Lighting apparatus

Abstract

In a lighting apparatus for conducting product inspection by irradiation of LED light at an improved inspection accuracy, an LED light source device for scattering lights of a plurality types of LEDs of different emission wavelengths by a light guiding member and irradiating them from a light emitting surface in the direction of the lighting optical axis is attached to a casing having a light transmitting imaging section through which an imaging optical axis extends, the light guiding member has a plurality of light guiding plates with the light emitting surface being directed to the lighting optical axis, each of the light guiding plates is mounted with LEDs at a predetermined pitch on the plane perpendicular to the light emitting surface, such that the combination of the emission wavelengths is identical for each of the rows in the direction of the lighting optical axis.

Description

technical field [0001] The present invention relates to an illumination device that scatters light irradiated from LEDs (light emitting diodes) of various colors inside a light guide, uniformly emits the scattered light from a light emitting surface, and irradiates an object to be photographed by an imaging device. Background technique [0002] The image inspection method is widely used in the inspection and quality control of industrial products. In order to clearly photograph products in factories, lighting devices that can continuously irradiate stable illumination light for a long period of time and consume less power are required. [0003] Therefore, there has been proposed a lighting device in which LEDs are arranged on the side of a transparent light guide whose front side serves as a light emitting surface, and the irradiation light from each LED is scattered inside the light guide to emit from the light emitting surface. [0004] [Patent Document 1] Patent No. 31872...

AI Technical Summary

Problems solved by technology

[0009] However, even if the LEDs of RGB colors are arranged without gaps, they have to be arranged with gaps of the diameter of the element, so there is a problem that the color lights cannot be mixed sufficiently, and color unevenness occurs.

In addition, when irradiating single-color illumination light, there is a gap of 3 gaps between LEDs of the same color, which causes uneven brightness, and since the number of elements of each color is 1 / 3, the brightness can be obtained by simple calculation. Also reduced to 1 / 3 of the problem

[0010] Therefore, such color unevenness and brightness unevenness cause reflections in the case of metal products, resin products, etc. that have undergone surface gloss treatment, and if product inspection is performed based on such images, the higher the accuracy of image analysis, the more accurate the image will be. A good product is detected as a bad product, and as a result, there is a contradiction that the detection accuracy decreases

[0011] In this regard, if a color LED with RGB chips arranged in each element is used, although the color unevenness caused by the arrangement gap will not appear, it is easy to cause the light emission characteristics (color tone, brightness) of each chip to be different. Color unevenness, since it is not yet possible to disassemble colored LEDs to exchange chips, it is difficult to eliminate such color unevenness

[0012] In addition, since a light-scattering treatment agent or the like is used to uniformly mix colors of light, there is a problem that the brightness further decreases.

[0013] Furthermore, in the case of monochromatic lighting, high-brightness LEDs have to be used in order to irradiate high-brightness light, and since the brightness depends on the optical characteristics of each element of the LED used, it cannot emit light with higher brightness.

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