LBTEK-Your Trusted Partner For Optoelectronic Experiments!

Product Description

OD value can be adjusted by rotating the filter angle
Circular shape, OD value continuously adjustable
Anti-reflection coating: 350 nm-700 nm

LBTEK continuous neutral density filters are constructed from UV-grade fused silica substrates, with a chromium-nickel-iron alloy coating applied to one side over a 0~270° angular region. Within the coated area, the optical density (OD) varies linearly with the rotation angle (θ), following the relationship OD = k * θ. By rotating the coated region of the filter, linear and adjustable attenuation of the light beam can be achieved. Additionally, the back surface of the filter is coated with an anti-reflection (AR) coating, which effectively suppresses stray light within the 350-700 nm operating wavelength range. Currently, the available OD ranges for continuous neutral density filters include 0.02-2.0, 0.02-4.0, and 0.02-6.0, with optional diameters of Ø25 mm, Ø50 mm, and Ø100 mm. In addition to standard products, LBTEK offers various customization services. For custom orders, please contact LBTEK technical support.

Attribute

Design wavelength350-700 nm

Substrate MaterialUV fused silica

CoatingInconel & Anti-Reflection Coating

Coated Radial Angle270°±5°

Surface finish (scratches/pits)60/40

Substrate thickness2.0 mm

Surface Parallelism<3 arcmin

Center hole diameterØ7.5 mm

Variable Neutral Density Filter Mount for Round Neutral Density Filters

M6 threaded hole on the main body, with M4 threaded hole adapter included
Compatible with NDFR series filters with center hole diameter Ø7.5 mm
Suitable for optical elements with a thickness of 2 mm

The LBTEK Neutral Density Filter Mount allows the installation of NDFR series filters with a central hole diameter of Ø7.5 mm onto the rotating shaft. To install the filter, first use the included 1.5 mm hex wrench to tighten the fixing screw on the side of the NDFR-PM to lock the rotation. Then, use the included 2 mm hex wrench to remove the silver hex socket screw. Place the filter between the two washers, then reassemble the rotating wheel and screw combination. Please note to maintain the original sequence of flat washers and wave springs when reassembling, and securely fasten the bolt. The package includes one each of 1.5 mm and 2.0 mm hex wrenches.

Neutral Density Filter Mount Assembly

	Product Model	Applicable Optical Component Center Hole Diameter	Applicable optical element thickness	Unit Price	Compare	Lead Time
	NDFR-PM	Ø7.5 mm	2 mm	$52.43		6 weeks

Continuous neutral density filter, operating wavelength: 350-700 nm, with mounting.

Installed in a mechanical housing with scale
Coating: Inconel & Anti-Reflection Coating
Dimensions: Ø25 mm, Ø50 mm, Ø100 mm
OD Range: 0.02-2.0, 0.02-4.0, 0.02-6.0

LBTEK's mechanical housing for installed continuous neutral density filters features angular scales and a rotation axis. The mount is precisely designed to minimize the impact on the optical element's clear aperture. The continuous neutral density filter is coated with a filtering film (Inconel film) on one side and an anti-reflection coating (A-coating) on the other. The side with the scale is the filtering film side, and for optimal performance, it is recommended to have light incident from this side. Although it is a reflective neutral density filter, the Inconel film still absorbs some of the incident light. Additionally, this unprotected metal film should be handled with care to avoid contact, and it is recommended to use an air blower for cleaning.

Continuous Neutral Density Filter Assembly with Installation

Product Model	Filter outer diameter	OD value range	Filter thickness	Unit Price	Lead Time
NDFR-25C-2M-A New	Ø25 mm	0.02^a-2.0	2.0 mm	$450.14	Contact
NDFR-25C-4M-A New	Ø25 mm	0.02^a-4.0	2.0 mm	$450.14	Contact
NDFR-25C-6M-A New	Ø25 mm	0.02^a-6.0	2.0 mm	$491.98	Contact
NDFR-50C-2M-A New	Ø50 mm	0.02^a-2.0	2.0 mm	$479.56	Contact
NDFR-50C-4M-A New	Ø50 mm	0.02^a-4.0	2.0 mm	$479.56	Contact
NDFR-50C-6M-A New	Ø50 mm	0.02^a-6.0	2.0 mm	$556.83	Contact
NDFR-100C-2M-A New	Ø100 mm	0.02^a-2.0	2.0 mm	$651.35	Contact
NDFR-100C-4M-A New	Ø100 mm	0.02^a-4.0	2.0 mm	$651.35	Contact
NDFR-100C-6M-A New	Ø100 mm	0.02^a-6.0	2.0 mm	$741.83	Contact

Continuous neutral density filter, operating wavelength: 350-700 nm, unmounted

Not installed
Coating: Inconel & Anti-reflection coating
Size: Ø25 mm, Ø50 mm or Ø100 mm
OD range: 0.02-2.0, 0.02-4.0, 0.02-6.0

LBTEK uninstalled continuous neutral density filters feature a central hole diameter of 7.5 mm, facilitating mechanical mounting. The OD value of the continuous neutral density filter can be adjusted by rotation. One side of the continuous neutral density filter is coated with a filter film (Inconel film), while the other side is coated with an anti-reflection coating (A-coating). For optimal performance, it is recommended that light enters from the filter film side. Although classified as a reflective neutral density filter, the Inconel film still absorbs a portion of the incident light. Additionally, this unprotected metal film should be handled with care to avoid contact; cleaning is recommended using an air blower.

Neutral Density Filter Mount Assembly

Product Model	Filter outer diameter	OD value range	Filter thickness	Unit Price	Lead Time
NDFR-25C-2-A New	Ø25 mm	0.02^a-2.0	2.0 mm	$352.48	Contact
NDFR-25C-4-A New	Ø25 mm	0.02^a-4.0	2.0 mm	$352.48	Contact
NDFR-25C-6-A New	Ø25 mm	0.02^a-6.0	2.0 mm	$403.6	Contact
NDFR-50C-2-A New	Ø50 mm	0.02^a-2.0	2.0 mm	$376.67	Contact
NDFR-50C-4-A New	Ø50 mm	0.02^a-4.0	2.0 mm	$376.67	Contact
NDFR-50C-6-A New	Ø50 mm	0.02^a-6.0	2.0 mm	$454.85	Contact
NDFR-100C-2-A New	Ø100 mm	0.02^a-2.0	2.0 mm	$426.09	Contact
NDFR-100C-4-A New	Ø100 mm	0.02^a-4.0	2.0 mm	$426.09	Contact
NDFR-100C-6-A New	Ø100 mm	0.02^a-6.0	2.0 mm	$530.94	Contact

Continuous neutral density filter, operating wavelength: 350 nm-700 nm