Lighting device, image reading apparatus , and image forming apparatus

Abstract

To effectively utilize a light quantity of a point source when a point source with little light quantity is used as a light source of a reading device. A lighting system is provided with a point source 32 emitting light to the surface of a document which is located on contact glass 12 and becomes a reading object, and a condensing body 33 which is arranged forward in the direction of emission of light emitted from the point source 32 and which condenses light emitted from the point source 32 within a reading width in the direction of a sub-scanning direction at the time of document reading. The condensing body 33 is arranged in a direction in which angles of all lights passing through the condensing body 33 are less than a critical angle '[theta]' totally reflected by the contact glass 12. Thus, all of the lights emitted from the point source 32 through the condensing body 33 are irradiated to the surface of the document without total reflection at the contact glass 12, thereby enabling all of the lights emitted from the point source 32 to be effectively used for lighting the document surface.

Description

technical field [0001] The invention relates to an illuminating device, an image reading device and an image forming device Background technique [0002] Conventionally, an image reading device such as a scanner has a light source that emits light onto a document surface of a document to be read on a contact glass, and the reading light that travels along the reading optical axis after being reflected by the document surface passes through a lens and passes through the lens. The original image is imaged on the photoelectric conversion device (CCD) and read. [0003] As a light source of such an image reading device, rod-shaped light sources such as fluorescent lamps and xenon lamps, and point light sources such as LEDs are used. [0004] In an image reading device using a rod-shaped light source, since the emission width of light emitted from the rod-shaped light source increases in the sub-scanning direction during document reading, stray light tends to occur. The so-call...

AI Technical Summary

Problems solved by technology

[0006] When a point light source is used as a light source, since a plurality of point light sources are arranged linearly in the main scanning direction (reading line direction), if the light emitted from each point light source directly irradiates the reading surface such as the document surface , illuminance fluctuations (uneven illuminance distribution) occur in the main scanning direction, and image density unevenness caused by illuminance fluctuations occurs when an image is formed based on the read image data

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