JP2016071260A - Optical modulator and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical modulator that has high use efficiency of light and can separately modulate light at a wavelength in a plurality of different wavelengths, and an image display device that includes the optical modulator and can display a high-quality image.SOLUTION: An optical modulator 30 includes: a main optical waveguide 302 (first optical waveguide) made of a material having an electro-optic effect; a wavelength selection unit 303 disposed in the main optical waveguide 302 and selecting a wavelength of light to be guided; and an optical modulation unit 304 disposed in the main optical waveguide 302 and modulating intensity of the light at the wavelength selected by the wavelength selection unit 303. The wavelength selection unit 303 includes: a first ring resonator 303R having a first annular optical waveguide optically coupled with the main optical waveguide 302; a second ring resonator 303G having a second annular optical waveguide optically coupled with the main optical waveguide 302; and a third ring resonator 303B having a third annular optical waveguide optically coupled with the main optical waveguide 302.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an optical modulator and an image display device.

  As one of the image display technologies of a head mounted display (HMD) and a head-up display (HUD), a display device that irradiates a laser directly on the retina of an eye and visually recognizes an image has recently attracted attention.

  Such a display device generally includes a light emitting device that emits light and a scanning unit that changes an optical path so that the emitted light scans the retina of the user. According to such a display device, the user can visually recognize both, for example, an outside scenery and an image drawn by the scanning unit at the same time.

  Patent Document 1 discloses a Mach-Zehnder interferometer that can sequentially enter a plurality of light beams having different wavelengths and modulate the intensity for each wavelength. In such an interferometer, the bias voltage is variably controlled so that the emitted light intensity falls within a predetermined allowable range for each wavelength. For this reason, even when light of a plurality of different wavelengths is sequentially incident on one interferometer, it is possible to prevent the modulation characteristics from being shifted for each wavelength.

  In Patent Document 2, a light source, a light beam combiner, a beam scanner operable to scan the light beam in a two-dimensional pattern, and the scanned light beam are received and moved from the output position to the visible region. An image generator (head-up display) is disclosed that includes a guide substrate configured to fire. Further, it is disclosed that a DPSS laser using external modulation such as an acousto-optic modulator (AOM) is employed as a light source (paragraph 0026 of Patent Document 1). An arbitrary image is displayed on the retina by modulating the output of the laser light respectively emitted from the red laser light source, the blue laser light source, and the green laser light source.

JP 2012-022233 A Special table 2009-516862 gazette

  By the way, in the Mach-Zehnder interferometer described in Patent Document 1, it is disclosed to use a light source having a structure for selectively emitting emitted light for each wavelength in a light source for making light incident on the Mach-Zehnder interferometer. ing. By using such a light source, exclusive intensity modulation can be performed on the time axis for each wavelength.

  Patent Document 1 discloses a light source having a structure that selectively emits emitted light for each wavelength. Examples of such a light source include a plurality of fixed wavelength light sources having different wavelengths, and these light sources. And an optical switch that selectively transmits the light emitted from the light source so as not to overlap each other on the time axis. In such a light source, a high degree of alignment accuracy is required for connection between a plurality of fixed wavelength light sources and an optical switch. For this reason, many difficulties are involved in manufacturing a display device including a light source, a wavelength selection unit such as an optical switch, and an intensity modulation unit such as a Mach-Zehnder interferometer. Further, when a modulator is formed by a plurality of different optical components, there is a risk that the loss at each optically connected portion is a product and the overall efficiency is greatly reduced. Furthermore, since it is easy for misalignment to occur, it is considered that light loss is likely to occur. For this reason, when such a modulator is used in a display device, there is a risk of causing an increase in power consumption if the light amount of the display image is insufficient or if the output of the light source is increased to compensate for the insufficient light amount. There is.

  Further, in order to form a high-quality image in the above-described display device, it is necessary to switch wavelengths at an extremely high speed. However, at present, since the speed of switching the wavelength of the emitted light is not sufficient in the light source, there is a problem that it is difficult to form a high-quality image because the wavelength switching cannot catch up with the light scanning speed.

  An object of the present invention is to provide an optical modulator that has a high light utilization efficiency and can be modulated for a plurality of different wavelengths, and an image display device that includes such an optical modulator and can display a high-quality image.

Such an object is achieved by the present invention described below.
The optical modulator of the present invention includes a first optical waveguide made of a material having an electro-optic effect,
A wavelength selection unit that is provided in the first optical waveguide and selects a wavelength of light guided through the first optical waveguide;
A light modulation unit that is provided in the first optical waveguide and modulates the intensity of light having a wavelength selected by the wavelength selection unit;
With
The wavelength selector is
An optical waveguide having an annular shape made of a material having an electro-optic effect, the first annular optical waveguide optically coupled to the first optical waveguide, and a first voltage applied to the first annular optical waveguide. A first ring resonator having a first voltage application unit to be applied;
An optical waveguide having an annular shape made of a material having an electro-optic effect, the second annular optical waveguide being optically coupled to the first optical waveguide, and the first voltage applied to the second annular optical waveguide. A second ring resonator having a second voltage application unit for applying a second voltage different from
It is characterized by including.

  Accordingly, the wavelength selection unit is configured in the first optical waveguide, and the optical modulation unit is also provided in the first optical waveguide. Therefore, an optical connection portion is provided between the wavelength selection unit and the optical modulation unit. There is no need. As a result, alignment that strictly considers the optical path length is not required, and no connection point is provided, so that it is difficult for light loss to occur, so that the light utilization efficiency of the optical modulator is increased. In addition, a first ring resonator and a second ring resonator are provided, and the first voltage and the second voltage are appropriately set, so that the wavelength selection unit guides the first optical waveguide. Since the wavelength of light can be easily selected, an optical modulator capable of modulating a plurality of lights having different wavelengths can be obtained.

The optical modulator of the present invention includes a first optical waveguide made of a material having an electro-optic effect,
A wavelength selection unit that is provided in the first optical waveguide and selects a wavelength of light guided through the first optical waveguide;
A light modulation unit that is provided in the first optical waveguide and modulates the intensity of light having a wavelength selected by the wavelength selection unit;
With
The wavelength selector is
An optical waveguide having an annular shape made of a material having an electro-optic effect, a first annular optical waveguide optically coupled to the first optical waveguide, and a voltage applied to the first annular optical waveguide. A first ring resonator having one voltage application unit;
An annular optical waveguide made of a material having an electro-optic effect, optically coupled to the first optical waveguide, and having a circumference different from the circumference of the first annular optical waveguide A second ring resonator having two annular optical waveguides, and a second voltage applying unit that applies a voltage to the second annular optical waveguide;
It is characterized by including.

  Accordingly, the wavelength selection unit is configured in the first optical waveguide, and the optical modulation unit is also provided in the first optical waveguide. Therefore, an optical connection portion is provided between the wavelength selection unit and the optical modulation unit. There is no need. As a result, alignment that strictly considers the optical path length is not required, and no connection point is provided, so that it is difficult for light loss to occur, so that the light utilization efficiency of the optical modulator is increased. In addition, since the first ring resonator and the second ring resonator are provided, the wavelength of the light guided through the first optical waveguide can be easily selected by the wavelength selection unit. An optical modulator capable of modulating a plurality of lights is obtained.

  In the optical modulator according to the aspect of the invention, it is preferable that the first optical waveguide has a light incident portion on which light is incident.

  Thereby, since the wavelength of the light incident on the first optical waveguide can be selected by the wavelength selection unit, the intensity of light having different wavelengths can be individually and accurately modulated by the light modulation unit.

  In the optical modulator of the present invention, the first optical waveguide joins the plurality of light incident portions, the plurality of branch optical waveguides connected to the plurality of light incident portions, and the plurality of branch optical waveguides. And a multiplexing unit.

  As a result, since the multiplexing unit, the wavelength selection unit, and the light modulation unit are provided on the same member, the optical modulator can be reduced in size as compared with the case where these portions are configured by different members. Figured. Moreover, since the optical coupling loss between each part can be reduced, the internal loss of the optical modulator can be suppressed.

In the optical modulator of the present invention, the first ring resonator is further optically coupled to the first annular optical waveguide, and further includes a first coupling light having a light incident portion on which light is incident. Having a waveguide,
The second ring resonator preferably further includes a second coupled optical waveguide that is optically coupled to the second annular optical waveguide and includes a light incident portion on which light is incident.

  As a result, when the light incident on the first coupled optical waveguide satisfies the resonance condition of the first annular optical waveguide, it is output to the first optical waveguide and the light incident on the second coupled optical waveguide is When the resonance condition of the two annular optical waveguides is satisfied, the light is output to the first optical waveguide. Thereby, since the light resonated in each annular optical waveguide can be output, light with high monochromaticity can be output.

  In the optical modulator according to the aspect of the invention, it is preferable that the second ring resonator includes a plurality of the second annular optical waveguides coupled to each other.

  As a result, the light is output to the first optical waveguide while sequentially resonating with the plurality of second annular optical waveguides coupled to each other, so that the wavelength selectivity in the wavelength selection unit is increased.

  In the optical modulator according to the aspect of the invention, it is preferable that the material having the electro-optic effect is lithium niobate.

  Since lithium niobate has a relatively large electro-optic coefficient, when selecting the wavelength of light transmitted through the wavelength selection section, the driving voltage can be lowered or the circumference of the annular optical waveguide can be shortened. The drive voltage can also be lowered when the light intensity is modulated in the light modulator. For this reason, the power consumption of the optical modulator can be reduced. Furthermore, since the area required for the wavelength selection unit and the light modulation unit to perform their functions can be reduced, the size of the light modulator can be reduced.

In the optical modulator according to the aspect of the invention, it is preferable that the optical modulation unit is a Mach-Zehnder type optical modulation unit.
As a result, the modulation at high speed becomes possible, so that the image quality of the displayed image is improved.

The optical modulator of the present invention includes a first optical waveguide made of a material having an electro-optic effect,
A wavelength selection unit that is provided in the first optical waveguide and selects a wavelength of light guided through the first optical waveguide;
A light modulation unit that is provided in the first optical waveguide and modulates the intensity of light having a wavelength selected by the wavelength selection unit;
With
The wavelength selector is
An optical waveguide having an annular shape made of a material having an electro-optic effect, having a first annular optical waveguide optically coupled to the first optical waveguide, and light having a first resonance wavelength A first ring resonator capable of resonating;
An annular optical waveguide made of a material having an electro-optic effect, and having a second annular optical waveguide optically coupled to the first optical waveguide, and different from the first resonance wavelength A second ring resonator capable of resonating light of a second resonance wavelength;
It is characterized by including.

  Accordingly, the wavelength selection unit is configured in the first optical waveguide, and the optical modulation unit is also provided in the first optical waveguide. Therefore, an optical connection portion is provided between the wavelength selection unit and the optical modulation unit. There is no need. As a result, alignment that strictly considers the optical path length is not required, and no connection point is provided, so that it is difficult for light loss to occur, so that the light utilization efficiency of the optical modulator is increased. In addition, a first ring resonator and a second ring resonator are provided, and the first voltage and the second voltage are appropriately set, so that the wavelength selection unit guides the first optical waveguide. Since the wavelength of light can be easily selected, an optical modulator capable of modulating a plurality of lights having different wavelengths can be obtained.

An image display device of the present invention includes a light source unit that emits a plurality of lights having different wavelengths from each other,
The light modulator of the present invention on which the light emitted from the light source unit is incident;
An optical scanner that spatially scans the light modulated by the light modulator;
It is characterized by providing.
Thereby, an image display device capable of displaying a high-quality image is obtained.

In the image display device of the present invention, in the first time zone, the wavelength selection unit is driven so that the light of the first selected wavelength is selected, and the intensity of the light of the first selected wavelength is modulated. The light modulator is driven so that
In the second time zone different from the first time zone, the wavelength selection unit is driven so that light having a second selection wavelength different from the first selection wavelength is selected, and the second The light modulator is driven to modulate the intensity of the light of the selected wavelength;
When transitioning from the first time zone to the second time zone, in the time zone between the first time zone and the second time zone, the light of the first selected wavelength and the first time zone It is preferable that the wavelength selection unit is driven so as not to select both of the light having the two selection wavelengths.

  As a result, the light modulator can intensity-modulate light having different wavelengths in a time-sharing manner, so that accurate intensity modulation can be performed. Further, in the time zone between the first time zone and the second time zone, both the light of the first wavelength and the light of the second wavelength are not transmitted through the wavelength selector, so the first time zone And the second time zone are prevented from overlapping. As a result, it is possible to prevent the image quality of the image displayed by the image display device from being deteriorated.

The image display device of the present invention further includes a reflective optical unit that reflects the light scanned by the optical scanner,
The reflection optical unit preferably includes a hologram diffraction grating.

  Thereby, the emission direction of the light reflected by the reflective optical unit can be adjusted, and the wavelength of the reflected light can be selected.

It is a figure which shows schematic structure of 1st Embodiment (head mounted display) of the image display apparatus of this invention. It is the elements on larger scale of the image display apparatus shown in FIG. It is a schematic block diagram of the signal generation part of the image display apparatus shown in FIG. It is a figure which shows schematic structure of the optical scanning part contained in the scanning light emission part shown in FIG. It is a figure for demonstrating typically the effect | action of the image display apparatus shown in FIG. It is a perspective view which shows schematic structure of the optical modulator shown in FIG. 3 (1st Embodiment of the optical modulator of this invention). FIG. 7 is a plan view of the optical modulator shown in FIG. 6. It is the elements on larger scale of the wavelength selection part shown in FIG. It is a figure for demonstrating operation | movement of the wavelength selection part shown in FIG. An example of a time transition (timing chart) of a voltage application pattern for driving the first ring resonator, the second ring resonator, and the third ring resonator, and at that time, emitted from the wavelength selection unit It is a figure which shows the color of light. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 2nd Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 2nd Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 3rd Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 3rd Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 4th Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 4th Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 4th Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 4th Embodiment. It is the elements on larger scale of the wavelength selection part contained in the optical modulator which concerns on 5th Embodiment. It is a figure which shows 6th Embodiment (head up display) of the image display apparatus of this invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical modulator and an image display device according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

<Image display device>
<< First Embodiment >>
First, a first embodiment of an image display device of the present invention and a first embodiment of an optical modulator of the present invention will be described.

  FIG. 1 is a diagram showing a schematic configuration of a first embodiment (head mounted display) of an image display device of the present invention, and FIG. 2 is a partially enlarged view of the image display device shown in FIG. 3 is a schematic configuration diagram of a signal generation unit of the image display apparatus shown in FIG. 1, FIG. 4 is a diagram showing a schematic configuration of an optical scanning unit included in the scanning light emitting unit shown in FIG. 1, and FIG. FIG. 2 is a diagram for schematically explaining the operation of the image display device shown in FIG. 1. 6 is a perspective view showing a schematic configuration of the optical modulator shown in FIG. 3 (first embodiment of the optical modulator of the present invention), and FIG. 7 is a plan view of the optical modulator shown in FIG. . In FIGS. 6 and 7, the wiring is not shown.

  In FIG. 1, for convenience of explanation, the X axis, the Y axis, and the Z axis are illustrated as three axes orthogonal to each other, and the distal end side of the illustrated arrow is “+ (plus)”, and the proximal end side Is “− (minus)”. A direction parallel to the X axis is referred to as “X axis direction”, a direction parallel to the Y axis is referred to as “Y axis direction”, and a direction parallel to the Z axis is referred to as “Z axis direction”.

  Here, the X-axis, Y-axis, and Z-axis indicate that the Y-axis direction is the vertical direction of the head H and the Z-axis direction is the head H when the later-described image display device 1 is mounted on the user's head H. The left-right direction and the X-axis direction are set to be the front-rear direction of the head H.

  As shown in FIG. 1, an image display device 1 according to the present embodiment is a head-mounted display (head-mounted image display device) having an appearance like glasses, and is mounted on a user's head H. Used to allow the user to visually recognize an image of a virtual image superimposed on an external image.

  As shown in FIG. 1, the image display device 1 includes a frame 2, a signal generation unit 3, a scanning light emitting unit 4, and a reflection unit 6.

  Moreover, the image display apparatus 1 is provided with the 1st optical fiber 71, the 2nd optical fiber 72, and the connection part 5, as shown in FIG.

  In the image display device 1, the signal generation unit 3 generates signal light modulated according to image information, and the signal light is transmitted through the first optical fiber 71, the connection unit 5, and the second optical fiber 72. 4, the scanning light emitting unit 4 scans the signal light (video light) two-dimensionally to emit scanning light, and the reflecting unit 6 reflects the scanning light toward the user's eye EY. Thereby, a user can visually recognize the virtual image according to image information.

  In the present embodiment, the signal generation unit 3, the scanning light emission unit 4, the connection unit 5, the reflection unit 6, the first optical fiber 71, and the second optical fiber 72 are provided only on the right side of the frame 2, and only the virtual image for the right eye is provided. However, by configuring the left side of the frame 2 in the same way as the right side, a virtual image for the left eye may be formed together with the virtual image for the right eye, Only a virtual image may be formed.

  Further, the means for optically connecting the signal generating unit 3 and the scanning light emitting unit 4 can be replaced with, for example, means via various light guides in addition to means via an optical fiber. Further, the first optical fiber 71 and the second optical fiber 72 may not be connected by the connecting unit 5, and the signal generating unit 3 and the scanning light emitting unit 4 are only connected by the first optical fiber 71 without using the connecting unit 5. And may be optically connected.

Hereinafter, each part of the image display device 1 will be sequentially described in detail.
(flame)
As shown in FIG. 1, the frame 2 has a shape like a spectacle frame, and has a function of supporting the signal generating unit 3 and the scanning light emitting unit 4.

  As shown in FIG. 1, the frame 2 includes a front part 22 that supports the scanning light emitting part 4 and the nose pad part 21, and a pair of temple parts that are connected to the front part 22 and come into contact with the ears of the user. (Vine part) 23 and the modern part 24 which is the edge part opposite to the front part 22 of each temple part 23 is included.

  The nose pad portion 21 is in contact with the user's nose NS during use, and supports the image display device 1 against the user's head. The front part 22 includes a rim part 25 and a bridge part 26.

  The nose pad portion 21 is configured to be able to adjust the position of the frame 2 with respect to the user during use.

  The shape of the frame 2 is not limited to that shown in the drawing as long as it can be mounted on the user's head H.

(Signal generator)
As shown in FIG. 1, the signal generation unit 3 is provided at one of the above-described frames 2 (on the right side in the present embodiment) on the modern unit 24 (the end of the temple unit 23 opposite to the front unit 22). Yes.

  That is, the signal generation unit 3 is disposed on the opposite side of the eye EY with respect to the user's ear EA during use. Thereby, the weight balance of the image display apparatus 1 can be made excellent.

  The signal generation unit 3 has a function of generating signal light scanned by an optical scanning unit 42 of the scanning light emitting unit 4 described later and a function of generating a drive signal for driving the optical scanning unit 42.

  As shown in FIG. 3, such a signal generation unit 3 includes an optical modulator 30, a signal light generation unit 31, a drive signal generation unit 32, a control unit 33, a light detection unit 34, and a fixing unit 35. With.

  The signal light generation unit 31 generates signal light that is scanned (optically scanned) by an optical scanning unit 42 (optical scanner) of the scanning light emitting unit 4 described later.

  The signal light generation unit 31 includes a plurality of light sources 311R, 311G, and 311B having different wavelengths and a plurality of drive circuits 312R, 312G, and 312B.

  The light source 311R (R light source) emits red light LR, the light source 311G (G light source) emits green light LG, and the light source 311B (B light source) emits blue light LB. Is. By using such three colors of light, a full color image can be displayed. When a full-color image is not displayed, one or two colors of light (one or two light sources) may be used, and four colors are used to improve the color rendering of the full-color image. The above light (four or more light sources) may be used.

  Such light sources 311R, 311G, and 311B are not particularly limited. For example, laser diodes and LEDs can be used.

  Such light sources 311R, 311G, 311B are electrically connected to drive circuits 312R, 312G, 312B, respectively.

  Hereinafter, the light sources 311R, 311G, and 311B are collectively referred to as “light source unit 311”, and the signal light generated by the signal light generation unit 31 is also referred to as “light emitted from the light source unit 311”.

  The drive circuit 312R has a function of driving the above-described light source 311R, the drive circuit 312G has a function of driving the above-described light source 311G, and the drive circuit 312B has a function of driving the above-described light source 311B.

  The three (three colors) light emitted from the light sources 311R, 311G, and 311B driven by the drive circuits 312R, 312G, and 312B are incident on the optical modulator 30, respectively.

((Light modulator))
An optical modulator 30 shown in FIG. 6 includes a substrate 301, a main optical waveguide (first optical waveguide) 302 formed on the substrate 301, and light provided in the main optical waveguide 302 and guided through the main optical waveguide 302. A wavelength selection unit 303 having a function of selecting a wavelength of the light, a light modulation unit 304 provided in the main optical waveguide 302 and having a function of modulating the intensity of light having a wavelength selected by the wavelength selection unit 303, and a substrate 301. Buffers interposed between voltage application units 3035R, 3035G, and 3035B (see FIG. 8 described later) provided in the wavelength selection unit 303 and between an electrode 3040 provided in the substrate 301 and the light modulation unit 304 A layer 305. Note that the buffer layer 305 is not necessarily provided over the entire surface of the substrate 301, and may be provided at least on the core portion 3021.

  The substrate 301 has a flat plate shape that is rectangular in a plan view, and is made of a material having an electro-optic effect. The electro-optic effect is a phenomenon in which the refractive index of a substance changes when an electric field is applied to the substance, and includes a Pockels effect in which the refractive index is proportional to the electric field and a Kerr effect that is proportional to the square of the electric field. When the main optical waveguide 302 branched in the middle of the substrate 301 is formed and an electric field is applied to one of the branched main optical waveguides 302, the refractive index can be changed. By using this, it is possible to perform intensity modulation based on the phase difference by giving a phase difference to the light propagating through the branched main optical waveguide 302 and recombining the branched light.

Examples of the material having an electro-optic effect include inorganic materials such as lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), lead lanthanum zirconate titanate (PLZT), and potassium phosphate titanate (KTiOPO ₄ ). In addition to system materials, polythiophene, and liquid crystal materials, electro-optic active polymers doped with charge transport molecules, charge-transport polymers doped with electro-optic dyes, inert polymers with charge transport molecules and electro-optic dyes And organic materials such as a material containing a charge transport site and an electro-optic site in the main chain or side chain of a polymer, a material doped with tricyanofuran (TCF) as an acceptor, and the like.

  Of these, lithium niobate is particularly preferably used. Since lithium niobate has a relatively large electro-optic coefficient, when selecting the wavelength of light to be transmitted in the wavelength selector 303, which will be described later, the drive voltage may be lowered or the circumference of the annular optical waveguide may be shortened. In addition, the drive voltage can be lowered when the light intensity is modulated by the light modulation unit 304 described later. For this reason, the power consumption of the optical modulator 30 and the image display apparatus 1 can be reduced. In addition, since the area required for the wavelength selection unit 303 and the light modulation unit 304 to perform their functions can be reduced, the light modulator 30 and the image display device 1 can be downsized.

  These materials are preferably used as single crystals or solid solution crystals. Thereby, the substrate 301 is provided with translucency, and the main optical waveguide 302 can be formed in the substrate 301.

  The main optical waveguide 302 is a light guide formed in the substrate 301. Examples of a method for forming the main optical waveguide 302 in the substrate 301 include a proton exchange method and a Ti diffusion method. Among them, the proton exchange method is a method in which the refractive index of the region is changed by immersing the substrate in an acid solution and allowing protons to enter the substrate in exchange for elution of ions in the substrate. According to this method, the main optical waveguide 302 having particularly excellent light resistance can be obtained. On the other hand, the Ti diffusion method is a method of changing the refractive index of the region by diffusing Ti into the substrate by performing a heat treatment after forming the Ti film on the substrate.

  The main optical waveguide 302 thus formed includes a core portion 3021 formed of a long portion having a relatively high refractive index in the substrate 301, and a cladding having a relatively low refractive index adjacent to the core portion 3021. Part 3022. In the main optical waveguide 302 shown in FIG. 7, when light is incident on the left end (incident surface) in FIG. 7, the incident light is reflected on the interface between the core part 3021 and the clad part 3022 while being reflected on the right side. And is emitted as emitted light L from the right end. That is, the core portion 3021 can be substantially regarded as the main optical waveguide 302.

  Among these, the core portion 3021 includes three light incident portions 3029R, 3029G, and 3029B that can receive light, and three core portions (branch optical waveguides) 3021R connected to these light incident portions 3029R, 3029G, and 3029B. , 3021G and 3021B.

  Of the three core portions 3021R, 3021G, and 3021B, the core portions 3021R and 3021G are curved so that the distance from each other gradually decreases toward the emission end side. At the same time, it merges into one core portion 3021. For this reason, the red light LR incident on the core portion 3021R, the green light LG incident on the core portion 3021G, and the blue light LB incident on the core portion 3021B are combined at the merge portion 3025. Then, the red light LR, the green light LG, and the blue light LB combined in the combining unit 3025 are guided to the wavelength selection unit 303. That is, the main optical waveguide 302 includes a multiplexing unit that multiplexes light having different wavelengths and connects them to the wavelength selection unit.

≪Wavelength selection part≫
A wavelength selection unit 303 is arranged in one core unit 3021 after joining.

  As shown in FIGS. 6 and 7, the wavelength selection unit 303 is a first ring resonance provided so as to be arranged in order from the incident end (incident surface) side of the core unit 3021 toward the outgoing end (exit surface) side. 303R, a second ring resonator 303G, and a third ring resonator 303B. The first ring resonator 303R, the second ring resonator 303G, and the third ring resonator 303B are optically coupled to the main optical waveguide 302 formed of the core portion 3021 and the cladding portion 3022, respectively. Resonate each light of a specific wavelength. Thereby, the wavelength of the light propagating through the main optical waveguide 302 can be selected, and the light of the selected wavelength can be emitted to the light modulation unit 304.

  FIG. 8 is a partially enlarged view of the wavelength selection unit 303 shown in FIG. 8 indicate the red light LR, the green light LG, and the blue light LB that are incident on the wavelength selection unit 303, and the dashed arrows are red that are emitted (dropped) from the wavelength selection unit 303. The light LR, the green light LG, and the blue light LB are shown, and the white arrow indicates the light (emitted light L) after the wavelength is selected by the wavelength selection unit 303.

  Of the wavelength selection unit 303, the first ring resonator 303R is a first annular optical waveguide 3031R which is an optical waveguide having an annular shape and optically coupled to the main optical waveguide 302, as shown in FIG. A first branch optical waveguide (first coupled optical waveguide) 3032R optically coupled to the first annular optical waveguide 3031R, and a first provided corresponding to the first annular optical waveguide 3031R. The annular electrode 3034R and a first circular electrode 3033R provided inside the first annular electrode 3034R are provided.

  The first annular optical waveguide 3031R has an annular shape with a substantially perfect outer shape in plan view. The first annular optical waveguide 3031R is formed adjacent to the main optical waveguide 302.

  The main optical waveguide 302 and the first annular optical waveguide 3031R are optically coupled. This “optical coupling” means that evanescent coupling EC occurs although the core portion 3021 of the main optical waveguide 302 and the core portion of the first annular optical waveguide 3031R are physically separated slightly. It means being in a state. The evanescent coupling EC is a state in which two optical waveguides are adjacent to each other so that an evanescent wave oozing from the core portion of one optical waveguide can enter the core portion of the other optical waveguide.

  On the other hand, the first branch optical waveguide 3032R is linearly formed so that the extending direction thereof is orthogonal to the extending direction of the main optical waveguide 302 in plan view. The first branch optical waveguide 3032R is formed adjacent to the first annular optical waveguide 3031R.

  The first branch optical waveguide 3032R and the first annular optical waveguide 3031R are optically coupled. In this “optical coupling”, the core portion of the first branch optical waveguide 3032R and the core portion of the first annular optical waveguide 3031R are physically slightly separated as described above. This indicates that an evanescent coupling EC is occurring.

  In the first annular optical waveguide 3031R, the light incident from the main optical waveguide 302 circulates. When the resonance condition is satisfied for the incident light, light having a specific wavelength that satisfies the resonance condition resonates and is output to the first branch optical waveguide 3032R with high intensity. Accordingly, even when light having a plurality of wavelengths is incident on the main optical waveguide 302, only light having a specific wavelength satisfying the resonance condition is transmitted through the first annular optical waveguide 3031R. Since the light is output to the waveguide 3032R, the first ring resonator 303R functions as a wavelength filter (optical switch) that removes the red light LR from the light propagating through the main optical waveguide 302.

  In addition, by applying a voltage between the first annular electrode 3034R and the first circular electrode 3033R, the core portion of the first annular optical waveguide 3031R located in the vicinity of the first annular electrode 3034R An electric field is generated. That is, the first annular electrode 3034R and the first circular electrode 3033R function as a first voltage application unit 3035R that can apply a voltage to the first annular optical waveguide 3031R. When an electric field is generated in the core portion of the first annular optical waveguide 3031R, the refractive index of the core portion changes, and the optical path length (optical distance) of the core portion, and hence the resonance condition changes. Therefore, it is possible to control whether or not the resonance condition is satisfied in the first annular optical waveguide 3031R by appropriately setting the presence / absence of voltage application or the magnitude of the voltage for the first voltage application unit 3035R. Thus, it is possible to control whether or not the wavelength filter of the first ring resonator 303R functions.

  Note that the first ring resonator 303R appropriately sets the physical length (peripheral length) of the first annular optical waveguide 3031R, thereby making the “first voltage” with respect to the first voltage application unit 3035R. Is applied so as to function as a wavelength filter that removes red light LR (light having a first resonance wavelength). On the other hand, the first ring resonator 303R may be configured so that the red light LR is not removed when the first voltage is not applied.

  Similarly, as shown in FIG. 8, the second ring resonator 303G includes a second annular optical waveguide 3031G optically coupled to the main optical waveguide 302, a second annular optical waveguide 3031G, and an optical A second branch optical waveguide (second coupled optical waveguide) 3032G coupled to the second annular optical waveguide 3031G, a second annular electrode 3034G provided corresponding to the second annular optical waveguide 3031G, and a second annular electrode 3034G. And a second circular electrode 3033G provided on the inner side.

  The second annular optical waveguide 3031G and the second branch optical waveguide 3032G are each configured in the same manner as the first ring resonator 303R. Therefore, the second ring resonator 303G functions as a wavelength filter (optical switch) that removes the green light LG from the light propagating through the main optical waveguide 302.

  The second annular electrode 3034G and the second circular electrode 3033G function as a second voltage application unit 3035G that can apply a voltage to the second annular optical waveguide 3031G. Whether or not the resonance condition is satisfied in the second annular optical waveguide 3031G can be controlled by appropriately setting the presence / absence of voltage application or the magnitude of the voltage to the second voltage application unit 3035G, As a result, it is possible to control whether or not the wavelength filter of the second ring resonator 303G functions.

  Note that the second ring resonator 303G appropriately sets the physical length (peripheral length) of the second annular optical waveguide 3031G, whereby the “second voltage” is applied to the second voltage application unit 3035G. Is applied so as to function as a wavelength filter that removes green light LG (light having a second resonance wavelength). On the other hand, the second ring resonator 303G may be configured so that the green light LG is not removed when the second voltage is not applied. Similar to the first annular optical waveguide 3031R, the circumference of the second annular optical waveguide 3031G can be regarded as the circumference at the center in the width direction of the second annular optical waveguide 3031G.

  Similarly, as shown in FIG. 8, the third ring resonator 303B includes a third annular optical waveguide 3031B optically coupled to the main optical waveguide 302, and a third annular optical waveguide 3031B. A third branch optical waveguide (third coupled optical waveguide) 3032B coupled to the third annular optical waveguide 3031B, a third annular electrode 3034B provided corresponding to the third annular optical waveguide 3031B, and a third annular electrode 3034B. And a third circular electrode 3033B provided on the inner side.

  The third annular optical waveguide 3031B and the third branch optical waveguide 3032B are each configured similarly to the first ring resonator 303R. Therefore, the third ring resonator 303B functions as a wavelength filter (optical switch) that removes the blue light LB from the light propagating through the main optical waveguide 302.

  Further, the third annular electrode 3034B and the third circular electrode 3033B function as a third voltage application unit 3035B that can apply a voltage to the third annular optical waveguide 3031B. Whether or not the resonance condition is satisfied in the third annular optical waveguide 3031B can be controlled by appropriately setting the presence / absence of voltage application or the magnitude of the voltage for the third voltage application unit 3035B, As a result, it is possible to control whether or not the wavelength filter of the third ring resonator 303B functions.

  Note that the third ring resonator 303B appropriately sets the physical length (peripheral length) of the third annular optical waveguide 3031B, whereby the “third voltage” is applied to the third voltage application unit 3035B. Is applied so as to function as a wavelength filter that removes blue light LB (light having a third resonance wavelength). On the other hand, the third ring resonator 303B may be configured so that the blue light LB is not removed when the third voltage is not applied. Similar to the first annular optical waveguide 3031R, the circumference of the third annular optical waveguide 3031B can be regarded as the circumference at the center in the width direction of the third annular optical waveguide 3031B.

  As described above, the wavelength selection unit 303 according to the present embodiment can individually control the transmission of the red light LR, the green light LG, and the blue light LB at high speed. Thus, the wavelength selection unit 303 selectively transmits only a specific wavelength (light) from the combined light, and the light modulation unit 304 arranged on the emission side of the wavelength selection unit 303 has a specific wavelength (color). ) Intensity can be modulated. As a result, the single light modulator 304 can accurately modulate the intensity of the red light LR, the green light LG, and the blue light LB individually, so that the light modulator 30 and the image display device 1 including the light modulator 30 can be used. It is possible to display a high-quality image composed of multiple colors such as full color while downsizing.

  In other words, the wavelength selection unit 303 according to the present embodiment includes the first ring resonator 303R, the second ring resonator 303G, and the third ring disposed along the optical waveguide direction of the main optical waveguide 302. And a resonator 303B. Since these ring resonators only need to have voltage application units 3035R, 3035G, and 3035B for applying an electric field to each of the annular optical waveguides 3031R, 3031G, and 3031B, they are arranged without dividing the main optical waveguide 302. Is possible. For this reason, the optical connection between the wavelength selection unit 303 (for example, between the first ring resonator 303R and the second ring resonator 303G) and between the wavelength selection unit 303 and the light modulation unit 304 is performed. There is no need to provide a place. As a result, there is no need for alignment that strictly considers the optical path length as in the prior art, and it is difficult to cause optical loss. Therefore, it is difficult to cause a shortage of the light amount of the display image, and it is possible to solve the problem of increasing the power consumption by increasing the output of the light source in order to compensate for the shortage of the light amount.

  In addition, as a method of forming each annular optical waveguide 3031R, 3031G, 3031B and each branch optical waveguide 3032R, 3032G, 3032B in the substrate 301, for example, as in the case of the main optical waveguide 302 described above, for example, proton exchange method, Ti A diffusion method or the like is used.

  In addition, each of the voltage application units 3035R, 3035G, and 3035B is formed by, for example, forming a conductive material and then patterning it into a target shape using a photolithography technique or an etching technique. Therefore, the electrodes of the voltage application units 3035R, 3035G, and 3035B and the light modulation unit 304 described later can be formed in a lump, and there is an advantage that the manufacturing is easy and the cost can be reduced.

  The first voltage applied to the first voltage application unit 3035R, the second voltage applied to the second voltage application unit 3035G, and the third voltage applied to the third voltage application unit 3035B. The voltage may be the same as or different from each other. For example, when they are the same as each other, the red light LR can be obtained by making the circumferential lengths of the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B different from each other as in the present embodiment. Since the transmission of the green light LG and the blue light LB can be individually selected, the first voltage application unit 3035R, the second voltage application unit 3035G, and the third voltage application unit 3035B are the same as each other. It is only necessary to apply a voltage, and it is possible to simplify the structure in which some electrodes are electrically connected to each other. On the other hand, when the first voltage, the second voltage, and the third voltage are different from each other, the physics of the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B. The target length (physical circumference) may be different from each other as in the present embodiment, or may be the same. In the latter case, there is an advantage that the design becomes easy.

  The red light LR output to the first branch optical waveguide 3032R, the green light LG output to the second branch optical waveguide 3032G, and the blue light LB output to the third branch optical waveguide 3032B are light The light may be emitted from the modulator 30 to the external space or may be absorbed by a light absorbing material that absorbs light. As a result, it is possible to prevent the output light from becoming stray light and hindering image display. Examples of the light absorbing material include carbon black and graphite.

  Furthermore, you may make it provide the light detection part which detects the light quantity of the output light. By detecting the amount of light output by the light detection unit, it is possible to confirm whether light is reliably selected in each of the ring resonators 303R, 303G, and 303B. Further, by feeding back the light amount data to the control unit 33, for example, the magnitude of the voltage applied to the first voltage application unit 3035R so that the red light LR is reliably removed in the first ring resonator 303R, for example. The sheath application timing can be adjusted as appropriate. As a result, the display image can be further improved in image quality. For example, a photodiode or the like is used as the light detection unit.

  Note that the shape and arrangement of each of the voltage application units 3035R, 3035G, and 3035B shown in FIG. It is appropriately set according to the electrode area.

  Further, the extending directions of the branch optical waveguides 3032R, 3032G, and 3032B shown in FIG. 8 are also examples, and are set as appropriate.

  Further, the shape of each of the annular optical waveguides 3031R, 3031G, and 3031B in plan view is not limited to a perfect circle as long as it is an annular shape. It may be a shape.

Next, a driving method of the wavelength selection unit 303 will be described.
In the signal generation unit 3 including the optical modulator 30 of the present invention, the transmission wavelength is selected by the wavelength selection unit 303 of the optical modulator 30 while continuously driving (CW driving) the light sources 311R, 311G, and 311B. The modulation unit 304 performs intensity modulation.

  FIG. 9 is a diagram for explaining the operation of the wavelength selection unit 303 shown in FIG. 9 indicate light propagating through the main optical waveguide 302, and broken arrows indicate light propagating through the branch optical waveguides 3032R, 3032G, and 3032B. Moreover, in FIG. 9, illustration of each voltage application part is abbreviate | omitted.

  FIG. 9A is a diagram for explaining the operation of selecting only the red light LR from the combined light and emitting it to the light modulation unit 304, and FIG. 9B selects only the green light LG. FIG. 9C is a diagram for explaining an operation of selecting only the blue light LB and emitting the light toward the light modulation unit 304. FIG. FIG.

  When only the red light LR is selected and emitted, the second ring resonator 303G and the third ring resonator 303B are driven. Thereby, the green light LG and the blue light LB are removed from the combined light, and only the red light LR is emitted from the wavelength selection unit 303.

  When only the green light LG is selected and emitted, the first ring resonator 303R and the third ring resonator 303B are driven. Thereby, the red light LR and the blue light LB are removed from the combined light, and only the green light LG is emitted from the wavelength selection unit 303.

  When only the blue light LB is selected and emitted, the first ring resonator 303R and the second ring resonator 303G are driven. Thereby, the red light LR and the green light LG are removed from the combined light, and only the blue light LB is emitted from the wavelength selection unit 303.

  In this way, the wavelength selection unit 303 can select the wavelength of the emitted light. At this time, for example, the time zone for emitting the red light LR, the time zone for emitting the green light LG, and the blue light LB are emitted. It is desirable that the time zones to be used do not overlap each other. If the time zone in which the red light LR is emitted and the time zone in which the green light LG is emitted overlap, light in which red and green are mixed is incident on the light modulation unit 304. Therefore, the light modulation unit 304 has an accurate intensity. Modulation may not be possible. As a result, an unintended change may occur in the color of the image displayed by the image display device 1, and the image quality may deteriorate.

  Therefore, when changing the light emitted from the wavelength selection unit 303, it is preferable to provide a time period during which all light is not emitted temporarily. By providing such a time zone, the red light LR, the green light LG, and the blue light LB are all removed, and the light does not pass through the wavelength selection unit 303. For example, the time zone for emitting the red light LR and the green light It is prevented that the time zone for injecting LG overlaps. As a result, it is possible to prevent the image quality of the image displayed by the image display device 1 from being deteriorated.

  FIG. 10 shows an example of a time transition (timing chart) of a voltage application pattern for driving the first ring resonator 303R, the second ring resonator 303G, and the third ring resonator 303B, and at that time It is a figure which shows the color of the light inject | emitted from the wavelength selection part 303. FIG. In FIG. 10, the voltage applied to the first voltage application unit 3035R included in the first ring resonator 303R is denoted as “R electrode voltage”. Similarly, the voltage applied to the second voltage application unit 3035G included in the second ring resonator 303G is referred to as “G electrode voltage”, and the third voltage application unit 3035B included in the third ring resonator 303B. The voltage applied to is indicated as “B electrode voltage”. Furthermore, in FIG. 10, when the color of the light emitted from the wavelength selection unit 303 is red, it is expressed as “R”, when it is green, it is expressed as “G”, and when it is blue Indicated as “B” and “K” when no light is emitted.

  For example, in the first time zone TZ1, a voltage is applied to the G electrode and the B electrode, respectively, while no voltage is applied to the R electrode. At this time, the red light LR is transmitted through the first ring resonator 303R, while the green light LG is removed by the second ring resonator 303G, and the blue light LB is removed by the third ring resonator 303B. As a result, only the red light LR propagates to the light modulation unit 304, and the intensity of the red light LR can be modulated.

  Next, in the second time zone TZ2, voltages are applied to the R electrode and the B electrode, respectively, while no voltage is applied to the G electrode. Thereby, only the green light LG propagates to the light modulation unit 304, and the intensity of the green light LG can be modulated.

  Here, when transitioning from the first time zone TZ1 to the second time zone TZ2, all of the R electrode, the G electrode, and the B electrode are between the first time zone TZ1 and the second time zone TZ2. It is preferable to provide a time zone TZ0 for applying a voltage to. By providing such a time zone TZ0, the wavelength selecting unit 303 removes all the light and eliminates the emitted light. Then, it is possible to prevent the first time zone TZ1 and the second time zone TZ2 from overlapping, and to prevent the light mixed with the red light LR and the green light LG from propagating to the light modulation unit 304. it can.

  The length of the time zone TZ0 depends on factors such as the time required to apply a predetermined voltage to each electrode and its variation, and the time required to stop applying the voltage to each electrode and its variation. As an example, it is set to about 1 nanosecond or more and 100 milliseconds or less. At this level, although depending on the content of the displayed image, it is unlikely that any light will be emitted (black display state), and there is little discomfort, so black display will be made. The resulting degradation in image quality can be minimized. Further, it is possible to minimize the deterioration in image quality caused by the overlap of the first time zone TZ1 and the second time zone TZ2.

  Similarly, when transitioning from the second time zone TZ2 to the third time zone TZ3, it is preferable to provide a time zone TZ0 in which a voltage is applied to all of the R electrode, the G electrode, and the B electrode. . This prevents the second time zone TZ2 and the third time zone TZ3 from overlapping, and prevents light mixed with the green light LG and the blue light LB from propagating to the light modulation unit 304. Can do.

≪Light modulation part≫
An optical modulation unit 304 is disposed on the emission surface side of the wavelength selection unit 303. The light modulation unit 304 may be any means as long as it can modulate the intensity of light propagating through the main optical waveguide 302. In this embodiment, the light modulation unit 304 is a light that adopts a Mach-Zehnder light modulation method. The modulation unit will be particularly described.

  In the portion corresponding to the light modulation unit 304 according to the present embodiment, as shown in FIGS. 6 and 7, the core unit 3021 is branched into two at the branch unit 3023, the core unit 3021 a and the core unit 3021 b. The light modulation unit 304 includes an electrode 3040 provided on the branched core unit.

  The core portion 3021a and the core portion 3021b are separated by a predetermined distance. The core portion 3021a and the core portion 3021b join again to one core portion 3021 at the joining portion 3024. And the core part 3021 after joining can radiate | emit the emitted light L from the output end (output surface).

The electrode 3040 includes a signal electrode 304a and a ground electrode 304b.
Among these, the signal electrode 304 a is disposed so as to overlap with the core portion 3021 a in a plan view of the substrate 301. On the other hand, the ground electrode 304b is disposed so as to overlap the core portion 3021b in the plan view of the substrate 301.

  A reference potential is applied to the ground electrode 304b. As an example, the ground electrode 304b is electrically grounded. On the other hand, a potential based on image information is applied to the signal electrode 304a so that a potential difference is generated between the signal electrode 304a and the ground electrode 304b. When a potential difference is generated between the signal electrode 304a and the ground electrode 304b in this way, an electric field is applied to the core portion 3021a through which the lines of electric force generated therebetween pass. As a result, the refractive index of the core portion 3021a changes based on the electro-optic effect.

  Here, the width of the signal electrode 304a is narrower than that of the ground electrode 304b. For this reason, electric lines of force concentrate on the core portion 3021a located immediately below the signal electrode 304a. That is, a relatively large electric field is applied from the signal electrode 304a to the core portion 3021a. On the other hand, the width of the ground electrode 304b is set sufficiently wide. For this reason, the lines of electric force do not concentrate much on the core portion 3021b located immediately below the ground electrode 304b. That is, a relatively small electric field is applied from the ground electrode 304b to the core portion 3021b.

  Since there is a difference as described above between the core part 3021a and the core part 3021b, when the potential difference as described above occurs with respect to the electrode 3040, the core part 3021a positioned corresponding to the signal electrode 304a The refractive index mainly changes, and the refractive index of the core part 3021b hardly changes. As a result, a refractive index shift occurs between the core part 3021a and the core part 3021b, and a phase difference based on a refractive index shift occurs between the light propagating through the core part 3021a and the light propagating through the core part 3021b. It will be. When the two lights having such a phase difference are combined at the combining unit 3024, combined light attenuated with respect to the incident intensity is generated. This combined light is emitted from the emission end of the core part 3021 toward the light detection part 34.

  At this time, the phase difference between the light propagating through the core part 3021a and the light propagating through the core part 3021b can be controlled by adjusting the potential difference applied between the signal electrode 304a and the ground electrode 304b. The attenuation width of the combined light with respect to the intensity can be controlled.

  For example, the potential difference generated between the signal electrode 304a and the ground electrode 304b is adjusted, and the difference between the phase of the light propagating through the core portion 3021a and the phase of the light propagating through the core portion 3021b is half-wavelength at the merging portion 3024. If they are shifted by the amount, the two lights cancel each other at the junction 3024, and the light intensity becomes substantially zero. Further, the light intensity of the combined light can be modulated by appropriately changing the phase shift amount.

  On the other hand, when the phases of the two lights are aligned at the merging portion 3024, combined light having a light intensity substantially equal to the incident intensity is obtained.

  In the present embodiment, the red light LR, the green light LG, and the blue light LB are incident on the light modulation unit 304 in a time division manner. Therefore, in the time zone in which the red light LR is incident, the light modulator 304 is driven so as to modulate the intensity of the red light LR based on the image information. Similarly, in the time zone in which the green light LG is incident, the light modulation unit 304 is driven so as to modulate the intensity of the green light LG based on the image information, and in the time zone in which the blue light LB is incident, based on the image information. Then, the light modulator 304 is driven so as to modulate the intensity of the blue light LB. Thereby, in one light modulation part 304, the intensity | strength modulation of the light of three colors, red light LR, green light LG, and blue light LB can be performed. As a result, the optical modulator 30 can be downsized and the structure can be simplified.

  Further, according to the image display device 1, the light modulation unit 304 can externally modulate the intensity of the three colors of light. For this reason, compared with the case where the intensity of the light of the three colors emitted from the light source unit 311 is directly modulated by the light source unit 311, it is possible to obtain high-quality light with no wavelength variation and to enable high-speed modulation. Become. In addition, by finely changing the voltage applied to the electrode 3040, the intensity of light emitted from the light modulator 30 can be finely adjusted with higher resolution. As a result, the gradation of the image drawn on the retina of the eye EY can be further increased, and further higher resolution can be achieved.

  Further, in the image display device 1, since it is not necessary to directly modulate the light source unit 311, the light source unit 311 may be driven so that signal light having a certain intensity is emitted. Therefore, the light source unit 311 can be driven under the conditions where the luminous efficiency is the highest, or the conditions where the luminous stability and the wavelength stability are the highest, so that the power consumption or operation of the image display device 1 can be reduced and the eye can be stabilized. The image quality of the image drawn on the EY retina can be improved. Since a driving circuit necessary for directly modulating the light source unit 311 is not required, and a circuit for continuously driving the light source unit 311 is relatively simple and low-cost, the cost of the light source unit 311 can be reduced and the light source unit 311 can be reduced. Can be miniaturized.

  Further, when a later-described hologram diffraction grating is used as the reflecting portion 6, the wavelength stability of the signal light can be increased, so that the signal light close to the design wavelength can be incident on the hologram diffraction grating. As a result, the deviation from the design value of the diffraction angle in the hologram diffraction grating can be reduced, and blurring of the image can be suppressed.

  The electrode 3040 includes a first voltage application unit 3035R included in the first ring resonator 303R of the wavelength selection unit 303 described above, a second voltage application unit 3035G included in the second ring resonator 303G, and a third Similar to the third voltage application unit 3035B included in the ring resonator 303B, for example, after forming a conductive material into a film, the conductive film is patterned into a desired shape using a photolithography technique or an etching technique. it can. Therefore, the electrodes 3040 can also be collectively formed when the voltage applying units 3035R, 3035G, and 3035B of the wavelength selection unit 303 are formed. As a result, the light modulation unit 304 can be efficiently manufactured, and cost reduction can be achieved. In addition, since it becomes easy to strictly control the position accuracy between the voltage applying units 3035R, 3035G, and 3035B of the wavelength selection unit 303 and the electrode 3040 of the light modulation unit 304, high position accuracy can be realized. . As a result, light color selection and intensity modulation can be performed with high accuracy, and a higher image quality of the displayed image can be achieved.

  Further, in this embodiment, a part (combining part) where the three core parts 3021R, 3021G, and 3021B are joined by the joining part 3025, the wavelength selecting part 303, and the light modulating part 304 are arranged on the same substrate 301. (Monolithic structure). For this reason, the optical modulator 30 can be downsized and the image display device 1 can be downsized as compared with the case where these portions are formed of different members. Moreover, since the optical coupling loss between each part can be reduced, the internal loss of the optical modulator 30 can be suppressed. As a result, the image quality can be improved and the power consumption can be reduced.

  Note that the optical modulator 30 including the main optical waveguide 302 has secondary effects such as increasing the beam quality of the emitted light L and reducing excess light. Thereby, it is possible to further improve the image quality of the displayed image.

  Of the secondary effects, the former effect is due to the trimming of the light beam (cutting off unnecessary portions). That is, the light beam emitted from the light source unit 311 usually has a high quality at the central portion (small wavelength distribution width) and a low quality at the peripheral portion in the cross section. Therefore, by providing the optical modulator 30 with the main optical waveguide 302, the peripheral portion of the beam can be trimmed in the main optical waveguide 302. As a result, only the central portion of the high quality beam can be modulated and emitted.

  On the other hand, among the secondary effects, the latter effect is based on the fact that part of light leaks by appropriately setting the shape of the core portion 3021 when light propagates through the main optical waveguide 302. This is because it can be easily reduced.

  Note that the shape of the electrode 3040 is appropriately set according to, for example, the direction of the crystal axis of the substrate 301, and may be, for example, a shape arranged corresponding to a position that does not overlap with the core portion 3021 a or the core portion 3021 b.

  In addition, since a voltage is applied to a region having a narrow cross section such as the main optical waveguide 302, an applied voltage necessary for a change in refractive index to cause a phase difference necessary for signal light modulation is applied to a bulk electro-optic material. It can be made smaller compared to the case where voltage is applied. Furthermore, controllability of intensity modulation can be enhanced by appropriately selecting the cross-sectional area of the main optical waveguide 302 (core portion 3021).

  In addition, the light modulation unit 304 described above externally modulates the intensity of the signal light using the electro-optic effect, but instead of the electro-optic effect, the acousto-optic effect, the magneto-optic effect, the thermo-optic effect, and the nonlinear optics. A light modulation effect such as an effect may be used.

  Note that, when a Mach-Zehnder light modulation method using the electro-optic effect is employed, modulation at a particularly high speed is possible, so that the contribution to high image quality of the displayed image is significant.

  Further, the modulation principle in the light modulation unit 304 is not limited to the Mach-Zehnder modulation principle described above. Alternative modulation structures include, for example, a directional coupled modulator, a branching interferometric modulator, a ring interferometric modulator, a total internal reflection optical switch using a Y-cut crossing waveguide, a branching switch, and a cutoff type Examples thereof include an optical modulator, a balanced bridge optical modulator, a Bragg diffraction optical switch, and an electroabsorption (EA) modulator.

  Note that the Mach-Zehnder type modulation structure can be realized with a relatively simple structure, and is easy to arbitrarily adjust the modulation width, so that it is useful as a modulation structure in the light modulation unit 304. Since the intensity of the signal light can be arbitrarily adjusted by arbitrarily adjusting the modulation width, for example, a high contrast of the display image can be achieved.

  The buffer layer 305 is provided between the substrate 301 and each electrode, and is made of a medium that absorbs less light guided through the main optical waveguide 302, such as silicon oxide or alumina.

  Thus, the emitted light L modulated by the optical modulator 30 in accordance with the image information is incident on one end of the first optical fiber 71 as signal light. Then, the signal light passes through the first optical fiber 71, the connection unit 5, and the second optical fiber 72 in this order, and is transmitted to the optical scanning unit 42 of the scanning light emitting unit 4 described later.

  Here, a light detection unit 34 is provided in the vicinity of the end of the first optical fiber 71 on the signal light incident side. The light detector 34 detects signal light. In addition, one end of the first optical fiber 71 and the light detection unit 34 are fixed to the fixing unit 35.

  The drive signal generating unit 32 generates a drive signal for driving an optical scanning unit 42 (optical scanner) of the scanning light emitting unit 4 described later.

  The drive signal generation unit 32 is orthogonal to the drive circuit 321 that generates a first drive signal used for scanning (horizontal scanning) in the first direction of the optical scanning unit 42 and the first direction of the optical scanning unit 42. And a drive circuit 322 for generating a second drive signal used for scanning in the second direction (vertical scanning).

  Such a drive signal generation unit 32 is electrically connected to an optical scanning unit 42 of the scanning light emitting unit 4 described later via a signal line (not shown). Accordingly, the drive signal generated by the drive signal generation unit 32 is input to the optical scanning unit 42 of the scanning light emitting unit 4 described later.

  The drive circuits 312R, 312G, and 312B of the signal light generation unit 31 and the drive circuits 321 and 322 of the drive signal generation unit 32 as described above are electrically connected to the control unit 33.

  The control unit 33 has a function of controlling driving of the drive circuits 312R, 312G, and 312B of the signal light generation unit 31 and the drive circuits 321 and 322 of the drive signal generation unit 32 based on the video signal (image signal). That is, the control unit 33 has a function of controlling the driving of the scanning light emitting unit 4. As a result, the signal light generation unit 31 generates signal light modulated according to the image information, and the drive signal generation unit 32 generates a drive signal according to the image information.

  Further, the control unit 33 has a function of controlling driving of the optical modulator 30. Specifically, the control unit 33 can drive the wavelength selection unit 303 and the light modulation unit 304 included in the optical modulator 30 individually and in cooperation with each other. As a result, light having different wavelengths can be transmitted mutually exclusively (in a time division manner) on the time axis in the wavelength selection unit 303, and the intensity of the transmitted light can be modulated in the light modulation unit 304 in accordance with the transmission timing. it can.

  Further, the control unit 33 is configured to control the drive of the drive circuits 312R, 312G, and 312B of the signal light generation unit 31 based on the light intensity detected by the light detection unit 34.

(Scanning light emitting part)
As shown in FIGS. 1 and 2, the scanning light emitting portion 4 is attached in the vicinity of the bridge portion 26 of the frame 2 described above (in other words, in the vicinity of the center of the front portion 22).

As shown in FIG. 4, such a scanning light emitting unit 4 includes a housing 41 (housing), an optical scanning unit 42, a lens 43 (coupling lens), a lens 45 (condensing lens), and a support. Member 46.
The housing 41 is attached to the front portion 22 via a support member 46.

  Further, the outer surface of the housing 41 is joined to a portion of the support member 46 on the side opposite to the frame 2.

  The housing 41 supports the optical scanning unit 42 and houses the optical scanning unit 42. A lens 43 and a lens 45 are attached to the housing 41, and the lenses 43 and 45 constitute a part of the housing 41 (a part of the wall).

  In addition, the lens 43 (the window portion that transmits the signal light of the housing 41) is separated from the second optical fiber 72. In the present embodiment, the end of the second optical fiber 72 on the output side of the signal light is a position facing the reflection unit 10 provided on the front part 22 of the frame 2 and is separated from the scanning light output unit 4. .

  The reflection unit 10 has a function of reflecting the signal light emitted from the second optical fiber 72 toward the optical scanning unit 42. The reflecting portion 10 is provided in a concave portion 27 that opens to the inside of the front portion 22. Note that the opening of the concave portion 27 may be covered with a window portion made of a transparent material. Moreover, this reflection part 10 will not be specifically limited if it can reflect signal light, For example, it can comprise with a mirror, a prism, etc.

  The optical scanning unit 42 is an optical scanner that two-dimensionally scans the signal light from the signal light generation unit 31. Scanning light is formed by scanning the signal light with the optical scanning unit 42. Specifically, the signal light emitted from the second optical fiber 72 is incident on the light reflecting surface of the light scanning unit 42 via the lens 43. Then, by driving the optical scanning unit 42 according to the drive signal generated by the drive signal generation unit 32, the signal light is scanned two-dimensionally.

  The optical scanning unit 42 includes the coil 17 and the signal superimposing unit 18 (see FIG. 4), and the coil 17, the signal superimposing unit 18, and the drive signal generating unit 32 are driving units that drive the optical scanning unit 42. Configure.

  The lens 43 has a function of adjusting the spot diameter of the signal light emitted from the second optical fiber 72. The lens 43 also has a function of adjusting the radiation angle of the signal light emitted from the second optical fiber 72 and making it substantially parallel.

  The signal light (scanning light) scanned by the optical scanning unit 42 is emitted to the outside of the housing 41 through the lens 45.

  Note that the scanning light emitting unit 4 may include a plurality of optical scanning units that scan the signal light in a one-dimensional manner instead of the optical scanning unit 42 that scans the signal light in a two-dimensional manner.

(Reflection part)
As shown in FIGS. 1 and 2, the reflection portion 6 (reflection optical portion) is attached to a rim portion 25 included in the front portion 22 of the frame 2 described above.

  In other words, the reflection unit 6 is disposed so as to be positioned in front of the user's eye EY and on the far side of the user from the optical scanning unit 42 during use. Thereby, it can prevent that the part which protruded ahead with respect to the user's face in the image display apparatus 1 is formed.

  As shown in FIG. 5, the reflection unit 6 has a function of reflecting the signal light from the optical scanning unit 42 toward the user's eye EY.

  In this embodiment, the reflection part 6 is a half mirror (semi-transparent mirror), and also has a function of transmitting external light (translucency for visible light). That is, the reflection unit 6 has a function (combiner function) of reflecting signal light (video light) from the optical scanning unit 42 and transmitting external light from the outside of the reflection unit 6 toward the user's eyes during use. Have. Thereby, the user can visually recognize the virtual image (image) formed by the signal light while visually recognizing the external image. That is, a see-through type head mounted display can be realized.

  In addition, the user-side surface of the reflecting portion 6 is a concave reflecting surface. For this reason, the signal light reflected by the reflection unit 6 is focused on the user side. Therefore, the user can visually recognize a virtual image that is enlarged as compared with the image formed on the concave surface of the reflecting portion 6. Thereby, the visibility of the image in a user can be improved.

  On the other hand, the surface of the reflecting portion 6 that is farther from the user is a convex surface having substantially the same curvature as the concave surface. For this reason, the external light reaches the user's eyes without being largely deflected by the reflecting portion 6. Therefore, the user can visually recognize an external image with little distortion.

  In addition, the reflection part 6 may have a diffraction grating. In this case, the diffraction grating can have various optical characteristics, so that the number of parts of the optical system can be reduced and the degree of freedom in design can be increased. For example, by using a hologram diffraction grating as the diffraction grating, the emission direction of the signal light reflected by the reflection unit 6 can be adjusted, and the wavelength of the reflected signal light can be selected. Further, by providing a lens effect to the diffraction grating, the imaging state of the entire scanning light composed of the signal light reflected by the reflecting portion 6 can be adjusted, or the aberration when the signal light is reflected by the concave surface can be corrected. You can also.

  In the present embodiment, since the optical modulator 30 is used as the external modulator, wavelength fluctuations that occur when the light source is driven to blink are reduced. Therefore, the diffraction angle fluctuation in the diffraction grating is suppressed, and an image with less image blur can be provided. As such a hologram diffraction grating, a three-dimensional diffraction grating formed in an organic material by light interference, or a diffraction grating in which irregularities are formed by a stamper on the surface of a resin material can be used.

  In addition, the reflection unit 6 may be, for example, a member obtained by forming a transflective film made of a metal thin film, a dielectric multilayer film, or the like on a transparent substrate, or a polarizing beam splitter may be used. In the case of using a polarization beam splitter, the signal light from the optical scanning unit 42 may be configured to be polarized, and the polarized light corresponding to the signal light from the optical scanning unit 42 may be reflected.

(First optical fiber, light detector and fixed part)
The fixing unit 35 has a function of fixing one end of the first optical fiber 71 at a position where the intensity of light incident on the first optical fiber 71 from the light source unit 311 is greater than 0 and equal to or less than a predetermined value. Thereby, the intensity | strength of the light which injects into the 1st optical fiber 71 from the light source part 311 can be made small.

  The fixing unit 35 also has a function of fixing the light detection unit 34. Accordingly, the remaining part of the light (signal light) emitted from the light source unit 311 that does not enter the first optical fiber 71 can be effectively used for detection by the light detection unit 34. Further, the positional relationship between the one end portion of the first optical fiber 71 and the light detection unit 34 can be fixed (maintained constant).

  Thus, the light detection unit 34 fixed to the fixed unit 35 can detect the intensity of the emitted light without providing an optical system for branching the signal light emitted from the light sources 311B, 311G, 311R. Can be detected. Further, the intensity of light emitted from the light sources 311B, 311G, and 311R can be adjusted by the control unit 33 based on the intensity of light detected by the light detection unit.

  The provision of the fixing portion 35 as described above is not essential, and the configuration may be such that the light emitted from the light source portion 311 is coupled to the first optical fiber 71 without intentionally dimming. In addition, it is not essential to provide the light detection unit 34 in the fixed unit 35, and the position of the light detection unit 34 is not particularly limited as long as the light amount of the light source unit 311 can be detected.

<< Second Embodiment >>
Next, a second embodiment of the optical modulator of the present invention will be described.

  FIGS. 11 and 12 are partial enlarged plan views of wavelength selection units included in the optical modulator according to the second embodiment. In addition, in FIG. 11, 12, illustration of each voltage application part is abbreviate | omitted.

  Hereinafter, although 2nd Embodiment is described, in the following description, it demonstrates centering around difference with 1st Embodiment mentioned above, The description is abbreviate | omitted about the same matter. Moreover, in the figure, the same code | symbol is attached | subjected about the matter similar to embodiment mentioned above.

  The optical modulator 30 shown in FIG. 11 is configured so that the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B share a common point 3028 between their core portions. The optical modulator 30 is the same as the optical modulator 30 according to the first embodiment except that they overlap each other.

  Such an optical modulator 30 is space-saving compared to the first embodiment. For this reason, further miniaturization of the optical modulator 30 and the image display device 1 can be achieved.

  Also in this embodiment, the optical path length (optical distance) of the core portion is different among the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B. However, it is preferable to realize this by making the physical distance (peripheral length) different from each other rather than making the electric field application conditions different. As a result, the shapes of the annular optical waveguides 3031R, 3031G, and 3031B overlap each other at the common point 3028, while the distance between the core portions increases in other portions, and the core portions are easily separated. For this reason, it is possible to prevent the resonance conditions from becoming too close between the ring resonators 303R, 303G, and 303B, and to prevent the light having a specific wavelength from being removed with high accuracy. In addition, it is possible to improve the manufacturability of the wavelength selection unit 303.

  Further, such an optical modulator 30 is particularly suitable for modulating signal light for image formation like the image display device 1. For example, a general optical modulator is often used for wavelength division multiplexing (WDM) or the like. In WDM, for example, optical communication is performed by multiplexing light of different wavelengths at a wavelength interval of about several nanometers. Therefore, in an optical modulator applied to such WDM, adjacent light is individually modulated at a wavelength interval of about several nanometers. There is a need to. For this reason, when a ring resonator is used for the optical modulator for such an application, the deviation of the circumferential length between the annular optical waveguides becomes very small, and it becomes difficult to overlap each other.

  On the other hand, in an application for modulating signal light for image formation, for example, light of three colors of red, green, and blue may be modulated, so that a wavelength interval of, for example, 50 nm or more can be secured. For this reason, as described above, even if the respective annular optical waveguides 3031R, 3031G, and 3031B are overlapped with each other, the difference in circumferential length is sufficiently large, so that it is easy to overlap each other. Therefore, the downsizing of the optical modulator 30 can be easily realized.

  When the circumferential lengths of the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B are different from each other, the red light LR having the longest wavelength is resonated. The circumference of the first annular optical waveguide 3031R may be made the longest, and the circumference of the third annular optical waveguide 3031B that resonates the blue light LB having the shortest wavelength may be made the shortest.

  The optical modulator 30 shown in FIG. 12 is configured so that the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B share a common point 3028 between their core portions. The first branch optical waveguide 3032R, the second branch optical waveguide 3032G, and the third branch optical waveguide 3032B join at a junction 3027 and are combined into one core portion (optical waveguide) 3032. The optical modulator 30 is the same as that of the optical modulator 30 according to the first embodiment except for being integrated.

  In addition, in the optical modulator 30 shown in FIG. 12, an optical modulator 304 (not shown) is not provided on the extended line of the emission end (so-called through port) of the main optical waveguide 302, but the branch optical waveguides 3032R and 3032G are provided. , 3032B are integrated into one, an optical modulation unit 304 (not shown in FIG. 12) is provided on the extended line of the emission end (so-called drop port) of the core unit 3032. That is, the optical modulator 30 shown in FIG. 12 emits the output light L in which one of the red light LR, the green light LG, and the blue light LB output to the branch optical waveguides 3032R, 3032G, and 3032B is selected as the signal light. 11 is different from the optical modulator 30 shown in FIG.

Such emitted light L is composed of only light having a narrow wavelength width satisfying the resonance condition in the first ring resonator 303R, the second ring resonator 303G, and the third ring resonator 303B. It can be said that the monochromaticity is higher. Therefore, according to the wavelength selection unit 303 shown in FIG. 12, for example, even when the quality of the light emitted from the light source unit 311 is low (the wavelength width is wide), the red color has a wavelength suitable for full-color image display. Light LR, green light LG, and blue light LB can be selected and emitted. For this reason, the selection range of a light source can be expanded. In addition, since the light modulation unit 304 can perform more accurate modulation, signal light that accurately reflects image information can be generated. In addition, such highly monochromatic light, for example, when the reflection unit 6 has a diffraction grating, can suppress a variation in diffraction angle depending on the wavelength, so that the light is more precise. This is useful in that an image can be displayed.
In the second embodiment as described above, the same operations and effects as in the first embodiment can be obtained.

«Third embodiment»
Next, a third embodiment of the optical modulator of the present invention will be described.

  FIGS. 13 and 14 are partially enlarged plan views of wavelength selection units included in the optical modulator according to the third embodiment. In FIGS. 13 and 14, illustration of each voltage application unit is omitted.

  Hereinafter, the third embodiment will be described. In the following description, differences from the first and second embodiments described above will be mainly described, and description of similar matters will be omitted. Moreover, in the figure, the same code | symbol is attached | subjected about the matter similar to embodiment mentioned above.

  The optical modulator 30 shown in FIG. 13 is different from the optical modulator 30 according to the first embodiment except that the arrangement of the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B is different. It is the same.

  That is, in the wavelength selection unit 303 shown in FIG. 13, when the substrate 301 is viewed in plan, the first ring resonator 303R, the third ring resonator 303B, and the second ring resonator 303G are connected to the main optical waveguide 302. They are arranged on opposite sides of each other. Accordingly, the ring resonators 303R, 303G, and 303B can be spatially dispersed and arranged, so that the wavelength selection unit 303 is reduced in space compared to the first embodiment, particularly, the optical waveguide of the main optical waveguide 302. The length in the direction can be shortened.

  The optical modulator 30 shown in FIG. 14 is different in the arrangement of the first annular optical waveguide 3031R, the second annular optical waveguide 3031G, and the third annular optical waveguide 3031B, and the core portion of the first annular optical waveguide 3031R. The optical modulator 30 is the same as the optical modulator 30 according to the first embodiment except that the core portion of the third annular optical waveguide 3031B is overlapped so as to share the common point 3028.

As a result, the wavelength selection unit 303 shown in FIG. 14 saves space compared to the wavelength selection unit 303 according to the first embodiment, and in particular, further shortens the length of the main optical waveguide 302 in the optical waveguide direction.
In the third embodiment as described above, the same operations and effects as in the first and second embodiments can be obtained.

<< Fourth Embodiment >>
Next, a fourth embodiment of the optical modulator of the present invention will be described.

  15 to 18 are partial enlarged plan views of wavelength selection units included in the optical modulator according to the fourth embodiment. 15-18, illustration of each voltage application part is abbreviate | omitted.

  Hereinafter, although 4th Embodiment is described, in the following description, it demonstrates centering around difference with the 1st-3rd embodiment mentioned above, and abbreviate | omits the description about the same matter. Moreover, in the figure, the same code | symbol is attached | subjected about the matter similar to embodiment mentioned above.

  In the optical modulator 30 shown in FIG. 15, the first branch optical waveguide 3032R, the second branch optical waveguide 3032G, and the third branch optical waveguide 3032B extend so as to be orthogonal to the main optical waveguide 302, respectively. Each branch optical waveguide 3032R, 3032G, 3032B has a light incident part and a light emission part, respectively. On the other hand, the main optical waveguide 302 has a light emitting part, but a light incident part is omitted. Except for such differences, the wavelength selection unit 303 shown in FIG. 15 is the same as the wavelength selection unit 303 shown in FIG.

  In such a wavelength selector 303, the red light LR is incident from the light incident portion of the first branch optical waveguide 3032R, the green light LG is incident from the light incident portion of the second branch optical waveguide 3032G, and the third Blue light LB is incident from the light incident portion of the branch optical waveguide 3032B.

When a voltage is applied to the first voltage application unit 3035R and the resonance condition of the first ring resonator 303R (first annular optical waveguide 3031R) is satisfied, the incident red light LR is the main line light The light is output to the waveguide 302 and emitted to the light modulation unit 304. Similarly, when a voltage is applied to the second voltage application unit 3035G and the resonance condition of the second ring resonator 303G (second annular optical waveguide 3031G) is satisfied, the incident green light LG is The light is output to the optical waveguide 302, is emitted to the light modulation unit 304, and a voltage is applied to the third voltage application unit 3035B to satisfy the resonance condition of the third ring resonator 303B (third annular optical waveguide 3031B). Then, the incident blue light LB is output to the main optical waveguide 302 and is emitted to the light modulation unit 304.
The outgoing light L whose wavelength has been selected in this way is output to the light modulator 304.

  Also in the present embodiment, as in the second embodiment, as the emitted light L, light resonated by the ring resonators 303R, 303G, and 303B is used. For this reason, light with high monochromaticity can be output. Therefore, as described above, the selection range of the light source can be widened, signal light that faithfully reflects the image information can be generated in the light modulation unit 304, and variations in diffraction angles in the diffraction grating can be suppressed. it can.

  In the present embodiment, since the light is incident on the wavelength selection unit 303 using the three branch optical waveguides 3032R, 3032G, and 3032B, the merge unit 3025 according to the first embodiment is not necessary. For this reason, the optical modulator 30 can be reduced in size accordingly.

  Furthermore, since the light incident portions of the three branch optical waveguides 3032R, 3032G, and 3032B are arranged in parallel to the optical waveguide direction of the main optical waveguide 302, the light sources 311B, 311G, and 311R are also guided. They can be arranged parallel to the wave direction. As a result, a sufficiently large arrangement space for the light sources 311B, 311G, and 311R can be secured, and the degree of freedom in designing the image display device 1 can be increased.

  In the optical modulator 30 illustrated in FIG. 16, the first branch optical waveguide 3032R, the second branch optical waveguide 3032G, and the third branch optical waveguide 3032B extend so as to be orthogonal to the main optical waveguide 302, respectively. Each branch optical waveguide 3032R, 3032G, 3032B has a light incident part and a light emission part, respectively. On the other hand, the main optical waveguide 302 has a light emitting part, but a light incident part is omitted. Except for these differences, the wavelength selection unit 303 shown in FIG. 16 is the same as the wavelength selection unit 303 shown in FIG.

  In such a wavelength selector 303, the red light LR is incident from the light incident portion of the first branch optical waveguide 3032R, the green light LG is incident from the light incident portion of the second branch optical waveguide 3032G, and the third Blue light LB is incident from the light incident portion of the branch optical waveguide 3032B.

When a voltage is applied to the first voltage application unit 3035R and the resonance condition of the first ring resonator 303R is satisfied, the incident red light LR is output to the main optical waveguide 302, and the light modulation unit It is injected into 304. Similarly, when a voltage is applied to the second voltage application unit 3035G and the resonance condition of the second ring resonator 303G is satisfied, the incident green light LG is output to the main optical waveguide 302 and is subjected to optical modulation. When the resonance condition of the third ring resonator 303B is satisfied by applying a voltage to the third voltage application unit 3035B and satisfying the resonance condition of the third ring resonator 303B, the incident blue light LB is output to the main optical waveguide 302 And emitted to the light modulation unit 304.
The outgoing light L whose wavelength has been selected in this way is output to the light modulator 304.

  Further, in the present embodiment, it is possible to particularly reduce the space of the wavelength selection unit 303, and the merging unit according to the first embodiment is unnecessary, so that the optical modulator 30 can be particularly downsized. it can.

  In the optical modulator 30 illustrated in FIG. 17, the first branch optical waveguide 3032R, the second branch optical waveguide 3032G, and the third branch optical waveguide 3032B extend so as to be orthogonal to the main optical waveguide 302, respectively. Each branch optical waveguide 3032R, 3032G, 3032B has a light incident part and a light emission part, respectively. On the other hand, the main optical waveguide 302 has a light emitting part, but a light incident part is omitted. Except for such differences, the wavelength selection unit 303 shown in FIG. 17 is the same as the wavelength selection unit 303 shown in FIG.

  In the optical modulator 30 shown in FIG. 18, the first branch optical waveguide 3032R, the second branch optical waveguide 3032G, and the third branch optical waveguide 3032B extend so as to be orthogonal to the main optical waveguide 302, respectively. Each branch optical waveguide 3032R, 3032G, 3032B has a light incident part and a light emission part, respectively. On the other hand, the main optical waveguide 302 has a light emitting part, but a light incident part is omitted. Except for such differences, the wavelength selection unit 303 shown in FIG. 18 is the same as the wavelength selection unit 303 shown in FIG.

  The optical modulator 30 shown in FIGS. 17 and 18 also has the same operations and effects as those of the optical modulator 30 shown in FIGS. The optical modulator 30 according to the present embodiment also has the same operations and effects as the optical modulator 30 according to the first to third embodiments.

«Fifth embodiment»
Next, a fifth embodiment of the optical modulator of the present invention will be described.

  FIG. 19 is a partially enlarged plan view of a wavelength selection unit included in the optical modulator according to the fifth embodiment. In FIG. 19, illustration of each voltage application unit is omitted.

  Hereinafter, although 5th Embodiment is described, in the following description, it demonstrates centering around difference with 1st-4th embodiment mentioned above, The description is abbreviate | omitted about the same matter. Moreover, in the figure, the same code | symbol is attached | subjected about the matter similar to embodiment mentioned above.

  The optical modulator 30 shown in FIG. 19 is different from the optical modulator 30 except that two second annular optical waveguides 3031G are optically coupled in series and three third annular optical waveguides 3031B are optically coupled in series. This is the same as the optical modulator 30 shown in FIG.

  That is, in the first ring resonator 303R shown in FIG. 19, the first annular optical waveguide 3031R is configured similarly to FIG. That is, the first annular optical waveguide 3031R is optically coupled to both the first branch optical waveguide 3032R and the main optical waveguide 302.

  On the other hand, in the second ring resonator 303G shown in FIG. 19, two second annular optical waveguides 3031G are optically coupled in series. Of the two second annular optical waveguides 3031G, one is optically coupled to the second branch optical waveguide 3032G, and the other is optically coupled to the main optical waveguide 302.

  Further, in the third ring resonator 303B shown in FIG. 19, three third annular optical waveguides 3031B are optically coupled in series. Of the three third annular optical waveguides 3031B, the third annular optical waveguide 3031B on one end side is optically coupled to the third branch optical waveguide 3032B, and the third annular optical waveguide on the other end side. The waveguide 3031B is optically coupled to the main optical waveguide 302.

  Such an optical modulator 30 is configured to modulate three types of light having different wavelengths. That is, the red light LR having the longest wavelength, the blue light LB having the shortest wavelength, and the green light LG having a wavelength between them are individually modulated. Here, when the wavelength selection unit 303 selects a wavelength, a difference in wavelength may affect the selectivity. Therefore, in the present embodiment, a plurality of annular optical waveguides are coupled in series in some ring resonators in order to compensate for the wavelength dependency of the selectivity.

  That is, in the present embodiment, the first ring resonator 303R that controls the waveguide of the red light LR includes one first annular optical waveguide 3031R, whereas the waveguide of the green light LG is controlled. The second ring resonator 303G includes two second annular optical waveguides 3031G, and the third ring resonator 303B that controls the waveguide of the blue light LB includes three third annular optical waveguides. 3031B is provided.

  In addition, the first annular optical waveguide 3031R has the longest circumference (the radius is large), the third annular optical waveguide 3031B has the shortest circumference (the radius is small), and the second annular optical waveguide 3031G has the smallest circumference. The circumference (radius) is between them.

  Depending on the emission wavelength width of the light source and the configuration of the reflecting portion 6, it is conceivable that the required monochromaticity of each color light differs. This embodiment corresponds to a case where monochromaticity is required in the order of blue light, green light, and red light (that is, the shorter the wavelength). Since the monochromaticity is improved as the number of annular optical waveguides is increased, in the present embodiment, it is desirable to increase the number of annular optical waveguides corresponding to a short wavelength. On the other hand, as the number of annular optical waveguides increases, the area occupied by the wavelength selection unit 303 increases. However, since the radius of the annular optical waveguide corresponding to a short wavelength is smaller, in the configuration of this embodiment, the wavelength selection unit The monochromaticity of a short wavelength emitted from the optical modulator 30 can be enhanced while suppressing an increase in the area occupied by 303.

  By using the wavelength selection unit 303 having such a configuration, it is possible to improve the image quality of the image display device 1 particularly when a hologram diffraction grating is used for the reflection unit 6.

  Note that the number of couplings of the second annular optical waveguide 3031G is not limited to the above number, and may be three or more. Similarly, the number of couplings of the third annular optical waveguide 3031B is not limited to the above number, and may be two or four or more. In addition, although there is one first annular optical waveguide 3031R in the above example, a plurality may be coupled in series.

  For example, when it is desired to increase the separation distance between the connection point between each ring resonator and the main optical waveguide 302 and the branch optical waveguide, the separation distance can be ensured by increasing the number of couplings of the annular optical waveguide. . As a result, since the separation distance between the branch optical waveguides can be freely selected, for example, when the size of the light source is large and it is desired to ensure the distance between the adjacent light sources, it is possible to sufficiently secure the arrangement space of the light sources. it can.

<< Sixth Embodiment >>
Next, a sixth embodiment of the image display device of the present invention will be described.

  FIG. 20 is a diagram showing a sixth embodiment (head-up display) of the image display device of the present invention.

  Hereinafter, the sixth embodiment will be described. In the following description, differences from the above-described first embodiment will be mainly described, and description of similar matters will be omitted. Moreover, in the figure, the same code | symbol is attached | subjected about the structure similar to embodiment mentioned above.

  The image display apparatus 1 according to the sixth embodiment is not mounted on the user's head, but is used while mounted on the ceiling of an automobile. Same as 1.

  That is, the image display device 1 according to the sixth embodiment is used by being mounted on the ceiling part CE of the automobile CA, and a state in which an image based on a virtual image is superimposed on an external image via the front window W of the automobile CA. Make it visible.

  As shown in FIG. 20, the image display device 1 includes a light source unit UT including a signal generation unit 3 and a scanning light emitting unit 4, a reflection unit 6, and a frame 2 ′ connected to the light source unit UT and the reflection unit 6. And comprising.

  In the present embodiment, the light source unit UT, the frame 2 ′, and the reflecting portion 6 are described as an example mounted on the ceiling part CE of the automobile CA. However, these are mounted on the dashboard of the automobile CA. Alternatively, a part of the configuration may be fixed to the front window W. Furthermore, the image display apparatus 1 may be mounted not only on automobiles but also on various moving bodies such as airplanes, ships, construction machines, heavy machinery, two-wheeled vehicles, bicycles, trains, and space ships.

Hereinafter, each part of the image display apparatus 1 according to the present embodiment will be sequentially described in detail.
The light source unit UT may be fixed to the ceiling part CE by any method, but is fixed by a method of mounting on the sun visor using, for example, a band or a clip.

  The frame 2 ′ includes, for example, a pair of long members, and fixes the light source unit UT and the reflection unit 6 by connecting the light source unit UT and both ends of the reflection unit 6 in the Z-axis direction. ing.

  The light source unit UT includes a signal generation unit 3 and a scanning light emitting unit 4, and the signal light L <b> 3 is emitted from the scanning light emitting unit 4 toward the reflection unit 6.

  The reflecting unit 6 according to the present embodiment is also a half mirror and has a function of transmitting the external light L4. In other words, the reflecting section 6 reflects the signal light L3 (video light) from the light source unit UT and transmits the external light L4 directed from the outside of the automobile CA through the front window W to the user's eye EY when in use. Have Thereby, the user can visually recognize the virtual image (image) formed by the signal light L3 while visually recognizing the external image. That is, a see-through type head-up display can be realized.

  Such an image display device 1 also includes the signal generation unit 3 according to the first embodiment as described above. For this reason, although a plurality of lights having different wavelengths can be modulated at a high speed, the light use efficiency is high, so that the display image can be improved in image quality. That is, the same operation and effect as the first embodiment can be obtained. In addition, since it is easy to downsize, there is an advantage that it is difficult to hinder the user's behavior.

  The optical modulator and the image display apparatus of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to these.

  For example, in the image display device of the present invention, the configuration of each unit can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration can be added.

Moreover, the reflection part may be provided with the flat reflective surface.
The embodiment of the image display device of the present invention is not limited to the above-described head mounted display or head up display, and can be applied to any form as long as it has a retinal scanning display principle.

  The light modulator of the present invention may be used for purposes other than the image display device. Examples of such applications include wavelength multiplexing optical communication, and examples of apparatuses include communication equipment and computer equipment.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Frame 2 'Frame 3 Signal generation part 4 Scanning light emission part 5 Connection part 6 Reflection part 10 Reflection part 17 Coil 18 Signal superimposition part 21 Nose pad part 22 Front part 23 Temple part 24 Modern part 25 Rim part 26 Bridge part 27 Recess 30 Optical modulator 31 Signal light generation part 32 Drive signal generation part 33 Control part 34 Light detection part 35 Fixing part 41 Housing 42 Optical scanning part 43 Lens 45 Lens 46 Support member 71 First optical fiber 72 Second optical fiber 301 Substrate 302 Main line optical waveguide 303 Wavelength selection unit 303B Third ring resonator 303G Second ring resonator 303R First ring resonator 304 Light modulation unit 304a Signal electrode 304b Ground electrode 305 Buffer layer 311 Light source unit 311B Light source 311G Light source 311R light source 312B drive circuit 312 G drive circuit 312R drive circuit 321 drive circuit 322 drive circuit 3021 core part 3021B core part 3021G core part 3021R core part 3021a core part 3021b core part 3022 clad part 3023 branch part 3024 merge part 3025 merge part 3027 merge point 3028 joint point 3029B light Incident portion 3029G Light incident portion 3029R Light incident portion 3031B Third annular optical waveguide 3031G Second annular optical waveguide 3031R First annular optical waveguide 3032 Core portion 3032B Third branch optical waveguide 3032G Second branch optical waveguide 3032R First One branch optical waveguide 3033B Third circular electrode 3033G Second circular electrode 3033R First circular electrode 3034B Third annular electrode 3034G Second annular electrode 3034R First annular electrode 3035B Third voltage application Part 3 35G 2nd voltage application part 3035R 1st voltage application part 3040 Electrode CA Car CE Ceiling part EA Ear EC Evanescent coupling EY Eye H Head L Output light L3 Signal light L4 External light LB Blue light LG Green light LR Red light NS Nose TZ0 Time zone TZ1 First time zone TZ2 Second time zone TZ3 Third time zone UT Light source unit W Front window

Claims (12)

A first optical waveguide made of a material having an electro-optic effect;
A wavelength selection unit that is provided in the first optical waveguide and selects a wavelength of light guided through the first optical waveguide;
A light modulation unit that is provided in the first optical waveguide and modulates the intensity of light having a wavelength selected by the wavelength selection unit;
With
The wavelength selector is
An optical waveguide having an annular shape made of a material having an electro-optic effect, the first annular optical waveguide optically coupled to the first optical waveguide, and a first voltage applied to the first annular optical waveguide. A first ring resonator having a first voltage application unit to be applied;
An optical waveguide having an annular shape made of a material having an electro-optic effect, the second annular optical waveguide being optically coupled to the first optical waveguide, and the first voltage applied to the second annular optical waveguide. A second ring resonator having a second voltage application unit for applying a second voltage different from
An optical modulator comprising: A first optical waveguide made of a material having an electro-optic effect;
A wavelength selection unit that is provided in the first optical waveguide and selects a wavelength of light guided through the first optical waveguide;
A light modulation unit that is provided in the first optical waveguide and modulates the intensity of light having a wavelength selected by the wavelength selection unit;
With
The wavelength selector is
An optical waveguide having an annular shape made of a material having an electro-optic effect, a first annular optical waveguide optically coupled to the first optical waveguide, and a voltage applied to the first annular optical waveguide. A first ring resonator having one voltage application unit;
An annular optical waveguide made of a material having an electro-optic effect, optically coupled to the first optical waveguide, and having a circumference different from the circumference of the first annular optical waveguide A second ring resonator having two annular optical waveguides, and a second voltage applying unit that applies a voltage to the second annular optical waveguide;
An optical modulator comprising:   The optical modulator according to claim 1, wherein the first optical waveguide has a light incident portion on which light is incident.   The first optical waveguide includes a plurality of the light incident portions, a plurality of branch optical waveguides connected to the plurality of light incident portions, and a multiplexing portion that joins the plurality of branch optical waveguides. The optical modulator according to claim 3. The first ring resonator further includes a first coupled optical waveguide that is optically coupled to the first annular optical waveguide and includes a light incident portion on which light is incident.
3. The second ring resonator further includes a second coupled optical waveguide that is optically coupled to the second annular optical waveguide and includes a light incident portion on which light is incident. An optical modulator according to 1.   6. The optical modulator according to claim 1, wherein the second ring resonator has a plurality of the second annular optical waveguides coupled to each other.   The optical modulator according to claim 1, wherein the material having an electro-optic effect is lithium niobate.   The optical modulator according to claim 1, wherein the optical modulation unit is a Mach-Zehnder type optical modulation unit. A first optical waveguide made of a material having an electro-optic effect;
A wavelength selection unit that is provided in the first optical waveguide and selects a wavelength of light guided through the first optical waveguide;
A light modulation unit that is provided in the first optical waveguide and modulates the intensity of light having a wavelength selected by the wavelength selection unit;
With
The wavelength selector is
An optical waveguide having an annular shape made of a material having an electro-optic effect, having a first annular optical waveguide optically coupled to the first optical waveguide, and light having a first resonance wavelength A first ring resonator capable of resonating;
An annular optical waveguide made of a material having an electro-optic effect, and having a second annular optical waveguide optically coupled to the first optical waveguide, and different from the first resonance wavelength A second ring resonator capable of resonating light of a second resonance wavelength;
An optical modulator comprising: A light source unit that emits a plurality of lights having different wavelengths;
The light modulator according to any one of claims 1 to 9, wherein light emitted from the light source unit is incident;
An optical scanner that spatially scans the light modulated by the light modulator;
An image display device comprising: In the first time zone, the wavelength selecting unit is driven so that light of the first selected wavelength is selected, and the light modulating unit is configured to modulate the intensity of the light of the first selected wavelength. Driven,
In the second time zone different from the first time zone, the wavelength selection unit is driven so that light having a second selection wavelength different from the first selection wavelength is selected, and the second The light modulator is driven to modulate the intensity of the light of the selected wavelength;
When transitioning from the first time zone to the second time zone, in the time zone between the first time zone and the second time zone, the light of the first selected wavelength and the first time zone The image display device according to claim 10, wherein the wavelength selection unit is driven so as not to select both of the light beams having the two selection wavelengths. Furthermore, a reflection optical unit that reflects light scanned by the optical scanner is provided,
The image display device according to claim 10, wherein the reflection optical unit includes a hologram diffraction grating.

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