Image analysis – Image enhancement or restoration
Reexamination Certificate
2000-10-20
2004-01-06
Au, Amelia M. (Department: 2623)
Image analysis
Image enhancement or restoration
C382S255000, C382S280000
Reexamination Certificate
active
06674913
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for obtaining an image; and more particularly, to a method and apparatus for obtaining a high-resolution image of a controllable rotating target by using an image reconstruction algorithm without interpolation.
DESCRIPTION OF THE PRIOR ART
Conventional imaging techniques including ISAR (Inverse Synthetic Aperture Radar), CT (Computerized Tomography) and MRI (Magnetic Resonance Imaging), for a controllable rotating target, have been used in various application areas, e.g., modeling and analysis of targets. Also, they have been adopted as a diagnostic method to support the medical and physical sciences and used to develop the target detection, recognition and classification techniques.
Referring to
FIG. 1
, there is shown a conventional imaging apparatus for obtaining a high resolution image of a rotating target, wherein the targets are linearly rotated. As shown in
FIG. 1
, the conventional imaging apparatus
100
generally samples a reflected signal from a target
180
on the polar coordinates of frequency and observation angle. The conventional imaging apparatus
100
comprises a rotating stage
110
, a driving unit
120
, a transmitting antenna
130
, a receiving antenna
140
, a reference signal generation unit
150
, a controlling & signal processing unit
160
and a display unit
170
.
The target
180
is mounted on the rotating stage
110
. The driving unit
120
includes, e.g., a motor for rotating the rotating stage
110
and is physically connected to the rotating stage
110
. Also, the driving unit
120
is electrically connected to the controlling & signal processing unit
160
. The transmitting antenna
130
is electrically coupled to the controlling & signal processing unit
160
via the reference signal generation unit
150
. The transmitting antenna
130
transmits to the target
180
a reference signal from the reference signal generation unit
150
, whereas the receiving antenna
140
receives a reflected signal from the target
180
to transfer it to the controlling & signal processing unit
160
. The controlling & signal processing unit
160
processes the reflected signal transferred from the receiving antenna
140
to provide a 2-dimensional image for the target
180
. In this processing, the controlling & signal processing unit
160
applies the conventional 2-dimensional image reconstruction algorithm including interpolation to the reflected signal containing measured data for the target
180
, thereby providing a 2-dimensional image.
For a small observation angle, a high-resolution image can be achieved in a short processing time by using an unfocused reconstruction algorithm because the received data can be modeled by samples of the Fourier transform on rectangular coordinates. But, if the observation angle range is not very small, the unfocused image is degraded by the blur effect. The blur effect can be removed by the reformatting of received data on rectangular lattice by using the interpolation in the focused image. However, the additional interpolation process leads to a longer processing time than the unfocused algorithm and the image degradation due to artifacts.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a method and apparatus for obtaining a high-resolution image of a controllable rotating target by using an image reconstruction algorithm without interpolation.
In accordance with one aspect of the present invention, there is provided an imaging method capable of obtaining 2-dimensional high-resolution image of a controllable rotating target during a short image processing time without degrading the quality of the image, wherein the imaging method is employed in an imaging apparatus comprising means for controlling the imaging apparatus and processing a signal reflected from the target, means for generating a reference signal, means for transmitting and receiving the reference signal and means for rotating the target, the method comprising the steps of: a) acquiring initial information concerning the imaging apparatus and the target; b) calculating parameters for use in rotating the target, the parameters including a rotational increment of the rotating means and a total rotation angle thereof; c) computing a start frequency ƒ
s
k
and a step frequency &dgr;ƒ
k
; d) measuring data for the target to store them based on the values obtained in the steps a) to c); e) determining whether or not the step d) is completed; f) if the determination result is negative, repeating the steps a) to e); and, if otherwise, obtaining the 2-dimensional high-resolution image by using an image reconstruction algorithm; and g) displaying the 2-dimensional high-resolution image, wherein the image reconstruction algorithm applies a Fast Fourier transform (FFT) process to the measured data to reconstruct the 2-dimesional high-resolution image without interpolation.
In accordance with another aspect of the invention, there is provided an apparatus for obtaining a 2-dimensional high-resolution image by rotating a controllable target and measuring data for the controllable target at each of rotating angles, comprising: means for rotating the controllable target to a predetermined angle, wherein intervals between the predetermined angles are not identical to each other; means for generating a first signal; means for transferring the first signal to the controllable target; means for receiving a second signal reflected from the controllable target; means for converting the first and the second signal into a third and fourth signal, respectively, wherein the frequency of the third signal is different from that of the forth signal; and means for processing the third and forth signal to reconstruct an image representing the controllable target, and for controlling the rotating means, wherein the controlling and signal processing means applies a FFT (Fast Fourier Transform) algorithm to the measured data without interpolation.
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Zhishun She; “Study of range-Doppler imaging using real data in microwave anecho chamber”, IEEE, International Conference Jun. 1991, pp.: 460-463 vol. 1.
Gum-Sil Kang
Kim Yong-Hoon
Au Amelia M.
Katten Muchin Zavis & Rosenman
Kwangju Institute of Science and Technology
Le Brian Q
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