WO2013010717A1

WO2013010717A1 - Illumination device and illumination method for adapting light to characteristic of target object

Info

Publication number: WO2013010717A1
Application number: PCT/EP2012/060588
Authority: WO
Inventors: Peng Chen; Aiai Li; Tingming LIU; Xiaoqing Sun
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2011-07-15
Filing date: 2012-06-05
Publication date: 2013-01-24
Anticipated expiration: 2014-01-15
Also published as: CN102883497A

Abstract

The present invention discloses an illumination device and an illumination method. The illumination device includes illumination units with at least two colors, wherein the proportion of light with a specific color in mixed light emitted from the illumination units with the at least two colors is set within a specific range according to a physical characteristic and/or an optical characteristic of an illumination object. The illumination method includes: setting the proportion of light with a specific color in mixed light emitted from illumination units with at least two colors according to a physical characteristic and/or an optical characteristic of an illumination object. According to the invention, the realistic color of a specific illumination object, e.g., meat, etc., can be well presented while improving the output efficiency and lowering the cost of the device.

Description

ILLUMINATION DEVICE AND ILLUMINA ION METHOD FOR ADAPTING LIGHT TO CHARACTERISTIC OF TARGET OBJECT The present invention relates to the field of illuminating an object and in particular to an illumination device and illumination method for illuminating a specific object.

Background of the Invention

At present, a traditional tubular fluorescent lamp is gen- erally used in a shop to illuminate a specific illumination object, e.g., meat, etc. The traditional tubular fluorescent lamp has the following drawbacks: the lamp has a large diameter, low energy efficiency, includes a harmful substance, e.g., mercury, etc., and a short lifetime. In addi- tion to the tubular fluorescent lamp in the traditional form, a hot white LED can also be used for illumination. However the hot white LED may cause a specific illumination object, e.g., meat to change in color due to inappropriate color coordinates. Furthermore a high power white LED and a high power red LED can be used in combination to illuminate a specific illumination object, e.g., meat, etc. However mixed light may not be uniform and a bright colored spot may be present for illumination in an ultra short distance in this illumination approach because light has to be mixed over a specific distance at a high cost.

Summary of the Invention

In view of the foregoing problem, an embodiment of the invention provides an illumination device and illumination method including LEDs with at least two colors to obviate at least one of the drawbacks in the prior art.

According to an aspect of the invention, there is provided an illumination device including illumination units with at least two colors, wherein the proportion of light with a specific color in mixed light emitted from the illumination units with the at least two colors is set within a specific range according to a physical characteristic and/or an optical characteristic of an illumination object.

According to another aspect of the invention, there is provided an illumination method including: setting the proportion of light with a specific color in mixed light emitted from illumination units with at least two colors according to a physical characteristic and/or an optical characteristic of an illumination object.

The illumination device and method according to the embodiments of the invention can present excellently the real color of a specific illumination object, e.g., meat, etc., while improving the output efficiency can be improved and lowering the cost of the device.

Brief Description of the Drawings

The foregoing and other objects, features and advantages of the invention will become more apparent from the following description of embodiments of the invention with reference to the drawings in which:

Fig. la and Fig. lb illustrate respectively a structural block diagram of an illumination device according to an em- bodiment of the invention;

Fig.2 is a curve diagram illustrating reflection coefficients of meat;

Fig.3 is a diagram illustrating the structure of the illumination device according to the embodiment of the inven- tion; Fig.4 illustrates a chromaticity diagram obtained when meat is illuminated in a short distance according to an embodiment of the invention;

Fig.5 illustrates in details a local enlarged diagram of the chromaticity diagram in Fig.4; and

Fig.6 is a flow chart illustrating an illumination method according to an embodiment of the invention.

Detailed Description of the Invention

Embodiments of the invention will be described below with reference to the drawings. An element and a feature described in a drawing or an embodiment of the invention can be combined with an element and a feature illustrated in one or more other drawings or embodiments. It shall be noted that the illustration and the description of compo- nents and processes irrelevant to the invention and known to those ordinarily skilled in the art will be omitted in the drawing and the description for the sake of clarity.

An illumination device according to the invention includes illumination units with at least two colors, wherein the proportion of light with a specific color in mixed light emitted from the illumination units with the at least two colors is set in a specific range according to an optical characteristic of an illumination object. Fig.1(a) illustrates schematically an example of the illumination device. In a preferred embodiment, the illumination device according to the invention can further include a control unit configured to adjust the proportion of light with the specific color according to the optical characteristic of the illumination object so that the proportion of light with the specific color is adapted to the optical characteristic of the illumination object. Fig.1(b) illustrates an example of the illumination device according to the preferred embodiment .

Although Fig.1(a) and Fig.1(b) illustrate illumination units with three colors, the number of colors of the illu- mination units will not be limited to three but can be set to any number larger than or equal to two as required for illumination of the illumination object. The numbers of illumination units with the respective colors in Fig.1(a) and Fig.1(b) are one but may alternatively be two or more. The invention will not be limited in this respect.

An example of the illumination device according to the embodiment of the invention will be illustrated below taking meat as an example of a specific illumination object.

In the case that an illumination object is meat, the illu- mination units in the illumination device according to the embodiment of the invention may be LEDs including white LEDs and red LED. It shall be appreciated that the illumination units according to the invention will not be limited to LEDs or white LEDs and red LEDs in combination, but LEDs with a combination of colors can be selected arbitrarily according to a physical characteristic (e.g., the color, etc.) and/or an optical characteristic (including the reflection coefficient, etc.) of the illumination object. For example, white LEDs, red LEDs, amber LEDs, etc. in combina- tion can also be selected for meat.

Reference is made to Fig.2 illustrating a curve of reflection coefficients of meat. As can be apparent from Fig.2, the reflection coefficients of meat are significant when the wavelength of incident light is above 600nm, and there- fore red light among visible light is the most important for the color of meat to be presented. Thus the red rate in mixed light eventually emitted from the white LEDs and the red LEDs (hereinafter red rate) will be important.

If the red rate is not appropriate, then meat will change in color from red and the natural color thereof can not be presented as it is. How to select an appropriate red rate will be described in details below.

Firstly several concepts will be defined. The total amount of energy of light radiated from an illuminant in a unit period of time is referred to as the radiant flux of a light source. Although the radiant flux is an objective physical quantity reflecting the intensity of light radiation, it can not fully reflect subjective perception of a person due to light energy, i.e., a visual intensity (or brightness) , because human eyes are differently sensitive to light waves at different wavelengths. For example, if a red LED at

has photo-electricity conversion efficiency up to 100%, that is, light power of 1W can be generated by applying electricity power of 1W to the PN junction of the LED, then its radiant light flux is 1401m and lumen efficiency is 1401m/W as determined from the curve of a visual function. Even if a blue LED at

has photoelectricity conversion efficiency up to 100%, its radiant light flux is only 411m and lumen efficiency is 411m/W as determined from the curve of the visual function. A relationship of the sensitivity of human eyes to light varying with the wavelength is referred to as a visual function of human eyes .

The product of the radiant flux of light and the corresponding visual function is referred to as the "light flux Φ" of the light. In mixed light resulting from the red LEDs and the white LEDs, the proportion of the light flux of red light to the light flux of visual light is defined as the red rate : e dLight φ(λ) λ)άλ

620

(•780 (Equation 1)

VisualLight φ{λ) λ)άλ

380

Where Φ represents the light flux, λ represents the wavelength of light, Φ(λ) represents the radiant flux, and ν(λ) represents the visual function.

The red rate in mixed light can be obtained by adjusting the light flux Φ of red light and/or white light respectively. In a specific implementation of the present embodiment, it is preferred to select the red rate ranging from 21.4% to 34.4%, and at this time the color of meat can be presented optimally.

Such an example has been described in which the red rate is set by the reflection coefficient of meat. The red rate can alternatively be set by an alternative optical characteristic of meat such as a refraction coefficient for an ideal illumination effect, for example, of presenting the color of meat optimally.

The red rate and an optimal range of the red rate for illuminating meat have been defined as above. The illumination device according to an embodiment of the invention is such a device that can produce such a red rate so that the color of meat can be presented optimally. The red rate can be set in the illumination device, for example, by selecting an appropriate LED model, setting the proportions of the numbers of LEDs with different colors, etc. Drive current for LEDs of different models falls into a specific range, and as can be apparent from the foregoing equation 1, the red rate in mixed light can be adjusted by selecting LEDs of different models. Similarly such adjusting can alternatively be made by setting the proportions of the numbers of LEDs with different colors. In the case that the control unit is arranged in the illumination device, the red rate can be adjusted for the illumination object (meat in this example) by the control unit adjusting current flowing through the red LEDs and the white LEDs respectively and further the light flux Φ of red light and/or white light. Various specific details of adjusting (for example, current of firstly the red LED and then the white LED is adjusted or current of the two types of LEDs is adjusted concurrently, etc.) can be set corre- spondingly dependent upon a practical application scenario, which will not be described here. In addition to adjusting of current flowing the LEDs, the red rate can be adjusted by the controlling unit switching between high power white and/or red LEDs and low power white and/or red LEDs or by the controlling unit disabling a part of the white and/or red LEDs or enabling more of the white and/or red LEDs.

The illumination device according to the present embodiment can present the color of meat realistically and naturally without distortion by setting the red rate as described above .

Correlated Color Temperature is also a very important factor for presentation of meat. According to the invention, color temperature is also set in an appropriate range by setting an appropriate red rate to thereby obviate such a problem in the prior art that meat changes in color due to inappropriate color coordinates .

Sometimes meat has to be illuminated in a short distance or in an ultra short distance. In the present embodiment, an operation distance (the distance from the surface of an il- lumination cover to the illumination object) smaller than ten times of the diameter of an LED lamp tube is defined as a short distance, and an operation distance smaller than five times of the diameter of an LED lamp tube is defined as an ultra short distance. Those skilled in the art can define a short distance and an ultra short distance in practice dependent upon the shape of the housing of an LED lamp, and the invention will not be limited in this respect .

In a specific implementation of the embodiment of the invention, low power white LEDs and low power red LEDs are used for illumination in a short distance and an ultra short distance. The use of low power LEDs can result in weakening of glaring strong light, the luminosity of the illumination object can be achieved at an appropriate level, and better color uniformity can also be achieved. Furthermore in the case that the low power LEDs are used, an FR4 plate can be used without any heat dissipation design to thereby lower the cost, lengthen the lifetime of the illumination device and improve the output efficiency. Low power LEDs can be used by selecting the low power LEDs when the illumination device is manufactured or by the con- trol unit controlling current flowing through the LEDs or selecting between from high power LEDs to low power LEDs, and the invention will not be limited in this respect.

Preferably the distance between LEDs is set below 20mm for better color uniformity in the case of illumination in a short distance and an ultra short distance. The distance between LEDs will not be limited to below 20mm but can be set arbitrarily in practice, and the invention will not be limited in this respect.

Preferably the illumination device can include a diffusion cover for better color uniformity.

Fig.3 illustrates a specific configuration example of the illumination device according to the embodiment of the in- vention. As illustrated in Fig.3, the cover can be arranged separate from the PCB plate at a distance which can be set by those skilled in the art as needed in practice. The control unit is arranged in the PCB but is not illustrated in the figure. The arrangement of the white LEDs and the red LEDs will not be limited to that illustrated in Fig.3 in which only an example of arranging the LEDs with the two colors is presented. Those skilled in the art can arrange the white LEDs and the red LEDs arbitrarily, for example, by arranging the LEDs with different colors in arrays, linearly, in an interlaced way or in a polygon, e.g., a circle, etc. Those skilled in the art can also set the proportion of the number of white LEDs to the number of red LEDs according to an expected red rate. The invention will not be limited in this respect. As can be apparent, the structure of the illumination device according to the embodiment of the invention is also very simple to thereby lower the manufacturing cost thereof .

Experimental Result

An experiment result of illuminating meat in an ultra short distance will be described below. In an experiment with an operation distance of 250mm and the proportion of mixing the light fluxes of the white LED and the red LED being set as 3.7+0.7, the numbers of LEDs and the light fluxes of the LEDs are set so that the luminosity of meat can be set to range from 7501x to 15001x in which meat can be presented with an optimal effect. Fig.4 illustrates a chromaticity diagram acquired under these experiment conditions. As illustrated in Fig.4, the coordinates of mixed light lie on a line connecting the coordinates of white light and red light. Fig.5 illustrates a local enlarged diagram of color coordinates and color temperature of red light, white light and mixed light in Fig.4, where quadrangles denoted with block dots represent regions of white light, mixed light and red light respectively from the left to the right. As illustrated in Fig.5, color coordinates X and Y of mixed light (abscissas and ordinates of four vertexes of the quadrangle where mixed light lies) are respectively:

As illustrated in Fig.5, the color temperature of mixed light lies in the range of 2900K to 3750K. At this time the illuminated meat has such good color uniformity that the color of meat is presented realistically without any distortion .

In this experiment, meat may be beef, pork, etc., and the invention will not be limited in this respect.

Undoubtedly the invention can also be applicable to illumination over a long distance, and at this time, illumination units (e.g., LEDs, etc) can be controlled, for example, through at least one of increasing the number of LEDs, increasing the contour size of LED lamps, using high power LEDs, etc., for the long operation distance.

As can be appreciated, the illumination device in an embodiment can include various types of illumination units (e.g., LEDs, etc.), e.g., illumination units with various colors, illumination units with various sizes, etc. The control unit can control which illumination units are operative and which illumination units are inoperative, control current of those operative illumination units, etc. Therefore the illumination capacity of the illumination device can vary with the characteristic (e.g., a physical characteristic, an optical characteristic, etc.) of the illumination object and/or an illumination condition (e.g., an illumination distance, etc.) to thereby improve greatly the applicability of the illumination device.

An illumination method according to an embodiment of the invention will be described below again taking meat as an example of a specific illumination object.

As described above, the illumination device may or may not include a control unit. With the absence of the control unit, the manufactured illumination device can illuminate directly a predetermined specific illumination object under a specific illumination condition (e.g., the distance to the illumination object, etc.) .

Another specific example of the illumination method will be described below for illumination by the illumination device with a control unit. In this illustrative method, an illumination object which is meat can be illuminated using LEDs

(including white LEDs and red LEDs) . It shall be appreciated that the illumination units of the invention will not be limited to LEDs or white LEDs and red LEDs in combination, but LEDs with a specific combination of colors can be selected arbitrarily according to a physical characteristic

(e.g., the color) and/or an optical characteristic (including a reflection coefficient, etc.) of an illumination object. In the case of meat, for example, white LEDs, red LEDs, amber LEDs, etc., are also possible.

Fig.6 illustrates an illustrative flow chart 600 of the illumination method according to the embodiment of the invention. As illustrated in Fig.6, firstly the distance from illumination units (LED lamps in the present embodiment) to meat is determined in the step S610. If the distance is determined as being short, then the LEDs are enabled in the step S620 to operate as low power LEDs. If the distance is determined as being long, then the LED is enabled in the step S630 to operate as high power LEDs. As describe above, the short distance and the long distance can be defined by those skilled in the art in practice, and the invention will not be limited in this respect. Adjusting can be made in the cases of a short distance and of a long distance similarly to the corresponding process described above for the illumination device, and reference can be made to the foregoing description. Furthermore the low power LEDs or the high power LEDs can be selected by the control unit adjusting current flowing through the LEDs or switching to the low power LEDs between the low power LEDs and the high power LEDs, and the invention will not be limited in this respect .

Next in the step S640, the red rate can be set by adjusting current flowing respectively through white LEDs and red LEDs so that finally the red rate will be set to range from 21.4% to 34.4%. Then in the step S650, illumination is enabled with the set red rate to finally present the inherent color of meat without any distortion. The red rate can be adjusted similarly to the corresponding process described above for the illumination device, and reference can be made to the foregoing description.

The foregoing step of selecting the power of the LEDs may not be necessary but the flow can go directly to the process of the step S640. However a better effect of the inven- tion can be achieved by selecting the power of the LEDs.

In analogy to the foregoing embodiment, the red rate can alternatively be adjusted by the reflection coefficient of meat in the present embodiment. The red rate can alternatively be adjusted by an alternative optical characteristic of meat such as a refraction coefficient.

As can be apparent from the foregoing description, the op- erations of the illumination method according to the embodiment of the invention will be straightforward to perform along with an optimum illumination effect.

As can be appreciated, if the illumination object is another object than meat and this object exhibits another color than red, then the object can be illuminated by adjusting the luminescence proportion of illumination units with corresponding colors in the illumination device according to a physical characteristic, e.g., the color, etc., and/or an optical characteristic, e.g., the reflec- tion coefficient, etc., of the object, as long as an illumination effect for the object can be better presented through the method of the invention.

Although the invention has been disclosed above in the description of the embodiments of the invention, it shall be appreciated that those skilled in the art can make various modifications, adaptations or equivalents of the invention without departing from the spirit and scope of the appended claims and these modifications, adaptations or equivalents shall also be constructed as falling into the scope of the invention.

Claims

Patent claims

1. An illumination device, comprising illumination units with at least two colors, wherein the proportion of light with a specific color in mixed light emitted from the illumination units with the at least two colors is set within a specific range according to a physical characteristic and/or an optical characteristic of an illumination obj ect .

2. The illumination device according to claim 1, wherein the physical characteristic of the illumination object is a color of the illumination object and the optical characteristic of the illumination object is a reflection coefficient of the illumination object.

3. The illumination device according to claim 1 or 2, further comprising a control unit configured to adjust the proportion of light with the specific color according to the optical characteristic of the illumination object so that the proportion of light with the specific color is adapted to the physical characteristic and/or the optical characteristic of the illumination object.

4. The illumination device according to claim 3, wherein the control unit is configured to adjust the proportion of light with the specific color through at least one of :

adjusting current flowing through the illumination units with at least one of the colors;

switching between high power and low power illumination units with at least one of the colors; and

increasing or reducing the number of illumination units with at least one of the colors for illuminating the illumination object.

5. The illumination device according to claim 3 or 4, wherein the control unit is configured to control the illumination units when the distance from the illumination units to the illumination object is below a specific first threshold to illuminate the illumination object through at least one of :

adjusting current flowing through the illumination units to make the power of the illumination units low;

switching to low power illumination units between high power and low power illumination units for illuminating the illumination object; and

reducing the number of illumination units for illuminating the illumination object.

6. The illumination device according to claim 3 or 4, wherein the control unit is configured to control the illumination units when the distance from the illumination units to the illumination object is above a specific second threshold to illuminate the illumination object through at least one of :

adjusting current flowing through the illumination units to make the power of the illumination units high; switching to high power illumination units between low power and high power illumination units for illuminating the illumination object; and

increasing the number of illumination units for illuminating the illumination object.

7. The illumination device according to any one of claims 1 to 6 , wherein the illumination units are LEDs .

8. The illumination device according to any one of claims 1 to 7 , wherein the illumination device comprises a diffusion cover arranged external to the illumination units and the control unit and configured to diffuse light emitted from the illumination units.

9. The illumination device according to any one of claims 1 to 8 , wherein the illumination object is meat, light with the specific color at the set proportion is red light, and the proportion of the red light in mixed light emitted from the illumination units with the at least two colors in the illumination device ranges from 21.4% to

34.4% .

10. The illumination device according to claim 9, wherein the illumination units comprise red illumination units and white illumination units.

11. An illumination method, comprising: setting the proportion of light with a specific color in mixed light emitted from illumination units with at least two colors according to a physical characteristic and/or an optical characteristic of an illumination object.

12. The illumination method according to claim 11, wherein the physical characteristic of the illumination object is the color of the illumination object and the optical characteristic of the illumination object is the reflection coefficient of the illumination object.

13. The illumination method according to claim 11 or 12, wherein the proportion of light with the specific color in mixed light emitted from the illumination units with the at least two colors is adjusted through at least one of: adjusting current flowing through the illumination units with at least one of the colors;

switching between high power and low power illumina- tion units with at least one of the colors; and increasing or reducing the number of illumination units with at least one of the colors for illuminating the illumination object.

14. The illumination method according to any one of claims 11 to 13, further comprising: controlling the illumination units when the distance from the illumination units to the illumination object is below a specific first threshold to illuminate the illumination object through at least one of :

15. The illumination method according to any one of claims 11 to 13, further comprising: when the distance from the illumination units to the illumination object is above a specific second threshold, illuminating the illumination object through at least one of:

16. The illumination method according to any one of claims 11 to 15, wherein the illumination units are LEDs .

17. The illumination method according to any one of claims 11 to 16, wherein the illumination object is meat, the light with the specific color is red light, and the proportion of the red light in mixed light emitted from the illumination units with the at least two colors in the illumination device is set to range from 21.4% to 34.4 %