JPH09236973A - Scanner driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent vibration and the noise of a scanner corresponding to the wide variable range with a low cost structure. SOLUTION: A microcomputer 2 supplies the current to a stepping motor 1 by selecting of the current I1 , I2 and I3 (I1 >I2 >I3 ) corresponding to the range of scanning speed corresponding to the variable power rate. This device is allowed to reduce the excessive torque by selecting for instance, the highest current I1 in the vicinity of the fast scanning velocity v50 at the time of 50% reduction, selecting the current I2 at the scanning velocity v100 at the time of 100% unmagnification, and selecting the lowest current I3 at the scanning velocity v200 at the time of 200% magnification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a scanner that reads an original by moving an optical system in the sub-scanning direction with respect to an original fixed on an original table, and particularly, the moving speed in the sub-scanning direction is changed. The present invention relates to a driving device for a scanner that performs zooming.

[0002]

2. Description of the Related Art Generally, in a fixed original type scanner, a first carriage on which a light source and a first mirror are mounted moves at a speed v, and a second carriage on which a second and a third mirror are mounted. By moving at the speed v / 2, the original is scanned and read in the sub-scanning direction. Further, when the original is scaled and read, the scaling range is generally 50 to 200%, but in recent years, it is possible to set the scaling range to 25 to 400%. When the variable magnification range of 50 to 200% is variable in units of 1%, it is necessary to stably drive the first and second carriages at 150 scanning speeds.

Although the first and second carriages are driven by the same scanner motor, for example, a stepping motor, the stepping motor often causes problems in terms of vibration and noise, in which case the image is deteriorated. .
This occurs due to the torque of the stepping motor, the magnitude of the detent torque, and the drive frequency, and occurs because the resonance point of the entire scanner or the reflection mirror coincides with the drive frequency corresponding to the variable power range. In order to solve this problem, conventionally, in addition to mounting the motor as a vibration-proof measure, a method of shifting the resonance point of the mirror or the vibration frequency of the motor with a damper or the like has been adopted.

[0004]

However, in the method of mounting the motor for anti-vibration or shifting the resonance point of the mirror or the vibration frequency of the motor by a damper or the like, the number of parts increases and the cost increases. There is a point. In addition, it is not possible to deal with a wide zoom range of 25 to 400% simply by shifting the frequency.

In view of the above conventional problems, it is an object of the present invention to provide a scanner driving device which is inexpensive and can prevent vibration and noise over a wide zoom range.

[0006]

In order to achieve the above object, the present invention provides a scanner driving apparatus for moving an optical system in a sub-scanning direction with respect to an original by a stepping motor, in which a current applied to the stepping motor is applied. It is characterized in that it has a control means for making it variable in accordance with the scaling ratio.

Further, the control means is characterized in that the applied current at the time of enlargement is made smaller than that at the same magnification.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a scanner driving device according to the present invention, FIG. 2 is an explanatory view showing scanning speeds at equal magnification and variable magnification, and FIG. 3 shows pulse speed-torque characteristics of a stepping motor. FIG.

In FIG. 1, a scanner motor (stepping motor) 1 selectively applies one of currents I ₁ , I ₂ and I ₃ under the control of a microcomputer 2 to drive the first and second carriages. . Although not shown, a light source, a first mirror, etc. are mounted on the first carriage to move at a speed v, and the second and third carriages are mounted on the second carriage.
It is equipped with a mirror and moves at a speed of v / 2.

[0010] In FIG. 2, at the time of 100% i.e. magnification reading, first and second carriages are in the range of time 0 to t ₁ is accelerated from the home position (slow-up), constant in the range of times t ₁ ~t ₂ The document is read from the time t _R by moving at a speed v ₁₀₀ , and is decelerated (slowed down) and stopped in the range of time t _{2 to} t ₃ after the reading is completed. Then, the range of times t ₄ ~t ₅ is accelerated to start the movement in the reverse direction (return), the range of times t ₅ ~t ₆ moving at a constant speed, the range of times t ₆ ~t ₇ Decelerate and stop at the home position. At the time of this return, it moves 3 to 5 times faster than the forward direction.

On the other hand, at the time of enlargement, the scanning speed, that is, the drive frequency of the motor 1 is controlled to be smaller than that at the same magnification. For example, the scanning speed v ₂₀₀ at the time of 200% enlargement is 1/2 of the scanning speed v ₁₀₀ at the same magnification. is there. Scanning speed of the reverse 50% reduction v ₅₀ is twice the scanning speed v _{10 0} at equal magnification. Also, 5
A scanner having a zoom function for varying the range of 0 to 200% in units of 1% has 150 scanning speeds v. Further, the velocity v at the time of return is 3 to 5 times as large as the scanning velocity v ₁₀₀ at the same magnification, and therefore it can be seen that the velocity range is very wide.

Here, each of the first to third reflecting mirrors attached to the first and second scanners has a natural vibration frequency f given by the following equation, and is a glass mirror having a thickness of about 5 mm, for example. Has a natural vibration frequency f of 100 to 2
It becomes 50 Hz.

[0013]

[Equation 1]

Further, as shown in FIG. 2, the characteristic of the stepping motor 1 is that the torque T becomes large at a low rotational speed, so that the torque becomes excessive during scanning during enlargement as compared with scanning during equal magnification. Further, when the image is magnified, the mirror is driven at a frequency close to the natural vibration frequency f, so that excessive torque may accelerate vibration and cause the mirror to resonate, resulting in extreme deterioration of the image.

[0015] Therefore, in the present embodiment, the excessive torque in order to reduce the resistance R _1, R ₂ as shown in FIG. 1 to generate a current I _1, The resistor R _3, the current through R ₄ I ₂ By means of resistors R ₅ and R ₆ , a current I ₃ (I ₁ > I ₂ >
I ₃ ), and the microcomputer 2 outputs _{one of} the currents I ₁ , I ₂ , and I ₃ in accordance with the range of the scanning speed according to the scaling ratio.
One of them is selected and applied to the stepping motor 1. Specifically, the highest I ₁ is obtained in the vicinity of the fast scanning speed v ₅₀ at the time of 50% reduction, and I ₂ is obtained at the scanning speed v ₁₀₀ at the 100% magnification.
Lowest I ₃ at slow scan speed v ₂₀₀ at 200% magnification
To reduce excess torque.

[0016]

As described above, according to the present invention, the current applied to the stepping motor is made variable according to the scaling factor, so that the excessive torque of the stepping motor is reduced, and therefore the cost is wide and the structure is inexpensive. Vibration and noise can be prevented in the variable power range.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a scanner driving device according to the present invention.

FIG. 2 is an explanatory diagram showing scanning speeds at equal magnification and variable magnification.

FIG. 3 is an explanatory diagram showing pulse speed-torque characteristics of a stepping motor.

[Explanation of symbols]

1 Scanner motor (stepping motor) 2 Microcomputer R _{1 to} R ₆ resistance

Claims (2)

[Claims] 1. A scanner driving device for moving an optical system with respect to a document in a sub-scanning direction by a stepping motor, having a control means for varying a current applied to the stepping motor in accordance with a magnification ratio. And scanner drive device. 2. The scanner driving device according to claim 1, wherein the control means reduces the applied current at the time of enlargement as compared with that at the same magnification.