Reflection-type optical encoder scale including a high reflection region and a low reflection region having a low reflection portion including a metallic chromium film, a chromium oxide film, and a chromium nitride film, and reflection-type optical encoder including same
A main object of the present disclosure is to provide a reflection-type optical encoder scale capable of sufficiently reducing the reflectance on a low reflection region. The present disclosure achieves the object by providing a reflection-type optical encoder scale comprising a high reflection region and a low reflection region alternately placed on a substrate, wherein the low reflection region includes a low reflection portion including a metallic chromium film formed on the substrate, and a chromium oxide film and a chromium nitride film randomly formed on the metallic chromium film; and the high reflection region has higher reflectance of incident light from opposite side to the substrate of the reflection-type optical encoder scale, than the low reflection region.
1. A reflection-type optical encoder scale comprising:
a high reflection region and a low reflection region, alternately placed on a substrate,
wherein the low reflection region includes a low reflection portion including a metallic chromium film placed on one surface of the substrate, and a chromium oxide film and a chromium nitride film placed on a surface of the metallic chromium film, on a side opposite to the substrate,
wherein the high reflection region has higher reflectance of incident light from the side opposite to the substrate of the reflection-type optical encoder scale than the low reflection region,
wherein the low reflection region includes the metallic chromium film,
wherein the chromium nitride film is placed on a surface of the metallic chromium film on the side opposite to the substrate, and
wherein the chromium oxide film is placed on a surface of the chromium nitride film on a side opposite to the metallic chromium film.
2. The reflection-type optical encoder scale according to claim 1 , wherein an outermost surface of the low reflection region is the chromium oxide film or the chromium nitride film.
3. The reflection-type optical encoder scale according to claim 1 , wherein the high reflection region includes the metallic chromium film formed on the substrate.
4. The reflection-type optical encoder scale according to claim 1 , wherein the high reflection region includes a metallic silver film or a silver alloy film containing silver as a main component, formed on the substrate.
5. The reflection-type optical encoder scale according to claim 1 , wherein the reflectance on the high reflection region, of any one of wavelengths in a wavelength range of 550 nm to 950 nm, is 60% or more, and
wherein a value of a ratio S/N represented by the following formula (1) is 100 or more,
the ratio S/N=the reflectance on the high reflection region/the reflectance on the low reflection region. (1)
6. A reflection-type optical encoder comprising:
the reflection-type optical encoder scale according to claim 1 ;
a light source configured to irradiate light to a surface of the reflection-type optical encoder scale, on a side wherein the low reflection portion is placed; and
a light detector configured to detect light from the light source, reflected by the reflection-type optical encoder scale.
7. A reflection-type optical encoder scale comprising:
a high reflection region and a low reflection region, alternately placed on a substrate,
wherein the low reflection region includes a low reflection portion including a metallic chromium film placed on one surface of the substrate, and a chromium oxide film and a chromium nitride film placed in any order on a surface of the metallic chromium film, on a side opposite to the substrate,
wherein the high reflection region has a higher reflectance of incident light from the side opposite to the substrate of the reflection-type optical encoder scale than the low reflection region,
wherein the reflectance on the high reflection region, of any one of wavelengths in a wavelength range of 550 nm to 950 nm, is 60% or more, and
wherein a value of a ratio S/N represented by the following formula (4) is 100 or more,
the ratio S/N=the reflectance on the high reflection region/the reflectance on the low reflection region. (4)
8. A reflection-type optical encoder comprising:
the reflection-type optical encoder scale according to claim 7 ;
a light source configured to irradiate light to a surface of the reflection-type optical encoder scale, on a side wherein the low reflection portion is placed; and
a light detector configured to detect light from the light source, reflected by the reflection-type optical encoder scale.