Dynamic focus calibration, such as dynamic focus calibration using an open-loop system in a bar code scanner
First Claim
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1. A method of dynamically recalibrating a bar code reader, the method comprising:
- reading data from multiple bar codes;
while reading data from multiple bar codes, receiving a recalibration signal or an indication of an error in reading an image of a bar code imaged by the bar code reader using a lens assembly calibrated to focus using a first focal length for reading the bar code, wherein the bar code reader employs open-loop auto focus controls;
in response to the recalibration signal and while reading data from multiple bar codes, measuring a distance between the bar code and a lens assembly in the bar code reader, wherein the distance is measured with a range finder carried by the bar code reader;
determining a second focal length of the lens assembly that provides a better image of the bar code; and
while reading data from multiple bar codes, recalibrating the open-loop auto focus controls of the bar code reader using the determined second focal length and the measured distance, and without need for a calibrated test system,wherein recalibrating the open-loop auto focus controls includes—
adjusting the open-loop auto focus controls by updating a transfer function of the bar code reader stored in a memory to correct focusing errors of the bar code reader present at a time of reading the image of one of the multiple bar codes,wherein subsequent focal lengths used by the bar code reader to read subsequent images of bar codes automatically correct for the focusing errors until another dynamic recalibration of the bar code reader occurs, andwherein the recalibrated open-loop auto focus controls are used for reading a subsequent image with the bar code reader.
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Abstract
A system and method for recalibrating a bar code scanner or other optical system is described. In some cases, the system dynamically adjusts the focal length of a lens assembly based on open-loop process, such as based on feedback related to a distance between the lens assembly and an imaged object. In some cases, the system dynamically adjusts the lens assembly in order to provide auto focusing or zoom adjustment.
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Citations
27 Claims
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1. A method of dynamically recalibrating a bar code reader, the method comprising:
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reading data from multiple bar codes; while reading data from multiple bar codes, receiving a recalibration signal or an indication of an error in reading an image of a bar code imaged by the bar code reader using a lens assembly calibrated to focus using a first focal length for reading the bar code, wherein the bar code reader employs open-loop auto focus controls; in response to the recalibration signal and while reading data from multiple bar codes, measuring a distance between the bar code and a lens assembly in the bar code reader, wherein the distance is measured with a range finder carried by the bar code reader; determining a second focal length of the lens assembly that provides a better image of the bar code; and while reading data from multiple bar codes, recalibrating the open-loop auto focus controls of the bar code reader using the determined second focal length and the measured distance, and without need for a calibrated test system, wherein recalibrating the open-loop auto focus controls includes— adjusting the open-loop auto focus controls by updating a transfer function of the bar code reader stored in a memory to correct focusing errors of the bar code reader present at a time of reading the image of one of the multiple bar codes, wherein subsequent focal lengths used by the bar code reader to read subsequent images of bar codes automatically correct for the focusing errors until another dynamic recalibration of the bar code reader occurs, and wherein the recalibrated open-loop auto focus controls are used for reading a subsequent image with the bar code reader. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A hand-held device configured to use dynamic recalibration to take an image of an object, comprising:
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a memory for storing open-loop auto focus controls; a lens assembly having an adjustable focal length for reading images of multiple selected objects, wherein the open-loop auto focus controls adjust the focal length; a range finder, wherein the range finder determines a distance between the hand-held device and a position on a selected object; an operation monitoring component, wherein the operation monitoring component receives an adjustment signal and initiates an adjustment of the focal length during the reading of images of the multiple selected objects; and a dynamic adjustment component coupled to the lens assembly and to the range finder, wherein the dynamic adjustment component adjusts the focal length of the lens assembly based on a) information received from the range finder and b) based on the received signal from the operation monitoring component to provide an improved image of one of the multiple selected objects and without need for a calibration test system, and further wherein the dynamic adjustment component recalibrates the open-loop auto focus controls using a) the adjusted focal length and b) the information received from the range finder to update a transfer function of the hand-held device stored in the memory to correct for focusing errors of the hand-held device present at a time of reading the image of one of the multiple selected objects and to adjust the open-loop auto focus controls, wherein subsequent focal lengths used by the hand-held device to read subsequent images automatically correct for the focusing errors until another dynamic recalibration of the hand-held device occurs. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A system for dynamically recalibrating a bar code reader, the method comprising:
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means for receiving an indication of an error in reading an image of a machine readable code imaged by the bar code reader using a lens assembly calibrated at a focal length and while gathering data from multiple machine readable codes; means for measuring a first distance and a second distance, wherein the first distance is a distance between a first position on a machine readable code and a lens assembly in the bar code reader and the second distance is a distance between a second position on the machine readable code and the lens assembly; means for determining an alternate focal length of the lens assembly that provides an adjusted image of the machine readable code; and means for recalibrating the bar code reader using the determined alternate focal length and the measured distances without use of a calibration test system, wherein recalibrating the bar code reader occurs while reading data from multiple machine readable codes and includes storing in a memory a) the determined alternate focal length and b) the measured distances, and adjusting a stored transfer function of the bar code reader to compensate for focusing errors of the bar code reader present at a time of reading the image of one of the multiple the machine readable codes, wherein subsequent focal lengths used by the bar code reader to read subsequent images automatically compensate for the focusing errors until another dynamic recalibration of the bar code reader occurs, and wherein the determined alternate focal length and the measured distances are used for reading a subsequent machine readable code with the bar code reader.
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26. A machine readable symbol reader configured to use dynamic recalibration to image a machine readable symbol, comprising:
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a memory for storing open-loop auto focus controls; a lens assembly having an adjustable focal length for imaging each of multiple machine readable symbols, wherein the open-loop auto focus controls adjust the focal length for imaging each of the multiple machine readable symbols; an open-loop measurement component, wherein the open-loop measurement component determines a distance between the machine readable symbol reader and a position on each of the multiple machine readable symbols; a focus adjustment component, wherein the focus adjustment component determines an adjusted focus of the lens assembly; and a dynamic adjustment component coupled to the lens assembly and open-loop measurement component, wherein the dynamic adjustment component adjusts the focal length of the lens assembly based on a) one or more determined distances and b) one or more focus adjustments to provide a better image of the selected machine readable symbol and to compensate for focusing errors of the reader present at a time of imaging multiple machine readable symbols, and without need for a calibration test system, wherein subsequent focal lengths used by the machine readable symbol reader to image subsequent machine readable symbols automatically compensate for the focusing errors until another dynamic recalibration of the machine readable symbol reader occurs, and further wherein the dynamic adjustment component recalibrates the open-loop auto focus controls using the adjusted focal length and the one or more determined distances by updating a transfer function stored in the memory to adjust the open-loop auto focus controls while reading data from multiple machine readable symbols. - View Dependent Claims (27)
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Specification