Abstract: A method and apparatus for determining the transitions between binary levels of an input signal such as a scanned bar code label by detecting zero crossings of an approximated second derivative of the input signal. Samples of the input signal are obtained by using delay lines, sample-and-hold circuits, an analog shift register or similar device. The first derivative of the signal is approximated by the slope of a straight line between two sampled points on the waveform. The second derivative is approximated by the difference between two first derivatives. Zero crossings of the second derivative indicating transitions of the input signal may be determined either by detecting a signal peak on both sides of the zero crossing, or by comparing the second derivative signal to zero when the first derivative exceeds a positive or negative threshold. The amount of shift in the zero crossings may be estimated by measuring relative amplitudes or widths of the surrounding signal lobes.

Abstract: A method and apparatus for determining the transitions between binary levels of an input signal such as a scanned bar code label by detecting zero crossings of an approximated second derivative of the input signal. Samples of the input signal are obtained by using delay lines, sample-and-hold circuits, an analog shift register or similar device. The first derivative of the signal is approximated by the slope of a straight line between two sampled points on the waveform. The second derivative is approximated by the difference between two first derivatives. Zero crossings of the second derivative indicating transitions of the input signal may be determined either by detecting a signal peak on both sides of the zero crossing, or by comparing the second derivative signal to zero when the first derivative exceeds a positive or negative threshold. The amount of shift in the zero crossings may be estimated by measuring relative amplitudes or widths of the surrounding signal lobes.

Abstract: A bar code scanning system such as for use in retail checkout having a scanner housing; a plurality of surfaces facing a scan volume from different directions; and sets of pattern mirrors positioned adjacent the respective surfaces, the housing being positioned above the scan volume and containing one or more laser beam modules and/or a scanning mechanism for producing scanning beams which are routed to the pattern mirrors and out through the respective surfaces into the scan volume.

Abstract: An optical system and method for data reading having a light source which generates an optical beam directed toward an object to be read and a focusing system in the outgoing light path which establishes multiple beam functions. In a preferred application, a scanning system includes a multifocal lens having a single lens element having an inner lens portion of a first focal length and an outer annular lens portion with a second focal length, the optical system of a bar code scanner therefore establishing two separate focal positions from a single light source. Alternately, the system includes a focusing lens system with an corrector element disposed in the outgoing optical path, the corrector element having a plurality of optical zones, each zone having a different optical characteristic for modifying a portion of the outgoing optical beam. A zone may be a refractive region, a reflective region, a diffractive region, an empty region, a window region, or combinations thereof.

Abstract: An optical system and method for data reading in which a light source generates an optical beam directed toward an object to be read and a variable aperture mechanism positioned in the outgoing light path establishes at least two separate focal planes. The variable aperture device may comprise a variable aperture system in which the size of the aperture is selectively varied about a range within the diffractive limit of the light beam. A preferred aperture mechanism is a liquid crystal aperture with one or more aperture regions which are selectively or consecutively activated. The optical system therefore establishes two or more separate waist locations from a single light source resulting in greater depth of field or multiple depths of field.

Abstract: A method and apparatus for determining the transitions between binary levels of an input signal such as a scanned bar code label by detecting zero crossings of an approximated second derivative of the input signal. Samples of the input signal are obtained by using delay lines, sample-and-hold circuits, an analog shift register or similar device. The first derivative of the signal is approximated by the slope of a straight line between two sampled points on the waveform. The second derivative is approximated by the difference between two first derivatives. Zero crossings of the second derivative indicating transitions of the input signal may be determined either by detecting a signal peak on both sides of the zero crossing, or by comparing the second derivative signal to zero when the first derivative exceeds a positive or negative threshold. The time between sample points may be adjusted to match a particular range setting of a scanner having a plurality of range settings.

Abstract: An optical system and method for data reading having a light source which generates an optical beam directed toward an object to be read and a focusing system in the outgoing light path which establishes multiple beam functions. In a preferred application, a scanning system includes a multifocal lens having a single lens element having an inner lens portion of a first focal length and an outer annular lens portion with a second focal length, the scanning system therefore establishing two separate focal positions from a single light source. Alternately, the system includes a focusing lens system with an corrector element disposed in the outgoing optical path, the corrector element having a plurality of optical zones, each zone having a different optical characteristic for modifying a portion of the outgoing optical beam. A zone may be a refractive region, a reflective region, a diffractive region, an empty region, a window region, or combinations thereof.

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: An automated retail point of sale scanning system includes a means for preferentially aligning an item traveling on an item path and through a scanning region such that two or more surfaces to be scanned are stably maintained in a substantially coplanar alignment with a corresponding focal plane of a bar code scanner. Two orthogonally disposed belts define an item path. The belts are tilted at an angle from the horizontal so that an item placed on either belt will have at least two surfaces stably registered by gravity, one surface to each adjacent belt. Alternatively, a stationary platen is disposed orthogonally to a transport belt such that at least two surfaces of the item being scanned are stabilized in a focal plane coplanar with a bar code scanner, one surface of the item being stabilized against the platen and another surface being stabilized against the adjacent transport belt.

Abstract: A video conferencing network for providing videos, audio, and data communication between remote video terminals. Each of the video terminals transmits and receives video, audio, and data information through the network. The network includes a central switching network for receiving audio and video information on one of a plurality of audio/video ports and selectively interconnecting this information to remaining audio/video ports. A centralized controller is in data communication with each of the video terminals and the switching network and controls the configuration of the switching network to provide the appropriate audio and video paths in response to the data received by the controller from the video terminals.

Abstract: A video conferencing network includes remote video terminals (10) interconnected to a switching network (66) through coaxial cables (16). The switching network (66) is operable to provide an audio and video data path between two or more video terminals (10). The switching network (66) operates as both an audio/video crosspoint switch and also as a network controller. In the network control mode, the switching network (66) operates in both a master mode for maintaining data communication with all of the video terminals (10) and also in a slave mode for maintaining status of devices attached to the switching network (66). In the master mode, the switching network (66) receives requests from each of the video terminals (10) and services these requests to determine available data paths for interconnection with other video terminals. In the slave mode, the switch (66) is in data communication with all of the video terminals (10) to determine the status thereof which is stored in a slave status table.

Abstract: A video conferencing network includes remote video terminals (10) interconnected to a switching network (66) through coaxial cables (16). The switching network (66) is operable to provide an audio and video data path between two or more video terminals (10). The switching network (66) operates as both an audio/video crosspoint switch and also as a network controller. In the network control mode, the switching network (66) operates in both a master mode for maintaining data communication with all of the video terminals (10) and also in a slave mode for maintaining status of devices attached to the switching network (66). In the master mode, the switching network (66) receives requests from each of the video terminals (10) and services these requests to determine available data paths for interconnection with other video terminals. In the slave mode, the switch (66) is in data communication with all of the video terminals (10) to determine the status thereof which is stored in a slave status table.

Abstract: The disclosed optical data link provides full-duplex, high-data rate optical communications between geographically separate data processing facilities by means of identical optical transceivers. Transmitter optics include an LED and a collimating Fresnel lens for providing a collimated, modulated light beam. Receiver optics include a focusing Fresnel lens and a photoreceptor for converting the impinging modulated light beam into corresponding electrical signals, which are amplified by a gain-controlled amplifier. The LED is selectively translatable along its optical axis to provide focal length correction for temperature-induced focal length distortion, while the photoreceptor is selectively translatable along its optical axis to provide, in addition to focal length correction, a preselected amount of optical energy attenuation.