Apparatus for and method of electro-optically reading a target in the presence of ambient light

摘要

A reader for electro-optically reading a target in the presence of ambient light, includes a scan component for scanning a laser beam across the target, a first filter for passing return laser light from the target and the ambient light to a first photodetector system for generating a first output signal constituted of an information signal and a first ambient light signal, a second filter for passing the ambient light to a second photodetector system for generating a second output signal constituted of a second ambient light signal, and signal processing circuitry for measuring a difference between the first and second ambient light signals, for equalizing the first and second ambient light signals when the difference exceeds a threshold, and for subtracting the second output signal from the first output signal to obtain a receiver output signal substantially constituted only of the information signal.

主权项

1. A reader for electro-optically reading a target in the presence of ambient light, comprising:
a laser for emitting a laser beam; a scan component for scanning the laser beam across the target for reflection and scattering therefrom as return laser light; a first filtering system for passing the return laser light from the target and the ambient light; a first photodetector system for receiving the return laser light and the ambient light passed by the first filtering system, and for generating a first analog electrical output signal constituted of an information signal bearing information related to the target from the return laser light, and a first ambient light signal from the ambient light; a second filtering system for passing the ambient light; a second photodetector system for receiving the ambient light passed by the second filtering system, and for generating a second analog electrical output signal constituted of a second ambient light signal from the ambient light; signal processing circuitry including a controller for measuring a difference between the first and second ambient light signals, the signal processing circuitry being operative for substantially equalizing the first and second ambient light signals when the difference exceeds a threshold, and for subtracting the second output signal from the first output signal when the first and second ambient light signals are equalized to obtain a receiver output signal substantially constituted only of the information signal; wherein the laser beam has a laser frequency, wherein the first filtering system has a first optical filter having a frequency passband for passing the laser frequency and a frequency of the ambient light, and wherein the second filtering system has a second optical filter having a frequency passband for attenuating the laser frequency and for passing the frequency of the ambient light; and wherein the first optical filter overlies the first and second photodetector systems, and wherein the second optical filter only overlies the second photodetector system.