Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1998-08-05
2001-11-27
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462450
Reexamination Certificate
active
06321990
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to electro-optical systems for reading indicia such as coded symbols and, more particularly, to simplifying the assembly and automatically testing the components in such systems.
2. Description of the Related Art
Electro-optical systems for reading coded indicia such as bar code symbols are well established in the art. See, for example, U.S. Pat. Nos. 4,251,798; 4,387,297; and 4,409,470, as well as the many other U.S. patents issued to Symbol Technologies, Inc., the assignee of the instant application.
Thus, a typical system includes a light source, such as a laser diode, for emitting a light beam toward a symbol for reflection therefrom. The reflected light is detected by a light sensor, such as a photodiode, over a field of view. The light beam and/or the field of view is scanned by an oscillating scan drive, typically including a light reflector. The sensor generates an electrical signal indicative of the symbol being scanned. This electrical signal is thereupon processed in a well known manner, typically to identify the item bearing the symbol, and then using this identification for inventory or check-out purposes. These electrical and optical components are often mounted in a hand-held, portable head or housing.
The assembly of the various system components is labor intensive. Various components, for example, the photodiode, are soldered to a printed circuit board on which electrical circuitry, for example, the signal processing, control and drive circuitry are mounted. Typically, a flexible strip cable is soldered to the laser diode and the circuit board. Also, an electro-magnetic interference (EMI) shield is soldered to the circuit board. Many screws are used to secure various system components in place within the housing, and even the housing itself is composed of parts that are fastened together with screws.
Aside from the labor-intensive nature of assembling the components by soldering and by manually turning multiple screws, there is also the labor-intensive procedure of manually adjusting certain optical components. Optical adjustment among the light source, light sensor, light reflector, and scan drive is critical for proper system operation. At present, three adjustments are required to manually set the “alignment” of the optical sub-system. First, the power level of the laser diode is adjusted manually by the operator by holding a power meter in front of the laser beam and simultaneously manually adjusting a potentiometer on the circuit board. Second, the position or height of the laser beam is set by adjusting the position of a laser spot from the laser beam to the center of a scan mirror on the light reflector. This is accomplished by the operator manually turning an adjustment screw while watching the location of the laser spot on a video monitor that shows a zoomed-in picture of the reflector. Third, the sweep or amplitude of the scan drive is set by lowering a mirror in the path of the laser beam so as to reflect the laser beam onto a movable plate. On the plate are etched-in tolerances for the scan width (representing the amplitude). The operator manually adjusts a potentiometer on the circuit board until the scan width falls into predetermined specifications.
After these initial adjustments are performed in a test fixture, they must be manually verified after the optical sub-assembly is mounted in the housing in which they are to finally reside. These final adjustments are not guaranteed to take place (unit could be assembled without full alignment taking place) or not be fully within specifications. Sometimes, re-work is necessary to correct the alignment, thereby leading to increased manufacturing cost and complexity.
SUMMARY OF THE INVENTION
OBJECTS OF THE INVENTION
It is a general object of this invention to simplify the mounting of components in electro-optical systems for reading coded indicia.
It is another object of this invention to automate the adjustment of the optical sub-assembly in such systems by reducing human involvement.
It is still another object of this invention to reduce overall manufacturing cost and complexity in such systems.
FEATURES OF THE INVENTION
In keeping with these objects and others which will become apparent hereinafter, one feature of this invention resides in supportably mounting a light source component for emitting a light beam, a light sensor component for detecting light from indicia over a field of view, and a light reflector component used for scanning at least one of the light beam and the field of view, on a chassis that, in turn, is snap-mounted in a housing. The chassis is used with an automated test fixture for automatically adjusting the laser power level, the laser beam height and the amplitude of the scan drive, thereby effectively reducing, if not eliminating, all operator judgment in aligning the optical sub-assembly and guaranteeing that all necessary adjustments will be made during manufacture and assembly. The automated fixture provides a higher level of accuracy and repeatability, and the need to re-work or verify the alignment in the housing should all but be eliminated.
In the preferred embodiment, the housing includes a cover that overlies, and is snap-mounted to, a housing shell in an assembled condition of use. A printed circuit board is mounted in the housing, preferably by being snap-mounted on the chassis. The cover has formations that clamp the circuit board to the chassis in the assembled condition of use. Also, the cover has additional formations for securing the position of an optical block or casing in which the light source component is mounted.
Other features of the invention include heating a light-transmissive window through which the light beam and the reflected light pass in opposite directions to prevent fogging, providing EMI protection for the light sensor component as well as good heat dissipation for the light source component, detachably mounting a boot or cap on the end of a handle connected to the shell, providing a cable connected to the housing with strain relief, self-supporting the housing on a horizontal support surface, providing the cover with light-absorbing and shock-absorbing properties, optimizing communication between a user and the system by improved visual, audio and vibratory status indicators for indicating system operation, providing a novel dual-finger trigger, pivoting the trigger at a new location on the housing, and forming certain system components with features to allow easy assembly.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
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patent: 5751257 (1998-05-01), Sutherland
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patent: DE 29 21 927 B1 (1980-02-01), None
patent: 0 367 298 A2 (1990-05-01), None
patent: WO 94/27248 (1994-11-01), None
Barile John
Barkan Edward
Chen Chang-Hong
Chew Steven
Doran Robert
Frech Karl D.
Kirschstein et al.
Symbol Technologies Inc.
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