JPH0834535B2 - Image reader - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device that reads a document by fixing it, for example.

2. Description of the Related Art As shown in FIG. 6, a conventional device of this type includes a reading unit 3 for reading a document 2 set on a fixed document table 1 line by line from the main scanning direction, and a reading unit 3 for reading the document. Drive mechanism 4 for moving the line reading position in the sub-scanning direction
A motor control circuit 6 for controlling the start and stop of the pulse motor 5 serving as the drive source of the drive mechanism 4 while performing slow-up and slow-down, and the line reading timing of the reading unit 3 for the operation of the motor 5. It has a timing control circuit 7 for controlling it together, and the line reading timing is adjusted to the operation of the motor 5 in order to obtain a reading output with a uniform line pitch. Note that φ is a reference clock given from the outside.

However, according to such a configuration, there is a problem that uneven reading occurs when starting or stopping the feeding operation for reading a document.

 The above problem occurs for the following reasons.

That is, in this type of image reading apparatus, in order to make the feeding operation for reading the original stable and reliable, as shown in FIG. 7, the start and stop of the pulse motor 5 which is the driving source thereof is slowed up. And control is performed while performing slowdown. The slow-up and slow-down are performed by gradually changing the drive pulse cycle of the pulse motor 5 at the time of starting and stopping.

At this time, in the conventional device, in order to keep the line pitch d given by the product of the line reading time interval t and the feed speed of the line reading position constant, that is, to eliminate the reading unevenness, the line reading timing is set to the pulse motor. It was synchronized with all movements, including 5 slow-ups and slow-downs.

However, at the time of transition during start-up or stop, the operation of the motor 5 and the operation of the motor 5 as a drive source are performed due to, for example, mechanical friction in the drive mechanism 4, inertia, belt extension, and gear backlash. The line feed operation does not always match.

Therefore, as shown in FIG. 8, even if the line reading timing is controlled in accordance with the operation of the motor 5, the relationship between the line reading time interval t and the line feed speed can be obtained when the motor 5 is started or stopped. Is not constant and the line pitch d is disturbed.

FIG. 8 is a graph showing a state where the pitch d is disturbed as described above. The vertical axis represents the line feed amount and the horizontal axis represents time.

In the same figure, the broken line part A of the graph curve shows the theoretical time change of the feed amount predicted by the operation of the motor 5, and if this broken line part A is obtained, from the start to the stop The line pitch d should be constant over the entire section of.

However, the actual transition of the line feed amount over time is different from the theoretical feed state predicted from the operation of the motor 5, especially at slowdown stop, as shown by the solid line portion B of the graph curve. For this reason, the line pitch d cannot be kept constant when the slowdown is stopped, and so-called reading unevenness C occurs.

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 apparatus that can correct reading unevenness that occurs when starting or stopping a feeding operation for reading a document.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a drive source for the above-mentioned feeding operation when feeding a line reading position in the sub-scanning direction while reading a document line by line from the main scanning direction. It controls the start and stop of the motor that makes up while slowing up and slowing down.
The line reading timing by the reading unit is controlled according to the operation of the motor, while the line reading timing when the motor is started or stopped is controlled by the operation of the motor according to a control pattern set in advance. It is equipped with a configuration that it is controlled independently from.

Advantageous Effects of Invention The present invention makes it possible to selectively correct the disturbance of the feeding operation that occurs when the motor is started or stopped, so that the feeding operation for reading a document is started or stopped. It is possible to correct uneven reading that sometimes occurs.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

 The parts common to the conventional ones are indicated by the same symbols.

FIG. 1 shows a schematic structure of an image reading apparatus according to an embodiment of the present invention. Reference numeral 1 is a fixed manuscript table, 2 is a manuscript set and fixed on the manuscript table 1, and 3 is the manuscript. A reading unit for reading the document 2 line by line from the main scanning direction, 4
Is a driving mechanism for moving the line reading position by the reading unit 3 in the sub-scanning direction, 5 is a pulse motor which is a driving source of the driving mechanism 4, and 6 is slow-up and slow-down for starting and stopping the pulse motor 5. A motor control circuit for controlling while reading, 7 is a first timing control circuit for controlling the line reading timing of the reading unit 3 in accordance with the operation of the motor 5, and 8 is the line reading according to a control pattern set in advance. It is a second timing control circuit that controls timing.

Here, the reading unit 3 includes a reading optical system 31 that forms an image on the document 2 and a photoelectric conversion unit 32 that converts the formed image into electrical image information by a line image sensor such as a CCD. Have and.

The drive mechanism unit 4 has a configuration example shown in FIG.
The rotation output of the motor 5 is converted into the linear motion of the reading unit 4 by the belts 41, 42 and the guide shaft 43.

The motor control circuit 6 operates based on a reference clock φ given from the outside, and generates a drive pulse of a predetermined cycle for step-driving the motor 5. At the same time, when the reading is started and stopped, the cycle of the drive pulse is changed stepwise to start and stop the motor 5 by slow-up and slow-down.

The first timing control circuit 7 controls the sampling timing of the line image information photoelectrically converted by the photoelectric conversion section 32 based on the drive pulse given to the motor 5 from the motor control circuit 6. That is, under the control of the first timing control circuit 7, line reading is performed in accordance with the operation of the motor 5.

In this embodiment, the second timing control circuit 8 includes a switching circuit 81 that operates when the motor 5 is started or stopped, and a programmable control pattern generation circuit 82 that generates a control pattern that is set in advance. It is composed by. Then, when the motor 5 is started or stopped, the line reading timing is controlled independently of the operation of the motor 5 by a control pattern arbitrarily set (programmed) in advance.

FIG. 3 shows an example of the programmable control pattern generation circuit 82 which is a main part of the second timing control circuit 8. The programmable control pattern generation circuit 82 illustrated here is incremented by n with the reference clock φ.
A digit binary counter 821 and an EP-ROM (electrically writable non-volatile memory) 822 addressed by an n-bit parallel count output of this binary counter 821 and an externally given start / stop command bit And this EP-R
The latch circuit 823 outputs the storage data Dout sequentially read from the OM822 according to the count value of the counter 821 as a control signal source of the line reading timing.

Here, the address (A0 to An) of the EP-ROM822 is divided into lower n bits (A0 to An-1) and upper 1 bit (An),
The lower n bits (A0 to An-1) have n of the binary counter 821.
Bit parallel count output is given, and start / stop command bit (“1” / “0”) is given to the upper 1 bit (An). And the command bit (An) is activated (An = "1")
, The parallel count output of counter 821 (A0 to An−
In the storage area addressed by 1), a line read timing control pattern that matches the actual line feed operation at startup is written in advance. Similarly, the storage area addressed by the parallel count output (A0 to An-1) of the counter 821 when the command bit (An) is stopped (An = "0") is the actual line feed at stop. A control pattern of the line reading timing suitable for the operation is written in advance.

Accordingly, the line reading timing can be controlled independently of the operation of the motor 5 by the control pattern set in advance.

The operation of the image reading apparatus configured as described above will be described below.

FIG. 4 shows the relationship between the drive speed of the pulse motor 5 and the line reading timing in the apparatus of the above-described embodiment.

In the figure, the line reading timing in the section in which the motor 5 is driven at a steady speed is controlled by the first timing control circuit 7 in accordance with the operation of the motor 5. However, the line reading timing t at the transition when the motor 5 is slow-up started and slow-down started is not set by the second timing control circuit 7 in advance according to the actual feeding operation, not the operation of the motor 5. It is controlled by the generated control pattern.

As a result, as shown in FIG. 5, the line pitch d
Will be kept constant even when the slowdown is stopped. In the operation example shown in the figure, there is a difference between the actual line feeding operation (curved portion B) and the theoretical line feeding operation (curved portion A) when the slowdown is stopped. Is controlled so as to match the actual line feed operation (curved portion B).

As described above, the disturbance of the feeding operation that occurs when the motor 5 is started or stopped can be selectively corrected by the second timing control circuit 8. Accordingly, it is possible to correct the reading unevenness that occurs when the feeding operation for reading the original 2 is started or stopped.

Although the embodiments have been described above, the present invention can have various modes other than those described above. For example, when only the reading unevenness when the reading operation is stopped becomes a problem, the second timing control circuit 8 may operate only when the slowdown of the motor 5 is stopped.

EFFECTS OF THE INVENTION As is clear from the above description, the present invention serves as a drive source for the feeding operation when the document is read line by line from the main scanning direction and the line reading position is fed in the sub scanning direction. The start and stop of the motor is controlled while performing slow-up and slow-down, and the line reading timing by the reading unit is controlled according to the operation of the motor, while the line reading is performed when the motor is started or stopped. Regarding the timing, by controlling the motor independently from the operation of the motor with a control pattern set in advance, it is possible to selectively correct the disturbance of the feed operation that occurs when the motor is started or stopped. So that you can start or stop the feeding operation to read the original. This has an effect that it is possible to correct the reading unevenness that occurs when the printing is stopped.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image reading apparatus according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a mechanical portion of the apparatus, and FIG. 3 is an example of a programmable control pattern generation circuit used in the apparatus. 4 is a timing chart showing the relationship between the operation of the motor and the line reading timing in the apparatus, and FIG. 5 shows an example of the line feeding operation performed by the apparatus in correspondence with the line reading timing. FIG. 6 is a characteristic diagram, FIG. 6 is a schematic configuration diagram of a conventional image reading apparatus, FIG. 7 is a timing chart showing the relationship between motor operation and line reading timing in the apparatus, and FIG. 8 is a line feed of a conventional apparatus. FIG. 10 is a characteristic diagram showing an operation example corresponding to line reading timing. DESCRIPTION OF SYMBOLS 1 ... Original document table, 2 ... Original document, 3 ... Reading unit, 4 ... Driving mechanism, 5
... pulse motor, 6 ... motor control circuit, 7 ... first timing control circuit, 8 ... second timing control circuit, 82 ...
Programmable control pattern generation circuit, t ... Line reading time interval, d ... Line pitch.

Claims (1)

[Claims] 1. A reading means for reading an original in a line unit from the main scanning direction, a drive mechanism for feeding the line reading position of the reading means in the sub-scanning direction, and a start-up of a motor serving as a drive source of the drive mechanism. Motor control means for controlling the stop while slowing up and slowing down, a first timing control circuit for controlling the line reading timing by the reading unit in accordance with the operation of the motor, and the motor is started or stopped. An image reading apparatus provided with a second timing control means for controlling the line reading timing at this time independently of the operation of the motor by a control pattern set in advance.