Optical scanner with extended depth of focus

A scanner with an extended depth of focus for electro-optically reading bar code symbols having parts of different light reflectivity, comprising:

• a. means for generating a radiation beam for illuminating a field of view;
• b. a multifocal length collection optical system, including a first mirror having at least a first focal length and a second mirror having a second focal length different from said first local length, for collecting radiation reflected from objects in the field of viwe wherein the area of the second mirror is larger than the area of the first mirror to compensate for the .sup.1 /f.sup.2 fall off in the signal collected by each mirror, where f is the focal length;
• and
• c. an optical detector for detecting radiation reflected from the field of view and directed thereto by the multifocal length optical system, and for generating an electrical output signal indicative of the radiation collected by said optical system.

A scanner with an extended depth of focus for electro-optically reading bar code symbols having parts of different light reflectivity, comprising:

• a. means for generating a radiation beam for illuminating a field of view;
• b. a multifocal length collection optical system, including a first mirror having at least a first focal length and a second mirror having a second focal length different from said first focal length, for collecting radiation reflected from objects in the field view wherein said first and second mirrors are positioned on a large scanning mirror surface which focuses an LED light source as a scanning beam directed at a field of view, and said first collection mirror focuses an image of a small aperture positioned in front of a photodiode detector at a near range in the field of view, and said second collection mirror focuses an image of the small aperture positioned in front of said photodiode detector at a far range in the field of view;
• and
• c. an optical detector for detecting radiation reflected from the field of view and directed thereto by the multifocal length optical system, and for generating an electrical output signal indicative of the radiation collected by said optical system.

A scanner with an extended depth of focus for electro-optically reading bar code symbols having parts of different light reflectivity, comprising:

• a. means for generating a radiation beam for illuminating a field of view;
• b. a multifocal length collection optical system, having at least a first component with a first focal length, and a second component with a second focal length different from said first focal length, said first and second components for jointly collecting radiation from objects in the field view;
• and
• c. an optical detector for detecting radiation reflected from the field of view and directed thereto by the multifocal length optical system, and for generating an electrical output signal indicative of the radiation collected by said first and second assemblies.

A method for electro-optically reading bar code symbols having parts of different light reflectivity, comprising the steps of:

• a. generating a radiation beam for illuminating a field of view;
• b. simultaneously collecting radiation reflected from objects in the field view using a multifocal length collection optical system, having at least a first near range focal length optical assembly and a second long range focal length optical assembly;
• and
• c. detecting radiation reflected from the field of view and directed thereto by the multifocal length optical system, and generating an electrical output signal indicative of the radiation collected simultaneously by said first and second assemblies.

A method of scanning with an extended depth of focus for electro-optically reading indicia having parts of different light reflectivity, comprising:

• a. generating a radiation beam for illuminating a field of view;
• b. collecting radiation reflected from objects in the field view with a multifocal length collection optical system, having at least a first optical assembly with a near range focal length with a first light collecting area and a second optical assembly with a long range focal length and a second light collecting area different from the first;
• and
• c. detecting radiation reflected from the field of view and collected by the multifocal length optical system, and generating an electrical output signal indicative thereof.

A method of scanning with an extended depth of focus for electro-optically reading bar code symbols having parts of different light reflectivity, comprising:

• a. generating a radiation beam for illuminating a field of view;
• b. collecting radiation from the field of view with a multifocal length collection optical system, including a first mirror having at least a first focal length and a second mirror having a second focal length different from said first focal length, wherein the area of the second mirror is larger than the area of the first mirror to compensate for the .sup.1 /f.sup.2 fall off in the signal collected by each mirror, where f is the focal length;
• and
• c. detecting radiation reflected from the field of view and directed thereto by the multifocal length optical system, and generating an electrical output signal indicative of the radiation collected by said optical system.

A method of scanning with an extended depth of focus for electro-optically reading bar code symbols having parts of different light reflectivity, comprising:

• a. generating a radiation beam for illuminating a field of view;
• b. collecting radiation from the field of view with a multifocal length collection optical system, including a first mirror having at least a first focal length and a second mirror having a second focal length different form said first focal length, for collecting radiation reflected from objects in the field of view wherein said first and second mirrors are positioned on a large scanning mirror surface which focuses an LED light source as a scanning beam directed at a field of view, and said first collection mirror focuses an image of a small aperture positioned in front of a photodiode detector at a near range in the field of view, and said second collection mirror focuses an image of the small aperture positioned in front of said photodiode detector at a far range in the field of view;
• and
• c. detecting radiation reflected from the field of view and directed thereto by the multifocal length optical system, and generating an electrical output signal indicative of the radiation collected by said optical system.