June 2014
Spotlight Summary by Martin Schrader
Visual space assessment of two all-reflective, freeform, optical see-through head-worn displays
Even though most consumers might not yet have had the chance to test the latest head-worn devices for themselves, those who have tried Google Glass or some recent model of high-tech eye-wear will surely testify to the increased comfort and level of experience provided by those devices, which manage to combine high computational and optical performance in a lightweight package.
Throughout the more than 50 years of head-worn display technology development, optical design has been one of the key technologies to enable the use of these devices in different industrial and lately also consumer electronics applications. Especially the desire for see-through optics with a small footprint has called for advanced optical design using for example diffractive optical elements or freeform optical surfaces. While freeform optical surfaces represent challenges for both optical design and manufacturing, advances have been made in each of these areas. During the design of most head-worn display optical systems using optical design software, rays are traced from the eye towards the image source. But in order to enable a good understanding of the user experience - and especially how it is impacted by manufacturing tolerances -, it is advantageous to flip the optical system, trace rays from the image source towards the eye and analyze the performance in the visual space. Bauer and Rolland apply this strategy when designing and analyzing two head-worn optical systems using freeform optical elements. During the design phase they utilize a set of polynomials that allows a simple aberration analysis and control to describe the surface shapes. They then analyze the visual performance of the design by simulating the impact of manufacturing tolerances on the frequency response of the flipped optical system.
The next couple of years will tell which of the competing optical approaches can dominate the fast growing markets for head-worn displays. The solid design and analysis demonstrated in the paper by Bauer and Rolland is a requirement for successful system designs using freeform optical surfaces in this now very competitive area of applied optical solutions.
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Throughout the more than 50 years of head-worn display technology development, optical design has been one of the key technologies to enable the use of these devices in different industrial and lately also consumer electronics applications. Especially the desire for see-through optics with a small footprint has called for advanced optical design using for example diffractive optical elements or freeform optical surfaces. While freeform optical surfaces represent challenges for both optical design and manufacturing, advances have been made in each of these areas. During the design of most head-worn display optical systems using optical design software, rays are traced from the eye towards the image source. But in order to enable a good understanding of the user experience - and especially how it is impacted by manufacturing tolerances -, it is advantageous to flip the optical system, trace rays from the image source towards the eye and analyze the performance in the visual space. Bauer and Rolland apply this strategy when designing and analyzing two head-worn optical systems using freeform optical elements. During the design phase they utilize a set of polynomials that allows a simple aberration analysis and control to describe the surface shapes. They then analyze the visual performance of the design by simulating the impact of manufacturing tolerances on the frequency response of the flipped optical system.
The next couple of years will tell which of the competing optical approaches can dominate the fast growing markets for head-worn displays. The solid design and analysis demonstrated in the paper by Bauer and Rolland is a requirement for successful system designs using freeform optical surfaces in this now very competitive area of applied optical solutions.
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Article Information
Visual space assessment of two all-reflective, freeform, optical see-through head-worn displays
Aaron Bauer and Jannick P. Rolland
Opt. Express 22(11) 13155-13163 (2014) View: Abstract | HTML | PDF