Opposite ofnotch filter

A literal illusion is when the image you see is different from the images that make it up. For example, the illustration Hill created which is actually two images strategically drawn to look like one fluid image is a literal illusion. Think of it as a reversible figure. The end result you see in a literal illusion is based on your perception. Both images exist.

Alluxa thin-film optical interference filters and dielectric mirrors are all hard-coated using our SIRRUS™ plasma deposition process on equipment that was designed and built by our team. This allows us to reliably and repeatedly produce the same high-performance thin-film notch filters over several different coating runs, which translates to consistent performance across all of your systems.

Notch filterschematic

ULTRA Series multi-notch filters can be designed with greater than OD8 blocking between bands, steep edges, and up to 98% transmission. They are perfect for applications that require simultaneous blocking of multiple laser lines.

The fascination with optical illusions has spanned the globe for centuries. Greek philosophers like Plato described them as tricks played on us by our senses and our minds. By the 19th century, a famous cartoonist W.E. Hill embraced the phenomena of optical illusions by skillfully sketching a picture that was simultaneously two images. The figure you saw was determined by your perception. It was either a young girl or an old woman.

Notch filterQ factor

Figure 1. Broad range transmission notch filter used for precision blocking of the 532 nm frequency-doubled Nd:YAG laser.

There are three main types of optical illusions including literal illusions, physiological illusions and cognitive illusions. All three types of illusions have one common thread.  The perception of the image given to the brain doesn’t measure up. That’s why optical illusions are referred to as a “trick” of the eye.

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ThorlabsNotch Filter

For example, the retinas in your eyes – the layer where visual images are formed – actually “sees” images upside down and backwards. Your brain flips them, so you see images right side up and reversed. Every single time. Yes, your brain is the original Photoshop genius.

The deep blocking, tight wavelength control, steep edges, and wide-range transmission of ULTRA Series thin-film notch filters all allow for precision blocking of lasers or other light sources, without sacrificing the quality of target signals.

Your eyes are amazing organs. Did you know if you have blue eyes, you share an ancestor with all other blue-eyed people on the planet? That’s because blue eyes are a genetic mutation that appeared more than 6,000 years ago. All humans originally had brown eyes.

Plus, your brain controls your entire nervous system. You would think it always reigns supreme, but sometimes it doesn’t. Once in a while your eyes are capable of tricking your brain into seeing things that aren’t really as they appear. Or are they? This is called an optical illusion.

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Alluxa is an ISO 9001:2015 certified, ITAR registered manufacturer of high-performance optical filters and thin-film coatings.

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ULTRA Series notch filters can also be custom designed with extremely steep edges for use in Raman spectroscopy applications. In some Raman applications, notch filters are used to block the excitation laser wavelength while simultaneously transmitting both Stokes and anti-Stokes signals to the detector. If the notch edges are not steep enough, then the signals close to the laser wavelength will be lost.

RFnotch filter

Each hard-coated ULTRA Series optical notch filter is designed and rigorously tested to exceed the the most advanced system requirements. They are all ideal for use in applications such as fluorescence microscopy, endoscopy, and DNA sequencing.

Depending on the wavelength ranges and requirements of your system, ULTRA Series notch filters can be custom designed to meet one or more of the following challenging specifications:

If you take a step beyond the interesting stories your eyes tell, you will discover how they actually work. Your eyes work in constant unison with your brain, which is why you see the world as you do.

This type of illusion is the most researched by scientists and psychologists because it is the most complex type of trick the eye can play on the brain.  Unlike other optical illusions, these illusions rely on what the subconscious mind thinks and how it relates one object to another.  In other words, what you see is believed to give insight into the depths of your thinking. A cognitive optical illusion uncovers what your brain infers and understands about something that has not been explained.

These types of optical illusions are more complex because they reply on the over stimulation of the brain’s senses. The eye “sees” so much light, movement, color, dimension and size that it confuses the brain. The mind benders you see like geometric illusions and impossible pictures are physiological optical illusions.  At first glance, a two-dimensional figure looks like it’s three-dimensional.  That’s because the brain immediately interprets it to be that way. Upon further investigation, the brain realizes what the eye is actually seeing.  The image in question does not exist in nature.