JP6613815B2 - Vibration mechanism, speckle canceling element - Google Patents

Description

  The present invention relates to a vibration mechanism and a speckle eliminating element.

  For example, an exposure machine or a projector using a diffusion plate is known. When a diffuser plate or the like is used, a light intensity distribution is manifested. The light intensity distribution is particularly noticeable when laser light is used, and this phenomenon is called speckle contrast.

  For example, as in an exposure machine, uniform intensity distribution is required for the purpose of irradiating light uniformly in an arbitrary range. Also in display devices such as projectors, the unevenness of the light intensity distribution and the appearance of speckle contrast in the laser light may directly lead to a decrease in display characteristics, and improvement is required.

  Therefore, various techniques for reducing speckle contrast have been proposed. For example, in an optical deflector that deflects and scans a light beam, the light from the light source is deflected in two axes, and the projection point of the light beam is shifted by causing the pedestal to vibrate in translation, thereby providing an optical path length difference and speckle contrast. Has been proposed (see, for example, Patent Document 1).

  The actuator device for an optical deflector includes a pedestal on which an optical deflector that deflects light from a light source is mounted, a piezoelectric actuator that translates the pedestal, and a support that supports the piezoelectric actuator, and translates the pedestal. Thus, a technique for reducing speckle contrast has been proposed (see, for example, Patent Document 2).

  However, all of the above-described techniques vibrate the object about one axis. Even in the above technique, two-axis driving is possible if two driving mechanisms are provided and an object is driven with respect to each axis, but there is a problem that the driving mechanism becomes complicated and large. In particular, when the object to be driven is a MEMS (Micro Electro Mechanical Systems) actuator, if the driving mechanism becomes complicated and large, the advantage of downsizing the apparatus using the MEMS actuator is offset.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a vibration mechanism that enables an operation equivalent to multi-axis vibration with a single-axis drive unit.

The present vibration mechanism has a vibration part made of an optical element and a support body that supports the vibration part via an elastic body, and is driven by a resonance frequency component of two or more in-plane resonance modes. only by the driver, it is required for the vibrating the optical element into two or more vibration direction does not depend on the direction of the one axis in the plane.

  According to the disclosed technology, it is possible to provide a vibration mechanism that enables an operation equivalent to multi-axis vibration with a single-axis drive unit.

It is a schematic diagram which illustrates the vibration mechanism which concerns on this Embodiment. It is a perspective view which illustrates the depolarization element concerning this example. It is sectional drawing of the vibration part in the position which follows the AA line of FIG. It is the top view which showed an example of the light polarizing element roughly. It is a figure which illustrates the relationship between the waveform of a drive signal, and the locus | trajectory of a round part. It is a figure which shows the example which uses the depolarizing element which concerns on a present Example for a laser printer. It is a figure which illustrates the multiplicity of the subwavelength structure area | region divided | segmented into the area | region.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

  FIG. 1 is a schematic view illustrating the vibration mechanism according to this embodiment. Referring to FIG. 1, the vibration mechanism 10 includes a uniaxial drive unit having a vibration unit 11, a support body 12, and an elastic body 13. The drive unit constituting the vibration mechanism 10 is, for example, a uniaxial translation actuator, and more specifically, for example, a MEMS actuator manufactured on a semiconductor substrate. The drive unit may be a piezoelectric actuator.

  The vibration unit 11 is supported on one axis by the support 12 via a pair of elastic bodies 13 having spring properties, and can vibrate by a predetermined drive signal from the drive unit 20. The vibration part 11, the support body 12, and the elastic body 13 can be formed using arbitrary materials, such as a silicon | silicone and resin, for example.

The vibration unit 11 has a plurality of resonance modes (in-plane resonance modes). For example, consider a case where the vibration unit 11 includes n resonance modes, and the resonance frequencies of the resonance modes are the resonance frequency f ₁ , the resonance frequency f ₂ ,... And the resonance frequency f _n . In this case, any two resonance frequencies (for example, the resonance frequency f ₁ and the resonance frequency f ₂ ) are selected from the n resonance frequencies, a composite wave including the selected resonance frequency component is generated, and the generated composite is generated. A wave is applied from the drive unit 20 to the vibration mechanism 10 as a drive signal.

  As a result, the vibration unit 11 vibrates at the two resonance frequencies included in the combined wave applied from the drive unit 20, and thus has a simple structure and a small uniaxial vibration mechanism 10 that is equivalent to biaxial vibration. Vibration can be realized. Note that a composite wave including three or more resonance frequency components may be applied from the drive unit 20 to the vibration mechanism 10.

  Note that the form of the drive unit 20 is not limited as long as a composite wave having two or more frequencies can be applied. The drive unit 20 can correspond to, for example, driving by electrostatic force, driving using electromagnetic force, driving using a piezoelectric effect, and the like. In FIG. 1, the driving unit 20 that is separate from the vibration mechanism 10 is illustrated, but the vibration mechanism 10 may include the driving unit 20. For example, the drive unit 20 can be provided on the support 12 of the vibration mechanism 10. Two or more drive units may be provided on one axis.

  The vibration mechanism 10 can be applied to various things. For example, when the vibration unit 11 is an optical element such as a depolarization element, the vibration mechanism 10 is a vibration mechanism that vibrates the optical element biaxially in a plane only by a uniaxial drive unit. Moreover, the vibration mechanism 10 can be used, for example, for a diffusion plate that makes the light intensity distribution uniform. In this case, the vibration part 11 serves as a diffusion plate, but by combining various vibration modes, it becomes possible to create many states of the diffusion plate on the time axis. Very advantageous. That is, a speckle eliminating element having the vibration mechanism 10 can be realized.

<Example>
In this embodiment, an example in which the vibration mechanism 10 is applied to a depolarizing element is shown. FIG. 2 is a perspective view illustrating the depolarizer according to this embodiment. FIG. 3 is a cross-sectional view of the vibrating portion at a position along the line AA in FIG.

  Referring to FIGS. 2 and 3, the depolarizing element 100 includes a vibrating part 110, a support 120, and an elastic body 130, and one of the light transmission regions of the vibrating part 110 serving as an optical polarizer. A plurality of subwavelength structure regions are arranged on the surface.

  The vibration unit 110 is supported on one axis by the support body 120 via a pair of elastic bodies 130 having spring properties, and can be changed to a plurality of vibrations by a predetermined drive signal. The vibration part 110, the support body 120, and the elastic body 130 can be formed by, for example, penetrating a silicon wafer (silicon substrate) having a thickness of 0.525 mm.

  More specifically, the vibration unit 110, the support body 120, and the elastic body 130 are formed by using a single silicon substrate 113 as a semiconductor by, for example, a silicon process method (photolithographic processing, nanoimprint processing, wet etching processing, dry etching processing, or the like). It is formed by processing including a thermal oxidation process.

  The vibration unit 110 includes a light transmission region 110a and a light polarization element 110b. For example, the light transmission region 110a is formed of silicon dioxide 115 in which a part of the silicon substrate 113 is thermally oxidized. The portion of the vibration part 110 that is thicker than the light transmission region 110 a has a surface formed of silicon dioxide 115 and an interior formed of a silicon substrate 113.

  The light polarizing element 110b is formed of silicon dioxide 115 on one surface (upper surface in FIG. 3) of the light transmission region 110a. The light polarizing element 110b is composed of a sub-wavelength structure that has grooves arranged repeatedly with a period shorter than the wavelength of light to be used and exhibits structural birefringence. The light polarizing element 110b is provided with a number of sub-wavelength structures having different characteristics on one surface of the light transmission region 110a, so that when the light passes through the light transmission region 110a, the light polarization element 110b has polarization corresponding to each sub-wavelength structure. The polarized light can be eliminated.

  Note that structural birefringence refers to a polarization component parallel to the stripe (TE wave) and a polarization component perpendicular to the stripe when two types of media having different refractive indexes are arranged in stripes with a period shorter than the wavelength of light. This means that the refractive index (referred to as effective refractive index) differs between (TM wave) and birefringence occurs.

  The support 120 supports the vibration unit 110 with one axis through the elastic body 130. The elastic body 130 is connected to the vibration unit 110 to vibrate the vibration unit 110. The support 120 and the elastic body 130 have a surface formed of silicon dioxide 115 and an interior formed of a silicon substrate 113.

  In the present embodiment, a pair of elastic bodies 130 are provided. More specifically, the base end portions of the pair of elastic bodies 130 are connected to the opposite sides of the vibrating portion 110, respectively. The tip of the drive unit 200 is connected to the tip of one elastic body 130 (right side in FIG. 2). The tip of the other elastic body 130 (left side in FIG. 2) is connected to the support body 120. The other opposite sides of the vibration unit 110 are in a state of being freely movable.

  The drive unit 200 is a part that vibrates the vibration unit 110 via the elastic body 130. As the drive unit 200, for example, a piezoelectric vibrator can be used, but as described above, the drive unit 200 is not limited to this.

  In the present embodiment, only one driving unit 200 is disposed, but a plurality of driving units 200 may be disposed on one axis. For example, a plurality of them may be connected or arranged on both sides of the vibration part. In that case, although the size is large, for example, a piezoelectric vibrator or the like can be driven at a lower voltage.

  The pedestal 300 is a rectangular frame member for fixing the position of the support 120 and the drive unit 200. The pedestal 300 can be made of metal, for example. However, the material and shape of the pedestal 300 are not limited to these. The pedestal 300, the support body 120, and the drive unit 200 can be joined by, for example, solder, an adhesive, or the like.

  In the light polarizing element 110b made of the sub-wavelength structure, for example, the concave / convex period (pitch) P is 150 to 250 nm, the width L of the convex land is 75 to 125 nm, and the width S of the concave groove made of the air layer is 75 to 75. 125 nm and P = L + S. For example, the depth d of the groove is 2 to 5 μm, and the thickness t of the combined portion of the light transmission region 110a and the light polarizing element 110b is 7 to 15 μm.

  In the vibration part 110, since the thickness t is about 7 to 15 μm, a frame having a thickness of about 0.525 mm is left on the outer periphery to ensure strength.

  The wavelength of light used in the depolarizing element 100 can be, for example, ultraviolet light (third harmonic of YAG laser: 355 nm) to near infrared light (fundamental wave of YAG laser: 1064 nm). Of course, it can also be used for visible light (350 to 700 nm).

  In addition, when the vibration unit 110 designed and manufactured by an example design has a wide target light wavelength band and is compatible, the light polarizing element 110b should be used in the target light wavelength band. Can do. Usually, the “target light wavelength” to be used is set, and the optical design is performed so as to match the wavelength.

  FIG. 4 is a plan view schematically showing an example of the light polarizing element. In the light polarizing element 110b, the sub-wavelength structure is divided into a plurality of sub-wavelength structure regions 110c. The plurality of sub-wavelength structure regions 110c are arranged with no gap therebetween. In FIG. 4, 16 × 16 = 256 sub-wavelength structure regions 110c are shown. However, the number of sub-wavelength structure regions 110c is not limited, and the sub-wavelength structure regions 110c are not limited. The larger the number of 110c, the better.

  For example, if the light polarizing element 110b is a square of 5 mm × 5 mm and the sub-wavelength structure region 110c is 50 μm × 50 μm, the light polarizing element 110b in which 100 × 100 = 10000 sub-wavelength structure regions 110c are arranged. Can be realized.

  The sub-wavelength structure region 110c has a striped concavo-convex structure constituted by grooves arranged repeatedly with a period shorter than the wavelength of light to be used. The arrangement direction of the stripe-shaped grooves (unevenness) is an optical axis, and the optical axis is indicated by an arrow in FIG.

  In this embodiment, each sub-wavelength structure region 110c has one optical axis. Here, the sub-wavelength structure regions 110c are arranged so that the optical axis directions are different between the adjacent sub-wavelength structure regions 110c so that the optical axis directions have different portions between the adjacent sub-wavelength structure regions 110c. Yes. For example, the optical axis direction of the sub-wavelength structure region 110c is formed so as to have any one of the directions obtained by dividing 360 degrees into 15 parts, and the optical polarizing element 110b has a random optical axis direction. A sub-wavelength structure region 110c is disposed.

  However, the number of optical axes in the sub-wavelength structure region 110c is not necessarily one, and the sub-wavelength structure region 110c can be formed so as to have optical axes in two directions orthogonal to each other. Further, the sub-wavelength structure region 110c may have three or more optical axes, and the grooves of the concavo-convex structure constituting the sub-wavelength structure are concentrically arranged so that the optical axis direction extends radially from the center. The sub-wavelength structure regions 110c may be arranged.

  The optical polarizing element 110b may have the same or different groove depth in the entire optical polarizing element 110b with respect to the depth of the concave-convex structure grooves constituting the sub-wavelength structure. Also good. When one having different depths is included, in one embodiment, the groove depth is uniform in each sub-wavelength structure region 110c, and the sub-wavelength structure regions 110c having different groove depths are randomly arranged. Is. In another embodiment, the groove depth is changed in each sub-wavelength structure region 110c.

  Returning to FIG. 2, the vibration unit 110 has a vibration mode indicated by an arrow B at a resonance frequency of 1153 Hz and a vibration mode indicated by an arrow C at a resonance frequency of 2007 Hz, and these vibration directions are substantially orthogonal to each other. In addition, the resonance frequency of the vibration part 110 can be adjusted by changing the spring constant of the elastic body 130, for example. Here, an example is shown in which the vibration directions of the two vibration modes are substantially orthogonal, but it is not an essential requirement that the vibration directions of a plurality of vibration modes intersect.

  At this time, the relationship between the drive signal (voltage) applied from the drive unit 200 and the change in the position of the circle D is as shown in FIG. 5A to 5C, the left side is the waveform of the drive signal applied from the drive unit 200, and the right side is the locus of the round part D.

  FIG. 5A shows a case where a simple AC wave of 1153 Hz is applied from the drive unit 200 (comparative example). FIG. 5B shows a case where a simple AC wave of 2007 Hz is applied from the drive unit 200 (comparative example). FIG. 5C shows a case where a combined wave of 1153 Hz and 2007 Hz is applied from the drive unit 200.

  As is clear when FIG. 5C is compared with FIG. 5A and FIG. 5B, a combined wave including a resonance frequency component selected from among a plurality of resonance frequencies of the vibration unit 110 is generated from the drive unit 200. When applied as a drive signal, the vibration unit 110 vibrates at two resonance frequencies included in the combined wave. Therefore, complicated vibration equivalent to biaxial vibration can be realized by the simple uniaxial depolarizing element 100 having a simple structure. Note that a synthesized wave obtained by synthesizing three or more frequencies may be applied from the driving unit 200 to the depolarizing element 100.

  The depolarizing element 100 can be used, for example, in an optical apparatus including an optical system that irradiates an object with laser light generated from a laser light source. That is, in order to change the polarization state of the laser light from the light source of the optical device to a random polarization state, the depolarizing element 100 can be disposed on the optical path of the optical system of the optical device. Examples of the optical device include a laser printer, an exposure device, a spectroscope using a laser light source, and a laser measuring device.

  FIG. 6 is a diagram illustrating an example in which the depolarizing element 100 is used in a laser printer. In FIG. 6, for example, a laser diode as a light source and a collimating lens that collimates a laser beam emitted from the laser diode are provided inside the laser diode unit 510.

  The laser beam emitted as parallel light from the laser diode unit 510 is deflected and scanned by a polygon mirror (rotating polygonal mirror) 520 and is turned back via an imaging lens system 530 including an F-θ lens and the like. Incident to 540. Then, the optical path is converted by the folding mirror 540 and an image is formed on the charged surface of the photosensitive drum 550.

  The depolarizing element 100 is disposed on the optical path between the laser diode unit 510 and the polygon mirror 520. As a result, the laser beam emitted from the laser diode unit 510 can be a laser beam having a random polarization state.

  Here, when the combined wave shown in FIG. 5C is applied from the drive unit 200 to the depolarization element 100 and the sub-wavelength structure region 110c divided into regions is vibrated, the light in different regions overlaps with time. Adapted. Therefore, the multiplicity (how to overlap) of the sub-wavelength structure region 110c obtained by dividing the region in the multiple vibration by the synthetic wave is as shown in FIG.

  FIG. 7B shows a simple uniaxial vibration multiplicity as a comparative example, and FIG. 7C shows a circular vibration multiplicity as a comparative example. FIG. 7A shows FIG. In addition, it can be understood that the multiplicity as a parameter of light is clearly increased as compared with FIG.

  In this example, when a simple alternating wave was applied as shown in FIG. 7B, a speckle contrast of 0.7 (30% reduction effect) was obtained. In the case of applying vibration in FIG. 7C, a speckle contrast of 0.4 (60% reduction effect) was obtained. On the other hand, when the application shown in FIG. 7A was applied, a speckle contrast of 0.3 (70% reduction effect) was obtained.

  Thus, since the multiplicity as a light parameter increases by vibrating the vibration unit 110 in a complicated manner, the speckle contrast can be further reduced as compared with the case of simple vibration. That is, it is possible to realize a speckle eliminating element having a vibration mechanism in which the optical element is a depolarizing element.

  The preferred embodiments and examples have been described in detail above, but the present invention is not limited to the above-described embodiments and examples, and the above-described embodiments are not deviated from the scope described in the claims. Various modifications and substitutions can be made to the embodiments.

  For example, in the above-described embodiment, the depolarizing element having the vibration mechanism is illustrated, but the vibration mechanism and the depolarizing element may be separately configured and combined. A speckle canceling element can be realized by combining the vibration mechanism and the depolarizing element.

DESCRIPTION OF SYMBOLS 10 Vibration mechanism 11, 110 Vibration part 12, 120 Support body 13,130 Elastic body 20,200 Drive part

JP 2009-223165 A JP 2010-237492 A

Claims (5)

A vibration part made of an optical element , and a support that supports the vibration part via an elastic body,
Only by the driving portion of the one-axis driven by two or more resonance frequency component of the plane resonant mode vibration mechanism for vibrating the optical element into two or more vibration direction does not depend on the direction of the one axis in the plane .   The vibration mechanism according to claim 1, wherein the driving unit is a uniaxial translational actuator.   The vibration mechanism according to claim 1, wherein the driving unit is a piezoelectric actuator.   The vibration mechanism according to any one of claims 1 to 3, wherein the vibration mechanism is manufactured on a semiconductor substrate.   The speckle eliminating element having a vibration mechanism according to any one of claims 1 to 4, wherein the optical element is a depolarizing element.