WO2023032094A1 - 光学素子およびこれを用いた光学系装置 - Google Patents
光学素子およびこれを用いた光学系装置 Download PDFInfo
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- WO2023032094A1 WO2023032094A1 PCT/JP2021/032171 JP2021032171W WO2023032094A1 WO 2023032094 A1 WO2023032094 A1 WO 2023032094A1 JP 2021032171 W JP2021032171 W JP 2021032171W WO 2023032094 A1 WO2023032094 A1 WO 2023032094A1
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- WIPO (PCT)
- Prior art keywords
- light
- optical element
- unevenness
- diffusion range
- recesses
- Prior art date
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- 230000003287 optical effect Effects 0.000 title claims abstract description 71
- 238000009792 diffusion process Methods 0.000 claims abstract description 34
- 230000000737 periodic effect Effects 0.000 claims abstract description 4
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 238000004088 simulation Methods 0.000 description 18
- 230000005672 electromagnetic field Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 7
- 238000004364 calculation method Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000003491 array Methods 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 238000005286 illumination Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
Definitions
- the present invention relates to an optical element and an optical system device using the same.
- Three-dimensional measurement sensors using the time-of-flight (TOF) method are about to be adopted in mobile devices, cars, robots, etc. This measures the distance to an object from the time it takes for the light emitted from the light source to the object to be reflected and returned. If the light from the light source irradiates a predetermined area of the object uniformly, the distance at each irradiated point can be measured and the three-dimensional structure of the object can be detected.
- TOF time-of-flight
- the sensor system for this purpose consists of a light source unit that irradiates an object with a beam (light), a camera unit that detects the light reflected from each point of the object, and a calculation that calculates the distance of the object from the signals received by the camera. consists of
- the unique part of the above system is the light source section consisting of the light source and diffusion filter (optical element).
- Diffusion filters optical elements
- which shape the beam by transmitting light, especially lasers, to uniformly irradiate the target in a controlled area are characteristic components of such systems.
- DOE diffractive optical element
- the microlens array used for the diffusion filter has an aspherical lens with a diameter of several 10 ⁇ m arranged over the entire surface of the filter.
- a microlens array type diffusion filter is often designed by determining the basic shape of lenses based on geometrical optics and arranging them in an array so as to satisfy specifications such as the illumination angle. For example, since it is desirable that the irradiation angle of a diffusion filter for TOF matches the viewing angle of the camera, it often has a rectangular projection pattern such as 60 ⁇ 45 or 110 ⁇ 85. When it is desired to have a rectangular projection pattern, such a light distribution can be easily obtained by arranging basic patterns having circular symmetry in a grid pattern.
- the microlens array has the disadvantage that it is difficult to spread light over a wide angle.
- a VCSEL light source in which lasers are arranged periodically on a chip is combined with a diffusion filter composed of microlenses that are similarly arranged in a periodic manner, interference fringes are observed in the irradiation intensity due to the moire of the VCSEL period and the period of the microlenses. may occur.
- the narrower the period of the microlens array the more likely speckle, in which light is concentrated in a specific place like a dot, is likely to occur due to the influence of light interference.
- the microlens arrays are also randomly arranged in order to obtain optical characteristics that do not depend on the arrangement of the VCSELs (see Patent Document 1, for example).
- an object of the present invention is to provide an optical element that has no discontinuous portions between lenses and suppresses the reduction in light efficiency and the occurrence of uneven light distribution due to scattering and the like.
- an optical element of the present invention is capable of diffusing incident light into a predetermined diffusion range, and includes a transparent body having unevenness on at least one surface, the diffusion range being a predetermined diffusion range.
- the unevenness has ridges and valleys without periodicity, the unevenness has a wavelength of the light of ⁇ and a refractive index of the transparent body of n 1 , where the refractive index of the medium surrounding the transparent body is n 0 , there is no portion where the slope of the unevenness changes by 180 degrees in the range of width ⁇ /(n 1 ⁇ n 0 ), and the unevenness is It is characterized in that 5% or less of the total area has a gradient that causes the incident light to be emitted to the area outside the diffusion range according to Snell's law.
- the irregularities are preferably formed so that the light distribution calculated by Snell's law monotonically increases from the center of the diffusion range toward the boundary, and preferably the distribution calculated by Snell's law. It is preferable that the light distribution is formed so as to be proportional to cos - n ⁇ (1 ⁇ n ⁇ 7) from the center to the boundary of the diffusion range.
- the unevenness preferably has a height of 2.5 times or more of ⁇ /(n 1 ⁇ n 0 ).
- an optical system device of the present invention is characterized by comprising the optical element of the present invention and a light source for irradiating the optical element with light.
- the optical element of the present invention and the optical system device using the same have few discontinuous portions between the lenses, and can suppress a decrease in light efficiency or uneven light distribution due to scattering or the like. can.
- FIG. 1 is a schematic perspective view showing an optical element of the present invention
- FIG. 1 is an enlarged cross-sectional view showing an optical element of the present invention
- FIG. It is a figure explaining refraction of the optical element of the present invention.
- 4 is a graph showing the relationship between the inclination angle ⁇ 1 of the uneven surface of the incident surface and the output angle ⁇ 4 of the light from the optical element 1.
- FIG. 1 is a schematic plan view showing an optical system device of the present invention
- FIG. 10 is a diagram showing the light intensity at the camera unit when the light intensity distribution P( ⁇ ) is proportional to cos ⁇ n ⁇ (n is 1 to 7) [P( ⁇ ) ⁇ cos ⁇ n ⁇ ].
- FIG. 4A is a diagram showing the size of unevenness 11, (b) light distribution by ray tracing simulation, and (c) light distribution by electromagnetic field simulation.
- FIG. 4A is a diagram showing the size of unevenness 11, (b) light distribution by ray tracing simulation, and (c) light distribution by electromagnetic field simulation.
- FIG. 4A is a diagram showing the size of unevenness 11, (b) light distribution by ray tracing simulation, and (c) light distribution by electromagnetic field simulation.
- FIG. 4A is a diagram showing the size of unevenness 11, (b) light distribution by ray tracing simulation, and (c) light distribution by electromagnetic field simulation.
- FIG. 4A is a diagram showing the size of unevenness 11, (b) light distribution by ray tracing simulation, and (c) light distribution by electromagnetic field simulation.
- FIG. 4A is a diagram showing the size of unevenness 11, (b) light distribution by ray tracing simulation, and (c) light distribution by electromagnetic field simulation.
- FIG. 4A is a diagram showing the size of unevenness 11, (b) light distribution by ray tracing simulation, and (c) light distribution by electromagnetic field simulation.
- the optical element 1 of the present invention will be described below.
- the optical element 1 of the present invention can diffuse incident light into a predetermined diffusion range 91, as shown in FIG.
- the diffusion range 91 is defined as the inside of a single closed curve 92 such as a polygon or an ellipse on a predetermined plane 90.
- the predetermined plane 90 referred to here is a plane perpendicular to the optical axis of the light source that irradiates the optical element with light, and is at least 100 times larger than the size of the light emitted from the light source 2 when emitted from the optical element 1. Detached plane means.
- the optical element 1 consists of a transparent body having unevenness 11 on at least one side, as shown in FIG.
- the unevenness 11 has a plurality of non-periodic ridges and valleys.
- ⁇ 4 g( ⁇ 1 )
- the light distribution of the output light that is, the intensity distribution at the output angle ⁇ 4 has a one-to-one relationship with the frequency distribution at the incident angle ⁇ 1 .
- the incident angle ⁇ 1 is the same as the inclination angle (gradient) of the uneven surface of the optical element 1, so the frequency distribution of the incident angle ⁇ 1 is the inclination angle of the uneven surface of the optical element 1.
- the frequency distribution of FIG. 4 shows the relationship between the inclination angle ⁇ 1 of the uneven surface of the incident surface and the output angle ⁇ 4 of the light from the optical element 1 when the exit surface is flat and the incident surface is uneven.
- y yo and ⁇ z/ ⁇ y
- y yo ))) becomes.
- x xo ))) becomes.
- the unevenness 11 should be designed by calculating the frequency distribution of the tilt angles (gradients) of the surface of the optical element 1 .
- the unevenness 11 is calculated according to Snell's law, 5% or less, preferably 3% or less of the entire area has a gradient that causes the incident light to be emitted to the area outside the diffusion range 91.
- it should be designed to be 1% or less.
- the unevenness 11 should have a height of at least 2.5 times ⁇ /(n 1 ⁇ n 0 ), preferably 5 times or more, and more preferably 10 times or more. Better.
- the height of the unevenness 11 here means the difference between the highest peak and the lowest valley of the unevenness 11 .
- the width is ⁇ /( n 1 ⁇ n 0 ), preferably 2 times or less, more preferably 3 times or less.
- the width means the width in the direction perpendicular to the z-axis direction (the direction parallel to the incident surface or the exit surface).
- a general sensor system as shown in FIG. It consists of a camera unit 30 that detects light and a calculation unit 40 that calculates the distance to an object from the signal received by the camera unit 30.
- FIG. the light intensity that is reflected at a wider angle and is incident on the camera unit 30 becomes lower. Therefore, it is preferable that the light distribution of the light from the light source unit 20 has a higher light intensity as the angle ⁇ increases so that the camera can also detect light incident from a wide angle. That is, it is preferable that the light distribution in the far-field from the light source unit 20 has a distribution in which the intensity increases as the angle ⁇ increases.
- the unevenness 11 is preferably formed so that the light distribution calculated by Snell's law monotonically increases from the center of the diffusion range 91 toward the boundary.
- the unevenness 11 of the optical element 1 may be designed so that the frequency distribution of the tilt monotonously increases as the tilt increases.
- the center of the diffusion range 91 means the position of the intersection of the optical axis of the light source 2 and the diffusion range 91 when the optical element 1 of the present invention is vertically irradiated with light from the light source 2.
- the boundary of the diffusion range 91 is a portion corresponding to the closed curve 92 described above, and means the position of the maximum peak in the light distribution intensity distribution in the cross section.
- the light intensity distribution P( ⁇ ) in the far-field from the light source unit 20 must be proportional to cos ⁇ 7 ⁇ [P( ⁇ ) ⁇ cos ⁇ 7 ⁇ ]. Therefore, it is most preferable that the light distribution of the light emitted from the light source 2 and transmitted through the optical element 1 is proportional to cos ⁇ 7 ⁇ .
- FIG. 6 shows the light intensity distribution P( ⁇ ) in the far-field from the light source unit 20 in an optical system in which the light emitted from the light source unit 20 is reflected on the screen and returned to the camera by cos - n ⁇ .
- 7 is a graph showing the intensity of light returning to the camera section calculated with respect to the incident angle ⁇ when proportional to (n is 1 to 7) [P( ⁇ ) ⁇ cos ⁇ n ⁇ ]. It can be seen that the larger the incident angle, the smaller the light intensity, but the larger the n, the smaller the difference. Also, it can be seen that if the light intensity distribution P( ⁇ ) is made proportional to cos ⁇ 7 ⁇ [P( ⁇ ) ⁇ cos ⁇ 7 ⁇ ], the intensity of the light returning to the camera becomes uniform with respect to the angle ⁇ .
- the unevenness 11 of the optical element 1 is formed so that the light distribution calculated by Snell's law is proportional to cos - n ⁇ (1 ⁇ n ⁇ 7) from the center of the diffusion range 91 toward the boundary. is better, preferably formed to be proportional to cos ⁇ 7 ⁇ .
- the frequency distribution of the inclination of the unevenness 11 of the optical element 1 is formed to be proportional to cos -n ⁇ (1 ⁇ n ⁇ 7), preferably to cos -7 ⁇ . be done.
- FREQUENCY ((n ⁇ 1) (arctan ( ⁇ z/ ⁇ y
- x xo )).
- the size of the diffusion filter is small.
- the steps of the unevenness 11 be small.
- the pattern size is reduced and the size of the crests and valleys becomes closer to the wavelength of light, the wave nature of light cannot be ignored, and structural design to obtain the desired light distribution needs to be corrected as a wave. become. This point will be described with reference to FIGS. 7 to 12.
- n 1 be the refractive index of the transparent body
- n 0 be the refractive index of the medium surrounding the transparent body.
- similar shape and the height of the unevenness 11 is ⁇ / (n 1 - n 0 ) 5 times or less (Fig. 7), 10 times or more (Fig. 8), 25 times or more (Fig. 9), 40 times or more ( 10), 50 times or more (FIG. 11), and 65 times or more (FIG. 12).
- the refractive index n 1 of the optical element 1 is 1.53, the refractive index n 0 was 1.
- the wavelength of incident light to the optical element 1 was 630 nm, and the unevenness 11 used had a light distribution proportional to cos ⁇ 7 ⁇ .
- the height of the unevenness 11 here means the difference between the highest peak and the lowest valley of the unevenness 11.
- Figures 7 to 12 (b) are ray tracings ignoring wave properties.
- Figures 7 to 12 (c) are the results obtained by electromagnetic field simulation taking into account the properties of waves.
- the unevenness 11 is large in that the influence of the properties of light as a wave can be reduced.
- the unevenness 11 should have a height of at least 5 times ⁇ /(n 1 ⁇ n 0 ), preferably 10 times or more, and more preferably 25 times or more. good.
- the exit surface is flat and the entrance surface is uneven, but conversely, the entrance surface may be flat and the exit surface may be uneven. Further, as long as it can be designed so that the incident light can be emitted within the diffusion range 91 according to Snell's law, it is not necessary that one of the surfaces be flat, and curved surfaces such as arches or spheres may be used. It is also possible to form
- the optical system device of the present invention is mainly composed of the above-described optical element 1 of the present invention and a light source 2 for irradiating the optical element 1 with light.
- the light source 2 is one that emits collimated light, but it is not limited to this, and any light source that can irradiate the optical element 1 with light may be used.
- a Vertical Cavity Surface Emitting Laser (VCSEL) or an LED can be used.
- the light source 2 may be arranged so that the optical element 1 can be irradiated with the light from the light source 2 .
- the optical system device of the present invention has a camera unit 30 for detecting light reflected from each point of the object 10, and a calculation unit 40 for calculating the distance of the object from the signal received by the camera unit 30. You may have
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Abstract
Description
h(θox)=FREQUENCY(θox)=FREQUENCY(g(θix))=FREQUENCY(g(arctan(∂z/∂x|y=yo)))
となる。
h(θoy)=FREQUENCY(θoy)=FREQUENCY(g(θiy))=FREQUENCY(g(arctan(∂z/∂y|x=xo)))
となる。
2 光源
11 凹凸
91 拡散範囲
92 閉曲線
Claims (5)
- 入射した光を所定の拡散範囲に拡散可能な光学素子であって、
少なくとも片面に凹凸を有する透明体を含み、
前記拡散範囲は、所定の平面における単一の閉曲線の内部として規定され、
前記凹凸は、周期性を持たない複数の稜部と谷部を有し、
前記凹凸は、前記光の波長をλ、前記透明体の屈折率をn1、当該透明体の周囲の媒質の屈折率をn0とすると、幅がλ/(n1-n0)の範囲において前記凹凸の勾配が180度変化する部分を有さず、
前記凹凸は、スネルの法則によって入射光を前記拡散範囲外の領域に出射させるような勾配を有する領域が全領域の5%以下であることを特徴とする光学素子。 - 前記凹凸は、スネルの法則によって計算される配光分布が前記拡散範囲の中央から境界に向けて単調増加するように形成されることを特徴とする請求項1記載の光学素子。
- 前記凹凸は、スネルの法則によって計算される配光分布が前記拡散範囲の中央から境界に向けてcos-nθ(1≦n≦7)に比例するように形成されることを特徴とする請求項2記載の光学素子。
- 前記凹凸は、λ/(n1-n0)の2.5倍以上の高さを有することを特徴とする請求項1ないし3のいずれかに記載の光学素子。
- 請求項1ないし4のいずれかに記載の光学素子と、
前記光学素子に光を照射する光源と、
を具備することを特徴とする光学系装置。
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Citations (3)
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WO2004021052A1 (ja) * | 2002-08-30 | 2004-03-11 | Kimoto Co., Ltd. | 光制御フィルム |
JP2006500621A (ja) | 2002-09-20 | 2006-01-05 | コーニング・インコーポレーテッド | 光線成形及び均一化のためのランダムマイクロレンズアレイ |
WO2017010257A1 (ja) * | 2015-07-16 | 2017-01-19 | デクセリアルズ株式会社 | 拡散板、表示装置、投影装置及び照明装置 |
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- 2021-09-01 JP JP2023511563A patent/JP7448272B2/ja active Active
- 2021-09-01 WO PCT/JP2021/032171 patent/WO2023032094A1/ja active Application Filing
Patent Citations (3)
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WO2004021052A1 (ja) * | 2002-08-30 | 2004-03-11 | Kimoto Co., Ltd. | 光制御フィルム |
JP2006500621A (ja) | 2002-09-20 | 2006-01-05 | コーニング・インコーポレーテッド | 光線成形及び均一化のためのランダムマイクロレンズアレイ |
WO2017010257A1 (ja) * | 2015-07-16 | 2017-01-19 | デクセリアルズ株式会社 | 拡散板、表示装置、投影装置及び照明装置 |
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