Abstract: A liquid crystal projector includes a light source, a color filter for adding color projection image, a liquid crystal panel for forming a projection image on it, a projection lens and an optical unit located between the color filter and the liquid crystal panel for optically coupling the color filter and the liquid crystal panel. The color filter is separately located from the liquid crystal, and therefore the increase in temperature on the color filter because of absorbing the light from the light source has less effect on the liquid crystal panel.

Abstract: Fluorine is recovered as calcium fluoride from a fluoroetchant solution composed mainly of hydrogen fluoride and ammonium fluoride using a sealed reaction tank equipped with a supply port for adding the fluoroetchant solution to the tank, a supply port for adding calcium carbonate to the tank, a vapor supply port for adding steam to heat the solution in the tank, an air supply port for providing air to aerate the contents of the tank, a stirrer for stirring the contents of the tank, an ejector for removing vapors from the tank connected to the tank via a mist separator for separating mist from the vapors being removed from the tank, and an exhaust port for removing calcium fluoride from the tank.

Abstract: Calcium fluoride with high purity of very small content of unreacted calcium carbonate and silica is recovered from an etchant mainly composed of hydrogen fluoride or hydrogen fluoride and ammonium fluoride. The etchant is reacted with calcium carbonate with transfer directions of the etchant and calcium carbonate being controlled within a composition region in which mole equivalent ratio of ammonium fluoride/hydrogen fluoride is specified.

Abstract: A flat fluorescent lamp comprises a flat glass container formed by a front glass panel, a rear glass panel and glass frames, a phosphor coating formed along the inner surface of the front glass panel, an anode disposed in the vicinity of the phosphor coating, a plurality of linear cathodes arranged in parallel to the anode and supported by support members, and at least one mesh electrode disposed between the anode and the cathodes The intensity of light of the lamp is adjusted by applying a pulse voltage to the mesh electrode.

Abstract: In a simultaneous communication as in a POS system in which the same data including a multiplicity of data blocks is transmitted from a controller to a multiplicity of terminals all at once, the controller transmits all of the data blocks to the terminals without receiving any acknowledgement from each of the terminals in the course of data transmission. Each time the data block is received, the terminals hold information concerning the acknowledgement of the data block. After the termination of transmission of the whole of the data, the controller receives the acknowledgement information from each terminal into a management table. Based on the contents of the mangement table, the controller retransmits the data to a terminal(s) indicative of a negative acknowledgement in a similar manner to the above-mentioned data transmission or while taking acknowledgement for each data block.