JP6680455B2 - Optical element and projection device - Google Patents

Description

  The present invention relates to an optical element, a projection device, and a method for manufacturing an optical element.

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

  By the way, when a light source having high coherence such as a laser is used, and in the case of a regular arrangement of microlenses, diffracted light is generated only in a predetermined direction according to the regularity of the arrangement, and the intensity distribution of the light flux is corrected. It may be insufficient. As a method of reducing such a diffraction effect, there is a method of introducing irregularity to a microlens array, and in particular, by introducing irregularity in a controlled range, light is diffused in a predetermined angle range. It is known how to do this. Patent Document 2 discloses a microstructure in which irregularity is introduced in the depth direction, and shows an example of a microstructure having a distribution range in the depth direction of 10 μm or more.

JP, 2007-233371, A U.S. Pat. No. 7,033,736

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

  Further, when laser light is incident, light resistance may be required, and it is preferable that the base material used is made 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 are restrictions on the shape that can be processed by wet etching, and it is described in Patent Document 2. As described above, when the uneven shape is formed deeply and at different depths, it is difficult to process it into a desired shape.

  On the other hand, as a method for processing the surface of glass or the like into a concavo-convex shape, there are also processing methods such as dry etching and press molding, but when the concavo-convex shape is formed deeply, there is a problem that the processing time in dry etching becomes long. Further, in the case of press molding, there is a problem that air enters during press molding, and a portion where the air enters becomes a defect.

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

According to one aspect of the present embodiment, a plurality of recesses are formed on the surface of the base material, and the recess has a curved surface portion formed by a curved surface, and the recessed portion has a plan view. In this case, the shape is surrounded by three or more ridge lines , and the plurality of recesses are formed such that the bottoms of the recesses are located at 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 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. If
2/7 ≦ | (n1-n2) × Δd | / λ ≦ 10
, And the said position of the bottom I irregular sequence der, when the pitch of the regular sequence is P, based on the center point of the bottom portion in a case where a regular arrangement is made, the bottom, It is characterized in that it is formed so as to exist within the range of a circle having a radius of 0.5 × P.

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 so that the positions of the tops of the convex portions are two or more different positions in the height direction, the refractive index of the base material is n1, and the periphery of the base material is When the refractive index of the medium is n2, the wavelength of the light beam incident on the base material is λ, and the range in the height direction of the tops of the plurality of convex portions 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 portion has a curved surface portion formed by a curved surface, Has a shape surrounded by three or more ridge lines in a plan view, and the plurality of recesses are formed such that the positions of the bottoms of the recesses are two or more different positions in the depth direction. When the refractive index of the medium around the base material is n2, 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 ≦ | 2 × n2 × Δd | / λ ≦ 10
, And the said position of the bottom I irregular sequence der, when the pitch of the regular sequence is P, based on the center point of the bottom portion in a case where a regular arrangement is made, the bottom, It is characterized in that it is formed so as to exist within the range of a circle having a radius of 0.5 × P.

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, When the wavelength of the light beam incident on the base material is λ and the range in the height direction of the tops of the plurality of convex portions is Δd,
2/7 ≦ | 2 × n2 × 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 base material, and wet etching the base material on which the mask is formed, A step of forming a plurality of recesses on the surface of the base material, wherein the plurality of openings are openings having different sizes of two or more, and the plurality of recesses are located at the bottom of the recess. Is 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 base material, and wet etching the base material on which the mask is formed, Forming a plurality of recesses on the surface of the base material, wherein at least two counterbore portions having different depths are formed in the base material in the region where the opening is formed. Characterize.

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

Structural diagram 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 manufacturing method 1 of optical element in the present embodiment Process drawing of the manufacturing method 2 of the optical element in this Embodiment Process drawing of manufacturing method 3 of optical element in the present embodiment Process drawing of manufacturing method 4 of the optical element in the present embodiment Structural diagram of another optical element in the present embodiment (1) Structural diagram of another optical element in the present embodiment (2) Structural diagram of the projection apparatus in the present embodiment Structural diagram of another projection device in the present embodiment Structure diagram 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 of the area ratio of the concave portion of the optical element and the relative position of the bottom surface of the concave portion in the height direction in Example 14.

  Modes for carrying out the invention will be described below. The same members and the like are designated by the same reference numerals and the description thereof will be omitted.

(Optical element)
The optical element according to the present embodiment will be described with reference to FIG. Note that FIG. 1A is a plan view of the optical element in the present embodiment, and FIG. 1B schematically shows a cross-sectional view taken along one-dot chain line 1A-1B in FIG. .

  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 a plurality of concave portions 12 are formed on the surface of the base material 11 will be described. However, the optical element according to 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 part of the recess 12 is the bottom 13, and the position of the bottom 13 in the recess 12 in the depth direction is not uniform, and the bottom 13 of the recess 12 is not uniform. The position in the depth direction is two or more values, and in the bottoms 13 of the plurality of recesses 12, the difference between the depth positions of the deepest bottom 13 and the shallowest bottom 13, that is, the height of the bottom 13. The difference is formed to be Δd.

  Next, the planar position of the bottom portion 13 will be described. In FIG. 2A, the position of the bottom portion 13 is indicated by "●". The positions of the bottom portions 13 may be regularly arranged, that is, arranged in a predetermined cycle, or may be irregularly arranged. When the positions of the bottom portions 13 are irregularly arranged, assuming that the pitch of the regular arrangement is P, the center point of the bottom portion when the regular arrangement is made (point at which the regular arrangement is made) Based on the above, the bottom portion 13 is preferably formed so as to exist within the range of a circle having a radius of 0.5 × P, and further, within the range of a circle having a radius of 0.25 × P. More preferably, it is formed so as to exist. In addition, in FIG. 2A, the positions of the points where the regular arrangement is performed are indicated by "x". In FIG. 2A, this regular array is an array in which the shape connecting the points of the closest regular array is a triangle.

Further, the bottoms may be arranged such that the average spacing between the bottoms in a certain first direction is P ₁ . At this time, the direction orthogonal to the first direction may be set as the second direction, and the centers of gravity of the positions of the bottoms in the row of the bottoms formed in the first direction may be arranged at the interval P ₂ . Since such an array is not based on a regular array, it is possible to further reduce the influence of periodicity due to the regular array. An example of such an array is shown in FIG. In FIG. 3, the position of the bottom is indicated by "●". In FIG. 3, a plurality of bottom rows are arranged in the first direction, and the barycentric position of some of the bottom rows in the second direction is shown by dotted lines 51a, 51b, 51c, and 51d. In the bottom row in which the position of the center of gravity is the dotted line 51a, the bottom spacing in the first direction is P ₁₁ , P ₁₂ , ..., P ₁₇ , respectively, and the average value thereof is P ₁ . Further, the bottom position in each bottom row is set to the second direction so that the intervals of the dotted line 51a, the dotted line 51b, the dotted line 51c, and the dotted line 51d, which are the barycentric positions in the second direction, are P ₂ with respect to the second direction. It's irregular. In FIG. 3, the center of gravity (dotted line 53) in the first direction of the bottom at the left end of the odd bottom row from the bottom of the drawing and the left bottom bottom of the even bottom row of the bottom 52 from the bottom of the drawing. 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. The spacing of the bottoms in the first direction in the bottom row is preferably (1 ± 0.25) P ₁ and more preferably (1 ± 0.15) P ₁ . Further, the position of each bottom portion with respect to the center of gravity position in the second direction of the bottom row is preferably ± 0.25P ₂ with respect to the center of gravity position, and more preferably ± 0.15P ₂ .

  When the arrangement of the bottom portion is irregular, the arrangement of the bottom portion may be point-symmetrical or line-symmetrical in a part of the area. By doing so, it is possible to make asymmetry less likely to occur in the positive and negative directions.

  In the optical element of the present embodiment, by forming in this way, light can be diffused efficiently in a predetermined angle range, as will be described later. Further, when the pitch of the regular array is different for each direction, the range in which the bottom portion 13 is located in the present embodiment may be elliptical depending on 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 the bisectors of the points that are regularly arranged adjacent to each other. Further, the bottom portion of the present embodiment is provided in a region surrounded by a perpendicular line at a position 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 is located. Here, the perpendicular line means a perpendicular line to a line segment that connects points that are regularly arranged and points that are adjacent and regularly arranged.

  In FIG. 2A, when the bottom portion 13 “●” is located in a region within ¼ of the pitch with respect to the position “x” of the points where the triangular regular array is formed. Is shown. 2B is a cross-sectional view taken along the alternate long and short dash line 2A-2B connecting the bottom portion 13a of the recess 12a and the bottom portion 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 have different positions in the depth direction, and the surface forming the recess 12a and the surface forming the recess 12b are different from each other. When the two have the same curvature, the point 14 which is the boundary between the recess 12a and the recess 12b is not located on the bisector of the bottom 13a and the bottom 13b. It should be noted that the case where the positions in the depth direction coincide with each other on the adjacent bottom portions is shown by a dotted line. In this case, the boundary point 15 is on the bisector of the bottom portion 13a and the bottom portion 13b ₁ .

  Generally, when a recess is formed by wet-etching a base material such as glass, the curvatures of the surfaces of adjacent recesses are about the same. Therefore, if the position of the bottom of the recess in the depth direction is greatly different, the position of the boundary point 14 is largely displaced from the bisector.

  When the concave portions are adjacent to each other at the boundary point 15, the inclination angles of the surfaces of the adjacent concave portions are the same, and the inclination angle of the concave portion at the boundary point 15 can be set to a predetermined diffusion angle. , It is possible to efficiently diffuse light within a predetermined diffusion angle range. On the other hand, when the concave portions are adjacent to each other at the boundary point 14, the inclination angles of the surfaces of the adjacent concave portions are different, and the inclination angle of the concave portion is smaller on one side and larger on the other side with respect to a predetermined diffusion angle. In this case, the amount of light diffused outside the predetermined diffusion angle range increases.

  As described above, when the position of the bottom portion 13 of the concave portion 12 in the depth direction is significantly different, light outside the predetermined diffusion angle range is likely to occur, and therefore the difference in the position of the bottom portion 13 of the concave portion 12 in the depth direction is , Smaller is preferable. However, when the positions of the bottom 13 of the recess 12 in the depth direction are all the same, the component of the light that goes straight forward increases. Therefore, in order to reduce the component of light that travels straight ahead, there is a method of causing a diffraction phenomenon in the component of light that travels straight ahead and diffusing it.

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

Although the case where the optical element is a transmissive optical element has been described above, the contents are as follows: the refractive index of the base material 11 in which the recess 12 is formed is n1, the refractive index of the medium around the recess 12 is n2, and the incident light is n2. When the wavelength of the luminous flux is λ, it is expressed by the following equation (1).

2/7 ≦ | (n1-n2) × Δd | / λ ≦ 10 ... (1)

The optical element according to the present embodiment preferably further satisfies the condition (2) below, and more preferably the condition (3) below.

2/7 ≦ | (n1-n2) × Δd | / λ ≦ 5 (2)

2/7 ≦ | (n1-n2) × Δd | / λ ≦ 2 (3)

Further, the position of the bottom portion 13 of the recess 12 in the depth direction may be formed at a plurality of levels (a plurality of depth positions) instead of being set at an arbitrary position. In this case, if the position in the depth direction is at least two levels (the depth position is a binary value) or more, the above-mentioned diffraction phenomenon can be obtained. It is more preferable that the position in the direction is 4 levels or more (the depth position is 4 values). Further, in order to efficiently generate the diffraction phenomenon, it is preferable that the bottom portion 13 is not distributed much at a position of a specific depth, and in the case of two levels, 75% at a position in a specific depth direction. It is preferable that more bottom portions 13 are not distributed. Further, in the case of 4 levels or more, it is preferable that more than 50% of bottom portions 13 are not distributed at a position in a certain depth direction.

  In addition, when the base material 11 has a warp, or when it has undulations that become uneven at a long pitch of several 100 μm or more, or when the base material 11 has undulations with a long pitch due to wet etching. There are cases. In such a case, the equation (1) may not be satisfied on the entire surface of the element due to the unevenness caused by the warp or undulation of the base material 11. In such a case, at least the adjacent bottom portions should satisfy the equation (1). You may make it satisfy.

When the displacement amount in the height direction of the point 14 which is the boundary between the bottom portion 13b, the concave portion 12a and the concave portion 12b is the displacement amount Δz, the optical path difference generated by the displacement amount Δz is smaller than the wavelength of the incident light. In that 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) * [Delta] z _avg | / [lambda], and it is more preferable to set [Delta] z _avg to satisfy 3/4 <| (n1-n2) * [Delta] z _avg | / [lambda]. 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, when the average shape of the concave portion is a spherical surface having a radius of curvature R _avg , the height of the spherical surface distant from the origin by r can be obtained by R _avg − (R _avg ² −r ² ) ^½ , and therefore Δz _It may be determined by _avg = R _avg − (R _avg ² −r _avg ² ) ^½ .

  When the optical element 10 is a transmissive optical element, a transparent material such as glass or resin can be used as the material forming the base material 11 having the recess 12 formed on the surface thereof. 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 antireflection film (not shown) may be formed on the surface of the optical element 10.

(Method of manufacturing optical element)
Next, a method for manufacturing the optical element according to the present embodiment will be described. The method of manufacturing the optical element 10 according to the present embodiment includes a method of forming the base material 11 by wet etching, and a method of forming the resist pattern by gray scale exposure and then dry etching the base material 11. Examples of the method include a method of forming by press molding with a molding die and the like, and a method of imprinting.

  As an example of the manufacturing method for manufacturing the optical element according to the present embodiment by wet-etching the base material 11, four manufacturing methods will be described below.

(Method 1 of manufacturing optical element)
First, the manufacturing method 1 of the optical element will be described with reference to FIG.

  In this method, first, as shown in FIG. 4A, a patterned mask 21 is provided on a base material 11 formed of glass or the like, and a counterbore portion 22 is formed on the base material 11 at the opening of the mask 21. Form. As the method of forming the mask 21 and the counterbore portion 22, a method of forming by a combination of processes such as photolithography, etching, and lift-off, and a method of blasting can be used.

  In the blasting process, it is generally difficult to control the depth of the countersunk portion 22 and the size of the opening of the mask 21. Therefore, it is preferable to use a method in which photolithography, etching, and lift-off are combined. . In the case of a method of forming by combining photolithography and etching, dry etching can be used when forming the countersink portion 22, and in this case, the bottom surface 22a of the countersunk portion 22 is processed into a flat surface.

  Next, as shown in FIG. 4B, a mask 21 is formed on the base material 11, and a counterbore portion 22 is formed in a region of the base material 11 where the opening of the mask 21 is formed. Wet-etch what has been done. As a result, a part of the base material 11 is removed by wet etching starting from the countersunk portion 22, and the recess 12 is formed on the surface of the base material 11. In wet etching, the base material 11 is isotropically removed by etching, so that the bottom of the recess 12 is formed by the flat portion 23. Therefore, the surface of the recess 12 is formed by the flat portion 23 and the curved surface portion 24. In the curved surface portion 24, the cross-section has a curved surface shape with an arc, but when the mask 21 has little resistance to wet etching, the shape of the edge portion of 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 that is an arc. The material forming the mask 21 is preferably a material that can be patterned and has a high resistance to wet etching, and is formed of, for example, a metal material such as chromium or molybdenum.

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

  The flat portion 23 of the concave portion 12 is a portion corresponding to the bottom portion 13 in FIGS. 1 and 2 and is formed by a surface perpendicular to the thickness direction of the base material 11. The boundary between the flat portion 23 and the curved surface 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 to change from a certain fixed value of the radius of curvature to an infinite radius of curvature. Ideally, such a change is a sharp change, but when the change at the boundary is not a sharp change, a predetermined radius of curvature such as a region that is α times or more the radius of curvature of the curved surface portion 24 is used. The above area can 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. When the curvature of the curved surface portion 24 becomes large, it may not be possible to confirm the change in the radius of curvature within the S / N range of the three-dimensional measuring device. However, in such a case, the size of the flat portion 23 and the boundary between the flat portion 23 and the curved surface portion 24 may be obtained by observing the shape of the concave portion 12 with an electron microscope or an atomic force microscope. .

(Method 2 of manufacturing optical element)
Next, the manufacturing method 2 of the optical element will be described with reference to FIG.

In the method shown in FIG. 4, the counterbore portion 22 is formed on the base material 11 such as glass. In this case, depending on the type of glass forming the base material 11, dry etching for forming the counterbore portion 22 is performed. In some cases, it may take a very long time to process, and in some cases, dry etching cannot be performed and the counterbore portion 22 cannot be formed. The method shown in FIG. 5 is a method in which a thin film layer 25 such as SiO ₂ or Ta ₂ O ₅ capable of dry etching is formed on the surface of the base material 11 in advance.

Specifically, first, as shown in FIG. 5A, a thin film layer 25 such as SiO ₂ or Ta ₂ O ₅ that can be dry-etched is formed on the surface of the base material 11, and the thin film layer 25 is then formed. The mask 21 is formed thereon, and the counterbore 26 is formed in a part of the opening of the mask 21 in the thin film layer 25. Thereby, the counterbore portion 26 can be easily formed, and the later wet etching can be performed.

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

  Next, as shown in FIG. 5C, by removing the mask 21 and the thin film layer 25, 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 a material having a smaller wet etching rate than glass. For example, Haxin Zhu et al. , J. Micromech. Microeng. 19 (2009) 065013 describe wet etching rates for various glass materials. According to this, the wet etching rate may differ ten times or more between quartz and glass materials having the same composition as SiO ₂ .

When the ratio of the wet etching rates of the base material 11 and SiO ₂ is r and the distribution range of the position in the depth direction of the bottom of the counterbore 26 of the thin film layer 25 is ΔD, the final depth of the bottom 13 of the recess 12 is set. The distribution range Δd of the positions in the depth direction is Δd = rΔD. Therefore, for example, when r is 10 and required Δd is 1 μm, ΔD is 100 nm. In this way, in addition to enabling the processing of various glass materials, the processing amount in the counterbore portion 26 can be reduced, so that the counterbore portion 26 can be formed in the thin film layer 25 by lift-off or sol-gel in addition to dry etching. Can be formed.

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

(Optical Element Manufacturing Method 3)
Next, the optical element manufacturing method 3 will be described with reference to FIG.

  The method shown in FIG. 6 is similar to the method shown in FIG. 5 in that the position of the bottom portion in the depth direction is adjusted using a thin film layer, but it is not formed with a counterbore part but is patterned. The thin film layer 27 is formed in a part of the opening of the mask 21. This makes it possible to adjust the time required for the wet etching solution to reach the base material 11 depending on the difference in the thickness of the thin film layer 27, so that the position of the bottom portion 13 of the recess 12 to be formed in the depth direction 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 of the mask 21 where the opening is formed is formed. In the part, the thin film layer 27 is formed on the base material 11 and the mask 21.

  Next, as shown in FIG. 6B, the thin film layer 27 and a part of the base material 11 are removed by wet etching the mask 11 and the thin film layer 27 formed on the base material 11. To be done. At this time, the base material 11 is isotropically removed by wet etching. Thereby, the recess 12 can be formed in the base material 11.

  Next, as shown in FIG. 6C, the mask 21 is removed to manufacture the optical element 10 according to the present embodiment.

  In the case shown in FIG. 6, the case where the thin film layer 27 is formed on the mask 21 has been described, but the mask 21 may be formed on the thin film layer 27 having the opening. The material forming the thin film layer 27 may be the same as the material forming the thin film layer 25, and the forming method may be the same as the case of the thin film layer 25.

(Optical Element Manufacturing Method 4)
Next, the manufacturing method 4 of the optical element will be described with reference to FIG.

  In the method shown in FIG. 5, the thin film layer 25 is formed, and in the method shown in FIG. 6, the thin film layer 27 is formed so that the bottom 13 of the recess 12 has different positions in the depth direction. Is. On the other hand, the method shown in FIG. 7 changes the size of the opening in the mask 28 to change the position of the bottom 13 of the recess 12 in the depth direction. The mask 28 is made 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 substrate 11 on which the mask 28 is formed is wet-etched to remove the substrate 11 in the opening of the mask 28. At this time, the base material 11 is isotropically removed by wet etching. Thereby, the recess 12 can be formed in the base material 11.

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

  In the method shown in FIGS. 4 to 6, the substrate 11 made of glass is removed from the opening formed on the mask 21 by wet etching. In this case, it is considered that the exchange efficiency of the etching liquid with respect to the base material 11 of the mask 21 and the etching liquid outside the mask 21 depends on the size of the opening of the mask 21. Therefore, when the opening of the mask is large, the etching liquid is exchanged more efficiently than when the opening of the mask is small, so that the etching rate in wet etching can be increased. Since the difference in the etching rate in the wet etching is the difference in the depth in the recess 12, it is possible to form the bottom 13 in the recess 12 at different positions in the depth direction. When the optical element is manufactured by the method shown in FIG. 7, the recess 12 having the flat portion 23 and the curved surface portion 24 to be formed becomes flatter as the position in the depth direction where the flat portion 23 is formed becomes deeper. The part 23 is formed to be large.

  In the method of manufacturing the optical element shown in FIG. 7, if the opening portion of the mask 28 is too large, the area occupied by the flat portion 23 in the recess 12 becomes large, so that the opening portion of the mask 28 has a width of 10 μm or less. The width is preferably 5 μm or less, and more preferably 5 μm or less. Further, when the positions of the bottoms are irregular, the intervals between the bottoms are irregular, and thus the time required for the base material 11 separating the adjacent recesses 12 to disappear in the process of wet etching changes. There is. In such a case, the state of the wet etching solution may change in each recess, so that the etching rate in each recess may change. In such a case, the depth direction of the bottom portion 13 can be changed even if the size of the opening of the mask 21 is the same.

  Further, in the method shown in FIGS. 4 to 7, when the masks 21 and 28 are peeled off or a local concentration distribution of the etching solution is generated, the recess 12 having a desired shape may not be formed. Therefore, the radius of curvature of the curved surface portion 24 is preferably formed within ± 50% of the average value of the radius of curvature. Further, it is more preferable to form it within ± 30%, and it is further preferable to form it within ± 10%.

  When the manufacturing method as described above is used, the deeper the position of the bottom portion 13b is, the farther the position of the point 14a is from the point 14b, as shown in FIG. 2B. Therefore, there is a correlation between the area of the polygon occupied by each recess 12 and the depth of the bottom 13 in the plan view as shown in FIG. 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 becomes 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. It is preferable to process the optical element so that the absolute value of the correlation coefficient is 0.4 or more.

(Optical elements with other structures)
Next, an optical element having another structure according to the present embodiment will be described.

  The optical element 30 having the structure shown in FIG. 8 has a structure in which a plurality of convex portions 32 are formed on the surface of the base material 31. Note that FIG. 8A is a plan view of the optical element according to the present embodiment, and FIG. 8B schematically shows a cross-sectional view taken along the chain line 8A-8B in FIG. 8A. . In the optical element 30, the base material 31 can be made of the same material as the base material 11 in the optical element 10. Further, in this optical element 30, the top 33 of the protrusion 32 corresponds to the bottom 13 of the recess 12 of the optical element 10, and the position of the top 33 of the protrusion 32 in the height direction is the same as that of 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 the base material by dry etching, or a method of forming the base material by press molding A method of transferring the unevenness of the molding die onto the surface can be used. Further, a method of arranging a resin material between the base material and the molding die and transferring unevenness to the resin material can be used.

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

  As the molding die in the above processing method, a molding die processed by the methods described in Manufacturing Methods 1 to 4 can be used in addition to the molding die by cutting. In addition, a replica of the molding die processed by the methods described in the manufacturing methods 1 to 4 may be prepared to be used as the molding die.

Further, the optical element 40 having the structure shown in FIG. 9 is a reflection type optical element, in which a plurality of concave portions 42 are formed on the surface of the base material 41, and the reflection film 44 is formed on the surface where the concave portions 42 are formed. Is formed. 9A is a plan view of the optical element according to the present embodiment, and FIG. 9B schematically shows a cross-sectional view taken along the alternate long and short dash line 9A-9B in FIG. 9A. . In this optical element 40, a bottom 43 is formed in the recess 42, similar to the bottom 13 of the recess 12. The reflective film 44 can be formed of a dielectric multilayer film or a metal film. In this optical element 40, when the refractive index of the medium around the concave portion 42 is n2 and the wavelength of the incident light flux is λ, the relationship shown in the following (4) is satisfied.

2/7 ≦ | 2 × n2 × Δd | / λ ≦ 10 (4)

The optical element according to the present embodiment preferably further satisfies the condition (5) below, and more preferably the condition (6) below.

2/7 ≦ | 2 × n2 × Δd | / λ ≦ 5 (5)

2/7 ≦ | 2 × n2 × Δd | / λ ≦ 2 (6)

In both cases of transmission and reflection, generally, when the optical path length difference (ΔL) corresponding to the position of the bottom portion 43 in the depth direction is used, the relationship of the formula shown in the following (7) is used. 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 as small as possible, and therefore preferably has the relationship shown in (8) below, and further has the relationship shown in (9) below. It is preferable.

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 in addition to glass.

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

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

  The laser light source 111b emits laser light in a green wavelength range, for example. The laser light emitted from the laser light source 111b is adjusted in 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 multiplexing prism 116 via the spatial light modulator 115b. In the spatial light modulator 115b, for example, laser light transmission / non-transmission control is performed for each pixel, and an image corresponding to green is formed.

  The laser light source 111c emits laser light in a blue wavelength range, for example. The laser light emitted from the laser light source 111c is adjusted in 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 is incident on the multiplexing prism 116 via the spatial light modulator 115c. In the spatial light modulator 115c, for example, transmission / non-transmission of laser light is controlled for each pixel, and an image corresponding to blue is formed.

  In the combining prism 116, the laser light from the spatial light modulator 115a, the laser light from the spatial light modulator 115b, and the laser light from the spatial light modulator 115c are incident, combined, and then emitted. In this way, the light flux of the combined laser light emitted from the combining prism 116 is projected onto the screen 118 via the lens 117.

  In the present embodiment, as the laser light sources 111a, 111b, 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 an emission port of a light beam propagated from the laser light source using an optical fiber or the like.

  Further, in FIG. 10, the laser is used for each of the red, green, and blue light beams, but the laser may be used for one or a plurality of light sources of red, green, and blue. The optical elements 113a, 113b, and 113c do not have to be used for all the red, green, and blue light fluxes, but may be used for at least one of the red, green, and blue light fluxes.

  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 the LCOS, since the DMD is a reflective spatial light modulator, it is not the transmissive arrangement as shown in FIG. The DMD may be installed in the latter stage, and the arrangement may be such that the reflected light from the DMD is projected by the lens 117.

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

  As shown in FIG. 12, the fluorescent wheel 205 is divided into three regions, an optical element region 205a, a green fluorescent substance region 205b, and a red fluorescent substance region 205c. A second optical element is formed in the optical element region 205a, a green phosphor (fluorescent material) is formed in the green phosphor region 205b, and a red phosphor region 205c is emitted in red. It is made of a phosphor. The second optical element in the optical element region 205a is formed by 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 rotation drive unit 205d such as a motor, and when the laser light from the blue laser light source 201 is applied to the green phosphor region 205b, green light can be obtained and red light can be obtained. When the phosphor region 205c is irradiated, red light can be obtained. When the laser light from the blue laser light source 201 is applied to the optical element region 205a, the blue light passes through the optical element region 205a. Therefore, in the fluorescent wheel 205, blue light, green light, and red light can be time-divided and emitted by being rotated by the rotation drive unit 205d. The fluorescence emission generated in the green phosphor region 205b and the red phosphor region 205c passes through the optical path indicated by the dotted line in FIG. 11, that is, passes through the lens 204, is reflected by the dichroic mirror 203, and enters the lens 212. . After passing through the lens 212, it is reflected by the combining mirror 211, passes through the lens 213, and then is irradiated onto 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.

The oxide-based and sulfide-based phosphors include YAG-based phosphors that emit yellow light (Y ₃ Al ₅ O ₁₂ : Ce, (Y, Gd) ₃ Al ₅ O ₁₂ : Ce), and TAG-based phosphors. (Tb ₃ Al ₅ O ₁₂ : Ce) or a silicate-based or alkaline-earth-based phosphor that emits fluorescence of each color depending on the additive element can be used. Further, as a nitride-based phosphor, α-sialon (SiAlON), which emits fluorescence of each color depending on the additive element, β-sialon (SiAlON: Eu), which emits green fluorescence, and Cazun (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 the oxynitride-based phosphor.

  When the second optical element in the optical element region 205a of the fluorescent wheel 205 is irradiated with the blue luminous flux, the blue luminous 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 that, 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 combining mirror 211, transmitted through the lens 213, and then transmitted to the integrator 214. Is irradiated.

  The blue, green, and red light fluxes 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 onto the spatial light modulator 219. . An image is formed in the spatial light modulator 219, and the formed image is projected onto an external screen (not shown) via the projection lens 220.

  Here, the first optical element 202 has a function of equalizing the intensity distribution of the light with which the fluorescent substance in the fluorescent wheel 205 is irradiated. The fluorescent material in the fluorescent wheel 205 is a mixture of a fluorescent material and a silicon resin, and when a blue light flux having a high peak value is irradiated, the silicon resin is irradiated in a region irradiated with the blue light having a high peak value. Deterioration. 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 a top-hat type emitted light distribution instead of a mountain-shaped emitted light distribution unlike a normal diffuser plate, so that the peak value of the light flux is It is possible to irradiate the phosphor with a light flux having a higher intensity. Further, the second optical element in the optical element region 205a of the fluorescent wheel 205 has a function of making the spatial intensity distribution uniform, and by rotating the second optical element, the uniformity can be further enhanced.

  Next, examples in the present embodiment will be described. Note that 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. Further, in each example, the full width at half maximum of the diffusion angle is 3 ° or less, but the present invention is not limited to this, and can be applied to the case 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 with reference to FIG.

  The base material 11 formed of glass having a refractive index of 1.53 is washed, and molybdenum having a thickness of 50 nm is formed as the mask 21. After forming the molybdenum film, a resist is applied, and photolithography and etching are performed to form openings of φ1 μm in the mask 21 in the arrangement shown in FIG. Note that FIG. 13A shows the positions of the openings within a square of about 1 mm, and the openings are arranged in the plane at a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. It is a thing. After forming the opening, 480 μm etching is performed by wet etching. 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 gradation, and the depth is displayed so that it becomes black.

  FIG. 13C shows a calculation of the emitted light distribution of light when a light having a wavelength of 450 nm is incident on such an optical element. The calculation was performed by obtaining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 13C, diffraction occurs due to the regular arrangement and strong light is generated in a specific direction. FIG. 13D is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 13C are averaged for each angle of 0.21 ° and plotted against the angle. As shown in FIG. 13C, strong light is generated in a specific direction. In addition, in FIG. 13C, the integrated light in the range of ± 1.25 ° was 75.2%. 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 of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. Note that FIG. 14A shows the positions of the openings within a square of about 1 mm, and the openings are arranged in the plane at a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. In contrast, the irregularity was introduced in the position at a value of 25% of the pitch. After forming the opening, 480 μm etching is performed by wet etching. 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 gradation, and the depth is displayed so that it becomes black.

  FIG. 14C shows a calculation of the outgoing light distribution of light when light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 14C, diffraction is generated due to the regular array, and strong light is generated in a specific direction, and particularly the amount of light that goes straight forward is large. FIG. 14D is a graph in which the intensities in the horizontal direction of the outgoing light distribution of FIG. 14C are averaged for each angle of 0.21 ° and plotted against the angle. As shown in FIG. 14C, strong light is generated in a specific direction. In addition, in FIG. 14C, when the light in the range of the angle ± 1.25 ° was integrated, it was 69.4%. 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 of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. Note that FIG. 15A shows the positions of the openings within a square of about 1 mm, and the openings are arranged in a plane at a pitch of 50 μm so that the shapes connecting the closest openings are equilateral triangles. In comparison with the thing, the irregularity was introduced in the position at the value of 50% of the pitch. After forming the opening, 480 μm etching is performed by wet etching. 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. 15B, the depth is displayed in black and white gradation, and the depth is displayed so that it becomes black.

  FIG. 15C shows a calculation of the outgoing light distribution of light when a light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 15C, the amount of light passing straight through is particularly large. FIG. 15D is a graph in which the intensities in the horizontal direction of the outgoing light distribution of FIG. 15C are averaged for each angle of 0.21 ° and plotted against the angle. As shown in FIG. 15C, strong light is generated in the straight transmission direction. In addition, in FIG. 15C, the total of light in the range of an angle of ± 1.25 ° was 62.9%. The value of | (n1−n2) × Δd | / λ was 0.

(Example 4)
Next, the optical element in Example 4 will be described with reference to FIG.

The base material 11 formed of glass having a refractive index of 1.53 is washed to form a SiO ₂ film of 45 nm as the thin film layer 25 and a molybdenum film of 50 nm as the mask 21. After forming a film of molybdenum, a resist is applied and photolithography and etching are performed to form openings of φ1 μm in the mask 21 in the arrangement shown in FIG. Note that FIG. 16 (a) shows the positions of the openings within a square of about 1 mm, which are arranged in a plane with a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. Is. After forming the opening, SiO ₂ is patterned by photolithography and etching so that the counterbore 26 has a binary value of 0 nm or 45 nm with respect to the reference depth. After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio between SiO ₂ and 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 of the position of the bottom portion 13 in the recess 12 in the depth direction is 450 nm. Here, the positions of the bottom portions 13 in the depth direction are arranged irregularly so that 75% or more of the bottom portions 13 are not arranged at a certain level of the binary distribution range of the position 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 gradation, and the depth is displayed so that it becomes black.

  FIG. 16C shows a calculation of the outgoing light distribution of light when a light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining 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. 16D is a graph in which the intensities in the horizontal direction of the emitted light distribution of FIG. 16C are averaged for each angle of 0.21 ° and plotted with respect to 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. In addition, in FIG. 16 (c), when the light in the range of the angle ± 1.25 ° was integrated, it was 71.2%. 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 of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. Note that FIG. 17A shows the positions of the openings within a square of about 1 mm, and the openings are arranged in a plane at a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. On the other hand, the irregularity is introduced in the position at a value of 25% of the pitch. After forming the opening, SiO ₂ is patterned by photolithography and etching so that the depth of the countersunk portion 26 becomes a binary value of 0 nm or 45 nm with respect to the reference depth. After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and 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 of the position of the bottom portion 13 in the recess 12 in the depth direction is 450 nm. Here, the positions of the bottom portions 13 in the depth direction are arranged irregularly so that 75% or more of the bottom portions 13 are not arranged at a certain level of the binary distribution range of the position 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 gradation, and it is displayed such that it becomes black as it gets deeper.

  FIG. 17C shows a calculation of the outgoing light distribution of light when a light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining 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. 17D is a graph in which the intensities in the horizontal direction of the outgoing light distribution 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. In addition, in FIG. 17C, when the light in the range of an angle of ± 1.25 ° was integrated, it was 67.2%. 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 of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. Note that FIG. 18A shows the positions of the openings within a square of about 1 mm, and the openings are arranged in a plane at a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. On the other hand, the irregularity is introduced in the position at a value of 50% of the pitch. After forming the opening, SiO ₂ is patterned by photolithography and etching so that the depth of the countersunk portion 26 becomes a binary value of 0 nm or 45 nm with respect to the reference depth. After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and 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 of the position of the bottom portion 13 in the recess 12 in the depth direction is 450 nm. Here, the positions of the bottom portions 13 in the depth direction are arranged irregularly so that 75% or more of the bottom portions 13 are not arranged at a certain level of the binary distribution range of the position 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 gradation, and the depth is displayed so that it becomes black.

  FIG. 18C shows a calculation of the emitted light distribution of light when a light having a wavelength of 450 nm is incident on such an optical element. The calculation was performed by obtaining 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 is a graph in which the intensities in the horizontal direction of the outgoing light distribution of FIG. 18C are averaged for each angle of 0.21 ° and plotted against 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. In addition, in FIG. 18C, when the light in the angle range of ± 1.25 ° was integrated, it was 60.4%. The value of | (n1−n2) × Δd | / λ was 0.53.

(Example 7)
Next, the optical element in Example 7 is demonstrated based on FIG.

The base material 11 formed of glass having a refractive index of 1.53 is washed, SiO ₂ is deposited to 90 nm as the thin film layer 25, and molybdenum is deposited to 50 nm as the mask 21. After forming the molybdenum film, a resist is applied, and photolithography and etching are performed to form openings of φ1 μm in the mask 21 in the arrangement shown in FIG. Note that FIG. 19A shows the positions of the openings within a square of about 1 mm, and the openings are arranged in a plane at a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. Is. After forming the opening, SiO ₂ is patterned by photolithography and etching, and the depth of the counterbore portion 26 is an eight-valued depth so that the depth interval of one step with respect to the reference depth is 11.25 nm. Try to be After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the concave portion 12 is approximately 480 μm, and the distribution range of the position of the bottom portion 13 in the concave portion 12 in the depth direction is 787.5 nm. Here, the positions of the bottoms 13 in the depth direction are arranged irregularly so that 50% or more of the bottoms 13 are not arranged at a level having eight values in the distribution range of the positions of the bottoms 13. 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 gradation, and the depth is displayed so that it becomes black.

  FIG. 19C shows a calculation of the outgoing light distribution of light when a light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 19C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 19D is a graph in which the intensities in the horizontal direction of the outgoing light distribution of FIG. 19C are averaged for each angle of 0.21 ° and plotted against the angle. As shown in FIG. 19C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Further, in FIG. 19 (c), when the light in the range of the angle ± 1.25 ° was integrated, it was 70.6%. The value of | (n1−n2) × Δd | / λ was 0.93.

(Example 8)
Next, the optical element in Example 8 will be described with reference to FIG. 20, focusing on the points different from Example 7.

Openings of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. Note that FIG. 20 (a) shows the positions of the openings within a square of about 1 mm, and the openings are arranged in a plane at a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. On the other hand, the irregularity is introduced in the position at a value of 25% of the pitch. After forming the opening, SiO ₂ is patterned by photolithography and etching, and the depth of the counterbore portion 26 is an eight-valued depth so that the depth interval of one step with respect to the reference depth is 11.25 nm. Try to be After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the concave portion 12 is approximately 480 μm, and the distribution range of the position of the bottom portion 13 in the concave portion 12 in the depth direction is 787.5 nm. Here, the positions of the bottoms 13 in the depth direction are arranged irregularly so that 50% or more of the bottoms 13 are not arranged at a level having eight values in the distribution range of the positions of the bottoms 13. 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 gradation, and the depth is displayed so that it becomes black.

  FIG. 20C shows a calculation of the outgoing light distribution of light when a light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 20C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. 20D is a graph in which the intensities in the horizontal direction of the outgoing light distribution of FIG. 20C are averaged for each angle of 0.21 ° and plotted against the angle. As shown in FIG. 20C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Further, in FIG. 20 (c), when the light in the range of the angle ± 1.25 ° was integrated, it was 66.6%. 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.

Openings of φ1 μm are formed in the mask 21 in the arrangement shown in FIG. Note that FIG. 21A shows the positions of the openings within a square of about 1 mm, which are arranged in the plane such that the shape connecting the nearest openings is a regular triangle at a pitch of 50 μm. On the other hand, the irregularity is introduced in the position at a value of 50% of the pitch. After forming the opening, SiO ₂ is patterned by photolithography and etching, and the depth of the counterbore portion 26 is an eight-valued depth so that the depth interval of one step with respect to the reference depth is 11.25 nm. Try to be After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the concave portion 12 is approximately 480 μm, and the distribution range of the position of the bottom portion 13 in the concave portion 12 in the depth direction is 787.5 nm. Here, the positions of the bottoms 13 in the depth direction are arranged irregularly so that 50% or more of the bottoms 13 are not arranged at a level having eight values in the distribution range of the positions of the bottoms 13. 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 gradation, and the depth is displayed so that the depth becomes black.

  FIG. 21C shows a calculation of the outgoing light distribution of light when a light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining the Fourier transform of the phase difference generated from the shape of FIG. As shown in FIG. 21C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. FIG. 21D is a graph in which the horizontal intensity in the outgoing light distribution of FIG. 21C is averaged for each angle of 0.21 ° and is plotted against the angle. As shown in FIG. 21C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Further, in FIG. 21 (c), when the light in the range of the angle ± 1.25 ° was integrated, it was 59.5%. The value of | (n1−n2) × Δd | / λ was 0.93.

(Example 10)
Next, the optical element in Example 10 is demonstrated based on FIG.

The base material 11 made of glass having a refractive index of 1.53 is washed to form a thin film layer 25 of SiO ₂ with a thickness of 24.3 nm and a mask 21 with a thickness of 50 nm. After forming a film of molybdenum, a resist is applied and photolithography and etching are performed to form openings of φ1 μm in the mask 21 in the arrangement shown in FIG. Note that FIG. 22A shows the positions of the openings within a square of about 1 mm, which are arranged in a plane at a pitch of 50 μm so that the shapes connecting the nearest openings are equilateral triangles. Is. After forming the opening, SiO ₂ is patterned by photolithography and etching so that the depth of the counterbore 26 becomes a binary value of 0 nm or 24.3 nm with respect to the reference depth. After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the concave portion 12 is approximately 480 μm, and the distribution range of the position of the bottom portion 13 in the concave portion 12 in the depth direction is 243 nm. Here, the positions of the bottom portions 13 in the depth direction are arranged irregularly so that 75% or more of the bottom portions 13 are not arranged at a certain level of the binary distribution range of the position of the bottom portions 13. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 22B, the depth is displayed in black and white gradation, and the depth is displayed so that it becomes black.

  FIG. 22C shows a calculation of the outgoing light distribution of light when light with a wavelength of 450 nm is incident on such an optical element. The calculation was performed by obtaining 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. 22D is a graph in which horizontal intensities of the outgoing light distribution of FIG. 22C are averaged for each angle of 0.21 ° and graphed with respect to the angle. As shown in FIG. 22C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. In particular, the amount of 0th-order light that passes straight before averaging is 1.6%, which is a half of 3.2% of the amount of 0th-order light of the optical element in Example 1. Further, in FIG. 22 (c), when the light in the range of the angle ± 1.25 ° was integrated, it was 73.2%. The value of | (n1−n2) × Δd | / λ was 0.29.

(Example 11)
Next, the optical element in Example 11 is demonstrated based on FIG.

The base material 11 formed of glass having a refractive index of 1.53 is washed, and SiO ₂ is deposited to a thickness of 450 nm as the thin film layer 25 and molybdenum is deposited to a thickness of 50 nm as the mask 21. After forming a film of molybdenum, a resist is applied and photolithography and etching are performed to form openings of φ1 μm in the mask 21 in the arrangement shown in FIG. Note that FIG. 23A shows the positions of the openings within a square of about 1 mm, and the openings are arranged in a plane at a pitch of 50 μm so that the shapes of the closest openings are connected to form an equilateral triangle. On the other hand, the irregularity is introduced in the position at a value of 50% of the pitch. After forming the opening, SiO ₂ is patterned by photolithography and etching, and the depth of the counterbore portion 26 is an eight-valued depth so that an interval of one step depth with respect to the reference depth is 56.25 nm. Try to be After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the concave portion 12 is approximately 480 μm, and the distribution range of the position of the bottom portion 13 in the concave portion 12 in the depth direction is 3937.5 nm. Here, the positions of the bottoms 13 in the depth direction are arranged irregularly so that 50% or more of the bottoms 13 are not arranged at a level having eight values in the distribution range of the positions of the bottoms 13. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 23B, the depth is displayed in black and white gradation, and it is displayed such that it becomes black as it gets deeper.

  FIG. 23C shows a calculation of the outgoing light distribution of light when a light having a wavelength of 450 nm enters such an optical element. The calculation was performed by obtaining 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. 23D is a graph in which the intensities in the horizontal direction of the outgoing light distribution of FIG. 23C are averaged for each angle of 0.21 ° and plotted with respect to the angle. As shown in FIG. 23C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. In addition, in FIG. 23D, when the light in the range of the angle ± 1.25 ° was integrated, it was 37.8%. In FIG. 23D, the value of the full width at half maximum of the light amount distribution is 2.9 °, which is 1.1 times the value of 2.6 ° which 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 is demonstrated based on FIG.

The base material 11 formed of glass having a refractive index of 1.53 is washed to form a thin film layer 25 of 900 nm of SiO ₂ and a mask 21 of 50 nm of molybdenum. After forming a film of molybdenum, a resist is applied and photolithography and etching are performed to form openings of φ1 μm in the mask 21 in the arrangement shown in FIG. Note that FIG. 24 (a) shows the positions of the openings within a square of about 1 mm, and the pitch is 50 μm, and the shapes in which the nearest openings are connected are arranged in an in-plane so as to form an equilateral triangle. On the other hand, the irregularity is introduced in the position at a value of 50% of the pitch. After forming the opening, the SiO ₂ is patterned by photolithography and etching, and the depth of the counterbore portion 26 is an eight-valued depth so that the depth interval of one step is 112.5 nm with respect to the reference depth. Try to be After forming the countersunk portion 26, 480 μm etching is performed with a wet etching solution adjusted so that the etching rate ratio of SiO ₂ and the glass substrate is 10. Therefore, the radius of curvature of the curved surface portion 24 in the concave portion 12 is approximately 480 μm, and the distribution range of the position of the bottom portion 13 in the concave portion 12 in the depth direction is 7875 nm. Here, the positions of the bottoms 13 in the depth direction are arranged irregularly so that 50% or more of the bottoms 13 are not arranged at a level having eight values in the distribution range of the positions of the bottoms 13. ing. The planar shape of the processed optical element is as shown in FIG. In FIG. 24B, the depth is displayed in black and white gradation, and the depth is displayed so that it becomes black.

  FIG. 24C shows a calculation of the outgoing light distribution of light when light with a wavelength of 450 nm is incident on such an optical element. The calculation was performed by obtaining 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. 24D is a graph in which the intensities in the horizontal direction in the outgoing light distribution of FIG. 24C are averaged for each angle of 0.21 ° and plotted against the angle. As shown in FIG. 24C, the influence of diffraction is reduced and the intensity of light emitted in a specific direction is reduced. Further, in FIG. 24 (d), when the light in the range of the angle ± 1.25 ° was integrated, it was 23.6%. In FIG. 24D, the value of the full width at half maximum of the light amount distribution is 4.7 °, which is 1.8 times the value of 2.6 ° which 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 9.3.

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

  A 2 mm-thick glass having a refractive index of 1.52 was washed, and by photolithography and etching processing, φ3 μm openings were arranged in a plane at a pitch of 60 μm so that the shape connecting the nearest openings became an equilateral triangle. A mask made of molybdenum having a thickness of 50 nm was prepared. Next, etching was performed with 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 point was 0.296 μm. The planar shape of the processed optical element was 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. 25 (b) 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 with reference to FIG.

By cleaning a glass having a refractive index of 1.52 with a thickness of 2 mm and performing photolithography and etching processing, the average interval P _{1 of the} openings with respect to the first direction becomes 60 μm, and the direction orthogonal to the first direction is set. As a second direction, a molybdenum mask having a thickness of 50 nm is prepared in which φ3 μm openings are arranged so that the interval P ₂ between the centers of gravity of the positions of the openings formed in the first direction is 52 μm. did. Each opening position has an irregularity of ± 25% of the average spacing in the first direction in the first direction and ± 25% of the average spacing in the second direction in the second direction. It had an irregularity of 25%. Next, etching was performed with a wet etching solution. When the curvature radius of the curved surface portion 24 in the concave portion 12 was measured at 9 points, the average value was 322 μm, and the distribution range in the depth direction of the position of the bottom portion 13 at the measurement point was 1.107 μm. The planar shape of the processed optical element was as shown in FIG.

  In addition, FIG. 27 shows the area ratio of the area of a polygon forming a concave portion at nine points for which the radius of curvature was measured and normalized by the minimum value, and the relative position in the height direction of the bottom portion of the concave portion. The correlation coefficient obtained from FIG. 27 was -0.6325.

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

  Although the embodiment of the present invention has been described above, the above contents do not limit the contents of the invention. The optical element of the present invention can be used not only in a projection device but also in various devices such as a three-dimensional measuring device. Further, it can be used as an optical element for controlling a diffusion state such as a diffusion plate for illumination, a focusing plate in a viewfinder of a camera, a screen of a projection device.

DESCRIPTION OF SYMBOLS 10 Optical element 11 Base material 12, 42 Recessed part 12a, 12b Recessed part 13, 43 Bottom part 13a, 13b Bottom part 14 Boundary point 15 Boundary point 21 Mask 22 Counterbore part 22a Bottom surface 23 Flat part 24 Curved part 25 Thin film layer 26 Counterbore Part 27 Thin film layer 28 Mask 30, 40 Optical element 31, 41 Base material 32 Convex part 33 Top 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 modulator 116 Multiplexing prism 117 Lens 118 Screen 200 Projector 201 Laser light source 202 First optical element 203 Dichroic mirror 204 Lens 205 Fluorescent wheel 206, 208, 210, 212, 213, 215, 217 Lenses 207, 209, 216, 218 Mirror 211 Multiplexing mirror 214 Integrator 219 Spatial light modulator 220 Projection lens

Claims (9)

A plurality of recesses are formed on the surface of the base material,
The concave portion has a curved surface portion formed by a curved surface,
The recess has a shape surrounded by three or more ridge lines in a plan view,
The plurality of recesses are formed such that the positions of the bottoms of the recesses are 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 the light flux incident on the base material is λ, and the range in the depth direction of the bottom of the plurality of recesses is If Δd,
2/7 ≦ | (n1-n2) × Δd | / λ ≦ 10
And
The position of the bottom I irregular sequence der, when the pitch of the regular sequence is P, based on the center point of the bottom portion in a case where a regular arrangement is made, the bottom, the radius is 0 An optical element which is formed so as to exist within a range of a circle of 0.5 × P.   The optical element according to claim 1, wherein the optical element transmits light. A plurality of recesses are formed on the surface of the base material,
The concave portion has a curved surface portion formed by a curved surface,
The recess has a shape surrounded by three or more ridge lines in a plan view,
The plurality of recesses are formed such that the positions of the bottoms of the recesses are two or more different positions in the depth direction,
When the refractive index of the medium around the base material is n2, 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 ≦ | 2 × n2 × Δd | / λ ≦ 10
And
The position of the bottom I irregular sequence der, when the pitch of the regular sequence is P, based on the center point of the bottom portion in a case where a regular arrangement is made, the bottom, the radius is 0 An optical element which is formed so as to exist within a range of a circle of 0.5 × P.   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 formed so as to exist within a range of a circle having a radius of 0.25 × P. The bottoms are arranged randomly in the first direction with an average spacing P ₁ .
In a second direction, which is a direction orthogonal to the first direction, the centers of gravity of the positions of the bottoms of the row of the bottoms formed in the first direction are arranged so as to have an interval P ₂ . Item 6. The optical element according to any one of Items 1, 3, and 5. The bottom has a bottom spacing in the first direction in the row of bottoms of (1 ± 0.25) P ₁ .
The optical element according to claim 6, wherein each position of the bottoms with respect to the center of gravity of the row of the bottoms in the second direction is ± 0.25P ₂ with respect to the center of gravity. An optical element according to any one of claims 1 to 7,
A light source for emitting light incident on the optical element,
Projector equipped with.   The projection device according to claim 8, wherein the light source is a laser.