Behind the Lens: Exploring UV Reflection

J. Fonseca

, P. Teixeira

and L. Ventura

University of São Paulo, Department of Eletrical and Computer Engineering, Brazil

Keywords: Sunglasses, UV Protection, Internal Reflection, Eye Damage, ISO 12312-1.

Abstract: Current UV protection regulations mainly center on sunglass lenses' light passage, using quantitative criteria

based on sunglass categories. Yet, studies, including this one, stress the necessity to enhance and adjust these

norms. Our findings underscore aligning standards, notably the Brazilian ISO NBR 12312-1, with ICNIRP

guidelines. Environmental radiation dispersion where sunglasses are worn can impact eye safety despite dark

lenses, potentially harming protection due to pupil dilation. This project marks a pivotal step in UV protection

analysis, crafting a methodology to measure light entering the eyes as UV rays penetrate sunglass lenses. We

devised an apparatus with LEDs, sensors, and a mannequin to gauge eye-reaching radiation. Preliminary

results reveal 10 to 15% of this wavelength's light penetrates the eyes, varying based on lens characteristics

like material and curvature. However, these initial tests only validated the system with red LEDs, limiting

their scope. Validating this research urges adapting existing norms to assess UV radiation reaching the eyes

and establish effective protection methods.

1 INTRODUCTION

Exposure to ultraviolet (UV) solar radiation poses a

significant threat to human health and well-being,

particularly concerning ocular health. The use of

sunglasses is of paramount importance as the primary

protective measure against this radiation, especially

in regions such as Brazil, characterized by high levels

of UV radiation

(VENTURA et al, 2022).

However, the

effectiveness of conventional dark lenses in

safeguarding against UV radiation warrants careful

examination.

These lenses, lacking adequate UV protection,

may hinder the natural movement of the pupil,

resulting in increased UV exposure and potentially

intensifying adverse ocular consequences. While

existing regulations, such as ISO 12312-

1:2022

(ABNT, 2014)

, are crucial for overseeing

sunglass standards and ensuring ocular safety, they

currently overlook a crucial aspect: the interaction of

UV rays reflected within the lenses and their impact

on ocular health.

This oversight becomes particularly pertinent

when contrasted with criteria established by the

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https://orcid.org/0009-0007-4233-6716

https://orcid.org/0000-0002-5292-6687

International Commission on Non-Ionizing Radiation

Protection (ICNIRP)

(ICNIRP, 2004)

, which delineates

limits for UV radiation exposure. The ISO

standardizes sunglass UV protection solely in terms

of lens 'darkening'

(DIFFEY, 2002)

, neglecting the

incorporation of structural geometry in ocular safety

considerations and failing to encompass the impact of

UV radiation diffused in the environment, which can

potentially harm the eyes. Consequently, these

disparities underscore the need for a broader scope of

considerations within sunglass standards to ensure

comprehensive ocular protection (MASILI, 2015).

The primary focus of this study was to develop a

prototype that quantifies the incident UV radiation

reaching the eyes due to the internal reflection of the

lenses.

2 STATE-OF-THE-ART

Human visual perception is a complex interplay

between light and the visual system. As light enters

the human eye, it undergoes a series of processes that

culminate in the formation of a conscious visual

Fonseca, J., Teixeira, P. and Ventura, L.

Behind the Lens: Exploring UV Reﬂection.

DOI: 10.5220/0012575500003657

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 17th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2024) - Volume 1, pages 191-194

ISBN: 978-989-758-688-0; ISSN: 2184-4305

191

impression. However, light represents just a portion

of the electromagnetic spectrum, typically associated

with visible light. Figure 01 depicts the

electromagnetic spectrum, housing Ultraviolet

Radiation (UV), the focus of this study, transmitted

by the sun. The incidence of this radiation until it

reaches the atmosphere undergoes several

phenomena, including reflection and backscattering.

Reflection is the primary physical phenomenon

enabling human visual perception

(HALLIDAY, 2012).

Figure 1: Electromagnetic Spectrum.

2.1 Albedo

Albedo, in essence, denotes the reflective property of

surfaces and materials, directly impacting how they

interact with incoming radiation. Its responsiveness

varies according to the wavelength of radiation,

implying that different wavelengths of light provoke

distinct levels of reflection from surfaces.

Specifically concerning ultraviolet (UV) radiation,

materials exhibit diverse albedo values, signifying

their capacity to reflect UV light

(MISILI, 2018).

Here are some examples of common materials and

their respective albedos in relation to UV radiation:

• Fresh snow: 80-90%

• Sand: 20-30%

• Concrete: 15-25%

• Grass: 5-10%

• Asphalt: 5-10%

• Clean water: 3-10%

These values may fluctuate based on specific

conditions such as surface texture, impurities, and

other influencing factors.

2.2 Standards and Regulations

The international standard ISO 12312-1, alongside

itsBrazilian translation, the NBR ISO 12312-1,

recognizesultraviolet radiation (UV) as composed of

three distinct subregions within the electromagnetic

spectrum: UV-A (320–400 nm), UV-B (280–320

nm),and UV-C (100–280 nm).

[7]

In the context of

protection against ultravioletradiation (UV),

addressing normative discrepancies betweenthe

international standard ISO 12312-1 and its

nationalcounterparts, such as ISO NBR 12312-1 in

Brazil, incomparison to guidelines established by the

InternationalCommission on Non-Ionizing Radiation

Protection (ICNIRP), is essential. One of the main

discrepancies lies in the definitionof the wavelength

range of UV radiation

(ICNIRP, 2004).

This division is

essential to understanding the effects of UV radiation

on objects and organisms, including humans.

3 MATERIALS AND METHODS

The following methodology outlines the development

of a prototype aimed at measuring the contribution of

internal reflection of UV radiation occurring within

the lenses of sunglasses and reaching the eyes. To

obtain this measurement, several parameters and

components need standardization for increased result

accuracy.

In this study, the primary focus will be measuring

the intensity of ultraviolet radiation that occurs

through reflections from sunglass lenses and reaches

the eyes, specifically targeting UV radiation in the

range of 380 – 400 nm. The system setup primarily

involves the utilization of emitting sources and

detectors within this spectral range.

To validate the proposed issue and identify if there

is a reflection coming from the sunglasses lenses, a

preliminary system was assembled using red LEDs in

the 640 nm range and visible sensors to collect light

values reaching the eyes originating from their

reflection. The developed configuration is illustrated

in Figure 02 below.

Figure 2: Proposed Experimental Setup.

3.1 Data Acquisition

Practically, the aim is to calculate and measure the

amount of radiation reaching the eyes from

reflections acquired withs sunglasses. To identify this

reflection parameter as a percentage, determining the

maximum experimental measurement without the

glasses and identifying all influencing parameters are

crucial for obtaining accurate results. The initial

methodology adopted is as follows:

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• Nominal Measure 100% (NM100)

To establish the nominal 100% system, direct

solar radiation incidence needs to be obtained without

sunglass interference. Experimentally, two sensors

(OPT101 model) representing the mannequin's eyes

and two fixed red LEDs are used—one simulating

total reflection (LED1) and the other imitating

reflections from albedos and surfaces (LED2).

The three contributing factors to the collected result

involve:

o Direct Incidence (DI): Radiation

directly incident on the sensor, from

LED1.

o LED1 Noise (N1): Contributing

radiation from above and laterally due

to LED1's opening, adding to the result.

o LED2 Noise (N2): Radiation reflected

by ambient surfaces reaching the

sensor, from LED2.

Mathematically:

𝑁𝑀100 = 𝐷𝐼 + 𝑁1 + 𝑁2

• Measure with Sunglasses (MWS)

Adding sunglasses to the equation introduces new

parameters. Experimentally, sunglasses with the lens

covered on the external side were used to maintain

transmittance, and LED2 was activated (Figure 18).

Results collected are contributions from:

o LED2 Noise (N2): Ambient-reflected

radiation reaching the sensor.

o Radiation Reflected by the Lens (RL):

The main value of interest in this study,

representing UV radiation reaching the

eyes due to sunglasses.

Mathematically:

𝑀𝑊𝑆 = 𝑁2 + 𝑅𝐿

To isolate ambient radiation values (AR) from

MD100 and MWS, a measure was taken to establish

a 0% baseline for this system.

• Measure of LED2 0% (ML2_0)

To determine only the fraction of radiation

reflected by the environment (AR), only LED2 was

turned on without the glasses, and the calculated

baseline value was observed.

To calculate the contribution of lens reflection to

the total percentage of solar incidence in nominal

conditions, the following steps are taken:

First, calculate only the lens reflection contribution

inside:

𝑅𝐿 = 𝑀𝑊𝑆 − 𝑁2

Then, eliminate noise values from NM100:

𝐷𝐼 = 𝑁𝑀100 − 𝑁1 − 𝑁2

Finally, to obtain the desired parameter as a

percentage:

𝐿𝑒𝑛𝑠 𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑖𝑜𝑛 % = 𝑅𝐿 / 𝐷𝐼

3.2 Electronic Components

To achieve the proposed data acquisition, the system

requires suitable and efficient components. The

activation of the project's main components involved

the following elements and connections:

1. Red LEDs (640 nm): Light-emitting diodes

that emit red light at a wavelength of 760

nanometers.

2. High-Power Resistor (10W): A resistor

designed to handle high power, in this case,

rated for 10 watts of power dissipation.

3. OPT101 Sensor: An analog photodiode sensor

used for precision light measurement,

converting light intensity into an electrical

signal.

4. Conversion Board with LM358: A board

utilizing the LM358 operational amplifier for

signal amplification or conditioning, often

used in sensor interfaces.

5. Low Pass Filter: An electronic filter that

allows low frequency signals to pass through

while attenuating higher frequencies, often

used to eliminate noise or unwanted high-

frequency components.

6. Resistive Divider: A circuit consisting of

resistors used to create a fraction of an input

voltage, commonly employed for voltage

scaling or level shifting.

7. ADS115 Analog-to-Digital Converter: An

ADC (Analog-to-Digital Converter) used to

convert analog signals (like voltage) into

digital data for processing by a

microcontroller or computer.

8. Arduino NANO: A small, versatile

microcontroller board based on the

ATmega328P chip, commonly used in various

electronic projects for control and data

acquisition.

9. Micro SD Card Adapter: An adapter allowing

a micro-SD card to be used with devices

designed for standard SD cards, enabling

storage or data logging capabilities.

These components were utilized and

interconnected to facilitate the functioning and data

acquisition process as part of the project's electronic

setup. The diagram in Figure 03 shows this

connection.

Behind the Lens: Exploring UV Reﬂection

193

Figure 3: Electronic system diagram.

4 RESULTS

The experiment utilized three different sunglass

samples, depicted in Figure 04. Two of these samples

(Sample 1 and 2) shared similar physical and visual

characteristics, a similarity reflected in the obtained

data respectively. The samples were identified as

follows: 1 – n°9, Lot 23; 2 – n°50, Lot 13; 3 – n°22,

Lot 23.

Figure 4: Samples used for testing.

Implementing the proposed methodology for data

treatment, collecting values at 100% and 0%, yielded

the following results presented in Table 01, based on

the samples from Figure 04, with 10 test runs

conducted. The standard LED power supply

for all tests remained at 10V.

Table 1: Preliminary results of reflection.

Table 01 provides preliminary results using

illumination and detection in the red spectral region.

These findings indicate the feasibility of the

experimental setup, here employing an LED with a

peak wavelength of 640 nm. It's noteworthy that the

final prototype aims to operate in the ultraviolet

region, around 390 nm, and is currently under

development at the Ophthalmic Instrumentation

Laboratory at USP São Carlos.

5 CONCLUSIONS

The study highlights the need for a significantly high-

intensity LED source, presenting challenges in

achieving a saturated 100% signal, particularly

affecting commonly used sensors. The validation

emphasizes the reflection of UV radiation in sunglass

lenses, despite being at low levels, which may

interfere with long-term vision. This work represents

an ongoing refinement process to quantify UV

radiation reaching the eyes, requiring the acquisition

and testing of robust components. There is a

substantial need for this study and adaptations in

standards to address these considerations. Future

work aims to develop a more complex prototype for

measuring the quality of lenses regarding UV

reflection, validating the research's importance by

revealing significant reflection indices.

REFERENCES

Ventura, L.; et al Ocular Bioengineering – Sunglasses and

their standards. Ponta Grossa – PR: Atena, 2022 p135.

Halliday, David; Resnick, Robert; Walker, Jearl. Princípios

de Física. 9ed. Rio de Janeiro: LTC, 2012. V.1.

Diffey, Bl. Sources and measurement of ultravioleta

radiation. Metrods. 2002;28(1);4-13.

Masili, M.; Shciabel, H.; Ventura, L. Contribuition to the

adiation protection for sunglasses standards. Radiation

Protection Dosimetry. V.164, p435, 2015.

ICNIRP, Internal Commision on Non-Ionizing Radiation

Protection. Guidelines on limits of exposure to

ultravioleta radiation of wavelenghts between 180nm

and 400nm (incoherent optical radiation). Health

Physics, ago. 2004.

Masili, M. Duarte, F.O., Ventura, L. Blue-light

transmittance in sunglasses over long-term irradiation

within a solar simulator. Res. Biomed. Eng. 2018.

ABNT NBR ISSO 12312-1: Sunglasses and related

products – Safety requirements and test methods. Rio

de Janeiro: ABNT, 2014.

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