Image analysis – Image compression or coding
Reexamination Certificate
1999-05-28
2003-05-20
Couso, Yon J. (Department: 2725)
Image analysis
Image compression or coding
C348S541000
Reexamination Certificate
active
06567553
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image frame generating method, and more particularly to a method for digitally generating a diversified image frame.
BACKGROUND OF THE INVENTION
Conventionally, an image frame is a 3:4 rectangle formed by a plurality of horizontal image signal-lines. The horizontal image signal-lines have a plurality of pixels respectively. For example, the VGA specification provides a image consisting of 480 horizontal image signal-lines. Each horizontal line has 640 pixels. Normally, such a specification is indicated as 640(H)×480(V). An object can be scanned to generate a digital image of the object. The digital image can be outputted through an electrical projector to a display such as a liquid crystal display or a monitor. The electrical projector may be a cathode ray tube (CRT), which generates the scan lines. Referring to
FIG. 1
, the object is scanned by the optical sensor of the scanner to generate an analog image signal (Step S
11
). Then, the analog image signal is converted to a digital image signal by an analog to digital converter in Step S
12
. In Step S
12
, the digital image signal is stored in a memory unit. Finally, in Step
14
, the digital image signal is converted by a digital to analog converter and outputted to the electrical projector.
The electrical project will then generates an image frame as shown in FIG.
2
(
a
). However, sometimes there may be an error in the projecting angle of the electrical projector. Accordingly, a keystone frame as shown in FIG.
2
(
b
) or FIG.
2
(
c
) may be generated because of the different optical path of the scan lines. Referring to FIG.
2
(
a
), the normal image frame will have a rectangular shape wherein the dots A, B, C and D are located at the four corners of the rectangular frame. If the image is projected at an elevated angle, the frame will become a keystone shape as shown in FIG.
2
(
b
). The scan line between upper dots B
1
and C
1
has a length larger than that of the scan line between lower dots A
1
and D
1
because the upper dots have optical paths longer than those of the lower dots. Of course, if the image is projected at an angle of depression, the image frame will be a keystone shape as shown in FIG.
2
(
c
). The scan line between the lower dots A
2
and D
2
will be longer than that between dots B
2
and C
2
because of a longer optical path.
To avoid the undesired keystone image frame, an optical set is mounted in front of the electrical projecting device to correct the projecting angle of the image. However, to add stitch an optical set is very expensive. Furthermore, the optical set will occupy a certain volume. Therefore, the overall projecting system cannot be scaled down if such an optical set is mounted. Another method for correcting the keystone image frame is needed.
Furthermore, the conventional method for correcting the keystone frame can only perform a symmetric correction. Accordingly, a method which can not only correct the keystone frame but also diversify the outline of the image frame is desirable.
It is then attempt by the present invention to solve the abovementioned problem.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for generating a diversified-shaped image frame.
Another object of the present invention is to provide a method for correcting a keystone projecting-image frame without needing of an expensive optical set.
A further object of the present invention is to reduce the size of an electrical projecting device.
The present invention provides a method for generating a diversified-shaped image frame formed by a plurality of image signal lines. The method includes steps of determining a specific pixel frequency of one of the plurality of image signal lines, and outputting said one image signal line according to said specific pixel frequency. The steps are repeated until all of said plurality of image signal lines are outputted.
The pixel frequency is preferably a dot clock frequency of said one image signal line. The dot clock frequency is preferably generated by a phase lock loop (PLL) technique and a frequency divider.
The plurality of image signal lines are preferably horizontal image signal lines.
The method preferably further comprising steps of adding a plurality of black pixels to the two ends of the image signal line when outputting image signal lines. When outputting the image signal line and the black pixels added beside the image signal line, a logic control technique is preferably used for switching between the black pixels and the image signal line.
The image frame may include n image signal lines. I
3k−2
, I
3k−1
and I
3k
are the pixels added beside one end of the k
th
one of the image signal lines, the k
th
one of the image signal lines and the pixels added beside the other end of the k
th
one image signal lines respectively. Steps for determining the specific pixel frequency may include calculating the total pixel number of (I
3k−2
+I
3k−1
+I
3k
) and calculating and outputting the specific pixel frequency, wherein the specific pixel frequency is equal to the total pixel number of (I
3k−2
+I
3k−1
+I
3k
) divided by a duty cycle of a horizontal image-synchronous-signal of the kth image signal line, wherein n and k are positive integers and 1≦k≦n.
The plurality of image-signal lines are outputted by an electrical projecting device with an projecting angle &thgr;. Accordingly, the method for calculating the total pixel number may include inputting a value of the projecting angle &thgr;, inputting values of geometrical variance coefficients &dgr;k
1
and &dgr;k
2
, calculating the pixel numbers of I
3k−2
and I
3k
, inputting the pixel number of I
3k−1
, and summing up the pixel numbers of I
3k−2
, I
3k−1
and I
3k
for obtaining the total pixel number. The pixel numbers of I
3k−2
may be equal to (n−k+1)×tan &thgr;+&dgr;k
1
, and the pixel numbers of I
3k
may be equal to (n−k+1)×tan &thgr;+&dgr;k
2
.
There may have another method for calculating I
3k−2
and I
3k
. In this case, I
3k−2
=n×tan &thgr;−mod(k/D), and I
3k
=n×tan &thgr;−mod(k/D), wherein D=mod(tan &thgr;).
Once the specific pixel frequency has been calculated, the image signal line may be outputted through the following steps: generating a horizontal projecting-image synchronous-orientation signal of the k
th
image signal line according to the horizontal image-synchronous-signal of the k
th
image signal line, outputting I
3k−2
according to the horizontal projecting-image synchronous-orientation signal of the k
th
image signal line, the specific pixel frequency and the pixel number of I
3k−2
, finishing outputting I
3k−2
, and outputting I
3k−1
according to the specific pixel frequency and the pixel number of I
3k−1
, finishing outputting I
3k−1
, and outputting I
3k
according to the specific pixel frequency and the pixel number of I
3k
, and finishing outputting I
3k
. Preferably, an ending signal is provided for finishing outputting I
3k−2
to output I
3k−1
, an ending signal is provided for finishing outputting I
3k−1
to output I
3k
, and an ending signal is provided for finishing outputting I
3k
to output the next image signal line.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which:
REFERENCES:
patent: 4595953 (1986-06-01), Willis
patent: 4679091 (1987-07-01), Kikuchi et al.
patent: 5404173 (1995-04-01), Parrish et al.
patent: 5600379 (1997-02-01), Wagner
patent: 5872601 (1999-02-01), Seitz
patent: 6292225 (2001-09-01), Champion et al.
Arent Fox Kintner Plotkin & Kahn
Couso Yon J.
Mustek Systems Inc.
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