SYSTEM FOR SCANNING AND READING SYMBOLS, SUCH AS BAR CODES, WHICH IS ADAPTED TO BE CONFIGURED IN A HAND HELD UNIT AND CAN AUTOMATICALLY READ SYMBOLS ON OBJECTS WHICH ARE PLACED INTHE DETECTION ZONE OF THE UNIT

摘要

SYSTEM FOR SCANNING AND READING SYMBOLS, SUCH AS BAR CODES, WHICH IS ADAPTED TO BE CONFIGURED IN A HAND HELD UNIT AND CAN AUTOMATICALLY READ SYMBOLS ON OBJECTS WHICH ARE PLACED IN THE DETECTION ZONE OF THE UNIT A unitary hand-held bar code scanner and reader produces an elliptical beam, oriented with its major axis along the direction of the bars, utilizing optics employing far field diffraction effects to shape the beam and maintain its elliptical aspect (length to width ratio) constant over a distance in front of the scanner were bar codes may be located. The optics eliminates parallax even though the photodetector and light source (preferably a laser diode) are located offset from each other on a board on which the optics are mounted. A housing assembly has channels which mount the board therein without shock absorbing devices. A digital microcomputer controller and peripheral devices regulate the optical power output from the laser diode and prevents catastrophic failure, if the electrical current through the laser diode exceeds safe limits. Digital control of the gain of the electronic circuits which provide the signals from which bar code information can be decoded and for the operation and control of a motor for oscillating a deflector which scans ML-0260F the beam across the code are also provided utilizing the microcomputer. The microcomputer also controls interface circuits to provide compatibility with auxiliary equipment and host computers which generate commands and requires data inputs of various polarity and format. When the scanner is mounted on an upright support which extends from a base of a stand, the ratio of the number of generated pulses to the reflected pulses is computed for a succession of pulses (ten pulses for example). Then the presence of the label is detected and the system, implemented in an application program in the microprocessor controller of the bar code scanner initiates scanning of the bar code when the ratio differs from a certain value. Upon the detection of the code (a good read) or under conditions where the label is removed before detection, or is not removed after detection, the scanning mode is discontinued and the pulsing mode is again initiated. The pulsing mode is initiated continually to test for the presence of a object carrying a bar code label, when not scanning. ML-0260F