Detector for detecting a predetermined image in an input image, and detection method and integrated circuit for performing the same

1. A detector for detecting a specified image in an input image, comprising:

an area determination unit operable to determine, in the input image, a detection target area in which the specified image potentially exists;

a setting unit operable to set positions of a plurality of matching target ranges in the detection target area, each of the matching target ranges being a predetermined size, so that the matching target ranges cover the detection target area, and each matching target range of the plurality of matching target ranges overlaps a neighboring matching target range by a predetermined overlap width;

a matching unit operable to detect the specified image by matching a portion of the input image encompassed by each matching target range set by the setting unit and a template image for detecting the specified image; and

a scaling ratio determination unit operable to determine a ratio for the portion of the input image encompassed by each matching target range of the plurality of matching target ranges, wherein

the setting of the position of each matching target range of the plurality of matching target ranges by the setting unit is performed so that the predetermined overlap width corresponds to the ratio determined by the scaling ratio determination unit, and

the matching of the portion of the input image encompassed by each matching target range of the plurality of matching target ranges and the template image is performed by the matching unit after a size of the portion of the input image encompassed by the matching target range of the plurality of matching target ranges has been changed according to the ratio determined by the scaling ratio determination unit.

2. The detector of claim 1 wherein

the detection target area is a square area that is a portion of the input image,

each matching target range of the plurality of matching target ranges is a square area that is a portion of the detection target area,

the ratio for the portion of the input image encompassed by each matching target range of the plurality of matching target ranges is one of a plurality of reduction ratios,

the detector further comprises a storage unit operable to store therein information indicating, for each reduction ratio of the plurality of reduction ratios, the overlap width corresponding to the reduction ratio,

the determination of the ratio by the scaling ratio determination unit and the setting of the position of each matching target range of the plurality of matching target ranges by the setting unit are performed in accordance with the information stored in the storage unit, and

the matching unit includes a reduction unit operable to, for each reduction ratio determined by the scaling ratio determination unit, reduce the portion of the input image by the reduction ratio.

3. The detector of claim 2 further comprising:

a second reduction unit operable to reduce the input image to a same size as a matching target range of the plurality of matching target ranges, so as to generate a reduced input image; and

a second matching unit operable to detect the specified image by matching the reduced input image and the template image.

4. The detector of claim 1 further comprising:

a detection unit operable to detect, in the input image, an area in which a moving object is shown, wherein

the area determination unit performs the determining of the detection target area based on the area detected by the detection unit.

5. The detector of claim 1 further comprising:

an image input unit operable to receive, in an order of being captured, an input of a plurality of input images sequentially captured by an external camera, wherein

the area determination unit, treating a predetermined number of the plurality of input images sequentially captured by the external camera as one unit, determines an entire area of an input image, of the plurality of input images, that is first in the order in each unit to be the detection target area, and when the specified image is detected by the matching unit in the input image that is first in the order, the detection target area of a subsequent input image in the order is determined to include an area that is in an identical position as the entire area in which the specified image has been detected in the input image that is first in the order.

6. A detection method used in a detector for detecting a specified image in an input image, comprising:

an area determination step of determining, in the input image, a detection target area in which the specified image potentially exists;

a setting step of setting positions of a plurality of matching target ranges in the detection target area, each of the matching target ranges being a predetermined size, so that the matching target ranges cover the detection target area, and each matching target range of the plurality of matching target ranges overlaps a neighboring matching target range by a predetermined overlap width;

a matching step of detecting the specified image by matching a portion of the input image encompassed by each matching target range set by the setting step and a template image for detecting the specified image; and

a scaling ratio determination step of determining a ratio for the portion of the input image encompassed by each matching target range of the plurality of matching target ranges, wherein

the setting step is performed so that the predetermined overlap width corresponds to the ratio determined by the scaling ratio determination step, and

the matching step is performed after a size of the portion of the input image encompassed by the matching target range of the plurality of matching target ranges has been changed according to the ratio determined by the scaling ratio determination step.

7. A detection integrated circuit used in a detector for detecting a specified image in an input image, comprising:

an area determination unit operable to determine, in the input image, a detection target area in which the specified image potentially exists;

a setting unit operable to set positions of a plurality of matching target ranges in the detection target area, each of the matching target ranges being a predetermined size, so that the matching target ranges cover the detection target area, and each matching target range of the plurality of matching target ranges overlaps a neighboring matching target range by a predetermined overlap width;

a matching unit operable to detect the specified image by matching a portion of the input image encompassed by each matching target range set by the setting unit and a template image for detecting the specified image; and

a scaling ratio determination unit operable to determine a ratio for the portion of the input image encompassed by each matching target range of the plurality of matching target ranges, wherein

the setting of the position of each matching target range of the plurality of matching target ranges by the setting unit is performed so that the predetermined overlap width corresponds to the ratio determined by the scaling ratio determination unit, and

the matching of the portion of the input image encompassed by each matching target range of the plurality of matching target ranges and the template image is performed by the matching unit after a size of the portion of the input image encompassed by the matching target range of the plurality of matching target ranges has been changed according to the ratio determined by the scaling ratio determination unit.