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Michael Feinberg is the Director of Product Marketing at Boston Micromachines Corporation.  He has over 10 years of marketing and engineering experience in various technology fields.  He can be reached at mrf@bostonmicromachines.com  and welcomes any comments about the content presented herein.

 

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Deformable mirrors in space???

Posted by Michael Feinberg on Thu, Jul 21, 2011 @ 11:14 AM
  
  
  
  
  

250px Crab Nebula

Boston Micromachines has been awarded US$ 1.2M in contracts by NASA's Small Business Innovation Research Program (SBIR) to support space-based astronomy research.  Now, one might wonder, considering this is astronomy, “why is anyone spending any money to develop deformable mirrors for use in space telescopes looking out at the stars?  I thought that deformable mirrors were used to remove aberrations introduced by the atmosphere.  There’s no atmosphere up there!”

Well, you’d be right:  There is no atmosphere up there.  But, there are aberrations:  In the optical system.  When systems are designed, none of them are completely perfectly aligned. There’s no such thing.  But, when you’re looking for planets around stars in other galaxies, you need things to be well aligned.  VERY well aligned.  So, to compensate for any misalignments introduced either during transit to space or thermal variations in the instrument, you can use a deformable mirror as part of an adaptive optics system.  So, for this, we are designing a 1021 segment (3063 actuator), tip-tilt-piston deformable mirror.  It is the largest ever designed of this type and is expected to be used as part of a coronagraph telescope for exo-planet research.

Two other things to worry about are power and weight.  In satellites, there is a very limited amount of power, and the weight greatly affects the cost to put the satellite into orbit.  In terms of the mirror, MEMS has that taken care of:  The power is extremely low and the weight is many orders of magnitude lower than traditional piezo-electric-based mirrors.  So, the other half of the equation is the drive electronics.  As part of this research, BMC is designing multiplexed drive electronics which will reduce the size and weight significantly and lower the power even further.

You put the two parts together, mirror hardware and drive electronics, and you have a low-cost, low-power, lightweight solution for the most cutting edge astronomy research going on right now.

If you have any questions, please contact me directly:  I would be happy to talk about these products or refer you to the folks who are attacking this challenging problem.

Link to press release.

(Image credit:  A giant Hubble mosaic of the Crab Nebula, a supernova remnant)

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How to select the right deformable mirror for you Part 2: Beam Shaping

Posted by Michael Feinberg on Tue, Jan 11, 2011 @ 11:37 AM
  
  
  
  
  

Laser spotIn our second installment of this series designed to boil down the questions that need to be answered before selecting the right mirror, we will review some of the past categories with alterations specific to laser beam shaping and introduce a few new ones that pertain only to beam shaping.  We plan to focus on pulse shaping applications in our third and final installment of this series.

So you have a beam (CW or pulsed) and you want to control it.  Below are the fundamental questions that need to be asked in order to ensure that you’re on the path to obtaining great results in your research or manufacturing application.  This list should be combined with Part 1 of this series to get the total picture of what’s needed.  I have left out the “pitch” and “response” categories, assuming that you have read the previous installment.  Click here, in case you haven’t.

1)      Aperture:  How big is your beam?

The size of the wavefront is the first and foremost issue to understand.  Some applications have no control over this while others can change the size of their wavefront through the use of some simple focusing optics.  Before doing research into your alternatives, you should figure out what your limitations are in relation to this.

2)      Control:  Phase control? Beam steering?

This will greatly affect the basic type of mirror you will need.  For phase control, most modern phase-only mirrors will work, depending on your requirement of resolution (see “2. Resolution” from Part 1 of this series).  However, if you get into beam steering, the amount you need to move your beam will greatly affect the type of mirror you need.  For example, if you’re trying to move the beam multiple degrees, a fast-steering mirror is probably a good place to start.  However, if you’re looking to only make very fine adjustments (milliradians), you can benefit from MEMS-based solutions which are usually referred to as tip-tilt-piston (TTP) devices or piston-tip-tilt, if you’re from one other particular company out there (you know who you are J).  Many customers have come to us asking about using our entire mirror surface to steer a beam.  For those asking for big angles, we unfortunately have to turn them away, but some want to steer it a very slight angle at high levels of precision and we can do that.  

3)      Speed:  Do you want to make fine adjustments?  Are you looking to phase-wrap?

If you’re shaping a beam that is pretty much static, then some low-cost solutions will work.  However, if you’re looking to change the profile at high speeds with high precision, MEMS solutions are a great bet.  The stroke is sufficient to accomplish phase-wrapping, using our SLM model (segmented surface). With sub-nanometer precision, very precisely-shaped beams are possible.

4)      PowerVisible laser

This is a biggie:  If you have a high-powered laser, your options become limited very quickly as most of the very precise devices are a bit fragile as well.  Lots of research is being conducted to steer big, powerful lasers and the bulk of the technologies out there fall short due the fact that they are made of thin-film surfaces and temperature-sensitive materials. My recommendation for this is to make sure you know the “big three” properties and contact individual manufacturers to see what their experience is. They are:

1)      Peak power (in W/cm2)

2)      Average power

3)      Pulse width (if applicable)

Most manufacturers probably can’t guarantee much, but if your application has beam characteristics close to some of the data points they have, then it will make you much more comfortable that you won’t be frying mirrors when you fire things up.  BMC has a database that is constantly being updated with new experience that we would be happy to discuss.  Also, see this paper for the latest published results from our friends at the UCO/Lick Observatory.

As I mentioned before, this is not exhaustive, but if you have these questions answered, your first conversation with either us or one of our competitors will be a pleasant one which will make you more confident of your purchase.

Please chime in and let me know what you think of this series!   Again, stay tuned for the final installment where I will talk about pulse-shaping and the different ways that deformable mirror technologies can be used to create the perfect pulse!

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Fly with me: UAV image enhancement

Posted by Michael Feinberg on Tue, Mar 30, 2010 @ 09:59 AM
  
  
  
  
  

MEMS deformable mirror(MEMS DM) technology UAV applies adaptive opticsis right now at the point where a high-volume application could propel the devices from being installed in very specialized setups to being a standard component in production equipment. The best avenue to jump this figurative chasm is to find applications where a moderate number of devices is required, but price sensitivity is low. One such application is advanced surveillance systems for unmanned aerial vehicles (UAVs).
The use of a camera on a UAV provides invaluable information in terms of reconnaissance applications and confirming location. In order to improve the imaging capability, an adaptive optics system containing a deformable mirror, high-speed wavefront sensor and control system could be used to remove atmospheric aberrations between the camera and objects of interest. With this in mind, four major issues need to be addressed:


1) Nature of the aberrations
Obtaining high resolution images from a UAV camera is a challenge due to the atmospheric turbulence around the UAV as it flies at high speeds past its target. This turbulence is separated into two categories: turbulent airflow near the camera due to the high speed of the UAV and normal atmospheric variations in temperature in the extended distance beyond the turbulent layer of air. There are no doubt a number of people currently working on this problem (both out in the open and covertly) to increase the usefulness of UAVs. Recent discussion took place at the Photonics West Conference in San Francisco in January of this year as part of the Free-Space Laser Communication Technologies XII and Atmospheric and Oceanic Propagation of Electromagnetic Waves IV tracks (Conferences 7587 and 7588, respectively). Click here and here to see abstracts of the sessions.


2 and 3) Portability and Low Power
The system would have to be portable and have low-power to even be considered for use. MEMS DMs are capable of both, with individual channel operational power in the microAmps and drive electronics which can fit in the mid- to large-sized UAVs in operation today. Work is in progress at Boston Micromachines to further reduce the size of the electronics through a recently-awarded SBIR to explore multiplexing of MEMS DM drive electronics. (See Press Release here)


4) High Speed
Finally, the device would have to be capable of operating at high speeds. MEMS DMs have been demonstrated to operate at speeds of 60kHz and recent developments at BMC have produced a driver that can operate up to 400kHz.


We look forward to discussions going forward, especially around efforts to model and correct for the aberrations in the optical path, and hope that we can one day make an impact on this challenging field.

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