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Talking with Ted McHenry, Engineering Process Leader

In this interview, we spoke to Ted McHenry, one of the initial team members of the Gray Optics team and one of the anchor points of the growing group. As the Mechanical Engineering Manager and Process Leader, he brings 16+ years of experience to our team. With his diverse knowledge in mechanical design for rapid prototyping development and internal process development keeps our standards ultra-high and forward-looking.

“The opportunity to make the world a better place lies solely in your desire to do so.”

 

Describe your current role – do you manage others or mentor other engineers?

In my current role as Mechanical Engineering Manager and Process Lead, I lead a team of 3 outstanding individuals with very unique backgrounds. I do my best to offer guidance to those who need it, but what my team may not realize is that they provide me just as much, if not more, in return. I am also a technical contributor to a number of projects that we have running at any given time, designing products to meet our customer’s product requirements. The third facet of my role is to make sure that Gray Optics is doing the best we can to be consistent across project teams through the creation and updating of various processes and internal guidelines to make sure that we are efficiently and effectively meeting our milestones and goals.

What gets you up in the morning?

My greatest desire and motivator is to leave things better than they were when I arrived. If I can change even just one thing for the better every day, then I feel I have made at least a small difference to someone out there. This filters up to the work that Gray Optics is doing to improve and save lives by constantly pushing the boundaries of technology with our partners.

How do industrial optic prototyping and engineering differ from medical device engineering? What are the challenges you see?

The major difference between industrial and medical device development is the level of testing (validation and verification) that is required to meet the necessary requirements put forth by the FDA. This pushes out the time to market for medical device projects, so it takes a bit longer to see the final product on the market making a difference. Regardless of the type of project, we always strive to provide the highest quality solution to our customers’ challenges that fit within the boundaries of cost, schedule, and scope.

How does being an engineer influence how your kids move through the world? What do you hope to change for them with your work?

I’ve always had a desire to understand how and why things work, which is how I found myself at the University of Maine in Orono as an undergrad pursuing a mechanical engineering degree. In guiding and learning from my children, one of the most important things that I try to instill in them is that everything we do has an effect on everything around us. It’s easy to explain this concept using tangible things, like fixing something broken together. Sure, we could throw it away and replace it…but now we’ve added something to a landfill and missed out on an opportunity to add life to something and learn something new together! As they are getting older and wiser, the lesson expands and becomes more personally meaningful. One small gesture: stopping to see if the car with hazards flashing on the side of the road needs help can completely change the outcome of that person’s day.

I genuinely hope that the work we do here at Gray Optics with our partners improves the lives of everyone out there, better diagnostics, improved test results, and quicker recovery times from surgical procedures should that be necessary. I hope my children see that no matter where you’re from or what school you went to, the opportunity to make the world a better place lies solely in your desire to do so.

Resolution and MTF Testing

In the past, when sensors only offered at most 640 pixels, it was easy to make an imaging lens that could outperform the camera’s sensor. Today, with pixel sizes less than 1 micron,  pixel count on sensors have significantly increased —sensors now regularly have over six million pixels. To keep up with this technological advancement and provide superior image quality, lens performance must increase, and measuring how well a lens performs requires the correct metrology. This is where resolution and modulation transfer function (MTF) testing comes in.

Read on to learn more about MTF testing, its benefits, common methods of evaluating lens resolution, and MTF and resolution testing components.

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What Is MTF Testing?

Since the introduction of linear system analyses to the optics field, demand for higher quality, higher resolution optical systems has increased. Designers and metrology scientists have turned to modulation transfer function (MTF) testing as a standardized method of optical system characterization.

MTF testing is the measurement of the ability of optical systems to transfer various levels of detail from an object to an image. Performance is measured in terms of contrast (the intensity difference between the image’s black and white regions) and accounts for real-world factors like optical blurring.

An MTF test bench’s calculations are contrasted as a function of spatial frequency within a two-, or three-dimensional coordinate system. This function reveals how well-resolved an object is based on its size.

Common Methods for Evaluating the Resolution of a Lens

There are three common methods of evaluating lens resolution:

• Reverse projection testing: This is a lens-only test where the lens is used as a projector, reversing the typical image. This method is a simple, low-cost, and fast resolution test. However, reverse projection testing can’t effectively measure contrast levels since it depends on the operator’s eyesight.
• Point-spread function (PSF) testing: This method relies on projecting a pin-point of light into the lens system and measuring the blurring at the image plane. From the measured PSF, the MTF is calculated and is the most direct way to measure MTF of a lens.
• Slanted-edge MTF testing: This is a system-level test that typically includes the impact of the image sensor MTF. Compared to PSF testing, slanted-edge MTF testing is quicker, more adaptable, and can capture the MTF across an entire image in one measurement.
• Camera testing: This test isolates the image sensor MTF from the lens MTF. Camera tests can test multiple field points simultaneously, are highly adaptable, and can be used to measure system-level performance, including the lens, camera, illumination, and image processing algorithms. However, camera testing results can be difficult to correlate.

Benefits of MTF Testing

There are several benefits of measuring MTF:

• Provides a direct, quantitative measure of image quality: MTF testing helps to quantify the overall imaging performance of a system in terms of contrast and resolution.
• Objective and universal: The test engineer doesn’t have to make subjective judgments about contrast, resolution, or image quality. With modulation transfer function testing, there are no standardization or interpretation challenges.
• Enables system testing that mimic application conditions: MTF testing is performed on the image or wavefront produced by an optical system, allowing the parameters influencing lens performance and design to be recreated precisely during testing. You can model the field angle positions, image plane architecture, conjugate ratios, and spectral regions in the test.
• Accurately predicted and toleranced: Almost all modern lens design software allows for precise graphical simulation  and the impact of tolerances on the polychromatic modulation transfer function. Measured MTFs can be compared to simulated MTFs.
• Testing versatility: MTF testing offers a method for directly measuring the image features related to overall system performance, such as field curvature, blur spot size, and distortion.

Components of MTF and Resolution Testing

These are the three main components of MTF and resolution testing:

• MTF vs Field of View: This involves measuring the MTF across different image points and observing the resolution changes
• Depth of field testing: This involves evaluating the MTF at different distances above and below the best focus.
• MTF vs Wavelength: This involves quantifying how the MTF of a lens changes across different wavelengths of light, including visible and near infrared spectrums.

Contact The Metrology and Testing Experts at Gray Optics

Resolution and MTF testing are critical in constructing the proper lens specifications. At Gray Optics, we specialize in metrology and are committed to delivering products that have undergone rigorous testing to ensure they meet the highest quality and performance requirements. To learn more about our metrology capabilities visit this page: Metrology & Test. Our highly experienced engineers and precision assembly teams use industry-standard test methods and can design and build custom solutions to meet your unique needs. Talk to an expert to get a conversation started.

Complex Optics Prototypes Created With Additive Manufacturing From Gray Optics

Portland, ME, July 8, 2022 – Gray Optics’ Additive Manufacturing experience combines component and optical design expertise with high-power additive laser metal manufacturing. Applications for these highly complex parts include dental implants to industrial parts, which are too difficult for lathe or millwork, and now are made with a metal powder bed fusion system. Melt pool diagnostics and calibration of your existing 3D printer are also available through the Gray Optics team with the development of additional sensors. 

Fully custom 3D printer systems with customer-controlled parameters and diagnostic sensors are also available for OEM manufacturers that require even more precise control over their technology. Gray Optics helps customers optimize the beam quality (shape and size) through detailed optical and mechanical modeling that follows a detailed Product Development Process.

“3D additive manufacturing allows for complex geometries, weight savings, and time savings. The process allows engineers to design the part in CAD software and directly export to the printing platform for fabrication. Our team supports development calibration and in-situ, real-time monitoring systems to optimize machine operation,” states Dan Gray, Owner, and Founder. “Our team forms a collaborative partnership at every stage of the product development process.”

One example of this technology from Gray Optics is the development of customer in-situ quality control measurements.  

The Problem: The existing optics used in the customer’s melt pool monitoring detection module did not provide the optimal spectral response, light transmission, and reflectivity efficiency that enabled high signal-to-noise (S/N) measurements. This insufficiency limited the end customer’s ability to accurately measure and understand how the build process progressed in real-time.

The Solution: Gray Optics developed a custom dichroic beamsplitter to provide high transmission of the laser light and high reflectivity over the most critical spectral ranges. The dichroic beamsplitter was designed to work with kilo-watt NIR lasers to ensure it would perform to specification under continuous use over the build process without laser damage. In addition, the developed coatings have been certified to continuously operate at significantly higher power densities offering adequate safety margin to support even higher laser products in the future.

Partner with Gray Optics for your subsequent OEM instrument product development. Learn more at GrayOptics.com

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ABOUT GRAY OPTICS

Gray Optics was established in 2018 in Portland, Maine, to bring engineering development and prototype advancements to the surgical, life sciences, and industrial optics marketplace. Product engineering, assembly, measurement, and testing teams handle each custom problem-solving target as an independent innovation partnership, finding the optimal solution for each challenge. The mission at Gray Optics is to change, improve, and save lives by developing new optical products for the medical, life sciences, and industrial markets.

Learn more about Gray Optics.