JPH0614146B2 - Projection optics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection optical system suitable for projecting an object plane, which is an original image, onto an image plane in an optical device such as an electrophotographic copying machine and a facsimile, and in particular, Suitable projection when projecting at various magnifications such as reducing or enlarging the object plane on the image plane using a so-called compound eye system in which a plurality of lens elements composed of a condensing light transmission body or microlenses are arranged in rows It relates to an optical system.

(Prior Art) Conventionally, in an optical apparatus such as an electrophotographic copying machine or a facsimile, a compound eye system is used to project an object plane on an image plane at a predetermined magnification. As the projection method, there are used two methods: a method by an erecting real image system that projects an object surface as an erecting real image on the image surface and a method by an inverted real image system that projects an object surface as an inverted real image on the image surface. Of these, the inverted real image system requires only one image formation as compared with the two times image formation of the erect real image system, so that the total optical length can be shortened, the entire optical system can be simplified, and the entire apparatus can be easily downsized. It has features.

Therefore, the inverted real image system is used in many electrophotographic copying machines. However, in the inverted real image system, the object image rotates 180 degrees on the image plane. Therefore, when the compound eye system is used, the object images of the respective inverted real image systems are each maintained on the image plane by using a reflecting mirror. Need to overlap.

Further, even if the above-mentioned 180 degree rotational deviation is corrected by an appropriate means, in the case of zooming, the "image shift" and "magnification shift" of the image, which are peculiar to zooming, are determined to determine the imaging performance of the compound eye system. Is there. Since the causes of these problems are the same in principle, the conventional erecting real image system will be described below as an example.

In an erecting real image system, a so-called erecting equal-magnification system having a projection magnification of 1 × has been proposed in, for example, Japanese Utility Model Publication No. 48-18204. In the same publication, as shown in FIG. 2, a compound eye system 20 is constituted by a plurality of erecting real image systems 21 composed of minute lenses, and a partial image of a predetermined range of the object plane 1 is projected on the image plane 2 and superposed. It forms an integral image. As a result, a large object plane that cannot be covered by one erecting real image system is projected onto the image plane.

The compound eye system shown in FIG. 2 is constructed such that the optical axes of the erect real image systems 21 are parallel to each other because the projection magnification is 1 ×, and each ray on the optical axis is an object plane 1 and an image plane 2. It is configured to intersect vertically with. As a result, each erect real image system 21
It is possible to form an integral image by superimposing projected images on the image surface, so-called multiple images, on the image surface.

Generally, when the object distance is changed from the state of the equal magnification system in order to make the projection optical system having the compound eye system a minute system or a magnifying system, the magnification of each erecting real image system changes, whereas that of each erecting real image system changes. Since the optical axis distance remains the same, the multiple images due to the erecting real image systems do not overlap on the image plane and are displaced, causing so-called image displacement. The image shift phenomenon at this time is a cause of significantly deteriorating the optical performance of the projected image. For example, Japanese Patent Application Laid-Open No. 57-16415 proposes a method of correcting an image shift of a multiple image when reduction projection or enlargement projection is performed using a compound eye system including a plurality of erect real image systems. In this publication, as shown in FIG. 3, a plurality of erecting real image systems 31 forming a compound eye system 30 are arranged so that their optical axes gradually incline with respect to the optical axis 311 of the central erecting real image system 310. This corrects the deviation of the multiple images. However, in this compound eye system, the optical performance and the high axis length (the optical length of the high axis from the object plane to the image plane) are different for each erect real image system. When the light rays on the optical axis of the erecting real image system for projection intersect the object plane and the image plane, they largely deviate from the vertical. Therefore, as shown in FIG. 4, in the erecting real image system 41 having a large inclination, the object surface having the same projection magnification is inclined from the normal object surface 1 and becomes like the object surface 42.

On the other hand, an image plane having the same projection magnification is also a normal image plane 2
It tilts with respect to the image plane 43. As a result, a so-called "magnification shift" occurs in which the imaging magnification is partially different in the same visual field range by an amount corresponding to the difference between the optical path lengths l41 and l42 shown in FIG. 4 around the object plane. Come on.

As described above, in the conventional projection optical system using the compound eye system, the magnification deviation occurs even if the deviation of the multiple images is corrected, and it is difficult to obtain a projection image having high optical performance in the projection other than the equal magnification. ing.

Further, in the same publication, the entrance end surface or the exit end surface of each erecting real image system is decentered or a refracting power is added as necessary to reduce the deviation in magnification, but this is the entire projection optical system. Becomes complicated. And in principle,
Since the optical axis of each erecting real image system cannot be perpendicular to the object plane and the image plane, there is a limit to such correction, and it is difficult to largely eliminate the magnification deviation by such means.

In addition, a compound eye system composed of a plurality of erecting real image systems is used to correct image shift of multiple images when performing reduced projection or enlarged projection, for example, Japanese Patent Laid-Open Nos. 59-45420 and Sho. It is proposed in Japanese Patent Publication No. 59-216115.

In Japanese Patent Laid-Open No. 59-45420, as shown in FIG. 5, at least one of the erecting real image system on the object plane 1 side or the image plane 2 side of the compound eye system 50 composed of a plurality of erecting real image systems 51. A projection optical system is proposed in which image deviation of a multiple image is corrected by disposing light beam deflecting members 52 and 53, which are Fresnel lenses having different deflection angles.

Further, in Japanese Patent Laid-Open No. 59-216115, as shown in FIG. 6, a plurality of spherical lenses 62 are provided on at least one of the object plane 1 side and the image plane 2 side of a compound eye system 60 composed of a plurality of erecting real image systems 61. A projection optical system in which 63 is arranged to correct the image shift of multiple images is proposed.

However, in the projection optical systems proposed in the above two publications, the erecting real image systems have different optical axis lengths,
Moreover, the optical axis of the erecting real image system that projects the periphery of the object plane is largely tilted with respect to the object plane and the image plane. Therefore, as described above, a magnification shift that can correct the image shift of the multiple images occurs, which causes a large reduction in the optical performance of the projected image.

The above-mentioned magnification shift similarly occurs when the compound eye system is configured by an inverted real image system due to the same cause as in the case of the erect real image system.

(Problem to be Solved by the Invention) When the present invention uses a compound eye system composed of a plurality of inverted real image systems to project an object plane including magnifications other than equal magnification such as reduction or enlargement, image shift of multiple images It is an object of the present invention to provide a projection optical system in which the optical performance of a projected image is improved by simultaneously correcting and correcting or eliminating the magnification shift.

(Means for Solving the Problems) The projection optical system of the present invention, when projecting and superimposing the object plane on the image plane at a reduction or enlargement magnification by a compound eye system having a plurality of inverted real image systems, creates a light beam in the optical path. Deflection means having a plurality of optical members for deflecting is arranged, and the plurality of inverted real image systems are configured such that the light rays on their optical axes intersect each other in space, and on the optical axes of the plurality of inverted real image systems. That each light ray is perpendicular to at least one of the object plane or the image plane, and the plurality of inverted real image systems are arranged on the same plane such that their optical path lengths are different from each other. It has a feature.

In particular, each of the plurality of optical members is composed of a plurality of reflecting mirrors facing each other for each of the plurality of inverted real image systems, and the angles of the plurality of reflecting mirrors are arranged to be changed for each of the inverted real image systems. The deflecting means is provided between at least one of the object plane and the compound eye system or between the image plane and the compound eye system, and the optical member is composed of a reflecting mirror, and the one reflecting mirror is used to form the optical member. At least two of the multiple inverted real image systems
The feature is that the light flux passing through one of them is deflected.

Besides, the features of the present invention are described in the embodiments.

(Embodiment) FIG. 1 is a schematic view of an optical system of an embodiment when the projection optical system of the present invention is constituted by a reduction system. In the figure, 1 is an object plane, 2 is an image plane, 10 is a compound eye system, and is composed of a plurality of inverted real image systems 11, 12, and 13.

The points A2, B2, C2 and the points A3, B3, C3 are positions where optical members for respectively deflecting the light fluxes passing through the inverted real image system are arranged in rows. Particularly in this embodiment, the optical member is composed of a reflecting mirror and is arranged with a predetermined inclination.

In this embodiment, the reflecting mirror is omitted for simplicity, and only the optical path of the light beam of the optical axis cormorant of each inverted real image system when reflected by the reflecting mirror is shown.

In this embodiment, points A2, B2, C2 and points A3, B3, C3
Each of the plurality of optical members arranged in a line along the line constitutes one deflecting unit.

Points A1, B1, C1 on the object plane 1 and points A4, B4, C4 on the image plane 2 are inverted real image systems 11, 12, 1.
This is the position where the light rays L1, L2, and L3 on the optical axis 3 intersect.

In this embodiment, a plurality of inverted real image systems are composed of lens elements having different optical characteristics, and their optical axes are set so that they are all located in the same plane. This simplifies the layout. The optical axis lengths of the plurality of inverted real image systems are different, and the optical axis length of the inverted real image system located in the central portion is the shortest, and the peripheral inverted real image systems are longer.

In this embodiment, a predetermined range of the object plane 1 is reflected by a reflector arranged at a point C3 by the inverted real image system 13 via a reflector having an object plane near the point C1 arranged at a position C2 with a predetermined inclination. After that, the image is reduced and projected in the vicinity of the point C4 on the image plane 2. At this time, in this embodiment, points C1, C2, C
3 and C4 are arranged on the same plane.
As a result, the loci of the optical axes of the inverted real image systems are on the same plane, and the projected images of the inverted real image systems are relatively rotated so as not to cause "rotation blur". These are exactly the same for other inverted real image systems, and a predetermined range of the object plane 1 is reduced and projected onto the image plane.

When the projection magnification is m, the points A1 and B on the object plane 1 are
Interval with 1 And the distance between points A4 and B4 on the image plane 2 The ratio with is set to m times. The same applies to the intervals at other points.

In the coordinate system shown in FIG. 1, for example, points B1, B2, B
3, when representing a B4 coordinate B1 = (x, l / 2 , h / 2) B2 = (x, l / 2, -h 1) B3 = (- mx, -l / 2, h 2) B4 = (-Mx, -l / 2, -h / 2).

At this time, the coordinate points h ₁ and h _{2 of} the points B2 and B3 in the Z-axis direction
Let L be the optical axis length of one inverted real image system Is configured to be. Here, the optical axis length L is expressed as a function of the projection magnification m, and is a value that varies depending on the projection magnification m.

In this embodiment, the projected images on the image plane formed by the respective inverted real image systems, so-called multiple images, are changed in shape and inclination of the plurality of reflecting mirrors provided on the object plane 1 and image plane 2 sides, respectively. The optical axes of the system intersect in space, that is, the optical axes intersect each other when projected onto one plane, so that they overlap each other to form an integral image as a whole, preventing image shift is doing.

In the present embodiment, the light ray L1 on the optical axis of each inverted real image system is used.
The inclinations of the inverted real image systems and the reflecting mirrors are set so that L3 intersects the object plane 1 and the image plane 2 at a right angle. That is, the light rays L1 to L3 on the optical axis of each inverted real image system are reflected by a reflecting mirror and then become parallel to each other and intersect perpendicularly to the object plane 1 and the image plane 2.

This prevents the occurrence of "magnification shift" that occurs when the ray on the optical axis described in FIG. 4 intersects the object plane or the image plane at an angle.

FIG. 7 is a top view of FIG. 1 at this time, and FIG. 8 is a side view of FIG.

Each reference numeral in FIGS. 7 and 8 is exactly the same as that shown in FIG.

In FIG. 7, a straight line D1 connecting the points A1, B1, C1 on the object plane 1 and a straight line D4 connecting the points A4, B4, C4 on the image plane 2 are parallel. And multiple inverted real image systems 1
Each element is set so as to intersect or simply intersect at a point O in the space when the optical axes of 1, 12, and 13 are extended.

When the projection magnification m of the projection optical system at this time is expressed by using the distances D71 and D72 between the elements shown in FIG. 7, m = D72 / D71.

Positions A2, B2, C2 and positions A3, B of each reflecting mirror
Although C3 and C3 can be arbitrarily set within the range that satisfies the expression (1), once each position of one reflecting surface is determined, the rest can be sequentially determined according to the characteristics of the inverted real image system.

In this embodiment, the case where the reflecting mirror is used as the optical member is shown. For example, as shown in FIG. 9, the prism members 90 and 91 are used.
, The ray L3 on the optical axis of the inverted real image system 13
Also, even if the optical axis and the image plane 2 intersect each other, the image shift and the magnification shift can be similarly prevented.

In the embodiment shown in FIG. 1, a case has been described in which the deviation of magnification is completely corrected by causing the light rays on the optical axis of the inverted real image system to vertically intersect the object plane and the image plane. If deviation is allowed, the light rays on the optical axis may intersect perpendicularly to at least one of the object plane and the image plane.

In the above embodiments, the crosstalk of each inverted real image system from the first reflecting mirror having a separate reflecting surface for each inverted real image system to the final reflecting mirror having a separate reflecting surface through the inverted real image system. In order to prevent this, it is preferable to arrange a light shielding member.

Further, in the above embodiments, the case where the projection optical system is applied to the reduction system has been described. However, when the projection optical system is applied to the enlargement system, the present invention is applied in the same manner if the entire reduction system is reversed. be able to.

In the present embodiment, a common reflecting surface for simply deflecting a light beam is provided on at least one of the object plane and the deflecting means or the image plane and the deflecting means, and the overall arrangement of the projection optical system is arranged. May be set arbitrarily.

Such setting is effective when the relative relationship between the object plane and the image plane is brought to a predetermined positional relationship and when the front-back relationship of the image is corrected.

In this embodiment, one mirror may be used to deflect the light fluxes from a plurality of inverted real image systems if a slight image shift or magnification shift is allowed.

In this embodiment, the case where the compound eye system is composed of three inverted real image systems is shown, but the object of the present invention can be achieved by providing two or more inverted real image systems.

In the present embodiment, two deflecting means are used and one reflecting mirror is used as one deflecting means. However, as described above, "rotational shake", "image shift", "magnification shift", etc. are corrected. A plurality of reflecting mirrors or refracting members may be used if the configuration and the object plane and the image plane are independently equivalent.
For example, as shown in FIG. 10 (A), the light rays from the object plane 1 may be guided not only in one plane but in another plane and then returned to the original plane. Further, as shown in FIG. 10 (B), when the number of reflecting mirrors constituting the deflecting means is increased so that the line segment 101 in one direction of the object plane 1 is projected onto the image plane 2 by each inverted real image system. If the image of the line segment 101 of each object plane is one line segment 102 on the image plane 2 so that there is no so-called rotational deviation, an arbitrary configuration according to the relative positional relationship between the object plane and the image plane can be obtained. Can be taken.

This is preferable because the degree of freedom in arrangement can be increased and an arbitrary configuration can be adopted according to the relative positional relationship between the object plane and the image plane.

Further, as shown in FIGS. 11A and 11B, a compound eye system 111 including a plurality of inverted real image systems is provided between the object plane 1 and the deflecting means or the image plane depending on the projection magnification and the object-image distance. It may be provided in any one direction between the two and the deflecting means.

According to this, the optical axes of all the inverted real image systems can be aligned and the structure is simplified, which is preferable.

In the present embodiment, when the inverted real image system has a space in the optical system such as a microlens, etc., FIG. 12 (A), (B),
As shown in (C), a deflecting means may be provided at the spatial position. In the figure, reference numeral 121 is a microlens.

(Effects of the Invention) According to the present invention, by using the deflecting means composed of a plurality of optical members for deflecting a light beam when the object plane is reduced or enlarged and projected using the compound eye system composed of a plurality of inverted real image systems. It is possible to achieve a projection optical system in which both image shifts and magnification shifts of multiple images on the image plane are well corrected.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical system of an embodiment of the present invention, FIG. 7 is a top view of FIG. 1, FIG. 8 is a partial side view of FIG.
Figure, Figure 10 (A), (B), Figure 11 (A), (B), Figure 12
(A), (B) and (C) are partial side views of another embodiment of the present invention, and FIGS. 2, 3, 5 and 6 are explanatory views of a part of a conventional projection optical system. , FIG. 4 is an explanatory view of a projected image of a part of FIG. In the figure, 1 is the object plane, 2 is the image plane, 10, 20, 30, 50,
Reference numeral 60 is a compound eye system, 11, 12, and 13 are inverted real image systems, A2, B2, C2, A3, B3, and C3 are positions where optical members are arranged, and L1 to L3 are optical axes of the inverted real image system. The upper ray.

Claims (4)

[Claims] 1. A deflection means having a plurality of optical members for deflecting a light beam in an optical path when an object plane is projected onto an image plane at a reduction or magnification ratio and superposed by a compound eye system having a plurality of inverted real image systems. Then, the plurality of inverted real image systems are configured such that the light rays on their optical axes intersect each other in space, and each light ray on the optical axes of the plurality of inverted real image systems is at least one of the object plane or the image plane. To be perpendicular to the plane of
A projection optical system in which the plurality of inverted real image systems are arranged on the same plane such that their optical path lengths are different from each other. 2. The plurality of optical members are composed of a plurality of reflecting mirrors facing each other for each of the plurality of inverted real image systems, and the angles of the plurality of reflecting mirrors are changed for each of the inverted real image systems. The projection optical system according to claim 1, wherein: 3. The projection optical system according to claim 2, wherein the deflecting means is provided between at least one of the object plane and the compound eye system or between the image plane and the compound eye system. system. 4. The optical member comprises a reflecting mirror, and the one reflecting mirror deflects a light beam passing through at least two of the plurality of inverted real image systems. The projection optical system according to item 1 above.