Using An OLED Display’s Light For Embedded Sensors

October 24, 2024 by Maya Posch 8 Comments

These days displays are increasingly expected to be bidirectional devices, accepting not only touch inputs, but also to integrate fingerprint sensing and even somehow combine a camera with a display without punching a hole through said display. Used primarily on smartphone displays, these attempts have been met with varying degrees of success. But a paper published in the Communications Engineering journal describes a version which combines an OLED with photosensors in the same structure — a design that may provide a way to make such features much more effective.

The article by [Chul Kim] and colleagues of the Samsung Display Research Center in South Korea the construction of these bidirectional OLED displays is described, featuring the standard OLED pixels as well as an organic photodiode (OPD) placed side-by-side. Focusing on the OLED’s green light for its absorption characteristics with the human skin, the researchers were able to use the produced OLED/OPD hybrid display for fingerprint recognition, as well as a range of cardiovascular markers, including heart rate, blood pressure, etc.

The basic principle behind these measurements involves photoplethysmography, which is commonly used in commercially available pulse oximeters. Before these hybrid displays can make their way into commercial devices, there are still a few technical challenges to deal with, in particular electrical and optical leakage. The sample demonstrated appears to work well in this regard, but the proof is always in the transition from the lab to mass-production. We have to admit that it would be rather cool to have a display that can also handle touch, fingerprints and record PPG data without any special layers or sensor chips.

Keeping Tabs On An Undergraduate Projects Lab’s Door Status

October 24, 2024 by Maya Posch 18 Comments

Over at the University of Wisconsin’s Undergraduate Projects Lab (UPL) there’s been a way to check whether this room is open for general use by CS undergraduates and others practically for most of the decades that it has existed. Most recently [Andrew Moses] gave improving on the then latest, machine vision-based iteration a shot. Starting off with a historical retrospective, the 1990s version saw a $15 camera combined with a Mac IIcx running a video grabber, an FTP server and an HP workstation that’d try to fetch the latest FTP image.

As the accuracy of this system means the difference between standing all forlorn in front of a closed UPL door and happily waddling into the room to work on some projects, it’s obvious that any new system had to be as robust as possible. The machine vision based version that got installed previously seemed fancy: it used a Logitech C920 webcam, a YOLOv7 MV model to count humanoids and a tie into Discord to report the results. The problem here was that this would sometimes count items like chairs as people, and there was the slight issue that people in the room didn’t equate an open door, as the room may be used for a meeting.

Thus the solution was changed to keeping track of whether the door was open, using a sensor on the two doors into the room. Sadly, the captive-portal-and-login-based WiFi made the straightforward approach with a reed sensor, a magnet and an ESP32 too much of a liability. Instead the sensor would have to communicate with a device in the room that’d be easier to be updated, ergo a Zigbee-using door sensor, Raspberry Pi with Zigbee dongle and Home Assistant (HA) was used.

One last wrinkle was the need to use a Cloudflare-based tunnel add-on to expose the HA API from the outside, but now at long last the UPL door status can be checked with absolute certainty that it is correct. Probably.

Featured image: The machine vision-based room occupancy system at UoW’s UPL. (Credit: UPL, University of Wisconsin)

Senoko natural gas and oil-fired power station, Singapore in 2007. (Credit: Terence Ong)

Singapore’s 4300 Km Undersea Transmission Line With Australia Clears Regulatory Hurdle

October 23, 2024 by Maya Posch 22 Comments

The proposed AAPowerLink transmission line between Darwin (Australia) and Singapore. (Credit: Sun Cable)

Recently Singapore’s Energy Market Authority (EMA) granted Sun Cable conditional approval for its transmission line with Australia. Singapore has been faced for years now with the dilemma that its population’s energy needs keep increasing year-over-year, while it has very little space to build out its energy-producing infrastructure, least of all renewables with their massive footprints. This has left Singapore virtually completely dependent on natural gas-burning thermal plants. Continue reading “Singapore’s 4300 Km Undersea Transmission Line With Australia Clears Regulatory Hurdle” →

Feeling A Pong Of Nostalgia: Does It Hold Up In 2024?

October 20, 2024 by Maya Posch 8 Comments

We have probably all been there: that sudden memory of playing a (video) game and the good memories associated with said memory. Yet how advisable is it to try and re-experience those nostalgic moments? That’s what [Matt] of the Techmoan YouTube channel decided to give a whirl when he ordered the Arcade1Up Pong 2 Player Countercade game system. This comes loaded with multiple variants of the Pong game, including Pong Doubles and Pong Sports, in addition to Warlords, Super Breakout and Tempest. This unit as the name suggests allows for head-to-head two-player gaming.

This kind of ‘countercade’ system is of course much smaller than arcade versions, but you would expect it to give the Pong clones which [Matt] played as a youngster a run for their money at least. Ultimately [Matt] – after some multiplayer games with the Ms. – concluded that this particular nostalgia itch was one that didn’t have to be scratched any more. While the small screen of this countercade system and clumsy interface didn’t help much, maybe Pong just isn’t the kind of game that has a place in 2024?

From our own point of view of having played Pong (and many other ‘old’ games) on a variety of old consoles at retro events & museums, it can still be a blast to play even just Pong against a random stranger at these places. Maybe the issue here is that nostalgia is more about the circumstances of the memory and less of the particular game or product in question. Much like playing Mario Kart 64 on that 20″ CRT TV with three buddies versus an online match in a modern Mario Kart. It’s just not the same vibe.

Continue reading “Feeling A Pong Of Nostalgia: Does It Hold Up In 2024?” →

Figuring Out The Most Efficient Way To Reuse Bags Of Desiccant

October 20, 2024 by Maya Posch 33 Comments

Everyone knows those small bags of forbidden “Do not eat” candy that come with fresh rolls of FDM filament as well as a wide range of other products. Containing usually silica gel but sometimes also bentonite clay, these desiccant bags are often either thrown away or tossed into bags of FDM filament with a ‘adding one can’t hurt’ attitude. As [Stefan] over at CNC Kitchen recently figured out, adding an already saturated bag of desiccant into e.g. an airtight container with a freshly dried spool of filament can actually make the humidity in the container spike as the desiccant will start releasing moisture. So it’s best to dry those little bags if you intend to reuse them, but what is the best way?

Among the ‘safe’ contenders are an oven, a filament dryer and the ‘filament drying’ option of [Stefan]’s Bambu Lab FDM printer. These managed to remove most of the moisture from the desiccant in a few hours. The more exciting option is that of a microwave, which does the same in a matter of minutes, requiring one or more ~5 minute sessions at low power, which effectively also used less power than the other options. Among the disadvantages are potentially melting bags, silica beads cracking, the bentonite clay desiccant heating up rather dangerously and the indicator dye in silica beads may be damaged by the rapid heating.

After all of this testing, it would seem that there are many good options to reuse those desiccant bags with a bit of care, although for those who happen to have a vacuum chamber nearby, that might be an even faster option.

Continue reading “Figuring Out The Most Efficient Way To Reuse Bags Of Desiccant” →

Double-Slit Time Diffraction At Optical Frequencies

October 18, 2024 by Maya Posch 11 Comments

The double-slit experiment, first performed by [Thomas Young] in 1801 provided the first definitive proof of the dual wave-particle nature of photons. A similar experiment can be performed that shows diffraction at optical frequencies by changing the reflectivity of a film of indium-tin-oxide (ITO), as demonstrated in an April 2024 paper (preprint) by [Romain Tirole] et al. as published in Nature Physics. The reflectivity of a 40 nm thick film of ITO deposited on a glass surface is altered with 225 femtosecond pulses from a 230.2 THz (1300 nm) laser, creating temporal ‘slits’.

Interferogram of the time diffracted light as a function of slit separation (ps) and frequency (THz). (Credit: Tirole et al., Nature Physics, 2024)

The diffraction in this case occurs in the temporal domain, creating frequencies in the frequency spectrum when a separate laser applies a brief probing pulse. The effect of this can be seen most clearly in an interferogram (see excerpt at the right). Perhaps the most interesting finding during the experiment was how quickly and easily the ITO layer’s reflectivity could be altered. With ITO being a very commonly used composition material that provides properties such as electrical conductivity and optical transparency which are incredibly useful for windows, displays and touch panels.

Although practical applications for temporal diffraction in the optical or other domains aren’t immediately obvious, much like [Young]’s original experiment the implications are likely to be felt (much) later.

Featured image: the conventional and temporal double-slit experiments, with experimental setup (G). (Credit: Tirole et al., Nature Physics, 2024)

What Would It Take To Recreate Bell Labs?

October 17, 2024 by Maya Posch 45 Comments

It’s been said that the best way to stifle creativity by researchers is to demand that they produce immediately marketable technologies and products. This is also effectively the story of Bell Labs, originally founded as Bell Telephone Laboratories, Inc. in January 1925. As an integral part of AT&T and Western Electric, it enjoyed immense funding and owing to the stable financial situation of AT&T very little pressure to produce results. This led to the development of a wide range of technologies like the transistor, laser, photovoltaic cell, charge-coupled cell (CCD), Unix operating system and so on. After the break-up of AT&T, however, funding dried up and with it the discoveries that had once made Bell Labs such a famous entity. Which raises the question of what it would take to create a new Bell Labs?

As described in the article by [Brian Potter], one aspect of Bell Labs that made it so successful was that the researchers employed there could easily spend a few years tinkering on something that tickled their fancy, whether in the field of semiconductors, optics, metallurgy or something else entirely. There was some pressure to keep research focused on topics that might benefit the larger company, but that was about it, as the leadership knew that sometimes new technologies can take a few years or decades to come to fruition.

Continue reading “What Would It Take To Recreate Bell Labs?” →