Linear Variable Neutral Density (LVND) Filters are precision optical components designed to vary optical density linearly across the surface, enabling fine and repeatable control of light intensity. By translating the filter relative to the beam—or by counter-translating paired elements—users can achieve smooth attenuation without introducing spectral distortion.
These filters are produced with tight control over surface quality, parallelism, and density linearity. Common substrates include B270 and fused silica, providing excellent optical clarity and thermal stability. Standard designs cover 380–2000 nm (B270) and 250–2500 nm (fused silica), making them suitable for a wide range of optical systems.
Key Features
- Precise Light Attenuation – Smooth, controlled modulation of light intensity
- Linear Density Gradient – Continuous optical density change along the filter length
- Versatile Operation – Suitable for laser and white-light applications
- High Optical Quality – Premium substrates ensure clarity, accuracy, and stability
- Custom Solutions – Wavelength range, OD profile, and size configurable
Spectrum Transmission
Standard transmission profiles are available. When standard components do not meet application needs, custom spectrum transmission curves can be designed to match specific wavelength ranges, attenuation levels, and optical performance requirements.
Coating Quality & Environmental Reliability
All LVND filters undergo rigorous testing to ensure durability and performance:
- Adhesion Test (MIL-C-675C) – No blistering or peeling after repeated tape removal
- Thermal Cycling – −62°C to +71°C with no coating detachment
- Abrasion Resistance (MIL-C-675C / CCC-C-440) – No damage after 25 cycles at 1.0 lb load
- Humidity Test – 95–100% RH at 49°C for 24 hours without defects
- Solvent Resistance – Stable after acetone and alcohol exposure
- Salt Spray Test – 100 hours at 35°C, 5% salt concentration with no degradation
Standard Specifications
| Feature | Specification |
|---|---|
| Materials | B270, Fused Silica |
| Diameter Tolerance | ±0.1 mm |
| Thickness Tolerance | ±0.05 mm |
| Surface Quality | 80-50 |
| Parallelism | ≤ 3′ |
| Coating Specs | R < 0.2% @ 1060–1080 nm |
| Design Wavelength | 380–2000 nm (B270), 250–2500 nm (Fused Silica) |
| Calibrated Wavelength | 550 nm |
Typical Applications
- Laser Systems – Power tuning for cutting, welding, and engraving
- White-Light Optics – Controlled attenuation in experiments and instruments
- Optical Testing & Metrology – Precise intensity adjustment without spectral shift
- Cameras & Sensors – Maintain optimal exposure levels
- Spectroscopy – Prevent detector saturation and control signal levels
Standard Products
| Item | Material | Wavelength Range | Size |
|---|---|---|---|
| LVND Filter (VIS–NIR) | B270 | 380–2000 nm | D22.4×4.1, D25.4×4 |
| LVND Filter (UV–IR) | Fused Silica | 250–2500 nm | D50×2, D50×3, D134×3 |
Additional sizes, OD gradients, and wavelength optimizations available upon request.