Pick and place machine with component placement inspection

• US 20070116352A1
• Filed: 01/18/2007
• Published: 05/24/2007
• Est. Priority Date: 11/13/2001
• Status: Abandoned Application

• Current Assignee: CyberOptics Corporation (Nordson Corporation)
• Original Assignee: CyberOptics Corporation (Nordson Corporation)
• Inventors: Fishbaine, David, Roth, Scott, Madsen, David, Bushman, Thomas, Haugen, Paul, Dale, Theodore, Liberty, Todd, Duquette, David, Buchika, Brant, Gaida, John
• Application Number:
  US11/654,791
• Publication Number:
  US 20070116352A1
• Time in Patent Office: Days
• US Class Current: 382/151
• CPC Class Codes: H04N 13/194 Transmission of image signals
• CPC Class Codes: H04N 13/207 using a single 2D image sensor
• CPC Class Codes: H04N 13/218 using spatial multiplexing
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects
• CPC Class Codes: H04N 2013/0081 Depth or disparity estimation from stereoscopic image signals
• CPC Class Codes: H05K 13/0812 the monitoring devices being integrated in the mounting machine, e.g. for monitoring components, leads, component placement
• CPC Class Codes: H05K 13/0818 Setup of monitoring devices prior to starting mounting operations; Teaching of monitoring devices for specific products; Compensation of drifts during operation, e.g. due to temperature shifts
• CPC Class Codes: Y10T 29/49778 with aligning, guiding, or instruction
• CPC Class Codes: Y10T 29/53087 with signal, scale, illuminator, or optical viewer
• CPC Class Codes: Y10T 29/53191 Means to apply vacuum directly to position or hold work part

Abstract

Improved component placement inspection and verification is performed by a pick and place machine. Improvements include stereovision imaging of the intended placement location; enhanced illumination to facilitate the provision of relatively high-power illumination in the restricted space near the placement nozzle(s); optics to allow image acquisition device to view the placement location from an angle relative to a plane of the placement location, thereby reducing the possibility of such images being obstructed by the component; techniques for rapidly acquiring images with commercially available CCD arrays such that acquisition of before and after images does not substantially impact system throughput; and image processing techniques to provide component inspection and verification information.

Claims

1. A method of processing a plurality of images of an intended placement location in a pick and place machine to verify component placement, the method comprising:

acquiring before-placement and after-placement images of an intended placement location;

selecting a region of interest in the before-placement and after-placement images;

generating a difference image based upon differences between the before-image and the after-image;

thresholding the difference image to produce a binary difference image;

performing connectivity analysis on the binary difference image to obtain an image metric; and

comparing the image metric with expected object metric to provide component placement verification.

2. The method of claim 1, and further comprising masking at least one area known to change in the before and after images.

3. The method of claim 2, wherein the area includes a nozzle of the pick and place machine.

4. The method of claim 1, and further comprising masking at least one area not within an expected envelope of the component.

5. The method of claim 1, and further comprising:

aligning the before-image with the after-image before obtaining the difference image.

6. The method of claim 5, wherein the step of aligning includes applying a correlation.

7. The method of claim 1, and further comprising:

performing a morphological erosion operation on the binary difference image.

8. The method of claim 7, wherein the morphological erosion operation is repeated.

9. The method of claim 1, and further comprising performing a morphological dilation operation on the binary difference image.

10. The method of claim 9, wherein the morphological dilation operation is repeated.

11. The method of claim 1, wherein the metric includes object centroid.

12. The method of claim 1, wherein the metric includes object length.

13. The method of claim 1, wherein the metric includes object width.

14. The method of claim 1, wherein the metric includes object area.

15. The method of claim 1, wherein the metric includes object rotation.

16. The method of claim 1, wherein the method is performed within an image acquisition device.

17. A method of processing a plurality of images of an intended placement location in a pick and place machine to verify component placement, the method comprising:

acquiring before-placement and after-placement images of an intended placement location;

selecting a region of interest in the before-placement and after-placement images;

generating a difference image based upon differences between the before-image and the after-image;

thresholding the difference image to produce a binary difference image;

calculate pixel change count of the intended placement location;

calculate total pixel count; and

comparing the pixel change count of the intended placement location with the total pixel count to provide component placement verification.

18. A method of processing a plurality of images of an intended placement location in a pick and place machine to verify component placement, the method comprising:

acquiring before-placement and after-placement images of an intended placement location;

selecting a region of interest in the before-placement and after-placement images;

generating a difference image based upon differences between the before-image and the after-image;

calculate difference intensity sum of the intended placement location;

calculate total pixel difference intensity sum; and

comparing the pixel difference intensity sum of the intended placement location with the total pixel difference intensity sum to provide component placement verification.