JP2647682B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION (Field of Industrial Application) The present invention relates to an image reading apparatus that optically scans an original surface to read an original image by driving a scanning optical system using a stepping motor.

BACKGROUND OF THE INVENTION In an image reading apparatus that optically reads a document, a motor is used to scan a light source. In particular, in a color image reading apparatus, a stepping motor is used instead of a DC motor or an AC motor for registration.

FIG. 3 is a characteristic diagram showing a torque-speed characteristic of the stepping motor. In this figure, (A) is a self-start area in which start, stop, and reverse rotation can be performed in synchronization with a pulse given to the stepping motor. (B) is a through region in which the motor is started in the self-starting region, and when the input pulse of the motor rotating synchronously is gradually increased, the motor can be synchronously rotated at an input frequency higher than the self-starting characteristic. The pull-in torque is the maximum torque generated when the motor starts without losing synchronization with the frequency of the input pulse, and the escape torque exceeds the self-starting range and increases the speed or torque. The maximum torque the motor can produce without loss of synchronization.

In an image reading apparatus using a stepping motor as a drive source of a scanning optical system, an exposure light source or the like of the scanning optical system is driven in a predetermined speed pattern (a relationship between a moving distance and a speed).

This speed pattern includes a rising part A, a constant velocity part B, and a falling part C, as shown in FIGS. 4 (a) to 4 (c), for example.
The pattern of the rising portion A and the falling portion C is selected as a self-starting region so that the stepping motor can move as quickly as possible within a range where step-out or the like does not occur. Further, the distance that the light source or the like of the scanning optical system moves, that is, the scanning distance changes depending on the size of the document and the magnification. So, in such a case,
As shown in FIGS. 6 (a) to 6 (c), the light sources and the like of the scanning optical system are driven by speed patterns having different lengths of the constant speed portion B. In the conventional apparatus, data for obtaining a speed pattern corresponding to each scanning distance is stored in a memory, and data for providing the speed pattern corresponding to the scanning distance is read out to drive a scanning optical system.

When the optical system reads an image during the forward movement and returns to the home position during the backward movement, the constant velocity portion B at the time of the backward movement increases the speed (faster than at the time of the forward movement) and is driven in the through area of the stepping motor. May be.

(Problems to be Solved by the Invention) In the conventional device, no consideration is given to the case where the stepping motor loses synchronism.

For example, a case where the stepping motor loses synchronism when the optical system moves forward (when reading an image) will be described. The moving distance of the optical system is determined by the number of pulses given to the stepping motor. Therefore, by stepping out,
The optical system moves only a distance shorter than the specified moving distance.
At this time, the CPU that is performing the control cannot detect this step-out. For this reason, when the optical system returns by the set pulse at the time of the backward movement, there is a problem that the optical system passes through the home position to be stopped, collides with the side plate of the apparatus, and is damaged.

Further, step-out may occur when the image reading is completed and the optical system returns to the home position. When returning,
Generally, since the stepping motor is driven at a high speed in the through region outside the self-starting region, once step-out occurs, it cannot be re-driven by a subsequent pulse and the optical system cannot be returned to the home position. There was also.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an image reading apparatus that can cope with a stepping motor out of synchronization.

(Means for Solving the Problems) The present invention for solving the above problems is directed to an image reading apparatus which optically scans a document surface to read a document image by driving a scanning optical system using a stepping motor. Stepping motor driving means for applying a driving pulse to the scanning optical system, a sensor provided in the scanning direction near the reference stop position of the scanning optical system, for detecting whether or not the scanning optical system has passed at the time of scanning return; Step-out detecting means for detecting a key, and control means for controlling the stepping motor to return the scanning optical system to the reference stop position when step-out of the stepping motor is detected by the step-out detecting means, The out-of-step detecting means determines the number of drive pulses required to return the scanning optical system to the position of the sensor and the number of drive pulses required to actually return the scanning optical system to the position of the sensor. A step-out detecting means for detecting a step-out at the time of forward movement by comparing the number of drive pulses required at the time of the forward movement, and a stepping motor for outputting a drive pulse necessary for returning the scanning optical system to the position of the sensor. And step-out detection means for detecting step-out at the time of return based on the detection result of the sensor when the voltage is applied to the sensor.

(Operation) In the image reading apparatus of the present invention, it is actually necessary to drive the scanning optical system to the position of the sensor based on the number of driving pulses required until the scanning optical system is driven and reaches the sensor. The step-out detecting means detects step-out of the stepping motor from the number of pulses or the position of the scanning optical system. When step-out is detected, the control means returns the scanning optical system to the reference stop position (home position).

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. First
FIG. 2 is a block diagram showing an electrical configuration of a main part of one embodiment of the present invention, and FIG. 2 is a schematic configuration diagram showing a mechanical configuration of one embodiment of the present invention.

First, in FIG. 2, reference numeral 1 denotes a platen glass on which a document 2 is placed, and 3 denotes a slide rail provided in the horizontal direction (sub-scanning direction) of FIG. 2, and a carriage 4 is arranged movably on the slide rail 3. Has been established. Reference numeral 5 denotes a halogen lamp as an exposure light source provided on the carriage 4 so that the tube axis is perpendicular to the plane of FIG. 2, and the original 2 is irradiated with light by the halogen lamp 5 which moves together with the carriage 4. Reference numeral 6 denotes an actuator provided on the carriage 4, and the carriage is driven by a wire locked to the actuator 6. 7 is a mirror for receiving the reflected light from the original 2, 8 is a movable mirror unit in which mirrors 9a and 9b are arranged in a V-shape with an opening angle of 90 °, 10 is a stepping motor for driving, and 11 to 15 are wires Is a pulley wound around. Actuator 6 of the carriage 4
Is fixed to a wire 16, and the support shafts of the pulleys 14 and 15 are attached to the movable mirror unit 8. The way to stretch the wire 16 is, for example, after locking one end of the wire 16 on the left side wall of the device, winding it around the pulley 14 and the pulley 13, and further driving the pulley 14 via the belt by the stepping motor 10.
After winding a plurality of times around the pulley 11, a method of winding around the pulley 12, locking to the actuator 6, winding around the pulley 15, and locking to the right side wall in the drawing is used. For this reason, when the stepping motor 10 starts, the pulleys 11 to 15 rotate, and the carriage 4 and the movable mirror unit 8 move at the speeds of V and V / 2 in the horizontal direction in FIG. 2, respectively.

Reference numeral 17 denotes a home position sensor for detecting whether the carriage 4 is at the home position (reference stop position). Reference numeral 18 denotes a home position sensor located at a predetermined position near the home position sensor 17 in the sub-scanning direction. The step-out detection sensor detects the occurrence of step-out of the stepping motor 10 depending on whether or not the stepping motor passes. The home position sensor 17 and the step-out detection sensor 18
The detection is performed when the actuator 6 provided in the sensor passes near the sensor. 21 mirrors the reflected light on the original surface
Lenses received through 7, 9a, 9b, 22 is a dichroic prism for dispersing light passing through lens 21, 23, 24
R-ch (red channel) image and C-ch (cyan channel) image separated by the dichroic prism 22 are respectively formed on the light receiving surface of the R-ch CCD, C-ch C
It is a CD. These CCDs 23 and 24 function as line image sensors, and the detection elements are arranged in a direction (main scanning direction) perpendicular to the paper surface of FIG.

This embodiment has a configuration in which one page of color image data is read by three scans.
Obtain red image data using the output of 3, obtain blue image data using the output of the CCD 24 in the second scan, and obtain black image data using the outputs of the CCDs 23 and 24 in the third scan ing.

FIG. 1 shows a configuration in which the halogen lamp 5 provided on the carriage 4 is moved in a predetermined speed pattern. In this figure, reference numeral 31 denotes the stepping motor 10 described above.
The stepping motor 10 is rotationally driven by a command from a control unit (which is constituted by a CPU in the present embodiment, and is hereinafter referred to as a CPU) 32. Reference numeral 33 denotes a memory in which a basic pattern of a pulse train applied to the stepping motor 10 and the like are stored.

When an image reading instruction is given from an operation unit (not shown),
The CPU 32 drives the stepping motor 10 by the driver 31 to execute image reading. First, a scanning optical system such as a light source is moved from the home position in the sub-scanning direction (forward movement).
Then, the image is read. After the reading is completed, the stepping motor is driven in the reverse direction (return) to return the scanning optical system to the home position. This operation is repeated three times in color image reading.

First, a case where the stepping motor loses synchronism during forward movement will be described. The moving distance of the carriage 4 and the movable mirror unit 8 is determined by the number of pulses given to the stepping motor 10. For this reason, the carriage 4 and the movable mirror unit 8 scan only a distance shorter than a predetermined distance. Therefore, this reading is bad. The CPU 32 determines the number of pulses P1 at the time when the carriage 4 has passed the out-of-step detection sensor 18 at the time of returning, and the carriage 4 detects the out-of-step when the out-of-step does not occur.
The pulse number is compared with a prescribed pulse number P2 (read from the memory 33) at the time of passing through 18. If step-out occurs during the forward movement and the scanning movement distance is short, the carriage 4 passes through the step-out detection sensor 18 when the number of applied pulses P1 is smaller than the specified number of pulses P2. Therefore, if P1 <P2, it is determined that step-out has occurred during the forward movement. The CPU 32 controls the carriage 4
Is driven at the home position to drive the stepping motor 10. By doing so, it is possible to prevent excessive return, and it is also possible to prevent equipment damage due to excessive return of the carriage 4. Here, the specified pulse number P2 differs depending on the scanning distance (reading size), but includes a mechanical error of the scanning system.

Next, a case where the step-out occurs at the time of the return movement will be described. At the time of return, the stepping motor is driven at a high speed outside the self-starting area, so once step-out occurs, the stepping motor does not restart with a subsequent pulse. Therefore, the CPU 32
At the point in time when the specified pulse number P2 has been reached, it is checked whether the carriage 4 has passed the step-out detection sensor 18. Therefore,
The carriage 4 loses synchronization at the specified pulse number P2.
If it has not passed through 18, it is determined that the motor is out of synchronization at the time of return, and a pulse in the self-starting area is given to the stepping motor 10 to return the carriage 4 to the home position at a constant speed. By doing so, the step-out at the time of the return can be easily detected and recovered.

(Effects of the Invention) As described in detail above, in the present invention, the number of pulses applied to the stepping motor required when the carriage has passed the out-of-step detection sensor is compared with the predetermined number of pulses to make the forward movement Step-out is detected, and step-out upon return is detected by confirming the position of the carriage when a predetermined pulse is applied to the stepping motor, and the carriage is returned to the home position when step-out occurs. I have.
Therefore, according to the present invention, it is possible to realize an image reading apparatus that can cope with step-out of the stepping motor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a main part of one embodiment of the present invention, FIG. 2 is a configuration diagram showing a mechanical configuration of one embodiment of the present invention, and FIG. 3 is a characteristic diagram of a stepping motor. ,
FIG. 4 is an explanatory diagram of a speed pattern. 2 Documents 4 Carriage 5 Halogen lamp 6 Actuator 8 Movable mirror unit 10 Stepping motor 17 Home position sensor 18 Step-out detection sensor 31 Driver 32 … CPU, 33 …… Memory

Claims (1)

(57) [Claims] An image reading apparatus for optically scanning a document surface to read a document image by driving a scanning optical system using a stepping motor, a stepping motor driving means for applying a driving pulse to the stepping motor, and scanning. A sensor provided on the scanning direction side near the reference stop position of the optical system, for detecting whether the scanning optical system has passed at the time of scanning return, step-out detecting means for detecting step-out of the stepping motor, and step-out detection means Control means for controlling the stepping motor to return the scanning optical system to the reference stop position when step-out of the stepping motor is detected by the detection means,
The step-out detecting means compares the number of driving pulses required to return the scanning optical system to the position of the sensor with the number of driving pulses required until the scanning optical system is returned to the position of the sensor. A step-out detection unit for detecting step-out during forward movement; and a return movement based on a detection result of the sensor when a drive pulse necessary for returning the scanning optical system to the position of the sensor is applied to the stepping motor. An image reading apparatus comprising: a step-out detection unit for detecting a step-out at the time of return.