Customize Long pass Infrared Black HWB Optical Filter Glass

Manufacturing Process and Workflow of HWB Optical Glass

The production of HWB optical glass is a highly precise and controlled sequence of operations designed to achieve specific optical properties such as refractive index, Abbe number, and high transmittance. The entire process can be broken down into the following key stages:

• Batching and Raw Material Preparation  

• Process: Ultra-high-purity raw materials (e.g., silicon dioxide, boron oxide, barium carbonate, and various other oxides and dopants) are precisely weighed according to the proprietary chemical formula for HWB glass.
• Purpose: To ensure the final glass has the exact chemical composition required for its target optical and physical properties. The mixture is called a "batch."

• Melting  

• Process: The mixed batch is fed into a high-temperature furnace. For high-quality optical glass like HWB, the melting pot or tank is often lined with platinum or similar inert materials to prevent contamination from the furnace walls.
• Conditions: Melting occurs at extreme temperatures, typically between 1300°C and 1600°C, depending on the composition.

• Refining and Homogenization 

• Refining (Fining): The molten glass is held at a high temperature to allow gas bubbles (seeds) to rise to the surface and escape. Chemical fining agents may also be used to help dissolve and remove these bubbles.
• Homogenization: The melt is vigorously stirred using a platinum stirrer to eliminate any striae or cord (local variations in composition). This step is critical for achieving the high optical homogeneity required for precision lenses.

• Forming  

• Process: The homogeneous, bubble-free melt is then shaped into a usable form. Common forming methods include:
• Molding: Pouring the melt into pre-heated molds to form rough lens blanks, prisms, or blocks.
•  Casting: Casting into large blocks which are later cut into smaller pieces.
•  Continuous Rolling: For producing large sheets of glass.

• Annealing  

• Process: The formed glass is transferred to a special furnace called an annealing lehr. Here, it is heated to a precise temperature below its melting point and then cooled very slowly according to a strictly controlled time-temperature profile.
• Purpose: To relieve internal stresses created during forming and cooling. Unrelieved stress can cause birefringence and make the glass prone to fracture, rendering it useless for optical applications.

• Cold Working / Precision Machining  

• This is typically done by optical component manufacturers who purchase the annealed glass blanks. The process involves:
• Cutting: Cutting large blocks into smaller, workable sizes.
• Grinding: Using diamond-impregnated wheels to shape the glass to the required curvature and dimensions (generating).
• Lapping and Polishing: Progressively using finer abrasives and finally a polishing slurry (e.g., cerium oxide) on a polishing pad to achieve an optical-quality surface with nanometer-level smoothness and minimal sub-surface damage.

• Coating  

• Process: After polishing, optical coatings (such as anti-reflection coatings) are often applied to the surfaces using techniques like Physical Vapor Deposition (PVD) or Sputtering.
• Purpose: To enhance light transmission and reduce reflections, improving the overall performance of the optical element.

• Quality Control and Inspection  

• This is an integral part of the entire process. Key parameters checked include:
• Optical Properties: Refractive index (nd) and Abbe number (νd).
• Internal Quality: Homogeneity, presence of bubbles, and inclusions.
• Stress: Level of residual internal stress, measured with a pol

Advantages of HWB Optical Glass

The primary advantages of HWB optical glass stem from its carefully engineered chemical composition, which typically offers a balance of the following properties:

• Excellent Transparency and High Transmittance

• It exhibits very high light transmittance across a broad spectral range, from the visible to near-infrared (or specific designed wavelengths), minimizing light loss within the optical system.

• Good Environmental Stability

• This glass typically possesses high resistance to environmental factors such as humidity, staining, and mild chemicals. This ensures long-term durability and reliability of optical components without significant degradation in performance.

• High Chemical Durability

• It often demonstrates strong resistance to corrosion and weathering, protecting the glass surface from attacks by water, acids, or alkalis, which helps maintain surface quality and optical clarity.

• Low Birefringence

• Through precise manufacturing and controlled annealing processes, HWB glass can achieve very low levels of internal stress, resulting in minimal birefringence. This is critical for high-precision applications like microscopy and lithography where polarized light is used.

• Good Mechanical Properties and Processability

• It has sufficient hardness and strength to withstand the rigors of optical fabrication, including cutting, grinding, and polishing, allowing it to be shaped into complex lenses and prisms with high precision.

Applications of HWB Optical Glass 

Due to its advantageous properties, HWB optical glass is widely used in various high-tech and industrial fields:

• Precision Imaging Lenses
• Microscopy
• Photographic Lenses
• Optical Instruments and Sensors
• Laser Systems