Optimal projector configuration design for 300-Mpixel multi-projection ...

Optimal projector configuration design for 300-Mpixel multi-projection 3D display Jin-Ho Lee,1,* Juyong Park,1 Dongkyung Nam,1 Seo Young Choi,1 Du-Sik Park,1 and Chang Yeong Kim2 1

Samsung Electronics, SAIT, Advanced Media Lab, San14, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do, 446-712, South Korea Samsung Electronics, Digital Media & Communications R&D Center, Maetan3-dong, Yeongtong-gu, Suwon-si, Gyeonggi-do, 443-742, South Korea * [email protected]

2

Abstract: To achieve an immersive natural 3D experience on a large screen, a 300-Mpixel multi-projection 3D display that has a 100-inch screen and a 40° viewing angle has been developed. To increase the number of rays emanating from each pixel to 300 in the horizontal direction, three hundred projectors were used. The projector configuration is an important issue in generating a high-quality 3D image, the luminance characteristics were analyzed and the design was optimized to minimize the variation in the brightness of projected images. The rows of the projector arrays were repeatedly changed according to a predetermined row interval and the projectors were arranged in an equi-angular pitch toward the constant central point. As a result, we acquired very smooth motion parallax images without discontinuity. There is no limit of viewing distance, so natural 3D images can be viewed from 2 m to over 20 m. ©2013 Optical Society of America OCIS codes: (100.6890) Three-dimensional image processing; (120.2040) Displays; (220.4830) Systems design.

References and links 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

T. Inoue and H. Ohzu, “Accommodative responses to stereoscopic three-dimensional display,” Appl. Opt. 36(19), 4509–4515 (1997). Y. Takaki, “Super multi-view display with 128 viewpoints and viewpoint formation,” Proc. SPIE 7237, 72371T, 72371T-8 (2009). H. Nakanuma, H. Kamei, and Y. Takaki, “Natural 3D display with 128 directional images used for humanengineering evaluation,” Proc. SPIE 5664, 28–35 (2005). M. Kawakita, S. Iwasawa, R. Lopez-Gulliver, M. Makino, M. Chikama, S. Gurbuz, N. Inoue, M. Sakai, Y. Haino, and M. Sato, “200-inch glasses-free 3D display with wide viewing angle,” in Proceedings of NAB BEC (2012), 455–460. T. Balogh, “The holovizio system,” Proc. SPIE 6055, 60550U, 60550U-12 (2006). M. Kawakita, S. Iwasawa, M. Sakai, Y. Haino, M. Sato, and N. Inoue, “3D image quality of 200-inch glassesfree 3D display system,” Proc. SPIE 8288, 82880B, 82880B-8 (2012). Y. Takaki and N. Nago, “Multi-projection of lenticular displays to construct a 256-view super multi-view display,” Opt. Express 18(9), 8824–8835 (2010). K. Kikuta and Y. Takaki, “Development of SVGA resolution 128-directional display,” Proc. SPIE 6490, 64900U (2007). Y. Takaki, “Thin-type natural three-dimensional display with 72 directional images,” Proc. SPIE 5664, 56–63 (2005). K. Nagano, A. Jones, J. Liu, J. Busch, X. Yu, M. Bolas, and P. Debevec, “An autostereoscopic projector array optimized for 3D facial display,” in Proceedings of ACM SIGGRAPH (2013), Emerging Technologies Article No.3. J. Jurik, A. Jones, M. Bolas, and P. Debevec, “Prototyping a light field display involving direct observation of a video projector array,” in Proceedings of Computer Vision and Pattern Recognition Workshops (CVPRW) (2011), 15–20. S. Yoshida, M. Kawakita, and H. Ando, “Light-field generation by several screen types for glasses-free tabletop 3D display,” in Proceedings of 3DTV Conference (2011), 1–4. G. Wetztein, D. Lanman, M. Hirsch, and R. Raskar, “Tensor displays: Compressive light field synthesis using multilayer displays with directional backlighting,” ACM Trans. Graph. 31(4), 1–11 (2012).

#195287 - $15.00 USD Received 5 Aug 2013; revised 22 Oct 2013; accepted 22 Oct 2013; published 30 Oct 2013 (C) 2013 OSA 4 November 2013 | Vol. 21, No. 22 | DOI:10.1364/OE.21.026820 | OPTICS EXPRESS 26820

14. D. Fattal, Z. Peng, T. Tran, S. Vo, M. Fiorentino, J. Brug, and R. G. Beausoleil, “A multi-directional backlight for a wide-angle, glasses-free three-dimensional display,” Nature 495(7441), 348–351 (2013). 15. O. Willemsen, S. de Zwart, M. Hiddink, D. de Boer, and M. Krijn, “Multi-view 3D displays,” in SID Int. Symp. Digest Tech Papers (2007), 1154–1157. 16. N. A. Dodgson, “Analysis of the viewing zone of multi-view autostereoscopic displays,” Proc. SPIE 4660, 254– 265 (2002). 17. C. de Boer, R. Verleur, A. Heuvelman, and I. Heynderickx, “Added value of an autostereoscopic multiview 3-D display for advertising in a public environment,” Displays 31(1), 1–8 (2010). 18. F. Okano, “3DTV with integral imaging,” Proc. SPIE 6983, 69830N (2008). 19. T. Ito, “Future television, Super Hi-vision and beyond,” in Proceedings of IEEE Asian Solid-State Circuits Conference (2010), 1–4. 20. Projector keystone correction: http://www.projectorpeople.com/resources/keystone-correction.asp. 21. J. Park, D. Nam, S. Y. Choi, J.-H. Lee, D. S. Park, and C. Y. Kim, “Light field rendering of multi-view contents for high density light field 3D display,” in SID Int. Symp. Digest Tech Papers (2013), 667–670.

1. Introduction Recent spread of 3D TV and various 3D contents has increased the demand for natural 3D displays. Although stereoscopic displays in conjunction with polarized eyeglasses are commonly used to achieve 3D effects, accommodation-vergence conflict; disagreement between the focal point of the eyes and the intersection point of the lines of sight [1], may cause eyestrain, and viewers often feel uncomfortable due to having to wear special 3D eyeglasses. Various studies are currently underway to develop glasses-free 3D displays in order to solve these problems [2–19]. But, lenticular lenses used in multi-view displays [16– 18] decrease the resolution of images by increasing the number of light rays emanating from each pixel, which limits the angle and the distance at which 3D images can be clearly viewed. As a result, changes of parallax images become discontinuous, so natural 3D images cannot be displayed. Light-field displays are good candidates for showing real 3D images without decreasing image resolution. So, we developed a multi-projection 3D display to increase the density of light-field rays. We used 300 projectors to increase the number of light-field rays emanating from each pixel to 300 in the horizontal direction. When the number of projectors is increased, the 3D depth resolution and the motion parallax of images will be more finely expressed, but the uniformity in brightness distribution of 3D images could be deteriorated. Since each projector has a certain volume, the projectors must be arranged in multiple rows. When the amount of vertical spaces between projectors is increased, the keystone phenomenon [20], which occurs when a projector is aligned nonperpendicularly to a screen and results in a trapezoidal rather than a square image, could become more prominent. Such deviations among projectors produce differences in the space between light-field rays. In this study, the optimal projector configuration was designed to minimize the brightness variation of 3D images, which increases with increasing number of projectors. A 300-Mpixel multi-projection display was developed using an optimized design. It has a viewing angle of 40° and unlimited viewing distance, and shows natural 3D video images with very smooth motion parallax. 2. Operating principle and basic design Horizontal parallax only (HPO) light-field displays show images that only have horizontal parallax, so such displays require specially designed vertical diffuser screen [2–6]. Figure 1 shows the basic configuration and operating principle of the multi-projection 3D display. Numerous projectors are horizontally and vertically arranged to produce a large number of light-field rays. Each projector is arranged at a different angle to the screen in order to separate the light-field rays into individual light rays. 3D images only have horizontal parallax, and the screen must compensate for the differences in the vertical position of the projectors. So, the vertical diffuser screen must have small horizontal and large vertical diffusion angles. When this vertical diffuser screen is used, an image from one projector is seen as one vertical block. Because two side mirrors (which are not shown in Fig. 1) are


arranged outside of the projectors, the perceived image is composed of 600 vertical light-field blocks with 300 projectors. That is, each block corresponds to a combination of a projected image and its reflection by side mirrors.

Fig. 1. Basic configuration and operating principle of multi-projection 3D display.

Figure 2 shows the overhead view of the basic arrangement of the multi-projection 3D display. The basic layout is determined by the viewing angle (θ0), the horizontal length of the screen (WS), and the total number of projectors (n). Two side mirrors are arranged between the projector array and the screen, and are slightly tilted to increase the viewing angle. The tilt angle of a mirror (θm) and the distance between mirrors near the projector array (W) can be calculated from the viewing angle and the horizontal length of the screen. The length of the viewing zone (WV) is expressed by Eq. (1):

WV  2  DO  tan (0 / 2),

(1)

where Do denotes the viewing distance. The maximum deflection angle of the light beam (θ) can be calculated by Eq. (2) and Eq. (3):

WS : WV  DP1 : DP 2 ,

1 WV ). 2 DP 2 The tilt angle of a mirror is expressed by Eq. (4):

(2)

  tan 1 ( 

(3)

1 2

(4)

1 2

 m  (   proj . ),

where θproj. denotes the horizontal projection angle of a projector. The distance between mirrors near the projector array is expressed by Eq. (5):

W  2  DP  tan (m )  WS ,

(5)

where Dp denotes the projection distance. The horizontal pitch (p) between projectors is the quotient of the distance between mirrors near the projector array and the total number of projectors, which is expressed by Eq. (6):

p W / n

(6)


The number of projectors in the vertical direction (nv) must be larger than the value of the projector width (w) divided by the horizontal pitch to maintain the distance of the horizontal pitch. However, small nv is advantageous for minimizing the keystone effect. There, nv should be made as small as possible, despite the addition of the projector alignment margin (m). The number of projectors in the horizontal direction (nh) is larger than the value of the total number of projectors divided by nv. The values of nv and nh are calculated by Eq. (7) and Eq. (8):

p

nv  (w  m) p ,

(7)

nh  n nv .

(8)

W

w

Projector m Mirror

Dp

Screen  proj.

WS  Dp1o





Do

Dp2

Wv Fig. 2. Overhead view of basic arrangement of multi-projection 3D display.

3. Projector configuration design 3.1 Design issues It is important to maintain light-field ray uniformity in multi-projection 3D display. So, the projector configuration design must be optimized to minimize the variation in brightness, which increases with increasing number of projectors. Generally, a projector projects an image with 100% offset ratio as shown in Fig. 3(a), and all projectors are arranged toward the screen, so the keystone shapes and light-field ray distributions are changed according to the arrangement positions of the projectors as shown in Fig. 3(b).


Fig. 3. Projection characteristics: (a) projection offset ratio, (b) keystone phenomenon.

Figure 4 shows the simulation results in which 50 projectors, two side mirrors, and a 70inch vertical diffuser screen that has a 1° and 60° horizontal and vertical diffusion angles, respectively, were used. In Fig. 4(a), the amount of vertical spaces between the rows of projectors is minimized. In Fig. 4(b), the amount of vertical spaces between the rows of projectors is 4 times wider than that between the rows of projectors shown in Fig. 4(a). The top part of the figure shows the configuration of 50 projectors, the middle part of the figure shows the overlapped projection area of all projectors and the horizontal light-field ray distribution on the screen, and the bottom part of the figure shows the luminance distribution of the front view simulated using the light-field conversion algorithm [21]. The right figure of the bottom part shows the relevant peaks in the brightness spectra produced by the center value of each vertical image line in the left figure. The projection area is horizontally extended wider than the screen width according to the arrangement positions of the projectors, and the projection area beyond the screen is gathered into the screen by side mirrors. Because the shapes of the keystone change along the vertical positions of projectors, the shapes of the projection area are expressed with 5 kinds of shapes when the projectors are arranged in 5 rows, as shown in Fig. 4. Therefore, the keystones can be thought of as the repeated patterns of shape bounded by 5 rows of projectors. In the left figure of the middle part, the colors of the lines are used for distinguishing the columns of projectors, clearly. In Fig. 4(a), when the projectors are compactly arranged, the intervals between projected images are relatively uniform. But, when the vertical spaces between the rows of projectors are enlarged as shown in Fig. 4(b), the differences of keystone shape become more prominent and the intervals between projected images are non-uniformly changed, and vacant spaces are formed. This light-field ray lacking areas are clearly seen in the middle part of Fig. 4(b). As a #195287 - $15.00 USD Received 5 Aug 2013; revised 22 Oct 2013; accepted 22 Oct 2013; published 30 Oct 2013 (C) 2013 OSA 4 November 2013 | Vol. 21, No. 22 | DOI:10.1364/OE.21.026820 | OPTICS EXPRESS 26824

result, the light-field ray uniformity decreases, and luminance distribution of the simulated image shown in Fig. 4(b) gets worse than that of the image shown in Fig. 4(a). This phenomenon becomes more prominent with the increasing number of projectors.

Fig. 4. Simulation results of luminance distribution: (a) arranged in the minimized vertical spaces, (b) arranged in the enlarged vertical spaces.


Figure 5 shows another example in which 200 projectors are arranged in series. Despite the dense arrangement of the projectors such as shown in Fig. 4(a), there are significant differences in the shapes of the projected keystone images due to the differences in the vertical positions of the projectors. The shapes of the projection area are expressed with 20 kinds of shapes when the projectors are arranged in 20 rows, as shown in Fig. 5. Therefore, the keystones can be thought of as the repeated patterns of shape bounded by 20 rows of projectors. The light-field ray lacking areas shown in the right side of the middle figure in Fig. 5 are clearer than those shown in Fig. 4(b). Therefore, the variation in the brightness of the light-field display will be more prominent.

Fig. 5. Two hundred projectors arranged in series.

3.2 Mixing rows of projector arrays The rows of projector arrays are mixed based on a certain mixing rule to solve the problem described in section 3.1. Figure 6 shows the even numbered rows of projectors in the arrays shown in Fig. 5 are arranged in a descending order. When the projectors are arranged in arrays, the vertical tilt angles of the projectors are adjusted so that the light-field rays are collected on the screen plane. In the arrays shown in Fig. 5, the bottom projectors are #195287 - $15.00 USD Received 5 Aug 2013; revised 22 Oct 2013; accepted 22 Oct 2013; published 30 Oct 2013 (C) 2013 OSA 4 November 2013 | Vol. 21, No. 22 | DOI:10.1364/OE.21.026820 | OPTICS EXPRESS 26826

positively tilted, and the top ones are negatively tilted in series. However, optically adjacent projectors are placed next to each other and are arranged with oppositely oriented vertical tilt angles in Fig. 6. This arrangement of projectors produces a more uniform distribution of the light-field rays and significantly decreases the variation in the brightness of the light-field display image by eliminating the vacant spaces in the light-field ray lacking areas shown in the right side of the middle figure in Fig. 5.

Fig. 6. Improved arrangement of 200 projectors.

The second method for mixing rows of projector arrays is repeatedly changing the rows according to a predetermined row interval. Figure 7(a) shows the example of changing by 7low interval in the sixteen-row projector arrays. The eighth row of projectors is moved to the second row, the fifteenth row of projectors is moved to the third row. After the sixteenth row, this process is repeated again from the first row, so the sixth row of projectors is moved to the fourth row. The positions of all projectors are changed and the projectors are uniformly mixed by repeating this step. Figure 7(b) shows the new projector configuration after the positions of all projectors have been changed.


Fig. 7. Improved arrangement of projectors: (a) before mixing, (b) after mixing.

3.3 Horizontal pitch control The horizontal pitch between projectors can be acquired by an equi-distant arrangement as shown in Fig. 8(a), and an equi-angular arrangement as shown in Fig. 8(b). To obtain the target viewing angle, two side mirrors are arranged with a tilted angle. The imaginary extension lines of the side mirrors meet at the imaginary central point O, and all projectors are tilted toward O as shown in Fig. 8. In this study, we acquired more uniform image using an equi-angular arrangement. When the projectors are arranged for the horizontal pitch, arrangement with a constant central point in front of the screen is better than arrangement with a central point on the screen to make a uniform image. One side of the side mirror is attached to the screen edge, so there is a limit of tilting of the side mirror inside of the screen. If the projectors are arranged toward a central point on the screen with a different direction point of the side mirrors, nonuniform light-field ray distribution could be happened between the rays from the projectors and the reflected lays by the side mirrors. So, when the projectors and the side mirrors are arranged toward the same central point, the best uniform image is acquired.

Fig. 8. Projector arrangement for horizontal pitch: (a) equi-distant arrangement, (b) equiangular arrangement.


3.4 Simulation results Figure 9 shows the results of the luminance distribution analysis for the design proposed in sections 3.2–3.3. The simulation was performed based on a multi-projection 3D display consisting of 300 projectors, two side mirrors, and a 100-inch vertical diffuser screen that has 0.2° and 40° horizontal and vertical diffusion angles, respectively. The projector configuration is shown in the left side of the figure. The number of projectors in the vertical direction (nv) is 16 and the number of projectors in the horizontal direction (nh) is 19. In the 19 × 16 projector arrays, 4 projector’s positions in the outer place are withdrawn for the configuration of 300 projectors. The brightness variation ratio (BVR) is calculated using the equation of (max.  min.)/max. and the relevant peaks in the brightness spectra produced by the average value of each vertical image line. As shown in Fig. 9(a), when the projectors are arranged in series and in an equi-distant pitch, the luminance distribution of the 3D image presented on the screen is very inhomogeneous. As shown in Fig. 9(b), when the projectors are arranged in series and in an equi-angular pitch, the luminance distribution of the 3D image presented on the screen is more uniform than that of the 3D image shown in Fig. 9(a). As shown in Fig. 9(c), when the even numbered rows of the projector arrays are arranged in a descending order and the projectors are arranged in an equi-angular pitch, the luminance distribution of the 3D image presented on the screen is more uniform than those of the 3D images shown in Fig. 9(a) and Fig. 9(b). As shown in Fig. 9(d), when the rows of the projector arrays are repeatedly changed according to a predetermined row interval and the projectors are arranged in an equi-angular pitch, the luminance distribution of the 3D image presented on the screen is more uniform than those of any of the 3D images shown in Fig. 9(a) to Fig. 9(c).

Fig. 9. Results of luminance distribution analysis for multi-projection 3D display consisting of 300 projectors: (a) arranged in series, equi-distant pitch, (b) arranged in series, equi-angular pitch, (c) arranged in a descending order (only even numbered rows), equi-angular pitch, (d) arranged in a predetermined row interval, equi-angular pitch.


4. Prototype system We designed the 300-Mpixel multi-projection 3D display system with the design parameters listed in Table 1. The configuration parameters about our system are given in Table 2. Figure 10(a) shows the 100-inch (2,154 × 1,346 mm, 16:10 aspect ratio) 300-Mpixel multiprojection 3D display system designed and fabricated based on the optimal projector configuration design described in section 3. Three hundred projectors are attached to the angularly controllable jigs that adjust the tilt angle of the projectors, and they are embedded into the frame for the projector arrays as shown in Fig. 10(b). Performance criteria of projectors such as small size, short projection distance, high resolution, and low power consumption are important. We adopted Vivitek QUMI Q2 projectors (resolution 1,280 × 800 pixels, size 160 × 102.4 × 32.3 mm), which use light-emitting diode (LED) light sources. A vertical diffuser screen that has a 0.2° horizontal diffusion angle, which is slightly higher than the 0.17° projection angular pitch on the screen, and a 40° vertical diffusion angle was used. Two side mirrors were tilted through 9.17° to acquire a 40° viewing angle. Table 1. Design parameters for 300-Mpixel multi-projection display system.

Screen size Number of projectors (n) Viewing distance (Do) Viewing angle (θ0) Projection distance (Dp)

100-inch (2,154 × 1,346 mm) 300 3,000 mm 40° 3,411 mm

Table 2. Configuration parameters for 300-Mpixel multi-projection display system.

Length of viewing zone @ 3m (WV) Tilt angle of a mirror (θm) Distance between mirrors near the projector array (W) Distance from the screen to the imaginary central point O Horizontal angular pitch between projectors (toward O) Number of projectors in the vertical direction (rows, nv) Number of projectors in the horizontal direction (columns, nh)

2,184 mm 9.17° 3,255 mm 6,671 mm 0.061° 16 19

An image distribution system was also designed and assembled to input 1,280 × 800 resolution video signals into the 300 projectors. Figure 11 shows the structure of image distribution system. It is composed of a control personal computer (PC), 7 graphics rendering PCs, and several solid state drive (SSD) storage devices assembled as a redundant array of independent disks (RAID) for high-speed processing of 300-Mpixel-grade super-highresolution data. Three or two high-performance ATI FirePro V9800 graphics cards are installed in a graphics rendering PC. The graphics card can generate 6 outputs of 2,560 × 1,600 (WQXGA) video images, but only 3 ~5 outputs are used to smoothly and synchronously play video images. Seventy-five image division boards embedded into the video wall controllers, which divide one 2,560 × 1,600 image into four 1,280 × 800 HD (WXGA) images, are linked between the projectors and the graphics cards.


Fig. 10. 100-inch, 300-Mpixel multi-projection display system.

Fig. 11. Image distribution system.


Using this system, we realized not only graphics but also actual 3D light-field still images and moving images. Figure 12 shows the displayed 3D images of graphics and actual images. The 300-Mpixel multi-projection 3D display uses 300 directional rays in all 1,280 × 800 pixels to show real 3D images. We acquired very smooth motion parallax images without discontinuity in the viewing angle of 40 degrees. There is no limit of viewing distance, so natural 3D images can be viewed from 2 m to over 20 m, and the motion parallax of the images is smooth in that range.

Fig. 12. Displayed 3D images: (a) graphics, (b) actual 3D images.

Figure 13 shows horizontal parallax images viewed from the left, center, and right. Clear 3D depth expression is obtained in the range of 0.5 m front to 1.0 m rear from the screen, and the 3D depth expression is acceptable and is not significantly blurry in the range of 1.0 m front to 1.5 m rear from the screen.


Fig. 13. Displayed 3D images showing horizontal parallax: (a) & (d) left, (b) & (e) center, and (c) & (f) right views. (Media 1)

There are some remaining issues of brightness fluctuation despite the optimal projector configuration design. This is mainly due to the characteristics of anisotropic diffuser screen. Figure 14 shows the characteristics of anisotropic diffuser screen and the results of intensity distribution according to the projector positions. As shown in Fig. 14(a), the intensity of the transmitted light (I) is changed according to the incident angle of light-field ray (θi) and vertical viewing angle of the viewer (θw). So, gradient brightness non-uniformity happens according to the vertical arrangement positions of the projectors. As shown in Fig. 14(b), in the top side of the screen, the incident angle (θi,k) of the bottom side of projectors (Prj k) is relatively larger than the angle (θi,k + 1) of the top side of projectors (Prj k + 1), and the transmitted light intensity (Ik) of Prjk projectors is relatively smaller than the light intensity (Ik + 1) of Prjk + 1 projectors. On the contrary, in the bottom side of the screen, incident angle of Prjk + 1 projectors is relatively larger than that of Prj k projectors, the transmitted light intensity of Prjk + 1 projectors is relatively smaller than that of Prj k projectors. So the gradient stripes are alternatively happened. The brightness fluctuation is also affected by the horizontal diffusion angle of the diffuser screen. This horizontal fluctuation could be controlled by adopting appropriate horizontal


diffusion angle of the diffuser screen [5,6]. To decrease the horizontal non-uniformity, the projection angular pitch on the screen was designed smaller than the horizontal diffusion angle of the diffuser screen. The remaining variation in brightness could be decreased by increasing the vertical diffusion angle of the diffuser screen. If we can acquire more compact projectors, the brightness variation of the projected images will be further decreased by changing the configuration of the projector arrays to have fewer rows of projectors. By using the compensating images with vertical gradation, we can decrease the remaining brightness variation, also. It will be the next research topic.

Fig. 14. Description of (a) characteristics of anisotropic diffuser screen, (b) intensity distribution according to the projector positions.

Angular light-field ray distributions are somewhat still not uniform. Actually, it comes from controlling projection distances of the projectors to fit the image size on the screen when the projectors are virtually moved to the horizontally centered position of the projector arrays, as shown in Fig. 15(a). By the keystone phenomenon, the projected image sizes are changed according to the vertical arrangement positions of the projectors at the same projection distance. In this study, the projection distances are adjusted according to the vertical arrangement positions of the projectors, so the z-axial arrangement positions are different for each row of projectors. The projection distances of the positively tilted projectors at the bottom side of the arrays are shortened, but the projection distances of the negatively tilted projectors at the top side of the arrays are lengthened. As a result, horizontal angular


uniformity of light-field rays at each pixel is somewhat broken. Figure 15(b) shows the simulation result of the horizontal angular light-field ray distribution on the screen at the center pixel considering the different projection distances of the projectors. In the sparse light-field ray points, dark stripes are happened, and in the dense light-field ray points, bright stripes are happened. It can be fixed by adjusting all projectors to the same projection distance. But in that case, we have to endure some losses of light-field rays. The projection distances of all projectors have to be adjusted to those of the projectors with the longest projection distance, which is actually needed at the negatively tilted projectors in the top of the arrays, and as a result, some over projected rays beyond the screen could be lost.

Fig. 15. Description of (a) adjusted projection images on the screen by controlling projection distances, (b) horizontal angular light-field ray distribution on the screen at the center pixel.

5. Conclusion A 100-inch, 300-Mpixel multi-projection 3D display was developed using an optimized projector configuration design to increase the number of light-field rays up to 300 in all HD pixels in order to express natural 3D images with smooth motion parallax. The multiprojection 3D display has a viewing angle of 40° and shows natural 3D images without limiting the viewing distance. It also demonstrates the ultimate goal of future 3D TV and can be used in industrial applications and consumer electronics in the near future. Acknowledgments The camera image sources of the graphics images are produced by DreamHans Co. in South Korea.


Optimal projector configuration design for 300-Mpixel multi-projection ...

Optimal projector configuration design for 300-Mpixel multi-projection ...

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