JP2008102191A - Scanning type optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning type optical device capable of causing a laser beam to scan with high accuracy in a simple configuration. <P>SOLUTION: The device includes: a light source device 11 emitting a laser beam; an electro-optical element 21 that allows the laser beam emitting from the light source device 11 to scan a projection object face by changing the refractive index distribution corresponding to the intensity of an electric field generated inside; and a diameter variable optical system having a condensing element 26 that condenses the laser beam exiting from at least the electro-optical element 21 and has different condensing rates along the electric field direction of the electro-optical element 21, and the optical system varying a beam diameter of the laser beam. <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 of the image signal is determined based on CRT (Cathode Ray Tube), after scanning from left to right, it returns to the left in a short time, and the format is adapted to scan again to the right (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.

  In the EO scanner, electrons are injected by applying a voltage to the EO crystal, and the electron distribution is biased. For this reason, a distribution also occurs in the refractive index change due to the Kerr effect, and the incident light is bent to the higher refractive index side, thereby enabling light scanning. Further, since the gradient of the refractive index distribution inside the EO crystal depends on the electron injection amount, that is, the applied voltage, the scan angle of light emitted from the EO crystal can be controlled by changing the applied voltage.

  However, since the EO scanner 100 is a scanner that utilizes the refraction of light, as shown in FIG. 7, the light emitted from the EO crystal when a predetermined voltage is applied is slightly higher on the higher refractive index side. In addition, since the refractive index is large, the scan angle becomes large. As a result, the beam diameter C2 of the light emitted from the EO crystal 101 when a voltage is applied is larger than the beam diameter C1 of the light emitted from the EO crystal 101 when no voltage is applied. In addition, as the applied voltage is increased, the scan angle of light emitted from the EO crystal 101 becomes larger, and the beam diameter C3 becomes larger than the beam diameter C2. When such a scanner is used for a display device, the pixels become larger toward the end of the projection surface.

  For example, when a crystal having a Kerr effect is used as the EO crystal, as shown in FIG. 8, when looking at the luminous flux when a predetermined voltage is applied to the EO crystal, the light traveling inside the EO crystal 101 is reflected. The scan angle θ1 of the light beam at the upper end 102 is 2.95 degrees, the scan angle θ2 of the light beam at the center (optical axis) 103 is 5.96 degrees, and the scan angle θ3 of the light beam at the lower end 104 is 8.92 degrees. is there. That is, since the scan angle increases toward the light beam having the higher refractive index (lower end 104), the beam diameter of the laser light emitted when a voltage is applied to the EO crystal is increased. When a crystal having the Pockels effect is used as the EO crystal, the scan angle of light on the side having a higher refractive index becomes the largest, although not as much as the EO crystal having the Kerr effect. As a result, similarly, the beam diameter of the laser beam emitted when a voltage is applied to the EO crystal is increased.

  SUMMARY An advantage of some aspects of the invention is that it provides a scanning optical device capable of scanning a laser beam with high accuracy with a simple configuration.

In order to achieve the above object, the present invention provides the following means.
The scanning optical device of the present invention includes a light source device that emits laser light and a laser light emitted from the light source device by changing a refractive index distribution according to the magnitude of an electric field generated inside. The laser having a condensing element that condenses at least laser light emitted from the electro-optical element and has a condensing rate along an electric field direction of the electro-optical element And a variable diameter optical system that varies the beam diameter of the light.

In the scanning optical device according to the present invention, an electric field is generated inside by applying a voltage to the electro-optical element. By this electric field, the refractive index distribution of the electro-optic element continuously increases or decreases in one direction. For this reason, the laser 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 emitted from the emission end face of the electro-optic element. Then, the laser light emitted from the electro-optical element passes through the beam diameter variable optical system.
At this time, the beam diameter of the laser light emitted through the electro-optical element when no voltage is applied is different from the beam diameter of the laser light emitted through the electro-optical element when the voltage is applied. Also, when the voltage applied to the electro-optic element is changed, the beam diameter of the emitted light varies depending on the value of the applied voltage. Here, the beam diameter of the laser beam emitted from the electro-optical element is condensed by the condensing element of the beam diameter variable optical system. That is, even when a voltage is applied to the electro-optic element and the beam diameter of the light emitted from the electro-optic element is increased, the light emitted from the electro-optic element is condensed along the electric field direction of the electro-optic element. The light is condensed by condensing elements having different rates, and the beam diameter is reduced. As a result, even when a voltage is applied to the electro-optical element, it is possible to scan light having the same beam diameter (a constant size), and thus it is possible to perform highly accurate laser beam scanning.

In the scanning optical device according to the aspect of the invention, it is preferable that the beam diameter variable optical system condenses the laser light so that the beam diameter of the laser light at a predetermined distance is constant by the condensing element.
In the scanning optical device according to the present invention, the laser light emitted from the electro-optical element is made constant by a condensing element of the beam diameter variable optical system, for example, the beam diameter of the laser light on the screen is constant. It is condensed so that it becomes. In this way, by performing the optical design of the condensing element, it becomes possible to scan the same size beam diameter at a predetermined position.

In the scanning optical device according to the present invention, it is preferable that the beam diameter variable optical system includes a collimating unit that collimates the laser beam condensed by the condensing element.
In the scanning optical device according to the present invention, the light emitted from the electro-optical element and condensed by the condensing element becomes parallel light by the collimating means. In other words, light having a constant beam diameter can be scanned toward the projection surface regardless of the distance between the projection surface to which the laser light emitted from the electro-optic element is projected and the electro-optic element. .

  The scanning optical apparatus of the present invention is preferably provided with a moving mechanism for moving the variable beam diameter optical system in parallel with the optical axis of the variable beam diameter optical system.

  In the scanning optical apparatus according to the present invention, when the distance between the electro-optical element and the projection surface changes, the beam diameter variable optical system is moved in parallel with the optical axis of the beam diameter variable optical system by the moving mechanism. . Thereby, the laser light emitted from the electro-optical element is condensed by the beam diameter variable optical system so that the beam diameter of the laser light becomes the same on the projection surface. Therefore, a laser beam having a fixed beam diameter can be scanned toward the projection surface. For example, when the scanning optical device of the present invention is used as an image display device, a high-quality image is received. It can be displayed on the projection surface.

  In the scanning optical device according to the aspect of the invention, the variable beam diameter optical system may be configured such that the scanning distance on the projection surface per unit time of the light emitted from the electro-optic element is emitted from the electro-optic element. It is preferable to focus the laser beam so that it is constant regardless of the deflection angle of the light.

  In the scanning optical device according to the present invention, the light emitted from the electro-optical element is scanned by the beam diameter variable optical system so that the scanning distance on the projection surface per unit time becomes the same. Thereby, the laser light emitted from the electro-optical element is scanned at a constant speed on the projection surface. Therefore, in the present invention, particularly when a scanning optical device is used as an image display device, image distortion on the projection surface that occurs when scanning at a non-constant speed does not occur. Therefore, a high quality image can be displayed on the projection surface.

  In the scanning optical device according to the aspect of the invention, it is preferable that the electro-optical element performs horizontal scanning.

In the scanning optical device according to the present invention, an inexpensive and high-performance scanning optical device can be realized by using an electro-optic element for horizontal scanning and using, for example, an inexpensive galvanometer mirror as vertical scanning.
Here, “horizontal scanning” refers to high-speed scanning in two directions, and vertical scanning refers to low-speed scanning.

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.

As shown in FIG. 1, the optical scanning unit 20 includes an electro-optic element 21 to which the laser beam emitted from the light source device 11 is incident and a beam diameter to which the light emitted from the emission end face 21 b of the electro-optic element 21 is incident. And a variable optical system 25.
First, the configuration of the electro-optic element will be described.
The 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. The electrode 22, the second electrode 23, and the 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 the arrow P). As a result, the refractive index of the electro-optic crystal increases from the first electrode 22 toward the second electrode 23.

Further, as shown in FIG. 1, the optical element 24 is arranged so that laser light is incident from the side near the first electrode 22 of the incident end face 21 a of the electro-optical element 21. As a result, the 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 on the second electrode 23 side due to the refractive index distribution of the electro-optical element 21, by making the laser light incident from the first electrode 22 side of the optical element 24, The scan range can be increased.
Further, the electro-optical element 21 is arranged so that the laser light L emitted from the light source device 11 is incident on the incident end face 21a perpendicularly.

Next, the operation of the 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, as shown in FIG. 1, 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 P generated inside the optical element 24 is deflected. Specifically, the laser light L incident from the incident end face 21a of the 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 L0 emitted from the light source device 11 and traveling through the optical element 24 travels straight, and the emission end face of the electro-optic element 21 Injected from 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 L 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 electro-optic element 21 is scanned in the same direction as the electric field direction P in the scan range.
Note that the initial value 0 V and the maximum voltage value +100 V, which are values of the applied voltage applied to the electro-optical element 21, are merely examples, and the magnitude of the deflection angle of the light emitted from the electro-optical element 21 and the optical element 24 It can be appropriately changed depending on the thickness.

Next, the variable beam diameter optical system will be described with reference to FIG.
Note that FIG. 1 illustrates a case where no voltage is applied and a case where a specific voltage is applied, in order to easily understand an optical path diagram of light emitted from the electro-optical element 21 and directed to the screen (projected surface) 15. Only the optical path of the light is shown.
As shown in FIG. 1, the beam diameter variable optical system 25 includes a condensing lens (condensing element) 26. The condensing lens 26 is a lens whose cross-sectional shape when cut along the electric field direction A gradually decreases in radius of curvature from the first electrode 22 side toward the second electrode 23 side. The condensing lens 26 condenses the laser light emitted from the exit end face 21b of the electro-optic element 21, and also has a different condensing rate along the electric field direction A, so that the beam diameter of the laser light is changed. It is possible to make it. Specifically, the condensing lens 26 condenses so that the spot diameter of the laser light L becomes the same diameter on the screen 15 when a voltage is applied to the optical element 24.

By the way, the laser beam L when a predetermined voltage is applied to the optical element 24 is slightly lower on the lower end L2 side (second electrode 23 side) than on the upper end L1 side (first electrode 22 side). The refractive index is large. Thereby, the beam diameter B1 of the laser beam L when the voltage is applied is larger than the beam diameter A of the laser beam L0 emitted from the electro-optical element 21 when no voltage is applied to the optical element 24. growing.
Here, since the laser light L emitted from the emission end face 21b of the electro-optic element 21 is condensed by passing through the condenser lens 26, the spot diameter (beam diameter) B2 of the laser light L on the screen 15 is set. The beam size is the same as the beam diameter A.
In other words, the laser light emitted from the electro-optic element 21 is condensed by the condenser lens 26 so that the spot diameter of the laser light is the same regardless of the position on the emission end face 21b. The
The spot diameter of the laser light in the direction orthogonal to the direction in which the laser light travels and the spot diameter of the laser light on the screen 15 (laser light in the surface direction of the screen 15) are strictly different. However, since the beam diameter of the laser light is very small, it can be considered that the spot diameters of both are substantially equal. Further, the laser beam may be condensed so that the spot diameter of the laser beam in the direction orthogonal to the traveling direction is slightly reduced so as to correct the minute difference.

In the scanning optical device 1 according to the present embodiment, when the beam diameter variable optical system 25 is provided, a voltage is applied to the electro-optical element 21 and the beam diameter of light emitted from the electro-optical element 21 is increased. The laser light L emitted from the electro-optical element 21 is condensed and the beam diameter is reduced. Therefore, the spot diameter of the laser light is the same at any position on the screen 15. As a result, even when a voltage is applied to the electro-optical element 21, it is possible to scan the laser beam having the same beam diameter (constant size). Can be used, a high-quality image with little blur can be displayed on the screen 15.
That is, the scanning optical device 1 according to the present embodiment can scan a laser beam with high accuracy with a simple configuration.
The number and shape of the lenses constituting the beam diameter variable optical system 25 are not limited to those shown in the condenser lens 26.

[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 differs from the first embodiment in the configuration of the beam diameter variable optical system 31.

The beam diameter variable optical system 31 includes a condensing lens (condensing element) 32 and a collimating lens (collimating means) 33. Similar to the condensing lens 26 of the first embodiment, the condensing lens 32 is a lens that condenses the laser light emitted from the emission end surface 21 b of the electro-optic element 21 and changes the beam diameter of the laser light.
The collimating lens 33 is a lens that is disposed on the rear side of the condenser lens 32 and converts the laser light collected by the condenser lens 32 into parallel light. Further, the collimating lens 33 is a lens that emits the laser light condensed at any position of the condenser lens 32 as parallel light having the same beam diameter.

  In the scanning optical device 30 according to the present embodiment, the same effects as the scanning optical device 1 of the first embodiment can be obtained. Further, in the scanning optical device 30 of the present embodiment, the collimating lens 33 converts the laser light emitted from the electro-optic element 21 into parallel light and the same beam diameter. Accordingly, regardless of the distance between the electro-optic element 21 and the screen 15, a beam having a certain size can be scanned toward the screen 15. That is, for example, it can be suitably used for a front type projector in which the position of the screen 15 changes.

[Modification of Second Embodiment]
In the second embodiment shown in FIG. 3, the collimating lens 33 is used as a means for making the spot diameters of the laser beams on the screen 15 the same. The scanning optical device 35 may be provided. The moving mechanism 36 moves the condenser lens 32 in parallel to the optical axis O1 of the beam diameter variable optical system.
For example, as shown in FIG. 4, when the screen 15a moves to the position of the screen 15b in a direction away from the electro-optical element 21, the screen 15b is emitted from the electro-optical element 21 and collected by the condenser lens 32a. The spot diameter of the laser light (broken line) is smaller than the beam diameter A of the laser light L0 emitted from the electro-optical element 21 when no voltage is applied to the optical element 24. Therefore, the moving mechanism 36 moves the condensing lens 32a to the position of the condensing lens 32b in a direction away from the electro-optic element 21. Thereby, the spot diameter B3 of the laser light emitted from the electro-optic element 21 can be made the same as the beam diameter A at the position of the screen 15b.
Note that the moving mechanism 36 of the present modification may be used in the scanning optical device 30 of the second embodiment to move the whole or part of the beam diameter variable optical system 31. In this configuration, the whole or part of the beam diameter variable optical system 31 is moved by the moving mechanism 36, whereby the spot diameter on the screen 15 can be uniformly increased or decreased uniformly.

[Third Embodiment]
The beam diameter variable optical system 41 includes a condenser lens 42 and a collimating lens 43 as shown in FIG. The beam diameter variable optical system 41 deflects the laser beam emitted from the second electrode 23 side so that the refraction angle becomes larger. Thus, the laser beam scanning distance on the screen 15 per unit time is corrected to be the same.

  The beam diameter variable optical system 41 includes a condenser lens 42 and a collimating lens 43 as shown in FIG. The beam diameter variable optical system 41 deflects the laser beam emitted from the second electrode 23 side so that the refraction angle becomes larger. Thus, the laser beam scanning distance on the screen 15 per unit time is corrected to be the same.

The beam diameter variable optical system 41 will be specifically described.
Of the light emitted from the electro-optic element 21, laser light emitted from the electro-optic element 21 at time T1 immediately before the voltage is applied to the optical element 24 is denoted by reference symbol LT1.
For example, the laser beam emitted from the electro-optical element 21 at time T2 after the elapse of time t from time T1 is denoted by reference symbol LT2. Further, the laser beam emitted from the electro-optic element 21 at time T3 after time t has elapsed from time T2 is denoted by reference symbol LT3.
Here, the scanning distance between the pixel region P1 irradiated with the laser beam LT1 on the screen 15 and the pixel region P2 irradiated with the laser beam LT2 is defined as Q1. Further, the scanning distance between the pixel region P2 irradiated with the laser beam LT2 on the screen 15 and the pixel region P3 irradiated with the laser beam LT3 is defined as Q2.

By the way, if the scanning optical device 40 does not include the beam diameter variable optical system 41, the deflection angle of the laser light emitted from the electro-optical element 21 increases as the second electrode 23 is approached. As a result, the speed of the laser beam that scans one end on the screen 15 becomes faster, and the image projected on the screen 15 is distorted.
Therefore, in the present embodiment, the beam diameter variable optical system 41 corrects the scanning distance of the laser beam on the screen 15 per unit time to be the same, so that the refractive index inside the optical element 24 changes from the exit end face 21b. Even if the deviation angles of the emitted laser light are different, the laser light emitted from the electro-optic element 21 is corrected so that the scanning distance Q1 and the scanning distance Q2 are the same distance. As a result, the laser light emitted from the electro-optical element 21 is scanned on the screen 15 at a constant speed.

The scanning optical device 40 according to the present embodiment can obtain the same effects as the image display device 1 of the first embodiment. Furthermore, in the scanning optical device 40 of the present embodiment, the laser light emitted from the electro-optical element 21 is scanned on the screen 15 at a constant speed. That is, the laser beam emitted from the exit end face 21b close to the second electrode 23 has a larger declination, so that the scanning speed of the laser beam applied to the screen 15 is increased, but the beam diameter variable optical system 41 of the present embodiment. By using, image distortion on the screen 15 that occurs when scanning is performed at non-uniform speed does not occur. Therefore, a high quality image can be displayed.
The number and shape of the lenses constituting the beam diameter variable optical system 41 are not limited to those shown in the condenser lens 42 and the collimating lens 43.

[Fourth Embodiment]
Next, a fourth embodiment according to the present invention will be described with reference to FIG.
In the first embodiment, a scanning optical device using a monochromatic light source device is used. However, the scanning optical device 50 according to the present embodiment uses three color light source devices to project an image on a screen. It is a display device. The optical scanning unit 20 used in this embodiment has the same configuration as that of the first embodiment.

  As shown in FIG. 6, the image display device 50 according to the present embodiment includes a red light source device (light source device) 50R that emits red laser light and a green light source device (light source device) 50G that emits green laser light. A blue light source device (light source device) 50B for emitting blue laser light, a cross dichroic prism 51, an electro-optical element 21 for scanning the laser light emitted from the cross dichroic prism 51 in the horizontal direction of the screen 55, A galvanometer mirror 52 that scans the laser beam emitted from the electro-optic element 21 in the vertical direction of the screen 55 is provided.

That is, as shown in FIG. 1, the optical scanning unit 20 in the horizontal direction scans light emitted from the light source devices 50R, 50G, and 50B among the scanning in the two directions (vertical direction v and horizontal direction h) on the screen 55. The galvano mirror 52 is a vertical scanning scanner that scans light emitted from the optical scanning unit 20 in the vertical direction v.
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.

Next, a method of projecting an image on the screen 55 using the image display device 50 of the present embodiment having the above configuration will be described.
The laser beams emitted from the light source devices 50R, 50G, and 50B are combined by the cross dichroic prism 51 so that the lasers of the respective colors overlap on the illumination optical axis and enter the electro-optical element 21. Laser light incident from the incident end face 21 a of the electro-optic element 21 is emitted from the emission end face 21 b toward the galvanometer mirror 52. In this way, the laser light is scanned in the horizontal direction of the screen 55 by the electro-optic element 21, scanned in the vertical direction by the galvanometer mirror 52, and projected onto the screen 55.

  In the image display device 50 according to the present embodiment, the same effects as those of the scanning optical device 1 of the first embodiment can be obtained. Furthermore, in the image display device 50 of the present embodiment, the spot diameter of the laser light emitted from the electro-optic element 21 is the same on the screen 55, so that all pixels in the image projected on the screen 15 have the same size. It can be displayed. Therefore, for example, blur can be suppressed and an image can be displayed more clearly on the screen 55 without causing deterioration in image quality.

In addition, since the scanning unit composed of the electro-optic element 21 can scan faster than the MEMS scanner, as in this embodiment, the electro-optic scanner is used for horizontal scanning, and the galvanometer mirror is used for vertical scanning with a high degree of scanning freedom. By using 52 (movable scanning means that reflects light by moving), it is possible to realize a high-performance image display device.
In place of the galvanometer mirror 52, scanning may be performed by an inexpensive polygon mirror which is one of movable scanning means. By using an inexpensive polygon mirror, it is possible to perform high-performance image display while reducing costs.
Further, in the image display device 50 of the present embodiment, the beam diameter variable optical system 25 of the first embodiment has been described. However, the beam diameter variable optical system 31 of the second and third embodiments (including modifications). , 41 can also be used.
Although the image display apparatus has been described as the scanning optical apparatus, the scanning optical apparatus according to the first to third embodiments (including modifications) can be applied to a laser printer.

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, in each of the above-described embodiments, the optical element has been described by taking a KTN crystal as an example. However, the present invention is not limited to this, and any element whose refractive index changes linearly may be used. For example, a dielectric crystal having an electro-optic effect such as LiNbO ₃ (lithium niobate) may be used, but a crystal having a composition such as LiNbO ₃ has a smaller scanning deflection angle than a KTN crystal, and driving Since the voltage is high, it is preferable to use a KTN crystal.

1 is a plan view showing a schematic configuration of a scanning optical device according to a first embodiment of the present invention. It is a figure which shows the waveform of the voltage applied to the electrode of the electro-optical element of the scanning optical apparatus which concerns on 1st Embodiment of this invention. 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 the modification 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. It is a perspective view which shows the scanning optical apparatus which concerns on 4th Embodiment of this invention. It is a top view which shows the conventional scanning optical apparatus. It is a top view which shows the conventional scanning optical apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,30,35,40 ... Scanning optical apparatus, 11 ... Light source device, 15 ... Screen (projection surface), 21 ... Electro-optical element, 25, 31, 41 ... Beam diameter variable optical system, 26, 32 ... Collection Optical lens (light condensing element), 33... Parallelizing lens (parallelizing means), 36... Moving mechanism, 50... Image display device (scanning optical device), 50 R. Red light source device (light source device), 50 G. Device (light source device), 50B ... Red light source device (light source device)

Claims (7)

A light source device for emitting laser light;
An electro-optic element that scans laser light emitted from the light source device toward a projection surface by changing a refractive index distribution according to the magnitude of an electric field generated inside;
Variable beam diameter for condensing at least laser light emitted from the electro-optical element and having a condensing element having a different condensing rate along the electric field direction of the electro-optical element. A scanning optical apparatus comprising: an optical system.   2. The scanning type according to claim 1, wherein the beam diameter variable optical system condenses the laser light by the condensing element so that the beam diameter of the laser light at a predetermined distance is constant. Optical device.   The scanning optical apparatus according to claim 1, wherein the beam diameter variable optical system includes a collimating unit that collimates the laser beam condensed by the condensing element.   3. A scanning optical apparatus according to claim 1, further comprising a moving mechanism for moving the beam diameter variable optical system in parallel with the optical axis of the beam diameter variable optical system.   The beam diameter variable optical system is configured such that the scanning distance on the projection surface per unit time of the light emitted from the electro-optic element is constant regardless of the deflection angle of the laser light emitted from the electro-optic element. The scanning optical apparatus according to claim 1, wherein the laser beam is condensed on the scanning optical device.   The scanning optical apparatus according to claim 1, wherein the electro-optical element performs horizontal scanning. The scanning optical apparatus according to claim 1, wherein the electro-optical element has a composition of KTa _1-x Nb _x O ₃ .

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