Abstract: A displacement measuring device allows a plurality of light beams to be incident at positions on a scale or diffracted at points on a scale grating, which are farther spaced away from each other than the diameter of the light beams on the scale grating, and makes an angle of incidence of each light beam on the scale equal generally to an angle of transmission of the diffracted light beam of each light beam. This makes the strength of a detection signal impervious to variations in pitch angle and allows for providing good signals. Accordingly, it is possible to attach the device easily to an apparatus and provide improved ease of use for the device.

Abstract: A displacement measuring device allows a plurality of light beams to be incident at positions on a scale or diffracted at points on a scale grating, which are farther spaced away from each other than the diameter of the light beams on the scale grating, and makes an angle of incidence of each light beam on the scale equal generally to an angle of transmission of the diffracted light beam of each light beam. This makes the strength of a detection signal impervious to variations in pitch angle and allows for providing good signals. Accordingly, it is possible to attach the device easily to an apparatus and provide improved ease of use for the device.

Abstract: A holographic grating 12 is formed on one surface of a scale substrate 11 in such a manner that a light source is disposed over the other surface of the scale substrate 11. The scale substrate 11 is formed of a transparent material. A reflection film 13 is directly deposited on the grating surface. A protection substrate 15 is adhered to the reflection film 13 on the scale substrate 11 with adhesive agent 14. Thus, a reflection-type hologram scale 1 is accomplished.