Cool Components III: Liquid Lens 2D Barcode Readers
I’ve used industrial barcode scanners a number of times, and they work well, especially the raster models.Â The laser barcode scanners have a wide scan range and can handle a substantial amount of variation in label position.
My favoriteÂ brandÂ is Microscan; I’ve also used other brands with good results.Â The Microscan QX-870 is a typicalÂ barcode scanner: it has 10 scan lines, can do 300 to 1400 scan/sec, hasÂ a read range of 1″ to 30″, can read all the normal 1D barcodes (UPC, Codabar, Code 39, Code 128, etc)Â as well as the PDF417 and Micro PDF417 2D barcodes.
However, most 2D barcodes (such as the popular Datamatrix) need an area sensor.Â In other words, you can’t use a laser scanner, you have to use a camera.Â Now finding a lens that has a 29″ depth of field (from 1″ to 30″) is challenging.Â Of course, the barcode reader could use autofocus, but with a normal lens, that adds a lot of complexity, cost, and still isn’t perfect.Â One Microscan 2D barcode reader had a halfway solution: the reader could cycle through a preset set of focus positions until it found a good read.Â I wasn’t impressed (although to be fair, I never tried that model).
To make matters worse, Datamatrix codes are often used in direct marked applications; for example, using a laser or ball-peen to create a barcode directly on a metal aircraft part.Â Creating lighting that is affordable, compact, and can work on anything from a shipping box to a reflective metal part is hard.
I’ve thought for a long time that liquid lenses (now available from optical suppliers such as
Linos(apparently Linos dropped Varioptic)) could solve the depth of field problem by allowing affordable and rapid autofocus.Â Well, they’re here (and both claim to be “the first”): Cognex has the Dataman 200 series, and Microscan has the QX Hawk with liquid lens and modular zoom.
I think this is a big deal; for example, the QX Hawk claims a read range of 1″ to infinity.Â Unfortunately I don’t have any personal experience with either reader, but if I need to read 2D barcodes in the future, I will definitely check both out.