JP2000349962A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read on image with high quality by driving an image sensor and a step motor synchronously with each other, even of a frequency of a clock which is a reference of managing a drive period of the image sensor and a frequency of a clock being a reference of managing a step period of the step motor differ from each other. SOLUTION: A motor drive section 9 drives a step motor 2 by one step every time a timer 8 goes into a time-out. An image sensor drive section 6 drives an image sensor 4 in a drive timing just after the step motor 2 is driven among drive timing for each image sensor drive period on the basis of a 1st clock given from a 1st clock source 5. A motor speed control section 10 makes a step period set to the timer 8 constant to a constant speed drive, and the timer 8 is reset at the timing when the image sensor 4 is driven in a state where the timer 8 is at time-out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image while performing sub-scanning by a driving force generated by a step motor.

[0002]

2. Description of the Related Art As shown in FIG. 4, an image sensor is basically driven repeatedly at equal intervals (Ts).

[0003] On the other hand, the step motor is driven so as to make one step each time the timer finishes measuring a predetermined step cycle, but as shown in FIG. Is gradually reduced, that is, a so-called through-up is performed. At the time of constant-speed rotation, the same step cycle as the drive cycle Ts of the image sensor is fixedly set in the timer, and the step motor is driven synchronously with the image sensor.

[0004]

However, a clock serving as a reference for managing the driving cycle Ts of the image sensor,
In some cases, the clock used as the reference for the timer to measure time is transmitted from different clock sources.

In such a case, since the frequencies of the two clocks are different from each other, the step cycle measured by the timer during the constant speed rotation is Ts' different from the drive cycle Ts of the image sensor. .

The driving cycle Ts of such an image sensor
And the step cycle Ts' gradually accumulates, so that the drive timing between the image sensor and the step motor is greatly shifted, and the reading quality is degraded due to skipping of the line. .

The present invention has been made in view of such circumstances, and a purpose thereof is to manage a clock serving as a reference for managing a driving cycle Ts of an image sensor and a step cycle of a step motor. Even if the frequency of the reference clock is different from each other, it is possible to provide an image reading apparatus that can drive the image sensor and the step motor in synchronization with each other, thereby performing high-quality reading. is there.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, at least one of a document and an image sensor is driven by a step motor to move the document and the image sensor relatively. A predetermined reading measured based on a predetermined first clock oscillated by a predetermined first clock source in an image reading apparatus that reads an image formed on the document by the image sensor while moving the image by force. An image sensor driving unit such as an image sensor driving unit that causes the image sensor to perform reading at a timing after the step motor is stepped during the immediately preceding reading cycle among read timings of each cycle; A predetermined second clock oscillated by a predetermined second clock source different from the first clock source And a stepping motor such as a motor driving unit for driving the stepping motor by one step every time the timer counts the stepping cycle. Driving means, at the time of acceleration of the stepping motor, resetting the timekeeping means every time the timekeeping means finishes measuring the step cycle while changing the step cycle timed by the timekeeping means, and At the time of high-speed rotation, the time-measuring unit keeps the step period measured by the time-measuring unit constant while the time-measuring unit finishes measuring the step period. And a timer control means such as a motor speed control means for resetting.

By taking such means, the stepping motor is driven by one step every time the clocking means finishes measuring the step period based on the second clock signal oscillated by the second clock source. However, the timer is reset each time the step period is counted when the stepping motor is accelerated, whereas the timer is reset when the image sensor is driven in a state where the step period is counted during the constant speed rotation. Is done. Therefore, at the time of constant-speed rotation, the step motor is driven by one step every time when the time counting means finishes counting a predetermined step cycle from the timing when the image sensor is driven. The driving of the image sensor is performed only at the timing after the step motor is stepped during the immediately preceding reading cycle among the reading timings for each predetermined reading cycle, so that the driving of the step motor is performed one step at a time. The driving of the image sensor occurs alternately once each time.

[0010]

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 diagram showing a main configuration of an image reading apparatus according to this embodiment.

As shown in FIG. 1, the image reading apparatus according to the present embodiment includes a document conveying mechanism 1, a step motor 2, a light source 3, an image sensor 4, a first clock source 5, an image sensor driving unit 6, and a second clock. It has a source 7, a timer 8, a motor driver 9, and a motor speed controller 10.

The document transport mechanism 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. The original transport mechanism 1 is configured such that the kick roller 1a, the self-supply roller 1c, the transmission drive roller 1d, and the transmission drive roller 1g receive the rotational force of the step motor 2 via a transmission mechanism (not shown) and rotate. The documents D set on the document tray T are conveyed one by one from right to left in the figure.

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

The image sensor 4 is formed by integrating a large number of photoelectric conversion elements (not shown) in a one-dimensional array, and the direction in which the photoelectric conversion elements are arranged intersects with the direction of conveyance of the document D (depth in the figure). Direction). The image sensor 4 generates and outputs one line of image signal by sequentially outputting electric charges obtained by each photoelectric conversion element performing photoelectric conversion of light emitted from the light source 3 and reflected by the document D. The drive control of the image sensor 4 is performed by the image sensor drive unit 6, and the above operation is repeated each time a drive signal is given from the image sensor drive unit 6.

The first clock source 5 oscillates a first clock serving as a reference for managing the driving cycle (reading cycle) of the image sensor 4. Then, the first clock source 5 supplies the oscillated first clock to the image sensor driver 6.

The image sensor driver 6 drives the image sensor 4 by giving a predetermined drive signal. The image sensor driving unit 6 includes, for example, a hardware timer or a software timer, and measures a predetermined reading cycle Ts based on the first clock by using the timer to determine a reading timing for each reading cycle Ts. Ask. Then, the image sensor driving section 6 generates a drive signal at a timing after the step of the step motor 2 is performed during the immediately preceding reading cycle Ts among the obtained reading timings.

The second clock source 7 oscillates a second clock serving as a reference for managing the step cycle of the step motor 2. Then, the second clock source 7 supplies the oscillated second clock to the timer 8.

The timer 8 measures a step cycle variably set by the motor speed controller 10 based on the second clock, and supplies a time-out signal to the motor driver 9 and the motor speed controller 10.

The motor driving section 9 drives the stepping motor 2 to cause the document transport mechanism 1 to transport the document D. The motor drive unit 9 sets the stepping motor 2 to 1 each time a time-out signal is output from the timer 8.
Drive for the number of steps.

The motor speed control unit 10 sets a step cycle for the timer 8 and resets the timer 8 in accordance with the driving signal output from the image sensor driving unit 6 and the timing of the timer 8 to perform a step. The rotation speed of the motor 2 is controlled.

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

The processing relating to the image signal is the same as that of a conventional general image reading apparatus, and therefore the description thereof will be omitted. Here, the operation relating to the drive control of the step motor 2 will be described.

First, when the start of reading is instructed from outside, the image sensor driving section 6 starts measuring the reading cycle Ts. After resetting the timer 8, the motor speed control unit 10 sets the initial value T0 of the step cycle for acceleration control in the timer 8.

Then, the timer 8 sets the second clock source 7
Is performed based on the second clock supplied from the controller, and a time-out signal is output when the set step cycle is completed.

Each time the timeout signal is output from the timer 8, the motor drive unit 9 drives the step motor 2 for one step.

Thereafter, the motor speed control unit 10 resets the timer 8 every time a time-out signal is output from the timer 8, and sets the next step cycle (T1, T1) for acceleration control.
2, T3, T4) are sequentially set in the timer 8.

Here, the step periods T0, T1, T2, T
3, T4 has a relationship of T0>T1>T2>T3> T4. Therefore, the step cycle of the step motor 2 is gradually reduced, and the rotation speed of the step motor 2 is increased.

Now, the last step cycle T for acceleration control
When the timer 8 finishes counting the time 4, the motor speed control unit 10 shifts to the constant speed rotation control state.

In this constant speed rotation control state, the motor control section 9 fixes the step cycle set in the timer 8 to the reading cycle Ts. Further, in the constant-speed rotation control state, the motor control unit 9 does not immediately reset the timer 8 when the timer 8 times out, and when the timer 8 times out as shown in FIG. Waiting for output from the unit 6, the timer 8 is reset in synchronization with the output timing of the drive signal.

Thus, after the timer 8 measures the step period Ts, the timer 8 measures the elapsed time from the timing when the image sensor 4 is driven.

The timer 8 counts the step period Ts. Due to the influence of the respective frequency errors of the first clock and the second clock, the period until the timer 8 times out after the reset is effected by the image sensor 4.
(Ts> T in FIG. 2), which is different from the driving cycle Ts of FIG.
s').

Even when the timer 8 times out in a time period different from the driving cycle Ts of the image sensor 4 as described above, the motor driving section 9 synchronizes with the time-out signal output from the timer 8 in the same manner as in the acceleration mode. 2 is driven.

However, since the timer 8 stops the counting operation after the step motor 2 is driven and before the image sensor 4 is driven, the actual step cycle of the step motor 2 is
Is the time obtained by adding the error between the driving cycles Ts and Ts 'to Ts', that is, the same time as the driving cycle Ts of the image sensor 4. The driving timing of the image sensor 4 and the step timing of the step motor 2 are the same as those in FIG. The relationship is maintained as shown in FIG.

Since the image sensor driving section 6 drives the image sensor 4 at the drive timing immediately after the step motor 2 is driven, every time the step of the step motor 2 is performed, the image sensor 4 is regularly operated immediately after that. It will be driven.

FIG. 2 shows a case where Ts 'is shorter than Ts. If Ts' is longer than Ts, the driving of the image sensor 4 is actually performed as shown in FIG. At the drive timing following the timing,
This means that the timer 8 has not timed out yet.

When the timer 8 has not timed out, the motor speed control unit 10 does not reset the timer 8 even when the drive timing of the image sensor 4 arrives.

At this time, the stepping motor 2 is driven between the previous driving timing and the present driving timing.
Is not performed, the image sensor driving section 6 does not drive the image sensor 4.

As a result, the driving of the image sensor 4 and the step of the step motor 2 are performed at a cycle of 2 Ts, and the reading speed is reduced, but the step of the step motor 2 is performed. Each time, it is possible to drive the image sensor 4 regularly immediately thereafter.

As shown in FIG. 2, [Ts>Ts']
Since the reading speed does not decrease if the following relationship is established, the first clock source 5 and the second clock source 7
It is desirable to set such that a clock signal that satisfies the relationship of [Ts> Ts ′] holds even if an error occurs.

As described above, according to the present embodiment, the period until the timer 8 times out after the reset is different from the driving cycle Ts of the image sensor 4 due to the influence of the frequency error between the first clock and the second clock. T
Even if it is s', the time relationship between the drive timing of the image sensor 4 and the step timing of the step motor 2 can be kept constant, and the original D can be read stably.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the type in which the sub-scan is performed by transporting the document D is illustrated. However, the type in which the sub-scan is performed by moving the image sensor 4 or the type in which the document D and the image sensor 4 are both moved. The present invention can also be applied to a type in which sub-scanning is performed by moving in different directions.

The pattern of the change of the step period during the acceleration control is not limited to the one described in the above embodiment, but may be arbitrary.

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

[0045]

According to the present invention, at least one of the original and the image sensor is moved by the driving force generated by the step motor so that the original and the image sensor are relatively moved. In an image reading apparatus for reading an image formed on the document, the last reading timing of a predetermined reading cycle measured based on a predetermined first clock oscillated by a predetermined first clock source is used. Image sensor driving means for causing the image sensor to perform reading at a timing after the step motor is stepped during the reading cycle, and oscillated by a predetermined second clock source different from the first clock source A clock means for clocking a predetermined step cycle based on a predetermined second clock; Every time the step cycle is completed, step motor driving means for driving the step motor by one step, and when accelerating the step motor, changing the step cycle timed by the time means, The timer is reset every time the step cycle is completed, and when the stepping motor is rotating at a constant speed, the timer measures the step cycle while keeping the step cycle measured by the timer constant. A time control means for resetting the time measuring means each time the image sensor is driven by the image sensor driving means in a state, so that the driving cycle of the image sensor and the time Error occurs between the time it takes to finish counting the step period Since the one-step drive of the step motor and the drive of the image sensor occur alternately one by one while maintaining a fixed timing relationship, a clock serving as a reference for managing the drive cycle Ts of the image sensor and a step The image sensor and the step motor can be driven in synchronization with each other even if the frequency of the clock which is the reference for managing the step period of the motor is different from each other. It becomes a reading device.

[Brief description of the drawings]

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

FIG. 2 shows a timing relationship between the drive timing of the image sensor 4, the step timing of the step motor 2, and the timing operation of the timer 8.
FIG. 9 is a timing chart when the actual timeout time Ts ′ is smaller than the reading cycle Ts.

FIG. 3 shows a timing relationship between the drive timing of the image sensor 4, the step timing of the step motor 2, and the timing operation of the timer 8.
FIG. 7 is a timing chart when the actual timeout time Ts ′ is longer than the reading cycle Ts.

FIG. 4 is a timing chart showing respective timing relationships of a drive timing of an image sensor, a step timing of a step motor, and a timing operation of a timer in a conventional image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Document conveyance mechanism part 2 ... Step motor 3 ... Light source 4 ... Image sensor 5 ... First clock source 6 ... Image sensor drive part 7 ... Second clock source 8 ... Timer 9 ... Motor drive part 10 ... Motor speed control part D … Manuscript

Claims (1)

[Claims] An image sensor formed on an original by the image sensor while moving at least one of the original and the image sensor by a driving force generated by a step motor so that the original and the image sensor relatively move. In an image reading apparatus for reading an image, a read timing is measured based on a predetermined first clock oscillated by a predetermined first clock source. Image sensor driving means for causing the image sensor to read at a timing after the stepping motor is stepped; and a predetermined second clock oscillated by a predetermined second clock source different from the first clock source. A time counting means for counting a predetermined step cycle based on said step; Each time the cycle is finished,
Step motor driving means for driving the step motor by one step; and when accelerating the step motor, changing the step cycle timed by the time counting means while changing the step cycle timed by the time counting means each time the time counting means finishes counting the step cycle. And when the stepping motor is rotating at a constant speed, the image sensor is driven by the image sensor driving means in a state where the time counting means finishes counting the step cycle while keeping the step cycle counted by the time counting means constant. An image reading apparatus, comprising: a clock control unit that resets the clock unit each time the printer is driven.