during operation and so do not become nearly as hot as the equivalent conventional filter (which attempts to absorb all energy except for that in the passband). (See Fabry–Pérot interferometer for a mathematical description of the effect.) Where white light is being deliberately separated into various color bands (for example, within a color video projector or color television camera), the similar dichroic prism is used instead. For cameras, however it is now more common to have an absorption filter array to filter individual pixels on a single CCD array. Applications Recessed or enclosed luminaires that are unsuitable for use with dichroic reflector lights can be identified by the IEC 60598 No Cool Beam symbol. In fluorescence microscopy, dichroic filters are used as beam splitters to direct illumination of an excitation frequency toward the sample and then at an analyzer to reject that same excitation frequency but pass a particular emission frequency. Some LCD projectors use dichroic filters instead of prisms to split the white light from the lamp into the three colours before passing it through the three LCD units. Older DLP projectors typically transmit a white light source through a color wheel which uses dichroic filters to rapidly switch colors sent through the (monochrome) Digital micromirror device. Newer projectors may use laser or LED light sources to directly emit the desired light wavelengths. They are used as laser harmonic separators. They separate the various harmonic components of frequency doubled laser systems by selective spectral reflection and transmission. Dichroic filters are also used to create gobos for high-power lighting products. Pictures are made by overlapping up to four colored dichroic filters. Photographic enlarger color heads use dichroic filters to adjust the color balance in the print. Advantages Dichroic filters have a much longer life than conventional filters; the color is intrinsic in the construction of the hard microscopic layers and cannot "bleach out" over the lifetime of the filter (unlike for example, gel filters). They can be fabricated to pass any passband frequency and block a selected amount of the stopband frequencies. Because light in the stopband is reflected rather than absorbed, there is much less heating of the dichroic filter than with conventional filters. Dichroics are capable of achieving extremely high laser damage thresholds, and are used for all the mirrors on the world's most powerful laser, the National Ignition Facility. Other uses Artistic glass jewelry is occasionally fabricated