What is different about USM motors is that they use ultrasonic vibration energy which is converted into rotational force. Play Video. To be effective, a ring-type USM motor needs to meet certain requirements. It must be powerful enough to drive the focusing lens group quickly and easily at low speed, so as to avoid the need for a gear system to reduce the speed.
It must exhibit high levels of holding power, so that once the motor is switched off, the focusing lens group is held in place without any further input needed. It should be simple to manufacture, and should start and stop quickly to ensure the best focus response.
It should also be as quiet as possible in use. In addition to these features, ring-type motors are also highly efficient and have low power consumption to maximise the camera battery life. Being ring-shaped, they are ideal for fitting within the lens barrel. The ring-type USM is actually very simple in operation. It is composed of a rotor and a stator — an elastic body with a piezoelectric ceramic voltage element attached to it.
Applying an AC current with a resonant frequency around 30kHz to the stator creates vibrations that cause the rotor to rotate continuously. The frequency of 30kHz is in the ultrasonic range, and this is where the USM motors derive their name. The piezoelectric element generates ultrasonic waves which, a bit like ocean waves propelling a surfer, cause the rotor to create a rotational force that moves the focusing group.
Switching the current between two different phases changes the direction of the ultrasonic waves. Consequently, the focusing group can be made to move in different directions, giving control over the direction, speed and degree of focus adjustment. Unlike the ring USM, where the stator and rotor are separate parts, in the Micro USM design the rotor, stator and drive gear are combined into one unit roughly half the weight of a ring-type USM motor.
While the more powerful ring-type USM is designed to fit in the circular barrel of a lens, making it ideal for use in large professional zoom lenses, the Micro USM motor was created to fit in a wide range of lenses without being restricted to the size of the lens barrel. Micro motors are also cheaper to produce, making them more suitable for use in consumer lenses where cost is an issue. There are four piezoelectric layers, each constructed from two alternating phase piezoelectric elements.
Applying an AC current to only the A-phase causes the stator to vibrate left and right. If current is applied to the B-phase, the stator will rotor forwards and backwards. When current is applied to both the A-phase and the B-phase, the resulting motion is rotational as the tip of the stator moves, for example, left, back, right, forward, left, back, right, forward.
This rotational force is applied to the main drive gear, which in turn is used to drive the gears of the focusing mechanism. It functions in a very similar way, but the length of the unit has been greatly reduced to allow it to be used in ultra-compact zoom lenses.
The reduction in size has been achieved by reconfiguring the rotor and stator so that, instead of the two being aligned in a row, part of the stator is placed inside the rotor. This required the creation of a new format of vibration, so that the resonant frequency of the piezoelectric elements was not too high, resulting in insufficient vibrational amplitude.
The next focusing motor technology developed was a little different. First introduced in , STM lenses are good for stills but they're great for video because the STM stepper motor produces smooth, quiet focusing movement. Download a user manual for your Canon product. Download firmware for your Canon product. Browse our frequently asked questions. Keep up to date on all latest product information.
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Canon Focusing Technology. When we look at a photograph or movie, one of the first things that we notice is whether it is in focus or not. Since , when Canon became the first company to integrate a focusing motor inside the lens, mulitple motors have been introduced that are designed to acquire and track focus for fast moving subjects. All while retaining control for focus accuracy, smoothness and silence. There are currently three main types of focusing motor technologies used within Canon lenses.
STM lenses shoot great photos and even better videos. Whilst some motors used in lenses make very audible and distracting mechanical noises when they focus, STM lenses focus quietly, allowing you to record more of what you naturally hear in an environment.
Canon's STM technology provides a range of extremely quiet lenses that are still fast enough to capture photos in most scenarios. USM lenses have been around for several years and are well known. A lens with almost no noise, fast, and a smooth-focus transition all in one. Looking back, Canon brought out their first lens in , the Serenar 50mm F3.
As a result, in , Canon introduced their first SLR single-lens-reflex camera with an AF autofocus drive motor function built into the body, the T Since then, Canon has realized the need for faster focusing speeds. Canon produced their first ring-type USM lens that was cost-effective.
It came out in and fitted into the EF mm F2. Much faster-focusing speed, much clearer pictures, with pinpoint accuracy on the focus point, and in some cases even assisted in the elimination of camera shake.
With autofocus, it became possible to photograph fast-moving objects with a sharp focus point and in lower light. Autofocus introduced track-and-shoot, an easier, more accurate setting to follow moving objects and still achieve a sharp focus point. These new advantages that the autofocus setting brought opened up doors to more creative photography. No more stagnant images; photographers were able to bring in the feeling of movement to their images.
The photos seemed as if they could come alive in your eyes. One is the speed at which you can focus. This system placed the autofocus motor—the motor that is used to drive a lens focusing mechanism—in the lens itself.
This was in contrast to other manufacturers, such as Nikon, who were placing the autofocus motor in the camera. These days, putting the AF motor in the lens is the standard, and pretty much every manufacturer makes lenses this way. Canon USM lenses use ultrasonic vibrations to power the autofocusing mechanism, and this comes with several clear advantages:. First, Canon USM lenses are fast.
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