NG9 Absorptive ND Filter, Ø25.4 mm, OD 3.0

Overview

This mounted absorptive neutral density filter carries a broadband AR coating (350–700 nm) on both surfaces, minimizing surface reflection (average R < 0.5% at normal incidence) to reduce stray light. It is mounted in an SM1-threaded Ø1" lens tube compatible with cage systems and lens tubes; the cell can be removed by loosening the retaining ring. Unlike metallic ND filters, absorptive ND filters are made from Schott-family glasses with a spectrally flat absorption coefficient, delivering uniform attenuation across the visible band.

Applications

• Broadband beam attenuation
• Laser power / intensity control
• Imaging & detector protection
• Optical measurement & illumination control

Construction & Performance

• Substrate: NG9 (Schott absorptive glass)
• Coating: AR Coating (BBAR, 350–700 nm)
• Dimensions: Ø25.4 mm
• Thickness: 2.1 mm
• Spectral range: 350–700 nm
• OD: 3.0
• Coating spec: BBAR@350-700 nm, Ravg<0.5%
• Clear aperture: >20 mm
• Mounting: SM1-threaded Ø1" lens tube (SM1L03)
• Overall thickness (housed): 11.4 mm
• Surface quality: 60-40 Scratch-Dig
• Surface flatness: λ/4 @ 633 nm

Storage & Handling

For optimal performance, store and use at 25 °C and 40–60% relative humidity. If the surface becomes contaminated, clean gently with ≥99% alcohol and lint-free lens tissue; never use coarse cloth, water, or abrasive cleaners, which may damage the optic.