| 摘要 |
PURPOSE:To reduce the exposure unevenness of a phosphor screen due to a step different part, by setting the central thickness of areas adjoined with each other by the step different part so as to cause this step different part to become the minimum or infinitesimality, in case of a correcting lens provided with a discontinuous curved surface having the discontinuous step different part. CONSTITUTION:An effective surface of a correcting lens 11 is divided into plural areas, and when thickness of the center of the area 12a is set to d1, thickness in the center of the 12b to d2, thickness of the center of the 12c to d3, thickness of the center of the 12d to d4, thickness of the center of the 12e to d5 and thickness of the center of the 12f to d6, respectively, those of d1, d2, d3, d4, d5 and d6 are all varied so as to cause step different parts 13a, 13b, 13c, 13d and 13e among these areas to become, for example, the minimum of 100mum or so or infinitesimality. Thus, each step different part is made into the minimum or infinitesimality whereby the degree of light and shade streaks on a phosphor screen comes possible to be checked. Thus, a factor controlling a congruity between an exposure beam at each area and an electron beam orbit comes to two parts, or the central thickness and a plane surface of the area or a tilt of the curved surface, so that the degree of freedom in a design for the correcting lens is increased.
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