Browse Prior Art Database

Printed Circuit Board Through-Hole Inspection Using Video Camera

IP.com Disclosure Number: IPCOM000039722D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Takeo, Y: AUTHOR

Abstract

Through-holes of multilayer printed circuit boards are inspected for epoxy smears by a video camera with its optical axis slanted with respect to the vertical axis. With the camera oriented in this manner, the through-hole is sensed as an elliptical image. To facilitate image processing, the elliptical image is coordinate-translated to a rectangular image. Fig. 1 shows the inspection arrangement. The printed circuit board to be inspected is placed on a frosted glass support plate illuminated from below. The optical axis of the video camera is oriented at an angle of 15o-45o with respect to vertical axis. Fig. 2A shows an elliptical through-hole image as viewed from the camera. As shown in Fig.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Printed Circuit Board Through-Hole Inspection Using Video Camera

Through-holes of multilayer printed circuit boards are inspected for epoxy smears by a video camera with its optical axis slanted with respect to the vertical axis. With the camera oriented in this manner, the through-hole is sensed as an elliptical image. To facilitate image processing, the elliptical image is coordinate- translated to a rectangular image. Fig. 1 shows the inspection arrangement. The printed circuit board to be inspected is placed on a frosted glass support plate illuminated from below. The optical axis of the video camera is oriented at an angle of 15o-45o with respect to vertical axis. Fig. 2A shows an elliptical through- hole image as viewed from the camera. As shown in Fig. 2B, a selected elliptical image portion C of the sensed through-hole image is coordinate-translated to a rectangular image D based upon an elliptical function obtained from the slant angle of the optical axis of the camera, the diameter of the through-hole and

(Image Omitted)

the coordinates of a reference point P. Then, as shown in Fig. 2C, an object area E for smear detection is extracted from the rectangular image D. The reflectance values of pixels of the area E are normalized based upon reflectances at dark portions A1 and A2 and light portion B and then accumulated for comparison with a reference value.

1

Page 2 of 2

2

[This page contains 5 pictures or other non-text objects]