Abstract
The fibrograph is an optical instrument employing photovoltaic cells for scanning samples of parallel fibres and tracing a type of length- frequency curve. The theory is developed for a sample of parallel fibres in which the fibres are positioned at random. The geometrical interpreta tion of the resulting curve, or fibrogram, indicates simple length and area measurements that give various average lengths and statistical quantities, such as standard deviation and coefficient of variation. Experimental fibrograms are compared with the equivalent data derived from absolute length measurements, using a projection method. The waviness and taper of the fibres, along with other minor factors, cause the fibrogram to be too short. When the length coördinates are increased 19%, the fibrogram is equivalent to the curve obtained from absolute measurements. The instrument makes possible the rapid measurement of fibre length and fibre-length uniformity of raw fibre samples.
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