Method of driving a plurality of visible and invisible LEDs so as to produce an illumination beam having a dynamically managed ratio of visible to invisible (IR) spectral energy/power during object illumination and imaging operations
A method of driving a plurality of visible and invisible laser diodes so as to produce an illumination beam having a dynamically managed ratio of visible to invisible (IR) spectral energy/power during object illumination and imaging operations. The method involves supplying a plurality of visible laser and invisible laser diodes with a predetermined/default values of diode drive currents so as to illuminate the object with a spectral mixture of illumination during object illumination and imaging operations. One or more digital images of the illuminated object are captured and the image contrast quality thereof is measured, in real-time, so as to generate feedback or control data. This feedback or control data is used to dynamically generate the necessary values for the adjusted diode drive currents that are used to drive the visible and invisible laser diodes and produce an illumination beam having a dynamically managed ratio of visible to invisible (IR) spectral energy/power required to produce images of sufficient image contrast to ensure satisfactory image processing, while minimizing visual brightness to humans, at a POS station during object illumination and imaging operations.
1. A method of driving a plurality of visible and invisible laser diodes to produce an illumination beam having a dynamically managed ratio of visible to invisible spectral power (VIS/IR) during object illumination and imaging operations associated with digital imaging based code symbol reading operations carried out at a point of sale (POS) station, said method comprising the steps of:
(a) at said POS station, supplying a plurality of visible laser and invisible laser diodes with default values of diode drive current so as to illuminate an object with a spectral mixture of illumination during object illumination and imaging operations;
(b) at said POS station, capturing one or more digital images of the illuminated object using a digital image detection array, and measuring, in real-time, image contrast quality using a digital image processor so as to generate feedback or control data; and
(c) at said POS station, using said feedback or control data to dynamically generate adjusted values of diode drive current for use in driving said plurality of visible and invisible laser diodes and producing an illumination beam having a dynamically managed ratio of visible to invisible spectral power (VIS/IR) required to produce digital images of sufficient image contrast to ensure satisfactory image processing, while minimizing visual brightness to humans, at said POS station during object illumination and imaging operations.
2. The method of claim 1 , wherein step (c) comprises controlling the ratio between visible and infrared wavelength components by adjusting said diode drive currents supplied to said visible and invisible laser diodes, respectively.
3. The method of claim 1 , wherein said illumination beam is an illumination beam selected from the group consisting of planar, narrow-area and wide-area illumination beams.
4. The method of claim 1 , wherein during step (a), each said visible laser diode is a VLD, and wherein each said invisible laser diode is an IR laser diode (IR-LD).