JP2002354207A - Image scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image scanner which has a high read precision by allowing the image scanner to have an automatic correction function which eliminates the read error caused by the positional deviation or the like between an optical system and a machine system. SOLUTION: Reference marks which are the reference or picture read position are provided in at least two positions on the outside of a document read area of a background plate constituting the upper part of a document read part, and positions of these reference marks are read by a photoelectric conversion part a the time of power-on and before read of a sheet document, and average values of current position values and preceding those of the reference marks are used to obtain reference values for read start position correction and inclination correction, and a picture is read on the basis of these reference values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a copying machine or a facsimile apparatus having a sheet feed scanner, or a sheet feed scanner.

[0002]

2. Description of the Related Art Conventionally, copiers and facsimile machines,
Alternatively, there is an image reading device such as a scanner. The scanner unit that constitutes this device can be roughly classified into a flatbed scanner type that scans the pixels of the linear image sensor and the direction (sub-scanning direction) orthogonal to the linear image sensor (sub scanning direction) by fixing the original and moving the optical system to read the image. On the contrary, there is a sheet feed scanner type in which an optical system is fixed and an image is read by moving and scanning a document in a direction orthogonal to the linear image sensor.

[0003] The latter apparatus having the sheet feed scanner type corresponds to a copying machine installed in a company or school in a familiar place. This copier has a flatbed scanner unit that reads an image by moving an optical system by placing one document on the contact glass surface and pressing down the start button, and a plurality of documents on a tray unit provided at the top of the copier. The sheet feeder unit is provided with a sheet feed scanner unit for reading an image by moving a document one sheet at a time to a fixed optical system by placing the sheets and pressing down a start button.

As this type of apparatus, for example, Japanese Patent Application Laid-Open
There are inventions disclosed in Japanese Patent No. 37596 and Japanese Patent Application Laid-Open No. H10-164363. When moving the first carriage by combining a plurality of operations, the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 8-37596 has a plurality of moving methods, and calculates required time for the plurality of moving methods. By making a comparison, an operation method capable of moving in the shortest time is selected, so that it is possible to prevent useless time from being moved.

On the other hand, the image reading apparatus disclosed in Japanese Patent Application Laid-Open No. H10-164363 performs shading correction processing and spatial filter processing which are necessary for obtaining black reference data and white reference data and reading an image with high image quality. In an image reading apparatus, a memory for averaging black reference data and white reference data and a memory for performing spatial filtering on an image are shared, thereby saving the number of memories and simplifying a circuit. Therefore, the cost can be reduced.

An image reading apparatus such as a copying machine or a facsimile apparatus having a sheet feed scanner unit or a sheet feed scanner depends on the accuracy of parts constituting the apparatus, the assembly accuracy of the apparatus, or the installation location of the apparatus. The document reading start position, that is, the reading origin may be slightly shifted. This will be described with reference to FIG. FIG. 5 exemplifies a case of a flood head scanner so as to be easily understood visually.

Originally, the range in which the scanner can read a document or the like, that is, the readable area A0 is set wider than the range in which the scanner actually reads the document or the like, that is, the reading area A1. In other words, by being configured to be mechanically movable in the sub-scanning direction, not all of the pixels of the CCD line sensor are used up in the main scanning direction, but only an area set with a certain margin is used. That is possible.

As described above, the main scanning direction is the electrical reading origin. For the sake of simplicity, if the upper left of the readable area A0 in the drawing is the standby position of the scanner, that is, the machine origin P0, the machine origin is usually the machine origin. At a predetermined position (X1, Y1) from P0, a predetermined position set in advance is set as the reading origin P1, and the scale S is arranged such that the orthogonal portion of the scale S for document positioning is located at the reading origin P1. By matching the mechanical system and the optical system, an original or the like is read accurately.

However, as described above, there are cases where the reading origin P1 is slightly deviated from the original position due to the assembling accuracy and the like (X2 and Y2 are deviated, and the rotation direction is also deviated). Conventionally, the test paper on which the test pattern is drawn is once read by the device,
Original reading origin P1 in design and origin P actually read
By comparing 2 and the like, the positional deviation in the main scanning direction and the positional deviation in the rotation direction between the optical system and the mechanical system, that is, the inclination (skew) is grasped, and fine adjustment is performed manually.

[0010]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. Hei 8-3
The inventions disclosed in Japanese Patent No. 7596 and Japanese Patent Application Laid-Open No. H10-164363 are considered effective for the respective problems. However, as described above, the present invention directly focuses on the problem relating to the correction of the reading area. What is out of the scope of the inventor's knowledge. Accordingly, it is an object of the present invention to provide an image reading apparatus having a high reading accuracy by providing the image reading apparatus itself with an automatic correction function for eliminating a reading error due to a positional shift between an optical system and a mechanical system.

[0011]

According to a first aspect of the present invention, there is provided a conveying means for conveying a sheet document to a document reading section and conveying the sheet document to a discharge section, and movable in a sub-scanning direction. Scanning means provided with a mirror unit for irradiating light from below the original conveyed to the original reading unit and guiding the reflected light to the photoelectric conversion unit, and having an image reading position outside the original reading area. At least two reference marks serving as references are provided on a background plate that is located above the document reading unit, and a power supply
At N and before reading the sheet document, the position of the reference mark is read by the photoelectric conversion unit, and the reading start position is corrected using the average value of the current reference mark position value and the previous reference mark position value. An image reading apparatus is configured such that the image is read based on the reference value of the inclination correction and the reference value.

According to a second aspect of the present invention, in the first aspect, an arbitrary upper and lower limit value is provided for the value of the position of the reference mark detected by the photoelectric conversion unit, and the detected value exceeds the upper and lower limit value. In this case, using the detection result within the upper and lower limits detected last time,
An image reading apparatus is characterized in that it is used as a reference value for output image correction and inclination correction of a read image.

According to a third aspect of the present invention, in the second aspect, when the value of the position of the reference mark detected last time exceeds the upper and lower limits, the correction value is set to an upper limit or a lower limit. The image reading apparatus is characterized in that:

According to a fourth aspect of the present invention, there is provided a conveying means for conveying a sheet document to a document reading section and conveying the sheet document to a discharge section, and a light source which is configured to be movable in the sub-scanning direction and emits light from below the document conveyed to the document reading section. Scanning means provided with a mirror unit for irradiating the light and guiding the reflected light to the photoelectric conversion unit, a reference mark for detecting the positional deviation amount of the reading start origin in the main scanning direction, and the positional deviation amount of the reading start origin in the rotation direction A reference mark for detecting the position of the original is provided above the document reading unit, and the mirror unit is moved to read the respective reference marks by the reading and scanning unit. Detection means for detecting an error of the reading start origin based on the output, and control means for determining an appropriate reading start origin using the respective errors detected by the detection means as correction amounts. In the image reading apparatus characterized by.

According to a fifth aspect of the present invention, in the fourth aspect, the conveying means is provided with a gap in which the sheet document can move with a lower plate portion on which the sheet document reading glass constituting the document reading section is attached. A conveyance path is formed with the upper plate portion provided above the lower plate portion, and the fiducial mark is provided on the inner surface of the conveyance path above the sheet original reading glass and at both ends in the main scanning direction so as to face each other. An image reading apparatus is characterized in that:

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described in detail. The image reading apparatus exemplified in this embodiment is suitable for reading a desired plurality of sheet documents or the like. The image reading apparatus according to the present embodiment includes a transport unit 1, a reading / scanning unit 2, and a control unit 3.

As shown in FIG. 1 and FIG.
, A tray section 11, a lower plate section 12, an upper plate section 13, and a roller section 14. The tray section 11 is a tray on which a plurality of sheet documents can be placed, and is attached to an upper portion of the main body frame. The lower plate portion 12 is a guide plate 121 for connecting the tray portion 11 and the discharge portion 1a from which the read document is carried out, and is provided so as to be substantially C-shaped when viewed from the side as illustrated. On the lowermost portion of the lower plate portion 12, a sheet document reading glass 122 having a substantially rectangular shape in plan view is provided.
Is attached to the body frame of the main body, and the lower plate 12
Is composed. This sheet original reading glass 122
The portion where is fitted serves as a document reading unit that reads a sheet document.

As shown in FIG. 2, the upper plate portion 13 is composed of a white plate 131 provided on the original side and a background plate 132 superposed on the white plate 131. ,
The sheet document is provided at a required interval along the lower plate portion 12 so that the sheet document can move. The lower plate portion 12 and the upper plate portion 13
And a transport path t for transporting the original is formed.
A black reference mark m is provided on the inner surface of the conveyance path t above the sheet document reading glass 122, that is, on the white plate 131, and at both ends in the main scanning direction so as to face each other. The roller unit 14 is provided in the vicinity of the tray unit 11 and has a pair of feed rollers 141 configured to be rotatable by a pulse motor as a driving source, and the lower plate unit 12 and the upper plate unit 13 so as to face each other and at a predetermined interval. And a pair of transport rollers 142 provided at four locations and rotatable by a pulse motor as a drive source.

The scanning means 2 includes a light source 21, a mirror 22, a lens 23, and a photoelectric converter 24. The light source unit 21 includes a lamp 211 for irradiating the original document conveyed to a sheet original reading glass 122 serving as an original reading unit from below and a reflecting mirror 212 for efficiently irradiating the original document. 122 is provided below. Mirror part 2
2 is a first mirror unit 221 for directly receiving the reflected light of the light emitted by the light source unit 21;
The second mirror unit 222 is provided so as to receive the reflected light of one and guide the reflected light to a photoelectric conversion unit 24 described later. The first and second mirror units 221, 2
Numeral 22 is configured to be movable in a sub-scanning direction (left-right direction in FIG. 1) using a pulse motor (not shown) as a driving source. Further, each mirror constituting this unit is formed over a required length which is longer than a scanner readable area in the main scanning direction.

The lens unit 23 includes a second mirror unit 22
2 and a photoelectric conversion unit 24 to be described later, the reflected light guided from the second mirror unit 222 is converged and guided to the photoelectric conversion unit 24. The photoelectric conversion unit 24 is a CCD sensor that performs main scanning, and has a pixel area of a readable width w (not an actual reading width) in FIG. All light can be converted into image data. The control unit 3 is a microcomputer that controls the entire apparatus according to a predetermined program, and the automatic correction function, which is a main part of the present invention, operates based on the mechanical and optical configurations and the predetermined program. Has become. The detecting means for obtaining the correction value is realized by the predetermined program.

Next, the operation of the image reading apparatus of the present embodiment configured as described above will be described with reference to FIG. In addition,
The description will be made assuming that the reading start position is shifted. In FIG. 3, the light source unit 21 and the first mirror unit 221 that have been waiting at the left end in the sub-scanning direction move in the sub-scanning direction during the homing operation and the shading operation when the main power supply of the apparatus body is turned on. However, at this time, the automatic correction function operates.

First, the light source unit 21 and the first mirror unit 221 are moved in the sub-scanning direction until the control means 3 detects the reference marks m provided on both ends of the white plate 131 in the main scanning direction via the photoelectric conversion unit 24. Move to At this time, if the optical system and the mechanical system are displaced in the rotation direction, one of the reference marks m is detected first. In FIG. 3, the position of the upper reference mark m is first detected (triggered by the change from the white area to the black area), and then the second reference mark m, that is, the lower reference mark m m is detected. Then, the shift amount a in the sub-scanning direction is calculated based on the amount of movement during that time based on the total amount of pulses of the pulse motor as the drive source and the amount of movement per pulse. Then, the shift amount a in the sub-scanning direction is divided by the distance c between the known reference marks m (a / c), and the tilt amount is calculated based on the result.

At this time, when the first reference mark m is detected, a predetermined reading start position in the main scanning direction, that is, a reading start position of the image data converted by the photoelectric conversion unit 24 and a reading reference position Reference mark m on the side
(The upper reference mark m in FIG. 3) is compared with the detected position, and the difference is defined as the positional deviation amount b in the main scanning direction. In this manner, the obtained inclination amount and the positional deviation amount in the main scanning direction, that is, the inclination (skew) correction value (a /
c) and the read image position correction value b is obtained.

Then, the operation for reading the actual sheet document is started. A desired plurality of sheet documents are placed on the tray unit 11 with the surfaces to be read facing up, and the start button of the input button unit (not shown) of the apparatus body is pressed down. Then, the feed roller 141 rotates to feed the uppermost document of the sheet document placed on the tray unit 11 into the transport path t, and then the sheet document reading glass 122 is fitted by the rotated transport roller 142. (Skew) obtained at the previous stage after being transported to the original reading section
The control means 3 controls the read start timing based on the correction value (a / c) and the read image position correction value b, and collects image data at an accurate position.

Further, once the power is turned off and then turned on again, the automatic correction function operates again together with the homing operation and the shading operation described above. At this time, the position of the reference mark m detected in the sub-scanning direction and the position of the reference mark m in the main scanning direction detected last time are recorded in the memory, and are averaged with the respective positions obtained in the main and sub-scanning directions obtained this time. Calculate the correction value. Then, the control means 3 controls the reading start timing with this correction value, and collects image data. This averaging process is performed every time the apparatus is started.

The upper and lower limits of the correction value are set at the design stage. That is, if the lower limit in the main scanning direction is b1 and the upper limit is b2, the read image position correction value b
Satisfies the relationship of b1 <b <b2. Similarly, the inclination (skew) correction value a / c has the relationship of a1 <(a / c) <a2, where a1 is the lower limit and a2 is the upper limit. By setting the upper and lower limits, it is possible to prevent a correction error due to abnormal detection of the CCD sensor for some reason when detecting the position with the CCD sensor. Here, a series of flows regarding the upper and lower limits of the correction value will be described with reference to the flowchart of FIG.

First, a correction value is calculated by averaging the respective positions of the reference mark m obtained in the previous activation in the main and sub scanning directions and the positions of the reference mark m obtained this time in the main and sub scanning directions (step). S1). At this time, it is determined whether or not a preset upper and lower limit value is exceeded (step S2).
When the correction value is within the upper and lower limit values (step S
2: No), the reading is performed based on the correction value (step S3), and the output of the read image is started gradually (step S4). If the correction value is not within the upper and lower limit values (step S2: Yes), it is determined whether or not the correction value detected last time has exceeded the previously set upper and lower limit value (step S5). ).

If the previous correction value is still within the upper and lower limit values (step S5: No), reading is performed based on the previous correction value (step S6), and the output of gradually read images is started. (Step S4). If the previous correction value is not within the upper and lower limit values even last time (step S5: Yes), the current correction value is set as the upper limit value or the lower limit value, and reading is performed based on the current correction value (step S7). ), Output of the gradually read image is started (step S4).

In this embodiment, it is assumed that the detection from the CCD sensor is abnormal. On the contrary, if a large correction value is obtained,
The position detection by the sensor may be normal, and the apparatus main body may be determined to be obviously abnormal. In that case, it is preferable to notify the result to a display unit using a liquid crystal or the like. Further, the reading operation may be performed with a newly obtained correction value every time the apparatus is started.

[0030]

As described above, the present invention has the following advantageous effects. According to the first aspect, at least two reference marks are provided on the background plate on the sheet original reading glass, and the distance between the start of detection of each reference mark m is detected by the photoelectric conversion unit, and the averaging process is performed. By using the obtained values, the exact document image position and the inclination (skew) can be known, and the distance from the end of the reference mark on the document reference surface to the start of document reading is detected by the photoelectric conversion unit. Since an accurate document image position can be known, by performing position correction and inclination correction using this value, an image without an accurate position and inclination can be output.

According to claim 2, for some reason,
If the current detection from the photoelectric conversion unit is an abnormal value, if that value is used as the reference value for correction, accurate correction cannot be performed, resulting in an abnormal image. If the predetermined correction value exceeds the upper and lower limit values, it is possible to prevent a correction error and avoid outputting an abnormal image by using the previous detection value.

According to claim 3, for some reason,
If the current detection from the photoelectric conversion unit is an abnormal value, if that value is used as a reference value for correction, accurate correction cannot be performed, resulting in an abnormal image. If the correction value exceeds the upper and lower limit values and the previous detection value also exceeds the upper and lower limit values, the correction value is set to the upper limit value or the lower limit value, and the correction is made as much as possible. Thus, output of an abnormal image can be avoided.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of a main part of the image reading apparatus.

FIG. 3 is a plan view of the image reading apparatus.

FIG. 4 is a flowchart illustrating a control flow when upper and lower limit values of the correction value are set in the correction value for correcting the inclination and the read image position.

FIG. 5 is a schematic diagram showing a state of misalignment between a mechanical system and an optical system in the flood head scanner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conveying means 1a Discharge part 12 Lower plate part 122 Document reading part (sheet document reading glass) 13 Upper plate part 2 Reading scanning means 22 Mirror part 24 Photoelectric conversion part 3 Control means m Reference mark t Transport path

Claims (5)

[Claims] A transport unit configured to transport a sheet document to a document reading unit and to a discharge unit, and irradiate light from below the document transported to the document reading unit so as to be movable in a sub-scanning direction and reflect the light. A reading plate provided with a mirror unit for guiding light to the photoelectric conversion unit, and at least two reference marks serving as references for an image reading position outside the document reading area, constituting a background plate above the document reading unit The position of the reference mark is read by the photoelectric conversion unit when the power is turned on and before the sheet document is read, and the average value of the value of the current reference mark position and the value of the previous reference mark position is used. As a reference value for reading start position correction and inclination correction,
An image reading apparatus configured to read an image based on the reference value. 2. An arbitrary upper and lower limit value is provided for the value of the position of the reference mark detected by the photoelectric conversion unit, and when the detected value exceeds the upper and lower limit value, the upper and lower limit value detected last time is set. 2. The image reading apparatus according to claim 1, wherein the reference values for the correction of the output position of the read image and the correction of the inclination of the read image are obtained using the detection results in the above. 3. The image reading apparatus according to claim 2, wherein the correction value is set to an upper limit value or a lower limit value when the value of the position of the reference mark detected last time exceeds the upper and lower limit values. apparatus. 4. A transport means for transporting a sheet document to a document reading section and transporting the sheet document to a discharge section, and irradiating light from below the document transported to the document reading section so as to be movable in a sub-scanning direction and reflecting the light. A reading / scanning unit provided with a mirror unit for guiding light to the photoelectric conversion unit, a reference mark for detecting the amount of displacement of the origin of reading in the main scanning direction, and a reference mark for detecting the amount of displacement of the origin of reading in the rotation direction. Are provided above the document reading unit, and based on the movement amount of the mirror unit when the reading and scanning unit reads the respective reference marks by moving the mirror unit and the read output of the reading and scanning unit. A detection unit that detects an error of a reading start origin; and a control unit that determines an appropriate reading start origin by using each error detected by the detection unit as a correction amount. Image reading device. 5. An upper plate provided above a lower plate portion with a gap allowing movement of a sheet document and a lower plate portion to which a sheet document reading glass constituting the document reading section is attached. And a reference mark is provided on an inner surface of the conveyance path above the sheet document reading glass and at both ends in the main scanning direction so as to face each other. 5. The image reading device according to 4.