14.1: Efficient and Compact Illumination in LED Projection Displays

Abstract

In this paper we propose an efficient illumination engine for LED based projection systems. Our design had to be both compact and efficient. We designed the projector with two LCOS light panels. We investigate two phenomena that affect the optical efficiency of this projector. We show that a relevant gain of the light output can be obtained by using certain methods.

P‐250L: Late News Poster: Low‐Speckle Laser Projection with a Broad‐Area VCSEL in the Incoherent Emission Regime

“…The projection system we use is based on a compact microlens beam homogenizer system described in [6], in which we use a VCSEL as illumination source. The beam homogenizer consists of two pairs of cylindrical lenses which are rotated by 90° with respect to each other.…”

Projection display for the generation of two orthogonal polarized images using liquid crystal on silicon panels and light emitting diodes

“…These LED modules consist of a 2 × 2 matrix of semiconductor dies, with a square shape, that emit directly into air with a Lambertian radiation pattern. Their light output is collimated by a transparent compound parabolic concentrator (CPC) with a square input facet [12] that matches the dimension of the LED matrix (4 dies of 1 mm × 1 mm with a 0:1 mm spacing). To increase the available light output we use two LED modules for each color, as shown in Fig.…”

“…Because the lens system preceding the lenslet integrator transforms the rectangular spatial light distribution of the collimation optics to a rectangular angular light distribution at the lenset integrator, these rays originate from the outer sides of both CPC output facets. Mirror recuperation can be used to convert part of this light within the system étendue [12]. For this, part of both CPC output facets needs to be covered with specularly reflective tape.…”

LED projector with two liquid crystal on silicon light valves and a fly’s eye integrator

“…This light is sent back to the light source which partially reflects it. It has then a new chance to fall within the system étendue and thus to contribute to the lumen output of the illumination system [5,6]. In projection systems that use the polarization state of the light to separate the ON-state from the OFF-state beam, polarization recuperation can be used to overcome that half of the light is lost.…”

“…In Ref. [6], a more compact system was presented with two square LEDs that illuminate a 0.83 00 LCOS panel. This architecture is further investigated and experimentally demonstrated in this publication.…”