Phase messaging method for time-of-flight cameras

Abstract

Ubiquitous light emitting devices and low-cost commercial digital cameras facilitate optical wireless communication system such as visual MIMO where handheld cameras communicate with electronic displays. While intensity-based optical communications are more prevalent in camera-display messaging, we present a novel method that uses modulated light phase for messaging and timeof-flight (ToF) cameras for receivers. With intensity-based methods, light signals can be degraded by reflections and ambient illumination. By comparison, communication using ToF cameras is more robust against challenging lighting conditions. Additionally, the concept of phase messaging can be combined with intensity messaging for a significant data rate advantage. In this work, we design and construct a phase messaging array (PMA), which is the first of its kind, to communicate to a ToF depth camera by manipulating the phase of the depth camera's infrared light signal. The array enables message variation spatially using a plane of infrared light emitting diodes and temporally by varying the induced phase shift. In this manner, the phase messaging array acts as the transmitter by electronically controlling the light signal phase. The ToF camera acts as the receiver by observing and recording a time-varying depth. We show a complete implementation of a 3 ⇥ 3 prototype array with custom hardware and demonstrating average bit accuracy as high as 97.8%. The prototype data rate with this approach is 1 Kbps that can be extended to approximately 10 Mbps.

Reading between the pixels: Photographic steganography for camera display messaging

“…Camera-Display Communication Electronic displays such as televisions, computer monitors, and projectors are traditionally used to display images, videos, and text -all human readable scenes. These devices can also display machinereadable images such as QR-codes [1,14,15,16,17,18,19,20]. Within the past 5 years, extensive work has been done to expand the capabilities of camera display messaging by increasing throughput.…”

Optimal radiometric calibration for camera-display communication

“…Recent work has been done in high speed visible light communications [32], but this work does not utilize existing displays and cameras and requires specialized hardware and LED devices. Time-of-flight cameras have recently been used for phase-based communication [39], but these methods require special hardware. Interest in cameradisplay messaging is also shared in the mobile communications domain.…”