Abstract: An optical device for measuring a distance includes a prism, a beam splitter, a detector and a light source. The prism has a first light-incident surface and a plurality of first light-transmitting surfaces. The first light-incident surface is opposite to the first light-transmitting surfaces. The first light-transmitting surfaces intersect at a vertex. The beam splitter has a light-passing surface, a second light-incident surface and a second light-transmitting surface. The second light-incident surface faces the first light-transmitting surfaces. The light-passing surface is opposite to the second light-incident surface. The beam splitter includes a partially mirror surface facing the light-passing surface and the second light-incident surface. The light-passing surface faces a grating. The detector corresponds to the second light-transmitting surface. The light source emits a light beam to the first light-incident surface. An optical axis of the light beam passes through the vertex and the beam splitter.

Abstract: An optical device for measuring a distance includes a prism, a beam splitter, a detector and a light source. The prism has a first light-incident surface and a plurality of first light-transmitting surfaces. The first light-incident surface is opposite to the first light-transmitting surfaces. The first light-transmitting surfaces intersect at a vertex. The beam splitter has a light-passing surface, a second light-incident surface and a second light-transmitting surface. The second light-incident surface faces the first light-transmitting surfaces. The light-passing surface is opposite to the second light-incident surface. The beam splitter includes a partially mirror surface facing the light-passing surface and the second light-incident surface. The light-passing surface faces a grating. The detector corresponds to the second light-transmitting surface. The light source emits a light beam to the first light-incident surface. An optical axis of the light beam passes through the vertex and the beam splitter.

Abstract: An apparatus for measuring pattern of a grating device is provided. In an embodiment, the apparatus comprises a light source unit, an image unit, a processing unit, and a movement unit. The light source unit irradiates to a surface of the grating device. The image unit acquires a plurality of first digital images including an image on the surface of the grating device and images due to Talbot effect between the surface and a first position with respect to the grating device. The image unit acquires a plurality of second digital images due to Talbot effect at a second position determined based on the first digital images when the movement unit produces a relative movement between the image unit and grating device. Based on the acquired digital images, analysis, inspection on the grating device, or comparison of the grating device with a reference grating scale, can be implemented optionally.

Abstract: An apparatus for measuring pattern of a grating device is provided. In an embodiment, the apparatus comprises a light source unit, an image unit, a processing unit, and a movement unit. The light source unit irradiates to a surface of the grating device. The image unit acquires a plurality of first digital images including an image on the surface of the grating device and images due to Talbot effect between the surface and a first position with respect to the grating device. The image unit acquires a plurality of second digital images due to Talbot effect at a second position determined based on the first digital images when the movement unit produces a relative movement between the image unit and grating device. Based on the acquired digital images, analysis, inspection on the grating device, or comparison of the grating device with a reference grating scale, can be implemented optionally.