Absolute position detection

• US 10,176,591 B2
• Filed: 04/27/2018
• Issued: 01/08/2019
• Est. Priority Date: 06/15/2012
• Status: Active Grant

• Current Assignee: Sage Vision Inc.
• Original Assignee: Sage Vision Inc.
• Inventors: Swiegot, Elmar, Shinn, Alan, Fan, Chiko, King, David, Elias, Elias
• Primary Examiner(s): Rahaman, Mohammed S
• Assistant Examiner(s): Lee, Jimmy S
• Application Number:
  US15/965,611
• Publication Number:
  US 20180276840A1
• Time in Patent Office: 256 Days
• Field of Search: 356498, 356496, 348135, 348141
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

A system for determining the absolute position of a first object with respect to a second object includes a scalar element attached to the first object and a measuring device attached to the second object. The scalar element comprises a series of coded regions. The coded region represents a number designating a position along an axis of the scalar element. The measuring device includes a two-dimensional optical sensor array configured to capture an image of a portion of the scalar element. The system also includes a processor configured to receive the image and determine an absolute position of the first object with respect to the second object based on at least one coded region of the series of coded regions.

Claims

1. A measurement system for measuring the absolute position of a first object with respect to a second object along an axis of motion representing a direction of relative motion between the first object and the second object, the system comprising:

a scalar element attached to the first object, the scalar element comprising a series of coded regions positioned along an axis of the scalar element, wherein the axis of the scalar element is parallel to the axis of motion, wherein;

each coded region of the series of coded regions comprises a respective pattern of a series of patterns,

each pattern of the series of patterns is formed on and along a respective line perpendicular to the axis of motion, and

variation of each of the respective patterns on and along the respective lines encodes information that represents a number designating a position of the respective line along the axis of the scalar element;

a measuring device attached to the second object, the measuring device comprising a two-dimensional optical sensor array configured to capture an image of a portion of the scalar element, the image comprising a first pattern in one coded region of the series of coded regions; and

a processor configured to;

receive the image; and

determine an absolute position of the first object with respect to the second object based on the first pattern, wherein determining the absolute position includes determining an offset from an optical center of the measuring device based on a difference between (a) a pixel group of the respective pattern on and along the respective line and (b) a center of the image.

2. The measurement system of claim 1, wherein each pattern of the series of patterns comprises a binary code that represents a respective number designating a respective position along the axis of the scalar element.

3. The measurement system of claim 1, further comprising a display configured to display the absolute position.

4. The measurement system of claim 1, further comprising a motion controller configured to receive the absolute position, and to cause a movement of the first object along the axis of motion based on the received absolute position.

5. The measurement system of claim 1, wherein

the measuring device is configured to capture a plurality of images as the first or second object move along the axis of motion, and

the processor is configured to determine, in real time, a respective absolute position for each of the plurality of images.

6. The measurement system of claim 1, wherein:

each coded region of the series of coded regions comprises a respective colored region, and

the processor is further configured to determine the absolute position of the first object with respect to the second object based on a first colored region included in the one coded region comprising the first pattern.

7. The measurement system of claim 1, wherein:

each coded region of the series of coded regions comprises a respective plurality of colored regions, and

the processor is further configured to determine the absolute position of the first object with respect to the second object based on a first plurality of colored regions included in one coded region comprising the first pattern.

8. The measurement system of claim 1, wherein the two-dimensional optical sensor array is a camera sensor.

9. The measurement system of claim 1, wherein the scalar element attached to the first object further comprises a series of regularly repeating optically readable index lines positioned along the axis of the scalar element.

10. The measurement system of claim 9, wherein the image of the portion of the scalar element comprises a first index line, a first coded region, and an additional feature that is either a second index line or a second coded region.

11. A method of determining absolute position of a first object with respect to a second object along an axis of motion representing a direction of relative motion between the first object and the second object, the method comprising:

acquiring an image of a portion of a scalar element attached to the first object using a measuring device attached to the second object, wherein;

the scalar element comprises a series of coded regions positioned along an axis of the scalar element, wherein the axis of the scalar element is parallel to the axis of motion, each coded region of the series of coded regions comprises a respective pattern of a series of patterns,

each pattern of the series of patterns is formed on and along a respective line perpendicular to the axis of motion,

variation of each of the respective patterns on and along the respective lines encodes information that represents a number designating a position of the respective line pattern along the axis of the scalar element; and

the measuring device comprises a two-dimensional optical sensor array configured to capture an image of a portion of the scalar element, the image comprising a first pattern in one coded region of the series of coded regions;

performing image processing on the acquired image to obtain a representation of the one coded region;

determining a number value represented by the representation of the one coded region, wherein the number value defines the absolute position of the first pattern along the axis of the scalar element based on the information encoded by the first pattern;

determining the absolute position of the first object with respect to the second object along the scalar element based on the number value, wherein determining the absolute position includes determining an offset from an optical center of the measuring device based on a difference between (a) a pixel group of the respective pattern on and along the respective line and (b) a center of the image.

12. The method of claim 11, further comprising displaying the absolute position on a display.