JP2019061269A - Optical element and projection device - Google Patents

Abstract

To provide a diffuser plate that can be processed by wet etching and shows high use efficiency of light.SOLUTION: A plurality of recesses 12 is formed on a surface of a substrate 11. Each recess 12 has a curved part formed by a curved plane. The plurality of recesses 12 is formed in such a manner that positions of bottoms 13 of the recesses 12 are located at two or more different positions in a depth direction. A refractive index of the substrate 11 is denoted by n1, a refractive index of a medium around the substrate 11 is denoted by n2, wavelength of a beam incident to the substrate 11 is denoted by λ, and a depth direction range of the bottoms 13 at the plurality of recesses 12 is denoted by Δd. In this case, relation of 2/7≤|(n1-n2)×Δd|/λ≤10 is satisfied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical element and a projection apparatus.

  In the case of a projection apparatus using a laser as a light source, a scattering plate as disclosed in Patent Document 1 may be used to correct the intensity distribution of a light beam emitted from the laser. However, since the scattering plate diffuses light due to random irregularities on the surface, the utilization efficiency of light is generally low, and it is preferable that the diffusion of light is within a predetermined range due to the refraction like a microlens array.

  By the way, when a highly coherent light source such as a laser is used, in the case of a microlens having a regular arrangement, diffracted light is generated only in a predetermined direction according to the regularity of the arrangement, and correction of the light intensity distribution is performed. It may be insufficient. As a method of reducing such diffraction effects, there is a method of introducing irregularity to a microlens array, and in particular, by introducing irregularity within a controlled range, light is diffused to a predetermined angular range. It is known how to make it happen. Patent Document 2 discloses a microstructure in which irregularities are introduced in the depth direction, and an example of a microstructure having a distribution range in the depth direction of 10 μm or more is shown.

Unexamined-Japanese-Patent No. 2007-233371 U.S. Pat. No. 7,033,736

  However, since the microstructure of Patent Document 2 has a large distribution in the depth direction, unnecessary scattered light may be generated when light such as diverging light is obliquely incident. .

  When laser light is made incident, light resistance may be required, and it is preferable that the substrate used be formed of a light resistant material such as glass. As a method of processing the surface of glass or the like into a concavo-convex shape, there is a method of processing by wet etching, but in general, there is a restriction on the shape that can be processed by wet etching, and it is described in Patent Document 2 As described above, in the case where the concavo-convex shape is formed deep and with different depths, it is difficult to process it into a desired shape.

  On the other hand, as a method of processing the surface of glass or the like into a concavo-convex shape, there is also a processing method by dry etching or press molding, but when the concavo-convex shape is formed deep, there is a problem that the processing time in dry etching becomes long. Also, in the case of press molding, there is a problem that air enters at the time of press molding, and a part where the air enters is a defect.

  Therefore, there is a need for an optical element that can be processed using wet etching and is a diffusion plate with high light utilization efficiency.

According to one aspect of the present embodiment, a plurality of concave portions are formed on the surface of the base material, and the concave portions have curved surface portions formed by curved surfaces, and the plurality of concave portions are: The position of the bottom of the recess is formed so as to be two or more different positions in the depth direction, the refractive index of the substrate is n1, and the refractive index of the medium around the substrate is n2. Assuming that the wavelength of the light beam incident on the substrate is λ, and the range in the depth direction of the bottom of the plurality of recesses is Δd,
2/7 ≦ | (n1−n2) × Δd | / λ ≦ 10
It is characterized by being.

Further, according to another aspect of the present embodiment, a plurality of concave portions are formed on the surface of the base material, and the concave portions have curved surface portions formed by curved surfaces, The concave portion is formed such that the position of the bottom of the concave portion is two or more different positions in the depth direction, and the refractive index of the substrate is n1, and the refractive index of the medium around the substrate Where n2 is the wavelength of the light beam incident on the base material is λ, and the range in the depth direction of the bottom of the plurality of recesses is Δd,
2/7 ≦ | (n1−n2) × Δd | / λ ≦ 10
And
The radius of curvature of the curved surface portion is formed so as to be within ± 50% with respect to the average value of the radius of curvature.

Further, according to another aspect of the present embodiment, a plurality of concave portions are formed on the surface of the base material, and the concave portions have curved surface portions formed by curved surfaces, The concave portion is formed such that the position of the bottom of the concave portion is two or more different positions in the depth direction, and the refractive index of the medium around the substrate is n2 and is incident on the substrate Assuming that the wavelength of the light flux is λ, and the range in the depth direction of the bottom of the plurality of concave portions is Δd,
2/7 ≦ | 2 × n 2 × Δd | / λ ≦ 10
And
The radius of curvature of the curved surface portion is formed so as to be within ± 50% with respect to the average value of the radius of curvature.

Further, according to another aspect of the present embodiment, a plurality of convex portions are formed on the surface of the base material, and the convex portions have a curved surface portion formed by a curved surface, The plurality of convex portions are formed such that the positions of the tops of the convex portions are two or more different positions in the height direction, and the refractive index of the medium around the base material is n2; Assuming that the wavelength of the light beam incident on the base material is λ, and the range in the height direction of the top portions of the plurality of convex portions is Δd,
2/7 ≦ | 2 × n 2 × Δd | / λ ≦ 10
It is characterized by being.

  Further, according to another aspect of the present embodiment, the step of forming a mask having a plurality of openings on the surface of the substrate, and wet etching the substrate on which the mask is formed, are performed. And forming a plurality of recesses on the surface of the substrate, wherein the plurality of openings are openings of two or more different sizes, and the plurality of recesses are positions of bottoms of the recesses. Are at two or more different positions in the depth direction.

  Further, according to another aspect of the present embodiment, the step of forming a mask having a plurality of openings on the surface of the substrate, and wet etching the substrate on which the mask is formed, are performed. Forming a plurality of recesses on the surface of the substrate, and in the region of the area in which the opening is formed, a counterbore portion of two or more different depths is formed It features.

  According to the present invention, it is possible to provide an optical element that can be processed using wet etching and is a diffusion plate with high light utilization efficiency.

Structural drawing of the optical element in the present embodiment Explanatory drawing (1) of the optical element in this Embodiment Explanatory drawing (2) of the optical element in this Embodiment Process drawing of optical element manufacturing method 1 in the present embodiment Process drawing of optical element manufacturing method 2 in the present embodiment Process drawing of optical element manufacturing method 3 in the present embodiment Process drawing of optical element manufacturing method 4 in the present embodiment Structural view of another optical element in the present embodiment (1) Structural view of another optical element in the present embodiment (2) Structural drawing of the projection apparatus in the present embodiment Structural drawing of another projection device in the present embodiment Structure of fluorescent wheel Explanatory drawing of the optical element in Example 1 Explanatory drawing of the optical element in Example 2 Explanatory drawing of the optical element in Example 3 Explanatory drawing of the optical element in Example 4 Explanatory drawing of the optical element in Example 5 Explanatory drawing of the optical element in Example 6 Explanatory drawing of the optical element in Example 7 Explanatory drawing of the optical element in Example 8 Explanatory drawing of the optical element in Example 9 Explanatory drawing of the optical element in Example 10 Explanatory drawing of the optical element in Example 11 Explanatory drawing of the optical element in Example 12 Explanatory drawing of the optical element in Example 13 Explanatory drawing of the optical element in Example 14 Correlation diagram between the area ratio of the recess of the optical element in Example 14 and the relative position in the height direction of the bottom of the recess

  The mode for carrying out the invention will be described below. In addition, about the same member etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

(Optical element)
The optical element in the present embodiment will be described based on FIG. FIG. 1 (a) is a plan view of the optical element in the present embodiment, and FIG. 1 (b) schematically shows a cross-sectional view cut along a dashed dotted line 1A-1B in FIG. 1 (a). .

  The optical element 10 in the present embodiment has a structure in which a plurality of recesses 12 are formed on the surface of a base material 11. In the description of the present embodiment, the case where the plurality of concave portions 12 are formed on the surface of the base material 11 will be described. However, the optical element in the present embodiment has a plurality of convex portions on the surface of the base material 11 May be formed.

  In the optical element according to the present embodiment shown in FIG. 1, the deepest portion of the recess 12 is the bottom 13, and the position of the recess 13 in the depth direction of the bottom 13 is not uniform. The position in the depth direction of the two or more values is two or more values, and the difference between the depth position of the deepest bottom 13 and the depth position of the shallowest bottom 13 in the bottoms 13 of the plurality of recesses 12 The difference is formed to be Δd.

  Next, the planar position of the bottom 13 will be described. In FIG. 2 (a), the position of the bottom 13 is indicated by "●". The positions of the bottoms 13 may be regular, that is, they may be arranged in a predetermined cycle, or they may be irregular. When the position of the bottom 13 is an irregular array, assuming that the pitch of the regular array is P, the center point of the bottom in the case of the regular array (the point at which the regular array is made) Preferably, the bottom 13 is formed to be within a circle of radius 0.5 × P, and further, within the range of a circle of radius 0.25 × P. More preferably, it is configured to be present. In FIG. 2A, the positions of the regularly arranged points are indicated by "x". In FIG. 2A, this regular arrangement is an arrangement in which the shape of the points where the nearest regular arrangement is made is a triangle.

Also, the bottoms may be arranged such that the average distance between the bottoms with respect to a certain first direction is P ₁ . And a direction perpendicular to the first direction at this time as the second direction, the centroid position of each bottom row of the bottom portion formed in the first direction may be disposed such that the interval P _2. Such arrangement is not based on the regular arrangement, and therefore the influence of periodicity by the regular arrangement can be further reduced. An example of such an arrangement is shown in FIG. FIG. 3 shows the position of the bottom by “●”. In FIG. 3, a plurality of bottom rows are arranged in the first direction, and the barycentric positions in the second direction of the bottom rows in part of the bottoms are indicated by dotted lines 51a, 51b, 51c, and 51d. In the bottom row in which the center of gravity position is the dotted line 51a, the intervals of the bottom in the first direction are P ₁₁ , P ₁₂ ,..., P ₁₇ respectively, and the average value is P ₁ . The second direction of the dotted line 51a is the centroid position, the dotted line 51b, the dotted line 51c, the position of the bottom in the column of each bottom and the interval between the dotted line 51d is P _2, respectively for the second direction It is irregular. In FIG. 3, the barycentric position (dotted line 53) in the first direction of the bottom of the bottom of the left end of the odd-numbered bottom row from the bottom of the drawing (dotted line 53) and the bottom of the bottom of the left end of the even-numbered bottom 52 from the bottom center of gravity of the first direction and (dashed line 54) is arranged such that _P ^1/2, which is to meet the _{^{3 0.5 / 2 × P 1 =}} P 2. First interval of the bottom of the direction in a column of the bottom preferable to be ₍₁ ± 0.25) _P 1, and more preferably a ₍₁ ± 0.15) _P 1. The position of each bottom with respect to the position of the center of gravity in the second row of the bottom row is preferably ± 0.25 P ₂ with respect to the position of the center of gravity, and more preferably ± 0.15 P ₂ .

  In addition, in the case where there is irregularity in the arrangement of the bottom, the arrangement of the bottom may be point-symmetrical or line-symmetrical within a part of the region. Asymmetry can be made less likely to occur in the positive direction and the negative direction of the direction which is to be done in this way.

  In the optical element in the present embodiment, by forming in this manner, light can be efficiently diffused in a predetermined angle range as described later. Further, when the pitch of the regular arrangement is different for each direction, the range in which the bottom portion 13 in the present embodiment is located may be an ellipse according to the ratio. In addition, the bottom portion 13 in the present embodiment may be formed so as to be located in a region surrounded by bisectors of adjacent regularly arranged points. Furthermore, the bottom portion in the present embodiment is in a region surrounded by a perpendicular line at a point where the distance between the regularly arranged points and the adjacent regularly arranged points is 1/4. It is more preferable to form so that 13 may be located. Here, the perpendicular means a perpendicular to a line connecting a point where regular arrangement is made and a point where adjacent regular arrangement is made.

  In FIG. 2A, when the bottom 13 "●" is located in the area within 1⁄4 of the pitch with respect to the position "x" of the point where regular arrangement of triangles is made Is shown. Further, FIG. 2B is a cross-sectional view taken along an alternate long and short dash line 2A-2B connecting the bottom 13a of the recess 12a and the bottom 13b of the recess 12b in FIG. 2A.

As shown in FIG. 2B, the bottom 13a of the recess 12a and the bottom 13b of the recess 12b are different in position in the depth direction, and the surface forming the recess 12a and the surface forming the recess 12b The point 14 which is the boundary between the concave portion 12a and the concave portion 12b is not located on the bisector of the bottom portion 13a and the bottom portion 13b in the case where the curvatures have the same curvature. Although the case where the position in the depth direction at the bottom adjacent matches are indicated by dashed lines, 15 point at the boundary in this case is bisector of the bottom 13a and the bottom 13b _1.

  Generally, in the case of forming a recess by wet etching a base material such as glass, the curvature of the surface of the adjacent recess is approximately the same. For this reason, if the position in the depth direction at the bottom of the recess is significantly different, the position of the point 14 serving as the boundary is largely deviated from the bisector.

  When the recesses are adjacent to each other at the position of the point 15 serving as the boundary, the inclination angles of the surfaces of the adjacent recesses are the same, and the inclination angle of the recess at the point 15 serving as the boundary can be a predetermined diffusion angle. The light can be diffused efficiently within a predetermined diffusion angle range. On the other hand, when the recesses are adjacent to each other at the position of the boundary point 14, the inclination angles of the surfaces of the adjacent recesses are different, and the inclination angles of the recesses are smaller on one side and larger on the other with respect to the predetermined diffusion angle. In this case, the amount of light diffused to the outside of the predetermined diffusion angle range increases.

  As described above, when the position of the bottom 13 of the recess 12 in the depth direction is largely different, light outside the predetermined diffusion angle range is easily generated. Therefore, the difference in the position of the bottom 13 of the recess 12 in the depth direction is , Smaller is preferable. However, in the case where the positions in the depth direction of the bottom 13 of the recess 12 are all the same, the component of the light to be transmitted straight is increased. Therefore, in order to reduce the component of the light to be transmitted straight, there is a method of causing the component of the light to be transmitted straight to be diffracted to cause the component to be diffused.

  In order to cause the diffraction phenomenon, it is preferable that the optical path difference generated by the position in the depth direction of the bottom portion 13 be 2/7 wavelength or more. Further, in order to cause the diffraction phenomenon most efficiently, it is preferable that the optical path difference caused by the position in the depth direction of the bottom portion 13 be about the wavelength, but in the diffraction phenomenon, if the remainder of the optical path difference wavelength is considered. In consideration of goodness and controllability by processing, it is preferable that an optical path difference caused by the position of the bottom 13 in the depth direction is 10 times or less of the wavelength.

In the above, the case where the optical element is a transmission type optical element has been described, but the above contents indicate that the refractive index of the substrate 11 in which the recess 12 is formed is n1, the refractive index of the medium around the recess 12 is n2, When the wavelength of the luminous flux to be made is λ, it is expressed by the following equation (1).

2/7 ≦ | (n1−n2) × Δd | / λ ≦ 10 (1)

Furthermore, in the optical element according to the present embodiment, it is more preferable that the conditions shown in the following (2) be provided, and it is further more preferable that the conditions shown in the following (3) be present.

2/7 ≦ | (n1−n2) × Δd | / λ ≦ 5 (2)

2/7 ≦ | (n1−n2) × Δd | / λ ≦ 2 (3)

Further, the position of the bottom 13 of the recess 12 in the depth direction may be formed at a plurality of levels (a plurality of depth positions) instead of an arbitrary position. In this case, if the position in the depth direction is two levels or more (the depth position is binary) or more, the above-mentioned diffraction phenomenon can be obtained, but in order to cause the diffraction phenomenon more efficiently, the depth It is more preferable to set the position in the direction to four or more levels (four in the depth position). Also, in order to cause diffraction efficiently, it is preferable that the bottom 13 not be distributed at a specific depth position, and in the case of two levels, 75% at a position in a specific depth direction. More bottom portions 13 are preferably not distributed, and furthermore, in the case of four or more levels, it is preferable that not more than 50% of the bottom portions 13 be distributed at a position in a specific depth direction.

  In addition, when the substrate 11 has a warp, has a waviness that becomes uneven at a long pitch of several hundred μm or more, or the substrate 11 has a waviness with a long pitch by wet etching processing There is a case. In such a case, the surface of the element may not satisfy the equation (1) on the entire surface of the element due to the warpage or waviness of the base material 11. In such a case, the equation shown in (1) at least at the adjacent bottom portion It may be satisfied.

When the displacement in the height direction of the point 14 which is the boundary between the bottom 13b and the recess 12a and the recess 12b is the displacement Δz, the optical path difference generated by the displacement Δz is smaller than the wavelength of the incident light. In such a case, the recess may not have a desired effect on light. Accordingly, an averaged value of Delta] z _avg displacement amount Delta] z in the device, Delta] z _avg is 2/7 ≦ | (n1- n2) × Δz avg | is preferably to satisfy the / lambda, Delta] z _avg 1 It is more preferable to satisfy / 2 ≦ | (n1−n2) × Δz _avg | / λ, and it is further preferable to set Δz _avg to satisfy 3⁄4 ≦ | (n1−n2) × Δz _avg | / λ. Delta] z _avg obtains the average shape of the recess, the half of the average spacing of the bottom portions may be approximated by the height of the average shape from the origin as r _avg of r _avg. For example, if the average shape of the recess is a spherical surface with a radius of curvature R _avg , the height of the spherical surface r away from the origin can be determined by R _avg − (R _avg ² −r ² ) ^1/2 , so Δz _avg = _R avg _- it may be obtained by ^{_{(R avg 2 -r avg 2)}} 1/2.

  In the case where the optical element 10 is a transmission type optical element, a transparent material such as glass or resin can be used as the material forming the base 11 on the surface of which the recess 12 is formed. When light from a light source such as a laser is incident, it is preferable to use an inorganic material such as glass having high light resistance.

  Further, in the present embodiment, an optical thin film such as an anti-reflection film (not shown) may be formed on the surface of the optical element 10.

(Method of manufacturing optical element)
Next, a method of manufacturing the optical element in the present embodiment will be described. In the method of manufacturing the optical element 10 according to the present embodiment, a method of forming the substrate 11 by wet etching, or a method of forming the resist pattern by gray scale exposure and then forming the substrate 11 by dry etching Examples include a method of forming by press molding using a molding die or the like, and a method of imprinting or the like.

  The following four manufacturing methods will be described as an example of the manufacturing method of manufacturing the optical element in the present embodiment by wet etching the base material 11.

(Method 1 of manufacturing an optical element)
First, the manufacturing method 1 of the optical element will be described based on FIG.

  In this method, first, as shown in FIG. 4A, a mask 21 patterned on a substrate 11 formed of glass or the like, and a spotted portion 22 on the substrate 11 at the opening of the mask 21. Form. The mask 21 and the counterbore portion 22 can be formed by a method of processing by combining photolithography and processes such as etching and lift-off, or a method of blast processing or the like.

  In blasting, it is generally difficult to control the depth of the counterbore 22 and the size of the opening of the mask 21. Therefore, it is preferable to use a process combining photolithography with processes such as etching and lift-off. . In the case of the method of forming by combining photolithography and etching, dry etching can be used when forming the counterbore portion 22. In this case, the bottom surface 22a of the counterbore portion 22 is processed into a planar shape.

  Next, as shown in FIG. 4B, the mask 21 is formed on the base material 11, and in the base material 11, the counterbore portion 22 is formed in the region where the opening of the mask 21 is formed. Wet etch what is being done. Thereby, a part of base material 11 is removed by wet etching starting from countersunk part 22, and crevice 12 is formed in the surface of base material 11. In wet etching, the base 11 is isotropically removed by etching, so the bottom of the recess 12 is formed by the flat portion 23. Thus, the surface of the recess 12 is formed by the flat portion 23 and the curved portion 24. In the curved surface portion 24, the cross section is a curved surface having an arc, but when the mask 21 does not have much resistance in wet etching, the shape of the edge portion in the recess 12 deviates from the arc due to peeling of the mask 21 or the like. There is. In this case, at least a part of the curved surface portion 24 connected to the flat portion 23 in the cross section has a curved surface shape which is an arc. The material forming the mask 21 is preferably one that can be patterned and has high wet etching resistance, and is formed of, for example, a metal material such as chromium or molybdenum.

  Next, as shown in FIG. 4C, the optical element 10 according to the present embodiment can be manufactured by removing the mask 21.

  In addition, the flat part 23 in the recessed part 12 is a part corresponded to the bottom part 13 in FIG.1 and FIG.2 grade | etc., And is formed of the surface which becomes perpendicular | vertical with respect to the thickness direction of the base material 11. FIG. The boundary between the flat portion 23 and the curved portion 24 can be obtained by measuring the value of the radius of curvature in the cross-sectional direction. In this case, the radius of curvature in the vicinity of the boundary between the flat portion 23 and the curved surface portion 24 is observed as changing from a certain value of the radius of curvature to an infinite radius of curvature. Such a change is ideally a sharp change, but if the change at the boundary does not become a sharp change, a predetermined curvature radius such as a region of α times or more of the curvature radius of the curved surface portion 24 or the like The above region can also be regarded as the flat portion 23. The value of α is preferably 1.1 or more. A three-dimensional measuring instrument can be used to measure such a radius of curvature. In addition, when the curvature of the curved surface portion 24 is increased, it may not be possible to confirm the change of the curvature radius within the S / N range of the three-dimensional measuring device. However, in such a case, the size of the boundary between the flat portion 23 and the curved portion 24 and the flat portion 23 may be determined by observing the shape of the recess 12 with an electron microscope, an atomic force microscope, or the like. .

(Method 2 of manufacturing an optical element)
Next, a method 2 of manufacturing an optical element will be described based on FIG.

In the method shown in FIG. 4, the counterbore portion 22 is formed on the substrate 11 such as glass, but in this case, depending on the type of glass forming the substrate 11, dry etching for forming the counterbore portion 22 is performed. The processing by the above-mentioned method may require a very long time, and furthermore, the dry etching may hardly be performed, and the counterbore portion 22 may not be formed. The method shown in FIG. 5 is a method in which a thin film layer 25 capable of dry etching such as SiO ₂ or Ta ₂ O ₅ is formed on the surface of the substrate 11 in advance.

Specifically, first, as shown in FIG. 5A, a thin film layer 25 capable of dry etching such as SiO ₂ or Ta ₂ O ₅ is formed on the surface of the base material 11, and the thin film layer 25 is formed. While forming the mask 21 on top of the thin film layer 25, the counterbore portion 26 is formed in a part of the opening of the mask 21. Thereby, the counterbore portion 26 can be easily formed, and processing by later wet etching becomes possible.

  Next, as shown in FIG. 5B, the thin film layer 25 and the mask 21 are stacked on the base material 11, and the thin film layer 25 is formed with the counterbore portion 26 by wet etching. By doing this, the thin film layer 25 and a part of the substrate 11 are removed. At this time, the base material 11 is isotropically removed by wet etching. Thereby, the recessed part 12 can be formed in the base material 11.

  Next, as shown in FIG. 5C, the mask 21 and the thin film layer 25 are removed, whereby the optical element 10 according to the present embodiment can be manufactured.

As a material for forming the thin film layer 25, it is preferable to select one having a wet etching rate smaller than that of glass. For example, Haixin Zhu et al. , J. Micromech. Microeng. 19 (2009) 065013 describes the wet etch rates for various glass materials. According to this, in the case of quartz and glass materials having the same composition as SiO ₂ , the wet etching rate may differ by 10 times or more.

Assuming that the ratio of the wet etching rate of the base material 11 to SiO ₂ is r and the distribution range of the position of the thin film layer 25 in the depth direction of the bottom of the counterbore 26 is ΔD, the depth of the bottom 13 of the final recess 12 is The distribution range Δd of the position in the longitudinal direction is Δd = rΔD. Thus, for example, if r is 10 and the required Δd is 1 μm, then ΔD is 100 nm. As described above, in addition to processing of various glass materials becomes possible, the processing amount in the counterbore portion 26 can be reduced. Therefore, the counterbore portion 26 is formed on the thin film layer 25 by liftoff or sol gel besides dry etching. It can be formed.

As a material for forming the thin film layer 25, sol-gel, an organic material can be used besides SiO ₂ , Ta ₂ O _{5 and the} like. In the case of using a sol-gel or an organic material, the thin film layer 25 may be patterned by an imprint process.

(Method 3 of manufacturing an optical element)
Next, manufacturing method 3 of the optical element will be described based on FIG.

  The method shown in FIG. 6 is to adjust the position of the bottom in the depth direction using the thin film layer in the same manner as the method shown in FIG. 5, but it is patterned instead of forming the counterbore portion in the thin film layer. The thin film layer 27 is formed in the opening of a part of the mask 21. Thereby, the time until the wet etching solution reaches the base material 11 can be adjusted by the difference in thickness of the thin film layer 27, and the position in the depth direction of the bottom portion 13 of the concave portion 12 to be formed is different. It becomes possible.

  In the manufacturing method shown in FIG. 6, first, as shown in FIG. 6A, a mask 21 having an opening is formed on the surface of the base material 11, and one of the regions where the opening of the mask 21 is formed. In part, the thin film layer 27 is formed on the substrate 11 and the mask 21.

  Next, as shown in FIG. 6 (b), the thin film layer 27 and a part of the base material 11 are removed by wet etching one in which the mask 21 and the thin film layer 27 are formed on the base material 11. Be done. At this time, the base material 11 is isotropically removed by wet etching. Thereby, the recessed part 12 can be formed in the base material 11.

  Next, as shown in FIG. 6C, the optical element 10 according to the present embodiment can be manufactured by removing the mask 21.

  Although the thin film layer 27 is formed on the mask 21 in the case shown in FIG. 6, the mask 21 may be formed on the thin film layer 27 having the opening. The material forming the thin film layer 27 can be the same as the material forming the thin film layer 25, and the forming method can also be formed by the same method as the thin film layer 25.

(Method 4 of manufacturing an optical element)
Next, a method 4 of manufacturing an optical element will be described based on FIG.

  In the method shown in FIG. 5, the thin film layer 25 is formed. In the method shown in FIG. 6, the thin film layer 27 is formed so that the position in the depth direction of the bottom 13 of the recess 12 is different. It is. On the other hand, the method shown in FIG. 7 changes the position in the depth direction of the bottom 13 of the recess 12 by changing the size of the opening in the mask 28. The mask 28 is formed of the same material as the mask 21 described above.

  In the manufacturing method shown in FIG. 7, first, as shown in FIG. 7A, masks 28 having different sizes of openings are formed on the surface of the base material 11.

  Next, as shown in FIG. 7B, the base 11 in the opening of the mask 28 is removed by wet etching the base 11 on which the mask 28 is formed. At this time, the base material 11 is isotropically removed by wet etching. Thereby, the recessed part 12 can be formed in the base material 11.

  Next, as shown in FIG. 7C, by removing the mask 28, the optical element 10 in the present embodiment can be manufactured.

  In the method shown in FIG. 4 to FIG. 6, the base material 11 formed of glass is removed from the opening formed on the mask 21 by wet etching. In this case, the replacement efficiency of the etching solution between the mask 21 and the base material 11 and the etching solution outside the mask 21 is considered to depend on the size of the opening of the mask 21. Therefore, when the opening of the mask is large, the etching solution is efficiently exchanged as compared to the case where the opening of the mask is small, and therefore the etching rate in the wet etching can be increased. Since the difference in etching rate in wet etching is the difference in depth in the recess 12, the position in the depth direction of the bottom 13 in the recess 12 can be different. When the optical element is manufactured by the method shown in FIG. 7, the concave portion 12 having the flat portion 23 and the curved portion 24 formed is flatter as the position in the depth direction in which the flat portion 23 is formed is deeper. The portion 23 is formed to be large.

  In the method of manufacturing the optical element shown in FIG. 7, if the opening of the mask 28 is too large, the occupied area of the flat portion 23 in the recess 12 becomes large, so the opening of the mask 28 has a width of 10 μm or less. It is preferable to form so that it may become, It is more preferable to form so that the width | variety may be set to 5 micrometers or less. Moreover, when the position of the bottom portion is irregular, the interval between the bottom portions becomes irregular, and thus the time required for the base material 11 separating the adjacent concave portions 12 to disappear in the process of wet etching changes. There is. In such a case, the etching rate in each recess may change as the state of the wet etching solution changes in each recess. In such a case, the depth direction of the bottom 13 can be changed even if the size of the opening of the mask 21 is the same.

  Further, in the methods shown in FIGS. 4 to 7, if peeling of the masks 21 and 28 or local concentration distribution of the etching solution may occur, the concave portion 12 having a desired shape may not be formed. Therefore, it is preferable to form the curvature radius of the curved surface portion 24 within ± 50% with respect to the average value of the curvature radius. Further, it is more preferable to form so as to be within ± 30%, and it is further preferable to form so as to be within ± 10%.

  Moreover, when using the above manufacturing methods, as shown in FIG.2 (b), the position of the point 14a will separate from the point 14b, so that the position of the bottom part 13b is deep. Therefore, there is a correlation between the area of the polygon occupied by each recess 12 in the plan view as shown in FIG. 2A and the depth of the bottom 13. Therefore, the correlation between the area of the polygon occupied by the recess 12 and the depth of the bottom 13 can be used as an index for determining the difference between the manufactured element and the design. Here, it is preferable to process the optical element so that the absolute value of the correlation coefficient is 0.2 or more when the correlation coefficient between the area of the polygon occupied by the recess 12 and the depth of the bottom 13 is calculated. Preferably, the optical element is processed so that the absolute value of the correlation coefficient is 0.4 or more.

(Optical element of other structure)
Next, optical elements of other structures in the present embodiment will be described.

  An optical element 30 having a structure shown in FIG. 8 has a structure in which a plurality of convex portions 32 are formed on the surface of a base 31. 8 (a) is a plan view of the optical element according to the present embodiment, and FIG. 8 (b) schematically shows a cross-sectional view taken along dashed dotted line 8A-8B in FIG. 8 (a). . In the optical element 30, the base 31 can be made of the same material as the base 11 in the optical element 10. Further, in the optical element 30, the top 33 of the projection 32 corresponds to the bottom 13 of the recess 12 of the optical element 10, and the position in the height direction of the top 33 of the projection 32 is the bottom 13. It corresponds to the position in the depth direction.

  As a method of manufacturing the optical element 30 in which the plurality of convex portions 32 are formed, a method of forming a predetermined resist shape by a gray scale mask or a molding die and transferring it to a substrate by dry etching A method of transferring the unevenness of the mold to the surface can be used. Alternatively, a method may be used in which a resin material is disposed between the base and the mold and the unevenness is transferred to the resin material.

In the case of dry etching or press molding, if the average displacement amount Δz _{avg in the} height direction is large, the etching amount of dry etching will be large and processing will be difficult, and if press molding is used, processing defects will occur From the viewpoint of processing, it is preferable to satisfy any of the formulas (1) to (3).

  As a mold in the above processing method, in addition to a mold by cutting, it is possible to use a mold processed by the method described in the manufacturing methods 1 to 4. Moreover, the replica may be used as a molding die by creating a replica of the molding die processed by the method described in the manufacturing methods 1 to 4.

Further, the optical element 40 having the structure shown in FIG. 9 is a reflection type optical element, in which a plurality of recesses 42 are formed on the surface of the base material 41, and a reflection film 44 is formed on the surface on which the recesses 42 are formed. Are of the structure formed. 9 (a) is a plan view of the optical element according to the present embodiment, and FIG. 9 (b) schematically shows a cross-sectional view taken along dashed dotted line 9A-9B in FIG. 9 (a). . In the optical element 40, the bottom portion 43 is formed in the recess 42 in the same manner as the bottom portion 13 in the recess 12. The reflective film 44 can be formed of a dielectric multilayer film or a metal film. In the optical element 40, when the refractive index of the medium around the recess 42 is n2 and the wavelength of the incident light beam is λ, the relationship of the equation (4) below is satisfied.

2/7 ≦ | 2 × n 2 × Δd | / λ ≦ 10 (4)

Furthermore, in the optical element according to the present embodiment, it is more preferable that the conditions shown in the following (5) be provided, and it is even more preferable that the conditions shown in the following (6) be provided.

2/7 ≦ | 2 × n 2 × Δd | / λ ≦ 5 (5)

2/7 ≦ | 2 × n 2 × Δd | / λ ≦ 2 (6)

Further, in either case of transmission and reflection, generally, when using the optical path length difference (ΔL) corresponding to the position of the bottom 43 in the depth direction, the relationship of the formula shown in (7) below It is in.

2/7 ≦ | ΔL | / λ ≦ 10 (7)

As described above, the distribution of the position of the bottom portion 43 in the depth direction is preferably smaller, so it is preferable to have the relationship shown in the following (8), and further, it has the relationship shown in the following (9) Is preferred.

2/7 ≦ | ΔL | / λ ≦ 5 (8)

2/7 ≦ | ΔL | / λ ≦ 2 (9)

In the optical element 40 shown in FIG. 9, the base material 41 can be made of an opaque material such as a metal or a semiconductor other than glass.

(Projecting device)
Next, the projection apparatus in the present embodiment will be described. FIG. 10 schematically shows the structure of the projection apparatus 100 in the present embodiment. The projection apparatus 100 includes laser light sources 111a, 111b and 111c, lenses 112a, 112b and 112c, optical elements 113a, 113b and 113c, lenses 114a, 114b and 114c, spatial light modulators 115a, 115b and 115c, a combining prism 116, A lens 117 is provided. In the present embodiment, the laser light or the like emitted from the laser light sources 111a, 111b, and 111c may be described as a light flux. Further, in the projection apparatus 100 according to the present embodiment, the optical element 10 or the like according to the above-described present embodiment is used as the optical elements 113a, 113b, and 113c.

  The laser light source 111a emits, for example, laser light in a red wavelength range, and the laser light emitted from the laser light source 111a is adjusted in the divergence angle of the laser light by the lens 112a and diffused by the optical element 113a. The divergence angle is adjusted again by the lens 114a, and the light enters the combining prism 116 through the spatial light modulator 115a. In the spatial light modulator 115a, for example, control of transmission and non-transmission of laser light is performed for each pixel, and an image corresponding to red is formed.

  The laser light source 111b emits, for example, laser light in a green wavelength range, and the laser light emitted from the laser light source 111b is adjusted in the divergence angle of the laser light by the lens 112b and diffused by the optical element 113b. The divergence angle is adjusted again by the lens 114b, and the light enters the combining prism 116 through the spatial light modulator 115b. In the spatial light modulator 115 b, for example, control of transmission and non-transmission of laser light is performed for each pixel, and an image corresponding to green is formed.

  The laser light source 111c emits, for example, laser light in a blue wavelength range, and the laser light emitted from the laser light source 111c is adjusted in the divergence angle of the laser light by the lens 112c and diffused by the optical element 113c. The divergence angle is adjusted again by the lens 114c, and the light enters the combining prism 116 through the spatial light modulator 115c. In the spatial light modulator 115 c, for example, control of transmission and non-transmission of laser light is performed for each pixel, and an image corresponding to blue is formed.

  In the beam combining prism 116, the laser beam from the spatial light modulator 115a, the laser beam from the spatial light modulator 115b, and the laser beam from the spatial light modulator 115c are incident, multiplexed, and then emitted. Thus, the light beam of the combined laser beam emitted from the combining prism 116 is projected on the screen 118 via the lens 117.

  In the present embodiment, as the laser light sources 111a, 111b, and 111c, various lasers such as a semiconductor laser and a solid state laser that generates a second harmonic can be used. Also, a plurality of lasers may be used. The laser light sources 111a, 111b, and 111c are not limited to the lasers themselves, and may correspond to the laser light sources 111a, 111b, and 111c, and may be light emission ports of light fluxes from the laser light sources using optical fibers.

  Further, in FIG. 10, a laser is used for each of red, green and blue luminous fluxes, but a laser may be used for one or more light sources among red, green and blue. The optical elements 113a, 113b, and 113c need not be used for all the red, green, and blue light beams, and may be used for one or more of the red, green, and blue light beams.

  As the spatial light modulators 115a, 115b, and 115c, LCOS (Lyquid crystal on Silicon) or DMD (Digital Mirror Device) can be used. Although FIG. 10 shows an example using LCOS, since the DMD is a reflection type spatial light modulator, it does not have a transmission type arrangement as shown in FIG. The DMD may be installed at a later stage, and the reflected light from the DMD may be projected by the lens 117.

  Next, a projector according to the present embodiment, which has another structure, will be described. FIG. 11 schematically shows a projection apparatus 200 having another structure according to the present embodiment. In this projection apparatus 200, the blue laser light source 201 is used as a light source, and a light flux emitted from the blue laser light source passes through the first optical element 202 and the dichroic mirror 203, and then passes through the lens 204 to the fluorescent wheel It is irradiated to 205. For the first optical element 202, the optical element 10 or the like in the above-described present embodiment is used.

  As shown in FIG. 12, the fluorescent wheel 205 is divided into three regions of an optical element region 205a, a green phosphor region 205b, and a red phosphor region 205c. The second optical element is formed in the optical element region 205a, and the green phosphor region 205b is formed of a phosphor (fluorescent material) that emits green light, and the red phosphor region 205c emits red light It is formed of a phosphor. The second optical element in the optical element region 205a is formed of an optical element having the same structure as the optical element 10 in the embodiment of the optical element.

  The fluorescent wheel 205 can be rotated by a rotational drive unit 205d such as a motor, and green light can be obtained when the laser light from the blue laser light source 201 is irradiated to the green phosphor region 205b, and red When the phosphor region 205c is irradiated, red light can be obtained. When the laser light from the blue laser light source 201 is irradiated to the optical element region 205a, the blue light passes through the optical element region 205a. Therefore, the blue light, the green light, and the red light can be time-divisionally emitted by rotating the fluorescent wheel 205 by the rotation drive unit 205d. The fluorescence emission generated in the green phosphor region 205 b and the red phosphor region 205 c passes through the optical path shown by a dotted line in FIG. 11, that is, transmits through the lens 204, is reflected by the dichroic mirror 203, and enters the lens 212. . After transmitting through the lens 212, the light is reflected by the multiplexing mirror 211, passes through the lens 213, and is then emitted to the integrator 214. In the present embodiment, a yellow phosphor region formed of a yellow phosphor may be provided instead of or in addition to the green phosphor region 205b and the red phosphor region 205c.

As oxide-based and sulfide-based phosphors, yellow-emitting YAG-based phosphors (Y ₃ Al ₅ O ₁₂ : Ce, (Y, Gd) ₃ Al ₅ O ₁₂ : Ce), TAG-based phosphors A silicate type or alkaline earth type phosphor or the like in which fluorescence of each color is generated by (Tb ₃ Al ₅ O ₁₂ : Ce) or an additive element can be used. In addition, α-sialon-based (SiAlON), which emits fluorescence of each color depending on the additive element as a nitride-based phosphor, β-sialon-based (SiAlON: Eu), which emits green fluorescence, and a cyan-based, which emits red fluorescence ( CaAlSi ₃ N ₃ : Eu) can be used. Further, La oxynitride (LaAl (Si ₆ -zAl ₂ ) N ₁₀ -zO ₂ : Ce) can be used as an oxynitride-based phosphor.

  When the second optical element in the optical element region 205 a of the fluorescent wheel 205 is irradiated with the blue light flux, the blue light flux diffused by the second optical element and transmitted through the second optical element is diverged by the lens 206. The corners are converted. After this, the blue light flux is reflected by the mirror 207, transmitted through the lens 208, reflected by the mirror 209, transmitted through the lens 210, transmitted through the multiplexing mirror 211, transmitted through the lens 213, and then transmitted to the integrator 214. It is irradiated.

  The blue, green, and red light beams emitted from the integrator 214 are transmitted through the lens 215, reflected by the mirror 216, transmitted through the lens 217, reflected by the mirror 218, and then irradiated to the spatial light modulator 219. . In the spatial light modulator 219, an image is formed, and the formed image is projected to an external screen (not shown) through the projection lens 220.

  Here, the first optical element 202 has a function of making the intensity distribution of the light irradiated to the phosphor in the fluorescent wheel 205 uniform. The fluorescent material in the fluorescent wheel 205 is a mixture of a fluorescent material with a silicone resin or the like, and when irradiated with a blue luminous flux having a high peak value, the silicon resin in a region irradiated with blue light with a high peak value. Degradation of the The first optical element 202 is used to reduce such deterioration. As described above, by using the first optical element 202, it is possible to realize top-hat-type emitted light distribution without achieving a mountain-shaped emitted light distribution like a normal diffusion plate, and therefore, the peak value of light flux Can be irradiated to the phosphor with a higher luminous flux. Further, the second optical element of the optical element area 205a in the fluorescent wheel 205 has a function of making the spatial intensity distribution uniform, and by rotating it, the uniformity can be further improved.

  Next, an example in the present embodiment will be described. Examples 1 to 3 are comparative examples, and examples 4 to 12 are examples. In addition, Example 13 is a comparative example, and Example 14 is an example. Here, in Examples 1 to 14, the refractive index n2 of the medium around the recess 12 is 1. Although each example shows an example in which the full width at half maximum of the diffusion angle is 3 ° or less, the present invention is not limited to this and can be applied to cases where the full width at half maximum of diffusion is 3 ° or more.

(Example 1)
First, the optical element in Example 1 will be described based on FIG.

  The base 11 formed of glass with a refractive index of 1.53 is cleaned, and molybdenum is deposited to a thickness of 50 nm as the mask 21. After depositing molybdenum, a resist is applied, and openings of φ 1 μm are formed in the mask 21 in the arrangement shown in FIG. 13A by photolithography and etching. FIG. 13 (a) shows the positions of the openings in an approximately 1 mm square, and they are arranged in a plane such that the shape connecting the nearest openings with a pitch of 50 μm is an equilateral triangle. It is a thing. After the openings are formed, the wet etching is performed to 480 μm. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is 480 μm. The planar shape of the processed optical element is as shown in FIG. In FIG. 13B, the depth is displayed in black and white gradations, and is displayed so as to be darkened as it gets deeper.

  What calculated the emitted light distribution of light when light with a wavelength of 450 nm is incident on such an optical element is shown in FIG. The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 13 (c), diffraction due to the regular arrangement occurs and strong light is produced in a specific direction. FIG. 13 (d) is a graph in which the intensity in the horizontal direction in the outgoing light distribution of FIG. 13 (c) is averaged at every angle of 0.21 ° and is plotted against the angle. As shown in FIG. 13 (c), strong light is generated in a specific direction. Moreover, it was 75.2% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.13 (c). The value of | (n1−n2) × Δd | / λ was 0.

(Example 2)
Next, the optical element in Example 2 will be described based on FIG. 14 focusing on the points different from Example 1.

  Openings with a diameter of 1 μm are formed in the mask 21 in the arrangement shown in FIG. FIG. 14 (a) shows the positions of the openings in a square of about 1 mm, and they are arranged in a plane such that the shape connecting the nearest openings with a pitch of 50 μm is an equilateral triangle. Irregularities are introduced in the position at a value of 25% of the pitch relative to the ones. After the openings are formed, wet etching is performed to 480 μm. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is 480 μm. The planar shape of the processed optical element is as shown in FIG. In FIG. 14B, the depth is displayed in black and white gradations, and is displayed so as to become darker as it gets deeper.

  What calculated the emitted light distribution of the light at the time of entering light with a wavelength of 450 nm to such an optical element is shown in FIG.14 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 14C, diffraction due to the regular arrangement occurs and strong light is generated in a specific direction, and in particular, the amount of light to be transmitted straight is large. FIG. 14 (d) is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 14 (c) are averaged at every angle of 0.21 ° and plotted against the angle. As shown in FIG. 14C, strong light is generated in a specific direction. Moreover, it was 69.4% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.14 (c). The value of | (n1−n2) × Δd | / λ was 0.

(Example 3)
Next, the optical element in Example 3 will be described based on FIG. 15 focusing on the points different from Example 1.

  Openings with a diameter of 1 μm are formed in the mask 21 in the arrangement shown in FIG. FIG. 15 (a) shows the positions of the openings in an approximately 1 mm square, and they are arranged in a plane such that the shape connecting the nearest openings with a pitch of 50 μm is an equilateral triangle. Irregularities are introduced in the position at a value of 50% of the pitch with respect to the ones. After the openings are formed, wet etching is performed to 480 μm. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is 480 μm. The planar shape of the processed optical element is as shown in FIG. In FIG. 15 (b), the depth is displayed in black and white gradations, and is displayed so as to be darkened as it gets deeper.

  What calculated the emitted light distribution of the light in case the light of wavelength 450nm injects into such an optical element is shown in FIG.15 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 15 (c), the amount of light that goes straight through is particularly large. FIG. 15 (d) is a graph in which the intensity in the horizontal direction in the outgoing light distribution of FIG. 15 (c) is averaged at every angle of 0.21 ° and is plotted against the angle. As shown in FIG. 15 (c), strong light is generated in the direction of straight transmission. Moreover, it was 62.9% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.15 (c). The value of | (n1−n2) × Δd | / λ was 0.

(Example 4)
Next, the optical element in Example 4 will be described based on FIG.

The base 11 formed of glass with a refractive index of 1.53 is cleaned, 45 nm of SiO ₂ is formed as the thin film layer 25, and 50 nm of molybdenum is formed as the mask 21. After depositing molybdenum, a resist is applied, and openings of φ 1 μm are formed in the mask 21 in the arrangement shown in FIG. 16A by photolithography and etching. FIG. 16 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. It is. After the openings are formed, the SiO ₂ is patterned by photolithography and etching so that the depth of the counterbore portion 26 becomes a binary value of 0 nm or 45 nm with respect to the reference depth. After the counterbore portion 26 is formed, 480 μm of etching is performed using a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 450 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 become irregular so that the bottom portions 13 of 75% or more are not arranged at a binary level of the distribution range in the depth direction of the positions of the bottom portions 13 ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 16B, the depth is displayed in black and white gradations, and is displayed so as to be darkened as it gets deeper.

  What calculated the emitted light distribution of the light at the time of entering light with a wavelength of 450 nm to such an optical element is shown in FIG.16 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 16C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 16 (d) is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 16 (c) are averaged at every angle of 0.21 ° and plotted against the angle. As shown in FIG. 16C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 71.2% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.16 (c). The value of | (n1−n2) × Δd | / λ was 0.53.

(Example 5)
Next, the optical element in Example 5 will be described based on FIG. 17 focusing on the points different from Example 4.

Openings with a diameter of 1 μm are formed in the mask 21 in the arrangement shown in FIG. FIG. 17 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. In contrast to the above, the irregularity of the position is introduced at a value of 25% of the pitch. After the openings are formed, SiO ₂ is patterned by photolithography and etching so that the depth of the counterbore portion 26 becomes a binary value of 0 nm or 45 nm with respect to the reference depth. After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 450 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 become irregular so that the bottom portions 13 of 75% or more are not arranged at a binary level of the distribution range in the depth direction of the positions of the bottom portions 13 ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 17B, the depth is displayed in black and white gradations, and is displayed so as to be darkened as it gets deeper.

  What calculated the emitted light distribution of the light in case the light of wavelength 450nm injects into such an optical element is shown in FIG.17 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 17C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 17 (d) is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 17 (c) are averaged at every angle of 0.21 ° and the angle is plotted. As shown in FIG. 17 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 67.2% when the light of the range of angle +/- 1.25 degrees was integrated in FIG.17 (c). The value of | (n1−n2) × Δd | / λ was 0.53.

(Example 6)
Next, the optical element in Example 6 will be described based on FIG. 18 focusing on the points different from Example 4.

Openings with a diameter of 1 μm are formed in the mask 21 in the arrangement shown in FIG. FIG. 18 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. The irregularity of the position is introduced at a value of 50% of the pitch. After the openings are formed, SiO ₂ is patterned by photolithography and etching so that the depth of the counterbore portion 26 becomes a binary value of 0 nm or 45 nm with respect to the reference depth. After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 450 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 become irregular so that the bottom portions 13 of 75% or more are not arranged at a binary level of the distribution range in the depth direction of the positions of the bottom portions 13 ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 18B, the depth is displayed in black and white gradations, and is displayed so as to be darkened as it gets deeper.

  What calculated the emitted light distribution of the light at the time of entering light with a wavelength of 450 nm to such an optical element is shown in FIG.18 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 18C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 18D shows the intensity in the horizontal direction of the emitted light distribution of FIG. 18C averaged at every 0.21 ° angle and graphed with respect to the angle. As shown in FIG. 18C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 60.4% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.18 (c). The value of | (n1−n2) × Δd | / λ was 0.53.

(Example 7)
Next, the optical element in Example 7 will be described based on FIG.

The base 11 formed of glass with a refractive index of 1.53 is cleaned, 90 nm of SiO ₂ is formed as the thin film layer 25, and 50 nm of molybdenum is formed as the mask 21. After depositing molybdenum, a resist is applied, and openings of φ 1 μm are formed in the mask 21 in the arrangement shown in FIG. 19A by photolithography and etching. FIG. 19 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. It is. After the openings are formed, the SiO ₂ is patterned by photolithography and etching, and the depth of the countersunk portion 26 is an eight-value depth such that the distance between the depths of one step with respect to the reference depth is 11.25 nm. To be After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 787.5 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 are irregular so that the bottom portions 13 of 50% or more are not arranged at a certain value level of the distribution range of the bottom portions 13 in the depth direction. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 19B, the depth is displayed in black and white gradations, and is displayed so as to be darkened as it gets deeper.

  What calculated the emitted light distribution of the light at the time of entering light with a wavelength of 450 nm to such an optical element is shown in FIG.19 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. 19 (b). As shown in FIG. 19C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 19 (d) is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 19 (c) are averaged at every angle of 0.21 ° and plotted against the angle. As shown in FIG. 19 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 70.6% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.19 (c). The value of | (n1−n2) × Δd | / λ was 0.93.

(Example 8)
Next, the optical element in Example 8 will be described based on FIG. 20, focusing on the difference from Example 7.

Openings of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. FIG. 20 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. In contrast to the above, the irregularity of the position is introduced at a value of 25% of the pitch. After the openings are formed, the SiO ₂ is patterned by photolithography and etching, and the depth of the countersunk portion 26 is an eight-value depth such that the distance between the depths of one step with respect to the reference depth is 11.25 nm. To be After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 787.5 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 are irregular so that the bottom portions 13 of 50% or more are not arranged at a certain value level of the distribution range of the bottom portions 13 in the depth direction. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 20B, the depth is displayed in black and white gradations, and is displayed so as to become darker as it gets deeper.

  What calculated the emitted light distribution of the light in case the light of wavelength 450nm injects into such an optical element is shown in FIG.20 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 20 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 20 (d) is a graph in which the intensity in the horizontal direction in the outgoing light distribution of FIG. 20 (c) is averaged at every angle of 0.21 ° and is plotted against the angle. As shown in FIG. 20 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 66.6% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.20 (c). The value of | (n1−n2) × Δd | / λ was 0.93.

(Example 9)
Next, the optical element in Example 9 will be described based on FIG. 21 focusing on the points different from Example 7.

An opening of φ1 μm is formed in the mask 21 in the arrangement shown in FIG. FIG. 21 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. The irregularity of the position is introduced at a value of 50% of the pitch. After the openings are formed, the SiO ₂ is patterned by photolithography and etching, and the depth of the countersunk portion 26 is an eight-value depth such that the distance between the depths of one step with respect to the reference depth is 11.25 nm. To be After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 787.5 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 are irregular so that the bottom portions 13 of 50% or more are not arranged at a certain value level of the distribution range of the bottom portions 13 in the depth direction. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 21B, the depth is displayed in black and white gradations, and is displayed so as to be darkened as it gets deeper.

  What calculated the emitted light distribution of the light at the time of entering light with a wavelength of 450 nm to such an optical element is shown in FIG.21 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. 21 (b). As shown in FIG. 21 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 21 (d) is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 21 (c) are averaged at every angle of 0.21 ° and plotted against the angle. As shown in FIG. 21 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 59.5% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.21 (c). The value of | (n1−n2) × Δd | / λ was 0.93.

(Example 10)
Next, the optical element in Example 10 will be described based on FIG.

The base material 11 formed of glass with a refractive index of 1.53 is cleaned, 24.3 nm of SiO ₂ is formed as the thin film layer 25, and 50 nm of molybdenum is formed as the mask 21. After depositing molybdenum, a resist is applied, and openings of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. 22A by photolithography and etching. FIG. 22 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. It is. After forming the opening, the SiO ₂ is patterned by photolithography and etching so that the depth of the counterbore portion 26 has a binary value of 0 nm or 24.3 nm with respect to the reference depth. After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 243 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 become irregular so that the bottom portions 13 of 75% or more are not arranged at a binary level of the distribution range in the depth direction of the positions of the bottom portions 13 ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 22 (b), the depth is displayed in black and white gradations, and is displayed so as to become darker as it gets deeper.

  What calculated the emitted light distribution of the light at the time of entering the light of wavelength 450nm to such an optical element is shown in FIG.22 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 22C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 22 (d) is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 22 (c) are averaged at every angle of 0.21 ° and plotted against the angle. As shown in FIG. 22 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. In particular, the light quantity of the 0th order light transmitted straight before averaging is 1.6%, and is reduced to half of 3.2% of the light quantity of the 0th order light of the optical element in Example 1. Moreover, it was 73.2% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.22 (c). The value of | (n1−n2) × Δd | / λ was 0.29.

(Example 11)
Next, the optical element in Example 11 will be described based on FIG.

The base 11 formed of glass with a refractive index of 1.53 is cleaned, and a thin film layer 25 is formed of 450 nm of SiO ₂ , and a mask 21 is formed of 50 nm of molybdenum. After depositing molybdenum, a resist is applied, and openings of φ 1 μm are formed in the mask 21 in the arrangement shown in FIG. 23A by photolithography and etching. FIG. 23 (a) shows the positions of the openings in an approximately 1 mm square, arranged at a pitch of 50 μm such that the shape connecting the nearest openings is an equilateral triangle. The irregularity of the position is introduced at a value of 50% of the pitch. After the openings are formed, SiO ₂ is patterned by photolithography and etching, and the depth of the counterbore 26 is an eight-value depth such that the distance between the depths of one step with respect to the reference depth is 56.25 nm. To be After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 3937.5 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 are irregular so that the bottom portions 13 of 50% or more are not arranged at a certain value level of the distribution range of the bottom portions 13 in the depth direction. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 23 (b), the depth is displayed in black and white gradations, and is displayed so as to become darker as it gets deeper.

  What calculated the emitted light distribution of the light at the time of entering light with a wavelength of 450 nm to such an optical element is shown in FIG.23 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 23C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 23 (d) is a graph in which the intensity in the horizontal direction in the outgoing light distribution of FIG. 23 (c) is averaged at every angle of 0.21 ° and the angle is plotted. As shown in FIG. 23 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 37.8% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.23 (d). The value of the full width at half maximum of the light amount distribution in FIG. 23D is 2.9 °, which is 1.1 times the value of 2.6 ° that is the value of the full width at half maximum of the light amount distribution in the optical element of Example 9. There is. The value of | (n1−n2) × Δd | / λ was 4.6.

(Example 12)
Next, the optical element in Example 12 will be described based on FIG.

The base 11 formed of glass with a refractive index of 1.53 is cleaned, and a thin film layer 25 is formed of 900 nm of SiO ₂ , and a mask 21 is formed of molybdenum of 50 nm. After depositing molybdenum, a resist is applied, and an opening of φ1 μm is formed in the mask 21 in the arrangement shown in FIG. 24A by photolithography and etching. FIG. 24 (a) shows the positions of the openings in an approximately 1 mm square, in which the pitches of 50 .mu.m and the nearest openings are arranged in a plane so as to form an equilateral triangle. Irregularity is introduced to the position at a value of 50% of the pitch. After the openings are formed, the SiO ₂ is patterned by photolithography and etching, and the depth of the counterbore 26 is an eight-value depth such that the distance between the depths of one step with respect to the reference depth is 112.5 nm. To be After the counterbore portion 26 is formed, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ to the glass substrate is 10. Accordingly, the radius of curvature of the curved surface portion 24 in the recess 12 is approximately 480 μm, and the distribution range in the depth direction of the position of the bottom portion 13 in the recess 12 is 7875 nm. Here, the bottom portions 13 are arranged so that the positions in the depth direction of the bottom portions 13 are irregular so that the bottom portions 13 of 50% or more are not arranged at a certain value level of the distribution range of the bottom portions 13 in the depth direction. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 24 (b), the depth is displayed in black and white gradations, and is displayed so as to become darker as it gets deeper.

  What calculated the emitted light distribution of the light in case the light of wavelength 450nm injects into such an optical element is shown in FIG.24 (c). The calculation was performed by determining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 24C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 24 (d) is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 24 (c) are averaged at every angle of 0.21 ° and plotted against the angle. As shown in FIG. 24 (c), the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Moreover, it was 23.6% when integrating | accumulating the light of the range of angle +/- 1.25 degrees in FIG.24 (d). The value of the full width at half maximum of the light amount distribution in FIG. 24D is 4.7 °, which is 1.8 times the value of the full width at half maximum of the light amount distribution of 2.6 in the optical element of Example 9 There is. The value of | (n1−n2) × Δd | / λ was 9.3.

(Example 13)
Next, the optical element in Example 13 will be described based on FIG.

  Clean the glass of 2 mm in thickness and 1.52 in refractive index, and arrange the openings of φ3 μm at a pitch of 60 μm so that the shape connecting the nearest openings becomes an equilateral triangle by photolithography and etching. A mask made of molybdenum having a thickness of 50 nm was produced. Next, etching was performed using a wet etching solution. When the curvature radius of the curved surface portion 24 in the concave portion 12 was measured at four points, the average value was 296 μm, and the distribution range in the depth direction of the position of the bottom portion 13 at the measurement points was 0.296 μm. The planar shape of the processed optical element is as shown in FIG.

  When a laser beam having a wavelength of 633 nm was incident on such an optical element, a projection pattern as shown in FIG. 25B was obtained, and a pattern of a diffraction pattern due to periodicity was observed.

(Example 14)
Next, the optical element in Example 14 will be described based on FIG.

The glass with a refractive index of 1.52 having a thickness of 2 mm is cleaned, and the average spacing P _{1 of the} openings is 60 μm with respect to the first direction by photolithography and etching, and the direction perpendicular to the first direction is as a second direction, a mask is fabricated of molybdenum with a thickness of 50nm which is arranged the opening of φ3μm so that the distance P ₂ of the center of gravity of the position of each aperture in the row of openings formed in the first direction is 52μm did. Each opening position has an irregularity of ± 25% of the average spacing in the first direction in the first direction, and ±± of the average spacing in the second direction in the second direction. It was made to have 25% irregularity. Next, etching was performed using a wet etching solution. When the curvature radius of the curved surface portion 24 in the concave portion 12 was measured at nine points, the average value was 322 μm, and the distribution range in the depth direction of the position of the bottom 13 at the measurement point was 1.107 μm. The planar shape of the processed optical element was as shown in FIG.

  Further, FIG. 27 shows an area ratio obtained by normalizing the area of a polygon forming the nine concave portions whose radius of curvature is measured by the minimum value thereof and the relative position in the height direction of the bottom of the concave portion. The correlation coefficient obtained from FIG. 27 is −0.6325.

  When a laser beam having a wavelength of 633 nm was incident on such an optical element, a projection pattern as shown in FIG. 26B was obtained, and the pattern of the projection pattern due to the periodicity was not observed.

  As mentioned above, although the form concerning the embodiment of the present invention was explained, the above-mentioned contents do not limit the contents of the present invention. The optical element of the present invention is not limited to a projection device, and can be used in various devices such as a three-dimensional measurement device. In addition, it can be used as an optical element for controlling the diffusion state such as a diffusion plate for illumination, a focusing plate in a finder of a camera, a screen of a projection apparatus, and the like.

DESCRIPTION OF SYMBOLS 10 optical element 11 base 12, 42 recessed part 12a, 12b recessed part 13, 43 bottom 13a, 13b bottom 14 bordering point 15 bordering point 21 mask 22 counterbore 22a bottom face 23 flatter 24 curved surface 25 thin film layer 26 counterbore Part 27 Thin film layer 28 Mask 30, 40 Optical element 31, 41 Base material 32 Convex part 44 Reflective film 100 Projection device 111a, 111b, 111c Laser light source 112a, 112b, 112c Lens 113a, 113b, 113c Optical element 114a, 114b, 114c Lenses 115a, 115b, 115c Spatial light modulators 116 Combined prism 117 Lens 118 Screen 200 Projection device 201 Laser light source 202 First optical element 203 Dichroic mirror 204 Lens 205 Fluorescent wheel 206, 208, 210, 212, 213, 215, 217 Lens 207, 209, 216, 218 Mirror 211 Combined mirror 214 Integrator 219 Spatial light modulator 220 Projection lens

Claims (13)

A plurality of recesses are formed on the surface of the substrate,
The recess has a curved portion formed by a curved surface,
The plurality of recessed portions are formed such that the position of the bottom of the recessed portion is two or more different positions in the depth direction,
The refractive index of the base material is n1, the refractive index of the medium around the base material is n2, the wavelength of a light beam incident on the base material is λ, and the range in the depth direction of the bottom of the plurality of recesses is In the case of Δd,
2/7 ≦ | (n1−n2) × Δd | / λ ≦ 10
And
An optical element characterized in that the radius of curvature of the curved surface portion is formed within ± 50% of the average value of the radius of curvature.   The optical element according to claim 1, wherein the optical element transmits light. A plurality of recesses are formed on the surface of the substrate,
The recess has a curved portion formed by a curved surface,
The plurality of recessed portions are formed such that the position of the bottom of the recessed portion is two or more different positions in the depth direction,
The refractive index of the medium around the substrate is n2, and the wavelength of a light beam incident on the substrate is λ.
Assuming that the range in the depth direction of the bottom of the plurality of recesses is Δd,
2/7 ≦ | 2 × n 2 × Δd | / λ ≦ 10
And
An optical element characterized in that the radius of curvature of the curved surface portion is formed within ± 50% of the average value of the radius of curvature.   The optical element according to claim 3, wherein the optical element reflects light.   The optical element according to claim 1, wherein the bottom portion is arranged at a predetermined cycle. The bottom is irregularly formed,
4. The optical device according to claim 1, wherein the bottom portion is present in a region surrounded by bisectors of adjacent points in the case of arranging at a predetermined cycle. element.   The said bottom part has a flat part, The optical element in any one of Claim 1, 3, 5, 6 characterized by the above-mentioned.   The optical element according to claim 7, wherein the flat portion includes two or more sizes.   In the case where the position of the bottom is an irregular array, assuming that the pitch of the regular array is P, the bottom has a radius of about the center point of the bottom when the regular array is formed. The optical element according to claim 1 or 3, wherein the optical element is formed to be within the range of a circle of 0.5 × P.   The optical element according to any one of claims 1, 3 and 9, wherein the bottom portion is formed so as to be within a circle having a radius of 0.25 × P. The bottoms are randomly arranged at an average spacing P1 in the first direction,
In the second direction which is a direction orthogonal to the first direction, the centers of gravity of the positions of the bottoms of the rows of bottoms formed in the first direction are arranged at an interval P 2. The optical element in any one of 1, 3, 9, 10. The bottom portion has a spacing of the bottom portion in the first direction in the row of bottom portions of (1 ± 0.25) P1.
The optical element according to claim 11, wherein the position of each of the bottoms with respect to the position of the center of gravity in the second direction of the row of bottoms is ± 0.25 P2 with respect to the position of the center of gravity. An optical element according to any one of claims 1 to 12,
A light source for emitting light incident on the optical element;
Projection device.