Abstract

Head-up display (HUD) systems have been used in recent car models to provide essential information to the drivers while keeping their eyes on the road. Virtual image HUD systems have been the preferred method, but they have the drawback of requiring a large volume of space in order to accommodate the relay optics that creates the virtual image. This is especially significant as the desired field of view increases. Direct projection HUD systems have been developed with a separate stand-alone microlens array (MLA)-based transparent screen on the dashboard, offering a compact solution. In this paper, we propose a direct projection HUD system based on a unique, windshield-embedded see-through screen that uses minimal space under the dashboard, offering an elegant and compact solution to the HUD problem. The screen is based on MLAs with varying surface normal angles such that the light from the projector is directed to the viewer’s eyes from all positions across the field of view. Varying tilts provide an efficient relay and high brightness even with a low-lumen output projector. The calculated screen gain is about 69 and the eyebox area is about 30cm×30cm.

© 2013 Optical Society of America

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References

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  1. Y.-C. Liu and M.-H. Wen, “Comparison of head-up display (HUD) vs. head-down display (HDD): driving performance of commercial vehicle operators in Taiwan,” Int. J. Human-Computer Studies 61, 679 (2004).
    [CrossRef]
  2. N. A. Kaptein, “Benefits of in-car head-up displays,” TNO Report TNO-TM 1994, B-20, TNO Human Factors Research Institute (1994).
  3. M. Ablassmeier, T. Poitschke, and G. Rigoll, “Eye gaze studies comparing head-up and head-down displays in vehicles,” in Proceedings of IEEE Conference on International Conference on Multimedia and Expo (IEEE, 2007), pp. 2250–2252.
  4. M. O. Freeman, “MEMS scanned laser head-up display,” Proc. SPIE 7930, 79300G (2011).
    [CrossRef]
  5. M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE 8428, 84280X (2012).
    [CrossRef]
  6. H. Urey and K. D. Powell, “Microlens-array-based exit-pupil expander for full-color displays,” Appl. Opt. 44, 4930–4936 (2005).
    [CrossRef]
  7. D. Fontijne and L. Dorst, “Modeling 3D Euclidean geometry,” IEEE Comput. Graph. Appl. 23, 68–78 (2003).
    [CrossRef]
  8. J. E. Dennis and R. B. Schnabel, Numerical Methods for Unconstrained Optimization and Nonlinear Equations (Prentice-Hall, 1983), Chap. 2.
  9. F. L. Pedrotti, L. M. Pedrotti, and L. S. Pedrotti, Introduction to Optics, 3rd ed. (Pearson Prentice-Hall, 2007).

2012 (1)

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE 8428, 84280X (2012).
[CrossRef]

2011 (1)

M. O. Freeman, “MEMS scanned laser head-up display,” Proc. SPIE 7930, 79300G (2011).
[CrossRef]

2005 (1)

2004 (1)

Y.-C. Liu and M.-H. Wen, “Comparison of head-up display (HUD) vs. head-down display (HDD): driving performance of commercial vehicle operators in Taiwan,” Int. J. Human-Computer Studies 61, 679 (2004).
[CrossRef]

2003 (1)

D. Fontijne and L. Dorst, “Modeling 3D Euclidean geometry,” IEEE Comput. Graph. Appl. 23, 68–78 (2003).
[CrossRef]

Ablassmeier, M.

M. Ablassmeier, T. Poitschke, and G. Rigoll, “Eye gaze studies comparing head-up and head-down displays in vehicles,” in Proceedings of IEEE Conference on International Conference on Multimedia and Expo (IEEE, 2007), pp. 2250–2252.

Dennis, J. E.

J. E. Dennis and R. B. Schnabel, Numerical Methods for Unconstrained Optimization and Nonlinear Equations (Prentice-Hall, 1983), Chap. 2.

Dorst, L.

D. Fontijne and L. Dorst, “Modeling 3D Euclidean geometry,” IEEE Comput. Graph. Appl. 23, 68–78 (2003).
[CrossRef]

Fontijne, D.

D. Fontijne and L. Dorst, “Modeling 3D Euclidean geometry,” IEEE Comput. Graph. Appl. 23, 68–78 (2003).
[CrossRef]

Freeman, M. O.

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE 8428, 84280X (2012).
[CrossRef]

M. O. Freeman, “MEMS scanned laser head-up display,” Proc. SPIE 7930, 79300G (2011).
[CrossRef]

Hedili, M. K.

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE 8428, 84280X (2012).
[CrossRef]

Kaptein, N. A.

N. A. Kaptein, “Benefits of in-car head-up displays,” TNO Report TNO-TM 1994, B-20, TNO Human Factors Research Institute (1994).

Liu, Y.-C.

Y.-C. Liu and M.-H. Wen, “Comparison of head-up display (HUD) vs. head-down display (HDD): driving performance of commercial vehicle operators in Taiwan,” Int. J. Human-Computer Studies 61, 679 (2004).
[CrossRef]

Pedrotti, F. L.

F. L. Pedrotti, L. M. Pedrotti, and L. S. Pedrotti, Introduction to Optics, 3rd ed. (Pearson Prentice-Hall, 2007).

Pedrotti, L. M.

F. L. Pedrotti, L. M. Pedrotti, and L. S. Pedrotti, Introduction to Optics, 3rd ed. (Pearson Prentice-Hall, 2007).

Pedrotti, L. S.

F. L. Pedrotti, L. M. Pedrotti, and L. S. Pedrotti, Introduction to Optics, 3rd ed. (Pearson Prentice-Hall, 2007).

Poitschke, T.

M. Ablassmeier, T. Poitschke, and G. Rigoll, “Eye gaze studies comparing head-up and head-down displays in vehicles,” in Proceedings of IEEE Conference on International Conference on Multimedia and Expo (IEEE, 2007), pp. 2250–2252.

Powell, K. D.

Rigoll, G.

M. Ablassmeier, T. Poitschke, and G. Rigoll, “Eye gaze studies comparing head-up and head-down displays in vehicles,” in Proceedings of IEEE Conference on International Conference on Multimedia and Expo (IEEE, 2007), pp. 2250–2252.

Schnabel, R. B.

J. E. Dennis and R. B. Schnabel, Numerical Methods for Unconstrained Optimization and Nonlinear Equations (Prentice-Hall, 1983), Chap. 2.

Urey, H.

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE 8428, 84280X (2012).
[CrossRef]

H. Urey and K. D. Powell, “Microlens-array-based exit-pupil expander for full-color displays,” Appl. Opt. 44, 4930–4936 (2005).
[CrossRef]

Wen, M.-H.

Y.-C. Liu and M.-H. Wen, “Comparison of head-up display (HUD) vs. head-down display (HDD): driving performance of commercial vehicle operators in Taiwan,” Int. J. Human-Computer Studies 61, 679 (2004).
[CrossRef]

Appl. Opt. (1)

IEEE Comput. Graph. Appl. (1)

D. Fontijne and L. Dorst, “Modeling 3D Euclidean geometry,” IEEE Comput. Graph. Appl. 23, 68–78 (2003).
[CrossRef]

Int. J. Human-Computer Studies (1)

Y.-C. Liu and M.-H. Wen, “Comparison of head-up display (HUD) vs. head-down display (HDD): driving performance of commercial vehicle operators in Taiwan,” Int. J. Human-Computer Studies 61, 679 (2004).
[CrossRef]

Proc. SPIE (2)

M. O. Freeman, “MEMS scanned laser head-up display,” Proc. SPIE 7930, 79300G (2011).
[CrossRef]

M. K. Hedili, M. O. Freeman, and H. Urey, “Microstructured head-up display screen for automotive applications,” Proc. SPIE 8428, 84280X (2012).
[CrossRef]

Other (4)

N. A. Kaptein, “Benefits of in-car head-up displays,” TNO Report TNO-TM 1994, B-20, TNO Human Factors Research Institute (1994).

M. Ablassmeier, T. Poitschke, and G. Rigoll, “Eye gaze studies comparing head-up and head-down displays in vehicles,” in Proceedings of IEEE Conference on International Conference on Multimedia and Expo (IEEE, 2007), pp. 2250–2252.

J. E. Dennis and R. B. Schnabel, Numerical Methods for Unconstrained Optimization and Nonlinear Equations (Prentice-Hall, 1983), Chap. 2.

F. L. Pedrotti, L. M. Pedrotti, and L. S. Pedrotti, Introduction to Optics, 3rd ed. (Pearson Prentice-Hall, 2007).

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Figures (11)

Fig. 1.
Fig. 1.

Real photograph of direct-projection HUD in operation. The unique structure of the screen provides good reflectance for the projected image coupled with very good transmittance. In this figure, the screen is not embedded into the windshield.

Fig. 2.
Fig. 2.

Because of the angle of the windshield, the natural input direction is behind the screen. The desired input direction is closer to the driver so that the geometric distortions are minimized and the projector has adequate distance to project onto the whole screen.

Fig. 3.
Fig. 3.

Simulated eyeboxes corresponding to the five points across the planar MLA screen that is illuminated from the natural input direction. This approach does not work, as there is no overlapping region of the individual eyeboxes so the full content on the screen cannot be seen from any position.

Fig. 4.
Fig. 4.

HUD system with the projector on the dashboard. The projection cone can be expanded with a small lens such that the whole screen can be projected with the desired image.

Fig. 5.
Fig. 5.

Side view of three sample microlenses across the screen. Each partially reflective coated microlens is rotated individually and sandwiched between the index matching layers of epoxy. The index matched structure does not distort the transmitted light, but the reflected light is expanded by the microlenses toward the eyebox.

Fig. 6.
Fig. 6.

Horizontal cross section of part of the screen in the Zemax model, showing five consecutive microlenses. Microlenses are placed 300 μm apart to eliminate shadowing. Spherical microlenses with rectangular apertures are used in the array.

Fig. 7.
Fig. 7.

(a) Because of the screen structure the incident and reflected light are subject to refraction. Based on the incident and reflected vectors on the micromirror, the surface normal is calculated. (b) The aiming point on the windshield should be calculated such that the refracted light passes through the desired point on the other side. The procedure of finding the incident and refracted vectors vi1 and vr1 is followed twice for each micromirror, from projector to the micromirror and from micro-mirror to the driver.

Fig. 8.
Fig. 8.

Contour plot of the calculated rotation angles of the whole screen in degrees. The tilt direction is normal to the contour lines.

Fig. 9.
Fig. 9.

Side view of the system, showing the focusing characteristic of our screen due to the rotated micro-mirrors used in the design.

Fig. 10.
Fig. 10.

True color image of the eyeboxes at the driver’s position, corresponding to the same sample points in Fig. 3. They overlap very well thanks to the rotated microlenses.

Fig. 11.
Fig. 11.

Horizontal cross section of the normalized eyebox intensity on top and the vertical cross section at the bottom. The horizontal uniformity is very good so the eyes perceive the same brightness.

Equations (9)

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

vr1=(sign(vi1·n)1η2+η2(vi1·n)2(vi1·n)η)n+ηvi1,
vd=d1vi1·nvi1+d2vr1·nvr1,
vi1=vdd2(1η(vi1·n)1η2+η2(vi1·n)2)nd1(vi1·n)+ηd21η2+η2(vi1·n)2,
f(x)=vi11.
vi2=vr12(vr1·nm)nm,
nm=vr1vi22(1(vi2·vr1)),
[cosφ0sinφsinφsinθcosθcosφsinθsinφcosθsinθcosφcosθ][001]=[xmymzm],
φ=sin1(xm),
θ=tan1(ymzm).

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