Object sensing system for bar code laser scanners

A method for automatically switching a laser scanning system from a sleep mode of operation to a scan mode of operation, said laser scanning system having a means for generating light over a scanning field and a means for receiving light reflected off an object or surface in said scanning field, said method comprising the steps of:

• a) generating a steady state voltage signal having a value proportional to the strength of reflected light received off a background surface or object when said system is in said sleep mode of operation;
• b) generating positive and negative threshold voltage signals having predetermined voltage levels respectively greater than and less than that of said steady-state voltage signal;
• c) detecting when an object is placed in said scanning field including the step of determining when said steady state voltage signal increases to a level above that of said positive threshold voltage signal or decreases to a level below that of said negative threshold voltage signal depending upon the object's reflectivity, and including the step of generating an output signal in response thereto;
• and
• d) switching said laser scanning system from said sleep mode into said scan mode upon receipt of said output signal.

A scanning system for reading bar code symbols, said systems having a sleep mode of operation and a scanning mode of operation, comprising:

• a. a first light source for emitting a light beam over a field of view;
• b. second light source for emitting a scanning light beam over said field of view during said scanning mode operation;
• and
• c. a sensor for detecting the variable intensity of the returning portion of the reflected light from said first and said second light sources over the field of view, and for generating a signal when an object is placed in the field of view to switch said system from said sleep mode to said scanning mode of operation.

Apparatus for reading bar code symbols or the like on a target comprising:

• a. means for generating a first fixed light beam directed towards a target in a field of view;
• b. means for receiving reflected light from such target to produce electrical signals corresponding to the reflectivity of the surface of the target;
• c. means for processing said electrical signals to detect if an object is moved into or through said field of view;
• and
• d. means for generating a scanning second light beam in response to the presence of an object in the field of view and processing said electrical signals to read a bar code symbol on a surface of such object.

Apparatus for reading bar code symbols or the like on a target comprising:

• a. means for generating a first light beam pulsed at a first predetermined frequency in a first mode of operation and operated continuously in a second mode of operation, said beam being directed towards a target in a field of view, and for receiving reflected light from such target to produce electrical signals corresponding to the reflectivity of the surface of the target;
• b. means for processing said electrical signals during said first mode of operation to detect if an object is moved into or through said field of view;
• and
• c. control means for responsive to the presence of an object in the field of view to generate a scanning second light beam to read a bar code symbol on a surface of such object.

Apparatus for reading bar code symbols or the like on a target comprising:

• a. means for generating a first fixed light beam directed towards a target in a field of view and having an active, an intermediate, and an "off" mode of operation;
• and
• b. detector means for receiving reflected light from such target to produce electrical signals corresponding to the reflectivity of the surface of the target;
• c. means for processing said electrical signals and determining if an object is moved into or through said field of view;
• and
• d. means for generating a scanning second light beam in response to the presence of an object in the field of view to read a bar code symbol on a surface of such object;
• and
• e. means for scanning said second light beam across said target.

A method for reading bar code symbols or the like on a target comprising the steps of:

• a. generating a first fixed light beam directed towards a target in a field of view, and receiving reflected light from such target to produce electrical signals corresponding to the reflectivity of the surface of the target;
• b. processing said electrical signals and detecting if an object is moved into or through said field of view;
• and
• c. generating a scanning second light beam in response to the presence of an object in the field of view to read a bar code symbol on a surface of such object.

A method for reading bar code symbols or the like on a target comprising the steps of:

• a. generating a first light beam pulsed at a first predetermined frequency in a first mode of operation and operated continuously in a second mode of operation, said beam being directed towards a target in a field of view, and for receiving reflected light from such target to produce electrical signals corresponding to the reflectivity of the surface of the target;
• b. processing said electrical signals during said first mode of operation to detect if an object is moved into or through said field of view;
• and
• c. generating a scanning second light beam to read a bar code symbol on a surface of such object responsive to the presence of an object in the field of view.