Abstract: A biaxially stretched polyester film comprising a polyester and zirconium as an internal particle material, produced by polycondensation of terephthalic acid or its esterified derivative and alkylene glycol as the major essential monomeric components in the presence of a polycondensation catalyst, during which zirconium in the form of any compound thereof in an amount of 80 to 2500 ppm in terms of zirconium atom to the polyester as produced being introduced into the reaction system at a stage after the initiation of the reaction and before the intrinsic viscosity of the reaction mixture reaching 0.2, and subjecting the produced polyester to film forming.

Abstract: A process for production of a polyester comprising units of ethylene terephthalate as the major repeating units by supplying terephthalic acid and ethylene glycol continuously or intermittently to bis(beta-hydroxyethyl) terephthalate or its oligomer so as to carry out esterification under a pressure of not more than about 1.0 kg/cm.sup.2, followed by polycondensation, which is characterized in that at least one magnesium compound is incorporated into the reaction system in an amount of about 30 to 400 ppm in terms of Mg to the polyester when the esterification rate in the step of esterification reaches about 20-80% and at least one phosphorus compound is incorporated into the reaction system in an amount as satisfying the following equation (I) at the stage after the esterification rate reaches not less than about 91% and before the termination of the initial condensation in the step of esterification:1.2.ltoreq.Mg/P.ltoreq.20 (I)wherein Mg/P is the atomic ratio of the magnesium atom to the phosphorus atom.

Abstract: A camera equipped with an automatic focus adjusting device in which a photographing lens is displaceable along its optical axis and is stopped at a proper photographing position by an engaging member operated in response to a ranging signal from a ranging device. The shutter is then released in a manner which is independent of the displacement of the photographing lens.

Abstract: In a grinding machine, a grinding wheel is digitally fed toward a workpiece being supported by a rest apparatus. Means is provided to measure a diametral dimension of the workpiece during a grinding operation. A taper amount of the workpiece ground under the support of the rest apparatus being positioned at its advanced position is calculated at the time when the measuring means generates a signal for finishing a grinding operation on the workpiece. An advanced position of the rest apparatus is compensated for a next grinding operation in response to the calculated taper amount.