Exploring the Precision Processing of Sapphire Glass Lens: Tackling the Precision Technology of Super hard Materials

At the core of high-end optical equipment, behind the crystal clear sapphire glass lenses, there is a contest between human craft and material limits. Sapphire glass (second only to diamond) with Mohs hardness of 9 has become an ideal material for protection covers of aerospace lenses, medical endoscopes and mobile phone cameras due to its excellent wear resistance and light transmittance. However, this “rigid and fragile” feature also makes its finishing become the “Everest” in the manufacturing industry – the edge collapse rate under the traditional process is as high as 5% – 8%, the scratch rework rate is nearly 20%, and the cost remains high. How to tame this super hard material? An innovation in precision manufacturing is under way.

1、 Finishing process: fine carving of superhard materials

The manufacturing of sapphire glass lens is a transformation process from rough to precise, which needs to go through more than ten processes:

Laser cutting: picosecond accurate cutting
Outsourced sapphire cylinder raw materials need to pass Picosecond laser cutting machine Make multiple cuts. The laser beam vaporizes the materials in the processing area within 10 picoseconds to form standard sheets. This “cold working” technology has a very small heat affected zone to avoid cracks and edge collapses caused by traditional mechanical cutting.
Grinding and fine grinding: micron level carving with rigid and flexible combination
- Rough grinding stage : Use high-precision grinder and diamond powder to remove surface burrs and cutting marks.
- Structured fine grinding : Customized tools are used for different parts of the lens:
  - R corner treatment : Bakelite grinding head rubs for 200-300 seconds under the pressure of 1-2kg to reduce the roughness to Sa50nm
  - Platform plane processing : Copper flat bottom right angle grinding head is finely polished with 2.5-5kg pressure to achieve Sa30nm level finish
  - Arc surface finishing : Solve the problem of edge collapse of small arc surface by using copper grinding head with R angle and oily grinding powder
Physical strengthening: a tough core endowed by thermodynamics
The ground lens needs to experience in the strengthening furnace Heating quench Process:
- Heat to specific temperature to relieve internal stress
- Rapid and uniform air cooling makes the surface layer form a compressive stress layer
  This process improves the impact strength by more than 3 times, ensuring the stability of the lens in extreme environments.
Ultrasonic Cleaning and Coating: Nanoscale Cleaning and Efficiency Enhancement
Adopt Three stage pure water cleaning system (Immersion spray countercurrent rinsing) to remove micron scale debris. In the coating process, magnesium fluoride is evaporated in the vacuum chamber to form a nanometer antireflective film on the lens surface, and the transmittance is increased to more than 98%.

2、 Technical breakthrough: break through the industry pain point

The difficulties in sapphire processing mainly focus on brittleness control and efficiency improvement:

Edge collapse control revolution ：
Developed by Xintenghui CNC Ceramic engraving machine By strengthening the rigidity of the machine tool, minimizing the machining vibration, and cooperating with the fully sealed dust-proof design, the edge collapse rate is reduced from 8% to less than 2%. National Olympic Laser Picosecond ultraviolet cutting system The 3D galvanometer technology is used to realize the non collapse processing of arc screen, cone and other special-shaped structures.
Scratch treatment scheme ：
Innovative use of Bourne Optics Four step fine grinding method : Through the combination process of bakelite grinding head → bakelite pen → copper grinding head → copper grinding head with R angle, the scratch rework rate is reduced to below 5%, and the yield rate is 95%.

3、 Leading edge technology: the future of ultra precision machining

Chemical mechanical grinding (CMP) technology
Add in mechanical grinding fluid Chemically active solution Through the synergistic effect of mechanical friction and chemical corrosion, atomic level surface removal can be achieved, and the roughness can be controlled at 0.1nm.
Breakthrough in laser micro welding
Used in the field of medical endoscope Pulsed laser welding Technology, precisely control the heat affected zone, realize the micron level sealing connection between the sapphire lens and the metal cavity, and completely solve the aging problem of traditional gluing.

4、 Application scenario: guardian of precision optics

Medical endoscope : Sapphire lens with diameter less than 3mm, sealed by ultrasonic welding technology, resistant to high temperature disinfection and mechanical friction in the body
Camera cover of mobile phone : Curved sapphire glass with a thickness of 0.3mm, after picosecond cutting and four step fine grinding, its scratch resistance is 10 times higher than that of traditional glass
Space observation lens : The physically strengthened sapphire lens has no fracture under the temperature difference of – 180 ℃~800 ℃, and is used in the optical system of the Mars probe

5、 Future road: integration of intelligence and ultra precision

With the popularization of femtosecond laser technology, the machining accuracy is leaping from the micron level to the nanometer level. Domestic manufacturer Ruxin Tenghui CNC has developed Full automatic fine carving production line , integrating machine vision real-time detection, and improving the processing efficiency by 40%. The iteration of vacuum coating technology enables the multi-layer composite film system to achieve 99.99% transmittance at specific wavelength, paving the way for quantum optical lenses.

The finishing of sapphire glass lens is a witness to the perfect integration of the rigidity of natural creation and the flexibility of technological process. When each lens is formed under picosecond laser, streamed under the copper grinding head, and transparent in the vacuum coating, what we see is not only the ultimate optical performance, but also the eternal challenge of precision manufacturing to the material limit.