JPS614363A - image input device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to image input systems used in information processing equipment such as computer input terminals, ultra-high-speed facsimiles, electronic filing systems, and intelligent copy machines. Regarding input devices.

Conventional Structure and Problems Image input devices that mechanically scan an original can be divided into cylindrical scanning, 27-plane scanning, and 7-plane scanning. In the cylindrical scanning method, documents are wound one by one into a cylinder, and main scanning is performed by rotating the cylinder, and sub-scanning is performed by relative movement of the scanning head and the cylinder in the axial direction of the cylinder. However, this method is limited to sheet-like originals, and problems such as separation of the original due to centrifugal force occur. Planar scanning devices use a method that moves the original in a flat state for sub-scanning, and there are methods that perform main scanning by sweeping the light spot and methods that use optical fibers arranged in a straight line, but none of these methods can be used. , which has the drawbacks of being mechanically complex and occupying a large space.

A solid-state scanning method is similar to the plane scanning method. This system inputs images using solid-state image sensors arranged on the object.Main scanning is performed by electronic switching of the image sensors, and sub-scanning is performed relative to the document on the image sensor including the array of image sensors. It is mechanically simple, takes up little space, and can be used not only for sheet-like documents but also for bound documents such as books.

However, conventional solid-state scanning type image input devices use a rotary type step motor or rotary type servo motor to move the imaging unit linearly through transmission members such as gears, rollers, pulleys, and wires. The most common method was to use a drive mechanism.

However, when using such a drive mechanism, there is a certain limit to the performance that can be obtained, as described below, and if you try to exceed it, it will be difficult both technically and cost-wise. However, I was unable to force myself to face a suddenly difficult situation.

The first problem is physical accuracy related to position accuracy, linearity, and reproducibility. For example, there is always a certain amount of backlash and dead zone in the gears, and there is slippage in the gears. Also, if the wire is long, its expansion and contraction will have a negative effect on accuracy. Since the Rokuri-type step motor does not have closed-loop control (so-called oven-loop control), the eccentricity of the gear has a subtle effect on linearity, and if you aim for high speed, it is easy to cause adjustment in transient conditions. There is also a fatal problem.

On the other hand, when using a rotary type servo motor, a linear potentiometer is often used at the point of action (control target) to achieve closed-loop control, which alleviates the accuracy deterioration factors caused by the transmission system. Accuracy degradation occurs due to linear potentiometer. Linear potentiometers that are currently widely used use a sliding brush on a wound wire or conductive plastic type resistor, and the nonlinearity of the resistor, hysteresis of the brush, backlash, and wear of the resistor are difficult to achieve. is greatly controlled.

The second problem is reliability, such as durability and lifespan.

The above-mentioned transmission system includes members that transmit force through frictional resistance, and uses a lot of rotating members such as rollers to bend the wire, so it is inevitable that wear and tear will occur in each part. It is inevitable that deterioration will occur. In addition, the N rate of wire deterioration and disconnection accidents is particularly high.

On the other hand, since most rotary type servo motors are made of brushed DC motors, there is a certain limit to their service life that must be taken into consideration. Furthermore, wear of the resistor of the potentiometer as described above is one of the factors that reduces reliability.

The third problem is noise. As mentioned above, in the conventional system, the rotational force of a rotary motor is transmitted to the controlled object via a number of transmission members and driven in a straight line, so there are many movable members, and each part generates a considerable amount of noise.

In particular, the resonance noise of the wire and the rotation noise of the rollers are relatively loud.

As a result, the quality of the equipment is often significantly impaired.

Due to the limited accuracy and reliability of the drive mechanism as described above, conventional performance such as resolution during image reading has a certain limit.

Purpose of the Invention In order to eliminate the above-mentioned conventional problems, the present invention employs a brushless linear servo motor as a drive mechanism, which has a simpler mechanism, has high precision and reliability, and occupies a small volume. The purpose is to provide a faster and more efficient image input device.

Structure of the Invention The image input device of the present invention includes a brushless linear servo motor and a solid-state image sensor for reading image information, and the solid-state image sensor is mounted on a movable element of the brushless linear servo motor to perform direct scanning. It is based on that.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a specific example of the configuration of an image input device according to the present invention. In the figure, a brushless linear servo motor 1 has a square rod-shaped stator 2. The movable member 39 includes a position detection sensor block 4, and the stator 2 is fixed to the housing 5 so as to be parallel to the document surface and the document sub-scanning direction. The imaging unit 6 includes a light source 7. Light guiding system 8. It is a side view of a bracket 6 parallel to the document surface, which is composed of a charging conversion unit 9 including a solid-state image sensor and a signal processing circuit. The movable element 3 is attached to a movable element frame 10, and the movable element frame 10 includes rollers that maintain a constant slight gap between the stator 2 and the movable element 3 and guide the movable element 3 smoothly. A guiding means 11 such as the one shown in FIG.

Next, the basic functions of the imaging unit 6 will be explained with reference to FIG. 2. The light r emitted from the light source 7 passes through the transparent glass plate 12 for placing the original and is reflected on the original surface 13.
The light enters the solid-state image sensor 9a through the light guiding system 8, is converted into an electrical signal, and is further outputted through the signal processing circuit 9b.

FIG. 3 is a perspective view for explaining in detail the main parts of a configuration example of a brushless linear servo motor that can be used in the present invention.

In the same figure, the longitudinal direction of the stator 2 (mover moving direction)
It has a large number of tooth-shaped irregularities (hereinafter referred to as magnetic pole teeth) 14 made of a magnetic material at a constant pitch. Mover 3
, a permanent magnet 15 magnetized in a plane perpendicular to the moving direction of the mover, two yokes 16A and 16B stacked so as to sandwich this from both sides, and a magnet wound around these yokes 16A and 16B. 3 phase 3 coils 17a, l 7b, 1
7c, three groups of magnetic pole teeth 18a, 18b, 18c cut out on the stator facing surface of the yoke 16A, and similarly the yoke 16B.
Three groups of magnetic pole teeth 19a, 19b,
19c (however, 19b and 19c are hidden from view in FIG. 3) and a non-contact position detection sensor block 4.

In this embodiment, a large number of knurled magnetic pole teeth are provided on the stator 2 at a constant pitch in the longitudinal direction, whereas the knurled magnetic pole teeth on the yokes 16A and 1.6B on the movable side are There are 6 groups in total, 3 groups in each group, and the pitch of the magnetic pole teeth within the same group is either equal to the stator pitch, or so that the phases are different between different groups.

That is, the magnetic pole tooth groups 18a, 18b are notched on the yoke 16A.
, 18c have a phase difference of 120° from each other. Similarly, magnetic pole tooth groups 19a and 19b are notched on the yoke 16B.
, 19c are also 120 degrees out of phase with each other. Furthermore, between the yokes 16A and 16B, each is 180 mm from each other.
°The phases are different. That is, 18a and 19a, 18b and 19b, and 18c and 19c are magnetic pole teeth each having a phase difference of 180°. Coils 17a, 17b.

17c are both wound around the yokes 16A and 16B. By sequentially applying current to the three three-phase coils, the movable element can be moved in the longitudinal direction on the stator.

In particular, if the coils are sequentially energized electronically according to the position information from the non-contact position detection sensor block 4, smooth and continuous movement can be achieved.

Now, since the linear servo motor shown in Fig. 3 has three phases and three coils, three pairs of sensor elements are required to be included in the non-contact position detection sensor block 4, and each pair corresponds to the unevenness of the stator magnetic pole teeth. For direct detection, they are positioned so that they are 120° out of phase with respect to their pitch L.

FIG. 4 shows an example of a sensor output waveform of the non-contact position sensor block 4. The outputs of the three three-phase sensors (light receiving elements) have waveforms that are shifted by 120 degrees.

Note that for reasons described later, each waveform must be as close to a stop string wave as possible.

Next, the electric circuit section in the image input device of the present invention will be explained.

FIG. 5 is a block diagram of the electric circuit section in the image input device of the embodiment, and the configuration is such that the position of a three-phase motor is controlled for motor control. In the figure, 50 is the mechanical part of the brushless linear servo motor mentioned above, and 51
53 is a stator, 53 is a movable element, and 57 is a non-contact position detection sensor block. 58 is a roller bearing, 60a,
60b and 60c indicate three phase three coils. 61a,
6 lb and 61c are position signal amplifiers that amplify the three-phase position signals of the non-contact position detection sensor block 57, respectively. The output of this position signal amplifier is a sine wave output shifted by 120 degrees (shifted by L/3) with a period equal to the magnetic pole tooth pitch L of the stator, and serves as a position signal of the electronic commutator. 62 is a three-phase motor drive circuit;
The three-phase motor coils are sequentially energized in accordance with the position signals output from the position signal amplifiers 61a, 6lb, and 61c. The magnitude of that current is proportional to motor command voltage input 63. The non-contact electronic commutator is composed of the sensor and electronic circuit described above.

Now, the position signal output of the position signal amplifier serves as a potentiometer in addition to the role of the electronic commutator. The remaining portions of the block diagram shown in FIG. 5 mainly relate to this potentiometer. This potentiometer is electronic rather than mechanical. This will be explained below. 6
4a, 64b, and 64c are all modulation circuits, and three sine wave outputs of position signal amplifiers 61a, 61b, and 61C provide a high frequency carrier signal 65a.

! This is a type of multiplier that modulates 65b and 65c, respectively. However, the phases of these three carrier signals are shifted by 120 degrees. Reference numeral 66 denotes an adder circuit for the three modulation circuits 64a.

The modulated outputs of 64b and 64c are added together. Reference numeral 67 denotes a low-pass filter, which has the role of removing harmonic components of the modulated outputs added by the adder circuit 66 and taking only the fundamental wave component. A waveform shaping circuit 68 converts the fundamental wave into a rectangular wave.

3 current position signal amplifiers 61a, 6lb, 61c
Kl(X), r<2(x), K3
(X)7 and it can be expressed as follows.

K, (x)-ksin [2xx/'L]K2(X)
=ksin [2rtx/ L −2π/ 3 ]K
3(x)-ksin [2zrx/L-4π/'3]
However, X is the displacement amount of the mover, L is the magnetic pole tooth pitch of the stator, and K is the half-width value of the amplitude.

On the other hand, the carrier signals 65a, 65b, 65c are connected to C1(
t), C2(t).

Suppose that C3(t) is expressed as follows.

C+(t)-sin(2xfct) C2(t)=sin< 2 xfct-2yt/ 3
)C3(t)-sin(2πfct-4yt/″3)
(However, fc is the carrier frequency) After modulation by the modulation circuits 64a, 64b, and 64c, the addition circuit 6
If the result of addition in step 6 is S(t, x), then S(t,
x)=to+(X)'C+(t)+to2(X)'C2(
t) + 3(X)・C3(t) −k(sin (2
zx/L>・5in(2πfct)+sin (2π
x/L-2π/3)・5in(2+rfct-2π
/3)+sin (2ix/L-4+r/3)・5in
(2πfct−4π/3)l −3/2 ・kcos
(2πfct−2πX/L). This is 2πx/L,! for a carrier with a frequency of Pc. : This means that the phase term is included. In other words, S(t,
In x), the position information X is converted into the form shown above in terms of phase information. Therefore, by demodulating the phase information of S(t, x), the position of the movable element 53 of the motor can be recognized. .

From the above 12s(t,'x), the conditions for accurately recognizing the position of the mover are (X), K2(X) for the position signal.
), the waveform of K3(X) is like a sine wave with little distortion with respect to position X. If the distortion is large, a potentiometer with many undulations and poor linearity will be created.

Now, since the modulated and added signal S(t, x) cannot be used as is, it is necessary to demodulate it and separate and extract only the position information. In the embodiment of the present invention, a PLL (Phase Locked Loop) including a frequency divider is used.
A demodulation method is used in which position information with high resolution is extracted by multiplying S(t, x) using a circuit and comparing it with a reference frequency. The PLL circuit has a phase comparator 69
, a low-pass filter 70 that filters the low frequency range of this output, and a VCO (Voltage Controlled Oscillator) controlled by this output.
ator) 71 (!l:, is composed of a frequency divider 72 that divides this frequency (denoted as fv) by 1/M (M is an integer).The input of the phase comparator 69 is the ,
x) into a rectangular wave by the waveform shaping circuit 68, and the frequency-divided VCO 71 output (output of the frequency divider 72)
It is. The output of the 7vC○71 configured in this way is the above-mentioned S(t,
L)-2π・Mfct-27[MX/L.

Here, a reference frequency generation circuit 73 that generates a reference frequency such as fo-M-fc is provided, and this reference frequency f
o7 By comparing the multiplied output of the VCO 71 above, only the phase information (2πMx/L>) can be separated. For this comparison and separation, a phase comparator 74, a low-pass filter 75, and a waveform shaping circuit 76 are used. The separated phase information (2πMx/L) is periodic with respect to X and 2πMx
/L-2nπ (n is an integer). The phase information converted into a rectangular wave pulse by the low-pass filter 75 and the waveform shaping circuit 76 is X=n・(L/M), and
The amount of displacement of the movable element 53 per pulse is L/M.

As is clear from the above, the displacement of the movable element 53 is recognized in steps, and the minimum step L/M is the resolution. This means that the pitch L of the magnetic pole teeth of the stator is divided by M at equal intervals.
This means interpolation.

Therefore, in order to increase the resolution and obtain smooth position information, L
It is sufficient to make M small and M large. 77 is a pulse separation circuit. Since the pulses output from the waveform shaping circuit 76 have no polarity, the direction cannot be determined even if the pulses are directly counted by a position counter. Therefore, the up count pulse is based on the moving direction of the movable element 53.

Separate down count pulse. 78 is this up count pulse.

This is a position counter that increments the down count pulse and displays the current position of the movable element 53 in real time. Reference numeral 79 is an origin/initial reset input for the position counter 78. Note that 80 is a three-phase frequency divider, which divides the reference frequency f of the reference frequency generation plane 73 by 1/M and generates three-phase carrier signals 65a, 65b, and 65c that are shifted by 120 degrees from each other. (Frequency f&c
).

With the above configuration, the position of the mover 53 is determined by the position counter 7.
8. Therefore, the output of the position counter 78 becomes the output of the potentiometer. The position control of the movable element 53 uses an error amplification circuit 82 that amplifies the difference between the position command input 81 and the output of the position counter 78, and provides the output to the three-phase motor drive circuit 62 as the motor command input 63. It is realized by doing.

In this embodiment, a case where position control is adopted as the control method is shown, but the present invention is not limited to this, for example, speed control may be used.

Effects of the Invention As is clear from the above description, the image input device of the present invention employs a brushless linear servo motor for driving, thereby achieving a number of excellent effects as described below.

(1) Since the imaging unit including the imaging element is directly linearly driven, it is possible to ensure positional accuracy and reproducibility that could not be obtained in the conventional example using a rotary type motor and transmission member. In addition, noise can also be added.

(2) The brushless linear servo motor has a built-in non-contact position sensor, which is used to configure an electronic commutator and an electronic potentiometer, eliminating any contact, so it has excellent durability. It is highly reliable and eliminates the brush hysteresis and backlash that occur with conventional potentiometers.

(3) The sensor of the built-in potentiometer is shared with the sensor of the electronic commutator, and the scale of the encoder is a stator with tooth-like unevenness (magnetic pole teeth) in the longitudinal direction. Since it is integrated, an independent linear potentiometer is no longer required, and it is possible to reduce the size and weight, which is advantageous in terms of cost.

(4) The stator has a simple structure with a large number of magnetic pole teeth made of magnetic material at a constant pitch in the longitudinal direction, and it can be lightweight because it does not include other magnetic circuit members such as permanent magnets.

(5) Compared to the conventional example, the number of parts of the transmission member and movable member is significantly reduced, and the number of assembly steps can be greatly reduced.

(6) Since it is a servo motor capable of closed loop control,
It is possible to increase speeds because open-loop control using conventional rotary type step motors does not easily cause tax adjustment when driving at high speeds.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the image input device of this invention, FIG. 2 is a side sectional view of the main part of FIG. 1, and FIG. FIG. 4 is a perspective view of the main parts of an example of a linear servo motor, FIG. 4 is an output waveform diagram of a non-contact position sensor block, and FIG. 5 is a block diagram of the electric circuit section of this embodiment. 1...Brushless linear servo motor, 2,5
1...Stator, 3.53...Movable element,
4,57... Non-contact position sensor block, 6.
...Imaging unit, 7...Light source, Death...
... Light guide system, 9 ... Photoelectric conversion unit, 9a
, 84... Solid-state image sensor, 9b... Signal processing circuit, 14... Stator magnetic pole tooth, 18a,
! 8b, 18c, l 9a, <19b, 19c)
......Mover magnetic pole tooth, 77...Pulse separation circuit, 78...Position counter.

Claims (3)

[Claims] (1) An image sensor array arranged parallel to the document surface and along the document main scanning direction, a light source, and an optical system that focuses reflected light from the document by the light source onto the image sensor array. a stator fixed to a housing parallel to the document surface and along the document sub-scanning direction perpendicular to the document main-scanning direction; and a stator mounted with the imaging unit and fixed directly in a straight line. A movable element that can move along the movable element while controlling its position or speed in a closed loop and has no electrical contacts, and a position signal generator that generates a position signal without contact as the movable element moves. An image input device comprising: a brushless linear servo motor including means. (2) A brushless linear servo motor includes a stator made of a magnetic material and having magnetic pole teeth on its surface consisting of a large number of tooth-like unevenness arranged at a constant pitch in the longitudinal direction, and a stator that faces the stator and runs along the A yoke that is movable in the longitudinal direction and that includes a permanent magnet, a yoke that stacks the permanent magnets from both sides, a group of magnetic pole teeth that are notched on a surface of the yoke facing the stator, and a yoke that is wound around the yoke. a movable element consisting of a multi-valent coil, a guide means that maintains a constant air gap with the stator and allows smooth movement along the stator; and a magnetic pole of the stator attached to the movable element. A plurality of non-contact sensors that detect irregularities on teeth, convert them into electrical signals, and output substantially sinusoidal position signals having mutually different phases, and sequentially energize the plurality of coils according to the position signals. electronic commutator means, electronic potentiometer means for electronically recognizing the position of said mover by demodulating phase information of a carrier signal modulated by said position signal, and an output and position command of said electronic potentiometer means. Claim (1) characterized by comprising: a motor drive circuit that extracts a difference from an input and applies a current proportional to the magnitude of the output to the plurality of coils to drive the movable element. Image input device described in Section 2. (3) The electronic potentiometer means includes a reference frequency generating circuit, a frequency dividing circuit that divides the output into 1/M (M is an integer) and generates a plurality of carrier signals having mutually different phases, and a frequency dividing circuit that divides the output into a plurality of carrier signals having mutually different phases. A plurality of modulation circuits modulated by the position signal, an addition circuit that adds the outputs of the modulation circuits, and a PLL circuit (Phase Locked Loop circuit) that multiplies the fundamental frequency component of the addition output of the addition circuit by M times.
a phase comparator that compares the phase of the multiplied output of the voltage controlled oscillation circuit in the PLL circuit and the reference frequency output of the reference frequency generation circuit; a low-pass filter that filters low-frequency components of this output; A patent characterized in that it includes a waveform shaping circuit that shapes the output of a filter to create a rectangular wave pulse, and a position counter that counts the rectangular wave pulse and digitally detects the position of the first movable element. An image input device according to claim (2).