LiFi Steerable Light

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LiFi communication has the potential of gigabits/sec data rate allowing much faster streaming of movies. It is also secure because light cannot penetrate walls. Only communication devices within illumination region can receive the data. However, there are drawbacks. First the light must stay on because illumination light is used for communication. Secondly LiFi is directional. It works best in line-of-sight. Away from the light source, illumination light becomes weaker leading to a lower data rate. Thirdly most of the light illuminates unintended area. This wastes LiFi signal. To mitigate these problems, an infrared(IR) LED or laser can be used as the transmitter source instead of the visible LED source for downlink. The uplink still uses WiFi because the upload data is usually small. The illumination light source is a white LED or other visible light source. The LiFi transmitter and illumination light sources are perpendicular to each other. A hot mirror which transmits visible light and reflects IR light can be inserted between the two at 45° angle. The LiFi light and the illumination light overlap spatially but separate spectrally as illustrated in Figure 1. The combined light source or light source module can be configured into a steerable light. The LiFi steerable light allows the user to access illumination and LiFi data anywhere within the steerable range. It guarantees line-of-sight illumination which means high data rate. Because it is a spot light, the waste of LiFi light is kept at minimum. Furthermore, the LiFi light and illumination light do not overlap spectrally. Because the two light sources are independent, the user can dim or even turn off the illumination light without affecting LiFi communication. Figure 2 shows the concept. To steer the light, a beam steering mechanism can be constructed out of a Fresnel lens and a rail system. The rail system comprises a vertical rail, inner rail/rails, and outer rails. The vertical rail is mounted on the inner rail/rails which are mounted on the outer rails. The light source module is mounted on the vertical rail. The rails can be moved by motors or manually. A Fresnel lens is placed in front of the light source module on the rail system. Figure 3 shows the side view and top view of the beam steering mechanism. Lateral translation of the light source along the rails relative to the fixed Fresnel lens allows the user to steer the illumination/LiFi beam to his/her desired location. The user can access high quality illumination and line-of-sight LiFi data at the same time. When he/she finishes the illumination, he/she can dim down or turn off the illumination light. Relative motion of the light source module toward or away from the Fresnel lens allows the user to change the size of the illumination/LiFi beam. This option allows more than one user to access LiFi by simply increasing the beam size. Mobile devices can be used to control the light. Hand gestures can also be another option if a camera is installed.


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  • Name:
    Chia Ming Chen
  • Type of entry:
    Team members:
    Huikai Xie
  • Profession:
    Business Owner/Manager
  • Patent status: