Illumination device

Abstract

To provide an illumination device in which the ratio between the size of a dot pattern and the interval between dot patterns does not change depending on the distance from a diffractive optical element.SOLUTION: An illumination device 10 includes: a diffractive optical element 50 for receiving laser light having a wavelength in a visible range and converting the laser light into a group of light rays corresponding to a group of dot patterns projected onto a projection surface; and an optical element 20 for diffusing the laser light incident on the diffractive optical element so that the ratio between the size of each dot pattern and the interval between the dot patterns does not change depending on the distance from the diffractive optical element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a lighting device. [Background technology]

[0002] There is known an illumination device (e.g., a projector) that uses multiple light sources that emit light of different wavelengths, such as RGB light sources, combines the light emitted by each light source using a dichroic mirror, then diffuses it using a homogenizer, and forms an image using a light modulation element such as LCOS (Liquid Crystal On Silicon) (see, for example, Non-Patent Document 1).

[0003] In response to this, the inventors considered forming an image composed of multiple dot patterns using a diffractive optical element that receives laser light with a wavelength in the visible range and converts the laser light into a group of rays corresponding to a group of dot patterns to be projected onto a projection surface. [Prior art documents] [Patent documents]

[0004] [Non-Patent Document 1] Optical Technology Information Magazine "Light Edge" No. 37 (Special Feature: Ushio's New Initiatives Part 2) [Retrieved February 19, 2024], Internet<URL:https: / / www.ushio.co.jp / jp / technology / lightedge / 201206 / 100438.html> Summary of the Invention [Problem to be solved by the invention]

[0005] However, after investigations by the inventors, it was discovered that although a group of dot patterns is formed (projected) on the projection surface when laser light (parallel light) is incident on a diffractive optical element, the ratio of the size of the dot patterns to the spacing between the dot patterns changes depending on the distance from the diffractive optical element.

[0006] The present disclosure has been made to solve such problems, and aims to provide an illumination device in which the ratio of the size of the dot pattern and the spacing between the dot patterns does not change depending on the distance from the diffractive optical element. [Means for solving the problem]

[0007] The lighting device according to the present disclosure includes a diffractive optical element that receives laser light of a wavelength in the visible range and converts the laser light into a group of rays corresponding to a group of dot patterns to be projected onto a projection surface, and an optical element that diffuses the laser light incident on the diffractive optical element so that the ratio of the size of the dot patterns to the spacing between the dot patterns does not change depending on the distance from the diffractive optical element.

[0008] With this configuration, it is possible to realize an illumination device in which the ratio of the size of the dot patterns to the spacing between the dot patterns does not change depending on the distance from the diffractive optical element.

[0009] Moreover, the above-described illumination device may further include a laser light source that emits the laser light, wherein the optical element is a lens through which the laser light emitted by the laser light source passes, and the position of the lens relative to the laser light source is adjusted so that the ratio of the size of the dot pattern to the spacing between the dot patterns does not change depending on the distance from the diffractive optical element.

[0010] Moreover, the above-described illumination device may further include a laser light source that emits the laser light, wherein, when a diffraction angle of the light diffracted by the diffractive optical element is α, a size of the dot pattern is D, and an interval between the dot patterns is L, a diffusion angle β of each of the order lights constituting the group of rays is calculated by tan(β)=tan(α)×(D / L), and each of the order lights constituting the group of rays is diffused by the calculated diffusion angle β.

[0011] Furthermore, in the above illumination device, a lens may be provided between the diffractive optical element and the laser light source, and the lens may be arranged so that the laser light incident on the diffractive optical element has the diffusion angle β.

[0012] Furthermore, the illumination device may include a plurality of combinations of the laser light source and the lens, and the diffusion angle β may be calculated for each combination, and the position of the lens relative to the laser light source may be adjusted.

[0013] In addition, in the above-described lighting device, the laser light source may have a first laser light source that emits a first laser light having a relatively long wavelength and a second laser light source that emits a second laser light having a relatively short wavelength, and the diffusion angle of the first laser light may be larger than the diffusion angle of the second laser light.

[0014] Furthermore, in the above-described illumination device, the lens may be a focusing lens, the laser light source may have a first laser light source that emits a first laser light having a relatively long wavelength, and a second laser light source that emits a second laser light having a relatively short wavelength, and the position of the focusing lens corresponding to the first laser light source may be located closer than the position of the focusing lens corresponding to the second laser light source.

[0015] In the above lighting device, the output of the first laser light source may be greater than the output of the second laser light source. [Effects of the Invention]

[0016] The present disclosure makes it possible to provide an illumination device in which the ratio of the size of the dot patterns to the spacing between the dot patterns does not change depending on the distance from the diffractive optical element. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram illustrating the configuration of a lighting device 10. FIG. [Figure 2]2(a) is an enlarged view of the diffractive optical element 50 in FIG. 1 as seen from the direction of arrow AR1, and FIG. 2(b) is a cross-sectional view taken along line AA in FIG. 2(a). [Figure 3] 10 is an example of a group of dot patterns DP projected onto a projection surface S (S1, S2). [Figure 4] 10(a) is a diagram of a group of rays Ray3 when laser light Ray2 (parallel light) is incident on the diffractive optical element 50, and FIG. 10(b) is a diagram of a group of rays Ray3 when laser light Ray2 (diffused light) is incident on the diffractive optical element 50. FIG. [Figure 5] 2 is an enlarged view of the physical mask 60 as seen from the direction of the arrow AR1 in FIG. 1. [Figure 6] This is an example of an image formed by a dot pattern DP (plurality of dots) formed on a projection surface S (S1, S2). DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an illumination device 10 (image forming device) according to an embodiment of the present disclosure will be described with reference to the accompanying drawings. Corresponding components in each drawing are designated by the same reference numerals, and redundant description will be omitted.

[0019] FIG. 1 is a schematic diagram of the configuration of a lighting device 10. As shown in FIG.

[0020] 1, the illumination device 10 includes a plurality of laser light sources 20 that emit laser light Ray1 having different wavelengths in the visible range. The plurality of laser light sources 20 are, for example, a laser light source 20R that emits red laser light, a laser light source 20G that emits green laser light, and a laser light source 20B that emits blue laser light. The laser light Ray1 emitted from each of the plurality of laser light sources 20 passes through a plurality of lenses 30 (condenser lenses) provided corresponding to the plurality of laser light sources 20 and is slightly diffused before entering a dichroic prism 40. This diffusion will be described in more detail below.

[0021] The laser light Ray1 of each color (each wavelength in the visible range) incident on the dichroic prism 40 is directed along the same optical axis AX 40 The laser beam Ray2 exits the dichroic prism 40 along the axis of the dichroic prism 40 as laser beam Ray2. The laser beam Ray2 (parallel light) exiting the dichroic prism 40 enters a diffractive optical element (DOE) 50. The beam diameter of the laser beam Ray2 entering the diffractive optical element 50 is, for example, 3 mm.

[0022] Fig. 2(a) is an enlarged view of the diffractive optical element 50 in Fig. 1 as seen from the direction of arrow AR1, and Fig. 2(b) is a cross-sectional view taken along line AA in Fig. 2(a). The cross-sectional view taken along line BB in Fig. 2(a) is the same as the cross-sectional view taken along line AA.

[0023] The diffractive optical element 50 includes a microlens array. It receives laser light Ray1 emitted by each laser light source 20, i.e., laser light Ray2 of each color (each wavelength in the visible range) that passes through the lens 30 and exits the dichroic prism 40. The diffractive optical element 50 converts (diffracts) the laser light Ray2 into a group of rays Ray3 corresponding to the dot pattern to be projected onto the projection surface S. That is, the diffractive optical element 50 diffracts and splits the incident laser light Ray2 in the vertical, horizontal, and vertical directions. The group of rays Ray3 becomes a bundle of light beams with multiple directions. For example, a diffractive optical element under the name "ardisia" by SciVax may be used as the diffractive optical element 50. Alternatively, for example, the diffractive optical element 50 described in Japanese Patent No. 7061823 may be used. However, the diffractive optical element 50 may have any configuration as long as it receives laser light and converts (diffracts) the laser light into a group of rays corresponding to the dot pattern to be projected onto the projection surface S (S1, S2). For example, it may be a general diffraction grating with a groove structure.

[0024] As shown in Figures 2(a) and 2(b), the microlens array of the diffractive optical element 50 includes a plurality of lenses 51 arranged two-dimensionally in the X and Y directions. Figures 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 light Ray2), but this is not limiting. The lenses 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 light Ray2 and the exit side of the laser light Ray2).

[0025] FIG. 3 shows an example of a group of dot patterns DP projected onto a projection surface S (S1, S2).

[0026] The dot pattern DP is, for example, circular (see FIG. 3), but is not limited to this and may be rectangular or another shape.

[0027] If the pitch P of the lenses 51 (see FIG. 2(b)) is too small compared to the wavelength λ of the laser light emitted by the laser light source 20, diffraction will be difficult to occur. Therefore, as long as there are enough lenses 51 within the distribution angle of the laser light to cause diffraction, the pitch P should be sufficiently larger than the wavelength λ of the laser light, for example, 5 times or more, and preferably 10 times or more.

[0028] The pitch P of the lenses 51 is, for example, 10 μm, and the height H is, for example, 7 μm.

[0029] The material of the diffractive optical element 50 is, for example, PDMS with a refractive index of 1.53.

[0030] Here, it is assumed that the laser light Ray2 incident on the diffractive optical element 50 is parallel light as shown in FIG. 4(a). FIG. 4(a) is a diagram of a group of rays Ray3 when the laser light Ray2 (parallel light) is incident on the diffractive optical element 50. In this case, the size D of the dot pattern DP (see FIG. 4(a)) is the same regardless of the distance LA from the diffractive optical element 50. For example, the size D of the dot pattern DP formed on the projection surface S1 in FIG. S1 and the dot pattern DP formed on the projection surface S2 S2On the other hand, the interval L between the dot patterns DP (see FIG. 4(a)) increases as the distance LA from the diffractive optical element 50 increases. For example, the dot patterns DP formed on the projection plane S2 in FIG. S2 Spacing L S2 is the dot pattern DP formed on the projection surface S1 S1 Spacing L S1 It becomes bigger.

[0031] The reason is as follows: the dot patterns DP are formed by the light of each order (diffracted light of each order) that constitutes the light ray group Ray3. For example, the 0th order light Ray3 that constitutes the light ray group Ray3 _0 is the dot pattern DP shown in Figure 4(a). _0 (DP S1 , D.P. S2 ) and forms the primary light Ray3 _1 is a dot pattern DP _1 (DP S1 , D.P. S2 ) is formed. At that time, the 0th order light Ray3 _0 and 1st light Ray3 _1 The angle between the laser beam Ray2 and the diffractive optical element 50 is angle α (hereinafter referred to as diffraction angle α). _0 , 1st light Ray3 _1 Both are parallel rays.

[0032] As a result, the size D (see FIG. 4(a)) of the dot patterns DP remains the same regardless of the distance LA from the diffractive optical element 50. On the other hand, the spacing L (see FIG. 4(a)) between the dot patterns DP increases as the distance LA from the diffractive optical element 50 increases.

[0033] In this way, if the ratio of the size D of the dot pattern DP to the spacing L between the dot patterns DP changes according to the distance LA from the diffractive optical element 50, the size D of the dot pattern DP becomes smaller relative to the spacing L between the dot patterns DP as the distance LA from the diffractive optical element 50 increases, which creates the problem that the image becomes difficult to recognize.

[0034] Next, a method for solving the above problem will be described.

[0035] FIG. 4(b) is a diagram of a group of rays Ray3 when laser light Ray2 (diffused light) is incident on the diffractive optical element 50.

[0036] To solve the above problem, each order light constituting the ray group Ray 3 is diffused by an angle β (diffusion angle β), which can be achieved, for example, by shifting the position of the lens 30 (condenser lens) toward the laser light source 20.

[0037] Specifically, the angle β is calculated by solving tan(β) = tan(α) × (D / L), which is derived from two simultaneous equations: K = D / L and K = tan(β) / tan(α). Note that the size D of the dot pattern DP and the spacing L between the dot patterns DP may be set arbitrarily and are known. The diffraction angle α is an angle specific to the diffractive optical element 50 and is known.

[0038] Then, the position of the lens 30 relative to the laser light source 20 is adjusted so that each of the order lights constituting the group of rays Ray3 is diverged by the angle β calculated above.

[0039] This makes it possible to prevent the ratio of the size D of the dot patterns DP to the spacing L between the dot patterns DP from changing depending on the distance LA from the diffractive optical element 50. As a result, it is possible to solve the problem that as the distance LA from the diffractive optical element 50 increases, the size D of the dot patterns DP becomes smaller relative to the spacing L between the dot patterns DP, making it difficult to recognize the image.

[0040] Since the diffraction angle α differs for each wavelength of the laser light, the angle β is calculated for each color of laser light (laser light source 20), and the position of the lens 30 corresponding to each color of laser light (laser light source 20) is adjusted. The lens 30 whose position is adjusted as described above is an example of the optical element of the present disclosure.

[0041] Generally, the diffraction angle tends to increase as the wavelength becomes longer, so the divergence angle β is set to a large value for laser light with a relatively long wavelength.

[0042] Specifically, by positioning the focusing lens 30 relative to the laser light source 20 that emits long-wavelength laser light closer to the laser light source than the positions of the laser light source 20 and focusing lens 30 for short-wavelength laser light, it is possible to set the diffusion angle of the long-wavelength laser light relatively large compared to the diffusion angle of the short-wavelength laser light.

[0043] In this case, increasing the diffusion angle of the long-wavelength laser light increases the area of ​​the projected dot pattern, but the brightness also decreases. Therefore, the brightness of the dot pattern can be maintained by increasing the output of the laser light source that emits the long-wavelength laser light.

[0044] The group of rays Ray3 converted by the diffractive optical element 50 is incident on the physical mask 60. Note that instead of the physical mask 60, a spatial modulation element may be used.

[0045] Physical mask 60 is disposed on the optical path of ray group Ray3 converted by diffractive optical element 50, and includes opaque regions that do not transmit ray group Ray3 and transparent regions that transmit visible light.

[0046] 5 is an enlarged view of physical mask 60 as seen from the direction of arrow AR1 in FIG. 5. In FIG. 5, arrowed region A1 in physical mask 60 represents an opaque region through which visible light does not pass. This opaque region is a filter region that reflects or absorbs visible light. On the other hand, hatched region HT1 in physical mask 60 represents a transmissive region through which visible light passes.

[0047] In the lighting device 10 configured as described above, when the laser light source 20G is turned on, an image formed on the projection surface S (S1, S2) will be described.

[0048] When the laser light source 20G is turned on, the green laser light Ray1 emitted by the laser light source 20G is converted into diffused light (diffusion angle β) by passing through the lens 30, and then enters the dichroic prism 40. The green laser light Ray1 that has entered the dichroic prism 40 is aligned along the same optical axis AX by the action of the dichroic prism 40. 40 The green laser light Ray1 emitted from the dichroic prism 40 is incident on the diffractive optical element 50. The diffractive optical element 50 receives the green laser light Ray1 emitted by the laser light source 20G, i.e., the green laser light Ray2 (diffused light) that passes through the lens 30 and is emitted from the dichroic prism 40, and converts the laser light Ray2 into a group of rays Ray3 that correspond to a group of dot patterns (see FIG. 3) to be projected onto the projection surface S (S1, S2).

[0049] The green light ray group Ray3 converted by the diffractive optical element 50 does not pass through the arrow area A1 (opaque area) of the physical mask 60. On the other hand, the green light ray group Ray3 converted by the diffractive optical element 50 passes through the hatched area HT1 (transmissive area) of the physical mask 60. As a result, as shown in Figure 6, a green image (arrow image) made up of dot patterns DP (plurality) is formed (projected) on the projection surface S (S1, S2). Figure 6 shows an example of an image made up of dot patterns DP (plurality) formed on the projection surface S (S1, S2).

[0050] Furthermore, when the other laser light sources 20R and 20B are turned on, similar to the laser light source 20G, images (arrow images) of each color composed of dot patterns DP (multiple) are formed (projected) on the projection surface S (S1, S2).

[0051] As described above, according to this embodiment, it is possible to realize an illumination device 10 in which the ratio of the size D of the dot patterns DP to the spacing L between the dot patterns DP does not change depending on the distance LA from the diffractive optical element 50.

[0052] Next, a modified example will be described.

[0053] In the above embodiment, an example has been described in which a plurality of combinations of the laser light source 20 and the lens 30 are used, but this is not limiting. For example, there may be only one combination of the laser light source 20 and the lens 30. In this case, the dichroic prism 40 may be omitted.

[0054] Furthermore, in the above embodiment, an example has been described in which the position of each lens 30 relative to the laser light source 20 is adjusted so that each of the order lights constituting the light ray group Ray3 is diffused by the calculated angle β, but the present invention is not limited to this. For example, without adjusting the position of each lens 30, that is, by fixing the positions of each lens 30 to the same position, each of the order lights constituting the light ray group Ray3 may be diffused by the calculated angle β by adjusting the shape of each lens 30.

[0055] All the numerical values ​​shown in the above embodiment are merely examples, and it goes without saying that other appropriate numerical values ​​can be used.

[0056] The above-described embodiments are merely examples in all respects. The present disclosure should not be construed as being limited by the description of the above-described embodiments. The present disclosure can be implemented in various other forms without departing from the spirit or main characteristics thereof. [Explanation of symbols]

[0057] 10...Lighting equipment 20, 20B, 20G, 20R...Laser light source 30...Condenser lens (lens) 40...Dichroic prism 50...Diffractive optical element 51...Lens 60...Physical mask DP, DP S1 , D.P. S2 , D.P. _0 , D.P. _1 ...Dot pattern HT1...Hatched area LA…Distance P...Pitch Ray1, Ray2...Laser light Ray3...ray group Ray3 _0 …0th order light Ray3 _1 …1st order light S, S1, S2…Projection surface α…diffraction angle β…diffusion angle

Claims

1. 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 group of dot patterns to be projected onto a projection surface; an optical element that diffuses the laser light incident on the diffractive optical element so that the ratio of the size of the dot pattern to the spacing between the dot patterns does not change depending on the distance from the diffractive optical element.

2. further comprising a laser light source that emits the laser light, the optical element is a lens through which the laser light emitted by the laser light source passes, 2. The illumination device according to claim 1, wherein the position of the lens relative to the laser light source is adjusted so that the ratio of the size of the dot pattern to the spacing between the dot patterns does not change depending on the distance from the diffractive optical element.

3. the optical system further includes a laser light source that emits the laser light, wherein a diffraction angle of the light diffracted by the diffractive optical element is α, a size of the dot pattern is D, and an interval between the dot patterns is L, a divergence angle β of each order light constituting the group of light rays is calculated by tan(β)=tan(α)×(D / L), The illumination device according to claim 1 , wherein each of the order lights constituting the group of light rays is diffused by the calculated diffusion angle β.

4. 4. The lighting device according to claim 3, further comprising a lens between the diffractive optical element and the laser light source, the lens being disposed so that the laser light incident on the diffractive optical element has the divergence angle β.

5. a plurality of combinations of the laser light source and the lens; The illumination device according to claim 4 , wherein the diffusion angle β is calculated for each of the combinations, and the position of the lens relative to the laser light source is adjusted.

6. the laser light source includes a first laser light source that emits a first laser beam having a relatively long wavelength and a second laser light source that emits a second laser beam having a relatively short wavelength; 4. The lighting device according to claim 3, wherein a divergence angle of the first laser light is larger than a divergence angle of the second laser light.

7. The lens is a condenser lens, the laser light source includes a first laser light source that emits a first laser beam having a relatively long wavelength and a second laser light source that emits a second laser beam having a relatively short wavelength; The illumination device according to claim 5 , wherein a position of a condenser lens corresponding to the first laser light source is closer than a position of a condenser lens corresponding to the second laser light source.

8. 8. The lighting device according to claim 6, wherein the output of the first laser light source is greater than the output of the second laser light source.

Images