2017 2nd International Conference on Artificial Intelligence: Techniques and Applications (AITA 2017) ISBN: 978-1-60595-491-2

Illumination Security of White LED in Visible Light Communication

Shu-yan REN*, Yan-qing SONG, Shi-gang CUI and Li ZHAO

Key Laboratory of Information Sensing & Intelligent Control, Tianjin University of Science and Technology, Tianjin, 300222, China

*Corresponding author

Keywords: Visible light communication, ELISA, RPE, Safety threshold.

Abstract. Medical experiments by white LED in visible light communication had been done to

explain influence on visual function. The isolated RPE cells were cultured and light source

illumination experiments with different illumination (lux), time and spectral range are designed.

Using ELISA, the intracellular transcription factors in each group were detected, which include

MCP-1 and IL-8. From experiments, the illumination safety threshold of white light is 500lux, and the

illuminance safety threshold of blue light is 300lux. Compared with illumination (lux), Spectral range

is the main factor of affecting visual function. In different spectral ranges, the magnitude of

illumination and the duration of irradiation also affect visual function.

Introduction

Compared with radio frequency wireless communication technology, the visible light

communication technology [1-2] based on white light LED has obvious advantages, which ensures

personal safety without electromagnetic radiation. It can be multiplexed with LED lighting devices to

achieve high bandwidth and high-speed optical communication access at low cost, which greatly

expanded the coverage of the network[3]. Therefore, the research on cooperative optimization of LED

lighting and communication parameters will supply a theoretical foundation for indoor applications of

visible light communication.

Through the basic medical experiments, the LED light source performance test and eye safety

assessment have been carried out. The isolated RPE cells were cultured[4-5], and different irradiation

experiments were carried out to obtain the response medical parameters. So a large number of

experimental data were provided for the visual safety evaluation[6]study. In the visible light office

communication demonstration system designed, signal transmitted by white LED light with different

illumination to obtain the communication rate, combined with the results of visual medical safety

experiments, to determine the communication parameters to conform to visual security of human and

provide reference data for the study of visible light communication.

Culture Experiments of RPE Cells

The retinal pigment epithelial cells (RPE) are shown in Figure 1, and the LED light source is arranged

at the top of the closed incubator without the interference of natural light. When illumination of LED

changes, the temperature of incubator is between 36.5℃ and 37.2℃. White LED light source is set to

1000lux, 500lux and 300lux, which continuously irradiate RPE cells for 6h, 12h and 24h respectively.

At the same time, the corresponding control group is also cultured with foil packs.

Figure 1. Culture experiments of RPE cells.

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RPE Cells Irradiation Experiments and Results Analysis

Experiments by Different Illumination and Time

The LED light source with different illumination and spectral range was used to irradiate the cells.

After the illumination was stopped, the general morphological changes of the cells were observed

under the invert microscope. MTT method was used to detect the proliferation of cells in each group

and control group, and the production of intracellular reactive oxygen species (ROS) in the light

group and control group was detected by DCFH-DA method.

RT-PCR is used to detect the expression of inflammatory factor MCP-1 and IL-8 mRNA. And

carried out the enzyme-linked immunosorbent assay (ELISA)[7] to detect the expression of

inflammatory factor MCP-1 and IL-8.

RPE cells irradiated by white LED with 1000lux and 500lux, and continuous irradiation keeps 24h,

the cells appeared obvious shrinkage, and shapes changed irregular, and cell connection is rare

(shown as Figure 2). After the intensity of 1000lux irradiated 12h, the size and morphology of cells

lost their typical polygon. After the intensity of 1000lux irradiated 6h, 500lux irradiated 12h, and the

intensity of 300lux irradiated 24h, cells were gradually circular, and polygonal shape is not typical.

But after the intensity of 300lux irradiated 12h, 500lux irradiated 6h and the intensity of 300lux

irradiated 6h, there was no obvious change in cells.

a) Intensity of 1000lux irradiated 24h b) Intensity of 500lux irradiated 24h

Figure 2. RPE cells irradiation experiments by LED light.

ELISA was used to detect the secretion of MCP-1 and IL-8 in RPE cells, and the supernatant of cell

culture was used to detect the secretion of MCP-1 and IL-8. Take the standard concentration standard

as the reference, curve was established. The 100ul sample was added to incubated for 2h at 37�,

followed by adding 100ul first antibody and 100ul enzyme labeled antibody and the 100ul substrate in

each hole, and incubated with the corresponding time. Finally 50ul termination liquid was added to

terminate the reaction.

1 2 3 4 5 6 7

200

210

220

230

EL

ISA

1 2 3 4 5 6 7

190

200

210

220

230

EL

ISA 不不时时时 1 2 3 4 5 6 7

180

190

200

210

220

EL

ISA

a) ELISA(IL-8)by 500lux white LED b) ELISA(IL-8)by 300lux blue LED c) ELISA(IL-8)by 500llux green LED

Figure 3. ELISA (IL-8) detection.

ELISA IL-8 concentration changes as shown in Figure 3. The coordinates of the 1 (first column) in

Figure3a is the concentration of IL-8 BOX with continuous 6h irradiation. Then each column denotes

extending the irradiation time of 3 hours in turn to detect IL-8 value, until the 7th column as the

irradiation time of 24 hours. From the figure, difference appeared in white light group with 500lux

illumination after 15 hours, but huge difference appeared 18 hours shown as the 5th column.

According to the Figure3b and 3c, obvious difference can been obtained in 300lux blue light group

after irradiation time of 12 hours. The experimental results show that the security threshold of white

light illumination is 500lux, and the blue light illumination safety threshold is 300lux. For the 500llux

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green group, 9 and 12 hours exposure data denote large individual differences, but the overall trend is

consistent although with some fluctuation in overall 1st~6th column data, and the 7th column at 21

hours irradiation shows a substantial difference between the values of ELISA.

1 2 3 4 5 6 7 8180

200

220

240

260

EL

ISA

1 2 3 4 5 6 7

190

200

210

220

230

240

EL

ISA

不不时时时 1 2 3 4 5 6 7 8180

200

220

240

260

EL

ISA

a) ELISA(IL-8)by 1000lux white LED b) ELISA(IL-8)by 500lux blue LED c) ELISA(IL-8)by 1000llux green LED

Figure 4. ELISA (IL-8) detection with changed parameters.

Similarly, the change of ELISAIL-8 concentration under high illumination is shown in figure 4.

Based on the above data, the cumulative threshold value of three different wavelengths of light based

on the change of ELISA IL-8 concentration index is obtained, as shown in table 1.

Table 1. The cumulative time limit of irradiation under different illumination.

White LED Green LED Blue LED

500lux 1000lux 500lux 1000lux 300lux 500lux

The

cumulative

time limit(h)

12 9 18 18 9 6

Meanwhile, ELISA was used to detect the secretion of MCP-1 in RPE cells to assist in the analysis

of the above experimental results, as shown in figures 5 and 6. And get the optimized time limit

threshold is shown in table 2.

1 2 3 4 5 6 7

48

50

52

54

56

MC

P-E

LIS

A

a) ELISA(MCP-1)by 500lux white LED b) ELISA(MCP-1)by 300lux blue LED c) ELISA(MCP-1)by 500lux green LED

Figure 5. ELISA (MCP-1) detection.

Table 2. The correct cumulative time limit of irradiation under different illumination.

White LED Green LED Blue LED

500lux 1000lux 500lux 1000lux 300lux 500lux

The

cumulative

time limit[h]

12 9 12 12 9 6

280

1 2 3 4 5 6 7 8

45

50

55

60

65

MC

P-E

LIS

A

a) ELISA (MCP-1) by 1000lux white LED b) ELISA (MCP-1) by 500lux blue LED

1 2 3 4 5 6 7

46

48

50

52

54

56

MC

P-E

LIS

A

c) ELISA (MCP-1) by 1000lux green LED

Figure 6. ELISA (MCP-1) detection with changed parameters.

Change the Spectral Section of the Light Source

Using three different spectral range of LED light source shown in Figure7 irradiated RPE cells, the

ELISA IL-8 concentration changed is shown in Figure 8. The 1st column, 2nd column and 3rd

denoted 500lux white light spectrum, 300lux blue spectrum and 500lux green spectrum respectively.

a) White light source spectrum b) Blue light spectrum c) Green light spectrum

Figure 7. Light source spectrum.

1 2 3

188

190

192

194

196

IL-E

LIS

A 不不不长长 1 2 3

180

185

190

195

200

205

IL-E

LIS

A

a) Irradiation for 6 hours with different spectrum b) Irradiation for 9 hours with different spectrum

1 2 3

195

200

205

210

IL-E

LIS

A

1 2 3

190

200

210

220

IL-E

LIS

A

c) Irradiation for 12 hours with different spectrum d) Irradiation for 15 hours with different spectrum

Figure 8. Comparison of IL-8 concentration under different spectral exposure.

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RPE cells experiments by LED light irradiation with three different spectral range were conducted.

And RT-PCR, MCP-1 concentration changes are shown in Figure 9. The 1st column, 2nd column and

3rd denoted 500lux white light spectrum, 300lux blue spectrum and 500lux green spectrum respectively.

1 2 30.5

1

1.5

2

2.5

3

3.5

RT

-PC

R

1 2 3

0.6

0.7

0.8

0.9

1

RT

-PC

R

不不不长长 a) Irradiation for 6 hours with different spectrum b) Irradiation for 9 hours with different spectrum

Figure 9. Comparison of MCP-1 concentration under different spectral exposure.

Compared with two cases of white and green light at the same irradiation time, the concentration

change of IL-8 and MCP-1 is smaller, and LED with blue spectrum affected IL-8 and MCP-1

concentration of RPE cells in the same exposure time, which is prone to damage.

Conclusion

From above, based on basic medical experiments, the visual security of LED light source in visible

light communication has been studied. RPE cells were cultured in vitro and subjected to different

irradiation experiments. ELISA was used to detect the concentration of MCP-1 and IL-8 in RPE cells,

which are used to research the visual function with different illumination, different spectrum and

different irradiation time. Compared with the illumination, the spectral range is the main factor that

affects the visual function In different spectral range, the magnitude of illumination and the time of

illumination also affect the visual function.

Acknowledgement

This research was financially supported by National high technology research and development plan

(863 plan) (No. 2015AA033303) and Tianjin Natural Science Foundation (17JCQNJC12700,

15JCQNJC02400) and the National Natural Science Fund Project (No. 61503283)and the Research

and Development fund of TUTE (No. RC14-58, RC14-18, RC14-49, No. RC14-59).

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