Projection device

Abstract

This technology facilitates the release of heat originating from the laser light emitted by an infrared laser from the collimator to the diffractive optical element. [Solution] The projection device is a diffractive optical element used for at least one of splitting and shaping a laser beam whose wavelength is in the near-infrared region, and comprises a substrate that transmits the laser beam, and a resin cured layer provided on the substrate that transmits the laser beam, wherein the resin cured layer has a plurality of protrusions on the surface of the diffractive optical element that exhibit diffraction, and each of the plurality of protrusions is in the shape of an inverse taper, an infrared laser that is set up facing the substrate with the resin cured layer in between and emits laser light toward the diffractive optical element, and a collimator that includes one or more lenses, and is set up between the diffractive optical element and the infrared laser so that the resin cured layer is in contact with one of the one or more lenses, collimates the laser light emitted by the infrared laser and causes it to be incident on the diffractive optical element as a laser beam.

Description

Technical Field

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

Background Art

[0002] In recent years, fingerprint authentication technology and face authentication technology have been used in smartphones as security measures. Compared with fingerprint authentication technology, face authentication technology can achieve a higher security level. In addition, since face authentication technology performs personal authentication without contact, it is more convenient than fingerprint authentication technology and has the characteristic of being stress-free.

[0003] However, face authentication technology has problems such as not being able to achieve high recognition accuracy in a dark environment. For this reason, infrared rays may be used for face authentication technology.

[0004] In face authentication technology using infrared rays, a projection device that projects infrared rays onto a face and a light receiving device that receives the infrared rays reflected by the face are used. For example, a projection device that irradiates a face with a plurality of laser beams is used, and a ToF (Time of Flight) type light receiving device is used. In this case, in addition to enabling face authentication in a dark environment, three-dimensional information of the face can be obtained, and the security level in a bright environment is also enhanced.

[0005] The above projection device includes, for example, an infrared laser, a collimator that collimates the laser beam emitted by the infrared laser, and a beam splitter or beam shaper that divides or shapes the collimated laser beam. When the beam splitter or beam shaper is composed of a lens and a prism, it is difficult to miniaturize the projection device. Therefore, a diffractive optical element (DOE) may be used as the beam splitter or beam shaper (see Patent Document 1).

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] International Publication No. 2019 / 240010 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a technology that reduces the likelihood of changes in the performance of a projection device caused by heat generation from a laser. [Means for solving the problem]

[0008] According to one aspect of the present invention, a projection device is provided comprising a diffractive optical element for use in at least one of splitting and shaping a laser beam having a wavelength in the near-infrared region, the diffractive optical element comprising a substrate that transmits the laser beam, and a resin cured layer provided on the substrate that transmits the laser beam, wherein the resin cured layer has a plurality of protrusions on the surface of the diffractive optical element that exhibit diffraction, and each of the plurality of protrusions is in the shape of an inverse taper, an infrared laser that is positioned facing the substrate with the resin cured layer in between and emits laser light toward the diffractive optical element, and a collimator that includes one or more lenses, and is positioned between the diffractive optical element and the infrared laser such that the resin cured layer is in contact with one of the one or more lenses, and collimates the laser light emitted by the infrared laser and causes it to be incident on the diffractive optical element as a laser beam.

[0009] According to another aspect of the present invention, a projection device is provided in which the plurality of protrusions form a striped pattern.

[0010] According to yet another aspect of the present invention, a projection device is provided relating to any of the above-mentioned sides, wherein each of the plurality of protrusions is within the range of 0.1° to 50° of the inclination angle θ of the side wall.

[0011] According to yet another aspect of the present invention, a projection device is provided relating to any of the above aspects, wherein each of the plurality of protrusions has a height H within the range of 0.1 μm to 10 μm.

[0012] According to yet another aspect of the present invention, a projection device is provided relating to any of the above-mentioned sides, wherein each of the plurality of protrusions has an upper surface width W1 within the range of 0.1 μm to 15 μm.

[0013] According to yet another aspect of the present invention, a projection device is provided relating to any of the above-mentioned sides, wherein each of the plurality of protrusions has a lower surface width W2 within the range of 0.05 μm to 10 μm.

[0014] According to yet another aspect of the present invention, a projection device is provided relating to any of the above aspects, wherein each of the plurality of protrusions has a ratio W1 / W2 of the width of the upper surface to the width W2 of the lower surface within the range of 1.05 or more and 2 or less.

[0015] According to yet another aspect of the present invention, a projection device is provided relating to any of the above aspects, wherein each of the plurality of protrusions has a ratio H / W1 of height to width W1 of the upper surface within the range of 0.2 to 10.

[0016] According to yet another aspect of the present invention, a projection device relating to any of the above aspects is provided, wherein the resin cured layer comprises an acrylic resin cured product.

[0017] According to yet another aspect of the present invention, a projection device is provided relating to any of the above aspects, wherein the resin cured layer further contains hollow particles.

[0018] According to yet another aspect of the present invention, a projection device is provided which includes a plurality of vertical cavity surface-emitting lasers as described above.

[0019] In yet another aspect of the present invention, a measuring device is provided comprising a projection device according to any of the above aspects, and a light receiving device that receives reflected light generated when a laser beam emitted by the projection device is reflected by an object. [Effects of the Invention]

[0020] According to the present invention, a technique is provided that makes it difficult for the performance of a projection device to change due to heat generation of a laser.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a schematic diagram showing a measuring device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a projection device included in the measuring device shown in FIG. 1. [Figure 3] FIG. 3 is a perspective view showing a part of the diffractive optical element of FIG. 1. [Figure 4] FIG. 4 is a diagram for explaining the shape of the convex portion of the diffractive optical element shown in FIG. 3. [Figure 5] FIG. 5 is a cross-sectional view showing a first step in an example of a method for manufacturing the diffractive optical element shown in FIG. 3. [Figure 6] FIG. 6 is a cross-sectional view showing a second step in an example of a method for manufacturing the diffractive optical element shown in FIG. 3. [Figure 7] FIG. 7 is a cross-sectional view showing a third step in an example of a method for manufacturing the diffractive optical element shown in FIG. 3. [Figure 8] FIG. 8 is a perspective view showing a part of a diffractive optical element according to a modified example.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are more specific examples of any of the above aspects. The matters described below can be incorporated into each of the above aspects alone or in combination.

[0023] In addition, the embodiments shown below illustrate configurations for embodying the technical idea of the present invention, and the technical idea of the present invention is not limited by the materials, shapes, and structures of the following constituent members. Various changes can be made to the technical idea of the present invention within the technical scope defined by the claims described in the claims.

[0024] Elements with similar or identical functions are given the same reference numerals in the drawings referenced below, and redundant explanations are omitted. Furthermore, the drawings are schematic, and the relationships between dimensions in one direction and those in another, and the relationships between the dimensions of one component and those of other components, may differ from reality.

[0025] <Overall configuration of the measuring device> Figure 1 is a schematic diagram showing a measuring device according to an embodiment of the present invention.

[0026] The measuring device 500 shown in Figure 1 includes a projection device 100 and a light receiving device 200. The measuring device 500 emits a laser beam from the projection device 100 toward the object to be irradiated, and the light receiving device 200 receives the reflected light generated by the reflection from the object to be irradiated, thereby acquiring distance information.

[0027] The projection device 100 includes a diffractive optical element 10, an infrared laser 20, and a collimator 30.

[0028] The diffractive optical element 10 is used for at least one of splitting and shaping a laser beam whose wavelength is in the near-infrared region. Here, the "near-infrared region" is a wavelength range of 780 nm to 1200 nm. Preferably, the wavelength is within the range of 920 nm to 960 nm. For example, the wavelength is 940 nm. The diffractive optical element 10 comprises a substrate that transmits the laser beam and a resin cured layer provided on the substrate that also transmits the laser beam. The resin cured layer generates a plurality of protrusions on the surface of the diffractive optical element 10 that exhibit diffraction. Each of the plurality of protrusions is in the shape of an inverse taper. Details of the diffractive optical element 10 will be described later.

[0029] The infrared laser 20 is positioned facing the substrate with a resin curing layer in between, and emits laser light toward the diffractive optical element 10. The infrared laser 20 is a semiconductor laser, such as a vertical cavity surface-emitting laser (VCSEL). The infrared laser 20 outputs a laser beam having the above wavelength. The infrared laser 20 may include multiple vertical cavity surface-emitting lasers.

[0030] The laser beam emitted by the infrared laser 20 is normally diffuse light. The collimator 30 collimates the laser beam emitted by the infrared laser 20.

[0031] The collimator 30 includes one or more lenses, and is positioned between the diffractive optical element 10 and the infrared laser 20 such that the resin curing layer is in contact with one of the one or more lenses. The collimator 30 collimates the laser light emitted by the infrared laser 20 and causes it to incident as a laser beam onto the main surface of the diffractive optical element on the resin curing layer side.

[0032] The diffractive optical element 10 performs at least one of splitting and shaping the laser beam. For example, when a laser beam is incident on the diffractive optical element 10, it splits the laser beam into three laser beams, specifically, one laser beam as zero-order diffracted light and two laser beams as first-order diffracted light. The projection device 100 projects these laser beams onto the object to be irradiated.

[0033] The light receiving device 200 includes an image sensor 40, a light collecting device 50, and a filter 60.

[0034] The focusing device 50 is positioned between the object to be illuminated and the image sensor 40. The focusing device 50 includes one or more lenses. The focusing device 50 focuses the reflected light generated by reflection from the object to be illuminated.

[0035] The filter 60 is installed between the focusing device 50 and the image sensor 40. The filter 60 exhibits high transmittance to light of the same wavelength as the laser beam and low transmittance to light of other wavelengths. The filter 60 transmits the reflected light focused by the focusing device 50 and blocks the ambient light that has passed through the focusing device 50.

[0036] The image sensor 40 includes a plurality of light-receiving elements, each containing a photoelectric conversion element. For example, each light-receiving element includes a plurality of pixels, each of which exhibits high sensitivity at the wavelength of the laser beam and low sensitivity at other wavelengths, such as the visible spectrum. The laser beam reflected from the object being irradiated reaches the image sensor 40 via the focusing device 50 and the filter 60.

[0037] For example, the measuring device 500 acquires information regarding the distance from the measuring device 500 to the beam spot on the object to be irradiated, for example, by the Time of Flight (ToF) method. Specifically, the measuring device 500 emits a laser beam in a pulsed manner from the projection device 100 toward the object to be irradiated, and the reflected light generated by reflection from the object to be irradiated is received by the light receiving device 200. The measuring device 500 calculates the distance from the measuring device 500 to the beam spot on the object to be irradiated from the delay time, which corresponds to the time from when the projection device 100 emits the laser beam until the light receiving device 200 receives the reflected light. The measuring device 500 may also acquire an infrared image having gradations corresponding to the distribution of the intensity of the reflected light.

[0038] <Example of a projection device> Figure 2 is a cross-sectional view showing an example of a projection device 100 included in the measuring device 500 shown in Figure 1. The projection device 100 shown in Figure 2 comprises a diffractive optical element 10, an infrared laser 20, a collimator 30, a first support 32, and a substrate 33.

[0039] The collimator 30 includes a second support 31 and one or more lenses. The second support 31 has a cylindrical shape. The second support 31 has a plurality of grooves on its inner surface that extend in the circumferential direction of the cylinder. The second support 31 is, for example, an assembly consisting of two parts. Each of the two parts has a shape obtained by dividing the second support 31 into two parts by a plane parallel to the height direction. The collimator 30 here includes one or more lenses: a first lens 30A, a second lens 30B, and a third lens 30C. As shown in Figure 2, these lenses are provided such that their thickness direction coincides with the height direction of the second support 31. The peripheral edges of each of the first lens 30A, the second lens 30B, and the third lens 30C are fitted into the grooves provided in the second support 31.

[0040] The first lens 30A faces the infrared laser 20 with an air gap in between. The third lens 30C is interposed between the first lens 30A and the diffractive optical element 10 and is in contact with the surface of the diffractive optical element 10 on the side of the resin cured layer 12. Specifically, the third lens 30C is in contact with the upper surface of the convex portion 12P (see Figure 3) included in the resin cured layer 12. The second lens 30B is interposed between the first lens 30A and the third lens 30C.

[0041] The first support 32 has a bottomed cylindrical shape. An opening is provided at the bottom of the first support 32. The diffractive optical element 10 is installed inside the first support 32 such that its peripheral edge is in contact with the bottom of the first support 32 and its central portion is exposed at the location of the opening.

[0042] A collimator 30 is fitted into the first support 32. The diffractive optical element 10 is sandwiched between the first support 32 and the collimator 30 at its peripheral edge.

[0043] The substrate 33 is a wiring board on which the infrared laser 20 is mounted. The first support 32 is fixed to the substrate 33. The above describes an example of the projection device 100.

[0044] Although the collimator 30 described above includes three lenses, the number of lenses included in the collimator 30 may be two or less, or four or more. Also, the second support 31 and the lenses may be fixed to each other with adhesive. The diffractive optical element 10, the collimator 30 and the first support 32 may also be fixed to each other with adhesive.

[0045] <Details of diffractive optical elements> Figure 3 is a perspective view showing a part of the diffractive optical element 10 shown in Figure 1. As described above, the diffractive optical element 10 shown in Figure 3 is a transmission-type diffractive optical element used for at least one of splitting and shaping a laser beam whose wavelength is in the near-infrared region.

[0046] The diffractive optical element 10 has a flat plate shape. For example, the maximum dimension of the diffractive optical element 10 in the direction perpendicular to its thickness is within the range of 1 mm to 50 mm.

[0047] The diffractive optical element 10 includes a substrate 11 and a resin cured layer 12.

[0048] The substrate 11 has first and second main surfaces that are perpendicular to the thickness direction of the diffractive optical element 10 and parallel to each other. The substrate 11 transmits the laser beam. One of the first and second main surfaces is the incident surface to which the laser beam is incident, and the other of the first and second main surfaces is the exit surface from which the laser beam is emitted.

[0049] The substrate 11 is made of, for example, an inorganic material. For example, the substrate 11 is a glass plate. The substrate 11 may also be made of an organic material such as a cured acrylic resin. The substrate 11 may be made of a single material or of multiple materials. For example, the substrate 11 may have a single-layer structure or a multi-layer structure.

[0050] The resin cured layer 12 is provided on the substrate 11, for example, on the first main surface. The resin cured layer 12 transmits the laser beam.

[0051] The resin curing layer 12 consists of a resin curing material such as an acrylic resin curing material. The resin curing layer 12 may further contain materials other than the resin curing material. For example, the resin curing layer 12 may be a mixture of the resin curing material and hollow particles having a small particle size. This mixture may have a smaller refractive index compared to the resin curing material it contains. As the hollow particles, for example, hollow silica particles can be used. The hollow particles preferably have an average particle size of several hundred nm as measured by the light scattering method. In one example, this average particle size is in the range of 100 nm to 1400 nm. The resin curing layer 12 has a refractive index at a wavelength of 940 nm, for example, in the range of 1.25 to 1.6.

[0052] The diffractive optical element 10 is positioned such that a portion of the surface of the resin cured layer 12 is in contact with a gas phase such as air. Reducing the refractive index reduces the difference between the refractive index of the resin cured layer 12 and the refractive index of the gas phase. Therefore, Fresnel reflection at the interface between the resin cured layer 12 and the gas phase is weakened, and the light utilization efficiency is increased. In addition, at least a portion of the laser beam reflected by Fresnel at the interface becomes stray light, which can reduce the measurement accuracy of the measuring device described above.

[0053] The "light utilization efficiency" is a value measured when a laser beam is incident on one main surface of the diffractive optical element 10, and is a value equivalent to the ratio E1 / E0 of the total energy E1 of the laser beam emitted from the other main surface of the diffractive optical element 10 to the energy E0 of the laser beam incident on the one main surface.

[0054] The resin curing layer 12 may be flexible. In this case, when the resin curing layer 12 is pressed against the lens included in the collimator 30, the upper surface of the convex portion 12P (see Figure 3) included in the resin curing layer 12 can deform to conform to the shape of the lens.

[0055] The resin curing layer 12 creates multiple protrusions 12P on the surface of the diffractive optical element 10 that exhibit diffraction. Specifically, the protrusions 12P create an optical path difference between the laser beam incident on the portion of the diffractive optical element 10 corresponding to the protrusions 12P and the laser beam incident on the portion of the diffractive optical element 10 corresponding to the recess, which is the gap between the protrusions 12P. The diffractive optical element 10 utilizes the interference resulting from this to perform at least one of splitting and shaping the laser beam. In other words, when a laser beam is incident on the diffractive optical element 10, it functions as at least one of a beam splitter and a beam shaper.

[0056] When the diffractive optical element 10 functions as a beam splitter, there is no limit to the number of laser beams emitted by the diffractive optical element 10 when a laser beam is incident on it, that is, the maximum number of beam spots that these laser beams can form on the object being irradiated. For example, the number of laser beams produced by passing through the diffractive optical element 10 may be 3 or more, 9 or more, 100 or more, 1000 or more, or even 10000. Here, as an example, let's assume that the diffractive optical element 10 functions as a beam splitter that divides a laser beam into three laser beams when it is incident on it.

[0057] The resin cured layer 12 includes a continuous film portion provided on the substrate 11 and a plurality of protrusions 12P provided thereon. The continuous film portion can be omitted.

[0058] The protrusions 12P here form a striped pattern. That is, each protrusion 12P extends in a first direction and is arranged spaced apart from one another in a second direction that intersects with the first direction.

[0059] As shown in Figure 3, each of the convex portions 12P has an inverse taper. That is, the cross section perpendicular to the length of each convex portion 12P has an inverse taper. For example, each of the multiple convex portions has a trapezoidal cross section perpendicular to its length, where the upper base is longer than the lower base. This cross section may also be an isosceles trapezoid where the upper base is longer than the lower base. Furthermore, this cross section may have a shape that is somewhat different from the trapezoidal shape described above. For example, this cross section may have a shape in which the corners at both ends of the upper base of the trapezoidal shape described above are rounded.

[0060] Each of the convex portions 12P is inversely tapered, and the upper surface of each convex portion 12P is in contact with one of the lenses included in the collimator 30 (see Figure 2). A projection device 100 with this configuration can efficiently dissipate heat originating from the infrared laser 20 from the collimator 30 to the diffractive optical element 10 compared to a case where the upper surface of the convex portion 12P is not in contact with the lens included in the collimator 30. Furthermore, a projection device 100 with the above configuration can increase the contact surface area between the convex portion 12P and the lens included in the collimator 30 compared to a case where the side walls of the convex portion 12P are not inclined and are perpendicular to the main surface of the substrate 11. As a result, heat originating from the infrared laser 20 can be efficiently dissipated from the collimator 30 to the diffractive optical element 10.

[0061] The reverse taper shape of the convex portion 12P will be further described below. Specifically, the preferred ranges for the "angle of inclination of the side wall θ", "height H", "width of the upper surface W1", "width of the lower end W2", "ratio of the width of the upper surface W1 to the width of the lower end W2 W1 / W2", and "ratio of the height H to the width of the upper surface W1 H / W1" will be described for the reverse taper shape of the convex portion 12P. For this explanation, Figure 4 shows an enlarged cross-section perpendicular to the length direction of the convex portion 12P, illustrating the "angle of inclination of the side wall θ", "height H", "width of the upper surface W1", and "width of the lower end W2".

[0062] Preferably, the inclination angle θ of the side wall of each of the protrusions 12P is within the range of 0.1° to 50°. More preferably, the inclination angle θ of the side wall is within the range of 0.5° to 20°, and even more preferably, within the range of 1° to 10°. When the inclination angle θ of the side wall is large, the contact surface area between the protrusion 12P and the lens included in the collimator 30 is large, making it easier to release heat originating from the infrared laser 20 from the collimator 30 to the diffractive optical element 10. On the other hand, when the inclination angle θ of the side wall is large, it may become difficult for the diffractive optical element 10 to achieve the desired optical effect. For this reason, it is preferable that the inclination angle θ of the side wall is within the above range.

[0063] Preferably, each of the protrusions 12P has a height H within the range of 0.1 μm to 10 μm. More preferably, the height H is within the range of 0.5 μm to 5 μm. When the height H is within the above range, the diffractive optical element 10 can easily achieve the desired optical effect and high heat dissipation.

[0064] Preferably, the upper surface width W1 of each of the protrusions 12P is within the range of 0.1 μm to 15 μm. More preferably, the upper surface width W1 is within the range of 0.5 μm to 10 μm. If the upper surface width W1 is large, the contact surface area between the protrusion 12P and the lens included in the collimator 30 increases, making it easier to release heat originating from the infrared laser 20 from the collimator 30 to the diffractive optical element 10. On the other hand, if the upper surface width W1 is large, it may become difficult for the diffractive optical element 10 to achieve the desired optical effect. For this reason, it is preferable that the upper surface width W1 is within the above range.

[0065] Preferably, the lower end width W2 of each of the protrusions 12P is within the range of 0.05 μm to 10 μm. More preferably, the lower end width W2 is within the range of 0.1 μm to 8 μm. When the lower end width W2 is within the above range, the diffractive optical element 10 can easily achieve the desired optical effect and high heat dissipation.

[0066] Preferably, the ratio W1 / W2 of the width of the upper surface to the width W2 of the lower end of each of the protrusions 12P is within the range of 1.05 to 2. More preferably, the ratio W1 / W2 is within the range of 1.05 to 1.5, and even more preferably, within the range of 1.05 to 1.2. When the ratio W1 / W2 is large, the area of ​​the contact surface between the protrusion 12P and the lens included in the collimator 30 is large, making it easier to release heat originating from the infrared laser 20 from the collimator 30 to the diffractive optical element 10. On the other hand, when the ratio W1 / W2 is large, it may become difficult for the diffractive optical element 10 to achieve the desired optical effect. For this reason, it is preferable that the ratio W1 / W2 is within the above range.

[0067] Preferably, the ratio H / W1 of the height H to the width W1 of the upper surface of each of the protrusions 12P is within the range of 0.1 to 10. More preferably, the ratio H / W1 is within the range of 0.2 to 5. When the ratio H / W1 is within the above range, the diffractive optical element 10 can easily achieve the desired optical effect and high heat dissipation.

[0068] The period of the arrangement of the protrusions 12P, i.e., the pitch P, is preferably in the range of 2.4 μm to 2.7 μm, and more preferably in the range of 2.5 μm to 2.6 μm. Reducing the pitch P increases the maximum value of the emission angle of the laser beam emitted by the diffractive optical element 10. In other words, reducing the pitch P widens the angular range of the laser beam emitted by the diffractive optical element 10. Increasing the pitch P decreases the maximum value of the emission angle of the laser beam emitted by the diffractive optical element 10. In other words, increasing the pitch P narrows the angular range of the laser beam emitted by the diffractive optical element 10.

[0069] <Method for manufacturing diffractive optical elements> The above-mentioned diffractive optical element 10 can be manufactured, for example, by the following method.

[0070] Figure 5 is a cross-sectional view showing the first step in an example of a method for manufacturing a diffractive optical element shown in Figure 3. Figure 6 is a cross-sectional view showing the second step in an example of a method for manufacturing a diffractive optical element shown in Figure 3. Figure 7 is a cross-sectional view showing the third step in an example of a method for manufacturing a diffractive optical element shown in Figure 3.

[0071] In the method shown in Figures 5 to 7, first, the substrate 11C shown in Figure 5 is prepared. The substrate 11C is the same as the substrate 11 described above, except that its dimensions in the direction perpendicular to the thickness direction are larger. For example, the maximum value of the dimension perpendicular to the thickness direction of the substrate 11C is within the range of 100 mm to 300 mm.

[0072] Next, a negative-type photosensitive resin is coated onto one main surface of the substrate 11C to obtain a resin layer 12R. This photosensitive resin is the raw material for the cured resin layer 12. For example, by using a resin that exhibits a large degree of attenuation of ultraviolet light in the thickness direction of the resin layer 12R as the photosensitive resin, the protrusions 12P can be made into an inverse tapered shape. For coating the photosensitive resin, for example, a spin coating method, a roll coating method, or a slot coating method can be used. With the spin coating method, the thickness of the resin layer 12R can be controlled by the rotation speed.

[0073] Next, the resin layer 12R is pattern-exposed. For example, as shown in Figure 6, ultraviolet light 16 is irradiated onto the resin layer 12R via a photomask 15. This causes a crosslinking reaction to occur in the exposed portion 12E of the resin layer 12R without causing a crosslinking reaction in the unexposed portion 12N of the resin layer 12R.

[0074] Next, the resin layer 12R is subjected to a developing process. In this developing process, for example, an alkaline aqueous solution is used as the developer. In this way, the aggregate element 10C shown in Figure 7 is obtained.

[0075] The aggregate element 10C includes a substrate 11C and a resin cured layer 12C provided on one of its main surfaces. The aggregate element 10C also contains multiple element regions, each corresponding to a diffractive optical element 10. Each portion of the resin cured layer 12C corresponding to these element regions corresponds to the resin cured layer 12 of the diffractive optical element 10. In the aggregate element 10C shown in Figure 7, the resin cured layer 12C consists only of multiple protrusions 12P, but the resin cured layer 12C may further include a continuous film portion interposed between these protrusions 12P and the substrate 11C. Subsequently, the aggregate element 10C is subjected to a dicing or other fragmentation process. This yields multiple diffractive optical elements 10, each corresponding to a multiple element region.

[0076] The diffractive optical element 10 can also be manufactured by other methods. For example, first, a resin layer 12R is formed on a substrate 11C. The material of the resin layer 12R may be a photosensitive resin or a non-photosensitive resin. Next, the resin layer 12R is cured, and a mask layer is formed on the resulting cured resin layer, with openings corresponding to the gaps between the protrusions 12P. Subsequently, the exposed parts of the cured resin layer are removed by dry etching to obtain a cured resin layer 12C. After that, the mask layer is removed from the cured resin layer 12C to obtain an aggregate element 10C. Furthermore, by subjecting the aggregate element 10C to a fragmentation process, multiple diffractive optical elements 10 can be obtained.

[0077] <Effects> In the projection device 100 described above, the resin cured layer 12 constituting the diffractive optical element 10 is in contact with one of the lenses included in the collimator 30. Specifically, the upper surface of the convex portion 12P included in the resin cured layer 12 is in contact with one of the lenses included in the collimator 30. Furthermore, in the projection device 100 described above, each of the convex portions 12P is in the shape of an inverse taper. Compared to cases where the upper surface of the convex portion 12P is not in contact with the lens included in the collimator 30, or where the side walls of the convex portion 12P are not inclined and are perpendicular to the main surface of the substrate 11, the projection device 100 with these configurations can efficiently dissipate heat originating from the infrared laser 20 from the collimator 30 to the diffractive optical element 10. The heat transferred to the diffractive optical element 10 is then released into the outside air or transferred to a member in contact with the diffractive optical element 10 (for example, the first support 32 in Figure 2).

[0078] Thus, the projection device 100 with the above configuration can not only release the heat originating from the infrared laser 20 to the ambient air surrounding the infrared laser 20, but also release it to the ambient air via the diffractive optical element 10. Therefore, the projection device 100 described above can dissipate the heat originating from the infrared laser 20 through more paths. Furthermore, the path through which heat is released via the diffractive optical element 10 achieves high heat dissipation because the convex portion 12P is in the shape of an inverse taper. Consequently, in the projection device 100 described above, the lens included in the collimator 30 is less likely to rise to an excessively high temperature, and as a result, it is possible to suppress changes in the refractive index of the lens and changes in the focal length. As described above, the projection device 100 described above can achieve the effect of being less susceptible to changes in performance caused by heat generation from the laser.

[0079] <Variation> The following describes some modified versions of the diffractive optical element 10 described above. Figure 8 is a perspective view showing a part of a modified diffractive optical element. The diffractive optical element 10 shown in Figure 8 is the same as the diffractive optical element 10 shown in Figure 3, except that it has a resin cured layer consisting of a first layer and a second layer, which will be described below, instead of the resin cured layer 12 shown in Figure 3.

[0080] The resin cured layer 12 shown in Figure 8 consists of a first layer 120 and a second layer 121. The first layer 120 is interposed between the second layer 121 and the substrate 11. In the resin cured layer 12 shown in Figure 8, a portion of the first layer 120 and the second layer 121 form the aforementioned multiple protrusions 12P. As the material for the first layer, a material that can achieve high durability, such as epoxy resin, silicone resin, or acrylic resin, can be used.

[0081] The second layer 121 includes the upper surface of the protrusion 12P. Examples of materials for the second layer include so-called sacrificial film materials, and it is preferable to use materials that can achieve high pattern accuracy, such as polymer-based materials, silicon oxides, and silicon nitrides.

[0082] The following describes an example of a manufacturing method for the diffractive optical element 10 shown in Figure 8. First, the substrate 11C is prepared. Next, the material for the first layer 120 is coated onto one main surface of the substrate 11C to obtain the first resin layer.

[0083] Next, a negative-type photosensitive resin is coated onto the first resin layer as the material for the second layer 121 to obtain the second resin layer. For coating the first and second resin layers, the above-described methods, such as the spin coating method, can be used.

[0084] Next, the second resin layer is pattern-exposed using the same method as the pattern exposure method for the resin layer 12R described above. Subsequently, the second resin layer is subjected to a development process using the same method as the development process for the resin layer 12R described above. In this way, the second resin layer is patterned.

[0085] Next, the first resin layer is etched using the patterned second resin layer as a mask. In this way, a resin cured layer 12 having the first layer 120 and the second layer 121 is obtained.

[0086] The above describes an example of a method for manufacturing a diffractive optical element having a resin cured layer with a first layer 120 and a second layer 121. This method yields a convex portion 12P with high pattern accuracy and excellent durability.

[0087] As another modification, the projection device 100 described above may further include a heat sink and a heat transfer element. For example, the projection device 100 shown in Figure 2 may further include a heat sink provided outside the first support 32 and a heat transfer element that guides heat from the diffractive optical element 10 to the heat sink.

[0088] Each of the heat transfer element and heat sink is made of, for example, a highly thermally conductive material. Highly thermally conductive materials include, for example, metals such as copper, aluminum, iron, silver, titanium, molybdenum, tantalum, tungsten, and niobium; alloys containing one or more of these metals; carbides such as tungsten carbide; carbon materials such as graphite, graphene, carbon nanotubes, and diamond; other insulating ceramics; or composite materials containing one or more of these. Each of the heat transfer element and heat sink may have a single-layer structure or a multi-layer structure.

[0089] If the projection device 100 further includes a heat transfer element and a heat sink, it can promote the release of heat transferred from the infrared laser 20 to the diffractive optical element 10 into the outside air. [Explanation of symbols]

[0090] 10...Diffractive optical element, 10C...Assembly element, 11...Substrate, 11C...Substrate, 12...Resin cured layer, 12C...Resin cured layer, 12E...Exposed area, 12N...Unexposed area, 12P...Convex area, 12R...Resin layer, 15...Photomask, 16...Ultraviolet light, 20...Infrared laser, 30...Collimator, 30A...First lens, 30B...Second lens, 30C...Third lens, 31...Second support, 32...First support, 33...Substrate, 40...Image sensor, 50...Collecting device, 60...Filter, 100...Projection device, 120...First layer, 121...Second layer, 200...Light receiving device, 500...Measurement device, H...Height, P...Pitch, W1...Width of top surface, W2...Width of bottom surface, θ...Side wall inclination angle.

Claims

1. A diffractive optical element for use in at least one of splitting and shaping a laser beam whose wavelength is in the near-infrared region, comprising a substrate that transmits the laser beam, and a resin cured layer provided on the substrate that transmits the laser beam, wherein the resin cured layer has a plurality of protrusions on the surface of the diffractive optical element that exhibit diffraction, and each of the plurality of protrusions is in the shape of an inverse taper diffractive optical element, An infrared laser is installed facing the substrate with the resin cured layer in between, and emits laser light toward the diffractive optical element. A collimator comprising one or more lenses, wherein the resin cured layer is positioned between the diffractive optical element and the infrared laser so as to be in contact with one of the one or more lenses, and the collimator collimates the laser light emitted by the infrared laser and causes it to be incident on the diffractive optical element as a laser beam. A projection device equipped with a projection system.

2. The projection device according to claim 1, wherein the plurality of protrusions form a stripe-like pattern.

3. The projection device according to claim 1, wherein each of the plurality of protrusions has a side wall inclination angle θ within the range of 0.1° to 50°.

4. The projection device according to claim 1, wherein each of the plurality of protrusions has a height H within the range of 0.1 μm to 10 μm.

5. The projection device according to claim 1, wherein each of the plurality of protrusions has an upper surface width W1 within the range of 0.1 μm to 15 μm.

6. The projection device according to claim 1, wherein each of the plurality of protrusions has a lower surface width W2 within the range of 0.05 μm to 10 μm.

7. The projection device according to claim 1, wherein each of the plurality of protrusions has a ratio W1 / W2 of the width of the upper surface to the width W2 of the lower surface within the range of 1.05 or more and 2 or less.

8. The projection device according to claim 1, wherein each of the plurality of protrusions has a ratio H / W1 of height to width W1 of the upper surface within the range of 0.2 to 10.

9. The projection apparatus according to claim 1, wherein the resin cured layer comprises an acrylic resin cured material.

10. The projection apparatus according to claim 1, wherein the resin cured layer further contains hollow particles.

11. The projection apparatus according to claim 1, wherein the infrared laser includes a plurality of vertical cavity surface-emitting lasers.

12. A projection device according to any one of claims 1 to 11, A light receiving device that receives reflected light generated when the laser beam emitted by the projection device is reflected by an object, and A measuring device equipped with the following features.

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