JPH04216261A - Image reader - Google Patents

Abstract

PURPOSE:To obtain a driving system to improve the accuracy of a step angle when stopping the device and to reduce energy consumption when driving the original lighting system of the image reader by a step motor. CONSTITUTION:At the image reader to drive the original lighting system by a step motor 34 and to read an original for the unit of one line, the number of pulses to be excited when stopping the motor is controlled so that the motor can be stopped in a one-pulse exciting state in a low-speed case and can be stopped in a two-pulse exciting state in a high-speed case corresponding to the speed of the step motor 34.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to driving means for a document illumination system of an image reading apparatus.

0002

2. Description of the Related Art As an image reading apparatus, an image reading apparatus is used which is configured to read an original image with an optical sensor, convert it into a density signal, digitize it with an analog/digital converter, etc., and then read the image. In this type of image reading device, a step motor or the like drives a document illumination unit to read the document line by line and convert it into an electrical signal.

[0003] In such an image reading device, when controlling each phase of the step motor, the step angle accuracy (angular error)
A one-phase excitation method is preferable when considering power consumption and power consumption, and a two-phase excitation method is used when considering static characteristics (small damped vibration) and torque.
A 1-2 phase excitation method is used when the step angle is set finely.

0004

[Problems to be Solved by the Invention] However, in an image reading device controlled as described above, when transferring image data to an external device, there is a problem that depending on the transfer speed of the interface and the memory capacity of the external device, There may be cases where data is transferred while stopping every other line. By the way, the speed at which the step motor drives when reading an image is, for example, 200% when the magnification rate is 100% mode.
The drive system will move at twice the speed when in mode. At that time, due to the difference in the speed at which the step motor is driven, if the step motor is stopped in one phase while moving at high speed, the damped vibration at the time of stop tends to be large and disordered, and if it is stopped in two phases while moving at low speed. If it is stopped, two phases are excited, which wastes power.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image reading system equipped with a drive system capable of improving step angle accuracy and reducing power consumption when the device is stopped. The purpose is to provide equipment.

[0006]

[Means for Solving the Problems] The present invention provides a driving means for driving an original illumination system by a step motor or the like, and an image reading apparatus for reading the original line by line using the driving means, in which a document illumination system is driven by a step motor or the like. Provided is an image reading device equipped with a drive system capable of improving step angle accuracy and reducing power consumption when the device is stopped by controlling the number of phases to be excited when the step motor is stopped. It is something.

In the above configuration, the step motor is
It is preferable to configure so that when driving at a low speed, it is stopped in a one-phase excitation state, and when driving at a high speed, it is stopped in a two-phase excitation state.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 7 is a schematic longitudinal sectional view showing the internal structure of an embodiment of an image reading apparatus according to the present invention. In FIG. 7, 1 is a document image reading device, 11 is a control unit of the image reading device, 12 is a CCD, 13 is a CCD unit, and 14 is a control unit of the image reading device.
15 is a lens, 15 is an original illumination unit, 16 is a reflecting mirror, 17 is a platen glass, 18 is an original placing section, 19 is a platen cover, and 24 is a lamp in the original illumination unit. When the original illumination unit 15 (lamp 24) illuminates the original image, the reflected light from the original is guided by the reflecting mirror 16 to the lens 14, and the lens 14 converts the CC
A document image is formed on D12.

FIG. 8 is a block diagram showing the circuit configuration of the image reading device shown in FIG. In FIG. 8, 21 is an interface circuit connected to an external device, 22 is a CPU, and 23 is an interface circuit connected to an external device.
is a lamp voltage control circuit, 24 is a lamp, 25 is a document, 2
6 is an amplifier circuit, 27 is an analog/digital converter, 28
is a binarization circuit, and 29 is a selector. The CPU 22 is
In addition to inputting and outputting various signals, it also inputs the illustrated optical position sensor signal and outputs a motor drive signal for driving the document illumination system. This motor drive signal is transmitted to a motor drive circuit (amplifier 33) via an input circuit 31 and a distribution circuit 32, which will be described later.

In FIGS. 7 and 8, an image reading device (
The scanner (hereinafter referred to as a scanner) is connected to an external device such as a digital printer or a personal computer, and communicates control signals with the external device and outputs images to the external device via an interface circuit 21. The document 25 on the platen glass 17 has the leading edge of the document on the platen glass 1.
7 (in FIG. 7). The position of this document 25 is confirmed by an optical position sensor (not shown).

Further, while the original 25 is placed on the platen glass 17, settings for various modes are inputted from an external device. For example, settings such as whether to set the enlargement/reduction ratio to 1% to 200% or whether to make the image signal a binary signal or a multivalued signal are input. C received this
The PU 22 outputs a control signal in advance to set the enlargement/reduction ratio and image signal. Next, when a document reading start command is input from an external device, the CPU 22 first outputs a signal to the lamp voltage control circuit 23 to turn on the lamp 24. At this point, the document reading operation does not start immediately, but waits for approximately 300 to 500 milliseconds until the light intensity of the lamp stabilizes. During this time, an image signal is input to the interface circuit 21, but is not output to an external device due to a control signal from the CPU 22. Thereafter, the document illumination unit 15 starts scanning in the direction of arrow B in FIG.

There is a distance of approximately 2 to 3 mm from the initial position of the original illumination unit 15 to the position of the leading edge of the original on the platen glass 17, and the scanning speed of the optical system by the motor is controlled to be stable during this time. When the original illumination unit 15 reaches the leading edge position of the original, the CPU 22 outputs a control signal to enable image signal output to the interface circuit 21, and the read image signals are sent one after another to an external device. The scanning length of the optical system is CP
Since it is uniquely determined by the number of motor drive pulses of U22, the CPU 22 determines that document reading is complete when the required number of pulses are output to the motor, and turns off the lamp 24.
It performs controls such as disabling image signal output and reversing the motor, and outputs a document reading completion signal to an external device.

Under the motor reversal control of the CPU 22, the original illumination unit 15 moves in the direction of arrow A in FIG. 7, and stops when the optical position sensor detects that it has reached the initial position. If the next document reading start command is not received from the external device during the return period of the optical system, the optical system stops at the initial position and ends the image reading operation.

FIG. 1 is an electric circuit diagram of a motor drive system of an image reading apparatus according to the present invention, FIG. 2 is a block diagram of the motor drive system of FIG. 1, and FIG. FIG. 2 is a wiring diagram of a step motor. In this embodiment, an example will be described in which a four-phase step motor is driven by a 1-2 phase excitation method as a motor for an original illumination system.

In FIGS. 1 and 2, a step motor drive signal (hereinafter abbreviated as pulse) is sent from the CPU 22 to the input circuit 31. The input circuit 31 adjusts the waveform when sending the input pulse to the distribution circuit 32,
One pulse corresponds to one step of the step motor 34 (FIG. 2). Further, the distribution circuit 32 distributes the applied input signal to each phase in a manner determined by the number of phases and the excitation signal. The step motor 34 is a four-phase step motor having four excitation phases A1, A2, B1, and B2, as shown in FIG. Furthermore, since this step motor 34 is excited in 1-2 phases, its excitation signal is of the 1-2 phase excitation method. The signal distributed by the distribution circuit 32 is input to an amplifier circuit 33 (FIG. 2), where it is amplified to a current necessary to excite the step motor 34.

The electric circuit of FIG. 1 is a diagram showing the circuit configuration of the input circuit 31 and distribution circuit 32 of FIG. 2. As shown in FIG. 1, the input circuit 31 receives excitation signals (D0, D1, D2) for controlling the step motor 34 from the CPU 22 (3-bit data), CLK (clock) signal, LOA
Input D signal. As shown in the figure, this input circuit 31 is composed of a NAND element, an EXOR element, a counter, etc., and further, a forward/reverse rotation signal U/D of a step motor 34 is inputted from the CPU 22 to the input circuit 31. . The distribution circuit 32 receives the signal from the input circuit 31 and divides each excitation phase A1, A2 of the step motor 34 into
, B1, and B2 are driven in high speed mode (driving for 4 steps) or low speed mode (driving for 2 steps).

FIG. 4 is a truth table of the 1-2 phase excitation method of the step motor 34 used in this embodiment. ) state, and S1, S2...S8 indicate each step of one cycle of the motor 34. As can be seen from FIG. 4, steps S1, S3, S5, and S7 are two-phase excitation, steps S2, S4, S6, and S8 are one-phase excitation, and S1-S2-S3-S4-
One cycle of the step motor 34 is formed by S5 - S6 - S7 - S8.

FIG. 5 shows the step motor 34 in the CPU 22.
This is a table showing control excitation signals, that is, control signals for setting the excitation state (one-phase excitation or two-phase excitation) when the step motor 34 stops.
, D1, D2 are 3-bit data, 0 means the input level is "Low", 1 means the input level is "Hi"
. As shown in FIGS. 1 and 8, the CPU 22 controls each phase A1, A2, and
B1 and B2 can be freely set (excited), and the 3-bit data D0, D1, D2 are combined as shown in FIG. 2 and sequentially input to the input circuit 31.
(FIG. 1), each step of the step motor 34 is set to S1, S2,...S as shown in FIG.
It can be excited in 8 states.

First, in FIG. 1, the CPU 22 initializes the forward/reverse rotation signal U/D of the step motor 34 and the 3-bit data D0, D1, D2. Here, when driving in 100% mode, the data [D0, D1, D2] should be set to 2 when stopped in order to set the conditions for stopping at high speed (conditions for stopping with two-phase excitation).
The state of step S1 [0, 0, 0
] is set.

Next, when the reading of the original image is started, the CPU 22 reads the original image for each line.
Four pulses are input to the input circuit 31. Upon receiving this, the input circuit 31 sends a signal to the distribution circuit 32 to drive the step motor 34 by four steps to drive at high speed. That is, counting from step S1, S1 - S2 - S3
-S4 -S5 are configured to be read as one line of the original image. Similarly, move the next line to S5.
The document is read in four steps: -S6 -S7 -S8 -S1, and the same operation continues until a command to stop reading the original image is received midway through.

[0021] When a reading stop command comes here, the CPU
22 stops pulse input after one line has been read, that is, when four pulses have been input. In other words, since 4 pulses are used as one block, the pulse motor 3
4 is always stopped in the two-phase excitation state of either S1 or S5. When an image reading command is received in this state, the CPU 22 sends a pulse to the input circuit 31 again, drives the pulse motor 34, and continues the same pulse input operation as described above until reading of the original image is completed.

Similarly, in the 200% mode (when driven at low speed), the CPU 22 outputs data [D0, D1
, D2] in the one-phase excitation state [1, 0,
0]. In this 200% mode, 10
In order to advance at half the speed of the 0% mode, two pulses are input to the input circuit 31 every time one line of the original image is read. The input circuit 31 that receives this inputs the distribution circuit 32.
A signal is output to drive the step motor 34 for two steps. That is, counting from step S2, S2 −
In S3 to S4, one line of the original image is read and controlled to be stopped in a one-phase excitation state (a state in which a one-phase excitation signal is output).

Similarly, the next line is S4 -S5 -S
Read in 2 steps of 6, then read the next line in S6
By reading in two steps -S7 -S8 and reading the next line in two steps S8 -S1 -S2, whenever a reading stop command comes,
The motor 34 is controlled to stop in one of the one-phase excitation states S2, S4, S6, and S8 (the state in which a one-phase excitation signal is output).

According to the embodiment described above, when the step motor 34 is stopped, one of the plurality of excitation phases constituting the step motor is always selected depending on the scanning speed of the drive system of the document illumination unit 15. In other words, when driving at low speed, only one phase is excited and stopped, and when driving at high speed, two phases are excited. An image reading device that is controlled to stop in a state of was gotten.

FIG. 6 shows a step motor 34 for driving the document illumination system in another embodiment of the image reading apparatus according to the present invention.
This is the truth table of the excitation method. This embodiment shows a case where the step motor 34 is of a three-phase excitation type having excitation phases A, B, and C. In addition, in FIG. 6, 1 indicates an excited (on) state, 0 indicates a non-excited (off) state, and S1
, S2...S6 indicate each step of one cycle of the motor 34.

When a three-phase step motor is used as in the embodiment shown in FIG. 6, if one line of the original image is to be read in four steps as the initial value of step S1, the step motor 34 is always stopped in the two-phase excitation state. can be done. Similarly, when one line of the original image is read in two steps with step S2 in the initial state, the step motor 34 can always be stopped in the one-phase excitation state. Therefore, this embodiment also has the same effect as the previous embodiment, that is, when driving at low speed, only one phase is excited and stopped, and when driving at high speed, two phases are excited. By controlling the motor to stop in a state of phase excitation, it is possible to improve the accuracy of the step angle of the motor when the device stops, and to reduce the power consumption for driving the motor. An image reading device was obtained.

[0027]

As is clear from the above description, according to the present invention, the drive means for driving the document illumination system by a step motor or the like, and the image reading apparatus for reading the document line by line using the drive means, can be used to Since the configuration controls the number of phases to be excited when the step motor is stopped according to the speed of the motor, the drive system is equipped with a drive system that can improve the accuracy of the step angle and reduce power consumption when the device is stopped. An image reading device is provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a motor control system of an image reading device according to the present invention.

FIG. 2 is a block diagram of a motor control system of an image reading device according to the present invention.

FIG. 3 is a wiring diagram of excitation phases of a four-phase step motor used in the motor control system of FIG. 1;

FIG. 4 is a truth table when the step motor of FIG. 3 is driven by a 1-2 phase excitation method.

FIG. 5 is a table showing data of initial setting values when the step motor of FIG. 3 is driven by a 1-2 phase excitation method.

FIG. 6 is a truth table when a three-phase step motor is driven by a 1-2 phase excitation method in the image reading device according to the present invention.

FIG. 7 is a schematic vertical cross-sectional view showing a schematic configuration of an embodiment of an image recording apparatus according to the present invention.

8 is a block diagram of a control system of the image recording apparatus shown in FIG. 7. FIG.

[Explanation of symbols]

11 Control unit 13 CCD unit 14 Lens 15 Original illumination unit 17 Platen glass 21 Interface circuit 22
CPU 24 Lamp 25 Original 31 Input circuit 32 Distribution circuit 34 Step motor

Claims (2)

[Claims] Claim 1: In an image reading device that includes a drive means for driving a document illumination system using a step motor or the like, and an image reading device that reads the document line by line using the drive means, when the step motor stops depending on the speed of the step motor. An image reading device characterized by controlling the number of phases to be excited. 2. Claim 1, characterized in that when the step motor is driven at a low speed, it is stopped in a one-phase excitation state, and when it is driven at a high speed, it is stopped in a two-phase excitation state. image reading device.