JPS63106639A - Light distribution correcting mechanism - Google Patents

Abstract

PURPOSE:To execute a sufficient light distribution against many projecting magnifications by a simple constitution, by providing the light shielding member of thin plate thickness, in which length in the transverse direction of an optical path cross section is varied unequally in an adjacent position, against an optical path whose cross section is regulated to a slender slit shape. CONSTITUTION:When the light distribution of a light source 3 is set so that a light beam is not shielded at the time of the maximum magnification and the peripheral light quantity separated from the optical axis 31 of a photosensitive body 12 becomes a necessary and sufficient light quantity, its periphery light quantity shows only an increasing tendency in decreasing the magnification. Accordingly, it may be sufficient that its increased portion is brought to light shielding by light shielding plates 23, 24 and corrected to the same degree as the light quantity of the optical axis 31 part, and a light quantity distribution characteristic of the surface of the photosensitive body 12 is made flat. In this state, when the light shielding plates 23, 24 are turned so that its surface is intersected orthogonally with the optical axis 31 of the optical path, the luminous fluxs of both sides of the optical path are shielded mainly, and when its surface is turned so as to be parallel to the optical axis 31, the thin light shielding plates 23, 24 scarcely interrupt the luminous flux.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light distribution correction mechanism applied to a projection mechanism of a copying machine.

[Prior art]

In the projection mechanism of an electrophotographic copying machine, a lens is essential in order to form a projected image on a photoreceptor as an image carrier. However, this lens has 'cos'
There is a characteristic called the law of θ, ``the luminous flux density at an image point off the optical axis decreases in proportion to cos 'θ of the luminous flux density at an image point on the optical axis.''

Therefore, in an electrophotographic copying machine capable of variable magnification, one side of a slit serving as an optical path regulating member is provided so as to be movable toward and away from the optical path to adjust the light distribution, as disclosed in Japanese Patent Application Laid-open No. 52-146630, for example. , or Japanese Patent Publication No. 57-73767
As in the publication, a light shielding member is provided separately from the slit,
Light distribution is adjusted by allowing this to move forward and backward perpendicular to the lens optical axis.

However, in these mechanisms, since the shape of the light shielding member that moves forward and backward with respect to the optical path is constant, it is not possible to perform good light amount correction for all of the many projection magnifications. In particular, if there is a region where no light shielding plate is present in the longitudinal direction of the cross section of the optical path formed by the slit (that is, if the amount of light shielding is discontinuous in the longitudinal direction), a portion with a locally high amount of light will be created.

Further, as shown in FIG. 27, if the optical path 2 is deviated from the position of the light shielding member 1, the amount of light shielding will change.

Furthermore, when moving from a certain magnification to a lower magnification, the cross-sectional shape of the optical path becomes smaller in both width and length, so the light shielding member must be moved by the amount that has become smaller, and then further moved by the amount necessary for light distribution correction. However, the mechanism becomes complicated.

Furthermore, if the reduction magnification is a relatively small value during reduction,
Since the cross-sectional shape of the optical path is smaller in both width and length, in order to correct the light distribution appropriately, higher precision is required for the amount of movement of the light shielding member than when magnifying the image. .

Furthermore, if the light shielding member enters in a straight line, a guide rail or link mechanism with many nodes is required.
The configuration becomes complicated.

Furthermore, the conventional light distribution correction mechanism is always in a partially shaded state, which means that the light source emits unnecessary light, which is uneconomical.

In addition to the above-mentioned publications, mechanisms with the above-mentioned problems include JP-A-54-136845 and JP-A-57-9234.
8, JP-A-57-154265, JP-A-60-134
There are some proposals in publications such as No. 226 and Japanese Unexamined Patent Publication No. 60-80828.

On the other hand, Japanese Utility Model Application Publication No. 57-121953 proposes a device in which a rectangular light-shielding plate is arranged perpendicular to the optical axis, and the light-shielding plate can be rotated in the front-rear direction of the optical axis. There is. This technology has the advantage of not losing much light when not shaded, but since the shape is rectangular,
There is a problem that light distribution correction cannot be performed appropriately.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks and to enable sufficient light distribution correction for many projection magnifications with a simple configuration.

[Structure of the invention]

To this end, the present invention provides a light source that illuminates a document, an optical path regulating member having a slit that regulates the cross-sectional shape of image light from the document, an image carrier that carries an image given by the image light, and a light source that illuminates the document. In an image projection mechanism having an imaging lens disposed in an optical path between a document and the image carrier, the optical path is regulated by the optical path regulating member into a long and thin slit-like cross section. A thin plate that rotates about an axis that intersects the optical axis of the optical path and along the length of the optical path, and that the length of the optical path in the width direction changes unevenly at adjacent positions due to the rotation. It was constructed by providing a light shielding member.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment in which the present invention is applied to an electrophotographic copying machine capable of variable magnification. FIG. 1 is a diagram showing an outline of the copying machine. Light emitted from a bar-shaped (long in the direction perpendicular to the paper surface) light source 3 that exposes and scans in the direction of the arrow X is reflected by the document 5 placed on the platen glass 4, where the reflected light carrying the document image (image light) is emitted. The optical path is changed by the mirrors 7 to 9 via the pickpocket 7) plate 6 as an optical path regulating member, and the optical path is further changed by the mirror 11 via the lens mechanism 10 for image formation. is guided to the photoreceptor drum 12 to form an electrostatic latent image thereon.

The photosensitive drum 12 rotates in the direction of the arrow y in synchronization with the scanning of the light source 3, and the electrostatic latent image is developed with toner in the developing section 13, and the transfer paper fed from the paper feeding section 14 is When the toner image is fed by the registration roller 15 in a timing with the leading edge of the image, the toner image is transferred thereto by the transfer pole 16.

The transfer paper is separated from the photoreceptor drum 12 by a separation pole 17, sent to a heat fixing roller 18, where the toner image is fixed, and discharged onto a paper discharge tray 19. 20 is a cleaning section, and 21 is a charging electrode.

In this copying machine, when the copying magnification is changed, the lens mechanism 1
In this embodiment, the light source 3 has a unique light distribution characteristic as described later, and the lens mechanism 10 is equipped with a light distribution correction mechanism 22. When the magnification is changed, the light distribution correction mechanism 22 operates to correct the light distribution.

As shown in FIG. 2, this light distribution correction mechanism 22 has two light shielding plates 23 and 24 made of wedge-shaped metal plates with a thin plate thickness (for example, 0.4 m). 23.24
The surface has a matte black finish. These light shielding plates 23 and 24 are rotatably attached to arms 26 and 27 extending from the lens holder 25 of the lens mechanism 10 at angular intervals of 180 degrees by shafts 28 and 29, and their tips are spaced apart from each other and face each other. are doing. The center of rotation is an axis 32 that is perpendicular to the optical axis 31 of the lens 30 of the lens mechanism 10 and parallel to the central axis of the slit in the slit plate 6 in the longitudinal direction (direction perpendicular to the paper surface). The light shielding plates 23 and 24 are connected by a connecting arm 33 so that both of them rotate in conjunction with each other, and are also connected to an arm 35 having a cam follower 34 attached to its tip. A cam 36 is fixed to the main body of the copying machine, and the cam follower 34 is always in contact with the cam surface 36a.

Therefore, when the lens mechanism 10 moves along the optical axis 31 for zooming, the arm 33.35 rotates due to the cam action, so the inclination angle of the light shielding plate 23.24 changes and becomes orthogonal to the optical axis 31. The shape projected onto the surface changes.

Then, the light shielding plates 23 and 24 are placed so that their surfaces are aligned with the optical axis 31 of the optical path 1.
When the light beam is rotated perpendicularly to the light beam, the light beams on both sides of the optical path 1 are blocked as shown in FIG. Also,
When the light shielding plates 23 and 24 are rotated so that their surfaces are parallel to the optical axis, as shown in FIG. 4, the thin shielding plates 23 and 24 hardly block the light flux.

Regarding the distribution of sources, we will first explain the ``cos'' θ law mentioned above. FIG. 5 is a diagram for explaining this, in which an image of the original 5 is formed by a lens 3o located at a distance a from the original 5 on a photoreceptor 12 located at a distance from the lens 30. In this case, point A on the original 5 (point on the optical axis 31)
Compared to the amount of light at point A' on the photoreceptor 12 on which the light is projected,
The amount of light at point B' on the photoreceptor 12 on which the same light at point B, which is distant from the optical axis 31 of the original 5, is projected is calculated as follows, assuming that the angle of incidence from point B to the lens 30 with respect to the optical axis 31 of the lens 3o is θ. ,
It becomes cos'θ(<1) times. In other words, point B is optical axis 3
1, the amount of light projected onto the photoreceptor 12 at point B' decreases in proportion to cos'θ.

Note that the distances a and b are the focal length of the lens 4, f, and the magnification, m.
Then, a = f (1+ 1/m) ・
...(1)b=f(1+m)・
... is given by (2).

Therefore, in this embodiment, the light distribution of the light source 3 (optically equivalent to the original 5) is defined as "the light distribution of the photoreceptor 12 after passing through the lens 30".
Set so that the light amount distribution on the top is uniform (flat) with no light shielding under the maximum magnification condition.

As mentioned above, the distance a between the document 5 and the lens 30 is given by the formula (1), but this formula decreases as the magnification m increases, indicating that the lens 30 is closest to the document 5 at maximum magnification. show. Therefore, the angle θ at this time becomes the largest, and the decrease in the amount of peripheral light due to the above-mentioned 'cos' θ law J becomes most noticeable at this maximum magnification.

Therefore, if the light distribution of the light source 3 is set so that at this maximum magnification, the amount of light in the periphery away from the optical axis 31 of the photoreceptor 12 without light shielding is a necessary and sufficient amount of light, then if the magnification is lowered, the amount of light will be the same. Since the amount of peripheral light tends to increase more and more, the increased amount is blocked by the light shielding plates 23 and 24 and the optical axis 3 is
It is only necessary to correct the light amount to the same extent as the light amount of one portion to flatten the light amount distribution characteristics on the surface of the photoreceptor 12.

An example of the light distribution set as described above is shown in FIG. The curve Q is the light distribution characteristic of the light source 3 (original 5) (symmetrical to the optical axis 31), and the straight line R is the light amount distribution characteristic of the photoreceptor 12. A light distribution that minimizes the amount of light emitted from the center of the optical axis 31 of the light source 3 (provided that a sufficient amount of light can be obtained at the optical axis portion of the photoreceptor 12), and increases the amount of light emitted from there toward the outside. Due to this characteristic, the amount of light on the surface of the photoreceptor 12 is constant regardless of the distance from the optical axis 3 (within a predetermined range).

The present inventor uses a light source 3 having a light distribution having the characteristics shown in FIG. 7, which is flat on the photoreceptor 12 at a magnification of m=1.55, and changes the magnification from m=0.5 to 0.1. 1 in increments
．． 5 to simulate the light amount distribution characteristics on the surface of the photoreceptor 12 when no light shielding is performed. The results are shown in Figures 8a-8. At any magnification, the amount of peripheral light is higher than the amount of light at the center.

As shown in FIGS. 8a to 8 above regarding the shape of the shield plate, the rate of increase in the amount of peripheral light relative to the central scene is greatest at the minimum magnification. Therefore, the amount of light shielded by the light shielding plates 23 and 24 installed on the photoreceptor 12 side of the lens 30 needs to be the maximum amount when the minimum magnification is achieved.

In this embodiment, the light shielding plate 23.2 is placed in the direction perpendicular to the optical axis 31.
4, and the light shielding plate is rotated in the front and back direction of the optical axis 31, so that effective light shielding is achieved by the shape projected onto a plane perpendicular to the optical axis 31, as described above.

Therefore, the angle that the surfaces of the light shielding plates 23 and 24 make with respect to the optical axis 31 also becomes maximum at the minimum magnification. If this angle is α, then 0≦α≦90@. Therefore, the shape of the light shielding plates 23 and 24 is ``When the surface is placed at a certain angle (≠0) to the optical axis of the lens, the shape projected onto a plane perpendicular to the optical axis is the shape at the minimum magnification. Set to a shape that flattens the light distribution on the photosensitive surface.

For example, when setting the magnification m=0.5 as the minimum magnification, the light shielding plate is placed so that its surface is orthogonal to the optical axis 31 (9
0@) When placed at an angle α, the light distribution on the surface of the photoreceptor 12 is flat.

This shape can be easily determined using a computer. That is, for a light beam incident on the optical axis 31 at an angle θ, the area occupied by the light beam on the light shielding plates 23 and 24 is set so that the light flux density is approximately the same as the light flux density of the light beam passing through the optical axis. All you have to do is decide. In FIG. 9, the light shielding plate 23.
24 does not block the light beam along the path A-A' passing through the optical axis 31 (FIG. 10(a)), but slightly blocks the light beam along the path B-B' (shaded area in FIG. 10(b)). and route c-
The light beam c' is significantly blocked (the shaded area in FIG. 10 (C1)). In other words, the amount of light blocked in the peripheral area is large.

The angle θ changes depending on the position of the lens 30, that is, the magnification, and the passing position of the light flux on the light shielding plates 23 and 24 changes depending on the value of θ, so starting from θ = 0 @ (no light shielding plate), the value of θ is What is necessary is to find a numerical value for the width of the light shielding plate that increases little by little so that the amount of light on the surface of the photoreceptor 12 becomes the same as that when θ=0''.

Now, here, the magnification for determining the shape of the light shielding plates 23 and 24 is the minimum, and the size of the surface of the original 5 or the photoreceptor 12 is limited. Therefore, the shape of the light-shielding plate determined by the above method may be considered to have a narrow range of θ that is valid only at this magnification, but when determining the shape, the size of the original or photosensitive surface must be determined based on the actual size. The value of θ corresponding to the maximum angle of view at the maximum magnification is calculated (see FIG. 11). Of course, it is assumed that the light distribution of the light source is also continuous within this range.

FIG. 12 is a diagram showing the planar shape of the light shielding plates 23 and 24 determined as described above. Using the light shielding plate shown in Fig. 12, we simulated the light distribution correction by giving a predetermined angle at each magnification. Figs. Show characteristics. The maximum magnification is m=1.55.

From the above, in a copying machine equipped with the exposure light source 3 and the light shielding plate 23.24, if the surface of the light shielding plate 23.24 is made parallel to the lens optical axis 31 at maximum magnification and the amount of light shielding is made almost zero,
The light distribution on the surface of the photoconductor 12 becomes almost flat, and at the minimum magnification, if the angle between the surface of the light shielding plate 23, 24 and the optical axis 31 is set to the above-mentioned α (90' in this embodiment). , the light amount distribution on the surface of the photoreceptor 12 at this magnification is also approximately flat.

At each magnification between the maximum and minimum, the cam 36
By appropriately setting the shape of the cam surface 36a of the light shielding plate 23.2,
By appropriately selecting the angle α between 4 and the optical axis 31,
As shown in FIGS. 13a to 13, a substantially uniform light amount distribution can be obtained over the entire magnification. Further, this angle α has the maximum amount of light shielding at the minimum magnification, and as the magnification increases, the amount of light shielding gradually decreases, and although there is some variation at any magnification, the light amount distribution is almost flat.

In this first embodiment, in order to emphasize theoretical rigor, it is assumed that the light distribution of the light source 3 is uniform on the photoreceptor at the maximum magnification, and the shape of the light shielding plates 23 and 24 is such that the light distribution is uniform on the photoreceptor at the minimum magnification. From a practical point of view, there is a certain tolerance for the shape of the body 12 to obtain a uniform light distribution.For example, the light distribution of the light source 3 may be difficult to achieve on the photoreceptor at a magnification slightly lower than the maximum magnification. The light shielding plate 23.
The same effect can be obtained even if the shape of 24 is such that a uniform light distribution can be obtained on the photoreceptor 12 at a magnification slightly higher than the minimum magnification.

In other words, the light distribution of the light source is defined as ``When the light distribution on the photoreceptor surface after passing through the lens is at the maximum magnification or near the maximum magnification,
The shape of the light shielding plate should be set so that its surface is at a certain angle (
≠0), the shape projected onto a plane perpendicular to the tip axis may be set to a shape that makes the light amount distribution on the photosensitive surface uniform when the magnification is at or near the minimum.

In this result, although the variation in the light amount distribution may be slightly large, it has almost no effect in practice.

From the above, the entire configuration is extremely simple, and it is possible to perform sufficient light amount correction over a wide variation range of magnification. Even if the optical path 1 fluctuates up and down to some extent as shown in FIG. 3, the light shielding plates 23 and 24 can be present in almost an appropriate shape in most of the longitudinal direction of the cross section of the optical path 1, so that local There will no longer be areas with high light intensity.

This is especially advantageous when the width of the optical path 1 becomes narrow during reduction. Further, the light shielding member does not move unnecessarily. Also, when reducing, especially when the reduction magnification is relatively small, the angle between the plane of the light shielding plate and the optical axis of the lens becomes close to a right angle. Even if there is variation, the area of the light shielding plate occupied in the optical path is not affected much, that is, when the reduction magnification is small, highly accurate light distribution correction can be performed. When the image is at the same magnification or enlarged, the area that is blocked is extremely small, so the light from the light source is not unnecessarily blocked.

As a result, when light distribution correction is not performed, as shown in Figure 14, when the reduction is 0.5 times, there is a difference in sight of more than 20% between the vicinity of the optical axis and the peripheral area. As a result of the correction, the difference in light amount was reduced to within 5% as shown in FIG. Further, the variation in the amount of light throughout the entire magnification (Xo, 5 to 1, 55) was about 10%, which was not a practical problem. Then, as shown by the broken line in Figure 15,
When the light intensity of the light source was increased during reduction, the variation in light intensity throughout all magnifications could be suppressed to 5% or less.

Modification 11 of Section 11 In the above embodiment, the light shielding plates 23 and 24 move together with the lens 30, but as shown in FIG. The light shielding plate 37 is attached to the support member 38 fixed to the main body of the copying machine.
Attach the pulley 40 to the shaft 39 of the
40 can be connected to the lens mechanism 10 by a wire 41, and the light shielding plate 37 can be rotated as the lens mechanism 10 moves, thereby correcting the light distribution.

Further, the shaft 39 is configured to be able to be driven by a motor or the like,
The inclination angle of the light shielding plate 37 can also be adjusted by rotating the shaft 39 in accordance with the magnification change. Furthermore, the light shielding plate 3 shown here
7 is one piece, but if this is done, the above-mentioned connecting arm 33 becomes unnecessary. Further, the rotation axis of the light shielding plate does not necessarily need to be orthogonal to the optical axis of the lens.

Further, as shown in FIG. 17, the rotation center axis 43 of the light shielding plate 42 does not need to be above the light shielding plate 42, and the shape of the light shielding plate 42 does not necessarily have to be symmetrical. In particular, in a copying machine or the like based on one side, it is preferable to make it asymmetrical with respect to the longitudinal direction.

-Whatever Happens ■Opening 1 As another embodiment when applied to a copying machine, the following is also possible. In other words, the light distribution of the exposure light source that illuminates the original is defined as "J type in which the light distribution on the photoreceptor surface after passing through the lens is uniform without light shielding when the magnification is at or near the minimum." The shape of the light-shielding plate is defined as ``When the surface is placed at a certain angle (≠O) to the lens optical axis, and the shape projected onto the plane perpendicular to the lens optical axis is at the maximum magnification or near it. It is also possible to set the shape J so that the light distribution on the surface of the photoreceptor is uniform.

This is the opposite of the case of Example 1 above, and if an exposure light source with no shading at the minimum magnification and a uniform light distribution on the photoreceptor surface is used, the amount of light in the periphery will increase as the magnification increases. It's getting lower. In other words, the amount of light at the center of the optical axis becomes higher than the amount of light at the periphery. Therefore, as the magnification increases, the amount of light at the center, which has become relatively high, is reduced.

In this case, the shape of the light shielding plate differs from the above case in that it is wide at the center and narrows toward the periphery. Then, at the maximum magnification or a magnification close to the maximum magnification, an angle α is formed with respect to the optical axis that provides the maximum amount of light shielding, and as the magnification decreases, the amount of light shielding decreases.

FIG. 18 shows the light distribution characteristics of the exposure light source 3 in this embodiment 2, and FIGS. 19 and 20 show the light distribution correction mechanism using the light shielding plate 44 in this embodiment 2. . 1st
Figure 9 shows the angle at maximum magnification, and Figure 20 shows the angle at minimum magnification.

As a further third embodiment, the following can be considered. In other words, the light distribution of the exposure light source □ after passing through the r lens on the surface of the photoreceptor is one distribution in which the light distribution on the photoconductor surface is uniform without light shielding at an intermediate magnification within the entire magnification range. When the shape projected onto a plane perpendicular to the lens optical axis is at or near the maximum magnification when the light-shielding plate is placed at a certain angle (≠0) to the lens optical axis, ``A shape that makes the light intensity distribution uniform on the photoreceptor surface'' and ``When that surface is placed at a different angle (≠0) to the lens optical axis, the shape is perpendicular to the lens optical axis. A shape that uniformizes the light intensity distribution on the photoreceptor surface when the projected shape is at the minimum magnification or near the minimum magnification.

In other words, this is a combination of the concepts of the first and second embodiments described above, but a new effect is produced when the intermediate magnification includes equal magnification within the variable magnification range. To do this, add the following conditions to the light shielding plate.

That is, the light shielding plate 23.2 of Example 1 shown in FIG.
4 is the shape of the light shielding plates 23' and 24' shown in FIG.
Similarly, the light shielding plate 44 of the second embodiment shown in FIG.
The shape of the light-shielding plate 44' shown in FIG. 22(b) is changed from 2 to 44', which exists only in one direction.

In addition, in the description of Examples 1 and 2, "r" are assumed to be equal, and this angle α is set to α≦90″.

Then, the light shielding plates 23', 24', and 44' having the shapes shown in FIG. 21 (bl) and FIG.
2, so that the angle between them is α,
It is integrally constructed as shown by reference numeral 45 in FIG.

With this configuration, there is only one rotary light shielding member, and the connecting arm 33 in the first embodiment becomes unnecessary. Furthermore, the variation in the overall light amount over the entire zoom range can be made smaller than in the two embodiments described above. This is because, in the case of no light shielding, the total light amount is maximum at the same magnification.

On the other hand, when using this light shielding plate, the amount of light shielding must be the same in the center and the periphery at the same magnification, but in this case, the projected area of the light shielding plate is the maximum, and the decrease in the overall light amount is also the largest. This is because. In this third embodiment as well, the light shielding plate is connected to the photoreceptor 12 of the lens mechanism 10.
It is provided integrally with the lens mechanism 10 on the side.

24(a) and (bl) show the state of the light shielding plate 45 at maximum magnification (1), FIGS. 25(a) and (b) show the state at same magnification, and FIGS. 26(a) and (b) The image is shown at minimum magnification.

〔Effect of the invention〕

As described above, according to the present invention, the entire structure is extremely simple, and the magnification can be varied over a wide range.

It is now possible to perform appropriate light distribution correction, and it is also possible to arrange the light shielding member in an almost appropriate shape in most areas in the longitudinal direction of the cross section of the optical path, which prevents the occurrence of locally high light intensity areas. It disappears. Furthermore, the light from the light source is no longer wasted.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a copying machine to which the present invention is applied, FIG. 2 is a perspective view of a light distribution correction mechanism of Embodiment 1, and FIG. 3 is a diagram of Embodiment 1.
Figure 4 is a front view of the same correction mechanism when maximum light is blocked (at minimum magnification), Figure 5 is an explanatory diagram of the 'cos' θ law', Fig. 6 is an explanatory diagram of the light distribution of the light source of Example 1, Fig. 7 is a specific light distribution characteristic diagram of the light source, and Figs. 9th light intensity distribution characteristic diagram of the photosensitive surface at each magnification in the case of
The figure is an explanatory diagram of light shielding by a light shielding plate, and Figures 10(a) to (C
1 is an explanatory diagram of the shielding of each light flux path in FIG.
The figure is an explanatory diagram for calculating the shape of the light-shielding plate in Example 1, FIG. 12 is a plan view showing the specific shape of the light-shielding plate, and the figures in FIGS. A light intensity distribution characteristic diagram on the photoreceptor surface at each magnification when using a light source with the light distribution shown and correcting the light distribution with a light shielding plate having the shape shown in Figure 12, and Figure 14 shows each magnification when the light distribution is not corrected. FIG. 15 is a characteristic diagram of the light quantity distribution on the photosensitive surface, FIG. 15 is a characteristic diagram of the same light quantity distribution when the light distribution is corrected in the first embodiment, and FIGS. 16 and 17 are variations of the light distribution correction mechanism of the first embodiment. Figure 18 is a light distribution characteristic diagram of the light source of Example 2, Figure 19 is a front view of the light distribution correction mechanism of Example 2 at maximum light shielding (at maximum magnification), and Figure 20 is a diagram of the same arrangement. Front view of the light correction mechanism when no light is blocked (at minimum magnification), 2nd
1 and 22 (a) and (b) are explanatory views of the production of the light shielding plate of Example 3, FIG. 23 is a perspective view of the light shielding plate of Example 3, and FIG. FIG. 25 is a front view showing the angular aspect of the light shielding plate at the minimum magnification, (b) is a side view, and FIG.
bl is a side view, and FIG. [b) is a side view,
FIG. 27 is an explanatory diagram of conventional light shielding. DESCRIPTION OF SYMBOLS 1... Conventional light shielding plate, 2... Optical path, 3... Bar-shaped light source for exposure scanning, 4... Platen glass, 5... Original, 6... Slit plate, 7-9.・・Mirror, 10・
... Lens mechanism, 11... Mirror, 12... Photosensitive drum, 13... Developing section, 14... Paper feeding section, 15...
...Registration roller, 16...Transfer pole, 1
7... Separation electrode, 18... Heat fixing roller, 19...
Paper discharge section, 20...Cleaning section, 21...Charging electrode, 22...Light distribution correction mechanism, 23.24...Example 1
Light shielding plate, 25... Lens holder, 26.27...
Arm, 28.29...axis, 30...lens, 31...
・Lens optical axis, 32...Rotation axis, 33...Connection arm, 34...Cam follower, 35...Arm, 36.
...Cam, 37... Light shielding plate of a modification of Example 1, 38
...Support member, 39...Shaft, 40...Pulley, 4
DESCRIPTION OF SYMBOLS 1... Wire, 42... Light shielding plate of another modification of Example 1, 43... Shaft, 44... Light shielding plate of Example 2, 4
5... Light shielding plate of Example 3. Agent Patent Attorney Tsuneaki Nagao Fig. 1 Fig. 3 Saikai 2 Medi 4 Tokwa,) Yuriq Fig. 4 Kuro Seigo 1 Tsubohiro) Fig. 5 Fig. 7 9f-1 Fig. 8c Figure 8d Figure 89 Figure 8h Figure 10 (a) (b) (C) A-A'
B-B'C-C' Fig. 12 16m -11111 Fig. 139 Fig. 13h Fig. 14 IC() 2C[][~IhJ
i 誼←鴬) Fig. 15 1 mark Zη th4'-Li, IZ+@fL (wx) Fig. 16 Fig. 18 Fig. 23 Fig. 26 E, 11゜ "Procedural amendment 9.." Commissioner of the Patent Office Black □ Akio Tono Show 1″62 Shizuki 2
6E] 1. Indication of the case Patent Application No. 082430 filed in 1982 2. Name of the invention Light distribution correction mechanism 3. Person making the amendment Relationship to the case Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Issue name
Name (127) Konishiroku Photo Industry Co., Ltd. 4, Agent address 3rd floor, Mizuho Daiichi Building, 4-12-1 Ginza, Chuo-ku, Tokyo 4B104 ffi 03-545-8
1506, number of inventions increased by amendment None 7,
Subject of amendment All aspects of the specification Particulars 1, Name of the invention Light distribution correction mechanism 2, Claim (l), A light source that illuminates a document and a slit that regulates the cross-sectional shape of image light from the document In an image projection mechanism, the image projection mechanism includes an optical path regulating member, an image carrier that carries an image provided by the image light, and an imaging lens disposed in an optical path between the document and the image carrier, With respect to an optical path whose cross section is regulated by the optical path regulating member in the shape of a long and narrow slit, the light beam rotates about an axis that intersects the optical axis of the optical path and along the length direction of the optical path cross section, and A light distribution correction mechanism comprising a thin light shielding member whose length in the width direction of the cross section of the optical path changes unevenly at adjacent positions due to rotation. (2) The light distribution on the image carrier after the light source passes through the lens has a light distribution characteristic that is uniform with no light blocking at a certain magnification, and the light blocking member covers the surface thereof. When a predetermined angle is made to the optical axis, the shape projected onto a plane perpendicular to the optical axis is a shape that makes the light distribution on the image carrier uniform at a certain magnification smaller than the above magnification. A light distribution correction mechanism according to claim 1, characterized in that: (3) The light distribution on the image carrier after the light source passes through the lens has a light distribution characteristic that is uniform with no light blocking at a certain magnification, and the light blocking member covers that surface. When a predetermined angle is made to the optical axis, the shape projected onto a plane perpendicular to the optical axis is a shape that makes the light distribution on the image carrier uniform at a certain magnification greater than the magnification. A light distribution correction mechanism according to claim 1, characterized in that: (4) The light distribution on the image carrier after the light source passes through the lens has a light distribution characteristic that is uniform with no light blocking at a certain magnification, and the light blocking member is arranged at a predetermined angle. When one of the planes is made at a certain angle to the optical axis, the shape projected onto a plane perpendicular to the optical axis is projected onto the image carrier at a certain magnification that is greater than the above magnification. When the light distribution is uniform and one other surface has a different angle with respect to the optical axis, the shape projected onto the surface perpendicular to the optical axis is smaller than the above magnification, and the above image is The light distribution correction mechanism according to claim 1, characterized in that the light distribution correction mechanism has a shape that makes the light distribution on the carrier uniform. 3. Detailed Description of the Invention [Field of Industrial Application] The present invention provides light distribution correction 1a applied to a projection mechanism of a copying machine.
Regarding the side. [Prior Art] In the projection mechanism of an electrophotographic copying machine, a lens is indispensable in order to form a projected image on a photoreceptor as an image carrier. However, this lens has 'cos'
There is a characteristic called the law of θ, in which the luminous flux density at an image point off the optical axis decreases in proportion to cos'θ of the luminous flux density at an image point on the optical axis. Therefore, in an electrophotographic copying machine capable of variable magnification, one side of a slit serving as an optical path regulating member is provided so as to be movable toward and away from the optical path to adjust the light distribution, as disclosed in Japanese Patent Application Laid-open No. 52-146630, for example. , or Japanese Patent Publication No. 57-7376
As in Publication No. 7, a light shielding member is provided separately from the slit, and the light distribution is adjusted by allowing the light shielding member to move forward and backward perpendicularly to the lens optical axis. However, in these mechanisms, since the shape of the light shielding member that moves forward and backward with respect to the optical path is constant, it is not possible to perform good light intensity correction for all of the many projection magnifications. If there is a region in which no light shielding plate exists in the cross-sectional longitudinal direction of the optical path (that is, if the amount of light shielding is discontinuous in the longitudinal direction), a portion with a locally high amount of light will be created. Furthermore, as shown in FIG. 27, if the relative positions of the light shielding member 1 and the optical path 2 are shifted in the vertical direction (in the direction of the arrow in the figure), the amount of light shielding changes significantly. Furthermore, when moving from a certain magnification to a lower magnification, the cross-sectional shape of the optical path becomes smaller in both width and length, so the light shielding member must be moved by the amount that has become smaller, and then further moved by the amount necessary for light distribution correction. However, the mechanism becomes complicated. Furthermore, if the reduction magnification is a relatively small value during reduction,
Since the cross-sectional shape of the optical path has become smaller in both width and length, in order to correct the light distribution accurately, the amount of movement of the light shielding member must be more accurate than when it is at the same magnification or magnification. be done. Furthermore, if the light shielding member enters in a straight line, a guide rail or link mechanism with many nodes is required.
The configuration becomes complicated. Furthermore, the conventional light distribution correction mechanism is always in a partially shaded state, which means that the light source emits unnecessary light, which is uneconomical. In addition to the above-mentioned publications, mechanisms with the above-mentioned problems include JP-A-54-136845 and JP-A-57-9234.
8, JP-A-57-154265, JP-A-60-134
There are some proposals in publications such as No. 226 and Japanese Unexamined Patent Publication No. 60-80828. On the other hand, Japanese Utility Model Application Publication No. 57-121953 proposes a device in which a rectangular light-shielding plate is arranged perpendicular to the optical axis, and the light-shielding plate can be rotated in the front-rear direction of the optical axis. There is. This technology has the advantage of not losing much light when not shaded, but since the shape is rectangular,
There is a problem that light distribution correction cannot be performed appropriately. [Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks and to enable sufficient light distribution correction for many projection magnifications with a simple configuration. [Structure of the Invention] To this end, the present invention provides a light source for illuminating the original, an optical path regulating member having a slot 7) for regulating the cross-sectional shape of the image light from the original, and a light path regulating member that carries an image given by the image light. In the image projection mechanism, the image projection mechanism includes an image carrier, and an imaging lens disposed in an optical path between the document and the image carrier, the cross section of which is regulated into a long and thin slit shape by the optical path regulating member. rotates about an axis that is perpendicular to the optical axis of the optical path and along the length direction of the cross-section of the optical path, and due to the rotation, the lengths of the cross-sections of the optical path in the width direction are adjacent to each other. It is constructed by disposing a light shielding member with a thin plate thickness that varies unevenly depending on the position. [Example] Varnish Example 1 The present invention will be described below using an example in which the present invention is applied to an electrophotographic copying machine capable of variable magnification. FIG. 1 is a diagram showing an outline of the copying machine. Light emitted from a bar-shaped (long in the direction perpendicular to the paper surface) light source 3 that exposes and scans in the direction of the arrow X is reflected by the document 5 placed on the platen glass 4, where the reflected light carrying the document image (image light) is emitted. The optical path is changed by the mirrors 7 to 9 via the slit plate 6 as an optical path regulating member, the optical path is further changed by the mirror 11 via the lens mechanism 10 for image formation, and the optical path is changed to the image carrier. The photoreceptor drum 12 forms an electrostatic latent image thereon. The photosensitive drum 12 rotates in the direction of the arrow y in synchronization with the scanning of the light source 3, and the electrostatic latent image is developed with toner in the developing section 13, and the transfer paper fed from the paper feeding section 14 is When the toner image is fed by the registration roller 15 in a timing with the leading edge of the image, the toner image is transferred thereto by the transfer pole 16. The transfer paper is separated from the photoreceptor drum 12 by a separation pole 17, sent to a heat fixing roller 18, where the toner image is fixed, and discharged onto a paper discharge tray 19. 20 is a cleaning section, and 21 is a charging electrode. In this copying machine, when the copying magnification is changed, the lens mechanism 1
In this embodiment, the light source 3 has a unique light distribution characteristic as described later, and the lens mechanism 10 is equipped with a light distribution correction mechanism 22. When the magnification is changed, the light distribution correction mechanism 22 operates to correct the light distribution. As shown in FIG. 2, this light distribution corrector FJI22 has two light shielding plates 23 and 24 made of model-shaped metal plates with a thin plate thickness (for example, 0.4 cranes). Board 23.
The surface of 24 is treated with a matte black finish. These light shielding plates 23 and 24 are connected to arms 26 and 27 that extend from the lens holder 25 of the lens mechanism 10 at angular intervals of 180 degrees.
are rotatably mounted by shafts 28, 29, the tips of which are spaced apart and facing each other. The center of rotation is an axis 32 that is perpendicular to the optical axis 31 of the lens 30 of the lens mechanism 10 and parallel to the central axis of the slit in the slit plate 6 in the longitudinal direction (direction perpendicular to the paper surface). The light shielding plates 23 and 24 are connected by a connecting arm 33 so that both of them rotate in conjunction with each other, and a cam follower 33 is attached to the tip.
It is also connected to an arm 35 to which a is attached. 3
6 is a cam fixed to the main body of the copying machine, and its cam surface 3
The cam follower 34 is always in contact with the cam follower 6a. Therefore, the lens mechanism 10 is aligned with the optical axis 31 for zooming.
33.3, the cam action causes the arm 33.3 to move along the
5 rotates, the inclination angle of the light shielding plates 23 and 24 changes, and the shape projected onto a plane perpendicular to the optical axis 31 changes. Then, the light shielding plates 23 and 24 are placed so that their surfaces are aligned with the optical axis 31 of the optical path 1.
When the light beam is rotated perpendicularly to the light beam, as shown in FIG. 3, the light beams on both sides of the optical path 1 are mainly blocked. Moreover, when the surface is rotated so that it becomes parallel to the optical axis, it becomes as shown in FIG.
hardly blocks the luminous flux. Regarding the light distribution of the source, the above-mentioned 'cos' θ law' will be explained first. FIG. 5 is a diagram for explaining this, in which an image of the original 5 is formed by a lens 30 located at a distance a from the original 5 on a photoreceptor 12 located at a distance from the lens 30. In this case, point A on the original 5 (point on the optical axis 31)
Compared to the amount of light at point A' on the photoreceptor 12 on which the light is projected,
The amount of light at point B' on the photoreceptor 12 on which the same light at point B, which is distant from the optical axis 31 of the original 5, is projected is as follows: If the angle of incidence from point B to the lens 30 with respect to the optical axis 31 of the lens 30 is θ, then ,
It becomes cos'θ (×1) times. In other words, point B is optical axis 3
1, the amount of light projected onto the photoreceptor 12 at point B' decreases in proportion to cos'θ. Note that the distance glta, b is a = f (1+ 1 /m) − where f is the focal length of the lens 4 and m is the magnification.
(11b=f (1+m)...
・Given by (2). Therefore, in this embodiment, the light distribution of the light source 3 (optically equivalent to the original 5) is adjusted to the photoreceptor 12 after passing through the r lens 30.
The light amount distribution above is set to be uniform (flat) with no light shielding under a certain magnification condition. here,
``For a certain magnification j, select the maximum value of the variable magnification range of the copying machine.As mentioned above, the distance flda between the original 5 and the lens 30
is given by equation (1), which becomes smaller as the magnification m increases, indicating that the lens 30 is closest to the document 5 side at the maximum magnification. Therefore, the angle θ at this time becomes the largest, and the decrease in the amount of peripheral light due to the above-mentioned 'cos' law j becomes most noticeable at this maximum magnification. Therefore, if the light distribution of the light source 3 is set so that at this maximum magnification, the amount of light in the periphery away from the optical axis 31 of the photoreceptor 12 without light shielding is a necessary and sufficient amount of light, then if the magnification is lowered, the amount of light will be the same. Since the amount of light at the periphery only shows a tendency to increase, the increased amount is blocked by the light shielding plates 23 and 24 and corrected to the same level as the amount of light at the optical axis 31 portion, thereby adjusting the light amount distribution characteristics on the surface of the photoreceptor 12. It is better to make it flat. An example of the light distribution set as described above is shown in FIG. The curve Q is the light distribution characteristic of the light source 3 (original 5) (symmetrical to the optical axis 31), and the straight line R is the light amount distribution characteristic of the photoreceptor 12. A light distribution that minimizes the amount of light emitted from the center of the optical axis 31 of the light source 3 (provided that a sufficient amount of light can be obtained at the optical axis portion of the photoreceptor 12), and increases the amount of light emitted from there toward the outside. Due to this characteristic, the amount of light on the surface of the photoreceptor 12 is constant regardless of the distance from the optical axis 31 (within a predetermined range). The inventor has determined that the photoreceptor 12 at a magnification m = 1.55
A light source 3 having the characteristics of the light distribution shown in Figure 7, which is flat at The light amount distribution characteristics on the surface of the photoreceptor 12 were simulated. The results are shown in Figures 8a-8. At any magnification, the amount of peripheral light is higher than the amount of light at the center. As shown in FIGS. 8a to 8 described above regarding the shape of the shielding plate, the rate of increase in the amount of peripheral light relative to the amount of light at the center is greatest at the minimum magnification. Therefore, the amount of light shielded by the light shielding plates 23 and 24 installed on the photoreceptor 12 side of the lens 3° needs to be the maximum amount at this minimum magnification. In this embodiment, the light shielding plate 23.2 is placed in the direction perpendicular to the optical axis 31.
4, and the light shielding plate is rotated in the front and back direction of the optical axis 31, so that effective light shielding is achieved by the shape projected onto a plane perpendicular to the optical axis 31, as described above. Therefore, the angle that the surfaces of the light shielding plates 23 and 24 make with respect to the optical axis 31 also becomes maximum at the minimum magnification. If this angle is α, then 0〈α≦90''.Therefore, the shape of the light shielding plates 23 and 24 is ``When the surface is placed at a certain angle (≠O) to the optical axis of the lens, the light A shape that flattens the light distribution on the photosensitive surface when the shape projected onto a plane perpendicular to the axis is at a certain magnification smaller than the magnification determined by the light source conditions. Here, the minimum magnification is selected from the variable magnification range of the copying machine. For example, when setting the magnification m=0.5 as the minimum magnification, the light shielding plate is placed so that its surface is orthogonal to the optical axis 31 (9
0') When arranged at an angle α, the light distribution on the surface of the photoreceptor 12 is flat. This shape can be easily determined using a computer. That is, for a light flux incident on the optical axis 31 at an angle θ, the area occupied in the light flux at the shading tJi 23.24 is determined so that the light flux density is approximately the same as the light flux density of the light flux passing through the optical axis. do it. In FIG. 9, the light shielding plate 2
3.24 is a diagonal line that does not block the light beam on the path A→A' passing through the optical axis 31 (Fig. 1O (a)), but slightly blocks the light beam on the path B, →B' (color in Fig. 10). part), and the light beam along the path c-c' is largely blocked (the shaded part in FIG. 10(C)). In other words, the amount of light shielding in the peripheral area is large. The angle θ changes depending on the position of the lens 30, that is, the magnification, and the passing position of the light beam on the light shielding plates 23 and 24 changes depending on the value of θ, so starting from θ = 0'' (no light shielding plate), the value of θ is determined. All you have to do is find the width of the light shielding plate that increases little by little so that the amount of light on the surface of the photoreceptor 12 is the same as that of θ = 0°. The required magnification is the minimum, and the size of the surface of the original 5 or photoreceptor 12 is limited.Therefore, the shape of the light-shielding plate determined by the above method has a narrow range of θ that is effective only at this magnification. Although it may be thought that the size of the original or photosensitive surface is much larger than the actual size, when calculating the shape, calculate the value of θ corresponding to the maximum angle of view at the maximum magnification. (See Fig. 11).Of course, it is assumed that the light distribution of the light source is also continuous within this range. Fig. 12 is a diagram showing the planar shape of the light shielding plates 23 and 24 determined as described above. Using the light shielding plate shown in Fig. 12, we simulated the light distribution correction by giving a predetermined angle at each magnification. Figs. The maximum magnification showing the characteristics is m = 1.55. From the above, in a copying machine equipped with the exposure light source 3 and the light shielding plate 23.24, at the maximum magnification, the surface of the light shielding plate 23.24 is aligned with the lens optical axis. If you make it parallel to 31 and make the amount of light shielding almost zero,
The light distribution on the surface of the photoreceptor 12 becomes almost flat, and at the minimum magnification, if the angle between the surface of the light shielding plate 23, 24 and the optical axis 31 is set to the above α (90° in this embodiment). , the light amount distribution on the surface of the photoreceptor 12 at this magnification is also approximately flat. At each magnification between the maximum and minimum, the cam 36
By appropriately setting the shape of the cam surface 36a of the light shielding plate 23.2,
By appropriately selecting the angle α between 4 and the optical axis 31,
As shown in FIGS. 13a to 13, a substantially uniform light amount distribution can be obtained over the entire magnification. Further, this angle α has the maximum amount of light shielding at the minimum magnification, and as the magnification increases, the amount of light shielding gradually decreases, and although there is some variation at any magnification, the light amount distribution is almost flat. In this first embodiment, in order to emphasize theoretical rigor, the maximum value of the variable magnification range of the copying machine is
Match the magnification so that the light distribution at the top is uniform without shading,
Further, the minimum value of the variable magnification range is set to a magnification at which the amount of light shielded by the light shielding plates 23 and 24 is maximum and the light distribution on the photoreceptor 12 is uniform. As long as the magnification range of the copying machine is within this range, by appropriately selecting the angle between the light shielding plates 23 and 24 and the optical axis 31, uniform light distribution can be achieved on the photoreceptor at any magnification within the range. distribution is obtained. However, from a practical point of view, there is a certain tolerance.For example, the maximum magnification is set to be slightly higher than the magnification at which the light distribution on the photoreceptor by the light source is uniform without light shielding, and the light shielding plate 2 The same effect can be obtained even if the magnification is slightly lower than the magnification at which the amount of light shielding is maximum by .24 and the light distribution on the photoreceptor 12 is uniform. That is, the light distribution of the light source is set to one condition such that the light distribution on the surface of the photoreceptor after passing through the r lens is uniform with no light blocking at a certain magnification, and the shape of the light blocking plate is rWhen the surface is placed at a certain angle (≠0) to the lens optical axis, the light intensity distribution on the photosensitive surface when the shape projected onto the plane perpendicular to the optical axis has a magnification smaller than the above certain magnification. It is sufficient that the magnification range approximately included in this range is set as the magnification range of the copying machine. In this result, the variation in the light intensity distribution is a little thick (although it may become so, it has almost no effect in practice.) From the above, the overall configuration is extremely simple, and it can be used over a wide range of magnification changes. It is possible to perform sufficient light amount correction.Even if the optical path 1 changes up and down a little as shown in Figure 3, the amount of light shielded at each position in the longitudinal direction of the optical path cross section hardly changes, so it is not affected much. There is no light shielding plate 2 in most of the longitudinal direction of the cross section of the optical path l.
3.24 can be made to exist in a substantially appropriate shape, so there will be no localized region with a high amount of light. This is especially advantageous when the width of the optical path 1 becomes narrow during reduction. Further, the light shielding member does not move unnecessarily. Also, during reduction, especially when the reduction magnification is relatively small, the angle between the plane of the light shielding plate and the optical axis of the lens becomes close to a right angle. Therefore, if the precision of the shape of the light shielding plate is good, this angle Even if there is some variation, the area occupied by the light shielding plate in the optical path is not affected much, that is, when the reduction magnification is small, highly accurate light distribution correction can be performed. When the image is at the same magnification or enlarged, the area that is blocked is extremely small, so the light from the light source is not unnecessarily blocked. As a result, when light distribution correction is not performed, as shown in Figure 14, when the reduction is 0.5 times, there is a difference in light amount of more than 20% between the optical axis vicinity and the peripheral area, but the above As a result of the correction, the difference in light amount was within 1% as shown in FIG. Further, the variation in the amount of light throughout the entire magnification (Xo, 5 to 1.55) was about 10%, which did not pose a practical problem. As shown by the broken line in FIG. 15, when the light intensity of the light source was increased during reduction, the variation in light intensity throughout all magnifications could be suppressed to 5% or less. Examples 1 and 5 In the above-described embodiments, the light shielding plates 23 and 24 move together with the lens 30, but as shown in FIG. is attached to the support member 38 fixed to the copying machine main body, and the light shielding plate 37
A pulley 40 is attached to the shaft 39 of the
0 can be connected to the lens mechanism 10 by a wire 41, and the light shielding plate 37 can be rotated as the lens mechanism 10 moves, thereby correcting the light distribution. Further, the shaft 39 is configured to be able to be driven by a motor or the like,
The inclination angle of the light shielding plate 37 can also be adjusted by rotating the shaft 39 in accordance with the magnification change. Furthermore, the light shielding plate 3 shown here
7 is one piece, but if this is done, the above-mentioned connecting arm 33 becomes unnecessary. Further, the rotation axis of the light shielding plate does not necessarily need to be orthogonal to the optical axis of the lens. Furthermore, as shown in FIG. 17, the rotation center axis 43 of the light shielding plate 42 does not need to be above the light shielding plate 42, and the shape of the light shielding plate 42 does not necessarily have to be symmetrical, especially on one side. In a standard copying machine or the like, it is preferable to make it asymmetrical in the longitudinal direction. Further, the position of the light shielding member does not necessarily need to be between the lens and the photoreceptor, and the same effect can be obtained even if it is placed between the document and the lens. (b), Embodiment 2 As another embodiment when applied to a copying machine, the following is also possible. That is, it is assumed that the light distribution of the exposure light source that illuminates the original is such that the light distribution on the surface of the photoreceptor after passing through the r lens is uniform with no light shielding at a certain magnification, and the light shielding plate The shape of r is set at a certain angle (
≠0), the shape projected onto a plane perpendicular to the lens optical axis can be set to a shape that makes the light distribution on the photoreceptor surface uniform when the magnification is larger than the above magnification. It is. This is the opposite of the case of Example 1 above, and if an exposure light source with no shading and uniform light distribution on the photoreceptor surface is used at a certain magnification, the amount of light in the periphery will be reduced at a higher magnification. It gets lower as it goes. In other words, the amount of light at the center of the optical axis becomes higher than the amount of light at the periphery. Therefore, as the magnification increases, the amount of light at the center, which has become relatively high, is reduced. In this case, the shape of the light shielding plate differs from the above case in that it is wide at the center and narrows toward the periphery. Then, at a certain magnification greater than the above magnification, an angle α is formed with respect to the optical axis that provides the maximum amount of light shielding, and as the magnification decreases, the amount of light shielding decreases. FIG. 18 shows the light distribution characteristics of the exposure light source 3 in this embodiment 2, and FIGS. 19 and 20 show the light distribution correction mechanism using the light shielding plate 44 in this embodiment 2. . 1st
FIG. 9 shows the angle at maximum light shielding, and FIG. 20 shows the angle state at no light shielding. As a further third embodiment of the non-dog owner, the following can be considered. In other words, the light distribution of the exposure light source is set to ``one distribution in which the light distribution on the photoreceptor surface after passing through the lens is uniform with no light blocking at a certain magnification, and the light blocking member is set on multiple surfaces. , one surface of T is at a certain angle (≠0
), the shape projected onto a plane perpendicular to the optical axis of the lens is a shape that uniformizes the light intensity distribution on the photoreceptor surface at a certain magnification greater than the above magnification, and is placed at a different angle (≠0) to the lens optical axis, and the light intensity distribution on the photoreceptor surface is uniform when the shape projected onto a plane perpendicular to the lens optical axis has a certain magnification smaller than the above magnification. It will be set up so that it has both of the following: In other words, this is a combination of the concepts of the first and second embodiments described above, but a new effect is produced when the intermediate magnification includes equal magnification within the variable magnification range. To do this, add the following conditions to the light shielding plate. That is, the light shielding plate 23.2 of Example 1 shown in FIG. 21(a)
The shapes of the light shielding plates 23' and 24' shown in FIG. 21 (hl) exist only in one direction from the rotational center axis 32, and the light shielding plates 44 of the second embodiment shown in FIG. The light shielding plate 44' is deformed into the shape of the light shielding plate 44' shown in FIG. Note that "a certain angle" in the description of the first embodiment and the second embodiment is assumed to be the same, and this angle α is assumed to be α≦90°. Then, the light-shielding plates 23', 24', and 44' having the shapes shown in FIG.
match, and the second
It is integrally constructed as shown by the reference numeral 45 in FIG. With this configuration, there is only one rotary light shielding member, and the connecting arm 33 in the first embodiment becomes unnecessary. Furthermore, the variation in the overall light amount over the entire zoom range can be made smaller than in the two embodiments described above. This is because, in the case of no light shielding, the total light amount is maximum at the same magnification. On the other hand, when using this light shielding plate, the amount of light shielding must be the same in the center and the periphery at the same magnification, but in this case, the projected area of this light shielding plate is the maximum, and the decrease in the overall light amount is also the largest. This is because. 24(a) and 24(b) show the appearance of the light shielding plate 45 when the amount of light blocking on the enlarged side is at its maximum, FIGS. (b) shows the state when the amount of light shielding on the reduction side is at its maximum. [Effects of the Invention] As described above, according to the present invention, the entire structure is extremely simple, and the magnification can be sufficiently changed over a wide range of changes. It becomes possible to perform light distribution correction, and furthermore, it becomes possible to arrange the light-shielding member in a substantially appropriate shape in most regions in the longitudinal direction of the cross section of the optical path, so that regions with a locally high amount of light do not occur. Furthermore, the light from the light source is not wasted. 4. Brief description of the drawings Fig. 1 is a schematic configuration diagram of a copying machine to which the present invention is applied, and Fig. 2 is a perspective view of the light distribution correction mechanism of Embodiment 1. Figure 3 is Example 1
Figure 4 is a front view of the correction mechanism when maximum light is blocked (at minimum magnification), Figure 4 is a front view of the same correction mechanism when no light is shielded (at maximum magnification), and Figure 5 is '
An explanatory diagram of the law j of cos'θ, FIG. 6 is an explanatory diagram of the light distribution of the light source of Example 1, FIG. 7 is a specific diagram of the light distribution characteristic of the light source, and FIGS. The figure is a characteristic diagram of the light intensity distribution on the photosensitive surface at each magnification when the light source shown in Figure 7 is used, Figure 9 is an explanatory diagram of light shielding by a light shielding plate, and Figures 10 (a) to (e).
is an explanatory diagram of the shading of each light beam path in FIG. 9, FIG. 11 is an explanatory diagram for calculating the shape of the shading plate in Example 1, and FIG. 12 is a plane showing the specific shape of the shading plate. figure,
Figures 13a to 13 are light intensity distribution characteristic diagrams on the photoreceptor surface at each magnification when a light source with the light distribution shown in Figure 7 is used and the light distribution is corrected by a light shielding plate having the shape shown in Figure 12. , 1st
Figure 4 is a characteristic diagram of the light quantity distribution on the photosensitive surface at each magnification without light distribution correction, Figure 15 is the same light quantity distribution characteristic diagram when light distribution is corrected in Example 1, and Figures 16 and 17 are the characteristic diagrams after implementation. A diagram showing a modification of the light distribution correction mechanism of Example 1, FIG. 18 is a light distribution characteristic diagram of the light source of Example 2, and FIG. 19 is a front view of the light distribution correction mechanism of Example 2 at maximum light shielding. FIG. 20 is a front view of the same light distribution correction mechanism when no light is blocked, FIGS. 21 and 22 (a) and (bl are explanatory diagrams of the fabrication of the light shielding plate of Example 3, and FIG. 23 is Example 3)
FIG. 24(a) is a perspective view of the light shielding plate of Example 3, FIG.
is a side view, FIG. 25(a) is a front view showing the angular aspect of the light shielding plate at the same magnification in Example 3, FIG. 26(b) is a side view, and FIG. 26+
a) is a front view showing the angular aspect of the light shielding plate when the amount of light shielding on the enlarged side is maximum in Example 3, FIG. 27 is a side view, and FIG. 27 is an explanatory diagram of conventional light shielding. DESCRIPTION OF SYMBOLS 1... Conventional light shielding plate, 2... Optical path, 3... Bar-shaped light source for exposure scanning, 4... Platen glass, 5... Original, 6... Slit plate, 7-9.・・Mirror, 10・
... Lens mechanism, 11... Mirror, 12... Photosensitive drum, 13... Developing section, 14... Paper feeding section, 15...
...Registration roller, 16...Transfer pole, 1
7... Separation electrode, 18... Heat fixing roller, 19...
Paper discharge section, 20...Cleaning section, 21...Charging electrode, 22...Light distribution correction mechanism, 23.24...Light blocking plate of Example 1, 25...Lens holder, 26. 27...
・Arm, 28.29...axis, 30...lens, 31・
... Lens optical axis, 32 ... Rotation axis 33 ... Connection arm, 34 ... Cam follower, 35 ... Arm, 36
... Cam, 37 ... Light shielding plate of a modification of Example 1, 3
8... Support member, 39... Shaft, 40... Pulley,
41... Wire, 42... Light shielding plate of another modification of Example 1, 43... Shaft, 44... Light shielding plate of Example 2,
45... Light shielding plate of Example 3.

Claims (4)

[Claims] (1) a light source that illuminates the original, an optical path regulating member having a slit that regulates the cross-sectional shape of the image light from the original, an image carrier that carries an image given by the image light, the original and the above; In an image projection mechanism having an imaging lens disposed in an optical path between the image carrier and the image carrier, the light of the optical path is regulated by the optical path regulating member to have a long and thin slit-like cross section. A thin light shielding member that rotates about an axis in a direction intersecting the axis and along the length direction of the optical path, and whose length in the width direction of the optical path changes unevenly at adjacent positions due to the rotation. A light distribution correction mechanism characterized in that it is configured by being deployed. (2) the light shielding member is disposed in the optical path between the lens and the image carrier, and the light distribution on the image carrier after the light source passes through the lens is at or near a maximum; When the light shielding plate has a uniform light distribution characteristic with no light blocking at a magnification of 2. The light distribution correcting mechanism according to claim 1, wherein the light distribution correction mechanism has a shape that makes the light distribution on the image carrier uniform at a magnification of or near the magnification. (3) the light shielding member is disposed on the optical path between the lens and the image carrier, and the light distribution on the image carrier after the light source passes through the lens is at or near a minimum; When the light shielding plate has a uniform light distribution characteristic with no light blocking at a magnification of 2. The light distribution correcting mechanism according to claim 1, wherein the light distribution correction mechanism has a shape that makes the light distribution on the image carrier uniform at a magnification of or near the magnification. (4) The light shielding member is disposed in the optical path between the lens and the image carrier, and the light distribution on the image carrier after the light source passes through the lens is within the entire magnification range. It has a light distribution characteristic that is uniform with no light blocking at an intermediate magnification within When the projected shape has a uniform light distribution on the image carrier at a maximum magnification or a magnification close to the maximum magnification, and when the surface has a different angle to the optical axis, it becomes a surface perpendicular to the optical axis. 2. The light distribution correction mechanism according to claim 1, wherein the projected shape is a shape that makes the light distribution on the image carrier uniform at a minimum magnification or a magnification close to the minimum magnification.