CALCULATING LINEAR DIMENSIONS FROM TV IMAGES

• US 3,773,422 A
• Filed: 04/07/1971
• Issued: 11/20/1973
• Est. Priority Date: 04/07/1971
• Status: Expired due to Term

• Current Assignee: Cae-Link Corporation
• Original Assignee: Donald Z. Blau, Gus Stavis, Robert A. Flower
• Inventors: Flower, Robert A., Blau, Donald Z., Stavis, Gus
• Primary Examiner(s): Schonberg, David
• Assistant Examiner(s): Evans, F. L.
• Application Number:
  US05/131,974
• Time in Patent Office: 958 Days
• Field of Search: 356/1,120,156,159,162,164-167,171 250/219WD,219LG,219TH
• US Class Current: 356/630
• CPC Class Codes: G01B 11/022 by means of tv-camera scanning
• CPC Class Codes: G01B 11/0691 of objects while moving G01B11/0616 takes precedence

Abstract

A video mensuration system wherein actual linear dimensions of objects may be calculated from the dimensions of video images of the objects without direct measurement of the camera to object distance. A beam of light is projected in a thin sheet to intersect the object across the dimension to be measured. The intersection appears as a line on the TV image and the actual dimension may be calculated from other known distances and geometric relationships.

Claims

1. A method of calculating the linear distance between two points on a surface of an object from a TV image thereof when the TV camera lens to object plane distance is unknown, said meThod comprising the steps of:

a. fixedly arranging a light source to project a beam from an emission point essentially in a plane transverse to and intersected by the two points between which the distance is to be calculated;

b. fixedly arranging a TV camera to view the intersection of the beam and object, with the camera optical axis at an angle to the beam, and the camera scan lines parallel to the image of the beam-object intersection;

c. measuring the distance (AB) along the camera optical axis from the lens to the point of intersection of the axis and the beam;

d. measuring the distance (BC) from the camera lens to the emission point;

e. measuring the distance (di) from the camera image centerline to the camera image of the intersection of the beam and object;

f. measuring the length (Ti) of the camera image of the intersection of the beam and object between the two points; and

g. calculating the linear distance (T) between the two points as follows;

T Ti (AB)(BC)/di (AB) + q(BC) where q is the camera lens to image plane distance.

2. The invention according to claim 1 including the step of using a laser as the light source.

3. The invention according to claim 1 including the step of positioning the camera with its optical axis normal to the surface of the object on which the two points lie.

4. A method of calculating the linear distance between two points on a surface from a TV image of a beam of light projected essentially in a plane to intersect the surface and extend linearly between the two points, said method comprising the steps of:

a. arranging a TV camera having a lens with its vidicon surface parallel to the plane of the light beam;

b. measuring the distance (p) along the camera optical axis from the lens to the point of intersection of the axis and the beam;

c. measuring the length (Ti) of the image of the beam between the two points; and

d. calculating the linear distance (T) between the two points as follows;

T (p/q) Ti where q is the camera lens to image plane distance.

5. The invention according to claim 4 including the step of projecting the beam from a monochromatic source.

6. The invention according to claim 5 and further including the step of interposing between the camera lens and the beam a filter which passes only light of the wavelength of the monochromatic source.