Features
- Adjustable Light Attenuation: Circular variable ND filters provide continuous, linear light attenuation by simple rotation, enabling precise control of transmitted intensity.
- Wide Spectral Coverage: Designed to operate from 380 nm to 2500 nm, suitable for VIS, NIR, and IR applications.
- Durable Optical Construction: Manufactured from K9 optical glass (with fused silica options), offering excellent durability and optical uniformity.
- High Optical Performance: Anti-reflection (AR) coatings ensure high transmission and low surface reflection across the operating wavelength range.
- Customizable Designs: Available in multiple diameters and density ranges, with custom sizes and specifications supported for OEM and research applications.
General Description
Shape Optics Technologies (SOT) supplies high-performance Circular Variable Neutral Density Filters designed for precise light attenuation in advanced optical systems. By rotating the filter, users can achieve smooth and repeatable intensity adjustment, making these filters ideal for applications involving white light sources and lasers.
Constructed from high-quality K9 optical material, SOT circular variable ND filters deliver reliable optical performance over a broad wavelength range. Counter-rotating filter designs allow attenuation over a large finite aperture, providing flexibility for complex optical setups.
Standard diameters include 25 mm, 50 mm, 60 mm, and 100 mm, with additional customization available to meet specific system requirements. These filters are widely used in scientific instrumentation, laser systems, optical testing, and measurement equipment where controlled light levels are essential.
Spectrum Transmission Curves & Customization
Standard spectral transmission curves are available for reference.
If standard products do not meet your needs, custom circular variable ND filters can be designed to match your exact wavelength range, density range, and aperture requirements.
Contact us to discuss custom configurations or request a quotation.
Coating Quality & Environmental Reliability
All circular variable ND filters are tested in accordance with MIL-C-675C and CCC-C-440 standards:
- Adhesion Test: LT-90 tape test; three removals with no blistering or peeling
- Temperature Cycling: −62 ± 1 °C to 71 ± 1 °C; no coating detachment
- Abrasion Resistance: ≥1.0 lb gauze test, 25 cycles; no surface damage
- Humidity Resistance: 49 ± 2 °C, 95–100% RH for 24 hours; film intact
- Solvent & Cleaning: Acetone and alcohol exposure; no peeling or scratches
- Salt Spray: 100 hours at 35 °C with 5% NaCl; excellent corrosion resistance
Standard Specifications
| Parameter | Specification |
|---|---|
| Material | K9 Optical Glass |
| Coated Area | 0° – 270° |
| Surface Quality | 80–50 |
| Outside Diameter | 25 mm, 50 mm, 60 mm, 100 mm |
| Inside Diameter | 7.5 mm, 8.0 mm, 8.3 mm |
| Thickness | 2.0 mm ± 0.05 mm |
| Design Wavelength | 380–2000 nm (B270), 250–2500 nm (Fused Silica) |
| Relative Density Range | 0–1.0, 0–1.5, 0–2, 0–3 |
Applications
Circular Variable Neutral Density Filters are widely used in applications requiring precise and adjustable light control, including:
- Scientific Instruments – Spectroscopy, optical testing, and laboratory experiments
- Laser Systems – Safe and controlled laser power attenuation
- Optical Measurement & Imaging – Fluorescence microscopy, biochemical analysis, and imaging systems
The rotational attenuation mechanism makes these filters especially valuable in both research and industrial environments where accurate light modulation is required.
SOT Strengths & Capabilities
SOT combines advanced optical coating expertise with precision manufacturing to deliver reliable and high-performance variable ND filters. With strong capabilities in custom optical filter design, SOT supports customers with tailored solutions that meet exact optical, mechanical, and environmental requirements—making us a trusted partner for high-precision optical components.
Standard Products
| Outside Diameter | Inside Diameter | Thickness | Density Range | Product Code |
|---|---|---|---|---|
| 25 mm | 7.5 mm | 2.0 mm ± 0.05 mm | 0–1.0 / 1.5 / 2 / 3 | CVND-25-7.5 |
| 50 mm | 8.0 mm | 2.0 mm ± 0.05 mm | 0–1.0 / 1.5 / 2 / 3 | CVND-50-8.0 |
| 60 mm | 8.3 mm | 2.0 mm ± 0.05 mm | 0–1.0 / 1.5 / 2 / 3 | CVND-60-8.3 |
| 100 mm | 8.3 mm | 2.0 mm ± 0.05 mm | 0–1.0 / 1.5 / 2 / 3 | CVND-100-8.3 |
Custom configurations are available upon request.