Displaying images on a plane of rotation via mutual inductance coupling wireless controls
Introduction
Human vision is generated by retinal photoreceptor cells, which release photo-pigment molecules under the light stimuli, and thus excite the sight neural currents [1]. Since the entire imaging process includes multiplex biochemical reactions that takes time, the temporary hysteresis of vision memory leads to the persistence of vision maintaining 50 – 200 ms. Based on this phenomenon, plenty of visual media, such as movie and cartoon, have been realized using a same fundamental principle [2]. That is, subsequently illuminating the pixels under the control of scan timing, and the imaging is realized via the persistence of vision.
We learn that the controllable cyclic scan of pixels is a universal requirement of image display, no matter the specific illumination mechanisms of pixels [3]. For instance, the magnetic-controlled electron-beam scan in cathode-ray tube (CRT) display, and the electronic signal driving in liquid crystal display (LCD) share the time-division scan principles basically same. Thereby, we consider that the collective movements of arranged illuminants may generate the vision effect equivalent to the pixel displaying. As a most representative behavior of cyclic scan, a rotating object (e.g., wheel or propeller) performs the vision of a circle plane. While a rectilinear array consisting of illuminant units is immobilized on a turntable, the stable image display on the plane of rotation would be possible, only if the timing control of illumination matches the rotation velocity. Following this inspiration, we here propose a rotating scan display scenario for the refit of rotatable objects, which enables the additional display function. Imagining that, the ad hoc screens based on common vehicle wheels or quadrotor helicopter propellers can conspicuously provide visible information (e.g., warnings or instructions) from various positions. The diversified origins of visible information may significantly enhance the information propagation efficiency in daily life.
In order to realize the image display function on the plane of rotation, there are two primary missions to be resolved. First, the rotating scan generating a 2D distribution of pixels are putting in the polar coordinates, other than the conventional Cartesian coordinates. Therefore, the pixel matrix of an image for the rotating scan display requires a coordinate transform. Second, the signals transmitting to the plane of rotation are confined by the cyclic rotation. The conventional electrical connections, such as slip-rings and brushes, inevitably confront the reliability and durability issues due to the vibration and friction. As a result, it would be better to transmit the signals through a wireless route [4]. In particular, the power supply for long-term display may rule out the standard commercial wireless modules (e.g., Bluetooth and Zigbee), due to the power consumption [5]. For these reasons, we prefer a feasible scenario with the passive electricity harvest capability and the simplified hardware implementation [6]. Here, a design based on the mutual inductance coupling is proposed in this work [7]. By employing a pair of coaxial coils, we experimentally show that the electrical signals can be wirelessly transmitted to the plane of rotation, together with the wireless transmission of electricity power. Without using sophisticated components and circuitries, the display function can be conveniently achieved. The scenario with cost-efficiency and long-term working reliability may significantly improve the user experience.
Section snippets
Display principle
On the basis of the aforementioned function requirements, we here discuss the display principle on the plane of rotation, and the feasible implementation approaches [8]. We first assume that the number of illuminant units for rotating scan is R. While they are immobilized on a rotatable substrate and arranged in a rectilinear form, the visual plane of rotation is given by R concentric rings as shown in Fig. 1a. Furthermore, a short stripe skimmed by a single illuminant unit under a timing
Basic hardware implementation
Based on the display principle we proposed above, the hardware implementation methods are further discussed. While the mechanical scanning display function is added, the rotation function cannot be affected. Consequently, the hardware system should be compact as much as possible. As shown in Fig. 3, the basic experimental setup is implemented by immobilizing an illuminant array on an electric motor. By the means of a turntable with proper rotary inertia, the mechanical rotation of motor
Noncontact electrical transmission
According to the requirement we proposed in the last section, the timing period signal Δt and power supply need to be transmitted to the rotating devices [6]. Obviously, the wired connection methods are unavailable. The slip-rings and electric brushes are also unreliable due to the shortcomings in stability and service life-time. To reduce the complexity of the overall system, the commercial wireless modules (e.g., Bluetooth and Zigbee) are also not appropriate. For these reasons, we here
Experimental demonstration and conclusion
Based on the principle analysis and hardware implementation above, a prototype of the rotation display screen was produced for the tests of displaying on the plane of rotation. In the experiments, we kept using the photographic work ′′Lena′′ as a representative. By utilizing the rectilinear illuminant array consisting of 40 color LEDs, the pixel density of image matrices Mr,θ(P) were set as 40 × 360 = 14400, as we discussed above. The rotation velocity ω variates in the range 300 – 2000 rpm.
The
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors are grateful to the Funding Program of Tianjin Higher Education Creative Team for the instrumentation assistance.
Jingjing Wu is an undergraduate student at Tianjin Normal University. She is pursing the B.E. degree in Communication Engineering, since 2017. She joined the Interdisciplinary Laboratory of Advanced Materials and Device (X-Lab) through the Excellent Undergraduate Training Pragram, in 2019, and executed the Undergraduate Entrepreneurial Creativity Research Project. Her research interest includes wireless information transmission and circuitry development.
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Jingjing Wu is an undergraduate student at Tianjin Normal University. She is pursing the B.E. degree in Communication Engineering, since 2017. She joined the Interdisciplinary Laboratory of Advanced Materials and Device (X-Lab) through the Excellent Undergraduate Training Pragram, in 2019, and executed the Undergraduate Entrepreneurial Creativity Research Project. Her research interest includes wireless information transmission and circuitry development.
Huanghui Shen is an undergraduate student at Tianjin Normal University. She is pursing the B.E. degree in Communication Engineering, since 2017. She joined the Interdisciplinary Laboratory of Advanced Materials and Device (X-Lab) through the Excellent Undergraduate Training Pragram, in 2019. Her research interest includes graphical information processing and computer graphics.
Ran Yin is an undergraduate student at Tianjin Normal University. She is pursing the B.S. degree in Electronic Information Science and Technology, since 2017. She joined the Interdisciplinary Laboratory of Advanced Materials and Device (X-Lab) through the Excellent Undergraduate Training Pragram, in 2019. Her research interest includes graphical information processing and pattern cognition.
Yashuo He is an undergraduate student at Tianjin Normal University. She is pursing the B.E. degree in Communication Engineering, since 2017. She joined the Interdisciplinary Laboratory of Advanced Materials and Device (X-Lab), in 2019, and executed the Undergraduate Entrepreneurial Creativity Research Project. Her research interest includes electromagnetic simulation analysis and wireless communications.
Jiatong Li is an undergraduate student at Tianjin Normal University. He is pursing the B.E. degree in Communication Engineering, since 2017. He joined the Interdisciplinary Laboratory of Advanced Materials and Device (X-Lab), in 2019. His research interest includes wireless networking algorithms and internet of things.
Cheng Wang is an assistant professor at Tianjin Normal University. He received the B.E. degree in Measurement Control Technology and Instrumentation from Xidian University, Xi′an, China, in 2006, the M.E. and Ph.D. degrees in Communication Engineering and Electrical Engineering from Nankai University, Tianjin, China, in 2010 and 2014, respectively. From 2012 to 2014, he worked in the Department of Mechanical Engineering, Columbia University, New York, United States, as a CSC joint-cultivation Ph.D. student, and switched his research interests into semiconductor physics. After an interdisciplinary postdoctoral research from 2015 to 2017, in Tsinghua University, Beijing, China, he joined Tianjin Normal University in 2017, as a principal investigator directing the Interdisciplinary Laboratory of Advanced Materials and Devices (X-Lab). He currently focuses on the researches of van der Waals heterostructures and two-dimensional devices, but still plays with electronic developments on occasion.
This work is partially funded by the Undergraduate Entrepreneurial Creativity Training Project of Tianjin (201910065372), the Natural Science Foundation of Tianjin Municipality (18JCYBJC86000), and the Natural Science Foundation of China (61901300).
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Jingjing Wu and Huanghui Shen are co-first authors.