Longpass Colour Filters
Longpass filters let longer visible and infrared wavelengths pass while
blocking the shorter ones. Useful for improving contrast, resolution and
separating colors in black/white or colour applications. Typically not
recommended for machine vision unless blocking of multiple wavelengths
is necessary.
LP500– Yellow
Longpass – blocks most blue and UV wavelengths |
Model |
Transmission |
Suitable for |
LP500 |
Passes
500nm and above
Absorbs 480nm and below |
• Increasing contrast and resolution in monochrome
cameras |
Colour
longpass filters are used with monochrome cameras to aid in increased
contrast and resolution. As the name implies, 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, the use of a broad colour bandpass filters (whose
designs incorporate these longpass filters) over these color longpass
filters alone.
The reason for this is that colour filters are usually specified
for use with similar monochromatic LED or laser diode colors in
order to block ambient light. When looking at the spectral response
of most CCD/CMOS camera sensors, it can be seen that they typically
have excellent deep red and near-infrared sensitivity. When super-imposing
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.
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
an LP500 filter, an alternative choice might be a BP525 filter.
While bandpass filters are more popular than longpass filters,
Longpass colour filters are still available for customers who are
more familiar with them and continue to request them. |
LP515 –
Yellow-Orange Longpass – blocks all blue and UV
|
Model |
Transmission |
Suitable for |
LP515 |
Passes 510nm and above
Absorbs 500nm and below |
• Increasing contrast and resolution in monochrome
cameras |
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,
the use of a broad colour bandpass filters (whose designs incorporate
these longpass filters) over these color longpass filters alone.
The The reason for this is that colour filters are usually specified
for use with similar monochromatic LED or laser diode colors in
order to block ambient light. When looking at the spectral response
of most CCD/CMOS camera sensors, it can be seen that they typically
have excellent deep red and near-infrared sensitivity. When super-imposing
any longpass filter's transmittance curve over a camera's spectral
response curve, t approximately half or more of the unwanted ambient
light – all of the longer wavelength light – is not
being blocked by the longpass 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
an LP515 filter, an alternative choice might be a BP535 filter
While bandpass filters are more popular than longpass filters,
Longpass colour filters are still available for customers who are
more familiar with them and continue to request them. |
|
Model |
Model # |
Dimensions |
4.5" x 5.0" x 2.5" |
|