Design Methodology for High Brightness Projectors

Abstract

The low luminance levels of light-emitting diodes (LEDs) compared to arc lamps make it difficult to design high-brightness LED-based projectors. Besides, the specificities of LEDs do not always allow using the same design schemes as with arc lamp-based projection displays. This paper performs a taxonomy of the techniques that can be used to increase the brightness of LED-based projection displays. We show that, in étendue-limited systems, the perceived brightness depends on the system étendue limit, the efficiency of the light engine, and the source luminance. The ability to improve each of these parameters depends on the design constraints. The system étendue limit can be increased at the expense of bulkier, more complex, and more expensive designs. The light engine efficiency can be increased by using free-form shape components adapted to the shapes and the emission patterns of the considered LEDs. The apparent source luminance can be increased at the expense of the flux by either recycling light or restricting the light collection to a smaller étendue with higher average luminance. Luminance can also be increased by using multiple color primaries (spatial multiplexing) or pulsed LEDs (temporal multiplexing). Finally, we review how light recycling can be implemented to convert polarization without increasing étendue.

Structural Effects on Highly Directional Far-Field Emission Patterns of GaN-Based Micro-Cavity Light-Emitting Diodes With Photonic Crystals

“…For highly directional light extraction enhancement, structural parameters including the GaN ultrathin cavity thickness , larger PhC lattice constant ( nm), and deep PhC holes ( approaching MQW layer) are optimized to achieve the LED with both high LEE and collimating far fields. Therefore, the study make the highly directional LED promising for entendue-limited application, like pico-projectors [20]. …”

Illumination design for extended sources based on phase space mapping

“…To do so, the method of phase space in optics is employed, which allows for a direct visualization of the etendue and radiance distribution. [13][14][15] There have already been attempts to illustrate the behavior of illumination systems in phase space, and they have proven to be helpful. However, in many references, this picture is limited to a conceptual or paraxial study.…”

Design of Wedge Projection System with Thin Slab Structure

“…Since the projection system is based on light ray propagation, the projection rays can be shaded by an object located on the path of the rays. To solve the occlusion problem, a wedge projection system has been proposed [1][2][3][4][5]. The wedge projection system can resolve the occlusion problem of the light rays and present the large scene on the screen within a narrow space.…”