Abstract

Recycling of light allows the luminance (radiance) emitted by a light source to be increased at the cost of reducing the total luminous flux (radiant power). Recycling of light means returning part of the emitted light to the source, where part of it will escape absorption. An optical design that is suitable for multiple and controlled recycling is described. Carambola optics is named for its resemblance to star fruit. Several pairs of mirrors or prisms redirect light repeatedly onto the source, thus achieving multiple transits of the light through the source. This recycled light exits the carambola in the same phase space as light directly emitted and not recycled.

© 2006 Optical Society of America

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References

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  1. L. Fu, R. Leutz, and H. Ries, "Light recycling in solid state devices," in Fifth International Conference on Solid State Lighting,Proc. SPIE 5941, doi: ( 2005).
    [CrossRef]
  2. L. Fu, R. Leutz, and H. Ries, " Spectroscopic measurement of radiation of high-pressure mercury discharge lamps," J. Appl. Phys. 97, 123302 ( 2005).
    [CrossRef]
  3. K. K. Li, " Illumination engine for a projection display using a tapered light pipe," U.S. patent 6,739,726 B2 (25 May 2004).
  4. K. K. Li, S. Sillyman, and S. Inatsugu, " Optimization of dual paraboloidal reflector and polarization system for displays using a ray-tracing model," Opt. Eng. 43, 1545- 1551 ( 2004).
    [CrossRef]
  5. H. Ries and W. Spirkl, " A generalized Kirchhoff law for quantum absorption and luminescence," Solar Energy Mater. Solar Cells 38, 39- 44 ( 1995).
    [CrossRef]
  6. S. M. Zimmerman, K. W. Beeson, and H. Zou, " Illumination system with light recycling to enhance brightness," U.S. patent 6,144,536 (7 November 2000).

2005 (2)

L. Fu, R. Leutz, and H. Ries, "Light recycling in solid state devices," in Fifth International Conference on Solid State Lighting,Proc. SPIE 5941, doi: ( 2005).
[CrossRef]

L. Fu, R. Leutz, and H. Ries, " Spectroscopic measurement of radiation of high-pressure mercury discharge lamps," J. Appl. Phys. 97, 123302 ( 2005).
[CrossRef]

2004 (1)

K. K. Li, S. Sillyman, and S. Inatsugu, " Optimization of dual paraboloidal reflector and polarization system for displays using a ray-tracing model," Opt. Eng. 43, 1545- 1551 ( 2004).
[CrossRef]

1995 (1)

H. Ries and W. Spirkl, " A generalized Kirchhoff law for quantum absorption and luminescence," Solar Energy Mater. Solar Cells 38, 39- 44 ( 1995).
[CrossRef]

Beeson, K. W.

S. M. Zimmerman, K. W. Beeson, and H. Zou, " Illumination system with light recycling to enhance brightness," U.S. patent 6,144,536 (7 November 2000).

Fu, L.

L. Fu, R. Leutz, and H. Ries, " Spectroscopic measurement of radiation of high-pressure mercury discharge lamps," J. Appl. Phys. 97, 123302 ( 2005).
[CrossRef]

L. Fu, R. Leutz, and H. Ries, "Light recycling in solid state devices," in Fifth International Conference on Solid State Lighting,Proc. SPIE 5941, doi: ( 2005).
[CrossRef]

Inatsugu, S.

K. K. Li, S. Sillyman, and S. Inatsugu, " Optimization of dual paraboloidal reflector and polarization system for displays using a ray-tracing model," Opt. Eng. 43, 1545- 1551 ( 2004).
[CrossRef]

Leutz, R.

L. Fu, R. Leutz, and H. Ries, "Light recycling in solid state devices," in Fifth International Conference on Solid State Lighting,Proc. SPIE 5941, doi: ( 2005).
[CrossRef]

L. Fu, R. Leutz, and H. Ries, " Spectroscopic measurement of radiation of high-pressure mercury discharge lamps," J. Appl. Phys. 97, 123302 ( 2005).
[CrossRef]

Li, K. K.

K. K. Li, S. Sillyman, and S. Inatsugu, " Optimization of dual paraboloidal reflector and polarization system for displays using a ray-tracing model," Opt. Eng. 43, 1545- 1551 ( 2004).
[CrossRef]

K. K. Li, " Illumination engine for a projection display using a tapered light pipe," U.S. patent 6,739,726 B2 (25 May 2004).

Ries, H.

L. Fu, R. Leutz, and H. Ries, " Spectroscopic measurement of radiation of high-pressure mercury discharge lamps," J. Appl. Phys. 97, 123302 ( 2005).
[CrossRef]

L. Fu, R. Leutz, and H. Ries, "Light recycling in solid state devices," in Fifth International Conference on Solid State Lighting,Proc. SPIE 5941, doi: ( 2005).
[CrossRef]

H. Ries and W. Spirkl, " A generalized Kirchhoff law for quantum absorption and luminescence," Solar Energy Mater. Solar Cells 38, 39- 44 ( 1995).
[CrossRef]

Sillyman, S.

K. K. Li, S. Sillyman, and S. Inatsugu, " Optimization of dual paraboloidal reflector and polarization system for displays using a ray-tracing model," Opt. Eng. 43, 1545- 1551 ( 2004).
[CrossRef]

Spirkl, W.

H. Ries and W. Spirkl, " A generalized Kirchhoff law for quantum absorption and luminescence," Solar Energy Mater. Solar Cells 38, 39- 44 ( 1995).
[CrossRef]

Zimmerman, S. M.

S. M. Zimmerman, K. W. Beeson, and H. Zou, " Illumination system with light recycling to enhance brightness," U.S. patent 6,144,536 (7 November 2000).

Zou, H.

S. M. Zimmerman, K. W. Beeson, and H. Zou, " Illumination system with light recycling to enhance brightness," U.S. patent 6,144,536 (7 November 2000).

J. Appl. Phys. (1)

L. Fu, R. Leutz, and H. Ries, " Spectroscopic measurement of radiation of high-pressure mercury discharge lamps," J. Appl. Phys. 97, 123302 ( 2005).
[CrossRef]

Opt. Eng. (1)

K. K. Li, S. Sillyman, and S. Inatsugu, " Optimization of dual paraboloidal reflector and polarization system for displays using a ray-tracing model," Opt. Eng. 43, 1545- 1551 ( 2004).
[CrossRef]

Proc. SPIE (1)

L. Fu, R. Leutz, and H. Ries, "Light recycling in solid state devices," in Fifth International Conference on Solid State Lighting,Proc. SPIE 5941, doi: ( 2005).
[CrossRef]

Solar Cells (1)

H. Ries and W. Spirkl, " A generalized Kirchhoff law for quantum absorption and luminescence," Solar Energy Mater. Solar Cells 38, 39- 44 ( 1995).
[CrossRef]

Other (2)

S. M. Zimmerman, K. W. Beeson, and H. Zou, " Illumination system with light recycling to enhance brightness," U.S. patent 6,144,536 (7 November 2000).

K. K. Li, " Illumination engine for a projection display using a tapered light pipe," U.S. patent 6,739,726 B2 (25 May 2004).

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Figures (6)

Fig. 1
Fig. 1

Schematic of recycling of light: Part of the emitted light is returned to the source, part of the returned light is absorbed, but the rest is available. The virtue of recycling light is that this part of the recycled light that escaped absorbtion is contained in the same phase space as that part of the emitted light that was not recycled in the first place. As a down side of this principle, the total luminous flux is reduced by the amount absorbed.

Fig. 2
Fig. 2

The reflective two-dimensional carambola consists of n 1 pairs of reflectors arranged similarly to a V trough. These pairs cover ( n 1 ) / n of the circumference of source S; the rest of the carambola constitutes the opening aperture, indicated by dashed lines. Assuming a transparent source, any ray directed to the source through the aperture is passed precisely n times through the source and reflected 2 n 2 times before reemerging through the same aperture. This figure illustrates the case n = 9 . In general n needs to be odd owing to the need for rotation. For perfect recycling the source needs to have n-fold symmetry.

Fig. 3
Fig. 3

Refractive linear carambola with three recirculations. Ray tracing simulation of the central ray from source S through point P. The carambola has n = 7 points [one remains open as the exit (dashed lines). The refractive index of the lens material is N = 1.52 . All reflections are by total internal reflection.

Fig. 4
Fig. 4

Reflective three-dimensional carambola with five recirculations. The carambola has only n = 3 ribs or points, but rays will be recycled between the upper half and the lower half of the optics. The maximum number of reflections is m 3D = 4 n 2 = 10 . The sphere in the center represents the source. Inset, top view of this carambola.

Fig. 5
Fig. 5

Reflective linear carambola with four recycles. Ray-tracing simulation of edge rays through point P. The source appears at angle α = 5.5 ° , filling nearly the complete exit aperture between points C and D. Central ray SP bisects angle SAB. Note the flipping of the image of the source during reflections in the points of the carambola.

Fig. 6
Fig. 6

Refractive linear carambola with four recycles. Ray-tracing simulation of edge rays through point P. The source appears at angle α = 2.75 ° at Q. The refractive version of the carambola is more sensitive to the size of the source than the reflective version (Fig. 5) owing to the increased optical path length by a factor given by the refractive index of the lens material, N = 1.52 .

Equations (6)

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m 2D = 2 n 2 ,
m 3 D = 4 n 2.
r s r c m 1 ,
r s r c N ( m 1 ) .
D 2 D = n r s ,
D 3D = 2 n r s .

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