Yeah, I understood that ring motors were applied in a "direct-drive"
configuration, and that USM micromotors, the rotating types, were used
as an alternative to and in the much the same way as conventional
motors. But rotating USM motors aren't all just high frequency AC
electric motors, they can be a pure USM system where the "slider" of a
linear or annular motor is in the form of a rotor that is spun by the
"stator" when it produces a wave of ultrasonic vibrations. Which
types of motor are in what brand of lens....... I don't know.
It was the third possibility that I was unsure of. That is, if any
lens used linear (ie straight not ring or micro) USM motors that
simply moved back and forth through a limited range and moved the
focusing group directly. If any lens had such a motor, I wondered if
it would have the power to do the job in direct-drive configuration,
or if it would need to work through a gear-train.
I'm not the gearhead that I once was, who knew the specs of every
camera in the stores. The insides of most cameras these days are a
complete mystery to me.
Life's simpler that way :-)
regards, Anthony
"Of what use is lens and light
to those who lack in mind and sight"
(Anon)
On 5 February 2010 13:23, Adam Maas <[email protected]> wrote:
> Ring-type USM motors do not use a gear-train, they are built into the
> focusing helical, this covers some USM and AF-S and all HSM and SSM
> motors. Micro-motor USM (which really isn't USM, Sony's Silent AF
> Motor [SAM] terminology is more correct) uses a gear-train but really
> is just a conventional motor with non-conventional power as they
> discovered that micromotors are much quieter when driven by
> high-frequency AC.
>
> -Adam
>
> On Thu, Feb 4, 2010 at 8:31 PM, Anthony Farr <[email protected]> wrote:
>> The short answer is to read this:
>> http://en.wikipedia.org/wiki/Ultrasonic_motor
>>
>> My understanding is that USM, HSM, SDM, etc, &s shouldn't be likened
>> to conventional electric motors with their armatures and brushes and
>> all the other stuff (I'm sure that's a technical term, I've heard an
>> engineer use it). In the most elegant examples the USM is an annular
>> linear motor that encircles the component to be shifted, be that the
>> focusing helix or the diaphram mechanism. In that application RPM
>> doesn't apply, because the total range of movement is less than 360
>> degrees. A straight linear motor applying its movement in one
>> location could possibly shift the focusing group directly without a
>> helix, but I'm unsure if any USM systems are powerful enough to
>> directly move the lens without a helix or gear train to step up the
>> torque, and I couldn't be arsed to research it myself. And some USM
>> motors resemble a can motor (one configuration of a standard electric
>> motor) with an output shaft, but differ in that they excite the
>> rotation by a different method which has less mechanical resistance
>> and thus spins more freely.
>>
>> IIRC the first linear drive lenses were in the Rolleiflex SLX 6x6
>> system, but don't know if USM was used. The technology ~was~
>> available at the time.
>>
>> regards, Anthony
>>
>> "Of what use is lens and light
>> to those who lack in mind and sight"
>> (Anon)
>>
>>
>>
>> On 5 February 2010 10:27, Larry Colen <[email protected]> wrote:
>>> Do the motors turn at 900,000 RPM (15,000 hz * 60)?
>>>
>>> --
>>> Larry Colen [email protected] sent from i4est
>>>
>>>
>>>
>>>
>>>
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>
>
> --
> M. Adam Maas
> http://www.mawz.ca
> Explorations of the City Around Us.
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