lighting device

Abstract

A lighting device includes a surface light source (101) and an optical element (103) which is provided with an incident surface (203) and first and second exit surfaces (205, 207). When the center of a light emitting surface (201) is set as P1, an edge point thereof is set as P2, and an axis which passes through P1 and is vertical to the light emitting surface is set as an optical axis, the optical element has such a shape that the optical axis and the vicinity thereof are recessed as compared to the edge. In the cross section of the optical element, when a point on the first exit surface which is disposed at a prospective angle of 15 degrees from the optical axis about P1 is set as P3, a point at which a light beam that exits P2 and travels in parallel to the optical axis intersects the first exit surface is set as P4, and an axis that connects P1 with P2 is set as an X axis, the X coordinate of a point farthest from the optical axis on the first exit surface is equal to or larger than 1.5-times value of P2, and the first exit surface is formed so that an incident angle of light that exits P1 is equal to or larger than a critical angle in 80% or more of an area where the X coordinate is equal to or larger than the value of P3 and an incident angle of light that exits P2 is smaller than the critical angle in 80% or more of an area where the X coordinate is equal to or smaller than the value of P4.

Description

technical field [0001] The present invention relates to a lighting device using a surface light source. Background technique [0002] Recently, light-emitting diodes (LEDs) with greatly improved luminance have started to be used as light sources for lighting devices (LED bulbs) instead of conventional incandescent bulbs due to their low energy consumption. At this time, the light distribution characteristics of the LED light bulb are required to be the same as those of the conventional incandescent light bulb. [0003] However, since blue LED chips have light emission distribution characteristics close to Lambertian, blue LEDs and LED light sources such as white and light bulb colors using phosphors also have light distribution characteristics approximately close to Lambertian. Here, Lambertian refers to a luminous distribution in which the distribution of luminous intensity with respect to the observation angle is proportional to the cos (cosine) of the observation angle. ...

AI Technical Summary

Problems solved by technology

The first method is a method of three-dimensionally arranging LED chips in various directions, but the manufacturing cost increases, and it also causes problems in thermal design of LEDs

The second method is to arrange optical elements for controlling the direction of light on the front of the light source. However, there is no optical element that efficiently forms an ideal light distribution.

Conversely, when the size of the optical element is the same as the size of the light source, since the optical surface of the optical element is near the light source, the direction of light incident on any position on the optical surface faces various directions, and the entire structure cannot be freely controlled.

[0006] Thus, there has not been developed a compact lighting device that uses optical elements to distribute light emitted from surface light sources such as LEDs so as to irradiate a sufficient amount of light in various directions for a solid angle of 2π or more.

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