How StunLight Works

Our incoherent light based non-lethal weapons, high intensity spotlights & searchlights, and long range infra-red (IR) illuminators support military, security, law enforcement, and general first responder applications.

Our StunLight non-lethal light beam light weapons provide a first responder with a new non-lethal tool and pain-free choice between shoot and don’t shoot, at ranges that are generally greater and more targeted than other non-lethal/ less-than-lethal) weapons. This helps to ensure the safety of the first responder, but also gives them time to decide on the proper level of force that should be used.

Those exposed to the StunLight beam are instantly unable to see their surroundings and their aggressive physical motions are curtailed. The subjects report the effect to being like repeated hits with brilliant flashes on steroids. Upon removing the StunLight Beam from the subject, they recovered within minutes to their pre-exposure condition.  There is no permanent structural or functional changes to their eyes or visual system.

The StunLight optical and electronic design incorporates considerations of retinal bleaching,  photopic and mesopic,  rhodopsin bleaching effects on Rods and Cones, and efficacy enhancement of  the lights strobing effect, and safety resulting in the neural mechanisms to cause fatigue in the central nervous system through temporal frequency characteristics of the neural response to visual stimuli to maximize disorientation.

What is the Visible Light Stun Effect?

The visible light stun effect is a temporary large reduction in visual sensitivity due to neural overload, in response to a sudden change in applied light.  It is a particular case of light adaptation, which is the process by which the eye adapts from a low intensity of applied light, to a high intensity of applied light.

Called the StunLight™, the effect has been described as being hit with a barrage of overpowering “light-bullets”.  It is similar to, but more intense than, what occurs when a person is exposed to a camera for flash photography.

What is the StunLight’s Strobe Effect?

The Strobe or Flicker results in vertigo, is an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a bright light.  The Strobe effect results in a induced disorientation, vertigo, and occasionally nausea when flashing at 3 Hz to 20 Hz, the frequency of human brainwaves.[2][3] [2]Bunker, Robert J. (July 1997), Nonlethal Weapons: Terms and References, p. 17, ISBN 9781428991934 [3] Lyell (September 1997), Non-lethal Weapons: Draft General Report (PDF), p. 3

What is StunLight’s Temporary Flashblindness?

Photoreception occurs in the retina.  Light receptive pigments absorb the applied light resulting in chemical reactions causing nerve impulses which are processed and perceived by us as an image.

The optic nerves converts the energy of light into electrical signals.  The retina is located at the back of the eye and contains rods and cones.  Approximately 125 million rods and 7 million cones are located in the retina.  Ganglion and bipolar cells provide the interconnections between the rods, cones, and the optic nerve.  The optic nerve has approximately 1 million fibers.

The rods provide night vision. A single photon absorbed by a cluster of adjacent rods is sufficient to send a signal to the brain.  However, since a single rod may be connected to multiple ganglions, and multiple rods may be connected to a single ganglion, the brain cannot determine exactly where a single rod is, and this results in un-sharp images.

The cones provide day vision.  They have a diameter of 1.0 to 1.5 μm, and a spacing of 2.0 to 2.5 μm.  There is one cone per nerve fiber, the resulting day vision is sharp and colored.

When the eye is dark adapted, the rods are active and when the eye is light adapted, the cones are active.

Rhodopsin is the light-absorbing rod pigment.  It absorbs the electromagnetic energy of the applied visible light wavelengths.  Since rhodopsin most strongly absorbs green-blue light, it appears to be reddish-purple, and is also called visual purple.

Figure 1.   Absorption spectra-Source: What ‘typical’ human cone cells respond to http://www.unm.edu/~toolson/human_cone_response.htm

Photopsins are the light-absorbing cone pigments.  There are three.  Each is composed of a unique opsin, and retinal, and each absorbs unique band of the visible light wavelengths, as shown in Figure 2.  Photopsin I, II, and III have peak absorptions at longer wave lengths of the yellow-red, medium wave lengths of green, and shorter wave lengths of blue-violet wavelengths.  This is how color is perceived.

The rhodopsin and the photopsins are the initial chemicals in the light conversion sequence into electrical signals.  In the absence of applied light, the retinal is in an 11-cis configuration, which has a link, and is bonded to opsin.  In response to the application of light, the energy provided by the absorbed photons causes the retinal chemically modify a carbon double bond into all-trans configuration. This change in the physical configuration of retinal is called isomerization, and is the basis of photoreception.

After the retinal isomerizes, it no longer fits on the opsin bonding site, and as a result, the pigments split into their respective opsins, and retinal.  This is called bleaching.  The bleaching, in turn, starts a sequence of electro-chemical reactions that result in your perception of an image.  The first chemical reaction occurs within a second after the application of the light.  If light is continuously applied, the rods and cones are in a steady state in which the rates of bleaching and regeneration of visual pigments are equal and no image or a whiteout is perceived.

How does the StunLight work?

To invoke the stun effect, a very bright white light from a LED light engine is instantaneously applied to the eyes.  When this occurs, all of the visual pigments are bleached and become temporarily unresponsive desensitizing the retina.

Prior to this desensitization a flood of electrical signals are produced and the retina is saturated.  The resulting perceived image is uniformly white, and, the subject is unable to see their surroundings.  This naturally results in tendency to stop physical activity that require gross motor skills such as walking, running, or aggressive movements.  This phenomenon is called stunned, dazzled, or temporarily incapacitated.  Some subjects have described the effect as being confused or having vertigo while not being able to see. .

Since the retina has no pain receptors, the effect is painless.

What is the typical recovery time?

The recovery from stun effect is process by which the retina’s image receiving capability returns.  It is best described as the process of adapting from a high intensity of applied light to a low intensity of applied light, aha dark adaptation.  It is similar to what occurs when a person walks into a completely darkened room at night from the outdoors on a bright sunny day.

When the eye is light adapted, the cones are active.  If the external light is suddenly removed, the resulting perceived image is uniformly black, because the cones function poorly in low light, and the rods are not yet adapted, because the visual pigments have been bleached out due to the bright light.

Once in the dark, the visual pigments regenerate.  The all-trans retinal is reduced to all-trans retinol, a second form of vitamin A, and travels back to the retinal pigment epithelium to be oxidized back into 11-cis retinal.  The 11-cis retinal then travels back to the rod outer segment, where it can again be bound with an opsin, which increases the retina sensitivity.

Figure 5 shows the dark adaptation response.  The horizontal axis is time, in minutes.  The vertical axis is the retina receive sensitivity, expressed as the logarithm of the magnitude of the luminance of the applied light, in micro-micro Lamberts (µµL), where one Lambert is candela per square centimeter, and where 1 candela is 1 lumen per steradian.   The shaded area represents 80% of the population.  Adaptation consists of two parts.  One, which is fast, is due to neural response.  The other, which is slow, is due to the regeneration of the visual pigments.  Full adaptation can take up to 30 minutes.

Figure 2.  Dark adaptation recovery response-Source: http://michaeldmann.net/The%20Nervous%20System%20In%20Action.html

Since the recovery from the stun effect is a particular case of dark adaptation, Figure 2 is an estimate of the time needed to fully recover from the stun.

What are the Safety Exposure Limits of Light?

StunLight™ is designed to only emit light in the visual wave length of 400nm to 700nm.  The StunLight’s bright flashes are specifically limited in duration to avoid thermal limits of the eye structure.

Thermal exposure limits are based the heat transfer characteristics of the eye components, and on involuntary eye movements.  The thermal limits are established to prevent damage by limiting the maximum temperature in cornea, lens, and retina.  The irradiance needed to cause temperatures of to 37 oC to 45 oC depend on the initial temperature of the retina, the magnitude and time of the irradiance applied, and the size of the image on the retina.

The International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the American Conference of Governmental Industrial Hygienists (ACGIH) have published limits for the exposure of humans to broadband incoherent optical radiation based on exposure limits for photo-chemical injury studies of corneal and retinal effects, and confirmed with human eye accident data. Guidelines on Limits of Exposure to Broad-Band Incoherent Optical Radiation (0.38 to 3 µm), published by the International Commission on Non-Ionizing Radiation Protection is a useful safety tool provide a technical data source for the protection of the general public from the potentially effects of long-term exposure to broadband incoherent optical radiation.

Also, the US FDA has established optical safety regulations for lasers and selected ultraviolet-emitting lamps, but does not have regulations for visible incoherent light sources.  FDA has previously approved the use of a laser dazzler for law enforcement use.

Since the application of incoherent light to the eye in the case of StunLight™ is for extremely short durations of time, the accumulated energy applied at the established minimum safe distances or greater distances does not result in ocular tissue damage in the way that laser light can. Therefore the use of incoherent light photons for a non-lethal disruptor is inherently safe.

Additionally, the human eye is naturally adapted to protect itself against sudden increases in directed incoherent light:

  1. The eye has an extremely wide operating range: rods are triggered by luminances between 10-6and 101 cd/m2; cones are triggered by luminances between 10-2 and 108 cd/m2; the retina has a range of 1014 cd/m2.
  2. The eye is adapted to sudden change in light intensity resulting in an involuntary pupil contraction (myosis) that occur within 20 milliseconds after the application of the light. This involuntary contraction minimizes the amount of energy protecting retina from thermal and photo-chemical injury.
  3. Sudden changes in applied light also result in involuntary closure of the eyelid in less than 250 milliseconds.  This natural response limits the duration of an exposure to a sudden increases in applied light protecting the cornea, lens, and retina.
  4. Sudden change in applied light results in an involuntary movement of the head to avoid the bright light further protecting the lens and retina from thermal injury
  5. Bleaching of the visual pigments in the retina when exposed to light is an involuntary response, that may also protects the rods and cones from over-stimulation.

It should be noted that an aggressor subject to StunLight™ that has voluntarily or involuntarily closed their eyes or turned around to avoid the bright light is effectively disabled and has been temporarily deprived of one of their senses, that of vision.