JPH06121163A - Image reader - Google Patents

Abstract

(57) [Summary] [Structure] Range in which the final movement amount of the line sensor in the array direction is equal to or greater than the length of the line sensor on the white reference plate that is at least twice the length of the line sensor. To obtain a correction value for shading correction at each place (S1 to S8), and average these values (S
9) is the shading correction value. [Effect] The unevenness and distortion of the white reference plate itself, which cannot be completely corrected by the conventional shading correction method, can be suppressed, and a more accurate image can be read.

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 line sensor.

More specifically, the present invention is an image reading apparatus which scans an original by dividing the original into several lines in a direction perpendicular to the array of the sensors by a line sensor having a predetermined length shorter than the length of the original. It is about.

Particularly, the present invention relates to a large plate size image reading apparatus having a wide maximum reading range.

[0004]

2. Description of the Related Art As is conventionally known, when a document is read by a line sensor, the output varies depending on each of the sensors arranged in a line. Further, the output level varies depending on the position of the sensor depending on the irradiation method of the exposure lamp. Therefore, in order to eliminate this variation and obtain a uniform output, a shading correction value is calculated and corrected.

In this correction, a line sensor is placed under a white reference plate, light is applied to the white reference plate, light reflected from the white reference plate is introduced into the line sensor, and the output from the sensor is detected. Then, the detected value is analyzed, a reference value is set, a correction value is determined so that the output of the sensor with a low output is high, and the output from each sensor is made uniform.

At this time, if the position of the line sensor is corrected to one position, if there is dust, scratches, stains, etc. on the white reference plate, the influence of the dust will remain as it is.
Therefore, in order to reduce such effects, the line
A method is also known in which the sensors are moved in a direction perpendicular to the array of sensors to obtain a shading correction value, and the results are averaged for correction.

Prior art 2 Further , in an image scanner whose reading range is at most A3 size, a line sensor is used in the reading section, and a line sensor is used in the short side direction or the long side direction of the maximum reading range.
A method of reading a desired reading range by arranging the sensors and moving the reading unit in a direction (sub-scanning direction) perpendicular to the direction of the pixels of the line sensor (main scanning direction) is known. It is taken. The reading unit of such an image scanner generally has a configuration of a reduction optical system using a mirror or a lens or a configuration of an equal-magnification optical system using a contact sensor.

Generally, these scanners perform necessary image processing on the read image and sequentially send the image data line by line in real time to an external device such as a host computer or a printer.

That is, since the image data needs to be sent out, for example, from right to left, from top to bottom, as specified in the interface specifications of the image scanner and the external device, the reading operation of the image scanner is performed. Inevitably, however, only the operations limited to the interface specifications can be performed.

[0010]

Problem 1 As described above, when the shading correction method is carried out by fixing the white reference plate at one position, the influence of scratches, stains and the like will remain. Therefore, if the sensors are moved in a direction perpendicular to the line sensor array, the effect is reduced.

However, all of these methods are performed on the assumption that the white reference plate itself has no unevenness and a uniform density. Further, in practice, the white reference plate also has manufacturing irregularities as shown in FIG. Furthermore, there is a possibility that unevenness may occur due to distortion or the like depending on how the white reference plate is fixed.

Therefore, when the output is small due to the influence of the white reference plate, the shading correction will result in a larger output than the actual value.

As described above, in the conventional shading correction, the unevenness of the line sensor and the unevenness due to the irradiation are corrected, but the unevenness of the white reference plate itself remains as it is.
It has not been possible to completely eliminate the unevenness of the sensor. Therefore, if the image is output with the shading correction being performed as it is, the unevenness of the white reference plate appears in the output image, and it cannot be said that the image is accurately read.

Therefore, in view of the above points, an object of the present invention is to provide an image reading apparatus in which the influence of unevenness of the white reference plate itself is suppressed.

Problem 2 Further , as the image scanner technology has advanced in recent years,
The development of image scanners for reading documents of A3 size or larger has come to be required. However, considering that such a large-sized scanner has the above-mentioned reduction optical system, it is necessary to make the optical path length extremely long in order to form an image of the original on the line sensor.
This is not practical because the structure of the reading unit becomes large.

Further, considering the use of the same-magnification optical system, a contact sensor capable of reading at least the short side length of the maximum reading range is required, but it is difficult to develop such a contact sensor with the current technology. Is. Even if it could be developed, it would be considerably costly, and the performance of the sensor itself would likely be unstable, so it would not be practical.

Further, since the conventional image scanner can operate only in the interface specification with the external equipment, the right-to-left reading is completed when the image data must be sent from right to left, for example. After that, it is necessary to return the reading unit from left to right, and that time becomes a complete dead time, leading to a meaningless extension of the reading time. Moreover, there is a problem in that it cannot be connected to external devices having different interface specifications.

Therefore, in view of the above points, an object of the present invention is to provide an image reading apparatus which is compatible with the reading of a large-sized document and does not have to comply with the interface specification with an external device.

[0019]

Means one invention SUMMARY OF] uses a short line sensor of a predetermined length than the short side of the document, scanning the document is divided into several times in SEQ perpendicular direction of the sensor In the image reading device that performs
A plurality of line sensors are arranged on a white reference plate having a length at least twice the length of the line sensors in a range in which the final movement amount is equal to or more than the length of the line sensors. It is provided with a movement control means for moving the line sensor and a shading correction means for obtaining a correction value for shading correction at each position where the line sensor has moved and performing shading correction based on an average value of these values. .

Means 2 According to the present invention, a reading means having a line sensor shorter than the short side direction of the maximum read area or an area sensor for reading a range narrower than the maximum read area, the short side direction and the short side direction. Long side direction, which is the direction perpendicular to
Direction, or a movement control means for repeating movement of the reading section in the combined direction of the two directions, and reads a desired reading range.

Here, it is preferable to further include a memory for storing the image data of the read image.

[0022]

Operation 1 In the above configuration of the present invention, the final movement amount of the line sensors in the arrangement direction is equal to or more than the length of the line sensor on the white reference plate that is at least twice the length of the line sensor. By moving multiple times within the range to obtain the correction value for shading correction at each place and averaging these values as the shading correction value, the effect of unevenness of the white reference plate itself can be suppressed. Is.

Function 2 According to the present invention, a normal image sensor is used for a large-sized image scanner, and the reading unit is moved in a direction (second direction) perpendicular to the pixel array direction (first direction) of the image sensor. To read a band-shaped image, and then move the reading unit in the first direction and then in the second direction,
This is to read all desired reading ranges by sequentially reading strip-shaped images and joining the read images.

Further, by further comprising a memory for storing the image data of the read image, the operation of the reading unit does not have to comply with the interface specifications with the external device, and the reading operation can be performed so that the reading time is the shortest. After writing the image data to the memory, the memory is controlled so as to be read according to the interface specifications.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment for solving the problem 1 will be described in detail below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is an external view of a digital color copying machine in this embodiment.

The digital color copying machine 10 is roughly composed of two elements. That is, the first
A color image scanner unit (hereinafter, abbreviated as “reader unit”) 12 that reads an original image located above in color and outputs digital color image data is provided as a main element. The reader unit 12 includes a controller unit 14 that performs various kinds of image processing of digital color image data and has a processing function such as an interface with an external device.

The second major element is the reader unit 1.
2, located below the controller unit 1 of the reader unit 12.
The printer unit 20 is provided for recording the color digital image signal output from the recording medium 4 on recording paper.

The reader unit 12 is placed on a document table (not shown) below the document holding plate 16 and faces downward, and images from documents of various shapes and sizes such as three-dimensional or sheet-like or large-sized sheet-like documents. It also has a built-in mechanism for reading information.

An operating portion 18 connected to the controller portion 14 is provided on one side of the upper surface of the reader portion 12. The operation unit 18 is for inputting various information and operation instructions for the copying machine.

Further, the controller unit 14 is the operation unit 1
It is configured to give an operation instruction to the reader unit 12 and the printer unit 20 in accordance with the information input via 8. Then, when it is necessary to perform a complicated editing process or the like, a digitizer or the like can be attached instead of the document pressing plate 16 and can be connected to the controller unit 14.
This enables more advanced image processing.

On the other hand, in the printer section 20 of this embodiment, a full-color ink jet printer using an ink bubble jet recording type recording head as described in JP-A-54-59936 is used. Is used.

The above-mentioned two major elements are separable from each other, and are set so that they can be installed at positions separated from each other by extending the connection cable.

The above-mentioned major elements will be described in detail below.

FIG. 2 is a sectional view schematically showing the internal structure of the digital color copying machine 10 shown in FIG. 1 when viewed from the side.

(Reader Unit 12) First, the structure of the reader unit 12 of the copying machine 10 will be described.

In the reader section 12, the exposure lamp 2
2, the lens 24, and a line sensor 26 (a CCD sensor is used in the present embodiment) capable of reading a line image in full color, an image of an original placed on the original glass 28, a projected image by a projector, or The image of the sheet-shaped document is read by the sheet feeding mechanism 30. At this time, the exposure lamp 22, the lens 24, and the line sensor 26 move together in the main scanning direction and the sub scanning direction to read an image.

Next, various image processing is performed on the image information read by the reader unit 12 in this way by the reader unit 12 and the controller unit 14, and then the read and image-processed information is processed by the printer unit. Sent to 20,
Here, it is recorded on the recording paper.

FIG. 3 shows a line for shading correction.
It is the figure which showed the sensor peripheral part in detail. Exposure lamp 2
2, the white reference plate 100 is uniformly illuminated, and shading correction is performed from the output of the line sensor 26 that receives the reflected light.

At this time, if the white reference plate 100 having substantially the same size as the line sensor 26 is used, the unevenness of the white reference plate remains as it is after the shading correction due to the above-mentioned reason.

Therefore, when performing the shading correction by using the method according to the present embodiment, when the shading correction of the present invention is performed by using the white reference plate having the minimum length, the image sensor 26 as shown in FIG. By moving the sensor on the white reference plate 101 having a length twice the
The influence of unevenness at each position of the white reference plate is canceled out.

FIG. 7 shows a block diagram of an embodiment of the present invention. Here, 7-1 is a CCD image sensor that converts the input light into an analog electric signal. 7-2 is
It is an A / D converter that converts an analog signal from the CCD 7-1 into a digital signal. Reference numeral 7-3 is an arithmetic circuit that performs shading correction when outputting an image. The data becomes through when the shading correction value is created. Reference numeral 7-4 is a RAM 1 for temporarily storing the data after A / D conversion when creating a shading correction value. Reference numeral 7-5 is an arithmetic circuit that calculates a shading value from the data from the RAM 1 and averages the shading values stored in the RAM 2. Reference numeral 7-6 is a RAM 2 for storing a specific number of shading correction values from the arithmetic circuit. Reference numeral 7-7 is a RAM 3 that stores the shading correction values averaged by the arithmetic circuit and outputs a predetermined value by a signal from a timing circuit (not shown) at the time of image output.

FIG. 8 shows a flowchart of shading correction of this embodiment. This process is divided into a procedure of creating a shading correction value and a procedure of outputting an image. When creating the shading correction value, the reflected light input from the white reference plate is converted into an analog electric signal by the CCD. The analog signal from the CCD is converted into a digital signal by the A / D converter.

A shading value is calculated from the data and stored in the RAM. Move the set distance and position,
Repeat this work. After repeating the set number of times, the average value of the stored shading correction values is calculated, the actual correction value is determined, and the value is stored in the correction value table. At the time of image output, a document image is read, shading correction is performed on the A / D converted data using the correction values stored in the correction value table, and the data is output as image data.

By the procedure described above, shading correction is performed by removing the unevenness of the white reference plate itself, and an accurate image is read.

Embodiment 2 If there is a sufficient space, a white reference plate 102 having a length three times as long as the image sensor 26 is prepared as shown in FIG. Move twice and average the output results. Then, the influence of unevenness at each position of the white plate is canceled.

In this example, three times were performed, but any number of times may be used as long as the length is at least twice as long as the space.

Embodiment 3 Considering the conventional method together with the present invention, as shown in FIG. 6, the white reference plate 103 is long not only in the horizontal direction but also in the vertical direction.
Using, the shading correction value can be calculated by moving the image sensor 26 not only in the sub scanning direction but also in the main scanning direction at the same time. By doing so, it is possible to correct unevenness not only in the sub-scanning direction of the white reference plate but also in the main scanning direction, and more accurate image reading becomes possible.

An embodiment corresponding to the problem 2 will be described below.

Embodiment 4 FIG. 9 is a diagram showing the appearance of the reading unit 111 of the image scanner to which the present invention is applied. The reading unit 111
It is attached to a part of the main scanning belt 112, and the main scanning motor 113 is rotated to move in the direction of arrow X in the drawing according to the main scanning guide 114 to read in the main scanning direction.

The structure of the reading unit 111 is shown in FIG.
Here, 122 is a light source for illuminating the original 126, 123 is a cylindrical lens (distributed index lens) array for forming an image of the original 126 illuminated by the light source 122 on the line sensor 124 at an equal size, and 125 is colorless. It is a transparent original glass table.

To simplify the description, it is assumed that the line sensor 124 has 10 photosensors per 1 mm, for a total of 100 photosensors. That is, it is possible to read an image with a width of 10 mm as it moves in the X direction.

Returning to FIG. 9 again, the description will be continued. The sub-scanning carriage 115 is attached to a part of the sub-scanning belt 116, and is moved in the direction of arrow Y in the drawing according to the sub-scanning guide 117 by the rotation of a sub-scanning motor (not shown) to perform sub-scanning movement. There is. The sub-scanning movement amount is set to a reading length for one line of the line sensor 124 = 10 mm. With such a configuration, images with a width of 10 mm are sequentially read and a desired reading range is read.

Next, how the reading section 111 moves during reading will be described with reference to FIG. The position A in the figure is the home position of the reading unit 111, and the reading is started from this position. First, the movement is performed in the direction of the arrow, and the first image reading with a width of 10 mm is performed.

When the first image reading is completed, the reading unit 111 moves to the position B by moving 10 mm in the direction of the arrow and then moves in the direction of the arrow to read the second 10 mm wide image. .

When the second image reading is completed, the reading unit 111 moves in the direction of the arrow and moves to the position C.
After moving to, move in the direction of the arrow and
An image reading with a width of mm is performed. By repeating such a series of operations, a desired reading range is read.

Next, the flow of image data will be described with reference to FIG.

The image data of the original image read by the line sensor 124 is signal-amplified by the analog amplifier 402 and then input to the A / D converter 403 to convert the analog image data into digital image data. A / D
The output of the converter 403 is input to the image processing circuit 404, subjected to image processing such as shading correction and edge enhancement, and then input to the binarization circuit 405 to binarize the image data. The image data output of the binarization circuit 405 is input to the memory 406 and the image data is stored.

At this time, the selector 407 selects the output of the write address generation circuit 408, and the output of the write address generation circuit 408 is input to the address bus of the memory 406.

When the desired image reading is completed and the image data is sent to the external device, the selector 407 selects the output of the read address generating circuit 409, and the output of the read address generating circuit 409 is sent to the address bus of the memory 406. input.

The read address generation circuit 409 accesses the address where the image data is stored so as to conform to the image data transmission format according to the interface specification of the external device connected to the image scanner, and the interface circuit 410 is operated to display the image. Send data.

The interface circuit 410 sends the image data to an external device together with the image data synchronizing signal and the image data enable signal.

Memory 406 in which image data is stored
FIG. 13 shows the address map of the above. In FIG. 13, an address map storing image data when a region of 30 mm × 100 mm is read is shown in order to simplify the description. In the write address generation circuit 408, an increment output of 1, 2, 3 is sequentially performed from the address 1 for each pixel data output of the line sensor 24.

Therefore, the image data at the position A shown in FIG. 11 is stored in the addresses 1-100. In addition, the first 1
The image data of the last line in the 0 mm width image reading is stored at addresses 99901 to 100000.

Subsequently, in FIG. 11, the image data at the position B is stored in the addresses 100001 to 100100 and the second data is stored.
The image data of the final line at the time of the 10th-width image reading is at addresses 199901 to 200,000.
Stored in.

Similarly, in FIG. 11, the image data at the position C is stored at addresses 200001 to 200100, and the image data of the last line in the third 10 mm width image reading is stored at 299901 to 300,000, which is 30 mm × 100 mm. The image reading is completed, and the address map shown in FIG. 13 is completed.

When the read image data is output to the external device after the reading is completed, the read address generation circuit 409 is set so that the image data is sent according to the interface of the external device. For example, when the connected external device is a printer such as an LBP (laser beam printer), the first line has addresses 1, 10
Settings are made so that 1000 pieces of image data are output to the outside via the interface circuit 410 in the order of 1,201 ... 99801, 99901.

In this way, by reading the memory sequentially from right to left and from top to bottom from the addresses shown in FIG. 13, image formation by the printer is performed. When the image data output order of the connected printer is different from the above, the read address generation circuit 409
It can be handled by changing the setting of.

Embodiment 5 In the above embodiment, an example of an image scanner using a line sensor has been described, but the present invention can also be implemented by using an area sensor that reads a range narrower than the maximum reading area. is there.

That is, as shown in FIG. 14, the reading areas are sequentially connected to perform reading, and the write address generator 408 or the read address generator 409 in FIG. 12 is read.
By changing the setting of, the image can be output with the same interface as the image scanner using the line sensor.

Since the area sensor can read several hundred lines of the line sensor by one reading operation, the reading time can be further shortened.

Embodiment 6 In the above embodiment, the reading section carries out the reading operation as shown in FIG. 15, but in this embodiment the image data is once stored in the memory and then sent out. It is not limited to the operation shown in 15.

For example, by performing the reading operation as shown in FIG. 16, it is possible to return the reading unit to the home position in an extremely short time as compared with the conventional case.
When an F (automatic document feeder) or the like is used, the reading speed per original can be improved.

Embodiment 7 Considering a cordless image scanner in the conventional image scanner, the transmission time of the image data in the transmitting section is extremely longer than the reading speed of the image scanner.

That is, since the scanner waiting time due to the transmission processing after reading one line is long and the image reading time per page is enormous, the cordless image scanner is not practical.

On the other hand, in the present embodiment, since the memory for storing the image data is provided, it is possible to read the entire original image once, dispense the image data from the memory and transmit the image data to the external device. Therefore, it is possible to realize a cordless image scanner.

[0077]

Effect 1 According to the present invention, it is possible to suppress the unevenness and distortion of the white reference plate itself, which cannot be completely corrected by the conventional shading correction method, and it is possible to read a more accurate image. become.

Effect 2 According to the present invention, a line sensor for reading a line shorter than the maximum reading area of the image scanner or an area sensor for reading a narrower area than the maximum reading area is used, and the original image is read in small areas. By reading, it is possible to realize an image scanner compatible with reading large-sized originals.

Further, by storing the read image data in the memory once and transmitting the image data according to the interface specification of the external device, it is possible to minimize the dead time during which the image cannot be read during the operation of the scanner. , The reading time of the scanner can be shortened, and a cordless image scanner can be realized.

[Brief description of drawings]

FIG. 1 is an external view of a digital color copying machine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing the internal structure of the digital color copying machine 10 shown in FIG. 1 when viewed from the side.

FIG. 3 is a detailed view of a peripheral portion of the line sensor.

FIG. 4 is a diagram showing Example 1.

FIG. 5 is a diagram showing a second embodiment.

FIG. 6 is a diagram showing a third embodiment.

FIG. 7 is a block diagram of an embodiment of the present invention.

FIG. 8 is a flowchart showing a control procedure of this embodiment.

FIG. 9 is a diagram showing an appearance of a reading unit of an image scanner embodying the present invention.

FIG. 10 is a diagram illustrating a configuration of a reading unit.

FIG. 11 is a diagram illustrating an operation of a reading unit when reading an image.

FIG. 12 is a block diagram showing an image scanner embodying the present invention.

FIG. 13 is a diagram showing a memory map of image data of a read document.

FIG. 14 is a diagram showing a reading operation in the embodiment when an area sensor is used.

FIG. 15 is a diagram showing a reading operation according to an embodiment of the present invention.

FIG. 16 is a diagram showing an example of a reading operation that realizes high-speed reading when an ADF is used.

[Explanation of symbols]

 10 Digital Color Copier 12 Reader Section (Color Image Scanner Section) 14 Controller Section 16 Document Holding Plate 18 Operation Section 20 Printer Section 111 Image Scanner Reading Section 112 Main Scan Belt 113 Main Scan Motor 114 Main Scan Guide 115 Sub Scan Carriage 116 Sub-scanning belt 117 Sub-scanning guide 122 Light source 123 Cylindrical lens array 124 Line sensor 125 Original glass plate 126 Original document 402 Analog amplifier 403 A / D converter 404 Image processing circuit 405 Binarization circuit 406 Memory 407 Selector 408 Write address Generator 409 Read address generator 410 Interface circuit

Claims (3)

[Claims] 1. A line of a predetermined length shorter than the short side of the original.
An image reading apparatus that uses a sensor to scan an original by dividing the original into a plurality of times in a direction perpendicular to the arrangement of the sensors, wherein a white reference plate having a length at least twice the length of the line sensor is used. And movement control means for moving the line sensor a plurality of times in the arrangement direction within a range in which the final movement amount is equal to or longer than the length of the line sensor, and shading at each position where the line sensor moves. An image reading apparatus comprising: a shading correction unit that obtains a correction value for correction and performs shading correction based on an average value of these correction values. 2. A reading means having a line sensor shorter than a short side direction of a maximum reading area or an area sensor for reading a range narrower than the maximum reading area, and a direction perpendicular to the short side direction and the short side direction. The image reading apparatus is characterized by including a movement control unit that repeats the movement of the reading unit with respect to the direction of the long side or the combined direction of the two directions, and reads a desired reading range. 3. The image reading device according to claim 2, further comprising a memory that stores image data of the read image.