Abstract:
The invention is directed to an optical reader station for reading an object and a method of controlling an illumination source in the station for illuminating the object. The optical reader station comprises a mount for an optical reader and a stand with a surface for receiving the object, the optical reader includes an imager with an object field of view in which the object to be read is positioned. The station further includes a radiation source positioned within the object field of view and arranged to be obstructed by the object when the object is in position to be read. A detection mechanism, which is positioned to receive radiation from the radiation source when the radiation source is not obstructed by the object, deactivates the illumination source when radiation source radiation is detected. The detector mechanism may form part of an auto-exposure control in the imager, which senses ambient light impinging on the imager including the radiation from the radiation source for controlling the illumination level of the illumination source, or it may be a separate detector, which senses the radiation from the radiation source for deactivating the illumination source. The radiation source, which may be an infrared source, a visible light source, a UV source or a luminescence emitter activated by a UV source, may be mounted within the surface of the stand.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to optical reader stations and more particularly to unobtrusive optical reader stations, with minimal user interaction, low latency, and low energy use. 
     BACKGROUND OF THE INVENTION 
     Optical reader stations for scanning symbols have applications such as inventory control, parcel tracking, identification and security, i.e. wherever an electronic database may be maintained against a set of tangible elements. In such a station, the symbology reader performs the necessary function of converting the tangible information into electronic information. 
     Scanners in the optical reader stations may be handheld, permanently mounted, or they may consist of handheld scanners with a complementary mount for use in presentation mode scanning. In particular situations such as grocery checkouts or identification queues, a scanner is preferably a fixed mount or in a presentation mode of operation. In general, it is desirable that such stations draw low power, operate under low component stress, are simple and cost-effective to manufacture, are unobtrusive in their deployment, and are retrofitable and make use of existing system resources when improvements are considered. 
     Each symbology reader has imaging and decoding functions. The imaging function acquires an image of a coded object and converts the optical image information to corresponding electronic information. The decoding function extracts the encoded message from the electronic information. 
     The reader may also include other major functions where necessary or advantageous. For example a reader may include the functions of illuminating and/or targeting the symbol to be read. Variable illumination may be required to supply sufficient photonic radiation to capture a suitable image in varying ambient conditions. The required level of illumination on the object may be controlled by an auto-exposure function within the reader. A targeting system aids in positioning the symbol in the field of view. 
     Different strategies have been used during the development of readers. Some reader systems have inactive and active states, wherein they are activated to scan an object in response to an event, such as the pressing of a button, after which they return to their inactive state. The event that activates this type of reader might also be the detection of the absence or presence of a predetermined symbology in the object field by periodically scanning it. The absence of the predetermined symbology may signify that a valid object has been placed in the object field. Other types of readers are always active once they are switched on in that they continuously scan the object field and attempt to decode the imaged information without regard to the presence of a valid symbol within the field. 
     One method for controlling the active/inactive states of a reader is described in U.S. Pat. Ser. No. 5,949,052, which issued to Longacre, Jr. et al on Sep. 7, 1999. This disclosure is directed to the use of a special default symbol, the detection of which places the reader in an active state. This device may employ a predetermined pattern of backlighting on the surface where an object is to be placed. The backlighting lights a predetermined symbol from the back, which is scanned periodically and decoded by the reader. When the predetermined symbol is detected, the reader is placed in an inactive mode, when the predetermined symbol is not detected and the reader is placed in an active mode. When the predetermined symbol is not detected, it means that an object to be read is obstructing the line of sight from predetermined symbol to the reader, and the reader is activated to operate in its normal operating mode. Another form that the backlighting technique may take is described in U.S. Pat. Ser. No. 6,298,175, which issued to Longacre, Jr. et al on Oct. 2, 2001, wherein the backlighting emits light in a predetermined pattern such as being intermittently on and off, which is recognized by the reader. Although this solution provides benefits such as power saving, a station must be modified to include new apparatus and programming to both generate and recognize the predetermined symbol, or pattern. Another drawback is the latency introduced by this approach arising from the duration of switching to an active state. Increased latency lowers station productivity. 
     Existing continuous scan configurations do not adequately conserve power, and often operate with a constant or pulsed illumination source, which is found to be obtrusively non-ergonomic. In addition, the systems described above are not satisfactory solutions for existing event driven or continuous configurations. They do not provide a sufficiently simple low latency, cost-effective option that minimizes the use of new resources by maximizing the incorporation with existing reader resources, making it retrofittable in a simple manner. 
     Therefore, there is a need for improved unobstusive optical reader stations, with minimal user interaction, low latency and low energy use. 
     SUMMARY OF THE INVENTION 
     The invention is directed to an optical reader station for reading an object. 
     The optical reader station comprises an optical reader having an imager with an object field of view in which an object that is to be read is positioned and a source of illumination for illuminating the object to be read. The station further includes a radiation source positioned within the object field of view and arranged to be obstructed by the object when the object is positioned to be read. A detection mechanism is positioned to receive radiation from the radiation source when the radiation source is not obstructed by the object for deactivating the illumination source. 
     In accordance with another aspect of the invention, the detector mechanism comprises an auto-exposure control coupled to the imager for sensing the radiation and to the illumination source for controlling the deactivation of the illumination source. 
     In accordance with a further aspect of the invention, the optical reader station for reading an object comprises an optical reader having an imager with an object field of view in which an object is to be positioned to be read, a source of illumination for illuminating the object to be read, and an auto-exposure controller coupled to the imager to control the illumination source in response to radiation on the imager. The optical reader station further includes a radiation source positioned within the object field of view to direct radiation towards the imager, wherein the radiation source is arranged to be obstructed by the object when the object is positioned to be read and wherein the illumination source is deactivated when the radiation source is unobstructed by the object and radiation from the radiation source impinges on the imager. 
     With regard to a particular aspect of the invention, the optical reader station further includes a stand for mounting the radiation source and for receiving the object to be read, and a mounting mechanism connected to the stand for receiving the optical reader in a fixed or a detachable manner. 
     In accordance with another aspect of the invention, an optical reader station for reading an object comprises an optical reader mount having a stand with a surface for receiving the object to be read and an optical reader fixed to the mount. The optical reader includes an imager facing the stand, a source of illumination for illuminating the object on the stand, and an auto-exposure control coupled to the imager to control the illumination source in response to radiation on the imager. The optical reader station further includes a radiation source mounted on the stand facing the imager for directing radiation to the imager, whereby the source of illumination is adapted to be deactivated by the auto-exposure control when the imager receives radiation from the radiation source. 
     With regard to a particular aspect of the invention, the optical reader is detachably fixed to the mount. 
     In accordance with a further particular aspect of the invention, the radiation source is mounted within the surface of the stand. 
     In accordance with other aspects of the invention, the radiation source is an infrared source, a visible light source, a UV source or a luminescence emitter activated by a UV source. 
     With regard to another particular aspect of the invention, the illumination source is a target source or includes a target source. 
     In accordance with a further aspect, the invention is directed to a method for controlling an illumination source in an optical reader for reading an object having an imager and an illumination source for illuminating the object to be read. The method comprises detecting ambient light impinging on the imager, controlling the intensity of the illumination source in proportion to the level of ambient light detected by the imager when the object is in a position to be read, and directing constant radiation having a predetermined threshold level at the imager when the object is not in a position to be read. 
     In accordance with another aspect of the invention, method for controlling an illumination source in an optical reader for reading an object having an imager and an illumination source for illuminating the object to be read, comprises detecting ambient light impinging on the imager, controlling the intensity of the illumination source in proportion to the level of ambient light detected by the imager when the object is in a position to be read, directing radiation having a predetermined threshold level at a detector when the object is not in a position to be read, and disabling the illumination source in response to the radiation detected by the detector. 
     With regard to a particular aspect of the invention, the directed radiation is infrared, visible, UV or luminescent radiation. 
     Other aspects and advantages of the invention, as well as the structure and operation of various embodiments of the invention, will become apparent to those ordinarily skilled in the art upon review of the following description of the invention in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram of a prior art optical reader station, 
         FIG. 2  is a functional block diagram of a prior art optical reader station; 
         FIG. 3  is a block diagram of the prior art optical reader station; 
         FIG. 4  is a schematic diagram of a portion of a prior art optical reader station using auto-exposure control; 
         FIG. 5  is a schematic diagram of an embodiment of an optical reader station in accordance with the present invention having an infrared radiation source; 
         FIG. 6  is schematic diagram of the optical path of a further embodiment of the optical reader station in accordance with the present invention having a visible light radiation source, 
         FIG. 7  is a schematic diagram of the optical path of another embodiment of the optical reader station in accordance with the present invention having a near UV light radiation source; 
         FIG. 8  is a schematic diagram of the optical path of a further embodiment of the optical reader station in accordance with the present invention having a luminescent radiation source; 
         FIG. 9  is a schematic diagram of the optical path of an embodiment of the optical reader station in accordance with the present invention having a light detector; and 
         FIG. 10  is a block diagram of a optical reader station in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic diagram of a basic optical reader station  100 . Station  100  includes an optical reader  110  and a mount  120  for receiving the optical reader. The mount  120  further includes a stand  130  on which an object  140  that is to be scanned is placed. The reader  110  may be permanently fixed to the mount  120 , or alternatively the reader  110  may be a portable optical reader that attaches to the mount  120  in a temporary fashion. The optical reader  110  faces the stand  130 , such that it can scan the object  140  placed on it. 
     Prior art optical readers  110  are capable of carrying out a number of functions when reading an object symbol  140 , some of the functions are schematically illustrated in  FIG. 2. A  reader  110  includes the ability of imaging  210  the object symbol  140  that is placed on the stand  130  in the reader&#39;s object field of view and then decoding  220  the symbol  140  from the electronic information provided by the imaging function  210 . The reader  110  may also include the functions of targeting  230  the object symbol  140  as well as illuminating  240  the object symbol  140  so that it can be properly imaged. The illumination  240  function may include an auto-exposure function  250 , for controlling the level of illumination depending on the ambient light during the imaging process. 
     Imaging  210  is necessary to acquire an optical image of a coded object symbol  140  and to convert the optical image information to equivalent electronic information. Decoding  220  is necessary to extract the message encoded in the object symbol  140  from the equivalent electronic information. The illumination function  240  supplies sufficient photonic radiation to suitably capture the image of the object symbol  140 , particularly through the use of auto-exposure  250 , which maintains a desirable level of radiation on the object in varying ambient light conditions. Targeting  230  aids in positioning the object symbol  140  on the stand  130  so that it is within the reader&#39;s object field of view. All of the above functions may be utilized whether the optical reader  110  is operated in an event driven mode or in a continuous scan mode. 
     A block diagram of the prior art optical reader  110  is shown in FIG.  3 . The optical reader  110  includes a computer system  310 , an imager  320 , imager optics  325 , incident optics  335 , and incident radiation sources  330 . The incident sources  330  include an illumination source  340  and may include a target source  350 . The imager optics  325  focuses an object  140  to be scanned onto the imager  320 . The incident optics  335  directs the light from the illumination source  340  onto the object  140  and may also direct a target source  350  marker onto the stand  130  to facilitate the placement of the object  140  in the object field of view for the imager  320 . 
     The computer system  310  typically comprises a bus  360 , processor  370 , a memory  380 , and an input/output interface  390 . Memory  380  will store the operating programs  400  such as the imaging and decoding operating programs as well as the auto-exposure program  410  if required, and the data  420 . The bus  360  interconnects the computer system  310  elements, along with imager  320  and incident sources  330 . Note that the prior art also includes systems with independent program and data memories. For purposes of the invention described below, either is compatible. The single memory prior art is selected for illustration, and one skilled in the art will understand the trivial adaptation necessary to employ independant program/data memories. 
     Using the program or programs  400  stored in and retrieved from memory  380 , the processor  370  operates the imager  320  and incident sources  330  according to good image acquisition practice, to acquire and decode the images of the object symbols  140 , and to store the results in the data memory  420  and/or communicate them externally via the I/O interface  390 . 
     In order to obtain satisfactory image acquisition in variable ambient light conditions, an auto-exposure function is highly desirable. In general, auto-exposure may affect exposure time, illumination and gain. Particularly interesting for the present invention, the auto-exposure function involves adjusting the illumination on the object symbol  140  to a suitable level by controlling the amount of light emanating from optical reader illumination source  340  in response to the overall amount of light detected by the imager  320  during a scan. Optical readers  110  of various types may use different measurements to control auto-exposure, for instance the response may be based on the average light detected over the entire imager  320  or over a portion of the imager. Typically the auto-exposure control includes the processor  370 , in conjunction with an auto-exposure program  410 , the imager  320  and the illumination source  340 . In this arrangement the processor  370  responds to a sample or aggregation of the imager  320  output to control the activation of the illumination source  340 . The source  340  usually has a range of brightness from a fully ON position to provide a brightness level necessary to scan an object  140  when there is no ambient light, to a fully OFF position when the ambient light is at or above a threshold level where there is sufficient light to scan the object  140 . 
       FIG. 4 , in a schematic diagram of a portion of the optical reader station  100 , shows the radiation directed to the object  140  and reflected from the object  140  to the imager  320 . The radiation travels along the path  401  from the illumination source  340  through the incident optics  335  to the surface of the object  140 . This radiation is reflected from the object  140  and continues along the path  401  through the imager optics  325  to the imager  320 . Depending on the imager optics  325 , the optical reader station  100  will have an object field of view, represented by the broken lines X, within which the imager  320  will register an image of the object  140 . The area that the imager  320  sees on the surface of the stand  130  is preferably only slightly bigger than the object  140  itself and may be rectangular, circular or any other desired shape as determined by the optics  325 . 
       FIG. 5  is a schematic diagram of a portion of an optical reader station  500  in accordance with the present invention. For clarity and to simplify the description, elements in the optical reader station  500  which are similar to those in the optical reader station  100  in  FIG. 4  carry the same reference numbers. The portion of the optical reader station  500  shown includes a stand  130  on which may be positioned the object  140  to be read, an imager  320  with its associated optics  325  as well as an illumination source  340  and its associated optics  335 . The stand  130  is depicted independently from whatever work surface it may be placed on, but a work surface integrated embodiment is also envisioned. In addition, in accordance with the present invention the optical reader station  500  includes a source of radiation  550  mounted in the stand  130  at the location where an object  140  to be read is to be positioned. The radiation beam from the source  550  is directed to the imager  320  through the imager optics  325  and would preferably be confined to the space defined by broken lines Y, but need not be so. The cross-section of the radiation beam may be circular, rectangular or any other appropriate shape, however it is shaped and positioned such that, when an object  140  is placed at its appropriate position on the stand  130  for scanning, it will obscure the source  550  radiation from the imager  320 . In order to direct the user to the field of view, the stand may be marked. 
     The radiation source  550  operates in conjunction with the auto-exposure control in the optical reader station  500  in the following manner. When an object  140  is not present within the object field of view as represented by broken lines X, the imager  320  will receive the radiation from the source  550  and the auto-exposure program will deactivate the illumination source  340 . To accomplish this the source  550  must provide sufficient radiation to the imager  325  so that the auto-exposure control will see it as being at or over its threshold of required exposure level. Thus illumination source  340  will remain turned off until radiation source  550  is obstructed. When an object  140  is placed in the object field of view, the object  140  substantially obstructs the radiation source  550  beam defined by broken lines Y and the imager  320  is no longer exposed to the radiation from source  550 . This will allow the over-exposure control to operate in the normal manner and set the illumination from the source  340  to a level required to properly image the object  140 . 
     In the preferred embodiment of the present invention, the radiation source  550  is a source of infrared light. Typically, imager sensors  320 , both CCD and CMOS, respond to infrared light as well as to visible light; the use of infrared light as the source  550  of continuous radiation is particularly advantageous in view of the size and the cost of infrared radiation sources as well as the fact that the infrared light source is much less obtrusive in situations where the level of the ambient light is low. 
       FIGS. 6 and 7  illustrate schematic diagram of a portion of optical reader stations  600  and  700  in accordance with the present invention, which are two alternate embodiments to the optical reader station  500 . Again, the elements in the optical reader stations  600  and  700 , which are similar to those in the optical reader station  100  in  FIG. 4  carry the same reference numbers. Thus the portion of the optical reader stations  600 ,  700  shown includes a stand  130  on which may be positioned the object  140  to be read, an imager  320  with its associated optics  325  as well as an illumination source  340  and its associated optics  335 . In these embodiments of the optical reader stations  600 ,  700 , the sources of radiation  650 ,  750  are in the visible light range and the near-violet UV range, respectively. Virtually all imagers  325  respond well to a source in the visible light range  650 , which, however, is more obtrusive then infrared, while imagers do not respond as well to the near-violet UV source  750  as they do to infrared, the radiation from the UV source  750  is less obtrusive than visible light. 
     In a further embodiment of the present invention illustrated in  FIG. 8 , which illustrates a schematic diagram of a portion of an optical reader station  800 , the elements in the optical reader station  800 , which are similar to those in the optical reader station  100  in  FIG. 4 , carry the same reference numbers. Thus the portion of the optical reader station  800  shown includes a stand  130  on which may be positioned the object  140  to be read, an imager  320  with its associated optics  325  as well as an illumination source  340  and its associated optics  335 . In addition, in accordance with the present invention the optical reader station  800  includes a fluorescent or phosphorescent emitter  855  mounted in the stand  130  at the location where an object  140  to be read would be positioned. Emitter  855  is induced to luminesce by a UV source  850  of radiation, which is positioned to direct UV radiation to the emitter  855  as represented by broken lines Z. The luminescent radiation from the emitter  855  is directed to the imager  320  through the imager optics  325  and would preferably be confined to the space defined by broken lines Y, but need not be so. 
     As in the previous embodiments, the luminescent radiation from emitter  855  operates in conjunction with the auto-exposure control in the optical reader station  800  in the following manner. When an object  140  is not present within the object field of view as represented by broken lines X, the imager  320  will receive the radiation from the emitter  855  and the auto-exposure program will deactivate the illumination source  340 . Thus illumination source  340  will remain turned off as long a nothing obstructs the emitter  855 , and in this embodiment as long as nothing obstructs the UV radiation from source  850  from impinging on the emitter  855 , as well. When an object  140  is placed in the object field of view, the object  140  substantially obstructs the emitter  855  radiation directed to the imager  320 . This will allow the auto-exposure function to control the illumination from the source  340  to a level required to properly image the object  140 . The same will occur if the UV radiation from source  850  is obstructed from impinging on the emitter  855 . 
     In the embodiment of the present invention illustrated in  FIG. 9 , which illustrates a schematic diagram of a portion of an optical reader station  900 , the elements in the optical reader station  900 , which are similar to those in the optical reader station  100  in  FIG. 4 , carry the same reference numbers. Thus the portion of the optical reader station  900  shown includes a stand  130  on which may be positioned the object  140  to be read, an imager  320  with its associated optics  325  as well as an illumination source  340  and its associated optics  335 . In addition, in accordance with the present invention the optical reader station  900  includes a source of radiation  950  mounted in the stand  130  at the location where an object  140  to be read would be positioned. The radiation source  950  may be the same as any one of the radiation sources  550 ,  650 ,  750  described with respect to  FIGS. 5 ,  6  or  7  respectively. However, in the present embodiment, the radiation beam from the source  950  is directed to a sensing detector  955  and would preferably be confined to the space defined by broken lines Y, but need not be so. The cross-section of the radiation beam may be circular, rectangular or any other appropriate shape, however it is shaped and positioned such that, when an object  140  is placed at the appropriate position on the stand  130  for scanning, it will obscure the source  950  radiation from the sensing detector  955 . The sensing detector  955  would preferably be located close to the imager  320  in the optical reader station  900 . 
     The sensing detector  955  is connected to the bus  360  in the computer system  310  as illustrated in  FIG. 10  such that under the control of processor  370 , the illumination source  340  is turned OFF and will remain in that state as long a nothing obstructs the radiation source  950 . When an object  140  is placed in the object field of view, the object  140  substantially obstructs the radiation source  950  beam and sensing detector  955  is no longer exposed to the radiation from source  950 . This will cause the processor to reactivate the illumination source  340  and will allow the auto-exposure to control the illumination from the source  340  to a level required to properly image the object  140 . 
     Modifications in accordance with the present invention made to the optical reader  110  illustrated in  FIG. 3 , are shown in the optical reader  1010  illustrated in FIG.  10 . For clarity and to simplify the description, elements in the optical reader  1010  which are similar to those in the optical reader station  110  in  FIG. 3  carry the same reference numbers. The optical reader  1010  includes a computer system  310 , an imager  320 , imager optics  325 , incident optics  335 . And incident radiation sources  330 . The incident sources  330  include an illumination source  340  and may include a target source  350 . The computer system  310  typically comprises a bus  360 , processor  370 , a memory  380 , and an input/output interface  390 . 
     In accordance with the present invention, the optical reader  1010  may include a radiation source  550 ,  650 ,  750 ,  850  or  950  of the type described with regard to  FIG. 5  to  9  respectively, which is connected to the bus  360  in order to be activated when the optical reader  1010  is turned on. For the embodiment described with respect to  FIG. 9 , the sensing detector  955  is also connected to the bus  360  such that the processor  370 , using the illumination source program  960 , will turn the illumination source  340  OFF or ON depending on whether the sensing detector  955  does or does not receive radiation from the radiation source  950  respectively. 
     In addition, as seen on  FIG. 10 , both the illumination source  340  and the target source  350  are connected to the bus  360  and are controlled by the processor  370 . In view of this, the target source  350  may also be controlled to be turned OFF at the same time as illumination source  340  in response to the sensing detector  955 . Conventionally, the illumination source  340  is designed to provide sufficient radiation to properly illuminate the object  140 . On the other hand target source  350  is designed to provide a relatively weak marker to assist in the placement of the object  140 . Power consumption may further be minimized by combining the illumination and the target functions into one incident source  330  calibrated to a level marginally more than sufficient to illuminate an object placed on the stand  130  for optical reading. In this way the incident source  330  will operate as a target marker, in such a manner that it can be varied in intensity from a predetermined minimum, a level at which it is still visible in bright ambient light, to a predetermined maximum intensity, a level at which it illuminates the object properly when no ambient light is present. 
     In a further embodiment of the invention, the mount  120 , shown in  FIG. 1 , may include a detector  960  located within it in order detect the physical presence of the optical reader  110 ,  1010  when attached to the mount  120 . When the portable optical reader  1100 ,  1010  is attached to the mount  120 , detector  960 , which is coupled to the bus  360 , provides a signal to the processor  370  to over-ride other illumination programs in order to deactivate the illumination source  340  and to activate the target source  350 . In this particular embodiment, the target source  350  would be calibrated in the same manner as the incident source  330  described above, to a level marginally more than sufficient to illuminate an object  140  placed on the stand  130  of the fixed mount  120  for optical reading. 
     From the above embodiments, it is seen that the present invention is particularly advantageous since virtually no modifications other then some programming are required to the computer system  310 , and existing functions of the optical reader are partially used to implement the invention. In addition only relatively inexpensive physical modifications such as the installation of a radiation source are required on the optical reader stations in order to implement the invention. At the same time, many advantages are reaped by minimizing the power consumption of the station, lowering component stress by shortening the operating time of certain components and by limiting the cycling rate of others, and by providing a more aesthetically acceptable station by reducing its obtrusive effects. 
     While the invention has been described according to what is presently considered to be the most practical and preferred embodiments, it must be understood that the invention is not limited to the disclosed embodiments. Those ordinarily skilled in the art will understand that various modifications and equivalent structures and functions may be made without departing from the spirit and scope of the invention as defined in the claims. Therefore, the invention as defined in the claims must be accorded the broadest possible interpretation so as to encompass all such modifications and equivalent structures and functions.