DESCRIPTION Title of Invention FLOATING IMAGE DISPLAY UNIT Technical Field [000 1] The teclmology relates to a floating image display unit that displays an image mspace. Background Art [0002] Patent Literature 1 discloses an optical system that uses a plane-symmetric imaging element to form an image of an object at a plane-symmetric position on topsurface side with respect to the element. The object is disposed on bottom-surface side of the element. ··A substrate· of the plane-symmetric imaging element used in the optical system is provided with a plurality of through holes arranged in a matrix, and an optical element including two mirrored surfaces that are orthogonal to each other is formed on an interior wall of each of the holes. When light outputted from the object passes through the holes, the light is reflected once by each of the two mirrored surfaces, and an image of the reflected light is formed at a plane-symmetric position with respect to the element. This causes an observer to see a formed image (a real image) as if the image is floating above the top surface of the element. Citation list Patent Literature [0003] Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2008-158114 Summary of Invention SP357100 [0004] In the optical system described in Patent Literature 1, a floating height of the real image from the top surface of the element is equal to a distance between the object and the bottom surface of the element. Therefore, in order to increase the foregoing floating height, it is necessary to move the object away from the bottom surface of the element accordingly. This causes· an issue of an increase in volumetric capacity of the optical system. [0005] It is therefore desirable to provide a floating image display unit that makes it possible to reduce a thickness of an optical system, as compared with a floating height of a real image. [0006] A floating image display unit according to an embodiment of the technology includes an optical plate and one or a plurality of reflectors. The optical plate includes a plurality of optical elements arranged in a matrix on a substrate having a normal in a Z-axis direction, and each of the optical elements is configured to regularly reflect an entering light beam of a Z-axis direction component and recursively reflect an entering light beam of an XY -axis direction component. The one or the plurality of reflectors are configured to reflect light outputted from a light emitter or a light irradiation target object disposed on the rear surface side of the optical plate, thereby causing the light to obliquely enter a rear surface of the optical plate, where a surface on viewer side of the optical plate is denoted as a front surface and a surface opposite to the front surface of the optical plate is denoted as the rear surface. [0007] In the floating image display unit according to the embodiment of the teclmology, the light outputted from the light emitter or the light irradiation target object disposed on the rear surface side of the optical plate is reflected by the one or the plurality of reflectors to obliquely enter the rear surface. As used herein, the term 2 SP357100 "symmetric position'' refers to a plane-symmetric position to a real image with respect to the optical plate. The real image is formed on the front surface side of the optical plate as a result of reflecting the light outputted from the light emitter or the light irradiation target object by the one or the plurality of reflectors and thereafter causing the light to pass through the optical plate from the rear surface side. At this occasion, for example, one reflector (a first reflector) is provided between the symmetric position and the plurality of optical elements to cause the light from the light emitter or the light irradiation target object to enter the first reflector from a position above the symmetric position, which makes it possible to form the foregoing real image. In other words, even if the light emitter or the light irradiation target object does not exist at the symmetric position, it is possible to form the foregoing real image as if the light emitter or the light irradiation target object exists at the symmetric position. As a result, it is possible to dispose the light emitter or the one or the plurality of reflectors closer to the rear surface of the optical plate than the symmetric position. [0008] According to the floating image display unit of the embodiment of the technology, providing the one or the plurality of reflectors makes it possible to dispose the light emitter or the one or the plurality of reflectors closer to the rear surface of the optical plate than the synm1etric position; therefore, it is possible to reduce a thickness of the floating image display unit, as compared with a floating height of the real image. It is to be noted that effects of the teclmology are not limited to effects described here, and may be any of effects described in the description. Brief Dcscdption of Drawings [0009] [FIG. I] FIG. I is a diagram of an example of a cross-sectional configuration of a floating image display unit according to a first embodiment of the technology. 3 SP357100 [FIG. 2] FIG. 2 is a diagram of an example of a planar configuration of an optical plate in FIG. I. [FIG. 3] FIG. 3 is a diagram of an example of workings of the optical plate in FIG. 1 in an XY plane. [FIG.-4] FIG. 4 is a diagram of an example of workings of the optical plate in FIG. 1 in an XZ plane and a YZ plane. [FIG. 5] FIG. 5 is a diagram of an example of workings of the floating image display unit in FIG. I. [FIG. 6] FIG. 6 is a diagram of a modification example of the floating image display unit in FIG. I. [FIG. 7] FIG. 7 is a diagram of an example of workings of the floating image display unit in FIG. 6. [FIG. 8] FIG. 8 is a diagram of a modification example of the floating image display unit in FIG. I. [FIG. 9] FIG. 9 is a diagram of a modification example of the floating image display unit in FIG. 6. [FIG. I Ol FIG. 10 is a diagram of an example of a cross-sectional configuration of a floating image display unit according to a second embodiment of the teclmology. [FIG. 11] FIG. 11 is a diagram of an example of workings of the floating image display unit in FIG. 10. .·. [FIG. 12] FIG. 12 is a diagram of a modification example of the floating image display unit in FIG. II. [FIG. 13] FIG. 13 is a diagram of an example of workings of the floating image display unit in FIG. 12. 4 SP357100 [FIG. 14] FIG. 14 is a diagram of a modification example of the floating image display unit in FIG. 13. [FIG. 15] FIG. 15 is a diagram of a modification example of the floating image display unit in FIG. I. [FIG. 16] FIG. 16 is a diagram of a modification example of the floating image display unit in FIG. 8. [FIG. 17] FIG. 17 is a diagram of a modification example of the floating image display unit in FIG. 6. [FIG. 18] FIG. 18 is a diagram of a modification example of the floating image display unit in FIG. 9. [FIG. 19] FIG. 19 is a diagram of a modification example of the floating image display unit in FIG. 10. [FIG. 20] FIG. 20 is a diagram of a modification example of the floating image display unit in FIG. 12. [FIG. 21] FIG. 21 is a diagram of a modification example of the floating image display unit in FIG. 14. [FIG. 22] FIG. 22 is a diagram of an example of an alternative to a display panel. MODE FOR CARRYING OUT THE INVENTION [00 1 0] In the following, some embodiments of the teclmology are described in detail with reference to the drawings. It is to be noted that description is given in the following order. I. First Embodiment (FIGs. I to 5) An example containing two reflectors and a light emitter 2. Modification Examples of First Embodiment (FIGs. 6 to 9) 5 SP357100 Modification Example A: An example in which the position of the light emitter is changed Modification Example B: An example including a light-shielding plate 3. Second Embodiment (FIGs. 10 and 11) An example containing one polarizer, two polarization reflectors, and a halfwave plate in addition to the two reflectors and the light emitter 4. Modification Examples of Second Embodiment (FIGs. 12 to 15) Modification Example C: An example in which the position of the light emitter is changed Modification ExampleD: An example including a light-shielding plate 5. Collllllon Modification Examples of Respective Embodiments and Modification Examples (FIGs.l6to 22) Modification Example E: An example in which the light emitter is externally attached Modification Example F: An example m which a translucent screen 1s provided in place of a display panel [0011] (1. First Embodiment) [Configuration] FIG. 1 illustrates an example of a cross-sectional configuration of a floating ;.. image display unit 1 according to a first embodiment of the technology. The floating ·image display unit I displays an image in space. The floating image display unit 1 may include, for example, an optical plate 10, reflectors 20 and 30, a display panel 40, a driving circuit board 50, and suppmiing plates 60 and 70. The optical plate 10, the reflectors 20 and 30, the display panel 40, and the supporting plates 60 and 70 form 6 SP357100 internal space. The suppmting plates 60 and 70 may be omitted as necessary. The optical plate I 0 corresponds to a specific example of an "optical plate" of the technology. The reflectors 20 and 30 correspond to a specific example of a "plurality of reflectors" of the technology. The reflector 20 corresponds to a specific example of a "second reflector" of the technology. The reflector 30 corresponds to a specific example of a "firs reflector" of the technology. The display panel 40 corresponds to a specific example of "light emitter" of the technology. [0012] (Optical Plate I 0) FIG. 2 illustrates an example of a planar configuration of the optical plate I 0. The optical plate I 0 includes a plate-like substrate II. As used herein, a surface on viewer 1000 side of the optical plate 10 (the substrate II) is denoted as a front surface lOA, and a surface opposite·to the front surface lOA of the optical plate 10 (the substrate II) is denoted as a rear surface lOB. Moreover, a plane parallel to the front surface 1 OA of the optical plate I 0, a plane parallel to a reflective surface 13A to be described later, and a plane parallel to a reflective surface 13B to be described later are respectively denoted as an XY plane, as an XZ plane, and an YZ plane. Further, a normal AX! to the optical plate 10 (the substrate 11) is parallel to a Z axis. [0013] The optical plate 10 (the substrate II) includes a plurality of apertures 12 arranged in a matrix in a plane parallel to the fi·ont surface I OA. Each of the apertures -12 penetrates tln·ough the optical plate I 0 in a thickness direction (a Z-axis direction), ,, and allows light entering from the rear surface lOB side of the optical plate 10 to pass therethrough to the front surface lOA side of the optical plate 10. A diameter of each of the apertures 12 may be, for example, submicron (smaller than I ~un), in Jlm order (from I ~unto 999 Jlm), or in mm order (from I mm to 9 mm). Each of the apertures 7 SP357100 12 may be, for example, an air gap. For example, the substrate II may have the apertures 12. A projected stmcturc formed on the front surface I OA of the substrate II may have the apetiures 12. The optical plate IO (the substrate II) may include a lightshielding (light-reflective or light-absorbent) member in a region other than a region where each of the apertures 12 is formed. [OOI4] An optical element 13 may be provided on a side surface of each of the apertures 12. In other words, the optical plate 10 includes a plurality of optical elements 13 arranged in a matrix in a plane parallel to the front surface I OA. Each of the optical elements 13 may include, for example, two reflective surfaces 13A and 13B that are orthogonal to each other. The reflective surface 13A is parallel to the XZ plane, and the reflective surface 13B is parallel to the YZ plane. The reflective surface 13A and the reflective surface·13B may be provided in a same layer or in different layers in the optical plate I 0. In a case in which the reflective surface 13A and the reflective surface 13B are provided in the same layer in the optical plate I 0, for example, an end of the reflective surface 13A is in contact with an end of the reflective surface 13B. In a case in which the reflective surface 13A and the reflective surface 13B are provided in different layers in the optical plate I 0, for example, one of four corners of the reflective surface 13A is iu contact with one of four corners of the reflective surface 13B. [0015] FIG. 3 illustrates an example of workings of the optical plate 10 in the XY ' plane. FIG. 4 illustrates an example of workings of the optical plate 10 in the XZ plane and in the YZ plane. In the XY plane, light L having entered fi·om the rear surface I OB side of the optical plate I 0 may enter the reflective surface I3A at an entry angle 8 and may be reflected at an exit angle 8 by the reflective surface 13A, and 8 SP357100 thereafter, the light L may enter the reflective surface 13B at an entry angle cp and may be reflected at an exit angle