Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-05-27
2003-09-02
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462130, C235S472010
Reexamination Certificate
active
06612493
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of optical scanners. More specifically, the invention relates to an optical scanner, such as a bar code scanner, which can operate in extreme thermal conditions without performance degradation due to condensation and frost.
BACKGROUND OF THE INVENTION
Electro-optical scanners, such as bar code symbol scanners, 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, when partitioned into groups, 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.
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
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
. An exit 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
, 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 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
, the reflected light reflects off a mirror
59
, passes through an optical filter
47
and impinges on the light sensitive detector
58
. The filter is typically designed to have a band-pass characteristic in order to pass the reflected (return) laser light and block the light coming from other optical sources. 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 autodiscrimination.
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 (readers) of the type discussed above, 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 can all be packaged in a “scanning module”, which in turn is placed into the scanner's, or terminal's housing.
Another type of an optical scanner is a solid state imaging (SSI) reader. The SSI reader will typically contain a solid state detector, such as a charge coupled device (CCD) or a metal-oxide semiconductor field effect transistor (MOSFET). Imaging scanners do not use a moving spot to illuminate an indicia being read, but instead flood illuminate the target, or use flood illumination from external sources, and detect the reflected light from at least a portion of the illuminated target.
Both, the scanning-type readers and the SSI-type readers have found wide acceptance in the retail, wholesale and industrial applications, such as point-of-sale, warehouse and manufacturing operations. Bar code readers are typically specified to operate in non-condensing environments. Certain applications require the reader to operate over a wide temperature range, for example from −30 to 50 degrees Celsius. In certain situations, such as when an operator must use the scanner inside and outside of a freezer, moving the scanner back and forth between hot to cold locations creates condensing environment around and inside the scanner. Condensation can
DeGiovine Carlo
Hoste Peter
Kehoe Timothy
Krichever Mark
Lert, Jr. John G.
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