JP2003046729A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader which is easy of read work, is simple of structure and is high in resolution. SOLUTION: The light from a manuscript is condensed by the condensing lens of the first optical system or the condensing lens of the second optical system. The condensing lens of the second optical system condenses light from the half region of a region in the direction of main scanning where the condensing lens of the first optical system condenses light, and lets a line sensor form an image. Therefore, the read region SB at the center in the direction of main scanning is read, and the resolution becomes twice that at reading all of the region in the direction of main scanning. The manuscript placed on a manuscript stage 20 is read half at a time, being divided in two times, by shifting the manuscript stage 20 in the direction of main scanning, and the full page of the manuscript is read with one time of manuscript setting. This image reader is simpler in structure than the case of shifting a carriage in two-axis direction. The aberration by lens is reduced and the image quality of the read image rises, by reading the center side in the direction of main scanning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus for reading a document placed on a document table has been known. The image reading device uses a CCD (Charge Coupled D
It is converted into an electric signal using an image sensor such as evice). The converted electric signal is output to an image processing device such as an external personal computer as digital image data. In the case of an image reading device, a line sensor in which a plurality of image pickup elements are arranged in the main scanning direction is used.
As the image reading apparatus, there are an image reading apparatus for a reflective original that reads light reflected on the surface of the original, and an image reading apparatus for a transparent original that reads light transmitted through the original. An opaque original such as paper is used as the reflective original, and a transparent original such as positive film or negative film is used as the transparent original.

In the image reading apparatus as described above, it is required to improve the resolution in order to improve the image quality of the image to be read. As a means for improving the resolution, it is possible to increase the number of image pickup devices forming the line sensor, or to divide an original into a plurality of areas and read the same without changing the number of image pickup devices forming the line sensor. Conceivable.

[0004]

However, when the number of image pickup devices forming the line sensor is increased, the length of the line sensor in the main scanning direction increases. Therefore, the number of line sensors and carriages increases, leading to an increase in the size of the image reading device. Also, with the increase in size of the carriage,
Increasing the size of the line sensor has many adverse effects, such as increasing the size of the driving means for driving the carriage and increasing the power consumed by the driving means.

As a method of reading an original by dividing it into a plurality of areas without changing the number of image pickup elements, for example, a method of reading a half area of the original in the main scanning direction and then moving the original to read the remaining half area There is. However, the user needs to move the document every time the document is read, and the reading operation is complicated. Further, in order to improve the image quality, it is necessary to position the document with high accuracy.

Therefore, as a method of reading a document by dividing it into a plurality of areas without moving it, it is conceivable to drive the carriage in the main scanning direction as well as in the sub scanning direction. However, in order to improve the quality of the image to be read, high precision is required for driving the carriage. That is, in order to drive the carriage in the biaxial directions with high accuracy, a driving means having a complicated structure is required.

By the way, in the case of a transparent original such as a film, the number of films read by one setting is determined by the original holder. For example, if the number of films held in the original holder is 10, the number of originals read by one setting is 10. The number of films that can be held in the document holder is determined by the size of the document holder, that is, the size of the document table on which the document holder is placed. Therefore, in order to read a large amount of film, it is necessary to repeatedly attach the film to the document holder, and the reading operation is complicated.

Therefore, an object of the present invention is to provide an image reading apparatus which has a simple reading operation and structure and has a high resolution. Another object of the present invention is to provide an image reading apparatus which has a simple reading operation, a high resolution, and a large number of originals can be read in one original setting.

[0009]

According to the image reading apparatus of the present invention, the platen is driven by the first driving means and the carriage is driven by the second driving means. For example, the structure can be simple as compared with the case where the carriage is driven in two axis directions. The optical system has a first optical system that collects light from a predetermined area in the main scanning direction and a second optical system that collects light from a 1 / n area of the predetermined area. By driving the original table in the main scanning direction and using the second optical system having a narrow reading area, the original is divided into a plurality of areas in the main scanning direction and is read for each area. By reading the original by dividing it into a plurality of areas in the main scanning direction, the reading range for each image pickup device that constitutes the line sensor becomes smaller. Therefore, the resolution is improved without changing the number of image pickup devices forming the line sensor. Further, the carriage is driven in the sub-scanning direction every time the document table is driven in the main scanning direction at a predetermined interval, and the document is read by the line sensor. Therefore, the entire area of the original can be read by placing the original once on the original table. Therefore, the resolution of an image read by a simple reading operation can be increased.

By moving the document table in the main scanning direction, the central portion side of the document table in the main scanning direction can be read. Therefore, it is not necessary to read the portions located at both ends in the main scanning direction of the document table, the resolution of which decreases due to the influence of the optical system. Therefore, the resolution and image quality of the read image can be improved.

For example, when an original is divided into two areas, each of which is half the area that can be read by the line sensor, and read, the resolution of the image read is twice as high as when the original is read without division. This means that if the number of pixels in the main scanning direction forming the line sensor is p (pixel) and the length of the document in the main scanning direction is L (inch), the resolution when the document is read without division is p / L (ppi: pixel per inc
This is because the resolution in the case of reading the document in two is p ÷ (L / 2) = 2p / L. That is, when reading a 1 / n area in which the original is divided into n in the main scanning direction, the resolution becomes n times. Therefore, the resolution of the image to be read can be improved. Further, by reading the original in n divisions, the line sensor can read an image corresponding to the central portion of the lens with high resolution. Therefore, it is possible to prevent the deterioration of the image quality due to the aberration of the lens of the optical system, and it is possible to improve the resolution and the image quality of the image to be read.

According to the image reading apparatus of the third or fourth aspect of the present invention, the document holder is driven by the first driving means, and the carriage is driven by the second driving means. For example, the structure can be simple as compared with the case where the carriage is driven in two axis directions. Further, by driving the document holder in the main scanning direction, the document holder holding the document can be read at a plurality of positions in the main scanning direction. By reading the document holder at a plurality of positions in the main scanning direction, the document can be attached in a plurality of rows at a plurality of positions in the main scanning direction of the document holder. Therefore, the number of documents held in the document holder increases. Therefore,
The number of manuscripts that can be read by one manuscript setting increases, and the reading operation can be simplified.

Further, by moving the document holder in the main scanning direction, it is possible to position the document held by the document holder at a position suitable for reading, for example, the central portion side of the line sensor in the main scanning direction. Therefore, it is not necessary to perform reading in a portion where the resolution is reduced due to the influence of the optical system. Therefore, the resolution and image quality of the read image can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of examples showing an embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 2 shows an image scanner to which the image reading apparatus according to the first embodiment of the present invention is applied. The image scanner 1 according to the present embodiment is a flat bed type image scanner in which a document table 20 is provided on the upper surface of a box-shaped casing 10 as shown in FIG. The platen 20 is composed of a glass plate 21 and a platen frame 22.
The document 2 is placed above the table. The original plate frame 22 provided on the peripheral portion of the glass plate 21 has an end portion on the glass plate 21 side serving as an original document guide for positioning the original document 2. A white reference 23 having a high reflectance uniform reflection surface is provided on the side opposite to the original placing side of the original frame 22.

A carriage 30 is housed inside the housing 10. The carriage 30 is indicated by arrows a1 and a in FIG.
As shown in 2, it reciprocates in the sub-scanning direction. A line sensor 31 is housed in the carriage 30. The line sensor 31 is composed of a plurality of image pickup elements, and a photoelectric conversion element such as a photodiode is used as the image pickup element. The plurality of image pickup elements are arranged on a straight line in the main scanning direction.

An on-chip color output system is adopted, and a 3-line or 6-line line sensor 31 in which a color filter array is formed on the light receiving portion on-chip.
Is used. The line sensor 31 outputs an electric signal according to the arrangement state of the color filter array. As a color filter array, for example, R (Re
Any of the primary color filters d), G (Green), and B (Blue) is used. An optical system for forming an original image on the line sensor 31 includes a light source 32 for a reflective original, a mirror 33, a condenser lens 34, and the like.

As the light source 32, a fluorescent tube lamp or the like is used,
It is extended in the main scanning direction and mounted on the carriage 30. As shown by the broken line in FIG. 2, the light emitted from the light source 32 is reflected by the surface of the original 2 placed on the original table 20, and the reflected light is reflected by an optical system such as a mirror 33 and a condenser lens 34. An image is formed on the light receiving portion of the sensor 31. The optical system includes a condenser lens 341 forming a first optical system that forms an image of light in a predetermined area in the main scanning direction on the line sensor 31 as shown in FIG. 3, and the predetermined area as shown in FIG. Of 1
/ N (n = 2 in the present embodiment) and a condenser lens 342 that forms a second optical system for forming an image on the line sensor 31.

As shown in FIG. 3, the condenser lens 341 of the first optical system corresponds to a predetermined area in the main scanning direction of the line sensor 31, for example, the width W of the glass plate 21 of the document table 20 in the main scanning direction. Light is collected from the area and imaged on the line sensor 31. That is, the condenser lens 341 of the first optical system forms an image on the line sensor 31 with the light incident from all areas of the reading area SA in the main scanning direction.

On the other hand, the condenser lens 342 of the second optical system is
1 / of the predetermined reading area SA of the line sensor 31
Light is collected from the area 2 and imaged on the line sensor 31.
For example, as shown in FIG.
When it corresponds to the width W of the glass plate 21 of 0 in the main scanning direction,
The condenser lens 342 of the second optical system condenses light from the area SB corresponding to the width D in the main scanning direction, which is the two central areas when the light is divided into four in the main scanning direction, and forms an image on the line sensor 31. To do. That is, when the condenser lens 342 of the second optical system is used, the shaded area SB in FIG. 5 is read. Therefore, the condenser lens 342 collects the light at the position corresponding to the central portion side of the document table 20 in the main scanning direction, and does not collect the light corresponding to both ends of the document table 20.

For example, if the number of pixels of the line sensor 31 is p
(Pixel) and the width W (inch) in the main scanning direction read by the condenser lens 341 of the first optical system,
The resolution (pixel per inch) is p / W. On the other hand, since the width D in the main scanning direction read by the condenser lens 342 of the second optical system is W / 2 as shown in FIG. 4, the resolution is p / (W / 2), that is, 2p / W. . As a result, by halving the area to be read, the resolution at the time of reading is doubled. Therefore, when the second optical system is used, the resolution of the image formed on the line sensor 31 is improved as compared with the case where the original 2 is read by the first optical system.

The condenser lens 341 of the first optical system and the condenser lens 342 of the second optical system are moved in the main scanning direction by a lens driving device (not shown). By moving the condenser lenses 341 and 342, the condenser lenses inserted in the optical path from the document 2 to the line sensor 31 are switched, and the resolution of the image formed on the line sensor 31 is changed. .

As shown in FIG. 6, the sensor driving section 311 for driving the line sensor 31 mainly operates electronically.
The sensor drive unit 311 is an electronic circuit that generates drive pulses such as shift pulses and transfer pulses necessary to drive the line sensor 31, and outputs the generated pulses to the line sensor 31. The sensor driving unit 311 is composed of, for example, a synchronization signal generator and a driving timing generator.

The processing section 40 includes an analog signal processing circuit 4
1, an A / D converter 42 and a digital signal processing section 43. In this embodiment, the analog signal processing circuit 41 and the A / D converter 42 of the processing section 40 are mounted on the carriage 30 together with the sensor driving section 311, and the digital signal processing section 43 is fixed to the housing 10 together with the control section 60. ing. Circuit mounted on carriage 30 and housing 1
The circuit fixed to 0 is connected by a flexible flat cable (not shown).

The analog signal processing circuit 41 subjects the analog electric signal output from the line sensor 31 to analog signal processing such as amplification and noise reduction processing, and outputs the processed signal to the A / D converter 42. Output. A /
The D converter 42 quantizes the analog electric signal output from the analog signal processing circuit 41 into a digital image signal with a predetermined gradation, and the image signal is digital signal processing unit 43.
Output to.

The digital signal processing section 43 performs various processes on the image signal output from the A / D converter 42 to generate image data to be transferred to the image processing apparatus 3 connected to the image scanner 1. It is a thing. Specifically, the digital signal processing unit 43 has the shading correction unit 4
31, a gamma correction unit 432 and other correction unit 433.

The shading correction unit 431 determines the variation in sensitivity of each pixel of the line sensor 31 or each block of several pixels, the distribution of the irradiation light amount of the light source 32 in the main scanning direction, the optical characteristics of the condenser lenses 341 and 342, and the like. Correct the resulting shading. The shading correction is performed by using the white reference data obtained by reading the white reference 23 when reading the original 2, or by using the white reference data and the black reference data stored in advance.

The gamma correction unit 432 performs gamma correction on the image signal according to the gamma characteristic of the image processing apparatus 3. This gamma correction is performed by a look-up table method, for example. The look-up table method is a method of searching for data written at an address corresponding to an input level of an image signal and reading it as an output signal.

The other correction unit 433 performs interpolation of defective pixels and other corrections. Other corrections include, for example, pixel number conversion processing, color correction for faithfully reproducing the colors of the original image, MTF correction for emphasizing and sharpening high frequency components of the image signal, and white using a multiplexer. Clip processing is performed. Further, depending on the type of the image processing apparatus 3, standardization processing, binarization processing, dither processing for reproducing halftones, or the like is performed. The various processes performed by the digital signal processing unit 43 can be replaced with processes by a computer program executed by the control unit 60 or the image processing apparatus 3.

The control unit 60 has a CPU 61, a RAM 62 and a ROM 63. The CPU 61 executes a computer program stored in the ROM 63 to control the operation of the line sensor 31, that is, the operation of the sensor driving unit 311, the movement of the carriage 30, the blinking of the light source 32, and the control of the amount of light, and the processing. The overall control of the image scanner 1 such as the operation control of each element of the unit 40 is performed. The RAM 62 temporarily stores the image signal processed by the digital signal processing unit 43, the image data generated by the digital signal processing unit 43, and the like.

The control unit 60 can be connected to the image processing apparatus 3 such as a personal computer through an interface (I / F) 11 provided in the housing 10. The control unit 60 executes, based on a read command signal from the connected image processing apparatus 3, one of the computer programs stored in the ROM 63 for reading a document. The image data created by the digital signal processing unit 43 after the document is read is transferred to the image processing apparatus 3 through the interface 11.

Next, the driving means will be described. In the case of the present embodiment, the image scanner 1 has a first drive section 51 and a second drive section 52 as drive means. The first drive unit 51 drives the document table 20 at regular intervals in the main scanning direction. The first drive unit 51 has a drive motor (not shown), and the document table 20 is driven by the drive force of the drive motor. The drive motor and the document table 20 are connected to each other via a driving force conversion means such as a rack and pinion, and the document table 20 is driven by the rotation of the drive motor.

The second drive section 52 drives the carriage 30 at regular intervals in the sub-scanning direction. The second drive unit 52 includes a drive motor 521 and a belt member 52 as shown in FIG.
Have two. The rotational force of the drive motor 521 is transmitted to the carriage 30 via the belt member 522. A reduction gear is attached to the drive motor 521, and the drive motor 5
After the rotational force of 21 is reduced by the reduction gear, the pulley 523
Is transmitted to the belt member 522 via. First drive unit 5
The drive motor (not shown) and the drive motor 521 of the second drive unit 52 are controlled by the CPU 61 of the control unit 60, respectively.

Next, the operation of the image scanner 1 will be described. The user of the image scanner 1 places the original 2 on the glass plate 21 of the original table 20, and then specifies the reading range and the reading resolution of the original 2 by an input operation to the image processing apparatus 3 to the image scanner 1. Command to scan the original. In response to the command, the image scanner 1 operates as follows.

(1) Light source 3 according to a command from controller 60
2 is lit. Further, the user inputs to the image scanner 1 via the image processing apparatus 3 which one of the first optical system and the second optical system is used for reading. The control unit 60 inserts the condenser lens 341 of the first optical system or the condenser lens 342 of the second optical system into the optical path by a lens driving device (not shown) based on a command from the image processing device 3. After that, the white reference 23 is read by the light of the light source 32 that is turned on, and the white reference data is created.
In this embodiment, reading by the second optical system will be described.

(2) When the white reference data is created, the second drive unit 52 moves the carriage 30 to the initial position which is the reading start position. On the other hand, the document table 20 on which the document 2 is placed is moved to a predetermined position by the first drive unit 51. In the case of the present embodiment, as shown in FIG. 1A, the document table 20 is arranged so that one end 21a of the glass plate 21 of the document table 20 in the main scanning direction overlaps one end SBa of the reading area SB. Driven. At this time, the image of the document in the reading area is formed on the line sensor 31 by the condenser lens 342 of the second optical system.

(3) The sensor drive unit 311 inputs a drive pulse such as a shift pulse to the line sensor 31 in a predetermined sequence. As a result, an amount of electric charge (signal electric charge) that correlates with the density of the original image is accumulated in the line sensor 31, and the accumulated electric charge is output to the processing unit (analog signal processing circuit) 41 as an electric signal by the CCD or the like. .

(4) The electric signal output from the line sensor 31 is processed by the processing unit 40, and the image data output as a result is transferred to the image processing apparatus 3. (5) While moving the carriage 30 at a constant speed by the second drive unit 52, the above (2) to (4) are repeatedly executed. As a result, the designated predetermined area, that is, the original 2
Half the area of is read.

(6) When the reading of the half area of the original 2 is completed, the control unit 60 drives the first drive unit 51 to move the original table 20 from the position shown in FIG. 1A to the position shown in FIG. Move to. At the same time, the control unit 60 drives the second drive unit 52 to move the carriage 30 to the initial position. The first drive unit 51 moves the document table 20 in the main scanning direction, and
As shown in (B), the document table 20 is driven so that the other end portion 21b of the glass plate 21 of the document table 20 in the main scanning direction overlaps with the other end portion SBb of the reading area SB.

(7) After the original table 20 is moved to the position shown in FIG. 1 (B), the steps (2) to (4) are repeatedly executed to obtain the remaining half of the original 2 Area is read.

As described above, according to the image scanner 1 according to the first embodiment of the present invention, the line sensor 3
The resolution is enhanced by reducing the area that can be read by 1. Therefore, it is not necessary to increase the length of the line sensor 31 in the main scanning direction to increase the resolution. Further, in order to compensate for the narrowed reading range by increasing the resolution, the document table 20 is moved in the main scanning direction. Therefore, it is not necessary to move and remount the document 2 every time a predetermined area of the document 2 is read. Therefore, the entire surface of the original 2 is read by one-time placement, and the resolution of an image to be read is improved without increasing the size of the line sensor 31 and the size of the image scanner 1 itself accompanying the increase in size of the line sensor 31. be able to.

In the first embodiment, the document table 20 is moved in the main scanning direction. Therefore, the carriage 30
Compared to the case of moving in the axial direction, the structure is simple and high accuracy is not required for the movement. Therefore, the configuration of the image scanner 1 is simple and the manufacturing cost does not increase. In the first embodiment, when reading with high resolution, the central portion side in the main scanning direction is read. Therefore, it is not necessary to read both end portions in the main scanning direction that are greatly affected by the aberration of the optical system, and the quality of the read image can be improved.

(Second Embodiment) FIG. 7 shows an image scanner according to the second embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The image scanner 4 according to the second embodiment of the present invention is different from that of the first embodiment in that a document holder 70 is provided. Document holder 70
Can be moved in the main scanning direction similarly to the document table of the image scanner according to the first embodiment. That is, the second
In the embodiment, a document holder 70 is assembled instead of the document table of the first embodiment. Descriptions of other configurations similar to those of the first embodiment will be omitted.

The document holder 70 holds a document 71 such as a negative film or a positive film which transmits light.
For example, in the case of a positive film, a mount provided around the film is inserted into the holding portion 72 of the original holder. Negative film, positive film, and the like have a small image to be read, and thus need to be read at high resolution. In the second embodiment, the document 71 is the same as in the first embodiment.
When reading with high resolution, the portion located on the central portion side in the main scanning direction is read. Then, by making the document holder 70 movable in the main scanning direction, in the case of the second embodiment, the document set on the document holder 70 is read in two areas as shown in FIG.

In the case of the second embodiment, since the light passes through the original 71 held by the original holder 70, the original 71 is irradiated with the light from the surface light source device 80 located above. Surface light source device 80
Is composed of a light emitting portion such as a fluorescent tube lamp and a light guide plate for guiding the light emitted from the light emitting portion toward the document. The light emitted from the light emitting portion is applied to the original as light having a uniform surface by the light guide plate.

In the case of the conventional structure in which the document holder 70 does not move, only the two rows of documents on the central side of the document holder 70 shown in FIG. 8 can be read. That is, conventionally, in the case of the document holder 70 shown in FIG. 8, only 10 documents can be read. On the other hand, in the case of the image scanner 4 according to the second embodiment of the present invention, not only the two rows on the central side of the document holder 70 but the entire surface of the document holder 70 is read, so that the document is read for four rows. That is, the number of readable originals is 20, and it is possible to read twice as many originals as compared with the conventional configuration. Therefore, the number of originals that can be read in one original setting is doubled. Further, in the case of the second embodiment, the document to be read is located at the center in the main scanning direction. Therefore, it is not necessary to read the originals at both ends in the main scanning direction, which are greatly affected by the aberration of the optical system, and the image quality of the read image can be improved.

As described above, in a plurality of embodiments of the present invention, the platen or the platen holder is moved in two steps so that the predetermined area is moved to one.
The configuration for reading the area of / 2 has been described. But,
It is possible to improve the resolution at the time of reading or increase the number of originals to be read by moving the original table or the original holder not only in two steps but also in more steps. Therefore, the present invention does not limit the movement of the document table or the document holder to two stages.

[Brief description of drawings]

1A and 1B are diagrams showing movement of a document table of an image scanner according to a first embodiment of the present invention, FIG. 1A is a schematic diagram showing a first reading position, and FIG. It is a schematic diagram which shows a position.

FIG. 2 is a schematic diagram showing the configuration of the image scanner according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing a reading range of the image scanner according to the first embodiment of the present invention, and is a diagram showing a reading range by the condenser lens of the first optical system.

FIG. 4 is a schematic diagram showing a reading range of the image scanner according to the first embodiment of the present invention, and is a diagram showing a reading range by the condenser lens of the second optical system.

FIG. 5 is a schematic diagram showing a reading range of the image scanner according to the first embodiment of the present invention.

FIG. 6 is a schematic block diagram showing an image scanner according to the first embodiment of the present invention.

FIG. 7 is a schematic diagram showing a configuration of an image scanner according to a second embodiment of the present invention.

8A and 8B are diagrams showing movement of a document holder of an image scanner according to a second embodiment of the present invention, FIG. 8A is a schematic diagram showing a first reading position, and FIG. It is a schematic diagram which shows a position.

[Explanation of symbols]

1, 4 image scanner 2 manuscripts 3 Image processing device 10 housing 20 Platen 30 carriage 31 line sensor 32 light source (optical system) 33 Mirror (optical system) 34 Condensing lens (optical system) 51 first drive 52 Second drive unit 70 Document Holder 80 Surface light source device (optical system) 341 Condensing lens (optical system) 342 Condensing lens (optical system)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G06T 1/00 430 G06T 1/00 430E 5C072 H04N 1/00 108 H04N 1/00 108Q 1/028 1/028 A 1/10 1/10 1/107 F term (reference) 2H012 BA08 2H108 AA01 BA00 CA07 CB01 FA01 HA01 5B047 AA01 AB04 BA02 BB02 BC05 BC09 BC11 BC16 CA07 CA14 CB09 5C051 AA01 BA03 DA03 DB01 DB22 DB24 DB28 DC07 DE09 EA01 AB04 5C02 AB33 AB36 AC02 AC07 AC11 AE03 5C072 AA01 BA16 CA02 DA02 DA04 EA05 NA01 RA04 VA03

Claims (4)

[Claims] 1. A document table on which a document is placed, a carriage having a line sensor in which a plurality of image pickup devices for converting light from the document into an electric signal are arranged in the main scanning direction, and a predetermined one in the main scanning direction. A first optical system that collects light from the area of 1) and forms an image on the line sensor; and a second optical system that collects light from the area of 1 / n of the predetermined area and forms an image on the line sensor. First driving means for driving the document table at a predetermined interval in the main scanning direction, and second driving means for driving the carriage in the sub-scanning direction each time the document table is driven at a predetermined interval. An image reading apparatus comprising: 2. The image reading apparatus according to claim 1, wherein the first driving unit drives the document table at the same interval as the length of the 1 / n region in the main scanning direction. 3. A document holder for holding a document, a carriage having a line sensor in which a plurality of image pickup devices for converting light from the document into an electric signal are arranged in the main scanning direction, and a predetermined carriage in the main scanning direction. A first optical system that collects light from a region and forms an image on the line sensor; a second optical system that collects light from a region of 1 / n of the predetermined region and forms an image on the line sensor; First driving means for driving the document holder in the main scanning direction at predetermined intervals, and second driving means for driving the carriage in the sub-scanning direction each time the document holder is driven at predetermined intervals. An image reading device characterized by the above. 4. The image reading apparatus according to claim 3, wherein the first driving unit drives the document holder at the same interval as the length of the 1 / n region in the main scanning direction.