Beam Angle and Its Impact on Red Light Therapy Results

 

 

 

Beam angle determines the level of intensity at which the beam of red light from each bulb in a panel connects with your skin. Red light therapy devices on the market today are available in a range of beam angles.

 

Before discussing the treatment implications of beam angle variations, it is helpful to understand the language of the LED lighting world.

If you wish to proceed directly to the “nuts and bolts” of LED beam angles, just scroll down to the next section and refer back to the “Technical Terms and Definitions” section as needed! This section is intended only to help you understand the technical terminology surrounding red light therapy and LED lighting.

 

 

Technical Terms and Definitions

Lens

In an LED bulb, a lens is a piece of transparent plastic material that has two opposite regular curved surfaces used to focus the rays of light. These surfaces can be convex (curved outwardly, causing light rays to converge at a specific focal point) or concave (curved inwardly, causing parallel light rays to diverge away from a central focal point). Due to the brightness of LED bulbs, a lens is used to evenly distribute light. In the case of red light therapy, a convex lens is typically used to refract light waves.

 

The beam angle is the angle between the two opposite directions over the beam axis for which the luminous intensity is half that of the maximum luminous intensity. Put more simply, the beam angle is the angle at which light is emitted from a source. To visualize this, picture a flashlight emitting a three-dimensional “cone” of light. At its source (the surface of the flashlight), it is the size of the flashlight’s diameter. As it is emitted, it radiates outwardly and the field becomes larger.

 

 

The inverse square law dictates that a specified physical quantity is inversely proportional to the square of the distance from its source. In other words, the intensity of light at any given distance from a device equals the inverse of the square of the distance from the source. Intensity decreases the further away from the source you are. The inverse square law dictates that if the source is 2 times as far away, the light is ¼ as intense as at the source. If it’s 10 times farther away, the radiation exposure is 100 times less.

 

 

This is the recommendation as to how far away from the device you should be during therapy. For most red light therapy panels, the minimum recommended distance is approximately four to six inches.

 

 

Light density simply means the intensity of light emitted from the surface of its source. The unit of measure for light density (L) is calculated in candela per square meter (cd/m²). One candela is the luminous intensity of a source that emits radiation at a frequency of 540 × 1012 Hz and has a radiant intensity of 1/683 watt per steradian, which is a measure of circular surface area. (Take heart: You will understand more about the differences between red light therapy beam angles even if you are not a mathematician!)

 

 

Irradiance is the amount of light energy from its source hitting a square meter of its target each second. As opposed to light density, irradiance relies upon the energy connecting with the target rather than the energy level at its source. The unit of measure for irradiance is watts per square meter (Wm²) (Read more about irradiance in red light therapy)

 

 

Light refraction is the bending of light from one transparent substance into another. Refraction makes it possible for us to have light-altering lenses, magnifying glasses, prisms, and rainbows. Even our daily eyesight depends upon this bending of light.

 

 

When light passes through one medium to another (air, for example) part of that light is absorbed by particles of the medium preceded by its ultimate source of absorption.

 

 

How Does Beam Angle Impact the Way Red Light Waves Connect With Your Body?

Red light therapy utilizes refractive lenses in its bulbs, providing maximum absorption of red light wavelengths into your body.

Red light density varies in irradiance level based upon the beam angle of your device.

Wider beam angles diversify (spread apart) red light waves more quickly due to the inverse square law. As beams of light diversify, they lose their intensity and intrinsic healing powers with increased distance between you and the device.

Narrower beams offer less bodily coverage since they are straighter and cover less surface area from a distance, but they do offer more concentrated intensity from longer distances, improving benefits.

It could be more beneficial for light to reach your body more directly in the form of perpendicular (more narrowly angled) beams of light.

Which is better? Greater bodily coverage with wider angled beams, or more targeted, straight light waves administered via lower angled beams? Light scatter and reflection decrease with a minimized distance, but light absorption is maximized at a greater distance. Therein lies the conundrum!

The verdict is not yet in. But, each option offers its own unique treatment solutions.

 

The Most Common Beam Angles for Red Light Therapy Device Bulbs and Their Attributes

A natural level for a general-purpose LED bulb angle is 120 degrees; however, via the use of lenses and reflectors, light beams can be focused to customized levels for red light therapy.

The most common red light therapy LED beam angles are 90, 60, 30, and 10 degrees. When selecting a red light therapy device, pay close attention to the recommended minimal usage distance. The closer you will be to the device during therapy, the less important the beam angle is.

The differing attributes of red light therapy derived from devices with various refracting lens beam angles:

 

 

This is the furthest distance to which red light waves project in mainstream red light therapy. When visualizing the cone-shaped light field projected by a 90-degree light panel, you would need to be further away to realize the maximum benefit of treatment. If you are too close, the light waves will disperse and be “wasted” because much of the red light power is dispersed around your body and never hits it.

 

 

The scattering and dispersion effects described in 90-degree light therapy are diminished with a lesser distance between you and the light source. There is still “light waste”, however, because some light waves are radiating outside of your field of treatment (sideways and beyond your body).

 

 

Light waves are concentrated more directly toward you. The potential for greater benefit exists; however, there is also more light waste (light evading you and escaping outwardly because you are now a smaller target in the field the light is projecting toward.)

 

 

This is a very specialized and straight projection of light. While you experience the maximum level of red light absorption, it might be too highly concentrated at the minimum usage distance. The beams of light may not yet be dispersed enough to provide thorough coverage.

 

To date, there is little evidence to support the supremacy of one lens beam angle over another. Consider your unique health and fitness goals when selecting a red light therapy device, bringing beam angle into the equation as you see fit.

Additional Resource Material

Not much research or reading material is currently available on optimal lens beam angles for red light therapy. Unless scientific studies begin to address the topic, it will remain up to you to determine how beam angle impacts your unique treatment needs.

For now, here is some additional reference material to help you further understand the science behind LED lenses and light beam angles.

• sciencedots.com - Inverse Square Law (opens in a new tab)
• sciencedirect.com - Beam Angle (opens in a new tab)
• sciencelearn.org.nz - Reflection of Light (opens in a new tab)
• sciencedirect.com - Light Irradiance (opens in a new tab)
• gsu.edu - Refraction of Light (opens in a new tab)
• physicsforums.com - What Is the Density of Light? (opens in a new tab)
• Role of EMF in red light therapy

Until a better understanding of beam angle impact upon the success of red light therapy success is gained, it is best to focus on other parameters when selecting a device. Pay more attention to the light intensity at the recommended minimum usage distance.

Personal objectives as to beam angle should be considered when selecting a red light therapy device. Until more concrete scientific evidence is available, however, the science behind the total therapeutic energy provided is a more reliable metric than beam angle.