CN101924855B - Method for correcting gray-level linear array scanning image - Google Patents

Abstract

The invention discloses a method for correcting a gray-level linear array scanning image, comprising the following steps of: firstly scanning white paper to obtain an initial scanning image; then calculating the correction factor of each sensor by utilizing software on a computer on the basis of the initial scanning image; and adding the digital signal of an A/D-converted real-time scanning image to the correction factor corresponding to the point by using an adder to obtain the value of the corrected pixel point. The method has the advantages that because the method comprises the steps of firstly calculating the correction factor by utilizing the software on the computer according to the initial scanning image obtained by scanning the white paper, then preposing and applying the correction factor by utilizing special hardware, sending the calculated correction factor to the adder by using the software and then performing a simple point-by-point addition operation by using the adder to accomplish image correction, the method reduces the realization difficulty of the hardware and also avoids the time delay caused by software correction. The original light and dark stripes of the corrected image are eliminated so that the corrected image is more uniform and truer.

Description

The modification method of gray-level linear array scanning image

Technical field

The present invention relates to a kind of gray scale scanning image correcting method, especially relate to a kind of modification method of plane antenna scanning grey pictures.

Background technology

Plane picture obtains extensively, is widely used in commercial production, business activity and the daily life, is divided into face battle array and linear array dual mode usually.The face system of battle formations has the advantages that as obtaining through camera or video camera speed is fast, cost is low, but often has the defective of edge deformation or whole distortion, can not directly be used for high-precision image processing.Linear array scanning such as flat bed scanner etc.; Can obtain high-precision plane picture; The problem that has anamorphose hardly can directly apply to the image processing field with strict quality requirement, like the online quality testing on the production line, ballot paper statistics, financial document processing etc.

The line scan image sensor array is used in linear array scanning usually; Gray scale scanning bar with the most widely used A4 breadth, 200DPI is an example, and on the length of 216mm, 40 led light sources are distributing; Simultaneously evenly distributed 1728 image sensor modules; Promptly the spacing of two modules is 125 μ m, has all comprised an optical lens, a transducer in each module, and other affiliated facilities.The corresponding pixel of sensor assembly.The irradiate light of light emitted is to scanned surface, and reflection gets into lens, focuses on sensor array and lists, and delivers to amplifier through shift register output, handles the back and transfers to computer through image pick-up card, promptly forms delegation's image.Along with scanned object at the uniform velocity passes through scan stripes, can form a width of cloth original scan image.

Because the optical characteristics of pointolite array, and scanned surface contacts with scan stripes apart from there being deviation, determined that original scan image inevitably light and dark striped will occur, and is as shown in Figure 1.This just need have a balance or a correction to the analog output signal of each transducer, lets them that less electrical differences is arranged under identical light signal.

Accomplish this correction and can use and be with degenerative analog circuit,, before A/D, accomplish image correction to suppress the variation difference of input analog signal.The cost of this method is higher, and development difficulty is bigger, is not suitable for high speed scanner cheaply.

Summary of the invention

In order to overcome the above-mentioned shortcoming of prior art; The invention provides a kind of modification method of gray-level linear array scanning image,, obtain initial scan image at first through blank sheet of paper is scanned; Utilize software on the basis of initial scan image, to calculate the correction factor of each transducer then on computers; To pass through the digital signal of the real time scan image of A/D conversion again, the correction factor corresponding with this point obtains the value of revised pixel through the adder addition.This modification method is simple, and the image that obtains after the correction has been eliminated the light and shade striped that exists in the existing modification method, and image more evenly, truly.

The technical solution adopted for the present invention to solve the technical problems is: a kind of modification method of gray-level linear array scanning image may further comprise the steps:

The first step, scanning a blank sheet of paper obtain the gradation data of initial scan image;

The gradation data of second step, the initial scan image that obtains according to blank sheet of paper scanning, calculate the correction factor of each point:

(1) suppose that the sampling line number is N, the transducer number is M, asks the mean value of capable each corresponding points of image of N of i transducer, obtains the row vector;

(2) mean value of the row vector of M transducer of calculating;

(3) correction factor of i transducer of calculating;

The 3rd step, through USB interface, the correction factor vector is write among the EEPROM of high speed scanner;

The 4th the step, in real-time image scanning; Earlier the analog signal of each pixel is converted to the digital signal of a byte through A/D converter; Then that it is corresponding with this some correction factor is through the adder addition: if do not have carry after the adder addition; Just directly export result of calculation, as the value of revised pixel by adder; If after the adder addition carry is arranged, just directly export maximum, as the value of revised pixel by adder.

Compared with prior art, good effect of the present invention is: the initial scan image that at first obtains according to the scanning blank sheet of paper, utilize the computed in software correction factor on computers; Utilize the preposition correction factor of using of specialized hardware again; Pass to adder under the correction factor after software will calculate, do simple pointwise add operation, accomplish image correction by adder; Both reduced the realization difficulty of hardware, the time-delay of having avoided software application to bring again; Eliminated original light and shade striped through revised image, become even more, true, as shown in Figure 2.

Description of drawings

The present invention will explain through example and with reference to the mode of accompanying drawing, wherein:

Fig. 1 is an original scan image of not doing any processing;

Fig. 2 adopts the real-time revised image of the inventive method;

Fig. 3 is the schematic diagram of the inventive method.

Embodiment

A kind of modification method of gray-level linear array scanning image, as shown in Figure 3, comprise the steps:

The first step, scanning a blank sheet of paper; Obtain initial scan image (with light and dark striped), the initial scan image of establishing i capable transducer of j is

;

Second step, according to the initial scan image

that blank sheet of paper scanning obtains, calculate the correction factor of each point:

if

(i: i transducer), wherein:

: the actual signal of each transducer output

: the ideal signal of each transducer output

: the noise signal of each transducer output.

According to each physical characteristics of sensors, the real output signal of transducer

is to be made up of its ideal signal

and noise signal

.Therefore; By formula , obtain ideal signal

.Because

is to specific transducer relative fixed; Just can synthesize desirable sensor signal so only need obtain it; This

is exactly the correction factor of i transducer, obtains through following steps:

(1) supposes that the sampling line number is N; The transducer number is M; Ask the mean value of capable each corresponding points of image of N of i transducer, obtain row vector

:

(2) calculation of M sensors row vector average

:

(3) correction factor of i transducer of calculating:

The 3rd step, through USB interface, the correction factor vector is write among the EEPROM of high speed scanner.

The 4th the step, in real-time image scanning; Earlier the analog signal of each pixel is converted to the digital signal of a byte through A/D converter; Correction factor vector that then will be corresponding with this point through the adder addition, obtains the value Rimage [i] [j] of revised pixel by following formula:

Rimage[i][j]=

If there is not carry after the addition, just directly export Rimage [i] [j] by adder; If carry is arranged after the addition, just directly get maximum " FF ", promptly 255 (greatest measures that byte can be represented) obtain revised scan image thus.

Claims (1)

1. correction ten thousand methods of a gray-level linear array scanning image is characterized in that: may further comprise the steps:

The first step, scanning a blank sheet of paper obtain the gradation data of initial scan image, and the initial scan image of establishing i capable transducer of j is Image [j] [i];

Second step, according to the gradation data Image [j] [i] that blank sheet of paper scanning obtains, calculate the correction factor of each point:

(1) suppose that the sampling line number is N, the transducer number is M, asks the mean value of capable each corresponding points of image of N of i transducer one by one, obtains row vectorial mVector [i]:

$\mathrm{mVector}\left[i\right]=\underset{j=0}{\overset{N-1}{\mathrm{\Σ}}}\mathrm{Image}\left[j\right]\left[i\right]/N$

(2) calculate the vectorial mean value Average of M sensor row:

$\mathrm{Average}=\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}\mathrm{mVector}\left[i\right]/M$

(3) the correction factor aVector [i] of i transducer of calculating:

aVector[i]＝Average-mVector[i]

The 3rd step, through USB interface, the correction factor vector is write among the EEPROM of high speed scanner;

The 4th the step, in real-time image scanning; Earlier the analog signal of each pixel is converted to the digital signal of a byte through A/D converter; Correction factor vector that then will be corresponding with this point through the adder addition, obtains the value Rimage [i] [j] of revised pixel by following formula:

$\mathrm{Rimage}\left[i\right]\left[j\right]=\underset{j=0}{\overset{N-1}{\mathrm{\Σ}}}\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}\left(\mathrm{Image}\right[j\left]\right[i]+\mathrm{aVector}[i\left]\right)$

If do not have carry after the adder addition, just directly export result of calculation Rimage [i] [j], as the value of revised pixel by adder; If after the adder addition carry is arranged, just directly export maximum " FF ", as the value of revised pixel by adder.

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