JP5084385B2 - Torsion spring, optical deflector, and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a torsion spring that elastically supports a member so as to allow torsional vibration, an optical deflector using the torsion spring, and an optical apparatus such as an image forming apparatus using the torsion spring. This optical deflector is suitably used for an image forming apparatus such as a projection display for projecting an image by light deflection scanning, a laser beam printer having an electrophotographic process, a digital copying machine, and the like.

  Conventionally, a micro mechanical member manufactured from a wafer by a semiconductor process can be processed on the micrometer order, and various micro functional elements have been realized using these. In particular, an optical deflector that torsionally vibrates a reflecting surface by an oscillator device formed by such a technique and performs optical scanning is compared with an optical scanning optical system that uses a rotating polygon mirror such as a polygon mirror as follows. There is a special feature. That is, the optical deflector can be miniaturized and has low power consumption. In particular, by driving near the frequency of the natural vibration mode of the torsional vibration of the oscillator device, low power consumption can be achieved.

Patent Document 1 applies a technique for forming a torsion spring having an X-shaped section by anisotropic etching of a Si wafer and an optical deflector having a torsion spring having an X-shaped section to an image forming apparatus or the like. Techniques to do this are disclosed.
JP 2004-34256 A

  However, when manufacturing a torsion spring from a wafer by a semiconductor process, there is a problem that if the thickness of the wafer varies, the spring constant of the torsion spring varies due to the variation.

  Therefore, an object of the present invention is to provide a torsion spring that can suppress variation in the spring constant of the torsion spring even when the thickness of the wafer varies.

In view of the above problems, the torsion spring according to the present invention has an X-shaped cross section perpendicular to the torsion axis, the torsion spring is formed of a single crystal silicon wafer, and the X-shaped upper surface and lower surface are (100) equivalent surfaces. in the configuration, the distance L1 connecting the respective bottom of the recess formed on the upper surface and the lower surface to each other, and the X-shaped respective bottom and connecting to each other a distance side of the formed recesses in the shape of L2 is 1.8 <L1 / L2 <2.2 is satisfied .

  In the torsion spring of the present invention, the cross-sectional shape perpendicular to the torsion axis is set to the preferred X shape as described above, so that it is possible to suppress variation in the torsion spring constant with respect to wafer thickness variation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIGS. 1A and 1B are top views showing the configuration of the torsion spring of this embodiment. FIG. 1B is a diagram in which the support substrate 2 and the movable portion 6 are connected to the torsion spring 1 of FIG.

  The torsion spring 1 in FIG. 1B has a structure in which a support substrate 2 and a movable portion 6 are connected. The torsion spring 1 supports the movable part 6 elastically about the B axis (that is, the torsion axis) and capable of torsional vibration in the E direction. The torsion spring 1 has a recess 5A as shown in FIG. The distance Ls shown here is the length of the torsion spring 1.

  The torsion spring of this embodiment is made of an integral single crystal silicon material. The term “integral single crystal silicon material” as used herein means a single crystal silicon material (wafer) that does not have a bonding interface inside the wafer.

  FIG. 2 shows a sectional view of the torsion spring 1 in a plane perpendicular to the torsion axis B along the line AA ′ in FIG. As shown in the drawing, the cross section of the torsion spring 1 is formed in an X shape by four concave portions 5A, 5B, 5C, and 5D formed on the upper and lower surfaces and both side surfaces of the torsion spring. The upper surface 10 and the lower surface 11 are constituted by a (100) equivalent surface (ie, {100} surface) of single crystal silicon. The upper surface 10 and the lower surface 11 are respectively formed with a recess 5A and a recess 5B extending in the direction of the torsion axis B and having a V-shaped cross section. The deepest portions of the recesses 5A and 5B (that is, the apex of the V-shaped recess forming the X shape) are defined as the bottoms 12A and 12B of the recesses, respectively. FIG. 3 shows an enlarged view of region Z in FIG. Strictly speaking, the bottom of the recess may have a radius of curvature as shown in the figure. In this case, the bottom of the recess is defined as an intersection where the V-shaped side surface of the recess is extended as shown in the figure. The shape having a radius of curvature as shown in FIG. 3 has an advantage that stress concentration due to torsional displacement can be relaxed.

  Further, the recesses 5C and 5D and the bottoms 12C and 12D of the recesses are formed in a direction in which the positional relationship between the opening portions of the recesses 5A and 5B and the bottoms 12A and 12B is rotated by 90 degrees. That is, the bottoms of the recesses 5C and 5D formed on the side surface of the X-shaped torsion spring are 12C and 12D, respectively. As described above, the cross section of the torsion spring 1 has an X shape by the four recesses 5A, 5B, 5C, and 5D. Here, the distance L1 between the bottoms 12A and 12B of the recesses and the distance L2 between the bottoms 12C and 12D of the recesses.

And the width Wg of the opening part of recessed part 5A, 5B is formed in the following dimension ranges with respect to the thickness t of a torsion spring (support substrate).
Wg <t / tan 54.7 ° (Formula 1)
According to the relationship of Formula 1, the recesses 5A and 5B penetrate and do not form one through-hole, but can have an X-shape. The surface of each recess formed in the torsion spring is composed of a (111) equivalent plane (ie, {111} plane) of single crystal silicon.

  In FIG. 1, concave portions 5 </ b> A and 5 </ b> B of the torsion spring are formed from the connection portion between the support substrate 2 and the torsion spring 3 and the connection portion between the movable portion 6 and the torsion spring 3. However, the positions where these recesses are formed may be slightly shifted from the respective connection portions toward the center of the torsion spring. By shifting the position where the concave portion is formed in this way, it is possible to prevent stress concentration on each connection portion.

  Next, the manufacturing method of the X-shaped cross section of the torsion spring 1 will be described with reference to FIG. 4A to 4C show how the cross section of the torsion spring 1 shown in FIG. 2 is manufactured. First, as shown in (a), the etching mask portions 101 are formed on both surfaces of the single crystal silicon wafer 100 whose crystal orientation is the <100> direction. For example, it can be formed by forming silicon nitride films on the upper and lower surfaces of a silicon wafer and dry etching them. The dimension Wg of the etching mask portion 101 satisfies the relationship of the above-described formula 1, and by setting the dimensions Wg and Ws to appropriate values, L1 / L2 can be set to a desired value for a wafer having a thickness t. it can.

  Subsequently, crystal anisotropic etching of silicon is performed. As an etching solution, for example, an aqueous potassium hydroxide solution can be used. In this etching, since the etching rate depends on the crystal orientation, when the etching proceeds, the recesses 5A and 5B are formed as shown in FIG. When the etching further proceeds, the recesses 5C and 5D are formed as shown in FIG. As described above, the X-shaped torsion spring 1 having the recesses 5A, 5B, 5C, and 5D as shown in (c) can be formed from a single silicon wafer 100 by a single etching process. The torsion spring 1 by this manufacturing method has the advantage that it can be manufactured at low cost.

  At this time, the positions of the upper surface 10 and the lower surface 11 are the (100) equivalent surface of the silicon wafer, and the X-shaped inclined surface is the (111) equivalent surface. When the cross-sectional shape is formed by the (111) equivalent surface, there is an advantage that the shape can be accurately formed by anisotropic etching.

  By using a single silicon wafer having no bonding interface, the internal friction of the material when the torsion spring is twisted can be reduced. Further, since bonding is not used when forming the torsion spring, damage at the bonding interface is difficult to occur.

  When the thickness t of the silicon wafer 100 in FIG. 4A has an error and varies, the dimensions Wg and Ws are not affected. However, the distances L1 and L2 of the bottoms 12A, 12B, 12C, and 12D of the recessed portions to be completed are affected, and the X-shaped cross section changes as follows. That is, if the thickness t is larger than the assumed value, L1 is large and L2 is small. Conversely, if the thickness t is smaller than the assumed value, L1 is small and L2 is large. This is because the torsion spring 1 has a shape using the (111) equivalent plane of the silicon crystal plane of a single wafer, and the depth of the recesses 5A and 5B is unchanged with respect to the error of the thickness t. This is because the depths of the recesses 5C and 5D change.

  The relationship between such characteristic cross-sectional shape change and spring constant change will be described below with reference to FIG. 5, and L1 / L2 that reduces the change in spring constant will be described.

  As described above, only the distances L1 and L2 are affected according to the thickness t, and the directions of increase / decrease are different from each other. Therefore, the torsion spring of this embodiment shows a characteristic change with respect to the thickness t.

  First, when an error occurs in the thickness t, it will be shown below that the torsion coefficient J determined by the cross-sectional shape is a main error factor of the torsion spring constant Ks of the torsion spring 1.

Assuming that the torque T and the torsion angle θ twist the movable part 6 relative to the support substrate 2, there are the following relationships.
T = Ks · θ (Formula 2)
Further, the torsion spring constant Ks can be expressed as follows using the transverse elastic modulus G of the material, the torsion coefficient J of the torsion spring cross section, and the length Ls of the torsion spring.
Ks = J · G / Ls (Formula 3)
In this case, the torsion coefficient J is a value determined from the shear stress generated according to the cross-sectional shape in the torsion state, and is a value depending on the cross-sectional shape of the torsion spring. For example, when the cross-sectional area of the torsion spring is circular, the secondary pole moment is obtained, but in the case of a general cross-sectional shape, it can be obtained from the relationship with the torque obtained by integrating the shear stress distributed over the cross-section. . Therefore, once the cross-sectional shape is determined, the torsion coefficient J can be accurately calculated by numerical analysis using a finite element method or the like. In the invention of the present embodiment, the torsion coefficient of the structure having an X-shaped cross section having each L1 / L2 is calculated by numerical analysis.

  As shown in Equation 3, G, which is a material property value, and length Ls are values that do not depend on thickness t. Therefore, it can be seen that J, which is a function of the cross-sectional shape and dimensions, is an error factor of Ks with respect to the variation in thickness t. Then, only L1 and L2 are affected by the thickness t, thereby changing J.

  For this reason, there is a characteristic correlation with the rate of change ΔJ / J of J due to thickness error using L1 / L2 as a parameter. FIG. 5 is a graph in which the vertical axis represents the change rate ΔJ / J of the torsion coefficient with respect to the thickness error Δt / t, and the horizontal axis represents L1 / L2. That is, the curve in FIG. 5 is a partial differentiation of the function of the torsion coefficient J with respect to L1 / L2 by the thickness t, and this curve is obtained by numerical analysis and plotted.

The torsion coefficient change (ΔJ / J) with respect to the thickness error (Δt / t) becomes a curve of FIG. 5 depending on L1 / L2 at any values of thickness t, Wg, and Ws. The curve in FIG. 5 can be approximated by the following function, for example.
ΔJ / J = c1 + c2 · (L1 / L2) ^ − 6 + c3 · (L1 / L2) ^ − 5 + c4 · (L1 / L2) ^ − 4 + c5 · (L1 / L2) ^ − 3 + c6 · (L1 / L2) ^ − 2 + c7 (L1 / L2) ^-1 + c8 (L1 / L2) ^-1/2 + c9 (L1 / L2) ^-1/3 + c10 * (L1 / L2) ^ 1/3 + c11 * (L1 / L2) ^ 1 / 2 (Formula 4)
It becomes. here,
c1 = 3.369 × 10 ^ 2
c2 = 3.675 × 10 ^ −6
c3 = −3.195 × 10 ^ −4
c4 = 1.175 × 10 ^ −2
c5 = −2.469 × 10 ^ −1
c6 = 3.660
c7 = −7.610 × 10 ^ 1
c8 = 6.342 × 10 ^ 2
c9 = −8.056 × 10 ^ 2
c10 = -1.204 × 10 ^ 2
c11 = 3.458 × 10 ^ 1
It is.

  From Expression 4, L1 / L2 at which ΔJ / J = 0 is 2.0. When L1 / L2 is 2.0, the torsion spring 1 of the present embodiment can minimize a change in the torsion coefficient J (and torsion spring constant Ks of the torsion spring 1) due to an error in the thickness t. In this case, the same effect can be obtained if the value of L1 is around 2.0 times (approximately twice) the value of L2. Particularly in the present invention, 1.8 <L1 / L2 <2.2 is a preferable range in which the effects of the present invention can be obtained.

Example 1
An embodiment of the torsion spring of the present invention will be described with reference to FIG. FIG. 6 shows the torsion spring constant error as a percentage when a torsion spring is formed using a silicon wafer having a thickness of 300 μm. In the figure, a case where an error of ± 10 μm occurs with respect to a thickness of 300 μm is shown. The curve 50 shows the case where L1 / L2 = 2, which is the torsion spring of the present invention, while the curve 51 shows the case where L1 / L2 = 1.4.

  Each torsion spring is formed by the manufacturing method described in FIG. The torsion spring of curve 50 has dimensions of Wg = 127 μm and Ws = 273 μm, and the torsion spring of curve 51 has dimensions of Wg = 140 μm and Ws = 283 μm.

  As shown in FIG. 6, the error of the torsion spring of the curve 51 is 2.5%, whereas when L1 / L2 = 2 of the curve 50, the error can be reduced to 0.4%. Further, while the curve 51 has an error in both the increase and decrease of the torsion spring constant, the curve 50 has an error in the direction in which the torsion spring constant decreases. Therefore, when L1 / L2 = 2, the torsion spring constant error is small with respect to the thickness error, and the error direction can be one direction. Since the torsion spring constant error can be unidirectional as in this embodiment, there is an advantage that the upper limit and lower limit of the torsion spring constant can be determined.

(Example 2)
7A to 7C are diagrams showing an embodiment of the optical deflector of the present invention. 7A is a top view of a torsion spring constituting the optical deflector, FIG. 7B is a top view of the optical deflector, and FIG. 7C is a cross-sectional view taken along the line CC ′. In FIG. 7, the same parts as those in FIG. As shown in FIG. 7A, the torsion springs constituting the optical deflector of the present embodiment are composed of a pair of torsion springs 1 and a support substrate 2 for one movable part 6. . The torsion spring 1 supports the movable portion 6 so as to be capable of torsional vibration about the torsion axis B. The pair of torsion springs 1 has an X-shaped cross section as shown in FIG. And the torsion spring 1 is manufactured in the manufacturing process shown in FIG.

  As shown in FIGS. 7B and 7C, the mirror portion 8 having the reflective surface 4 is bonded to the movable portion 6. The mirror unit 8 is made of, for example, silicon, and is bonded to the movable unit 6 with an adhesive. Further, a permanent magnet 7 is bonded to the opposite side of the surface on which the mirror portion 8 is formed as shown in (c). The permanent magnet 7 has a magnetic pole in the direction shown in the figure.

  The permanent magnet 7 receives a crossing magnetic field generated by energizing a coil (not shown) and generates torque. By setting the AC frequency near the resonance frequency of the torsional vibration mode of the optical deflector, large scanning can be realized with a small amount of power.

  The mirror portion 8 has a dimension of 1 mm in the torsional axis B direction and a length perpendicular to it (the width of the mirror portion) of 4 mm. The resonance frequency of the torsional vibration mode is 2 kHz.

  In the optical deflector of the present embodiment, the spring constant of the torsion spring that greatly affects the resonance frequency can be made constant with respect to the thickness error, so that the drive frequency fluctuation due to the manufacturing error of the optical deflector can be reduced.

  When a torsional resonance system is configured by using a silicon torsion spring, many shapes can be taken. However, in the case of a microelement of micro to milliorder as in this embodiment, the Q value of the vibration is larger than 500. There are many cases. Further, in order to cause a large displacement with power saving, it is desirable that the Q value is large because the rate at which the amplitude is amplified becomes large. At that time, it is preferable that the error of the spring constant is as small as possible in order to make the drive frequency determined by the application coincide with the resonance frequency of the optical deflector as much as possible. In particular, a silicon wafer has a dimensional tolerance of ± 10 μm with respect to a thickness of 300 μm. When a wafer with higher precision than this is used in production, a special process is required for wafer production. Therefore, if the change in torsional coefficient (ΔJ / J) with respect to the thickness error (Δt / t) becomes 1/10 of this thickness error, the spring constant error can be suppressed to about ± 0.3%. This indicates that the frequency fluctuates by about ± 0.15% as a frequency error.

  As described above, when the torsion coefficient change (ΔJ / J) with respect to the thickness error (Δt / t) is within one tenth of the thickness dimension error, the order of the error of the spring constant can be reduced. At this time, L1 / L2 is in the range of 1.8 to 2.2.

  In particular, the spring constant error can be reduced to 1% or less as a whole even for a wafer of 200 μm ± 10 μm. Therefore, it becomes possible to drive the resonator having a resonance frequency characteristic Q value larger than 300 within a half-value width near the resonance peak. This is a typical Q value range for a millimeter-sized torsional vibrator formed of silicon. Therefore, a large scan can be realized with a small amount of power.

(Example 3)
FIGS. 8A to 8C are diagrams showing an embodiment of the optical deflector of the present invention. 8A is a top view of a torsion spring constituting the optical deflector, FIG. 8B is a top view of the optical deflector, and FIG. 8C is a cross-sectional view taken along the line DD ′. In FIG. 8, the same parts as those in FIG. As shown in FIG. 8A, the torsion spring constituting the optical deflector of this embodiment is composed of two torsion springs 1 and one support substrate 2 having different spring constants with respect to two movable parts 6. Composed. The torsion spring 1 supports the movable portion 6 so as to be capable of torsional vibration about the torsion axis B. The torsion spring 1 is manufactured by the manufacturing process shown in FIG. 4 as described in the embodiment. The torsion spring 1 has an X-shaped cross section as shown in FIG. The two torsion springs 1 have different Wg and Ws dimensions and different spring constants, but both L1 / L2 are 2.

  Then, as shown in FIGS. 8B and 8C, the mirror portion 8 having the reflecting surface 4 is bonded to the movable portion 6. The mass part 3 is bonded to the other movable part 6. And the permanent magnet 7 is adhere | attached on the opposite side of the surface in which the mass part 3 is formed as shown in FIG.

  Unlike the second embodiment, the optical deflector of this embodiment has a plurality of movable parts. A two-degree-of-freedom vibration system is formed in the torsional vibration about the torsion axis B by the two inertia moments of the mirror part 8 and the mass part 3 and the two torsion springs 1. Therefore, there are two torsional vibration modes. That is, it has a reference vibration mode which is a natural vibration mode of a reference frequency and a natural vibration mode having a frequency which is substantially an integer multiple of the reference frequency. Here, “substantially an integer multiple” means 0.98n to 1.02n times when n is an integer of 2 or more. The multiple of these two vibration modes can be changed by the vibration of the movable part to be obtained.

  In this embodiment, in particular, the frequency of these two torsional vibration modes is approximately double (1.98 to 2.02 times). Specifically, the fundamental frequency is 2 kHz, and the secondary resonance frequency is 4 kHz.

  Furthermore, torque is generated by a crossing magnetic field generated by applying an alternating current to a coil (not shown) to excite the torsional vibration mode of the optical deflector. At this time, the fundamental frequency and two torsional vibration modes twice as much are excited simultaneously. In this way, if two components having a double relationship are excited with a favorable amplitude ratio and phase difference, the temporal change in the scanning angle can be made substantially sinusoidal instead of sinusoidal. Thereby, the angular velocity of scanning can be made substantially constant.

  In the optical deflector of the present embodiment, the two resonance frequencies need to be approximately doubled. Therefore, it is necessary to reduce the error of the spring constant of two torsion springs having different spring constants. Therefore, by setting the torsion spring to have a cross-sectional shape according to the present invention, the spring constants of the two torsion springs can be made constant even when there is a thickness error in the wafer, and the two resonance frequencies due to the manufacturing error of the optical deflector. Variation can be reduced.

  In this embodiment, one element has two torsion springs. However, since the thickness is uniform in one wafer, when a large number of elements are formed in the wafer, the processing error is reduced. it can. In particular, in the present embodiment, two torsion springs are provided in one element, but they can be made to have substantially the same thickness.

Example 4
FIG. 9 is a schematic perspective view showing an embodiment of an optical apparatus using the optical deflector of the present invention.

  First, an image forming apparatus which is one of optical devices will be described. In FIG. 9, reference numeral 3003 denotes an optical deflector according to the present invention, which scans incident light in this embodiment. Reference numeral 3001 denotes a laser light source. Reference numeral 3002 denotes a lens or lens group, 3004 denotes a writing lens or lens group, and 3005 denotes a photosensitive member.

  The laser light emitted from the laser light source 3001 is subjected to a predetermined intensity modulation related to the timing of light deflection scanning. This intensity-modulated light passes through a lens or lens group 3002 and is scanned by an optical scanning system (optical deflector) 3003. The scanned laser light forms an image (electrostatic latent image) on the photosensitive member 3005 by a writing lens or lens group 3004.

  The photosensitive member 3005 rotated around the rotation axis in a direction perpendicular to the scanning direction is uniformly charged by a charger (not shown), and by scanning light on the photosensitive member 3005, the scanning portion on the photosensitive member is applied. An electrostatic latent image is formed. Next, a toner image is formed on the image portion of the electrostatic latent image by a developing device (not shown), and an image is formed on the paper by, for example, transferring and fixing the toner image on the paper (not shown).

  By using the optical deflector 3003 of the present invention for the image forming apparatus, it is possible to form a good image. Further, if the optical deflector of the third embodiment is used, the angular speed of the light deflection scanning can be made substantially equal on the photosensitive member 3005, and an image forming apparatus capable of generating a clearer image can be provided. it can.

  When the optical deflector according to the present invention is used for an image display device such as a projection display, the following configuration is adopted. The light beam from the light source that generates the light beam modulated based on the image data is deflected by the light deflector according to the present invention, and the light beam is irradiated to the irradiated object to form an image. The optical deflector is configured to deflect the light beam in the main scanning direction and the sub-scanning direction on the irradiated object.

  As described above, the optical deflector according to the present invention can be applied to such an optical apparatus.

(A), (b) It is a top view of the torsion spring of this invention. It is sectional drawing of the torsion spring of this invention. It is an enlarged view of the bottom of the recessed part 12A of the torsion spring of this invention. (A), (b), (c) It is sectional drawing which shows the manufacturing method of the torsion spring of this invention. It is a graph which shows the torsional constant change per L1 / L2 and thickness error of the torsion spring of this invention. It is a graph which shows the board | substrate thickness and spring constant error of Example 1 of this invention. (A), (b) It is a top view of the optical deflector of Example 2 of this invention. (C) It is sectional drawing of the movable part of the optical deflector of Example 2 of this invention. (A), (b) It is a top view of the optical deflector of Example 3 of this invention. (C) It is sectional drawing of the movable part of the optical deflector of Example 3 of this invention. 1 is a perspective view showing an embodiment of an image forming apparatus using an optical deflector of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Torsion spring 2 Support substrate 3 Mass part 4 Reflecting surface 5A 5B 5C 5D Recessed part 6 Movable part 7 Permanent magnet 8 Mirror part 10 Upper surface 11 Lower surface 12A 12B 12C 12D Bottom of recessed part 50 Torsion spring spring constant when the present invention is applied Error 51 Spring constant error of torsion spring when the present invention is not applied 100 Silicon wafer 101 Etching mask portion 3001 Light source (laser light source)
3003 Optical deflector (optical scanning system)
3005 Photoconductor

Claims (6)

In a torsion spring whose cross section perpendicular to the torsion axis is X-shaped,
The torsion spring is formed of a single crystal silicon wafer,
Said upper and lower surfaces of the X-shape is constituted by (100) equivalent plane and the distance L1 connecting the respective bottom of the recess formed on the upper surface and the lower surface to each other, the X-shaped side surface recess formed in the The distance L2 connecting the bottoms to each other is
A torsion spring satisfying a relationship of 1.8 <L1 / L2 <2.2 . The torsion spring according to claim 1, wherein the torsion spring includes a (100) equivalent plane and a (111) equivalent plane which are silicon crystal planes. A support substrate;
A movable part having a reflective surface;
Connects the said supporting substrate and the movable unit, the light deflector, characterized in that it has a, a torsion spring according to claim 1 or 2 torsional oscillation be supported around a torsion axis relative to said support substrate vessel. 3. An optical deflection comprising a support substrate, a plurality of movable parts, and the torsion spring according to claim 1 that supports the support substrate and the plurality of movable parts so as to be capable of torsional vibration about a torsion axis. A vessel,
The optical deflector has a reference vibration mode that is a natural vibration mode of a reference frequency, and a natural vibration mode having a frequency that is an integral multiple of the reference frequency. A light source, an optical deflector according to claim 3 or 4 , and a photoreceptor.
The image forming apparatus, wherein the light deflector deflects a light beam from the light source and irradiates at least a part of the light beam onto the photoconductor to form an electrostatic latent image. A light source, and an optical deflector according to claim 3 or 4 ,
An image display device, wherein an image is formed by deflecting a light beam from the light source with the light deflector and irradiating the irradiated body with the light beam.

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