The Definitive Guide to Photonic Barriers (Part 1)

Photonic Barriers are often misunderstood as a single type of visually obstructive phenomenon, but the truth is photonic barriers come in several different variations. In this article, we are going to dive into what exactly photonic barriers are, and how to quickly assess the type of photonic barrier. In Part 2, we'll go over how to overcome these obstructive phenomena passively and actively... So stay tuned!

First, let us broadly define the Photonic Barrier

Photonic: Radiant energy relating to quantum packets of light.

Barrier: An obstacle that prevents access.

So... Light that prevents access?... Yeah. Pretty much. But I'll formalize it for you-

Photonic Barrier: Light in ones field of view that obscures a subject or area of interest by means of overexposing, oversaturating, or shadowing.

     Let’s break down this definition. "Light in one's field of view," refers to when light propagates inside ones immediate visual perspective. "Obscures a subject or area of interest," refers to when light interferes with a person, place or thing by darkening, abberating, or distorting it's visual information. "By means of overexposing, oversaturating-” is a phenomenon in which an organic (ex. Human eyes), analog (ex. image intensifier tube), or digital (ex. CMOS Sensor) photodetector is capturing excessive light. "Or shadowing" is when light casts on an object (or person) producing a dark sillouhette on the opposite side of the object. Shadowing causes intense low visibility within a sillouhetted area relative to the illuminated area in your field of view..

Photonic Barriers Relating to the Area or Subject of Interest: Involved & Uninvolved

     The most common misconception for photonic barriers is that the obscuring light in a scene must be directly in front, behind, or beside the subject of interest in a scene-- this is simply not the case. Photonic barriers DO NOT need to be in the same vicinity to obscure a subject. 

When something is being obscured by light, and the photonic barrier is in its immediate vicinity, it is called an Involved Photonic Barrier.

When something is being obscured by light, but the photonic barrier is NOT in its immediate vicinity, it is called an Uninvolved Photonic Barrier.

     "But wait!!!-" you say, "what if something is being obscured by multiple light sources, and the photonic barriers are both in-and not in- its direct vicinity?!"

     I hear you, my overly complicated friend. And to this I say that these are technically referred to as a complex photonic barriers. However, involved photonic barriers will always be more severe than uninvolved photonic barriers. So the method you use to overcome an involved photonic barrier will simutaneously overcome an uninvolved photonic barrier. So for redundancy's sake, we will not be including complex photonic barriers in this discussion.

Uninvolved Photonic Barrier Example: On a dark night in the forest, a blazing campfire to the right of you is making the distant woodland to the left of you dark and indistinguishable.

     As you can infer from the previous example, the photonic barrier (campfire) is uninvolved with the area of interest (distant woodland). It is uninvolved because the campfire's light is not casting directly in front, behind, or immediately beside the distant area (key word is distant). The campfire is still obstructing the visual information of the distant woodland because your eyes are being overexposed by the light. Because your eyes have natural irises, they can (and will) constrict when too much visible light enters your eye. This constriction limits the amount of intense light that enters the eye. Since this is a uniform limitation of light, all other areas in the field of view will be dimmed proportionally to the fire.

     As previously touched upon, photonic barriers can be especially apparent to Night Vision Devices. Modernly equipped NVD's usually have an electronic protective feature built in to them called Autogating. This feature allows the device to uniformly and proportionally limit the amount of light that the tube can amplify-thereby increases a tube's life. External irises or pinhole covers are often attached to the objective lens of the NVD to mimic the natural light limiting mechanism of the human eye's. Autogating, however, will not suffer from mechanical aberrations such as diffraction, like irises will.

Involved Photonic Barrier Example: You are driving westward on your way home from work. You stop at a red light but notice it is extremely difficult to make out the rest of the streetlight. The sun happens to be right behind the streetlight, almost completely obstructing your view of the streetlight.

     As you can infer from the example above, the sun is an involved photonic barrier because it is in the direct vicinity (behind) of the subject of interest (streetlight). 

     Now I know what you're thinking- Involved Photonic Barriers... Uninvolved Photonic Barriers... this is confusing. Well, buckle up cause I'm about to make your life more confusing. But I promise it's for your own good. 

Photonic Barriers Relating to your Field of View: Internal, External, and Compound

     Alright, so up until this point, we have discussed photonic barriers relating to the thing they're obscuring. Now we must discuss and define the photonic barrier as they relate to your field of view. (Field of view-whether we talk about night vision, cameras, or your eyeballs-will always mean the limited area you can see in.)

An Internal Photonic Barrier is when a light source is radiating within your field of view.

An External Photonic Barrier is when a light source is radiating outside your field of view, but has propagated inside your field of view.

A Compound Photonic Barrier is a combination of both Internal and External photonic barriers within your field of view. 

Internal Photonic Barrier Example: A man of interest is shining a flashlight directly at you making it hard to see. 

     As you can infer from the example above, the flashlight is the main photonic barrier, and the man of interest is the "subject of interest" within your field of view. Since the flashlight is emitting light within your field of view, the flashlight is classified as an Internal Photonic Barrier. Since the photonic barrier is also in the same vicinity as your subject of interest, it is an Involved Photonic Barrier as well. We can now define it officially as an Internal-Involved Photonic Barrier.

See? Not so bad, right?

But wait! What would be an example of an internal-uninvolved photonic barrier?

Well, I'm glad you asked. 

Internal-Uninvolved Photonic Barrier Example: You are traveling on the interstate highway late at night. The only illumination you have to see the road in front of you are your headlights. Suddenly, across the median, a large truck with its high beams, fog lights, and top-mounted off-road lights comes barreling down the road. You are immediately blinded from the intense light coming from this electromagnetic douchebag, and now the road in front of you seems all but dark and featureless. 

     As you can infer from the example above, the photonic barrier is the truck with bright light going in the opposite direction down the road across the median. Since the truck lights are inside the driver's field of view, it is an internal photonic barrier, however, since the truck lights are not in the same direct vicinity as the area of interest (road in front of you) this example would be categorized as an uninvolved photonic barrier. Therefore its full classification would be an Internal-Uninvolved Photonic Barrier. 

     Next, we'll move on to the next category of Photonic Barriers: External. External Photonic Barriers are those in which light is being radiated outside the field of view where the light is reflected off an object or feature of the environment. So anytime the emission of photons is outside your view yet still being cast on the environment, it is an external photonic barrier. External light barriers are mainly a problem when they radiate intensely off a very reflective object and back to your eye.

[This is a good time to note that photonic barriers are notorious for casting shadows as their main form of interference, and external photonic barriers are an ugly culprit of this. Shadows caused from photonic barriers are apparent when something in your foreground is being illuminated, causing a prominent shadow in your background. The darker your environment is, the more intense shadows will obstruct your subject when made from an internal or external source.]

External-Involved Photonic Barrier Example: You decide you want to go outside late one night to star-gaze. You are disappointed when you notice that there is an atmospheric haze reflecting the surrounding city lights above you. The diffuse reflection of the city lights makes it almost impossible to see fainter stars or galactic detail.

     As you can infer from the example above, the external photonic barrier is the light from the city lights because photons are emitting from an origin not in your field of view. This light is being diffusely redirected in the atmosphere back down to your eye. Since your area of interest is the entirety of the night sky, and the lights are radiating inside your field of view, this example is classified as an External-Involved Photonic Barrier.

But what about External-Uninvolved?

External-Uninvolved Photonic Barrier Example: You are trying to look out your bedroom window late one night. You notice that your ceiling-mounted lights are reflecting off your white walls surrounding the window. Because of this reflection, everything outside your window looks pitch black. 

     As you can infer from the example above, the external Photonic barriers are the ceiling-mounted lights since they are emitting outside your field of view. Since the reflected light from the walls is inside your field of view, but NOT in the immediate vicinity of the area of interest (outside your window), this is classified as a External-uninvolved Photonic Barrier.

     Last, but certainly not least, is the category of compound photonic barriers. Compound Photonic barriers are the combination of Internal and External Photonic Barriers in a scene. At first you might think that these are a rarity, but when multiple active illumination sources from a team are behind and in front of you, it is easy to come into the clutches of a Compound Photonic Barrier. 

     Below I have two tables showing all the variations of Photonic Barriers previously described. The first table is a written description of the combinations, and the second table is the same format but with picture examples. The columns (Involved and Uninvolved) categorize the type of photonic barrier relative to the subject or area of interest that is being obscured. The rows (Internal, External, and Compound) categorize the type of photonic barrier relating to whether or not photon emission originates inside or outside of a field of view. 

Table 1:

Table 2 consists of visual examples of the different photonic barriers as described in the previous table. Each Picture has the same subject of interest (Snellen Letter Eye Chart) and the same field of view. The only thing that changes in each picture is the photonic barrier. Notice how each photonic barrier is different at obscuring the Letter Chart.

Eye Chart with no Photonic Barrier with adequate illumination (Control):

 Table 2:

Types of Photonic Barriers	Involved
Internal
External
Compound

Table 2 Continued:

(Cont.)	Uninvolved
Internal
External
Compound