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Dichroic filters can be used with a white LED array to selectively illuminate a sample with a particular color.
Thorlabs offers high-quality Additive and Subtractive Dichroic Filters with a strong emphasis on durability. Unlike plastic filters or gels, these coatings will not fade with time and can handle much higher temperatures. Our dichroic color filters can be mounted in our Ø1" lens tubes or filter mounts.
Additive and Subtractive Dichroic filters are used to separate color in CCD imaging, digital projection, machine vision, and printing. These filters allow only a portion of the visible spectrum to pass and reject (reflect) the rest.
In the simplest case, using the Red, Green, and Blue additive filters in succession with a black and white CCD camera, a high-contrast color image may be achieved. Unlike the traditional color CCD, which uses groups of three spatially separated pixels to achieve this effect, using filters maintains the resolution of the camera. In digital projection, additive filters are used to enhance contrast. In machine vision, a single filter can be placed before the CCD camera to increase contrast, which makes sorting items much simpler. Often, copy machines and print preprocessing centers use subtractive filters to make the images that will later be printed in ink.
Below are plots showing the percent transmission versus wavelength of our dichroic filters for four different angles of incidence (AOI). Please note that for clarity reasons we have only plotted data for four different AOIs. You can obtain raw data in 5o increments (i.e., at 0o, 5o, 10o, 15o, 20o, 25o, 30o, 35o, 40o, and 45o) by clicking on the link below the graph.
The FD1D Dichroic Filter Set includes one of each of our Red, Green, and Blue Additive Filters as well as one of each of our Cyan, Magenta, and Yellow subtractive filters, each housed in an SM1-Compatible housing engraved with the part number.