Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
1999-10-04
2001-09-04
Karlsen, Ernest (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S754120
Reexamination Certificate
active
06285207
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to testing substrates and more particularly to testing electrically conductive substrates.
In recent years, small “laptop” computers have become popular. Because of their size and portability, small flat panel screens are used in laptop computers instead of more traditional video displays.
FIG. 1A
shows a laptop computer
10
with a flat panel display
12
.
A side view of a typical flat panel display
12
is shown in FIG.
1
B. During operation, selected pixels
14
on an active matrix plate are switched on or off. For a color display, the pixels
14
are grouped in triplets corresponding to the colors red, green, and blue. A liquid crystal
18
is sandwiched between the active matrix plate
16
and a color filter plate
20
having color filters
22
. Seals
24
at edges of the flat panel display
10
uphold the active matrix plate
16
, the liquid crystal
18
, and the color filter plate
20
together and prevent the liquid crystal
18
from spilling out of the active matrix plate
16
.
The pixels
14
which are turned on are set at various voltages. The voltages affect parallel and perpendicular dielectric constants of the liquid crystal
18
. By changing these dielectric constants, the liquid crystal's ability to polarize light also changes. Light impinging upon the active matrix plate
16
is indicated by upward arrows in FIG.
1
B. During operation, light shines through the active matrix plate
16
and is polarized in the liquid crystal
18
. The light is then filtered by the color filters
22
to make an image on the flat panel display
12
.
FIG. 1C
shows a schematic representation of an active matrix
26
on an active matrix plate
16
. Each pixel
14
is controlled by a transistor
28
. By applying a voltage to one of an odd set of data electrodes
30
or even set of data electrodes
32
, a source side of each transistor
28
can be biased. By applying another voltage to a gate of a selected biased transistor
28
via either odd gate electrodes
33
or even gate electrodes
34
, a drain for the selected biased transistor
28
is activated, and a voltage is applied to the corresponding pixel
14
. In this way, each pixel
14
in the active matrix plate
16
can be activated.
As with other electrical devices, flat panel displays
12
and the active matrix plates
16
are tested for quality assurance.
FIG. 2A
is a diagrammatic representation of a side view of a conventional active matrix plate tester
40
. Under testing, a probe frame
42
with probe leads
43
sits atop the active matrix plate
16
. The probe frame
42
electrically connects a pattern generator
44
to the data electrodes
30
,
32
and gate electrodes
33
,
34
. The pattern generator
44
outputs voltages to the active matrix plate electrodes
30
,
32
, and
34
to activate the various transistors
28
and pixels
14
.
Motors (not shown) horizontally and vertically position a sensing head
46
over a local area of the active matrix plate
16
to be tested. The plate rests on a support
45
. Once positioned, other motors (not shown) orient the sensing head
46
with respect to an upper surface
48
of the active matrix plate
16
. Similarly, a half-silvered mirror
50
is horizontally and vertically positioned and oriented with respect to the sensing head
46
.
During testing, the pattern generator
44
attempts to activate a specific pixel or pixels
14
by sending voltages to the active matrix plate
16
as described above and electrically biasing a rigid sensing material
47
on the sensing head
46
. The rigid sensing material
47
responds to voltage changes generated by the pixels
14
by changing its optical properties. The pattern generator
44
commands a light source
51
to shine a beam of light onto the half-silvered mirror
50
. The half-silvered mirror
50
reflects the beam through the rigid sensing material
47
and sensing head
46
. The light then travels down and is reflected back up by a mirrored bottom of the rigid sensing material
47
. The reflected light then passes upward through the sensing head
46
and the half-silvered mirror
50
.
A camera
52
photographs the reflected light. The pattern generator
44
directs the camera
52
to photograph the light once the sensing head
46
and the half-silvered mirror
50
are positioned and oriented and after the light source has emitted its beam of light.
Since the sensing head
46
can only be in proximity to part of the active matrix plate
16
, the conventional active matrix plate tester
40
must make several iterations of the above procedure resulting in several pictures of local areas of the active matrix plate
16
. Either before or after the camera
52
takes all the pictures, each picture is transferred into a digital format. Because the rigid sensing material
47
provides relatively weak optical signature, image processing is required to extract defect information from the digitized pictures. Therefore, an image processor
54
must process the pictures before defect patterns can be shown on a monitor
56
.
FIG. 2B
is a diagrammatic representation of a sensing head
46
while testing a local area of an active matrix plate
16
. Generally, the rigid sensing material is glued to the sensing head
46
. Because the sensing material
47
is rigid, the sensing material does not contact a surface
25
of the active matrix plate
16
because the rigid sensing material
47
may damage the active matrix plate
16
. Furthermore, the surface irregularities create irregular distances between surface
25
of the active matrix plate
16
and the rigid sensing material
47
. Thus, the sensitivity of the rigid sensing material
47
to pixel voltages is drastically degraded. Largely because of this, the pictures taken by the camera
52
must undergo image processing as described above.
FIG. 3
is a flow diagram summarizing a typical conventional method
60
of testing an active matrix plate
16
beginning at a step
62
. This conventional method
60
was just described with reference to the conventional active matrix plate tester
40
in FIG.
2
A. Initially, the active matrix plate
16
is placed in the tester
40
in a step
64
. Then, the probe frame
42
is positioned on the active matrix plate
16
in a step
66
. The sensing head
46
with the rigid sensing material
47
is then placed over a local area to be tested in a step
68
and the sensing head
46
and rigid sensing material
47
are oriented with respect to the local area in a step
70
. In a step
72
, the pattern generator
44
applies voltages to the active matrix plate
16
via data electrodes
30
,
32
and gate electrodes
33
,
34
. Step
74
applies a voltage to bias the rigid sensing material
47
at an operating voltage. As with the light source
52
and half-silvered mirror
50
as discussed above, the local area is illuminated in a step
76
. After being reflected off a bottom of the rigid sensing material
47
and passing through the rigid sensing material
47
, the camera detects the light in step
78
. The camera pictures are image processed in step
80
to remove noise.
Step
82
determines whether all test patterns for a particular voltage have been sent to the active matrix plate
16
. Generally, a voltage signal is applied to the odd electrodes
30
followed by the same signal to the odd electrodes
30
with negative voltage magnitude. Step
82
determines that not all signals have been applied after the positive and negative voltage signals have both been applied to the odd electrodes
30
. Then the same signals are “reversed” in a step
84
by applying them to even electrodes
32
. Steps
76
,
78
, and
80
are then repeated for the positive and negative voltage signals applied to the even electrodes
32
. Then step
82
answers yes, and step
86
determines whether all local areas have been tested. If not, conventional method
60
returns to step
68
to repeat steps
68
,
70
,
72
,
74
,
76
,
78
,
80
,
82
, and
84
for a new local area. Once all local areas have been t
Fish & Richardson P.C.
Karlsen Ernest
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