Automatic saw-mark defect inspection in solar wafer images

lynxherringΤεχνίτη Νοημοσύνη και Ρομποτική

18 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

80 εμφανίσεις

Automatic saw
-
mark
defect
inspection

in solar wafer images



D
u
-
Ming Tsai
,
Wei
-
Chen

Li



Department of Industrial Engineering and Management, Yuan
-
Ze University
,

No. 135 Yuan
-
Tung Road, Chungli, Taoyuan,

Taiwan

iedmtsai@saturn.yzu.edu.tw



Abstrac
t
:

This paper
presents

a
method

of automatic defect inspection
for

the photovoltaic industry, with a special focus
on multicrystalline solar wafers. It presents a machine vi
sion
-
based scheme to automatically detect

saw
-
mark defects in
solar wafer surfaces. A saw
-
mark defect is a severe flaw that occurs
when

a silicon ingot is cut into wafers.
On
-
line
inspection of sliced wafers ensures product quality and prevents inferior wafers from reaching the back
-
end processin
g
.

It
also can avoid
the downstream manufacturer
from

work
ing

on a flawed wafer and thus can decrease unnecessary
operation cost
s

and rework
ing
.

A multicrystalline solar wafer surface pres
ents random shapes, sizes, and orientations of
crystal grains in th
e surface, making the automatic detection of saw
-
mark defects extremely difficult.


The proposed saw
-
mark detection scheme involves two main procedures: 1) Fourier image reconstruction to remove the
multi
-
grain background of a solar wafer image, and 2) a
line detection process in the reconstructed image to locate
saw
-
marks. The Fourier transform (FT) is used to eliminate crystal grain patterns and results in a non
-
textured surface in
the reconstructed image. Since a saw
-
mark is presented horizontally in th
e sliced wafer, vertical scan lines in the
reconstructed image are individually evaluated by a line detection process. A pixel far away from the line sought can then
be effectively identified as a defect point. Experimental results show that the proposed m
ethod can effectively detect
various saw
-
mark defects, specifically black lines, white lines, and impurities in multicrystalline solar wafers.



Keywords:
Surface inspection; Defect detection;

Solar wafer
; Saw mark
; Machine vision


Topic:

Manufacturing/Ind
ustrial Automation