Lighting device for glare with light-emitting diodes

Abstract

The invention relates to a lighting device intended for glare comprising one or more light-emitting diodes without attached lenses associated with an optical system with several lenses including a Fresnel lens making it possible to produce a substantially uniform illumination at a distance. [Fig 2] to be published with the abstract.

Description

Title of the invention: Lighting device for glare with light-emitting diodes

[0001] The present invention relates generally to the field of lighting, in particular lighting which must meet particular specifications, in particular capable of producing concentrated illumination over an area a few meters away, and has as its subject a lighting device with light-emitting diodes (generally designated by DEL or LED) whose luminous flux is expressed in lumens.

[0002] In certain fields or certain applications, it is necessary to have lighting that meets certain technical or even regulatory specifications, for example in terms of intensity or uniformity of lighting in the area to be lit.

[0003] This is particularly the case in the case of lighting intended for army or police interventions for the purpose of detecting or dazzling human threats. In close combat or during hostile demonstrations, it is essential to allow an operator on foot to be able to illuminate with sufficient power an area in front of him close to him. In a particular operating mode, a so-called threat zone of 1 square meter at a distance of 5 meters would be the most favorable. In a particular operating mode for police officers operating during demonstrations, the lighting device is fixed on a shield held on the arm by the operator. In the case of such use, the size and weight of the lighting device must be minimal.

[0004] The devices of the aforementioned type, which are currently marketed, generally comprise as light source(s) conventional white LEDs whose emitting zone, generally referred to as a chip, is a square with a side of 1 to 2 mm. These LEDs are generally each associated with a collimator such as those marketed by the company Gaggione which reduces the divergence angle of the radiation of the LED. The maximum light output of said LEDs is limited depending on the model to between 150 and 300 lumens; these devices are marketed for example by the company Extrême Vision.

[0005] To obtain a sufficient dazzling effect, under the aforementioned conditions, the various physiological studies show that an ocular illumination greater than 10,000 lux (1 lux is equal to 1 lumen per square meter) is necessary.

[0006] To achieve such illumination with a small and light-weight lighting device, the luminance called L0, expressed in candelas per square meter, of the LED chip is a determining factor. The luminance L1 of the radiation emitted by the lighting device is slightly lower than LO, the attenuation being caused by the transmission coefficient of the optical elements composing the device. The illumination of the threat zone being always proportional to Ll, it is thus shown that, for an optical device of given size, the luminance LO is one of the main factors of efficiency. LEDs such as the Osram Ostar LECG type models which can emit a luminous flux of 8000 lumens make it possible to achieve a luminance of 400 million candelas per square meter, i.e. more than 8 times the luminance of a usual white LED. LEDs such as the LECGP2 or LECGP3 model do not have attached lenses and require a dedicated optical system which is claimed in this invention.

[0007] In a non-exhaustive mode of operation, the device uses LECGP2 LEDs whose spectrum has a maximum emission close to 550 nm which is the wavelength where the eye is most sensitive. [Fig.l] represents on the same graph the spectrum of an LED such as the LECGP2 model (1) and the function V(l) (2) which characterizes the sensitivity of the eye as a function of the wavelength 1. These two spectra are substantially superimposed and thus allow good luminous efficiency.

[0008] Many LEDs are topped with a lens made of plastic or silicone material attached to the LED which fits the collimators as described above and used by the state of the art for devices intended for glare. High power LEDs as described above such as the Osram LECGP2 or LECGP3 model are devoid of these lenses and consequently give a Lambertian emission diagram having a perfectly constant luminance over a half-space.

[0009] The object of the present invention is the design of an optical system adapted to the aforementioned types of LEDs making it possible to efficiently collect such Lambertian radiation in order to illuminate the threat zone in a substantially uniform manner.

[0010] On the other hand, taking into account the fact that the use of this device is carried out by an external operator most often on foot, the LEDs are controlled by a power supply powered by a rechargeable battery.

[0011] To carry out efficient collection of the luminous flux of the LED, the optical device has at least two lenses made of transparent material, a first lens advantageously plano-convex, having its substantially flat face facing the LED at a distance close to the LED, its convex face possibly being aspherical, and a second lens which is advantageously a so-called Fresnel lens.

[0012] the first lens is made of transparent material which can be glass or plastic, its position is close to the LED, the distance between the LED and the first lens always being less than the thickness of the lens at its center.

[0013] The second lens is advantageously a so-called Fresnel lens which can be made of glass or plastic, the focal length and position of which make it possible to modify the width of the illuminated area at a given distance. The advantage of using a Fresnel lens compared to a conventional lens of the same focal length is the saving in weight and space. This is particularly advantageous for use by a man on foot.

[0014] Thus, according to the invention, the lighting device intended for dazzling comprises a light-emitting diode or LED without an attached lens controlled by an electronic circuit powered by a rechargeable battery and associated with an optical system capable of recovering the luminous flux emitted by said LED and of producing at a distance a substantially uniform illumination, said optical system comprising at least two lenses made of transparent material, characterized in that the optical system comprises a first lens whose distance from the surface of the LED is less than the central thickness of said first lens and a second lens which is a so-called Fresnel lens.

[0015] According to different embodiments, a dazzling device may comprise one or more assemblies each comprising a power LED and the two lenses described, the device as a whole being enclosed in a waterproof case and powered by a rechargeable battery.

[0016] The external optical face of the waterproof housing which emits light can be the flat face of the Fresnel lens or that of an additional window made of transparent material.

[0017] In a particular embodiment, this window can be easily exchanged in the event of damage.

[0018] According to another embodiment, the outer face comprises a transparent protective element which can be easily replaced in the event of scratches and dirt.

[0019] According to another embodiment, the electronic circuit allows a stroboscopic operating mode whose light pulses have an adjustable timing.

[0020] According to another embodiment, the timing of the light pulses has a period which varies randomly during its operation.

[0021] According to various embodiments, the first lens may be plano-convex and may have one or more aspherical faces.

[0022] The invention will be better understood, thanks to the following description, which relates to a preferred embodiment, given by way of non-limiting example, and explained with reference to the appended schematic drawings, in Figures 1 to 4:

[0023] [Fig. 1] represents on the same graph the spectrum of the Osram LECGP2 LED (1) and the curve of the sensitivity of the eye (2), the quasi-superposition of the two curves attest to the sensitivity effectiveness of the LED radiation for glare purposes

[0024] [Fig.2] shows in section the LED (3) and a two-lens optical system comprising a first lens (4) having a flat surface (5) and a convex surface (6), and a Fresnel lens (7).

[0025] [Fig.3] represents a device comprising two Osram LECGP2 LEDs (8), two plano-convex lenses (9) and two Fresnel lenses (10), shown in front view (H).

[0026] [Fig.4] represents the mechanical housing (12) containing the double optical system, detailed [Fig.3], having an easily replaceable transparent element (13), said housing being connected to a second box (14) containing the rechargeable battery.

Claims

Claims

1. Lighting device intended for dazzling comprising at least one light-emitting diode (3), generally designated by LED, without an attached lens, controlled by an electronic circuit powered by a rechargeable battery and associated with an optical system capable of recovering the luminous flux emitted by said LED and of producing at a distance a substantially uniform illumination, said optical system comprising at least two lenses made of transparent material, characterized in that the optical system comprises a first lens (4) whose distance from the surface of the LED is less than the central thickness of said first lens and a second lens (7) which is a so-called Fresnel lens.

2. Device according to claim 1 characterized in that the lighting device comprises one or more LEDs each associated with an optical system, said device being enclosed in a mechanical housing (12) having an external light-emitting face.

3. Device according to claim 2 characterized in that the mechanical housing has (12), on its light-emitting face, an external window made of transparent material.

4. Device according to claims 2 and 3 characterized in that the external face of the mechanical case has an external transparent element (13) which is easily exchangeable.

5. Device according to claim 1 characterized in that the electronic circuit (14) which controls the LED allows stroboscopic light emission.

6. Device according to claims 1 and 5 characterized in that the electronic circuit (14) which controls the LED allows a stroboscopic light emission whose timing of the light pulses has a period which varies randomly during its operation.

7. Device according to claim 1 characterized in that said first lens (4) has a substantially flat face (5) facing the LED (3).

8. Device according to claim 1 characterized in that the LED used is the LECGP2 model (8).

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