JP7526798B2 - Wireless power supply system and receiving unit - Google Patents

Description

The present invention relates to a wireless power supply system for charging rechargeable devices such as smartphones in stores, etc., and a receiving unit used in this wireless power supply system.

2. Description of the Related Art Wireless power supply systems are known in which an infrared laser or the like is irradiated onto a rechargeable device such as a smartphone, and the light is converted into electricity by a photoelectric conversion element such as a solar cell within the device to charge the device.
In such a wireless power supply system, an infrared laser or the like is irradiated onto a photoelectric conversion element attached to the device, and the laser light is photoelectrically converted by the photoelectric conversion element, thereby charging the device.

Although this method has a high transmission power, the laser light may have an effect on the human body.
As a system capable of solving such problems, a wireless power supply system (space-distributed laser resonator) is known, as described in Patent Document 1. The configuration of this wireless power supply system is conceptually shown in FIG.

The wireless power feeding system 200 shown in FIG. 10 includes a transmitting unit 204 and a receiving unit 206 .
The transmitting unit 204 is a part that irradiates the receiving unit 206 with laser light, such as an infrared laser, for photoelectric conversion.
On the other hand, the receiving unit 206 is a part that receives the laser light irradiated from the transmitting unit 204 and performs photoelectric conversion. The receiving unit 206 is incorporated in a portable, rechargeable electronic device such as a smartphone or a tablet terminal, for example.

The transmitting section 204 includes a gain medium 208, a resonance mirror 210, a lens 212 and a mirror 214, and a lens 216. In the transmitting section 204, the lens 212 and the mirror 214 form a retroreflector.
On the other hand, the receiving unit 206 has a condenser lens 218, a half mirror 220, and a photoelectric conversion element 224. In the receiving unit 206, the condenser lens 218 and the half mirror 220 form a retroreflector.

In the wireless power supply system 200, when wireless power supply is not being performed, i.e., when the receiving unit 206 is not present in the wireless power supply area of the transmitting unit 204, the gain medium 208 of the transmitting unit 204 isotropically emitting light of a predetermined wavelength, for example, infrared light, by excitation light irradiated from an excitation source (not shown).
In this state, a device having a receiver 206 is brought into a wireless power supply area (light irradiation area) by the transmitter 204, that is, an area where light emitted isotropically by the gain medium 208 reaches. As a result, the light is collected by the collecting lens 218 of the receiver 206 and enters the half mirror 220, a part of which is transmitted and enters the photoelectric conversion element 224, and a part of which is retroreflected by the retroreflector consisting of the collecting lens 218 and the half mirror 220, as shown by the white arrow in the figure.

The light (open arrow) retroreflected by the retroreflector of the receiving section 206 returns along the original optical path, passes through lens 216, enters the gain medium 208, is reflected by the resonance mirror 210, and enters the retroreflector consisting of lens 212 and mirror 214, where it is retroreflected (black arrow).
The lens 216 is provided to expand the range over which the light emitted isotropically by the gain medium 208 reaches the receiving unit 206, and also to expand the range over which the light reflected back from the receiving unit 206 can properly enter the transmitting unit 204.

In the transmitting section 204, the light (black arrow) retroreflected by a retroreflector consisting of a lens 212 and a mirror 214 similarly travels back along the original optical path, enters the gain medium 208, is reflected by the resonant mirror 210, passes through the lens 216, and again enters the receiving section 206.
Of the light re-entering the receiving section 206 , part passes through the half mirror 220 and enters the photoelectric conversion element 224 , as before, and part is retroreflected by the retroreflector consisting of the condenser lens 218 and the half mirror 220 .
The light (white arrow) retroreflected at the receiving unit 206 is reflected by the resonance mirror 210, then retroreflected by a retroreflector consisting of a lens 212 and a mirror 214 (black arrow), and similarly enters the receiving unit 206, where a portion of it is retroreflected, and then enters the transmitting unit 204 and is retroreflected repeatedly.

As a result, light is repeatedly reflected between the two retroreflectors of the transmitting unit 204 and the receiving unit 206 and the resonant mirror 210, sandwiching the gain medium 208. This forms an optical resonant system (optical resonator), and the light excited by the gain medium 208 is amplified and oscillated as a laser. As a result, the transmitting unit 204 irradiates laser light of sufficient power, which enters the receiving unit 206, allowing the photoelectric conversion element 224 to output the desired power.

In such a wireless power supply system 200, when wireless power supply is performed by retroreflection between the transmitting unit 204 and the receiving unit 206, laser light with sufficient power is output from the transmitting unit 204 and can be received by the receiving unit 206.
However, if a human hand or other object enters the optical path of the laser light between the transmitting unit 204 and the receiving unit 206, the laser light is instantly blocked and resonance is stopped, so that the laser oscillation stops at that point and the person will not be injured by the high-power laser light.
Therefore, according to the wireless power feeding system 200, the danger of laser light is significantly reduced, and wireless power feeding using laser light with sufficient output is possible.

Patent No. 6169570

As described above, in the wireless power supply system 200, the receiving unit 206 is provided in a rechargeable, portable electronic device such as a smartphone or a tablet terminal.
On the other hand, in the wireless power supply system 200, in order to resonate light between the two retroreflectors of the transmitting unit 204 and the receiving unit 206 and the resonance mirror 210, it is necessary to properly focus the light on the surface of the half mirror 220. For this reason, an inorganic lens such as a glass lens is used for the focusing lens 218 constituting the receiving unit 206.
Moreover, in order to obtain the lens power required for focusing, the focusing lens 218 needs to have a certain thickness.

Therefore, in the wireless power supply system 200, it is unavoidable that the receiver 206 becomes large due to the focusing lens 218. As a result, it is difficult to mount the receiver in a small device, and this may also be an obstacle to miniaturization of the device incorporating the receiver.

The object of the present invention is to solve the problems of the conventional technology by providing a wireless power supply system having a transmitting unit and a receiving unit, which supplies power to the receiving unit by irradiating light, in which the receiving unit can be made compact, making it easy to install in small devices and to miniaturize the devices, and by providing a receiving unit for use in this wireless power supply system.

In order to achieve this objective, the present invention has the following configuration.

[1] A wireless power supply system having a transmitting unit and a receiving unit,
The transmitter section includes a gain medium and a transmission-side reflector.
the receiving unit has a diffractive lens, a photoelectric conversion element, and a receiving-side reflecting member disposed between the diffractive lens and the photoelectric conversion element, the receiving member reflecting a portion of the light transmitted through the diffractive lens;
A wireless power supply system in which light amplified by a gain medium disposed between a transmitting-side reflecting member and a receiving-side reflecting member passes through a diffractive lens and the receiving-side reflecting member and is incident on a photoelectric conversion element.
[2] A diffractive lens is a liquid crystal diffractive lens having an optically anisotropic layer formed using a composition containing a liquid crystal compound,
The optically anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction radially from the inside to the outside, and
The wireless power supply system described in [1], in which in a liquid crystal orientation pattern, when the length of a 180° rotation of the optical axis direction originating from the liquid crystal compound in one direction in which the direction of the optical axis originating from the liquid crystal compound changes while continuously rotating, is defined as one period, the length of one period gradually becomes shorter from the inside to the outside.
[3] The wireless power supply system according to [1] or [2], wherein the receiving unit has a λ/4 plate between which a diffractive lens is sandwiched.
[4] The wireless power supply system according to [3], wherein the receiving side reflective member is a half mirror.
[5] The transmitting side reflecting member is a half mirror or a total reflection type mirror. [3]
Or the wireless power supply system according to [4].
[6] The receiving side reflective member has a cholesteric liquid crystal layer or a dielectric multilayer film.
The wireless power supply system according to [1] or [2].
[7] The transmitting side reflecting member has a cholesteric liquid crystal layer or a dielectric multilayer film.
The wireless power supply system according to [6].
[8] The wireless power supply system according to any one of [1] to [7], wherein the focal position of the diffractive lens is located at a distance of 7 mm or less from the surface of the receiving side reflecting member.
[9] A plurality of diffractive lenses are arranged one-dimensionally or two-dimensionally. [1]
The wireless power supply system according to any one of claims 1 to 8.
[10] A receiving unit used in a wireless power supply system,
A receiving section having a diffractive lens, a photoelectric conversion element, and a receiving-side reflecting member disposed between the diffractive lens and the photoelectric conversion element, which reflects a portion of the light transmitted through the diffractive lens.
[11] A liquid crystal diffractive lens having an optically anisotropic layer formed using a composition containing a liquid crystal compound,
The optically anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction radially from the inside to the outside, and
The receiving unit described in [10], in which in a liquid crystal orientation pattern, when the length of the optical axis direction originating from the liquid crystal compound rotates 180° in one direction in which the direction of the optical axis originating from the liquid crystal compound changes while continuously rotating, the length of one period gradually becomes shorter from the inside to the outside.
[12] The receiving unit according to [10] or [11], having a λ/4 plate sandwiched between a diffractive lens.
[13] The receiving unit according to [12], wherein the receiving-side reflective member is a half mirror.
[14] The receiving section according to [10] or [11], wherein the receiving-side reflective member has a cholesteric liquid crystal layer or a dielectric multilayer film.
[15] The receiving unit according to any one of [10] to [14], wherein the focal position of the diffractive lens is located at a distance of 7 mm or less from the surface of the receiving side reflecting member.
[16] The receiving unit according to any one of [10] to [15], wherein a plurality of diffractive lenses are arranged one-dimensionally or two-dimensionally.

According to the present invention, in a wireless power supply system in which power is supplied to a receiving unit by irradiating light, the receiving unit can be made smaller, making it easier to install it in small devices and to miniaturize the devices.

1 is a diagram conceptually illustrating an example of a wireless power supply system according to the present invention. FIG. 13 is a diagram conceptually illustrating another example of a wireless power supply system according to the present invention. FIG. 13 is a diagram conceptually illustrating another example of a wireless power supply system according to the present invention. FIG. 1 is a diagram conceptually illustrating an example of a liquid crystal diffractive lens used in the wireless power supply system of the present invention. FIG. 2 is a diagram conceptually illustrating an example of a layer structure of the liquid crystal diffractive lens illustrated in FIG. 1 . FIG. 1 is a conceptual diagram for explaining the liquid crystal orientation pattern of a liquid crystal diffractive lens. FIG. 4 is a conceptual diagram for explaining the function of the liquid crystal diffractive lens shown in FIG. 3 . FIG. 4 is a conceptual diagram for explaining the function of the liquid crystal diffractive lens shown in FIG. 3 . FIG. 1 is a conceptual diagram of an example of an exposure apparatus for exposing an alignment film. FIG. 1 is a diagram conceptually illustrating an example of a conventional wireless power supply system.

The present invention will be described in detail below.
The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.

The wireless power supply system is a laser light-based wireless power supply system that has a transmitting unit and a receiving unit, and supplies power by receiving the laser light emitted by the transmitting unit and performing photoelectric conversion on it.

FIG. 1 conceptually illustrates an example of a wireless power supply system according to the present invention.
1 includes a transmitting unit 102 and a receiving unit 104. The transmitting unit 102 is a unit that irradiates (transmits) laser light such as an infrared laser to the receiving unit 104. On the other hand, the receiving unit 104 is a unit that receives the laser light irradiated from the transmitting unit 102 and performs photoelectric conversion.

The wireless power supply system 100 is a system for charging a device equipped with a receiving unit 104 by irradiating the device with laser light.
In the present invention, there is no limitation on the equipment (apparatus, device, article) in which the receiving unit 104 is mounted, and various types of equipment can be used.
Examples include portable electronic devices such as smartphones, mobile phones, tablet devices, and mobile PCs (Personal Computers); watches such as wristwatches; OA (Office Automation) devices such as projectors, printers, and computers; specialized devices such as electronic locks and bathroom faucet sensors; and robots such as cleaning robots, autonomous robots, and drones.
Furthermore, the receiving unit 104 may be a charger that is attachable to or detachable from these devices.

On the other hand, there is no restriction on the mounting position of the transmitter 102, and various positions are available.
Examples include ceilings and walls inside a store, a house, and a factory.

In the wireless power supply system 100 of the illustrated example, the transmitter 102 has a gain medium 108, a resonance mirror 110, a lens 112 and a cholesteric mirror 114, a lens 116, and a detector 118. In the transmitter 102, the lens 112 and the cholesteric mirror 114 form a retroreflector.
On the other hand, the receiving section 104 has a liquid crystal diffractive lens 120, a cholesteric mirror 124, and a photoelectric conversion element 126. In the receiving section 104, the liquid crystal diffractive lens 120 and the cholesteric mirror 124 form a retroreflector.

First, we will explain the liquid crystal diffractive lens 120 of the receiving unit 104 in the wireless power supply system 100 and the receiving unit 104.

FIG. 4 is a plan view of the liquid crystal diffractive lens 120, and FIG. 5 conceptually shows the layer structure of the liquid crystal diffractive lens 120. As shown in FIG.
The plan view is a view of the liquid crystal diffractive lens 120 viewed from the optical axis direction of the lens, that is, from a direction perpendicular to the main surface of the optically anisotropic layer 26 described later. The main surface is the largest surface of a sheet-like object (plate-like object, film, layer).

In the illustrated example, the liquid crystal diffractive lens 120 includes a support 20 , an alignment film 24 , and an optically anisotropic layer 26 .
The optically anisotropic layer 26 is formed using a composition containing a liquid crystal compound. The optically anisotropic layer 26 has a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction, radially from the inside to the outside. That is, the liquid crystal orientation pattern of the optically anisotropic layer 26 shown in FIG. 4 is a concentric pattern in which the direction of the optical axis derived from the liquid crystal compound 30 changes while continuously rotating in one direction, concentrically from the inside to the outside.
In addition, since a rod-shaped liquid crystal compound is illustrated as the liquid crystal compound 30 in FIGS. 4 to 8, the direction of the optical axis coincides with the longitudinal direction of the liquid crystal compound 30.

In the optically anisotropic layer 26, the direction of the optical axis of the liquid crystal compound 30 changes while continuously rotating along a number of directions from the center of the optically anisotropic layer 26 toward the outside, for example, the direction indicated by the arrow _A1 , the direction indicated by the arrow _A2 , the direction indicated by the arrow _A3 , the direction indicated by the arrow _A4 , ....
Therefore, the rotation direction of the optical axis of the liquid crystal compound 30 is the same in all directions (one direction) in the optically anisotropic layer 26. In the illustrated example, the rotation direction of the optical axis of the liquid crystal compound 30 is counterclockwise in all directions indicated by the arrows _A1 , _A2 , _A3 , and _A4 .
That is, when the arrows _A1 and _A4 are regarded as one straight line, the rotation direction of the optical axis of the liquid crystal compound 30 is reversed at the center of the optically anisotropic layer 26 on the straight line. As an example, the straight line formed by the arrows _A1 and _A4 is directed to the right direction in the figure (the direction of the arrow _A1 ). In this case, the optical axis of the liquid crystal compound 30 first rotates clockwise from the outside of the optically anisotropic layer 26 toward the center, reverses the rotation direction at the center of the optically anisotropic layer 26, and then rotates counterclockwise from the center of the optically anisotropic layer 26 toward the outside.

In addition, in the optically anisotropic layer 26 of the liquid crystal diffraction lens 120, when the length of one period is defined as the length of the optical axis direction originating from the liquid crystal compound rotating 180° in one direction in which the direction of the optical axis of the liquid crystal compound 30 changes while rotating continuously, the length of one period gradually becomes shorter from the inside to the outside.

The absolute phase of the circularly polarized light incident on the optically anisotropic layer 26 having this liquid crystal orientation pattern changes in each local region having a different optical axis direction of the liquid crystal compound 30. At this time, the amount of change in each absolute phase differs depending on the optical axis direction of the liquid crystal compound 30 into which the circularly polarized light is incident.
In an optically anisotropic layer (liquid crystal optical element) having a liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound 30 changes while rotating continuously in one direction, the refraction direction of the transmitted light depends on the rotation direction of the optical axis of the liquid crystal compound 30. That is, in this liquid crystal orientation pattern, when the rotation direction of the optical axis of the liquid crystal compound 30 is reversed, the refraction direction of the transmitted light is reverse to the one direction in which the optical axis rotates.
Moreover, the shorter one period, the larger the diffraction angle by the optically anisotropic layer 26. That is, the shorter one period, the larger the refraction of light by the optically anisotropic layer 26.

Therefore, the optically anisotropic layer 26 having such a concentric liquid crystal orientation pattern, i.e., a liquid crystal orientation pattern in which the optical axis changes by continuously rotating radially, can transmit a plurality of incident light beams (light beams) while diverging or converging them depending on the rotation direction of the optical axis of the liquid crystal compound 30 and the rotation direction of the incident circularly polarized light. The liquid crystal diffractive lens 120 utilizes this principle to focus the incident light.
The liquid crystal diffractive lens 120 will be described in more detail below.

As described above, the liquid crystal diffractive lens 120 includes, for example, the support 20, the alignment film 24, and the optically anisotropic layer 26 described above.
In the wireless power supply system and the receiving unit of the present invention, the layer structure of the liquid crystal diffractive lens is not limited to this. That is, the liquid crystal diffractive lens may be one that is composed of the alignment film 24 and the optically anisotropic layer 26 obtained by peeling off the support 20 from the liquid crystal diffractive lens 120 shown in Fig. 5, or one that is composed of only the optically anisotropic layer 26 obtained by peeling off the support 20 and the alignment film 24 from the liquid crystal diffractive lens 120 shown in Fig. 5, or one in which a sheet-like material such as another substrate is attached to the optically anisotropic layer 26.
In other words, in the wireless power supply system and receiving unit of the present invention, the liquid crystal diffractive lens can have various layer configurations as long as it has an optically anisotropic layer having a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound as described above changes while continuously rotating in one direction, radially (concentrically) from the inside to the outside.

<<Support>>
In the liquid crystal diffractive lens 120 , the support 20 supports the alignment film 24 and the optically anisotropic layer 26 .

The support 20 may be any sheet-like material (film, plate-like material) as long as it can support the alignment film 24 and the optically anisotropic layer 26 .
The support 20 is preferably a transparent support, and examples of such support include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, cycloolefin polymer films (for example, trade name "Arton" manufactured by JSR Corporation, trade name "ZEONOR" manufactured by Zeon Corporation), polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride. The support is not limited to a flexible film, and may be a non-flexible substrate such as a glass substrate.

There is no limitation on the thickness of the support 20, and the thickness capable of supporting the alignment film and the optically anisotropic layer may be appropriately set depending on the application of the liquid crystal diffractive lens 120 and the material from which the support 20 is formed.
The thickness of the support 20 is preferably from 1 to 1000 μm, more preferably from 3 to 250 μm, and even more preferably from 5 to 150 μm.

<<Alignment film>>
In the liquid crystal diffractive lens 120 , an alignment film 24 is formed on the surface of the support 20 .
The alignment film 24 is an alignment film for aligning the liquid crystal compound 30 in a predetermined liquid crystal alignment pattern when the optically anisotropic layer 26 of the liquid crystal diffractive lens 120 is formed.

As described above, in the liquid crystal diffractive lens 120, the optically anisotropic layer 26 has a liquid crystal orientation pattern in which the direction of the optical axis 30A (see FIG. 6) derived from the liquid crystal compound 30 changes while continuously rotating along one in-plane direction (such as the direction of the arrow A1 described above) radially from the inside to the outside. In other words, in the liquid crystal diffractive lens 120 used as a lens element in the present invention, the liquid crystal orientation pattern of the optically anisotropic layer 26 is a concentric pattern in which the direction of the optical axis derived from the liquid crystal compound 30 changes while continuously rotating, concentrically from the inside to the outside.
In addition, in the present invention, the liquid crystal orientation pattern of the optically anisotropic layer 26 is such that, in one direction in which the orientation of the optical axis 30A changes while continuously rotating, the length of one period (rotation period of the optical axis) is the length over which the orientation of the optical axis 30A rotates 180°, and the length of one period gradually becomes shorter from the inside to the outside (from the center to the outside).
Therefore, the alignment film of the liquid crystal diffractive lens 120 is formed so that the optically anisotropic layer 26 can form this liquid crystal alignment pattern.

In the following explanation, "the orientation of the optical axis 30A rotates" will also be referred to simply as "the optical axis 30A rotates."

As the alignment film, various known films can be used.
Examples of such films include a rubbed film made of an organic compound such as a polymer, an obliquely evaporated film of an inorganic compound, a film having a microgroove, and a film obtained by accumulating LB (Langmuir-Blodgett) films made by the Langmuir-Blodgett method of an organic compound such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate.

The alignment layer formed by rubbing treatment can be formed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.
Preferred examples of materials used for the alignment film include polyimide, polyvinyl alcohol, polymers having a polymerizable group described in JP-A-9-152509, and materials used for forming alignment films and the like described in JP-A-2005-97377, JP-A-2005-99228, and JP-A-2005-128503.

In the liquid crystal diffractive lens 120, a so-called photo-alignment film, which is an alignment film formed by irradiating a photo-alignable material with polarized or non-polarized light, is preferably used as the alignment film 24. That is, in the liquid crystal diffractive lens 120, a photo-alignment film formed by applying a photo-alignment material onto the support 20 is preferably used as the alignment film 24.
The photo-alignment film can be irradiated with polarized light from a vertical direction or an oblique direction, while the photo-alignment film can be irradiated with unpolarized light from an oblique direction.

Examples of photo-alignment materials used in the photo-alignment film that can be used in the present invention include those described in JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, and JP-A-2007-160144. azo compounds described in JP-A-07-133184, JP-A-2009-109831, JP-B-3883848 and JP-B-4151746; aromatic ester compounds described in JP-A-2002-229039; maleimides having photo-orientable units described in JP-A-2002-265541 and JP-A-2002-317013; and/or alkenyl-substituted nadimide compounds, photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides and photocrosslinkable esters described in JP-T-2003-520878, JP-T-2004-529220 and JP-T-4162850, and photodimerizable compounds described in JP-A-9-118717, JP-T-10-506420, JP-T-2003-505561, WO 2010/150748, JP-A-2013-177561 and JP-A-2014-12823, in particular cinnamate compounds, chalcone compounds and coumarin compounds, are exemplified as preferred examples.
Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable esters, cinnamate compounds, and chalcone compounds are preferably used.

There is no limitation on the thickness of the alignment film, and the thickness may be appropriately set so as to obtain the necessary alignment function depending on the material from which the alignment film is formed.
The thickness of the alignment film is preferably from 0.01 to 5 μm, and more preferably from 0.05 to 2 μm.

There are no limitations on the method of forming the alignment film, and various known methods can be used depending on the material used to form the alignment film. One example is a method in which an alignment film is applied to the surface of the support 20 and dried, and then the alignment film is exposed to laser light to form an alignment pattern.

FIG. 9 conceptually shows an example of an exposure apparatus for exposing an alignment film to light to form an alignment film 24 having this alignment pattern.
The exposure device 80 has a light source 84 equipped with a laser 82, a polarizing beam splitter 86 that splits laser light M from the laser 82 into S-polarized light MS and P-polarized light MP, a mirror 90A arranged in the optical path of the P-polarized light MP and a mirror 90B arranged in the optical path of the S-polarized light MS, a lens 92 arranged in the optical path of the S-polarized light MS, a polarizing beam splitter 94, and a λ/4 plate 96.

The P-polarized light MP split by the polarizing beam splitter 86 is reflected by a mirror 90A and enters a polarizing beam splitter 94. On the other hand, the S-polarized light MS split by the polarizing beam splitter 86 is reflected by a mirror 90B, collected by a lens 92, and enters the polarizing beam splitter 94.
The P-polarized light MP and the S-polarized light MS are combined by the polarizing beam splitter 94 , and are converted by the λ/4 plate 96 into right-handed circularly polarized light and left-handed circularly polarized light according to the polarization direction, and are incident on the alignment film 24 on the support 20 .
Here, due to interference between the right-handed and left-handed circularly polarized light, the polarization state of the light irradiated onto the alignment film 24 changes periodically in the form of interference fringes. As the crossing angle between the left-handed and right-handed circularly polarized light changes from the inside to the outside of the concentric circles, an exposure pattern is obtained in which the pitch changes from the inside to the outside. As a result, a radial (concentric) alignment pattern in which the alignment state changes periodically is obtained in the alignment film 24.

In this exposure device 80, one period of the liquid crystal orientation pattern in which the optical axis of the liquid crystal compound 30 continuously rotates 180° along one direction can be controlled by changing the refractive power of the lens 92 (the F-number of the lens 92), the focal length of the lens 92, and the distance between the lens 92 and the orientation film 24, etc.
In addition, by adjusting the refractive power of the lens 92 (the F-number of the lens 92), the length of one period of the liquid crystal alignment pattern can be changed in one direction in which the optical axis rotates continuously.
Specifically, the length of one period of the liquid crystal orientation pattern can be changed in one direction in which the optical axis rotates continuously, depending on the spread angle of the light spread by the lens 92 that interferes with the parallel light. More specifically, when the refractive power of the lens 92 is weakened, the light approaches parallel light, so that the length Λ of one period of the liquid crystal orientation pattern gradually shortens from the inside to the outside, and the F-number becomes larger. Conversely, when the refractive power of the lens 92 is strengthened, the length Λ of one period of the liquid crystal orientation pattern suddenly shortens from the inside to the outside, and the F-number becomes smaller.

As described above, in the liquid crystal diffractive lens 120, the alignment film 24 is provided as a preferred embodiment, but is not an essential component.
For example, by forming an orientation pattern on the support 20 by a method such as rubbing the support 20 or processing the support 20 with laser light, it is possible to configure the optically anisotropic layer 26, etc., to have a liquid crystal orientation pattern in which the direction of the optical axis 30A derived from the liquid crystal compound 30 changes while continuously rotating radially (concentrically) along one direction.

<<Optical anisotropic layer>>
In the liquid crystal diffractive lens 120 shown in FIGS. 4 and 5, an optically anisotropic layer 26 is formed on the surface of the alignment film 24 .
In Fig. 4 (and Figs. 7 and 8 described later), in order to simplify the drawings and clearly show the configuration of the liquid crystal diffractive lens 120, the optically anisotropic layer 26 is shown only with the liquid crystal compound 30 (liquid crystal compound molecules) on the surface of the alignment film 24. However, the optically anisotropic layer 26 has a structure in which aligned liquid crystal compounds 30 are stacked, similar to an optically anisotropic layer formed using a composition containing a normal liquid crystal compound, as conceptually shown in Fig. 5.

As described above, in the liquid crystal diffractive lens 120, the optically anisotropic layer 26 is formed using a composition containing a liquid crystal compound.
When the in-plane retardation value is set to λ/2, the optically anisotropic layer 26 has the function of a typical λ/2 plate, that is, the function of imparting a phase difference of half the wavelength, i.e., 180°, to two mutually orthogonal linearly polarized components contained in the light incident on the optically anisotropic layer.

The optically anisotropic layer 26 has a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while rotating continuously in one direction (such as the direction of arrows _A1 to _A4 in FIG. 4) radially from the inside to the outside within the plane of the optically anisotropic layer. That is, the liquid crystal orientation pattern of the optically anisotropic layer 26 is a concentric pattern in which the direction of the optical axis derived from the liquid crystal compound 30 changes while rotating continuously in one direction concentrically from the inside to the outside.
The optical axis 30A derived from the liquid crystal compound 30 is the axis along which the refractive index is highest in the liquid crystal compound 30, that is, the so-called slow axis. For example, when the liquid crystal compound 30 is a rod-shaped liquid crystal compound, the optical axis 30A is aligned along the long axis direction of the rod shape.
In the following description, the optical axis 30A originating from the liquid crystal compound 30 is also referred to as "the optical axis 30A of the liquid crystal compound 30" or "the optical axis 30A".

Hereinafter, this optically anisotropic layer 26 will be described with reference to an optically anisotropic layer 26A having a liquid crystal orientation pattern in which the optical axis 30A changes while continuously rotating in one direction as indicated by arrow A, the plan view of which is conceptually shown in FIG.
Even in the liquid crystal orientation pattern shown in Figure 4, in which the optical axis changes while rotating continuously in a radial (concentric) manner from the inside to the outside, the liquid crystal orientation pattern exhibits optical effects similar to those of the liquid crystal orientation pattern shown in Figure 6, with respect to the direction in which the optical axis changes while rotating continuously.

In the optically anisotropic layer 26A, the liquid crystal compound 30 is two-dimensionally aligned in a plane parallel to one direction indicated by an arrow A and a Y direction perpendicular to the direction of the arrow A. In Fig. 5 and Figs. 7 and 8 described later, the Y direction is perpendicular to the paper surface.
In the following description, "the direction indicated by the arrow A" will also be simply referred to as "the direction of the arrow A."
In the optically anisotropic layer 26 shown in FIG. 4, the circumferential direction of the concentric circles in the concentric liquid crystal alignment pattern corresponds to the Y direction in FIG.

6, in order to clearly show the configuration of the liquid crystal diffraction lens 120, only the liquid crystal compound 30 on the surface of the alignment film 24 is shown, as in FIG. 4. However, this optically anisotropic layer 26A also has a structure in which liquid crystal compounds 30 are stacked in the thickness direction, starting from the liquid crystal compound 30 on the surface of the alignment film, as shown in FIG.

The optically anisotropic layer 26A has a liquid crystal alignment pattern in which the direction of an optical axis 30A derived from a liquid crystal compound 30 changes while continuously rotating along the direction of arrow A within the plane of the optically anisotropic layer 26A.
The direction of the optical axis 30A of the liquid crystal compound 30 changes while continuously rotating in the direction of the arrow A (a predetermined direction), specifically means that the angle between the optical axis 30A of the liquid crystal compound 30 aligned along the direction of the arrow A and the direction of the arrow A varies depending on the position in the direction of the arrow A, and the angle between the optical axis 30A and the direction of the arrow A changes sequentially from θ to θ+180° or θ-180° along the direction of the arrow A.
The difference in angle between the optical axes 30A of the liquid crystal compounds 30 adjacent to each other in the direction of the arrow A is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

On the other hand, the liquid crystal compounds 30 forming the optically anisotropic layer 26A are arranged at equal intervals in the Y direction perpendicular to the direction of the arrow A, i.e., in the Y direction perpendicular to the direction in which the optical axis 30A continuously rotates, with the liquid crystal compounds 30 having the same optical axis 30A orientation.
In other words, in the liquid crystal compounds 30 forming the optically anisotropic layer 26, the angles between the optical axes 30A and the direction of the arrow A are equal between the liquid crystal compounds 30 aligned in the Y direction.
In the optically anisotropic layer 26A shown in FIG. 6, annular regions with the same center are formed, each having an optical axis 30A aligned in the same direction.

In a liquid crystal orientation pattern in which the optical axis 30A rotates continuously in one direction, the length (distance) over which the optical axis 30A of the liquid crystal compound 30 rotates 180° is defined as the length Λ of one period in the periodic structure of the liquid crystal orientation pattern, i.e., the diffraction element.
6, the length (distance) over which the optical axis 30A of the liquid crystal compound 30 rotates 180° in the direction of the arrow A, in which the orientation of the optical axis 30A changes continuously in the plane, is defined as the length Λ of one period in the liquid crystal alignment pattern. In other words, the length of one period in the liquid crystal alignment pattern is defined as the distance from when the angle between the optical axis 30A of the liquid crystal compound 30 and the direction of the arrow A changes from θ to θ+180°.
That is, the length Λ of one period is defined as the distance between the centers in the direction of arrow A of two liquid crystal compounds 30 that are arranged at the same angle with respect to the direction of arrow A. Specifically, as shown in Fig. 3, the length Λ of one period is defined as the distance between the centers in the direction of arrow A of two liquid crystal compounds 30 whose directions of arrow A and optical axes 30A coincide with each other.
In the following description, the length Λ of one period is also referred to as "one period Λ."
In the optically anisotropic layer 26A (optically anisotropic layer 26), the liquid crystal alignment pattern of the optically anisotropic layer repeats this one period Λ in the direction of arrow A, that is, in one direction in which the direction of the optical axis 30A changes by continuously rotating.

In addition, the liquid crystal diffractive lens 120 used in the wireless power supply system and receiving unit of the present invention has a radial (concentric) liquid crystal orientation pattern in which the optical axis 30A rotates continuously, and one period Λ in the optical anisotropic layer 26 gradually becomes shorter from the inside (center) to the outside.

As described above, in the optically anisotropic layer 26A, the liquid crystal compounds aligned in the Y direction have the same angle between their optical axes 30A and the direction of the arrow A (one direction in which the orientation of the optical axes of the liquid crystal compounds 30 rotates). A region in which the liquid crystal compounds 30 having the same angle between their optical axes 30A and the direction of the arrow A are arranged in the Y direction is referred to as a region R.
In this case, the value of the in-plane retardation (Re) in each region R is preferably half the wavelength, i.e., λ/2. These in-plane retardations are calculated by the product of the refractive index difference Δn associated with the refractive index anisotropy of the region R and the thickness of the optically anisotropic layer. Here, the refractive index difference associated with the refractive index anisotropy of the region R in the optically anisotropic layer is a refractive index difference defined by the difference between the refractive index in the direction of the slow axis in the plane of the region R and the refractive index in the direction perpendicular to the direction of the slow axis. That is, the refractive index difference Δn associated with the refractive index anisotropy of the region R is equal to the difference between the refractive index of the liquid crystal compound 30 in the direction of the optical axis 30A and the refractive index of the liquid crystal compound 30 in the direction perpendicular to the optical axis 30A in the plane of the region R. That is, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.
In addition, in the optically anisotropic layer 26 of the liquid crystal diffractive lens 120 having a radial liquid crystal orientation pattern as shown in Figure 4, in which the optical axis 30A rotates continuously in one direction, the region formed in a circular ring shape with the same center and in which the optical axis 30A has the same direction corresponds to region R in Figure 6.

When circularly polarized light is incident on such an optically anisotropic layer 26A, the light is refracted and the direction of the circularly polarized light is changed.
This effect is conceptually shown in Figures 7 and 8. It is assumed that the product of the refractive index difference of the liquid crystal compound and the thickness of the optically anisotropic layer 26A is λ/2.
As described above, this effect is exactly the same in the liquid crystal diffractive lens 120 used in the wireless power supply system and receiving unit of the present invention, which has a radial liquid crystal orientation pattern in which the optical axis 30A rotates continuously in one direction.

As shown in FIG. 7, when the product of the refractive index difference of the liquid crystal compound in the optically anisotropic layer 26 and the thickness of the optically anisotropic layer is λ/2, when left-handed circularly polarized incident light _L1 enters the optically anisotropic layer 26, the incident light _L1 is given a phase difference of 180° by passing through the optically anisotropic layer 26A, and the transmitted light _L2 is converted into right-handed circularly polarized light.
In addition, when the incident light _L1 passes through the optically anisotropic layer 26A, the absolute phase changes according to the direction of the optical axis 30A of each liquid crystal compound 30. At this time, the direction of the optical axis 30A changes while rotating along the direction of the arrow A, so the amount of change in the absolute phase of the incident light _L1 differs according to the direction of the optical axis 30A. Furthermore, since the liquid crystal orientation pattern formed in the optically anisotropic layer 26A is a periodic pattern in the direction of the arrow A, the incident light _L1 that passes through the optically anisotropic layer 26 is given a periodic absolute phase Q1 in the direction of the arrow A corresponding to the direction of each optical axis 30A, as shown in FIG. 7. As a result, an equiphase surface E1 inclined in the opposite direction to the direction of the arrow A is formed.
Therefore, the transmitted light _L2 is refracted (diffracted) so as to be tilted toward a direction perpendicular to the equiphase surface E1, and travels in a direction different from that of the incident light _L1 . In this way, the left-handed circularly polarized incident light _L1 is converted into right-handed circularly polarized transmitted light _L2 that is tilted at a certain angle in the direction of arrow A with respect to the incident direction.

On the other hand, as conceptually shown in FIG. 8, when the product of the refractive index difference of the liquid crystal compound in the optically anisotropic layer 26A and the thickness of the optically anisotropic layer is λ/2, when right-handed circularly polarized incident light _L4 is incident on the optically anisotropic layer 26A, the incident light _L4 is given a phase difference of 180° by passing through the optically anisotropic layer 26 and is converted into left-handed circularly polarized transmitted light _L5 .
Furthermore, when the incident light _L4 passes through the optically anisotropic layer 26A, the absolute phase of the incident light L4 changes depending on the direction of the optical axis 30A of each liquid crystal compound 30. At this time, the direction of the optical axis 30A changes while rotating along the direction of the arrow A, so the amount of change in the absolute phase of the incident light _L4 differs depending on the direction of the optical axis 30A. Furthermore, since the liquid crystal orientation pattern formed in the optically anisotropic layer 26A is a periodic pattern in the direction of the arrow A, the incident light _L4 that passes through the optically anisotropic layer 26 is given a periodic absolute phase Q2 in the direction of the arrow A corresponding to the direction of each optical axis 30A, as shown in FIG.
Here, since the incident light _L4 is right-handed circularly polarized light, the periodic absolute phase Q2 in the direction of arrow A corresponding to the direction of the optical axis 30A is opposite to that of the incident light _L1 which is left-handed circularly polarized light. As a result, the incident light _L4 forms an equiphase surface E2 which is inclined in the direction of arrow A opposite to that of the incident light _L1 .
Therefore, the incident light _L4 is refracted so as to be tilted toward a direction perpendicular to the equiphase surface E2, and travels in a direction different from the traveling direction of the incident light _L4 . In this way, the incident light _L4 is converted into left-handed circularly polarized transmitted light _L5 that is tilted at a certain angle in the direction opposite to the direction of arrow A with respect to the incident direction.

In the optically anisotropic layer 26, the in-plane retardation value of the multiple regions R is preferably a half wavelength, and the in-plane retardation Re(550)=Δn ₅₅₀ ×d of the multiple regions R of the optically anisotropic layer 26 for incident light having a wavelength of 550 nm is preferably within the range defined by the following formula (1): where Δn ₅₅₀ is the refractive index difference associated with the refractive index anisotropy of the regions R when the wavelength of the incident light is 550 nm, and d is the thickness of the optically anisotropic layer 26.
200nm≦Δn ₅₅₀ ×d≦350nm...(1)
It is the optically anisotropic layer 26 that functions as a so-called λ/2 plate. However, in the present invention, when the support 20 and the alignment film 24 are provided, the laminate integrally including these may function as a λ/2 plate.

Here, the optically anisotropic layer 26A can adjust the angles of refraction of the transmitted light _L2 and _L5 by changing one period Λ of the formed liquid crystal orientation pattern. Specifically, the shorter one period Λ of the liquid crystal orientation pattern is, the stronger the interference between the lights that have passed through the adjacent liquid crystal compounds 30 becomes, and therefore the greater the refraction of the transmitted light _L2 and _L5 can be achieved.
The angles of refraction of the transmitted light _L2 and _L5 with respect to the incident light _L1 and _L4 vary depending on the wavelengths of the incident light _L1 and _L4 (transmitted light _L2 and _L5 ). Specifically, the longer the wavelength of the incident light, the greater the refraction of the transmitted light. For example, when the incident light is red, green, and blue light, the red light is refracted the most and the blue light is refracted the least.
Furthermore, by reversing the direction of rotation of the optical axis 30A of the liquid crystal compound 30, which rotates along the direction of the arrow A, the direction of refraction of the transmitted light can be reversed.

As described above, in the liquid crystal diffractive lens 120 shown in Figure 4, the optically anisotropic layer 26 has a liquid crystal orientation pattern in which the optical axis 30A rotates in one direction, and one period Λ of the liquid crystal orientation pattern gradually becomes shorter from the inside (center) to the outside.
Therefore, by setting the direction of rotation of the optical axis 30A from the inside to the outside so as to refract the light toward the center of the liquid crystal diffraction lens 120 depending on the wavelength and polarization state of the incident light, and by appropriately adjusting the degree of gradual decrease in the length of one period Λ of the liquid crystal orientation pattern, the degree of focusing of the light toward the center (optical axis) of the liquid crystal diffraction lens 120 can be adjusted.
That is, by gradually decreasing the length of one period Λ of the liquid crystal orientation pattern, the liquid crystal diffractive lens 120 can be made to function as a condenser lens (convex lens).
Furthermore, the optically anisotropic layer 26 (liquid crystal diffractive lens 120) rotates the circularly polarized light to be collected (diffused) in the opposite direction depending on the direction of incidence, i.e., whether the light is incident from one principal surface or the other principal surface. That is, when right-handed circularly polarized light is collected when light is incident from one principal surface, left-handed circularly polarized light is collected when light is incident from the other principal surface.

The optically anisotropic layer 26 is formed using a liquid crystal composition containing a rod-shaped liquid crystal compound or a discotic liquid crystal compound, and has a liquid crystal orientation pattern in which the optical axis of the rod-shaped liquid crystal compound or the optical axis of the discotic liquid crystal compound is oriented as described above.
An alignment film 24 having an alignment pattern corresponding to the above-mentioned liquid crystal alignment pattern is formed on a support 20, and a liquid crystal composition is applied onto the alignment film 24 and cured to obtain an optically anisotropic layer consisting of a cured layer of the liquid crystal composition.
The liquid crystal composition for forming the optically anisotropic layer 26 contains a rod-shaped liquid crystal compound or a discotic liquid crystal compound, and may further contain other components such as a leveling agent, an alignment control agent, a polymerization initiator, and an alignment assistant.

In addition, the optically anisotropic layer 26 is preferably broadband with respect to the wavelength of the incident light, and is preferably constructed using a liquid crystal material with a birefringence that exhibits reverse dispersion. It is also preferable to make the optically anisotropic layer substantially broadband with respect to the wavelength of the incident light by imparting a twist component to the liquid crystal composition or by laminating different retardation layers. For example, a method of realizing a broadband patterned λ/2 plate by laminating two layers of liquid crystal with different twist directions in the optically anisotropic layer 26 is shown in JP 2014-089476 A and the like, and can be preferably used in the present invention.

- Rod-shaped liquid crystal compounds -
As the rod-shaped liquid crystal compound, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexane carboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles are preferably used. Not only the above-mentioned low molecular weight liquid crystal molecules, but also polymeric liquid crystal molecules can be used.

In the optically anisotropic layer 26, it is more preferable to fix the alignment of the rod-like liquid crystal compound by polymerization. As the polymerizable rod-like liquid crystal compound, there is known a compound described in Makromol. Chem. , Vol. 190, p. 2255 (1989), Advanced Materials Vol. 5, p. 107 (1993), U.S. Patent Nos. 4,683,327, 5,622,648, 5,770,107, WO 95/22586, 95/24455, 97/00600, 98/23580, 98/52905, JP-A-1-272551, 6-16616, 7-110469, 11-80081, and compounds described in Japanese Patent Application No. 2001-64627 can be used.
Furthermore, as the rod-shaped liquid crystal compound, for example, those described in JP-T-11-513019 and JP-A-2007-279688 can also be preferably used.

-Disc-shaped liquid crystal compounds-
As the discotic liquid crystal compound, for example, those described in JP-A-2007-108732 and JP-A-2010-244038 can be preferably used.
In addition, when a discotic liquid crystal compound is used in the optically anisotropic layer, the liquid crystal compound 30 stands up in the thickness direction in the optically anisotropic layer, and the optical axis 30A derived from the liquid crystal compound is defined as an axis perpendicular to the disc surface, that is, a so-called fast axis.

The liquid crystal diffractive lens 120 having such an optically anisotropic layer 26 is in a sheet shape and does not have an uneven surface that a convex lens made of an inorganic material such as glass has. The liquid crystal diffractive lens 120 has a thickness of, for example, 1 to 100 μm.
Therefore, by using this liquid crystal diffractive lens 120 as a focusing lens that forms a retroreflector together with a half mirror (cholesteric mirror) in the receiving section that constitutes the wireless power supply system, the receiving section can be made smaller (thinner), and the entire wireless power supply system can be made smaller by miniaturizing the device in which the receiving section is incorporated, and the receiving section can be incorporated into small devices, thereby improving the versatility of the wireless power supply system.

In the optical wireless power supply system and the receiving section of the present invention, the diffractive lens used in the receiving section is not limited to the liquid crystal diffractive lens described above.
That is, in the present invention, in addition to the liquid crystal diffractive lens, various known diffractive lenses (so-called DOE (Diffractive Optical Element) lenses) can be used as the diffractive lens.
However, the above-mentioned liquid crystal diffractive lens is preferably used because it can be used to effectively reduce the size (thinness) of the receiving unit, has a wide and easy adjustment range for the focal length (lens power), and has excellent diffraction efficiency.

As described above, the wireless power supply system 100 shown in FIG. 1 includes the transmitting unit 102 and the receiving unit 104 .
The transmitting section 102 is a section that irradiates the receiving section 104 with laser light, such as an infrared laser, which is photoelectrically converted by a photoelectric conversion element 126 of the receiving section 104. Such a transmitting section 102 has a gain medium 108, a resonance mirror 110, a lens 112, a cholesteric mirror 114, a lens 116, and a detector 118.

In the transmitting section 104, the gain medium 108 is a known gain medium (laser medium) used in a so-called laser oscillator (laser light source). Therefore, the gain medium 108 is irradiated with pumping light from a pumping source (not shown) and outputs a laser light.
A known gain medium can be used as the gain medium 108. One example of the gain medium 108 is Nd:YAG.

In the wireless power supply system 100 of the present invention, there is no limitation on the wavelength of the laser light irradiated by the gain medium 108, i.e., the transmitting unit 102. In other words, the laser light irradiated by the transmitting unit 102 may be in a wavelength range in which the photoelectric conversion element 126 of the receiving unit 104 can perform photoelectric conversion.
Among them, a preferable example is invisible laser light, and among them, infrared light, for example, infrared light having a wavelength of 800 to 3000 nm, is a suitable example.

The resonance mirror 110 reflects the retroreflected light reflected by the cholesteric mirror 114 and the retroreflected light from the receiving section 104 .
The resonance mirror 110 may be the same as a reflecting mirror used in an optical resonator such as a laser light source.

The lens 112 and the cholesteric mirror 114 constitute a retroreflector on the side of the transmitter 102. The cholesteric mirror 114 is a transmission-side reflecting member in the wireless power supply system of the present invention.
The lens 112 is a known convex lens.

The cholesteric mirror 114 has a cholesteric liquid crystal layer.
The cholesteric liquid crystal layer is a known cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase in which a liquid crystal compound is cholesterically aligned.

As is well known, a cholesteric liquid crystal phase has a helical structure in which liquid crystal compounds are spirally rotated and stacked, and the liquid crystal compounds are stacked in a spiral shape, with one helical pitch being one rotation (360° rotation) of the liquid crystal compounds, and the helically rotated liquid crystal phase has a structure in which multiple pitches are stacked.
The cholesteric liquid crystal phase selectively reflects circularly polarized light in a wavelength-selective manner according to the length of one pitch of the helix, and also selectively reflects right-handed or left-handed circularly polarized light according to the direction of rotation of the helix.

Thus, for example, if gain medium 108 emits an infrared laser, the cholesteric liquid crystal layer constituting cholesteric mirror 114 has a helical pitch that corresponds to the wavelength of the infrared laser and selectively reflects light of this wavelength.
In the illustrated example, the cholesteric liquid crystal layer of the cholesteric mirror 114 selectively reflects right-handed circularly polarized light.

In addition, in the present invention, a dielectric multilayer film having a similar optical effect may be used in place of the cholesteric liquid crystal layer in the transmitting side reflective member of the transmitting section.

The detector 118 is a known photodetector that detects light transmitted through the cholesteric mirror 114. The detector 118 is provided as a preferred embodiment.
By using the detector 118 to detect the intensity of the light transmitted through the cholesteric mirror 114, it becomes possible to detect the presence or absence and the number of receiving sections 104 present in the area where the transmitting section 102 (gain medium 108) isotropically irradiates light.

Lens 116, like lens 216 described above, is a lens provided to expand the range over which light emitted isotropically by gain medium 108 reaches receiving unit 104, and to expand the range over which light reflected back from receiving unit 104 can properly enter transmitting unit 102.
The retroreflected light from the receiving unit 104 will be described in detail later.

On the other hand, the receiving section 104 is a section that receives the laser light irradiated from the transmitting section 102 and performs photoelectric conversion.
In the illustrated wireless power supply system 100, the receiver 104 has a liquid crystal diffractive lens 120, a cholesteric mirror 124, and a photoelectric conversion element 126. The cholesteric mirror 124 is a receiver-side reflecting member in the wireless power supply system and receiver of the present invention.

The liquid crystal diffractive lens 120 is the liquid crystal diffractive lens shown in Fig. 4 etc. In the illustrated example, the liquid crystal diffractive lens 120 is, for example, a liquid crystal diffractive lens that collects left-handed circularly polarized light (left-handed circularly polarized light component) and converts it into right-handed circularly polarized light.
The cholesteric mirror 124 has a cholesteric liquid crystal layer similar to that of the above-mentioned cholesteric mirror 114. The cholesteric mirror 124 has a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light. As with the transmitting unit 102, the receiving side reflecting member may also be a dielectric multilayer film instead of a cholesteric liquid crystal layer.
In the receiving section 104, the liquid crystal diffractive lens 120 and the cholesteric mirror 124 form a retroreflector on the receiving section side.

Here, the focal point of the liquid crystal diffraction lens 120 is preferably located within 7 mm of the surface of the cholesteric mirror 124 (the receiving side reflecting member), more preferably within 2 mm of the surface of the cholesteric mirror 124, and even more preferably on the surface of the cholesteric mirror 124.
This makes it possible to preferably configure a resonance system between the resonance mirror 110 and the retroreflector of the transmitting section 102 and the retroreflector of the receiving section 104 .

The photoelectric conversion element 126 receives the light transmitted through the cholesteric mirror 124 and performs photoelectric conversion. For example, a device equipped with the receiving unit 104 is charged with the power photoelectrically converted by the photoelectric conversion element 126 and driven.
There is no limitation on the photoelectric conversion element 126, and all known photoelectric conversion elements 126 can be used. Examples include a solar cell and a photodiode.

The operation of the wireless power supply system 100 will be described below.
In the wireless power feeding system 100, when wireless power feeding is not performed, i.e., when the receiving unit 104 is not present in the wireless power feeding area of the transmitting unit 102, the gain medium 108 of the transmitting unit 102 is irradiated with excitation light from an excitation source (not shown) and emits light of a predetermined wavelength, for example, infrared light, isotropically. This emitted light is unpolarized.
In this state, a device having a receiving unit 104 is brought into a wireless power supply area (light irradiation area) by the transmitting unit 102, that is, an area where the light emitted isotropically by the gain medium 108 reaches. As a result, the light is incident on the liquid crystal diffractive lens 120 of the receiving unit 104.
As described above, the liquid crystal diffractive lens 120 is, for example, a liquid crystal diffractive lens that collects left-handed circularly polarized light and converts it to right-handed circularly polarized light. Therefore, of the unpolarized light incident on the liquid crystal diffractive lens 120, the left-handed circularly polarized component is converted to right-handed circularly polarized light, collected, and incident on the cholesteric mirror 124. Of the light incident on the liquid crystal diffractive lens 120, the right-handed circularly polarized component is converted to left-handed circularly polarized light and diffused.

Of the right-handed circularly polarized light that enters the cholesteric mirror 124, a portion is transmitted and enters the photoelectric conversion element 126, and a portion is collected and retroreflected by the retroreflector consisting of the liquid crystal diffraction lens 120 and the cholesteric mirror 124, as indicated by the white arrow in the figure.
Here, the retroreflected light is converted into left-handed circularly polarized light by the liquid crystal diffractive lens 120 .

Left-handed circularly polarized light (white arrow) retroreflected by the retroreflector (liquid crystal diffractive lens 120 and cholesteric mirror 124) of the receiving unit 104 returns along the original optical path, passes through lens 116, enters gain medium 108, and is reflected by resonance mirror 110. This reflection converts the left-handed circularly polarized light into right-handed circularly polarized light.
The right-handed circularly polarized light (white arrow) reflected by the resonance mirror 110 is transmitted through a lens 112 and collected, and is reflected by a cholesteric mirror 114 that selectively reflects right-handed circularly polarized light.
As described above, the lens 112 and the cholesteric mirror 114 constitute a retroreflector of the transmitting section 102. Therefore, the right-handed circularly polarized light (black arrow) reflected by the cholesteric mirror 114 returns along the original optical path by retroreflection, enters the gain medium 108, and is reflected by the resonance mirror 110. This reflection converts the right-handed circularly polarized light into left-handed circularly polarized light.

The left-handed circularly polarized light (black arrow) reflected by the resonance mirror 110 passes through the lens 216 so as to return along the original optical path, and enters the receiving unit 104 again.
The left circularly polarized light re-entering the receiving unit 104 is, as before, focused by the liquid crystal diffractive lens 120 and converted into right circularly polarized light (black arrow), part of which passes through the cholesteric mirror 124 and enters the photoelectric conversion element 126, and part of which is retroreflected by the retroreflector consisting of the liquid crystal diffractive lens 120 and the cholesteric mirror 124. During this retroreflection, the right circularly polarized light is focused by the liquid crystal diffractive lens 120 and converted into left circularly polarized light.
The left-handed circularly polarized light (white arrow) retroreflected by the receiving unit 104 returns along the original optical path and enters the transmitting unit 102, and similarly, is retroreflected as left-handed circularly polarized light, returns along the original optical path and enters the receiving unit 104, and similarly, a portion of the light is retroreflected as left-handed circularly polarized light, and once again enters the transmitting unit 102 and is retroreflected, repeating the process.

As a result, light is repeatedly reflected across the gain medium 108 between the two retroreflectors of the transmitting unit 102 and the receiving unit 104 and the resonance mirror 110. As a result, an optical resonance system (optical resonator) is formed, and the light excited by the gain medium 108 is amplified and lased. As a result, the transmitting unit 102 irradiates laser light with sufficient power, which enters the receiving unit 104, enabling the photoelectric conversion element 126 to output the desired power.
In addition, since the laser light from the gain medium 108 is obtained by stimulated emission, light with the same polarization component as the incident light is emitted and amplified. Therefore, in the wireless power supply system 100, it is possible to efficiently amplify only the desired polarization component that is repeatedly retroreflected.

In such a wireless power supply system 100, when wireless power supply is performed by retroreflection between the transmitting unit 102 and the receiving unit 104, laser light with sufficient power is output from the transmitting unit 102 and can be received by the receiving unit 104.
However, if a person's hand or the like enters the optical path of the laser light between the transmitter 102 and the receiver 104, the laser light is instantly blocked and resonance is stopped, so that the laser oscillation stops at that point. As a result, the person is not injured by the high-power laser light.
Therefore, according to the wireless power feeding system 100 of the present invention, the danger of laser light is significantly reduced, and wireless power feeding using laser light with sufficient output is possible.
Moreover, the receiver 104 uses the liquid crystal diffractive lens 120 as the retroreflector, rather than a lens made of glass or the like. As described above, the liquid crystal diffractive lens 120 is very thin, and therefore the receiver 104 can be made smaller (thinner), which can reduce the size of the entire wireless power supply system 100 by reducing the size of the device incorporating the receiver 104, and can improve the versatility of the wireless power supply system by enabling the receiver 104 to be incorporated into small devices.
The above-mentioned operational effects also apply to a wireless power feeding system 130 shown in FIG. 2 below.

FIG. 2 conceptually illustrates another example of a wireless power supply system according to the present invention.
In addition, in the wireless power feeding system 130 shown in FIG. 2, the same components as those in the wireless power feeding system shown in FIG. 1 are denoted by the same reference numerals, and the following description will mainly focus on the differences.

The wireless power supply system 130 shown in FIG. 2 includes a transmitting unit 132 and a receiving unit 134 .
The transmitting unit 132 has a configuration in which a half mirror 136 is used instead of the cholesteric mirror 114 in the transmitting unit 102 of the wireless power supply system 100 described above. In the transmitting unit 132, the lens 112 and the half mirror 136 configure a retroreflector on the transmitting unit side.
A known half mirror can be used for the half mirror 136, but it is preferable that the half mirror 136 has a high reflectance. Specifically, it is preferable that the half mirror 136 has a reflectance that transmits enough light to be detected by the detector 118 when one receiving unit 134 is being wirelessly powered. In addition, if the transmitting unit 132 does not have the detector 118, it is preferable to use a total reflection mirror instead of the half mirror 136.

On the other hand, the receiving unit 134 of the wireless power supply system 130 shown in FIG. 2 has a configuration in which a half mirror 136 is used instead of the cholesteric mirror 124 in the receiving unit 104 of the wireless power supply system 100 described above, and a λ/4 plate 140 and a λ/4 plate 142 are provided to sandwich the liquid crystal diffractive lens 120 in the traveling direction of the laser light.
In the receiving section 134, the liquid crystal diffractive lens 120 and the half mirror 146 form a retroreflector on the receiving section side.
In the receiving unit 134 of the wireless power supply system 130, the liquid crystal diffractive lens 120 is a liquid crystal diffractive lens that collects right-handed circularly polarized light and converts it into left-handed circularly polarized light.

The half mirror 136 is also a half mirror with high reflectance.
An example of the half mirror 136 is a half mirror used on the side from which laser light is extracted in an optical resonator of a laser light source.

In the wireless power supply system 130, the receiving unit 134 has a λ/4 plate 140 and a λ/4 plate 142 so as to sandwich the liquid crystal diffractive lens 120 in the traveling direction of the laser light. The receiving unit 134 has the λ/4 plate 140 and the λ/4 plate 142, and the λ/4 plate 140 and the λ/4 plate 142 are arranged so as to sandwich the liquid crystal diffractive lens 120 in the traveling direction of the laser light.
The λ/4 plate is a phase difference plate that shifts the phase of incident polarized light by λ/4.
There is no limitation on the direction of the slow axis of the λ/4 plate. The λ/4 plate 140 and the λ/4 plate 142 have the same direction of the slow axis.
In the illustrated example, the λ/4 plate 140 and the λ/4 plate 142 have their slow axes oriented in such a way as to convert linearly polarized light in the vertical direction in the figure into right-handed circularly polarized light, for example.

In the present invention, a known λ/4 plate (¼ wavelength plate) can be used.
Therefore, the λ/4 plate may be a single-layer type composed of one optically anisotropic layer, or a laminated type wave plate composed of a laminate of two or more optically anisotropic layers each having a plurality of different slow axes.
Examples of laminated λ/4 plates include those described in International Publication No. WO 2013/137464, International Publication No. WO 2016/158300, JP 2014-209219, JP 2014-209220, International Publication No. WO 2014/157079, JP 2019-215416, and International Publication No. WO 2019/160044. In the present invention, the laminated λ/4 plate is not limited to these.

The operation of the wireless power supply system 130 will be described below.
In the wireless power feeding system 130, when wireless power feeding is not performed, that is, when the receiving unit 134 is not present in the wireless power feeding area of the transmitting unit 132, the gain medium 108 of the transmitting unit 132 is irradiated with excitation light from an excitation source (not shown) and emits light of a predetermined wavelength, for example, infrared light, isotropically. This emission is unpolarized.
In this state, a device having a receiver 134 is brought into a wireless power supply area (light irradiation area) by the transmitter 132, that is, an area where the light emitted isotropically by the gain medium 108 reaches. As a result, as shown by the black arrow, the light is incident on the λ/4 plate 140 of the receiver 134 and then on the liquid crystal diffractive lens 120.
As described above, the λ/4 plate 140 converts linearly polarized light in the vertical direction in the figure into right-handed circularly polarized light. Therefore, of the light incident on the λ/4 plate 140, the linearly polarized light component in the vertical direction in the figure is converted by the λ/4 plate 140 into right-handed circularly polarized light.
Moreover, as an example, the liquid crystal diffractive lens 120 is a liquid crystal diffractive lens that collects right-handed circularly polarized light and converts it to left-handed circularly polarized light. Therefore, the right-handed circularly polarized light incident on the liquid crystal diffractive lens 120 is converted to left-handed circularly polarized light and collected. Of the light incident on the liquid crystal diffractive lens 120, light other than the right-handed circularly polarized component is converted to left-handed circularly polarized light and diffused.

The left-handed circularly polarized light transformed by the liquid crystal diffractive lens 120 then enters the λ/4 plate 142 (black arrow).
The λ/4 plate 142 has a slow axis in the same direction as the λ/4 plate 140. Furthermore, the light incident on the λ/4 plate 142 is left-handed circularly polarized light converted from right-handed circularly polarized light. Therefore, the left-handed circularly polarized light incident on the λ/4 plate 142 is converted into linearly polarized light in a direction perpendicular to the paper surface.

The linearly polarized light in the direction perpendicular to the paper surface, which has been converted by the λ/4 plate 142 , then enters a half mirror 146 .
Of the linearly polarized light that enters the half mirror 146, a portion of it is transmitted and enters the photoelectric conversion element 126, and a portion of it is collected and retroreflected by a retroreflector consisting of the liquid crystal diffractive lens 120 and the half mirror 146, as indicated by the white arrow in the figure.
Here, this retroreflected light is converted from linearly polarized light in a direction perpendicular to the paper surface to left-handed circularly polarized light by the λ/4 plate 142, converted to right-handed circularly polarized light by the liquid crystal diffraction lens 120, and further converted to linearly polarized light in the vertical direction in the figure by the λ/4 plate 140.

The linearly polarized light (indicated by the white arrow) in the vertical direction in the figure, which is retroreflected by the retroreflector (liquid crystal diffraction lens 120 and half mirror 146) of the receiving unit 104, returns to the original optical path, passes through lens 116, enters gain medium 108, and is reflected by resonance mirror 110.
The linearly polarized light (indicated by the white arrow) reflected by the resonance mirror 110 in the vertical direction in the figure is transmitted through the lens 112 and collected, and is reflected by the half mirror 136 .
As described above, the lens 112 and the half mirror 136 constitute a retroreflector of the transmitting unit 102. Therefore, the linearly polarized light in the vertical direction in the figure reflected by the half mirror 136 returns along the original optical path by retroreflection, enters the gain medium 108, and is reflected by the resonance mirror 110.

The linearly polarized light (black arrow) reflected by the resonance mirror 110 in the vertical direction in the figure passes through the lens 116 and enters the receiving unit 104 again.
The linearly polarized light in the vertical direction in the figure that re-enters the receiving unit 104 is converted into right-handed circularly polarized light by the λ/4 plate 140, as before, and then focused by the liquid crystal diffraction lens 120 and converted into left-handed circularly polarized light (black arrow), and further converted into linearly polarized light in a direction perpendicular to the plane of the paper by the λ/4 plate 142, a portion of which passes through the half mirror 136 and enters the photoelectric conversion element 126, and a portion of which is retroreflected by the retroreflector consisting of the liquid crystal diffraction lens 120 and the half mirror 136.
During this retroreflection, the linearly polarized light in a direction perpendicular to the paper surface is converted into left-handed circularly polarized light by the λ/4 plate 142, concentrated by the liquid crystal diffraction lens 120 and converted into right-handed circularly polarized light, and then converted into linearly polarized light in the vertical direction in the figure by the λ/4 plate 140.

The linearly polarized light in the vertical direction in the figure (white arrow) that is retroreflected by the receiving unit 104 returns along the original optical path and enters the transmitting unit 102, and similarly is retroreflected as linearly polarized light in the vertical direction in the figure, returns along the original optical path and enters the receiving unit 104, and similarly a portion of the light is retroreflected as linearly polarized light in the vertical direction in the figure, and again enters the transmitting unit 102 and is retroreflected again, repeating the process.

As a result, similar to the wireless power supply system 100 described above, sufficient safety is ensured when laser light of sufficient power is output from the transmitter 102 and received by the receiver 104 for photoelectric conversion. In addition, the receiver 134 can be made smaller (thinner), which allows the size of the device incorporating the receiver 134 to be reduced, and the versatility of the wireless power supply system 130 to be improved.

2 does not require a special mirror such as a cholesteric mirror, and can use an ordinary mirror or a half mirror in the transmitter 132. Therefore, the versatility of the transmitter 132 can be increased.
In the wireless power supply system 130 shown in FIG. 2, if the detector 118 is not present, the retroreflector on the transmitting side is not limited to one consisting of a lens 112 and a half mirror 136 (mirror), and various known retroreflectors such as a corner cube and a microbead array can be used.

In the wireless power supply system 130 shown in FIG. 2, it is preferable to use, as the detector 118, a known detector capable of detecting the direction of linearly polarized light, such as a detector in combination with a rotating polarizer.
As described above, in the receiving unit 134 of the wireless power supply system 130, a linearly polarized light component in an arbitrary direction can be converted into circularly polarized light, and the circularly polarized light can be collected and retroreflected by the liquid crystal diffractive lens 120. In the wireless power supply system 13, this arbitrary linearly polarized light is repeatedly retroreflected between the transmitting unit 132 and the receiving unit 134, and resonates.
Therefore, by using the detector 118 that can detect the direction of linearly polarized light, it becomes possible to determine the presence or absence and the number of the above-mentioned wirelessly powered receiving units 134, as well as the type of the wirelessly powered receiving units 134, by detecting the polarization direction. Also, it is possible to detect the number of the wirelessly powered receiving units 134 with higher accuracy.

In the above example, the receiving section has one liquid crystal diffractive lens, but the present invention is not limited to this, and a plurality of liquid crystal diffractive lenses (diffractive lenses) may be arranged and used.
By arranging a plurality of liquid crystal diffractive lenses, i.e., small liquid crystal diffractive lenses, one-dimensionally or two-dimensionally, the focal point of the liquid crystal diffractive lens can be shortened, thereby shortening the optical distance between the liquid crystal diffractive lens and the receiving side reflecting member.
As a result, the receiving section can be further miniaturized (thinned), which is preferable.
The arrangement of the liquid crystal diffractive lenses may be regular or irregular. When a plurality of liquid crystal diffractive lenses are arranged, a receiver-side reflecting member may be arranged between one of the plurality of liquid crystal diffractive lenses and the photoelectric conversion element. When a plurality of liquid crystal diffractive lenses are arranged, a plurality of receiver-side reflecting members may also be arranged.

In addition, in the above example, the transmitting section has a resonance mirror 110 fixed to the gain medium 108, and the resonance mirror 110, the transmitting section, and the receiving section constitute an optical resonance system (optical resonator), but the present invention is not limited to this.
For example, as shown in FIG. 3 as an example of the wireless power supply system 130 of FIG. 2 , the gain medium 108 may not have the resonant mirror 110, and a transmitter 132 and a receiver 134 may be provided to sandwich the gain medium 108, so that the transmitter 132 and the receiver 134 form an optical resonant system sandwiching the gain medium 108.

The optical wireless power supply system and receiving unit of the present invention have been described in detail above, but the present invention is not limited to the above examples, and various improvements and modifications may of course be made without departing from the gist of the present invention.

It can be ideally used for various devices that are powered by charging.

20 Support 24 Alignment film 26, 26A Optically anisotropic layer 30 Liquid crystal compound 30A Optical axis 80 Exposure device 82 Laser 84 Light source 86, 94 Polarizing beam splitter 90A, 90B Mirror 96 λ/4 plate 92 Lens 100, 130, 200 Wireless power supply system 102, 132, 204 Transmitter 104, 134, 206 Receiver 108, 208 Gain medium 110, 210 Resonator mirror 112, 116, 216, 212 Lens 114, 124 Cholesteric mirror 118 Detector 120 Liquid crystal diffraction lens 126, 224 Photoelectric conversion element 136, 146, 220 Half mirror 140, 142 λ/4 plate 218 Condenser lens M Laser light MP P-polarized light MS S-polarized light _L1 , _L4 Incident light _L2 , _L5 Transmitted light Q1, Q2 Absolute phase E1, E2 Equi-phase surface

Claims (11)

A wireless power supply system having a transmitter and a receiver,
The transmitting section includes a gain medium and a transmitting side reflecting member,
the receiving unit includes a diffractive lens, a photoelectric conversion element, a receiving-side reflecting member disposed between the diffractive lens and the photoelectric conversion element, the receiving member reflecting a portion of the light transmitted through the diffractive lens, and a plurality of λ/4 plates ;
the gain medium is disposed between the transmitting reflector and the receiving reflector;
The light amplified by the gain medium passes through the diffractive lens and the receiving-side reflecting member and is incident on the photoelectric conversion element; and
A wireless power supply system , wherein the receiving unit includes the λ/4 plate, the diffractive lens, the λ/4 plate, the receiving side reflecting member, and the photoelectric conversion element, arranged in this order . The diffractive lens is a liquid crystal diffractive lens having an optically anisotropic layer formed using a composition containing a liquid crystal compound,
The optically anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction, radially from the inside to the outside, and
2. The wireless power supply system according to claim 1, wherein in the liquid crystal orientation pattern, when the length of one period is defined as the length of a 180° rotation of an optical axis direction originating from the liquid crystal compound in the one direction, the length of one period gradually becomes shorter from the inside to the outside. The wireless power supply system according to claim 1 , wherein the receiving side reflecting member is a half mirror. 4. The wireless power supply system according to claim 1 , wherein the transmission side reflecting member is a half mirror or a total reflection type mirror. The wireless power supply system according to any one of claims 1 to 4 , wherein the focal position of the diffractive lens is located at a distance of 7 mm or less from the surface of the receiver-side reflecting member. The wireless power supply system according to claim 1 , wherein a plurality of the diffractive lenses are arranged one-dimensionally or two - dimensionally. A receiving unit used in a wireless power supply system,
a diffractive lens; a photoelectric conversion element; a receiving-side reflecting member disposed between the diffractive lens and the photoelectric conversion element, the receiving-side reflecting member reflecting a portion of light transmitted through the diffractive lens; and a plurality of λ/4 plates;
A receiving section in which the λ/4 plate, the diffractive lens, the λ/4 plate, the receiving side reflecting member, and the photoelectric conversion element are arranged in this order . The diffractive lens is a liquid crystal diffractive lens having an optically anisotropic layer formed using a composition containing a liquid crystal compound,
The optically anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction, radially from the inside to the outside, and
The receiving unit described in claim 7, wherein in the liquid crystal orientation pattern, when the length of one period is defined as the length of a 180° rotation of the direction of the optical axis originating from the liquid crystal compound in the one direction, the length of one period gradually becomes shorter from the inside to the outside. 9. The receiver according to claim 7 , wherein the receiving side reflecting member is a half mirror. 10. The receiver according to claim 7, wherein the focal position of the diffractive lens is located at a distance of 7 mm or less from the surface of the receiver-side reflecting member. 11. The receiving section according to claim 7, wherein a plurality of the diffractive lenses are arranged one-dimensionally or two-dimensionally.