Optical method of detecting defect and apparatus used therein

• US 5,894,345 A
• Filed: 05/20/1997
• Issued: 04/13/1999
• Est. Priority Date: 05/22/1996
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Takamoto, Kenji, Takata, Kazumasa, Ito, Masami, Fukui, Atsushi, Nishii, Kanji
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US08/859,423
• Time in Patent Office: 693 Days
• Field of Search: 356/237, 356/239, 356/237.1, 356/239.1
• US Class Current: 356/237.1
• CPC Class Codes: G01N 21/8903 using a multiple detector array

Abstract

An array light source 1 with semiconductor laser sources disposed one-dimensionally and a projective lens 2 are used to illuminate an inspected object so that light beams projected from the array light source form a dotted line on the object. A line sensor is used to receive through an objective lens 3 light emitted from an imaging area 11 away from an illuminated area 12. An image signal, fed to an image processing unit 8 through a pre-processing unit 7 producing an image from signals from the line sensor 4 and a stage 5 is processed, while the stage 5 bearing the object 6 is being gradually moved, to inspect the object 6 for crack defects 9 and 10 by detecting an optically nonhomogeneous portion of the object. The method allows a crack defect of an object, such as a ceramic substrate or a sintered metal product, to be detected fast with high accuracy.

Claims

1. An optical defect detecting apparatus comprising:

illuminating means for illuminating an inspected object so that light beams aimed at the object form a dotted line on a surface thereof,

imaging means for detecting light beams emitted from a linear area parallel to an illuminated area formed on the surface of the object by said illuminating means,

image processing means for detecting an optically unhomogeneous portion of said object based on an imaging signal detected by said imaging means, and

drive means for relatively moving said object with respect to said illuminating means and said imaging means.

2. An optical defect detecting apparatus comprising:

illuminating means for illuminating an inspected object by one-dimensionally scanning the object, while varying illumination intensity,

imaging means for detecting light beams emitted from a linear area parallel to an illuminated area formed on the surface of the object by said illuminating means,

image processing means for detecting an optically unhomogeneous portion of said object based on an imaging signal detected by said imaging means, and

drive means for relatively moving said object with respect to said illuminating means and said imaging means.

3. An optical defect detecting apparatus comprising:

illuminating means for illuminating an inspected object by projecting light beams through slits forming a dotted line,

imaging means for detecting light beams emitted from a linear area parallel to an illuminated area formed on the surface of the object by said illuminating means,

image processing means for detecting an optically unhomogeneous portion of said object based on an imaging signal detected by said imaging means, and

drive means for relatively moving said object with respect to said illuminating means and said imaging means.

4. An optical defect detecting apparatus comprising:

illuminating means for illuminating an inspected object through a reflector so that light beams aimed at the object form a dotted line on a surface thereof,

imaging means for detecting through said reflector light beams emitted from a linear area parallel to an illuminated area formed on the surface of the object by said illuminating means,

image processing means for detecting an optically unhomogeneous portion of said object based on an imaging signal detected by said imaging means, and

drive means for turning said reflector back and forth by a predetermined angle.

5. An optical defect detecting apparatus comprising:

illuminating means for aiming light beams composed of light rays belonging to different wavelength bands at a surface of an inspected object so that the light beams differ in intensity at the surface and do not interfere with each other,

chromatic resolving means for separating into wavelength bands light rays emitted from a parallel to an illuminated area formed on the surface of the object by said illuminating means to detect the rays,

image processing means for detecting an optically unhomogeneous portion of said object based on an imaging signal detected by said imaging means, and

drive means for relatively moving said object with respect to said illuminating means and said imaging means.

6. An optical method of detecting a defect, comprising the steps of:

(a) aiming light beams at a surface of an inspected object, said light beams differing in intensity in the form of a dotted line on the surface of the object;

(b) detecting light beams emitted from a linear area on the surface of the object after the light beams aimed at the surface of the object have entered the object; and

(c) detecting an optically unhomogeneous portion of the object by detecting changes in the intensity of the light beams detected.

7. An optical method for detecting a defect, comprising the steps of:

(a) aiming light beams composed of light rays belonging to a plurality of wavelength bands at a surface of an inspected object, said light beams differing in intensity in the form of a dotted line on the surface of the object without interfering with each other;

(b) detecting light beams emitted from a linear area on the surface of the object after the light beams aimed at the surface of the object have entered the object; and

(c) detecting an optically unhomogeneous portion of the object by detecting changes in the intensity of the light beams detected.