JPH0816704A - Braking device for scanning driving mechanism for information reader - Google Patents

Abstract

PURPOSE:To provide a braking device for scanning driving mechanism for information reader with which linear scanning is realized and braking is stopped in a short time after the end of scanning while miniaturizing and lightening a scanning driving mechanism to scan light for information reading and reducing cost. CONSTITUTION:This scanning driving mechanism for information reader is composed of a mirror driving device 3 for scanning laser light generated by a light source part 2 on a bar code by being repeatedly operated within a prescribed range while reflecting the laser light with a scan mirror 15 by a turning operation to be repeated by attracting force due to a permanent magnet 31 and a coil 30 at a movable part 5 and the recovery force of an elastic object 32 clamped on both sides by a damper 34, information reading part 4 for reading information from return light from the bar code, and braking device composed of a short-circuiting part for grounding the first-order side potential of the coil 31 when scanning is finished, braking and stopping the turn of the movable part 5.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In general, a label attached to identify an article is a bar code having a coded pattern composed of adjacent bars and spaces in rows of various widths instead of letters and numbers. Is listed.
This bar code contains various information such as information on the type of article and manufacturing.

Various information reading devices for identifying the bar code have been developed and are now widely used. Specifically, this information reading device irradiates a bar code displayed on the surface of a label or article with infrared light, laser light, or the like, and causes light reflection caused by a difference in width between a bar and a space. The difference between the characteristics is detected, the barcode pattern is read, and the label or the article is identified.

For example, Japanese Unexamined Patent Publication (Kokai) No. 2-17888 discloses an information reading device having a handle portion and a head portion and having a gun shape as a whole. This information reading device can read a bar code by irradiating a desired label with a laser beam from a distance of several meters, for example, without contacting the bar code.

Further, the head portion of this apparatus has a laser diode (LD) for generating a laser beam, a scanning mirror for reflecting the light emitted from the LD, and a bar of the laser beam for rotating the scanning mirror. A scanning motor for scanning the code and a reading unit for reading the barcode information by reflecting the return light from the barcode by the scanning mirror are provided.

[0006]

However, in the information reading apparatus disclosed in the above-mentioned publication, the rotation of the motor (repetitive operation) is used to rotate the scanning mirror. Since the space for the drive circuit is required at the minimum, and even if the light emitting source is downsized, the space for the motor and the motor drive circuit, which occupies the space, cannot be reduced. Therefore, the information reader is downsized and lightweight. Difficult to turn into.

Further, it is desirable that the information reading light (laser light) is read by linearly scanning at a constant speed in the arrangement direction of the bar codes. Therefore, a high-performance small motor is required for the scanning mirror to perform stable rotation, resulting in high cost.

It is also conceivable to shake (rotate) the scanning mirror using an elastic body instead of a small motor, but the vibration of the elastic body does not converge immediately after the required scanning is completed, If an attempt is made to start the next scan while the vibration is not converged, the behavior immediately after the start of the operation becomes unstable, and there is a risk that it will be read as incorrect information. Therefore, it has to be stopped by some method.

Therefore, the present invention realizes linear scanning while reducing the size and weight of the scanning drive mechanism for scanning the information reading light and reducing the cost, and information for stopping the vibration in a short time after the scanning is completed. An object of the present invention is to provide a braking device for a scanning drive mechanism in a reading device.

[0010]

In order to achieve the above-mentioned object, the present invention emits information reading light from a light source to information written by a coded pattern and reads information written by the information reading means from reflected light. In the information reading device,
The light source is provided with a scanning mirror that emits and condenses information reading light at one end and a movable portion that has a magnet at the other end, and is rotatably supported around a central position of the movable portion as a rotation center point. And a fixed part fixed to the substrate provided with 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, and the fixed part. From the side, 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 is sandwiched from both sides or one side of the elastic body and fixed to the fixed portion, and the natural frequency of the elastic body is fixed. The elastic body deflection correcting means for maintaining the planar rotation while holding the magnetic field and the magnetic force for attracting the magnet by the predetermined tanming, and the elastic body restoring force are used to rotate the movable portion. Rotation drive means for repeating the operation, and the rotation drive A scanning drive mechanism of an information reading apparatus including a rotation braking unit that stops and brakes the rotation operation of the movable portion by setting the output potential of the coil for generating the magnetic force provided in the step to the ground potential. To provide a braking device.

Further, the rotation braking means includes a short-circuited portion on the primary side of the coil for grounding the potential, and a waveform shaping means for generating a pulse train of a signal synchronized with the rotation in the movable portion. When the scanning state changes from the scanning state to the non-scanning state, the short-circuited part is made conductive in accordance with the phase of the voltage generated in the coil due to rotation, and the magnet of the movable part is temporarily attracted to the coil to brake the movable part. Provided is a scan drive mechanism of an information reading device.

[0012]

The scanning drive mechanism of the information reading apparatus having the above-described structure is repetitively operated by utilizing the attraction force by the combination of the permanent magnet and the coil and the restoring force of the elastic body formed in the plate shape. The scanning mirror is rotated while reflecting the laser light, and the barcode is scanned with the laser light. In addition, the elastic body on the side of the fixed portion of the scanning drive mechanism is clamped and fixed from both sides (both sides) by dampers having elastic force to reduce distortion and twist generated when the elastic body is bent and restored,
The scanning mirror is stably rotated to linearly scan the laser beam in the direction in which the barcodes are arranged.

Then, in the non-scanning state in which the scanning is ended and the rotation is stopped, the output potential of the coil is set to the ground potential to brake and stop the rotation operation of the permanent magnet. Or, when the movable part changes from the scanning state to the non-scanning state, the short-circuit part is made conductive in accordance with the phase of the voltage generated in the coil due to the rotation, and the movable part moves when the movable part rotates away from the coil. Temporarily attracts the magnet of the part to brake and stop the movable part.

[0014]

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

This information reading apparatus includes a light source section 2 for generating a laser beam and a mirror driving apparatus for reflecting the laser beam and repeating (shaking) a predetermined range to scan the laser beam on the bar code. 3 and an information reading unit 4 that reads information from the return light from the barcode are arranged on the substrate 1. The light source unit 2 is disposed obliquely in front of a mirror driving device 3 outside a return light width region, which will be described later, and the information reading unit 4 is composed of a photodiode (PD) or the like and is emitted in front of the mirror driving device 3. It is arranged at a position where the return light is condensed below the optical axis of the laser light.

With such an arrangement, the laser light generated by the light source section 2 is reflected while rotating by the plane mirror section (emission section) 15a of the scanning mirror 15 of the mirror driving device 3 at a predetermined angle, not shown. Illuminate the barcode. And
Return light (reflected light) from the barcode is condensed by the spherical mirror portion (condenser portion) 15b and is incident on the information reading portion 4.

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

In the present embodiment, the light source unit 2 is set so that the return light from the above-mentioned bar code enters in the range A, and the laser diode 2 has the substrate 1 outside the range A region. It is placed on top.

Next, the mirror driving device 3 will be described. The mirror driving device 3 is for oscillating the scanning mirror by using a magnetic force and an elastic body to scan the laser light, and is roughly classified into a scanning mirror 15 including a mirror having a reflecting surface of a spherical shape, and the scanning. A U-shaped movable part 5 for fixing the mirror 15 at one end; a fixed part 6 fixed to the substrate 1 and rotatably supported by the movable part 5 and connected by an 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 in which the permanent magnet 31 is hollowly provided so as to be removable, and when the attraction force generated by the coil 30 is lost, the restoring force is used to return to the center of the swing range. And an elastic body 32 that operates. In this embodiment, the elastic body is not limited as long as it is a member such as a thin metal plate or a polyester sheet that can be used as a leaf spring.

Further, since this elastic body is used as a thin plate, in addition to the planar bending due to bending, twisting or distortion may occur when the bending is restored (deflected). If the elastic body is twisted when it is restored, for example, as shown in FIG. 8A, the laser beam is not irradiated linearly in the direction in which the barcodes are arranged, and an irregular curve is drawn. . Further, when the scanning is performed by the repetitive operation, as shown in FIG. 8B, the laser light may draw infinity. When the bar code is read by such scanning with the laser light, the interval between the bars is different, so that the bar code is erroneously read.

Therefore, in the present embodiment, as shown in FIG. 9, 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 side of the elastic body fixing portion 33a. The damper 34 is made of the elastic body 3
It is necessary to provide it so that the natural frequency of 2 does not change, and it is shorter than the length from the elastic body fixing portion 33a to the axis B. The damper 34 is preferably a thin plate made of metal, plastic, rubber or the like and has an elastic force.

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 the same. Match on a straight line. The main surface (horizontal surface) of the substrate 1 with the straight line as the rotation axis
, Perpendicularly intersect with each other. Therefore, the movable part 5 rotates parallel to the substrate surface.

The coil 30 is composed of 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. This sensor coil can detect the magnetic force generated by the insertion / removal of the permanent magnet 31 to know the insertion / removal state (deflection position).

The scanning mirror 15 is composed of a condensing portion 15b having a spherical reflecting surface and a plane mirror emitting portion 15a provided at the center thereof. This injection part 15
a is such that the surface thereof extends along the axis B and the light from the light source 2 is emitted vertically from the surface including the edge 1a of the substrate 1 at the initial position where the scanning mirror 15 is not driven. Keep the angle. Further, the light condensing portion 15b is set so as to condense light onto 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 so as to be perpendicular to the optical axis of the condensing unit 15b.

The movable portion 5 has a U-shape that is suspended, 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, and one side of the elastic body 32 is fixed. A cylindrical permanent magnet 31 is attached to the other end of the U-shaped movable portion 5 in the intersecting direction. Further, a shaft B extending perpendicularly to the surface of the substrate 1 is provided in the central portion of the movable portion 5 and is fixed to the fixed portion 6 so that it can rotate within a predetermined angle range about this. ing.

Further, below the one end of the movable portion 5, there is formed an anti-sway portion 36 extending from the end portion to a position below the axis B, and is fitted in a groove provided in the lower portion of the fixed portion. 5 is prevented from swinging too much, and swinging is prevented from rattling.

The cylindrical coil 30 is arranged in a position where it can be inserted into and removed from the hollow even if the cylindrical permanent magnet 31 rotates. Further, the fixed portion 6 has a bottom surface fixed to the substrate 1, an arm portion for fixing the axis B of the movable portion 5 to a fixed portion, a groove fixed to the substrate for restricting the movement of the shake 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, in the scanning drive mechanism of this embodiment, the movable portion 5 and the fixed portion 6 are connected by the elastic body 32, the axis B of the movable portion 5 is supported by the fixed portion 6, and is rotatable. Moving part 5
Both ends (scanning mirror side and permanent magnet side) repeatedly rotate about the axis B by the attraction force by the magnetic field and the restoring force of the elastic body 32.

Next, driving of the optical head portion of the thus constructed information reading apparatus will be described. First, FIG.
The operation of the scanning drive mechanism of the information reading apparatus of this embodiment will be described with reference to FIG. In FIG. 3, the upper part shows the detected value of the sensor coil (the deflection state of the movable part), and the lower part shows the voltage applied to the coil.

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

First, based on the configuration shown in FIGS. 4 and 5 which will be described later, a predetermined voltage is applied to the coil 30 to generate an N-pole magnetic field and an attractive force to the permanent magnet 31. Due to this attractive force, the permanent magnet 31 of the movable portion 5 is rotated to the m side with the axis B as the fulcrum (center point), and conversely, the scanning mirror 15 is rotated to the m ′ side.

Next, when the application of the predetermined voltage to the coil 30 is stopped, the elastic body 32 is rotated in the opposite directions n and n'to try to return to the initial position by the restoring force of the elastic body 32. Then, due to the inertial force, when it passes the initial position and reaches a certain point based on the spring coefficient, it tries to return further in the m direction. At that time, a predetermined voltage is applied again to the coil 30 to generate a magnetic field of the N pole and generate an attractive force. The movable portion 5 vibrates at a certain frequency depending on 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 and vibrated, and the radar light from the emitting portion 15a is reflected by the emitting portion 15a of the scanning mirror to scan the radar light.

FIG. 4 shows the block configuration of the drive circuit of the information reading apparatus, and FIG. 5 shows the configuration of the drive circuit including the braking circuit of the scanning drive mechanism of the information reading apparatus. As shown in FIG. 4, the drive circuit of the information reading apparatus includes an analog signal generation circuit 21 and a scan drive circuit 23 that drives a scan drive mechanism.
A laser diode (LD) drive circuit 24, a digital data generation circuit 25, and a control circuit 22 for controlling these circuits. These circuits are custom IC2.
6 is formed as one integrated circuit. The custom IC 26 operates according to two control signals, a run permission signal and a laser emission permission signal.

As shown in FIG. 5, the scanning drive circuit 23 is connected to one side terminals of the primary side coil 41a and the secondary side coil 41b of the electromagnetic coil 41 (the coil 30). 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 opposite terminal 41b' on the secondary side is connected to the reference voltage of AC GND. . Further, the primary coil 41
a and 41a 'are short-circuited parts 42,
The current paths of 43 are respectively connected and turned on at the same time, so that both ends of the primary side coils 41a and 41a 'are GN.
Grounded to D.

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

In the drive circuit thus constructed,
When the user finishes reading the information and wants to stop the scanning, the scanning permission signal is set to the non-permission and turned off. At that time, the H level changes to the power supply voltage control unit 44 and the short-circuit units 42 and 43.
Therefore, the generation of the voltage output from the power supply voltage control unit 44 is prohibited, and the primary coil ends 41 of the electromagnetic coil 41 are prevented.
Since the short-circuited portions 42, 43 connected to a, 41a 'are electrically connected to GND, kinetic energy can be rapidly consumed by causing the electromotive force generated in the electromagnetic coil 41 to flow to GND via the resistance component of the coil itself. , The brake is applied to brake the rotation of the movable part.

FIG. 6 shows the waveform of the electromotive force generated by the sensor coil when the short-circuit parts 42 and 43 are not turned on, and FIG. 7 is the electromagnetic coil 4 when the short-circuit parts 42 and 43 are turned on.
FIG. 3 is a diagram showing a waveform of an electromotive force generated by the sensor coil when both ends 41a and 41a ′ of the primary coil of No. 1 are set to the ground potential.

Therefore, according to the present embodiment, when the braking permission signal is turned from on to off (t1), both ends 41a and 41a 'of the primary side coil of the electromagnetic coil 41 are set to the ground potential, and the generated coil voltage rapidly. Is attenuated to, and converges to almost the reference potential until it is turned on (t2) again, and a stable rise occurs even when turned on again.

From the above, when the movable part (scanning mirror) changes from the operation-permitted state to the non-operational state, the short-circuited part is connected between both ends of the electromagnetic coil and GND, whereby the movable part rotates ( By vibrating), the resistance of the electromotive force generated in the electromagnetic coil can be quickly consumed and the moving part can be stopped immediately, so it is possible to restart the moving part in a stable and short time. From
The scanning drive mechanism of the information reading apparatus according to the present embodiment is repetitively operated by using the attraction force by the combination of the permanent magnet and the coil and the restoring force of the elastic body, without using a small motor having high accuracy which has been used conventionally. Since the scanning mirror is rotated, the size and weight can be easily reduced with a simple structure.
In addition, it can be configured without using expensive parts, and low cost is realized.

Further, the plate-shaped elastic body used in this embodiment is fixed and clamped from both sides (both sides) with dampers having elastic force, so that the elastic body is bent and restored. Unstable rotation of the scanning mirror due to distortion or twist can be prevented, and linear scanning of laser light can be realized. In addition, by setting the length of the damper to be equal to or less than the distance from the fixed portion to the center of rotation (1/2 or less of the length of the elastic body), the natural vibration of the elastic body is not changed.

Next, a modification of the above-described embodiment will be described. The configuration of the scan drive mechanism of this modification is equivalent to the configuration shown in FIG. 2, but the operation is different. FIG. 10 shows the configuration of a braking device of a modified example, and FIG. 11 shows the waveform of each part of the device.

In this braking device, an amplifying section 71 is connected to one side terminal 41b of the secondary coil of the electromagnetic coil 41 to amplify the signal synchronized with the rotation of the movable section to an optimum level, and the waveform shaping section 72 causes a pulse train. Convert to. The pulse train generated by the waveform shaping unit 72 is connected to the primary coil 41a of the electromagnetic coil 41 with the pulse width output from the generating unit 73 at the timing so as to match the phase with the rising edge of the scanning permission signal of the scanning drive mechanism. At the short-circuit portion 74, the control current of the electromagnetic coil is connected so as to flow to the ground.

The one side terminal 41a of the primary coil is also connected in parallel to the drive circuit in the custom IC. When a scanning permission signal is input to the scanning drive mechanism by such a braking device, the drive circuit in the custom IC causes a control current to flow in the primary coil of the electromagnetic coil 41. When the control current flows, the permanent magnet fixed to the movable portion 5 is attracted to the electromagnetic coil 41, and the oscillatory motion is started. The amplifier 71 is
By connecting to the one side terminal 41b of the secondary coil, the voltage generated in the secondary coil is AC-amplified to an appropriate level, and converted by the waveform shaping section 72 into a pulse train of a signal synchronized with the rotating operation of the movable section. This converted pulse train is preferably
The duty is 50%.

Next, this pulse train is supplied to the timing generator 73.
And the pulse train generated when the permanent magnet 31 moves in a direction away from the electromagnet 41 are matched with each other, and a pulse generator (not shown) generates a pulse for a predetermined time. generate. This pulse for a certain period of time activates the short-circuited portion 74 and causes the current of the primary coil to flow toward the ground for a certain period of time, so that the permanent magnet is momentarily attracted to the electromagnetic coil 41 side to rotate the movable portion. Stop.

As described above, when the movable portion changes from the operating state to the non-operating state, the phase of the voltage generated in the electromagnetic coil due to the oscillating motion is monitored and is fixed at the moment when the reading device is in the non-operating state. Since the movable part is stopped instantly by applying the braking pulse for a certain period, the movable part is stopped immediately because the braking pulse is applied for a certain period at the moment when the movable part becomes inactive. Even if the scanning permission signal is input immediately after, the movable portion can be stably and quickly started up.

[0047]

As described above in detail, according to the present invention, linear scanning is realized while the size and weight of the scanning drive mechanism for scanning the information reading light are reduced and the cost is reduced, and after the scanning is completed. An object of the present invention is to provide a braking device for a scanning drive mechanism in an information reading device that stops vibration in a short time.

[Brief description of drawings]

FIG. 1A is a diagram showing a configuration of a scanning drive mechanism (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 an information reading light scanning drive mechanism (optical head portion) in the information reading apparatus according to the present embodiment as viewed obliquely.

FIG. 3 is a diagram showing a relationship between a shake state of a movable portion and a voltage applied to a coil for rotating the movable portion of the scanning drive mechanism.

FIG. 4 is a block diagram showing a configuration of a drive circuit of the information reading device of the present embodiment.

FIG. 5 is a diagram showing a configuration of a drive circuit including a braking device of a scan drive mechanism of the information reading device.

FIG. 6 is a diagram showing a relationship between a conventional scanning permission signal and an electromotive force of a coil.

FIG. 7 is a diagram showing a relationship between a scanning permission signal and an electromotive force of a coil according to the present embodiment.

FIG. 8 is a diagram showing a drawing line of laser light for scanning a barcode when a twist occurs when the elastic body provided in the scanning drive mechanism is restored.

FIG. 9 is a diagram showing a configuration in which a damper is provided on an elastic body provided on the scanning drive mechanism.

FIG. 10 is a diagram showing a configuration of a modified example of a drive circuit including a braking device for a scan drive mechanism according to the present invention.

11 is a diagram showing a waveform of each part of the device shown in FIG.

[Explanation of symbols]

1 ... Substrate, 2 ... Light source part (laser diode: LD), 2
a ... Ejection point, 2b ... LD holding part, 3 ... Mirror drive device,
4 ... Information reading part (photodiode: PD), 5 ... Movable part, 6 ... Fixed part, 15 ... Scanning mirror, 15a ... Planar mirror part (emission part), 15b ... Spherical mirror part (light condensing part),
21 ... Analog signal generating circuit, 22 ... Control circuit, 23 ...
Scanning drive circuit, 24 ... Laser diode (LD) drive circuit, 25 ... Digital data generating circuit, 30, 41 ... Electromagnet (electromagnetic coil), 31 ... Permanent magnet, 32 ... Elastic body, 3
3a ... Elastic body fixing part, 34 ... Damper, 36 ... Shake prevention part, 42, 43, 74 ... Short circuit part, 44 ... Power supply voltage control part, 71 ... Amplification part, 72 ... Waveform shaping part, 73 ... Generation part.

Claims (2)

[Claims] 1. An information reading device which emits information reading light from a light source for reading information 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 part that includes a scanning mirror that emits light and a magnet at the other end, and a substrate that is rotatably supported with a position near the center of the movable part as a rotation center point and that is provided with the light source and information reading means. A fixed part to be fixed, a plate-shaped elastic body connecting the fixed part and the other end of the movable part provided with the scanning mirror, and a substantially central point of the elastic body from the fixed part side. A damper having an elastic force that does not reach the center of rotation is sandwiched from both sides or one side of the elastic body and fixed to the fixed portion, and the planar frequency is maintained while maintaining the natural frequency of the elastic body. Elastic body deflection correction A step, a rotation driving means for causing the magnet to generate a magnetic force attracted by a predetermined tamming, and using the restoring force of an elastic body to repeat the rotation operation of the movable part, and the rotation driving means. And a rotation braking means for stopping and braking the rotation operation of the movable part by setting the primary side potential of the coil for generating the generated magnetic force to the ground potential. Scan drive mechanism. 2. The rotation braking means includes a short-circuited portion on the primary side of the coil for grounding the potential, and a waveform shaping means for generating a pulse train of a signal synchronized with the rotation in the movable portion. When the part changes from the scanning state to the non-scanning state, the short-circuited part is brought into conduction in accordance with the phase of the voltage generated in the coil due to the rotation, and the magnet of the movable part is temporarily attracted to the coil to move the movable part. A scanning drive mechanism of an information reading device characterized by braking.