JPH05100320A - Peripheral light quantity adjustment device for optical device - Google Patents

Abstract

PURPOSE:To provide a peripheral light quantity adjustment device which can adjust peripheral light quantity with high accuracy and well-balanced at the time of varying power which is suitable to be miniaturized and which can correct the complicated correction of the light quantity by simple constitution. CONSTITUTION:When a traveling body 2 moved, a cam plate 4 is moved in a direction which is orthogonal to an optical path (alpha) with respect to the traveling body 2 and the relative positional relation thereof with respect to the traveling body 2 is changed. Thus, the relation of an engagement position between a follower 4c projectingly provided on the plate 4 and the mask plate 5a of a light quantity restriction means 5 is changed by the follower 4c and the light quantity is precisely adjusted according to the change of magnification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, as an optical device for image formation in a variable-magnification copying machine, and adjusts the peripheral light amount of light passing through an optical system during variable power. The present invention relates to a peripheral light amount adjusting device.

[0002]

2. Description of the Related Art A copying machine is provided between a subject side and an image forming body side.
That is, the optical system for image formation is arranged in the optical path between the original table and the photosensitive surface. In recent years, not only copying at the same size but also enlargement copying and reduction copying are possible. Things are becoming widely used. in this way,
To enable not only the same size but also enlargement / reduction copying,
The optical system must have a variable magnification mechanism. As the variable magnification mechanism, a fixed focus lens is used as the optical system itself, and the entire optical system is moved along the optical path to the subject side and the image forming side. And a zoom lens in which some of the lenses that make up the optical system are movable lenses.
In some cases, the zoom lens is moved along the optical path and the movable lens is moved during zooming. Also in this zoom lens system, in order to perform a so-called corner registration in which the reference position for placing the document and the reference position on the photosensitive surface at the time of zooming are made to coincide with each other, or for correcting the common length, the optical system There is one that is designed to be moved in its entirety.

By the way, in the lens, the amount of peripheral light decreases due to the cos ⁴ rule, and the central part of the screen is bright, but the peripheral part decreases in light amount and becomes dark, resulting in an unbalanced amount of light within the angle of view range. Tend. However, when it is necessary to make the image quality of the entire image forming surface uniform, such as in a copying machine, it is necessary to correct the light amount so as to balance the light amounts of the central portion and the peripheral portion. In order to correct the peripheral light amount, there has been an example in which a light source lamp that illuminates a subject is used so that the peripheral portion has a larger light amount than the central portion.

[0004]

When the copying magnification is fixed, a light source lamp with a large amount of peripheral light can be used to correct the light amount for the entire angle of view, but the magnification can be changed. In a copying machine or the like, when the magnification is changed, it is impossible to follow the change and increase or decrease the peripheral light amount.

That is, as shown in FIG. 4, when the optical system L placed on the optical path R between the object plane P and the image plane P'is arranged at a position of a magnification β ₁ , Comparing the amount of light in the peripheral portion and the amount of light in the peripheral portion of the angle of view when the lens is displaced to the position of the magnification β ₂ , assuming that the lens is not vignetted, the angle of view at the position of the magnification β ₁ is Since it is θ ₁ , the peripheral light amount is cos ⁴ θ ₁ with respect to the central light amount.
Therefore, in order to make the light amount uniform within the range of the angle of view θ ₁ ,
At this position, the amount of light in the peripheral portion must be increased by 1 / cos ⁴ θ _{1 with} respect to the amount of light in the central portion. On the other hand, the magnification β
_At the position of _2, the angle of view is θ ₂ , so that the peripheral light amount decreases by cos ⁴ θ ₂ with respect to the central light amount. Therefore, in order to make the light amount uniform, the light amount in the peripheral portion (angle of view θ ₂ ) must be increased by 1 / cos ⁴ θ _{2 with} respect to the light amount in the central portion. As a result, in the case where the light amounts of the central portion and the peripheral portion are balanced at the position of the magnification β ₁ , when the optical system L is displaced to the position of the magnification β ₂ , The amount of light in the peripheral portion must be reduced by a few.

[0006]

[Equation 1]

However, as in the prior art described above, if the light amount distribution in the light source lamp is constant, it is not possible to adjust the peripheral light amount according to the change in magnification, and for this reason it is possible to change the magnification and the like. However, in the case of the above configuration, there is a drawback that there is no unevenness in the amount of light in all magnification ranges and a clear copy image or the like cannot be obtained.

The present invention has been made in view of the above points, and an object thereof is to enable the peripheral light amount of an image to be adjusted accurately and in a well-balanced manner during zooming. Another object of the present invention is to provide a peripheral light amount adjusting device for an optical device, which can be downsized and can perform complicated light amount correction with a simple configuration.

[0009]

That is, according to the present invention, a lens barrel having a built-in lens is mounted, and when the image of a subject is taken by changing the magnification, the traveling is performed along the optical path direction of the lens. A body, a light amount correction means provided in the lens barrel to move integrally with the lens barrel when the magnification is changed to regulate a light flux from a subject, and a cam with which the lens barrel is engaged via the running body. A plate and a follower provided on the cam plate, and as the traveling body moves in the optical path direction, the follower slides in pressure contact with the light amount correction means, whereby the light amount correction means is It regulates the luminous flux.

[0010]

In the peripheral light amount adjusting device of the optical device according to the present invention, when the traveling body is moved to a predetermined position in accordance with the magnification during zooming, the traveling travels while the cam plate is guided by the guide means. The optical path moves in a direction orthogonal to the body, and the relative position of the cam plate with respect to the traveling body changes. Since the relative position of the follower attached to this cam plate also changes, the mask plate engaged with the follower changes its distance from the optical axis as the follower moves, and the light flux passing through the lens is changed. It is adjusted according to the magnification of the optical system.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a peripheral light amount adjusting device of an optical device according to the present invention. This peripheral light amount adjusting device includes a base 1, a traveling body 2, a lens barrel 3, a cam plate 4, and a light flux limiting unit. It comprises means 5 and actuating means 6.

The base 1 is arranged immediately below the optical path α between the object plane (not shown) side and the image plane (not shown) side in the optical device (not shown). A slide rail 7 and a rack 8 arranged parallel to the optical path α are attached to the. A guide rail 9 is attached to the base 1 in a state of expanding toward the image plane side, that is, in a state of being inclined at a constant angle with respect to the optical path α.

The traveling body 2 has a slide rail 7 on the base 1.
It is adapted to move in translation in a direction parallel to the optical path α while being guided along. That is, the traveling body 2 is a flat plate and is formed in a substantially rectangular shape, and the lens barrel 3 is attached to the central portion of the upper surface. The lens barrel 3 is formed in a substantially box shape and is screwed onto the traveling body 2, and accommodates a plurality of lenses 10 inside, and moves in the optical path α direction as the magnification of the optical system is changed. Is configured.

The cam plate 4 is mounted on the lower surface of the traveling body 2 so as to be movable in the direction (Y direction) orthogonal to the optical path α. When changing the magnification of the optical system, the relative position of the cam plate 4 with respect to the traveling body 2 is changed, the distance between the lenses in the lens barrel 3 is changed, and at the same time, the light amount of the light flux passing through the lenses is adjusted. Is also supposed to be done. This cam plate 4
As shown in FIG. 3, there is a substantially arcuate cam hole 4a (see FIG. 2) through which the engaging protrusion 11 attached to the lens frame (not shown) in which the lens 10 and the like in the lens barrel 3 are attached is inserted. A pair is formed. Further, in order to change the relative position of the cam plate 4 with respect to the traveling body 2 as shown in FIG.
A pair of guide holes 4b are formed, and the guide holes 4b
A guide pin 2a protruding from the lower surface of the traveling body 2 is inserted into and engaged with this. Further, on the cam plate 4, a follower 4c for driving the light flux limiting means 5 is provided so as to project upward. An engaging pin 4d that engages with the guide rail 9 is provided on the cam plate 4 so as to project downward at one corner of the lower surface.
The tension spring 1 for pressing the guide rail 9 into the guide rail 9
3 is stretched between the cam plate 4 and the traveling body 2.

The luminous flux limiting means 5 is for variably limiting the luminous flux incident on the lens 10 or the luminous flux emitted from the lens 10 according to the magnification of the optical system. In this embodiment, as shown in FIG. The lens barrel 3 is composed of a pair of mask plates 5a and 5b pivotally supported on the incident surface 3a side.
The mask plate 5a has a cam surface 5c whose lower side surface is formed in a predetermined shape according to the magnification and engages with the follower 4c, and has a length at the center side through which the interlocking pin 3b described below is inserted. The hole 5d is formed. In addition, the mask plate 5b is provided with an interlocking pin 3b at an intermediate portion overlapping with the mask plate 5a. When the mask plate 5a rotates with the movement of the cam plate 4, the interlocking pin 3b follows. Is vertically displaced, and the mask plate 5b is also rotated in the opposite direction via the interlocking pin 3b. The mask plate 5a is
A spring 12 is stretched between the tip and the traveling body 2 so that the cam surface 5c is always in pressure contact with and engaged with the follower 4c.

Further, as the light flux limiting means, it is not always necessary to use a pair of mask plates of two kinds as in this embodiment. It is possible to perform complicated light amount correction. Further, it is possible to attach a mask plate of the same kind not only on the exit surface of the lens barrel but also on the entrance surface side to perform more complicated light amount correction. The actuating means 6 moves the traveling body 2 in a predetermined direction according to the magnification and moves the cam plate 4 relative to the traveling body 2 to a specific position. In this embodiment, the traveling body 2 is moved. And a pinion 6a which is driven and rotated by the motor and meshes with the rack 8.

Next, the operation of this embodiment will be described. For example, when the magnification of the optical system in the optical device is converted to perform imaging at a low magnification, the previous motor is operated to rotate / drive the pinion 6a counterclockwise in FIG. Then, the traveling body 2 provided with the pinion 6a at the left position in the figure moves to the two-dot chain line position on the right side in the figure along the slide rail 7 by the meshing of the pinion 6a and the rack 8. .

By the movement of the traveling body 2 to the right (+ X direction), the cam plate 4 is restricted by the slide pin 2a on the traveling body 2 side while the traveling body 2 is in the backward direction (+ Y direction).
To move to. As a result, the relative position of the cam plate 4 with respect to the traveling body 2 changes, and accordingly, the follower 4c provided on the cam plate 4 also relatively moves in the back direction (+ Y direction) of the traveling body 2. Therefore, in FIG. 3, the mask plate 5a and the mask plate 5b that interlocks with the mask plate 5a via the interlocking pin 3b.
And rotate in the direction to close each other. As a result, the dimming of the lens 10 by the pair of mask plates 5a and 5b is
It increases as the magnification decreases, and becomes maximum dimming at the minimum magnification. At this time, the traveling body 2 and the lens barrel 3 attached to the traveling body 2 come closest to the rightmost image forming side on the base 1 shown in FIG.

[0019]

As described above, according to the peripheral light amount adjusting device for the optical device of the present invention, when the relative position between the traveling body and the cam plate is changed, the cam plate is changed in accordance with the change in the relative position. The cam surface position of the mask plate that is press-fitted to the follower protruding from the lens is displaced, and the mask plate is rotated / displaced in accordance with this displacement operation, whereby the light flux passing through the lens is changed to the imaging magnification of the optical system. Accordingly, it is possible to appropriately adjust with high accuracy, and it is possible to provide a high quality optical device. Further, according to the peripheral light amount adjusting device of the optical device of the present invention, the cam surface is formed on at least one of the mask plates used as the light flux limiting means, while the cam plate for adjusting the inter-lens distance is used. Has a follower that engages with the cam surface, and in particular, a dedicated drive means for the light flux limiting means is not separately provided, and by simply pressing the cam surface against the follower, the distance between the lens and the amount of light transmitted through the lens are Since both adjustments can be performed, there is an effect that the configuration is simple, the device can be downsized, and the occurrence of failures is small. Further, according to the peripheral light amount adjusting device for an optical device according to the present invention, it is possible to perform a complicated light amount correction by configuring a large number of mask plates to partially overlap as the light flux limiting means. Higher quality and higher functionality can be achieved.

[Brief description of drawings]

FIG. 1 is a plan view showing a peripheral light amount adjusting device of an optical device according to the present invention.

FIG. 2 is an exploded perspective view of essential parts showing a peripheral light amount adjustment device for an optical device according to the present invention.

FIG. 3 is an explanatory diagram illustrating an operation of the peripheral light amount adjustment device shown in FIG.

FIG. 4 is an explanatory diagram for explaining a problem during zooming in a conventional optical device.

[Explanation of symbols]

 2 traveling body 3 lens barrel 3b interlocking pin 4 cam plate 4c follower 5 light quantity limiting means 5d long hole

Claims (1)

[Claims] 1. A traveling body on which a lens barrel having a built-in lens is placed, and which moves along the optical path direction of the lens when an image of a subject is taken by changing the magnification, the traveling body is provided in the lens barrel. A light amount correction unit that moves together with the lens barrel to change the light flux from the subject when the magnification is changed, a cam plate with which the lens barrel is engaged via the traveling body, and a cam plate. An optical device having a follower, wherein the light amount correcting unit regulates the light flux as the follower slides in pressure contact with the light amount correcting unit as the traveling body moves in the optical path direction. A peripheral light intensity adjustment device.