Laser beam scanner with low cost ditherer mechanism

A resonant mechanical bar code scanning system for multiplexing at least two scanning beams from a beam of focused laser light and for collecting reflected light from a bar code comprising:

• first and second cantilever beams comprised of bimorphous piezoelectric material each having an end fixed in a supporting base and a free end for oscillation;
• first and second mirror means each attached to a corresponding free end of one of said first and second cantilever beams for scanning said focused laser light to a bar code and for collecting light reflected from said bar code;
• control means for alternately applying an ac voltage at or near resonant frequency to said first and second cantilever beams to cause said first and second mirror means to resonantly deflect substantially 90 degrees out of phase with one another such that the resonant deflection of said first mirror means is just sufficient to enable said focused laser light to strike said second mirror means during the linear portion of the second mirror's oscillation;
• a collection lens to receive the full aperture of both said first and second mirror means for collecting reflected light;
• decoder means responsive to said collected light and for producing an output signal representative of the information derived from said collected light.

A resonant mechanical scanning system for multiplexing at least two scanning beams from a beam of focused laser light comprising:

• first and second cantilever beams each having a first end fixed in a supporting base and a free end for oscillation;
• first and second mirror means each mounted on a respective free end of said first and second cantilever beams for scanning said beam of focused laser light into a plurality of desired scan lines;
• first and second coil means mounted to said supporting base in close proximity with said first and second cantilever beams for receiving an ac applied current;
• oscillating means, provided in said first and second cantilever beams, magnetically responsive to said ac current applied to said corresponding first and second coil means;
• control means for alternately applying said ac current at or near resonant frequency to said first and second coil means for oscillating said first and second cantilever beams in a sine wave 90 degrees out of phase with each other such that said beam of focused laser light is scanned by said first mirror means during the linear portion of its oscillation and the deflection of said first mirror means by reason of said oscillation is sufficient to enable said beam of focused laser light to be scanned by said second mirror means during the linear portion of the second mirror's oscillation;
• collection means for collecting light reflected from the scanned beams;
• decoder means for decoding information from said reflected light.

A resonant scan generator for multiplexing a scanning beam for scanning a bar code comprising:

• first and second cantilever beams, each having a free end for oscillation and an opposite, supporting end fixed in a base, such that the longitudinal axis of deflection of said first cantilever beam is disposed orthogonally with respect to the longitudinal axis of deflection of said second cantilever beam;
• first and second mirror means each mounted on the respective oscillating free end of said first and second cantilever beams, for scanning a focused laser beam through a locus of points defining a scan line;
• means for oscillating said first and second cantilever beams in a sine wave at a resonant frequency substantially 90 degrees out of phase such that said first and second mirror means are alternately activated for scanning said focused laser beam during the substantially linear portion of said sine wave oscillation;
• means for collecting the light reflected from said bar code being scanned;
• decoder means including detection means responsive to said collected light for decoding information from said collected light.

A resonant mechanical scan generator for scanning a bar code label comprising:

• first and second cantilever beams each having a free end for oscillation and an opposite end fixed in a supporting base such that the axis of deflection of said first cantilever beam is disposed orthogonally to the axis of deflection of said second cantilever beam;
• first and second laser diodes including focusing means each disposed on a corresponding free end of said first and second cantilever beams;
• means for oscillating said first and second cantilever beams in a sine wave at a resonant frequency, 90 degrees out of phase with each other;
• control means for alternately activating said first and second laser diodes during a substantially linear portion of said sine wave oscillation.

A bar code scanner for scanning a bar code comprising:

• at least one laser light source for producing a focused laser beam;
• a scan generator means comprising three or more substantially adjacent resonant mechanical systems, each oscillating in a sine wave generally equally out of phase with an adjacent one of said three or more resonant mechanical systems, wherein each of said resonant mechanical systems is sequentially activated for scanning during a substantially linear portion of said sine wave oscillation;
• collection means for collecting the light reflected from a bar code being scanned;
• electronic detection means responsive to said collected light for processing and decoding information from said collected light.

A method for scanning a bar code comprising the steps of:

• producing a focused laser beam;
• oscillating a plurality of scanning mirrors at a resonant frequency sequentially in a sine wave motion and generally equally out of phase with each other;
• activating each of said plurality of mirrors to sequentially scan said focused beam during the linear portion of each mirror's sine wave oscillation;
• collecting light reflected from the bar code;
• detecting said collected light;
• processing and decoding information from said collected light.