JPS63287160A - Picture reader - Google Patents

Abstract

PURPOSE:To correct difference in the output picture density caused when an original is located from an original radiating means by using the white level calibration plate of a 1st mode reading the stop original and a 2nd mode white calibration plate of a 2nd mode reading the carried original. CONSTITUTION:A transparent Mylar film 41 is provided between a platen glass 27 and an original read path 32 at a sheet mode. The original is radiated by the lighting unit 24 through the film 41 and the reflected light from the original reaches a CCD 22. The distance from the radiation unit 24 to the original differs from the light reflection position (b) in the book mode and the light reflecting position S in the sheet mode. The difference of the luminous quantity on the CCD face caused in reading between the sheet mode and the book mode for the picture of the same density is corrected by using white calibration plates 28, 29 provided separately and a shading correction circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is an apparatus that reads an original image using an optical sensor and converts it into a density signal, and then digitizes and reads the image using an A/D converter or the like. The present invention relates to an image reading device having a mode for reading a placed original and a mode for reading an original being transported.

[Conventional technology]

Conventionally, this type of image reading device has two modes: a mode in which a first reading means scans and reads the surface of a document placed on a glass or the like (hereinafter referred to as "book mode"), and a mode in which the document is conveyed by a conveying means. In some cases, copying machines and the like have been proposed that have a mode in which the document is read by a second reading means (hereinafter referred to as "sheet mode"), and the operation time t in sheet mode refers to the time when the document is once transported to the book mode position. After stopping the machine, it performs the Boo, Ku mode and reads the original.

However, such a configuration reduces throughput and
Since copying machines are not suitable for high-speed reading, there are also known copying machines that have a mode in which a document is read by a fixed reading means while being conveyed, and a book mode.

[Problem that the invention seeks to solve]

However, the document position in each mode must be placed at the same position with respect to the main body of the reading device.
There was a problem in that the arrangement of the conveyance path in both modes was difficult.

The present invention has been made by focusing on the above-mentioned problem, and by outputting a signal with a constant density even if the document position relative to the reading means is different between the book and sheet modes, it is possible to improve the transport path in both modes. The aim is to increase freedom of arrangement Jti.

(Means for Solving the Problems) In the image reading device according to the present invention, the stopped document placement means and the conveyed document placement device have different distances from the document irradiation device, but can read documents of the same density. When reading, white calibration plates are provided separately for the first mode and the second mode, and a shading correction means is connected to the output side of the A/D converter.

(Function) The image reading device of the present invention is characterized by the fact that the image reading device according to the present invention has a CCD reading mode that is
Using a white calibration plate, a shading correction means corrects the difference in the amount of light between the surfaces to an image signal that can be reproduced as the same density.

(Example) An example of this embodiment will be described below based on the drawings.

FIG. 1 is a block diagram showing the internal configuration of an image reading apparatus (hereinafter referred to as "reader") 1 of the present invention and the circuit configuration of a control unit.

Reference numeral 2 denotes a reader main body, in which a document on a platen glass 27 serving as stopped document placement means is irradiated by a document irradiation unit (hereinafter referred to as "irradiation unit") 24 serving as document irradiation means, and a reflecting mirror 25 . The light amount detection means 2 via the lens 26
A document image is formed on the CCD 22 of No. 1.

The light amount detection means 21 includes a COD drive circuit 203. which drives the CCD 22. It consists of an AMP 20 that amplifies the analog signal output from the COD driver 23 and the CCD 22, and an A/D converter 202 that converts the analog signal into a digital image signal and outputs it to the control unit 20.

3 is an automatic document feeder (hereinafter referred to as "ADF"),
The original on the original placing table 31 is conveyed in the direction of arrow B shown by the broken line, passes through the original reading path 32 as means for placing the conveyed original on the Mylar film 41, and is ejected to the original ejecting table 33. ing. (See FIG. 2) Next, the operation of the reader 1 will be described.

The reader 1 has a book mode, which is a first reading means, in which a bound original such as a book is placed on the platen glass 27 and the image is read by scanning with an optical system, and a general paper manuscript without a binding is read using the ADF 3. There are two modes: a sheet mode in which the second reading means reads the image while conveying the sheet;

First, regarding seat mode, the reader is always connected to an external device (digital, personal computer, etc.)
5, and control with these external devices 5 (communication with No. 3 and output of image signals to the external device 5 is performed via the interface circuit 207).

First, with a document placed on the document table 31 of the ADF 3 in the image orientation, the external device 5 sets the pixel density to 400 dpi and 300 dpi, for example.

200 dpi or set the image signal to 2
When an instruction for various modes, such as whether to use a value signal or a multi-value signal, is input, the CPU 208 that has received the input inputs the timing signal generation circuit 209 and the selector 20 in advance.
A control signal is output to B to set the pixel density and image signal.

゛ Also, it is confirmed whether or not the irradiation unit 24 is at the document reading position (the position shown in FIG. 2) in the ADF 3 using the signal 301 from the optical position sensor (not shown), and if it is not at the reading position. In this case, the irradiation unit 24 is moved to a predetermined position before starting the reading operation in response to the next document reading start command. When the start command is input from the external device 5 in this state, the CPO 208 outputs a lamp control signal 303 to turn on the lamp, and outputs a document feeding start command to the ADF 3 using an ADFftJI control signal 302. As a result, the original placed on the original placing table 31 is moved along the path shown by the broken line in FIG.
conveyed in the direction.

Note that this reader 1 uses a stepping motor as the motor used to transport the document and drive the optical system scanning, so by changing the frequency of the pulses used to drive the motor, transport and scanning can be controlled. You can freely choose the speed. Further, it is well known that whether or not the leading edge of the document has reached the document illumination position of the league main body 2 can be detected by a document leading edge detection sensor (not shown) provided in the ADF 3.

Until the document reaches the document illumination position, the image formed on the CCD 22 is converted into a digital value and input to the interface circuit 207 as described later, but since this is not the original image, the CPU 208 A control signal is given to the interface circuit 207 so as not to output the image signal.

When the document reaches the document illumination position, the CPO 208 outputs a control signal to enable image signal output to the interface circuit 207, and the read image signals are sent one after another to the external device 5. When the trailing edge of the document has finished passing the document illumination position, this is detected by the document leading edge detection sensor, and a control signal disabling image signal output is again given to the interface circuit 207 to stop outputting the image signal, and the document A reading end signal is output to the external device 5.

Thereafter, if a document reading start command is not received from the external device 5 within a certain period of time, the CPU 208 outputs a lamp control signal 303 to the lamp to turn it off and terminate the operation.

Next, we will discuss book mode.

In FIG. 2, the document is placed on the platen glass 27 so that the right end is the leading edge of the document, and the irradiation unit 24 has its right end in its initial position, and the optical position sensor (not shown) is placed in the sheet mode. (omitted) to confirm the position. Note that the pixel density and image signal settings before the start of document reading are the same as in the sheet mode.

When a document reading start command is input from the external unit 35, the CP
The O208 first outputs the lamp control signal 303 to turn on the lamp, but does not immediately start scanning for reading, and waits approximately 300 to 500 ms until the light intensity of the lamp stabilizes.
ec Wait. During this time, as in the sheet mode, the image signal is input to the interface circuit 207, but is not output to the external device 5 due to the control signal of the CPU 208.

When a document reading start command is input from the external unit N5, the irradiation unit 24 immediately starts scanning in the direction of arrow A. There is a distance of approximately 2 to 3 mm from the initial position of the irradiation unit 24 to the leading edge position of the document on the platen glass 27, and a motor drive control signal 304 is output and controlled so that the scanning speed of the optical system by the motor is stabilized during this time. ing. When the irradiation unit 24 reaches the leading edge position of the document, the CPU
208 outputs a control signal to enable image signal output to the interface circuit 207, and the read image signals are sent to the external device 5 one after another. The scanning length of the optical system is CPU20
8 is uniquely determined by the number of pulses that drive the motor, so when the CPU 20B outputs the required number of pulses, it determines that document reading is complete and turns off the lamp OF.
F, Image A No. 3 cannot be output, one control of motor reversal is performed, and document reading completion No. 18 is output to the external device 5.

By the motor reversal control of the CPU 208, the irradiation unit 2
4 moves in the direction of the arrow and stops when the optical position sensor detects that the initial position has been reached. If the next reading start command does not come from the external device 5 during this optical system return period, it stops at the initial position and moves to the operating path r.

Next, the circuit operation of this embodiment will be described using the block diagram of the circuit configuration of the control unit 21 shown in FIG.

The CCD 22 in the CCD driver 23 is connected to the control unit 2.
It is driven through the COD drive circuit 203 by the timing signal No. 5 305 generated by the timing signal generation circuit 209 of 0F.

The analog image signal output from the CCD 22 is an AMP
201 and converted into a digital image signal by A/D converter 202, which is output to control unit 20. The control unit 20 obtains a digital image signal that has been subjected to shading correction according to a shading correction circuit 211 as a shading correction means, so that this image signal can be processed in one of two modes, that is, a binary mode or a multi-value mode. can be output to the external device 5.

In the binary mode, the image signal is converted into 1 bit by the binarization circuit 205 according to the slice level output from the CPU 208, and is input to the selector 206.

The slice level includes a slice level specified by the external device 5 that is output as is, and a slice level determined by the background density detection circuit 204.

Next, the operation of the main parts will be explained with reference to FIG. 2, which is an enlarged block diagram of the document reading part of this embodiment.

The document is placed on the platen glass 27 in the book mode with its reading surface facing the irradiation unit 24, but in the sheet mode, the document is moved in the direction of the arrow B following the path indicated by the broken line as described above. and passes through the J3I reading path 32.

Since a transparent Mylar film 41 is provided between the platen glass 27 and the Jfy and light reading path 32 during sheet mode, the document is irradiated by the irradiation unit 24 through the film 41, and the reflection from the JFY is The light reaches the CCD 22 along the path shown by the solid line.

However, not only is the distance from the irradiation unit 24 to the document different between the light reflection position in the book mode and the light reflection position S in the sheet mode, but also due to the influence of the Mylar film 41, the CCD 22 The four light receiving surfaces on the surface are different.

Therefore, the tree reader 1 determines in advance whether to operate in the book or sheet mode, and when reading in the sheet mode, the second sheet reader 1 is used in addition to the white calibration plate 28 in the first book mode. A mode white calibration plate 29 is provided at the top of the document reading path 32 to perform shading correction.

This allows the shading correction circuit 211 to correct the difference in light amount on the C0D 22 surface that occurs when an image of the same density is read in sheet mode and book mode, using separately provided white calibration plates 28 and 29. It is possible to reproduce the same density.

〔Effect of the invention〕

As explained above, the present invention eliminates the difference in output image density caused by the difference in output that occurs when the stopped original storage means and the conveyed original document storage means are located at different distances from the original irradiation means. By providing separate white calibration plates for shading correction in mode and second mode, not only can the density be corrected to the same level, but the arrangement of the document conveyance path can also be freely selected. There is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an internal configuration of an image reading apparatus and a circuit configuration of a control unit in an embodiment of the present invention, and FIG. 2 is an enlarged view of the configuration of a document reading portion. 21... Light amount detection means 24... Original irradiation unit 27... Platen glass 28... White calibration plate 29... White calibration plate 32・・・・・・Manuscript reading path

Claims (1)

[Claims] A stopped original placing means and a conveyed original placing means having different distances from the original irradiation means, a light amount detection means for detecting the amount of light from each original placed on the original placing means, and a first original reading means for reading the stopped original. An image reading device comprising: a white calibration plate in a second mode; a white calibration plate in a second mode for reading a conveyed original; and shading correction means for performing shading correction using both white calibration plates.