camera culture logo

A Compressive Light Field Projection System

Matthew Hirsch* Gordon Wetzstein* Ramesh Raskar
MIT Media Lab - Camera Culture Group - *Joint first authorship.

SIGGRAPH 2014. ACM Transactions on Graphics 33(4).


Compressive light field projection for glasses-free 3D display. The system comprises a single light field projector and a completely passive screen. The angular range of the light field emitted from the projector is limited to the size of the projection lens aperture, hence very small. Keplerian telescopes inspire our screen design - the angular range of incident light is expanded for an observer on the other side, creating a field of view that is suitable for glasses-free 3D display. A prototype projector was implemented from scratch using two high-speed spatial light modulators (SLMs); a prototype screen was fabricated from two lenticular sheets with different focal lengths, mounted back-to-back. With the implemented system, we achieve high-rank light field synthesis (center) for human observers with a critical flicker fusion threshold that is smaller than the product of the SLM refresh rates and the rank of the synthesized light field. Note that color results above are composited from multiple images captured from our grayscale prototype.

Image credit: MIT Media Lab, Camera Culture Group

Abstract

For about a century, researchers and experimentalists have strived to bring glasses-free 3D experiences to the big screen. Much progress has been made and light field projection systems are now commercially available. Unfortunately, available display systems usually employ dozens of devices making such setups costly, energy inefficient, and bulky. We present a compressive approach to light field synthesis with projection devices. For this purpose, we propose a novel, passive screen design that is inspired by angle-expanding Keplerian telescopes. Combined with high-speed light field projection and nonnegative light field factorization, we demonstrate that compressive light field projection is possible with a single device. We build a prototype light field projector and angle-expanding screen from scratch, evaluate the system in simulation, present a variety of results, and demonstrate that the projector can alternatively achieve super-resolved and high dynamic range 2D image display when used with a conventional screen.

Sound credit: Tom Baran composed the background song exclusively for this video


In the News

  Engadget - Glasses-free 3D projector offers a cheap alternative to holograms, May 2014

  Gizmag - MIT develops glasses-free 3D projector as a practical alternative to holographic video, May 2014

  MIT News - Glasses-free 3-D projector, May 2014

  Kurzweil - Glasses-free 3D projector, May 2014

  Adafruit - Glasses-free 3D projector, May 2014

  Physics World - Glasses-free 3-D projector, May 2014

  Display Central - MIT Unveils Glasses-Free 3D Projection, May 2014


Files

Citation

M. Hirsch, G. Wetzstein, R. Raskar. A Compressive Light Field Projection System. ACM Proc. of SIGGRAPH (Transactions on Graphics 33, 4), 2014.

BibTeX
@article{Hirsch:2014:LightFieldProjection,
author = {M. Hirsch and G. Wetzstein and R. Raskar},
title = {{A Compressive Light Field Projection System}},
journal = {ACM Trans. Graph. (Proc. SIGGRAPH)},
volume = {33},
number = {4},
year = {2014},
publisher = {ACM},
pages = {1--12},
address = {New York, NY, USA}
}

Additional Information

Illustration of concept. A light field projector, build using readily-available optics and electronics, emits a 4D light field onto a screen that expands the field of view so that observers on the other side of the screen can enjoy glasses-free 3D entertainment. No mechanically moving parts are used in either the projector or the screen. Additionally, the screen is completely passive, potentially allowing for the system to be scaled to significantly larger dimensions.

Image credit: MIT Media Lab, Camera Culture Group



Overview of light field projection system. Two spatial light modulators, g and h, synthesize a light field inside a projector (top right). The projection screen is composed of an array of angle-expanding pixels (bottom). Inspired by Keplerian telescopes, these pixels expand the field of view of the emitted light field for an observer on the other side of the screen.

Image credit: MIT Media Lab, Camera Culture Group



Top: parts of the prototype angle-expanding screen: a) Fresnel lens, back-to-back lenticular sheets on b) projector-side, and c) viewer-side, and d) overlaid vertical diffuser. Bottom: test images captured from the extreme viewing angles demonstrating parallax. The closeups show vertical stripes caused by the lenticular of the angle expanding screen. These are not apparent when observed by eye.

Image credit: MIT Media Lab, Camera Culture Group



Overview of prototype light field projection system. The projector (right) emits a 4D light field with a narrow field of view that only varies over the projection lens (b, Nikkor 35mm f/1.4 AI-s). This angular range is expanded by the screen (left) for an observer on the other side. The screen (a) is composed of passive pixels that each expand the angles of all incident light, just like a Keplerian telescope. No special calibration w.r.t. the projector is necessary beyond focusing the latter on the screen. The projector emits a 4D light field, which is synthesized by two reflective spatial light modulators (SLMs, Silicon Micro Display ST1080). Their contribution is optically combined by a 1:1 relay lens (h, 2x Canon EF 50 mm f/1.8 mounted face-to-face). The light source (10W LED) is synchronized to the refresh rate (240 Hz) of the SLMs by a custom board (e). The SLMs use liquid crystal on silicon (LCoS) technology, which requires polarizing beam splitter cubes (c), and are connected to a standard graphics card via a driver board (d).

Image credit: MIT Media Lab, Camera Culture Group



Front perspective of projector.

Image credit: MIT Media Lab, Camera Culture Group



Rear perspective of projector.

Image credit: MIT Media Lab, Camera Culture Group



Two lasers with different colors aimed at the angle-expanding screen from different points of the projector aperture (not seen). The screen amplifies the incident angles of the lasers, creating enough angular separation to provide clearly distinguishable viewing zones for a human observer.

Image credit: MIT Media Lab, Camera Culture Group



Light field captured from experimental projector and screen prototype. Color results are composited from three photos of our grayscale prototype.

Image credit: MIT Media Lab, Camera Culture Group



Light field captured from experimental projector and screen prototype. Color results are composited from three photos of our grayscale prototype.

Image credit: MIT Media Lab, Camera Culture Group



Light field captured from experimental projector and screen prototype. Color results are composited from three photos of our grayscale prototype.

Image credit: MIT Media Lab, Camera Culture Group



Light field captured from experimental projector and screen prototype. Color results are composited from three photos of our grayscale prototype.

Image credit: MIT Media Lab, Camera Culture Group



Illustration of superresolution display with light field projector and conventional, diffuse screen. The maximum image frequencies of each SLM (center) in the projector (left) are optically multiplied, which corresponds to a convolution in the frequency domain (right). Although the image of one of the SLMs is out of focus on the screen due to defocus blur, the effective resolution of the display is increased by a factor of 2x in each dimension compared to a conventional projection system (vertical dotted lines on the right).

Image credit: MIT Media Lab, Camera Culture Group



Superresolution and high dynamic range projection. The proposed light field projector can be used with a conventional, diffuse screen to increase image resolution and contrast (second row) as compared to conventional projection with a single spatial light modulator (first row). Close-ups show clear improvements in resolution and dynamic range (third row). Color results are composited from three photos of our grayscale prototype.

Image credit: MIT Media Lab, Camera Culture Group







Contact

Technical Details
Gordon Wetzstein, PhD
MIT Media Lab
gordonw (at) media.mit.edu

Matthew Hirsch
MIT Media Lab
mhirsch (at) media.mit.edu




Press
Alexandra Kahn, Senior Press Liaison, MIT Media Lab
akahn (at) media.mit.edu or 617/253.0365


Related Projects

Compressive Light Field Photography Tensor Displays Layered 3D Polarization Fields Adaptive Image Synthesis
Compressive Light Field Photography (SIG '13)
Tensor Displays (SIG '12)
Layered 3D (SIG '11)
Polarization Fields (SIG Asia '11)
Adaptive Image Synthesis (SIG '13)

MIT Media Lab - All rights reserved.