Follow the traditional evaluation method for the absolute testing of three optic flats, the result of the deviation can be evaluated by the deviation on two perpendicular diameters, its evaluation method is different from the true surface graph exactly.

• 摘要按传统三面互检法评价平面度偏差，结果只能由评价平晶在两条相互垂直的直径线上的测量数值得到，其评价方法与平晶的真实面形偏差存在差异。