JP7618928B2 - Projection equipment - Google Patents

Description

This disclosure relates to a projection device.

Diffractive optical elements are known that use the diffraction phenomenon of light to spatially branch light. Diffractive optical elements are small and lightweight, yet can achieve the same functions as refractive optical elements such as lenses and prisms, and are used in a variety of fields such as lighting and optical measurement.

A projection device has also been disclosed that uses a diffractive optical element in which basic units are periodically arranged in two dimensions and diffracts incident light in two dimensions to project a linear pattern onto a projection surface (see, for example, Patent Document 1).

International Publication No. 2020/158419

In the projection device described in Patent Document 1, the smaller the diameter of the light incident on the diffractive optical element, the thinner the line pattern that is obtained. Here, the line width of the linear pattern refers to the width of the linear pattern in a direction perpendicular to the direction in which the linear pattern extends.

However, in the projection device described in Patent Document 1, the spacing between multiple bright spots generated on the projection surface by the diffracted light from the diffractive optical element and the positional shift of the bright spots due to distortion become larger as the diameter of the light incident on the diffractive optical element becomes smaller. Therefore, if the diameter of the light incident on the diffractive optical element is reduced to narrow the line width of the linear pattern, the spacing between the bright spots will become larger, causing parts of the linear pattern to split, or the positional shift of the bright spots will cause parts of the linear pattern to become wavy, raising concerns that the quality of the linear pattern will be reduced.

One aspect of the present disclosure aims to provide a projection device capable of projecting linear patterns with narrow line widths and good quality.

A projection device according to one aspect of the present disclosure includes a light source that emits parallel light, a diffractive optical element arranged on the side of the light source from which the parallel light is emitted, and a lens arranged on the opposite side of the diffractive optical element from the light source and having a curvature in a predetermined direction, the lens projects a linear pattern extending along the perpendicular direction onto the projection surface by generating a plurality of bright spots arranged in a direction perpendicular to the predetermined direction, the length of the bright spots along the perpendicular direction being equal to or greater than the distance between adjacent bright spots among the plurality of bright spots along the perpendicular direction, and the length of the bright spots along the predetermined direction for all of the plurality of bright spots is shorter than the length of the bright spots along the perpendicular direction.

According to one aspect of the present disclosure, it is possible to provide a projection device capable of projecting linear patterns with narrow line widths and good quality.

1 is a diagram illustrating an example of an overall configuration of a projection device according to an embodiment. 2 is a plan view illustrating the configuration of a diffractive optical element included in the projection device of FIG. 1 . 3 is a plan view of a concave-convex pattern of a basic unit in the diffractive optical element of FIG. 2. This is a cross-sectional view taken along line AA in FIG. 2A to 2C are schematic views illustrating linear patterns according to the embodiment; FIG. 6 is an enlarged view of region B in FIG. 5 . 11 is a diagram illustrating an evaluation area of a linear pattern on a projection surface. FIG. FIG. 8 is an enlarged view of region C in FIG. 7 . FIG. 9 is a diagram showing the four corner areas in FIG. 8 . FIG. 1 is a table showing the specifications and evaluation results of Examples 1 to 5. 11A and 11B are diagrams illustrating simulation results of a linear pattern according to Example 1. 13A and 13B are diagrams illustrating simulation results of a linear pattern according to Example 2. 13A and 13B are diagrams illustrating simulation results of a linear pattern according to Example 3. 13A and 13B are diagrams illustrating simulation results of a linear pattern according to Example 4. 13A and 13B are diagrams illustrating simulation results of a linear pattern according to Example 5. FIG. 13 is a diagram showing the specifications and evaluation results of Examples 6 to 8. FIG. 13 is a diagram showing the specifications and evaluation results of Examples 9 to 11. 13A and 13B are diagrams illustrating simulation results of a linear pattern according to Example 6. FIG. 13 is a diagram illustrating a simulation result of a linear pattern according to Example 7. 13 is a diagram illustrating a simulation result of a linear pattern according to Example 8. FIG. FIG. 13 is a diagram illustrating a simulation result of a linear pattern according to Example 9. FIG. 13 is a diagram illustrating a simulation result of a linear pattern according to Example 10. FIG. 13 is a diagram illustrating a simulation result of a linear pattern according to Example 11.

Below, the embodiments for implementing the invention will be described in detail with reference to the drawings. However, the embodiments shown below are merely examples of projection devices for realizing the technical concept of the present embodiment, and are not limited to the following. Note that the size and positional relationship of components shown in each drawing may be exaggerated for clarity of explanation. In each drawing, the same components are given the same reference numerals, and duplicate explanations will be omitted as appropriate.

In the figures shown below, directions may be indicated by the x-axis, y-axis, and z-axis, with the y-direction along the y-axis indicating a specific direction within the projection plane. The x-direction along the x-axis indicates a direction perpendicular to the y-direction within the projection plane. The z-direction along the z-axis indicates a direction perpendicular to the projection plane. The planar view in the embodiments refers to viewing the diffractive optical element provided in the projection device according to the embodiment from the z-direction. However, these do not limit the orientation of the projection device when in use, and the orientation of the projection device is arbitrary.

<Embodiment>
(Example of overall configuration of projection device 1)
1 is a diagram showing an example of the overall configuration of a projection device 1 according to the present embodiment. The projection device 1 includes a light source 10, a diffractive optical element 20, and a lens 30.

The light source 10 emits parallel light toward the diffractive optical element 20. In this embodiment, the light source 10 is a semiconductor laser, and emits a laser beam that is a substantially parallel bundle of light rays. "Substantially parallel" does not require strict parallelism, but means that a deviation from parallelism that is generally recognized as an error is acceptable.

The cross-sectional shape of the laser beam in a plane perpendicular to the central axis of the laser beam emitted by the light source 10 is, for example, approximately circular. "Approximately circular" does not require a strict perfect circle, but means that a deviation from a perfect circle that is generally recognized as an error is acceptable. In this case, "a deviation that is generally recognized as an error" is, for example, a difference of 1/10 or less of the laser beam diameter.

The wavelength of the light emitted by the light source 10 is not particularly limited, but for example, a wavelength in the visible light region from approximately 380 nm to approximately 780 nm or a wavelength in the near infrared region from approximately 800 nm to approximately 1200 nm can be used. The light source 10 is not limited to a semiconductor laser, and an LED (Light Emitting Diode) or the like may also be used.

The diffractive optical element 20 is an optical element arranged on the side of the light source 10 where the parallel light is emitted. The diffractive optical element 20 diffracts the parallel laser beam incident from the light source 10 in two-dimensional directions so as to generate multiple bright spots arranged in a two-dimensional array on the projection surface S, and emits multiple parallel laser beams toward the lens 30.

The lens 30 is disposed on the opposite side of the diffractive optical element 20 from the light source 10, and is a lens that has a curvature in a predetermined direction. In this embodiment, the lens 30 is a cylindrical lens that has a curvature in the y direction and no curvature in the x direction. The lens 30 has refractive power (lens power) only in the y direction. The y direction corresponds to the predetermined direction, and the x direction corresponds to the direction perpendicular to the predetermined direction.

Lens 30 may be a plano-convex, biconvex, or meniscus cylindrical lens. Lens 30 having a curvature in the y direction may also be constructed by combining multiple lenses, prisms, or other optical elements.

The lens 30 receives the parallel laser beam emitted from the diffractive optical element 20 and emits focused light. From the viewpoint of suppressing aberration, it is preferable that the lens 30 is arranged so that the surface with the larger curvature faces the light source 10.

The lens 30 projects multiple bright spots on the projection surface S, which are formed by converging multiple laser beams diffracted by the diffractive optical element 20 in the y direction. In other words, the lens 30 can project a linear pattern extending along the x direction on the projection surface S by generating multiple bright spots aligned in the x direction on the projection surface S.

In FIG. 1, three linear patterns L arranged along the y direction are illustrated as an example, but there is no particular limit to the number of linear patterns L arranged along the y direction, and the number may be one, or any number of two or more.

The projection surface S is typically a screen, but is not limited to this and may be, for example, the wall of a building, or a virtual plane in space.

(Configuration Example of Diffractive Optical Element 20)
The configuration of the diffractive optical element 20 will be described with reference to Fig. 2 to Fig. 4. Fig. 2 is a plan view illustrating the configuration of the diffractive optical element 20. Fig. 3 is a plan view illustrating the concave-convex pattern of the basic unit 21 in the diffractive optical element 20. Fig. 4 is a cross-sectional view taken along line AA in Fig. 2.

As shown in FIG. 2, the diffractive optical element 20 includes a plurality of basic units 21 that are periodically arranged two-dimensionally along each of the x and y directions. The plurality of basic units 21 are arranged at a pitch Px in the x direction and at a pitch Py in the y direction. Here, the pitch refers to the distance between the centers of adjacent basic units 21. In FIG. 2, the adjacent basic units 21 are arranged without a gap, so that the pitch Px coincides with the length of the basic unit 21 in the x direction, and the pitch Py coincides with the length of the basic unit 21 in the y direction. In this embodiment, the diameter of the laser beam emitted by the light source 10 is larger than the pitch Px. Note that, when the specification value of the line width LW is LT, the diameter R of the laser beam satisfies the following formulas (1) and (2) regardless of the number of lines Ln.
R≧√(Px ² + Py ² ) ... (1)
R≧(4×λ×f) / (π×LT) ... (2)

As shown in FIG. 3, the basic unit 21 has a periodic structure of a concave-convex pattern as a binary phase distribution. Each of the basic units 21 has the same periodic structure of a concave-convex pattern. In FIG. 3, the black filled areas indicate convex portions, and the white areas indicate concave portions. The concave-convex pattern of the basic unit 21 diffracts the parallel light incident from the light source 10 in two-dimensional directions.

As shown in FIG. 4, the diffractive optical element 20 includes a light-transmitting member 22 made of glass or the like, and convex portions 23 formed on the surface of the light-transmitting member 22. In the diffractive optical element 20, the areas on the surface of the light-transmitting member 22 where the convex portions 23 are not formed become concave portions 24. The convex portions 23 and the concave portions 24 form an uneven pattern layer 25 on the light-transmitting member 22. The convex portions 23 can be made of a material such as glass or resin.

The light-transmitting member 22 can be made of various materials such as glass and resin, as long as they are transparent to the incident light. The use of optically isotropic materials such as glass and quartz is more preferable from the viewpoint of improving the quality of the linear pattern L projected by the projection device 1, since these materials do not have birefringence. For example, it is preferable to form an anti-reflection film made of a multilayer film on the interface between the light-transmitting member 22 and the air, since this can reduce light reflection by the light-transmitting member 22.

In FIG. 4, a configuration in which an uneven pattern is formed on one side of the light-transmitting member 22 is illustrated, but the diffractive optical element 20 may have an uneven pattern formed on both sides of the light-transmitting member 22. The phase distribution in the basic unit 21 of the diffractive optical element 20 is not limited to one based on an uneven pattern, and may have a refractive index that changes two-dimensionally, as long as it can impart a phase difference to the incident light.

The number of basic units 21 in the diffractive optical element 20 does not need to be an integer, and for example, the boundary between an area, such as the periphery, that does not have a concave-convex pattern and an area that has a concave-convex pattern does not necessarily need to coincide with the boundary of the basic units 21.

2 and 3 show an example of a configuration in which the planar portion of the diffractive optical element 20 and the projection surface S are approximately parallel, but they do not necessarily have to be approximately parallel and may be tilted.

(An example of the linear pattern L)
Fig. 5 is a schematic diagram illustrating the linear pattern L. Fig. 6 is an enlarged view of a region B in Fig. 5 .

In FIG. 5, the diffraction divergence angles θx and θy represent the divergence angles of the entire laser beams diffracted by the diffractive optical element 20. The diffraction divergence angle θx is the divergence angle in the x direction, and the diffraction divergence angle θy is the divergence angle in the y direction.

The lens distance ZL represents the distance between the surface of the diffractive optical element 20 facing the light source 10 and the principal point (optical center) of the lens 30. The projection distance ZS represents the distance between the surface of the diffractive optical element 20 facing the light source 10 and the projection surface S.

As shown in FIG. 6, the linear pattern L is composed of multiple bright spots Ls arranged in the x direction. The bright spots Ls are generated by each of the multiple laser beams diffracted by the diffractive optical element 20. The cross-sectional shape of the bright spots Ls in a plane perpendicular to the central axis of the laser beam becomes a substantially elliptical shape with the y direction as the minor axis by being focused in the y direction by the lens 30.

In FIG. 6, bright spot length Qx represents the length of each of the multiple bright spots Ls along the x direction. Bright spot length Qy represents the length of each of the multiple bright spots Ls along the y direction. Bright spot length Qx corresponds to the major axis length of the ellipse that constitutes the bright spot Ls, and bright spot length Qy corresponds to the minor axis length of the ellipse. Bright spot intervals Vx and Vy represent the distance between the centers of adjacent bright spots in the multiple bright spots Ls. Bright spot interval Vx represents the bright spot interval in the x direction, and bright spot interval Vy represents the bright spot interval in the y direction.

In this embodiment, the bright spot length Qx is longer than the bright spot interval Vx, and all of the multiple bright spots Ls have a bright spot length Qy shorter than the bright spot length Qx. The projection device 1 generates multiple bright spots Ls on the projection surface S such that the bright spots Ls are aligned along the x direction, thereby projecting a linear pattern L extending along the x direction onto the projection surface S. For all of the multiple bright spots Ls, the bright spot length Qy and the bright spot length Qx satisfy the relationship of the following formula (3).
Qy≦Qx×{π×(LT ² )} / (4×λ×f) ... (3)

The distortion ε refers to the distance between the center of the bright spot Ls located lowest in the y direction (negative side of the y axis) and the center of the bright spot Ls located highest in the y direction (positive side of the y axis) among the multiple bright spots Ls included in one linear pattern L. Note that the positive side of the y axis refers to the direction in which the arrow indicating the y axis points, and the negative side of the y axis refers to the direction opposite to the direction in which the arrow indicating the y axis points.

Here, when the central axis of the diffractive optical element 20 and the central axis of the projection surface S are approximately aligned, the multiple bright spots Ls generated on the projection surface S may have a greater positional deviation the closer they are to the four corners of the projection surface S. This positional deviation occurs due to the distortion of diffracted light by the diffractive optical element 20. Figure 6 shows the multiple bright spots Ls that have been displaced due to pincushion distortion. The distortion ε is a value that indicates the amount of positional deviation due to such distortion.

The line width LW represents the width of the linear pattern L along the y direction. In this embodiment, the line width LW is the sum of the bright spot length Qy and the distortion ε.

Examples and Comparative Examples
Examples and Comparative Examples will be described below, but the present invention is not limited to these Examples. Example 1 is an Example, Examples 2 to 5 are Comparative Examples, and Examples 6 to 11 are Examples.

(Evaluation Method)
Table 1 shows the main specifications of the projection devices in the examples and the comparative examples. In Table 1, the wavelength λ represents the wavelength of the parallel light emitted by the light source 10, and the number of lines Ln represents the number of linear patterns L projected onto the projection surface S.

In the examples and comparative examples, a diffractive optical element 20 that satisfies the specification values shown in Table 1 was designed by simulation, and the linear pattern L projected using the designed diffractive optical element 20 was determined by simulation and evaluated.

In the design of the diffractive optical element 20 and the simulation for evaluating the linear pattern, the iterative Fourier transform algorithm (IFTA), which repeats Fourier transform and inverse Fourier transform, and the ray tracing method were used.

(Evaluation area of linear pattern L on projection surface S)
Fig. 7 is a diagram for explaining an evaluation region of a linear pattern L on a projection surface S in an example and a comparative example. Fig. 8 is an enlarged view of a region C in Fig. 7. Fig. 9 is a diagram showing the four corner regions in Fig. 8.

In the evaluation of the linear pattern L, as shown in FIG. 7, the projection surface S was represented by x and y coordinates, and ten linear patterns L that were approximately parallel to each other were projected onto the projection surface S. The length of the projection surface S was 600.0 mm in the x direction and 440.0 mm in the y direction. Area C is the area that corresponds to the first quadrant on the projection surface S.

As shown in FIG. 8, area C includes five of the ten linear patterns, linear pattern L1 to linear pattern L5. The size of area C was 300.0 mm in the x direction and 220.0 mm in the y direction.

As shown in FIG. 9, in the examples and comparative examples, the areas D1, D2, D3, and D4 at the four corners of area C were used as evaluation areas, and the linear patterns L1 and L5 included in the evaluation areas were evaluated.

(Evaluation Results)
Fig. 10 is a diagram showing a list of specifications and evaluation results of Examples 1 to 5. Figs. 11 to 15 are diagrams showing simulation results of the linear pattern L.

In the diagram showing the configuration of each example in Figure 10, only the main components are shown for convenience in order to show the differences between the examples. The bright spot interval Vx, bright spot interval Vy, distortion ε, and line width LW vary within one linear pattern L, but Figure 10 shows the maximum values for each. This also applies to Figures 16 and 17 shown below.

In Figures 11 to 15, region D1 indicates the region where the x-coordinate is 0.0 mm to 40.0 mm, and region D2 indicates the region where the x-coordinate is 260.0 mm to 300.0 mm. Region D3 indicates the region where the x-coordinate is 0.0 mm to 40.0 mm, and region D4 indicates the region where the x-coordinate is 260.0 mm to 300.0 mm.

<Example 1>
As shown in Figure 10, the projection device 1 of Example 1 is configured to include a diffractive optical element 20 and a lens 30 having a curvature only in the y direction, similar to that shown in Figure 1, and the incident beam diameter φ is 7200.0 μm.

In Example 1, the configuration of the uneven pattern layer 25 in the diffractive optical element 20, the pitches Px and Py, the lens distance ZL, the focal length f, etc. were optimized, resulting in a distortion ε of 63.0 μm or less and a line width LW of 98.0 μm or less. The bright spot length Qy was 1/205 of the bright spot length Qx. Note that at a lens distance ZL such that all of the diffracted light by the diffractive optical element 20 is incident on the lens 30, ZL=ZS-f always holds.

As shown in FIG. 11, in each of the regions D1 to D4, splitting and distortion were suppressed, and a linear pattern L of good quality was obtained. Here, splitting of the linear pattern L means that the linear pattern L is divided into multiple independent parts.

<Example 2>
As shown in Fig. 10, the projection device 1X2 according to Example 2 includes a diffractive optical element 20X2 and does not include a lens, and the incident beam diameter φ is 100.0 μm. The distortion ε is 4053.0 μm or less, and the line width LW is 4153.0 μm or less. The bright spot length Qy is equal to the bright spot length Qx.

As shown in FIG. 12, the linear pattern L in each region was split into multiple point-like bright spots Ls. The bright spot lengths Qx and Qy were 100.0 μm, but as in region D2, the positional deviation of the bright spots Ls due to the strain ε became large, and as a result, the line width LW became thicker than in Example 1.

<Example 3>
As shown in Fig. 10, the projection device 1X3 according to Example 3 includes a diffractive optical element 20X3 and does not include a lens, and the incident beam diameter φ is 800.0 μm. The distortion ε is 546.0 μm or less, and the line width LW is 1346.0 μm or less. The bright spot length Qy is equal to the bright spot length Qx.

As shown in Figure 13, no splitting was observed in the linear pattern L in each region, but the wavy positional deviation became larger. In addition, the linear pattern L became thicker overall compared to Example 1 in response to the increase in the incident beam diameter φ.

<Example 4>
As shown in Fig. 10, the projection device 1X4 according to Example 4 includes a diffractive optical element 20X4 and a lens 30X4 having a curvature only in the x-direction, and the incident beam diameter φ is 100.0 μm. The distortion ε is 3762.0 μm or less, and the line width LW is 3862.0 μm or less. The bright spot length Qy is 1/100 of the bright spot length Qx.

As shown in FIG. 14, a large displacement and split occurred in the linear pattern L in region D2. Although the individual linear patterns L themselves became thinner, the large displacement resulted in a thicker line width LW compared to Example 1.

<Example 5>
As shown in Fig. 10, the projection device 1X5 according to Example 5 includes a lens 30X5 having a curvature only in the x direction and a diffractive optical element 20X5 arranged on the projection surface S side of the lens 30X5, and the incident beam diameter φ is 100.0 μm. The distortion ε is 3882.0 μm or less, and the line width LW is 3982.0 μm or less. The bright spot length Qy is 1/102 of the bright spot length Qx.

As shown in FIG. 15, a large positional shift and split occurred in the linear pattern L in region D2. Although the individual linear patterns L themselves became thinner, the positional shift of the bright spots Ls became larger, resulting in a thicker line width LW compared to Example 1.

From the above results, it was found that, among Examples 1 to 5, the configuration of the projection device 1 in Example 1 is more suitable for projecting a linear pattern L having a narrow line width LW and good quality.

Next, examples 6 to 11 will be described. In examples 6 to 11, similar to the projection device 1 in example 1, a diffractive optical element 20 and a lens 30 having a curvature only in the y direction are provided, and the values of each parameter are changed from those in example 1.

Figure 16 is a diagram showing the specifications and evaluation results of Examples 6 to 8. Figure 17 is a diagram showing the specifications and evaluation results of Examples 9 to 11. Figures 18 to 23 are diagrams illustrating simulation results of linear patterns. Figure 18 shows the results of Example 6, Figure 19 shows the results of Example 7, Figure 20 shows the results of Example 8, Figure 21 shows the results of Example 9, Figure 22 shows the results of Example 10, and Figure 23 shows the results of Example 11.

In Figures 18 to 23, region D1 indicates the region where the x coordinate is from 0.0 mm to 40.0 mm, and region D3 indicates the region where the x coordinate is from 0.0 mm to 40.0 mm.

In Figures 18, 19, and 22, region D2 indicates the region with x-coordinates between 260.0 mm and 300.0 mm, and region D4 indicates the region with x-coordinates between 260.0 mm and 300.0 mm.

In FIG. 20, area D2 indicates the area where the x coordinate is from 300.0 mm to 340.0 mm, and area D4 indicates the area where the x coordinate is from 300.0 mm to 340.0 mm.

In FIG. 21, area D2 indicates the area with x-coordinates from 110.0 mm to 150.0 mm, and area D4 indicates the area with x-coordinates from 110.0 mm to 150.0 mm.

In FIG. 23, area D2 shows linear pattern L5 in the area where the x coordinate is from 130.0 mm to 170.0 mm, and area D4 shows linear pattern L1 in the area where the x coordinate is from 130.0 mm to 170.0 mm.

<Example 6>
16, in Example 6, the number of lines Ln was changed to 20 in Example 1. As shown in FIGS. 16 and 18, in Example 6, the distortion ε and line width LW did not change compared to Example 1.

<Example 7>
As shown in Fig. 16, in Example 7, the pitches Px and Py of the basic units in the diffractive optical element 20 were changed from those in Example 1. In Example 7, the line width LW was changed to be about twice that of Example 1, resulting in a change in the incident beam diameter and a change in the pitches Px and Py. The distortion ε was 127.0 μm and the line width LW was 198.0 μm, which were thicker than those in Example 1. The bright spot length Qy was 1/51 of the bright spot length Qx. As shown in Fig. 19, no splitting or distortion was observed in the linear pattern L in each evaluation area, and a linear pattern L of good quality was obtained.

<Example 8>
As shown in FIG. 16, in Example 8, the incident beam diameter φ was changed to 8000.0 μm, and the pitches Px and Py of the basic units in the diffractive optical element 20 and the diffraction divergence angles θx and θy were changed. In Example 8, the diffraction divergence angles θx and θy were changed from those in Example 1, resulting in a change in the incident beam diameter and a change in the pitches Px and Py. The distortion ε was 68.0 μm, and the line width LW was 100.0 μm, which were almost the same as those in Example 1. The bright spot length Qy was 1/250 of the bright spot length Qx. As shown in FIG. 20, no splitting or distortion was observed in each evaluation area, and a linear pattern L of good quality was obtained.

<Example 9>
As shown in FIG. 16, in Example 9, the incident beam diameter φ was changed to 3600.0 μm, and the pitches Px and Py of the basic units in the diffractive optical element 20 and the focal length f of the lens 30 were changed compared to Example 1. In Example 9, the projection distance ZS was changed from Example 1, resulting in a change in the focal length f, and the incident beam diameter and pitches Px and Py were also changed. The distortion ε was 63.0 μm, and the line width LW was 98.0 μm, which was almost the same as Example 1. As shown in FIG. 21, in each evaluation region, although some intensity fluctuation was observed in the linear pattern L, no splitting or distortion was observed, and a linear pattern L of good quality was obtained. The bright spot length Qy was 1/103 of the bright spot length Qx.

<Example 10>
As shown in FIG. 16, in Example 10, the wavelength λ was changed to 850.0 nm, the incident beam diameter φ was changed to 15200.0 μm, and the pitches Px and Py of the basic units in the diffractive optical element 20 were changed, compared to Example 1. In Example 10, the wavelength λ was changed from Example 1, resulting in a change in the incident beam diameter, and the pitches Px and Py were also changed. The distortion ε was 64.0 μm, and the line width LW was 99.0 μm, which were almost the same as those in Example 1. The bright spot length Qy was 1/434 of the bright spot length Qx. As shown in FIG. 22, no splitting or distortion was observed in each evaluation area, and a linear pattern L of good quality was obtained.

<Example 11>
As shown in FIG. 16, in Example 11, the wavelength λ was changed to 850.0 nm, the incident beam diameter φ was changed to 4200.0 μm, and the pitch Px and Py of the basic unit in the diffractive optical element 20 and the diffraction divergence angles θx and θy were changed. In Example 11, all the parts changed in Examples 6 to 10 above were changed from Example 1, and as a result, the focal length f was changed, and the incident beam diameter and pitch Px and Py were also changed. The distortion ε was 132.0 μm, and the line width LW was 195.0 μm, which was thicker than Example 1. The bright spot length Qy was 1/67 of the bright spot length Qx. As shown in FIG. 23, in each evaluation area, no splitting or distortion was observed, and a linear pattern L of good quality was obtained.

From the results shown in Figures 16 to 23, it was found that in Examples 6 to 11, linear patterns L with a narrow line width LW and good quality could be projected. From the viewpoint of narrowing the line width LW, it was found that the line width LW is preferably 250.0 μm or less, and more preferably 100.0 μm or less.

In addition, the thinner the line width LW is, the smaller the bright spot length Qy must be, and when the specification value of the line width LW is LT, the incident beam diameter R must satisfy the following two equations.
R≧(4×λ×f) / (π×LT) ... (4)
R≧√(Px ² + Py ² ) ... (5)
As a result, the pitches Px and Py can be increased as the line width LW becomes narrower, and therefore the bright spot interval and distortion can be reduced. Since the ratio of the bright spot interval and distortion to the line width LW is almost constant even if the line width changes, it can be considered that the ratio is almost constant regardless of the line width LW from the viewpoint of improving the quality of the line width LW.

Here, when the minimum line width LW that can be realized by the diffractive optical element 20 alone was examined, it was found that the following points affect the line width LW.
Wavelength λ: The longer the wavelength, the larger the line width LW.
Projection distance ZS: the longer it is, the larger the line width LW becomes.
Diffraction spread angle θx: the wider the angle, the larger the line width LW.
Diffraction spread angle θy: the wider the angle, the larger the line width LW.
Length of the linear pattern L in the x direction: the shorter it is, the easier it is to reduce the line width LW.
When one linear pattern L is projected, the line width LW is smallest.
In consideration of these, the line width LW was calculated using realistic specifications that make it easy to reduce the line width LW, and it was found that the line width LW is preferably 250.0 μm or less.

<Functions and Effects of Projection Device 1>
As described above, the projection device 1 includes the light source 10 that emits parallel light, the diffractive optical element 20 that is disposed on the side of the light source 10 from which the parallel light is emitted, and the lens 30 that is disposed on the opposite side of the diffractive optical element 20 from the light source 10 and has a curvature in the y direction (a predetermined direction). The lens 30 projects a linear pattern L extending along the x direction onto the projection surface S by generating a plurality of bright spots Ls arranged in the x direction (a direction perpendicular to the predetermined direction) on the projection surface S. The bright spot length Qx (the length of the bright spots along the x direction) is equal to or longer than the bright spot interval Vx (the interval between adjacent bright spots in the plurality of bright spots along the x direction), and all of the plurality of bright spots Ls have a bright spot length Qy (the length of the bright spots along the y direction) that is shorter than the bright spot length Qx. In all of the plurality of bright spots Ls, the bright spot length Qy and the bright spot length Qx satisfy the relationship of the above formula (3).

By making the bright spot length Qx longer than the bright spot interval Vx, it is possible to project a linear pattern L of good quality with reduced splitting and distortion. Furthermore, by making the bright spot length Qy shorter than the bright spot length Qx, it is possible to narrow the line width LW of the linear pattern L extending along the x direction. As a result, it is possible to provide a projection device 1 capable of projecting a linear pattern L of good quality with a narrow line width LW.

In the projection device described in Patent Document 1, the distance between multiple bright spots generated on the projection surface by the diffracted light from the diffractive optical element and the positional deviation of the bright spots due to distortion become larger as the diameter of the light incident on the diffractive optical element becomes smaller. The smaller the pitches Px and Py are, the larger the distance between the bright spots and the distortion become. When the diameter of the incident light is R, the pitches Px and Py must satisfy the following formula:
R≧√(Px ² +Py ² )

In addition, in the case of a diffractive optical element alone, the diameter of the incident light must be equal to the diameter of the bright spot. Therefore, to narrow the line width with a diffractive optical element alone, the diameter of the incident light must be reduced. As a result, the smaller the diameter of the incident light, the greater the positional deviation, which is due to the small pitch.

From the viewpoint of narrowing the line width LW of the linear pattern L, it is preferable that the bright spot length Qy of the multiple bright spots Ls is 1/50 or less of the bright spot length Qx. It is more preferable that the bright spot length Qy is 250.0 μm or less, and even more preferable that it is 100.0 μm or less.

In this embodiment, the lens 30 projects multiple linear patterns L onto the projection surface S, and the multiple linear patterns L are parallel to each other. For example, when the projection device 1 is used for sensing purposes and the linear pattern L is projected from the projection device 1 as probe light, the probe light can be irradiated over a wider range with high spatial resolution.

In this embodiment, the cross-sectional shape of the laser beam (parallel light) in a plane perpendicular to the central axis is substantially circular. This makes it possible to suppress the anisotropy of diffraction by the diffractive optical element 20.

In this embodiment, the diffractive optical element 20 includes a plurality of basic units 21. Each of the basic units 21 has the same concave-convex pattern layer 25 and is formed in a line at least along the x direction at a predetermined pitch Px, and the incident beam diameter φ is larger than the pitch Px. If the specification value of the line width LW is LT, the diameter of the laser beam satisfies the above formulas (1) and (2) regardless of the number of lines Ln. With this configuration, a single laser beam incident on the diffractive optical element 20 can be efficiently diffracted in the x direction using one entire basic unit 21.

In this embodiment, the diffractive optical element 20 emits a substantially parallel laser beam (parallel light), and the lens 30 receives the substantially parallel laser beam emitted from the diffractive optical element 20. In other words, the lens 30 is an object-side telecentric lens. With this configuration, the distance between the diffractive optical element 20 and the lens 30 does not affect the linear pattern L on the projection surface S, improving the degree of freedom in component placement, etc. in the projection device 1.

Although the preferred embodiment has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the claims.

The projection device according to the embodiment can be applied to a variety of fields that use optical methods, such as light-based sensing, such as LiDAR (Light Detection and Ranging), and image projection devices, such as projectors.

Reference Signs List 1 Projection device 10 Light source 20 Diffractive optical element 21 Basic unit 22 Light-transmitting member 23 Convex portion 24 Concave portion 25 Concave-convex pattern layer 30 Lens L Line pattern S Projection surface Px, Py Pitch θx, θy Diffraction spread angle ZL Lens distance ZS Projection distance Ls Bright spot LW Line width Vx, Vy Bright spot interval Qx, Qy Bright spot length ε Distortion D1, D2, D3, D4 Area f Focal length φ Incident beam diameter

Claims (8)

A light source that emits parallel light;
a diffractive optical element disposed on a side of the light source from which the parallel light is emitted;
a lens disposed on the opposite side of the diffractive optical element from the light source and having a curvature in a predetermined direction;
the lens generates a plurality of bright points aligned in a direction perpendicular to the predetermined direction on a projection surface, thereby projecting a linear pattern extending along the perpendicular direction onto the projection surface;
a length of the bright spot along the vertical direction is equal to or greater than a distance between adjacent bright spots in the plurality of bright spots along the vertical direction,
A projection device in which all of the plurality of bright spots have a length of the bright spot along the predetermined direction that is shorter than the length of the bright spot along the perpendicular direction. The projection device of claim 1, wherein the length of the plurality of bright spots along the predetermined direction is 1/50 or less of the length of the bright spots along the perpendicular direction. The projection device according to claim 1 or 2, wherein the length of the bright spot along the predetermined direction is 250 μm or less. The projection device according to any one of claims 1 to 3, wherein the length of the bright spot along the predetermined direction is 100 μm or less. The lens projects the plurality of linear patterns onto the projection surface,
The projection device according to claim 1 , wherein the linear patterns are parallel to each other. The projection device according to any one of claims 1 to 5, wherein the cross-sectional shape of the parallel light in a plane perpendicular to the central axis of the parallel light is substantially circular. The diffractive optical element includes a plurality of basic units,
The plurality of basic units each have the same concave-convex pattern layer and are formed side by side at least at a predetermined pitch along the perpendicular direction,
The projection device according to claim 6 , wherein a diameter of the approximately circular cross-sectional shape of the parallel light is larger than the pitch. The diffractive optical element emits parallel light,
The projection device according to claim 1 , wherein the lens receives the parallel light emitted from the diffractive optical element.

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