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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: 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

Reflective Optical Chopper Outperforms the Rest

Posted by Angelica Perrone on Thu, Jun 20, 2013 @ 02:11 PM

Tags: adaptive optics, boston micromachines, product information, response time, BMC, free-space communication, modulating retroreflector, optical chopper, optical modulator, chopper, pulse, ultrafast lasers, CLEO, AOM, acousto-optic modulator, SNR, signal-to-noise, speed, shutter

As Boston Micromachines' newest member, I would first and foremost like to introduce myself. My name is Angelica and I have joined the BMC team as their Marketing and Communications Associate. It has been some time now since our last blog and I thought it would be appropriate to discuss our most recent product; The Reflective Optical Chopper, or ROC.ROC with driver 130326 No Logo

               Optical Choppers, being frequently used for signal recovery in improving signal-to-noise ratio, are used to convert a continuous laser beam into a chopped one. Traditional Optical Choppers offer various pains, such as the need to alter the beam size to fit through wheel spokes, challenging stability at low speeds, the need for costly lock-in amplifier equipment and complex calibration procedures. The innovative, low-cost ROC simply eliminates all of these, outperforming traditional optical choppers.

                Drive electronics are paired with BMC’s MEMS Optical Modulator technology to create the ROC. The ROC provides beam chopping at impressive speeds without beam size modification. With a frequency range of DC to 150 kHz with better than 40 µs response time, control increments of .01 Hz and a contrast ratio exceeding 90% up to 100 kHz, the value of the ROC ‘speaks’ for itself. For signal-to-noise ratio improvement, the drive signal can be used as the sync signal, allowing it to be painlessly synchronized.

                Many industrial, scientific, medical, aerospace and military applications call for the need of reliable and advanced equipment. The ROC has superior capabilities such as high speed, large frequency range, reliability, stability and usefulness in SNR improvement applications. Basically, the Reflective Optical Chopper is an advance in optical chopping technology which is available at a low price.

How to select the right deformable mirror for you Part 1: Imaging

Posted by Michael Feinberg on Tue, Jun 15, 2010 @ 02:10 PM

Tags: deformable mirror, adaptive optics, boston micromachines, Boston University, product information, Woofer Tweeter, resolution, response time

deformable mirrorIn this multi-part series, I will be exploring the basic questions that one needs to answer in order to determine which type of deformable mirror is best suited for their application. This list is by no means exhaustive, but if one has an understanding of these topics, the journey to creating spectacular images will be much smoother and equally as rewarding. I am starting with imaging since this is a field that is constantly expanding to new disciplines and often involves researchers who are not familiar with adaptive optics. The next topic will be beam shaping, with further topics to be introduced in the future.
Potential customers come to us at Boston Micromachines to design an adaptive optics system for many different applications: Confocal microscopy, conventional microscopy, astronomy, etc. However, many of them don't know their options when selecting the right mirror. We think we've reduced the questions you need to ask to four simple topics. If each customer reviews this list before giving us a call, finding a mirror best suited for their application will be as exciting as viewing that killer image you're trying to get:

1) Aperture: How big is your image? How big (or small) can you make it?
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) Resolution: How complex are your aberrations? zernike
Having the right aperture is great, but if your mirror does not have a high enough level of precision, your image improvement will be greatly limited. In the deformable mirror industry, we call this distance between control points, "pitch." In our devices, it is the distance between actuators. In membrane-type mirrors, it will be the distance between electrodes that are underneath but not directly connected to the surface. If your aperture can be manipulated, the precision to which you can control the wavefront will most likely be directly affected by this adjustment. Also, the size of the pitch can affect the price of the mirror. So, understanding what the relationship is between aperture, pitch and price can help you not only find the right mirror, but minimize your costs.

3) Aberration: How big (deep) are your aberrations?DM  Profile
While aperture and resolution cover you in two dimensions, depth is the final critical physical dimension. The size of your aberrations will directly impact the necessary stroke (the distance the surface of the mirror can travel up and down). If you have very small aberrations and require a high level of precision to correct your wavefront, you can focus on MEMS-based solutions, like those provided by Boston Micromachines (available stroke is between 1.5 and 5.5um). However, if you require larger stroke, you may need to focus on more flexible electro-static or piezo-electrically motivated membrane surfaces. Most recently, some have executed what we call a woofer-tweeter approach where a larger mirror corrects for the larger aberrations (the woofer) and a smaller, more precise mirror fine-tunes the image (the tweeter). You can see an article on this in the June 2010 issue of Photonics Spectra: "Dual Deformable Mirror Systems Take the High and Low Roads to Imaging Success." Size of the aberrations is a critical point to understand due the fact that if you don't have enough stroke or high enough level of precision, your image may not improve enough to be impactful.

4) Response: How fast do your aberrations move?
If you're dealing with static medium, then this is not an issue. However, if you are dealing with atmospheric turbulence, as in astronomy, or in vivo conditions in live specimens, then this is a critical parameter. While this is dependent on the structural composition and design of the mirror, it is also dependent on the drive electronics and controller. So, make sure that both your system (PC or other controller) and the electronics associated with the mirror are up to snuff for your application.

Purchasing a deformable mirror should be an exciting endeavor: The images obtained to date have been astounding. I'm sure that with proper preparation and understanding, it can be successful for you as well.

Website Update: More information for you, our customers

Posted by Michael Feinberg on Tue, Mar 23, 2010 @ 11:40 AM

Tags: adaptive optics, boston micromachines, product information

To add to the diversity of our blog posts, I'm takingNew manuals for BMC deformable mirrors this opportunity to let you know that we've made a change to our website to give potential and current customers more access to data on our products.
Today we launched the Customer Support page in our Product Information section (www.bostonmicromachines.com/support). On this page you can:
1) Obtain copies of our product manuals through a simple request form. After submitting the form, an e-mail will automatically be sent to you with instructions on how to download the documents.
2) Request the latest software for our devices (see screen shot to the right of our latest beta test software). Whether you're curious about updates to software you already have or you want to request new software, just fill out the form and a customer representative will contact you to find out what you need. We'll do our best to get it to you in a timely manner.
I hope you're enjoying the blog thus far and please leave a comment either way!
P.S. If you are a current customer and either of the images you see with this post is unfamiliar to you, definitely send in a request!