Lighting device
The lighting device uses a diffractive optical element and controlled optical elements to enhance image resolution and sharpness by managing light rays at the cellular level, forming high-resolution images with clear outlines.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- STANLEY ELECTRIC CO LTD
- Filing Date
- 2024-10-16
- Publication Date
- 2026-04-28
AI Technical Summary
Existing lighting devices using diffractive optical elements and optical elements form images with low resolution and blurred outlines.
A lighting device comprising a diffractive optical element that converts laser light into a group of rays corresponding to dot patterns, and an optical element such as a transmissive liquid crystal element, DMD, or reflective liquid crystal element that blocks or reflects light rays based on control, ensuring one or fewer rays incident on each cell, to form high-resolution images with sharp contours.
The device achieves high-resolution images with sharp contours on the projection surface by controlling light transmission or reflection at the cellular level.
Smart Images
Figure 2026070539000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a lighting device.
Background Art
[0002] There is known a lighting device (for example, a projector) that uses a plurality of light sources that emit lights having different wavelengths from each other such as RGB light sources, combines the lights emitted from each light source by a dichroic mirror, and then diffuses the combined light by a homogenizer to form an image by an optical modulation element such as a liquid crystal on silicon (LCOS) (see, for example, Non-Patent Document 1).
[0003] In contrast, the present inventors have considered forming an image composed of a plurality of dot patterns by using a diffractive optical element that receives laser light having a wavelength in the visible range and converts the laser light into a group of light rays corresponding to a dot pattern group projected onto a projection surface, and an optical element such as a liquid crystal element including a plurality of cells that can be switched between an on state and an off state according to control from a control device.
Prior Art Documents
Patent Documents
[0004]
Non-Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, the inventors' investigations revealed that when using the above-mentioned diffractive optical element and optical element to form an image composed of multiple dot patterns, the resolution of the image formed on the projection surface is low and the outline may be blurred.
[0006] This disclosure is made to solve these problems and aims to provide an illumination device that can form an image with high resolution and sharp contours on the projection surface. [Means for solving the problem]
[0007] The illumination device according to this disclosure includes a diffractive optical element that receives laser light of a visible wavelength and converts the laser light into a group of rays corresponding to a group of dot patterns projected onto a projection surface, and an optical element disposed between the diffractive optical element and the projection surface, which forms an image on the projection surface by blocking at least a portion of the group of rays converted by the diffractive optical element, wherein the optical element includes a plurality of cells that are switched on or off according to control from a control device, and one or fewer rays constituting the group of rays are incident on each of the plurality of cells.
[0008] This configuration makes it possible to realize a lighting device that can form a high-resolution image with sharp contours on the projection surface.
[0009] In the above-described lighting device, the optical element is a transmissive liquid crystal element including a plurality of cells that can be switched on or off according to control from a control device, wherein one or fewer light rays incident on an on cell are transmitted through the cell, and one or fewer light rays incident on an off cell are not transmitted through the cell and are blocked.
[0010] Furthermore, in the above-described lighting device, the optical element is a DMD including a plurality of micromirrors that can be switched on or off according to control from a control device, wherein the 1 or less light rays incident on the on-state micromirrors are reflected in the direction of the projection plane, and the 1 or less light rays incident on the off-state micromirrors are reflected in a direction other than the projection plane.
[0011] Furthermore, in the above-described lighting device, the optical element is a reflective liquid crystal element including a plurality of cells that are switched on or off according to control from a control device, wherein the 1 or less light rays incident on the cells in the on state are reflected in the direction of the projection plane, and the 1 or less light rays incident on the cells in the off state are reflected in a direction other than the projection plane. [Effects of the Invention]
[0012] This disclosure provides an illumination device that can form an image with high resolution and sharp contours on the projection surface. [Brief explanation of the drawing]
[0013] [Figure 1] This is a schematic diagram of the lighting device 10. [Figure 2] (a) An enlarged view of the diffractive optical element 50 in Figure 1, seen from the direction of arrow AR1, and (b) A cross-sectional view of AA in Figure 2(a). [Figure 3] This is an example of a group of dot patterns DP projected onto a projection surface S. [Figure 4] (a) and (b) are diagrams showing how one or fewer rays R constituting the Ray 2 group are incident on each of multiple cells C, and (c) is an example of an image formed on the projection plane S when one or fewer rays R constituting the Ray 2 group are incident on each of multiple cells C (simulation result). [Figure 5](a) Diagram showing the state where more than one ray R that constitutes the ray group Ray2 is incident on each of the plurality of cells C, and (b) An example (simulation result) of an image formed on the projection surface S when more than one ray R that constitutes the ray group Ray2 is incident on each of the plurality of cells C. [Figure 6] It is a schematic configuration diagram of the lighting device 10A which is Modification 1.
Embodiments for Carrying Out the Invention
[0014] Hereinafter, the lighting device 10 (image forming device) which is an embodiment of the present disclosure will be described with reference to the accompanying drawings. The same reference numerals are assigned to corresponding components in each figure, and overlapping descriptions are omitted.
[0015] FIG. 1 is a schematic configuration diagram of the lighting device 10.
[0016] As shown in FIG. 1, the lighting device 10 includes a laser light source 20 that emits laser light Ray1 having a wavelength in the visible range, a lens 30, a diffractive optical element 50 (DOE: Diffractive Optical Element), and an optical element 60 that forms an image on the projection surface S by blocking at least a part of the ray group Ray2 converted by the diffractive optical element 50 (for example, reflection, absorption), and a control device 70.
[0017] The laser light source 20 is, for example, a laser light source that emits green laser light. The laser light Ray1 emitted by the laser light source 20 is transmitted through the lens 30 (collimating lens) and converted into parallel light, and then enters the diffractive optical element 50. The beam diameter of the laser light Ray1 incident on the diffractive optical element 50 is, for example, about 3 mm.
[0018] FIG. 2(a) is an enlarged arrow view of the diffractive optical element 50 in FIG. 1 as viewed from the direction of the arrow AR1, and FIG. 2(b) is a cross-sectional view taken along the line A-A of FIG. 2(a). Note that the cross-sectional view taken along the line B-B of FIG. 2(a) is the same as the cross-sectional view taken along the line A-A.
[0019] The diffractive optical element 50 includes a microlens array, receives the laser beam Ray1 emitted from the laser light source 20, and converts or branches (diffracts) the laser beam Ray1 into a group of light rays Ray2 corresponding to a dot pattern group projected onto the projection surface S. That is, the diffractive optical element 50 diffracts and splits the incident laser beam Ray1 in the vertical, horizontal, and lateral directions. The group of light rays Ray2 becomes a bundle of light beams having multiple directions. As the diffractive optical element 50, for example, the product named "ardisia" by scivax may be used. Also, as the diffractive optical element 50, for example, those described in Japanese Patent No. 7061823 may be used. Without being limited thereto, the diffractive optical element 50 may have any configuration as long as it receives a laser beam and converts (diffracts) the laser beam into a group of light rays corresponding to a dot pattern group projected onto the projection surface S. For example, a general diffraction grating having a groove structure may be used.
[0020] As shown in FIGS. 2(a) and 2(b), the microlens array of the diffractive optical element 50 includes a plurality of lenses 51 two-dimensionally arranged in the XY direction. FIGS. 2(a) and 2(b) show an example in which the lenses 51 are provided on the incident side of the diffractive optical element 50 (the incident side of the laser beam Ray1), but the present invention is not limited thereto. The lens 51 may be provided on at least one of the incident side and the exit side of the diffractive optical element 50 (the incident side of the laser beam Ray1 and the exit side of the laser beam Ray1).
[0021] FIG. 3 shows an example of a dot pattern DP group projected onto the projection surface S.
[0022] The dot pattern DP is, for example, circular (see FIG. 3), but is not limited thereto, and may be rectangular or have other shapes.
[0023] Note that if the pitch P of the lenses 51 (see FIG. 2(b)) becomes too small compared to the wavelength λ of the laser beam emitted from the laser light source 20, diffraction becomes difficult to occur. Therefore, as long as the lenses 51 sufficient to cause diffraction within the light distribution angle of the laser beam are included, the pitch P is preferably sufficiently larger than the wavelength λ of the laser beam, for example, 5 times or more, preferably 10 times or more.
[0024] The pitch P of lens 51 is, for example, 10 μm, and the height H is, for example, 7 μm. The diffractive optical element 50 may be a transmissive diffractive optical element (DOE) or a reflective diffractive optical element (DOE). The material of the transmissive diffractive optical element 50 is, for example, polydimethylsiloxane (PDMS) with a refractive index of 1.53, but other materials such as acrylic or polycarbonate may be used as long as they are light-transmitting materials with a refractive index greater than 1.0. On the other hand, the material of the reflective diffractive optical element 50 may be a metallic material.
[0025] The optical element 60 is positioned between the diffractive optical element 50 and the projection surface S, and forms an image on the projection surface S by blocking at least a portion of the Ray 2 light group converted by the diffractive optical element 50. For example, the optical element 60 is a transmissive liquid crystal element that includes a plurality of cells C (pixels) which are individually switched on or off according to control from the control device 70. The plurality of cells C may be, for example, 256 × 256 cells. For example, the size of one cell may be 400 μm × 400 μm. As shown in Figure 4(a) or Figure 4(b), one or fewer rays R constituting the Ray 2 group are incident on each of the multiple cells C. Figures 4(a) and 4(b) illustrate how one or fewer rays R constituting the Ray 2 group are incident on each of the multiple cells C. This is achieved by designing the diffractive optical element 50 and the optical element 60 so that one or fewer rays R constituting the Ray 2 group are incident on each of the multiple cells C. Alternatively, this can be achieved by setting the distance L1 (see Figure 1) between the diffractive optical element 50 and the optical element 60 (transmissive liquid crystal element) so that one or fewer rays R constituting the Ray 2 group are incident on each of the multiple cells C. Furthermore, in the case of Figure 4(a), one ray R is incident on one of the three cells C arranged vertically or horizontally, and one ray R is incident across the remaining two cells C. In Figure 4(b), one ray R is incident on each of the two cells C arranged vertically or horizontally, while no ray R is incident on the central cell C. In Figure 4(a), by looking at the setting of two rays R spanning two cells C, it can be defined that one or fewer rays R constituting the Ray2 ray group are incident on each of the two adjacent cells C, and it can also be defined that two or fewer rays R constituting the Ray2 ray group are incident on each of the three adjacent cells C. In Figure 4(b), by looking at the fact that one ray R is incident on either of the two adjacent cells C, it can be defined that one or fewer rays R constituting the Ray2 ray group are incident on each of the two adjacent cells C, and it can also be defined that two or fewer rays R constituting the Ray2 ray group are incident on each of the three adjacent cells C. For example, the beam diameter of ray R is 100 μm.
[0026] In this disclosure, "one or fewer rays R constituting the ray group Ray2 are incident on each of several cells C" includes at least one of the following cases: when one ray R is incident on one cell C (see Figures 4(a) and 4(b)), when one ray R is incident across multiple cells C (see Figure 4(a)), or when no ray R is incident on one cell C. Rays incident on an ON cell C (e.g., one or fewer rays R) are transmitted through the cell. On the other hand, rays incident on an OFF cell C (e.g., one or fewer rays R) are not transmitted through the cell C but are blocked (reflected or absorbed).
[0027] Figure 4(c) shows an example of an image (simulation result) formed on the projection plane S when one or fewer rays R constituting the ray group Ray2 are incident on each of multiple cells C. The downward-pointing arrow image in Figure 4(c) is composed of multiple green dot patterns. The distance L1 (see Figure 1) between the diffractive optical element 50 and the optical element 60 (transmissive liquid crystal element) is 100 mm. The vertical and horizontal axes in Figure 4(c) represent distance [m].
[0028] The effect of the case where one or fewer rays R, which constitute the ray group Ray2, are incident on each of the multiple cells C as described above will be explained using a comparative example.
[0029] In the comparative example, the distance L1 (see Figure 1) between the diffractive optical element 50 and the optical element 60 (transmissive liquid crystal element) is 50 mm. All other conditions are the same as in the embodiment described above. In the comparative example, as shown in Figure 5(a), more than one ray R constituting the ray group Ray2 is incident on each of the multiple cells C. Figure 5(a) is a diagram showing the situation in which more than one ray R constituting the ray group Ray2 is incident on each of the multiple cells C.
[0030] Figure 5(b) shows an example of an image (simulation result) formed on the projection plane S when more than one ray R constituting the Ray group Ray2 is incident on each of multiple cells C. The downward-pointing arrow image in Figure 5(b) is composed of multiple green dots. The vertical and horizontal axes in Figure 5(b) represent distance [m].
[0031] In the comparative example, that is, when more than one ray R constituting the Ray group Ray2 is incident on each of the multiple cells C (see Figure 5(a)), it can be seen that the resolution of the image formed on the projection plane S (here, the downward-pointing arrow image) is low and the outline is blurred (see Figure 5(b)).
[0032] In contrast, in the embodiment, that is, when one or fewer rays R constituting the ray group Ray2 are incident on each of the multiple cells C (see Figures 4(a) and 4(b)), it can be seen that the image formed on the projection plane S (here, the downward-pointing arrow image) has high resolution and a sharp outline (see Figure 4(c)).
[0033] As described above, by having one or fewer rays R that constitute the Ray2 group incident on each of the multiple cells C, a high-resolution image with sharp contours can be formed on the projection surface S.
[0034] As described above, according to this embodiment, it is possible to form an image with high resolution and sharp contours on the projection surface S.
[0035] Next, I will explain some variations.
[0036] Figure 6 is a schematic diagram of the lighting device 10A, which is a modified example 1.
[0037] In the above embodiment, an example was described in which a transmissive liquid crystal element including a plurality of cells C (pixels) that can be switched on or off according to control from the control device 70 is used as the optical element 60, but the invention is not limited to this.
[0038] For example, as shown in Figure 6, a Digital Mirror Device (DMD) including a plurality of micromirrors (not shown) that can be individually switched on (on position) or off (off position) according to control from a control device 70 may be used as the optical element 60. Light rays incident on the on-state micromirrors (e.g., light rays R 1 or less above) are reflected in the direction of the projection plane S. On the other hand, light rays incident on the off-state micromirrors (e.g., light rays R 1 or less above) are reflected in directions other than the projection plane S.
[0039] In this manner, by using a DMD as the optical element 60, and by having one or fewer rays R constituting the ray group Ray2 incident on each of the multiple cells (micromirrors) as in the above embodiment, a high-resolution image with a sharp outline can be formed on the projection surface S.
[0040] Furthermore, the optical element 60 may be a reflective liquid crystal element including a plurality of cells (not shown) that can be individually switched on or off according to control from the control device 70. Light rays incident on an on-state cell (for example, light rays R 1 or less above) are reflected in the direction of the projection plane S. On the other hand, light rays incident on an off-state cell (for example, light rays R 1 or less above) are reflected in a direction other than the projection plane S.
[0041] By using a reflective liquid crystal element as the optical element 60 in this way, and by having one or fewer rays R constituting the ray group Ray2 incident on each of the multiple cells, as in the above embodiment, a high-resolution image with a sharp outline can be formed on the projection surface S.
[0042] All the numerical values shown in the above embodiments are examples only, and it goes without saying that other appropriate numerical values can be used.
[0043] The embodiments described above are in all respects merely illustrative. The description of the embodiments above should not be construed as limiting the disclosure. The disclosure can be implemented in a variety of other ways without departing from its spirit or main features. [Explanation of Symbols]
[0044] 10, 10A…Lighting device 20…Laser light source 30... Lens 50…Diffractive optical elements 51... Lens 60…Optical elements 70...Control device C...Cell DP... Dot Pattern P...Pitch R...light ray Ray1…Laser light Ray2…ray group S…Projection surface
Claims
1. A diffractive optical element that receives laser light in the visible wavelength range and converts the laser light into a group of rays corresponding to a group of dot patterns projected onto a projection surface, The optical element comprises an optical element disposed between the diffractive optical element and the projection surface, which forms an image on the projection surface by blocking at least a portion of the group of light rays converted by the diffractive optical element, The optical element includes a plurality of cells that are switched on or off according to control from a control device. An illumination device in which one or fewer light rays constituting the light ray group are incident on each of the multiple cells.
2. The optical element is a transmissive liquid crystal element that includes multiple cells which are switched on or off according to control from a control device. The light rays, one or less in number, that enter the cell in the ON state pass through the cell. The lighting device according to claim 1, wherein the light rays 1 or less incident on the cell in the off state do not pass through the cell and are shielded.
3. The optical element is a DMD that includes a plurality of micromirrors that are switched on or off according to control from a control device. The light rays 1 or less that enter the ON-state micromirror are reflected in the direction of the projection surface. The lighting device according to claim 1, wherein light rays 1 or less incident on the micromirror in the off state are reflected in a direction other than the projection surface.
4. The optical element is a reflective liquid crystal element that includes multiple cells which are switched on or off according to control from a control device. The light rays 1 or less that enter the cell in the ON state are reflected in the direction of the projection surface. The lighting device according to claim 1, wherein the light rays 1 or less incident on the cell in the off state are reflected in a direction other than the projection plane.