Position encoder system which utilites the fundamental frequency of a ruled scale on an object
First Claim
1. A method for determining position of an object comprising theobtaining a continuous representation of a continuous section of the object, the section having indicia thereon;
- determining, from the continuous representation, frequency of changes on the indicia; and
determining phase between the determined frequency and a reference to obtain actual position of the object.
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Abstract
A position encoder system is disclosed for determining the position of an object. The system includes a camera, a ruled scale, and a control system. The system first obtains a pixel brightness image of the ruled scale attached to the object and downloads this data image to a computer. The computer, running a fast position determination, determines the fundamental frequency of the image through the use of a Fourier transform of the pixel brightness variations in the image. The phase difference between the fundamental frequency and a reference is then converted into an actual position of the object since the spacing of the individual rulings on the scale is known and one cycle of the fundamental frequency corresponds to one spacing interval on the rulings. With this measurement of the actual position, the control system compares it to the desired position and, if necessary, corrects the position of the object.
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Citations
33 Claims
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1. A method for determining position of an object comprising the
obtaining a continuous representation of a continuous section of the object, the section having indicia thereon; -
determining, from the continuous representation, frequency of changes on the indicia; and determining phase between the determined frequency and a reference to obtain actual position of the object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for determining the position of an object comprising the steps of:
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detecting a continuous representation of a continuous section of a ruled scale coupled to the object; converting the detected continuous representation to a pixel brightness representation of the continuous section of rulings on the scale; determining, based on the pixel brightness representation, fundamental frequency of the representation; and determining phase between the fundamental frequency and a reference. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A position encoder system for determining the position of an object comprising:
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indicia on the object; detecting means for obtaining a continuous representation of a continuous section of the indicia; determining means coupled to the detecting means for determining the fundamental frequency of the continuous representation; comparing means for comparing the fundamental frequency to a reference; and means for determining the actual position of the object as a function of output of the comparing means. - View Dependent Claims (26, 27, 28)
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29. A position encoding system for determining the position of an object, comprising:
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a ruled scale coupled to an object; means for obtaining the image of a continuous section of the ruled scale; and means for determining a frequency of the image and determining phase between the frequency and a reference to obtain an actual position of the object. - View Dependent Claims (30, 31, 32)
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33. A method for determining the position of an object comprising the steps of:
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detecting a representation of a ruled scale coupled to the object; converting the detected representation to a pixel brightness representation of rulings on the scale; determining fundamental frequency of the representation; and determining phase between the fundamental frequency and a reference, wherein the step of determining the frequency further comprises the steps of; analyzing the representation of the ruled scale to detect whether a gap exists in individual rulings of the ruled scale; moving to a side of the gap of the ruled scale; and resuming calculation with a proper offset corresponding to any phase difference caused by the gap in the ruled scale.
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Specification