JPH0635214Y2 - Optical deflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a resonant vibration type optical deflector suitable for use in an optical scanning device.

<Prior Art> Conventionally, when scanning a light beam, a polygon mirror rotating at a constant speed or a galvanometer mirror driven by a sawtooth wave signal is used.

<Problems to be Solved by the Invention> However, the conventional optical scanning device using the polygon mirror or the galvanometer mirror is expensive and large in size. Further, in the case of a polygon mirror, a motor with less rotation unevenness is required, and since a galvanometer is used in the forced vibration region (frequency region lower than the natural frequency), distortion of the excitation signal occurs and the scanning speed becomes uneven. Further, since it has a mechanical component, it has a problem in long-term use, and the entire configuration becomes complicated.

The present invention was made in order to solve the above-mentioned problems of the prior art, and an object thereof is to obtain an optical deflector having a simple structure, small size, low cost, and uniform characteristics.

<Means for Solving Problems> In order to solve the above problems, the present invention has a predetermined length formed by a photo-linography technique using a crystal plate cut out perpendicularly to the Z axis. A spring part having a rectangular cross section and a movable part supported by the fit part, a reflecting mirror formed on the movable part, and a longitudinal direction of the spring part as an X axis (or a Y axis) and a Y axis ( Alternatively, it is characterized by comprising an electrode formed so as to generate an electric field in the (X axis) direction and a self-exciting circuit connected to the electrode, and torsionally vibrating at a natural vibration frequency determined by the reflecting mirror and a spring. It is a thing.

<Embodiment> FIG. 1 is a structural perspective view showing an embodiment of an optical deflector according to the present invention. In the figure, 1 is a substrate having a piezoelectric effect (for example, quartz), and a Z plate (substrate perpendicular to the Z axis) having a thickness of about 0.03 to 0.5 mm is used. Reference numeral 2 is an upper spring, 3 is a lower spring, and 10 is a movable part supported by upper and lower springs 2 and 3, which are formed by processing by a photolithography technique. A reflecting mirror (not shown) is formed on the movable part 10,
Electrodes 4a and 4b are formed on the lower spring (hereinafter, the movable portion 10 is referred to as a reflecting mirror).

2 (a) and 2 (b) are XX cross-sectional views showing an example in which an electrode is formed on the lower spring shown in FIG. 1. In FIG. 2 (a), the electrode is located at a corner in the longitudinal (X-axis) direction of the spring. Four locations are formed along both sides. In the above structure, by applying a voltage to the diagonal electrodes 4a and 4b, the spring receives a torsional force as indicated by the arrow. Figure (b) shows the length of the spring (Y
Four electrodes are formed on both sides along the corners in the (axis) direction, and an electrode 4c is also provided at the center. Even in the above electrode formation, the spring receives a torsional force as shown by the arrow. In such a configuration, it can be considered as a one-degree-of-freedom vibration system having a reflecting mirror as a mass, and its natural frequency f can be expressed by the following equation.

Here, K; spring constant of the torsion spring J; moment of inertia in the case of the shape of the moment of inertia for example reflectors of the reflector was set to rectangle ^{J = 1 / 12ρabt (a 2} + t 2) a, b; rectangular Length of one side t; Thickness of reflector ρ; Density of reflector If quartz is used as the substrate, quartz can generate three shear strains, as shown in Fig. 2 (a) and (b). If the electrodes are arranged, the torsional strain can be easily excited. In this case, the relationship between the shear strain, the piezoelectric coefficient of each crystal axis, and the electric field can be expressed by the following equation.

e _yz = d ₁₄ Ex e _zx = -d ₁₄ Ey e _xy = -d ₁₁ Ey e; Shear strain E; Electric field d; Piezoelectric constant In addition to the above shear strain, stretching strain may be used.

FIG. 3 shows a self-exciting circuit 30 in the electrode portion of the optical deflector shown in FIG.
FIG. 3 is a configuration diagram in which the optical deflector is the first
As shown in the figure, the spring part is twisted in the direction of the arrow, and the incident light (e) incident on the reflecting mirror 10 is deflected by θ according to the twisting strength and reflected as a reflecting mirror (f). .

FIG. 4 is a perspective view of a structure in which hollow strain absorbing springs 40a and 40b are formed in the upper and lower springs of the optical deflector shown in FIG. 1, and the optical deflector has a case (not shown) according to the above configuration. When it is fixed to, for example, it is possible to prevent the phenomenon that the strain caused by the difference in the coefficient of linear expansion changes the natural vibration frequency, and in extreme cases, damages the spring.

FIG. 5 is an enlarged plan view showing the absorption spring portion of the portion A shown in FIG. 4, and the absorption spring portion is formed in a square shape and the absorption spring is deformed even when the spring portion receives a force in the direction of the arrow. However, the state in which the force is absorbed is shown.

In this embodiment, the shape of the movable portion (reflecting mirror) is shown as a rectangular shape, but the shape is not limited to this and various modifications are possible. Further, the method of forming the electrodes is not limited to the embodiment shown in FIG. Further, in this embodiment, the electrodes are formed only on the lower springs, but they may be formed on both the upper and lower springs. In this case, the reflector becomes a low-impedance oscillator, further improving the excitation efficiency. Further, the spring portion may be provided only at one place on the upper part or the lower part.

<Effect of the Invention> According to the present invention as specifically described in connection with the above embodiments, the reflecting mirror vibrates at the natural frequency, so that it is several tens to several thousand as compared with the case of forced vibration such as a galvanometer. Double vibration amplitude can be obtained, and sinusoidal scanning with significantly less distortion can be obtained.

Since the upper and lower springs and the reflecting mirror are manufactured by photolithography technology, a large number of small-sized optical deflectors with uniform characteristics can be obtained and cost can be reduced.

Since the optical deflector can be configured only by the optical deflector and the self-exciting circuit, the configuration is simplified, and since the reflecting mirror vibrates due to the natural frequency, the vibration amplitude is Q times. Therefore, the excitation power is 1 / Q, and the power consumption can be reduced, and the distortion of the excitation waveform is 1 / Q compared to the forced vibration (vibration below the resonance frequency), so pure vibration can be obtained. It is possible to perform optical scanning with less.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of an embodiment of the present invention, FIGS. 2 (a) and 2 (b) are sectional views taken along the line XX of the lower spring shown in FIG. 1, and FIG. 3 is the optical diagram shown in FIG. FIG. 4 is a configuration diagram in which a self-exciting circuit is connected to the electrode portion of the deflector, FIG. 4 is a configuration perspective view showing another embodiment, and FIG. 5 is a plan view showing an enlarged absorption spring portion of portion A shown in FIG. It is a figure. 1 ... Substrate, 2 ... Upper spring, 3 ... Lower spring, 4a, 4b ... Electrode, 10 ...
Moving parts (reflector), 40a, 40b ... Absorption springs.

Claims (2)

[Scope of utility model registration request] 1. A spring section having a rectangular cross section and having a predetermined length, which is formed by a photolithography technique using a quartz plate cut out perpendicularly to the Z axis, and a movable section supported by the spring section. A reflecting mirror formed on the movable part, and a spring part along the longitudinal direction so that an electric field is generated in the Y-axis (or X-axis) direction with the longitudinal direction of the spring part as the X-axis (or Y-axis). 2. An optical deflector comprising a plurality of electrodes formed on both surfaces of the electrode and a self-exciting circuit connected to the electrodes, and torsionally vibrating at a natural vibration frequency determined by the reflecting mirror and a spring. 2. An optical deflector according to claim 1, wherein a strain absorbing spring is formed at the end of the spring.