WO2013030731A2 - An illumination apparatus - Google Patents

An illumination apparatus Download PDF

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Publication number
WO2013030731A2
WO2013030731A2 PCT/IB2012/054285 IB2012054285W WO2013030731A2 WO 2013030731 A2 WO2013030731 A2 WO 2013030731A2 IB 2012054285 W IB2012054285 W IB 2012054285W WO 2013030731 A2 WO2013030731 A2 WO 2013030731A2
Authority
WO
WIPO (PCT)
Prior art keywords
light
lighting pattern
light source
color temperature
correlated color
Prior art date
Application number
PCT/IB2012/054285
Other languages
French (fr)
Other versions
WO2013030731A3 (en
Inventor
Di LOU
Jun She
Sheng Peng
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Priority to CN201290000782.3U priority Critical patent/CN204176560U/en
Publication of WO2013030731A2 publication Critical patent/WO2013030731A2/en
Publication of WO2013030731A3 publication Critical patent/WO2013030731A3/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
    • F21V9/08—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters for producing coloured light, e.g. monochromatic; for reducing intensity of light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B35/00—Electric light sources using a combination of different types of light generation
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/20—Controlling the colour of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/155—Coordinated control of two or more light sources
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S6/00—Lighting devices intended to be free-standing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21W—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO USES OR APPLICATIONS OF LIGHTING DEVICES OR SYSTEMS
    • F21W2131/00—Use or application of lighting devices or systems not provided for in codes F21W2102/00-F21W2121/00
    • F21W2131/40—Lighting for industrial, commercial, recreational or military use
    • F21W2131/402—Lighting for industrial, commercial, recreational or military use for working places
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2113/00—Combination of light sources
    • F21Y2113/10—Combination of light sources of different colours
    • F21Y2113/13—Combination of light sources of different colours comprising an assembly of point-like light sources
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00—Light-generating elements of semiconductor light sources
    • F21Y2115/10—Light-emitting diodes [LED]

Definitions

  • the present invention relates to an illumination luminaire, particularly a desktop illumination luminaire.
  • U.S. Patent Application No. 2010/0232153A1 discloses a lighting device comprising a plurality of light sources which are capable of emitting light towards a surface.
  • the lighting device is arranged in such a way that light from at least one first light source forms a first lighting pattern of white light on said surface and light from a plurality of second light sources forms a second lighting pattern of light of a different color on said surface.
  • the second lighting pattern substantially surrounds said first white lighting pattern.
  • the lighting device By using the lighting device to direct the white lighting pattern to the product, the product is illuminated and has a natural appearance, whereas the surrounding lighting pattern of light of a different color from that of the first lighting pattern is capable of creating a desired ambience and attracting and maintaining the attention of customers.
  • the foveal system of the human eye is the part of the retina that permits 100% visual acuity, and it covers about 2 degrees in the center of the visual field.
  • Peripheral vision is a part of vision that occurs outside the very center of gaze.
  • white light of higher correlated color temperature (also referred to as cool white light) is less demanding in respect of the facility of accommodation of a person's eyes.
  • cool white light users normally have a reduced accommodation error and thus a smaller degree of blurred vision, which makes it easier for users to distinguish or recognize the content in the task area, resulting in improved reading speed and accuracy.
  • cool white light contains more blue spectral components, which can increase users' alertness and concentration level.
  • white light of lower correlated color temperature also referred to as warm white light
  • white light of lower correlated color temperature has a positive effect on relaxation and soothing of users' eye muscles over a prolonged period of time.
  • the inventor Based on the effect of cool/warm white light and the impact of light on foveal/peripheral vision, the inventor has realized that if an illumination apparatus is designed to generate cool white light and make it fall largely into the foveal vision area, and to generate warm white light and make it fall largely into the peripheral vision area, with the light falling on the retina having a gradient correlated color temperature changing from the foveal vision area to the peripheral vision area, then a balance between eyecare and work performance can be achieved because the cool white light in the foveal vision area helps users accommodate their eyes more easily and also helps them recognize the details of an object, while the warm white light in the peripheral vision area helps users ease and relax their eye muscles, and thus provides eyecare in the long run.
  • an illumination apparatus comprising:
  • a first light source configured to emit light towards a surface
  • the element being arranged such that the light generated from the illumination apparatus forms a first lighting pattern of a first correlated color temperature on the surface, a second lighting pattern of a second correlated color temperature on the surface, the second lighting pattern being around the first lighting pattern, and a third lighting pattern between the first lighting pattern and the second lighting pattern on the surface, wherein the third lighting pattern has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
  • At least three lighting patterns namely the first, second and third lighting pattern, having different correlated color temperatures can be achieved on a surface.
  • the surface can be a target reading area, which can be a paper, a book, a desktop area for (?) placing reading material, etc.
  • the second lighting pattern of a second correlated color temperature is around the first lighting pattern of a first correlated color temperature, and in the transition area from the first lighting pattern to the second lighting pattern, there is the third lighting pattern having a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature, which makes the transition from the first lighting pattern to the second lighting pattern less noticeable, or not noticeable at all, to the user.
  • the first correlated color temperature is in the range [6000K, 6800K]
  • the second correlated color temperature is in the range [2500K, 3000K].
  • the element is further arranged such that the angle between the optical axis of light generated by the first light source and a virtual line connecting the external edge of the first lighting pattern and the first light source is in the range [3°, 7°], and the angle between the optical axis of light generated by the first light source and a virtual line connecting the internal edge of the second lighting pattern and the first light source is in the range [35°, 45°].
  • the area of the first lighting pattern having a first correlated color temperature in the range [6000K, 6800K] substantially corresponds to the foveal vision area of the user's eyes, which helps the user accommodate his eyes more easily and also helps him recognize the details of an object; and the area of the second lighting pattern having a second correlated color temperature in the range [2500K, 3000K] substantially corresponds to the peripheral vision area of the user's eyes, which helps the user ease and relax his eye muscles and thus prevents or slows down eyestrain accumulation in the long run.
  • the third lighting pattern with a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature, which makes the transition from the first correlated color temperature to the second correlated color temperature less noticeable, or not noticeable at all, to the user. Therefore, a balance between eyecare and work performance during reading can be well achieved.
  • the element may be a plurality of second light sources arranged adjacent to the first light source, the luminous intensity distributions of the first light source and each second light source being designed such that the first part of the light generated from the first light source forms the first lighting pattern on the surface, the first part of the light generated from the plurality of second light sources forms the second lighting pattern on the surface, and the mixture of the second part of the light generated from the first light source and the second part of the light generated from the plurality of second light sources forms the third lighting pattern.
  • the element may be an optical attenuator arranged beneath the first light source, the optical attenuator having a first region of a first transmittance of blue light, a second region of a second transmittance of blue light and a third region of a gradient transmittance of blue light changing from the first transmittance of blue light to the second transmittance of blue light, such that the light from the first light source passing through the first region of the optical attenuator forms the first lighting pattern on the surface, the light from the first lighting source passing through the second region of the optical attenuator forms the second lighting pattern on the surface and the light from the first lighting source passing through the third region of the optical attenuator forms the third lighting pattern on the surface.
  • the element may be a plate coated with phosphor arranged beneath the first light source, the plate having a first region of a first kind of phosphor, a second region of a second kind of phosphor and a third region of at least two kinds of phosphor, such that the light from the first light source passing through the first region of the plate forms the first lighting pattern on the surface, the light from the first light source passing through the second region of the plate forms the second lighting pattern on the surface and the light from the first light source passing through the third region of the plate forms the third lighting pattern on the surface.
  • FIG. 1 is a schematic view of an illumination apparatus according to one embodiment of the invention.
  • FIG. 2 is a top view of an exemplary illumination apparatus according to one embodiment of the invention and of its lighting pattern on the surface;
  • FIG. 3 is a cross-sectional view of FIG. 2;
  • FIG. 4 is a top view of another exemplary illumination apparatus according to one embodiment of the invention and of its lighting pattern on the surface;
  • FIG. 5 is a cross-sectional view of FIG. 4;
  • FIG. 6 is a top view of a further exemplary illumination apparatus according to one embodiment of the invention and of its lighting pattern on the surface;
  • Fig.7 is a cross-sectional view of FIG. 6.
  • like reference numerals will be understood to refer to like, similar or corresponding features or functions.
  • FIG. 1 shows a schematic view of an illumination apparatus 10 according to one embodiment of the invention.
  • the illumination apparatus 10 may be a desk lamp for example.
  • the illumination apparatus 10 comprises a first light source 102 configured to emit light towards a surface S.
  • the first light source 102 may be a fluorescent lamp or a light emitting diode (LED) lamp, for example.
  • the illumination apparatus 10 further comprises an element 104.
  • the element 104 is arranged such that the light generated from the illumination apparatus 10 forms a first lighting pattern PI of a first correlated color temperature on the surface S, a second lighting pattern P2 of a second correlated color temperature on the surface S, the second lighting pattern P2 being around the first lighting pattern PI, and a third lighting pattern P3 between the first lighting pattern PI and the second lighting pattern P2 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
  • the element 104 may be a plurality of second light sources arranged adjacent to the first light source 102, or an optical attenuator arranged beneath the first light source 102, or a plate coated with phosphor arranged beneath the first light source 102, which will be respectively described in great detail later.
  • the first lighting pattern PI may be of any shape, but a circular shape is preferred.
  • the third lighting pattern P3 and the second lighting pattern P2 may be of any shape, but a ring shape is more desirable when the first lighting pattern PI is of circular shape.
  • the third lighting pattern P3 fully surrounds the first lighting pattern PI, and likewise the second lighting pattern P2 fully surrounds the third lighting pattern P3. It is to be noted that in practical usage the third lighting pattern P3 may also partially surround the first lighting pattern PI and likewise the second lighting pattern P2 may also partially surround the second lighting pattern P3.
  • the average rate of change of the gradient correlated color temperature of the third lighting pattern P3 is less than a threshold, for example less than 300K/degree.
  • the change of the gradient correlated color temperature of the third lighting pattern P3 may be linear or log-linear for example.
  • the first correlated color temperature may be in the range [6000K, 6800K]
  • the second correlated color temperature may be in the range [2500K, 3000K].
  • the angle a between the optical axis of light generated by the first light source 102 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 102 may be in the range [3°, 7°]
  • the angle ⁇ between the optical axis of light generated by the first light source 102 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 102 may be in the range [35°, 45°].
  • the area of the first lighting pattern having a first correlated color temperature in the range [6000K, 6800K] substantially corresponds to the foveal vision area of the user's eyes, which helps the user accommodate his eyes more easily and enables him to recognize the details of an object more easily; and the area of the second lighting pattern having a second correlated color temperature in the range [2500K, 3000K] substantially corresponds to the peripheral vision area of the user's eyes, which helps the user ease and relax his eye muscles and thus prevents eyestrain accumulation in the long run.
  • FIG. 2 shows an exemplary illumination apparatus 20 according to one embodiment of the invention and its lighting pattern on the surface S.
  • the exemplary illumination apparatus 20 comprises a first light source 202 and a plurality of second light sources 204 that are arranged adjacent to the light source 202.
  • the luminous intensity distributions of the first light source 202 and of each second light source 204 is designed such that the first part of the light generated from the first light source 202 forms the first lighting pattern PI of the first correlated color temperature on the surface S, the first part of the light generated from the plurality of second light sources 204 forms the second lighting pattern P2 of the second correlated color temperature on the surface S, and the mixture of the second part of the light generated from the first light source 202 and the second part of the light generated from the plurality of second light sources 204 forms the third lighting pattern P3 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
  • the first light source 202 may be a fluorescent lamp or a LED lamp for example, and likewise, each of the plurality of second light sources 204 may be a fluorescent lamp or a LED lamp for example.
  • the first correlated color temperature of the first lighting pattern PI may be in the range [6000K, 6800K]
  • the second correlated color temperature of the second lighting pattern P2 may be in the range [2500K, 3000K].
  • the first light source 202 is configured to be capable of generating the cool white light of the correlated color temperature in the range [6000K, 6800K]
  • each of the second light sources 204 is configured to be capable of generating the warm white light of the correlated color temperature in the range [2500K. 3000K].
  • the angle a between the optical axis of light generated by the first light source 202 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 202 may be in the range [3°, 7°]
  • the angle ⁇ between the optical axis of light generated by the first light source 202 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 202 may be in the range [35°, 45°].
  • the plurality of second light sources 204 may be arranged around the first light source 202 and are equally spaced apart, as shown in FIG. 2. It is to be noted that in practical usage, the interval between two adjacent second light sources 204 may also be different.
  • the design of luminous intensity distributions of the first light source 202 and of each second light source 204 will be described using 6500K as an example of the first correlated color temperature, 2700K as an example of the second correlated color temperature, 5° as an example of the angle a, and 40° as an example of the angle ⁇ .
  • FIG. 3 shows a cross-sectional view of FIG. 2, in which S denotes the surface on which the light from the illumination apparatus 20 is incident, XI represents the optical axis of light generated by the first light source 202, and X2 represents the optical axis of light generated by the second light source 204.
  • the power of the first light source 202 is the same as that of the second light source 204, the optical axis XI of light generated by the first light source 202 is perpendicular to the surface S, and the optical axis X2 of light generated by the second light source 204 deviates from the optical axis XI of light generated by the first light source 202 by 40°, being the angle between the optical axis X2 of light generated by the second light source 204 and the optical axis XI of light generated by the first light source 202, which is equal to the angle ⁇ .
  • the powers of the first light source 202 and the second light source 204 may be different.
  • the angle between the optical axis XI of light generated by the first light source 202 and the optical axis X2 of light generated by the second light source 204 may be set in accordance with engineering requirements.
  • the design of luminous intensity distributions of the first light source 202 and of the second light source 204 will be described in relation to light generated on the side to the left of the optical axis XI by the first light source 202.
  • Ro represents the region of the first lighting pattern PI with the first correlated color temperature of 6500K, the first lighting pattern PI being formed by the first part of light generated from the first light source 202.
  • R4 represents the region of the second lighting pattern P2 with the second correlated color temperature of 2700K, the second lighting pattern P2 being formed by the first part of light generated from the second light source 204.
  • the third lighting pattern P3 is divided into three equal parts, namely, Ri, R 2 and R 3 .
  • the third lighting pattern P3 has a gradient correlated color temperature changing from 6500K to 2700K, which is formed by the mixture of the second part of light generated from the first light source 202 and the second part of light generated from the second light source 204.
  • division of the third lighting pattern into three equal parts is only an illustrative example, and in practical usage the third lighting pattern may be divided into two parts or into more than three parts. It will be appreciated that the more parts the third lighting pattern P3 is divided into, the better the gradient effect of the correlated color temperature in the third lighting pattern P3 will be.
  • point D represents the junction of region Ro and Ri
  • point C represents the junction of region Ri and R 2
  • point B represents the junction of region R 2 and R 3
  • point A represents the junction of region R 3 and R4.
  • point A has the correlated color temperature of 2700K
  • point D has the correlated color temperature of 6500K
  • the correlated color temperature of point B may be set to 4000K and the correlated color temperature of point C may be set to 5200K.
  • the length of DO, AO and AD can be calculated by means of the following formulas:
  • the angle ⁇ between the optical axis XI of light generated by the first light source 202 and a virtual line connecting point C and the first light source 202 can be obtained as follows.
  • the angle ⁇ 2 between the optical axis XI of light generated by the first light source 202 and a virtual line connecting point B and the first light source 202 can be obtained as follows.
  • the mixture of the light generated from the first light source 202 and deviating from the optical axis XI of light generated by the first light source 202 by 20° and the light generated from the second light source 204 and deviating from the optical axis X2 of light generated by the second light source 204 by 20° should have a correlated color temperature of 5200K at point C; and the mixture of the light generated from the first light source 202 and deviating from the optical axis XI of light generated by the first light source 202 by 30° and the light generated from the second light source 204 and deviating from the optical axis X2 of light generated by the second light source by 10° should have a correlated color temperature of 4000K at point B.
  • the ratio of luminous intensities of the first light source 202 and the second light source 204 at point C may be set to be (2/3):(l/3). That is to say, the relative luminous intensity of the first light source 202 in a direction that deviates from the optical axis XI of light generated by the first light source 202 by 20° may be set to be 2/3; and the relative luminous intensity of the second light source 204 in a direction that deviates from the optical axis X2 of light generated by the second light source 204 by 20° may be set to be 1/3.
  • the ratio of luminous intensities of the first light source 202 and the second light source 204 at point A may be set to be 0: 1. That is to say, the relative luminous intensity of the first light source 202 in a direction that deviates from the optical axis XI of light generated by the first light source 202 by 40° may be set to be 0, which means that the light of the first light source 202 is terminated at point A; and the relative luminous intensity of the second light source 204 in the direction of its optical axis X2 may be set to be 1.
  • FIG. 4 shows another exemplary illumination apparatus 30 according to one embodiment of the invention and its lighting pattern on the surface S.
  • the exemplary illumination apparatus 30 comprises a first light source 302 and an optical attenuator 304 arranged beneath the first light source 302.
  • the optical attenuator 304 has a first region Tl of a first transmittance of blue light, a second region T2 of a second transmittance of blue light and a third region T3 of a gradient transmittance of blue light changing from the first transmittance to the second transmittance.
  • the light generated from the first light source 302 passes through the first region Tl of the optical attenuator 304 and then forms the first lighting pattern PI of the first correlated color temperature on the surface S; the light generated from the first light source 302 passes through the second region T2 of the optical attenuator 304 and then forms the second lighting pattern P2 of the second correlated color temperature on the surface S; and the light generated from the first light source 302 passes through the third region T3 of the optical attenuator 304 and then forms the third lighting pattern P3 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
  • the first light source 302 may be a fluorescent lamp or a LED lamp for example, and the optical attenuator 304 may for example be a thin film attenuator, which has a gradient transmittance of blue light.
  • the distance between the first light source 302 and the optical attenuator 304 may be 5- 10cm, for example.
  • the first correlated color temperature of the first lighting pattern PI may be in the range [6000K, 6800K]
  • the second correlated color temperature of the second lighting pattern P2 may be in the range [2500K, 3000K].
  • the first light source 302 is configured to be capable of generating cool white light of a correlated color temperature in the range [6000K, 6800K].
  • the angle a between the optical axis of light generated by the first light source 302 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 302 may be in the range [3°, 7°]
  • the angle ⁇ between the optical axis of light generated by the first light source 302 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 302 may be in the range [35°, 45°].
  • the first region Tl, the third region T3 and the second region T2 of the optical attenuator 302 may be configured as concentric rings, as shown in FIG. 4. It is to be noted that in practical usage, the first region Tl, the third region T3 and the second region T2 of the optical attenuator 302 may also be other shapes.
  • the design of the transmittance of blue light of the optical attenuator 304 will be described using 6500K as an example of the first correlated color temperature, 2700K as an example of the second correlated color temperature, 5° as an example of the angle a, and 40° as an example of the angle ⁇ .
  • FIG. 5 shows a cross-sectional view of FIG. 4, in which S denotes the surface on which the light from the illumination apparatus 30 is incident, and XI represents the optical axis of light generated by the first light source 302.
  • the optical axis XI of light generated by the first light source 302 is perpendicular to the surface S. Furthermore, as the sides to the left and to the right of the optical axis XI of light generated by the first light source 302 are symmetrical, for the purpose of simplicity, the design of the transmittance of blue light of the optical attenuator 304 will be described in relation to the side to the left of the optical axis XI of light generated by the first light source 302.
  • Ro represents the region of the first lighting pattern PI with the first correlated color temperature of 6500K, the first lighting pattern PI being formed by the light from the first light source 302 passing through region ro on the optical attenuator 304.
  • R4 represents the region of the second lighting pattern P2 with the second correlated color temperature of 2700K, the second lighting pattern P2 being formed by the light from the first light source 302 passing through region r 4 on the optical attenuator 304.
  • the third lighting pattern P3 may be divided into three equal parts, namely Ri , R 2 and R 3 .
  • the third lighting pattern P3 has a gradient correlated color temperature changing from 6500K to 2700K, which is formed by the light from the first light source 302 passing through region r l s r 2 and r 3 respectively.
  • division of the third lighting pattern into three equal parts is only an illustrative example, and in practical usage the third lighting pattern may be divided into more than three parts or only into two parts. It will be appreciated that the more parts the third lighting pattern P3 is divided into, the better the gradient effect of the correlated color temperature in the third lighting pattern P3 will be.
  • the correlated color temperature of region Ri may be set to be 5500K
  • the correlated color temperature of region R 2 may be set to be 4600K
  • the correlated color temperature of region R 3 may be set to be 3700K.
  • angle ⁇ and ⁇ 2 may be the same as those in relation to FIG. 3, which will not be described here for the purpose of simplicity.
  • the length of ro, r l s r 2 , and r 3 can be calculated by means of the following formulas:
  • the length of r 4 may be designed in accordance with practical requirements.
  • the transmittance of blue light of region ro should be designed such that the light from the first light source 302 passing through region r 0 has the correlated color temperature of 6500K, i.e. the transmittance of blue light of region ro is 100%.
  • the transmittance of blue light of region ri should be designed such that the light from the first light source 302 passing through region ri has the correlated color temperature of 5500K.
  • the transmittance of blue light of region r 2 should be designed such that the light from the first light source 302 passing through region r 2 has the correlated color temperature of 4600K.
  • the transmittance of blue light of the region r 3 should be designed such that the light from the first light source 302 passing through region r 3 has the correlated color temperature of 3700K.
  • the transmittance of blue light of region r 4 should be designed such that the light from the first light source 302 passing through region r 4 has the correlated color temperature of 2700K.
  • FIG. 6 shows a further exemplary illumination apparatus 40 according to one embodiment of the invention and its lighting pattern on the surface S.
  • the exemplary illumination apparatus 40 comprises a first light source 402 and a plate 404 coated with phosphor arranged beneath the first light source 402.
  • the plate 404 has a first region Tl of a first kind of phosphor, a second region T2 of a second kind of phosphor and a third region T3 of at least two kinds of phosphor.
  • the light generated from the first light source 402 passes through the first region Tl of the plate 402 and then forms the first lighting pattern PI of the first correlated color temperature on the surface S; the light generated from the first light source 402 passes through the second region T2 of the plate 404 and then forms the second lighting pattern P2 of the second correlated color temperature on the surface S; and the light generated from the first light source 402 passes through the third region T3 of the plate 404 and then forms the third lighting pattern P3 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
  • the first light source 402 may be a blue LED lamp for example; and the plate 404 may be coated with phosphor of YAG or TAG, for example.
  • the plate 404 may be made of glass, ceramic or plastic, for example.
  • the phosphor is coated on the glass or ceramic; when the plate 404 is made of plastic, the phosphor is sintered in the plastic.
  • the thickness of the plate 404 may be in the range [1mm, 3mm].
  • the distance between the first light source 402 and the plate 404 may be 2-3cm, for example.
  • the first correlated color temperature of the first lighting pattern PI may be in the range [6000K, 6800K]
  • the second correlated color temperature of the second lighting pattern P2 may be in the range [2500K, 3000K].
  • the angle a between the optical axis of light generated by the first light source 402 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 402 may be in the range [3°, 7°]
  • the angle ⁇ between the optical axis of light generated by the first light source 402 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 402 may be in the range [35°, 45°].
  • the first region Tl, the third region T3 and the second region T2 of the plate 404 may be configured as concentric rings, as shown in FIG. 6. It is to be noted that in practical usage, the first region Tl, the third region T3 and the second region T2 of the plate 404 may also be other shapes.
  • the design of the phosphor on the plate 404 will be described using 6500K as an example of the first correlated color temperature, 2700K as an example of the second correlated color temperature, 5° as an example of the angle a, and 40° as an example of the angle ⁇ .
  • FIG. 7 shows a cross-sectional view of FIG. 6, in which S denotes the surface on which the light from the illumination apparatus 40 is incident, and XI represents the optical axis of light generated by the first light source 402.
  • the optical axis XI of light generated by the first light source 402 is perpendicular to the surface S. Furthermore, as the sides to the left and to the right of the optical axis XI of light generated by the first light source 402 are symmetrical, for the purpose of simplicity, the design of the phosphor on the plate 404 will be described in relation to the side to the left of the optical axis XI of light generated by the first light source 402.
  • Ro represents the region of the first lighting pattern PI with the first correlated color temperature of 6500K, the first lighting pattern PI being formed by the light from the first light source 402 passing through region ro on the plate 404.
  • R4 represents the region of the second lighting pattern P2 with the second correlated color temperature of 2700K, the second lighting pattern P2 being formed by the light from the first light source 402 passing through region r 4 on the plate 404.
  • the third lighting pattern P3 may be divided into three equal parts, namely, Ri, R 2 and R 3 .
  • the third lighting pattern P3 has a gradient correlated color temperature changing from 6500K to 2700K, which is formed by the light from the first light source 402 passing through region r ls r 2 and r 3 respectively.
  • division of the third lighting pattern into three equal parts is only an illustrative example, and in practical usage the third lighting pattern may be divided into more than three parts or only into two parts. It will be appreciated that the more parts the third lighting pattern P3 is divided into, the better the gradient effect of the correlated color temperature in the third lighting pattern P3 will be.
  • the correlated color temperature of region Ri may be set to be 5500K
  • the correlated color temperature of region R 2 may be set to be 4600K
  • the correlated color temperature of region R 3 may be set to be 3700K.
  • angle ⁇ and ⁇ 2 may be the same as those in relation to FIG. 3, which will not be described here for the purpose of simplicity.
  • the length of r 0 , r l s r 2 , and r 3 can be calculated by means of the following formulas:
  • the length of r 4 may be designed in accordance with practical requirements.
  • the desired lighting pattern may be achieved by adjusting the component ratio of YAG in the respective regions r 0 , r ls r 2 , r 3 and r 4 .
  • the component ratio of YAG in region r 0 should be adjusted such that the light from the first light source 402 passing through region ro has the correlated color temperature of 6500K.
  • the component ratio of YAG in region ri should be designed such that the light from the first light source 402 passing through region ri has the correlated color temperature of 5500K.
  • the component ratio of YAG in region r 2 should be designed such that the light from the first light source 402 passing through region r 2 has the correlated color temperature of 4600K.
  • the component ratio of YAG in the region r 3 should be designed such that the light from the first light source 402 passing through region r 3 has the correlated color temperature of 3700K.
  • the component ratio of YAG in region r 4 should be designed such that the light from the first light source 402 passing through region r 4 has the correlated color temperature of 2700K.

Abstract

The disclosure provides an illumination apparatus comprising: a first light source, configured to emit light towards a surface; and an element, the element being arranged such that the light generated by the illumination apparatus forms a first lighting pattern of a first correlated color temperature on the surface, a second lighting pattern of a second correlated color temperature on the surface, the second lighting pattern being around the first lighting pattern, and a third lighting pattern between the first lighting pattern and the second lighting pattern on the surface, wherein the third lighting pattern has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.

Description

AN ILLUMINATION APPARATUS
Field of the Invention
The present invention relates to an illumination luminaire, particularly a desktop illumination luminaire.
Background of the Invention
U.S. Patent Application No. 2010/0232153A1 discloses a lighting device comprising a plurality of light sources which are capable of emitting light towards a surface. The lighting device is arranged in such a way that light from at least one first light source forms a first lighting pattern of white light on said surface and light from a plurality of second light sources forms a second lighting pattern of light of a different color on said surface. The second lighting pattern substantially surrounds said first white lighting pattern.
By using the lighting device to direct the white lighting pattern to the product, the product is illuminated and has a natural appearance, whereas the surrounding lighting pattern of light of a different color from that of the first lighting pattern is capable of creating a desired ambiance and attracting and maintaining the attention of customers.
Object and Summary of the Invention
The foveal system of the human eye is the part of the retina that permits 100% visual acuity, and it covers about 2 degrees in the center of the visual field. Peripheral vision is a part of vision that occurs outside the very center of gaze. Through a number of experiments, the inventor has found that light in the peripheral vision area has more impact on eyestrain than light in the foveal vision area, whereas light in the foveal vision area directly impacts work performance.
Furthermore, researchers have found that white light of higher correlated color temperature (also referred to as cool white light) is less demanding in respect of the facility of accommodation of a person's eyes. Under cool white light, users normally have a reduced accommodation error and thus a smaller degree of blurred vision, which makes it easier for users to distinguish or recognize the content in the task area, resulting in improved reading speed and accuracy. Moreover, cool white light contains more blue spectral components, which can increase users' alertness and concentration level. Conversely, white light of lower correlated color temperature (also referred to as warm white light) has a positive effect on relaxation and soothing of users' eye muscles over a prolonged period of time.
Based on the effect of cool/warm white light and the impact of light on foveal/peripheral vision, the inventor has realized that if an illumination apparatus is designed to generate cool white light and make it fall largely into the foveal vision area, and to generate warm white light and make it fall largely into the peripheral vision area, with the light falling on the retina having a gradient correlated color temperature changing from the foveal vision area to the peripheral vision area, then a balance between eyecare and work performance can be achieved because the cool white light in the foveal vision area helps users accommodate their eyes more easily and also helps them recognize the details of an object, while the warm white light in the peripheral vision area helps users ease and relax their eye muscles, and thus provides eyecare in the long run.
According to one embodiment of the invention, there is provided an illumination apparatus comprising:
a first light source, configured to emit light towards a surface;
an element, the element being arranged such that the light generated from the illumination apparatus forms a first lighting pattern of a first correlated color temperature on the surface, a second lighting pattern of a second correlated color temperature on the surface, the second lighting pattern being around the first lighting pattern, and a third lighting pattern between the first lighting pattern and the second lighting pattern on the surface, wherein the third lighting pattern has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
With the illumination apparatus, at least three lighting patterns, namely the first, second and third lighting pattern, having different correlated color temperatures can be achieved on a surface. The surface can be a target reading area, which can be a paper, a book, a desktop area for (?) placing reading material, etc. The second lighting pattern of a second correlated color temperature is around the first lighting pattern of a first correlated color temperature, and in the transition area from the first lighting pattern to the second lighting pattern, there is the third lighting pattern having a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature, which makes the transition from the first lighting pattern to the second lighting pattern less noticeable, or not noticeable at all, to the user.
Advantageously, the first correlated color temperature is in the range [6000K, 6800K], and the second correlated color temperature is in the range [2500K, 3000K].
Advantageously, the element is further arranged such that the angle between the optical axis of light generated by the first light source and a virtual line connecting the external edge of the first lighting pattern and the first light source is in the range [3°, 7°], and the angle between the optical axis of light generated by the first light source and a virtual line connecting the internal edge of the second lighting pattern and the first light source is in the range [35°, 45°].
When the user reads under the illumination apparatus, the area of the first lighting pattern having a first correlated color temperature in the range [6000K, 6800K] substantially corresponds to the foveal vision area of the user's eyes, which helps the user accommodate his eyes more easily and also helps him recognize the details of an object; and the area of the second lighting pattern having a second correlated color temperature in the range [2500K, 3000K] substantially corresponds to the peripheral vision area of the user's eyes, which helps the user ease and relax his eye muscles and thus prevents or slows down eyestrain accumulation in the long run. Between the first lighting pattern and the second lighting pattern, there is the third lighting pattern with a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature, which makes the transition from the first correlated color temperature to the second correlated color temperature less noticeable, or not noticeable at all, to the user. Therefore, a balance between eyecare and work performance during reading can be well achieved.
Advantageously, the element may be a plurality of second light sources arranged adjacent to the first light source, the luminous intensity distributions of the first light source and each second light source being designed such that the first part of the light generated from the first light source forms the first lighting pattern on the surface, the first part of the light generated from the plurality of second light sources forms the second lighting pattern on the surface, and the mixture of the second part of the light generated from the first light source and the second part of the light generated from the plurality of second light sources forms the third lighting pattern.
Advantageously, the element may be an optical attenuator arranged beneath the first light source, the optical attenuator having a first region of a first transmittance of blue light, a second region of a second transmittance of blue light and a third region of a gradient transmittance of blue light changing from the first transmittance of blue light to the second transmittance of blue light, such that the light from the first light source passing through the first region of the optical attenuator forms the first lighting pattern on the surface, the light from the first lighting source passing through the second region of the optical attenuator forms the second lighting pattern on the surface and the light from the first lighting source passing through the third region of the optical attenuator forms the third lighting pattern on the surface.
Advantageously, the element may be a plate coated with phosphor arranged beneath the first light source, the plate having a first region of a first kind of phosphor, a second region of a second kind of phosphor and a third region of at least two kinds of phosphor, such that the light from the first light source passing through the first region of the plate forms the first lighting pattern on the surface, the light from the first light source passing through the second region of the plate forms the second lighting pattern on the surface and the light from the first light source passing through the third region of the plate forms the third lighting pattern on the surface.
Brief Description of the Drawings
The invention is explained in further detail, and by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic view of an illumination apparatus according to one embodiment of the invention;
FIG. 2 is a top view of an exemplary illumination apparatus according to one embodiment of the invention and of its lighting pattern on the surface;
FIG. 3 is a cross-sectional view of FIG. 2;
FIG. 4 is a top view of another exemplary illumination apparatus according to one embodiment of the invention and of its lighting pattern on the surface;
FIG. 5 is a cross-sectional view of FIG. 4;
FIG. 6 is a top view of a further exemplary illumination apparatus according to one embodiment of the invention and of its lighting pattern on the surface; and
Fig.7 is a cross-sectional view of FIG. 6. Throughout the drawings, like reference numerals will be understood to refer to like, similar or corresponding features or functions.
Detailed Description
Reference will now be made to embodiments of the invention, one or more examples of which are illustrated in the figures. The embodiments are provided by way of explanation of the invention, and are not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield still a further embodiment. It is intended that the invention encompass these and other modifications and variations as come within the scope and spirit of the invention.
FIG. 1 shows a schematic view of an illumination apparatus 10 according to one embodiment of the invention. The illumination apparatus 10 may be a desk lamp for example.
The illumination apparatus 10 comprises a first light source 102 configured to emit light towards a surface S. The first light source 102 may be a fluorescent lamp or a light emitting diode (LED) lamp, for example.
The illumination apparatus 10 further comprises an element 104. The element 104 is arranged such that the light generated from the illumination apparatus 10 forms a first lighting pattern PI of a first correlated color temperature on the surface S, a second lighting pattern P2 of a second correlated color temperature on the surface S, the second lighting pattern P2 being around the first lighting pattern PI, and a third lighting pattern P3 between the first lighting pattern PI and the second lighting pattern P2 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
For example, the element 104 may be a plurality of second light sources arranged adjacent to the first light source 102, or an optical attenuator arranged beneath the first light source 102, or a plate coated with phosphor arranged beneath the first light source 102, which will be respectively described in great detail later.
The first lighting pattern PI may be of any shape, but a circular shape is preferred. The third lighting pattern P3 and the second lighting pattern P2 may be of any shape, but a ring shape is more desirable when the first lighting pattern PI is of circular shape. Advantageously, the third lighting pattern P3 fully surrounds the first lighting pattern PI, and likewise the second lighting pattern P2 fully surrounds the third lighting pattern P3. It is to be noted that in practical usage the third lighting pattern P3 may also partially surround the first lighting pattern PI and likewise the second lighting pattern P2 may also partially surround the second lighting pattern P3.
To make the change of the gradient correlated color temperature of the third lighting pattern P3 less noticeable or not noticeable at all to users, advantageously, the average rate of change of the gradient correlated color temperature of the third lighting pattern P3 is less than a threshold, for example less than 300K/degree. The change of the gradient correlated color temperature of the third lighting pattern P3 may be linear or log-linear for example.
Advantageously, the first correlated color temperature may be in the range [6000K, 6800K], and the second correlated color temperature may be in the range [2500K, 3000K]. Advantageously, the angle a between the optical axis of light generated by the first light source 102 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 102 may be in the range [3°, 7°], and the angle β between the optical axis of light generated by the first light source 102 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 102 may be in the range [35°, 45°].
When the user reads under the illumination apparatus 10, the area of the first lighting pattern having a first correlated color temperature in the range [6000K, 6800K] substantially corresponds to the foveal vision area of the user's eyes, which helps the user accommodate his eyes more easily and enables him to recognize the details of an object more easily; and the area of the second lighting pattern having a second correlated color temperature in the range [2500K, 3000K] substantially corresponds to the peripheral vision area of the user's eyes, which helps the user ease and relax his eye muscles and thus prevents eyestrain accumulation in the long run. Between the first lighting pattern and the second lighting pattern, there exists the third lighting pattern with a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature, which makes the transition from the first correlated color temperature to the second correlated color temperature less noticeable or not noticeable at all to the user. Therefore, a balance between eyecare and work performance during reading can be well achieved.
Hereinafter, for illustrative purposes only, the implementation/configuration of the illumination apparatus of the invention will be described in detail using a plurality of second light sources, an optical attenuator and a plate coated with phosphor as illustrative examples of the element 104. FIG. 2 shows an exemplary illumination apparatus 20 according to one embodiment of the invention and its lighting pattern on the surface S.
The exemplary illumination apparatus 20 comprises a first light source 202 and a plurality of second light sources 204 that are arranged adjacent to the light source 202. The luminous intensity distributions of the first light source 202 and of each second light source 204 is designed such that the first part of the light generated from the first light source 202 forms the first lighting pattern PI of the first correlated color temperature on the surface S, the first part of the light generated from the plurality of second light sources 204 forms the second lighting pattern P2 of the second correlated color temperature on the surface S, and the mixture of the second part of the light generated from the first light source 202 and the second part of the light generated from the plurality of second light sources 204 forms the third lighting pattern P3 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
The first light source 202 may be a fluorescent lamp or a LED lamp for example, and likewise, each of the plurality of second light sources 204 may be a fluorescent lamp or a LED lamp for example.
Advantageously, the first correlated color temperature of the first lighting pattern PI may be in the range [6000K, 6800K], and the second correlated color temperature of the second lighting pattern P2 may be in the range [2500K, 3000K]. In this regard, the first light source 202 is configured to be capable of generating the cool white light of the correlated color temperature in the range [6000K, 6800K], and each of the second light sources 204 is configured to be capable of generating the warm white light of the correlated color temperature in the range [2500K. 3000K].
Advantageously, as shown in FIG. 2, the angle a between the optical axis of light generated by the first light source 202 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 202 may be in the range [3°, 7°], and the angle β between the optical axis of light generated by the first light source 202 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 202 may be in the range [35°, 45°].
To achieve ring-shaped lighting patterns on the surface S, advantageously, the plurality of second light sources 204 may be arranged around the first light source 202 and are equally spaced apart, as shown in FIG. 2. It is to be noted that in practical usage, the interval between two adjacent second light sources 204 may also be different.
Hereinafter, for illustrative purposes only, the design of luminous intensity distributions of the first light source 202 and of each second light source 204 will be described using 6500K as an example of the first correlated color temperature, 2700K as an example of the second correlated color temperature, 5° as an example of the angle a, and 40° as an example of the angle β.
FIG. 3 shows a cross-sectional view of FIG. 2, in which S denotes the surface on which the light from the illumination apparatus 20 is incident, XI represents the optical axis of light generated by the first light source 202, and X2 represents the optical axis of light generated by the second light source 204.
For the ease of design, in this embodiment, it is assumed that the power of the first light source 202 is the same as that of the second light source 204, the optical axis XI of light generated by the first light source 202 is perpendicular to the surface S, and the optical axis X2 of light generated by the second light source 204 deviates from the optical axis XI of light generated by the first light source 202 by 40°, being the angle between the optical axis X2 of light generated by the second light source 204 and the optical axis XI of light generated by the first light source 202, which is equal to the angle β. It is to be noted that, in practical usage, the powers of the first light source 202 and the second light source 204 may be different. The angle between the optical axis XI of light generated by the first light source 202 and the optical axis X2 of light generated by the second light source 204 may be set in accordance with engineering requirements.
Furthermore, as the sides to the left and to the right of the optical axis XI of light generated by the first light source 202, are symmetrical, for the purpose of simplicity, the design of luminous intensity distributions of the first light source 202 and of the second light source 204 will be described in relation to light generated on the side to the left of the optical axis XI by the first light source 202.
As shown in FIG. 3, Ro represents the region of the first lighting pattern PI with the first correlated color temperature of 6500K, the first lighting pattern PI being formed by the first part of light generated from the first light source 202. R4 represents the region of the second lighting pattern P2 with the second correlated color temperature of 2700K, the second lighting pattern P2 being formed by the first part of light generated from the second light source 204. The third lighting pattern P3 is divided into three equal parts, namely, Ri, R2 and R3. The third lighting pattern P3 has a gradient correlated color temperature changing from 6500K to 2700K, which is formed by the mixture of the second part of light generated from the first light source 202 and the second part of light generated from the second light source 204.
It is to be noted that division of the third lighting pattern into three equal parts is only an illustrative example, and in practical usage the third lighting pattern may be divided into two parts or into more than three parts. It will be appreciated that the more parts the third lighting pattern P3 is divided into, the better the gradient effect of the correlated color temperature in the third lighting pattern P3 will be.
Still referring to FIG. 3, point D represents the junction of region Ro and Ri, point C represents the junction of region Ri and R2, point B represents the junction of region R2 and R3, and point A represents the junction of region R3 and R4. As point A has the correlated color temperature of 2700K and point D has the correlated color temperature of 6500K, to achieve a gradient correlated color temperature, changing from 6500K to 2700K, of the third lighting pattern P3, the correlated color temperature of point B may be set to 4000K and the correlated color temperature of point C may be set to 5200K.
Assuming that the vertical distance d between the illumination apparatus 20 and the surface S is 40cm, which is the standard reading distance of a user, the length of DO, AO and AD can be calculated by means of the following formulas:
DO=d* tga=40*tg5°~4cm
AO= d* tgP=40*tg40°~34cm
AD=AO-DO~30cm
As the third lighting pattern P3 is divided into three equal parts, AB=BC=CD~10cm. The angle θι between the optical axis XI of light generated by the first light source 202 and a virtual line connecting point C and the first light source 202 can be obtained as follows.
9i=arctg(CD+DO)/d=arctgl4/40~20°
The angle θ2 between the optical axis XI of light generated by the first light source 202 and a virtual line connecting point B and the first light source 202 can be obtained as follows.
92=arctg(BC+CD+DO)/d=arctg24/40~30°
As will be clear from the above deduction, to achieve a gradient correlated color temperature of the third lighting pattern P3, the mixture of the light generated from the first light source 202 and deviating from the optical axis XI of light generated by the first light source 202 by 20° and the light generated from the second light source 204 and deviating from the optical axis X2 of light generated by the second light source 204 by 20° should have a correlated color temperature of 5200K at point C; and the mixture of the light generated from the first light source 202 and deviating from the optical axis XI of light generated by the first light source 202 by 30° and the light generated from the second light source 204 and deviating from the optical axis X2 of light generated by the second light source by 10° should have a correlated color temperature of 4000K at point B.
To achieve the correlated color temperature of 5200K at point C, the ratio of luminous intensities of the first light source 202 and the second light source 204 at point C may be set to be (2/3):(l/3). That is to say, the relative luminous intensity of the first light source 202 in a direction that deviates from the optical axis XI of light generated by the first light source 202 by 20° may be set to be 2/3; and the relative luminous intensity of the second light source 204 in a direction that deviates from the optical axis X2 of light generated by the second light source 204 by 20° may be set to be 1/3.
To achieve the correlated color temperature of 4000K at point B, the ratio of luminous intensities of the first light source 202 and the second light source 204 at point B may be set to be (l/3):(2/3). That is to say, the relative luminous intensity of the first light source 202 in a direction that deviates from the optical axis XI of light generated by the first light source 202 by 30° may be set to be 1/3; and the relative luminous intensity of the second light source 204 in a direction that deviates from the optical axis X2 of light generated by the second light source 204 by 10° may be set to be 2/3.
To achieve the correlated color temperature of 2700K at point A, the ratio of luminous intensities of the first light source 202 and the second light source 204 at point A may be set to be 0: 1. That is to say, the relative luminous intensity of the first light source 202 in a direction that deviates from the optical axis XI of light generated by the first light source 202 by 40° may be set to be 0, which means that the light of the first light source 202 is terminated at point A; and the relative luminous intensity of the second light source 204 in the direction of its optical axis X2 may be set to be 1.
To achieve the correlated color temperature of 6500K at point D, the ratio of luminous intensities of the first light source 202 and the second light source 204 at point D may be set to be 1 :0. That is to say, the relative luminous intensity of the first light source 202 in a direction that deviates from the optical axis XI of light generated by the first light source 202 by 5° may be set to be 1, and the relative luminous intensity of the second light source 204 in a direction that deviates from the optical axis X2 of light generated by the second light source 204 by 35° may be set to be 0.
FIG. 4 shows another exemplary illumination apparatus 30 according to one embodiment of the invention and its lighting pattern on the surface S.
The exemplary illumination apparatus 30 comprises a first light source 302 and an optical attenuator 304 arranged beneath the first light source 302. The optical attenuator 304 has a first region Tl of a first transmittance of blue light, a second region T2 of a second transmittance of blue light and a third region T3 of a gradient transmittance of blue light changing from the first transmittance to the second transmittance. The light generated from the first light source 302 passes through the first region Tl of the optical attenuator 304 and then forms the first lighting pattern PI of the first correlated color temperature on the surface S; the light generated from the first light source 302 passes through the second region T2 of the optical attenuator 304 and then forms the second lighting pattern P2 of the second correlated color temperature on the surface S; and the light generated from the first light source 302 passes through the third region T3 of the optical attenuator 304 and then forms the third lighting pattern P3 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
The first light source 302 may be a fluorescent lamp or a LED lamp for example, and the optical attenuator 304 may for example be a thin film attenuator, which has a gradient transmittance of blue light. The distance between the first light source 302 and the optical attenuator 304 may be 5- 10cm, for example.
Advantageously, the first correlated color temperature of the first lighting pattern PI may be in the range [6000K, 6800K], and the second correlated color temperature of the second lighting pattern P2 may be in the range [2500K, 3000K]. In this case, the first light source 302 is configured to be capable of generating cool white light of a correlated color temperature in the range [6000K, 6800K].
Advantageously, as shown in FIG. 4, the angle a between the optical axis of light generated by the first light source 302 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 302 may be in the range [3°, 7°], and the angle β between the optical axis of light generated by the first light source 302 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 302 may be in the range [35°, 45°].
To achieve ring-shaped lighting patterns on the surface S, advantageously, the first region Tl, the third region T3 and the second region T2 of the optical attenuator 302 may be configured as concentric rings, as shown in FIG. 4. It is to be noted that in practical usage, the first region Tl, the third region T3 and the second region T2 of the optical attenuator 302 may also be other shapes.
Hereinafter, for illustrative purposes only, the design of the transmittance of blue light of the optical attenuator 304 will be described using 6500K as an example of the first correlated color temperature, 2700K as an example of the second correlated color temperature, 5° as an example of the angle a, and 40° as an example of the angle β.
FIG. 5 shows a cross-sectional view of FIG. 4, in which S denotes the surface on which the light from the illumination apparatus 30 is incident, and XI represents the optical axis of light generated by the first light source 302.
For the ease of design, in this embodiment, it is assumed that the optical axis XI of light generated by the first light source 302 is perpendicular to the surface S. Furthermore, as the sides to the left and to the right of the optical axis XI of light generated by the first light source 302 are symmetrical, for the purpose of simplicity, the design of the transmittance of blue light of the optical attenuator 304 will be described in relation to the side to the left of the optical axis XI of light generated by the first light source 302.
As shown in FIG. 5, Ro represents the region of the first lighting pattern PI with the first correlated color temperature of 6500K, the first lighting pattern PI being formed by the light from the first light source 302 passing through region ro on the optical attenuator 304. R4 represents the region of the second lighting pattern P2 with the second correlated color temperature of 2700K, the second lighting pattern P2 being formed by the light from the first light source 302 passing through region r4 on the optical attenuator 304. The third lighting pattern P3 may be divided into three equal parts, namely Ri , R2 and R3. The third lighting pattern P3 has a gradient correlated color temperature changing from 6500K to 2700K, which is formed by the light from the first light source 302 passing through region rl s r2 and r3 respectively.
It is to be noted that division of the third lighting pattern into three equal parts is only an illustrative example, and in practical usage the third lighting pattern may be divided into more than three parts or only into two parts. It will be appreciated that the more parts the third lighting pattern P3 is divided into, the better the gradient effect of the correlated color temperature in the third lighting pattern P3 will be.
To achieve a gradient correlated color temperature, changing from 6500K to 2700K, of the third lighting pattern P3, for example, the correlated color temperature of region Ri may be set to be 5500K, the correlated color temperature of region R2 may be set to be 4600K, and the correlated color temperature of region R3 may be set to be 3700K.
In this embodiment, the calculations and values of angle θι and θ2 may be the same as those in relation to FIG. 3, which will not be described here for the purpose of simplicity.
Assuming that the vertical distance di between the first light source 302 and the optical attenuator 304 is 5cm, the length of ro, rl s r2, and r3 can be calculated by means of the following formulas:
r0=di* tga=5*tg5°~0.44cm
ri=di*(tg0i-tga)=5*(tg2O°-tg5 4.38cm
Figure imgf000015_0001
The length of r4 may be designed in accordance with practical requirements.
As will be clear from the above deduction, to obtain a gradient correlated color temperature of the third lighting pattern P3, the transmittance of blue light of region ro should be designed such that the light from the first light source 302 passing through region r0 has the correlated color temperature of 6500K, i.e. the transmittance of blue light of region ro is 100%. The transmittance of blue light of region ri should be designed such that the light from the first light source 302 passing through region ri has the correlated color temperature of 5500K. The transmittance of blue light of region r2 should be designed such that the light from the first light source 302 passing through region r2 has the correlated color temperature of 4600K. The transmittance of blue light of the region r3 should be designed such that the light from the first light source 302 passing through region r3 has the correlated color temperature of 3700K. The transmittance of blue light of region r4 should be designed such that the light from the first light source 302 passing through region r4 has the correlated color temperature of 2700K.
FIG. 6 shows a further exemplary illumination apparatus 40 according to one embodiment of the invention and its lighting pattern on the surface S.
The exemplary illumination apparatus 40 comprises a first light source 402 and a plate 404 coated with phosphor arranged beneath the first light source 402. The plate 404 has a first region Tl of a first kind of phosphor, a second region T2 of a second kind of phosphor and a third region T3 of at least two kinds of phosphor. The light generated from the first light source 402 passes through the first region Tl of the plate 402 and then forms the first lighting pattern PI of the first correlated color temperature on the surface S; the light generated from the first light source 402 passes through the second region T2 of the plate 404 and then forms the second lighting pattern P2 of the second correlated color temperature on the surface S; and the light generated from the first light source 402 passes through the third region T3 of the plate 404 and then forms the third lighting pattern P3 on the surface S, wherein the third lighting pattern P3 has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
The first light source 402 may be a blue LED lamp for example; and the plate 404 may be coated with phosphor of YAG or TAG, for example.
The plate 404 may be made of glass, ceramic or plastic, for example. When the plate 404 is made of glass or ceramic, the phosphor is coated on the glass or ceramic; when the plate 404 is made of plastic, the phosphor is sintered in the plastic. The thickness of the plate 404 may be in the range [1mm, 3mm].
The distance between the first light source 402 and the plate 404 may be 2-3cm, for example.
Advantageously, the first correlated color temperature of the first lighting pattern PI may be in the range [6000K, 6800K], and the second correlated color temperature of the second lighting pattern P2 may be in the range [2500K, 3000K].
Advantageously, as shown in FIG. 6, the angle a between the optical axis of light generated by the first light source 402 and a virtual line connecting the external edge of the first lighting pattern PI and the first light source 402 may be in the range [3°, 7°], and the angle β between the optical axis of light generated by the first light source 402 and a virtual line connecting the internal edge of the second lighting pattern P2 and the first light source 402 may be in the range [35°, 45°].
To achieve ring-shaped lighting patterns on the surface S, advantageously, the first region Tl, the third region T3 and the second region T2 of the plate 404 may be configured as concentric rings, as shown in FIG. 6. It is to be noted that in practical usage, the first region Tl, the third region T3 and the second region T2 of the plate 404 may also be other shapes.
Hereinafter, for illustrative purposes only, the design of the phosphor on the plate 404 will be described using 6500K as an example of the first correlated color temperature, 2700K as an example of the second correlated color temperature, 5° as an example of the angle a, and 40° as an example of the angle β.
FIG. 7 shows a cross-sectional view of FIG. 6, in which S denotes the surface on which the light from the illumination apparatus 40 is incident, and XI represents the optical axis of light generated by the first light source 402.
For the ease of design, in this embodiment, it is assumed that the optical axis XI of light generated by the first light source 402 is perpendicular to the surface S. Furthermore, as the sides to the left and to the right of the optical axis XI of light generated by the first light source 402 are symmetrical, for the purpose of simplicity, the design of the phosphor on the plate 404 will be described in relation to the side to the left of the optical axis XI of light generated by the first light source 402.
As shown in FIG. 7, Ro represents the region of the first lighting pattern PI with the first correlated color temperature of 6500K, the first lighting pattern PI being formed by the light from the first light source 402 passing through region ro on the plate 404. R4 represents the region of the second lighting pattern P2 with the second correlated color temperature of 2700K, the second lighting pattern P2 being formed by the light from the first light source 402 passing through region r4 on the plate 404. The third lighting pattern P3 may be divided into three equal parts, namely, Ri, R2 and R3. The third lighting pattern P3 has a gradient correlated color temperature changing from 6500K to 2700K, which is formed by the light from the first light source 402 passing through region rls r2 and r3 respectively.
It is to be noted that division of the third lighting pattern into three equal parts is only an illustrative example, and in practical usage the third lighting pattern may be divided into more than three parts or only into two parts. It will be appreciated that the more parts the third lighting pattern P3 is divided into, the better the gradient effect of the correlated color temperature in the third lighting pattern P3 will be.
To achieve a gradient correlated color temperature, changing from 6500K to 2700K, of the third lighting pattern P3, for example, the correlated color temperature of region Ri may be set to be 5500K, the correlated color temperature of region R2 may be set to be 4600K, and the correlated color temperature of region R3 may be set to be 3700K.
In this embodiment, the calculations and values of angle θι and θ2 may be the same as those in relation to FIG. 3, which will not be described here for the purpose of simplicity.
Assuming that the vertical distance di between the first light source 402 and the plate 404 is 2cm, the length of r0, rl s r2, and r3 can be calculated by means of the following formulas:
Figure imgf000018_0001
ri=di*(tg9i-tga)=2!i:(tg20o-tg5o)~0.55cm
Figure imgf000018_0002
The length of r4 may be designed in accordance with practical requirements.
As the plate 404 is divided into five parts, namely r0, rl s r2, r3 and r4, five kinds of phosphor are required to achieve the desired lighting pattern on surface S. Using YAG as an illustrative example of phosphor on the plate 404, the desired lighting pattern may be achieved by adjusting the component ratio of YAG in the respective regions r0, rls r2, r3 and r4. To be specific, the component ratio of YAG in region r0 should be adjusted such that the light from the first light source 402 passing through region ro has the correlated color temperature of 6500K. The component ratio of YAG in region ri should be designed such that the light from the first light source 402 passing through region ri has the correlated color temperature of 5500K. The component ratio of YAG in region r2 should be designed such that the light from the first light source 402 passing through region r2 has the correlated color temperature of 4600K. The component ratio of YAG in the region r3 should be designed such that the light from the first light source 402 passing through region r3 has the correlated color temperature of 3700K. The component ratio of YAG in region r4 should be designed such that the light from the first light source 402 passing through region r4 has the correlated color temperature of 2700K.
It should be noted that the above embodiments are given for describing rather than limiting the invention, and it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the invention and the appended claims. The protective scope of the invention is defined by the accompanying claims. In addition, any of the reference numerals in the claims should not be interpreted as a limitation to the claims. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The indefinite article "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.

Claims

What is claimed is:
1. An illumination apparatus (10, 20, 30, 40) comprising:
- a first light source (102, 202, 302, 402) configured to emit light towards a surface;
- an element (104, 204, 304, 404), the element being arranged such that the light generated from the illumination apparatus forms a first lighting pattern of a first correlated color temperature on the surface, a second lighting pattern of a second correlated color temperature on the surface, the second lighting pattern being around the first lighting pattern, and a third lighting pattern between the first lighting pattern and the second lighting pattern on the surface, wherein the third lighting pattern has a gradient correlated color temperature changing from the first correlated color temperature to the second correlated color temperature.
2. The illumination apparatus of claim 1 , wherein the element is further arranged such that the angle between the optical axis of light generated by the first light source and a virtual line connecting the external edge of the first lighting pattern and the first light source is in the range [3°, 7°], and the angle between the optical axis of light generated by the first light source and a virtual line connecting the internal edge of the second lighting pattern and the first light source is in the range [35°, 45°].
3. The illumination apparatus of claim 1 or 2, wherein the first correlated color temperature is in the range [6000K, 6800K], and the second correlated color temperature is in the range [2500K, 3000K].
4. The illumination apparatus (20) of claim 1 , wherein the element comprises a plurality of second light sources (204) arranged adjacent to the first light source (202), the luminous intensity distributions of the first light source and each second light source being designed such that the first part of the light generated from the first light source forms the first lighting pattern on the surface, the first part of the light generated from the plurality of second light sources forms the second lighting pattern on the surface, and the mixture of the second part of the light generated from the first light source and the second part of the light generated from the plurality of second light sources forms the third lighting pattern.
5. The illumination apparatus of claim 4, wherein the first light source generates cool white light of a correlated color temperature in the range [6000K, 6800K], and each second light source generates warm white light of a correlated color temperature in the range [2500K. 3000K].
6. The illumination apparatus (30) of claim 1 , wherein the element comprises an optical attenuator (304) arranged beneath the first light source (302), the optical attenuator having a first region of a first transmittance of blue light, a second region of a second transmittance of blue light and a third region of a gradient transmittance of blue light changing from the first transmittance of blue light to the second transmittance of blue light, such that the light from the first light source passing through the first region of the optical attenuator forms the first lighting pattern on the surface, the light from the first lighting source passing through the second region of the optical attenuator forms the second lighting pattern on the surface and the light from the first lighting source passing through the third region of the optical attenuator forms the third lighting pattern on the surface.
7. The illumination apparatus of claim 6, wherein the first light source generates cool white light of a correlated color temperature in the range [6000K, 6800K].
8. The illumination apparatus (40) of claim 1 , wherein the element comprises a plate (404) coated with phosphor arranged beneath the first light source (402), the plate having a first region of a first kind of phosphor, a second region of a second kind of phosphor and a third region of at least two kinds of phosphor, such that the light from the first light source passing through the first region of the plate forms the first lighting pattern on the surface, the light from the first light source passing through the second region of the plate forms the second lighting pattern on the surface and the light from the first light source passing through the third region of the plate forms the third lighting pattern on the surface.
9. The illumination apparatus of claim 8, wherein the first light source generates blue light.
10. The illumination apparatus of claim 1 , wherein the average rate of change of the gradient correlated color temperature from the first correlated color temperature to the second correlated color temperature is less than a threshold.
11. The illumination apparatus of claim 1 , wherein the gradient correlated color temperature of the third lighting pattern changes linearly from the first correlated color temperature to the second correlated color temperature.
12. The illumination apparatus of claim 1 , wherein the gradient correlated color temperature of the third lighting pattern changes log-linearly from the first correlated color temperature to the second correlated color temperature.
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