JP2949949B2 - Variable magnification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable magnification device such as a copying machine and an image reader.

[0002]

2. Description of the Related Art Conventionally, with the movement of a lens using a fixed focus lens, (1) an object-side mirror group moves to correct a conjugate length to change the magnification (2) an image-side mirror group moves and becomes conjugate Device for Correcting Length and Changing Magnification (3) There is a device for correcting conjugate length by reciprocal movement of the object-side mirror group and the image-side mirror group to change the magnification.

[0003] In any case, however, the movable range of the mirror group is limited by the movable range of the fixed focus lens.

On the other hand, a zoom lens is used to change the magnification while keeping the conjugate length constant. (1) Apparatus for moving the zoom lens (2) The zoom lens is fixed, and the object-side or image-side mirror group is moved. An apparatus (see Japanese Patent Application Laid-Open No. 221465/1990) has been proposed.

However, this method is not sufficiently wide because the range in which zooming is possible is limited by the variable range of the focus of the zoom lens.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to enable zooming in a wide range.

[0007]

SUMMARY OF THE INVENTION The present invention provides a zoom lens system that performs zooming by moving and zooming the zoom lens when the magnification is within the zooming allowable range, and zooms the zoom lens when the magnification is out of the zooming allowable range. While the focal length of the zoom lens is kept constant, zooming is performed by moving the zoom lens and moving the image side mirror group and / or the object side mirror group.

[0008]

When the magnification is within the zooming allowable range, the conjugate length is kept constant by zooming of the zoom lens. When the magnification is out of the zooming allowable range, the image side mirror group and / or the object side mirror group is maintained. By performing the conjugate length correction by moving the image, it is possible to perform a zooming wider than the conventional copying zooming.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below using a copying machine as an example.

As shown in FIG. 1, the optical system of the copying machine irradiates the original 1 with an exposure lamp 12 and scans the original.
2, a first mirror 2 moving integrally with the second mirror 2, an object-side mirror group having a second mirror 3 and a third mirror 4, a zoom lens 5, and an image-side mirror having a fourth mirror 6 and a fifth mirror 7. A group and a sixth mirror 8 are provided to project reflected light from the document 1 onto the photosensitive drum 9.

FIG. 2 shows a detailed description of the zoom lens and the image side mirror group.

A guide rod 20 extending in the optical axis direction is provided on the base plate 10 (see FIG. 1).
Holds a lens unit 21 having the zoom lens 5. Further, on the base plate 10, a lens unit drive motor M1, pulleys 22, 23, gears 24,
5 and a drive pulley 26 are provided.
The lens unit 21 is fixed to a wire 27 stretched between the pulley 22 and the pulley 23, and when the driving motor M1 rotates, the lens unit 21 moves in the optical axis direction. ing.

A guide rod 30 extending in the optical axis direction is provided on the base plate 11 (see FIG. 1).
An image side mirror group holder 31 having a fourth mirror 6 and a fifth mirror 7 is held. Also, on the base plate 11,
Image side mirror group holder drive motor M2, pulley 3
2, 33, gears 34, 35, and a drive pulley 36 are provided. The drive pulley 36, the pulley 32, and the pulley 3
When the holder 31 is fixed to the wire 37 stretched between the three and the drive motor M2 rotates,
The holder 31 is configured to move in the optical axis direction.

FIG. 1 shows the operation when reducing the magnification from the original copy.
This will be described with reference to FIG.

At the time of 1: 1 copying, the zoom lens 5 and the image side mirror groups 6 and 7 are at the positions indicated by solid lines.

When a reduction magnification within the zooming allowable range of the zoom lens is input, the zoom lens moves to the left in the drawing and performs zooming to keep the conjugate length constant.
Therefore, the positions of the image-side mirror groups 6 and 7 are fixed (solid lines). At the time of the minimum reduction within the zooming allowable range, the zoom lens is at the position 5a.

When further reducing or changing the magnification, that is, when a reduction magnification outside the allowable zooming range is input, the magnification cannot be changed only by zooming. Therefore, the zoom lens is further moved to the left side of the drawing from the position 5a of the zoom lens at the time of the minimum reduction within the zooming allowable range. However, if the image-side mirror group is fixed at the position indicated by the solid line, the focal length does not match and the image is disturbed. Therefore, the image side mirror group is moved to the left side of the drawing while maintaining the focal length at the time of the minimum reduction within the zooming allowable range.
When the zoom lens is moved to the position 5a (broken line),
The fourth mirror 6 and the fifth mirror 7 of the image side mirror group move to the positions 6a and 7a (broken lines), respectively.

The correction of the conjugate length by the movement of the image side mirror group at this time is controlled based on a known imaging formula. The focal length of the zoom lens at that time is the focal length at the time of the minimum reduction within the zooming allowable range.

Next, the correlation between the movement of the zoom lens and the zooming will be described in detail.

Zooming is for moving an internal lens group in a zoom lens. The movement of the inner lens group is caused by the pins implanted in the inner cylinder holding the inner lens group,
It is engaged with a cam groove formed in the outer cylinder, and the rotation of the outer cylinder causes the inner cylinder to move back and forth.

In the present invention, zooming is performed at the time of zooming within the allowable zooming range, and no zooming is performed at the time of zooming out of the allowable range. Therefore, the cam groove is inclined in the optical axis direction within the allowable zooming range. In addition, it is formed perpendicular to the optical axis direction outside the zooming allowable range.

Control during zooming will be described with reference to the control block diagram of FIG. 3 and the flowchart of FIG.

First, a copy magnification is input on a document panel or the like. The microcomputer CPU determines whether the input is within the zooming allowable range of the zoom lens (step 1).

If the CPU determines that the zooming is within the allowable range, the driving motor M2 for the mirror group is stopped (step 2), and the driving motor M1 for the zoom lens is started (step 3). As a result, movement and zooming of the zoom lens are performed. If the CPU determines that the zooming is out of the allowable range, the mirror group driving motor M
2. The drive motor M1 of the zoom lens is started together (steps 4 and 5). At this time, the zoom lens also moves, but zooming of the lens is not performed.

When the setting is completed, the motor M
1. Turn off M2 (steps 6 and 7) and return to the main routine.

In this embodiment, only the case of zooming in and out is shown. However, even in the case of zooming in and out, the movement and zooming of the zoom lens when zooming within the zooming allowable range are performed. Zooming is performed with the conjugate length kept constant, and when zooming outside the allowable zooming range, the zoom lens is moved, and the conjugate length is corrected by moving the object-side mirror group while maintaining the zooming focal length. It is possible.
Further, at the time of zooming out of the zooming allowable range in the reduction zooming, the image-side mirror group is moved. Instead, the object-side mirror group can be moved to zoom.

[0027]

According to the present invention, at the time of zooming within the zooming allowable range, zooming is performed by moving the zoom lens and zooming. At the time of zooming outside the zooming allowable range, the zoom lens is moved and the image side is moved. By moving the mirror group and / or the object side mirror group, wide zooming is possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an optical system according to the present invention.

FIG. 2 is a perspective view of a drive system for a zoom lens and a mirror group.

FIG. 3 is a control block diagram during zooming.

FIG. 4 is a flowchart illustrating an operation during zooming.

[Explanation of symbols]

 5 Zoom lens 21 Zoom lens unit 31 Image side mirror group holder M1 Zoom lens drive motor M2 Image side mirror group holder drive motor

Claims (1)

(57) [Claims] 1. A zooming device including a zoom lens, an object-side mirror group, and an image-side mirror group, wherein: a means for holding the zoom lens movably in the optical axis direction; and an object-side mirror group and / or an image. Means for holding the side mirror group movably in the optical axis direction, magnification input means, and when inputting a magnification within the zooming allowable range of the zoom lens,
Zooming is performed by keeping the conjugate length constant by moving the zoom lens and zooming.
Magnification means for moving the image-side mirror group and / or the object-side mirror group together with the movement of the zoom lens, and correcting the conjugate length while changing the magnification while maintaining the focal length of the zoom lens. Variable magnification device.