JPH11196241A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader with excellent quality that reads an image with a stabilized density independently of the flapping of an original to be carried. SOLUTION: An original tail end sensor in an original carrying path detects the head and tail end of an original, and after start of reading the original (S1) and the tail end of the original passes through the original tail end sensor, the number of steps is counted (S2), after a prescribed step number (e.g. 300 steps) is counted (S3), it is discriminated that the original tail end approaches a read-out point (the original tail end passes a folded part of the carrying path), a read-out slice level is decreased (S4), and the slice level is restored (S5) after finishing the read-out of the tail end.

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 having a function of reading an image on a sheet document, such as a facsimile or a copying machine.

[0002]

2. Description of the Related Art Conventionally, as this type of image reading apparatus, for example, there are a facsimile and a copying machine.

For example, in a facsimile, two pairs of document conveying rollers are provided upstream and downstream of a reading means for reading a document image, and the document is read while being conveyed.

A reading device as a reading means includes a CCD.
An optical system composed of an inexpensive reduction optical system having a large depth of focus and a close contact type image sensor having a small depth of focus but a small device itself is used.

Usually, in a system for horizontally transporting a document, since the document does not flutter up and down, the document is urged by a simple urging means using a flexible member using a contact type image sensor having a small document focal depth.

Further, in a V-shaped document conveying path where the fluttering of the document is large, a reduction optical system having a large depth of focus is used, or when a contact type image sensor is used, the document is conveyed to the sensor while being conveyed. An uncontacted contact roller is used.

[0007]

However, in the case of the above-described prior art, the following problems have occurred.

Generally, in a device for reducing the installation area of the apparatus so that the document discharge tray does not protrude out of the apparatus, a configuration is adopted in which the document conveyance path is formed into a U-shaped path and discharged to the same side as the document insertion position. I have.

Also, a device having only one document reading means, a so-called book scanner which moves a reading device and performs a flat scan, and a sheet scanner which reads a document with a fixed reading device while conveying a sheet document. In the provided apparatus, the sheet document descends from the sheet document separation unit to the position of the platen glass for performing the flat reading, and thus the document path becomes V-shaped.

In such a U-shaped or V-shaped document path, the document flutters at the reading point because of a large amount of flutter. Therefore, a roller is used to bring the document into close contact with the reading point.
Immediately after that, the fluttering of the document tends to occur, and depending on the illuminance of the light source and the light transmission ability of the document, the light irradiated from obliquely below is transmitted and attenuated depending on the height of the document, and the document reading density decreases. There is.

This will be described in more detail with reference to FIGS. 5 and 6 are schematic configuration diagrams of an image reading unit of the image reading device.

FIG. 5 shows that the rear end of the original is still in the original conveying path 106k.
The document is conveyed by rollers (the peripheral speed of the discharge-side roller is set to be higher than that of the upstream side) on the upstream side and the downstream side of the document conveying path formed by the V-shaped path when the sheet is in the middle. The original is brought into close contact with the contact roller 107a, and the light from the light source 108 is reflected by a light beam a1 that is hardly transmitted through the original and is reflected.
A light beam b1 is transmitted through the document and attenuated and returned in the gap between the back surface of the document and the contact roller 107a.

On the other hand, FIG. 6 shows a state in which the trailing edge of the sheet document S has fallen on the platen glass through the paper feed roller and the document conveyance path 106k. In this state, the document is conveyed only from the paper discharge roller side. Because of the force, the contact roller 107
a, a gap is formed between the back surface of the document and the contact roller 107a, and the light flux from the light source is attenuated from a1 and c1
Enters the reading point.

Further, since the gap between the back surface of the document and the close contact roller 107a is large even on the slightly upstream side, the light flux transmitted through the document and returned also enters the reading point with d1 darker than b1.

Due to the above phenomenon, in a document reading apparatus in which a gap is provided between the platen glass and the document contact roller in the V-shaped document conveying path, the light amount at the rear end of the document decreases, and However, there was a tendency for shadows to be easily formed (different in density) at the rear end of the document.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an image reading apparatus capable of reading an image at a stable density regardless of the fluttering of a conveyed document. An object of the present invention is to provide an image reading apparatus excellent in the above.

[0017]

In order to achieve the above object, according to the present invention, there is provided a conveying roller for conveying a document to be conveyed while regulating the position on the downstream side of a bent portion of a bent conveying path, A light source that irradiates the document from an upstream side of a position at which a conveying force is applied by the conveying roller, and a reading unit that reads reflected light of a document image obtained by irradiation by the light source, Density correction means is provided for reading a document at a constant reference density even with respect to changes in the amount of reflected light and the amount of transmitted light caused by a change in the distance between the surface of the transport roller and the document.

Accordingly, the original can be read at a constant reference density by the density correction means.

The density correcting means corrects the density by an amount corresponding to the reflectance, which is reduced by the distance between the surface of the conveying roller and the original being widened by the rear end of the original being conveyed passing through the bent portion of the conveying path. Good to do.

It is preferable to provide a detecting means for detecting that the rear end of the document to be conveyed has passed the bent portion of the conveying path.

The detecting means may include a detecting sensor for detecting the passage of the trailing end of the document upstream of the bent portion, and a measuring means for measuring a moving distance of the document after the passage is detected. .

Preferably, the density correcting means is performed by adjusting a slice level.

Further, the density correction means can be performed by adjusting the amount of illumination by the light source.

[0024]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, relative arrangement, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

(First Embodiment) An image reading apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a flowchart of the image reading apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic perspective view of the image reading apparatus according to the embodiment of the present invention. 1 is a schematic sectional view of the configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 4 is a partial perspective view of a main part of the image reading apparatus according to the embodiment of the present invention, and FIG. 7 is a block diagram of the image reading apparatus according to the embodiment of the present invention.

In FIG. 7, reference numeral 323 denotes a document detecting means for judging that the leading and trailing edges of the document have been detected by the document detecting sensor 25 (see FIG. 3). A step counter (measurement means) for counting the number of feed steps; 325, an image sensor control means for controlling the operation of the contact type image sensor 108 having a built-in Xe tube light source;
08 is a light amount adjusting means for adjusting the light amount of the light source inside 32.
Reference numeral 7 denotes a slice level adjusting means for determining a reading density.

In FIG. 1 and FIG.
The leading and trailing edges of the original document are detected by the original trailing edge detection sensor 25 during the period k, and after the reading of the original document is started (s1), the counting of the number of steps is started after the trailing edge of the original document passes through the original trailing edge detection sensor 25 (s2). ), Predetermined steps (for example, 300s
Step) After counting (s3), it is determined that the trailing edge of the document approaches the reading point (the trailing edge of the document passes through the bent portion of the transport path), and the reading slice level is lowered (s4). After the end, the slice level is restored (s5).

In a specific experimental example, in the case of an original having a thickness of 75 μm, the reading density at the rear end of the original is 0.2 to 0.4 as an OD value.
(Macbeth density).

As described above, the slice level can be changed based on the experimental data to correct the decrease in the amount of light at the rear end of the document.

Reference numeral 108 denotes a contact image sensor.
Equipped with a long focal length SELFOC lens 108a inside,
The focus is set so as to be focused on the platen glass 130a having a thickness of 3 mm.

A light source provided by a xenon tube 108b is provided inside, and has a long focal length and a main scan of 0.7 msec / l.
High-speed scanning up to about ine is possible.

The optical unit 3 is slidably supported in the thrust direction (that is, in the sub-scanning direction) with respect to the guide shaft 6 via the bearing 3b.

This bearing position is provided at a position deviated from the center of gravity of the optical unit composed of the contact image sensor 108, the optical unit 3, the adjusting unit 1, and the biasing spring 4 in the main scanning direction.

A sliding member 13 is provided below the end of the optical unit 3 in a direction opposite to the direction in which the bearing position is shifted.
Is provided.

The guide shaft 6 has a frame 13 at both ends.
0b and fixed horizontally.

A slide rail 14 is provided on the frame 130b in parallel with the guide shaft. When the slide member 13 comes into contact with the slide rail 14, the contact type image sensor 108 can be kept horizontal. When the optical unit 3 moves in the sub-scanning direction along the guide shaft 6, the sliding member 13 moves while contacting the slide rail 14.

Reference numeral 7 denotes a timing belt for moving the optical unit 3 in the sub-scanning direction, and reference numeral 8 denotes a drive unit provided with a stepping motor.

Reference numeral 2 designates the timing belt 7 connected to the optical unit 3
The surface in contact with the timing belt 7 is provided with at least two convex portions parallel to the peak of the belt at intervals of an integral multiple of the pitch of the timing belt 7. The member 2 is made of a resin material having high rigidity and elasticity (Young's modulus is 2500 kgf / mm ² or less).

Reference numeral 130a denotes a platen glass. On the back surface, a contact image sensor 108 is urged from below, and the distance between the contact image sensor 108 on the optical unit that moves in the sub-scanning direction and the upper surface of the platen glass 130a. Is always kept constant.

This configuration eliminates factors that cause the position of the optical unit 3 to vary in the vertical direction, such as the height of the guide shaft 6 and the height of the rail 14 of the frame 130b, and can eliminate the influence of the focal length shift.

Therefore, since the component accuracy can be designed at the general intersection level, the cost can be reduced.

Reference numeral 102 denotes a pressure plate, which can be opened and closed up and down, and urges a sheet document or book placed on the platen glass 130a from above to bring the read image surface of the document into close contact with the platen glass 130a. Things.

Reference numeral 20 denotes a photo interrupter, which is a home position sensor (hereinafter referred to as HPS: Home Position Sensor) for detecting a reference position of the optical unit 3. Reference numeral 21 also denotes a photo interrupter. And a right end position sensor (hereinafter referred to as RES: Right End Sensor) which detects an infrared light shielding portion 3C provided in the optical unit 3.

When the optical unit 3 is at the position of the HPS 20, the reading point of the image sensor 108 is the size index 115
Is directly under.

It is to be noted that a white sheet is provided on the back surface of the size index 115 and pre-scanned by the image sensor 108 to be used as a white reference when reading an original.

Reference numeral 106 denotes a sheet document transport unit provided on the pressure plate 102, which moves up and down as the pressure plate 102 opens and closes.

The sheet original transport section 106 sequentially separates a plurality of sheet originals stacked on the pressure plate 102 from below and transports them to the sheet original reading position 107.

Reference numeral 107a denotes a document contact roller (conveyance roller)
At both ends, bearings 107b having a diameter 0.3 mm larger than the roller diameter are provided, and the bearings 107b abut against the platen glass 130a to keep the gap between the close contact roller 107a and the platen glass 130a constant.

Even if the document fluctuates up and down between the gaps, the document reading point always exists within the document depth of focus range.

Reference numeral 106k denotes an original path through which the original conveyed by the paper feed roller 106f passes. Mylar 106m is a flexible member constituting the lower side of the original path 106k. It is arranged so that when the rear end of the original passes through the front end of the mylar 106m, the original gradually advances to the original reading point 107.

As described above, when the trailing edge of the document sheet passes through the bent portion of the transport path, the decrease in the reading density caused by the decrease in the light amount due to the trailing edge passing through the bent portion is reduced by lowering the slice level. This can be corrected by the following.

Therefore, an image can be read at a stable density.

(Second Embodiment) FIG. 8 shows a second embodiment of the present invention. In the above-described first embodiment, the configuration in which the reading density is adjusted by the slice level adjustment is described. In the present embodiment, the configuration in which the reading density is adjusted by adjusting the light amount of the light source is shown.

Other configurations and operations are the same as those of the first embodiment, and therefore, the same components will be denoted by the same reference characters and description thereof will be omitted.

FIG. 8 is a flowchart of the image reading apparatus according to the second embodiment of the present invention.

In FIG. 8, s11 to s13 are the same as s1 to s3 in the flowchart of FIG. 1 shown in the first embodiment.

Then, in the present embodiment, s14
By increasing the light amount of the light source by the light amount adjusting means, transmission and attenuation at the rear end of the document are corrected.

After the reading is completed, the light source is turned off (s15).

Even with such a configuration, when the rear end of the original sheet passes through the bent portion of the transport path, the decrease in the reading density caused by the decrease in the light amount due to the rear end passing through the bent portion is reduced by the light source. It can be corrected by increasing the amount of light.

Therefore, an image can be read at a stable density.

[0063]

As described above, according to the present invention, the density at which the original is read at a constant reference density even with respect to the change in the amount of reflected light and the amount of transmitted light caused by the change in the distance between the surface of the conveying roller and the original. Since the correction means is provided, the document can be read at a stable density regardless of fluttering of the conveyed document, and the quality is improved.

The density correcting means corrects the density by an amount corresponding to the reflectance, which is reduced by the distance between the surface of the conveying roller and the original being widened by the rear end of the original being conveyed passing through the bent portion of the conveying path. And can be read at a stable concentration.

The density correcting means can be performed by adjusting the slice level or adjusting the amount of illumination by the light source.

[Brief description of the drawings]

FIG. 1 is a flowchart of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration perspective view of the image reading apparatus according to the embodiment of the present invention.

FIG. 3 is a schematic sectional view of an image reading apparatus according to the embodiment of the present invention;

FIG. 4 is a partial perspective view of a main part of the image reading apparatus according to the embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an image reading unit of the image reading device.

FIG. 6 is a schematic configuration diagram of an image reading unit of the image reading device.

FIG. 7 is a block diagram of the image reading apparatus according to the embodiment of the present invention.

FIG. 8 is a flowchart of the image reading apparatus according to the second embodiment of the present invention.

[Explanation of symbols]

 25 Document detection sensor 106k Document conveyance path 107a Document contact roller 108 Contact image sensor 108b Xenon tube 323 Document detection means 324 Step counter 326 Light quantity adjustment means 327 Slice level adjustment means

Claims (6)

[Claims] A transport roller for transporting a document to be transported while restricting the position thereof on a downstream side of a bent portion of the bent transport path, and irradiating the document from an upstream side of a position where a transport force is applied by the transport roller. And a reading means for reading reflected light of the document image obtained by irradiation of the light source, wherein the amount of reflected light and the transmission caused by a change in the distance between the surface of the transport roller and the document. An image reading apparatus comprising a density correction unit for reading a document at a constant reference density even when a light amount changes. 2. The density correction means according to claim 1, wherein the density is reduced by an amount corresponding to a reflectance that is reduced by an increase in the distance between the surface of the transport roller and the original when the rear end of the original to be transported passes through a bent portion of the transport path. The image reading apparatus according to claim 1, wherein the correction is performed. 3. An image reading apparatus according to claim 1, further comprising detecting means for detecting that the rear end of the document to be conveyed has passed the bent portion of the conveyance path. 4. The detecting means comprises a detecting sensor for detecting the passage of the rear end of the document upstream of the bent portion, and a measuring means for measuring a moving distance of the document after the passage is detected. The image reading device according to claim 3, wherein: 5. An image reading apparatus according to claim 1, wherein said density correction means performs the adjustment by adjusting a slice level. 6. The apparatus according to claim 1, wherein said density correction means adjusts the amount of illumination by said light source.
5. The image reading device according to 3 or 4.