Dataform reader including dual laser and imaging reading assemblies

A hand held dataform reader for reading 1D and 2D bar codes and matrix dataforms is disclosed. The dataform reader includes a dataform reader module having a laser bar code dataform reading assembly, for reading 1D bar codes, and an imaging dataform reading assembly, for reading 2D bar codes and matrix codes. The dataform reader module further includes selection and control circuitry for energizing a selected one of the reading assemblies. In operation, the laser reading assembly is energized first. If the target dataform is a 1D bar code, a decodable signal will be generated and decoding circuitry will decode the target dataform. If a decodable signal is not generated by the laser reading assembly, the selection and control circuitry turns off the laser reading assembly and energizes the imaging dataform reading assembly. If the target dataform is a 2D bar code or matrix dataform, the imaging dataform reading assembly will generate a decodable composite video signal representing the image of the dataform. If the video signal is decodable, the decoding circuitry will decode the target dataform.

FIELD OF THE INVENTION 
The present invention relates to a dataform reader and method for reading 
dataforms including bar codes and matrix codes and, more particularly, to 
a dataform reader including a laser bar code dataform reading assembly for 
reading one dimensional bar code dataforms and a high resolution imaging 
dataform reading assembly for reading two dimensional bar code and matrix 
code dataforms. 
BACKGROUND OF DATAFORM READER 
Present portable data collection terminals having integrated laser bar code 
dataform scanners or one dimensional (1D) charge coupled device (CCD) bar 
code readers are not well suited for reading two dimensional (2D) bar code 
dataforms. Laser bar code scanners are non-imaging systems in that they 
operate by projecting a narrow laser beam of light which forms an 
intensely illuminated spot on a bar code dataform in a target area and one 
or more photodetectors collect the reflected illumination from the entire 
bar code. Oscillating mirrors continually redirect the laser beam so that 
the spot moves in a sweeping or a raster pattern. Generally a sweeping 
pattern refers to oscillation of the beam along the horizontal axis 
without any vertical oscillation. A raster pattern refers to a rapid 
oscillation along the horizontal axis and a slower oscillation along the 
vertical axis so that raster pattern appears to be a sweeping pattern 
moving up and down. A photodetector collects illumination from the entire 
target area. When the moving or flying spot is incident on a highly 
reflective portion of the target bar code, such as a white background, 
light reflected from the spot is incident on the photosensor. When the 
flying spot is incident on a less reflective portion of the bar code, such 
as a black bar, less light is reflected towards the photodetector or 
photodetectors. 
A laser scanner does not have an internal synchronization mechanism. The 
laser scanner calculates the laser spot's relative horizontal position 
based on known self-synchronizing patterns in the 1D bar code. This can be 
referred to as a code self-synchronized system. A raster pattern laser 
scanner can read a 2D stacked bar code such as PDF-417 because PDF-417 has 
particular row indicator patterns which are recognizable and used by the 
scanner for vertical synchronization. A typical laser scanner has very 
little rotation angle tolerance, because the scanner can not recognize a 
row indicator pattern or other code word pattern unless the spot sweeps 
across the entire pattern. 
The advantage of a laser scanner is that it can read a 1D bar code which is 
as wide as the beam sweep. However, a laser scanner can not read 2D matrix 
codes such as the Maxicode and the Datamatrix because such codes do not 
have row indicator patterns for vertical synchronization. 
In addition to laser scanners, there are 1D charge coupled device (CCD) bar 
code readers. CCD readers are imaging based systems in that the CCD reader 
operates by imaging a long and thin target area onto a one dimensional 
photodetector array rather than scanning a spot of illumination across the 
bar code symbol. If the CCD reader is positioned relative to a target 1D 
bar code so that the imaged target area falls relatively evenly across the 
bar code, the bar code can be decoded based on the run-length sequences of 
gray scale values derived from the photosensors or pixels on which each 
bar and space of the bar code is imaged. The maximum length of 1D code 
that a CCD reader can read is dependent on the number of photosensors or 
pixels in the photosensor array. Typically, each bar or space, including 
the smallest bar or space, must be imaged onto at least two pixels. 
Therefore, a linear photosensor array with 2056 pixels can be used to read 
a code up to 1028 modules wide. Similar to the laser scanner, the 1D CCD 
reader does not have vertical synchronization capability and must rely on 
row indicator patterns for vertical synchronization. 
A two dimensional (2D) CCD contact reader has been marketed by Tokyo 
Electric Company. A two dimensional CCD reader images an area onto a two 
dimensional array of photodetectors. Such a device is capable of reading 
matrix codes because the two dimensional photodetector or pixel array 
provides both horizontal and vertical synchronization. 
The problem associated with two dimensional CCD readers is that the array 
is typically only 756 pixels wide. This pixel count limits the maximum 
width of 1D codes that can be read. Therefore, there is a need to have a 
non-contact 2D imaging based dataform reader which is capable of reading 
2D stacked bar codes and matrix codes. Furthermore, the reader should have 
a non-imaging based system for reading wide 1D bar codes. 
SUMMARY OF THE INVENTION 
In accordance with this invention, a portable dataform reader module is 
provided that includes a non-imaging laser bar code dataform reading 
assembly for reading 1D bar code dataforms and an imaging dataform reading 
assembly for reading 2D bar code and matrix code dataforms. 
In a first embodiment of the reader module, the imaging dataform reading 
assembly includes a camera assembly including a two dimensional 
photosensor array positioned to view a dataform positioned in a target 
area. An optic element is positioned to the front of the photosensor array 
for focusing an image of the target dataform onto the photosensor array. A 
housing supports the optic element and shrouds ambient illumination from 
the photosensor array. The camera assembly is secured to a base printed 
circuit board of the dataform reader. Further, the camera assembly may 
include an array of LED illuminators for uniformly illuminating the target 
area. 
The laser dataform reading assembly includes a laser positioned adjacent to 
the camera assembly which, when energized, projects a laser beam toward 
the target dataform. The laser is secured to a platform which is mounted 
to the base member with four flexures which enable the platform and laser 
to rock in an oscillating motion. An electromagnetic assembly is employed 
to drive the laser in an oscillating motion causing the projected laser 
beam to sweep across the target area. A photodetector is secured to the 
oscillating platform for detecting the varying intensity of the reflected 
laser illumination. 
In operation, a dataform reading session commences with energization of the 
laser dataform reading assembly to detect the high contrast transitions of 
a dataform and decode 1D dataforms if present. If high contrast 
transitions are present, but a 1D dataform is not decodable, then the 
laser reading assembly is shut down and an image of the target area is 
captured by the camera assembly for decoding. 
In a second embodiment of the reader module of the present invention, the 
laser dataform reading assembly includes a fixed mounted laser source and 
an oscillating mirror for sweeping the beam across a dataform in a target 
area. One or more photodetectors are positioned to receive reflected 
illumination from the entire target area or positioned to receive 
reflected illumination from the oscillating mirror (retro-reflective). 
In a third embodiment of the reader module of the present invention, the 
laser dataform reading assembly does not include a photodetector. Instead, 
the two dimensional photosensor array associated with the imaging dataform 
reading assembly is used to detect the varying intensity of reflected 
laser illumination. A housing of the camera assembly includes a member 
which is pivotable between two positions. In a first position, the member 
permits the photosensor array to receive an image of the target area 
thereby permitting dataform reading utilizing the imaging dataform reading 
assembly. In a second position, the member permits the photosensor array 
to receive reflected illumination from the target area resulting from the 
laser beam oscillating across the target dataform. 
The photosensor array preferably comprises an array of photodiodes and read 
out circuitry such that each photodiode can be read out independently and 
in a random order, or groups of photodiodes can be read out 
simultaneously, thereby generating a signal representative of the average 
illumination on the photosensor array. 
The aforementioned and other aspects of the present invention are describe 
in more detail in the detailed description and accompanying drawings which 
follow.

DETAILED DESCRIPTION 
A dataform reader module in accordance with the present invention is shown 
generally as 10 in FIG. 1. The reader module includes an dataform capture 
assembly 12 and a control and decoder board 14. 
The dataform capture assembly 12 includes a laser bar code dataform reading 
assembly 15a for reading one dimensional (1D) bar code dataforms and an 
imaging dataform reading assembly 15b for reading two dimensional (2D) bar 
codes and matrix codes. The dataform capture assembly 12 is disposed on 
three spaced apart printed circuit boards 16a, 16b and 16c (corresponding 
to first, second and third printed circuit boards). The laser reading 
assembly 15a includes an oscillating laser assembly 24 secured to the 
second printed circuit board 16b. The second printed circuit board 16b is 
larger than the first printed circuit board 16a and spaced apart from the 
first circuit board so that operation of the laser bar code reading 
assembly 15a does not interfere with operation of the circuitry on the 
first printed circuit board 14a. 
The oscillating laser assembly 24 includes an oscillating platform 26 which 
is secured to the second printed circuit board 16b with four flexures 28. 
Each flexure 28 is made of a thin flexible material such as MYLAR.TM.. 
Supported by the flexures 28, the oscillating platform 26 rocks back and 
forth with respect to the circuit board 16b. The laser reading assembly 
15a also includes a pair of electromagnets 30 secured to circuit board 
16b. A permanent magnet 32 is secured to the backside of the oscillating 
platform 26. During a portion of a dataform reading session in which the 
laser reading assembly 15a is operational, the electromagnets are 
alternately energized causing the platform 26 to rock back and forth. A 
laser diode assembly 34 is secured to the oscillating platform 26 and when 
energized, generates a laser beam directed into a target area to the front 
of the reader module 10 to read a dataform 36 affixed to an object. A 
target bar code dataform is shown in dashed lines in FIG. 1. 
The laser beam sweeps back and forth across the target dataform 36 as the 
oscillating platform 26 rocks back and forth. Two unfocused photodetectors 
40 are supported on the oscillating platform 26 for collecting reflected 
illumination from the target area generally in the same direction in which 
the laser is instantaneously directed while the platform 26 is rocking. 
Preferably, the photodetectors 40 may be positioned behind holographic 
illumination collectors 42 which increase the quantity of illumination 
incident on the photodetectors 40. An oscillating platform laser 
illumination and collection system in accordance with this invention is 
described in more detail in U.S. Pat. Nos. 5,115,120 and 5,422,472, both 
of which are assigned to PSC, Inc. of Webster, N.Y. U.S. Pat. Nos. 
5,115,120 and 5,422,472 are incorporated herein in their entireties by 
reference. 
The imaging reading assembly 15b is supported by the first printed circuit 
board 16a and includes a two-dimensional photosensor array 44 positioned 
to receive reflected illumination from the dataform 36 in the target area. 
An optic assembly 46 is positioned between the photosensor array 44 and 
the target dataform 46 to focus an image of the target dataform on the 
photosensor array. A camera housing 22 is secured to the first printed 
circuit board 16a overlying the photosensor array 44. The camera housing 
48 supports the optic assembly 46 and shrouds the photosensor array 44 
from ambient illumination. 
The three printed circuit boards 16a, 16b, and 16c include output signal 
generating circuitry 50 (FIG. 8) for generating decodable output signal 
transmitted along a conduction path 51. The decodable output signal is 
representative of the target dataform in the target area and is decodable 
by decoding circuitry 52 mounted on the control and decoder board 14 
(FIGS. 1 and 8). 
Referring to FIG. 8, when the laser reading assembly 15a is operational, 
the photodetectors 40 generate a raw voltage signal 53 wherein the 
instantaneous voltage magnitude represents the accumulated illumination 
incident on the photodetectors 40 for a brief exposure period. During the 
laser beam sweep across the target bar code dataform 36, the quantity of 
reflected illumination will vary as the laser beam passes across highly 
reflected spaces and less reflective bands of the dataform. Therefore, the 
voltage signal from the photodetectors 40 will vary in magnitude 
exhibiting peaks and troughs which correspond to the varying widths of the 
bars and spaces of the target bar code dataform 36. Signal processing 
circuitry 54, well known in the art of laser bar code scanners, is 
provided to convert the raw voltage signal 53 to an industry standard 
square wave signal 55 and generates industry standard synchronization 
signals including the start of scan (SOS) signal indicating when the 
oscillating laser diode assembly 34 is at its extreme of travel. 
The photosensor array 44 is an interlaced charge coupled device (CCD). When 
operational, the photosensor array 44 generates a raw video signal 56 
wherein the instantaneous voltage magnitude during a readout period 
represents the quantity of illumination accumulated on an individual 
photosensor element or pixel of the photosensor array 44 during an 
exposure period. The order in which the pixels are read out is interlaced. 
The three printed circuit boards 16a, 16b and 16c include image control 
circuitry 57 for controlling the exposure period for the photosensor array 
44, generating clock signals to drive the read out of the photosensor 
array 44, amplifying the raw video signal and generating industry standard 
synchronization signals and black level signals necessary to generate an 
industry standard composite video signal 58. 
The square wave signal 55 generated by operation of the laser bar code 
reading assembly 15a and the composite video signal 58 generated by 
operation of the imaging bar code dataform reading assembly 15b are 
transferred to the control and decoder board 14 through the conductor path 
51. A single conductor path 50 may be used for transferring both signals 
55, 58 because, as will be discussed later, the laser reading assembly 15a 
and the imaging reading assembly 15b do not operate simultaneously during 
a dataform reading session. 
The control and decoder board 14 includes the decoding circuitry 52 
comprising 1D bar code dataform decoder circuitry 59 for decoding the 
square wave signal 55, signal processing circuitry 60 and 2D decoder 
circuitry 61 for decoding a dataform represented by the composite video 
signal 55, exposure parameter control circuitry 62 for determining the 
appropriate exposure period, gain and reference voltages for operating the 
imaging reading assembly 15b. The control and decoder board further 
includes selection circuitry 63 for selecting operation of the laser bar 
code dataform reading assembly 15a and the imaging dataform reading 
assembly 15b. Each of these circuits may be embodied in whole or in part 
in code executed by a microprocessor 62 (FIG. 1). 
The signal processing circuitry 60 and 2D decoder circuitry 61 include an 
analog to digital converter for transforming the composite video signal 58 
into a series of gray scale values representative of the quantity 
illumination incident on each pixel during the exposure period and a 
memory for storing the gray scale values. The signal processing circuitry 
60 also includes circuitry for selectively accessing gray scale values 
from memory 64 (FIGS. 1 and 8), detecting transition points between dark 
and light areas of the dataform represented in the memory 64 and decoding 
the dataform. A more complete description of appropriate signal processing 
and 2D decoder circuitry can be found in U.S. patent application Ser. No. 
08/438,889, filed May 10, 1995, entitled "Oblique Access to Image Data for 
Reading Dataforms", Ser. No. 08/456,113, filed May 31, 1995, entitled 
"Maxicode Data Extraction Using Spatial Domain Features", Ser. No. 
08/543,122, filed Oct. 13, 1995, entitled "Sub Pixel Dataform Reader With 
Dynamic Noise Margins", all of which are assigned to the same assignee as 
the assignee of the present application. Application Ser. Nos. 08/438,889, 
08/456,113, and 08/543,122 are all incorporated herein in their entireties 
by reference. 
The exposure parameter control circuitry 62 includes fuzzy logic control 
circuitry 65 for analyzing the composite video signal 58 and determining 
an appropriate exposure period and gain setting for operating the imaging 
based reader system and an appropriate set of reference voltages for 
operating the analog to digital converter of the signal processing 
circuitry 60 and the 2D decoder circuitry 61. The control and decoder 
board 14 outputs control signals 65a to the image capture assembly 12. A 
more complete description of the fuzzy logic control circuitry 65 is 
disclosed in patent application Ser. No. 08/544,618, filed Oct. 18, 1995 
and entitled "Extended Working Range Dataform Reader Including Fuzzy Logic 
Image Control Circuitry", which is incorporated in its entirety herein by 
reference. 
FIG. 2 is a flow chart illustrating operation of the reader module 10 in 
accordance with this invention. A dataform reading session is initiated or 
started at step 66. Starting a reading session causes the laser reading 
assembly 15a to be energized in an attempt to read a 1D bar code dataform 
(step 67). The laser reading assembly 15a begins generating the square 
wave signal 55 representing the time varying laser illumination reflected 
from the dataform 36 in target area. At step 68, the control and decoder 
board 14 determines if the square wave signal 55 is decodable. If the 
square wave signal 55 is determined to decodable, the signal is decoded 
and the decoded data is output (step 70). If the square wave signal 55 is 
undecodable, the control and decoder board 14 at step 72 determines 
whether the square wave signal 55 is consistent with the high contrast 
transitions between the bars and spaces of a dataform in the target area. 
If the control and decoder board 14 determines that the square wave signal 
55 does not indicate the presence of a dataform, decode session is 
terminated (step 74). 
During the aforementioned operation, the imaging reading assembly 15b is 
turned of to conserve power. If, the control and decoder board 14 
determines that the square wave 55 indicates the presence of a dataform in 
the target area, albeit an undecodable one, the laser reading assembly 15a 
is turned off and the image reading assembly 15b is energized to capture 
of an image of the target area (step 76). At step 78, the control and 
decoder board 14 attempts to decode the captured image. If decoding is 
successful, decoded data is output at 80. If unsuccessful, the reader 
module 10 returns to step 64 wherein the laser reading assembly 15a is 
again turned on. The purpose of returning to an energized laser reading 
assembly state is that the intensity of the laser illumination is easy for 
an operator to see and thus assists the operator in aiming the reading 
module 10. If after a predetermined period, a dataform is not successfully 
decoded, the reader module 10 will time out and turn off. 
FIG. 3 illustrates an alternative embodiment of the reader module 10' of 
the present invention. While the control and decoder board 14 (not shown) 
is unchanged from the description in the first embodiment, the image 
capture assembly is modified. The modified image capture assembly 12' 
includes a laser bar code dataform reading assembly 15a' which is mounted 
on a printed circuit board 16b'. The board 16b' is intermediate two 
circuit boards 16a' and 16c. The imaging dataform reading assembly 15b is 
mounted on the first board 16a' and is unchanged from the first 
embodiment. The laser reading assembly 15a' includes a laser 90 secured to 
the second printed circuit board 16b'. When energized, the laser 90 
directs a laser beam along a path 100 generally parallel to the circuit 
board 16b'. An oscillating mirror 92 is positioned in the laser path 100 
and redirects the laser beam towards a dataform (not shown) in a target 
area. The oscillating mirror 92 is secured to the second printed circuit 
board 16b' by a MYLAR.TM. flexure 94 (only a portion of which can be seen 
in FIG. 3). An electromagnet 96, secured to printed circuit board 16b, 
co-acts, when energized, with a magnet (not shown) secured to a back of 
the oscillating mirror 92 causing the mirror to oscillate. A more complete 
disclosure of such a laser bar code dataform reading assembly 15a' is 
found in U.S. Pat. No. 5,367,151 assigned to Symbol Technologies Inc., of 
Bohemia, N.Y. U.S. Pat. No. 5,367,151 is incorporated herein in its 
entirety by reference. As an alternative to securing each element of the 
laser reading assembly 15a' to circuit board 16b', an integrated modular 
laser scan engine such as the Model SE-1000 available from Symbol 
Technologies of Bohemia, N.Y. may be secured to the circuit board 16a'. 
FIGS. 4A and 4B illustrate cross-sectional views of yet another embodiment 
of the reader module 10" of the present invention. Similar to the first 
embodiment, an oscillating platform 26" is secured to a second printed 
circuit board 16b" with four flexures 28". Electromagnets 30" secured to 
printed circuit board 16b". When energized, the electromagnets 30" co-act 
with a permanent magnet 32" causing the oscillating platform 26" to rock 
back and forth. A laser 34" is secured to the oscillating platform 26" and 
directs a laser beam towards a dataform (not shown) in a target area. 
A two-dimensional photosensor array 44" is secured to a printed circuit 
board 16a" and receives reflected illumination from the target area 
through an optic assembly 46". A camera housing 48" supports the optic 
assembly 46" and shrouds ambient illumination from photosensor array 44". 
The housing 48" includes a door portion 102 which swings about a hinge 108 
into a closed position (shown in FIG. 4A) and an open position (shown in 
FIG. 4B). When in the closed position (FIG. 4A), the door 102 blocks 
ambient illumination from the photosensor array 44" and only illumination 
from the target area focused through optic assembly 46" is incident on the 
photosensor array. 
A top surface 110 of the door 102 includes a reflective coating. When the 
door 102 is in the open position (FIG. 4B), illumination focused through 
the optic assembly 46" is blocked and only unfocused illumination from the 
target area is incident onto the photosensor array 18. Illumination from 
the target area is generally incident on a reflective surface 112 which is 
secured to the oscillating platform 26". The reflective surface 112 
redirects the illumination downward to the reflective surface 110 on the 
top of the door, which redirects the illumination onto photosensor array 
44". 
In operation, the door 102 is in the open position (FIG. 4B) when the laser 
reading assembly 15a" is operating such that the unfocused illumination 
represents the varying intensity of laser illumination reflected from the 
bars and spaces of a bar code dataform in the target area as the laser 
beam traverses across the dataform. The door 102 is in the closed position 
(FIG. 4A) when the imaging reading assembly 15b" is in operation such that 
a read out of individual pixels of the photosensor array 44" represents 
the image of a dataform in the target area. 
Because the reader module 10" utilizes the photosensor array 44" for both 
the imaging reading assembly 15b" and the laser reading assembly 15a", the 
photosensor array 44" operates in a selected one of two modes. In one mode 
all the pixels can be read out simultaneously such that the signal 
represents average illumination incident on the entire array. In the other 
mode, the pixels can be read out individually. This mode is used in 
connection with capturing an image of the target area. FIG. 5 represents a 
block diagram of read out circuitry 115 associated with the photo sensor 
array 44" in accordance with this invention. 
The photosensor array 44" includes a plurality of sensor elements such as 
photodiodes 120 arranged in rows and columns. A row control shift register 
140 which is coupled to a set of horizontal or row conductors 142a-142h 
through a corresponding set of flip flops 144a-144h. Each horizontal 
conductor 142a-142h connects each photodiode 120 in a given row. The 
photodiodes 120 in a column are connected to a common column conductor 
146a-146g. The column conductors 146a-146g can be selectively connected to 
a reference potential through corresponding ground switches 148a-148g or 
selectively connected to corresponding sample and hold amplifier 150a-150g 
through output switch 152a-152g. An output shift register 154 controls 
connecting of each sample and hold amplifier 150a-150g to a common output 
port 156 through a series of switches 158a-158g controlled by flip flops 
160a-160g. 
The row conductors 142a-142h control connection of each photodiode 120 in a 
particular row to its respective column conductor 146a-146g. The column 
conductors 146a-146h may be selectively connected to a reference potential 
to "dump" any accumulated charge on the photodiode so that a controlled 
exposure period may be started or may be selectively connected to the 
column's corresponding sample and hold amplifier 150a-150g to read out an 
accumulated charge after a controlled exposure period. It should be 
appreciated that each photodiode 120 may be read out individually. 
Alternately, by simultaneously connecting each photodiode in the array 44" 
to its respective column conductor 146a-146g and simultaneously connecting 
each column conductor 146a-146g to its respective sample and hold 
amplifier 150a-150g and then closing all read out switches 158a-158g 
simultaneously, the entire array 44" can be read out as if it were a 
single photodetector. Repetitive read out of all pixels (photodiodes) 120 
simultaneously can be used to generate a square wave signal emulating that 
of a single photodetector typically used with laser scanners (single 
detector emulation mode). 
A more detailed description of such a photosensor array is disclosed in 
U.S. Pat. No. 5,262,861 which is assigned to Rutgers University. U.S. Pat. 
No. 5,262,861 is incorporated herein in its entirety by reference. 
FIGS. 6 and 7 illustrate a portable data collection system 400 in 
accordance with this invention. The system 400 may utilize either of the 
three reader module embodiments 10, 10', 10" previously discussed. The 
portable data collection system 400 comprises a housing 410 which is 
generally a gun shaped. The housing 410 includes an upper portion 412, 
forming an upper enclosure, and a handle portion 414 extending below the 
upper portion 412. The housing 410 is constructed of a suitable impact 
resistant plastic that provides both durability and is lightweight. A 
two-position trigger switch 416 is appropriately mounted and used to 
provide a signal to initiate a dataform reading session. A plurality of 
key switches 422 and a display screen 432 with an overlaying touch panel 
444 are visible through an aperture in the upper portion 412 facing the 
operator. 
As can best be seen in FIG. 7, the portable data collection system 400 
includes a reader module 10 comprising an image capture assembly 12 
including a laser bar code dataform reading assembly 15a and an imaging 
dataform reading assembly 15b. The reading assemblies 15a, 15b are 
supported on printed circuit boards 16b and 16a respectively. The image 
capture assembly 12 further includes a control and decoder board 14 which 
is electrically coupled to the reading assembly 15a, 15b. The imaging 
dataform reading assembly 15b is positioned inside of the housing 410 and 
a portion of the camera housing 48 extends through an aperture 417 in a 
front portion 418 of the housing 410 and an aligned aperture in an 
illumination module 428. The illumination module 428 comprises a set of 
illumination light emitting diodes (LEDs) and a pair of targeting or 
aiming LEDs. The illumination module 428 is energized in conjunction with 
operating the imaging dataform reading assembly 15b to provide sufficient 
illumination to permit the imaging dataform reading assembly to capture a 
decodable image in the reader module's target area. Details of a suitable 
illumination module are disclosed in application Ser. No. 08/484,435, 
filed Jun. 26, 1995, entitled "Extended Working Range Dataform Reader". 
Ser. No. 08/484,435 is assigned to the assignee of the present application 
and is incorporated herein in its entirety by reference. The laser bar 
code dataform reading assembly 15a is mounted on the board 16b. The laser 
beam exits through a transparent member or window 429 overlying a second 
aperture in the housing front portion 418. The window 429 may be moved at 
the Bragg angle to avoid internal reflection 
The illumination module 428 is mounted to the housing front portion 418. A 
seal (not shown) may be placed around a nose of the camera housing 48 to 
create a tight seal between the camera housing and the system housing 410 
to prevent dirt and moisture from entering the interior of the system 
housing through the aperture 417. 
In the preferred embodiment, the control and decoder board 14 is coupled to 
a main control board 431 which includes a microprocessor 413 for further 
processing the data transferred from the control and decoder board to the 
main control board via a data transfer link. 
The main control board 431 includes a serial output port coupled to a 
connector (not shown) on the housing 410 operative to transfer the decoded 
data or image data to a remote terminal through a cable connection (not 
shown). The connector may be a traditional pin connector to which a mating 
connector is secured. Alternatively, the connector may comprise conductive 
contact surfaces 460 on the exterior of the housing 410 which align with 
mating contact surfaces when the device is placed in a docking station 
(not shown). 
Because the data collection system 400 is intended for portable use, a 
wired connection to a host computer is impractical in many situations. 
Therefore, the portable data collection system 400 includes a spread 
spectrum micro radio mounted on a board 433 (FIGS. 11 and 13) providing a 
wireless link between the main control board 431 and a remote host 
computer (not shown). An external antenna 446 operates to improve radio 
communication reception. The spread spectrum radio board 433 includes 
digital and analog circuitry for transmitting and receiving data in a 
wireless network such as an IEEE 802.11 compatible direct sequence spread 
spectrum or frequency hopping spread spectrum network. 
Power is supplied to the circuitry of the system 400 by a power cell 448. 
The spread spectrum radio and the dataform reader module both draw 
significant current from the power cell 448. Therefore, the radio should 
not operate during a dataform reading session and a dataform reading 
session should not start during communication to limit peak current draw. 
Therefore, the radio circuitry and the reader module provide blocking 
signals to each other to assure that both components doe not draw power 
simultaneously. The blocking signal from the radio to the reader module 
will prevent the initiation of a reading session. The session will be 
delayed until the signal desists. The blocking signal from the reader 
module to the radio will prevent the radio from sending or receiving data 
packets. Therefore, the network transmission protocol must be such that 
the radio in the portable dataform reader has complete control over when 
to transmit a packet and when it can receive a data packet. One such 
network protocol is the reverse poll protocol as described in U.S. Pat. 
No. 5,276,680 and assigned to Telesystems S/W Inc. U.S. Pat. No. 5,276,680 
is hereby incorporated in its entirety by reference. 
In the reverse poll protocol network, the portable device radio may 
transmit data packets to a network access point at any time, subject to 
the carrier frequency being free. However, the access point can only send 
a packet to the portable device within a time window following receipt of 
a packet from the portable device. To assure that the access point has 
enough opportunities to transmit data to the portable device, the portable 
device will periodically send packets even though the packets contain no 
significant data. 
While the spread spectrum radio is effective for transmitting the decoded 
contents of a dataform, the radio's limited bandwidth makes it impractical 
for transmitting an entire uncompressed image. An image compression 
algorithm useful to reduce the size of a digital image file is the 2D 
wavelet transform as described in "A 64 kb/s Video Code Using the 2-D 
Wavelet Transform" by A. S. Lewis and G. Knowles, published in IEEE 
Computer Society Press, Order Number 2202. For example, the HARC wavelet 
transform system, available from Houston Advance Research Center in 
Houston, Texas, can be used to compress the photographic image before it 
is transmitted with an image compression ratio of up to 400:1. 
While the description has described the currently preferred embodiments of 
the invention, those skilled in the art will recognize that other 
modifications may be made without departing from the invention and it is 
intended to claim all modifications and variations as fall within the 
scope of the invention. 
In compliance with the statute, the invention has been described in 
language more or less specific as to structural and methodical features. 
It is to be understood, however, that the invention is not limited to the 
specific features shown and described, since the means herein disclose 
comprise preferred forms of putting the invention into effect. The 
invention is, therefore, claimed in any of its forms or modifications 
within the proper scope of the appended claims appropriately interpreted 
in accordance with the doctrine of equivalents.