United States Patent 
[li] Patent Number: 4,901,073  Date of Patent: * Feb. 13, 1990
 ENCODER FOR MEASURING THE ABSOLUTE POSITION OF MOVING ELEMENTS
 Inventor: Robert I. Kibrick, Santa Cruz, Calif.
 Assignee: Regent of the University of California, Alameda, Calif.
[ * ] Notice: The portion of the term of this patent subsequent to Apr. 5, 2005 has been disclaimed.
 Appl. No.: 176,109
 Filed: Mar. 30, 1988
Related U.S. Application Data
 Continuation-in-part of Ser. No. 938,164, Dec. 4, 1986, Pat. No. 4,736,187.
 Int. CI.4 H03M 1/22
 U.S. CI 341/13; 341/3
 Field of Search 341/13; 250/231 SE,
250/237 G; 235/462
 References Cited
U.S. PATENT DOCUMENTS
4,074,258 2/1978 Dore et al 341/13
4,631,519 12/1986 Johnston 341/13
4,633,224 12/1986 Gipp et al 341/13
4,720,699 1/1988 Smith 341/13
4,736,187 4/1988 Kilbrick et al 341/13
Primary Examiner—William M. Shoop, Jr.
Assistant Examiner—Marc S. Hoff
Attorney, Agent, or Firm—Owen, Wickersham &
An optical encoding system for determining the absolute position of a movable member relative to a stationary member. For example, a bar-code scanner may be supported by a stationary member for scanning barcode symbols in its field of view. An encoding band may be supported by the movable member so that a portion of the band is scanned by the bar-code scanner. Affixed to or otherwise marked on the band is a sequential series of bar-code symbols, each symbol encoding the absolute position of its location on the band. A barcode decoding system, actuated by the signals produced by the bar-code scanner, decodes the bar-code symbol scanned by the scanner, and determines the absolute position of a movable member relative to the stationary member.
14 Claims, 8 Drawing Sheets