Long range triangulating coordinate finder

• US 5,057,681 A
• Filed: 07/27/1990
• Issued: 10/15/1991
• Est. Priority Date: 07/27/1990
• Status: Expired due to Fees

• Current Assignee: Range Vision Incorporated
• Original Assignee: Range Vision Incorporated
• Inventors: Dieno, David A., Cornwall, Gordon E., Lang, Curtis E., Sloan, David S., Beder, Douglas S.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Shami, Khaled
• Application Number:
  US07/558,458
• Time in Patent Office: 445 Days
• Field of Search: 250/561, 250/208.3, 250/208.2, 356/1, 356/4, 356/141, 356/12, 356/375, 356/376
• US Class Current: 250/208.2
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves

Abstract

A system for establishing a base between a light projecting station and a light receiving station of a triangulating coordinate finder incorporates a target on the light transmitting station and a reflector appropriately positioned relative to a photo sensitive receiving array in the light receiving station. A beam of light is directed through a peep hole through the target onto the reflector and is reflected back onto the target. By adjusting the relative orientation of the two stations so that the light beam is reflected back from the reflecting surface in a direction substantially co-axial with the beam of light projecting through the peep hole the bases of the two stations are arranged to be substantially in the same plane and on a base line. The base length between the two stations is measured and the orientation of the projected beam and the focal axis of the receiving station are established relative to the base line to provide coordinates for the triangulating coordinate finder.

When scanning over long distances, or under conditions of varying ambient light and different colored background, the amount of light received in the light receiving station may vary due to conditions other than the change in distance. It is therefore preferred to threshold the signal received and use only those signals above a pre-determined threshold to establish accepted signals and to examine the overall signal and determine those areas where no accepted signal has been registered and rescan those areas using a slower scan rate, i.e. a longer illumination time (more light applied) per unit area per unit time of exposure or increase the exposure per unit area scanned.

Claims

1. A method for adaptively scanning a surface comprising scanning said surface at a first scan rate by directing a beam of light onto said surface, sensing said light beam reflecting from said surface in a detector station having a detector array with detectors arranged in mutually perpendicular rows in a plane substantially perpendicular to a focal axis of said detector station and producing a discrete digitized signal from each said detectors of said array, said signals having an intensity corresponding to the amount of light received by its respective said detector, thresholding said signals to determine those signals having strengths above a selected value indicating locations on said array to which said beam is reflected, determining areas on said surface from which no signal having a strength above said threshold has been received and rescanning at least one of said areas at a second scan rate slower than said first scan rate by increasing the amount of illumination per unit area scanned to which said detectors are subjected to obtain a second scan of said selected area.

2. A method as defined in claim 1 wherein said second scan rate is obtained by directing said beam of light onto said areas for a longer period of time during which said array of detectors is exposed to light reflected from said areas.