close
Choose Your Site
Global
Social Media
Unlike wavelength-selective filters (e.g., bandpass, longpass) that block specific wavelengths, ND filters reduce power across all wavelengths equally, preserving color balance in imaging and spectral integrity in measurements. Our variable ND filters offer adjustable attenuation to meet dynamic lighting conditions (e.g., changing sunlight intensity in photography, varying laser power in research), eliminating the need for multiple fixed-density filters. Manufactured using high-purity substrates (UV fused silica) and advanced coating technology (metallic Inconel or dielectric coatings), our ND filters ensure flat spectral response (<2% transmission variation across the operating range), high durability (resistant to scratches and chemical exposure), and long-term stability (<1% transmission drift per year). With applications from consumer photography to industrial laser testing, they meet the performance standards of ISO 12233 (imaging) and MIL-PRF-13830B (optical components).
Optical Density (OD) Ranges: Available in 0.04–2.0 (low attenuation, 90–1% transmission) and 0.04–4.0 (high attenuation, 90–0.01% transmission) ranges, where OD 2 reduces transmission to 1% (10⁻⊃2;) and OD 4 to 0.01% (10⁻⁴). The 0.04–2.0 range is ideal for photography (e.g., long exposures in bright sunlight), while 0.04–4.0 suits laser applications (e.g., reducing 1W laser power to 10μW for detector calibration) .
Linear Adjustment: Continuously variable attenuation via 270° rotation, with linear density gradients (10.9nm/mm or 12.7nm/mm) ensuring predictable attenuation changes. For example, a 12.7nm/mm gradient means rotating the filter 1mm increases OD by 0.127, simplifying precise power control. The rotation mechanism uses ball bearings for smooth operation and repeatability (<0.01 OD variation per rotation cycle) .
Broadband Operation: Effective from 240nm to 1200nm (uncoated) or 350–1050nm (AR-coated), covering UV, visible, and near-infrared wavelengths. Uncoated models are suitable for general applications (e.g., photography), while AR-coated models reduce reflection loss to <1% per surface, improving transmission flatness in high-precision measurements (e.g., spectrophotometry) .
Flat Response: Maintains uniform attenuation across wavelengths to preserve color balance and spectral integrity. For example, an AR-coated ND filter with OD 2 has <1% transmission variation between 400nm (blue) and 700nm (red), ensuring no color shift in photography or spectral distortion in laser spectroscopy .
Substrate Quality: UV fused silica substrates ensure <λ per cm² surface flatness (λ=633nm) for minimal wavefront distortion—critical for laser systems where wavefront error can cause beam divergence or focusing issues. The substrates have high mechanical strength (Mohs hardness 7) and resistance to thermal shock (ΔT > 200°C), making them suitable for harsh industrial environments .
Coating Technology: Metallic Inconel coatings (for 240–1200nm) provide uniform attenuation and high abrasion resistance (meets MIL-C-48497 standards), while dielectric coatings (for 350–1050nm) offer higher transmission flatness and lower absorption. Both coating types are deposited via magnetron sputtering, ensuring strong adhesion to the substrate (>5N adhesion force) and resistance to humidity (95% RH, 40°C for 1000 hours) .
Mounting Options: Available in mounted versions with angular graduations (0–270°) for precise OD adjustment, and adapters for 8-32 and M4 mounting holes to fit standard optical posts. Mounts are made of anodized aluminum to prevent corrosion and ensure compatibility with laboratory and industrial equipment. Unmounted versions are also available for custom integration (e.g., camera lens filters) .
High-Resolution Cameras: Enables longer exposures in bright conditions without overexposure. For example, a variable ND filter with OD 0.04–2.0 allows exposures of 1–30 seconds in sunlight, capturing smooth water motion in landscape photography or light trails in night photography. The flat spectral response ensures no color cast (e.g., yellow or blue tint) in images .
Projectors: Controls light output in entertainment systems to match ambient lighting. In large-venue projectors, a fixed ND filter with OD 1 reduces output from 10,000 lumens to 1,000 lumens, preventing eye strain in dark rooms while maintaining image contrast and color accuracy .
Beam Attenuation: Safely reduces laser power for detector calibration and eye-safe measurements. For example, a variable ND filter with OD 0.04–4.0 reduces 10W laser power to 10μW (OD 4), allowing calibration of photodiodes without damaging the detector. The linear adjustment enables precise power stepping (e.g., 0.1W increments) for dose-response studies in laser-material interaction .
Spectroscopy: Prevents detector saturation in high-intensity light sources. In atomic absorption spectroscopy, an ND filter with OD 2 reduces the intensity of the hollow cathode lamp (HCL) to within the linear range of the detector, ensuring accurate concentration measurements of trace elements (e.g., lead in water samples) .
Sensor Calibration: Provides known attenuation levels for validating light sensors. In automotive manufacturing, ND filters with calibrated OD values (e.g., OD 1.00 ±0.02) are used to test ambient light sensors in cars, ensuring they correctly adjust dashboard brightness based on sunlight intensity .
Environmental Monitoring: Controls light intensity in gas detection systems. In UV-visible spectrophotometers used for water quality analysis, an ND filter with OD 1.5 reduces light intensity to avoid detector saturation when measuring high-concentration pollutants (e.g., nitrates), ensuring accurate absorbance readings (0–2 AU) .
Q: How does optical density (OD) relate to transmission?
A: Transmission (T) is calculated using the formula T = 10^(-OD), where OD is optical density. For example, OD 3 provides 0.1% transmission (10⁻⊃3;), while OD 4 reduces light to 0.01% (10⁻⁴). Our variable ND filters allow continuous adjustment between minimum (OD 0.04, ~90% transmission) and maximum (OD 4.0, ~0.01% transmission) OD, enabling precise control over light intensity. We provide a calibration chart with each filter to convert rotation angle to OD/transmission for easy use .
Q: Are ND filters wavelength-specific?
A: No, our neutral density filters provide uniform attenuation across their spectral range (240–1200nm for uncoated, 350–1050nm for AR-coated), unlike color filters that attenuate specific wavelengths. This flat response is critical for applications like photography (preserving color balance) and spectroscopy (maintaining spectral integrity). For example, an ND filter with OD 2 attenuates 400nm (blue) and 700nm (red) light equally, ensuring no color shift in images or spectral distortion in measurements .
Q: Can variable ND filters replace fixed-density filters?
A: Yes, their 0.04–4.0 OD range covers multiple fixed filter densities (e.g., OD 0.3, 0.6, 1.0, 2.0, 3.0, 4.0), simplifying setups and reducing inventory. A single variable ND filter eliminates the need to swap 6+ fixed filters, saving time and reducing alignment errors (common when changing filters). Variable filters are especially useful in dynamic environments (e.g., outdoor photography with changing light, laser research with variable power levels) where fixed filters would require frequent adjustments .
Q: What mounting options are available?
A: Mounted versions include rotating axles with angular graduations (0–270°) for precise OD adjustment, and adapters for 8-32 (imperial) and M4 (metric) mounting holes to fit standard optical posts (e.g., Thorlabs, Newport). The mounts have locking screws to secure the filter in place once the desired OD is set, preventing drift during operation. Unmounted versions (bare filters) are available in standard diameters (25mm, 50mm, 75mm) for custom mounting (e.g., camera lens filters with adapter rings, industrial machine vision systems). We also offer custom mounts (e.g., motorized rotation for automated systems) upon request .
