Name: Neutral Density Filter
Rating: 4.5 (100 reviews)

Key Features

Materials

Optical glass such as K9, fused silica, sapphire, MgF2, silicon (Si), ZnSe, ZnS, etc. These materials possess high transmittance, low absorption, low scattering, uniform refractive index, and specific dispersion characteristics.
Shape

Precisely hemispherical. The machining precision of the center and radius of curvature of the sphere is extremely high.
Surface Quality

The surface is precision polished to an optical grade of 10-5 to ensure image quality and reduce scattering and aberrations.
Coating

An AR coating is typically applied to the concave surface to maximize the transmittance of specific wavelengths of light (e.g. visible light) and reduce reflection loss.

Drawing

Ecoptik China makes fixed OD value neutral density filter by depositing Inconel film on a clear cubstrate. The advantage of the optical density filter is in the broader band and lower ripple than that of absorptive density filter. The coated wavelengthcan be extended to 200nm to 1100nm or more. The disadvantage is that there is some reflective light on the optical filter glass. The OD value can vary from 0.1 to 0.5. The OD value is controlled by coating inconel thin film thickness. Regular thickn thickness of the NDF is 1.1mm or 0.55mm.

This kind of optical density filters can be used for video, waterfalls, ophthalmology and landscape photography.

Specification of Neutral Density Filter

Material	BK7
Diameter tolerance	+0.0/-0.1mm
Thickness tolerance	±0.1mm
Parallelism	<3 arc min
Flatness	λ~λ/10
Clear aperture	>90%
Density tolerance	±2%

Part No.	Wanvelength Range (nm)	Optical Density (OD) @550nm
ND01	400-1100	0.1
ND02	400-1100	0.2
ND03	400-1100	0.3
ND04	400-1100	0.4
ND05	400-1100	0.5
ND06	400-1100	0.6
ND07	400-1100	0.7
ND08	400-1100	0.8
ND09	400-1100	0.9
ND10	400-1100	1
ND20	400-1100	2
ND30	400-1100	3
ND40	400-1100	4
ND50	400-1100	5

Typical Application Areas

Underwater Photography and Detection:

Observation windows for underwater cameras, ROVs (Remotely Operated Vehicles), and AUVs (Autonomous Underwater Vehicles). The hemispherical design provides a near 180° wide field of view while withstanding water pressure.
Underwater Photography and Detection:

Observation windows for underwater cameras, ROVs (Remotely Operated Vehicles), and AUVs (Autonomous Underwater Vehicles). The hemispherical design provides a near 180° wide field of view while withstanding water pressure.
Underwater Photography and Detection:

Observation windows for underwater cameras, ROVs (Remotely Operated Vehicles), and AUVs (Autonomous Underwater Vehicles). The hemispherical design provides a near 180° wide field of view while withstanding water pressure.