Imaging device and lens focusing method

A lens focusing method, which is applied to an imaging device, wherein the imaging device comprises a focusing wheel, two photoelectric sensors, at least three gratings, a processor, a motor, and a lens, wherein gratings of the at least three gratings are distributed on an inner sidewall of the focusing wheel, grating gaps having a same width exist between adjacent gratings, when the focusing wheel rotates, a grating of the at least three gratings passes the two photoelectric sensors;

• the method comprises:
• the processor determining a first electrical signal generated by a first photoelectric sensor of the two photoelectric sensors, wherein a level of the first electrical signal changes when a grating of the at least three gratings passes the first photoelectric sensor;
• determining a second electrical signal generated by a second photoelectric sensor of the two photoelectric sensors, wherein a level of the second electrical signal changes when a grating of the at least three gratings passes the second photoelectric sensor;
• determining a current rotation direction of the focusing wheel based on the first electrical signal and the second electrical signal as well as a preset parameter table, wherein the parameter table contains a correspondence among the first electrical signal, the second electrical signal, and a rotation direction of the focusing wheel;
• determining a current rotation angle of the focusing wheel based on the number of level jumps of the first electrical signal or the number of level jumps of the second electrical signal, wherein the level jump is a jump from high level to low level or a jump from low level to high level;
• driving the motor to focus the lens according to the current rotation direction and the current rotation angle of the focusing wheel wherein, the imaging device further comprises a fixing member, on which the two photoelectric sensors are mounted;
• a grating ratio is a preset value, and a current phase difference between positions of the two photoelectric sensors on the fixing member with respect to the grating period conforms to a preset phase difference;
• wherein, the grating ratio is a ratio of a width of one grating to a width of one grating period, and one grating period consists of one grating and one adjacent grating gap;
• the current phase difference is calculated based on the grating period angle and a sensor angle, the grating period angle is an angle of one grating period on the inner sidewall of the focusing wheel, and the sensor angle is an angle between the two photoelectric sensors on the inner sidewall of the focusing wheel;
• wherein, if the grating ratio d is d=0.5, the preset phase difference ω is:
• 0<ω<360° and ω≠180°,
• if the grating ratio d is 0<d<0.5, the preset phase difference ω is:
• 0<ω<d*360° or (1−d)*360°<ω<360°,
• if the grating ratio d is 0.5<d<1, the preset phase difference ω is:
• 0<ω<(1−d)*360° or d*360°<ω<360°.

An imaging device, wherein the imaging device comprises a focusing wheel, two photoelectric sensors, a fixing member, a processor, a motor, a main lens barrel, a focusing lens barrel, and a first lens;

• the focusing lens barrel is disposed within the main lens barrel to be axially movable;
• the first lens is disposed fixedly within the main lens barrel;
• at least two gratings are disposed on an inner sidewall of the focusing wheel, and grating gaps between two adjacent gratings are equal;
• a grating of the at least two gratings passes the two photoelectric sensors when the focusing wheel rotates;
• the fixing member is fixed on an outer sidewall of the main lens barrel close to the motor;
• the two photoelectric sensors are mounted on the fixing member, the focusing wheel is rotatably mounted on an outer sidewall of the main lens barrel away from the motor, a first gap exists between the focusing wheel and the fixing member along an axial direction of the main lens barrel;
• the motor is mounted on an outer sidewall of the main lens barrel;
• the photoelectric sensors are configured to generate electrical signals and send the generated electrical signals to the processor;
• wherein, the electrical signals generated by the photoelectric sensors change when a grating passes the photoelectric sensors;
• the processor is electrically connected to the motor, and the processor is configured to drive the motor to move the focusing lens barrel according to the electrical signals sent by the photoelectric sensors.