Abstract: A computer model of a virtual environment is continuously modified by input from various participants. The virtual environment is displayed to the participants using sensory displays such as head-mounted visual and auditory displays which travel with the wearer and track the position and orientation of the wearer's head in space. Participants can look at each other within the virtual environment and see virtual body images of the other participants in a manner similar to the way that people in a physical environment see each other. Each participant can also look at his or her own virtual body in exactly the same manner that a person in a physical environment can look at his or her own real body. The participants may work on a common task together and view the results of each other's actions.

Abstract: A radiation source directs radiation toward a radiation sensor in such a way that the intensity of radiation sensed by the radiation sensor alternates in a periodic manner as the radiation source moves radially relative to the radiation sensor. The radiation sensor generates either a "1" or a "0" depending upon whether the intensity of the radiation sensed by the radiation sensor is above or below a particular reference value. Thus, the angular position of the radiation source relative to the radiation sensor is indicated by an alternating series of "1"s and "0"s. A multi-bit binary value which indicates the absolute position of the radiation source relative to the radiation sensor can be generated. In this case, a band of radiation is directed toward the radiation sensor. The radiation band is separated into a plurality of portions, the intensity of each successive portion being twice the frequency of the preceding portion. Each portion of the radiation band impinges upon a corresponding sensor.

Abstract: A hologram is directly recorded in a sensitized metal substrate. The hologram may be an amplitude hologram, or may be treated to produce a phase relief hologram which may be stamped into a plastic material for reproduction, be archivally stored, or used as a master for electroforming a second durable surface relief hologram for use as an embossing master. A suitable material is prepared from a polished silver plate exposed to halogen vapors. After exposure, the plate is developed and fixed, and the surface is differentially etched to form a surface relief suitable for hologram embossing. Daguerreotype processes are modified to make surface amplitude holograms and phase holograms. By etching through a metal film a semiconductor mask is obtained. By depositing a silver film directly on a wafer, masks are made with very high feature definition.