KR930007975B1 - Shading compensating circuit and method - Google Patents

Abstract

The shading compensation circuit compensates distortion of image caused by contamination of a white roller equipped in optical unit of contact image sensor. The circuit includes a controller (1) for generating shading waveform start signal, read enable signal and reset signal, an image signal level selector (4) for adjusting output level of signal according to a first and a second image level signal, a RAM (9) for storing compensation coefficient, a shading compensating unit (7) for generating compensation level according to compensation waveform, for compensating shading waveform using compensation coefficient stored on the RAM (9) and for generating overflow signal, and an overflow signal detector (2) for detecting overflow signal generated by the shading compensator (7).

Description

Fade's Shading Compensation Circuit and Method Using Close-type Image Sensors

1 is a conventional shedding compensation circuit diagram.

2 is a shedding compensation circuit diagram according to the present invention.

3 is a shading waveform diagram of an image signal according to the present invention.

4 is a flow chart according to the present invention.

* Explanation of symbols for main parts of the drawings

1 control unit 2 overflow detection unit

3: white roller 4: image level selector

5: Close Image Type Sensor 7: Shading Compensation Circuit

9: ram

The present invention relates to a shading compensation circuit using a close-type image sensor in a facsimile system, and more particularly, to a shading compensation circuit and a method for preventing distortion of image quality caused by contamination of a white roller in an optical unit.

In general, the facsimile system has a shedding compensation by scanning the image data using a CCD, there is a problem that the image quality is poor due to the imbalance of the amount of fluorescent light. Therefore, in order to solve such a problem, as shown in FIG. 1, the image signal of the original was read using an image sensor in close contact with the optical unit.

When an original is inserted into the optical unit A, the control unit 1 generates a shading waveform start start signal and applies it to the shedding compensator 7 through the line b.

As a result, the shading compensator 7 generates a shedding waveform by receiving a signal read based on an arbitrary line of the white roller 3 positioned on the top of the close-up image sensor 5.

At this time, the shedding waveform generated by the shedding compensator 7 based on the first arbitrary line is compensated for all the input image signals by the shedding compensating reference waveform and is applied to the controller 1 through the line a. In addition, the control unit 1 outputs a read signal to the shedding compensator 7 through one line of the original through the line C when the original is inserted.

However, the shading compensation circuit using the conventional CIS, such as the first diagram, solves the problem of deterioration in image quality due to the unbalance of the amount of fluorescent lamps in the shading compensation circuit using the CCD. By compensating for all the input image signals, the shading compensation waveform is distorted due to the contamination with white roll, resulting in a problem of poor image quality.

Accordingly, an object of the present invention is to provide a shedding compensation circuit and method which can prevent distortion of image quality caused by contamination of a white roller in a facsimile using a close-type image sensor.

Another object of the present invention is to provide a shedding compensation circuit and method which can obtain a clear image quality by preventing distortion of a reference shedding waveform which may occur due to contamination of a white roller which is a reference when forming a shedding waveform.

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

2 is a shedding compensation circuit diagram according to the present invention, which generates a shedding waveform start signal, a line read signal of a document, a first-second image level selection signal, and receives an overflow detection signal, the overflow detection unit 20 described below. A control unit 1 for controlling the overall operation of the system by outputting a reset signal and inputting an image compensation signal, a white roller 3 for generating a white reference signal, and a white reference of the white roller 3 A close-up image sensor 5 that reads a signal and outputs an image signal, and inputs an image signal from the close-up image sensor 5 to selectively output the level of the image signal differently according to the control signal of the controller 1. An image signal level selector 4, a RAM 9 for storing a compensation coefficient value for each pixel, and an image signal selected by the image signal level selector 4 to receive a shading compensation waveform. Compensating the shading waveform based on the compensation coefficient value stored in the RAM 9 when generating a different compensation coefficient, and comparing the shading waveforms of different image signals selected by the image signal level selector 4 and over. A shedding compensator 7 for outputting a flow signal and an overflow detector 2 for detecting an overflow signal output from the shedding compensator 7.

In the configuration, the image signal level selector 4 has a normal cross terminal NC of the switch SW1 connected to the output terminal of the close-type image sensor 5 and a resistance at the output terminal of the close-up image sensor 10. R1) is connected to the normal open terminal NO of the switch SW1, and the common terminal C of the switch SW1 is configured to be connected to the input terminal of the shedding compensator 7.

3 is a shading waveform diagram of an image signal according to the present invention, 3A) is a waveform diagram when no overflow occurs and 3B) is a waveform diagram when an overflow occurs.

4 is a first step of generating an image level selection signal for differently outputting levels of an image signal according to the present invention, and a step of searching for whether an image level selection signal is generated and overflow occurs in the first step. In the second process, when the overflow occurs in the second process, the third process of resetting the overflow detecting unit 2 and returning to the first process, and when the overflow does not occur in the second process A fourth process is performed to perform normal shedding compensation.

One embodiment of the present invention based on the above configuration will be described in detail with reference to FIGS.

When an original is inserted into the optical unit A, the controller 1 generates a shedding waveform formation start signal and applies it to the shedding compensation unit 7 through the line b. In addition, the close-type image sensor 5 outputs an image signal read based on an arbitrary line of the white roller 3 located at the top. At this time, the control unit 1 generates a first image level selection signal and outputs it to the switch SW1 through the line d. Then, the switch SW1 is connected to the common terminal C and the normal cross terminal NC.

As a result, the shedding compensator 7 inputting the image signal from the close-type image sensor 5 generates a reference shedding waveform. The compensation coefficient value for the reference shedding waveform generated by the shedding compensator 7 is stored in the RAM 9. Thereafter, the control unit 1 outputs the second image level selection signal through the line d so that the switch SW1 is connected to the common terminal C and the normal open terminal NC.

At this time, the close-up image sensor 5 outputs an image signal in which an arbitrary next line of the white roller 3 is read. The image signal output from the close-type image sensor 5 is applied to the shedding compensator 7 by decreasing the level through the resistor R1. As a result, the shading compensator 7 detects an overflow by comparing the compensation coefficient value stored in the RAM 9 with the compensation coefficient value for the image signal input through the resistor R1.

At this time, if the overflow detection unit 2 detects an overflow, the control unit 10 outputs a reset signal to reset the overflow detection unit 2 to perform the above-described operation until no overflow is detected. Repeat. However, if the overflow signal is not detected by the overflow detection unit 2, it is input as a shedding compensation coefficient value for the output image signal when the common terminal C and the normal cross terminal NC of the switch SW1 are connected. Shading compensation of the image signal is normally performed.

That is, the first generated shedding waveform is recognized as valid, and one page of the original is shedding-compensated by this shedding compensation coefficient and read. Here, the process of detecting the overflow signal will be described as an example. When the common terminal C and the normal cross terminal NC of the switch SW1 are connected, the shading waveform for the image signal is P1 in FIG. 3 and the switch ( When the common terminal C and the normal open terminal NO of SW1) are connected, if the shedding waveform is in the P2 state of FIG. 3, if the large part of the P2 level or more does not occur as shown in FIG. Is detected as missing. However, as shown in FIG. 3B, a large portion Q above the P2 level is detected as no occurrence overflow.

Meanwhile, referring to the flowchart of FIG. 4 according to the present invention, when an original is inserted into the optical unit A, in step 4a, the controller 10 generates the first image level selection signal so that the switch SW1 is the normal cross terminal ( NC) and perform step (4b).

In the step (4b), the switch SW1 is connected to the normal black terminal NC to receive the image signal output from the close-type image sensor 5, and the shading compensation coefficient value generated by the shading compensating unit 7 is ram. In step (4C), the second image level signal is generated to connect the switch SW1 to the normal open terminal NO, and then, the step (4d) is performed. In step (4b), the next line of the white roller (3) is read to generate a shedding compensation coefficient value for the image signal through the resistor (R1), and the step (4f) is performed.

In step (4f), the shedding compensation waveform first generated in step (4d) and the shedding compensation waveform generated in step (4b) are compared to check whether an overflow occurs. If no overflow occurs, perform step (4g) to perform normal shading compensation for the original of the page based on the shading compensation waveform generated in step (4d).

In step (4h), the overflow detection unit (2) is reset, and the process is repeated again from step (4a) until no overflow occurs.

As described above, in the facsimile system using the close-type image sensor, the shading waveform is formed by setting the level of the image signal differently, and comparing the different shading waveforms so that the overflow is detected so that the shading is not detected when the overflow is not detected. By performing the compensation, it is possible to prevent distortion of the shading compensation waveform due to contamination of the white roller of the optical unit, thereby obtaining clean image quality and improving the reliability of the product.

Claims (2)

In a shading compensation circuit of a facsimile system using a close-type image sensor, an overflow detection unit which generates a shedding waveform start signal, a one-line read signal of a document, and a first-second image level selection signal and receives an overflow detection signal to be described later. A control unit 1 for outputting the reset signal of 20 and inputting an image compensation signal to control the overall operation of the system; and inputting an image signal from the image sensor 5, An image signal level selector 4 for selectively outputting a level of an image signal differently by a second image level select signal, a RAM 9 for storing a compensation coefficient value for each pixel, and the image signal level selector Receives the image signal selected in (4) to generate a compensation coefficient according to the shedding compensation waveform, and compensates the shedding waveform based on the compensation coefficient value stored in the RAM 9 when the original is read. The shading compensator 7 outputs an overflow signal by comparing the shading waveforms of different image signals selected by the image signal level selector 4 and the overflow signal output from the shedding compensator 7 is detected. Shading compensation circuit, characterized in that consisting of an overflow detection unit (2) for. In the shedding compensation method of a system using a close-type image sensor, the first step of generating an image level selection signal for outputting different levels of the image signal, and generates and overflows the image level selection signal in the first step A second process of searching for whether or not occurs; a third process of resetting the overflow detection unit 2 and returning back to the first process when an overflow occurs in the second process; and Shading compensation method characterized in that the fourth step of performing a normal shedding compensation when no overflow occurs.