Patent ID: 6294870
Filing Date: 2001-09-25
Classification: H01J

Abstract:
A high pressure discharge lamp comprising:a discharge casing having an airtight discharge space;a pair of electrodes disposed in the discharge space with one end of an electrode facing an end of the other electrode;a pair of first sealed portions respectively sealing the other ends of the electrodes in an airtight state;a lead portion provided at either one of the ends or each end of the discharge casing in such a manner that one end of each lead portion is connected to said other end of the electrode disposed at the same side of the discharge casing and airtightly sealed in the corresponding first sealed portion;a second sealed portion for airtightly sealing the other end of said one lead portion;each said sealed portion including an air tight space, a separate metal conductor, and a lead wire electrically connected thereto;a middle chamber which is provided between each second sealed portion and the first sealed portion located in an airtight state so that the corresponding lead portion passes through the middle chamber;wherein one of the two electrodes serves as a cathode while the other electrode serves as an anode, and the high pressure discharge lamp is so designed as to be lit in a position with the anode located above the cathode;the discharge casing is provided with a convex portion constituting a discharge space; andthe dimensions of various components of the lamp are set such that:0.29<{(a-n)/L}<2.75L<Dwhen the distance between the upper end and the lower end of the convex portion is represented by 2a;a reference axis of 2a defined as an axis along the discharging path between the pair of opposing electrodesthe distance from the lower outer end of the convex portion to the midpoint of the distance between the two electrodes is represented by n;the distance between the anode and the cathode is represented by L; andthe diameter of the discharge space formed in the convex portion is represented D.