KR20000050717A - Apparatus and method for shading correction in the scanning system - Google Patents

Abstract

PURPOSE: A device for correcting a shading in a scanning system is provided to get more exquisite images, by scanning a white panel, before scanning a real draft, and once more executing shading correcting operations of an incident light for an acquired shading data. CONSTITUTION: A scanning system reads an image data of a draft, through an image sensor which converts a light emitted from a lamp and reflected in the draft and a white panel into an electronic analog image signal. A method for correcting a shading of the scanning system comprises the steps of: scanning a white panel, by turning-on a lamp; detecting a shading data, by scanning the white panel; detecting an environment data, by scanning a previously predetermined region for detecting amounts of an incident light; detecting last shading data compensated a white level according to amounts of the incident light, by operating the shading data and the environment data; executing shading correcting operations, by scanning a real draft, and adjusting last shading data to the scanned data; and being output a completed data by the shading correcting operations.

Description

Shading correction method and apparatus for scanning system {APPARATUS AND METHOD FOR SHADING CORRECTION IN THE SCANNING SYSTEM}

The present invention relates to a method and apparatus for shading correction of a scanning system, and more particularly, to external shading data obtained by scanning a white panel before scanning an actual document. The present invention relates to a shading correction method and apparatus for a scanning system that enables a more accurate image to be obtained by performing shading correction operation on incident light once more.

Image scanning devices, such as scanners, are the most common means for scanning (printing, reading) color or black-and-white texts or pictures in the form of prints, photographs, or memos written by human hands. Computer Aided Design) is an essential component such as a computer, facsimile, character recognizer and digital copier.

The image scanning device is largely a sheet-fed system and a flat-bed system. The sheet-fed system is configured to read a single document like a general facsimile, and the image sensor is fixed. In the way that the document moves, the addition of an ADF (Automatic Document Feeder) device can automatically read multiple sheets, and the flatbed system is designed to allow book scanning as well as single sheets like a normal copier. It's fixed and the way the image sensor moves.

In such an image scanning device, an image sensor such as a CCD (Charge Coupled Device) or a CIS (Contact Image Sensor) converts into a pixel pattern corresponding to an original image by performing photoelectric conversion in proportion to light reflected from an original to be scanned. .

1 is a schematic structural diagram of a conventional flat bed scanning system.

Referring to FIG. 1, the document table 2 on which the document D is placed is provided on the upper surface of the main body 1 of the apparatus, and the cover 3 is hinged on the one side edge of the upper surface of the main body 1 of the apparatus. ), And the document 4 is supported by the hinge 4 while being rotated in the direction of the arrow A in FIG. 1.

In addition, an elastic member 5 such as a sponge having a predetermined thickness is attached to the inner surface of the cover 3, and the disturbance of the document D placed on the document table 2 on the elastic member 5 is prevented. A white plate 6 is attached for this purpose.

When the hinge coupling structure of the cover 3 is demonstrated, the hinge 4 is comprised from the fixing part 4a and the rotation part 4b, and the cover 3 also consists of the fixing part 3a and the rotation part 3b. It is comprised, The fixing part 3a of the cover 3 is fixed to the fixing part 4a of the said hinge 4, The rotating part 3b of the cover 3 is fixed to the rotation part 4b of the hinge 4 Are fixed respectively.

The flatbed scanning system configured as described above rotates the cover 3 in the orientation of the document glass 2 in the state where the document D is placed on the document glass 2 of the apparatus main body 1. When positioned at, the white plate 6 attached to the inner side of the cover 3 brings the document D into close contact with the document table 2.

At this time, since the elastic member 5 is attached to the inner side of the cover 3, the elastic member 5 is elastically pressed to prevent the flow by pressing the document (D). In this way, the original D is read in the state in which the original D is stably supported on the document table 2.

After the document D is placed on the platen glass 2, when a predetermined predetermined button for scanning is selected, the lamp (not shown) is turned on to light the document D while moving in the longitudinal direction of the document. Will emit. The light emitted from the lamp and reflected from the document (D) measures the amount of light in the image sensor. The image sensor generates a voltage signal whose value is proportional to the amount of light received by the image sensor, and the analog image signal is converted into a pixel pattern corresponding to the original image by a circuit built into the scanner.

However, if the light reflected from the original (D) is not accurately incident on the image sensor, or if a deviation occurs due to optical system assembly tolerance, the amount of light reflected from the original (D) may not be accurately measured by the image sensor. The image is distorted, which is called a shading phenomenon.

Therefore, the scanning system performs shading correction before scanning the actual document so that data can be read at a stable level when scanning the actual document.

Shading correction is to adjust the white level by performing a dummy scan on the white panel before scanning the actual original to compensate for the shading phenomenon in which the brightness is partially read differently. To this end, a white panel is formed between the home position of the image sensor and the area where the actual scan is performed, that is, the document glass 2.

The shading correction operation will be described in more detail with reference to FIGS. 2 to 4.

FIG. 2 is a waveform diagram illustrating shading errors occurring when a white panel is scanned in a typical scanning system, FIG. 3 is a waveform diagram illustrating correction factors of shading errors occurring in FIG. 2, and FIG. 4. The waveform diagram of the shading data correcting the actually scanned data according to the shading correction element of FIG. 3 is shown.

First, when a predetermined button is selected to perform a scanning operation, the lamp is turned on to scan the white panel.

Light emitted from the lamp and reflected from the white panel is incident on the image sensor, and the image sensor generates a voltage having a value proportional to the amount of incident light.

Analog image information output from the image sensor is converted into digital image data. In this case, the digital image data for the white panel, that is, the brightness value, must be maintained at a constant level at a point shown in FIG. 2.

However, since the voltage level output from the image sensor is reduced when the light reflected from the white panel is not accurately incident on the image sensor, the shading phenomenon in which the white level is reduced and the image is distorted, as in the shaded area in the graph shown in FIG. This happens.

Shading correction method for correcting such a shading phenomenon, as shown in Figure 3, the shading correction factor (shading correction factor corresponding to the reduced white level so that the brightness value obtained by scanning the white panel is kept constant at a point) ).

The shading correction element detected by scanning the white panel is applied to each pixel position with respect to the scanning data scanned by the actual original. That is, as shown in Fig. 4, the distorted image is corrected by adding shading data for correcting the reduced white level to the scanning data scanning the actual original.

However, according to the shading correction method of the conventional scanning system, the following problems occur.

That is, when the original placed on the platen of the flatbed scanning system is a thick book or wrinkled original, or due to a user's mistake, the cover may not properly adhere the original to the platen, and the actual original may be scanned. When the light is incident from the outside.

Therefore, even if the shading correction is performed on the data scanned by the actual original using the shading data obtained by scanning the white panel, since the light incident from the outside cannot be corrected, the image quality is deteriorated because accurate shading correction is not performed. do.

Accordingly, an object of the present invention is to solve such a problem, and an object of the present invention is to scan shading data by scanning a white panel before scanning an actual document, and to detect the shading data according to the amount of light incident from the outside. The present invention provides a method and apparatus for shading correction of a scanning system capable of acquiring more sophisticated images.

1 is a schematic configuration diagram of a conventional flat bed scanning system,

2 is a waveform diagram illustrating a shading error occurring when a white panel is scanned in a typical scanning system;

3 is a waveform diagram illustrating a correction factor of a shading error occurring in FIG. 2;

4 is a waveform diagram of shading data for correcting actual scanned data according to the shading correction element of FIG. 3.

5 is a schematic structural diagram of a flat bed scanning system according to the present invention;

6 is a schematic block diagram showing a shading correction apparatus of a flat bed scanning system according to the present invention;

7 is an operation flowchart showing a process of performing a shading correction method according to the present invention;

8 is a waveform diagram of environmental data according to the amount of external light incident on the environmental recognition section;

FIG. 9 is a waveform diagram illustrating final shading data obtained through the process of FIG. 7; FIG.

A feature of the present invention for achieving this object is shading correction of a scanning system that reads image data of an original by an image sensor that converts light emitted from a lamp and reflected from the original and the white panel into an electrical analog image signal. A method comprising: turning on a lamp to scan a white panel, scanning a white panel to detect shading data, and turning off the lamp to detect an amount of light incident from the outside Detecting environmental data by scanning a predetermined region, calculating shading data and environmental data, detecting final shading data whose white level is compensated according to the amount of light incident from the outside, and scanning an actual original To apply the final shading data to the scanned data System, and lies in that the shading correction operation includes the step of outputting the data is completed.

Preferably, the method of detecting final shading data is that if the shading data at each pixel position is larger than the environmental data, the final shading data is a value obtained by subtracting the environmental data from the shading data, and the shading data at each pixel position is the environment. If smaller than the data, the final shading data is characterized by being zero.

Preferably, the predetermined area is characterized in that it is located between the point where the document is actually placed at the start point of the platen on which the original is placed.

Another aspect of the invention is a shading correction apparatus of a scanning system for reading image data of an original by an image sensor which converts light emitted from a lamp and reflected from the original and white panel into an electrical analog image signal: A scanning controller for controlling on / off, an analog / digital converter for converting an electrical analog image signal output from the image sensor into digital image data, and converting the white panel into digital image data by scanning a white panel And a shading data detector for detecting shading data for outputting the digital image data to maintain a constant white level, and environmental data output from an analog / digital converter by scanning a predetermined area formed between the white panel and the document. Environment day to detect A detection unit, a data operation unit for calculating final shading data by processing the shading data detected by the shading data detection unit and the environmental data detected by the environment data detection unit, a shading memory for storing the final shading data detected by the data operation unit, and a document And a shading correction unit configured to scan and apply the final shading data stored in the shading memory to the digital image data output from the analog / digital converter.

Preferably, if the shading data at each pixel position detected by the shading data detector is larger than the environmental data at each pixel position detected by the environment data detector, the data operation unit subtracts the environmental data from the shading data to determine the final shading data. If the shading data at each pixel position detected by the shading data detector is smaller than the environmental data at each pixel position detected by the environment data detector, the final shading data is detected as zero.

Preferably, the scanning control unit is characterized in that the lamp is turned on when scanning the white panel, turned off when scanning a predetermined area, and turned on when scanning the document.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even if they are displayed on different drawings. In addition, in the following description there are shown a number of specific details, such as components of the specific circuit, which are provided only to help a more general understanding of the present invention that the present invention may be practiced without these specific details. It is self-evident to those of ordinary knowledge in Esau. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Figure 5 is a schematic block diagram of a flat bed scanning system according to the present invention, Figure 6 is a schematic block diagram showing a shading correction device of the flat bed scanning system according to the present invention, Figure 7 FIG. 8 is a flowchart illustrating an operation of the shading correction method according to the present invention. FIG. 8 illustrates a waveform diagram of environmental data according to the amount of external light incident from the environmental recognition section, and FIG. A waveform diagram showing the final shading data obtained through the process is shown.

The flat bed scanning system according to the present invention shown in FIG. 5 is distinguished from the conventional flat bed scanning system shown in FIG. 1 in that an environmental awareness section I is formed between a white panel and an area where an actual scan is performed. .

The environmental recognition section (I) is a shading data obtained by scanning a white panel. When correcting data scanned by an actual original, the image sensor is reflected from the white panel to prevent the image from being distorted due to external light incident. This is the area to detect the amount of light incident from the outside after detecting the amount of light that is being reflected and before detecting the amount of light reflected from the actual document.

To this end, the environmental recognition section I has a predetermined length at the starting position of the document glass 2 on which the document D is placed, and the document D is after the environmental recognition section I formed on the document glass 2. Will be put on.

Therefore, when the scanning operation is started, the image sensor scans the white panel after leaving the home position, scans the environmental recognition section I, and then scans the actual document D placed on the document glass 2. At this time, the lamp is turned on when scanning the white panel, turned off when scanning the environmental awareness section (I), and turned on again when scanning the actual document (D).

The shading correction apparatus of the flatbed scanning system configured as described above will be described with reference to FIG. 6.

The scanning control unit 10 generates a timing signal for performing a series of scanning operations and controls the operation of the entire system.

The memory 11 stores a program having a certain flow and temporary data generated while the scanning control unit 10 controls the system so that the scanning control unit 10 can control the scanning system in a predetermined order.

The lamp driver 12 controls the light emitting state of the lamp 13 according to the control signal of the scanning controller 10, and the lamp 13 is turned on / off under the control of the lamp driver 12.

The image sensor 14 photoelectrically converts the incident reflected light into an electrical analog image signal, in which the amount of light reflected from the white panel or the document D and the lamp 13 are turned off while the lamp 13 is turned on. In this state, a voltage signal having a value proportional to the amount of external light incident through the environmental recognition section I is generated.

The analog / digital conversion unit 15 converts the image information of the analog form photoelectrically converted by the image sensor 14 into digital image data having a predetermined number of bits (m). For example, assuming that image information in analog form is converted into 8-bit digital image data, the maximum brightness value M of the converted digital image data is 255 by 2 ^m −1 (ie, 2 ⁸ −1 = 255). Is determined. Here, as the gradation of the binarization target image used in the present invention, it is preferable to use 256 gradations representing 8 bits of a single pixel as in a normal case, but bits allocated according to respective application fields can be added or subtracted. The more bits that are assigned to a pixel when performing an analog-to-digital conversion, the more precise and detailed the pixel can be represented, but on the other hand, more resources must be allocated and the processing cost must increase exponentially. Ham is a well-known fact.

The shading data detector 16 scans the white panel and detects the shading data for the digital image data output from the analog / digital converter 15 to maintain a constant level and stores the shading data in the shading memory 17 (FIG. 4). Reference).

The environmental data detector 18 scans the environmental recognition section I, detects digital image data output from the analog / digital converter 15, and stores the digital image data in the shading memory 17 (see FIG. 8).

The data operation unit 19 processes the shading data detected by the shading data detection unit 16 and the environmental data detected by the environment data detection unit 18, detects the final shading data, and stores the final shading data in the shading memory 17 (FIG. 9). That is, the incident white level is corrected when scanning the environmental recognition section I from the white level attenuated when scanning the white panel.

Equation for calculating the shading data and the environmental data in the data operation unit 19 is well shown in the equation (1).

Here, the shading data acquired by the shading data detector 16 is called shading data (S), and the environment data obtained by the environment data detector 18 is called A (Ambient data), and the data operation unit 19 performs arithmetic processing. The final shading data that corrects the data scanned by the actual original is called F (final shading data).

here, Where x and y are experimentally set coefficients.

here, X and y are experimentally set coefficients.

For example, a method of detecting the final shading data by the data calculating unit 19 in the state where the coefficient values of x and y are assumed to be 1 will be described below.

As shown in FIG. 4, digital image data at a predetermined pixel position b is detected at 120 levels from the digital image data detected by the shading data detection unit 16, and as shown in FIG. 8, the environmental data detection unit ( If digital image data at a predetermined pixel position (b) is detected at 50 levels in the digital image data detected in 18), the data calculating unit 19 receives light from which the attenuated white level is incident from the outside when scanning the white panel. Because it is compensated by, subtract 50 levels from 120 levels. That is, the data calculating unit 19 subtracts the environmental data from the shading data when the shading data detected by the shading data detector 16 is larger than the environmental data detected by the detector 18. The calculation result in the data calculating section 19, i.e., the 70-level digital image data is stored in the shading memory 17 (see Fig. 9).

In other words, the data obtained by scanning the actual original is corrected by adding 70 levels of the final shading data to the digital image data at the predetermined pixel position (b) among the data output from the analog / digital converter 15.

In addition, as shown in FIG. 4, digital image data at a predetermined pixel position c is detected as zero level in the digital image data detected by the shading data detection unit 16, and the environmental data as shown in FIG. 8. If the digital image data detected at the predetermined pixel position (b) is detected at 70 levels in the digital image data detected by the detector 18, the data calculating unit 19 detects that the attenuated white level is incident from the outside when scanning the white panel. Since all the light is compensated for, there is no need to correct the data scanned by the actual original. That is, if the shading data detected by the shading data detector 16 is smaller than the environment data detected by the environment data detector 18, it is not necessary to correct the data scanned by the actual document, so that it is outputted from the data operator 19. The final shading data is at zero level (see FIG. 9).

In other words, the data scanned by the actual original is corrected by adding zero level, the final shading data, to the digital image data at the predetermined pixel position c among the data output from the analog / digital converter 15.

The shading memory 17 performs shading data detected by the shading data detector 16, environmental data detected by the environment data detector 18, and final shading data obtained by processing shading data and environment data by the data operation unit 19. Is stored.

The shading correction unit 20 stores the final shading data stored in the shading memory 17 in the digital image data output from the analog / digital converter 15 when performing real scanning to scan an original document. By outputting the digital image data shading-corrected by addition, the digital image data in which the distorted image is corrected can be obtained.

Such a shading correction method of the present invention will be described in detail with reference to the accompanying drawings.

First, when a user selects a predetermined function key to perform a scanning function (S700), this operation signal is input to the scanning controller 10. The scanning control unit 10 controls the lamp driver 12 to turn on the lamp 13 (S701), and moves the lamp 13 to scan the white panel (S702).

Accordingly, the light emitted from the lamp 13 is reflected by the white panel and received by the image sensor 14. The image sensor 14 converts the light reflected from the white panel into an electrical signal and provides the analog signal to the analog / digital converter 15. The analog / digital converter 15 is an analog type provided by the image sensor 14. Converts electrical signals into digital form. In this case, the digitized data is divided into 256 levels (8 bits) of brightness data from 0 to 255 and outputted.

As described above, when the brightness data at each pixel position of the white panel is output by the analog / digital converter 15, the shading data detector 16 has a constant digital image data output from the analog / digital converter 15. Shading data for maintaining the level is detected (S703), and the detected shading data is stored in a predetermined area of the shading memory 17 (S704).

Here, the constant level that the digital image data output from the analog / digital converter 15 by scanning the white panel must hold is 255 levels. That is, since the light emitted from the lamp 13 must be reflected in all of the white panel, and the light reflected from the white panel is incident from the image sensor 14, the maximum brightness value among the 0-255 levels should be maintained at 255 levels. It is.

When the shading data detected by the shading data detector 16 is stored in a predetermined area of the shading memory 17, the scanning controller 10 controls the lamp driver 12 to turn off the lamp 13 (S705). The lamp 13 is moved to the environmental recognition section I to detect the amount of light incident from the outside (S706).

The light incident from the environmental recognition section I is received by the image sensor 14, and the image sensor 14 converts the incident light into an electrical signal and then provides the analog / digital converter 15. The digital conversion unit 15 converts an analog signal provided by the image sensor 14 into a digital form. In this case, the digitized data is divided into 256 levels (8 bits) of brightness data from 0 to 255 and outputted.

When the brightness data at each pixel position of the environmental recognition section I is output by the analog / digital converter 15 as described above, the environmental data detector 18 is a digital image output from the analog / digital converter 15. The data is detected, and the detected environmental data is stored in a predetermined area of the shading memory 17 (S707) (see FIG. 8).

When the environmental data detected by the environmental data detector 18 is stored in the shading memory 17, the data operation unit 19 calculates and processes the shading data and the environmental data stored in the shading memory 17 (S708), and the final shading data. Is detected (S709) (see Fig. 9).

When the final shading data is detected by the data calculating unit 19, the detected final shading data is stored in a predetermined region of the shading memory 17 (S710).

Thereafter, the scanning controller 10 drives the lamp driver 12, the lamp 13, and the image sensor 14 to scan an image recorded on the document D placed on the document table 2 (S711). Light emitted from the lamp 13 and reflected from the document D is converted into an electrical signal by the image sensor 14, and converted into digital image data by the analog / digital converter 15 and output.

The shading correction unit 20 adds and outputs the final shading data stored in the shading memory 17 for each pixel position to the digital image data of the actual document D output from the analog / digital conversion unit 15, thereby shading. The corrected digital image data is provided (S712).

That is, the digital image data of the actual document D output from the analog / digital converter 15 is added and output for each pixel position. For example, the final shading data level 70 at the pixel position b is an actual document. The digital image data of (D) is added to the data of point b and output, and the final shading data 0 level of the pixel position c is added to the data of point c of the digital image data of the actual document D and output.

Therefore, the shading correction for the white panel and the external light can be performed to obtain a more stable shading correction result.

As described above, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As described above, according to the shading correction method of the flat bed scanning system according to the present invention, in performing shading correction on the scanned data by scanning an actual document, shading data scanned from the white panel and light incident from the outside The shading correction operation on the environmental data obtained by sensing the amount of light can be performed simultaneously to output a more precise image.

Claims (6)

A shading correction method of a scanning system in which image data of an original is read by an image sensor that converts light emitted from a lamp and reflected from an original and a white panel into an electrical analog image signal: Turning on the lamp to scan the white panel; Scanning the white panel to detect shading data; Detecting environmental data by turning off the lamp to scan a predetermined predetermined area for sensing the amount of light incident from the outside; Computing the shading data and the environmental data to detect final shading data whose white level is compensated according to the amount of light incident from the outside; Scanning an actual original and applying the final shading data to the scanned data to perform shading correction; And outputting the data in which the shading correction operation is completed. The method of claim 1, wherein the final shading data is detected. If the shading data at each pixel position is larger than the environmental data, the final shading data is a value obtained by subtracting the environmental data from the shading data. If the shading data at each pixel position is smaller than the environmental data, the final shading data is 0. Shading correction method of the scanning system, characterized in that. The method of claim 1, wherein the predetermined area, And a position between the point where the document is actually placed and the starting point of the document bed on which the document is placed. A shading correction apparatus of a scanning system for reading image data of an original by an image sensor which converts light emitted from a lamp and reflected from the original and the white panel into an electrical analog image signal: A scanning controller to control on / off of the lamp; An analog / digital converter configured to convert the electrical analog image signal output from the image sensor into digital image data; A shading data detector configured to scan the white panel and detect shading data to convert the output digital image data into a digital image data from the analog / digital converter to maintain a constant white level; An environmental data detection unit scanning a predetermined area formed between the white panel and the original to detect environmental data output from the analog / digital converter; A data calculation unit configured to process the shading data detected by the shading data detection unit and the environmental data detected by the environment data detection unit to detect final shading data; A shading memory configured to store the final shading data detected by the data calculating unit; And a shading correction unit configured to scan the original and apply the final shading data stored in the shading memory to the digital image data output from the analog / digital converter. The method of claim 4, wherein the data operation unit, If the shading data at each pixel position detected by the shading data detector is larger than the environment data at each pixel position detected by the environment data detector, the final shading data is detected by subtracting the environmental data from the shading data, If the shading data at each pixel position detected by the shading data detector is smaller than the environmental data at each pixel position detected by the environment data detector, the final shading data is detected as 0. Device. The method of claim 4, wherein the scanning control unit, And turn on when the lamp scans the white panel, turn off when scanning the predetermined area, and turn on when scanning the document.