JPH06338991A - Image reader - Google Patents

Abstract

PURPOSE:To provide an image reader whereby vibration due to a shift scanning driving source is restricted and the deterioration of an image is prevented. CONSTITUTION:The image reader is characterized by providing document stand glass 100, a reading unit 107 being an image recording means which shift-scans a document P placed on the document stand glass 100 while executing illumination to it, permits reflection image light to be formed on an image sensor or a photosensitive body, etc., with a lens 105 and a pulse motor 127 being the shift scanning driving source of the reading unit 107 and by having a plunger solenoid 130 being a scanning and driving load changing means for changing the scanning and driving load of the reading unit 107 in accordance with set scanning speed in the image reader 1 whereby the scanning speed of the reading unit 107 is change possible by chaning-over the driving frequency of the pulse motor 127.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to drive transmission means for an image reading apparatus.

[0002]

2. Description of the Related Art As an image reading apparatus of this type which has been widely used in the past, there is, for example, one shown in FIG. FIG. 3 is a schematic diagram of the configuration of the color image reading apparatus.
In the figure, P'is a read document placed on the platen glass 200, and the reflected light emitted from the light source 201 is reflected by the mirrors 202, 203, and 204, and is reflected by the lens 20.
5 forms an image on the image sensor 206. Light source 20
1 and mirrors 202, 203 and 204, lens 20
5. The entire page is read by scanning the reading unit 207 on which the image sensor 206 is fixedly mounted in parallel with the original table glass 200.

In FIG. 4, the image on the original is the image sensor 2.
6 is a schematic drawing of how an image is formed on the light receiving unit 06. Around the light receiving portion of the image sensor 206, a portion for accumulating charges photoelectrically converted by the light receiving portion and a portion for transferring a signal to the output stage are adjacent to each other.
R, 206G, and 206B are lined up at intervals.

Since the image sensor 206 is moved relative to the original to read the same position of R, G, and B, the distance between the light receiving portions is an integral multiple of the width of the square light receiving element. When there is an interval of m lines between RGs and an interval of n lines between GBs, the G image signal of one line on the document is R
Image signal of m lines, B image signal is (m +
n) The line is read with a delay.

FIG. 5 is a block diagram of read image data processing by the color image sensor. The image data of each color read by the image sensor 206 is sent to the amplifiers 221R, 221G, 221B and amplified, respectively, and then converted into digital image signals by the A / D converters 222R, 222G, 222B. As described above, since the light receiving portions of each color of the image sensor 206 are lined up with an interval, in order to match the phase before the image signal is input to the image processing circuit 224, (m + n) is provided in the subsequent stage of the A / D converter 222R. A / D converter 22 for line
The buffer memory 223R for N lines is provided in the latter stage of 2G,
223G is provided and is output according to the B signal read at the end. The image processing circuit 224 outputs an image signal after color correction calculation and binarization processing.

Generally, an image reading apparatus used by being connected to a computer requires at least two scans to read necessary image data. In the first scan, the entire reading area is read and displayed on the display, and the reading area is specified from the image and 2
This is because the second scan is performed and necessary image data is read. The first scan is usually called a pre-scan, but the image quality such as the gradation that reduces and displays the image on the display does not necessarily have to be at the same level as the data to be finally read. From the point of view, it is desirable to finish the reading in a short time, and thus the reading is performed in a shorter time than the time required for the second scan (final scan). Further, it is desirable that the return of the reading unit to the home position after the reading is completed in a short time from the viewpoint of operability.

On the other hand, reading in the final scan mode is required to obtain a high quality image. A color image reading apparatus requires gradation reproducibility of about 256 gradations per color, but in order to obtain sufficient gradation, it is necessary that the output of the image sensor is sufficiently large. I need time. Further, the image reading apparatus may be interrupted / restarted during reading depending on the processing conditions of the computer, which is one of the performances required to smoothly connect the images before and after the interruption. Therefore, the reading unit is required to run stably regardless of interruption / resumption during reading.

A pulse motor is usually used as the scanning drive source of the image reading apparatus. This is because it is necessary to synchronize the motor with the reading cycle of the image sensor and the control is simple.

[0009]

The pulse motor has the characteristic that the torque decreases as the driving frequency increases. Therefore, in the case of having a plurality of scan modes having different speeds as described above, it is necessary to use a motor having a torque sufficient to scan the reading unit even when driving at the maximum driving frequency used.
However, when such a motor is used, the drive frequency becomes smaller in the final scan mode, and the surplus energy causes vibration, which may lead to deterioration of image quality. Especially when the reading is suspended / restarted, the image is significantly disturbed.
It is necessary to provide switching means for providing a means for canceling the load, increasing the drive load during the final scan, switching the current value of the motor, and reducing the current value during the final scan.

If a large motor is used, the external dimensions of the device, the power consumption, and the temperature rise will be adversely affected.

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 which suppresses vibration due to a moving scanning drive source and prevents deterioration of image quality. It is in.

[0012]

In order to achieve the above object, according to the present invention, an original placing glass and an original placed on the original placing glass are moved and scanned while illuminating the original, and the original is placed on the original placing glass. An image recording unit that forms reflected image light on an image sensor or a photoconductor through a lens and records it, and a moving scanning drive source of the image recording unit are provided, and the drive frequency of the moving scanning drive source is switched. Thus, the image reading apparatus in which the scanning speed of the image recording means can be changed has a scanning drive load changing means for changing the scanning drive load of the image recording means according to the set scanning speed.

Further, the image recording means is connected to the scanning driving force transmitting means at both ends thereof, and the scanning driving load changing means controls the scanning driving load by adjusting the tension applied to the scanning driving force transmitting means. You should change it.

Further, the image recording means may switch the scanning drive load changing means by moving to either the front or rear end of the movable scannable area.

[0015]

According to the image reading apparatus constructed as described above, the scanning drive load changing means for changing the scanning drive load of the image recording means according to the set scanning speed is provided.
The load on the moving scan drive source can be adjusted.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. (First Embodiment) FIG. 1 shows an image reading apparatus according to the first embodiment of the present invention. In the figure, reference numeral 1 denotes an image reading apparatus main body, which is a light source 101 for a document placed on a document table glass 100.
The reflected light emitted by the mirrors 102, 103, 10
The image is reflected by 4 and is imaged on the image sensor 106 by the lens 105. Light source 101 and mirror 10
2, 103, 104, lens 105, image sensor 1
Reading unit 1 as an image recording means on which 06 is fixedly mounted.
The entire page is read by scanning 07 on the platen glass 100 in parallel.

The plan view of FIG. 1 (a) shows a state where the upper cover and the platen glass 100 are removed.
Reference numerals 1 and 122 denote the reading unit 107 and the platen glass 10
It is a rail that slidably supports parallel to 0. The rail 121 is a round shaft and is fitted with bearings 108 fixed to the front and rear ends of the reading unit 107. Rail 1
Reference numeral 22 denotes a sheet metal rail on which the sliding member 109 attached to the reading unit 107 is placed. The rail 122
It is also possible to use a round shaft.

In the vicinity of the bearing 108 and the sliding member 109 of the reading unit 107, drive transmission belts 110 and 111 are fixed. Also belts 110 and 1
11 is hung on pulleys 123 to 126 provided near the reading start end and near the reading end end on the apparatus body, respectively. A driving force is transmitted to the pulley 123 from a pulse motor 127, which is a moving scanning driving source, via a belt 128. The pulley 124 is attached coaxially with the pulley 123 and rotates integrally. The pulley 125 is an idle pulley, and the belt 110 is stretched between the pulley 123 and the pulley 125 with appropriate tension. The pulley 126 is also an idle pulley, but its supporting member 12
Reference numeral 9 is linked to a plunger solenoid 130 which is a scanning drive load changing means, and a belt 111 stretched between a pulley 124 and an idle pulley 126 is attracted to the belt 110 when the solenoid is excited. The same level of tension is applied. When the solenoid is not excited, the tension applied to the belt 111 is almost zero.
Becomes

Next, the operation of the image reading apparatus configured as described above will be described.

When the computer instructs reading in the prescan mode, the solenoid 130 is not energized and scanning starts. At this time, the belt 111
Since the tension applied to is almost zero, the torque required by the motor 127 is the friction load generated when the reading unit 107 slides and the tension applied to the belt 110. High-speed scanning is performed by using the slow-up / slow-down control of the pulse motor 127. Even when the reading unit 107 returns to the home position, the solenoid 130 is driven at high speed without being excited.

The image data obtained by the prescan is often used as a reference for designating the reading range in the final scan and determining the brightness and contrast. Therefore, in order to obtain desired image data with as few scans as possible, it is desirable to obtain an image sensor output similar to that of final scan even in prescan. If the drive frequency of the image sensor 106 is constant irrespective of the reading speed, for example, when prescan is performed at a speed three times faster than the final scan, the same image sensor output can be obtained by subscanning for three lines of normal reading. Therefore, if the thinning rate of the data in the main scanning direction is adjusted to this, it is 1/3 of the actual size.
Large prescan data can be obtained. Since the resolution of the display is lower than that of the image reading apparatus, the display is further thinned out and displayed, so that the data is sufficiently large as data for prescan. Conversely, it is possible to increase the speed within the range of the performance of the motor 127 by calculating from the resolution of the display and the image reading device and the size displayed on the display.

When reading in the final scan mode, the solenoid 130 is excited. As a result, the same tension as that of the belt 110 is applied to the belt 111, and the load applied to the motor 127 is increased accordingly. Therefore, the excess torque that is converted into vibration is reduced. Further, since both ends of the reading unit 107 are driven to be driven, the reading unit 1 due to the looseness of the fitting of the rail 121 and the bearing 108.
There is no blurring as indicated by the arrow A of 07, and even if the computer is unable to process the data during the reading and is temporarily interrupted, the images before and after the interruption / resumption are smoothly connected.

The image reading apparatus having such a structure has the following merits.

Since the device structure is simple, the reliability is high.

The speed of the high speed scan can be greatly increased as compared with the normal scan.

In contrast to the conventional method of using a large motor capable of high-speed scanning to cancel the excess torque during normal scanning by increasing the driving load or decreasing the current value, the present invention uses the driving load itself during high-speed scanning. Since this method reduces the number of motors, it does not require a large motor, and is advantageous in terms of the external dimensions of the device, power consumption, and temperature rise.

In the normal scan, a high quality image can be obtained.

In the present embodiment, a light source, a mirror, a lens, and an image sensor are incorporated into one scanning unit as an image reading device equipped with a transparent original projection device.
Although the image reading apparatus of the integrated optical system has been described, the present invention is not limited to this, and the image reading apparatus of the 1: 1/2 optical system or the like can be similarly mounted. Further, the present invention is not limited to the color image reading device and can be applied to a monochrome reading device.

In this embodiment, the drive load is switched by providing two modes, one of which is a state in which tension is applied and the other is a state in which tension is not applied. It is also possible to switch between two stages and to change the driving load during prescan and final scan. (Second Embodiment) Since the solenoid is used in the first embodiment described above, a circuit for driving the solenoid is also required. In this embodiment, by adding simple mechanical parts,
A configuration that brings about the same effect will be described.

FIG. 2 is a schematic view of this embodiment. The same components as those in the first embodiment are designated by the same reference numerals.

Numerals 131 and 132 are levers as scanning drive load changing means which are attached to the main body so that the fulcrums 131a and 132a are swingable outside the scanning range of the reading unit 107. The two levers are connected and linked by a link 133. Also part of these levers 131
b and 132b are the lever portion 107 of the reading unit 107.
The position is switched when the reading unit 107 scans up to the area where the lever is located, which is opposed to a and 107b. A plate spring 134 for position switching / holding is attached near the lever 132 of the main body. Also lever 132
The idle pulley 126 is rotatably attached to the belt, and when the lever 131 rotates in the direction of arrow B, the idle pulley 126 pulls the belt 111 to apply tension to the belt 111. The lever 131 can take two positions, that is, a position where the idle pulley 126 releases the tension of the belt 111 or a position where the tension is applied to the belt 111 by the action of the leaf spring 134.

Next, the operation of the image reading apparatus having this structure will be described.

FIG. 2B shows the initial state before the start of reading, in which the reading unit 107 is stopped at the home position. At this time, the levers 131 and 132 are in positions where the idle pulley 126 releases the tension of the belt 111. Therefore, the load on the motor 127 is light, and the reading unit can scan at high speed.
The prescan and the return to the home position are performed with the lever in this position.

When a final scan is instructed by the computer, the reading unit 107 once moves in the direction opposite to the reading. This operation causes the lever 131 to move to the position shown in FIG.
It is pushed down in the direction of arrow B shown in (c), and the lever 132 is interlocked by the link 133 to switch the idle pulley 126 to a position where tension is applied to the belt 111. Since the load on the motor 127 increases and the reading unit 107 is supported by the belts 110 and 111 at both ends, the scanning of the optical system is stable, and a high-quality image can be obtained even if the reading is suspended / restarted. it can.

At the end of scanning, the protrusion 107b of the reading unit 107 pushes the lever 132, and therefore the lever 132 is returned to the initial position, so that the tension applied to the belt 111 is released and the home position is returned to the high speed mode. It will be possible.

According to this structure, since the solenoid and its drive circuit are not required, the same effect as that of the first embodiment can be achieved at a lower cost.

[0037]

The present invention having the above-described structure and operation has the scanning driving load changing means for changing the scanning driving load of the image recording means in accordance with the set scanning speed. It is possible to adjust the load applied to the image recording means and reduce the excessive torque that causes the vibration of the image recording means.

Further, since the driving load itself is reduced during high-speed scanning, a large motor is not required, which is advantageous in terms of external dimensions of the device, power consumption, temperature rise, and the like.

Further, the speed of the high speed scan can be greatly increased as compared with the speed of the normal scan, and desired image data can be read in a short time scan.

[Brief description of drawings]

1A, 1B, and 1C are a plan view, a side view, and a schematic view of a main part of an image reading apparatus according to a first embodiment of the present invention, respectively.

2A, 2B, and 2C are a plan view, a side view, and a schematic view of a main part of an image reading apparatus according to a second embodiment of the present invention, respectively.

3A and 3B are a plan view and a side view of a conventional image reading apparatus, respectively.

FIG. 4 is a schematic diagram showing how an image on a document is formed on a light receiving portion of an image sensor.

FIG. 5 is a block diagram of read image data processing by a color image sensor.

[Explanation of symbols]

P, P'reading originals 1, 2 image reading device 100, 200 original platen glass (original placing glass) 101, 201 light source of image reading device 105, 205 lens 107, 207 reading unit (image recording means) 110, 111 belt 123,124,125,126 Pulley 127 Pulse motor (moving scanning drive source) 130 Plunger solenoid (scanning drive load changing means) 131,132 Lever (scanning drive load changing means)

Claims (3)

[Claims] 1. A document placing glass and a document placed on the document placing glass are moved and scanned while being illuminated, and reflected image light of the document is imaged on an image sensor or a photoconductor through a lens. An image reading device that includes an image recording unit that records the image, and a moving scanning drive source of the image recording unit, and the scanning speed of the image recording unit can be changed by switching the driving frequency of the moving scanning drive source. An image reading apparatus having a scan driving load changing means for changing a scan driving load of the image recording means according to a set scanning speed. 2. The image recording means is connected at both ends thereof to a scanning driving force transmitting means, and the scanning driving load changing means controls the scanning driving load by adjusting tension applied to the scanning driving force transmitting means. The image reading apparatus according to claim 1, wherein the image reading apparatus is changed. 3. The image reading apparatus according to claim 1, wherein the image recording means switches the scanning drive load changing means by moving to either the front or rear end of the movable scannable area. .