Colour Bandpass Filters

BP470 filters are recommended for use in most blue LED (~470nm) and many UV-excited blue fluorescence (430-500nm) imaging applications. Important for both applications is the breadth of the bandwidth. In the case of blue LEDs, frequent variations in center wavelengths and angles of incidence can easily be accommodated. BP470 ABSORBS lower wavelengths (e.g., UV) and REFLECTS longer wavelengths (e.g., 500-1150nm). This material does not auto-fluoresce.

For typically weak blue fluorescence applications, it is important to be able to detect as much of the blue emission as possible while effectively blocking all of the UV light. Since more than 90% of all industrial UV fluorescence applications involve imaging a blue-colored “glow,” it can be summarized that most applications involving a UV light REQUIRE the use of a BP470 filter. Without this filter, it is virtually impossible to successfully image the desired feature.

The BP470 blue bandpass filter is recommended over all other blue filters because of its broad peak (T>90%), high transmission, far superior blocking of shorter UV and longer IR wavelengths, and far steeper cut-on and cut-off slopes. All of this results in far brighter, higher contrast images when using the BP470 compared to other filters currently available.

These single substrate, hard-coated filters are about 2mm thick and can withstand very high temperatures. The coatings are just as or MORE durable than the glass. Therefore the limiting factor is the transformation temperature and thermal gradient/shock values for the glass.

The BP505 filter was designed for use with 500-510nm cyan LED lighting. It also has a function in UV fluorescence imaging of some commonly used stains.

The BP505 single substrate, hard-coated filter is designed to match the output of most cyan LEDs, widely considered to currently be the brightest "monochrome" LEDs available. Coupled with the spectral sensitivity of most CCD/CMOS sensors in use today that also peak in this range, this filter will result in images that are especially bright and very high in contrast.

The BP505 filter is particularly designed for use in line-scan/wide angle applications where they are extremely resistant to the effects of "blue shifting." Used together with the right lensing, a line of uniform end-to-end brightness can be imaged at wide angles.

BP525 filters have been designed for use in almost all green LED or laser diode applications. These single substrate, hard-coated filters also have wide application in UV fluorescence imaging of various commonly used stains and plastic materials that fluoresce in the green portion of the spectrum.

We strongly recommends the BP525 s because of its broad passband, far higher peak transmission, superior blocking of UV and IR wavelengths, and reduced sensitivity to angle of incidence changes.

The BP525 will nearly always result in significantly brighter and higher contrast images.

(left) Monochrome image with white light.
(center) Commonly used photographic filter doesn't help at all.
(right) The BP525 clearly brings out the details and improves subject recognition.

BP590 single substrate, hard-coated filters are recommended for use in systems that use amber or orange LED lighting. They are also very widely used in fluorescence imaging applications, particularly with certain inks and ethidium bromide, Qdot 605 and other similar stains.

Peak transmission is greater than 90%. Blocking of shorter AND longer wavelengths averages >99% when used in conjunction with any sensor that has a typical silicon response. This is particularly important in situations where infrared light may be present. Orange longpass filters have traditionally been recommended for these applications, but they offer no such IR blocking and therefore contrast can suffer.

Recommended for 610-650nm LED and laser diode lighting. Because of its broad bandwidth and high peak transmission, the single substrate, hard-coated BP635 works very well for all lighting applications in this range.

Coloured longpass filters have long been recommended for use 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 or sensor, We will often recommend the use of a broad color bandpass filter (whose designs incorporate these longpass filters) over color longpass filters alone.

Because of its ample bandwidth and excellent in-band transmission, it works very well for all camera-related applications in this range and is a popular product.

Colour longpass filters, sometimes referred to as "sharp cut" filters, are often suggested by others for creating increased contrast and resolution. They will block UV and shorter visible wavelengths but still pass all longer wavelengths. Except in those few cases where an IR-blocking or other shortpass filter is incorporated into the camera or sensor, we will, for the most part, recommend the use of one of the broad colour bandpass filters (such as the BP660) over these "sharp cut" longpass filters alone. The results are consistently improved contrast in most inspection applications over the long term.