Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-06-04
2002-03-26
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S182000
Reexamination Certificate
active
06362802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for acquiring an image for inspection of a flat panel display which can be advantageously used in inspecting a pixel defect, an uneven display or the like of a flat panel display such as, for example, a liquid crystal display (LCD), a plasma display (PDP) or the like, and to an apparatus for acquiring an image for inspection of such flat panel display using this method.
2. Description of the Related Art
An apparatus for inspecting quality of a picture or an image of a flat panel display (an image quality inspection apparatus for a flat panel display) such as a liquid crystal display, a plasma display or the like mainly comprises an inspection image acquisition apparatus for acquiring an image data for inspection, and an image quality inspection apparatus for inspecting whether or not any pixel defect (loss), an uneven display, or the like exists, using an image data acquired by this inspection image acquisition apparatus.
FIG. 17
is a block diagram showing a general construction of the portion of an inspection image acquisition apparatus in the image quality inspection apparatus for a flat panel display. As illustrated, this inspection image acquisition apparatus comprises a panel driver part
2
for driving a flat panel display (for example, a liquid crystal display)
8
to be inspected, a camera part
3
having a camera (for example, a CCD (charge coupled device) camera) therein for photographing (picking up as an image) a displayed image on the flat panel display
8
, an analog-to-digital (AD) converter
4
for converting a photographed analog image signal from the camera part
3
into a digital signal, an image memory
7
for storing therein the converted digital image signal, a pre-sampling processing part
5
for pre-sampling the digital image signal and converting the pre-sampled digital image signal into an image data in which each pixel thereof has the same size as that of the display screen (panel) of the flat panel display
8
, and a control part
1
for directly controlling the panel driver part
2
as well as controlling the AD converter
4
, the pre-sampling processing part
5
and the image memory
7
via a bus (BUS).
The flat panel display
8
to be inspected displays on its panel a test image or picture having a predetermined light and darkness (shade) based on a driving signal outputted from the panel driver part
2
under the control of the control part
1
(usually constituted by a CPU). The light and darkness image of the flat panel display
8
is photographed (picked up as an image) by the camera (solid state image pickup element) of the camera part
3
to supply it to the AD converter
4
. The analog image signal from the camera part
3
is converted by the AD converter
4
into digital pixel data of light and darkness (hereinafter, referred to as pickup pixel data), which is in turn temporarily stored in the image memory
7
.
The pickup pixel data converted into a digital signal is pre-sampled by the pre-sampling processing part
5
, and is converted into an image data in which each pixel thereof has the same size as that of the panel of the flat panel display
8
. The converted image data is hereinafter referred to as pre-sampling image data or a display pixel data. The converted display pixel data is stored in the image memory
7
. Further, since the method for converting pickup pixel data to pre-sampling image data is described in detail in Japanese Patent Applications (refer to Japanese Patent Application Laid Open No. Hei 8-29360 (29360/1996) and Japanese Patent Application Laid Open No. Hei 10-31730 (31730/1998)) previously proposed by the present applicants, reference should be made to those Japanese Patent Applications or Japanese Patent Application Laid Open Publications thereof. In addition, the descriptions of those Japanese Patent Applications are incorporated into the present specification.
In order to suppress the occurrence of any moiré in the display pixel data obtained by converting an analog image signal picked up by the camera part
3
into digital pickup pixel data and applying the pre-sampling processing to the pickup pixel data with higher accuracy, it is desired that the pixel magnification is an integer magnification such as two times or so. Here, the pixel magnification is defined as a ratio of the number of pixels of the panel of the flat panel display
8
to the number of pixels of the solid state image pickup element (for example, CCD element) of the camera part
3
. As an example, the condition that one pixel of the panel of the flat panel display
8
is photographed or picked up by 2×2 pixels of the solid state image pickup element of the camera part
3
is said that the pixel magnification is two.
However, with the progress of a fine pitched and high precision flat panel display
8
, and by a limitation of pixel size of the camera part
3
on the other side, there often occurs a case that the pixel magnification to be set is unavoidably set to a non-integer magnification less than 2.
When the pixel magnification is set to a non-integer magnification less than 2, a periodic pixel value fluctuation occurs in each of the pickup pixel data and the pre-sampling image data or display pixel data, the pickup pixel data being acquired by the camera part
3
and being converted into digital data, the display pixel data being obtained by applying a pre-sampling processing to the pickup pixel data. This periodic pixel value fluctuation is called moiré of image.
FIG. 18
shows an example of the result obtained by that in case of setting the pixel magnification to 1.8, pixel values (each corresponding to brightness of a pixel) of the display pixel data acquired by the camera part
3
and stored in the image memory
7
are summed up, for the same X address (X address is defined as horizontal or lateral axis herein), in Y address direction (vertical or longitudinal axis direction). In
FIG. 18
, it is recognized that a moiré of approximately five-pixel period has occurred, that is, a moiré occurs approximately at intervals of five pixels. There is a problem that this moiré comes to a noise component, resulting in great decrease in the inspection accuracy of the flat panel display
8
.
The moiré of an image has already occurred in the state that the distribution of light intensity of the flat panel display
8
is sampled by pixels of the image pickup element (for example, CCD) of the camera part
3
. This is primarily caused by that the difference of relative position between a display pixel of the flat panel display
8
and a pixel of the image pickup element of the camera part
3
is reflected to the display pixel data (pre-sampling image data). Further, hereinafter, a pixel of the image pickup element of the camera part
3
is referred to as a pickup pixel, and a display pixel of the panel of the flat panel display
8
is referred to as a display pixel.
FIG. 19
shows an example of relative position between a pickup pixel and a display pixel in the case of the pixel magnification of 1.8. In this example, the pickup pixels are pixels of the CCD image pickup element, and the display pixels are display pixels of the panel of a liquid crystal display (LCD). Further, in this case, in order to simplify the explanation, the description will be given based on a one-dimensional signal.
Since the pixel magnification is 1.8, as shown in
FIG. 19A
, 9 pixels of the pickup pixels correspond to 5 pixels of the display pixels, and this positional relationship is periodically repeated. The sampling values G(n) (n is an integer from 1 to 10) (refer to FIG.
19
C), in this case, sampled by the first to the tenth pickup pixels with respect to the periodic light intensity distribution g(x) (refer to
FIG. 19B
) of the display pixels are shown by the following equation (1).
G
(
1
)
=
∫
x
0
x
1
g
(
x
-
x
0
+
x
2
2
)
ⅆ
x
G
(
2
)
=
∫
x
1
x
2
g
(
x
-
x
0
+
x
2
2
)
ⅆ
x
+
Fujiwara Kiyoshi
Ichikawa Masayoshi
Advantest Corporation
Gallagher & Lathrop
Lathrop, Esq. David N.
Patel Nitin
Shalwala Bipin
LandOfFree
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