JP3200125B2 - Image scanner apparatus and image scanning method - 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 scanner and an image scanning method for reading an original while transporting the original in a printing machine or the like.

[0002]

2. Description of the Related Art A conventional image scanner of this type is disclosed in Japanese Utility Model Laid-Open Publication No. 63-144751, and its main part is as shown in FIG. Here, 1 'is an original pressing plate, 2 is a contact glass, 3 is a reflecting mirror, 4 is a light source, 5 is a reflecting mirror, and 6 is an original. The light is radiated from the light source 4 and read while moving in the direction of the arrow between and the image passes through the contact glass 2 and is sent to the reflection mirror 3.

The image signal read by scanning the original in this manner includes uneven illuminance of the original 6 and COS 3 of the lens 3.
This includes distortion due to a power law, a variation in sensitivity of each pixel of the one-dimensional image sensor 11 described later, and the like, and this distortion is generally called shading distortion. If such a shading distortion is left unattended, it adversely affects the copied image. Therefore, correction is performed by a shading correction device. A general operation procedure at that time is to first read a white reference image and to correct the image signal of the next document to be read using the image signal as a shading distortion signal. As A
Next, a method of changing the conversion voltage range of the / D conversion circuit will be described.

FIG. 4 shows an operation control circuit of the shading correction device. In such a circuit, the surface of the original pressure plate 1 'on the side of the contact glass 2 is white so as to be used as a reference surface of a white image. Surface-treated,
First, light is irradiated from the light source 4 and read without transporting the original 6 between the original pressing plate 1 ′ and the contact glass 2, and the white reference image thus read is reflected by the reflection mirror 3. Then, the light is guided to the lens 10 and formed on the one-dimensional image sensor 11. Then, the read white reference image signal is amplified by the amplifier 12, and the voltage Vs
ig (FIG. 6) is output, and this signal is input to a peak hold circuit 13, an A / D conversion circuit 16, and a black level detection circuit 14. At this time, the peak hold circuit 13 holds and outputs the highest voltage Vw (FIG. 6) among the input image signals, and this voltage Vw is input to the A terminal 21 of the analog switch 15. When the analog switch 15 reads the shading distortion signal, the voltage Vw is input to the VH terminal 23 of the A / D conversion circuit 16 because the A terminal 21 and the output terminal 22 are conductive when the shading distortion signal is read.
, The black reference voltage Vb in the input image signal
(FIG. 6) is detected and output, and this black reference voltage Vb is A /
It is input to the VL terminal 24 of the D conversion circuit 16. The A / D conversion circuit 16 sets the voltage Vw as an upper limit and the black reference voltage Vb as a lower limit.
A / D conversion is performed on the white reference image signal, that is, the shading distortion signal input to the terminal 26, and the result is output as a digital signal from the D terminal 25. At the same time, this digital signal is input to the input terminal 27 of the line memory 17 and Remembered,
Thus, the reading of the white reference image signal, that is, the shading distortion signal is completed.

Next, the reading of a document will be described. The original 6 is conveyed between the original pressing plate 1 'and the contact glass 2, and the original 6
Is input to the VH terminal 23 of the A / D conversion circuit 16, while the shading distortion signal stored in the line memory 17 is output from the output terminal 28, and this digital signal is
The signal is input to the D terminal 29 of the / A conversion circuit 18. This D /
The A conversion circuit 18 supplies the voltage Vw and the voltage Vb to the VH terminal 31,
The voltage is input to the L terminal 32, and the upper limit of the voltage Vw
D / A conversion of the digital signal is performed with the lower limit as a result. As a result, a voltage V <subscript D / A> is output from the A terminal 33, and the shading distortion signal previously read in this way is reproduced. Analog switch 15 when scanning originals
The B terminal 34 and the output terminal 22 are electrically connected to each other, and the reproduced shading distortion signal (V ▲ D / A ▼) is input to the VH terminal 23 of the A / D conversion circuit 16 and the VL terminal 24 Is the voltage Vb, and the image signal of the original is
A / D conversion is performed using the white reference image signal, that is, the shading distortion signal as an upper limit and the voltage Vb as a lower limit, and an image digital signal corrected for shading distortion is output from the D terminal 25.

When the shading correction is performed as described above, the surface of the original pressure plate 1 'is used as a reference for a white image. At this time, if the surface of the original pressure plate 1' is dirty, the original shading distortion is generated. In addition, as shown in FIG. 7, a noise component due to dirt on the surface of the original pressure plate 1 'is read as a white reference signal, so that shading distortion cannot be properly corrected, and the dirt is extremely difficult. However, there is a problem in that a white streak-shaped abnormal image appears in the sub-scanning direction at a position corresponding to the stain on the read image.

[0007]

In the conventional image scanner apparatus, as described above, the original pressing plate 1 'has a flat surface over its entire surface. Since the entire surface contacts the original 6, if images are present on both sides of the original 6, the surface of the original 6 is stained with an image material. Filling processing is performed using a filler called a filler such as titanium oxide, and since these fillers have high hardness, the surface of the original platen 1 'is shaved and becomes uneven, so that the image material is more easily attached. In addition, the dirt is hardly peeled off even after cleaning, and it is extremely difficult to prevent the dirt. Therefore, there is a problem that the shading distortion cannot be properly corrected.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional image scanner and image scanning method as described above, so that the image material of the original adheres to the surface of the original platen or is cut off by a filler to remove irregularities. It is an object of the present invention to provide an image scanning apparatus and an image scanning method that can appropriately correct shading distortion without causing the surface of the original pressure plate to become dirty without becoming dirty.

[0009]

SUMMARY OF THE INVENTION The present invention, in order to accomplish the above objects, the invention according to claim 1, Hara
Image scanner that scans documents while transporting them
, The white reference image for shading correction
The original pressure plate having a concave portion and a flat portion, and when reading a white reference image signal for shading correction,
Recess of the document pressing plate is disposed in the image reading position, the original
During image reading of manuscript it is characterized in that it has a pressing plate support mechanism for moving the flat portion of the document pressing plate to said image <br/> image reading position. According to a second aspect of the present invention, there is provided an image scanning method for reading a document while transporting the document , wherein a concave portion and a flat portion are provided in a document pressure plate used as a white reference image for shading correction, and shading is performed by a document pressure plate support mechanism. those during white reference image signal read for the correction, the recess of the document pressing plate disposed in the image reading position, at the time of image reading of the document, characterized by moving the flat portion of the document pressing plate to the image reading position It is.

[0010]

According to the first aspect of the present invention, since an area including a portion corresponding to an image reading position used as a white reference image for shading correction of a document pressure plate is formed as a concave portion, the image scanner provided with the concave portion. Depending on the device, when used in the same manner as the conventional image scanner device, the original does not come into contact with this portion, so that the original material adheres to the surface of the original pressure plate, or is shaved by the filler to become uneven. As a result, the surface of the document pressure plate is not stained, and the shading distortion can be corrected properly. According to the second and third aspects of the present invention, when used in the same manner as in the first aspect, when reading the white reference signal, the white reference signal is read in the same manner as in the first aspect of the invention, and the original is read. When reading the original, the original platen is moved in the sub-scanning direction, and the concave portion of the original platen is shifted from the position corresponding to the image reading position. This prevents the influence of the shadow of illumination from increasing at both ends of the document in the main scanning direction without increasing the level difference between the surface of the document and the surface of the document pressure plate.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the present invention shown in the drawings, the same parts as those of the prior art are denoted by the same reference numerals, and description thereof will be omitted, and different parts will be mainly described. In the embodiment of the present invention shown in FIGS.
Is an area including a portion corresponding to an image reading position used as a white reference image for shading correction is defined as a concave portion 7. An image scanner provided with such a document pressing plate 1 is used in the same manner as an image scanner including the above-mentioned conventional shading correction device, but since the document pressing plate 1 has a concave portion 7, As shown in FIG. 2, the original 6 does not come into contact with this portion, and therefore, the image material of the original 6 does not adhere to the surface of the original platen 1 or is not shaved by the filler to form irregularities. The surface is not stained, and the shading distortion in the shading correction device can be appropriately corrected.

In the above-described apparatus, the reading of the white reference signal is performed without any problem.
Since the step between the surface of the document 6 and the surface of the document pressure plate 1 is slightly increased, there is a problem that the influence of the illumination shadow is greater than that without the concave portion 7. The other embodiment shown in FIG. 3 can solve such a problem. In this embodiment, a vertical bracket 35 is attached to the back surface of the document pressing plate 1, and a long hole 36 is vertically provided in the bracket 35, while a solenoid 37 is attached to a printing machine body (not shown) and provided on an operating rod 38 thereof. The pin 39 is slidably fitted in the elongated hole 36, and a spring 40 is stretched between the tip of the pin 39 and the printing press main body. In such a case, when reading the white reference signal, the solenoid 37 is deactivated, and the original pressure plate 1 is pulled by the spring 40 and is at the solid line position. I do. When reading a document, the document pressure plate 1 is slightly moved upward by the document 6 to be carried in, and the solenoid 37 is operated.
The document pressure plate 1 is moved in the sub-scanning direction to the dashed line position against the force of the spring 40, and the concave portion 7 of the document pressure plate 1 is shifted from the position corresponding to the image reading position.
The surface between the surface of the document 6 and the surface of the document pressure plate 1 is slightly increased at both ends of the document in the main scanning direction, thereby increasing the influence of the shadow of illumination. To prevent

[0013]

The present invention is as described above. According to the first aspect of the present invention, a document is read while being conveyed.
In image scanners, shading correction
Used as a white reference image for
A document pressing plate that, the document at the time of white reference image signal read for shading correction, the recess of the document pressing plate is disposed at the image reading position, at the time of image reading of the document to move the flat portion of the document pressing plate to the image reading position Since the document scanner has a pressure plate support mechanism , in an image scanner apparatus having a document pressure plate disposed on the back of a document image conveyed and set at a reading position, the document pressure plate has a flat portion and a concave portion on the surface facing the document. Also, a document pressure plate support mechanism is provided so that a white reference image reading for shading correction and a document image reading are performed, and the concave portion of the document pressure plate is used when reading the white reference image. In the above, the document pressing plate is formed in an area of the flat portion facing the white reference image, and the reading platen is used when reading the white reference image. As a result, the concave portion is opposed to the white reference image, and the flat portion is arranged at a position not opposed to the white reference image. When reading the document image, the document pressing plate is moved by the support mechanism so that the flat portion is Since the concave portion is arranged so as to face the image and the concave portion thereof is not opposed to the original image, when the original is used in the same manner as the conventional image scanner device, the original is placed in a portion corresponding to the image reading position of the original pressing plate. Without touching
Therefore, the image material of the document does not adhere to the surface of the document pressing plate or is not shaved by the filler to form irregularities, the surface of the document pressing plate is not stained, and the shading distortion can be corrected properly. There is. According to a second aspect of the present invention, there is provided an image scanning method for reading an original while conveying the original, wherein the original pressing plate used as a white reference image for shading correction has
Section and a plane section, and when reading a white reference image signal for shading correction by the document pressure plate support mechanism,
Place the concave portion of the document pressing plate to the image reading position,
Since the time of image reading of the document to move the flat portion of the document pressing plate to said <br/> image reading position, both ends of the main scanning direction of the document, the step between the surface and the document pressing plate surface of the original is larger There is also an effect of preventing the influence of the shadow of illumination from increasing.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional front view when the sheet is passed.

FIG. 3 is a longitudinal sectional front view of another embodiment of the present invention.

FIG. 4 is a drawing similar to FIG. 2 of a conventional image scanner device of the same type as the present invention.

FIG. 5 is an operation control circuit diagram of the shading correction device according to the first embodiment;

FIG. 6 is a state diagram of a white reference image signal in the above.

FIG. 7 is a diagram showing a noise component generation state in the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original pressure plate 2 Contact glass 3 Reflection mirror 4 Light source 6 Document 10 Lens 11 One-dimensional image sensor 13 Peak hold circuit 14 Black level detection circuit 15 Analog switch 16 A / D conversion circuit 17 Line memory 18 D / A conversion circuit

Continuation of the front page (56) References JP-A-3-268676 (JP, A) JP-A 1-254063 (JP, A) JP-A 1-233874 (JP, A) Japanese Utility Model Application No. Sho 59-57212 ( Microfilm (JP, U) photographing the contents of the specification and drawings attached to the application form (Japanese Utility Model Application No. 60-169969) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/04- 1/207 G03B 27/50 G03B 27/62-27/64 G03G 15/00 303 H04N 1/40-1/409

Claims (2)

(57) [Claims] An image reading unit that reads an original while conveying the original;
For shading correction in a page scanner
Original that has a concave portion and a flat portion used as a white reference image of
And draft pressure plate, at the time of white reference image signal read for shading correction, the recess of the document pressing plate is disposed at the image reading position, at the time of image reading of the document the flat portion of the pressing plate
Image scanner, characterized in that it comprises a pressing plate support mechanism for moving the image reading position. 2. An image scanning method for reading a document while conveying the document , wherein a concave portion and a flat portion are formed on a document pressure plate used as a white reference image for shading correction.
A surface portion provided at the time of white reference image signal read for shading correction by the document pressing plate support mechanism, the arranged recesses of the original <br/> manuscript platen to the image reading position, at the time <br/> image reading of the document image scanning method characterized by moving the flat portion of the document pressing plate to the image reading position.