Tandem linear scanning confocal imaging system with focal volumes at different heights

• US 5,248,876 A
• Filed: 04/21/1992
• Issued: 09/28/1993
• Est. Priority Date: 04/21/1992
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Mandeville, Jon R., Kerstens, Pieter J., Wu, Frederick Y.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Messinger, Michael
• Application Number:
  US07/871,458
• Time in Patent Office: 525 Days
• Field of Search: 250/216, 250/201.3, 250/234-236, 250/561, 250/227.2, 250/227.26, 356/376, 356/371, 359/372, 359/368
• US Class Current: 250/559.05
• CPC Class Codes: G01B 11/0608 Height gauges
• CPC Class Codes: G01B 9/04 Measuring microscopes
• CPC Class Codes: G02B 21/004 fixed arrays, e.g. switchable aperture arrays
• CPC Class Codes: G02B 6/04 formed by bundles of fibres G02B6/24 takes precedence

Abstract

A confocal imaging system utilizes an opaque mask with a slit and a row of pinpoint sensors or utilizes an opaque mask with a skewed pattern of pinholes and an array of isolated pinpoint sensors in a matching pattern in order to obtain sufficient data to provide a complete image for imaging and/or inspecting an object such as electronics in a single one-dimensional scan. The system also simultaneously produces multiple images at different heights in the single one-dimensional scan of the viewed object, and also simultaneously produces images taken in different spectral bands in the same one-dimensional scan of the object to be imaged and/or inspected. The relative height or depth of the different images can be modified by simply adjusting the inclination between the confocal imaging system and a path followed by the object that is to be imaged and/or inspected during the one-dimensional scan. The optical confocal imaging system requires no moving parts and the only moving parts of the system are for motorized conveying of the object to be imaged and/or inspected along the path. In one arrangement of the confocal imaging system, color imaging and/or inspecting of the object can be performed. In another arrangement of the confocal imaging system, simultaneous brightfield and darkfield imaging and/or inspecting of an object can be performed.

Claims

1. A confocal imaging system for inspecting and/or imaging an object, comprising:

means for conveying the object along a path;

means for providing focused radiation in a pattern of multiple focal volumes at different heights and which are spatially separated from each other in a lateral direction in relation to said object in said path along which said object is conveyed, said radiation being transmitted or reflected in response to the topography of said object as it moves along said path;

an array of detectors in an expanded pattern matched with said pattern of multiple focal volumes of focused radiation, each of said detectors in said array being sensitive to radiation from only one focal volume; and

means for directing and focusing said transmitted or reflected radiation from said object onto said array of detectors.

2. The confocal imaging system of claim 1 in which said means for providing focused radiation in a pattern of multiple focal volumes comprises:

a mask with a pattern of multiple confocal apertures with a width approximately equal to or smaller than the diffraction limit of the radiation and separated by several times the diffraction limit to minimize crosstalk;

a source for directing radiation through said apertures; and

means for directing and focusing the radiation into fields of view in the path along which the object is moving so that the object reflects or transmits the radiation depending upon the topography of the object.

3. The confocal imaging system of claim 2 in which the apertures are pinholes and the pattern of apertures comprise,

a matrix of pinholes in said opaque mask positioned in an offset pattern for obtaining a complete image of said object in one continuous scan of said object.

4. The confocal imaging system of claim 3 in which the pattern of pinhole apertures comprise,

a plurality of said matrices, each matrix of said plurality of matrices is positioned at a different distance from said path of the object for simultaneously obtaining multiple images of said object, each of said images being at a different level during one continuous scan of said object.

5. The confocal imaging system of claim 1 wherein said means for providing focused radiation in a pattern of multiple focal volumes comprises:

a mask with a pattern of multiple confocal apertures; and

a source for directing radiation through said multiple confocal apertures.

6. The confocal imaging system of claim 5 in which said confocal apertures in said mask are pinholes and said pattern of multiple confocal apertures comprises,

a matrix of pinholes in said mask positioned in an offset pattern for obtaining a complete image of said object in one continuous scan of said object.

7. The confocal imaging system of claim 6, further comprising:

a plurality of said matrices of pinholes, each matrix of said plurality of matrices being positioned at a different distance from said path of said object for simultaneously obtaining multiple images of said object, each of said images being at a different level during one continuous scan of said object.

8. The confocal imaging system of claim 5 in which said confocal apertures in said mask are confocal slits.

9. The confocal imaging system of claim 8, further comprising at least one wide gap slit in said mask for performing non-confocal microscopy in combination with said confocal slits of said pattern of multiple confocal apertures.

11. The confocal imaging system of claim 1 wherein said means for providing focussed radiation in a pattern of multiple focal volumes comprises:

a source of radiation; and

a plurality of fiber optic cables, each cable having a first end positioned to receive light from said source and a second end positioned to direct light towards said object.

12. The confocal imaging system of claim 11, further comprising,

a mask with a pattern of multiple confocal apertures, said second end of each of said fiber optic cables being directed at an aperture of said multiple confocal apertures in said mask.

13. The confocal imaging system of claim 1, further comprising:

a source for producing radiation that is directed towards said object; and

a beamsplitter positioned between said source and said object, said beamsplitter operating in conjunction with said means for directing and focussing said transmitted or reflected radiation from said object onto said array of detectors.

14. The confocal imaging system of claim 13 wherein said array of detectors is secured to said beamsplitter.

15. The confocal imaging system of claim 13, further comprising:

a mask with a pattern of multiple confocal apertures, said mask being secured to said beamsplitter.

16. The confocal imaging system of claim 1 wherein said means for providing focused radiation in a pattern of multiple focal volumes comprises a source of radiation and a source mask with a pattern of multiple confocal apertures wherein said source of radiation generates radiation that is directed through said multiple confocal apertures in said source mask, and wherein said means for directing and focussing said transmitted or reflected radiation from said object onto said detectors comprises a sensor mask positioned between said object and said array of detectors, said sensor mask being matched with said source mask.

17. The confocal imaging system of claim 16 wherein said source mask has a stepped surface with multiple confocal apertures on at least two steps of said stepped surface.

18. The confocal imaging system of claim 17 wherein said sensor mask has a stepped surface with openings on a least two steps of said stepped surface which correspond with said multiple confocal apertures on said stepped surface of said source mask.

19. The confocal imaging system of claim 1 wherein said means for providing focussed radiation in a pattern of multiple confocal volumes comprises a mask with a stepped surface with a pattern of multiple confocal apertures on at least two steps of said stepped surface.

20. The confocal imaging system of claim 1, further comprising a means for polarizing said focused radiation from said means for providing focussed radiation.

21. The confocal imaging system of claim 1 wherein said array of sensors are charge coupled device radiation sensors.

22. The confocal imaging system of claim 1 wherein said path on which said object is conveyed is non-perpendicular relative to a direction of said radiation provided by said means for providing focussed radiation.

23. The confocal imaging system of claim 1, further comprising an electronic processor for acquiring data signals from said array of sensors.

24. The confocal imaging system of claim 23, further comprising a means for smoothing data signals and generating height and extended focus images.

25. The confocal imaging system of claim 1 wherein said means for providing focussed radiation in a pattern of multiple focal volumes comprises a mask with both a pattern of multiple confocal apertures for confocal imaging and a window sufficiently wide for non-confocal imaging of said object.

26. The confocal imaging system of claim 1, further comprising:

one or more additional arrays of detectors for detecting radiation of different electromagnetic frequency;

means for separating said different frequencies of reflected or transmitted radiation and directing said radiation to said arrays of detectors;

and in which,

said means for supplying focused radiation supplies radiation in a multiple of different frequencies.

27. The confocal imaging system of claim 1, further comprising a means for adjusting a distance between said means for conveying said object along said path and said means for providing focused radiation in response to a determined height of a surface on said object.

28. The confocal imaging system of claim 1, further comprising a dark field imaging means associated with said means for providing focussed radiation and said array of detectors.

10. The confocal imaging system of claim wherein said means for providing focussed radiation in a pattern of multiple focal volumes comprises:

a mask with a pattern of multiple confocal apertures;

a source for directing radiation through said multiple confocal apertures; and

a condenser positioned to collect light from said source and an array of lenses positioned to receive said collected light and direct said light through said multiple confocal apertures in said mask.

29. A method for inspecting and/or imaging an object, comprising the steps of:

conveying an object along a path;

providing focused radiation in a pattern of multiple focal volumes at different heights and which are spatially separated from each other in a lateral direction in relation to said object in said path along which said object is conveyed; and

detecting radiation that is transmitted or reflected in response to the topography of said object as it moves along said path with an array of detectors in an expanded pattern matched with said pattern of multiple focal volumes with each detector in said array detecting radiation from only on focal volume.

30. A method as recited in claim 29 wherein said step of detecting radiation comprises the steps of directing and focusing said transmitted or reflected radiation from said object onto said array of detectors.

31. A method as recited in claim 29 wherein said step of providing focused radiation comprises the step of directing radiation from a source through a pattern of multiple confocal apertures in a mask.

32. A method as recited in claim 29 further comprising the step of polarizing said focused radiation.

33. A method as recited in claim 29 wherein said step of providing focused radiation comprises supplying radiation in a multiple of different frequencies, and further comprising the steps of separating said different frequencies of radiation and detecting said different frequencies of radiation.

34. A method as recited in claim 29 further comprising the step of adjusting a distance between said path along which said object is conveyed and a means for providing said focussed radiation in response to a determined height of a surface on said object.

35. A method as recited in claim 29 further comprising the step of generating a dark field image.

36. A method as recited in claim 29 further comprising the step of adjusting an incline of said path on which said object is conveyed.

37. A method as recited in claim 29 further comprising the steps of generating both a dark field image and a bright field image.