Film-Tech Forum ARCHIVE: How does 3D work with laser based systems?

This is topic How does 3D work with laser based systems? in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Mark J. Marshall (Member # 1409) on 11-29-2015, 08:59 PM:

For IMAX laser 3D - How is the 3D separated? Is it circular, linear, light frequency based ala Dolby 3D, or something else?

Also, how does the new Dolby Vision 3D work?

Posted by Dave Macaulay (Member # 813) on 11-30-2015, 06:45 AM:

IMAX Laser 3D uses a 6P system and colour filter glasses similar to Dolby. There is no filter on the projector as the 6 laser sources each produce single wavelength light.

Posted by Carsten Kurz (Member # 5396) on 11-30-2015, 07:16 AM:

Both IMAX and Dolby Cinema/Vision Cinema 3D works per spectral separation.

The Barco laser has two sets of laser light sources with different wavelengths in one projector head. The Christie/Dolby Cinema System uses two heads in a sort-of stacked operation (Christie Duo), each head emitting one set of laser triples simultaneously. The Barco switches between both triple sources in 3D mode.

The Barco Laser can be used with other 3D systems as well, like active shutter or polarization. But 'their' Dolby 3D is preferred by most locations for obvious reasons. The new glasses for both IMAX, Dolby Cinema and Barco Laser 3D have much larger see-through areas than the previous standard Dolby 3D glasses had.

- Carsten

Posted by Mark J. Marshall (Member # 1409) on 11-30-2015, 11:42 PM:

Are the light frequencies the same in all of these systems? In other words would a set of standard Dolby 3D glasses work on all of these new laser systems as well, or are the lenses different?

Does anyone have a picture of the new IMAX glasses?

Posted by Carsten Kurz (Member # 5396) on 12-01-2015, 05:30 AM:

I don't know about glasses compatibility between Dolby Cinema, Barco Laser, and IMAX. I would assume they are all the same, also because there is only a limited range of laser wavelenghts available that can be used in a 2*3 primary set, you can not simply choose any wavelength. Also I think all of these systems use laser sources by Necsel, and they will certainly limit their products to the economically feasible. The glasses I have seen all look pretty much the same, aside from branding. They appear similar to the Infitec high-grade glasses that were available from Infitec previouly.

Ordinary (Xenon) Dolby glasses do not work with the laser systems.

Some people were upset about the amount of eye-reflection they get with the new IMAX glasses. I tried Barco Laser glasses and actually found the amount of eye reflection reduced over the traditional Dolby 3D glasses. I always liked Dolby 3D for it's channel separation, but I hated the glasses because of that eye reflection and their small viewing angle. The new laser glasses look near perfect to me. I am sure they are a lot more expensive even than the old standard Dolby 3D glasses.

A picture of the new IMAX glasses can be seen here:

https://www.geekwire.com/wp-content/uploads/2015/04/IMG_8786-620x413.jpg

- Carsten

Posted by Marco Giustini (Member # 4544) on 12-01-2015, 06:47 AM:

If the reflection is reduced and the viewing area improved it'd be great. Especially if you wear glasses, Dolby 3D is awful on that respect

Posted by Dave Macaulay (Member # 813) on 12-01-2015, 07:50 AM:

Searching "Dolby Vision 3D" comes up with a reference to "no glasses" 3D for "any display". I'd also like to know how that works. They also say it's adjustable for the amount of 3D effect.

The bigger laser 3D glasses do have pretty bad eye reflection, it's weird with house lights on but I did not notice it with the movie on.

Posted by Carsten Kurz (Member # 5396) on 12-01-2015, 08:10 AM:

Glasses free 'Dolby Vision 3D' is probably a consumer system targeted at self-illuminating displays, we should not mix it with 'Dolby 3D in Dolby Vision Cinemas'.

- Carsten

Posted by Mark J. Marshall (Member # 1409) on 12-01-2015, 01:12 PM:

Do the lasers (and lack of filters on the projectors) also compensate for the severe light loss inherent in other 3D systems?

Posted by Carsten Kurz (Member # 5396) on 12-01-2015, 06:31 PM:

No. Efficiency if used with shutter or polarization systems will be the same as with Xenon based projectors. That is, the Barco 3D or Dolby Laser 3D will not even be more light-efficient than these other options. But because of improved separation, it is still the better choice and a vast improvement over classic Dolby 3D. Also, no additional external gear needed as with shutter glasses' IR-Transmitters or 'Z-Screens'.
And then, even with a decent amount of light loss still there, you start with 60.000 lumens from a single projector head.

- Carsten

Posted by Mike Renlund (Member # 4675) on 12-02-2015, 02:22 PM:

With the high cost of laser light sources, preservation of light is a critical design goal.

Dolby 3D is precisely engineered to match the wavelengths of the laser light sources so there is no "in projector" filter (spinning or static) needed.

Because of this, Dolby 3D is the most efficient system for 6P laser projectors and surpasses polarized systems in efficiency. The light transmissivity with Dolby 3D/6P laser is 90%. This means that 90% of the light intended for each eye, makes it to each eye.

Image ghosting (crosstalk), which is often an issue with polarized solutions is extremely low due to the separation of the color bands. High color integrity is also a major factor and is highly accurate with Dolby 3D...especially with moderate gain white screens.

The laser wavelengths are not the same across all projector brands...meaning that there are custom glasses that only work with that brand of projector.

Hope this info helps.

Mike Renlund
Dolby Laboratories

Posted by Carsten Kurz (Member # 5396) on 12-02-2015, 05:26 PM:

Mike - a Barco presentation quotes >22% overall efficiency for the Barco DP2k-60L with 'their' implementation. And

'- 2x higher efficiency than Dolby3D (with a single projector)
- Similar efficiency as RealD XL'

How do these numbers compare?

I understand, with separate or switchable light sources, it makes all the difference what your 100% reference actually is. ;-)

Also: http://www.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=16;t=002458#000008

- Carsten

Posted by Steve Guttag (Member # 268) on 12-02-2015, 08:29 PM:

Mike...I would find it odd if 90% made it to each eye...I could believe 90% makes it to the glasses but I don't believe that the glasses are 90% transmissive (and that is presuming that you were 100% efficient from the laser though the optics to the screen and back).

Posted by Marco Giustini (Member # 4544) on 12-03-2015, 03:13 PM:

Maybe is 90% of 50% of light (3P out of 6P) which in more comparable terms is 45% which in the real world may be 40%?