JP2001358912A - Reader and image processing unit provided with the reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier drive means that provides a stable reading by decreasing fluctuations to the utmost in a relative speed between 1st and 2nd carriers on which a read optical system moving in a scanning direction is mounted. SOLUTION: It is required for read scanning to select a ratio of a pitch circle of a large diameter timing pulley to a pitch circle of a small diameter timing pulley of a drive pulley 8b to be 2:1 and a speed ratio of a 1st carrier to a 2nd carrier 3 fixed to timing belts 9b, 10b whose transmission teeth mesh with each other is selected to be 2:1. Number of the transmission teeth of the large diameter and that of the small diameter pulleys of the drive pulleys are selected equal (the pitch is 2:1) and a phase of teeth meshing with each other of the small diameter pulley at the same time is selected the same as that of the large diameter pulley so as to reduce fluctuations in the relative speed of the 1st and 2nd carriers on which the read optical system is mounted to the utmost so as to make a conjugate length from a read original face to a CCD constant thereby enhancing the image quality without causing an MTF deterioration in the read image and a magnification deviation in the main scanning direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading apparatus for reading an image in a scanning format provided in an image processing apparatus such as a scanner, a facsimile, a transfer machine, and a copying machine. And a reading apparatus for performing scanning driving of a carrier capable of performing stable reading with a small variation in relative speed between carriers (vibration) and an image processing apparatus including the reading apparatus Related to the device.

[0002]

2. Description of the Related Art A reading device provided in an image scanner device places a document on a document table, and optically scans a document surface fixed on the platen, while reading figures, characters, etc. represented on the document surface. Read image information. In such an apparatus, a lens and a CCD reading circuit among the elements constituting the photoelectric reading means are fixedly installed on the frame side of the apparatus, and an image on the document surface to be scanned is transmitted to the lens and the CCD reading circuit. An optical system such as a light source (lamp) and a mirror is mounted separately on two carriers, the first carrier is scanned along the document surface at a scanning (scanning) speed, and the second carrier is moved at half the speed. Generally, a two-carrier system is used. Note that the relationship between the speeds of the first and second carriers is as follows from the document surface to the CCD.
This is a condition for keeping the distance (conjugate length) to the constant (see FIG. 1 described later).

In a two-carrier type image scanner, means for driving two carriers has conventionally been a case using a wire and a case using a timing belt. FIG. 10 shows a schematic configuration of a carrier driving unit using a wire system. In the wire type driving means, as shown in FIG.
0 denotes a driven pulley 4 fixed to the left and right after being wound around a drive pulley 41 attached to the drive shaft 6 a plurality of times.
2 and 42, and further wrap each end side around the pulley 43 of the second carrier 3, and then fix both ends. The first carrier 2 is fixed to the wire crawled in this way,
The fixed first carrier 2 moves and scans at the linear speed of the wire 40 according to the input from the drive shaft 6. Further, the second carrier 3 moves accurately at half the linear velocity of the wire 40 because the pulley 43 serves as a moving pulley. As described above, the feature of the wire method is that since there is no meshing or the like, the speed fluctuation of the first carrier 2 is small, and the linear velocity of the second carrier 3 is exactly の of the linear velocity of the first carrier. In addition, the distance (conjugate length) from the document surface to the CCD becomes constant, and the optical performance hardly fluctuates, so that the read image accuracy can be improved.

FIGS. 2 and 3 show a carrier driving means based on a timing belt system. In the carrier driving means of the timing belt system, as shown in FIGS. 2 and 3, the first carrier 2 and the second carrier 3 are large-diameter pulleys of driving pulleys 8a and 8b each composed of timing pulleys having different pitch circles of different sizes. , The first and second timing belts 9 stretched over a small-diameter pulley having a half of the diameter thereof.
(A, b) and 10 (a, b). Therefore, each of the carriers 2 and 3 is engaged with the timing belts 9 and 10 and the teeth formed on the driving pulleys 8a and 8b by the meshing.
The driving pulleys 8a and 8b move along with the timing belts 9 and 10 driven at a linear speed equal to the peripheral speed of the timing circle of the timing pulleys of different pitch circles to perform scanning (note that
The details will be described in an embodiment of the present invention described later). This method is based on the timing belts 9,
Since it is only necessary to fix the first and second carriers 2 and 3 to the apparatus 10, there is an advantage that the assembly of the apparatus becomes very simple.

[0005]

However, in the case of the wire system, as described above, since the way of laying the wire is complicated, there is a problem that the assembling work of the apparatus becomes very difficult. Further, in the case of the timing belt system, the operation is performed by the engagement of the transmission belts of the timing belts 9 and 10 and the driving pulleys (timing pulleys) 8a and 8b, so that the first carrier 2 and the second carrier 3 have slight speed fluctuations. Would. In other words, for reading,
The speed fluctuation of the first carrier 2 causes a magnification deviation in the sub-scanning direction (carrier moving direction) and image jitter, and the fluctuation of the relative speed of the second carrier 3 with respect to the first carrier 2 is a conjugate length. Is changed, the MT of the read image is changed.
It appears as F or magnification deviation in the main scanning direction. When such a speed fluctuation becomes remarkable, the read image is deteriorated. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art in a two-carrier type reader, and has as its object to reduce the relative position of the second carrier to the first carrier without requiring a difficult assembling operation. Provided is a reading device that scans a carrier that enables stable reading while minimizing fluctuations in speed, and an image processing device (eg, a scanner, a digital copier, a facsimile, etc.) including the reading device. It is in.

[0006]

SUMMARY OF THE INVENTION The present invention employs a timing belt (belt having transmission teeth) system as a driving means for a carrier which does not require a difficult assembling operation, and employs transmission teeth having a plurality of different pitch circles. The present invention solves the conventional problem by improving a driving mechanism including a belt having transmission teeth bridged between a driving pulley and a driven pulley, and has a plurality of different pitch circles. A reading device which mounts a carrier having reading means on each of the belts stretched between a driving pulley having transmission teeth and a driven pulley, and scans and drives each carrier at a predetermined speed ratio determined by a pitch circle of the driving pulley. In the above, the number of transmission teeth having a plurality of different pitch circles of the drive pulley is equal to each other, and the phases of the teeth are provided in the same phase. Preparative a reading device according to claim.

According to a second aspect of the present invention, in the reader according to the first aspect, drive pulleys having transmission teeth having a plurality of different pitch circles are provided on both sides of a common drive shaft, respectively. Wherein one of the carriers is attached to each belt stretched between a pulley having transmission teeth having the same pitch circle and a driven pulley.

According to a third aspect of the present invention, in the reading device according to the second aspect, the transmission pulleys provided on both sides of a common drive shaft are provided with transmission teeth having the same phase. Is what you do.

According to a fourth aspect of the present invention, there is provided an image processing apparatus comprising the reading device according to any one of the first to third aspects.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the following embodiments shown in the accompanying drawings. FIG. 1 is a diagram illustrating a schematic configuration of an image reading apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 20 denotes an apparatus main body. Device body 2
A contact glass 39 for setting the original 21 to be read is provided on the upper surface of the reference numeral 0. The reading optical system A performs exposure scanning on the image surface of the fixed document 2 from the lower surface side of the contact glass 39. For the exposure scanning, the first carrier 2 is provided in the apparatus main body 20 so as to be movable in parallel with the contact glass 39.
And the second carrier 3 are provided. FIG. 1A shows a state in which both carriers are at the reading start position, and FIG.
Indicates the state at the reading end position. The first carrier 2 includes a light source 32 of the reading optical system A and a first mirror-3.
And the second carrier 3 has a first mirror 31
A second mirror 33 that reflects the reflected light of
And a third mirror 34 for reflecting the reflected light. Third
An optical imaging lens 35 for converging the reflected light from the third mirror 34 to form an image on the optical path of the reflected light of the mirror 34; For example, a photoelectric conversion element 36 composed of a CCD is provided.

Next, a description will be given of a carrier driving mechanism for moving both carriers to perform the above-described exposure scanning by the reading optical system A. 2 and 3 are views showing a driving mechanism of the carrier according to the present invention. FIG. 2 is a perspective view, and FIG.
The plan view is shown. In FIGS. 2 and 3, only the drive unit is shown and the details of the carrier and the optical system mounted thereon are omitted for easy understanding. The configuration of the carrier driving mechanism and its operation will be described mainly with reference to FIGS. The first carrier 2 and the second carrier 2 shown in FIG.
The carrier 3 is each of the carriers 2 and 3 shown in FIG.
The first mirror 31 and the illumination lamp 32 described above, and the second mirror 33 and the third mirror 34 described above are mounted, respectively. Both ends of the first and second carriers 2 and 3 are fixed to the first and second timing belts 9 (a, b) and 10 (a, b) by fixing means 29 (a, b) and 30 (a, b), respectively. The rotation speeds of the first and second timing belts 9 and 10 are changed depending on the difference in the pitch circle of the timing pulleys of the driving pulleys 8a and 8b which are wound and engaged with each other. In this example, the linear velocity of the second carrier 3 needs to be exactly の of the linear velocity of the first carrier. Therefore, the diameter of the pitch circle of the timing pulley meshed with the second timing belt 10 is set to the first timing belt. 9 is set to be 1/2 of the diameter of the meshing timing pulley. That is, the pair of first timing belts 9
a and 9b are stretched between the large-diameter timing pulleys of the drive pulleys 8a and 8b and the driven pulleys 23a and 23b, respectively, and a pair of second timing belts 10a and 10b.
b is bridged between the small-diameter timing pulleys of the driving pulleys 8a and 8b and the driven pulleys 24a and 24b, respectively, and the pitch circle of the small-diameter timing pulley with respect to the large-diameter timing pulley of the driving pulley 8 is set to 2: 1.

A driving force input mechanism for moving the timing belt to which the carrier is fixed will be described with reference to FIG. Drive pulleys 8a and 8b for driving the timing belts 9 and 10 are fixed to both sides of the drive shaft 6, and the drive shaft 6 is supported by front and rear bent portions of the apparatus frame 1 via bearings 16a and 16b. . Drive shaft 6
A deceleration pulley 7 is fixed to the rear end, and the driving force of the scanner motor 4 is transmitted to the deceleration pulley 7 via a driving timing belt 5 laid on the deceleration pulley 7. At the time of reading, the driving force of the scanner motor 4 is changed to the driving pulleys 8a, 8
The first carrier 2 and the second carrier 3 transmitted to the first timing belts 9a and 9b and the second timing belts 10a and 10b meshing with the large-diameter and small-diameter timing pulleys of FIG. Slide on the guide rails 15a and 15b at a moving speed ratio of 2: 1.

In the case where the above-described transmission mechanism using the driving pulley 8 and the timing belts 9 and 10 as a carrier driving mechanism, that is, a mechanism for transmitting a driving force by meshing teeth provided on the pulley side and the belt side, is used. It is ideal to operate the scanner motor 4 at a constant speed and move the timing belts 9 and 10 at a constant speed.
A slight speed fluctuation always occurs due to meshing of the teeth. FIG. 4 shows the structure of the drive pulley 8 that has been conventionally used.
FIG. 4 shows a large-diameter timing pulley 85 and a small-diameter timing pulley 86 provided with transmission teeth, respectively. As shown in the figure, the pitch of the timing belt 9 that meshes with the large-diameter pulley 85 is a case where the pitch is the same as the pitch of the timing belt 10 that meshes with the small-diameter pulley 86. Specifically, the number of teeth of the large-diameter pulley 85 is There are 16 teeth, and the number of teeth of the small-diameter pulley 86 is 8. When the timing belts 9 and 10 are driven by using the driving pulley 8 as described above, the speed fluctuation as described above is caused by the first carrier 2 and the second carrier 3.
Occurs.

FIG. 5A shows the first carrier 2 during driving.
And the speed fluctuation of the second carrier 3. FIG.
As shown in (A), the speed fluctuation of the second carrier 3 is twice as long as the speed fluctuation of the first carrier 2.
FIG. 5B shows a change in the relative speed of the second carrier 3 with respect to the first carrier 2 at the time of driving, that is, the speed of the second carrier 3 based on a half speed of the first carrier 2. Indicates fluctuation. 5B means that the distance (conjugate length) from the document surface to the CCD is not constant when scanning the optical system according to the configuration of FIG. This appears as MTF deterioration of the read image or magnification deviation in the main scanning direction. Conventionally, the deterioration of the read image due to the minute speed fluctuation caused by the meshing of the teeth was rarely considered as a problem. However, in recent years, the image quality has been required to be improved. There is a need for a countermeasure for suppressing the fluctuation of the relative speed as shown in FIG.

Therefore, in the present invention, as a result of examining the relative relationship between the tooth profile and the position so as to minimize the fluctuation of the relative speed of the second carrier 3 with respect to the first carrier 2, the large diameter of the driving pulley 8 is obtained. The pitch of the timing belt meshing with the small-diameter timing pulley with respect to the pitch of the timing belt meshing with the timing pulley is set to 2: 1, that is, in the drive pulley 8, the number of teeth of the large-diameter and small-diameter timing pulleys is made equal, and It is effective to make the phases of the simultaneously meshing teeth of the small-diameter pulleys in-phase with each other, and the problem is to be solved by this method. FIG. 8 shows the structure of the driving pulley 8 according to the embodiment of the present invention. FIG. 8 shows a large-diameter timing pulley 81 and a small-diameter timing pulley 82 each having a transmission tooth. As shown in the figure, the pitch of the timing belt 9 that meshes with the large-diameter pulley 81 is a case in which the pitch is equal to twice the pitch of the timing belt 10 that meshes with the small-diameter pulley 82. The number of teeth of the small diameter pulley 82 is the same number of 16 teeth. The timing belts 9 and 1 are formed by using such a driving pulley 8.
When 0 is driven, speed fluctuation occurs in the first carrier 2 and the second carrier 3 respectively.

FIG. 9A shows the first carrier 2 during driving.
And the speed fluctuation of the second carrier 3. FIG.
As shown in (A), the period and phase of the speed fluctuation of the second carrier 3 are the same as the speed fluctuation of the first carrier 2. FIG. 9B shows a change in the relative speed of the second carrier 3 with respect to the first carrier 2 during driving, that is, the first speed.
The speed fluctuation of the second carrier 3 with reference to the half speed of the carrier 2 is shown. In this example, since the period and phase of the speed fluctuation of the first carrier 2 and the second carrier 3 are the same, the fluctuation of the relative speed shown in FIG. 9B is the same as the conventional method (see FIG. 5B). ) Can be reduced. Note that the half of the first carrier 2 in FIG.
It is needless to say that the relative speed can theoretically be eliminated by adjusting the speed fluctuation of each carrier (shown in FIG. 9A) so that the speed of the second carrier 3 and the amplitude of the speed fluctuation of the second carrier 3 are made equal. By configuring the drive pulley 8 in this manner, the second speed with respect to half the speed of the first carrier
It is possible to make the relative speed fluctuation of the carrier sufficiently small,
The distance (conjugate length) from the document surface to the CCD becomes sufficiently constant, and MTF deterioration of the read image and magnification deviation in the main scanning direction are prevented, thereby improving image quality.

However, as shown in FIG. 6, when the phases of the large-diameter timing pulley 81 'and the small-diameter timing pulley 82' each having transmission teeth are out of phase (in this example, they are out of phase by half a cycle), FIG. 7A shows the speed fluctuation of each of the first carrier 2 and the second carrier 3 during driving.
The state illustrated in FIG. In this case, 1 of the first carrier 2
The variation in the relative speed of the second carrier 3 with respect to the / 2 speed shows a variation as shown in FIG. 7B, and the variation in the relative speed cannot be sufficiently reduced.
The distance (conjugate length) to the CD is not constant, and MTF deterioration of the read image and magnification deviation in the main scanning direction occur. Therefore, as shown in FIG. 8, it is necessary to match the phases of the large-diameter timing pulley 81 and the small-diameter timing pulley 82.

Further, the drive mechanism of the above-described embodiment, that is, a mechanism in which the number of teeth of each of the large-diameter and small-diameter timing pulleys is made equal, and the phases of simultaneously meshing teeth of the small-diameter pulley with respect to the large-diameter pulley are mutually the same. Is applied to a two-sided drive system using a pair of drive pulleys 8a and 8b fixed to both sides of the drive shaft 6. As in the embodiment shown in FIGS. 2 and 3, a pair of first and second timing belts 9 (a, b), 10 are respectively attached to a pair of drive pulleys 8a, 8b fixed to both sides of the drive shaft 6. (A, b)
In the two-sided drive system, the large-diameter timing pulley 81 and the small-diameter timing pulley 82 on each side are phase-aligned as described in the previous embodiment.
If there is a phase shift between the two drive pulleys without being adjusted, the perpendicularity of the first carrier 2 and the second carrier 3 to the optical axis of the lens 35 changes (rotationally displaces) for each scanning position, and an image is displayed. Fluctuation will occur. For this reason, the transmission teeth provided between the drive pulleys 8a and 8b are also attached to the drive shaft in the same phase (with the same phase) to prevent the image fluctuation due to the rotational displacement.

[0019]

(1) Effects corresponding to the first aspect of the invention Since the number of teeth of each of the plurality of transmission teeth of the drive pulley having different pitch circles is equal to each other and the phases of the teeth are provided in the same phase. The fluctuation of the relative speed between the timing belts moved by the driving force input from the driving pulley via the transmission teeth can be sufficiently reduced. In other words, the variation in the distance (conjugate length) from the document surface to the CCD which causes a reading error in the reading means mounted on each carrier fixed to each timing belt is small, and the conjugate length can be made substantially constant. Therefore, the MTF deterioration of the read image and the magnification deviation in the main scanning direction are prevented, and the image quality of the read image is improved as compared with the related art. (2) Effects corresponding to the second aspect of the invention In addition to the effects of the above (1), a drive pulley is provided on both sides of a common drive shaft, and each drive pulley has a transmission tooth having the same pitch circle. By attaching one of the carriers to each belt spanned between and the driven pulley,
Even if the reading surface is large and the carrier is elongated, stable driving can be performed. (3) Effects corresponding to the third aspect of the invention In addition to the effects of the above (1) and (2), the phases of the transmission teeth of the drive pulleys provided on both sides of the common drive shaft are provided in the same phase. Accordingly, the orthogonality of each carrier does not change (rotationally displace) for each scanning position, so that image fluctuation can be prevented, and the image quality of a read image can be further improved. (4) Effects corresponding to the invention of claim 4 By using the reading device according to any one of claims 1 to 3 as a component of an image processing apparatus, the effects of the above (1) to (3) can be obtained by a scanner. This can be realized in an image processing apparatus such as a copying machine and a facsimile, and the performance of the apparatus can be improved.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of an image reading apparatus according to an embodiment of the present invention, a state at a reading start position (A), and a state at a reading end position (B).

FIG. 2 is a perspective view showing a carrier driving mechanism according to the embodiment of the present invention.

FIG. 3 is a plan view showing a carrier driving mechanism according to the embodiment of the present invention.

FIG. 4 shows the structure of a conventional drive pulley composed of large-diameter and small-diameter timing pulleys.

5 shows the speed fluctuation of the first and second carriers by the driving pulley of FIG. 4 (A) and the relative speed fluctuation of the second carrier with respect to half the speed of the first carrier (B).

FIG. 6 shows the structure of a drive pulley in which large-diameter and small-diameter timing pulleys are out of phase.

7 shows the speed fluctuation of the first and second carriers by the driving pulley of FIG. 7 (A), and the relative speed fluctuation of the second carrier with respect to half the speed of the first carrier (B).

FIG. 8 shows the structure of a drive pulley according to an embodiment of the present invention, which includes large-diameter and small-diameter timing pulleys.

9 shows the speed fluctuation of the first and second carriers by the driving pulley of FIG. 8 (A) and the relative speed fluctuation of the second carrier with respect to half the speed of the first carrier (B).

FIG. 10 shows a schematic configuration of a conventional carrier driving means using a wire method.

[Explanation of symbols]

2: 1st carrier, 3: 2nd carrier, 6: drive shaft, 8, 8a, 8
b: drive pulley, 9a, 9b: first timing belt,
10a, 10b... Second timing belts 15a, 15b
... guide rails 81, 81 ', 85 ... large-diameter timing pulleys, 82, 82', 86 ... small-diameter timing pulleys.

Claims (4)

[Claims] 1. A carrier carrying reading means is attached to each of belts stretched between a driving pulley having transmission teeth having a plurality of different pitch circles and a driven pulley, and a predetermined belt determined by the pitch circle of the driving pulley. In a reading device that scans and drives each carrier at a speed ratio, the number of teeth of each of a plurality of transmission teeth having a plurality of different pitch circles of the driving pulley is equal to each other, and the phases of the teeth are provided in the same phase. Reading device. 2. The reading device according to claim 1, wherein drive pulleys having transmission teeth having the plurality of different pitch circles are provided on both sides of a common drive shaft, and the same pitch circle of each drive pulley is set. A reading device, wherein one of the carriers is attached to each belt stretched between a pulley having transmission teeth and a driven pulley. 3. The reading device according to claim 2, wherein the phases of the transmission teeth of the drive pulleys provided on both sides of a common drive shaft are provided in the same phase. 4. An image processing apparatus comprising the reading device according to claim 1. Description: