Abstract: A property of the surface such as height is sensed as a function of position on the surface. A statistical spread in the sensed property as a function of the position is computed. Regions where the material is present are distinguished from other regions on the basis of the spread, e.g. conductor tracks on a PCB assembly are distinguished from a PCB substrate by having lower spread.

Abstract: A property of the surface such as height is sensed as a function of position on the surface. A statistical spread in the sensed property as a function of the position is computed. Regions where the material is present are distinguished from other regions on the basis of the spread, e.g. conductor tracks on a PCB assembly are distinguished from a PCB substrate by having lower spread.

Abstract: A calibration method and device are described, notably for a component-placement machine for placing components (30) on a carrier (3), which machine comprises carrier-positioning means (50) and component-positioning means (26, 27, 11; 40). The positions of components placed on a calibration carrier (60, 65) during a calibration procedure is detected by means of a calibration carrier detection device (50) which is present in the machine itself. For obtaining a satisfactory contrast between the components (30) and the calibration carrier surface, the latter may be provided with a reflecting and adhesive foil (65, 66). In a machine provided with a production carrier detection device, this device may be used as a calibration carrier detection device.FIG. 3.