Filter Glasses With Band-Pass Characteristics For The Red Region Of The Visible Spectrum

The purpose of this investigation was to develop filter glasses showing band-pass characteristics in the red region of the visible spectrum. Filters were made with transmission peaks spaced from 1 to 12nm (about 4nm on average). This was achieved by colouring 7 different base glasses with Ni0, by developing "mixed" glasses (eg borosilicate and mixed alkali-alumina-phosphate glasses coloured with Ni0) and by introducing supplementary oxides with cut-on and band-reject characteristics into the Ni0-coloured glasses. Examples of the factors responsible for the changes in transmittance characteristics are briefly discussed and recommendations are made regarding futher improvement of the Ni0-coloured band-pass filter glasses.