Safety device and method for monitoring a machine

A method for safeguarding a machine having a first machine part and a second machine part, wherein said first machine part carries out a working movement towards the second machine part in order to machine a workpiece, and wherein said first machine part has a leading edge in a direction of movement, said leading edge defining a movement plane, the method comprising the following steps:

• acquiring a plurality of images having a plurality of pixels, with respective images from the plurality of images including spatially resolved representations of the edge, at least a part of the workpiece, and a protective region defined between the edge and the second machine part,
• determining a motion speed of the first machine part relative to the second machine part in the course of the working movement on the basis of the plurality of images,
• comparing the motion speed to a reference speed value, said reference speed value defining a nominal speed of the first machine part relative to the second machine part during the working movement and a tolerance interval, and
• stopping the working movement if the motion speed determined on the basis of the plurality of images deviates from the reference speed value beyond the tolerance interval.