Abstract: An improved photodetector integrator circuit is provided having a photodetector, such as a photodiode, which produces photocurrent responsive to incident illumination. The photodetector is coupled to an integrator stage which converts the photocurrent into voltage and integrates the voltage over an integration period to provide an output signal. A window comparator in the circuit receives the output signal from the integrator stage and compares the output signal to a first threshold and a second threshold to provide, as a measurement signal, a pulse having a width which corresponds to the time interval over which the output signal increases from the first threshold to the second threshold. In the window comparator, the second threshold is greater than the first threshold.

Abstract: A system for bar code reading and scanning is provided having automatic bar code signal size control. The scanner includes a processor which calculates, in response to a signal power level of the symbol which has been read, a first optical power level when the beam is scanned in a first direction and a second optical power output level when the beam is scanned in a second direction. This calculation is responsive to the power level and the detected signal size of the preceding scan.

Abstract: A laser drive and control system which provides protection for a laser diode by preventing excess current from a power source, that normally supplies power to the laser diode, from destroying the laser diode when the voltage supplied by the power source to the laser diode decreases below a certain voltage which causes excess current. The system is implemented in CMOS circuitry for miniaturization into an integrated circuit chip.

Abstract: An electro-optical sensor senses marks on a sheet which travels longitudinally with respect to a printed circuit board, carrying linear arrays of light sources (LEDs) and photodetectors and optics which define zones displaced laterally across the width of a sheet of paper, longitudinal columns of which can contain marks, the presence and absence of which marks is detected by the sensor. The sensor is especially adapted for use in detecting marks which indicate votes on paper ballots in electronic, computerized vote counting apparatus.

Abstract: 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.

Abstract: A bar code label is read by automatically initiated scanning of the bar code symbol by a beam of light, as from a laser in a bar code scanner. Initially, the scanner is operated in a pulsed mode with low duty cycle (5%) pulses. These pulses are reflected from a reflective tape on one side of a detection zone or from an object carrying the label in the beam path. Then (because the beam is not scanning across the code) the reflected pulses (which are detected much like the bars and spaces of the code) are not detected. The ratio of the number of generated pulses to the reflected pulses is computed for a succession of pulses (ten pulses for example). If this ratio exceeds two (i.e., that the number of effective bars is less than the number of generated pulses during the succession), then the presence of the object 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.

Abstract: A reflective deflector of a light beam which scans in opposite directions across a bar code is controlled in scan angle by monitoring the AC component of a current passing through a winding of a scanning motor which oscillates the deflector to scan the beam across the code over a scan angle. The inductance of the winding corresponds to the length of the scan angle and is measured in terms of the peak to peak value of the AC component during a scan period or frame which occurs over an interval corresponding to the reciprocal of the scan rate. During successive periods, successive trains of pulses are generated. The number of pulses or their duty cycle during each period is changed in accordance with an error signal corresponding to the difference between the desired scan angle and the peak to peak value of the AC component.

Abstract: A bar code label is ready by automatically initiated scanning of the bar code symbol by a scanner on a stand. Light is reflected back to the scanner as from the bars of a code being scanned. Initially, the scanner is operated in a pulsed mode with low duty cycle (5%) pulses. These pulses are reflected from a reflective area unless an object is inserted and blocks the beam path. Then (because the beam is not scanning across the code) the reflected pulses (which are detected much like the bars and spaces of the code) are not detected. The ratio of the number of generated pulses to the reflected pulses is computed for a succession of pulses. If this ratio exceeds two (i.e., that the number of effective bars is less than the number of generated pulses during the succession), then the presence of the object is detected. The system, implemented in an application program in the microprocessor controller of the bar code scanner, initiates scanning of the bar code.

Abstract: 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.