Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
2002-07-12
2004-07-20
Mehta, Bhavesh M. (Department: 2621)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C358S002100, C358S003270, C358S447000, C358S525000, C358S532000, C382S199000, C382S203000, C382S266000, C382S274000
Reexamination Certificate
active
06766068
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an interpolating operation method and apparatus for an image signal.
2. Description of the Prior Art
Techniques for photoelectrically reading out a radiation image, which has been recorded on a photographic film, in order to obtain an image signal, carrying out appropriate image processing on the image signal, and then reproducing a visible image by use of the processed image signal have heretofore been known in various fields.
Also, it has been proposed to use stimulable phosphors in radiation image recording and reproducing systems. Specifically, a radiation image of an object, such as a human body, is recorded on a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet). The stimulable phosphor sheet, on which the radiation image has been stored, is then exposed to stimulating rays, such as a laser beam, which cause it to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal. The image signal is then processed and used for the reproduction of the radiation image of the object as a visible image on a recording material, such as photographic material, or on a display device, such as a cathode ray tube (CRT) display device. Radiation image recording and reproducing systems, which use stimulable phosphor sheets, are advantageous over conventional radiography using silver halide photographic materials, in that images can be recorded even when the energy intensity of the radiation, to which the stimulable phosphor sheet is exposed, varies over a wide range.
In image recording and reproducing systems, in which an image signal is obtained in the manner described above and a visible is reproduced from the image signal, in cases where the region of interest in the visible image is to be viewed in more detail, the region of interest is often enlarged and reproduced. In such cases, in order for the enlarged image to be obtained, a predetermined interpolating operation may be carried out on the original image signal, which has been obtained by reading out an original image and is made up of a series of image signal components representing sampling points in the original image, and an interpolation image signal, which is a secondary image signal and is made up of a number of image signal components different from that of the original image signal, may thereby be formed. A visible image may then be reproduced from the interpolation image signal. In such cases, depending upon the image size enlargement scale factor, it often occurs that several interpolation points overlap upon the sampling points.
Ordinarily, as an aid in facilitating the constitution of image input and output devices, the sampling points (i.e., picture elements of the original image), which are represented by the image signal components of the original image signal, are arrayed at predetermined intervals along horizontal and vertical directions in a square lattice-like form, and an image is thereby formed. In such cases, as the interpolating operation in the image size enlargement processing, a linear interpolating operation is carried out on the original image signal components representing four sampling points located in the vicinity of an interpolation point, which is to be newly set from the interpolating operation, and an interpolated image signal component corresponding to the interpolation point is thereby obtained.
For example, as illustrated in
FIG. 5A
, picture elements S, S, . . . of an original image, which are indicated by the “o” mark, may be arrayed in a square lattice-like form. Interpolated image signal components corresponding to interpolation points S′, S′, . . . , which are indicated by the “x” mark and are arrayed at intervals different from the intervals of the picture elements S, S, . . . , may then be obtained. In such cases, for example, the interpolated image signal component corresponding to an interpolation point S′
0
is obtained in the manner described below.
In the calculation of the interpolated image signal component corresponding to the interpolation point S′
0
, image signal components S
A
, S
B
, S
C
, and S
D
representing four picture elements S
A
, S
B
, S
C
, and S
D
of the original image, which picture elements are located in the vicinity of the interpolation point S′
0
so as to surround it (and which constitute the unit lattice constituting the square lattice), are used. (As an aid in facilitating the explanation, the same symbol as that of a picture element is used for the image signal component representing the picture element.) This means that a square mask of the unit lattice containing the interpolation point is set, and the image signal components representing the sampling points, which are located in the square mask, are used.
The pitch between the picture elements S
A
and S
B
, the pitch between the picture elements S
C
and S
D
, the pitch between the picture elements S
A
and S
C
, and the pitch between the picture elements S
B
and S
D
are respectively taken as being equal to 1. Also, as illustrated in
FIG. 5B
, the distance between the picture element S
A
(or S
C
) and the interpolation point S′
0
, the distance being taken along the x axis direction (i.e., the horizontal direction), is represented by Tx. The distance between the picture element S
A
(or S
B
) and the interpolation point S′
0
, the distance being taken along the y axis direction (i.e., the vertical direction), is represented by Ty. In such cases, interpolated image signal components Sm and Sn, which respectively correspond to interpolation points Sm and Sn, that correspond to the positions of the interpolation point S′
0
taken respectively from the picture elements S
A
and S
C
along the x axis direction, are calculated with linear interpolating operations represented by Formulas (28) and (29) shown below:
Sm
=(1
−Tx
)
S
A
+TxS
B
(28)
Sn
=(1
−Tx
)
S
C
+TxS
D
(29)
Thereafter, a linear interpolating operation is carried out for the interpolation point S′
0
and with respect to the y axis direction by using the interpolated image signal components Sm and Sn, and an interpolated image signal component S′
0
is thereby calculated. The linear interpolating operation is represented by Formula (30) shown below:
S′
0
=(1
−Ty
)
Sm+TySn
(30)
The same operations as those described above are also carried out for the other interpolation points S′, S′, . . . , and the corresponding interpolated image signal components S′, S′, . . . can thereby be obtained.
The interpolation method described above is not limited to the use in cases where the image size is to be enlarged, and can be applied when the image size enlargement or reduction is not carried out. The interpolation method described above can also be applied when details of the image are to be reproduced appropriately, e.g., when a high-resolution image is to be reproduced.
Also, the sampling points, from which the interpolated image signal component is to be calculated, are not limited to the four sampling points located in the vicinity of the interpolation point. For example, sampling points located in a square mask, which comprises 4×4 sampling points and contains the four sampling points located in the vicinity of the interpolation point, may be utilized.
For example, as in a radiation image containing bone patterns, a reproduced visible image ordinarily contains an image edge portion, at which the image density (or the luminance) changes sharply. It often occurs that the image edge portion is enlarged.
However, in cases where the picture elements of the original image are arrayed in the form of the square lattice (the unit lattice), it
Aoyama Tatsuya
Ito Wataru
Desire Gregory
Fuji Photo Film Co. , Ltd.
Mehta Bhavesh M.
Sughrue & Mion, PLLC
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