JP2009512127A - Light emitting diode lighting device - Google Patents

Abstract

LED lighting device comprises an optical system (3) with at least two lenses, the first of which is an aspherical lens (5) and a second concave lens (6) arranged between the first lens and the LED (2). The inner and outer radii of curvature of the second lens conform to a logarithmic espression.

Description

  The present invention relates widely to the field of lighting, and more particularly to lighting that responds to unique characteristics, particularly lighting that is suitable for producing uniform illuminance, comprising a light emitting diode lighting device and such light emission. The lighting equipment includes at least two diode lighting devices.

  Depending on the field or application, it may be necessary to use lighting that meets certain technical specifications or even regular specifications, for example in terms of intensity and uniformity of illumination in the area to be illuminated. .

  This applies in particular to the field of dentistry, for example. In fact, a lighting device with high operability used in this field must satisfy the evaluation standards of the French standard NF, the European standard EN, and the international standard ISO 9680 and meet the requirements.

  The above-mentioned type of device is also called a dental lamp or a surgical light sialic (scientificique registered name) with high operability, and is currently commercially available. Generally, a halogen bulb or a light source is used as a light source. An incandescent lamp is provided, and the halogen lamp or the incandescent lamp is coupled to a reflective surface (reflector) and a protective window on the front, and is suspended from the end of a support arm that is pivotally pivotable in its entirety, It is locked exactly at the stop position.

  However, these existing devices are relatively heavy, not very small (requires a power supply at the base or base of the support arm), and do not provide illuminance with good uniformity in the target area to be illuminated. Absent.

  Moreover, due to the nature of the light source used, these known lighting devices generate a lot of heat (uncomfortable for both patient and doctor) and often need to be bothered to change the bulb (50 hours) ~ Up to 2000 hours limit life).

  On the other hand, a lighting device using a light emitting diode (hereinafter referred to as French DEL, that is, an English LED) is known. These light emitting diodes have a long lifetime, low power consumption and do not generate excessive heat.

  In particular, in recent years, there has been a white LED that has become increasingly powerful and powerful in terms of luminous intensity, and this white LED can replace incandescent or halogen bulbs.

  However, these LEDs need to be associated with an apparatus or system that allows the light flux emitted by the LEDs to be collected and directed to the surface area to be illuminated.

These devices are only effective if the following three evaluation criteria are satisfied.
-As much light flux as possible is collected (best efficiency),
-Uniform illumination
-The illuminated area is adapted to the object desired to be illuminated,
It is.

  An existing device that enables the maximum collection of the luminous flux of the LED is an optical element that is placed relative to the LED and is called a collimator.

  However, these collimators are very bad in terms of uniformity and do not allow correct illumination of a given area.

  In fact, these collimators give strong illumination on the ± 5 ° axis, but the illumination decreases regularly without going off until ± 30 °.

The present invention more particularly relates to an LED having a Lambert Law light emission pattern. For full Lambertian law radiation, the light radiation pattern is
I = I ₀ ^* cos (θ),
Where I ₀ is the luminous intensity in the direction of the light emission axis of the luminous flux of the LED, the unit is candela or watts / steradian, and I is on the axis It is the luminous intensity in a direction that forms an angle θ with respect to the angle.

  Some commercially available LEDs, such as those known under the name Luxeon III, structurally have a pattern whose variation is very similar to the above formula.

  This emitted light covers the entire half space in front of the LED, and has a total solid angle Ω = 2π steradians (approximately 6.28 steradians).

  In order to project this light beam onto an object about to illuminate a remote screen (20 cm to several meters), it consists of one or more lenses and / or one mirror, or a plurality of mirrors, or a reflector. It is necessary to prepare an optical device.

  The lensed device is preferred in that it produces a very sharp image of the light emitting surface of the LED, which is very uniform to obtain illumination that is uniformly defined and localized to the effective area. It is advantageous.

  However, using multiple lenses can be a delicate problem and can lead to complex and costly structures.

  Lighting devices that use reflection, or lighting devices that use a combination of refraction and reflection, such as the Luxeon collimator, do not produce uniform illumination.

  A known simple solution is to use an LED and a single lens. In order to obtain a clear image of the light emitting area on the screen and collect the maximum luminous flux, it is desirable that the lens has at least one aspherical surface.

  Preferably, such a lens has a flat first surface facing the LED and an aspherical second surface with a conical apex, for example, the radius of curvature of the cone is R = 9 mm. And the gradual reduction parameter is k = −0.6.

  As is known, the cone vertex equation is described as follows:

For a 60 lumen Luxeon III type white LED, with the aspheric lens defined above, the total luminous flux collected on a screen 700 mm away is 20 lumens, thus the energy efficiency is 33% (collected by the lens). Ratio F _L / F _O ) of the total light flux F _{L that} is refracted and refracted and the total light flux F _O emitted by the LED.

  This low efficiency is due to the fact that only a portion of the light rays exiting the LED are collected by the lens. In terms of solid angle, even the best lenses on the market can collect only a quarter of the solid angle of LEDs.

  Thus, the main problem imposed on the present invention makes it possible to greatly improve the efficiency of the above-mentioned known solution (LED + aspheric lens), and the three criteria mentioned above, namely the light collection. A simple solution that makes it possible to provide a light-emitting diode illuminator that meets the criteria of having as much luminous flux as possible, the illumination intensity is uniform and that the illuminated area is suitable for the desired object To provide.

Therefore, the present invention is directed to a light-emitting diode illuminating device, which includes a light-emitting diode, that is, an LED, which is suitable for collecting most of the light beam emitted by the LED, and is referred to as illuminance. A device coupled to an optical system (3) suitable for creating a substantially uniform illumination spot at a point from a distance,
The optical system comprises on the one hand optical means for projecting illumination, and on the other hand comprises a lens arranged between an LED and optical means for projecting illumination, the lens being directed to the LED; It has a concave spherical entrance surface with a radius of curvature R1 and a convex spherical exit surface with a radius of curvature R2, R2> R1, and the entrance surface is viewed from the axis of symmetry of the lens, The center of the curvature radius of curvature located in the vicinity of the light emission area or the light emission area of the LED, and the maximum thickness e made of a transparent material having a refractive index n forms the lens, and the relation e = The light-emitting diode illuminating device is characterized by substantially satisfying R2x (1 + 1 / n) -R1.

  In connection with a preferred variant embodiment of the invention and / or a preferred additional feature of the invention, the device according to the invention can further comprise the following features individually or cumulatively, Is

  The optical means for projecting illumination comprises at least one aspheric lens;

  The surface of the entrance surface of the lens has a radius of curvature R1 equal to or slightly greater than the radius of curvature of the substantially spherical outer surface of the exit surface of the LED;

  The lens is bonded by its entrance surface to the outer surface of the exit surface of the LED via a layer of transparent adhesive;

  The surface of the exit surface of the lens corresponds to a spherical portion of a size larger than the hemisphere,

  The aspheric lens has at least one surface with a conical vertex;

  An aspheric lens has on one hand an entrance surface that is directed to the LED and whose surface is supported by a spherical surface with a flat or very large radius of curvature, in particular a very large radius of curvature for R2. Having an exit surface opposite the surface and the surface being aspheric;

  The aspheric lens is rotationally symmetric about the optical axis;

  The aspheric lens has an entrance or exit surface with a biconic surface;

  The aspherical lens has an entrance or exit surface whose surface corresponds to a portion of an annular or cylindrical surface;

  The optical means for projecting the illumination includes a zoomable adjustable optical subsystem;

  The optical means for projecting illumination includes optical means for refocusing the collected light flux into the optical waveguide;

The refocusing optical means comprises two aspheric lenses arranged symmetrically with respect to the optical axis of the lens or a plane perpendicular to the symmetry axis;
It is.

  The present invention also relates to a dental illuminating device with high operability that provides illumination without projection shadow, and the device includes the two light emitting diode illumination devices described above, and the two light emitting diode illuminations. The devices are mounted side by side and are characterized in that each of the luminous fluxes of the two light emitting diode illuminating devices is directed so as to be united at the area to be illuminated.

  Furthermore, the present invention also relates to a highly operable surgical illumination device that provides illumination without projection shadows, the device comprising at least two light emitting diode illuminators as described above, wherein the two light emitting diodes. The illuminating devices are mounted side by side, and each light flux of the two light emitting diode illuminating devices is directed so as to be integrated at a portion of an area to be illuminated.

  Preferably, the plurality of light-emitting diode illuminating devices forming each of the above-described devices are, for example, in a single protective cover or case fixed to the end of a support arm that is pivotally supported pivotally. Can be installed together.

The invention will be better understood by the following description of preferred embodiments, given by way of non-limiting example and described in conjunction with the accompanying schematic drawings, in which:
1A and 1B are schematic views of a light-emitting diode illuminating device according to two alternative embodiments of the present invention;
FIG. 2 is a cross-sectional view showing a lens having a spherical entrance surface and an exit surface forming a part of the light-emitting diode illuminating device of FIG. 1 on a scale different from FIG.
FIGS. 3 and 4 are projection screens showing the distribution of illuminance provided by an LED coupled to a single aspheric lens (FIG. 3) or an LED coupled to an optical system according to the invention (FIG. 4). Is a diagram (gradation display in lux units) showing the image of
FIG. 5 is a view similar to FIGS. 3 and 4, showing the illuminance provided by the light-emitting diode illuminating device according to the invention with a biconical aspheric lens;
6A and 6B are schematic views of a light-emitting diode illuminating device according to two alternative embodiments of the present invention incorporating re-condensing means (FIG. 6B is different from that shown in FIG. 1B) With optical means 5), and
FIG. 7 is a schematic view of a lighting apparatus including two light-emitting diode illuminating devices according to the present invention, and the two light-emitting diode illuminating devices are supported on a support arm that is pivotally pivotable in an articulated manner. It is attached in the case.

  As shown in FIGS. 1 and 6 of the accompanying drawings, the light-emitting diode illuminating device 1 includes a light-emitting diode LED2, which is suitable for collecting most of the light beam emitted by the LED and has an illuminance. In that respect, it is coupled to an optical system 3 suitable for producing a substantially uniform illumination spot 7 from a distance.

  According to the invention, the optical system 3 comprises on the one hand optical means 5 for projecting illumination and on the other hand comprises a lens 6 arranged between the LED 2 and the optical means 5 for projecting said illumination, said lens 6 Has a concave spherical entrance surface 6 ′ with a radius of curvature R 1 and a convex spherical exit surface 6 ″ with a radius of curvature R 2, and R 2> R 1. 6, the incident surface 6 ′ has a center point of a curvature radius of curvature located in the vicinity of the light emitting area of the LED 2 or in the vicinity of the light emitting region 2 ′, and is transparent with a refractive index n. The maximum thickness e made of a material forms the lens 6 and substantially satisfies the relational expression e = R2x (1 + 1 / n) −R1.

  Thus, the basic principle of the present invention is that the lens 6 is an optical element made of glass or a transparent plastic material (such as polycarbonate or acrylic) that enables an improvement in efficiency between the LED 2 and the projection optical means 5. It consists of interposing.

  The projection optical means 5 preferably comprises or includes at least one aspherical lens 8 (FIG. 1A) or a double convex lens (FIG. 1B).

  The optical element 6 is preferably a lens, and the entrance surface 6 'of the lens is a concave spherical surface. The lens has a radius of curvature R1 and is close to the radius of curvature of the exit surface 4 of the LED. The lens is preferably placed in close proximity to the surface of the LED 2. In the preferred embodiment, the entrance surface 6 ′ is substantially hemispherical because it is placed in contact with the LED 2.

  Preferably, the exit surface 6 ″ of the lens 6 is also spherical, and its surface is preferably larger than a hemisphere (also called a super hemisphere).

  This lens 6 is intended to collect a larger solid angle coming out of the LED. In practice, this lens will be selected so that this solid angle is doubled by a factor comprised between 2.5 and 3, and the collected light beam is doubled by a factor of approximately 2. .

  LEDs with patterns that do not follow Lambert's law will receive an overall improvement in collimation efficiency in the context of the present invention, because the light-emitting diode illuminator 1 collects a larger solid angle from the LEDs. .

  The lens 6 has a spherical incident surface 6 'having a radius R1 and a spherical exit surface having a radius R2. The vertices of the two surfaces are separated by e, which is the thickness of the lens 6 at the optical axis or symmetry axis.

  This lens 6 is made of a material with a refractive index n, preferably the first surface of the radius of curvature R1, the entrance surface 6 'is curved very close to the light emitting area of the LED 2 or the surface of the light emitting area 2'. The center point of the radius of curvature.

  In a preferred embodiment, the radius R1 is almost the same as the radius of curvature of the LED exit surface 2 'and these two surfaces 2', 6 'can be bonded together with a transparent adhesive 4' to be united. it can. The advantage is that the lens 6 is fixed to the LED, and this fixing makes it possible to determine a complete and non-removable position and to improve the lighting efficiency, because of this adhesion, This is because most of the illumination lost by reflection at the surfaces 4, 6 'facing the lens 6 is eliminated.

  The adhesive is preferably of a transparent resin type, and preferably has a refractive index included between the refractive index value of the LED and the refractive index value of the lens 6.

  For example, a transparent resin adhesive having a refractive index of 1.53 known by the name E501 by EPOTECNY may be used.

  The second surface, exit surface 6 '', has a radius of curvature R2 that forms a spherical surface separating two homogeneous transparent media having different refractive indices, and the two homogeneous transparent media having different refractive indexes. The surface separating the two is refracted by using a non-aberration conjugate coupling of Young's point.

This conjugate bond is
e + R1 = R2 ^* (1 + 1 / n)
Therefore, from this equation:
e = R2 ^* (1 + 1 / n) −R1,
This occurs for the relational expression between R1, R2, e and n.

  The radius of curvature R2 is not determined and is selected for reasons such as space occupied by the device, mechanical and optical implementation and cost.

  Preferably, a radius R1 equal to the radius of the exit surface 4 of the LED will be selected, at which time the entrance surface 6 'of the lens 6 is glued to the LED, and the LED 2 and, for example, the aspheric lens 8 In view of the space available between the shaped projection optical means 5, a radius R 2 is selected that allows the use of the super-hemispherical lens 6.

Example:
The aspherical lens 8 is made of a transparent material (BK7 glass or B270 glass, acrylic, etc.) with a focal length of 28 mm and a refractive index close to 1.5.
The super-hemispherical lens 6 is made of polycarbonate with n = 1.585, R1 = 3 mm, R2 = 6 mm and e = 6.8 mm.
-The focal length of the entire two lenses 6 and 8 is 18 mm.

  Regarding the objective comparison of the luminous intensity measurement results obtained by projection on the screen, the lens 6 and the aspherical lens 8 having a focal length of 28 mm are compared with a single aspherical lens having a focal length of 18 mm alone. This is possible because the resulting image is the same size.

  The results of both these simulations show that the presence of the super-hemispherical lens 6 provides double photometric efficiency for similar results in terms of image size on a screen placed at a fixed distance from the illuminating device. (Comparison between FIG. 3 and FIG. 4).

For FIG.
Average at the center of −10 cm ² = 6200 lux,
-Total luminous flux incorporated into the image = 20 lumens,
And for FIG.
Average at the center of −10 cm ² = 12000 lux,
-Total luminous flux incorporated in the image = 40 lumens,
It is.

  In some specific cases, extended illumination in only one direction may be required. For example, this is the case for surgical light sialicics in the field of dentistry.

  By selecting a special shape adapted for the aspherical lens 8, it is possible to obtain such an effect without changing the super hemispherical lens 6. At this time, the aspherical lens is not rotationally symmetric.

  It is possible to realize this type of illumination because of the various shapes of the lens 8, and for example, it can be an annular surface or a biconical surface.

  Preferably, the entrance surface 8 ′ is flat or slightly spherical and the exit surface 8 ″ is aspheric, which is in two perpendicular planes corresponding to the two extended directions of illumination on the screen. With two different aspherical vertices.

  One example of such a surface is a biconic surface, and the two perpendicular vertices of the biconic surface are each parameterized by a radius of curvature R and a decreasing property k.

  In one preferred embodiment, the lens 8 is made of glass or plastic of a material with a refractive index close to 1.5.

  The face 8 'facing the LED is flat.

Ejection surface 8 ''
Along Y, Ry = 13 mm, ky = −0.6,
Along X, Rx = 15.5 mm, kx = −0.4,
It features two conical vertices.

  This result shows extended illumination and a very good efficiency of around 70% (see FIG. 5).

  In the application of dental or surgical surgical lamps to sialic, at least two light emitting diode illuminators 1 (LED 2, super hemispherical lens 6 and optical means 5 for projection in the form of an aspherical lens 8, for example) are used. This makes it possible to obtain shadowless lighting as defined in the current standard.

  In another application, a single aspheric lens 8 can be replaced by a set of at least two lenses 8 and 9, at least one of which is aspheric. With this device, the focal length can be continuously varied, so that a zoom-type effect can be obtained, and the illumination area can be varied freely.

  Another application type is directional lighting for paintings in art museums, and the light-emitting diode illuminating device 1 according to the present invention extends the lighting in one direction so as to obtain a rectangular illumination, thereby providing an illumination area. Is fully adapted to this application.

  Another application type is the collection of the luminous flux of the LED 2 in the optical waveguide 10. At this time, it is important to refocus most of the light flux into the waveguide 10, and the waveguide can be a block of transparent parts or an assembly of optical fibers. The light-emitting diode illuminating device according to the invention makes it possible to collect this light beam collected into the waveguide 10 by the projection optical means 5 in the form of a re-condensing means. The same second aspherical lens 9 (FIG. 6A) arranged symmetrically with the first aspherical lens 8 enables this type of re-condensing and also a double convex lens (FIG. 6B). The same applies to.

  Of course, the invention is not limited to the embodiments described and the embodiments shown in the accompanying drawings. Changes that do not depart from the scope of protection of the present invention are possible, particularly from the perspective of configuration with various elements or by replacement with equivalent techniques.

Schematic of one embodiment of a light-emitting diode illuminating device according to the present invention. Schematic of another embodiment of a light-emitting diode illuminating device according to the present invention. Sectional drawing of the lens of the light emitting diode illuminating device of FIG. Illuminance distribution and projection screen image for a single aspheric lens Illuminance distribution and projection screen image for a biconical aspheric lens Illuminance distribution for a biconical aspherical lens Schematic diagram of a light-emitting diode illuminator incorporating re-condensing means Schematic diagram of a light-emitting diode illuminator incorporating re-condensing means Schematic of lighting equipment including two lighting devices according to the present invention

Explanation of symbols

1 LED illuminator 2 LED
2 'light emission region 3 optical system 4 exit surface 5 optical means 6 lens 6' entrance surface 6 '' exit surface 7 illumination spot 8 aspheric lens 8 'entrance surface 9 aspheric lens 10 optical waveguide 11 protective case

Claims (16)

A light-emitting diode illuminator comprising a light-emitting diode or LED, said LED being suitable for collecting the majority of the light beam emitted by said LED and leaving a substantially uniform illumination spot in terms of illuminance An apparatus (1) coupled to an optical system (3) suitable for producing from
Said optical system (3) comprises on the one hand optical means (5) for projecting illumination and on the other hand a lens (6) arranged between the LED (2) and the optical means (5) for projecting said illumination. ), And the lens (6) is directed to the LED (2) and has a concave spherical entrance surface (6 ′) with a radius of curvature R1 and a convex spherical exit surface (with a radius of curvature R2). 6 ″), R2> R1, and when viewed with respect to the axis of symmetry (X) of the lens (6), the entrance surface (6 ′) is the light emitting area or light of the LED (2). A maximum thickness e made of a transparent material having a refractive index n and having a center point of a curvature radius of curvature located in the vicinity of the radiation region (2 ′) forms the lens (6), and the relation e = A light-emitting diode illuminating device characterized by substantially satisfying R2x (1 + 1 / n) -R1.   Light emitting diode illuminating device according to claim 1, characterized in that the optical means (5) for projecting the illumination comprises at least one aspheric lens (8).   The surface of the entrance surface (6 ′) of the lens (6) has a radius of curvature R1 that is equal to or slightly above the radius of curvature of the substantially spherical outer surface of the exit surface (4) of the LED (2). The light-emitting diode illuminating device according to claim 1 or 2, characterized by comprising:   The lens (6) is connected to the outer surface of the exit surface (4) of the LED (2) by a light-incident surface (6 ′) through a transparent adhesive layer (4 ′). The light-emitting diode illuminating device according to any one of claims 1 to 3.   Light emission according to any one of claims 1 to 4, characterized in that the surface of the exit surface (6 '') of the lens (6) corresponds to a part of a spherical surface with a size larger than a hemispherical surface. Diode lighting device.   3. As far as the claim 2 or 2 is concerned, the aspheric lens (8) has at least one surface (8 'or 8' ') with a conical apex. The light emitting diode illuminating device according to any one of the above.   Said aspherical lens (8), on the one hand, is directed to the LED (2) and has an incident surface (8) supported by a spherical surface with a flat or very large radius of curvature, in particular a very large radius of curvature for R2. Claimed insofar as it relates to claim 2 or claim 2, characterized in that it has an exit surface (8 '') that is opposite to the entrance surface (8 ') and whose surface is aspheric. Item 7. The light-emitting diode illuminating device according to any one of Items 3 to 6.   8. The aspherical lens (8) according to any one of claims 3 to 7, as far as claim 2 or 2 is concerned, characterized in that the aspheric lens (8) is rotationally symmetric about its optical axis. Light emitting diode lighting device.   Claim as far as claim 2 or claim 2, characterized in that the aspheric lens (8) has an entrance surface (8 ') or an exit surface (8' ') with a biconical surface. The light-emitting diode illuminating device according to any one of 3 to 7.   3. The aspherical lens (8) according to claim 2, wherein the aspherical lens (8) has an entrance surface (8 ') or an exit surface (8' ') whose surface corresponds to a part of an annular surface or a cylindrical surface. The light-emitting diode illuminating device according to any one of claims 3 to 7, as far as the item 2 is concerned.   11. A light-emitting diode illuminating device according to any one of the preceding claims, characterized in that the optical means (5) for projecting the illumination includes an adjustable optical subsystem having a zoom effect. .   The optical means (5) for projecting the illumination includes optical means (8, 9) for refocusing the collected light flux into the optical waveguide (10). The light-emitting diode illuminating device according to any one of the above.   The optical means for re-condensing includes two aspheric lenses (8 and 9), and the two aspheric lenses are in a plane perpendicular to the optical axis of the lens (6) or the axis of symmetry (X). The light-emitting diode illuminating device according to claim 12, wherein the light-emitting diode illuminating devices are arranged symmetrically.   It is a dental illuminating device with high operability that provides illumination without projection shadow, and includes two light emitting diode illuminating devices (1) according to any one of claims 1 to 13, wherein the two light emitting diode illuminating devices are provided. Are mounted side by side, and each of the light beams of the two light-emitting diode illuminating devices is directed so as to be integrated at a portion of the area to be illuminated.   A surgical illuminating device having high operability for providing illumination without projection shadow, comprising at least two light emitting diode illuminating devices (1) according to any one of claims 1 to 13, wherein the two light emitting diode illuminations are provided. A lighting device, characterized in that the devices are mounted side by side and each of the light beams of the two light emitting diode lighting devices are oriented so as to be integrated at the site of the area to be illuminated.   16. A lighting device according to claim 14 or 15, characterized in that a plurality of light emitting diode lighting devices (1) are mounted together in a single protective case (11).

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