JP5589933B2 - Projector, projection unit and electronic blackboard - Google Patents

Description

  The present invention relates to a projector, a projection unit, and an electronic blackboard, and more particularly to a projector for proximity projection.

  In recent years, projectors equipped with a projection optical system for so-called proximity projection that can display a large screen at a short projection distance have been commercialized. By adopting this projection optical system, it is possible to display a large screen (for example, 100 inches at a projection distance of 40 cm) at a very short distance compared to a conventional front projection type projector. These projectors are generally only usable for ultra-short-distance projection, and they can be used according to their purpose, from ultra-short-distance projection to medium- and long-distance projections that have been widely known in the past. It is expected to be possible. For example, Patent Document 1 proposes a projector technology that enlarges the zoom ratio by a reflection projection unit attached to the screen side with respect to the projection lens. Images with different zoom ratios can be obtained depending on whether the reflection projection unit is attached or removed.

  If the reflection projection unit according to Patent Document 1 is applied to ultra-short distance projection, it is necessary to greatly enlarge the zoom ratio. In this case, it is very difficult to reduce aberration as the zoom ratio is increased. In addition, since a configuration is adopted in which a plurality of curved mirrors are arranged decentered with respect to the optical axis (center axis) of the lens, a slight deviation of the optical elements often has a large effect on the image. Become. For this reason, in order to obtain the desired optical performance, it is necessary to adjust with very high accuracy, and it becomes difficult to reduce the aberration caused by the decentered optical system.

  In recent years, so-called interactive boards used in the education field, presentations, and the like are becoming widespread due to an increase in multimedia contents. The interactive board is characterized in that a user can write to the content while displaying the content. Usually, an interactive board is the same size as a conventional blackboard or white board, and therefore, a display over a relatively wide range is required. When a general direct-view type monitor is applied to a wide range display on an interactive board, problems occur in terms of the weight, power consumption, and cost of the entire apparatus.

  For example, Patent Documents 2 and 3 propose an electronic blackboard technique in which video light projected from a projector is reflected by a plane mirror and incident on a transmissive screen. Patent Document 4 proposes a technology of an electronic blackboard provided with a projector for ultra short distance projection. A wide range of display is possible by magnifying projection using a projector. By using a projector, weight, power consumption, and cost can be reduced. However, in the case of the techniques of Patent Documents 2 and 3, there is a problem in that the size in the depth direction is increased and the installation property is lowered because a vast plane mirror is installed with an inclination with respect to the transmission screen. It becomes. The projector in the technique of Patent Document 4 is applied only to ultra-short-distance projection, and has a problem in that the convenience is low because the usage is limited.

JP 2002-6398 A JP 2003-136892 A JP 2004-252345 A JP 2009-83277 A

  The present invention has been made in view of the above-described problems, and a projector for realizing projection of an image by close projection at an ultra short distance and projection of an image by projection at a medium and long distance, and the projector It is a first object to provide a projection unit used for the above.

  A second object of the present invention is to provide a highly convenient electronic blackboard that can reduce weight, power consumption, cost, and depth size.

  In order to solve the above-described problem and achieve the object, a first projector according to the present invention (a) emits light from a light source, a display surface illuminated with light from the light source, and light from the display surface. And a main body including an emission optical system capable of making light from the display surface into light that forms an image plane of the display surface that is once inclined with respect to the display surface, and (b) the display surface emitted from the emission optical system A projection unit having a concave widening mirror that projects light from the projection surface toward the illuminated surface and reflects and forms a wide angle by reflecting the light that forms the image plane of the display surface that has a positive power and is tilted with respect to the display surface (C) One of the main body and the projection unit has a variable power optical system that converts the magnification of an image forming an image plane of the display surface tilted with respect to the display surface.

  In the first projector, the main body and the projection unit are combined to enable ultra-short distance projection. The main body unit can perform medium-long distance projection by itself with the projection unit removed. Here, by the wide-angle mirror provided in the projection unit, the image plane sufficiently tilted with respect to the display surface or the optical axis (that is, sufficiently tilted with respect to the normal of the optical axis or a plane perpendicular to the optical axis). Since the light forming the image plane is reflected to widen the angle, it is possible to perform good close-up projection while suppressing the occurrence of aberrations such as distortion without using an eccentric optical system. In addition, it is possible to reduce the chromatic aberration due to the widening of the angle by widening the light forming the image by the reflection by the concave widening mirror. Furthermore, the image forming the image plane tilted with respect to the display surface by the variable magnification optical system can be appropriately sized. Thereby, it is possible to obtain a projector capable of projecting an image by close projection at an ultra short distance and projecting an image by medium to long distance projection.

  In a specific aspect of the present invention, in the first projector, the zoom optical system reduces the image forming the image plane of the display surface tilted with respect to the display surface relatively. It is. Thereby, it is possible to perform close-up projection by reducing an image forming an image plane tilted with respect to the display surface.

  In another aspect of the present invention, the projection unit forms an image of the display surface tilted with respect to the display surface on an irradiated surface parallel to the display surface. That is, it is possible to observe an appropriate image without inclination.

  In another aspect of the present invention, the emission optical system has a normal display state in which an image forming an image plane of a display plane parallel to the display plane is formed in a first range at a relatively long distance along the optical axis. It is possible to switch to a macro display state in which an image forming an image surface of the display surface tilted with respect to the display surface in a relatively short second range along the optical axis is formed. A relatively large image can be formed at a relatively long distance by the emission optical system in the normal display state, and a relatively small image can be formed at a relatively short distance by the emission optical system in the macro display state.

A second projector according to the present invention includes: (a) a light source; a display surface illuminated with light from the light source; a main body unit including an emission optical system that emits light from the display surface; and (b) emission optics. A projection unit having a concave widening mirror that projects light from the display surface emitted from the system toward the irradiated surface and has a positive power to reflect and widen the light from the display surface. And (c) light forming an image plane of a display surface parallel to the display surface in a first range at a relatively long distance along the optical axis, and displayed in a second range at a relatively short distance along the optical axis. The light forms the image plane of the display surface tilted with respect to the plane.

  In the second projector, the main body and the projection unit are combined to enable ultra-short distance projection. The main body unit can perform medium-long distance projection by itself with the projection unit removed. Here, by the wide-angle mirror provided in the projection unit, the image plane sufficiently tilted with respect to the display surface or the optical axis (that is, sufficiently tilted with respect to the normal of the optical axis or a plane perpendicular to the optical axis). Since the light forming the image plane is reflected to widen the angle, it is possible to perform good close-up projection while suppressing the occurrence of aberrations such as distortion without using an eccentric optical system. In addition, it is possible to reduce the chromatic aberration due to the widening of the angle by widening the light forming the image by the reflection by the concave widening mirror. Thereby, it is possible to obtain a projector capable of projecting an image by close projection at an ultra short distance and projecting an image by medium to long distance projection.

  In specific aspects of the first and second projectors, the main body is detachable from the projector. As a result, it is possible to carry out medium and long distance projection by taking out a relatively lightweight main body from the projector.

  In another aspect of the present invention, the emission optical system and the projection unit are arranged with their optical axes aligned. Thereby, adjustment of the optical system for obtaining desired optical performance and processing of the optical element can be facilitated. In particular, it is possible to easily align the main unit and the projection unit.

  In yet another aspect of the present invention, the emission optical system and the projection unit constitute a shift optical system that advances light from the display surface while shifting it from the optical axis. Thereby, the interference of the light reflected by the wide angle mirror with the optical element on the optical axis can be avoided, and the wide angle light can be advanced to the irradiated surface.

  The projection unit according to the present invention is used in combination with a main body including (a) a light source, a display surface irradiated with light from the light source, and an emission optical system that emits light from the display surface. A projection unit that projects light from a display surface emitted from a system toward an irradiated surface, and (b) a light having a positive power and forming an image surface of the display surface tilted with respect to the display surface A concave widening mirror that reflects and widens the angle; and (c) a variable power optical system that converts the magnification of an image forming an image plane of the display surface tilted with respect to the display surface. As a result, a projection unit can be obtained for switching from the projection of an image by projection at a medium and long distance to the projection of an image by projection at a very short distance.

  Furthermore, the electronic blackboard according to the present invention includes (a) the first and second projectors, and (b) a screen display unit that includes an illuminated surface and allows writing of other information on the illuminated surface. (C) Of the projector, the main body including the emission optical system is detachable.

  The electronic blackboard displays an image on a screen display unit by proximity projection from a projector in which a main body unit and a projection unit are combined. By adopting the configuration for close-up projection, the size in the depth direction can be kept small. In addition, the main body including the emission optical system is detachable from the electronic blackboard, and medium-long distance projection can be performed with the main body alone, thereby ensuring high versatility and convenience. Electronic blackboards can be reduced in weight, power consumption, and cost by applying a projector for enlarged projection. Thereby, weight, power consumption, cost reduction, depth size can be suppressed, and an electronic blackboard with high convenience can be obtained.

1 is a diagram illustrating a schematic configuration of a projector according to a first embodiment of the invention. It is a figure which shows schematic structure of a main-body part. (A) is a schematic diagram explaining projection by a main body unit alone, and (B) is a schematic diagram explaining projection when a projection unit is combined with the main body unit. It is a figure which shows the cross-sectional structure of a projection unit, and the light ray of image light. It is a schematic diagram explaining the function of each optical element shown in FIG. It is a figure explaining the relationship between the image height and light ray distance at the time of medium-long distance projection. It is a figure explaining the case of proximity projection. The figure explaining the proximity | contact and the change of a light ray distance. (A) And (B) is a figure explaining the method for obtaining the tilted image surface with a master lens. The figure explaining back focus and the fall of an image surface. It is a figure explaining the optical system of the Example of 1st Embodiment. It is a figure explaining the proximity projection by the optical system of the Example shown in FIG. The state where the projection unit is detached from the main body is shown. It is a figure explaining middle and long distance projection when a projection unit is separated from a main part. 14A is a diagram showing a state where the projection unit is removed from the system of FIG. 14B, and FIG. 14B is a diagram showing a state where the projection unit is partially removed from the system of FIG. It is. It is a schematic diagram of each optical element of the projector which concerns on 2nd Embodiment of this invention. It is a schematic diagram of each optical element of the projector which concerns on 3rd Embodiment of this invention. The front side perspective view of the electronic blackboard which concerns on 4th Embodiment of this invention. The back side perspective view of an electronic blackboard. (A) is a figure which shows a projector fixing | fixed part and its peripheral part, (B) is a figure which shows the state from which the main-body part was removed from the state shown to (A). The figure which shows a projector fixing | fixed part provided with a guide structure. The cross-sectional schematic diagram of the Fresnel lens currently formed in the screen display part. The front side perspective view of the electronic blackboard which concerns on the modification of 4th Embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing a schematic configuration of a projector 1 according to the first embodiment of the present invention. The projector 1 has a main body 2 and a projection unit 3. The main body 2 emits image light corresponding to the image signal. The projection unit 3 projects the image light from the main body 2 toward the irradiated surface of the screen SC.

  FIG. 2 is a diagram illustrating a schematic configuration of the main body 2. The light source 10 is an ultra high pressure mercury lamp, for example, and emits light including R light, G light, and B light. Here, the light source 10 may be a discharge light source other than an ultra-high pressure mercury lamp, or may be a solid light source such as an LED or a laser. The first integrator lens 11 and the second integrator lens 12 have a plurality of lens elements arranged in an array. The first integrator lens 11 splits the light flux from the light source 10 into a plurality of parts. Each lens element of the first integrator lens 11 condenses the light beam from the light source 10 in the vicinity of the lens element of the second integrator lens 12. The lens element and superimposing lens 14 of the second integrator lens 12 form images of the lens elements of the first integrator lens 11 on the liquid crystal display panels 18R, 18G, and 18B. With such a configuration, the light from the light source 10 illuminates the entire desired area (image display surface) of the liquid crystal display panels 18R, 18G, and 18B with substantially uniform brightness.

  The polarization conversion element 13 converts light from the second integrator lens 12 into predetermined linearly polarized light. The superimposing lens 14 superimposes the image of each lens element of the first integrator lens 11 on the irradiation surface of the liquid crystal display panels 18R, 18G, and 18B.

  The first dichroic mirror 15 reflects R light incident from the superimposing lens 14 and transmits G light and B light. The R light reflected by the first dichroic mirror 15 passes through the reflection mirror 16 and the field lens 17R and enters the liquid crystal display panel 18R which is a spatial light modulator. The liquid crystal display panel 18R modulates the R light according to the image signal.

  The second dichroic mirror 21 reflects the G light from the first dichroic mirror 15 and transmits the B light. The G light reflected by the second dichroic mirror 21 passes through the field lens 17G and enters the liquid crystal display panel 18G which is a spatial light modulator. The liquid crystal display panel 18G modulates the G light according to the image signal. The B light transmitted through the second dichroic mirror 21 enters the liquid crystal display panel 18B, which is a spatial light modulator, via the relay lenses 22 and 24, the reflection mirrors 23 and 25, and the field lens 17B. The liquid crystal display panel 18B modulates the B light according to the image signal.

  A cross dichroic prism 19 that is a color combining optical system combines light modulated by the liquid crystal display panels 18R, 18G, and 18B into image light, and advances it to the projection lens 20. The projection lens 20 functions as an emission optical system that emits image light from the main body 2. As the spatial light modulator, a reflective liquid crystal display panel may be employed instead of the transmissive liquid crystal display panels 18R, 18G, and 18B. Further, as the spatial light modulation device, a reflection type device (for example, a micro mirror device) may be employed.

  FIG. 3A is a schematic diagram for explaining a projection distance when image light is projected by the main body 2 alone. The main body 2 is detachable from the projector 1. The single main body 2 removed from the projector 1 projects an image on the irradiated surface by the image light projected from the projection lens 20. In this case, the main body 2 is installed with the projection lens 20 facing the screen SC side. The main body 2 is assumed to be able to focus, for example, with the same screen size between the distance A and the distance B (A <B).

  FIG. 3B is a schematic diagram for explaining the projection distance when image light is projected by combining the projection unit 3 with the main body 2. The projector 1 projects the image light emitted from the projection lens 20 by the projection unit 3 and displays an image on the irradiated surface. In this case, the main body 2 is attached to the projector 1 with the projection lens 20 facing the projection unit 3 on the side opposite to the screen SC. The projector 1 can project at a distance C shorter than the distance A.

  FIG. 4 is a diagram illustrating a cross-sectional configuration of the projection unit 3 and image light rays before and after entering the projection unit 3. The projection unit 3 includes a first lens 31, a second lens 32, and a wide angle mirror 33 as optical elements. The first lens 31 and the second lens 32 are arranged at positions facing the projection lens 20. The first lens 31 and the second lens 32 may be spherical lenses, for example. The first lens 31 and the second lens 32 are supported on the substrate 36 by the lens support portion 34.

  The widening mirror 33 is provided at a position where the image light from the first lens 31 and the second lens 32 is incident. The widening mirror 33 is a concave aspherical mirror that reflects video light and widens the angle. The widening mirror 33 is supported on the substrate 36 by a mirror support portion 35. The first lens 31 and the second lens 32 and the widening mirror 33 are positioned and fixed via a common substrate 36.

  The widening mirror 33 has a shape that is substantially rotationally symmetric with respect to the central axis (optical axis), for example, an aspherical shape obtained by cutting a part of a mortar shape. The symmetry axis or optical axis of the widening mirror 33 coincides with the optical axis AX of the projection lens 20. The optical axes of the first lens 31 and the second lens 32 also coincide with the optical axis AX of the projection lens 20. As described above, the projection lens 20, the first lens 31, the second lens 32, and the widening mirror 33 are arranged so that the optical axes AX coincide with each other.

  The projection lens 20, the first lens 31, the second lens 32, and the widening mirror 33 shift the light modulated in accordance with the image signal to a specific side and advance it. Specifically, on the image side, the light is shifted and advanced to a vertically lower side that is a specific side with respect to the optical axis AX. The center normal of the image plane virtually formed on the incident surface of the cross dichroic prism 19 (equal to the center normal of the image display surface area of the display surface DS described later) is parallel to the optical axis AX. Thus, the optical axis AX is on the vertical upper side opposite to the specific side.

  In the description of the projection lens 20 and the projection unit 3, the object side is the liquid crystal display panel 18G (18R, 18B) side, and the image side is the image plane IMG side or the screen SC side.

  For example, the main body 2 has a completely separate structure from the projection unit 3 and is detachable from the projector 1. The main body 2 may be moved within the projector 1 and may be configured integrally with the projection unit 3. For example, in the case of medium-long distance projection, the main body 2 may be moved to a position where the image light projected from the projection lens 20 is not blocked by the projection unit 3. When the main body 2 and the projection unit 3 are configured integrally, it is possible to improve the convenience of the user by, for example, omitting the position adjustment of the projector 1 after carrying it. Of course, the main body 2 may be fixed and the projection unit 3 may be moved to a position where the image light projected from the projection lens 20 is not blocked by the projection unit 3.

  FIG. 5 is a schematic diagram conceptually showing each optical element constituting the projection optical system of the projector 1. The projection lens 20 includes a master lens ML for enlargement projection, and enables medium and long distance projection as shown in FIG. In combination with the projection lens 20, the projection unit 3 enables close-up projection at a very short distance to a screen SC (not shown) disposed behind and above the projection lens 20. Here, the projection unit 3 is divided into an adjustment lens L1 corresponding to the refractive optical system 30 and disposed on the master lens ML side, and an aspherical mirror AM corresponding to the widening mirror 33 and on the screen SC side. Can do.

A movable mechanism 26 is attached to the master lens ML, and the position of the master lens ML in the optical axis AX direction can be relatively changed manually or electrically when the projection unit 3 is attached or detached. . The adjustment lens L1 at the front stage of the projection unit 3 has a positive power as a whole, and is arranged at the first lens 31 of negative power arranged on the master lens ML side or the light incident side, and on the light emission side. And a second lens 32 having a positive power. The adjustment lens L1 functions as a reduction optical system R that reduces the intermediate image formed by the master lens ML by bringing the image plane of the master lens ML closer to the object side. The aspherical mirror AM has a role of re-imaging an intermediate image formed on the light exit side of the refractive optical system 30 on a screen SC (not shown).

  As described above, the projection unit 3 is a combination of the adjustment lens L1 having a relatively small positive power and the aspherical mirror AM having a relatively large positive power, and is a Keplerian afocal system. The focal length is shortened and the magnification of the image is increased. That is, the projection unit 3 is a front converter for the master lens ML or the projection lens 20 (in this case, a wide converter for widening the angle). Here, if the projection unit 3 as a front converter is configured only by a lens, it is not easy to suppress chromatic aberration, and the occurrence of chromatic aberration becomes remarkable when attempting to achieve a wide angle of, for example, 130 degrees or more. For this reason, the high power portion of the projection unit 3 is composed of the aspherical mirror AM to suppress the occurrence of chromatic aberration. When such an aspherical mirror AM is used, the light is turned back by reflection, so it is necessary to avoid interference of light rays in the vicinity of the optical axis AX. For this reason, the display surface DS as an object is removed from the optical axis AX, and the master lens ML, the adjustment lens L1, and the aspherical mirror AM are used as a shift optical system. The display surface DS corresponds to an image display surface on which an image corresponding to an image signal is formed on the liquid crystal display panels 18R, 18G, and 18B of the main body 2 shown in FIG. Further, in the shift optical system as described above, there is an increasing tendency that the peripheral portion separated from the axis AX is used in each optical element constituting the projection unit 3 and the like, and the screen SC is greatly separated from the axis AX. For this reason, by forming one or more optical elements (specifically, aspherical mirror AM) constituting the projection unit 3 or the like as aspherical surfaces, aberrations at positions far away from the optical axis AX are greatly reduced. ing.

  FIG. 6 is a diagram for explaining the relationship between the image height and the light ray distance during medium and long distance projection with the master lens ML alone. The image height is the height of the image in the vertical direction with respect to the optical axis AX. In the case of general medium and long distance projection using only the master lens ML, the magnification as0 / ap of the portion where the image height is minimum and the magnification bs0 / bp of the portion where the image height is maximum are close to each other, and the image plane IMG0. Is substantially perpendicular to the optical axis AX (substantially parallel to the display surface DS).

FIG. 7 is a diagram for explaining the case of close projection at an ultra short distance in which the projection unit 3 is added to the master lens ML. In the case of ultra-short-distance close-up projection, an intermediate image II of the display surface DS is formed on the set image surface IMGb between the adjustment lens L1 and the aspherical mirror AM by the master lens ML or the like. In order to form the intermediate image II at such a position, the details will be described later. First, the master lens ML is appropriately moved along the optical axis AX direction by the movable mechanism 26 , and an aspherical surface as shown in FIG. The intermediate image II of the display surface DS is once formed on the image surface IMGa provided on the screen SC side from the position where the mirror AM or the like is to be disposed. Furthermore, by arranging the projection unit 3, the adjustment lens L1 functioning as the reduction optical system R reduces the intermediate image II only by the master lens ML, and the position of the image plane IMGa only by the master lens ML is aspherical mirror AM. Is moved to the position of the image plane IMGb on the image side. When the intermediate image II can be formed on the image side image surface IMGb of the aspherical mirror AM only by moving the master lens ML, the adjustment lens L1 does not need to have the function as the reduction optical system R.

上記式の分数項は、基準となる非球面形状を表す項であって、ｋ＝０である場合に球面形状を表す。補正項は、その基準となる非球面形状からのずれを表す。上記式は、基準となる非球面形状が補正項によって補正されても、中心軸に関して回転対称な非球面形状を表している。なお、多項式ｈにおける補数項の個数は、任意であるものとする。 The aspherical mirror AM includes an aspherical shape represented by the following polynomial h. Here, y is the height of the image from the optical axis AX (image height), c is the curvature of the spherical surface as a reference for the shape of the aspherical mirror AM, k is the conic constant, A2, A4, A6, A8, A10, Each of... Is a predetermined correction term.

The fractional term in the above formula represents a reference aspherical shape, and represents a spherical shape when k = 0. The correction term represents a deviation from the reference aspherical shape. The above formula represents an aspheric shape that is rotationally symmetric with respect to the central axis even if the reference aspheric shape is corrected by the correction term. Note that the number of complement terms in the polynomial h is arbitrary.

In the case of widening the image light, in general, aberrations such as distortion are more likely to occur in the peripheral part farther from the optical axis AX, and in particular, a design that greatly reduces the aberration in the peripheral part is required. In the present embodiment, the polynomial h representing the shape of the aspherical mirror AM includes a complement term, so that the quadratic curve defined by c and k has a shape corresponding to the height y from the optical axis AX. Correction is possible. Since each complement term is multiplied by a power of y, the portion where y becomes larger is effectively corrected. Accordingly, even if the master lens ML is shortened by the projection unit 3 including the aspherical mirror AM or the like, it is possible to realize a high-performance optical system with very little aberration such as distortion in the peripheral portion. The formula representing the shape of the aspherical mirror AM is not limited to that described in the present embodiment, and may be modified as appropriate. Further, the shape of the widening mirror 33 may be a free-form surface expressed as an XY polynomial.

  As shown in FIG. 8, when the screen SC and the aspherical mirror AM are further brought closer to each other, the distance of the light ray changes from bs to bs ′ in the portion where the image height is maximum. For a portion with a high image height, an effective correction can be made by adjusting the polynomial representing the shape of the aspherical mirror AM so as to change the distance of the light beam. When the approach is advanced, correction is required to change the distance of the light beam from as to as ′ not only in a portion where the image height is high but also in a portion where the image height is low. The lower the image height, the more difficult the correction by the polynomial of the aspherical mirror AM is. Therefore, in the present embodiment, the aberration correction is performed using the optical characteristics of the master lens ML for the portion where the image height is low, without performing the aberration correction by the aspherical mirror AM.

  Hereinafter, the optical characteristics of the master lens ML in the present embodiment will be described with reference to FIG. The image plane formed by the master lens ML is upright or inverted perpendicularly to the optical axis AX (substantially parallel to the display surface DS) in an imaging range that is a range farther than a predetermined distance, and a range closer thereto. Is tilted with respect to the normal N of the optical axis AX. The master lens ML independently performs medium and long distance projection using the first range FL1 in which the image plane is erect or inverted parallel to the display surface DS. Further, the master lens ML creates an image surface IMGa inclined with respect to the normal N as shown by a thick broken line in the second range FL2 closer to the master lens ML than the first range FL1. For short-range close-up projection.

  9A and 9B are diagrams illustrating a method for obtaining a tilted image plane by the master lens ML. FIG. 9A shows the case of medium and long distance projection with the back focus set to fa (first mode). The first mode is a mode in which an image is displayed on the irradiated surface with the main body 2, that is, the master lens ML alone, and corresponds to a normal display state. FIG. 9B shows the case of close-up projection over a very short distance with the back focus set to fa ′ (fa <fa ′) (second mode). The second mode is a mode in which the main body 2 and the projection unit 3 are combined to display an image on the irradiated surface, and corresponds to a macro display state.

In the second mode (macro display state), the movable lens 26 in FIG. 5 causes the master lens so that the back focus becomes longer than the normal position of the master lens ML in the first mode (normal display state). ML is moved in the optical axis AX direction. When the paraxial image formation position is moved to the master lens ML side, generally, the image plane caused by the image light away from the optical axis AX is tilted. For example, as shown in FIG. 10, as the back focus is expanded from +0, the image plane tilts irregularly, and is completely tilted with respect to the normal N in the vicinity of +0.4 and +0.3.

  When the master lens ML is manufactured so that the second mode for ultra-short distance projection can be realized, and the main body 2 including the master lens ML is combined with the projection unit 3 including the aspherical mirror AM or the like. In addition, high optical performance can be exhibited. Since the mode can be converted by a simple operation of moving the master lens ML in the main body 2 in the optical axis AX direction, a simple and highly accurate configuration can be realized with almost no increase in cost. Note that the method of obtaining the tilted image plane IMGa as shown in FIG. 6 by the master lens ML is not limited to moving the master lens ML in the direction of the optical axis AX. The tilted image plane IMGa may be obtained by changing the tilt of at least one lens constituting the master lens ML. Also in this case, the mode can be converted by a simple operation. In the second mode, as already described, the image plane IMGa formed by the master lens ML is reduced to a small image plane IMGb by the reduction optical system R and arranged in front of the aspherical mirror AM. . The image light from the reduced image surface IMGb is reflected by the aspherical mirror AM, and is upright or inverted substantially parallel to the display surface DS and is connected on the screen SC substantially perpendicular to the optical axis AX. Imaged (see FIG. 7).

  Hereinafter, functions of the projection unit 3 and the projection lens 20 constituting the projector 1 will be described in detail with reference to FIG. The projection lens 20 corresponding to the master lens ML can form an image plane IMGa (see FIG. 6) tilted with respect to the normal N of the optical axis AX. The projection lens 20 has a function of correcting aberration particularly in a portion where the image height is low. The projection unit 3, that is, the first lens 31, the second lens 32, and the widening mirror 33 function as a front converter that enlarges an image.

In this embodiment, since the shift optical system is employed for the projection unit 3 that functions as a front converter, the focal position is slightly shifted when projecting onto the screen SC. For various aberrations that occur for this reason, correction by the wide-angle mirror 33 and measures for using a lens for reducing aberration can be taken. Further, the first lens 31 and the second lens 32 constituting the refractive optical system 30 may be provided with a function of correcting aberration by adopting an aspheric lens instead of the spherical lens. By combining a plurality of optical elements having an aberration correction function in this way, it is possible to satisfy high-performance optical specifications . In particular, in the lens group constituting the refractive optical system 30, it is possible to reduce the number of lenses and reduce the size of the lens by adopting an aspherical lens or a free-form surface lens instead of the spherical lens. Become. Thereby, cost reduction and size reduction of a lens frame are attained.

  The first lens 31 that is a negative power optical element and the second lens 32 that is a positive power optical element are tilted by the projection lens 20 between the projection lens 20 and the widening mirror 33 (AM). It functions as a reduction optical system R that reduces the image plane IMGa. That is, the reduction optical system R including the first lens 31 and the second lens 32 functions as a variable magnification optical system that converts the magnification of an image forming the image plane IMGa tilted with respect to the normal line N of the optical axis AX. To do.

  The wide-angle mirror 33 corresponding to the aspherical mirror AM folds the image light so that the image plane IMGb (see FIG. 7) reduced by the reduction optical system R is substantially parallel to the irradiated surface of the screen SC. Project. Further, the wide angle mirror 33 has a function of correcting aberrations particularly in a portion where the image height is high.

  The wide-angle mirror 33 can be easily aligned with the optical axis AX with other configurations (projection lens 20 and refractive optical system 30) by forming a substantially rotationally symmetric shape with respect to the central axis. Further, since the widening mirror 33 can be processed by a lathe or the like, it can be manufactured easily and with high accuracy. The projector 1 can employ a normal coaxial optical system design method by employing a coaxial optical system. Therefore, it is possible to realize an optical system with a small number of man-hours for designing the optical system and with few aberrations.

  Since this embodiment employs a configuration in which a plurality of optical elements are arranged at a predetermined interval along the optical axis AX, assembly can be facilitated by aligning the optical axis AX, and high performance can be realized. It becomes. In particular, when the main body 2 is attached or detached, high-precision alignment between the projection lens 20 of the main body 2 and each optical element of the projection unit 3 is required. By making the optical axis AX common, it is possible to easily adjust the position of the optical element on the main body 2 side and the optical element on the projection unit 3 side. In the case of a coaxial optical system, the change in optical performance from the optical axis AX toward the periphery can be made gentler than the change in optical performance in the decentered optical system. For this reason, it is possible to provide a certain degree of allowance for the placement accuracy, so that a configuration suitable for the present invention can be realized.

  As described above, it is possible to realize near-short distance projection and medium-long distance projection by a single projector 1 without degrading image quality. A single projector 1 can cover a wide projection distance from a very short distance to a medium to long distance. Note that the projection unit 3 of the present embodiment may be combined with a conventional projection type projector. By applying the projection unit 3 to a conventional projector having a projection lens capable of forming an image of a tilted image plane in the second range FL2 as shown in FIG. 6, close projection similar to the present embodiment can be realized. .

  The projection unit 3 only needs to have at least the wide-angle mirror 33 and may be appropriately modified. For example, the function of the first lens 31 or the functions of both the first lens 31 and the second lens 32 may be provided in the optical system of the main body 2, for example, the projection lens 20. Also in this case, the projector 1 can perform proximity projection.

  FIGS. 11 and 12 are diagrams for explaining a specific example 1 of proximity projection in which the projection lens 20 and the projection unit 3 in the second mode are combined. Here, the projection lens 20 includes lenses L01 to L10. In addition, the projection unit 3 includes first and second lenses 31 and 32 and a widening mirror 33. Among these, the first lens 31 includes three lenses 31a, 31b, and 31c.

実施例１において、投写レンズ２０や投写ユニット３は、基本的に球面で形成されているが、第５レンズＬ０５の出射面と、第９レンズＬ０９の入出射面と、第１レンズ３１に含まれる１つのレンズ３１ｃの入出射面と、第２レンズ３２の入出射面と、広角化ミラー３３とについては、非球面となっている。これらの非球面形状の光軸ＡＸ方向の面頂点からの変位量は、上述の多項式ｈとして与えられる。実施例１を構成する非球面の円錐定数「ｋ」、高次補正項「Ａ２」〜「Ａ１０」の値については、下記の表２に示した通りである。

図１２は、本体部２に投写ユニット３を接続した場合のスクリーンＳＣへの投写状態を示している。図からも明らかなように、スクリーンＳＣ上に良好な結像状態で近接投写が行われている。 Table 1 below shows lens data and the like of Example 1. In Table 1, “surface number” is a number assigned to each lens surface in order from the display surface DS side. “Surface type” indicates that the surface is a spherical surface or an aspherical surface or a reflective surface, “R” indicates a radius of curvature, and “D” indicates a lens thickness or air space between the next surface and the surface. Represents. Further, “Nd” represents the refractive index of the lens material at the d-line, and “νd” represents the dispersion of the lens material.

In the first embodiment, the projection lens 20 and the projection unit 3 are basically formed of a spherical surface, but are included in the exit surface of the fifth lens L05, the entrance / exit surface of the ninth lens L09, and the first lens 31. The incident / exit surface of one lens 31c, the incident / exit surface of the second lens 32, and the widening mirror 33 are aspherical. The amount of displacement from the surface apex in the optical axis AX direction of these aspherical shapes is given as the polynomial h described above. The values of the aspherical conical constant “k” and the higher-order correction terms “A2” to “A10” constituting Example 1 are as shown in Table 2 below.

FIG. 12 shows a state of projection onto the screen SC when the projection unit 3 is connected to the main body 2. As is apparent from the drawing, the proximity projection is performed on the screen SC in a good image formation state.

  FIG. 13 shows a state where the projection unit 3 is detached from the main body 2 and the projection lens 20 is in the first mode. In this case, compared with the state of FIG. 11, the first lens L01 to the tenth lens L10 are integrally moved to the object side to be in the normal display state.

  FIG. 14 corresponds to FIG. 13 and shows a projection state on the screen SC when the projection unit 3 is detached from the main body 2. In this case, the projection lens 20 is in a normal display state. As is apparent from the figure, the projection lens 20 alone is used to perform close-up projection on the screen SC in a good image formation state.

  FIG. 15A shows a case where the projection unit 3 is removed from the state of FIG. 12 or 11 and the projection lens 20 remains in the macro surface state, and the image plane IMG is formed on the front screen SC. It can be seen that the image plane IMGa is formed at a position close to the projection lens 20.

FIG. 15B is a diagram showing an imaging state when the projection lens 20 is in the macro display state, the refractive optical system 30 is left in the projection unit 3, and only the wide-angle mirror 33 is removed. By arranging the refractive optical system 30 in this way, it can be seen that an image surface IMGb that is greatly inclined is formed at a position relatively close to the projection lens 20.

[Second Embodiment]
FIG. 16 is a schematic diagram functionally illustrating each optical element of the projector according to the second embodiment of the invention. In this embodiment, the refractive optical system 30 that functions as the reduction optical system R is omitted from the projection unit 3, and the lens portion 24 that functions as the reduction optical system R is provided in the projection lens (exit optical system) 20. As a result, an image plane IMGa that is moderately inclined with respect to the display surface DS and the optical axis AX can be formed in front of the aspherical mirror AM, and close-up projection can be performed on the screen SC in a good imaging state. it can.

[Third Embodiment]
FIG. 17 is a schematic diagram functionally illustrating each optical element of the projector according to the third embodiment of the invention. In the present embodiment, the refractive optical system 30 that functions as the reduction optical system R is omitted from the projection unit 3, and the projection lens (exit optical system) 20 itself is placed on the display surface DS and the optical axis AX in front of the aspherical mirror AM. On the other hand, the image plane IMGa inclined moderately is formed. Thereby, it is possible to perform proximity projection on the screen SC in a favorable image formation state.

[Fourth Embodiment]
FIG. 18 is a front perspective view of an electronic blackboard 50 according to the fourth embodiment of the present invention. The electronic blackboard 50 includes a projector 51 configured similarly to the projector 1 according to the first to third embodiments (see FIG. 1 and the like) and a screen display unit 54 disposed above the projector 51. Here, the projector 51 includes a main body 52 and a projection unit 53.

  The main body 52 emits video light corresponding to the image signal. The projection unit 53 projects the image light from the main body unit 52 toward the screen display unit 54. The main body 52 and the projection unit 53 are configured similarly to the main body 2 (see FIG. 2 and the like) and the projection unit 3 (see FIG. 4 and the like) described in the first to third embodiments, respectively. The optical element of the projection unit 53 is housed in a housing. The housing includes an opening for emitting image light.

  The screen display unit 54 displays an image with the video light incident from the projector 51 and enables writing of the video on the display surface. The screen display unit 54 is made of translucent glass or synthetic resin that transmits light. The user writes characters, drawings, and the like on the screen display unit 54 using a writing tool such as a pen or a pointing stick. In addition, the user erases the writing to the screen display unit 54 by using an erasing tool or the like.

  In addition to the above, the electronic blackboard 50 includes a reading device (not shown). The reading device displays the written content written on the display surface of the screen display unit 54, the video displayed on the screen display unit 54, information input by bringing a tool into contact with or close to the screen display unit 54, and the like. Read. For example, an image sensor such as a CCD camera is used as the reading device. By providing the reading device for the electronic blackboard 50, it is possible to record the contents written to the screen display unit 54, the video displayed at that time, input information, and the like.

  The screen display unit 54 is attached to and installed on a frame-like base 55. A projector fixing portion 56, which is a plate-like member that fixes the projector 51, is provided on the prism 55 that connects the two legs 58 of the base 55. The projector 51 is attached vertically below the screen display unit 54 by a projector fixing unit 56. The four rod-shaped members 57 that extend radially connecting the projector fixing portion 56 and the base 55 function as reinforcing members for reinforcing the mounting strength of the projector fixing portion 56 on the base 55. Each rod-like member 57 is arranged between the projector 51 and the screen display unit 54 so as not to obstruct the image light around the area where the image light travels as indicated by a broken-line arrow in the drawing.

  FIG. 19 is a rear perspective view of the electronic blackboard 50. The projector 51 projects the image light close to the back surface of the screen display unit 54 opposite to the front side where the image is observed. The screen display unit 54 transmits the image light from the projector 51 incident on the back surface (that is, the irradiated surface) to the front side. The screen display unit 54 has light diffusibility for diffusing video light incident from the projector 51. The screen display unit 54 superimposes and displays characters, drawings, and the like written on the front surface on an image displayed by entering image light from the back surface. The observer observes characters and drawings written on the surface and video light diffused by the screen display unit 54.

  FIG. 20A is a diagram showing the projector fixing portion 56 and its peripheral portion of the electronic blackboard 50 in a state where the projector 51 is installed. In the electronic blackboard 50, the projector 51 can be held in a state of being positioned with high accuracy with respect to the screen display unit 54 by fixing the projector 51 to the base 55 by the projector fixing unit 56. As a result, a high-definition video can be displayed on the screen display unit 54. The projection unit 53 of the projector 51 is fixed to the projector fixing unit 56, and the main body unit 52 of the projector 51 is separable from the projection unit 53 and can be detached from the projector fixing unit 56 alone. Can do.

  FIG. 20B is a diagram showing a state where the main body 52 is removed from the state shown in FIG. The main body portion 52 can be appropriately attached to and detached from the projector fixing portion 56 and can be used alone. Thereby, the use as the electronic blackboard 50 (proximity projection) by attaching the main body 52 to the projector fixing portion 56 and the medium and long distance projection by taking out the main body 52 from the electronic blackboard 50 become possible.

  By adopting a configuration in which the projector 51 is arranged vertically below the screen display unit 54, the main body unit 52 is installed at a lower position in the electronic blackboard 50. Thereby, attachment of the main-body part 52 to the electronic blackboard 50 can be made easy.

  As shown in FIG. 21, the projector fixing portion 56 may include a guide structure 60 for positioning the main body portion 52. As the guide structure 60, for example, a plate-like member formed along the side surface of the main body 52 is used. The main body portion 52 is positioned by sliding on the projector fixing portion 56 along the guide structure 60 and bringing it into contact with the case of the projection unit 53. Thereby, whenever the main-body part 52 is attached to the electronic blackboard 50, the main-body part 52 can be easily installed in an exact position. The guide structure 60 is not limited to the configuration shown here, and any configuration may be adopted as long as the main body 52 can be positioned with respect to the projection unit 53 and the like in the electronic blackboard 50.

  FIG. 22 is a schematic cross-sectional view of the Fresnel lens 61 formed in the screen display unit 54. The Fresnel lens 61 is formed on the back surface of the screen display unit 54 on the side on which the image light from the projector 51 is incident. The Fresnel lens 61 functions as an angle conversion unit that converts the angle of the image light. The Fresnel lens 61 includes a plurality of prism structures 62 having a substantially triangular cross-sectional shape. The prism structures 62 are arranged in a substantially concentric circle centered on the optical axis AX (see FIG. 4 and the like), for example. The Fresnel lens 61 efficiently advances the image light traveling obliquely to the screen display unit 54 in the direction of the observer by converting the angle. Thereby, the electronic blackboard 50 can display a bright and uniform video on the screen display unit 54.

  The electronic blackboard 50 suppresses the size in the depth direction by employing the projector 51 for close-up projection at an ultra short distance. Further, by enabling medium and long distance projection with the main body 52 alone, high versatility and convenience can be secured. The electronic blackboard 50 can be reduced in weight, power consumption, and cost by applying the projector 51 for enlargement projection that can secure a sufficient size in the vicinity. As a result, the weight, power consumption, cost can be reduced, and the depth size can be reduced, thereby providing an effect that high convenience can be obtained.

  FIG. 23 is a front perspective view of an electronic blackboard 70 according to a modification of the present embodiment. The electronic blackboard 70 according to this modification is characterized in that the projector 51 is attached vertically above the screen display unit 54. The projector fixing unit 56 fixes the projector 51 to the prisms 71 provided on the top of the screen display unit 54 in the base 55.

  By disposing the projector 51 vertically above the screen display unit 54, image light is incident on the screen display unit 54 from the vertically upper side. When the user writes to the screen display unit 54, the shadow of the writing tool is generated vertically downward. As a result, it is possible to reduce the number of cases where the writing position is lost due to shadows, and to improve convenience.

The projectors 1 and 51 of the above embodiment illuminate the entire desired area of the liquid crystal panels 18R, 18G, and 18B with substantially uniform brightness using an optical system that includes a first lens array, a second lens array, and a superimposing lens. However, the present invention is not limited to this, and the entire desired area of the liquid crystal panels 18R, 18G, and 18B can be obtained with substantially uniform brightness using another illumination optical system such as an optical system including a light guide rod. It can also be illuminated.

The projectors 1 and 51 of the first to fourth embodiments are applied as, for example, a front-type projector that shows through from the side for observing the projected image when projecting at a medium to long distance. Can also be applied to rear-type projectors that project from the opposite side.

The projectors 1 and 51 of the above embodiment have been described by exemplifying a projector using three liquid crystal panels. However, the present invention is not limited to this, and one, two, or four or more liquid crystal panels are used. It can also be applied to a projector using the projector.

  DESCRIPTION OF SYMBOLS 1 Projector, 2 Main-body part, 3 Projection unit, SC screen, 10 Light source, 11 1st integrator lens, 12 2nd integrator lens, 13 Polarization conversion element, 14 Superimposition lens, 15 1st dichroic mirror, 16, 23, 25 Reflection Mirror, 17R, 17G, 17B Field lens, 18R, 18G, 18B Liquid crystal display panel, 19 Cross dichroic prism, 20 Projection lens, 21 Second dichroic mirror, 22, 24 Relay lens, 31 First lens, 32 Second lens, 33 Wide-angle mirror, 34 Lens support part, 35 Mirror support part, 36 Substrate, AX optical axis, N normal, IMG, IMGa, IMGb image plane, R reduction optical system, 50 electronic blackboard, 51 projector, 52 main body part, 53 Projector Tsu DOO, 54 screen display unit, 55 base plate, 56 projectors fixing portion 60 guide structure, 61 a Fresnel lens, 62 prism structure, 70 electronic blackboard

Claims (8)

A light source, a display surface illuminated with light from the light source, and an image surface of the display surface that emits light from the display surface and is once inclined with respect to the display surface. A main body including an emission optical system that can be formed into light;
Projects light from the display surface emitted from the emission optical system toward the irradiated surface and reflects light forming an image surface of the display surface that has a positive power and is inclined with respect to the display surface. A projection unit having a concave widening mirror for widening, and
One of said body portion and said projection unit is to have a variable magnification optical system for converting the magnification for image forming the image plane of the display surface which is inclined with respect to the display surface,
The emission optical system includes a display state in which an image forming an image surface of the display surface parallel to the display surface is formed in a first range far from a predetermined distance along the optical axis, and the optical axis Switching to a display state in which an image forming an image surface of the display surface tilted with respect to the display surface in a second range that is closer than the predetermined distance is formed .
projector.   The projector according to claim 1, wherein the variable magnification optical system is a reduction optical system that relatively reduces an image forming an image surface of the display surface tilted with respect to the display surface.   The said projection unit forms an image on the said to-be-irradiated surface parallel to the said display surface with the image surface of the said display surface inclined with respect to the said display surface as described in any one of Claims 1 and 2. projector. A light source, a display surface illuminated with light from the light source, and a main body unit including an emission optical system that emits light from the display surface;
Projection having a concave widening mirror that projects light from the display surface emitted from the emission optical system toward an irradiated surface and has positive power to reflect and widen the light from the display surface A unit,
The light forms an image surface of the display surface parallel to the display surface in a first range at a relatively long distance along the optical axis, and the display in a second range at a relatively short distance along the optical axis. A light that forms an image surface of the display surface inclined with respect to the surface;
projector. Said body portion is detachably attached to the projector, the projector according to any one of claims 1 to 4. The projector according to any one of claims 1 to 5 , wherein the emission optical system and the projection unit are arranged with their optical axes aligned. The projector according to claim 6 , wherein the emission optical system and the projection unit constitute a shift optical system that advances the light from the display surface while shifting the light from the optical axis. A projector according to any one of claims 1 to 7 ,
A screen display unit that includes the irradiated surface and enables writing of other information on the irradiated surface;
Of the projectors, the main body including the emission optical system is detachable.

Images