An imaging system (40), safety system (58) or combined imaging and safety system (FIG. 1) for an industrial machine (20), including a light transmitter (26) and a corresponding receiver (28). In an imaging application, image data relating to a machine tool (22) and/or work piece (32) is derived from said at least one receiver and processed by an image processing means to determine information regarding said tool and/or tool position and/or extent of work carried out on said work piece. A screen (34, 46), such as a shadow screen, can be used to form an image of a profile of the tool tip and end of the workpiece. Took tip position and extent of work on the workpiece can be derived from the image, e.g., via a camera viewing an image formed on the screen. Multiple cameras may be used. A safety system application (FIGS. 10a to 10d) for halting the machine or tool when a light beam is interrupted can include a broad or block beam (62) and can provide progressive muting of beam interruption detection by progressively muting detection. Progressive muting can be achieved by systematically disregarding or muting signals from rows of receiver array elements as the beam passes through a mute point (66) ahead of the tool tip (60).