Transmission characteristics of a bidirectional transparent screen based on reflective microlenses

Abstract

A microlens array (MLA) based see-through, front projection screen, which can be used in direct projection head-up displays (HUD), color teleprompters and bidirectional interactive smart windows, is evaluated for various performance metrics in transmission mode. The screen structure consists of a partially reflective coated MLA buried between refractive-index-matched layers of epoxy as reported in Ref [1]. The reflected light is expanded by the MLA to create an eyebox for the user. The brightness gain of the screen can be varied by changing the numerical aperture of the microlenses. Thus, using high gain designs, a low-power projector coupled with the screen can produce high-brightness and even 3D images as the polarization is maintained at the screen. The impact of the partially reflective coatings on the transmitted light in terms of resolution and modulation transfer function associated with the screen is studied. A condition similar to the Rayleigh criteria for diffraction-limited imaging is discussed for the microlens arrays and the associated coating layers. The optical path difference between the light transmitted from the center and the edges of each microlens caused by the reflective layer coatings should not exceed λ/4. Furthermore, the crosstalk between the front and rear projected images is found to be less than 1.3%.

16-3: A Novel Transparent Screen Using Cholesteric Liquid Crystal Dots

“…In the past, various transparent screens have been proposed. Those using scattering by small particles [1,2,3], those making patterns with scattered particle portions and transparent portions [4], those using a microlens array [5], and those using a combination of prism-like structure and particle scattering [6] are known. However, in all of these transparent screens, if reflection intensity is raised, haze also becomes large.…”

Light-efficient augmented reality 3D display using highly transparent retro-reflective screen

“…Augmented reality 3D displays have been widely explored for their ability to blend virtual and real word and can be used for variety of applications including entertainment, medical visualization and education. Most of the augmented reality systems are based on one more image sources and optically transparent surfaces [1][2][3][4][5][6][7]. Several techniques have been proposed to realize the augmented reality displays, where most of the effort has been focused on the development of near-to-eye augmented reality displays [3][4].…”

“…With the availability of high resolution micro-displays, the current nearto eye display can produce decent image quality and resolution, but often involve bulky optics and have limited field of view. An alternative approach uses image projectors together with distant transfer screens or real-objects to overlay virtual content [5][6][7][8], which includes the integral imaging [5], holographic recorded micro-lens arrays [6], partially reflective or notch coated micro-lens arrays [7] and plasmonic nanocubes [8] based AR displays. The use of additional tunable transmittance liquid crystal film to increase the ambient contrast in wearable augmented reality display have also been demonstrated [9].…”

Augmented reality 3D display using head-mounted projectors and transparent retro-reflective screen

“…The near-to-eye displays can provide quality images without occluding real-world scene, but usually suffer from reduced field of view and involve bulky optical configuration. Various augmented reality systems use headmounted or fixed projectors and distant see-through screens as transfer medium [6][7][8][9] , which include the micro-lens array 7 or resonant nano-particle 8 based see-through screens. The high brightness gain and personalized display is achieved by using retro-reflective surfaces in the surrounding instead of diffusing screens [10][11] , however to use such surfaces for augmented reality applications requires them to have optical see-through capability and brightness gain.…”