavefront for it.
    - bobsil1 10y ago
      One of their patents mentions using stacked diffraction optical elements. Details unclear: >[0216] Such may be used to cancel light from the planar waveguides with respect to light from the background or real world, in some respects similar to noise canceling headphones. http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220150016777%22.PGNR.&OS=DN/20150016777&RS=DN/20150016777 http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=H...
      - mojomark 10y ago
        > One of their patents mentions using stacked diffraction optical elements [DOE]. > http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=H.. http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=H.... I believe this particular excerpt is referring to the use of the layered and controllable DOEs to curve light projected from their scanning fibers that ultimately forms the virtual object image on the retina, rather than using the DOEs to attenuate ambient light (see my reply to Kelsolaar above). However, if I'm interpreting their literature correctly, you are correct in that they are able to use (at least a portion of) these DOE layers to generate the moire patterns that will ultimately be capable of form black/clear image masks.
    - hawski 10y ago
      Would collimator in front help?
    - mojomark 10y ago
      I agree that the lack of coherence (spatial & temporal) of ambient lighy would makes the use of diffraction gratings to actively create destructive interference patterns on the retina a futile efftort. Ambient light is generally a white lighy (lacks temporal coherence) and many wavefronts originate closer to the eye than the optical infinity (~8m) and are therefore fairly divergent (curved and thus lack spatial coherence). The resulting interference patterne would therefore be very blurry. Too blurry to form a useful black pixel image on the retina. On the other hand, I believe ML is proposing to use a gratings to display black/clear images. In this setup, the incident ambient light wavefronts are selectively redirected using bragg gratings (why they keep saying Braff gratings" in their literature is beyond me). This technique has been around for many years and is still captivating to watch even in this day and age - see: https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DS5W5JJXtqhw&ved=0ahUKEwj4loTjlpnQAhXE6yYKHUb1AkEQtwIIGjAA&usg=AFQjCNGVVlv9xxrd7RlmDFyp7czhQgiiUg&sig2=1H7cDmEQ31j-uEdjVaVjLw https://www.google.com/url?sa=t&source=web&rct=j&url=https:/... The realization that this affect retains its "sharpness" for near eye applications in concert with (I believe) the realization that you can utilize the electonically-controlled diffraction grating layers you already have in your device (for the purpose of controlling wavefront curvature to support eye depth accommodation) depth is really quite clever. It's truly an exciting prospectct!

Depends on size of occluded area? If I block the sun with my thumb, some light does go around, but it's still a decently effective mask.

by bobsil1 10y ago

Depends on size of occluded area? If I block the sun with my thumb, some light does go around, but it's still a decently effective mask.

mojomark 10y ago

If you hold out your thumb between your eye and the sun, such that your thumb appears to just block the edges of the sun, then you will be effectively blocking the entire set of overlapping wavefronts emanating from the sun (that would have formed multiple "pixels" forming the sun image on your retina), preventing their arrival at your cornea and ultimately entering your pupil. Notice that your thumb is about about 1.5ft from your eye. Could you emulate that with a transparent LCD display? Yes, but that display would need to be large and about 1.5ft from your eye. Not really practical for a near eye (head mounted display). If you try to accomplish this occlusion directly with an LCD microdiplay (such as those found in many projectors) in a near eye application, at best you end up with a blackish smudge with very fuzzy edges. To see this in action, look at Figure 11.D in the following paper: http://www.cs.unc.edu/~maimone/media/pinlights_siggraph_2014.pdf http://www.cs.unc.edu/~maimone/media/pinlights_siggraph_2014...

bobsil1 10y ago
Thanks for the paper link. Is there a plausible way to use destructive interference to create true black? I remember patents around this.
- kelsolaar 10y ago
  Most of the light that is received by the retina in day to day life is highly incoherent thus it is unlikely that you can produce a destructive wavefront for it.
  - bobsil1 10y ago
    One of their patents mentions using stacked diffraction optical elements. Details unclear: >[0216] Such may be used to cancel light from the planar waveguides with respect to light from the background or real world, in some respects similar to noise canceling headphones. http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220150016777%22.PGNR.&OS=DN/20150016777&RS=DN/20150016777 http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=H...
    - mojomark 10y ago
      > One of their patents mentions using stacked diffraction optical elements [DOE]. > http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=H.. http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=H.... I believe this particular excerpt is referring to the use of the layered and controllable DOEs to curve light projected from their scanning fibers that ultimately forms the virtual object image on the retina, rather than using the DOEs to attenuate ambient light (see my reply to Kelsolaar above). However, if I'm interpreting their literature correctly, you are correct in that they are able to use (at least a portion of) these DOE layers to generate the moire patterns that will ultimately be capable of form black/clear image masks.
  - hawski 10y ago
    Would collimator in front help?
  - mojomark 10y ago
    I agree that the lack of coherence (spatial & temporal) of ambient lighy would makes the use of diffraction gratings to actively create destructive interference patterns on the retina a futile efftort. Ambient light is generally a white lighy (lacks temporal coherence) and many wavefronts originate closer to the eye than the optical infinity (~8m) and are therefore fairly divergent (curved and thus lack spatial coherence). The resulting interference patterne would therefore be very blurry. Too blurry to form a useful black pixel image on the retina. On the other hand, I believe ML is proposing to use a gratings to display black/clear images. In this setup, the incident ambient light wavefronts are selectively redirected using bragg gratings (why they keep saying Braff gratings" in their literature is beyond me). This technique has been around for many years and is still captivating to watch even in this day and age - see: https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DS5W5JJXtqhw&ved=0ahUKEwj4loTjlpnQAhXE6yYKHUb1AkEQtwIIGjAA&usg=AFQjCNGVVlv9xxrd7RlmDFyp7czhQgiiUg&sig2=1H7cDmEQ31j-uEdjVaVjLw https://www.google.com/url?sa=t&source=web&rct=j&url=https:/... The realization that this affect retains its "sharpness" for near eye applications in concert with (I believe) the realization that you can utilize the electonically-controlled diffraction grating layers you already have in your device (for the purpose of controlling wavefront curvature to support eye depth accommodation) depth is really quite clever. It's truly an exciting prospectct!