Machine vision methods and apparatus for machine vision illumination of an object

• US 5,953,130 A
• Filed: 01/06/1997
• Issued: 09/14/1999
• Est. Priority Date: 01/06/1997
• Status: Expired due to Term

• Current Assignee: Ametek Incorporated
• Original Assignee: Cognex Corporation
• Inventors: Jones, Michael, Benedict, George
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): STAFIRA, MICHAEL PATRICK
• Application Number:
  US08/779,312
• Time in Patent Office: 981 Days
• Field of Search: 356/429, 356/430, 356/431, 356/239.1, 356/240, 356/237.1, 348/131, 348/370
• US Class Current: 356/429
• CPC Class Codes: G01N 21/8901 Optical details; Scanning details per se G02B

Abstract

The invention provides methods and apparatus for machine vision illumination by moving a non-diffuse light beam over selected points on the object so that each is illuminated at substantially the same angle by multiple rays during acquisition of an image frame. An apparatus for illuminating an object to facilitate its being imaged by an image acquisition device, e.g., a camera, includes a radiation source that generates and transmits to a region of the a non-diffuse beam of imaging radiation having a non-point cross-section. A dithering element moves the beam so that at least a region of the object is illuminated at substantially the same angle by multiple rays during an image acquisition period.

Claims

1. A system for illuminating an object to facilitate imaging thereof by an image acquisition device, the system comprising:

A. a first radiation source that generates and transmits to a region of the object to be imaged a non-diffuse beam of imaging radiation having a non-point cross-section;

B. a dithering element that moves the beam such that each point in the region of the object to be imaged is illuminated at substantially the same angle by multiple rays from the beam during an image frame acquisition period of the image acquisition device.

5. A system according to claim 1, wherein the first radiation source generates and transmits to the region of the object to be imaged a beam of imaging radiation having a substantially linear cross-section.

6. A system according to claim 1, wherein the dithering element comprises any of a lens and a mirror.

7. A system according to claim 1, wherein the dithering element moves the beam in an oscillatory manner across the region of the object to be imaged.

8. A system according to claim 1, wherein the first radiation source comprises a source of coherent imaging radiation.

9. A system according to claim 8, wherein the first radiation source comprises a laser.

2. A system for illuminating an object to facilitate imaging thereof by an image acquisition device, the system comprising:

A. a first radiation source that generates and transmits to a region of the object to be imaged a non-diffuse beam of imaging radiation having a non-point cross-section;

B. a dithering element that moves the beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays from the beam during an image frame acquisition period of the image acquisition device,

C. wherein the beam is incident on the object at a grazing angle with respect to the portion of the object to be imaged.

3. A system for illuminating an object to facilitate imaging thereof by an image acquisition device the system comprising:

A. a first radiation source that generates and transmits to a region of the object to be imaged a non-diffiuse beam of imaging radiation having a non-point cross-section,

B. a dithering element that moves the beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays from the beam during an image frame acquisition period of the image acquisition device,

C. wherein the beam provides dark field illumination of the region of the object to be imaged with respect to the image acquisition device.

4. A system for illuminating an object to facilitate imaging thereof by an image acquisition device, the system comprising:

A. a first radiation source that generates and transmits to a region of the object to be imaged a non-diffuse beam of imaging radiation having a non-point cross-section;

B. a dithering element that moves the beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays from the beam during an image frame acquisition period of the image acquisition device,

C. wherein the first radiation source generates and transmits to the region of the object to be imaged a plurality of non-diffuse beams of imaging radiation, each having a non-point cross-section, and each illuminating the region at a different angle than the others.

10. A system for illuminating an object to facilitate imaging thereof by an image acquisition device, the system comprising:

A. a first radiation source that generates and transmits to a region of the object to be imaged a coherent beam of light having a non-point cross-section, the beam providing dark field illumination with respect to the image acquisition device;

B. the first radiation source including a dithering element that moves the beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays from the beam during an image frame acquisition period of the image acquisition device, the beam moving in an oscillatory manner across the portion of the object to be imaged.

11. A system for illuminating an object to facilitate imaging thereof by an image acquisition device, the system comprising:

A. a first radiation source that generates and transmits to a region of the object to be imaged a non-diffuse beam of imaging radiation having a non-point cross-section;

B. the first radiation source including a dithering element that moves the beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays of the beam during an image frame acquisition period of the image acquisition device; and

C. a second radiation source for illuminating at least the region of the object to be imaged with diffuse light.

12. A system according to claim 11, wherein the second radiation source illuminates the region of the object to be imaged at a grazing angle.

13. A system according to claim 11, wherein the second radiation source provides--with respect to the image acquisition device--dark field illumination of the region of the object to be imaged.

14. A system according to claim 11, wherein the second radiation source illuminates the region of the object to be imaged at an angle different from that at which the first radiation source transmits the beam to the object.

15. A method for illuminating an object to facilitate imaging thereof by an image acquisition device, the method comprising the steps of:

A. illuminating a region of the object to be imaged with a non-diffuse beam of imaging radiation having a non-point cross-section; and

B. moving that beam such that each point the region of the object to be imaged is illuminated at substantially the same angle by multiple rays during an image frame acquisition period of the image acquisition device.

19. A method according to claim 15, comprising the step of illuminating the object with a beam of non-diffuse radiation having a substantially linear cross-section.

20. A method according to claim 15, comprising the step of moving the beam with any of lens and a mirror.

21. A method according to claim 15, comprising the step of moving the beam in an oscillatory manner across the region of the object to be imaged.

22. A method according to claim 15, comprising the step of illuminating the object with coherent imaging radiation.

23. A method according to claim 22, comprising the step of illuminating the object with a laser.

16. A method for illuminating an object to facilitate imaging thereof by an image acquisition device, the method comprising the steps of:

A. illuminating a region of the object to be imaged with a non-diffuse beam of imaging radiation having a non-point cross-section; and

B. moving that beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays during an image frame acquisition period of the image acquisition device,

C. wherein the illuminating step comprises illuminating the object by transmitting the beam at a grazing angle with respect to the region of the object to be imaged.

17. A method for illuminating an object to facilitate imaging thereof by an image acquisition device, the method comprising the steps of:

A. illuminating a region of the object to be imaged with a non-diffuse beam of imaging radiation having a non-point cross-section; and

B. moving that beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays during an image frame acquisition period of the image acquisition device,

C. wherein the illuminating step comprises illuminating the object by transmitting the beam to the object so as to provide--with respect to the image acquisition device--dark field illumination of the region of the object to be imaged.

18. A method for illuminating an object to facilitate imaging thereof by an image acquisition device, the method comprising the steps of:

A. illuminating a region of the object to be imaged with a non-diffuse beam of imaging radiation having a non-point cross-section; and

B. moving that beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays during an image frame acquisition period of the image acquisition device,

C. wherein the illuminating step comprises illuminating the object with a plurality of non-diffuse beams of imaging radiation, each having a non-point cross-section, where each beam illuminates the object at a different angle than the other beams.

24. A method for illuminating an object to facilitate imaging thereof by an image acquisition device, the method comprising the steps of

A. illuminating a region of the object to be imaged with a coherent beam of light having a non-point cross-section, the beam providing dark field illumination with respect to the image acquisition device;

and

B. moving the beam in an oscillatory manner such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays during an image frame acquisition period of the image acquisition device.

25. A method for illuminating an object to facilitate imaging thereof by an image acquisition device, the method comprising the steps of

A. illuminating a region of the object to be imaged with a non-diffuse beam of imaging radiation having a non-point cross-section;

B. moving the beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays during an image frame acquisition period of the image acquisition device; and

C. illuminating at least the region of the object to be imaged with diffuse light.

26. A method according to claim 25, comprising the step of illuminating the object at a grazing angle with the diffuse light.

27. A method according to claim 25, comprising the step of illuminating the object with diffuse radiation for dark field imaging.

28. A method according to claim 25, comprising the step of illuminating the object a differing angles with each of the diffuse and non-diffuse radiation.

29. A system for illuminating an object to facilitate imaging thereof by an image acquisition device, the system comprising:

A. a first radiation source that generates and transmits to a region of the object to be imaged a non-diffuse beam of imaging radiation having a non-point cross-section;

B. the first radiation source including a dithering element that moves the beam such that the region of the object to be imaged is illuminated at substantially the same angle by multiple rays of the beam during an image frame acquisition period of the image acquisition device; and

C. the first radiation source focussing the non-diffuse beam so that it has a wider cross-section in regions from which radiation reflected from the object is forward-scattered to the image acquisition device and has a narrower cross-section in regions from which radiation reflected from the object is back-scattered to the image acquisition device.

30. A system according to claim 29, wherein the first radiation source focusses the non-diffuse beam so that it is substantially 3 to 5 times wider at a point from which radiation reflected from the object is forward-scattered to the image acquisition device than at a point from which radiation reflected from the object is back-scattered to the image acquisition device.