Image processing device and image processing method with sequential error detection

An image processing device, comprising:

• a light source to irradiate a document with light, the light including visible light and invisible light;
• a reference plate to absorb the invisible light, the reference plate being disposed behind the document reflecting the light;
• an image sensor configured to:
• receive the light reflected by the document,
• capture an image of the document with the light from the light source, the image including a visible image being captured with the visible light and an invisible image being captured with the invisible light, and
• generate read data of the image;
• and
• first image processing circuitry including a first edge detection circuit, a second edge detection circuit, a tilt detection circuit and a detection result selection circuit, wherein
• the first edge detection circuit detects coordinates of a plurality of first points on a boundary area between the document and the reference plate in the visible image based on a shadow of the document cast on the reference plate in the visible image,
• the second edge detection circuit detects coordinates of a plurality of second points on the boundary area between the document and the reference plate in the invisible image based on incidence or non-incidence of light from the document and the reference plate in the invisible image,
• the tilt detection circuit is configured to:
• calculate a first detection result and first detection error information, the first detection result representing a tilt of the document detected in the visible image based on the coordinates of the plurality of first points, and the first detection error information representing accuracy of detection of the tilt of the document in the visible image, and
• after completion of calculation of the first detection result and the first detection error information, calculate a second detection result and second detection error information, the second detection result representing a tilt of the document detected in the invisible image based on the coordinates of the plurality of second points, and the second detection error information representing accuracy of detection of the tilt of the document in the invisible image, and
• the detection result selection circuit selects one of the first detection result of the visible image and the second detection result of the invisible image based on the first detection error information and the second detection error information.

An image processing method performed by an image processing device including a light source to irradiate a document with light, the light including visible light and invisible light, a reference plate for absorbing the invisible light, the reference plate being disposed behind the document reflecting the light, and an image sensor which receives the light reflected by the document, captures an image of the document with the light from the light source, and generates read data of the image, the image including a visible image being captured with the visible light and an invisible image being captured with the invisible light, the image processing method comprising:

• detecting coordinates of a plurality of first points on a boundary area between the document and the reference plate in the visible image based on a shadow of the document cast on the reference plate in the visible image;
• detecting coordinates of a plurality of second points on the boundary area between the document and the reference plate in the invisible image based on incidence or non-incidence of light from the document and the reference plate in the invisible image;
• calculating a first detection result and first detection error information, the first detection result representing a tilt of the document detected in the visible image based on the coordinates of the plurality of first points, and the first detection error information representing accuracy of detection of the tilt of the document in the visible image;
• after completion of the calculating the first detection result and the first detection error information, calculating a second detection result and second detection error information, the second detection result representing a tilt of the document detected in the invisible image based on the coordinates of the plurality of second points, and the second detection error information representing accuracy of detection of the tilt of the document in the invisible image;
• and
• selecting one of the first detection result of the visible image and the second detection result of the invisible image based on the first detection error information and the second detection error information.