JPS59177532A - Original lighting device of image forming device - Google Patents

Abstract

PURPOSE:To uniform the illuminance on a photosensitive drum and to prevent image unevenness by arranging a toric lens which is different in curvature in the lengthwise direction and short-side direction between a light source and an original and forming an illuminance distribution on an original surface. CONSTITUTION:The toric lens 4 is arranged between the light source 1 and platen glass 2. A light beam 6 from the light source 1 is reflected by a reflecting plate 5 and converged to an original 3. The toric lens 4 is different in curvature in the lengthwise and short-side direction. The light is converged to the original 3 in the short-side direction, and the light in the lengthwise direction is converted at circumferential parts A and C and diverged at the center part B, thus obtaining the illuminance distribution. Further, the section of the lengthwise center part has a small curvature at a point B and a large curvature at a point A. Conseqeuntly, the light is diverged at the center part B to decrease the illuminance at the center part B of the original 3 and the light is converged at the circumferential parts A and C of the original 3 to make the illuminance on the surface of the photosensitive drum uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a document illumination device for an image forming apparatus.

In general, as shown in FIG. 7, a document illumination device of an image forming apparatus such as an electrophotographic copying machine is provided with a light source, a platen glass plate, and a condenser lens q' having a cylindrical surface for the document 3. This capacitor sensor
The light is focused on the document 3. ＃Go゛-゛i power; However, when the illuminance distribution on the document surface is uniform, the CO8 of the lens is
Due to the power law, the illuminance of the photosensitive surface decreases toward the periphery, and the illuminance becomes non-uniform. This causes unevenness in the amount of light on the photosensitive drum, and this unevenness in the amount of light causes unevenness in the image formation.

Conventionally, in order to correct unevenness in the amount of light on the photoreceptor drum, a method has been proposed in which a slit is provided along the optical path, and a method in which a light shielding plate is provided around the light source has been proposed. This has the drawback of complicating the mechanism of the entire image forming apparatus and increasing the cost.

The present invention was proposed in order to solve the above-mentioned drawbacks, and by increasing the illuminance on the document surface at the periphery and making the illuminance uniform on the photoreceptor, the light intensity correction of the slit or light shielding plate, etc. It is an object of the present invention to provide a document illumination device for a 1d11 image forming apparatus that does not require any means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the drawings. FIG. 3 is a schematic configuration diagram of an image forming apparatus to which an embodiment of the present invention is applied, and FIG. 3 is a perspective view of the image forming apparatus. A reflector plate is disposed around the light source 7, and the left reflector reflects and condenses the light beams A and B emitted from the light jlj]j/ in the direction of the document 3. This reflected light from the original 3 is reflected by mirrors 7A and 7B.
, g and passes through lens qA. The light is further reflected by a mirror 98 and irradiated onto the photoreceptor drum 2 to form an electrostatic latent image. It is uniformly charged in advance by the charger 10, and one electrostatic layer is formed. A toner image is formed by the developer///, a toner image is transferred onto the copy paper/111 sheet/l by the tongue transfer charger/3, and this toner image is fixed by the roller/S, thus completing the copying process. After transfer, the photoreceptor drum 7.2 is cleaned by a cleaning blade/filter and the toner is used again in the copying process. A toric lens is disposed between the light source and the document table glass. The light rays emitted from the light source are reflected by a reflection plate S, or pass through a link lens 11 degrees from the light source, and are focused on the document 3.

The toric lens has the shape shown in FIG. 7(a). Figure (b) is a front view of toric lens q.
FIG. 7(C) is also a side view, and has unique curvatures in the longitudinal direction and short side direction. As shown in FIG. 2, the light is focused on the document 3 in the short side direction, and in the longitudinal direction, it is focused on the peripheral parts A and C as shown in FIG.
The center area B has a diverging illuminance distribution. Also, Figure 4 ta
), the cross section along the line B-B at the center in the longitudinal direction has a small curvature as shown in FIG.
As shown in FIG. 4(C), the line 1 fold plane is a cross section of the peripheral portion in the longitudinal direction, and is formed to have a large curvature. When formed in this way, the center part B will have the shape shown in Figure 4 (CI).
As shown in Figure 4 (e
), the light is focused and the illuminance on the photoreceptor tram surface is made uniform. Further, the present invention is provided with a reflector k.
・Applicable to image forming devices as well.

According to the present invention, as explained above, a 1-link lens having a toric surface having different curvatures independently in the direction of force and the direction of the short side is disposed between the light source and the document. By creating an illuminance distribution, the illuminance of the photoreceptor drum is thereby made uniform, and image unevenness is effectively reduced by one degree.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional document illumination device applied in an image forming apparatus. FIG. 1 is a schematic block diagram of an image forming apparatus to which an embodiment of the present invention is applied. FIG. 3 is a block diagram of an image forming apparatus. Configuration diagram of an embodiment of the present invention applied in a device, 1st
llq is a partial perspective view of the image forming apparatus in Figure Ω, and Figure S (
a) (b) (C) is a shape diagram of a toric lens that constitutes the embodiment of Figure Ω, Figure 4 is an explanatory diagram showing the illuminance distribution of a document in the image forming apparatus of Figure 2, Figure (a) is a front view of the toric lens constituting the embodiment of Figure 2, ai'g Figure 7 (b) is (a) 0) B
7 (C) is a sectional view taken along line A-A of (a), and FIG. ／...Light source, 2...Document glass. 3...Document, Ri...Toric lens. S...Reflection Plate. Fig. 3-227- L) A'-5 (e Fig. 7

Claims (1)

[Claims] A document illumination device for an image forming apparatus, characterized in that a toric lens having a toric surface having independent curvature in the short side direction and the longitudinal direction is provided between a light source and the light source and the document.