Tag system with low-powered tag and depth sensing camera

Abstract

A tag system is proposed that offers a practical approach to ubiquitous computing. It provides small and low-power tags that are easy to distribute; does not need a special device to read the tags (in the future), thus enabling their use anytime, anywhere; and has a wide reading range in angle and distance that extends the design space of tag-based applications. The tag consists of a kind of liquid crystal (LC) and a retroreflector, and it sends its ID by switching the LC. A depth sensing camera that emits infrared (IR) is used as the tag reader; we assume that it will be part of the user's everyday devices, such as a smartphone. Experiments were conducted to confirm its potential, and a regular IR camera was also tested for comparison. The results show that the tag system has a wide readable range in terms of both distance (up to 8m) and viewing angle offset. Several applications were also developed to explore the design space. Finally, limitations of the current setup and possible improvements are discussed.

Low-Power Driving Technique for 1-Pixel Display Using an External Capacitor

“…There are various PDLC applications that focus on its high efficiency. In the active tag [1] mentioned before, using a PDLCD can extend the readable range. Eye glasses with PDLCDs to prompt the user to blink offer high transmittance and do not disturb daily activity [19].…”

“…Lowering the driving frequency was examined in [20], applying lower voltage at the cost of lower contrast, or the use of memory display are candidates for successfully reducing the power consumption, however they are not suitable for some applications such as the active tag [1] or shutters. The charge sharing technique would work effectively for 1-pixel displays.…”

“…Examples of LCD-based devices include the active tags that we have developed [1]. The tag consists of a 1-pixel display with PDLC (polymer dispersed liquid crystal), a retroreflector, a micro-controller and a power source, see Fig.…”

“…An IR-based depth sensing camera emitting continuous IR can be used as the tag reader. Since the transmittance of the PDLCD is high and the retroreflector reflects light strongly, the tag can be decoded even if its physical size occupies less [1]; one of the target applications of this technique. The tag consists of a PDLCD, a retroreflector, a micro-controller and a power source and sends its ID by switching the PDLCD.…”

Low power driving techniques for 1-pixel displays

“…The active tag that we have developed [1] is one example of such devices. It has a 1-pixel display with PDLC and switches it to send its ID.…”