JP2011150369A - Projection optical system and projection display device including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection optical system capable of adjusting height of a projected image while having a simple mechanism and a high elevation angle and capable of adjusting variation of the height of the image due to focus adjustment or change of a projection face. <P>SOLUTION: The projection optical system for projecting a light beam passing through image display elements on a screen includes only a plurality of mirrors and has an adjusting function for adjusting a projection angle of projecting the image on the screen. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging optical system used in an image projection apparatus, such as a transmission / reflection type liquid crystal panel, a digital micromirror device (DMD) manufactured by Texas Instruments, Inc., or a grating light valve (GLV) manufactured by Sony Corporation. This is suitable for a projection optical system for projecting an illumination light beam modulated corresponding to each pixel by an image display element such as a screen, and a projection display device having the projection optical system.

  2. Description of the Related Art In recent years, an image projection device that uses an image display element such as a DLP or a liquid crystal panel to perform an enlarged projection on a screen or the like has been provided. The image display element is illuminated with a light source light beam, and transmitted light or reflected light modulated there is projected by a projection optical system.

  Hereinafter, in the present invention, an image projection device is a front projector that projects outside the device.

  First, the projection elevation angle of the image projection device will be described.

  Here, the projection optical system is premised on a general coaxial refraction lens system. As is well known, the coaxial lens system shares one rotational symmetry axis (the so-called optical axis of the lens) at the center. In the device, the so-called principal ray connecting the screen center of the image display element and the screen center of the projected image with respect to the optical axis of the coaxial lens system is a projection elevation angle (or simply an elevation angle). The plane in which the projection elevation angle is defined is the meridional plane. Generally, it is a plane parallel to the vertical direction. In addition, when the device is suspended from the ceiling and projected to a position lower than the device, it is a depression angle. Since the technique of the present invention is substantially the same for the depression angle, it is represented by the elevation angle.

  Further, at this time, the designed maximum angle of view (most off-axis image height) of the coaxial lens system is a light beam reaching both corners (corners) of the upper part of the projected image.

  In a general image projection apparatus using a coaxial refraction lens system, the projection elevation angle is often fixed (cannot be changed). Therefore, when using the device, there is a limitation in arrangement. That is, when the projection screen size is determined, the projection distance is roughly determined (although it can be adjusted by zooming). Since the projection elevation angle is constant, the position in the height direction of the screen is determined simultaneously with the projection distance. Therefore, the installation location of the device may be adjusted according to the desired size and position of the projection image, but this is not very easy.

  For example, in order to move the position of the projected image up and down, the end of the projection device is moved up and down to tilt it, and the elevation angle is changed. That is, the angle of the optical axis with respect to the image plane is tilted from a predetermined state. Then, trapezoidal distortion occurs in the projected image. Some devices have a function of applying reverse distortion on the image display element and correcting the distortion. However, in this method, since the image on the image display element is intentionally reduced and partially displayed, a part of the resolving power inherent in the image display element is lost. This is not preferable because of the demand for higher image definition that has been strengthened in recent years.

  On the other hand, some devices using a coaxial refraction lens system have a projection angle adjustment mechanism called lens shift. It has problems as described below.

  As is well known, the coaxially refracting lens system has a circularly good image range (image circle) that is rotationally symmetric in design around the optical axis. In general, the vicinity of the optical axis (on the axis) has the highest imaging performance, and the performance is lower in the peripheral part (off-axis to off-axis) from the optical axis. Usually, an imaging lens such as a camera mainly uses a range centered on the axis. However, in the case of a projection lens of an image projection device, a portion (off-axis region) that is off the optical axis is mainly used. The reason for this is that the projection elevation angle becomes small when used on the axis.

  In order to maximize the elevation angle, an arrangement is used in which both corners at the lower end of the image display element on the object side are inscribed in the image circle and the upper side coincides with the optical axis. That is, only half of the lens image circle (half angle of view) is used.

  In order to further increase the elevation angle, the image circle is designed to be large (the angle of view is widened), and the image display element is shifted to a place where the optical axis is not included in the screen. That is, only the off-axis region is used in the entire screen. This is shown in FIG. However, the imaging performance decreases as the distance from the optical axis increases. A lens with a large angle of view is difficult to design and manufacture. Also, it is useless to use no on-axis portion with good performance. Therefore, the practical limit of the maximum elevation angle is half angle of view and is generally about 10 to 15 °.

  In this lens shift mechanism, the positional relationship between the image display element and the coaxial lens system is shifted within the meridional plane. From the state of maximum elevation angle described above (position where the image is highest), the image display element is relatively shifted in parallel so that the center of the image display element approaches the optical axis. If the shift is made until the optical axis coincides with the center of the element (horizontal), the projection height of the image decreases. With this operation, the height of the projected image can be continuously varied in the range up to the state of projecting in the horizontal direction. Normally, it is the lens that actually moves.

  However, since the maximum elevation angle is a half angle of view as described above, the variable range in this method can only be varied from horizontal to the maximum elevation angle. This can only lower the image down from the same height as the image height of the fixed device.

  On the other hand, various imaging systems have recently been proposed that use off-axis optical systems to reduce the size of the entire optical system. In the off-axis optical system, it is possible to construct an optical system in which aberrations are sufficiently corrected by making the constituent surface a free-form non-rotationally symmetric aspherical surface, a so-called free-form surface. For example, Patent Document 1 discloses the design method, and Patent Documents 2 and 3 disclose the design example.

  In addition, an image projection device using this has been proposed. There are a combination of a free-form reflecting surface and a coaxial refractive lens system, and a configuration in which the entire optical system is formed of a free-form reflecting surface.

As a feature of these optical systems,
・ High degree of freedom in optical path placement,
In the case of an optical system composed only of reflective surfaces,
・ No chromatic aberration in principle
Because not all surfaces are facing like a coaxial refraction lens system,
・ Repetitive reflections between each surface are unlikely to occur.
・ In other words, ghosts and flares are unlikely to occur.
There are features such as.

  Patents of the projection optical system using the curved reflection optical system (some of which also use a refractive optical element such as an aspheric lens) are disclosed in Patent Documents 4 (Minolta), 5 (Minolta), 6 (Nichijo Giken), etc. It is disclosed.

  If these configurations are used for a front projector, a large projection elevation angle exceeding 40 °, for example, can be designed with good performance.

  The elevation angle of a projection system that originally uses a coaxial refraction lens system is as low as about 10 to 15 °. So if you want to project to a higher position, you need to move the device away from the screen. Then, the projection screen may become unnecessarily large. In addition, problems such as thermal exhaust and noise occur when the projection device gets close to the viewer. On the other hand, if the device is tilted to raise the projection position, a trapezoidal distortion is generated, and when this is electrically corrected, the image quality deteriorates. Even in the case of having a lens shift adjustment mechanism, the maximum projection elevation angle does not exceed the previous 10 to 15 degrees. In addition, the elevation angle adjustment range at this time can only be changed within the range from the maximum elevation angle to 0 ° (horizontal) projection. That is, it can only be changed within a low range.

  On the other hand, if it is a projection optical system using a reflective surface, what does not produce trapezoidal distortion even at a high projection elevation angle exceeding 40 °, for example, can be realized. Further, the off-axis free-form surface reflecting optical system is easy to adopt a short distance high magnification (wide) configuration as compared with the coaxial optical system. Since it is a large screen projection at a short distance, if the device is moved a small distance back and forth, the screen size will change greatly. If this effect is used, the screen size can be easily adjusted without a zoom mechanism.

JP 9-005650 A JP-A-8-292371 JP-A-8-292372 JP 2001-215212 A JP 2001-215612 A International Publication No. WO 97/01787

  However, such a projection apparatus capable of projecting at a high elevation angle has the following problems. Originally, a large projection elevation angle is a disaster, and the height of the image greatly moves up and down as the device moves back and forth. Similarly, the screen moves up and down for focusing. In the case of the coaxial system, the same phenomenon occurs, but it is not noticeable because the elevation angle is small.

In order to solve the above problems, a projection optical system of the present invention is a projection optical system for projecting a light beam that has passed through an image display element, and adjusts an angle at which the light beam that has passed through the image display element is projected. And a focus adjustment function for performing focus adjustment on a predetermined surface, and the projection angle adjustment function is a projection image by the projection optical system on the predetermined surface in synchronization with the focus adjustment function. The angle is adjusted so that the change in the height is kept within a predetermined range.

Furthermore, the projection angle adjustment function adjusts the angle so as to keep the height of the projection image constant in synchronization with the focus adjustment function. In addition, the focus adjustment function performs an autofocus operation when the distance between the surface and the projection optical system changes, and the projection angle adjustment function is synchronized with the autofocus operation. Then, the angle is adjusted so that the change in the height of the projected image is kept within the predetermined range.

A projection optical system according to another aspect of the present invention is a projection optical system for projecting a light beam that has passed through an image display element, and a projection angle adjusting function that adjusts an angle at which the light beam that has passed through the image display element is projected. A focus adjustment function for performing focus adjustment on a predetermined surface, and the projection angle adjustment function synchronizes with the focus adjustment function to increase a height of a projection image by the projection optical system on the predetermined surface. The angle is adjusted so that the change of the height follows a predetermined locus.

Further, the focus adjustment function performs an autofocus operation when the distance between the surface and the projection optical system changes, and the projection angle adjustment function is synchronized with the autofocus operation. The angle is adjusted so that the change in the height of the projected image follows a predetermined trajectory.

  Further, it is desirable that the above-described projection optical system is configured by combining only a plurality of surface reflection mirrors.

  Moreover, the projection type display apparatus of this invention has an at least 1 image display element and the projection optical system in any one of Claims 1 thru | or 15 which projects the light from the said at least 1 image display element. It is characterized by.

  It is possible to provide a projection optical system that can adjust the height of the projected image while maintaining a high elevation angle with a simple mechanism, and that can adjust fluctuations in the image height due to focus adjustment or change of the projection surface.

Schematic diagram of essential parts of the projection optical system of the first embodiment of the present invention Overview of the entire effective range optical path of the projection optical system of the first embodiment of the present invention Overview of the downward shift of the projection optical system of the first embodiment of the present invention Schematic of the upward shift of the projection optical system of the first embodiment of the present invention Functional explanatory diagram of the first embodiment of the present invention Overview of the projection optical system of the first embodiment of the present invention Operational function explanatory diagram of the second embodiment of the present invention Operational function explanatory diagram of the third embodiment of the present invention Conventional example of projection imaging system by refraction system

  In the off-axis projection optical system using the reflecting surface, the above-mentioned problems remain although various advantages are obvious. Therefore, we devised a method to solve these problems and to bring about new effects. As a means for this, the concept of lens shift used in the coaxial lens system is introduced to the reflective optical system. By applying it to a reflective optical system, a greater effect than in the case of a coaxial refraction system can be obtained. The off-axis projection optical system described in the present embodiment is a projection optical system constituted by a free-form curved reflecting surface (rotationally asymmetric reflecting surface), and preferably formed by only the reflecting surface. A refracting optical element such as a lens, a diffractive optical element, or the like may be provided on both sides or one side (on the optical path) of the free-form curved reflecting surface.

  Hereinafter, the off-axis projection optical system of this embodiment will be described.

  Since the off-axis projection optical system of the reflecting surface does not originally have an on-axis / off-axis concept, it is possible to set a high projection elevation angle as the center use range in advance during design. The optical system has a characteristic that it can be designed to have suitable performance in many cases even if the angle is so large that the half angle of view of the coaxial system cannot be designed. .

  An optical system is designed for a certain projection elevation angle, and this is defined as a reference projection elevation angle state. Next, an effective area size on each reflecting surface is designed to be extended and enlarged one-dimensionally by a predetermined size in both the upper and lower directions corresponding to the meridional surface. Alternatively, there is a method in which an optical system is designed for a temporary image display element in which the size of the image display element is previously extended and enlarged by a predetermined area vertically in the meridional direction.

  The enlargement of the effective area is determined in consideration of the size of the optical system itself, the mechanical interference of the constituent mirrors, and the adjustable amount of the image display position. A wider adjustable range is better, but even if it is wider than necessary, if it is practically hardly used, the optical system becomes large and wasted. Practically, when the projection elevation angle is around 45 °, it is reasonable to increase the height by 20 to 30% with respect to the length of the side in the meridional direction of the projection screen.

  The positional relationship between the image display element and the projection optical system is initially at a reference position (for example, near the center of the adjustment range), and the optical system as a whole moves relatively in the meridional direction as necessary. By this movement, the vertical position of the projected image moves according to the set range, and for example, 30% of the screen vertical size can be adjusted.

  Such a shift mechanism using an off-axis reflection system is superior to that of a coaxial lens system in its effect. That is, it is possible to project at a large projection elevation angle that cannot be realized by a coaxial lens system, and the image height position can be adjusted up and down around the projection elevation angle. In the case of the optical system, since there is no distinction between on-axis and off-axis, a standard projection elevation angle is treated as if it is on an axis in a refraction system, and a design that can be adjusted in a direction that gives a larger elevation angle therefrom. it can.

  However, it should be noted that the elevation angle may not be increased without limit. Although the imaging performance in the direction perpendicular to the optical axis on the image plane is good, the effective resolution in the meridional direction depends on the incident angle θ on the image plane at an angle of view with a large incident angle on the image plane. Will be damaged. This is because the spot size (or the minimum circle of confusion) on the image plane increases by 1 / COSθ times at the incident angle θ. The light beam reaching the viewer is a diffuse reflection component by the screen. Therefore, in the case of a screen with extremely low diffusivity (smooth near a mirror surface), the screen may appear dark at the upper end of the screen where the incident angle is large (when projecting from below). This is because the light beam incident on the upper end of the screen is almost regularly reflected without being scattered and escapes upward.

  However, according to the method of the present invention, the mechanism is simple because it is only necessary to shift the entire optical system as a unit relative to the image display element. In addition, since the optical system is vulnerable to a displacement error in the relative positional relationship of the mirrors, it is preferable not to move the mirrors individually in order to sufficiently exhibit the imaging performance.

  For the focusing mechanism of the projection optical system of the present case, for example, a method in which the entire optical system is extended to the image display element is suitable. In the case of such an overall extension, since only the direction is different from that of the above-mentioned shift mechanism, it is easy to adopt a common structure mechanically. However, even in the case of a partial focusing structure in which only a part of the reflecting surfaces are moved for focusing, the application of the present invention has no problem and the effect does not change.

  Although details will be described later, the screen moves up and down when adjusting the screen size by moving the device back and forth as described above or when performing focusing. At this time, if synchronized with the projection elevation angle adjusting mechanism, a new effect is obtained.

  As described above, in the case of a projection device that is short-range, high-magnification (wide) and capable of high-elevation projection, the image can be displayed by adjusting the screen size or performing a focusing operation by moving the device body back and forth with respect to the image plane. A vertical movement of the height occurs. Here, the height adjustment mechanism of the projected image by shifting the off-axis reflecting optical system can readjust this and substantially cancel it.

  There is also a method of adjusting the image height in synchronism with the vertical movement of the projected image generated by the back-and-forth movement of the projection device for adjusting the screen size. In this case, the optical system shift mechanism is interlocked so as to cancel the fluctuation of the image height due to the image size adjustment operation. As a result, the height position of the image can be kept constant even when the image size adjustment operation is performed.

  Even when the screen height is kept constant, the center height of the screen can be maintained, or the heights of the upper and lower edges of the screen can be fixed arbitrarily. Further, there is a method that dares to change the image height within a desired range, for example, to change the image height gently, or to change to follow a desired locus including a curve.

  Further, there is a method of adjusting the image height by the above-described optical system shift in synchronization with the projected image height moving up and down by the focusing operation. In this case, the optical system shift is interlocked so as to cancel the change in the image height due to the focusing operation. As a result, the height of the image can be kept constant even when the focus operation is performed.

  Even during focusing, it is possible to maintain the center height of the screen even when the screen height is kept constant, or to fix the heights of the upper and lower ends of the screen. Further, there is a method that dares to change the image height within a desired range, for example, to change the image height gently, or to change to follow a desired locus including a curve.

  Next, in order to specifically describe the embodiment, first, three items of a reference optical axis, a global coordinate system, and a local coordinate system will be 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 from the center of the image display element to the center of the projection image 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. The global origin is defined as the intersection of the object plane and the reference optical axis. The global origin is located at the center of the image display element that 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 manner, 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.

  Only the local coordinate system of the first embodiment (details will be described later) in FIG. 1 is displayed on each mirror surface (not shown 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 (unit is omitted below) 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 global coordinates and 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 asymmetrical aspherical reflecting surface, and the shape thereof is a function using the position in the xy plane as a parameter in each surface local coordinate system. (Sag amount of the surface).

  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. Also, the local origin of each surface is not necessarily within the effective ray area of that surface.

  FIG. 6 is an overall view when the apparatus is used, including the optical system of the image projection apparatus of the first to third embodiments according to the present invention. The present embodiment is a projection optical system that enlarges and projects an image displayed on an image display element onto a screen. In the case of this example, the projection elevation angle in the reference state is 40 °.

[First embodiment]
FIG. 1 shows a first embodiment of the present invention.

  In FIG. 1, there is an illumination optical system (not shown) on the back side of the image display element, which illuminates the element 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. The first mirror is located closest to the image display element, and numbers are sequentially assigned in the order of the second mirror to the fifth mirror in the light beam traveling direction.

  FIG. 2 shows a state in which the light beam passes through all the effective portions of the optical system design according to the first to third embodiments of the present invention. In FIG. 2, the luminous flux when the image display element is at the center of the vertical adjustment range is indicated by a black solid line. In the same figure, there are luminous fluxes indicated by dotted lines above and below the luminous flux. This simultaneously shows a state in which the light beam passes through the effective portion enlarged up and down when the image display element and the projection optical system are relatively shifted upward or downward. Here, the effective portion is designed to be set large in the vertical direction by a size corresponding to 30% of the vertical size of the image display element.

  FIG. 3 shows a case where the optical system is shifted downward with respect to the image display element. Thinly drawn are the optical paths when the optical system is not shifted. By this shift, the projected image can be shifted upward by 30% of the vertical side at the maximum.

  FIG. 4 shows a case where the optical system is shifted upward with respect to the image display element. Thinly drawn are the optical paths when the optical system is not shifted. By this shift, the projected image can be shifted downward by up to 30% of the vertical side.

  Since it is a high-magnification projection, the amount of movement of the optical system for shifting the projected image by 30% is very small as far as the shift amount of the image is understood, as can be seen from FIGS. Therefore, a large-scale mechanism is not necessary.

  FIG. 5 schematically shows how the height of the projected image changes when the optical system is shifted upward. As shown in this figure, the height of the projected image can be further moved 30% up and down from the original high-elevated-angle projected position by the vertical shift of the optical system.

  The present invention adjusts the height of the projected image independently to a desired height by shifting the entire optical system in a direction substantially parallel to the image display element surface in accordance with the principle described above.

  Although not shown, in the first to third embodiments, focusing can be performed by minutely shifting the entire off-axis reflecting optical system in the Z-axis direction in the global system.

  In addition, it is possible to change not the height of the projected image but the horizontal position by shifting the entire optical system in the horizontal direction with respect to the image display element. In this case, the effective area of each mirror of the off-axis reflection optical system needs to be expanded in the horizontal direction.

[Second Example]
FIG. 7 shows a second embodiment of the present invention.

  The second embodiment will be described below.

  The present embodiment is basically the same as the first embodiment with respect to the configuration of the optical system and the image height adjustment principle mechanism by the shift. Therefore, the description of overlapping detailed drawings is omitted. In this embodiment, a new effect is manifested by the device in use.

  First, the projection device was in focus on the surface A with respect to the position A ′ where the actual screen is located. Next, in order to focus the projected image on the actual screen position, the optical system was extended to focus on the A ′ plane.

  At this time, conventionally, the height of the image is lowered to the position indicated by the thick dotted line in the figure. However, in the present invention, the projection image shifts upward because the optical system shifts downward (similar to that shown in FIG. 3) in synchronization with the payout for focusing of the optical system. By executing these operations in synchronization, it is possible to cancel the movement of the projected image in the vertical direction by the focus adjustment. That is, even if the focus adjustment is performed within a predetermined range, the effect is obtained that the height of the projected image remains substantially fixed and the focus is adjusted.

  In the present embodiment, the Z-axis direction shift of the optical system for focus adjustment and the Y-axis direction shift of the optical system for adjustment of the projected image height must be interlocked while maintaining a predetermined relative positional relationship. is there. These may be configured to be interlocked according to a mechanical cam or guide in a guide groove. Alternatively, each may be configured to move electrically, and the way of interlocking may be configured to follow a predetermined programmed trajectory that is optimal according to conditions such as the projection distance.

  FIG. 7 shows an example in which the center of the screen is always maintained at a constant height in the method of maintaining the height of the projected image. However, the center height of the screen is not necessarily fixed, but there are other cases as shown below. For example, the bottom end of the screen is always maintained at the same height, or the top end of the screen is always maintained at the same height. There is also a method of keeping any part of the screen at the same height. In addition, there is a method in which the height of the screen is changed as needed. In this case, as a matter of course, a desired height change, which is different from the screen height fluctuation that has occurred in the conventional focusing, is artificially applied. Specifically, various applications such as changing the height of the screen abruptly due to focusing to a gradual change or changing the height in a curved manner can be considered.

[Third embodiment]
FIG. 8 shows a third embodiment of the present invention.

  The third embodiment will be described below.

  The present embodiment is basically the same as the first embodiment with respect to the configuration of the optical system and the image height adjustment principle mechanism by the shift. Therefore, the description of overlapping detailed drawings is omitted. In this embodiment, a new effect is manifested by the device in use.

  First, the projection device was in focus with respect to the screen. The size of the projected image at this time is C. Then, the projection device was brought closer to the screen to reduce the size of the projected image on the screen to D. When the optical system was extended and focused, the screen size changed to D (reduced).

  At this time, conventionally, the height of the image is lowered to the position indicated by the thick dotted line in the figure. However, in the present invention, the projection image shifts upward because the optical system shifts downward (similar to that shown in FIG. 3) in synchronization with the payout for focusing of the optical system. By executing these operations in synchronization, it is possible to cancel the upward and downward movement of the projected image by adjusting the screen size. In other words, even if the projection device is moved back and forth within a predetermined range and the screen size is changed, the effect is obtained that the height of the projected image is maintained at a substantially constant height when the focus is adjusted.

  In this embodiment, the Z-axis direction shift of the optical system for focus adjustment and the Y-axis direction shift of the optical system for adjustment of the projected image height must be linked while maintaining a predetermined relative positional relationship. There is. These may be configured to be interlocked according to a mechanical cam or guide in a guide groove.

  Alternatively, each may be configured to move electrically, and the way of interlocking may be configured to follow a predetermined programmed trajectory that is optimal according to conditions such as the projection distance.

  As a further advanced configuration, it is more convenient to incorporate an autofocus that automatically focuses on the screen when the projection device is moved back and forth. At this time, the image height adjusting mechanism is operated in synchronization with the autofocus. In this configuration, when the device main body is slid back and forth, the autofocus maintains the focused state on the screen, and at the same time, the screen size changes (adjustable) while keeping the image height constant.

  FIG. 8 shows an example in which the center of the screen is always maintained at a constant height in the method of maintaining the height of the projected image. However, the center height of the screen is not necessarily fixed, but there are other cases as shown below. For example, the bottom end of the screen is always maintained at the same height, or the top end of the screen is always maintained at the same height. There is also a method of keeping any part of the screen at the same height. In addition, there is a method in which the height of the screen is changed as needed. In this case, as a matter of course, a desired height change, which is different from the screen height fluctuation that has occurred in the conventional focusing, is artificially applied. Specifically, various applications such as changing the height of the screen abruptly due to focusing to a gradual change or changing the height in a curved manner can be considered.

  According to the present embodiment, in the off-axis reflecting surface projection optical system that enables high-angle projection at a short distance and high magnification, it is possible to adjust the height of the projected image while maintaining a high elevation angle with a simple mechanism. In addition, it is possible to adjust the fluctuation of the image height due to focus adjustment and change of the projection surface, and in addition to the former, it is possible to keep the height of the desired part in the image constant under any projection conditions become. Alternatively, the screen height can be changed as desired. Further, in an image projection optical system using an off-axis reflective surface optical system capable of high-elevation and short-distance high-magnification projection, the projection elevation angle is obtained by shifting the optical system relative to the image display element. Adjustable projection optical system. Furthermore, the up / down movement of the image during focusing or when the projection distance is changed, which is a harmful effect of high elevation angle projection, or the image height is maintained within a desired range in conjunction with these, or the desired change You can do things like that.

  In addition, the projection optical system of this embodiment can be applied to a projection display device. For example, a light source, an illumination optical system that illuminates an image display element (one or more) with light from the light source, and light from the illuminated image display element is projected onto a screen or the like. The above-described projection optical system may be used. Here, the image display element may be a transmissive liquid crystal panel, a reflective liquid crystal panel, or a micromirror device such as a DMD. Here, when there are a plurality of image display elements, it is desirable that the color combining optical system for combining the light (optical paths) emitted from these image display elements has a polarization beam splitter. Further, there is no image display element, and the light from the laser light source may be guided to the projection optical system without passing through the image display element. In that case, an image can be formed by modulating light itself emitted from a laser light source based on an image signal. Furthermore, when the light from the laser light source is guided to the projection optical system without going through the image display element or the like, it is desirable to provide a scanning optical system that scans the light from the laser light source two-dimensionally.

Claims (7)

A projection optical system for projecting a light beam that has passed through an image display element,
A projection angle adjusting function to adjust the angle for projecting a light beam having passed through the image display device,
And a focus adjustment function of performing focus adjustment for a predetermined plane,
Said projection angle adjusting function, in conjunction the focus adjustment function and synchronization, a change in the height of the projected image by the projection optical system in the predetermined plane to adjust said angle so coercive one within a predetermined range Projection optical system. The projection optical system according to claim 1, wherein the projection angle adjustment function adjusts the angle so as to keep the height of the projection image constant in synchronization with the focus adjustment function. The focus adjustment function, when the distance between the projection optical system and the surface is changed, and performing an autofocus operation,
The projection angle adjustment function adjusts the angle so that a change in height of the projection image is maintained in the predetermined range in synchronization with the autofocus operation. The projection optical system described. A projection optical system for projecting a light beam that has passed through an image display element,
A projection angle adjusting function to adjust the angle for projecting a light beam having passed through the image display device,
And a focus adjustment function of performing focus adjustment for a predetermined plane,
It said projection angle adjusting feature, and characterized in that said interlocking focus adjustment function and synchronization, the change in height of the projected image by the projection optical system in the predetermined plane to adjust the angle to follow a predetermined trajectory Projection optical system. The focus adjustment function, when the distance between the projection optical system and the surface is changed, and performing an autofocus operation,
Said projection angle adjusting function, in synchronism with the said autofocus operation, the projection optics according to claim 4, the change in height of the projected image and adjusting the angle to follow a predetermined trajectory system. The projection optical system, projection optical system according to any one of claims 1 to 5, characterized in that it is constituted by combining a plurality of only the surface reflecting mirror. At least one image display element, the projecting light from the at least one image display element, a projection display device characterized by having a projection optical system according to any one of claims 1 to 6.

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