Apparatus and method for processing image signal, imaging apparatus, and method for displaying image

1. An image signal processing apparatus comprising:

down-converter circuitry configured to down-convert an image signal having a first resolution into an image signal having a second resolution lower than the first resolution;

high-frequency-band-edge detection circuitry configured to perform filtering on the image signal having the first resolution to extract components in a higher frequency band than a frequency corresponding to the second resolution and to perform down-conversion on an edge detection signal obtained through the filtering to obtain an edge detection signal having the second resolution; and

combination circuitry configured to combine the edge detection signal having the second resolution obtained by the high-frequency-band-edge detection circuitry with the image signal having the second resolution generated by the down-converter circuitry so as to obtain an image signal having the second resolution for display,

wherein assuming that a down-conversion ratio is N:1, N being an integer of 2 or more, the down-conversion performed by the high-frequency-band-edge detection circuitry includes dividing the edge detection signal obtained through the filtering into units of 2N pixels, generating continuous 2N sets of two pixels from edge detection signals corresponding to 2N pixels of each division unit and the first pixel of a next division unit following said each division unit, the 2N pixels and the first pixel being continuous, and extracting, from the 2N sets, a set of two pixels having the largest absolute difference.

2. The image signal processing apparatus according to claim 1 ,

wherein the first resolution is a 4K resolution, and

wherein the second resolution is an HD resolution.

3. An imaging apparatus comprising:

an image signal processing apparatus according to claim 1 ; and

an imaging unit configured to obtain the image signal having the first resolution.

4. An image signal processing apparatus comprising:

down-converter circuitry configured to down-convert an image signal having a first resolution into an image signal having a second resolution lower than the first resolution;

high-frequency-band-edge detection circuitry configured to perform filtering on the image signal having the first resolution to extract components in a higher frequency band than a frequency corresponding to the second resolution and to perform down-conversion on an edge detection signal obtained through the filtering to obtain an edge detection signal having the second resolution; and

combination circuitry configured to combine the edge detection signal having the second resolution obtained by the high-frequency-band-edge detection circuitry with the image signal having the second resolution generated by the down-converter circuitry so as to obtain an image signal having the second resolution for display,

wherein the high-frequency-band-edge detection circuitry normalizes the edge detection signal obtained through the filtering by dividing the edge detection signal by an average of levels of the image signal having the first resolution and performs the down-conversion on the normalized edge detection signal.

5. An imaging apparatus comprising:

an image signal processing apparatus according to claim 4 ; and

an imaging unit configured to obtain the image signal having the first resolution.

6. An image signal processing apparatus comprising:

down-converter circuitry configured to down-convert an image signal having a first resolution into an image signal having a second resolution lower than the first resolution;

high-frequency-band-edge detection circuitry configured to perform filtering on the image signal having the first resolution to extract components in a higher frequency band than a frequency corresponding to the second resolution and to perform down-conversion on an edge detection signal obtained through the filtering to obtain an edge detection signal having the second resolution;

combination circuitry configured to combine the edge detection signal having the second resolution obtained by the high-frequency-band-edge detection circuitry with the image signal having the second resolution generated by the down-converter circuitry so as to obtain an image signal having the second resolution for display; and

low-frequency-band-edge detection circuitry configured to obtain an edge detection signal having the second resolution on the basis of the image signal having the second resolution generated by the down-converter circuitry, wherein

the combination circuitry combines, with the image signal having the second resolution generated by the down-converter circuitry, a first edge detection signal being the edge detection signal having the second resolution obtained by the high-frequency-band-edge detection circuitry and a second edge detection signal being the edge detection signal obtained by the low-frequency-band-edge detection circuitry so as to obtain the image signal having the second resolution for display.

7. The image signal processing apparatus according to claim 6 , wherein the combination circuitry combines the first and second edge detection signals with the image signal having the second resolution in such a manner that edge information displayed based on the first edge detection signal is distinguishable from edge information displayed based on the second edge detection signal.

8. The image signal processing apparatus according to claim 7 , wherein distinction between the edge information displayed based on the first edge detection signal and the edge information displayed based on the second edge detection signal is made by a difference in one of hue, luminance, and line type.

9. An imaging apparatus comprising:

an image signal processing apparatus according to claim 6 ; and

an imaging unit configured to obtain the image signal having the first resolution.

10. An image signal processing apparatus comprising:

down-converter circuitry configured to down-convert an image signal having a first resolution into an image signal having a second resolution lower than the first resolution;

high-frequency-band-edge detection circuitry configured to perform filtering on the image signal having the first resolution to extract components in a higher frequency band than a frequency corresponding to the second resolution and to perform down-conversion on an edge detection signal obtained through the filtering to obtain an edge detection signal having the second resolution; and

combination circuitry configured to combine the edge detection signal having the second resolution obtained by the high-frequency-band-edge detection circuitry with the image signal having the second resolution generated by the down-converter circuitry so as to obtain an image signal having the second resolution for display,

wherein the image signal having the first resolution is an image signal outputted from a single-CCD color imaging unit including an image sensor having a Bayer color filter array, and

wherein the high-frequency-band-edge detection circuitry obtains the edge detection signal having the second resolution on the basis of signals of diagonally arranged green pixels.

11. An imaging apparatus comprising:

an image signal processing apparatus according to claim 10 ; and

an imaging unit configured to obtain the image signal having the first resolution.

12. A method for displaying an image, the method comprising:

displaying, on a display device, an image based on an image signal, first edge information based on an edge detection signal detected on the basis of components of the image signal in a lower frequency band than a predetermined frequency, and second edge information based on an edge detection signal detected on the basis of components of the image signal in a higher frequency band than the predetermined frequency in such a manner that the first edge information and the second edge information are superimposed on the image and can be distinguished from each other,

wherein distinction between the displayed first edge information and the displayed second edge information is made by a difference in one of hue, luminance, and line type.

13. The method for displaying an image according to claim 12 , wherein the predetermined frequency is a frequency corresponding to a resolution of the display device.

14. The method for displaying an image according to claim 12 ,

wherein the image signal is an output image signal from an imaging unit having a 4K resolution, and

wherein the display device has an HD resolution.

15. An image signal processing apparatus comprising:

down-converter circuitry configured to down-convert an image signal having a first resolution into an image signal having a second resolution lower than the first resolution;

high-frequency-band-edge detection circuitry configured to perform filtering on the image signal having the first resolution to extract components in a higher frequency band than a frequency corresponding to the second resolution and to perform down-conversion on an edge detection signal obtained through the filtering to obtain an edge detection signal having the second resolution, without incurring a loss of information in the extracted components in the higher frequency band; and

combination circuitry configured to combine the edge detection signal having the second resolution obtained by the high-frequency-band-edge detection circuitry with the image signal having the second resolution generated by the down-converter circuitry so as to obtain an image signal having the second resolution for display.

16. The image signal processing apparatus according to claim 15 , wherein:

the image signal having the first resolution is an image signal outputted from a single-CCD color imaging unit including an image sensor having a Bayer color filter array, and

the high-frequency-band-edge detection unit obtains the edge detection signal having the second resolution on the basis of signals of diagonally arranged green pixels.

17. The image signal processing apparatus according to claim 15 , wherein the first resolution is a 4K resolution and the second resolution is an HD resolution.

18. An imaging apparatus comprising:

an image signal processing apparatus according to claim 15 ; and

an imaging unit configured to obtain the image signal having the first resolution.