exactly i will make a white spot to reflect the light , i want t use ir because i think it is easy and i only want the spot , the optical need an extra round thing to measure the slots . i am sorry for my bad English
exactly i will make a white spot to reflect the light , i want t use ir because i think it is easy and i only want the spot , the optical need an extra round thing to measure the slots . i am sorry for my bad English