BP1940-20 Bandpass Filter(CWL=1940nm,FWHM=20nm)

For size options, unmounted and mounted filters use different size references.

Unmounted filters

• Listed size refers to the actual filter size
  
• Example: 12.5mm unmounted means the bare filter is 12.5mm in diameter
  

Mounted filters

• Listed size usually refers to the outside size of the mount
  
• The filter inside is typically smaller than the mount
  
• Example: 12.5mm mounted means the mount outside is 12.5mm, while the filter inside is slightly smaller
  
• The inside filter is usually about 1–1.5mm smaller than the mounted outer diameter
  

Mount type

• Mounted does not automatically mean threaded
  
• If only labeled as mounted, it usually means a smooth, non-threaded mount
  
• Threaded mounts should specify a thread standard, such as M25.5 × 0.5mm or SM1
  

Note

• If your system has strict requirements for outer diameter, clear aperture, thickness, or thread standard, please confirm before ordering.

Filter thickness depends on whether the filter is supplied unmounted or mounted.

Unmounted filters

• Usually 0.5mm–2mm
  
• Common thicknesses: 0.5mm, 1.1mm, 1.5mm
  
• Other cases may range from about 0.3mm–3mm
  
• Thickness may vary by substrate, coating design, or customer requirement
  

Mounted filters

• Total outside thickness depends on the mount structure
  
• Non-threaded mount: usually around 3.5mm or 6mm
  
• Metric threaded mount: usually around 6.5mm–7.5mm
  

Note

• If your system has a strict thickness limit, please confirm the required thickness before ordering.

The fixing method depends on whether the mount is threaded or non-threaded.

Non-threaded mounts

• Filter is usually fixed with adhesive
  
• The filter is secured inside the mount after assembly
  
• The filter is generally not removable after mounting
  

Threaded mounts

• Filter is usually held with a retaining ring
  
• Adhesive is usually not required
  
• The filter can usually be removed or replaced later
  

Note

• If you need the filter to be removable, please request a threaded mount with retaining ring before ordering.

Yes, but the spectrum may shift when the filter is used away from normal incidence.

Narrow bandpass filters

• Around 10nm FWHM: small angles such as 0–5° usually have limited effect
  
• At 10–15°, wavelength shift may become noticeable
  
• Tight spectral systems should check AOI carefully before ordering
  

Wide bandpass filters

• Around 50–100nm FWHM: usually more tolerant of angle shift
  
• Around 15–20° may still be acceptable in some systems
  
• Final suitability depends on the required passband and blocking range
  

Note

• Non-normal incidence may also introduce polarization-related effects
  
• If your system uses larger AOI, polarized light, or tight wavelength tolerance, please confirm before ordering.

Yes. We can provide AOI (angle-of-incidence) testing at selected angles.

AOI testing options

• Common test angles: 5°, 10°, 15°, 20°, 30°
  
• Used to review wavelength shift under non-normal incidence
  
• Suitable for laser, imaging, or angle-sensitive optical systems
  

Cost

• USD 35 per angle
  
• Minimum: 2 angles per request
  

Note

• AOI testing can be requested before placing an order
  
• This allows you to review measured performance before confirming system compatibility

If you are not sure, testing a sample in your own system is often the best way to confirm fit.

Sample testing

• Available for eligible company, laboratory, university, or research-group customers
  
• Usually applies to products or orders below USD 150
  
• You may test first and pay only if the filter works for your system
  

Return after testing

• If the filter is not suitable, you may return it after testing
  
• Return approval depends on product condition and review
  
• Custom, modified, damaged, or contaminated products may not be eligible
  

Note

• Please contact us before ordering if you want to check whether sample testing is available.