JP2803817B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly, reciprocates an image reading head mounted on a carriage along a material to be read. The present invention relates to an image reading apparatus capable of reading an image one scan at a time. [Prior Art] FIG. 4 shows an example of a conventional image reading apparatus. Where 1
Denotes an image reading head mounted on the carriage 2, 3 denotes a read object (hereinafter referred to as a document) held along a platen 4, and a light source (not shown) for irradiating the document 3 to the image reading head 1 and the document A photoelectric conversion unit that converts the reflected light from 3 into an electric signal is provided. 5 is a guide bar for moving the image reading head 1 along the document for main scanning, 6 is a wire fixed at both ends to the carriage 2 and stretched between pulleys 7, 8 is a drive Pulse motor. In the image reading apparatus configured as described above, the main scanning of the image reading is performed by the movement of the carriage 2 and the sub-scanning is performed by the sheet feeding by the platen 4 in the direction of the arrow P. The home position sensor 9 is provided for detecting the position of the home position sensor 9. When the carriage 2 moves to this position, the light blocking plate 10 provided on the carriage 2 cuts off the optical path of the home position sensor 9. The initial position is recognized. Conventionally, the main scanning of the image reading is performed only in one direction, for example, only on the outward path. The reason is that, in FIG. 4, for example, when the carriage 2 moves from the illustrated position to the left point Q and stops, and when the carriage 2 moves from the position further left than the point Q to the right point Q and stops. In this case, a shift occurs between the stop positions due to backlash in the pulse motor 8, the pulley 7, and the like. Therefore, if an image is read on both the forward path and the return path, the shift between the read images is in a state where the read images are combined. As a result, there is a problem in that a connection between the upper and lower sides cannot be obtained even if the recording means tries to output this. [Problems to be Solved by the Invention] That is, as described above, in the conventional image reading apparatus, when trying to perform image reading on both the outward path and the return path, a shift in the main scanning direction occurs during that time, Since a correct image cannot be reproduced, the image is read only in one-way main scanning, and there is a drawback that the reading takes a long time. SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that can be controlled so as to eliminate the above-described shift that occurs during image reading in bidirectional image reading in order to solve the above problems by focusing on the conventional problems described above. Is to do. [Means for Solving the Problems] In order to achieve the above object, the present invention includes an image reading unit mounted on a carriage, and a pulse motor that is step-driven by applying a drive pulse and scans the carriage. An image reading device that is arranged at a home position and detects the presence or absence of the carriage during the scanning of the carriage by the pulse motor on the forward path and the backward path by the image reading unit. A position detection sensor, a counter that counts clock pulses during a driving cycle T of the pulse motor from the start of driving of the pulse motor in one step, and the presence of the carriage in the return path of the carriage by the position detection sensor. And the count value of the counter when the Based on the count value of the counter when the presence is detected, a displacement between the forward and backward scanning of the carriage is calculated, and the timing of the reading operation on the forward and backward scanning during the scanning of the carriage is determined by the position. And control means for controlling so as to suppress the displacement of the read image due to the displacement. [Operation] According to the present invention, when the carriage is guided to the home position on the return path and the home position sensor is blocked by the light blocking plate provided on the carriage side, the carriage moves from the home position toward the outward path. Is started, and the phase of the pulse motor is different between when the light blocking state of the home position sensor is released by the light blocking plate. Therefore, a counter that counts clock pulses within the driving cycle of one step of the pulse motor is used. This makes it possible to detect the amount of shift between the forward movement and the backward movement within the movement range of the carriage associated with one-step driving, and to determine the timing of image reading in the forward movement and the timing of image reading in the backward movement based on the amount of movement. Control to shift the image in the main scanning direction. Can be erased. [Example] Hereinafter, an example of the present invention will be described in detail and specifically with reference to the drawings. FIG. 1 shows an example of a circuit configuration for carrying out image reading according to the present invention. Here, an image reading head (hereinafter referred to as an image reading unit) 1 includes a light emitting unit 11, a light emitting unit driving circuit 12, It has an A / D converter 14 for A / D converting the electric signals from the sensor 13 and the image sensor 13. Fifteen
Denotes a central processing unit CPU, and the CPU 15 includes a light emitting unit driving circuit 12
The light emitting unit 11 is driven for the document irradiation time via the
The image sensor uses the reflected light obtained by illuminating the original from 11
A / D converter 14 converts the electrical signal into an A / D signal.The digital signal is input as image information 16 and a counter 20 is provided. Counting the number. Reference numeral 17 denotes a storage device RAM that stores the image information 16 input as the digital value and is used as a work area of the CPU 15, and reference numeral 18 denotes a storage device ROM that stores programs, data, and the like of the CPU 15. 19 is Carriage 2
A circuit for driving the pulse motor 8 for driving the
In step 5, the pulse motor 8 is driven at a period T, which will be described later, and the image reading unit 1
Is read. By the way, in the image reading apparatus thus configured, the carriage 2 is now driven by the driving of the pulse motor 8.
When moving as a return path, that is, when moving from the right side to the left side in the example of FIG. 4, the light-shielding plate 10 moves the optical path of the home position sensor 9 as a position detection sensor for detecting the presence or absence of the carriage 2 at the home position. The point of interruption is indicated by X in FIG. 2A. Here, T is the above-described period of the pulse motor 8, and time X is the time TB elapsed from the B phase to the A phase in the pulse motor 8, and at this time X, the signal of the home position sensor 9 is output. Changes from “L” level to “H” level. Next, the time when the shutter 10 opens the optical path of the home position sensor when the carriage moves rightward from the state where the carriage 2 is stopped at the position of the home position sensor 9 in the example of FIG. This is shown as Y in FIG. 2B. In this case, if there is no mechanical displacement due to backlash or the like in the drive system of the carriage, this time Y exactly matches the time X shown in FIG. 2A, and the sum of the times TA and TB shown here is obtained. Should coincide with the period T, but actually a deviation occurs, so that the time points X and Y do not coincide,
The time point Y is a time point TA from the phase A to the phase B, and at this time Y, the signal of the home position sensor 9 changes from the “H” level to the “L” level. That is, when expressed as time in a cycle unit, (T−
(TA−TB), and when the movement distance of the carriage 2 corresponding to the cycle T is S, the shift amount S _L
Is Becomes Therefore, when it is considered that there is no deviation, the read timing on the return path is set to be (T
The above-described deviation can be corrected by performing control so as to be delayed by (−TA−TB) time. FIG. 3 shows an operation procedure of the above-described shift correction according to the present invention. First, in step S1, the counter is reset to zero, and in the next step S2, the pulse motor 8 is advanced in the backward direction by one pulse at a period T, and in step S3, whether or not the home position sensor 9 has been turned on during that period. Judge. If it is determined that the sensor 9 is not turned "on", the process branches to step S31 to determine whether or not the time of the cycle T has passed. If it has passed, the process returns to step S1 and returns to steps S1 to S3. Repeat the operation. If the time of the cycle T has not passed in step S31, the process returns to step S3. Furthermore, if it is determined in step S3 that the home position sensor 9 has been turned "ON", then step S4
To the counter value at the time when it was turned “ON”
TB is read, the pulse motor 8 is stopped in step S5, the counter is reset to zero in the next step S6, and the process proceeds to step S7, where the pulse motor 8 is driven in the forward direction by one step with a period T. Thus, in step S8, it is determined whether or not the home position sensor 9 has been turned "off".
It is determined whether or not the time of the cycle T has passed. If it is determined that the time has passed, the process returns to step S6 and the operations of steps S6 to S8 are repeated. If the period T has not passed in step S81, the process returns to step S8. Further steps
If it is determined in S8 that the sensor 9 is "OFF", the counter value TA at the time of "OFF" is read in Step S9, and the value of (T-TA-TB) is calculated in Step S10. Thereafter, the CPU 15 may control the reading time by the image reading head 1 on the return path to be delayed from the outward path by a time corresponding to (T-TA-TB). It is assumed that the counter is counted up in a time sufficiently shorter than the cycle T after reset. [Effect of the Invention] As described above, according to the present invention, an image reading head is used by using a counter that counts clock pulses during the driving cycle of the pulse motor from the start of driving within one step of the pulse motor. In a step of the stepping motor between the time when the carriage mounted with the carriage returns to the home position on the return path is detected by the home position sensor and the time when the carriage moves from the home position on the outward path and is detected by the home position sensor. To detect the phase shift,
By controlling the image reading timing between the forward path and the return path in accordance with the deviation so as to suppress the above-described deviation, it is possible to eliminate the deviation of the image reading in the reciprocating scanning.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a control circuit according to the present invention, FIG. 2A and FIG. 2B are explanatory diagrams of the principle of detecting an image shift according to the present invention, and FIG. FIG. 4 is a flowchart showing a control operation procedure, and FIG. 4 is a perspective view showing an example of the configuration of a conventional image reading apparatus. DESCRIPTION OF SYMBOLS 1 ... Image reading head, 2 ... Carriage, 3 ... Reading object, 4 ... Platen, 8 ... Pulse motor, 9 ... Home position sensor, 10 ... Shutter plate, 15 ... Central processing unit, 20 …… Counter.

Claims (1)

(57) [Claims] An image reading means mounted on the carriage, and a pulse motor for stepwise driving the carriage to scan the carriage by applying a driving pulse, and wherein the image reading means reads the image while the carriage scans the forward and backward paths of the carriage. An image reading apparatus configured to read from a body, a position detection sensor disposed at a home position and detecting the presence or absence of the carriage, and driving of the pulse motor from a start of driving of the pulse motor in one step. A counter that counts clock pulses during a period T; a count value of the counter when the presence of the carriage is detected on the return path of the carriage by the position detection sensor; and absence of the carriage on the outward path. The carriage based on the count value of the counter when detected. Control means for calculating a position shift between the forward scan and the return scan, and controlling the timing of the reading operation on the forward scan and the return scan during the scanning of the carriage so as to suppress the shift of the read image due to the position shift. An image reading apparatus comprising: