Saab-scania Aktiebolag

Saab-scania Ab

Bo Sjodin

An array camera used to scan elongated workpieces moving through a measuring zone transversely to their lengths has its photoresponsive detector elements aligned lengthwise of the workpieces, with optical axes of the elements lying in a common plane intersecting the measuring zone. Each element 'sees' only a small (e.g., 8.times.8 mm) pixel. Radiation sources are located at opposite sides of said plane and emit radiation towards the measuring zone to be reflected to the elements from workpieces. During each of a succession of short measuring cycles (e.g., 4 millisecond duration) each element is exposed successively to radiation originating from each radiation source to the exclusion of the other, to thus produce an A output and a B output during each cycle, and is also exposed to substantially low level radiation to produce an R output. For each cycle, the R output of at least certain elements is subtracted from the A and the B outputs of the same elements for the same cycle, to produce .DELTA.A and .DELTA.B difference signals. Timing is such that .DELTA.A and .DELTA.B signals for the same element and cycle originate from one and the same small surface area on the workpiece, and therefore inclination of that surface area is ascertainable as a function of the .DELTA.A and .DELTA.B values. During a fourth interval in each cycle, certain elements detect radiation from a laser that has its beam in said plane and oblique to the workpiece surface, and such elements then produce an L output. From the particular elements that produce L outputs, local thickness of the workpiece is ascertainable.

Scanning of workpieces such as lumber cants

A conveyor defines a plane in which elongated workpieces, substantially parallel to one another, are transported transversely to their lengths through a measuring zone at which each workpiece is illuminated from above and lengthwise scanned by an array camera. A pit at the measuring zone has its bottom below said plane and in shadow, to provide a strongly contrasting background for the workpiece being scanned. To accommodate skewed workpieces, the array camera makes repeated scans of each workpiece as it passes the measuring zone, and data from such scanning is stored in a computer memory. Detectors cooperate with the array camera and the computer, signaling entry of each workpiece into the measuring zone and its departure therefrom. Thickness of each workpiece is measured near the measuring zone; and in calculating length of a workpiece from the stored scanning data for it, compensation is made for scanning parallax due to thickness.

Automatic measurement of lengths of elongated workpieces

For enabling a computer to calculate locations of cuts across an elongated workpiece that will divide it into standardized length finished pieces of optimum economic value, the workpiece is established between parallel, spaced boundaries of an inspection zone, lengthwise parallel to them. From a movable light source a beam is projected down onto the inspection zone that defines a line of illumination extending from one to the other of the boundaries. A manually operable control member, movable parallel to the boundaries, actuates the light source to move the line of illumination lengthwise along a workpiece. An output is produced that has a unique magnitude for each incrementally different position of the line of illumination. When the line of illumination is located at a boundary between unlike-quality lengthwise extending portions of the workpiece, actuation of a pushbutton delivers the then-existing output magnitude to the computer as an input.

Growing community of inventors

Jonkoping, Sweden

Bo Sjodin