Pick and place machine with component placement inspection

An image acquisition device for use in a pick and place machine, the device comprising:

• a detector array;
• optics having an optical axis to view an intended placement location at an angle with respect to a plane of the intended placement location and adapted to focus an image of the intended placement location on the detector array;
• and
• wherein the detector array is disposed at an angle relative to the optical axis.

A method of acquiring a plurality of images in a pick and place machine, the method comprising:

• resetting photosites of a photosensitive array;
• acquiring a first image on the photosites;
• transferring the first image to a non-photosensitive area of the array;
• resetting the photosites of the photosensitive array to clear the first image;
• and
• generating a controlled exposure to acquire a second image before the first image is read completely from the non-photosensitive area of the array.

A method of acquiring a plurality of images of a placement location in a pick and place machine, the method comprising:

• resetting photosites of a first photosensitive array;
• acquiring a first image on the photosites of the first photosensitive array;
• resetting photosites of a second photosensitive array;
• and
• acquiring a second image on the photosites of the second photosensitive array;
• wherein the first and second arrays acquire images sequentially through common optics.

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.

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.

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.

A pick and place machine for placing a component upon a workpiece, the machine comprising:

• an image acquisition system having a CCD array;
• optics including multiple image paths to simultaneously focus a plurality of images of an intended placement location upon the CCD array;
• wherein the image acquisition system acquires a plurality of before placement images of the intended location before the component is placed, and acquires a plurality of after placement images of the intended placement location after the component is placed;
• and
• a host controller coupled to the image acquisition system compares the before placement images with the after placement images to verify component placement.

A method of calibrating an off-axis image system in a pick and place machine, the method comprising:

• placing a known target in an intended placement location;
• acquiring an off-axis image of the known target;
• determining initial positions of known artifacts on the known target from the acquired image;
• and
• calculating a transformation matrix.

A method of calibrating a plurality of image acquisition devices in a pick and place machine, the method comprising:

• placing a known target in an intended placement location;
• acquiring an image of the known target with each image acquisition device;
• determining positions of known artifacts on the known target from the acquired images;
• and
• comparing the determined positions from each acquired image to calibrate for depth.