Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-03-24
2002-03-26
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462370, C235S472010
Reexamination Certificate
active
06360949
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to electro-optical readers or scanning systems, such as bar code symbol scanners, and more particularly to retro-reflective laser scanning modules for use in applications requiring particularly compact scanners.
2. Description of the Related Art
Electro-optical readers, such as bar code symbol readers, are now quite common. Typically, a bar code symbol comprises one or more rows of light and dark regions, typically in the form of rectangles. The widths of the dark regions, i.e., the bars, and/or the widths of the light regions, i.e., the spaces, between the bars indicate encoded information to be read.
A bar code symbol reader illuminates the symbol and senses light reflected from the coded regions to detect the widths and spacings of the coded regions and derive the encoded information. Bar code reading type data input systems improve the efficiency and accuracy of data input for a wide variety of applications. The ease of data input in such systems facilitates more frequent and detailed data input, for example to provide efficient inventories, tracking of work in progress, etc. To achieve these advantages, however, users or employees must be willing to consistently use the readers. The readers therefore must be easy and convenient to operate.
A variety of scanning systems are known. One particularly advantageous type of reader is an optical scanner which scans a beam of light, such as a laser beam, across the symbols. Laser scanner systems and components of the type exemplified by U.S. Pat. Nos. 4,387,297 and 4,760,248 —which are owned by the assignee of the instant invention and are incorporated by reference herein—have generally been designed to read indicia having parts of different light reflectivity, i.e., bar code symbols, particularly of the Universal Product Code (UPC) type, at a certain working range or reading distance from a hand-held or stationary scanner.
FIG. 1
a
illustrates an example of a prior art bar code symbol reader
10
implemented as a gun shaped device, having a pistol-grip type of handle
53
. A lightweight plastic housing
55
contains a light source
46
, a detector
58
, optics
57
, signal processing circuitry
63
, a programmed microprocessor
40
, and a power source or battery
62
. A light-transmissive window
56
at the front end of the housing
55
allows an outgoing light beam
51
to exit and an incoming reflected light
52
to enter. A user aims the reader at a bar code symbol
70
from a position in which the reader
10
is spaced from the symbol, i.e. not touching the symbol or moving across the symbol.
As further depicted in
FIG. 1
a,
the optics may include a suitable lens
57
(or multiple lens system) to focus the scanned beam into a scanning spot at an appropriate reference plane. The light source
46
, such as a semiconductor laser diode, introduces a light beam into an optical axis of the lens
57
, and the beam passes through a partially-silvered mirror
47
and other lenses or beam shaping structures as needed. The beam is reflected from an oscillating mirror
59
which is coupled to a scanning drive motor
60
energized when a trigger
54
is manually pulled. The oscillation of the mirror
59
causes the outgoing beam
51
to scan back and forth in a desired pattern.
A variety of mirror and motor configurations can be used to move the beam in a desired scanning pattern. For example, U.S. Pat. No. 4,251,798 discloses a rotating polygon having a planar mirror at each side, each mirror tracing a scan line across the symbol. U.S. Pat. Nos. 4,387,297 and 4,409,470 both employ a planar mirror which is repetitively and reciprocally driven in alternate circumferential directions about a drive shaft on which the mirror is mounted. U.S. Pat. No. 4,816,660 discloses a multi-mirror construction composed of a generally concave mirror portion and a generally planar mirror portion. The multi-mirror construction is repetitively reciprocally driven in alternative circumferential directions about a drive shaft on which the multi-mirror construction is mounted.
The light
52
reflected back by the symbol
70
passes back through the window
56
for transmission to the detector
58
. In the exemplary reader shown in
FIG. 1
a,
the reflected light reflects off of mirror
59
and partially-silvered mirror
47
and impinges on the light sensitive detector
58
. The detector
58
produces an analog signal proportional to the intensity of the reflected light
52
.
The signal processing circuitry includes a digitizer
63
mounted on a printed circuit board
61
. The digitizer processes the analog signal from detector
58
to produce a pulse signal where the widths and spacings between the pulses correspond to the widths of the bars and the spacings between the bars. The digitizer serves as an edge detector or wave shaper circuit, and a threshold value set by the digitizer determines what points of the analog signal represent bar edges. The pulse signal from the digitizer
63
is applied to a decoder, typically incorporated in the programmed microprocessor
40
which will also have associated program memory and random access data memory. The microprocessor decoder
40
first determines the pulse widths and spacings of the signal from the digitizer. The decoder then analyses the widths and spacings to find and decode a legitimate bar code message. This includes analysis to recognize legitimate characters and sequences, as defined by the appropriate code standard. This may also include an initial recognition of the particular standard to which the scanned symbol conforms. This recognition of the standard is typically referred to as auto discrimination.
To scan the symbol
70
, the user aims the bar code reader
10
and operates movable trigger switch
54
to activate the light source
46
, the scanning motor
60
and the signal processing circuitry. If the scanning light beam
51
is visible, the operator can see a scan pattern on the surface on which the symbol appears and adjust aiming of the reader
10
accordingly. If the light beam
51
produced by the source
46
is marginally visible, an aiming light may be included. The aiming light, if needed produces a visible-light spot which may be fixed, or scanned just like the laser beam
51
. The user employs this visible light to aim the reader at the symbol before pulling the trigger.
The reader
10
may also function as a portable data collection terminal. If so, the reader would include a keyboard
48
and a display
49
, such as described in the previously noted U.S. Pat. No. 4,409,470.
In electro-optical scanners of the type discussed above, the “scan engine” including the laser source, the optics the mirror structure, the drive to oscillate the mirror structure, the photodetector, and the associated signal processing and decoding circuitry all add size and weight to the scanner. In applications involving protracted use, a large heavy hand-held scanner can produce user fatigue. When use of the scanner produces fatigue or is in some other way inconvenient, the user is reluctant to operate the scanner. Any reluctance to consistently use the scanner defeats the data gathering purposes for which such bar code systems are intended. Also, a need exists for compact scanners to fit into small compact devices, such as notebooks or palm size computers.
Thus, an ongoing objective of bar code reader development is to miniaturize the reader as much as possible, and a need still exists to further reduce the size and weight of the scan engine and to provide a particularly convenient to use scanner. The mass of the moving components should be as low as possible to minimize the power required to produce the scanning movement.
It is also desirable to modularize the scan engine so that a particular module can be used in a variety of different scanners. A need exists, however, to develop a particularly compact, lightweight module which contains all the necessary scanner components.
Smaller size scanning components tend to operate at higher s
Barkan Edward D.
Bridgelall Raj
Dvorkis Paul
Gurevich Vladimir
Katz Joseph
Fureman Jared J.
Kirschstein et al.
Lee Michael G.
Symbol Technologies Inc.
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