Bandpass Filter

Bandpass filter is a component that allows a specific range of wavelengths to pass through while blocking the others. It is widely used in Machine Vision, Lidar, Fluorescence, Spectroscopy, Astronomy and Solar Simulation.

Bandpass Filter Banner
BP660-3 Bandpass Filter(CWL=660nm,FWHM=3nm)
$168.00
660nm
3nm
OD5@200-1100nm
BP365-10 Bandpass Filter(CWL=365nm,FWHM=10nm)
$65.00
365nm
10nm
OD5@200-1100nm
BP1060-50 Bandpass Filter(CWL=1060nm,FWHM=50nm)
$45.00
1060nm
50nm
OD2@400-1100nm
BP585-40 Bandpass Filter(CWL=585nm,FWHM=40nm)
$55.00
380nm
40nm
OD5@200-1000nm
BP475-75 Bandpass Filter(CWL=475nm,FWHM=75nm)
$45.00
475nm
75nm
OD2@200-1100nm
BP945-50 Bandpass Filter(CWL=945nm,FWHM=50nm)
$45.00
945nm
50nm
OD2@400-1100nm
BP930-40 Bandpass Filter(CWL=930nm,FWHM=40nm)
$45.00
930nm
40nm
OD2@400-1100nm
BP920-30 Bandpass Filter(CWL=920nm,FWHM=30nm)
$45.00
920nm
30nm
OD2@400-1100nm
BP915-25 Bandpass Filter(CWL=915nm,FWHM=25nm)
$45.00
915nm
25nm
BP905-35 Bandpass Filter(CWL=905nm,FWHM=35nm)
$45.00
905nm
35nm
OD2@400-1100nm
BP905-25 Bandpass Filter(CWL=905nm,FWHM=25nm)
$45.00
905nm
25nm
OD2@400-1100nm
BP885-40 Bandpass Filter(CWL=885nm,FWHM=40nm)
$45.00
885nm
40nm
OD2@400-1100nm
BP870-35 Bandpass Filter(CWL=870nm,FWHM=35nm)
$45.00
870nm
35nm
OD2@200-1100nm
BP865-50 Bandpass Filter(CWL=865nm,FWHM=50nm)
$45.00
865nm
50nm
OD2@400-1100nm
BP860-35 Bandpass Filter(CWL=860nm,FWHM=35nm)
$45.00
860nm
35nm
OD2@400-1100nm
BP855-45 Bandpass Filter(CWL=855nm,FWHM=45nm)
$45.00
855nm
45nm
OD2@400-1100nm

Basic Specifications

You can search BP[CWL]-[FWHM] to find the Bandpass Filter directly.

BP266-10 = Bandpass Filter with Center Wavelength=266nm, FWHM=10nm

  • Center Wavelength (CWL)

    Center Wavelength refers to the wavelength that is located at the midpoint of the filter's passband.

    Classification by CWL

    • UV Range (193nm-400nm)
    • VIS Range (400nm-800nm)
    • NIR Range (800nm-1400nm)
    • IR Range (1400nm - 1mm)

    Substrate material may vary based on the center wavelength range.

  • FWHM (Full Width at Half Maximum)

    FWHM represents the width of the wavelength range where the filter transmits light at 50% or more of its peak transmission.

    Classification by FWHM

    • Narrowband (FWHM≤ 10nm) are used for laser purification and chemical sensing.
    • Standard band filters (FWHM 25-50nm) work well for machine vision.
    • Broadband filters (FWHM > 50nm) are commonly used in fluorescence microscopy.

  • Peak Transmission (Tpk)

    Peak Transmission (Tpk) represents the maximum percentage of light that can pass through the filter within the transmission area.

  • Blocking Region

    The blocking region, refers to the range of wavelengths or frequencies that an optical filter effectively attenuates or completely blocks.

    Typical Range:

    • 200-1100nm (for VIS & UV)
    • 400-7000nm (for IR)

  • Optical Density

    Optical Density (OD) is a measure of how much light is absorbed or blocked by a material as it passes through.

    Typical Range of OD

    • Commerical Use: OD2 - OD4
    • Scientific Research: OD5- OD6

UV Range Bandpass Filter usually have lower transmission

The transmittance of UV bandpass filters generally falls between 15-30%.This relatively low transmission is inherent to UV filter design and materials.

Limiting Factors

Several factors contribute to the lower transmission rates:

Material Limitations

  • Most materials used in UV filters have inherent absorption in the UV range
  • The absorption of UV light by materials makes it difficult to achieve high transmission while maintaining deep blocking over wide wavelength ranges

Design Challenges

  • The refractive index difference of dielectric materials decreases at shorter wavelengths, requiring more layers to achieve desired spectral control.
  • Complex designs with multiple layers are needed for effective UV filtering, which can increase optical scatter and reduce transmission.

Infrared (IR) range Bandpass filter are more costly

Cost Factors

IR bandpass filters are indeed typically more expensive than visible and NIR counterparts due to:

  • Limited material choices suitable for IR wavelengths
  • More complex fabrication processes

Substrate Materials for IR range

Germanium (Ge)

  • Excellent transmission properties in MWIR to FIR ranges
  • Particularly effective for wavelengths from 1.7 µm and longer
  • Features high refractive index and high Knoop hardness
  • Ideal for thermal imaging and rugged IR imaging applications

Silicon (Si)

  • Cost-effective solution for IR applications
  • Transmission starts from approximately 1.2 µm
  • Lightweight material with good performance
  • Commonly used in spectroscopy, MWIR laser systems, and THz imaging

Sapphire (Al₂O₃)

  • Known for exceptional durability and scratch resistance
  • Provides broad transmission capabilities
  • Particularly effective in NIR applications
  • Used in IR laser systems, spectroscopy, and rugged environmental equipment

Using Condition

Different using condition may result in spectral characteristic changes.

  • Angle of Incidence

    When increasing the Angle of Incidence (AOI) in a Bandpass Filter.

    The most significant change is the Spectral Shift, where the transmission spectrum shifts toward shorter wavelengths as the AOI increases.

  • Temperature Effects

    Most filters show a red shift (shift to longer wavelengths) with increasing temperature.

    And filter will have blue shift (shit to shorter wavelength) with decreasing temperature.

Spectral Features

Spectral performance is decided by the coating design,substrate selection and coating machine.

  • Gaussian Type Bandpass Filter

    The Gaussian type bandpass filter creates a bell-shaped (Gaussian) transmission curve.

    Commonly used in

    • LED-based systems
    • Cost sensitive solution

  • Flat-Top Bandpass Filter

    A flat-top type Bandpass Filter provides consistent light transmission across a specific wavelength range.

    Commonly used in

    • Laser-based remote sensing
    • Where AOI may slightly changes

Why Flat-Top spectral is needed in LiDAR system?

Footprint Elongation

The laser footprint becomes elongated due to:

  • Changes in scan angle during flight
  • Variations in terrain slope
  • Combined effects of both factors affecting the AOI

When an optical interference filter is tilted from normal:

  • The transmission spectrum experiences a "blue shift" toward shorter wavelengths
  • The shift becomes more pronounced with increasing AOI
  • The flat-top design provides a wider tolerance window for these shifts

Bandpass Filter Construction

  • Laminate Filter

    Multiple Filters bonded together

    • Protected by sealing and ring assemblies
    • Often mounted in protective housing

    CONS of Laminate Filter

    • Low Durability
    • Moderate Spectral Performance
    • Ghost Image may occur

  • Hard Coating Filter

    Hard coated filters are manufactured using plasma deposition processes with computer-controlled precision

    • Even layer distribution
    • Superior environmental durability

    CONS of Hard Coating Filter

    • Expensive
    • Less Flexible Combination

Moutning Solution

  • Unmounted

    Unmounted optical filters are typically packaged as a sandwich structure with protective films on both sides, then wrapped in foam or bubble wrap for additional protection during shipping and storage.

  • Threaded Mounting

    Threaded mounting is a mechanical method for securely attaching optical filters to lenses or equipment using standardized threaded rings.

  • Filter Wheel

    A filter wheel is a rotatable mechanical device designed to hold multiple optical filters and sequentially select them into the light path.

  • Fiber Optic Filter Muont

    A fiber optic filter mount is a specialized optical device designed to integrate filters and other optical components into fiber-based light paths.

  • Filter Cube

    A filter cube is a specialized optical assembly used primarily in fluorescence microscopy to control and manipulate specific wavelengths of light.

  • Customized Structure

    We offer custom optomechanical design and fabrication services from your 3D drawings, with prototype builds starting at $150.

    • MOQ start from 1 unit

Services

  • Dicing

    We provide dicing services to cut larger filters into smaller piece.

    Example:

    • Dia100mm (1pcs) -> 10x10mm (40pcs)
    • Price = 50USD
    • When order in larger quantity (and customization), dicing service is free.

  • Transmission Inspection

    We use Cary Spectrophotometer for bandpass filter inspection. You can request raw data from us before ordering.

    • Request existing testing data is free
    • Extra transmission testing will cost $35 per sample

    >> sample data.csv

Optical FIlter usually produced in a large wafer

  • Filters are typically produced as large plates (up to 12" diameter) with coatings applied first
  • The coated plates are then cut into desired dimensions using various methods:
  1. Dicing with ultra-thin blades for precise cuts
  2. CNC sawing for squares and rectangles
  3. Diamond core drilling for circular shapes

The large-plate approach for filters offers several advantages:

  • Multiple filters can be produced from a single coated plate
  • Reduces overall production time compared to individual processing
  • Allows for better quality control of coating uniformity

Bandpass Filter Directory

uv (100-400nm)

vis (400-800nm)

nir (800-1400nm)

swir (1400-3µm)

ir (>3µm)

Customization

We provide bandpass filter customization service for small and large scale project.

  • What you need to know before customization

    • Minimum Order Quantity depends on the Coating Chamber size.
    • Require quantity less than the minimum yield won't lower the price a lot.
    • Minimum Cost will start from 1,500$ per chamber coating.
    • Leadtime will be usually within 2-6 weeks

  • Customization Range

    Below are the specification we can achieve. (But not together on one product)

    • Center Wavelength = 220nm - 10500nm
    • Minimum FWHM = 0.8nm
    • Optical Density = OD6