Abstract:
An imager ( 12 ) is provided for imaging target objects ( 26 ) comprising an illumination source ( 22 ) for providing illumination ( 24 ) that is reflected ( 30 ) from a target object ( 26 ), an intensity of the illumination being a function of a magnitude of current provided to the illumination source ( 22 ) and photosensitive circuitry ( 36 ) located within the imager ( 12 ) for capturing an image reflected from the target object ( 26 ) to the imager ( 12 ) while the imager is activated during an exposure period. The imager ( 12 ) further comprises a selectively adjustable imaging mode ( 120 ) for selecting either of: the magnitude of current ( 130 ) provided to the illumination source ( 22 ) or exposure period ( 230 ) of the imager such that the other of the magnitude of current or exposure period of the imager is automatically adjusted ( 150, 240 ) as a result of the selection.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a controlled imaging scanner and more specifically, an imaging scanner having controlled illumination and exposure modes for capturing target objects. 
       BACKGROUND OF THE INVENTION  
       [0002]    Various electro-optical systems have been developed for reading optical indicia, such as bar codes. A bar code is a coded pattern of graphical indicia comprised of a series of bars and spaces of varying widths, the bars and spaces having differing light reflecting characteristics. Some of the more popular bar code symbologies include: Uniform Product Code (UPC), typically used in retail stores sales; Code 39, primarily used in inventory tracking; and Postnet, which is used for encoding zip codes for U.S. mail. Systems that read and decode bar codes employing charged coupled device (CCD) or complementary metal oxide semiconductor (CMOS) based imaging systems are typically referred to hereinafter as imaging systems, imaging-based bar code readers, or imaging scanners. 
         [0003]    Imaging systems electro-optically transform the graphic indicia into electrical signals, which are decoded into alphanumerical characters that are intended to be descriptive of the article or some characteristic thereof. The characters are then typically represented in digital form and utilized as an input to a data processing system for various end-user applications such as point-of-sale processing, inventory control and the like. 
         [0004]    Imaging systems that include CCD, CMOS, or other imaging configurations comprise a plurality of photosensitive elements (photosensors) or pixels typically aligned in an array pattern that could include a number of arrays. The imaging-based bar code reader systems employ light emitting diodes (LEDs) or other light sources for illuminating a target object, e.g., a target bar code. Light reflected from the target bar code is focused through a lens of the imaging system onto the pixel array. As a result, the focusing lens generates an image from its field of view (FOV) that is projected onto the pixel array. Periodically, the pixels of the array are sequentially read out creating an analog signal representative of a captured image frame. The analog signal is amplified by a gain factor, by for example, an operational amplifier. The amplified analog signal is digitized by an analog-to-digital converter. Decoding circuitry of the imaging system processes the digitized signals representative of the captured image frame and attempts to decode the imaged bar code. 
         [0005]    As mentioned above, imaging scanners typically employ an illumination system to flood a target object with illumination from a light source such as an LED in the reader. Light from the light source or LED is reflected from the target object. The reflected light is then focused through a lens of the imaging system onto the pixel array, the target object being within a field of view of the lens. It is not uncommon for a single imaging scanner to employ as an illumination source multiple LEDs or cluster of LEDs for producing illumination that is reflected from the target object. Such configurations undesirably demand a significant amount of power, reducing the battery life on portable or remote imaging scanners. A fixed amount of illumination is not always necessary based on environmental or imaging application changes. In order to conserve battery life or reduce power requirements, the following changes to conventional imaging scanner technology is proposed. 
       SUMMARY OF THE INVENTION  
       [0006]    The present invention relates to an imager for imaging target objects comprising an illumination source for providing illumination directed toward a target object, an intensity of the illumination being a function of a magnitude of current provided to the illumination source and photosensitive circuitry located within the imager for capturing an image from the target object while the imager is activated during an exposure period. The imager further comprises a selectively adjustable imaging mode for selecting either of: the magnitude of current provided to the illumination source or the exposure period of the imager such that the other of the magnitude of current or the exposure period is automatically adjusted as a result of the selection. 
         [0007]    The present invention also relates to a method for imaging target objects comprising illuminating a target object with an illumination source to produce a reflected image of the target object, an intensity of the illumination being a function of a magnitude of current provided to the illumination source and capturing the reflected image of the target object on photosensitive circuitry located within the imager while the imager is activated during an exposure period. The method further comprises selecting an adjustable imaging mode for selecting either of: the magnitude of current provided to the illumination source or exposure period of the imager and automatically adjusting the other of the magnitude of current provided to the illumination source or exposure period of the imager as a result of the selection of the adjustable imaging mode. 
         [0008]    The present invention further relates to an imager for imaging target objects comprising an illumination means for providing illumination that is reflected from the target object, an intensity of the illumination means being a function of a magnitude of current provided to the illumination means and capturing means located within the imager for capturing the image reflected from a target object to the imager while the imager is activated during an exposure period. The imager further comprises a selectively adjustable imaging mode for selecting either of: the magnitude of the current provided to the illumination source or exposure period of the imager such that the other of the magnitude of current or exposure period of the imager is automatically adjusted as a result of the selection. 
         [0009]    The present invention yet further relates to an imaging-based reader for imaging target objects comprising an imager for imaging a target object. The imager is energized by a power source and an illumination source is provided for illumination that is directed toward the target object, an intensity of the illumination being a function of a magnitude of current provided to the illumination source. Photosensitive circuitry is located within the imager for capturing an image from the target object while the imager is activated during an exposure period. The imaging-based reader further comprises a selectively adjustable imaging mode for selecting either of: the magnitude of the current provided to the illumination source or the exposure period of the imager such that the other of the magnitude of current or exposure period of the imager is automatically adjusted as a result of the selection. A check routine is provided for determining the type of power source used to energize the imager. The adjustable imaging mode is disabled when the determined type of power source is an in-line power and the adjustable imaging mode is enabled when the determined type of power source is a remote power source. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0010]    The foregoing and other features and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which: 
           [0011]      FIG. 1  is a side elevation view of an imaging scanner constructed in accordance with one example embodiment of the present invention; 
           [0012]      FIG. 2  is a schematic diagram illustrating a scan engine located within the imaging scanner of  FIG. 1 ; 
           [0013]      FIG. 3  is a block diagram illustrating an exemplary embodiment constructed in accordance with the present invention; 
           [0014]      FIG. 4  is a block diagram illustrating another exemplary embodiment constructed in accordance with the present invention; 
           [0015]      FIG. 5  is a block diagram illustrating another exemplary embodiment constructed in accordance with the present invention; 
           [0016]      FIG. 6  is a block diagram illustrating another exemplary embodiment constructed in accordance with the present invention; and 
           [0017]      FIG. 7  is a block diagram illustrating another exemplary embodiment constructed in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0018]    An imaging system  10  includes an imaging scanner  12  in communication  14  either through hard-wire or over-the-air (remote communication) to a host computer  16  as shown schematically in  FIG. 1 . The imaging scanner  12 , in addition to imaging both 1D and 2D bar codes and postal codes, is also capable of capturing images and signatures. In one exemplary embodiment of the present invention, the imaging scanner  12  is a hand held portable imager supported in a housing  18  that can be carried and used by a user walking or riding through a store, warehouse, or plant for imaging bar codes for stocking and inventory control purposes. 
         [0019]    However, it should be recognized that the imaging system  10  of the present invention, to be explained below, may be advantageously used in connection with any type of scanner or imaging device, be it portable or stationary. It is the intent of the present invention to encompass all such scanners and imagers. 
         [0020]    Internal to the imaging scanner  12  is a scan engine  20 . The scan engine  20  includes an illumination source  22  such as a light emitting diode (LED) or bank of LEDs for projecting light  24  at a target object  26  such as a bar code. The imaging scanner  12  can be automatically enabled, continuously enabled, or enabled by engaging a trigger  28 , which initiates the projection of the light  24  in the hand-held system  10  as it is directed by a user toward the target object  26 . 
         [0021]      FIG. 2  is a schematic illustration of the scan engine  20  associated with the imaging scanner  12 . Reflected light  30  from the target object  26  passes through a window  32  located in the housing  18  of the imaging scanner  12  onto a focusing lens  34  internal to the scan engine  20 . The lens  34  focuses the reflected light onto a pixel array  36  of an imager element  38 . The imager element  38  includes photosensitive elements such as the imaging pixel array  36  that could be for example, a charged coupled device (CCD) array or complementary metal oxide semiconductor (CMOS) array. The imager element  38  also includes an analog-to-digital (A/D) converter  40  for converting an analog signal produced by the imager element  38  over to the digital domain. 
         [0022]    A bus connection  42  provides a communication link between the imager element  38  and a decoder  44 . The bus connection  42  is a high-speed (8) bit parallel interface for providing a digital signal to the decoder  44  representative of the captured image frame. The decoder  44  processes the digitized signals and attempts to decode the target object  26  into decoded information  46 . The decoded information  46  can be stored locally by the scan engine  20  in memory  48  and/or communicated to a peripheral device (not shown) such as a monitor or remote computer through an output port  50 . 
         [0023]    The amount of power consumed by imaging scanner is an important issue, especially for portable scanners powered by their own remote (non-lined) power supply, such as a battery. The more power used during the scanning operation the greater the operating costs, and for portable scanners, the greater the power consumption, the greater the reduction in power or battery life. One of the largest sources of power and operating costs in the imaging scanners is the illumination source, which can include a single or multiple LEDs for capturing images of the target objects. Conventional imaging scanners typically provide a fixed amount of illumination, independent of the application or surrounding conditions. 
         [0024]    In an exemplary embodiment, the imaging system  10  of  FIG. 1  advantageously provides an imaging scanner with selectable exposure control that regulates that amount of illumination being used based on, for example, the imager&#39;s application, use, or environment. The selectable exposure control is programmable such that the scan engine  20  or imaging scanner  12  can be optimized for a particular product (for example stationary or portable scanners) and for the application in which the imaging scanner  12  is used. For example, applications where the barcode or scanner is in motion may require a shorter exposure time and will likely use the brightest available illumination. Alternatively, other applications where overall power consumption or maximum peak current is most critical, the illumination can be selectively controlled to a lower illumination setting and the exposure is controlled to allow for longer exposure times. 
         [0025]    In the illustrated exemplary embodiment of  FIG. 1 , the imaging scanner  12  includes a selectable control  52  that could represent a dial, dual in-line package (DIP) type switch or any other type of switch that would allow for a manual adjustment to selectively control the amount of illumination or exposure time of the imaging scanner  12 . In an alternative exemplary embodiment, the illumination or exposure time is adjusted automatically by electronics or programming located in the imaging scanner  12  and/or the host computer  16 . 
         [0026]      FIG. 3  illustrates one exemplary embodiment of an imaging scanning process  100  of the imaging system  10  in which the amount of current provided to the illumination source  22  is selectively controlled. The imaging or scanning process is initiated at  110  by for example, engaging the trigger  28 , or providing power to the imaging scanner  12  through a remote power supply located within the imaging scanner  12 , or from a signal or power provided from the host computer  16 . The imaging mode  120  is selected either manually by a user at  122  or automatically by the host computer  16  at  124 . The manual selection of the imaging mode  120  is achieved, for example, by the selectable control  52  located on the imaging scanner  12  or equivalent type switch located on the host computer  16 . 
         [0027]    The imaging mode  120  controls in the scan engine  20  the amount of illumination provided by the illumination source  22  by controlling the amount of current used at  130 . The adjustment of the illumination current  130  can be incremental, having two or more incremental values or settings at  132 , or alternatively, could be any value selected on a continuous scale at  134 . 
         [0028]    Once the adjustment to the illumination current is made at  130 , the illumination source  22  illuminates the target object  26  at  140 . Substantially simultaneously, the exposure time of the scan engine  20  is automatically adjusted at  150  to compensate for the selected illumination current at  130 . The automatic adjustment of scan engine  20  exposure time at  150  is achieved, for example, by a look-up table programmed into the scan engine  20 , host computer  16 , or related circuitry, in which the amount of exposure time is set for the amount of current provided to the illumination source  22 . The automatic exposure time adjustment changes the total amount of light that the scan engine  20  allows on the photosensitive sensor, such as the pixel, CMOS, or CCD array  36 . If the current selection  130  is relatively low, then the exposure time is longer, providing more light to the array  36 . Alternatively, if the current selection is relatively high, then the exposure time is shorter, providing less light to the array  36 . 
         [0029]    The imaging mode  120  controlling the scan engine  20  is achieved through the electronics in the scan engine, an application specific integrated circuit (ASIC) coupled to the scan engine, computer readable programming read by the scan engine, or any combination thereof. Once the target object  26  is illuminated and the exposure time of the scan engine  20  is adjusted, the target object is imaged by the scan engine at  160 . 
         [0030]      FIG. 4  illustrates one exemplary embodiment of an imaging scanning process  200  of the imaging system  10  in which the amount of exposure time in the imaging scanner  12  is selectively controlled. The imaging or scanning process is initiated at  210  by for example, engaging the trigger  28 , or providing power to the imaging scanner  12  through a remote power supply located within the imaging scanner  12 , or from a signal or power provided from the host computer  16 . The imaging mode  220  is selected either manually by a user at  222  or automatically by the host computer  16  at  224 . The manual selection of the imaging mode  220  is achieved, for example, by the selectable control  52  located on the imaging scanner  12  or equivalent type switch located on the host computer  16 . 
         [0031]    The imaging mode  220  controls in the scan engine  20  the amount of exposure time provided by the scan engine  20  to the pixel array  36  at  230 . The exposure time adjustment  230  can be incremental, having two or more incremental values or settings at  232 , or alternatively, could be any value selected on a continuous scale at  234 . 
         [0032]    Once the adjustment to the exposure time is made at  230 , an automatic adjustment is made to the amount of current that is provided to the illumination source  22  at  240 . The automatic adjustment of the current at  240  provided to the illumination source  22  is achieved, for example, by a look-up table programmed into the scan engine  20 , host computer  16 , or related circuitry, in which the amount of current is set for the amount of exposure selectively controlled at  230 . Selection of the imaging mode  220  adjusts the amount of light and duration that the scan engine  20  allows on the photosensitive sensor, such as the pixel, CMOS, or CCD array  36 . If the selected exposure is relatively slow, then the exposure time is longer, requiring less current to the illumination source  22  in order to provide the necessary illumination to the array  36 . Alternatively, if the exposure is relatively fast, then the exposure time is shorter, requiring more current to the illumination source  22  in order to provide the necessary illumination to the array  36 . 
         [0033]    The imaging mode  220  controlling the scan engine  20  is achieved through the electronics in the scan engine, an (ASIC) coupled to the scan engine, computer readable programming read by the scan engine, or any combination thereof. Once the auto-adjustment to the illumination current  240  occurs, the target object  26  is illuminated at  250  and imaging of the target object  26  commences by the scan engine  20  at  260 . 
         [0034]      FIG. 5  illustrates one exemplary embodiment of an imaging scanning process  300  of the imaging system  10  in which the amount of current provided to the illumination source  22  in the imaging scanner  12  is selectively controlled and the exposure time is auto-adjusted by heuristic techniques. The imaging or scanning process is initiated at  310  by for example, engaging the trigger  28 , or providing power to the imaging scanner  12  through a remote power supply located within the imaging scanner  12 , or from a signal or power provided from the host computer  16 . The imaging mode  320  is selected either manually by a user at  322  or automatically by the host computer  16  at  324 . The manual selection of the imaging mode  320  is achieved, for example by the selectable control  52  located on the imaging scanner  12  or equivalent type switch located on the host computer  16 . 
         [0035]    The imaging mode  320  controls in the scan engine  20  the amount of illumination provided by the illumination source  22  by controlling the amount of current used at  330 . The adjustment of the illumination current  330  can be incremental, having two or more incremental values or settings at  332 , or alternatively, could be any value selected on a continuous scale at  334 . 
         [0036]    Once the adjustment to the illumination current is made at  330 , the exposure time of the scan engine  20  is automatically adjusted at  340  to compensate for the selected illumination current at  330 . Illumination is then provided to the target object  26  at  350 . A determination is then made at  360  as to whether the amount of exposure time was sufficient, by for example, algorithms or heuristic techniques programmed within the scan engine  20  or host computer  16 . If the determination at  360  finds that the amount of illumination is insufficient, the exposure time is adjusted appropriately at  365 , by for example, an incremental increase in the exposure time. An attempt to illuminate the target object  26  is again made at  350 . If the determination at  360  is in the affirmative, the target object  26  is imaged at  370 . 
         [0037]      FIG. 6  illustrates one exemplary embodiment of an imaging scanning process  400  of the imaging system  10  in which the amount of exposure time in the imaging scanner  12  is selectively controlled and the amount of illumination current provided to the illumination source  22  is auto-adjusted by heuristic techniques. The imaging or scanning process is initiated at  410  by for example, engaging the trigger  28 , or providing power to the imaging scanner  12  through a remote power supply located within the imaging scanner  12 , or from a signal or power provided from the host computer  16 . The imaging mode  420  is selected either manually by a user at  422  or automatically by the host computer  16  at  424 . The manual selection of the imaging mode  420  is achieved, for example by the selectable control  52  located on the imaging scanner  12  or equivalent type switch located on the host computer  16 . 
         [0038]    The imaging mode  420  controls in the scan engine  20  the amount of exposure time provided by the scan engine  20  to the pixel array  36  at  430 . The exposure time adjustment  430  can be incremental, having two or more incremental values or settings at  432 , or alternatively, could be any value selected on a continuous scale at  434 . 
         [0039]    Once the adjustment to the exposure time is made at  430 , an automatic adjustment is made to the amount of current that is provided to the illumination source  22  at  440 . Illumination is then provided to the target object  26  at  450 . A determination is then made at  460  as to whether the amount of illumination provided at  450  was sufficient, by for example, algorithms or heuristic techniques programmed within the scan engine  20  or host computer  16 . If the determination at  460  finds that the amount of illumination is insufficient, the amount of current is adjusted appropriately at  465 , by for example, an incremental increase to the current supplied to the illumination source  22 . An attempt to illuminate the target object  26  is again made at  450 . If the determination at  460  is in the affirmative, the target object  26  is imaged at  470 . 
         [0040]      FIG. 7  illustrates another exemplary embodiment of an imaging scanning process  600  in which the process applied to the imaging scanner  12  is a function of the source of power supplied to the imaging scanner  12 . The process is initiated at  610  by for example, engaging the trigger  28 , or providing power to the imaging scanner  12  through a remote power supply located within the imaging scanner  12 , or from a signal or power provided from the host computer  16 . Throughout the imaging process  600  a check  640  is made as to the source of power provided to the imaging scanner  12 . If the imaging scanner is operating from in-line power (either alternating current or direct current), the target object  26  is imaged at  660  without altering the amount of current provided to the illumination source  22 . If the check at  640  determines that the imaging scanner has a change in its power source (such as changing from in-line to battery power), or is on remote (battery) power, conservation techniques such as the processes  100 ,  200 ,  300 , or  400  are implemented to conserve the remote power. 
         [0041]    While the present invention has been described with a degree of particularity, it is the intent that the invention includes all modifications and alterations from the disclosed design falling within the spirit or scope of the appended claims.