JPH09233266A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary a read speed without degrading image quality and to perform variable power read by changing one line scanning time without degrading the image quality. SOLUTION: By respectively changing the carrying speed of an original D by an original carrying mechanism part 1 and the scanning time of one line of a line sensor 4, the read speed is changed. Also, by fixing the carrying speed of the original D by the original carrying mechanism part 1 and then changing the scanning time of one line of the line sensor 4, the variable power read is realized. Prior to the read of the original D, a line sensor control part 6 turns the scanning time of one line of the line sensor 4 to a value corresponding to a desired read form and then, controls the emitted light intensity of a light source 3 by controlling a light quantity varying part 11 until it is detected that the level of signals obtained by photoelectrically converting reflected light from a transmission white roller 1f in the line sensor 4 becomes higher than a prescribed level in a light quantity detection part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a line sensor to read an original document conveyed by an original document conveyance mechanism, and has an image reading function which has a function of changing the reading speed and performing variable-magnification reading. Regarding the device.

[0002]

2. Description of the Related Art A line sensor is usually used with a constant scanning time for one line. Therefore, when the reading speed is controlled in the image reading apparatus using the line sensor, the feeding speed of the document is changed by step feed of the motor, or the document is intermittently fed by operating the motor intermittently.

On the other hand, when performing variable-magnification reading (enlargement reading or reduction reading), generally, the data read once at the same size is held in a memory or the like, and enlargement processing or reduction processing by data processing is performed.

[0004]

When the step feed speed of the motor is changed, the step feed speed of the motor is
When the motor is driven by 1-2 phase excitation, it can be changed only in units of even multiples, so there is a limitation that the reading speed can only be made even multiples. Further, when the motor is operated intermittently, the reading operation is repeatedly stopped and started, which deteriorates the image quality of the read image. Further, since the scanning time for one line is not changed in either of the above two methods, the data of the same line is repeatedly read when the document feed speed is reduced, and therefore, a process of discarding a part of the read data can be performed. Was needed.

Further, it is necessary to hold data for at least one line in order to perform enlargement processing or reduction processing by data processing, and to hold data for two or more lines in order to improve the image quality of a processed image, which is a large capacity. Requires memory.

As another method of performing variable-magnification reading, there is a method of changing the scanning time of one line while keeping the document feeding speed constant. According to this method, image processing is almost unnecessary, a line memory for holding data is unnecessary, and a 1-bit to 2-bit latch unit is sufficient. However, since the scanning time for one line is changed, the amount of light incident on each photoelectric conversion element of the line sensor changes, and the level of the image signal output by the line sensor changes. Therefore, in order to keep the relative ratio of the black image level and the white image level when the image signal is digitally converted, it is necessary to increase the signal level of the image signal by using an amplifier circuit, which leads to deterioration of image quality. .

The present invention has been made in consideration of such circumstances, and the first object thereof is to provide an image reading apparatus capable of varying the reading speed without deteriorating the image quality. To provide.

A second object of the present invention is to provide an image reading apparatus capable of performing variable-magnification reading by changing the one-line scanning time without degrading the image quality.

[0009]

In order to achieve the above first object, the present invention provides a reading speed by changing the scanning time for one line of a line sensor and the document conveying speed by a document conveying mechanism. In the image reading apparatus capable of changing the line sensor, the light emission intensity of the light source for irradiating the original with light is determined according to the scanning time of one line of the line sensor, for example, the line sensor from the reflected light from a predetermined reference surface. The light emission intensity control means, which includes, for example, a light amount detection unit, a line sensor control unit, and a light amount variable unit, is provided so as to control the level of the image signal generated by the device to a predetermined level.

In order to achieve the above second object, according to the present invention, variable-magnification reading is performed by changing the scanning time of one line of the line sensor while keeping the original conveying speed by the original conveying mechanism constant. According to the scanning time of one line of the line sensor, an image reading device that can perform
The emission intensity of the light source for irradiating the original with light is controlled, for example, so that the level of the image signal generated by the line sensor from the reflected light from the predetermined reference surface becomes a predetermined level.
For example, an emission intensity control unit including a light amount detection unit, a line sensor control unit, and a light amount variable unit is provided.

By taking such a means, even if the scanning time for one line of the line sensor is changed to change the reading speed or to perform the variable magnification reading, the line sensor can change the scanning time. The variation in the amount of received light is compensated by controlling the emission intensity of the light source.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram showing the main configuration of the image reading apparatus according to this embodiment.

This image reading apparatus includes a document transport mechanism section 1,
It has a motor 2, a light source 3, a line sensor 4, a light amount detection unit 5, a line sensor control unit 6, a line scanning control unit 7, a clock switching unit 8, a main control unit 9, a motor control unit 10, and a light amount variable unit 11. It becomes.

The document transport mechanism section 1 includes a kick roller 1a,
It comprises a self-supplying rubber plate unit 1b, a self-supplying roller 1c, a transmission driving roller 1d, a pinch roller 1e, a transmission white roller 1f, a transmission driving roller 1g, and a pinch roller 1h. In the original document transport mechanism section 1, the kick roller 1a, the self-feeding roller 1c, the transmission drive roller 1d, and the transmission drive roller 1g receive the rotational force of the motor 2 via a transmission mechanism (not shown) and rotate, respectively. The sheet D is conveyed from right to left in the figure.

The light source 3 irradiates the document D conveyed by the document conveying mechanism 1 with light below the transmission white roller 1f.

The line sensor 4 is composed of a large number of photoelectric conversion elements (not shown) which are one-dimensionally arranged and integrated, and the arrangement direction thereof is a direction intersecting the conveyance direction of the document D (depth direction in the drawing). It is arranged along. The line sensor 4 generates and outputs an image signal for one line by sequentially outputting charges obtained by each photoelectric conversion element performing photoelectric conversion of light emitted from the light source 3 and reflected by the document D. And
The image signal output by the line sensor 4 is given to the light amount detection unit 5 and the line sensor control unit 6, respectively.

The light amount detecting section 5 comprises a comparator 5a and resistors 5b and 5c. The light amount detection unit 5 uses the comparator 5a to determine whether the image signal output from the line sensor 4 has a level higher than the reference voltage Vref generated by dividing the voltage V2 by the resistors 5b and 5c. And the image signal is the reference voltage Vre
When it has a level higher than f, an output signal of "H" level is given to the line sensor control section 6.

The line sensor control unit 6 has a synchronization signal and clock switching unit 8 provided from the one-line scanning control unit 7.
The line sensor 4 is driven by applying a transfer pulse or a transfer clock generated based on a clock signal supplied from the line sensor 4. Further, the line sensor control unit 6 performs processing such as digitization and binarization on the image signal output by the line sensor 4 and outputs binary image data. Further, the line sensor control unit 6 also has a function of controlling the light amount variable unit 7 to adjust the emission intensity of the light source 3.

The 1-line scanning control section 7 gives a synchronization signal to the line sensor control section 6 and the motor control section 10, and a selection signal to the clock switching section 8, respectively.
The period of the synchronization signal and the type of the selection signal are changed according to the reading speed or the reading magnification instructed by the main control unit 9.

The clock switching unit 8 is supplied with a plurality of types (here, three types) of clock signals having different frequencies. The clock switching unit 8 selects one of a plurality of types of clock signals designated by a selection signal and supplies it to the line sensor control unit 6.

The main control section 9 controls the respective sections of the image reading apparatus of this embodiment as a whole to realize the operation as the image reading apparatus. The main control unit 9 receives the designation of the reading speed or the reading magnification from the outside (for example, designation by the user) and instructs the 1-line scanning control unit 7 to do so.

The motor control unit 10 drives the motor 2 in synchronization with the synchronization signal given from the 1-line scanning control unit 7 so that the document conveying mechanism unit 1 conveys the document D.

The light quantity varying unit 11 includes M resistors 11a.
(11a-1, 11a-2 ..., 11a-M) and M switches 1
1b (11b-1, 11b-2, ..., 11b-M). Resistor 1
1a is connected in series via a switch 11b. The side of the resistor 11a-1 to which the switch 11b-1 is not connected is connected to the drive voltage V1 of the light source 3. The side of the resistor 11a-M to which the other resistor 11a is not connected is connected to the light source 3 via the switch 11b-M. The switch 11b has a fixed contact and a movable contact on one side of the resistor 11b.
It is arranged so as to be connected to a. Each switch 11
The other movable contact of b is connected to the drive voltage V by the bypass line.
It is directly connected to 1. Then, each of the switches 11b is switched according to the control signal given from the line sensor control unit 6.

Next, the operation of the image reading apparatus configured as described above will be described. First, the motor control unit 10 drives the motor 2 in synchronization with the synchronization signal given from the 1-line scanning control unit 7, whereby the document conveying mechanism unit 1 operates and the document D is conveyed. When the leading edge of the document D reaches below the transmission white roller 1f, the line sensor control unit 6 drives the line sensor 4 to start reading the document D.

The image signal generated and output by the line sensor 4 is given to the line sensor control section 6, where it is subjected to digitization processing, binarization processing and the like and converted into binary image data.

By the way, for example, when scanning an A4 original at a standard speed (reading an A4 original at time T1) at the same magnification, the scanning time for one line is L1, the clock required by the reading element control unit 4 is CLK2, and the original is Paper feed speed is 1 / L1pps (However, if you want to make the reading area of one step, that is, the step angle smaller,
L1 is an integer multiple).

Thus, when reading at the same speed at the standard speed T1, the one-line scanning control section 7 gives a synchronization signal having a cycle of L1 to the line sensor control section 6 and the motor control section 10, and Clock signal CLK
A selection signal indicating selection of 2 is given to the clock switching unit 8.
Then, the clock switching unit 8 causes the clock signal CLK2
To the line sensor controller 6.

At this time, the line sensor control unit 6 generates necessary signals such as a transfer pulse and a transfer clock for scanning one line during the time L1 from the synchronizing signal and the clock signal, and these signals are generated. The line sensor 4 is driven by.

On the other hand, when the reading speed is increased to three times the standard speed (one-size reading), the time required to read an A4 original is (1/3) T1, so the main control unit 9 sends one line. (1/3) L1 for the scan controller 7
Scan speed is specified. At this time, the clock required by the reading element control unit 4 is CLK1.

The 1-line scanning controller 7 has a cycle of (1 /
3) The synchronization signal of L1 is given to the line sensor control unit 6 and the motor control unit 10, and the clock signal C
A selection signal indicating selection of LK1 is given to the clock switching unit 8. Then, the clock switching unit 8 causes the clock signal CL
K1 is given to the line sensor controller 6.

At this time, the line sensor control unit 6 determines that the line sensor control unit 6 is 1 during the time (1/3) L1 from the synchronization signal and the clock signal.
Necessary signals such as a transfer pulse and a transfer clock for scanning the line are generated, and the line sensor 4 is driven by these signals. Thus, three lines can be scanned during L1, thus achieving a read speed three times the standard speed. In addition, when lowering the reading speed,
The procedure is similar to that described above.

Next, the case where the reading speed is the standard speed and variable-magnification reading is performed will be described. The variable-magnification reading (enlargement / reduction) is performed by changing the scanning time of one line while keeping the motor 2 at a constant speed and keeping the conveyance speed of the document D constant. For example, in the case of magnified reading, the main control unit 9 receives the designation of the scaling factor n% and instructs the 1-line scanning control unit 7.

The 1-line scanning controller 7 has a cycle L of (10
A sync signal of 0 / n) L1 is output to the line sensor control unit 6. Further, at this time, the 1-line scanning control unit 7 gives the clock switching unit 8 a selection signal for designating a clock signal according to the 1-line scanning time L1. FIG. 2 shows the correspondence relationship of the clock signal with respect to the 1-line scanning period or the scaling ratio, which is the basis for the 1-line scanning control unit 7 to determine the clock signal to be selected.

At this time, the line sensor control unit 6 generates a necessary signal such as a transfer pulse or a transfer clock for scanning one line during the time (100 / n) L1 from the synchronization signal and the clock signal. Then, the line sensor 4 is driven by these signals.

Thus, if enlargement reading is designated and a value larger than 100% is designated as the scaling factor n%, the 1-line scanning time L is the 1-line scanning time L at the same magnification.
Although it becomes smaller than 1, the reading speed becomes faster, but since the document feed speed is constant, the line data generated from a constant document area increases, and the line sensor control unit 6
The binary image data generated in step 1 corresponds to the enlarged image.

On the other hand, reduction reading is designated, and the scaling factor is n%.
If a value smaller than 100% is specified as, 1
The line scanning time L is longer than the 1-line scanning time L1 at the same magnification and the reading speed becomes slower, but since the original feeding speed is constant, the line data generated from a constant original area decreases. The binary image data generated by the line sensor control unit 6 corresponds to the reduced image.

The image signal output from the line sensor 4 corresponds to the image enlarged or reduced only in the sub-scanning direction (paper feed direction). Therefore, the line sensor control unit 6 enlarges or reduces the main scanning direction by interpolating or thinning the pixel data in the main scanning direction. For this processing, a line memory for holding data is not particularly necessary, and a 1-bit to 2-bit latch unit is sufficient.

The document reading process is performed as described above. Prior to this, the line sensor control unit 6
The following processing is performed. That is, as shown in FIG. 3, the line sensor control unit 6 first clears the variable N to "0" (step ST1). And the line sensor control unit 6
Causes all of the switches 11b of the light quantity varying unit 11 to select the resistor side (step ST2), and then starts driving the line sensor 4.

At this time, the light source 3 has M resistors 11b.
Since the drive voltage is supplied through all of the above, the light emission intensity of the light source 3 is adjusted to the minimum. Since the document D is not yet conveyed here, the light emitted from the light source 3 is applied to the transmission white roller 1f. The surface of the transmission white roller 1f is coated in white and serves as a reference surface.
Therefore, if the line sensor 4 is driven, the line sensor 4
Will photoelectrically convert the reflected light from the reference surface. The line sensor 4 is driven during the scanning time for reading the document D.

After starting the driving of the line sensor 4, the line sensor control unit 6 takes in the output of the light amount detection unit 5 (step ST4) and judges whether or not it is at the "H" level (step ST4). Step ST5).

Here, when the output level of the line sensor 4 is lower than the reference voltage Vref, that is, when the line sensor 4 cannot receive a sufficient amount of light, the output of the light amount detecting section 5 becomes "L" level. ing. Therefore, at this time, the line sensor control unit 6 increments the variable N by 1 (step ST6) and then causes the Nth switch 11b-N to select the bypass side. This makes it 1 more than ever
Since many resistors 11a are bypassed, the voltage applied to the light source 3 increases, and the light emission intensity of the light source 3 increases.

Thereafter, the line sensor control section 6 repeats the processing of steps ST4 to ST7 until the output of the light quantity detection section 5 becomes "H" level, and gradually increases the voltage applied to the light source 3. Then, when the output of the light amount detection unit 5 becomes the “H” level, that is, when the light emission intensity of the light source 3 exceeds the predetermined reference level, the above-described document reading process (step ST8) is started.

As described above, according to the present embodiment, by changing the scanning time for one line of the line sensor 4, the reading speed can be made variable and variable-magnification reading can be performed.
When the scanning time of one line of the line sensor 4 is changed,
Although the amount of light received by the line sensor 4 during the one-line scanning period is reduced, in the present embodiment, the light source 3 is provided so that the line sensor 4 can receive a constant amount of light while the scanning time for one line is changed. Since the light emission intensity is adjusted, the change in the amount of received light is compensated for, and high-quality reading can be performed by keeping the relative ratio of the white image and the black image constant regardless of the scanning time of one line.

Further, according to the present embodiment, the line sensor 4
The output signal level of the light source 3 is monitored and the light emission intensity of the light source 3 is adjusted by feedback control. Can be adjusted to.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the image reading device capable of both the change of the reading speed and the variable-magnification reading is illustrated, but the present invention can be implemented as an image reading device capable of only one of them. Is.

In the above embodiment, the light emission intensity of the light source 3 is adjusted by the feedback control. However, a table showing the relationship between the scanning time of one line and the light emission intensity of the light source 3 is prepared, and the open loop is prepared. The emission intensity of the light source 3 may be adjusted by control.

In the above embodiment, the light emission intensity of the light source 3 is adjusted before starting the document reading process, but the same control is performed while the document is being read or between pages. You may do it.

In addition, various modifications can be made without departing from the gist of the present invention.

[0049]

The present invention provides an image reading apparatus capable of changing the reading speed by changing the scanning time of one line of the line sensor and the document feeding speed by the document feeding mechanism. According to the scanning time of one line, the light emission intensity of the light source for irradiating the original with light is adjusted so that the level of the image signal generated by the line sensor from the reflected light from the predetermined reference surface becomes a predetermined level. Since the light emission intensity control means including a light amount detection unit, a line sensor control unit, and a light amount variable unit, which is controlled in accordance with the above, is provided, the image reading apparatus can change the reading speed without degrading the image quality.

The present invention also provides an image reading apparatus capable of performing variable-magnification reading by changing the scanning time of one line of the line sensor while keeping the original feeding speed of the original feeding mechanism constant. Depending on the scanning time of one line of the line sensor, the emission intensity of the light source for irradiating the document with light is set such that, for example, the level of the image signal generated by the line sensor from the reflected light from a predetermined reference surface is a predetermined level. Since the light emission intensity control means including, for example, a light amount detection unit, a line sensor control unit, and a light amount variable unit is provided, the variable-magnification reading while changing the one-line scanning time does not deteriorate the image quality. The image reading apparatus can be realized.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a main configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a correspondence relationship of clock signals with respect to one line scanning period or a scaling ratio.

FIG. 3 is a flowchart showing a processing procedure of a line sensor control unit 6 relating to adjustment of light emission intensity of a light source 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Original document conveyance mechanism section 2 ... Motor 3 ... Light source 4 ... Line sensor 5 ... Light amount detection section 6 ... Line sensor control section 7 ... 1 line scanning control section 8 ... Clock switching section 9 ... Main control section 10 ... Motor control section 11 ... Light amount variable section 11a (11a-1, 11a-2 ..., 11a-M) ... Resistor 11b (11b-1, 11b-2 ..., 11b-M) ... Switch

Claims (3)

[Claims] 1. A line comprising a light source for irradiating a document with light and a large number of photoelectric conversion elements arranged one-dimensionally, and photoelectrically converting reflected light from the document to generate an image signal line by line. A sensor; and a document transport mechanism for transporting the document in a direction intersecting the arrangement direction of the photoelectric conversion elements, the scanning time for one line of the line sensor, and the document transport mechanism transporting the document. An image reading apparatus capable of changing a reading speed by changing the speed and a light emission intensity control means for controlling a light emission intensity of the light source according to a scanning time of one line of the line sensor. An image reading device characterized by the above. 2. A line for arranging a light source for irradiating a document with light and a large number of photoelectric conversion elements one-dimensionally, and photoelectrically converting reflected light from the document to generate an image signal line by line. The line sensor includes a sensor and a document transport mechanism that transports the document in a direction intersecting with the arrangement direction of the photoelectric conversion elements. The line sensor is configured to have a constant document transport speed by the document transport mechanism. In an image reading apparatus capable of performing variable magnification reading by changing the scanning time of one line, the emission intensity control means for controlling the emission intensity of the light source according to the scanning time of one line of the line sensor, An image reading apparatus comprising: 3. The light emission intensity control means controls the light emission intensity of the light source so that the level of the image signal generated by the line sensor from the reflected light from the predetermined reference surface becomes a predetermined level. The image reading device according to claim 1 or 2.