Psc Scanning, Inc.

Psc Inc.

Spectra-physics Scanning Systems, Inc.

Datalogic Adc, Inc.

Datalogic Scanning, Inc.

James E Colley

Bryan L Olmstead

James W Ring

Thomas C Arends

Edward P Coleman

Alexander Malcolm McQueen

Matt D Schler

Kevin J Williams

Donald S Peterson

Phillip C Gummeson

Blaine F Loris

Anthony S Bailey

Systems process an input signal, derived from a binary optical code, having a series of multiple successive local peaks of the same given polarity. The circuit comprises a peak detector, a node in the peak detector, and a set-reset flip-flop. The peak detector has an input receiving the input signal and produces an output that approximately tracks the input signal while it is sloping in the direction of the given polarity and that approximately holds near those local peaks having successively larger magnitude. A node in the peak detector has a voltage indicative of whether the peak detector is in a tracking or holding state. The set-reset flip-flop has a set input connected to the node, whereby the output of the flip-flop is high when the peak detector is in a tracking state. The circuit is useful for qualifying optical edges in a bar code.

System, circuit, and method for edge detection in a binary optical code

Systems better detect transitions in a binary optical code signal and thus better detect edges in binary optical codes, such as bar codes. The optical code signal imperfectly indicates perceived regions of relatively dark and light areas arranged in an alternating pattern as part of an optical code. That signal is differentiated to form a first derivative. Due to various non-ideal conditions, the first derivative may have a series of successive local peaks of the same polarity. Peaks in the series having a peak value less than a previous peak value in the series are ignored, thereby resulting in a set of unignored peaks. From the unignored peaks in the series is chosen the one peak occurring last in order. According to the chosen peak, there is generated a signal more reliably indicating the true edge position between light and dark areas in the pattern.

A method for driving a resonant electromagnetically-actuated motor, such as those used to scan a light source for date reading applications, wherein drive current is applied when the back-EMF induced in the actuator coil is zero and has a specific slope, and that drive current is removed after the induced back-EMF voltage has changed by a predetermined constant value. The drive circuit will drive the motor across a scan angle which remains substantially constant regardless of changes in ambient temperature, changes in motor orientation, or externally applied forces.

Resonant motor driver system for data reading

A system and method for improving the accuracy of edge detection under high Inter-Symbol Interference, or ISI, conditions is disclosed. The amplified and filtered first derivative signal is offset by equal amounts in both directions to generate positive and negative offsets which serve as inputs to negative and positive peak detectors, respectively. The offset is determined by a fast adaptive peak detector provided by attenuating and AC-coupling the first derivative signal to the positive supply to drive a peak detector with a fairly short attack time, such that its output is nearly settled on the first peak of the first derivative signal, but having a decay time long enough to keep the threshold level approximately constant across the label. Peaks are qualified if the peak in question differs in amplitude from the previously qualified peak by the offset amount. Thus, peaks are qualified if their modulation depth exceeds a threshold, regardless of the absolute level of the peaks (such qualification strategy is referred to as modulation depth gating).

Fast edge detection system tolerant of high degree of intersymbol interference

A compact scan module including a resonantly driven dithering assembly employing feedback and/or travel stops for scanning an illumination beam of a barcode scanner. In one construction the dithering assembly includes one or more travel stops to limit the motion of the mirror assembly with the two travel stop(s) fabricated from damped resilient material to absorb excess energy imparted on the dithering assembly. A first preferred feedback embodiment employs a Hall effect sensor wherein a feedback magnet is connected to the dithering assembly with a Hall effect sensor positioned to sense the varying magnetic field resulting from the varying position of the feedback magnet. A second feedback embodiment incorporates piezoelectric feedback wherein one or more piezoelectric strain sensors are attached to the bending member to provide the position sensing.

Dithering assemblies for barcode scanners

An optical or symbol reader including CMOS circuitry preferably integrated on a single chip. A CMOS optical reader chip comprises a CMOS imaging array having a plurality of pixels each with a dedicated pixel-site circuit. Charge is accumulated at each pixel location transferred upon demand to a common bus. In a preferred embodiment, exposure time of the imaging array is controlled using a feedback loop. One or more exposure control pixels are positioned adjacent to or within the imaging array and receive light along with the imaging array. The charge of the exposure control pixel or pixels is measured against a threshold level, and the amount of time taken to reach the threshold level determines the time exposure of the pixels of the imaging array. CMOS signal processing circuitry is employed which, in combination with the exposure control circuitry, minimizes time-to-read over a large range of light levels, while performing spatially optimal filtering. Clocking cycles and control signals are time-adjusted in accordance with the varying output frequency of the imaging array so as to provide invariant frequency response by the signal processing circuitry. A multi-dimensional CMOS imaging array is also provided having simultaneous pixel exposure with non-destructive readout of the pixel contents.

Optical reader with condensed CMOS circuitry

Optical reader with adaptive exposure control

Optical reader with addressable pixels

A method and apparatus for improving the accuracy of bar and space measurements in a barcode scanner system utilizing second derivative signal processing is provided wherein edges are more accurately detected under low signal-to-noise conditions, such as when shot noise is the major source of noise in an input signal and the larger noise levels present during the light portions of the input signal may cause premature triggering of a light-to-dark transition in the output signal. In a preferred embodiment, an input capture circuit captures and stores the time of successive assertions of an STV signal corresponding to light-to-dark transitions. Upon detection by a second input capture circuit of a first assertion, following the STV assertions, of an RTV signal corresponding to dark-to-light transitions, the last STV signal time is stored and used with a previously stored RTV time to determine a space width. The new RTV signal time and the last STV signal time are then used to determine a bar width. Thus, light-to-dark transitions in the output signal are triggered on the last second derivative zero crossing which occurs within a comparator gate instead of the first zero crossing. Subsequent assertions of an RTV signal are preferably ignored until after one or more additional STV signal assertions occur. The entire process repeats for each light and dark position until the entire signal has been processed.

Edge detection method and apparatus for shot noise limited signals

An electronic edge detection system for use in a barcode scanning system utilizing second derivative signal processing wherein the temporal offset between the first and second derivative signals is eliminated so as to enable edge detection for signal levels down to the noise level of an input signal. In a preferred embodiment, an overall filter network receives an input signal and comprises two real poles as the last elements of two parallel output channels. The first output channel terminates with a low pass filter and produces the first derivative of the input signal. The second output channel terminates with a high pass filter and produces the second derivative of the input signal. Implementing the second differentiator as one real pole of the overall edge detection system filter polynomial and placing the poles of the two output filters at the same frequency eliminates the temporal offset. Substantially constant and equal group delay over the system passband for both first and second derivative signals is also provided.

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Junction City, OR, United States of America

James E Colley