Indication device

Abstract

To improve display accuracy of a stereoscopic image.SOLUTION: A display device 10E comprises: a display body 12C in which a plurality of fluorescent layers containing fluorescent bodies and a plurality of separation layers containing no fluorescent body are alternately laminated; a first irradiation unit 16 which emits first excitation light 20 incident in a lamination direction on the display body 12C and exciting the fluorescent bodies while changing a position in an in-plane direction; and a second irradiation unit 90 which emits second excitation light 88 incident in the in-plane direction on the plurality of fluorescent layers and exciting the fluorescent bodies while changing the position in the lamination direction.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a display device.

Background Art

[0002] As a display device for a stereoscopic image, a configuration has been proposed in which quantum dot blocks are three-dimensionally combined and irradiated with ultraviolet light (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above prior art, the control of the irradiation position of the ultraviolet light irradiated to the quantum dot block is not mentioned. In order to accurately display the intended stereoscopic image, it is preferable to appropriately control the irradiation position. <000003*2> The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for improving the display accuracy of a stereoscopic image.

Means for Solving the Problems

[0006] A display device according to an aspect of the present invention includes a display body in which a plurality of phosphor layers containing phosphors and a plurality of separation layers not containing phosphors are alternately laminated, a first irradiation unit that irradiates the display body with first excitation light that is incident in the lamination direction and excites the phosphors while changing the position in the in-plane direction, and a second irradiation unit that irradiates the plurality of phosphor layers with second excitation light that is incident in the in-plane direction and excites the phosphors while changing the position in the lamination direction.

[0007] *Note: There seems to be a typo in the original text where

[0005] is likely a misprint. I've left it as is in the translation but it should be checked. Also, and

[0005] are preserved as they are in the source text.Furthermore, any combination of the above components, or any substitution of components or expressions of the present invention between methods, apparatus, systems, etc., is also valid as an embodiment of the present invention. [Effects of the Invention]

[0008] According to the present invention, the display accuracy of stereoscopic images can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] This figure schematically shows the configuration of the display device according to the first embodiment. [Figure 2] This graph schematically shows the relationship between the excitation light intensity and emission intensity of a phosphor. [Figure 3] This diagram schematically shows the relationship between the thickness of the fluorescent layer and the Rayleigh length of the excitation light. [Figure 4] This figure schematically shows the configuration of the display device according to the second embodiment. [Figure 5] This diagram schematically shows the configuration of the display device according to the third embodiment. [Figure 6] This diagram schematically shows the arrangement of the first, second, and third focusing positions. [Figure 7] This figure schematically shows the configuration of the display body according to the fourth embodiment. [Figure 8] This diagram schematically shows the relationship between the thickness of the fluorescence layer and separation layer and the Rayleigh length of the excitation light. [Figure 9] This diagram schematically shows the arrangement of the first, second, and third focusing positions in the fifth embodiment. [Figure 10] This figure schematically shows the configuration of the display device according to the sixth embodiment. [Figure 11] This figure schematically shows the configuration of the display device according to the seventh embodiment. [Figure 12] This figure schematically shows the configuration of the display unit and the second irradiation unit according to the seventh embodiment. [Figure 13] This figure schematically shows the configuration of the display device according to the eighth embodiment.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The specific numerical values and the like shown in such embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the drawings, elements not directly related to the present invention are not shown. For the sake of helping the understanding of the description, the dimensional ratios of the respective components in each drawing do not necessarily match the actual dimensional ratios.

[0011] (First Embodiment) FIG. 1 is a diagram schematically showing the configuration of a display device 10 according to the first embodiment. The display device 10 includes a display body 12, an irradiation unit 16, and a control unit 18. The display device 10 is a so-called volume display, and is configured to draw a stereoscopic image S inside the display body 12.

[0012] The display body 12 has a first surface 13 and a second surface 14, and includes a plurality of stacked bodies 30 stacked in the z direction from the first surface 13 toward the second surface 14. Each of the plurality of stacked bodies 30 has a first fluorescent layer 31, a second fluorescent layer 32, and a third fluorescent layer 33. The display body 12 has a structure in which a plurality of fluorescent layers are stacked in order, such as the first fluorescent layer 31, the second fluorescent layer 32, the third fluorescent layer 33, the first fluorescent layer 31, the second fluorescent layer 32, the third fluorescent layer 33, ···. For example, the plurality of second fluorescent layers 32 are alternately arranged with the plurality of first fluorescent layers 31, and the plurality of third fluorescent layers 33 are alternately arranged with the plurality of first fluorescent layers 31 and the plurality of second fluorescent layers 32.

[0013] The first fluorescent layer 31 is a fluorescent layer containing a first phosphor having a light emission wavelength in the visible region, and includes, for example, a first phosphor having a light emission color of red (R). The second fluorescent layer 32 is a fluorescent layer containing a second phosphor having a light emission wavelength in the visible region different from that of the first phosphor, and includes, for example, a second phosphor having a light emission color of green (G). The third fluorescent layer 33 is a fluorescent layer containing a third phosphor having a light emission wavelength in the visible region different from those of the first phosphor and the second phosphor, and includes, for example, a third phosphor having a light emission color of blue (B).

[0014] The materials of the first phosphor, the second phosphor, and the third phosphor are not particularly limited. For example, quantum dot phosphors can be used. By using quantum dot phosphors, the excitation wavelengths of the first phosphor, the second phosphor, and the third phosphor can be made common, and the emission wavelengths (i.e., emission colors) of the first phosphor, the second phosphor, and the third phosphor can be made different. As an example of a phosphor, nanocrystal particles of cesium lead halide perovskite (CsPbX3, where X is a halogen, either Cl, Br, I, or a mixture thereof) can be used. With an excitation wavelength of ultraviolet light of 300 nm to 400 nm, the emission wavelengths of RGB can be obtained.

[0015] The base materials of the first phosphor layer 31, the second phosphor layer 32, and the third phosphor layer 33 are made of materials that are transparent to visible light, and are made of resin materials or glass materials. By mixing phosphors into the transparent base materials, the first phosphor layer 31, the second phosphor layer 32, and the third phosphor layer 33 can be formed respectively. By laminating the first phosphor layer 31, the second phosphor layer 32, and the third phosphor layer 33 in order, the display body 12 can be formed.

[0016] The display body 12 is configured to have an overall solid column shape, and is configured to be a cylindrical shape, a polygonal prism shape, or a rectangular parallelepiped shape. The display body 12 is configured such that the surface of the display body 12 is mirror-finished so that the inside of the display body 12 can be seen through from the outside. The display body 12 is formed such that the plurality of phosphor layers 31, 32, 33 are integrated so that the interfaces of the plurality of phosphor layers 31, 32, 33 are invisible or difficult to see.

[0017] The size of the display unit 12 is not particularly limited, but for example, the size in the stacking direction (z direction) can be about 100 mm to 1000 mm, and the size in the directions perpendicular to the stacking direction (x and y directions) can be about 100 mm to 1000 mm. The thickness of each of the multiple fluorescent layers 31, 32, and 33 can be, for example, about 10 μm to 10 mm. As an example, the size of the display unit 12 in the x, y, and z directions can be 200 mm, and the thickness of each of the multiple fluorescent layers 31, 32, and 33 can be 200 μm.

[0018] The irradiation unit 16 irradiates the display unit 12 with excitation light 20 to excite the phosphor. The excitation light 20 is incident on the first surface 13 of the display unit 12 and irradiates the display unit 12 such that the focusing position 24 of the excitation light 20 changes over time inside the display unit 12. The irradiation unit 16 includes a light source 40, a focusing lens 42, a lens driving mechanism 44, a mirror 46, and a mirror driving mechanism 48.

[0019] The light source 40 generates excitation light 20 to excite the first phosphor, the second phosphor, and the third phosphor. The light source 40 generates ultraviolet light as the excitation light 20, with a central wavelength in the range of 300 nm to 400 nm. The type of light source 40 is not limited, but for example, a gallium nitride (GaN) semiconductor laser or semiconductor LED (Light Emitting Diode) can be used as the light source 40.

[0020] The focusing lens 42 focuses the excitation light 20 generated by the light source 40 toward the inside of the display unit 12. The lens driving mechanism 44 is configured to change the position of the focusing lens 42 in the optical axis direction A. By changing the position of the focusing lens 42, the lens driving mechanism 44 changes the focusing position 24 of the excitation light 20. The lens driving mechanism 44 makes the focusing position 24 in the direction of irradiation of the excitation light 20 variable, and also makes the focusing position 24 in the direction intersecting the first surface 13 variable. Alternatively, instead of the focusing lens 42 and the lens driving mechanism 44, a variable focus lens may be used to make the focusing position 24 in the direction intersecting the first surface 13 variable.

[0021] The mirror 46 reflects the excitation light 20 that has passed through the focusing lens 42 toward the display unit 12. The mirror 46 reflects the excitation light 20 so that it is incident on the first surface 13. The mirror driving mechanism 48 is configured to change the orientation of the mirror 46. The mirror driving mechanism 48 is configured to make the orientation of the mirror 46 variable in two axes, and changes the focusing position 24 of the excitation light 20 reflected by the mirror 46 in a direction along the first surface 13 (x direction and y direction). In the illustrated example, one mirror 46 is used, but a first mirror for scanning in the x direction and a second mirror for scanning in the y direction may be combined.

[0022] The light intensity at the focusing position 24 of the excitation light 20 is set to be greater than or equal to the threshold of the amplified spontaneous emission (ASE) of the phosphor contained in the display unit 12. For example, it is set to be between 1.3 and 1.5 times the threshold of amplified spontaneous emission (ASE threshold). Amplified spontaneous emission (ASE), also known as superluminescence, is a phenomenon in which a population inversion is generated in the phosphor by the excitation light, and the emission intensity of the phosphor is amplified. The threshold of amplified spontaneous emission (ASE threshold) corresponds to the minimum light intensity of the excitation light required to produce ASE.

[0023] Figure 2 is a schematic graph showing the relationship between the excitation light intensity and emission intensity of a phosphor, illustrating an example where the phosphor is a nanocrystal of cesium lead halide perovskite. The light intensity of the excitation light irradiated onto the phosphor is the ASE threshold (0.45 mJ / cm² in Figure 2). 2 When the ASE threshold is exceeded, the ratio (slope) of emission intensity to excitation light intensity increases. By setting the excitation light intensity at the focusing position 24 to be above the ASE threshold, the emission intensity of the phosphor at the focusing position 24 can be further increased. On the other hand, by setting the excitation light intensity at locations other than the focusing position 24 to be below the ASE threshold, the emission intensity of the phosphor at locations other than the focusing position 24 can be reduced, thereby increasing the contrast ratio with the focusing position 24.

[0024] Figure 3 schematically shows the relationship between the thickness of the fluorescence layer and the Rayleigh length Zr of the excitation light 20. Figure 3 shows the state where the focal position 24 of the excitation light 20 coincides with the first fluorescence layer 31. The excitation light 20 is configured to have a minimum beam radius w0 at the focal position 24, and the beam radius expands as it moves away from the focal position 24. The Rayleigh length Zr is the distance from the focal position 24 to the position 28 where the beam radius of the excitation light 20 expands by √2 times, where Zr = πw0 2 It can be expressed as / λ, where λ is the wavelength of the excitation light 20. The minimum beam radius w0 depends on the optical system of the irradiation unit 16, and is, for example, about 1 μm to 30 μm. In this case, the Rayleigh length Zr is about 10 μm to 10 mm.

[0025] At position 28, where the Rayleigh length is Zr, the beam radius becomes √2 × w0, so the beam intensity becomes half that of position 24. If the beam intensity at position 24 is 1.3 to 1.5 times the ASE threshold, the beam intensity at position 28, where the Rayleigh length is Zr, becomes 0.65 to 0.75 times the ASE threshold, and ASE does not occur. Here, if the thickness t1 of the first fluorescence layer 31 is set to more than twice the Rayleigh length Zr of the excitation light 20, the occurrence of ASE in the fluorescence layers adjacent to the first fluorescence layer 31 (second fluorescence layer 32 and third fluorescence layer 33) can be prevented, and color bleeding and a decrease in drawing contrast can be suppressed.

[0026] Figure 3 shows the case where the focusing position 24 of the excitation light 20 coincides with the first fluorescence layer 31, but the same applies when the focusing position 24 of the excitation light 20 coincides with the second fluorescence layer 32 or the third fluorescence layer 33. The thickness t2 of the second fluorescence layer 32 is at least twice the Rayleigh length Zr of the excitation light 20 when the focusing position 24 of the excitation light 20 coincides with the second fluorescence layer 32. The thickness t3 of the third fluorescence layer 33 is at least twice the Rayleigh length Zr of the excitation light 20 when the focusing position 24 of the excitation light 20 coincides with the third fluorescence layer 33. There are no particular upper limits for the thicknesses t1, t2, and t3 of the first fluorescence layer 31, second fluorescence layer 32, and third fluorescence layer 33, respectively, but for example, they are 5 times or less, 4 times or less, or 3 times or less, respectively, the Rayleigh length Zr of the excitation light 20.

[0027] The thicknesses t1, t2, and t3 of the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33, respectively, may vary depending on their position in the z-direction within the display body 12, for example, depending on the distance from the first surface 13. As shown in Figure 1, when the focusing position 24 of the excitation light 20 is changed by the position A in the optical axis direction of a single focusing lens 42, the beam diameter w0 at the focusing position 24 changes according to the position of the focusing lens 42. Specifically, as the focusing position 24 moves away from the first surface 13 (i.e., as the focusing position 24 approaches the second surface 14), the beam diameter w0 at the focusing position 24 increases. Since the Rayleigh length Zr is proportional to the square of the beam diameter w0, the Rayleigh length Zr increases as the focusing position 24 moves away from the first surface 13. In accordance with the change in Rayleigh length Zr corresponding to the position of the light-gathering position 24 in the z-direction, the thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, multiple second fluorescent layers 32, and multiple triple fluorescent layers 33 may be made different. In other words, the thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, multiple second fluorescent layers 32, and multiple triple fluorescent layers 33 may be configured to increase as they move away from the first surface 13.

[0028] Returning to Figure 1, the control unit 18 controls the operation of the irradiation unit 16. The control unit 18 can be implemented hardware-wise using components and mechanical devices such as a computer's CPU and memory, and software-wise using computer programs. The various functions provided by the control unit 18 can be realized through the cooperation of hardware and software.

[0029] The control unit 18 controls the focusing position 24 of the excitation light 20 in three dimensions (x, y, and z directions) by controlling the operation of the lens drive mechanism 44 and the mirror drive mechanism 48. For example, the control unit 18 periodically operates the lens drive mechanism 44 and the mirror drive mechanism 48 so that the focusing position 24 of the excitation light 20 is scanned in three dimensions inside the display body 12.

[0030] The control unit 18 controls the on / off state of the light source 40 according to, for example, the focusing position 24 of the excitation light 20. The control unit 18 turns on the light source when the focusing position 24 of the excitation light 20 is a location within the display body 12 that should be drawn. The control unit 18 turns off the light source when the focusing position 24 of the excitation light 20 is a location within the display body 12 that should not be drawn.

[0031] The control unit 18 controls the on / off state and emission intensity of the light source 40 based, for example, on three-dimensional contour image data generated from three-dimensional image data. The three-dimensional contour image data is data that specifies the three-dimensional position and display color of the contour of the three-dimensional image S to be drawn on the display body 12. The control unit 18 controls the display color by controlling the light intensity of the excitation light 20 irradiated onto each of the adjacent first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33. Specifically, by controlling the amount of red light emitted in the first fluorescent layer 31, the amount of green light emitted in the second fluorescent layer 32, and the amount of blue light emitted in the third fluorescent layer 33, the control unit 18 controls the emission color in full color by mixing red, green, and blue at the emission position.

[0032] The display device 10 may further include an image sensor 50. The image sensor 50 is a two-dimensional photodetector such as a CCD sensor or a CMOS sensor, and is provided to measure the spot size of the excitation light 20. The image sensor 50 is positioned adjacent to the display body 12 and corresponding to the first surface 13. The image sensor 50 may be provided at a location other than the one shown in the figure, as long as it is a position into which the excitation light 20 can be incident.

[0033] The control unit 18 operates the lens drive mechanism 44 and the mirror drive mechanism 48 so that excitation light 20 is incident on the image sensor 50. The control unit 18 measures the size of the excitation light 20 at the image sensor 50 while changing the position of the focusing lens 42, thereby identifying the position of the focusing lens 42 that minimizes the spot size of the excitation light 20. The identified position of the focusing lens 42 can be used as a reference for z-direction positioning to align the focusing position 24 of the excitation light 20 with the first surface 13. Based on the measurement results from the image sensor 50, the control unit 18 can calibrate the focusing position 24 of the excitation light 20.

[0034] The display device 10 may further include an optical sensor 52. The optical sensor 52 is configured to measure light intensity at different wavelengths. For example, the optical sensor 52 is configured to measure the light intensity of the first emission color (e.g., red) of the first phosphor, the light intensity of the second emission color (e.g., green) of the second phosphor, and the light intensity of the third emission color (e.g., blue) of the third phosphor. The optical sensor 52 includes, for example, a first sensor 54 having a first filter that selectively transmits red light, a second sensor 56 having a second filter that selectively transmits green light, and a third sensor 58 having a third filter that selectively transmits blue light. The optical sensor 52 is arranged, for example, on the second surface 14 of the display body 12. The optical sensor 52 may be provided at a location other than the one shown, as long as it is in a position where it can detect the light emission generated by the display body 12.

[0035] The control unit 18 operates the lens drive mechanism 44 to change the position of the focusing lens 42 and acquires the light intensity of the first, second, and third emission colors measured by the photosensor 52. By changing the focusing position 24 of the excitation light 20, the degree to which the excitation light 20 is strongly focused on the first fluorescence layer 31, the second fluorescence layer 32, and the third fluorescence layer 33 changes, and the light intensity of the first, second, and third emission colors changes. For example, the position of the focusing lens 42 where the light intensity of the first emission color measured by the photosensor 52 is maximum (or extremely large) can be used as a reference for z-direction positioning to align the focusing position 24 of the excitation light 20 with the first fluorescence layer 31.

[0036] The control unit 18 can calibrate the focusing position 24 of the excitation light 20 based on the measurement results of the optical sensor 52. The control unit 18 may calibrate the focusing position 24 before the start of drawing the stereoscopic image S based on the measurement results of the optical sensor 52. The control unit 18 may also calibrate the focusing position 24 during the drawing of the stereoscopic image S or at the timing between drawing each frame of the stereoscopic image S which is a video, based on the measurement results of the optical sensor 52. By calibrating the focusing position 24 of the excitation light 20 based on the measurement results of the optical sensor 52, the positional accuracy of drawing the stereoscopic image S can be improved, and the display accuracy of the stereoscopic image S can be improved.

[0037] Next, the operation of the display device 10 will be described. The control unit 18 acquires three-dimensional contour image data and operates the illumination unit 16 based on the three-dimensional contour image data. The control unit 18 controls the operation of the lens drive mechanism 44 and the mirror drive mechanism 48 to perform a three-dimensional scan of the focusing position 24 of the excitation light 20 inside the display body 12. The control unit 18 controls the output intensity of the light source 40 according to the focusing position 24 of the excitation light 20 so that the display color specified for each drawing position by the three-dimensional contour image data is realized. As a result, a three-dimensional image S corresponding to the three-dimensional contour image data can be drawn inside the display body 12.

[0038] The control unit 18 may acquire three-dimensional contour image data corresponding to each frame of the video data, and a different three-dimensional image S may be drawn for each frame. This may cause the three-dimensional image S, which constitutes the video, to be displayed.

[0039] The control unit 18 may calibrate the focusing position 24 of the excitation light 20 based on the measurement results of the image sensor 50. The control unit 18 may calibrate the focusing position 24 before the start of drawing the stereoscopic image S based on the measurement results of the image sensor 50. The control unit 18 may calibrate the focusing position 24 during the drawing of the stereoscopic image S or at the timing between drawing each frame of the stereoscopic image S which is a video, based on the measurement results of the image sensor 50.

[0040] According to this embodiment, by making the thicknesses t1, t2, and t3 of the first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33 contained in each of the multiple laminates 30 at least twice the Rayleigh length Zr, light emission at locations other than the focusing position 24 can be suppressed. This suppresses light emission in adjacent fluorescent layers of different emission colors, thereby suppressing color bleeding and contrast reduction. Furthermore, by setting the light intensity at the focusing position 24 to 1.3 to 1.5 times the ASE threshold of the phosphor, strong light emission due to ASE can be obtained at the focusing position 24, while preventing ASE from occurring in adjacent fluorescent layers of different emission colors, thereby suppressing color bleeding and contrast reduction. As a result, the display accuracy of the stereoscopic image S can be improved.

[0041] (Second Embodiment) Figure 4 is a schematic diagram showing the configuration of the display device 10A according to the second embodiment. The second embodiment differs from the first embodiment described above in that the irradiation unit 16A further includes a collimating lens 41. The second embodiment will be described below, focusing on the differences from the first embodiment, and common points with the first embodiment will be omitted as appropriate.

[0042] The display device 10A comprises a display body 12, an illumination unit 16A, and a control unit 18. The display device 10B may or may not include an image sensor 50 and a light sensor 52. The display body 12 and the control unit 18 are configured in the same manner as in the first embodiment.

[0043] The illumination unit 16A includes a light source 40, a collimating lens 41, a focusing lens 42, a lens driving mechanism 44, a mirror 46, and a mirror driving mechanism 48. The light source 40, the focusing lens 42, the lens driving mechanism 44, the mirror 46, and the mirror driving mechanism 48 are configured in the same manner as in the first embodiment.

[0044] The collimating lens 41 parallelizes the excitation light 20 generated by the light source 40. The focusing lens 42 focuses the excitation light 20 parallelized by the collimating lens 41 towards the inside of the display unit 12. The lens driving mechanism 44 changes the focusing position 24 of the excitation light 20 by changing the position of the focusing lens 42.

[0045] According to this embodiment, by using the collimating lens 41, changes in the beam diameter w0 and Rayleigh length Zr at the focusing position 24 caused by changes in the focusing position 24 of the excitation light 20 can be suppressed. In one example of this embodiment, by parallelizing the excitation light 20 using the collimating lens 41, the focusing position 24 can be changed while keeping the beam diameter w0 and Rayleigh length Zr at the focusing position 24 constant. As a result, the thicknesses t1, t2, and t3 of the multiple first fluorescence layers 31, multiple second fluorescence layers 32, and multiple third fluorescence layers 33 constant can be configured such that these thicknesses t1, t2, and t3 are at least twice the Rayleigh length Zr.

[0046] (Third embodiment) Figure 5 is a schematic diagram showing the configuration of the display device 10B according to the third embodiment. The third embodiment differs from the second embodiment described above in that the illumination unit 16B is equipped with a plurality of light sources 61, 62, and 63. The third embodiment will be described below, focusing on the differences from the second embodiment, and common points with the second embodiment will be omitted as appropriate.

[0047] The display device 10B comprises a display unit 12, an illumination unit 16B, and a control unit 18. The display device 10B may or may not include an image sensor 50 and a light sensor 52. The display unit 12, the control unit 18, the image sensor 50, and the light sensor 52 are configured in the same manner as in the second embodiment.

[0048] The illumination unit 16B includes a first light source 61, a second light source 62, a third light source 63, a first collimating lens 64, a second collimating lens 65, a third collimating lens 66, a first half mirror 67, a second half mirror 68, a third mirror 69, a condensing lens 42, a lens driving mechanism 44, a mirror 46, and a mirror driving mechanism 48. The condensing lens 42, the lens driving mechanism 44, the mirror 46, and the mirror driving mechanism 48 are configured in the same manner as in the second embodiment.

[0049] The first light source 61 generates first excitation light 21 for exciting the first phosphor contained in the first fluorescent layer 31. The second light source 62 generates second excitation light 22 for exciting the second phosphor contained in the second fluorescent layer 32. The third light source 63 generates third excitation light 23 for exciting the third phosphor contained in the third fluorescent layer 33. The first excitation light 21, the second excitation light 22, and the third excitation light 23 are ultraviolet light with a central wavelength in the range of 300 nm to 400 nm. The central wavelengths of the first excitation light 21, the second excitation light 22, and the third excitation light 23 may be the same or different from each other. For example, the central wavelength of the first excitation light 21 may be 400 nm, the central wavelength of the second excitation light 22 may be 350 nm, and the central wavelength of the third excitation light 23 may be 300 nm. As the first light source 61, the second light source 62, and the third light source 63, semiconductor lasers and semiconductor LEDs can be used, similar to the light source 40 according to the first embodiment.

[0050] The first collimating lens 64 parallelizes the first excitation light 21 generated by the first light source 61. The second collimating lens 65 parallelizes the second excitation light 22 generated by the second light source 62. The third collimating lens 66 parallelizes the third excitation light 23 generated by the third light source 63. The first half mirror 67 reflects the first excitation light 21, which has been parallelized by the first collimating lens 64, toward the focusing lens 42. The second half mirror 68 reflects the second excitation light 22, which has been parallelized by the second collimating lens 65, toward the focusing lens 42. The second excitation light 22 reflected by the second half mirror 68 passes through the first half mirror 67 and heads toward the focusing lens 42. The third mirror 69 reflects the third excitation light 23, which has been parallelized by the third collimating lens 66, toward the focusing lens 42. The third excitation light 23 reflected by the third mirror 69 passes through the second half mirror 68 and the first half mirror 67 and heads toward the focusing lens 42. The first excitation light 21, the second excitation light 22, and the third excitation light 23 are superimposed on the same optical path by the first half mirror 67 and the second half mirror 68 before being incident on the focusing lens 42.

[0051] The focusing lens 42 focuses the excitation light 20, which is formed by the superposition of the first excitation light 21, the second excitation light 22, and the third excitation light 23, toward the interior of the display unit 12. The mirror 46 reflects the excitation light 20 that has passed through the focusing lens 42 toward the display unit 12. The first excitation light 21 is focused by the focusing lens 42 to the first focusing position 25. The second excitation light 22 is focused by the focusing lens 42 to the second focusing position 26. The third excitation light 23 is focused by the focusing lens 42 to the third focusing position 27.

[0052] The first focusing position 25, the second focusing position 26, and the third focusing position 27 are set to be slightly different in the direction of irradiation (z-direction) of the excitation light 20. For example, the first focusing position 25, the second focusing position 26, and the third focusing position 27 can be shifted relative to each other by fine-tuning the degree of parallelization of the first excitation light 21, the second excitation light 22, and the third excitation light 23 by the first collimating lens 64, the second collimating lens 65, and the third collimating lens 66.

[0053] Figure 6 schematically shows the arrangement of the first focusing position 25, the second focusing position 26, and the third focusing position 27. Figure 6 shows the case where the first focusing position 25 of the first excitation light 21 coincides with the first fluorescence layer 31. In the state shown in Figure 6, the second focusing position 26 of the second excitation light 22 coincides with the second fluorescence layer 32, and the third focusing position 27 of the third excitation light 23 coincides with the third fluorescence layer 33. By setting the arrangement of the first focusing position 25, the second focusing position 26, and the third focusing position 27 as shown in Figure 6, the first fluorescence layer 31, the second fluorescence layer 32, and the third fluorescence layer 33 contained in a single laminate 30 can be excited simultaneously. Furthermore, by individually setting the light intensity of the first excitation light 21, the second excitation light 22, and the third excitation light 23, the amount of red light emitted in the first fluorescence layer 31, the amount of green light emitted in the second fluorescence layer 32, and the amount of blue light emitted in the third fluorescence layer 33 can be controlled, allowing for full-color control of the emitted light color resulting from the mixing of red, green, and blue at the emission position.

[0054] In the example in Figure 6, the distance between the first focusing position 25 and the second focusing position 26 coincides with the first pitch p1, which is the distance between the centers of the first fluorescent layer 31 and the second fluorescent layer 32. The first pitch p1 coincides with half of the sum of the thickness t1 of the first fluorescent layer 31 and the thickness t2 of the second fluorescent layer 32 (t1+t2) / 2. Also, the distance between the second focusing position 26 and the third focusing position 27 coincides with the second pitch p2, which is the distance between the centers of the second fluorescent layer 32 and the third fluorescent layer 33. The second pitch p2 coincides with half of the sum of the thickness t2 of the second fluorescent layer 32 and the thickness t3 of the third fluorescent layer 33 (t2+t3) / 2. The first pitch p1 may coincide with the thickness t1 of the first fluorescent layer 31 or the thickness t2 of the second fluorescent layer 32. The second pitch p2 may coincide with the thickness t2 of the second fluorescent layer 32 or the thickness t3 of the third fluorescent layer 33.

[0055] In this embodiment as well, it is preferable that the thickness of the fluorescent layer be at least twice the Rayleigh length at the focusing position. The thickness t1 of the first fluorescent layer 31 is at least twice the first Rayleigh length Zr1 at the first focusing position 25 of the first excitation light 21, and is 5 times or less, 4 times or less, or 3 times or less the first Rayleigh length Zr1. The first Rayleigh length Zr1 is the minimum beam diameter w at the first focusing position 25 when the beam diameter of the first excitation light 21 is 01 This is the position that is √2 times the length. The thickness t2 of the second fluorescence layer 32 is 2 times or more the second Rayleigh length Zr2 at the second focusing position 26 of the second excitation light 22, and is 5 times or less, 4 times or less, or 3 times or less the second Rayleigh length Zr2. The second Rayleigh length Zr2 is the minimum beam diameter w at the second focusing position 26 when the beam diameter of the second excitation light 22 is 2 times the length. 02 This is the position that is √2 times the length. The thickness t3 of the third fluorescence layer 33 is 2 times or more the third Rayleigh length Zr3 at the third focusing position 27 of the third excitation light 23, and is 5 times or less, 4 times or less, or 3 times or less the third Rayleigh length Zr3. The third Rayleigh length Zr3 is the minimum beam diameter w at the third focusing position 27 when the beam diameter of the third excitation light 23 is 2 times the length. 03 It is the position that is √2 times the original position.

[0056] In this embodiment as well, it is preferable that the light intensity at the excitation light collection position is 1.3 times or more and 1.5 times or less the ASE threshold of the phosphor. The light intensity of the first excitation light 21 at the first collection position 25 is 1.3 times or more and 1.5 times or less the ASE threshold of the first phosphor contained in the first fluorescence layer 31. By setting the light intensity of the first excitation light 21 in this way, it is possible to cause ASE in the first fluorescence layer 31 due to the first excitation light 21, while preventing ASE from occurring in the second fluorescence layer 32 and the third fluorescence layer 33 due to the first excitation light 21. Similarly, the light intensity of the second excitation light 22 at the second collection position 26 is 1.3 times or more and 1.5 times or less the ASE threshold of the second phosphor contained in the second fluorescence layer 32. By setting the light intensity of the second excitation light 22 in this way, it is possible to cause ASE in the second fluorescence layer 32 due to the second excitation light 22, while preventing ASE from occurring in the first fluorescence layer 31 and the third fluorescence layer 33 due to the second excitation light 22. Furthermore, the light intensity of the third excitation light 23 at the third focusing position 27 is between 1.3 and 1.5 times the ASE threshold of the third phosphor contained in the third fluorescence layer 33. By setting the light intensity of the third excitation light 23 in this way, it is possible to prevent ASE from occurring in the third fluorescence layer 33 due to the third excitation light 23, while preventing ASE from occurring in the first fluorescence layer 31 and the second fluorescence layer 32 due to the third excitation light 23. As a result, color bleeding and a decrease in drawing contrast can be suppressed, and the display accuracy of the stereoscopic image S can be improved.

[0057] (Fourth Embodiment) The fourth embodiment differs from the first embodiment in that a separation layer without phosphor is provided between two fluorescent layers with different emission colors. According to the fourth embodiment, by providing a separation layer, color bleeding and a decrease in drawing contrast can be more effectively suppressed. According to the fourth embodiment, by providing a separation layer, the pitch between the two fluorescent layers with different emission colors can be made smaller, making it possible to draw a more high-resolution three-dimensional image S. The fourth embodiment will be described below, focusing on the differences from the first embodiment, and common points with the first embodiment will be omitted as appropriate.

[0058] Figure 7 is a schematic diagram showing the configuration of the display unit 12C according to the fourth embodiment. The display unit 12C includes a plurality of laminates 30 stacked in the z direction. Each of the plurality of laminates 30 includes a first fluorescent layer 31, a first separation layer 34, a second fluorescent layer 32, a second separation layer 35, a third fluorescent layer 33, and a third separation layer 36, which are stacked sequentially in the z direction. The first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 are configured in the same way as in the first embodiment.

[0059] The first separation layer 34, the second separation layer 35, and the third separation layer 36 are layers that do not contain phosphors and are made of a resin material or glass material that is transparent to visible light. Preferably, the first separation layer 34, the second separation layer 35, and the third separation layer 36 are made of the same material as the base material of the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33. The first separation layer 34, the second separation layer 35, and the third separation layer 36 are integrally formed such that the interface with the first fluorescent layer 31, the second fluorescent layer 32, or the third fluorescent layer 33 is invisible or difficult to see.

[0060] Figure 8 schematically shows the relationship between the thickness of the fluorescence layer and the separation layer and the Rayleigh length Zr of the excitation light 20. Similar to Figure 3, Figure 8 shows the state in which the focal position 24 of the excitation light 20 coincides with the first fluorescence layer 31. In Figure 8, if the second fluorescence layer 32 is further away from the focal position 24 than the position 28 where the Rayleigh length Zr is, the generation of ASE in the second fluorescence layer 32 can be prevented. Therefore, the sum of half the thickness t1 of the first fluorescence layer 31 and the thickness t4 of the first separation layer 34 is preferably greater than or equal to the Rayleigh length Zr (i.e., t1 / 2 + t4 ≥ Zr). Similarly, the sum of half the thickness t2 of the second fluorescence layer 32 and the thickness t5 of the second separation layer 35 is preferably greater than or equal to the Rayleigh length Zr (i.e., t2 / 2 + t5 ≥ Zr), and the sum of half the thickness t3 of the third fluorescence layer 33 and the thickness t6 of the third separation layer 36 is preferably greater than or equal to the Rayleigh length Zr (i.e., t3 / 2 + t6 ≥ Zr).

[0061] In this embodiment, by providing the first separation layer 34, the first pitch p1, which is the distance between the centers of the first fluorescent layer 31 and the second fluorescent layer 32, can be made smaller compared to the first embodiment. In the first embodiment shown in Figure 3, the thicknesses t1 and t2 of the first fluorescent layer 31 and the second fluorescent layer 32 had to be at least twice the Rayleigh length Zr, so the first pitch p1 of the first fluorescent layer 31 and the second fluorescent layer 32 was also at least twice the Rayleigh length Zr. On the other hand, in the fourth embodiment shown in Figure 8, it is possible to set the first pitch p1 of the first fluorescent layer 31 and the second fluorescent layer 32 to be greater than 1x the Rayleigh length Zr and less than 2x. For example, if the thicknesses t1 and t2 of the first fluorescence layer 31 and the second fluorescence layer 32 are set to the Rayleigh length Zr (t1=t2=Zr), and the thickness t4 of the first separation layer 34 is set to half the Rayleigh length Zr (t4=Zr / 2), then the first pitch p1 of the first fluorescence layer 31 and the second fluorescence layer 32 can be set to 1.5 times the Rayleigh length while satisfying the condition for preventing ASE generation in the second fluorescence layer 32 (t1 / 2+t4≧Zr). Similarly, by providing a second separation layer 35, it becomes possible to set the second pitch p2, which is the distance between the centers of the second fluorescence layer 32 and the third fluorescence layer 33, to be greater than 1 times the Rayleigh length Zr and less than 2 times. Furthermore, by providing a third separation layer 36, it becomes possible to set the third pitch p3, which is the distance between the centers of the third fluorescence layer 33 and the first fluorescence layer 31, to be greater than 1 time the Rayleigh length Zr and less than 2 times.

[0062] In this embodiment, the first pitch p1 may be equal to or greater than the sum of half the thickness of the first fluorescent layer 31 (or the second fluorescent layer 32) and the Rayleigh length Zr (i.e., p1 ≥ t1 / 2 + Zr, or p1 ≥ t2 / 2 + Zr). Similarly, the second pitch p2 may be equal to or greater than the sum of half the thickness of the second fluorescent layer 32 (or the third fluorescent layer 33) and the Rayleigh length Zr (i.e., p2 ≥ t2 / 2 + Zr, or p2 ≥ t3 / 2 + Zr). Furthermore, the third pitch p3 may be equal to or greater than the sum of half the thickness of the third fluorescent layer 33 (or the first fluorescent layer 31) and the Rayleigh length Zr (i.e., p3 ≥ t3 / 2 + Zr, or p3 ≥ t1 / 2 + Zr).

[0063] In the fourth embodiment, the thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, multiple second fluorescent layers 32, and multiple third fluorescent layers 33 may be made different in accordance with the change in Rayleigh length Zr corresponding to the position of the light-gathering position 24 in the z direction. That is, the thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, multiple second fluorescent layers 32, and multiple third fluorescent layers 33 may be configured to increase as they move away from the first surface 13. Similarly, the thicknesses t4, t5, and t6 of the multiple first separation layers 34, multiple second separation layers 35, and multiple third separation layers 36 may be configured to increase as they move away from the first surface 13.

[0064] As a modification of the fourth embodiment, the irradiation unit 16A according to the second embodiment may be used. In this case, the thicknesses t1, t2, and t3 of the plurality of first fluorescent layers 31, plurality of second fluorescent layers 32, and plurality of third fluorescent layers 33 may be kept constant, and the thicknesses t4, t5, and t6 of the plurality of first separation layers 34, plurality of second separation layers 35, and plurality of third separation layers 36 may be kept constant.

[0065] (Fifth embodiment) The display device according to the fifth embodiment comprises a display body 12C according to the fourth embodiment, an illumination unit 16B according to the third embodiment, and a control unit 18. The fifth embodiment will be described below, focusing on the differences from the third and fourth embodiments, while commonalities with the third and fourth embodiments will be omitted as appropriate.

[0066] Figure 9 is a schematic diagram showing the arrangement of the first focusing position 25, the second focusing position 26, and the third focusing position 27 in the fifth embodiment. The display body 12C according to the fifth embodiment is configured such that the laminate 30 includes a first fluorescent layer 31, a second fluorescent layer 32, a third fluorescent layer 33, a first separation layer 34, a second separation layer 35, and a third separation layer 36, similar to the fourth embodiment. Figure 9 shows the case where the first focusing position 25 of the first excitation light 21 coincides with the first fluorescent layer 31. In the state shown in Figure 9, the second focusing position 26 of the second excitation light 22 coincides with the second fluorescent layer 32, and the third focusing position 27 of the third excitation light 23 coincides with the third fluorescent layer 33.

[0067] In the example in Figure 9, the distance between the first focusing position 25 and the second focusing position 26 coincides with the first pitch p1, which is the distance between the centers of the first fluorescence layer 31 and the second fluorescence layer 32. The first pitch p1 coincides with the sum of half the thickness t1 of the first fluorescence layer 31, the thickness t4 of the first separation layer 34, and half the thickness t2 of the second fluorescence layer 32 (t1 / 2 + t4 + t2 / 2). The first pitch p1 can be set, for example, to be greater than 1 times and less than 2 times the first Rayleigh length Zr1 of the first excitation light 21, or greater than 1 time and less than 2 times the second Rayleigh length Zr2 of the second excitation light 22. In the example in Figure 9, the range of the first Rayleigh length Zr1 at the first focusing position 25 and the range of the second Rayleigh length Zr2 at the second focusing position 26 can be overlapped in the first separation layer 34, so the first pitch p1 can be made smaller compared to the case in Figure 6. As a result, the first fluorescent layer 31 and the second fluorescent layer 32, which emit different colors, can be brought closer together, enabling the rendering of a more detailed three-dimensional image S. The first pitch p1 may be equal to or greater than the sum of half the thickness of the second fluorescent layer 32 (or the first fluorescent layer 31) and the first Rayleigh length Zr1 (or the second Rayleigh length Zr2) (i.e., p1 ≥ t2 / 2 + Zr1, or p1 ≥ t1 / 2 + Zr1).

[0068] The distance between the second focusing position 26 and the third focusing position 27 is equal to the second pitch p2, which is the distance between the centers of the second fluorescence layer 32 and the third fluorescence layer 33. The second pitch p2 is equal to the sum of half the thickness t2 of the second fluorescence layer 32, the thickness t5 of the second separation layer 35, and half the thickness t3 of the third fluorescence layer 33 (t2 / 2 + t5 + t3 / 2). The second pitch p2 can be set, for example, to be greater than 1x and less than 2x the second Rayleigh length Zr2 of the second excitation light 22, or greater than 1x and less than 2x the third Rayleigh length Zr3 of the third excitation light 23. The second pitch p2 may be equal to or greater than the sum of half the thickness of the third fluorescent layer 33 (or the second fluorescent layer 32) and the second Rayleigh length Zr2 (or the third Rayleigh length Zr3) (i.e., p2 ≥ t3 / 2 + Zr2, or p2 ≥ t2 / 2 + Zr3).

[0069] The third pitch p3, which is the distance between the centers of the third fluorescence layer 33 and the first fluorescence layer 31, is equal to the sum of half the thickness t3 of the third fluorescence layer 33, the thickness t6 of the third separation layer 36, and half the thickness t3 of the first fluorescence layer 31 (t3 / 2 + t6 + t1 / 2). The third pitch p3 can be set, for example, to be greater than 1 times and less than 2 times the third Rayleigh length Zr3 of the third excitation light 23, or greater than 1 times and less than 2 times the first Rayleigh length Zr1 of the first excitation light 21. The third pitch p2 may be equal to or greater than the sum of half the thickness of the first fluorescence layer 31 (or third fluorescence layer 33) and the third Rayleigh length Zr3 (or first Rayleigh length Zr1) (i.e., p3 ≥ t1 / 2 + Zr3, or p3 ≥ t3 / 2 + Zr1).

[0070] The first pitch p1, second pitch p2, and third pitch p3 may be equal to the sum of the thicknesses of the first fluorescent layer 31 and the first separation layer 34 (t1+t4), or the sum of the thicknesses of the second fluorescent layer 32 and the second separation layer 35 (t2+t5), or the sum of the thicknesses of the third fluorescent layer 33 and the third separation layer 36 (t3+t6).

[0071] (Sixth Embodiment) Figure 10 is a schematic diagram showing the configuration of the display device 10D according to the sixth embodiment. The sixth embodiment differs from the first embodiment described above in that, in addition to the first irradiation unit 16 that irradiates excitation light 20 toward the first surface 13 of the display body 12, it further includes a second irradiation unit 17 that irradiates excitation light 80 toward the second surface 14 of the display body 12. The sixth embodiment will be described below, focusing on the differences from the first embodiment, and common points with the first embodiment will be omitted as appropriate.

[0072] The display device 10D comprises a display body 12, a first irradiation unit 16, a second irradiation unit 17, and a control unit 18. The first irradiation unit 16 irradiates the display body 12 with excitation light 20 such that the focusing position 24 of the excitation light 20 is variable in the range from the first surface 13 to the intermediate surface 15. The second irradiation unit 17 irradiates the display body 12 with excitation light 80 such that the focusing position 84 of the excitation light 80 is variable in the range from the second surface 14 to the intermediate surface 15. The intermediate surface 15 is set at any position between the first surface 13 and the second surface 14, for example, in the middle of the first surface 13 and the second surface 14.

[0073] The second illumination unit 17 is configured similarly to the first illumination unit 16. The second illumination unit 17 includes a light source 70, a focusing lens 72, a lens driving mechanism 74, a mirror 76, and a mirror driving mechanism 78. The light source 70, like the light source 40, generates excitation light 80 to excite the first phosphor, the second phosphor, and the third phosphor. The focusing lens 72 focuses the excitation light 80 generated by the light source 70 toward the interior of the display unit 12. The lens driving mechanism 74 changes the position of the focusing lens 72 in the optical axis direction B, thereby changing the focusing position 84 of the excitation light 80. The mirror 76 reflects the excitation light 80 that has passed through the focusing lens 72 so that it is incident on the second surface 14. The mirror driving mechanism 78 changes the orientation of the mirror 76, thereby changing the focusing position 84 of the excitation light 80 reflected by the mirror 76 in the direction (x and y directions) along the second surface 14.

[0074] The control unit 18 controls the operation of the first irradiation unit 16 and the second irradiation unit 17. The control unit 18 acquires three-dimensional contour image data and operates the first irradiation unit 16 based on data that draws the range from the first surface 13 to the intermediate surface 15 of the three-dimensional contour image data. The control unit 18 operates the second irradiation unit 17 based on data that draws the range from the intermediate surface 15 to the second surface 14 of the three-dimensional contour image data. According to this embodiment, since the three-dimensional image S can be drawn using excitation light 20, 80 incident on the first surface 13 and the second surface 14 respectively, the drawing can be made faster compared to the case where only excitation light 20 is used.

[0075] The thicknesses t1, t2, and t3 of the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 included in the display body 12 may differ depending on their position in the z direction. The thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, the multiple second fluorescent layers 32, and the multiple third fluorescent layers 33 may be configured to increase from the first surface 13 toward the intermediate surface 15. The thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, the multiple second fluorescent layers 32, and the multiple third fluorescent layers 33 may be configured to increase from the second surface 14 toward the intermediate surface 15.

[0076] In a modified version of the sixth embodiment, the irradiation unit 16A according to the second embodiment may be used as the first irradiation unit 16 and the second irradiation unit 17. In this case, the thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, multiple second fluorescent layers 32, and multiple third fluorescent layers 33 may be kept constant. Alternatively, the irradiation unit 16B according to the third embodiment may be used as the first irradiation unit 16 and the second irradiation unit 17. Furthermore, the display body 12C according to the fourth embodiment may be used instead of the display body 12.

[0077] (Seventh Embodiment) Figure 11 is a schematic diagram showing the configuration of the display device 10E according to the seventh embodiment. The seventh embodiment includes a display body 12C that includes a separation layer similar to that of the fourth and fifth embodiments. The seventh embodiment differs from the embodiments described above in that, in addition to the first irradiation unit 16 that irradiates the first excitation light 20 toward the first surface 13 of the display body 12C, it further includes a second irradiation unit 90 that irradiates the second excitation light 88 toward the side surface 86 of the display body 12C. The seventh embodiment will be described below, focusing on the differences from the embodiments described above, and common points with the embodiments described above will be omitted as appropriate.

[0078] The display device 10E comprises a display body 12C, a first illumination unit 16, a second illumination unit 90, and a control unit 18. The display device 10E may or may not include an image sensor 50 and a light sensor 52. The first illumination unit 16 is configured in the same way as the illumination unit 16 according to the first embodiment. The control unit 18, image sensor 50, and light sensor 52 are also configured in the same way as in the first embodiment.

[0079] The display body 12C has side surfaces 86. The side surfaces 86 are located between the first surface 13 and the second surface 14 and extend in the stacking direction of the display body 12C. If the display body 12C is a rectangular parallelepiped, the display body 12C has four rectangular side surfaces 86. If the display body 12C is a cylinder, the display body 12C has side surfaces 86 that form a cylindrical surface.

[0080] The second irradiation unit 90 is located to the side of the display unit 12C and irradiates the second excitation light 88 toward the side surface 86 of the display unit 12C. The second irradiation unit 90 irradiates the second excitation light 88 toward one of the fluorescent layers contained in any of the multiple laminates 30. The second excitation light 88 is incident on the fluorescent layer to be irradiated in the in-plane direction and excites the phosphors contained in the fluorescent layer to be irradiated. The second irradiation unit 90 irradiates the fluorescent layer to be irradiated with the second excitation light 88 over the entire in-plane direction.

[0081] The second irradiation unit 90 is configured to switch the fluorescent layer to be irradiated by changing the position of the second excitation light 88 in the stacking direction. The second irradiation unit 90 selectively irradiates one fluorescent layer contained in any of the multiple stacks 30 with the second excitation light 88. The second irradiation unit 90 irradiates the second excitation light 88 toward one fluorescent layer corresponding to the focusing position 24 of the first excitation light 20.

[0082] At the focusing position 24 of the first excitation light 20, the phosphor emits light upon irradiation with both the first excitation light 20 and the second excitation light 88. At the focusing position 24 of the first excitation light 20, the light intensities of the first excitation light 20 and the second excitation light 88 are below the threshold of the phosphor's naturally emitted amplified light (i.e., below the ASE threshold). At the focusing position 24 of the first excitation light 20, the sum of the light intensities of the first excitation light 20 and the second excitation light 88 is above the threshold of the phosphor's naturally emitted amplified light (i.e., above the ASE threshold). This allows for strong emission due to ASE at the focusing position 24, while preventing ASE from occurring in adjacent phosphor layers of different emission colors, thereby suppressing color bleeding and contrast reduction. As a result, the display accuracy of the stereoscopic image S can be improved.

[0083] Figure 12 is a schematic diagram showing the configuration of the display unit 12C and the second irradiation unit 90 according to the seventh embodiment. The display unit 12C includes a plurality of laminates 30 stacked in the z direction. Each of the plurality of laminates 30 includes a first fluorescent layer 31, a first separation layer 34, a second fluorescent layer 32, a second separation layer 35, a third fluorescent layer 33, and a third separation layer 36, which are stacked sequentially in the z direction. The first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 are configured in the same way as in the first embodiment.

[0084] The first separation layer 34, the second separation layer 35, and the third separation layer 36 are layers that do not contain phosphors and are composed of transparent resin or glass materials to visible light. The refractive index of the first separation layer 34, the second separation layer 35, and the third separation layer 36 (collectively referred to as the separation layer) is lower than the refractive index of the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 (collectively referred to as the fluorescent layer). The refractive index of the separation layer is slightly lower than the refractive index of the fluorescent layer. The difference between the refractive index of the separation layer and the refractive index of the fluorescent layer is, for example, 0.01 or more and 0.05 or less, preferably 0.02 or more and 0.04 or less.

[0085] The second irradiation unit 90 comprises a plurality of light source units 91, 92, and 93. The second irradiation unit 90 comprises a plurality of first light sources 91, a plurality of second light sources 92, and a plurality of third light sources 93. Each of the plurality of first light sources 91 irradiates the corresponding first fluorescent layer 31 with second excitation light 88 in the in-plane direction of the first fluorescent layer 31. Each of the plurality of second light sources 92 irradiates the corresponding second fluorescent layer 32 with second excitation light in the in-plane direction of the second fluorescent layer 32. Each of the plurality of third light sources 93 irradiates the corresponding third fluorescent layer 33 with second excitation light in the in-plane direction of the third fluorescent layer 33.

[0086] The first light source 91 includes a light-emitting element 94 that outputs a second excitation light 88, and a collimating lens 95 that collimates the second excitation light 88 output from the light-emitting element 94. The light-emitting element 94 is a semiconductor laser or a semiconductor LED. The collimating lens 95 ensures that the beam angle of the second excitation light 88 incident on the first fluorescence layer 31 is less than or equal to a predetermined value. The beam angle of the second excitation light 88 collimated by the collimating lens 95 is 30 degrees or less, preferably 20 degrees or less, or 10 degrees or less. The second light source 92 and the third light source 93 are configured in the same manner as the first light source 91.

[0087] The first light source 91 selectively irradiates the corresponding first fluorescent layer 31 with the second excitation light 88. The second excitation light 88 incident on the first fluorescent layer 31 propagates in the in-plane direction within the first fluorescent layer 31 while being reflected at the interface of the first fluorescent layer 31. Since the refractive index of the first fluorescent layer 31 is higher than that of the adjacent first separation layer 34 and third separation layer 36, the second excitation light 88 can undergo total internal reflection at the interface of the first fluorescent layer 31. When the refractive index difference between the adjacent first separation layer 34 and third separation layer 36 and the first fluorescent layer 31 is between 0.01 and 0.05, the critical angle at the interface of the first fluorescent layer 31 is between 75 degrees and 84 degrees. Therefore, by irradiating the first fluorescence layer 31 with collimated second excitation light 88, it is possible to prevent the second excitation light 88 from leaking outside the first fluorescence layer 31 and selectively irradiate only the first fluorescence layer 31 with the second excitation light 88.

[0088] The second light source 92, like the first light source 91, can selectively irradiate only the corresponding second fluorescence layer 32 with the second excitation light 88. Similarly, the third light source 93, like the first light source 91, can selectively irradiate only the corresponding third fluorescence layer 33 with the second excitation light 88.

[0089] If there is a difference in refractive index between the fluorescent layer and the separation layer, the first excitation light 20 may be reflected at the interface between these layers and lost. However, if the difference in refractive index between the fluorescent layer and the separation layer is between 0.01 and 0.05, the bidirectional transmittance of the first excitation light 20 passing through both the interface into the fluorescent layer and the interface out of the fluorescent layer is 99.94% or higher. Therefore, even if the number of alternating layers of the fluorescent layer and the separation layer is 1000, an overall transmittance of 58% or higher can be achieved. For example, if the difference in refractive index between the fluorescent layer and the separation layer is 0.025, the bidirectional transmittance of the first excitation light 20 is 99.98% or higher, and the transmittance when the number of alternating layers is 1000 is 87% or higher. Here, the case where the alternating number of fluorescent layers and separation layers is 1,000 is when the sum of the number of layers of the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 is 1,000, and the sum of the number of layers of the first separation layer 34, the second separation layer 35, and the third separation layer 36 is 1,000.

[0090] The control unit 18 controls the operation of the first irradiation unit 16 and the second irradiation unit 90. The control unit 18 acquires three-dimensional contour image data and operates the first irradiation unit 16 and the second irradiation unit 90 based on the three-dimensional contour image data. The control unit 18 controls the operation of the lens drive mechanism 44 and the mirror drive mechanism 48 to perform a three-dimensional scan of the focusing position 24 of the first excitation light 20 inside the display body 12C. The control unit 18 operates the second irradiation unit 90 so that the second excitation light 88 is selectively irradiated onto the fluorescent layer corresponding to the focusing position 24 of the first excitation light 20. The control unit 18 lights up the first light source 91, the second light source 92, or the third light source 93 to irradiate the fluorescent layer corresponding to the focusing position 24 of the first excitation light 20 with the second excitation light 88. The control unit 18 controls the output intensity of the light source 40 according to the focusing position 24 of the first excitation light 20 so that the display color specified for each drawing position by the three-dimensional contour image data is realized. The control unit 18 may control the output intensity of the light-emitting element 94 according to the focusing position 24 of the first excitation light 20, so that a display color specified for each drawing position is realized by the three-dimensional contour image data. This allows a three-dimensional image S corresponding to the three-dimensional contour image data to be drawn inside the display unit 12.

[0091] According to this embodiment, ASE can be generated in a limited region 98 where the first excitation light 20 and the second excitation light 88 overlap, and ASE can be prevented from occurring outside the limited region 98. As a result, color bleeding and a decrease in drawing contrast can be suppressed, and the display accuracy of the stereoscopic image S can be improved. For example, even if the thickness t1 of the first fluorescence layer 31 is smaller than the Rayleigh length Zr of the first excitation light 20, the occurrence of ASE in the adjacent second fluorescence layer 32 and third fluorescence layer 33 can be suitably prevented. In this embodiment as well, similar to the fourth and fifth embodiments, even if the sum of the thicknesses of the fluorescence layer and the separation layer is greater than 1 times and less than 2 times the Rayleigh length Zr of the first excitation light 20, the occurrence of ASE in fluorescence layers other than the collection position 24 of the first excitation light 20 can be suitably prevented.

[0092] In this embodiment, by making the thickness of the fluorescent layer approximately the same as the spot size w0 at the focusing position 24 of the first excitation light 20, the region 98 where ASE occurs can be made nearly spherical. More specifically, by making the thickness of the fluorescent layer 0.5 times or more and 2 times or less the spot size w0 at the focusing position 24 of the first excitation light 20, the region 98 where ASE occurs can be made nearly spherical. By making the region 98 where ASE occurs nearly spherical, it becomes possible to draw a more detailed three-dimensional image S.

[0093] As a modification of the seventh embodiment, a plurality of second irradiation units 90 may be used. For example, the display device according to the modification may include a plurality of second irradiation units that irradiate a plurality of sides of the display body 12C with second excitation light. Each of the plurality of second irradiation units is configured to irradiate the second excitation light toward the same fluorescent layer corresponding to the focusing position 24 of the first excitation light 20. According to this modification, by irradiating the second excitation light from a plurality of sides, it is possible to irradiate the fluorescent layer to be irradiated with second excitation light more uniformly over the entire in-plane direction.

[0094] As a modification of the seventh embodiment, a reflective film that reflects the second excitation light 88 may be provided on at least one of the multiple sides of the display body 12C. For example, the reflective film may not be provided on the first side where the second excitation light 88 from the second irradiation unit 90 is incident, but on a second side different from the first side. The reflective film may be configured to selectively reflect the wavelength of the second excitation light 88 and selectively transmit the emission wavelength of the fluorescent layer. By providing a reflective film on the side of the display body 12C, the fluorescent layer to be irradiated can be irradiated with the second excitation light 88 more efficiently. In addition, the fluorescent layer to be irradiated can be irradiated with second excitation light more uniformly over the entire in-plane direction.

[0095] In the seventh embodiment, the thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, multiple second fluorescent layers 32, and multiple third fluorescent layers 33 may be made different in accordance with the change in Rayleigh length Zr corresponding to the position of the light-gathering position 24 in the z direction. That is, the thicknesses t1, t2, and t3 of the multiple first fluorescent layers 31, multiple second fluorescent layers 32, and multiple third fluorescent layers 33 may be configured to increase as they move away from the first surface 13. Similarly, the thicknesses t4, t5, and t6 of the multiple first separation layers 34, multiple second separation layers 35, and multiple third separation layers 36 may be configured to increase as they move away from the first surface 13.

[0096] In the seventh embodiment, the irradiation unit 16A according to the second embodiment may be used. In this case, the thicknesses t1, t2, and t3 of the plurality of first fluorescent layers 31, plurality of second fluorescent layers 32, and plurality of third fluorescent layers 33 may be kept constant, and the thicknesses t4, t5, and t6 of the plurality of first separation layers 34, plurality of second separation layers 35, and plurality of third separation layers 36 may be kept constant.

[0097] In the seventh embodiment, the irradiation unit 16B according to the third embodiment may be used. In this case, the second irradiation unit 90 may simultaneously irradiate the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33, which correspond to the first focusing position 25, the second focusing position 26, and the third focusing position 27, with excitation light. For example, a fourth excitation light may be irradiated from the first light source 91 toward the first fluorescent layer 31 to excite the first phosphor, a fifth excitation light may be irradiated from the second light source 92 toward the second fluorescent layer 32 to excite the second phosphor, and a sixth excitation light may be irradiated from the third light source 93 toward the third fluorescent layer 33 to excite the third phosphor. The emission wavelengths of the fourth, fifth, and sixth excitation lights may be the same or different.

[0098] (Eighth embodiment) Figure 13 is a schematic diagram showing the configuration of the display device 10F according to the eighth embodiment. The irradiation unit 16F according to the eighth embodiment does not include a focusing lens 42 and a lens driving mechanism 44, and is configured to irradiate the display body 12C with the first excitation light 20F collimated by the collimating lens 41. The eighth embodiment will be described below, focusing on the differences from the seventh embodiment described above, and the common points with the seventh embodiment described above will be omitted as appropriate.

[0099] The display device 10F comprises a display body 12C, a first illumination unit 16F, a second illumination unit 90, and a control unit 18. The display device 10F may not include an image sensor 50 and a light sensor 52. The display body 12C, the second illumination unit 90, and the control unit 18 are configured in the same manner as in the seventh embodiment described above.

[0100] The first illumination unit 16F includes a light source 40, a collimating lens 41, a mirror 46, and a mirror driving mechanism 48. The first illumination unit 16F does not include a focusing lens 42 and a lens driving mechanism 44. The mirror 46 reflects the first excitation light 20F, which has been parallelized by the collimating lens 41, toward the first surface 13 of the display unit 12C. The mirror driving mechanism 48 changes the in-plane position (x-direction and y-direction) of the first excitation light 20F by changing the orientation of the mirror 46.

[0101] In this embodiment, the light intensities of the first excitation light 20F and the second excitation light 88 are each below the threshold of the phosphor's naturally emitted amplified light (i.e., below the ASE threshold), and the sum of the light intensities of the first excitation light 20 and the second excitation light 88 is equal to or greater than the threshold of the phosphor's naturally emitted amplified light (i.e., equal to or greater than the ASE threshold). Therefore, ASE occurs at the intersection 100 where the first excitation light 20F and the second excitation light 88 overlap, but not at locations other than the intersection 100.

[0102] The control unit 18 controls the operation of the first irradiation unit 16F and the second irradiation unit 90. The control unit 18 acquires three-dimensional contour image data and operates the first irradiation unit 16F and the second irradiation unit 90 based on the three-dimensional contour image data. The control unit 18 controls the operation of the mirror drive mechanism 48 to change the in-plane position of the first excitation light 20F inside the display body 12C. The control unit 18 controls the operation of the second irradiation unit 90 to change the position of the second excitation light 88 in the stacking direction. As a result, the control unit 18 controls the three-dimensional position where the contour of the three-dimensional image S should be displayed. The control unit 18 may control the output intensity of at least one of the first excitation light 20F and the second excitation light 88 according to the in-plane position of the first excitation light 20F and the stacking direction of the second excitation light 88, so that the display color specified for each drawing position by the three-dimensional contour image data is realized.

[0103] According to this embodiment, there is no need to control the focusing position 24 of the first excitation light 20 in three dimensions, and the irradiation direction of the excitation light 20F only needs to be controlled in two dimensions, making it easy to control the three-dimensional position of the intersection 100 where ASE occurs.

[0104] Although the present invention has been described above with reference to the embodiments described above, the present invention is not limited to the embodiments described above, and the present invention is also included in combinations or substitutions of the configurations shown in each example.

[0105] Several embodiments of the present invention will be described below.

[0106] [Aspect 1] A display body comprising a plurality of fluorescent layers containing a phosphor, laminated from a first surface to a second surface, wherein the thickness of each of the plurality of fluorescent layers increases as it moves away from the first surface; A display device comprising: an irradiation unit that irradiates excitation light incident on the first surface of the display body to excite the phosphor, while changing the focusing position of the excitation light within the display body. [Aspect 2] The display device according to embodiment 1, wherein the thickness of each of the plurality of fluorescent layers is at least twice the Rayleigh length of the excitation light when the focusing position of the excitation light coincides with each of the plurality of fluorescent layers. [Aspect 3] The display device according to embodiment 1 or 2, wherein the light intensity of the excitation light at the focusing position is 1.3 times or more and 1.5 times or less the threshold of the naturally emitted amplified light of the phosphor. [Aspect 4] The display device according to any one of embodiments 1 to 3, wherein the display body further comprises a plurality of separation layers that do not contain phosphors and are alternately stacked with the plurality of fluorescent layers. [Aspect 5] The display device according to embodiment 4, wherein the thickness of each of the plurality of separation layers is configured to increase as it moves away from the first surface.

[0107] [Aspect 6] A display body comprising a plurality of first fluorescent layers containing a first phosphor and a plurality of second fluorescent layers containing a second phosphor having a different emission wavelength from the first phosphor, stacked alternately. A display device comprising: an irradiation unit that superimposes a first excitation light incident on the display body to excite the first phosphor and a second excitation light incident on the display body to excite the second phosphor, and irradiates the display body while changing the first focusing position of the first excitation light and the second focusing position of the second excitation light within the display body. [Aspect 7] The display device according to embodiment 6, wherein the distance between the first light-gathering position and the second light-gathering position within the display body is equal to the thickness of the first fluorescent layer or the second fluorescent layer. [Aspect 8] The display device according to embodiment 6, wherein the distance between the first focusing position and the second focusing position within the display body is equal to half the sum of the thicknesses of the first and second fluorescent layers. [Aspect 9] The thickness of each of the plurality of first fluorescence layers is at least twice the Rayleigh length of the first excitation light. The display device according to any one of embodiments 6 to 8, wherein the thickness of each of the plurality of second fluorescent layers is at least twice the Rayleigh length of the second excitation light. [Aspect 10] The light intensity of the first excitation light at the first focusing position is 1.3 times or more and 1.5 times or less the threshold of the naturally emitted amplified light of the first phosphor. The display device according to any one of embodiments 6 to 9, wherein the light intensity of the second excitation light at the second focusing position is 1.3 times or more and 1.5 times or less the threshold of the naturally emitted amplified light of the second phosphor.

[0108] [Aspect 11] A display body in which multiple laminates are stacked from a first surface to a second surface, wherein each of the multiple laminates is a display body that includes a fluorescent layer containing a phosphor and a separation layer that does not contain a phosphor, A display device comprising: an irradiation unit that irradiates the display body with excitation light, which is incident on the display body to excite the phosphor, by changing the focusing position of the excitation light within the display body. [Aspect 12] The display device according to embodiment 11, wherein the sum of half the thickness of the fluorescent layer and the thickness of the separation layer in each of the plurality of laminates is greater than or equal to the Rayleigh length of the excitation light when the focal position of the excitation light coincides with each of the plurality of laminates. [Aspect 13] The display device according to embodiment 11 or 12, wherein the sum of the thickness of the fluorescent layer and the thickness of the separation layer contained in each of the plurality of laminates is greater than 1 and less than 2 times the Rayleigh length of the excitation light when the focal position of the excitation light coincides with each of the plurality of laminates. [Aspect 14] The display device according to any one of embodiments 11 to 13, wherein the light intensity of the excitation light at the focusing position is 1.3 times or more and 1.5 times or less the threshold of the naturally emitted amplified light of the phosphor. [Aspect 15] The display device according to any one of embodiments 11 to 14, wherein the thickness of the separation layer contained in each of the plurality of laminates increases as it moves away from the first surface.

[0109] [Aspect 16] A display body comprising multiple laminates stacked together, wherein each of the multiple laminates has a structure in which a first fluorescent layer containing a first phosphor, a first separation layer not containing a phosphor, a second fluorescent layer containing a second phosphor having a different emission wavelength from the first phosphor, and a second separation layer not containing a phosphor are stacked in that order, A display device comprising: an irradiation unit that superimposes a first excitation light incident on the display body to excite the first phosphor and a second excitation light incident on the display body to excite the second phosphor, and irradiates the display body while changing the first focusing position of the first excitation light and the second focusing position of the second excitation light within the display body. [Aspect 17] The display device according to embodiment 16, wherein the distance between the first focusing position and the second focusing position within the display body is greater than or equal to the sum of half the thickness of the second fluorescent layer and the Rayleigh length of the first excitation light, or greater than or equal to half the thickness of the first fluorescent layer and the sum of the Rayleigh length of the second excitation light. [Aspect 18] The display device according to embodiment 16 or 17, wherein the distance between the first focusing position and the second focusing position within the display body is equal to the sum of half the thickness of the first fluorescent layer, the thickness of the first separation layer, and half the thickness of the second fluorescent layer. [Aspect 19] The display device according to any one of embodiments 16 to 18, wherein the distance between the first focusing position and the second focusing position within the display body is greater than one times and less than two times the Rayleigh length of the first or second excitation light. [Aspect 20] The light intensity of the first excitation light at the first focusing position is 1.3 times or more and 1.5 times or less the threshold of the naturally emitted amplified light of the first phosphor. The display device according to any one of embodiments 16 to 19, wherein the light intensity of the second excitation light at the second focusing position is 1.3 times or more and 1.5 times or less the threshold of the naturally emitted amplified light of the second phosphor.

[0110] [Aspect 21] A display unit comprising multiple fluorescent layers containing phosphors and multiple separation layers not containing phosphors, stacked alternately, A first irradiation unit irradiates the display body with first excitation light incident in the stacking direction to excite the phosphor, while changing its position in the in-plane direction. A display device comprising: a second irradiation unit that irradiates the plurality of fluorescent layers with a second excitation light incident in the in-plane direction to excite the phosphors, while changing the position in the stacking direction. [Aspect 22] The display device according to embodiment 21, wherein the refractive index of the plurality of separation layers is lower than the refractive index of the plurality of fluorescent layers. [Aspect 23] The display device according to embodiment 22, wherein the difference between the refractive index of the plurality of separation layers and the refractive index of the plurality of fluorescent layers is 0.01 or more and 0.05 or less. [Aspect 24] The light intensity of the first excitation light and the second excitation light are each below the threshold of the naturally emitted amplified light of the phosphor. The display device according to any one of embodiments 21 to 23, wherein the sum of the light intensities of the first excitation light and the second excitation light is greater than or equal to a threshold value of the naturally emitted amplified light of the phosphor. [Aspect 25] The display device according to any one of embodiments 21 to 24, wherein the sum of the thicknesses of each of the plurality of fluorescent layers and each of the plurality of separation layers is greater than 1 times and less than 2 times the Rayleigh length of the first excitation light. [Aspect 26] The display device according to any one of embodiments 21 to 25, wherein the thickness of each of the plurality of fluorescent layers is 0.5 times or more and 2 times or less the spot size of the first excitation light focusing position. [Explanation of Symbols]

[0111] 10...Display device, 12...Display body, 13...First surface, 14...Second surface, 16...Irradiation unit, 18...Control unit, 20...Excitation light, 21...First excitation light, 22...Second excitation light, 23...Third excitation light, 24...Focusing position, 25...First focusing position, 26...Second focusing position, 27...Third focusing position, 30...Laminate, 31...First fluorescence layer, 32...Second fluorescence layer, 33...Third fluorescence layer, 34...First separation layer, 35...Second separation layer, 36 ...Third separation layer, 40...light source, 41...collimating lens, 42...focusing lens, 44...lens drive mechanism, 46...mirror, 48...mirror drive mechanism, 16B...irradiation unit, 61...first light source, 62...second light source, 63...third light source, 64...first collimating lens, 65...second collimating lens, 66...third collimating lens, 67...first half mirror, 68...second half mirror, 69...third mirror.

Claims

1. A display unit comprising multiple fluorescent layers containing phosphors and multiple separation layers not containing phosphors, stacked alternately, A first irradiation unit irradiates the display body with first excitation light incident in the stacking direction to excite the phosphor, while changing its position in the in-plane direction, The system includes a second irradiation unit that irradiates the plurality of fluorescent layers with a second excitation light incident in the in-plane direction to excite the phosphors, while changing the position in the stacking direction. The plurality of separation layers transmit the first excitation light with a predetermined transmittance and have a predetermined refractive index difference from the plurality of fluorescent layers. The second irradiation unit incidents the second excitation light onto the fluorescent layer at an incident angle corresponding to a critical angle based on the predetermined difference in refractive index, such that the second excitation light undergoes total internal reflection at the interface between the separation layer and the fluorescent layer. Display device.

2. The display device according to claim 1, wherein the refractive index of the plurality of separation layers is lower than the refractive index of the plurality of fluorescent layers.

3. The display device according to claim 2, wherein the difference between the refractive index of the plurality of separation layers and the refractive index of the plurality of fluorescent layers is 0.01 or more and 0.05 or less.

4. The light intensity of the first excitation light and the second excitation light are each less than the threshold of the naturally emitted amplified light of the phosphor. The display device according to any one of claims 1 to 3, wherein the sum of the light intensities of the first excitation light and the second excitation light is equal to or greater than the threshold value of the naturally emitted amplified light of the phosphor.

5. A display unit comprising multiple fluorescent layers containing phosphors and multiple separation layers not containing phosphors, stacked alternately, A first irradiation unit irradiates the display body with first excitation light incident in the stacking direction to excite the phosphor, while changing its position in the in-plane direction, The system includes a second irradiation unit that irradiates the plurality of fluorescent layers with a second excitation light incident in the in-plane direction to excite the phosphors, while changing the position in the stacking direction. The sum of the thicknesses of each of the plurality of fluorescent layers and each of the plurality of separation layers is greater than one time and less than two times the Rayleigh length of the first excitation light. Display device.

6. A display unit comprising multiple fluorescent layers containing phosphors and multiple separation layers not containing phosphors, stacked alternately, A first irradiation unit irradiates the display body with first excitation light incident in the stacking direction to excite the phosphor, while changing its position in the in-plane direction, The system includes a second irradiation unit that irradiates the plurality of fluorescent layers with a second excitation light incident in the in-plane direction to excite the phosphors, while changing the position in the stacking direction. The thickness of each of the plurality of fluorescent layers is 0.5 times or more and 2 times or less the spot size at the focusing position of the first excitation light. Display device.

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