Method to obtain consistent image quality measurements from different image input devices
First Claim
1. An image quality analysis system for an image output device that is input device independent, comprising:
- a test pattern pertinent to image quality determination;
a scanner that scans a hardcopy test image, which has been generated by the output device based on the test pattern, to form a digital raster image, the scanner having a predetermined modulated transfer function (MTF);
means for blurring the digital raster image by a differential transfer function (DTF) corresponding to the modulation transfer function (MTF) divided by the visual transfer function (VTF) corresponding to a human visual system to form a blurred image; and
an image quality analysis module that receives the blurred image, distinguishes one or more test targets from the blurred image, and performs image quality analysis on the test targets to obtain results quantifying image quality, wherein the results of the image quality analysis are scanner independent and the blurred image from which the image analysis was conducted corresponds to an image perceived by a human viewer when viewing the hardcopy test image.
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Abstract
An image quality analysis system is provided for image output devices, such as printers and copiers, that overcomes problems with differences in analysis results caused by use of different image input devices. This is achieved by computing a differential transfer function that makes subsequent analysis device independent. Moreover, the analysis is performed on an image that has been blurred to also reflect absolute image quality metrics as seen by a human observer. By determining the resolving characteristics of the input scanner, the scanned image can be processed, with little or no artifacts, to resemble the image as perceived by a human observer, while at the same time eliminating differences that would arise when using a scanner having a different spatial resolving power.
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Citations
19 Claims
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1. An image quality analysis system for an image output device that is input device independent, comprising:
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a test pattern pertinent to image quality determination;
a scanner that scans a hardcopy test image, which has been generated by the output device based on the test pattern, to form a digital raster image, the scanner having a predetermined modulated transfer function (MTF);
means for blurring the digital raster image by a differential transfer function (DTF) corresponding to the modulation transfer function (MTF) divided by the visual transfer function (VTF) corresponding to a human visual system to form a blurred image; and
an image quality analysis module that receives the blurred image, distinguishes one or more test targets from the blurred image, and performs image quality analysis on the test targets to obtain results quantifying image quality, wherein the results of the image quality analysis are scanner independent and the blurred image from which the image analysis was conducted corresponds to an image perceived by a human viewer when viewing the hardcopy test image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of performing image quality analysis on an image output device having an output station that generates a hardcopy image from a digital image, the method comprising:
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generating a hardcopy test image from the image output device based on a predetermined test pattern pertinent to image quality determination;
scanning the hardcopy test image using a scanner to form a digital raster image;
determining a Modulation Transfer Function (MTF) for the scanner at different spatial frequencies;
determining a Visual Transfer Function (VTF) to take into account the sensitivity of a human visual system (HVS);
calculating a Differential Transfer Function (DTF) at each spatial frequency reflecting the difference between MTF and VTF;
transforming the scanned digital test image according to the DTF to degrade or blur the image to some extent from that achieved by the scanner such that this blurred image represents the image perceived by the human vision system (HVS); and
performing the image quality analysis based on the blurred image. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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- 18. A multi-function output device, including a scanner, and an associated data file provided on a storage medium that defines pre-determined data, usable to transform images scanned by the device into device-independent images that represent how the scanned sample would be perceived by a human observer, the data defining a single transform representing a Differential Transfer Function (DTF) that reflects a difference between a Modulation Transfer Function (MTF) that takes into account the scanner resolving power of the scanner and a Visual Transfer Function (VTF) that takes into account the sensitivity of a Human Visual System (HVS).
Specification