Method and apparatus for controlling the focus of a read/write head for an optical scanner

An optical scanning device, comprising:

• a scanning head with an array of optical fibers, each extending to an outside of said scanning head, resulting in an array of light output apertures coinciding with ends of said optical fibers;
• a focusing element with one-to-one mapping ratio to a target surface on which light from said output is imaged;
• said focusing element being such that an amount of return light returned from said target surface back to said output when said focusing element is properly focused is at a maximum;
• said focusing element being such that an amount of return light returned from said target surface back to said output when said focusing element is improperly focused is less than said maximum;
• a detector in a return path of light in said scanning head, said detector generating an output responsive to said return light;
• a controller programmed to control a configuration of said focusing element responsive to said output such that said return light is maintained at said maximum.

A method of controlling a focus of a scanning device comprising the steps of:

• imaging, with a one-to-one mapping, an output of said scanning device through a focusing element and onto a target surface to be read by said scanning device;
• receiving, at an aperture, light returned from the target surface;
• and
• controlling a focus by adjusting a position of said focusing element to maintain the returned light at a maximum.

An optical scanning device, comprising:

• a scanning head with an array of light guides, each extending to an aperture from which light injected into said each of said array is emitted;
• a focusing element for focusing light onto a target surface;
• said focusing element and said apertures being such that light returned from said target surface back to said each of said apertures is rejected when said return light is light reflected from one of said array other than said each;
• and
• a detector in a return path of light from said each of said apertures, said detector generating an output responsive to said return light.

An optical scanning device, comprising:

• a scanning head with a light output aperture;
• a focusing element to image light from said output aperture onto a target surface;
• said focusing element being effective to image a first amount of return light returned from said target surface back to said output aperture when said focusing element is properly focused;
• said focusing element being effective to image a second amount of said return light returned from said target surface back to said output aperture when said focusing element is improperly focused;
• a detector in a return path of light from said output aperture, said detector generating an output responsive to said return light;
• a controller programmed to vary a configuration of said focusing element to determine a direction of a change of said configuration that corresponds to a proper focus in a first step, and responsively to so determining a direction, to systematically change in said direction to bring said configuration to said proper focus;
• and
• wherein said first amount of return light is different from said second amount of return light.

An optical scanning device comprising:

• a focusing element having an optical axis;
• an optical fiber having an output end optically coupled to said focusing element;
• a plurality of piezoelectric elements coupled to said output end of said optical fiber;
• a voltage source connected to said plurality of piezoelectric elements supplying voltage to said piezoelectric elements to cause said output end of said optical fiber to move along a plane perpendicular to said optical axis.

An optical scanning device comprising:

• a focusing element having an optical axis;
• an optical fiber having an output end optically coupled to said focusing element;
• a piezoelectric element coupled to said output end of said optical fiber;
• a voltage source connected to said piezoelectric element supplying voltage to said piezoelectric element to cause said output end of said optical fiber to move relative to said optical axis while remaining the same distance from said focusing element.