LCD projector

Abstract: We have constructed a simple color electroholography system that has excellent cost performance. It uses a graphics processing unit (GPU) and a liquid crystal display (LCD) projector. The structure of the GPU is suitable for calculating computer-generated holograms (CGHs). The calculation speed of the GPU is approximately 1,500 times faster than that of a central processing unit. The LCD projector is an inexpensive, high-performance device for displaying CGHs. It has high-definition LCD panels for red, green and blue. Thus, it can be easily used for color electroholography. For a three-dimensional object consisting of 1,000 points, our system succeeded in real-time color holographic reconstruction at rate of 30 frames per second.

Abstract: A mount that secures a projector to a ceiling is disclosed. The mount includes an upper element which is attached to the ceiling, and a lower element which is attached to the projector. The two elements are adapted to slidably engage and disengage for quick mounting without having to detach the upper element from the ceiling and the lower element from the projector. The mount may include a spring-biased latch which locks the two elements together to prevent accidental disengagement. The latch may include a safety lock feature which prevents inadvertent actuation of the latch and subsequent disengagement of the elements.

Abstract: Projection systems have become the ubiquitous infrastructure for presentation technology. However, unless the projector is precisely aligned to the presentation screen, the resulting image suffers from perspective (keystone) distortions requiring manual optical or digital correction. This tedious process must be repeated whenever the projector or screen is moved and is increasingly relevant given the emerging trend towards highly-portable LCD projection systems. This paper presents a presentation interface that pre-warps the image to be projected in such a way that the distortions induced by the projector-screen geometry precisely negate the warping. An uncalibrated, low-resolution digital camera is used to infer the projector-screen geometry and to automatically determine the pre-warping parameters. This vision-based system is augmented with a natural interface that enables the user to interactively refine the suggested rectification. Arbitrary distortions due to projector placement are negated, allowing the projector (and camera) to be placed anywhere in the presentation room -- for instance, at the side rather than the center of the room. Our solution works with existing projector hardware, and could easily be incorporated into the next generation of LCD projector systems.

Abstract: A human-robot interface system is under development that takes into account the flexibility of the DigitalDesk approach. The prototype consists of a projector subsystem for information display and a real-time tracking vision subsystem to recognize the human's action. Two levels of interaction using a virtual operational panel and interactive image panel have been developed. This paper presents the third subsystem, the interactive hand pointer used for selecting objects or positions in the environment via the operator's hand gestures. The system visually tracks the operator's pointing hand and projects a mark at the indicated position using an LCD projector. Since the mark can be observed directly in the real work space without monitor displays or HMDs, correction of the indicated position by moving the hand is very easy for the operator. The system enables projection of a mark not only at a target plane with a known height but also to a plane with an unknown height. Experimental results of a pick-and-place task demonstrate the usefulness of the proposed system.