Laser marking bitmap images using lasers has been difficult to create in any great definition. Contrast levels within images, along with limitations of the lasers to modify parameter settings on the fly have provided, at best, unattractive results.
laser marking bitmap images versus vector images
A bitmap, is a series of tiny dots known as pixels. In reality, each pixel is actually a small square that has been asigned a colour. Its colour and position are used to form the overall image you are looking at.
A laser marking system uses a raster scanning technique to travel over the image area placing an energy pulse where each pixel would normally be. Because the laser can not produce colour in each pixel, it requires the image to be less complex. In most cases, the image would be translated to black and white, reducing the number of pixels creating a less defined image overall. The laser then pulses on for each black or white pixel depending on how the process setup.
Vector images are not based on the same pixel format. They use a series of lines (vectors) generated from mathematical formulas. The vector image, contains much less data than the bitmap and processes much faster than its bitmap counterpart. The ability to scale vector images much easier than bitmaps makes them much more commercially acceptable.
Personalisation is a growing market
There seems to be a commercial requirement to create photographic images in order to personalise products such as iPhones, iPads etc. The main market being the Far East. The process can by no means be qualified as 100% successful, but with selected materials matched to good images, the results can be quite stunning. Before you ask, the results will always be monochrome.
To produce the images shown, the laser marking system was a flash lamped Nd:YAG. Run in a lower mode level, the material used was an anodised aluminium plate, which helps provide the contrast levels equating to grey levels. The dot density can be increased or decreased in the conversion software to create the dark and light shade areas.
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