Precision solder resist registration inspection method

• US 8,648,906 B2
• Filed: 10/13/2010
• Issued: 02/11/2014
• Est. Priority Date: 10/13/2010
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Delaney, Mark Lawrence
• Primary Examiner(s): Vo, Tung
• Assistant Examiner(s): SOSANYA, OBAFEMI OLUDAYO
• Application Number:
  US12/904,013
• Publication Number:
  US 20120092488A1
• Time in Patent Office: 1,217 Days
• Field of Search: 348 84- 86, 348125-135
• US Class Current: 348/128
• CPC Class Codes: G01B 11/0608 Height gauges
• CPC Class Codes: G01B 11/0658 with measurement of emissivity or reradiation
• CPC Class Codes: G01N 21/95684 Patterns showing highly reflecting parts, e.g. metallic elements
• CPC Class Codes: G06T 2207/10056 Microscopic image
• CPC Class Codes: G06T 2207/10064 Fluorescence image
• CPC Class Codes: G06T 2207/20081 Training; Learning
• CPC Class Codes: G06T 2207/30152 Solder
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

A method is disclosed for operating a machine vision inspection system to determine a fluorescent imaging height for acquiring a fluorescent image for repeatably determining the location of a feature within the fluorescent material. The height of an exposed workpiece portion exposed outside of the fluorescent material is determined (e.g., using a height sensor or autofocus operations). The determined height is repeatable. The exposed portion has a characteristic height relative to the fluorescent material and/or features located therein. The fluorescent imaging height, which may be inside the fluorescent material, is determined relative to the determined height of the exposed portion. The fluorescent imaging height is determined such that it enhances the detection of the desired feature located within the fluorescent material in the resulting fluorescent image. For a variety of workpieces, the method provides automatic acquisition of appropriately focused fluorescent image more reliably than previously known methods.

Claims

1. A method for operating a machine vision inspection system to determine a fluorescent imaging height for acquiring a fluorescent image for repeatably determining the location of a workpiece feature edge that is located within a layer of fluorescent material on a workpiece, the method comprising:

(a) positioning an exposed portion of a surface of the workpiece such that its height is able to be determined by the machine vision inspection system, wherein the exposed portion is not covered by the layer of fluorescent material and has a characteristic surface height along a focus axis relative to a height within the layer of fluorescent material;

(b) configuring the machine vision inspection system to determine the height of the exposed portion;

(c) determining the height of the exposed portion;

(d) using the determined height of the exposed portion, determining a fluorescent imaging height to be used for fluorescent imaging of the workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material, wherein the fluorescent imaging height is determined in relation to the determined height of the exposed portion; and

performing at least one of (e) and (f), wherein (e) comprises;

(e) storing the determined fluorescent imaging height in association with a part program for later use when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material,

and (f) comprises;

(f) using the fluorescent imaging height determined in relation to the determined height of the exposed portion during execution of a part program when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material.

2. The method of claim 1, wherein the workpiece is a representative workpiece and the method is performed in association with a learn mode of operation of the machine vision inspection system, which is used for creating a part program to be used for inspecting workpieces similar to the representative workpiece, and the method comprises performing the steps (a), (b), (c), (d) and (e).

3. The method of claim 2, further comprising:

(g) positioning the workpiece feature edge that is located within the layer of fluorescent material in a field of view of the machine vision inspection system;

(h) positioning the machine vision inspection system at the determined fluorescent imaging height;

(i) illuminating the field of view using an excitation wavelength profile which causes the fluorescent material to fluoresce and output fluorescent imaging light;

(j) acquiring a fluorescent image of the field of view using the fluorescent imaging height while illuminating the field of view using the excitation wavelength profile; and

(k) determining a location of the workpiece feature edge that is located within the fluorescent material based on a location of a corresponding intensity change in the fluorescent image.

4. The method of claim 3, wherein step (k) comprises configuring the parameters of an edge detection video tool of the machine vision inspection system, and using that edge detection video tool in order to determine the location of the workpiece feature edge on the representative workpiece, and the method further comprises:

(l) storing the configured parameters of the edge detection video tool in association with the part program, for later use to determine the location of the workpiece feature edge in fluorescent images of workpieces similar to the representative workpiece.

5. The method of claim 1, wherein the method is performed in association with a run mode of operation of the machine vision inspection system by executing a part program that includes inspecting the workpiece feature edge that is located within the fluorescent material on a workpiece that is similar to a representative workpiece used to create the part program, and the method comprises performing the steps (a), (b), (c), (d) and (f), wherein in step (d) determining the fluorescent imaging height to be used for fluorescent imaging of the workpiece feature edge comprises recalling fluorescent imaging height information stored in association with that workpiece feature edge in the part program, and determining the fluorescent imaging height based on that information.

6. The method of claim 5, comprising:

(g) positioning the workpiece feature edge that is located within the layer of fluorescent material in the field of view of the machine vision inspection system;

(h) positioning the machine vision inspection system at the determined fluorescent imaging height;

(i) illuminating the field of view using an excitation wavelength profile which causes the fluorescent material to fluoresce and output fluorescent imaging light;

(j) acquiring a fluorescent image of the field of view using the fluorescent imaging height while illuminating the field of view using the excitation wavelength profile; and

(k) determining a location of the workpiece feature edge that is located within the fluorescent material based on a location of a corresponding intensity change in the fluorescent image.

7. The method of claim 6, wherein step (k) comprises configuring an edge detection video tool of the machine vision inspection system according to associated parameters stored in the part program, and using that edge detection video tool in order to determine the location of the workpiece feature edge in the fluorescent image.

8. The method of claim 6, further comprising:

(l) determining the location of an edge of the layer of fluorescent material; and

(m) determining a measurement of a dimensional relationship between the location of the edge of the layer of fluorescent material layer and the location of the workpiece feature edge that is located within the layer of fluorescent material.

9. The method of claim 8, wherein:

the edge of the layer of fluorescent material is an edge included in the fluorescent image of the field of view acquired in step (j); and

in step (l), determining the location of an edge of the layer of fluorescent material comprises locating the edge of the layer of fluorescent material in the fluorescent image acquired in step (j).

10. The method of claim 1, wherein the machine vision inspection system comprises a fluorescent imaging filter that blocks at least one wavelength of an excitation wavelength profile used as illumination when acquiring a fluorescent image and passes at least one wavelength of fluorescent imaging light emitted by the fluorescent material, and in step (j), acquiring the fluorescent image comprises using the fluorescent imaging filter to filter the image light used to form the fluorescent image.

11. The method of claim 1, wherein the fluorescent imaging height is determined as an offset dimension in relation to the determined height of the exposed portion.

12. The method of claim 1, wherein the fluorescent imaging height is determined such that it falls within the layer of fluorescent material.

13. The method of claim 1, wherein the exposed portion is selected such that it has a surface height that falls within a height dimension of the layer of fluorescent material.

14. The method of claim 13, wherein the exposed portion of the surface of the workpiece is selected such that it is nominally located at the same surface height as a surface of a material layer that has the workpiece feature edge that is located within the fluorescent material.

15. The method of claim 1, wherein:

the machine vision inspection system comprises a surface height sensor comprising one of a touch probe type sensor, an optical triangulation type sensor, and a focus signal sensor;

step (a) comprises positioning the exposed portion in a working range of the surface height sensor;

step (b) comprises configuring the machine vision inspection system to use the surface height sensor to determine the height of the exposed portion; and

step (c) comprises using the surface height sensor to determine the height of the exposed portion.

16. The method of claim 1, wherein:

step (a) comprises positioning the exposed portion in a field of view of the machine vision inspection system;

step (b) comprises configuring the machine vision inspection system in a first configuration to provide an image of at least the exposed portion; and

step (c) comprises determining a focus height of the exposed portion based on images of the exposed portion acquired at different heights while the machine vision inspection system is in the first configuration and using that focus height as the determined height of the exposed portion.

17. The method of claim 16, wherein:

the machine vision inspection system comprises controllable lighting that is controllable to output at least two wavelength profiles comprising;

a non-excitation wavelength profile which illuminates the workpiece such that the workpiece provides primarily reflected image light and an insignificant amount of fluorescent light in response to the non-excitation wavelength profile, such that the non-excitation wavelength profile may be used to acquire non-fluorescent images, and

an excitation wavelength profile which causes the layer of fluorescent material to fluoresce and output a significant amount of fluorescent imaging light such that the excitation wavelength profile may be used to acquire the fluorescent image; and

in step (b), the first configuration includes configuring the controllable lighting to output the non-excitation wavelength profile and to not output the excitation wavelength profile.

18. The method of claim 17, wherein the controllable lighting comprises a ring light, and the first configuration includes outputting the non-excitation wavelength profile from the ring light.

19. The method of claim 17, wherein acquiring the fluorescent image includes configuring the controllable lighting to output the excitation wavelength profile and to not output the non-excitation wavelength profile.

20. A non-transitory computer-readable storage medium with instructions stored thereon that are executable by a processor in a machine vision inspection system to perform operations of:

(a) positioning an exposed portion of a surface of a workpiece such that its height is able to be determined by the machine vision inspection system, wherein the exposed portion is not covered by a layer of fluorescent material and has a characteristic surface height along a focus axis relative to a height within the layer of fluorescent material;

(b) configuring the machine vision inspection system to determine the height of the exposed portion;

(c) determining the height of the exposed portion;

(d) using the determined height of the exposed portion, determining a fluorescent imaging height to be used for fluorescent imaging of a workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material, wherein the fluorescent imaging height is determined in relation to the determined height of the exposed portion; and

performing at least one of (e) and (f), wherein (e) comprises;

(e) storing the determined fluorescent imaging height in association with a part program for later use when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material,

and (f) comprises;

(f) using the fluorescent imaging height determined in relation to the determined height of the exposed portion during execution of a part program when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material.

21. A machine vision inspection system for performing measurement operations on a workpiece, the machine vision inspection system comprising:

a memory for storing programmed instructions; and

a processor configured to execute the programmed instructions to perform operations including;

(a) positioning an exposed portion of a surface of the workpiece such that its height is able to be determined by the machine vision inspection system, wherein the exposed portion is not covered by a layer of fluorescent material and has a characteristic surface height along a focus axis relative to a height within the layer of fluorescent material;

(b) configuring the machine vision inspection system to determine the height of the exposed portion;

(c) determining the height of the exposed portion;

(d) using the determined height of the exposed portion, determining a fluorescent imaging height to be used for fluorescent imaging of a workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material, wherein the fluorescent imaging height is determined in relation to the determined height of the exposed portion; and

performing at least one of (e) and (f), wherein (e) comprises;

(e) storing the determined fluorescent imaging height in association with a part program for later use when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material,

and (f) comprises;

(f) using the fluorescent imaging height determined in relation to the determined height of the exposed portion during execution of a part program when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material and is covered by the fluorescent material.