Scan module and reader for, and method of, electro-optically reading a target by adjusting reading parameters based on target distance

A reader for electro-optically reading a target located in a range of working distances relative to the reader, the reader comprising:

• a housing having a light-transmissive window;
• and
• a module mounted in the housing, the module including
• a laser for emitting a laser beam through the window to the target for reflection and scattering therefrom as return laser light,
• a first photodetector having a first collection area that is positioned on the module to receive the return laser light through the window, the first photodetector being operative for generating a first analog electrical output signal having a first magnitude upon receipt of the return laser light,
• a second photodetector having a second collection area that is positioned on the module to receive the return laser light through the window and that is in close proximity to the first collection area, the second photodetector being operative for generating a second analog electrical output signal having a second magnitude upon receipt of the return laser light, and
• signal processing circuitry including a controller for processing the first output signal to obtain information related to the target, for processing the first and the second output signals to determine a working distance to the target from the module, and for modifying at least one reading parameter by which the reading is performed based on the determined working distance,
• wherein the signal processing circuitry includes a first receiver channel connected to the first photodetector to process the first output signal, and a second receiver channel connected to the second photodetector to process the second output signal;
• and wherein the controller is operatively connected to the first and the second receiver channels, for processing the first and the second output signals to determine a ratio of the second magnitude to the first magnitude, for determining the working distance to the target from the module based on the determined ratio, and for modifying the at least one reading parameter based on the determined working distance.

A method of electro-optically reading a target located in a range of working distances, the method comprising:

• emitting a laser beam from a module to the target for reflection and scattering therefrom as return laser light;
• positioning a first collection area of a first photodetector to receive the return laser light, and to generate a first analog electrical output signal having a first magnitude upon receipt of the return laser light;
• positioning a second collection area of a second photodetector to receive the return laser light, and to generate a second analog electrical output signal having a second magnitude upon receipt of the return laser light;
• configuring the second collection area to be in close proximity to the first collection area;
• connecting a first receiver channel to the first photodetector to process the first output signal;
• connecting a second receiver channel to the second photodetector to process the second output signal;
• processing the first and the second output signals to determine a ratio of the second magnitude to the first magnitude;
• processing the first output signal to obtain information related to the target;
• processing the first and the second output signals to determine a working distance to the target from the module based on the determined ratio;
• and
• modifying at least one reading parameter by which the reading is performed based on the determined working distance.