JP2683034B2 - Image reading device - Google Patents

Description

The present invention relates to an image reading apparatus for reading a document image.

[Conventional technology]

Conventionally, in facsimile machines, a sheet-shaped document is conveyed by rollers or the like, and a document image conveyed at a predetermined reading position is photoelectrically read using a CCD image sensor or the like.

Further, when the original is read by the CCD, the shading correction due to the variation of each bit of the CCD or the nonuniformity of the illuminance of the fluorescent lamp is performed. That is, the conveyance of the document is temporarily stopped before the reading position, and the light source is turned on at that time,
The all-white reference member on the reading position is read before the original is read (prescan), and the image signal output by the subsequent original is corrected using the data obtained by this prescan.

[Problems to be solved by the invention]

Recently, high-speed image reading has become possible due to improvements in the performance of image reading sensors and circuit elements for image signal processing. For that purpose, a document must be moved at a predetermined reading position at high speed.

However, when a pulse motor is used as the drive source for the document transport roller, the pulse motor is, for example, 1440 pps.
In order to rotate at a high speed as described above, it is necessary to increase the number of drive pulses to the pulse motor stepwise in a plurality of steps from 400 pps to 1440 pps as shown in FIG. That is, it takes some time to bring the pulse motor from the stopped state to a predetermined high speed rotation.

Therefore, in the case of performing such high-speed reading, as described above, in the configuration in which the document being conveyed is temporarily stopped, the prescan is performed, and the document is conveyed again after the prescan, the time required to convey the document at a predetermined high speed is increased. However, it is necessary to construct a long transport path for the approach run.

[Means for solving the problem]

In view of the above-described problems, the present invention is capable of conveying an original at a high speed and reading the original, and in an apparatus for reading a reference member before starting the reading of the original, an apparatus capable of reducing the time until the reading of the original is started. The purpose is to provide.

[Means for Solving Problems] In order to solve the above-mentioned problems, the present invention includes a conveying unit that conveys a document to a document reading position, and a reading unit that reads the document conveyed at the document reading position. Correction means for correcting the reading signal of the original image based on the reference signal obtained by reading the reference member by the reading means, and conveying the original document to the conveying means so that the original document passes through the original reading position at high speed. Acceleration control for accelerating the speed is executed, the accelerated document is read by the reading unit, and after the acceleration control is started, the reading unit starts reading the reference member to obtain the reference signal, and the correction is performed. And a control unit for correcting the reading signal of the document image based on the reference signal.

〔Example〕

Hereinafter, the present invention will be described using preferred embodiments.

FIG. 2 is a block diagram of a facsimile transmission apparatus to which the present invention is applied.

In FIG. 2, reference numeral 6 is a document, and this document 6 is placed on the document table 7 with the document surface facing down. At this time, one set can be slid left and right on the document table 7. It is placed between sliders (not shown) attached to the. A document sensor 5 is provided for detecting the presence or absence of a document on the document table 7.

Above the rear half of the upper surface of the apparatus, there is provided an operation display section that constitutes the upper part of the document feeding mechanism section 2, and a start key is provided at a part of this operation display section.

When the document 6 is set as described above and the start key is pressed, the drive mechanism starts operation and the document 6 is fed by the document feeding mechanism unit 2
Send in.

A square roller 11 and a back-up roller 12 which is in contact with the square roller 11 are arranged on the entrance end side of the document feeding mechanism section 2, and the document 6 is fed intermittently by the cooperation of both.

A separation roller 13 is provided behind the square roller 11, and a separation piece 14 is arranged above the separation roller 13 in a state of lightly contacting it.

By the cooperation of the separating roller 13 and the separating piece 14, a plurality of originals are sequentially separated one by one from the lower side and further fed to the downstream side.

The document 6 that has left the separation roller 13 is sandwiched between the conveyance rollers 15 and 15 and further fed, and is ejected outside the apparatus by the ejection rollers 16 and 16. The transport roller 15 and the discharge roller 16 are rotationally driven by a pulse motor.

The document reading position 17 is arranged between the transport roller 15 and the discharge roller 16 described above.

Reference numeral 18 denotes a document leading edge sensor provided a predetermined distance before the document reading position 17 to detect the leading edge of the document 6 and control the timing such as the start of reading.

On the other hand, a light source 19 such as a fluorescent lamp is arranged below the reading position 17, and a contact glass 20 is arranged at the reading position 17. The original is read through the contact glass 20, but by providing this glass, foreign matter such as dust falls into the apparatus from the vicinity of the reading position 17 and adheres to the optical system, or a mechanism by dropping pins or clips. It is possible to prevent damage to the parts.

The light from the light source 19 illuminates the document 6 on the contact glass 20, and the reflected light is reflected forward by the first mirror 21 arranged immediately below the reading position 17, and again by the second mirror 22. 1 A lens 23 arranged below the mirror 21
An image is formed on the image sensor 25 on the printed circuit board 24 via. The image sensor 25 is composed of a plurality of light receiving elements arranged in a line, and repeatedly reads an original image line by line.

The reflected light from the shielding plate 26 is guided to the image sensor 25 in the state where no document is present at the reading position 17.

The shading plate 26 is a uniform white plate, and is used for measuring the shading distortion due to the non-uniformity of the illuminance distribution in the longitudinal direction of the light source 19 and the non-uniform light amount ratio of the light passing through the lens 23 in the central portion and the peripheral portion. It is a reference member. The reading scan of the shielding plate 26 is called a prescan.

The components such as the above-mentioned mirror and lens are the reading optical system unit 3.
Is composed.

Figure 3 shows the document sensor (DS sensor) in the document transport path.
5 is a diagram showing a positional relationship among a document leading edge sensor (DES sensor) 18, a reading position (R, P) 17, and a prescan start position (P, S). The distance between the document detection position of the DES sensor and the reading position (R, P) is B, and
The prescan is started at the time point when it is conveyed to the prescan start position (P, S) separated by the distance A from the DES sensor. The distance B is an approach distance required for the document to be conveyed at a predetermined speed at the reading position (R, P) by at least the acceleration control, and the distance A is the time required for prescan.
And C is the distance by which the document is conveyed during the time t, it is set so as to satisfy the relationship of A + C <B.

Also, the original detected by the DS sensor is, for example, 400p
When the leading edge of the document conveyed by the DES sensor is conveyed by the roller according to the pulse motor driven by ps, the rotation speed of the pulse motor is increased stepwise,
When the document reaches the document reading position (R, P), the pulse motor is driven at 1440 pps, for example, and the acceleration is controlled so that the document passes the reading position (R, P) at a predetermined transport speed.

FIG. 1 is a block diagram showing a circuit configuration example of the facsimile transmission device shown in FIG.

A reading unit 31 is a CCD 32 corresponding to the image sensor 25 shown in FIG. 2, a CCD driver 36 that drives the CCD 32, and an analog-digital (A / D) converter that converts an analog image signal from the CCD 32 into a digital image signal. 33, the CCD 32 outputs the output signal from the A / D converter 33 at the time of reading the original image based on the read signal from the line memory 34 and the line memory 34 which stores the output signal read by the shielding plate 26 shown in FIG. A correction circuit 35 for performing the shading correction on the original image signal is included.

Reference numeral 37 denotes a communication control unit, which is a coding circuit 38 that performs known MH coding, MR coding, and other compression coding on the original image signal from the reading unit 31, and a modulation that performs a modulation process on the coded image signal. A circuit 39 and a network control circuit (NCU) 40 for controlling the transmission of the modulated image signal to a transmission line such as a public line are included.

42 is a document transport unit, which is a transport roller 15 and a discharge roller.
A pulse motor 43 for driving 16, a motor driver 44 for outputting a pulse to the pulse motor 43 to drive the pulse motor 43, and a timing controller 45 for controlling the rotation direction, speed, and number of steps of the pulse motor 43 are included.

Reference numeral 46 is a light source corresponding to the light source 19 shown in the second illustration, and 47 is an operation display unit on which an operator inputs a telephone number and gives a start command, and various displays are made.

Reference numerals 48 and 49 are a DS sensor and a DES sensor corresponding to the document sensor 5 and the document leading edge sensor 18, respectively, shown in FIG.

30 is mainly composed of a microcomputer and has a memory ROM5
This is a main control unit that controls the operation of each block described above by using 0 and the memory RAM 51.

When the pulse motor 43 is driven one step, the document is conveyed by a distance of l. Also, the document conveying speed can be changed by changing the number of steps per unit time. Therefore, the main control unit 30 controls the pulse motor per unit time by the timing controller 43 with respect to the document conveying unit 42.
The document conveying speed is controlled by controlling the number of driving steps of 43, and the document position is recognized by counting the number of driving steps of the pulse motor 43.

Therefore, a table for speed control of the pulse motor 43 is stored in advance in the memory ROM 50 of the main control unit 30. That is, as described above, the pulse motor is used from when the leading edge of the document is detected by the DES sensor until it reaches the document reading position (R, P).
The memory ROM50 stores a table that is addressed by the data indicating the document position and outputs the data of the number of steps according to the position for the acceleration control to increase the number of driving steps per unit time to 43 in a stepwise manner. To be done.

FIG. 4 is a flow chart showing an operation control procedure by the main control unit 30. When the start key of the operation / display section 43 is pressed, in step S1 it is checked whether the DS sensor is ON (there is a document). If it is OFF (there is no document), the operation is finished.
If so, the light source 46 is turned on, and the process proceeds to step S2. Step
In S2 and S3, the pulse motor 43 (hereinafter referred to as P.M43) is driven one step at a time, and this is repeated until the DES sensor is turned on (the document start edge is on the sensor). When the DE sensor is turned on, the register X of the RAM 51 is set to 0 at step S4. As a result, P.M43 enters the acceleration control described above. That is, in step S5, the number of steps per unit time of P.M43 is sequentially changed according to the data previously set in the table of the ROM 50, and step S6 drives P.M43.

At step S7, P.M43 is driven to accumulate the step number in the register X. Then, in step S8, the value of register X sets the distance A from the DES sensor to the PS position to 1
Check if it is smaller than A / l divided by the document movement amount l per step. If the value of the register X is smaller than A / l, the process returns to step S5 and the acceleration control of P.M43 is repeated. On the other hand, if the value of register X is not smaller than A / l and it is determined in step S9 that prescan is not yet performed,
In step S10, a command to start scanning is sent to the reading unit 31.

In response to the prescan start command, the reading unit 31 stores the read signal obtained by scanning the shielding plate 26 by the CCD 32 in the line memory 34.

If the prescan is already executed at step S9 or after the prescan is performed at step S10, the value of the register X is divided by the value l of the document reading position RP from the DES sensor at step S11. See if it is B / l. If the value of the register X has not reached B / l, the process returns to step S5 and the acceleration control of P.M43 is continued. On the other hand, if the value of register X becomes B / l,
Since the original has reached the reading position, the acceleration control of P.M43 is finished and the operation of reading the original image by the CCD 32 is performed.

In the operation of reading the original image, based on the data stored in the line memory 34 by the prescan operation of step S10, the original image signal from the CCD 32 is
Performs shading correction processing. Then, the shading-corrected image signal is transmitted to the communication control unit 37, subjected to predetermined processing, and then transmitted to the external receiving device via the transmission line.

After scanning the one-page original, return to step S1 and DS
If the document is detected by the sensor, and if the document is detected further, the process proceeds to step S2 and the same process as described above is executed. finish.

In this way, when the document leading edge sensor DES detects the document leading edge, the acceleration control for moving the document at the high speed on the reading position is performed, and the prescan operation is performed at a predetermined timing without interrupting the acceleration control. It is something to do. As a result, the prescan operation can be efficiently performed without extending the time for high-speed conveyance.

In this embodiment, the shading correction of the image signal is performed by the data obtained by the prescan operation, but the present invention is not limited to this, and the defective pixel correction of the CCD line sensor and the density characteristic correction of the read signal may be executed. It is also possible to perform color balance correction in the case of reading a color image.

Further, although the pulse motor has been described as the drive source in the present embodiment, the invention can be similarly applied to the case of using a motor having other configuration.

Further, needless to say, the present invention can be applied not only to facsimile transmission devices but also to document reading by digital copying machines and electronic file devices.

[Advantages of the Invention] Claim 1 of the present invention has been made in view of the above points, and a document is conveyed to a document reading position, the document conveyed at the document reading position is read, and a reference member is read. The reading signal of the original image is corrected based on the obtained reference signal, and the acceleration control is executed to accelerate the original feeding speed so that the original passes through the original reading position at high speed. After the control is started, the reading of the reference member is started, the reference signal is acquired, and the read signal of the original image is corrected based on the reference signal, so that the original can be conveyed and read at high speed, and the acceleration control is started. It is possible to shorten the time required to start the reading of the document as compared with the conventional apparatus in which the document feeding is temporarily stopped, the reference member is read, the document feeding is restarted after the reading of the reference member, and the acceleration control is started.

Further, according to claim 2 of the present invention, the document is started to be transported at a low speed, and the acceleration control is started in response to the document leading edge sensor detecting the leading end of the document being transported at a low speed, and the document after the acceleration control is started. When the conveyance distance reaches a predetermined value, the reference member is read and the reference member is acquired.Therefore, the document conveyance is temporarily stopped before the acceleration control is started, the reference member is read, and the reference member is read. Compared to the conventional device that restarts document transportation and starts acceleration control, it can start acceleration without stopping document transportation, shorten the acceleration time and the approach distance required for acceleration, and start reading the reference member. It is not necessary to provide a dedicated sensor for.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration example of a facsimile transmission device to which the present invention is applied, FIG. 2 is a configuration diagram of the facsimile transmission device, FIG. 3 is a diagram showing arrangement of various elements in a document feeding path, and FIG. Fig. 5 is a flow chart showing the control procedure, Fig. 5 is a diagram showing the acceleration control of the pulse motor, 30 is a main control unit, 32 is a CCD, 37 is a communication control unit, 42 is a document transport unit, and 43 is a pulse. A motor, 48 is a document sensor, and 49 is a document leading edge sensor.

Claims (2)

(57) [Claims] 1. A document image based on a transporting unit for transporting a document to a document reading position, a reading unit for reading a document transported at the document reading position, and a reference signal obtained by reading a reference member by the reading unit. Correction means for correcting the reading signal of the reading means, and an acceleration control for accelerating the feeding speed of the original to the conveying means so that the original passes through the original reading position at high speed, and the reading means for reading the accelerated original. Control means for causing the reading means to start reading the reference member after the acceleration control is started to acquire the reference signal, and causing the correction means to correct the read signal of the original image based on the reference signal. An image reading apparatus comprising: 2. A document sensor for detecting the presence or absence of the document,
A document leading edge sensor for detecting the leading edge of the document is provided, and the control means causes the transporting means to start transporting the document at a low speed based on the detection of the document by the document sensor. In response to the sensor detecting the leading edge of the original document being conveyed at low speed, the acceleration control is started without stopping the original document conveyance, and the conveyance distance of the original document after the acceleration control is started is detected to accelerate the acceleration. 2. The image reading device according to claim 1, wherein the reference signal is acquired by causing the reading unit to read a reference member in response to the conveyance distance of the original document after the start of control reaching a predetermined value. apparatus.