real time render when?

[KimB]

I'm not sure how that would work (i.e. how you would get digital data translated into holographic data on the display surface).

 

[Alejux]

There's only one kind of display that I put faith on, in giving us 3D eye-resolution displays with active eye/pupil tracking.

http://www.spectrum.ieee.org/WEBONLY/publicfeature/may04/0504reti.html

 

[KimB]

Yeah, the military's been using that kind of tech for a while now. I had the opportunity to check out a flight simulator at the Patuxent River Naval Air Station about 8-10 years ago that used this sort of system. The main problem with the technology is that you have to be looking right at the display for it to work. There's no simple way to allow the eye to move around and still display an image with this technology.

 

[Alejux]

Yeah, the military's been using that kind of tech for a while now. I had the opportunity to check out a flight simulator at the Patuxent River Naval Air Station about 8-10 years ago that used this sort of system. The main problem with the technology is that you have to be looking right at the display for it to work. There's no simple way to allow the eye to move around and still display an image with this technology.

They're working on many theories for that, from what I heard, using mirrors, deformable membranes, etc.. I'm sure they're going to get there soon enough, specially with mems technology evolving at the current pace. The main challenges for the VRD so far are the miniaturization issues and the availability of cheap green/blue laser technology. If I had to take a wild guess, based on all the predictions I read, I'd say that we might have a fully functional 3D color VRD in 10 years. I can't wait for something like that to come along. I can only begin to imagine what it will be like to play games using that kind of technology.

 

[KimB]

Yeah, it would definitely be very cool, since you could have a display expand through your entire peripheral vision. But I still have serious doubts that it can work in a way that you don't have to look straight ahead the entire time (though the laser-based display is vastly easier on the eyes than current 3D glasses).

 

[Dave B(TotalVR)]

I'm not sure how that would work (i.e. how you would get digital data translated into holographic data on the display surface).

All a hologram is just a diffraction pattern stored in the surface of a photographic film. You could simulate this with an LCD display, though you would need some fangled comuter wizzardry to work out what the diffraction pattern would be. It may require multi[ple layers of LCD too, im not sure if the holographic information is stored merely art the surface or down through it for a given thickness.


But a holographic image on a photographic plate is the superposition of a coherent monochromatic waveform (laser light) and the diffuse reflections off the object in question from the same light source. Also very importantly in the same coherence. So you shine the laser, collimate it and what not so its not a thin beam but actually a usuable light beam. You split this beam in two using a semi silvered mirror. You then shine one beam onto the plate and the other onto the object letting the diffuse reflections hit the plate anhd interefere constructively/destructively with the original beam. The path difference between the two must be less than the coherence length of the laser beam (the length along the beam before there is an unpredictable phase change).

When the hologram is made you re-create it by shining the same beam back through it, beam as this beam you are shinig through has left its mark in the photographic film, it will be mostly blocked, but because it has been interfered with right left and centre you end up with the diffuse reflections from the object photographed (not just the object).

Trouble with using an LCD display to cre-create this is the resolution must be far in excess of what we can produce right now. Plus if we ever wanted to make an animated colour holographic display (which would be sweet bejesus I tell ya) we'd also need that superhi rez LCD to switch about 100x as fast as we can at the moment.

With currrent LCD's though you may be able to produce a stationary very low rez holographic image though. As for calculating what to actually display on the LCD... gah, thats gonna require some horsepower. Might only be possible using raytracing algorithms. You would also always be having to look down the LCD, so its no good using an LCD projector and shining it onto a screen (though saying that, it might work I just dunno)

 

[Dave B(TotalVR)]

There's only one kind of display that I put faith on, in giving us 3D eye-resolution displays with active eye/pupil tracking.

http://www.spectrum.ieee.org/WEBONLY/publicfeature/may04/0504reti.html

interesting, but Ive seen way too many films with peoples eyes being zapped by over powerful lasers

 

[KimB]

interesting, but Ive seen way too many films with peoples eyes being zapped by over powerful lasers

You just have to keep the intensity in check. This isn't a problem in the least. As I said, I've used the technology in a military flight sim, and it was very nice indeed.

Edit:
As you said yourself, a laser is nothing more than coherent light. There's nothing inherently dangerous about it. The thing that makes many lasers dangeorus is that they are highly-focused. But as long as the laser is meant to be focused into the eye, it should be no problem to keep the intensity well within acceptable bounds.

As a side comment, though, this sort of technology could give us truly high dynamic range.

 

[KimB]

All a hologram is just a diffraction pattern stored in the surface of a photographic film. You could simulate this with an LCD display, though you would need some fangled comuter wizzardry to work out what the diffraction pattern would be. It may require multi[ple layers of LCD too, im not sure if the holographic information is stored merely art the surface or down through it for a given thickness.

Yeah, um, it'd be vastly easier to just let the laser itself send the information, rather then attempting to encode it on a contact lens.

 

[Dave B(TotalVR)]

As you said yourself, a laser is nothing more than coherent light. There's nothing inherently dangerous about it. The thing that makes many lasers dangeorus is that they are highly-focused. But as long as the laser is meant to be focused into the eye, it should be no problem to keep the intensity well within acceptable bounds.

As a side comment, though, this sort of technology could give us truly high dynamic range.

The thing that makes laser light dangerous is that the light is (almost) perfectly parallel. Parallel beams of light can be considered to come from an infinitely far laight source. You eye focuses light from infinity to a point, so the intensity per unit area when the laser light hits the retina is very high indeed.

 

[Dave B(TotalVR)]

Yeah, um, it'd be vastly easier to just let the laser itself send the information, rather then attempting to encode it on a contact lens.

But then you have to worry about eyeball orientation (needing to move ur laser), the focus of the eyeball and the tracking of the laser beam on the patch of retina you want to display.

All these things are avoided with a holographic plate on the eye. You track eye movement, but dont need to move anything in response, just change the image on the lcd. The need for focus and tracking across the retina would be eliminated because the diffracted light from the hologram should already be in a 'format' (for want of a better expression) where the eye thinks it is seeing a real object. I.e. you are recieving light coming from the directions you would expect, not a single beam that would kinda bypass the focusing mechanism in the eye.

 

[KimB]

The thing that makes laser light dangerous is that the light is (almost) perfectly parallel. Parallel beams of light can be considered to come from an infinitely far laight source. You eye focuses light from infinity to a point, so the intensity per unit area when the laser light hits the retina is very high indeed.

Right, they focus it to a point called the focal point. The focal point is not on the (inner) surface of the eye.

Edit:
Anyway, your hesitance to like the laser imaging technique would apply in the exact same way to your holographic idea.

 

[KimB]

All these things are avoided with a holographic plate on the eye. You track eye movement, but dont need to move anything in response, just change the image on the lcd. The need for focus and tracking across the retina would be eliminated because the diffracted light from the hologram should already be in a 'format' (for want of a better expression) where the eye thinks it is seeing a real object. I.e. you are recieving light coming from the directions you would expect, not a single beam that would kinda bypass the focusing mechanism in the eye.

I just don't think it's feasible. The resolution required would just be fantastically high, and yes, multiple layers would almost certainly be required.

And as for direction, the only thing that matters is where the light hits on the retina, so a laser imaging system would simply make use of the optics in the lens to get the light to wherever it wants.

 

[TomW]

As a side comment, though, this sort of technology could give us truly high dynamic range.

Yup, as high as you like, including Sun bright (as long as you are willing to accept retina damage!). I'm starting to think of A Clockwork Orange, unfortunately.

Tom

 

[Alejux]

There's a good paper regarding the safety issues with VRD.

http://www.hitl.washington.edu/publications/r-97-31/

According to it, the worst thing that could happen, would be if there was a general scanner failure with both the horizontal and vertical beam controllers failing which would lead to a 1 milliwatt continuos laser exposure. But that would be an absolute worst case scenario, and could easily be circumvented by creating a failsafe interlock shutting down the system within a millisecond of scanner failure.

According to the paper, VRDs could safelly show daylight level brightness. In fact, no display we know could come close to the dynamic range levels that could be displayed with this tecnology.