JP2020118902A - Diffraction optical element, lighting device, projection device, and projection display device - Google Patents

Abstract

SOLUTION: A diffraction optical element 40 includes a first element diffraction optical element 41A and a second element diffraction optical element 41B that diffract incident light toward lighted areas. The first element diffraction optical element 41A and the second element diffraction optical element 41B include a plurality of unit pixels that modulate the phase or amplitude of the incident light. Arrangement directions d1 and d2 of the plurality of unit pixels in the first element diffraction optical element 41A are not in parallel with the arrangement directions of the plurality of unit pixels in the second element diffraction optical element 41B.EFFECT: It is possible to effectively make uneven luminance in a lighted area inconspicuous.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a diffractive optical element, a lighting device, a projection device, and a projection display device.

For example, as disclosed in Patent Document 1, an illumination device including a light source and a diffractive optical element is known. In the illumination device disclosed in Patent Document 1, the diffractive optical element diffracts the light from the light source, so that the illuminated area located on the projection surface can be illuminated with a desired pattern.

JP, 2005-132707, A

As a diffractive optical element, a computer-generated hologram (CGH) is known. A computer generated hologram is produced by designing a structure having an arbitrary diffraction characteristic by calculation on a computer. As a specific example, a desired pattern to be illuminated as an illuminated area is considered as an aggregate of point images, and an interference pattern between divergent light from each point image and light scheduled to enter the diffractive optical element is calculated. A diffractive optical element can be obtained by producing a structure corresponding to the interference pattern.

Strictly speaking, the image reproduced by the diffractive optical element thus manufactured is a set of reproduced images for reproducing each point image. The diffractive optical element has a large number of unit pixels that modulate the phase or amplitude of incident light. When the array of unit pixels included in the diffractive optical element is miniaturized and the number of unit pixels is increased, the point images can be reproduced close together at high density. However, there is a limitation in arranging the point images close to each other at a high density because of the restrictions such as the amount of calculation in the computer. As a result, light and dark corresponding to the array of point images occur in the illuminated area, and the illuminated area cannot be illuminated with uniform brightness.

The present disclosure has been made in consideration of the above points, and an object thereof is to make brightness unevenness in an illuminated region inconspicuous.

A diffractive optical element according to the present disclosure comprises
A first element diffractive optical element having a plurality of unit pixels that modulate the phase or amplitude of incident light, and diffracting the incident light toward an illuminated region;
A second element diffractive optical element that has a plurality of unit pixels that modulate the phase or amplitude of the incident light and that diffracts the incident light toward the illuminated region;
The arrangement direction of the plurality of unit pixels in the first element diffractive optical element is not parallel to the arrangement direction of the plurality of unit pixels in the second element diffractive optical element.

In the diffractive optical element according to the present disclosure,
A plurality of unit pixels of the first element diffractive optical element are arranged in both a first direction and a second direction,
A plurality of unit pixels of the second element diffractive optical element are arranged in both a fourth direction and a fifth direction,
The first direction is non-parallel to the fourth direction and non-parallel to the fifth direction,
The second direction may be non-parallel to the fourth direction and non-parallel to the fifth direction.

In the diffractive optical element according to the present disclosure, the arrangement direction of the plurality of unit pixels in the first element diffractive optical element is larger than 22.5° with respect to the arrangement direction of the plurality of unit pixels in the second element diffractive optical element. It may be inclined at an angle smaller than 67.5.

In the diffractive optical element according to the present disclosure, the orientation of the first element diffractive optical element may be different from the orientation of the second element diffractive optical element.

In the diffractive optical element according to the present disclosure, the outer contour of the first element diffractive optical element may be different from the outer contour of the second element diffractive optical element.

In the diffractive optical element according to the present disclosure,
A plurality of the first element diffractive optical elements are provided in a certain region,
A plurality of the second element diffractive optical elements may be provided in another area different from the one area.

In the diffractive optical element according to the present disclosure,
The first element diffractive optical elements are regularly arranged in the one area,
The second element diffractive optical elements may be regularly arranged in the other one region.

A lighting device according to the present disclosure,
A coherent light source,
A shaping optical system that shapes the coherent light emitted from the coherent light source,
One of the diffractive optical elements according to the present disclosure described above, which includes a diffractive optical element that diffracts coherent light shaped by a shaping optical system.

The projection device according to the present disclosure is
A coherent light source,
A shaping optical system that shapes the coherent light emitted from the coherent light source,
Any of the diffractive optical elements according to the present disclosure described above, which diffracts coherent light shaped by a shaping optical system,
And a spatial light modulator which is disposed so as to overlap the illuminated area and which is illuminated by the coherent light diffracted by the diffractive optical element.

The projection display device according to the present disclosure is
Any one of the projection devices according to the present disclosure described above,
A screen onto which the modulated image obtained on the spatial light modulator is projected.

According to the present disclosure, it is possible to effectively make the uneven brightness in the illuminated area inconspicuous.

FIG. 1 is a diagram for explaining one embodiment and is a plan view showing an illumination device, a projection device, and a projection type display device. FIG. 2 is a plan view showing an example of the diffractive optical element included in the illumination device of FIG. FIG. 3A is a plan view showing an example of a first element diffractive optical element included in the diffractive optical element of FIG. 2. FIG. 3B is a plan view showing an example of a second element diffractive optical element used together with the first element diffractive optical element shown in FIG. 3A. FIG. 4 is a sectional view taken along line ZZ of FIGS. 3A and 3B. FIG. 5 is a flowchart showing an example of the processing procedure of the iterative Fourier transform method. FIG. 6A is a plan view showing an illuminated region illuminated by the first element diffractive optical element. FIG. 6B is a plan view showing an illuminated region illuminated by the second element diffractive optical element. FIG. 7 is a plan view showing an illuminated region illuminated by a diffractive optical element including a first element diffractive optical element and a second element diffractive optical element. FIG. 8A is a diagram for explaining a modification of the diffractive optical element and is a plan view showing the diffractive optical element. FIG. 8B is a plan view showing an example of the second element diffractive optical element included in the diffractive optical element of FIG. 8A. FIG. 9A is a diagram for explaining another modification of the diffractive optical element and is a plan view showing the diffractive optical element. FIG. 9B is a plan view showing an example of the second element diffractive optical element included in the diffractive optical element of FIG. 9A. FIG. 10 is a diagram for explaining still another modification of the diffractive optical element, and is a plan view showing the diffractive optical element. FIG. 11 is a diagram for explaining still another modification of the diffractive optical element, and is a plan view showing the diffractive optical element. FIG. 12 is a perspective view showing a modification of the lighting device. FIG. 13 is a perspective view showing another modification of the lighting device. FIG. 14 is a perspective view showing still another modified example of the lighting device.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In addition, in the drawings attached to the present specification, for convenience of illustration and understanding, the scale, the vertical and horizontal dimension ratios, etc. are appropriately changed and exaggerated from the actual ones.

Further, as used in the present specification, for specifying shapes and geometric conditions and their degrees, for example, terms such as “parallel”, “orthogonal”, “identical”, and values of length and angle are strictly It should be understood that the same function is included in a range that can be expected without being bound by any meaning.

1 to 14 are diagrams for explaining one embodiment and a modification example thereof. Among these, FIG. 1 is a plan view showing a lighting device. 2 to 5 are diagrams for explaining the diffractive optical element incorporated in the illumination device. Furthermore, FIG. 6A to FIG. 7 show a state in which the illuminated area LZ on the illuminated surface IP is illuminated using the illumination device.

The illumination device 20 according to the present embodiment includes a coherent light source 25, a shaping optical system 30 that shapes the coherent light emitted from the coherent light source 25, and a diffractive optical element 40 that diffracts the coherent light shaped by the shaping optical system 30. ,have. The illumination device 20 illuminates the illuminated area LZ on the illuminated surface IP by diffracting the coherent light by the diffractive optical element 40 and irradiating the illuminated surface IP with a plurality of unit images UI. In particular, the lighting device 20 according to the present embodiment is devised to illuminate the illuminated area LZ with uniform brightness. Hereinafter, the illumination device 20 according to the embodiment will be described with reference to the illustrated specific example.

In the example shown in FIG. 1, the lighting device 20 is applied to the projection display device 10 and the projection device 15. The illumination device 20 constitutes the projection device 15 together with the spatial light modulator 50. Further, the projection device 15 constitutes the projection type display device 10 together with the screen 12. That is, in the illustrated example, the illumination device 20 illuminates the incident surface of the spatial light modulator 50 as the illuminated area LZ. In this example, the illuminated region LZ can have, for example, a rectangular shape.

The spatial light modulator 50 is arranged in the illuminated region LZ. The spatial light modulator 50 is then illuminated by the illumination device 20 to form a modulated image. Preferably, the light from the illumination device 20 illuminates only the entire illuminated region LZ. The incident surface of the spatial light modulator 50 preferably has the same shape and size as the illuminated region LZ illuminated by the illumination device 20. In this case, the light from the illumination device 20 can be used with high utilization efficiency for generating a modulated image.

The spatial light modulator 50 is not particularly limited, and various known spatial light modulators can be used. For example, a digital mirror device (DMD), a transmissive liquid crystal microdisplay, or a reflective LCoS (Liquid Crystal On Silicon (registered trademark)) can be used as the spatial light modulator 50.

When the spatial light modulator 50 is a transmissive liquid crystal microdisplay as in the example shown in FIG. 1, the spatial light modulator 50 illuminated by the illumination device 20 in a planar manner causes coherent light for each pixel. Is selected and transmitted, a modulated image is formed on the screen of the display forming the spatial light modulator 50. The modulated image thus obtained is finally projected to the screen 12 by the projection optical system 13 with the same magnification or with a variable magnification. As a result, the modulated image is displayed on the screen 12 in the same size or in a scaled manner, and the observer can observe the image. The screen 12 may be a transmissive screen or a reflective screen.

Next, the lighting device 20 will be described. As described above, the illumination device 20 has the coherent light source 25, the shaping optical system 30, and the diffractive optical element 40. The illumination device 20 may further include a casing that houses the coherent light source 25, the shaping optical system 30, and the diffractive optical element 40.

The coherent light source 25 can emit coherent light having the same wavelength and phase. As the coherent light source 25, various types of light sources can be used. Typically, as the coherent light source 25, a laser light source that oscillates laser light can be used. As a specific example, the illustrated coherent light source 25 is configured as a semiconductor laser light source and is supported on, for example, a circuit board. In the example shown in FIG. 1, the coherent light source 25 includes a single light source. Therefore, in the illustrated example, the illuminated area LZ is illuminated with a color corresponding to the wavelength range of the coherent light emitted from the coherent light source 25.

However, the coherent light source 25 may include a plurality of coherent light sources 25, and the lights emitted from the respective coherent light sources 25 may be directed to the shaping optical system 30 and the diffractive optical element 40 after being superposed. Further, as in the modified example shown in FIG. 12, the coherent light emitted from each coherent light source 25 has shaping optical systems 30A, 30B, 30C and diffractive optical elements 40A, which are provided corresponding to the coherent light source 25. After passing through 40B and 40C, they may be superimposed on the illuminated region LZ after that. In such an example, the plurality of coherent light sources 25 included in the lighting device 20 may emit coherent light in the same wavelength range or may emit coherent light in different wavelength ranges. Good. Since the illuminating device 20 includes the plurality of coherent light sources 25 that emit light in the same wavelength range, the illuminated area IA can be illuminated brightly.

On the other hand, in the example shown in FIG. 12, the coherent light source 25 has a first coherent light source 25A, a second coherent light source 25B, and a third coherent light source 25C that emit coherent light in different wavelength ranges. The illumination color and brightness of the illuminated region LZ may be controlled by adjusting the emission of the coherent light from each of the coherent light sources 25A to 25C, more specifically, the start and stop of the emission and the emission output.

The shaping optical system 30 shapes the coherent light emitted from the coherent light source 25. In other words, the shaping optical system 30 shapes the shape of the cross section orthogonal to the optical axis of the coherent light and the three-dimensional shape of the light flux of the coherent light. Typically, the shaping optical system 30 expands the luminous flux cross-sectional area of the coherent light in a cross section orthogonal to the optical axis of the coherent light.

In the illustrated example, the shaping optical system 30 shapes the coherent light emitted from the coherent light source 25 into a widened parallel light flux. That is, the shaping optical system 30 functions as a collimating optical system. As shown in FIG. 1, the shaping optical system 30 has a first lens 31 and a second lens 32 in the order along the optical path of coherent light. The first lens 31 shapes the coherent light emitted from the coherent light source 25 into a divergent light beam. The second lens 32 reforms the divergent light flux generated by the first lens 31 into a parallel light flux. That is, the second lens 32 functions as a collimator lens.

From the viewpoint of improving the shaping accuracy of the shaping optical system 30, the shaping optical system 30 preferably includes at least one concave lens and at least one convex lens. In the example shown in FIG. 1, both the first lens 31 and the second lens 32 are configured as convex lenses, but either one of the first lens 31 and the second lens 32 may be a concave lens. Since the concave lens and the convex lens have powers of opposite positive and negative powers, the influences of mutual aberrations are alleviated. That is, by combining a concave lens and a convex lens, it is possible to mitigate the influence of the aberration generated in the lens. Thereby, the light can be projected onto the projected area with higher accuracy. Further, in the illustrated example, the shaping optical system 30 includes two lenses, but the present invention is not limited to this example, and may include three or more lenses.

Further, instead of the shaping optical system 30 including the concave lens and the convex lens, the shaping optical system 30 may include an aspherical lens. By using the aspherical lens including both the portion having the positive power and the portion having the negative power, the influence of the aberration generated in the lens can be mitigated. As a result, it becomes possible to project light with higher accuracy onto a desired region on the irradiation surface IP.

The lens included in the shaping optical system 30 preferably has a rectangular shape when observed from the optical axis direction of the lens. By trimming the unnecessary portion of the lens, it is possible to reduce the size and weight of the lighting device 20.

Next, the diffractive optical element 40 will be described. The diffractive optical element 40 is an element that exerts a diffracting action on the light emitted from the coherent light source 25. The diffractive optical element 40 diffracts the coherent light from the coherent light source 25 and directs it to the illuminated region LZ on the illuminated surface IP. Therefore, as shown in FIG. 1, the illuminated region LZ is illuminated by the diffracted light of the diffractive optical element 40.

As shown in FIG. 2, the diffractive optical element 40 has a plurality of element diffractive optical elements 41. The plurality of element diffractive optical elements 41 are arranged on the same plane, for example. Each element diffractive optical element 41 can exert a diffracting action on the coherent light emitted from the coherent light source 25. Each element diffractive optical element 41 diffracts the coherent light from the coherent light source 25 and directs it to the illuminated region LZ.

In the present embodiment, the diffractive optical element 40 includes a first element diffractive optical element 41A and a second element diffractive optical element 41B as each of the plurality of element diffractive optical elements 41. The first element diffractive optical element 41A and the second element diffractive optical element 41B have different diffractive structures. However, the first element diffractive optical element 41A and the second element diffractive optical element 41B diffract the coherent light from the coherent light source 25 and direct it to the same illuminated region LZ. Then, the coherent light diffracted by the first element diffractive optical element 41A and the coherent light diffracted by the second element diffractive optical element 41B overlap in the illuminated region LZ.

In the illustrated example, the first element diffractive optical element 41A irradiates the entire illuminated region LZ with diffracted light, and the second element diffractive optical element 41B similarly irradiates the entire illuminated region LZ with diffracted light. Further, in the example shown in FIG. 2, the diffractive optical element 40 includes a plurality of first element diffractive optical elements 41A and a plurality of second element diffractive optical elements 41B. The plurality of first element diffractive optical elements 41A are staggered, and the plurality of second element diffractive optical elements 41B are staggered. The first element diffractive optical element 41A and the second element diffractive optical element 41B are alternately arranged along the first direction d1 and the second direction d2 along the surface defined by the diffractive optical element 40. ..

In the illustrated example, each element diffractive optical element 41 has a quadrangular shape, more specifically, a square shape or a rectangular shape in plan view. In particular, the first element diffractive optical element 41A and the second element diffractive optical element 41B have the same shape in plan view. However, the orientation of the second element diffractive optical element 41B is the orientation obtained by rotating the first element diffractive optical element 41A by 45°. The corner portion of the second element diffractive optical element 41B is in contact with the linear edge portion of the adjacent first element diffractive optical element 41A.

In addition, in order to clarify the directional relationship between the drawings, in some drawings, the first direction d1, the second direction d2, the third direction d3, the fourth direction d4, and the fifth direction d5 are common to the drawings. It is shown as the direction to do. The first direction d1 and the second direction d2 are orthogonal to each other. The fourth direction d4 and the fifth direction d5 are orthogonal to each other. The third direction d3 is orthogonal to the first direction d1 and is orthogonal to the second direction d2. That is, the third direction d3 is orthogonal to the surface defined by the diffractive optical element 40. Further, the third direction d3 is orthogonal to the fourth direction d4 and is orthogonal to the fifth direction d5.

The element diffractive optical element 41 is typically a hologram element. By using a hologram element as the element diffractive optical element 41, it becomes easy to design the diffraction characteristics of the hologram element. Designing a hologram element capable of projecting coherent light only in the entire illuminated region LZ having a predetermined position, size, and shape can be relatively easily performed.

The illuminated area LZ is set, for example, in an angular space so as to have a predetermined size and shape at a predetermined position with respect to the element diffractive optical element 41. The position, size and shape of the illuminated area LZ depend on the diffraction characteristics of the element diffractive optical element 41, and by adjusting the diffraction characteristics of the element diffractive optical element 41, the position, size and shape of the illuminated area LZ. Can be adjusted arbitrarily. Therefore, when designing the element diffractive optical element 41, the position, size, and shape of the illuminated area LZ are first determined, and the element diffractive optical element 41 is arranged so that coherent light can be projected over the determined illuminated area LZ. The diffraction characteristics of the element 41 may be adjusted.

The element diffractive optical element 41 can be manufactured as a computer-generated hologram (CGH). A computer generated hologram is produced by calculating a structure having an arbitrary diffraction characteristic on a computer. Therefore, by producing the element diffractive optical element 41 using the computer-generated hologram, it is not necessary to generate the object light and the reference light using the coherent light source or the optical system, or to record the interference fringes on the hologram recording material by the exposure. Can be For example, as shown in FIG. 1, the illumination device 20 is assumed to illuminate the illuminated area LZ having a predetermined size and shape at a predetermined position with respect to the element diffractive optical element 41. By inputting the information about the illuminated region LZ to the computer as a parameter, it is possible to specify the structure for realizing the diffractive characteristic capable of illuminating the illuminated region LZ, for example, the uneven surface, by calculation by the computer. By forming the specified structure by, for example, resin molding, the element diffractive optical element 41 as a computer-generated hologram can be manufactured at low cost by a simple procedure.

As shown in FIGS. 6A to 7, the element diffractive optical element 41 of the diffractive optical element 40 diffracts the coherent light from the shaping optical system 30 to reproduce a plurality of unit images UI on the illuminated surface IP. The illuminated area LZ on the illuminated surface IP is illuminated by the aggregate of the plurality of unit images UI. The element diffractive optical element 41 is designed as follows. First, as shown in FIG. 6A, a point image pattern formed by arranging point images PI capable of irradiating coherent light by the element diffractive optical element 41 on the irradiation surface IP is set. Next, the shape of the illuminated area LZ is set on the illuminated surface IP. After that, the point image PI located in the illuminated region LZ is selected as the position where the coherent light should be actually emitted. The point image to be irradiated with the coherent light is spread or dispersed in the illuminated area LZ on the illuminated surface IP. The outer contour of the array pattern of the point images to be irradiated with the coherent light substantially matches the outer contour of the illuminated region LZ.

Next, the incident light to the element diffractive optical element 41 and the divergent light traveling from the point image to be irradiated with each coherent light toward the element diffractive optical element 41 are set. Here, the “incident light to the element diffractive optical element 41” is the light that enters the element diffractive optical element 41 from the shaping optical system 30 in a state where the element diffractive optical element 41 is incorporated in the illumination device 20. The light travels in the same optical path. The “divergent light traveling from each point image toward the element diffractive optical element 41 ”is diffracted light that is diffracted at each position of the element diffractive optical element 41 and travels toward each point image position when the illumination device 20 is actually used. The light travels in the opposite direction on the optical path of, and enters from the position of the point image to each position in the element diffractive optical element 41. After that, the interference pattern on the element diffractive optical element 41 formed by the incident light to the element diffractive optical element 41 and the divergent light traveling from each point image toward the element diffractive optical element 41 is specified, and it corresponds to this interference pattern. Create a fine structure. The calculation of the interference pattern can be executed by a computer, including model design of “incident light to the element diffractive optical element 41” and “divergent light from each point image toward the element diffractive optical element 41”.

The element diffractive optical element 41 may be a phase type diffractive optical element or an amplitude type diffractive optical element. Further, although the element diffractive optical element 41 is configured as a transmissive type in the example shown in FIG. 1, it may be configured as a reflective type. When the element diffractive optical element 41 is configured as a phase type diffractive optical element, the fine structure forming the element diffractive optical element 41 has a concavo-convex pattern structure in which the optical path length changes according to the incident position of the coherent light, or the A pattern structure having a different refractive index depending on the incident position can be adopted. The fine structure including the concavo-convex pattern is preferable because it can be mass-produced by resin molding using a photolithography technique. Further, when the element diffractive optical element 41 is configured as an amplitude type diffractive optical element, the fine structure forming the element diffractive optical element 41 can adopt a structure having different transmittance depending on the incident position of the coherent light. ..

Here, a specific example of the element diffractive optical element 41 will be further described with reference to FIGS. 3A, 3B, and 4. The element diffractive optical element 41 shown in FIGS. 3A, 3B and 4 is configured as a phase modulation type Fourier transform hologram. The phase modulation type Fourier transform hologram is a hologram having an uneven surface produced by recording the phase information of the Fourier transform image as a multi-valued depth on the medium, that is, the surface layer, and The optical image of the original image is reproduced from the reproduction light by utilizing the diffraction phenomenon based on it.

3A and 3B are plan views showing one element diffractive optical element 41, respectively. As a specific example, FIG. 3A shows one first element diffractive optical element 41A, and FIG. 3B shows one second element diffractive optical element 41B. These element diffractive optical elements 41 have a plurality of unit pixels 45. The unit pixel 45 is a minimum unit for adjusting the modulation amount that affects the incident light. In the illustrated phase type element diffractive optical element 41, the phase of incident light can be modulated by different amounts for each unit pixel 45. FIG. 4 shows an example of a cross section taken along line ZZ of FIG. 3A and an example of a cross section taken along line ZZ of FIG. 3B. In the element diffractive optical element 41 shown in FIG. 4, the unit pixel 45 is set to any of eight heights along the third direction d3. Therefore, in the illustrated element diffractive optical element 41, the amount of phase modulation applied to the incident light can be controlled in eight steps. However, the number of steps of the unit pixel 45 is not particularly limited.

In the element diffractive optical element 41 divided into a large number of unit pixels 45, the incident light to the element diffractive optical element 41 can be diffracted by giving a periodic structure to the large number of unit pixels 45. Assuming that the pitch of the periodic structure along the arrangement direction of the unit pixels 45 is P [nm] and the wavelength of the incident light is λ [nm], the element diffractive optical element 41 has a diffraction angle θ [rad. ], it is possible to bend the traveling direction of the incident light so that the position where the diffracted light proceeds shifts along the arrangement direction of the unit pixels 45.
Sin θ=λ/P

The minimum diffraction angle θ _min in the element diffractive optical element 41 is the case where the pitch of the periodic structure is equal to the length A [nm] of one side of the element diffractive optical element 41, specifically, Sin ^−1. (Λ/A) [rad]. On the other hand, considering that the element diffractive optical elements 41 are continuously arranged in parallel, the pitch of the periodic structure in the element diffractive optical element 41 is A/k [nm] using the natural number k. When the pitch of the periodic structure is A/k [nm], the diffraction angle θ _k is Sin ⁻¹ (k×λ/A) [rad]. Here, when “λ/A” is sufficiently small, the diffraction angle θ _k is k times the minimum diffraction angle θ _min . Therefore, when the element diffractive optical element 41 has a sufficient number of unit pixels 45 arranged in one direction, it becomes possible to change the diffraction angle in the same angular interval along one direction.

Here, in the example of the first element diffractive optical element 41A shown in FIG. 3A, the unit pixels 45 are arranged in the first direction d1 and also in the second direction d2. Due to the diffractive action of the first element diffractive optical element 41A, the traveling direction of the incident light is bent with respect to the traveling direction of the 0th-order light, and the incident position of the diffracted light is changed from the position where the 0th-order light should be incident to It can be shifted in each of the first direction d1 and the second direction d2. FIG. 6A is a plan view showing an array pattern of point images that can be illuminated by the first element diffractive optical element 41A shown in FIG. 3A in, for example, an angular space. In the example shown in FIG. 6A, the unit image UI is reproduced at the position of the point image PI located in the illuminated region LZ among the point images PI arranged in the first direction d1 and the second direction d2. ..

On the other hand, in the example of the second element diffractive optical element 41B shown in FIG. 3B, the unit pixels 45 are arranged in the fourth direction d4 which is non-parallel to the first direction d1 and the second direction d2, and the first direction d1. And arranged in a fifth direction d5 which is non-parallel to the second direction d2. Due to the diffractive action in the second element diffractive optical element 41B, the traveling direction of the incident light is bent with respect to the traveling direction of the 0th-order light, and the incident position of the diffracted light is changed from the position where the 0th-order light should be incident to It can be shifted in each of the four directions d4 and the fifth direction d5. FIG. 6B is a plan view showing an array pattern of point images that can be illuminated by the second element diffractive optical element 41B shown in FIG. 3B in, for example, an angular space. In the example shown in FIG. 6B, of the point images PI arranged in the fourth direction d4 and the fifth direction d5, the unit image UI is reproduced at the position of the point image PI located in the illuminated region LZ. ..

Further, as shown in FIG. 7, the illuminated area LZ illuminated with the diffracted light from the first element diffractive optical element 41A and the illuminated area LZ illuminated with the diffracted light from the second element diffractive optical element 41B are , Match. That is, the illuminated area LZ when designing the diffraction characteristics of the first element diffractive optical element 41A and the illuminated area LZ when designing the diffraction characteristics of the second element diffractive optical element 41B are, for example, in the same angular space. In the same position. As a result, the first element diffractive optical element 41A and the second element diffractive optical element 41B come to diffract incident light toward the same illuminated region LZ.

The length WA of one side of the element diffractive optical element 41 can be set to several μm to several mm. For example, the planar shape of the element diffractive optical element 41 may be a square of 2 mm square. The length WB of one side of the unit pixel 45 is preferably in the range of 10 nm or more and 10 μm or less, more preferably in the range of 50 nm or more and 5 μm or less, and further preferably in the range of 100 nm or more and 2 μm or less. Further, the uneven depth of the uneven structure forming the element diffractive optical element 41, that is, the maximum height difference HB in the third direction d3 is preferably in the range of 50 nm to 20 μm, and in the range of 80 nm to 15 μm. It is more preferably 100 nm or more and 10 μm or less.

For designing the element diffractive optical element 41, for example, an iterative Fourier transform method is used. FIG. 5 is a flowchart showing an example of the processing procedure of the iterative Fourier transform method. The processing procedure of FIG. 5 is performed using the diffraction image obtained on the irradiation surface IP as a Fraunhofer diffraction image.

First, the radiation intensity distribution of the incident light on the element diffractive optical element 41 is set and a random phase distribution is prepared (step ST1). Next, a complex amplitude distribution is generated by combining the radiation intensity distribution set in step ST1 and the random phase distribution (step ST2). Then, inverse Fourier transform (IFT) is applied to the obtained complex amplitude distribution to generate a complex amplitude distribution on the irradiation surface IP (step ST3).

The obtained complex amplitude distribution is calculated using a random phase distribution, and reflects the random phase distribution. Next, the real part of the complex amplitude distribution on the irradiated surface IP obtained in step ST3 is corrected based on the radiation intensity distribution to be obtained by the diffraction in the element diffractive optical element 41 (step ST4). After that, in step ST4, the real part-corrected complex amplitude distribution is subjected to Fourier transform to calculate the complex amplitude distribution on the element diffractive optical element 41 (step ST5). Next, the real part of the complex amplitude distribution on the element diffractive optical element 41 obtained in step ST5 is corrected based on the radiation intensity distribution of the incident light on the element diffractive optical element 41 set in step ST1 (step ST6). ).

Then, using the complex amplitude distribution generated in step ST6, the processing from step ST3 is repeated. As the processes of steps ST3 to ST6 are repeated, the real part of the complex amplitude distribution on the element diffractive optical element 41 approaches the radiation intensity distribution set in step ST1.

As described above, the structure of the element diffractive optical element 41 for realizing a desired diffraction characteristic can be designed. The diffractive optical element 40 includes a plurality of element diffractive optical elements 41. The plurality of element diffractive optical elements 41 may be designed to be the same, ignoring a slight difference in the arrangement position between the plurality of element diffractive optical elements 41, or between the plurality of element diffractive optical elements 41. The plurality of element diffractive optical elements 41 may be separately designed in consideration of the slight difference in the arrangement position in the above.

As described above, the element diffractive optical element 41 in the present embodiment includes the first element diffractive optical element 41A and the second element diffractive optical element 41B as each of the plurality of element diffractive optical elements 41. The first element diffractive optical element 41A and the second element diffractive optical element 41B have different diffractive structures. Specifically, the array direction of the point images PI that is the original image when designing the first element diffractive optical element 41A, and the array of the point image PI that is the original image when designing the second element diffractive optical element 41B. The directions and are not parallel. As a result, the arrangement directions d1 and d2 of the plurality of unit pixels 45 in the first element diffractive optical element 41A are not parallel to the arrangement directions d4 and d5 of the plurality of unit pixels 45 in the second element diffractive optical element 41B.

The arrangement directions d1 and d2 of the plurality of unit pixels 45 in the first element diffractive optical element 41A may be different from the arrangement directions d4 and d5 of the plurality of unit pixels 45 in the second element diffractive optical element 41B by 10° or more. Preferably, the difference is more than 22.5°, more preferably. 3A and 3B are particularly preferable. The arrangement directions d1 and d2 of the plurality of unit pixels 45 in the first element diffractive optical element 41A are the same as the arrangement directions d4 and d5 of the plurality of unit pixels 45 in the second element diffractive optical element 41B. Inclined by 45° with respect to.

In the illumination device 20 configured as described above, the coherent light emitted from the coherent light source 25 is shaped by the shaping optical system 30. In the illustrated example, the coherent light is shaped into a parallel light beam having an expanded light beam cross-sectional area. The coherent light shaped by the shaping optical system 30 enters the diffractive optical element 40. The coherent light is diffracted by the first element diffractive optical element 41A or the second element diffractive optical element 41B of the diffractive optical element 40 depending on the incident position.

The coherent light diffracted by the first element diffractive optical element 41A goes into the illuminated region LZ on the illuminated surface IP. The coherent light diffracted by the first element diffractive optical element 41A is projected at the position of the assumed point image PI in the illuminated region LZ on the illuminated surface IP to reproduce the unit image UI. Similarly, the coherent light diffracted by the second element diffractive optical element 41B goes into the illuminated region LZ on the illuminated surface IP. The coherent light diffracted by the second element diffractive optical element 41B is projected at the position of the assumed point image PI in the illuminated area LZ on the illuminated surface IP to reproduce the unit image UI. That is, in the illumination device 20 according to the present embodiment, the illuminated region LZ on the illuminated surface IP is illuminated in a predetermined pattern as a group of unit images UI.

In the example shown in FIG. 1, the illuminated region LZ is formed by the incident surface of the spatial light modulator 50. The spatial light modulator 50 irradiated with the coherent light by the illumination device 20 forms a modulated image. The modulated image is projected on the screen 12 via the projection optical system 13. An image observed by an observer is displayed on the screen 12.

By the way, the diffractive optical element has a plurality of unit pixels that modulate the phase or amplitude of incident light. Then, by increasing the length WA of one side of the element diffractive optical element 41, the point images PI, which are the original images of the unit images UI, can be arranged close to each other with high density. That is, it is possible to reproduce the unit images UI closely at high density. However, there is a limitation in arranging the point images PI that can be illuminated by the unit pixels 45 in close proximity to each other at a high density due to restrictions such as the amount of calculation in a computer and the device size. As a result, in the conventional illumination device, light and dark depending on the arrangement of the unit images may be visually recognized in the illuminated area.

In order to deal with such a problem, in the diffractive optical element 40 included in the illumination device 20 of the present embodiment, the arrangement directions d1 and d2 of the plurality of unit pixels 45 in the first element diffractive optical element 41A are the second element. The diffractive optical element 41B is not parallel to the arrangement directions d4 and d5 of the plurality of unit pixels 45, and is particularly inclined. Therefore, the array direction of the point images PI that can be illuminated by the first element diffractive optical element 41A is non-parallel to the array direction of the point images PI that can be illuminated by the second element diffractive optical element 41B. As a result, when the same illuminated area LZ is illuminated using the diffracted light from the first element diffractive optical element 41A and the second element diffractive optical element 41B, the illuminated area LZ is illuminated with more uniform brightness. The uneven brightness can be made inconspicuous.

More specifically, as shown in FIG. 7, the arrangement direction of the unit image UI reproduced by the diffracted light from the first element diffractive optical element 41A is reproduced by the diffracted light from the second element diffractive optical element 41B. The unit image UI is not parallel to the arrangement direction of the unit image UI and is inclined. Therefore, in the illuminated region LZ, the position of the unit image UI reproduced by the diffracted light from the first element diffractive optical element 41A and the position of the unit image UI reproduced by the diffracted light from the second element diffractive optical element 41B. The position easily shifts in the illuminated area LZ. For example, the length WA of one side of the element diffractive optical element 41 and the length WB of one side of the unit pixel 45 match between the first element diffractive optical element 41A and the second element diffractive optical element 41B. In this case, the position of the unit image UI formed by the first element diffractive optical element 41A and the position of the unit image UI formed by the second element diffractive optical element 41B are displaced at least partially due to the difference in the arrangement direction of the unit pixels 45. .. As a result, when the same number of element diffractive optical elements 41 are used, it is possible to reproduce the unit image UI in a larger area of the illuminated area LZ, and the uneven brightness in the illuminated area LZ can be effectively prevented. You can make it inconspicuous.

The arrangement directions d1 and d2 of the unit pixels 45 in the first element diffractive optical element 41A are inclined by 45° with respect to the arrangement directions d4 and d5 of the unit pixels 45 in the second element diffractive optical element 41B. Is highly preferred. Further, the arrangement directions d1 and d2 of the unit pixels 45 in the first element diffractive optical element 41A are larger than 22.5° with respect to the arrangement directions d4 and d5 of the unit pixels 45 in the second element diffractive optical element 41B. It can be said that the inclination is smaller than 67.5°, which is an advantageous condition. Although it depends on the length WA of one side of the first element diffractive optical element 41A and the second element diffractive optical element 41B and the length WB of one side of the unit pixel 45, as described above, the first element diffractive optical element 41A and the second element diffractive optical element 41A By adjusting the arrangement direction of the unit pixels 45 between the element diffractive optical elements 41B, the position of the unit image UI by the first element diffractive optical element 41A and the position of the unit image UI by the second element diffractive optical element 41B are displaced. This makes it easier to make the uneven brightness in the illuminated region LZ inconspicuous effectively.

As described above, the diffractive optical element 40 in the present embodiment has the plurality of unit pixels 45 that change the phase or amplitude of the incident light, and diffracts the incident light toward the illuminated region LZ. The element diffractive optical element 41A and the second element diffractive optical element 41B having a plurality of unit pixels 45 for varying the phase or amplitude of the incident light and diffracting the incident light toward the illuminated region LZ are included. .. The arrangement directions d1 and d2 of the unit pixels 45 in the first element diffractive optical element 41A are not parallel to the arrangement directions d4 and d5 of the unit pixels 45 in the second element diffractive optical element 41B. According to the present embodiment as described above, the position of the unit image UI diffracted by the first element diffractive optical element 41A and applied to the illuminated area LZ and the diffracted by the second element diffractive optical element 41B. The position of the unit image UI irradiated in the illuminated area LZ can be shifted. Therefore, the illuminated region LZ can be illuminated by a larger number of unit images UI. As a result, it is possible to illuminate the illuminated area LZ with more uniform brightness and make the uneven brightness in the illuminated area LZ less noticeable.

An illumination device using a coherent light source such as laser light has a problem of speckle generation. Speckle is a speckled pattern that appears when a scattering surface is irradiated with coherent light such as laser light, and is observed as speckled brightness unevenness (brightness unevenness), which is observed by an observer. It becomes a factor that exerts a negative influence. According to the present embodiment, the coherent light diffracted by the first element diffractive optical element 41A and the coherent light diffracted by the second element diffractive optical element 41B overlap with each other in the illuminated region LZ, so that speckles are conspicuous. It is possible to eliminate it.

In one specific example of the embodiment described above, the orientation of the first element diffractive optical element 41A is different from the orientation of the second element diffractive optical element 41B. For example, the first element diffractive optical element 41A and the second element diffractive optical element 41B may have the same outer contour. According to such a specific example, by using the diffractive optical element 40 having a simple structure, it is possible to effectively make the uneven brightness in the illuminated region LZ inconspicuous.

Although one embodiment has been described with a plurality of specific examples, these specific examples are not intended to limit the one embodiment. The above-described embodiment can be implemented in various other specific examples, and various omissions, replacements, changes, and additions can be made without departing from the spirit of the invention.

Hereinafter, an example of the modification will be described with reference to the drawings. In the following description and the drawings used in the following description, for portions that may be configured in the same manner as the above-described specific example, the same reference numerals as those used for the corresponding portions in the above-described specific example are used, and overlapping description is given. Is omitted.

For example, in the above-described specific example, the example in which the first element diffractive optical element 41A and the second element diffractive optical element 41B have the same outer contour has been shown, but the present invention is not limited to this example. As shown in FIG. 8A, the outer contour of the first element diffractive optical element 41A may be different from the outer contour of the second element diffractive optical element 41B. In the example shown in FIG. 8A, the first element diffractive optical element 41A has a square shape or a rectangular shape. On the other hand, as shown in FIGS. 8A and 8B, the second element diffractive optical element 41B has an outer contour in which four corners of a square shape or a rectangular shape are removed. In this example, the second element diffractive optical element 41B has an octagonal outer contour. In FIG. 8B, the outer contour of the first element diffractive optical element 41A is shown by a chain double-dashed line, overlapping the second element diffractive optical element 41B. As shown in FIG. 8B, the second element diffractive optical element 41B has an outer contour that is inscribed in the outer contour of the first element diffractive optical element 41A. As a result, as shown in FIG. 8A, the first element diffractive optical element 41A and the second element diffractive optical element 41B can be arranged at a high density, and the diffractive optical element 40 can be downsized. The second element diffractive optical element 41B shown in FIG. 8B can be manufactured by cutting the four corners of the second element diffractive optical element 41B shown in FIG. 3B.

Further, as shown in FIGS. 9A and 9B, the one-element diffractive optical element 41A and the second-element diffractive optical element 41B may have the same outer contour and the same direction. According to the first element diffractive optical element 41A and the second element diffractive optical element 41B having the same outer contour and the same orientation, as shown in FIGS. 9A and 9B, the first element diffractive optical element 41A and The second element diffractive optical elements 41B can be arranged at a high density, and the diffractive optical element 40 can be downsized.

Further, in the above-mentioned specific example, the example in which the first element diffractive optical element 41A and the second element diffractive optical element 41B are arranged in a mixed manner is shown, but the present invention is not limited to this example. In the example shown in FIG. 10, the diffractive optical element 40 includes a first area A1 and a second area A2. The first area A1 and the second area A2 do not overlap. Although the first area A1 and the second area A2 are in contact with each other in the illustrated example, the present invention is not limited to this example, and the first area A1 and the second area A2 may be separated from each other.

A plurality of first element diffractive optical elements 41A are arranged in the first area A1. The plurality of first element diffractive optical elements 41A have the same outer contour. Therefore, the plurality of first element diffractive optical elements 41A can be regularly arranged in the first region A1 and arranged at a high density. Typically, the plurality of first element diffractive optical elements 41A can be spread adjacent to each other in the first region A1 without a gap. Similarly, a plurality of second element diffractive optical elements 41B are arranged in the second area A2. The plurality of second element diffractive optical elements 41B have the same outer contour. Therefore, the plurality of second element diffractive optical elements 41B can be regularly arranged in the second region A2 and arranged at a high density. Typically, the plurality of second element diffractive optical elements 41B can be spread adjacent to each other in the second area A2 without a gap. As a result, as shown in FIG. 10, the first element diffractive optical element 41A and the second element diffractive optical element 41B can be arranged at a high density, and the diffractive optical element 40 can be downsized.

In the specific example described above, the diffractive optical element 40 includes the first element diffractive optical element 41A and the second element diffractive optical element 41B. However, as shown in FIG. You may make it further have the 3rd element diffractive optical element 41C which has the some unit pixel 45 which modulates the phase or amplitude of incident light, and diffracts incident light toward the to-be-illuminated area LZ. In this example, the arrangement direction of the plurality of unit pixels 45 in the third element diffractive optical element is not parallel to at least one of the arrangement directions d1 and d2 of the plurality of unit pixels 45 in the first element diffractive optical element 41A, and , May be non-parallel to at least one of the arrangement directions d4 and d5 of the plurality of unit pixels 45 in the second element diffractive optical element 41B. According to this example, the unevenness of the brightness in the illuminated region LZ can be made more inconspicuous by superimposing the unit images UI from the first to third element diffractive optical elements.

Furthermore, as one specific example described above, an example in which the illuminated region LZ has a rectangular shape has been shown, but the present invention is not limited to this example. The illuminated area LZ may include a pattern representing one or more of a character, a picture, a color pattern, a symbol, a mark, an illustration, a character, and a pictogram. By using the element diffractive optical element 41, the shape of the illuminated region LZ can be changed with a high degree of freedom. As a result, various effect effects can be realized.

Further, an example in which the spatial light modulator 50 is arranged so as to overlap the illuminated region LZ has been shown, but the present invention is not limited to this example. The illumination device 20 may reproduce the unit image UI on the screen 12 directly or via the projection optical system. That is, in this example, the screen 12 is provided on the irradiation surface IP. Further, as another example, as shown in FIG. 13, the shaping optical system 30 may illuminate the illuminated region LZ on the road surface with the road surface as the illuminated surface IP. Alternatively, the illumination device 20 illuminates the illuminated area LZ on the illuminated surface IP by using the ground other than the road surface, the structure such as a building, the water surface such as the lake surface or the sea surface as the illuminated surface IP. Good.

Further, as shown in FIG. 14, the lighting device 20 may be configured as a portable device. The lighting device 20 shown in FIG. 14 has a cylindrical outer shape and can be held with one hand. The lighting device 20 has a casing 21. The coherent light source 25, the shaping optical system 30, and the diffractive optical element 40 are held by the casing 21. The diffractive optical element 40 forms a coherent light emission surface and is held on the end surface of the casing 21. The coherent light source 25 and the shaping optical system 30 are housed in the casing 21 together with a power source (not shown) and the like. A switch 22 for controlling the lighting device 20 is provided on the outer surface of the casing 21.

10 Projection Display Device 12 Screen 13 Projection Optical System 15 Projection Device 20 Illumination Device 21 Casing 22 Switch 25 Coherent Light Source 25A First Coherent Light Source 25B Second Coherent Light Source 25C Third Coherent Light Source 30 Shaping Optical System 31 First Lens 32 Second Lens 40 Diffractive optical element 41 Element diffractive optical element 41A First element diffractive optical element 41B Second element diffractive optical element 45 Unit pixel 50 Spatial light modulator UI Unit image PI Point image IP Illuminated surface LZ Illuminated area d1 First direction d2 second direction d3 third direction d4 fourth direction d5 fifth direction

Claims (9)

A first element diffractive optical element having a plurality of unit pixels that modulate the phase or amplitude of incident light, and diffracting the incident light toward an illuminated region;
A second element diffractive optical element that has a plurality of unit pixels that modulate the phase or amplitude of the incident light and that diffracts the incident light toward the illuminated region;
The diffractive optical element, wherein the arrangement direction of the plurality of unit pixels in the first element diffractive optical element is non-parallel to the arrangement direction of the plurality of unit pixels in the second element diffractive optical element. The arrangement direction of the plurality of unit pixels in the first element diffractive optical element is inclined by an angle larger than 22.5° and smaller than 67.5 with respect to the arrangement direction of the plurality of unit pixels in the second element diffractive optical element. The diffractive optical element according to claim 1, wherein The diffractive optical element according to claim 1, wherein the orientation of the first element diffractive optical element is different from the orientation of the second element diffractive optical element. The diffractive optical element according to claim 1, wherein an outer contour of the first element diffractive optical element is different from an outer contour of the second element diffractive optical element. A plurality of the first element diffractive optical elements are provided in a certain region,
The diffractive optical element according to any one of claims 1 to 4, wherein a plurality of the second element diffractive optical elements are provided in another area different from the one area. The first element diffractive optical elements are regularly arranged in the one area,
The diffractive optical element according to claim 5, wherein the second element diffractive optical elements are regularly arranged in the other one region. A coherent light source,
A shaping optical system that shapes the coherent light emitted from the coherent light source,
An illumination device comprising: the diffractive optical element according to claim 1, further comprising: a diffractive optical element that diffracts coherent light shaped by a shaping optical system. A coherent light source,
A shaping optical system that shapes the coherent light emitted from the coherent light source,
The diffractive optical element according to claim 1, wherein the diffractive optical element diffracts coherent light shaped by a shaping optical system,
A spatial light modulator which is disposed so as to overlap the illuminated area and which is illuminated by the coherent light diffracted by the diffractive optical element. A projection device according to claim 8;
A projection type display device, comprising: a screen onto which a modulated image obtained on the spatial light modulator is projected.

Images