JP2008102190A - Scanning type optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning type optical device capable of giving a large deviation angle and saving electric power even when a plurality of electro-optical elements are used. <P>SOLUTION: The device includes: a light source device 11 emitting a laser beam; a light scanning unit 20 having a first electro-optical element 21 that allows the laser beam emitting from the light source device 11 to scan in one direction by changing the refractive index distribution corresponding to the intensity of an electric field generated inside and a second electro-optical element 26 that allows the laser beam exiting from the first electro-optical element 21 to scan in a direction different from the first direction; and a polarization direction rotating means 25 which is disposed on an optical path between the first electro-optical element 21 and the second electro-optical element 26 and rotates the polarization direction of the light exiting from the first electro-optical element 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a scanning optical device.

  2. Description of the Related Art In recent years, scanning image display apparatuses that display an image by raster scanning beam-like light such as laser light on a projection surface have been proposed. In this apparatus, since the complete black can be expressed by stopping the supply of the laser light, a high contrast display is possible as compared with, for example, a projector using a liquid crystal light valve. In addition, image display devices that use laser light have characteristics such as high color purity because the laser light has a single wavelength and high coherence, so that the beam is easy to shape (easy to squeeze). It is expected as a high-quality display that realizes resolution and high color reproducibility. In addition, unlike a liquid crystal display, a plasma display, or the like, a scanning image display device does not have a fixed pixel, and therefore has an advantage that the resolution is easily converted without the concept of the number of pixels.

In order to generate an image with a scanning image display device, it is necessary to scan light two-dimensionally using a scanner such as a polygon mirror or a galvanometer mirror. There is a method of scanning light two-dimensionally while swinging one scanner in two directions, the horizontal direction and the vertical direction, but in this case, there is a problem that the configuration and control of the scanning system become complicated. In view of this, a scanning type image display apparatus has been proposed in which two sets of scanners for scanning light in one dimension are prepared, and each of them has a horizontal scanning and a vertical scanning. Conventionally, both scanners normally use a polygon mirror or a galvanometer mirror, and a projection apparatus using a rotating polygon mirror (polygon mirror) for both scanners is disclosed in Patent Document 1 below.
JP-A-1-245780

  However, in Patent Document 1, an apparatus using a polygon mirror is introduced. However, as the resolution of an image format is increased, the scanning frequency is also increasing, and the polygon mirror and the galvanometer mirror are reaching their limits. Therefore, in recent years, a system using MEMS (Micro Electro Mechanical Systems) technology for a high-speed scanner has been announced. A scanner using MEMS technology (hereinafter simply referred to as a MEMS scanner) is manufactured using a microfabrication technology of a semiconductor material such as silicon, and drives a mirror supported by a torsion spring or the like by electrostatic force or the like. It is. This scanner can scan the light by reciprocating the mirror by the interaction between the electrostatic force and the restoring force of the spring. By using the MEMS scanner, it is possible to realize a scanner having a high frequency and a large deflection angle as compared with a conventional scanner. This makes it possible to display a high-resolution image.

By the way, in order to realize a high-speed MEMS scanner, the mirror must be reciprocated at the resonance point. Therefore, considering the light utilization efficiency, the scanning line scans from left to right as viewed from the viewer, and then These scanning lines are scanned from right to left (both sides scanning).
On the other hand, since the standard for image signals is determined based on CRT (Cathode Ray Tube), after scanning from left to right, it returns to the left in a short time and then scans to the right again (one side scan). It has become. Therefore, in the case of the MEMS scanner, since some data must be displayed by reversing the order of the input signals, the signal control becomes complicated.
Therefore, an electro-optic (EO) scanner can be considered as a scanning means other than the MEMS scan. An EO scanner is an element that changes the traveling direction of light transmitted through a crystal by applying a voltage to the EO crystal. As described above, since the scan angle can be controlled by the voltage in the EO scanner, drawing by one-sided scanning can be performed in the same manner as the CRT.

  Some EO crystals have a Pockels effect or a Kerr effect, and this effect has a dependency on the vibration direction of incident light, and a large declination is obtained for light in a specific vibration direction. However, a large deflection angle cannot be obtained for light in a vibration direction orthogonal to a specific vibration direction. Therefore, when performing two-dimensional scanning using a plurality of EO scanners, the light emitted from the preceding EO element is taken into consideration without considering the vibration direction (polarization plane) of the light incident on the EO element disposed in the subsequent stage. If the light is incident as it is, a large deflection angle cannot be obtained, and it is difficult to scan light in a desired shape (the aspect ratio of the irradiated region is 4: 3, 16: 9, etc.). For this reason, in order to obtain a large deflection angle, it is necessary to make the voltage applied to the EO element higher than the characteristics of the EO element, leading to an increase in power consumption.

  The present invention has been made in order to solve the above-described problem. Even when a plurality of electro-optical elements are used, a large deviation angle can be obtained and power saving can be achieved. An object of the present invention is to provide a mold optical device.

In order to achieve the above object, the present invention provides the following means.
The scanning optical device of the present invention has a light source device that emits laser light and a laser light emitted from the light source device in one direction by changing a refractive index distribution according to the magnitude of an electric field generated inside. A first electro-optical element that scans; a light scanning unit that includes a second electro-optical element that scans laser light emitted from the first electro-optical element in a direction different from the one direction; the first electro-optical element; And a polarization direction rotating unit provided on an optical path between the second electro-optical element and rotating the polarization direction of the light emitted from the first electro-optical element.

First, the properties of the electro-optical element will be described.
In the electro-optic element, an electric field is generated when a voltage is applied, and the refractive index distribution continuously increases or decreases in the direction of the electric field. For this reason, the light traveling in the direction perpendicular to the electric field generated inside the electro-optic element is bent from the low refractive index side to the high side and is emitted from the electro-optic element. In the scanning optical device of the present invention, the light emitted from the light source device and incident on the first electro-optic element is bent from the low refractive index side to the high side and scanned in one direction. The polarization plane of the light emitted from the first electro-optical element is rotated by the polarization direction rotating means. Then, the light whose polarization plane is rotated enters the second electro-optic element, is bent from the low refractive index side to the high side, and is scanned in the other direction.

  Here, when the light emitted from the first electro-optical element is directly incident on the second electro-optical element without considering the polarization direction, the second electro-optical element scans in a direction different from that of the first electro-optical element. For this reason, the plane of polarization deviates from the polarization direction in which the maximum deflection angle of the second electro-optic element can be obtained, and it is necessary to apply a voltage more than necessary to obtain the desired deflection angle. However, in the present invention, since the polarization direction rotating means is provided, the light emitted from the electro-optic element is made closer to the light in the polarization direction capable of obtaining the maximum deflection angle of the second electro-optic element. The light can enter the optical element. Accordingly, when the same voltage is applied to the second electro-optical element, a larger declination can be obtained as compared with the case where the polarization direction is not taken into consideration. Therefore, the illumination area of the light emitted from the second electro-optical element can be set to a desired value. It becomes easy to scan in a shape. That is, the scanning optical device of the present invention does not need to apply a high voltage so as to obtain a large deflection angle as in the prior art. It becomes possible to improve. As a result, it is possible to realize low power consumption for the entire apparatus.

  Further, the polarization direction rotating means obtains the maximum deviation angle of the second electro-optical element when the polarization direction of the laser light emitted from the first electro-optical element is obtained from the light emitted from the first electro-optical element. It is preferable to rotate in the polarization direction so that the polarization direction becomes possible.

  In the scanning optical device according to the present invention, the polarization direction of the light emitted from the first electro-optic element is changed to a polarization direction that can obtain the maximum deflection angle of the second electro-optic element by the polarization direction rotating means. It is rotated. Therefore, it is not necessary to increase the voltage applied to the second electro-optical element in order to obtain a desired deflection angle. As a result, since the performance of the second electro-optic element can be utilized to the maximum, the efficiency of the scan angle with respect to the applied voltage of the second electro-optic element can be further improved.

In the scanning optical device of the present invention, it is preferable that the polarization direction rotating means is a half-wave plate.
In the scanning optical device according to the present invention, since the polarization direction rotating means is a half-wave plate, the polarization direction of the light emitted from the first electro-optical element is changed by rotating the polarization direction by, for example, 90 degrees. It is possible to rotate the polarization direction so that the maximum deflection angle of the second electro-optic element can be obtained. Therefore, since the polarization direction rotating means is a half-wave plate, the polarization direction of the light emitted from the first electro-optic element can be accurately converted to a desired polarization direction with a simple configuration.

In the scanning optical device of the present invention, the polarization direction rotating means may be made of a material having optical activity instead of the polarization direction rotating means being a half-wave plate.
In the scanning optical device according to the present invention, when the light emitted from the first electro-optic element passes through the polarization direction rotating means made of a material having optical rotation, the plane of polarization is rotated. As described above, by using the polarization direction rotating means made of a substance having optical rotation, the polarization direction of the light emitted from the first electro-optical element can be converted into a desired polarization direction at a low cost.

  In the scanning optical device according to the aspect of the invention, it is preferable that the scanning directions of the first electro-optical element and the second electro-optical element are orthogonal to each other.

  In the scanning optical device according to the present invention, since the first electro-optical element and the second electro-optical element are arranged orthogonally, one of the first electro-optical element and the second electro-optical element is horizontally scanned. The other can be used for vertical scanning. Therefore, the scan range of the laser light emitted from the first and second electro-optical elements can be further increased.

  In the scanning optical device according to the aspect of the invention, the electro-optical effect of the first electro-optical element and the second electro-optical element may have a crystal orientation dependency, and the polarization direction rotating unit may include the first electro-optical element. The polarization direction of the laser light emitted from the first electro-optic element matches the crystal orientation of the second electro-optic element capable of obtaining the maximum deflection angle of the second electro-optic element. It is preferable to rotate in such a polarization direction.

  In the scanning optical device according to the present invention, the polarization direction of the laser light emitted from the first electro-optic element is the maximum of the second electro-optic element, with respect to the light emitted from the first electro-optic element by the polarization direction rotating means. The polarization direction is rotated so as to coincide with the crystal orientation of the second electro-optic element capable of obtaining the declination. Therefore, by matching the polarization direction of the light incident on the second electro-optic element and the crystal orientation of the second electro-optic element, it becomes possible to emit laser light having the maximum deflection angle from the second electro-optic element.

In the scanning optical device according to the aspect of the invention, it is preferable that the electro-optic element has a composition of KTa _1-x Nb _x O ₃ .

In the scanning optical device according to the present invention, the electro-optic element is a crystal having a composition of KTa _1-x Nb _x O ₃ (potassium niobate tantalate), which is a dielectric material having a high dielectric constant (hereinafter, referred to as “crystal”). (Referred to as KTN crystal). KTN crystals have the property of changing the crystal system depending on temperature from cubic to tetragonal to rhombohedral, and it is known that cubic crystals have a large secondary electro-optic effect. In particular, in a region close to the phase transition temperature from cubic to tetragonal, a phenomenon in which the relative permittivity diverges occurs, and the secondary electro-optic effect proportional to the square of the relative permittivity is a very large value. Therefore, the crystal having the composition of KTa _1-x Nb _x O ₃ can suppress the applied voltage required when changing the refractive index as compared with other crystals. Accordingly, it is possible to provide a scanning optical device that can realize power saving.

  Embodiments of a scanning optical device according to the present invention will be described below with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

[First Embodiment]
As shown in FIG. 1, the scanning optical device 1 includes a light source device (LD: laser diode) 11 that emits laser light, and an optical scanning unit 20 that scans the laser light emitted from the light source device 11. Yes.

The optical scanning unit 20 includes two electro-optic elements 21 and 26 arranged on the optical path of the laser light emitted from the light source device 11 and a half wavelength arranged on the optical path between the electro-optic elements 21 and 26. And a plate 25 (polarization direction rotating means). Here, the electro-optical element 21 disposed on the side closer to the light source device 11 is referred to as a first electro-optical element, and the electro-optical element 26 disposed on the side far from the light source device 11 is referred to as a second electro-optical element.
The first and second electro-optical elements 21 and 26 used in the present embodiment emit light having the maximum deflection angle from the electro-optical element when the voltage application direction and the polarization direction of incident light are the same. It is a possible element.

The first electro-optic element 21 is used for vertical scanning that scans light emitted from the light source device 11 in the vertical direction (one direction) v out of scanning in the two directions (vertical direction v and horizontal direction h) in the illumination region K. The second electro-optical element 26 is a scanner for horizontal scanning that scans light emitted from the first electro-optical element 21 in a horizontal direction (a direction different from one direction) h.
The “horizontal scanning scanner” mentioned here is a scanner responsible for high-speed scanning out of two directions, and the “vertical scanning scanner” is a scanner responsible for low-speed scanning.

First, the first electro-optical element will be described.
As shown in FIG. 1, the first electro-optic element 21 scans the laser light emitted from the light source device 11 by changing the refractive index distribution according to the magnitude of the electric field generated inside. As shown in FIG. 1, a first electrode 22, a second electrode 23, and an optical element 24 are provided.
The optical element 24 is a dielectric crystal (electro-optic crystal) having an electro-optic effect, and is composed of a crystal material having a composition of KTN (potassium niobate tantalate, KTa _1-x Nb _x O ₃ ) in this embodiment. Has been. The KTN crystal is a crystal utilizing the Kerr effect (a phenomenon in which birefringence occurs when an electric field is applied to an isotropic material, and is proportional to the square of the strength of an electric field generated by an applied voltage).
The optical element 24 has a rectangular parallelepiped shape, and the first electrode 22 is disposed on the upper surface 24a of the optical element 24, and the second electrode 23 is disposed on the lower surface 24b. A power source E for applying a voltage is connected to the first electrode 22 and the second electrode 23. Further, as shown in FIG. 1, the first electrode 22 and the second electrode 23 have substantially the same size in the traveling direction of the laser light L traveling in the optical element 24. As a result, an electric field is generated in the optical element 24 between the first electrode 22 and the second electrode 23. For example, when a voltage higher than the second electrode 23 is applied to the first electrode 22, an electric field is generated from the first electrode 22 toward the second electrode 23 (in the direction indicated by arrow A). As a result, the refractive index of the electro-optic crystal increases from the first electrode 22 toward the second electrode 23. An arrow A indicates the arrangement direction of the first and second electrodes 22 and 23, that is, the voltage application direction.

In addition, as shown in FIG. 1, the optical element 24 is arranged so that laser light is incident from the side of the incident end face 21 a of the first electro-optic element 21 close to the first electrode 22. As a result, the first electro-optic element 21 of the present embodiment performs one-side scanning that scans one side with reference to the incident laser light. That is, because the laser light incident on the optical element 24 is bent only to the second electrode 23 side due to the refractive index distribution of the first electro-optical element 21, the laser light is allowed to enter from the first electrode 22 side of the optical element 24. This makes it possible to increase the scan range.
The light source device 11 emits laser light of linearly polarized light (hereinafter referred to as v-polarized light) parallel to the vertical direction v as indicated by an arrow. That is, by matching the voltage application direction A of the first electro-optic element 21 with the polarization direction (v-polarized light) of the laser light emitted from the light source device 11, the light having the maximum deflection angle from the first electro-optic element 21. Can be injected.
Further, the light source device 11 is disposed so that the emitted laser light L is incident on the incident end face 21 a of the electro-optic element 21 perpendicularly.

Next, the operation of the first electro-optic element will be described.
For example, a voltage of +100 V is applied to the first electrode 22 by the power source E, and a voltage of 0 V, for example, is applied to the second electrode 23 from the power source E. By applying a voltage to the first and second electrodes 22 and 23, an electric field is generated in the optical element 24 from the first electrode 22 toward the second electrode 23. As a result, the refractive index of the optical element 24 decreases on the first electrode 22 side and gradually increases toward the second electrode 23 side. Thereby, the laser beam traveling in the direction perpendicular to the electric field direction A generated inside the optical element 24 is refracted. Specifically, the laser light L incident from the incident end face 21a of the first electro-optic element 21 is bent toward the second electrode 23 side where the refractive index of the optical element 24 is high.

Next, scanning of laser light emitted from the light source device will be described.
The waveform of the voltage applied to the first electrode 22 is, for example, a sawtooth waveform as shown in FIG. When the voltage of the initial value S1 (0 V) is applied to the first electrode 22, as shown in FIG. 1, the laser light L1 emitted from the light source device 11 and traveling through the optical element 24 travels straight and travels through the first electro-optic element 21. Injected from the injection end face 21b.

  Further, when the voltage value applied to the first electrode 22 is gradually increased as shown in the voltage waveform of FIG. 2, the refractive index gradient of the optical element 24 increases. As a result, when the voltage applied to the first electrode 22 is increased and gradually increased to the maximum voltage value S2 (+100 V), the laser light L2 emitted from the light source device 11 and traveling through the optical element 24 as shown in FIG. In the optical element 24, the light gradually refracts as the applied voltage increases. Thereby, the light emitted from the emission end face 21 b of the first electro-optic element 21 is scanned in the same direction as the electric field direction A in the scan range.

2 is applied to the first electrode 22, the laser light L emitted from the light source device 11 is scanned by the electro-optic element 21 from the laser light L1 to the laser light L2. (Scanning range) is scanned. In other words, by changing the voltage applied to the first electrode 22, the laser light emitted from the emission end face 21 b of the first electro-optic element 21 is scanned in a one-dimensional direction.
Note that the initial value 0 V and the maximum voltage value +100 V, which are values of the applied voltage applied to the first electro-optic element 21, are merely examples, and the magnitude of the deflection angle of the light emitted from the first electro-optic element 21, The thickness can be appropriately changed depending on the thickness of the optical element 24.

  As shown in FIG. 1, the half-wave plate 25 has an optical axis (a direction that is not divided into ordinary light and extraordinary light) P and the polarization direction (v-polarized light) of the incident laser light. They are arranged at an angle of 45 degrees. With this arrangement, the laser light emitted from the first electro-optic element 21 passes through the half-wave plate 25 and the plane of polarization is rotated 90 degrees due to the birefringence effect. Therefore, the laser light after passing through the half-wave plate 25 is linearly polarized light (hereinafter referred to as h-polarized light) parallel to the horizontal direction h.

Next, the second electro-optical element will be described.
The second electro-optical element 26 has the same configuration as that of the first electro-optical element 21 and differs only in arrangement and size.
That is, the second electro-optical element 26 includes the first electrode 27, the second electrode 28, and the optical element 29, similarly to the first electro-optical element 21. Note that, similarly to the first electro-optic element 21, the second electro-optic element 26 is also a one-side scan that scans one side with reference to the incident laser beam.
Further, the size of the optical element 29 is a size having an incident end face 26a on which the laser beam scanned from the first electro-optic element 21 can be incident.
Further, when a voltage higher than the second electrode 28 is applied to the first electrode 27, an electric field is generated from the first electrode 27 toward the second electrode 28 (in the direction indicated by arrow B). As a result, the refractive index of the electro-optic crystal increases from the first electrode 22 toward the second electrode 23. An arrow B indicates the arrangement direction of the first and second electrodes 27 and 28, that is, the voltage application direction.

  In the KTN crystal, the voltage application direction A and the scan direction substantially coincide with each other, so the first electro-optical element 21 scans the laser light emitted from the light source device 11 in the vertical direction, and the second electro-optical element 26 To scan the laser light emitted from the first electro-optic element 21 in the horizontal direction, the voltage application direction A of the first electro-optic element 21 and the voltage application direction B of the second electro-optic element 26 are substantially orthogonal. Let them be arranged. Specifically, the second electro-optical element 26 is a laser beam emitted from the light source device 11 in a state in which the second electro-optical element 26 is rotated 90 degrees around the optical path of the laser beam L1 with respect to the arrangement of the first electro-optical element 21. It is arranged on the optical path. Accordingly, the light emitted from the emission end face 26b of the second electro-optic element 26 is scanned in the same direction as the electric field direction B in the scan range.

Next, scanning of the laser light emitted from the light source device 11 will be described.
The laser light L1 emitted from the first electro-optical element 21 is scanned within the scan range (scanning range) from the laser light L1a to the laser light L1b by the second electro-optical element 26. Similarly, the laser light L2 emitted from the first electro-optical element 21 is also scanned within the scan range (scanning range) from the laser light L2a to the laser light L2b by the second electro-optical element 26. .

Here, the v-polarized light emitted from the first electro-optical element 21 and traveling toward the second electro-optical element 26 is converted into h-polarized light by the half-wave plate 25. At this time, the second electro-optical element 26 scans the laser light emitted from the light source device 11 in the horizontal direction, and therefore, the second electro-optical element 26 is 90 degrees around the optical path of the laser light L1 with respect to the arrangement of the first electro-optical element 21. It is arranged in a rotated state. As a result, the polarization direction of the light incident on the second electro-optical element 26 coincides with the voltage application direction B of the second electro-optical element 26, and thus the light having the maximum deflection angle is emitted from the second electro-optical element 26. It is possible.
The magnitude of the deflection angle of the laser light emitted from the second electro-optical element 26 depends on the voltage applied to the first and second electrodes 27 and 28 according to the size of the illumination region K, the optical element 29, and the like. The thickness can be changed as appropriate.

In the scanning optical device 1 according to the present embodiment, by providing the half-wave plate 25, the polarization direction of the light emitted from the first electro-optical element 21 can be rotated. Accordingly, since the polarization direction of the light incident on the second electro-optical element 26 can be matched with the electric field direction B of the second electro-optical element 26, the second electro-optical element 26 transmits the light having the maximum deflection angle to the second electric optical element 26. The light can be emitted from the optical element 26. Therefore, the efficiency of the scan angle (scan angle) with respect to the voltage applied to the second electro-optical element 26 can be improved. That is, low power consumption can be realized for the entire apparatus.
Furthermore, since the performance of the second electro-optic element 26 can be utilized to the maximum, light can be emitted with a large deflection angle. Thereby, it becomes easy to make the illumination region K into a desired shape by controlling the voltage applied to the first and second electro-optic elements 21 and 26.
Also in the first electro-optic element 21, since the polarization direction of the incident laser light and the voltage application direction A of the first electro-optic element 21 coincide with each other, the voltage applied to the first electro-optic element 21 is The efficiency of the scan angle (scan angle) can be improved.
That is, the scanning optical device 1 of the present embodiment can obtain a large declination even when a plurality of electro-optical elements are used, and can save power.

In the present embodiment, the laser light emitted from the first and second electro-optical elements 21 and 26 is scanned only on one side, but the laser light may be scanned on both sides. In this configuration, by changing the voltage applied to the first electrode 22 from a positive voltage to a negative voltage, laser light incident from the center of the incident end faces 21a and 26a of the first and second electro-optical elements 21 and 26 is obtained. Can be scanned on both sides around the laser beam. Further, the light emitted from one of the electro-optical elements may be scanned on one side, and the light emitted from the other electro-optical element may be scanned on both sides.
Furthermore, although the optical axis P of the half-wave plate 25 is arranged to form an angle of 45 degrees with the polarization direction of the laser light emitted from the first electro-optic element 21, the voltage of the second electro-optic element 26 is arranged. The angle formed between the polarization direction of the laser light emitted from the first electro-optic element 21 and the optical axis P may be set in accordance with the application direction of.
Further, the half-wave plate 25 may be disposed so as to be rotatable in a plane perpendicular to the optical axis. With this configuration, even if the polarization direction of the laser light emitted from the first electro-optic element 21 and the voltage application direction B of the second electro-optic element 26 are not shifted by 90 degrees, the half-wave plate 25 is rotated. It becomes possible to adjust by.

[Modification of First Embodiment]
In the first embodiment shown in FIG. 1, the half-wave plate is used as the polarization direction rotating means, but it may be made of a substance having optical rotation. Specifically, as the polarization direction rotating means, an optical rotatory crystal such as quartz or a liquid crystal element may be used. Optical rotation is also called optical activity, and examples of optically active chemical substances include substances such as sugar, amino acids, and cholesterol. When the light emitted from the first electro-optical element 21 is incident on this aqueous solution having optical activity, the plane of polarization rotates. Therefore, such an aqueous solution is used as the polarization direction rotating means, and the polarization plane of the light incident on the second electro-optical element 26 is converted into light having a polarization direction capable of obtaining the maximum deflection angle of the second electro-optical element 26. It is also possible to do.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described with reference to FIG. In each embodiment described below, portions having the same configuration as those of the scanning optical device 1 according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.
The scanning optical device 30 according to the present embodiment is different from the first embodiment in that LiNbO ₃ (lithium niobate) is used as the first and second electro-optical elements 31 and 36. The configurations and functions of the first and second electro-optical elements 31 and 36 are the same as those of the first and second electro-optical elements 21 and 26 of the first embodiment.

As shown in FIG. 3, the first electro-optic element 31 includes a first electrode 32, a second electrode 33, and an optical element 34, similar to the first electro-optic element 21. The optical element 36 includes a first electrode 37, a second electrode 38, and an optical element 39.
The optical elements 34 and 39 are dielectric crystals (electro-optic crystals) having an electro-optic effect, and in this embodiment, are composed of a crystal material having a composition of LiNbO ₃ (lithium niobate: hereinafter referred to as LN). Has been.

Since the first electro-optic element 31 is made of an LN crystal, there is a crystal orientation C1 that can obtain the maximum deflection angle of the first electro-optic element 31. Similarly, since the second electro-optical element 36 is also made of an LN crystal, there is a crystal orientation C2 that can obtain the maximum deflection angle of the second electro-optical element 36.
Here, the first and second electro-optical elements 31 and 36 used in the present embodiment include the voltage application direction, the polarization direction of the light emitted from the light source device 11, and the first and second electro-optical elements 31 and 36. If the crystal orientation is the same, the first and second electro-optic elements 31 and 36 are elements capable of emitting light having the maximum deflection angle.
Accordingly, the first and second electrodes 32 and 33 of the first electro-optic element 31 are arranged along the crystal orientation C1 so that a voltage is applied to the crystal orientation C1. Similarly, the first and second electrodes 37 and 38 are arranged along the crystal orientation C2 so that a voltage is applied to the crystal orientation C2.

In addition, since the crystal orientations C1 and C2 of the LN crystal substantially coincide with the scan direction, the first electro-optical element 31 scans the light emitted from the light source device 11 in the vertical direction, and the second electro-optical element 36 In order to scan the light emitted from the first electro-optic element 31 in the horizontal direction, the crystal orientation C1 of the first electro-optic element 31 and the crystal orientation C2 of the second electro-optic element 36 are arranged substantially orthogonal to each other. .
Further, the v-polarized light emitted from the first electro-optic element 31 and traveling toward the second electro-optic element 36 is converted into h-polarized light by the half-wave plate 25. As a result, the light incident on the second electro-optical element 36 matches the crystal orientation C2 of the second electro-optical element 36, so that light having the maximum deflection angle can be emitted from the second electro-optical element 36. .

  As described above, in the first embodiment, since the isotropic KTN crystal is used as the optical element, it is not necessary to consider the crystal orientation. However, like the LN crystal used in the present embodiment, the electro-optic When the effect has crystal orientation dependency, it is necessary to consider the crystal orientation. Therefore, as in this embodiment, the polarization direction of the light emitted from the first electro-optic element 31 is converted, and the polarization direction of the light incident on the second electro-optic element 36 is changed to the crystal orientation of the second electro-optic element 36. Match C2. Thereby, the efficiency of the scan angle (scan angle) with respect to the applied voltage of the second electro-optical element 36 can be improved.

[Third Embodiment]
Next, a third embodiment according to the present invention will be described with reference to FIG.
In the first embodiment, an example of a scanning optical device using a monochromatic light source device has been described. However, the scanning optical device 40 according to this embodiment projects an image on a screen using a three-color light source device. This is an image display device. The optical scanning unit 20 used in the present embodiment is the same as in the first and second embodiments.

As shown in FIG. 4, the image display device 40 according to the present embodiment includes a red light source device (light source device) 40R that emits red laser light and a green light source device (light source device) 40G that emits green laser light. A blue light source device (light source device) 40B that emits blue laser light, a cross dichroic prism 46, and the first electro-optical element 21 that scans the laser light emitted from the cross dichroic prism 46 in the vertical direction of the screen 45. And a second electro-optical element 26 that scans the laser light emitted from the first electro-optical element 21 in the horizontal direction of the screen 45.
A half-wave plate 25 is provided on the optical path between the first electro-optic element 21 and the second electro-optic element 26.

Next, a method of projecting an image on the screen 45 using the image display device 40 of the present embodiment having the above configuration will be described.
The plurality of laser beams emitted from the light source devices 40R, 40G, and 40B are combined by the cross dichroic prism 46 and enter the electro-optical element 21. The laser light incident on the first electro-optical element 21 is scanned in the vertical direction of the screen 45, scanned in the horizontal direction by the second electro-optical element 26, and projected onto the screen 45.

  In the image display device 40 according to the present embodiment, the same effect as that of the scanning optical device 1 of the first embodiment can be obtained. Further, in the image display device 40 of the present embodiment, since the declination of the laser light emitted from the first and second electro-optic elements 21 and 26 is large, the image display device 40 supports resolutions such as 4k of the DCI (Digital Cinema Initiatives) specification. It becomes possible. Therefore, the image can be displayed more clearly on the screen 45 without causing deterioration in image quality. Further, in the image display device 40 of the present embodiment, the efficiency of the scan angle with respect to the voltage applied to the second electro-optic element 26 can be improved, so that the power consumption of the entire device can be reduced.

  In addition, since the scanning unit including the first and second electro-optical elements 21 and 26 can perform scanning at a higher speed than the MEMS scanner, both horizontal scanning and vertical scanning are performed using electro-optical elements as in the present embodiment. By using the means, it can be expected to realize a high-performance image display apparatus.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, a light source device that emits v-polarized laser light is used, but a light source device that emits h-polarized laser light may be used. In the case of this configuration, the first electro-optic element and the second electro-optic element may be arranged in a state where the arrangement is rotated 90 degrees around the optical path of the laser beam.
The first electro-optic element and the second electro-optic element can also be used when the polarization direction capable of obtaining the maximum deflection angle of the first and second electro-optic elements is a direction that vibrates in a direction perpendicular to the voltage application direction. What is necessary is just to arrange | position the electro-optical element in the state rotated 90 degree | times centering on the optical path of a laser beam.
Further, although the polarization direction of the light incident on the second electro-optical element is made to coincide with the voltage application direction of the second electro-optical element, the light incident on the second electro-optical element can be simply moved closer to the voltage application direction. A large deflection angle can be obtained as compared with the case where the polarization direction and the voltage application direction of the second electro-optic element are shifted by 90 degrees.

Further, although the electro-optical element that performs vertical scanning is disposed in the preceding stage on the optical path of the laser light, the electro-optical element that performs horizontal scanning may be disposed in the preceding stage.
Furthermore, although two electro-optical elements have been described, the number is not limited to this. For example, an electro-optic element may be provided on the rear side of the second electro-optic element in order to increase the declination of light emitted from the second electro-optic element or correct the distortion.
In the third embodiment, the image display apparatus is described as the scanning optical apparatus. However, the present invention is not limited to this, and the present invention can be applied to an apparatus that scans laser light in two directions.

1 is a plan view showing a schematic configuration of a scanning optical device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a waveform of a voltage applied to an electrode of the electro-optic element in FIG. 1. It is a top view which shows schematic structure of the scanning optical apparatus which concerns on 2nd Embodiment of this invention. It is a top view which shows schematic structure of the scanning optical apparatus which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  C1, C2 ... crystal orientation, 1, 30, 40 ... scanning optical device, 11 ... light source device, 20 ... optical scanning unit, 21, 31 ... first electro-optic element, 26, 36 ... second electro-optic element, 25 ... 1/2 wavelength plate (polarization direction rotating means), 40R ... red light source device (light source device), 40G ... green light source device (light source device), 40B ... blue light source device (light source device)

Claims (7)

A light source device for emitting laser light;
The refractive index distribution changes according to the magnitude of the electric field generated inside, so that the first electro-optic element that scans the laser light emitted from the light source device in one direction and the first electro-optic element emitted from the first electro-optic element An optical scanning unit having a second electro-optic element that scans laser light in a direction different from the one direction;
And a polarization direction rotating means provided on an optical path between the first electro-optical element and the second electro-optical element, and configured to rotate a polarization direction of light emitted from the first electro-optical element. Scanning optical device.   The polarization direction rotating means obtains the maximum deflection angle of the second electro-optic element when the polarization direction of the laser light emitted from the first electro-optic element is obtained from the light emitted from the first electro-optic element. The scanning optical apparatus according to claim 1, wherein the scanning optical apparatus is rotated in a polarization direction such that a possible polarization direction is obtained.   The scanning optical device according to claim 1, wherein the polarization direction rotating unit is a half-wave plate.   The scanning optical device according to claim 1, wherein the polarization direction rotating unit is made of a material having optical activity.   5. The scanning optical device according to claim 1, wherein scanning directions of the first electro-optical element and the second electro-optical element are arranged orthogonal to each other. 6. The electro-optic effect of the first electro-optic element and the second electro-optic element has crystal orientation dependence,
The polarization direction rotating means obtains the maximum deflection angle of the second electro-optic element when the polarization direction of the laser light emitted from the first electro-optic element is obtained from the light emitted from the first electro-optic element. 6. The scanning optical device according to claim 1, wherein the scanning optical device is rotated in a polarization direction so as to coincide with a crystal orientation of the possible second electro-optical element. 7. 6. The scanning optical apparatus according to claim 1, wherein the first electro-optical element and the second electro-optical element have a composition of KTa _1-x Nb _x O _3. .

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