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 conditioning an input signal from an optical detector includes a controller for dynamically modifying adjustable delay elements connected to the input signal, thereby modifying characteristics of the signal conditioning circuitry. The method and apparatus determines 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.

Abstract: A laser bar code system is described which includes a first scan module releasably affixed to a housing, which scan module is readily interchangeable with and plug compatible with a second scan module which is configured at least partly differently from the first scan module. In addition, a partitioned scan module is described which comprises a first laser diode subsystem, a first scanning subsystem, a first collection subsystem, and a first signal processing subsystem, a selected one of which is releasably affixed to a chassis, and readily interchangeable and plug compatible with a second laser diode subsystem, a second scanning subsystem, a first collection subsystem, and a second signal processing subsystem, respectively, which is configured at least partly differently from the first.

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 laser bar code system is described which includes a first scan module releasably affixed to a housing, which scan module is readily interchangeable with and plug compatible with a second scan module which is configured at least partly differently from the first scan module. In addition, a partitioned scan module is described which comprises a first laser diode subsystem, a first scanning subsystem, a first collection subsystem, and a first signal processing subsystem, a selected one of which is releasably affixed to a chassis, and readily interchangeable and plug compatible with a second laser diode subsystem, a second scanning subsystem, a first collection subsystem, and a second signal processing subsystem, respectively, which is configured at least partly differently from the first.

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: A signal processing apparatus and method adapted for use in bar code scanners is described. The apparatus forms a derivative signal, and utilizes the derivative signal to detect transition points from white to black bars and vice-versa. Then, the apparatus starts and stops the generation of digital pulses at or about the transition points, thereby generating pulses having widths corresponding to the widths of the bars making up the bar code symbol. The apparatus is capable of successively scanning a bar code symbol more than once, and varying various processing parameters used in forming the derivative signal over the successive scans, including threshold level, overall bandpass, overall amplification, and the like.

Abstract: A scanner includes a microprocessor for controlling operation of the scanner, and an interface circuit, which connects the microprocessor to a host computer and transfers data from the microprocessor to the host computer. Interface apparatus provides an interface between the scanner interface circuit and a personal computer, permitting the personal computer to act as a host. The interface apparatus includes a printed circuit board, output means, mounted on the printed circuit board, for transmitting data from the personal computer to the scanner interface circuit under control of an output strobe signal, and input means, also mounted on the printed circuit board, for transmitting data from the scanner interface circuit to the personal computer under control of an input strobe signal. The interface apparatus further includes an address means, mounted on the printed circuit board, for providing the output and input strobe signals to the output means and the input means, respectively.

Abstract: A scanner for scanning bar code labels and for providing data related thereto to a host computer includes a scanning apparatus for optically scanning bar code labels and for providing an electrical signal in response thereto, and a decoding circuit, responsive to the scanning apparatus for translating the electrical signal into a digital signal. A microprocessor, responsive to the decoding circuit, controls operation of the scanner and translates the digital signal into data to be provided to the associated host computer under control of control characters. The scanner further includes a non-volatile random access control memory in which control characters are stored, and an interface, connected to the host computer and to the microprocessor, for transferring data from the microprocessor to the host computer and for transferring control characters from the host computer to non-volatile random access control memory via the microprocessor.

Abstract: The scanner includes scanning circuitry for optically scanning bar code labels and providing an electrical signal in response thereto, decoding circuitry, responsive to the scanning circuitry for translating the electrical signal into a digital signal, and a microprocessor, responsive to the decoding circuitry, for controlling operation of the scanner and for translating the digital signal into data to be provided to the associated host computer under control of control characters. A non-volatile random access control memory is provided for storing control characters. Interface circuitry, connected to the host computer and to the microprocessor, transfers data from the microprocessor to the host computer. A switch enables the microprocessor to translate the digital signal into control characters and enables the microprocessor to store the control characters in the non-volatile random access control memory.

Abstract: A power supply circuit for a gas laser has primary circuitry and secondary circuitry supplied by the primary circuitry. A transformer is positioned between the primary circuitry and a secondary circuitry. Within the secondary circuitry is a spark gap and associated circuitry for creating a voltage buildup to achieve a high ionization voltage required for the laser and for releasing the high ionization voltage in pulses for starting the laser. The circuit further includes laser operating supply circuitry associated with the secondary circuitry and the primary circuitry for supplying the laser at a normal operating voltage much lower than the ionization voltage after the laser has started.