LED lighting source for improved cognitive performance and with sun-light properties

Abstract

A subject of the invention is the source of LED lighting that improves human cognitive performance during work activities or in any activity and simulates sun radiation in the biologically beneficial range 460 to 660 nm, for more than 90%. The whole system of the LED lighting source is set in such a way that 4.5 to 6% of blue and turquoise light radiation is added to the light radiation emitted from white LED chips, and it is advantageous if of equal radiation intensity. This measurement will provide for balancing of radiation intensity to 90% of the sunshine level. The generated combined light radiation of the cognitive LED lighting source has CRI 98 and correlated colour temperature 4000 to 4700 K, the sun radiation has correlated colour temperature 4982 K and CRI 99.5.

Claims

1. An LED lighting source to improve cognitive performance and with sun-light properties with 90% balance of maxima and minima in distribution of light energy in range 460 to 660 nm comprising: at least one white LED chip (1) emitting light with wavelength from 380 nm to 700 nm, and at least one monochromatic blue LED chip (2) emitting light with wavelength from 470 nm to 480 nm, wherein said LED chips are connected to an electric current source; and at least one monochromatic turquoise LED chip (3) emitting light with wavelength from 490 nm to 500 nm, wherein the at least one white LED chip has correlated colour temperature 3800 to 4200 K and CRI 90 to 98, the at least one monochromatic blue LED chip (2) and turquoise LED chip (3) each generate 3 to 7% of a total emitted power of the LED lighting source or a light flux from the blue LED chips (2) amount to 1 to 4% of a total light flux of the LED lighting source and a light flux of the turquoise LED chips (3) amount to 4 to 7% of a total light flux of the LED lighting source and the white LED chips provide for a main emitted power and a main light flux.

2. The LED lighting source according to claim 1 further comprising at least one PC lime LED chip (11) with radiation in range of 500 to 650 nm for green-yellow wavelengths, wherein the at least one PC lime LED chip (11) utilizes 6 to 9% in a total emitted power or 10 to 15% of a total light output of the source.

3. The LED lighting source according to claim 2 wherein the PC lime LED chip (11) comprises of blue LED chip (2) excited in range 420±5 nm covered with a luminophore.

4. The LED lighting source according to claim 1 wherein the white LED chip (1) consists of a blue LED chip (2), different than the at least one monochromatic blue LED chip (2), covered with luminophores.

5. The LED lighting source according to claim 1 wherein a ratio of output of the at least one monochromatic blue LED chip (2) and the at least one turquoise LED chip (3) is 1:1.

6. The LED lighting source according to claim 2 wherein a ratio of light output of the at least one monochromatic blue LED chip (2), and the at least one turquoise LED chip (3) and the at least one PC lime LED chip (11) is 1:2:3.

7. The LED lighting source according to claim 2 wherein the total intensity of radiation of the LED lighting source is provided from 4.5 to 7% from the at least one blue LED chip (2), from 4.5 to 8% from the at least one turquoise LED chip (3), from 6 to 10% from the at least one PC lime LED chip (11) and from 78 to 88% from the at least one white LED chip (1).

8. The LED lighting source according to claim 1 wherein the total output of the at least one monochromatic blue LED chip (2) and the total output of the at least one turquoise LED chip (3), each generate 5% of the total output of the at least one white LED chip (1).

9. The LED lighting source according to claim 1 wherein four of the at least one white LED chips (1), the at least one blue LED chip (2) and the at least one turquoise LED chip (3) are positioned on 1.25 cm of printed circuit (4, 7).

10. The LED lighting source according to claim 1 wherein four of the at least one white LED chips (1), two of the at least one monochromatic blue LED chips (2) and the at least one turquoise LED chip (3) are positioned on 1.25 cm of printed circuit (4, 7) and the at least one monochromatic blue LED chip (2) has half the output of the at least one turquoise LED chip (3).

11. The LED lighting source according to claim 1 wherein four of the at least one white LED chips (1), the at least one monochromatic blue LED chip (2) and two of the at least one turquoise LED chips (3) are positioned on 1.25 cm of printed circuit (4, 7), and the at least one turquoise LED chip (3) has half the power of the at least one monochromatic blue LED chip (2).

12. The LED lighting source according to claim 2 wherein a light output of the at least one monochromatic blue LED chip (2) amounts to 27 to 32 lm/W, a light output of the at least one turquoise LED chip (3) amounts to 63 to 66 lm/W, light output of the at least one PC lime LED chip (11) amounts to 85 to 100 lm/W, and a light output of the at least one white LED chip (1) amounts to 70 to 90 lm/W.

13. The LED lighting source according to claim 2 further comprising two channels, wherein the two channels comprise: a I channel comprising 20 to 80 of the at least one white LED chips (1); and a II channel comprising one to eight groups of the at least one monochromatic blue-turquoise PC lime LED chips, and one group of the at least one monochromatic blue-turquoise PC lime LED chips consists of only one of the at least one monochromatic blue LED chip (2), only one of the at least one one turquoise LED (3) chip, and only one of the at least one PC lime LED chip (11).

14. The LED lighting source according to claim 13 wherein the I channel comprises 40 to 60 of the at least one white LED chips and the II channel comprises four groups of the at least one monochromatic blue-turquoise PC lime LED chips.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: Light spectrum of day sunlight

(2) FIG. 2: Light spectrum of classic LED with correlated colour temperature 4000 K with CRI 80.

(3) FIG. 3: Light spectrum of white LED chip with correlated colour temperature 3957 K and CRI 98

(4) FIG. 4: Light spectrum of strip with white LED chips and correlated colour temperature 3806 K and CRI 97.8

(5) FIG. 5: Scheme of electric connection of light source to improve cognitive performance

(6) FIG. 6: Figure with printed circuit with LED chips according to Example 1

(7) FIG. 7: Light spectrum of light strip with monochromatic blue and turquoise LED chips

(8) FIG. 8: Spectrofotometric spectrum emitted by cognitive LED lighting source according to Example 4.

(9) FIG. 9: Spectrofotometric spectrum emitted by cognitive LED lighting source according to Example 2.

(10) FIG. 10: Detail of spectrum in FIG. 9

(11) FIG. 11: Spectrofotometric spectrum emitted by cognitive LED lighting source according to Example 1.

(12) FIG. 12: Detail of spectrum in FIG. 11.

(13) FIG. 13: Light strip equipped with LED chips in two channels according to Example 5

(14) FIG. 14: 14A: Light spectrum emitted by strip according to Example 5 when only II channel was on and current was 350 mA, 14B: Light spectrum emitted by strip according to Example 5 when only II channel was on and current was 500 mA, 14C: Light spectrum emitted by strip according to Example 5 when only II channel was on and current was 600 mA, 14 D: Light spectrum emitted by strip according to Example 5 when only II channel was on and current was 700 mA.

(15) FIG. 15: Spectrum emitted by LED lighting source according to Example 5

(16) FIG. 16: 16A: Comparison of spectra of light sources: Spectrum of white LED chip with correlated colour temperature 4000 K and CRI 90 16B: Comparison of spectra of light sources: Spectrum emitted by LED lighting source according to Example 1, cognitive light source 16C: Comparison of spectra of light sources: Spectrum emitted by LED lighting source according to Example 5, with properties of sun radiation 16D: Comparison of spectra of light sources: Spectrum of day sunlight

(17) FIG. 17: Graph of spectra of all light sources of used LED chips, A-white LED chip 4000 K, B-blue LED chip, C-turquoise LED chip, D-PC lime LED chip, E-LED lighting source with properties of sun radiation according to Example 5

(18) FIG. 18: Voltage responses of LED chips as depending on transient current

(19) FIG. 19: Results of tests of cognitive performance−group average+average deviation. The star marks statistically significant difference according to Example 7.

(20) FIG. 20: Averages of subjective assessment of tested (GNP, n=51) and reference (GULZ, n=53) groups according to Example 7.

(21) FIG. 21: Scheme of printed circuit of LED lighting source produced according to Example 5 fitted with LED chips

(22) FIG. 22: Scheme of printed circuit of LED lighting source produced according to Example 5 fitted with LED chips

(23) FIGS. 23A & B: Scheme of connection of LED lighting source produced according to Example 5

(24) FIG. 24: Graph of spectra of all light sources of used LED chips, A-white LED chip 2700, B-blue LED chip, C-turquoise LED chip, D-PC lime LED chip, E—LED lighting source according to Example 6

(25) FIG. 25: Spectrofotometric spectrum emitted by cognitive LED lighting source according to Example 4

EXAMPLES OF INVENTION EXECUTION

Example 1—Two Light Strips, Blue and Turquoise LED Chips with Equal Light Output

(26) The white LED chip consisted of a blue LED chip with semiconductor InGaN covered with luminophore. It was advantageous if used luminophores were with commercial name ZYP630G3, emitting light with maximum at wavelength of 628 nm and ZYP555G3, emitting light with maximum at wavelength of 555 nm which were dispersed in a silicone case that was applied over the blue LED diode. The case of the LED diode can have various shape, and it is advantageous if the slope of a wall of the case of the LED diode is inclined by 20° against level.

(27) A cognitive LED lighting was created with two 1 m long light strips 5 and 6 which consisted of printed circuits fitted with LED chips, and the strips were connected to voltage multipliers 9 which were connected to current source 10. White light strip 5 was fitted with 240 white LED chips 1 which were positioned in two lines and one printed circuit 4 with length of 5 cm was fitted with 12 white LED chips 1. White LED chip 1 consisted of a blue LED chip of InGaN semiconductor, covered with luminophore with marks ZYP555G3 and ZYP63063 in ratio 1:2. The light emitted from the white LED chip 1 formed a continuous band spectrum at wavelength 380 to 700 nm with correlated colour temperature 3957 K and CRI 98. White light strip 5 with white LED chips 1 had light output 41 W/m. Light strip for blue and turquoise chips 6 with length of 1 m was fitted with 55 monochromatic blue LED chips 2 of InGaN semiconductor with maximum radiation at 475 nm and 55 monochromatic turquoise LED chips 3 of InGaN semiconductor with maximum radiation at 495 nm. One printed circuit 4 with length of 7.2 cm was fitted with four blue LED chips 2 and four turquoise LED chips 3 which alternated. Light strip for blue and turquoise chips 6 had output 3 W/m. The ratio of luminosity of LED chips white:blue:turquoise was 1:0.3:0.3. The share of chips was 4:1:1.

(28) Characteristic parameters were measured with a manual spectrometer UPRtek for this source, emitted light had CRI 89 with correlated colour temperature 4603 and the spectrum of irradiated light was in range 420 to 760 nm, rated field of radiation from range 460 to 650 nm generated 80% of light intensity of sun radiation, as shown in FIG. 10.

(29) Reception of cognitive LED lighting was also measured, it was 80.2 W.

Example 2—Two Light Strips, Blue and Turquoise LED Chips with Different Light Output

(30) A cognitive LED lighting was created with two 1 m long light strips, a light strip of white chips 5 and a light strip of blue and turquoise chips 6 which consisted of printed circuits fitted with LED chips, and the strips were connected to voltage multipliers 9 which were connected to current source 10. The light strip of white chips 5 was fitted with 240 white LED chips 1 in two lines, and the one printed circuit 4 with length of 5 cm was fitted with 12 white LED chips 1. White LED chip 1 consisted of a blue LED chip of ZnS semiconductor, covered with luminophore with mark ZYP555G3 and ZYP63063 in ratio 1:2. The resulting light emitted from the white LED chip 1 formed a continuous band spectrum with wavelengths 380 to 700 nm with correlated colour temperature 4000 K. One white LED chip 1 had output 0.17 W, this means that the whole one-meter long white strip had output 41 W/m.

(31) The light strip with blue and turquoise chips 6 with length of 1 m was fitted with 110 monochromatic blue LED chips 2 of InGaN semiconductor with maximum radiation at 475 nm with light output 4 mW and 55 monochromatic turquoise LED chips 3 of semiconductor with maximum radiation at 495 nm with light output 7 mW, this means that the whole one-meter long light strip of blue and turquoise chips 6 had output 825 mW/m. One printed circuit 4 with length of 7.2 cm was fitted with six blue LED chips 2 and two turquoise LED chips 3. Coloured LED chips alternated always as 2 blue and 1 turquoise chips. Characteristic parameters were measured with a manual spectrometer UPRtek for this source, emitted light had CRI 91.3 with correlated colour temperature 4397, and the spectrum of irradiated light was in range 420 to 760 nm, rated field of radiation from range 460 to 650 nm generated 78% of light intensity of sun radiation, as shown in FIG. 10.

(32) Reception of cognitive LED lighting was also measured, it was 77.2 W.

Example 3—Three Light Strips, Blue and Turquoise LED Chips with Different Light Output

(33) Three one meter long light strips were created, a light strip with white chips 5, a light strip for blue chips and a light strip for turquoise chips, and LED chips were fitted in them. The light strip of white chips 5 was fitted with 240 white LED chips 1 and printed circuit 4 with length of 5 cm was fitted with 12 white LED chips 1, positioned one after another. White LED chip 1 consisted of a blue LED chip of ZnS semiconductor, covered with luminophore with marks ZYP555G3 and ZYP63063 in ratio 1:2. The resulting light emitted from the white LED chip 1 had correlated colour temperature 4000 K, and light wavelength was 380 to 700 nm. One white LED chip had output 0.17 W, this means that the whole one-meter long white strip had output 41 W/m.

(34) The light strip for blue chips with length of 1 m was fitted with 219 monochromatic blue LED chips 2 of InGaN semiconductor with maximum radiation at 475 nm with total light output 1.5 W/m, output of one chip was 7 mW. The light strip for turquoise LED chips with length of 1 m was fitted with 110 monochromatic turquoise LED chips 3 of InGaN semiconductor with maximum radiation at 495 nm and the total light output 1.4 W/m, output of one chip was 12 mW. Characteristic parameters were measured with a manual spectrometer UPRtek for this source, emitted light had CRI 90 with correlated colour temperature 4650 and the spectrum of irradiated light was in range 420 to 760 nm, rated field of radiation from range 460 to 650 nm generated 80% of light intensity of sun radiation.

(35) Reception of cognitive LED lighting was also measured, it was 80 W.

Example 4—Three Chips

(36) A round light source was fitted with three LED chips, one white LED chip with output 2 W with correlated colour temperature 3957 K and CRI 98 of a continuous band spectrum of visible light at wavelength 440 nm to 700 nm, one blue LED chip with output of 60 mW and a turquoise LED chip with output of 60 mW. The white LED chip emitted a continuous band spectrum of visible light at wavelength 440 nm to 700 nm and correlated colour temperature CCT 3800 to 4200 K, and CRI 98. The blue LED chip was of InGaN with maximum radiation at 475 nm and the turquoise LED chip was of InGaN with maximum radiation at 495 nm. Characteristic parameters were measured with a manual spectrometer UPRtek for this source, emitted light had CRI 89.5 with correlated colour temperature 4810 and the spectrum of irradiated light was in range 420 to 760 nm, rated field of radiation from range 460 to 650 nm generated 81% of light intensity of sun radiation, as shown in FIG. 8.

Example 5

(37) A LED lighting source was created that contained one light strip with three lines, and the first and the third lines were fitted with 24 white LED chips, thus 48 white LED chips in total, and connected to the I channel in parallel with 12 chips connected in series, with correlated colour temperature 4000 K and CRI 98, and the middle line was fitted with 4 blue monochromatic LED chips with radiation maximum at 473 to 475 nm, 4 turquoise monochromatic LED chips with radiation maximum at 495 nm, 4 PC Lime LED chips with radiation maximum at 520 nm emitted at 420 nm and 12 white LED chips and connected to the II channel in parallel with 12 chips connected in series, and the middle line consisted of white LED chips alternated with blue, turquoise and PC lime LED chips, this means white, blue, white, turquoise, white, PC lime, white, blue etc.

(38) Properties of the chips were as follows:

(39) white LED chip

(40) output: 0.31 W per one chip in I channel containing 48 chips units, 15.1 Win total, and 0.93 W per one chip in II channel containing 12 chips, 11.1 W in total and total output of white chips: 26.2 W

(41) light efficiency: 70 lm/W

(42) share in total light power: 51.2%

(43) blue monochromatic LED chip with radiation maximum at 475 nm

(44) output: 0.35 W per one chip in II channel containing 4 chips units, 1.4 W in total

(45) light efficiency: 29.45 lm/W

(46) share in total light power: 20%

(47) turquoise monochromatic LED chip with radiation maximum at 495 nm

(48) output: 0.38 W per one chip in II channel containing 4 chips units, 1.5 W in total

(49) light efficiency: 64.1 lm/W

(50) share in total light power: 20%

(51) PC Lime LED chips with radiation maximum at 520 nm

(52) output: 0.78 W per one chip in II channel containing 4 chips units, 3.1 W in total

(53) light efficiency: 96 lm/W

(54) share in total light power: 8.8%

(55) The total output of the source amounts to 32.2 W, 72 units of LED chips

Example 6

(56) A LED lighting source was created that contained one light strip with three lines and the first and the third lines were fitted with 24 white LED chips, thus 48 white LED chips in total, and it was connected to the I channel in parallel with 12 chips connected in series, with correlated colour temperature 2700 K and CRI 98 and the middle line was fitted with 4 blue monochromatic LED chips with radiation maximum at 473 to 475 nm, 4 turquoise monochromatic LED chips with radiation maximum at 495 nm, 4 PC Lime LED chips with radiation maximum at 520 nm emitted at 420 nm, and 12 white LED chips with correlated colour temperature 2700 K and CRI 98, and connected to the II channel in parallel with 12 chips connected in series, and the middle line consisted of white LED chips alternating with blue, turquoise and PC lime LED chips, this means white, blue, white, turquoise, white, PC lime, white, blue etc. The spectrum of this source was measured and found unsuitable for use as a LED lighting source with properties of the sun radiation due to low radiation intensity in the blue range and imbalance of the spectrum in the required biologically beneficial range 460 to 660 nm.

Example 7

(57) In a Prague school—Gymnázium Na Pražačce (GNP), equipment of LED lighting to improve cognitive performance according to Example 1 was installed in a part of the building. Due to the blue spectral component of light, particularly cognitive performance of the students was facilitated in the teaching rooms. Other monitored parameters were for example concentration, attention, reaction time, retention and thought rate, recalling from memory, physical performance, visual comfort and subjective content of the students and the teachers—overview of all the subjective parameters is shown in FIG. 20. The experiment was performed in two representative periods of time—before installation of the LED lighting and after, another school—Gymnázium u Libeňského zamku (GULZ) was selected as a control group. The experiment ran parallel in both the objects (GNP and GULZ). The experiment was assessed using two sets of specially designed psychological tests where one set of tests concentrated on objective parameters linked to the students' ability to learn, and the other set concentrated on subjective reception of the LED lighting by the students and the teachers. The results show that the students exposed to the LED lighting according to Example 1, show better study results, better health—the assessment parameters involved also monitoring of absence due to diseases and oversleep, and better satisfaction in comparison with control groups of students. The experiments are presented in examples below. All measurement were done using a spectrophotometer.

Example 7A Measurement of Illuminance

(58) Measurement of illuminance in the working area recorded the actual light conditions in the teaching rooms during lessons. The established intensity of illuminance was comparable in all the teaching rooms in both the schools where the tests were carried out. Horizontal illuminance of forms and desks under invented and standard lighting amounts to some 800 lx, and the light falling in student's eye (ie. biologically efficient light) amounts to some 300-330 lx according to the position in the teaching room and a view direction.

(59) Adequate illuminance of surface took effect when assessing legibility of texts on a blackboard which was similar in teaching rooms of the same size, very good. Though illuminance of surface in the teaching rooms is comparable, 25% students in reference teaching rooms assessed the space as too light, while only 6% of students had this opinion in new lighting. The difference in assessment is statistically important (T-test, n=104, p=0.01). The explanation of this effect can lay in better distribution and more balanced spectral composition of the new light.

Example 7B Measurement of Biological Efficiency

(60) Measurement of the spectral curve showed that in spite of comparable level of illuminance, the new lighting achieved 0.47-0.36 W/m.sup.2 in assessment of biological efficiency according to Brainard while the lighting in the reference teaching room only achieved some 0.25 to 0.20 W/m.sup.2. This is possible thanks to the balanced spectral composition of the light with high share of the blue spectral component which is the key factor to achieve the required positive effect on cognitive performance and endurance and good synchronisation of biological clock of the organism.

Example 7C Objective Assessment—Tests on Cognitive Performance

(61) Objective assessment of the effect of light was performed using tests on cognitive performance. The tests monitored concentration and short-term memory. The first stage of testing, ie. after 3 months since the lighting was installed, indicates significantly better results with the students who learn early morning in a teaching room equipped with the new cognitive lighting. These students made less mistakes in the tests (T-test, n=104, p<0.05), their recent memory was significantly better (T-test, n=104, p<0.02) compared to students of common teaching rooms. The testing results are reviewed in FIG. 19.

Example 7D Measurement of Colour Rendering Index Ra

(62) New lighting also achieved higher colour rendering index Ra. Originally, lighting with Ra 60 was installed in all the teaching rooms in GNP as well as in the reference teaching rooms monitored in GULZ. This does not satisfy the requirements of the standard on lighting of space for long-term stay of persons, the requirement is Ra 80 and more. The new light system achieves Ra 91 which is important not only because the school focuses on art education. This was likely present in subjective assessment of students, there was a tendency to better evaluate the naturalness of the colors of the new lighting. While in the new lighting, 85% of people evaluate the skin color to be natural or relatively natural, in the original one it is only 69% of people. For averages of subjective assessment of the tested (GNP, n=51) and reference (GULZ, n=53) groups, see FIG. 20.

Example 7E Energy Savings

(63) The new lighting was installed in some half of the teaching rooms where it replaced the original fluorescent and common savings LED lighting. The measurement was carried out for the whole object. Despite the significant increase in illuminance and, above all, the increase in lighting quality in approximately half of the space, the power consumption did not increase year-on-year. On the contrary, there was a small drop in consumption by 5% in the last quarter of the year.

Example 7F Psychological Effect

(64) The newly installed classroom lighting was subjectively assessed as more pleasant when compared with the common lighting (t-test, n=104, p<0.01). While lighting in reference classrooms is rated only by 32% of students as pleasant or basically pleasant, in the new installed lighting it is 53%.

LIST OF MARKS FOR TERMS

(65) 1 white LED chip 2 blue LED chip 3 turquoise LED chip 4 printed circuit of white strip 5 light strip of white chips 6 light strip of blue and turquoise chips 7 printed circuit of light strip of blue and turquoise chips 8 dimer 9 voltage multiplier 10 supply 11 yellow-green PC lime LED chip

APPLICABILITY IN INDUSTRY

(66) A light source that stimulates the cognitive performance of a person is therefore suitable wherever there is a need for great concentration and attention.