Design and calibration of curved and see-through integral imaging 3D display

Heads-up displays that are ‘see-through’ and ‘curved’ and capable of displaying 3D contents are considered crucial for augmented reality-based navigation in automobiles. Here we report the development, calibration and experimental evaluation of a 3D display system that satisfies the above requirements. Integral imaging is used as the 3D display technique, which is realized using a flexible ‘concave-micro-mirror array’ screen (equivalent of a ‘micro-lens array’, but working in reflection mode). The screen itself is fabricated as a holographic optical element. The holographic nature of the screen enables a ‘see-through’ effect. The 3D content to be displayed is served by a 2D projector as integral images. A novel calibration method is developed which employs diffusive markers, that are invisible to the naked eye, being placed at one corner of each elemental micro-mirror. The calibration enables proper treatment of the effects and artifacts caused by screen ‘curvature’, but the presence of markers itself does not degrade the display characteristics. A curved micro-mirror array screen of size 10 cm × 10 cm consisting of 100 × 200 elemental concave mirrors is fabricated as a flexible holographic optical element with diffusive markers of size 300 m × 300 m. The screen, when illuminated with a projector (that serves integral images), was able to reconstruct a 3D scene of size 10 cm × 10 cm with a depth of 5 cm. The novel calibration method employing diffusive markers demonstrates significant improvement in calibration accuracy. The curved and see-through nature of the display screen makes it a good choice for windshield displays. The reported system requires further improvements in enlarging the screen size and increasing depth of the 3D scene in order to meet real-world requirements, which can be achieved by scaling-up the system.