JPH06303391A - Picture reader - Google Patents

Abstract

PURPOSE:To provide a picture reader whose actuation is improved and sure by defining one side of a planar member as a reflection surface and defining the other side as the surface of a certain density to be the reference of shading correction and switching them as needed. CONSTITUTION:An original 201 is held there between by carrier rollers 202-205 and sent to the direction of an arrow mark B. At this time, the planar members 208 and 209 are hooked so as to make the reflection surfaces 208a and 209a approximately perpendicular to the reflected light 227 of fluorescent lights 214 and 215 on an original surface. Thus, a light quantity can be increased compared with the case of performing illumination by the fluorescent lights 214 and 215 alone. When the original 201 is not present on a carrier path A, the planar members 208 and 209 are rotationally moved and become approximately parallel to the original 201. At this time, the surfaces 208b and 209b formed in a certain density of the members 208 and 209 are irradiated by the fluorescent lights 214 and 215 and the illuminating lights are guided to mirrors 216 and 221, further through image forming lenses 219 and 224 guided to CCDs 220 and 225 similarly to picture lights.

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 in a facsimile, a copying machine or the like.

[0002]

2. Description of the Related Art Next, a conventional technique will be described.

<Prior Art Example 1> In a conventional image reading apparatus, a document is illuminated by a linear light source such as a fluorescent lamp, and the light of the document image is formed on an image reading sensor such as a CCD by a lens to form an image. An image reading device for reading is known.

In this apparatus, a plate having a constant density surface is inserted in the vicinity of the document reading portion in order to correct the reduction of the peripheral light amount due to the lens and the unevenness of the light amount of the fluorescent lamp, and the CCD output for the reflected light is inserted. To be constant,
So-called shading correction is performed. FIG. 6 shows a cross section of an image reading apparatus including a mechanism for performing the shading correction.

In FIG. 6, the image on the original 300 is nipped by conveyance rollers 301, 302 and 303, 304, and the gap A formed by the guide plates 305, 306 is fed in the direction of arrow B, while the guide plate is being guided. It is read through the transparent portion 305a provided on the 305. 307
Is a linear light source such as a fluorescent lamp for illuminating a document.
Reference numeral 308 is a shading reference plate having a surface 308b formed to have a constant density, and is rotatably attached with a shaft 309a of an arm 309 provided at an end of the shading reference plate as a spindle. When the shading correction is performed, it is at the position shown by the two-dot chain line in the figure, and when reading the original image, it is at the position shown by the solid line in the figure. These positions on the shading reference plate are solenoids (not shown)
It is controlled by turning on / off.

On the other hand, in order to read an original image at a high speed, when the sensitivity of the CCD is limited, it is necessary to increase the light amount of a fluorescent lamp which is a light source for illuminating the original. As a conventional method for doing so, as shown in FIG. 7, a reflecting plate 310 having a reflecting surface 310a is provided at a position facing the fluorescent lamp 307, and the reflected light of the illumination light on the original surface is reflected again on this surface to scan the original. The amount of light is increased by illuminating it.

<Conventional Example 2> A conventional film image reading apparatus, particularly a microfilm reader scanner, will be described as an example.

A CCD or the like is often used as a photoelectric conversion element of an image reading apparatus, but the microfilm on which an image is imprinted at a resolution much higher than that of the CCD has various reduction ratios and sizes. In order to read this image, it is effective to enlarge the original document size using a projection lens such as a zoom lens and read it by a photoelectric conversion element having an effective reading length corresponding to the original document width.

However, the amount of light on the image plane formed by this projection lens is generally smaller toward the periphery as compared with the vicinity of the optical axis due to lens aberration and the like. In order to improve the quality of the read image, it is necessary to remove the uneven light amount in some way. However, it is difficult to completely remove the unevenness of the light quantity, and in an array including a plurality of photoelectric conversion elements such as CCD, there is a sensitivity variation of each element, and it is necessary to make an electrical correction. An electrical method has been often used for the correction of the uneven light amount, that is, the shading correction.

In a document scanner or the like, a uniform reflecting plate is used, and the reflected light from the reflecting plate is read every time scanning is performed, and is taken in as a white level reference signal to be used as correction data, so a line memory is sufficient. However, in film scanners, the film is irradiated with light from a pseudo point light source, and in order to read the transmitted light, the reflected light from the reference plate that is the reference for each scan is read and used as correction data. The above method cannot be used.

Therefore, it is necessary to store the state when there is no film and use it as the data for correction, so that the page memory becomes necessary. Since the light amount unevenness also changes every time the magnification of the projection lens changes, if the data of the light amount unevenness is stored for each magnification, a huge amount of memory is required and the cost becomes extremely high.

Therefore, a method has been considered in which the correction is performed based on only the information of the line having the peak light amount in both the main scanning direction and the sub scanning direction. Here, the main scanning direction refers to the longitudinal direction of the photoelectric conversion element, and the sub scanning direction refers to the direction in which the photoelectric conversion element moves.

A conventional shading correction circuit will be described below with reference to the drawings.

FIG. 31 is a block diagram of a conventional shading correction circuit. Both 791 and 792 are ROMs.

H (x) is correction data in the main scanning direction, V
(Y) is correction data in the sub-scanning direction, D (x, y) is image data before correction, DH (x, y) is image data after correction in the main scanning direction, and DHV (x, y) is main scanning direction. The image data after the sub-scanning direction correction is shown. Now, the case where image processing is performed with 8 bits will be described as an example. H (x) in ROM
The image data D (x, y) to be corrected is input to the upper 8 bits of the 791, and the lower 8 b of the ROM 791 is input.
Enter it.

Image data DH (x, after correction in the main scanning direction)
y) is given by DH (x, y) = D (x, y) * (256 / H (x)) (1).

V (y) is input to the upper 8 bits of the ROM 792, and the main scanning direction corrected image data DH (x, y) to be corrected is stored in the lower 8 bits of the ROM 792.
To enter.

The image data DHV (x, y) after correction in the main scanning direction and the sub scanning direction is DHV (x, y) = DH (x, y) * (256 / V (y)) (2) or DHV ( x, y) = (D (x, y) * (256 / H (x))) * (256 / V (y)) (3)

[0019]

However, the conventional examples 1 and 2 have the following problems.

That is, the mechanism of Conventional Example 1 needs to be provided in the vicinity of the reading section for reading the original image, and it is difficult to simultaneously provide the mechanism shown in FIGS. 6 and 7 in a limited space. Therefore, when giving priority to uneven light quantity,
Regarding increasing the light quantity of the fluorescent lamp by inserting the shading correction mechanism as shown in FIG. 6, the light quantity of the fluorescent lamp itself must be increased instead of the method shown in FIG. Further, when the light quantity of the fluorescent lamp is prioritized, a reflector as shown in FIG. 7 is provided, and instead of the method shown in FIG. 6, light quantity unevenness adjustment is performed, and a slit for light quantity adjustment is provided near the lens with high accuracy. Had to do it in no way.

An object of the present invention is to provide a mechanism for performing shading correction as shown in FIG. 6 and a system for increasing the amount of light as shown in FIG. 7 in a limited space. It is a thing.

Further, when the correction as in the second conventional example is performed, there is a problem that the gradation cannot be obtained when the correction amount is large. For example, assuming that the amount of light in the surrounding area is half that in the vicinity of the optical axis, if shading correction is performed using the above method,
While there are 256 gradations near the optical axis, there are 64 gradations in the periphery.

Another object of the present invention is to solve the above-mentioned problems and to provide an image reading apparatus which operates well and is reliable.

[0024]

In order to achieve the above object, one solution means according to the present invention is to illuminate an original image with a linear light source such as a fluorescent lamp, and to use an image reading sensor such as a CCD to read the original. In an image reading device for reading an image, a reflecting surface is formed on one surface of a plate-like member provided in the vicinity of the image reading portion, and a surface having a constant density is formed on the opposite surface of the plate-shaped member. The position at which the reflection surface side of the plate member is substantially perpendicular to the reflected light of the illumination light on the original surface is the first position, and the surface of the plate member formed at a constant density is substantially perpendicular to the optical path of the image. Then, the position illuminated by the illumination light from the fluorescent lamp directed to the document surface reading position is set as the second position, and the first position and the second position can be switched appropriately. According to the solving means, one side of the plate-like member provided in the vicinity of the original image reading position is used as a reflection surface, and the other side is used as a surface having a constant density that serves as a reference for shading correction, and these surfaces are required. It is performed by switching accordingly.

Another solution of the present invention relates to an image reading apparatus which illuminates an original image with a linear light source such as a fluorescent lamp and reads the original image with an image reading sensor such as a CCD. It is characterized in that it is fixed in the vicinity of the reading unit, and the image light of the original document and the reflected light of the plate-like member having a constant density are appropriately switched and read by an image reading sensor such as CCD. According to the solution,
A surface having a constant density that serves as a reference for shading correction is fixed near the image reading unit at a position different from the image reading position, and the optical path is appropriately switched between reading the original image and shading correction.

Another solution of the present invention is to read an image formed by a plurality of photoelectric conversion elements on an image plane formed by irradiating a developed film with light and enlarging and projecting the transmitted light. In a device for scanning image information by scanning with a sensor and converting the analog signal into a digital signal, a magnification detecting unit for detecting a magnification of a projection lens, a unit for storing shading information in a sub-scanning direction, and a light receiving unit of a photoelectric conversion element. In addition to the means for varying the area of the section, the magnification of the projection lens at the time of scanning is read by a scanning start command, and shading correction is performed while varying the area of the light receiving section based on the shading information read in advance in the sub-scanning direction. It is characterized by performing. According to the solving means, the light receiving area of the photoelectric conversion element is varied based on the pre-measured shading correction data in the sub-scanning direction, so that it is possible to easily perform the shading correction and maintain the gradation.

[0027]

EXAMPLES Next, examples of the present invention will be described.

<Embodiment 1> An embodiment of the present invention will be described in detail with reference to FIGS.

(Arrangement of Apparatus) FIG. 1 is a sectional view of a reading portion of an image reading apparatus incorporating the present invention, and FIG. 2 is a perspective view thereof. The image reading unit shown in FIG. 1 is configured to read both sides of a document. Figure 1
In the figure, 201 is a manuscript, and 202, 203 and 20
Reference numerals 4 and 205 denote transport rollers which are in pressure contact with each other and rotate in the direction of the arrow. Reference numerals 206 and 207 are guide plates, which are provided in parallel so as to form the document conveyance path A. Guide plate 20
6, 207 are provided with transparent portions 206a, 207a. Reference numeral 214 denotes a fluorescent lamp, which has a transparent opening 214a and a reflecting surface 214b (hatched portion in the figure) on the inner wall of the tube of the fluorescent lamp, and directs the transparent opening 214a to the original reading position.
The surface of the original 201 is illuminated through the transparent portion 206a of the guide plate 206. Reference numeral 216 is a plane mirror, 219 is an imaging lens, and 220 is an image reading sensor such as a CCD. Reference numeral 208 denotes a plate-shaped member that is rotatably attached around the axis 208d. One surface 20 of the plate member 208
A reflecting surface is formed on the surface 8a, and a surface having a reflection density that serves as a reference when shading correction is performed is formed on the other surface 208b. Further, an arm 208c is provided at the end of the plate member 208, and a spring 220 is attached to the end of the arm 208c to urge the plate member 208 counterclockwise. At this time, the plate member 208 is locked at the position shown in the figure by the stopper 212. The position of the plate member 208 at this time is the fluorescent lamp 214.
When the illumination light 226 directed to the document surface is the incident light and the reflected light on the document surface is 227, the reflection surface 208a is at a position substantially perpendicular to the reflected light 227.
A plunger 210a is attached to the arm 208c of the plate member 208, and when the solenoid 210 is energized, the plate member 20 is resisted against the spring 220.
8 is rotated clockwise to be rotationally moved to a position indicated by a chain double-dashed line substantially parallel to the original 201.

The above is the apparatus configuration for reading the surface of the original 201. Next, a device configuration for reading the back surface of the original 201 will be described.

Reference numeral 215 is a fluorescent lamp for illuminating the back surface of the original.
221 is a plane mirror, 224 is an imaging lens, 225 is C
An image reading sensor for a CD or the like. Reference numeral 209 denotes a plate-shaped member similar to the plate-shaped member 208 described above, and has a reflecting surface 209.
a and a surface 209b having a reflection density that serves as a reference when shading correction is performed. 213 is a stopper, 222 is a spring, and 211 is a solenoid.

The operations of the plate member 209, the spring 222, the solenoid 211, etc. are the same as those of the plate member 208, the spring 220, and the solenoid 210 described above.

(Operation of Apparatus) The original 201 is nipped by the conveying rollers 202, 203 and the conveying rollers 204, 205 and is fed in the direction of arrow B at a constant speed. At this time, the plate-like members 208 and 209 have reflection surfaces 208a, 208a for the reflected lights 227, 227 on the original surfaces of the fluorescent lamps 214, 215.
Springs 212 and 2 so that 209a is at a substantially right angle.
22 in the position shown by the solid line in the figure. As a result, the reflected light 2 on the original surface of the fluorescent lamps 214 and 215 is reduced.
27 and 227 are reflected by the reflecting surfaces 208a and 209a of the plate member, and the reflected light illuminates the original surface again, and the fluorescent lamp 2
The amount of light can be increased as compared with the case of illuminating the surface of the original with only 14 and 215.

When the original 201 is not in the conveyance path A, the solenoids 210 and 211 are energized, and the plate members 208 and 209 are moved by the respective plungers 208d and 209d.
Is rotated about the axis to reach a position substantially parallel to the original 201, which is indicated by a chain double-dashed line in the figure. At this time, the plate-shaped member 20
Surfaces 208b, 209 formed with a constant density of 8,209
b is illuminated by the fluorescent lamps 214 and 215, and the illumination light thereof is the same as the image light (shown by the one-dot chain line in the figure).
And 221 and C through the imaging lenses 219 and 224.
It is led to CD220,225.

Here, since the original illumination light by the reflector is not included in the illumination light for shading correction, the illumination light for the original is different from the illumination light for shading correction. However, since the amount of illumination light from the reflector is 20% to 30% of the amount of light from the fluorescent lamp, the unevenness of the amount of light caused by this can be practically ignored as an error. However, the light quantity of the reflector with respect to the light quantity of the fluorescent lamp can be approximated by multiplying the light quantity of the fluorescent lamp by a constant coefficient. Therefore, it is possible to improve the accuracy of the shading correction by making the correction in consideration of that amount.

<Embodiment 2> FIG. 3 is a sectional view showing another embodiment of the present invention.

Reference numeral 231 in the drawing denotes a plate-like member rotatably mounted around the axis 231d. A reflecting surface is formed on one surface 231a of the plate member 231, and the other surface 23
On 1b, a surface having a reflection density that serves as a reference when shading correction is performed is formed. Reference numeral 230 denotes a guide plate having a transparent portion 230a for reading a document image. Further, a moltoprene 235 is attached around the image reading portion 230a of the guide plate 230. Arms 231c are provided at both ends of the plate member 231,
A spring 233 is attached to the end of the arm 231c, and urges the plate member 231 in the clockwise direction to lock the plate member 231 at the position indicated by the chain double-dashed line in the figure. 23
Reference numeral 4 denotes a solenoid, which is an arm 231 of the plate member 231.
Through the plunger 234a attached to c, the plate member 231 is rotated counterclockwise about the axis 231d to the position shown by the solid line in the figure. That is, the solenoid 2
By turning on / off 34, the plate-like member 231 is switched between the position shown by the solid line and the position shown by the chain double-dashed line as shown in the above embodiment, and functions to increase the light amount when reading the original image, and at other times. Performs shading correction.

Here, when the plate-shaped member 231 is in the position shown by the chain double-dashed line, the plate-shaped member 231 is in the form of maltoprene 235.
And press the button on the surface of the image reading unit 230a.
It covers 30b. Therefore, the image reading unit 23
The surface 230b of 0a is shielded from the outside.

However, the moltoprene 235 is the plate-shaped member 2
It is not particularly necessary if the surface 230b of the image reading section is shielded from the outside by only 31.

If dust or the like adheres to the image reading portion of the transparent portion 230a of the guide plate 230, the image of that portion cannot be read. In particular, when reading digitally pixel by pixel using an image reading sensor such as a CCD, even a small amount of dust affects the reading of an image.

Normally, the side of the surface 230c that contacts the original document can be divided by the conveying path, that is, the surface indicated by the original document 1, in consideration of the case where a thin original document is jammed. Therefore, although dust can be easily cleaned on the 230c surface side of the document reading portion (the side in contact with the document 1),
Dust cannot be easily cleaned on the opposite surface 230b side. However, as shown in the present invention, the plate-shaped member 231 is operated when the apparatus is not operating except when the image is read.
By covering the image reading section with, it is possible to prevent the attachment of dust. However, in this case, dust adheres to the reference surface for shading correction of the plate-shaped member, but in the case of shading correction, the place where the change in the light amount changes abruptly should be removed as an abnormal state due to dust. This can avoid this problem.

<Third Embodiment> FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 4 shows a case where the reading member of the guide plate 230 shown in FIG. 3 does not have the transparent member 230a. In FIG. 4, reference numeral 240 is a guide plate, and a slit-shaped hole 240a is provided in the image reading unit. And around the slit-shaped hole, as in the case shown in FIG.
5 is attached. Reference numeral 241 is a plate-like member similar to that described above, and is switchably attached to the position shown by the solid line and the position shown by the chain double-dashed line in the figure. Then, at the position indicated by the chain double-dashed line, the moltoprene 245 is pressed and the slit-like holes are closed.

If the image reading section shown in FIG. 4 does not have a transparent member, dust will not adhere to the reading section, but foreign matter will enter the apparatus when the conveyance path is opened due to a jam of a thin paper document or the like. There is a risk of entering. But Figure 4
Such a problem can be prevented by closing the hole with the plate member 241 as shown in FIG.

<Embodiment 4> FIG. 5 is a sectional view showing another embodiment of the present invention.

FIG. 5 shows the plate member 208 shown in FIG. 1 in which the reflecting surface side is concave. As a result, when the reflected light of the document illumination light on the document surface is reflected again on the surface 251a of the plate-shaped member 251, the reflected light can be condensed on the image reading unit, and the light amount can be further increased. Further, by forming the plate-shaped member 251 in the shape as shown in the figure, the strength in the longitudinal direction (direction perpendicular to the paper surface) can be increased, and uneven reflection due to bending of the plate-shaped member can be prevented.

<Embodiment 5> FIG. 8 is a sectional view of an image reading apparatus which best shows the features of the present invention. The image reading unit shown in FIG. 8 is configured to read both sides of a document. In FIG. 8, S is the originals 401 and 40.
Numerals 2 and 403, 404 are conveying rollers which are in pressure contact with each other and rotate in the direction of the arrow. Reference numerals 405 and 406 denote guide plates which are parallel to each other so as to form a document conveyance path, and transparent portions 405a and 405.
6a is provided. Reference numeral 411 denotes a fluorescent lamp, which has a transparent opening 411a and a reflecting surface 411b on the inner wall of the fluorescent lamp.
A transparent opening 411a having a (shaded area in the figure) is directed to the original reading position, and the surface of the original S is illuminated through the transparent portion 405a of the guide plate 405. 414, 415, 41
8 is a plane mirror, 416 is an imaging lens, 417 is a CCD
An image reading sensor such as the above, and the reading system unit H. Reference numerals 407 and 408 denote shading reference plates, on which surfaces 407a and 408a having reflection densities serving as a reference when performing shading correction are formed. Reference numerals 409 and 410 are plate-shaped members, and reflection surfaces 409a and 41
0a is formed and the illumination light 412 directed to the document surface of the fluorescent lamps 411 and 411 is the incident light, and the reflected light on the document surface is 413, the reflected surface 409 is reflected by the reflected light 413.
The positions a and 410a are substantially right angles. The above is the apparatus configuration for reading the image of the original S, and the reading system unit H is shown only on the front side in FIG. 8, but the same unit configuration is also provided on the back side (not shown).

The original S is nipped by the conveying rollers 401, 402 and 403, 404 and is fed in the direction of arrow A at a constant speed. At this time, the plane mirror 418 closest to the imaging lens in the reading system unit H is at the solid line position, the optical path of the image light becomes B, and the image is formed on the image reading sensor 417 such as CCD. Further, when the document S is not in the image reading section, the plane mirror 418 is at the position of the chain double-dashed line, and the shading reference plate 40 illuminated by the fluorescent lamp 411.
The illumination light reflected by the reflection surface 407a of the optical path 7 passes through the optical path C and is imaged on the image reading sensor 417 such as CCD.

Next, FIG. 9 and FIG. 10 are a perspective view and a sectional view showing the operation of the plane mirror 418. Ha, H
Reference numeral b is a sheet metal cut and raised from the reading system unit. The flat mirror 418 is pulled by the spring 421 around the fulcrum 420a when the original image is read, and the flat mirror 418 is attached to the flat metal plate 4.
It moves in the X direction in FIG. The plane mirror 418 moved in the X direction is positioned by hitting the sheet metal Ha cut and raised from the reading system unit H at two points and at Hb at one point. At the time of shading correction, the solenoid 422 is energized, the plane mirror 418 moves in the Y direction in FIG. 9, and is abutted and positioned at one point on the sheet metal Ha and at two points on Hb. The reason why the plane mirror 418 closest to the imaging lens can be moved is that the closer to the imaging lens 416, the longer the mirror length in the longitudinal direction as shown in the plan view in which the image reading width direction is linearly shown in FIG. Can be shortened. Since the plane mirror 418 is positioned by the cut-and-raised portions 419a of the metal plate 419 located substantially in the center of the flat-mirror 418 and the cut-and-raised portions Ha and Hb of the reading system units H at both ends, the plane mirror is long in the longitudinal direction. The longer the length, the easier the distortion.

<Embodiment 6> FIG. 12 is a sectional view of an image reading portion showing another embodiment of the present invention. 45 in the figure
Reference numerals 1 and 452 are surfaces of constant density that serve as a reference for shading correction. By mounting the shading reference plate on the side of the document S conveyance path, the shading correction can be performed at substantially the same position as the image reading position, so that more accurate shading correction can be performed. G in the figure
Is an optical path for shading correction, and F is an optical path for image reading, and switching is appropriately performed.

<Embodiment 7> FIG. 13 is a sectional view of a reading system unit according to another embodiment of the present invention. In the figure, reference numeral 461 is a plane mirror closest to the imaging lens side for refracting the original image light. When the original image is read when the plane mirror 461 is at the solid line position, the optical path of the original image light is D (two-dot chain line), and the image is formed on the image reading sensor 417 such as CCD by the imaging lens 416. At the time of shading correction, the plane mirror 461
, The angle is switched to the position of the broken line, and the illumination light at this time becomes the optical path E (one-dot chain line), and C is generated by the imaging lens 416.
An image is formed on an image reading sensor 417 such as a CD. The conversion of the angle of the plane mirror 461 can be appropriately switched by a solenoid (not shown) or the like. Further, the image reading unit (not shown) is the same as in the above-described embodiment, and the illumination light E from the shading reference plate has a slight difference in angle with respect to the right angle, but it can be practically ignored as an error. In this device,
By minutely changing the angle of the plane mirror 461, the reading of the original image and the switching of the shading correction can be switched, which is advantageous in that the apparatus can be simplified.

<Embodiment 8> FIG. 14 is a sectional view of a reading system unit according to another embodiment of the present invention. At the time of reading the original image, the reading system unit H is at the solid line position, and the original image light becomes F (two-dot chain line), and is imaged by the image forming lens 416 on the image reading sensor 417 such as CCD. At the time of shading correction, the entire reading system unit H moves to the position of H ', and the plane mirrors 414, 415, 418 move to 414', 415 ', 41.
The 8'imaging lens 416 moves the image reading sensor 417 such as 416'CCD to 417 '. The optical path of the illumination light from the shading reference plate is G (one-dot chain line)
Becomes The image reading unit is not shown. Further, in this apparatus, since the switching of the optical path is the entire movement of the reading system unit H, even if the movement is performed with a little rough movement, there is not much influence.

<Embodiment 9> FIG. 18 is a schematic diagram showing the construction of a ninth embodiment of the present invention.

This is a microfilm reader scanner and has the following structure.

The light from the exposure lamp 701 which is a light source is
The light is condensed by the condenser lens 702, and the mirror M1
The light is directed upward at and is further condensed by the field lens 703. The microfilm F sandwiched by the film carrier 704 is irradiated from below. The image on the microfilm F is magnified by the projection lens 705, turned by the mirrors M2 and M31, and projected on the screen 706. This optical path is the leader optical path. The reader is effective for various settings such as confirmation during image reading and image editing.

Next, the reading optical path will be described. Here, the photoelectric conversion element 707 uses a line sensor such as a CCD. When an image reading is instructed from the operation unit or the like, the mirror 731 is rotated around M0 up to the position of M32 and then stopped, and then the photoelectric conversion element 707 is moved to the image plane 7
The image can be read by scanning 08 to the position 771 to prepare for image reading and then scanning to the position 772. The photoelectric conversion element 70 is used except when reading an image.
7 is stopped at the position shown in the figure. Therefore, the image plane 70
Since the image at 8 is magnified by the projection lens 705 to have the size of the original document, the length of the photoelectric conversion element 707 must be greater than or equal to the width of the size of the original document. Reference numeral 709 denotes a photoelectric conversion element 707 tilting mechanism of the present invention. (See FIG. 27 for details) FIG. 19 is a block diagram showing the flow of an image signal. The image on the microfilm is photoelectrically converted by the photoelectric conversion element 707 and input to the amplifier circuit 721. It is input to the image processing circuit 724 through the A / D conversion circuit 722 and the shading correction circuit 723. After the image processing, the image is output to the image forming apparatus 727 such as a printer through the printer interface circuit 725. Reference numeral 726 is an operation unit.

FIG. 20 shows an image area on the image plane 708. The x direction indicates the main scanning direction, and the y direction indicates the sub scanning direction. The xy plane becomes the image plane 708. The origin is the center of the optical axis.

Now, by examining how the light amount unevenness in the image area on the image plane 708 is examined with the above-mentioned structure, it is as shown in FIG. In FIG. 9A, the horizontal axis represents the position x in the main scanning direction, and the vertical axis represents the light amount I (x) at that position. Further, in (o), the horizontal axis represents the position y in the sub-scanning direction, and the vertical axis represents the light amount I (y) at that position. The amount of light is the most along the optical axis, and the amount of light decreases toward the periphery.

FIG. 24 shows a case where the image forming surface 708 is moved in parallel with the photoelectric conversion element 707 facing downward on the optical axis. The point P is the position of the pupil of the projection lens 705. The distance from the point P to the center O of the optical axis of the image plane is L0. When the photoelectric conversion element 707 moves from point O to y2, the light receiving portion is inclined by θ. This θ is represented by the following equation.

Θ = tan ⁻¹ (y2 / L0) (4) Therefore, the apparent light receiving area S ′ is given by the following equation.

S ′ = S * (cos θ) (5) The reduction of the apparent light receiving area also reduces the read data.

This means that the photoelectric conversion element 707
The data read by means that it is necessary to consider the inclination θ from the normal to the point P of the photoelectric conversion element 707, in addition to the uneven light amount due to the aberration of the projection lens shown in FIG.

The intentional use of this is
This is the content of Example 9.

As shown in FIG. 25, at the same position y2 as the above position, by tilting the photoelectric conversion element 707 by the inclination δ from the normal to the point P, the apparent light receiving area S ″ is given by the following equation. .

S ″ = S * (cos δ) (6) FIG. 23 is a diagram summarizing the above and explaining in principle how shading correction should be applied.

In FIG. 23A, the cross section in the main scanning direction passing through the optical axis, that is, the horizontal axis is the position y from the optical axis in the sub scanning direction, and the vertical axis is the data D (y) read by the photoelectric conversion element 707. It is a thing. The data of the image edge y1 is D. Figure 2
In (3), (b), the horizontal axis is the position y from the optical axis in the sub-scanning direction, and the vertical axis is the apparent light receiving area S ′ (y) of the photoelectric conversion element 707. . S is θ = 0
When the angle is °, that is, the area of the light-receiving portion originally possessed.

The relationship between S '(y) and the sub-scanning direction shading correction data V (y) can be expressed by the following equation.

S ′ (y) = S * D / V (y) (7) In FIG. 23C, the horizontal axis represents the position y from the optical axis in the sub-scanning direction, as in (A). The vertical axis represents P of the photoelectric conversion element 707.
The inclination angle θ (y) from the normal to the point is taken.

The relationship between θ (y) and S '(y) can be expressed by the following equation.

S ′ (y) = S * cos θ (y) (8) From formulas (7) and (8), cos θ (y) = D / V (y) (9), and satisfy this. It is understood that the shading correction in the sub-scanning direction can be performed by tilting the photoelectric conversion element 707 by θ (y).

Since the output is lowered because it is adjusted to D, it is necessary to increase the gain in the amplifier circuit 721 by 256 / D times when reading the actual image data, compared with when reading the shading correction data.

Since the value of the shading correction data V (y) varies depending on the magnification of the projection lens 705, it is necessary to detect the magnification. FIG. 26 shows its schematic structure. A black-and-white label 731, that is, an encoder is attached to the outer periphery of the projection lens 705, the rotation angle is read by the reflection type photo interrupter 732, and the magnification is detected from the relationship table of the rotation angle and the magnification stored in advance. When there are many projection lenses, although not shown, it is naturally necessary to identify the lenses.

FIG. 27 is a schematic structure of a mechanism for tilting the photoelectric conversion element 707.

Reference numeral 741 denotes a bearing of a shaft 745 attached to the photoelectric conversion element 707, and a gear 742 attached to the shaft 745 is connected to a gear 743 attached to the shaft of the stepping motor 744. Although not shown here, these are mounted on a scanning table for scanning in the sub-scanning direction.

FIG. 28 is a block diagram of a controller section which controls the series of operations. CPU752
Counts the pulses sent from the reflection type photo interrupter 732 via the interface 755, detects the magnification from the information stored in the memory 756, and calls the shading correction data corresponding thereto from the memory 756. The CPU 752 is the operation unit 757.
Scanning is started by the scanning command from and the motor drive 7
By 54, the scan motor 744 begins to rotate. A stepping motor is often used as the scan motor 744. For stepping motors, CPU
Since the position of 752 in the sub-scanning direction is known, the stepping motor 751 for tilting the photoelectric conversion element 707 is rotated via the motor drive 753 based on the correction value for that position.

The result of the shading correction applied in this way is as shown in FIG.

<Embodiment 10> Embodiment 10 is a further modification of the portion of Embodiment 9 for varying the light receiving portion area.

As shown in FIG. 29, the photoelectric conversion element 707 is used.
The shutters 761 and 762 are arranged directly under the shutter, and the light receiving area is changed by hiding a part of the light receiving portion 707 ′ of the photoelectric conversion element 707 with the shutters 761 and 762. The stepping motor (not shown) is rotated by an amount corresponding to the position of the photoelectric conversion element 707 in the sub-scanning direction,
Rotate the gears 763 and 764 to release the shutters 761 and 76.
It is to move 2.

As described in the ninth embodiment, the moving amount is such that S '(y) that satisfies the expression (7) is obtained.

<Embodiment 11> Embodiments 9 and 10
The shading correction in the sub-scanning direction has been described above. However, in the eleventh embodiment, the shading correction in the main-scanning direction can be, of course, a conventional correction method using a ROM. (Refer to the formula (1) in the conventional example.) However, when the correction amount is large, the gradation decreases.
Therefore, in the present embodiment, shading correction is simultaneously applied in the main scanning direction and the sub scanning direction. Figure 3
0 is a view as seen from the light receiving portion side of the photoelectric conversion element 707. An opaque elastic body 782 having a hollowed inside is arranged on the upper surface of the light receiving portion 707 ', and a plurality of cams 781 are provided outside thereof.
Is arranged so that the area of the light receiving portion 707 'can be made variable.

In the cross section in the sub-scanning direction including the optical axis, if the data at the end in the main scanning direction is E, the light receiving area S '(x,
y) can be expressed by the following equation.

S ′ (x, y) = S * E * D / (H (x) * V (y)) The cam 781 is rotated so as to meet this expression, and shading in the main scanning direction and the sub-scanning direction is performed. Can be corrected.

[0083]

As described above, according to the first to fourth aspects of the present invention, one of the plate-like members is a reflecting surface and the other is a surface having a constant density which serves as a reference for shading correction. Since the surface is switched as needed, a mechanism for increasing the amount of illumination light on the image reading surface and a mechanism for shading correction can be realized in a limited small space. Moreover, when the image reading unit is provided with a transparent member except when the original image is being read, that is, when the apparatus is not operating, dust is not transferred to the image reading unit when the image reading unit is provided with a transparent member. Adhesion can be prevented, and if the image reading unit is not provided with a transparent member, there is an advantage that foreign matter is prevented from entering the apparatus.

According to the fifth to eighth aspects, a surface having a constant density serving as a reference for shading correction is fixed near the image reading portion at a position different from the image reading position, and at the time of reading the original image, By switching the optical path appropriately during shading correction, there is an effect that a space near the image reading unit can be secured and highly accurate shading correction can be performed. Moreover, there is an advantage that the reflection plate is provided at a position facing the fluorescent lamp by securing a space near the image reading unit, and the reflected light of the illumination light on the document surface is reflected again to illuminate the document, thereby increasing the light amount. .

According to the ninth aspect, by changing the light receiving area of the photoelectric conversion element, it is possible to perform shading correction without impairing gradation. Further, as in the conventional case, since the correction data is stored in lines in both the main scanning direction and the sub scanning direction, the correction can be performed with a very small amount of memory.

[Brief description of drawings]

FIG. 1 is a sectional view of an image reading unit in an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the image reading apparatus shown in FIG.

FIG. 3 is a diagram showing a second embodiment of the image reading apparatus according to the present invention.

FIG. 4 is a diagram showing a third embodiment of the image reading apparatus according to the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the image reading apparatus according to the present invention.

FIG. 6 is a cross-sectional view showing an example of an image reading unit in a conventional image reading apparatus.

FIG. 7 is a cross-sectional view showing another example of the image reading unit in the conventional image reading apparatus.

FIG. 8 is a diagram showing a fifth embodiment of the image reading apparatus according to the present invention.

FIG. 9 is a perspective view of a plane mirror operation unit.

10 is a cross-sectional view of the operation unit of FIG.

FIG. 11 is a plan view linearly showing the image reading width direction.

FIG. 12 is a sectional view of an image reading unit in a sixth embodiment according to the present invention.

FIG. 13 is a sectional view of an image reading system unit according to a seventh embodiment of the present invention.

FIG. 14 is a sectional view of an image reading system unit according to an eighth embodiment of the present invention.

FIG. 15 is a schematic configuration diagram of a ninth embodiment of the present invention.

FIG. 16 is a block diagram showing the flow of an image signal.

FIG. 17 is an explanatory diagram of an image area on the image plane.

FIG. 18 is a conceptual diagram of light amount unevenness in the image area on the image plane.

FIG. 19 is data after shading correction of the present invention.

FIG. 20: Shading correction data and photoelectric conversion element 7
07 Explanatory diagram of relationship with tilt angle

FIG. 21 is an explanatory diagram of changes in the light-receiving area by conventional scanning.

FIG. 22 is an explanatory diagram of a light receiving area change of the present invention.

FIG. 23 is a schematic diagram of a magnification detection mechanism for projection magnification.

FIG. 24 is a schematic view of a photoelectric conversion element 707 tilting mechanism of the present invention.

FIG. 25 is a block diagram of a photoelectric conversion element 707 tilting mechanism control according to the present invention.

FIG. 26 is a schematic diagram of a shutter mechanism of the tenth embodiment.

FIG. 27 is a schematic diagram of a light-receiving area variable mechanism of Example 11.

FIG. 28 is a conventional shading correction block diagram.

[Explanation of symbols]

202, 203, 204, 205 ... Conveying rollers 206, 207 ... Guide plates 208, 209 ...
Plate-shaped members 210, 211 ... Solenoids 212, 213 ...
Stoppers 214, 215 ... Fluorescent lamps 220, 222 ...
Spring 230 ... Guide plate 231 ... Plate member 233 ... Spring 234 ... Solenoid 251 ... Plate member S ... Original document 401, 402, 403, 404 ... Conveying roller 405, 406 ... Guide plate 407, 408 ... Shading reference plate 409, 410 ... Reflector 411 ... Fluorescent lamp 414, 415, 418 ... Planar mirror 416 ... Imaging lens 417 ... Image reading sensor 707 ... Photoelectric conversion element 732 ... Photo interrupter 751 ... Stepping motor 752 ... CPU

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiko Ito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akira Fukasawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Naoki Manabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (9)

[Claims] 1. An image reading apparatus for illuminating a document image with a linear light source such as a fluorescent lamp and reading the document image with an image reading sensor such as a CCD, wherein one surface of a plate-like member provided in the vicinity of the image reading section is provided. Forms a reflecting surface, and a surface having a constant density is formed on the opposite surface thereof, and the reflecting surface side of the plate member is substantially perpendicular to the reflected light of the illumination light from the fluorescent lamp on the original surface. With the position being the first position, the surface of the plate-shaped member formed at a constant density is substantially perpendicular to the optical path of the image,
An image reading apparatus characterized in that a position illuminated by illumination light from a fluorescent lamp directed to a document surface reading position is set as a second position, and the first position and the second position can be appropriately switched. . 2. The plate-shaped member in the image reading device,
When the second position is substantially perpendicular to the image light, the plate-shaped member covers the surface of the image reading unit made of a transparent member provided on the guide plate to form the image reading unit. The image reading apparatus according to claim 1. 3. The plate-shaped member in the image reading device,
When the second position is substantially perpendicular to the image light, the plate-shaped member covers the image reading portion, which is a slit-shaped hole provided in the guide plate to form the image reading portion. The image reading apparatus according to claim 1. 4. A plate-shaped member of the image reading apparatus, wherein a surface of the plate-shaped member corresponding to the reflected light of the document illumination light on the document surface is formed in a concave shape so as to be focused on the image reading position. The image reading device according to claim 1. 5. An image reading apparatus for illuminating an original image with a linear light source such as a fluorescent lamp and reading the original image with an image reading sensor such as a CCD, wherein a plate-like member having a constant density is fixed near the reading portion, An image reading apparatus characterized in that the image light of a document and the reflected light of a plate-like member having a constant density are appropriately switched and read by an image reading sensor such as a CCD. 6. When the original image light of the image reading device is refracted by a plane mirror and an image is formed on an image reading sensor such as a CCD by an image forming lens, the plane mirror closest to the image forming lens is positioned with respect to the reflecting surface. 6. The document image light and the reflected light of a plate-shaped member having a constant density are appropriately switched by moving in the vertical direction.
The image reading device described. 7. When the original image light of the image reading device is refracted by a plane mirror and an image is formed on an image reading sensor such as a CCD by an image forming lens, the plane mirror closest to the image forming lens is reflected by the original image light. 6. The image reading apparatus according to claim 5, wherein the image light of the original document and the reflected light of the plate-shaped member having a constant density are appropriately switched by rotating around the position. 8. An original image light and a constant density are obtained by moving an entire reading system including an image reading sensor such as CCD, an image forming lens, a plane mirror, etc. in the image reading apparatus in parallel with a document conveying direction. The image reading apparatus according to claim 5, wherein the reflected light of the plate-shaped member is appropriately switched. 9. An image reading sensor made up of a plurality of photoelectric conversion elements scans an image plane formed by irradiating the developed film with light and enlarging and projecting the transmitted light to obtain image information. In a device for reading and converting the analog signal into a digital signal, a magnification detecting means for detecting the magnification of the projection lens, a means for storing shading information in the sub-scanning direction, and a means for varying the area of the light receiving portion of the photoelectric conversion element. An image characterized by reading the magnification of the projection lens at the time of scanning by a scan start command, and performing shading correction while varying the area of the light receiving unit based on the shading information in the sub-scanning direction that was read in advance. Reader.