JPH06125430A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce the load on a driving system by reading data at a high speed and smoothly starting and stopping a scanner. CONSTITUTION:The scanner is started with a margin at a read start time t0 and reaches a certain speed V at a time t4 without repeatedly overshooting neither downshooting the target speed V and continues to read data and is stopped with a margin at a read end time t5 to t6. A picture processing and memory part 4 thins picture data from an A/D converter 3 in a ratio v/V in each line based on the speed (v) of a document scanning means at the time of acceleration and deceleration of the scanner so that the picture is not extended in the subscanning direction, and the result is stored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a scanner for reading a document.

[0002]

2. Description of the Related Art Generally, when a scanner such as an optical scanner or a document table is moved in the sub-scanning direction to read a document at a constant speed, a start-up distance and a start-up time are required. This approach distance and approach time must be shortened to read. As a conventional method, for example, as shown in JP-A-61-145540, the start position is changed according to the magnification, or JP-A-61-1484.
As disclosed in Japanese Unexamined Patent Publication No. 39-39, an electric power applied to a clutch mechanism that transmits a driving force to a scanning system is controlled to prevent overshoot, and as disclosed in Japanese Unexamined Patent Publication No. 63-206066, the image reading density is reduced. It is known that a reading speed is set in accordance with the reading speed, and a buffer memory for storing a read image at the time of stopping or starting the scanner during reading is provided as disclosed in Japanese Patent Laid-Open No. 2-202167.

The speed v with respect to the reading time t of the conventional scanner will be described with reference to FIG. In this example, in order to perform reading at a constant speed V, the scanner starts moving toward the speed V at time t0 and accelerates at a constant acceleration, repeating overshoot and downshoot with respect to the target speed V. Constant speed at time t1
The reading becomes V, and reading is started from the leading edge of the document. Then, when the reading is completed at the time t2, the reading is decelerated at a constant acceleration, the reading completion position is overrun, and the reading is stopped at the time t3. Although not shown,
The scanner at this position moves in the reverse direction and returns to the movement start position at time t0.

[0004]

However, in the above conventional method, the run-up distance at time (t1 -t0) and the overrun distance at time (t3 -t2) have a great influence on the size of the entire apparatus such as a copying machine. It is desirable to make it as short as possible, but if this distance is shortened, the scanner must be suddenly started up and down.
Not only a powerful motor is required, but also a large load is generated on the entire drive system, and noise and vibration also increase.

In addition, it is difficult to maintain a constant speed and it is impossible to prevent overrun. This problem becomes remarkable when an attempt is made to increase the reading speed V for speeding up. Become. further,
In order to increase the speed, the scanner must be returned to the initial position at high speed, so that the problem of overrun also occurs.

In view of the above-mentioned conventional problems, the present invention can prevent the run-up distance for the scanner to reach the reading speed and the overrun after the reading is completed, and can read at high speed, and the scanner can be started up smoothly. An object of the present invention is to provide an image forming apparatus that can be turned down to reduce the load on the drive system.

[0007]

In order to achieve the above object, a first means is a reading means for accelerating a scanner from a stop to maintain a constant speed, and decelerating from the constant speed to read an original. And an image processing unit for correcting the image read by the reading unit so as not to extend in the sub-scanning direction during acceleration and deceleration of the scanner.

The second means is the ratio v / V of the speed v when the scanner shifts the speed of the image read by the reading means by the image processing means of the first means and the constant speed V.
The image is corrected by thinning out so that the image does not extend in the sub-scanning direction. In a third means, the reading means has a CCD in the first means, and the image processing means changes the accumulation time of the CCD when the scanner shifts the speed, whereby the image read by the reading means is sub-scanned. The feature is that correction is performed so that the direction does not extend.

A fourth means is characterized in that the image processing means of the third means changes the image density when thinning out the image read by the reading means.

A fifth means is that the image processing means of the first to fourth means thins out the image read by the reading means during acceleration of the scanner and stores it in a memory.
It is characterized in that after the scanner reaches the constant speed, the data is output as it is without being stored in the memory.

[0011]

According to the first means, the original can be read at the time of accelerating and decelerating the scanner, so that the original can be read at a substantially high speed, and the scanner can be smoothly started up and started up. Since it can be lowered, the load on the drive system can be reduced.

Since the second means thins out the image based on the speed of the scanner, it is possible to properly read the original even when the speed is changed.

The third means thins out the image by changing the accumulation time of the CCD, so that the original can be properly read even when shifting.

The fourth means changes the image density when thinning out the images, so that the original can be properly read even during shifting.

Since the fifth means stores the read image in the memory only when the scanner is accelerated, the memory capacity can be minimized.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the image forming apparatus according to the present invention, and FIG. 2 is an explanatory diagram showing changes in the speed of the scanner in the image forming apparatus of FIG.

The CCD 1 shown in FIG. 1 is fixed so as to read an original (not shown) in the main scanning direction, and the original can be read in two dimensions when the optical scanner or the scanner of the original table moves in the sub scanning direction. The signal read by the CCD 1 is amplified by the amplifier 2, converted into a digital signal by the A / D converter 3, and then taken into the image processing and memory 4.

As shown in FIG. 2, the scanner is started up with a margin at the time t0 of reading, and reaches a constant speed V at time t4 without repeating overshooting and downshooting with respect to the target speed V and reading. Is continued, and even when the reading is completed during the time t5 to t6, it can be shut down with a margin. That is, the original is read at time t1 to t2 in the conventional example, and is read at time t0 in this embodiment.
Read at ~ t6. Therefore, as in the conventional example, the approaching distance and time (t3 -t0) at time (t1 -t0)
No overrun distance in 2) is required.

When the image thus read is recorded on the recording paper as it is through the photoconductor, the read image at the speed increase (t0 to t4) and deceleration (t5 to t6) of the scanner is subscanning direction. It will extend to, and impair the equality.
Therefore, in the present embodiment, the image processing and memory unit 4 determines, based on the speed v of the scanner, during acceleration and deceleration,
The image data from the A / D converter 3 is thinned out and stored for each line at a ratio of v / V so that the image does not extend in the sub-scanning direction. The speed v may be read from an encoder in the scanner driving motor, or may be read by a non-contact gap sensor, acceleration sensor, magnescale,
A pattern with a constant width can be detected by a method of reading with a sensor.

Then, in order to minimize the memory capacity,
When the speed v reaches a constant speed V, the writing control unit 5 starts writing at the timing when all the data accumulated in the memory is output. Although the memory capacity increases, the read data of the original document may be stored in the memory as it is, and the speed of reading from the memory may be changed based on the speed v at the time of reading.

As the thinning method, the data transfer timing from the CCD 1 may be changed based on the speed v at the time of reading the data. Figure 3 (a)
(B) shows the transfer pulse timing of the CCD 1 when the scanner is accelerated, and shortens the accumulation time when the speed v is slow. The data stored in this CCD 1 is shown in FIG.
As shown in (c), it is fetched through the shift register 10.

Further, as shown in FIG. 4, for example, an image density conversion table for each speed v of four stages is provided in the image processing unit 4, and the reading density D0 is converted to a low value at a low speed to properly reproduce the original density. can do. further,
According to the above embodiment, the image is thinned out based on the speed v of the scanner during acceleration and deceleration so that the image does not extend in the sub-scanning direction. Therefore, by appropriately controlling the light accumulation time of the CCD 1 and the document illumination light amount, the CCD 1 It is possible to keep the reading condition of the constant.

[0023]

As described above, according to the first aspect of the invention, the scanner is accelerated from the time of stop to maintain a constant speed, and the reading means for decelerating from the constant speed to read a document, and the scanner. Since the image processing means for correcting the image read by the reading means so as not to extend in the sub-scanning direction is provided at the time of acceleration and deceleration, the original can be read at the time of acceleration and deceleration of the scanner. , The original can be read at substantially high speed. Further, since the scanner can be smoothly started up and down, the load on the drive system can be reduced.

According to a second aspect of the present invention, the image read by the image processing means according to the first aspect is thinned out at a ratio v / V of the speed v at the time of shifting the scanner and the constant speed V. As a result, the image is corrected so that it does not extend in the sub-scanning direction, so that the original can be properly read even during shifting.

According to a third aspect of the present invention, in the first aspect of the present invention, the reading means has a CCD, and the image processing means changes the accumulation time of the CCD when the scanner shifts the speed. Since the read image is corrected so as not to extend in the sub-scanning direction, the original can be properly read even during shifting.

According to a fourth aspect of the present invention, the image processing means according to the third aspect changes the image density when thinning out the image read by the reading means, so that the original can be properly read even during gear shifting. You can

The invention according to claim 5 is the invention according to claims 1 to 4.
Since the image processing means described above thins out the image read by the reading means in the memory during acceleration of the scanner and stores it in the memory, and outputs it as it is without storing it in the memory after the scanner reaches the certain speed. The capacity can be minimized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a change in speed of a scanner in the image forming apparatus of FIG.

FIG. 3 is an explanatory diagram showing an example of changing a transfer timing of a CCD.

FIG. 4 is an explanatory diagram showing a document density conversion table.

FIG. 5 is an explanatory diagram showing a conventional scanner speed.

[Explanation of symbols]

 1 CCD 4 Image processing and memory

Claims (5)

[Claims] 1. A reading unit for accelerating a scanner from a stop to maintain a constant speed, and decelerating from the constant speed for reading an original, and an image read by the reading unit during acceleration and deceleration of the scanner. An image forming apparatus comprising: an image processing unit that corrects so that the sub scanning direction does not extend. 2. The image processing means thins out the image read by the reading means at a ratio v / V of the speed v at the time of shifting the scanner and the constant speed V, so that the image does not extend in the sub-scanning direction. The image forming apparatus according to claim 1, wherein the correction is performed as described above. 3. The reading unit has a CCD, and the image processing unit changes the accumulation time of the CCD when the scanner shifts speed so that the image read by the reading unit does not extend in the sub-scanning direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is corrected. 4. The image forming apparatus according to claim 1, wherein the image processing unit changes the image density when thinning out the image read by the reading unit. 5. The image processing unit thins out the image read by the reading unit when accelerating the scanner, stores the thinned image in a memory, and outputs the image as it is without storing it in the memory after the scanner reaches the certain speed. The image forming apparatus according to any one of claims 1 to 4, characterized in that: