Digital image capturing and processing system employing automatic object detection and spectral-mixing based illumination techniques
A 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 module 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 module includes a spectral-mixing based 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 produce a composite illumination field that is at least substantially coextensive with the FOV of the image sensing array. An automatic object detection subsystem automatically detects 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 operations so as to achieve sufficient image contrast in captured digital images to ensure satisfactory image processing.
1. A digital image capturing and processing system comprising:
a system housing having an imaging window;
an area-type illumination and imaging module 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 module includes
(i) an image formation and detection (IFD) subsystem having an image sensing array and optics providing a field of view (FOV) on said 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 illumination field that is at least 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 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 detection subsystem for automatically detecting 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 detection subsystem, for controlling and/or orchestrating the operations of the subsystems within said area-type illumination and imaging module.
2. The 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) during system operation by controlling the drive currents supplied to said arrays of visible LEDs and IR LEDs during object illumination and imaging operations.
3. The digital image capturing and processing system of claim 2 , wherein said relative power ratio of visible and invisible illumination is realized by setting one or several different preset values of drive current supplied to drive said arrays of visible and IR LEDs employed in said spectral-mixing based illumination subsystem.
4. The digital image capturing and processing system of claim 3 , wherein said illumination control subsystem dynamically and adaptively controls said relative power ratio of visible illumination and invisible illumination during system operation by controlling the drive currents supplied to said arrays of visible LEDs and IR LEDs during object illumination and imaging operations.
5. The digital image capturing and processing system of claim 4 , wherein said drive current supplied to said arrays of visible LEDs and IR LEDs are controlled, during object illumination and imaging operations, by the following process:
(i) driving said array LEDs and IR LEDs with a 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 adjusted drive currents that are used to drive said array of visible LEDs and IR LEDs and produce an optimal mixture of illumination during object illumination and imaging operations.
6. The digital image capturing and processing system of claim 5 , 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.
7. The 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.
8. The 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.