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Infrared Longpass - Visible Block Filters

Filters for passing select infrared wavelength ranges. Infrared pass filters are considered mandatory for all near-infrared applications in order to block the visible wavelengths that negate the effects of seeing in the IR

• BP735 – IR Bandpass – IR LEDs @ 735nm • BP800 – IR Bandpass – thin filter • BP850 – IR Bandpass – high-power IR LEDs @ 850nm



LP695 IR Longpass Filter - IR LED's @ 720nm
Model
Transmission
Features
Suitable for
LP695
Passes 700nm and above
• Absorbs 690nm and below
• Lets through a small amount of deep red light
• Almost completely blocks all 660nm red light and all shorter visible wavelengths
Used with monochrome cameras to aid in increased contrast and resolution


The single substrate LP695 Longpass Filter cuts on sharply at the beginning of the infrared portion of the spectrum, passing the complete near-IR spectrum out to approximately 3000nm. It lets through a small amount of deep red light and almost completely blocks all 660nm red light and all shorter visible wavelengths.

Colour longpass filters are used with monochrome cameras to aid in increased contrast and resolution. These filters block UV and shorter visible wavelengths and pass longer wavelengths of light. Except in those few cases where an IR blocking or other shortpass filter is incorporated into the camera/sensor, for the most part Adept will recommend the use of a broad colour bandpass filter (whose designs incorporate these longpass filters) over colour longpass filters alone.

This is because colour filters are usually specified for use with similar monochromatic LED or laser diode colours in order to block ambient light. The spectral response of most CCD/CMOS camera sensors, typically have excellent deep red and near-infrared sensitivity. When superimposing any longpass filter's transmittance curve over a camera's spectral response curve, approximately half or more of the unwanted ambient light – all of the longer wavelength light – is not being blocked by the longpass filter. Consequently, if it makes sense to employ a longpass filter to block some of the ambient light, it makes even more sense to block the rest of it, using a bandpass filter. In comparative testing where the difference between a longpass and a bandpass filter may not seem to be dramatic, the bandpass filter will also provide insurance for what might happen at some point in the future. By blocking almost all of the unwanted light, the effects of any change in ambient or introduced lighting that often occur at a later date can be nullified. Instead of a LP695 filter, a better alternative might be a BP735 filter.



LP780 IR Longpass Filter – IR diode lasers @ 810nm
Model
Transmission
Features
Suitable for
LP780
Passes 790nm
and above
• Absorbs 775nm and below Structured laser diode modules and LED lighting that operate in the range around 810-830nm


The single substrate LP780 IR Longpass Filter is a commonly used filter for several near-IR wavelengths found in machine vision applications.

There are both structured laser diode modules and LED lighting that operate in the range around 810-830nm, and this filter is recommended for these.

 

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LP830 IR Longpass Filter – general IR +880nm IR LEDs
Model
Transmission
Features
Suitable for
LP830
Passes 830nm and above
• Absorbs 815nm and below When LED is lighting chosen for illumination purposes


An LP830 filter is recommended when LED lighting is chosen for illumination purposes, 90% of all applications are either 880nm or 850nm LED lighting. The LP830 filter for 880nm is also recommended when the choice of IR lighting will be made at a later time.

A longpass filter is sufficient for most IR lighting applications. Since ANY camera's sensitivity drops quickly beyond 880nm, there is little or no appreciable benefit to blocking these longer wavelengths as the camera can take care of these itself.

These single substrate filters are supplied with hard-coated surfaces to improve transmission and inhibit staining. Staining is a problem common to infrared filter glasses that can be found particularly on unprotected polished surfaces which manifests as a cloudy, white film that etches into the polished glass. Over time, staining can greatly reduce transmission and resolution, and cannot be simply wiped away. Factors determining the time required and severity of staining include the year-round heat, humidity and air quality of the surrounding area. In certain environments, coatings are an absolute necessity.

 

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LP920 IR Dichroic Longpass – IR LEDs @ 940nm
Model
Transmission
Features
Suitable for
LP920
Passes 920nm and above
• Absorbs 690nm and below
• Reflects 690-910nm
• Use with infrared LEDs
• Imaging applications which employ IR vidicon or InGaAs cameras.


The single substrate, hard-coated LP920 IR Longpass filter has been designed for use with 940nm LED illumination.

Its excellent lower wavelength blocking (10-5 blocking into the near-IR) allows these filters to block visible emissions (particularly the red "glow") when placed in front of multi-spectral lighting used in semi-covert or photographic darkroom applications. Note that the "pink" reflective surface must be mounted facing toward the light source in these situations.

It is also a useful filter for imaging applications which employ IR vidicon or InGaAs cameras.

 


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LP1000 IR Longpass – IR Vidicon/InGaAs cameras
Model
Transmission
Features
Suitable for
LP1000
Passes1010nm and above
• Absorbs 980nm and below

• IR Vidicon/InGaAs cameras

The LP1000 filter cuts on very gradually starting at 860nm, reaching its peak at 1600nm. As such, it has few applications when used with CCD/CMOS cameras, as it greatly attenuates the longer wavelength infrared light that most of these cameras will respond to.

The single substrate LP1000 is more frequently used with infrared vidicon or InGaAs cameras, where it cuts off wavelengths below the 1550nm telecommunications band.

 

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BP695 IR Longpass Filter - NIR fluorescence
Model
Transmission
Features
Suitable for
BP695
Passes 670-715nm
• Absorbs 660nm and below
• Reflects 720-1100nm
• Use with near-infrared LEDs
Imaging typically weak luminescence in the 680-710nm range where the subject is often excited with 635nm or 660nm red LED lighting
• Use with laser diode illumination.


The BP695 is designed to function in the 680-715nm range such as with 700nm LED lighting.

It is particularly useful for imaging typically weak luminescence in the 680-710nm range where the subject is often excited with 635nm or 660nm red LED lighting.

The single substrate, hard-coated BP695 filter blocks most of these (and lower) excitation wavelengths to remove interference from the source. This filter is also excellent for use with laser diode illumination.

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BP735IR Longpass Filter - IR LEDs @ 735nm
Model
Transmission
Features
Suitable for
BP735
Passes 700-770nm
• Absorbs 690nm and below
• Reflects 780-1065nm
• Use with near-infrared LEDs
• Imaging in the 700-770nm range and especially weak luminescence in the 715-765nm range


This filter is designed for viewing subjects in the 700-770nm range.

It is particularly useful for imaging typically . In these situations, the subject is often excited with 635nm or 660nm red LED lighting, and the BP735 single substrate, hard-coated filter blocks these (and lower) excitation wavelengths to remove interference from the source.

This filter is also excellent for use with 720-735nm LED illumination.

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BP800 IR Bandpass – thin filter
Model
Transmission
Features
Suitable for
BP800
Passes 730-1030nm
• Absorbs 720nm and below, 1050nm and above • Use with near-infrared lighting
• Several commonly used LED and laser diode wavelengths


The single substrate, hard-coated BP800 filter is a very broad absorptive bandpass filter that cuts on sharply at 725nm (50% point), peaks at about 800nm, and cuts off very gradually over a range from 900 to 1200nm a cut-off range that is largely beyond the range of sensitivity of most CCD cameras and for most machine vision applications it is probably best to think of this as a 725nm Longpass Filter. It can be used in conjunction with several commonly used LED and laser diode wavelengths.

Two other uses for this filters are:

a) When used with infrared vidicon or InGaAs cameras with their sensitivities typically out to 1800nm or 2200nm, the BP800 acts as a bandpass filter.

b) Whenever a special application arises calling for a very thin infrared filter – thickness 1.5mm and below; e.g. for mounting above a sensor – this is the filter of choice. The BP800 will generally not transmit visible light even when thinned to less than 1mm.

This is an ionically coloured filter glass, whereas all other visible blocking/infrared passing filter glasses are colloidally coloured. Colloidally coloured IR filter glass will pass significant amounts of visible light when made thinner.

 

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BP850 IR Bandpass – high-power IR LEDs @ 850nm
Model
Transmission
Features
Suitable for
BP850
Passes IR 810-990nm
• Absorbs 200-800nm
• Reflects 1010nm and above
• High transmission and broad bandwidth
• Protective coating - resists staining
Use with high-power IR LEDs


To significantly improve and maximize contrast when working in the infrared, the use of a filter is almost mandatory.

High transmission and broad bandwidth
In well over 90% of all infrared inspection applications, 850nm or 880nm LEDs are employed. The single substrate, hard-coated BP850 offers very high peak transmission (typically >99%) and the coatings used are very dense, hard and environmentally stable.

While this filter's bandwidth is quite broad, ANY camera's sensitivity drops quickly beyond 880nm so there is normally little appreciable benefit in blocking these longer wavelengths as the camera sensor essentially takes care of this all by itself.

Resists staining
These IR filters feature fully-coated surfaces that improve transmission and inhibit staining which is a problem common to almost all IR filter glasses if they have unprotected, polished surfaces. The problem manifests itself in time as a cloudy, white film that etches into the polished glass surfaces. Over longer periods, staining can greatly reduce transmission and resolution, and cannot be simply wiped away. Factors determining the timing required and severity of staining include year-round heat, humidity and the air quality of the surrounding area. In certain climates and environments, protective coatings are an absolute necessity.

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BP880 IR Bandpass – IR Bandpass – IR LEDs @ 880nm
Model
Transmission
Features
Suitable for
BP880
Passes IR 840-1010nm
• Absorbs 200-840nm
• Reflects 1010nm and above
• High transmission and broad bandwidth
• Protective coating - resists staining
Use with high-power 880nm IR LEDs


The use of a filter is almost mandatory to significantly improve and maximize contrast when working in the infrared. When high-power LED lighting is being used, the use of either BP850 or BP880 filters are recommended.

High transmission and broad bandwidth
In well over 90% of all infrared inspection applications, 850nm or 880nm LEDs are employed. This single substrate, hard-coated BP880 or BP850 offers very high peak transmission (typically >99%) and the coatings used are very dense, hard and environmentally stable.

While this filter's bandwidth is quite broad, ANY camera's sensitivity drops quickly beyond 880nm so there is normally little appreciable benefit in blocking these longer wave lengths... the camera sensor essentially takes care of this all by itself.

Resists staining
This filter features a fully-coated surface that improves transmission and inhibits staining. Staining is a problem common to almost all IR filter glasses if they have unprotected, polished surfaces. The problem manifests itself in time as a cloudy, white film that etches into the polished glass surfaces. Over longer periods, staining can greatly reduce transmission and resolution, and cannot be simply wiped away. Factors determining the timing required and severity of staining include year-round heat, humidity and the air quality of the surrounding area. In certain climates and environments, protective coatings are an absolute necessity.

 

 

 

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