This paper describes a theoretical analysis in accordance with the characteristics and main points of calculating the gear drive with low number of teeth and presents a basis for the rational choice of gear parameters in order to avoid the undercut and pointed teeth of pinions.

The minimum number of teeth of double involute gear to avoid undercutting is studied in transverse plane.

Gear involute-error measurement of the small module gear based on CCD;

Aim at the measuring difficulty of the small module gear, the measurement method of gear parameters based on the ma-chine vision is presented.

Especially aimed to the small module gear with small dimension, the method can carry out on-line non-touch measurement and solve the difficult problems, which can't solve through the traditional measurement.

The transmission gears used in high precise apparatuses and instruments are mostly fine-pitch gears that can drive stably.

Fine-pitch gear is widely used in high precision instruments and meters, and its accuracy has direct influence on the instruments operational performance and work life span, so the detection and measurement of fine-pitch gear is vital.

The bi-meshing detecting technology, high-resolution raster system, and infinitely variable speed 'flexible' driving are used to detect and sort micron gear's composite error rapidly and automatically, and the apparatus are also developed.

According to the feature of involute micron gear, a measuring system of involute straight spur gear is designed .