Christopher Cotton, ASE Optics GM and optical engineer, answers audience questions in the Laser Focus World webcast, Design for Aspheres

Audience Questions & Answers

Q: How do you tolerance aspheres to manufacturers?

A: The standard way to do this is similar to tolerancing any other optical surface. Define departure you’ll allow from surface. Determine fringes of power and irregularity. As we get more into machines making optics and smaller tool polishing you have to define surface slope to avoid ripples/features you’re not expecting in the system. Aspheric defines the difference between the surface you’re getting and the ideal surface. Allowing change in power on asphere is similar to finding it for a spherical element. In addition to regularity, define slope tolerance.

Q: What are problems and sensitivities of aspherical mirrors?

A: The common aspherical mirror is a parabolic surface, found in Newtonian telescopes. It produces perfect focus on axis but as you move off axis you get coma and astigmatism very quickly. You find that you have to spend a lot of time designing them if you want to get the field angle you’re looking for. These are used in common astronomical telescopes.

Q: Are there databases of previously designed aspheres or do you have to start anew?

A: RPO lenses are available through RPO and in catalogs. All those designs are available in Zemax so you can bring them in and adapt them to your system. If you’re just going to use one or two, they’ll be difficult to manufacture.

Q: Do you prefer odd or even polynomial surfaces?

A: I’m not 100% sure of the definition people use. I look at it based on change in sag of surface. Some people look at change in derivative of surface instead. The even asphere is rotationally symmetric. Odd aspheres have cosine or sine—changes with the angle.

Q: What design tools are best for aspheres?

A: Code V, Oslo, Zemax. All are useful and pretty similar. The biggest change is the way that you use each tool. Overall I like Zemax because I treat optical designs like a video game.

Q: How do you know how many surfaces you need to make aspheric?

A: Look at surfaces that do the most work, have the lowest R number. They’re most likely to benefit from having an asphere.

Q: Are aspheres used in common photographic lenses as well?

A: There is a line of photo lenses that uses aspheres designed for digital cameras to get a smaller angle at sensor. Nikon lenses have plastic aspheres in them. Aspheric can be made cheaply in large volumes.

Q: Does the shape of the asphere affect if it can be asphere-ized?

A: Not necessarily. Shorter radii and small diameters are hard to make aspheric. When molding plastics, it depends on how much time you’re willing to spend to get a good surface with your tools.

Q: Is there any rule of thumb about the cost of an aspheric surface?

A: Depends on plastic, glass, crystal. If you’re diamond turning it’s about $100 per surface. If you’ve got one that is polished there’s not an easy guess. If it’s moldable then you can you can say between 12 and 20,000 dollars tooling (but don’t quote me). For plastic, $25000 to make the tools and then make samples. It really depends on the object.

Q: Are these used in precision optical systems?

A: Yes, military IPT and objective. They have tight tolerances and high performance requirements.

Q: What is limit to slope on an aspheric surface?

A: Stay away from inflection points so slope of zero is bad. When you get to high slope, it depends on surface. Stay away from 30 degree slope and don’t go past that. Whenever you make something more difficult, you make it more expensive.

Q: Which asphere mathematical equation do you recommend?

A: Political question. Each person will have a different answer. Zernicke and Forbes are both great approaches. I prefer Zernicke is it’s easier to get to rotational equation.

Have a question we haven't answered? Please ask it in the comments below. We'll answer them in a future blog post.

ASE Optics GM Christopher Cotton presents Designing with Aspheres, a Laser Focus World webcast sponsored by ASE Optics, Rochester Precision Optics, PLS Launch Solutions, Optimax, and RRPC.

Hello, I'm Christopher Cotton, GM of ASE Optics, presenting today on designing aspheres to improve system performance. We’re going to look at:

• 3 locations in a system where aspheres are useful
• 3 ways to specify an asphere: forbes polynomial, vertice polynomial vs traditional 
• Audience Q&A about designing aspheric lenses

[Click to view a lens design demonstration, with examples of where and how aspheres are best used to improve system performance.]

3 locations where aspheres are useful

The asphere at the stop generally controls elaborational systems and has some effect on off axis spherical or oblique spherical, but that’s when you have larger field angles. If you shift aspheres away from the stop then you can control field aberrations (coma, astigmatism, distortion). There, you introduce more spherical at the lens that’s moved away from the stop that you then have to add more aspheric power to the element that is at the stop in order to compensate for that. Putting an asphere near the image plane allows you to control the field curvature and the astigmatism in the system without having a great effect on the spherical aberration or the coma in the system. They still have some effect but the effects are minimized.

3 concerns when designing aspheres

1. Succinct sampling of the pupil. If you’re thinking about focus, you only need 2 rays. If you’re thinking about 3rd order spherical, you need three rays. If you’re adding an asphere to correct 3rd order spherical, you need three rays. When you start adding extra aspheric terms you need to add one ray per every aspheric term you add.
2. Large number of field points. As you add aspheres, the field aberrations will be affected not necessarily in a linear way. We’re used to coma being linear with the field. When you have aspheres affecting the coma, you don’t necessarily have coma that’s linear with the field, the same with astigmatism and distortion.
3. Chromatics. If you add a spheric term you don’t necessarily change the crematic aberrations in the system. It does allow you to have more power in each of the elements, which can then allow you to adjust chromatic aberrations in the systems.

3 ways to specify aspheres

Traditional

Traditional aspheres are defined by power series. The standard definition for a spherical surface is a conic constant; K is the conic constant. C is one over the radius of curvature of the element, and R is the aperture point. It used to be that people would only start with the 4^th order but in the past few years, people started using the parabolic term as well. I don’t because it affects the focal length of the lens and is often not taken into consideration when doing things like paraxial solve to get the focal length correct. Advantages of power series are it’s easy to understand and it’s understood and supported by manufacturers. They have software tools to get those shapes into their grinding or diamond polishing tools. They understand how to test for that. Disadvantages are it’s difficult to scale. To make an element larger, edges will go crazy because it’s difficult to scale with aperture. It’s also not an octagonal set. If you change one, you’re going to make a significant change to the surface. Trying to fit certain shapes may not be accurate since it’s not octagonal.

Zernike

Zernike polynomial approach to defining a surface has its advantages. People know how they’re defining the surface, people have used them for a long time, and they can be expanded to odd orders. The problem you have is there are odd orders also, and in order to get a reasonable set of symmetric polynomials, you have to go to greater than 28 terms so you get 2 aspheres: power, 4^th order and 6^th order. This is computationally difficult because lens design codes are retracing to all the terms even though majority of terms are zero, so this can slow optimization.

Forbes Polynomial

Third approach is new, about 5 yrs old, its advantages are that it’s an octagonal set and only considers even powers (less computationally difficult to mange). The disadvantage is it’s not widely accepted. I’m always a few versions behind to assure I don’t have issues with bugs. Mine has an external that defines forbes polynomoial. It’s not immediately recognizable. Greg Forbes is really smart and can probably look at the equation and tell you what it’s doing without turning on computer which I cannot. This makes perfect sense to me without much thought but, if you’re going to increase the amount of power you have often, it takes extra thought and learning.

Aspheres are powerful systems. You can often get rid of other elements, which helps higher performance. I’ll reiterate to make sure you’re sampling the pupil and image plane to make sure the merit function isn’t escaping. If you're considering designing aspheres into your next optical system and have questions, please feel free to contact me directly.

ASE Optics' GM Christopher Cotton is featured in a video on Laser Focus World discussing techniques to improve performance of lens systems for aerial applications. Vibration control is the primary detractor to the image quality that these systems demand.

In aerial applications, cameras are focused weeks in advance in a warm lab, and rely on the hardware to maintain focus and prevent lens motion. On the ground, in commercial applications and for the amateur photographer, this is easy. People don't vibrate, fingers make for a soft mount and refocusing is usually possible.

For aerial camera systems we design and build, we built the lens in a fixture separate from the camera. We focus the lens separately in the lab with an interferometer. Our customer can then mount it to the camera, ready to be used in flight.

Bayonet mounts commonly used on commercial cameras tend to wobble. They are just not meant to survive in an aerial environment.

Accurate and repeatable mounting of the lens to the camera is required to negate the need for recalibration when removing and remounting the lens on the camera.

We have overcome this problem by attaching the lenses with a hydrostatic mounting technique. We have also designed the focusing mechanism for the lens to be secured by a compressible clamp with fingers that exert pressure on the barrel. Loctite is then used as a final securing mechanism. The Loctite can be broken apart later if changes are needed.

Temperature changes from the lab to the aerial platform will cause the focus of the lens to change. The correct choice of materials and design are critical to getting our passive thermal compensation scheme correct.

Weight is especially important for UAV applications. You need to use just enough metal to maintain stability. Glass lenses have less thermal stability issues, exacerbating the weight issue. We have had the best success using off the shelf lenses in the $50-3000 price range . These lenses can be ruggedized and athermalized. This can be very economical for quantities less than 10. They can be taken off the shelf, taken apart and then reengineered.

We have used these techniques in designing lenses for Geospatial Systems, whose high-definition imaging technology was used to map the regions of Haiti devastated by the 2010 earthquake. Aid workers used these maps to determine the full extent of the damage to this small country.

Questions about your application? Comment and ask us or contact us directly.

An important step in the design of an optical system is to consider how difficult it will be to manufacture. An optical design can look great on paper, but a tolerance analysis may reveal that it will be very costly to build. Sensitivities are often overlooked until a problem is found after the lens system is assembled and the performance does not meet expectations. A simple metric for estimating the difficulty of putting together a lens is very useful. One such metric was discussed at a recent ASE Optics lunch meeting by one of my colleagues, Peter Emmel. Peter described what he always thought of as the “Hopkins number” from his days of working at Tropel. He referred to it as such because it originated from Robert E. Hopkins, who was a co-founder of Tropel and is considered by many to be the “father of optical engineering.”

The Hopkins number is equal to the number of resolvable spots in the image and can be used to gauge the difficulty associated with making a lens. A “resolvable spot” is loosely defined in this case and depends upon what is limiting the system performance. For example, it may be the Airy disk for a diffraction-limited system, the geometric spot for a system with aberrations, or the pixel size for a sensor-limited system. The value can be computed from the 2D image area or, as Hopkins preferred, a 1D slice of the image area based upon its largest dimension. For example, with a rectangular image it would be number of resolvable spots along the diagonal.

At Tropel, Hopkins found that this number usually correlated with difficulties encountered in producing lenses across the full range of lens types and applications. Systems that had worse than anticipated performance almost always turned out to have a large Hopkins number. According to Emmel, one benchmark value was 6,600. “That was the 1D number for a particular first-generation microlithography lens that Tropel designed and built for Bell Labs in the 1970s. Tropel succeeded where two other firms had tried and failed to build lenses for this then-new application.” People learned to be wary of systems that had such a large Hopkins number because difficulties would be virtually guaranteed. For comparison, a Zeiss Distagon camera lens (T* 3.5/60 CFi for example) which has a 1D Hopkins number on the order of 3,900 would be considered “moderately difficult”. A point-and-shoot digital camera might have a 1D Hopkins number of roughly 2,500 and would be considered “easy”.

In Emmel’s opinion, the most important use of this metric is in the planning and cost estimating stages of a new prototype project. It provides a first indication of the likely sensitivity of a system to manufacturing tolerances. “Best of all,” says Emmel, “it can usually be calculated directly from the specifications, before a design is even started, making it a measure of the degree of difficulty inherent in the application.” Recognizing that a system may be particularly sensitive at the outset is much better than being surprised by poor performance after hardware has been built.

Technically speaking, the Hopkins number is related to the space-bandwidth product (SBP). For an optical system the SBP is equal to the image size divided by the size of the Airy disk and is therefore directly related to the diffraction-limited resolution. According to Goodman, “The space-bandwidth product of a function is a measure of its complexity. The ability of an optical system to accurately handle inputs and outputs having large space-bandwidth products is a measure of performance, and is directly related to the quality of the system.” [Goodman, “Introduction to Fourier Optics,” 3rd ed., Section 2.4.2, (2005)] For a diffraction-limited system where the Airy disk size is driving the performance, the Hopkins number is equal to the space-bandwidth product. For more on the SBP, see for example:

• Z. Zalevsky, D. Mendlovic, and A. W. Lohmann, "Optical systems with improved resolving power," Prog. Opt., 40, 271-341 (1999).
• W. Lohmann, R. G. Dorsch, D. Mendlo vic, Z. Zalevsky, and C. Ferreira, "Space-bandwidth product of optical signals and systems," J. Opt. Soc. Am. A 13, 470-473 (1996).

The Hopkins number is a very handy metric for quickly estimating the degree of difficulty of an optical system. A high value means a challenging project, but steps can be taken in lens design to reduce tolerance sensitivities and in mount design to mitigate their impact.

Tolerance analyses and innovative mount designs are an integral part of the engineering work done at ASE Optics to ensure manufacturability. For “Hopkins number appropriate” optical system design, give us a call!

The work of Ren Ng on digital light field photography is coming to fruition and has the potential to revolutionize picture-taking. Lytro Inc., the company founded by Ng, recently announced that it will offer a consumer-level digital light field camera by the end of this year. A light field camera allows digital images to be captured now and focused later. When the pictures are shared, the viewer can choose which part of the image is in focus: the foreground, the background, or something in between. It will allow people to capture a moment and dynamically relive it and share it in different ways, as determined by the eye of the beholder of the photograph instead of just the eye of the photographer. The images are described as “living pictures” that can be altered in real time with the click of a mouse. You can try it for yourself by viewingLytro’s picture gallery. In addition, pictures can converted for viewing in 3D. Dig out your red and blue 3D glasses and take a look at the demo on Lytro’s blog site.

These capabilities are made possible by using software and computing power to alter the image after it is acquired. In addition to making the novel features of the Lytro camera possible, digital post-processing can also be used to remove aberrations and improve image quality. Ng discusses digital correction of lens aberrations in light field photography is his Ph.D. thesis.

For more “standard” imaging methods, post processing for distortion correction is very important for some applications. In aerial photography, for example, obtaining an accurate representation of what is on the ground can be critical. ASE Optics has patented a methodology and optical system as well as an aerial camera that can characterize errors in an image or portion of an image and correct for them. A set of fiducials is projected onto the focal plane array as an image is being acquired. The difference between the ideal and actual fiducial locations is used to characterize the main optical system. Distortion coefficients are computed to back out aberrations. Since the fiducials are created along with every image, the effects of dynamic changes that cause errors during image acquisition can also be removed. The result is improved image quality and more precise geolocation information.

It will be interesting to see what the future has in store for photography as ever-increasing computing power leads to more and more post-processing capabilities.

Are you shifting to post-processing in any applications? If ASE's computational imaging capabilities can help, consider our discovery service.

Micromirror arrays are commonly found in digital projectors. However, they can be utilized for other applications. For example, in a past project for Geospatial Systems, Inc. (GSI, now Optech), ASE creatively used an off-the-shelf projector array in the construction of a multi-object spectrometer. The array is used for target selection in place of a conventional slit mask or fiber bundle. It allows the system to be rapidly reconfigured and makes it well suited for studying objects that cover a small field of view, such as star clusters.

A recent article in “MEMS Investor Journal” describes another interesting application, a variable focal length lens to improve the zoom performance of cell phone cameras. Currently, camera phones do not contain moving lens elements to vary the focal length like a regular zoom lens. Instead, images are zoomed digitally, which results in lower image quality compared to optical zoom. Micromirrors placed in concentric circles within a plane can be used to produce optical zoom. The tilt of the mirrors is different from circle to circle such that light is focused to a single point. The tilt angles can be adjusted to vary the focal length, which provides the same effect as moving lens elements. The researchers have designed a system that would deliver 3.5x optical zoom. They plan to build prototypes this year.

Consumers would certainly appreciate improved zoom capabilities in camera phones and it would add to the ever-expanding list of features for these handheld devices. Perhaps the need for stand-alone point-and-shoot digital cameras will someday be eliminated.

I just caught an interesting interview with Dr. Henry Petroski over on the Groks Science Radio Show (a quirky show that I loved long before its co-producer, Charles Lee, moved to my undergraduate alma mater). Petroski is a professor of civil engineering over at Duke, and he's got a new book out entitled Essential Engineering, which deals with why engineering is essential in the modern world, and how engineering is different from basic science. The subtitle of the book is "Why Science Alone Will Not Solve Our Global Problems." That phrasing may sound critical of basic science, but that certainly isn't the intent. Rather Petroski is seeking to elevate the importance of engineering in the public eye so that science and engineering are seen as a partnership and not as a hierarchy. In particular he takes issue with the common misconception that engineering is "just applied science." On the contrary people often engineer a device before the scientific principles underlying it are understood. This is certainly true in optics. For example magnifying lenses have been used for thousands of years (for example Aristophanes mentions a "crystal lens" in his play The Clouds, circa 420 BCE), but the theory of refraction was not described mathematically until around 1000 CE. (As to who first devised the laws of refraction... I'll let the debate continue to rage on Wikipedia.)

Solar power is an increasingly popular topic as the need to develop sustainable sources of “clean” energy grows. The April 2011 issue of Optics and Photonics News (OPN) has an interesting article on research being done to improve solar cells by incorporating the features of compound fly’s eyes.  See "Insect Eyes Inspire Improved Solar Cells" on pages 39-43 for more information. 

The article begins with “a short history of solar power”. It mentions the legend that Archimedes set enemy ships on fire during an attack on Syracuse, presumably by focusing the sun’s rays using reflectors. Interestingly enough, there have been three episodes of Discovery Channel’s MythBusters on the “Archimedes Death Ray”. In the first episode in 2004 it was declared a myth after determining that the size of the mirror needed would be unrealistically large and would not be able to raise the temperature of wood enough to start a fire. Viewers were then challenged to devise a means of showing that the myth was plausible. In 2005, MIT students set fire to a wooden ship 100 feet away using 127 flat mirrors arranged in a parabola to focus the sunlight. (http://www.wonderbarry.com/deathray.html,http://history.howstuffworks.com/ancient-greece/archimedes-death-ray2.htm) They were invited onto the show to recreate what they had done. However, in the end it took too long for the fire to start and only worked with a stationary ship much closer than what was described in the legend. Therefore, the myth was again declared “busted”. A third episode was done in 2010 with President Barack Obama challenging the MythBusters to once again revisit the myth. This time 500 high school students each aimed a mirror. In spite of the extra mirrors a fire could not be started under the conditions in the legend and the myth was busted a third time.

Legends aside, modern-day use of solar power could be improved by designing solar cells to collect as much sunlight as possible and by increasing the efficiency of silicon solar cells. To address these challenges the authors’ research, as described in OPN, involves making the field of view of a solar cell as large as possible and minimizing reflections at the air-to-solar cell interface by using features found in a compound fly’s eye. They have used numerical simulations to demonstrate an increase in efficiency by modeling the curved, textured, outer surface of a compound eye on the surface of a solar cell. They have also formulated a nanomanufacturing method for replicating multiple copies of corneal “biotemplates”. Developing this capability would allow actual fly’s eye corneal layers to be replicated multiple times, perhaps to form an array placed over a solar cell. Overall they are working towards duplicating a fly’s eye as realistically as possible in 3D to maximize solar cell light collection and efficiency.

This is yet another example of how optics found in nature can be adapted and applied to solve real-world problems. Perhaps one day (soon?) fly’s eye solar cells will be commonplace.

Readers, please welcome our newest poster, Jennifer Rouke. With Jennifer’s help, we’ll be better able to bring you interesting topics while balancing the demands of our clients’ projects and our own research. Jennifer is an optical engineer on the ASE Optics team. Her doctoral research at the Institute of Optics at the University of Rochester was on birefringence in gradient-index (GRIN) materials. Read more about Jennifer’s background.

It's been a really hectic few months here, what with SBIR proposals, a fewconferences, and, of course, actual engineering. We're not complaining about being busy, of course, and we recently hired a new scientist, Wade Cook, to act as Engineering Manager. You can expect to read posts from him here in the near future.

John Hammond (our patent agent over at  Patent Innovations) and his colleague Bob Gunderman are the authors of a really nice newsletter called The Limited Monopoly. A few years ago they wrote a hysterical article entitled "Patentability and the 'Long-Felt Unmet Need'—The Christmas Tree Stand as a Case Study." In the spirit of the season, John has given us permission to share it here. Enjoy!

Got a general optics question?

We're looking for blog topics that interest you. Email us your question and include your mailing address. If we pick your question, we'll send you an ASE Optics lens cloth!

Dr. Daniel Fletcher's research group at University of California Berkley has developed a microscope attachment for cell phones. Termed the "CellScope", the attachment turns "the camera of a standard cell phone into a diagnostic-quality microscope with a magnification of 5x-50x." We think this is cool. We think it's even cooler that Aardman Animation (the folks behind the fantastic Wallace & Gromit films) have used the CellScope to make the world's smallest stop-motion animated film. Here's a link to the film, "Dot"; and here's a link to how it was made

CNN has a nice glossy article on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). The goal of NIF is to generate energy through controlled fusion triggered by laser pulses. NIF is now the largest laser in the world, a title formerly held by the Laboratory for Laser Energetics (LLE) here in Rochester, NY. There's some friendly competition between the two projects, but the relationship is fundamentally collaborative. There is a constant flow of technology, knowledge, and even personnel between the two projects. ASE is quite proud of our long history of supporting LLE (almost everyone who works here as also worked at LLE directly or indirectly over ASE's history). My big contribution to the lab was developing the alignment method for the large mirrors that focus the back and side illumination onto the target during some experiments, a topic we may cover in a future entry, as it has a very nice blend of optics and mathematics (which is what I do best). ASE also has had a big hand in developing the many optical diagnostic packages that monitor the quality of the system as a whole.

t's been twenty years since the Hubble Space Telescope (HST) was launched on April 24, 1990. The Connecticut Post has a really nice article describing how the engineers who designed HST still remain emotionally attached to the project.

As is well known, when the first images arrived from HST, it was discovered that the primary mirror was flawed. The flaw was caused because of an error in the reference optics used by Perkin-Elmer to test the mirror. Rochester, NY has two notable connections to fixing this problem. First, Eastman Kodak's Commercial and Government Systems Group (now a part of ITT Space Industries) had independently manufactured a back-up mirror for the HST. Unfortunately it was not feasible to replace the primary mirror while the HST was in orbit. Second, Jim Fienup (now a professor at the University of Rochester Institute of Optics) developed "phase retrieval" computer algorithms that were able to diagnose and digitally correct the images Hubble was sending back. This information was later helpful in designing the Corrective Optics Space Telescope Axial Replacement (COSTAR) that was added to Hubble to correct the spherical aberration.

The Giants' Shoulders (originally organized by a colleague over at Skulls in the Stars) is a monthly event in which bloggers from a variety of disciplines and backgrounds all write about science history on the same day (more or less). It's always an interesting read, and this month it's hosted at The Lay Scientist. You can see a list of the articleshere.

Peter Emmel just notified me that the White House has put forth a request for information (RFI) for new "Grand Challenges" for the 21st Century. In essence they are soliciting ideas for a new "Moon Shot." There are no formal formatting instructions, and anyone can participate. It is essentially a public opinion poll on how research dollars will be spent... So speak up! The main PR site is here, but more detailed information is available from the original press release.

I wanted to point people toward a really good article that appeared in the SPIE Professional back in October 2009 entitled "Productive Stupidity" by Martin A. Schwartz. It's a reprint of his article "The importance of stupidity in scientific research", which previously appeared in Journal of Cell Science 121, 1771 (2008). The thrust of the article is that "science is supposed to be hard," and most of the time you're going to be wrong... at least if you're doing it right. That fact can be extremely difficult to accept, especially when we have built our entire education system around getting answers "right" on an exam. Even classroom laboratory research is generally focused on reproducing a certain result, rather than self-discovery. The upshot is that most science students leave college still believing that getting the "wrong" result is bad. If you are truly doing new research, then you are testing things that no one has done before, and that means that most of the time what your experiments reveal will not be quite what you expected. Figuring out the how and the why of unexpected results is what scientific research is really all about. (As Celia recently discovered over at Ph.D.) And just to drive this point home one more time, I encourage folks to listen to this interview with 2009 Physics Nobel Laureate George E. Smith. Around the 11 minute mark he talks about what it was about the Bell Labs environment that made their discovery of the CCD camera possible. He summarizes it this way:

In the exploratory efforts we had... we thought that if half of the projects you started actually worked, you weren't being imaginative enough... not taking enough risks.

Welcome to the blog for ASE Optics, Inc., a contract engineering firm out of Rochester, NY specializing in "inspired optical engineering." We create applied engineering solutions for a wide range of applications. Our focus is on innovative, cost-effective designs. We enjoy solving problems with creativity and collaboration. Our highly skilled PhD, MS, and BS level engineers bring extensive experience and knowledge of both theoretical and applied systems. Drawing on the depth of optical talent in the Rochester, New York region, our team has the expertise to tackle the most complex of challenges.

This is just under the wire, but Greg Gbur over at Skulls in the Stars put up a nice article on women in science that alerted me that today is "Ada Lovelace Day." In the words of the Ada Lovelace Day organizers:

Ada Lovelace Day is an international day of blogging (videologging, podcasting, comic drawing etc.!) to draw attention to the achievements of women in technology and science.

Ada Lovelace is widely regarded as the mother of computer programming, as she was the first person to develop a computational algorithm for Charles Babbage's analytic engine. As it turns out, women have also been a driving force in the field of optics. I would like to take a moment to highlight someone particularly important to Rochester, NY: Hilda Kingslake.

The name "Kingslake" is famous in optics because of Rudolf Kingslake, but, as it turns out, Rudolf actually married into the field. Hilda Conrady, born 1902, was the very first full-time student in the Technical Optics Department of the Royal College of Science, a unit of the Imperial College of Science and Technology in London. Furthermore Hilda was already a second-generation optical scientist, as her father was Alexander Eugen Conrady, a professor of optical design.

Rather than recount the story of Hilda and Rudolf Kingslake's amazing 74 year joint career in optics, I will instead point people to a wonderful memorial written by Brian Thompson for the 75th Anniversary of the Institute of Optics at the University of Rochester. The article is chapter 6 in the book A Jewel in the Crown, edited by Carlos Stroud. (Incidentally, for those considering a career in Optics, you may be further tempted by chapter 37, by David Aronstein: "Mmm... Doughnuts", which traces an Institute of Optics weekly tradition that now spans four decades.)