KR100813970B1 - Stable level outputting method in image forming apparatus - Google Patents

Abstract

The present invention discloses a method for controlling a uniform image output level in an image forming apparatus. A light source for emitting light to the document, an optical source controller for supplying a control voltage to the light source, a CCD module for photoelectric conversion of the light reflected from the original, and an AFE for converting the photoelectrically converted analog signal into a digital signal based on an offset value. In the image forming apparatus having a control method for a uniform image output level, the duty ratio of the PWM voltage until the PWM duty ratio of the predetermined target level is reached from the PWM voltage of the duty ratio initially applied to the light source. Sequentially applying the light source in a stepwise manner; Checking a duty ratio of the applied PWM voltage to determine whether a PWM duty ratio of a target level has been reached; And fixing the duty ratio of the PWM voltage and adjusting the offset of the AFE when the PWM voltage of the duty ratio is checked as the target level.

Description

Uniform level outputting method in image forming apparatus

1 is a block diagram illustrating a structure of an image scanning unit in a general image forming apparatus.

FIG. 2 is a block diagram illustrating control of a CCFL light source in the image forming apparatus of FIG. 1.

3 is a flowchart illustrating a control method for a uniform image output level according to the present invention.

FIG. 4 is a flowchart illustrating a detailed control method of detailed AFE offset adjustment of FIG. 3.

Explanation of symbols on the main parts of the drawings

100: image sensor module 104: light source

106: image sensor 108: AFE

110: SRAM 112: image processor

114: light source controller 116: CPU

The present invention relates to a method for controlling image level output in an image forming apparatus. More particularly, the present invention relates to a light source control of an image scanning unit and an offset of an analog front end (AFE) in an image forming apparatus. The present invention relates to a method for controlling a uniform image level output in an image forming apparatus capable of compensating for a characteristic change of a device that may be caused by the device and outputting a stable scan image level.

An image forming apparatus having an image reading function, such as a multifunction printer or a scanner, illuminates a photo or a print from a light source, and performs photoelectric conversion on a charge coupled device (CCD) or contact image sensor (CIS) in proportion to the intensity of reflected light, thereby Convert the image to the pattern.

As a light source, a CCFL (Cold Cathode Fluorescent lamp) light source, which is a fluorescent lamp used for a backlight of an LCD display device, is used.

1 is a block diagram illustrating a structure of an image scanning unit in a general image forming apparatus.

The image scanning unit includes an image including a CCFL light source 104 that shines light on the document 102 and a one-dimensional image sensor 106 which receives the intensity of light reflected from the document 102 in units of lines and converts it into an electrical analog signal. The sensor module 100, a motor driver not shown to move the image sensor module 100 to scan in units of lines, an AFE (Analogue Front End) and SRAM (converting analog signals into digital signals according to offset values) 110), an image processor 112 for processing image data, a CPU 116 for controlling overall data processing, storing data for performing shading acquisition and compensation, and for storing operating programs and processing data. Memory 118 configured as volatile and nonvolatile.

FIG. 2 is a block diagram illustrating control of a CCFL light source in the image forming apparatus of FIG. 1.

The CCFL light source 104 sends a high voltage current to the electrodes and electrodes connected to the sealed glass tube and the electrode connected to the end of the lead wire extending into the glass tube. When the mercury is released, an ionization reaction occurs, the mercury is excited to emit ultraviolet light, and the phosphor inside the glass tube emits light while changing the ultraviolet light into the visible wavelength range.

The power applied to the CCFL light source 104 is controlled by a PWM signal. The light source control signal controlled and output by the light source controller 114 is driven by the optical power MOSFET 200 and then the peripheral circuit unit 210 and Controlled power is applied to the CCFL light source 104 via the CCDM inverter 22.

In addition, the analog voltage output from the image sensor 106 is output to the image processor 112 as a data value obtained by converting the analog signal into a digital signal in the AFE 108. After the converted pixel pattern is corrected by the generated shading data, the image processor 112 performs a post-processing process.

In the prior art, the scan unit of such an image forming apparatus applies a fixed CCFL or Xe light source voltage and an AFE offset when generating shading data, which is reference data for adjusting the variation in the amount of light. Therefore, the scanning is performed by external environment such as the temperature and the deviation of the sensitivity of the electrical signal output in response to the reflected light from the image sensor 106 constituting the image forming apparatus, the intensity of the light source, the lamp inverter current, the lens transmittance and the like. There is a problem that the output signal is not uniform, there is a deviation for each set, and in extreme situations, the difference between the original image and the original image is severe when the scanned image data is printed out.

The technical problem of the present invention is to adjust the PWM control signal for controlling the voltage applied to the CCFL light source, which is an analog control element, and the offset register value of the AFE in the image forming apparatus having a scan function, thereby reducing external environmental factors or deviation of the CCD module. It is to provide a control method for a uniform image output level in an image forming apparatus having a stable output of a scan unit by being corrected.

In order to achieve the above technical problem, a light source for emitting light to an original according to the present invention, a light source controller for supplying a control voltage to the light source, a CCD module for photoelectrically converting light reflected from the original, and a photoelectrically converted analog signal The control method for the uniform image output level in the image forming apparatus having an AFE for converting the signal into a digital signal based on the offset value,

Sequentially increasing the duty ratio of the PWM voltage from the PWM voltage of the duty ratio applied to the initial light source until the PWM duty ratio of a predetermined target level is reached; Checking a duty ratio of the applied PWM voltage to determine whether a PWM duty ratio of a target level has been reached; And adjusting the offset of the AFE when the PWM voltage of the duty ratio of the target level is checked.

In addition, the offset of the AFE is set to 0 during the process of adjusting the duty ratio of the PWM voltage.

In addition, the duty ratio adjustment of the PWM voltage is close to the target level value so that the duty ratio is set to a middle value between the target level value and the duty ratio value of the current PWM voltage each time the PWM voltage is checked. It is characterized by adjusting by binary scan method.

In addition, the process of adjusting the AFE offset,

A first step of calculating an A / D conversion level (OBavg) in an average optical black (OB) region of the CCD; A second step of calculating an A / D conversion level CENavg near the center of the effective pixel of the CCD; Setting a value obtained by multiplying the CENavg by a predetermined ratio or by multiplying the maximum A / D conversion value (ADCMax) of the AFE by a predetermined ratio to a target OB level (OBtarget); A fourth step of calculating an absolute value (Diff) of a difference value between the OBtarget and the OBavg; Calculating a value (Vgap) multiplied by the input range of the AFE and the Diff / ADCMax; Calculating a Vgap / Vout offset with respect to the offset register of the AFE as an increase / decrease offset value; A seventh step of checking whether the increase / decrease offset value is calculated as a value having a predetermined number of consecutive zeros; If it is not continuously calculated as 0 in the seventh process, repeating the first process by adding the increase / decrease offset value to the current value of the current offset of the AFE; And if the increase / decrease offset is continuously calculated as 0 in step 7, the value of the offset register is fixed and applied during A / D conversion.

In addition, the number of times of checking the increase / decrease offset in the seventh step is preferably set to three times.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the exemplary embodiment of the present invention, the deviation between the external environment and the CCD module is corrected by controlling the PWM control signal for adjusting the voltage applied to the CCFL light source, which is an analog control element, and the offset register value embedded in the AFE.

An image scanning unit of an image forming apparatus such as a multifunction printer or a scanner reads a white patch, which is a reference plane, and performs shading acquisition for use as a correction value during an actual scan. The CCFL light source has a higher amount of light than the initial time as the time passes after the lighting is turned on and saturates after a certain time. Therefore, there is a difference in the amount of light at the time of acquiring shading and at the actual copying operation. A method of reducing these differences will be described.

3 is a flowchart illustrating a control method for a uniform image output level according to the present invention.

When the image forming apparatus is powered on or woken up, the light source control unit 114 is centered on the dispersion among the plurality of CCD modules and is based on an experimental value that can produce a target amount of light determined by the designer based on data obtained in a normal ambient temperature environment. The duty ratio of the PWM voltage is determined to initialize the voltage of the light source 104. At this time, if the current voltage can immediately deteriorate the power MOSFET 200 when it is directly adjusted to the duty ratio of the target level, the PWM voltage is applied to the light source 104 by adjusting the duty ratio stepwise (300 and 310). step).

The area for checking whether the target level has been reached is a constant pixel area in the center of the CCD effective pixel and an Optical Black (OB) area of the CCD which is the image sensor 106. The process of determining the inverter applied voltage by the PWM duty ratio uses only the pixel average value in the center region. Since the same output cannot be produced every time due to the external environment and the deviation of the CCD and the light source 104, the designated target level must be checked. The area for checking whether the target level has been reached is a constant pixel area in the center of the CCD effective pixel and an OB area of the CCD. The process of determining the inverter applied voltage by the PWM duty ratio uses only the pixel average value in the center region.

Check the level of the ADC value in these two areas. When adjusting the PWM duty ratio, which is a control element, the binary scan method is applied as follows. For example, if the PWM duty ratio is 60% and the checked duty ratio is less than 100% of the target level, proceed to binary scan to 80% between 60% and 100%. If you stand, get close to the target level by 70%. At this time, since the next correction value can be determined only when the duty ratio or the AFE offset change history is known, a memory area for storing the change history is allocated. When adjusting the PWM duty ratio, the AFE offset is preferably set to 0 (steps 320 and 330).

In operation 340, when the PWM duty ratio reaches the target value, the offset of the AFE 108 is adjusted and the shading data is obtained, or the copy or scan is performed (operation 350).

4 is a flowchart illustrating a detailed method of adjusting the detailed AFE 108 offset of FIG. 3.

The determined PWM duty ratio is fixed and the AFE 108 offset is changed as shown in FIG. The average value of the OB area and the effective pixel center area is obtained, and the target level of the OB area is determined by a constant ratio of the central effective pixel level or the ADC maximum level (for example, 65535 for 16-bit resolution). The AFE 108 is adjusted repeatedly until there is little difference between the target level and the OB level.

First, the A / D conversion level OBavg in the average OB area of the CCD is calculated, and the A / D conversion level CENavg of the central effective pixel of the CCD is calculated (steps 400 and 402). For example, a value multiplied by 0.9% or a value multiplied by a predetermined ratio to the maximum A / D conversion value ADCMax of the AFE 108 is set as a target OB level OBtarget, and an absolute value of the difference between the OBtarget and OBavg is obtained. The value Diff is calculated (steps 404 and 406). Here, ADCMax is 65535 when the AFE 108 converts an analog signal into a digital signal with 16 bits.

The value Vgap obtained by multiplying the Diff / ADCMax by the input range of the AFE 108 is calculated, and the Vgap / Vout offset with respect to the offset register is calculated as the increase / decrease offset value (steps 408 and 410).

It is checked whether the increase / decrease offset is calculated to be a predetermined number of consecutive zeros. If the increase / decrease offset is not continuously calculated as 0, the increase / decrease offset value is added to the current value of the current offset of the current AFE 108 to repeat from step 400 (412, Step 414). If the increase or decrease offset is continuously calculated as 0, the value of the offset register is fixed (step 416).

According to the present invention, in the image forming apparatus having the scanning function, the PWM control signal for adjusting the voltage applied to the light source 104 and the offset register value of the AFE are adjusted to correct external environmental factors or the deviation of the CCD module. A control method for a uniform image output level in an image forming apparatus having an output of a scan unit is provided. In addition, the rapid change of the voltage applied to the light source is controlled to prevent rapid deterioration of the light source.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (5)

 A light source for emitting light to the document, an optical source controller for supplying a control voltage to the light source, a CCD module for photoelectric conversion of the light reflected from the original, and an AFE for converting the photoelectrically converted analog signal into a digital signal based on an offset value. In the uniform image output level control method in the image forming apparatus having a, Sequentially increasing the duty ratio of the PWM voltage from the PWM voltage of the duty ratio applied to the initial light source until the PWM duty ratio of a predetermined target level is reached; Checking a duty ratio of the applied PWM voltage to determine whether a PWM duty ratio of a target level has been reached; And And adjusting the offset of the AFE when the PWM voltage of the duty ratio of the target level is checked. The method of claim 1, wherein the offset of the AFE is set to 0 during the stepwise step of increasing the duty ratio of the PWM voltage. The method of claim 1, wherein the step of sequentially raising the duty ratio of the PWM voltage stepwise sets the duty ratio to an intermediate value between the target level value and the value of the duty ratio of the current PWM voltage every time the PWM voltage is checked. And adjusting the duty ratio of the PWM voltage in a binary scan manner as close to the target level as possible. The method of claim 1, wherein adjusting the AFE offset comprises: A first step of calculating an A / D conversion level (OBavg) in an average optical black (OB) region of the CCD; A second step of calculating an A / D conversion level CENavg near the center of the effective pixel of the CCD; Setting a value obtained by multiplying the CENavg by a predetermined ratio or by multiplying the maximum A / D conversion value (ADCMax) of the AFE by a predetermined ratio to a target OB level (OBtarget); A fourth step of calculating an absolute value (Diff) of a difference value between the OBtarget and the OBavg; Calculating a value (Vgap) multiplied by the input range of the AFE and the Diff / ADCMax; Calculating a Vgap / Vout offset with respect to the offset register of the AFE as an increase / decrease offset value; A seventh step of checking whether the increase / decrease offset value is calculated as a value having a predetermined number of consecutive zeros; Repeating the first step by adding the increase / decrease offset value to the current value of the current offset of the AFE if it is not continuously calculated as 0 in the seventh step; And And adjusting the value of the offset register to apply the A / D conversion when the increase / decrease offset is continuously calculated as 0 in the seventh step. 5. The method according to claim 4, wherein the number of times of checking the increase / decrease offset in step 7 is three times.

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