Why Beam Angle and Light Delivery Matter in Red Light & Near-Infrared Therapy

ONYX LIGHT THERAPY

Our tight 20 degree beam angle gives you the edge for efficiently delivering more deep-penetrating light.

When people compare red and near-infrared (NIR) light therapy devices, most attention goes to wavelength and total power. While those factors matter, they don’t tell the full story.

One of the most overlooked—but critically important—factors is beam angle, which determines how efficiently light is delivered into the body.

Beam angle directly affects:

1. How much light actually enters the skin

2. How much is reflected away

3. The percentage of light that reaches deeper tissue

4. The percentage of light that unintentionally saturates the surface

In short, how light is delivered is often more important than how much light is produced.

What Beam Angle Really Means

Beam angle describes how widely light spreads as it leaves a source.

We use a method accepted from the industry standard which defines beam angle using a 50% intensity standard, also known as full width at half maximum (FWHM). This means the stated beam angle is the width of a light beam at which the intensity drops to 50% of its maximum.

Why Beam Angle Affects Penetration

1. Irradiance Drops as Light Spreads

As beam angle increases, the same amount of energy is spread across a larger surface area. This causes irradiance (mW/cm²) to fall rapidly with distance.

A wider beam may appear bright at the surface, but its energy becomes diluted before reaching deeper tissue—reducing biological effectiveness at depth.

2. Angle of Incidence Influences Reflection

Light striking the skin at an angle reflects more than light delivered straight on. As the incident angle becomes more oblique, reflection at the air–skin interface increases, reducing the amount of light that actually enters the tissue.

This phenomenon has been directly measured in biological tissue, where reflectance increases and transmitted energy decreases as the angle of incidence moves away from perpendicular (Fleischer et al., 1988).

Once light is reflected, it is biologically unavailable—no matter how powerful the source is.

3. Tissue Scattering Magnifies Inefficiency

After light enters the body, scattering and absorption rapidly redirect and weaken photons. Collagen, fat, and cellular structures scatter light laterally, reducing forward penetration (Hamblin & Demidova, 2006).

Because penetration is already limited by tissue optics, starting with a high forward-directed photon density becomes essential. If light is excessively dispersed at the source, scattering losses compound and reduce the amount of energy that reaches deeper layers. In addition, excessive surface dispersion can unintentionally oversaturate or overheat superficial tissues.

What Research and Measurements Show

Experimental measurements of red and near-infrared light consistently demonstrate steep attenuation in biological tissue:

1. A large portion of light energy is absorbed within the first few millimeters

2. Over 90% of near-infrared energy is absorbed within the first ~10 mm of tissue

This has been directly measured in musculoskeletal tissue, where the vast majority of NIR laser energy was absorbed within the first centimeter, with only a small fraction remaining beyond that depth (Tedford et al., 2022).

Measurements taken on the opposite side of tissue samples confirm that only a minimal amount of emitted energy remains after passing through biological tissue (Jagdeo et al., 2012).

These findings highlight an important reality:

Because penetration is inherently limited, preserving irradiance at the surface becomes critical.

Beam angle and delivery geometry therefore have a disproportionate impact on real-world effectiveness.

Note: Emerging research suggests that connective tissue and fascial planes may guide light deeper via fiber-optic-like effects, which may help explain some downstream biological responses beyond measured penetration depth (Hamblin, 2017).

Narrow vs. Wide Beams: Delivery Matters

A narrow beam delivered closer to perpendicular concentrates photons into a smaller surface area, resulting in:

1. Higher surface irradiance per LED

2. Less reflection

3. Greater forward-directed energy

This increases the probability that usable light reaches deeper targets before scattering dominates.

Wider beams, by contrast:

1. Spread energy laterally

2. Reduce photon density

3. Favor superficial exposure over depth

While wide beams may cover more area, they often sacrifice penetration efficiency—especially in thicker or denser tissue.

Onyx’s standard ensures that the majority of photons remain tightly controlled and forward-directed at real treatment distances—where therapy actually occurs.

Why This Design Choice Matters

By maintaining a high percentage of light within a narrow beam:

1. More photons enter the skin instead of reflecting away

2. Irradiance remains higher through the skin and fat layers

3. More usable energy reaches muscle and deeper tissue

This approach aligns with established principles of physics and tissue optics. Though our irradiance is still one of the highest in the Industry, efficient delivery matters more than raw output numbers.

Conclusion: Beam Angle Is Not a Minor Detail

Red and near-infrared light therapy is limited by absorption, scattering, and reflection. These limitations cannot be eliminated—but they can be managed.

The available evidence and physical principles strongly support that:

1. Narrower beams preserve irradiance

2. Perpendicular delivery reduces reflection

3. Controlled light distribution improves penetration efficiency

Onyx Light Therapy’s 20° beam angle, is an engineering decision rooted in how light actually behaves in biological tissue—not just how it looks on a spec sheet.

In a field where millimeters matter, precision in light delivery can make the difference between surface illumination and meaningful biological impact.

References

1. Fleischer, D. E., et al. (1988). Reflection and transmission of laser light from tissue as a function of incident angle.

2. Tedford, C. E., et al. (2022). More than ninety percent of near-infrared laser energy is absorbed within the first ten millimeters of tissue.

3. Jagdeo, J., et al. (2012). Transcranial red and near-infrared light penetration in human tissues.

4. Hamblin, M. R., & Demidova, T. N. (2006). Mechanisms of low-level light therapy.

5. Hamblin, M. R. (2017). Photobiomodulation and the potential role of connective tissue light guidance.