Active safety apparatus for a disc cutter

A power-driven disc cutter configured for cutting a workpiece, the cutter comprising:

• a frame;
• an arbor attached to the frame;
• a supporting shaft supported in the arbor
• a rotatable disc blade with a cutting edge held on the supporting shaft;
• a controllable motor connected to rotate the supporting shaft;
• a safety apparatus operatively connected to the controllable motor, the safety apparatus comprising an optical imaging portion connected to the frame, the optical imaging portion being configured to sense a gloved hand within an exclusion volume that includes the cutting edge, the optical imaging portion comprising:
• a single camera having an image sensor chip;
• a lens aligned with the sensor chip and positioned to focus incoming light onto the sensor chip;
• four sets of mirrors arranged to project, respectively, four separate views of the exclusion volume, each of the four sets of mirrors comprising:
• a first mirror configured to reflect a corresponding one of the four separate views toward an optical axis of the lens;
• and
• a second mirror configured to receive the corresponding one of the four separate views reflected by the first mirror and reflect the corresponding one of the four separate views along a respective one of four separate optical axes passing through the lens;
• wherein the optical imaging portion is configured so that each of the four separate views of the exclusion volume is focused on a respective one of four separate, non-overlapping portions of a surface of the image sensor chip;
• and
• wherein each of the four separate optical axes associated with the four second mirrors defines a corner edge of the exclusion volume, the exclusion volume having a shape of either a right frustrum or a cuboid.