Bar code scanner laser radiation exposure limit control system

摘要

In order to meet the requirements for laser radiation safety, namely laser output which can enter the naked human eye indefinitely and cause no discernible damage (Class I emission limit) in a code symbol (bar code) scanner, a mode controller is used for generating a laser enabling the signal so as to turn the laser on in a search mode until the symbols are acquired and in an in-code mode while the symbols are being scanned. When the laser is turned on it operates at a power output which would exceed the Class I emission limits if operated continuously. Circuitry is provided for operating the mode controller so that the laser is not enabled to turn on for a period long enough to exceed Class I limits. Such circuitry may be an integrator or accumulator which responds to the time that the mode controller turns the laser on and which provides an output for inhibiting the mode controller from turning the laser on for a period of time sufficient to prevent the Class I emission limit from being exceeded. The circuitry may alternatively be a pulse generator which permits the mode controller to turn the laser on repetetively during a "find paper" mode with a duty cycle such that the Class I emission limits are not exceeded.