JPH1093778A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader superior in usability, capable of converting an original image including color information into the data quantity of absolute minimum for image data. SOLUTION: In the image reader, having a structure with an open area existing for the setting of an original between an original table and an optical system, an area sensor 36 for resolving a projected optical image into plural images different in color and reading them, and a line sensor 31 capable of reading at a higher resolution than the area sensor 36 are provided as image pickup means, an optical system OS is constructed, so that a luminance component L1 is led to the line sensor 31 and a color component L2 is led to the area sensor 36, and a sub-scanning means 35, for relatively moving the projected image of the luminance component L1 and the line sensor 31 in the orthogonal direction to a pixel alignment on the light-receiving surface of the line sensor 31, is provided.

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 suitable for reading bound originals such as books and magazines.

[0002]

2. Description of the Related Art An image reading apparatus called a book scanner has been commercialized. In this apparatus, an image pickup system is arranged above a document table, and an open space having a height of several tens cm exists between the document table and the image pickup system. In a book scanner, a line sensor (one-dimensional imaging device) is used as an imaging device in order to realize high-resolution reading at the same level as a copier.

When reading a book-shaped original such as a book or magazine (this is called a "book original"), a user sets the book original upward on a platen with the book opened. The illumination lamp is turned on in response to the start key being turned on, and preliminary scanning is performed first. The operation is set based on the information obtained by the preliminary scanning, and then the main scanning is started. In the main scanning, the read images are sequentially output to an external device. If the external device is a printer, a copied image is formed in real time. When a book scanner is used, pages can be turned on a document table, so that the efficiency of reading many pages can be improved. Further, compared to the case where the book is opened and the book is set face down (downward), the damage to the book can be significantly reduced. The book manuscript includes a filed document.

Unlike a single-sheet sheet document, the document surface (reading target surface) of a book document is curved. That is, the height of the document surface varies depending on the position in the left-right direction (spreading direction). Therefore, the read image is out of focus or distorted in accordance with the bending state. The book scanner measures the curvature,
Focus adjustment and distortion correction are performed according to the result. A read image having the same image quality as when a sheet document is read is output to the external device. As a method of measuring the curved state of the document surface, a method of performing image analysis by photographing an end face which is a portion called “head” in a book (Japanese Patent Application Laid-Open No. Hei 5-
No. 161002). By arranging the mirror obliquely upward on the platen, an end surface (top) can be photographed using an imaging system for reading a document image.

[0005]

The use of book scanners is expanded by achieving color reading. For example,
A magazine color photograph can be digitized and easily input to a copier, an image processing device (computer system), or the like.

However, if a color line sensor is used to read an image after separating the image into three colors (RGB, YMC, etc.), the amount of image data increases three times that in the case of a monochrome image. A large load is applied to a signal processing system for transmitting the data, and the output speed of the read image is reduced. Attempting to maintain processing speed will increase prices significantly. In addition, since the amount of light is attenuated by the filter for color separation, it is necessary to extend the photoelectric conversion time per line, which increases the time required for reading. Particularly, in reading an old document, the amount of illumination light needs to be reduced in order to prevent discoloration and deterioration of the paper quality, so that the required time is further increased. Although the problem of required time can be solved by a color area sensor used in a video camera or the like, it is impossible to obtain the same resolution as a line sensor at present. For example, when reading a document in which a color image and a character image are mixed like an encyclopedia, the characters are hard to read. It is impossible to adjust the focus for each line according to the bending state of the document.

On the other hand, conventionally, since various reading environments including the curved state of the document surface are measured by the line sensor, there is a problem that the time required for the preliminary scanning is long.

According to the present invention, an original image containing color information is
It is an object of the present invention to provide an image reading apparatus which can be converted into image data having a minimum necessary data amount and has excellent practicality. Another object is to speed up reading.

[0009]

A line sensor and an area sensor are used together. The incident light from the document is separated into a luminance component and other color components, and a line sensor is used for photoelectric conversion of the luminance component, and an area sensor is used for photoelectric conversion of the color component. In the case of imaging with R, G, and B, of these three colors, G, which is the color component with the highest relative luminosity factor of humans, is treated as the luminance component. Other color components (R, B) are imaged by the area sensor.

[0010] Even if the color components have a low resolution, they have little effect on the image quality. Therefore, an area sensor having a lower resolution (the number of pixels per line) than the line sensor is used. As a result, the amount of photographing data can be reduced. When it is necessary to make the resolutions of the three colors uniform when reproducing the read image, interpolation of the area sensor output or thinning out of the line sensor output using a linear method or the like is performed inside or outside the image reading apparatus. It is sufficient to carry out either.

By performing the preliminary photographing for measuring the reading environment such as the curved state of the document surface by the area sensor, the time required for the preliminary photographing can be remarkably reduced as compared with the case of using the line sensor. Further, when a rotary scanning mechanism is used for sub-scanning for reading by the line sensor, the mechanism configuration is simplified, the reliability of electrical connection is increased, and noise is less likely to occur as compared with the case where the line sensor is moved.

According to a first aspect of the present invention, there is provided an apparatus comprising: a document table for supporting a document; image pickup means for converting an optical image into an electric signal; An image reading apparatus having a structure in which an open space for setting a document exists between the document table and an optical system, wherein the image pickup unit separates a projected optical image into a plurality of images of different colors. And a line sensor capable of reading at a higher resolution than the area sensor, wherein the optical system guides a luminance component of incident light to the line sensor and converts a color component into the area. And a sub-scanning unit configured to relatively move the projected image of the luminance component and the line sensor in a direction orthogonal to a pixel array on a light receiving surface of the line sensor. .

According to a second aspect of the present invention, there is provided an apparatus for projecting, onto the area sensor, an optical image of an end face of a double-page spread original in a state of being spread right and left in a direction perpendicular to the left-right direction; Means for measuring the curved state of the document surface based on the imaging information of the end face.

According to a third aspect of the present invention, the sub-scanning means is a rotary scanning mechanism for deflecting the luminance component.

[0015]

FIG. 1 is a perspective view showing an appearance of a book scanner 1, and FIG.

The book scanner 1 is an image reading apparatus suitable for reading a book original (spread original), and includes a main body housing 10 for accommodating a power supply circuit and the like, a dark original platen 20 for supporting the original, and an electric image for the original. An image pickup unit 30 converts the image into a signal, and a lamp unit 40 illuminates the original. The document table 20 is arranged on the front side of the main body housing 10. The imaging unit 30 is a document table 2
, And is supported in a cantilever manner by a column 12 extending upward from the upper surface of the main body housing 10. The lamp unit 40 has a straight tube lamp (not shown) and a reflector (not shown).
0 is fixed at a position on the lower surface side. That is, platen 2
0 is illuminated by the lamp unit 40 from above the rear end side. Space 8 between platen 20 and imaging unit 30
0 is open to a free space outside the apparatus, and has a sufficient area for setting a book document. The distance between the document table 20 and the lower surface of the imaging unit 30 is 30 cm or more.

An operation panel OP including a liquid crystal display is provided at the upper end of the front surface of the main body housing 10.
A projection plate 18 for detecting the height of the document surface is fixed to the lower end side. The front surface of the projection plate 18 is a glossy surface and is a 45 ° inclined surface with respect to the upper surface of the document table 20. An image of the end surface S3 of the book document BD in a direction orthogonal to the left-right direction is reflected on the projection plate 18, and the projection plate 18 in that state
Is photographed together with the original image. The upper end surface of the projection plate 18 is a flat surface parallel to the document table 20 and is used as a white plate 19 for shading correction.

Operation panel O in main body housing 10
A main switch 51 is provided on a side surface on the right side toward P. A start key 5 for the user to instruct the start of reading is provided on both sides of the platen 20 in the left-right direction.
2 and 53 are provided one by one, and an armrest 25 is provided on the front side.

In FIG. 1, the imaging unit 30 has a line sensor 31, an area sensor 36, and an optical system OS. The line sensor 31 and the area sensor 36
Both are imaging devices composed of a CCD array. However, the number of pixels of the area sensor 36 in the main scanning direction is smaller than that of the line sensor (for example, 1/10). The optical system OS is
It comprises a mirror 31, an image forming lens 32, a filter mirror 34, and the like, and reduces and projects a document image on respective light receiving surfaces (imaging surfaces) of the line sensor 31 and the area sensor 36. The main scanning direction of the document image is a front-back direction on the document table 20 and a vertical direction on the imaging surface.

When using the book scanner 1, the user places the book document BD upward on the document table 20 with the book document BD open as shown in FIG. At this time, the boundary between the left and right pages is aligned with the center of the document table 20 in the left and right direction, and the book document BD is pressed against the lower edge of the projection plate 18 to perform positioning in the front and rear direction. The boundary between the projection plate 18 and the document table 20 is a reference line for setting the document. As shown in FIG. 2, the document table 20 is supported by a spring mechanism so that it can move up and down independently of the left and right in accordance with the weight of the document. Thus, regardless of the thickness of the book document BD, the height of the left and right pages becomes substantially the same regardless of which page is opened, and the shooting distance is a value within a certain range.

FIG. 3 is a diagram showing a configuration of a main part of the optical system OS.
FIG. 4 is a diagram showing a spectral filter pattern of the area sensor 36. 3, the light L0 transmitted through the imaging lens 32 is separated by the filter mirror 34 into a luminance component L1 which is a G wavelength component of R, G, and B and a color component L2 which is another wavelength component. Is done. That is, the luminance component L1 is reflected by the filter mirror 34, and the color component L2 is transmitted by the filter mirror 34. Such wavelength selection characteristics can be realized by applying a predetermined substance to a glass plate or providing an interference film (dichroic mirror).

The filter mirror 34 is attached to a rotating shaft of a motor 35. This rotation axis is a line sensor 31
Are parallel to the pixel array direction (main scanning direction). The luminance component L1 reflected by the filter mirror 34 is
And enters the line sensor 31. As the filter mirror 34 rotates, original images (G component optical images) are sequentially formed on the light receiving surface of the line sensor 31 one line at a time. That is, the document image is scanned in a direction (sub-scanning direction) orthogonal to the main scanning direction. The relay lens 37 is provided movably in the optical axis direction, and is positioned by an AF mechanism (lens drive system) not shown.

On the other hand, the color component L2 transmitted through the filter mirror 34 is incident on the area sensor 36 through the variable stop 39 and the relay lens 38 in order. Area sensor 36
Represents a portion for selectively transmitting the R component as shown in FIG.
It has a spectral filter in which portions for selectively transmitting components are arranged in a stripe shape, and reads the optical image of the color component L2 by separating the optical image into an R component image and a B component image.

Here, the reading resolution will be described. Generally, in order to clearly read a monochrome image such as a document document, a resolution of about 16 dpm (400 dpi) is required. This is for A4 size documents
This is equivalent to subdividing into about 00 × 3500 (= 17.5 million) pixels. Therefore, the number of images of the line sensor 31 is selected to be about 5000. On the contrary,
The number of pixels of the area sensor 36 is 500 × 700 (= 35
10,000). The resolution of the G color component in human visual characteristics is much higher than that of the R / B color component. Generally 10
It is said to be several tens of times. Therefore, there is no practical problem even if the resolution in each scanning direction is set to 1/10 of the line sensor 31. The line sensor 31 whose resolution is thus selected
When reading a document of A4 size, the number of pixels is one.
7.85 million (= 17.5 million + 350,000), which is 52.5 million (= 17.5 million ×
It will be greatly reduced compared to 3).

There are a monochrome mode and a color mode for reading by the book scanner 1 configured as described above. In either mode, the book scanner 1 performs preliminary shooting and main shooting for the same document. In the book document BD, since the document surface S1 is curved unlike the sheet document, it is necessary to perform focus adjustment according to the curved state. Correction processing of image distortion is also required. For this reason, preliminary photographing by the area sensor 36 is performed to detect the bending state. In the preliminary photographing, the measurement of the document size necessary for setting the effective reading range and the background luminance of the document surface S1 necessary for contrast adjustment are also performed. The operating conditions for the main photographing are set based on the results of these measurements.

In the monochrome mode, actual photographing is performed using only the line sensor 31, and in the color mode, actual photographing is performed using both the line sensor 31 and the area sensor 36. In general, a character image requiring a high resolution is a monochrome image. Therefore, a necessary resolution can be secured by using a line sensor for reading a monochrome image. In the actual photographing, focus adjustment for moving the relay lens 37 according to the measurement result of the curved state of the document surface S1 is performed in accordance with the progress of the sub-scanning of the line sensor 31. Regarding the area sensor 36, focus adjustment is performed by optimizing the aperture diameter of the variable diaphragm 39 according to the measurement result of the bending state, that is, by changing the depth of the subject. Then, necessary data processing is added to the image data of each line photographed in the focused state, and the processed image data is output to the external device as read image information.

Here, assuming that the time required for the main photographing of the A4 size document is 1.4 seconds, the photographing time per line by the line sensor 31 (integration time for accumulating charges).
Is 0.4 milliseconds (= 1.4） 3500). The photographing time of the area sensor 36 is set to 1.4 which is the same as the required time.
When set to seconds, the line sensor 31 and the area sensor 36
And the ratio of the photographing time for one pixel to 1: 350
It becomes 0. The sensitivity of both sensors is the same and the area sensor 36
Assuming that the transmittance of the R / B spectral filter is 1/10 of G, the ratio of the actual imaging time between both sensors is 1: 3
It becomes 50. In order to make the photographing times of R, G and B the same in the color mode, the aperture ratio of the lens needs to be about 20: 1 which is the inverse ratio of the square root of the ratio of the photographing times. Generally, when the aperture of the lens is reduced to １ ／, the depth of the subject is increased by about 2 to 4 times. Therefore, the aperture of the relay lens 38 on the area sensor side is reduced to の of that on the line sensor side.
If it is set to 0, the depth of the subject will be several tens times. Assuming that the depth of the subject photographed by the line sensor 31 is 5 mm, the depth of the subject photographed by the area sensor 36 is 100 mm.
mm or more. The thickness of books on the market is approximately 1
Since the distance is equal to or less than 00 mm, the sharpness of an image equivalent to that of the line sensor 31 can be ensured by photographing with the area sensor 36 by narrowing the aperture of the lens without performing AF during actual photographing.

On the other hand, the measurement of the curved state does not require a high sharpness as in reading an original image. Therefore,
At the time of preliminary photographing, by setting the photographing time of the area sensor 36 to be equal to the photographing time of one line of the line sensor 31 (0.4 millisecond), the time required for preliminary photographing can be significantly reduced.

FIG. 5 is a diagram for explaining a method of measuring the curved state of the document surface. The broken line in FIG. 5B indicates the position of the line of interest. The read image G0 is composed of a photographed image (upper surface image) G1 of the upper surface of the book document BD, a photographed image G20 of the document table 20, and a photographed image G18 of the projection plate 18. The image G181 of the photographed image G18 indicates the shape of the upper end surface (portion called “heaven” in the book) of the set book document BD. Image 18 other than image (end face image) G181 of photographed image G18
0 is a background image reflected on the projection plate 18.

As described above, since the document table 20 is colored dark, the photographed image G20 is darker than other images. Further, the background image 180 is also darker than the end face image G181. Therefore, the upper surface image G1 and the end surface image G181 can be extracted by judging the magnitude of the luminance. Specifically, the luminance (pixel value) is checked in order from the top pixel in the main scanning direction for each line, and the top pixel position (pixel number) n1 in the range where the luminance exceeds the first threshold th1 and the luminance is Then, pixel positions n3 and n4 on the leading and trailing ends of the range exceeding the threshold value th2 (th2> th1) of 2 are detected. A known pixel position n corresponding to the pixel position n1 and the front edge of the projection plate 18
2 corresponds to the height of the document surface S1 in the line, and the number of pixels between the pixel positions n3 and n4 corresponds to the document size in the main scanning direction. The actual size is obtained by the calculation of dividing the number of pixels by the imaging resolution. The curved state of the document surface S1 is specified by a set of data indicating the height of the document surface S1 in each of all the lines. Further, the respective positions of the first line and the last line where the pixel positions n3 and n4 are detected correspond to both end positions of the document in the sub-scanning direction.

In the read image G0, the top image G
1 is curved at the original surface S1.
Is not constant. That is, a subject near the imaging surface is imaged larger than a distant subject. At the time of the actual photographing, image processing (image distortion correction) for correcting the curved upper surface image G1 into an image when the height of the document surface S1 is constant is performed based on the height information of the document surface S1 obtained at the time of the preliminary photographing. Done. Specifically, with respect to the main scanning direction, a plane at a position at a fixed distance (for example, 5 cm) above the document table 20 is used as a reference surface, and the height difference between the reference surface and the document surface S1 at each position in the sub-scanning direction is calculated. The upper surface image G1 is scaled accordingly. In the sub-scanning direction, the upper surface image G1 is scaled according to the ratio of the creeping distance of the document surface S1 to the projection distance of the document surface S1 onto the document table 20 for each minute section.

FIG. 6 shows the signal processing system 10 of the book scanner 1.
0 is a block diagram of FIG. The signal processing system 100 includes a CPU 1
01, AD conversion units 102 and 103, illuminance correction unit 104,
105, image processing circuit 106, output circuit 107, RAM
109 and a height measuring unit 110.

At the time of preliminary photographing, the area sensor 36
The R and B photoelectric conversion signals output from are converted by the AD converter 103 into, for example, 8-bit image data. The R and B imaging data are input to the illuminance correction unit 105 in the order of pixel arrangement. The illuminance correction unit 105 corrects for uneven light distribution. In this embodiment,
The image data of R corrected by the illuminance correction unit 105 is input to the height measurement unit 110. This is because a fluorescent lamp widely used for indoor lighting has a small R component, so that the influence of external light can be minimized by using the R image data for measuring the curved state.

The height measuring section 110 comprises a comparator 111 and a counter 112. The comparator 111 compares the input imaging data with the threshold values th1 and th2, and
Notify U101 and counter 112. Counter 11
2 counts the number of pixels whose luminance exceeds the threshold th1. That is, the height of the document surface S1 is measured. CPU10
1 fetches the count value of the counter 112 and generates height data DH indicating the curved state (height distribution) of the document surface S1. In addition, the pixel positions n3 and n4 detected by the comparator 111 are fetched to generate size data DS indicating the size of the document in plan view. Height data DH and size data DS are temporarily stored in RAM 105. After the completion of the preliminary photographing, the CPU 101 generates control data for image distortion correction and focus adjustment as preparation for main photographing based on the height data DH and the size data DS, and generates an output image range (effective reading range). Make settings.

At the time of actual photographing, the output of the area sensor 36 is input to the low-resolution processing unit 620 of the image processing circuit 106 through the AD conversion unit 103 and the illuminance correction unit 105 in order similarly to the time of preliminary photographing. The G photoelectric conversion signal output from the line sensor 31 is converted into, for example, 8-bit image data by the AD conversion unit 102 and the illuminance correction unit 1
After receiving a predetermined correction in step 04, the signal is input to the high resolution processing unit 610 of the image processing circuit 106. High resolution processing unit 61
0 and the low-resolution processing unit 620
Processing such as MTF correction for image quality improvement, scaling processing including correction of image distortion due to the curvature of the document surface S1, density correction, and masking for blanking the outside of the output image range are performed. The imaging data that has undergone predetermined image processing is output to an output circuit 1.
In step S07, the document image is output to an external device as image information obtained by reading the document image. Examples of the external device include a printer, a display, an image memory, a processing / editing device (computer system), and an interface that outputs the data at the subsequent stage with the same resolution of R, G, and B. The interface is necessary, for example, when software used for processing an image requests input of color image data of three colors having the same resolution. This interface can be built in the book scanner 1.

The CPU 101 includes a scanner driving unit 135 for driving the motor 35, an imaging control circuit 131 for supplying a clock to the line sensor 31, an imaging control circuit 136 for supplying a clock to the area sensor 36, and an AF control unit for positioning the relay lens 37. 137, an aperture drive unit 139 for driving the variable aperture 39, and a drive system including a lamp control unit 140. The CPU 101 has an operation panel O
P and various switches are connected.

FIG. 7 is a flowchart showing the general operation of the book scanner 1. The reading mode is set in response to the mode designation operation (# 11, # 12). When one of the pair of start keys 52 and 53 is turned on (# 13), C
The PU 101 instructs the lamp control unit 140 to turn on the lamp (# 14), and instructs the imaging control circuit 136 to start preliminary photographing (# 15). The height of the document surface S1 is measured based on the imaging data obtained in the preliminary photographing (#
16) Set operating conditions such as the content of image processing and output format. Thereafter, the mode is confirmed and the operation shifts to the main photographing operation (# 17).

In the case of the monochrome mode, the start of the main photographing is instructed to the scanner drive unit 135 and the image pickup control circuit 131 (# 18). During the actual shooting, the focus adjustment is performed by moving the relay lens 37 as described above (# 19), and image processing such as distortion correction is sequentially performed (# 19).
20). When the main photographing is completed (# 21), the lamp is turned off and the process returns to the standby state (# 28).

In the case of the color mode, the aperture of the variable aperture 39 is set to an optimum value (# 22), and photographing by the line sensor 31 and the area sensor 36 is started (# 23, # 2).
4). Focus adjustment and image processing are performed in the same manner as in the case of the monochrome mode (# 25, # 26).
And the lamp is turned off (# 27, # 2)
8).

In the above embodiment, the line sensor 3
1 may be realized by the parallel movement of the line sensor 31 or the rotation of the relay lens 37. Focusing (focus adjustment) can be performed by moving only the line sensor 31 or the line sensor 31 and the relay lens 37. A sensor capable of reading three colors of R, G, and B is provided as the area sensor 36,
Color imaging can be performed using only the area sensor 36. In this case, the reflectance of the G component on the filter mirror 34 is reduced. Thus, high-speed reading of a natural object (three-dimensional object) having a relatively monotonous outer shape and not requiring high resolution can be realized. By increasing the depth of field, an output with sufficient image quality can be obtained.

In the above-described embodiment, the configuration in which the optical system is shared by the line sensor 31 and the area sensor 36 has been exemplified. However, if an optical system is provided for each sensor, it is not necessary to separate light by the filter mirror 34. . If the mirror for sub-scanning is set to be retractable, an image is first captured by the area sensor 36 at the retracted position, and then the mirror is inserted into the optical path to perform image capturing by the line sensor 31. Instead of 34, a total reflection mirror can be used.

[0042]

According to the first to third aspects of the present invention,
A document image including color information can be converted into image data having a minimum necessary data amount.

According to the second aspect of the present invention, it is possible to shorten the measurement time of the curved state of the document surface and to speed up the reading. According to the third aspect of the invention, the size of the device can be reduced, and the line sensor can be fixedly arranged, so that the reliability of the electric circuit can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an appearance of a book scanner.

FIG. 2 is a diagram illustrating a movable function of a document table.

FIG. 3 is a diagram illustrating a configuration of a main part of an optical system.

FIG. 4 is a diagram illustrating a spectral filter pattern of an area sensor.

FIG. 5 is a diagram for explaining a method of measuring a curved state of a document surface.

FIG. 6 is a block diagram of a signal processing system of the book scanner.

FIG. 7 is a flowchart illustrating a schematic operation of the book scanner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Book scanner (image reading apparatus) 18 Projection board (means for projecting an optical image to an area sensor) 20 Platen 31 Line sensor (imaging means) 34 Filter mirror (spectral means) 35 Motor (sub-scanning means) 36 Area sensor ( Image pickup means) 80 Space (open space) 100 Signal processing system 110 Height measurement unit (means for measuring curved state) BD Book original (spread original) G181 Edge image (image information of end surface) L0 Incident light L1 Luminance component L2 Color Component OS Optical system S3 End face

Claims (3)

[Claims] An image processing apparatus includes: an original support supporting an original; an imaging unit configured to convert an optical image into an electric signal; and an optical system configured to project an original image onto a light receiving surface of the imaging unit. An image reading device having a structure in which there is an open space for setting a document between the image reading device, and as the imaging unit, an area sensor that reads a projected optical image by separating it into a plurality of images of different colors, A line sensor capable of reading at a higher resolution than the area sensor, wherein the optical system is configured to guide a luminance component of the incident light to the line sensor and guide a color component to the area sensor. An image reading apparatus comprising: a sub-scanning unit that relatively moves a projection image of the luminance component and the line sensor in a direction orthogonal to a pixel array on a light receiving surface of the line sensor. 2. A means for projecting, onto the area sensor, an optical image of an end face in a direction orthogonal to the left-right direction of a double-page spread original in a left-right spread state, based on imaging information of the end face obtained by the area sensor. 2. The image reading apparatus according to claim 1, further comprising: means for measuring a curved state of a document surface. 3. An image reading apparatus according to claim 1, wherein said sub-scanning means is a rotary scanning mechanism for deflecting said luminance component.