KR100315639B1 - Method for image compensation according to temperature variation in scanning system - Google Patents

Abstract

The present invention detects a change in the amount of light of a light source according to an ambient temperature in a scanning system using a color image sensor, and adjusts the shading value and the turn-on time of the light source to automatically compensate for image quality. It is about a method.

To this end, in the scanning system using a color CIS, when a light quantity change occurs in one light emitting diode, the present invention detects and updates a shading correction factor for one light emitting diode, and updates the remaining light emitting diodes on-time. By reducing the time required to detect shading data, the shading data and LED turn-on time can be readjusted according to the change of ambient temperature of the scanning system from store to store. You can check for the best picture quality.

Description

Image quality compensation method according to temperature change in scanning system {METHOD FOR IMAGE COMPENSATION ACCORDING TO TEMPERATURE VARIATION IN SCANNING SYSTEM}

The present invention relates to a method for compensating image quality according to temperature change in a scanning system. More particularly, a shading value and turn-on time of a light source are detected by detecting a light quantity change of a light source according to an ambient temperature in a scanning system using a color image sensor. The present invention relates to a method for compensating image quality according to a temperature change in a scanning system that automatically compensates image quality by adjusting.

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 AidedDesign) is a prerequisite for computers, facsimiles, character recognizers, and digital copiers.

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 configured 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. .

Scanners using CCDs typically use halogen lamps or fluorescent lamps as light sources, while scanners using CIS typically use small light emitting diodes (LEDs) as light sources.

The black and white CIS uses only one type of green LED to read the black and white of the original, while the color CIS uses the red LED, the green LED, and the blue LED. Are alternately irradiated to read the amount of light for each light emitting diode and the original color is recognized by the combination of these three values.

Such a small light emitting diode is very important to mechanically prevent the CIS from being exposed to external light because the amount of light is significantly smaller than that of lamps as well as external light. This is because when the external light is mixed with the light reflected from the original, the amount of incident light increases, thereby reading the color of the original into an image close to white. The scanning device of the seat fed system is easy to block external light because it is not exposed to external light, but the scanning device of the flat bed system is exposed to external light when the scanning cover is open. Much attention should be paid to blocking.

On the other hand, if the light reflected from the original is not incident on the image sensor correctly, or if the deviation occurs due to the optical system assembly tolerance, the amount of light reflected from the original cannot be accurately measured by the image sensor, resulting in image distortion. This phenomenon is called a shading phenomenon.

Therefore, the scanning apparatus 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 constructed between the home position of the image sensor and the area where the actual scan is performed.

Here, the shading correction operation will be briefly described with reference to FIG. 1.

The light emitted from the light emitting diode is reflected by the white panel and 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, that is, the brightness value of the white panel, must be maintained at a constant level at a point shown in FIG. 1A.

However, if the light reflected from the white panel is not accurately incident on the image sensor, the voltage level output from the image sensor is reduced, so that the white level is reduced by the shaded area in the graph shown in FIG. This happens.

Shading correction method for correcting such a shading phenomenon, as shown in Figure 1b 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. 1C, the distorted image is corrected by adding shading data correcting the reduced white level to the scanning data scanning the actual original.

This shading correction process detects when the light emitted from the light emitting diode is not accurately incident on the image sensor or when external light is incident and compensates for the shading value when reading the document. The assumption is that it does not change.

However, the scanning system using the CIS mainly uses a light emitting diode having a characteristic inversely proportional to the ambient temperature in order to reduce the size and cost of the product. Therefore, when the ambient temperature decreases, the amount of light emitted by the light emitting diode increases and when the ambient temperature increases, the light emitting diode It has a characteristic of reducing the amount of light emitted.

Therefore, even if the shading correction is performed after scanning the white panel to detect the shading data before scanning the actual original, the amount of light emitting diode changes according to the change of the ambient temperature of the scanning system using the CIS.

That is, the change in the light quantity of the light emitting diode according to the change of time is minute and can be ignored. However, the change in the light quantity of the light emitting diode according to the change in ambient temperature affects the quality of scan or radiation, resulting in a problem of poor image quality.

In order to solve this problem, the light quantity change of the light emitting diode with temperature or time must be compensated for.

The method of compensating the light quantity change of the light emitting diode according to the temperature or the time is to repeat the shading process to detect the shading correction factor every time the store manuscript is read, or to detect the ambient temperature if necessary by detecting the ambient temperature. Shading process should be performed.

If the store's manuscript detects the shading correction factor repeatedly and performs the shading process, or if the ambient temperature is detected and the change in the light quantity of the light emitting diode is detected, the shading correction factor is detected and the shading process is performed. Even if the amount of light of the light emitting diode changes according to the change, the shading correction is performed immediately, thereby reducing the quality of the image by affecting the scan or radiation quality.

However, this method causes the following problems in the case of a scanning system using a color CIS.

First, scanning systems using color CIS typically have more than 300 DPI (Dot Per Inch) pixels, and new on-time for each of the red (R), green (G), and blue (B) light emitting diodes. Real-time shading is impossible because time and shading correction factors have to be detected, and this problem is more serious when multiple copies are made.

Second, in the case of performing the shading process by detecting the change in the ambient temperature, a separate temperature sensing circuit must be added to detect the ambient temperature, and a large amount of experimental data must be accumulated so that the image quality does not change badly at a predetermined temperature. do.

Third, when the scanning cover is opened by a user's mistake in the flat bed scanning system, the light shading of the red, green, and blue light emitting diodes all change to the high side, and thus the wrong shading correction factor is detected. This results in a severe black background, and in the case of an inkjet system, it consumes a lot of ink.

Accordingly, an object of the present invention is to solve such problems, and an object of the present invention is to detect a shading correction factor for one light emitting diode again when a light quantity change occurs in one light emitting diode in a scanning system using a color CIS. By updating and correcting the on-time of the other remaining light emitting diodes, an optimum image quality is obtained by compensating for the light quantity change of the light emitting diodes according to the change of ambient temperature.

Another object of the present invention is to determine whether the scanning cover of the flat bed scanning system is opened or closed in response to the light quantity change of one light emitting diode.

1 is a waveform diagram illustrating a shading correction process in a scanning system.

1A is a waveform diagram illustrating a shading error occurring when scanning a white panel;

FIG. 1B is a waveform diagram illustrating a correction element of a shading error occurring in FIG. 1A;

1C is a waveform diagram of shading data for correcting actual scanned data according to the shading correction element of FIG. 1B;

2 is a schematic block diagram of a scanning system according to the present invention;

3 is a view showing a change in the amount of light of the light emitting diode according to the change of the ambient temperature,

3A is a view showing a change in light quantity of a green light emitting diode;

3b is a view showing a change in light quantity of a blue light emitting diode;

3c is a view showing a change in light quantity of a red light emitting diode;

Figure 4 is a flow chart for compensating for the image quality in accordance with the change in the ambient temperature according to the present invention.

<Description of the code | symbol about the principal part of drawing>

10: shading memory 11: memory

12: light emitting diode (LED) 13: image sensor (CIS)

14: analog / digital converter 15: shading data detector

16: shading memory 17: shading correction unit

18: LED drive data storage unit 19: LED drive correction data storage unit

20: ambient temperature detector

In order to achieve the above object, a feature of the present invention is a method for compensating image quality of a color CIS (Contact Image Sensor) scanning system using red, green, and blue light emitting diodes as a light source: detected during initial operation of the scanning system. LED driving data detection step of storing turn-on time of each of red, green and blue light emitting diodes and shading data obtained by scanning the maximum voltage level and white panel and the number of saturated pixels reaching the maximum voltage level, and scanning system LED drive correction data detection step of storing the turn-on time of the green and blue LEDs corresponding to the change of the ambient temperature in the form of a look-up table, and driving the red light-emitting diodes during the turn-on time stored in the LED drive data detection step. And whether the amount of light of the red light emitting diode has increased from that of the initial operation of the scanning system. The number of saturated pixels reaching the maximum voltage level stored in the LED driving data detection step and checking the number of the green and blue light emitting diodes corresponding to the identified number of saturated pixels. Detecting the turn-on time in the look-up table stored in the LED driving correction data detecting step; and if the amount of light of the red light emitting diode has not increased, detecting the maximum voltage level of the red light emitting diode and corresponding to the detected maximum voltage level. Detecting the turn-on time of the green and blue light emitting diodes in the lookup table stored in the LED driving correction data detection step; and when the turn-on time of the green and blue light emitting diodes is detected in the lookup table, The shading is performed by scanning the white panel by driving for the turn-on time saved in the driving data detection step. And a shading correction step of scanning the actual document with reference to shading data detected in the reshading step and turn-on times of the green and blue light emitting diodes detected in the lookup table. do.

Preferably, further comprising the step of identifying an increased amount of light of the red light emitting diode in excess of 30%; If the amount of light of the increased red light emitting diode does not exceed 30%, a step of checking the number of saturated pixels reaching the maximum voltage level stored in the LED driving data detection step among the pixels of a line is performed, and the increased red light emitting diode When the amount of light exceeds 30%, it is determined that the scanning cover of the scanning system is opened, and the actual shading is performed by referring to the turn-on time and shading data of the red, green, and blue light emitting diodes stored in the LED driving data detection step. Perform the calibration step.

Here, the LED driving correction data detecting step includes: dividing the operating temperature of the scanning system into N, and a maximum voltage level higher than the maximum voltage level of the red light emitting diode stored in the LED driving data detection step among the N divided operating temperatures. Storing the turn-on time of the green and blue light emitting diodes detected during the shading process to scan the white pattern corresponding to the maximum voltage level, and red light stored in the LED driving data detection step among N divided operating temperatures. Storing the number of saturated pixels greater than the number of saturated pixels for the diode and the turn-on times of the green and blue light emitting diodes detected during the shading process of scanning the white pattern corresponding to the number of saturated pixels. .

Here, the step of checking the amount of light of the red light emitting diode may include reducing the ambient temperature of the scanning system if the number of saturated pixels for the red light emitting diode emitted in the red light emitting diode driving step and the number of saturated pixels stored in the LED driving data detection step are increased. If it is determined that the amount of light of the red light emitting diode has increased, and if the voltage level of the red light emitting diode emitted in the red light emitting diode driving step is lower than the voltage level stored in the LED driving data detecting step, the ambient temperature of the scanning system is increased to increase the red light emitting diode. It is determined that the amount of light is lowered.

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 2 is a schematic block diagram of a scanning system according to the present invention, Figure 3 is a view showing a change in the light amount of the light emitting diode according to the change in the ambient temperature, Figure 4 shows the change in the ambient temperature according to the present invention According to the operation flow chart for compensating for the image quality is shown.

Referring to FIG. 2, the scanning controller 10 generates a timing signal for performing a series of scanning operations and controls the operation of the entire scanning system. In particular, according to a preferred embodiment of the present invention, each component is controlled as a whole to readjust the shading data and turn-on time of the light emitting diode 12 in accordance with the change of the ambient temperature of the scanning system.

The memory 11 stores programs 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 light emitting diode (LED) 12 is turned on / off under the control of the scanning controller 10. Here, the LED includes red (R), green (G), and blue (B) LEDs, and the red, green, and blue LEDs are turned on / off by receiving respective control signals from the scanning controller 10.

The image sensor (hereinafter referred to as 'CIS') 13 photoelectrically converts incident reflected light into an electrical analog image signal, which is reflected from a white panel or an original while the LED 12 is turned on. And generates a voltage signal having a value proportional to the amount of incident light.

The analog / digital converting unit 14 converts the image information of the analog form photoelectrically converted by the image sensor 13 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 15 scans the white panel and detects shading data for storing the digital image data output from the analog / digital converter 14 to a constant level and stores the shading data in the shading memory 16 (FIG. 1B). Reference).

The shading memory 16 stores shading data detected by the shading data detector 15.

The shading correction unit 17 performs real scanning to scan an original to add the shading data stored in the shading memory 16 to the digital image data output from the analog / digital converter 14 for each pixel position. To output shading-corrected digital image data.

The LED driving data storage unit 18 stores the turn-on times of the red, green, and blue LEDs applied when scanning the white panel or the document before performing the shading process for detecting the shading data.

That is, since the red, green, and blue LEDs of the LED 12 are turned on / off by respective control signals from the scanning controller 10, the turn-on times of the red, green, and blue LEDs are determined by the scanning controller 10. Adjust as required under the control of). Of course, the longer the turn-on time of the LED, the greater the amount of light (voltage level) of the CIS, the shorter the turn-on time of the LED, the lower the amount of light of the CIS. Therefore, the scanning control unit 10 should appropriately set the turn-on time of the red, green, and blue LEDs before driving the LED 12 and the CIS 13 to scan the white panel.

To this end, the scanning control unit 10 gradually increases the turn-on time of the red, green, and blue LEDs of the LED 12, and converts one line converted through the CIS 13 and the analog / digital conversion unit 14. Among the information of the digital image data, that is, whether or not the specific number Np of all the pixels in one line reaches the maximum brightness value.

When the specific number Np of all the pixels in one line reaches the maximum brightness value, the scanning controller 10 stores the turn-on times for the red, green, and blue LEDs at this time.

Here, the number of specific pixels reaching the maximum brightness value among all the pixels in one line is at least one, which is called a saturation pixel.

The LED driving correction data storage unit 19 is composed of a lookup table in which the amount of light of the red LED and the turn-on time of the green and blue LEDs detected when the shading process is performed in response to the change of the ambient temperature of the scanning system are performed. And stored.

This is to prevent the image quality from deteriorating due to the change in the amount of light of the LED 12 according to the change of the ambient temperature, which is stored in advance before performing the scanning operation in the scanning system.

To do this, first divide the operating temperature of the scanning system by N and store the light quantity (voltage level) of the red LED at each temperature (Tn) divided by N and the turn-on times of the corresponding green and blue LEDs by experiment. do.

The ambient temperature of the scanning system may be higher or lower than the ambient temperature of the initial operation of the scanning system.

When the ambient temperature of the scanning system rises above the ambient temperature during the initial operation, since the amount of light of the LED 12 decreases, the amount of red LED light at each temperature Tn and the shading process of detecting the shading data at this time are performed. The turn-on times of the detected green and blue LEDs are stored in the form of a lookup table.

In addition, when the ambient temperature of the scanning system falls below the ambient temperature at the time of initial operation, the amount of light of the LED 12 increases, so that the number of saturated pixels of the red LED at each temperature Tn and shading data are detected at this time. The turn-on time of the green and blue LEDs detected when the shading process is performed is detected as a lookup table.

Here, when checking the light quantity change of the LED 12 according to the change of the ambient temperature of the scanning system, checking the light quantity of the red LED among the LEDs 12 is an operating temperature of the normal office equipment as shown in FIG. This is because the amount of change in the amount of light corresponding to the change in the ambient temperature from 0 degrees to 40 degrees is the most severe in the red LED.

The ambient temperature detector 20 detects the ambient temperature of the scanning system and inputs it to the scanning controller 10. That is, the ambient temperature detector 20 is red among the LEDs 12 with the turn-on time stored in the LED driving data storage unit 18 under the control of the scanning controller 10 before performing the shading process for detecting the shading data. By comparing the number of saturated pixels actually detected when the LED is turned on with the number of saturated pixels set in the initial operation of the scanning system to determine whether the ambient temperature of the scanning system is lowered, When the red LED is turned on, the amount of light actually detected is compared with the amount of red LED detected at the initial operation of the scanning system to determine whether the ambient temperature of the scanning system is increased.

An operation of the present invention having such a configuration will be described in detail with reference to FIG. 4.

In the present invention, the red, green, and blue LEDs are driven by the turn-on time stored in the LED driving data storage unit 18 during the initial operation of the scanning system, and accordingly, the red, green, and blue outputs from the CIS 13 are output. The amount of light (voltage level) and the number of saturated pixels of the LED are stored. If the ambient temperature of the scanning system is changed while the scanning operation is continued, the light quantity of the red, green, and blue LEDs changes, so that the turn-on time and the amount of the red, green, and blue LEDs stored in the LED driving data storage unit 18 and This is to obtain an optimum image quality by rapidly responding to the image quality change by referring to the number of saturated pixels.

To this end, the scanning control unit 10 performs a shading process for detecting shading data for shading correction before scanning the actual original.

In order to perform the shading process, the scanning controller 10 drives a red LED among the LEDs 12 during the turn-on time stored in the LED driving data storage unit 18 (S401).

When the light emitted from the red LED is incident on the CIS 13 after being reflected by the white panel, the CIS 13 photoelectrically converts the incident reflected light into an electric analog image signal and outputs a predetermined voltage signal (S402).

The ambient temperature detector 20 controls a predetermined voltage signal output from the CIS 13 under the control of the scanning controller 10, that is, a light amount of the red LED whose light amount (voltage level) of the red LED is set during the initial operation of the scanning system. It is determined whether the increase has been made (S403). Here, if the amount of light of the red LED increases, it means that the ambient temperature of the scanning system is lowered.

As a result of the determination, if the amount of light of the red LED is increased, the scanning controller 10 checks whether the amount of light of the increased red LED exceeds 30% (S404). In other words, it is to check how much the ambient temperature of the scanning system is lower than the ambient temperature at the time of initial operation of the scanning system.

If the amount of light of the increased red LED does not exceed 30%, the scanning controller 10 checks the number of saturated pixels by checking the digital image data output from the analog / digital converter 14 (S405).

That is, the analog image information photoelectrically converted by the CIS 13 is converted into digital image data having a predetermined number of bits (m) by the analog / digital conversion unit 14 and output. The number of saturated pixels reaching the maximum brightness value is checked.

When the saturation pixel count is checked in one line of digital image data output from the analog / digital converter 14, the scanning control unit 10 selects from the data stored in the form of a lookup table in the LED driving correction data storage unit 19 (step 405). The turn-on time of the green and blue LEDs corresponding to the number of saturated pixels checked in S405 is detected (S406).

That is, the scanning control unit 10 detects the number of saturated pixels checked in step 405 (S405) among the data stored in the LED driving correction data storage unit 19, and turns the green and blue LEDs corresponding to the detected number of saturated pixels. -To detect the on time.

Thereafter, the shading data detector 15 scans the white panel and detects shading data for storing the digital image data output from the analog / digital converter 14 to maintain a constant level, and stores the shading data in the shading memory 16. A shading process is performed (S407).

The shading control unit 10 refers to the readjusted shading data and the turn-on times of the green and blue LEDs when the shading data of the red LEDs and the turn-on times of the green and blue LEDs are detected according to the change of the ambient temperature of the scanning system. The digital image data shading-corrected for the actual original is output (S408).

On the other hand, if the light amount (voltage level) of the red LED is increased compared to the light amount of the red LED set at the initial operation of the scanning system, the determination result in step 403 (S403), when the light amount of the red LED does not increase, the scanning control unit 10 detects the peak level among the voltage levels of the red LED output from the CIS 13 (S409). Here, when the amount of light of the red LED does not increase, that is, the decrease in the amount of light of the red LED means that the ambient temperature of the scanning system is increased.

When the maximum level is detected among the voltage levels of a line of red LEDs output from the CIS 13, the scanning controller 10 may be configured to correspond to the maximum level detected among the data stored in the LED driving correction data storage unit 19. The turn-on time of the blue LED is detected (S410).

Thereafter, the shading data detector 15 scans the white panel and detects shading data for storing the digital image data output from the analog / digital converter 14 to maintain a constant level, and stores the shading data in the shading memory 16. A shading process is performed (S407).

The shading control unit 10 refers to the readjusted shading data and the turn-on times of the green and blue LEDs when the shading data of the red LEDs and the turn-on times of the green and blue LEDs are detected according to the change of the ambient temperature of the scanning system. The digital image data shading-corrected for the actual original is output (S408).

In addition, if it is determined that the light amount of the increased red LED exceeds 30% and the result of the check in step 404 (S404) exceeds 30%, the scanning control unit 10 determines that the scanning cover is opened in the flat bed scanning system. (S411), the process branches to step 408 (S408) of scanning the actual original to output shading-corrected digital image data. At this time, the shading data is the data detected in the initial operation of the scanning system and stored in the shading memory 16.

Therefore, whenever scanning the store's manuscript, it detects a change in the ambient temperature of the scanning system, and if the ambient temperature of the scanning system changes, the shading data of the red LED and the turn-on times of the green and blue LEDs are readjusted to deteriorate the image quality. Can be prevented.

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 image quality compensation method according to the temperature change in the scanning system according to the present invention has the following advantages.

First, when the ambient temperature change of the scanning system is detected, shading data is detected for each store for the red LED and compensation for the green and blue LEDs with a preset turn-on time can effectively reduce the time for detecting the shading data. have.

Second, in each store, the shading data and the turn-on time of the LED are readjusted according to the change of the ambient temperature of the scanning system, and the flat bed scanning system can check the opening state of the scanning cover to obtain the optimum image quality.

Claims (4)

In the image quality compensation method of a color CIS (Contact Image Sensor) scanning system using red, green, and blue light emitting diodes as a light source: The turn-on time and maximum voltage level of each of the red, green, and blue light emitting diodes detected during the initial operation of the scanning system, and the number of shading data obtained by scanning the white panel and the number of saturated pixels reaching the maximum voltage level. LED driving data detection step of storing; LED driving correction data detection step of storing the turn-on time of the green and blue light emitting diode corresponding to the change of the ambient temperature of the scanning system in the form of a look-up table; Driving the red light emitting diode for a turn-on time stored in the LED driving data detection step; Checking whether the amount of light of the red light emitting diode has increased from that of an initial operation of the scanning system; As a result of the check, if the amount of light of the red light emitting diode is increased, the number of saturated pixels reaching the maximum voltage level stored in the LED driving data detection step among the pixels of the line is checked, and the number of the saturated pixels confirmed is determined. Detecting a turn-on time of a corresponding green and blue light emitting diode in the lookup table stored in the LED driving correction data detecting step; If the amount of light of the red light emitting diode has not increased, a maximum voltage level is detected among the voltage levels of the red light emitting diode, and the turn-on time of the green and blue light emitting diodes corresponding to the detected maximum voltage level is determined. Detecting in the lookup table stored in the LED driving correction data detection step; When the turn-on time of the green and blue LEDs is detected in the look-up table, the red LED is driven for the turn-on time stored in the LED driving data detecting step to scan the white panel to detect shading data. Reshading step; And a shading correction step of scanning the actual original by referring to the shading data detected in the reshading step and the turn-on times of the green and blue light emitting diodes detected by the lookup table. Image quality compensation method. The method of claim 1, Identifying an increased amount of light of said red light emitting diode in excess of 30%; Checking the number of saturated pixels reaching the maximum voltage level stored in the LED driving data detecting step among the pixels of the line if the amount of light of the increased red light emitting diode does not exceed 30%; If the amount of light of the red light emitting diode exceeds 30%, it is determined that the scanning cover of the scanning system is opened, and the turn-on time and the shading data of the red, green, and blue light emitting diodes stored in the LED driving data detection step are determined. The image quality compensation method according to the temperature change in the scanning system, characterized in that for performing the shading correction step of scanning the actual original with reference to. The method of claim 1, wherein the LED driving correction data detection step, Dividing the operating temperature of the scanning system into N pieces; The maximum voltage level higher than the maximum voltage level of the red light emitting diode stored in the LED driving data detection step and the white pattern corresponding to the maximum voltage level are detected during the shading process. Storing turn-on times of the green and blue light emitting diodes; Shading process of scanning the white pattern corresponding to the number of saturated pixels and the number of saturated pixels more than the number of saturated pixels for the red light emitting diode stored in the LED driving data detection step among the N divided operating temperatures And storing turn-on times of the green and blue light-emitting diodes detected at the time of detection. According to claim 1, wherein the step of checking the light amount of the red light emitting diode, If the number of saturated pixels for the red light emitting diode emitted in the red light emitting diode driving step and the number of the saturated pixels stored in the LED driving data detection step increase, the ambient temperature of the scanning system is lowered to Judging by the increase in the amount of light If the voltage level of the red light emitting diode emitted in the red light emitting diode driving step is lower than the voltage level stored in the LED driving data detecting step, the ambient temperature of the scanning system is increased to determine that the amount of light of the red light emitting diode is lowered. Image quality compensation method according to the temperature change in the scanning system, characterized in that.