Schematic diagram of optical coatings

1. Introduction to PVD Filter Manufacturing

Filter fabrication primarily uses Physical Vapor Deposition (PVD), where film materials are vaporized into atoms/molecules (or ionized) under vacuum, then deposited onto substrates. For fluorescence detection filters, the industry commonly employs three coating systems, detailed below with their unique features.

2. Three Key Coating Equipment Types

2.1 Evaporation Coating Equipment

• Advantages: High deposition rate, large single-batch output, low cost
• Limitations: Max ~100 coating layers; thickness control error ~0.5%
   To achieve OD6 isolation for excitation/emission filters, 4–5 sub-filters must be glued together.

2.2 Magnetron Sputtering Equipment

Compared to evaporation systems:

• Advantages: Better film uniformity; higher thickness precision (error ~0.2%); max ~200 layers
• Limitations: Smaller batch output; higher cost
   For OD6 filters, a dual-side coating approach on one substrate is feasible.

2.3 Ion Beam Sputtering Equipment

• Advantages: Excellent uniformity; ultra-precise thickness control (error ~0.1%); >500 layers
• Limitations: Slow deposition rate; minimal batch output; highest cost
   Enables single-side coating for OD6 filters on a single substrate.

3. Critical Considerations for Equipment Selection

- Substrate Quality: Sputtering methods (magnetron/ion beam) require high surface finish substrates to avoid surface hazing.   - Process Monitoring: Advanced thickness control is essential to minimize spectral deviation from design specs.  Conclusion: Each system offers trade-offs. Optimal selection balances spectral requirements, manufacturing difficulty, and cost—e.g., evaporation for high-volume/low-layer needs, sputtering for precision/high-layer applications.