Abstract: Electrical power consumption is saved in a low-cost scanner for reading bar code symbols by oscillating a tall, narrow light collector, e.g., mirror, either by mechanical power along or by a low-power electrical drive. The collecting mirror has a width along the scan direction which is no more than about one-fifth its height, as considered along an orthogonal non-scan direction. A linear array of light emitting diodes is employed to illuminate the symbols.

Abstract: A packet data transmission system is used to link a number of remote hand-held data-gathering units such as bar code readers to a central computer which maintains a database management system. Data packets are sent from the remote units by an RF link to intermediate base stations, then sent by the base stations to the central computer by a serial link. Direct sequence spread spectrum modulation is used for the RF link. The remote hand-held units initiate an exchange using RF transmission to and from the base stations, receiving only during a rigid time window following a transmission from the remote unit. The base stations cannot initiate communication to the remote units, but instead send data to the remote units only as part of the exchange.

Abstract: A drive circuit for a bar code scanner for driving an oscillatory resonant motor therein which periodically oscillates in opposite rotary directions to impart an oscillatory motion to a scanning mirror of the bar code scanner. In the disclosed drive arrangement, the motor is driven at its own natural resonant frequency, which requires very little current to maintain the oscillatory motion. A scanning beam is directed against the oscillating scanning mirror, which causes the beam to be periodically scanned across a field of view of the bar code scanner. A detector detects reflections of the scanned beam, as by a bar code symbol being scanned, and generates an output signal representative thereof.

Abstract: A laser scanning system for reading bar code symbols in which the "dead zone" is minimized by appropriate positioning and size of the optical components. The vertical height (non-scan direction) of the collecting mirror is minimized, while the horizontal width (scan direction) is increased proportionally, thereby collecting less specular reflected light. The optical components are mounted on a single printed circuit board so that the optical paths are angularly offset for minimizing the specular component, while maintaining an optically-aligned relationship. The printed circuit board may be mounted in hand held laser scanning head having a single exit window.

Abstract: In a bar code laser scanning system operable in a continuous scan mode and a sleep mode, an object sensing circuit for automatically switching said laser scanning system from the sleep mode to the scan mode is provided to help extend the operational lifetimes of the system components such as the laser diode and the scanning motors. When in the sleep mode, pulsed light is received and processed to generate a steady state voltage signal. Derived from the steady state voltage signal is a positive threshold voltage signal and a negative threshold voltage signal each having a magnitude respectively greater than and less than that of the steady state voltage level. The steady state, positive threshold and negative threshold voltage signals are input to a comparator means which detects when an object is placed in the scanning field of the laser scanning system.

Abstract: The method and apparatus of this invention facilitate operation of a bar code reader over a wider range of working angle and for a wider range of bar code densities. The invention includes improved optics and sensing elements. The optics and sensing elements and/or the associated circuitry are arranged to provide two channels of data derived form the scanned bar code. The two channels have differing resolutions. Analysis of the data from the two channels provides a single decoded result. As the working angle and density vary at least one of the resolutions will be appropriate for sensing all or most of the bar coded data. The data from the channel producing a valid result can be used, or if neither channel produces a valid result by itself, data from each channel can be analyzed and valid portions of the data from both channels combined to produce the single decoded result.

Abstract: A method for decoding bar code symbols in which a bar code reader and associated components scan a bar code symbol, produce a representation of the symbol, and attempt to decode that representation in order to produce a character message. The method consists of the steps of storing a first representation of the bar code symbol corresponding to a first scan path through a first portion of said symbol smaller than the entire symbol, and storing a second representation of the bar code symbol corresponding to a second scan path through the symbol. The method then processes said representations in the event a successful decode has not taken place by utilizing the signal from a first scan with the signal from a subsequent scan to determine the best alignment at which successive scans can be concatenated to form a combined signal. The process is repeated with different subsequent scans until successful decoding of the combined signal.

Abstract: Collection optics are eliminated in the return path of a retro-reflective scanner for reading bar code symbols.

Abstract: A bar code scanner employs a digitizer for the signal produced by a photodetector in response to light reflected from a bar code symbol. The digitizer uses a first derivative of the signal to detect peaks, and determines the amount of movement of the signal after each peak to see if a threshold amount of movement has occurred. A second derivative of the signal is used to detect inflection points, and when one occurs after the threshold amount of movement following a peak, a valid transition of the signal is signalled. These valid transitions are decoded to recover the bar code pattern. The threshold used is adjustable to optimize the digitizing for different types of bar code symbols and other conditions, or to provide a squelch function. Dynamic control of the threshold provides a varying response to the scanned bar code symbol. Zero-crossing detectors used with the first and second derivative circuits may also have variable thresholds.

Abstract: A bar code scanner which is responsive to the movement of the scanner to activate its light source. The scanner includes a motor having a moving member which is set in motion when the scanner is displaced from a rest position. The moving member generates a voltage in a coil, which activates the operation of the bar code scanner.

Abstract: A dual motor speed control circuit for providing independent speed control of two motors in a laser scanning device is disclosed herein. This apparatus utilizes a single input signal having variable frequency and duty cycle components. The speed of the first motor is controlled by utilizing the frequency component of said input signal while the speed of the second motor is controlled by utilizing the frequency and duty cycle components of said input signal. Specifically, a DC signal is generated that is dependent upon the duty cycle component of said input signal and said DC signal is utilized to offset the speed of the second motor from the speed value as determined by the frequency component of said input signal.

Abstract: A scanning arrangement located within a scanning device which is operative for repetitively scanning indicia having parts of different light reflectivity, for example, bar code symbols, and more particularly, pertains to a novel scanning motor of the arrangement for enabling a scan element which is supported by a holder structure mounted on a mylar motor to implement angular oscillatory movements in a linear scan direction between a pair of scan end positions. Hereby, pursuant to the structure of the scanning device, the scanning arrangement is preferably mounted on a single printed circuit board located within a lightweight scanning device of a hand-held housing of gun-shaped configuration which may be readily held and manipulated by a user of the scanning device.

Abstract: A scanning head for reading bar code symbols includes a laser source producing a beam which is scanned across a symbol to be read by a moving mirror arrangement, and a photodetector responsive to light reflected from the symbol. The signal from the photodetector is digitized and decoded to recover bar code data. The scanning head includes a keyboard for entering data, and a display from showing data, and a microprocessor in the head controls the operations of the various components. A transmitter and receiver may be located in the scanning head for communication with a central computer, and a battery included in the head as a power supply, so that the scanning head need not be connected by a cable to a terminal.

Abstract: A method for reading bar code symbols which enables legitimate characters recognized by the code in use to be derived from a plurality of scans corresponding to illegitimate characters not recognized by the code in use is disclosed. The method includes the steps of storing representations of the bar code symbol which cannot be decoded to produce legitimate character(s). One of the representations is improved, or corrected, using another representation, and an attempt is made at decoding the corrected representation to produce a legitimate character. If the decoding attempt is not successful, further corrections are made in order to provide a representation which may be decoded to produce a legitimate character.

Abstract: A bar code scanner employs an electronic means for causing the light beam to scan a bar code symbol, rather than using a mechanical device to generate the scan. A linear array of light sources, activated one at a time in a regular sequence, may be imaged upon the bar code symbol to simulate a scanned beam. Instead of a single linear array of light sources, a multiple-line array may be employed, producing multiple scan lines. The multiple scan lines may be activated in sequence, or activated simultaneously (time-division or frequency-division multiplexed. The multiple scan lines can provide signal enhancement, noise reduction or fault correction if directed to the same bar code pattern. Multiple scan lines may be generated using a single light source and a beam splitter, with mechanical scanning, as well as by the sequentially-activated light suorces. Multiple simultaneous scan lines may be employed to generate a raster scan at lower mechanical scan frequency.