During fluorescence imaging, the item being inspected absorbs a shorter wavelength of light (usually ultraviolet (UV) light) that excites a specific fluorophore, causing it to release photons that fluoresce and emit light at a longer wavelength. In industrial applications this fluorescence is most often a blue color. By using an appropriate bandpass filter centered at the wavelength of the emission (such as a blue bandpass filter), all other wavelengths of light are blocked. Most importantly, excitation wavelength(s), which will always be far brighter than the fluorescent glow are blocked. In these types of applications, it’s mandatory to use a bandpass filter in order to effectively image the lower energy luminescence.
UV fluorescence applications require a filter that blocks the UV light source, transmitting only the weaker fluorescence emission. Common fluorescent excitations include 365nm, 395nm and 400nm. It’s important to note that in UV fluorescence applications, the filter is used for passing the fluorescence emission wavelength and blocking the excitation light source. 

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Applications Solutions

  • Flourescence Imaging
    Original Color Image
    Before: UV excited 2D matrix with a cyan fluorescence that is nearly overwhelmed by a UV light source and ambient light.
    After: A BP505 Cyan Bandpass Filter used on the lens blocks the UV light source and other ambient light, passing the cyan fluorescence and thus creating necessary contrast.
  • Fluorescence Imaging
    Before: Without a filter over the lens, the 395nm LED light overpowers the fluorescence emission that would allow the 2D matrix to be read by the camera.
    After: A BP470 Blue Bandpass Filter mounted on the camera lens effectively blocks UV wavelengths, passing only the blue fluorescence emission from the 2D matrix while blocking all other unwanted light.
  • Fluorescence Imaging
    Before: A postal bar code printed on the back of an envelope for high speed sorting is excited under UV light. Without a filter on the camera, the orange characters go undetected. In this case, the camera sensor is overcome by visible and UV output from the light.
    After: A BP590 Orange Bandpass Filter mounted on the lens creates greater contrast by passing the orange fluorescence while blocking UV, near-IR and other visible wavelengths.
  • Fluorescence Imaging
    Before: Light from a UV LED light source overpowers blue fluorescence emitted by this part, making the characters virtually undetectable.
    After: A BP470 Blue Bandpass Filter threaded to the lens blocks the overpowering UV light source, passing only the blue emission in the area of interest.
  • Fluorescence Imaging
    Before: The contrast between the UV-excited blue fluorescence and background is not sufficient to reliably image the code marking.
    After: A BP470 Blue Bandpass Filter darkens the background by blocking reflected UV light used to excite the blue fluorescence, creating sufficient contrast.
  • Increase Contrast & Reduce Glare
    Before: The surfaces of a stent reflect light unevenly, making it difficult to selectively examine desired features.
    After: The use of a PR032 Linear Polarizer and a BP635 Light Red Bandpass Filter, mounted together over the camera lens, eliminates glare and darkens the background to highlight the features of interest.
  • Fluorescence Imaging
    Before: Hundreds of tiny plastic particles in the bottle cap reflect light at certain angles, creating noise in the background. This interferes with the ability to inspect the characters printed on the cap.
    After: A Linear Polarizer Filter mounted on the lens and properly aligned extinguishes the direct reflection of light from the particles, eliminating background noise entirely.