JP7797864B2 - display device - Google Patents

Description

The present invention relates to a display device.

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

Japanese Patent Application Laid-Open No. 2015-165611

The above-mentioned prior art does not mention controlling the irradiation position of the ultraviolet light irradiated onto the quantum dot block. In order to accurately display the intended three-dimensional image, it is preferable to appropriately control the irradiation position.

The present invention was made in consideration of the above circumstances, and aims to provide technology that improves the display accuracy of stereoscopic images.

A display device according to one embodiment of the present invention comprises a display element in which multiple laminates are stacked from a first surface to a second surface, each of the multiple laminates including a fluorescent layer containing a phosphor and a separation layer not containing a phosphor; and an irradiation unit that irradiates the display element with excitation light that is incident on the display element and excites the phosphor, changing the focusing position of the excitation light within the display element.

In addition, any combination of the above components, or any mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc., are also valid aspects of the present invention.

This invention can improve the display accuracy of stereoscopic images.

1 is a diagram schematically illustrating a configuration of a display device according to a first embodiment. 1 is a graph schematically showing the relationship between excitation light intensity and emission intensity of a phosphor. FIG. 10 is a diagram schematically showing the relationship between the thickness of a fluorescent layer and the Rayleigh length of excitation light. FIG. 10 is a diagram schematically illustrating a configuration of a display device according to a second embodiment. FIG. 10 is a diagram schematically illustrating a configuration of a display device according to a third embodiment. FIG. 2 is a diagram schematically illustrating the arrangement of a first light collecting position, a second light collecting position, and a third light collecting position. FIG. 10 is a diagram schematically illustrating the configuration of a display according to a fourth embodiment. FIG. 10 is a diagram schematically showing the relationship between the thickness of the fluorescent layer and the separation layer and the Rayleigh length of the excitation light. FIG. 13 is a diagram schematically illustrating the arrangement of a first light collecting position, a second light collecting position, and a third light collecting position in a fifth embodiment. FIG. 10 is a diagram schematically illustrating a configuration of a display device according to a sixth embodiment.

Embodiments of the present invention will now be described with reference to the drawings. Specific numerical values and other information shown in these embodiments are merely examples intended to facilitate understanding of the invention, and do not limit the present invention unless otherwise specified. Elements not directly related to the present invention are not shown in the drawings. To facilitate understanding of the explanation, the dimensional ratios of the components in each drawing do not necessarily correspond to the actual dimensional ratios.

(First embodiment)
1 is a diagram schematically illustrating the configuration of a display device 10 according to a 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 render a three-dimensional image S inside the display body 12.

The display body 12 has a first surface 13 and a second surface 14, and includes multiple laminates 30 stacked in the z-direction from the first surface 13 to the second surface 14. Each of the multiple laminates 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 multiple 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 multiple second fluorescent layers 32 are arranged alternately with the multiple first fluorescent layers 31, and the multiple third fluorescent layers 33 are arranged alternately with the multiple first fluorescent layers 31 and the multiple second fluorescent layers 32.

The first fluorescent layer 31 is a fluorescent layer containing a first phosphor with an emission wavelength in the visible range, for example, a first phosphor with an emission color of red (R). The second fluorescent layer 32 is a fluorescent layer containing a second phosphor with an emission wavelength in the visible range different from that of the first phosphor, for example, a second phosphor with an emission color of green (G). The third fluorescent layer 33 is a fluorescent layer containing a third phosphor with an emission wavelength in the visible range different from that of the first and second phosphors, for example, a third phosphor with an emission color of blue (B).

The materials for the first phosphor, the second phosphor, and the third phosphor are not particularly limited, but for example, quantum dot phosphors can be used. By using quantum dot phosphors, the first phosphor, the second phosphor, and the third phosphor can share a common excitation wavelength, 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, nanocrystalline particles of cesium lead halide perovskite (CsPbX ₃ , where X is a halogen and is either Cl, Br, or I, or a mixture thereof) can be used, and the excitation wavelength is set to ultraviolet light of 300 nm to 400 nm, and RGB emission wavelengths can be obtained.

The base material of the first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33 is made of a material that is transparent to visible light, such as a resin material or a glass material. The first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33 can each be formed by mixing a phosphor into the transparent base material, and the display 12 can be formed by stacking the first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33 in order.

The display body 12 is configured so that the entire body has a solid columnar shape, and can be configured to have a cylindrical, polygonal prism, or rectangular parallelepiped shape. The display body 12 is configured so that the surface of the display body 12 has a mirror finish so that the interior of the display body 12 can be seen from the outside. The display body 12 is formed so that the multiple fluorescent layers 31, 32, and 33 are integrated together so that the interfaces between the multiple fluorescent layers 31, 32, and 33 are invisible or difficult to see.

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

The irradiation unit 16 irradiates the display 12 with excitation light 20 that excites the phosphor. The excitation light 20 is incident on the first surface 13 of the display 12 and is irradiated onto the display 12 so that the focusing position 24 of the excitation light 20 changes over time inside the display 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.

The light source 40 generates excitation light 20 for exciting the first phosphor, the second phosphor, and the third phosphor. The light source 40 generates ultraviolet light with a central wavelength in the range of 300 nm to 400 nm as the excitation light 20. Any type of light source 40 can be used, but for example, a gallium nitride (GaN) semiconductor laser or a semiconductor light-emitting diode (LED) can be used as the light source 40.

The condensing lens 42 condenses the excitation light 20 generated by the light source 40 toward the inside of the display body 12. The lens driving mechanism 44 is configured to change the position of the condensing lens 42 in the optical axis direction A. The lens driving mechanism 44 changes the focusing position 24 of the excitation light 20 by changing the position of the condensing lens 42. The lens driving mechanism 44 varies the focusing position 24 in the irradiation direction of the excitation light 20, and also varies the focusing position 24 in a direction intersecting with the first surface 13. Note that a variable focus lens may be used instead of the condensing lens 42 and lens driving mechanism 44 to vary the focusing position 24 in a direction intersecting with the first surface 13.

The mirror 46 reflects the excitation light 20 that has passed through the condensing lens 42 toward the display 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 change the orientation of the mirror 46 along two axes, and changes the focusing position 24 of the excitation light 20 reflected by the mirror 46 in directions along the first surface 13 (x direction and y direction). In the example shown in the figure, a single 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 also be combined.

The light intensity of the excitation light 20 at the focused position 24 is set to be equal to or greater than the amplified spontaneous emission (ASE) threshold of the phosphor contained in the display 12, for example, 1.3 to 1.5 times the amplified spontaneous emission threshold (ASE threshold). Amplified spontaneous emission (ASE), also known as superluminescence, is a phenomenon in which excitation light generates a population inversion in the phosphor, amplifying the phosphor's luminescence intensity. The amplified spontaneous emission threshold (ASE threshold) corresponds to the minimum light intensity of the excitation light required to generate ASE.

Figure 2 is a graph schematically showing the relationship between excitation light intensity and emission intensity of a phosphor, showing an example in which the phosphor is a cesium lead halide perovskite nanocrystal. When the light intensity of the excitation light irradiated onto the phosphor exceeds the ASE threshold (0.45 mJ/ ^cm2 in Figure 2), the ratio (slope) of emission intensity to excitation light intensity increases. By setting the excitation light intensity at the focusing position 24 to be equal to or greater than 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 a location other than the focusing position 24 below the ASE threshold, the emission intensity of the phosphor at a location other than the focusing position 24 can be reduced, thereby increasing the contrast ratio with the focusing position 24.

FIG. 3 is a diagram schematically illustrating the relationship between the thickness of the fluorescent layer and the Rayleigh length Zr of the excitation light 20. FIG. 3 illustrates a state in which the focusing position 24 of the excitation light 20 coincides with the first fluorescent layer 31. The excitation light 20 has a minimum beam radius _w0 at the focusing position 24, and the beam radius increases with increasing distance from the focusing position 24. The Rayleigh length Zr is the distance from ^the focusing position 24 to a position 28 where the beam radius of the excitation light 20 increases by √2, and can be expressed as Zr = _πw02 /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, approximately 1 μm to 30 μm. In this case, the Rayleigh length Zr is approximately 10 μm to 10 mm.

At position 28 of the Rayleigh length Zr, the beam radius is √2×w ₀ , and the beam intensity is half that at position 24. When the beam intensity at position 24 is 1.3 to 1.5 times the ASE threshold, the beam intensity at position 28 of the Rayleigh length Zr is 0.65 to 0.75 times the ASE threshold, and ASE does not occur. Here, if the thickness t1 of the first fluorescent layer 31 is set to be at least twice the Rayleigh length Zr of the excitation light 20, it is possible to prevent ASE from occurring in the fluorescent layers (second fluorescent layer 32 and third fluorescent layer 33) adjacent to the first fluorescent layer 31, and it is possible to suppress color bleeding and a decrease in drawing contrast.

Figure 3 shows the case where the focusing position 24 of the excitation light 20 coincides with the first fluorescent layer 31, but the same applies when the focusing position 24 of the excitation light 20 coincides with the second fluorescent layer 32 or the third fluorescent layer 33. The thickness t2 of the second fluorescent 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 fluorescent layer 32. The thickness t3 of the third fluorescent 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 fluorescent layer 33. There are no particular upper limits to the thicknesses t1, t2, and t3 of the first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33, respectively, but they may be, for example, no more than five, four, or three times the Rayleigh length Zr of the excitation light 20.

The thicknesses t1, t2, and t3 of the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 may vary depending on the position in the z direction within the display body 12, for example, depending on the distance from the first surface 13. When the focusing position 24 of the excitation light 20 is changed depending on the position in the optical axis direction A of a single focusing lens 42 as shown in FIG. 1 , the beam diameter _w0 at the focusing position 24 varies depending on the position of the focusing lens 42. Specifically, the beam diameter _w0 at the focusing position 24 increases as the focusing position 24 moves away from the first surface 13 (i.e., as the focusing position 24 moves closer to the second surface 14). The Rayleigh length Zr is proportional to the square of the beam diameter _w0 , and therefore, the Rayleigh length Zr increases as the focusing position 24 moves away from the first surface 13. The thicknesses t1, t2, t3 of the first fluorescent layers 31, the second fluorescent layers 32, and the third fluorescent layers 33 may be varied in accordance with the change in the Rayleigh length Zr depending on the position in the z direction of the focusing position 24. In other words, the thicknesses t1, t2, t3 of the first fluorescent layers 31, the second fluorescent layers 32, and the third fluorescent layers 33 may be configured to increase with increasing distance from the first surface 13.

Returning to Figure 1, the control unit 18 controls the operation of the irradiation unit 16. In terms of hardware, the control unit 18 can be realized by elements and mechanical devices such as a computer's CPU and memory, and in terms of software, it can be realized by a computer program, etc. The various functions provided by the control unit 18 can be realized by a combination of hardware and software.

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 driving mechanism 44 and the mirror driving mechanism 48. The control unit 18, for example, periodically operates the lens driving mechanism 44 and the mirror driving mechanism 48, thereby causing the focusing position 24 of the excitation light 20 to be scanned three-dimensionally within the display body 12.

The control unit 18 controls the on/off of the light source 40, for example, according to 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 at a location inside the display body 12 where rendering should be performed. The control unit 18 turns off the light source when the focusing position 24 of the excitation light 20 is at a location inside the display body 12 where rendering should not be performed.

The control unit 18 controls the on/off and light emission intensity of the light source 40 based on, for example, 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 by the first fluorescent layer 31, the amount of green light emitted by the second fluorescent layer 32, and the amount of blue light emitted by the third fluorescent layer 33, the control unit 18 controls the full color of the emitted light produced by mixing red, green, and blue at the light-emitting positions.

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 CMOS sensor, and is provided to measure the spot size of the excitation light 20. The image sensor 50 is disposed adjacent to the display body 12 at a position corresponding to the first surface 13. The image sensor 50 may be disposed at a position different from that shown in the figure, as long as the excitation light 20 can be incident on it.

The control unit 18 operates the lens driving mechanism 44 and the mirror driving mechanism 48 so that the excitation light 20 is incident on the image sensor 50. The control unit 18 measures the size of the excitation light 20 using the image sensor 50 while changing the position of the condenser lens 42, thereby identifying the position of the condenser lens 42 at which the spot size of the excitation light 20 is smallest. The identified position of the condenser lens 42 can be used as a reference for positioning in the z direction to align the condensing position 24 of the excitation light 20 with the first surface 13. The control unit 18 can calibrate the condensing position 24 of the excitation light 20 based on the measurement results of the image sensor 50.

The display device 10 may further include an optical sensor 52. The optical sensor 52 is configured to be able to measure the light intensity for each wavelength. For example, the optical sensor 52 is configured to be able 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 disposed, for example, on the second surface 14 of the display 12. The optical sensor 52 may be located at a position different from that shown in the figure, as long as it is able to detect the light emitted from the display 12.

The control unit 18 operates the lens drive mechanism 44 to change the position of the condenser lens 42, while acquiring the light intensities of the first, second, and third emitted colors measured by the optical sensor 52. Changing the condensing position 24 of the excitation light 20 changes which of the first fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 the excitation light 20 is more strongly condensed at, and changes the light intensities of the first, second, and third emitted colors. For example, the position of the condenser lens 42 at which the light intensity of the first emitted color measured by the optical sensor 52 is maximized (or local maximum) can be used as a reference for positioning in the z direction to align the condensing position 24 of the excitation light 20 with the first fluorescent layer 31.

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 also calibrate the focusing position 24 based on the measurement results of the optical sensor 52 before starting to draw the three-dimensional image S. The control unit 18 may also calibrate the focusing position 24 based on the measurement results of the optical sensor 52 while the three-dimensional image S is being drawn or at the timing between drawing each frame of the three-dimensional image S that will become a video. By calibrating the focusing position 24 of the excitation light 20 based on the measurement results of the optical sensor 52, the positional accuracy for drawing the three-dimensional image S can be improved, and the display accuracy of the three-dimensional image S can be improved.

Next, the operation of the display device 10 will be described. The control unit 18 acquires the three-dimensional contour image data and operates the irradiation unit 16 based on the three-dimensional contour image data. The control unit 18 controls the operation of the lens driving mechanism 44 and the mirror driving mechanism 48 to three-dimensionally scan 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. This allows a three-dimensional image S corresponding to the three-dimensional contour image data to be drawn inside the display body 12.

The control unit 18 may acquire three-dimensional contour image data corresponding to each frame of the video data, and may render a different three-dimensional image S for each frame. This may allow the three-dimensional image S to be displayed as a video.

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 also calibrate the focusing position 24 before starting to draw the three-dimensional image S based on the measurement results of the image sensor 50. The control unit 18 may also calibrate the focusing position 24 while drawing the three-dimensional image S or at the timing between drawing each frame of the three-dimensional image S that will become a video, based on the measurement results of the image sensor 50.

According to this embodiment, by setting the thicknesses t1, t2, and t3 of the first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33 included in each of the multiple laminates 30 to at least twice the Rayleigh length Zr, it is possible to suppress light emission at locations other than the light-condensing position 24. This suppresses light emission in adjacent fluorescent layers of different light-emitting colors, thereby reducing color bleeding and contrast degradation. Furthermore, by setting the light intensity at the light-condensing position 24 to be between 1.3 and 1.5 times the ASE threshold of the phosphor, it is possible to obtain strong light emission due to ASE at the light-condensing position 24 while preventing ASE from occurring in adjacent fluorescent layers of different light-emitting colors, thereby reducing color bleeding and contrast degradation. As a result, the display accuracy of the 3D image S can be improved.

Second Embodiment
4 is a diagram schematically illustrating the configuration of a display device 10A according to a second embodiment. The second embodiment differs from the first embodiment in that the irradiation unit 16A further includes a collimating lens 41. The following description of the second embodiment will focus on the differences from the first embodiment, and will omit commonalities with the first embodiment as appropriate.

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

The irradiation unit 16A includes a light source 40, a collimating lens 41, a condensing lens 42, a lens driving mechanism 44, a mirror 46, and a mirror driving mechanism 48. The light source 40, 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 first embodiment.

The collimating lens 41 collimates the excitation light 20 generated by the light source 40. The condensing lens 42 focuses the excitation light 20, which has been collimated by the collimating lens 41, toward the inside of the display body 12. The lens driving mechanism 44 changes the position of the condensing lens 42, thereby changing the focusing position 24 of the excitation light 20.

According to this embodiment, by using the collimating lens 41, it is possible to suppress changes in the beam diameter _w0 and the Rayleigh length Zr at the focusing position 24 of the excitation light 20, which are caused by changes in the focusing position 24. According to one example of this embodiment, by collimating the excitation light 20 using the collimating lens 41, it is possible to change the focusing position 24 while keeping the beam diameter _w0 and the Rayleigh length Zr at the focusing position 24 constant. As a result, it is possible to configure the plurality of first fluorescent layers 31, the plurality of second fluorescent layers 32, and the plurality of third fluorescent layers 33 so that their respective thicknesses t1, t2, t3 are constant and are at least twice the Rayleigh length Zr.

(Third embodiment)
5 is a diagram schematically illustrating the configuration of a display device 10B according to a third embodiment. The third embodiment differs from the second embodiment in that an irradiation unit 16B includes a plurality of light sources 61, 62, and 63. The following description of the third embodiment will focus on the differences from the second embodiment, and will omit commonalities with the second embodiment as appropriate.

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

The irradiation 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.

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, second excitation light 22, and third excitation light 23 are ultraviolet light having center wavelengths in the range of 300 nm to 400 nm. The center wavelengths of the first excitation light 21, second excitation light 22, and third excitation light 23 may be the same or different from each other. For example, the center wavelength of the first excitation light 21 may be 400 nm, the center wavelength of the second excitation light 22 may be 350 nm, and the center wavelength of the third excitation light 23 may be 300 nm. As with the light source 40 according to the first embodiment, semiconductor lasers or semiconductor LEDs can be used as the first light source 61, second light source 62, and third light source 63.

The first collimating lens 64 collimates the first excitation light 21 generated by the first light source 61. The second collimating lens 65 collimates the second excitation light 22 generated by the second light source 62. The third collimating lens 66 collimates the third excitation light 23 generated by the third light source 63. The first half mirror 67 reflects the first excitation light 21 collimated by the first collimating lens 64 toward the condenser lens 42. The second half mirror 68 reflects the second excitation light 22 collimated by the second collimating lens 65 toward the condenser lens 42. The second excitation light 22 reflected by the second half mirror 68 passes through the first half mirror 67 toward the condenser lens 42. The third mirror 69 reflects the third excitation light 23 collimated by the third collimating lens 66 toward the condenser 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 proceeds toward the condenser 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 and then enter the condenser lens 42.

The focusing lens 42 focuses the excitation light 20, which is a superimposed combination of the first excitation light 21, the second excitation light 22, and the third excitation light 23, toward the inside of the display body 12. The mirror 46 reflects the excitation light 20 that has passed through the focusing lens 42 toward the display body 12. The first excitation light 21 is focused at the first focusing position 25 by the focusing lens 42. The second excitation light 22 is focused at the second focusing position 26 by the focusing lens 42. The third excitation light 23 is focused at the third focusing position 27 by the focusing lens 42.

The first focusing position 25, the second focusing position 26, and the third focusing position 27 are set so that their positions in the irradiation direction (z direction) of the excitation light 20 are slightly different. For example, by fine-tuning the degree of collimation 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, the first focusing position 25, the second focusing position 26, and the third focusing position 27 can be shifted from one another.

Figure 6 is a schematic diagram showing 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 fluorescent layer 31. In the state of Figure 6, 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. 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 fluorescent layer 31, the second fluorescent layer 32, and the third fluorescent layer 33 included in one laminate 30 can be excited simultaneously. Furthermore, by individually setting the light intensity of each of the first excitation light 21, second excitation light 22, and third excitation light 23, the amount of red light emitted from the first fluorescent layer 31, the amount of green light emitted from the second fluorescent layer 32, and the amount of blue light emitted from the third fluorescent layer 33 can be controlled, allowing full color control of the emitted light color resulting from the mixing of red, green, and blue at the light-emitting position.

6, the distance between the first focusing position 25 and the second focusing position 26 is equal to the first pitch p1, which is the center-to-center distance between the first fluorescent layer 31 and the second fluorescent layer 32. The first pitch p1 is equal to half the sum of the thickness t1 of the first fluorescent layer 31 and the thickness t2 of the second fluorescent layer 32, i.e., (t1 + t2)/2. The distance between the second focusing position 26 and the third focusing position 27 is equal to the second pitch p2, which is the center-to-center distance between the second fluorescent layer 32 and the third fluorescent layer 33. The second pitch p2 is equal to half the sum of the thickness t2 of the second fluorescent layer 32 and the thickness t3 of the third fluorescent layer 33, i.e., (t2 + t3)/2. The first pitch p1 may be equal to the thickness t1 of the first fluorescent layer 31 or the thickness t2 of the second fluorescent layer 32. The second pitch p2 may be equal to the thickness t2 of the second fluorescent layer 32 or the thickness t3 of the third fluorescent layer 33.

In this embodiment, too, the thickness of the fluorescent layer is preferably 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 of the first excitation light 21 at the first focusing position 25, and is not more than five, four, or three times the first Rayleigh length Zr1. The first Rayleigh length Zr1 is the position at which the beam diameter of the first excitation light 21 is √2 times the minimum beam diameter _w01 at the first focusing position 25. The thickness t2 of the second fluorescent layer 32 is at least twice the second Rayleigh length Zr2 of the second excitation light 22 at the second focusing position 26, and is not more than five, four, or three times the second Rayleigh length Zr2. The second Rayleigh length Zr2 is the position at which the beam diameter of the second excitation light 22 is √2 times the minimum beam diameter _w02 at the second focusing position 26. The thickness t3 of the third fluorescent layer 33 is at least twice the third Rayleigh length Zr3 of the third excitation light 23 at the third focusing position 27, and is not more than five, four, or three times the third Rayleigh length Zr3. The third Rayleigh length Zr3 is the position where the beam diameter of the third excitation light 23 is √2 times the minimum beam diameter _w03 at the third focusing position 27.

In this embodiment, too, the light intensity at the focusing position of the excitation light is preferably 1.3 to 1.5 times the ASE threshold of the phosphor. The light intensity of the first excitation light 21 at the first focusing position 25 is 1.3 to 1.5 times the ASE threshold of the first phosphor contained in the first fluorescent layer 31. By setting the light intensity of the first excitation light 21 in this manner, ASE caused by the first excitation light 21 can be generated in the first fluorescent layer 31, and ASE caused by the first excitation light 21 can be prevented from being generated in the second fluorescent layer 32 or the third fluorescent layer 33. Similarly, the light intensity of the second excitation light 22 at the second focusing position 26 is 1.3 to 1.5 times the ASE threshold of the second phosphor contained in the second fluorescent layer 32. Setting the light intensity of the second excitation light 22 in this manner allows ASE to be generated in the second fluorescent layer 32 due to the second excitation light 22, while preventing ASE from being generated in the first fluorescent layer 31 or the third fluorescent 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 1.3 to 1.5 times the ASE threshold of the third phosphor contained in the third fluorescent layer 33. Setting the light intensity of the third excitation light 23 in this manner allows ASE to be generated in the third fluorescent layer 33 due to the third excitation light 23, while preventing ASE from being generated in the first fluorescent layer 31 or the second fluorescent layer 32 due to the third excitation light 23. As a result, color bleeding and a decrease in rendering contrast can be suppressed, improving the display accuracy of the 3D image S.

(Fourth embodiment)
The fourth embodiment differs from the first embodiment in that a separation layer containing no phosphor is provided between two fluorescent layers that emit different colors. According to the fourth embodiment, the provision of the separation layer can more effectively suppress color bleeding and a decrease in image contrast. According to the fourth embodiment, the provision of the separation layer can further reduce the pitch between the two fluorescent layers that emit different colors, thereby enabling the rendering of a three-dimensional image S with higher resolution. Below, the fourth embodiment will be described, focusing on the differences from the first embodiment, and commonalities with the first embodiment will be omitted as appropriate.

Figure 7 is a diagram schematically illustrating the configuration of a display 12C according to the fourth embodiment. The display 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 in this order 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 manner as in the first embodiment.

The first separation layer 34, the second separation layer 35, and the third separation layer 36 do not contain phosphor and are made of a resin material or glass material that is transparent to visible light. The first separation layer 34, the second separation layer 35, and the third separation layer 36 are preferably 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 so 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.

Figure 8 is a schematic diagram showing the relationship between the thickness of the fluorescent layer and separation layer and the Rayleigh length Zr of the excitation light 20. Similar to Figure 3, Figure 8 shows a state in which the focusing position 24 of the excitation light 20 coincides with the first fluorescent layer 31. In Figure 8, if the second fluorescent layer 32 is farther away from the focusing position 24 than position 28, which is the Rayleigh length Zr, the generation of ASE in the second fluorescent layer 32 can be prevented. Therefore, the sum of half the thickness t1 of the first fluorescent layer 31 and the thickness t4 of the first separation layer 34 is preferably greater than the Rayleigh length Zr (i.e., t1/2 + t4 ≧ Zr). Similarly, the sum of half the thickness t2 of the second fluorescent 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 fluorescent 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).

In this embodiment, by providing the first separation layer 34, the first pitch p1, which is the center-to-center distance between the first fluorescent layer 31 and the second fluorescent layer 32, can be made smaller than in the first embodiment. In the first embodiment of 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 between the first fluorescent layer 31 and the second fluorescent layer 32 is also at least twice the Rayleigh length Zr. On the other hand, in the fourth embodiment of Figure 8, it is possible to set the first pitch p1 between the first fluorescent layer 31 and the second fluorescent layer 32 to be more than one time but less than two times the Rayleigh length Zr. For example, if the thicknesses t1 and t2 of the first fluorescent layer 31 and the second fluorescent layer 32 are the Rayleigh length Zr (t1 = t2 = Zr) and the thickness t4 of the first separation layer 34 is half the Rayleigh length Zr (t4 = Zr/2), the first pitch p1 between the first fluorescent layer 31 and the second fluorescent layer 32 can be set to 1.5 times the Rayleigh length while still satisfying the condition for preventing ASE generation in the second fluorescent layer 32 (t1/2 + t4 ≥ Zr). Similarly, by providing the second separation layer 35, the second pitch p2, which is the center-to-center distance between the second fluorescent layer 32 and the third fluorescent layer 33, can be set to more than 1 time but less than 2 times the Rayleigh length Zr. Furthermore, by providing the third separation layer 36, the third pitch p3, which is the center-to-center distance between the third fluorescent layer 33 and the first fluorescent layer 31, can be set to more than 1 time but less than 2 times the Rayleigh length Zr.

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).

In the fourth embodiment, 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 varied in accordance with the change in the Rayleigh length Zr depending on the position of the focusing position 24 in the z direction. In other words, 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 with increasing distance from the first surface 13. Similarly, the thicknesses t4, t5, and t6 of the multiple first separation layers 34, the multiple second separation layers 35, and the multiple third separation layers 36 may be configured to increase with increasing distance from the first surface 13.

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 first fluorescent layers 31, the second fluorescent layers 32, and the third fluorescent layers 33 may be constant, and the thicknesses t4, t5, and t6 of the first separation layers 34, the second separation layers 35, and the third separation layers 36 may be constant.

Fifth Embodiment
The display device according to the fifth embodiment includes the display 12C according to the fourth embodiment, the irradiation unit 16B according to the third embodiment, and the control unit 18. The following description of the fifth embodiment will focus on the differences from the third and fourth embodiments, and omit commonalities with the third and fourth embodiments as appropriate.

Figure 9 is a diagram schematically illustrating the arrangement of the first focusing position 25, second focusing position 26, and third focusing position 27 in the fifth embodiment. Similar to the fourth 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. Figure 9 illustrates a case in which the first focusing position 25 of the first excitation light 21 coincides with the first fluorescent layer 31. In the state of 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.

In the example of Figure 9, the distance between the first focusing position 25 and the second focusing position 26 corresponds to the first pitch p1, which is the center-to-center distance between the first fluorescent layer 31 and the second fluorescent layer 32. The first pitch p1 corresponds to the sum (t1/2 + t4 + t2/2) of half the thickness t1 of the first fluorescent layer 31, the thickness t4 of the first separation layer 34, and half the thickness t2 of the second fluorescent layer 32. The first pitch p1 can be set, for example, to be greater than 1 time but less than 2 times the first Rayleigh length Zr1 of the first excitation light 21, or greater than 1 time but less than 2 times the second Rayleigh length Zr2 of the second excitation light 22. In the example of 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 overlap in the first separation layer 34, allowing the first pitch p1 to be smaller than in the case of Figure 6. As a result, the first fluorescent layer 31 and the second fluorescent layer 32, which emit light of different colors, can be brought closer together, enabling the rendering of a higher-resolution 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).

The distance between the second focusing position 26 and the third focusing position 27 corresponds to the second pitch p2, which is the center-to-center distance between the second fluorescent layer 32 and the third fluorescent layer 33. The second pitch p2 corresponds to the sum (t2/2 + t5 + t3/2) of half the thickness t2 of the second fluorescent layer 32, the thickness t5 of the second separation layer 35, and half the thickness t3 of the third fluorescent layer 33. The second pitch p2 can be set, for example, to be greater than 1 and less than 2 times the second Rayleigh length Zr2 of the second excitation light 22, or greater than 1 and less than 2 times 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).

The third pitch p3, which is the center-to-center distance between the third fluorescent layer 33 and the first fluorescent layer 31, is equal to the sum (t3/2 + t6 + t1/2) of half the thickness t3 of the third fluorescent layer 33, the thickness t6 of the third separation layer 36, and half the thickness t3 of the first fluorescent layer 31. The third pitch p3 can be set, for example, to be greater than one time but less than two times the third Rayleigh length Zr3 of the third excitation light 23, or greater than one time but less than two 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 fluorescent layer 31 (or the third fluorescent layer 33) and the third Rayleigh length Zr3 (or the first Rayleigh length Zr1) (i.e., p3 ≥ t1/2 + Zr3, or p3 ≥ t3/2 + Zr1).

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 may be equal to the sum of the thicknesses of the second fluorescent layer 32 and the second separation layer 35 (t2 + t5), or may be equal to the sum of the thicknesses of the third fluorescent layer 33 and the third separation layer 36 (t3 + t6).

Sixth Embodiment
10 is a diagram schematically illustrating the configuration of a display device 10D according to a sixth embodiment. The sixth embodiment differs from the first embodiment in that the sixth embodiment further includes a second irradiation unit 17 that irradiates excitation light 80 toward the second surface 14 of the display body 12, in addition to a first irradiation unit 16 that irradiates excitation light 20 toward the first surface 13 of the display body 12. The following description of the second embodiment will focus on the differences from the first embodiment, and commonalities with the first embodiment will be omitted as appropriate.

The display device 10D includes a display body 12, a first irradiator 16, a second irradiator 17, and a controller 18. The first irradiator 16 irradiates excitation light 20 so 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 of the display body 12. The second irradiator 17 irradiates excitation light 80 so 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 of the display body 12. The intermediate surface 15 is set at any position between the first surface 13 and the second surface 14, for example, midway between the first surface 13 and the second surface 14.

The second irradiation unit 17 is configured similarly to the first irradiation unit 16. The second irradiation unit 17 includes a light source 70, a condensing lens 72, a lens driving mechanism 74, a mirror 76, and a mirror driving mechanism 78. Similar to the light source 40, the light source 70 generates excitation light 80 for exciting the first, second, and third phosphors. The condensing lens 72 condenses the excitation light 80 generated by the light source 70 toward the interior of the display body 12. The lens driving mechanism 74 changes the position of the condensing lens 72 in the optical axis direction B, thereby changing the condensing position 84 of the excitation light 80. The mirror 76 reflects the excitation light 80 that has passed through the condensing 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 condensing position 84 of the excitation light 80 reflected by the mirror 76 in directions (x and y directions) along the second surface 14.

The control unit 18 controls the operation of the first irradiator 16 and the second irradiator 17. The control unit 18 acquires three-dimensional contour image data and operates the first irradiator 16 based on data from the three-dimensional contour image data that depicts the range from the first surface 13 to the intermediate surface 15. The control unit 18 operates the second irradiator 17 based on data from the three-dimensional contour image data that depicts the range from the intermediate surface 15 to the second surface 14. According to this embodiment, 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, thereby enabling faster drawing compared to when only excitation light 20 is used.

The thicknesses t1, t2, and t3 of the first fluorescent layer 31, second fluorescent layer 32, and third fluorescent layer 33 included in the display 12 may vary depending on the position in the z direction. 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 from the first surface 13 toward the intermediate surface 15. 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 from the second surface 14 toward the intermediate surface 15.

In a modified example 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 plurality of first fluorescent layers 31, the plurality of second fluorescent layers 32, and the plurality of third fluorescent layers 33 may be constant. Furthermore, the irradiation unit 16B according to the third embodiment may be used as the first irradiation unit 16 and the second irradiation unit 17. Additionally, the display 12C according to the fourth embodiment may be used instead of the display 12.

The present invention has been described above with reference to the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, and appropriate combinations or substitutions of the configurations shown in each display example are also included in the present invention.

Several aspects of the present invention are described below.

[Aspect 1]
a display body in which a plurality of fluorescent layers containing a phosphor are stacked from a first surface to a second surface, and the thickness of each of the plurality of fluorescent layers increases with increasing distance from the first surface;
an irradiation unit that irradiates excitation light that is incident on the first surface of the display body and excites the phosphor, while changing a focusing position of the excitation light within the display body.
[Aspect 2]
2. The display device according to claim 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]
3. The display device according to aspect 1 or 2, wherein the light intensity of the excitation light at the focused position is 1.3 to 1.5 times the threshold value of the amplified spontaneous emission light of the phosphor.
[Aspect 4]
4. The display device according to any one of aspects 1 to 3, wherein the display body further includes a plurality of separation layers that do not contain phosphors and are alternately stacked with the plurality of phosphor layers.
[Aspect 5]
5. The display device according to claim 4, wherein the thickness of each of the plurality of separation layers increases with increasing distance from the first surface.

[Aspect 6]
a display body in which a plurality of first fluorescent layers containing a first phosphor and a plurality of second fluorescent layers containing a second phosphor having an emission wavelength different from that of the first phosphor are alternately stacked;
a display device comprising: an irradiation unit that superimposes first excitation light that is incident on the display body and excites the first phosphor and second excitation light that is incident on the display body and excites the second phosphor, and irradiates the display body by changing a first focusing position of the first excitation light and a second focusing position of the second excitation light within the display body.
[Aspect 7]
7. The display device according to claim 6, wherein a distance between the first light-condensing position and the second light-condensing position in the display element corresponds to a thickness of the first fluorescent layer or the second fluorescent layer.
[Aspect 8]
7. The display device of claim 6, wherein a distance between the first light-collecting position and the second light-collecting position in the display element is equal to half the total thickness of the first fluorescent layer and the second fluorescent layer.
[Aspect 9]
a thickness of each of the plurality of first fluorescent layers is equal to or greater than twice the Rayleigh length of the first excitation light;
9. The display device according to any one of aspects 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]
a light intensity of the first excitation light at the first focusing position is 1.3 times or more and 1.5 times or less a threshold value of the amplified spontaneous emission light of the first phosphor;
10. The display device according to any one of aspects 6 to 9, wherein the light intensity of the second excitation light at the second focusing position is 1.3 to 1.5 times the threshold value of the amplified spontaneous emission light of the second phosphor.

[Aspect 11]
A display body in which a plurality of laminates are stacked from a first surface to a second surface, each of the plurality of laminates including a fluorescent layer containing a phosphor and a separation layer not containing a phosphor;
an irradiation unit that irradiates the display body with excitation light that is incident on the display body and excites the phosphor, while changing a focusing position of the excitation light within the display body.
[Aspect 12]
The display device described in aspect 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 equal to or greater than the Rayleigh length of the excitation light when the focusing position of the excitation light coincides with each of the plurality of laminates.
[Aspect 13]
The display device described in aspect 11 or 12, wherein the sum of the thickness of the fluorescent layer and the thickness of the separation layer included in each of the plurality of laminates is greater than 1 time but less than 2 times the Rayleigh length of the excitation light when the focusing position of the excitation light coincides with each of the plurality of laminates.
[Aspect 14]
14. The display device according to any one of aspects 11 to 13, wherein the light intensity of the excitation light at the focused position is 1.3 to 1.5 times the threshold value of the amplified spontaneous emission light of the phosphor.
[Aspect 15]
15. The display device according to any one of aspects 11 to 14, wherein the thickness of the separation layer included in each of the plurality of stacked bodies increases with increasing distance from the first surface.

[Aspect 16]
a display body having a plurality of laminated bodies stacked together, each of the plurality of laminated bodies having a structure in which a first fluorescent layer containing a first phosphor, a first separation layer containing no phosphor, a second fluorescent layer containing a second phosphor having an emission wavelength different from that of the first phosphor, and a second separation layer containing no phosphor are stacked in this order;
a display device comprising: an irradiation unit that superimposes first excitation light that is incident on the display body and excites the first phosphor and second excitation light that is incident on the display body and excites the second phosphor, and irradiates the display body by changing a first focusing position of the first excitation light and a second focusing position of the second excitation light within the display body.
[Aspect 17]
The display device of aspect 16, wherein a distance between the first focusing position and the second focusing position within the display is equal to or greater than the sum of half the thickness of the second fluorescent layer and the Rayleigh length of the first excitation light, or equal to or greater than the sum of half the thickness of the first fluorescent layer and the Rayleigh length of the second excitation light.
[Aspect 18]
18. The display device of claim 16 or 17, wherein a distance between the first focusing position and the second focusing position within the display element 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]
19. The display device according to any one of aspects 16 to 18, wherein a distance between the first focusing position and the second focusing position within the display body is greater than one time and less than two times the Rayleigh length of the first excitation light or the second excitation light.
[Aspect 20]
a light intensity of the first excitation light at the first focusing position is 1.3 times or more and 1.5 times or less a threshold value of the amplified spontaneous emission light of the first phosphor;
20. The display device according to any one of aspects 16 to 19, wherein the light intensity of the second excitation light at the second focusing position is 1.3 to 1.5 times the threshold value of the amplified spontaneous emission light of the second phosphor.

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 fluorescent layer, 32... second fluorescent layer, 33... third fluorescent layer, 34... first separation layer, 35... second separation layer, 36 ...Third separation layer, 40...light source, 41...collimating lens, 42...condensing lens, 44...lens driving mechanism, 46...mirror, 48...mirror driving 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 (3)

A display body in which a plurality of laminates are stacked from a first surface to a second surface, each of the plurality of laminates including a fluorescent layer containing a phosphor and a separation layer not containing a phosphor;
an irradiation unit that irradiates excitation light that is incident on the display body and excites the phosphor while changing a focusing position of the excitation light within the display body,
a sum of half the thickness of the fluorescent layer and the thickness of the separation layer in each of the plurality of laminates is equal to or greater than the Rayleigh length of the excitation light when the focusing position of the excitation light coincides with each of the plurality of laminates. A display body in which a plurality of laminates are stacked from a first surface to a second surface, each of the plurality of laminates including a fluorescent layer containing a phosphor and a separation layer not containing a phosphor;
an irradiation unit that irradiates excitation light that is incident on the display body and excites the phosphor while changing a focusing position of the excitation light within the display body,
a display device in which the sum of the thickness of the fluorescent layer and the thickness of the separation layer included in each of the plurality of laminates is greater than one and less than two times the Rayleigh length of the excitation light when the focusing position of the excitation light coincides with each of the plurality of laminates. A display body in which a plurality of laminates are stacked from a first surface to a second surface, each of the plurality of laminates including a fluorescent layer containing a phosphor and a separation layer not containing a phosphor;
an irradiation unit that irradiates excitation light that is incident on the display body and excites the phosphor while changing a focusing position of the excitation light within the display body,
The thickness of the separation layer included in each of the plurality of stacked bodies increases with increasing distance from the first surface.