Method and apparatus for capturing text images
First Claim
1. An apparatus for capturing an image of a document, comprising:
- an image capture device for capturing a digital image of a document in a field of view of the image capture device;
a resolution analyzer for analyzing the image to determine an approximate resolution of text characters in the image;
a comparison device responsive to the determined resolution of text characters, for comparing the determined resolution with predetermined data representing a maximum desired image resolution and a minimum desired image resolution;
an output device for generating a first output to indicate to the user a condition that the resolution is less than the desired minimum resolution, and a second output to indicate to the user a condition that the resolution is greater than the desired maximum.
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Abstract
A device and method are described for capturing an image of a document using a digital camera. The invention includes a resolution analyzer for analyzing the resolution of text characters in the image, to assess whether the resolution is suitable for OCR. In one aspect, if the resolution is too small or too large, an indicator is generated to guide the user as to the corrective movement of the camera to improve the resolution for OCR. In a second aspect, an electronic zoom control is controlled to alter the magnification of the captured image, to correct the resolution. In a third aspect, a method is described for analyzing the image to determine the resolution according to the height of text characters in the image. The method includes analyzing the run lengths of pixels in the image to identify a predominant length corresponding to the average character height (in pixels).
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Citations
20 Claims
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1. An apparatus for capturing an image of a document, comprising:
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an image capture device for capturing a digital image of a document in a field of view of the image capture device;
a resolution analyzer for analyzing the image to determine an approximate resolution of text characters in the image;
a comparison device responsive to the determined resolution of text characters, for comparing the determined resolution with predetermined data representing a maximum desired image resolution and a minimum desired image resolution;
an output device for generating a first output to indicate to the user a condition that the resolution is less than the desired minimum resolution, and a second output to indicate to the user a condition that the resolution is greater than the desired maximum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for capturing an image of a document, comprising:
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an image capture device for capturing a digital image of a document in a field of view of the image capture device;
a variable zoom lens system for adjusting the optical image formed at the image capture device, the variable zoom lens system being responsive to an electronic zoom control signal, a resolution analyzer for analyzing the image to determine an approximate resolution of text characters in the image;
a comparison device responsive to the determined resolution of text characters, for comparing the determined resolution with predetermined data representing at least one threshold resolution, and for generating an error output if the determined resolution does not meet the threshold requirement; and
a zoom control device for generating said zoom control signal, in response to said error output, to adjust the magnitude of zoom of said field of view, to correct the image resolution. - View Dependent Claims (11, 12, 13, 14)
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15. A method of determining the resolution of text characters in a digital image of a document, the method comprising:
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determining run lengths of runs of pixels in the digital image; and
analyzing the run lengths to identify a predominant length corresponding to the average character height. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification