JP3333049B2 - Scanning drive mechanism of information reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reading apparatus for reading an optical symbol such as a bar code, and more particularly to a scanning drive mechanism for scanning a laser beam for reading.

[0002]

2. Description of the Related Art Generally, a bar code is formed on a label to be attached to identify an article, in place of letters or numbers, in a coded pattern composed of adjacent bars and spaces in rows of various widths. Is described.
The barcode includes various information such as information on the type and manufacture of the article.

[0003] Various information reading devices for identifying the barcode have been developed conventionally and are now widely used. Specifically, this information reading device irradiates a bar code displayed on a label, a surface of an article, or the like with infrared light, laser light, or the like, and reflects light reflected from a difference in width between the bar and the space. A difference in characteristics is detected, a bar code pattern is read, and a label or an article is identified.

For example, Japanese Patent Laying-Open No. 2-17888 discloses an information reading apparatus having a handle portion and a head portion and having a gun shape as a whole. This information reading device can read a barcode by irradiating a desired label with laser light from a distance of several meters, for example, without being in close contact with the barcode.

[0005] The head of the apparatus includes a laser diode (LD) for generating a laser beam, a scanning mirror for reflecting the light emitted from the LD, and a laser beam for rotating the scanning mirror to generate a laser beam. A scanning motor for scanning the code is provided, and reading means for reading the bar code information by reflecting the return light from the bar code by the scanning mirror is provided.

[0006]

However, in the information reading apparatus disclosed in the above-mentioned publication, the scanning mirror is rotated by using the rotation (repetitive operation) of the motor. Minimizing the space for the motor and the circuit for driving the motor, which requires a minimum space for the driving circuit and realizing the miniaturization of the light emitting source, makes it possible to reduce the size and weight of the information reading device. It is difficult to convert.

It is desirable that the information reading light (laser light) be read by scanning at a constant speed linearly in the direction in which the bar codes are arranged. Therefore, in order for the scanning mirror to rotate stably, a high-performance small motor is required, which also increases the cost.

Accordingly, the present invention provides a scanning drive mechanism of an information reading apparatus that scans a bar code linearly while reducing the size, weight, and cost of a scanning drive mechanism that scans information reading light. The purpose is to:

[0009]

In order to achieve the above object, the present invention emits information reading light from a light source and reads information described by information reading means from reflected light in information notation by a coded pattern. In the information reading device,
A scanning mirror for emitting and condensing light for reading information is provided at one end, and a U-shaped movable portion having a magnet at the other end, and a rotatable support centering around the center of the movable portion is provided as a rotation center point. And
A fixed part fixed to the substrate provided with the light source and the information reading means, a plate-shaped elastic body connecting both ends of the fixed part and the other end of the movable part provided with the scanning mirror, A damper having an elastic force of a length that does not reach the rotation center point that substantially coincides with the center point of the elastic body from the fixed part side is sandwiched from both sides or one side of the elastic body, and is fixed to the fixed part. An elastic body deflection correcting means for maintaining a planar rotation while maintaining a frequency; and a magnet for generating a magnetic force that is attracted by a predetermined tamping, and using a restoring force of the elastic body, Provided is a scanning drive mechanism of an information reading device including a rotation drive unit that repeats a rotation operation.

[0010]

The scanning drive mechanism of the information reading apparatus having the above-described configuration is operated repeatedly by utilizing the attraction force of the combination of the permanent magnet and the coil and the restoring force of the elastic body formed in a plate shape. The scanning mirror is rotated while reflecting the laser light, and the bar code is scanned with the laser light. Further, the elastic body on the fixed portion side of the scanning drive mechanism is sandwiched and fixed by a damper having elastic force from both sides (both sides) to reduce distortion and torsion generated when the elastic body bends and recovers,
The scanning mirror is rotated stably to scan the laser beam linearly in the direction in which the barcodes are arranged.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2 show a schematic configuration of an information reading apparatus as an embodiment according to the present invention, and will be described. FIG.
(A) shows a configuration of a scanning drive mechanism (optical head portion) of information reading light in the information reading device, and (b) of FIG.
FIG. 2A shows a cross section along the line bb in FIG. 2A, and FIG. 2 shows a configuration in which the optical head portion is viewed obliquely.

The information reading apparatus includes a light source section 2 for generating a laser beam, and a mirror driving apparatus for performing a repetitive operation (deflection operation) in a predetermined range while scanning the laser beam on a bar code while reflecting the laser beam. 3 and an information reading section 4 for reading information from return light from a bar code are arranged and configured on the substrate 1. The light source unit 2 is disposed obliquely forward of a mirror driving device 3 outside a width region of return light, which will be described later. The information reading unit 4 includes a photodiode (PD) or the like, and is emitted from the front of the mirror driving device 3. It is disposed below the optical axis of the laser beam at a position where the return light is collected.

With such an arrangement, the laser light generated by the light source unit 2 is reflected while rotating at the plane mirror unit (emission unit) 15a of the scanning mirror 15 of the mirror driving device 3, and is not shown at a predetermined angle. Irradiate the barcode. And
The return light (reflected light) from the bar code is condensed by the spherical mirror (condenser) 15b and is incident on the information reader 4.

The light source section 2 is composed of, for example, a laser diode (LD), and is held in an LD holding section 2b so that the emission direction of laser light can be freely adjusted.
The optical path from the light source a to the emission part 15a is parallel to the main surface of the substrate 1. Further, the LD holding part 2b is formed of metal or the like, and has a high heat radiation effect.

In the present embodiment, the light source unit 2 is set so that the return light from the above-described bar code is incident in the range A. The laser diode 2 is mounted on the substrate 1 outside the area of the range A. Is placed on top.

Next, the mirror driving device 3 will be described. The mirror driving device 3 scans a laser beam by causing a scanning mirror to oscillate using a magnetic force and an elastic body, and is roughly divided into a scanning mirror 15 having a reflecting surface formed of a spherical mirror, A U-shaped movable portion 5 for fixing the mirror 15 to one end, a fixed portion 6 fixed to the substrate 1 and connected to the movable portion 5 rotatably supported by the elastic body 32,
A permanent magnet 31 attached to the other end of the movable part 5,
A cylindrical electromagnet (hereinafter referred to as a coil) 30 provided so that the permanent magnet 31 can be inserted and removed in a hollow state, and when the attraction force generated by the coil 30 is lost, the restoring force attempts to return to the center of the swing width. And the elastic body 32 which is formed. In this embodiment, the elastic body is not limited as long as it can be used as a leaf spring, such as a thin metal plate or a polyester sheet.

Further, since the elastic body is used as a thin plate, twisting or distortion may occur when the bending is restored (vibrated), in addition to the planar bending due to the bending. If the elastic body is twisted when it is restored, for example, as shown in FIG. 6A, the laser light is not linearly irradiated in the direction in which the barcodes are arranged, and draws an irregular curve. . In addition, when scanning is performed by a repetitive operation, as shown in FIG. 6B, the laser light may draw an infinity. If a bar code is read by such scanning of a laser beam, the bar-to-bar distance will be different, and the bar code will be read erroneously.

Therefore, in this embodiment, as shown in FIG. 7, the elastic body 32 is sandwiched and fixed from both sides by dampers 34 made of an elastic body on both sides or one side of the elastic body 32 on the elastic body fixing portion 33a side. The damper 34 is formed of the elastic body 3
2 must be provided so as not to change the natural frequency, which is shorter than the length from the elastic body fixing portion 33a to the axis B. The damper 34 is desirably made of a thin plate made of metal, plastic, rubber, or the like to have elasticity.

The positional relationship between the center of rotation (B-axis) of the movable part 5 and the elastic body 32 is such that the middle point of the effective length of the elastic body 32 excluding the fixed portion and the B-axis are equal to each other. Match on a straight line. The principal surface (horizontal plane) of the substrate 1 using the straight line as a rotation axis.
, Perpendicularly intersect at right angles. Therefore, the movable part 5 rotates parallel to the substrate surface.

The coil 30 comprises a sensor coil and a drive coil. In this embodiment, the coil 30 is a two-layer coil in which the drive coil is wound inside and the sensor coil is wound outside. The sensor coil detects the magnetic force generated by the detachment of the permanent magnet 31 and can know the detachment state (the position of the shake).

The scanning mirror 15 comprises a condensing part 15b having a spherical reflecting surface and an emission part 15a of a plane mirror provided at the center thereof. This injection unit 15
a is such that the light from the light source 2 is emitted perpendicularly from the surface including the edge 1a of the substrate 1 at an initial position where the scanning mirror 15 is not driven while the surface extends along the axis B. Maintain the angle. The condensing section 15b is set so as to condense the light on the photodiode 4 provided in the area of the range A of the reflected light on the substrate 1. The light receiving surface 4a of the photodiode 4 is arranged at an angle perpendicular to the optical axis of the light condensing part 15b.

The movable section 5 has a U-shape, and one end thereof is fixed to the back side of the scanning mirror 15. An elastic body fixing portion 33b is provided at this fixing portion,
One side of the elastic body 32 is fixed. Further, a columnar permanent magnet 31 is attached to the other end of the U-shaped movable section 5 in the cross direction. Further, an axis B extending perpendicularly to the surface of the substrate 1 is provided at the center of the movable portion 5,
It is fitted to the fixed part 6 and is rotatable around this within a range of a predetermined angle.

Under the one end of the movable portion 5, a swing preventing portion 36 extending from the end portion to a position below the axis B is formed, and is fitted to the bracket portion 35 to prevent the movable portion 5 from swinging excessively. It also prevents vibration and rattling.

The cylindrical coil 30 is arranged at a position where it can be inserted into and removed from the hollow even if the columnar permanent magnet 31 rotates. The fixed portion 6 has a bottom surface fixed to the substrate 1, an arm portion fitted with the axis B of the movable portion 5, a bracket portion 35 fixed to the substrate and restricting the movement of the swing preventing portion 36. An elastic body fixing portion 33a for fixing the other side of the elastic body 32 is provided, and the other side of the elastic body 32 is fixed.

Therefore, the scanning drive mechanism of the present embodiment is configured such that the movable part 5 and the fixed part 6 are connected by the elastic body 32, the axis B of the movable part 5 is supported by the fixed part 6, and is rotatable. Movable part 5
(The scanning mirror side and the permanent magnet side) are repeatedly rotated about the axis B by the attractive force of the magnetic field and the restoring force of the elastic body 32.

Next, a description will be given of a drive circuit and an operation for driving the optical head portion of the information reading apparatus thus configured. FIG. 4 shows a block configuration of a driving circuit of the information reading device, and FIG. 5 shows a configuration of a driving circuit of a scanning drive mechanism of the information reading device.

As shown in FIG. 4, the drive circuit of this information reading apparatus includes an analog signal generation circuit 21, a scan drive circuit 23 for driving a scan drive mechanism, and a laser diode (L).
D) drive circuit 24, digital data generation circuit 25,
The control circuit 22 controls these circuits, and these circuits are formed as one integrated circuit as a custom IC 26. The custom IC 26 is operated by two control signals, a running permission signal and a laser emission permission signal.

As shown in FIG. 5, one terminal of a primary coil 41a and one terminal of a secondary coil 41b of an electromagnetic coil 41 (the coil 30) are connected to the scanning drive circuit 23, and The voltage of the power supply voltage Vcc is transformed into a desired voltage by the power supply voltage control circuit 44 and applied to the opposite terminal 41a ', and the secondary terminal 41b' is connected to the AC GND reference voltage. . Further, the primary coil 41
a, 41a 'include a short-circuit portion 42 made of a transistor,
43 are connected to each other and turned on at the same time, so that both ends of the primary side coils 41a and 41a 'are GN.
D is grounded.

The control lines of the short circuits 42 and 43 are provided with a time constant by a capacitor C and a resistor R.
Even if the scanning permission signal is turned off and the power supply is stopped, the short-circuit portions 42 and 43 are activated for a while. In addition, short-circuit part 4
2, 43 and the power supply voltage control unit 44 are connected so as to synchronize with an operation permission signal for controlling whether or not the information reading device is allowed to operate.

Referring to FIG. 3, the operation of the scanning drive mechanism of the information reading apparatus according to the present embodiment will be described. In FIG. 3, the upper part shows the detection value of the sensor coil (the swing state of the movable part),
The lower row shows the voltage applied to the coil.

For example, assume that the coil side of the permanent magnet 31 is an S pole. Here, the direction in which the scanning mirror of the movable section 5 faces is the direction orthogonal to the edge 1a of the substrate 1 as described above, and it is assumed that this is at the initial position.

First, based on the configuration shown in FIGS. 4 and 5, a predetermined voltage is applied to the coil 30 to generate an N-pole magnetic field and generate an attractive force to the permanent magnet 31. By this attraction, the permanent magnet 31 of the movable section 5 is turned to the m side around the axis B as a fulcrum (center point), and the scanning mirror 15 is turned to the m ′ side.

Next, when the application of the predetermined voltage to the coil 30 is stopped, the elastic member 32 rotates in the opposite directions n and n 'to return to the initial position by the restoring force. Then, when the inertial force passes the initial position and reaches a certain point based on the spring coefficient, it attempts to return to the m direction. At that time, a predetermined voltage is again applied to the coil 30 to generate an N-pole magnetic field to generate an attractive force.

The movable portion 5 vibrates at a certain frequency by the timing of applying the predetermined voltage and the elastic force of the elastic body.
Due to such vibration, the scanning mirror 15 is repeatedly operated to vibrate, and the radar light from the emission unit 15a is reflected by the emission unit 15a of the scanning mirror, and the radar light is scanned.

Therefore, the scanning drive mechanism of the information reading apparatus of the present embodiment can reduce the attractive force by the combination of the permanent magnet and the coil and the restoring force of the elastic body without using the conventionally used small motor with high accuracy. Since the scanning mirror is rotated by utilizing the operation, the size and weight can be easily reduced with a simple structure. Further, the configuration can be performed without using expensive parts, and low cost can be realized.

Further, the elastic member formed into a plate shape used in this embodiment is fixed by sandwiching and fixing the fixed portion side of the elastic member from both sides (both sides) with a damper having an elastic force. Unstable rotation of the scanning mirror due to distortion or twist can be prevented, and linear scanning of laser light can be realized. By making the damper less than the distance from the fixed portion to the center of rotation (less than half the length of the elastic body), the natural vibration of the elastic body does not change.

[0037]

As described above in detail, according to the present invention, while reducing the size and weight of the scanning drive mechanism for scanning the information reading light and reducing the cost, the information for linearly scanning the bar code can be obtained. A scanning drive mechanism of the reading device can be provided.

[Brief description of the drawings]

FIG. 1A is a diagram showing a configuration of a scanning drive mechanism (an optical head portion) of information reading light in an information reading apparatus as an embodiment according to the present invention, and FIG. It is a figure which shows the structure of the cross section along the bb line in FIG.

FIG. 2 is a perspective view of a scanning drive mechanism (an optical head portion) of information reading light in the information reading apparatus of the present embodiment as viewed obliquely.

FIG. 3 is a diagram illustrating a relationship between a swing state of the movable unit and a voltage applied to a coil for rotating the movable unit of the scanning drive mechanism.

FIG. 4 is a block diagram illustrating a configuration of a drive circuit of the information reading apparatus according to the embodiment.

FIG. 5 is a diagram illustrating a configuration of a drive circuit of a scanning drive mechanism of the information reading device.

FIG. 6 is a diagram showing a drawing line of a laser beam for scanning a barcode when a torsion occurs when an elastic body provided in the scanning drive mechanism is restored.

FIG. 7 is a diagram illustrating a configuration in which a damper is provided on an elastic body provided in the scanning drive mechanism.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Light source part (laser diode: LD), 2
a: emission point, 2b: LD holding unit, 3: mirror driving device,
4 information reading section (photodiode: PD), 5 movable section, 6 fixed section, 15 scanning mirror, 15a plane mirror section (exit section), 15b spherical mirror section (light collecting section),
21 ... analog signal generation circuit, 22 ... control circuit, 23 ...
Scanning drive circuit, 24 laser diode (LD) drive circuit, 25 digital data generation circuit, 30 electromagnet (coil), 31 permanent magnet, 32 elastic body, 33a elastic body fixing section, 34 damper, 35 ... Bracket part, 36
… Sway stopper.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G06K 7/10 G02B 26/10 101

Claims (1)

(57) [Claims] 1. An information reading apparatus which emits information reading light from a light source in information notation by a coded pattern and reads information written by information reading means from reflected light, wherein the information reading light is emitted and collected at one end. A movable portion having a scanning mirror that emits light, a magnet provided at the other end, and a rotatably supported center near the center of the movable portion as a rotation center point, on a substrate provided with the light source and the information reading means. A fixed portion to be fixed, a plate-shaped elastic body connecting both ends of the fixed portion and the other end of the movable portion provided with the scanning mirror, and a substantially central point of the elastic body from the fixed portion side A damper having an elastic force of a length that does not reach the rotation center point that is the same as that of the elastic body is sandwiched from both sides or one side of the elastic body, and is fixed to the fixed portion. Elastic body that keeps moving Correction means, and a rotation driving means for generating a magnetic force that is attracted by the magnet at a predetermined tamping, and using a restoring force of an elastic body to repeat a rotation operation of the movable portion. A scanning drive mechanism of an information reading device, which is characterized by the following.