JPH0378773A - Copying machine - Google Patents

Abstract

PURPOSE:To eliminate the generation of the uneveness in the density an original latent image and to prevent the generation of the uneveness in the density of a copied original by providing a half mirror between an illuminating lamp and the original. CONSTITUTION:Luminous flux emitted from the illuminating lamp 1 when the original is being read is directed in the original 3 direction by a reflecting plate 2 and since the illuminating lamp is positioned vertically below the original 3, the illumination on an original plane is roughly uniform. For example, when the original 3 is a monochrome original having the uniform density, since the illumination on the original3 is roughly uniform, reflecting light shows almost uniform light quantity distribution, the reflected light directs vertically below from the original 3 plane and the direction is changed by a half mirror 5 plane. The reflected light irradiates a photosensitive drum 8 through a reflecting mirror 6, a lens 6, etc., and since there is no factor to change the light quantity distribu tion of the reflected light in this process, the light quantity distribution on the photosensitive drum plane is maintained nearly uniform. Thus, the generation of the uneveness in the original latent image density is eliminated and the generation of the uneveness in the density of the copied original is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention applies light emitted from an illumination lamp to a document in the process of forming a latent image on the document, and the reflected light is reflected using an optical system consisting of a reflecting mirror, a lens, etc. The present invention relates to a copying machine that exposes the surface of a photoreceptor by applying light to the photoreceptor drum to form a latent image of an original on the photoreceptor drum.

Prior Art In the process of forming a latent image in a conventional copying machine, light emitted from an illumination lamp is applied to a document, and the reflected light is directed onto a photoreceptor drum by an optical system consisting of a reflecting mirror, a lens, etc., and the photoconductive phenomenon occurs. A latent image of the document is formed on the photoreceptor drum using

The latent image forming process will be explained below with reference to FIGS. 2 and 3. This process usually involves the following (1) to (3):
A latent image on the document is formed by the process.

(1) The light emitted from the illumination lamp 1 is reflected on the inner surface of, for example, an elliptical reflecting plate 2 to irradiate a luminous flux in the direction of the original 3.

(2) The reflected light from the original is reflected by the reflector 6. It is applied to a predetermined position corresponding to the original on the photosensitive drum 8 via the lens 7 and the like.

(3) As the original is scanned, the photoreceptor drum surface is exposed to light reflected from the original, and a latent image of the original is formed on the photoreceptor drum at a density corresponding to the total exposure amount.

The process (3) above will be explained in more detail using FIGS. 4, 5, and 6.

In FIG. 4, it is assumed that at time t1, when the illumination lamp 1 is at the position pl, light is shining on the document 3 in a range from dl to d2. At this time, on the surface of the photosensitive drum 8 shown in FIG. 5, the reflected light falls on the range from dl to d2 corresponding to the original. In FIG. 4, the time is 1 from tl. ,．
13, the illumination lamp changes from p, to p21 p
3, and the portion of the original that is illuminated by light moves accordingly. Assuming that when the illumination lamp moves to position p3, the photoreceptor drum also rotates and comes to the position shown in FIG. This corresponds to the range from f1, that is, d2 to f2. From the above, if we pay attention to point d2 on document 3, the total amount of light reflected at point d2 on the document and reaching the photoconductor drum during the time the illumination lamp moves from p to p3 is the amount of light that is exposed to light. The density of the latent image at point d2 on the body drum is determined.

The illumination lamp moves from pl to p3 (time is at point d on the document)
The total exposure amount is determined by the total amount of light hitting the photoreceptor drum surface.

Problems to be Solved by the Invention However, when forming a latent image of a document on a photosensitive drum with the above-described configuration, the following phenomenon occurs.

As shown in FIG. 2, the light beam emitted from the illumination lamp strikes the original at a certain angle that is not perpendicular to it. If you hit like this, for example, a, b on the original 3.
, the illuminance of the light at point c is not the same. This results in
For example, even if the original is a monochromatic original with uniform density, the distribution of the amount of reflected light is not uniform, and such reflected light is transmitted to the reflecting mirror 6. When the light reaches the surface of the photoreceptor drum 8 via the lens 7 or the like, the distribution of the amount of light is obviously not uniform on the surface of the photoreceptor drum 8.

The results of actually verifying this phenomenon through experiments are shown in FIGS. 7 and 8. FIG. 7 is an explanation of the experimental apparatus. A measuring device 9 for measuring the amount of light is installed at a location corresponding to the latent image formation position on the photoreceptor drum surface, and an original reading operation is performed using a uniformly gray original. The amount of light was measured. FIG. 8 shows the measurement results, where the horizontal axis is the width of the light hitting the photosensitive drum (in millimeters), and the vertical axis is the amount of light (in lux). As can be seen from this, even though the density of the original is uniform, the light amount distribution on the surface of the photoreceptor drum is not uniform.

As described above, when the light intensity distribution of the reflected light does not match the density distribution of the original, the following problems occur. For example, during the process of forming a latent image on a monochromatic document with uniform density, such as a uniformly gray document, some disturbances such as the movement of the optical system, such as a reflecting mirror or lens, or uneven rotation of the photoreceptor drum may cause the document to If the reflected light deviates from the original position on the photoreceptor drum when scanning a portion, the density of the latent image of the original on the photoreceptor drum surface will not be uniform (and the final copy of the original will be different). There will be unevenness in the concentration.

This will be explained using FIGS. 9 and 10.

It is assumed that the original has a uniform density of gray, and for the sake of simplicity, the amount of reflected light has a distribution as shown in FIG. first,
The case where there is no disturbance will be explained.

In FIG. 10, at time t, the illumination lamp comes to the position pl, and light begins to shine on point g on the document, and at time t
Assuming that the illumination lamp is illuminated until it reaches position p2, the part corresponding to point g on the photoreceptor drum surface will be exposed with a light amount of Ll at time t1, and will be exposed with a light amount of L2 at time t2. ing.

In this case, the total exposure amount of the portion corresponding to point g on the photosensitive drum is given by the area of the shaded portion in FIG.

Now, consider a case where, at a certain time t3, the reflected light is momentarily shifted backward by a certain distance d from the position on the photoreceptor drum surface where it should originally strike due to a disturbance.

In FIG. 11, if the reflected light deviates from its original position and the light intensity distribution on the photoreceptor drum surface shifts to the shaded position, then the point g on the photoreceptor drum surface at time t3
The exposure amount of the portion corresponding to is less than the original exposure amount by an amount corresponding to L3.If the light hits the original position on the photoreceptor drum surface other than time t3, then the light will be at point g. The total exposure amount in the corresponding portion is less than the original total exposure amount by an amount corresponding to L3, and therefore, if the exposed portion becomes white, the density of the latent image on the document will also become darker than originally. If the reflected light shifts forward, the latent image on the original will become thinner than it should be.The light intensity distribution of the reflected light is not limited to the shape shown in Figure 9; Needless to say, the same applies if you have one.

As can be seen from the above, in the conventional method, the distribution of the amount of reflected light is not uniform, and as a result, disturbances cause the latent image of the original to have dark and thin parts, resulting in the final density of the copied original. The problem was that it caused unevenness.

Means for Solving the Problems The technical means of the present invention for solving the above problems are as follows:
A feature is that a /'%-humirror is used between the illumination unit that illuminates the original and the original.

For production The effect of this technical means is as follows.

By using a half mirror, it is possible to arrange an illumination section, which includes an illumination lamp serving as a light source and a reflection plate for irradiating light toward the document, approximately vertically below the document. As a result, the light beam emitted from the illumination lamp hits the original at a substantially right angle, and the illuminance of the light hitting the original can be made approximately equal. Thereby, the light amount distribution of the reflected light corresponds to the density distribution of the original. For example, if the original is a monochromatic original with uniform density, the light amount distribution of the reflected light can also be made approximately equal. Furthermore, even if the above-mentioned disturbance occurs, it is possible to prevent the occurrence of density unevenness in the latent image of the original, and it is possible to prevent the occurrence of density unevenness in the final copied original. .

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG. In FIG. 1, 1 is an illumination lamp that shines light on the original, 2 is a reflector for irradiating the light from the illumination lamp 1 in the direction of the original, 3 is the original, 4 is a contact glass that supports the original, and 5 is a light source from the original. This is a half mirror for changing the direction of reflected light.

During a document reading operation, the light beam emitted from the illumination lamp 1 is directed toward the document by the reflecting plate 2. At this time, since the illumination lamp is located vertically below the document, the illuminance of the light on the surface of the document is approximately equal.

Now, taking as an example the case where the original is a monochromatic original with uniform density, the illuminance of the light hitting the original is approximately uniform, so the reflected light also exhibits an approximately uniform light amount distribution. This reflected light travels vertically downward from the document surface, and its direction is changed at the half mirror 5 surface. Further, the reflected light passes through a reflecting mirror, a lens, etc., and is irradiated onto the photosensitive drum. In this process, since there is no factor that changes the light amount distribution of the reflected light, the light amount distribution of the light reaching the photoreceptor drum surface is kept approximately equal.

FIG. 12 shows the results of measuring the light intensity distribution on the photoreceptor drum surface when reading a uniformly gray original using the above method. The measurement method is the same as described above. As can be seen from this figure, the distribution of the amount of reflected light on the surface of the photoreceptor drum is approximately equal. In actual tests using gray originals, the uniformity of the density distribution of the copied originals was significantly improved. Note that although the above description is about a monochrome original with uniform density, it is not necessarily necessary that the entire original is a monochrome original with uniform density (even if some parts of the original have monochrome parts with uniform density) Needless to say, they are similar.

Effects of the Invention As described above, the present invention uses a half mirror in the illumination unit that illuminates the original, so that the original can be illuminated at right angles, thereby substantially reducing the distribution of the amount of light reflected from the original. It can be made even. Furthermore, this effect makes it possible to prevent density unevenness in the copied document due to disturbances such as vibrations of the optical system and uneven rotation of the photoreceptor drum.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the main parts of an illumination device in an embodiment of the present invention, FIG. 2 is a configuration diagram of the main parts of an illumination device of a conventional copying machine, and FIG. 3 is a diagram of the optical system of a conventional copying machine. Layout diagrams, Figures 4, 5, and 6 are explanatory diagrams of illumination conditions of a document and a photoreceptor drum in a conventional example, and Figure 7 is an apparatus for measuring the light intensity distribution on the surface of a photoreceptor drum. FIG. 8 is a graph showing the light amount distribution on the photosensitive drum surface in the conventional example, FIGS. 9, 10, and 1.
FIG. 1 is an explanatory diagram of the density unevenness of a latent image due to disturbance, and FIG. 12 is a graph showing the light quantity distribution on the photosensitive drum surface in one embodiment of the present invention. 1...Illumination lamp, 2...Reflector, 3
...Manuscript, 4...Contact glass,
5...Half mirror-0

Claims (2)

[Claims] (1) The light emitted from the illumination lamp is applied to the original, and the reflected light is applied to the photoreceptor drum using an optical system consisting of a reflecting mirror, lens, etc., thereby exposing the surface of the photoreceptor to light and forming a latent image on the original. A copying machine formed on a photosensitive drum, characterized in that a half mirror is provided between an illumination lamp and a document. (2) The copying machine according to claim 1, wherein the illumination section comprising an illumination lamp and a reflection plate for irradiating light toward the document is located substantially vertically below the document.