Abstract:
An arrangement for and a method of collecting and displaying information in real time along a line of sight from a human operator to remote targets located at variable distances therefrom and identifiable by machine-readable indicia. A two-dimensional image is automatically projected along the line of sight on the target alongside the indicia while maintaining the image size relatively constant over an extended range of working distances.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to an electro-optical arrangement for and method of collecting and displaying information in real time along a line of sight from a human operator to remote targets located at variable distances therefrom and identifiable by machine-readable indicia and, more particularly, to automatically displaying a two-dimensional image on each target adjacent its indicia along the line of sight while maintaining a size of the image relatively constant over an extended range of the distances. 
   2. Description of the Related Art 
   It is generally known to project a two-dimensional image on a screen based on a pair of scan mirrors which oscillate in mutually orthogonal directions to scan a laser beam over a raster pattern. However, the known image projection systems have limited resolution, typically less than a fourth of video-graphics-array (VGA) quality of 640×480 pixels. Also, the image produced by the known projection systems is typically only sharp and clear at a single distance, or at most, a limited range of distances, away from the systems. The physical size and power consumption of the known projection systems are relatively high, thereby rendering them impractical for use in miniature, battery-operated, operator-wearable, hand-held or finger-supported applications. 
   It is also generally known to display an image on a screen of a data collection terminal worn on an operator&#39;s wrist or belt. Data is entered in such wrist- or belt- worn terminals, either manually by keyboard entry, or automatically by an electro-optical reader mounted on the back of one or more of the operator&#39;s fingers. The data captured by the reader is sent by wired or wireless link to the terminal, and information corresponding to the captured data is displayed on the terminal screen, typical a liquid crystal display (LCD) device. See, for example, U.S. Pat. No. 5,578,810; No. 5,410,140; No. 5,543,610 and No. D-391,250, for examples of known finger-mounted optical readers. 
   Experience has shown, however, that the known data collection systems that employ a wrist- or belt- worn terminal coupled to a finger-mounted reader are not altogether satisfactory due to the requirement that the operator has to repeatedly redirect his/her line of sight during use. Under normal operation, the operator initially directs his/her eyes along a line of sight to indicia, such as a bar code symbol, typically printed on a label affixed to a target, such as a parcel to be delivered. The operator aims the reader at the symbol, initiates a scan, and then waits for auditory or visual confirmation that the symbol has been successfully read. 
   The system then processes the data collected by the reader and typically displays information related to the processed data on the terminal. Since the terminal is mounted, as previously described, on one&#39;s wrist or belt, the operator must turn his/her head, or at least redirect the focus of his/her eyes along a different light of sight in order to see the displayed information on their wrist or belt. When performing multiple repeated scans of successive symbols on successive targets, this constant redirection of one&#39;s eyes slows productivity and causes discomfort. 
   SUMMARY OF THE INVENTION 
   OBJECTS OF THE INVENTION 
   Accordingly, one object of this invention is to collect and automatically display information in real time along a line of sight from a human operator to a remote target. 
   Another object of this invention is to reduce, if not eliminate, the requirement for an operator to shift his/her gaze during data collection and display. 
   Still another object of this invention is to improve productivity and reduce operator discomfort during use of data collection and display arrangements. 
   FEATURES OF THE INVENTION 
   In keeping with the above objects and others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an arrangement for, and a method of, collecting and displaying information in real time along a line of sight from a human operator to remote targets located at variable distances therefrom. Each target is identifiable by a machine-readable indicium associated therewith. For example, the indicium may be a one-or two-dimensional bar code symbol printed on a label that is adhered to a parcel to be delivered. The symbol identifies the parcel, and the operator may be a commercial courier whose job is to pick up and deliver the parcel, as well as to read the symbol and enter its encoded data into a tracking network so that the parcel can be tracked during delivery. 
   The operator initiates reading of the symbol by looking at the symbol, aiming an electro-optical reader at the symbol, and manually actuating the reader. During these actions, the operator&#39;s gaze is directly on the symbol to insure that light emitted, or captured, by the reader is directed to, or reflected off, the symbol. The reader processes data read from the symbol and retrieves information for display. The retrieved information can be a price obtained from a look-up table, an inventory number obtained from a database and, in short, any information which it is desired for the operator to know at the time of data collection. 
   The reader, or at least major components thereof, is contained in a portable housing supported by the operator. For example, the housing can include a ring mount for supporting the housing on the back of one or more of the operator&#39;s fingers. 
   Also contained in the housing is an image projector. The projector includes a light source, for example, a solid-state laser for emitting a laser beam, a scanner for sweeping the light beam in a pattern of scan lines on the target, each scan line having a number of pixels, and a controller for choosing selected pixels in the pattern based on the data obtained by the reader, and for causing the selected pixels to be illuminated and rendered visible by the laser beam, thereby producing a two-dimensional image on the target adjacent the symbol on the target. 
   In accordance with one aspect of this invention, the projection of the image on the target automatically occurs after reading of the symbol and, in order to view the image, the operator need not avert his/her gaze. During data collection and display, the operator need never move his/her head or eyes, or change their point of view, which is always directed to the target. This feature improves productivity and operator comfort. 
   Still another feature of this invention resides in controlling the size of the image over an extended range of distances between the target and the housing. Thus, a target may be several inches, or many feet, away from the housing supported by the operator. A projected image increases in area as a function of increasing distance from the projector, and vice versa. In some cases, the image may be too small for a close-in target, or too big for a far-out target. The operator typically moves his/her hand toward and away from the target to obtain an image more amenable to be easily viewed. 
   This invention provides a rangefinder for determining the distance of the target, and for controlling the size of the image based on the determined distance. Preferably, the size of the image is kept relatively constant over an extended range of distances in which the targets may be located. A constant image size provides the operator with a constant viewing experience and avoids the hand movements described above which, over time, leads to operator fatigue. The rangefinder can be mounted on the housing. It is also possible to have a prior knowledge of the size of the indicia being read and to use that information to determine distance. 
   The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a data collection and display system according to this invention; 
       FIG. 2  is a perspective view of one embodiment of a finger-mounted housing for use in the system of  FIG. 1 ; 
       FIG. 3  is a perspective view of another embodiment of a finger-mounted housing for use in the system of  FIG. 1 ; 
       FIG. 4  is a block diagram of a reader for use in the system of  FIG. 1 ; 
       FIG. 5  is a block diagram of an image projector for use in the system of  FIG. 1 ; 
       FIG. 6  is a perspective view of still another embodiment of a finger-mounted housing during image projection; and 
       FIG. 7  is a perspective view of a module on which components of the reader and projector are mounted for installation in a housing for use in the system of FIG.  1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference numeral  10  generally identifies a data collection and display system according to this invention. System  10  includes a mobile terminal  12  worn on a belt  14  of an operator  16 , a wrist-worn peripheral  18  including a wrist strap  20  worn around a wrist  22  of the operator  16 , and a finger-mounted housing  24  mounted on a forefinger  26  of the operator  16 . 
   As explained in detail below, the operator  16  directs his eyes along a line of sight, points his outstretched forefinger  26 , and aims the housing  24 , at a target  28 , for example, a shipping carton, on which an indicium, for example, a two-dimensional bar code symbol  30 , is printed on a label  32  adhered to the carton  28 . The operator then manually actuates an electro-optical reader mounted in the housing  24  by manually depressing a trigger  34  with his thumb  36 . The reader reads and processes the symbol, and passes processed information to the peripheral  18  by means of a cable  38 . The peripheral  18 , in turn, passes the processed information to the terminal  12  by a wireless link  40 , for example, using a short-haul protocol, such as Bluetooth™ The terminal  12 , in turn, forwards the received information over another wireless link  42  to a wireless router  44  via an IEEE 802.11 protocol. The router  44 , in turn, forwards the information to a wired server  46  which accesses a database or lookup table and retrieves information therefrom for display to the operator. The server  46  sends this retrieved information to the router  44 , the terminal  12 , the peripheral  18  and to an image projector in the finger-mounted housing  24 . The image projector, as detailed below, projects a two-dimensional image  48 , for example, the price: “$12.99” on the carton  28  adjacent the symbol  30 . This image  48  is visible to the operator who need not turn his/her head, or change his/her gaze or line of sight to read the image. The operator&#39;s attention is always on the carton, thereby improving operator productivity and comfort. 
     FIG. 2  depicts the housing  24  on the outstretched finger  26 . An electro-optical reader  60  and an image projector  62 , or at least major components thereof, are mounted in the housing  24 .  FIG. 4  depicts circuit components of the reader  60 .  FIG. 5  depicts circuit components of the projector  62 . As explained below, the reader generates an analog signal indicative of the variable intensity of light received from the symbol. This analog signal is digitized by a digitizer  50  and then decoded by a decoder  52 . In  FIG. 2 , the analog signal is conducted along the cable  38  to the peripheral  18  in which the digitizer  50  and decoder  52  are contained. In  FIG. 3 , the digitizer  50  and the decoder  52  are contained within the housing  24 , thereby eliminating the cable  38  and the peripheral  18 . A wireless transceiver  54  in the housing  24  is used to communicate with a corresponding transceiver  56  in the terminal  12 .  FIGS. 2 and 3  both show a ring mount  58  for mounting the housing on a finger of the operator. The housing  24  includes a pair of light-transmissive windows  62 ,  64 , one for the reader, and the other for the projector, although it is possible to incorporate both windows  62 ,  64  into a single window, as described below. 
   Before turning to the block diagrams of  FIGS. 4-5 , it should be mentioned that many variants of the system  10  are possible. As previously described, the cable  38  and the peripheral  18  could be eliminated. The housing  24  itself need not be finger-mounted, but could be held in one&#39;s hand like a pen, a gun, a flashlight, or a personal digital assistant, or could be supported by another part of the operator&#39;s body, or could be worn on one&#39;s clothing or body as, for example, incorporated into eyeglasses or a helmet. The wired or wireless links between the terminal, router and server could be changed and, indeed, in some applications one or more of these pieces of equipment could be eliminated. 
   Referring now to  FIG. 4 , the reader  60  includes a light source, such as a solid-state, visible laser diode  66  operative for directing a laser beam through focusing optics  68  to a scan mirror  70  oscillatable by a scanner  72  to sweep the laser beam through the window  62  on and across the indicia  30  on the target  28 . The illustrated arrangement generates a single scan line extending in one direction across the symbol which is suitable for reading one-dimensional symbols, such as UPC symbols. A second scan mirror and scanner can be employed to generate a pattern of scan lines arranged along a second direction perpendicular to said one direction, the pattern being suitable for reading two-dimensional symbols. 
   Light reflected off the symbol is detected by a sensor  74 , for example, a photodiode, operative for generating an electrical analog signal indicative of the detected intensity of the light reflected from the symbol. This analog signal, as previously mentioned, is digitized in the digitizer  50 , decoded in the decoder  52 , and sent by the transceiver  54  to an antenna  76 , all under control of a controller  80 , e.g., a programmed microprocessor. A battery  78 , preferably rechargeable, is used to supply electrical power to all the electronic components in the housing  24 . The trigger  34  is connected to the controller  80 . 
   The reader  60  thus generates a decoded signal which identifies the target or some characteristic thereof. The system employs this identifying signal to access a database or look-up table to retrieve some information corresponding to the identifying signal. This could be a shipping price, or an amount of goods in inventory, or the like. This retrieved information is sent back by the system to the projector  62  for the purpose of displaying the retrieved information. 
   Before turning to  FIG. 5 , it should be mentioned that the reader need not employ a laser  66  and photodiode  74 , as is used in moving beam readers, but could be an imager in which a charge-coupled device (CCD) array, or similar two-dimensional array, is used to image the symbol, and then to decode the symbol based on analysis of the image. 
   The image projector  62  of  FIG. 5  includes a light source such as a laser  82  energized by a drive  84  to emit a laser beam to a first X-mirror  86  oscillatable by an X-drive  88  for horizontally moving the laser beam back and forth at a first sweep frequency f h  along a first direction, commonly termed “X-axis” sweeping, and, in turn, to a second Y-mirror  90  oscillatable by a Y-drive  92  for vertically moving the laser beam up and down at a second sweep frequency f v  along a second direction, commonly termed “Y-axis” sweeping. The first and second directions are mutually orthogonal. The first or horizontal sweep frequency is generally much faster than the second or vertical sweep frequency. In the preferred embodiment, f v ≧40 Hz and f h ≧3.8 kHz or n(f v ) where n is the number of pixels within one horizontal sweep. 
   A control processor  94  is operative for controlling a time synchronizing generator  96  which, in turn, controls the X-drive  88  and the Y-drive  92  to insure that the X-mirror  86  and the Y-mirror  90  oscillate at the correct speeds. An X-scanner feedback circuit  98  and a Y-scanner feedback circuit  100  monitor the sweep frequencies and scan angles of the mirrors  86 ,  90  and assist the drives  88 ,  92  in maintaining the rated speeds and scan angles. A crystal oscillator  102  serves as the master clock. In addition, the feedback circuits  98 ,  100  can be used to control the brightness of the laser spot as it traverses the screen so that uniform brightness across the screen is obtained. The time synchronizing generator  96  also controls the laser drive  84  to control when the laser  82  is energized to emit its laser beam. 
   The same laser  66 ,  82  can be used for reading and for image projection. The mirrors  70 ,  86  and their drives can also be shared. The Y-mirror  90  is shared only when two axis reading is desired. The controllers  80 ,  94  are shared. 
     FIG. 6  depicts a modified finger-mounted housing  110 , again containing the reader  60  and the projector  62  therein, and sharing as many of the components described above as possible in order to make the housing more compact and lightweight. A single window  112  is shown for both reading and image projection. A strap  114  allows the housing to be sized on one or more of the operator&#39;s fingers. A pair of triggers  116 ,  118  is provided to initiate different operational modes as described below. 
   The projector produces a resulting light pattern known as a “raster” which is identified in  FIG. 6  by the reference numeral  120 . Starting at point A, a spot of focused light from the laser  82  is swept by the drive  88  at the horizontal frequency along the X-direction to the point B to form a first scan line. Thereupon, the drive  92  sweeps the spot from the point B at the vertical frequency along the Y-direction to form a second scan line. The formation of successive scan lines proceeds in the same manner. In a preferred embodiment, for a display area measuring on the order of 4 square inches (e.g., 2.25 inches×1.75 inches) at a distance of about 5 inches from the window  112 , the resolution of the raster is about 120 lines or pixels along the height (Y-direction) and about 64 pixels along the width (X-direction). 
   The image  48  is created in the raster pattern  120  by pulsing the laser  82  on and off at selected times under the control of the processor  94  and the generator  96  which, in turn, control the laser drive  84 . The laser  82  produces visible light and is turned on only when a pixel in the desired image is desired to be seen. For example, the numeral “1” in the image word “$12.99” in  FIG. 6  is formed by turning the laser on at pixel D in a scan line, and again at pixel E in another scan line, and so on until the vertical leg of the numeral “1” is formed. 
   Every letter or number can be formed by this technique. Indeed, any image, including graphical designs and logos, and even bar code symbols, can be formed from a plurality of such illuminated pixels arranged along the X- and Y- axes. Fonts can be stored in a font file  122  in memory  124  for access by the processor  94 . 
   The image area is roughly 4 to 8 square inches to achieve a contrast ratio of around 4:1 to enable easy viewing. A larger image area would require the laser power to exceed CDRH-II safety levels if the display brightness and contrast ratio are to be maintained. Conversely, the brightness and contrast ratio are reduced for an increased display area if the laser power is kept constant. 
   The display area can be changed dynamically by changing the scan angles of the mirrors  86 ,  90 , by changing the actuation power to the scan mirrors, or by slightly changing the drive frequencies. The image height is scanned at a minium of 40 Hz to reduce flicker. The X-mirror  86  is preferably a flat mirror mounted on a torsional band. The center of rotation of the mirror is symmetrical to the rotating axis to minimize audible noise. The display area is preferably rectangular. 
   The laser power is preferably varied with the scan speed to maintain a display of uniform visibility. The product of laser power and pixel duration should remain a constant throughout the display. The on-off duration of each spot during a scan line can be varied so that the lines resolution can be considered “infinite”. 
   The assembly can fit in a volume of about 0.5 cubic inches and, hence, can fit in a housing configured as a pen, a ring, a key chain, a pendant, or any other device having a small form factor. Preferably, the components of the assembly are mounted on a common support, such as a printed circuit board, and constitute a compact module  130  of rectangular, parallelepiped shape. 
   Referring to  FIG. 7 , the module  130  includes a support  132 , for example, a printed circuit board, and a laser/optics casing  134  in which are mounted the laser  82  (see  FIG. 5 ) and optics operative for optically modifying a laser beam emitted by the laser. 
   The laser beam exiting the casing  134  is directed to, and reflected off, a stationary bounce mirror  136 . A scanner is also mounted on the board  132  and includes the first scan mirror  86  oscillatable by the inertial drive  88  at a first scan rate to sweep the laser beam reflected off the bounce mirror over a first horizontal scan angle, and the second scan mirror  90  oscillatable by the electromagnetic drive  92  at a second scan rate to sweep the laser beam reflected off the first scan mirror  86  over a second vertical scan angle. 
   The inertial drive  88  is a high-speed, low electrical power-consuming component. Details of the inertial drive can be found in U.S. patent application Ser. No. 10/387,878, filed Mar. 13, 2003, assigned to the same assignee as the instant application, and incorporated herein by reference thereto. 
   The electromagnetic drive  92  includes a permanent magnet  138  jointly mounted on and behind the second scan mirror  90 , and an electromagnetic coil  140  operative for generating a periodic magnetic field in response to receiving a periodic drive signal. The coil  140  is adjacent the magnet  138  so that the periodic field magnetically interacts with the permanent field of the magnet  138  and causes the magnet and, in turn, the second scan mirror  90  to oscillate. The coil  140  is supported by an upright wall  142  connected to the board  132 . 
   The inertial drive  88  oscillates the scan mirror  86  at a high speed at a scan rate preferably greater than 5 kHz and, more particularly, on the order of 18 kHz or more. This high scan rate is at an inaudible frequency, thereby minimizing noise and vibration. The electromagnetic drive  92  oscillates the scan mirror  90  at a slower scan rate on the order of 40 Hz which is fast enough to allow the image to persist on a human eye retina without excessive flicker. 
   The faster mirror  86  sweeps a horizontal scan line, and the slower mirror  90  sweeps the horizontal scan line vertically, thereby creating a raster pattern which is a grid or sequence of roughly parallel scan lines from which the image is constructed. Each scan line has a number of pixels. The image resolution is preferably VGA quality of 640×480 pixels. In some applications, a one-half VGA quality of 320×480 pixels, or one-fourth VGA quality of 320×240 pixels, is sufficient. 
   The image is constructed by selective illumination of the pixels in one or more of the scan lines. As described above, the controller  94  causes selected pixels in the raster pattern to be illuminated, and rendered visible, by the laser beam. For example, the laser drive  84  conducts an electrical current to the laser  82  to energize the latter to emit light at each selected pixel, and does not conduct an electrical current to the laser  82  to deenergize the latter to non-illuminate the other non-selected pixels. The resulting pattern of illuminated and non-illuminated pixels comprise the image  48 , which can be any display of human- or machine-readable information or graphic. Instead of the laser drive  84 , an acousto-optical modulator could be used to deflect the laser beam to any desired pixel in the raster pattern to illuminate the pixel, or to deflect the laser beam away from any desired pixel to non-illuminate the pixel. 
   The common trigger  34  can be used to initiate the reading and to control the duration of the projection display. For example, activation of the reading occurs on the initial press. By holding down the trigger, the projection is enabled until the button is released and is then re-armed for a subsequent read. By holding the trigger, the operator can shift the image  48  to any desired projection surface. Other than using a single trigger, the dual triggers  116 ,  118  could be independently operable, one for reading, and the other for image projection. 
   The data projected is designed to be relatively limited in content and programmable from the mobile terminal  12 . For example, the operator may take the terminal  12  off of the belt  14  and, using a small keypad  150  and a display  152 , the operator might select an option to project price, or inventory quantity. Once configured, the terminal is placed back on the belt. By limiting the amount of information displayed, it becomes more intelligible when projected on complex surfaces. Alternatively, the arrangement may incorporate switching mechanisms allowing the operator to project configuration options and to select the desired information to be displayed. 
   Furthermore, the size of the image is configurable. It is desirable for any form of data collection device to have a wide working range and be able to read a symbol within close proximity thereof or at a far distance therefrom. If the scan angles are constant, then the operator sees a different size image depending on the distance from the device to the projection plane. This causes the operator to move his/her hand either further from, or closer to, the projection plane to obtain a more amenable image. To provide a constant experience without such compensating hand movement, the housing can be supplemented with a ranging mechanism  154  to measure its distance from the projection plane. Based on the measured distance, the controller varies the scan angles so as to maintain a constant image size. Rather than varying the scan angles, the size of the field of view could be changed, although at the cost of poorer image resolution. The ranging mechanism  154  can be an infrared or ultrasonic rangefinder. 
   In order to be effective (small size, long battery life), the arrangement must take measures to reduce power consumption. Given the approximate equivalent of VGA resolution (640×480 pixels) and 8 bits/pixel for quantizing or processor packing, the complete image occupies 300 kilobytes. In conventional systems, the image would be transferred into an external memory, and then accessed by the processor from external memory. External bus devices present high capacitive loads causing CMOS based electronics to consume high levels of power. It is proposed that the exemplary embodiment of this invention use a processor with embedded DRAM. Image data captured from the reflection of the laser will be transferred to and processed directly from the embedded DRAM. The decoded image will be moved to either external memory or transferred across the wireless link to the belt-worn terminal. 
   In addition, the arrangement will be configurable to read either one-dimensional or two-dimensional symbols. When configured for one-dimensional barcodes, the laser&#39;s rastering is disabled and a more simplistic decode algorithm is applied, both of which reduce power consumption as compared to a two-dimensional scan. 
   In a minimalist configuration, the trigger  34  controls the reading and the projection of pre-configured information. It is possible that configuration can be achieved by either using a more complex switch (e.g., a scroll wheel with activation) or through a sequence of timed switch triggers. For example, the user may rapidly double-click the trigger, thereby putting the arrangement into a configuration mode. The arrangement can project a set of options, of which the top one would be highlighted. A single click can scroll down. Once the desired option is found, the operator may press and hold the trigger down to activate the desired option and return to an operational state. 
   It will be understood that each of the elements described above, or two or more together, also may find a useful application in other types of constructions differing from the types described above. 
   While the invention has been illustrated and described as embodied in an arrangement for and method of collecting and displaying information in real time along a line of sight, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   For example, rather than reading bar code symbols, the target can be equipped with a radio frequency (RF) tag or transponder electronically programmed with unique information related to the target, and an RF identification system can include a reader or interrogator configured as a handheld device. The reader typically includes an antenna or coil packaged with a transceiver (with decoder). The reader emits radio waves in range of one inch to 100 feet or more depending upon power output and frequency. When the tag passes through the zone of radio waves, it detects the reader&#39;s activation signal. The reader decodes the data encoded in the tag, and the decoded data is passed to a host for processing. The tags can be active or passive. Other types of readers could be used, such as magnetic stripe readers. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims. 
   What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.