An online vision system is at the heart of a new fully-automated production line for the volume manufacture of optical tiles that can be joined together to create video walls and advertising displays without visible joins or image variations. The new machine builds eight high performance tiles at once, each with 31,000 individually moulded light channels or pixels. It is 10 times faster than the previously developed semi-automated machines and requires just one part-time operator.
The vision system – comprising two line scan cameras, two high speed matrix LEDs, simple mirrors and an image processor – has proved essential in helping control the tile assembly process, while at the same time significantly improving yield and cutting costs.
Each tile is built up from 152 rows of angled, moulded light channels that need to be precisely positioned with the glue accommodating tolerance variations in the mouldings. The tiles work by projecting and magnifying an image input from the back to their front surface; with the quality of displayed image relying on the precise registration of the tile’s light guides with pixels in the source image. As expected, registration accuracy and ultimately tile performance depends on three factors: the location, uniformity and thickness of glue dispensed; the precision of the thermoforming process to shape the fibre optic channels without damage; and the repeatability of placement of the parts relative to each other.