Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
1998-07-29
2003-10-07
Mehta, Bhavesh M. (Department: 2625)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C358S525000, C348S538000, C345S472000
Reexamination Certificate
active
06631216
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image interpolating apparatus adapted for use in a digital camera or the like.
2. Related Background Art
Recent progress in the digital signal processing technology has greatly contributed to the expansion of the imaging. The emergence of digital recording media such as digital video camera and digital still camera has realized an environment where the recording, editing and working of image data can be easily achieved with high image quality by the personal computer or the like.
In such environment, the technology of image reduction and enlargement on real time basis within the image pickup apparatus itself is anticipated to become more and more important in the future.
The conventional digital video cameras are usually provided with a function of so-called electronic zooming, for enlarging the picked-up image by interpolation, in order to obtain an image enlarged beyond the optical zooming. There can also be achieved other processes such as electronic zoom-out for obtaining a reduced image.
In case of linearly interpolating continuous image data, obtained by sampling with a certain sampling frequency, with a sampling pitch of another sampling frequency, there is required a relative positional data k indicating the relative relationship in time between the original pixel data adjacent to an interpolated pixel and such interpolated pixel.
For obtaining such data in continuous manner, there is known a method of employing memory readout means utilizing an accumulator as disclosed in the U.S. Pat. No. 4,774,581.
FIG. 1
is a schematic view showing a part of the image of a field, stored in a field memory, wherein S
n
and S
n−1
indicate stored pixel data and S′ indicates data of the interpolated pixel.
In the illustrated situation, the relationship of S
n
, S
n−1
and S′ is represented by:
S′=S
n
·k+S
n−1
·(1−
k
).
In order to achieve this calculation with a digital circuit, with a reduced number of multipliers, this equation is modified as:
S′=
(
S
n
−S
n−1
)·
k+S
n−1
.
FIG. 2
shows an example of the electronic zoom in the horizontal direction in the conventional linear interpolation as disclosed in the Japanese Patent Application Laid-Open No. 5-83612, wherein a field memory
1
receives, through an input terminal, the image signal outputted with a sampling frequency determined by the image pickup element and stores the image data of a field.
Memory readout means
2
receives a zoom ratio set value “zoom” from a microcomputer
3
, correspondingly determines the position of the interpolated pixel in continuous manner and sends a readout control signal Cr to the field memory
1
in such a manner that, the pixel data S
n
immediately after the position of the interpolated pixel, among the original image data stored in the field memory, is output at the determined position of the interpolated pixel.
Based on the readout control signal Cr from the memory readout means
2
and the zoom ratio setting value “zoom” from the microcomputer
3
, a coefficient generation circuit
4
supplies a linear interpolation circuit
6
with a relative positional data k indicating the relationship in time between the interpolated pixel S′ and the original sampling pixel data S
n
positioned immediately behind the interpolated pixel S′.
The field memory
1
outputs the pixel data S
n
instructed by the signal Cr while delay means
5
outputs a pixel data S
n−1
delayed by a clock of the original sampling frequency, and both data are simultaneously entered at a time to the linear interpolation circuit
6
.
The linear interpolation circuit
6
executes the calculation:
S′=
(
S
n
−S
n−1
)·
k+S
n−1
according to the foregoing linearly interpolating equation, utilizing a subtractor
61
, a multiplier
62
and an adder
63
, to output an interpolated pixel data S′.
The conventional linear interpolation utilizing the two adjacent pixels as explained in the foregoing simplifies the circuit configuration but the image is reduced or enlarged without improvement in definition, since the frequency characteristics are monotonously sloped as shown in FIG.
6
.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an image enlargement/reduction circuit capable of attaining high image quality with improvement in image definition, with a simple circuit configuration, and an image pickup apparatus utilizing such circuit.
The above-mentioned object can be attained, according to a first aspect of the present invention, by an image interpolation apparatus comprising a memory for storing digital image signal; memory readout means for reading pixel data in succession from the memory; consecutive first, second and third delay means for respectively delaying the image signal S
n
, read by the memory readout means, to form pixel signals S
n−1
, S
n−2
, S
n−3
; first, second, third and fourth coefficient generation circuits for generating interpolation coefficients k
1
, k
2
respectively corresponding to the pixel signals S
n
, S
n−1
, S
n−2
, S
n−3
and determined by N-th order functions from the position of the interpolated pixel S′ positioned between the pixel signals S
n−1
and S
n-2
; and a signal synthesis circuit for calculating the sum of respective product of pixel signal S
n
and interpolation coefficient k
n
.
According to a second aspect of the present invention there is provided an image interpolation apparatus comprising a memory for storing digital image signal; memory readout means for reading pixel data in succession from the memory; first, second and third consecutive delay means for respectively delaying the image signal, read by the memory readout means, to respectively form pixel signals S
n−1
, S
n−2
, S
n−3
; first and second coefficient generation circuits for generating interpolation coefficients k
1
, k
2
determined by N-th order functions from the position of the interpolated pixel S′ positioned between the pixel signals S
n−1
and S
n−2
; first and second interpolation circuits for executing a calculation P=k
1
·S
x
+(1−k
1
)·S
y
on two arbitrary pixel signals S
x
, S
y
; and a signal synthesis circuit; wherein the pixel signals S
n
, S
n−3
are entered into the first interpolation circuit while the pixel signals S
n−1
, S
n−2
are entered into the second interpolation circuit and the first and second interpolation circuits execute interpolation with the interpolation coefficient k
1
, while the outputs P
n
, P
n−1
of the first and second interpolation circuits are entered into the signal synthesis circuit, which outputs the interpolated pixel signal S′ based on an equation k
2
·(P
n−1
−P
n
)+P
n−1
utilizing the interpolation coefficient k
2
.
According to a third aspect of the present invention there is provided an image interpolation apparatus comprising a memory for storing digital image signal; memory readout means for reading pixels in succession in the horizontal direction from the memory; consecutive first, second and third delay means for respectively delaying the image signal read by the memory readout means; a coefficient generation circuit for determining, by an accumulator, an interpolation coefficient k indicating the position of the interpolated pixel S′ positioned between the pixel signals S
n−1
and S
n−2
based on the current pixel signal S
n
read by the memory readout means, the pixel signal S
n−1
from the first delay means, the pixel signal S
n−2
from the second delay means and the pixel signal S
n−3
from the third delay means; first and second interpolation circuits for executing a calculation P=k
1
·S
x
+(1−k)·S
y
on two arbitrary pixel signals S
x
, S
y
, and a signal synthesis circuit, wherein the pixel
Hieda Teruo
Terasawa Ken
Kassa Yosef
Mehta Bhavesh M.
LandOfFree
Image interpolation apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image interpolation apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image interpolation apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3113125