Chinese name: ultrasonic motor mbth: ultrasonic motor type: photography belongs to the origin, definition, development, working principle and characteristics of numbers. Before the ultrasonic motor appeared, there were actually piezoelectric motors driven by the vibration characteristics of piezoelectric materials, but its frequency was not limited to the range of ultrasonic waves. As early as 1948, William and Brown applied for the American patent of piezoelectric motor. 196 1 year, baoluhua watch company developed a watch driven by a tuning fork; From 1970 to 1972, Siemens and Panasonic developed off-line piezoelectric stepping motors, but they were not widely used at that time because they could not achieve greater output and efficiency. 1973, H.V. Barth of IBM Company of the United States first proposed a motor driven by ultrasonic vibration using piezoelectric elements. However, due to the problem of wear, just like the previous watch case, it was published without practical application. Almost at the same time, V.H. Lavrinenko of Russia also designed some motor structures with the same driving principle; 1978, P.E. Vasiliev used ultrasonic transducer as the driving source of the motor, but did not develop a complete motor structure. 1980, Toshiiku Sashida of Japan developed an ultrasonic motor driven by a vibrating plate, which has a relatively complete motor structure. At this point, the concept of driving the motor by ultrasonic vibration generated by piezoelectric materials began to develop slowly. Although these ultrasonic motors still have no practical application because of wear and temperature rise, they have the characteristics of high precision, low speed and high torque. It was not until 1982 that Nian Shengzhi developed a new driving mode of ultrasonic motor, and the improvement of wear was considered in the design. This is the first ultrasonic motor with real commercial application value, and it has been applied to the automatic focusing system of cameras for the first time, which is also the most used field of ultrasonic motors at present. Canon's EF autofocus lens has two built-in motors, one for autofocus and the other for electromagnetic aperture. There are three types of Canon autofocus motors: arc drive (AFD), ultrasonic motor (USM) and micro motor (MM). Arc motor is the earliest motor used in Canon EF autofocus lens. It is an arc brushless motor, so that it can be placed in a cylindrical lens barrel without changing the shape of the lens barrel. Because of its small rotor size, it has very good start/stop response and control, and because of its brushless design, it has a long service life. Although with the appearance of high-performance ultrasonic motor and low-cost micromotor, the lens using this motor is rare now, we can still "see" it in some famous EF lenses, such as EF50mm f/2.5 compact macro and EF 100-300mm f/5.6 L and EF 135mm f/2.8. Ultrasonic motor is very different from traditional motor. No matter how many kinds of traditional motors there are, their principle is generally to convert electromagnetic force into rotating force, and the rotating force of ultrasonic motor is generated by the energy of ultrasonic vibration. As mentioned above, ultrasonic motors can be divided into two types: ring and miniature ultrasonic motors. The diameter of the stator and rotor of the ring ultrasonic motor is equivalent to the diameter of the lens barrel, which can be perfectly combined with the lens barrel. The advantages of ultrasonic motor are as follows: 1. Because of its low speed and large torque, it can directly drive the lens without additional deceleration mechanism; Second, the positioning torque is large, in other words, when the motor stops, the lens automatically stops focusing like a brake; 3. The structure is very simple; 4. The start-stop control ability is very good, it can be started quickly or stopped immediately, and the control is very accurate; 5. The operation is very quiet-almost silent. In addition, Canon's ring ultrasonic motor has the following characteristics: 6. Its high efficiency and low energy consumption make it possible to use the battery of the camera to supply power; 7. The ring motor and lens barrel are very suitable; 8. Low rotation speed is very suitable for lens driving; 9. The rotating speed can be continuously and steplessly adjusted in a large range from 0.2RPM (one revolution every five minutes) to 80RPM (80 revolutions per minute), so the lens can be driven at high speed with high precision; 10. It can realize high-precision manual electric drive focusing, which is the so-called full-time manual function; 1 1. The working temperature range is very wide, and it can work normally in the temperature environment of minus 30 degrees Celsius to minus 60 degrees Celsius, ensuring stable work in harsh environment. Different from ring ultrasonic motor, the stator and rotor of micro ultrasonic motor are integrated in a very small device. Compared with the ring ultrasonic motor, the micro ultrasonic motor has the following characteristics: because there is no limit on the diameter of the lens, the micro ultrasonic motor can be installed in various lenses without considering the structure of the optical system; Its rotor, stator and energy output are integrated into a very small device, so its volume and weight are only about half of that of the ring ultrasonic motor; Its cost is only one-third of that of ordinary ring ultrasonic motor, so it can be used for low-cost lenses on a large scale. Generally speaking, the ring ultrasonic motor is mainly used for L-class professional lenses, and the micro ultrasonic motor is mainly used for what we call amateur lenses, but Canon's amateur lenses also use the ring ultrasonic motor, namely: EF20-35 MF/3.5-4.5 USM; EF24-85mm f/3.5-4.5 USM； EF28- 105mm f/3.5-4.5 USM/EF28- 105mm f/3.5-4.5 USM II； EF28- 135mm f/3.5-5.6 are USM and EF 100-300mm f/4.5-5.6 USM. As ordinary photographers, if we use the above lens, we can also feel the quiet, high-speed autofocus and full-time manual fun brought by the ring ultrasonic motor. Micro-motor, in addition to arc motor and ultrasonic motor, Canon has another kind of motor-micro-motor, which is generally used in Canon's low-priced mass lenses, such as EF50mm f/ 1.8II and those non-USM mass zoom lenses, such as Ef28-80mm f/3.5-5.6; EF75-300mm f/4-5.6, etc. However, Canon has a "famous" lens that also uses a micromotor, which is EF 100mm f/2.8 Macro macro macro lens. I think Canon thinks that people who use macro generally don't use autofocus. The application of full-time manual operation and internal focus/back focus in Canon EF lens Generally speaking, the lens using ring ultrasonic motor can realize full-time manual operation, while the lens using micro ultrasonic motor cannot, but this does not mean that micro ultrasonic motor cannot realize full-time manual operation. For example, the famous EF50mm f/ 1.4 uses a miniature ultrasonic motor, but it is the same as those lenses using a ring ultrasonic motor. Can also be full-time manual, so we can say that Canon is unwilling to hand over the very useful function of full-time manual to all miniature ultrasonic motors in order to maintain the "superiority" of ring ultrasonic motors. The lens using ring ultrasonic motor generally adopts internal focusing or rear focusing structure, so the front lens of the lens will not rotate when focusing, while most micro ultrasonic motors and micromotors and many lenses using arc motors can't. Of course, there are exceptions. For example, the EF 135mm f/2.8 soft-focus lens uses an arc motor. EF lenses such as EF24mm f/2.8 and EF20-35mm f/2.8 L, which have been replaced by EF 17-35mm f/2.8 L USM, define that the frequency range of sound that the human ear can hear is about 20 Hz ~ 20 kHz, and frequencies above 20 kHz that the human ear cannot recognize are called ultrasonic waves. So what exactly is an ultrasonic motor? What is its basic working principle? To put it simply, the piezoelectric material is made to generate mechanical vibration of ultrasonic frequency by using the characteristic that the input voltage will deform, and then the ultrasonic motor is made to rotate or move linearly like an electromagnetic motor through the design of the friction drive mechanism. Usually, when the electromagnetic motor is running, we will feel noise, because the internal structure of the motor is vibrating, and the vibration frequency is just within the frequency range that our ears can feel. The vibration frequency of ultrasonic motor is designed outside the range that human ears can hear, so we can't feel any sound when it runs, so we feel very quiet, which is a very important feature of ultrasonic motor. Development 1987. Canon introduced the first lens with annular USM: EF 300/2.8L USM. Anatomy map 1990, Canon realized mass production and began to apply annular USM in a large number of ordinary lenses. 1992, Canon developed a miniature USM, which accelerated the process of full USM of EF lens. Working principle The structure and principle of annular USM can be divided into three types according to the mode of ultrasonic vibration energy conversion: 1, standing wave type; Schematic diagram 2, traveling wave type; 3. Vibrating reed type. USM used in CANONEF lens is traveling wave type. The ring ultrasonic motor has a simple structure and consists of an elastic stator and a rotor. The stator is a metal ring with piezoelectric ceramic elements at the bottom and trapezoidal protrusions at the top. The stator is made of special materials, and its thermal expansion coefficient is the same as that of piezoelectric ceramic elements, which can avoid the influence of temperature change. The rotor is an aluminum ring and is combined with the stator through a flange spring. Because the aluminum material is soft, the joint has been specially treated to increase the wear resistance. Features The basic characteristics of USM are: 1, with low speed and large torque output characteristics; 2, the braking torque is large; 3, the structure is simple; 4. The controllability of motor starting and braking is very good; 5, the rotating sound is very small, almost silent. In addition to the above basic characteristics, Canon annular USM has its own characteristics: schematic diagram 6, high efficiency and low power consumption; 7. The ring motor can be perfectly combined with the mirror body; 8. Low speed, especially suitable for AF driving of lens; 9. The rotating speed can be arbitrarily controlled within the range of 0.2 rpm to 80 rpm; 10, which can realize electronic MF with adjustable sensitivity; 1 1. The working environment temperature is -30℃ ~ +60℃. Canon announced three specifications of annular USM: USM-M1USM-L1USM-L2 size (mm): φ 62-54x10φ 77-67x/KLOC-0. EF 100/2 USM； EF 200/2.8L USM； EF 300/4L USM； EF 28-80/3.5-5.6 USM； EF 28- 105/3.5-4.5 USM； EF 35- 135/4-5.6 USM； EF 35-350/3.5-5.6L USM； EF 70-2 10/3 . 504 . 5 USM； EF 100-300/4.5-5.6 USM； EF 50/ 1.0L USM； EF 85/ 1.2L USM； EF 200/ 1.8L USM； EF 300/2.8L USM； EF 400/2.8L USM； EF 500/4.5L USM； EF 600/4L USM； EF 28-80/2.8-4 liters USM weight (grams): 26 45 45...USM-M 1 and USM-L 1 are basically used now, but USM-L2 is no longer used.