JPS63235925A - Correcting mechanism for light distribution and light quantity of image projecting mechanism - Google Patents

Abstract

PURPOSE:To perform stable and secure light distribution correction and light quantity correction over a wide range by providing a swing member, and bringing one end part of the swing member into contact with a frame body at different positions from respective shafts and the other end part into contact with a cam fixed to a main body. CONSTITUTION:A light distribution adjusting member 46 is rotatable around shafts 46' and 46'A and a light quantity adjusting member 48 is rotatable around a shaft 48'. The light distribution adjusting member 46 is moved by a lens moving base 40 to a prescribed position together with a projection lens 7 according to magnification M. At this time, the frame 45A where the light distribution adjusting member 46 has its shaft 46'A received by bearings 41 and 42A and a lever 113 which swings around a support shaft 112 fixed at a different position of the bearing 42A is provided as the swing member; and a pin 114 as a guide member is fixed at an end part of the lever and the pin 114 is fitted in the long-sized guide groove 45B of the frame 45A. Further, a pin 52 as a guide member is fixed at the other end part of the lever. Consequently, the displacement quantity L1 of the cam is smaller than the movement distance of the lens moving base 40 and the slope of the cam is reduced to smooth the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light distribution and overall light amount correction mechanism applied to a projection mechanism of an image forming apparatus such as a copying machine.

[Conventional technology]

In a projection mechanism such as an electrophotographic copying machine, a lens is essential in order to form a projected image on an image carrier such as a photoreceptor. However, in this lens 7, as shown in FIG. 4(a),
(b) As shown in (c), there is a law called "cos4θ law" [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."
It has characteristics.

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. As in Japanese Patent Application Laid-Open No. 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 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. Especially when there is a region where no light shielding plate exists in the longitudinal direction of the cross section of the optical path formed by the slit (in other words, when the amount of light shielding is discontinuous in the longitudinal direction)
, a region with a locally high amount of light is created.

Also, if the optical path is misaligned with respect to the position of the light shielding member,
The amount of light shielding changes.

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, an idle rail or a link mechanism with many nodes is required.
The configuration becomes complicated.

In addition to the above-mentioned publications, there are other mechanisms that have the above-mentioned problems, such as JP-A-54-138845 and JP-A-57-92348.
, vf Yami-Sho 57-154265, JP-A-60-1342
26, JP-A No. 60-80828, etc.

In order to avoid the above-mentioned drawbacks of the prior art, the present applicant provided a rotatable light distribution adjusting member 46 behind the projection lens 3 in Japanese Patent Application No. 108543/1983, and adjusted the projection magnification. Depending on the change, the rotation angle was changed each time to adjust the degree of light shielding of the optical path, so that the light distribution at each magnification was made uniform.

That is, in the optical system as shown in FIG. 4(a'), when the luminous flux density distribution of the reflected light from the document screen after passing through the slit is set as shown by S in FIG. 4(d), When the magnification is at the maximum (1.55 times), the exposure amount distribution on the imaging plane becomes uniform light as shown by the line r in FIG. 4(e). At this time, the rotational position of the light distribution adjusting member 46 is such that it hardly blocks light. Next, if you change the magnification M and leave the light distribution adjustment member as it is (for example, when M: 0.5 on the reduction side), the exposure distribution will become as shown by q in Figure 4(e). Put it away. Correcting this, uniform exposure amount q
'), the light distribution adjusting member 46 is rotated to an appropriate position. Similarly, when the magnification is close to the same magnification, for example, when M is 1.00, if the light distribution adjusting member is left as is, the exposure amount distribution will be expressed as p. In order to avoid this, the light distribution i111 member is rotated to provide a uniform exposure amount p'. However, as shown in Figure #4 (e), p' and q
There is an exposure difference of 12 between ' and 12-1 between p' and r.
．． There is a difference in exposure amount. In order to correct this, the applicant provided a rotatable light amount adjusting member 48 near the light distribution adjusting member 46.

That is, a mechanism having a light distribution adjusting member is provided at a position a certain distance behind the lens 7, and a mechanism having a light amount adjusting member is further provided at a position a certain distance from the member, and each member is perpendicular to the optical axis. It is possible to swing around the axis in the slit direction. Since both mechanisms are similar, only the light distribution adjusting member will be explained. As shown in the front and side views of the light distribution adjustment mechanism in FIGS.
is fixed by pins 45', 51' to the support shaft 46''
is rotatably pivoted to a bearing 42. The opposite side of the frame is also fitted into a support shaft 46' which is coaxial with the support shaft 46'' which is pivotally fixed to the bearing 41, so that it can be rotated on both sides.

A roller 52 is rotatably fixed to the other end of the lever 51 and pressed against the cam surface of a cam 57'.

The bearings 41 and 42 are fixed together with the lens 7 to a movable table 40 for changing the lens position during magnification conversion. The moving table 40 has a guide rail 5 fixed to the main body 1.
5 and is guided by rollers 54 so that it can move the required distance according to each magnification.

The cam surface is set so that the light distribution adjusting member 46 has an appropriate inclination angle in accordance with each magnification.

[Problem that the invention seeks to solve]

The amount of lens movement is about 250,112 in the entire magnification conversion range. On the other hand, the inclination angle range of the light distribution adjusting member is required to be approximately 90°. The auxiliary angle of the lever 51 is the same, and the corresponding maximum value L2 of the displacement of the cam 57 is approximately 3011, and the slope of the cam curve becomes too large to operate the cam mechanism, resulting in a lack of smooth operation. be. The same applies to light amount correction.

It is an object of the present invention to solve these problems and provide a light distribution correction mechanism and a light amount correction mechanism that are stable and reliable over a wide range.

[Means for solving problems]

The purpose of this is to provide a projection mechanism that includes an optical path regulating member that regulates the cross section of reflected light or transmitted light from the document screen into a slit shape, and a lens that forms an image of the screen. With respect to the optical path regulated in the shape of A light distribution adjusting member fixedly attached to a movable frame body is provided, and a swinging member that rotates around an axis different from the above-mentioned axis is provided, and one end of the swinging member is arranged at a position different from the respective axes. Light distribution correction can be achieved by a light distribution correction mechanism in an image projection mechanism, which is characterized in that the light distribution correction mechanism is in contact with the frame and the other end is in contact with a cam fixed to the main body.

In addition, in a projection mechanism that includes an optical path regulating member that regulates the cross section of the reflected light or transmitted light from the document screen into a slit shape, and a lens that forms an image of the screen, the optical path regulating member allows the cross section to be rectangular or close to the rectangular shape. With respect to the optical path defined by the shape, on a lens moving table that is movable in the optical axis direction in the inner region in the longitudinal direction of the cross section, the lens is centered on an axis that intersects the optical axis and runs along the longitudinal direction of the slit. A light amount adjusting member fixed to a rotatable frame is provided, and a capturing member is provided that rotates around an axis different from the above-mentioned axis, and one end of the capturing member is different from each of the above-mentioned axes. The light amount correction can be achieved by the light amount correction mechanism in the image projection mechanism, which is characterized in that the image projection mechanism is in contact with the frame at one end and the other end is in contact with a cam fixed to the main body.

〔Example〕

FIG. 2 is a schematic diagram showing relevant parts of an image forming apparatus incorporating a light distribution and light amount correction mechanism in an image projection mechanism of the present invention.

That is, the original image on the document table 80 is irradiated by the lamp 2 on the first traveling table A, and the reflected light passes through the mirror 5.6 of the second traveling table B, which travels on a sleeve, and then passes through the projection lens 7 and the light distribution. An image is formed on the surface of the photoreceptor drum 9 via the adjustment member 46, the light amount adjustment member 48, and the mirror 8.

The image projection mechanism in such an image forming apparatus has a variable magnification M of the projected image with respect to the document, and the position of the projection lens 7 and the positions of the mirrors 5 and 6 are respectively determined for each magnification number. be.

That is, when M=1, the position of the mirror 5.6 at the start of scanning and the fixed position of the lens 7 are as shown by the solid line in FIG.

M can be finely changed almost steplessly, but in this case, in addition to M = 1, M = 1.5 as an expansion.
M=0.5 is exemplified as 5 reduction. This M= 1.5
5 and M=0.5, the lens 7 and mirrors 5 and 6 are arranged at the positions indicated by dotted lines in FIG. 2, respectively. mirror 5
, 6, that is, the difference in the position of the second traveling platform B is M=1 and M=0.5.
Between 58.75ml1. M=1 and M=1.
55 is 22.93 mm, and the difference in the fixed position of the projection lens 7 is M=1. 117.5mm between M=0.5
, 129.25m+ between M=1 and M=1.55
Al is doing well.

Next, a mechanism for how to change the starting point of the second traveling platform B and the set position of the projection lens each time the first and second traveling platforms move and magnification is changed will be explained.

In FIG. 1(a), the scanning system is driven by winding a single wire around a pulley 11 connected to the shaft of a motor 10 (perhaps via a clutch brake, not shown). The front half Wl of
0 with a stopper fitting 1. The pulleys 14 and 16 mentioned above are pulleys installed on a movable pulley base, and the other pulleys, except for the pulley 12 attached to the second traveling white B, are pulleys that rotate around an axis fixed to the main body 1. be.

Also, the rear half W2 of the wire wound around the pulley 11 is
Wire WI is connected to the pulley 12 via pulleys 18 and 19.
The pulleys 21 and 22 are wound in the opposite direction to the
Pulley 26 on movable pulley platform 70 via 23.24.25
(pulley 26 applies tension to the wire, not shown) and connects to a symmetrical wire as described below, forming a closed loop. The pulleys 22, 24° 25, 26 are provided on a movable pulley platform 70.

Further, each pulley is provided on the opposite side in a symmetrical position as shown in FIG. 1(a), and a similar wire WI is provided on the opposite side.

W2 is applied so that the wire tension on both sides remains constant even when driving force is applied.

Also, the wire W has a lamp 2, a slit 3, and a mirror 4.
The first running base A incorporating the is attached, and the pulley 12 is
(2) It is rotatably pivoted to a shaft attached to a second traveling platform B consisting of mirrors 5 and 6.

Although the first and second carriages are not shown, they are movable while being guided by rails provided in their respective running directions (indicated by arrows X). The movable pulley base 70 also has rollers 72 attached thereto, for example, as shown in FIG.
As shown in a), the arrow X is guided by the rails 73 on both sides.
It is possible to move in any direction.

On the other hand, as shown in FIGS. 1(a), (b), and (c), the lens moving table 40 on which the projection lens, the light distribution adjusting member, and the light amount adjusting member are mounted is moved by the rollers 54 provided thereon.
' is guided by the rail 55' so that it can also move in the direction of arrow X.

Further, an id pin 33 is provided on the lens moving table 40, and a wire whose one end is fixed on the table via a spring 34 is wound around a pulley 28 driven by a drive motor 58 via a boot 932, and is wound around a pulley 29. The other end is then fixed onto the lens moving table 40 again.

Each time the setting of the magnification M is changed, the stepping motor 58 fixed to the main body 1 is actuated to rotate the pulley 28 directly connected to the stepping motor 58, and the lens moving stage connected to both ends of the wire wound around it is direction and set in a predetermined position.

Then, the pulley 30 is rotated by the drive transmission of the wire, and the cam 85 integrated with the pulley is rotated to a predetermined position.
The cam 7 lowerer 86, which is in contact with the cam 85, also moves the movable pulley platform 70 in the X direction and sets it in a predetermined position, thereby causing the second running right B or mirror 5.
The initial position of No. 6 in the X direction is set. The cam 85 and the cam 7 lower 86 are brought into contact by being pressed by a spring 71 stretched between the main body 1 and the movable pulley base 70. Further, during the conversion operation of the magnification M, the operation of the motor 10 or the clutch brake attached to the motor 10 is stopped, and therefore the Boo IJ11 stops rotating and the first traveling platform is not moved. No matter how the magnification M changes, it does not move during magnification conversion and always stands by at a fixed position.

When the lens movable base 40 is fixed according to the set magnification M, the position of the movable pulley base is determined, which determines the position of the second traveling base, that is, the mirrors 5 and 6, and the light distribution adjustment and the like described below are performed. Light intensity adjustment is also performed at the same time, allowing preparations to be made according to each magnification.

The pulleys 14, 16, 22, and 24 on the movable pulley platform are the pulleys 15, 15, and 15, which are pivoted on a shaft fixed to the main body 1. ia and 23, 21 via respective wires W,, W2. Therefore, for the movement d of the pulley base in the X direction, the wire Wlf at pulley 13.21 and pulley 12
Each movement of W2 has a magnitude of 3d. Therefore, for example, the above-mentioned magnification Mf) change, M=0.5-1-1.55*
The maximum difference in setting values for mirrors 5 and 6 between the two is 58 and 75 m.
m, the movement of W + - W 2 with respect to it is a maximum of 58,75
By setting this short stroke, the cam 85 can easily operate smoothly with less load.

The above-mentioned pulley stand 70 is installed in the middle with a body fixing boot.
1715.23, the amount of movement for changing the magnification of the pulley base 70 and the stroke of the cam 85 can be greatly reduced, contributing to the miniaturization of the entire device.

In this way, for any magnification setting, the projection lens,
When the positions of the pulley base and mirrors 5 and 6 are determined and scanning is started, the wire tension varies greatly as the scanning is driven.

Due to the above-described mechanism, this variation in tension is tripled and acts on the pulley base. This is especially true when the scanning system changes the forward and return directions, causing the pulley to vibrate or move and become misaligned. The first traveling platform A equipped with
Vibrations may occur in the second traveling base B on which the mirrors 5 and 6 are mounted, and errors may occur in the positional relationship between the two.
This can cause distortion, shaking, blurring, and blurring in image formation.

Therefore, it is necessary to apply a brake to prevent the movable pulley platform 70 from moving during scanning. Therefore, a friction member 74 is provided on the side of the pulley base, and a friction member 75 rotating around a fulcrum 76 is pressed against the friction member 74 by a spring 77, thereby completely blocking the movement of the movable pulley base 70 and fixing it. .

In this way, it becomes possible to stabilize images during high-speed scanning.

On the other hand, as the cam 85 rotates as the lens moving table 40 moves during the magnification conversion operation, the movable pulley table 70 moves through the cam 7 lowerer 86 that comes into contact with it. Since the pulley stand will not move if the brake is in place, the solenoid 78 is actuated on the brake member 75 to overcome the force of the spring 7 and release the brake.

Although this brake is provided only on one side as shown in FIG. 1, it is of course possible to provide it on both sides almost symmetrically.

In addition, although a brake is used in this embodiment, the movable pulley platform 70
The same purpose can be achieved by providing a bottle hole corresponding to each magnification on the side or bottom surface of the magnification, and inserting a pin to fix the position upon completion of movement according to each magnification setting. However, it can be said that the brake method is easier to accommodate stepless and fine magnification settings.

Now, at the rear position of the projection lens 7 on the lens moving table 40, there are
As shown in (b) and (c), a light distribution adjusting member 46 rotatable around shafts 46' and 46'A and a light amount adjusting member 48 rotatable around a shaft 48' are provided. .

The light distribution adjusting member 4B is moved to a predetermined position together with the projection lens 7 by the lens moving table 40 according to the magnification M. At this time, the frame 45A to which the light distribution adjustment member 46 is mounted has its shaft 46'A supported by bearings 41 and 42A, and a lever movable around a support shaft 112 fixed at another position of the bearing 42A. 113 is provided as a contact member, and a pin 114 as a guide member is fixed to the end of the lever.
It is inserted into B. A pin 52 serving as a guide member is fixed to the other end of the lever. The pin is attached to a rotatable roller.

The pin 52 is fixed to the rail cam 57 on the main body frame 1 by the movement of the lens moving table 40 for magnification conversion.
The lever 113 is rotated by being guided by the guide surface 115 of A.

Although the lever 113 is not shown, it is always urged by a torque spring attached around the support shaft 112 so as to be pressed against the guide surface 113 of the cam 57A.

In this way, the amount of displacement of the cam compared to the moving distance of the lens moving table 40 is about one-fifth of L2 in the conventional example, so the inclination of the cam is small and the operation is smoother than in the conventional case. - With such a device, by sequentially changing the angular position of the light distribution adjusting member 46 according to the magnification as shown in FIGS. 3(a), (b), and (e), the image shown in FIG. As shown by the dotted lines, the exposure amounts are arranged to have flat distributions q' and p', respectively. That is, when M=0.5, Q'M=
If it is 1.0, it is p'.

Then, the exposure amount difference I1. with the exposure amount distribution r of the combination of M=1.55. and 12-1. The frame 47A to which the light amount adjusting member 48 is mounted is also configured to move the member 48 to the bearing 4 according to the magnification M using the same operating mechanism as the light distribution adjusting member.
3.44 and is guided on the rail cam 57A fixed to the main body 1, the angular position of the light amount adjusting member 48 is changed as shown in FIGS. 3(a), (b), and (c). As shown in Figure 4(e), p', q'', r
This is done to eliminate the difference in exposure between the two.

This point will be explained in more detail as follows.

The left arrow shown in Figure 3 (,), (b), and (c) indicates the maximum width of the document on the document table (approx. 300zz for A4 size and A3 size).
In other words, the size of the slit screen during document scanning is determined. The arrow on the right side represents the size of the formed slit image. Then, when enlarged, M = 1.55 is (a), when the same size is M = 1, (b), when reduced, M =
0.5 is shown in (c). Furthermore, the projection lens 7 light distribution adjusting member 46 and light amount adjusting member 48 are integrated and change positions according to each magnification. At the same time, although not shown in this figure, the position of the second traveling platform changes, and the overall optical path length changes depending on each magnification as shown in (aHb) (c).

When a slit screen with a light source luminous flux density distribution as shown by the curve S in Fig. 4(d) is used and the angle of the incident light with respect to the optical axis of the lens is θ, cos'
The θ law works and when the maximum magnification is M-1°55, Figure 4 (e
), a flat image exposure amount distribution indicated by r is obtained.

Therefore, when the maximum magnification M = 1.55, the light distribution adjusting member 46 rotates around the axis 46', and as shown in FIG.
As shown in , the position is parallel to the lens optical axis and does not contribute to adjusting the light distribution. Further, in order to slightly lower the light amount, the light amount adjusting member 48 is rotated and positioned by a shaft 48' so that it forms an appropriate angle to the lens optical axis.

When M=1, the total light amount is the highest, so the light amount adjustment member 48 is positioned perpendicular to the lens optical axis. Further, at this time, since the amount of light in the periphery increases slightly, the light distribution adjusting member 46 is positioned at a slight angle.

At the minimum magnification M=0.5, the axis 46',
By rotating around 46'A, the light distribution adjusting member 46 is made perpendicular to the lens optical axis as shown in FIG. The flat luminous flux density distribution shown in e) is adopted.

In this case, since the overall light amount is the lowest, the light amount adjustment member is parallel to the lens optical axis to avoid light amount attenuation.

In this way, the difference in luminous flux density at each magnification is 11°12-
1' becomes O.

The light distribution adjusting member 46 and the light amount adjusting member 48 are mounted on the same axis at an appropriate angle and rotatably fixed by a bearing, and guided on a rail cam 57A fixed to the main body frame 1, each magnification M is adjusted. Appropriate light distribution adjustment member 4 at the position
It is also possible to make the rotation angles of the light amount adjustment member 6 and the light amount adjustment member 48 determined.

Almost the same as the diagram shown in Figure 4(e), the magnification M is 1.
, 0.5 and 1.55, a uniform exposure distribution that does not cause any practical problems can be obtained, and furthermore, the exposure amount differences between each magnification can be removed to the extent that it does not cause any practical problems. .

In the above embodiment, the light distribution correction mechanism and the light amount correction mechanism were set separately and the two were used to interpolate each other, but it is of course possible to provide one of the two mechanisms and use a different method for the other. Even if only one of the light distribution correction mechanism and the light amount correction mechanism is provided, each effect can be exerted independently.

〔Effect of the invention〕

According to the present invention, it has become possible to perform wide-range adjustment of light distribution correction and/or light amount correction reliably, smoothly, and accurately using a simple mechanism. It is now possible to flatten the light distribution for each magnification conversion and to make the exposure amount of image light constant, making it possible to obtain stable images of good quality and appropriate density.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view of an image projection mechanism incorporating an embodiment of the present invention. FIG. 1(b) is a front view of one embodiment of the light distribution adjustment mechanism of the present invention. FIG. 1(c) is a side view thereof. FIG. 2 is a schematic diagram showing relevant parts of an image forming apparatus incorporating one embodiment of the present invention. FIGS. 3(a), 3(b), and 3(c) are positional relationship diagrams of the slit screen, projection lens, light distribution adjustment member, light amount adjustment member, and imaging plane in enlargement, normal magnification, and reduction. FIG. 4 (,) is a diagram showing the change in the angle of incidence θ on the lens when the magnification is changed. FIG. 4(a') is a diagram in which a light distribution adjusting member is provided in FIG. 4(a). FIG. 4(b) is a diagram showing that the luminous flux density of the original reflected light is made flat. FIG. 4(e) is a diagram showing the distribution of exposure amount at the imaging position in that case. FIG. 4(d) is a diagram showing that the luminous flux density of the original reflected light is increased at the end. FIG. 4(e) is a diagram showing the exposure amount distribution on the imaging plane in that case. FIG. 5 is a front view of a light distribution adjustment mechanism conventionally proposed by the applicant. FIG. 6 is a side view thereof. 1-----1 Main body frame A-----1st traveling base 2-----Light source lamp B-----1 second traveling base 3-----Slit 4-----1st 1 Mirror 5.6.8 ----- Mirror 7 --- Projection lens 9 --- Photoreceptor 40 --- Lens moving table 41.42, 42^, 43.44 --- - Bearing 45.
45^, 47, 47^---1---Frame 45B---
- Guide groove 46---Light distribution adjustment member 46', 46'^---One-axis 48---One light amount adjustment member 50.51, 113---Lever 52.114--- ---Pin 57.57^-1--Rail cam 58--Stepping motor 70--1 Moving pulley base 112--1 Support shaft 115--Guide surface Applicant Roku Konishi Photo Industry Co., Ltd. 1N 1986-235925 (11) Procedural amendment (
Method) July 23, 1986

Claims (2)

[Claims] (1) In a projection mechanism that includes an optical path regulating member that regulates the cross section of reflected light or transmitted light from the side surface of the document into a slit shape, and a lens that forms an image of the screen, the cross section of the optical path regulating member is rectangular or close to the rectangular shape. With respect to the optical path regulated in the shape of A light distribution adjusting member fixedly attached to a rotatable frame body is provided, and a swinging member is provided that rotates around an axis different from the above-mentioned axes, and one end of the swinging member is located at a position different from the respective axes. A light distribution correction mechanism in an image projection mechanism, characterized in that the other end is in contact with the frame and the other end is in contact with a cam fixed to the main body. (2) In a projection mechanism that includes an optical path regulating member that regulates the cross section of reflected light or transmitted light from a document screen into a slit shape, and a lens that forms an image of the screen, the cross section of the optical path regulating member is rectangular or close to the rectangular shape. With respect to the optical path regulated in the shape of A light amount adjusting member circumferentially surrounded by a rotatable frame body is provided, and a swinging member that rotates around an axis different from the above-mentioned axes is provided, and one end of the swinging member is set at a position different from the respective axes. A light amount correction mechanism for an image projection mechanism, characterized in that the other end is in contact with a frame and the other end is in contact with a cam fixed to the main body.