Optical evaluation using a hologram barrier filter

Abstract

Optical detection apparatus and process which, in its optimum configuration, utilizes holographic optical elements both as a dichroic beamsplitter and as a selective notch-type barrier filter to enhance the amount of light to reach the detector while barring undesirable wavelengths from reaching the detector. The apparatus, when incorporated into a fluorescent-light detecting process, has the advantage of minimizing loss of light suffered because of a small Stokes shift, which shift occurs between the wavelength of the light transmitted to a sample target area and the increased wavelength of fluorescent light emitted from the sample for collection by a detection device. This advantage which is allowed by sharper cut-on of optical transmission properties relative to wavelength by a barrier filter (or filters) comprised of holographic optical element (or elements) provides an important increase in the fluorescence-collecting capacity of the apparatus and the sensitivity of detection processes carried out with the apparatus. Those optical detection systems which use a dichroic beamsplitter benefit by using a holographic optical element which can serve multiple purposes by acting as an exciter filter, selecting the wavelength band from the input light, as a highly efficient mirror to enhance the amount of light reaching the sample and, also, as a barrier filter as described above.