Linear edge sensor

Abstract

In modern industrial process controls, web guiding is becoming very demanding due to variations in web materials, variable web widths, and the need for better guiding accuracy. Selecting the appropriate sensor for various types of web materials and repositioning the sensors for variable web widths can be very expensive and time-consuming. At present, some web guiding applications where wide web width variations are desirable, require the sensor positioner to electromechanically reposition the sensors to accommodate the web width variations. With time, a system using electromechanical means suffers in terms of reliability and consistency in guiding accuracy.

To address these needs, a solid-state, laser-based, multiprocessing sensing scheme can be a viable option. This new sensing technique is based on a segmented, multiple transmit-receive pair scanning topology. A wide sensor field of view is achieved by staggering multiple sets of transmit-receive segments. On the transmitter side, a collimated light curtain is obtained by using a set of cross cylindrical lens-based optics with a semiconductor laser diode. Each receiver segment is: made of a linear photodiode array that is independently scanned by a dedicated microcontroller. The main sensor synchronizes multiple segment scanning, processes segment information, delivers output based on web edge position.