In 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?
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?
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.
This year at the Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting, there were some notable differences from past years. There was a shift in focus in the use of adaptive optics from talking about the technology to making discoveries. Here are the two major indicators:
Adaptive Optics is leaving the Title Page
In past years, there has been amazing research produced from the labs the likes of Roorda, Burns and Williams. But, you'll have to admit that for many of these studies the big "wow" in using adaptive optics for imaging the eye has been the technological innovation and the impressive science and not necessarily the clinical applications. One indicator of this change is the fact that until this year, most of the papers presented at ARVO which used adaptive optics contained the term "adaptive optics" in the title and not just the abstract. This year, that number dwindled significantly as the main focus shifted away from coolness factor. Whether it be new discoveries of cone structure properties with subjects which have genetic mutations or realizations about different types of color blindness, it is now the science and the promise of clinical applications that is center stage and not the technology.
Posters and presentations are showing fewer optical layouts
I spent three days last week at ARVO reaching out to the community and listening in on what is new and interesting. I found it difficult to figure out which mirror was used in any given experiment. This is simply due to the fact that most of the presentations and posters did not specifically call out what equipment was used in their research. As much as this made my job a little more difficult, I welcome this progression. It means that AO is becoming just another piece of equipment rather than a unique addition.
I welcome you to visit the ARVO site and type "adaptive optics" into the keyword finder. There, you'll discover all of the interesting research that is going on in the industry related to our mirrors. The main takeaways that I had from the show:
Precision+stroke = success
The removal of higher-order aberrations is most often paramount in obtaining high-quality images. However, while low-order aberrations can be removed with fixed optics, increased stroke is key to convenience and in some cases, performance. To that end, more and more woofer-tweeter systems (using two deformable mirrors: one long-stroke, low precision and the other short-stroke, high precision) are being used to obtain great images. Check out the upcoming June issue of Photonics Spectra for a byline article on the topic.
Two-photon: The next frontier in vision science?
While there were very few groups using this two-photon fluorescent microscopy, this is a discipline that I found very interesting and I think it could be a new avenue beyond scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) for retinal imaging.
Until recently, the only way to image a large region of the eye and gain any perspective on where you were imaging was to use a fundus image and take the small-area images from the AO imaging system and line them up with key features: Not an easy task. This year, Steve Burns unveiled his newest instrument where he was able to scan over multiple areas using an adaptive optics SLO and create a composite wide-field image of the retina. While this task is equally difficult, it offers a new exciting approach to this process and holds promise for advances in imaging the retina.
MEMS deformable mirror(MEMS DM) technology is 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.
To add to the diversity of our blog posts, I'm taking 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!
A question that is asked from time to time around here is, “What is your relationship with Boston University? “ People want to know: Are you a spin-off from their incubation program? Do you receive financial support from BU? Do they own your technology? Well, the short answer is yes and no. Here’s a summary:
We are an independent company which receives no financial support from BU and has a close relationship with the University for a few reasons:
We license some of BU’s MEMS technology manufacturing process from the University so that we may profit from it and contribute back to the University
Our founders are a BU professor (Tom Bifano, Director of the Photonics Center) and a BU grad (Paul Bierden, CEO, BSME ’92, MSME ’94).
We collaborate on focused development which includes both fundamental research and advanced development.
We are connected due to our mutual interest in photonics technology and expertise in the field.
It has been a beneficial relationship to both parties and we hope to continue the relationship as we move forward with new projects and new technological improvements.
A major area of research using adaptive optics is retinal imaging. And, with that interest, BMC has been fortunate to participate in the advancement the field by improving imaging techniques through the use of deformable mirrors. We have been directly or indirectly involved in many types of research.
In this post we will focus on our recent project in collaboration with Dr. Steve Burns at the University of Indiana to build an AO SLO system for use in a clinical setting. This project began as a National Eye Institute grant and has developed into a company endeavor to include our technology in a commercially available instrument that can be used for the early detection of such eye diseases as Diabetic Retinopathy and Age-related Macular Degeneration (AMD). Dr. Burns is putting the final touches on a device for use by clinicians. Pictures of the demonstrated ability to image retinal vasculature through the use of AO and the latest version of the instrument (with graduate student Zhangyi Zhong for size reference) are shown below. Also check out our Facebook page to view a video of the instrument in action: http://bit.ly/9w2y9x
Individual Nerve Fibers can be seen Crossing over a Superficial Blood Vessel:
Vessels down to the smallest Capillaries can be imaged:
We are currently accepting applications for the use of this device for research on the early detection of eye diseases and enabling treatment to slow down or prevent the spread of disease. Please contact us if you are interested in using this instrument as we are anxious to enable new research that can help to stop the progression of debilitating eye diseases.
We will be sure to keep the imaging community updated on the progress of this research and offer glimpses into what is being discovered using the instrument and what it means for eye care in the future.
Welcome to the Boston Micromachines Corporation blog, where we will strive to talk about the latest news in our company as well as in the adaptive optics industry at large.
When we decided to undertake this initiative, we asked ourselves, "How can we make an impact?" Well, there are of course many ways to make an impact: Increasing sales, increasing awareness of adaptive optics and deformable mirrors or even giving people a window into our operation and what we do. We decided that we would do all of these and more. It's great for the company to increase sales, it's great for everyone to increase awareness and it's definitely interesting to let people know about activities in our company. But, will this really make an impact? We think we can go further by not just letting everyone know about the latest news, but giving our perspectives and opinions, based on over 10 years of experience in the field. We also want all of you to chime in as well: By including an array of opinions and viewpoints, we feel that it will lead to better technology and more innovative efforts and maybe even convince some people who aren't quite convinced that AO is the way to go with their optical instrument.
So, please feel free to chime in and help us make an impact. We plan to present lots of content on things around the industry from major construction projects to new markets down to small research grants (which we know aren't small to those who get them!).
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