JP3164644B2 - Image reading device - Google Patents

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 provided with a shading correction circuit for correcting uneven light quantity (shading) depending on the location of an image.

[0002]

2. Description of the Related Art As shown in FIG.
2. The projection lens 315, the first mirror 317, and the second mirror (rotatable) 3 transmit transmitted light when illuminating a subject (for example, a microfilm) using the field lens 313.
A function as a reader for enlarging and projecting the image information on the screen 319 at 18 to make the image information of the subject visible, and a projection image plane formed by the projection lens 315, the first mirror 317, and the rotated second mirror 318 The image sensor unit 301 scans the image information 320 to read image information, performs various types of image processing using the image processing unit on the image processing board 321, and performs external output using the external output unit 311. Some image reading apparatuses have a prism 316 for rotating an image in order to improve the visibility of image information in a reader. That is, some of the above-mentioned subjects have vertically written image information and some have horizontally written image information. Therefore, when the image information is projected on the screen 319 in accordance with the state of the image information, it becomes easier to visually recognize the subject. Therefore, the above-mentioned image reading apparatus has a screen of a size that allows the image to be projected vertically and horizontally as shown in FIG. 4, and the image is rotated by 90 degrees by rotating the prism 316 every 45 degrees. In which the direction can be selected according to the state. Note that the image information on the subject described above is written vertically or horizontally, and is rarely written diagonally. Therefore, in consideration of the fact that the carrier 314 holding the subject is generally rotatable, the prism is If it is configured to rotate every 0 to 45 degrees, it can function sufficiently.

(1) FIG. 13 shows a configuration in which shading correction is not performed, image information read by the image sensor unit 301 is subjected to various types of image processing by an image processing unit 310, and then externally output by an output unit 311. 1 shows an image reading device. In this image reading device, in order to prevent the image quality obtained from the output unit 311 from changing even when the prism 316 is rotated, the shading on the projection imaging plane 320 is not affected at all prism angles to be used. It is necessary to use an optical system that can be kept at a minimum.

(2) FIG. 14 shows an image reading apparatus provided with a circuit for performing shading correction with certain shading correction data in order to correct shading on the projection image plane 320. Image sensor unit 301
The main scanning direction correction means (controlled by the count output of the main scanning direction counter means 308) using the main scanning shading correction data stored in the main scanning direction correction data storage means 302 3
03, the main scanning shading correction is performed.
The sub-scanning direction correction unit 305 performs sub-scanning shading correction using the sub-scanning direction correction data storage unit 304 (controlled by the count output of the sub-scanning direction counter unit 309). After the image processing unit 310 performs various types of image processing, the output unit 311 performs external output. In this image reading apparatus, it is necessary to use an optical system that does not change the shading pattern on the projection image plane 320 even when the prism 316 is rotated.

(3) FIG. 15 shows an image reading apparatus provided with a shading correction circuit for taking in shading correction data every time the prism 316 is rotated from the light quantity distribution on the projection image forming surface 320 and performing shading correction with the correction data. Show. The projected image plane 320 is scanned by the image sensor unit 301 while the subject on the carrier 314 is retracted out of the optical path. At this time, the main switching means 330
The image data from the image sensor unit 301 is sent to the main scanning direction correction data storage means 302, whereby the main scanning direction shading correction data is obtained from the light intensity distribution on the projection imaging plane 320, and the main scanning direction correction data storage is performed. It is stored in the means 302. Next, the main switching means 33
0 is switched to the direction in which data is sent to the main scanning direction correction means 303 and the sub-switching means 331 is switched to the direction in which data is sent to the sub-scanning direction correction data storage means 304. , And using the main scanning direction shading correction data stored in the main scanning direction correction data storage unit 302 to perform sub-scanning direction shading correction from image data obtained by performing main scanning direction shading correction by the main scanning direction correction unit 303. The data is obtained and stored in the sub-scanning direction correction data storage unit 304. When actually printing the image information of the subject, the switching means 330 and 331 are switched to send data to the scanning direction correction means 303 and 305, respectively. The main scanning direction correction unit 303 performs main scanning shading correction on the image information read by the image sensor unit 301 using the main scanning direction shading correction data stored in the main scanning direction correction data storage unit 302. Further, sub-scanning shading correction was performed by the sub-scanning direction correction unit 305 using the sub-scanning shading correction data stored in the sub-scanning direction correction data storage unit 304, and various image processes were performed by the image processing unit 310. Thereafter, external output is performed by the output unit 311.

[0006]

However, each of the above conventional examples has the following disadvantages.

(A) An optical system which does not affect image information read by an image sensor section on a projection image forming plane for all prism angles used as shown in the conventional examples (1) and (2). It is very difficult to construct an optical system in which the shading pattern on the projection image plane does not change. As shown in FIG. 5, since the light distribution characteristics of the irradiation lamp differ depending on each irradiation direction, the light amount distribution on the projection image forming surface on which the irradiation light is projected is not uniform, and the prism is rotated. This is due to a change in the shading tendency of the projection image plane.

By the way, as shown in FIG. 4 (a), a screen 19 having a size capable of projecting an image vertically and horizontally is provided, and the image reading area 99 corresponds to only one of the vertical and horizontal states. In the image reading apparatus, it is necessary to match the image to the image reading area 99 when performing printing. For example, in order to print an image in a horizontal state by an image reading apparatus having an image reading area 99 in a vertical state as shown in FIG. 4A, the image is rotated 90 degrees by rotating the prism by 45 degrees. (B) as shown in FIG.

Here, as shown in FIG. 3B, the light quantity distribution on the projection image plane during printing has different shading characteristics between the main scanning direction and the sub-scanning direction due to the difference in the light distribution characteristics of the lamp. Drawing a ray of light produces a concentric ellipse. Further, generally, when the prism angle is 0 degree, the major axis or the minor axis of the above-mentioned equal light amount line coincides with the main scanning direction or the sub-scanning direction. Therefore, as shown in FIG.
When rotated by 0 degrees, the main scanning direction and the sub-scanning direction of the projection image plane are switched from those at 0 degree, so that appropriate correction is performed with shading correction data that matches the light amount distribution on the projection image plane before the rotation of the prism. It cannot be understood that it can be performed.

(B) In the configuration shown in the conventional example (3),
When the power is turned on and when the prism is rotated, the shading correction data stored in the shading correction circuit may not match the shading state when actually printing. Therefore, the shading correction data must be re-acquired again in a printing state. At this time, since the shading correction data is obtained from the result of reading the light amount distribution on the projection image forming surface 320 without the influence of the subject, it is necessary to retreat the subject existing in the optical path to the outside of the optical path. As described above, taking in the shading correction data requires not only the trouble of retreating the subject out of the optical path, but also temporarily retrieving the subject out of the optical path when taking in the shading correction data. Even if automatic means for returning to the original position is provided, a problem occurs in the accuracy of the return position of the subject.

Even when the subject is not present in the optical path, dust such as a pressure plate glass (not shown) for fixing the subject on the carrier 314 affects the light amount distribution on the projection image forming surface 320. In some cases, data may be affected, and appropriate shading correction may not be performed.

It is an object of the present invention to provide an image reading apparatus which solves the above problems.

[0013]

In order to achieve the above object, the present invention provides a reading means for reading image information through a prism for rotating an image, a prism angle detecting means for detecting an angle of the prism, Storage means for storing shading correction data corresponding to the angle of the prism in advance; selecting means for selecting shading correction data suitable from the storage means in accordance with information from the prism angle detecting means; And a correcting means for performing shading correction on the image information from the reading means according to the shading correction data.

[0014]

According to the present invention, appropriate shading correction can always be performed on read image information regardless of the prism angle used.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIGS. 1 to 7 show a first embodiment of the present invention.
FIG. 1 is a block diagram of an electric circuit of an image reading device that best illustrates the features of the present invention, and FIG. 2 is a cross-sectional view of the image reading device. In the figure,
Reference numeral 1 denotes an image sensor unit (including an amplification amplifier and an A / D converter) that reads out image information on the projection imaging plane 20 and outputs it as a digital signal. The image sensor unit 1 includes a main scanning synchronization signal (HS) sent from an output unit 11 (described later).
Output starts in accordance with a start signal (ST signal) synchronized with a YNC signal), and an image signal is sent out in synchronization with a drive signal. Reference numeral 2 denotes a main scanning direction correction data storage unit that stores shading correction data in the main scanning direction. Reference numeral 3 denotes a main scanning direction that is connected to the image sensor unit 1 and the main scanning direction correction data storage unit 2 and performs shading correction in the main scanning direction. The correction unit 4 is a sub-scanning direction correction data storage unit that stores shading correction data in the sub-scanning direction. Here, the main-scanning correction data storage unit 2 and the sub-scanning direction correction data storage unit 4 constitute a storage unit 40. Reference numeral 5 denotes a sub-scanning direction correction unit which is connected to the main scanning direction correction unit 3 and the sub-scanning direction correction data storage unit 4 and performs shading correction in the sub-scanning direction. Here, the main scanning direction correcting unit 3 and the sub-scanning direction correcting unit 5 constitute a correcting unit 50. 6 is a prism angle detecting means for detecting the angle of the prism indicated by 16 in FIG.
Selecting means for selecting and outputting appropriate data from the shading correction data stored in the main scanning direction correction data storage means 2 and the sub-scanning direction correction data storage means 4 in accordance with the data relating to the angle of the prism detected in 8
Corresponds to the output of the image sensor unit 1 in the main scanning direction.
Main scanning direction counter means for detecting the position in the main scanning direction of the image information sent from the image sensor 1 so that the main scanning direction correction data storage means 2 outputs the main scanning shading correction data. The counter value of the main scanning direction counter means 8 is cleared by the above-mentioned ST signal, and thereafter, the counting operation is performed in accordance with the above-mentioned driving signal. Reference numeral 9 denotes a projection image forming surface 20
Is moved in the sub-scanning direction to match the sub-scanning position of the image information being read and output. The sub-scanning direction counter means detects the position in the sub-scanning direction so that the sub-scanning direction correction data storage means 4 outputs the sub-scanning shading correction data. The counter value of the sub-scanning direction counter 9 is cleared by a signal from a home position sensor (not shown) for detecting that the image sensor 1 is at a reference position (home position). A count operation is performed in accordance with a signal that synchronizes a signal for driving a driving unit (not shown) that moves in the sub-scanning direction with the above-described ST signal. Reference numeral 10 denotes an image processing unit for performing various image processing on the output of the sub-scanning direction correction unit 5;
Is output means for outputting the output of the image processing means 10 to the outside.

As shown in FIG. 3A, the main scanning direction is a direction in which sensor chips (not shown) in the image sensor unit 1 are arranged with respect to the projection image plane 20, and The direction is a direction in which the image sensor unit 1 moves for scanning.

FIG. 2 is a sectional view showing the structure of an image reading apparatus to which the present invention is applied. In FIG. 2, reference numeral 12 denotes a lamp for irradiating a microfilm (not shown) as a subject, and 13 Is a field lens for condensing light from the lamp 12 onto the subject, 14 is a carrier for holding the subject, 15 is a projection lens for enlarging and projecting light transmitted through the subject, and 16 is light emitted from the projection lens 15 Is a prism that rotates image information by rotating the mirror, 17 is a first mirror that changes the optical axis of light emitted from the prism 16, 18 changes the direction of light coming from the first mirror, and A second mirror 19, which switches between the reader and printer modes by moving (rotating), is provided with an image information of the subject enlarged and projected by the projection lens 15 in the reader mode. Screens for SHOW, 20 projection imaging plane formed by the projection lens 15 to the printer mode, 21 is an image processing board, the image sensor unit 1 in FIG. 1, the prism angle detecting means 6, the output unit 1
Elements other than 1 are configured on the image processing board 21.

Next, the operation will be described. The transmitted light including the image information of the object obtained by irradiating the object with the lamp 12 is enlarged and projected by the projection lens 15. In the printer mode, the projection image plane 2 is projected by the projection lens 15.
0 is formed, and the projected image plane 20 is
Scans the image information of the subject.

Here, the projection image plane 20 is originally shown in FIG.
Since the light amount distribution has shading characteristics as shown in FIG. 1, shading correction needs to be performed on the image information read by the image sensor unit 1. In FIG. 1, a digital output (G (x, y); x is a value of the main scanning direction counter means 8 and y is a value of the sub-scanning counter means 9) of image information read by the image sensor unit 1 is main scanning. The main scanning direction correction data (H) is stored in the main scanning direction correction data storage unit 2 in synchronization with the timing of input to the direction correction unit 3.
(X) is sent to the main scanning direction correction means 3. Digital output G (x, y) and main scanning correction data (x)
Are both 8 bits, the main scanning direction correcting means 3 performs the processing shown in the equation (1) to obtain an output AH (x, y) after the main scanning correction.

[0021]

AH (x, y) = G (x, y) / H (x) * 255 (1) Next, when the output AH (x, y) is input to the sub-scanning direction correction means 5, Synchronously, the sub-scanning direction data storage unit 4 sends the sub-scanning correction data V (y) to the sub-scanning correction unit 5. In the sub-scanning direction correcting means 5, the processing shown in equation (2) is performed, and the output AHV (x,
y) is obtained.

[0022]

AHV (x, y) = AH (x, y) / V (y) * 255 (2) When the equation (1) is substituted into the equation (2), the equation (3) is obtained, and the image sensor unit is obtained. It can be seen that the output of No. 1 is subjected to shading correction for main scanning and sub-scanning.

[0023]

AHV (x, y) = (G (x, y) / H (x) * 255) / V (y) * 255 (3) The output AHV (x, y) of the sub-scanning direction correction means 5 Is sent to the image processing means 10 and subjected to various image processings, and then sent to the output means 11 to obtain an external output.

In this embodiment, the main scanning direction correction data storage means 2 and the sub-scanning direction correction data storage means 4 store the correction data (pattern A) and the prism angle 45 corresponding to the prism angle of 0 degree, respectively. Correction data corresponding to the light intensity distribution at the time of degree (pattern B)
I remember.

Each of the correction data storage means 2 and 4 has the configuration shown in FIG.
The pattern A and the pattern B are stored as shown in (1), and the area to be output is switched according to the signal from the selection means 7.

The prism angle detecting means 6 has the structure shown in FIG. 7, and detects whether the angle of the prism is 0 degree or 45 degrees. In FIG. 7, reference numeral 200 denotes a prism 1
6 and an area of 0 ± 22.5 degrees and 45 ± 22.
The reflectivity is made different in the region of 5 degrees.
A label 201 which is repeated at every 0 degree, 201 is a reflection type photo interrupter for detecting the angle of the prism 16 by reading the reflectance of the label 200.

According to the result detected by the prism angle detecting means 6, the selecting means 7 switches the address areas in the main scanning correction data storing means 2 and the sub-scanning correction data storing means 4. As a result, the main-scanning correction data storage unit 2 and the sub-scanning correction data storage unit 4 can output correction data corresponding to the angle of the prism to each of the scanning direction correction units 3 and 5, respectively. This makes it possible to perform various shading corrections.

If the light quantity distribution on the projection imaging plane 20 is point-symmetric with respect to the center by 180 degrees, when the image is rotated 90 degrees by rotating the prism by 45 degrees,
Since only the light distribution characteristics in the main scanning direction and the sub-scanning direction are interchanged, even when the prism makes one rotation at 45-degree intervals, when the angle of the prism is an integral multiple of 90 degrees, pattern A is selected as the correction data, and the angle of the prism is changed. The prism detecting means 6 is configured to select the pattern B when the angle is shifted by 45 degrees with respect to the above angle, so that appropriate shading correction can always be performed.

It should be noted that the prism angle detecting means 6 may be any configuration as long as it can detect whether the angle of the prism is an integral multiple of 90 degrees or an angle shifted by 45 degrees from the above angle. It goes without saying that it can be used.

(Embodiment 2) FIG. 8 is a drawing showing the features of Embodiment 2 best. In contrast to the first embodiment, a correction data external storage unit 24 storing shading correction data
And that the main scanning direction correction data storage means 2 and the sub-scanning direction correction data storage means 4 use a RAM having a capacity sufficient to hold one shading correction data. is there.

On the other hand, as for the operational characteristics, the selecting means 7 operates in accordance with the prism angle data detected by the prism angle detecting means 6, as in the first embodiment. 24, the selected shading correction data in each scanning direction is sent from the correction data external storage unit 24 to the main scanning direction correction data storage unit 2 and the sub-scanning direction correction data storage unit 4, respectively, and held. As a result, the shading correction according to the prism angle becomes possible as in the first embodiment.

In the first embodiment, the part that operates at the highest speed is the part that moves in synchronization with the output of the image sensor unit 1. By the way, the ROM used for each of the correction data storage means 2 and 4 generally has a longer access time than the RAM as a characteristic, and it may be difficult to operate in synchronization with the output of the image sensor unit 1. Further, a ROM that can operate at high speed with a short access time is expensive, which leads to an increase in the cost of a shading correction circuit. That is, the speed of the image sensor unit 1 is hindered.

On the other hand, in the second embodiment, the correction data storage means 2 and 4 are stored in the external storage means 24 by the selection means 7.
Since the configuration includes a RAM having a capacity to store the shading correction data selected from the above, high-speed operation is possible. Therefore, even when the speed of the image sensor unit 1 is increased, the synchronization operation can be sufficiently performed.

Since the sub-scanning direction counter 9 indicating the position in the sub-scanning direction of the image sensor unit 1 is configured to count every one line in the main scanning direction, the sub-scanning direction correction data storage means which operates according to the sub-scanning direction counter 9 is provided. 4
Operates at a lower speed than the main scanning direction correction data storage means 2. Therefore, even when the image sensor unit 1 operates at a high speed, the sub-scanning direction correction data storage unit may be able to cope with the configuration of the first embodiment. That is, the configuration of the first embodiment and the configuration of the second embodiment can be used together.

(Embodiment 3) Embodiments 1 and 2 are directed to a case where the projection imaging plane 20 has a light quantity distribution symmetrical with respect to the center by 180 degrees. Therefore, when the prism is rotated every 45 degrees, appropriate shading correction can always be performed by having the shading correction data (pattern A and pattern B) for 0 degree and 45 degrees.

On the other hand, as shown in FIG.
If the light amount distribution is not 180 ° point-symmetric with respect to the center, it is necessary to have shading correction data for each prism angle used. However, since the image rotates twice for one rotation of the prism, the prism angle is 180 degrees.
It is clear that the light intensity distributions at different positions are equal,
In addition to the patterns A and B, a pattern C corresponding to 90 degrees and a pattern D corresponding to 135 degrees may be stored in advance.

In this embodiment, as compared with the first and second embodiments, the number of detected angles by the prism angle detecting means 6 is increased, the number of selected by the selecting means 7 is increased, and the shading correction data to be stored is stored. The only difference is that the capacity of both scanning direction correction data storage means 2 and 4 of the first embodiment or the correction data external storage means 24 of the second embodiment is increased due to the increase in the number of patterns.

FIG. 10 shows an example of the configuration of the prism angle detecting means 6 used in this embodiment. In FIG. 10, reference numeral 202 denotes a label on the outer periphery of the prism 16 that represents the angle of rotation of the prism 180 degrees in four different states every 45 degrees, and reference numeral 203 denotes the angle of the prism 16 by reading the state of the label 202. Is a double reflection type photo interrupter.

The double reflection type photo interrupter 203
By reading the state of the label 202, the prism angles are 0 degree (= 180 degrees), 45 degrees (= 225 degrees), and 90 degrees (= 2 degrees).
70 degrees) and 135 degrees (= 315 degrees). According to the detection result of the prism detecting unit 6, the selecting unit 7 stores both the scanning direction correction data storing units 2 and 4 (FIG. 1) storing the shading correction data as shown in FIG. The pattern of the shading correction data is changed by changing the address of FIG.

Note that even when it is necessary to detect the prism angle in eight states at 45 degree intervals, the label 202 is changed to a label displayed in eight states, and the dual photo interrupter 203 is changed to a triple photo interrupter. This can be dealt with by increasing the number of selections by the selection means 7 and by increasing the capacity of both the scanning direction correction data storage means 2 and 4 or the correction data external storage means 24, and it is clear that no adverse effect is caused by the change. It is.

It goes without saying that all the prism angle detecting means 6 can be used as long as it can detect the required number of states of the prism.

To summarize the above, when a conventional image reading apparatus uses a prism that changes the direction of an image in order to improve the visibility at the time of reading, an appropriate shading correction is performed because the light amount distribution changes due to the rotation of the prism. It could not be performed, affecting the image quality. Alternatively, a means of retreating the subject to the outside of the optical path in order to re-capture the shading correction data while printing is performed, or the use of the automatic means for performing the above operation requires a considerable return position accuracy to the means. Since the matter cannot be escaped and the influence of dust in the light path cannot be ignored, strict control of dust in the light path had to be performed.

On the other hand, each embodiment of the present invention has shading correction data adapted to each light amount distribution even if the light amount distribution changes when the direction of the image is changed using the prism. Therefore, appropriate shading correction can always be performed regardless of the prism angle, and a change in shading does not affect the image quality. Further, since all the shading correction data to be used are stored in advance, not only does it not have to take the trouble of evacuating the subject from the optical path to take in the shading correction data, but also the automatic means for performing the above operation is unnecessary. Therefore, operability can be improved and cost can be reduced. Further, since dust in the optical path does not affect the shading correction data, the influence of dust in the optical path on an image is reduced as compared with the conventional method of taking in shading correction data.

[0044]

As described above, according to the present invention,
Optimal shading correction can always be performed on the read image information obtained through the prism regardless of the angle of the prism.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a structural diagram of an image reading apparatus to which each embodiment of the present invention is applied.

FIG. 3A is a diagram illustrating a relationship between an image sensor unit and a main scanning direction and a sub-scanning direction, and FIG. 3B is a diagram illustrating a light amount distribution (180-degree point symmetry) of a projection imaging surface. is there.

FIGS. 4A and 4B are diagrams respectively showing a relationship between a projected image, a screen, and an image reading area.

FIG. 5 is a diagram illustrating light distribution characteristics of an irradiation lamp.

FIG. 6 is a diagram showing an address map of a shading correction data storage unit in each scanning direction of the first embodiment of the present invention or an external storage unit of shading correction data of the second embodiment.

FIGS. 7A and 7B are structural diagrams of a prism angle detecting means used in the first and second embodiments of the present invention.

FIG. 8 is a block diagram of a second embodiment of the present invention.

FIG. 9 is a diagram showing a light amount distribution (180-degree point symmetry) of a projection image forming plane.

FIGS. 10A and 10B are structural views of a prism angle detecting means used in a third embodiment of the present invention.

FIG. 11 is a diagram showing an address map of shading correction data used in a third embodiment of the present invention.

FIG. 12 is a structural diagram of a conventional image reading apparatus.

FIG. 13 is a block diagram of a portion related to an image signal of Conventional Example 1.

FIG. 14 is a block diagram of a portion related to an image signal of Conventional Example 2.

FIG. 15 is a block diagram of a portion related to an image signal of a conventional example 32.

[Explanation of symbols]

1 image sensor (including amplification amplifier and A / D converter) 2 main scanning direction shading correction data storage means 3 main scanning direction correction means 4 sub scanning direction shading correction data storage means 5 sub scanning direction correction means 6 prism angle detection means 7 Selection means 8 Main scanning direction counter means 9 Sub-scanning direction counter means 10 Image processing means 11 External output means 12 Irradiation lamp 13 Field lens 14 Carrier 15 Projection lens 16 Prism 17 First mirror 18 Second mirror 19 Screen 20 Projection Image plane 21 Image processing board 24 Shading correction data external storage means 99 Image reading area 200 Prism label (two states) 201 Reflection type photo interrupter 202 Prism label (Four states) 203 Double reflection type photo interrupter 30 Image sensor unit (including amplification amplifier and A / D converter) 302 Main scanning direction shading correction data storage unit 303 Main scanning direction correction unit 304 Sub-scanning direction shading correction data storage unit 305 Sub-scanning direction correction unit 306 Prism angle detection unit 307 Selection means 308 Main scanning direction counter means 309 Sub scanning direction counter means 310 Image processing means 311 External output means 312 Irradiation lamp 313 Field lens 314 Carrier 315 Projection lens 316 Prism 317 First mirror 318 Second mirror 319 Screen 320 Projection Image plane 321 Image processing board 330 Main switching means 331 Secondary switching means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/401 G03B 21/10 H04N 1/19-1/195

Claims (1)

(57) [Claims] 1. A reading means for reading image information passing through a prism for rotating an image, a prism angle detecting means for detecting an angle of the prism, and shading correction data adapted to the angle of the prism are stored in advance. Storage means for storing, selecting means for selecting shading correction data suitable from the storage means according to the information from the prism angle detecting means, and image information from the reading means according to the shading correction data selected by the selection means. An image reading apparatus comprising: a correction unit that performs shading correction.