JP2524799B2 - Light incident angle detector - Google Patents
Light incident angle detectorInfo
- Publication number
- JP2524799B2 JP2524799B2 JP63048460A JP4846088A JP2524799B2 JP 2524799 B2 JP2524799 B2 JP 2524799B2 JP 63048460 A JP63048460 A JP 63048460A JP 4846088 A JP4846088 A JP 4846088A JP 2524799 B2 JP2524799 B2 JP 2524799B2
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- Prior art keywords
- light
- incident angle
- diffracted light
- saw
- substrate
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Description
【発明の詳細な説明】 〔産業上の利用分野〕 この発明は、光の到来方向を、受光器側において正確
に検出できるようにした、光入射角検出装置に関する。
ロボットの眼のような機能にあっては光がどの方向から
入ってくるかを正確に検出する必要がある。Description: TECHNICAL FIELD The present invention relates to a light incident angle detection device capable of accurately detecting the arrival direction of light on the light receiver side.
In a function like the eyes of a robot, it is necessary to accurately detect from which direction light enters.
この種の機能をもつものとして、従来は反射鏡又は受
光器を用い、その位置を動かすこと、例えば回転などに
よって、入射角を測定するという方法が行なわれてき
た。As a method having this type of function, conventionally, a method has been performed in which a reflection mirror or a light receiver is used, and the incident angle is measured by moving the position, for example, by rotating.
近年、産業用ロボットが普及し、機能が高級なものに
なるにつれて、次第にロボットの眼にも光の到来方向を
検知する等の高度な機能が要求されるようになった。In recent years, as industrial robots have become widespread and their functions have become more sophisticated, the robot's eyes have also been required to have sophisticated functions such as detecting the direction of light.
しかし、従来技術における反射鏡又は受光器を回転さ
せる方法では、光の入射角の検出精度が機械的な回転機
構の精度により決定される上、受光器を稼働して光を検
出できる位置まで動かすためには長い時間を要してい
た。However, in the method of rotating the reflecting mirror or the light receiver in the conventional technology, the detection accuracy of the incident angle of light is determined by the accuracy of the mechanical rotation mechanism, and the light receiver is operated to a position where light can be detected. It took a long time to get there.
この発明は、光の入射角度の検出精度をより正確にす
べきであるとの要望を満たすべくなされたもので、その
ための技術的手段として、光透過性を有する圧電性基板
を用い、該圧電性基板の表面上に電気信号により、表面
弾性波（SAW:Surface Acoustic Wave）を発生させ、該
表面弾性波を光に対する空間的位相格子として使用し、
更に該位相格子に照射されたのち、該圧電性基板を透過
してきた光を反射鏡により反射し、再び、該位相格子に
照射するようにしている。The present invention has been made to meet the demand that the detection accuracy of the incident angle of light should be made more accurate, and as a technical means therefor, a piezoelectric substrate having optical transparency is used. The surface acoustic wave (SAW: Surface Acoustic Wave) is generated by an electric signal on the surface of the flexible substrate, and the surface acoustic wave is used as a spatial phase grating for light.
Furthermore, after the phase grating is irradiated, the light that has passed through the piezoelectric substrate is reflected by a reflecting mirror and is again irradiated to the phase grating.
また、団体表面上を伝搬するSAWは正弦波に近い波形
を有するため、SAWによる位相格子は正弦波回折格子と
みなすことができ、この回折格子を透過した光（透過
光）は正弦波的な位相変調を受ける。Further, since the SAW propagating on the surface of the group has a waveform close to a sine wave, the phase grating by the SAW can be regarded as a sine wave diffraction grating, and the light transmitted through this diffraction grating (transmitted light) has a sine wave shape. It undergoes phase modulation.
このため、該透過光は、正弦波格子の格子定数に応じ
た回折角を有する回折現象を呈し、特に正弦波位相格子
特有の性質である格子定数で定められた±１次の回折輝
点位置に、±１次の回折光と呼ばれる輝点を生ずる。前
記SAWによる位相格子の格子間隔は電気信号の周波数
（この周波数は発生するSAWの周波数に等しい）により
制御できる。Therefore, the transmitted light exhibits a diffraction phenomenon having a diffraction angle according to the lattice constant of the sine wave grating, and in particular, the ± 1st-order diffracted bright spot positions determined by the lattice constant which is a characteristic peculiar to the sine wave phase grating. In addition, a bright spot called ± first-order diffracted light is generated. The lattice spacing of the SAW phase grating can be controlled by the frequency of the electrical signal (this frequency is equal to the frequency of the generated SAW).
前述したように、光はSAWによる位相格子を２回透過
するので、最初に透過したときに生じた±１次の回折光
は、再度通過したときに生じた同じ次数の回折光と干渉
を引き起し、その結果、同じSAWの周波数あるいは同じ
光の入射角度に対し、＋１次の回折光の光量と−１次の
回折光の光量とが異なるという現象を呈する場合があ
る。As described above, the light passes through the SAW phase grating twice, so the ± 1st order diffracted light generated when it first penetrates interferes with the diffracted light of the same order generated when it again passes. As a result, the light quantity of the + 1st-order diffracted light and the light quantity of the −1st-order diffracted light may be different for the same SAW frequency or the same incident angle of light.
この現象を利用し、例えばSAWの周波数を所定の幅だ
け走査して、±１次回折光量を測定すれば、その測定結
果から光の入射角度を同定（ident-ify）することがで
きる。Utilizing this phenomenon, if the ± 1st-order diffracted light amount is measured by scanning the SAW frequency by a predetermined width, for example, the incident angle of light can be identified from the measurement result.
そこで、以下に発明者の行なった本発明に係る光入射
角検出装置についての実験と、その理論的検討を述べ
る。Therefore, an experiment and a theoretical examination of the light incident angle detecting device according to the present invention conducted by the inventor will be described below.
第１図に、SAWの周波数又は光の入射角度を変化さ
せ、±１次回折光量を測定するための実験系を示す。FIG. 1 shows an experimental system for measuring the ± first-order diffracted light amount by changing the SAW frequency or the incident angle of light.
この実験系は、光透過性を有する圧電性基板１と、こ
の圧電性基板１の表面にSAWを発生させるために設けら
れた交差指形電極２と、この交差指形電極２に高周波電
力を供給するための周波数可変信号発生器（電源）３
と、前記圧電性基板１の裏面に金属蒸着により作製され
た反射鏡（反射板）４と、±１次の回折光の光量を測定
するための光検出器（測定器）５と、該圧電性基板１が
固定されており、光の入射角度を変化できる回転ステー
ジ（基台）６及び光源７とからなり、実線８は主軸光の
光路を表わし、破線９は回折光の光路を表わす。In this experimental system, a piezoelectric substrate 1 having optical transparency, an interdigital finger 2 provided on the surface of the piezoelectric substrate 1 for generating SAW, and a high frequency power is applied to the interdigital electrode 2. Frequency variable signal generator (power supply) for supplying 3
A reflecting mirror (reflecting plate) 4 formed on the back surface of the piezoelectric substrate 1 by metal vapor deposition; a photodetector (measuring device) 5 for measuring the quantity of ± 1st order diffracted light; The solid substrate 1 is fixed and comprises a rotary stage (base) 6 and a light source 7 capable of changing the incident angle of light. A solid line 8 represents the optical path of the principal axis light, and a broken line 9 represents the optical path of diffracted light.
第２図に、光の入射角度を５度,10度,20度,40度と
し、それぞれの入射角度に対して電気信号の周波数を掃
引したときの±１次回折光量と信号周波数との関係につ
いての測定結果を示す。このようにして得られた測定結
果のことを回折光量の周波数特性と略称する。Fig. 2 shows the relationship between the ± 1st-order diffracted light quantity and the signal frequency when the incident angle of light is 5 °, 10 °, 20 °, and 40 °, and the frequency of the electrical signal is swept for each incident angle. The measurement result of is shown. The measurement result thus obtained is abbreviated as the frequency characteristic of the amount of diffracted light.
この第２図に示す測定では、入力電力の周波数ｆ＝10
6MHzで、最も効率良くSAWを励振する交差指形電極を用
いて行なった。なお、実線は＋１次回折，点線は−１次
回折を示す。In the measurement shown in FIG. 2, the input power frequency f = 10
At 6MHz, the interdigitated electrodes that excite the SAW most efficiently were used. The solid line shows the + 1st-order diffraction and the dotted line shows the -1st-order diffraction.
第２図に示すように、±１次回折光量の周波数特性
は、光の入射角度に依存して変化し、また同じ入射角度
で±１次回折光量の周波数特性が異なることがわかる。
後者を、特に±１次回折光量の非対称性と以後，略称す
る。As shown in FIG. 2, it can be seen that the frequency characteristics of the ± first-order diffracted light amount change depending on the incident angle of light, and the frequency characteristics of the ± first-order diffracted light amount are different at the same incident angle.
The latter is abbreviated as “asymmetry of ± first-order diffracted light amount” hereinafter.
かかる周波数特性が理論的に計算できれば、測定結果
と理論値との比較により、光の入射角度が同定できるこ
とになる。If the frequency characteristic can be theoretically calculated, the incident angle of light can be identified by comparing the measurement result with the theoretical value.
第３図に、SAWの周波数を106MHzに固定したときの±
１次回折光量（実線は＋１次回折を表わし，点線は一次
回折を表わす）と光入射角度の関係についての測定結果
を示す。このようにして得られる測定結果のことを回折
光量の角度依存性と略称する。この図に示すように、回
折光量は入射角度に対し振動しつつ、その極大値が単調
に減少するが、その角度依存性は±１次回折光の間で異
なる（この現象も、±１次回折光量の非対称性とい
う）。すなわち、±１次回折光量は、異なる光の入射角
度において極値をとるのである。この角度依存性も、理
論的に計算できれば、周波数特性と同様に光の入射角度
の同定に利用できる。Fig. 3 shows the ± when the SAW frequency is fixed at 106MHz.
The measurement results of the relationship between the amount of first-order diffracted light (solid line represents + 1st-order diffraction and the dotted line represents first-order diffraction) and the light incident angle are shown. The measurement result thus obtained is abbreviated as the angle dependence of the diffracted light amount. As shown in this figure, the amount of diffracted light oscillates with respect to the incident angle, but its maximum value monotonously decreases, but the angle dependence differs between ± 1st-order diffracted light (this phenomenon also occurs in ± 1st-order diffracted light). Asymmetry of the amount of light). That is, the ± first-order diffracted light amounts have extreme values at different incident angles of light. If this angle dependency can be theoretically calculated, it can be used for identifying the incident angle of light as well as the frequency characteristic.
まず、±１次の回折光量の非対称性について述べる。
本発明では、SAWによる位相格子中を２回光が透過する
ことが特徴であり、該透過するごとに回折光を生じる。First, the asymmetry of the ± 1st order diffracted light amounts will be described.
The present invention is characterized in that light is transmitted twice through the SAW phase grating, and diffracted light is generated each time the light is transmitted.
第４図（ａ）は、基板の内部と基板の近傍における光
路を示したものである。図において、実線は主軸光の光
路を表わし、点線及び破線は回折光の光路を表わす。FIG. 4A shows an optical path inside the substrate and in the vicinity of the substrate. In the figure, the solid line represents the optical path of the principal axis light, and the dotted line and the broken line represent the optical path of the diffracted light.
最初に位相格子を透過したときに生じた回折光（1a、
1b）は、再度位相格子を透過したときに生じた回折光
（2a、2b）と光路長の違いから干渉を引き起こす。そこ
で、光の入射角度をθｉ、屈折角をθ、回折角をδθ、
基板の厚みをｄとして光路差を評価する。Diffracted light (1a,
1b) causes interference due to the difference in optical path length between the diffracted light (2a, 2b) generated when the light is transmitted through the phase grating again. Therefore, the incident angle of light is θ i , the refraction angle is θ, the diffraction angle is δθ,
The optical path difference is evaluated with the thickness of the substrate being d.
まず、基板内での主軸光と±１次回折光との光路差
（ΔＰ±）は、次式のようになる。First, the optical path difference (ΔP ±) between the principal-axis light and the ± first-order diffracted lights in the substrate is given by the following equation.
ΔＰ±＝2d|1/cos（θ±δθ）−1/cosθ｜ ＝（2d/cosθ）（（tanθ）（δθ）±（（1/2） ＋tan2θ）（δθ）２）＋０（δθ３） ……（１） ここで、０（δθ３）はδθ３のorderの量を表わす。ΔP ± = 2d | 1 / cos (θ ± δθ) -1 / cosθ | = (2d / cosθ) ((tanθ) (δθ) ± ((1/2) + tan 2 θ) (δθ) 2) +0 (δθ 3 ) (1) where 0 (δθ 3 ) represents the order quantity of δθ 3 .
つぎに、基板の外部での同じ次数の回折光の間におけ
る光路差をΔＬ±とすると、次式のようになる。Next, letting ΔL ± be the optical path difference between diffracted lights of the same order outside the substrate, the following equation is obtained.
ΔＬ±＝2d|tan（θ±δθ）−tanθ｜nosin（θ±δ
θ） ＝（2dno/cosθ）（（tanθ）（δθ） ±（δθ）２／cos2θ）＋０（δθ３）……（２） ここで、noは基板の屈折率である。ΔL ± = 2d | tan (θ ± δθ) -tan θ | n o sin (θ ± δ
θ) = (2dn o / cosθ ) ((tanθ) (δθ) ± (δθ) 2 / cos 2 θ) +0 (δθ 3) ...... (2) where, n o is the refractive index of the substrate.
したがって、±１次回折光における正味の光路差より
生じる位相差をΔφ±とすると、λを真空中での光の波
長として、次の式が得られる。Therefore, when the phase difference caused by the net optical path difference in the ± 1st order diffracted light is Δφ ±, the following equation is obtained with λ being the wavelength of light in vacuum.
Δφ＋＝｜ΔＰ＋／（λ／n0）−ΔＬ＋／λ｜ ＝Δφ− ……（３） 第４図（ｂ）は、回折角度δθ、主軸光の波数ベクト
ル（kx,ky）およびSAWの波数ベクトル（ka,0）について
の相互関係を示す。図より tan（θ±δθ） ＝（kx±ka）／ky ＝tanθ±（ka／ky） ……（４） SAWの波数ベクトル（ka,0）は、 SAWの音速をｖ、周波数をｆとすると、 ka＝２πf/vであり、 ky＝２πn0cosθ／λと合わせて、 δθ＝（λfcosθ／n0ｖ） ……（５） となる。この（５）式を前記（３）式に代入して、＋１
次光の位相差Δφ＋と−１次光の位相差Δφ−とを求め
る。Δφ + = | ΔP + / (λ / n 0 ) −ΔL + / λ | = Δφ− (3) FIG. 4 (b) shows the diffraction angle δθ, the wave vector (k x , k y ) of the principal axis light and the SAW. Shows the mutual relation of the wave vector (k a , 0) of. From the figure, tan (θ ± δθ) = (k x ± k a ) / k y = tan θ ± (k a / k y ) (4) The SAW wave vector (k a , 0) is the SAW sound velocity. If v is the frequency and f is f, then k a = 2πf / v, and in combination with k y = 2πn 0 cos θ / λ, δθ = (λf cos θ / n 0 v) (5) Substituting this equation (5) into the equation (3), +1
The phase difference Δφ + of the next light and the phase difference Δφ− of the −1st light are obtained.
Δφ＋＝Δφ− ＝（λd/n0）(f/v)2cosθ ……（６） この（６）式から、＋１次光の位相差Δφ＋と−１次
光の位相差Δφ−とは、同一であることがわかる。した
がって、この考えでは、±１次光の非対称性は説明でき
ない。Δφ + = Δφ − = (λd / n 0 ) (f / v) 2 cosθ (6) From this equation (6), the phase difference Δφ + of the + 1st order light and the phase difference Δφ− of the −1st order light are It turns out that they are the same. Therefore, this idea cannot explain the asymmetry of ± first-order light.
また、前記（６）式から、位相が１回転するのに要す
るSAWの周波数の周期を評価しても、第２図で回折光量
が一つの極大値から次の極大値をとるまでの周波数の間
隔とは一致しない。Further, even if the period of the SAW frequency required to make one rotation of the phase is evaluated from the equation (6), the frequency of the diffracted light amount from one maximum value to the next maximum value in FIG. Does not match the interval.
そこで、一つの試みとして、基板の外部における光路
差を無視してしまう。Therefore, as one attempt, the optical path difference outside the substrate is ignored.
SAWは基板の表面にその波長程度の厚みをもって分布
している。SAW is distributed on the surface of the substrate with a thickness of about that wavelength.
したがって、主軸光が回折をうける位置にも、該厚み
程度の不定性がある。この不定性は基板の厚みに比べて
十分小さいので、基板の内部の光路長への影響は無視で
きる。Therefore, even at the position where the principal axis light is diffracted, there is indefiniteness of the thickness. Since this indeterminacy is sufficiently smaller than the thickness of the substrate, the influence on the optical path length inside the substrate can be ignored.
一方、基板の外部の光路長で、２つの回折光の光路差
に寄与する部分は、この不定性と同程度であるため、ど
こで回折光が生じたと考えるかによって光路差は異な
り、前記（２）式で該光路差を確定できない。On the other hand, the portion of the optical path length outside the substrate that contributes to the optical path difference between the two diffracted lights is about the same as this indefiniteness, and therefore the optical path difference differs depending on where the diffracted light is considered to occur. ), The optical path difference cannot be determined.
例えば、この厚み内のあらゆる場所で平均的に回折光
が生じるとすると、基板外の該光路差による干渉の効果
は、相殺される可能性もある。For example, if diffracted light is generated on average anywhere in this thickness, the effect of interference due to the optical path difference outside the substrate may be canceled out.
そこで、前記（１）式のみを用いて、±１次回折光の
位相差（Δφ±）を求めると、 Δφ±＝ΔＰ±／（λ（n0） ＝2d（tanθ（f/v）±（d/n0）（1/2＋tan2θ） ×cosθ(f/v)2） ……（７） となる。Therefore, when the phase difference (Δφ ±) of the ± 1st-order diffracted light is obtained using only the equation (1), Δφ ± = ΔP ± / (λ (n 0 ) = 2d (tan θ (f / v) ± ( d / n 0 ) (1/2 + tan 2 θ) × cos θ (f / v) 2 ) ... (7)
この場合、＋１次回折光の位相差と−１次回折光の位
相差の関係は、Δφ＋≠Δφ−であり、その差は、次の
ようになる。In this case, the relationship between the phase difference of the + 1st order diffracted light and the phase difference of the −1st order diffracted light is Δφ + ≠ Δφ−, and the difference is as follows.
｜（Δφ＋）−（Δφ−）｜ ＝（4dλ／n0）cosθ（1/2＋tan2θ） ×(f/v)2 ……（８） 実験条件として、ｄ＝1mm,λ＝0.6328μm,n0＝2.286,
θ＝５度,v＝3470m/sで計算すると、ｆ＝106MHzで＋１
次回折光の位相差と−１次回折光の位相差の差0.5を得
る。│ (Δφ +)-(Δφ-) │ = (4dλ / n 0 ) cos θ (1/2 + tan 2 θ) × (f / v) 2 (8) As experimental conditions, d = 1 mm, λ = 0.6328 μm, n 0 = 2.286,
Calculating at θ = 5 degrees and v = 3470m / s, +1 at f = 106MHz
The difference 0.5 between the phase difference of the second-order diffracted light and the phase difference of the -1st-order diffracted light is obtained.
よって、上記（８）式より得られる計算結果は、第２
図及び第３図で±１次回折光量が相補的であること（す
なわち、＋１次回折光量が極大値をとる取る時、−１次
回折光量が極小値をとること、逆も同様）をよく説明し
ている。Therefore, the calculation result obtained from the above equation (8) is the second
It is often the case that the ± first-order diffracted light amounts are complementary in the figures and FIG. 3 (that is, when the + 1st-order diffracted light amount takes a maximum value, the −1st-order diffracted light amount takes a minimum value, and vice versa). Explaining.
第５図に、上記（７）式を用いて±１次回折光量とSA
W周波数の関係を計算したものと実験結果を並べて示
し、また第６図に、±１次回折光量と光の入射角度との
関係を上記（７）式を用いて計算したものと実験結果を
並べて示した。第５図及び第６図とも上記（７）式が実
験結果をよく再現することを示している。In Fig. 5, the ± 1st order diffracted light quantity and SA are calculated by using the above equation (7).
The calculated W frequency relationship and the experimental results are shown side by side, and Fig. 6 shows the relationship between the ± 1st order diffracted light quantity and the incident angle of the light calculated using the above equation (7) and the experimental result. Shown side by side. Both FIGS. 5 and 6 show that the above equation (7) reproduces the experimental results well.
つぎに、回折光量が光の入射角度が大きくなるに従い
減少することについて述べるが、これには次の３つの原
因が考えられる。Next, it will be described that the amount of diffracted light decreases as the incident angle of light increases, and there are three possible causes for this.
第１に、光の入射角度が大きくなるに従い基板の反射
率が増大し透過率が減少するのでSAWによる回折作用を
受ける主軸光が減少してしまう。First, as the incident angle of light increases, the reflectance of the substrate increases and the transmittance decreases, so that the main-axis light that is diffracted by SAW decreases.
第２に、やはり光の入射角度が大きくなるに従い、基
板内で光の通過する距離が長くなり光が減衰してしま
う。Secondly, as the incident angle of light increases, the distance that light passes through the substrate becomes longer and the light is attenuated.
第３に、これは後に詳しく述べる位相変化の相殺とい
う現象である。Thirdly, this is a phenomenon called phase cancellation which will be described in detail later.
まず、第１の点については、本実験では基板の表面で
の光の反射を防ぐために基板の表面に誘電体薄膜による
コーティング（coating）を行なっている。このコーテ
ィングを施した基板の光透過率と光入射角度との関係に
ついての実験結果を第７図に示す。第２図および第３図
に示した実験では光の入射角度は最大45度であり、第７
図ではその範囲で光透過率95％以上を示しており、従っ
て反射光の増大による回折光量の減少では実験結果を説
明できない。First, regarding the first point, in this experiment, the surface of the substrate is coated with a dielectric thin film in order to prevent reflection of light on the surface of the substrate. FIG. 7 shows the experimental result on the relationship between the light transmittance and the light incident angle of the substrate provided with this coating. In the experiments shown in FIGS. 2 and 3, the incident angle of light is 45 degrees at maximum, and
In the figure, the light transmittance is 95% or more in that range, and therefore the experimental result cannot be explained by the decrease of the diffracted light amount due to the increase of the reflected light.
つぎに、第２の基板内の光路長の増大であるが屈折角
θのときの基板内の光路長は、2d/cosθである。入射角
がθｉのときのθは、sin-1（sinθｉ／n0）で与えら
る。最大入射角θｉ＝45度の場合、θ＝18度であって基
板内の光路長は入射角５度の場合から５％長くなるに過
ぎない。Next, although the optical path length in the second substrate is increased, the optical path length in the substrate at the refraction angle θ is 2d / cos θ. When the incident angle is θ i , θ is given by sin −1 (sin θ i / n 0 ). When the maximum incident angle θ i = 45 degrees, θ = 18 degrees, and the optical path length in the substrate is only 5% longer than when the incident angle is 5 degrees.
一方、第２図および第３図の実験結果において入射角
45度のときの回折光量は入射角５度のときの約30％に減
少しており、したがって、基板内の光路長の増大による
光の減衰によっても実験結果は説明できない。On the other hand, in the experimental results of Figs. 2 and 3, the incident angle
The amount of diffracted light at 45 degrees is reduced to about 30% when the incident angle is 5 degrees. Therefore, the experimental result cannot be explained even by the attenuation of light due to the increase of the optical path length in the substrate.
第３の位相差の相殺の現象について述べるために、ま
ずSAWの位相格子による光の回折について説明してお
く。In order to describe the third phenomenon of canceling the phase difference, first, the diffraction of light by the SAW phase grating will be described.
第８図（ａ）は、SAWの位相格子に光が垂直入射（θ
ｉ＝０度）し、その透過した光から回折光が生じる現象
を示したものである。FIG. 8 (a) shows that light is vertically incident on the SAW phase grating (θ
i = 0 degree), and a phenomenon in which diffracted light is generated from the transmitted light is shown.
SAWはその伝搬する媒質内に屈折率が周期的に変化す
る構造を作り出す。SAW creates a structure in which the refractive index changes periodically in the propagating medium.
垂直入射した光（平面波）の等位相面は（それはFour
ier変換して波数空間で表示すれば、唯一つの波数成分
を持つ）、前記媒質中を透過すると屈折率の分布に依存
して位相の進み方が異なるため、透過した後の等位相面
は平面波とは異なる形をしている。この等位相面をFour
ier変換して波数空間で表示すれば、複数の波数成分を
持つ、すなわち回折光が生じることになる。Equal phase plane of vertically incident light (plane wave) is
If it is transmitted through the medium, it will have a single wavenumber component), and since the phase progress will differ depending on the distribution of the refractive index when transmitted through the medium, the isophase surface after transmission will be a plane wave. Has a different shape from. This equal phase plane is Four
If it is ier-transformed and displayed in the wave number space, it has a plurality of wave number components, that is, diffracted light is generated.
さて、有限の入射角でSAWの位相格子に入射した光
は、その波面をSAWの波長、すなわち屈折率の周期構造
に比べて十分微小な部分に分割して考えれば、各微小部
分の中には、屈折率の高い（低い）部分から低い（高
い）部分へと進むものがあり、その部分については屈折
率の変化による位相変化の効果が相殺されてしまうの
で、回折光への寄与も相殺される。この位相差の相殺の
起きる領域を示したのが第８図（ｂ）である。Now, the light incident on the SAW phase grating at a finite angle of incidence is divided into each minute portion if the wavefront is divided into sufficiently minute portions compared to the SAW wavelength, that is, the periodic structure of the refractive index. Has a part that has a high (low) refractive index and a part that has a low (high) refractive index, and the effect of the phase change due to the change in the refractive index is canceled in that part, so the contribution to the diffracted light is also canceled. To be done. FIG. 8B shows a region where the phase difference is canceled.
SAWによる屈折率の変化は、基板の表面から数波長の
深さの部分で起きている。ここで、その深さをSAWの２
波長分と仮定すると、屈折角θのとき、入射光の2tan
θの部分が位相差による相殺の現象を受け、θｉ20度
（θ＝8.6度）のとき回折光量は垂直入射のときの70％
となり、θｉ＝45度（θ＝18度）で回折光量は垂直入射
のときの35％にそれぞれ減少することが計算されるが、
これは第２図および第３図の実験結果をよく説明してい
る。The change in the refractive index due to SAW occurs at a portion several wavelengths deep from the surface of the substrate. Here, the depth of SAW is 2
Assuming the wavelength, 2 tan of the incident light when the refraction angle is θ
When θ i is 20 degrees (θ = 8.6 degrees), the amount of diffracted light is 70% of that at vertical incidence when θ is subject to the phenomenon of cancellation due to the phase difference.
Therefore, it is calculated that the amount of diffracted light decreases to 35% of that at vertical incidence when θ i = 45 ° (θ = 18 °).
This well explains the experimental results of FIGS. 2 and 3.
以上述べたように、基板の内部の光路差のみを考慮し
た干渉という観点から±１次回折光量の非対称性が、ま
た位相差の相殺という観点から光の入射角度の増大に伴
なう回折光量の減少が（その現象自体は）説明できるこ
とが明らかになった。As described above, the asymmetry of the ± first-order diffracted light amount from the viewpoint of interference considering only the optical path difference inside the substrate, and the diffracted light amount accompanying the increase of the incident angle of light from the viewpoint of canceling the phase difference. It became clear that the decrease of (the phenomenon itself) can be explained.
第９図は、以上述べた現象を利用した本発明に係る光
入射角検出装置の実施例における構成を示す。なお、構
成の基本部分は第１図に示した実験系統と変らないの
で、同じ構成番号を用いた。図中、10は制御手段、11は
信号処理手段、12はスリットを示す。FIG. 9 shows a configuration of an embodiment of a light incident angle detecting device according to the present invention which utilizes the above-mentioned phenomenon. Since the basic part of the configuration is the same as that of the experimental system shown in FIG. 1, the same configuration number was used. In the figure, 10 is a control means, 11 is a signal processing means, and 12 is a slit.
制御手段10は、基台６を回転ステージとして回転さ
せ、かつ、電源３より交差指形電極２に供給される電力
周波数を所定の幅だけ走査する。The control means 10 rotates the base 6 as a rotary stage, and scans the power frequency supplied from the power source 3 to the interdigital electrode 2 by a predetermined width.
信号処理手段11は、光検出器５から得られる回折光量
から光の入射角度の情報を得るための信号処理を行な
う。The signal processing means 11 performs signal processing for obtaining information on the incident angle of light from the amount of diffracted light obtained from the photodetector 5.
スリット12は、主軸光８・回折光９のうち、いずれか
１つを選択的に前記光検出器５へ導くもので前記制御手
段10により制御される。The slit 12 selectively guides one of the principal axis light 8 and the diffracted light 9 to the photodetector 5, and is controlled by the control means 10.
以下、本実施例により光の入射角度の情報を得る過程
について述べる。The process of obtaining information on the incident angle of light according to this embodiment will be described below.
光源７が任意の方向に与えられたとき、圧電性基板２
の裏面に形成された反射鏡４を単なる反射板として用
い、前記光検出器５により反射光（主軸光）８が検出さ
れるように回転ステージ（基台６）を回転させる。この
ときは、交差指形電極２には電力は供給しない。When the light source 7 is applied in an arbitrary direction, the piezoelectric substrate 2
Using the reflecting mirror 4 formed on the back surface of the above as a simple reflecting plate, the rotary stage (base 6) is rotated so that the photodetector 5 detects the reflected light (main axis light) 8. At this time, no electric power is supplied to the interdigital electrode 2.
したがって、回折光９は生じていないので、このと
き、基台６の回転角から光の入射角度の大体の値を得る
こともできる。この場合の精度は、回転の機械的精度に
より決まる。Therefore, since the diffracted light 9 is not generated, at this time, the approximate value of the incident angle of light can be obtained from the rotation angle of the base 6. The precision in this case depends on the mechanical precision of the rotation.
つぎに、電源３の周波数を所定の幅走査し、その走査
により生じた±１次回折光を、前記スリット12を制御し
て光検出器５へ導き、回折光量の周波数特性を測定す
る。Next, the frequency of the power source 3 is scanned by a predetermined width, and the ± 1st-order diffracted light generated by the scanning is guided to the photodetector 5 by controlling the slit 12, and the frequency characteristic of the amount of diffracted light is measured.
この測定により得られた回折光量の最大値とすでに得
られている主軸光量との比、いわゆる回折効率から、回
折光量の極大値が光の入射角度の増大に伴ない減少する
現象（第３図に示す）を利用し、大体の光の入射角度を
得る（入射角度０度のとき、得られる最大の回折効率
は、供給する電力が決まれば、理論的に得ることができ
る）。The phenomenon that the maximum value of the diffracted light amount decreases with the increase of the incident angle of light from the ratio between the maximum value of the diffracted light amount obtained by this measurement and the already obtained light amount of the main axis, so-called diffraction efficiency (Fig. 3 Is used to obtain an approximate incident angle of light (when the incident angle is 0 degree, the maximum diffraction efficiency obtained can be theoretically obtained if the supplied power is determined).
このようにして得られた角度の近傍で、回折光量の周
波数特性を前記（７）式により計算し、測定値と比較し
て入射角度の精密な同定を行なう。In the vicinity of the angle thus obtained, the frequency characteristic of the amount of diffracted light is calculated by the equation (7), and compared with the measured value, the incident angle is precisely identified.
以上の過程により、光の入射角度が精密に同定できる
ことを実証するために、発明者の行なった実験と計算を
述べる。In order to prove that the incident angle of light can be accurately identified by the above process, the experiments and calculations performed by the inventor will be described.
第10図は光の入射角度を約10度に設定したときの回折
光量の周波数特性と、角度９度,9.5度および10度におい
て計算した回折光量の周波数特性を示す。ここで約10度
と述べたのは、光の入射角度は零度調整を目視により行
なうため、その絶対値が正確に設定されないことによ
る。FIG. 10 shows the frequency characteristic of the amount of diffracted light when the incident angle of light is set to about 10 degrees, and the frequency characteristic of the amount of diffracted light calculated at angles of 9 degrees, 9.5 degrees, and 10 degrees. The reason for saying about 10 degrees here is that the absolute value of the incident angle of light is not set accurately because the zero degree is adjusted visually.
第10図より明らかに、光の入射角度は9.5度と同定さ
れ、このように単純なパターンマッチングによっても、
0.5度の精度で光の入射角度の同定が可能である。Obviously from Fig. 10, the incident angle of light was identified as 9.5 degrees, and even by simple pattern matching like this,
It is possible to identify the incident angle of light with an accuracy of 0.5 degree.
以上述べたように、電気信号で発生させたSAWの光の
回折格子として用い、このSAWによる光回折格子を、反
射板を用いて光が２回通過する構成をとることにより、
±１次回折光量の周波数特性が特徴を持って現れる現象
を見出し、かつ、その現象自体は理論的に予測可能であ
ることから光の入射角を精度良く同定することが可能と
なった。この発明はロボットの眼のセンサ（トランスジ
ューサ）として有用なものである。As described above, by using it as a diffraction grating of SAW light generated by an electric signal, and by adopting a configuration in which light passes through the light diffraction grating of this SAW twice using a reflector,
We found a phenomenon in which the frequency characteristics of the ± 1st-order diffracted light quantity have characteristics, and since the phenomenon itself can be predicted theoretically, it became possible to identify the incident angle of light with high accuracy. The present invention is useful as a sensor (transducer) for the eyes of a robot.
第１図は±１次回折光量とSAW周波数及び光入射角度の
関係を測定するための実験系を、第２図は光入射角度を
５度,10度,20度,40度にそれぞれ固定したときの±１次
回折光量とSAW周波数との関係の測定結果を、第３図はS
AW周波数を106MHzに固定したときの±１次回折光量と光
入射角度との関係の測定結果を、第４図は基板の内部お
よび基板の表面の近傍における主軸光と回折光の光路を
示し、さらに主軸光,SAW及び回折光それぞれの波数ベク
トルの間の関係をそれぞれ示す。第５図は第２図に示し
た測定結果と，理論的に計算された±１次回折光量とSA
W周波数の関係を、また、第６図は第３図に示した測定
結果と、理論的に計算された±１次回折光量と光入射角
度の関係を並べて示す。第７図はコーティングを施した
基板の光透過率と光入射角度との関係の測定結果を、第
８図は屈折率の周期的に変化する媒質による光の位相変
調の原理と有限の入射角度で媒質に入射した光波面が，
媒質中を進行する際に位相差相殺現象の生じる領域を、
第９図は本発明に係る光入射角検出装置の一実施例にお
ける構成を、第10図は本発明により光入射角度の同定が
可能であることを示すために行なった実験と計算の結果
を示す。 図において、１は圧電性基板、２は交差指形電極、３は
電源（周波数可変信号発生器）、４は反射板（反射
鏡）、５は光検出器（測定器）、６は基台（回転ステー
ジ）、７は光源、８は主軸光の光路、９は回折光の光
路、10は制御手段、11は信号処理手段、12はスリットを
それぞれ示す。Fig. 1 shows the experimental system for measuring the relationship between the ± 1st order diffracted light quantity, the SAW frequency and the light incident angle, and Fig. 2 shows the light incident angle fixed to 5 °, 10 °, 20 ° and 40 °, respectively. Fig. 3 shows the measurement result of the relationship between the ± 1st-order diffracted light quantity and the SAW frequency at
The measurement results of the relationship between the ± 1st-order diffracted light quantity and the light incident angle when the AW frequency is fixed to 106 MHz are shown in FIG. 4, which shows the optical paths of the principal axis light and the diffracted light inside the substrate and in the vicinity of the surface of the substrate. Furthermore, the relationships between the wavenumber vectors of the principal axis light, SAW and diffracted light are shown respectively. FIG. 5 shows the measurement results shown in FIG. 2 and the theoretically calculated ± first-order diffracted light quantity and SA.
FIG. 6 shows the relationship between the W frequencies, and FIG. 6 shows the measurement results shown in FIG. 3 and the theoretically calculated relationship between the ± first-order diffracted light amount and the light incident angle. FIG. 7 shows the measurement results of the relationship between the light transmittance and the light incident angle of the coated substrate, and FIG. 8 shows the principle of phase modulation of light by a medium whose refractive index changes periodically and a finite incident angle. The light wavefront incident on the medium at
The region where the phase difference cancellation phenomenon occurs when traveling through the medium,
FIG. 9 shows the configuration of an embodiment of the light incident angle detecting device according to the present invention, and FIG. 10 shows the results of experiments and calculations performed to show that the light incident angle can be identified by the present invention. Show. In the figure, 1 is a piezoelectric substrate, 2 is an interdigital finger electrode, 3 is a power source (frequency variable signal generator), 4 is a reflector (reflector), 5 is a photodetector (measuring instrument), and 6 is a base. (Rotation stage), 7 is a light source, 8 is an optical path of principal axis light, 9 is an optical path of diffracted light, 10 is control means, 11 is signal processing means, and 12 is a slit.
Claims (1)
形成する表面弾性波を発生させるための交差指形電極
（２）と、 該交差指形電極に電気信号を供給するための電源（３）
と、 前記圧電性基板を透過した光を、前記表面弾性波の存在
する表面に向けて反射させるための反射板（４）と、 前記光回折格子により回折される光を検出するための光
検出器（５）と、 前記電源の周波数を所定の幅だけ走査する制御手段（1
0）と、 該走査のときに得られた検出信号から光の入射角度に係
る情報を得るための信号処理をなす信号処理手段（11）
とを備えた光入射角検出装置。1. A piezoelectric substrate (1) having optical transparency, and an interdigital electrode (1) provided on the surface of the piezoelectric substrate for generating a surface acoustic wave forming an optical diffraction grating on the surface. 2) and a power supply (3) for supplying an electric signal to the interdigital electrode.
A reflection plate (4) for reflecting the light transmitted through the piezoelectric substrate toward the surface where the surface acoustic wave exists, and a light detection device for detecting the light diffracted by the light diffraction grating. And a control means (1) for scanning the frequency of the power source within a predetermined width.
0) and signal processing means (11) for performing signal processing for obtaining information relating to the incident angle of light from the detection signal obtained during the scanning.
And a light incident angle detection device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63048460A JP2524799B2 (en) | 1988-03-01 | 1988-03-01 | Light incident angle detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63048460A JP2524799B2 (en) | 1988-03-01 | 1988-03-01 | Light incident angle detector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01221625A JPH01221625A (en) | 1989-09-05 |
| JP2524799B2 true JP2524799B2 (en) | 1996-08-14 |
Family
ID=12803977
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63048460A Expired - Lifetime JP2524799B2 (en) | 1988-03-01 | 1988-03-01 | Light incident angle detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2524799B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100436570B1 (en) * | 2001-05-25 | 2004-06-16 | 동부전자 주식회사 | Method and apparatus for measuring a tilt angle in a serial type ion implantation unit |
| JP7190667B2 (en) * | 2018-06-14 | 2022-12-16 | パナソニックＩｐマネジメント株式会社 | object detector |
-
1988
- 1988-03-01 JP JP63048460A patent/JP2524799B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01221625A (en) | 1989-09-05 |
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