JPS62163458A - Image reader - Google Patents

Abstract

PURPOSE:To read sharply an image even in case a lens system whose depth of field is shallow has been used, by providing a prescribed interval being roughly equal to thickness of an original, between an original carrying rotary roller and a read surface. CONSTITUTION:On both ends of a shaft 9a of an original carrying rotary roller 9, an interval forming member (roller) 10 which is cylindrical and runs idle is provided so as to be freely rotatable. An external form of the interval forming member 10 is formed so as to be larger by t1 than the external form of a rotary roller, and it always contact the lower face of a transparent glass plate 8. The interval t1 is set so as to be roughly equal to thickness of an original form, and the best focus surface is maintained by the rotary roller 9. Accordingly, an image of an original 12 can always be read sharply in the best focus state, and a lens 42 whose depth of field and depth of focus are shallow can be used. Also, in case there is no original, the rotary roller 9 runs idle by keeping an interval t1, therefore, a sudden increase of a load of a paper feed motor can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image reading device, and more specifically, the present invention relates to an image reading device, and more specifically, it feeds a document in the main and sub-scanning directions, and images the document image at the reading position on a reading sensor using an optical system. The present invention relates to an image reading device that reads images.

[Prior Art] Conventionally, in such an image reading device, a document is intermittently fed in the sub-scanning direction, and while the document is stationary, a reading sensor consisting of an optical lens system, a CCD, etc., and a light source for illuminating the document are activated. The integrated reading unit is moved in the main scanning direction over the document surface, and the document image at the reading position is focused on a reading sensor by a lens system to read the document image.

In addition, such a reading optical system and a recording head are integrally mounted and scanned back and forth, and the document paper and recording paper are conveyed in opposite directions in intermittent sub-scanning, and the main and sub-scanning are alternately repeated. 2. Description of the Related Art There are also known reading and recording apparatuses that read image information using an optical system and quickly copy it onto recording paper.

[Problems to be Solved by the Invention] Incidentally, in an image reading device used in a facsimile machine, etc., a document is sent to a reading section by a document conveying roller, and a line image of the document, which is imaged through a lens system, is captured by a similar reading sensor. It is read by photoelectric conversion, but
The lens system used has a relatively long focal length, and the distance between the lens system and the reading sensor surface and the distance between the lens system and the document surface are also set relatively large. Therefore, both the depth of focus and the depth of field are relatively deep, and the range of the so-called best focus plane, where the document surface at the reading position is in focus and the best image formation is obtained, is relatively large. For this reason, the interval between the document transport paths that regulate the position of the document is 1 to 1.
．． It is set relatively wide at 5 mm, and in this case there is no problem and the focus will not shift.As an extreme example, there are devices that only have a guide plate on the lower side in the document conveyance path.

On the other hand, image reading devices that integrate a recording unit and a reading optical system are strongly required to be smaller and thinner, so a lens system with a short focal length and wide angle of view is used. The distance between the sensor surfaces and the distance between the lens system and the document surface are made small. For this reason, it is advantageous to use, as a lens system, a so-called selfoc lens (row-shaped converging light guide lens), which has a small Tc value, that is, a short focusing distance between the document surface and the sensor surface.

However, with lens systems like the one above, the depth of focus.

Both the depth of field becomes very shallow, and during reading, it is necessary to correctly set the relative positions of the document surface, lens system, and sensor surface within extremely small dimensions (for example, 0.2 to 0.3 mm).

Here, if the lens system and the reading sensor are integrated into a unit, the accuracy of the distance between the lens system and the sensor surface can be easily achieved.

In addition, as a conventional structure that achieves accuracy in the distance between the lens system and the document surface, at the document reading position, the bottom surface of the transparent glass plate serves as the reading surface and is positioned at the desired position of the document surface in relation to the lens system, that is, the best focus surface. There is a structure in which a transparent glass plate is arranged so that the document is conveyed at a reading position on the lower surface thereof, and the original is pressed against the reading position by a conveying roller, and the original is sent by rotating the roller.

However, with this structure, when the end of the document passes the reading position, the surface of the transport roller comes into direct contact with the glass surface with high friction, causing a sudden increase in load, but even under this condition the transport roller still needs to rotate. . Therefore, a powerful motor with a large torque is required as a drive motor for the conveyance roller, and there is a problem in that the roller surface is worn out due to friction.

[Means for Solving the Problems] In order to solve the above-mentioned problems, according to the present invention, in an image reading device that forms an image of image information of a document on a reading sensor using an optical system and reads the image information, a lower part of the document reading surface is provided. A configuration is adopted in which a document conveying means is provided, and a means for separating the document reading surface and the conveying means by a predetermined distance, and the document is conveyed by the document conveying means and the document is maintained at a predetermined position with respect to the optical system. .

[Function] According to this structure, the document can be supported in contact with the reading surface by the rotating roller serving as the document conveying means, and if the reading surface is set as the best focus surface, the image can be read sharply, and the end edge of the document can be read. When the reading surface passes between the rotating rollers, the rotating roller does not come into contact with the reading surface, and the load on the driving motor of the rotating roller does not increase rapidly.

[Embodiments] Hereinafter, details of embodiments of the present invention will be described with reference to the attached drawings. Note that although an image reading device used in the document reading section of the above-mentioned reading and recording device with a copy function will be described as an example, the present invention can also be applied to an image reading device that does not include a recording device.

Figures 1 and 2 illustrate the structure of this embodiment.
FIG. 2 is a vertical side view and a vertical front view showing the structure around the document reading section of the reading and recording device.

In both figures, reference numerals 13 and 14 indicate an upper guide plate and a lower guide plate, which constitute a conveyance path for the original 12 to the reading position indicated by two dashed lines in FIG. Above the reading position, a transparent glass plate 8 of uniform thickness is placed horizontally with its lower surface serving as the reading surface f of the original 12.
The position of this reading surface f is positioned at the above-mentioned best focus surface in relation to the positional relationship with the reading system described later.

A rotating roller 9 is located below the reading position of the transparent glass plate 8.
is provided to sandwich the original 12 between it and the transparent glass plate 8 in order to read the original surface and position it at f (best focus surface). The rotating roller 9 is made of resin, rubber, etc., and is preferably white. As shown in FIGS. 2 to 4, cylindrical spacing members (rollers) 10 are provided at both ends of the shaft 9a of the rotating roller 9 which is supported on the frame 5.
is rotatably supported on a bearing. As shown in FIG. 4, the outer diameter of the spacing member 10 is the outer diameter D2 of the rotating roller 10.
Since the spacing forming members 10.10 on both sides are in constant contact with the lower surface of the transparent glass plate 8 on the outer side of the reading area, a spacing t1 is formed between the transparent glass plate 81 and the rotating roller 9. The size of the interval t1 is set approximately equal to the thickness of a thin letter manuscript paper (approximately 501 Lm), so that the rotating roller 9 maintains the best focus surface and allows the document to be conveyed.

Further, one sensor S for detecting the presence or absence of a document 12 is installed near the lower side of the transparent glass plate 8.

Furthermore, on the downstream side (the first
On the right side of the figure, there are two pairs of conveyor rollers 6.7, 6', and 7'.
are placed at intervals.

The conveyor rollers 6, 7, 6', 7' and the rotary roller 9 are supported in parallel between the frames 5 of the main body, and are interlocked via a gear mechanism such as an idle gear 11 so that the peripheral speeds are the same. The document 12 is rotated by the drive of a sub-scanning feed motor (not shown) and transferred to the roller 9. Conveyance roller 6.7.6
', 7': Send to the right in Figure 51. *Feed roller 6
A tray (not shown) is arranged downstream of ', 7', and the original 12 is discharged onto this tray.

In addition, a platen roller 30 is attached to the 7 frame 5 slightly above the pair of conveyor rollers 6.7 and 6', 7'' so that it can rotate while being in pressure contact with the roller 6.6'. The recording paper 32 inserted from the rear upper part of the device along the line 31 is held between the rollers 6'30 and the guide plate 33.
It passes between the recording head 20 and the flat platen roller 30, is held between the rollers 6 and 30, is curved into a U-shape, and is ejected upward through the space between the recording head 20 and the elastic portion 35 of the flat platen 34.

In addition, the platen 30. Transport roller 6.7.6'.

7' and the rotary roller 9 are configured so that they can be rotated together by the same sub-scanning Nolls motor through pressure contact or gears, etc., so that the original 12 and the recording paper 32 are completely synchronously conveyed in the sub-scanning direction. can be done.

Further, in FIGS. 1 and 2, a reference numeral 41 indicates a light source that illuminates the surface of the document at the reading position. Also code 4
Reference numeral 2 denotes a lens, which in this case is configured as the SELFOC lens mentioned above, which captures the image of the document surface at the reading position using CO2.
The image is formed on the sensor surface of a reading sensor 43 made up of D and the like.

The light source 41, lens 42, and reading sensor 43 are integrally combined as a reading unit, and the recording head 2
0 and is mounted on the top of carriage 44. The carriage 44 is slidably provided on a rail 45 installed parallel to the transparent glass plate 8 and the rotating roller 9.
It slides on the rail 45 by driving a pulse motor (not shown), and moves the reading unit and the recording head 20 in the main scanning direction.

Note that what is indicated by the reference numeral 46 is a photoelectric conversion circuit that converts information read by the reading sensor 43 into an electrical signal.

Next, the operation of the device configured as described above will be explained. First, operate the platen roller 30 to move the recording paper 32 to its leading edge (
The predetermined position you want to record) is the recording area.

set so as to face the card 20.

Next, the original 12 is manually inserted between the upper and lower guide plates 13 and 14 from the left side of FIG.
It is inserted until it abuts between the three-rotation rollers 9.

Next, operation of the apparatus is started by operating an operation key (not shown), and the rotation roller 9 is rotated as shown by the arrow in FIGS.
is sent in the right direction in FIG. 1 (in the direction of arrow A in FIG. 3) while being pressed against the lower surface of the transparent glass plate 8. When the leading edge of the document 12 is detected by the sensor S, the paper feed motor is stopped, and the document 12 is stopped at the position shown in FIG.

Next, the light source 41 is turned on, and the carriage 44 is moved in the main scanning direction (rightward in FIG. 2 along the longitudinal direction of the transparent glass plate 8) by driving a scanning pulse motor (not shown). As a result, as shown in FIGS. 3 and 4, the light source 4
1. Lens 42. The unit of the reading sensor 43 is moved in the direction of the arrow X.

Then, as shown in FIG. 3, the surface of the document 12 in contact with the lower surface of the transparent glass plate 8 is scanned with a reading width yi. Note that the reading width Y1 can be arbitrarily set depending on the number of bits of the sensor elements arranged in the sub-scanning direction of the reading sensor 33. Further, as shown in FIG. 3, a cylindrical lens may be used as the lens 42.

An image of the document 12 is formed on the sensor surface of the reading sensor 43 via the lens 42 by the reflected light from the light source 41 . The bit signal accumulated for a certain period of time is photoelectrically converted into a digital image signal by a photoelectric conversion circuit 46. Subsequently, this image signal is manually applied to the recording head 20 and synchronously recorded on the recording paper 32.

In order to perform such synchronous recording, the original 12 and the recording paper 32 are
are arranged shifted by a distance L in the main scanning direction as shown in FIG.

By the way, when reading in this way, the area of the reading width Y1 on the document surface as shown in FIGS. 3 and 4 is the document 12.
Transparent glass plate 8 is rotated by rotating roller 9 over the entire width of
The reading surface f, that is, the best focus surface on the lower surface of the lens is pressed against or in contact with, and is positioned at the best focus surface. Therefore, the image of the document 12 can always be read clearly and in the best focus state.

When one main scan is completed, the document 12 is sent to the right in FIG. 2 (width scanning direction) by a reading width of 71 minutes, and the carriage 44 is moved in the opposite direction, causing the reading unit to move in the direction of arrow Z and return to the home position. Return to

By repeating the above, when reading of the entire surface of the original 12 is completed and the end of the original 12 passes between the transparent glass plate 81 and the rotating roller 9, the rotating roller 9 does not contact the transparent glass plate 8 with an interval t1. Since the paper feed motor idles, the load on the paper feed motor does not increase rapidly unlike in the conventional case. Therefore, a paper feed motor with low torque can suffice to feed the document.

As described above, according to this embodiment, sharp reading can be performed at all times in the best focus state, a lens 42 with a shallow depth of field and a shallow depth of focus can be used, and a paper feed motor with a small torque can be used. Used.

It goes without saying that the above-described structure related to the spacing between the rotating rollers and the reading surfaces can also be applied to other image reading devices used in facsimile machines and the like.

[Effects] As is clear from the above description, according to the present invention, a constant distance approximately equal to the thickness of the original is provided between the rotating roller for transporting the original and the reading surface, so that the rotating roller can read the original. The device can be supported in contact with the surface, that is, the best focus surface, and can read sharp images even when using a lens system with a shallow depth of field, and the motor for feeding the document can be of low torque, making the device smaller and thinner. can be achieved.

[Brief explanation of drawings]

The drawings are for explaining the present invention in detail. FIG. 1 is a longitudinal sectional side view of an image reading section of a reading/recording device employing the present invention, FIG. 2 is a longitudinal sectional front view showing the image reading section of the same device, and FIG. 3 and 4 are explanatory diagrams of the reading operation, respectively. 8...Transparent glass plate 9...Rotating roller 10.
...Space forming member 12...Document 41...Light source
42...Lens 43...Reading sensor

Claims (1)

[Claims] An image reading device that forms and reads image information of a document on a reading sensor using an optical system, which includes a document conveying means disposed below the document reading surface, and a means for separating the document reading surface and the conveying means by a predetermined distance. . An image reading device, wherein the document is conveyed by the document conveyance means and the document is maintained at a predetermined position with respect to an optical system.