Open Access
Add to BibSonomy
Abstract
This paper presents the Fantatrope, an improvement of the pre-cinematographic devices such as the zoetrope, which creates a comfortable 3D display with the addition of ultra-realistic full-color holograms. The Fantatrope is built with a set of holograms of 3D-printed figurines mounted on a cylinder rotating at constant speed. A stroboscopic RGB LED lamp synchronized with the rotation successively illuminates the different frames and the recorded character is animated like in a stop-motion movie. All principal functions of this new device can be adjusted and this paper evaluates its performances. The operation of the Fantatrope is successfully demonstrated and shows the effect of a true 3D display without the need for special glasses or other viewing aids.
© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
For more than a century, three-dimensional display technologies have been a major topic of research [1–6]. As written by Jason Geng in 2013 in his paper Three-dimensional display technologies [7], “To create a true 3D display is the Holy Grail of visualization technology.” Most of the current approaches use a stereoscopic principle [8] that shows the plasticity of objects well, but causes visual discomfort and fatigue [9–11]. The objective of this research is to create a comfortable 3D display that can show a short animation in full color. To achieve this goal, the hypothesis is that one can create such a device by combining holography with pre-cinematographic mechanisms, such as the zoetrope.
Holography, invented in 1948 by physicist Dennis Gabor [12], is the only technique that records the light scattered from an object and reconstructs it in real 3D. For a viewer, there is no difference between watching the real objects and watching its hologram, in particular with the latest generation of ultra-realistic full-color analog holograms, such as those recorded on the Ultimate U04 silver halide material [13].
The zoetrope, invented in 1834 by the mathematician William G. Horner [14] belongs to the family of pre-movie animation devices [15], which produce the illusion of motion from a rapid succession of static images. A classic zoetrope consists of a rotating cylinder with several slits cut vertically in its sides. A set of sequenced images is put on the inner surface of the cylinder as shown in Fig. 1. The user turns the cylinder by hand and looks through the slits at the opposite side of the interior to see a rapid succession of images alternating with black, producing the illusion of motion. Multiple viewers can observe the animation simultaneously through different slits. The set of images can be replaced easily with another one. The device is transportable and can work in any place with ambient light.
But the classic zoetrope has some limitations. As the device is turned by hand, the rotation speed and the animation are not constant. Furthermore, the animation is not observed directly by the users but through a slot. Another limitation is that zoetrope images are always displayed with a continuous motion as opposed to cinema, where each image is stopped shortly during the projection. This continuous motion creates blur for the viewer. Its intensity depends on the width of the slots and the speed of rotation. Large slots show brighter but blurred images, and narrow slots produce darker but sharper images. The faster the zoetrope is turned, the smoother the animation appears. If the speed is too low, the animation is perceived as jerky. The term “frame rate”, expressed in frames per second or fps—also called frame frequency, expressed in hertz—refers to the number of individual images or frames that consecutively appear on a display. A century ago, the first silent movies set a frame rate of 16 to 24 fps [16] to produce a continuously moving picture. However, this rate was chosen for large cinema screens of several meters. This experience is very different from observing a zoetrope, where the viewer is very close to a smaller image. The frame rate needed to have a fluid animation with a zoetrope has never been precisely established in the literature.
Public interest in this device faded at the beginning of the 20th century with the development of the cinema, but has for some years been renewed, as shown by the number of keywords in patents filed over 150 years for zoetropes and similar technologies (see Fig. 2).
The 3D zoetropes use the same operating principle as did the classic zoetrope, but move 3D objects instead of 2D images. Since the early twenty-first century and the appearance of 3D printers, several modern 3D zoetropes using 3D printed objects have been used for artwork, advertising, and entertainment, and are contemporary attractions as in the Ghibli Museum [17] or the Pixar’s Toy Story 3D zoetrope [18]. These 3D zoetropes use flashing strobe lights to illuminate the models and are motorized. The 3D zoetropes show several improvements over the classic zoetrope: a motor rotates the 3D zoetrope at a constant speed; 3D objects are more attractive and offer a more realistic experience than do 2D images; the moving objects are directly observable by many people at the same time; and the flashing strobe light produces clearer and sharper distortion-free results.
An important limitation is the flickering created by the strobe light. Flickering is a visible luminance variation between images; its consecutive appear on a display can cause various symptoms, such as eyestrain and headaches. Flickering rates and frame rates are not the same. The frame rate necessary to prevent the perception of flicker differs greatly, depending on the frequency, the amplitude, the intensity, the wavelengths, the brightness change, and the viewing environment. The observer can be also influenced by factors such as stress and fatigue [19]. In addition, the 3D zoetrope has other limitations: the models appear all in motion at the same time; the animation can only be observed in darkness to get the strobe light effect; large 3D zoetropes need dozens of strobe lights to illuminate all the characters simultaneously; 3D models must be fixed/glued very precisely on the turning table and are not easily demountable; and large 3D zoetrope are heavy, bulky, fragile, and difficult to transport. As a result, the field of applications is very limited, and the general public has very little opportunity to see large zoetropes, except for exceptional exhibitions.
Few researchers have tried to combine holography with the zoetrope operating principle. In 1986 Betsy Connors [20] chose the setup of the praxinoscope [21], the zoetrope’s successor, to create a holographic animation. The praxinoscope has replaced the narrow viewing slits of the zoetrope with an inner circle of mirrors. For her holographic praxinoscope, Connors recorded eight monochrome analog holograms placed so that the reflections of the images in the mirrors appeared to be stationary as the wheel turned. The main disadvantage of the praxinoscope is that the animation could not be observed directly but only through mirrors. This created image distortions and a distance to the viewer. In 2010, a Disney research team created an interactive zoetrope [22] with a single hologram showing eight different facial expressions of a talking head. This team recorded a monochrome hologram using a multiplexing technique that allows recording many images into the same hologram. The final image is used to animate a talking character's mouth in real time in response to human speech. These two first attempts can be improved a lot thanks to the progress made in recent years in full-color holography and RGB LED (Light-Emitting Diode) illumination.
The purpose of this research is to build a new 3D display called the Fantatrope. To continue a long tradition of naming, the name Fantatrope (or Fantasmatrope) is composed of two Greek root words: Phantasma (ghost) and Tropos (turning). This new 3D display combines the advantages of the previously described devices while correcting their limitations and improving the results. To build the Fantatrope, a set of ultra-realistic full-color analog holograms of 3D printed objects are recorded. The images are then mounted in a rotating cylinder and illuminated with a synchronized RGB (Red Green Blue) strobe LED. All principal functions of this new device can be adjusted, and this paper evaluates its performances.
2. Materials and methods
2.1. Material to record holograms
The set of ultra-realistic full-color analog holograms were recorded on silver-halide holographic Ultimate U04 glass plates 4”x5”. This material is specially designed for recording full-color analog holograms without any diffusion and is set to iso-panchromatic for all the common visible lasers used in color holography. The main advantage of silver-halide emulsions compared with photopolymers is a much higher sensitivity (300 times higher); they therefore require only low-power lasers to record holograms. Furthermore, a short exposure time is always recommended in analog holography because of vibration and movement problems. Ultimate U04 can also be coated on glass plates and film, and needs a wet processing. The material on which the emulsion is coated is important for the final quality of the hologram, and the best choice is glass because it is mechanically stable and optically inactive.
2.2. Method to create the content
The content for the Fantatrope was created with stop-motion animation [23]. There are many different types of stop-motion animation, such as object animation, clay animation (or Claymation), puppet animation, and cut-out animation. During the hologram recording, the subject has to be very stable to get a bright image. To avoid any moving, a set of 3D printed characters was chosen instead of animating a puppet or clay model. Recent American blockbuster stop-motion animation movies like Coraline or Kubo and the Two Strings from LAIKA studio [24] use similar techniques of production.
All the elements of the scene, the main character of the animation and the background, were designed with Autodesk's Tinkercad, a free online 3D CAD (Computer Aided Design) software. A cyclic sequence of different poses was then created, and the elements were printed by an FDM (Fused Deposition Modeling) monochrome 3D printer [25] with a white PLA (Polylactic Acid) filament, and then painted by hand with Tamiya Colour acrylic paint.
The background was fixed in a rigid wooden box, and the different 3D printed characters, corresponding to the different animation phases, were placed one after another in the box to allow the recording of the holograms.
2.3. Method to record holograms
Holograms were recorded on U04 glass plate with the single-beam method introduced by Yuri Denisyuk in 1963 [26]. This method allows the recording of ultra-realistic [27] holograms with a 180° parallax, both horizontally and vertically. A typical Denisyuk single-beam full-color setup [28] uses three different lasers (red, green, and blue). The three laser beams are combined with an X-cube prism to get a white laser beam and are passed through the same beam expander and the same spatial filter. The divergent beam illuminates, with an angle of 45 degrees, both the holographic plate and the real object (see Fig. 3).
To record the different holograms, the three RGB lasers used were as follows: a red Thorlabs HeNe 633 nm 20 mW, a green Cobolt DPSS (Diode-Pumped Solid-State) 532 nm adjusted to 20 mW, and a blue Cobolt DPSS 473 nm adjusted to 20 mW.
2.4. Method of positioning the character before recording
Onion skinning is a procedure usually used in stop-motion animation to see two different frames at the same time. With this technique, the animator can decide how to record a new image based on the previous image in the sequence, to move characters and give a smooth motion.
In the same way, in order to place the different objects in the recording box with the greatest precision, a holographic onion-skin method was applied by replacing the first transparent hologram at its recording position, to observe both images at the same time under laser illumination and to check that the new character was well positioned.
2.5. Method to calculate the exposure time
The exposure time has to be calculated before recording the holograms. The exposure time t (s) for a given holographic material depends on the sensitivity of the material H (J/cm2) and on the intensity of the lasers E (W/cm2) at the position of the holographic plate. The exposure time is given by the following expression:
The sensitivity of U04 is 200 μJ/cm2 per laser for a full-colour (RGB) hologram. The intensity of each laser at the position of the holographic plate was measured with a power-meter before each recording and the correct exposure time was calculated.2.6. Method to develop holograms
Each hologram was developed with the two baths of chemicals recommended by the manufacturer. These chemicals are safe for both holographers and the environment and are easy to use. The processing steps are shown in Table 1. After drying, a black adhesive was laminated on the back of each hologram to increase the contrast and protect the gelatin from scratches.
Table 1. Standard Ultimate U04 processing steps
2.7. Method to create the illusion of movement
The method to create the illusion of movement used the zoetrope principle. Holograms were arranged in a chronological sequence, mounted in an acrylic cylinder with regularly placed frames. A Direct Current (DC) gear motor, fixed in a pedestal and attached under the cylinder, rotated the device clockwise at a constant speed. To create a rapid succession of images producing the illusion of movement, a single strobe light quickly flashed the holograms one after the other.
To illuminate and reconstruct the hologram, the lamp has to be placed facing the image at the correct angle and position. The choice of the illumination source is critical in full-color reflection holography, because the light must be a source point and match the wavelengths of the original recording lasers. RGB LEDs offer currently the best solution, because their wavelengths are centered on the lasers’ wavelengths, with no unwanted colors, which usually create diffusion [29]. To illuminate the Fantatrope, a 30 W RGB LED was chosen and placed at 50 cm from the center of the hologram at a 45-degree angle with a rectangle exit pupil located in front. In addition, the color balance of the RGB LED was electronically adjustable. Our RGB LED was narrow bands and had three spikes: a red 630 nm, a green 530 nm and a blue 460 nm. The spectrum and the color gamut in CIE 1931 color space of our RGB LED are shown in Fig. 4(a) and Fig. 4(b).
A central processing unit (CPU) installed in the pedestal simultaneously controlled three tasks: the rotation speed of the motor, the sound emitted by the speaker, and the flash duration. Magnets were positioned under each hologram; when the cylinder rotated, flashes were triggered by the magnetic sensor connected to the CPU. The electrical behavior of the RGB LED was controlled by a field-effect transistor (FET) and the CPU. A background melody was played when the Fantatrope turned. The complete electronic block diagram is shown in Fig. 5.
2.8. Method to get a sharp image
To get a sharp image, the stroboscopic light has to freeze each frame of the rotating Fantatrope. A stroboscope or strobe produces short and repetitive flashes of light with a rate adjustable to different frequencies. Its parameters are the duration of the flash or strobe rate, the period between two flashes or flash rate, and the intensity of each flash. As the images are illuminated one after another, the flash rate is always the same as the frame rate.
An image appears fixed and sharp when, during the strobe rate, a point in the image travels a distance smaller than the resolving power of the human eye. Resolving or separating power is the capacity of an optical instrument to resolve two points that are close together. The separating power of a normal eye α, is 3.10−4 radians or 1 minute of angle (1/60 degrees) [30]. For a given distance D between an image and an observer, the separating distance d between two undistinguished points is given by the following expression:
The calculations show that for a distance of one meter, the separating distance is about 3.10−4 m or 0.3 mm (see Fig. 6).
Fig. 6 Separating distance d between two undistinguished points at one meter (figure not drawn to scale).
So at a given distance and for each rotation speed, there is a maximal strobe rate at which an observer cannot see any blur in the image. The maximal strobe rate t (s) is given by the following expression:
where α is the separating power of a normal eye, D the distance between image and observer, ω (rad/s) the angular speed of the Fantatrope and r (m) the radius of the cylinder.The relationship between the rotation speed ω (rad/s), the frame and flash rate F (Hz) and the number N of images in the Fantatrope is given by the expression:
The maximal strobe rate t (s) is given by expression (5):To solve the motion blur problem, the CPU had to be programmed to adjust the duration of the flash automatically, according to the frames number, the radius of the base, the observation distance, and the frame rate.2.9. Method to get a smooth animation
A century ago, the minimum frame rate set by the first silent movies to produce a continuously moving picture for large cinema screens, was 16 fps. This experience is very different from observing the Fantatrope, where the viewer is very close to a smaller image. The following subjective survey was carried out, to determine the minimum frame rate needed to get a smooth animation without jerking for the Fantatrope. This frame rate was then compared with the value of 16 fps.
A group of 12 people of different nationalities, between the ages of 23 and 50 years, participated in a survey. All participants had a normal or corrected-to-normal vision and provided informed consent. The group consisted of three women and nine men. The cylinder was placed 1.50 m high on the pedestal to allow easier observation at a distance of one meter by viewers who were free to move from right to left (see Fig. 7). This distance prevented motion blur according to the previous method and unwanted contact with the rotating device. The RGB white LED flashed as each successive frame passed the same spot. The room was illuminated with ambient light at 150 lumen/m2.
The rotation speed of the device was gradually increased from zero, and the test persons were asked the following question in the survey: “At what moment does the motion of the character become fluid”? Frame rates according to the test persons’ answers were measured with an oscilloscope and collected for analysis. Mean value and standard deviation were then calculated. A one-sample t test was then applied to compare the mean with the value of 16.
3. Results
3.1. Content
An original 3D model of the main character of the animation, named Angry Boy, was created according to the method. The character had round shapes to be easy to paint with different colors. To accentuate the 3D effect of the scene and give more depth to the holographic scene, a 2.5-D bas-relief background was also created as shown in Fig. 8(a). For the first animation, a very simple movement of the character from the bottom up was imagined. In order to reduce the number of different frames and the number of characters to print, a cyclic sequence of twelve images was created with five poses played twice forward and backwards, in the following order: 1, 2, 3, 4, 5, 6, 7, 6, 5, 4, 3 and 2, as shown in Fig. 8(b).
Fig. 8 Computer Generated Models: 3D “Angry Boy” character and 2.5-D background (a), and the complete cyclic sequence (b).
The seven different characters, related to the seven different images, were 6 to 7 cm high (see Fig. 9(a)) and printed together with the background. It can be noted that the FDM monochrome 3D printer left small printing defects. Sandpaper was used to largely remove them. Different elements were then painted by hand, creating new small imperfections and irregularities between the characters, but the final result remained homogeneous (see Fig. 9(b)).
Fig. 9 The seven different 3D printed characters of the animation before (a) and after painting (b). The different characters are printed with an FDM monochrome 3D printer and painted by hand with acrylic paint.
3.2. Recording and developing holograms
The first 4”x5” hologram was recorded according to the Denisyuk method and developed with the two baths of chemicals recommended by the manufacturer. The intensity of each laser at the position of the holographic plate, measured with a power-meter, was 17 μW/cm2, and the exposure time calculated according to formula (1) was 12 seconds. An ultra-realistic, very bright, colorful and transparent image with a 180° parallax, both horizontally and vertically, was obtained (see Fig. 10(a)). A video showing this hologram and its large field of view is given in Visualization 1.
Fig. 10 Three different views of an ultra-realistic, very bright, colorful, and transparent full-colour hologram (a). Under the white laser beam, the new character, corresponding to the new pose, shares the same space with the previous hologram. The background and its holographic image merge and become indistinguishable. (b). Final sequence of twelve holograms (c).
The holographic onion-skin method was applied by replacing the first transparent hologram at its recording position, to check that the new character, corresponding to the new pose, was well positioned. At this moment, the real background and its holographic image merged and became indistinguishable (see Fig. 10(b)). The process was repeated to record twelve holograms with the same brightness and transparency. The final holographic sequence is shown on Fig. 10(c). All the holograms were successful at the first recording.
3.3. Fantatrope assembly
The twelve holograms were mounted on an acrylic cylinder. The cylinder had a diameter of 45 cm with twelve regularly placed frames, each measuring 10 cm horizontally and 12.7 cm vertically. A DC gear motor (fixed with the controller in a pedestal) attached under the cylinder rotated the device clockwise at a constant speed (from 0 to 500 rpm). The schematic diagram for the proposed Fantatrope structure is shown in Fig. 11(a). When rotation speed of the cylinder accelerated and the holograms were illuminated by the RGB LED strobe light, the character recorded on the holograms appeared to the viewer as if it was in motion (see Fig. 11(b)). First observations showed that the Fantatrope could work well without a dark room, and the flickering of the strobe light was very diminished by the room illumination.
Fig. 11 Schematic diagram for the proposed Fantatrope structure (a). When rotation speed of the cylinder accelerated the character appeared if it was in motion (b).
A video of the Fantatrope in action is given in Visualization 2. To obtain high quality single images, this video was recorded using 24 frames in progressive mode. The image sensor capturing the images was synchronized with the pulsing light source in order to avoid interference and flicker artifacts. The Visualization 2 parameters are shown in Table 2.
Table 2. Visualization 2 parameters.
3.4. Motion blur
To solve the motion blur problem, the CPU was programmed according to formula (5) to automatically adjust the duration of the flash, with the frames number (12 holograms), the radius of the base (0.225 m), the distance from the viewer (1 m), and the frame rate. The observations made confirmed that there was no blur in the image whatever the speed of rotation of the cylinder. When the rotation speed of the Fantatrope increased, the duration of the strobe rate decreased in a non-linear way, as shown in Fig. 12.
3.5. Smooth animation
The mean values and the standard deviations of all participants' answers to the question (“At what moment does the motion of the character become fluid?”) were calculated. The mean was 10.42 and the standard deviation was 1.16. Figure 13 shows the bar-chart distribution of responses.
The difference between the hypothetical mean and the actual mean was 5.58, and the 95% confidence interval of this difference was from −6.3170 to −4.8430. The two-tailed p value was less than 0.0001. By conventional criteria, this difference is considered to be extremely statistically significant.
4. Discussion
The different results obtained confirm the initial hypothesis. It is possible to create a display that can show a short full-colour animation in real 3D by combining the holographic technique with the zoetrope principle. The optimal operating parameters for this Fantatrope to get a fluid motion of the character without blur for a viewer placed at a distance of one meter are to rotate the device at a minimum frame rate of 11 fps in a room illuminated with ambient light like in a theatre and without any direct lighting other than the stroboscopic light.
The use of holographic glass plates made it easy to record the twelve different holograms necessary for the Fantatrope. After processing, the images obtained were ultra-realistic, very bright, colorful, and transparent, with a full parallax of 180°. For the viewer, there was no difference between watching the real objects and watching the holograms. These holograms can be now used as masters to make contact copies on silver-halide or photopolymer films. Theses copies are no longer only behind the recording glass plate, but can be “in between” or even totally floating in front of it. Modern audiences like this kind of 3D transplane images, which are spectacular and fascinating. Holograms on glass can be broken during transport, but a Fantatrope using holograms on films rather than on glass will be lighter, more transportable, and more solid. Masters can also be used to produce copies of holograms and zoetropes in series.
The use of 3D printed objects was a good choice, because they allowed us to create a fluid movement that could be calculated in advance with a definite number of poses. The use of a puppet would have been more difficult, and it could have moved when recording holograms. Defects created by the printing and painting can be solved with the use of a colour 3D printer with a better definition.
This first test presented a very simple movement of the character from the bottom up. It is possible to use the same technique to create a more complex and fluid animation with gushing images.
The results of the survey about jerking indicated that, for this Fantatrope, a frame rate of 10.42 fps was enough to get the sense of fluid motion. The calculated p value confirmed that there is a big difference between this result and the theory about frame rates set by the first silent movies to produce a continuously moving picture. As fluent motion can be observed with low frame rates, it becomes possible to imagine longer content for the Fantatrope in the future.
The Fantatrope has corrected the main defects of the classic zoetrope, because the animation is now observed directly by the users and not through a slot. Moreover, the blur created by the constant rotation of the device, can be controlled with the CPU.
In contrast to the 3D zoetrope, the Fantatrope shows only one character in movement in the same time. A single RGB LED strobe light was needed to illuminate the new device, whereas dozens of lamps are needed for large 3D zoetropes. If the Fantatrope is placed in the middle of a room, it is possible to increase the number of strobe lights to augment the viewpoints and the number of spectators. The Fantatrope structure is very light and easy to assemble and disassemble. The Fantatrope can be flattened and carried easily. It is also possible to change the set of holograms to play other movies. Furthermore, it was not necessary to operate in the dark, since the Fantatrope can work with an ambient illumination. For all these reasons, the number of potential applications increases.
First observations show that the flickering of the RGB LED strobe light is significantly diminished thanks to the room illumination. Perception of flicker of a pulsed light source differs strongly from one test person to another and with the ambient light. A larger number of test persons and room illumination conditions would be necessary to study the particular flickering of the Fantatrope and can be the subject of further research.
5. Conclusion
In this research we have presented the construction of the Fantatrope, a comfortable 3D display that can show a short animation in full colour without the need for special glasses or other viewing aids. When this new device plays at a frame rate greater than 11 fps with ambient light, 3D objects recorded on the holograms appear to a viewer as if they were moving with a fluid motion.
The Fantatrope can work in a public room and does not require a dark room. It is lightweight, easy to transport, and needs only a single strobe light to work. The set of holograms can be easily changed, and the same Fantatrope can play different movies. Applications for this new device include entertainment parks, museums, nightclubs, or malls. The display can also be used for movie trailers in theaters and artistic creations. The Fantatrope can boost the popularity of ultra-realistic full-colour holograms and meets the expectations of a modern audience that likes 3D moving images.
Funding
Institute for Information and communications Technology Promotion (IITP) (IITP-2018-2015-0-00448).
References
1. T. Sugie, T. Akamatsu, T. Nishitsuji, R. Hirayama, N. Masuda, H. Nakayama, Y. Ichihashi, A. Shiraki, M. Oikawa, N. Takada, Y. Endo, T. Kakue, T. Shimobaba, and T. Ito, “High-performance parallel computing for next-generation holographic imaging,” Nat. Electron. 1(4), 254–259 (2018). [CrossRef]
2. H. Liao, “Super long viewing distance light homogeneous emitting three-dimensional display,” Sci. Rep. 5(1), 9532 (2015). [CrossRef] [PubMed]
3. S. Yamada, T. Kakue, T. Shimobaba, and T. Ito, “Interactive Holographic Display Based on Finger Gestures,” Sci. Rep. 8(1), 2010 (2018). [CrossRef] [PubMed]
4. N. A. Dodgson, “Autostereoscopic 3D displays,” Computer 38(8), 31–36 (2005). [CrossRef]
5. Y. Lim, K. Hong, H. Kim, H. E. Kim, E. Y. Chang, S. Lee, T. Kim, J. Nam, H. G. Choo, J. Kim, and J. Hahn, “360-degree tabletop electronic holographic display,” Opt. Express 24(22), 24999–25009 (2016). [CrossRef] [PubMed]
6. E. Y. Chang, J. Choi, S. Lee, S. Kwon, J. Yoo, M. Park, and J. Kim, “360-degree color hologram generation for real 3D objects,” Appl. Opt. 57(1), A91–A100 (2018). [CrossRef] [PubMed]
7. J. Geng, “Three-dimensional display technologies,” Adv. Opt. Photonics 5(4), 456–535 (2013). [CrossRef] [PubMed]
8. K. N. Ogle, “Some Aspects of Stereoscopic Depth Perception,” J. Opt. Soc. Am. 57(9), 1073–1081 (1967). [CrossRef] [PubMed]
9. M. Lambooij, W. Ijsselsteijn, M. Fortuin, and I. Heynderickx, “Visual discomfort and visual fatigue of stereoscopic displays: a review,” J. Imaging Sci. Technol. 53(3), 30201 (2009). [CrossRef]
10. J. C. A. Read, J. Simonotto, I. Bohr, A. Godfrey, B. Galna, L. Rochester, and T. V. Smulders, “Balance and coordination after viewing stereoscopic 3D television,” R. Soc. Open Sci. 2(7), 140522 (2015). [CrossRef] [PubMed]
11. S. Reichelt, R. Häussler, G. Fütterer, and N. Leister, “Depth cues in human visual perception and their realization in 3D displays,” Proc. SPIE 7690(1), 76900B (2010). [CrossRef]
12. D. Gabor, “A new microscopic principle,” Nature 161(4098), 777–778 (1948). [CrossRef] [PubMed]
13. P. Gentet, Y. Gentet, and S.H. Lee, “Ultimate 04 the new reference for ultra-realistic color holography,” in 2017 International Conference on Emerging Trends & Innovation in ICT (ICEI) (IEEE, 2017), pp. 162–166. [CrossRef]
14. W. G. Horner, “XI. On the properties of the Dædaleum, a new instrument of optical illusion,” Philos. Mag. 3, 36–41 (1834).
15. N. J. Wade, “Capturing motion and depth before cinematography,” J. Hist. Neurosci. 25(1), 3–22 (2016). [CrossRef] [PubMed]
16. J. Card, Seductive Cinema: The Art of Silent Film (University Of Minnesota, 1999).
17. R. Denison, “Anime tourism: discursive construction and reception of the Studio Ghibli Art Museum,” Jpn. Forum 22(3–4), 545–563 (2010). [CrossRef]
18. E. Markham, “Human after All: Pixar: 20 Years of Animation,” Screen Education 47, 50–54 (2007).
19. S. W. Davis, “Auditory and visual flickerfusion as measures of fatigue,” Am. J. Psychol. 68(4), 654–657 (1955). [CrossRef] [PubMed]
20. B. Connors, Holographic moving images, dissertation, MIT, 1986.
21. J. Kermabon, Du praxinoscope au cellulo: un demi-siècle de cinéma d'animation en France (1892–1948) (Scope, 2007).
22. L. Smoot, K. Bassett, K. S. Hart, D. Burman, and D. A. Romrell, “An interactive zoetrope for the animation of solid figurines and holographic projections,” in SIGGRAPH Emerging Technologies (ACM, 2010), article 6.
23. K. A. Priebe, The advanced art of stop-motion animation (Cengage Learning, 2011).
24. S. Emerson, “Visual effects at LAIKA, a crossroads of art and technology,” in ACM SIGGRAPH 2015 Talks (ACM, 2015), article 1.
25. K. Kun, “Reconstruction and development of a 3D printer using FDM technology,” Procedia Eng. 149, 203–211 (2016). [CrossRef]
26. Y. N. Denisyuk, “On the reproduction of the optical properties of an object by the wave field of its scattered radiation,” Opt. Spectrosc. (USSR) 14, 279–284 (1963).
27. H. Bjelkhagen and D. Brotherton-Ratcliffe, Ultra-realistic imaging: advanced techniques in analog and digital colour holography (CRC, 2016).
28. S. Graham and S. Zacharovas, Practical Holography, Fourth Edition (CRC, 2015).
29. P. Gentet, Y. Gentet, and S. H. Lee, “New LED’s Wavelengths Improve Drastically the Quality of Illumination of Pulsed Digital Holograms,” in Digital Holography and Three-Dimensional Imaging (Optical Society of America, 2017), paper M3A–4.
30. H. Hartridge, “Visual acuity and the resolving power of the eye,” J. Physiol. 57(1-2), 52–67 (1922). [CrossRef] [PubMed]
