JPH0635215Y2 - Optical deflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical deflector suitable for use in an electromagnetic oscillograph, an optical deflector for scanning a light beam, and the like.

<Prior Art> FIG. 5 is a perspective view showing an example of an optical deflector of this type proposed by the inventors of the present application in Japanese Patent Application No. 57-174020.
This optical deflector supports a movable part 2 on a frame 1 through a thin spring part 32, and at the same time, the movable part 2 has a reflecting mirror 4
And a coil pattern 5 are formed. flame
1, the movable part 2 and the spring part 32 have a heat of 5 × 10 ^{−5 to} 5 for example.
It is composed of a crystal substrate of about 10 ^-4 m, and these shapes, reflecting mirrors, and coil patterns are created by using photolithography (etching) and etching techniques.

In the optical deflector configured in this way, the coil pattern 5 is arranged in a magnetic field in the direction of the arrow (the same direction as the plane direction of the substrate) shown in the drawing, and a current is passed through the coil pattern to move the movable portion 2 to the spring 32. The light beam incident on the reflecting mirror 4 can be deflected by displacing it as an axis in the direction of arrow a.

The optical deflector having such a configuration can produce a large number of high-performance optical deflectors of uniform quality at one time.

<Problems to be Solved by the Invention> By the way, in the above conventional optical deflector, the torsion spring 32
Is supported by a single spring part 32 on a frame as a fixed part, and the light is deflected by the torsion of the spring 32. The maximum deflection angle is the shear stress due to the torsion of the torsion spring part and the breaking stress. It depends on the angle you reach. Normally, when designing such an optical deflector, the design specifications include the size of the movable part as well as the frequency, but the torsion spring constant is inevitably determined from that condition. When designing a torsion spring having this determined torsion spring constant, the longer the length of the spring, the larger the maximum deflection angle can be, but on the other hand, vibration from the outside causes the arrows B and C shown in FIG. There is a problem that it is easy to cause various displacements.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an optical deflector that is small in size, has a large deflection angle, and has a small error due to external vibration.

<Means for Solving Problems> According to the configuration of the present invention for solving the above problems, the movable portion is constituted by an insulating substrate, and the movable portion is supported as a cantilever beam via a spring portion, In an optical deflector in which a coil pattern and a reflecting mirror are formed on the movable portion, and a radio wave is applied to the coil pattern to displace the reflecting mirror formed on the movable portion, the spring portions are arranged in parallel and close to each other. It is characterized by comprising two torsion springs.

<Example> Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of an optical deflector according to the present invention. The same elements as those of the conventional example shown in FIG. In the present invention, two springs 33, 34 are formed in close proximity to each other to support the movable portion 2 in parallel.
And the substantially central portion of these springs is engaged by the engaging portion 35. The frame shown in the figure is not always necessary.

Here, the maximum deflection angle and the deflection error (vibration of reflection) with respect to the vibration in the case of one spring (33, 34) and in the case of two springs will be described with reference to FIGS. 2 and 3. In addition,
Here, in order to simplify the equation, the shape of the spring will be described as a round bar.

First, in the case of two springs, the relationship between the total torsion spring constant of the two springs and the torsion spring constant of each spring will be explained (Fig. 2 shows that the two springs at the AA position are twisted). It shows a state in which it receives a force and rotates by an angle θ, and the upper part moves to the position of BB).

Here, Knt; total torsion spring constant n; torsion spring constant for each spring y; bending spring constant for each Y direction R; half of center distance between two springs. Since the bending in the X direction is slight, the total torsion spring constant “Knt” can be expressed by the following equation.

Knt = 2n + 2R ² · y ... Here, if R (distance between springs) is minimized, the equation becomes as follows.

Knt = 2n ... That is, the total torsion spring constant of the spring portion composed of two springs is twice the torsion spring constant for each spring if the distance between the springs is small.

Now, the same spring constant as a design specification is given to two springs (spring constant n ₁ ) close to one spring (spring constant n _o ), and the length of the spring is constant. Consider the case of designing as.

Since both the total spring constant is the same n _o = 2n ₁ ... the spring are the same length (see Figure 3) l _o = l ₁ ... ^- a. From round bar of the torsion spring constant formula _{Kn = G · πd 4 / 32l} (G is a modulus of transverse elasticity), Kn∞d ⁴ / l ... a because, ^- from the equation Becomes In addition, the maximum shear stress of the rod when the spring is twisted by θ can be expressed by τmax = Gθd / 2l to τmax∞θd / l ...

As the twist angle θ increases, τmax increases from the above equation, but rupture occurs when τmax reaches a certain value. If the angles at that time are θ _o and θ ₁ , respectively, then ⁻ and the equation, d _o θ _o = d ₁ θ ₁ …. According to the equation, θ ₁ ≈1.2 θ _o … According to the equation, when a torsion spring with a limited spring length and a certain spring constant is desired, the maximum deflection angle is about 20% by using two springs. Can be raised.

Next, let us consider the error due to vibration, that is, the reduction of roll. In order to reduce the rolling, it is sufficient that the torsion spring portion has a large bending spring constant.

Now, make the total torsion spring constant of both the same (
(n _o = 2n ₁ ), the equation is 1 / 2d ^o4 / lo = d ¹⁴ / l ₁ …, and assuming the same breaking angle, τmax∞dθ / l, so d _o / l _o = d ₁ / l ₁ It becomes ... , From the formula, 1 / 2d ^o3 = d ¹³ ... Therefore, d ₁ = 0.79d _o ..., From the formula, ₁ = 0.79l _o ... On the other hand, since the general formula of the bending spring constant of a round bar is K = 3EI / l ³ (E is the longitudinal elastic modulus), it can be expressed as K∝d ₄ / l ³ ...

Therefore, if the bending spring constant of a torsion spring with one structure is _o and the bending spring constant per one of the torsion spring with two structures is ₁ , then ₁ = 0.79 _o In the case of a torsion spring, the total bending spring constant is 2 ₁ , so 2 ₁ = 1.58 _o , so if a constant torsion spring constant is desired, use 2 springs.
By using a book, the strength against lateral shaking can be improved by about 60%.

FIG. 4 is a schematic front view showing the effect of connecting the middle of the spring in an H-shape, and the mode in which the spring tends to bend in the direction of the arrow can be prevented by providing the engaging portion 35.

In addition, in the calculation example, the spring is calculated as a round bar, but the same effect can be obtained for a square bar and a twisted bar having another shape.

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, since the movable portion is supported by the two springs arranged in parallel and close to each other, the vibration is caused by the same spring constant. The error with respect to can be reduced, and a compact optical deflector with a large maximum deflection angle can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing the construction of an embodiment of the optical deflector of the present invention, and FIGS. 2 and 3 are simplified diagrams for explaining the maximum deflection angle and the deflection error (fluctuation of the reflecting mirror) with respect to vibration. FIG. 4 is a front view showing a state in which a vibration mode is prevented by the present invention, and FIG. 5 is a perspective view showing a configuration of a conventional example. 1 ... Frame, 2 ... Movable part, 4 ... Reflector, 5 ... Coil pattern, 33, 34 ... Spring part, 35 ... Coupling part.

Claims (2)

[Scope of utility model registration request] 1. A movable part is constituted by an insulating substrate, said movable part is supported as a cantilever through a spring part, a coil pattern and a reflecting mirror are formed on said movable part, and a current is applied to said coil pattern. An optical deflector in which a reflecting mirror formed in the movable part is caused to flow and is displaced, wherein the spring part is composed of two torsion springs arranged in parallel and close to each other. 2. The optical deflector according to claim 1, wherein the torsion spring is connected in an H-shape in the middle thereof.