Abstract

A novel light luminaire is proposed and experimentally analyzed, which efficiently mixes and projects the tunable light from red, green and blue (RGB) light-emitting diodes (LEDs). Simultaneous light collimation and color mixing is a challenging task because most collimators separate colors, and most color mixers spread the light beam. Our method is simple and compact; it only uses a short light pipe, a thin diffuser, and a total internal reflection lens. We performed an experimental study to find a balance between optical efficiency and color uniformity by changing light recycling and color mixing.

© 2011 OSA

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References

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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  15. C. M. Cheng and J. L. Chern, “Illuminance formation and color difference of mixed-color light emitting diodes in a rectangular light pipe: an analytical approach,” Appl. Opt.47(3), 431–441 (2008).
    [CrossRef] [PubMed]
  16. Y. K. Cheng and J. L. Chern, “Irradiance formations in hollow straight light pipes with square and circular shapes,” J. Opt. Soc. Am. A23(2), 427–434 (2006).
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    [CrossRef] [PubMed]
  19. We chose a 29 cm diameter because more than 95% of the luminous energy is enclosed within this circle. At this radial position the view angle of the circle is 20 degrees. From Fig. 5b it can be seen that the intensity is quite low at this emission angle.

2011 (2)

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

J. Muschaweck, “Randomized Micro Lens Arrays for Color Mixing,” Proc. SPIE7954, 79540A (2011).
[CrossRef]

2010 (4)

2009 (1)

2008 (3)

C. M. Cheng and J. L. Chern, “Illuminance formation and color difference of mixed-color light emitting diodes in a rectangular light pipe: an analytical approach,” Appl. Opt.47(3), 431–441 (2008).
[CrossRef] [PubMed]

W. J. Cassarly, “Recent Advances in Mixing Rods,” Proc. SPIE7103, 710307 (2008).
[CrossRef]

W. J. Cassarly, “High-brightness LEDs,” Opt. Photon. News19(1), 18–23 (2008).
[CrossRef]

2007 (3)

E. Bailey, “Narrow beam RGB array optic,” Proc. SPIE6669, 666917 (2007).
[CrossRef]

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

I. Moreno and U. Contreras, “Color distribution from multicolor LED arrays,” Opt. Express15(6), 3607–3618 (2007).
[CrossRef] [PubMed]

2006 (2)

2005 (1)

E. F. Schubert and J. K. Kim, “Solid-state light sources getting smart,” Science308(5726), 1274–1278 (2005).
[CrossRef] [PubMed]

2004 (1)

2003 (1)

Alferink, R. G.

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

Bailey, E.

E. Bailey, “Narrow beam RGB array optic,” Proc. SPIE6669, 666917 (2007).
[CrossRef]

Cassarly, W. J.

W. J. Cassarly, “Recent Advances in Mixing Rods,” Proc. SPIE7103, 710307 (2008).
[CrossRef]

W. J. Cassarly, “High-brightness LEDs,” Opt. Photon. News19(1), 18–23 (2008).
[CrossRef]

Cheng, C. M.

Cheng, Y. K.

Chern, J. L.

Chien, W. T.

Contreras, U.

Cooijmans, H.

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

Deller, C.

Dong, J. T.

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

Esparza, D.

D. Esparza and I. Moreno, “Color patterns in a tapered lightpipe with RGB LEDs,” Proc. SPIE7786, 77860I (2010).
[CrossRef]

Franklin, J.

Hoelen, C. G. A.

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

Hsiao, S. L.

Hsieh, C. T.

Huang, S.-M.

Kim, J. K.

E. F. Schubert and J. K. Kim, “Solid-state light sources getting smart,” Science308(5726), 1274–1278 (2005).
[CrossRef] [PubMed]

Lee, T.-X.

Lee, X. H.

Lee, Y.-L.

Li, Q.

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

Lin, M. C.

Lu, R. S.

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

Ma, S.-H.

Moreno, I.

Muschaweck, J.

J. Muschaweck, “Randomized Micro Lens Arrays for Color Mixing,” Proc. SPIE7954, 79540A (2011).
[CrossRef]

Mutsaers, C. A.

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

Ruckstuhl, T.

Schubert, E. F.

E. F. Schubert and J. K. Kim, “Solid-state light sources getting smart,” Science308(5726), 1274–1278 (2005).
[CrossRef] [PubMed]

Seeger, S.

Shi, Y. Q.

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

Smith, G.

Sun, C. C.

Sun, C.-C.

van As, M. A.

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

van Gorkom, R. P.

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

Verbeek, G. M.

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

Xia, R. X.

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

Xiang, H.

Xu, L.

Xu, Y.

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

Zhenrong, Z.

Appl. Opt. (3)

J. Opt. Soc. Am. A (2)

Opt. Eng. (1)

J. T. Dong, R. S. Lu, Y. Q. Shi, R. X. Xia, Q. Li, and Y. Xu, “Optical design of color light-emitting diode ring light for machine vision inspection,” Opt. Eng.50(4), 043001 (2011).
[CrossRef]

Opt. Express (3)

Opt. Lett. (2)

Opt. Photon. News (1)

W. J. Cassarly, “High-brightness LEDs,” Opt. Photon. News19(1), 18–23 (2008).
[CrossRef]

Proc. SPIE (5)

J. Muschaweck, “Randomized Micro Lens Arrays for Color Mixing,” Proc. SPIE7954, 79540A (2011).
[CrossRef]

W. J. Cassarly, “Recent Advances in Mixing Rods,” Proc. SPIE7103, 710307 (2008).
[CrossRef]

D. Esparza and I. Moreno, “Color patterns in a tapered lightpipe with RGB LEDs,” Proc. SPIE7786, 77860I (2010).
[CrossRef]

E. Bailey, “Narrow beam RGB array optic,” Proc. SPIE6669, 666917 (2007).
[CrossRef]

R. P. van Gorkom, M. A. van As, G. M. Verbeek, C. G. A. Hoelen, R. G. Alferink, C. A. Mutsaers, and H. Cooijmans, “Etendue conserved color mixing,” Proc. SPIE6670, 66700E (2007).
[CrossRef]

Science (1)

E. F. Schubert and J. K. Kim, “Solid-state light sources getting smart,” Science308(5726), 1274–1278 (2005).
[CrossRef] [PubMed]

Other (1)

We chose a 29 cm diameter because more than 95% of the luminous energy is enclosed within this circle. At this radial position the view angle of the circle is 20 degrees. From Fig. 5b it can be seen that the intensity is quite low at this emission angle.

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Figures (11)

Fig. 1
Fig. 1

Typical color mixing of color LEDs. (a) Direct combination, and (b), using a traditional mixing element. (c) Light projection.

Fig. 2
Fig. 2

The optical structure of the proposed lamp for color mixing and light collimation.

Fig. 3
Fig. 3

Light pattern produced by the projection lamp shown in Fig. 2, without (a) and with (b) diffuser.

Fig. 4
Fig. 4

Experiment setup with an integrating sphere for measuring the optical efficiency. (a) LED light flux, and (b) light flux of the projection lamp, which is integrated by LED + lightpipe + diffuser + lens.

Fig. 5
Fig. 5

(a) Experiment setup for measuring the color uniformity. (b) Radiation pattern of the projection luminaire for different measuring distances. The normalized cross correlation (NCC) measures the similarity of radiation pattern [17].

Fig. 6
Fig. 6

Spatial distribution of sampling points for the measurement of color uniformity. (a) Light pattern under test, (b) 73 measurement positions, (c) 37 points, (d) 37 non-aligned points, (e) 25 points, and (f) 25 non-aligned points. We used configuration (d) for the experimental analysis in Section 5.

Fig. 7
Fig. 7

Lamp parts used in the experimental analysis. (a) RGB LED, (b) Circular and square light guides with diffuser, and (c) TIR collimating lens.

Fig. 8
Fig. 8

Optical performance of the multicolor LED collimating lamp. (a) Relationship between optical efficiency and color uniformity when using different types of diffuser. This plot also shows the difference between using a square lightpipe and a circular lightpipe. (b) Image of the projected light pattern of the lamp with square tube. It is displayed for diffusers D1-D4, and the three CCTs.

Fig. 9
Fig. 9

(a) Optical efficiency vs. color uniformity for several lightpipe lengths. Here the length and cross section of tube are L, and D = 7mm, respectively. The diffuser is D2. The green line is the average from the three CCTs. (b) Optical efficiency and color uniformity in function of the lightpipe length.

Fig. 10
Fig. 10

(a) Relationship between optical efficiency and color uniformity in function of relative position of diffuser. The green line is the average from the three CCTs. Here D = 7mm, L = 7mm, and the diffuser is D2. (b) Images of the projected light pattern for positions L1/L = 0.3, 0.45, 0.7, and 1.0.

Fig. 11
Fig. 11

(a) Optical efficiency and color uniformity for different positions of a 2nd diffuser. The green line is the average of the three CCTs. Here D = 7mm, and L = 7mm. The top diffuser is D3 and the inner is D5. (b) Images of the projected light pattern for positions L2/L = 0.3, 0.45, 0.7, 0.85, and 1.

Equations (2)

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Colo r Uniformit y = 100 1+kΔu v rms [%],
Δu v rms = 1 M i M [ ( u i u avg ) 2 + ( v i v avg ) 2 ] ,

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