Method for detecting a code with the aid of a mobile station
First Claim
1. A method for detecting a code (40), in which method a mobile station (50) is used to capture an image of the subject (40) and the image is analysed and decoded into a numerical form in the mobile station (50), characterized in that, before the decoding of the bar code in the mobile station a calculated quality indicator is defined in real time from each camera image from the variance of the grey tones, which depicts the probability that the bar code is in the image field and can be interpreted correctly, on the basis of the quality indicator, a decision is made as to whether the bar code is 1D or 2D, in the case of a 1D bar code, the quality indicator is calculated from the Line of Interest, in which the differences between the grey tones along the line are greatest, in the case of a 2D bar code, the quality indicator is calculated on the basis of the difference histogram of the grey tones of the image above the assumed bar code, the value of the quality indicator is shown to the user on the display of the telephone, by using graphical signs, for example, in such a way that poorer visibility of the code is shown with red and higher visibility with yellow and green, and a high-resolution image is captured once the quality indicator of the bar code exceeds a specified threshold level and the Line of Interest defined in the low-resolution stage is interpreted.
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Accused Products
Abstract
The invention relates to a method for detecting a code (40), and a mobile station adapted to the method. In the method, the mobile station (50) is used to capture an image of the subject (40) and the image is analysed and decoded into a numerical form in the mobile station (50). According to the invention, before the decoding of the bar code in the mobile station the edges of the subject (40) are determined from a high-resolution image, in the case of a 2D code, the location of the corner point of the subject (49) are estimated on the basis of adaptive thresholding, and in the case of a 2D code, a perspective transformation is formed.
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Citations
23 Claims
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1. A method for detecting a code (40), in which method a mobile station (50) is used to capture an image of the subject (40) and the image is analysed and decoded into a numerical form in the mobile station (50),
characterized in that, before the decoding of the bar code in the mobile station a calculated quality indicator is defined in real time from each camera image from the variance of the grey tones, which depicts the probability that the bar code is in the image field and can be interpreted correctly, on the basis of the quality indicator, a decision is made as to whether the bar code is 1D or 2D, in the case of a 1D bar code, the quality indicator is calculated from the Line of Interest, in which the differences between the grey tones along the line are greatest, in the case of a 2D bar code, the quality indicator is calculated on the basis of the difference histogram of the grey tones of the image above the assumed bar code, the value of the quality indicator is shown to the user on the display of the telephone, by using graphical signs, for example, in such a way that poorer visibility of the code is shown with red and higher visibility with yellow and green, and a high-resolution image is captured once the quality indicator of the bar code exceeds a specified threshold level and the Line of Interest defined in the low-resolution stage is interpreted.
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8. A method for detecting a code (40), in which method a mobile station (50) is used to capture an image of the subject (40) and the image is analysed and decoded into a numerical form in the mobile station (50),
characterized in that before the decoding of the bar code in the mobile station the edges of the subject (40) are determined from a high-resolution image, in the case of a 2D code, the location of the corner point of the subject (40) are estimated on the basis of adaptive thresholding, and a perspective transformation is formed in the case of a 2D code.
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9. A method according to claim 9, characterized in that using the mobile station (50) the subject is repeatedly imaged in low-resolution mode prior to capturing the image to be analysed.
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15. A mobile station for detecting a code (40), which mobile station includes means for capturing an image of the subject (40) and means for analysing the subject (40) decoding it into a numerical form,
characterized in that the mobile station (50) includes means for defining a quality indicator in real time from each camera image from the variance of the grey tones, which indicator depicts the probability that the bar code is in the image field and can be interpreted correctly, in the case of a 1D bar code, for calculating a quality indicator from the variance of the grey tones of the horizontal lines of the image, in the case of a 2D bar code, for calculating a quality indicator from the variance of the grey tones of the image, for showing the value of the quality indicator to the user on the display of the telephone, by using graphical signs, for example, in such a way that poorer visibility of the code is shown with red and higher visibility with yellow and green, and for capturing a high-resolution image once the quality indicator of the bar code exceeds a specified threshold level.
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22. A mobile station for detecting a code (40), which mobile station includes means for capturing an image of the subject (40) and means for analysing the subject (40) and decoding it into a numerical form,
characterized in that the mobile station (50) includes means for determining the edges of the subject (40) from a high-resolution image, in the case of a 2D code, for estimating the location of the corner point of the subject (40) on the basis of adaptive thresholding, and for forming a perspective transformation in the case of a 2D code.
Specification