JPH07115513A - Image reader - Google Patents

Abstract

PURPOSE:To always attain excellent reading independently of a magnification or reduction factor by devising the reader such that its read means is moved smoothly at a wide variety of speed. CONSTITUTION:A CPU 20 recognizes a designated operation on an operating panel 21 and recognizes a designated magnification or reduction factor. Then the CPU 20 gives a current according to the magnification or reduction factor to a drive current setting circuit 24, which adjusts a currant given to a drive motor 11 by a motor drive circuit 25 to be a current corresponding to setting data, that is, a current corresponding to the magnification or reduction factor.

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 moving an image reading section to perform sub-scanning and generating an image signal corresponding to a document.

[0002]

2. Description of the Related Art FIG. 4 is a diagram schematically showing a general structure of an optical system of an image reading apparatus. In the figure, 1 is a document placing table 2
It is a light source that irradiates the document 3 placed on the. 4 is
It is a first mirror that reflects the reflected light from a predetermined position of the original 3 to the second mirror 6. The light source 1 and the first mirror 4
Are mounted on the first carriage 5.

The second mirror 6 changes the optical axis of the light coming from the first mirror 4 by 90 ° and guides it to the third mirror 7. Third
The mirror 7 further changes the optical axis of the light coming from the second mirror 6 by 90 ° and guides it to the lens 9. The second mirror 6 and the third mirror 7 are mounted on the second carriage 8.

The lens 9 images the light coming from the third mirror 7 on the CCD 10. The CCD 10 generates an electric signal having a level corresponding to the amount of incident light, that is, an image signal corresponding to the image of the original 3.

By the way, the first carriage 5 and the second carriage 8 are reciprocally moved in the direction of the arrow shown by the drive mechanism as shown in FIG. That is, the first carriage 5 is provided with the belt fixing portion 5a at one end thereof and the two pulleys 8a and 8b on one side surface of the second carriage 8, respectively. Further, a pulley 11b is provided at one end of the drive shaft 11a of the drive motor 11 serving as a drive source, and a pulley 12 is provided at the opposite side of the drive motor 11 to a fixing member (not shown) fixed to the housing, for example. . Then, the pulley 8a → the pulley 11b → the pulley 12 → the belt fixing portion 5a.
→ The timing belt 13 is stretched in the order of the pulley 8b. Both ends of the timing belt 13 are fixed to fixing members (not shown) fixed to the housing, for example. Further, a structure similar to the above structure is also provided on the other end side, whereby a drive mechanism is constituted. Thus, by rotating the drive motor 11, the first carriage 5 and the second carriage 8 reciprocate, and the document 3 is scanned in the sub-scanning direction.

Now, the CCD 10 performs photoelectric conversion operation at a constant cycle. Therefore, the magnification of reading can be changed by changing the moving speed of the first carriage 5, and this is used to perform the enlarged reading and the reduced reading. That is, by enlarging the reading by lowering the rotation speed of the drive motor 11 and decreasing the moving speed of the first carriage 5, conversely, increasing the rotation speed of the drive motor 11 and increasing the moving speed of the first carriage 5. By doing so, reduction reading is performed.

When enlarging / reducing by changing the moving speed of the first carriage 5 as described above, it is necessary to variably control the number of rotations of the drive motor 11, which is, for example, a step motor. If used, it can be easily controlled by the frequency (pulse rate) of the drive signal.

Now, focusing on the current value of the drive signal, the higher the current value, the greater the torque that can be obtained. However, if the difference (margin) between the current value that can obtain the required torque and the current value of the drive signal is large, the rotation unevenness of the drive motor 11 increases and vibration (and thus noise) occurs.
Grows larger.

FIGS. 6 and 7 are views showing the results of measurement of motor rotation fluctuation unevenness by Optoflow manufactured by Yerman Co., Ltd. FIG. 6 shows a case where a sufficient margin is taken, and FIG.
Indicates the case where the margin is minimized. In addition,
The pulse rate of the drive signal is 200 pps. This Figure 6
As can be seen from FIG. 7 and FIG. 7, the higher the current value margin, the larger the variation unevenness. Under such circumstances, it is desirable that the current value of the drive current of the drive motor 11 is set to the necessary minimum.

However, the torque generated by the drive motor 11 varies depending on the current value of the drive signal, and the minimum current value at which the required torque can be obtained varies depending on the rotation speed of the drive motor 11.

8 and 9 are views showing the relationship between the torque of the motor and the pulse rate of the control signal. FIG. 8 shows the case where the current value of the control signal is high, and FIG. 9 shows the case where the current value of the control signal is low. Each time is shown. As can be seen from FIGS. 8 and 9, when the pulse rate is the same (when the rotation speed is the same), the higher the current value, the larger the torque. When the current value is constant and the pulse rate is high (the rotation speed is high), the torque decreases.

Therefore, if the current value of the drive signal is set so that the margin is maintained even in the high speed rotation range, the margin becomes large in the low speed rotation range, resulting in large fluctuation unevenness. Therefore, if the current value of the drive signal is set to have an optimal margin in the low speed rotation range in order to reduce the fluctuation unevenness in the low speed rotation range, the torque becomes insufficient in the high speed rotation range, and step-out occurs during slew-up. There is a risk.

[0013]

As described above, the prior art is as follows.
Since the current value of the drive signal of the drive motor is constant, it is not possible to prevent fluctuation fluctuations in the low-speed rotation range or insufficient torque in the high-speed rotation range. If you change the speed,
There was a problem that the reading means could not be driven smoothly.

The present invention has been made in consideration of such circumstances, and an object thereof is to make it possible to smoothly move the reading means at a wide range of speeds, and thereby to enlarge or reduce the magnification. An object of the present invention is to provide an image reading device that can always perform excellent reading regardless of the above.

[0015]

In order to achieve the above object, the present invention generates an image signal corresponding to a reflected light image from a document at a predetermined cycle, such as a first carriage, a second carriage and a CDD. And a drive motor, and the rotational speed of the drive motor along the document so as to change the read position of at least part of the read means (for example, the first carriage and the second carriage). Moving means to move at a speed according to
Receiving means such as an operation panel for receiving the designation of the reduction ratio, and speed control such as a motor drive circuit for changing the moving speed of the reading means by the moving means according to the magnification received by the receiving means. And a supply current control unit configured to change the drive control current value supplied to the drive motor in accordance with the magnification received by the reception unit, for example, a CPU, a drive current setting circuit, and a motor drive circuit.

[0016]

By taking such means, the rotational speed of the drive motor is adjusted so as to change the moving speed of the reading means in order to change the magnification of enlargement / reduction during reading. Then, the current value of the drive control current applied to the drive motor is changed according to the magnification of enlargement / reduction. Therefore, the drive motor can be driven by the drive control current having a current value corresponding to the rotation speed of the drive motor.

[0017]

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. The same parts as those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

The image reading apparatus of this embodiment has an optical system similar to that shown in FIG. Then, the first carriage 5 and the second carriage 8 are reciprocally moved in the direction of the arrow shown by the drive mechanism similar to that shown in FIG. That is, the first carriage 5 has a belt fixing portion 5 at one end thereof.
a has two pulleys 8a on one side surface of the second carriage 8,
8b are provided respectively. A pulley 11b is provided at one end of the drive shaft 11a of the drive motor 11 serving as a drive source.
However, on the opposite side of the drive motor 11, for example, a pulley 12 is provided on a fixing member (not shown) fixed to the housing. Then, the pulley 8a → the pulley 11b → the pulley 1
The timing belt 13 is stretched in the order of 2 → belt fixing portion 5a → pulley 8b. The timing belt 13
Both ends of are fixed to, for example, fixing members (not shown) fixed to the housing. Further, a structure similar to the above structure is also provided on the other end side, whereby a drive mechanism is constituted.

The image reading apparatus of this embodiment further includes
CPU 20, operation panel 21, ROM 22, I / O port 23, drive current setting circuit 24, and motor drive circuit 2
Have five.

The CPU 20 is for variably controlling the current value of the drive signal of the drive motor 11, recognizes the magnification of enlargement / reduction based on the designation of the operator received on the operation panel 21, and determines the magnification. The setting data indicating the corresponding current value is taken out from the ROM 22 and output to the I / O port 23.

In the ROM 22, setting data indicating the current value is registered in advance in association with the enlargement / reduction ratio.
The I / O port 23 supplies four setting signals corresponding to the supplied setting data to the drive current setting circuit 24.

The drive current setting circuit 24 generates a reference voltage having a value corresponding to the states of the four setting signals (corresponding to the current value corresponding to the magnification of enlargement / reduction), and the motor drive circuit 2
Give to 5.

The motor drive circuit 25 generates a drive signal having a current value corresponding to the reference voltage supplied from the drive current setting circuit 24, and drives the drive motor 11 by this drive signal.

FIG. 2 is a diagram showing a specific configuration of the drive current setting circuit 24 and the motor drive circuit 25. The drive current setting circuit 24 includes resistors R ₁ , R ₂ , R ₃ , R ₄ , R ₅ ,
R ₆ , analog switches 30a, 30b, 30c, 30
d and input ports 31a, 31b, 31c, 31d. The resistors R _{1 to} R ₆ are R ₁ , R ₂ , R ₃ ,
R ₄ , R ₅ , and R ₆ are connected in series in this order, the auxiliary power supply V _CC2 is connected to one end of the resistor R ₁ , and one end of the resistor R ₆ is grounded. The connection point between the resistors R ₁ and R ₂ is connected to the motor drive circuit 25. The resistors R _{2 to} R ₆ have different resistance values, for example, R ₂ = 22 KΩ, R ₃ = 10 KΩ, R ₄
= 5600Ω, R ₅ = 2200Ω, and R ₆ = 1KΩ.

Among the analog switches 30a to 30d, the analog switch 30a is a resistor R ₂ , the analog switch 30b is a resistor R ₃ , the analog switch 30c is a resistor R ₄ , and the analog switch 30d is a resistor R ₅ . It is connected in parallel. Also analog switch 30
The setting signals output from the I / O port 23 via the input ports 31a to 31d are applied to the a to 30d, respectively. Analog switch 30a-30
d is ON / OFF according to the state of the given setting signal
And short the corresponding resistor.

The motor drive circuit 25 includes a comparison amplification section 50,
Trigger pulse oscillation circuit 51, current control unit 52, excitation signal amplification unit 53, back electromotive force elimination unit 54, Zener diode Z
D and a resistor R _S.

The connection point between the resistors R ₁ and R ₂ of the drive current setting circuit 24 is connected to one input end of the comparison and amplification section 50. At the other input end of the comparison amplification unit 50,
The voltage V _S generated in the resistor R _S is input. The comparison and amplification unit 50 compares the voltages input to the two input terminals and outputs a voltage according to the difference.

The connection point between the resistors R ₁ and R ₂ of the drive current setting circuit 24 is also connected to the trigger pulse oscillation circuit 51. The trigger pulse oscillator circuit 51 includes a resistor R
A trigger pulse having a frequency corresponding to the potential of the connection point between ₁ and the resistor R ₂ is generated.

The current control unit 52 controls the current supplied from the main power supply V _CC1 to the drive motor 11 to a value according to the voltage output from the comparison amplification unit 50. Excitation signal amplifier 5
3 controls the excitation of the drive motor 11 at the timing based on the four-phase excitation signals given from the outside.

The counter electromotive voltage elimination unit 54 is connected to the main power supply V _CC1 via the Zener diode ZD and also connected to the excitation signal amplification unit 53 to prevent the generation of the counter electromotive voltage in the drive motor 11. To do. The resistor R _S is connected in series to the coil of the drive motor 11 and generates a voltage V _S according to the level of the current flowing through the coil of the drive motor 11.

Next, the operation of the image reading apparatus configured as described above will be described according to the control procedure of the CPU 20 shown in FIG. First, in the standby state, the CPU 20 determines whether or not the enlargement / reduction ratio has been designated (step a) and whether or not the reading start has been designated (step b).
It is carried out.

In this standby state, when the operator operates the operation panel 21 to specify the enlargement / reduction, the CPU 20 shifts the processing from step a to step c, and the enlargement / reduction specified in this step c. After recognizing the magnification of, return to the standby state.

On the other hand, in the standby state, the operation panel 21
When an operator gives an instruction to start reading at step S20, the CPU 20 executes the process from step b to step d.
Move to. Then, the CPU 20 reads out the setting data corresponding to the designated magnification from the ROM 22 (step d) and outputs the setting data to the drive current setting circuit 24 as a setting signal via the I / O port 23 ( Step e).

In the drive current setting circuit 24, the auxiliary power source V is generated by the potential at the connection point between the resistors R ₁ and R ₂ , that is, the combined resistance of the resistors R ₁ and R _{2 to} R _6.
The voltage obtained by dividing the voltage of _CC2 is applied to the motor drive circuit 25 as a reference voltage. However, the analog switches 30a to 30d are respectively turned on or off depending on the state of the corresponding setting signal. The resistor in parallel with the turned-on analog switch is short-circuited by the analog switch. Therefore, the voltage obtained by dividing the combined resistance of the resistor and the resistor R ₆ in parallel with the turned off analog switch and the resistor R ₁ becomes the reference voltage. That is, all of the setting signals are at "L" level, and all of the analog switches 30a to 30d are OF.
If F, the reference voltage becomes large due to the combined resistance of the resistors R _{2 to} R _{6 having} a large resistance value. Also if all the ON analog switches 30 a to 30 d, the combined resistance becomes smaller and the resistance value of the resistor R ₆ only, the reference voltage is small. Then, the reference voltage is changed in 16 steps by other combinations of the resistors R _{2 to} R ₆ .

In the motor drive circuit 25, the excitation signal having the pulse rate corresponding to the enlargement / reduction ratio is supplied to the excitation signal amplifier 5
3, the drive motor 11 is energized at a rate according to the scaling factor. As a result, the drive motor 11 rotates at a rotation speed according to the pulse rate, and the first
The carriage 5 is carried at a speed v corresponding to the pulse rate, and the second carriage 8 is carried at a speed v / 2.

When the drive motor 11 is thus energized and a current flows through the coil of the drive motor 11, a current also flows through the resistor R _S and a voltage V _S corresponding to the current value is generated. This voltage V _S is compared with the reference voltage in the comparison amplification unit 50, and a voltage corresponding to the difference is given to the current control unit 52. The current control unit 52 controls the level of the current flowing to the drive motor 11 so that the output voltage of the comparison amplification unit 50 becomes zero, that is, the voltage V _S matches the reference voltage.

In this way, the current applied to the drive motor 11 is variably controlled according to the enlargement / reduction ratio. Here, the drive current setting circuit 24 outputs a reference voltage corresponding to a current value obtained by adding an optimum margin to the current value required to obtain a constant torque (for example, 400 gf · cm) at each rotation speed of the drive motor 11. As described above, the setting data and the resistance values of the resistors R _{1 to} R ₆ are set,
As a result, the current supplied to the drive motor 11 is adjusted to the minimum value in the range where torque shortage does not always occur. Therefore, no matter what magnification is used for enlarging / reducing reading, smooth scanning can be performed without causing out-of-step of the drive motor 11 and variation fluctuations can be kept small, and extremely good image reading can be performed. be able to. Moreover, since the fluctuation unevenness is always suppressed to a small level, the vibration is also suppressed to a small level.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the configuration is shown in which the current value flowing through the drive motor 11 can be controlled in 16 steps, but the number of control steps for the current value may be arbitrary. Further, the configuration for controlling the current value is not limited to that described in the above embodiment.

In the above embodiment, the reading means is the first carriage 5, the second carriage 8, the lens 9 and the CCD 1.
Divided into 0, the first carriage 5 and the second carriage 8
Although the image reading apparatus in the form of carrying out only the sub-scanning by conveying only is illustrated, if the image reading apparatus of the form carrying out the sub-scanning by moving at least a part of the components of the reading means, For example, the present invention can be applied to other forms such as a form in which the CCD 10 is also moved or a form using a contact image sensor. In addition, various modifications can be made without departing from the scope of the present invention.

[0040]

According to the present invention, there is provided a reading means including a first carriage, a second carriage, a CDD, etc. for generating an image signal corresponding to a reflected light image from a document in a predetermined cycle, and a drive motor. However, at least a part of the reading means (for example, the first carriage and the second carriage)
Moving means for moving the reading position along the document at a speed corresponding to the rotation speed of the drive motor, and a receiving means such as an operation panel for receiving the designation of the enlargement / reduction magnification. And speed control means such as a motor drive circuit for changing the moving speed of the reading means by the moving means according to the magnification received by the receiving means, and the drive according to the magnification received by the receiving means. Since the drive control current value supplied to the motor is changed, for example, a supply current control means including a CPU, a drive current setting circuit and a motor drive circuit is provided, the reading means can be smoothly moved at a wide range of speeds. As a result, the image reading apparatus can always perform good reading regardless of the enlargement / reduction magnification.

[Brief description of drawings]

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

2 is a diagram showing a specific configuration of a drive current setting circuit 24 and a motor drive circuit 25 in FIG.

FIG. 3 is a C for controlling a current value given to the drive motor 11.
The flowchart which shows the control procedure of PU20.

FIG. 4 is a diagram schematically showing a general configuration of an optical system of the image reading apparatus.

FIG. 5 is a diagram schematically illustrating a general configuration of a transport mechanism for realizing sub scanning in the image reading apparatus.

FIG. 6 is a view showing a measurement result of motor rotation fluctuation unevenness when a sufficient current margin is taken.

FIG. 7 is a view showing a measurement result of motor rotation fluctuation unevenness when the current margin is minimized.

FIG. 8 is a diagram showing the relationship between the torque and the pulse rate of the control signal when the drive motor is driven with a large current.

FIG. 9 is a diagram showing a relationship between torque and a pulse rate of a control signal when the drive motor is driven with a small current.

[Explanation of symbols]

 5 ... 1st carriage 5a ... Belt fixing part 8 ... 2nd carriage 11 ... Drive motor 11a ... Drive shaft 8a, 8b, 11b, 12 ... Pulley 13 ... Timing belt 20 ... CPU 21 ... Operation panel 22 ... ROM 23 ... I / O port 24 ... Drive current setting circuit 25 ... Motor drive circuit

Claims (1)

[Claims] 1. A reading unit for generating an image signal corresponding to a reflected light image from a document at a predetermined cycle, and a drive motor, and at least a part of the reading unit,
Moving means for moving the reading position along the document at a speed corresponding to the rotation speed of the drive motor, acceptance means for accepting designation of magnification for enlargement / reduction, and acceptance by this acceptance means A speed control means for changing the moving speed of the reading means by the moving means in accordance with the applied magnification, and a supply current for changing the drive control current value supplied to the drive motor in accordance with the magnification received by the receiving means. An image reading apparatus comprising: a control unit.