OPTICAL FOCUSING DEVICE

A hand held, omnidirectional symbology or bar code reader for imaging linear and two dimensional (matrix, maxi-code) bar codes over relatively long working distances. The reader includes an imaging system including a focusing objective taking lens and a two-dimensional photodetector that operate to form an image of a bar code in X and Y directions simultaneously and generate an electrical signal representative of the code for subsequent downstream processing which extracts information embedded in a bar code. Focusing is achieved via a rotating disk that carries a plurality of optical shims for different focus zones. A through-the-lens (TTL) targeting system is provided to visually assist the user in positioning the reader 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 when the lens 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. Elements of the photodetector are used to assess available light levels and activate the artificial illumination system when ambient light levels are low. Ranging through the lens using elements of the photodetector is included to provide information to set the focus of the objective lens in one of many possible focusing zones. All of the reader's components are housed in an ergonomically designed shell to reduce user repetitive stress injuries while providing access to a user interface and a protective cover for the reader's various systems.