First move the cutting head to the front, and then prepare the masking paper. Note: the fan cannot be turned on to prevent dust from entering when changing the lens and contaminating the focusing lens, collimating mirror, etc. on it. Unscrew the screws and tear off a section of masking paper, pull out the drawer that protects the lens, and seal the opening with masking paper to prevent dust from entering, then take out the phone, turn on the light, and shine on the lens from bottom to top to check whether the lens is polluted. For a replacement, to replace the lens, first take out the gland, then take out the lens, take care to take the side of the lens, do not touch the lens, put the new lens back after replacement, put the gland on, press it, and then use it again Use the same method to observe whether the lens is contaminated. If there is no pollution, tear off the masking paper, tighten the two screws protecting the lens, and then replace the lens.
