KR101009344B1 - Method and apparatus for detecting foreign substance in image sensor - Google Patents

Abstract

Disclosed are a method and apparatus for detecting a foreign material of an image sensor. The foreign material detection method of the image sensor includes the steps of (a) setting the turn-on time to N steps; (b) scanning the white panel while driving a light source with a predetermined turn-on time set for each step; (c) comparing the brightness deviation of the image block output from the scanned result image sensor with a predetermined threshold in each step; (d) determining that foreign matter exists in the image sensor when it is determined that at least one of the brightness deviations of the N level is larger than a corresponding threshold; And (e) determining that no foreign matter exists in the image sensor when it is determined that none of the brightness deviations of the N stages is greater than a corresponding threshold.

Description

Method and apparatus for detecting foreign substance in image sensor

1 is a block diagram showing the configuration of a foreign material detection apparatus of an image sensor according to an embodiment of the present invention in a scanner system;

2 is a view showing a white panel used to detect a foreign material of the image sensor in the present invention,

3 is a flowchart illustrating a foreign material detection method of an image sensor according to an embodiment of the present invention in a scanner system, and

4 is a flowchart illustrating a detailed operation of step 330 of FIG. 3.

DESCRIPTION OF THE REFERENCE NUMERALS

100 ... shading section 110 ... scanning control section

120 ... drive 130 ... light source

140 ... first storage 140 ... second storage

150 ... image sensor 160 ... comparator

170 ... Foreign body judgment part

The present invention relates to a scanner system, and more particularly to a method and apparatus for detecting foreign matter present in an image sensor.

The scanner system includes a scanner or a multifunction peripheral (MFP) capable of performing a scanning function. A multifunction device is a device that can perform a combination of printing, data transmission and reception, copying and scanning functions. In such a scanner system, 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. For example, the black and white CIS uses only one type of green light emitting diode to read the black and white of the original, while the color CIS alternately illuminates the red, green and blue light emitting diodes to read the amount of light for each light emitting diode. By combining these three values, the original color is recognized.

As such, manufacturers of image sensors, which play an important role in the scanner system, typically produce image sensors and then characterize values such as, for example, pixel to pixel uniformity as specified in the specification of the component. It is possible to check whether or not it is satisfied through a simple procedure. However, even if the quality of the image sensor is confirmed, foreign matter may be attached to the image sensor during the process of being mounted on the scanner or the multifunction device set. If the image quality defect appears due to this, the set itself detects the foreign material present in the image sensor. There is a difficult problem.

An object of the present invention is to provide a method and apparatus for detecting foreign matter in an image sensor in a scanner system.

In order to achieve the above technical problem, a foreign material detection method of an image sensor in a scanner system includes: (a) setting a turn-on time to N steps; (b) scanning the white panel while driving a light source with a predetermined turn-on time set for each step; (c) comparing the brightness deviation of the image block output from the scanned result image sensor with a predetermined threshold in each step; (d) determining that foreign matter exists in the image sensor when it is determined that at least one of the brightness deviations of the N level is larger than a corresponding threshold; And (e) determining that no foreign matter exists in the image sensor when it is determined that none of the brightness deviations of the N stages is greater than a corresponding threshold.

In order to achieve the above technical problem, a foreign material detection apparatus of an image sensor in a scanner system includes: a shading unit configured to generate a reference turn-on time by performing shading; A scanning controller configured to set the turn-on time of the light source to N steps by using the reference turn-on time, and control to scan the white panel while driving the light source with a predetermined turn-on time set for each step; A comparison unit for comparing the brightness deviation of the image block output from the scanned result image sensor with a predetermined threshold in each step; And a foreign material determining unit determining whether or not foreign matter exists in the image sensor according to the comparison result in the comparing unit.

The method may preferably be implemented as a computer readable recording medium having recorded thereon a program for execution on a computer.

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

1 is a block diagram showing the configuration of a foreign material detection apparatus of an image sensor according to an embodiment of the present invention in the scanner system, the shading unit 100, the scanning control unit 110, the first storage unit 120, 2 consists of the storage unit 130, the light source 140, the image sensor 150, the comparison unit 160 and the foreign material determination unit 170.

Referring to FIG. 1, the shading unit 100 determines a reference turn-on time by performing white shading and black shading in a scanning system, and stores the determined reference turn-on time in the second storage unit 130.

The scanning controller 110 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, the reference turn-on time of the light source 140 is adjusted to N (where N is an integer of 1 or more), and the brightness deviation of the light reflected from the white panel with respect to the turn-on time of each step is adjusted. By comparing the respective thresholds, each component is generally controlled to detect foreign substances in the image sensor 150.                     

The first storage unit 120 stores a program having a certain flow and temporary data generated while the scanning control unit 110 controls the system so that the scanning control unit 110 can control the scanning system in a predetermined order. The second storage unit 130 stores the initial turn-on time and the reference turn-on time of the red, green, and blue light emitting diodes applied when scanning the white panel or the original before performing the shading process.

The light source 140 is turned on or off under the control of the scanning controller 110. Here, the light source 140 includes red, green, and blue light emitting diodes, and the red, green, and blue light emitting diodes are turned on / off by receiving respective control signals from the scanning controller 110.

The image sensor 150 photoelectrically converts reflected light reflected from a white panel or an original placed on a document glass into an electrical analog image signal, and is reflected from the white panel or the original while the light source 140 is turned on. A voltage signal having a numerical value proportional to the amount of incident external light is generated. Here, the image sensor 150 is preferably made of a contact image sensor (CIS).

The comparator 160 stores the thresholds of the N brightness deviations corresponding to the turn-on time of N steps, and the light source 140 is the k-th turn-on time of the turn-on time of the N steps, where k is 1 to N. After being turned on, the voltage signal in analog form proportional to the amount of light provided from the image sensor 150 is converted into digital image data having a predetermined number of bits. Calculate the brightness of each set of image blocks, for example P (where P is an integer of 2 or more), from the converted digital image data, calculate the brightness deviation of the P image blocks, and compare them with the k th threshold do.

The foreign material determination unit 170 determines that there is a foreign material in the image sensor 150 when the deviation of the brightness at the k-th turn-on time is greater than the k-th threshold value in the N stages. In the case where the deviation of the brightness at each turn-on time is smaller than each threshold for all of the N steps, it is determined that no foreign matter exists in the image sensor 150.

FIG. 2 is a view illustrating a white panel used to detect a foreign material of an image sensor in the present invention, which is generally used in white and black shading. In FIG. 2, reference numeral 210 denotes a white panel, 220 denotes a scanning direction, 230 denotes an image sensor module, and 240 denotes an apparatus including a document glass.

3 is a flowchart illustrating a foreign material detection method of an image sensor according to an exemplary embodiment of the present invention.

Prior to the description of the present invention, a general process of setting the reference turn-on time of the light source 140 and the turn-on time for detecting the foreign matter will be described.

Since the light source 140 is turned on / off by a control signal from the scanning controller 110, the turn-on time is adjusted as necessary under the control of the scanning controller 110. Of course, when the turn-on time of the light source 140 is long, the light amount of the light source 140, that is, the voltage level of the image sensor 150 is increased, and when the turn-on time of the light source 140 is short, the light amount of the light source 140, that is, the image The voltage level of the sensor 150 is lowered. Therefore, the scanning controller 110 drives the light source 140 and the image sensor 150 to appropriately preset the initial turn-on time of the red, green, and blue light emitting diodes before scanning the white panel for shading correction. It is stored in the storage unit 130. The scanning control unit 110 gradually increases the turn-on time of the red, green, and blue diodes of the light source 140 from the initial turn-on time, and, among the information of one line of digital image data converted through the image sensor 140, that is, Check if the specific number of pixels among the pixels in the line reaches the maximum brightness value. At this time, the number of specific pixels is at least one, which is usually referred to as a saturated pixel. When the specific number of pixels among the pixels in a line reaches the maximum brightness value, that is, when the shading is completed, the second storage unit 130 sets the respective turn-on time for the red, green, and blue light emitting diodes as the reference turn-on time. Store in Such a reference turn-on time is preferably obtained in advance through the above process and stored in the second storage unit 130.

On the other hand, in order to detect the foreign material of the image sensor 140, preferably from 90% to 40% of the reference turn-on time is reduced by a predetermined interval, for example, by 10% unit to generate N, here six turn-on time do. When the white panel is scanned by adjusting the turn-on time of the light source 140 step by step, the output of the image sensor 150 obtained in each step is obtained by scanning the gray panel including a plurality of gray levels once. It has the same meaning as the output of.

Referring to FIG. 3, in step 310, white tuning and black shading are performed in the scanning system to perform basic tuning of the image sensor 150, and then a reference turn-on time is determined.

In step 320, the turn-on time of step N used to detect the foreign material of the image sensor 150 is determined by using the reference turn-on time obtained in step 310, and the light source 140 is turned on as the turn-on time of each step to turn white. Scan the panel. At this time, it is not necessarily limited to the reference turn-on time determined during shading, and it is also possible to determine the turn-on time of N steps using the experimentally obtained turn-on time.

In operation 330, as a result of scanning in operation 320, the brightness deviation of the image block obtained from the image sensor 150 is calculated for each step of the turn-on time, and the calculated brightness deviation is compared with a corresponding threshold. Here, the brightness deviation is a range that brightness of an effective pixel included in one image block may have. To do this, obtain the average brightness of the pixels constituting the scanned image block in each step of the turn-on time, add the difference between the brightness and the average brightness of each pixel, and divide by the total number of pixels. The brightness deviation is obtained.

In operation 340, when at least one of the N brightness deviations is greater than a corresponding threshold, it is determined that foreign matter exists in the image sensor 150. In operation 350, when none of the N brightness deviations is greater than a corresponding threshold, it is determined that no foreign matter exists in the image sensor 150.

4 is a flowchart for describing a detailed operation of step 330 of FIG. 3.

Referring to FIG. 4, the variable k is initialized to 1 in step 410.

In operation 420, the light source 140 is driven at the k-th turn-on time, and then it is determined whether the brightness deviation of each image block obtained from the image sensor 150 is greater than the k-th threshold. As a result of the determination in step 420, when the brightness deviation with respect to the k-th turn-on time is greater than the k-th threshold, the process proceeds to step 340 of FIG. 3 to determine that there is a foreign material in the image sensor 150. That is, when the light source 140 is turned on at a predetermined turn-on time, the white panel is scanned, and the brightness deviation of the image block is compared with a corresponding threshold. This indicates that the change in the brightness in the E exceeds the allowable range, which means that the image sensor 150 has a foreign material.

As a result of the determination in step 420, if the brightness deviation with respect to the k-th turn-on time is not greater than the k-th threshold, it is determined whether k is equal to N in step 430. Here, N represents the number of steps of turn-on time obtained using the reference turn-on time, and an arbitrary number of steps is usually obtained within a range of 90% to 40% of the reference turn-on time. As a result of the determination in step 430, when k is equal to N, the process proceeds to step 350 of FIG. 3 to determine that no foreign matter exists in the image sensor 150. That is, after adjusting the turn-on time of the light source 140 to N steps, the brightness deviation of the image block is compared with the corresponding threshold by scanning the white panel every step, and thus the brightness deviation of any one step throughout the N steps. Since the threshold value has not been exceeded, this means that the image sensor 150 has no foreign material.

As a result of the determination in step 430, if k is not equal to N, in step 440, k is increased by 1 and the process returns to step 420, and the subsequent process is repeatedly performed.

The embodiment is turned on by applying a predetermined turn-on time to at least one of the red, green, and blue light-emitting diodes constituting the light source 140, and then comparing the corresponding threshold with the brightness deviation at each step of the turn-on time. In addition, it may be determined whether a foreign material exists in the image sensor 150.

In another embodiment, the red, green, and blue light emitting diodes constituting the light source 140 are sequentially turned on at each stage of the turn-on time, and the image is compared by the largest brightness deviation and the corresponding threshold value at each stage of the turn-on time. It may be determined whether foreign matter exists in the sensor 150. This is because, when the color of the foreign material present in the image sensor 150 is green, when the green light emitting diode is turned on for scanning, it has a greater brightness deviation than when the red or blue light emitting diode is turned on for scanning. to be. As described above, the foreign material of the image sensor 150 may be detected more accurately by using the largest brightness deviation among the scanning results of the three light emitting diodes.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, which are also implemented in the form of a carrier wave (for example, transmission over the Internet). It also includes. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. And functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

As described above, according to the present invention, by scanning the white panel by adjusting the turn-on time of the light source step by step, and comparing the brightness deviation of the image block from the image sensor as a result of the scanning by the corresponding threshold value, assembling the scanning system as a finished product Prior to the following, defects in the image sensor which may be caused when assembling the parts may be detected simply without using a separate foreign matter detection panel. Accordingly, it is possible to contribute to improving the performance of the finished product by improving the productivity by reducing the defect of the scanning system as a finished product.

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

Claims (5)

In the scanning system, (a) setting the turn on time to N steps; (b) scanning the white panel while driving a light source with a predetermined turn-on time set for each step; (c) comparing the brightness deviation of the image block output from the scanned result image sensor with a predetermined threshold in each step; (d) determining that foreign matter exists in the image sensor when it is determined that at least one of the brightness deviations of the N level is larger than a corresponding threshold; And and (e) determining that no foreign matter exists in the image sensor when none of the brightness deviations of the N stages is greater than a corresponding threshold value. The foreign material detection method of claim 1, wherein the turn-on time of the light source is set in N steps using a reference turn-on time determined by performing shading. The method of claim 1, wherein the step (b) is performed on at least one of red, green, and blue diodes constituting the light source. The method of claim 1, wherein step (b) is performed sequentially for all the red, green, and blue diodes constituting the light source, and step (c) compares the largest brightness deviation obtained by scanning with the threshold value. Foreign object detection method of the image sensor, characterized in that. In the scanning system, A shading unit configured to perform shading to generate a reference turn-on time; A scanning controller configured to set the turn-on time of the light source to N steps by using the reference turn-on time, and control to scan the white panel while driving the light source with a predetermined turn-on time set for each step; A comparison unit for comparing the brightness deviation of the image block output from the scanned result image sensor with a predetermined threshold in each step; And And a foreign material judging unit for determining whether or not foreign matter exists in the image sensor according to the comparison result in the comparing unit.

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