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Abstract
Led based projectors have numerous advantages compared to traditional projectors, such as: compact, larger color gamut, longer lifetime, lower supply voltage, etc. As LED's can switch rapidly, there is the possibility to pulse. However, there is also an important disadvantage. The optical power per unit of etendue of a LED is significantly lower than e.g. an UHP-lamp (approximately 50 times). This problem can be remedied partly by pulsing of the LED's. If one drives a LED with a pulsed current source, the peak luminance can be higher, albeit that the average luminance will not increase. By pulsing X LED's alternately, their increased flux can be added up in time and will generate a higher average flux within the same etendue. This can be carried out in a number of different configurations. The first configuration uses moving components where a number of LED's (e.g. 8) are mounted on a carrousel and consecutively the pulsed LED is brought in the light path of the projector to fill tip the time with its peak flux. An alternative without moving components can be reached with 2 LED's which are combined with a PBS. By alternately pulsing the LED's with 50% duty cycle and changing the polarisation of one LED with a switchable retarder, one can combine the flux of both LED's in the same etendue. Because of its fast switching time ferro-electric retarders are used here. This can be extended further to 4,8,16... LED's, at the price of a larger and more complicated optical architecture.
Keywords
etendue, projector, micro display, pulsed, LED

Citation

Please use this url to cite or link to this publication:

MLA
Murat, Hüseyin, Herbert De Smet, Dieter Cuypers, et al. “Increased Lumens Per Etendue by Combining Pulsed LED’s.” Proceedings of the Society of Photo-optical Instrumentation Engineers (spie). Ed. Ming H Wu. Vol. 5740. Bellingham, WA, USA: SPIE, the International Society for Optical Engineering, 2005. Print.
APA
Murat, H., De Smet, H., Cuypers, D., Meuret, Y., Thienpont, H., Vervaeke, M., & Desmet, L. (2005). Increased lumens per etendue by combining pulsed LED’s. In M. H. Wu (Ed.), PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) (Vol. 5740). Presented at the Conference on Projection Displays XI, Bellingham, WA, USA: SPIE, the International Society for Optical Engineering.
Chicago author-date
Murat, Hüseyin, Herbert De Smet, Dieter Cuypers, Youri Meuret, Hugo Thienpont, Michael Vervaeke, and Lieven Desmet. 2005. “Increased Lumens Per Etendue by Combining Pulsed LED’s.” In Proceedings of the Society of Photo-optical Instrumentation Engineers (spie), ed. Ming H Wu. Vol. 5740. Bellingham, WA, USA: SPIE, the International Society for Optical Engineering.
Chicago author-date (all authors)
Murat, Hüseyin, Herbert De Smet, Dieter Cuypers, Youri Meuret, Hugo Thienpont, Michael Vervaeke, and Lieven Desmet. 2005. “Increased Lumens Per Etendue by Combining Pulsed LED’s.” In Proceedings of the Society of Photo-optical Instrumentation Engineers (spie), ed. Ming H Wu. Vol. 5740. Bellingham, WA, USA: SPIE, the International Society for Optical Engineering.
Vancouver
1.
Murat H, De Smet H, Cuypers D, Meuret Y, Thienpont H, Vervaeke M, et al. Increased lumens per etendue by combining pulsed LED’s. In: Wu MH, editor. PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE). Bellingham, WA, USA: SPIE, the International Society for Optical Engineering; 2005.
IEEE
[1]
H. Murat et al., “Increased lumens per etendue by combining pulsed LED’s,” in PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE), San José, CA, USA, 2005, vol. 5740.
@inproceedings{335781,
  abstract     = {Led based projectors have numerous advantages compared to traditional projectors, such as: compact, larger color gamut, longer lifetime, lower supply voltage, etc. As LED's can switch rapidly, there is the possibility to pulse. However, there is also an important disadvantage. The optical power per unit of etendue of a LED is significantly lower than e.g. an UHP-lamp (approximately 50 times). This problem can be remedied partly by pulsing of the LED's. If one drives a LED with a pulsed current source, the peak luminance can be higher, albeit that the average luminance will not increase. By pulsing X LED's alternately, their increased flux can be added up in time and will generate a higher average flux within the same etendue. This can be carried out in a number of different configurations. The first configuration uses moving components where a number of LED's (e.g. 8) are mounted on a carrousel and consecutively the pulsed LED is brought in the light path of the projector to fill tip the time with its peak flux. An alternative without moving components can be reached with 2 LED's which are combined with a PBS. By alternately pulsing the LED's with 50% duty cycle and changing the polarisation of one LED with a switchable retarder, one can combine the flux of both LED's in the same etendue. Because of its fast switching time ferro-electric retarders are used here. This can be extended further to 4,8,16... LED's, at the price of a larger and more complicated optical architecture.},
  author       = {Murat, Hüseyin and De Smet, Herbert and Cuypers, Dieter and Meuret, Youri and Thienpont, Hugo and Vervaeke, Michael and Desmet, Lieven},
  booktitle    = {PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE)},
  editor       = {Wu, Ming H},
  isbn         = {0-8194-5714-0},
  issn         = {0277-786X},
  keywords     = {etendue,projector,micro display,pulsed,LED},
  language     = {eng},
  location     = {San José, CA, USA},
  pages        = {12},
  publisher    = {SPIE, the International Society for Optical Engineering},
  title        = {Increased lumens per etendue by combining pulsed LED's},
  url          = {http://dx.doi.org/10.1117/12.588312},
  volume       = {5740},
  year         = {2005},
}

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