Method and apparatus for extending operating range of bar code scanner
AssigneeWelch Allyn Data Collection, Inc.
InventorsWilliam H. Havens, Charles M. Hammond
Life of this patent
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Abstract
Briefly stated, the operating depth of field for a bar code scanner, preferably a laser scanner, is increased by placing a cubic phase mask (CPM) in the scanning beam. The masked beam is then scanned and reflected off a bar code and received by a photodetector. The received signal is then processed to recover the original unperturbed representation of the bar code pattern. The processed signal has an increased depth of field over an unmasked scanner signal.
Claims56
An optical reader for reading an optically encoded indicia, the optical reader having a maximum amount of misfocus error and an operational depth of field, the optical reader comprising:
- an illumination source configured to emit a light beam;
- an illumination optical assembly coupled in the illumination source, the illumination optical assembly including at least one phase mask, the at least one phase mask being configured to modify a phase of the light beam in a predetermined manner such that a phase modified light beam illuminates the optically encoded indicia;
- and
- an image processing assembly configured to receive the phase modified light beam reflected from the optically encoded indicia, the image processing assembly being configured to employ a recovery function to thereby generate a corrected image signal having a reduced focusing error and increased depth of field relative to the maximum amount of misfocus error and the operational depth of field.
A method for reading an optically encoded indicia with an optical reader, the optical reader having a maximum amount of misfocus error and an operational depth of field, the method comprising:
- transmitting a light beam;
- modifying a phase of the light beam in a predetermined manner such that a phase modified light beam illuminates the optically encoded indicia;
- and
- receiving the phase modified light beam reflected from the optically encoded indicia;
- converting the reflected phase modified light beam into an intermediate signal;
- processing the intermediate signal using a recovery function to thereby generate a corrected image signal, the corrected image signal having a reduced focusing error and increased depth of field relative to the maximum amount of misfocus error and the preliminary depth of field.
An apparatus for scanning an object that encodes data, said apparatus including:
- an optical assembly that is configured to receive light from a data encoding object, said data encoding object constituting a 2-D bar coda symbol and encoding data that includes one or more values, said optical assembly including:
- a phase mask for modifying incoming light from said data encoding object, said phase mask outputting phase modified light by modifying the phase of said incoming light;
- a lens configured for receiving, focusing and outputting light from said data encoding object;
- an imager including an array of photosensitive elements for receiving focused and phase modified light from said data encoding object and for forming a representation of an image of said data encoding object from said focused and phase modified light;
- and
- a decoder for processing said representation of an image of said data encoding object to determine one or more values of data encoded by said data encoding object.
A method for scanning an object that encodes data, said method including the steps of:
- identifying a data encoding object that constitutes a 2-D bar code symbol;
- providing a handheld scanning a apparatus that includes:
- an optical assembly that is configured to receive light from said data encoding object, said data encoding object encoding data that includes
- one or more values, said optical assembly including:
- a phase mask for modifying incoming light from said data encoding object, said phase mask outputting phase modified light by modifying the phase of said incoming light;
- a lens configured for receiving, focusing and outputting light from said data encoding object;
- an imager including an array of photosensitive elements for receiving focused and phase modified light from said data encoding object and for forming a representation of an image of said data encoding object from said focused and phase modified light;
- and
- a decoder for processing said representation of an image of said data encoding object to determine one or more values of data encoded by said data encoding object;
- and
- operating said handheld scanning apparatus to decode said data encoding object.
A system for scanning an object that encodes data, said system including:
- an optical assembly that is configured to receive light from a data encoding object constituting a 1-D bar code symbol, said data encoding object encoding data that includes one or more values, said optical assembly including:
- a non-cubic phase mask for modifying incoming light from said data encoding object, said phase mask outputting phase modified light by modifying the phase of said incoming light;
- a lens configured for receiving, focusing and outputting light from said data encoding object;
- an imager including an array of photosensitive elements for receiving focused and phase modified light from said data encoding object and for forming a representation of an image of said data encoding object from said focused and phase modified light;
- and
- a decoder for processing said representation of an image of said data encoding object to determine one or more values of data encoded by said data encoding object.
Dependencies are inferred from the claim text.