JPH08237478A - Image reader - Google Patents

Abstract

PURPOSE: To provide the image reader including a shading correction device conducting correction based on white reference data not including defective picture elements and a device detecting automatically deterioration in a light source. CONSTITUTION: The reader executes reading a white reference image from a prescribed read area of a white reference board 15 and storing the result as white reference data, and discriminates presence of defective picture elements in the stored white reference data repetitively, selects a prescribed read area of the white reference board 15 without defective picture element and uses a white reference image read as white reference data to conduct shading correction, detects deterioration in a light source 4a through the hold processing of white reference data, especially maximum level data, controls an amplification factor of a variable amplifier circuit 3 to ope with deterioration in the light source 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus having a shading correction device used in image scanners, facsimile machines, copying machines and the like.

[0002]

2. Description of the Related Art As a shading correction device used in a conventional image reading device, for example, Japanese Patent Laid-Open No. 3-2898
As shown in Japanese Patent Publication No. 72, several lines of white reference plate for reading white reference data are read, and white reference data for shading correction is obtained by performing averaging processing between lines regardless of the presence or absence of defective pixels. Alternatively, as shown in Japanese Patent Laid-Open No. 6-121162, several lines of a white reference plate for white reference data are read, defective pixels are determined, and this defective pixel data is not incorporated in the white reference data. Things are proposed.

[0003]

However, the one disclosed in Japanese Patent Laid-Open No. 289872/1993, in which white reference data is obtained by performing averaging processing between lines regardless of the presence or absence of defective pixels, If defective pixels are included in the data, the correction will be incomplete even if rounding processing by averaging is used, and the defective pixels will be judged and the data judged as defective pixels will be incorporated into the white reference data. In Japanese Unexamined Patent Publication No. 6-121162, when there is data including defective pixels that are not taken in, white reference data is taken in while verifying the line data up to data that does not include defective pixels. Occurs, this processing becomes an overhead and hinders high-speed reading.

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and provide an image reading apparatus including a shading correction apparatus that enables correction based on white reference data that does not include defective pixels.

[0005]

In order to solve the above problems, the present invention is an image reading apparatus for reading an image using a line sensor having a plurality of one-dimensionally arranged photoelectric conversion elements. By verifying the maximum level and minimum level of the stored white reference data, means for storing the white reference image in the predetermined reading area of the white reference member read by the sensor as white reference data,
And a shading correction unit that corrects the output of the line sensor that has read the image of the document based on the stored white reference data. To do.

Further, when it is judged by the means for judging the presence / absence of a defective pixel that there is a defective pixel in the white reference data, the other reading area of the white reference member is read by the line sensor, stored as white reference data, and the defect is detected. It is characterized by further comprising means for repeating the determination of the presence or absence of a pixel.

Further, when it is determined by the means for determining the presence or absence of the defective pixel that there is no defective pixel in the white reference data, the means for reading the white reference data from the reading area of the white reference member which has read the white reference data is subsequently used. It is further characterized by being provided.

Further, it is characterized by further comprising means for detecting deterioration of the light quantity of the light source by verifying the maximum level and the minimum level of the stored white reference data.

Further, when the means for detecting the light quantity deterioration of the light source determines that the light quantity of the light source has deteriorated, the amplifier gain of the amplification processing section for amplifying the output of the line sensor which has read the image of the document based on the judgment result. Is provided so that the same image data output can be obtained even when the light amount is deteriorated.

[0010]

In the image reading apparatus according to the present invention, the predetermined reading area of the white reference member is automatically searched for an area not including a defective pixel, the area position is stored, and the white reference image read from this area is used. Since the shading correction is performed as the white reference data, the accurate shading correction is performed and the high speed reading can be performed. In addition, since the amplifier gain of the amplification processing unit that amplifies the output of the line sensor that has read the image of the original is controlled by the means for detecting the light quantity deterioration of the light source, even when the light quantity deterioration of the light source occurs You can get the output.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image reading apparatus of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic side view showing the overall structure of the image reading apparatus of the present invention. The basic structure of the apparatus is that an automatic paper feeding device 2 and an original reading table 3 are provided on the upper right side of the main body device 1. Composed. Reference numeral 4 is a first traveling body provided with a light source 4a and a mirror 4b, 5 is a second traveling body provided with mirrors 5a and 5b, 6 is a lens, 7 is a one-dimensional photoelectric conversion element using a CCD (hereinafter CCD), 8 is a stepping motor, and an exposure scanning optical system 9 is constituted by these components.
Is configured. The ADF (Automatic
A document feeder unit 10 and a document table 11 are provided, the ADF unit 10 is provided with a stepping motor 12, and a document pressing plate 14 is rotatably provided on the document reading table 3 (upper and lower in the drawing). (Orientation) and the original 13 is set under the original pressing plate 14. A white reference plate 15 for shading correction is arranged at the end of the document reading table 3. The processing of the image data read by the exposure scanning optical system 9 of the image reading apparatus configured as described above is performed by the control circuit shown in FIG. 2, and the original reading mode is as shown in FIG. There are a book mode in which a document is directly placed on the reading table 3 and an image is read, and an ADF mode in which an image is read by feeding a document onto the document reading table 3 using the automatic paper feeder 2 as shown in FIG. Done.

First, the operation of the book mode as shown in FIG. 3 will be described. After the document 13 is set on the document reading table 3 under the document pressing plate 14, when the operation is started, as shown in FIG.
The CPU 16 shown in FIG.
Turn on a (in this case, use a fluorescent lamp) and turn on the CCD driver 18
The white reference plate 15 is read by the CCD 7 driven by, and its output is analog / digital converted by an A / D converter (not shown) in the image processing unit 19 to obtain white reference data for shading correction of the image data. It is stored in the RAM (not shown) in the image processing unit 19. Furthermore, CP
U16 drives the motor driver 20 to operate the stepping motor 8, whereby the traveling body 4 moves to the lower surface position of the document 13. When the traveling body 4 scans the document surface at a constant speed, the image data of the document 13 is transferred to the CCD 7.
Is photoelectrically converted by. FIG. 5 shows the most basic internal configuration of the image processing section 19. The analog video signal a photoelectrically converted by the CCD 7 is digitally converted by the analog video processing section 21 and then subjected to shading correction. The processing unit 22 and the image data processing unit 23 respectively perform shading correction and various kinds of image data processing, and the binarization processing unit 24 performs a desired binarization process.
The binarized data b is created and sequentially stored in the scan buffer 25 of FIG. I / F controller 26
Controls to output the data in the scan buffer 25 to an external device such as a host computer (not shown). The buffer controller 27 manages input / output of image data to / from the scan buffer 25.

The basic operation of image reading in the book mode is as described above. Next, the basic operation of image reading in the ADF mode in which image data is read using the automatic paper feeder 2 will be described.

In this case, first, after the white reference plate 15 is read, the CPU 16 drives the motor driver 28 to operate the stepping motor 12, and the original 13 set on the original table 11 is conveyed by the separation roller 29 and conveyed. It is conveyed by the roller 30 and conveyed to a predetermined reading position of the traveling body 4. At this time, the manuscript
13 is conveyed at a constant speed, and the traveling body 4 reads the image data of the document surface with the CCD 7 while the traveling body 4 is stopped. Thereafter, the same processing as in the book mode is performed, and the binarized image data is sequentially stored in the scan buffer 25 of FIG.
It is sent to a device such as an external host computer (not shown) via the I / F controller 26.

The outline of the configuration and the operation of the image reading apparatus of the present invention is as described above, and the shading correction means, which is the essence thereof, will be described below with reference to this.

The block diagram shown in FIG. 6 is a subdivided, schematic, and excerpted portion of the image reading apparatus shown in FIGS. 1 to 5, which is related to shading correction means. The same parts as those shown in FIG. 5 are designated by the same reference numerals. In FIG. 6, the original 13 is illuminated by the light source 4a, and the reflected light is reflected by the shading adjusting plate 32.
The basic structure is such that light is collected by the lens 7 via the lens and imaged on the CCD 7 which is a line sensor. Here, the shading adjusting plate 32 is a line sensor CC.
It plays a role of adjusting the amount of light for eliminating the difference in the amount of reflected light between the central portion and the end portion of D7, and if there is too much difference in the amount of reflected light between the central portion and the end portion of the CCD 7 in shading calculation processing, it is possible. Since only the calculation result including distortion is obtained, the shading calculation process is performed after the difference in the reflected light amount is eliminated in advance. The function of the shading adjusting plate 32 will be described with reference to FIGS. 7 (a) and 7 (b). FIG. 7A shows a reproduction level distribution when the video data of the white reference plate 15 is read without the shading adjustment plate 32. The level is high at the center and drops at the edges. FIG. 7B shows the same reproduction level distribution when the shading adjustment plate 32 is provided, and it can be seen that the levels are averaged. Next, after photoelectric conversion by the CCD 7, the level is adjusted as analog video data by the level adjuster 33, amplified by the variable amplifier circuit 34, and then converted to A /
Digital conversion is performed by the D converter 35. The black arithmetic circuit 36 removes the portion of the digitized video data that is the offset on the black side, and the shading correction arithmetic circuit
Send to 37. When the output of the CCD 7 which is the line sensor has two channels, the offset portion on the black side includes a difference between the channels, and the purpose of the arithmetic operation by the black arithmetic circuit 36 is to remove the difference. is there.
For the shading correction calculation, the white reference data read from the white reference plate 15 is stored in the line buffer 31, and when the actual document is read, the shading calculation process is performed between the white reference data and the document read data. It is performed and is output to the next stage as image data. As a method of storing the white reference data obtained by reading the white reference plate 15 in the line buffer 31 in the present embodiment, reading of a plurality of lines,
There are a method of storing while performing the averaging process and a method of storing for one line, but either method is acceptable.

The first reading area of the white reference plate 15 (reading area 1
FIG. 8 shows an example of the white reference data read from the following, and if there are defective pixels as indicated by A and B,
This is detected as follows. FIG. 9 schematically shows the means, which is obtained by extracting the detection operation from the operations included in the components of the shading correction calculation circuit 37 and the line buffer 31 shown in FIG.
The white reference data read from the reading area 1 of the white reference plate 15 is stored in the line buffer after the white reference data averaging process or without this process, and the stored white reference data is fetched. Then, the maximum value and the minimum value in the white reference data are held, that is, the data is sampled, and the maximum value and the minimum value are determined by performing an arithmetic operation on the data, and the level is set to the level assumed in advance. If it is not, it is determined that the white reference data including the defective pixel is stored in the line buffer. If the assumed level is not clear, the white reference data stored in the line buffer is averaged, or the standard deviation is calculated, and the variation is measured to determine the white reference data to be stored. A level range is determined, and the maximum value and the minimum value are held, that is, data is sampled, and if out of the range, it is determined that white reference data including defective pixels is stored in the line buffer.

It is determined whether or not there is a defective pixel in the white reference data stored in this way, and if it is determined that the white reference data read from the reading area 1 of the white reference plate 15 has a defective pixel, the white reference data is white. The white reference data is read from the next reading area (referred to as reading area 2) of the reference plate 15, and the presence or absence of the defective pixel is determined in the same manner as described above. If it is determined that the defective pixel is present, the white reference plate 15 is continued. The control system that reads the white reference data from the next read area (referred to as the read area 3) and determines whether there is a defective pixel operates. By repeating the control by, the white reference data having no defective pixel is finally obtained. Since the operation of reading the white reference data without defective pixels is required every time the shading correction is performed, once the best reading area is determined, it is stored in some memory, for example, a memory with a battery backup, or a flash type. If a control system different from the above-mentioned control system for controlling the system to read the white reference data from the best reading area is stored from the next reading operation, it will be stored once The white reference data having no defective pixel can be read by the reading operation of.

Further, the deterioration of the light source can be detected by the holding process of the maximum value and the minimum value in the white reference data, particularly the holding process of the maximum value. To do this, the level range of the white reference data is set in advance, and when the level falls below the set level range, it is determined that the level of the white reference data stored in the line buffer has dropped due to deterioration of the light source. It is possible to take measures such as repairing the light source and increasing the amplification factor of the variable amplification circuit 34 shown in FIG. 6. Particularly, if a feedback loop for controlling the amplification factor of the latter variable amplification circuit 34 is formed, It can respond automatically to deterioration.

[0021]

As described above, according to the first aspect of the invention, the image reading apparatus of the present invention can immediately determine the presence or absence of the defective pixel in the stored white reference data.

According to the second aspect of the invention, it is possible to store white reference data that does not include a defective pixel.

According to the third aspect of the invention, it is possible to eliminate the overhead that occurs each time the white reference data is stored.

According to the invention described in claim 4, it is possible to detect the deterioration of the light source.

According to the invention described in claim 5, by providing the feedback circuit for increasing the amplification factor of the amplification system of the white reference data when the deterioration of the light source is detected, it is not affected by the deterioration of the light quantity.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an embodiment of an image reading apparatus of the present invention.

FIG. 2 is a block diagram showing main components of an embodiment of the image reading apparatus of the present invention.

FIG. 3 is a schematic side view showing an essential part of image reading in the book mode, showing an embodiment of the image reading device of the present invention.

FIG. 4 is a schematic side view showing an embodiment of the image reading apparatus of the present invention and showing a main part of image reading in the ADF mode.

FIG. 5 is a block diagram showing details of an image processing unit in main components of an embodiment of the image reading apparatus of the present invention.

FIG. 6 is a block diagram for explaining a shading correction operation in the image reading apparatus of the present invention.

FIG. 7 is a waveform diagram showing a signal level state for explaining the function of the shading adjustment plate during the shading correction operation of the image reading apparatus of the present invention.

FIG. 8 is a waveform diagram showing an example of white reference data during a shading correction operation of the image reading apparatus of the present invention.

FIG. 9 is a schematic diagram for explaining a means for detecting the presence or absence of a defective pixel of white reference data during a shading correction operation of the image reading apparatus of the present invention.

[Explanation of Codes] 1 ... Main unit, 2 ... Automatic paper feeder, 3 ... Original reading stand, 4 ... First traveling body, 5 ... Second traveling body, 6 ...
Lens, 7 ... CCD (line sensor), 8 ... Stepping motor, 9 ... Exposure scanning optical system, 10 ... ADF unit, 11 ... Original plate, 11a ... Locking part, 12 ... Stepping motor, 13 ... Original, 14 ... Original Presser plate, 15 ...
White reference plate, 16 ... CPU, 17 ... Light source driver, 18
... CCD drive section, 19 ... Image processing section, 20 ... Motor driver, 21 ... Analog video processing section, 22 ... Shading correction processing section, 23 ... Image data processing section, 24 ... Binarization processing section, 25 ... Scan buffer, 26 ... I / F controller, 27 ... Buffer controller, 28 ... Motor driver, 29 ... Separation roller, 30 ... Conveying roller, 31 ... Line buffer, 32 ... Shading adjustment plate, 33 ... Level adjuster, 34 ... Variable amplification circuit, 35 ... A / D converter, 36 ... Black arithmetic circuit, 37 ... Shading correction arithmetic circuit.

Claims (5)

[Claims] 1. An image reading apparatus for reading an image using a line sensor having a plurality of one-dimensionally arranged photoelectric conversion elements, the white reference image in a predetermined reading region of a white reference member read by the line sensor. Is stored as white reference data, determination means for determining the presence or absence of defective pixels in the stored white reference data by verifying the maximum level and the minimum level of the stored white reference data, An image reading apparatus comprising: a shading correction unit that corrects an output of a line sensor that reads an image based on the stored white reference data. 2. When the determination means for determining the presence or absence of a defective pixel determines that there is a defective pixel in the white reference data, a line sensor reads another reading area different from the reading area of the white reference member, and The image reading apparatus according to claim 1, further comprising a control system that repeats storage as reference data and determination of presence / absence of defective pixel until it is determined that there is no defective pixel in the white reference data. 3. A control system for reading the white reference data from a reading area of a white reference member which has read the white reference data when it is determined by the means for determining the presence or absence of the defective pixel that there is no defective pixel in the white reference data. The image reading apparatus according to claim 1, further comprising: 4. The image reading apparatus according to claim 1, further comprising detection means for detecting deterioration of the light amount of the light source by verifying the maximum level and the minimum level of the stored white reference data. 5. An amplifier of an amplification processing unit for amplifying the output of a line sensor that has read an image of a document based on the detection result when the detection unit for detecting the light amount deterioration of the light source detects the light amount deterioration of the light source. 5. The image reading apparatus according to claim 4, further comprising means for increasing the gain so as to obtain the same image data output as in a steady state even when the light amount is deteriorated.