Abstract: A three-dimensional photonic crystal of the present invention has a complete photonic band gap in a wide wavelength region and that can be easily produced. A three-dimensional photonic crystal in which a plurality of layers including a periodic-refractive-index structure are periodically stacked includes, a first layer having holes provided at lattice points of a first rectangular lattice and a second rectangular lattice, a second layer having columnar structures at lattice points of a face-centered rectangular lattice, a third layer having a periodic structure the same as that of the first layer and disposed at a shifted position, and a fourth layer having a periodic structure the same as that of the second layer.

Abstract: A three-dimensional photonic crystal has periodic-refractive-index structures including a first layer having a periodic structure based on a first rectangular lattice having a period of A along a first axis and a period of B along a second axis orthogonal to the first axis in the plane direction, a second layer having a periodic structure disposed at a position shifted by +3B/8 along the second axis with respect to the position of the first rectangular lattice, a third layer having a periodic structure disposed at a position shifted by A/2 along the first axis and B/2 along the second axis with respect to the position of the periodic structure in the first layer, and a fourth layer having a periodic structure disposed at the same position as the periodic structure in the second layer.

Abstract: An image observation system includes a pair of image observation devices each having i) an image pickup device, ii) an image pickup optical system for directing light rays from an outside world to the image pickup device, iii) a display device for displaying an outside world image obtained by the image pickup system, and iv) a display optical system for directing light from the display device to an observing eye. The optical axis of the image pickup system and the optical axis of the display system are disposed coaxially, wherein the optical axes of the image pickup systems of the pair of image observation devices define a point of intersection, and wherein a focal plane being at a position conjugate with a surface of the image pickup device with respect to the image pickup optical system is disposed at a side of the intersection point of the optical axes of the image pickup systems, which side faces an observer.

Abstract: At least one exemplary embodiment is directed to a waveguide including a plurality of linear defects of a three-dimensional photonic crystal, the plurality of linear defects include a first defect formed by changing the medium of some of columnar structures to a medium different from that of the columnar structures and a second linear defect formed by shifting the position or changing the shape of some of the columnar structures extending in the same direction as the first linear defect, and the first linear defect and the second linear defect are disposed apart by 0.5 times the out-of-plane lattice period or more in the stacking direction of the three-dimensional photonic crystal.

Abstract: At least one exemplary embodiment is directed to a waveguide, which includes a three-dimensional photonic crystal including a first linear defect and a second linear defect. The first linear defect is disposed at part of columnar structures and is formed of a medium different from the columnar structures. The second linear defect is disposed at part of columnar structures extending in the longitudinal direction of the first linear defect and is formed of a medium having a refractive index different from that of the medium used for the columnar structures. The second linear defect is separated from the first linear defect by a distance of at least 0.5 times the out-of-plane lattice period of the three-dimensional photonic crystal in a direction in which layers including the columnar structures are stacked.

Abstract: A three-dimensional photonic crystal of the present invention has a complete photonic band gap in a wide wavelength region and that can be easily produced. A three-dimensional photonic crystal in which a plurality of layers including a periodic-refractive-index structure are periodically stacked includes, a first layer having holes provided at lattice points of a first rectangular lattice and a second rectangular lattice, a second layer having columnar structures at lattice points of a face-centered rectangular lattice, a third layer having a periodic structure the same as that of the first layer and disposed at a shifted position, and a fourth layer having a periodic structure the same as that of the second layer.

Abstract: Provided is a resonator using a three-dimensional photonic crystal. In the resonator, a range of choice of a resonance wavelength is wide and a desirable electric field distribution is obtained. The resonator according to the present invention includes a plurality of point defects provided in the three-dimensional photonic crystal. At least one of the plurality of point defects does not include a eigenmode in a photonic band gap of the three-dimensional photonic crystal.

Abstract: An image observation system includes a pair of image observation devices each having i) an image pickup device, ii) an image pickup optical system for directing light rays from an outside world to the image pickup device, iii) a display device for displaying an outside world image obtained by the image pickup system, and iv) a display optical system for directing light from the display device to an observing eye. The optical axis of the image pickup system and the optical axis of the display system are disposed coaxially, wherein the optical axes of the image pickup systems of the pair of image observation devices define a point of intersection, and wherein a focal plane being at a position conjugate with a surface of the image pickup device with respect to the image pickup optical system is disposed at a side of the intersection point of the optical axes of the image pickup systems, which side faces an observer.

Abstract: A three-dimensional photonic crystal operating at a plurality of design wavelengths, in which the photonic band gap can be adjusted to a desired wavelength band without changing the lattice period, and an optical element that can contain a defect resonator or a defect waveguide in the three-dimensional photonic crystal are provided.

Abstract: At least one exemplary embodiment is directed to a method for fabricating a three-dimensional photonic crystal. In the method for fabricating the three-dimensional photonic crystal, a plurality of layers can be defined as one unit, and the total thickness of the one unit can be controlled such that an average layer-thickness of the plurality of layers in the one unit is about equal to the ideal layer-thickness so that a photonic band-gap occurs in a desired wavelength region.

Abstract: A three-dimensional photonic crystal includes a first region including a first layer, a second layer, a third layer, a fourth layer and a second region including the first layer, the second layer, the third layer, the fourth layer, and additional layers including discrete structures spaced from each other. The horizontal interval and the vertical interval of the rod-shaped structures in the first region are the same as those of the rod-shaped structures in the second region, respectively.

Abstract: Provided is a resonator using a three-dimensional photonic crystal. In the resonator, a range of choice of a resonance wavelength is wide and a desirable electric field distribution is obtained. The resonator according to the present invention includes a plurality of point defects provided in the three-dimensional photonic crystal. At least one of the plurality of point defects does not include a eigenmode in a photonic band gap of the three-dimensional photonic crystal.

Abstract: A three-dimensional photonic crystal includes a first region including a first layer, a second layer, a third layer, a fourth layer and a second region including the first layer, the second layer, the third layer, the fourth layer, and additional layers including discrete structures spaced from each other. The horizontal interval and the vertical interval of the rod-shaped structures in the first region are the same as those of the rod-shaped structures in the second region, respectively.

Abstract: At least one exemplary embodiment is directed to a method for manufacturing a three-dimensional photonic crystal including a plurality of stacked layers having periodic structures where the thickness of the periodic structures in a layer are adjusted such that the layer satisfies the following equation: neff1×H1×M=neff×H wherein H1 represents the actual thickness of the layer, neff1 represents the actual refractive index of the periodic refractive index structure, H represents the design thickness of the layer, neff represents the design effective refractive index of the periodic refractive index structure, and M represents a coefficient inclusive and between 0.5 and 2.0.

Abstract: A three-dimensional periodic structure exhibiting a complete photonic band gap in a wide wavelength range and being readily produced, as well as a functional element including the same, is provided. In the three-dimensional periodic structure exhibiting a photonic band gap according to the present invention, layers composed of a plurality of square columns spaced apart by a predetermined interval are stacked sequentially with additional layers therebetween, rectangular parallelepipeds contained in the additional layers are disposed at the positions corresponding to the intersections of the square columns, and 1.21?W1/W?2.39 and W/W1<W2/W are satisfied, where W1 and W2 represent lengths of sides of the rectangular parallelepiped and W represents the width of the square column, each in a plane parallel to the layer containing the square columns.

Abstract: A display optical system for guiding light from an original picture to an eye of an observer or a surface to have an image projected thereon is provided with a first optical system and a second optical system. The first optical system is provided with a first surface that is formed on a transparent body and has at least a reflecting action, a second surface for reflecting light reflected on the first surface toward the first surface again, and a third surface that is formed on the transparent body in the same manner as the first surface and transmits the light from the original picture. The light transmitted through the third surface travels toward the first surface and reflected for the first time on the first surface. In addition, a principal ray at central angle of view to be reflected for the last time on the first surface is reflected and travels to a side opposite to a side of the first reflection on the first surface with respect to a normal line of a surface on a hit point thereof.

Abstract: Provided is a small size, high resolution display element with an extremely high utilization efficiency of light emitted by a light source unit and a high contrast. A display element of the present invention has a photonic crystal, a light source unit, and a control unit. The control unit changes the resonance wavelength of point defect resonators formed within the photonic crystal, thus effecting a control between a state in which light guided from the light source unit to a linear defect waveguide is emitted to the outside of the photonic crystal, and a state where emission of light to the outside of the photonic crystal is blocked.

Abstract: A resonator is provided which is produced by a defect formed in a three-dimensional photonic crystal. The three-dimensional photonic crystal can include layers containing a plurality of columnar structures with discrete structures in sublayers.

Abstract: What is disclosed is an eye detection apparatus which can detect the pupil position accurately. The apparatus has an image taking unit that picks up an image of an eye and a pupil detection unit that detects the position of the pupil in the eye based on an image picked up by the image taking portion. The pupil detection unit determines the pupil position based on images picked up by the image taking unit in a plurality of states.

Abstract: A small optical system that is capable of widening an angle of view is provided. This optical system is provided with a first surface having a reflecting action and a second surface that reflects a light beam reflected on this first surface toward the first surface again. Then, a principal ray at central angle of view that is made incident on the first surface again is reflected and travels to a side opposite to a side of the last time it was reflected from the first surface with respect to a normal line of a surface at a hit point thereof.