用双管显微镜检测▽_7～▽_9光洁度时,可采用倒算法计算其等级。计算公式如下: a=2vh 式中,h——光洁度各等级的微不平度值; a——仪器读数鼓轮两次读数之差; V——所选用镜头的倍数,如60×镜头V=33。具体做法是事先查出各等级光洁度微不平度数值的范围,例如R_2=0.8～1.6μm,代入上式,即可算出a在5.3～10.5格之间。只要熟记这些数字,即可知道所测光洁度 Using double-tube microscopy ▽ _7 ~ ▽ _9 finish, you can use the inverted algorithm to calculate the level. The formula is as follows: a = 2vh Where, h - smoothness of the micro-level values ​​of each level; a - instrument reading drum difference between the two readings; V - the multiple of the selected lens, such as 60 × lens V = 33. The specific method is to find out the range of micro-roughness value of each grade in advance, for example R_2 = 0.8 ~ 1.6μm. Substituting into the above formula, we can calculate that a is between 5.3 and 10.5. Just remember these numbers, you can know the measured finish