JPS60425A - Flare light shielding device of variable power optical system - Google Patents

Abstract

PURPOSE:To execute exactly light shielding of a flare by forming at least one of a fixed light shielding plate and a movable light shielding plate with an elastically deformable plate material. CONSTITUTION:A variable power copying machine having an invariable conjugate length, in which a main lens 6 moves by a prescribed range in the optical axis direction, and with respect to each magnification, one prescribed piece of additional lenses 7, 8, 9 and 10 can go in and out of an optical path so that the main lens 6 and the optical axis coincide with each other is shown in the figure. An original moving on an original guide glass 1 is irradiated from a light source, and its reflected light is reflected by the first mirror 2 and the second mirror 3 which are fixed, focused by the main lens 6, and one of the additional lenses 7-10 brought onto the optical axis, reflected by the third mirror 4 and the fourth mirror 5 which are fixed, and an image is formed on a photosensitive body 12.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a method of moving a main lens along an optical path axis within a predetermined range and performing variable magnification projection onto an imaging plane using the main lens alone or in combination with 1 and an additional lens. This invention relates to a flare light shielding device for an optical system that allows for

In prior art variable-magnification copying machines and the like, the projection magnification onto the imaging plane is changed by moving the imaging lens along the optical path axis. In this case, the optical path length from the document surface to the imaging surface, that is, the conjugate length, also changes, so in an optical system of a moving scanning type with a fixed mirror on the document, the conjugate length is generally changed by also moving some of the mirrors.

However, in the case of the original moving type, mirror scanning is not performed, so it is convenient to keep the conjugate length unchanged even when changing the magnification. In that case, the -1 additional lens may be inserted into the optical path so that its optical axis coincides with that of the main lens, and the combined focal length may be changed.

Conventionally, the method for inserting the additional lens into the optical path when changing magnification is to attach the main lens and the additional lens to the same carriage, and when the carriage is moved for changing the magnification, the additional lens is inserted into the optical path using a cam or the like. I was trying to bring it into position. Therefore, the mass of the carriage containing the lenses increases, the power required for movement increases, and the number of additional lenses is limited, making it unsuitable for multi-stage magnification.

Therefore, instead of attaching several additional lenses to the main lens carriage, multiple additional lenses are mounted on separate carriages and moved in a direction perpendicular to the optical path axis so that they can enter and exit the optical path, and the magnification can be changed to the desired magnification. In this case, an optical system has been proposed in which the main lens is moved to a predetermined position, and an additional lens corresponding to its magnification is inserted into the optical path so that its optical axis is aligned with the main lens, or is moved out of the optical path. ing.

In this case, if an attempt is made to move the light shielding plate over the entire irradiation width integrally with the lens as in the conventional method, the light shielding plate will be obstructed by the additional lens and cannot be moved.

In addition, even when changing the magnification by moving only the main lens, moving the light shielding plate over the entire width together with the lens increases the moving mass, so the light shielding plate should be fixed to the machine frame as much as possible. It is desirable to When the rays of light reach the imaging plane, it is inevitable that flare will occur. In order to block the light rays that cause flare, if a light shield is installed on both sides of the lens at right angles to the fixed light shield so that the light shielding area overlaps with the fixed light shield, the lens may overlap with the fixed light shield. This interferes with the light and prevents it from passing through the aperture of the light shielding plate. For this reason, a flare light shielding device has been proposed in which the light shielding plate is movable within its entire plane using a cam or the like so that the degree of opening of the aperture can be varied, but this method has the disadvantage of being complicated in construction.

Purpose The present invention solves the above-mentioned drawbacks of the conventional flare light-shielding device when fixed to a light-shielding sheet metal machine frame with an optical system that enables variable magnification projection by moving the main lens away from the optical path axis. It is an object of the present invention to provide a device that has a simple configuration, can reliably block flare light, and can move a lens to a predetermined position.

Configuration The present invention will now be described in detail based on embodiments shown in the drawings.

In FIG. 1, the main lens 6 moves within a predetermined range in the direction of the optical axis, and for each magnification, a predetermined one of the additional lenses 7, 8, 9, and 10 aligns with the main lens. This is an embodiment in which the present invention is applied to a variable magnification copying machine whose conjugate length remains unchanged and which can enter and exit the optical path.

The document moving on the document guide glass is illuminated by a light source (not shown), and the reflected light is reflected by a fixed first mirror 2;
It is reflected by the second mirror 3, brought to the main lens 6 and on the optical axis, focused by at least one additional lens, reflected by the fixed third mirror 4 and fourth mirror 5, and then onto the photoreceptor 12. It is designed to form an image.

The variable magnification copying machine ij of this embodiment has a magnification of 1.41 times,
It is possible to make copies at the same magnification, 0.707x, and 0.5x, and in each case, the main lens 6 is used as the optical axis and moved to a predetermined position, and at each of the above magnifications. Correspondingly, one of the additional lenses 7.8, 9, 10) is brought into the optical path and positioned so that its optical axis coincides with that of the main lens 6. Figure 1 shows the main lens 6 for 1.41x enlarged copying.
and the position of the additional lens 7 are shown by solid lines. The other additional lenses 8, 9, and 10 are retracted to positions where they do not block the optical path.

FIG. 2 is a plan view illustrating flare in which light reflected from the surface of the document irradiated by the light source enters the surface of the photoreceptor 12 without passing through the lens.

The waist of the envelope of the outermost ray of the light beam that forms an image on the photoreceptor at each magnification (in the figure, between the additional lenses 7 and 8)
A light shielding plate 11 is fixedly provided on the side plate 14. This fixed light shielding plate 11vC is provided with an aperture that does not block light from the optical path from the original to the image forming area on the photoreceptor 12 at any magnification. I'm in a good mood. Both ends of the a and bij openings in FIG. 2 are shown. When the magnification is 1.41 times, the light ray passing outside the outer circumference point d of the lens cell of the lens 7 points to the intersection A of the straight line passing through the above 98 points and the above d point and the photoreceptor surface 12.
, flare occurs in the direction of point C at the end of the imaging range on the opposite side with respect to the optical axis. Similarly, a light ray passing outside a point E on the opposite side of the outer periphery of the lens cell of the additional lens 7 causes a flare in the direction C' from the intersection N between the extension of the straight line EB and the surface of the photoreceptor 12.

Also, when the magnification is 05x, the main lens / lens 6 and additional lens IO
is at the position indicated by the chain line in FIG. 2, which in this case is a point ♂ on the outer periphery of the lens cell of the main lens 6.

A point a on the light shielding plate 11 is caused by a ray passing outside e'.

Flares occur in the direction of C9σ from the intersections B and B' of the extension of the straight line connecting b, at, and e/ with the surface of the photoreceptor 12, respectively.

In the present invention, in order to block this flare light (indicated by 7-cutting in FIG. 2), main lenses 6 are installed on both sides of the main lens 6 in a direction perpendicular to the optical axis, as shown in FIGS. 1 and 3. A movable light shielding plate 13 is provided so as to move together. The range in which the movable light-shielding plate 13'j5 is provided is such that even when the magnification is 9, the light that is reflected from the original and passes through the outside of the lens blocks the light rays that pass inside points a and b on the fixed light-shielding plate. ,
In other words, the setting is such that the light rays passing outside the outermost point f+g of the movable light shielding plate 11 do not pass through the opening (between points a and b) of the fixed light shielding plate. If the range of the movable light-shielding plate 13 is determined in this way, the flare light will be reliably blocked, but as is clear from FIG.
The length between g is longer than the opening width ab of the fixed light shielding plate 11.

In the present invention, the movable light shielding plate 13 is made of a flexible light shielding material,
For example, it is made of black Mylar film or the like. In addition,
In this optical system, the width of the reflected light beam from the original in the scanning direction (vertical direction in FIG. 1) is regulated by a slit (not shown), so the vertical width of the movable light shielding plate 13 is as shown in FIG. Even if it is narrow, light will not leak from above and below.Since this light shielding device is constructed as described above, it can reliably shield flare light at any magnification, and When the main lens 6 is moved through the aperture of the fixed light shielding plate 11 to change the magnification, the movable light shielding plate 13 is easily bent when it is pressed by the fixed light shielding plate 11 and passes through the aperture. Once this is completed, the movable light-shielding plate immediately returns to its original straight state due to the elasticity of the movable light-shielding plate, exerting its flare light-shielding function.

Note that it is desirable to not only make the Mylar film or the like that makes up the movable light-shielding plate black, but also to make the surface matte in order to prevent reflections.

In the above embodiment, the movable light-shielding plate that moves together with the lens is made of an elastic thin plate such as Mylar film, but the fixed light-shielding plate can also be made of an elastic plate. It can be relaxed.

Further, the present invention can be applied not only to the variable magnification photosphere system in which the conjugate length remains unchanged as shown in the embodiment, but also to an optical system that performs variable magnification projection by moving the main lens and some mirrors.

Effects As described above, according to the present invention, when the lens is moved for variable power in a variable power optical system, especially when the additional lens is aligned with the optical axis of the main lens and moved in and out of the optical path, the light shielding plate is used. The lens can be moved with a simple configuration without requiring a driving means, and flare can be reliably blocked.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a schematic diagram illustrating the occurrence of flare when there is no movable light shielding plate in the optical system of the above embodiment, and FIG. 3 is a diagram according to the present invention. FIG. 3 is a schematic diagram illustrating the relationship between the opening of the fixed light shielding plate and the movable light shielding plate of the light shielding device. 6...Main lens 7, 8, 'J, lO...
・Additional lens 11...Fixed light shielding plate 12...Photoreceptor (imaging surface)

Claims (2)

[Claims] (1) In a flare light shielding device for an optical system, the main lens is moved over a predetermined range along the optical path axis VC together with a carriage carrying the main lens, and enables variable magnification projection of reflected light from an original onto an imaging plane. a fixed light-shielding plate provided in a plane that crosses the optical path in the middle of the range of movement of the lens and having an aperture that does not block the optical path even when the magnification is high; It has movable light shielding plates provided on both sides of the lens, and the fixed light shielding plate and the movable light shielding plate have overlapping ranges of blocking light reflected from the original.
At any magnification, light rays passing outside the movable light shielding plate are prevented from passing through the opening of the fixed light shielding plate, and at least one of the fixed light shielding plate and the movable light shielding plate is made of an elastically deformable plate material. A flare light blocking device with a variable magnification optical system that is characterized by its sharpness. (2) The variable magnification optical system described above is an optical system whose conjugate length remains unchanged, consisting of a main lens that can move within a predetermined range along the optical path axis, and an additional lens that moves in and out of a predetermined position in the optical path. A flare light shielding device for a variable power optical system according to claim 1, wherein the flare light shielding device is a variable power optical system.