Abstract

A microlens array (MLA) based see-through, front projection screen, which can be used in direct projection head-up displays (HUD), color teleprompters and bidirectional interactive smart windows, is evaluated for various performance metrics in transmission mode. The screen structure consists of a partially reflective coated MLA buried between refractive-index-matched layers of epoxy as reported in Ref [1]. The reflected light is expanded by the MLA to create an eyebox for the user. The brightness gain of the screen can be varied by changing the numerical aperture of the microlenses. Thus, using high gain designs, a low-power projector coupled with the screen can produce high-brightness and even 3D images as the polarization is maintained at the screen. The impact of the partially reflective coatings on the transmitted light in terms of resolution and modulation transfer function associated with the screen is studied. A condition similar to the Rayleigh criteria for diffraction-limited imaging is discussed for the microlens arrays and the associated coating layers. The optical path difference between the light transmitted from the center and the edges of each microlens caused by the reflective layer coatings should not exceed λ/4. Furthermore, the crosstalk between the front and rear projected images is found to be less than 1.3%.

© 2013 OSA

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE8428, 84280X1–84280X-6 (2012).
    [CrossRef]
  2. P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
    [CrossRef]
  3. A. Olwal, C. Lindfors, J. Gustafsson, T. Kjellberg, and L. Mattsson, “ASTOR: an autostereoscopic optical see-through augmented reality system,” Mixed and Augmented Reality, Proceedings. Fourth IEEE and ACM International Symposium on. IEEE (2005).
    [CrossRef]
  4. J. P. Rolland and H. Fuchs, “Optical versus video see-through head-mounted displays in medical visualization,” Presence (Camb. Mass.)9(3), 287–309 (2000).
    [CrossRef]
  5. M. K. Hedili, M. O. Freeman, and H. Urey, “Microlens array-based high-gain screen design for direct projection head-up displays,” Appl. Opt.52(6), 1351–1357 (2013).
    [CrossRef] [PubMed]
  6. H. Urey and K. D. Powell, “Microlens-array-based exit-pupil expander for full-color displays,” Appl. Opt.44(23), 4930–4936 (2005).
    [CrossRef] [PubMed]
  7. H. Urey, “Diffractive exit-pupil expander for display applications,” Appl. Opt.40(32), 5840–5851 (2001).
    [CrossRef] [PubMed]
  8. G. Hass and J. E. Waylonis, “Optical constants and reflectance and transmittance of evaporated aluminum in the visible and ultraviolet,” JOSA51(7), 719–722 (1961).
    [CrossRef]
  9. M. Estribeau and P. Magnan, “Fast MTF measurement of CMOS imagers using ISO 12233 slanted edge methodology,” Proc. SPIE5251, 243–252 (2004).
    [CrossRef]
  10. J. Canny, “A computational approach to edge detection,” IEEE Trans. Pattern Anal. Mach. Intell.8(6), 679–698 (1986).
    [CrossRef] [PubMed]
  11. K. Pearson, “LIII. On lines and planes of closest fit to systems of points in space,” The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science2.11, 559-572 (1901).
  12. D. G. Voelz, Computational Fourier Optics: A Matlab Tutorial (SPIE, 2011).
  13. W. J. Smith, Modern Optical Engineering (Tata McGraw-Hill Education, 2000).
  14. A. D. Rakić, “Algorithm for the determination of intrinsic optical constants of metal films: application to aluminum,” Appl. Opt.34(22), 4755–4767 (1995).
    [CrossRef] [PubMed]

2013 (1)

2012 (1)

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE8428, 84280X1–84280X-6 (2012).
[CrossRef]

2006 (1)

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

2005 (1)

2004 (1)

M. Estribeau and P. Magnan, “Fast MTF measurement of CMOS imagers using ISO 12233 slanted edge methodology,” Proc. SPIE5251, 243–252 (2004).
[CrossRef]

2001 (1)

2000 (1)

J. P. Rolland and H. Fuchs, “Optical versus video see-through head-mounted displays in medical visualization,” Presence (Camb. Mass.)9(3), 287–309 (2000).
[CrossRef]

1995 (1)

1986 (1)

J. Canny, “A computational approach to edge detection,” IEEE Trans. Pattern Anal. Mach. Intell.8(6), 679–698 (1986).
[CrossRef] [PubMed]

1961 (1)

G. Hass and J. E. Waylonis, “Optical constants and reflectance and transmittance of evaporated aluminum in the visible and ultraviolet,” JOSA51(7), 719–722 (1961).
[CrossRef]

1901 (1)

K. Pearson, “LIII. On lines and planes of closest fit to systems of points in space,” The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science2.11, 559-572 (1901).

Becker, E.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Canny, J.

J. Canny, “A computational approach to edge detection,” IEEE Trans. Pattern Anal. Mach. Intell.8(6), 679–698 (1986).
[CrossRef] [PubMed]

Estribeau, M.

M. Estribeau and P. Magnan, “Fast MTF measurement of CMOS imagers using ISO 12233 slanted edge methodology,” Proc. SPIE5251, 243–252 (2004).
[CrossRef]

Freeman, M. O.

M. K. Hedili, M. O. Freeman, and H. Urey, “Microlens array-based high-gain screen design for direct projection head-up displays,” Appl. Opt.52(6), 1351–1357 (2013).
[CrossRef] [PubMed]

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE8428, 84280X1–84280X-6 (2012).
[CrossRef]

Fuchs, H.

J. P. Rolland and H. Fuchs, “Optical versus video see-through head-mounted displays in medical visualization,” Presence (Camb. Mass.)9(3), 287–309 (2000).
[CrossRef]

Görrn, P.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Hass, G.

G. Hass and J. E. Waylonis, “Optical constants and reflectance and transmittance of evaporated aluminum in the visible and ultraviolet,” JOSA51(7), 719–722 (1961).
[CrossRef]

Hedili, M. K.

M. K. Hedili, M. O. Freeman, and H. Urey, “Microlens array-based high-gain screen design for direct projection head-up displays,” Appl. Opt.52(6), 1351–1357 (2013).
[CrossRef] [PubMed]

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE8428, 84280X1–84280X-6 (2012).
[CrossRef]

Johannes, H. H.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Kowalsky, W.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Kröger, M.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Magnan, P.

M. Estribeau and P. Magnan, “Fast MTF measurement of CMOS imagers using ISO 12233 slanted edge methodology,” Proc. SPIE5251, 243–252 (2004).
[CrossRef]

Meyer, J.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Pearson, K.

K. Pearson, “LIII. On lines and planes of closest fit to systems of points in space,” The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science2.11, 559-572 (1901).

Powell, K. D.

Rakic, A. D.

Riedl, T.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Rolland, J. P.

J. P. Rolland and H. Fuchs, “Optical versus video see-through head-mounted displays in medical visualization,” Presence (Camb. Mass.)9(3), 287–309 (2000).
[CrossRef]

Sander, M.

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Urey, H.

Waylonis, J. E.

G. Hass and J. E. Waylonis, “Optical constants and reflectance and transmittance of evaporated aluminum in the visible and ultraviolet,” JOSA51(7), 719–722 (1961).
[CrossRef]

Adv. Mater. (1)

P. Görrn, M. Sander, J. Meyer, M. Kröger, E. Becker, H. H. Johannes, W. Kowalsky, and T. Riedl, “Towards see‐through displays: fully transparent thin‐film transistors driving transparent organic light‐emitting diodes,” Adv. Mater.18(6), 738–741 (2006).
[CrossRef]

Appl. Opt. (4)

IEEE Trans. Pattern Anal. Mach. Intell. (1)

J. Canny, “A computational approach to edge detection,” IEEE Trans. Pattern Anal. Mach. Intell.8(6), 679–698 (1986).
[CrossRef] [PubMed]

JOSA (1)

G. Hass and J. E. Waylonis, “Optical constants and reflectance and transmittance of evaporated aluminum in the visible and ultraviolet,” JOSA51(7), 719–722 (1961).
[CrossRef]

LIII. On lines and planes of closest fit to systems of points in space (1)

K. Pearson, “LIII. On lines and planes of closest fit to systems of points in space,” The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science2.11, 559-572 (1901).

Presence (Camb. Mass.) (1)

J. P. Rolland and H. Fuchs, “Optical versus video see-through head-mounted displays in medical visualization,” Presence (Camb. Mass.)9(3), 287–309 (2000).
[CrossRef]

Proc. SPIE (2)

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE8428, 84280X1–84280X-6 (2012).
[CrossRef]

M. Estribeau and P. Magnan, “Fast MTF measurement of CMOS imagers using ISO 12233 slanted edge methodology,” Proc. SPIE5251, 243–252 (2004).
[CrossRef]

Other (3)

A. Olwal, C. Lindfors, J. Gustafsson, T. Kjellberg, and L. Mattsson, “ASTOR: an autostereoscopic optical see-through augmented reality system,” Mixed and Augmented Reality, Proceedings. Fourth IEEE and ACM International Symposium on. IEEE (2005).
[CrossRef]

D. G. Voelz, Computational Fourier Optics: A Matlab Tutorial (SPIE, 2011).

W. J. Smith, Modern Optical Engineering (Tata McGraw-Hill Education, 2000).

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (12)

Fig. 1
Fig. 1

Transparent microlens array screen can be used from both sides simultaneously with negligible crosstalk between the images on two sides. The screen offers a gain and viewing angle controlled by the numerical aperture of the MLA.

Fig. 2
Fig. 2

The partially reflective coated MLA is buried between index-matched layers of epoxy and glass. The reflected portion of the incident light is expanded by the MLA towards the user to create an eyebox, whereas the transmitted light remains unaffected due to the index-matched structure. The screen can be used from both sides at the same time with less than 1.3% crosstalk, if the input beam directions are adjusted accordingly.

Fig. 3
Fig. 3

a) The Zemax layout of the simulation scheme. b)The grayscale image of the simulated eyeboxes corresponding to the 50 sample points on the screen that are shown above. The overlapped region of the eyeboxes is 65cm wide at the desired viewing distance of one meter. Even though the shape of the microlenses is a regular hexagon, the shape of the eyebox is an elongated hexagon due to the increased incidence angles along the horizontal direction.

Fig. 4
Fig. 4

a) For a planar MLA screen the eyeboxes for each pixel on the screen shift laterally with changing angle of incidence. The overlapped region of these shifted eyeboxes becomes the vignetting-free eyebox. b) By rotating each microlens individually to achieve 100% overlapped region increases the screen efficiency substantially.

Fig. 5
Fig. 5

The transmittance spectrum of the desired notch coating at the top, the measured transmittance spectrum of the fabricated screen at the bottom. The green lines mark the laser wavelengths of the laser pico-projector.

Fig. 6
Fig. 6

a) A resolution chart imaged by a camera lens through the transparent screen. b) Three pictures correspond to no screen, metal coated screen and notch coated screen placed at 1m distance to the camera. Note that the notch coating has a blurring effect on the image compared to the metal coating and it introduces undesired coloration to the image, which makes this notch coating unacceptable for a see-through screen.

Fig. 7
Fig. 7

a) The image of a slanted edge captured by the camera without using an MLA screen. b) The edge is straightened by the image processing software based on the computed angle of the edge. c) The average of the columns in Fig. 7(b) is computed to get the 1D edge spread function (ESF) of the system. d) The derivative of the ESF in Fig. 7(c) results in the point spread function (PSF) of the system.

Fig. 8
Fig. 8

Experimental MTFs of the screens with different coatings. The metal coating has negligible effect on the MTF but the notch coating reduces the bandwidth at MTF50 almost by half, which explains the blurring effect of the notch coating.

Fig. 9
Fig. 9

a) The log10 of the experimental PSF of the notch coated screen. b) The log10 of the simulated PSF of the notch coated screen. c) The encircled energy plot of the experimental PSF of the notch coated screen. With the see-through screen geometry in Fig. 2, the transmitted light should not have seen a phase variation across the screen but the diffraction orders in the PSFs show that the notch coating violates this condition.

Fig. 10
Fig. 10

a) Cross-section of a single lens with a uniformly thick coating. The transmitted light through the coating travels different path lengths due to the curvature of the microlenses and the refractive index difference, which creates an optical path difference across the microlenses. b) A parametric plot of the OPD as a function of lens and coating parameters shown in Fig. 10(a).

Fig. 11
Fig. 11

a) The simulated periodic phase function to find out the effect of the coating on the quality of the screen transparency. Each hexagon has the phase function shown in Eq. (1). b) The horizontal cross-section of the phase function in (a).

Fig. 12
Fig. 12

The left column shows the real part of the phase function of a single microlens for different coating thicknesses and the right column shows the Strehl ratio for the corresponding optical paths. As seen from the three examples above, the real part of the phase function should be greater than zero for a diffraction limited system, which is defined as Strehl ratio greater than 0,8.

Tables (1)

Tables Icon

Table 1 Luminance values for the crosstalk measurements

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

Δ=( p(x,y)t )( n 3 n 2 )
ϕ(x,y)=exp( j 2π λ Δ )
t(x,y)=ϕ(x,y) i j δ(xi d x )δ(yj d y )

Metrics