invention

Impact of lamps' light and spectrum on health

There are incandescent,fluorescent and LED lamps whose voltage waveform,principle and spectrum are different.

Let's talk about incandescent lamp that is light bulb with filament

1.Incandescent lamp brings low frequency flicker light and infrared.

1.1 Incandescent lamp brings low frequency flicker light

110volt 60 Herts AC sinusoidal voltage is across the incandescent lamp. When sinusoidal voltage reaches peak value, the lamp is brightest; when sinusoidal voltage reaches 0 point, the lamp is darkest. In one second, the brightness of lamp varies 60 cycles.(Hertz(Hz): times in one second for the cycles that voltage starting from peak value, passing 0 volt, reaching valley value and coming back to peak value

sinsoidal

Figure1 Voltage waveform across incandescent lamp

Pupils will constrict under bright environment and will dilate under dark environment. Pupils is controlled by Ciliary(eye muscles) to dilate and constrict 60 cycles per second. Long term so frequent dilation and constriction leads to ciliary eye muscles loose and not able to adjust eyes to see distant object. That results in myopia

Poland Wroclaw university of Technology measured the size of pupil under flicker light [1]

China NanTong university hospital found myopia can be induced by low frequency flicker light.[2]

La Trobe University in Australia found low frequency temporal modulation of light promotes a myopic shift[3]

incandescent flicker

Figure2 High speed camera photo of Incandescent lamp with low frequency flicker light (left), photo taken under low frequency flicker light(middle); pupils photos under darkness and light(dilate under darkness; constrict under light.)

http://en.wikipedia.org/wiki/Power-line_flicker explained how voltage variation in power system caused flicker.

IEEE Par 1789 group summarize research on Biological Effects and Health Hazards From Flicker,Including Flicker That is Too Rapid To See in Table1 showed flicker light impact on vision and health.[4]

1.2 Incandescent Lamp brings Infrared Light:

The filament of incandescent lamp can reach thousands of degree Celcius and energy created by incandescent bulbs is in the form of infrared radiation (heat). Long term infrared expose can cause damage in ocular lens and retina.

Uppsala University in Sweden found near infrared radiation may cause cumulative damage in the ocular lens.[5]

University of Texas at Austin found the 1300-nm ocular damage data have yielded unusual characteristics where continuous wave retinal damage was observed in rabbit models.[6]

2. Then someone will ask how about fluorescent lamp that saves energy?

Fluorescent lamp brings high frequency flicker light and ultraviolet.

2.1 (higher than 100Hz)high frequency flicker light; Notebook computer and smart phone's screens have high frequency flicker light at dimming condition

Ballast is used for Fluorescent lamp to generate high frequency sinusoidal voltage across the Fluorescent lamp.The lamp's brightness varies with the voltage variation at the same frequency.

50kvoltage

Figure 3 voltage waveform across fluorescent lamp

fluorescentflicker

Figure 4 High speed camera photo of fluorescent lamp with high frequency flicker light

Fluorescent tube lamp with high frequency flicker light(left);Compact fluorescent lamp with high frequency flicker light(right)

Eye muscles can not adjust pupils with so fast frequency flicker light. Strong peak fickler light shine directly on the retina. In the long term, people will feel eye irritation, headache and decreased vision. Many kids play smart phones, PC tablets and have decreased vision that is related to high frequency flicker.

IEEE Par 1789 group summarize research on Biological Effects and Health Hazards From Flicker, Including Flicker That is Too Rapid To See in Table1 showed flicker light impact on vision and health.[4]

University of Florida found association between severity of light exposure and age-related macular degeneration that is a leading cause of blindness in the western world.[7]

University of Essex; UK,National Research Council Canada and Northeastern University found low-frequency flicker between 3 and 70 Hz can cause seizures; invisible flicker (70 Hz) above can cause malaise, headache and visual impairment.[8]

2.2 Ultraviolet

The electric current (in the gas) excites mercury vapor which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the bulb to fluoresce, producing visible light. So fluorescent lamps emit ultraviolet (UV).

Fordham University, New York City found Ultraviolet(UV) radiation as a risk factor for cataract and macular degeneration. The removal of these wavelengths UV-A and UV-B from ocular exposure will greatly reduce the risk of early cataract and retinal damage.[9]

3.Recently, LED comes into market that is saving more energy than fluorescent lamp.Is LED perfect for vision and health?

Answer is No. LED on market brings high frequency ripple flicker light by switching power supply,low frequency ripple by battery, dimming flicker light and unsafe blue light.

3.1 Battery is used to be power supply of LED lamp to bring low frequency flicker

There is long wire between battery and LED lamp. Battery voltage=wire voltage+LED lamp voltage, wire voltage=wire resistanceXcurrent, when current pass through wires, wires are heated to cause resistance up, then wire voltage goes up, Battery voltage is constant, so LED lamp voltage goes down, LED lamp becomes darker, LED current goes down, wire current goes down,so wire voltage goes down, now LED lamp voltage goes up, LED lamp becomes brighter, back and forth, LED lamp has low frequency flicker light.

Pupils dilate and constrict with low frequency flicker light. After long term, muscles controlling pupils to dilate and constrict so many times become loose and cannot adjust eyes to see distant object finally leading to myopia.

3.2 High frequency ripple voltage cause high frequency flicker light by switching power supply(constant voltage source is used for LED power supply)

LEDripple

Figure 5 Voltage Across LED Lamp With Ripple

High frequency flicker light is so fast that the pupils can not keep up with fast brightness variation. So strong light will shine on retina. Long term strong light cyclic stimulation will cause eye irritation, headache and decreased vision.

LED power supply will produce high frequency voltage ripple. The ripple is the small voltage variation around DC output voltage. Because the LED current depends on LED voltage exponentially, small voltage variation will cause dramatic current variation thus dramatic high frequency flicker light is produced.

V&I LED

Figure 6 voltage and current relation of LED based on Shokley equation

When operation point moves between point Va and point Vb with a small variation for voltage ripple, the current has a dramatic change from Ia to Ib, the output power at point b is Pb=Ib*Vb, that is much higher than power at point a which is Pa=Ia*Va, the brightness of LED is proportional to output power, so small voltage ripple cause a huge flicker light.

LED flicker light

Figure7 high speed camera photos of LED lamp with high frequency flicker

3.3 constant current mode control use switching power supply for LED. The turn on/off of the switch will bring voltage spike that will cause high frequency flicker.

3.3 High End LED lamp has dimming function. Most of them turn switch on/off to dim the light. High frequency lamp ON/OFF produces high frequency flicker light that is harmful to vision as described in 3.1.

3.4 Market dimming way is based on switch on/off to dim the light. High frequency lamp ON/OFF produces high frequency flicker light that is harmful to vision as described in 3.2.

dimming

Figure 8 LED dimming based on switch ON/OFF

3.5 On market, most of LEDs' spectrum contains strong blue light component related to macular generation.

Northrop Grumman Information Technology, San Antonio found that exposure to near-UV/blue wavelength sources induce a veiling glare intense enough to degrade visual performance[10].

University of Texas Southwestern medical center in Texas found strong blue light can cause macular degeneration and other vision problem[11].

As above,

To prevent myopia and minimize eye fatigue, low frequency flicker and high frequency flicker must be removed from the lamp. So low frequency AC sinusoidal voltage, high frequency AC sinusoidal voltage must not be applied across the lamp. The ripple voltage around DC voltage must be removed. To get constant brightness light, constant DC voltage or DC current without ripple or spike should be applied across the lamp;

To prevent cataracts, ultraviolet must be removed from the light spectrum.

To prevent retinal damage, infrared must be removed from the light spectrum.

To prevent macular degeneration, hazard blue light must be removed from the light spectrum.

The vision protection LED desk lamp designed by Upright Lighting LLC, (www.uprlt.com) with US patent have the required features:

No low frequency flicker light;

No high frequency flicker light;

Electromagnetic radiation meet international standard;

Premium LED lamp has no infrared, no ultraviolet, no harmful blue light;

Premium LED lamp has continuous smooth light spectrum simulated to sun light without strong monotonic color light.

Theory is published in international journal of ophthalmology;cited by US National Library of Medicine National Institutes of Health.

US safety company UL approved our power supply.

China national household appliances quality supervision and inspection center inspected the product. Test was passed.

Why our invention is better than other LEDs on the market:

Three control ways are used for LED power supply on market:

1.Battery is connected to LED lamp without feedback

There is long wire between battery and LED lamp. Battery voltage=wire voltage+LED lamp voltage, wire voltage=wire resistanceXcurrent, when current pass through wires, wires are heated to cause resistance up, then wire voltage goes up, Battery voltage is constant, so LED lamp voltage goes down, LED lamp becomes darker, LED current goes down, wire current goes down, so wire voltage goes down, now LED lamp voltage goes up, LED lamp becomes brighter, back and forth, LED lamp has low frequency flicker light.

Pupils dilate and constrict with low frequency flicker light. After long term, muscles controlling pupils to dilate and constrict so many times become loose and cannot adjust eyes to see distant object finally leading to myopia.

2.Constant voltage source is used as power supply for LED lamp

constantvoltageripple

Figure9 voltage ripple of a LED power supply with constant voltage source,Voltage ripple is 40mv that will cause high frequency flicker to hurt retina and cause headache.

3.Constant current source is use as power supply for LED

constantcurrentripple

Figure10 voltage spike ripple of a LED power supply with constant current source,Switch brings 20mv voltage spike that will cause high frequency flicker which can hurt retina and cause headache.

Our invention solved all the problems of 3 control ways for LED lamp on market. Our lamp has 0 ripple.

invention0ripple

Figure11 voltage of Upright Lighting LED desk lamp, 0 ripple. Mimimize eyes' fatigue

Reference

  • [1]Anna Sobaszek,Wioletta Nowak,Andrzej Hachol,Zbigniew Moron, Wroclaw University of Technology, Measurement of the eye pupil response to light stimuli with regulated waveform, wavelength and photopic level, Journal of Physics: Conference Series 238 (2010) 012032 doi:10.1088/1742-6596/238/1/012032
  • [2] Yu Y, Chen H, Tuo J, Zhu Y, Effects of flickering light on refraction and changes in eye axial length of C57BL/6 mice, Ophthalmic Res.2011;46(2):80-7.doi:10.1159/000323179. Epub 2011 Jan 26
  • [3] Crewther SG, Barutchu A, Murphy MJ, Low frequency temporal modulation of light promotes a myopic shift in refractive compensation to all spectacle lenses, Exp Eye Res. 2006 Aug;83(2):322-8. Epub 2006 Mar 31.
  • [4]Biological Effects and Health Hazards From Flicker, Including Flicker That is Too Rapid To See. IEEE Standard P1789 2/15/10
  • [5] Soderberg PG, Optical radiation and the eyes with special emphasis on children. Prog Biophys Mol Biol. 2011 Dec;107(3):389-92. doi: 10.1016/j.pbiomolbio.2011.09.009. Epub 2011 Sep 21.
  • [6] Vincelette RL, Welch AJ, Thomas RJ, Rockwell BA, Lund DJ, Thermal lensing in ocular media exposed to continuous-wave near-infrared radiation: the 1150-1350-nm region. J Biomed Opt.2008 Sep-Oct;13(5):054005.doi:10.1117/1.2978066
  • [7] Chalam KV, Khetpal V, Rusovici R,Balaiya S, A review: role of ultraviolet radiation in age-related macular degeneration, Eye Contact Lens. 2011 Jul;37(4):225-32. doi: 10.1097/ICL.0b013e31821fbd3e.
  • [8]Wilkins, A.,Veitch, J.,Lehman, B. LED Lighting Flicker and Potential Health Concerns: Energy Conversion Congress and Exposition(ECCE),2010 IEEE, Date of Conference: 12-16 Sept. 2010, page 173.
  • [9] Roberts JE, Ultraviolet radiation as a risk factor for cataract and macular degeneration, Eye Contact Lens.2011 Jul;37(4):246-9.doi:10.1097/ICL.0b013e31821cbcc9
  • [10]Zuclich JA, Previc FH, Novar BJ, Edsall PR, Near-UV/blue light-induced fluorescence in the human lens: potential interference with visual function, J Biomed Opt. 2005 Jul-Aug;10(4):44021
  • [11]Walker DP, Vollmer-Snarr HR, Eberting CL., Ocular hazards of blue-light therapy in dermatology.J Am Acad Dermatol. 2012 Jan;66(1):130-5. doi: 10.1016/j.jaad.2010.11.040. Epub 2011 May 4.