Abstract: A method and apparatus for holding an otherwise variable parameter in a scanner approximately constant over a desired scan volume to improve the ability to compensate for unwanted variations in the amplitude modulation depth of a signal is provided, the signal being determined from collected light reflected from a target. In one embodiment, the time domain impulse response of the opto-mechanical system is the parameter which is held approximately constant by appropriately positioning the beam waist so that the beam spot size diverges approximately linearly along the beam axis within the scan volume.

Abstract: The operating speed of a brushless DC motor is maintained at a desired speed by controlling the voltage level of power supplied to the motor. The motor includes a rotor carrying permanent magnets, cooperating electromagnets contained in a stationary armature and Hall effect devices for sensing the operating speed and position of the rotor. Circuitry connected to the Hall effect devices generates angular sector signals corresponding to activation periods or periods during which power is applied to the electromagnets to operate the motor. A processor connected to one of the Hall effect devices monitors the operating speed of the motor and generates an error signal representative of the difference between the operating speed of the motor and a desired reference speed. A power supply is controlled by the processor to generate power having a voltage level corresponding to the error signal.

Abstract: An optical wand interface for coupling electrical output signals representative of a bar code scanned by an optical wand to a fixed bar code scanner with no electrical connection for the signals comprises circuitry for amplifying the output signals from the wand and a light emitter for generating light signals representative of the output signals. The amplifier and light emitter are supported within a housing which includes an optical lens for focusing the light signals generated by the light emitter into the optical input window of the fixed bar code scanner when the housing is positioned thereon. In this way, the electrical output signals generated by an optical wand are converted into light signals which are passed directly to and can be processed by the conventional optical receiving portion of a fixed bar code scanner.

Abstract: A method and apparatus are disclosed for controlling an off-line dc power supply circuit including a printed circuit board. The power supply circuit comprises a source of unregulated dc input power and a power transformer which separates the circuit into a primary side and a secondary side. An error amplifier compares an output dc voltage generated at a secondary winding of the power transformer to a reference voltage to generate an error signal representative of the difference error therebetween. The error signal is coupled from the secondary side of the power supply circuit to the primary side of the power supply circuit by means of a capacitor formed from traces on opposite sides of the printed circuit board. A solid state switch selectively connects the unregulated dc input power to a primary winding of the power transformer to regulate the power supply circuit in the primary side of the circuit in response to the error signal which is generated in the secondary side of the circuit.

Abstract: A system and method are provided for determining the occurrence of transitions in a binary encoded analog input signal. The system includes a threshold circuit, responsive to the input signal, for generating first and second grating signals in dependence upon whether the input signal exceeds or is less than a first threshold level, respectively. A first circuit means, responsive to the input signal, differentiates the input signal to form a first derivative signal. A threshold circuit, responsive to the first derivative signal, generates third and fourth gating signals in dependence upon whether the first derivative signal exceeds a second threshold level or is less than a third threshold level, respectively. A second circuit means, responsive to the first derivative signal, differentiates the first derivative signal to form a second derivative signal.

Abstract: A laser scanner having a rotating mirror, such as a POS scanner as used in supermarkets, uses a closed-loop velocity controlled DC brushless motor for rotating the mirror. In addition to providing a hall effect motor speed signal which is used for monitoring and safety features in association with the scanner, the DC brushless motor provides the advantages of greatly reduced power consumption, decreased temperature rise, less electrical noise in the analog scanner circuitry, reduced cost, and greatly reduced size, sometimes over 80%. The use of the inherent motor speed signal from the DC brushless motor also enables elimination of costly mechanical windswitches as typically used in prior scanners.