POS-based digital image capturing and processing system using automatic object detection, spectral-mixing based illumination and linear imaging 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 a coplanar illumination and imaging station for projecting at least one coplanar illumination and imaging plane into an imaging volume during object illumination and imaging operations. The coplanar illumination and imaging station includes an illumination subsystem for producing a first field of visible illumination from an array of visible VLDs, and producing a second field of invisible illumination from an array of infrared (IR) laser diodes (IR-LDs). Wherein the first and second fields of illumination spatially overlap and intermix with each other and are substantially coplanar with the FOV of the linear image sensing array. An automatic object detection subsystem automatically detects an object moving through the 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 point of sale (POS)-based digital image capturing and processing system illuminating objects using automatic object detection, spectral-mixing based illumination and linear imaging techniques, said POS-based digital image capturing and processing system comprising:
a system housing installable at a POS station, and having an imaging window;
a coplanar illumination and imaging station disposed within said system housing, for projecting a coplanar illumination and imaging plane through said imaging window into an imaging volume during object illumination and imaging operations;
wherein said coplanar illumination and imaging station includes
(i) an image formation and detection (IFD) subsystem having a linear image sensing array and optics providing a field of view (FOV) on said linear image sensing array and extending into said imaging volume;
(ii) a spectral-mixing based illumination subsystem producing a first field of visible illumination from an array of visible laser diodes (VLDs), and producing a second field of invisible illumination from an array of infrared (IR) laser diodes (LDs);
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 coplanar 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 one or more digital images of an illuminated object detected by said linear image sensing array;
a digital image processing subsystem for automatically processing said one or more buffered digital images so as to read one or more 1D and/or 2D code symbols graphically represented in said one or more digital images;
an automatic object motion detection subsystem for automatically detecting the object moving through said 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 coplanar 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 the subsystems within said coplanar 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 illuminated object 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 the VLDs and IR-LDs during object illumination and imaging operations.
4. The POS-based digital image capturing and processing system of claim 3 , wherein said static 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 VLDs and IR-LDs 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 illumination at the POS station to ensure humans are not disturbed by said 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 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 the LEDs and IR-LDs during object illumination and imaging operations.
7. The POS-based digital image capturing and processing system of claim 6 , wherein said current supplied to the LEDs and IR-LDs are controlled, during object illumination and imaging operations, by the following process:
(i) driving the VLDs and IR-LDs with predetermined/default values of drive currents 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 the necessary values for the adjusted VLD and/or IR-LDs current control signals that are used to drive said LEDs and IR-LDs 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 of one or more digital images of the illuminated object and measuring image contrast quality is carried out within said image capturing and buffering 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 matrix symbols.