JPH0884225A - Original reader - Google Patents

Abstract

PURPOSE: To eliminate the unstable period of multiple pulses by using plase A, B pulses for the multiple pulses to detect a moving speed of a carriage with high accuracy and multiplying either of the phase A, B pulses so as to produce the multiple pulses. CONSTITUTION: A timing between a leading timing of a phase A output pulse and a leading timing of the succeeding output pulse is measured as pitch time P1, the time P1 is divided equally by 4 as T1, T2, T3, T4 respectively. Thus, the time multiplied by 4 is expressed as T1=P1/4, T2=P1/4, T3=P1/4, and T4=P1/4, then the encoder output is corrected entirely accurately. Similarly assuming that the pitch time of succeeding output pulses be P2 and each time multiplying the time by 4 be P2, the time to multiply the pitch is similarly T5=P2/4, T6=P2/4, T7=P2/4, and T8=P2/4. The speed control is made accurate by specifying the pitch and the output pulse similarly to above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading device for reading document information while driving and scanning a scanning optical system.

[0002]

2. Description of the Related Art In a document reading apparatus for reading document information while driving and scanning a scanning optical system, the scanning optical system is controlled so that a document is scanned at a constant speed. The detection of the moving speed of the scanning optical system is performed using a pulse output from an encoder such as a linear encoder or a rotary encoder. The number of pulses counted per unit time is proportional to the moving speed.

Normally, the pulse output from the encoder is composed of, for example, an A-phase pulse and a B-phase pulse having a phase difference of 90 degrees from each other because it is necessary to identify the moving direction.

Further, in order to detect the displacement amount and the moving speed with high accuracy, the A-phase pulse and the B-phase pulse are multiplied and the number of reference clocks included in the generated multiplied pulses is counted.

That is, when speed control is performed using a linear encoder, A output from the linear encoder
The phase and B phase pulses are used twice (double) and four times (four) to artificially increase the resolution.

Particularly, when used by multiplying by four, it is often used because it is more cost effective than using an expensive linear encoder and linear slit for high resolution. Further, if the resolution can be increased, the sampling frequency for speed control can be increased, which is advantageous.

The multiplication method will be described below with reference to FIG. The linear encoder has a structure for outputting A-phase and B-phase pulses output from two channels that are out of phase with each other by 90 °. When the linear encoder crosses the linear slit, the A phase and the B phase are output as shown in FIG. 5 according to the bright and dark portions of the linear slit. In the case of multiplication by one, the rising of one channel is used for timing, and the cycle error from the rise to the fall is usually the minimum error. Therefore, multiplication by one gives the most accurate position information. The doubling is a method of forming a pulse at the timing of the rising and falling edges of one channel. Quadrupling is a method of making a pulse at the rising and falling edges of both channels.
This also applies to rotary encoding.

[0008]

However, the conventional document reading apparatus as described above has the following problems. That is, for example, in the case of the output pulse of quadrupling which is used with the highest resolution, the four pulse intervals are often not uniform as shown in FIG. This is because there are variations in the electrical characteristics of the light emitting diodes and phototransistors that make up the encoder, and assembly errors. Therefore, when speed control is performed using a pulse that has been multiplied by 4, accurate speed control cannot be performed, and in some cases speed fluctuations may increase.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems of the prior art and to provide a high-resolution document reading apparatus capable of controlling the speed of a scanning optical system with high accuracy.

[0010]

In order to achieve the above-mentioned object, a document reading apparatus according to the present invention is a document reading apparatus for illuminating a document and receiving reflected light to read document information from a light source. An optical system that forms an optical path that reflects generated light and guides it to a document, a carriage that is equipped with the optical system and is driven while keeping the length of the optical path constant, and a carriage that moves the carriage along a predetermined movement path. A moving mechanism for moving the carriage, an encoder for detecting a displacement amount of the carriage, and a pulse output from the encoder for multiplying one of an A-phase pulse and a B-phase pulse having a predetermined phase difference, And a correction circuit for generating a multiplied pulse for detecting the moving speed of the.

[0011]

Since the multiplying pulse for detecting the moving speed of the carriage with high accuracy is generated by multiplying one of the A phase pulse and the B phase pulse, the multiplying pulse is generated as the A phase pulse and the B phase pulse. Since both pulses are multiplied to generate the multiplied pulse, the period of the multiplied pulse is prevented from becoming unstable, and the moving speed of the carriage can be detected with high accuracy.

Further, even when the density of the image data read using the position information is corrected, accurate correction can be performed.

[0013]

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

First, with reference to FIGS. 3 and 4, a schematic structure of the document reading apparatus will be described. FIG. 3 shows a general document reading apparatus 1 having a reduction optical system. In the document reading apparatus 1, a document 3 on which characters, images, etc. are recorded is placed on a glass table 5 which is a document table.
The original information is scanned by the scanning optical system 7 disposed below the.

The scanning optical system 7 includes a first carriage 9 arranged below the glass table 5, a second carriage 11 arranged below the first carriage 9, and an optical path from the second carriage 11. And a one-dimensional CCD image sensor that converts the reflected light from the original 3 into density data line by line.

The first carriage 9 includes a fluorescent lamp 15 for irradiating the original 3 on the glass table 5 with the light transmitted through the glass table 5.
It is composed of a mirror 17 on which the reflected light of the fluorescent lamp 15 reflected downward by the original 3 is incident. Also,
The first carriage 9 can be reciprocated in the left-right direction of the paper surface of FIG.

The second carriage 11 has two mirrors 23, 2 whose reflecting surfaces are opposed to each other at an angle of 45 °.
It is composed of 5. The mirror 23 is the first carriage 9
The light reflected by the mirror 17 is incident, and is reflected downward toward the mirror 25 at a right angle. The mirror 25 reflects the reflected light from the mirror 23 in the horizontal direction.
Further, the second carriage 11 can be reciprocated in the left-right direction (the arrow a1 direction and a2 direction in the drawing) of the paper surface of FIG. 3 by the moving mechanism 33.

Therefore, although the first carriage 9 and the second carriage 11 move in the left-right direction on the paper surface,
The moving speed of the second carriage 11 is set to 1/2 of the moving speed of the first carriage because the optical path lengths to the mirrors 17, 23, 25 and the lens 13 need to be always constant.

Information on the original 3 which has passed through the lens 13 is incident on the image sensor 31. Next, the reading operation of the scanning optical system 7 will be described with reference to FIG. When reading the information of the document 3 placed on the glass table 5, the first carriage 9 is moved in the direction of the arrow a1 in the figure while irradiating the document 3 with light by the fluorescent lamp 15, and the second carriage 11 is also used. Is moved in the same direction at a speed half that of the first carriage 9 to read.
The reflected light from the original 3 is applied to the mirror 17, and the mirror 1
The light reflected from 7 is reflected by the mirror 2 of the second carriage 11.
The light radiated to the lenses 3 and 25 and transmitted through the lens 13 is imaged on the image sensor 31. This image sensor 31
Scans and reads a document for each line of a predetermined width sequentially at a certain reading cycle, and stores it in a storage unit (not shown).

Further, when reading a document by reducing or enlarging it, the lens 13 is read by moving it in the direction of arrow b1 or b2 in the figure according to each magnification.

As described above, in the scanning optical system 7, the first carriage 9 and the second carriage 11 are used during reading.
Only the lens 13 and the image sensor 31 do not move.

FIG. 4 shows a moving mechanism 70 for moving the first carriage 9 and the second carriage 11. 5
Reference numerals 0a, 50b, 50c and 50d are side plates and 50e is a bottom plate. A pair of rails (first and second rails) 51a, 5 arranged in parallel on the side plates 50a, 50b.
1b is fixed. Reference numeral 8 is a motor, and a helical gear 62 is attached to a motor shaft (not shown). A helical gear 63 having a large diameter is meshed with the helical gear 62, thereby forming a reduction mechanism.
A pulley 64 having a double thread is attached coaxially with the helical gear 63, and the four wires 52a, 52
b, 52c and 52d are wound around.

The wire 52a extends from the pulley 64 to the pulley 53.
And then fixed to the first carriage 9 by a wire retainer 69a provided on the first carriage 9, and then wound on a pulley 55a of the second carriage 11,
Further, it is wound around the pulley 54a, and the end portion is fixed to the tension spring 67a.

The wire 52b extends from the pulley 64 to the pulley 5
3 and then to the pulley 57a.
It is wound around the pulley 55a of the carriage 11 and then around the pulley 56a, and the end of the wire is fixed to the tension spring 67a.

The wire 52c and the wire 52d are symmetrical with respect to the wire 52a and the wire 52b, respectively.

That is, the wire 52c is the pulley 64 → the pulley 53b → the wire retainer 69b of the first carriage 9.
(Not shown) → Pulley 55b of second carriage 11 → Pulley 54b → Tension spring 67b. The wire 52d is connected to the pulley 64 → the pulley 53b → the pulley 57b → the pulley 55b of the second carriage 11 → the pulley 56b → the tension spring 67b.

The first carriage 9 is mounted with the fluorescent lamp 15 and the first mirror 17 being fixed by a mounting member (not shown). Four bearings (first bearing portions) are attached to the support portion 9a of the first carriage 9, respectively. That is, one end of the first carriage 9 is tilted by + 45 ° with respect to the horizontal plane and the two bearings 58 are provided.
a and 58b are attached, and in the lower part with respect to the horizontal plane-
Two bearings 58c, 58 (not shown) inclined at 45 °
b is attached. That is, the bearing 58a,
58b and bearings 58c and 58d are attached with an angle difference of 90 °. Then, at the other end of the first carriage 9, four bearings 59a, 59b,
59c and 59d are attached.

On the other hand, the second carriage 11 is formed on a frame having a hollow portion and has a second mirror 23 which is an optical system.
And a third mirror 25 is mounted. Second carriage 1
Similarly to the first carriage 9, four bearings (second bearing portions) 60a, 60 are provided on the first support portion 11a.
b, 60c, 60d and 61a, 61b, 61c, 6
1d is attached.

Further, the linear encoder 65 is attached to one of the first carriages, and the linear scale 66 is attached to the fixed portion to control the speed, so that the rotary encoder is mounted coaxially with the outside of the carriage, for example, the motor 8. This enables highly accurate speed control.

The document information of the document 3 can be read by the document reading device 1 configured as described above. Then, when the information of the original 3 is read by enlarging and reducing, the moving speeds of the first carriage 9 and the second carriage 11 are controlled so as to be changed according to the enlarging ratio and the reducing ratio. In order to widen the enlargement / reduction range, the moving speeds of the first carriage 9 and the second carriage 11 may be changed according to the enlargement ratio and the reduction ratio.

Next, the portion related to the correction circuit of this embodiment will be described with reference to FIG.

FIG. 1 is a schematic diagram of this embodiment including a correction circuit 75. In FIG. 1, reference numeral 1 is an image scanner main body, and the carriage 9 is moved by driving a DC motor 8 after being amplified by an amplifier 73 in response to a signal from a control circuit 71.

A linear encoder 65 and a linear scale 66 are attached to the carriage 9, and the output of position information of the linear encoder 65 is corrected by a correction circuit 75 and converted into speed information in a control circuit 71 for speed control. It is like this.

The light emitted from the fluorescent lamp 15 mounted on the carriage 9 is reflected by the original 3 and is incident on the lens 13 via the mirror 17, and the one-dimensional CCD image sensor 3
1 is imaged. Thereafter, the CCD image sensor 31 converts the information of the document into density data line by line, and the image processing circuit 72 performs image correction and the like and sends the density data to the printer 74. While moving the carriage 9, the CCD image sensor 31 is driven at a predetermined cycle and converted into density data line by line, and the carriage 9 is moved to an arbitrary size of the original to convert original information into digital data. It is supposed to do.

Next, a correction method performed by the correction circuit 75 will be described. FIG. 2 is an explanatory diagram showing an embodiment of a linear encoder output correction method according to the present invention.

As described with reference to FIG. 6, by using the rising and falling edges of both the A-phase and B-phase output pulses that are output when the linear encoder 65 crosses the bright and dark parts of the linear scale 66. When multiplied, the pulse intervals multiplied by 4 are not equal.

Therefore, the present invention proposes a method of multiplying by four by using only one of the output pulses of both the A phase and the B phase, for example, the rising timing of the A phase.

That is, the time between the rising timing of the pulse of the A phase output and the rising timing of the next output pulse is measured, and this is defined as the pitch time P1. The times taken are T1, T2, T3, and T4, respectively.

In this way, all the times multiplied by 4 are T1 = P1 / 4, T2 = P1 / 4, T3 = P1 / 4, T
4 = P1 / 4, and the correct encoder output can be corrected. Similarly, set the pitch time of the next output pulse to P
If it is set to 2, the time multiplied by 4 is T5.
= P2 / 4, T6 = P2 / 4, T7 = P2 / 4, T8 =
It becomes P2 / 4. After that, the same method is used.

This is because the data is taken in at the time of pre-scanning before reading the original, and the linear encoder output in the reading area in the correction circuit 75 shown in FIG.
The output is corrected to an accurate linear encoder and stored as data in a memory, and the speed is controlled by using the data in this memory at the time of reading.

As a result, accurate speed control can be performed without using encoder outputs that are not evenly spaced during one cycle as in the conventional case. Alternatively,
Correction circuit 7 for the pitch time data in advance before shipment from the factory
Alternatively, a method may be employed in which the speed is controlled without reading the pre-scan when reading the document by storing the data in the memory in the memory 5.

Even when the image information is read out and printed out at the same time (for example, PPC), the image is read out and stored in the memory and printed out later (for example, scanner). In that case, the correction can be performed by the same method.

Although the correction method of the quadruple multiplication has been described here, the same can be applied to the doubling multiplication.
In this case, for example, the time T1 obtained by dividing the pitch P1 into two equal parts,
T2 may be used as T1 = P1 / 2 and T2 = P1 / 2.

[0044]

As described above, according to the configuration of the present invention, one of the A-phase pulse and the B-phase pulse is multiplied as the multiplication pulse for detecting the moving speed of the carriage with high accuracy. Since the multiplied pulse is generated by multiplying both the A-phase pulse and the B-phase pulse to generate the multiplied pulse, it is possible to avoid instability in the cycle of the multiplied pulse, and the carriage moving speed can be accurately controlled. Can be detected. As a result, the resolution of the document reading device can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a document reading apparatus according to the present invention.

FIG. 2 is a diagram for explaining the operation of a correction circuit according to the present invention.

FIG. 3 is a diagram showing a general schematic configuration of a document reading device.

FIG. 4 is a perspective view showing a moving mechanism of the document reading apparatus shown in FIG.

FIG. 5 is a diagram showing a relationship between an ideal A-phase pulse, a B-phase pulse, and a multiplied pulse of an encoder.

FIG. 6 is a diagram showing a relationship among a conventional A-phase pulse, B-phase pulse, and multiplied pulse of the encoder.

[Explanation of symbols]

1 Document Reading Device 3 Document 8 Motor 9 First Carriage 11 Second Carriage 13 Lens 15 Fluorescent Lamp 17, 23, 25 Mirror 51a, 51b Rail 52a, 52b, 52c, 52d Wire 69a, 69b Rail Support Member 58a, 58b, 58c, 58d, 59a, 59b, 5
9c, 59d Bearings 60a, 60b, 60c, 60d, 61a, 61b, 6
1c, 61d Bearing 65 Linear encoder 66 Linear scale 71 Control circuit 72 Image processing circuit 75 Correction circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/04 105

Claims (1)

[Claims] 1. An optical system for forming an optical path for reflecting light emitted from a light source and guiding it to an original in an original reading device which irradiates the original with light and receives the reflected light to read original information. A carriage that is driven while keeping the length of the optical path constant, a moving mechanism that moves the carriage along a predetermined movement path, an encoder that detects the amount of displacement of the carriage, and The output pulse is multiplied by one of the A-phase pulse and the B-phase pulse having a predetermined phase difference,
An original reading apparatus, comprising: a correction circuit that generates a multiplied pulse for detecting the moving speed of the carriage.