Meeting the challenges of developing LED-based projection displays

Geißler, Enrico

doi:10.1117/12.664031

Cited by 21 publications

(5 citation statements)

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“…Conventional systems typically combine different colors of light from separate LEDs using tilted dichroic mirrors. [2][3][4][5][6] The most compact arrangement places the mirrors at 45°to the light bundle. This configuration suffers efficiency losses due to polarization-dependent effects and because of the angular spread of the light bundle.…”

Section: Tilted Dichroic Mirrorsmentioning

confidence: 99%

Compact, high‐brightness LED illumination for projection systems

Bruzzone

English²,

Aastuen

2009

J Soc Info Display

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Abstract— An arrangement consisting of a polarizing beam splitter, retarders, and dichroic mirrors provides a compact and efficient combiner for red, green, and blue light from separate LED packages. The resulting illuminating beam is unpolarized. In initial tests, a 0.55‐in. DMD engine based on this illuminator produced an on‐screen flux of 188 lm from 58 W of LED input power, using an f/2.4 pupil. Subsequent work with the same imager and LED set has resulted in a compact and efficient 300‐lm projector.

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Section: Tilted Dichroic Mirrorsmentioning

confidence: 99%

Compact, high‐brightness LED illumination for projection systems

Bruzzone

English²,

Aastuen

2009

J Soc Info Display

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“…Meeting the brightness requirements of the applications is the main challenge in developing LED-based projection systems 1 .Take the GaN-LED as an example, its light extraction efficiency is only a few percent which is partly resulted from the limited critical angle of 24 degrees at the interface of p-GaN and air. Photons emitted beyond this angle will be internally confined due to the effect of total reflection.…”

Section: Introductionmentioning

confidence: 99%

Both improvements of the light extraction efficiency and scattered angle of GaN-LED using sub-micron Fresnel lens array

Gu¹,

Chen²,

Shen³

et al. 2015

SPIE Proceedings

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With the demanding requirements for light source, light emitting diodes (LED) attracts more and more attention because of its inherent advantages such as low power consumption, high reliability and longevity. However, there are two disadvantages for LED, one is the low light extraction efficiency resulting from the total internal reflection, and the other is the relative large scattered angle. In order to improve the light extraction efficiency and collimate the out-coupling light, a sub-micron Fresnel lens array is introduced and investigated in this paper. The focal length of the proposed Fresnel lens is 3µm and the minimum width of the outmost ring is about 150nm. To calculate and analyze the light extraction efficiency and the scattered angle of LED with such Fresnel lens array structure, we optimize the parameters of the Fresnel lens, such as the depth of the Fresnel lens array structure and the thickness of the p-type gallium nitride layer by using the finite difference time domain method (FDTD). By comparing the discussed patterned GaN-based LED with that traditional flat LEDs, it can be found that significant enhancement factor of the light extraction efficiency, which is improved by 3.5 times, can be obtained and the scattered angle at half maximum can be decreased 50° from 60° with this novel Fresnel lens structure. It will be expected that the proposed sub-micron structure can find wide applications in LEDs industry.

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“…For this reason it is currently difficult to obtain LED projectors with brightness levels comparable to lamp-based projectors. Nonetheless, the form factor and low power consumption of LEDs have created a research effort toward compact LED projectors that project images the size of a large computer screen [2][3][4]. If we look at the rate of increase of LED luminance during the past decade, we can predict that luminance levels of approximately 300 Mcd=m 2 will be reached by 2010, thus matching the effective luminance of arc lamps [5].…”

Section: Introductionmentioning

confidence: 99%

Optimization of freeform lightpipes for light-emitting-diode projectors

Fournier

Rolland

2008

Appl. Opt.

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Standard nonimaging components used to collect and integrate light in light-emitting-diode-based projector light engines such as tapered rods and compound parabolic concentrators are compared to optimized freeform shapes in terms of transmission efficiency and spatial uniformity. We show that the simultaneous optimization of the output surface and the profile shape yields transmission efficiency within the étendue limit up to 90% and spatial uniformity higher than 95%, even for compact sizes. The optimization process involves a manual study of the trends for different shapes and the use of an optimization algorithm to further improve the performance of the freeform lightpipe.

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Meeting the challenges of developing LED-based projection displays

Cited by 21 publications

References 0 publications

Compact, high‐brightness LED illumination for projection systems

Compact, high‐brightness LED illumination for projection systems

Both improvements of the light extraction efficiency and scattered angle of GaN-LED using sub-micron Fresnel lens array

Optimization of freeform lightpipes for light-emitting-diode projectors

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