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Midopt Filters
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• Machine vision
• License-plate recognition
• Security
• Photography
• Astronomy
• Biological imaging

Filter types: Select link below to view each 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    

About MidOpt and their products
The MidOpt company began in 1988 as a manufacturer of custom-precision optical components and systems, their growth involvement the company in the design and development of optic systems for the industrial imaging world.

MidOpt's Machine Vision Filters offer excellent light transmission, a range of stock filters to cover nearly every type of lighting and/or subject, and a bandpass width that accommodates variations in LED output and are available in shortpass, longpass, bandpass, polarizing, neutral density, IR and UV types. 


Why use MidOpt filters?

The MidOpt line of mounted, single substrate, hard-coated filters are specifically created for industrial machine vision applications. They:
• are very durable
• are non-hydroscopic
• withstand repeated cleaning with solvents
• withstand high heat, humidity, vibration
• have an almost-unlimited life

For machine vision, the ideal filter should be an immediate solution that provides greater contrast, improved transmission and resolution, and long term control over the variability of ambient light
Good contrast enables increased accuracy and speed. Because ambient light is everywhere, filters create the contrast needed to control lighting
By increasing the contrast, filters improve the ability of the system to distinguish desired characteristics
Lenses are a critical part of any vision system so they need to be protected from dust and scratches. Filters provide that protection
Left: Kale leaves under white light through a monochrome camera.
Right: MidOpt Bandpass Filter creates much greater contrast.
Left: unfiltered monochrome image with ambient light
Right: Correctly aligned polarising filter eliminates the reflections

Working with filters
Filter selection is made by matching a filter type to the available lighting.

When matched with the correct lighting, optical filtering is one of the most important factors that contributes to the ability of any vision system to perform reliably over the intended lifespan. Consequently, selecting the right filter for the job is critical, not just at the time it is first put into service but also for the long term. Filters are designed to work with a wide variety of lighting: monochromatic or white LED, fiber optic, structured diode-generated patterns and other lighting commonly used in machine vision applications. Their job is to increase the contrast of the subject under inspection, improving the ability of the system to distinguish desired characteristics. Increased contrast allows for increased accuracy and speed. Because lighting will change over time and ambient light is everywhere, filters create the contrast needed.

Filter selection is made by matching a filter type to the lighting and sizing to the diameter of the camera lens and filters should be designed with the capacity to mount, quickly and securely, to the smaller diameter lenses used by CCD and CMOS cameras. MidOpt filters are engineered and sized to each mount for maximum field of view and are ready to use right out of the box. See filter mounts.

Additionally, lenses are a critical part of any vision system, so at the very least, need to be protected from dust and scratches by using a filter.

Typical results and benefits when using machine vision filters

1.
Colour recognition and separation of subject matter
Lower cost better speed, higher contrast and more consistent reliability can be achieved in some cases by using filters with a monochrome camera as compared to using a color camera alone.
2.
Suppress the strong blue "spike"of standard white LED and metal halide lighting
Lower costs, brighter images and longer system lifetimes can be achieved by using the LA120 with standard lighting versus selecting "warm white" LED lighting
 
3.
Improve lens resolution and contrast by reducing the colour range being imaged
Better resolution reduces false accepts and false rejects, and the more expensive "megapixel" lensing may not be needed. See image above, left
 
4.
Eliminate glare
When it is not possible to adjust a system's lighting configuration, polarized glare is selectively removed only through the use of a polarizing filter. See image above, right
 
5.
Test the effects of Infrared light... and see what eyes can’t
The very best contrast and separation of subject matter is often achieved by working in the infrared. The odds of this being immediately successful are about 50/50; testing is usually the only way to make such a determination.
   
6.
Enhance contrast for improved viewing of desired features
Fluorescence applications require a filter to block the overwhelming light source that excites the fluorescence. Detecting the much weaker fluorescence is difficult/impossible without blocking the light source and ambient light. A bandpass filter that only passes the limited fluorescence will significantly improve the contrast and allow the weak glow to be detected.
   
7.
Test LED colors without the expense and lead time of the lighting
Quickly test common LED lighting colours without the expense and time wasted while waiting for the appropriate LED lighting. Cut the lead time for bringing a system on-line by as much as several weeks
   
8.
Radiation and temperature IR blocking
Certain machine vision filters can be used to block the bright glow of hot metals, glass and other material. Shortpass filters allow light up to a specific wavelength to pass through while blocking all light at higher wavelengths. This useful feature permits, for example, the viewing of hot rolled steel to see certain temperature areas while not blinding the system from the brighter, hotter areas.


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Alphabetic list of filters
Narrow Blue Bandpass/UV block 450-495nm IR Longpass – IR Vidicon/InGaAs cameras
Narrow Green Bandpass 515-560nm Yellow Longpass – blocks most blue and UV wavelengths
Narrow Orange Bandpass 570-615nm Yellow-Orange Longpass – blocks all blue and UV
Narrow Light Red Bandpass/UV block 610-650nm IR Longpass – IR LED's @ 720nm
Narrow Dark Red Bandpass/UV block 640-680nm IR Longpass – IR diode lasers @ 810nm
Narrow IR Bandpass 720-770nm IR Longpass – general IR +880nm IR LEDs
Narrow IR Bandpass 760-805nm IR Dichroic Longpass – IR LEDs @ 940nm
Narrow IR Bandpass 825-870nm Optical Density = 0.3 (T = 50%) – reduces light intensity
Broadband UV Bandpass – deep broadband UV imaging OD = 0.6 (T = 25%) – reduces light intensity
UV 'A+B' Bandpass – mid- to near-UV imaging OD = 0.9 (T = 12.5%) – reduces light intensity
Blacklite/UV 'A' Bandpass – UV imaging/UV lighting dichroic filter OD = 1.2 (T = 6.3%) – for viewing into lamps
Blue Bandpass - blue LEDs/UV fluorescence Magenta Dichroic Shortpass – blocks green & passes blue & red wavelengths
Cyan Bandpass – for 505nm LED lighting Optical Density = 0.3 (50%) – reduces light intensity
Light Green Bandpass – green LEDs/fluorescence OD = 0.6 (25%) – reduces light intensity
NIR-UV Block/Visible Pass – 400-700nm OD = 0.9 (12.5%) – reduces light intensity
Orange Bandpass – amber/orange LEDs/UV fluorescence OD = 1.2 (6.3%) – for viewing into lamps, furnaces, welding processes, etc.
Light Red Bandpass – high-power red LEDs Circular Polarizer – reduces glare; for autofocus or autoiris lenses; for visible spectrum
Dark Red Bandpass – darker red LEDs and structured laser diodes IR Linear Polarizer – reduces only infrared glare
IR Bandpass – NIR fluorescence Rotating Linear Polarizer with locking screw – reduces glare in the visible spectrum
IR Bandpass – IR LEDs @ 735nm Blue Dichroic Shortpass – for sorting gold from silver or plated metal parts
IR Bandpass – best choice if thin filter needed over sensor Blue-Green Dichroic Shortpass – blocks orange to NIR
IR Bandpass – high-power IR LEDs @ 850nm Cyan Dichroic Shortpass – blocks red and very near IR
IR Bandpass – IR LEDs @ 880nm Blue-Orange Dichroic Shortpass – blocks deep red/NIR
Dual Bandpass VIS+850 IR - visible 385-650nm +IR 820-880nm Mid-Red/NIR Dichrioc Block – best IR/mid-red block
Dual Bandpass VIS+940 IR- visible 385-650 + 910-970nm Deep Red/NIR Dichrioc Block – best IR/deep red block
Minus Green – removes green cast from fluorescent lighting Hot Mirror/NIR Dichroic Block – standard IR block, for use with monochrome cameras
Minus Blue + – removes blue cast from white LED and metal halide lighting Hot Mirror/NIR Colourless Block – standard IR blocking, for use with colour cameras
Minus Red – removes yellow cast from halogen lighting
 

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Filters by type
BP470 – Blue Bandpass - blue LEDs/UV fluorescence
PR032 – Rotating Linear Polarizer with locking screw – reduces glare in the visible spectrum
BP505 – Cyan Bandpass – for 505nm LED lighting PC052 – Circular Polarizer – reduces glare; for autofocus or autoiris lenses; for visible spectrum apps
BP525 – Light Green Bandpass – green LEDs/fluorescence I035 – IR Linear Polarizer – reduces only infrared glare
BP590 – Orange Bandpass – amber/orange LEDs/UV fluorescence  
BP635 – Light Red Bandpass – high-power red LEDs  
BP660 – Dark Red Bandpass – darker red LEDs and structured laser diodes  
COLOUR NARROW BANDPASS
NEUTRAL DENSITY - ABSORPTIVE FILTERS
BN470 – Narrow Blue Bandpass/UV block 450-495nm ND030 – Optical Density = 0.3 (T = 50%) – reduces light intensity
BN532 – Narrow Green Bandpass 515-560nm ND060 – OD = 0.6 (T = 25%) – reduces light intensity
BN595 – Narrow Orange Bandpass 570-615nm ND090 – OD = 0.9 (T = 12.5%) – reduces light intensity
BN630 – Narrow Light Red Bandpass/UV block 610-650nm ND120 – OD = 1.2 (T = 6.3%) – for viewing into lamps
BN660 – Narrow Dark Red Bandpass/UV block 640-680nm  
INFRARED NARROW BANDPASS
NEUTRAL DENSITY - LOW-REFLECTIVITY FILTERS
BN740 – Narrow IR Bandpass 720-770nm NI030 – Optical Density = 0.3 (50%) – reduces light intensity
BN785 – Narrow IR Bandpass 760-805nm NI060 – OD = 0.6 (25%) – reduces light intensity
BN850 – Narrow IR Bandpass 825-870nm NI090 – OD = 0.9 (12.5%) – reduces light intensity
  NI120 – OD = 1.2 (6.3%) – for viewing into lamps, furnaces, welding processes, etc.
DUAL BANDPASS
UV BANDPASS
DB850 – Dual Bandpass VIS+850 IR - visible 385-650nm +IR 820-880nm BP250 – Broadband UV Bandpass – deep broadband UV imaging
DB940 – Dual Bandpass VIS+940 IR- visible 385-650 + 910-970nm BP324 – UV 'A+B' Bandpass – mid- to near-UV imaging
  BP365 – Blacklite/UV 'A' Bandpass – UV imaging/UV lighting dichroic filter
INFRARED PASS - VISIBLE BLOCK
SHORTPASS/NOTCH COLOUR
LP695 – IR Longpass – IR LED's @ 720nm SP510 – Blue Dichroic Shortpass – for sorting gold from silver or plated metal parts
LP780 – IR Longpass – IR diode lasers @ 810nm SP570 – Blue-Green Dichroic Shortpass – blocks orange to NIR
LP830 – IR Longpass – general IR +880nm IR LEDs SP585 – Cyan Dichroic Shortpass – blocks red and very near IR
LP920 – IR Dichroic Longpass – IR LEDs @ 940nm SP625 – Blue-Orange Dichroic Shortpass – blocks deep red/NIR
LP1000 – IR Longpass – IR Vidicon/InGaAs cameras NF550 – Magenta Dichroic Shortpass – blocks green & passes blue & red wavelengths
BP695 – IR Bandpass – NIR fluorescence BP850 – IR Bandpass – high-power IR LEDs @ 850nm  
BP735 – IR Bandpass – IR LEDs @ 735nm  
BP800 – IR Bandpass – best choice if thin filter needed over sensor  
BP850 – IR Bandpass – high-power IR LEDs @ 850nm  
BP880 – IR Bandpass – IR LEDs @ 880nm  
INFRARED BLOCK - VISIBLE PASS
LONGPASS COLOUR
BP550 – NIR-UV Block/Visible Pass – 400-700nm LP500 – Yellow Longpass – blocks most blue and UV wavelengths
SP645 – Mid-Red/NIR Dichrioc Block – best IR/mid-red block LP515 – Yellow-Orange Longpass – blocks all blue and UV
SP675 – Deep Red/NIR Dichrioc Block – best IR/deep red block  
SP700 – Hot Mirror/NIR Dichroic Block – standard IR block, for use with monochrome cameras  
SP730 – Hot Mirror/NIR Colourless Block – standard IR blocking, for use with colour cameras  
WHITE LIGHT BALANCING
ACRYLIC LONGPASS
LA120 – Minus Blue + – removes blue cast from white LED and metal halide lighting AC380 A/R Acrylic Protective Window – abrasion, scratch, breakage- and solvent-resistant acrylic
LB080 – Minus Red – removes yellow cast from halogen lighting AC685 Acrylic NIR Longpass – allows through mainly IR light
FL550 – Minus Green – removes green cast from fluorescent lighting AC760 Acrylic NIR Longpass – allows through mainly IR light and also blocks very near IR

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