JP5181637B2 - Image projection device - Google Patents

Description

  The present invention relates to an image projection apparatus.

  In recent years, various techniques relating to a projection optical system including a mirror have been developed.

  For example, Patent Document 1 discloses a first reflecting mirror having a rotationally symmetric aspherical concave reflecting surface with a reflecting surface facing an imaging surface on which an image forming element is to be disposed, and the first reflecting mirror. A second reflecting mirror having a convexly reflecting surface having a rotationally symmetric aspherical shape with a reflecting surface facing the light beam from the light source, and a concave surface having a rotationally symmetric aspherical shape having the reflecting surface directed to the light beam from the second reflecting mirror A third reflecting mirror having a convex reflecting surface, and a fourth reflecting mirror having a convex reflecting surface having a rotationally symmetric aspherical shape with the reflecting surface facing the light beam from the third reflecting mirror, and A reflective coupling optical system is disclosed that is a telecentric optical system.

  The reflection-type coupling optical system disclosed in Patent Document 1 has a telecentric system with four mirrors as a constituent requirement, but the mirror is exposed, dust is easily attached, and the performance of the optical system may be deteriorated. .

  Further, in Patent Document 2, in a projector that projects image light from a reflecting mirror in a housing toward a screen through an opening formed in the upper portion of the housing, the projector is placed near the opening so as to close the opening. There is disclosed a projector comprising a transparent member that is provided and transmits the image light, and a shutter that covers the transparent member so as to be openable and closable.

  Further, Patent Document 2 discloses an image projection apparatus that irradiates a light valve that forms an image according to a modulation signal with illumination light from a light source, and enlarges and projects an image formed on the light valve using a projection optical system. A projection optical system for enlarging and projecting an image formed on the light valve, wherein the first and second elements are arranged on the projection side of the light valve in the first and second order from the light valve side. An optical system, wherein the first optical system includes one or more refractive optical systems and has positive power, and the second optical system includes one or more reflecting surfaces having power and has positive power. And an image formed by the light valve is formed as an intermediate image on the optical path of the first and second optical systems, and the intermediate image is further enlarged and projected. A system is described. Also in the image projection apparatus disclosed in Patent Document 2, when the mirror is exposed, it is considered that dust is likely to be attached to the mirror portion. In this case, there is a possibility that the performance of the optical system is deteriorated. there were.

  In the prior art disclosed in Patent Document 3, dust and scratches are prevented from being formed on the reflecting surface of the reflecting mirror of the ALL mirror type front projector. Further, the projector disclosed in Patent Document 3 is configured by an optical system in which the enlargement-side reflection mirror is a convex mirror. For this reason, an opening larger than this convex mirror on the enlarged projection image side is required for dust-proof measures. That is, the area of the film in the projector disclosed in Patent Document 3 is larger and the cost is increased.

Patent Document 4 describes a technique relating to a rear projection or a front projection device that performs enlarged projection using a refracting system and a concave mirror. According to this conventional example, there is a figure (FIG. 19 or the like) in which the projection light passes through a mask having a transparent area and a black area after the concave mirror.
JP 2003-177320 A JP 2004-258620 A JP-A-2005-316250 International Publication No. 2006/058884 Pamphlet

A reference object of the present invention is to provide a projection optical system capable of reducing deterioration in optical performance at a lower cost.

    An object of the present invention is to provide an image projection apparatus capable of reducing deterioration of optical performance at a lower cost.

According to a first aspect of the present invention, there is provided a projection optical system including at least one optical element having power and projecting an image conjugate with an object toward a projection surface, and at least one optical device having the power. A member having an opening having an area smaller than the maximum cross-sectional area of the light beam incident on the optical element in the element, and light that covers at least a part of the opening and is projected toward the projection surface An image projection apparatus including a projection optical system, wherein the image projection apparatus includes a light transmissive member that transmits light.

According to a second aspect of the present invention, there is provided an image projection apparatus for projecting an image onto a projection surface, the image projection apparatus including a projection optical system according to the first aspect of the present invention. .
An aspect of the present invention is an image projection apparatus that includes a housing and a concave mirror, and includes a projection optical system that projects an image conjugate with an object toward a projection surface. The housing is reflected by the concave mirror. A first opening for passing the projection light beam in the vicinity of a position where a plurality of projection light beams intersect, the projection optical system is all housed inside the housing, and the first opening is is located in the recess at least one end is formed in said housing, a layout in which one of the projection light of the plurality of projection light is incident perpendicular to the first opening, the first The first opening is inclined with respect to the second opening which is the opening of the depression, and the area of the first opening is smaller than the cross-sectional area of the light beam of the projection light beam in the concave mirror, and the depression is the first opening . image, characterized in that does not block the projection beam passing through the aperture of the A projection device.

According to the first reference aspect and the second reference aspect of the present invention, it is possible to provide an image projection apparatus including a projection optical system capable of reducing deterioration in optical performance at a lower cost.

  According to the aspect of the present invention, it is possible to provide an image projection apparatus capable of reducing deterioration in optical performance at a lower cost.

  Next, embodiments of the present invention will be described with reference to the drawings.

  A first embodiment of the present invention includes at least one optical element having power in a projection optical system that includes at least one optical element having power and projects an image conjugate with an object toward a projection surface. The projection optical system includes a member having an opening having an area smaller than the maximum value of the cross-sectional area of the light beam incident on the optical element.

  An example of the projection optical system is a so-called projector optical system.

  Here, the at least one optical element having the power may be any of a refractive optical element such as a lens, a reflective optical element such as a mirror, and a combination of a refractive optical element and a reflective optical element.

  The cross-sectional area of the light beam incident on the optical element in the at least one optical element having the power is the area of the region where the light beam incident on the optical element having the power illuminates the optical element. means.

  Further, the maximum value of the cross-sectional area of the light beam incident on the optical element in the at least one optical element having the power is the at least one optical element obtained for each of the at least one optical element having the power. The cross-sectional area having the maximum value among the cross-sectional areas of the incident light beam is meant.

  In addition, the member having an opening may be, for example, a diaphragm having an opening, or a housing having an opening surrounding at least a part of at least one optical element having the power. . Furthermore, the area of the opening in the member having the opening means the area of the space portion as the opening surrounded by the member having the opening.

  Further, the projection surface may be a component of the projection optical system or may not be included in the component of the projection optical system. The projection surface is, for example, a screen.

  According to the first embodiment of the present invention, it is possible to provide a projection optical system capable of reducing deterioration in optical performance at a lower cost.

  For example, by including a member having an opening having an area smaller than the maximum value of the cross-sectional area of a light beam incident on the optical element in at least one optical element having the power, at least one optical having the power It is possible to reduce adhesion of at least one of dust, dust and dirt to at least one optical element included in the element, and / or at least one optical element included in at least one optical element having the power It becomes possible to reduce that a human hand contacts an optical element. As a result, it is possible to reduce deterioration of the optical performance of the projection optical system.

  In the first embodiment of the present invention, the projection optical system includes at least one optical element having power and projects an image conjugate with the object toward the projection surface. A first optical system to be formed; and a second optical system that includes at least one optical element having the power and projects a second image conjugate with the first image toward the projection surface. A projection optical system may be used.

  In this case, the at least one optical element having the power, which is a target for obtaining the maximum value of the cross-sectional area of the light beam incident on the optical element in the at least one optical element having the power, is the second optical element. This is an optical element included in the optical system.

  The member provided with the opening is provided in the optical path between the second optical system and the second image.

  In addition, when a 1st image is located between a 1st optical system and a 2nd optical system, a 1st image may be called an intermediate image.

  Similarly, in the first embodiment of the present invention, the projection optical system includes at least one optical element having power and projects an image conjugate with the object toward the projection surface. And a second optical system that projects a second image conjugate with the first image toward the projection surface, and the first optical system. And at least one of the second optical system includes at least one optical element movable relative to the object, in a projection optical system, by moving at least one of the optical elements relative to the object The projection optical system may be characterized in that the image distance of the projection optical system is changed and the size of the second image is changed.

  In the projection optical system, the first optical system includes at least one optical element having the power, and moves at least one of the optical elements included in the first optical system with respect to the object. It may be a projection optical system that moves the first image with respect to the object.

  In this case, it is possible to provide a projection optical system that can change the image distance of the projection optical system and change the size of the second image. In particular, even when the image distance of the projection optical system is short, it is possible to provide a projection optical system having a high rate of change in the size of the second image.

  In the projection optical system, the size of the second image can be changed, and the half angle of view of the principal ray projected toward the projection surface can be substantially constant. is there.

  Here, the principal ray projected toward the projection surface means a ray at the center of the light beam projected toward the projection surface. The half angle of view of the principal ray projected toward the projection surface is 90 ° − (the normal vector of the projection surface and the direction vector of the principal ray at the point where the principal ray is incident on the projection surface. Is an angle between the two (less than 90 °). Further, that the half field angle of the principal ray projected toward the projection surface is substantially constant means that the image distance of the projection optical system is changed and the size of the second image is changed. This means that the variation of the half field angle of the principal ray projected toward the projection surface is within ± 2 °.

  In this case, the half field angle of the principal ray projected toward the projection surface is substantially constant, while changing the image distance of the projection optical system and the size of the second image. It is possible to provide a projection optical system capable of changing the thickness.

  In the first embodiment of the present invention, preferably, the at least one optical element having the power includes a reflective optical element having a positive power. The reflective optical element having positive power is a so-called concave mirror.

  A plurality of light fluxes from an object usually diverge toward an image, but when at least one optical element having the power includes a reflective optical element having a positive power, reflective optics having a positive power is used. By the element, a plurality of light beams from the object can be crossed. Here, the flare component can be reduced by positioning the opening of the member having the opening at a location where a plurality of light beams from the object intersect. Accordingly, the contrast of the image can be improved.

  Alternatively, in the projection optical system in which the first optical system, the first image, and the second optical system are arranged, the plurality of light beams from the first image are normally directed toward the second optical system. In the case where at least one optical element that diverges but has the power included in the second optical system includes a reflective optical element having a positive power, the reflective optical element having a positive power causes the first optical element to A plurality of luminous fluxes from the image can be crossed. Here, the flare component can be reduced by positioning the opening of the member having the opening at a location where a plurality of light beams from the first image intersect. Accordingly, the contrast of the second image can be improved.

  In the first embodiment of the present invention, preferably, the reflective optical element having the positive power includes an optical element having a rotationally asymmetric aspherical surface.

  Here, the rotationally asymmetric aspheric surface means all aspheric surfaces except the rotationally symmetric aspheric surface.

In the rotationally symmetric aspherical surface, Z is the depth in the optical axis direction, c is the paraxial radius of curvature, r is the distance in the optical axis orthogonal direction from the optical axis, and k is the cone. Assuming that A, B, C,... Are high-order aspheric coefficients, the equation (a)
Z = c · r2 / [1 + √ {1− (1 + k) c2r2}] + Ar4 + Br6 + Cr8 (a)
Means an aspherical surface represented by

  An example of the rotationally asymmetric aspheric surface is a free-form surface.

  Examples of free-form surfaces include anamorphic polynomial free-form surfaces.

An anamorphic polynomial free-form surface is defined as “X2, Y2, X2Y” assuming that the short axis direction is the Y direction, the long axis direction is the X direction, and the depth of the curved surface is in the Z direction with reference to the center of the projection image. , Y3, X2Y2,...
Z = X2, x2 + Y2, y2 + X2Y, x2y + Y3, y3 + X4, x4 + X2Y2, x2y2 + Y4, y4 + X4Y, x4y + X2Y3, x2y3 + Y5, y5 + X6, x6 + X4Y2, x4Y, 2yX4Y4
Is an aspherical surface.

  In this case, the aberration in the image can be reduced more favorably by improving the degree of freedom in designing the reflective optical element having the positive power. In addition, the number and size of the reflective optical elements having the positive power can be reduced. Thereby, the apparatus of a projection optical system can be reduced in size. In addition, the cost of the projection optical system can be reduced.

  The first embodiment of the present invention preferably further includes a light-transmitting member that covers at least a part of the opening and transmits light projected toward the projection surface.

  Here, covering at least part of the opening includes covering both of the opening and covering part of the opening. Covering at least a portion of the opening includes both covering at least a portion of the opening adjacent to it and covering it away from at least a portion of the opening.

  Further, transmitting light projected toward the projection surface completely transmits light projected toward the projection surface, and light projected toward the projection surface. Including both transmitting a part of the.

  The shape of the light transmissive member is not particularly limited, but may be, for example, a film shape or a plate shape. The material of the light transmissive member is not particularly limited as long as it is a material that transmits light projected toward the projection surface. For example, glass or plastic may be used.

  The arrangement of the light transmissive member is determined in consideration of aberrations generated in the light projected toward the projection surface by the light transmissive member. Further, when the shape of the light transmissive member is a film shape or a plate shape, the thickness of the light transmissive member along the optical path of the light projected toward the projection surface is the light transmissive member. It is determined in consideration of the aberration generated by the light projected toward the projection surface by the sex member.

  In this case, it is possible to provide a projection optical system that can further reduce deterioration of optical performance at a lower cost.

  For example, by further including a light transmissive member that covers at least a part of the opening and transmits light projected toward the projection surface, at least one optical element having the power includes at least one optical element. It is possible to reduce or prevent at least one of dust, dust, and dust from adhering to the optical element, and / or manual operation is required for at least one optical element included in at least one optical element having the power. It is possible to prevent contact. As a result, it is possible to further reduce the deterioration of the optical performance of the projection optical system.

  In addition, it further includes a light transmissive member that covers at least a part of the opening and transmits light projected toward the projection surface, thereby suppressing loss of light projected toward the projection surface. In addition, an image conjugate with the object can be projected toward the projection surface.

  In the first embodiment of the present invention, preferably, the light transmissive member is a film.

  Here, the film is preferably optically thin but preferably has a thickness that does not affect the optical performance. Specifically, the film has a thickness of 0.01 mm to 0.5 mm. Means that.

  In this case, the light transmissive member has appropriate durability and can reduce the aberration generated in the light by the light transmissive member. That is, when the thickness of the film is 0.01 mm or more, it is possible to provide a light transmissive member having appropriate durability. Moreover, it becomes possible to reduce the aberration which generate | occur | produces in light by the light transmissive member because the thickness of a film is 0.5 mm or less. As a result, the resolution of the image can be improved, and the optical performance of the projection optical system can be improved.

  In the first embodiment of the present invention, preferably, the light transmissive member is movably provided.

  In this case, a part of the light transmissive member covering at least a part of the opening is contaminated, and the transmittance of light projected toward the projection surface through the light transmissive member is reduced. Even in this case, by moving the light transmissive member, it is possible to cover at least a part of the opening with a portion of the light transmissive member without contamination. As a result, it is possible to reduce or prevent the deterioration of the optical performance of the projection optical system by moving the light transmissive member.

In the first embodiment of the present invention, preferably, the light transmissive member is detachably provided.

  In this case, a part of the light transmissive member covering at least a part of the opening is contaminated, and the transmittance of light projected toward the projection surface through the light transmissive member is reduced. Even in this case, it is possible to cover at least a part of the opening with a new light-transmitting member that is not contaminated by replacing the light-transmitting member with a new one. As a result, it is possible to reduce or prevent deterioration of the optical performance of the projection optical system by replacing the light transmissive member with a new one.

  In the first embodiment of the present invention, preferably, the member having the opening is a housing surrounding at least a part of at least one optical element having the power.

  For example, when the projection optical system includes the first optical system and the second optical system, the member having the opening is at least one of the first optical system and the second optical system. It is the housing | casing which encloses a part.

  In this case, at least a part of the at least one optical element having the power is protected by the casing having the opening surrounding at least a part of the at least one optical element having the power, and the casing. This opening makes it possible to reduce the deterioration of the optical performance of the projection optical system.

  Furthermore, the casing surrounding at least a part of at least one optical element having the power may be a casing of an image projection apparatus that projects an image onto a projection surface, including a projection optical system.

  In this case, the housing having the opening can reduce adhesion of at least one of dust, dust, and dust not only to the projection optical system but also to the components included in the image projection apparatus. . Examples of the components included in the image projection apparatus include an image forming engine of the image projection apparatus.

  In the first embodiment of the present invention, preferably, the light transmissive member is fixed to the casing. For example, the housing includes a fixing portion that fixes the light transmissive member, and the light transmissive member is fixed to the housing. The fixing part may be a concave part into which the light transmissive member can be fitted. In this case, the light transmissive member is fitted into the fixing portion and fixed to the casing.

  When the light transmissive member is fixed to the housing, the light transmissive member can seal at least one optical element having the power together with the housing. When at least one optical element having the power is sealed with the casing and the light transmissive member, the at least one optical element included in the at least one optical element having the power has dust, dust, and the like. It is possible to reduce or prevent the adhesion of at least one of dust and / or dust and / or to prevent human hands from contacting at least one optical element included in at least one optical element having the power. It becomes possible. As a result, it is possible to further reduce the deterioration of the optical performance of the projection optical system.

  A second embodiment of the present invention is an image projecting apparatus that projects an image onto a projection surface, and includes the projection optical system according to the first embodiment of the present invention.

  As an image projection device, for example, a light valve having an image forming unit that modulates or deflects light in pixel units according to an image signal, an illumination device, and illumination light emitted from the illumination device is applied to the light valve. And a projection display device characterized in that an enlarged projection image is obtained from the image formed by the optical system and the light valve by the projection optical system according to the first aspect of the present invention.

  According to the second embodiment of the present invention, it is possible to provide an image projection apparatus capable of reducing deterioration in optical performance at a lower cost.

  Next, specific embodiments of the present invention will be described with reference to the drawings.

( Reference Example 1)
FIG. 1 is a diagram schematically showing one example of a projection optical system in Reference Example 1 (hereinafter abbreviated as Example 1) . FIG. 2 is a diagram schematically illustrating another example of the projection optical system according to the first embodiment.

  An object plane 1, a first optical system 2, and a second optical system (for example, a mirror optical system having a positive power) 3 are arranged as shown in FIG. The light beam 6 emitted from the object plane 1 reaches the first optical system 2. In the first optical system 2, the light beam is condensed to form an intermediate image 7, and then becomes a divergent light beam and reaches the second optical system 3. The second optical system 3 further enlarges the intermediate image to form an enlarged image on the image plane. At this time, the second optical system 3 may be a refractive system.

  More preferably, the second optical system 3 can be provided with a large power by being composed of a reflecting mirror. Hereinafter, the function of the second optical system 3 will be described assuming a concave mirror.

  The light beam reflected by the mirror optical system constituting the second optical system 3 is converted into a condensed light beam and passes through the opening 5. The light beam that has passed through the opening 5 is condensed on the enlargement conjugate plane 4 that is the image plane. In the above description, the plurality of light beams emitted from different positions on the object plane 1 can cross the optical paths when the mirror has positive power after being reflected by the mirror optical system.

  At this time, in the vicinity of the position where the optical paths intersect, the total luminous flux reflected from the mirror constituting the second optical system 3 converges smaller than the largest cross-sectional area A among the elements constituting the second optical system. Has been. An opening 5 having an area B smaller than the cross-sectional area A is arranged between the second optical system and the magnified image plane.

  FIG. 2 shows a configuration example in which the light beam emitted from the refraction system 2 is guided to a positive mirror without forming an intermediate image. In this case, the structure having the positive mirror is the second optical system 3 ′. Also in this case, the light beams intersect on the optical path until the light beam reflected by the positive mirror is collected on the enlargement conjugate plane 4, and the opening 5 is provided in the vicinity of the intersecting position.

  In the arrangement shown in FIG. 1 or 2, the area B or B ′ of the opening 5 is set to be smaller than the cross-sectional area A or A ′ of the light beam in the mirror.

  Although not shown, the mirror optical system and the refractive optical system 2 constituting the second optical system 3 or 3 'are not touched directly from the part other than the opening, and the mirror The optical system and the refractive optical system 2 are usually housed in a housing 14 of the apparatus.

  By adopting such a configuration, there is no opportunity to touch the mirror or the like by mistake. In addition, so-called unnecessary flare light is shielded by the opening 5 and does not reach the enlarged conjugate plane 4. Thereby, the contrast of the image can be improved. In addition, it is difficult for light from the outside to enter the inside of the optical system, and it is possible to suppress the generation factor of irregularly reflected light, and the contrast performance can be improved. Further, the opening 5 may be provided in a part of the casing 14 in the front projector device.

  Since the opening of the opening 5 is small, dust and dust from the outside of the housing 14 are difficult to enter. Dust and dust often adhere to optical elements such as mirrors, and cause deterioration of optical characteristics such as reflectance and transmittance. By adopting a configuration in which dust and dust are difficult to enter, it is possible to avoid the deterioration of the optical element and the accompanying deterioration of the image quality. The above effects are particularly effective when a front projector is configured.

  1 and 2 schematically show the optical system in order to explain the function of the present invention. As a specific example of the applied optical system, it is most effective to apply to a conventional intermediate image forming optical system.

(Example 2)
FIG. 3 is a diagram illustrating an example of a specific projection optical system as the front projector optical system according to the second embodiment. 3A is a cross-sectional view of the projection optical system in the vertical direction, and FIG. 3B is a cross-sectional view of the projection optical system in the horizontal direction. FIG. 4 is a diagram illustrating another example of a specific projection optical system as the front projector optical system according to the second embodiment. FIG. 5 is a diagram illustrating still another example of a specific projection optical system as the front projector optical system according to the second embodiment.

  The specific design was performed by existing optical simulation. Example 2 applied to the configuration of the present invention will be described.

  By making the mirror optical system having positive power constituting the second optical system 3 in Embodiment 1 into a rotationally asymmetric mirror shape, a better aberration correction effect can be obtained. An example of a rotationally asymmetric surface shape is a free curved surface, but other curved surfaces may be used.

  FIG. 3 shows an example of a concave mirror having different vertical and horizontal curvatures as the mirror shape. However, only the projection optical system is drawn as a necessary component for explaining the second embodiment of the present invention, and as described in FIG. 1, the cross-sectional area of the light beam in the mirror is between the mirror and the projection image. An opening having a smaller area is provided. As shown in FIGS. 3A and 3B, the size of the opening is characterized in that A> B, where A is the cross-sectional area of the light beam in the mirror and B is the area B of the opening.

  When the object surface is rectangular, the shape of the effective area where the mirror receives the light beam is approximately rectangular. When this optical system is used in a projection apparatus, the shape of the light valve disposed on the object plane is generally rectangular, and at this time, the shape of the effective area of the mirror is approximately rectangular. In an optical system employing such a concave mirror, an opening having an area smaller than the cross-sectional area of the light beam in the mirror is provided in the vicinity of the cross. Further, it is desirable that the opening has a size that does not block an effective projection light beam.

  Although not shown in the drawings, the shape does not necessarily need to be rectangular, and may be circular, elliptical, or trapezoidal. Is obtained.

  The light beams reflected from the mirror intersect and converge the entire light beam in the vicinity thereof, so that the opening of the opening 5 can be narrower than the length in either the short side direction or the long side direction of the mirror. As a result, as in the first embodiment, unnecessary flare light is blocked by the opening and does not reach the enlarged conjugate plane 4. Thereby, the contrast of the image can be improved. Further, the opening 5 may be provided in a part of the casing 14 in the front projector apparatus. Since the opening 5 is small, dust and dust from the outside of the housing 14 are difficult to enter. Dust and dust often adhere to optical elements such as the mirror 3 and cause optical characteristics such as reflectance and transmittance to deteriorate. By adopting a configuration in which dust and dust are difficult to enter, it is possible to avoid the deterioration of the optical element and the accompanying deterioration of the image quality. The above effects are particularly effective when a front projector is configured.

  Further, as shown in the example of FIG. 4, if the position of the opening 5 is selected, it is possible to arrange the opening further smaller than the example of FIG. In other words, by arranging one of the projection light rays forming the projection image to be perpendicularly incident, a smaller opening can be obtained, and the above effect works most effectively.

3 shows a configuration that is bent twice inside the first optical system, FIG. 4 shows a configuration that is never bent, and FIG. 5 shows a configuration that is bent once. In either case, the optical system can be bent to efficiently fit inside the housing 14 due to the size of the projection apparatus.

(Example 3)
FIG. 6 is a diagram for explaining the arrangement of the transparent members in the third embodiment.

In Example 3, in addition to the configuration of Example 1 or 2, a light-transmitting transparent member is disposed in the opening. FIG. 2 shows an embodiment in which no intermediate image is formed. The transparent member is preferably connectable to the housing. In addition, as shown in FIG. 6, a gap can be eliminated by providing an opening hole in a part of the frame 9 of the housing and fitting the transparent member 8 therein. Note that reference numeral 10 in FIG. 6 schematically shows a transmitted light beam. By eliminating the gap, a higher dustproof effect can be obtained. The above effects are particularly effective when a front projector is configured.

  If necessary, an antireflection coat may be provided on the surface of the transparent member. The antireflection coat is more preferably on both sides of the transparent member, but it is also effective on one side.

  As shown in the example of FIG. 5, by providing an opening substantially perpendicular to the optical path, the influence of aberration can be reduced. What is necessary is just to arrange | position so that at least one of the projection light beams may be perpendicularly incident.

Example 4
FIG. 7 is a diagram illustrating the transparent member in Example 4.

  In Example 4, a light transmissive film was used as the transparent member of Example 3. In FIG. 7, the film 11 is disposed so as to cover the opening 5, and the film 11 is fixed to the housing frame 9 by the fixing member 12. In Example 4, since the transparent member is the film 11, it can be made thinner than when a glass or plastic material is used. Therefore, the occurrence of optical aberration can be almost ignored even when light passes. Also, it is inexpensive in terms of cost.

  If necessary, an antireflection coat may be provided on the surface of the film 11. The antireflection coat is more desirable on both sides of the film 11, but it is also effective on one side.

(Example 5)
FIG. 8 is a diagram illustrating the configuration of the transparent member in the fifth embodiment.

  In Example 5, it was set as the structure which a translucent location can move.

  As a specific configuration, as shown in FIG. 8, a film 11 that is a translucent member is arranged in a belt shape, and rotation mechanisms for rotating the belt-shaped film 11 are provided at both ends of the belt. The light transmission region of the belt-like film 11 can be changed by the rotation mechanism. When the film 11 deteriorates, the film 11 can be rotated to use an area that has not deteriorated. As a result, the film 11 can be used for a long time without replacement. In the illustrated example, the film 11 is wound around the roll 13 in a roll shape, and the film 11 is wound on the roll 13 ′ side. Rolls 13 and 13 'rotate clockwise.

  It is preferable to have a nail for winding the roll. It is advisable to continuously make holes that engage with the claws in the area where light on the near side and the far side of the film in FIG. 8 does not transmit light.

(Example 6)
Since a part of the light transmission surface of the open window member can be exposed to the outside of the casing, there is a possibility of deterioration due to damage or dust burn-in. In Example 6, in FIG. It was configured to be detachable by being used without being attached to the body part without being attached or screwed. As a result, the element can be easily replaced when it deteriorates.

(Example 7)
FIG. 9 is a diagram schematically illustrating an image projection display apparatus according to the seventh embodiment.

  As shown in FIG. 9, the illumination device 21, the light valve 22, and the projection optical system 23 in which the concave mirror described so far in Embodiments 1 to 6 is arranged on the enlargement side are configured. In the optical path that has passed through the mirror, an opening having an area smaller than the cross-sectional area of the light beam in the concave mirror is provided.

  As the illuminating device 21, a halogen lamp, a xenon lamp, a metal halide lamp, an ultrahigh pressure mercury lamp, or the like is used as a light source. Alternatively, an LED light source or an LD light source may be used.

  Further, the light may be reflected and condensed by a reflector so that the illuminance can be obtained efficiently. As an illumination optical system as an optical system for efficiently illuminating the light valve, it is possible to employ an optical system that reduces uneven illuminance irradiated to the light valve by combining a fly-eye lens called an integrator. Further, an illumination optical system that efficiently leads to the light valve 22 in combination with a condenser lens may be used.

  In an illumination system using polarization characteristics, the illumination light becomes more efficient when the polarization is aligned, and a so-called polarization converter may be used. The polarization converter is composed of a polarization converter combining a PBS array and a wave plate, which is a conventional technique, and is efficiently converted into one direction of polarization. A configuration combined with a lens array in accordance with the PBS array pitch is adopted as necessary. Furthermore, when it is desired to improve the degree of polarization and ensure the contrast performance, a linear polarizer is inserted after the polarization converter for incident light.

  If it is possible to use a light source with high polarization, such as a higher-power laser light source, the polarization converter is not necessarily required.

  The light valve 22 is illuminated by the above illuminating means, and the transmitted light formed by the light valve 22 or the modulated image light that has become reflected light is enlarged and projected onto the screen 24 by the projection optical system 23.

  By adopting such a configuration, the area of the opening is set smaller than the cross-sectional area of the light beam in the mirror, so there is a much greater opportunity to touch the mirror than when a conventional convex mirror is used. Reduced, stable quality can be maintained. In addition, the illumination light is irradiated not only on the necessary area of the light valve 22, but also on the periphery, and this light may become unnecessary flare light inside the optical system and reach the projection conjugate plane. However, it is shielded by the opening of the present invention and does not reach the enlarged conjugate plane. By cutting the flare, the contrast of the image is improved.

(Example 8)
In the magnifying projection device, an opening is provided in a part of the casing of the magnifying projection device. As shown in FIG. 4 or FIG. 5, an opening is provided in a part of the casing 14 of the front projector apparatus, and light is an apparatus configuration that projects an image through the opening.

  As already described, a light-transmitting member is further disposed in the opening, so that the effect of avoiding deterioration of the element due to the inclusion of foreign matter is enhanced. Alternatively, the member can be attached to and detached from the housing 14 to realize a device that can be easily replaced at the time of deterioration, or can be used without giving optical aberrations by being formed into a film. It is also possible to roll the file so that the degraded part is not used.

  Next, the opening part and the light transmissive member of this example will be described in more detail. FIG. 10 shows a top view and a front view of a transparent member arranged in close contact with a light shielding member having an opening. The opening has a horizontally long elliptical shape. Since the projection screen is horizontally long, it may be made a minimum size so as not to obstruct the necessary projection light. This area is smaller than the cross-sectional area of the light beam in the concave mirror. The transparent member is preferably a glass member, a translucent plastic member such as PC or PMMC. The thinner the transparent member is, the smaller the deterioration in optical performance due to transmission.

Example 9
As Example 9, the configuration of another light transmissive member is shown. FIG. 11 shows a top view and a front view in a state where a light shielding layer and a transparent member are closely arranged on the light shielding member of this embodiment. In this embodiment, a light shielding layer is provided on the surface of the light transmissive member, and an opening is formed in the light shielding layer so that the light shielding layer blocks a part of the opening of the light transmissive member. The transparent member is closely disposed on the light shielding layer so as not to block the opening formed by the light shielding layer. The light shielding layer functions sufficiently only on one side. Rather, in the case of double-sided formation, there arises a problem that a necessary optical path is interrupted if the mask position is shifted. The mask may be formed by an existing printing technique, a lift-off method, or the like.

  Furthermore, the example of detailed opening shape is shown. Before that, description will be made on the assumption that the optical system is a projection optical system having a concave mirror as shown in FIG. In this optical system, a concave mirror has the largest effective aperture among optical elements having power, and the effective reflection area of the concave mirror was evaluated by existing optical design simulation software. .

  As an example, FIG. 12 shows an optical state in which an intermediate image is once formed by a refractive optical system and enlarged and projected by a concave mirror. A state where a 0.7 inch diagonal panel is enlarged to a size of about 100 inches (ray tracing diagram on one side only) is shown. An enlarged view of this optical system is shown in FIG. Here, the aperture member and the transparent plate 15 are arranged at a position where the luminous flux gathers after being reflected by the concave mirror 3 which is the second optical system (FIG. 13 shows the aperture portion because the figure becomes complicated). Is not shown).

  The transparent plate 15 is a white plate glass of about 1 mm and is inclined 45 degrees with respect to the optical axis of the first optical system 2. In this optical system, in order to show the effective reflection area of the concave mirror 3 and the effective transmission area of the transparent plate 15, rays emitted from an object position of 5 × 5 = 25 angle of view on one side with respect to the vertical line at the center of the screen. I tried to plot the passing position.

  FIG. 14 shows the reflection region 16 of the concave mirror. Seen from the front of the reflective surface. FIG. 15 shows the effective transmission area 18 of the transmission member. Of course, there is a ray on the opposite side of the center, but it is omitted because it is a left-right symmetric optical system. It can also be seen that the light beam reflected on the right side of the concave mirror is a position passing the left side of the opening of the transmission member. Although there is no description between the points of each of the 25 angles of view, it is sufficient to determine the effective area. The effective areas of the mirror and the transparent member are both drawn on the same scale. As can be seen from FIGS. 14 and 15, the effective transmission region of the transmission member is clearly smaller than the area of the reflection region of the mirror. It is also obvious that even the region indicated by the dotted line need only be transmitted. FIG. 16 shows a state in which the transparent members are arranged almost horizontally. It can also be seen that the shape of the effective transmission region has changed. As described above, the effective transmission region changes depending on the position of the transmission member. However, if it is limited by the opening of a region larger than the effective transmission region (a dotted line region in FIG. 15 or a dotted line region in FIG. 16), stray light can be prevented. Will also be very strong.

  Therefore, as an example of a structure that is more resistant to stray light, FIG. 17 shows another example in which the light-shielding member having the above-described opening in the dotted line region and a transparent member are used. An opening is provided on the surface of the transparent member so as to be larger than the effective projected light beam cross-sectional area. Since the shape is not a simple shape such as a circle or an ellipse, it may be formed using a replication technique using a mask pattern. Although not shown in the drawings, it can also be formed by a light shielding member such as a sheet metal. An accurate and highly accurate opening shape can also be formed by a press die.

  The light-shielding member having the opening may be any material that blocks light, such as a sheet metal member or a plastic member. It may be configured integrally with the lens housing of the projection optical system or the housing of the projector device, or may be held via a separate member.

  Next, the thickness of the transparent member will be described. In a conventional optical simulation, the relationship between the thickness of the transparent member and the MTF indicating the resolution performance was calculated for an optical system that was optimized for the projection optical system in the absence of the transparent member. As shown in FIG. It can be seen that a very thin transparent member having an MTF exceeding 70% is less than 70% when the thickness increases to exceed 2 mm. As a guideline for lowering the MTF, it can be determined that up to about 4.5 mm is acceptable if a line that secures 90% or more from the initial value without the transparent member is determined. This value naturally changes depending on the design of the projection optical system, but here, a phenomenon is shown in which the resolution performance changes due to a change in thickness.

  As already described, it has been found that the transparent member is made to be a film having a thickness of less than 0.5 mm so that the MTF hardly deteriorates. However, in order to give the transparent member some strength, when using a glass substrate or a substrate such as plastic, a thickness of several mm may be required. Of course, a desired thickness may be set in advance, and the entire optical system may be optimized based on the thickness. In this case, it is obvious that when the thickness of the transparent substrate increases, the occurrence of critical aberration and coma due to oblique incidence cannot be ignored.

  Therefore, the openings are arranged so as to include light rays that are perpendicularly incident among light rays that are incident on the transmissive member. By adopting such a configuration, it is possible to reduce the deterioration sensitivity due to the occurrence of critical aberration and coma aberration due to the oblique incidence described above.

  As described above, according to the embodiments of the present invention, it is possible to realize an image projection apparatus in which the optical element and the image quality of the projected image are less deteriorated due to dust of the apparatus. The effect is particularly great when applied to a front projector.

  Further, in this embodiment, since the opening and the transparent member are separated from each other, the stray light prevention and the dust prevention measures are effectively performed while maintaining the projection performance.

  Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to these embodiments and examples, and these embodiments and examples of the present invention are not limited thereto. Can be changed or modified without departing from the spirit and scope of the present invention.

  The present invention can be applied to, for example, a front-type projector optical system and an imaging optical system in which two-dimensional information is reduced and imaged and image information is read by a CCD.

  Further, the present invention can be applied to an optical system and a projection apparatus that prevent the mirror portion from being protected from dust and coming into contact with human hands, and that do not cause deterioration in optical performance. In particular, the present invention can be applied to prevent contamination of the reflecting mirror and the lens surface in the front projector optical system.

FIG. 1 is a diagram schematically illustrating an example of a projection optical system according to the first embodiment. FIG. 2 is a diagram schematically illustrating another example of the projection optical system according to the first embodiment. FIG. 3 is a diagram illustrating an example of a specific projection optical system as the front projector optical system according to the second embodiment. FIG. 4 is a diagram illustrating another example of a specific projection optical system as the front projector optical system according to the second embodiment. FIG. 5 is a diagram illustrating still another example of a specific projection optical system as the front projector optical system according to the second embodiment. FIG. 6 is a diagram for explaining the arrangement of the transparent members in the third embodiment. FIG. 7 is a diagram illustrating the transparent member in Example 4. FIG. 8 is a diagram illustrating the configuration of the transparent member in the fifth embodiment. FIG. 9 is a diagram schematically illustrating an image projection display apparatus according to the seventh embodiment. FIG. 10 is a diagram illustrating the configuration of the opening and the transparent member in the eighth embodiment. FIG. 11 is a diagram illustrating the configuration of the opening and the transparent member in the ninth embodiment. FIG. 12 is a diagram illustrating a projection optical path diagram as a front projector optical system according to the tenth embodiment. FIG. 13 is an enlarged view of a projection optical path diagram as a front projector optical system in the tenth embodiment. FIG. 14 is a diagram illustrating the effective reflection area of the concave mirror according to the tenth embodiment. FIG. 15 is a diagram for explaining an effective transmission region (when tilting 45 degrees) of the transparent member in Example 10. FIG. 16 is a diagram for explaining an effective transmission region (when tilted by 90 degrees) of the transparent member in Example 10. FIG. 17 is a diagram illustrating the configuration of the opening and the transparent member in the tenth embodiment. FIG. 18 is a diagram illustrating the relationship between the thickness of the transparent member and the MTF.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Object surface 2 1st optical system 3, 3 '2nd optical system 4 Magnification conjugate surface 5 Aperture part 6 Light beam 7 Intermediate image 8 Transparent member (light transmissive member)
9 Housing frame (light shielding material)
9-1 Light-shielding layer 10 Light beam 11 Film 12 Fixing member 13, 13 'Roll 14 Case 15 Transparent plate 16 Effective transmission area in case of rectangular reflection effective reflection area 17 Effective transmission area 21 of translucent member 21 Illumination device 22 Light valve 23 Projection optical system 24 Screen T Light beam passing direction

Claims (4)

A housing,
In an image projection apparatus having a concave mirror and a projection optical system that projects an image conjugate with an object toward a projection surface,
The housing includes a first opening for passing the projection light beam in the vicinity of a position where a plurality of projection light beams reflected by the concave mirror intersect,
All the projection optical systems are housed inside the housing,
The first opening has at least one end in a recess formed in the housing, and any one of the plurality of projection light beams is perpendicularly incident on the first opening. Arrangement,
The first opening is inclined with respect to a second opening which is the opening of the depression;
The area of the first opening is smaller than the cross-sectional area of the light beam of the projection light beam in the concave mirror,
The image projection apparatus, wherein the depression does not block the projection light beam that has passed through the first opening. The image projection apparatus according to claim 1, wherein a light transmissive member is disposed in the first opening.   The image projection apparatus according to claim 2, wherein the light transmissive member is disposed in close contact with the casing.   The image projection apparatus according to claim 1, wherein the image projection apparatus is a front projector.

Images