company news about The Precision Molding Technology Analysis of Optical Aspherical Lens

The Precision Molding Technology Analysis of Optical Aspherical Lens 

The molding technology is a high-precision optical component manufacturing process. It involves placing softened glass into high-precision molds, where it is directly formed into optical parts meeting usage requirements through one-step molding under heating, pressure, and oxygen-free conditions.

Since its successful development in the mid-1980s, this technology has evolved over decades and now stands as one of the world’s most advanced optical component manufacturing methods, reaching practical production stages in numerous countries.

The widespread adoption of this technology represents a revolutionary advancement in optical glass component processing. By enabling direct molding of precision aspherical optical components, it has ushered in an era where aspherical glass optics can be widely integrated into optical instruments.

Consequently, this innovation has transformed optical system design : reducing instrument size and weight, saving materials, decreasing coating and assembly workloads, lowering costs, while simultaneously enhancing optical performance and imaging quality.

Advantages of Molded Optical Glass Components:

1. Eliminates traditional grinding, polishing, edging, and centering processes while achieving high dimensional accuracy, surface figure precision, and low surface roughness.
2. Reduces requirements for production equipment, auxiliary tools, factory space, and skilled labor – enabling high productivity even in small workshops.
3. Facilitates economical mass production of precision aspherical optical components.
4. Ensures dimensional accuracy and repeatability through precise control of temperature and pressure parameters.
5. Enables molding of small aspherical lens arrays.
6. Allows integration of optical components with mounting reference surfaces into single units.

Current Production Specifications for Aspherical Components:

• Diameter: 2–50 mm (±0.01 mm tolerance)

• Thickness: 0.4–25 mm (±0.01 mm tolerance)

• Radius of curvature: ≥5 mm

• Surface figure accuracy: 1.5λ

• Surface roughness: Compliant with U.S. Military Standard 80-50

• Refractive index control: ±5×10⁻⁴

• Refractive homogeneity: <5×10⁻⁶

• Birefringence: <0.01λ/cm

Key Aspects of Precision Glass Molding Technology

This comprehensive technology requires specialized molding machines, high-quality molds, and optimized process parameters. Critical elements include molding methods, glass selection, blank preparation, and mold materials/fabrication.

1. Molding Methods
Precision molding became viable through developing mold materials that resist adhesion to softened glass. Early methods involved pouring molten glass blanks into molds >50°C above glass transition temperature (Tg), causing adhesion, porosity, surface defects, and poor form accuracy.

Modern Isothermal Pressing:

• Uses specially engineered molds

• Heats glass and molds together to near-softening point in oxygen-free environments

• Applies pressure at uniform temperature

• Maintains pressure while cooling below Tg
  (Glass viscosity: ~10⁷·⁶ poise at softening point; ~10¹³·⁴ poise at Tg)
  Advantage: High-precision mold replication.
  Limitation: Slow heating/cooling cycles reduce throughput.

Improvements & Alternatives:

• Multi-mold setups increase productivity (though costly for aspherical molds)

• Non-isothermal Pressing: Higher speed and mold longevity by operating closer to blank-forming conditions

• Ongoing R&D in direct molding of molten glass streams

2. Glass Types and Blanks
Blank quality directly affects molded products. While most optical glasses are moldable, high-softening-point glasses accelerate mold degradation. Preferred materials are low-Tg glasses (∼600°C) that:

• Permit cost-effective blank production

• Exclude environmentally hazardous substances (e.g., PbO, As₂O₃)

Blank Requirements:

• Smooth, clean pre-molding surface

• Optimized geometry (spherical, disc-shaped, or meniscus)

• Precise volume control
  Blanks are typically formed by cold grinding or hot pressing.

3. Mold Materials & Fabrication
Ideal Mold Properties:

• Defect-free, polishable optical surfaces

• Oxidation resistance and structural stability at high temperatures

• Non-reactive with glass, easy demolding

• High-temperature hardness and strength

Common Mold Solutions:

• Noble metal/TiN-coated carbide substrates

• Carbon/diamond-like-carbon films on SiC/carbide bases

• Cr₂O-ZrO₂-TiO₂ ceramic composites

Precision Machining Requirements:

• Ultra-precision CNC machines (≤0.01 μm resolution)

• Diamond grinding wheels for shaping

• Subsequential polishing to optical finish

• Advanced aspheric metrology for quality control (critical for micro-lens arrays)

4. Applications
Current mass production capabilities include:

• Precision spherical/aspherical lenses (standard: Ø15 mm; large: Ø50 mm)

• Micro-lens arrays (single lens: Ø100 μm)

Key Implementations:
① Military/civil optical instruments (lenses, prisms, filters)
② Fiber-optic communication aspherical couplers
③ Optical disk pickup lenses: One molded asphere replaces three spherical lenses, reducing weight and cutting costs by 30–50% while improving axial aberration control at high NAs.
④ Camera viewfinders, projector/camera lens aspherics