JPH01287554A - Exposing device - Google Patents

Abstract

PURPOSE:To achieve exposure readily and inexpensively by setting the distribution of a light shielding part of in illumination correcting member roughly uniform in terms of illuminance on an exposure surface. CONSTITUTION:A photographing lens 5 is disposed on the central part of the bottom of housing 1, and its upper part is covered with a cover 6. The illumination correcting member 7 is fitted to top of the cover 6, and comprises by drawing plural coaxial rings with a white paint on the surface of a circular transparent substrate 8 (transparent glass or transparent plastic) to partially form a light shielding part 9. Its distribution is set such a way that its density increases in the central part of the transparent substrate 8 and decreases toward its periphery, and the illuminance on the exposure surface 10 can be made roughly uniform. Thus, the structure is simplified to reduce the cost, and uniform exposure is attainable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flash lamp exposure type exposure apparatus used in high-speed copying machines and the like.

(Prior Art) An exposure device using a flash lamp exposure method is suitable for high-speed copying because it can instantaneously expose the entire surface of a document.

As shown in FIG. 4, the exposure device includes an illumination housing b whose inner surface a is painted white, a flash lamp C provided within the housing b, and an original glass d provided on the top surface of the housing. A projection lens e is provided at the bottom of the housing, and a flash lamp C illuminates the entire interior of the housing b by multiple reflections.

), the document f on the document glass d is uniformly illuminated, and the light image thereof is projected onto the exposure surface of the photoreceptor belt g through the projection lens e.

By the way, in the flash lamp exposure method, when the light image of the document f is exposed on the exposure surface through the projection lens e, the illuminance distribution on the exposure surface is smaller than that of the document r in the center. A problem arises in which the image is relatively bright and the peripheral area is relatively dark (cosine fourth law problem). This cosine fourth law problem was solved in Japanese Patent Application Laid-Open No. 58-19202.
As described in detail in Publication No. 9, as a solution to this problem, an illumination corrector i such as a variable density filter is arranged within the field of view of the projection lens e, so that uniform exposure can be obtained on the exposure surface. 1 prior art is disclosed.

In addition, in the flash lamp exposure method, there is a problem in the distribution of the amount of light reflected from the surface of the original glass d reaching the exposed surface, in that a spot-shaped portion darker than the other portions appears in the center of the exposed surface. This is because the distribution of the amount of light reflected on the surface of the original glass d is extremely small at the portion facing the pupil of the projection lens e, and the diffused light from the white-painted portion of the inner surface a of the housing is extremely small in other portions. In order to eliminate this dark spot, the pupil of the projection lens e should also be painted white to make the distribution of the amount of light reflected on the surface of the original glass d uniform. However, this is impossible because the function of the projection lens e will be lost.To solve this problem, Japanese Patent Laid-Open No. 6
In JP 0-241036, an auxiliary lighting means j is provided,
A second prior art is proposed in which a spot light is applied to the darkened portion of the exposed surface.

(Intelligence M that the invention seeks to solve) The first prior art alone cannot solve the problem of dark areas caused by surface reflection of the original glass, and the second prior art alone cannot solve the problem of the cosine fourth power law. cannot be resolved.

Even if the exposure apparatus shown in FIG. 4 could be achieved by combining the two, two special parts, the illumination correction body i and the auxiliary illumination means j, would be required, resulting in a complicated structure and high cost.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a lighting housing whose inner surface is formed of a reflective material with good diffusivity, a flash lamp provided in the housing, and a lighting housing provided on the top surface of the housing. In an exposure apparatus equipped with an original glass and a projection lens provided at the bottom of the housing, an illumination correction member is disposed between the original glass and the projection lens, and this illumination correction member is disposed on a transparent substrate with a diffusive effect. It is characterized by partially forming light-shielding portions using a highly reflective material, and the distribution of the light-shielding portions is set so that the illuminance on the exposed surface is approximately uniform.

(Function) According to the present invention, the illumination correction member is disposed between the original glass and the projection lens, and the light-shielding portion is partially formed on the transparent substrate of the illumination correction member, so that the distribution of the light-shielding portion is adjusted. Since the illuminance on the exposure surface is set to be substantially uniform, the illumination correction body of the first prior art operates in the same manner as the illumination correction body and can solve the problem of the cosine fourth power law.

Furthermore, since the light shielding section is formed of a reflective material with good diffusivity, the diffused light reflected thereby reaches the surface of the original glass, and the diffused light reflected by the reflective material with good diffusivity on the inner surface of the housing is reflected from the document glass. In addition to reaching the surface of the glass, the light intensity distribution of the reflected light on the glass surface of the document becomes substantially uniform over the entire surface, which eliminates the occurrence of dark spots on the exposed surface. That is, it is possible to solve the problem of dark areas caused by reflections on the surface of the original glass, without separately providing auxiliary illumination means as in the second prior art.

(Embodiment) The embodiment of the present invention shown in FIG. 1 shows an exposure apparatus using a flash lamp exposure method, and is used in a high-speed copying machine.

The inner surface 2 of the upwardly open box-shaped illumination housing 1 is coated with white paint (reflective material with good diffusivity) over its entire surface. A document glass 3 is provided on the top surface of the housing 1, and a document 4 is placed on the document glass 3.

A projection lens 5 is disposed at the center of the bottom of the housing 1.
The upper part of this projection lens 5 is covered with a cover 6. An illumination correction member 7 is attached to the top surface of the cover 6. The illumination correction member 7 is formed by painting a plurality of concentric rings as shown in FIG. 2 on the surface of a circular transparent substrate (transparent glass or transparent plastic) 8 with white paint, and partially forming a light shielding part 9. It has become. The distribution of the light shielding portions 9 is such that the density is high in the center of the transparent substrate 8, and the density decreases toward the periphery, solving the problem of the fourth power of cosine, and
The illuminance at 0 is set to be approximately uniform. Third
As shown in the figure, a large number of dots are painted on the surface of the transparent substrate 8 with white paint, and the distribution of the light-shielding area 9 made up of these dots is such that the density is high in the center and toward the periphery. The density may be set to be small.

The outer surface 12 of the cover 6 is coated with white paint, and a pair of left and right flash lamps 11.11 are arranged below it. The light from the flash lamp 1111 is covered by the cover 6 so that it does not directly enter the original glass 3 or the projection lens 5. The light from the flash lamp 11.11 is transmitted to the inner surface 2 of the housing 1 and the outer surface 1 of the cover 6.
2, the light becomes diffused light, and thereafter multiple reflections occur to uniformly illuminate the entire interior of the housing 1. The optical image of the original 4 on the original glass 3 that is uniformly illuminated is projected by the projection lens 5.
The exposure surface 10 on the photoreceptor belt 13 is exposed by projection through the photoreceptor belt 13. The photoreceptor belt 13 stretched by the driving roller 14 and the driven rollers 15.16 is exposed to the flash light from the flash lamp 11.11 when the photoreceptor belt 13 is stopped. An image is formed instantly. Since the function of the illumination correction member 7 has already been described, its explanation will be omitted.

(Effects of the Invention) According to the present invention, by providing only one illumination correction member, the problem of the cosine fourth power law and the problem of dark areas caused by reflection on the document glass surface can be solved at once, and the structure It is possible to provide an exposure apparatus that can perform uniform exposure while having a simple and low-cost configuration.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a plan view showing the surface state of the illumination correction member, and FIG. 3 is a plan view showing the surface state of the illumination correction member of another embodiment. FIG. 4 is a sectional view showing a conventional example.

Claims (1)

[Claims] (1) An illumination housing whose inner surface is made of a reflective material with good diffusivity, a flash lamp provided within the housing, and a document glass provided on the top surface of the housing;
In an exposure device equipped with a projection lens provided at the bottom of the housing, an illumination correction member is arranged between the original glass and the projection lens, and this illumination correction member is partially coated with a reflective material with good diffusivity on a transparent substrate. 1. An exposure apparatus characterized in that a light-shielding portion is formed in the light-shielding portion, and the distribution of the light-shielding portion is set so that illuminance on an exposure surface is substantially uniform.