Television – Camera – system and detail – Swing driven
Reexamination Certificate
1997-12-23
2002-09-24
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Swing driven
C348S246000, C382S264000
Reexamination Certificate
active
06456324
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image pick-up apparatus that is capable of providing images with high resolution, and more particularly, concerns an image pick-up apparatus which picks up a plurality of images by relatively shifting imaging light from a subject, and combines these images into an image with an enhanced resolution.
BACKGROUND OF THE INVENTION
Recently, still-image pick-up apparatuses, so-called electronic still cameras, have been put into practical use as image pick-up apparatuses for picking up still images. Further, home-use video cameras have been put into practical use as motion-image pick-up apparatuses for picking up motion images. In these image pick-up apparatuses, a charge-coupled device is used as a means for picking up an image by receiving imaging light from a subject.
The charge-coupled device is a so-called two-dimensional CCD image sensor. In the charge-coupled device, a plurality of light-receiving regions are arranged in a matrix format on an image-forming surface that is a two-dimensional plane.
The image pick-up apparatus converges imaging light from a subject onto the image-forming surface of the charge-coupled device, and allows the light-receiving regions to receive the light. The imaging light is photoelectrically transferred to an electric signal indicating the quantity of light receipt within the light-receiving region, and then recorded in a recording medium as an image signal. This image signal, when visually displayed alone on a display device, forms a still image. Further, these image signals, when visually displayed successively in the order in which they were picked up form motion images.
In the image pick-up apparatus of this type, an image that has been picked up consists of pixels that correspond to light-receiving regions of the charge-coupled devices. In other words, the operation of each charge-coupled device is the same as sampling the quantity of imaging light that spatially varies in succession by using a spatial sampling frequency. The spatial sampling frequency is given as an inverse number to the array period of the pixels. Therefore, the change in light quantity of imaging light is smoothed for each pixel. Consequently, the higher the number of pixels, the more the resolution of an image is improved.
As one of the methods for improving the resolution of an image, CCD image pick-up apparatuses using an image shift have been proposed. The image shift is a technique for shifting a light-receiving position of imaging light that is directed to the charge-coupled device. In the CCD image pick-up apparatus using the image shift, a plurality of image pick-up processes are carried out while shifting the light-receiving position of imaging light from a subject on the image-forming surface. The images, picked up in this manner, are superimposed so that the light-receiving positions of the image are coincident with one another, thereby forming an output image.
Japanese Laid-Open Patent Publication No. 284980/1988 (Tokukaishou 63-284980) discloses one of such CCD image pick-up apparatuses using the image-shift system. In this CCD image pick-up apparatus, a parallel flat plate, which transmits light, is interpolated between a light-converging lens for converging light from a subject and a charge-coupled device. The parallel flat plate is aligned in either of two states, that is, the first state in which it is aligned perpendicular to the light axis and the second state in which it is inclined in an diagonal direction of 45 degrees with respect to the horizontal and vertical directions of visual field. When the parallel flat plate is aligned in the first state, the charge-coupled device picks up a first image, and thereafter, when the parallel flat plate is aligned in the second state, it picks up a second image.
FIG. 32
is a drawing that shows a pixel array equivalent to an output image. This output image forms a monochrome image. The light-receiving regions of the charge-coupled device are arranged in a matrix format with a horizontal array period PH and a vertical array period PV. Here, it is supposed that the first image and the second image have been picked up while shifting light from a subject in a diagonal direction by ½ pixel from each other. In this case, in the output image formed by combining the two sheets of images, the pixels are arranged with a horizontal array period of (PH/
2
) and a vertical array period of (PV/
2
). In other words, the number of pixels is increased fourfold in the entire image.
In
FIG. 32
, pixels s
1
represent actual pixels whose pixel data has been obtained from the first original image that has been picked up in the first state. Further, pixels s
2
represent actual pixels whose pixel data is obtained from the second original image that has been picked up in the second state. In
FIG. 32
, these actual pixels are indicated by hatched regions. Thus, in the output image, the actual pixels whose pixel data has been obtained are arranged in a diced pattern.
Each of the pixels that have no pixel data (known as virtual pixels) are adjacent to two actual pixels in each array direction. The pixel data of these virtual pixels can be obtained by, for example, interpolating the average value of the pixel data of the adjacent four actual pixels. In this manner, a conventional CCD image pick-up apparatus can obtain a high-resolution image consisting of pixels the number of which is four times as many as the number of the light-receiving regions of the charge-coupled device.
In the above-mentioned CCD image pick-up apparatus, image signals corresponding to one sheet of an output image are generated from the two original images that have been successively picked up through the image shifting process. Accordingly, in this apparatus, it is desirable to have equal exposing time upon picking up the two original images so as not to cause a difference in light quantity between the two original images. However, even in the case of equal exposing time, a difference in light quantity may occur between the two original images due to flickers of a fluorescent lamp or other reasons.
If there is a difference in light quantity between the two sheets of original images, a diced pattern, which is originally not supposed to appear in the imaging light, tends to appear in the output image, resulting in degradation in the image quality.
FIG. 33
shows an example of the diced pattern that appears even when an image of a flat blank pattern is picked up. In
FIG. 33
, figures given in the respective pixels represent values of the pixel data in the corresponding pixels, and it is defined that pixel s
1
in the first image has pixel data of 100, that is, the light quantity. Further, pixel s
2
of the second image, which is originally supposed to have pixel data of 100, has a reduced light quantity due to the above-mentioned phenomenon so that it merely has pixel data of 90. In this case, if the image data of a virtual pixel is found by carrying out an average interpolation on the pixel data of the adjacent four actual pixels, the pixel data is calculated as 95. In this manner, if there is a difference in light quantity between the two sheets of images, a diced pattern appears as shown in
FIG. 33
, instead of a blank pattern that is originally supposed to be obtained from pixel data of 100 in all the pixels.
In order to solve the above-mentioned problem, the applicant of the present application has proposed several methods for correcting light-quantity differences in an image pick up apparatus having a light-quantity-difference correcting means that was previously filed in Japan, that is, “Image pick-up apparatus” (Japanese Patent Application No. 267552/1996 (Tokuganhei 8-267552)). The methods for correcting light-quantity differences, proposed by the applicant of the present application, will be described below.
First, referring to
FIGS. 34 through 36
, the first light-quantity-difference correction method (light-quantity-difference correction method (I)) will be discussed as follows:
FIG. 3
Harada Toshiaki
Iwaki Tetsuo
Yamada Eiji
Birch & Stewart Kolasch & Birch, LLP
Garber Wendy R.
Sharp Kabushiki Kaisha
Tillery Rashawn N.
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