Photoelectric detection unit, photoelectric encoder system, and motor

A photoelectric detection system, comprising:

• a light source;
• a grating having a plurality of slits for measurement, wherein a slit period of the grating is P;
• and
• a photoelectric detection device, wherein it is able to form a relative displacement between the photoelectric detection device and the grating, the light source casts on the photoelectric detection device scanning light stripes which represents the relative displacement, there are a plurality of photoelectric detection units formed on the photoelectric detection device, and the photoelectric detection units are configured to detect the scanning light stripes and convert the scanning light stripes into an electrical signal representing the relative displacement;
• a processing circuit, configured to convert the electrical signal into a relative displacement;
• wherein:
• a geometric shape of the photoelectric detection units comprises a first edge and a second edge, and two vertices of the first edge and two vertices of the second edge coincide with each other to form a closed graph;
• the geometric shape of the photoelectric detection unit is that:
• after the geometric shape of the photoelectric detection unit undergoes a fan-shape-to-rectangle transformation, the first edge is described by a first description function and the second edge is described by a second description function;
• alternatively, the geometric shape of the photoelectric detection unit is that:
• the first edge is described by the first description function and the second edge is described by the second description function;
• and
• the first description function comprises a first tilting function and a first harmonics filtering function, the second description function comprises a second tilting function and a second harmonics filtering function, and a difference between the first description function and the second description function is a function directly proportional to cos ω0x, wherein ω0=2π/P, and x is a coordinate value taken along a grating-period direction.