Abstract

We analyze the color uniformity in the far field of spotlight systems to estimate visual perception with a merit function derived from human factor experiments. A multi-colored light-emitting diode (LED) light engine with different light mixing levels is combined with several reflectors and total internal reflection (TIR) lenses. The optimized systems are analyzed at several color uniformity levels with regard to the efficiency, peak luminous intensity and dimensions. It is shown that these properties cannot all be optimized at the same time. Furthermore, excellent color uniformity can be reached by a light mixing layer in the light engine or by adding mixing elements to the secondary optics.

© 2015 Optical Society of America

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References

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  1. Y. Ohno, “Spectral design considerations for white led color rendering,” Opt. Eng. 44(11), 111302 (2005).
    [Crossref]
  2. I. Moreno and U. Contreras, “Color distribution from multicolor LED arrays,” Opt. Express 15(6), 3607–3618 (2007).
    [Crossref] [PubMed]
  3. F. R. Fournier, “A review of beam shaping strategies for LED lighting,” Proc. SPIE 8170, 817007 (2011).
    [Crossref]
  4. C.-C. Sun, I. Moreno, Y.-C. Lo, B.-C. Chiu, and W.-T. Chien, “Collimating lamp with well color mixing of red/green/blue LEDs,” Opt. Express 20(1S1), A75–A84 (2012).
    [PubMed]
  5. E. Chen, R. Wu, and T. Guo, “Design a freefrom microlens array module for any arbitrary-shape collimated beam shaping and color mixing,” Opt. Commun. 321, 78–85 (2014).
    [Crossref]
  6. A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of a merit function for the visual perception of color uniformity in spot lights,” Color Res. Appl. (2014), doi:.
    [Crossref]
  7. G. M. Johnson, X. Song, E. D. Montag, and M. D. Fairchild, “Derivation of a color space for image color difference measurement,” Color Res. Appl. 35(6), 387–400 (2010).
    [Crossref]
  8. X. Zhang and B. A. Wandell, “A spatial extension of cielab for digital color-image reproduction,” J. Soc. Inf. Disp. 5(1), 61–63 (1997).
    [Crossref]
  9. A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
    [Crossref]
  10. J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
    [Crossref]

2014 (2)

E. Chen, R. Wu, and T. Guo, “Design a freefrom microlens array module for any arbitrary-shape collimated beam shaping and color mixing,” Opt. Commun. 321, 78–85 (2014).
[Crossref]

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
[Crossref]

2012 (2)

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

C.-C. Sun, I. Moreno, Y.-C. Lo, B.-C. Chiu, and W.-T. Chien, “Collimating lamp with well color mixing of red/green/blue LEDs,” Opt. Express 20(1S1), A75–A84 (2012).
[PubMed]

2011 (1)

F. R. Fournier, “A review of beam shaping strategies for LED lighting,” Proc. SPIE 8170, 817007 (2011).
[Crossref]

2010 (1)

G. M. Johnson, X. Song, E. D. Montag, and M. D. Fairchild, “Derivation of a color space for image color difference measurement,” Color Res. Appl. 35(6), 387–400 (2010).
[Crossref]

2007 (1)

2005 (1)

Y. Ohno, “Spectral design considerations for white led color rendering,” Opt. Eng. 44(11), 111302 (2005).
[Crossref]

1997 (1)

X. Zhang and B. A. Wandell, “A spatial extension of cielab for digital color-image reproduction,” J. Soc. Inf. Disp. 5(1), 61–63 (1997).
[Crossref]

Benitez, P.

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Benítez, P.

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
[Crossref]

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of a merit function for the visual perception of color uniformity in spot lights,” Color Res. Appl. (2014), doi:.
[Crossref]

Bergenek, K.

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
[Crossref]

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of a merit function for the visual perception of color uniformity in spot lights,” Color Res. Appl. (2014), doi:.
[Crossref]

Chaves, J.

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Chen, E.

E. Chen, R. Wu, and T. Guo, “Design a freefrom microlens array module for any arbitrary-shape collimated beam shaping and color mixing,” Opt. Commun. 321, 78–85 (2014).
[Crossref]

Chien, W.-T.

Chiu, B.-C.

Contreras, U.

Cvetkovic, A.

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Dross, O.

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Fairchild, M. D.

G. M. Johnson, X. Song, E. D. Montag, and M. D. Fairchild, “Derivation of a color space for image color difference measurement,” Color Res. Appl. 35(6), 387–400 (2010).
[Crossref]

Fournier, F. R.

F. R. Fournier, “A review of beam shaping strategies for LED lighting,” Proc. SPIE 8170, 817007 (2011).
[Crossref]

Guo, T.

E. Chen, R. Wu, and T. Guo, “Design a freefrom microlens array module for any arbitrary-shape collimated beam shaping and color mixing,” Opt. Commun. 321, 78–85 (2014).
[Crossref]

Hernandez, M.

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Johnson, G. M.

G. M. Johnson, X. Song, E. D. Montag, and M. D. Fairchild, “Derivation of a color space for image color difference measurement,” Color Res. Appl. 35(6), 387–400 (2010).
[Crossref]

Lo, Y.-C.

Miñano, J. C.

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
[Crossref]

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of a merit function for the visual perception of color uniformity in spot lights,” Color Res. Appl. (2014), doi:.
[Crossref]

Mohedano, R.

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Montag, E. D.

G. M. Johnson, X. Song, E. D. Montag, and M. D. Fairchild, “Derivation of a color space for image color difference measurement,” Color Res. Appl. 35(6), 387–400 (2010).
[Crossref]

Moreno, I.

Ohno, Y.

Y. Ohno, “Spectral design considerations for white led color rendering,” Opt. Eng. 44(11), 111302 (2005).
[Crossref]

Song, X.

G. M. Johnson, X. Song, E. D. Montag, and M. D. Fairchild, “Derivation of a color space for image color difference measurement,” Color Res. Appl. 35(6), 387–400 (2010).
[Crossref]

Sun, C.-C.

Teupner, A.

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
[Crossref]

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of a merit function for the visual perception of color uniformity in spot lights,” Color Res. Appl. (2014), doi:.
[Crossref]

Vilaplana, J.

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Wandell, B. A.

X. Zhang and B. A. Wandell, “A spatial extension of cielab for digital color-image reproduction,” J. Soc. Inf. Disp. 5(1), 61–63 (1997).
[Crossref]

Wirth, R.

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
[Crossref]

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of a merit function for the visual perception of color uniformity in spot lights,” Color Res. Appl. (2014), doi:.
[Crossref]

Wu, R.

E. Chen, R. Wu, and T. Guo, “Design a freefrom microlens array module for any arbitrary-shape collimated beam shaping and color mixing,” Opt. Commun. 321, 78–85 (2014).
[Crossref]

Zhang, X.

X. Zhang and B. A. Wandell, “A spatial extension of cielab for digital color-image reproduction,” J. Soc. Inf. Disp. 5(1), 61–63 (1997).
[Crossref]

Color Res. Appl. (1)

G. M. Johnson, X. Song, E. D. Montag, and M. D. Fairchild, “Derivation of a color space for image color difference measurement,” Color Res. Appl. 35(6), 387–400 (2010).
[Crossref]

J. Soc. Inf. Disp. (1)

X. Zhang and B. A. Wandell, “A spatial extension of cielab for digital color-image reproduction,” J. Soc. Inf. Disp. 5(1), 61–63 (1997).
[Crossref]

Opt. Commun. (1)

E. Chen, R. Wu, and T. Guo, “Design a freefrom microlens array module for any arbitrary-shape collimated beam shaping and color mixing,” Opt. Commun. 321, 78–85 (2014).
[Crossref]

Opt. Eng. (1)

Y. Ohno, “Spectral design considerations for white led color rendering,” Opt. Eng. 44(11), 111302 (2005).
[Crossref]

Opt. Express (2)

Proc. SPIE (3)

F. R. Fournier, “A review of beam shaping strategies for LED lighting,” Proc. SPIE 8170, 817007 (2011).
[Crossref]

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of optical systems for LED spot lights concerning the color uniformity,” Proc. SPIE 9190, 91900J (2014).
[Crossref]

J. Chaves, A. Cvetkovic, R. Mohedano, O. Dross, M. Hernandez, P. Benitez, J. C. Miñano, and J. Vilaplana, “Inhomogeneous source unifomization using a shell mixer Koehler integrator,” Proc. SPIE 8550, 85502X (2012).
[Crossref]

Other (1)

A. Teupner, K. Bergenek, R. Wirth, J. C. Miñano, and P. Benítez, “Optimization of a merit function for the visual perception of color uniformity in spot lights,” Color Res. Appl. (2014), doi:.
[Crossref]

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Figures (6)

Fig. 1
Fig. 1 Simulated far fields of five different spotlights, (a - d) are TIR lens spotlights, and (e) is a reflector spotlight, all with multi-colored light engines.
Fig. 2
Fig. 2 Levels of perceived color uniformity in simulated spotlights with their corresponding far fields resulting of a LED light source in combination with different reflectors.
Fig. 3
Fig. 3 The three setups of the light engine with a 9 mm diameter light-emitting area: background: (a) with clear cast, (b) low scattering particle density, (c) high scattering particle density; foreground: far fields of spotlights for each corresponding light engine and specular standard reflector. Usl values are 145, 46 and 38 for (a), (b), and (c), respectively.
Fig. 4
Fig. 4 Scattering process: a) no scattering particles are present and light passes through the layer without distortions; b) some scattering particles mix the rays and result in improved color blending and enlarge the FWHM angle; c) a very large number of scattering particles decrease the efficiency (reduced number of less forward traveling rays) and local scattering is too large to yield further improvements in color blending.
Fig. 5
Fig. 5 Optimized optics: (a1) plain TIR lens, (a2) TIR lens with rough outer surface, (a3) TIR lens with lens array (18 × 18), (b1) plain reflector, (b2) reflector with 100 radial and 50 axial facets, (b3) plain reflector and shell mixer. The specifications in the second row represent the product of the dimension of each element length (l) and its diameter (d) [mm].
Fig. 6
Fig. 6 Plot of luminous intensity distributions (normalized at 0°) for the four selected optical systems; left: complete intensity distribution, right: detailed intensity distribution of the edge of the spotlight far fields.

Tables (3)

Tables Icon

Table 1 Overview of Usl values for the optical systems: formed by the combination of the three light engines shown in Fig. 3 and the secondary optics in Fig. 4; table entries with the green background denote excellent color uniformity levels while yellow and red background entries denote acceptable and insufficient color uniformities, respectively.

Tables Icon

Table 2 Efficiencies of the optical systems, measured at a spherical far field receiver around the optical system assuming that the system is encased. Light emitted from the optical front surface is represented as a percentage of the best system LE1-b1. Green-, yellow-, and red-background entries represent excellent, acceptable, and insufficient color uniformity levels, respectively.

Tables Icon

Table 3 Peak luminous intensity for all optimized systems as a percentage of the best system LE2-a1. Green-, yellow-, and red-background entries represent excellent, acceptable, and insufficient color uniformity levels, respectively.

Equations (1)

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U sl = a 1 Δa b mean + a 2 Gra d ab + a 3 S rad + a 4 S lin

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