POS-based digital image capturing and processing system employing automatic object motion detection and spectral-mixing based illumination techniques
A POS-based digital image capturing and processing system for illuminating objects using automatic object detection and spectral-mixing illumination technique. The system comprises an area-type illumination and imaging station for projecting a coextensive area-type illumination and imaging field (i.e. zone) into a 3D imaging volume during object illumination and imaging operations. The area-type illumination and imaging station includes an illumination subsystem for producing a first field of visible illumination from an array of visible LEDs, and producing a second field of invisible illumination from an array of infrared (IR) LEDs. wherein the first and second fields of illumination spatially overlap and intermix with each other and are substantially coextensive with the FOV of the image sensing array. An automatic object motion detection subsystem automatically detects the motion of an object moving through the 3D imaging volume, while an illumination control subsystem controls the relative power ratio (VIS/IR) of visible illumination and invisible illumination during system operation so as to minimize the amount of visible illumination energy required to capture sufficiently high-contrast images of said objects and successfully process the same.
1. A POS-based digital image capturing and processing system illuminating objects using automatic object detection and spectral-mixing based illumination techniques, said POS-based digital image capturing and processing system comprising:
a system housing installable at a POS station, and having an imaging window;
an area-type illumination and imaging station disposed within said system housing, for projecting a coextensive area-type illumination and imaging field through said imaging window into a 3D imaging volume during object illumination and imaging operations;
wherein said area-type illumination and imaging station includes
(i) an image formation and detection (IFD) subsystem having an area-type image sensing array and optics providing a field of view (FOV) on said area-type image sensing array and extending into said 3D imaging volume;
(ii) a spectral-mixing based illumination subsystem producing a first field of visible illumination from an array of visible light emitting diodes (LEDs), and producing a second field of invisible illumination from an array of infrared (IR) LEDs;
wherein said first and second fields of illumination spatially overlap and intermix with each other to produce a composite spectrally-mixed illumination beam that is substantially coextensive with said FOV;
(iii) an illumination control subsystem for controlling the relative power ratio of visible illumination and invisible illumination (VIS/IR) during system operation; and
(iv) an image capturing and buffering subsystem for capturing and buffering digital images of the illuminated object detected by said area-type image sensing array;
a digital image processing subsystem for automatically processing said buffered digital images so as to read one or more 1D and/or 2D code symbols graphically represented in said digital images;
an automatic object motion detection subsystem for automatically detecting the motion of an object moving through said 3D imaging volume, and generating signals indicative of said detected object motion; and
a control subsystem, responsive to said signals generated by said automatic object motion detection subsystem, for controlling and/or orchestrating the operations of the subsystems within said area-type illumination and imaging station.
2. The POS-based digital image capturing and processing system of claim 1 , wherein said control subsystem controls and/or orchestrates the operations of subsystems within said area-type illumination and imaging station, so as to minimize the amount of visible illumination energy contained within said composite spectrally-mixed illumination beam and required to capture sufficiently high-contrast images of said objects and successfully process the same.
3. The POS-based digital image capturing and processing system of claim 1 , wherein said illumination control subsystem statically controls the relative power ratio of visible illumination and invisible illumination (VIS/IR) within said composite spectrally-mixed illumination beam during system operation, by way of controlling the current supplied to said visible LEDs and infrared LEDs during object illumination and imaging operations.
4. The POS-based digital image capturing and processing system of claim 3 , wherein said statically-controlled relative power ratio of visible illumination and invisible illumination (VIS/IR) is realized by setting one or several different preset values of current supplied to drive said arrays of visible and IR LEDs employed in said spectral-mixing based illumination subsystem.
5. The POS-based digital image capturing and processing system of claim 1 , wherein said relative power ratio of visible illumination and invisible illumination (VIS/IR) is optimized under different operating situations in an effort to (i) reduce the visual brightness of said composite spectrally-mixed illumination beam at the POS station to ensure humans are not disturbed by the illumination field, as well as to (ii) achieve sufficient image contrast in captured digital images to ensure satisfactory image processing in said POS-based digital image capturing and processing system.
6. The POS-based digital image capturing and processing system of claim 5 , wherein said spectral mixing based illumination control subsystem dynamically and adaptively controls the relative power ratio of visible illumination and invisible illumination (VIS/IR) during system operation by controlling the current supplied to said visible LEDs and IR-LEDs during object illumination and imaging operations.
7. The POS-based digital image capturing and processing system of claim 6 , wherein said current supplied to said visible LEDs and IR LEDs sre controlled, during object illumination and imaging operations, by the following process:
(i) driving said visible LEDs and said IR LEDs with predetermined/default values of current so as to illuminate the object with a spectral mixture of illumination;
(ii) capturing one or more digital images of the illuminated object and measuring image contrast quality so as to generate feedback or control data; and
(iii) using this feedback or control data to dynamically generate adjusted values of current supplied to drive said visible LEDS and IR LEDs, and produce an optimal mixture of illumination during object illumination and imaging operations.
8. The POS-based digital image capturing and processing system of claim 7 , wherein said capturing one or more digital images of the illuminated object and measuring image contrast quality is carried out within said digital image processing subsystem.
9. The POS-based digital image capturing and processing system of claim 1 , wherein said automatic object motion detection subsystem comprises an imaging-based object motion detection subsystem including an area-type image acquisition subsystem and a digital signal processing chip to support digital image capture and processing operations required for real-time object motion detection.
10. The POS-based digital image capturing and processing system of claim 1 , wherein said 1D and/or 2D code symbols are selected from the group consisting of 1D bar code symbols, 2D bar code symbols and 2D data matrix symbols.