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MEMS Deformable Mirrors vs. Liquid Crystal-Based Devices

Posted by Angelica Perrone on Tue, Sep 30, 2014 @ 03:00 PM

Tags: deformable mirror, adaptive optics, boston micromachines, product information, response time, mirror technology, SLM, spatial light modulator, BMC, segmented, speed, Reflectivity


New Mini mount resized 600Before Deformable Mirrors became popular in the Adaptive Optics industry, consumers would generally turn to liquid crystal-based device (LCOS) spatial light modulators to confront their challenges. Here at BMC, we regularly receive questions on how all deformable mirrors, in addition to our MicroElectroMechanical (MEMS) deformable mirrors, compare to LCOS devices. Below I have touched upon some of the top differences between the two devices that I believe should play an important factor in one’s decision to purchase a wavefront shaping device.

1)      LCOS devices are only available in a segmented architecture, where MEMS DMs offer both continuous and segmented styles in various styles and options. Although both layouts have their own advantages, most researchers favor the continuous model. Due to discontinuities between the actuators, it prevents any sharp edges within the image, making it well suited for imaging applications. Claire Max at UC Santa Cruz has explained and presented calculations on how you can achieve higher level of correction capability with a continuous mirror. Check out slide 47, which goes over her calculations here.  

2)       With MEMS DMs, we are able to offer strokes up to 5.5um (1.5um, 3.5um and 5.5um available), while LCOS SLMs are generally limited to only a stroke of 2PI in the visible region. This can be a major inconvenience for certain applications with higher amplitude aberrations. 

3)      The response time of our devices have always been much faster than any liquid crystal device on the market, while recent updates to our product line achieve even FASTER rates than before. Our devices can operate up to 60 kHz with our new high speed Kilo-S Driver or our Low-Latency Driver, whereas LCOS devices are limited to only a few hundred Hertz at best.  

4)      For the most part, LCOS devices are transmission based, causing light to be absorbed by the medium and resulting in lost light. There have been reflective devices introduced recently, however, they tend to scatter large amounts of light due to the small segment sizes. With a MEMS device, our segmented mirrors are over 98% reflective and our continuous mirrors are greater than 99%. Of course, this is the case only with the appropriate coating for the wavelength at which you are operating.  

If you're interested in learning more about the differences between MEMS DMs and LCOS devices or the differences between any other mirrors currently on the market, please feel free to contact us here.  

FAQ: Flatness of BMC Deformable Mirrors

Posted by Angelica Perrone on Thu, Jan 16, 2014 @ 11:36 AM

Tags: deformable mirror, adaptive optics, boston micromachines, mirror technology, spatial light modulator, BMC, imaging systems, Mirrors

Happy New Year! Hope everyone had a great holiday and is staying warm.

To continue addressing our FAQ's, another recurring question BMC recieves is on the flatness of our deformable mirrors.  The figure below shows an unpowered BMC DM and a flattened BMC DM. 

Flatness

The surface figure of our unpowered deformable mirrors has a low-order surface bow. The amount of stroke needed to flatten the DM is between .5 µm and 1 µm, depending on the model. We can guarantee that the stroke needed to flatten the deformable mirror will not exceed this amount and tends to be lower for the lower stroke devices.

However, researchers in the past have been able to achieve flattening the wavefront without using up any stroke on the DM. If you are able to include additional optics into your setup, the low order bow can be taken out with static optics. Just something to keep in mind as you are designing your system and trying to determine how much stroke is required to achieve your wavefront correction needs.

If you have any additional questions in regards to the flatness of our mirrors or are interested in seeing what the typical unpowered surface figure is, please contact us at moreinfo@bostonmicromachines.com or visit us online at www.bostonmicromachines.com

FAQ: BMC Deformable Mirror Reflectivity

Posted by Angelica Perrone on Fri, Dec 20, 2013 @ 09:00 AM

Tags: deformable mirror, adaptive optics, boston micromachines, product information, mirror technology, BMC, Mirrors, Coatings, Reflectivity, Thorlabs

Over the past couple of months we have been receiving an assortment of questions in regards to our products. We thought it would be a good idea to share the more popular questions and answers as they stream in to keep everyone updated.

One question that tends to be asked quite often is the reflectivity our deformable mirrors can achieve. This depends on a couple of factors such as mirror coating, protective window AR coating and the wavelength of the light. 

Figure 1

We offer gold, aluminum and protected silver coating on almost all of our deformable mirrors. When selecting a coating, you should pay particular attention to the wavelength(s) of light you use. The BMC DM Coating Reflectivity chart to the right illustrates the reflectivity of each of our standard coatings.

Our standard windows with AR coating are BK-7.  We offer a few options, depending on which size mirror you select.  For our smaller DMs, we offer the standard coatings from Thorlabs as well as a few more versatile options.  You may choose either uncoated, 350-700nm, 650-1050nm or 1050-1620nm.  We also offer a 400-1100nm window and 550-2400nm, the latter for an additional cost.  For our larger DMs, various coating options are available. We do offer customizable options for an extra fee, so please contact us with your specifications if you require this.

The N-BK7 Broadband Antireflection Coatings chart from Thorlabs below depicts the percentage of  light lost for each AR coated window. Similar curves are available for our other coatings.Antireflection coatings Thorlabs
               

If you are looking for additional information on our standard windows, please visit our friends at Thorlabs online. If you have any further questions on the reflectivity of our mirrors, click here to send us an e-mail or visit us online at www.bostonmicromachines.com

What Do You REALLY Want in a Deformable Mirror?

Posted by Michael Feinberg on Wed, Oct 17, 2012 @ 04:00 PM

Tags: deformable mirror, adaptive optics, response time, laser science, mirror technology, microscopy, astronomy

This past summer, Boston Micromachines Corporation conducted a survey of nearly 300 members of the business and scientific community to find out what features were valued in a deformable mirror for adaptive optics and other wavefront correction applications.  Respondents came from our three major vertical markets: microscopy, deformable mirror survey resized 600astronomy and laser science.  In this survey, we asked some fundamental questions and had respondents choose between three DMs with properties varying in categories of actuator count, stroke, response time and price in various combinations. We were able to drill down to what each respondent valued.  Here are some of our key findings:

1)      Actuator count was the most valued property

Across all verticals, this was true.  Overall, respondents preferred an  average of 1000 actuators. While microscopists preferred 140 actuators by almost 2 to 1 over other models, those who identified as laser scientists were looking for an average of 1001 actuators and astronomers preferred, on average, 1800 actuators.

This was very interesting to us considering we are the only player in the market to provide deformable mirrors with these actuator counts as standard products or are developing DM systems which meet these specific needs (we have a 2000 element mirror in the works).

2)      High speed is important

The most frequently chosen option for response time amongst laser scientists was 50μs and all other disciplines preferred average response better than 300μs. This is great news for the industry considering that most mirror architectures can respond adequately to meet the needs of the users. Our DM architectures are available with response times up to 22μs and we are able to drive these mirrors with our X-Driver (response time down to 4μs), satisfying high speed requirements as well.

3)      Low price is desired

As we hear so often, most users were looking for low-priced devices. This was the second    preferred property after actuator count. While those of us in the industry talk about lower prices with higher volumes, the volumes just haven’t been there yet to make this prophecy come true.  The hope in the future is that the DMs based on scalable technologies, such as MEMS, will take off and lower-priced devices will be available.

We definitely learned a lot from this survey, above and beyond what is mentioned above.  If you have any questions about our methods or are interested in discussing more specifics about the responses, I would be glad to chat further.  Just contact me at support@bostonmicromachines.com.

 

Wavefront Sensorless Adaptive Optics Now a Reality

Posted by Michael Feinberg on Mon, Oct 01, 2012 @ 11:57 AM

Tags: deformable mirror, adaptive optics, boston micromachines, laser beam, laser science, mirror technology

WASO for blog

 

Up until recently nearly all adaptive optics (AO) systems used wavefront sensors for correction. But with recent advances, off-the-shelf wavefront sensorless AO is becoming a reality.  Benefits of this type of AO include enhanced aberration correction due to the elimination of non-common path errors and wavefront sensor noise.

BMC has developed a Wavefront Sensorless AO Demonstrator (WS-AOD) which provides a platform for utilizing metric-based wavefront control with BMC MEMS deformable mirror (DM) technology. While conventional AO systems perform closed-loop DM control using direct measurements of the wavefront as feedback, the metric-based approach uses details in the aberrated light to improve clarity. Two versions are available; one is optimized for beam shaping applications and the other is designed for imaging applications.

We see laser beam shaping as a key area in this exciting technology and our demonstrator is built to address the unique challenges of this field. Our WS-AOD serves as an introduction to wavefront sensorless adaptive optics principles. It allows users to understand the details involved in properly implementing a metric-based adaptive optics solution on an optical system. The demonstrator can also be used as a stand-alone aberration compensator. By introducing aberrations in the sample stage, the system can be optimized for a multitude of use cases from laser research applications to scanning laser microscopy. Additionally, the user can easily integrate the hardware into an existing optical system and utilize the open source software code for metric-based correction.

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Schematic of WS-AOD for beam shaping applications. Also available for imaging applications.

To compensate for phase aberrations the WS-AOD uses BMC’s deformable mirror (DM) technology. BMC’s DM is a continuous facesheet deformable mirror that is controlled by hysteresis-free electrostatic actuators located on a square grid. The full DM activemulti DM aperture can be as little as 1.5 mm to as much as 25 mm across. Each actuator can provide up to 5.5 µm of mechanical stroke, which corresponds to about 11 µm of phase control. The electrostatic actuator array is driven using independent high voltage channels with 14-bit resolution. This corresponds to sub-nanometer displacement precision. The drive electronics can provide frame rates of from about 4.6 kHz up to 100 kHz.

The control software for WS-AOD allows the user to correct for aberrations introduced as well as generate a random aberration using the DM. The software is open source code based in Mathwork’s Matlab and runs on platforms using Windows operating systems. By utilizing the included algorithm to manipulate the mirror surface, the mirror compensates for aberrations and converges to an optimal profile. The user has access to the open source code to balance correction capability between maximum signal and minimal time.

To learn more please click here for a copy of our Wavefront Sensorless Adaptive Optics white paper.

SPIE Mirror Tech Days: Highlights and Takeaways

Posted by Michael Feinberg on Wed, Sep 05, 2012 @ 02:11 PM

Tags: deformable mirror, mirror technology, BMC, imaging systems, SPIE, Photonics West, telescopes, NASA, SBIR/STTR

 

describe the imageThe SPIE Mirror Technology SBIR/STTR Workshop was held in Rochester, NY this year at the end of July. This is always a good conference for BMC, and we go every year.  The conference can best be summarized from their website:

Tech Days annually summarizes the USA Government's investment strategies and activities in developing technology for any application (such as telescopes, imaging systems, seeker/trackers, high-energy laser systems, solar energy, etc.) which requires optical components. Tech Days covers technology investment efforts in: optical materials; substrate design & manufacture; optical fabrication and metrology technology; optical coatings; wavefront sensing and control via adaptive optics; nano-technology imaging technologies; etc.

I highlighted the text for emphasis as to why we attend:  You can see why this is a great place for BMC to be. We get to present the latest progress on our NASA SBIRs (of which we have 4 ongoing), see some of the other great research that is going on in the field, and learn from the NASA Program Scientist what the future needs are for mirror technology.  Also this year, BMC was a sponsor/exhibitor.  This gave us a chance to set up a table displaying some mirrors and information about our products and technology. It was in a great spot at the conference where lunch, coffee breaks and the Tuesday night reception were held. While the conference was not as big as some other SPIE events (e.g. Photonics West and Optics and Photonics), it was a great opportunity to meet with some key people.

A couple of takeaways from the meeting were

(1)    NASA SBIR/STTR program is strong and growing. 

They are using the research funding they have for strategic programs that will help with technology development, which was called out in the decadal survey  as an, if not the, important push for the next ten years.

(2)    There is a continuing need for BMC mirror technology. 

There are a number of projects that will require the wavefront control that our DMs can provide.

Both of these items point to a rich future for BMC and the deformable mirror industry as a whole. We look forward to connecting with these folks again next year and for many years to come.