Machine-vision ring-reflector illumination system and method

• US 6,022,124 A
• Filed: 08/19/1997
• Issued: 02/08/2000
• Est. Priority Date: 08/19/1997
• Status: Expired due to Term

• Current Assignee: Datalogic Automation Incorporated (Datalogic S.p.A.)
• Original Assignee: PPT Vision, Inc. (Datalogic S.p.A.)
• Inventors: Bourn, Charles T., Lebens, Gary A.
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): HOPPER, TODD R
• Application Number:
  US08/914,441
• Time in Patent Office: 903 Days
• Field of Search: 362/247, 362/11, 362/231, 362/252, 362/33, 348/370, 348/131, 382/141
• US Class Current: 362/247
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/9036 using arrays of emitters or receivers
• CPC Class Codes: G01N 21/909 in opaque containers or opaque container parts, e.g. cans, tins, caps, labels
• CPC Class Codes: G01R 31/308 using non-ionising electromagnetic radiation, e.g. optical radiation investigating or analysing materials by the use of optical means G01N21/00; image analysis G06T7/00
• CPC Class Codes: G03B 15/03 Combinations of cameras with lighting apparatus; Flash units

Abstract

An illumination method and apparatus for machine-vision systems, including a ring-light source (e.g., LEDs arranged in one or more circular rows), and a reflective-ring focusing element. The illumination source exhibits multidirectional ring-illumination properties which are useful for illumination of small components (which are being inspected or measured) without unwanted shadows. One embodiment provides a darkfield illumination system. One embodiment of the present invention uses a strobed (or pulsed) power supply to drive the LEDs. Yet another embodiment of the present invention uses a xenon strobe ring-light source and a backplane slit in place of the row of LEDs 25. In one such xenon strobe embodiment, a color filter is also placed in series with the light path in order to obtain a monochromatic light. While xenon flashtube light sources tend to exhibit a five per cent (5%) flash-to-flash variation in intensity which makes accurate measurements of certain characteristics difficult, they are useful in certain cases where intense white, or especially ultraviolet, light is desired. Strobed LEDs provide very little flash-to-flash variation in intensity. The compact ring-light generator has little, if any, shadowing. The present invention also provides an inexpensive apparatus and method for changing the light-source-to-optical-axis angle.

Claims

1. An illumination source for illuminating an object in a machine-vision system, the system having an optical axis, comprising:

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring light source comprises a plurality of light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis and wherein each LED has a focal centerline emission axis along which emission is centered, and each LED'"'"'s emission axis is parallel to the optical axis.

24. The illumination source as recited in claim 1, wherein the light emitted from the LEDs is primarily two or more different colors selected from the following group:

infra-red, red, amber, yellow, green, blue, violet, ultraviolet, and white.

25. The illumination source as recited in claim 1, wherein the ring reflector reflective surface is changeable from a first ring reflective surface configuration to a second ring reflective configuration different than that of the first ring reflective surface configuration.

2. An illumination source for illuminating an object in a machine-vision system, the system having an optical axis, comprising:

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring light source comprises a plurality of light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis, and wherein the light emitted from the LEDs is primarily within an angle of about 5 degrees from a focal centerline of each individual LED.

3. An illumination source for illuminating an object in a machine-vision system, the system having an optical axis, comprising:

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring light source comprises a plurality of light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis, and further comprising a focusing element that includes a cylindrical ring lens having at least one convex face.

4. An illumination source for illuminating an object in a machine-vision system, the system having an optical axis, comprising:

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring reflector has a surface that enhances its reflectivity at one or more selected wavelengths of the ring light source.

26. The illumination source as recited in claim 4, wherein the ring reflector reflective surface is changeable from a first ring reflective surface configuration to a second ring reflective configuration different than that of the first ring reflective surface configuration.

5. An illumination source for illuminating an object in a machine-vision system, the system having an optical axis, comprising:

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring reflector and ring light source are configured to produce a darkfield illumination.

27. The illumination source as recited in claim 5, wherein the ring reflector reflective surface is changeable from a first ring reflective surface configuration to a second ring reflective configuration different than that of the first ring reflective surface configuration.

6. A method for illuminating an object located along, an optical axis, comprising the steps of:

(a) emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

(b) reflecting the emitted light from the light source inwards and generally towards the object at the optical axis or in an area around the optical axis,

wherein the step of emitting light include emitting light from one or more light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis, and wherein each LED has a focal centerline emission axis along which emission is centered, and each LED'"'"'s emission axis is parallel to the optical axis.

40. The method for illuminating an object as recited in claim 6, wherein the object is an electrical connector, and further comprising the step of acquiring a machine-vision image of the electrical connector.

7. A method for illuminating an object located along an optical axis, comprising the steps of:

(a) emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

(b) reflecting the emitted light from the light source inwards and generally towards the object at the optical axis or in an area around the optical axis,

wherein the step of emitting light include emitting light from one or more light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis, and wherein each LED has an focal centerline emission axis along which emission is centered, and each LED'"'"'s emission axis is perpendicular to the optical axis, and further comprising the step of focusing the emitted light to a circular line.

8. A machine-vision illumination system comprising:

an imaging device;

an image processor coupled to the imaging device; and

an illumination source coupled to the image processor, the illumination source comprising;

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring light source comprises a plurality of light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis, and wherein each LED has a focal centerline emission axis along which emission is centered, and each LED'"'"'s emission axis is parallel to the optical axis.

9. A machine-vision illumination system, comprising:

an imaging device;

an image processor coupled to the imaging device; and

an illumination source coupled to the image processor, the illumination source comprising;

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring light source comprises a plurality of light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis, and wherein the light emitted from the LEDs is primarily within an angle of about 5 degrees from a focal centerline of each individual LED.

10. A machine-vision illumination system, comprising:

an imaging device;

an image processor coupled to the imaging device; and

an illumination source coupled to the image processor, the illumination source comprising;

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring light source comprises a plurality of light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis, and further comprising a focusing element that includes a cylindrical ring lens having at least one convex face.

11. A machine-vision illumination system comprising:

an imaging device;

an image processor coupled to the imaging device; and

an illumination source coupled to the image processor, the illumination source comprising;

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring reflector has a surface that enhances its reflectivity at one or more selected wavelengths of the ring light source.

12. A machine-vision illumination system, comprising:

an imaging device;

an image processor coupled to the imaging device; and

an illumination source coupled to the image processor, the illumination source comprising;

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring reflector and ring light source are configured to produce a darkfield illumination.

13. A ring reflector for use in reflecting light from a ring light source, the ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects an optical axis, the ring reflector comprising:

a substantially circular exit opening though which the optical axis passes and

a reflective surface surrounding the exit opening, the reflective surface extending from approximately a first circle centered on the optical axis and having a first radius, to approximately a second circle centered on the optical axis and having a second radius, the second radius being larger than the first radius, the first radius being larger than the difference between the second radius and the first radius, whereby the emitted light from the ring light source being generally directed centered on lines that intersect the reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the reflective surface comprises a plurality of adjoining conical sections.

14. The ring reflector as recited in claim 13, wherein the plurality of adjoining conical sections includes a first conical section having a reflective surface at a first conical angle to the optical axis, and a second conical section having reflective surface at a second conical angle to the optical axis.

38. The ring reflector as recited in claim 13, wherein the plurality of adjoining conical sections includes a first conical section having a reflective surface at a first conical angle to the optical axis, and a second conical section having reflective surface at a second conical angle to the optical axis, and wherein both the first and second conical sections are configured to reflect light originally directed parallel to the optical axis.

39. The ring reflector as recited in claim 13, wherein the plurality of adjoining conical sections includes a first conical section having a reflective surface at a first conical angle to the optical axis, and a second conical section having reflective surface at a second conical angle to the optical axis, and wherein both the first and second conical sections are configured to reflect light originally directed perpendicular to the optical axis.

15. A ring reflector for use in reflecting light from a ring light source, the ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects an optical axis, the ring reflector comprising:

a substantially circular exit opening though which the optical axis passes; and

a reflective surface surrounding the exit opening, the reflective surface extending from approximately a first circle centered on the optical axis and having a first radius, to approximately a second circle centered on the optical axis and having a second radius, the second radius being larger than the first radius, the first radius being larger than the difference between the second radius and the first radius, whereby the emitted light from the ring light source being generally directed centered on lines that intersect the reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the reflective surface comprises a plurality of reflective facets.

16. The ring reflector as recited in claim 15, wherein, for a plurality of the facets, a line normal to the facet surface passes through the optical axis.

17. A ring reflector for use in reflecting light from a ring light source, the ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects an optical axis, the ring reflector comprising:

a substantially circular exit opening though which the optical axis passes; and

a reflective surface surrounding the exit opening, the reflective surface extending from approximately a first circle centered on the optical axis and having a first radius, to approximately a second circle centered on the optical axis and having a second radius, the second radius being larger than the first radius, the first radius being larger than the difference between the second radius and the first radius, whereby the emitted light from the ring light source being generally directed centered on lines that intersect the reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the reflective surface comprises a first conical section, and

wherein the ring reflector further comprises a second conical section, the first and second conical sections each having a unique conical angle.

18. An illumination source for illuminating an object in a machine-vision system, the system having an optical axis, comprising:

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having, an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring reflector includes a reflective surface comprising a plurality of conical sections each having a unique conical angle.

28. The illumination source as recited in claim 18, wherein the ring reflector reflective surface is changeable from a first ring reflective surface configuration to a second ring reflective configuration different than that of the first ring reflective surface configuration.

19. An illumination source for illuminating an object in a machine-vision system, the system having an optical axis, comprising:

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis, and

further comprising;

a ring-reflector holder that holds one of a plurality of interchangeable ring reflectors in optical communication with the ring-light source, said plurality of interchangeable ring reflectors including the first ring reflector.

29. The illumination source as recited in claim 19, wherein the ring light source comprises a plurality of light-emitting diodes (LEDs) arranged substantially along a circle disposed perpendicular to and centered on the optical axis.

30. The illumination source as recited in claim 29, wherein each LED has a focal centerline emission axis along which emission is centered, and each LED'"'"'s emission axis is parallel to the optical axis.

31. The illumination source as recited in claim 29, wherein each LED has a focal centerline emission axis along which emission is centered, and each LED'"'"'s emission axis is perpendicular to the optical axis.

32. The illumination source as recited in claim 29, wherein the light emitted from the LEDs is two or more selected from the following:

infra-red, red, amber, yellow, green, blue, violet, ultraviolet, or white in color.

33. The illumination source as recited in claim 29, wherein the light emitted from the LEDs is primarily within an angle of about 5 degrees from a focal centerline of each individual LED.

34. The illumination source as recited in claim 19, further comprising a focusing element that includes a cylindrical ring lens having at least one convex face.

35. The illumination source as recited in claim 19, wherein the ring reflector has a surface that enhances its reflectivity at one or more selected wavelengths of the ring light source.

36. The illumination source as recited in claim 19, wherein the ring reflector and ring light source are configured to produce a darkfield illumination.

37. The illumination source as recited in claim 19, wherein the ring reflector reflective surface is changeable from a first ring reflective surface configuration to a second ring reflective configuration different than that of the first ring reflective surface configuration.

20. A method for illuminating an object located along an optical axis, comprising the steps of:

(a) emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

(b) reflecting the emitted light from the light source inwards and generally towards the object at the optical axis or in an area around the optical axis,

wherein the step of reflecting the emitted light includes reflecting the light from a plurality of reflective conical sections each having a unique conical angle.

21. A method for illuminating an object located along an optical axis, comprising the steps of:

(a) emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis;

(b) reflecting the emitted light from the light source inwards and generally towards the object at the optical axis or in an area around the optical axis; and

(c) changing a first ring reflective surface having a first reflective configuration to a second ring reflective surface having a different reflective configuration than that of the first ring reflective surface.

41. The method for illuminating an object as recited in claim 21, wherein the object is an electrical connector, and further comprising the step of acquiring a machine-vision image of the electrical connector.

42. The method for illuminating an object as recited in claim 21, wherein the step of changing the ring reflective surface comprises replacing a ring reflector.

43. The method for illuminating an object as recited in claim 21, wherein the step of changing the ring reflective surface comprises changing a compression on a pliable gasket.

22. A machine-vision illumination system, comprising:

an imaging device;

an image processor coupled to the imaging device; and

an illumination source coupled to the image processor, the illumination source comprising;

a ring light source emitting light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis,

wherein the ring reflector includes a reflective surface comprising a plurality of conical sections each having a unique conical angle.

23. A machine-vision illumination system, comprising:

an imaging device;

an image processor coupled to the imaging device; and

an illumination source coupled to the image processor, the illumination source comprising;

a ring light source emitting, light from a plurality of points or from a line, the points or line being substantially in a plane that intersects the optical axis, each of the points or the line disposed at least a first distance from the optical axis and less than a second distance from the optical axis; and

a first ring reflector, the ring, reflector having an exit opening though which the optical axis passes, the emitted light from the ring light source being generally directed centered on lines that intersect a reflecting surface of the ring reflector, the ring reflector reflecting the emitted light from the light source though the exit opening inwards and generally towards the optical axis or an area around the optical axis, and

further comprising;

a ring-reflector holder that holds one of a plurality of interchangeable ring reflectors in optical communication with the ring-light source, said plurality of interchangeable ring reflectors including the first ring reflector.