Optics 101

Looking Into The Diverse Area Of Wearable Optics

The realization of advanced optical fibers and thinner optical lenses has enabled there to be a surge in wearable optics. Wearable optics come in many different forms, from the low-tech aesthetics by integrating optical fibers with clothing, to newly created advanced optical sensors and creating high-tech applications, such as integrating advanced optical components into augmented reality (AR) headsets.

In this article, we look at the full spectrum of wearable optics, from the low-tech to the high-tech applications.

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Aesthetic Wearables

Whilst it is not a high-tech application of optical technology, optical fibers have been implanted into various types of clothing in recent years. The purpose of the implantation being purely to enhance the aesthetics of garments, particularly in dresses and coats.

Despite their fashion appeal, the realisation of these garments does rely on optics to achieve the desired effect. Given the nature of the market of these optical fibers, they are often made of plastic rather than the glass (as usually seen with complex communication technologies). However, they still transmit light along the fiber using the same internal reflection principles.

There are a few different types of optical fiber employed in low end wearables, and these include end emitting fibers and side emitting fibers, among other less common optical fiber variants. End emitting fibers have been around for a long time and light can be seen at the tip (end) of each fiber, whereas side emitting fibers are a newer (and much thicker) fiber optical variant where the light is emitted at all points along the optical fiber (due to a thinner cladding that enables some light to escape).

Wearable Optical Sensors

Some big news emerged in the optical sector in 2017 regarding a new type of optical sensor that can be used on humans to capture bodily motions. It has since seen a lot of investment and it appears that a lot more research is going to be going into this kind of research to develop new optical sensing tools that can provide real-time monitoring, more advanced gaming systems and build robots that have a lighter touch.

This area is now possible thanks to researchers from China who created the fiber optic sensor from polydimethylsiloxane (PDMS). The structural nature of the fiber enables it to be stood up and detect strain (and thus body movements) by elongating itself. It can also return to its original conformation so that it can be reused.

So how does it measure strain? As the fiber is an optical fiber, there is a given amount of light that passes through the fiber. The fiber is also doped with a dye, Rhodamine B, which has a light wavelength-dependent absorption and will absorb a given amount of light in the fibers natural state. Therefore, it can be used to sense changes in the amount of light passing by the walls of the fiber. When the fiber is stretched under movement, the diameter of the fiber becomes thinner and the dye absorbs more light. Similarly, if the fiber compressed, then the diameter of the fiber will increase and the light absorption will be less. Thus, it can be used to detect compression and stretching movements to determine the movement of the user.

Wearable Optics and Augmented Reality (AR)

This is a new area, and given the potential for this kind of technology, it is an area currently dominated by a series of patents. Advanced optics, such as waveguides, diffraction gratings, vector gratings and pico projectors, can be used to project images into the field of view of the user, and the user can often issue commands based off to real-world data and data within the augmented world itself. Recent advances have been able to tailor the amount of information projected by the AR headsets as to not overload the user with too many objects and information. However, when required, AR headsets that use advanced optics can have commands issued by voice and touch, as well as provide a visible environment that can be navigated.

Because AR headsets use lenses, they are even adaptable to users with impaired vision by tailoring the orientation of the lens. The world where AR and optics meets also extends to wearable contact lenses, i.e. the ability to put a usable computer in to your eye. Whilst they do rely on more than just optics, various optical components and optical sensors do play a big part in AR/VR headsets.

Sources:

  1. Instructables: https://www.instructables.com/id/The-Beginners-Guide-to-Fiber-Optics/
  2. Optical Society of America: https://www.osa.org/en-us/about_osa/newsroom/news_releases/2017/in_a_first_for_wearable_optics_researchers_develo/
  3. Optics and Photonics: https://www.osa-opn.org/home/newsroom/2017/october/optical_strain_sensor_for_wearable_tech/
  4. Photonics Media: https://www.photonics.com/Articles/Optics_Transforming_AR_Wearables_and_Beyond/a62813
  5. Laser Focus World: https://www.laserfocusworld.com/articles/print/volume-54/issue-02/features/photonics-applied-wearable-photonic-technology-photonics-gets-up-close-and-personal-advancing-wearable-technology-with-light.html
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