Projection lens unit of projector and projector capable of suppressing image deterioration

A projection lens unit (15) of a projector (10) is disposed in a state in which an optical axis (CL) of the projection lens unit deviates from a center of an image forming panel (14); a first lens holder (43) of a lens barrel (40) includes holding pieces (55a, 55b) that are provided at intervals in a circumferential direction of a first lens group (L1) and are engaged with a first portion (A1) of the first lens group positioned on a side to which the image forming panel is shifted, and a holding piece (55c) that is engaged with a second portion (A2) of the first lens group positioned on a side opposite to the side to which the image forming panel is shifted; and the linear expansion coefficient of each of the holding pieces is lower than the linear expansion coefficient of the holding piece.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projection lens unit of a projector and a projector.

2. Description of the Related Art

A projector projects light, which is applied to an image forming panel from a light source, onto a projection surface through a projection lens unit to display an image. In a recent projector, the illuminance of a projected image has been further improved through the improvement of an image forming panel and a light source than in the related art. As a result, unnecessary light, which does not contribute to the formation of an image, is also increased, and the temperature of a lens barrel of a projection lens unit becomes higher than that in the related art in a case in which the unnecessary light is removed by the lens barrel or a light screen of the projection lens unit.

In a projector disclosed in JP2005-128217A, a reflective region is provided on a portion, which receives unnecessary light, of a lens holder, a stop, or the like of a lens barrel and the absorption of unnecessary light is suppressed. Accordingly, a rise in the temperature of the lens barrel is suppressed, so that the deformation of the lens barrel caused by a rise in temperature is suppressed.

In a projector disclosed in JP2014-59333A, an unnecessary light-receiving member overlaps with a lens holder of a lens barrel, and the surface of a contact portion of the lens holder, which is in contact with the unnecessary light-receiving member, is formed in an uneven shape. Accordingly, the transfer of heat to the lens holder from the unnecessary light-receiving member is reduced in comparison with a case in which the entire surface of the unnecessary light-receiving member is in contact with the lens holder. Therefore, a rise in the temperature of the lens barrel is suppressed, so that the deformation of the lens barrel caused by a rise in temperature is suppressed.

Further, the following projectors are known. The projectors are adapted to displace a lens group, which is held by a holding member, in the direction of an optical axis through the thermal expansion of the holding member holding some lenses of a lens barrel against the change of a focal position, which occurs due to the deformation of the lens barrel caused by heat, to correct the change of the focal position (for example, JP2009-271448A and JP2012-242728A).

SUMMARY OF THE INVENTION

In a wide-angle projector that can perform short-distance projection, there is a case where the optical axis of a projection lens unit is disposed to deviate from the center of an image forming panel so that the projector projects light onto a screen, where the screen is located at a position higher than the position of a main body of the projector in a state in which the main body of the projector is installed on a table. In this case, since a deviation occurs in the projection of unnecessary light onto the lens barrel, distribution is caused in the temperature of the lens barrel in the circumferential direction. As a result, distribution in a circumferential direction is caused in the thermal expansion of the lens barrel in the direction of the optical axis and the inclination of a lens group with respect to the optical axis of the projection lens unit is caused. For this reason, there is a concern that image quality may deteriorate.

In the projectors disclosed in JP2005-128217A and JP2014-59333A, the temperature distribution of the lens barrel in the circumferential direction is not canceled and the inclination of the lens group caused by the temperature distribution of the lens barrel in the circumferential direction is not canceled. Even in the projectors disclosed in JP2009-271448A and JP2012-242728A, the lens group is merely displaced in the direction of the optical axis through the thermal expansion of the holding member and the inclination of the lens group caused by the temperature distribution of the lens barrel in the circumferential direction is not canceled.

The invention has been made in consideration of the above-mentioned circumstances, and an object of the invention is to provide a projection lens unit and a projector that can suppress the deterioration of an image caused by temperature distribution of a lens barrel in a circumferential direction.

A projection lens unit according to an aspect of the invention is a projection lens unit of a projector projecting light, which is applied to an image forming panel from a light source, onto a projection surface as image light and disposed in a state in which an optical axis of the projection lens unit deviates from a center of the image forming panel. The projection lens unit comprises a lens barrel that is provided with one or more lens groups and one or more lens holders holding the lens groups, respectively. At least one of the lens holders includes a plurality of holding pieces that are provided at intervals in a circumferential direction of the lens group held by the lens holder and are engaged with an outer peripheral portion of the lens group, of a first portion and a second portion of the lens group where the lens group is divided as to the two portions by a plane perpendicular to a shift direction in which the image forming panel is shifted from the optical axis and including the optical axis, the plurality of holding pieces including one or more holding pieces engaged with the first portion, which is positioned on a side to which the image forming panel is shifted, and one or more holding pieces engaged with the second portion that is positioned on a side opposite to the side to which the image forming panel is shifted. A linear expansion coefficient of a first material, which forms the holding pieces engaged with the first portion, is lower than a linear expansion coefficient of a second material that forms the holding pieces engaged with the second portion.

Further, a projector according to an aspect of the invention comprises the projection lens unit, an image forming panel that is disposed such that a center of the image forming panel deviates from an optical axis of the projection lens unit, and a light source that applies light to the image forming panel.

In a case in which the invention is used, it is possible to provide a projection lens unit and a projector that can suppress the deterioration of an image caused by a deviation in the temperature of a lens barrel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows the structure of an example of a projector illustrating an embodiment of the invention.

In the projector10shown inFIG. 1, a light source13, an image forming panel14, a projection lens unit15, and a control unit17are received in a case11. A zoom dial21, a light quantity adjustment dial22, a focus dial23, a vertical attitude adjustment dial24, a horizontal attitude adjustment dial25, and an image correction dial26are provided on the upper surface of the case11.

A transmission type liquid crystal panel is used as the image forming panel14. The light source13is disposed on the back surface of the image forming panel14, that is, on the side of the image forming panel14opposite to the projection lens unit15. An image is given to light, which is emitted from the light source13, on an image forming surface14aof the image forming panel14, and the light to which the image is given is projected onto the projection surface through the projection lens unit15as image light.

The control unit17allows a red-green-blue (RGB) color image to be displayed on the image forming surface14aof the image forming panel14. In addition, the control unit17also performs the following control. For example, in a case in which the control unit17receives an operation signal of the zoom dial21, the control unit17adjusts the size of the image to be projected onto a screen20. In a case in which the control unit17receives an operation signal of the light quantity adjustment dial22, the control unit17adjusts the brightness of the image to be projected onto the screen20. In a case in which the control unit17receives an operation signal of the focus dial23, the control unit17allows a focus adjustment mechanism (not shown) of the projection lens unit15to operate to adjust the focus of a central portion of the image projected onto the screen20. In a case in which the control unit17receives an operation signal of the vertical attitude adjustment dial24, the control unit17allows a first motor of an attitude adjustment device (not shown) to be driven. Accordingly, the control unit17allows the projection lens unit15to be rotated about a horizontal axis orthogonal to an optical axis CL to adjust the inclination of the projection lens unit15in an up-down direction. In a case in which the control unit17receives an operation signal of the horizontal attitude adjustment dial25, the control unit17allows a second motor of the attitude adjustment device to be driven. Accordingly, the control unit17allows the projection lens unit15to be rotated about a vertical axis orthogonal to the optical axis CL to adjust the inclination of the projection lens unit15in a lateral direction. In a case in which the control unit17receives an operation signal of the image correction dial26, the control unit17changes the display size and shape of an image to be formed on the image forming surface14aof the image forming panel14. For example, the control unit17changes the display size and shape of an image so that a rectangular image is not displayed as a trapezoidal image according to the inclination angle of the projection lens unit15.

FIG. 2shows the structure of the light source13.

The light source13includes a light emitting diode (LED)31R that emits red (R) light, a LED31G that emits green (G) light, and a LED31B that emits blue (B) light. Light emitted from the LED31R is reflected by a dichroic mirror32. Light emitted from the LED31G is reflected by a dichroic mirror33, and is transmitted through the dichroic mirror32. Light emitted from the LED31B is transmitted through the dichroic mirror32and the dichroic mirror33. Accordingly, three kinds of color light, that is, R light, G light, and B light are emitted to the same optical path. A xenon lamp, a halogen lamp, or a super high-pressure mercury lamp, which emits white light, may be used instead of the LED31R, the LED31Q and the LED31B of the light source13.

FIG. 3shows the structure of the projection lens unit15.

Light emitted from the projection lens unit15is projected onto the screen20, which is a projection surface, vertically above the optical axis CL of the projection lens unit15, as image light. The center of the image forming panel14is disposed so as to be shifted from the optical axis CL in a direction opposite to a direction where the central position of the image projected onto the screen20is shifted from the optical axis CL, that is, to the vertically lower side of the optical axis CL.

Here, the shift ratio of the image forming panel14will be described with reference toFIG. 4.

In a case in which a shift amount (distance) between the optical axis CL of the projection lens unit15and the center of the image forming panel14is denoted by Y and the length of the image forming panel14in a shift direction is denoted by H, the shift ratio S of the image forming panel14is defined by “S=Y/H”. That is, in the case of “S=0.5”, the upper end face of the image forming panel14coincides with the optical axis CL of the projection lens unit15as shown inFIG. 4. Further, in the case of “S>0.5 (S is larger than 0.5)”, the image forming panel14deviates from the optical axis CL of the projection lens unit15. Furthermore, in the case of “S=0”, the center of the image forming panel14and the optical axis CL of the projection lens unit15coincide with each other and the disposition of the image forming panel14and the projection lens unit15is close to a long-distance projection type in the related art.

It is preferable that the shift ratio S of the image forming panel14is set to exceed 0.4 and to be lower than 0.7. In a case in which the shift ratio S exceeds 0.4, the influence of temperature on the projection lens unit15in a vertical direction does not appear in comparison with a case in which the shift ratio S is 0.4 or less. On the other hand, in a case in which the shift ratio S is lower than 0.7, the shift amount Y of the image forming panel14is not excessively increased, an increase in the size of a lens system is suppressed, and the deterioration of manufacturing suitability is prevented in comparison with a case in which the shift ratio S is 0.7 or more. Accordingly, in a case in which the shift ratio S of the image forming panel14is set in the above-mentioned range, it is possible to provide a high-performance product while reducing the influence of temperature on the projection lens unit15in the vertical direction. It is more preferable that the shift ratio S of the image forming panel14is set to exceed 0.45 and to be lower than 0.6.

Referring toFIG. 3again, the projection lens unit15includes: six lens groups, that is, a first lens group L1, a second lens group L2, a third lens group L3, a fourth lens group L4, a fifth lens group L5, and a sixth lens group L6arranged in this order from the image forming panel14; an aperture stop49that adjusts the brightness (F-Number) of the projection lens unit15; and a lens barrel40that receives the first to sixth lens groups L1to L6and the aperture stop49. Each of the first to sixth lens groups L1to L6is formed of one or a plurality of lenses.

The structure of each of the first to sixth lens groups L1to L6is exemplary, and can be appropriately modified according to an optical design. Further, the aperture stop49is disposed between the second lens group L2and third lens group L3in an example shown inFIG. 3, but the disposition of the aperture stop49is also exemplary, and can be appropriately modified according to an optical design.

The lens barrel40includes a cylindrical lens barrel body41, a cam barrel42, a first lens holder43, a second lens holder44, a third lens holder45, a fourth lens holder46, a fifth lens holder47, and a sixth lens holder48.

The first to sixth lens holders43to48are disposed in the lens barrel body41, the first lens holder43holds the first lens group L1, the second lens holder44holds the second lens group L2, the third lens holder45holds the third lens group L3, the fourth lens holder46holds the fourth lens group L4, the fifth lens holder47holds the fifth lens group L5, and the sixth lens holder48holds the sixth lens group L6.

Further, the first lens holder43is fixed to an end portion of the lens barrel body41facing the image forming panel14, and the sixth lens holder48is fixed to an end portion of the lens barrel body41facing the screen20. Furthermore, the second to fifth lens holders44to47are adapted to be movable in the direction of the optical axis in the lens barrel body41, and are moved in the direction of the optical axis by the cam barrel42.

FIG. 5shows the structure of a mechanism for moving the second lens holder44.

A plurality of cam pins52are mounted on the outer periphery of the second lens holder44by mounting screws53. The cam pins52protrude outward from notches41athat are formed at the lens barrel body41in parallel with the optical axis CL, and are engaged with cam grooves42athat are formed at the cam barrel42so as to be inclined with respect to the optical axis CL. In a case in which the cam barrel42is rotated relative to the lens barrel body41, the second lens holder44is moved in the direction of the optical axis.

Since the third to fifth lens holders45to47also have the same structure as the second lens holder44, the third to fifth lens holders45to47are moved in the direction of the optical axis with the rotation of the cam barrel42. For example, an operation for adjusting a focus, an operation for changing magnification, or the like is performed in a case in which the second to fifth lens holders44to47are appropriately moved in the direction of the optical axis.

The lens barrel body41, the cam barrel42, and the first to sixth lens holders43to48are made of, for example, a synthetic resin, such as polycarbonate.

FIGS. 6 to 8show the structure of the first lens holder43.

The first lens holder43includes a holding piece55a, a holding piece55b, and a holding piece55cthat are engaged with the outer peripheral portion of the first lens group L1, and a substantially cylindrical frame portion56that supports these three holding pieces.

A plurality of fixing portions57, which are to be fixed to the lens barrel body41, are provided on the outer peripheral surface of the frame portion56. The fixing portions57are provided on the same circumference on the outer peripheral surface of the frame portion56, are arranged at substantially regular intervals in a circumferential direction, and are formed integrally with the frame portion56so as to protrude outward from the frame portion56.

The holding piece55a, the holding piece55b, and the holding piece55care provided on an inner edge portion of one end face of the frame portion56at substantially regular intervals in the circumferential direction, and are formed integrally with the frame portion56so as to protrude from the frame portion56along the optical axis CL of the projection lens unit15. The distal end portion of each of the holding piece55a, the holding piece55b, and the holding piece55care engaged with the outer peripheral portion of the first lens group L1at substantially regular intervals in the circumferential direction of the first lens group L1.

In a case in which the first lens group L1is divided into a first portion A1positioned on a side to which the image forming panel14is shifted (vertically lower side) and a second portion A2positioned on a side opposite to the side to which the image forming panel14is shifted (vertically upper side) by a plane B that is perpendicular to the shift direction where the image forming panel14is shifted from the optical axis CL of the projection lens unit15and includes the optical axis CL, as shown inFIG. 7, the holding pieces55aand55bare engaged with the first portion A1and the holding piece55cis engaged with the second portion A2. Further, the linear expansion coefficient of each of the holding pieces55aand55bto be engaged with the first portion A1is set to be lower than the linear expansion coefficient of the holding piece55cto be engaged with the second portion A2.

The above-mentioned first lens holder43can be produced, for example, as described below by multi-color molding using different resin materials. First, the holding piece55cand the frame portion56are primarily molded integrally with each other using a second resin material. Next, only a cavity mold of a core mold and a cavity mold used in the primary molding is exchanged, and the holding pieces55aand55bare secondarily molded integrally with the primarily molded body, which is formed of the holding piece55cand the frame portion56, using a first resin material of which the linear expansion coefficient is lower than the linear expansion coefficient of the second resin material. Accordingly, the first lens holder43, of which the holding pieces55a,55b, and55care integrated with the frame portion56and the linear expansion coefficient of each of the holding pieces55aand55bto be engaged with the first portion A1is lower than the linear expansion coefficient of the holding piece55cto be engaged with the second portion A2, is obtained.

Further, the first lens holder43can also be produced, for example, as described below by insert molding. First, the holding pieces55aand55bare produced in advance using the first resin material. Next, the holding pieces55aand55b, which have been produced in advance, are inserted into a mold for integrally molding the holding piece55cand the frame portion56, and the mold is filled with the second resin material to mold the holding piece55cand the frame portion56integrally with the holding pieces55aand55bin a state in which the holding pieces55aand55bare inserted into the mold. Accordingly, the first lens holder43, of which the holding pieces55a,55b, and55care integrated with the frame portion56and the linear expansion coefficient of each of the holding pieces55aand55bto be engaged with the first portion A1is lower than the linear expansion coefficient of the holding piece55cto be engaged with the second portion A2, is obtained.

In terms of increasing the joint strength between the holding pieces55aand55bmade of the first resin material and the frame portion56made of the second resin material, it is preferable that compatibility between the first and second resin materials is high in all of the multi-color molding and the insert molding. Accordingly, it is preferable that composite materials, which are obtained by adding fillers to a common resin base material and have different linear expansion coefficients according to the filler contents, are used as the first and second resin materials. The filler is an additive to be added to the resin base material. Particularly, in this specification, the filler means a material that adjusts the linear expansion coefficient of the resin base material according to the amount thereof to be added. For example, in a case in which polycarbonate is used as the resin base material and a glass fiber is used as the filler, the linear expansion coefficient of a simple substance of polycarbonate is 6.5×10−5/° C., the linear expansion coefficient of a composite material of which the content percentage of a glass fiber per unit weight is 20% is 2.5×10−5/° C., and the linear expansion coefficient of a composite material of which the content percentage of a glass fiber per unit weight is 40% is 1.9×10−5/° C.

Further, at least one of the holding pieces55aand55bor the holding piece55cmay be formed separately from the frame portion56, and the separately formed holding piece may adhere to the frame portion56or may be fitted to the frame portion56so as to be joined to the frame portion56. In this case, it is easy to manage the dimensions of each member. Furthermore, the structure of a mold can also be simplified in comparison with a case in which the holding pieces55aand55b, the holding piece55c, and the frame portion56are integrally molded. Moreover, since stable joint strength can be obtained between the frame portion56and the holding piece formed separately from the frame portion56regardless of compatibility between the material of the frame portion56and the material of the holding piece formed separately from the frame portion56, the holding piece formed separately from the frame portion56can be made of various materials, such as metal, instead of a resin.

Next, the meaning of making the linear expansion coefficient of each of the holding pieces55aand55bbe lower than the linear expansion coefficient of the holding piece55cwill be described with reference toFIG. 8.

Light, which is more than the light applied to the holding piece55cengaged with the second portion A2of the first lens group L1positioned on the side opposite to the side to which the image forming panel14is shifted, is applied to the holding pieces55aand55b, which are engaged with the first portion A1of the first lens group L1positioned on the side to which the image forming panel14is shifted, from the light source13. As a result, the temperature of each of the holding pieces55aand55bbecomes higher than the temperature of the holding piece55cdue to the turning-on of the light source13.

A rise in the temperature of each of the holding pieces55aand55band the holding piece55c, which is caused by the turning-on of the light source13, is also changed depending on the quantity of light, which is emitted from the light source13, per unit time, or the like. However, here, it is assumed that the temperature of each of the holding pieces55aand55brises up to 80° C. from the room temperature (25° C.) and the temperature of the holding piece55crises up to 40° C. from the room temperature.

Further, the diameter of the first lens group L1is set to 20 mm; a distance a between each fixing portion57of the frame portion56, which is fixed to the lens barrel body41, and the proximal end portion of each of the holding pieces55aand55band the holding piece55cin the direction of the optical axis is set to 5 mm; and a distance b between the proximal end portion of each of the holding pieces55aand55band the holding piece55cand a distal end portion of each holding piece, which is a portion of each holding piece engaged with the outer peripheral portion of the first lens group L1, in the direction of the optical axis is set to 30 mm.

First, in a case in which all of the holding pieces55aand55b, the holding piece55c, and the frame portion56are made of a simple substance of polycarbonate (linear expansion coefficient: 6.5×10−5/° C.) and the temperature of each of the holding pieces55aand55brises up to 80° C. from the room temperature (25° C.) due to the turning-on of the light source13, a change in a distance a+b between the fixing portion57and the distal end portion of each of the holding pieces55aand55bbecomes “(80° C.−25° C.)×6.5×10−5/° C.×35 mm≅12.5×10−2mm”. On the other hand, in a case in which the temperature of the holding piece55crises up to 40° C. from the room temperature due to the turning-on of the light source13, a change in the distance a+b between the fixing portion57and the distal end portion of the holding piece55cbecomes “(40° C.−25° C.)×6.5×10−5/° C.×35 mm≅4.6×10−2mm”. In this case, the inclination of the first lens group L1with respect to a plane perpendicular to the optical axis CL corresponds to 0.2°.

Next, in a case in which each of the holding pieces55aand55bis made of a composite material (linear expansion coefficient: 1.9×10−5/° C.) in which 40% of a glass fiber per unit weight is contained in polycarbonate, each of the holding piece55cand the frame portion56is made of a simple substance of polycarbonate (linear expansion coefficient 6.5×10−5/° C.), and the temperature of each of the holding pieces55aand55brises up to 80° C. from the room temperature (25° C.) due to the turning-on of the light source13, a change in the distance a+b between the fixing portion57and the distal end portion of each of the holding pieces55aand55bbecomes “(80° C.−25° C.)×6.5×10−5/° C.×5 mm+(80° C.−25° C.)×1.9×10−5/° C.×30 mm≅4.9×10−2mm”. On the other hand, in a case in which the temperature of the holding piece55crises up to 40° C. from the room temperature due to the turning-on of the light source13, a change in the distance a+b between the fixing portion57and the distal end portion of the holding piece55cbecomes “(40° C.−25° C.)×6.5×10−5/° C.×35 mm≅4.6×10−2mm”. In this case, the inclination of the first lens group L1with respect to a plane perpendicular to the optical axis CL corresponds to 0.0008°.

In a case in which the linear expansion coefficient of each of the holding pieces55aand55bto be engaged with the first portion A1of the first lens group L1, which is positioned on the side to which the image forming panel14is shifted, is set to be lower than the linear expansion coefficient of the holding piece55cto be engaged with the second portion A2of the first lens group L1that is positioned on the side opposite to the side to which the image forming panel14is shifted as described above, it is possible to suppress the inclination of the first lens group L1that is caused by the temperature distribution of the lens barrel40in the circumferential direction. Accordingly, it is possible to suppress the deterioration of an image.

The first lens holder43provided with three holding pieces, that is, the holding pieces55a,55b, and55chas been described so far, but the first lens holder43may include one or more holding pieces to be engaged with the first portion A1of the first lens group L1and one or more holding pieces to be engaged with the second portion A2of the first lens group L1.

FIGS. 9 and 10show the structure of a modification example of the first lens holder43, and the first lens holder43includes one holding piece55dto be engaged with the first portion A1of the first lens group L1and one holding piece55eto be engaged with the second portion A2of the first lens group L1. The linear expansion coefficient of the holding piece55dto be engaged with the first portion A1is set to be lower than the linear expansion coefficient of the holding piece55eto be engaged with the second portion A2.

The holding pieces55dand55ehave a structure in which a substantially cylindrical frame body coaxial with the optical axis CL of the projection lens unit15is formed on an inner edge portion of one end face of the frame portion56. Further, the holding pieces55dand55ehave a structure in which two slits58extending parallel to the optical axis CL are formed at portions of the frame body crossing a plane B dividing the first lens group L1into a first portion A1and a second portion A2and the frame body is divided from each other in the circumferential direction by the slits58.

In a case in which the linear expansion coefficient of the holding piece55dto be engaged with the first portion A1of the first lens group L1, which is positioned on the side to which the image forming panel14is shifted, is set to be lower than the linear expansion coefficient of the holding piece55eto be engaged with the second portion A2of the first lens group L1that is positioned on the side opposite to the side to which the image forming panel14is shifted, it is possible to suppress the inclination of the first lens group L1, which is caused by the temperature distribution of the lens barrel40in the circumferential direction, even in the first lens holder43of this modification example. Accordingly, it is possible to suppress the deterioration of an image.

Further, it is possible to produce the first lens holder43of this modification example by multi-color molding using different resin materials or insert molding as in the case of the first lens holder43shown inFIGS. 6 to 8, or it is also possible to produce the first lens holder43by forming at least one of the holding piece55dor the holding piece55eseparately from the frame portion56and joining the separately formed holding piece to the frame portion56. Since the holding pieces55dand55eare larger than the holding pieces55aand55band the holding piece55cof the first lens holder43shown inFIGS. 6 to 8, it is easy to produce the first lens holder43even though the first lens holder43is produced by any method of them.

A structure in which the linear expansion coefficient of the holding piece to be engaged with the first portion A1of the first lens group L1positioned on the side, to which the image forming panel14is shifted, among the plurality of holding pieces of the first lens holder43is set to be lower than the linear expansion coefficient of the holding piece to be engaged with the second portion A2of the first lens group L1positioned on the side opposite to the side, to which the image forming panel14is shifted, has been described above by using the first lens holder43, which is fixed to the end portion of the lens barrel body41facing the image forming panel14, among the first to sixth lens holders43to48, as an example. However, the above-mentioned structure of the first lens holder43can also be used for the other lens holders. Particularly, since the deviation of light applied from the light source13is relatively large in the second lens holder44disposed closer to the image forming panel14than the aperture stop49as in the first lens holder43, the above-mentioned structure of the first lens holder43can also be suitably used for the second lens holder44.

Further, the transmission type liquid crystal panel is used as the image forming panel14in the embodiment, but a reflection type liquid crystal panel or a digital micro mirror device (DMD) can also be used. In this case, the light of the light source13is applied to the front surface of the image forming panel from the front side of the image forming panel14through an illumination optical system using a known prism (not shown) and the like.

As described above, a projection lens unit disclosed in this specification projects light, which is applied to an image forming panel from a light source, onto a projection surface as image light and is disposed in a state in which an optical axis of the projection lens unit deviates from a center of the image forming panel. The projection lens unit of a projector includes a lens barrel that is provided with one or more lens groups and one or more lens holders holding the lens groups, respectively. At least one of the lens holders includes a plurality of holding pieces that are provided at intervals in a circumferential direction of the lens group held by the lens holder and are engaged with an outer peripheral portion of the lens group. Of a first portion and a second portion of the lens group where the lens group is divided as to the two portions by a plane perpendicular to a shift direction in which the image forming panel is shifted from the optical axis and including the optical axis, the plurality of holding pieces include one or more holding pieces engaged with the first portion, which is positioned on a side to which the image forming panel is shifted, and one or more holding pieces engaged with the second portion that is positioned on a side opposite to the side to which the image forming panel is shifted. A linear expansion coefficient of a first material, which forms the holding pieces engaged with the first portion, is lower than a linear expansion coefficient of a second material that forms the holding pieces engaged with the second portion.

Further, in the projection lens unit disclosed in this specification, the lens holder including the holding pieces further includes a frame portion that supports the holding pieces, the frame portion and the holding pieces are made of a resin material and are integrated with each other, and a first resin material as the first material, which forms the holding pieces engaged with the first portion, and a resin material, which forms the holding pieces engaged with the second portion, are formed of second resin materials as second materials having different linear expansion coefficients, respectively.

Furthermore, in the projection lens unit disclosed in this specification, the lens holder including the holding pieces further includes a frame portion that supports the holding pieces, and at least one of the holding pieces engaged with the first portion and the holding pieces engaged with the second portion is formed separately from the frame portion and is joined to the frame portion.

Moreover, in the projection lens unit disclosed in this specification, the first material which forms the holding pieces engaged with the first portion and the second material which forms the holding pieces engaged with the second portion are composite materials, which are obtained by adding fillers for adjusting linear expansion coefficients to a common resin base material, and content percentages of the fillers are different from each other.

The projection lens unit disclosed in this specification further includes an aperture stop, and the lens holder, which holds the lens group disposed closer to the image forming panel than the aperture stop, includes the holding pieces.

A projector disclosed in this specification includes an image forming panel that is disposed such that a center of the image forming panel deviates from an optical axis of the projection lens unit, and a light source that applies light to the image forming panel.

Further, in the projector disclosed in this specification, in a case in which a distance between the optical axis of the projection lens unit and a center of the image forming panel is denoted by Y, a length of the image forming panel in a shift direction where the image forming panel is shifted from the optical axis is denoted by H, and a shift ratio of the image forming panel obtained by dividing the length H into the distance Y is defined by “S=Y/H”, and “0.4<S<0.7” is satisfied.

EXPLANATION OF REFERENCES

13: light source

14: image forming panel

14a: image forming surface

15: projection lens unit

17: control unit

21: zoom dial

22: light amount adjustment dial

23: focus dial

24: vertical attitude adjustment dial

25: horizontal attitude adjustment dial

26: image correction dial

41: lens barrel body

43: first lens holder

44: second lens holder

45: third lens holder

46: fourth lens holder

47: fifth lens holder

48: sixth lens holder

49: aperture stop

52: cam pin

55a: holding piece

55b: holding piece

55c: holding piece

55d: holding piece

55e: holding piece

56: frame portion

A1: first portion

A2: second portion

CL: optical axis

L1: first lens group

L2: second lens group

L3: third lens group

L4: fourth lens group

L5: fifth lens group

L6: sixth lens group