After the optical lens is finely ground by grinding solution, there is still a crack layer about 2 – 3 m thick on its surface. The method to eliminate the crack layer is polishing. The mechanism of polishing is the same as that of grinding, but the material used is different from that of slurry. The materials used in polishing are cloth, polyurethane and pitch. Usually, the polishing surface with high precision is achieved, and the material often used is polishing pitch. The use of asphalt for polishing is to drive the polishing solution to grind the lens surface to generate heat through the fine surface of asphalt, so that the glass can melt and flow, remove the rough vertices and fill the bottom of the crack, and gradually remove the crack layer.
The role of quality area in optical lens is very important: with the optical axis as the center of a specific area, the surface quality in this area is applicable to the scar / bright spot gauge - quality area: with the optical axis as the center of a specific area, the surface quality in this area is applicable to the scar / bright spot gauge, and the surface outside this quality area has no quality requirements except for special provisions There is no quality requirement for the surface outside this quality area, unless otherwise specified(general appearance inspection assumes that the global area is the quality area) (general appearance inspection assumes that the global area is the quality area)
(1) Generally, the size of large crack edge is indicated on the drawing, but the crack and scratch are not indicated.
(2) -- split edge: refers to the defect at the edge of the lens, and the glass on the edge surface of the lens falls off.
--Crack: refers to the defect at the edge of the lens, the surface of the edge of the lens has cracks, but the glass does not fall off. --Crack: refers to the defect at the edge of the lens, the surface of the edge of the lens has cracks, but the glass does not fall off.
--Scratch: refers to the bad edge of the lens, a group of short scars. --Scratch: refers to the bad edge of the lens, a group of short scars.
(3) Unless otherwise specified, the acceptance of these three defects can be judged according to the specification of the split edge.
The main use of organic solvent cleaning agent is to clean asphalt and paint. In the past, trichloroethane or trichloroethylene was used as solvent cleaner. Trichloroethane is an ODS (ozone depleting substance) product, which is currently in the phase of compulsory elimination. Long term use of trichloroethylene is easy to cause occupational diseases, and because trichloroethylene is very unstable and easy to hydrolyze to acid, it will corrode lenses and equipment. In this regard, domestic detergent manufacturers have developed and produced a series of non ODS solvent based cleaners, which can be used to clean optical glass; and the products have different physicochemical indexes, which can effectively meet the requirements of different equipment and process conditions.
Criteria of scratch in optical lens processing
(1) L '= ≤ 1 / 4 × D ﹥ is acceptable when there is only large scar
(2) L '= ∑ [(w / N) × l] ≤ 1 / 2 × D] is acceptable when there are large and small scars at the same time
(3) When ∑ W '= the total scar length of the lens is less than or equal to L' = the total scar length of the lens
(4) Ex.1: for the 80 / 50 lens with a diameter of 40mm, after checking the surface of the lens, the following scars were found: 80 scars 8mm
L '= 8mm ≤ 1 / 4 × 40 = 10mm = > acceptable
Ex.2: for the 80 / 50 lens with a diameter of 8.2mm, after checking the lens surface, the following scars were found: 80 scar 8mm, 60 scar 4mm, 40 scar 6mm
L '= (80 / 80) × 8 ＋ (60 / 80) × 4 ＋ (40 / 80) × 6 = 14mm ≤ [1 / 2 × 40 = 20mm] = > acceptable ex.3: for 80 / 50 lens with a diameter of 40mm, after checking th
lens surface, the following scars were found: 60 scars 8mm, 40 scars 6mm, 20 scars 8mm
L '= (60 / 80) × 8 ＋ (40 / 80) × 6 ＋ (20 / 80) × 8 = 10mm ≤ 40mm = > allowable L' = (60 / 80) × 8 ＋ (40 / 80) × 6 ＋ (20 / 80) × 8 = 10mm ≤ 40mm = > allowable
(5) The scar standard of the coated reflective film shall be determined according to the specification of "scar / bright spot" in the drawing.