Optics - Filter Properties & manipulation of light in flow cytometry

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Slide 8

Interference filters

They are composed of transparent glass or quartz substrate on which multiple thin layers of dielectric material, sometimes separated by spacer layers .

Permit great selectivity.

Slide 9

Standard Band Pass Filters

Transmitted Light

White Light Source

630 nm BandPass Filter

620 -640 nm Light

Slide 10

Standard Long Pass Filters

Transmitted Light

Light Source

520 nm Long Pass Filter

>520 nm Light

Transmitted Light

Light Source

575 nm Short Pass Filter

<575 nm Light

Standard Short Pass Filters

Slide 11

Dichroics

They used to direct light in different spectral region to different detectors.

They are interference filters , long pass or short pass.

"dichroic" Di- is Greek for two, and -chroic is Greek for color - from Greek dikhroos, bicolored

Slide 12

Optical Filters

Dichroic Filter/Mirror at 45 deg

Reflected light

Transmitted Light

Light Source

Slide 13

Dichroic Filters

Transmitted

Light

Reflected

Light

Filter acting as a DICHROIC

Slide 14

Construction of Filters

Filter

components

Single Optical

filter

“glue”

Interference filters

Slide 15

Transmission determination

Constructive and destructive interference occurs between reflections from various layers

Transmission determined by :

thickness of the dielectric layers

number of these layers

angle of incidence light on the filters

Slide 16

Absorptive filters

Such as coloured glass filters which absorb unwanted light.

Consist of dye molecules uniformly suspended in glass or plastic.

Remove much more of the unwanted light than do the interference filters

Will often fluoresce (not good!)

Slide 17

Filters transmission

Bandpass filters: characterized by there

T max and (the Full Width at Half Maximum) FWHM

Notch filters are band pass filters in the upside down position

Long pass and Short pass filters: characterized by their T max and cuton, cutoff wavelength.