Technology fundamentals determine the major performance differences between laser scanners and 2D imagers. Laser scanners were developed specifically for reading linear bar codes. They work by oscillating a laser spot across the bars of the symbol. Bars and spaces are recognized based on where light is reflected back to the photodiode and where it was absorbed. Lasers cannot read matrix bar code formats, including Data Matrix codes that are commonly used for direct part marking and product authentication, MaxiCode used on UPS package labels, Aztec codes used on mobile phones, or QR Codes, which are used in marketing and other scan-to-web applications.