JPH07199111A - Actuator for scanning - Google Patents

Abstract

PURPOSE:To provide a small-sized actuator having a high driving efficiency and a high durability. CONSTITUTION:The scanning actuator Which displaces a light beam to scan an optical signal is provided with a torsion bar 37 which holds a mirror 40 and a magnet 39 so that the magnet 39 is arranged on the rear face of the mirror 40, a flat spring 35 which gives an approximately certain tensile force to the torsion bar 37, and a shake means which shakes the mirror 40 held on the torsion bar 37 by the magnetic force and its moment of inertia. Thus, the small-sized actuator having a high driving efficiency is realized. Since a motor is not used, the structure is simplified, and the high durability is realized with a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning actuator, and more particularly to a scanner actuator suitable for reading optical symbols such as bar codes.

[0002]

A bar code is a coded pattern of adjacent bars and spaces of varying widths and columns. Various scanners for identifying this barcode have been developed and are now widely used. The scanner illuminates the bar code displayed on the surface of the label or article, and reads the bar code pattern by using the light reflection property caused by the difference in the width between the bar and the space to read the label or article. Have identified.

There are various types of reading methods, which can be roughly classified into two types, a CCD type and a laser type. Among them, the laser type scanner supplies a scanning light having a straight-line property such as a laser light, scans a bar code, and changes the intensity of scattered reflected light due to a difference in reflectance between a bar and a space at that time to a photodiode. Information is read by detecting using a light receiving element such as.

The configuration will be described in detail below with reference to FIG. Laser light emitted from the laser device 1, in this case a gas laser, is converted into a predetermined shape through an optical system 2 and then reaches a scanning mirror (hereinafter referred to as a mirror) 3. The mirror 3 swings or rotates at a constant cycle, and the laser light reflected by the mirror 3 linearly scans the barcode 4. When the bar code 4 is irradiated with this laser light, the intensity of scattered reflected light changes due to the difference in reflectance between the bar 4a and the space 4b.
When this scattered reflected light is received by the light receiving element 5 such as a photodiode, the intensity of the scattered reflected light is obtained by the analog signal 6 due to the difference in reflectance. This analog signal 6 is A / D
A / D conversion is performed by the converter 7 into a digital signal 8, and the binarized pattern of this digital signal 8 is decoded by the decoder as the information of the barcode 4, and the information of the barcode 4 is read.

Since the laser type configuration is as described above, it has the advantage of being able to read a barcode that is far from the scanner or a barcode that is wide, and has recently been remarkably popular. However, there are some parts that use mechanical structures such as swinging and rotating the mirror, and the bar code reading performance is affected by the performance such as durability, scanning angle amount, and scanning speed. Various proposals have been made for.

As one of the laser scanner actuators, a polygon mirror 9 having a large number of reflecting surfaces as shown in FIG. 14 may be used. In this method, a motor 10 is used to rotate the polygon mirror 9 at a constant cycle so that the laser light is constantly reflected by each reflection surface and is scanned. Further, there is an actuator that does not use a polygon mirror such as the polygon mirror 9 but uses a simple one-sided mirror as shown in FIG. This is different from the motor 10 that rotates in one direction described above, and by using the vibration motor 11 that alternately performs forward rotation and reverse rotation, the one-way mirror is swung and the laser is swung to scan. And is disclosed in Japanese Patent Application Laid-Open No. 2-288987. A single-sided mirror of this type is generally called a galvanometer mirror 12.

The structure of the actuator using the galvano mirror 12 will be described below. The vibration motor 11 that swings the galvanometer mirror 12 is generally a stepping motor in which two coils are arranged along the rotation axis direction. The vibration motor 11 includes a first housing 13 and a second housing 14. A rotor 15 made of a permanent magnet is arranged in the central portion of the first and second housings 13 and 14. This rotor 15
Is rotatable about the stub shaft 16,
The output shaft 17 is mounted on the rotor 15 coaxially with the stub shaft 16. A galvanometer mirror 12 for reflection is fixed to the tip of the output shaft 17, which is a swinging portion exposed to the outside of the motor.

A first stator coil (hereinafter referred to as a first coil) 18 is provided in the first housing 13 so as to surround the rotor 15 and a second housing 1 is provided.
Second stator coils (hereinafter, referred to as second coils) 19 are arranged in the respective units 4. A direct current is supplied to the first coil 18 by the first drive circuit 20, and a pair of magnetic poles (not shown) whose polarity does not change is generated in the first coil 18 by the direct current. This pair of magnetic poles
The galvano mirror 12 is held at a predetermined reference position in cooperation with the rotor 15.

An alternating current is supplied to the second coil 19 by a second drive circuit 21. Due to this alternating current, another pair of magnetic poles (not shown) displaced by 90 ° with respect to the pair of magnetic poles formed by the first coil 18 is generated in the second coil 19. The polarities of the pair of magnetic poles formed by the second coil 19 change depending on the cycle of the alternating current passed through the second coil 19. By this change in polarity,
The rotor 15 is rotated against the holding force of the magnetic poles of the first coil 18, and as a result, the galvanometer mirror 12 held at the reference position by the magnetic poles of the first coil 18 rotates clockwise and counterclockwise from the reference position. It is rocked.

[0010]

However, the scanning actuator using the motor as described above has a rattling state depending on the rattling in the axial direction of the rotating shaft of the motor, the fitting rattling of the bearing, and the posture of use of the scanner. Changes, this change in backlash affects the scanning angle and scanning speed,
Further, it has a drawback that even affects the reading performance.

Further, in order to drive the stepping motor, it is necessary to sequentially switch the currents flowing through the plurality of coils to create a rotating magnetic field, and it is impossible to excite with a single-phase driving current. In other words, a switching circuit including a dedicated control IC and a transistor for obtaining a multi-phase driving current, and a pulse generating circuit including a pulse generator exclusively used for supplying a switching current to this circuit are required. . For this reason, there is a drawback that the driving circuit becomes complicated and the cost becomes high.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a small-sized actuator having high driving efficiency. Another object of the present invention is to provide a low cost actuator having a simple structure and good durability.

[0013]

In order to achieve the above object, the scanning actuator of the present invention is a scanning actuator for displacing a light beam to scan an optical symbol, wherein a magnetic material is provided on the back surface of the reflecting member. An elastic member that holds the reflecting member and the magnetic body so as to be arranged, a means that applies a substantially constant tension to the elastic member, and a swing that swings the reflecting member held by the elastic member by the magnetic force and its moment of inertia. And means are provided.

Further, the scanning actuator is provided with adjusting means for adjusting the tension of the elastic member.

[0015]

According to the present invention, a member for arranging a magnetic material on the back surface of a reflecting member is held by an elastic member, and the elastic member is swung by a magnetic force and a moment of inertia to displace the light beam, and an optical symbol is displayed. To scan. Further, the tension of the elastic member can be adjusted to be constant by the adjusting means.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. (First Embodiment) FIG. 1 is a constitutional view of a scanning actuator according to a first embodiment of the present invention. FIG. 1 (a) is a right side sectional view of the actuator, and FIG. 1 (b) is a front view thereof. It is a thing.

The outer frame of the actuator 30 is composed of a yoke 34 made of a magnetic material having an electromagnet 33 having a drive coil 32 wound around an iron core 31 and fixed inside. As the shape of the yoke 34, for example, a cylindrical shape having an opening at one end is used. One end of the yoke 34 has an opening, and the electromagnet 33 fixed inside is fixed to the closed end inside the yoke 34 so that the iron core 31 on the opening end side slightly protrudes from the drive coil 32 and fits inside the opening end. To do.

Further, a member having a "U-shape" is installed on the yoke 34. For the "U-shaped" member, an elastic member is used as an example. In this embodiment, a leaf spring 35 is used as an elastic member that can move up and down. The leaf spring 35 has one end slightly protruding toward the open end (the portion 35a), the abdomen of the leaf spring 35 passes over the upper surface of the yoke 34, and the other end is screwed to the closed end of the yoke 34. Use and fix. Then, a projecting member 36 forming a similar projecting portion is provided at a position facing the projecting portion 35a of the projecting leaf spring at the opening end of the yoke 34.

A torsion bar (thickness: 0.05 mm, width: 0.8 mm, effective length: 10.0 mm, for example) 37 used as an elastic member has one end on the protrusion 35a side of the leaf spring 35 and the other end on the protrusion. The projecting member 36 forming the above is mounted by using a screw or the like for the mounting member. Also, the torsion bar 37
Since it also serves as a connecting member for attaching the reflecting member, the mirror holding member 38 is fixed to the central portion thereof. The iron core 31 in the yoke 34 of the mirror holding member 38
On the side, a plate-shaped magnetic body having NS or SN arranged on the left and right around the torsion bar 37, for example, a magnet 39 is fixed by an adhesive or the like so as to be substantially parallel to the opening of the yoke 34. Then, on the opposite side to the fixed side of the magnet 39, a mirror 40 as a reflection surface for scanning is fixed to the opening of the yoke 34 with an adhesive or the like so as to be substantially parallel to the magnet 39. At this time, the magnet 37
A scanning space is always provided between the iron core 31 inside the yoke 34 and the yoke 34.

FIG. 2 shows an example of the drive pulse generation circuit 41 connected to the drive coil 32. The reason why the torsion bar 37 is used in this embodiment is that the swinging mechanism of the mirror 40 is made to utilize the moment of inertia of the torsion bar 37. The operation of the actuator 30 using the torsion bar 37 will be described below.

In a scanning unit (not shown) provided with the actuator 30, simultaneously with the emission of the visible semiconductor laser for scanning, the drive pulse generating circuits 41 to 3 shown in FIG. Drive pulses of positive and negative rectangular waves as shown in FIG. The polarity of the electromagnet 33 in the yoke 34 is sequentially switched to N and S by the drive pulse of the positive (+ V) and negative (-V) rectangular waves as shown in FIG.
Magnet 3 fixed to the polarity and torsion bar 37
The polarity of 9 is used to swing the mirror 40.

FIG. 4 shows the manner of swinging. FIG. 4A shows a state where the actuator 30 is stopped, and FIG. 4B shows that a positive (+ V) or negative (-V) drive pulse is applied to the drive coil 32 to change the polarity of the electromagnet 33 to S. Alternatively, when set to N, the plate-shaped magnet 39 fixed to the torsion bar 37 is repelled between the same poles around the torsion bar 37, and is attracted between the different poles, and the magnet 39 and the mirror holding member 38 are interposed. It shows a state in which the fixed and fixed mirror 40 is turned to the left. Figure 4
In (c), since the drive pulse is cut, the polarity of the electromagnet 33 is lost, and the torsion bar 37 is moved by the moment of inertia as shown in FIG.
The state where the mirror 40 passes the same position as (a) is shown. FIG. 4D shows the mirror 4 according to the principle opposite to that of FIG.
The state where 0 is directed to the right side is shown. Also, FIG.
FIG. 4E also shows a state in which the mirror 40 has passed the stop position by the principle opposite to that in FIG. 4C.

Based on the above principle, the torsion bar 37 of the actuator 30 is swung. By swinging using the magnetic force between the magnetic bodies and the moment of inertia of the elastic member,
The swinging force of the magnet 39 is transmitted to the mirror 40 via the mirror holding member 38. The scanning speed due to the swing of the mirror 40 can be controlled by the rectangular wave of the drive pulse to the drive coil 32.

At that time, generally, the number of times f of oscillation of the torsion bar 37 (one reciprocation) is f = 1 / 2π (k / J) ^1/2 k: a constant J depending on the shape of the torsion bar and others. It is expressed by the formula of the moment of inertia of the object to be moved.
It also changes depending on the tension of 7. Therefore, in order to keep the number of swings f of each actuator 30 constant, it is desirable that the plate spring 35 apply a substantially constant tension to the torsion bar 37.

By using this embodiment, the power consumption required to control the mirror of the actuator can be minimized. Further, unlike the case where the motor is used, the structure of the actuator is simplified, which makes it possible to manufacture an extremely small-sized actuator, and further, it is possible to manufacture an actuator which is free from rattling that occurs when the motor is used.

Further, the driving efficiency can be improved, the number of parts required for the actuator can be reduced, and a durable actuator which does not use complicated and expensive parts can be provided at low cost. (Second Embodiment) FIG. 5 is a right side sectional view of a scanning actuator according to the second embodiment. The same parts as in FIG. 1 will be described using the same reference numerals.

The actuator 50 described in this embodiment
Is substantially the same as the configuration of the first embodiment, but is different from the first embodiment in that an adjusting member that can finely adjust the substantially constant tension applied to the torsion bar 37 from the state of zero tension is provided. In the second embodiment, a screw 51 is provided as an adjusting member between the U-shaped leaf spring 35 and the yoke 34 described in the first embodiment. The screw 51 is attached to the screw hole provided in the yoke 34.

By using the above construction, the natural frequency of the torsion bar 37 in each actuator 50 is shown in FIG. 6 simply by adjusting the screw 51 even when the tension of the torsion bar 37 is zero. Can be adjusted to minimize the power consumption required for controlling the mirror 40. As a result, it is possible to obtain a desired product with accurate specifications.

Further, without using the "U-shaped" leaf spring 35, other members can be used as long as they have elasticity to some extent. (Third Embodiment) FIG. 7 is a right side sectional view of a scanning actuator according to the third embodiment. The same parts as in FIG. 1 will be described using the same reference numerals.

In the actuator 60 of this embodiment, two kinds of coils are wound around the electromagnet 33 provided inside the yoke 34 in this order from the opening end side to the drive coil 32 and the sensor coil 61. The drive coil 32 in the yoke 32 is connected to a drive circuit formed on the substrate of a scanning unit (not shown), and the sensor coil 61 is connected to a pulse generation circuit (not shown).
The pulse generating circuit is, for example, as shown in FIG.
When c is set, the drive current Ia is turned on or off when the current Ib reaches the reference value Ic.
An example is a Schmitt trigger circuit. Also,
In the third embodiment, the drive current is Ia. Since the other configurations are similar to those of the first embodiment, detailed description will be omitted.

The operating principle of the actuator 60 of the third embodiment will be described below with reference to FIG. Here, as in the first embodiment, the iron core 31 is excited to become the electromagnet 33, and the N or S of the magnet 39 fixed to the torsion bar 37.
One of the poles is attracted by the magnetic force of the electromagnet 33 and the torsion bar 37 is twisted (FIG. 8a). At that time, a rise of the current Ib due to electromagnetic induction occurs in the sensor coil 61 connected to the Schmitt trigger circuit, the Schmitt trigger circuit detects the current Ib, and the current Ib is detected.
Before reaching the maximum value, the drive current Ia is cut off from the drive coil 32 at the reference value Ic (FIG. 8b). Therefore, the polarity of the electromagnet 33 is lost, and the free torsion bar 37 tries to restore the twist by the moment of inertia. Further, the force of the torsion of the torsion bar 37 causes the mirror 40 to pass in front of the actuator 60,
The mirror 40 twists the torsion bar 37 to the opposite position. Next, the torsion bar 37 is folded back in the direction opposite to the moving direction due to the inertia moment as before, and the mirror 40 passes the front of the actuator 60 again. At that time, a current Ib rises in the sensor coil 61 due to electromagnetic induction, the Schmitt trigger circuit detects the current Ib (FIG. 8b), and the drive current Ia is supplied to the drive coil 32 (FIG. 8a). Thereafter, the same operation is repeated by returning to the initial state.

As described above, in the actuator 60 described in the third embodiment, the drive coil 32 has a constant drive current Ia.
The sensor coil 61 and the Schmitt trigger circuit automatically control the natural frequency of the torsion bar 37 to perform the optimum scanning to minimize the power consumption, and the temporary drive current Ia Since energization leads to further minimization of power consumption, FIG. 2 that generates positive (+ V) and negative (−V) rectangular wave drive pulses as in FIG. 3 described in the first embodiment. The drive pulse generating circuit 41 shown is not necessary, and it is possible to excite with the single-phase drive current Ia.

Further, the number of parts used in the actuator can be reduced, and an actuator with good durability can be realized at low cost. In addition, since the actuator can be made smaller, the scanner can be made compact. An example of a scanner using the actuator 30 of the first embodiment among these embodiments will be described below with reference to FIGS. 9 to 10.

The scanner 70 shown in FIG. 9 is a handheld type, and is called a pistol type in which it is easy to aim at the bar code 71 as an optical symbol. This scanner includes a barrel portion 72, and a scanning unit 73, which will be described later, is housed inside the barrel portion 72. Figure 10
10A is a top view of the scanning unit 73 housed inside the barrel 72, and FIG. 10B is a right side view of the scanning unit 73. The scanning unit 73 includes a board 74 on which electrical components (not shown) are mounted, an optical system 75, and the actuator 30 described above, and the barrel portion of the scanner 70 via four plug pins 76. Mounted within 72. Further, in this case, as shown in FIG. 9, the decoding module 77 and the scanning unit 73 provided outside are connected by using a cable 78 or the like, and the decoding module 77 and the host device 79 are also connected. There is.

The optical system 75 includes a block 80 integrally molded with a plug pin 76, and the block 80.
As the laser device 81 assembled in, for example, a visible semiconductor laser, a heat dissipation plate 82, an optical system 83, and a photodiode (not shown) having a viewing area for scattered reflected light from the barcode 71 are formed. ing. The photodiode is located within the optical system 75.

The operation of the scanner 70 using the actuator 30 of the present invention having the above structure will be described below. The optical system 75 causes the laser light emitted from the laser device 81 via the optical system 83 to be reflected by the mirror 40 of the actuator 30 whose position is adjusted so that the laser light is incident from the condenser mirror 84 having a hole and hits a flat surface. The reflected laser light linearly scans the barcode 71 by the swing of the mirror 40.

The scattered reflected light from the bar code 71 passes through the entrance / exit window provided in the scanner 70 as in the outward path, and strikes the fixed condenser mirror 84. The impinging light is reflected and condensed by the condensing mirror 84, enters the photodiode in the optical system 75, and is photoelectrically converted. By this photoelectric conversion, the intensity of the scattered reflected light from the barcode 71 is converted into an analog signal, and this analog signal is converted into a digital signal by an A / D converter (not shown) provided inside the scanner. The information of the bar code 71 that has become a digital signal is read by decoding the information of the bar code 71 by a decoding module 77 provided outside the scanner 70.

When the actuator 30 of the present invention is used in the hand scanner, the unit used in the conventional scanner can be made more compact and the scanner as a whole can be made smaller accordingly. Furthermore, since it is easy to downsize the actuator,
Instead of using the scanner in a hand-held type, it is possible to realize a scanner that is built into a small scanner and is fixed to a finger, an arm, or the back of a hand by using a fixing means such as Velcro. For fixing a small scanner,
This will reduce the burden on the user due to long-term use.

Further, in the actuator 30 shown in FIG. 1, the cylindrical yoke 34 and the "U-shaped" member are formed separately, but a yoke member and an elastic member as shown in FIG. 11 are used. It can also be integrally formed. Figure 1
In No. 1, the magnetic plate is bent into a box shape, and elasticity is obtained by making a cut on the elastic part at the back surface of the box so that the elastic part has elastic force. Be done.

In addition to the adjusting device described in the second embodiment, a structure as shown in FIG. 12 can be considered. The same parts as those in FIG. 1 will be described using the same reference numerals. In this adjusting device, a "F-shaped" plate spring 90 for fixing one end of the torsion bar 37 and a projection 91 provided on the yoke 34 side are located at the abdominal position of the plate spring 90, and the other end of the plate spring 90 is provided. A leaf spring 90, to which the torsion bar 37 is fixed, is attached like a seesaw around the protrusion 91 provided on the yoke 34 side, and the screw 92 is screwed in to finely adjust the tension of the torsion bar 37. To do.

Further, in the second embodiment, the torsion bar 37 is used.
The adjusting means screw 51 provided for adjusting the natural frequency is not particularly required if the mirror 40 is oscillated by the drive pulse and the specification accuracy is not required. However, if the torsion bar 37 is not provided, the natural frequency varies depending on the width and size of the torsion bar 37. Therefore, the magnitude of power consumption when swinging the mirror 40 is extremely different as shown in FIG. It can be understood that the accuracy is better when the member of 37 which can adjust the tension is provided.

The torsion bar provided for swinging the mirror or the like may be a leaf spring or a wire.
For example, metal is stainless steel, phosphor bronze or the like, plastic is polyester, polyimide or the like, and also rubbers and members such as combinations with the previous members are described in this embodiment. It can be used for a torsion bar, and is attached in the same manner as in the example.

In addition to the structure of the actuator described above, an actuator having a magnet in the yoke and an electromagnet in the mirror holding member can be considered from the present invention. Further, as described above, in the above-described embodiment, the size in the height direction, which is required when using the motor, can be reduced, and further, the positioning member for regulating the rotation angle, the expensive and bulky polygon mirror, and the like. Since there is no complicated circuit for controlling the actuator, it is possible to reduce the number of parts and provide a low cost actuator.

Further, an elastic member gives a substantially constant tension to the torsion bar, in particular, a deviation of the natural frequency due to a dimensional error of the torsion bar due to the variation of the constituent members in the scanning unit, and an adjusting member is provided. A desired natural frequency can be obtained by finely adjusting the tension of the torsion bar. Therefore, a drive circuit corresponding to this can be created relatively easily compared to the one using a motor, and there is no rattling when using the motor, so the effect of rattling can be prevented and an actuator with excellent scanning speed can be easily performed. realizable.

[0045]

As described above, according to the present invention, it is possible to realize a small-sized actuator having high driving efficiency. Further, since no motor is used, the structure is simple, and an actuator with good durability can be realized at low cost.

[Brief description of drawings]

FIG. 1A is a right side sectional view showing the structure of a scanning actuator according to a first embodiment of the present invention. (B) is (a)
The front view of the actuator shown in FIG.

FIG. 2 shows an example of a drive pulse generation circuit.

FIG. 3 is a diagram showing drive pulses generated by the circuit shown in FIG.

4A to 4E shown in FIG. 1 are upper cross-sectional views for explaining the operation of the actuator.

FIG. 5 is a right side sectional view showing the structure of the scanning actuator of the second embodiment of the present invention.

FIG. 6 is a diagram in which power consumption is plotted on the vertical axis and applied frequency is plotted on the horizontal axis to show the resonance frequency of the torsion bar used in the examples.

FIG. 7 is a right side sectional view showing the structure of the scanning actuator according to the third embodiment of the present invention.

FIG. 8A is a diagram showing a drive current supplied to a drive coil. FIG. 7B is a diagram showing a waveform detected by the sensor coil.

9 is a perspective view showing an outline when the actuator of FIG. 1 is used in a scanner.

10A is a top view showing a configuration of a scan unit when the actuator of FIG. 1 is arranged inside. FIG.
(B) is a right side view of the scan unit shown in (a).

FIG. 11 is a perspective view showing an example of the shape of a yoke.

FIG. 12 is a right side sectional view showing an application example of the scanning actuator of the second embodiment.

FIG. 13 is a diagram for explaining a scanning mechanism of a conventional laser type scanner.

FIG. 14 is a perspective view showing a scanning mechanism of a conventional scanner using a polygon mirror.

FIG. 15 is a sectional view showing a scanning mechanism of a conventional scanner using a one-sided mirror.

[Explanation of symbols]

 30, 50, 60 actuator 31 iron core 32 drive coil 33 electromagnet 34 yoke 35, 90 leaf spring 36 member forming a protrusion 37 torsion bar 38 mirror holding member 39 magnet 40 mirror 41 drive pulse generation circuit 51 screw 61 sensor coil 70 Scanner 71 Bar code 72 Barrel 73 Scanning unit 74 Substrate 75 Optical system 76 Plug pin 77 Decode module 78 Cable 79 Host device 80 Block 81 Laser device 82 Heat sink 83 Optical system 84 Condenser mirror 91 Projection 92 Screw

Claims (2)

[Claims] 1. A scanning actuator for displacing a light beam to scan an optical symbol, an elastic member holding a reflective member and a magnetic member so that a magnetic member is disposed on the back surface of the reflective member, and the elastic member. A scanning actuator comprising: a means for applying a substantially constant tension to the member; and a swinging means for swinging the reflecting member held by the elastic member by a magnetic force and its moment of inertia. 2. The scanning actuator according to claim 1, further comprising adjusting means for adjusting the tension of the elastic member.