JPS63172260A - Image exposing device - Google Patents

Abstract

PURPOSE:To correct uneven exposure independently of variable power by arranging a light shielding member for regulating light flux through a point-symmetical slit hole near a lens and rotating the member around the optical axis of a lens in accordance with the variable power. CONSTITUTION:The light shielding member 10 forms the approximately long elliptic slit hole 10a on its center position and is fitted so as to be rotated around the optical axis of the lens 8. Projected light L with equal power forms its image on a photosensitive drum 12 without being shielding by the light shielding member 10, and since light distribution characteristics are determined so that the influence of the COS 4-th power rule of the lens 8 upon the light flux is corrected at the time of equal power, the uniform distribution of illumination in the longitudinal direction can be obtained. Consequently, the peripheral part of the projected light flux L is regulated by rotating the member 10 around the optical axis of the lens 8 by an angle theta also at the time of contraction and the uniform distribution of illumination can be obtained in the longitudinal direction.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an image exposure device for correcting exposure unevenness, and particularly in a slit exposure type copying machine, etc., the so-called lens C
The present invention relates to an image exposure apparatus that corrects the exposure distribution according to the O54 power law and applies uniform exposure in the longitudinal direction of a slit regardless of magnification conversion (hereinafter referred to as variable magnification).

(Prior Art) Conventionally, in variable magnification copying machines using a slit exposure method, when the slit area of a document is projected onto a photoreceptor drum by a lens, exposure unevenness occurs in the longitudinal direction of the slit according to the angle of view, based on the so-called CO34 law. occurs. To solve this,
When using a light source with a uniform luminance distribution, it is necessary to provide a diaphragm plate in the optical path to correct the CO34 power law. For example, a device that moves a large number of slits in and out according to the magnification ratio, or a device that moves a slit plate near the photoreceptor drum in a direction perpendicular to the longitudinal direction of the slit (scanning direction) as the lens moves when changing the magnification. Various methods have been proposed.

However, the following problems remain with these methods. That is, in the former case, in which a large number of slit plates are inserted and removed, the number of mechanical parts increases, and the switching operation for each magnification change or the shape adjustment of the slit plate for each magnification change, etc.
It was complicated and costly. Furthermore, in the latter case, in which the slit is moved near the photoreceptor drum, it is difficult to install a moving mechanism spatially, and the apparatus becomes large.

As a means of solving this problem, as shown in FIG. A diaphragm plate 110 that corrects the CO54 power law distribution and acts as an aperture diaphragm is disposed on the lens 10 when changing the magnification.
There is a system that corrects exposure unevenness at each magnification ratio by moving the diaphragm plate 110 integrally with the lens 108 while maintaining the relative relationship with the lens 108.

(Problem to be Solved by the Invention) However, in such a conventional example, only one diaphragm plate 110 for CO34 power law correction is required regardless of the magnification change, and the lens of the diaphragm plate 110 for each magnification change is Although the mechanism is simplified because there is no need to change the relative positional relationship with respect to Since the number is substantially darkened, it is inefficient in terms of light amount. As a means to solve this problem, the light source such as a halogen lamp has a luminance distribution that corrects the CO34 power law in the longitudinal direction, that is, a distribution that increases the brightness in the peripheral region compared to the central region, and the CO54 power law of the lens. There are measures to correct exposure unevenness.

This has the problem that although exposure unevenness can be corrected at a certain magnification due to a change in the angle of view accompanying zooming, it is not possible to correct exposure unevenness at other magnifications.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and its purpose is to provide an image exposure apparatus that has a simple configuration and can correct exposure unevenness regardless of the magnification ratio. Our goal is to provide the following.

(Means for Solving the Problems) In order to achieve the above object, the image exposure apparatus according to the present invention converts an original image illuminated by a light source into various magnifications through a lens. In an image exposure apparatus that projects and forms an image on an image carrier, a light shielding member is provided near the lens to regulate the light flux by a point-symmetrical slit hole, and the light shielding member is arranged near the lens to control the light beam around the optical axis of the lens according to the conversion magnification. It is constructed by rotating the light shielding member and adjusting the amount of light after passing through the light shielding member.

(Function) In the present invention having the above configuration, near the lens,
A light shielding member is provided that regulates the light flux using a point-symmetrical slit hole, and the amount of light after passing through the light shielding member is adjusted by rotating the light shielding member around the optical axis of the lens according to the conversion magnification. This makes the illuminance distribution on the image carrier uniform.

(Example) The present invention will be explained below based on the illustrated example. 1st
The figure is a schematic diagram showing an embodiment of a variable magnification copying machine to which an image exposure device according to the present invention is applied. The document 2 to be placed is illuminated by the illumination light source 3, and the image light from the slit area regulated by the slit regulating member 4, which has a constant width regardless of the magnification, passes through the mirrors 5, 6.7, and further passes through the mirrors. 11 and is projected onto a photosensitive drum 12 as an image carrier in the form of a slit having a width that varies depending on the magnification. 9 is a diaphragm plate (pupil) provided with a circular hole that regulates the amount of light placed inside the lens 8; 10 is a lens 8;
This is a light shielding member disposed near the.

In addition, as shown in FIG. 2, the illumination light source 3 corrects the CO54 power law of the lens 8 at a predetermined magnification to make the illuminance distribution on the photoreceptor drum 12 uniform, so that the peripheral area is brighter than the central area. It has light distribution characteristics. And when changing magnification,
The lens 8 and the light shielding member 10 are displaced in the optical axis direction to the position of the lens 8' and the light shielding member 10' indicated by the broken line shown in FIG. 1, and the focal length is changed to maintain the imaging relationship during zooming. .

By the way, when the magnification is changed with the illuminance distribution on the document surface as shown in FIG. 2, the illuminance distribution on the photosensitive drum 12 will not be uniform. That is, when the light distribution characteristic of the illumination light source 3 is corrected at the same magnification as the reference magnification, the illuminance becomes high in the peripheral area during reduction, and the illuminance becomes low in the peripheral area during enlargement. Therefore, in this embodiment, as described above, a light blocking member 10 is provided near the lens 8 to block the light beam from the light source. This light shielding member 10 has a point-symmetrical, substantially oblong slit hole 10a formed at its center, and allows a light beam to pass through the slit hole 10a.

Further, the light shielding member 10 is attached to be rotatable around the optical axis of the lens 8. For example, a gear portion is formed on the outer periphery of the light shielding member 10, and the driving force of a servo motor (not shown) is transferred to the gear or the like. It rotates by transmitting it to the gear section via the transmission means. Then, the position of the light shielding member lO with respect to the aperture plate 9 is changed to regulate the light flux and correct the exposure unevenness.

Next, the operation of this embodiment will be explained based on FIGS. 3 and 4. FIG. 3 is a cross-sectional view of the projection light beam at a standard magnification, for example, the same magnification, and the projection light beam at the same magnification forms an image on the photoreceptor drum 12 without being blocked by the light shielding member 10. At the same magnification, the light distribution characteristics are determined as described above so as to correct the influence of the CO34 power law of the lens 8 on the luminous flux, so it is possible to obtain a uniform illuminance distribution in the longitudinal direction on the photoreceptor drum 12''. can. Moreover, FIG. 4 is a cross-sectional view of the projected light beam during reduction, and at this time, by rotating the light shielding member lO by an angle of 0 around the optical axis of the lens 8,
The peripheral portion of the projection light beam is regulated, the above-mentioned problem of high peripheral light amount is solved, and a uniform illuminance distribution can be obtained on the photoreceptor drum 12 in the longitudinal direction.

Therefore, with an extremely simple configuration in which the light shielding member 10 is rotated by an angle θ corresponding to the magnification ratio around the optical axis of the lens 8, the projection light beam passing through the aperture plate 9 is regulated. Exposure unevenness during zooming can be corrected without displacing the lens 9.

Further, in the above embodiment, the exposure unevenness correction during reduction has been described, but correction during enlargement is not so necessary since the magnification range on the enlargement side is usually narrower than on the reduction side. If the magnification range on the enlargement side is wide and requires correction,
Instead of setting the reference magnification as the same magnification, the light shielding member 10 is rotated by a predetermined angle and the light flux in the peripheral area is regulated so that the same magnification or reduction is set, so that the amount of light from enlargement to reduction can be adjusted. Distribution correction becomes possible.

In addition, in the actual flow side, the case where the shape of the slit hole 10 of the light shielding member 10 is approximately an oblong shape has been described, but the shape and position of the aperture plate 9 or the light distribution characteristics of the light source are not limited to this. Any suitable shape determined according to the above may be used.

Further, in the above embodiment, the light shielding member 10 is disposed near the image plane side of the lens 8, but the light shielding member 10 is not limited to this, and may be disposed near the object side of the lens 8, or a plurality of light shielding members 10 may be disposed distributed on both sides. Good too.

(Effects of the Invention) The image exposure device according to the present invention has the above-described configuration and operation, and has an extremely simple configuration in which the light shielding member is rotated around the optical axis of the lens according to the conversion magnification. This has the effect of being able to correct exposure unevenness in the main scanning direction of the image carrier.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a copying machine to which an embodiment of the image exposure device according to the present invention is applied, FIG. 2 is an explanatory diagram showing the light distribution characteristics of the light source in the embodiment, and FIG. FIG. 4 is a cross-sectional view showing the projection light flux at the time of reference magnification, FIG. 4 is a cross-sectional view showing the projection light flux at the time of reduction in the same embodiment, and FIG. 5 is an explanatory diagram showing an exposure unevenness correction device in a conventional image exposure apparatus. Explanation of symbols

Claims (1)

[Claims] In an image exposure device that converts an original image illuminated by a light source into various magnifications through a lens and projects the image onto an image carrier, a light beam is regulated by a point-symmetrical slit hole near the lens. An image exposure apparatus characterized in that a light shielding member is provided, and the amount of light after passing through the light shielding member is adjusted by rotating the light shielding member around the optical axis of the lens according to a conversion magnification.