OPTICAL FOCUSING DEVICE

A hand held, omnidirectional symbology or bar code reader (10) images linear and two-dimensional bar codes (28; 34; 40; 52; 54) over relatively long working distances. The reader (10) includes an imaging system including a focusing objective taking lens (92) and a two-dimensional photodetector (93) that forms an image of a bar code in X and Y directions simultaneously and generates an electrical signal representative of the code for subsequent downstream processing. Focusing is achieved via a rotating disk (94) that carries a plurality of optical shims (130) or other tight controlling surfaces for different focus zones. A through-the-lens (TTL) targeting system is provided to visually assist the user in positioning the reader (10) for a variety of code modalities to assure that a bar code will be captured within the field of view and be sharply imaged on the photodetector (93) when the lens (92) is focused. Two different forms of artificial illumination are provided to accommodate nearby codes that may be either specular or partially diffuse and more distant codes where the reflection characteristics have less impact on code contrast. All of the reader's components are housed in an ergonomically designed shell (12) to reduce user repetitive stress injuries while providing access to a user interface anda protective cover for the reader's various systems.