Apparatus for measuring dimensions of objects

• US 5,481,298 A
• Filed: 03/14/1995
• Issued: 01/02/1996
• Est. Priority Date: 02/25/1991
• Status: Expired due to Fees

• Current Assignee: Mitsui Engineering & Shipbuilding Company Limited (Mitsui E&S Holdings Co., Ltd.), Toyama Light Metal Industry Company Limited
• Original Assignee: Mitsui Engineering & Shipbuilding Company Limited (Mitsui E&S Holdings Co., Ltd.), Toyama Light Metal Industry Company Limited
• Inventors: Kaneko, Masaaki, Sasaki, Masahiko
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): HARVEY, MINSUN OH
• Application Number:
  US08/403,950
• Time in Patent Office: 294 Days
• Field of Search: 348/86, 348/87, 348/61, 348/135, 348/142, 356/237
• US Class Current: 348/135
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates

Abstract

An object dimension measuring apparatus consists of: a CCD camera mounted on an X- and a Y-axis table with its optical axis aligned with a Z-axis; a specimen table containing a light source and having its specimen mounting surface formed transparent; a light diffusion plate mounted on the specimen; and a computer. Using the CAD data, the computer moves the CCD camera. From the measured values obtained from the photographed images of the end portions of the specimen and from the distance traveled by the CCD camera, the computer calculates the dimensions of the specimen.

Claims

1. An object dimension measuring apparatus for measuring dimensions of objects which are too large to be taken in a single field of view comprising:

a CCD camera moveably mounted to an X- and a Y-axis table so that the optical axis of the CCD camera is aligned with a Z-axis;

a specimen table incorporating a light source and having a specimen mounting surface formed of a transparent member;

a light-diffusion plate of semi-transparent material mounted on a specimen; and

a computer, the computer including

a control means for moving a field of view of the CCD camera by using a CAD data,

a coordinate detecting means for detecting coordinates of the CCD camera'"'"'s field of view on the X- and Y-axis table,

an image processing means for processing output signals from the CCD camera,

an intensity reversing point detecting means for detecting intensity reversing points on an image produced by the image processing means,

a coordinate calculation means for calculating the coordinates of the intensity reversing points on the image, and

a calculation means for calculating the dimensions of the specimen from a distance traveled by the CCD camera and x, y coordinates of the image.

2. A method of measuring dimensions of objects which are too large to be taken in a single field of view comprising the steps of:

moving a CCD camera'"'"'s field of view until an upper left corner of a viewing field is at a first predetermined point;

photographing a left side portion of a shadow of a specimen;

moving said CCD camera'"'"'s field of view until a right corner of said viewing field is at a second predetermined point;

photographing a right side portion of said shadow of said specimen;

detecting a distance travelled by the CCD camera between said first and second predetermined points;

sorting an intensity output from each pixel of said CCD camera into a plurality of levels to identify an intensity of each pixel image;

determining a location of each pixel image;

sampling a plurality of pixel images to determine intensity reversing points;

calculating a distance of each sampled pixel image from an origin and calculating an angle with respect to an X-axis;

estimating an edge of said specimen based on said intensity reversing points, distance and angle from said origin; and

determining a width of said specimen based upon said edge.