Single-track absolute grating scale and image coding method thereof

A single-track absolute grating scale and image encoding method thereof, comprising a light source, a reflector, incremental scale grating lines, a glass substrate, a movable diaphragm, a photoelectric receiver, and an indication grating; the light source and the reflector are combined into an illumination light path; the incremental scale grating lines having the same width are engraved on the glass substrate at equal intervals; milestone flags are engraved in parallel at equal intervals below the incremental scale grating lines on the glass substrate; the indication grating is embedded in an opening at the left upper part of the movable diaphragm; an upper and a lower CMOS sensors are respectively embedded in an upper and a lower symmetrical openings on the right of the movable diaphragm; the indication grating is installed closely against the glass substrate; the installation position of the upper CMOS aligns to the incremental scale grating lines; the installation position of the lower CMOS aligns to the milestone flags; and the light beams of the incremental scale grating lines and the indication grating form Moire fringes projected onto the photoelectric receiver. The present invention improves the acquisition speed of image information, improves code measurement accuracy, and can reliably encode, simply decode and quickly output a result.