JPH04360366A - Picture reader - Google Patents

Abstract

PURPOSE:To realize the picture reader able to obtain a picture without uneven speed of a tip of a picture at reduction read and able to reduce a read cycle at nonmagnification read used usually and frequently. CONSTITUTION:The reader is provided with an approach pattern decision means 1 varying an approach start point of a motor with a command of a read speed, a driving current decision means 2 varying a driving current of the motor with acceleration/deceleration of a scan unit and at a constant speed state and a motor drive means 3 controlling a driving speed of the motor with a control signal from the approach pattern decision means 1 and a control signal from the driving current decision means 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device used in an image input device or the like.

0002

2. Description of the Related Art In recent years, image reading devices have a function of varying the reading speed of an original in order to read an image at the same magnification, enlarge or reduce the image, and change the resolution.

An example of the above-mentioned conventional image reading device will be described below with reference to the drawings.

FIG. 4 shows a configuration diagram of a conventional image reading device. In FIG. 4, reference numeral 51 denotes an original table glass for holding the original 4, and 52 represents an original regulating plate for regulating the position where the original is placed. Figure 5 shows the scan unit.
Illumination lamp 53 and optical mirror 54 for illuminating the document surface
It is equipped with 55 is a unit called a half-speed unit, and is equipped with optical mirrors 56 and 57. The scanning unit 5 and the half-speed unit 55 move parallel to the document 4 in the direction of arrow A (referred to as the sub-scanning direction) by the driving force of the driving stepping motor 7 (this is called the sub-scanning direction). (or scanning in the sub-scanning direction). This half-speed unit 55 moves at half the moving speed of the scanning unit 5 in the sub-scanning direction.
Move in the sub-scanning direction. By scanning in the sub-scanning direction by the scanning unit 5 and the half-speed unit 55, the reflected light from the document surface passes through the optical mirrors 54, 56, 57 and passes through the optical lens 5.
8 forms an image on the image sensor 59. The direction perpendicular to the plane of the drawing is called the main scanning direction, and the image sensor 59 converts the optical image formed thereon into an electrical signal, scans it in the main scanning direction, and sends it out as a read signal. In addition, 6 is an origin sensor for detecting the origin position of the scan unit, 60 is a motor drive means for driving the driving stepping motor 7, and 43
is the enclosure of the image reading device. Further, the scanning unit 5 and the half-speed unit 55 are referred to as scanning means.

Next, FIG. 5 shows an operation plan for the image reading operation in the conventional example, in which the horizontal axis represents the moving distance of the scanning unit 5 in the sub-scanning direction, and the rotational speed of the driving stepping motor 7 is plotted. is taken on the vertical axis. The moving distance in the sub-scanning direction is from the origin sensor 6 to arrow A.
This is the distance measured in the direction of . That is, the origin O in FIG. 5 corresponds to the position of the origin sensor 6. The positive direction of the vertical axis indicates the rotational speed of the driving stepping motor 7 when driving the scan unit 5 in the direction of arrow A in FIG. Stepping motor 7 for driving when driving
represents the rotation speed. In FIG. 5, arrows 63, 64, 65, 66, and 67 indicate the operation plan at the same magnification. Also, arrows 67, 68, 6 indicate the operation plan at maximum reduction.
9, 70, and 71.

In the image reading apparatus configured as described above, the image reading operation will be explained below. First, the reading operation at the same magnification will be explained. When the power is turned on, the driving stepping motor 7 rotates negatively and moves the scan unit 5 toward the origin sensor 6 (in the opposite direction of arrow A in FIG. 4). Origin sensor 6 is scan unit 5
The driving stepping motor 7 rotates in the forward rotation direction several millimeters further from the point where it is detected. The point at which the origin sensor 6 no longer detects the scan unit 5 is defined as the origin position O in FIG. When the scan unit 5 has further advanced a predetermined distance (home position P), the driving stepping motor 7 stops and waits for the start of the reading operation.

[0007] When the reading start request is turned on, the driving stepping motor 7 performs forward acceleration rotation as indicated by an arrow 63 to accelerate the scanning means in the sub-scanning direction. When the rotational speed of the driving stepping motor 7 corresponding to the scanning speed at the same magnification of the scanning means is set as VA, when the rotational speed reaches VA, the driving stepping motor 7 rotates at a constant speed shown by an arrow 64 and performs scanning. The means scans the original 4 at the same scanning speed. The home position P is the approach start point, and the approach distance Lu is from the approach start point to the point U where the constant scanning speed starts.
It is. When reading of the original 4 is completed, the driving stepping motor 7 performs a normal rotation deceleration driving operation as indicated by an arrow 65 to reduce the speed of the scanning unit 5. When the normal rotation deceleration driving operation is completed, the driving stepping motor 7 performs the negative rotation acceleration driving operation as indicated by the arrow 66. When the negative rotation acceleration drive operation is completed, the driving stepping motor 7 performs a negative rotation deceleration drive operation as indicated by an arrow 67. When the negative rotation deceleration driving operation is completed, the driving stepping motor 7 stops and waits for the next reading operation to start. Thereafter, a continuous image reading operation is performed by repeating the same operation.

Furthermore, since the scanning speed of the scanning means during reduction is higher than the scanning speed during normal magnification, the rotational speed of the driving stepping motor 7 during constant speed also increases correspondingly. At the maximum reduction, the rotational speed of the driving stepping motor 7 at constant speed becomes the value VB shown in FIG. Therefore, in the image reading operation at the maximum reduction, the arrows 63, 64, 65, 66, 67 of the reading operation at the same magnification are
68, 69, 70, and 71. In other words, the run-up distance is Lt at the maximum reduction and Lu at the same magnification.
Become bigger. Further, in the image reading operation at maximum magnification, the above arrows are 67, 72, 73, 74, 75, and the run-up distance is Lw at maximum magnification, which is smaller than Lu at normal magnification.

As explained above, the rotational speed of the driving stepping motor 7 during constant speed scanning differs depending on the magnification of reduction/enlargement. It is larger when it is enlarged to the same size, larger when it is reduced than when it is enlarged, and it is maximum when it is reduced to the maximum size.

Therefore, the home position 62 is set so that sufficient acceleration can be achieved even when the rotational speed during constant-speed driving is at its maximum.

[0011]

However, in the above configuration, since the distance Lp between the home position P and the position O of the origin sensor 6 is constant, the driving stepping motor 7 and the scanning unit 5 are driven at a constant speed. The position will be point W at maximum magnification, and the origin sensor 6 at that time will be
The distance from is Lw. Similarly, the constant speed driving point at the same magnification is point U and the distance is Lu, and the constant speed driving point at maximum reduction is point T and the distance is Lt. On the other hand, since the leading edge position of the original 4 is fixed, the distance L between the leading edge position Q of the original and the origin sensor 6 is
q is constant. Therefore, in order to achieve sufficient acceleration at maximum reduction, Lt must be equal to Lq or L
It must be smaller than q. Therefore, in the case of the conventional example, when reading at the same magnification, which is usually used most often, there was a problem that the time required to read the Lq-Lu distance was unnecessarily long. Further, at maximum enlargement, the time required to read Lq-Lw is wasted. Therefore, if the distance Lq between the leading edge position of the document 4 and the origin sensor 6 is shortened in an attempt to shorten the above-mentioned wasted time, when reading an image at maximum reduction, reading of the document will start before reaching a constant speed. Therefore, there is a problem in that image unevenness occurs at the leading edge of the read image due to uneven reading speed.

In view of the above-mentioned problems, the present invention changes the position of the home position P depending on the specified constant velocity value, and sets the acceleration start point near the original at a velocity that is normally frequently used. , an image reading device that aims to shorten the reading cycle by shortening the acceleration time, and that can obtain good image quality by sufficiently accelerating from near the origin at speeds that tend to cause reading speed unevenness at the leading edge of the image. It provides:

[0013]

[Means for Solving the Problems] In order to solve the above-mentioned problems, an image reading apparatus of the present invention includes a scanning means for scanning a document on a document table and converting it into an electric signal in a sub-scanning direction; A motor that drives the scanning means, a reading speed determining means that calculates and outputs a reading speed from a given scaling factor, and an approach pattern that calculates and outputs an approach start point and acceleration of the motor based on the output value of the reading speed. a determining means; a driving current determining means for calculating and outputting the length of time for accelerating and decelerating the scan unit, the current value during acceleration and deceleration, and the length of time and current value during constant speed driving based on the output value of the reading speed; The present invention includes motor drive means for controlling the drive speed of the motor in accordance with the output of the run-up pattern determination means and the output of the drive current determination means.

[0014]

[Operation] With the above-described configuration, the present invention changes the position of the home position depending on the instructed speed, and sets the acceleration start point near the original at a speed that is normally frequently used.
By shortening the acceleration time and shortening the reading cycle,
In addition, at a speed that tends to cause unevenness in reading speed at the leading edge of the image, good image quality can be obtained by sufficiently accelerating from near the origin.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an image reading apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart regarding control of the run-up pattern determining means 1 and drive current determining means 2 shown in FIG. 1, and FIG. It is an operation plan diagram at the time.

In FIG. 1, numeral 43 is the mechanical section of the image reading apparatus described in the conventional example, so detailed explanation will be omitted. Based on the value input by the reduction/enlargement ratio input means 20 in FIG. 1, the reading speed determining means 21 calculates and outputs the reading speed during constant speed scanning. Reference numeral 1 denotes a run-up pattern determining means which calculates and outputs the run-up distance and acceleration based on the output value of the reading speed determining means 21. The run-up distance and acceleration described above are called a run-up pattern. Reference numeral 2 denotes a drive current determining means which calculates and outputs the length of time for accelerating and decelerating the scan unit, the current value during acceleration and deceleration, and the length of time and current value during constant speed driving based on the output value of the reading speed. 3 is the run-up pattern determining means 1 and drive current determining means 2.
This is a motor driving means that supplies a current to drive a driving stepping motor based on the output of the motor.

As shown in FIG. 3, in the embodiment of the present invention, the home position is changed depending on the scaling factor. In other words, the home position is set to P1 when the maximum reduction is made, to P2 when the same size is used, and to P when the maximum enlargement is made.
It is placed at 3. As a result, even if the enlargement/reduction magnification changes, the distance Lt' from the position O of the origin sensor 6 of the positions T', U', and W' at which constant speed rotation is reached always remains unchanged. The leading position of the document 4 is assumed to be the position indicated by Q.

In order to realize the operation plan diagram of FIG. 3, the flowchart of FIG. 2 will be explained. In FIG. 2, when the reading start request is turned on, the reading speed determining means 2 calculates the reading speed based on the input value of the reduction/enlargement ratio, and determines whether the reading speed has been changed since the previous reading instruction (step 8). )I do. If there is no change in the reading speed, a reading operation (step 18) is performed, and if there is a change in the reading speed, it is determined whether the reading speed is the same as the original magnification (step 9). When it is determined that the reading speed is the speed at 1x, the run-up distance determining means 1 calculates an acceleration pattern of the run-up distance and acceleration for 1x (step 10).Next, the drive current determining means 2 Find the drive current pattern for (step 11) acceleration start point P2
(Step 17). Reading speed determining means 2
If the reading speed in is not the same as the speed at the same magnification, it is determined whether the reading speed is faster than at the same magnification (step 12). If the reading speed is faster than the speed at the same magnification, the run-up distance determining means 1 calculates an acceleration pattern of the run-up distance and acceleration for high speed (step 13).Next, the drive current determining means 2 calculates a drive current pattern for high speed. (Step 14) Move to the acceleration start point P1 (Step 17). If the reading speed in the reading speed determining means 2 is slower than the speed at the same magnification, the run-up distance determining means 1 calculates an acceleration pattern of the run-up distance and acceleration for low speed (step 15). Next, the drive current pattern for low speed is determined. (step 16), and moves to the acceleration start point P3 (step 17). Once the movement to the acceleration start point is completed, read operation (step 18)
I do. As already explained, the reading operation is the acceleration indicated by the arrows 22, 28, and 34 in FIG.
Constant speed scan shown at 29, 35, arrows 24, 30, 36
, acceleration of negative rotation as shown by arrows 25, 31, and 37, and deceleration of negative rotation as shown by arrows 26, 32, and 38. Once the reading operation is finished,
It is determined whether it is a continuous scan (step 19). If it is a continuous scan, the process returns to step 18. If the scan is not continuous, the process ends.

As described above, according to the present embodiment, depending on the reading speed instruction value, the run-up pattern determining means 1 for varying the run-up start point of the motor and the scan unit are accelerated and decelerated, and when the scan unit is in a constant speed state. A drive current determination means 2 for varying the drive current of the motor, and a motor drive means 3 for controlling the drive speed of the motor by a control signal from the run-up pattern determination means and a control signal from the drive current determination means. When reading at the same magnification used, it is possible to read for a short time, and when reading at reduced size, it is possible to obtain an image with no speed unevenness at the leading edge of the image.

[0021]

As described above, the image reading device of the present invention changes the position of the home position according to the speed instructed by the above-described configuration, and at the speed that is usually frequently used, the acceleration start point is changed from the position of the document. To shorten the reading cycle by shortening the acceleration time by setting the sensor close to the origin, at speeds that tend to cause uneven reading speed at the leading edge of the image, it is possible to obtain good image quality by accelerating sufficiently from near the origin. can.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an image reading device in an embodiment of the present invention.

[Fig. 2] Flowchart regarding control of approach distance determining means and drive current determining means

[Fig. 3] Operation plan diagram at the time of reading in one embodiment of the present invention

[Figure 4] Configuration diagram of a conventional image reading device

[Figure 5] Operation plan diagram when reading images (conventional example)

[Explanation of symbols]

1 Run-up pattern determining means 2 Drive current determining means 3 Motor drive means 4 Manuscript 5 Scan unit (scanning means) 6 Origin sensor 7 Drive stepping motor 21 Reading speed determining means 55 Half speed unit

Claims (1)

[Claims] Claim 1: Scanning means for scanning a document on a document table in a sub-scanning direction to convert it into an electrical signal; a motor for driving the scanning means; and a scanning device that calculates a reading speed from a given enlargement/reduction ratio. a reading speed determining means to output; a run-up pattern determining means to calculate and output a run-up starting point and acceleration of the motor based on the output value of the reading speed; and a length of time for accelerating or decelerating the scan unit based on the output value of the reading speed. a drive current determining means for calculating and outputting a motor drive current value during acceleration/deceleration, a length of time during constant speed drive, and a motor drive current value, an output of the run-up pattern determining means and an output of the drive current determining means; and motor drive means for correspondingly controlling the drive speed of the motor.