Abstract: A photo cathode used for an electron image projection apparatus has a silver layer as a photo electric material and a layer of an alkali metal or alkaline earth metal, such as cesium, coated on the silver layer. The cesium is as thick as several atomic layers, and reduces the work function of the photo cathode. The silver layer may be coated all over a substrate, and portions other than the cathode may be masked by a non photoelectric metal, or non transparent metal, such as platinum. Or, the silver layer may be patterned on the layer of a non photoelectric metal coated on the substrate. An excitation light to the photo cathode may be irradiated onto the surface of the silver, or onto the back of the silver layer through a transparent substrate. After depositing the cesium layer on the silver, the layers are heated in a vacuum at 50.degree. to 200.degree. C., thus a contrast ratio, i.e. ratio of electron current from the cathode and from the non cathode portion, is achieved as high as 20.

Abstract: A photoelectron image projection apparatus has a device for detecting an image of a pattern of a mask within a predetermined projection region of the mask. An image signal describing the detected image is compared with a reference image signal which is known from the pattern of the mask, and a defect in the projection pattern is detected when the two compared image signals differ.

Abstract: A photo-cathode image projection apparatus includes a light source for producing an optical beam, a photoelectron mask disposed so as to be irradiated by the optical beam and a photoelectron mask patterned according to a desired pattern with a material that emits photoelectrons in response to irradiation by an optical beam. The apparatus also includes a focusing device for focusing the emitted photoelectrons to form a photoelectron beam focused on the object, an acceleration electrode disposed along the path of the photoelectron beam for accelerating the photoelectrons in the beam, an elongated passage defined in the acceleration electrode to permit passage of a part of the photoelectron beam, and a stage disposed for supporting the object in a position such that the focused photoelectron beam is focused on the object. Also included is a voltage source for applying an acceleration voltage between the photoelectron mask and the acceleration electrode.

Abstract: A photoelectron mask for photo cathode image projection includes a transparent substrate, and a pattern formed on a main surface of the transparent substrate. The pattern includes a non-transparent material. The mask also includes a photoelectron emission film formed so as to cover the main surface of the transparent substrate on which the pattern is formed. The photoelectron emission film includes a material selected from the group consisting of pure platinum, a platinum-rich material containing platinum as the major component, and a platinum compound.