Image analysis – Image enhancement or restoration – Image filter
Reexamination Certificate
1999-07-07
2003-09-30
Lee, Tommy D. (Department: 2624)
Image analysis
Image enhancement or restoration
Image filter
C382S162000
Reexamination Certificate
active
06628841
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image sensing apparatus, and, more particularly, to an image sensing apparatus which switches between color image sensing and monochromatic image sensing.
An electronic still camera provides computer equipment with the image information of a three-dimensional object. The still camera includes an image sensor, a driver for the image sensor, and a signal processing circuit which generates an electrical signal of the object image in one screen picked up by the image sensor.
FIG. 1
is a schematic block diagram of a conventional electronic still camera
100
, and
FIG. 2
is a timing diagram for describing the operation of the camera
100
of FIG.
1
. The still camera
100
includes an image sensor
1
, a color separation filter
2
, a lens
3
, a driver
4
, an analog processing circuit
5
, an A/D convertor
6
and a digital processing circuit
7
.
The image sensor
1
is preferably a charge-coupled device (CCD) image sensor and includes a plurality of light receiving pixels (picture elements), which are arranged in a matrix and accumulate an information charge by photoelectric conversion, and a plurality of shift registers which transfer the information charge accumulated in each light receiving pixel in a predetermined order. A plurality of the shift registers includes a plurality of vertical shift registers, which transfer the information charge in each column of the light receiving pixel, and a horizontal shift register which transfers the output of a plurality of the vertical shift registers. The color separation filter
2
has a plurality of segments mounted on the light receiving surface of the image sensor
1
. The plurality of segments are formed by the three primary colors of light or their complementary color elements arranged in accordance with a predetermined rule. By using the color separation filter
2
, each light receiving pixel is associated with a specific color component. The color separation filter
2
may also be formed as an on-chip filter by laminating a layer on the semiconductor image sensor
1
. The lens
3
is arranged on the color separation filter
2
and guides the light from an object to the light receiving surface of the image sensor
1
via the color separation filter
2
.
The driver
4
generates a vertical transfer clock &phgr;V, a horizontal transfer clock &phgr;H and a discharge clock &phgr;D for pulse-driving the image sensor
1
in accordance with an instruction from a timing control circuit
8
. As shown in
FIG. 2
, after the information charge of the light receiving pixel is fully discharged in accordance with the discharge clock &phgr;D and a predetermined period L elapses, the information charge is transferred from each light receiving pixel to the corresponding vertical shift register in accordance with the vertical transfer clock &phgr;V. At this time, the information charge is transferred to the vertical direction in a unit of one line by a vertical shift register. The information charge from a vertical register is transferred to the horizontal direction every pixel by a horizontal shift register in accordance with the horizontal transfer clock &phgr;H. Thus the image information of one screen is successively output from the image sensor
1
in a unit of one line as an image signal A
0
(t).
The analog processing circuit
5
receives the image signal A
0
(t) from the image sensor
1
, performs processing such as sample holding and level correction on an image signal, and generates a formatted analog image signal A
1
(t). The A/D convertor
6
receives an analog image signal A
1
(t) from the analog processing circuit
5
and converts the analog image signal A
1
(t) to digital image data D
1
(n) every pixel. The digital processing circuit
7
receives the digital image data D
1
(n) from the A/D convertor
6
, performs processing such as color separation and matrix operation on the digital image data D
1
(n), and generates luminance data Y which represents luminance information and two types of chrominance data U and V which represent the chrominance information. The luminance data Y and the chrominance data U and V are transferred to a computer in units of one screen.
For example, the luminance data Y is generated by combining the three primary colors (red: R, green: G, and blue: B) of light generated by color separation at a ratio of 0.3 R+0.6 G+0.1 B. The chrominance data U and V are generated by subtracting the red component R and the blue component B from the luminance data Y.
The timing control circuit S controls each of the circuits
4
to
7
in accordance with a reference clock CK. For example, the timing control circuit
8
controls the driver
4
such that an accumulation time L of the information charge is set in accordance with the exposed state of the image sensor
1
and an image signal A
0
(t) having an appropriate level can be obtained. Further, the timing control circuit
8
sets the processing conditions of the analog and digital processing circuits
5
and
7
so that the processing of the analog and digital processing circuits
5
and
7
is synchronized with the operation of the image sensor
1
.
The image information supplied to the computer also includes a monochromatic image of a document on which characters are written and graphics are drawn. Accordingly, it is preferable that an electronic still camera be provided with a color image sensing mode in which an object is photographed, and a monochromatic image sensing mode which generates an image representing only the light and shade of the object. The image sensing mode can be switched by changing the arithmetic operation processing of the digital processing circuit
7
. The monochromatic image sensing mode is effective for improving resolution to preferentially process the luminance information. However, to obtain high resolution based on the image signal D
1
(t) generated using the color separation filter
2
, complicated filtering processing must be performed on the separated color component data, which makes the circuit configuration of the digital processing circuit
7
complex.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image sensing apparatus which switches between color image sensing and monochromatic image sensing without making the configuration of a digital processing circuit complex.
In one aspect of the present invention, an image sensing apparatus is provided that includes a solid-state image sensor having a plurality of light receiving elements which accumulate an information charge by photoelectric conversion. A color separation filter is arranged in front of the solid-state image sensor and has a plurality of filter segment groups. Each filter segment group corresponds to each of the plurality of light receiving elements, respectively and includes a first color filter segment having a first color selected from the three primary colors of light and second and third color filter segments having the complementary colors of the non-selected two of the three primary colors. A monochromatic filter is movably arranged between a position in an optical path to the plurality of light receiving elements and a position away from the optical path to the plurality of light receiving elements. The monochromatic filter has substantially the same first color as the first color filter segment. A driver transfers the information charge accumulated by the plurality of the light receiving elements in a predetermined order and drives the solid-state image sensor so as to output an image signal therefrom.
In another aspect of the present invention, an electronic camera is provided that includes an image sensor including a plurality of light receiving pixels that receive light irradiated on a surface of the image sensor. The image sensor accumulates an information charge by photoelectric conversion of the received light. A color separation filter is arranges adjacent to the image sensor. The color separation filter has a plurality of segments formed by at l
Brinich Stephen
Lee Tommy D.
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