Solid‐state lasers for projection

Abstract

Abstract— The unique advantage of projection displays is the ability to produce large images from small devices. The use of lasers as the projection light source will mean a further step in terms of compactness as well as efficiency for projection systems. However, the advent of laser projection is currently still limited by the availability of low‐cost green lasers. Blue‐diode‐pumped solid‐state lasers are one promising way to realize green as well as red lasers that are specifically suited for projection applications. An efficient solid‐state laser that is based on Pr3+:YLF as the laser material, pumped by a blue‐laser diode and emitting at 523 nm, is presented here. The laser reaches power‐conversion efficiencies of more than 7% and output powers of up to 378 mW at green wavelengths. By making only minor modifications to the laser resonator, a red laser emitting at 640 nm can be realized within the same setup. An output power of 166 mW at a power‐conversion efficiency of 6.9% is demonstrated in the red. By combining a red‐ and a green‐emitting blue‐diode‐pumped solid‐state laser with another blue diode, an integrated RGB projection light source can be realized that is based on a single‐diode technology.

47.2: Solid‐State Lasers Emitting at Red, Green and Orange Wavelengths for Projection Applications

“…This means an increase of 20% in luminous efficacy. The efficacy could even reach values well above 20lm/W, when the improvements in power conversion effiency that were already demonstrated for the green laser [7] are also realized for the red and orange emission wavelengths.…”

“…In these experiments we used a relatively long laser crystal with uncoated facets. For the green laser a much higher efficiency of 7% and above has been reached by using shorter laser crystals with appropriately coated facets [6], [7]. With these improvements, the maximum output power of the green laser could also be scaled to 380mW.…”

10-3: A Pragmatic Speckle Measurement Method

“…The idea of laser-based projection display has been considered as a promising display technology ever since the first laser was invented by Charles H. Townes and Arthur Leonard Schawlow in 1958. This is due to its advantages of extended color gamut, small étendue and low power consumption of the laser source [1][2][3]. It is even more interesting for automotive applications e.g.…”

The influence of a light pipe on the coherence properties in laser projectors

“…[1][2][3] Inherently connected to the use of lasers is the appearance of speckle. A speckle pattern is created by interference of (at least partially) coherent radiation that is scattered from a random surface that is rough on the scale of the optical wavelength.…”