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. This low temperature heat processing prevents lateral diffusion of the mask metal, resulting in a sharp edge of the cathode pattern. Silver and the cesium thereon are not susceptive to open air atmosphere, thus allowing long life and easy handling for an efficient lithography processing. The low absorption edge of the silver allows the use of a high pressure mercury lamp whose light is easily focused by a lens.