Photovoltaic device comprising a conventional photovoltaic cell and a series of thin layers successively applied on the photocell surface, said layers being of different compositions and selected in such a manner that the light energy in a spectrum zone, falling on the outermost layer, may be transferred successively in cascade, through the intermediary of the various layers, up to the spectral sensitivity zone of the photovoltaic cell.

An arrangement of selective filters, an optical converter layer and optoelectric device is disclosed having high sensitivity, linearity, and selectivity of wavelength band. The arrangement is demonstrated effectively as an ultraviolet sensing device using a commercial silicon phototransistor. An ultraviolet sensing device coupled with suitable electronics is disclosed which is capable of measuring the amount of exposure to ultraviolet light.

The radiation dosimeter for the detection/and or dosimetry of radiation, particularly UV radiation, is provided with a housing comprising an opening. A sensor device sensitive to the radiation of interest is arranged below the diffuser cover layer (10). The diffuser cover layer (10) covers an opening and is transmissive at least to the radiation of interest.

A sensor for the measurement of UV radiation is disclosed which comprises a first layer of phosphor particles directly exposed to incident radiation, which absorb incident radiation and emit visible radiation, a filter for absorbing UV disposed after the phosphor layer and chosen to permit the visible light emitted by the phosphor to pass through, and a photosensor sensitive to the visible light emitted by the phosphors. By disposing the filter after the phosphors, solarization of the filter is substantially eliminated and the sensor remains accurate over long periods of time.

An apparatus designed for monitoring the administering of ultraviolet therapy, particularly for portable use such as at the beach, has a control system adapted to monitor the instantaneous intensity of the ultraviolet light received by a subject being treated, wherein the instantaneous intensity is integrated by means of a rechargeable electrochemical cell to measure the total ultraviolet energy per unit area received by the subject during a given time. The apparatus is so controlled that when the total energy received by the subject as measured by the apparatus reaches a predetermined preset value as determined by the discharged state of the electrochemical cell, a warning signal either visible or audible is given to the subject. In an improved embodiment an electronic means is used to subtract the energy measured at one wavelength from the energy measured at other wavelengths, thereby providing a low cost filter means for selecting the desired wavelength to be measured.