Display device and projection device

Abstract

The present invention provides a light source device that can suppress the increase in size, and a projection device equipped with this light source device. [Solution] The display device 20 comprises three light sources 30R, 30G, and 30B that emit coherent light of different colors in substantially the same direction, three diffractive optical elements 40R, 40G, and 40B provided corresponding to each light source 30R, 30G, and 30B, which are incident on and diffracted by light from each light source 30R, 30G, and 30B, and a liquid crystal display element 50 that is irradiated with light diffracted by each diffractive optical element 40R, 40G, and 40B from the light emitted from each light source 30R, 30G, and 30B, and each diffractive optical element 40R, 40G, and 40B is positioned to irradiate the liquid crystal display element 50 with light that has a different diffraction angle depending on the difference in the color of the incident light, so as to overlap with each other.

Description

Technical Field

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

Background Art

[0002] Conventionally, a projection device including a display device that diffracts light from a light source such as a laser diode by a diffractive optical element (DOE; Diffractive Optical Element) and irradiates a display element to generate image light has been disclosed. For example, Patent Document 1 discloses a projector including a projection unit having an illumination device including a laser light source device that emits red laser light, an illumination device including a laser light source device that emits green laser light, and an illumination device including a laser light source device that emits blue laser light. Each illumination device includes a diffractive optical element that generates diffracted light by the incident laser light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In each illumination device of the projector disclosed in Patent Document 1 above, the incident surface illuminated by each illumination device is provided at a position where non-diffracted light, that is, 0th-order light generated from the diffractive optical element is not incident. However, since each diffractive optical element provided in each illumination device is dispersedly arranged around the dichroic mirror and emits light toward the dichroic mirror, that is, in different directions, there is a risk that the device becomes large-sized.

[0005] In view of the above points, an object of the present invention is to provide a light source device capable of suppressing an increase in size and a projection device including this light source device. [Means for solving the problem]

[0006] The display device of the present invention comprises a plurality of light sources that emit coherent light of different colors in substantially the same direction; a plurality of diffractive optical elements provided corresponding to each of the plurality of light sources, which are incident on and diffracted by light from the plurality of light sources; and an irradiated object to which light diffracted by each of the diffractive optical elements from the light emitted from the plurality of light sources is irradiated. Each of the plurality of diffractive optical elements is positioned to irradiate the irradiated object with light having different diffraction angles depending on the difference in the color of the incident light, so as to overlap with each other.

[0007] Another display device of the present invention comprises: a plurality of light sources that emit coherent light having different emission wavelengths; a plurality of diffractive optical elements provided to correspond to each of the plurality of light sources, which are incident on and diffracted by light from the plurality of light sources; and an irradiated object provided in an arrangement to be irradiated with light diffracted by the diffractive optical elements from the light emitted from the plurality of light sources, and not irradiated with light that is not diffracted by the diffractive optical elements. The light source includes a first light source that emits light in a first wavelength band with relatively long wavelengths, and a second light source that emits light in a second wavelength band with relatively short wavelengths, and each of the plurality of diffractive optical elements has a diffraction grating spacing set such that the diffraction angle when light from the second light source is incident on it is greater than the diffraction angle when light from the first light source is incident on it.

[0008] The projection apparatus of the present invention comprises a display element that generates image light, a display device, and a projection optical system that projects the image light generated by the display element onto the projection object. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a light source device that can suppress the increase in size, and a projection device equipped with this light source device. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic plan view showing the general configuration of a projection device equipped with a display device according to the first embodiment. [Figure 2] (a) is a schematic plan view showing the display device according to the first embodiment, and (b) is a schematic side view showing the display device according to the first embodiment. [Figure 3] This is a schematic perspective view of the display device according to the first embodiment. [Figure 4] (a) is a schematic side view of a red diffractive optical element in a display device according to the first embodiment, and (b) is a schematic diagram showing the angular range of diffractive light irradiated from the exit surface of the red diffractive optical element to the incident surface of the liquid crystal display element in a display device according to the first embodiment. [Figure 5] (a) is a schematic plan view showing an outline of a modified display device according to the first embodiment, and (b) is a schematic side view showing an outline of a modified display device according to the first embodiment. [Figure 6] (a) is a schematic plan view showing the display device according to the second embodiment, and (b) is a schematic side view showing the display device according to the second embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, a first embodiment of the present invention will be described with reference to Figures 1 to 5. As shown in Figure 1, the projection device 10 of this embodiment comprises a housing 12, a display device 20 provided inside the housing 12, and a projection optical system 16. The display device 20 comprises at least three light sources 30R, 30G, and 30B, three lenses 36R, 36G, and 36B provided on the light emission side of each light source 30R, 30G, and 30B corresponding to each light source 30R, 30G, and 30B, three diffractive optical elements 40R, 40G, and 40B provided on the light emission side of each lens 36R, 36G, and 36B corresponding to each light source 30R, 30G, and 30B, and a liquid crystal display element (illuminated object) 50 provided on the light emission side of each diffractive optical element 40R, 40G, and 40B.

[0012] The projection device 10 irradiates the liquid crystal display element 50 with light emitted from each of the light sources 30R, 30G, and 30B via the diffractive optical elements 40R, 40G, and 40B, thereby forming an optical image on the liquid crystal display element 50. The projection optical system 16 then projects the image outwards from the housing 12 (see the direction of the arrows in Figure 1) onto a projection surface 90, such as a screen. Inside the housing 12, a single heat sink 70 is commonly arranged for each of the light sources 30R, 30G, and 30B. In other words, the surfaces of each light source 30R, 30G, and 30B that come into contact with the heat sink 70 are arranged on substantially the same virtual plane. In addition, a single cooling fan 80 is positioned to blow air toward each of the light sources 30R, 30G, and 30B (from back to front in the figure). Furthermore, the control unit for managing the electrical configuration of each light source 30R, 30G, and 30B, as well as the cooling fan 80, is provided on a single circuit board, rather than being separated for each light source 30R, 30G, and 30B. In this way, by arranging each light source 30R, 30G, and 30B in parallel and with the light emission direction being approximately the same, there is no need to provide a heat sink 70 or cooling fan 80 for each light source, making layout design easier and reducing the volume inside the housing 12, thus allowing the entire projection device 10 to be downsized.

[0013] For convenience, as shown in Figure 1, the projection direction from the projection device 10 to the object to be projected onto 90 (the direction of the arrow in Figure 1) will be considered the front, and the opposite side will be considered the rear. Therefore, the direction from each light source 30R, 30G, and 30B toward the liquid crystal display element 50 will be approximately the front direction. Furthermore, the direction along the plane of Figure 1 that is perpendicular to the front-to-back direction will be considered the left-to-right direction (the right side when viewed from the rear toward the front), and the direction perpendicular to both the front-to-back and left-to-right directions will be described as the up-and-down direction (the direction from the front to the back of the plane of Figure 1, and the direction from the back toward the front).

[0014] As shown in Figure 2, each light source 30R, 30G, and 30B is a semiconductor light-emitting element that emits coherent laser light. It includes a red light source (first light source) 30R that emits laser light in the red wavelength band (e.g., 640-770 nm) (first wavelength band light), a green light source (second light source) 30G that emits laser light in the green wavelength band (e.g., 490-550 nm) (second wavelength band light), and a blue light source 30B that emits laser light in the blue wavelength band (e.g., 430-490 nm). Each light source 30R, 30G, and 30B is arranged such that the optical axis direction of the emitted light is aligned with the front-to-back direction, and emits laser light forward. Hereafter, the front-to-back direction will also be referred to as the optical axis direction.

[0015] Furthermore, as shown in Figure 3, each light source 30R, 30G, and 30B is positioned on the same virtual plane VP in space. As shown in Figure 2, the red light source 30R and the green light source 30G are positioned side by side horizontally so that they are at the same height vertically, while the blue light source 30B is positioned between the red light source 30R and the green light source 30G, but lower vertically than both. That is, the blue light source 30B is positioned diagonally below and to the right of the red light source 30R and diagonally below and to the left of the green light source 30G. Therefore, the line segment connecting the rear surfaces of each light source 30R, 30G, and 30B on the virtual plane VP is represented as a triangle (see Figure 3).

[0016] Each lens 36R, 36G, and 36B includes a red light source lens 36R positioned on the far side (light emission side) along the optical axis of the red light source 30R, a green light source lens 36G positioned on the forward side (light emission side) along the optical axis of the green light source 30G, and a blue light source lens 36B positioned on the forward side (light emission side) along the optical axis of the blue light source 30B; all are convex lenses. Each lens 36R, 36G, and 36B converts the laser beam emitted from each light source 30R, 30G, and 30B into parallel light parallel to the optical axis and directs it onto the incident surfaces 40R1, 40G1, and 40B1 of each diffractive optical element 40R, 40G, and 40B.

[0017] Each of the folding optical elements 40R, 40G, and 40B is an optical element configured by overlapping a plurality of substantially plate-shaped diffraction gratings with different lattice intervals formed of a fine uneven structure, so that their functions are integrated as if they were a single sheet. Each of the folding optical elements 40R, 40G, and 40B includes a red folding optical element 40R disposed on the front side along the optical axis direction of the red light source lens 36R between the red light source lens 36R and the liquid crystal display element 50, a green folding optical element 40G disposed on the front side along the optical axis direction of the green light source lens 36G between the green light source lens 36G and the liquid crystal display element 50, and a blue folding optical element 40B disposed on the front side along the optical axis direction of the blue light source lens 36B between the blue light source lens 36B and the liquid crystal display element 50, and they are provided separately from each other. Each of the folding optical elements 40R, 40G, and 40B diffracts the laser light incident parallel from each of the lenses 36R, 36G, and 36B and emits it toward the liquid crystal display element 50.

[0018] Each of the folding optical elements 40R, 40G, and 40B is arranged such that the surface directions of their incident surfaces 40R1, 40G1, and 40B1 and the surface directions of their exit surfaces 40R2, 40G2, and 40B2 are orthogonal to the optical axis direction. In other words, the normal directions of the incident surfaces 40R1, 40G1, and 40B1 and the normal directions of the exit surfaces 40R2, 40G2, and 40B2 are substantially parallel to the optical axis direction. Also, each of the folding optical elements 40R, 40G, and 40B is arranged such that the exit surfaces 40R2, 40G2, and 40B2, which are diffraction surfaces, are parallel to each other and are offset in the direction along the optical axis. Specifically, regarding the distances between each of the folding optical elements 40R, 40G, and 40B and the liquid crystal display element 50, the distance between the red folding optical element 40R and the liquid crystal display element 50 is the shortest, the distance between the green folding optical element 40G and the liquid crystal display element 50 is the longest, and the distance between the blue folding optical element 40B and the liquid crystal display element 50 is set to be intermediate between the above two distances.

[0019] In this embodiment, each diffractive optical element 40R, 40G, 40B is manufactured based on a substantially identical optical design and is set with the same grating pitch P. For example, taking the red diffractive optical element 40R as an example, as shown in Fig. 4(a), the grating pitch P on the exit surface (diffraction surface) 40R2, that is, the interval P between the concave portion 42a and the convex portion 42b constituting one grating, is within the range of 1.5 to 5 μm. From the exit surface 40R2 of the red diffractive optical element 40R, the light diffracted by the red diffractive optical element 40R (first-order light: m = ±1) and the non-diffracted light (zero-order light: m = 0) are emitted. Here, the diffraction angle θ of the light diffracted by each diffractive optical element 40R, 40G, 40B is expressed by an approximate formula including λ / P when the wavelength of the laser light emitted from each light source 30R, 30G, 30B is λ (nm). Note that each diffractive optical element 40R, 40G, 40B has the same grating pitch P, but the grating patterns including the depth of the concave portion 42a, the height of the convex portion 42b, and the arrangement of the concavo-convex structure are different. Each diffractive optical element 40R, 40G, 4OB can be manufactured by a known manufacturing method such as photolithography.

[0020] In this embodiment, vibration devices (vibration members) 60 constituted by an electromagnetic method, piezoelectric elements, etc. are provided above each diffractive optical element 40R, 40G, 40B (see Fig. 3). Then, by causing each diffractive optical element 40R, 40G, 40B to vibrate slightly in the vertical and horizontal directions by these vibration devices 60, as a result of the laser light emitted from each light source 30R, 30G, 30B passing through the diffractive optical elements 40R, 40G, 40B, the generation of speckle noise is suppressed.

[0021] The liquid crystal display element 50 is a horizontally elongated, roughly rectangular plate-shaped member having a long side and a short side. Its incident surface (irradiation surface) 50a, which is the incidentable region 50I, and its exit surface 50b are arranged to be parallel to the exit surfaces (diffraction surfaces) 40R2, 40G2, and 40B2 of each diffractive optical element 40R, 40G, and 40B. The liquid crystal display element 50 is a general type with high linearity and low diffusion. A voltage is applied to the liquid crystal display element 50, and the control unit switches between an ON state (voltage applied) and an OFF state (voltage not applied). Inside the liquid crystal display element 50, liquid crystal (not shown) is sealed in a predetermined orientation direction in the OFF state. When the liquid crystal display element 50 switches to the ON state by applying a voltage, the orientation direction of the internal liquid crystal is switched by 90°. In the liquid crystal display element 50, the switching between the ON state and the OFF state is controlled by the control unit in a time-division multiplexer.

[0022] The liquid crystal display element 50 is positioned such that its long side (hereinafter referred to as "long side 50L") is aligned in the left-right direction, and its short side (hereinafter referred to as "short side 50S") is aligned in the up-down direction. The incident surface 50a of the liquid crystal display element 50 has an incident area 50I with the upper left corner 50LU, the lower left corner 50LL, the upper right corner 50RU, and the lower right corner 50RL, which are configured to allow incident light to be appropriately emitted when viewed from the light sources 30R, 30G, and 30B. The liquid crystal display element 50 is positioned such that light diffracted by each diffractive optical element 40R, 40G, and 40B from the light emitted from each light source 30R, 30G, and 30B is incident on the incident surface 50a, while light not diffracted by each diffractive optical element 40R, 40G, and 40B is not incident on the incident surface 50a. Specifically, the liquid crystal display element 50 is arranged such that the approximate center of the output surface 40R2 of the red diffractive optical element 40R is shifted to the left (offset position) relative to the incident surface 50a of the liquid crystal display element 50, the approximate center of the output surface 40G2 of the green diffractive optical element 40G is shifted to the right (offset position) relative to the incident surface 50a of the liquid crystal display element 50 (see Figure 2(a)), and the approximate center of the output surface 40B2 of the blue diffractive optical element 40B is shifted downward (offset position) relative to the incident surface 50a of the liquid crystal display element 50 (see Figure 2(b)).

[0023] Next, with reference to Figures 2 and 3, the incidence and emission of light in each component constituting the display device 20 will be described. Light emitted from the red light source 30R is made into parallel light through the red light source lens 36R and incident on the incident surface 40R1 of the red diffractive optical element 40R. When light from the red light source 30R is incident on the red diffractive optical element 40R, diffracted light (first-order light) (hereinafter referred to as "red first-order light RL1") and undiffracted light (zero-order light) (hereinafter referred to as "red zero-order light RL0") are emitted from the emission surface 40R2 of the red diffractive optical element 40R. Of these, the red first-order light RL1 is diffracted toward the liquid crystal display element 50 side (right side) and incident on the incident surface 50a of the liquid crystal display element 50. On the other hand, the red zero-order light RL0 travels in a straight line along the optical axis, so it is not incident on the liquid crystal display element 50 and is not projected from the projection device 10 toward the object to be projected 90.

[0024] Light emitted from the green light source 30G is converted into parallel light via the green light source lens 36G and incident on the incident surface 40G1 of the green diffractive optical element 40G. When light from the green light source 30G is incident on the green diffractive optical element 40G, diffracted light (first-order light) (hereinafter referred to as "green first-order light GL1") and undiffracted light (zero-order light) (hereinafter referred to as "green zero-order light GL0") are emitted from the exit surface 40G2 of the green diffractive optical element 40G. Of these, the green first-order light GL1 is diffracted toward the liquid crystal display element 50 side (left side) and incident on the incident surface 50a of the liquid crystal display element 50. On the other hand, the green zero-order light GL0 travels in a straight line along the optical axis, so it is not incident on the liquid crystal display element 50 and is not projected from the projection device 10 toward the object to be projected 90. In other words, the red diffractive optical element 40R and the green diffractive optical element 40G are positioned offset to the left and right so that the red zero-order light and the green zero-order light do not overlap with the incident surface 50a of the liquid crystal display element 50 in the optical axis direction.

[0025] Light emitted from the blue light source 30B is converted into parallel light via the blue light source lens 36B and incident on the incident surface 40B1 of the blue diffractive optical element 40B. When light from the blue light source 30B is incident on the blue diffractive optical element 40B, diffracted light (first-order light) (hereinafter referred to as "blue first-order light BL1") and undiffracted light (zero-order light) (hereinafter referred to as "blue zero-order light BL0") are emitted from the exit surface 40B2 of the blue diffractive optical element 40B. Of these, the blue first-order light BL1 is diffracted toward the liquid crystal display element 50 side (upper side) and incident on the incident surface 50a of the liquid crystal display element 50. On the other hand, the blue zero-order light BL0 travels in a straight line along the optical axis, so it is not incident on the liquid crystal display element 50 and is not projected from the projection device 10 toward the object to be projected 90. In other words, the blue diffractive optical element 40B is positioned so as to be offset vertically so that the blue zero-order light BL0 does not overlap with the incident surface 50a of the liquid crystal display element 50 in the optical axis direction.

[0026] Here, since diffractive optical elements have the characteristic that the diffraction angle is larger the longer the wavelength of the incident light, when the lattice spacing P of each diffractive optical element 40R, 40G, and 40B is the same, as in this embodiment, the order of magnitude of the diffraction angles of the red primary light RL1 (hereinafter referred to as "red diffraction angle θR"), the green primary light GL1 (hereinafter referred to as "green diffraction angle θG"), and the blue primary light BL1 (hereinafter referred to as "blue diffraction angle θB") is red diffraction angle θR > green diffraction angle θG > blue diffraction angle θB. By making the red diffraction angle θR, green diffraction angle θG, and blue diffraction angle θB different in this way, it is possible to easily increase the diffraction efficiency of the red primary light RL1, green primary light GL1, and blue primary light BL1. Then, with this order of magnitude, the red primary light RL1, green primary light GL1, and blue primary light BL1 incident on the incident surface 50a of the liquid crystal display element 50 generate image light in the liquid crystal display element 50. This image light is emitted from the emission surface 50b of the liquid crystal display element 50, passes through the projection optical system 16, and is emitted to the outside of the projection device 10.

[0027] Next, referring to Figures 3 and 4(b), the minimum incident angle θmin and maximum incident angle θmax of the red primary light RL1, green primary light GL1, and blue primary light BL1 incident on the liquid crystal display element 50 will be described. Here, the light incident at the minimum incident angle θmin is defined as the minimum incident light Lmin, and the light incident at the maximum incident angle θmax is defined as the maximum incident light Lmax. As shown in Figure 4, for example, the angular range of the red diffraction angle θR (irradiation range α of the primary red light RL1) incident on the incident surface 50a of the liquid crystal display element 50 from the exit surface 40R2 of the red diffractive optical element 40R is such that the minimum incident angle θmin occurs when the primary red light RL1 is incident on the left middle end 50LM, which is at the midpoint of the incidentable region 50I, on the left end in the long side direction (the end on the left short side side 50S), and is at a position equal to the distance from the upper left corner 50LU and the lower left corner 50LL of the incidentable region 50I. The maximum incident angle θmax occurs when the primary red light RL1 is incident on the upper right corner 50RU and the lower right corner 50RL of the incidentable region 50I on the right end in the long side direction (the end on the right short side side 50S).

[0028] Furthermore, the angular range of the green diffraction angle θG (irradiation range α of the green primary light GL1) is determined by the incident angle θmin when the green primary light GL1 is incident on the right-center corner 50RM, which is at the midpoint of the incidentable region 50I on the right end of the long side (the end on the right short side 50S side) of the incident surface 50a, at a distance equal to the upper right corner 50RU and the lower right corner 50RL. The incident angle θmax is determined when the green primary light GL1 is incident on the upper left corner 50LU and the lower left corner 50LL of the incidentable region 50I on the left end of the long side (the end on the left short side 50S side). Furthermore, the angular range of the blue diffraction angle θB (the irradiation range α of the blue primary light BL1) is determined by the lower middle end 50ML of the incident surface 50a, which is at the lower end in the short-side direction (the end on the lower long-side surface 50L) and is at the midpoint where the distance from the lower left corner 50LL and the lower right corner 50RL of the incidentable region 50I is equal, resulting in the minimum incident angle θmin. The maximum incident angle θmax is determined by the upper left corner 50LU and the upper right corner 50RU of the incidentable region 50I, which is at the upper end in the short-side direction (the end on the upper long-side surface 50L). Note that the above is an example where the incident regions of the red primary light RL1, green primary light GL1, and blue primary light BL1 on the incident surface 50a of the liquid crystal display element 50 are aligned, but they may be slightly offset from each other in the vertical and / or horizontal directions.

[0029] At this time, the irradiation distance d from each diffractive optical element 40R, 40G, 40B to the incident surface 50a of the liquid crystal display element 50 can be calculated using an approximate formula that includes the minimum incident angle θmin, the maximum incident angle θmax, the length dimension in the long side direction of the incidentable region 50I of the incident surface 50a, and the length dimension in the short side direction of the incidentable region 50I of the incident surface 50a. Furthermore, the offset distance β of each diffractive optical element 40R, 40G, 40B with respect to the incident surface 50a of the liquid crystal display element 50 can be calculated using the calculated irradiation distance d and the formula that includes the minimum incident angle θmin. Then, the angle of the line connecting each diffractive optical element 40R, 40G, 40B and the center of the incident area 50I of the incident surface 50a of the liquid crystal display element 50, in other words, the angle of the center position of the minimum incident angle θmin and the maximum incident angle θmax (hereinafter referred to as "set incident angle θset"), can be calculated using an equation that includes the calculated offset distance β, the length dimension in the long side direction of the incident area 50I of the incident surface 50a, and the length dimension in the short side direction of the incident area 50I of the incident surface 50a. Here, the light incident at the set incident angle θset is called the set incident light Lset.

[0030] In this embodiment, the set incidence angle θset is set for the red primary light RL1, green primary light GL1, and blue primary light BL1 irradiated onto the incident surface 50a of the liquid crystal display element 50 so that the irradiation range of the red primary light RL1, green primary light GL1, and blue primary light BL1 is approximately equal to the incident area 50I. Based on the set incidence angle θset, the red diffraction angle θR, green diffraction angle θG, blue diffraction angle θB, and the arrangement of each diffractive optical element 40R, 40G, and 40B along the optical axis are set. In this way, the red primary light RL1, green primary light GL1, and blue primary light BL1 irradiate the incident area 50I of the incident surface 50a in overlapping manner, making the components of each color approximately equal. As a result, it is possible to prevent bias in any of the red, green, or blue colors in the image light generated by the liquid crystal display element 50, and to project a clear image onto the object to be projected.

[0031] Next, a modified display device 120 of the first embodiment will be described with reference to Figures 5(a) and (b). As shown in Figures 5(a) and (b), the display device 120 of this modified embodiment differs from the display device 20 of the first embodiment in that the green diffractive optical element and the blue diffractive optical element are integrated. The other components of the display device 120 are the same as those of the first embodiment, so their description will be omitted or simplified. In Figure 5, in the display device 120 of this modified embodiment, components with the same configuration as those of the display device 20 of the first embodiment are denoted by the same reference numerals.

[0032] As shown in Figures 5(a) and (b), in the display device 120 according to this modified example, the green diffractive optical element and the blue diffractive optical element are integrated by a light-transmitting member 140BG. The light-transmitting member 140GB is made of light-transmitting glass and is sized to span both the front side of the green light source lens 36G and the front side of the blue light source lens 36B. Similar to the red diffractive optical element 40R, the light-transmitting member 140GB is positioned such that the plane direction of its incident surface 140GB1 and the plane direction of its exit surface 140GB2 are perpendicular to the optical axis direction, that is, the normal direction of the incident surface 140GB1 and the normal direction of the exit surface 140GB2 are parallel to the optical axis direction. On the incident surface 140GB1 of the light-transmitting member 140GB, on the front side of the green light source lens 36G, that is, at the position where light is incident through the green light source lens 36G, a green diffractive optical region 144G on which the diffractive optical element is formed is located. Furthermore, a blue diffractive optical region 144B, on the front side of the blue light source lens 36B of the light-transmitting member 140GB2, that is, at the position where light is incident through the blue light source lens 36B, is arranged in which a diffractive optical element is formed.

[0033] Here, the set incident light Lset distance from the blue diffractive optical region 144B to the incident surface 50a of the liquid crystal display element 50, after light emitted from the blue light source 30B, is approximately the thickness of the translucent member 140GB, and is longer than the set incident light Lset distance from the green diffractive optical region 144G to the incident surface 50a of the liquid crystal display element 50, after light emitted from the green light source 30G. In other words, by adjusting one or both of the combination of the blue diffraction angle θB in the relatively short-wavelength blue diffractive optical region 144B and the green diffraction angle θG in the relatively long-wavelength green diffractive optical region 144G, and the distance between the emission surface of the blue diffractive optical region 144B and the green diffractive optical region 144G in the optical axis direction, the light emitted from the green light source 30G and the blue light source 30B can be appropriately incident into the incident area 50I.

[0034] The diffractive optical elements formed in the green diffractive optical region 144G and the diffractive optical elements formed in the blue diffractive optical region 144B are both formed with the same lattice spacing P as the red diffractive optical element 40R. Even with this configuration, the incidence and emission of light in each component constituting the display device 120 is the same as in the display device 20 of the first embodiment. That is, light emitted from the green light source 30G is made into parallel light by the green light source lens 36G and incident on the green diffractive optical region 144G of the translucent member 140BG, and primary green light and zero-order green light are emitted from the emission surface 140BG2 of the translucent member 140BG. Similarly, light emitted from the blue light source 30B is made into parallel light by the blue light source lens 36B and incident on the blue diffractive optical region 144B of the translucent member 140BG, and primary blue light and zero-order blue light are emitted from the emission surface 140GB2 of the translucent member 140BG. The emission and incidence of light emitted from the red light source 30R are the same as in the first embodiment.

[0035] As described above, the display device 20 according to this embodiment comprises three light sources 30R, 30G, and 30B that emit coherent light of different colors in substantially the same direction, three diffractive optical elements 40R, 40G, and 40B provided corresponding to each light source 30R, 30G, and 30B, which are incident on and diffracted by light from each light source 30R, 30G, and 30B, and a liquid crystal display element 50 that is irradiated with light diffracted by each diffractive optical element 40R, 40G, and 40B from the light emitted from each light source 30R, 30G, and 30B (red primary light RL1, green primary light GL1, and blue primary light BL1), and each diffractive optical element 40R, 40G, and 40B is positioned to irradiate the liquid crystal display element 50 with light of different diffraction angles according to the difference in the color of the incident light, so as to overlap with each other.

[0036] As a result of the above-described configuration, the display device 20 of this embodiment is configured such that the primary red light RL1, primary green light GL1, and primary blue light BL1 emitted from each diffractive optical element 40R, 40G, and 40B irradiate the liquid crystal display element 50, while the zeroth-order red light RL0, zeroth-order green light GL0, and zeroth-order blue light BL0 emitted from each diffractive optical element 40R, 40G, and 40B do not irradiate the liquid crystal display element 50. Therefore, color unevenness in the image light generated by the liquid crystal display element 50 can be reduced. Furthermore, each diffractive optical element 40R, 40G, and 40B can be manufactured according to the same optical design, thereby reducing manufacturing costs.

[0037] Furthermore, in the display device 20 of this embodiment, by providing diffractive optical elements 40R, 40G, and 40B corresponding to each light source 30R, 30G, and 30B, the red primary light RL1, green primary light GL1, and blue primary light BL1 emitted from each diffractive optical element 40R, 40G, and 40B can be directly incident onto the liquid crystal display element 50 due to the difference in diffraction angles. Therefore, there is no need to arrange multiple components to guide the light emitted from the diffractive optical elements to the liquid crystal display element 50, and the size of the display device 20 can be kept down compared to conventional configurations using diffractive optical elements. In addition, by arranging the red primary light RL1, green primary light GL1, and blue primary light BL1 with different diffraction angles in this way, the diffraction efficiency of the red primary light RL1, green primary light GL1, and blue primary light BL1 can be increased.

[0038] Furthermore, in the display device 20 of this embodiment, each light source 30R, 30G, and 30B is arranged on the same virtual plane VP. With this configuration, cooling devices such as heat pipes for cooling each light source 30R, 30G, and 30B can be arranged in a space-saving manner, and the cooling efficiency of each light source 30R, 30G, and 30B can be increased.

[0039] Furthermore, in the display device 20 of this embodiment, the liquid crystal display element 50 is positioned so that it is not irradiated with light that is not diffracted by the respective diffractive optical elements 40R, 40G, and 40B from the light emitted from each light source 30R, 30G, and 30B. This makes it possible to reduce color unevenness on the projection surface 90.

[0040] Furthermore, in the display device 20 of this embodiment, each diffractive optical element 40R, 40G, and 40B has equal grid spacing, and their diffracting surfaces, the emitting surfaces 40R2, 40G2, and 40B2, are parallel to each other and positioned offset from each other along the optical axis. With this configuration, by adjusting the position of each diffractive optical element 40R, 40G, and 40B along the optical axis according to the magnitude and relative size of the red diffraction angle θR, green diffraction angle θG, and blue diffraction angle θB, the irradiation size (irradiation range) of the red primary light RL1, green primary light GL1, and blue primary light BL1 irradiated from each diffractive optical element 40R, 40G, and 40B onto the liquid crystal display element 50 can be made approximately equal. As a result, it is possible to prevent bias in any of the red, green, or blue colors in the image light generated by the liquid crystal display element 50.

[0041] Furthermore, in the display device 20 of this embodiment, the light sources 30R, 30G, and 30B include a red light source 30R that emits red wavelength band light, a green light source 30G that emits green wavelength band light, and a blue light source 3B that emits blue wavelength band light. The lattice pattern of the diffraction grating of each diffractive optical element 40R, 40G, and 40B is set such that the diffraction angle (red diffraction angle θR) is largest when light from the red light source 30R is incident, and the diffraction angle (blue diffraction angle θB) is smallest when light from the blue light source 30B is incident. With this configuration, a display device 20 equipped with a red light source 30R, a green light source 30G, and a blue light source 30B can be realized. Here, if the lattice spacing P of each diffractive optical element 40R, 40G, and 40B is the same, the diffraction angle is larger the longer the wavelength of the incident light, so the relationship red diffraction angle θR > green diffraction angle θG > blue diffraction angle θB holds true. Therefore, the diffraction efficiency of each color, red, green, and blue, can be increased.

[0042] Furthermore, in the display device 20 of this embodiment, the liquid crystal display element 50 includes a substantially rectangular illumination surface 50a having a long side and a short side, with the short side arranged along the thickness direction of the display device 20. Of the red light source 30R, green light source 30G, and blue light source 30B, the red light source 30R and green light source 30G are arranged to be aligned along the long side direction of the incident surface 50a, and the blue light source 30B is positioned at a different location from the red light source 30R and green light source 30G in the short side direction of the incident surface 50a. With this configuration, for example, among the light sources 30R, 30G, and 30B, the red light source 30R, which has the largest diffraction angle of primary light, and the green light source 30G, which has the next largest diffraction angle of primary light, are arranged side by side along the longer side, while the blue light source 30B, which has the smallest diffraction angle of primary light, is positioned differently from the red light source 30R and the green light source 30G in the shorter side. This makes it easier to adjust the irradiation size (irradiation range) of the red primary light RL1, green primary light GL1, and blue primary light BL1 to be approximately equal.

[0043] Furthermore, in the display device 20 of this embodiment, the red diffractive optical element 40R and the green diffractive optical element 40G are positioned offset in the direction of the long side of the liquid crystal display element 50 so that the red zero-order light RL0 and the green zero-order light GL0 do not overlap with the incident surface 50a in the optical axis direction, and the blue diffractive optical element 40B is positioned offset in the direction of the short side of the liquid crystal display element 50 so that the blue zero-order light BL0 does not overlap with the incident surface 50a in the optical axis direction. This makes it possible to realize a specific configuration for a display device comprising a red light source 30R, a green light source 30G, a blue light source 30B, and a liquid crystal display element 50 having a substantially rectangular incident surface 50a, in which each of the red zero-order light RL0, green zero-order light GL0, and blue zero-order light BL0 is not incident on the incident surface 50a.

[0044] Furthermore, in the display device 120 according to a modified example of this embodiment, of the red diffractive optical element 40R, green diffractive optical element 40G, and blue diffractive optical element 40B, two of them, the green diffractive optical element 40G and the blue diffractive optical element 40B, are integrated by a light-transmitting member 140GB. With this configuration, while increasing the diffraction efficiency of the red primary light RL1, green primary light GL1, and blue primary light BL1, it is possible to reduce manufacturing costs and save space by using a light-transmitting member 140GB in which the green diffractive optical element 40G and the blue diffractive optical element 40B are integrated.

[0045] Furthermore, in the display device 20 of this embodiment, each light source 30R, 30G, and 30B is a light-emitting element that emits laser light, and is equipped with a vibration device 60 that vibrates each of the diffractive optical elements 40R, 40G, and 40B. With this configuration, the vibration device 60 vibrates each of the diffractive optical elements 40R, 40G, and 40B in the vertical and horizontal directions, thereby reducing the generation of speckle noise caused by the laser light.

[0046] The projection device 10 of this embodiment includes a liquid crystal display element 50 that generates image light as the object to be projected, a display device 20, and a projection optical system 16 that projects the image light generated by the liquid crystal display element 50 onto the object to be projected. This makes it possible to reduce the manufacturing cost of each diffractive optical element 40R, 40G, and 40B while preventing bias in any of the colors in the image light generated by the liquid crystal display element 50, thereby realizing a projection device 10 that can project a clear image onto the object to be projected.

[0047] Next, with reference to Figure 6, a display device 220 according to the second embodiment of the present invention will be described. As shown in Figure 6, the display device 220 according to this embodiment differs from the display device 20 of the first embodiment in the relative magnitudes of the red diffraction angle θR, the green diffraction angle θG, and the blue diffraction angle θB, and in the relative positions of each diffractive optical element 40R, 40G, and 40B along the optical axis. The other configurations of the display device 220 are the same as those of the first embodiment, so their description will be omitted or simplified. In Figure 6, in the display device 220 according to this embodiment, the same reference numerals are used for components that have the same configuration as those of the display device 20 according to the first embodiment.

[0048] As shown in Figures 6(a) and (b), in the display device 220 according to this embodiment, the grid spacing P is not the same for each diffractive optical element 40R, 40G, and 40B. By adjusting the grid spacing P and the grid pattern, the relative magnitudes of the red diffraction angle θR, green diffraction angle θG, and blue diffraction angle θB are set to blue diffraction angle θB > red diffraction angle θR > green diffraction angle θG. The relative positions of each diffractive optical element 40R, 40G, and 40B along the optical axis are adjusted according to this relative magnitude. Specifically, the blue diffractive optical element 40B, which has the largest diffraction angle of the emitted primary light, is positioned to have the shortest distance from the liquid crystal display element 50, and the green diffractive optical element 40G, which has the smallest diffraction angle of the emitted primary light, is positioned to have the shortest distance from the liquid crystal display element 50. The red diffractive optical element 40R is positioned between the blue diffractive optical element 40B and the green diffractive optical element 40G in the optical axis direction.

[0049] Here, since each light source 30R, 30G, and 30B is a semiconductor light-emitting element that emits laser light, the relationship between their luminous efficiency is generally blue light source 30B > red light source 30R > green light source 30G. In the display device 220 of this embodiment, by setting each light source 30R, 30G, and 30B so that the diffraction angle of the primary light increases as the luminous efficiency increases, the efficiency between each light source 30R, 30G, and 30B and the liquid crystal display element 50 (efficiency including both luminous efficiency and diffraction efficiency) can be equalized. As a result, the energy efficiency of the display device can be increased. In addition, the size of the display device 220 can be kept down compared to the conventional configuration.

[0050] The embodiments described above are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and essence of the invention, as well as in the claims of the invention and its equivalents.

[0051] For example, in the above embodiments, a liquid crystal display element was used as an example of the irradiated object, but the invention is not limited to this. For example, a DMD (Digital Micromirror Device) and a structure that forms an optical image with the reflected light of the DMD may be provided as the irradiated object, or a grating light bulb, light tunnel, microlens array, etc. may be provided. Also, in the above embodiments, a configuration in which no other members are placed between each diffractive optical element and the liquid crystal display element was used as an example, but a configuration in which lenses, reflective mirrors, dichroic mirrors, etc. are placed between each diffractive optical element and the liquid crystal display element is also possible. Furthermore, in the above embodiments, a configuration in which the pattern output from each diffractive optical element (the incident surface of the liquid crystal display element) is rectangular was used as an example, but a configuration in which a distorted rectangular shape is output by incidenting the liquid crystal display element from an oblique direction is also possible. [Explanation of Symbols]

[0052] 20: Display device, 30R: Red light source, 30G: Green light source, 30B: Blue light source, 40R: Red diffractive optical element, 40G: Green diffractive optical element, 40B: Blue diffractive optical element, 50: Liquid crystal display element, P: Grid spacing

Claims

1. Multiple light sources that emit coherent light of different colors in approximately the same direction, A plurality of diffractive optical elements are provided so as to correspond to each of the plurality of light sources, and light from the plurality of light sources is incident on them and diffracted; The system comprises an irradiated object to which light diffracted by each of the diffractive optical elements from the light emitted from the plurality of light sources is irradiated, Each of the plurality of diffractive optical elements is positioned to irradiate the object to be irradiated with light that has a different diffraction angle depending on the color of the incident light, so that the two beams overlap. Display device.

2. Each of the aforementioned multiple light sources is arranged on the same virtual plane. The display device according to claim 1.

3. The irradiated object is positioned such that it is not irradiated by light emitted from the plurality of light sources that is not diffracted by the diffractive optical element. The display device according to claim 1.

4. Each of the plurality of diffractive optical elements is arranged such that the lattice spacing is equal to each other, the diffraction planes are parallel to each other, and they are offset from each other along the optical axes of the light from the plurality of light sources. The display device according to claim 1.

5. The light source includes a red light source that emits light in the red wavelength band, a green light source that emits light in the green wavelength band, and a blue light source that emits light in the blue wavelength band. Each of the plurality of diffractive optical elements is configured such that the diffraction angle is largest when light from the red light source is incident on it, and the diffraction angle is smallest when light from the blue light source is incident on it. The display device according to claim 1.

6. The irradiated object includes a substantially rectangular irradiation surface having a long side and a short side, with the short side positioned along the thickness direction of the display device. Of the red light source, the green light source, and the blue light source, any two are arranged so as to be aligned along the long side of the illumination surface, and the other one is positioned differently from the other light sources in the short side of the illumination surface. The display device according to claim 5.

7. The diffractive optical elements corresponding to the red light source and the diffractive optical elements corresponding to the green light source are arranged offset in the direction of the longer side such that the light that is not diffracted does not overlap with the illumination surface in the optical axis direction. The diffractive optical element corresponding to the blue light source is positioned offset in the short-side direction such that the light that is not diffracted does not overlap with the illumination surface in its optical axis direction. The display device according to claim 6.

8. Two of the diffractive optical elements corresponding to the red light source, the diffractive optical elements corresponding to the green light source, and the diffractive optical elements corresponding to the blue light source are integrated by a light-transmitting member having light-transmitting properties. The display device according to claim 5.

9. Each of the aforementioned plurality of light sources is a light-emitting element that emits laser light, The system includes a vibrating member that vibrates each of the plurality of diffractive optical elements. The display device according to claim 1.

10. Multiple light sources that emit coherent light with different emission wavelengths, A plurality of diffractive optical elements are provided so as to correspond to each of the plurality of light sources, and light from the plurality of light sources is incident on them and diffracted; The irradiated object is arranged such that, of the light emitted from the plurality of light sources, the light diffracted by the diffractive optical element is irradiated, and the light not diffracted by the diffractive optical element is not irradiated. The light source includes a first light source that emits light in a first wavelength band with relatively long wavelengths, and a second light source that emits light in a second wavelength band with relatively short wavelengths. Each of the plurality of diffractive optical elements has a diffraction grating spacing set such that the diffraction angle when light from the second light source is incident on it is greater than the diffraction angle when light from the first light source is incident on it. Display device.

11. The irradiated object is a display element that generates image light, A display device according to any one of claims 1 to 10, The system comprises a projection optical system that projects the image light generated by the display element onto an object to be projected onto. Projection device.

Images