A laser focus control system including a laser for generating a scanning light beam to visually illuminate an information encoded bar code symbol. A segmented photodiode detects light reflected from the symbol and generates a plurality of electrical signals, each signal based on the light energy incident on the segments of the photodiode, thereby representing the spatial intensity variations of the symbol. A scanning zone processor then filters, averages, and compares the electrical signals to a noise threshold, and assigns logic levels based on the comparisons. Thereafter, a scanning zone detector determines the corresponding scanning zone distance based on the combination of logic levels and determines whether the system has stabilized within the zone distance. The scanning zone distance is then furnished to the laser focus controller in order to adjust the laser focus of the scanning device. The system is incorporated in a shock-resistant hand-held device.