Computer graphics processing and selective visual display system – Computer graphic processing system
Reexamination Certificate
1999-06-15
2004-06-29
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphic processing system
C345S530000, C345S565000, C345S659000
Reexamination Certificate
active
06756985
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processor for processing image data and newly generating purposed image data to be displayed and an image display.
2. Description of the Related Art
In general, a projection display M such as a projection TV is mounted on a base B at a predetermined elevation angle &thgr; to project the light emitted from the display M on a screen S a predetermined distance L away from the display M.
Heretofore, a display for directly projecting the light of a CRT on a screen has been generally used so far for the projection display M. However, a display is recently used which uses a pixel structure such as a liquid-crystal panel or plasma display panel as a light bulb.
In this case, if the projection display M is set with the surface upward, a distorted image A
1
like a trapezoid with a long upper side is formed when projecting an originally-rectangular normal image A
0
on the display panel of the display M on the screen S as shown in FIG.
11
(
a
) and thereby, it is difficult to see the image A
1
.
Accordingly, it is necessary to display the normal image A
0
on the screen S by correcting the distortion of such an image A
1
.
Therefore, as shown in FIG.
11
(
b
), by previously deforming the normal image A
0
to obtain an image A
2
like a trapezoid with a long bottom side and projecting the image A
2
on the screen S, the normal rectangular image A
0
is displayed.
Thus, such a technical idea as to form the image A
2
obtained by previously deforming the normal image A
0
for distortion correction (hereafter, this processing is referred to as inverse correction) makes it possible to easily perform inverse correction and relatively easily correct the distortion of an image because a display such as a conventional CRT does not have any pixel structure and thereby, an image is deformed by changing the magnetic field of a deflecting coil.
However, as for the projection display M provided with a display panel having a pixel structure of liquid crystal or plasma, it is difficult to obtain the inversely-corrected image A
2
unless a video signal is digitally image-processed.
In this case, to form the image A
2
obtained by inversely correcting the normal image A
0
it is necessary to rewrite the data present at a certain coordinate position Q to other coordinate position P, as shown in FIG.
11
(
b
).
In this case, the relation between the both coordinate positions Q and P can be logically obtained by using a geometric relation based on such setting conditions as the elevation angle &thgr; and the projection distance L of the projection display M. Therefore, a transformation formula led from the geometric relation will be slightly described below by referring to FIGS.
12
(
a
) and
12
(
b
). That is, in FIGS.
12
(
a
) and
12
(
b
), it is assumed that the enlargement magnification of the display size on a screen surface
1202
is k, the projection distance is L, and the elevation angle is &thgr; on the basis of the size of a liquid-crystal panel surface
1201
. Moreover, when it is assumed that the coordinates of a point P on the liquid-crystal panel surface is P(x,y) and the coordinates of a point Q on the screen surface is Q(X,Y), the transformation formula between the points P and Q is shown as the following expression (Equation 1). In this case, the vertical/horizontal inversion phenomenon due to a lens system is not considered.
Y
(
y
)=
L·k·y
/(
L
·cos &thgr;−
k·y
·sin &thgr;)
X
(
x
)={
L
·cos &thgr;/(
L
·cos &thgr;−
k·y
·sin &thgr;}·
k·x
[Equation 1]
However, when a frame memory for storing a video signal can store data only in pixel unit and a display panel has a pixel structure, data can be displayed only in pixel unit. Therefore, when the value of the coordinate position P obtained through a simple logical computation has a fraction lower than a decimal point, the obtained coordinate position P does not match with a position where an actual pixel is present on a display panel.
Therefore, as shown in
FIG. 13
, the point P is set as a coordinate position where a display pixel is actually present on the display panel to conversely obtain the coordinate position of the point Q on the basis of the point P. In this case, because the coordinate position Q is a value merely obtained through computation, it does not always fit the coordinate position on a pixel of the frame memory and therefore, it may be shifted from coordinate positions Q
1
, Q
2
, . . . of actual pixels. Thus, actual data is not present on the coordinate position Q.
Therefore, in this case, coordinate positions Q
1
to Q
4
of peripheral pixels (four pixel in this case) are obtained from the coordinate position Q (hereafter, the coordinate positions Q
1
to Q
4
are referred to as reference pixel coordinates) to generate the data at the coordinate position of the point Q in accordance with the actual data stored in the reference pixel coordinates Q
1
to Q
4
(hereafter, the above data interpolation is referred to as filtering).
For example, when assuming pixel data values on the reference pixel coordinates Q
1
to Q
4
as D
1
to D
4
, the data D on the coordinate position Q necessary for inverse correction is computed in accordance with the following expression (Equation 2).
D=a
1
·
D
1
+
a
2
·
D
2
+
a
3
·
D
3
+
a
4
·
D
4
[Equation 2]
where a
1
to a
4
denote filter coefficient (weighting coefficient) and satisfy the relation of the following expression (Equation 3).
a
1
+
a
2
+
a
3
+
a
4
=1 [Equation 3]
When the data D on the coordinate position Q is made through filtering, it is possible to display an image by rewriting the data D to the coordinate position P and inversely correcting the image.
By performing the filtering for all pixels, the inversely-corrected image A
2
can be obtained on the display panel. Therefore, by projecting the image A
2
on the screen S, the normal image A
0
free from distortion is projected.
FIG. 14
is a block diagram showing the configuration of a conventional projection display D having a function for correcting the above distorted image, particularly that of an image processing circuit provided with a liquid-crystal panel serving as a light bulb.
In
FIG. 14
, symbol
81
denotes an DA converter for converting an input video signal into a digital value,
82
denotes a DA converter for converting a video signal into an analog value and outputting it,
83
and
84
denote RAMs for storing video-signal data, and
85
denotes a computing circuit for image-processing a video signal and controlling various sections.
A pair of RAMs
83
and
84
is used because, while data is transferred to one RAM such as the RAM
83
from the AD converter
81
, the computing circuit
85
cannot access the RAM
83
and therefore, the other RAM
84
is provided and the circuit
85
accesses the other RAM
84
so that the AD converter
81
and computing circuit
85
can apparently make an access at the same time.
In the above configuration, an input video signal is converted into a digital value by the AD converter
81
and its image data is written in the RAM
83
or
84
.
The computing circuit
85
reads image data from the RAM
83
or
84
, inversely corrects the image data, and writes the inversely-corrected image data in the RAM
83
or
84
again. Then, the circuit
85
transfers the inversely-corrected image data to the DA converter
82
from the RAM
83
or
84
and outputs an inversely-corrected video signal from the DA converter
82
.
FIG. 15
is a flow chart showing the image processing procedure by the computing circuit
85
.
Setting conditions such as the elevation angle &thgr; shown in FIG.
10
and the projection distance L are previously inputted (step
1
). It is enough to perform the above operation only one time when setting the projection display D.
Then, the pointer showing a pixel is initialized (hereafter referred to as output pixel pointer initial
Hirotsune Satoshi
Muraji Tsutomu
Bella Matthew C.
Matsushita Electric - Industrial Co., Ltd.
Monestime Mackly
Smith , Gambrell & Russell, LLP
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