JPH07122730B2 - Variable magnification image forming device - Google Patents

Description

The present invention relates to a variable magnification image forming apparatus having a light distribution correction mechanism.

[Prior art]

In a projection mechanism of an electrophotographic copying machine, a lens is indispensable for forming a projected image on a photoconductor as an image carrier. However, this lens has a characteristic of “law of cos ⁴ θ” that “the luminous flux density at an image point outside the optical axis decreases in proportion to cos ⁴ θ of the luminous flux density at the image point on the optical axis”.

Therefore, in a variable-magnification electrophotographic copying machine, one side of a slit as an optical path regulating member is provided so as to advance and retreat with respect to the optical path, as in JP-A-52-146630, for example, to adjust the light distribution. Or, as in JP-A-57-73767,
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 optical axis of the lens.

However, in these mechanisms, since the shape of the light blocking 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, when there is a region where the light shielding plate does not exist in the longitudinal direction of the cross section of the optical path formed by the slit (that is, when the light shielding amount is discontinuous in the longitudinal direction), a locally high light amount portion is generated.

Further, as shown in FIG. 27, when the relative position between the light shielding member 1 and the optical path 2 is displaced in the vertical direction (the arrow direction in the figure),
The amount of shading changes significantly.

Furthermore, when the magnification is changed from a certain magnification to a lower magnification, the cross-sectional shape of the optical path becomes smaller in both width and length.Therefore, the light-shielding member must be moved by the smaller amount and then moved by an amount necessary for light distribution correction. It has to be complicated and its mechanism is complicated.

Furthermore, when the reduction ratio is a relatively small value during reduction,
Since the cross-sectional shape of the optical path is small in both width and length, in order to perform appropriate light distribution correction for this, the movement amount of the light shielding member is required to have higher accuracy than in the case of equal magnification or enlargement. .

Furthermore, if the light-shielding member enters linearly, a guide rail and a link mechanism with many nodes are required,
The configuration becomes complicated.

Further, since the conventional light distribution correction mechanism is always in the partial light shielding state, the light source emits useless light, which is uneconomical.

As a mechanism having the above problems, in addition to the above publications, JP-A-54-136845, JP-A-57-92348, and JP-A-57-1542
65, JP-A-60-134226, JP-A-60-80828 and the like.

On the other hand, Japanese Utility Model Application Laid-Open No. 57-121953 proposes a rectangular shading plate disposed so as to be orthogonal to the optical axis so that the shading plate can rotate in the front-back direction of the optical axis. There is. This technique has an advantage in that the light amount is hardly lost when the light is not shielded, but since the shape is rectangular, there is a problem that the light distribution correction cannot be properly performed.

Furthermore, in JP-A-56-6272, a light-shielding member is arranged between the lens and the slit, and the light-shielding member is moved or rotated in association with the movement of the lens, if necessary. A light correction is proposed. According to this technique, it is possible to correct the change in the amount of light in the lens scanning direction caused by the lens scanning due to the lens characteristics.

However, this technique is not based on the slit exposure method in which the light distribution is changed in the slit longitudinal direction,
Even if this technique is applied to the slit exposure method, it is not possible to perform correction in the slit longitudinal direction, and in particular, when performing variable-magnification copying using a light source having a light amount distribution, it cannot be dealt with at all. .

[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 Invention]

The object is to provide a light source for illuminating a document, an optical path regulating member for regulating the cross section of the reflected light from the document into an elongated shape, and an optical axis for forming an image of the reflected light regulated by the optical path regulating member. In a variable-magnification image forming apparatus having an image forming unit having the image forming unit and an image carrier for carrying an image formed by the image forming unit, a part of the light flux in the regulated optical path regulated by the optical path regulating member is There is a light flux regulating plate for regulating, and the light flux regulating plate is always arranged in a region inside the cross section in the lateral direction of the cross section perpendicular to the optical axis of the regulated optical path, and the image carrier. In order to make the light amount distribution in the longitudinal direction of the cross section substantially uniform, the cross sectional lengths in the lateral direction are different in the longitudinal direction of the cross section, and the image forming magnification With the change,
This is achieved by a variable-magnification image forming apparatus characterized by rotating about the longitudinal direction of the cross section as a rotation center.

〔Example〕

(A). Embodiment 1 An embodiment in which the present invention is applied to a variable magnification electrophotographic copying machine will be described below. FIG. 1 is a diagram showing an outline of the copying machine. Light emitted from a rod-shaped (long in the direction perpendicular to the paper surface) light source 3 that exposes and scans in the direction of arrow x is reflected by a document 5 placed on a platen glass 4, and reflected light (image light) carrying a document image there. Changes the optical path with the mirrors 7 to 9 through the slit plate 6 serving as the optical path restricting member, the diameter of the image forming lens mechanism 10 is changed, and the optical path is further changed with the mirror 11 so that the photosensitive member as the image carrier is exposed. It is guided to the drum 12 and forms an electrostatic latent image there.

The photosensitive drum 12 is rotating in the direction of arrow y in synchronization with the scanning of the light source 3, and the electrostatic latent image is toner-developed by the developing unit 13, and the transfer paper fed from the paper feeding unit 14 is transferred. When the registration roller 15 feeds the image at the timing of the front end of the image, the transfer electrode 16 transfers the toner image thereto. Then, this transfer paper is separated from the photoconductor drum 12 by the separation pole 17, is sent to the heat fixing roller 18, the toner image is fixed, and is discharged to the paper discharge tray 19. Reference numeral 20 is a cleaning unit, and 2 is a charging electrode.

In this copier, changing the copy magnification causes the lens mechanism 10
And the mirrors 8 and 9 move to the proper positions. In this embodiment, the light source 3 has a unique light distribution distribution characteristic as will be described later, and the lens mechanism 10 is provided with a light distribution correction mechanism 22. When the magnification is changed, the light distribution correction mechanism 22 The light distribution is corrected by operating.

As shown in FIG. 2, the light distribution correction mechanism 22 has two light shielding plates 23 and 24, which are thin metal plate (for example, 0.4 mm) wedge-shaped metal plates, as optical path control plates. , Those shading plates
The surfaces of 23 and 24 are matt black treated.
These light shielding plates 23 and 24 are lens holders of the lens mechanism 10.
Arms 26 and 27 extending at an angle interval of 25 to 180 degrees are rotatably attached by shafts 28 and 29, and their tips are opposed to each other. The center of rotation is the lens mechanism.
The axis 32 is perpendicular to the optical axis 31 of the lens 30 and parallel to the central axis of the slit of 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 also connected to an arm 35 having a cam follower 34 attached to the tip thereof. 36 is a cam fixed to the main body of the copying machine,
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 cam action causes the arm 33,
Since 35 rotates, the inclination angles of the light shielding plates 23 and 24 change,
The shape projected on the plane orthogonal to the optical axis 31 changes.

When the light shielding plates 23 and 24 are rotated so that their surfaces are orthogonal to the optical axis 31 of the optical path 1, the light beams on both sides of the optical path 1 are mainly shielded as shown in FIG. . When the surface is rotated so as to be parallel to the optical axis, the result is as shown in FIG. 4, and the thin light shielding plates 23 and 24 hardly block the light flux.

Regarding Light Distribution of Light Source First, the above-mentioned “law of cos ⁴ θ” will be described. FIG. 5 is a diagram for explaining that, so that the image of the original 5 is formed on the photoconductor 12 separated by the distance b from the lens 30 by the lens 30 located at the distance a from the original 5. In this case, the light amount at the point A (point on the optical axis 31) of the original 5 is compared with the light amount at the point A ′ of the photoconductor 12 onto which the optical axis 31 of the original 5 is projected.
The amount of light at the point B ′ of the photoconductor 12 that projects the same light at the point B distant from is cos ⁴ θ (< 1) Double.
That is, as the point B moves away from the optical axis 31, the amount of light at the point B ′ projected on the photoconductor 12 decreases in proportion to cos ⁴ θ.

The distances a and b are f, the focal length of the lens 4, and m, the magnification.
Then, a = f (1 + 1 / m) (1) b = f (1 + m) (2)

Therefore, in this embodiment, when the light distribution of the light source 3 (optically equivalent to the original 5) is "a light amount distribution on the photoconductor 12 after passing through the lens 30 is under a certain magnification condition, no light shielding is performed. To be uniform (flat) ”. here,
Select the maximum value of the zoom range of the copier for "A certain magnification".

As described above, the distance a between the original 5 and the lens 30 is given by the equation (1), but this equation becomes smaller as the magnification m increases, and the lens 30 is closest to the original 5 side at the maximum magnification. Show. Therefore, the angle θ at this time becomes the largest, and the decrease in the peripheral light amount due to the “law of cos ⁴ θ” described above becomes the most remarkable at this maximum magnification.

Therefore, at this maximum magnification, the optical axis of the photoconductor 12 is not shaded.
So that the peripheral light quantity away from 31 becomes the necessary and sufficient light quantity,
When the light distribution of the light source 3 is set, the peripheral light amount tends to increase only when the magnification is decreased. Therefore, the increased amount is shielded by the light shielding plates 23 and 24, and the light amount of the optical axis 31 is reduced. It is sufficient to make the light amount distribution characteristic of the surface of the photoconductor 12 flat by performing correction to the same degree as.

FIG. 6 shows an example of the light distribution distribution set as described above. The curve Q indicates the light distribution distribution characteristic of the light source 3 (original 5) (optical axis
It becomes symmetrical to 31. ), The straight line R is the light amount distribution characteristic of the photoconductor 12. A light distribution in which the amount of light emitted from the center of the optical axis 31 of the light source 3 is minimized (however, a value sufficient for the optical axis of the photoconductor 12 can be obtained), and the amount of emitted light is increased further from there. Due to the characteristics, the amount of light on the surface of the photoconductor 12 is constant regardless of the distance (within a predetermined range) from the optical axis 31.

The inventor has found that the light source 3 having a light distribution having the characteristic shown in FIG.
Was used and the magnification was changed from m = 0.5 to 1.5 in steps of 0.1 to simulate the light amount distribution characteristic on the surface of the photoconductor 12 when no light shielding was performed. The results are shown in Figures 8a to 8k.
Shown in the figure. At any magnification, the peripheral light amount is higher than the central light amount.

Regarding the shape of the light shielding plate As shown in FIGS. 8a to 8k described above, the increase rate of the peripheral light amount with respect to the central light amount is the largest at the minimum magnification. Therefore, the amount of light shielded by the light shielding plates 23 and 24 installed on the side of the lens 12 of the photoconductor 12 must be the maximum amount at the minimum magnification.

In this embodiment, the light blocking plates 23 and 24 are arranged in the direction orthogonal to the optical axis 31, and the light blocking plate is rotated in the front-back direction of the optical axis 31,
As described above, the effective light blocking is performed by the shape projected on the plane perpendicular to the optical axis 31.

Therefore, the angle formed by the surfaces of the light shielding plates 23 and 24 with respect to the optical axis 31 also becomes maximum at the minimum magnification. When this angle is α, 0 <α ≦ 90 °. Therefore, the shape of the light shielding plates 23 and 24 is "the surface is at an angle (≠ 0) with respect to the lens optical axis.
, The shape projected on a plane perpendicular to the optical axis makes the light distribution distribution on the photosensitive surface flat at a certain magnification smaller than the magnification that defines the condition of the light source. Here, the minimum magnification is selected from the variable magnification range of the copying machine.

For example, when the minimum magnification is set to m = 0.5, the surface of the light shield plate is orthogonal to the optical axis 31 (90 °) at the minimum magnification.
When arranged at the angle α, the light distribution on the surface of the photoconductor 12 is flat.

This shape can be easily obtained by using a computer. That is, with respect to a light beam incident on the optical axis 31 at an angle θ, the area occupied by the light beams in the light shielding plates 23 and 24 is set so that the light beam density becomes approximately the same as the light beam density of the light beam passing through the optical axis. Just decide. In FIG. 9, the shading plates 23 and 24 are the optical axes.
The light flux on the path A → A ′ passing through 31 is not blocked (first
10 (a)), the light flux of the path B → B ′ is slightly shielded (hatched portion in FIG. 10 (b)), and the light flux of the path C → C ′ is significantly shielded (shaded line in FIG. 10 (c)). Section). That is, the amount of shading increases toward the periphery.

The angle θ changes depending on the distance from the optical axis, and the passing position of the light flux on the light blocking plates 23 and 24 changes depending on the value of θ, so the value of θ gradually increases starting from θ = 0 ° (no light blocking plate). The value of the width of the light shielding plate may be calculated so that the light amount on the surface of the photoconductor 12 increases and becomes equal to that of the case where θ = 0 °.

Now, here, the magnification for obtaining the shapes of the light shielding plates 23 and 24 is the minimum, and the size of the surface of the original 5 or the photoconductor 12 is limited. Therefore, the shape of the shading plate obtained by the above method is
It may be considered that the range of θ that is effective only at this magnification is narrow, but in determining the shape, assuming that the size of the original or photosensitive surface is much larger than the actual size, Calculate up to the θ value corresponding to the maximum angle of view (see Fig. 11). Of course, it is assumed that the light distribution of the light source is continuous up to this range.

FIG. 12 is a diagram showing the planar shapes of the light shielding plates 23 and 24 determined as described above. Since the light shielding plate shown in FIG. 12 was used to simulate the light distribution correction by giving a predetermined angle at each magnification, FIGS. 13a to 13k show the resulting photoconductors.
The light intensity distribution characteristics of 12 surfaces are shown. The maximum magnification is m = 1.55.

From the above, in the copying machine provided with the exposure light source 3 and the light shielding plates 23 and 24, at the maximum magnification, if the surfaces of the light shielding plates 23 and 24 are parallel to the lens optical axis 31 and the light shielding amount is substantially zero, the exposure is performed. The light distribution on the surface of the body 12 is almost flat, and at the minimum magnification, if the angle formed by the surfaces of the light shielding plates 23 and 24 and the optical axis 31 is set to α (90 ° in this embodiment), The light amount distribution on the surface of the photoconductor 12 at this magnification is also substantially flat.

At each magnification between maximum and minimum, the cam 36
By properly setting the shape of the cam surface 36a of the above and appropriately selecting the angle α formed by the light shielding plates 23 and 24 and the optical axis 31, as shown in FIGS. It is possible to obtain a substantially uniform light amount distribution. Further, this angle α has the maximum light-shielding amount at the minimum magnification, and the light-shielding amount gradually decreases as the magnification increases, and the light amount distribution becomes almost flat although there is some variation at any magnification.

In the first embodiment, in order to theoretically emphasize the rigor, the maximum value of the zooming range of the copying machine is matched with the magnification at which the light distribution by the light source on the photoconductor 12 becomes uniform without shading. Further, the minimum value of the variable power range is a magnification at which the light blocking amount by the light blocking plates 23 and 24 is maximum and the light distribution on the photoconductor 12 becomes uniform. As long as the zooming range of the copying machine is set within this range, the light distribution is uniform on the photoconductor at any magnification in the zooming range by appropriately selecting the angle formed by the light-shielding plates 23 and 24 and the optical axis 31. The distribution is obtained. However, from a practical point of view,
There is a slight allowable range.For example, the maximum magnification is slightly higher than the magnification at which the light distribution on the photoconductor by the light source becomes uniform without light shielding, and the light shielding amount by the light shielding plates 23 and 24 is the maximum. A similar effect can be obtained even when the magnification is slightly lower than the magnification at which the light distribution on the body 12 becomes uniform.

That is, the light distribution of the light source is set to "the light distribution on the surface of the photoconductor after passing through the lens is uniform without shading at a certain magnification", and the shape of the shading plate is " When the surface is arranged at an angle (≠ 0) with respect to the lens optical axis, the shape projected on the surface perpendicular to the optical axis shows a light amount distribution on the photosensitive surface when the magnification is smaller than the certain magnification. "Shape to be shaped", and the magnification range generally included in this range may be set as the variable range of the copying machine.

Then, in this result, although the variation of the light amount distribution may be slightly large, there is practically no influence in practice.

From the above, the entire structure is extremely simple, and it becomes possible to perform sufficient light amount correction over a wide change range of the magnification. Even if the optical path 1 fluctuates up and down a little as shown in FIG. 3, it is hardly affected because the light shielding amount at each position in the longitudinal direction of the optical path cross section hardly changes. In addition, the light-shielding plate 2 is provided in most of the area in the longitudinal direction of the cross section of the optical path 1.
Since 3 and 24 can be made to exist in an almost proper shape, a region having a high light amount is not locally generated. In particular, it is advantageous when the width of the optical path 1 becomes narrow at the time of reduction. Further, the light blocking member does not move unnecessarily much. In addition, at the time of reduction, particularly when the reduction magnification is relatively small, the angle formed by the plane of the light shield plate and the lens optical axis is close to a right angle, so if the shape of the light shield plate is accurate, this angle may be slightly different. Even if there are variations, the area of the light-shielding plate occupying the optical path will not be affected so much. That is, when the reduction ratio is small, highly accurate light distribution correction can be performed. Since the light-shielded region is very small at the time of equal-magnification and at the time of enlargement, the light of the light source is not unnecessarily blocked.

From the above, if the light distribution is not corrected, as shown in Fig. 14, when reducing the magnification by 0.5, it is
Although there was a difference in the amount of light exceeding%, the above correction made the difference in the amount of light fall within 1% as shown in FIG. And, the fluctuation of the light quantity through all magnifications (× 0.5 to 1.55) was about 10%, which was not a practical problem. And, as shown by the broken line in FIG. 15, when the light quantity of the light source is increased during the reduction, the fluctuation of the light quantity through all the magnifications is 5%.
I was able to hold down to the following.

Modification of Embodiment 1 In the embodiment described above, the light blocking plates 23 and 24 are a mechanism that moves together with the lens 30, but as shown in FIG. The pulley 40 is attached to a support member 38 fixed to the main body of the copying machine, a pulley 40 is attached to a shaft 39 of the light shielding plate 37, and the pulley 40 is connected to the lens mechanism 10 by a wire 41. It is also possible to rotate the light blocking plate 37 to correct the light distribution.

Further, the shaft 39 can be configured to be drivable by a motor or the like, and the shaft 39 can be rotated according to zooming to adjust the inclination angle of the light shielding plate 37. Further, the number of the light shielding plate 37 shown here is one, but in this case, the connecting arm 33 described above 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 shaft 43 of the light shielding plate 42 is
Does not need to be on the baffle 42, nor is it
The shape of does not have to be symmetrical. In particular, in a one-sided reference copying machine or the like, it is preferable to make the longitudinal direction asymmetric.

Further, the position of the light shielding member does not necessarily have to be between the lens and the photoconductor, and the same effect can be obtained by disposing the light shielding member between the document and the lens.

(B). Embodiment 2 The following is also possible as another embodiment when applied to a copying machine. That is, the light distribution of the exposure light source that illuminates the original is set so that "the light distribution on the surface of the photoconductor after passing through the lens becomes uniform without shading at a certain magnification". When the surface is placed at an angle (≠ 0) with respect to the lens optical axis, the shape projected on the surface perpendicular to the lens optical axis has a larger magnification than the above magnification. It is also possible to set the shape so that the light distribution is uniform ”.

This is the reverse of the case of the above-described first embodiment, and when an exposure light source that does not shield light at a certain magnification and has a uniform light distribution on the surface of the photoconductor is used, the peripheral light amount is set to a larger magnification. It gets lower as it goes. In other words, the light amount at the center of the optical axis becomes higher than the light amount at the periphery. Therefore, as the magnification increases, the amount of light in the central portion, which has become relatively high, is decreased.

In this case, the shape of the light shielding plate is different from the above-mentioned case, and has a shape in which the width of the central portion is wide and becomes narrower toward the periphery. Then, at a certain magnification greater than the above magnification, an angle α that is the maximum light shielding amount with respect to the optical axis is formed, and the light shielding amount decreases as the magnification decreases.

FIG. 18 shows the light distribution distribution characteristic of the exposure light source 3 in the case of the second embodiment, and FIGS. 19 and 20 show the light distribution correction mechanism using the light shielding plate 44 in the case of the second embodiment. . FIG. 19 shows the angle when maximum light is blocked, and FIG. 20 shows the angle when no light is blocked.

(C). Example 3 The following can be considered as a further third example. That is, the light distribution of the exposure light source is set to be “the light distribution on the surface of the photoconductor after passing through the lens is uniform without shading at a certain magnification”, and the light shielding member is formed on a plurality of surfaces. It is configured as follows: "One surface is angled with respect to the optical axis of the lens (≠
0), the shape projected onto the surface perpendicular to the lens optical axis has a shape that makes the light amount distribution on the surface of the photoconductor uniform at a certain magnification larger than the above magnification. When the surface is placed at another angle (≠ 0) with respect to the lens optical axis, the light quantity distribution on the surface of the photoconductor when the shape projected on the surface perpendicular to the lens optical axis is a certain magnification smaller than the above magnification It is set so as to have both of "uniform shape".

That is, although the idea of Example 1 and Example 2 described above is combined, a new effect is produced in a range in which the intermediate magnification includes equal magnification in the variable magnification range. To do this, add the following conditions to the shading plate.

That is, the shading plates 23, 24 of the first embodiment shown in FIG. 21 (a) have the shapes of the shading plates 23 ', 24' shown in FIG. 21 (b) which exist only in one direction from the rotation center axis 32, and Similarly, the shading plate 44 of the second embodiment shown in FIG. 22 is also deformed into the shape of the shading plate 44 'shown in FIG. 22 (b) which exists in only one direction from the central axis 32 of rotation. In the description of the first and second embodiments, the “certain angle” is the same, and the angle α is α ≦ 90 °.

Then, the light-shielding plates 23 ', 24', and 44 'having the shapes shown in FIGS. 21 (b) and 22 (b) are aligned with the rotation center axis 32, and the angle between them becomes α. As shown in FIG. 23, reference numeral 45
It is constructed integrally as shown in.

According to this structure, there is only one rotary light-shielding member, and the connecting arm 33 in the first embodiment is unnecessary.
Further, the fluctuation of the total light amount through the entire variable power range can be made smaller than that of the above two embodiments. This is because in the case of no light shielding, the total amount of light becomes maximum at the same magnification. On the other hand, when using this shading plate, at the same magnification, the shading amount must be the same in both the central portion and the peripheral portion, but at this time, the projection area of this shading plate becomes maximum, and the total light amount also decreases. It is because

Figures 24 (a) and 24 (b) show the light shield plate when the maximum light shield amount is applied.
The aspect of 45 is shown in FIGS.
FIGS. 26 (a) and 26 (b) show a mode in which the light blocking amount on the reduction side is maximum.

〔The invention's effect〕

From the above, according to the present invention, the entire structure is extremely simple, and it is possible to perform sufficient light distribution correction over a wide change range of the magnification, and moreover, in almost all regions in the longitudinal direction of the cross section of the optical path. It is possible to arrange the light shielding member in an almost proper shape, and it is possible to prevent a region having a high light amount from being locally generated. Further, the light of the light source is not wasted.

[Brief description of drawings]

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 a first embodiment, and FIG. 3 is a first embodiment.
Front view of the correcting mechanism of the maximum light blocking (when magnification minimum) of FIG. 4 is a front view thereof at the time of no light shielding (at magnification up), FIG. 5 is an explanatory view of a "law of cos ⁴ theta", a FIG. 6 is an explanatory view of the light distribution of the light source of Example 1, FIG. 7 is a specific light distribution distribution characteristic diagram of the light source, and FIGS. 8a to 8k are diagrams when the light source of FIG. 7 is used. Light amount distribution characteristic diagram of the photosensitive surface at each magnification, FIG. 9 is an explanatory diagram of light shielding by a light shielding plate, FIGS. 10 (a) to (c) are explanatory diagrams of light shielding of each light flux path in FIG. 9, and FIG. Figure shows Example 1
FIG. 12 is an explanatory view for the calculation for obtaining the shape of the shading plate, FIG. 12 is a plan view showing the concrete shape of the shading plate, FIGS. 13a to 1
Fig. 3k is a light amount distribution characteristic diagram of the photoconductor surface at each magnification when the light source of the light distribution shown in Fig. 7 is used and the light distribution is corrected by the shading plate of the shape shown in Fig. 12, and Fig. 14 is the distribution diagram. FIG. 15 is a light amount distribution characteristic diagram on the photosensitive surface of each magnification without light correction, FIG. 15 is a light amount distribution characteristic diagram when light distribution is corrected in Example 1, and FIGS. 16 and 17 are distribution diagrams of Example 1. The figure which shows the modification of a light correction mechanism,
FIG. 18 is a light distribution distribution characteristic diagram of the light source of the second embodiment, FIG. 19 is a front view of the light distribution correction mechanism of the second embodiment when maximum light is blocked, and FIG. 20 is a front view of the light distribution correction mechanism when no light is blocked. 21 (a) and 21 (b) are explanatory views of the production of the light shielding plate of Example 3, FIG.
FIG. 23 is a perspective view of the light shielding plate of the third embodiment, FIG. 24 (a) is a front view showing the angle mode of the light shielding plate when the reduction side light shielding amount is the maximum of the third embodiment, (b) is a side view, and FIG. FIG. 7A is a front view showing the angle mode of the light shielding plate at the same magnification as in Embodiment 3, and FIG.
FIG. 26 (a) is a front view showing the angle mode of the light blocking plate when the maximum expanded light blocking amount is used in Embodiment 3, FIG. 26 (b) is a side view, and FIG. 27 is a conventional light blocking explanatory diagram. 1 ... Conventional light shielding plate, 2 ... Optical path, 3 ... Rod-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 …… Developer, 14…
… Paper feeder, 15 …… Registration roller, 16 …… Transfer pole, 17 …… Separation pole, 18 …… Thermal fixing roller, 19 …… Paper ejection section, 20 …… Cleaning section, 21 …… Band electrode, 22 ... Light distribution correction mechanism, 23, 24 ... Shade plate of the first embodiment, 25 ... Lens holder, 26, 27 ... Arm, 28, 29 ... Axis, 30 ... Lens,
31 …… Lens optical axis, 32 …… Rotating axis, 33 …… Coupling arm,
34 …… Cam follower, 35 …… Arm, 36 …… Cam, 37 ……
Light-shielding plate of a modification of the first embodiment, 38 ... Supporting member, 39 ...
Shaft, 40 ... Pulley, 41 ... Wire, 42 ... Shading plate of another modified example of the first embodiment, 43 ... Shaft, 44 ... Shading plate of the second embodiment, 45 ... Shading of the third embodiment Board.

Claims (3)

[Claims] 1. A light source for illuminating an original, an optical path restricting member for restricting a cross section of the reflected light from the original to a narrow shape, and an optical axis for forming an image of the reflected light restricted by the optical path restricting member. In a variable-magnification image forming apparatus having an image forming unit having an image forming unit and an image carrier for carrying an image formed by the image forming unit, a part of the light flux in the regulated optical path regulated by the optical path regulating member. A light flux regulating plate for regulating the image carrying member, the light flux regulating plate is always arranged in a region inside the cross section in the lateral direction of the cross section perpendicular to the optical axis of the regulated optical path, and In order to make the light amount distribution in the longitudinal direction of the cross section on the body substantially uniform, the cross sectional length in the lateral direction is different in the longitudinal direction of the cross section, and the image forming magnification Due to the change of Variable magnification image forming apparatus, characterized in that rotating the side direction as the pivot center axis. 2. The light source according to claim 1, wherein at least one predetermined image forming magnification between the normal image forming magnification and the maximum image forming magnification, the angle between the light flux regulating plate and the optical axis is substantially zero. The light flux regulating plate has a light intensity distribution characteristic such that the light intensity distribution in the longitudinal direction of the cross section on the image carrier becomes substantially uniform, and the light flux regulating plate has the light flux regulating plate as the image forming magnification decreases. By increasing the angle of the cross section with respect to the optical axis, the length of the cross section in the lateral direction is set to be substantially uniform so that the light amount distribution in the longitudinal direction of the cross section on the image carrier becomes substantially uniform. The variable-magnification image forming apparatus according to claim 1, wherein the variable-magnification image forming apparatus has a shape in which the direction is reduced toward the vicinity of the optical axis. 3. The light source when the angle between the light flux regulating plate and the optical axis is substantially zero at at least one predetermined image forming magnification between the normal image forming magnification and the minimum image forming magnification. The light flux regulating plate has a light intensity distribution characteristic such that the light intensity distribution in the longitudinal direction of the cross section on the image carrier is substantially uniform, and the light flux regulating plate increases as the image forming magnification increases. In order to make the light amount distribution in the longitudinal direction of the cross section on the image carrier substantially uniform by increasing the angle with respect to the optical axis, The variable-magnification image forming apparatus according to claim 1, wherein the variable-magnification image forming apparatus has a shape in which the direction is increased toward the vicinity of the optical axis.