JP2007155902A - Optical image forming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that the volume of an optical image forming system constituted by combining a plurality of curved surface reflection mirrors becomes large because an optical system bends laterally in principle. <P>SOLUTION: The optical system has space between the mirrors, and the space gets useless when equipment is not used. When the equipment is not used, the space between the mirrors is made small by moving the mirrors with a mirror having a large eccentricity sensitive allowable value as center, or another mirror is housed in the space, thereby reducing the volume of the optical system. A movable mirror can be very indisputably set by selecting the mirror having the large eccentricity sensitive allowable value though the optical system has high eccentricity sensitivity originally. Since constitution reducing the space is selected regardless of the following order of an optical path, the optical system is effectively miniaturized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention generally relates to an optical apparatus using an aspherical reflecting mirror in an image forming optical system. Among such apparatuses, the present invention is particularly suitable for a projection-type image display apparatus that enlarges and projects an image of an image display device. is there.

  Conventionally, a reflection optical system using an aspherical mirror is often proposed, but there is an imaging optical system configured by combining a plurality of reflection surfaces in place of a refractive lens. By combining a plurality of aspherical surfaces (so-called free-form surfaces) reflecting surfaces that do not have a rotationally symmetric axis, an optical system that realizes good aberration correction is possible.

  When the optical system is composed of a plurality of reflecting surfaces, the optical axis is not a single straight line but bends every time it passes through the surface. Therefore, it is difficult for repeated reflection between multiple surfaces, which is common in conventional coaxial refraction lens systems, and it is difficult to reach the image plane, so there is less ghost and flare than the coaxial refraction lens system. There is.

  When the optical system is composed of only a plurality of reflecting surfaces, there is a merit that there is no chromatic aberration in principle.

  In addition, there is an advantage that the degree of freedom in handling the optical path is greater than that of the coaxial refractive optical system. An arrangement in which the position of the image plane is largely offset from the object plane cannot be realized unless the coaxial refraction system has a large angle of view and only the off-axis end portion is used. Even with such an arrangement, an arrangement configuration with a high degree of freedom can be realized without being severe in performance.

  Some of these reflection optical systems are configured as a back-surface reflection mirror by directly forming a plurality of free-form reflection surfaces on the block (block) surface of a transparent optical material and attaching a reflection film. What was comprised as a combination of a surface reflective mirror becomes object.

  In the latter case, the reflecting surfaces manufactured as a plurality of surface reflecting mirrors are combined with a predetermined accuracy. In this case, of course, the medium between the reflecting surfaces is air.

  In the present invention, the optical system is also effective in an optical system in which all optical elements are not reflective surfaces but are combined with a refractive lens.

  By the way, a projection type image display apparatus will be described as an example of a device using such an optical system. In the apparatus, generally, a light source beam is condensed using a mirror, a lens, etc., and illuminates an image display device such as a liquid crystal or DMD. The illumination light beam is two-dimensionally modulated in accordance with image information displayed on the device by transmitting or reflecting on the device. This is a configuration in which this is projected onto a screen or the like by a projection optical system constituted by a coaxial refraction lens system or the like. For example, in the case of the current general configuration of a three-plate type liquid crystal projector using three liquid crystal display panels, the illumination light beam of the light source is divided into RGB three color components by a dichroic mirror or the like, and image information corresponding to RGB is obtained. Each of the three transmissive liquid crystal panels to be displayed is irradiated. Although each liquid crystal display panel itself can only display in black and white, a transmitted light beam having RGB three-color image information can be obtained by modulating RGB three-color illumination light beams. These are synthesized using a dichroic mirror, a dichroic prism, or the like, and a light beam that has become a color image is projected onto a screen by a projection optical system.

  For such a device, since a high contrast is particularly required for a projected image, a projection optical system with a little ghost and flare constituted by an aspherical reflecting surface is a particularly suitable means. In addition, since the degree of freedom in handling the optical path is large, it is possible to realize a short-distance projection at a high elevation angle, and there is an advantage that the projection device can be placed away from the viewer.

  Even when applied to an imaging optical system, the advantage of less ghost and flare is also effective. Further, from the viewpoint of the degree of freedom of optical path arrangement, it is possible to capture images without distortion even if the imaging optical system is shifted from the front of the imaging target.

As another conventional example, Patent Literature 1 and Patent Literature 2 can be cited.
JP 2002-189172 A JP 11-119343 A

  In a reflective optical system, a light beam incident on a reflecting surface and an emitted light beam are always present on the same side of the reflecting surface, and the incident light beam does not exit from the opposite side of the element as in a refractive lens. Therefore, the two reflecting surfaces through which the light beam continuously passes must be spaced apart from each other in consideration of the width of the incident and emitted light beams. Unlike the refractive lens system, it is impossible to arrange the exit surface of one lens and the entrance surface of the next lens close to each other (sometimes with zero surface separation). Therefore, there is a problem that the size of the optical system tends to increase.

  This problem is a structural principle problem in an optical system composed of reflecting surfaces. Accordingly, it is not easy to directly solve the problem that the essential size such as the area of the reflecting surface is reduced without changing the specifications such as the brightness and focal length of the optical system, and the entire optical system is downsized.

Depending on the arrangement of the surfaces of the optical system, a configuration such as crossing the optical paths in space may be taken, and there may be a device such as reducing the volume of the entire optical system, but the optical system is compared with a case where the configuration is not used. The problem of size is only slightly mitigated. (Ineffective)
The problem that the size of the optical system having such a reflecting surface configuration is large becomes a problem when the optical system is applied to some device.

  For example, when the optical system is applied to the projection optical system, the optical system portion is large and the form is far from the cylindrical shape in the case of the refractive lens system as compared with the case where the conventional refractive lens system is used. For this reason, there is a problem that the shape of the device housing is increased irregularly / asymmetrically such that only the optical system part of the housing of the liquid crystal projector, which is usually cubic, protrudes greatly. There were problems with storage and design. Examples of such a housing shape are shown in FIGS. 9A and 9B.

  In the case of an ordinary conventional coaxial refraction lens system, a lens group that is drawn out at a predetermined interval along the optical axis and arranged in a straight line is used when using the device. A technique called “collapse”, which is reduced in the total length by moving the lens in one direction (usually toward the inside of the device) on the optical axis and reducing the distance between the lenses, is used in, for example, a camera taking lens. I came.

  Even in an optical system that uses surface reflecting mirrors (air between the surfaces), the space between the reflecting mirrors is virtually wasted when the device is not in use, and this is the size of this type of optical system This is one of the reasons for increasing the size. Therefore, when the optical system is not used, the optical system portion can be made compact when the device is not used, for example, by reducing this space as in the case of the above-mentioned collapsing.

  These are examples disclosed in Patent Document 1. This is shown in FIGS. 10 (a) and 10 (b). This is a combination of the coaxial refractive lens systems 130 and 131 and the variable shape mirror 115. (B) When the deformable mirror 115 rotates to create a space as shown in the figure, one group 130 is retracted along the bent optical axis. In the case of this example, the most object-side lens group called a so-called front lens moves, and has the largest aperture in the entire lens system. Although it is difficult to understand in the cross section in the direction of the figure shown in this example, the depth direction has a width corresponding to the same length (diameter) as the width of 130 in the figure. It is necessary that a space enough for 130 to be accommodated in FIG. 7B is secured in the lens barrel in advance, and the lens barrel partial volume around 115 must be increased even when 130 is not stored. Accordingly, while the protruding portion of 130 protruding upward in FIG. 10 (a) is lowered, it is necessary to enlarge the lens barrel volume around the storage destination 115 in advance. Even if it is not, the effect of reducing the overall size is small.

  In particular, the effect of downsizing is small even when compared with the case of a collapsible lens having only a common coaxial refraction lens system.

  In the case of an optical system using a reflecting surface, the optical axis is bent many times, so that the distance between the reflecting surfaces is gradually reduced from the end along the optical axis, following the example of the coaxial refraction lens system. Is mechanically difficult or impossible. Unlike the refractive lens system, the postures (angles) maintained in the space for each surface are various, so that even if they are shifted along the optical axis, they may not be sufficiently compact. Also, depending on the reflecting surface, the sensitivity to decentration is strict, and if it is moved in the dark, the position reproduction accuracy is not guaranteed when it is returned to its original position, which may hinder imaging performance.

  By the way, decentration sensitivity is the tendency for performance degradation to occur when an optical element is displaced in parallel from a predetermined position (hereinafter referred to as parallel shift) and rotated from a predetermined angle (or tilted, hereinafter tilted). It is a degree. When this performance deterioration is significant for a constant parallel shift and tilt, it is expressed that the decentration sensitivity of the optical element in a certain optical system is high.

  Japanese Patent Application Laid-Open No. 11-119343 discloses a projection imaging optical system using only a reflecting surface. This is shown in FIG. This is a projection optical system using only a reflecting surface.

  In this conventional invention, the reflection mirror closest to the image plane is attached to the back side of the lid of the light beam exit of the housing. When the device is not in use, the reflection mirror is closed together with the lid against the outer wall of the housing. In this conventional invention, the image of the liquid crystal display element is projected and imaged while monotonically expanding in the reflection optical system. Therefore, the size of the last mirror is particularly large, and the size of the device becomes too large when the lid is opened (the final mirror is unfolded). Therefore, it seems that some means for downsizing the equipment is essential. However, in this conventional example, only the last mirror is folded, so it can be said that the effect of downsizing is insufficient. In addition, since the operation is limited to the mirror rotation, the operation of opening the lid of the device in use is the operation of unfolding the mirror to the use state rather than the storing operation for miniaturization when not in use. Although it is simple in part, it is not devised and the effect is insufficient.

  Although details will be described later, in the case of such an optical system, since the decentering sensitivity tends to be lower in the image side mirror, it can be said that the adoption of the movable configuration of the final mirror is a means having relatively little adverse effect. However, when considered strictly, in the configuration in which the lid is rotated in this way, the axis of rotation is very close to the mirror, and the tilt error of the mirror is likely to occur, which is not preferable compared to the parallel shift. .

As a method proposed by the present invention, for example, in an imaging optical system constituted by a plurality of aspherical surface reflecting mirrors, by moving a part of reflecting surfaces in an optimum direction by an optimum distance, It is to reduce the space existing between the reflecting surfaces and to reduce the volume of the entire optical system. (This is referred to as “store” below)
In particular, by introducing a predetermined movement method that takes into account the characteristics of the optical system in the way of moving the reflecting surface, devices that incorporate these optical systems "store" the optical system when it is not in use. The housing shape of the device is made into a compact form that does not partially protrude and is easy to store.

  First, as a feature of such an optical system, there is a tendency that the surface located on the reduction side of the optical system has a higher decentration sensitivity. That is, in the case of a liquid crystal projector, the liquid crystal panel is an object plane, and this is enlarged and projected onto a screen which is an image plane. In such an optical system, the reflection surface closest to the liquid crystal panel has the highest decentration sensitivity, and becomes desensitized as the distance from the liquid crystal panel increases.

  An application example in which an object and an image are reversed in an optical system having the same configuration as the projection imaging optical system as another device will be described. A position corresponding to the screen in the above example is a document surface. This is the object plane. Also, a CCD image sensor is placed at a position corresponding to the liquid crystal panel, and this is used as an image plane. This is a configuration of a document camera that reads a document. Of course, since the specifications of the optical system are different, the magnification and brightness are different. In this case, generally, in such an optical system, the reflection surface closest to the CCD image sensor has the highest decentration sensitivity, and becomes desensitized as the distance from the CCD increases.

  Thus, if the surface magnification is not the same magnification system, the eccentricity sensitivity tends to increase as the surface is located on the reduction side. Therefore, moving the reflecting surface with high sensitivity is not a good idea from the viewpoint of securing the performance, and it is preferable to move the dull surface because it has little influence.

  Also, parallel shift and tilt are completely different concepts, so they cannot be compared in the same row. However, when compared with the reproducibility of the position / posture (residual position error amount) that is mechanically possible or easy when returning from the movement for “storage”, the parallel shift is more relative than the tilt. Is less affected.

  Specifically, it is a “storage” method in which a plurality of reflecting surfaces are moved according to the following items.

  The movement is a linear shift of the trajectory, a non-linear shift of the trajectory, rotation, and / or a combination thereof.

(Note that if the trajectory is either linear or non-linear, the position after movement return is different from the original state (the angle is the same), it is a parallel shift)
◎ Group multiple faces as a group that moves and a group that does not move.

  ◎ In a moving group, the relative positional relationship within the group does not change.

  In the case of tilting, it is preferable that the position of the rotation axis is away from the position of the tilting surface (or group).

  ◎ At least one surface (or group) does not move.

  A surface (or group) that does not move is a relatively sensitive surface.

  ◎ Close the distance between two adjacent faces (or groups).

  Move the moving surface (or group) so that the moving surface (or the surface of a part of the group) comes in the space near or inside the non-moving surface (or group).

  ◎ When moving in multiple stages, the group combination may change at each stage of movement.

According to the present invention,
(1) It is possible to alleviate the problem of the size of the volume peculiar to the imaging optics using the reflecting surface and the problem that the appearance of the device using the same becomes large and unclean.
(2) Taking into account the eccentric sensitivity of each reflecting surface, the movement of the reflecting surface is less likely to affect the imaging performance.
(3) It is possible to effectively use the space where the element does not move, such as storing the moving surface in the space between the non-moving surface.
(4) A moving method and a storing method in consideration of the difference in sensitivity between the parallel shift and the tilt are made possible.
(5) A method that achieves both miniaturization and performance maintenance, such as grouping and devising the moving direction, is made possible.
(6) When the device is stored, the same form and storage property as the conventional refractive system can be shown.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  In order to describe the embodiment, first, three items of a reference optical axis, a global coordinate system, and a local coordinate system are defined and described.

  The optical system that is the subject of the present invention is an off-axis reflection optical system (or includes this), and therefore each surface constituting the reflection optical system does not have a common optical axis. In the embodiment of the present invention, first, a light ray passing through the center of the pupil of the optical system is considered as a reference, and this light ray is defined as a reference optical axis. The reference optical axis is not clearly drawn separately from other light beams in the embodiment drawings.

  Next, consider a global coordinate system defined for the entire optical system (global coordinates are expressed in capital letters XYZ). The axes of the XYZ coordinate system described in the drawings of the respective examples are the orientations of the global coordinate system defined with respect to the entire optical system of FIG. The coordinate system is a right-handed system. Although depending on the direction of illustration of the embodiment, in any embodiment of the present invention, the reference optical axis always exists in the YZ plane. Although the global origin differs depending on the embodiment, the intersection of the object plane or the image plane and the reference optical axis is defined as the origin. The XY plane exists in the object plane or the image plane (the one with the global origin).

  Only the diagram of the first embodiment of FIG. 1-1 (details will be described later) displays the global coordinate system in alignment with the global origin. In this embodiment, the global origin is located at the center of the liquid crystal panel, which is the object plane.

  As a method for expressing the surface shape of the m-th surface constituting the optical system, it is difficult to understand the notation of the shape of the m-th surface using the global coordinate system. Therefore, we will introduce a local coordinate system for each surface. A point advanced by a predetermined interval (local origin interval) from the local origin of the m-1st surface to the mth surface is defined as the local origin of the mth surface. In this way, a local coordinate system (local coordinates are expressed in lower case xyz) is set for each surface. In the object plane (or image plane), the global origin coincides with the local origin of the plane.

The local coordinate system is displayed so as to coincide with each mirror surface only in the diagram of the first embodiment of FIG. 1-1 (details will be described later). (Omitted in other figures)
The local coordinate system is also a right-handed system. Also, the tilt of the surface is expressed by tilting the local coordinate system corresponding to each surface. The tilt angle in the YZ plane of the local coordinate system corresponding to the m-th plane is represented by an angle θm [omitted from unit degrees or less] with the counterclockwise direction being positive with respect to the Z axis of the global coordinate system. Therefore, as a matter of course, in the embodiment of the present invention, the origins of the local coordinates of each surface are all on the YZ plane. There is no surface eccentricity in the XZ and XY planes. In both the global coordinates and the local coordinates, the YZ and yz planes are meridional sections of the optical system.

  The optical system of the present invention has at least one rotationally asymmetric aspherical reflecting surface, and its shape is expressed in a form that gives z (surface Sag amount) as a xy polynomial function in the local coordinate system.

  The passing point on each surface of the previous reference optical axis is independent of the position of the origin of the local coordinate system on that surface. Further, the local origin of each surface is not necessarily in the ray effective portion of that surface.

[First embodiment]
FIG. 8 is an overall view when the apparatus is used, including the optical system of the image projection apparatus of the first to fourth embodiments according to the present invention. In this embodiment, an optical system that enlarges and projects an image displayed on a liquid crystal panel onto a screen. However, the measures and effects of the present invention can be applied to an imaging optical system for other applications. The same applies when applied.

  In FIG. 8, there is an illumination optical system (not shown) on the back side of the liquid crystal panel to illuminate the panel from the back side. In this figure, all the three color optical paths of RGB are not shown and other than the G optical path is omitted, but the optical path of RB is conjugate with the G optical path. The RGB luminous flux synthesized by the color synthesizing prism is projected onto the screen by a projection optical system constituted by free-form reflecting mirrors of the first to fifth mirrors in FIG.

  FIG. 1A shows an optical system portion of the image projection apparatus according to the first embodiment of the present invention. The first mirror is located closest to the liquid crystal panel, and numbers are sequentially assigned in the order of the second mirror to the fifth mirror in the light beam traveling direction.

  FIG. 2 is a table showing an example in which allowable values of the eccentric amount (parallel shift and tilt) of this optical system are allocated. As shown here, the allowable value for the parallel shift is the smallest for the first mirror, and the allowable value for the parallel shift increases as the mirror moves to the image side mirror. This means that the decentering sensitivity becomes weaker as the image side mirror is. Similarly, the allowable tilt value increases as it goes from the first mirror to the image side as in the previous example.

  Therefore, the mirror closest to the image side is held by a movable holding means, and when the apparatus is not used, the mirror or a plurality of mirrors near the image side are moved and stored, and the volume of the optical system is reduced. A method of reducing the size is conceivable.

  On the other hand, after moving and storing the mirrors, when using the devices, they must be moved again to reproduce the state of being held at the original position with a predetermined accuracy.

  The degree of difficulty is different between mechanically realizing the allowable position accuracy of the parallel shift and the tilt-related one with respect to the distributed parallel shift and the allowable value of the tilt. Considering the mechanical feasibility, it is easier to reproduce the accuracy of the parallel shift. Therefore, for the movement for storage, it is easy to make a device by mainly using a parallel shift that easily reproduces the positional accuracy after returning.

  The movement of the mirror of the first embodiment is as follows. As shown in FIG. 1-1, the fifth mirror is first shifted in parallel toward the third and fourth mirrors, and then the third, fourth, and fifth mirrors are integrated as shown in FIG. Parallel shift in the direction toward the first and second mirrors. It moves in the direction in which the fourth mirror is housed in the space between the first mirror and the second mirror.

  Each mirror is held at the end (one or both ends) in the X-axis direction shown in the figure, and if a mechanism such as the holding part moves while holding the mirror is adopted, it should be configured so as not to interfere with other mirrors. Can do.

  FIG. 3 shows how all the mirrors are finally stored. In the figure, the mirror arrangement before storage and the volume of the optical system are overlapped so that they can be compared after storage. Thus, when the apparatus is not used, the projection optical system portion can be stored compactly. Therefore, it is not necessary to worry about the size, which is a drawback of the reflective optical system, when the device is cleared when not in use. When the device is used, the optical system is pulled out and becomes large. However, even if the optical system part protrudes to some extent during general use, it does not seem that much.

  In particular, in the case of the liquid crystal projector of the present embodiment, the projector is installed so as to be able to project at a large elevation angle at a location close to the screen by taking advantage of the reflection optical system having a large degree of freedom in optical path arrangement. For this reason, the device can be installed at a place away from the viewer, and the size of the device can be further avoided during use.

  The power for storing the optical system may be manual or electric. In the case of electric drive, there is a problem of cost and size, but if the optical system shifts from the retracted state to the automatically expanded state in conjunction with the operation of turning on the main power, the usability is good.

[Second Embodiment]
FIG. 4 shows how the mirror moves in the second embodiment.

  The third, fourth, and fifth mirrors are integrally shifted in the direction toward the first and second mirrors. It moves in the direction in which the fourth mirror is housed in the space between the first mirror and the second mirror.

  In the case of this example, the third, fourth, and fifth mirrors move together and are not configured to move in two stages as in the first embodiment. Therefore, the mechanism for movement is simplified compared to the first embodiment. In addition, although the fifth mirror on the most image side has a large allowable eccentricity, an error factor increases if it has a mechanism for moving it alone. The advantage is that it is easy to maintain the relative positional accuracy between the third, fourth, and fifth mirrors.

  On the other hand, the effect of miniaturization is also lost, and the amount of the fifth mirror protruding to the image plane side after storage is larger than that of the first embodiment.

  Each mirror is held at the end (one or both ends) in the X-axis direction shown in the figure, and if a mechanism such as a holding member that moves while holding the mirror is adopted, it should be configured so as not to interfere with other mirrors. Can do.

  Others are the same as the first embodiment.

[Third embodiment]
FIG. 5 shows how the mirror moves in the third embodiment.

  The third, fourth, and fifth mirrors are integrally driven to rotate (rotate) in the direction toward the first and second mirrors. The axis of rotation is parallel to the X axis. The center of rotation (the position of the shaft) is offset from the location of the mirror group that actually moves as shown in the figure so that it rotates in the direction in which the fourth mirror is housed in the space between the first mirror and the second mirror. ing.

  In this example, compared with the shift of the second embodiment shown in FIG. 4, a configuration of a rotational operation in which a tilt that is slightly difficult to achieve accuracy (at the time of returning the posture from the storage) is likely to occur is employed.

  In the case of this example, the third, fourth, and fifth mirrors move together and are not configured to move in two stages as in the first embodiment. Therefore, the mechanism for movement is simplified compared to the first embodiment. In addition, although the fifth mirror on the most image side has a large allowable eccentricity, an error factor increases if it has a mechanism for moving it alone. The advantage is that it is easy to maintain the relative positional accuracy between the third, fourth, and fifth mirrors.

  In the case of the rotation operation, the mechanism is slightly simpler than the parallel movement mechanically. It is only necessary to provide a rotating shaft at a predetermined position of the member to be rotated and rotate around it. However, the center axis of rotation is preferably not in the vicinity of any mirror. This is because the sensitivity of the tilt is slightly higher than that of the parallel shift as described above, so that it is difficult to be affected by the tilt.

  When the rotation axis is virtually set at a position away from the moving object, there are mechanical means such as providing an arcuate guide for guiding the moving object.

  Also in this embodiment, the third, fourth, and fifth mirrors are moved together, so that the effect of miniaturization is lost, and the amount that the fifth mirror protrudes to the image plane side is larger than that in the first embodiment.

  Each mirror is held at the end (one or both ends) in the X-axis direction shown in the figure, and if a mechanism such as a holding member that moves while holding the mirror is adopted, it should be configured so as not to interfere with other mirrors. Can do.

  Others are the same as the first embodiment.

[Fourth embodiment]
FIG. 6 shows how the mirror moves in the fourth embodiment.

  Only the fifth mirror moves following a predetermined curved locus in the direction toward the third mirror. The 1234 mirror does not move.

  In the case of this method, there may be a case where the linear movement trajectory interferes with other mirrors at the time of storage and cannot be sufficiently reduced in size. In the present embodiment, by moving in a curved line, the mirror can be prevented from interfering with each other, so that it can be sufficiently miniaturized.

  Each mirror is held at the end (one or both ends) in the X-axis direction shown in the figure, and if a mechanism such as a holding member that moves while holding the mirror is adopted, it should be configured so as not to interfere with other mirrors. Can do.

  Others are the same as the first embodiment.

[Fifth embodiment]
Details of the fifth embodiment are shown in FIG. This embodiment is different from the previous embodiments in the configuration of the projection optical system as a base. The configuration up to the liquid crystal panel is the same as in the above embodiment. The number of free-form surface mirrors is six, and the configuration and some specifications such as how to bend the optical path are different from those of the other embodiments, but the functions, effects, and sensitivity tendencies are the same.

  The first and second mirrors are fixed. The third and fourth mirrors form an integral group and move in parallel by a predetermined distance in a direction approaching the first and second mirrors. The sixth mirror alone is translated in a direction approaching the third mirror. The fifth mirror alone is also translated in a direction approaching the fourth mirror.

The distance traveled at this time is as shown in FIG.
5th mirror travel distance = L3
6th mirror travel distance = L2
Third and fourth mirror travel distance = L1
As
L3>L2> L1
Move different distances. The order of movement is
(1) Third and fourth mirrors (2) The sixth mirror and the fifth mirror may be moved sequentially. However, each moving speed is set according to the moving distance, and the configuration in which all the mirrors start to move at the same time and stop at the same time is considered to be easy to use with little waiting time for the completion of movement. At least the final stop position of the fifth mirror overlaps with the place where the fourth mirror is located at the beginning, so the fourth mirror movement (retraction) needs to be completed first before the fifth mirror stops. There is.

  In this embodiment, the reference optical axes between the second to third mirrors, the fourth to fifth mirrors, and the sixth mirror to the image plane are all parallel. That is, it is parallel to the optical axis projected from the projection device to the screen (the center of the screen). The movement trajectory of each mirror is also parallel to this reference optical axis. However, this is not an essential condition for the configuration.

  As in this embodiment, by changing the moving distance according to the initial position of each mirror, the compactness at the time of storing the optical system becomes more effective.

1-1 is a description of the first embodiment of the present invention. Expansion of projection optical system optical path diagram. Description of the first stage of the storage method of the optical system in translation. 1-2 is a description of the first embodiment of the present invention. Expansion of projection optical system optical path diagram. Explanation of the second stage of the storing method of the optical system in translation. Description of the first embodiment of the present invention. Allowable eccentricity distributed to the optical system. Description of the first embodiment of the present invention. Explanation of a state in which the volume of the optical system is reduced as a result of storage. Explanation of the second embodiment of the present invention. Explanation of the storage method of the optical system in translation. Explanation of the third embodiment of the present invention. A description of the method of storing the optical system in rotation. Description of the fourth embodiment of the invention Description of the method by which the mirror is stored with a non-linear trajectory. Explanation of the fifth embodiment of the present invention. Description of how mirrors are stored at different travel distances for each individual / group. The optical path figure of the whole optical system of the 1st-4th Example of this invention. The external view of the conventional image projection apparatus. Explanatory drawing disclosed by Unexamined-Japanese-Patent No. 11-119343 of a prior art example. Explanatory drawing disclosed by Unexamined-Japanese-Patent No. 2002-189172 of a prior art example.

Claims (13)

An imaging optical system configured by combining a plurality of curved reflecting mirrors, the medium between the mirrors is air, and forms an image of the object plane on the image plane at a predetermined magnification,
When the imaging optical system is not used, the space between the mirrors is reduced by means of changing the position of the at least one mirror without changing its inclination, and the volume necessary for housing the entire imaging optical system is reduced. An imaging optical system characterized by having a function of reducing. An imaging optical system configured by combining a plurality of curved reflecting mirrors, the medium between the mirrors is air, and forms an image of the object plane on the image plane at a predetermined magnification,
When the imaging optical system is not used, the function of changing the tilt and position of at least one mirror reduces the space between the mirrors and reduces the volume required to accommodate the entire imaging optical system. An imaging optical system comprising: Means described in the imaging optical system according to claim 1 or 2,
Image forming characterized in that the mirrors constituting the optical system are divided into two groups, a large decentering sensitivity group and a small decentering group, and executed on at least one of the latter mirrors. Optical system. Means described in the imaging optical system according to claim 1 or 2,
An imaging optical system characterized in that, among the mirrors constituting the optical system, a mirror having the lowest decentration sensitivity is selected in order and executed on at least one mirror. Means described in the imaging optical system according to claim 1 or 2,
An imaging optical system, which is executed for at least one mirror on the enlargement side among the mirrors constituting the optical system.   6. The imaging optical system according to claim 1, wherein a locus of movement of the mirror by the means described in the imaging optical system is linear or non-linear.   The plurality of mirrors are set as at least one group, and the means according to any one of claims 1 to 6 is collectively executed on the group so that the relative positional relationship between the mirrors in the group does not always change. An imaging optical system characterized by that.   The means according to any one of claims 1 to 7 is divided into a plurality of stages having different amounts and directions for changing the position and angle, and each of the stages is sequentially executed. Image optics.   9. An imaging optical system, wherein the breakdown of a mirror or a group of mirrors to be changed is changed at each stage included in the means according to claim 8.   9. The imaging optical system according to claim 2, wherein when the mirror is tilted, the center of rotation is away from the rotating mirror.   11. The imaging optical system according to claim 1, wherein at least one mirror (or group) does not change its inclination or position.   12. The imaging optical system according to claim 11, wherein an adjacent mirror (or group) is brought close to a mirror (or group) whose tilt and position do not change, thereby accommodating the entire imaging optical system. An imaging optical system characterized in that a required volume is reduced.   12. The imaging optical system according to claim 11, wherein the surface (or a part of a group or group) moves into a space between the surfaces of the mirror (or group) whose tilt and position do not change. An imaging optical system characterized in that the volume required to accommodate the entire imaging optical system is reduced by moving the moving surface (or group) so that the

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