JPH10339846A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical scanner whose durability to repetitive fatigue is excellent and in which the fluctuation of an optical scanning angle is small even in the case the ambient temp. is largely fluctuated by setting the driving frequency of the device to the natural vibration frequency at the lowest temp. being in the range of use environmental temps or the vibration frequency near it. SOLUTION: A torsion spring 5 is consisting of shape memory alloy whose reversal deformation temp. is higher than the use environmental temps. A magnetic field generating means (coil) 7 is constituted so as to vibrate a vibrating body with the natural vibrating frequency has by a vibrating system to be formed by the vibrating body and the torsion spring 5 at the lowest use environmental temps. or the vibrating frequency near it. In this device, a small magnet 3 is fixed in the vicinity of the roughly center of the torsion spring 5 with adhesive. Then, the small magnet 3 is resonated by allowing a rectangular wave current to be impressed on the coil 7 by an alternate pulse current generator 9 and a laser beam 10 which is emitted from a light source 11 to be made incident on the mirror surface 3m of the small magnet 3 is scanned at a prescribed scanning angle to be scanned on a non-scanning surface 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a laser pointer,
The present invention relates to an optical scanning device used for office equipment such as a laser printer, a barcode reader, and a laser scan micrometer, and a measuring instrument.

[0002]

2. Description of the Related Art Heretofore, the present applicant has filed Japanese Patent Application No.
No. 2 proposes an optical scanning device using a Galvano oscillation provided with a mirror with a magnet and a coil for generating an AC magnetic field.

In this optical scanning device, as shown in FIG. 7, an elastic linear member 5a made of stainless steel or the like is pulled by an appropriate tension and a housing 1 is fixed by a fixing jig 2a.
a. Approximately at the center of the elastic linear member 5a, a magnet-equipped mirror 3 having at least one boundary surface processed.
a is bonded and fixed with an adhesive (not shown).

On the other hand, a coil 7a is wound around the core 6a. The coil 7a is fixed to the housing 1a by a screw (not shown) in a screw hole 8a provided in the core 6a and a hole 4a provided in the housing 1a. Then, an alternating magnetic field is generated by passing a predetermined current through the coil by the alternating pulse current generator 9a, and the mirror with magnet 3a vibrates. The driving frequency of the alternating pulse is set to the mechanical natural frequency of the mirror with magnet 3a and the linear elastic member 5a. And the light source 1a
The laser beam 10a emitted from the mirror 3
The light is reflected by a, and the non-scanning surface 12a is scanned by the resonance of the magnetized mirror 3a.

[0005] Further, the present applicant has filed Japanese Patent Application No. Hei 8-2-2261.
No. 8 proposes an optical scanning device which is extremely excellent in durability against repeated fatigue by using a shape memory alloy as the elastic linear member.

[0006]

However, because of the occurrence of the phenomenon that the natural frequency changes with temperature, the conventional optical scanning device can be used only under conditions of small temperature changes. was there. Hereinafter, such a phenomenon will be described with reference to the drawings.

FIG. 8 shows the conventional optical scanning device.
It is the graph which showed an example in which the deflection angle relative value of the vibration of the mirror with magnet 3a with respect to the drive frequency of an alternating pulse changes. In FIG. 8, at a high temperature (temperature T = 40 ° C.), the natural frequency is as low as f0, while at a low temperature (T = 0 ° C.), the natural frequency is high as f1. Therefore, for example, the drive frequency of the alternating pulse is set to f so that the deflection angle becomes maximum at a low temperature.
When set to 1, when the temperature rises and the natural frequency becomes f0, the deflection angle sharply drops to 1/5 or less, so that the light scanning angle becomes extremely small. Therefore, the conventional optical scanning device can be used only under a temperature condition near a temperature at which the driving frequency of the alternating pulse is set.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an optical scanning device which is excellent in durability against repeated fatigue and has a small variation in an optical scanning angle even when the ambient temperature greatly varies. The purpose is to provide.

[0009]

To achieve this object, an optical scanning device according to the first aspect of the present invention has a torsion spring stretched and supported, and is fixedly supported at an intermediate portion of the torsion spring. A vibrating body having a magnet and a mirror surface is vibrated around the torsion spring by the action of a magnetic field formed by a magnetic field generating means, and a light beam emitted from a light source is incident on the mirror surface, whereby the mirror surface In particular, the torsion spring is made of a shape memory alloy whose reverse transformation temperature is equal to or higher than the use environment temperature, and the magnetic field generation means is used for the lowest use. Vibrating the vibrating body at a natural frequency of a vibrating system formed by the vibrating body and the torsion spring at ambient temperature or a frequency near the natural frequency; It is sea urchin configuration.

Therefore, the torsion spring is always in the martensite phase within the operating environment temperature range, so that it is excellent in durability against repeated fatigue and can perform optical scanning with a long life. Also, even if the natural frequency of the vibration system changes due to a temperature change within the operating environment temperature range, the deflection angle of the vibrating body does not greatly change, so that the magnetic field generating means is not affected by the temperature change. Optical scanning can be performed by vibrating the vibrating body largely near the maximum amplitude.

Further, in the optical scanning device according to the present invention, the magnetic field generating means may include a vibration frequency or a vibration frequency at which the amplitude of the vibrating body at the lowest use environment temperature and the amplitude of the vibrator at the highest use environment temperature match. The vibrating body is configured to vibrate at a frequency in the vicinity thereof. Therefore, the magnetic field generation means can always vibrate the vibrating body within an operating environment temperature range with an amplitude equal to or greater than the amplitude at the lowest operating environment temperature and the highest operating environment temperature. Optical scanning can be performed by vibrating the vibrating body largely near the maximum amplitude.

Further, the optical scanning device according to the third aspect is configured such that the magnetic field generating means generates an alternating magnetic field having a constant frequency. Therefore, the alternating magnetic field generated by the magnetic field generating means can be configured as a single frequency,
The configuration of the device can be simplified.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of an optical scanning device embodying the present invention. The small magnet 3 is a small magnet made of Ni—Co (nickel cobalt) or Sm—Co (samarium cobalt) having a length of 4 mm, a width of 8 mm, and a thickness of 0.4 mm, and a surface 3 m of which is a laser beam to be described later. It is mirror-finished to reflect light. Instead of mirror-finishing the surface of the small magnet 3, a mirror may be attached to the surface of the small magnet 3 by bonding or the like. This small magnet 3 has a residual magnetic flux density of about 10,000 Gauss. A torsion spring 5 made of Ni-Ti which is a shape memory alloy is attached to the back surface of the small magnet 3 having a mirror surface 3m. The wire diameter of the torsion spring 5 is about 300.
μm, and the length is about 25 mm. The torsion spring 5 has its upper and lower ends fixed to a rectangular housing 1 whose center is formed in a rectangular shape by a jig 2.

With respect to the housing 1, a torsion spring 5
A method for supporting the small magnet 3 will be described.

First, the torsion spring 5 is fixed to the housing 1 by the jig 2 with screws in a state where both ends are pulled by a predetermined tension. Then, the above-mentioned small magnet 3 is fixed to the torsion spring 5 fixed in this manner in the vicinity of the center of the torsion spring 5 with an adhesive. Incidentally, the torsion spring 5 is fixed to the housing 1 in a state of being pulled by a predetermined stress.

A coil 7 is provided on the rear surface of the housing 1. Incidentally, the coil 7 constitutes the magnetic field generating means of the present invention. This coil 7 is provided with a winding having a density of 300 turns / cm around a cylindrical core 6, and is provided through a screw hole 8 formed in the core 6 and a hole 4 formed in the housing 1. Screwed to the housing 1. An alternating pulse current generator 9 is connected to both ends of the winding of the coil 7, and a current of about 100 mA at 5 V can flow through the coil 7. That is, by passing the current through this coil, 300 [turns /
cm] × 100 [mA] = 3000 [A / m]. When a predetermined rectangular wave current is applied to the coil 7 by the alternating pulse current generator 9, the small magnet 3 resonates by a mechanism described later, and is emitted from the light source 11 and incident on the mirror surface 3 m of the small magnet 3. The beam 10 is scanned at a predetermined scanning angle and the non-scanning surface 1
2 is scanned.

The material of the torsion spring 5 in the present embodiment is a Ni-Ti alloy, which is a kind of a shape memory alloy, as described above, which gives a predetermined tension to the housing 1 in a martensitic phase. Installed.

Here, the phase transformation of the shape memory alloy will be described with reference to FIG.

The shape memory alloy is divided into a shape memory region and a superelastic region at a reverse transformation start temperature As point and a reverse transformation end temperature Af point. When used at a temperature lower than the reverse transformation start temperature As point, a so-called shape memory effect is exhibited, and at a temperature higher than the reverse transformation end temperature Af point, a superelastic effect is exhibited. The transformation temperature is the temperature at which the alloy changes from the austenite phase to the martensite phase, and is the temperature at which the alloy changes from the martensite phase to the austenite phase, contrary to the reverse transformation temperature.

In this embodiment, the reverse transformation end temperature Af point is set to be equal to or higher than the use environment temperature (60 ° C. in this embodiment).
At the operating environment temperature, the shape memory region of the martensite phase is always used.

In order to explain the fatigue characteristics of the shape memory alloy in the martensite phase, the difference in deformation between a normal metal material and its alloy when a shear stress is applied will be described with reference to the schematic diagram of FIG.

In the case of a normal metal material, when the shear stress as an external force is applied to a limit or more, atoms slide adjacent to each other as shown in FIG. In this case, even if the external force is removed, the distortion does not return to the original state because the energy is stable. That is, as stress is applied repeatedly, this strain accumulates and eventually leads to fracture, commonly referred to as metal fatigue.

On the other hand, in the case of the shape memory alloy, when the Af point is higher than the use environment temperature, it is always in a martensite phase at room temperature.
As shown in FIG. 3B, siblings indicated by A and B are generated. The boundary between A and B (twin plane) is relatively soft because it moves with low stress, and when an external force is applied, a sibling A having a preferred orientation to the external force grows, and as a result, shear deformation occurs. Become. When the external force is unloaded, it is not completely restored to its original state. However, in the case of the present embodiment, the reverse torque is immediately applied by the alternating magnetic field, so that the original state is completely restored. That is, by the external force and the restoring force, FIG.
It reciprocates between (1) and (2) of (b). The load in this case is a combination of the external force that the small magnet receives from the alternating magnetic field and the restoring force from the torsion spring. As shown in FIG. 3B, the shape memory alloy in the martensite phase does not cause atomic slip unlike a general metal and does not accumulate strain because only a twin plane moves. Therefore, the durability against repeated vibration is extremely high.

Next, the operation of the optical scanning device having the above configuration will be described.

As shown in FIG. 1, when an alternating pulse current is applied to the coil 7, the area around the coil 7 becomes as shown in FIG.
A so-called alternating magnetic field H is formed as shown in FIG. The small magnet 3 whose center is fixed to the torsion spring 5 and installed in front of the coil 7 receives a torque of MHcos θ by the alternating magnetic field (where M is the magnetic moment of the small magnet 3, and H is the magnetic field Is the deflection angle). When the torsion angle is θ, the torsion spring 5
(Where k is the spring constant of the torsion spring 5). Further, when the small magnet 3 vibrates at a high speed, a damping force proportional to dθ / dt is also received due to frictional resistance with air and frictional resistance inside the torsion spring 5. When the torque is applied periodically (angular frequency ω), the small magnet 3 starts torsional vibration. When this vibration system is expressed by an equation, the following equation is obtained.

[0027]

(Equation 1)

This is an equation when a forcing force is applied to the damped vibration system, and its general solution is expressed by the following equation.

[0029]

(Equation 2)

Here, the natural angular frequency ωp at which θ becomes the maximum is
Is represented by the following equation.

[0031]

(Equation 3)

That is, when the angular frequency ω of the current coincides with the natural angular frequency ωp of the mechanical system composed of the small magnet 3 and the torsion spring 5, a so-called resonance state occurs, and the maximum deflection angle is obtained.

In the case of this embodiment, for example, when the voltage applied to the coil 7 is 5 V at room temperature of about 0 ° C. and the current flowing through the winding is about 100 mA, resonance occurs at an oscillation frequency of about 400 Hz, and the deflection angle of the small magnet 3 is It will be about 40 degrees. That is, the laser beam 10 emitted from the light source 11 and reflected by the mirror surface 3m formed on the surface of the small magnet 3 has a scan angle of about 80.
The non-scan surface 12 is scanned in degrees.

The relationship between the deflection angle and the natural frequency fp (= ωp / (2π)) in the resonance state between the small magnet 3 and the torsion spring 5 when the temperature is constant is shown in FIG.
As shown in FIG. 7, the characteristic frequency fp decreases as the deflection angle increases.

The reason will be described below. That is, FIG.
As shown in (b), the movement of the sibling increases as the deflection angle increases, the frictional resistance inside the torsion spring 5 increases, and the damping coefficient μ increases. On the other hand, when the ambient temperature is constant, the undamped natural angular frequency ωo is constant.
Ωp, ie, fp, is reduced.

FIG. 6 shows the change in the deflection angle with respect to the driving frequency f (= ω / (2π)) at the temperatures T = 0 ° C. and 40 ° C. In FIG. 6, for example, T =
As shown in the graph at 0 ° C., when the driving frequency f is smaller than the deflection angle maximum frequency fa, that is, the natural frequency fp at T = 0 ° C., the drop of the deflection angle becomes steep,
When the drive frequency f is larger than the maximum swing angle frequency fa, the swing angle decreases gradually. That is, for example, starting from a drive frequency f smaller than fa and increasing f, if the deflection angle starts to increase as approaching fa,
Since the natural frequency fp decreases as shown in FIG. 5, the swing angle rapidly increases, and the maximum swing angle θ at the drive frequency f = fa.
a (= about 80 degrees). As the drive frequency f is further increased, the deflection angle starts to decrease. However, as shown in FIG. 5, since the natural frequency fp increases as the deflection angle decreases, the decrease in the deflection angle is alleviated by the increase in fp. The decrease in angle is gradual.

For this reason, as shown in FIG. 6, for example, with the drive frequency f set to the maximum swing angle frequency fa at T = 0 ° C., the temperature rises to T = 40 ° C., and the maximum swing angle frequency becomes fb, the driving frequency f = f
The deflection angle at a only decreases from 80 ° to 72 °, and the rate of decrease is as small as about 10%.

Therefore, by setting the driving frequency to the natural frequency at the lowest temperature within the operating environment temperature range (the lowest operating environment temperature) or a frequency near the natural frequency, the fluctuation of the scanning angle due to the temperature change is small, and the operation is improved. It has become possible to provide a stable optical scanning device.

The present invention is not limited to the embodiment described in detail above, and various changes can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, the driving frequency is set as the natural frequency fp (= fa) at T = 0 ° C. However, if the change in the deflection angle due to the temperature change is small, the frequency range is small. Any area may be used for driving. For example, the drive may be configured such that the drive frequency is set to a frequency at which the amplitude at the lowest use environment temperature matches the amplitude at the highest use environment temperature, or a frequency in the vicinity thereof. For example, in the graph of FIG. 6, the driving frequency is the frequency fc at the intersection of the deflection angle curve at T = 0 ° C. and the deflection angle curve at T = 40 ° C. At the time of the temperature and at the time of the lowest use environment temperature, the deflection angle becomes minimum, and at a temperature between those temperatures, the deflection angle is always larger than the minimum deflection angle. Therefore, it is possible to realize an optical scanning device in which the fluctuation of the deflection angle with respect to the temperature change is smaller than in the above-described embodiment.

In the above-described embodiment, the resonance phenomenon is used to suppress the current flowing through the coil 7. However, if there is sufficient power, the resonance point may be removed to drive the optical scanning device. There is no functional problem.

Further, in the above embodiment, the present invention is realized by using a Ni—Ti alloy which is a shape memory alloy.
Au-Cd, Cu-Sn, Cu-Al-Ni, Ni-A
1, any Fe-Pt or other martensitic phase of a shape memory alloy can be used.

In the above embodiment, the torsion spring 5 and the small magnet 3 are arranged on the front surface of the coil 7 for the sake of convenience. However, the alternating magnetic field around the coil 7 is substantially orthogonal to the magnetic moment M of the small magnet 3. Where it occurs in the direction
It can be placed anywhere.

In the above-described embodiment, the current waveform applied to the coil 7 is a rectangular wave in order to maximize the scanning width. However, if there is a margin in the scanning width, a periodic waveform such as a SIN wave or a triangular wave may be used. The voltage waveform applied to the coil 7 is a rectangular wave, S
It may be configured as a periodic waveform such as an IN wave or a triangular wave.

[0045]

As is apparent from the above description,
The optical scanning device according to claim 1, wherein the torsion spring is made of a shape memory alloy whose reverse transformation temperature is equal to or higher than a use environment temperature, and wherein the magnetic field generating unit includes the vibrator at a minimum use environment temperature. The torsion spring is configured to vibrate the vibrating body at a natural frequency of a vibration system formed by the torsion spring or at a frequency near the natural frequency. Therefore, the torsion spring is always in the martensite phase within the operating environment temperature range, so that it is excellent in durability against repeated fatigue and can perform optical scanning with a long life. Further, even if the natural frequency of the vibration system changes due to a temperature change within a use environment temperature range, the deflection angle of the vibrating body does not greatly change, so the magnetic field generating unit includes:
Irrespective of the temperature change, it is possible to perform optical scanning by vibrating the vibrating body largely near the maximum amplitude.

Also, in the optical scanning device according to the present invention, the magnetic field generating means may include a frequency or an amplitude at which the amplitude of the vibrating body at the lowest use environment temperature matches the amplitude of the vibrator at the highest use environment temperature. The vibrating body is configured to vibrate at a frequency in the vicinity thereof. Therefore, the magnetic field generation means can always vibrate the vibrating body within an operating environment temperature range with an amplitude equal to or greater than the amplitude at the lowest operating environment temperature and the highest operating environment temperature. Optical scanning can be performed by vibrating the vibrating body largely near the maximum amplitude.

Further, the optical scanning device according to the third aspect is configured such that the magnetic field generating means generates an alternating magnetic field having a constant frequency. Therefore, the alternating magnetic field generated by the magnetic field generating means can be configured as a single frequency,
The configuration of the device is simplified, and the device can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an optical scanning device according to an embodiment.

FIG. 2 is a diagram illustrating a phase transformation with respect to temperature and stress of a shape memory alloy used in the present embodiment.

FIG. 3 is a schematic diagram showing a shear strain due to a phase transformation of a shape memory alloy in a martensite phase and a shear strain of a general metal.

FIG. 4 is a schematic diagram of a small magnet used in the present embodiment receiving torque from an alternating magnetic field.

FIG. 5 is a graph showing a relationship between a deflection angle and a natural frequency in a resonance state between a small magnet and a torsion spring at a constant temperature.

FIG. 6 is a graph showing a change in a deflection angle with respect to a driving frequency at a temperature of 0 ° C. and 40 ° C.

FIG. 7 is a perspective view illustrating a configuration of a conventional optical scanning device.

FIG. 8 is a graph showing an example of a change in a swing angle relative value with respect to a driving frequency of an alternating pulse in a conventional optical scanning device.

[Explanation of symbols]

 Reference Signs List 1 housing 3 small magnet 3m mirror surface 5 torsion spring 7 coil 9 pulse current generator 10 laser beam

Claims (3)

[Claims] 1. A torsion spring is stretched and supported, and a vibrating body having a magnet and a mirror surface fixedly supported at an intermediate portion of the torsion spring is moved by the action of a magnetic field formed by magnetic field generating means. In the optical scanning device, the light beam emitted from the light source is made incident on the mirror surface, and the light beam is scanned based on the vibration of the mirror surface. The magnetic field generating means is formed of a shape memory alloy having a temperature equal to or higher than a use environment temperature, and the natural frequency of a vibration system formed by the vibrating body and the torsion spring at the lowest use environment temperature or a vibration frequency near the natural frequency. An optical scanning device, characterized in that the vibrating body is configured to vibrate. 2. The magnetic field generating means vibrates the vibrating body at a frequency at which the amplitude of the vibrating body at the lowest use environment temperature coincides with the amplitude of the vibrator at the highest use environment temperature or at a frequency near the same. The optical scanning device according to claim 1, wherein the optical scanning device is configured to cause the scanning. 3. The optical scanning device according to claim 1, wherein said magnetic field generating means is configured to generate an alternating magnetic field having a constant frequency.