Optical Filters

Machine vision filters for controlling wavelength, contrast and glare

Optical filters selectively pass (transmit) light of specific wavelength or range of wavelengths while blocking the remainder. For example longpass filters pass long wavelengths only, shortpass pass short wavelengths only, bandpass pass a band of wavelengths. The passband may be narrow or wide depending on the filter type and the transition or cutoff between maximal and minimal transmission can be sharp or gradual.

Optical filters can be used to increase the contrast of features of interest in a scene in order to make it simpler for imaging software to detect and measure.

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Filter Types

Dual bandpass optical filter

Dual Bandpass filters

Dual BP filters transmit wavelengths within two separate ranges and block all others, including those between the two bands. This is often used in traffic applications.

View Filters

Midwest Optical Filters: select by type

Colour Bandpass UV Bandpass Colour Narrow Bandpass Infrared Narrow Bandpass Dual Bandpass Infrared Pass - Visible Block Infrared Block - Visible Pass Longpass - Colour Neutral Density Polarizing Shortpass / Notch Colour White-Light Balancing Acrylic Filter Mounts

Compare Midwest Optical Filters

Model Colour Passes Absorbs Reflects Applications and comments

Colour Bandpass
BP470 Blue 435-490nm UV 270-380nm Most visible and IR Recommended for use with 470nm blue LEDs and for UV fluorescence imaging
BP505 Cyan 475-565nm UV and deep blue 570-1100nm For use with 500-510nm cyan LED lighting. Also has a function in UV fluorescence imaging of some commonly-used stains
BP525 Light green 495-565nm UV and blue 570-1100nm Recommended for use with green LEDs and fluorescence imaging
BP590 Orange 555-615nm 200-550nm 620-1090nm Recommended for use with amber/orange LEDs and fluorescence imaging
BP635 Light Red 600-660nm 200-590nm 670-1080nm Recommended for use with red laser diodes and LEDs
BP660 Dark Red 635-690nm 200-630nm 695-1100nm Recommended for use with dark red LEDs
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Model Colour Passes Absorbs Reflects Applications and comments

UV Bandpass
BP250 Broadband UV 290-380nm N/A 390-1200nm Requires camera with deep-UV sensitivity and lens designed specifically for UV imaging
BP324 UV-A/B* (UV) 270-375nm and (NIR) 690-750nm Visible and most IR N/A *UV-A = 400-320nm; UV-B = 320-290nm; UV-C = 290-100nm. Particularly useful in true UV imaging applications, where blocking longer wavelengths is essential
BP365 Blacklite/UV-A UV 315-400nm, 815nm and above N/A Visible light and near-IR: 410-805nm Blocks visible light at the source while passing UV. Good for filtering visible light from mercury and metal halide lighting.
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Model Colour Transmission range Applications and comments

Colour Narrow Bandpass
BN470 Narrow Blue UV Block 450-495 nm Narrow design for overwhelming ambient light conditions. Suitable for laser diodes. Commonly used in fluorescence applications. Less sensitive to angle of incidence variations than traditional interference filters.
BN532 Narrow Green 515-560 nm
BN595 Narrow Orange 570-615 nm
BN630 Narrow Light Red 610-650 nm
BN660 Narrow Dark Red 640-680 nm
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Model Transmission range Applications and comments

Infrared Narrow Bandpass
BN740 720-770 nm Narrow design for overwhelming ambient light conditions. Types offered for all wavelengths commonly found in IR illuminations. Ideal for security, traffic control and industrial inspection applications. Suitable for laser diodes. Less sensitive to angle of incidence variations than traditional interference filters.
BN785 760-805 nm
BN850 825-870 nm
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Model Transmission range Applications and comments

Dual Bandpass
DB850 Visible + 850 nm IR. Visible 385-650 nm. Infrared 820-880 nm Colour camera day/night applications. Blocks interfering IR wavelength range to achieve accurate colour rendition. Allows the ability to view a scene with appropriate IR illumination at night.
DB940 Visible + 940 nm IR. Visible 385-650 nm. Infrared 910-970 nm
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Model Filter type Passes Absorbs Reflects Applications and comments

Infrared Pass - Visible Block
LP695 IR Longpass 700nm and above 690nm and below N/A Used with monochrome cameras to aid in increased contrast and resolution
LP780 IR Longpass 790nm and above 775nm and below N/A For structured laser diode modules and LED lighting that operate in the range around 810-830nm
LP830 IR Longpass 830nm and above 815nm and below N/A 90% of all applications is either 880nm or 850nm LED lighting. Recommend for 880nm when the choice of IR lighting will be made at a later time
LP920 IR Dichroic longpass 920nm and above 690nm and below 690-910nm Lower wavelength blocking allows these filters to block visible emissions when placed in front of multi-spectral lighting
LP1000 IR Longpass 1010nm and above 980nm and below N/A Used with infrared vidicon or InGaAs cameras, where it cuts off wavelengths below the 1550nm telecommunications band
BP695 IR Bandpass / NIR fluorescence 670-715nm 660nm and below 720-1100nm Designed to function in the 680-715nm range such as with 700nm LED lighting.
BP735 IR Bandpass / IR LEDs @ 735nm 700-770nm 690nm and below 780-1065nm Particularly useful for imaging typically weak luminescence in the 715-765nm range
BP800 IR Bandpass 730-1030nm 720nm and below, 1050nm and above N/A Best choice if thin filter needed over sensor. Recommended for use with near-infrared lighting.
BP850 IR Bandpass / High-power IR LEDs @ 850nm IR 810-990nm 200-800nm 1010nm and above Recommended for use with high-power IR LEDs
BP880 IR Bandpass / IR LEDs @ 880nm IR 840-1010nm 200-840nm 1010nm and above Recommended for use with high-power 880nm IR LEDs. Significantly improves and maximizes contrast when working in the infrared
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Model Filter type Passes Absorbs Reflects Applications and comments

Infrared Block - Visible Pass
BP550 NIR+UV Block/Visible Pass 410-690nm N/A 350-400nm and 710-1550nm For all colour applications where filtering is not provided with the camera's sensor
SP645 Mid-Red/NIR Dichroic Block 380-640nm N/A 650-1065nm Best IR/mid-red block
SP675 Deep Red/NIR Dichroic Block 380-670nm N/A 680-1080nm Best IR/deep red
SP700 Hot Mirror/NIR Dichroic Block 410-690nm N/A 350-400nm and 710-1550nm Standard IR block, for use with monochrome cameras
SP730 Hot Mirror/NIR Colourless Block 370-725nm N/A 735-1100nm Standard IR blocking, for use with colour cameras
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Model Filter type Passes Absorbs Reflects Applications and comments

Polarizing
PR032 Rotating Linear Polarizer Visible (340nm+) and IR UV 200-340nm N/A Used to eliminate glare in the visible spectrum.
PC052 Circular Polarizer Visible (340nm+) and IR UV 200-340nm N/A Reduces glare; for autofocus or autoiris lenses; for visible spectrum applications
PI035 IR Linear Polarizer Visible (340nm+) and IR, or only IR UV 200-340nm N/A Reduces only infrared glare. Do not work in the near-infrared.
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Model Passes Applications and comments

Neutral Density - Absorptive
ND030 380nm and above Optical Density = 0.3 (T = 50%). Sometimes referred to as "2X" filters
ND060 389nm and above Optical Density = 0.6 (T = 25%). Sometimes referred to as "4X" filters
ND090 390nm and above Optical Density = 0.9 (T = 12.5%). Sometimes referred to as "8X" filters
ND120 395nm and above Optical Density = 1.2 (T = 6.3%). Sometimes referred to as "16X" filters

Neutral Density - Low Reflectivity
NI030 350nm and above Optical Density = 0.3 (T = 50%) Visible and Near-IR Imaging
NI060 350nm and above Optical Density = 0.6 (T = 25%) Visible and Near-IR Imaging
NI090 350nm and above Optical Density = 0.9 (T = 12.5%) Visible and Near-IR Imaging
NI0120 350nm and above Optical Density = 1.2 (T = 6.25%) Visible and Near-IR Imaging
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Model Colour Passes Absorbs Reflects Applications and comments

Longpass Colour
LP500 Yellow 500nm and above 480nm and below N/A Blocks most blue and UV wavelengths used with mono cameras for improving contrast and resolution.
LP515 Yellow-Orange 510nm and above 500nm and below N/A Blocks all blue and UV while passing all other wavelengths.
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Model Colour Passes Reflects Applications and comments

Shortpass / Notch Colour
SP510 Blue Dichroic 350-500nm, 810nm and above 510-800nm For sorting gold from silver or plated metal parts
SP570 Blue-Green Dichroic 400-570nm 500-1060nm Blocks orange to NIR
SP585 Cyan Dichroic 370-580nm, 830nm and above 590-820nm Blocks red and very near IR
SP625 Blue-Orange Dichroic N/A N/A Blocks deep red/NIR
NF550 Magenta Dichroic (Green Block) 320-465nm, 610nm and above 470-600nm Blocks green while passing blue and red wavelengths.
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Model Colour Passes Absorbs Reflects Applications and comments

White Light Balancing
LA120 Minus Blue + 500nm+ UV and blue 200-500nm 400-500nm Removes blue cast from white LED and metal halide lighting.
LB080 Minus Red 370-520nm 360nm and below; 540-1100nm N/A Removes yellow cast from halogen lighting.
FL550 Minus Green 400nm and above 390nm and below N/A Removes green cast from fluorescent lighting.
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Model Description

Acrylic Filters
AC380 Useful range: 450 - 850nm. A/R Acrylic Protective Window – abrasion, scratch, breakage- and solvent-resistant acrylic window for regulated applications where glass can't be used
AC685 Useful range: 700 - 1100nm. Acrylic NIR Longpass – allows through mainly IR light
AC760 Useful range: 450 - 850nm. Acrylic NIR Longpass – allows through mainly IR light and also blocks very near IR
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What is Optical Density (OD)?

Optical density is a measure of how much light is blocked by a filter.

Optical Density (OD) = -log10 (T)

A filter with 1% transmission has an OD of 2.

Issues to consider

  • Problems with filters are more likely to be the result of using the wrong filters
  • Filters degrade overtime, so they have to be changed - their life is finite
  • Absorption results in conversion of light into heat and laser beams hitting colour glass filters may destroy the filters
  • Use the least number of filters necessary to reduce signal loss
  • High-quality filters are a better investment than cheaper ones
  • The wavelength at which Dichroic filters transmit light shifts slightly with the angle at which light hits the filter
  • The wavelength at which Dichroic filters transmit light shifts slightly with temperature. This is important to consider for narrow bandpass filters.

Need help selecting optical filters?

Talk to our machine vision engineers about wavelength selection, contrast enhancement, glare reduction and filter compatibility.

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