JP2899298B2 - Electronic still camera system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention corrects a shift between two field images obtained from a solid-state image sensor that electronically captures a subject image in a frame-sequential manner, and eliminates flicker. The present invention relates to an electronic still camera system capable of obtaining an image.

[Related Art] In recent years, instead of a still camera using a so-called silver halide film, an electronic still image signal electronically imaged using a solid-state image sensor such as a CCD is recorded on a floppy disk, a memory card, or the like. A solid-state imaging device that uses this recorded image for image display on a TV monitor or the like has attracted attention as an electronic still camera. According to this type of electronic still camera (solid-state imaging device), unlike recording a still image using a silver halide film, the captured image (still image) can be easily monitored without performing a film development process or the like. It has excellent features such as being able to be used directly for image data communication in news organizations and the like.

By the way, as a method of electronically capturing a subject image using a solid-state image sensor, a method of directly obtaining one frame image to be used for image reproduction (display) by a TV monitor from the solid-state image sensor, There is a method of obtaining two field images (an odd field image and an even field image used for image reproduction by a TV monitor) in a frame sequence. In the method of obtaining two field images in a frame sequence, the number of pixels is substantially doubled compared to the case of directly obtaining a frame image from a solid-state image sensor, and an electronic still image (frame image) is obtained. ) Is formed, so that it is possible to effectively utilize the number of pixels of the solid-state imaging device to obtain an extremely fine high-quality electronic still image.

[Problems to be Solved by the Invention] However, when two field images are obtained from a solid-state imaging device in a plane-sequential manner, it is unavoidable that a slight time lag occurs in the imaging timing of these field images. This time shift generally tends to cause a subject image shift between two field images. In particular, when the subject is moving, this image shift significantly occurs.

Such a shift between the field images hardly causes a problem in the case of a movie image, but in the case of an electronic still image, these two field images are repeatedly reproduced and output. Since an image is displayed, a shifted portion of the image is likely to appear as flicker (so-called flicker). Such flicker not only makes the displayed image very difficult to see, but also causes a reduction in the quality of the reproduced image.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide an electronic still camera system capable of effectively obtaining a high-quality frame image without flicker from two field images obtained from a solid-state image sensor in a frame-sequential manner.

[Means for Solving the Problems] An electronic still camera system according to the present invention is a solid-state camera that photoelectrically converts a subject image formed via an imaging optical system and accumulates signal charges corresponding to the amount of light of the subject image. In an electronic still camera system that obtains two field images in a frame sequence from an image sensor, two frame images determined in a frame sequence are independently subjected to field interpolation processing to obtain temporary frame images, respectively. The amount of shift between the two field images is obtained from the correlation between the frame images of the two images, and the image shift between the two field images is corrected according to the obtained amount of image shift. A frame image is obtained by synthesizing the obtained two field images, and means for performing these operations is recorded on a recording medium by recording the frame image. Recording unit, or is one which is characterized by comprising a playback unit which outputs the frame image on the image monitor.

In particular, the correlation calculation for obtaining the shift amount is performed for each region obtained by dividing the field image into blocks of a predetermined size, and the shift correction is performed for each block divided region. It is.

[Operation] According to the electric still camera system according to the present invention configured as described above, the difference between the two field images obtained from the solid-state imaging device in a frame-sequential manner is due to the field interpolation of these field images. It is obtained from the correlation between the two processed temporary frame images, and after the image shift between the two field images is corrected in accordance with the shift amount obtained from the correlation, the two corrected frame images are corrected. Since the frame image is obtained by synthesizing the field images, it is possible to obtain a high-quality frame image free from flicker due to image shift due to a time shift.

Also, by performing the above-described misalignment correction for each area obtained by dividing the field image into blocks of a predetermined size,
It is possible to effectively perform the shift correction only on the image portion where flicker is noticeable without performing the shift correction on the entire image.

Hereinafter, an electronic still camera system according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an image shift correction circuit unit having a characteristic processing function in the system of the embodiment.
The system of this embodiment includes a solid-state imaging device such as a CCD as shown in FIG.
The two field images that are captured and input by the imaging unit 1 and obtained in a frame-sequential manner are recorded on a memory card 2 as a predetermined recording medium, and the two field images recorded on the memory card 2 are recorded. An electronic still image composed of images is displayed on an image monitor 3 such as a TV receiver.

That is, two field images read out from the imaging unit 1 in a frame-sequential manner are composed of an odd-numbered field image and an even-numbered field image for providing an image display by so-called interlaced scanning, as one set of image data (electronic still image). Handled. Then, these two field images are respectively subjected to predetermined signal processing such as gamma correction in the signal processing unit 4 and then converted into digital image data of a predetermined number of bits by the A / D converter 5. Is done. This A / D conversion processing is basically performed for each pixel constituting a field image that has been captured and input. The coding and writing circuit 6 performs data compression by block coding and the like on the two field images digitized in this manner, and records the data on the memory card 2. The recording of the electronic still image on the memory card 2
For example, by adding an image frame number to each field image,
This is performed while individually managing the captured images.

On the other hand, the electronic still image recorded on the memory card 2 is selectively read in units of the two field images described above under the control of the read decoding circuit 7 and decoded by the read decoding circuit 7. In this decoding process, as described above, since the field image is subjected to data compression by block coding or the like for recording on the memory card 2,
This is performed to restore the original field image data. The inter-field motion detecting section 8 and the image correcting section 9 constitute an image shift correcting circuit section shown in FIG. 1, and basically, the inter-field motion detecting section 8 controls the two field images. It is configured to detect a shift amount of an image between them, and to perform a correction process in order to detect the shift in the image correcting unit 9 according to the detected shift amount. The two field images corrected in this way are D / A
The image data is output to the image monitor 3 via the converter 10 and converted into, for example, an NTSC TV image signal for image display. That is, when interlaced scanning is performed using two field images (an odd field image and an even field image) read from the memory card 2 and an image is displayed as one frame image, the present apparatus uses the interleaving between the two field images. Is obtained, a correction process for eliminating the deviation is performed, and then the image is displayed by the above-described interlaced scanning.

Next, the detection of the shift between the field images by the inter-field motion detecting section 8 and the image shift correcting process by the image correcting section 9 will be described in more detail.

As shown in FIG. 1, an image shift correction circuit section mainly including the inter-field motion detection section 8 and the image correction section 9 includes an odd field image memory 11 for storing two field images and an even field image memory. A memory 12 is provided. The image is captured by an electronic still camera,
Are stored in the odd-numbered field image memory 11 and the even-numbered field image memory 12, respectively.

Thus, the interpolation processing units 13 and 14 independently perform the field interpolation processing on the odd field image and the even field image stored in the odd field image memory 11 and the even field image memory 12, respectively.
A temporary frame image is being created. More specifically, as shown in FIG. 3 (a), the interpolation processing unit 13 performs a predetermined interpolation calculation process on an even field image signal component between the lines from an odd field image signal indicated by a solid line, for example, a corresponding pixel between lines. A temporary frame image based on an odd-numbered field image is obtained as shown by a broken line by a weighted average process of pixel signals at positions. Similarly, the interpolation processing unit
Reference numeral 14 denotes a tentative frame image based on the even-numbered field image obtained by obtaining the odd-numbered field image signal component from the even-numbered field image signal indicated by the solid line by a predetermined interpolation operation as shown in FIG. Seeking.

The secondary temporary frame images obtained in this manner are supplied to the correlation operation unit 15 and are used for detecting the image shift between the odd field image and the even field image. For example, as shown in FIG. 4, the correlation calculation unit 15 sets a comparison reference point A in one image as a reference, and performs comparison and reference so as to surround a point corresponding to the comparison reference point A in the other image. An area B is set. The comparison reference area B is scanned to check the correlation between each scan point and the comparison reference point A, and the scan point having the highest correlation value is set as the comparison point C for measuring the amount of image shift. By calculating the amount of deviation between the comparison point and the comparison reference point, the amount of image deviation (the vector D indicated by the arrow in the figure) is measured.

It is also possible to set a plurality of comparison reference points for the measurement of the image shift amount, and to perform the measurement for each of these comparison reference points. In addition, a comparative reference area having a predetermined size is set in place of the comparative reference point, and a comparative reference area surrounding the comparative reference area is scanned to find an area having the highest correlation with the comparative reference area, and the It is also possible to obtain the shift amount. Further, as shown in FIG. 5, it is also possible to divide the image area into blocks of a predetermined size, and obtain the deviation of the image individually for each of the divided block areas.

In the above-described correlation operation, for example, the pixel data set as the comparison reference point of the odd-numbered field image is represented by f _(x) , and the pixel data of the even-numbered field image at the point where the comparison reference point is separated by the distance t is represented by g _{(x + t)} , It is sufficient to search for a point at which φ _(t) is minimized by the following correlation operation.

Alternatively, a dispersion method is introduced, and V _{(s) is} calculated by an operation of V _(s) = <(f _(x) −g _{(x + t)} ² > − <f _(x) −g _{(x + t)} > ^2. May be detected as the corresponding point having the highest correlation, where <> in the above equation is This is an operator representing the average value.

The shift amount between the temporary frame images obtained as described above is captured as the shift amount between the two field images described above, and the image reconstructing unit 16 performs a shift correction process on the image. In this embodiment, since the shift amount of the even field image is calculated based on the odd field image, the even field image stored in the even field image memory 12 is read out to the image reconstructing unit 16, and the image By writing the above-mentioned even-numbered field image in the position of the field image memory 17 where the shift has been corrected under the control of the section 16, the image shift is corrected.

In addition, as for the shift correction by the reconstruction of the even-numbered field image, the shift of the entire image may be collectively corrected according to the shift amount of the image obtained at the representative point.
In the case where the shift amount is obtained for each of the plurality of comparison reference points as described above, or in the case where the shift amount is obtained for each of the divided blocks as shown in FIG. , Respectively. In particular, it is possible to control so as to correct the shift only for the image portion having a large shift.

Performing image display by interlaced scanning using the even-numbered field image, which can be corrected (reconstructed) in the field image memory 17 in this manner, and the odd-numbered field image stored in the odd-numbered field image memory 11 Accordingly, it is possible to obtain a frame image free from flicker due to image displacement.

Thus, according to the present system including the above-described circuit for correcting a shift between field images, since two field images are obtained in a frame-sequential manner, an image shift occurs due to a time shift. Even if the deviation causes a flicker at the time of reproducing the still image, the flicker can be effectively removed. In particular, in the case where only the image portion where the image is shifted is partially corrected, a new flicker is generated in another image portion in order to prevent the occurrence of flicker due to the partial image shift. There is no inconvenience that would occur. In other words, by correcting the shift only in the moving part of the subject image, it is possible to prevent flicker without adversely affecting the entire image.

Note that the present invention is not limited to the above-described embodiment. Here, it is recorded on a memory card. Although the example of performing the shift correction on the field image has been described,
For example, it is also possible to construct a system in which a field image itself obtained in a frame-sequential manner from a solid-state imaging device is directly subjected to a shift correction, and this is recorded on a memory card or the like or supplied to a display on an image monitor. is there. Further, the algorithm for detecting the amount of image shift by the correlation operation and the method for correcting the image shift based on the detected amount of shift may be determined according to the system specifications. In short, the present invention departs from the gist of the present invention. Various modifications can be made without departing from the scope.

[Effects of the Invention] As described above, according to the present invention, the shift amount between the field images is obtained from the correlation of the temporary frame image subjected to the field interpolation, and the shift between the field images is corrected. Even in the case where an electronic still image is repeatedly reproduced using the electronic still image, a great effect can be obtained in practical use, such as good image display without flicker.

[Brief description of the drawings]

FIG. 1 shows an electronic still camera system according to an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of an image shift correction circuit unit exhibiting a characteristic processing function in the embodiment system, and FIG. FIG. 3 is a diagram showing an example of the overall configuration of an example system, FIG. 3 is a diagram for explaining field interpolation processing on a field image, and FIGS. 4 and 5 are diagrams for explaining displacement detection between field images. It is. DESCRIPTION OF SYMBOLS 1 ... Image pick-up part, 2 ... Memory card, 3 ... Image monitor, 8 ... Inter-field motion detection part, 9 ... Image correction part, 11 ... Odd field image memory, 12 ... Even field image memory, 13, 14 ... interpolation processing unit, 15 ... correlation operation unit, 16 ... image reconstruction unit, 17 ... field image memory.

Claims (2)

(57) [Claims] An electronic device that photoelectrically converts a subject image formed via an imaging optical system and obtains two field images in a frame sequential manner from a solid-state imaging device that accumulates signal charges corresponding to the light amount of the subject image. In the still camera system, a means for independently obtaining two frame images by field interpolation processing of the two field images determined in the frame sequential order to obtain temporary frame images, and a method for obtaining the two field images from a correlation between these temporary frame images. A correlation calculating unit for calculating a shift amount between the images; a unit for correcting a shift of the image between the two field images according to the shift amount of the image obtained by the correlation calculating unit; Means for combining a plurality of field images to obtain a frame image; and a recording unit for recording the frame image on a recording medium, or an image monitor for displaying the frame image. Electronic still camera system characterized by comprising a reproducing unit for outputting. 2. A correlation calculating section for calculating a shift amount between two field images from a correlation between two interpolated field images, wherein each of the image fields is divided into blocks each having a predetermined size. The means for calculating the shift amount, and for correcting the shift amount of the image between every two field images, corrects the shift amount for each image area corresponding to the block divided area for which the shift amount is obtained. The electronic still camera system according to claim 1.