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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 10 — May. 9, 2011
  • pp: 9942–9949
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Stereogram implemented with a holographic image splitter

Wei-Chia Su, Chien- Yue Chen, and Yi-Fan Wang  »View Author Affiliations


Optics Express, Vol. 19, Issue 10, pp. 9942-9949 (2011)
http://dx.doi.org/10.1364/OE.19.009942


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Abstract

A special holographic optical element (HOE) which is used as an image splitter is developed to generate a stereogram on a 2.2-in. liquid crystal display panel. The special designed holographic optical element can be attached on the conventional panel directly to replace the traditional image splitter in a stereoscopic display panel. Experimental results show that two images corresponding to slightly different viewing angles displayed on a panel can be separated effectively and can be delivered to the right eye and left eye of an observer individually. The diffraction efficiency for individual right and left image in this developed holographic optical element is about 43%, and the contrast ratio of the diffracted images induced by cross talk is larger than 60%. Theoretical analyses show the proposed technique generates good contrast ratio and brightness performance for stereogram application.

© 2011 OSA

1. Introduction

One economic method to generate autostereoscopic effect without wearing eyeglasses on a liquid crystal display (LCD) is using the so called multiplexed-2D-images technology [1

1. J. Y. Son, V. V. Saveljev, Y. J. Choi, J. E. Bahn, S. K. Kim, and H. Choi, “Parameters for designing autostereoscopic imaging systems based on lenticular, parallax barrier, and integral photography plates,” Opt. Eng. 42(11), 3326–3333 (2003).

] based on binocular parallax of human beings. This technology is implemented by displaying two similar plane images but with a slightly different viewing angle on the panel simultaneously and then let these two individual images only propagate to their corresponding single eye of an observer. To display these two similar plane images on the panel simultaneously, one of them can be shown on odd column pixels only and another one can be shown on even column pixels. If the image shown on odd column pixels only propagates to observer’s right eye and the image shown on even column pixels only propagates to observer’s left eye, we can obtain the stereoscopic vision. Accordingly, an image splitter used to separate these two images is an essential optical element for stereoscopic display in a LCD panel.

Present device for image splitter in stereo-display focuses on lenticular lens [2

2. W. X. Zhao, Q. H. Wang, A. H. Wang, and D. H. Li, “Autostereoscopic display based on two-layer lenticular lenses,” Opt. Lett. 35(24), 4127–4129 (2010). [PubMed]

,3

3. M. P. C. M. Krijn, S. T. de Zwart, D. K. G. de Boer, O. H. Willemsen, and M. Sluijter, “2-D/3-D displays based on switchable lenticulars,” J. Soc. Inf. Disp. 16(8), 847–855 (2008).

] and parallax barrier [4

4. Y. H. Tao, Q. H. Wang, J. Gu, W. X. Zhao, and D. H. Li, “Autostereoscopic three-dimensional projector based on two parallax barriers,” Opt. Lett. 34(20), 3220–3222 (2009). [PubMed]

,5

5. C. H. Chen, Y. P. Huang, S. C. Chuang, C. L. Wu, H. P. D. Shieh, W. Mphepö, C. T. Hsieh, and S. C. Hsu, “Liquid crystal panel for high efficiency barrier type autostereoscopic three-dimensional displays,” Appl. Opt. 48(18), 3446–3454 (2009). [PubMed]

] technology. They both are economic methods and have been widely used in the commercial market for their low cost. However, the disadvantage of the current lenticular display is that the considerable cross talk noise could be induced by the fabrication error of the lenticular sheet or the alignment error between the lenticular sheet and the display panel [6

6. T. Järvenpää and M. Salmimaa, “Optical characterization of autostereoscopic 3-D displays,” J. Soc. Inf. Disp. 16(8), 825–833 (2008).

8

8. Q. H. Wang, X. F. Li, L. Zhou, A. H. Wang, and D. H. Li, “Cross-talk reduction by correcting the subpixel position in a multiview autostereoscopic three-dimensional display based on a lenticular sheet,” Appl. Opt. 50(7), B1–B5 (2011). [PubMed]

]. The other method, parallax barrier technology, is implemented by pixel shielding with a binary grating. Inherently, the barrier technology reduces the brightness of displays. Recently, Chen et al. proposed an improvement method by coating a reflection layer inside the panel to enhance the brightness in a stereo-display with barrier shielding [9

9. C. Y. Chen, M. C. Chang, M. D. Ke, C. C. Lin, and Y. M. Chen, “A novel high brightness parallax barrier stereoscopy technology using a reflective crown grating,” Microw. Opt. Technol. Lett. 50(6), 1610–1616 (2008).

]. However, the current best brightness performance can be reached in a barrier stereo-display is only 43% of the original brightness [9

9. C. Y. Chen, M. C. Chang, M. D. Ke, C. C. Lin, and Y. M. Chen, “A novel high brightness parallax barrier stereoscopy technology using a reflective crown grating,” Microw. Opt. Technol. Lett. 50(6), 1610–1616 (2008).

]. Moreover, unlike the lenticular sheet which is attached on the image panel, the binary grating should be placed in front of the panel with a finite distance and accordingly an additional precise alignment could be required in the assemble process of a barrier stereo-display.

In this paper, we have proposed a new type HOE to generate an image splitter for stereogram application on a LCD panel. The holographic image splitter is designed to locate at the image panel to separate and direct light for images with different viewing angles to propagate into observer’s corresponding eyes. Once the holographic image splitter is fabricated and attached on a conventional panel with proper alignment, an autostereoscopic display can be obtained. Experimental results show that two images corresponding to slightly different viewing angles displayed on a panel can be separated effectively and can be delivered to the right eye and left eye of an observer individually. The diffraction efficiency for right and left image in this developed holographic optical element is about 43%, and the contrast ratio of the diffracted images induced by cross talk is larger than 60%. Theoretical analyses show the proposed technique generates good contrast ratio and brightness performance for stereogram application. The proposed holographic image splitter performs high potential as an alternative competing technology with the lenticular and barrier methods.

2. Stereogram principle

Figure 1
Fig. 1 A holographic image splitter for stereogram.
shows our proposed stereogram principle. To generate a autostereogram on such a liquid crystal panel, an image splitter is essentially required to direct the image on odd column pixels to propagate to right eye and simultaneously direct the image on even column pixels to propagate to left eye of the an observer. The whole image splitter is a holographic optical element composed of several sub-holograms attached on each column pixels. The odd column pixels are marked with R and the even column pixels are marked with L. The sub-holograms above the odd column pixels will diffract the images shown on R column pixels to propagate to right eye, and sub-holograms above the even column pixels will diffract the images shown on L column pixels to propagate to left eye.

In order to experience the stereo vision described above, the left and right images have to be delivered into observer’s left and right eye respectively with proper propagation angles. As shown in Fig. 2
Fig. 2 Calculation of the HOE split angle.
, we assume the distance between the two eyes is 2W and the distance between panel and the observer is H, the propagation angle of the diffraction beam from the sub-holograms on even and odd column pixels can be calculated by

α=tan1WH
(1)

where α is defined as the split angle of the holographic image splitter. In this study, we assume the binocular distance 2W is 6cm and the viewing distance H is 20cm. From formula (1), the required split angle is about 8 degrees. Split angle is an important parameter which is corresponding to the holographic interference angle in the following fabrication process of the required HOE.

3. Optical experiments

3.1 Fabrication of HOE

3.2 Result of image split

An experimental setup shown as Fig. 5
Fig. 5 The experimental architecture for implementing a stereogram using the proposed HOE.
was used to demonstrate a monochromatic stereogram implemented with the proposed HOE. The HOE was attached on a 2.2-in. liquid crystal display panel and it was carefully aligned with the display pixels. In our demonstration, the laser is replaced by a green LED and the emitted central wavelength is 530nm. The beam emitted from the LED is collimated and incident on the LCD panel. We found the spatial-multiplexed image prepared for stereo-effect on LCD was effectively separated via the HOE and this leaded to a stereoscopic vision with an around 20 cm viewing distance for observers. The separated right and left images were individually captured by CCD cameras, and they were also shown in Fig. 5. A further experiment is demonstrated to prove the validness of the image splitter. A special designed spatial-multiplexed image was prepared. This spatial-multiplexed image displayed on R column pixels of the panel is a character “L” and the image displayed on L column pixels is a character “V”. Once the backlight pass through the LCD and HOE, two images on odd and even column pixels would be separated. Figure 6
Fig. 6 Experimental result of a holographic image splitter.
shows the experimental result. Two images “L” and “V” were separated by our holographic beam splitter element and these two images were projected on a screen. Though the fabricated HOE generated −1 order diffraction, there was no obvious observed cross talk noise in our practical experiments.

4. Discussions

4.1 Brightness

4.2 Cross talk

The cross talk performance can be investigated by the contrast ratio (CR) of the diffracted images [15

15. C. Y. Chen, Q. L. Deng, and H. C. Wu, “A high-brightness diffractive stereoscopic display technology,” Displays 31(4-5), 169–174 (2010).

]. The contrast ratio for right eye, CRR, and contrast ratio for left eye, CRL, can be defined as:

CRR=RrRlRr+Rl×100%CRL=LlLrLl+Lr×100%
(2)

where Rr is the diffracted intensity of the image on R column pixels measured on location of the right eye, and Rl is the diffracted intensity of the image on L column pixels measured on location of the right eye. Similarly, Ll is the diffracted intensity of the image on L column pixels measured on location of the left eye, and Lr is the diffracted intensity of the image on R column pixels measured on location of the left eye. When the incident intensity is 42μW/cm2, the measured intensity Rr, Rl, Ll, and Lr are listed in Table1

Table 1. Diffraction intensity from even and odd pixels measured at location of right and left eye

table-icon
View This Table
. According to Eq. (2), the contrast ratios for right eye and left eye using the holographic splitter are about 76.5% and 60.9%, respectively. Our device shows good contrast ratio for stereogram application, and it leads to perform high potential in obtaining high stereoscopic image quality.

Noteworthily, the fabricated holographic image splitter shown in this experiment is currently designed for monochromatic stereoscopic images only. Using the current presented HOE for color multiplexed-2D-images on LCD panel will induce color blur effect which is caused by chromatic dispersion of HOE. The color blur also generates cross talk noise for stereoscopic images. An effective solution for this phenomenon is using three independent devices to separate the red, green, and blue image pairs shown on the color LCD panel individually [16

16. C. Y. Chen, T. Y. Hsieh, Q. L. Deng, W. C. Su, and Z. S. Cheng, “Design of a novel symmetric microprism array for dual-view display,” Displays 31(2), 99–103 (2010).

]. From Ref. [16

16. C. Y. Chen, T. Y. Hsieh, Q. L. Deng, W. C. Su, and Z. S. Cheng, “Design of a novel symmetric microprism array for dual-view display,” Displays 31(2), 99–103 (2010).

], we can realize one pixel on a LCD panel usually contains three horizontal sub-pixels for showing RGB color. Accordingly, each odd or even column pixel as shown in Fig. 1 indeed contains three RGB sub-column pixels. One technique to eliminate color blur of the proposed technique is to generate three sub-holograms for directing the RGB images shown on each R column pixels or on each L column pixels respectively. Notably, the current presented HOE is generated with only one sub-hologram for each R column pixels or for each L column pixels. Fabrication of the advance HOE for color stereoscopic vision is our future work.

5. Conclusions

A new type of image splitter for stereoscopic vision on LCD panel is presented. The special designed holographic optical element can be attached on a conventional 2.2-in. liquid crystal display panel directly to replace the traditional image splitter in a stereoscopic display panel. The experimental results prove the proposed principle work successfully. The proposed technique can be further improved by using a thick recording material which can generate higher diffraction efficiency. Experimental results show the proposed technique generates good contrast ratio and brightness performance for stereogram application. The proposed holographic image splitter accordingly performs high potential as an alternative competing technology with lenticular and barrier stereo-displays.

Acknowledgments

This work is supported by the National Science Council of Taiwan under Contract No. NSC 97-2221-E-108-002-MY3.

References and links

1.

J. Y. Son, V. V. Saveljev, Y. J. Choi, J. E. Bahn, S. K. Kim, and H. Choi, “Parameters for designing autostereoscopic imaging systems based on lenticular, parallax barrier, and integral photography plates,” Opt. Eng. 42(11), 3326–3333 (2003).

2.

W. X. Zhao, Q. H. Wang, A. H. Wang, and D. H. Li, “Autostereoscopic display based on two-layer lenticular lenses,” Opt. Lett. 35(24), 4127–4129 (2010). [PubMed]

3.

M. P. C. M. Krijn, S. T. de Zwart, D. K. G. de Boer, O. H. Willemsen, and M. Sluijter, “2-D/3-D displays based on switchable lenticulars,” J. Soc. Inf. Disp. 16(8), 847–855 (2008).

4.

Y. H. Tao, Q. H. Wang, J. Gu, W. X. Zhao, and D. H. Li, “Autostereoscopic three-dimensional projector based on two parallax barriers,” Opt. Lett. 34(20), 3220–3222 (2009). [PubMed]

5.

C. H. Chen, Y. P. Huang, S. C. Chuang, C. L. Wu, H. P. D. Shieh, W. Mphepö, C. T. Hsieh, and S. C. Hsu, “Liquid crystal panel for high efficiency barrier type autostereoscopic three-dimensional displays,” Appl. Opt. 48(18), 3446–3454 (2009). [PubMed]

6.

T. Järvenpää and M. Salmimaa, “Optical characterization of autostereoscopic 3-D displays,” J. Soc. Inf. Disp. 16(8), 825–833 (2008).

7.

C. H. Chen, H. H. Huang, T. H. Hsu, M.-H. Kuo, and C. H. Tsai, “Optical simulation for cross-talk evaluation and improvement of autostereoscopic 3-D displays with a projector array,” J. Soc. Inf. Disp. 18(9), 662–667 (2010).

8.

Q. H. Wang, X. F. Li, L. Zhou, A. H. Wang, and D. H. Li, “Cross-talk reduction by correcting the subpixel position in a multiview autostereoscopic three-dimensional display based on a lenticular sheet,” Appl. Opt. 50(7), B1–B5 (2011). [PubMed]

9.

C. Y. Chen, M. C. Chang, M. D. Ke, C. C. Lin, and Y. M. Chen, “A novel high brightness parallax barrier stereoscopy technology using a reflective crown grating,” Microw. Opt. Technol. Lett. 50(6), 1610–1616 (2008).

10.

D. Trayner and E. Orr, “Autostereoscopic display using holographic optical elements,” Proc. SPIE 2653, 65–74 (1996).

11.

D. Trayner and E. Orr, “Developments in autostereoscopic displays using holographic optical elements,” Proc. SPIE 3012, 167–174 (1997).

12.

B. C. Cho, J. S. Gu, W. Y. Kim, and E. S. Kim, “Multiview autostereoscopic 3D display system using volume holographic optical element,” Proc. SPIE 4471, 43–50 (2001).

13.

B. C. Cho, J. S. Gu, and E. S. Kim, “Implementation of multiview 3D display system using volume holographic optical element,” Proc. SPIE 4567, 224–232 (2002).

14.

Y. H. Cho, R. Kawade, T. Kubota, and Y. Kawakami, “Control of morphology and diffraction efficiency of holographic gratings using siloxane-containing reactive diluent,” Sci. Technol. Adv. Mater. 6(5), 435–442 (2005).

15.

C. Y. Chen, Q. L. Deng, and H. C. Wu, “A high-brightness diffractive stereoscopic display technology,” Displays 31(4-5), 169–174 (2010).

16.

C. Y. Chen, T. Y. Hsieh, Q. L. Deng, W. C. Su, and Z. S. Cheng, “Design of a novel symmetric microprism array for dual-view display,” Displays 31(2), 99–103 (2010).

OCIS Codes
(090.2890) Holography : Holographic optical elements
(120.2040) Instrumentation, measurement, and metrology : Displays
(230.1950) Optical devices : Diffraction gratings

ToC Category:
Holography

History
Original Manuscript: March 23, 2011
Revised Manuscript: May 3, 2011
Manuscript Accepted: May 4, 2011
Published: May 5, 2011

Citation
Wei-Chia Su, Chien- Yue Chen, and Yi-Fan Wang, "Stereogram implemented with a holographic image splitter," Opt. Express 19, 9942-9949 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-10-9942


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References

  1. J. Y. Son, V. V. Saveljev, Y. J. Choi, J. E. Bahn, S. K. Kim, and H. Choi, “Parameters for designing autostereoscopic imaging systems based on lenticular, parallax barrier, and integral photography plates,” Opt. Eng. 42(11), 3326–3333 (2003).
  2. W. X. Zhao, Q. H. Wang, A. H. Wang, and D. H. Li, “Autostereoscopic display based on two-layer lenticular lenses,” Opt. Lett. 35(24), 4127–4129 (2010). [PubMed]
  3. M. P. C. M. Krijn, S. T. de Zwart, D. K. G. de Boer, O. H. Willemsen, and M. Sluijter, “2-D/3-D displays based on switchable lenticulars,” J. Soc. Inf. Disp. 16(8), 847–855 (2008).
  4. Y. H. Tao, Q. H. Wang, J. Gu, W. X. Zhao, and D. H. Li, “Autostereoscopic three-dimensional projector based on two parallax barriers,” Opt. Lett. 34(20), 3220–3222 (2009). [PubMed]
  5. C. H. Chen, Y. P. Huang, S. C. Chuang, C. L. Wu, H. P. D. Shieh, W. Mphepö, C. T. Hsieh, and S. C. Hsu, “Liquid crystal panel for high efficiency barrier type autostereoscopic three-dimensional displays,” Appl. Opt. 48(18), 3446–3454 (2009). [PubMed]
  6. T. Järvenpää and M. Salmimaa, “Optical characterization of autostereoscopic 3-D displays,” J. Soc. Inf. Disp. 16(8), 825–833 (2008).
  7. C. H. Chen, H. H. Huang, T. H. Hsu, M.-H. Kuo, and C. H. Tsai, “Optical simulation for cross-talk evaluation and improvement of autostereoscopic 3-D displays with a projector array,” J. Soc. Inf. Disp. 18(9), 662–667 (2010).
  8. Q. H. Wang, X. F. Li, L. Zhou, A. H. Wang, and D. H. Li, “Cross-talk reduction by correcting the subpixel position in a multiview autostereoscopic three-dimensional display based on a lenticular sheet,” Appl. Opt. 50(7), B1–B5 (2011). [PubMed]
  9. C. Y. Chen, M. C. Chang, M. D. Ke, C. C. Lin, and Y. M. Chen, “A novel high brightness parallax barrier stereoscopy technology using a reflective crown grating,” Microw. Opt. Technol. Lett. 50(6), 1610–1616 (2008).
  10. D. Trayner and E. Orr, “Autostereoscopic display using holographic optical elements,” Proc. SPIE 2653, 65–74 (1996).
  11. D. Trayner and E. Orr, “Developments in autostereoscopic displays using holographic optical elements,” Proc. SPIE 3012, 167–174 (1997).
  12. B. C. Cho, J. S. Gu, W. Y. Kim, and E. S. Kim, “Multiview autostereoscopic 3D display system using volume holographic optical element,” Proc. SPIE 4471, 43–50 (2001).
  13. B. C. Cho, J. S. Gu, and E. S. Kim, “Implementation of multiview 3D display system using volume holographic optical element,” Proc. SPIE 4567, 224–232 (2002).
  14. Y. H. Cho, R. Kawade, T. Kubota, and Y. Kawakami, “Control of morphology and diffraction efficiency of holographic gratings using siloxane-containing reactive diluent,” Sci. Technol. Adv. Mater. 6(5), 435–442 (2005).
  15. C. Y. Chen, Q. L. Deng, and H. C. Wu, “A high-brightness diffractive stereoscopic display technology,” Displays 31(4-5), 169–174 (2010).
  16. C. Y. Chen, T. Y. Hsieh, Q. L. Deng, W. C. Su, and Z. S. Cheng, “Design of a novel symmetric microprism array for dual-view display,” Displays 31(2), 99–103 (2010).

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