Laser scanner for controlling the optical scanning of bar codes

This application is a continuation-in-part of U.S. patent application Ser. No. 08/294,438 (abandoned), filed Aug. 23, 1994. This application is also related to U.S. patent application Ser. No. 818,731, filed Jan. 6, 1992, now U.S. Pat. No. 5,229,591, which was a continuation of Ser. No. 07/506,674 (abandoned). This application is further related to U.S. patent application Ser. No. 07/317,433, filed Mar. 1, 1989 (abandoned); to U.S. patent application Ser. No. 07/520,464, filed May 8, 1990, which issued as U.S. Pat. No. 5,168,149; and U.S. patent application Ser. No. 07/544,628, filed Jun. 27, 1990, which issued as U.S. Pat. No. 5,117,098. All of these applications and patents have been assigned to Symbol Technologies, Inc. A scanner determines whether a target is a bar code symbol and, if so, whether that symbol is one-dimensional or two-dimensional. For two-dimensional symbols, the scanner aligns a scanning pattern with the symbol and expands the scanning pattern to reach only to the top and bottom edges of the symbol, not beyond. The scanner also has a microprocessor-control scanning engine that uses a coil to drive a scanning element and pick up feed back signals from the scanning element. A pulse-width-modulated regulator also provides fast and efficient operation for driving the coil. The scanning engine can also be designed to generate a pattern that precesses across the target, and a powerful interface to the scanning engine allows decoding and control logic to work efficiently with and independently of the scan engine.