Diffractive optical elements

Abstract

This technology provides a way to facilitate the handling of diffractive optical elements. [Solution] The diffractive optical element 10A 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 11 that transmits the laser beam and a second surface which is the back surface of the first surface, and a resin cured layer 12 provided on the first surface that transmits the laser beam, wherein the resin cured layer has a plurality of protrusions 12P on the surface of the diffractive optical element that cause diffraction of the laser beam, and the second surface has an uneven structure that includes a plurality of protrusions or recesses whose diameter or width is within the visible wavelength range.

Description

Technical Field

[0001] The present invention relates to a diffractive optical element.

Background Art

[0002] In recent years, fingerprint authentication technology and face authentication technology have been used as security measures in smartphones. Face authentication technology can achieve a higher security level compared to fingerprint authentication technology. Furthermore, since face authentication technology performs personal authentication in a non-contact manner, it is characterized by being more convenient and stress-free than fingerprint authentication technology.

[0003] However, face authentication technology has problems such as being unable to achieve high recognition accuracy in dark environments. For these reasons, infrared rays are sometimes used in face authentication technology.

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

[0005] The aforementioned projection device includes, for example, an infrared laser, a collimator that collimates the laser beam emitted from the infrared laser, and a beam splitter or beam shaper that splits or shapes the collimated laser beam. When the beam splitter or beam shaper is configured with lenses and prisms, it is difficult to reduce the size of the projection device. Accordingly, a diffractive optical element (DOE) is sometimes used as the beam splitter or beam shaper (see Patent Document 1).

Prior Art Literature

Patent Literature

[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 can facilitate the handling of diffractive optical elements. [Means for solving the problem]

[0008] According to one aspect of the present invention, a diffractive optical element is provided 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 having a first surface and a second surface which is the back surface thereof, and a first resin cured layer provided on the first surface that transmits the laser beam, wherein the first resin cured layer has a plurality of protrusions on the surface of the diffractive optical element that cause diffraction of the laser beam, and the second surface has an uneven structure including a plurality of first protrusions or first recesses whose diameter or width is within the visible wavelength range.

[0009] According to another aspect of the present invention, a diffractive optical element is provided, which includes a plurality of first protrusions or first recesses, the ratio of height or depth to diameter or width being within the range of 0.1 to 10.

[0010] According to yet another aspect of the present invention, a diffractive optical element is provided that further includes a plurality of second protrusions or second recesses having a diameter or width larger than the visible wavelength range, wherein the plurality of second protrusions or second recesses have a height or depth of 900 nm or less.

[0011] According to yet another aspect of the present invention, the second aspect provides a diffractive optical element having light scattering properties that scatter light in the visible wavelength range, relating to any of the above aspects.

[0012] According to yet another aspect of the present invention, a diffractive optical element is provided relating to any of the above aspects, wherein the first surface is a smooth surface.

[0013] According to yet another aspect of the present invention, a diffractive optical element is provided in which the substrate includes a glass plate, according to any of the above aspects.

[0014] According to yet another aspect of the present invention, a diffractive optical element is provided, wherein the substrate further includes a second resin cured layer that faces the first resin cured layer with the glass plate in between, and that gives the second surface the uneven structure.

[0015] According to yet another aspect of the present invention, a diffractive optical element is provided which further comprises a conductive inorganic oxide layer interposed between the glass plate and the second resin cured layer.

[0016] According to yet another aspect of the present invention, there is an aggregate element that includes a plurality of element regions and is fragmented into a plurality of diffractive optical elements corresponding to each of the plurality of element regions, wherein each of the plurality of diffractive optical elements is a diffractive optical element according to any of the above aspects.

[0017] In yet another aspect of the present invention, a projection device is provided comprising a diffractive optical element according to any of the above aspects and an infrared laser that emits the laser beam.

[0018] According to yet another aspect of the present invention, a measuring device is provided comprising a projection device according to the above aspect 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]

[0019] According to the present invention, a technique is provided that can facilitate the handling of diffractive optical elements. [Brief explanation of the drawing]

[0020] [Figure 1]FIG. 1 is a perspective view showing a part of a diffractive optical element according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a first step in an example of a method of manufacturing the diffractive optical element shown in FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view showing a second step in an example of a method of manufacturing the diffractive optical element shown in FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view showing a third step in an example of a method of manufacturing the diffractive optical element shown in FIG. 1. [Figure 5] FIG. 5 is a perspective view showing a part of a diffractive optical element according to a modified example. [Figure 6] FIG. 6 is a diagram schematically showing an example of a measuring device. MODE FOR CARRYING OUT THE INVENTION

[0021] Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below further embody any of the above aspects. The matters described below can be incorporated into each of the above aspects alone or in combination of two or more.

[0022] The embodiments described below illustrate configurations for embodying the technical idea of the present invention. The drawings are schematic, and the relationship between dimensions in one direction and dimensions in another direction, the relationship between dimensions of one member and dimensions of another member, and the like may differ from actual ones. The technical idea of the present invention is not limited by the material, shape, structure, etc. of the constituent members described below. Various changes can be added to the technical idea of the present invention within the technical scope defined by the claims set forth in the claims.

[0023] Elements having the same or similar functions are denoted by the same reference numerals in the drawings referred to below, and duplicate explanations are omitted.

[0024] FIG. 1 is a perspective view showing a part of a diffractive optical element according to an embodiment of the present invention. The diffractive optical element 10A shown in Figure 1 is a transmissive diffractive optical element 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 the 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.

[0025] The diffractive optical element 10A has a flat plate shape. For example, the maximum dimension of the diffractive optical element 10A in the direction perpendicular to its thickness is within the range of 1 mm to 50 mm.

[0026] The diffractive optical element 10A includes a substrate 11 and a resin cured layer 12.

[0027] The substrate 11 has first and second surfaces that are perpendicular to the thickness direction of the diffractive optical element 10A and parallel to each other. The substrate 11 transmits the laser beam. One of the first and second surfaces is the incident surface to which the laser beam is incident, and the other of the first and second surfaces is the exit surface from which the laser beam is emitted.

[0028] The substrate 11 is made of, for example, an inorganic material. Here, as an example, the substrate 11 is assumed to be a glass plate 11G.

[0029] The substrate 11 may 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. Here, as an example, the substrate 11 will be assumed to have a single-layer structure.

[0030] As will be described later, a resin curing layer 12 is provided on the first surface of the substrate 11. The first surface of the substrate 11 is, in one example, a smooth surface. Such a first surface does not produce visible light scattering when illuminated with visible light, for example, white light.

[0031] The second surface of the substrate 11 has the uneven structure described below. The uneven structure may be provided over the entire surface of the second surface. Alternatively, the second surface may include one or more regions with the uneven structure and one or more regions without the uneven structure.

[0032] The uneven structure imparts light scattering properties to the second surface, for example, by scattering light within the visible wavelength range. Here, the uneven structure includes a plurality of protrusions or recesses distributed in an island-like manner, with at least one of their shape and arrangement being irregular. The uneven structure may also include a plurality of protrusions or recesses, each having a shape extending in one direction, adjacent in the width direction, with irregular distances between adjacent parts in the width direction, or having different lengths in the width direction, or having both of these structures.

[0033] The uneven structure on the second surface includes a plurality of first protrusions or first recesses whose diameter or width is within the visible wavelength range. Here, the visible wavelength range is the wavelength range of 380 nm to 750 nm. Preferably, the first protrusions or first recesses include those whose diameter or width is within the range of 400 nm to 700 nm. When the first protrusions or first recesses whose diameter or width is within the above range are illuminated with light whose wavelength is within the visible wavelength range, such as white light, they can generate highly intense scattered light.

[0034] The first protrusion or first recess preferably includes a protrusion or recess in which the ratio of height or depth to diameter or width is in the range of 0.1 to 10, and more preferably includes a protrusion or recess in which the ratio of height or depth to diameter or width is in the range of 0.5 to 5. Such protrusions or recesses contribute greatly to the effect of generating scattered light with high intensity when illuminated with light whose wavelength is in the visible wavelength range, such as white light.

[0035] In the uneven structure provided on the second surface, the number of first protrusions or first recesses per apparent area of ​​the uneven structure is 10 per mm 2 More than 3000 pieces / mm 2 Preferably, it should be within the following range: 100 pieces / mm 2More than 1000 pieces / mm 2 It is more preferable that the following ranges apply. Furthermore, in the uneven structure provided on the second surface, if the ratio of height or depth to diameter or width of the first protrusion or first recess is within the above range, the number of uneven structures per apparent area is 5 / mm². 2 More than 2000 pieces / mm 2 The following range is preferred, with 50 pieces / mm 2 More than 500 pieces / mm 2 It is more preferable that the range be within the following limits.

[0036] The uneven structure on the second surface may further include a plurality of second protrusions or second recesses whose diameter or width is larger than that of the visible wavelength range. The height or depth of the second protrusions or second recesses is preferably 900 nm or less, and more preferably 800 nm or less. Such second protrusions or second recesses have a low ability to scatter light with wavelengths in the visible wavelength range, such as white light, but also have a low ability to scatter laser beams with wavelengths in the near-infrared region.

[0037] The uneven structure on the second surface may further include a plurality of third protrusions or third recesses whose diameter or width is smaller than that of the visible wavelength range. Such third protrusions or third recesses have a particularly low ability to scatter laser beams in the near-infrared wavelength region.

[0038] The resin curing layer 12 is the first resin curing layer. The resin curing layer 12 is provided on the first main surface of the substrate 11. The resin curing layer transmits the laser beam described above.

[0039] 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.

[0040] The resin curing layer 12 generates multiple protrusions 12P on the surface of the diffractive optical element 10A 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 10A corresponding to the protrusions 12P and the laser beam incident on the portion of the diffractive optical element 10A corresponding to the recess, which is the gap between the protrusions 12P. The diffractive optical element 10A utilizes the interference resulting from this to perform at least one of splitting and shaping the laser beam. That is, when a laser beam is incident on the diffractive optical element 10A, it functions as at least one of a beam splitter and a beam shaper. The diffractive optical element 10A may also function as a collimator when a laser beam is incident on it.

[0041] When the diffractive optical element 10A functions as a beam splitter, there is no limit to the number of laser beams emitted by the diffractive optical element 10A 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. For example, the number of laser beams produced by passing through the diffractive optical element 10A 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 10A functions as a beam splitter that divides a laser beam into three laser beams when it is incident on it.

[0042] 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.

[0043] 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.

[0044] Each of the protrusions 12P has a rectangular cross-section perpendicular to its length. This cross-section may be tapered or tapered, but it is preferably rectangular.

[0045] Each of the protrusions 12P, for example, has a height H within the range of 0.5 μm to 1.7 μm and a width W within the range of 0.3 μm to 2.0 μm. If the protrusion 12P is not rectangular, the width W of the protrusion 12P is the width of the protrusion 12P at half its height.

[0046] 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 10A. In other words, reducing the pitch P widens the angular range of the laser beam emitted by the diffractive optical element 10A. Increasing the pitch P decreases the maximum value of the emission angle of the laser beam emitted by the diffractive optical element 10A. In other words, increasing the pitch P narrows the angular range of the laser beam emitted by the diffractive optical element 10A.

[0047] The above-mentioned diffractive optical element 10A can be manufactured, for example, by the following method.

[0048] Figure 2 is a cross-sectional view showing the first step in an example of a method for manufacturing a diffractive optical element shown in Figure 1. Figure 3 is a cross-sectional view showing the second step in an example of a method for manufacturing a diffractive optical element shown in Figure 1. Figure 4 is a cross-sectional view showing the third step in an example of a method for manufacturing a diffractive optical element shown in Figure 1.

[0049] In the method shown in Figures 2 to 4, first, the substrate 11C shown in Figure 2 is prepared. Substrate 11C is the same as 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 substrate 11C is within the range of 100 mm to 300 mm.

[0050] As the substrate 11C, for example, one in which the first surface is a smooth surface and the above-mentioned uneven structure is provided on the second surface, which is the back surface. Such a substrate 11C can be obtained, for example, by forming an uneven structure on one surface of a plate material that has smooth surfaces on both sides by etching and sandblasting.

[0051] Next, a negative-type photosensitive resin is coated onto the first 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 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.

[0052] Next, the resin layer 12R is pattern-exposed. For example, as shown in Figure 3, 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.

[0053] 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 4 is obtained.

[0054] The aggregate element 10C includes a substrate 11C and a resin cured layer 12C provided on one of its main surfaces. Furthermore, each aggregate element 10C contains multiple element regions corresponding to diffractive optical elements 10A. 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 10A. While the aggregate element 10C shown in Figure 4 consists only of multiple protrusions 12P in the resin cured layer 12C, the resin cured layer 12C may further include a continuous film interposed between these protrusions 12P and the substrate 11C.

[0055] Subsequently, the aggregate element 10C is subjected to a fragmentation process such as dicing. This yields multiple diffractive optical elements 10A, each corresponding to a different element region.

[0056] The diffractive optical element 10A 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 10A can be obtained.

[0057] The diffractive optical element 10A can be distributed individually. That is, multiple diffractive optical elements 10A can be distributed individually rather than as a set. However, it is common practice to distribute an assembly of multiple diffractive optical elements 10A.

[0058] Instead of distributing the diffractive optical element 10A or element assembly as a finished product, an intermediate product, the element assembly 10C, may be distributed. That is, the element assembly 10C may be distributed first, and then the individual diffractive optical elements 10A may be separated from it.

[0059] The diffractive optical element 10A described above has a smooth upper surface on the convex portion 12P, and the region on the resin cured layer 12 side of the surface sandwiched between adjacent convex portions 12P is also smooth. Therefore, for example, under conditions where the diffractive optical element 10A is illuminated with white light from the resin cured layer 12 side and an observer observes the diffractive optical element 10A from the resin cured layer 12 side, the diffractive optical element 10A does not emit high-intensity scattered light toward the observer.

[0060] In contrast, the second surface of the substrate 11 is provided with the aforementioned uneven structure. Therefore, for example, under conditions where the diffractive optical element 10A is illuminated with white light from the substrate 11 side and an observer observes the diffractive optical element 10A from the substrate 11 side, the diffractive optical element 10A can emit scattered light of higher intensity toward the observer.

[0061] Thus, under illumination conditions with visible light, the diffractive optical element 10A exhibits different light scattering properties on one side and the other. Therefore, it is possible to distinguish the front and back sides of the diffractive optical element 10A based on the above-mentioned difference in optical behavior. Consequently, the diffractive optical element 10A is easy to handle.

[0062] Furthermore, the uneven structure on the second surface does not strongly scatter laser beams in the near-infrared wavelength range. In other words, the uneven structure on the second surface does not significantly affect the function of the diffractive optical element 10A as a beam splitter and beam shaper, and facilitates the handling of the diffractive optical element 10A.

[0063] The diffractive optical element 10A and the aggregate element 10C described above can be modified in various ways. Figure 5 is a perspective view showing a part of a modified diffractive optical element.

[0064] The diffractive optical element 10B shown in Figure 5 is the same as the diffractive optical element 10A described above, except for the following: In the diffractive optical element 10B, the glass plate 11G has the following structure. Furthermore, the substrate 11 of the diffractive optical element 10B further includes a resin cured layer 11R and a conductive inorganic oxide layer 11I.

[0065] The glass plate 11G is the same as the glass plate 11G of the diffractive optical element 10A, except that both sides are smooth surfaces. Here, the glass plate 11G is a substrate that supports the resin cured layer 11R and the conductive inorganic oxide layer 11I. The substrate 11 may include an organic material such as an acrylic resin cured product instead of the glass plate 11G as the substrate. The substrate may consist of a single material or multiple materials. For example, the substrate may have a single-layer structure or a multilayer structure.

[0066] The resin curing layer 11R is the second resin curing layer. The resin curing layer 11R faces the resin curing layer 12 with the glass plate 11G in between, creating an uneven surface on the second surface of the substrate 11. This uneven surface is similar to the uneven surface on the second surface of the substrate 11 of the diffractive optical element 10A.

[0067] The resin curing layer 11R includes, for example, a cured product of an ultraviolet-curable resin, a cured product of a thermosetting resin, a thermoplastic resin, or two or more of these. The resin curing layer 11R may have a single-layer structure or a multilayer structure. In one example, the resin curing layer 11R is a continuous film having the above-described uneven structure on its surface. In another example, the resin curing layer 11R is a film having a plurality of through-holes, each extending in the thickness direction. In yet another example, the resin curing layer 11R is a layer consisting of a plurality of island-like portions spaced apart from each other.

[0068] The resin cured layer 11R can be formed, for example, by forming a photosensitive resin layer on the conductive inorganic oxide layer 11I, and then sequentially performing pattern exposure and development processing on it. Alternatively, the resin cured layer 11R can be formed by forming a thermosetting resin layer or a photosensitive resin layer on the conductive inorganic oxide layer 11I, pressing a plate against it, heating or irradiating with light in that state to cure the resin, and then removing the plate from the cured resin layer. Alternatively, the resin cured layer 11R can be formed by forming a thermoplastic resin layer on the conductive inorganic oxide layer 11I, pressing a heated plate against it, cooling it to cure the resin, and then removing the plate from the cured resin layer. Alternatively, the resin cured layer 11R can be formed by preparing a coating liquid containing particles, resin, and solvent, applying this coating liquid to the conductive inorganic oxide layer 11I, and drying the coating film. Alternatively, the resin cured layer 11R can also be formed by at least partially transferring a transfer material, which is peelably supported by a support, from the support onto the conductive inorganic oxide layer 11I.

[0069] The conductive inorganic oxide layer 11I is interposed between the glass plate 11G and the resin curing layer 11R. The diffractive optical element 10A may be damaged, for example, if the projection device or measuring device containing it is dropped. If the diffractive optical element 10A is damaged and its optical diffraction ability decreases, there is a risk that the laser beam may be irradiated onto a human body without being diffracted. By providing the conductive inorganic oxide layer 11I, the electrical properties of the conductive inorganic oxide layer 11I change when the diffractive optical element 10B is damaged. Therefore, by providing the conductive inorganic oxide layer 11I, for example, it becomes possible to detect damage to the diffractive optical element 10B by an electrical method and to stop the power supply to the laser when damage is detected.

[0070] The conductive inorganic oxide layer 11I is a layer made of a conductive inorganic oxide such as indium tin oxide. The conductive inorganic oxide layer 11I can be formed, for example, by a vapor deposition method such as sputtering. The conductive inorganic oxide layer 11I can be omitted.

[0071] This diffractive optical element 10B produces the same effect as the diffractive optical element 10A described above. Furthermore, the aggregate element 10C can also be modified in the same way as the diffractive optical element 10B described above.

[0072] The diffractive optical elements 10A and 10B described above can be used, for example, in a projection device. Furthermore, a projection device including the diffractive optical element 10A or 10B can be used, for example, in a measuring device.

[0073] Figure 5 is a schematic diagram showing an example of a measuring device. The measuring device 500 shown in Figure 5 includes a projection device 100 and a light receiving device 200.

[0074] The projection device 100 includes a diffractive optical element 10, an infrared laser 20, and a collimator 30.

[0075] The diffractive optical element 10 is the diffractive optical element 10A or 10B described above. In one example, the diffractive optical element 10 is installed so that the resin cured layer 12 faces the infrared laser 20. In another example, the diffractive optical element 10 is installed so that the substrate 11 faces the infrared laser 20.

[0076] The infrared laser 20 is, for example, a semiconductor laser. For example, the infrared laser 20 is a surface-emitting laser with one or more vertical cavity chambers. The infrared laser 20 outputs a laser beam having the wavelength described above.

[0077] The laser beam output by the infrared laser 20 is normally diffuse light. The collimator 30 collimates the laser beam output by the infrared laser 20. Note that if the diffractive optical element 10 performs the role of a collimator, the collimator 30 can be omitted.

[0078] A collimated laser beam is incident on the diffractive optical element 10. This laser beam may be incident on either of the main surfaces of the diffractive optical element 10. For example, the laser beam is incident on the main surface of the diffractive optical element 10 on the side of the resin cured layer 12. For another example, the laser beam is incident on the main surface of the diffractive optical element 10 on the side of the substrate 11.

[0079] The diffractive optical element 10 performs at least one of splitting and shaping the laser beam. As described above, 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 target object.

[0080] The light receiving device 200 receives reflected light generated when the laser beam emitted by the projection device 100 is reflected by an object. The light receiving device 200 includes a light concentrator 50, an optical filter 60, and an image sensor 40.

[0081] The focusing device 50 is positioned between the object and the image sensor 40. The focusing device 50 focuses the reflected light generated by the reflection from the object. The focusing device 50 includes one or more lenses.

[0082] The optical filter 60 is installed between the light concentrator 50 and the image sensor 40. The optical filter 60 exhibits high transmittance to light of the same wavelength as the laser beam and low transmittance to light of other wavelengths. The optical filter 60 transmits the reflected light focused by the light concentrator 50 and blocks the ambient light that has passed through the light concentrator 50.

[0083] The image sensor 40 includes multiple light-receiving elements, each containing a photoelectric conversion element. These light-receiving elements exhibit high sensitivity at the wavelength of the laser beam mentioned above.

[0084] The measuring device 500 obtains distance information by emitting a laser beam from the projection device 100 toward the object and receiving the reflected light generated by the reflection from the object with the light receiving device 200. For example, the measuring device 500 obtains distance information from the measuring device 500 to the beam spot on the object, 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 and receives the reflected light generated by the reflection from the object with the light receiving device 200. The measuring device 500 calculates the distance from the measuring device 500 to the beam spot on the object 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 further acquire an infrared image having gradations corresponding to the distribution of the intensity of the reflected light. [Explanation of Symbols]

[0085] 10...Diffractive optical element, 10A...Diffractive optical element, 10B...Diffractive optical element, 10C...Assembly element, 11...Substrate, 11C...Substrate, 11G...Glass plate, 11I...Conductive inorganic oxide layer, 11R...Resin cured layer, 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, 40...Image sensor, 50...Light focusing device, 60...Optical filter, 100...Projection device, 200...Light receiving device, 500...Measurement device, H...Height, P...Pitch, W...Width.

Claims

1. A diffractive optical element used for at least one of splitting and shaping a laser beam whose wavelength is in the near-infrared region, A substrate having a first surface and a second surface which is the back surface, through which the laser beam is transmitted, A first resin cured layer provided on the first surface, which transmits the laser beam, Equipped with, The first resin cured layer has a plurality of protrusions on the surface of the diffractive optical element that cause diffraction in the laser beam, The second surface is a diffractive optical element having an uneven structure that includes a plurality of first protrusions or first recesses whose diameter or width is within the visible wavelength range.

2. The diffractive optical element according to claim 1, wherein the plurality of first protrusions or first recesses have a ratio of height or depth to diameter or width within the range of 0.1 to 10.

3. The diffractive optical element according to claim 1, wherein the uneven structure further includes a plurality of second protrusions or second recesses having a diameter or width larger than the visible wavelength range, and the plurality of second protrusions or second recesses have a height or depth of 900 nm or less.

4. The diffractive optical element according to claim 1, wherein the second surface has light scattering properties that scatter light in the visible wavelength range.

5. The diffractive optical element according to claim 1, wherein the first surface is a smooth surface.

6. The diffractive optical element according to claim 1, wherein the substrate includes a glass plate.

7. The diffractive optical element according to claim 6, wherein the substrate further includes a second resin cured layer facing the first resin cured layer with the glass plate sandwiched in between, and the second surface having a plurality of protrusions or recesses.

8. The diffractive optical element according to claim 7, wherein the substrate further comprises a conductive inorganic oxide layer interposed between the glass plate and the second resin cured layer.

9. An aggregate element comprising a plurality of element regions, which are fragmented into a plurality of diffractive optical elements corresponding to each of the plurality of element regions, wherein each of the plurality of diffractive optical elements is a diffractive optical element according to any one of claims 1 to 8.

10. A diffractive optical element according to any one of claims 1 to 8, An infrared laser that emits the aforementioned laser beam and A projection device equipped with a projection system.

11. The projection device according to claim 10, 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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