Abstract: A method and apparatus for reading encoded symbols such as bar code labels at any orientation to a raster scanning device. Objects bearing encoded symbols are transported from one conveyor across a relatively narrow gap to a second conveyor, with a linear scanner positioned beneath the conveyors so as to read the encoded symbols through the narrow gap as the objects pass over. A pattern of virtual scan lines is selected over the two-dimensional imaging region according to the specifications of the images to be read. The pattern is generated by defining a family of parallel lines of a certain spacing and rotating the family by a specified angle until the two-dimensional imaging region is covered. In a preferred embodiment, only the data at selected raster locations on the virtual scan lines is stored and processed. One-dimensional signal processing methods are used to detect edges and decode the encoded symbols.

Abstract: A method and apparatus for reading bar codes or other images while reducing or eliminating the need for self-generated illumination. An image reader is preferably embodied as a handheld unit and comprises an efficient optical collection system including an aperture with a high aspect ratio and/or a multi-focal lens or lenses. An optically transmissive spacer affixed to the front of the handheld unit allows ambient light to be collected at close range, and a diffuser may be used to reflect ambient light from the handheld unit to provide additional illumination at close range. A masked CCD detector with rectangular pixels receives collected light and is coupled to an adaptive exposure circuit for preventing saturation of the CCD detector at high illumination levels. A correlated double sampling circuit coupled to the adaptive exposure circuit rejects common mode noise and allows operation in lower light levels.

Abstract: In a method of and an apparatus for detecting three-dimensional defects in he automatic inspection of moving surfaces by means of a color vision system the surface of a moving test specimen which is to be inspected is illuminated with light of different colors simultaneously from at least two different directions, such that edges of three-dimensional defects on the surface appear with a different coloring, and on the basis of the altered coloring, at least two channels of the color image are evaluated to detect three-dimensional defects and to differentiate same from planar defects.

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 method and apparatus for reading bar codes or other images while reducing or eliminating the need for self-generated illumination. An image reader is preferably embodied as a handheld unit and comprises an efficient optical collection system including an aperture with a high aspect ratio and/or a multi-focal lens or lenses. An optically transmissive spacer affixed to the front of the handheld unit allows ambient light to be collected at close range, and a diffuser may be used to reflect ambient light from the handheld unit to provide additional illumination at close range. A masked CCD detector with rectangular pixels receives collected light and is coupled to an adaptive exposure circuit for preventing saturation of the CCD detector at high illumination levels. A correlated double sampling circuit coupled to the adaptive exposure circuit rejects common mode noise and allows operation in lower light levels.

Abstract: The crystal isolation system of the present invention protects a laser crystal from environmental factors such as humidity and dust. A crystal is placed in a housing which has two ports in it, and flexible tubes are placed in each port. Cap pieces cover the ends of the tubes and prevent deleterious environmental factors such as dust and moisture from entering the isolation system while allowing laser light to enter the system. A desiccator attached to the system removes moisture from the air inside the system, and an led and detector apparatus are is used to help indicate the remaining useful life of the desiccant in the desiccator.

Abstract: The present invention is a system and method for mode-locking a laser, comprising reversibly converting radiation in the laser at a fundamental frequency into radiation at a second harmonic frequency, discriminating the radiation at the fundamental frequency using a polarization of the radiation at the fundamental frequency, and reconverting the radiation at the second harmonic frequency into radiation at the fundamental frequency.

Abstract: An oscillator system is provided which produces a single mode output from a multimode seed beam and a multimode optical power source. The seed source employed in the oscillator system produces a multimode seed beam that is used to injection seed a multimode optical power source. The optical power source has a short cavity such that the longitudinal modes of the multimode optical power source are sufficiently spaced apart that a mode of the optical power source can be positioned relative to the multimode seed beam such that the beam does not significantly overlap with neighboring longitudinal modes of the optical power source. By positioning a single longitudinal mode to overlap with the seed beam a high energy single longitudinal mode output is produced. The oscillator system preferably includes an output controller loop which serves to center the longitudinal mode output of the optical power source relative to the center of the seed beam.

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 laser or laser amplifier apparatus has a diode pump source producing a polarized pump beam. A laser head includes a gain medium that produces an output beam. One or more optical fibers are coupled to the diode pump source and deliver the pump beam to the laser head. A depolarization device is coupled to the diode pump source, laser head or optical fiber and produces an depolarized pump beam. By depolarizing the output beam, movement, including rotation, of the pump source does not comprise the output beam produced from the laser head.

Abstract: A diode pumped, multi axial mode, intracavity doubled, intracavity tripled laser, includes at least two resonator mirrors defining a resonator cavity. A laser crystal and a doubling crystal are positioned in the resonator cavity. A tripling crystal is also positioned in the resonator cavity. A diode pump source supplies a pump beam to the laser crystal and produces a laser crystal beam with a plurality of axial modes that are incident on the doubling crystal. This produces a frequency doubled output beam.Further, a diode pumped, multi axial mode, intracavity nonlinearly-converted laser is provided and includes at least two resonator mirrors defining a resonator cavity, a laser crystal and a nonlinear conversion apparatus positioned in the resonator cavity. A nonlinear conversion apparatus is also positioned in the resonator cavity.

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 an electronically actuable mechanism with no moving parts which may include 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: In an optical scanning system, a method and apparatus for decoding labels of single or multiple block formats by stitching together partial label segments obtained from multiple optical scans across the label is provided. Partial scans are decoded into strings of character information which are assembled by locating sub-strings of common elements between two strings. Strings in which the common elements occur at the ends are merged by deleting one set of redundant common characters and joining the remaining characters in proper sequence. The method assembles strings in which the common elements occur in the middle of one or both strings by testing for valid string combinations made by deleting characters adjacent to the common sub-string, on opposing ends of each string, and merging the resulting strings. Feature characters, parity information, checksum digits, and other label structural characteristics are used to verify resulting strings and completed blocks and labels.

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 diode pumped laser includes a resonator mirror and an output coupler, defining a laser resonator with a resonator optical axis. A strong thermal lens gain medium with a TEM.sub.00 mode diameter is mounted in the resonator along the resonator optical axis. The dopant level of the gain medium is in the range of 0.01 to less than 0.5 percent. A diode pump source supplies a pump beam to the gain medium in the laser resonator, and produces an output beam with a diameter larger than the TEM.sub.00 mode diameter to reduce thermal birefringence. A power source supplies power to the diode pump source. A polarizing element can be positioned in the resonator, along with a aperture stop The laser operates well over a large range of pump powers. Its slope efficiency in the TEM.sub.00 mode is greater than 40%, with an overall efficiency greater than 25%. One of the gain mediums used is Nd:YVO.sub.4. This material exhibits high gain and a short upper state lifetime.

Abstract: An interface selection and configuration system for a computer peripheral in which configuration for the peripheral and/or the host interface is at least in part accomplished by the interface connector cable. In a preferred embodiment, the computer peripheral is equipped with one or more hardware interfaces. The interface connector cable has a first end connector for attaching to the computer peripheral. The first end connector of the interface connector cable is typically a multiple pin connector constructed and arranged to be properly physically and electrically connectable only to a specific computer peripheral or class of computer peripherals, the first end connector including at least one electrical connection between two pins for completing a circuit within the computer peripheral thereby enabling the computer peripheral.

Abstract: A laser includes a laser head and a power supply. At least two resonator mirrors define a resonator cavity. A gain medium is positioned in the resonator cavity. A temperature controller is positioned in the laser head and is coupled to the gain medium. The temperature controller maintains the gain medium at a temperature of 25 degrees C. or greater. A pump source supplies a pump beam to the gain medium and producing an output beam. The power source is coupled to the pump source.

Abstract: An oscillator system is provided which produces a single mode output from a multimode seed beam and a multimode optical power source. The seed source employed in the oscillator system produces a multimode seed beam that is used to injection seed a multimode optical power source. The optical power source has a short cavity such that the longitudinal modes of the multimode optical power source are sufficiently spaced apart that a mode of the optical power source can be positioned relative to the multimode seed beam such that the seed beam does not significantly overlap with neighboring longitudinal modes of the optical power source. By positioning a single longitudinal mode to overlap with the seed beam where the seed beam does not significantly overlap with neighboring longitudinal modes of the optical power source, a high energy single longitudinal mode output is produced.

Abstract: Method and apparatus for scanning items with a compact scanner which is mountable onto and/or integral with a pointing instrument. The scanner module may be equipped with an aiming beam for additional help in directing the scan line toward the object to be read. The pointing instrument may be a pen or pencil or alternately a pen-based computer stylus for use with an integrated data terminal module operably connected to the scanner module. Security for preventing separation of the module may be provided by a wireless link.