JP2019184943A - Optical control element - Google Patents

Abstract

Provided is an optical control element capable of controlling the deflection angle and width of output light while handling light of a plurality of wavelengths and reducing the element size to increase the density. An optical control element includes a waveguide, an optical input unit, and a modulation unit. The waveguides are arranged in an array. The light input unit inputs light of a plurality of different wavelengths to the waveguide in a time division manner. The modulator modulates at least one of a phase and an amplitude of the light on the waveguide. [Selection diagram] Fig. 1

Description

  The present invention relates to a light control element.

A phased array can be used to control the deflection angle and beam width of the output light beam.
Appropriately controlling the deflection angle and beam width of the light beam leads to, for example, improving the quality of a stereoscopic image displayed by the integral method.

  The integral method used for displaying stereoscopic images is based on the principle of stereoscopic photography technology called Integral Photography (IP) announced by Lippmann in 1908. In integral photography, a subject is photographed through a lens array in which many small element lenses are two-dimensionally arranged. Each light beam emitted from the subject is acquired by a pixel in the image sensor as an element image through an element lens. Further, at the time of display, each of the above pixels is arranged at the same position as the positional relationship of each imaging pixel with respect to the lens array used for photographing. Then, each pixel of the display element emits a light beam modulated to a captured pixel value (brightness), and this light beam passes through the lens array, so that the light beam is incident on the imaging element in the opposite direction at the time of photographing. proceed. The light beam forms a stereoscopic image equivalent to the subject at the position where the subject is present. Since the observer sees the stereoscopic image formed in this space, he does not need special glasses and can see the stereoscopic image in the same way as he normally sees.

  The resolution limit of the aerial image reproduced by the integral method is determined by the number of lenses in the lens array. On the other hand, the resolution of a stereoscopic image reproduced in front of or behind the lens array is determined by the number of pixels of the element image corresponding to the element lens. Therefore, in order to reproduce a high-definition stereoscopic image in a wide range in the depth direction, it is necessary to reduce the aperture of the element lens constituting the lens array and to narrow the pixel interval of the display that displays the element image. That is, in order to enlarge the reproduced image, it is necessary to increase the number of lenses and the number of pixels while keeping the aperture and pixel interval of the lens, and it is necessary to increase the area of the lens array and the display.

In the integral system, a method of emitting an element image to a space through an element lens exists as a conventional technique.
Further, in the integral method, for example, in each of the light sources of three primary colors of red (R), green (G), and blue (B), the direction of the light beam to be output is controlled in a time-sharing manner using an optical deflection element. However, it exists as a prior art.
Non-Patent Document 1 (particularly, Fig. 1 and Fig. 3) discloses a backlight for three-dimensional display that outputs light beams in multiple directions using a diffraction grating.

David Fattal, Zhen Peng, Tho Tran, Sonny Vo, Marco Fiorentino, Jim Brug, Raymond G. Beausoleil, “A multi-directional backlight for a wide-angle, glasses-free three-dimensional display”, Nature, VOL.495, p.348-351, 21 MARCH 2013

  According to the conventional method of emitting an element image to a space through an element lens, a color moire is generated by changing a pixel seen through the lens array depending on a viewpoint position. Usually, the liquid crystal display displays one pixel by three dots that respectively display RGB. Therefore, there is a problem in that the color that can be seen through the lens changes depending on the viewpoint position in the R, G, or B pixels, making it difficult to see.

  In the integral method, for example, in each of the light sources of the three primary colors of red (R), green (G), and blue (B), the direction of the light beam to be output is time-division using a light deflecting element. However, there is a problem that it is difficult to increase the density. In other words, in this technique, in order to reproduce a high-definition stereoscopic image, it is not necessary to reduce the element image to a narrow pixel pitch and an extremely large number of pixels, and the element image and the lens are shifted from a desired position. Degradation of the image can be eliminated. However, when color display is performed using this technique, three light deflection devices of R, G, and B are required in one element image, and the size of one element image is also increased. Is difficult.

  Also in the method described in Non-Patent Document 1, it is necessary to produce diffraction gratings having different sizes according to the wavelengths of light of R, G, and B, and it is difficult to increase the density of a stereoscopic image. It is.

  The present invention has been made based on the recognition of the above problems, and controls the deflection angle and width of output light while handling light of a plurality of wavelengths, reducing the size of the element and increasing the density. It is an object of the present invention to provide a light control element that can be used.

  [1] In order to solve the above-described problem, a light control element according to an aspect of the present invention inputs a plurality of waveguides arranged in an array and a plurality of lights having different wavelengths to the waveguide in a time-sharing manner. And an optical input unit that modulates at least one of a phase and an amplitude of the light on the waveguide.

  [2] Further, according to one aspect of the present invention, in the light control element described above, the modulation unit includes a phase difference between the adjacent waveguides on the array according to a wavelength of light input to the waveguide. And a phase modulation section that makes the difference.

  [3] Further, according to one aspect of the present invention, in the light control element described above, the phase modulation unit may cause a phase difference between the waveguides to obtain a predetermined deflection angle of light input to the waveguides. The light is phase-modulated so as to be inversely proportional to the wavelength.

  [4] Further, according to one aspect of the present invention, in the light control element, the modulation unit has an output intensity of the light from the number of the waveguides according to a wavelength of the light input to the waveguides. An amplitude modulation unit that modulates the amplitude of the light in the waveguide so as to be zero.

  [5] Further, according to one aspect of the present invention, in the light control element described above, the amplitude modulation unit may be configured such that a number of the waveguides whose output intensity is non-zero to obtain a predetermined output light beam width is a reference value. The amplitude of the light is controlled so as to be based on a value obtained by multiplying the reference number in the case of the reference wavelength, which is the wavelength of the light to be obtained, by the ratio of the wavelength of the light input to the waveguide with respect to the reference wavelength.

  [6] Further, according to one aspect of the present invention, in the light control element, the plurality of waveguides may be N rows and 1 column or 1 row and N columns (provided that N Are arranged in an array of 2 or more integers).

  [7] Further, according to one embodiment of the present invention, in the light control element, the plurality of waveguides may have M rows and N columns (where M and N are each 2 when viewed from the light output end side). Are arranged in an array of the above integers).

  [8] One embodiment of the present invention is the light control element according to the above light control element, wherein the plurality of different wavelengths are three kinds of wavelengths respectively corresponding to red, green, and blue.

  According to the present invention, it is possible to make the deflection angle of the output light constant or to make the width of the spread of the output light constant regardless of the wavelength of the light input to the light control element. It becomes.

It is a functional block diagram which shows the function structure of the light control element by 1st Embodiment of this invention. It is a functional block diagram which shows the further detailed functional structure of the modulation part by the embodiment. It is a block diagram which shows the structure of the light control element by the same embodiment further in detail. It is sectional drawing in the predetermined cross section of the amplitude modulation part by the embodiment. It is a perspective view which shows the more detailed structure of the phase modulation part by the embodiment. It is the schematic (figure seen from the output end side) which shows arrangement | positioning of the output end of the waveguide by the same embodiment. It is the schematic for demonstrating the effect | action by the modulation part in the embodiment. It is the schematic which shows the structural example of the time division light emission part which is a part of light input part by the embodiment. It is a graph which shows the intensity | strength of the light corresponding to a deflection angle in case the light of wavelength 460nm ((lambda) _min ) which is the shortest wavelength is input in the embodiment. It is a graph which shows the relationship between the phase difference between adjacent waveguides, and the maximum deflection angle for every wavelength of input light in the same embodiment. It is a graph which shows the breadth (width) of the output light beam for every wavelength of input light by the embodiment. It is a block diagram which shows the structure of the modulation part by 2nd Embodiment. It is a block diagram which shows the structure of the modulation part by 3rd Embodiment. It is the schematic (figure seen from the output end side) which shows arrangement | positioning of the output end of a waveguide by 4th Embodiment.

Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a functional block diagram showing a functional configuration of the light control element according to the first embodiment. As shown in the figure, the light control element 10 includes an optical input unit 1, a plurality of waveguides 2, and a modulation unit 3 in each waveguide 2.
The light input unit 1 inputs light into the waveguide 2. Specifically, the light input unit 1 inputs light of a plurality of different wavelengths to the waveguide 2 in a time division manner. There are three types of wavelengths of light corresponding to, for example, red (R), green (G), and blue (B). However, the light input unit 1 may input light having a different wavelength set to the waveguide 2 in a time division manner.
The light input unit 1 includes, for example, a time division light emitting unit that emits light of different wavelengths in a time division manner, and a light beam splitter that branches light emitted from the time division light emission unit into a plurality of waveguides 2. The time division light emitting unit and the light beam splitter will be described later in detail.
Each of the waveguides 2 guides light input from the light input unit 1 from an input end (right side in the figure) to an output end (left side in the figure). The light is output from the output end of the waveguide 2. The plurality of waveguides 2 are arranged in an array as viewed from the output end side. Here, the array arrangement is an arrangement arranged in M rows and N columns. Here, M and N are integers, and at least one of M and N is 2 or more. A modulation unit 3 is provided on each waveguide 2.
The modulation unit 3 modulates at least one of the phase and the amplitude of the light input from the light input unit 1 on the waveguide 2. Specifically, the modulation unit 3 in the present embodiment modulates both the phase and the amplitude of the input light.

  The output end (left side in the figure) of the waveguide 2 is a phased array optical antenna. When the phased array arranged in the figure is viewed in plan, that is, when viewed from the left side of FIG. 1, the optical antennas are arranged in an array of N rows and 1 column.

  FIG. 2 is a functional block diagram showing a more detailed functional configuration of the modulation unit 3. As shown in the figure, the modulation unit 3 includes a phase modulation unit 31 and an amplitude modulation unit 32.

The phase modulation unit 31 modulates the phase of light on the waveguide 2. The phase modulation unit 31 includes a material having an electro-optic effect (EO effect) in the waveguide 2 and electrodes sandwiching the material. By applying a predetermined voltage to this electrode, the phase of light is modulated by changing the refractive index of light. As a material having an electro-optic effect, for example, lithium niobate (LiNbO ₃ , Lithium Niobate, LN), potassium tantalate niobate (KTa _1-x Nb _x O ₃ , KTN), EO polymer, or the like is used. it can. For example, when an EO polymer optical waveguide is used, an element having a high response speed (several tens of gigahertz (GHz) or higher) can be realized.
The phase modulation unit 31 varies the phase difference between the adjacent waveguides on the array according to the wavelength of the light input to the waveguide 2.
As will be described later, in order to obtain a predetermined deflection angle, the phase modulation unit 31 phase-modulates light so that the phase difference between the waveguides is inversely proportional to the wavelength of light input to the waveguides.

The amplitude modulation unit 32 modulates the amplitude of light on the waveguide 2. As the amplitude modulation unit 32, for example, a Mach-Zehnder modulator can be used. The Mach-Zehnder modulator modulates the amplitude by the phase difference between two lights separated from one light source. For the phase modulation in the Mach-Zehnder modulator, a material having an electro-optic effect such as the above-mentioned EO polymer can be used.
The amplitude modulator 32 modulates the amplitude of light in the waveguide 2 so that the output intensity of light from the number of waveguides 2 corresponding to the wavelength of light input to the waveguide 2 becomes zero.
Specifically, as will be described later, in the amplitude modulation unit 32, the number of the waveguides 2 whose output intensity is non-zero in order to obtain a predetermined output light beam width is the reference wavelength of light. The amplitude of the light is controlled so as to be based on a value obtained by multiplying the reference number in the case of the reference wavelength by the ratio of the wavelength of light input to the waveguide with respect to the reference wavelength.

FIG. 3 is a configuration diagram showing the configuration of the light control element 10 in more detail.
In the figure, 21 is a light beam splitter. The optical beam splitter 21 is provided with an input optical waveguide. Through this input optical waveguide, light of different wavelengths is input to the light beam splitter 21 in a time division manner. In this example, as shown in the figure, light of three types of wavelengths of λ _max , λ, and λ _min is input to the light beam splitter 21 in a time division manner. These wavelengths λ _max , λ, and λ _min correspond to, for example, red, green, and blue colors, respectively. At one time point, light of one of these three wavelengths is input to the light beam splitter 21. A plurality of waveguides 2 are connected to the light beam splitter 21. The light beam splitter 21 distributes the input light to each waveguide 2.

On the waveguide 2, a phase modulation unit 31 and an amplitude modulation unit 32 are provided in order from the upstream side.
The phase modulation unit 31 itself is configured using a conventional technique. The phase modulation unit 31 includes an electro-optic material 313 and electrodes 311 and 312 for applying a voltage to the electro-optic material. The phase modulation voltage 33 is connected to one of the electrode pairs (electrode 311), and the other (electrode 312) of the pair is connected to the ground. That is, the phase modulation voltage 33 is applied to the electro-optic material 313. Application of the phase modulation voltage 33 modulates the phase of light for each waveguide 2.
Further, the amplitude modulation section 32 itself is configured using a conventional technique. The amplitude modulation unit 32 is realized using, for example, a Mach-Zehnder modulator. The amplitude modulation unit 32 includes an electro-optic material 303 and electrodes 301 and 302 for applying a voltage to the electro-optic material. The amplitude modulation voltage 34 is connected to one of the pair of electrodes (electrode 301), and the other (electrode 302) of the pair is connected to the ground. That is, the amplitude modulation voltage 34 is applied to the electro-optic material 303. The amplitude modulation unit 32 includes polarizers 300A and 300B. The polarization plane of the polarizer 300A and the polarization plane of the polarizer 300B intersect. The polarizer 300A is provided on the input side to the electro-optic material 303, and the polarizer 300B is provided on the output side from the electro-optic material 303. Application of the amplitude modulation voltage 34 modulates the amplitude of light for each waveguide 2.

As shown in the figure, numbers 1, 2,..., N _max are assigned to the respective waveguides. When the output ends of the N _max waveguides 2 are viewed in plan, that is, when viewed from the left side of FIG. 3, these output ends are arranged vertically with a pitch p.

  FIG. 4 is a perspective view showing a more detailed configuration of the amplitude modulation section 32. As illustrated, the amplitude modulation unit 32 includes a phase modulation unit 31 therein. The input light to the amplitude modulation unit 32 is demultiplexed by a demultiplexer or the like and guided to two waveguides. By providing the phase modulation section 31 only in one of these two waveguides, a light phase difference occurs between the two waveguides. The light passing through these two waveguides is interfered and synthesized by a multiplexer or the like. The amplitude of the light output when the phase difference between the light passing through the two waveguides is zero is a maximum value. Further, the phase difference between the light passing through the two waveguides is π [rad. ], The amplitude of the light output at the time becomes the minimum value. That is, by controlling the phase by changing the applied voltage in the phase modulation unit 31 in the amplitude modulation unit 32, the light input to the amplitude modulation unit 32 is amplitude-modulated and output.

  FIG. 5 is a perspective view showing a more detailed configuration of the phase modulation unit 31. As illustrated, the phase modulation unit 31 includes electrodes 311 and 312, an optical waveguide core (electro-optical material) 316, and an optical waveguide cladding 317. The electrodes 311 and 312 are as described with reference to FIG. Note that the electrode 311 may be referred to as an upper electrode, and the electrode 312 may be referred to as a lower electrode. The optical waveguide core 316 and the optical waveguide 317 have different refractive indexes, and input light travels through the optical waveguide core 316. Then, phase modulation of light traveling in the optical waveguide core 316 is performed by an electric field generated between the electrodes 311 and 312.

FIG. 6 is a schematic diagram showing the arrangement of the output ends of the waveguide 2. As illustrated, N _max output ends are arranged in an array of N _max rows and one column on the yz plane in the xyz space (or on a plane parallel to the yz plane). As shown also in FIG. 3, the output ends of the waveguide 2 are arranged at a pitch p.

  Returning to FIG. 3, the light output from the waveguides 2 interferes with each other by the action of the modulation unit 3 in each waveguide 2, and is output at a predetermined deflection angle (deflection in the z-axis direction in FIG. 6). The In addition, the light output from the waveguides 2 is output with a predetermined beam width by the action of the modulation unit 3 in each waveguide 2.

FIG. 7 is a schematic diagram for explaining the operation of the modulation unit 3. As illustrated, the light control element 10 includes an input optical waveguide 51, an electrode signal line 52, a phase modulation unit 31, and an amplitude modulation unit 32.
On each waveguide 2, a phase modulation unit 31 in FIG. 5 and an amplitude modulation unit 32 in FIG. 4 (divided into two waveguides) are provided. Detailed configurations of the phase modulation section 31 and the amplitude modulation section 32 in the element shown in FIG. 7 are as described below.
The electrode signal line 52 may be provided on either the front or back side of the element shown in FIG. The detailed configuration in each case is as follows.
When the electrode signal line 52 is formed on the substrate side (the back side and the lower side in FIG. 7), the electrode signal line 52 includes both the lower electrode 312 of the phase modulation unit 31 and the lower electrode 302 of the amplitude modulation unit 32. It is connected to the. In this case, the upper electrode 311 of the phase modulation unit 31 and the upper electrode 301 of the amplitude modulation unit 32 face the lower electrode 312 of the phase modulation unit 31 and the lower electrode 302 of the amplitude modulation unit 32, respectively. It is formed as a uniform electrode film on the surface side and is connected to ground.
On the other hand, when each electrode signal line 52 is formed on the element surface side (the front side and the upper side in FIG. 7), the electrode signal line 52 includes the upper electrode 311 of the phase modulation unit 31 and the upper electrode 301 of the amplitude modulation unit 32. And connected to. In this case, the substrate is arranged such that the lower electrode 312 of the phase modulation unit 31 and the lower electrode 302 of the amplitude modulation unit 32 face the upper electrode 311 of the phase modulation unit 31 and the upper electrode 301 of the amplitude modulation unit 32, respectively. It is formed as a uniform electrode film on top and connected to ground.
In FIG. 7, the detailed configuration described here is omitted, and the waveguide 2 is illustrated.
In FIG. 3 described above, the upper electrode 311 of the phase modulation unit 31 and the upper electrode 301 of the amplitude modulation unit 32 are connected to the electrode signal line, and the lower electrode 312 of the phase modulation unit 31 and the amplitude modulation unit 32 are connected. The case where the lower electrode 302 is connected to the ground is shown.

The input optical waveguide 51 takes in input light from the outside. The wavelength of the input light is λ _i (where i = 1, 2, 3), and the wavelength is switched at a predetermined timing.
The light beam splitter 21 branches the light acquired from the input optical waveguide 51 into a plurality (N) of waveguides 2.
The electrode signal line 52 is a signal line connected to an electrode for applying a voltage to the phase modulation unit 31 and the amplitude modulation unit 32.
The phase modulation unit 31 shifts the phase of the light in each waveguide 2 by the applied voltage (or current). By appropriately controlling the phase of each waveguide 2, the light output from the output end of the waveguide 2 interferes with each other to form a light beam. For example, the phase difference between the adjacent waveguides 2 is fixed to Δφ. At this time, the relationship between the phase difference Δφ and the deflection angle θ of the output light (displacement from the 0 degree direction shown in the figure) is expressed by the following equation (1).

In equation (1), λ _i is the wavelength of light. Further, p is the pitch of the output end of the disposed waveguide 2. That is, p is an arrangement pitch of the optical antennas of the phased array.

FIG. 8 is a schematic diagram illustrating a configuration example of the time-division light emitting unit. The time division light emitting unit 60 emits light of a plurality of different wavelengths in a time division manner. The time division light emitting unit 60 includes semiconductor lasers 61-1, 61-2, 61-3, light shielding switches 62-1, 62-2, 62-3, mirrors 63-1, 63-2, 63-3, Have
The semiconductor lasers 61-1, 61-2, and 61-3 emit light having wavelengths λ ₁ , λ ₂ , and λ ₃ , respectively. As the light source, an LED (light emitting diode) or the like may be used instead of the laser. It is desirable to use a light source with high coherence.
The light shielding switches 62-1, 62-2, and 62-3 switch whether to transmit or block light from the semiconductor lasers 61-1, 61-2, and 61-3, respectively, based on the control signal. Only one of the light shielding switches 62-1, 62-2, and 62-3 transmits light at a temporary point by the control signal.
Each of the mirrors 63-1, 63-2, and 63-3 reflects light from above in the drawing to the left and transmits light from the right in the drawing.
With the above configuration, the time division light emitting unit 60 emits light of different wavelengths in a time division manner. The light emitted from the time division light emitting unit 60 is input to the light beam splitter 21 (FIG. 7 and the like).
In this example, the time division light emitting unit 60 emits light of three types of wavelengths, but the number of types of wavelengths may be two or four or more.

  As described above with reference to FIGS. 1 to 8, the light control element 10 time-divides each of the input light beams (for example, three colors of R, G, and B) having different wavelengths. Thus, an output light beam having a predetermined spread (beam width) and a deflection angle is output. The wavelength and deflection angle of light can be appropriately switched every predetermined period. That is, by arranging a large number of such light control elements 10, a color stereoscopic image by an integral method can be displayed.

For a certain input wavelength λ _min , the number of elements of the optical antenna of the phased array that can obtain the beam width W _beam and the maximum deflection angle ± θ _max is N _min, and the pitch of the (light) antenna is P _min . A light beam having an input wavelength λ longer than the wavelength λ _min is input to the phased array in a time division manner. The maximum value of the input wavelength λ is λ _max . The pitch of the optical antenna of the phased array is fixed at P _min and the maximum number of elements N _max of the optical antenna is set to a value represented by the following expression (2) or expression (3). _However, as even-odd properties between the _{N max} and _{N min} are identical, determine the _{N max} by selecting any of the formulas (2) or formula (3).

However, in Expression (2) and Expression (3), round () is a function that rounds off the decimal part to make an integer.
N _max calculated by the above formula (2) or formula (3) is the maximum number of elements of the optical antenna required to obtain a desired beam width on the assumption that the maximum wavelength is λ _max. Value. In other words, the light control element 10 may be configured to have the N _max waveguides 2.

In this phased array, when a light beam having a wavelength λ is input in a time division manner, the value of N is obtained by the following equation (4) or equation (5). However, N is obtained by selecting either equation (4) or equation (5) so that the even-oddity matches between N and N _min .

Based on N _max and N obtained by the above equations (2), (3), (4), and (5), the modulation by the modulation unit 3 is adjusted as follows. That is, when N _max optical antennas, which is the maximum number of elements, are arranged in a row, the intensity is such that the output of ((N _max −N) / 2) optical antennas is 0 from both ends. Modulate.
In other words, the amplitude modulation unit 32 sets the reference number when the number of the waveguides 2 whose output intensity is non-zero to obtain a predetermined output light beam width is a reference wavelength that is the wavelength of the reference light, The amplitude of the light is controlled so as to be based on a value obtained by multiplying the ratio (λ / λ _min ) of the wavelength of light input to the waveguide with respect to the reference wavelength.

  Further, modulation is performed so that a desired deflection angle of the output light beam is obtained. Further, phase modulation is performed so that the phase difference between adjacent optical antennas becomes a value represented by the following expression (6).

That is, in order to obtain a predetermined deflection angle, the phase modulation unit 31 performs phase modulation on the light so that the phase difference between the waveguides is inversely proportional to the wavelength of the light input to the waveguides.
Thereby, irrespective of the value of the wavelength λ of the input light, the width and the maximum deflection angle of the output light beam can be set to the same values as the W _beam and ± θ _max , respectively.

  Next, a more specific configuration example when the light control element according to the present embodiment is used for a specific application will be described. As an example, a case where the light control element is used in an integral type stereoscopic display device will be described.

The light input unit 1 inputs light of RGB colors to the waveguide 2 in a time division manner. Therefore, a semiconductor laser beam having a wavelength of 640 nm, 520 nm, and 460 nm is used as a light source for each of R, G, and B colors.
As an element used for the integral type stereoscopic display device, it is desirable that the viewing zone is about 30 degrees or more. In addition, if two or more light beams passing through one point in the space are simultaneously incident on the observer's pupil of the stereoscopic image, the eyes can be focused on the point, and thus a more natural stereoscopic display can be achieved. . This is reported in the reference [Y. Takaki: “Density Directional Display for Generating Natural Three-Dimensional Images”, Proc. IEEE, Vol. 94, pp. 654-663 (2006)]. For example, to achieve this at an observation distance of about 1 to 2 meters (viewing range of about 30 degrees), it is necessary to set the angular pitch of the light beam to about 0.5 degrees or less. Therefore, for example, the maximum deflection angle is 30 degrees (that is, ± 15 degrees from the center), and the deflection angle beam width (half-power width) is 0.5 degrees.

FIG. 9 is a graph showing light intensity when light having a wavelength of 460 nm (λ _min ), which is the shortest wavelength, is input. In the graph of the figure, the horizontal axis corresponds to the deflection angle, and the vertical axis corresponds to the relative intensity of light. As shown in the figure, the number of elements of the optical antenna of the phased array that can obtain the beam width W _beam = 0.5 degrees and the maximum deflection angle θ _max = 15 degrees with respect to the shortest wavelength of 460 nm is N _min = 58. The pitch of the optical antennas arranged in an array is P _min = 460 nm × 1.8 = 828 nm. When the phase difference of light between adjacent waveguides 2 is π [rad, radians] or more, the main lobe and the grating lobe simultaneously enter the viewing zone angle as shown in the figure.

In addition, when light having a wavelength of 640 nm (λ _max ), which is the longest wavelength, is input, if the pitch of the optical antenna is maintained at P _min = 460 nm × 1.8 = 828 nm, the number of optical antenna elements N _max is as described above. According to formula (2) or formula (3). That is, when the even / oddity of the number of elements N _max is adjusted to N _min , N _max = 82 using the equation (3). That is, the number of waveguides 2 in the light control element 10 is 82.

In addition, when light having a wavelength λ = 520 nm is input, if the pitch of the optical antenna is maintained at P _min = 460 nm × 1.8 = 828 nm, the number N of elements of the optical antenna to be used can be calculated by the above formula (4). Or according to equation (5). That is, when the even / oddity of the number of elements N _max is matched with N _min , N = 66 using equation (4).

  In order to make the deflection angle and the beam width of the light beam coincide with each other regardless of the input wavelength, the modulation unit 3 performs the following modulation (described in FIGS. 10 and 11). Control is sufficient.

FIG. 10 is a graph showing the relationship between the phase difference between adjacent waveguides and the maximum deflection angle for each wavelength of input light. FIG. 4A is a graph when the phase difference between adjacent waveguides is not adjusted according to the wavelength of light. FIG. 4B is a graph in the case of adjusting the phase difference between adjacent waveguides according to the wavelength of light. In these graphs, the horizontal axis represents the phase difference between adjacent waveguides. The vertical axis is the maximum deflection angle. As a premise of these graphs, the number of waveguides is N _max = 82, and the arrangement pitch is P _min = 460 nm × 1.8 = 828 nm.

As shown in FIG. 10A, R (λ = λ _max = 640 nm) light, G (λ = 520 nm) light, and B (λ = λ _min = 460 nm) light pass through the waveguide 2 as they are. If you pass,
That is, when the phase difference between adjacent waveguides is Δφ _λmin , the maximum deflection angle deviates.
As shown in FIG. 10B, when the phase difference between the adjacent waveguides is changed according to the wavelength λ of the input light, that is, the phase difference between the adjacent waveguides is (Δφ _λmin × (λ _min / λ)). In this case, the maximum deflection angles of the light of each wavelength are the same.
As shown in FIG. 10B, in order to obtain a result in which the maximum deflection angles coincide with each other, the phase modulation unit 31 adjusts the phase difference between adjacent waveguides according to the wavelength of light input in time division. To do.

FIG. 11 is a graph showing the spread (width) of a light beam for each wavelength of input light. FIG. 4A is a graph when the number of waveguides N is not adjusted according to the wavelength of light. FIG. 5B is a graph when the number of waveguides N is adjusted according to the wavelength of light. In these graphs, the horizontal axis represents the displacement angle (both positive and negative directions) from the center of the light beam. The vertical axis represents the relative intensity of light. As a premise of these graphs, the maximum number of waveguides is N _max = 82, and the arrangement pitch is P _min = 460 nm × 1.8 = 828 nm.

In the case shown in FIG. 11A, the minimum number of waveguides N (the number of elements of the optical antenna) is 58. At this time, the way the beam spreads differs depending on the wavelength of the input light. In other words, the beam spread (width) is the largest when light of R (λ = λ _max = 640 nm) is input, and the beam spread (light) when light of B (λ = λ _min = 460 nm) is input. (Width) is the smallest. When light of G (λ = 520 nm) is input, the beam spread (width) belongs to these two intermediate regions. In other words, in the case of FIG. 11A, the beam widths are not uniform with light of different wavelengths.
In the case shown in FIG. 11B, the number of waveguides N is changed in accordance with the wavelength of input light. That is, the number N of waveguides is changed using the formula (4) or the formula (5). Here, λ _min = 460 nm and N _min = 58. In this case, the width of the output light beam can be made uniform regardless of the wavelength of the input light.
As shown in FIG. 11B, in order to make the beam divergence equal (0.5 degrees), the amplitude modulation unit 32 is provided in the adjacent waveguide according to the wavelength of the light input in time division. Adjust the light amplitude. That is, the amplitude modulation unit 32 has the output intensity of ((N _max −N) / 2) optical antennas from both ends of the 82 (N _max ) elements, which is the maximum number of optical antenna elements. Amplitude modulation is performed so as to be zero. Here, N is an integer calculated as described above according to the wavelength of input light. Since N _max and N's even-oddity match, ((N _max −N) / 2) is an integer value.

  In the description of FIGS. 10 and 11, the values used as the wavelength of light, the pitch of the optical antenna, the beam width, and the deflection angle are examples, but the same applies when different values are used for these. Calculation is valid.

  The light control element 10 includes a control unit (not shown) that controls the light input unit 1 and the modulation unit 3. The control unit performs control to switch the wavelength of light input to the waveguide 2 by the light input unit 1 every predetermined period. The control unit also controls how the phase modulation unit 31 performs phase modulation and how the amplitude modulation unit 32 performs amplitude modulation. Specifically, the voltage applied to each of the phase modulation unit 31 and the amplitude modulation unit 32 in the modulation unit 3 in each waveguide is controlled.

The control unit controls the light input unit 1 to supply only the light having a predetermined wavelength to the waveguide 2 for each period.
The control unit controls the phase in each waveguide so that the deflection angle of the light beam output from the optical antenna array 8 becomes a desired angle. As shown in FIG. 10B, the control unit adjusts the phase difference between the waveguides according to the wavelength of the light input to the waveguide 2, thereby deflecting the output light regardless of the wavelength of the light. The angle is controlled to be a desired angle. Specifically, when the wavelength of the input light is λ, the control unit controls the phase modulation unit 31 so that the phase difference between the adjacent waveguides satisfies the formula (6).
The control unit may sequentially change the deflection angle of the output light.
Further, the control unit controls the amplitude of light in each waveguide so that the spread of the light beam output from the optical antenna array 8 has a desired width. As shown in FIG. 11B, the control unit adjusts the amplitude of the light on the waveguide according to the wavelength of the light input to the waveguide 2, thereby allowing the output light to be output regardless of the wavelength of the light. Control the spread to a desired width. Specifically, when the wavelength of the input light is λ, the control unit obtains the value of N based on the above formulas (4) and (5). Then, the amplitude modulation unit 32 is controlled so that the intensity of light output from other than the number of optical antenna elements of the number N obtained is 0 (or almost 0).

  According to the light control element of the present embodiment, it is possible to output a light beam having the same deflection angle and spread even when the wavelength of input light is different. As an example, when light of three colors of red (R), green (G), and blue (B) is input in a time division manner, the deflection angle and the spread are made to coincide with each other regardless of the color (that is, the wavelength) (or Can be outputted. For example, in the case where an integral type stereoscopic display device is configured using this light control element, it is possible to achieve high-definition video and to solve the problem of color moire.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, about the matter already demonstrated in previous embodiment, description may be abbreviate | omitted below. Here, the description will focus on matters specific to the present embodiment.
The feature in this embodiment is the structure of a modulation part. That is, in the first embodiment, the modulation unit 3 includes the phase modulation unit 31 and the amplitude modulation unit 32 (see FIG. 2). On the other hand, the configuration of the modulation unit in the present embodiment is different.

  FIG. 12 is a block diagram showing the configuration of the modulation unit in this embodiment. As illustrated, in the present embodiment, the modulation unit 4 includes a phase modulation unit 31. Further, the modulation unit 4 does not have an amplitude modulation unit. That is, the light control element in the present embodiment controls the deflection angle of the light beam that is output by performing phase modulation in the waveguide, and therefore aligns the deflection angle in a desired direction regardless of the wavelength of the input light. Can do. However, in the light control element in the present embodiment, the width of the output light beam differs depending on the wavelength of the input light.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. Note that description of matters already described up to the previous embodiment may be omitted below. Here, the description will focus on matters specific to the present embodiment.
The feature in this embodiment is the structure of a modulation part. That is, in the first embodiment, the modulation unit 3 includes the phase modulation unit 31 and the amplitude modulation unit 32 (see FIG. 2). On the other hand, the configuration of the modulation unit in the present embodiment is different.

  FIG. 13 is a block diagram showing a configuration of the modulation unit in the present embodiment. As illustrated, in the present embodiment, the modulation unit 5 includes an amplitude modulation unit 32. Further, the modulation unit 5 does not have a phase modulation unit. That is, the light control element in this embodiment controls the width of the light beam to be output by performing wavelength modulation in the waveguide. Thus, the light control element can align the spread of the output light beam to a desired width regardless of the wavelength of the input light. However, in the light control element according to the present embodiment, the deflection angle of the output light beam differs depending on the wavelength of the input light.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. Note that description of matters already described up to the previous embodiment may be omitted below. Here, the description will focus on matters specific to the present embodiment.
In the first to third embodiments, as shown in FIG. 6, the optical antenna (the output end of the waveguide 2) is arranged as a one-dimensional array (one row). In the present embodiment, the optical antenna is arranged as a two-dimensional array.

FIG. 14 is a schematic view showing the arrangement of the optical antennas according to the present embodiment. Each of the optical antennas shown in the figure is the output end side of a waveguide having a modulation section, similar to the waveguide 2 shown in FIG. FIG. 14 is an arrangement viewed from the light output end side. In the illustrated example, a total of 16 optical antennas of 4 rows × 4 columns are arranged on the yz plane in the xyz space (or on a plane parallel to the yz plane). Note that the number of rows and columns in the arrangement may be other than 4 rows and 4 columns. Further, the number of rows and the number of columns may not be the same. Further, the optical antenna disposed, pitch in the y-axis direction is p _y, the pitch of the z-axis direction is p _z. In addition, p _y = p _z may be sufficient, and p _y ≠ p _z may be sufficient.

In the present embodiment, the modulation unit provided in the waveguide 2 may be the same as the modulation unit 3 in the first embodiment, or the same as the modulation unit 4 in the second embodiment. The same as the modulation unit 5 in the third embodiment may be used.
In the present embodiment, when the modulation unit includes the phase modulation unit 31, a control unit (not shown) controls the deflection angle of the output light beam. In this case, the control unit controls the deflection angles in the y-axis direction and the z-axis direction, respectively. In addition, as described in the first embodiment, the control unit is configured so that each of the y-axis direction and the z-axis direction can obtain a desired deflection angle according to the wavelength of light input to the waveguide 2. The phase difference between adjacent waveguides is controlled.
In the present embodiment, when the modulation unit includes the amplitude modulation unit 32, the control unit controls the spread of the output light beam. In this case, the control unit controls the spread (width) in the y-axis direction and the z-axis direction, respectively. Further, as described in the first embodiment, the control unit is configured for each of the y-axis direction and the z-axis direction so that a desired beam width is obtained according to the wavelength of light input to the waveguide 2. The amplitude of light in each waveguide is controlled.
The control unit controls the deflection angle and the beam width for each of the y-axis direction and the z-axis direction. In the present embodiment, since the optical antennas are two-dimensionally arranged, an effect of superimposing the control in each axial direction is obtained as a result.

As described above, according to at least one embodiment, the deflection angle and width of the output light beam can be made constant regardless of the wavelength of light.
When the array of waveguides is arranged in N rows and 1 column or 1 row and N columns (where N is an integer of 2 or more), in other words, in the case of a one-dimensional array, the light control element outputs in that direction. It is possible to provide a light deflection angle and control the width of output light.
When the array of waveguides is arranged in M rows and N columns (where M and N are each an integer of 2 or more), in other words, in the case of a two-dimensional array, the light control elements are respectively in the row direction and the column direction. In this direction, the deflection angle of the output light can be given, or the width of the output light can be controlled.

  The function of the control unit in each embodiment described above may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” is a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, a DVD-ROM, a USB memory, or a storage device such as a hard disk built in a computer system. That means. “Computer-readable recording medium” means a program that temporarily and dynamically holds a program, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside the computer system serving as a server or a client may be included, and a program that holds a program for a certain period of time may be included. The program may be a program for realizing a part of the above-described functions, or may be a program that can realize the above-described functions in combination with a program already recorded in a computer system.

Although a plurality of embodiments have been described above, the present invention can also be implemented in the following modifications.
An example of a modification is application to a light control element for a micro projector capable of projecting an image on a retina. Laser retinal scanning ultra-compact projectors are characterized by being less susceptible to wearer's visual acuity and focus position by projecting images directly onto the retina, but because of the use of MEMS, response speed and power consumption There is a problem. When the light control element according to the present invention is applied to an ultra-compact projector, the response speed is high and power can be saved, and color scanning of a plurality of colors (RGB, etc.) is performed on the retina with one light control element. realizable.

  The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to this embodiment, and includes a design and the like within a range not departing from the gist of the present invention.

  The present invention can be used for an apparatus for controlling the deflection angles and beam widths of light beams having a plurality of wavelengths. As an example, the present invention can be used for an integral stereoscopic display device. However, the scope of use of the present invention is not limited to those exemplified here.

DESCRIPTION OF SYMBOLS 1 Optical input part 2 Waveguide 3, 4, 5 Modulation part 8 Optical antenna array 10 Optical control element 21 Optical beam splitter 31 Phase modulation part 32 Amplitude modulation part 33 Phase modulation voltage 34 Amplitude modulation voltage 51 Input optical waveguide 52 Electrode signal line 60 Time Division Light Emitting Units 61-1, 61-2, 61-3 Semiconductor Lasers 62-1, 62-2, 62-3 Shading Switches 63-1, 63-2, 63-3 Mirrors 300A, 300B Polarizer 301, 302 Electrode 303 Electro-optic material 311, 312 Electrode 313 Electro-optic material 316 Optical waveguide core (electro-optic material)
317 Optical waveguide cladding

Claims (8)

A plurality of waveguides arranged in an array; and
A light input section for inputting light of a plurality of different wavelengths to the waveguide in a time-sharing manner;
A modulator that modulates at least one of a phase and an amplitude of the light on the waveguide;
A light control element comprising: The modulator is
A phase modulation unit that varies a phase difference between the waveguides adjacent on the array according to a wavelength of light input to the waveguide;
The light control element according to claim 1. The phase modulation unit phase-modulates the light so that a phase difference between the waveguides for obtaining a predetermined deflection angle is inversely proportional to a wavelength of light input to the waveguides;
The light control element according to claim 2. The modulator is
An amplitude modulation unit that modulates the amplitude of the light in the waveguide so that the output intensity of the light from the number of the waveguides corresponding to the wavelength of the light input to the waveguide becomes zero;
The light control element according to any one of claims 1 to 3. The amplitude modulation unit is configured to set the reference wavelength to a reference number when the number of the waveguides whose output intensity is non-zero to obtain a predetermined output light beam width is a reference wavelength that is a wavelength of reference light. The amplitude of the light is controlled to be based on a value obtained by multiplying the ratio of the wavelength of light input to the waveguide with respect to
The light control element according to claim 4. The plurality of waveguides are arranged in an array of N rows and 1 column or 1 row and N columns (where N is an integer of 2 or more) when viewed from the light output end side.
The light control element according to any one of claims 1 to 5. The plurality of waveguides are arranged in an array of M rows and N columns (where M and N are each an integer of 2 or more) when viewed from the light output end side.
The light control element according to any one of claims 1 to 5. The plurality of different wavelengths are three types of wavelengths corresponding to red, green, and blue, respectively.
The light control element according to any one of claims 1 to 7.

Images