System and method of optical reading employing virtual scan lines

Optical reading system and methods having multiple modes of operation, for example: omnidirectional and single-code picking; fixed and handheld reading; 1D and 2D code reading. In one configuration, an image-based system obtains input data via an area sensor (e.g., a 2D COD array) with only data corresponding to a pattern of virtual scan lines being stored and processed. A user may implement different operating modes such as a first mode reading codes in any location or orientation and a second mode reading only a code oriented along a particular virtual scan line or group thereof. Alternately, the data reader is operable to switch between handheld mode selecting a first pattern of virtual scan lines to process and/or decode and a fixed mode selecting a second pattern of virtual scan lines to process and/or decode. Virtual scan patterns in either mode can change from frame to frame.

BACKGROUND

The field of the present invention relates to data capture devices, such as scanners and other optical code and object reading devices. In certain embodiments, optical readers and methods of reading are described herein which employ virtual scan lines.

A barcode label comprises a series of parallel dark bars of varying widths with intervening light spaces, also of varying widths. The information encoded in the barcode is represented by the specific sequence of bar and space widths, the precise nature of this representation depending on which particular barcode symbology is in use. Typical methods for reading barcodes comprise generation of an electronic signal wherein a signal voltage alternates between two preset voltage levels, one representing a dark bar and the other representing a light space. The temporal widths of these alternating pulses of high and low voltage levels correspond to the spatial widths of the bars and spaces. It is this temporal sequence of alternating voltage pulses of varying widths which is presented to an electronic decoding apparatus for decoding.

In one method of reading, referred to as a “scanning,” an illumination beam is moved (i.e., scanned) across the barcode while a photodetector monitors the reflected or backscattered light. For example, the photodetector may generate a high voltage when a large amount of light scattered from the barcode impinges on the detector, as from a light space, and likewise may produce a low voltage when a small amount of light scattered from the barcode impinges on the photodetector, as from a dark bar. The illumination source in spot scanners is a typically a laser, but may comprise a coherent light source (such as a laser or laser diode) or non-coherent light source (such as light emitting diode). A laser illumination source may offer advantages of higher intensity illumination which may allow barcodes to be read over a larger range of distances from the barcode scanner (large depth of field) and under a wider range of background illumination conditions.

Another method of reading is referred to as the “imaging” method whereby light reflecting off a surface is detected by an array (commonly a charge-coupled device or CCD) of optical detectors. The scan surface is typically illuminated by some uniform light source, such as a light-emitting diode (LED). Alternately, the illumination may be provided by ambient light such as disclosed in U.S. Pat. No. 5,814,803 hereby incorporated by reference. In such an imaging technique, as with a scanning laser, an electrical signal is generated having an amplitude determined by the intensity of the collected light. In either the scanning laser or CCD technique, the amplitude of the electrical signal has one level for dark bars and a second level for light spaces. As the label is scanned, positive-going and negative-going transitions in the electrical signal occur, signifying transitions between bars and spaces. Techniques are known for detecting edges of bars and spaces by detecting the transitions of the electrical signal. Techniques are also known for determining the widths of bars and spaces based on the relative location of the detected edges and decoding the information represented by the bar code.

An imaging system may comprise a linear (one-dimensional) array or may comprise a two-dimensional array of CCD elements to obtain an entire image of the optical code at one time. However, the drawback of these two-dimensional devices is that large amounts of memory are needed to store the image to be processed, and large amounts of computation are needed to extract the edge location data from the stored image. Further, complicated algorithms are necessary to determine the orientation and characteristics of the bar code label. One method of overcoming certain of these drawbacks is described in U.S. Pat. No. 6,142,376, hereby incorporated by reference, which discloses a method for reading encoded symbols such as bar code labels by making efficient use of area scanned input. Input data is provided by an area sensor such as a two dimensional CCD array or a video tube, or a single line sensor (such as a single line CCD or a single line laser scanner) combined with either movement of the item or an additional transverse scanning mechanism providing the second axis of the raster scan. Not all of the scanning data, but only a select portion of the data corresponding to virtual scan lines is stored and processed. A pattern of virtual scan lines is defined based on the dimensions of bar code labels to be scanned, the size of the scanning area, and the characteristics of the scanning sensor and optics. The virtual scan lines are mapped onto the raster pattern, allowing the pixels of the raster which fall on the virtual scan lines to be identified. As the raster scan proceeds, information regarding the intensity of the detected light is stored only for the pixels comprising the virtual scan lines. The amount of data stored is a fraction of the total data in the raster. After the pixel values have been stored for a virtual scan line, the edges of the bars and spaces crossed by the line is determined by a suitable method such as analog or digital processing.

Generally, there are typically two types of scanners: handheld or fixed. In a fixed scanner, there are two modes of operation: “sweep” mode and “presentation” mode. In sweep mode, bar coded items are moved through a scan volume in front of the scanner, the scanner typically taking advantage of the movement of the item to enhance potential read coverage. In presentation mode, the item may be held by the operator in front of the scanner, the scanner preferably producing a sufficiently omnidirectional scan pattern to read the bar code in any orientation.

In a handheld scanner, an operator holds the scanner and manually aims a scan pattern at a bar code. Handheld single line scanners, whether imaging or flying spot laser, require that an operator aim and orient the scanner relative to the bar code so that the scan line is substantially perpendicular to the bar code edges. Such operation requires some care on the part of the operator and reduces productivity. Furthermore, these devices are sensitive to label defects, as detection of bar and space edges is typically done along a single narrow scan line. To maximize the productivity of the operator and minimize stresses due to repetitive motions of the operator's body, and to minimize sensitivity to label defects, it is generally desirable to read bar codes which may be at any orientation relative to the scanning device.

In the fixed mode of operation, a relatively wide angular field of view is required so that a barcode label can be read from the largest possible fraction of the surface of the barcoded object. Since objects are often passed through the scan volume in random orientations, a multi-dimensional pattern is necessary to efficiently read the barcode. In addition, a high scan rate is desirable to allow successful reading of barcodes which are quickly passed through the scan volume.

A simpler scan pattern or a single scan line is often sufficient for portable operation, since the relatively small portable barcode scanner can be rotated to orient the scan line correctly across the barcode. A relatively small angular field of view and a relatively longer depth of field are desirable in this mode of operation. The longer depth of field may also allow the operator to read the barcode from a greater (or closer) distance. The reduced angular field of view reduces the likelihood of inadvertent scanning of other barcode labels, but in turn leads to tighter aiming requirements. To facilitate proper orientation of the scan line relative to the barcode and aiming of the scanner, the scan line may be made sufficiently intense to be seen by the operator. Alternatively, a portable barcode scanner may be provided with pointer illuminators to facilitate aiming of the barcode scanner.

There are also hybrid scanners designed to operate both in fixed and handheld modes of operation. U.S. Pat. No. 6,575,368, hereby incorporated by reference, discloses a dual mode laser scanner that is switchable between a handheld mode generating a single scan line and a fixed mode generating a multiple scan line omnidirectional scan pattern. In one embodiment, the '368 patent discloses generating both sets of scan patterns, but only decoding the single scan line during handheld mode of operation.

The present inventor has recognized there is still a need for versatile and effective data readers of different configurations.

SUMMARY

The present invention is directed to optical reading systems. In a preferred embodiment, the system has multiple modes of operation, for example: (1) omnidirectional and single-code picking; (2) fixed and handheld reading; (3) 1D and 2D code reading. In a preferred configuration, the reading system is an image-based system wherein the input data may be provided by an area sensor such as a two dimensional CCD array, CMOS or a video tube, or other suitable mechanism. Preferably only a select portion of the data corresponding to virtual scan lines is stored and processed. The image is typically read out in a predefined pattern, such as a raster pattern, due to the limitations of the imaging device. A complete raster pattern from the top to the bottom of the image is termed a frame. As the raster scan proceeds, information regarding the intensity of the detected light is stored only for the pixels comprising the virtual scan lines. The amount of data stored is a fraction of the total data in the raster.

In certain embodiments the system may permit complex patterns of scan lines to be read and processed by a simple, compact sensing device. The system may permit the user to implement different operating modes such as a first mode of reading optical codes in any location or orientation and a second mode of reading only an optical code oriented along a particular virtual scan line or group of lines, for example lines intersecting an aiming pattern or a band of parallel virtual scan lines.

In another embodiment, the virtual scan pattern changes from frame to frame. The pattern may begin with an omnidirectional pattern and then change to a different omnidirectional pattern to provide more dense coverage. Such dense coverage may be useful, for example, to read highly truncated labels.

In another embodiment, the virtual scan pattern changes from frame to frame. The pattern may begin with an omnidirectional pattern and then change to a directional pattern, such as a set of parallel lines, as the system recognizes portions of a barcode to be read. This enables higher performance with a lower processing burden, as more of the virtual scan lines become oriented in the direction of the barcode.

In another embodiment, the data reader comprises a portable unit enabled to be operated in a handheld mode. Preferably, the portable unit has multiple operating modes. For example, the data reader may be operable to switch between operating in a handheld mode selecting a first pattern of virtual scan lines to process and/or decode and a fixed mode selecting a second pattern of virtual scan lines to process and/or decode.

The foregoing and other objects, features, and advantages will become apparent from the following more detailed description set forth in conjunction with the accompanying drawings. It is intended that each of these disclosed embodiments may be implemented individually or in combination with other of the embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments will now be described with reference to the drawings. Certain preferred embodiments may be described with respect to barcodes (1D and 2D codes), but the disclosure should be understood as applicable to various types of optical codes (e.g. MaxiCode and PDF417) as well as other recognition elements such as fingerprints.

FIG. 1is a block diagram of a scanning system1according to a preferred embodiment, wherein the system1may be divided at an abstract level into an image acquisition block2, a virtual scan line generator block4, and an edge detection and decode block6. Referring toFIG. 2, the image acquisition block2comprises a light source10illuminating a optical label11and an imaging sensor12comprised of optics (not shown) detecting the reflected and/or refracted light from the optical label11. The imaging sensor12has a planar imaging region13and may be, for example, a two-dimensional CCD array. Alternatively, the planar imaging region13of the optical sensor12may be a linear CCD array that obtains a second dimension of raster input by relative motion of the optical sensor12to the optical label11. The relative motion may be created by sweeping the optical sensor12across an optical label11, or by sweeping the optical label11manually or automatically (e.g., by conveyor) across the optical sensor12. In the case of a linear CCD array, one dimension of the imaging region13is defined by the relative motion of the optical sensor12to the optical label11over some period of time. Although the imaging region13may be various shapes, a planar imaging surface is preferred. In contrast to a conventional multi-line laser scanner having a laser and mirrors, the optical sensing portion of an area scanning system may be quite small because of the relatively small size of the CCD array.

Any suitable imaging mechanism may be employed, preferably one capable of detecting a 2-D image, including CCD or CMOS. Preferably, the sensing mechanism is an image-based solid state device comprising either a single detector or an array of detectors.

In another system where a moving spot laser is scanned in a sufficiently dense pattern so as to create/approximate a 2-D sensor array output, typically a single detector may be employed. The data may be processed in several fashions. In one processing system, the data is dropped in serial fashion into a buffer array, the array is then processed by selecting the data points corresponding to the virtual scan line pattern. Alternately, as the signal is detected, the data points corresponding to the virtual scan lines may picked off as they arrive and sent directly to the processor (for decoding), thus not requiring a buffer at all. In another preferred method, the data points corresponding to the virtual scan lines are picked off as they arrive and placed into smaller virtual scan line buffers, one virtual scan line buffer corresponding to each virtual scan line. As each virtual scan line buffer is completed, that virtual scan line buffer data is sent to the processor for decoding. Since horizontal virtual scan lines are complete within a single row of the 2D array, then such a horizontal virtual scan line may be sent directly to the processor without buffering. The Bresenham line drawing algorithm is an efficient software algorithm to implement the choosing of virtual scan line pixels.

In a 2D imaging array, the image is acquired onto the sensor array, and then the pixel information from the array is stored in memory (e.g. a memory buffer) corresponding to the sensor array.FIG. 3illustrates a preferred system in which a pattern250of virtual scan lines252,254,256,258,260,262is generated within the imaging region to capture the barcode with a minimum amount of memory storage. Preferably, the pixel data from the imaging array is read out serially, and the data points corresponding to the virtual scan lines are picked off as they arrive and placed into smaller virtual scan line buffers, one virtual scan line buffer corresponding to each virtual scan line. As each virtual scan line buffer is completed, that virtual scan line buffer data is sent to the processor for decoding. Since horizontal virtual scan lines are complete within a single row of the 2D array, then such a horizontal virtual scan line (e.g., line252inFIG. 3) may be sent directly to the processor without buffering. The Bresenham line drawing algorithm is an efficient software algorithm to implement the choosing of virtual scan line pixels. Though only six virtual scan lines252-262are shown, other number of virtual scan lines or patterns may be employed. The asterisk pattern250of virtual scan lines provides a reasonable likelihood of capturing a barcode label (e.g. label240) disposed at various orientation within the imaging region230. It is noted that the configuration of the particular virtual scan line pattern depends upon the dimensions and type of the optical code to be scanned, the size of the scanning area, and the characteristics of the scanning sensor and optics.

In the system ofFIG. 3, a targeting or aiming pattern236is generated and disposed at the center of the imaging region230to assist the user in locating the barcode on the item at an optimum position relative to the scanner. In this example, the aiming pattern236is illustrated as a large circular spot at the center of the scan pattern250. Alternately, the aiming pattern may comprise any suitable shape, such as an aiming spot, a geometric shape, a two-dimensional image, an aiming line segment, a geometric pattern, a logo image, or a recognizable pattern such as an image of a barcode or a shipping label. Other shapes or images of aiming pattern are described in U.S. Pat. No. 6,223,986 hereby incorporated by reference. Preferably the aiming pattern is generated by a separate light source than the system's illumination source, but it may be generated by the same source via a suitable method such as methods disclosed in U.S. Pat. No. 6,575,368, 5,296,689, or 5,146,463 each hereby incorporated by reference. The aiming pattern may be employed in any one or more of the various modes of operation. The aiming pattern may be generated by any suitable mechanism such as LED, laser diode, halogen, broad band or white light source, or any suitable visible light.

InFIG. 3, barcodes240,242,243,244,245, and248can be decoded by one of the virtual scan lines252,256,258, and260. It is often desirable that only the barcode that intersects the aiming pattern236be acknowledged and transmitted to the host terminal. In this case, the location along the virtual scan lines of each barcode that can be identified is determined and compared with the location of the aiming pattern on the corresponding virtual scan line. If at least a portion of the barcode is determined to be close to or intersecting the aiming pattern236, the data is then acknowledged and transmitted to the host terminal.

InFIG. 3, only barcode240meets this positional condition. Although barcodes243,244,245,248, and252are capable of being read, once enough information is gathered to determine that they are not within a predetermined range of the center of the aiming pattern, they are ignored. In some cases, all of the barcodes may be read by the scanner in order to verify their locations along the virtual scan lines but only barcode240will be acknowledged and transmitted to the host terminal.

Various activation schemes for the aiming pattern may be employed. For example, the aiming pattern may be on continuously and even used as non-ambient lighting for the image reading. The aiming pattern may be used in a wake-up feature. In another configuration, since the aiming pattern may interfere with reading, the aiming pattern may be cycled on and off intermittently with reading process such as:turning aiming pattern on;turning aiming pattern off;acquiring an image;turning aiming pattern on;turning aiming pattern off;acquiring an image; etc.
Instead of alternating, the system may use a filter or dichroic mirror to allow simultaneous aiming pattern projection and image reading. The aiming pattern may alternately be generated from a specific color of light that does not interfere with the imaging process or may be readily filtered.

Preferably the aiming pattern is coincident (or alternately parallel or coaxial) with the field of view of the reader so that the axis of the light that generates the aiming pattern is coincident or parallel with the axis of the imaging system. The larger, more diffuse the aiming pattern/spot the less parallel/coincident the aiming pattern need be.

It is noted that the likelihood of a bar code being successfully read by this pattern250depends upon both the orientation and location of the bar code within the scan region230. In this pattern, a bar code240located near the center within the aiming spot236has the highest likelihood of being successfully read. Further out from the center, bar codes oriented such as labels242,243,244,245aligned with a respective virtual scan line are successfully read. A bar code such as label248located in an outer portion of the scan region230and obliquely intersecting virtual scan line248may also be successfully read by a single virtual scan line.

When operated as a sweep scanner, the item being scanned is moved into and through the scan volume230. This movement gives the scan lines the opportunity for a complete scan (or partial scan which may be stitched with other code segments) of a bar code as it is passed across a scan line.

When operated in a presentation mode or a handheld mode, the bar code label remains generally stationary relative to the pattern so if the code does not fall on a virtual scan line, the code may not be successfully read. Since the scan lines of the virtual pattern are arbitrary and controlled via software, the pattern may be changed to enhance the probability of a successful scan. For example, the asterisk pattern250may be rotated 2° for each consecutive scan thereby enhancing the probability of scanning all the segments of code anywhere in the scan volume230. Other schemes for modifying of the virtual scan patterns may be employed.

FIG. 4illustrates another system in which a pattern350of virtual scan lines352,354,356,358,360,362is generated within the imaging region330to capture a barcode. Only six virtual scan lines352-362are shown. The asterisk pattern350of virtual scan lines provides a reasonable likelihood of capturing a barcode label (e.g. label346) disposed at various orientations within the imaging region330. It is noted that the configuration of the particular pattern depends upon the dimensions of the bar code labels to be scanned, the size of the scanning area, and the characteristics of the scanning sensor and optics.

In the system ofFIG. 4, a targeting or aiming pattern336is generated and disposed at the center of the imaging region330to assist the user in locating the barcode on the item at an optimum position relative to the scanner. In this example, the aiming pattern336is illustrated as a small circular spot at the center of the scan pattern350. Alternately, the aiming pattern may comprise any suitable shape such as described previously.

In the system ofFIG. 4, the aiming pattern336is smaller than aiming pattern236ofFIG. 3. In this case, the scanner may be configured to acknowledge and send barcode346to the host even though it is not completely enclosed by aiming pattern336. In the extreme case where the radius of aiming pattern336becomes very small, the scanner can be configured to acknowledge and transmit barcodes that intersect a certain region around the aiming pattern. This region can be configured to be different sizes and shapes, depending on the application.

It is noted that the likelihood of a bar code being successfully read by this pattern350depends upon both the orientation and location of the bar code within the scan region330. In this pattern, a bar code346located near the center within the aiming pattern/spot336has the highest likelihood of being successfully read and since it intersects the aiming/spot336it may be selectively read by the system. Further out from the center, bar codes oriented such as labels342,344,348aligned with a respective virtual scan line may be successfully read, but may be selectively excluded as not intersecting the aiming pattern336.

FIG. 5illustrates a preferred system in which a pattern of virtual scan lines50is generated within the imaging region to provide a high likelihood of capture of the barcode with a minimum amount of memory storage. The asterisk pattern of virtual scan lines50provides a high likelihood of capturing any of the barcode label40,42,44,46disposed at any orientation within the imaging region30. The particular pattern depends upon the dimensions of the bar code labels to be scanned, the size of the scanning area, and the characteristics of the scanning sensor and optics. The pattern is designed so a minimum decodable piece of a barcode label40which is positioned anywhere in the imaging region30and at any orientation, will be readable by at least one virtual scan line.

In the system ofFIG. 5, a targeting or aiming pattern36is generated and disposed at the center of the imaging region30. In this example, the aiming pattern36is illustrated as a large circular spot at the center of the scan pattern50. Alternately, the aiming pattern may comprise any suitable shape, such as an aiming spot, a geometric shape, a two-dimensional image, an aiming line segment, a geometric pattern, a logo image, or a recognizable pattern such as an image of a barcode, a shipping label. Other shapes or images of aiming pattern are described in U.S. Pat. No. 6,223,986 hereby incorporated by reference. Preferably the aiming pattern is generated by a separate light source than the system's illumination source, but it may be generated by the same source via a suitable method such as methods disclosed in U.S. Pat. No. 6,575,368, 5,296,689, or 5,146,463 each hereby incorporated by reference. The aiming pattern may be employed in any one or more of the various modes of operation.

In one embodiment, the scan pattern50is comprised of a plurality of bands52,54,56,58,62,64,66,68,70,72,74each of a plurality of generally parallel virtual scan lines. In the embodiment ofFIG. 5, there are eleven generally parallel virtual scan lines in each band52,54etc., with each band being rotationally offset by about 15° to the band adjacent thereto. Other suitable virtual scan line patterns may be employed such as a raster pattern, an asterisk pattern, a multiple raster with lines at varying angles, or an omnidirectional pattern such as emulating scan patterns generated by laser scanners such as the PSC Inc. Magellan® scanner described in U.S. Pat. No. 5,475,207 or the PSC Inc. Duet® scanner described in U.S. Pat. No. 6,575,368, each of these hereby incorporated by reference. Though a band of parallel lines provides certain advantages when picking out a single barcode, a single line pattern may be preferred in certain applications.

A first embodiment comprises a reading system and method whereby a single barcode40out of a plurality of barcodes40,42,44,46within the scan region30is reported and/or decoded.FIG. 6illustrates a first preferred method100that may comprise the following steps:Step110: Start.Step112: Projecting an aiming pattern36into the scan region30by, for example, one of the suitable methods described above.Step114: The operator (not shown) positioning the aiming pattern36onto the optical code40which is desired to read out of the plurality of optical codes40,42,44,46in the scan region30. There are multiple ways of positioning the scan pattern. If the data reader is handheld, the operator manipulates the reader so as to aim/move the aiming pattern onto the barcode. If the data reader is a fixed unit, the operator moves the item bearing the barcode into the scan region, positioning the item such that the barcode is positioned within or intersecting the spot.Step116: Forming an image of the scan region30onto a sensor array or imaging sensor12and detecting the image.Step118: Storing only a selected portion of data comprised of selected points of the image corresponding to a pattern of virtual scan lines50. In the illustrated pattern50ofFIG. 5, there are 264 virtual scan lines, eleven scan lines in each of the 24 bands52to98of virtual scan lines.Step120: Processing the stored data to locate an optical code.Step122: Determining if the aiming pattern intersects the optical code found in Step120. If the aiming pattern is determined to intersect the optical code, proceeding to Step124.Step124: Acknowledging and transmitting data acquired from the optical code.

In Steps122and the previous Step120, the system reads the optical code that is intersected by the aiming pattern36. For example, inFIG. 3, only optical code40is intersected by the aiming pattern36. Thus only optical40is read, the system acknowledging with the customary successful read “beep” for example, and the data from that code is then transmitted to the host or POS.

If it is determined in Step122that the optical code found does not intersect the aiming pattern, that optical code is ignored.

The process is repeated from step112as the operator moves the aiming pattern onto the desired optical code.

The selected portion of data may be decoded at any suitable stage, including (1) prior to determining if the aiming pattern intersects the optical code, (2) after determining if the aiming pattern intersects the optical code and prior to transmitting, or (3) after transmitting.

Alternately, the system may selectively switch between (a) a first mode of operation wherein an optical code is acknowledged and transmitted only if the aiming pattern is determined to intersect the optical code and (b) a second mode of operation wherein an optical code is acknowledged and transmitted regardless of whether the aiming pattern is determined to intersect the optical code.

The system may be provided with a switch whereupon the system switches modes upon actuation of the switch by the operator. For example, an external switch or button may be provided on the reader housing. Upon actuation of the switch by the operator, the reader may switch into the code picking mode whereby the reader activates the aiming pattern and only reads the barcode intersecting the aiming pattern.

In another embodiment, a first switch activation may be used to initiate the aiming pattern and a second activation of the same switch or another switch may be used to read the optical code intersecting the aiming pattern.

In another embodiment, the reader may comprises a portable unit operable in a fixed mode and a handheld mode. The switch may comprise either a manually actuated switch on the housing or alternately a sensor which senses when the reader is moved (using a motion sensor or accelerometer) or is grasped by the operator (such as a contact sensor). Upon sensing that the reader has been moved or grasped, the reader activates the aiming pattern and only reads the barcode intersected by the aiming pattern.

In another preferred method, a single optical code out of a plurality of optical codes present in the scan region is acknowledged and transmitted by the steps ofAcquiring an image of a scan region30into a sensor array12.Reading only a selected optical code40out of a plurality of optical codes40,42,44,46present within the scan region30, by the steps ofprojecting an aiming pattern36into the scan region30;positioning (preferably by action of an operator) the aiming pattern36onto the selected optical code40;processing a selected portion of data at only selected points along a pattern of virtual scan lines50in the scan region30and thereby locating an optical code;determining if the aiming pattern36intersects the optical code that has been located;if the aiming pattern36is determined to intersect the optical code that has been located, acknowledging and transmitting the optical code.While operating in the handheld mode, switching between operating in the first mode and operating in the second mode.

The selected portion of data may be decoded at any suitable stage, including (1) prior to determining if the aiming pattern intersects the optical code, (2) after determining if the aiming pattern intersects the optical code and prior to transmitting, or (3) after transmitting. Alternately, the system may selectively switch between (a) a first mode of operation wherein an optical code is acknowledged and transmitted only if the aiming pattern is determined to intersect the optical code and (b) a second mode of operation wherein an optical code is acknowledged and transmitted regardless of whether the aiming pattern is determined to intersect the optical code. The method may comprise reading optical codes with a portable data reader operable in a fixed mode and a handheld mode.

Another preferred method for reading optical symbols with a data reader, may comprise the following steps:Acquiring an image of a two-dimensional imaging region into a sensor array.Operating in a first mode by processing a selected portion of data at only selected points along a pattern of virtual scan lines arranged in multiple directions about the two-dimensional imaging region.Operating in a second mode by processing a selected portion of data at only selected points along a pattern of virtual scan lines consisting of a band of a plurality of generally parallel virtual scan lines.FIG. 5illustrates a specific band52of eleven generally parallel virtual scan lines. The band of lines provides for added density along a scan direction for reading optical codes such as barcodes and PDF-417 codes.Decoding the selected portion of data according to the pattern of virtual scan lines.

As with previous embodiments, the reader may comprise a housing suitable for portable operation. A switch provided on the reader housing permits the operator to switch between the first mode and the second mode via actuation of the switch. Alternately a portable unit may include a sensor for sensing either motion of the unit or grasping by the operator and switching from the first mode to the second mode upon sensing that the data reader has been grasped by the user.

In another embodiment, optical codes are read by the steps of:Acquiring an image of a two-dimensional imaging region30into a sensor array12.Operating in a handheld mode by processing a only selected portion of data at selected points along a pattern of virtual scan lines consisting of (a) a single virtual scan line or (b) a band of a plurality of generally parallel virtual scan lines;Operating in a fixed mode by processing only a selected portion of data at only selected points along a pattern of virtual scan lines arranged in multiple directions about the two-dimensional imaging region;Decoding the selected portion of data according to the pattern of virtual scan lines.

In a method according to another embodiment, optical codes are read with a data reader by the steps ofAcquiring an image of a two-dimensional imaging region into a sensor array.Operating in a handheld mode by (1) generating an aiming pattern whereby a user positions the aiming pattern onto an optical code within the imaging region, and (2) storing data at only selected points along a pattern of virtual scan lines intersecting the aiming pattern.Decoding data that has been stored.

This method may be operable for switching as between the fixed mode of operation and the handheld mode of operation. In one embodiment, when operating in the fixed mode, the reader stores only a selected portion of data at selected points along a pattern of a plurality of virtual scan lines spanning the two-dimensional imaging region in multiple directions. That selected portion is a subset of the entirety of virtual scan lines such as (1) a single scan line, (2) a band of a plurality of parallel scan lines, (3) a specialized pattern for example designed for efficient reading of particular label such as PDF-417 symbology.

In yet another embodiment, a data reader may read optical symbols by the steps of:Acquiring an image of a two-dimensional imaging region into a sensor array.Projecting an aiming pattern into the two-dimensional imaging region.Operating in a first mode by processing only a selected portion of data at only selected points along a pattern of virtual scan lines arranged in multiple directions about the two-dimensional imaging region.Operating in a second mode by processing only a selected portion of data at only selected points along a pattern of virtual scan lines intersecting the aiming pattern.Decoding the selected portion of data according to the pattern of virtual scan lines.

The scan region is preferably imaged by a sensor array such as a CCD CMOS with a pattern of virtual scan lines defining a selected portion of the image data to be stored and processed. The above methods may be implemented in a system with the scan data generated by a laser beam. In such a system, the laser beam is scanned by rotating or oscillating mirror(s), or other suitable method, to produce a desired two-dimensional scan pattern such as an asterisk pattern. Return signal is collected onto a detector. Applied to one of the above-described methods, knowing the identity/location or each scan line, only the bar code intersecting the aiming pattern is acknowledged.

The size and shape of the aiming pattern may be optimized to obtain desired functionality. For example, the aiming spot236ofFIG. 3is relatively large, that is significantly larger than a typical UPC/EAN barcode. Of course the size of the spot236will likely depend in part upon the distance of the barcode from the scanner. The relative spot size is considered at a typical reading distance. In one methodology, the system may select to decode or read only barcodes that fall completely within the aiming spot236such as barcode240. Alternately, the system may decode or read only barcodes that intersect the spot236.

In another example, the aiming spot336ofFIG. 4is relatively small and the system may selectively decode, read or report only barcodes such as barcode346that intersect the spot.

Another system430is shown inFIG. 7wherein the virtual scan pattern450may be any suitable configuration, here again shown as an asterisk pattern. In this system, the aiming pattern436is rectangular with its long axis oriented horizontally. Such a shaped pattern may urge the user to orient the barcode440in a similar orientation as shown in the figure.

The virtual scan line system may also be adaptive, changing the scan pattern based upon reading. As shown inFIG. 8, if while scanning a PDF417 barcode445and the system detects this particular type of barcode, the system may adapt, changing the aiming spot from the smaller rectangle436ofFIG. 7to another configuration such as to larger rectangle437, and also changing the scan pattern450for example by adding some additional scan lines455(the figure shows only four additional horizontal virtual scan lines, but a larger number of such lines would be preferred) for optimizing reading of this type of optical code.

FIGS. 10a-dare diagrams showing a progression of virtual scan patterns according to another embodiment. In this embodiment, a denser scan pattern is created by rotating a sparser pattern from frame to frame.FIG. 10ashows a captured frame that is processed with six vertical scan lines and five horizontal scan lines.FIG. 10bshows the subsequent frame with the virtual scan pattern rotated 22 degrees.FIG. 10cshows a subsequent frame with another 23 degree rotation for a total of 45 degrees.FIG. 10dshows a subsequent frame with a total of 67 degree rotation fromFIG. 10a. The next frame would continue with the scan pattern ofFIG. 10a. In this manner, the combined scan pattern of four frames has 44 scan lines in 8 different orientations, while being implemented with a scan pattern that has only 11 scan lines per frame in two orientations. This method allows for improved reading of truncated barcodes without additional processing of scan lines per frame. In addition to rotation, the virtual scan lines may be offset from each other on subsequent frames to create a more dense pattern when averaged over more than one frame.

FIGS. 11a-cfurther illustrates the adaptive scan line concept. InFIG. 11athe scan pattern is designed for omnidirectional reading. If one of the scan lines inFIG. 11ahas a decodable portion of a barcode, the scan pattern is modified to include scan lines of similar orientation. A set of parallel lines of similar orientation and nearby orientation are generated to more accurately line up with the barcode, as shown inFIG. 11b, the so-called “reduced search pattern”. Subsequent frames could use virtual scan lines that use more parallel lines with fewer orientations, as the orientation of the barcode is discovered by which virtual scan lines have the most decodable information contained within them, as shown inFIG. 11c. While this scheme is particularly effective with stacked codes like PDF417, it also improves the read rate of linear codes like UPC. The virtual scan line pattern may adapt, changing the virtual pattern even as frequently as between frames. Alternately, a different scan pattern may be applied to the same frame if the frame data is stored in memory.

For example, a preferred method of adapting as between frames may comprise the following steps:acquiring data from a two-dimensional scan region;in a first frame, storing portions of the two-dimensional scan region along a virtual scan pattern according to a first pattern of virtual scan lines;processing data from the virtual scan lines of the first pattern to find decodable data;in a second frame, changing the virtual scan pattern to a second pattern of virtual scan lines, such as based on location and orientation of decodable data in the first frame;storing (or selecting) portions of the two-dimensional scan region along a virtual scan pattern according to a second pattern of virtual scan lines;processing data from the virtual scan lines of the second pattern to find decodable data.

Additional, the method may include further steps of (1) changing the virtual scan pattern from frame to frame from a predefined sequence of virtual scan patterns or (2) changing the virtual scan pattern on a subsequent frame based on content of the decodable data of the virtual scan lines of the previous frame.

FIG. 12represents a common application where many barcodes are printed on a single sheet but only bar code505is to be transmitted to the host. Although aiming pattern501is very small, compared with bar code505, the transmit region502is a large circle with a radius sufficient to allow ease of aiming. Any bar code that intersects transmit region502will be acknowledged and transmitted to the host. Region502is limited in size to insure that it does not intersect adjacent barcodes506and507.

FIG. 13represents a different application where the barcodes are closer together and in a single column. Only bar code508is to be transmitted to the host. In this case, transmit region504is configured to be a narrow rectangle to optimize ease of aiming without allowing barcodes509or510to be transmitted accidentally.

FIG. 9illustrates an industrial design according to one preferred embodiment for use with the reading systems and methods described herein. The reader500includes a reader section510extending vertically from base section520. The base section520includes a pivoting mechanism525to allow the reader section510to pivot relative to the base section so as adjust the field of view on front of the read window515. The reader section510may be grasped by the user and manipulated as a palm-style, portable scanner and aimed at the target in a handheld operating mode. The unit500may be movable for handheld operation with the base section520remaining attached to the reader section510or the reader section may be disconnected from the base section520.

While various aspects of invention have been particularly shown and described with reference to certain embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention.