Variable angle optical sensing system for determining the orientation of weft threads

摘要

An optical sensing system that detects the angular orientation of weft threads in a moving web of a textile has a sensor array that receives light transmitted through the web from a light source. The sensor array is preferably a single monolithic chip that includes a radial pattern of photosensitive areas that each generate an electrical signal proportional to the total intensity of the light incident on the area. The areas are elongated and narrow so the moving shadow of a weft thread passing over the area will modulate the output signal. The modulation is strongest when the thread is generally aligned with the area. Electronic circuitry generates a DC signal associated with each area that is proportional both to the magnitude and frequency of the modulation of the signal. The circuitry also compares these signals, selects the largest one, and generates an analog output voltage characteristic of the area associated with the largest signal. The circuitry optionally further includes a feedback circuit responsive to the selected maximum signal which controls a variable power supply for the light source and a switched gain amplifier responsive to extremes of light source voltage level. A mounting system provides a coordinated rotation of the light source and the sensor array to vary the angle of incidence of the light beam on the web.