Optics is downright complicated. This branch of physics studies how light interacts with the objects around it. Naturally, that tends to include everything, making it relevant to a plethora of fields. For that reason, keeping optics simple is pretty close to impossible.
Take your eyeball. It is made up of many different parts including the pupil, the retina and right at the front, a curved lens. Everything we see is in fact light reflecting off of that thing and hitting your eye. The pupil surrounding the lens controls the amount of light the brain is letting in and automatically brings it to focus. Because of the curve in the lens the light is forced to bend, and the image actually registers upside down. It’s your brain that is responsible for flipping it right side up as it travels through your retina and optic nerve. Cool, no?
Cool indeed, but now let’s take it up a notch. According to the Vision Council of America, 75% of adults use vision correction products worldwide. Vision impairments come in every shape and size: near-sighted, far-sighted, astigmatisms, etc. They are all managed with the use of lenses, tailored to each eye. One tool will resolve opposite issues when used the right way. Think of a telescope versus a microscope. The result is completely derived from the construction and assembly of a lens (or combination of lenses) and grouped with a system, creating an optical device.
Boresight into the Future
Optical devices are already prevalent in everyday life above and beyond eyesight, of course. At the core, an optical device is a lens (or sensor, or laser) attached to a processor known as a system. It's these devices that are shaping innovation and bringing the future to the present. That future is being driven by artificial intelligence (AI) and that intelligence needs a set of eyes. Autonomous vehicles, smart manufacturing, robotic surgery and virtual reality are all possible because of cameras and other optical devices. It is not surprising that the design, assembly and validation processes need to be executed flawlessly. Active alignment is the most dependable method for this type of assembly, because it is a dynamic process. During active alignment, an optical component is set within a device as the system’s power is being manipulated while simultaneously measuring the image quality repeatedly. The key to a crystal-clear image is the smart alignment and fixation of the lens to the imaging sensor on the device, supporting large fields of view and boresight optimization.
Five things need to happen to make this work flawlessly:
Preparation
First things first, and perhaps most crucial is the preparation stage. Each component needs to be inspected to confirm there are zero defects and no particles are present. They must be cleaned, treated and verified before assembly begins. The appropriate lens quality needs to be chosen to perform a chip test that will detect any dysfunctional pixels in addition to all other required tests. If any of the components in the assembly are off, the end result will enhance those flaws. Not good.
Glue Dispensation
Once the quality of the components is confirmed, the pieces can be glued together. This is nothing like kindergarten crafts. Dispensation is executed very skillfully to avoid creating deformities caused by misplacing or mismanaging the glue. Multiple techniques can be used including jetting (non-contact) and volumetric (contact). Parameters are controlled to compensate for varying glue conditions caused by internal friction. Friction can change the consistency of glue and needs to be managed the right way to avoid a gloopy mess...also known as a scrapped system. Machine vision technology is used to measure the exact dispensing position as well as analysing results from beginning to the end of the process.
Alignment
Within a clean room, alignment is done using a multi-axis motion system. The components are assembled together using a variety of targets (either real or projected) while verifying touch-points throughout. Testing and substantiation are also performed dynamically to produce accuracy to the micrometer. Applications that are using optical devices like mirrorless cars don’t allow for a lot of wiggle room, it’s not the time to mess around.
Curing
You didn’t think we were done with the glue? UV-curing of the glue is necessary for a sturdy structure but can and will shift components from their original setting. This variance is known and must be factored into the original measurements and tests. This is what makes checking the test points throughout the assembly process so crucial. Thermal curing needs to be repeated a few times to make sure the device won’t fall apart.
Validation
And of course, final validation. Even though verifications are being repeated over and over throughout assembly, each step has the potential to create a unique defect on its own. Final validation will verify the state of the components one last time, in addition to the inspection of boresight, MTF, distortion, stray light, EFL, and field curvature at the very least.
Lead the Way to the New Everyday
Optics is a science that is used every day and is completely taken for granted. It is the kind of thing that goes completely unnoticed, until something is not the way it’s supposed to be. We are about to open the door to a lifestyle that includes very sophisticated artificial intelligence, and will be dependent on this science. The potential of what AI can accomplish has so much value and can improve the world in dramatic ways. From driving a car, to hospital intervention, to your fridge telling you when you need more milk, when you consider how many things will be managed on our behalf, it’s nice to know they can see properly.
For a crash course in optical alignment, please visit Averna’s website, or ask to speak with one of our Vision experts.
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