Abstract: Apparatus is disclosed to count and control crimps in a moving tow of yarn. The apparatus comprises a target (the tow of yarn), a stroboscopic light, condenser lens, mirror, transparent support for the target, focusing lens, diode array to sense variations in light intensity from the striations in the target, electronic board circuit with terminal board, programmable calculator, and read-out means, such as a light emitting diode display. When used to control the crimping apparatus it also comprises a controller, exit control gate of the crimper and means to exert pressure on the exit control gate. The method for use of this apparatus is to cause an intense light pulse to issue from the stroboscopic light, passing the pulse of light through the condenser lens against the mirror through the transparent support to reflect from the striations in the yarn tow back through the focusing lens into the diode array which counts the variations in light intensity caused by the striations.