1. Optical processing is generally divided into two types: thermal processing and cold processing.

Thermal processing refers to the method of hot pressing forming, such as the processing of aspheric surfaces and LED lenses.

Cold processing mostly utilizes traditional physical grinding methods. Currently, most spherical lenses belong to cold processing.

2. Introduction to the processes of optical cold processing.

1. Cutting

2. Sanding

3. Grinding

4. Core extraction

5. Coating

6. Bonding

7. Inking

8. Cleaning

3. Characteristics of defects and non-characteristic defects.

Characteristic defects refer to defects caused by specific processes in optical cold processing.

Non-characteristic defects refer to defects that may occur in various processes of optical cold processing.

4. Classification of product defects:

1) Incoming material defects.

Incoming material defects are generally divided into dimensional defects and material defects.

Dimensions refer to outer diameter, chamfering, thickness, and R refers to exceeding the drawing dimensions of the blank.

Material defects generally refer to issues with the material itself, such as impurities, bubbles, etc.

2) Grinding defects.

Scratches: During grinding, improper handling or measurement methods, or poor particles on the grinding plate can scratch the surface of the lens. They can be linear, point-like, or arc-shaped.
Striped and point-like.
Grain: The polished surface of the lens may leave point-like or mesh-like defects due to rough grinding or insufficient fine grinding.
Point-like and mesh-like.
Analysis of grinding defects:

1. Peripheral: Incomplete grinding or insufficient wear, resulting in flickering bright spots on the edges of the lens grinding surface.

2. Overall: Incomplete grinding or insufficient wear, resulting in flickering brightness across the entire lens grinding surface.

3. Coarse bright spots: Incomplete grinding or insufficient wear on the lens grinding surface, forming coarser flickering bright spots.
3) Characteristic defects.

Core extraction defects: Poor appearance, dimensional defects, clamping injuries: Core extraction processing clamps have burrs, causing arc-shaped or point-like scratches.

Cracks: The edges of the lens grinding surface may crack due to uneven force. Cracks caused by core extraction are often serrated, resulting from too fast cutting or poor grinding of the grinding wheel.

Bright spots: Due to rough edges from core extraction, the ink cannot penetrate evenly after inking, resulting in granular white bright spots.

Poor back turning: The lens is turned over before core extraction, causing issues on the back after core extraction.

4) Coating defects.
A. Film shedding: Insufficient adhesion of the vapor-deposited film layer on the lens surface, resulting in strip-like or block-like film shedding after cleaning or wiping. The causes of this defect include insufficient cleanliness of the substrate before coating, inadequate vacuum during vapor deposition, or insufficient baking temperature.

B. Film absence: Point-like or strip-like areas on the film surface that are not coated or inconsistencies in the film layer. The causes of this defect include dust or fluff on the lens surface during vapor deposition.

C. Film shortage: Areas around the lens grinding surface that are not coated (crescent-shaped, full perimeter, one side). The cause of this defect is poor fit between the lens and the coating fixture.

D. Large particles: During the coating process, splashing or spraying of the vaporized material adheres to the lens.

E. Film color NG, heavy film, etc.

5) Bonding defects.

A. Bubbles: The bonding layer has circular bubble-like defects, caused by uneven mixing of glue or incomplete air release during bonding.

B. Dry glue: The bonding layer has dried glue on the outer diameter surface, appearing shiny or cracked, caused by scraping or wiping the glue that eroded the bonding layer.

C. Internal contamination: Impurities or dirt in the bonding layer, appearing as point-like distributions, caused by insufficient cleaning of the bonding surface.

D. Delamination: The bonding layer separates, showing interference stripes, points, and other peeling phenomena.

Dimensional defects in bonding refer to thickness and eccentric thickness: After bonding two lenses, improper matching of individual lens thickness can cause the finished product to exceed thickness specifications.

Eccentricity: After bonding two lenses, the degree of overlap of the central optical axis exceeds specifications.

6) Inking defects: Poor appearance, dimensional defects:

A. Ink overflow: Due to excessive ink or improper technique, ink overflows the inking area.

B. Uneven inking: The ink is unevenly applied or the ink color is inconsistent; C. Light ink: The ink color is too light to achieve the desired matte effect.

D. Stains: After inking, dense point-like or fingerprint-like marks appear, caused by contamination of the inking surface before inking.

E. Incomplete coverage: The inking area is not fully covered.

F. Ink removal: The adhesion of the ink is insufficient, causing the ink layer to detach from the lens under external forces (such as ultrasonic cleaning, etc.).