OSA's Digital Library

Virtual Journal for Biomedical Optics

Virtual Journal for Biomedical Optics

| EXPLORING THE INTERFACE OF LIGHT AND BIOMEDICINE

  • Editor: Gregory W. Faris
  • Vol. 2, Iss. 9 — Sep. 26, 2007
« Show journal navigation

Short period holographic structures for backlight display applications

Roberto Caputo, Luciano De Sio, Martin J.J. Jak, Eefje J. Hornix, Dick K.G. de Boer, and Hugo J. Cornelissen  »View Author Affiliations


Optics Express, Vol. 15, Issue 17, pp. 10540-10552 (2007)
http://dx.doi.org/10.1364/OE.15.010540


View Full Text Article

Acrobat PDF (932 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

The use of holographic structures is promising for the realization of efficient systems in backlight applications for displays. By applying surface relief gratings on top of a side-lit lightguide we realize a backlight that avoids the use of color filters. The grating is used as a light outcoupling and color-separating element. The demands for this grating are stringent and calculations have been performed to meet them. A prototype backlight, including the grating structure, has been assembled and characterized. Results of experiments are discussed.

© 2007 Optical Society of America

1. Introduction

In the last few years, a lot of attention has been devoted to the realization of new devices based on holographic diffractive structures. These diffractive elements can be implemented in many configurations. The amount of possibilities is quite vast including beam steering devices [1

1. S. Serak, N. Tabiryan, and B. Zeldovich, “High-efficiency 1.5 µm thick optical axis grating and its use for laser beam combining,” Opt. Lett. 32, 169–171 (2007). [CrossRef]

,2

2. X. Wang, D. Wilson, R. Muller, P. Maker, and D. Psaltis, “Liquid-crystal blazed-grating beam deflector,” Appl. Opt. 39, 6545–6555 (2000). [CrossRef]

], organic lasers [3

3. D. Wright, E. Brasselet, J. Zyss, G. Langer, and W. Kern, “Dye-doped organic distributed-feedback lasers with index and surface gratings: the role of pump polarization and molecular orientation,” J. Opt. Soc. Am. B 21, 944–950 (2004). [CrossRef]

,4

4. R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning, and R. A. Vaia, “Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals,” Appl. Phys. Lett. 85, 6095 (2004). [CrossRef]

], smart sensors [5

5. M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, “Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration,” Appl. Phys. Lett. 89, 251104 (2006). [CrossRef]

] and wavelength selective filters[6

6. J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim “Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films,” Appl. Phys. Lett. 82, 3823 (2003). [CrossRef]

], lighting and display systems [7

7. C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen, and D. J. Broer, “An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram,” Appl. Phys. Lett. 87, 094101 (2005). [CrossRef]

]. In the last case, usually waveguides are used in which light propagates by means of total internal reflection (TIR). If a grating is accurately designed and integrated in the waveguide, a precise control of the light extraction process can be achieved. In this paper we consider the design and realization of a high quality short-pitched diffraction grating used for improving the efficiency of backlit displays. The light management in present liquid crystal displays (LCDs) is not very efficient: only a small percentage (~4–6%) of the light generated in the backlight of the device reaches the eyes of the user. One of the main challenges in display research is the realization of systems optimized for reducing power consumption. An innovative way for achieving this result has been proposed by Taira et al., [8

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, F. Yamada, S. Ono, and Y. Taira, “Low-power LCD using a novel optical system,” SID 02 Digest1313-1315 (2002); “Dual layered very thin flat surface micro prism array directly molded in an LCD cell,” Eurodisplay 2002, 339–342 (2002). [CrossRef]

] who demonstrated how the color-dispersion power of a diffraction grating can be efficiently employed to avoid the use of color filters. Since the percentage of light absorbed in these filters can be estimated to be 65–70%, there could be a considerable advantage in designing and adopting diffractive structures for display applications. The grating separates the incoming light into fundamental colors with different angles. The obtained light rays impinge on a microlens array that properly redirects the colors to the pixels of the LCD. A similar approach was taken by De Boer et al., [9

9. D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, and M. J. J. Jak “Diffractive grating structures for colour-separating backlights,” Proc. SPIE 6196, 241 (2006).

] who applied the grating directly on top of a lightguide (Fig. 1).

Fig. 1. Color-filterless display configuration including a grating structure. The grating on top of a lightguide separates incoming light into red, green and blue colors. A lens array put in front of the grating images the various beams on the LC layer forming an RGB pixel structure. The figure is not to scale: the pitch of the grating is of the order of visible wavelengths, Λ≈400nm while the pitch of the lens array is d≈800µm.

In another work by Xu et al. [10

10. M. Xu, H. P. Urbach, and D. K. G. de Boer, “Simulations of birefringent gratings as polarizing color separator in backlight for flat-panel displays,” Opt. Express 15, 5789 (2007). [CrossRef] [PubMed]

], a birefringent grating was considered and the advantages of polarized outcoupling were studied.

2. Design of a grating for a backlight system

If a grating is considered for backlight applications, its design must fulfill several conditions in order to obtain a working device. As a starting point, we can assume that the lamp illuminating the side facet of the light guide emits light in a Lambertian (cosine) way. In case we have a PMMA light guide (refractive index n=1.5), the light rays coming from the lamp will be refracted at the entrance facet of the guide and will then propagate with angles restricted to the interval ±42° with respect to the normal to the facet. This implies that these rays make angles between 48° and 90° with the normal to the grating (Fig. 2). Without grating the light is simply captured inside the light guide by total internal reflection (TIR). In the presence of the grating we expect that the light is partly diffracted and partly reflected back into the guide. The number of diffraction orders in which it is coupled out depends on the grating properties. In order to realize the configuration of Fig. 1, it is preferable that all the light that is incident on the grating is diffracted in a single order and angularly separated depending on the wavelengths present in its spectrum.

Fig. 2. Light propagating inside the lightguide is restricted to angles of ±42° with the normal to the entrance facet of the guide due to refraction. The light rays that are incident on the grating will make angles between 48° and 90° with the normal to its surface. Due to the Lambertian intensity distribution of light entering the lightguide, light incident on the grating with small angles (close to 48°) is less intense than light incident with steeper angles (close to 90°).

The conditions necessary for obtaining this result can be calculated by using the grating equation:

mλ=Λ(n2sinθdifn1sinθinc)
(1)

Here, λ is the wavelength of the light, m is an integer number corresponding to the considered diffraction order, Λ is the period of the grating, n1 is the refractive index of the light guide, θinc is the angle formed by the beam incoming on the grating with its normal and θdif is the angle formed instead by the mth diffracted beam. For diffraction into air (light transmitted, T) n2=1, for diffraction into the lightguide (light reflected, R) n2=n1. By using Eq. (1), we can determine the number of diffraction orders that are coupled out from the structure and what the diffracted angles are. In Fig. 3, we show the behavior for three different values of Λ (700nm, 500nm, 300nm) and three values of the wavelength λ of the incoming beam (615nm, 545nm, 450nm). The choice of short periods in the calculations is aimed to obtain a good angular separation between various colors. For what concerns the wavelengths, they represent typical peak values in the spectral range of a CCFL (cold-cathode fluorescence lamp) lamp commonly used in backlights. Instead, LEDs emitting around these wavelengths could be used.

Fig. 3. Estimation of the number of diffraction orders coupled out by a diffraction grating and of angles that they form with the normal to it for different periods (700nm, 500nm, 300nm). In all cases the same incidence angle θinc=69° is considered.

Fig. 4. Contour plots of the diffraction efficiency of the grating for the first diffraction order (sum of -1T and -1R) versus incidence angle θinc and wavelength λ. In a given row, the number above every plot indicates the depth L of the grating. (a) Λ=300nm; (b) Λ=400nm, (c) Λ=500nm. The red rectangles in the Figure indicate the intervals for the grating depth that gives a smooth, decreasing DE as function of incident angle simultaneously for all wavelengths of interest (450nm<λ<650nm).

2. Configuration of the backlight system

Fig. 5. Optimal backlight configuration. Light from opposite directions is diffracted by the grating and generates a symmetric RGBGR pattern which avoids color-mixing problems. The figure is not to scale: the pitch of the grating is of the order of visible wavelengths, Λ≈400nm while the pitch of the lens array is d≈800µm.

3. Experimental evaluation of a working prototype

Fig. 6. (a). Sketch of the whole process for the realization of grating structures; (b) Optical setup for making the holographic gratings; M, mirrors; L1, L2, lenses; I, aperture; P, polarizer beam splitter; HWP, half-wave plate; θc, recording beam angle; S, sample.

The period of the grating can be easily changed by varying θc according to the formula:

Λ=λ2sinθc
(2)

Fig. 7. SEM picture of a typical structure obtained by holographic techniques with photoresist materials. The structure is highly regular by observing the sample both in cross-section (a) and in top view (b).

A grating depth L=210nm has been achieved by illuminating the sample with a dose D=100µW*20sec=2000µJ. This particular dose value is the result of the empirical procedure described above. In particular, we fixed the power to the value where the laser showed a good stability (P=100µW) and then changed the exposure times for finding the optimal interval. The extreme values of this interval are obtained for times tlow=17sec. and thigh=25sec. which correspond to depth values for the grating of Llmin≈120nm and Lmax≈600nm, respectively. The SEM micrograph of the realized grating is shown in Fig. 8(a).

Fig. 8. (a). SEM picture of the realized grating structure. The fringe spacing is about Λ=320nm and the thickness of the grating about L=210nm; (b) diffraction efficiency plot of the realized grating. Dots indicate experimental measurements while solid lines (red and blue curves) are the GSolver fits for the same structure. Theoretical values of the intensities for the 0R and -1R orders (magenta and green curves respectively) are also reported as a reference.

In order to test the obtained grating before including it in the display structure, we measured its diffraction efficiency with a He-Ne laser (λ=632.8 nm) as a probe and compared the result with the GSolver simulation of the same structure (Fig. 8(b)). For the simulation we assumed a structure with same period and depth as the real grating and a rectangular refractive index profile with a duty cycle of 50%. The refractive index of the photoresist material has been estimated to be 1.6 for the wavelengths of interest. The agreement between experiment and simulation is quite satisfactory. By using the same simulation parameters, we also plotted the diffraction efficiency (only for the -1T order) for the three fundamental colors (615nm, 545nm, 450nm) versus diffraction angles produced by this grating (Fig. 9(a)). Gray curves show what would be the diffraction intensities of the various colors if there were no restrictions on the incident beam angles (0°<θinc<90°). Dashed rectangles indicate the overlap regions between various colors. The presence of two colors in the same region possibly results in an issue for the color purity of the obtained device. This problem can be prevented by restricting the angular range of the light coming to the grating from the lightguide. In that case, the angular cones spanned by the various colors are reduced and the overlap regions are limited or completely avoided. In Fig. 9(b) a plot is shown of the diffraction angle (obtained from the grating Eq. (1)) that illustrates how the color overlap could be prevented by reducing the incidence interval to 62°<θinc<90°. As it is clearly visible in the Figure, in this case the angular ranges of the diffracted beams have no intersections at all. Collimation of the input light can be achieved by a funnel shaped entrance of the lightguide. In case LEDs are used as light source, reflective and/or refractive optics close to the LEDs are commonly used for such a purpose.

Fig. 9. (a). Plot of the diffraction efficiency versus diffracted angle. Colored curves show the outcoupled beams from the lightguide in a red-green-blue-green-red sequence. Gray curves represent the behavior of the grating when the incoming beams have no angular constraints (i.e. all incident angles occur). Dashed rectangles show the overlap regions between outcoupled colors. (b). Plot of the diffraction angle versus incident angle for a grating with a periodicity Λ=320nm.

In Fig. 8(b), the theoretical curves for the 0R and -1R orders (magenta and green curves respectively) have been included as a reference. It can be noticed that the DE value of the -1R order is also considerable in the angular range of interest (48°<θinc<90°). In order to recycle this order and to avoid optical losses, a reflective layer has been imcluded underneath the lightguide. From Eq. (1), it can be seen that the -1R contributions reflected by this layer are transmitted by the grating into the same direction as the -1T order, for every angle belonging to 48°<θinc<90° (Fig. 10). This is true for every wavelength propagating in the lightguide. One may worry about the subsequent diffraction of the -1R rays reflected by the reflective layer. However, also from Eq. (1), it can be shown that these rays belong to an angular interval of incidence on the grating (e.g. -23°<θ-1R<-8° for the green) where no transmitted diffracted orders (1T or -1T) are allowed by the chosen periodicity (Λ=320nm, see Fig. 9(b)). Only another reflected diffracted order is present that we have indicated in Fig. 10 as -1R(-1R)which has the same angle as the initial incident ray (I).

Fig. 10. Rays inside the lightguide. The incident beam I is partly reflected by the grating (0R), partly diffracted in transmission (-1T) and partly diffracted in reflection (-1R). The diffracted reflected beam is reflected once more at the reflective layer put on the base of the lightguide and comes again to the grating (-1R(0R)). It diffracts in reflection again by the grating (-1R(-1R) into the same direction as the incident beam I. This behavior is verified for every beam I with incidence angle in the interval 48°<θinc<90° and for every wavelength of interest.

The lens array that is needed to image the colors on the appropriate pixels needs to match exactly to the pixel structure of the LCD panel and the angular distribution of the light extracted from the light guide by the grating. The geometry is sketched in Fig. 11. The sub-pixel pitch is denoted by p, the focal length of the lenses by f, and the width of the lenses by D.

Fig. 11. Geometry of the lens array in front of the pixels.

If we assume that the grating spacing is chosen such that blue is emitted along the normal, and that the angle between the green and blue rays is roughly equal to the angle between the red and green rays, and that both angles are equal to α, the following equations apply to the lens parameters:

D=4p;f=ptanα;f#=fD=14tanα

f=1n1R

However, for the strong lenses required here spherical aberrations will play an important role. Therefore we used ray-tracing simulations of the lens geometry in order to find the proper radius of curvature for the required focal length. In these simulations we also took the refraction by the glass substrate of the display into account. Our target display has a pixel pitch of 207µm, and therefore the pitch of the lens array is chosen to be 4×207=828µm. The total thickness of the panel, including polarizer foils, was measured to be 2.2mm.

Based upon our simulations a lens array was made with a radius of curvature of the lenses of 543µm, and a refractive index of 1.57. The lens array needs to be placed in close contact with the display in order to be close enough to focus the color lines on the position of the pixels within the LCD panel.

4. Evaluation of the backlight system

The experimental testing of the backlight system has been performed in several steps. At first we characterized the angular distribution of light outcoupled from the grating with an EZContrast 160 conoscope from Eldim S.A.15. The lightguide with the grating on top was placed in a side-lit configuration with a cold-cathode fluorescence lamp (CCFL) and a mirror at the other end of the lightguide. Results of this analysis are reported in Fig. 12 and clearly confirm the idea sketched in Fig. 5: a pattern of colors symmetric around zero azimuthal angle can be observed.

Fig. 12. Measurement of angular distribution of the light outcoupled from the grating. Some color overlap can be observed in the picture as predicted in Fig. 9(a).

Colors vary, from bottom to top, passing by red, green and dark blue and again green and red. Some overlap is however present between red and green and green and blue and it shows up with hybrid tonalities. This qualitatively corresponds to the results of Fig. 9(a).

The second measurement was with the microlens array in front of the grating. A picture of the resulting color distribution has been taken by a CCD camera and it is shown in Fig. 13(a). We observe a periodical sequence of colored stripes that is to be imaged by the system (grating + microlens array) onto the diffuser in front of the LC layer. At this stage, the width of the various stripes is not exactly the same for all the colors. This is probably due to a not perfect focal strength of the microlens array used for the experiment and to an unequal spacing of wavelengths of the light source. We analyzed the pattern of Fig. 13(a) in order to measure how wide the gamut of our display could be. The obtained graph (Fig. 13(b)) shows several groups of points that mainly correspond to the peaks present in the spectral range of our light source (Fig. 13(c)). The dashed triangle represents the gamut of a common LCD-TV display. By comparing the triangle to our result we notice that the red peak (λ=615nm) is in our case absent. This is due to the color overlap between red and green already evidenced in Figs. 9, 12. The main result of this overlap is the orange color that we observe in the periodical structure of Fig. 13(a).

Fig. 13. (a). Photograph of periodically striped pattern as produced by a microlens array put in front of the grating. The image shows the RGBGR sequence of stripes. (b). Gamut of the obtained display. Several groups of points correspond to the peaks present in the spectral range of our light source. The dashed triangle represents the gamut of a common LCD-TV display. (c). Spectrum of a CCFL lamp.

5. Conclusions

Holographic diffraction gratings are very flexible optical elements that can be designed for a large range of applications. In this paper we have considered the realization of a grating for display applications. If the grating is used as a color-separating element, color-filters in front of the LC layer of the display can be avoided and the obtained configuration is very efficient. Several simulations have been performed to identify the features of the grating needed for obtaining best performances. Results show that period and depth are key-parameters. We realized a grating with a period of Λ=320nm and depth of L=210nm. This structure diffracts light coming from opposite directions into a symmetric RGBGR ray pattern. If a microlens array is put in front of the grating, the colored rays can be imaged onto the LCD with a periodically striped sequence forming a new pixel structure. A first prototype using this concept has been realized and its performance has been analyzed. The results confirm the usability of the RGBGR pixel structure but unfortunately the color gamut of this system is not yet perfect because of some overlap between colored rays coming from the grating. Of course, color filters could be used to clean up the colors in which case the efficiency of the backlight would still be much better than without color separation. Alternatively, this issue can be resolved more efficiently by reducing the angular range of the light coming to the grating from the lightguide.

References and links

1.

S. Serak, N. Tabiryan, and B. Zeldovich, “High-efficiency 1.5 µm thick optical axis grating and its use for laser beam combining,” Opt. Lett. 32, 169–171 (2007). [CrossRef]

2.

X. Wang, D. Wilson, R. Muller, P. Maker, and D. Psaltis, “Liquid-crystal blazed-grating beam deflector,” Appl. Opt. 39, 6545–6555 (2000). [CrossRef]

3.

D. Wright, E. Brasselet, J. Zyss, G. Langer, and W. Kern, “Dye-doped organic distributed-feedback lasers with index and surface gratings: the role of pump polarization and molecular orientation,” J. Opt. Soc. Am. B 21, 944–950 (2004). [CrossRef]

4.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning, and R. A. Vaia, “Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals,” Appl. Phys. Lett. 85, 6095 (2004). [CrossRef]

5.

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, “Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration,” Appl. Phys. Lett. 89, 251104 (2006). [CrossRef]

6.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim “Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films,” Appl. Phys. Lett. 82, 3823 (2003). [CrossRef]

7.

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen, and D. J. Broer, “An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram,” Appl. Phys. Lett. 87, 094101 (2005). [CrossRef]

8.

Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, F. Yamada, S. Ono, and Y. Taira, “Low-power LCD using a novel optical system,” SID 02 Digest1313-1315 (2002); “Dual layered very thin flat surface micro prism array directly molded in an LCD cell,” Eurodisplay 2002, 339–342 (2002). [CrossRef]

9.

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, and M. J. J. Jak “Diffractive grating structures for colour-separating backlights,” Proc. SPIE 6196, 241 (2006).

10.

M. Xu, H. P. Urbach, and D. K. G. de Boer, “Simulations of birefringent gratings as polarizing color separator in backlight for flat-panel displays,” Opt. Express 15, 5789 (2007). [CrossRef] [PubMed]

11.

Y-S. Choi, J-S. Choi, J-H. Min, J-H. Kim, and S-M. Lee, “Backlight unit for flat panel display and flat panel display apparatus having the same,” U.S. patent application publication US2006/0285185 (Dec. 21, 2006).

12.

Grating solver development company. www.gsolver.com

13.

M. G. Moharam and T. K. Gaylord, “Rigorous coupled-wave analysis of planar-grating diffraction,” J. Opt. Soc. Am. 71, 811 (1981). [CrossRef]

14.

AZ Electronic Materials. www.az-em.com

15.

ELDIM manufacturer of 2D photometers & colorimeters and Inspection systems. www.eldim.fr

OCIS Codes
(050.7330) Diffraction and gratings : Volume gratings
(220.4830) Optical design and fabrication : Systems design
(330.1710) Vision, color, and visual optics : Color, measurement

ToC Category:
Diffraction and Gratings

History
Original Manuscript: June 18, 2007
Revised Manuscript: August 2, 2007
Manuscript Accepted: August 2, 2007
Published: August 6, 2007

Virtual Issues
Vol. 2, Iss. 9 Virtual Journal for Biomedical Optics

Citation
Roberto Caputo, Luciano De Sio, Martin J. J. Jak, Eefje J. Hornix, Dick K. G. de Boer, and Hugo J. Cornelissen, "Short period holographic structures for backlight display applications," Opt. Express 15, 10540-10552 (2007)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-15-17-10540


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. S. Serak, N. Tabiryan and B. Zeldovich, "High-efficiency 1.5 ?m thick optical axis grating and its use for laser beam combining," Opt. Lett. 32, 169-171 (2007). [CrossRef]
  2. X. Wang, D. Wilson, R. Muller, P. Maker and D. Psaltis, "Liquid-crystal blazed-grating beam deflector," Appl. Opt. 39, 6545-6555 (2000). [CrossRef]
  3. D. Wright, E. Brasselet, J. Zyss, G. Langer and W. Kern, "Dye-doped organic distributed-feedback lasers with index and surface gratings: the role of pump polarization and molecular orientation," J. Opt. Soc. Am. B 21, 944-950 (2004). [CrossRef]
  4. R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004). [CrossRef]
  5. M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006). [CrossRef]
  6. J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003). [CrossRef]
  7. C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005). [CrossRef]
  8. 8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002). [CrossRef]
  9. D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).
  10. M. Xu, H. P. Urbach and D. K. G. de Boer, "Simulations of birefringent gratings as polarizing color separator in backlight for flat-panel displays," Opt. Express 15, 5789 (2007). [CrossRef] [PubMed]
  11. Y-S. Choi, J-S. Choi, J-H. Min, J-H. Kim, S-M. Lee, "Backlight unit for flat panel display and flat panel display apparatus having the same," U.S. patent application publication US2006/0285185 (Dec. 21, 2006).
  12. Grating solver development company. www.gsolver.com
  13. M. G. Moharam and T. K. Gaylord, "Rigorous coupled-wave analysis of planar-grating diffraction," J. Opt. Soc. Am. 71, 811 (1981). [CrossRef]
  14. AZ Electronic Materials. www.az-em.com
  15. ELDIM manufacturer of 2D photometers & colorimeters and Inspection systems. www.eldim.fr

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited