JPH04369163A - Picture reader - Google Patents

Abstract

PURPOSE:To read an original with any resolution without complicated device configuration and to attain high-speed reading at a low resolution by setting variably an original carrier speed and an interleaving line. CONSTITUTION:This picture reader prepares plural kinds of original carrier speeds to set variably a read line density in the subscanning direction and plural kinds of interleave line numbers to a read picture signal and decides in advance plural kinds of combinations among original carrier speeds and interleave line numbers corresponding to the read line density. Furthermore, the picture reader is provided with a selection means 1000 selecting an original carrier speed and an interleave line number corresponding to the read line density commanded externally among predetermined plural combinations, with a control means 1100 carrying an original at a selected speed and with a picture processing means 1200 interleaving a picture signal at the selected interleave number. Through the constitution above, the picture read processing time is reduced.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention converts an original image into an analog image signal by reading it with a CCD image sensor.
Regarding image reading devices that can digitize image signals using an A/D converter and transfer them to an external device, there are two modes in particular: a mode for reading fixedly placed originals (hereinafter referred to as book mode), and a mode for reading originals while being transported. The present invention relates to an image reading device having a mode for reading a document (hereinafter referred to as sheet mode).

0002

2. Description of the Related Art Conventionally, when an image reading apparatus of this type reads an original in sheet mode, a means for transporting the original (hereinafter referred to as an ADF unit) is attached to the main body of the apparatus. In order to externally output an image signal having a reading line density (hereinafter referred to as resolution) in the sub-scanning direction specified from the outside, thinning processing is performed on the read image signal line by line in the main-scanning direction.

[0003] Furthermore, by making the number of lines to be thinned out variable, reading at various resolutions is realized.

0004

However, in the thinning process described above, it is necessary to fix the reading speed of the CCD image sensor and the document conveyance speed. For this reason,
Even if the resolution was low, it was not possible to increase the reading speed. As a countermeasure, an image processing method is known in which the resolution is varied by changing the transport speed of the document instead of thinning processing, but in order to satisfy the range from high resolution to low resolution, precise speed control is required. This poses a problem in that the device for driving the conveyance system becomes expensive.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to enable reading from low resolution to high resolution in sheet mode reading without complicating the device configuration; An object of the present invention is to provide an image reading device that can read images at increased speed.

[0006]

[Means for Solving the Problems] In order to achieve such an object, the present invention provides an image reading device that reads an image while conveying a document in the sub-scanning direction, in which the reading linear density in the sub-scanning direction is variable. In order to set the settings, multiple types of document conveyance speeds and multiple types of numbers of thinned lines for read image signals are prepared, and multiple combinations of document conveyance speeds and numbers of thinned lines corresponding to the size of the read line density are set. a selection means for selecting from among the plurality of predetermined combinations a document transport speed and a number of thinning lines corresponding to a reading line density in the sub-scanning direction that is predetermined and instructed from the outside; The present invention is characterized in that it includes a control means for transporting the original at a selected original transport speed, and an image processing means for thinning out the read image signal of the original at the selected number of thinning lines.

[0007]

[Operation] In the present invention, by variably setting the document conveyance speed and thinning lines, it is possible to read at any resolution in the sub-scanning direction. In addition, at low resolution, it is possible to read at high speed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the basic configuration of an embodiment of the present invention.

The image reading device of this embodiment is an image reading device that reads an image while conveying a document in the sub-scanning direction.

In addition, in this image reading device, in order to variably set the reading line density in the sub-scanning direction, a plurality of types of document conveyance speeds and a plurality of types of thinning line numbers for the read image signal are prepared, and the reading line density is set as follows. A plurality of combinations of the document transport speed and the number of thinning lines corresponding to the size of the document are predetermined.

[0012]Furthermore, this image reading device has a selection method for selecting a document conveyance speed and a number of thinning lines corresponding to a reading line density in the sub-scanning direction instructed from the outside from among the plurality of predetermined combinations. means 1000, and control means 1100 for transporting the original at the selected original transport speed.
and an image processing means 1200 that thins out the read image signal of the document by the selected number of thinning lines.

FIG. 2 shows the internal configuration of an image reading device to which the present invention is applied.

In the figure, 2 is the main body of the original image reading device;
The document on the platen glass 27 is illuminated by the document illumination unit 24, and the document image is formed on the CCD 22 by the lens 26. Reference numeral 3 denotes an automatic document feeder, in which the document on the document placement table 31 is conveyed in the direction of an arrow B shown by a broken line, and is ejected onto the document discharge table 32.

FIG. 3 shows the circuit configuration of the CCD driver 23 and control unit 21.

The operation of the document reading device will be explained using FIGS. 2 and 3. The document reading device in this case has a sheet mode in which the image is read while conveying ordinary paper documents without binding using the automatic document feeder (ADF unit) 3, and a sheet mode in which documents with binding such as books are read on the platen glass 27. There are two modes: book mode, which reads images by scanning the optical system.

First, the sheet mode will be explained. The image reading device (hereinafter referred to as a reader) in this case is always connected to an external device (such as a personal computer) 250, and communication of control signals with these external devices and image signal output to the external device 250 are performed in parallel. This is done via the interface circuit 207. First, AD
With the original placed on the original placing table 31 of F3, instructions for various modes are inputted from the external device 250. Upon receiving this, the arithmetic processor (CPU) 208 sets control signals in the timing generation circuit 209 and the binarization circuit 206 in advance. Further, an optical position sensor (not shown) confirms whether the original illumination unit 24 of the optical system is at the original reading position (the position shown in FIG. 2) in the ADF.

If the document is not at the ADF document reading position, the document illumination unit 24 is moved by the next document reading start command before starting the reading operation. When a command to start reading is input from an external device in this state, the CPU 208 outputs a lamp control signal to turn on the lamp, and outputs a command to start document feeding to the ADF 3 via the ADF interface circuit 211. do. As a result, the original placed on the original placing table 31 of the ADF 3 is conveyed in the direction of arrow B toward the path indicated by the broken line in FIG.

In this reader, since a stepping motor is used for the motor used to transport the ADF document and drive the optical system scanning, the speed of transport scanning can be adjusted freely by changing the pulse frequency for driving the motor. It can be changed to Furthermore, it is well known that whether or not the leading edge of the document has reached the document illumination position of the reader can be detected by a document leading edge detection sensor (not shown) provided in the ADF 3.

When the document reaches the document illumination position, the CPU 2
08 outputs a control signal enabling image signal output to the parallel interface circuit 207, and the read image signals are sent one after another to the external device 250. Then, when the trailing edge of the document has finished passing the document illumination position (detected by the document trailing edge detection sensor), the parallel interface circuit 20
By giving a control signal that disables image signal output to 7,
The parallel interface 207 stops outputting the image signal and transmits the document reading end signal to the external device 25.
Output to 0. After this, the CPU turns off the lamp (OFF
) to end the operation.

Next, the book mode will be explained.

In the book mode, the original is placed on the platen glass 27. Further, the initial position of the optical illumination unit 24 is at the right end in FIG. 2, and the position is confirmed by an optical position sensor (not shown) as in the sheet mode. Image signal settings before starting document reading are the same as in sheet mode.

When a document reading start command is input from external device 250, CPU 208 outputs a lamp control signal to turn on the lamp. Next, after waiting about 600 msec until the light intensity of the lamp becomes stable, scanning is started in the direction of arrow A in FIG. At the same time, the CPU 208 outputs a control signal to enable image signal output to the parallel interface circuit 207, and the read image signals are sent to the external device 20 one after another.
Sent to 0. After transferring a predetermined number of data set in advance by the external device 250, the CPU 208 outputs a lamp control signal to turn off the lamp, reverses the original illumination unit 24, and detects that the initial position has been reached by the optical position sensor. The operation ends after detection.

Next, the circuit operation of the control system will be explained using the block diagram of FIG.

(CCD driver 23 side) In FIG.
201 is an amplifier that amplifies the output of the CCD 22; 202 is an A/D converter that performs A/D conversion of the amplified output to obtain, for example, an 8-bit digital output; and 203 is an A/D converter for regulating the reading timing from the control unit 11; This is a drive circuit that drives the CCD 22 as a reading means in accordance with a supplied timing signal.

(Control unit 11 side) 207 is a parallel interface circuit, which receives control signals and outputs image signals with an external device 250, such as a personal computer, which serves as a host device for the image reading device according to this embodiment. Do this. 211 is an ADF interface circuit, which is used for communication for controlling the ADF when the ADF is used. 208 is a CPU in the form of a microcomputer, for example, and a ROM 2 that stores processing procedures.
08A (backed up by a power source not shown) and a working RAM 208B, and controls each part according to the procedure stored in the ROM 208A.

[0027] While transferring the original image information, the CPU 208
Determine whether information can be transferred from the external device side. CPU
208, binarization circuit 206 and interface circuit 2
A transfer unit is configured to transfer the document image information read by 07 and the internal state of the main body determined by the CPU 208 to the external device 250.

The shading RAM 204 is a RAM for storing the light distribution characteristics of the illumination lamp FL. The shading control circuit 205 includes a shading ROM storing shading correction coefficients and a shading RA.
The illumination lamp FL is configured from a circuit for controlling M204 and is stored in the shading RAM 204.
Based on the light distribution characteristic data, the image signal inputted from the A/D converter 202 is subjected to shading correction and outputted to the binarization circuit 206.

210 is a crystal oscillator, 209 is a CP
This is a timing signal generation circuit that frequency-divides the output of the oscillator 210 according to the settings of U208 to generate various timing signals that serve as operating standards.

Next, the resolution conversion procedure according to the present invention will be explained using the time chart shown in FIG.

Before going into the actual explanation, the structure of the automatic document transport speed type will be explained. The transport system is driven by a stepping motor, and the resolution is 300D.
PI, 150DPI, and 75DPI can be set, and for each resolution, document transport speeds of 4 pulses, 2 pulses, and 1 pulse are available as the number of pulses required to transport one line in the sub-scanning direction. It is assumed that there is

In FIG. 4, HSYNC 101 is CC
This is the synchronization signal of the D image sensor, and the period is 4 msec.
shall be. 102 is the CCD output when read by a 4 pulse/line ADF, and the number written in this signal indicates the position of the line stored in the CCD. 3
PMCK is a clock for driving the stepping motor, and the excitation pattern changes at the rising edge of the pulse, and the speed of 4 pulses in 4 msec, or 1000 PP.
S (pulse/S).

104 indicates the number of lines actually read when no thinning processing is performed, and corresponds to 300 DPI (dots/inch). 105 indicates the number of lines actually read in the first thinning mode, which corresponds to 150 DPI since the lines are thinned out to 1/2.

106 indicates the number of lines actually read in the second thinning mode, which is thinned out to 1/4, which corresponds to 75 DPI.

107 indicates the number of lines accumulated on the CCD when reading at an automatic document conveyance speed of 2 pulses/line. Since 2 lines are accumulated in 1 HSYNC period, it corresponds to 150 DPI.

108 indicates the number of lines accumulated on the CCD when read at an automatic conveyance speed of 1 pulse/line. Since 4 lines are accumulated in 1 HSYNC period, it corresponds to 75 DPI.

Next, the control procedure of the CPU 208 in variable setting of resolution according to the present invention will be explained with reference to the flowchart of FIG.

[0038]Currently, as a means for detecting the set automatic transport speed, a CPU (not shown) is installed in the ADF3.
is installed, and the number of pulses required to transport one line is calculated by the CPU 20 through the ADFI/F circuit 211.
8.

When the CPU 208 in FIG. 3 receives the read instruction command from the external device 250, it executes the control procedure in FIG. 5 as the selection means of the present invention. That is, step S1
, set the stepping motor drive frequency to 1000PP.
S, and the flag for setting the thinning mode is cleared in step S2. In step S3, if the set resolution is 300 DPI, proceed to step S4, otherwise proceed to step S6, and if the automatic conveyance speed set in step S4 is 4 pulses/line, this process ends. If not, the process advances to step S5, and since reading is not possible with the set ADF, an error flag is set and the process is terminated.

Next, in step S6, if the set resolution is 150 DPI, the process proceeds to step S7; otherwise, since it is 75 DPI, the process proceeds to step S9. In step S7, if the set automatic conveyance speed is 4 pulses/line, it is necessary to thin out to 1/2, so the process proceeds to step S11, sets the first thinning mode flag, and ends the process. If not, the process advances to step S8, and the set automatic transport speed is set to 2.
If it is a pulse/line, the process is immediately terminated; otherwise, since reading is impossible, an error flag is set and the process is terminated.

Next, in step S9, if the set automatic conveyance speed is 4 pulses/line, it is necessary to thin out to 1/4, so proceed to step S12, and set a second thinning mode flag. Terminate the process. If not, proceed to step S10, and if the set automatic conveyance speed is 2 pulses/line, 1/2
Since it is necessary to thin out the first
The thinning mode flag is set and the process is terminated. If not, the set automatic conveyance speed is 1 pulse/line, so the process is terminated.

Reading is executed at the document conveyance speed set in this manner. C when performing this document transport speed control
The PU 208 (or the CPU within the ADF 3) operates as a control means of the present invention.

[0043] Also, when thinning out the read image signal, the CP
U208 operates as an image processing means of the present invention.

[0044] Since the control process for conveying the document at a preset conveyance speed and the process for thinning out the read image signal by a preset number of thinning lines can be performed using well-known processing procedures, a detailed explanation will be provided. omitted.

In this embodiment, the resolutions that can be set are only 300, 150, and 75 DPI, but if the 2/3 thinning mode is set using the 4-pulse/line ADF, 200 DPI can also be set. , it goes without saying that if you set the thinning mode to 1/3, it is possible to set 100 DPI.

[0046]

[Effects of the Invention] As explained above, according to the present invention,
In order to change the resolution in the sub-scanning direction in the sheet-through mode, the number of thinning lines and the document conveyance speed are respectively set variably. Therefore, the control performance of the document conveyance speed can be lowered more than the resolution change of only the conveyance speed, that is, the structure of the conveyance system can be simplified.

Furthermore, since the conveyance speed can be set high when the resolution is low, the image reading processing time can be shortened.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the main cross-sectional structure of an image reading device to which the present invention is applied.

FIG. 3 is a block diagram showing an example of a circuit configuration of an image reading device according to an embodiment of the present invention.

FIG. 4 is a time chart illustrating a resolution changing procedure according to an embodiment of the present invention.

FIG. 5 is a flowchart specifically showing the processing operation of the embodiment of the present invention.

[Explanation of symbols]

2 Manuscript reading device 3 Automatic document feeder (ADF) 21 Control unit 22 CCD 23 CCD driver 24 Original illumination unit 25 Reflection mirror 26 Lens 27 Platen glass 31　Original placing table 32 Original output table 208 CPU

Claims (1)

[Claims] Claim 1: In an image reading device that reads an image while conveying a document in the sub-scanning direction, in order to variably set the reading line density in the sub-scanning direction, multiple types of document conveyance speeds and multiple speeds for read image signals are set. The number of lines to be thinned out is prepared, multiple combinations of the document transport speed and the number of lines to be thinned out corresponding to the reading line density are predetermined, and the reading line density in the sub-scanning direction is determined from an external instruction. a selection means for selecting a document transport speed and a number of thinning lines corresponding to the document transport speed from among the plurality of predetermined combinations, a control means for transporting the document at the selected document transport speed, and a control means for transporting the document at the selected document transport speed; An image reading device comprising an image processing means for thinning out a read image signal of a document by the number of thinning lines.