An optical see-through head-mounted display is a wearable device that has the capability of reflecting projected images as well as allowing the user to see through it. In some cases, this may qualify as augmented reality (AR) technology. OHMD technology has existed since 1997 in various forms, but despite a number of attempts from industry, has yet to have had major commercial success.

Types

Various techniques have existed for see-through HMDs. Most of these techniques can be summarized into two main families: "Curved Mirror" (or Curved Combiner) based and "Waveguide" or "Light-guide" based. The curved mirror technique has been used by Vuzix in their Star 1200 product, by Olympus, and by Laster Technologies. Various waveguide techniques have existed for some time. These techniques include diffraction optics, holographic optics, polarized optics, and reflective optics: * Diffractive waveguide – slanted

diffraction grating In optics, a diffraction grating is an optical grating with a periodic structure that diffraction, diffracts light, or another type of electromagnetic radiation, into several beams traveling in different directions (i.e., different diffractio ...

elements (nanometric 10E-9). Nokia technique now licensed to Vuzix. * Holographic waveguide – 3 holographic optical elements (HOE) sandwiched together (RGB). Used by

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and

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. * Polarized waveguide – 6 multilayer coated (25–35) polarized reflectors in glass sandwich. Developed by Lumus. * Reflective waveguide – A thick light guide with single semi-reflective mirror is used by Epson in their Moverio product. A curved light guide with partial-reflective segmented mirror array to out-couple the light is used by tooz technologies. * "Clear-Vu" reflective waveguide – thin monolithic molded plastic w/ surface reflectors and conventional coatings developed by Optinvent and used in their ORA product. * Switchable waveguide – developed by SBG Labs, now known as DigiLens.

Input devices

Head-mounted display A head-mounted display (HMD) is a display device, worn on the head or as part of a helmet (see helmet-mounted display for aviation applications), that has a small display optic in front of one (monocular HMD) or each eye (binocular vision, bi ...

s are not designed to be workstations, and traditional input devices such as keyboards do not support the concept of smart glasses. Input devices that lend themselves to mobility and/or hands-free use are good candidates, for example: *

Touchpad A touchpad or trackpad is a type of pointing device. Its largest component is a tactile sensor: an electronic device with a flat surface, that detects the motion and position of a user's fingers, and translates them to 2D motion, to control a Cu ...

button A button is a fastener that joins two pieces of fabric together by slipping through a loop or by sliding through a buttonhole. In modern clothing and fashion design, buttons are commonly made of plastic but also may be made of metal, wood, or ...

s * Compatible devices (e.g.

smartphone A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as multi ...

s or control unit) *

Speech recognition Speech recognition is an interdisciplinary subfield of computer science and computational linguistics that develops methodologies and technologies that enable the recognition and translation of spoken language into text by computers. It is also ...

Gesture recognition Gesture recognition is an area of research and development in computer science and language technology concerned with the recognition and interpretation of human gestures. A subdiscipline of computer vision, it employs mathematical algorithms to ...

Eye tracking Eye tracking is the process of measuring either the point of gaze (where one is looking) or the motion of an eye relative to the head. An eye tracker is a device for measuring eye positions and eye movement. Eye trackers are used in research ...

Brain–computer interface A brain–computer interface (BCI), sometimes called a brain–machine interface (BMI), is a direct communication link between the brain's electrical activity and an external device, most commonly a computer or robotic limb. BCIs are often dire ...

Recent developments

2012

* On 17 April 2012, Oakley's CEO Colin Baden stated that the company has been working on a way to project information directly onto lenses since 1997, and has 600 patents related to the technology, many of which apply to optical specifications. * On 18 June 2012,

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announced the MR (Mixed Reality) System which simultaneously merges virtual objects with the real world at full scale and in 3D. Unlike the Google Glass, the MR System is aimed for professional use with a price tag for the headset and accompanying system is $125,000, with $25,000 in expected annual maintenance.

2013

* At MWC 2013, the Japanese company Brilliant Service introduced the Viking OS, an operating system for HMDs which was written in

Objective-C Objective-C is a high-level general-purpose, object-oriented programming language that adds Smalltalk-style message passing (messaging) to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was ...

and relies on gesture control as a primary form of input. It includes a

facial recognition system A facial recognition system is a technology potentially capable of matching a human face from a digital image or a Film frame, video frame against a database of faces. Such a system is typically employed to authenticate users through ID verif ...

and was demonstrated on a revamp version of Vuzix STAR 1200XL glasses ($4,999) which combined a generic RGB camera and a PMD CamBoard nano depth camera. * At Maker Faire 2013, the startup company Technical Illusions unveiled castAR augmented reality glasses which are well equipped for an AR experience: infrared

LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...

s on the surface detect the motion of an interactive infrared wand, and a set of coils at its base are used to detect RFID chip loaded objects placed on top of it; it uses dual projectors at a framerate of 120 Hz and a retroreflective screen providing a 3D image that can be seen from all directions by the user; a camera sitting on top of the prototype glasses is incorporated for position detection, thus the virtual image changes accordingly as a user walks around the CastAR surface.

2016

* The Latvian-based company NeckTec announced the smart necklace form-factor, transferring the processor and batteries into the necklace, thus making facial frame lightweight and more visually pleasing.

2018

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

announces Vaunt, a set of smart glasses that are designed to appear like conventional glasses and are display-only, using retinal projection. The project was later shut down. * Zeiss and

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partners up to for
tooz technologies GmbH
to develop optical elements for smart glass displays.

Market structure

Analytics company IHS has estimated that the shipments of smart glasses may rise from just 50,000 units in 2012 to as high as 6.6 million units in 2016. According to a survey of more than 4,600 U.S. adults conducted by

Forrester Research Forrester Research, Inc. is a research and advisory firm. Forrester serves clients in North America, Europe, and Asia Pacific. The firm is headquartered in Cambridge, Massachusetts, Cambridge, MA with global offices in Amsterdam, London, New D ...

, around 12 percent of respondents are willing to wear Google Glass or other similar device if it offers a service that piques their interest.

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's BI Intelligence expects an annual sales of 21 million Google Glass units by 2018. According to reliable reports, Samsung and Microsoft are expected to develop their own version of Google Glass within six months with a price range of $200 to $500. Samsung has reportedly bought lenses from Lumus, a company based in Israel. Another source says Microsoft is negotiating with Vuzix. In 2006,

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filed patent for its own HMD device. In July 2013, APX Labs founder Brian Ballard stated that he knows of 25-30 hardware companies who are working on their own versions of smart glasses, some of which APX is working with.

Comparison of various OHMDs technologies