JPS625131A - Optical scale - Google Patents

Abstract

PURPOSE:To obtain an optical scale of high resolution in a simple manner and at low cost by a method wherein a light-transmitting portion and a non- light-transmitting portion having a slanting surface whose incident angle in relation to incident light is larger than a critical angle are formed alternately on the surface of a member of polycarbonate. CONSTITUTION:A light-transmitting portion 9 having a flat surface 9a and a non-light-transmitting portion 10 having a slanting surface whose angle to incident light is larger than a critical angle are formed alternately at the same pitch on the lower surface of an optical scale 3, and a fixed optical lattice 4 formed in the same shape with the scale 3 is disposed below it. The light passes through the scale and the lattice when the phases of irregularities of the two accord with each other, and it returns onto the incidence side through two total reflections and does not reach a light-receiving element 5. Since the scale 3 is formed of polycarbonate having a small critical angle, the light falling obliquely onto the slanting surface of the non-transmitting portion 10 is totally- reflected as well. Therefore the light is hardly transmitted and the restriction to an incident angle is reduced. Thus, the optical scale of high resolution can be obtained simply at low cost.

Description

【発明の詳細な説明】 〔技術分野〕 本発明は光学式スケールに関し、特に光学式エンコーダ
等に用いるのに適した光学式スケールに関する。。DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical scale, and particularly to an optical scale suitable for use in an optical encoder or the like. .

〔従来技術〕[Prior art]

従来、電子タイプライタ−等の情報機器において、キャ
リッジ等の可動部の位置・速度を検出する為に、光学式
エンコーダが多く用いられてきた。このような光学式エ
ンコーダは、通常可動部に固定され、光学式符号が記録
された光学式スケールに光を投射し、変調された光を光
電変換することによって前記可動部の位置情報を符号化
された電気信号として取り出すように構成されていた。Conventionally, optical encoders have been widely used in information devices such as electronic typewriters to detect the position and speed of movable parts such as carriages. Such an optical encoder is usually fixed to a movable part, projects light onto an optical scale on which an optical code is recorded, and encodes the position information of the movable part by photoelectrically converting the modulated light. It was configured so that it could be extracted as an electrical signal.

そして、光学式スケールとしては。And as an optical scale.

（１）金属板にエツチングによりスリットを加工したも
の （π）ガラス、プラスチック等の透明基板上に銀、銅、
クロム、アルミニウムなどの金属を蒸着し、金属層のみ
をエツチングによってスリット状に削除したもの 等が用いられていた。(1) A metal plate with slits processed by etching (π) Silver, copper, etc. on a transparent substrate such as glass or plastic.
The metal layer used was one in which a metal such as chromium or aluminum was vapor-deposited and only the metal layer was removed in the form of a slit by etching.

しかし、これらはエツチング可能なスリット幅が金属の
厚みの２倍以上に制限され、微細な符号を記録すること
が困難であった。また、製作工程が複雑で、しかもエツ
チングに高価な感光性樹脂を用いる為、コスト高になる
といった欠点があった。However, in these methods, the slit width that can be etched is limited to at least twice the thickness of the metal, making it difficult to record fine symbols. In addition, the manufacturing process is complicated, and expensive photosensitive resin is used for etching, resulting in high costs.

〔発明の概要〕[Summary of the invention]

本発明の目的は、上記従来技術の欠点を解消し、簡単・
低コストに作製出来、しかも、高分解能の光学式スケー
ルを提供することにある。The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art, and to provide a simple and
The object of the present invention is to provide an optical scale that can be manufactured at low cost and has high resolution.

本発明の上記目的は、ポリカーボネート（ｐｏ　１ｙｃ
ａｒｂｏｎａｔｅ、以下ＰＣと称す）から成る透光性部
材の表面に、光透過部と、入射する光線に対しその入射
角が臨界角以上に設定された傾斜面から成る光非透過部
とを交互に形成した光学式スケールによって達成される
。The above object of the present invention is to obtain polycarbonate (polycarbonate).
arbonate (hereinafter referred to as PC)), a light-transmitting portion and a light-non-transmitting portion consisting of an inclined surface whose incident angle is set to be equal to or greater than a critical angle with respect to the incident light ray are alternately formed. This is achieved by means of a formed optical scale.

〔実施例〕〔Example〕

以下、本発明の実施例を図面を用いて詳細に説明する。 Embodiments of the present invention will be described in detail below with reference to the drawings.

第１図は、本発明の光学式スケールを用いて光学式エン
コーダを構成した例を示す斜視図である０図において、
１は光源、２はコリメータレンズ、３は本発明に基づい
たロータリー型の光学式スケールで、回転軸７に固定さ
れ、この駆動に伴なって回転する。４はＰＣから成る固
定光学格子で、５は前記光学格子４を透過した光を電気
信号に変換する受光素子、６は波形整形回路で、受光素
子５からの信号を波形整形して図の右側にＳで示したよ
うな信号波形に整形するものである。FIG. 1 is a perspective view showing an example of an optical encoder configured using the optical scale of the present invention.
1 is a light source, 2 is a collimator lens, and 3 is a rotary type optical scale based on the present invention, which is fixed to a rotating shaft 7 and rotates in accordance with the drive thereof. 4 is a fixed optical grating made of a PC; 5 is a light-receiving element that converts the light transmitted through the optical grating 4 into an electrical signal; 6 is a waveform shaping circuit that shapes the waveform of the signal from the light-receiving element 5 and displays it on the right side of the figure. The signal waveform is shaped into the signal waveform shown by S in FIG.

第２図は、前記光学式スケール３を下面から見た概略図
である。光学式スケール３はＰＣの透光性基板から成り
、その下面の周囲に、凸状に形成された標識部８を有し
ている。また、この標識部８には、光透過部９と光非透
過部１０とが交互に規則正しく形成され、第１図のよう
に照射された光を変調する。FIG. 2 is a schematic diagram of the optical scale 3 viewed from below. The optical scale 3 is made of a transparent PC board, and has a convex marker 8 around its lower surface. In addition, light transmitting parts 9 and light non-transmitting parts 10 are regularly and alternately formed in this marker part 8, and the irradiated light is modulated as shown in FIG.

第３図は、第２図の標識部の部分断面図である。前述の
光透過部９は、入射光Ｌ１に対し、その入射角が臨界角
より小さな角度をなす、例えば９ａのような平坦面から
成る。また、光非透過部ｌＯは、入射光Ｌ２に対し、そ
の入射角が臨界角以上の角度となるように傾斜している
傾斜面１０ａ及びｌＯｂから成る０例えば、傾斜面１０
ａと１０ｂのなす角度を９０”とし、傾斜面１０ａと１
０ｂとを合わせた水平方向の幅Ｗｌ（入射光の光軸に垂
直な面への傾斜面の投影像の幅を示す）と平坦面９ａ夫
々の幅Ｗ２とを同一とする。すると１図から明らかなよ
うに、傾斜面１０ａに入射した光は入射角が４５°とな
るので全反射されて直角に反射され、もう１つの他の傾
斜面１０ｂに４５＠の角度をなして入射し、再び全反射
されて直角に反射されてもとの入射側に戻る。又、傾斜
部１０ｂに入射した光についても上記と同様に入射側に
戻る。ところが、平坦面９ａに入射する光はそのまま透
過してしまう、このことは平坦面のみがスリットの役割
を果たすことを意味する。従って、この光学式スケール
３は丁度スリットと遮光部が同一幅１等ピッチで配列さ
れたものと同じとなる。また、前述の固定光学格子４に
も光学式スケール３と同様の凹凸が形成されている。FIG. 3 is a partial cross-sectional view of the marker portion of FIG. 2. The light transmitting portion 9 described above is made of a flat surface, such as 9a, which has an angle of incidence smaller than the critical angle with respect to the incident light L1. Furthermore, the light non-transmissive portion 10 is composed of inclined surfaces 10a and 10b that are inclined such that the incident angle thereof is equal to or greater than the critical angle with respect to the incident light L2.For example, the inclined surface 10
The angle between a and 10b is 90", and the inclined surfaces 10a and 1
The width Wl in the horizontal direction (indicating the width of the projected image of the inclined surface on the plane perpendicular to the optical axis of the incident light), which is the sum of the widths W1 and 0b, is the same as the width W2 of each of the flat surfaces 9a. Then, as is clear from Figure 1, the light incident on the inclined surface 10a has an incident angle of 45 degrees, so it is totally reflected and reflected at a right angle, and it forms an angle of 45@ to another inclined surface 10b. The light enters, is totally reflected again, is reflected at right angles, and returns to the original incident side. Further, the light incident on the inclined portion 10b also returns to the incident side in the same manner as described above. However, the light incident on the flat surface 9a is transmitted as is, which means that only the flat surface plays the role of a slit. Therefore, this optical scale 3 is exactly the same as one in which slits and light shielding parts are arranged with the same width and equal pitch. Furthermore, the above-described fixed optical grating 4 is also formed with concavities and convexities similar to those of the optical scale 3.

次に、本発明の光゛学式スケールを用いた光学式エンコ
ーダの動作を第１図及び第４図（Ａ）。Next, the operation of an optical encoder using the optical scale of the present invention is shown in FIGS. 1 and 4 (A).

（Ｂ）を用いて説明する。第４図は、光学式スケール３
．固定光学格子４及び受光素子５の略断面図で、（Ａ）
が光学式スケール３と固定光学格子４とに形成された標
識の位相が一致した状態、（Ｂ）が１／２周期位相がず
れた状態を示す、第１図において、光源ｌからの光はコ
リメータレンズ２により平行光とされ光学式スケール３
の上方から入射する。上述のように上方から入射した光
はその平坦面で光学式スケール３を透過する。又その傾
斜面では２回全反射されて光学式スケール３を透過しな
い、従って、光学式スケール３を透過した光により規則
的な光の明暗分布を生じる。This will be explained using (B). Figure 4 shows optical scale 3.
．． (A) is a schematic cross-sectional view of the fixed optical grating 4 and the light receiving element 5;
In FIG. 1, the light from the light source l is The collimator lens 2 converts the light into parallel light, and the optical scale 3
incident from above. As described above, the light incident from above is transmitted through the optical scale 3 through its flat surface. Further, the light is totally reflected twice on the inclined surface and does not pass through the optical scale 3. Therefore, the light that has passed through the optical scale 3 produces a regular brightness/dark distribution of light.

ここで光学式スケール３はその回転軸７と共に図示矢印
方向に回転し、その明暗分布も同方向に移動する。ここ
で、固定光学格子４と光学式スケールとに形成された符
号は同一、即ち、固定光学格子４の明暗分布と、入射す
る光の明暗分布とは等ピッチとなっているので、双方の
凹凸の位相が第４図（Ａ）の如く一致した時には、光学
式スケール３を透過した光は全て固定光学格子４を透過
するので受光素子５へ入射する光量は最大となる。Here, the optical scale 3 rotates in the direction of the arrow shown in the figure together with its rotation axis 7, and its brightness distribution also moves in the same direction. Here, the signs formed on the fixed optical grating 4 and the optical scale are the same, that is, the brightness distribution of the fixed optical grating 4 and the brightness and darkness distribution of the incident light are at the same pitch, so the unevenness of both When the phases match as shown in FIG. 4(A), all of the light that has passed through the optical scale 3 passes through the fixed optical grating 4, so the amount of light that enters the light receiving element 5 becomes maximum.

又、凹凸の位相が第４図（Ｂ）のように１７２周期ズし
た時には光学格子同士の傾斜面と平坦面とが夫々対応し
た位置となるので、光学式スケール３を透過する光は全
て固定光学格子４の傾斜面で２回全反射されて入射側に
戻り、受光素子５へ入射する光量は最小となる。Furthermore, when the phase of the concave and convex shifts by 172 periods as shown in Figure 4 (B), the inclined surfaces and flat surfaces of the optical gratings are in corresponding positions, so that all the light that passes through the optical scale 3 is fixed. The light is totally reflected twice on the inclined surface of the optical grating 4 and returns to the incident side, and the amount of light incident on the light receiving element 5 is minimized.

そして、この光量が最大になるときと最小になるときと
の間には、光学式スケール３の平坦面と固定光学格子４
の平坦面とが部分的に一致し、その一致した部分の面積
の割合に応じた光量を受光素子５は受光する。従って、
受光素子５からの信号は正弦波状となり、この信号は波
形整形回路６により第１図のＳのようなパルス状の信号
に整形される。Between the time when the amount of light is maximum and the time when it is minimum, there is a gap between the flat surface of the optical scale 3 and the fixed optical grating 4.
The light-receiving element 5 receives a light amount corresponding to the proportion of the area of the matched portion. Therefore,
The signal from the light-receiving element 5 has a sinusoidal waveform, and this signal is shaped by the waveform shaping circuit 6 into a pulse-like signal such as S in FIG.

ここでＰＣは、光透過率が高く、熱的にも安定で、前記
構造の光学式スケールを形成する材料として特に適して
いる。また、ＰＣは比較的高い屈折率（ｎ＝　１．５８
）を有しており、迷光が生じにくい利点を有する。これ
を以下に説明する。Here, PC has a high light transmittance and is thermally stable, making it particularly suitable as a material for forming the optical scale of the structure. In addition, PC has a relatively high refractive index (n = 1.58
), which has the advantage that stray light is less likely to occur. This will be explained below.

第５図は、本発明の光学式スケールの部分拡大断面図で
ある。ここで、光学式スケール３に垂直に照射された光
は、第３図で説明したような挙動を示すが、一般には光
源部の乱反射等で生じた光が、光学式スケール３に斜め
に入射する場合がある０例えば、光線Ｌ３が傾斜面ｆｏ
ｂに入射角（傾斜面の法線Ｎに対する角度）θで入射す
る場合、光学式スケール３をＡＢＳ樹脂等の屈折率の低
い材料で形成したのでは、臨界角θ２〉θとなり、光線
Ｌ３の一部が透ｍして迷光Ｌ５となってしまう、その点
、本発明のように光学式スケールをＰＣで形成すれば、
臨界角θ１が小さく、θ〉θ１となって光線Ｌ３は傾斜
面１０ｂで全反射されて反射光Ｌ４となり、光学式スケ
ール３を透過しない、このようにＰＣを用いると全反射
する入射角の範囲が広く、迷光が生じにくい為、光学式
エンコーダ等に用いた場合にＳＮ比の高い信号検出が可
能である。また、入射角に対する制限が緩和される為、
光源等の設計が容易になる。FIG. 5 is a partially enlarged sectional view of the optical scale of the present invention. Here, the light irradiated perpendicularly to the optical scale 3 exhibits the behavior explained in FIG. For example, the ray L3 may fall on the inclined surface fo
If the optical scale 3 is made of a material with a low refractive index such as ABS resin, the critical angle will be θ2>θ, and the light ray L3 will be On the other hand, if the optical scale is formed using a PC as in the present invention, a part of the scale will be transmitted through and become stray light L5.
The critical angle θ1 is small, θ>θ1, and the light ray L3 is totally reflected on the inclined surface 10b and becomes reflected light L4, which does not pass through the optical scale 3. If a PC is used in this way, the range of incident angles where total reflection occurs Since the sensor has a wide area and does not easily generate stray light, it is possible to detect signals with a high signal-to-noise ratio when used in an optical encoder or the like. In addition, since the restrictions on the angle of incidence are relaxed,
Design of light sources, etc. becomes easier.

本発明は１以上の実施例に限らず、種々の応用が可能で
ある０例えば、光学式エンコーダに用いる場合、透過光
ではなく、反射光を検出するようにしてもかまわない、
又、ロータリー型の光学式スケールだけでなく、リニア
型の光学式スケールにも適用出来るのは言うまでもない
。The present invention is not limited to one or more embodiments, and can be applied in various ways.For example, when used in an optical encoder, reflected light may be detected instead of transmitted light.
Furthermore, it goes without saying that the present invention can be applied not only to rotary type optical scales but also to linear type optical scales.

〔発明の効果〕〔Effect of the invention〕

以上説明したように１本発明はＰＣの基板に光非透過部
を構成する傾斜面を加工することによって光学式スケー
ルを形成したので、高分解能のスケールを簡単に、しか
も高精度に作製出来る効果を有する。As explained above, in the present invention, an optical scale is formed by processing a sloped surface that constitutes a non-light-transmitting part on a PC board, so the effect is that a high-resolution scale can be easily manufactured with high precision. has.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明の光学式スケールを用いて光学式エンコ
ーダを構成した例を示す斜視図、第２図は本発明の光学
式スケールの一実施例を示す概略図、第３図は第２図の
光学式スケールの部分断面図、第４図（Ａ）、（Ｂ）は
夫々第１図の光学式エンコーダの動作を説明する要部断
面図、第５図は光学式スケールに斜めに入射した光線の
挙動を説明する略断面図である。 ３−ｍ−光学式スケール、　８−一一標識部、９−−一
光透過部、　　　　９ａ−−一平坦面、１０−ｍ−光非
透過部、１０ａ、１０ｂ−ｍ−傾斜面。FIG. 1 is a perspective view showing an example of an optical encoder configured using the optical scale of the present invention, FIG. 2 is a schematic diagram showing an example of the optical scale of the present invention, and FIG. 4(A) and 4(B) are sectional views of main parts explaining the operation of the optical encoder shown in FIG. 1, and FIG. 5 is a partial cross-sectional view of the optical scale shown in FIG. FIG. 3-m-optical scale, 8-11 labeled portion, 9--one light transmitting portion, 9a--one flat surface, 10-m-light non-transmitting portion, 10a, 10b-m-slanted surface.

Claims (1)

【特許請求の範囲】[Claims] （１）ポリカーボネートから成る透光性部材の表面に、
光透過部と、入射する光線に対しその入射角が臨界角以
上に設定された傾斜面から成る光非透過部とを交互に形
成した光学式スケール。(1) On the surface of a translucent member made of polycarbonate,
An optical scale in which light-transmitting parts and non-light-transmitting parts each consisting of an inclined surface whose angle of incidence is set to be greater than a critical angle with respect to an incident light beam are alternately formed.