While virtual imaging technology has permeated other industries such as entertainment and military, it has yet to make a significant impact in medical. However, as newer, more advanced capabilities are introduced, designers may take advantage of this offering more often. This article looks at virtual imaging for medical device applications.

Gaming, video entertainment, military viewers, and training have been the main drivers for the creation and use of video eyewear and virtual reality headsets over the last couple of decades. However, recent advances in organic light emitting diode (OLED) microdisplay technology, combined with innovative see-through and wide field-of-view optics, offers tremendous potential for near-eye, medical device applications.

These high-definition OLED flat panel displays are less than an inch diagonal and weigh less than three grams, allowing virtual imaging devices to comfortably provide critical information on the move or in very compact packages for the medical theater, whether in the operating room or for training applications.

View from a first responder wearing augmented reality glassesThese virtual imaging applications can provide doctors with immersive, high-definition 3D or 2D diagnostic imagery during procedures. Additionally, they enable overlays of vital signs, items of interest, and other guidance for surgical trainers and simulators.

Data glasses or goggles can provide EMTs and ER personnel with key vital sign data and medical history at the scene of an incident, as well as during triage and transport, keeping the data overlain in their vision and their hands free to perform necessary actions and procedures throughout.

These applications are not just “gee-whiz” ideas for the future but possible now. Delivery of similar information is already available to medical personnel today and new OLED microdisplay breakthroughs now offer innovative medical device product developers the opportunity to design new solutions. The promise of virtual imaging products is providing high-quality, high performance visual systems that can make a difference in the delivery of patient care by providing the information in a hands-free, compact package.

Near-to-Eye Terminology
For the purpose of this article, virtual imaging is defined as images created by an optical display system that creates a larger screen than is physically presented to the user. These optical display systems are used in head-mounted displays (HMD) or goggles.

The simplest form of virtual imaging is found in electronic viewfinders for digital cameras where the microdisplay receives an image from the charged coupling device sensor and transfers it to the viewer’s eye through relatively simple magnifying in-line optical elements or eyepiece. In this case, the viewer is seeing the object as captured by the camera.

A similar approach is used in HMDs where the source imagery is provided by a camera, computer, or video source. However, within the HMD, the image displayed on the microdisplay is magnified through lightweight optics that usually conform to human ergonomics and provide a virtual image equivalent to viewing a 60-inch or 100-inch monitor at a distance of 10 to 12 feet.

An example of the effectiveness of a head-mounted display in a medical application is viewing ultrasound images with the BUG (Binocular Ultrasound Goggle) created by BCF Technologies. It is used by veterinarians to screen cattle and sheep for pregnancy and/or disease in muddy and dusty fields and bright sunlight.

HMDs can also be used to provide augmented vision (AV), augmented reality (AR), virtual reality (VR), or mixed reality (MR) through differing optical design forms and, of course, the information provided.

AV is the process of overlaying the viewer’s vision with data that is “see-through” so it appears to float in the user’s vision, similar to a heads-up display used in aircrafts or automobiles. While the microdisplays themselves may become transparent at some time in the future, enabling data glasses that look like a regular pair of glasses, AR can be accomplished today by using beam-splitter optics that combine normal vision path with images provided by a microdisplay usually mounted above or to the side of the optical lens.

AV is particularly effective in delivering simple data at the point of task or procedure, while allowing the user to have both hands free and maintain full situational awareness, as the real world is not occluded to any great extent.

AR takes this a step further by allowing the overlay information to be queued to the real world via visible fiduciaries or through sophisticated eye or head tracking. AR can be very effective in simulation systems such as surgical trainers and is currently used in ophthalmology simulators marketed by VRmagic, a German company.

MR is very similar to AR, but in this case, the real world images are provided by a camera or cameras mounted on the HMD. These images are combined with images created by a computer using fully-occluded optics to create an immersive visual experience.

VR is usually a fully stereoscopic 3D environment created by a computer image generator and displayed using an immersive HMD or helmet, with occluded or see-through optics that provide a wide field-of-view. Used typically for computer gaming or simulation and training applications, VR has been effective in treating post-traumatic stress syndrome and other phobia disorders using eMagin Corporation’s Z800 3DVisor.

Today’s Reality for Virtual Imaging Products
Development and adoption of HMDs and other virtual imaging near-to-eye products in the medical industry has been limited by the low resolution and small field-of-view of prior generation microdisplays and optics.

The recent success of active matrix OLED microdisplays in military viewer and electronic viewfinder applications has lead to development and availability of resolutions up to 1920 pixels by 1200 pixels with even higher resolutions on the way. There are also innovative and lightweight optical solutions available to provide a field of view of 65 degrees and more.

While other microdisplay technologies exist, such as LCOS and LCD, OLED microdisplays provide vivid, accurate color and extremely high contrast. Additionally, very low power is required for use with portable HMDs. Recent advances in OLED technology will provide medical HMDs with high brightness and long lifetime to support AR products in both bright operating rooms and outdoor applications.

Adoption of virtual image and simulation head-mounted devices will naturally depend on their ergonomics and the advantages these products can provide for medical applications. Considering the need for more and more data while on the move, the crowded real estate in the operating theater, and the need for effective training in the use of image and computer-guided procedures, the healthcare industry can expect product designers to create breakthrough applications enabling virtual imaging to become a useful tool.