HK1110945B - Projection lens and projector - Google Patents

Description

Projection lens for projector and projector

Technical Field

The present invention relates to a projector device for projecting an image based on image information such as a video signal, and more particularly to a projection-side optical system of a projector.

Background

In these days, video projectors, which are image projection apparatuses for projecting a screen of a personal computer, a video image, or the like on a screen, are widely used.

The projector incorporates a high-luminance light source, and light emitted from the light source is changed into red light, green light, and blue light by a light source side optical system using a red filter, a green filter, and a blue filter in order, the red light, the green light, and the blue light are condensed on a light modulation device such as a liquid crystal display element called a micromirror display element or a DMD (digital micromirror device) or the like through a lens or the like for constituting an illumination side optical system, and the light is directed toward a projection port of the projector by the light modulation device and a color image is displayed on a screen by the amount of transmitted or reflected light.

The micromirror display element controls the direction of reflected light by swinging the micromirror unit with a control signal, sets light reflected in the direction of a projection lens, which is a projection-side optical system, of light incident ON the display element through the illumination-side optical system to ON (ON) state light and light reflected in the direction of a light absorbing plate to OFF (OFF) state light, controls the time during which red, green, and blue light are in an ON state, and projects a color image ON a screen.

Further, there is proposed a technique of adjusting a white balance (white balance) of a projector by detecting off-state light not incident on the projection lens by an optical sensor using off-state light (for example, patent document 1).

The liquid crystal display element forms an image by blocking or transmitting light transmitted through the minute liquid crystal elements. In this liquid crystal display device, when the transmitted light is imaged on a screen by a projection lens, the following is proposed: in order to improve the contrast of an image, a diaphragm having a triangular opening is provided on a projection lens (for example, patent document 2).

Patent document 1: japanese patent laid-open No. 2001 and 188196

Patent document 2: japanese patent laid-open publication No. 2004-157346

However, when the aperture of the illumination-side optical system or the like is increased in order to realize high luminance in the projector, as the aperture of the illumination-side optical system increases, the aperture of each of the light beams increases, the on-state light beam, which is a light beam in an on state, or the off-state light beam, which is a light beam in an off state on the incident side of the projection-side optical system, and the stray light beam, which is a light beam such as flat stray light that is reflected from a flat portion around the protective glass or the mirror unit of the display element, or the like.

Therefore, as the aperture of the projection side optical system increases, the chance of stray light entering the projection lens, which is the projection side optical system, and the amount of incident light increase, and thus there is a problem that the contrast of an image decreases due to the stray light and the like.

Disclosure of Invention

The present invention has been made to solve the above-described drawbacks, and an object thereof is to provide a projection lens for a projector capable of forming a bright and clear image on a screen, and to provide a projector capable of obtaining a clear image.

A projection lens for a projector according to a preferred embodiment of the present invention includes a movable diaphragm movable in an optical axis direction in accordance with movement of a movable lens group, and an opening of the movable diaphragm is circular around an optical axis of the projection lens, and the projection lens includes a projection portion projecting in a curved shape toward an inner side of the opening in a part of a periphery of the opening, and the projection portion projects toward the inner side of the opening of the movable diaphragm in a circular arc shape with a center of curvature of a stray light flux as a center of curvature.

Further, another preferred embodiment of the present invention is a projector including: the projection-side optical system includes a movable aperture that is movable in an optical axis direction as a movable lens group moves in the optical axis direction, and the movable aperture has a circular opening centered on an optical axis position of the projection-side optical system, and has a protruding portion protruding in a central direction of a stray light beam from a center of the opening in a peripheral edge portion in the central direction of the opening.

The present invention provides a projection lens for a projector capable of forming a bright and clear image on a screen, and a projector capable of obtaining a clear image.

Drawings

Fig. 1 is an external view of a projector of the present invention;

fig. 2 is an internal structural view of the projector of the present invention;

fig. 3 is a schematic view of a projection side optical system of the projector of the present invention;

FIG. 4 is a schematic illustration of on-state and off-state light beams and stray light beams in a projector;

fig. 5A is a schematic diagram of the relationship between the on-state light beam and the projection-side optical system in the projector;

fig. 5B is a schematic diagram of the relationship between the off-state light beam and the projection-side optical system in the projector;

fig. 5C is a schematic diagram of the relationship between stray light in the projector and the projection side optical system;

fig. 6 is a diagram of a movable diaphragm used in the projector of the present invention;

fig. 7 is a schematic view of a stray light blocking state by the movable diaphragm in the projector of the present invention;

fig. 8 is a schematic view of an example in which the aperture of the movable diaphragm is increased in the projector of the present invention;

FIG. 9 is a schematic view of the projector showing other positional relationships between the ON-state and OFF-state light beams and stray light beams and the optical axis of the projection lens;

fig. 10 is a schematic diagram of a stray light beam state of a projection side optical system of the projector of the present invention in a wide-angle end state;

fig. 11 is a schematic diagram of a beam state at the most dense position of the stray light beam in the projector of the present invention.

Fig. 12 is a schematic diagram of a beam state of a lens surface position in the projector of the present invention;

fig. 13 is a schematic diagram of a change in beam state of a lens surface position in the projector of the present invention;

fig. 14 is a diagram of the change in the light speed state in the vicinity of the position where the stray light beam is most intense in the projector of the present invention;

fig. 15 is a schematic view of a state of stray light beams when the projection side optical system is at the intermediate position in the projector of the present invention;

fig. 16 is a schematic view of a state of stray light beams in a telephoto end state of the projection side optical system in the projector of the present invention;

fig. 17 is a sectional view of a main portion of an example of a movable diaphragm mounted state in the projector according to the present invention.

Fig. 18 is an exploded perspective view of a main part of a movable lens group in the projector of the present invention.

Detailed Description

A projector according to a preferred embodiment of the present invention incorporates a microcomputer that controls a micromirror display element 51 and the like based on an input video signal and the like, and includes: a light source device 41; a light source side optical system including a color wheel (not shown), a light guide rod 45, and the like; an illumination-side optical system including an illumination lens 46, a mirror 47, or the like; a micromirror display element 51 including a condenser lens 55 and a cover glass 53 for making light incident on the display element 51 from the illumination side optical system into parallel beams; and a projection lens 60 as a projection side optical system, the projection lens 60 being a lens group including a zoom lens for projecting an image on a screen or the like by an on-state light flux from the display element 51, and having an iris 70.

Therefore, the movable diaphragm 70 of the projection lens 60 having the zooming function is provided in a space between the lens groups, is movable in the direction of the optical axis 69 together with the movable lens group movement in a manner consistent with the zooming state of the projection lens 60, and has: an annular portion 71 formed with a circular opening 75 centered on the optical axis 69 of the projection lens 60; the portion of the on-state light flux P passing through the opening 75 on the stray light beam R side is blocked by the protruding portion 73 together with the stray light by the circular protruding portion 73 protruding (swellen) from the annular portion 71, which is the peripheral edge of the circular opening 75 in the center direction of the stray light beam R, toward the opening 75.

A projector 10 according to the present invention incorporates a microcomputer as a projector control device, and as shown in fig. 1, a projection port 13 with a lens cover 11 is provided on the front surface of a substantially rectangular parallelepiped housing, keys and indicators such as a power key 21 or an automatic image quality adjustment key 23, a manual image quality adjustment key 25, a power indicator lamp 31, a light source indicator lamp 33, and an overheat indicator 35 are provided on the upper surface of the housing, and a power connector and a USB terminal connected to a personal computer, a video terminal for inputting an image signal, and various signal input terminals such as a small D-sub terminal are provided on the rear surface not shown in the figure.

The opening/closing cover 27 on the upper surface has sub-buttons for fine adjustment of image quality and image and setting of various operation operations of the projector 10, and the side surface of the housing has an intake/exhaust port 29 for a cooling fan.

As shown in fig. 2, the projector 10 includes: a light source device 41 incorporating an ultra-high pressure mercury lamp or the like; and a color wheel or light guide rod 45 as a light source side optical system; and a plurality of illumination lenses 46 and a reflecting mirror 47 as an illumination-side optical system.

Further, the projector 10 incorporates: a microcomputer that is a projector control device that controls lamp lighting of the light source device 41 or the display element 51 based on an image signal; and a circuit board 37 having a power supply circuit for supplying power to the light source device 41, the projector control device, the cooling fan 39, and the like.

The color wheel is a circular disk in which fan-shaped red, green and blue filters are arranged in a circular shape, and light emitted from the light source device 41 by rotating the color wheel by the wheel motor 44 is transmitted through the respective filters arranged in the circular shape, whereby white light emitted from the light source device 41 is made into three primary colors of red, green and blue in sequence.

The light guide rod 45 makes the intensity distribution of the light transmitted through the color wheel uniform and then enters the illumination lens 46 of the illumination side optical system, and the illumination lens 46 focuses the light transmitted through the light guide rod 45 on the display element 51.

Therefore, when the mirror unit of the display element 51 is tilted in one direction, the mirror 47 irradiates the display element 51 with light transmitted through the illumination lens 46 from the tilted direction so that the reflected light from the display element 51 is directed in the front direction of the display element 51.

The reflecting mirror 47 irradiates the display element 51 with the reflected light from the reflecting mirror 47 in a direction in which the difference in the optical axis angle between the on-state light flux P reflected in the front direction of the display element 51 and the off-state light flux Q reflected by the display element 51 when the mirror unit is tilted in the other direction is extremely large.

The display element 51 is a rectangular DMD (micromirror device) having a length and a width of a dozen or so micrometers, and fifty to several hundred thousand mirror units are arranged in a lattice shape, and each mirror unit is disposed so as to be inclined at an angle of ten to several tens of degrees respectively from a planar position to one direction or the other.

In addition, in front of the display element 51, there are provided: a protective glass 53 for protecting the display element 51; and a condenser lens 55 for converting the light reflected by the reflecting mirror 47 of the illumination side optical system into a parallel beam to be irradiated to the display element 51.

As shown in fig. 3, the on-state light flux P reflected in the front direction by the display element 51 enters a projection lens 60 provided in front of the display element 51 as a projection-side optical system, the projection lens 60 is formed as a variable focus lens composed of a fixed lens group 61, a first movable lens group 63, and a second movable lens group 65, and the projection-side optical system composed of the zoom lens is provided with a movable stop 70 at a spatial position in front of or behind the movable lens group 63, so that adjustment of the zoom magnification and focus of the projection image on the screen are possible.

Therefore, as shown in fig. 4, an on-state light flux P centered on the optical axis 69 of the projection lens 60, which is a projection-side optical system, is formed at the position of the movable diaphragm 70, and a stray light flux R composed of flat stray light reflected by the plane of the protective glass 53 and the display element 51 is theoretically formed so as to approach the on-state light flux P, and an off-state light flux Q is formed in a direction opposite to the on-state light flux P so as to approach the stray light flux R.

That is, when light incident on the display element 51 from the mirror 47 is reflected by the display element 51, as shown in fig. 5A, the on-state light beam P enters the projection lens 60 as a projection-side optical system in parallel with or intersecting at a small angle with the projection-side optical system optical axis 69, and as shown in fig. 5B, the off-state light beam Q is reflected by the display element 51 in a direction not entering the projection lens 60.

Therefore, a stray light beam R such as a small amount of light reflected by a surface perpendicular to the optical axis of the projection lens 60, such as the protective glass 53 of the display element 51, the periphery of the mirror unit of the DMD, or the like, or light reflected by a plane other than the mirror unit on the surface of the display element 51 is reflected in the intermediate direction between the on-state light beam P and the off-state light beam Q, and the arrangement of the display element 51 and the projection-side optical system, the incident angle of the light from the mirror 47 of the light source-side optical system to the display element 51, and the like are usually set so that most of the stray light does not enter the projection-side optical system, and as shown in fig. 5C, a part of the stray light enters the projection lens 60 from the entrance side of the projection-side optical system and then exits the projection lens 60 to the screen, thereby deteriorating the projected image.

For this reason, the position and shape of the movable diaphragm 70 and the arrangement of the projection side optical system are determined in such a manner that stray light incident from the incident side of the projection side optical system is absorbed by the lens barrel inner wall and blocked by the movable diaphragm 70, thereby not passing through the projection lens 60.

Further, the center of the on-state light beam P, the center of the off-state light beam Q, and the center of the stray light beam R are theoretically a straight line.

As described above, in the on state, the light beam P and the stray light beam R approach each other, and a part of the stray light beam R is absorbed by the inner wall of the lens barrel and blocked by the movable diaphragm 70, and the distance between the projection lens 60 and the condenser lens 55 is reduced, whereby the projector 10 is downsized, as shown in fig. 6, the movable diaphragm 70 has a circular outer shape, and an annular portion 71 having a circular opening 75 with an inner radius R, and a part of the opening 75 has one protruding portion 73 protruding inward from the annular portion 71.

As shown in fig. 7, the movable diaphragm 70 is incorporated in the projection-side optical system so that the center of the opening 75 coincides with the optical axis 69 of the projection lens 60, and the projection portion 73 projects in an arc shape toward the inside of the opening 75 and has a circular arc shape with a radius t, the center of the circular arc being the center of the stray light beam R with the same radius R as the on-state light beam P which comes into contact with the on-state light beam P.

In this way, since the outer edge of the on-state light flux P and the outer edge of the stray light flux R are in a theoretically tangential (tangent) state and the projection portion 73 is provided in a part of the circular opening 75 with the position deviated from the optical axis 69 of the projection lens 60 by 2 times the radius R of the two light fluxes as the center of curvature of the arc-shaped projection portion 73, even when the diffusion region S occurs around the range of the theoretical stray light flux R adjacent to the theoretical on-state light flux P, the stray light diffused in the diffusion region S is blocked by the projection portion 73, and a clear image can be formed.

Further, since the protruding portion 73 can block stray light close to the on-state light flux P, as shown in fig. 8, the diameter of the opening 75 is increased to increase the entire light amount of the on-state light flux transmitted through the movable diaphragm 70, and a bright projection image can be formed.

That is, the radius of the opening 75 where the outer edge of the on-state light flux P and the outer edge of the stray light flux R overlap is determined by the normal direction of the display element 51, the reflection angle of the on-state light flux P reflected by the display element 51, the reflection angle of the off-state light flux Q reflected by the display element 51, the distance from the display element 51 to the movable stop 70, the F number of the fixed lens group 61, and the like, whereby the opening radius of the projection lens 60 is increased, and the arc-shaped protruding portion 73 protruding from the annular portion 71 toward the opening 75 is formed in the center direction of the off-state light flux Q, whereby the stray light of the theoretical stray light flux R and the diffusion region S thereof is blocked, and a bright and clear projection image is formed.

Further, not only when the optical axis 69 of the projection lens 60, which is the projection-side optical system, coincides with the center of the on-state light flux P as shown in fig. 4 and 7, but also when the optical axis 69 of the projection lens 60 of the projector is moved in parallel and the projector 10 is shifted from the center of the on-state light flux P to the optical axis 69 in order to prevent interference with the on-state light flux by the mirror 47 of the illumination-side optical system, as shown in fig. 9, the amount of incidence of the on-state light flux on the projection-side optical system can be prevented from decreasing by increasing the opening T of the projection lens 60.

Even in this case, in theory, stray light can be effectively blocked by the movable stop 70 having the projection 73 formed at the y position of the peripheral edge of the projection lens 60, which is located at the center of the on-state light flux P, the center of the stray light flux R, and the center of the off-state light flux Q, which are theoretically aligned, from the optical axis 69.

Therefore, the position determination (positioning) when the movable stop 70 is disposed in the space between the lens groups is performed by calculating the position where stray light is most intense by computer simulation because the optical paths of the on-state light flux and the stray light flux are different due to the combination of the single lens or the like constituting the projection lens 60 having the zoom function of the projection-side optical system.

As shown in fig. 10, in the case of a zoom lens of, for example, a 4-group movable type, a position V at which the area of the stray light beam R is most densely packed in a space between lens groups and a lens group from the front first lens group 101 to the fourth lens group 104 is found by the simulation.

All of the first lens group 101, the second lens group 102, the third lens group 103, and the fourth lens group 104 shown in fig. 10 are movable lens groups, and the lens group positions shown in fig. 10 are positions indicating a state in which the projection lens 60 is at the wide-angle end.

Then, the shape of the stray light beam R at the closest position V is obtained by simulation, and as shown in fig. 11, the shape of the protruding portion 73 covering the region RW of the stray light beam R is determined so that the stray light beam R can be blocked.

In the single lens surface positions constituting the first lens group 101 to the fourth lens group 104 for forming the projection lens 60, the stray light beam R is formed in the area RW where the stray light beam R is most intense on the surface position of the second lens group 102, as shown in fig. 12. Therefore, when the projection 73 for blocking the stray light beam R is formed, the projection 73 attenuates the on-state light beam PW at the wide-angle end by 3.4%.

When the projection 73 is formed to shield the stray light beam by setting the movable stop having the projection 73 at the most dense position V shown in fig. 11, the projection 73 reduces the attenuation of the on-state light beam PW in the on state at the wide-angle end by 2.4%, as opposed to the lens surface position of the second lens group 102 blocking the stray light beam.

Therefore, when the zoom ratio of the projection lens 60 generated by the first lens group 101 to the fourth lens group 104 is sequentially changed from the wide-angle end state to the telephoto end state, the field of the on-state light flux P is changed and the field of the stray light flux R is also changed, and the field of the stray light flux R at the front surface position of the second lens group 102 appears only at the edge of the lens surface when the projection lens 60 is in the telephoto end state.

That is, as shown in fig. 13, the region RT of the stray light beam R in the telephoto end state is very small, and the region RM of the stray light beam R in the intermediate position state is larger than the region RT in the telephoto end state and smaller than the region RW in the wide-angle end state shown in fig. 12.

Therefore, at this time, as shown in fig. 13, the on-state light beam P also changes from the on-state light beam region PW at the wide-angle end to the on-state light beam region PM in the intermediate state and the on-state light beam region PT in the telephoto end state.

Therefore, in the space between the first lens group 101 located forward of the most dense position V and the second lens group 102 located rearward of the most dense position V, as the projection lens 60 changes from the wide-angle end state to the telephoto end state, the region of the on-state light flux P also changes from the on-state light flux region PW in the wide-angle end state to the region PM in the intermediate state and the region PT in the telephoto end state.

Therefore, when the area of the on-state light flux P in the space between the first lens group 101 and the second lens group 102 changes and the projecting portion 73 blocks the stray light flux R as shown in fig. 14, the projecting portion 73 projects into the position where the area ratio is the smallest in each of the areas PW, PM, and PT of the on-state light flux P sequentially changing from the wide-angle end state to the intermediate state and the telephoto end state.

As a result, the position of the movable stop 70 is set at a position directly in front of the second lens group 102, as in the stop position in the intermediate state shown in fig. 15 and the stop position in the telephoto end state shown in fig. 16, whereby the amount by which the on-state light flux P is blocked by the protruding portion 73 can be reduced in the intermediate state or the telephoto end state of the projection lens 60.

Therefore, when the projection 73 is formed at the front surface position of the second lens group 102 shown in fig. 12, the attenuation ratio of the on-state light flux P is 3.6% when the on-state light flux P is blocked by the projection 73 in the telephoto end state, whereas the attenuation ratio of the on-state light flux is 3.1% when the movable stop 70 is positioned slightly in front of the second lens group 102, and the blocking ratio can be reduced.

Therefore, as shown in fig. 17, the movable diaphragm 70 is slidably fitted and attached to the first barrel 171 for fixedly supporting the first lens group 101 via the elastic body 175 in a compressed state at an end of the diaphragm support cylinder 190, and the movable diaphragm 70 having the protruding portion 73 is fixed in the vicinity of the other end of the diaphragm support cylinder 190.

As shown in fig. 18, the first barrel 171 having the first lens group 101 fixed therein or the second barrel 181 having the second lens group 102 fixed therein has protruding pins (cam pin)173 and 183 on the outer circumference thereof, and the first barrel 171 and the second barrel 181 are mounted in the holding cylinder 151.

The holding cylinder 151 has a linear front slide groove 153 in the axial direction thereof in the vicinity of the front end thereof, and a linear rear slide groove 155 in the axial direction thereof in the vicinity of the rear end thereof, the first barrel 171 is slidably accommodated in the holding cylinder 151 in the axial direction, and the front end of the first boss pin 173 of the first barrel 171 protrudes from the front slide groove 153, and similarly, the second barrel 181 is slidably accommodated in the holding cylinder 151 in the axial direction, and the front end of the second boss pin 183 of the second barrel 181 protrudes into the rear slide groove 155.

The holding cylinder 151 is fixed inside the projector with its front end supported by the front fixed cylinder 157 and its rear end supported by the rear fixed cylinder 158, and the cam cylinder 161 is held by the front fixed cylinder 157 and the rear fixed cylinder 158 in a rotatable manner while its axial movement is restricted by the front fixed cylinder 157 and the rear fixed cylinder 158, so that the holding cylinder 151 is stored inside the cam cylinder 161.

Therefore, the cam cylinder 161 is designed with a rotation tooth 167 at its outer periphery, and has a front cam groove 163 for insertion of the first boss pin 173 and a rear cam groove 165 for insertion of the second boss pin 183, and when the cam cylinder 161 is rotated by the rotation tooth 167, the first boss pin 173 and the second boss pin 183 can be moved in the axial direction, thereby moving the first barrel 171 and the second barrel 181 in the direction of the optical axis 69.

Similarly, the third lens group 103 and the fourth lens group 104 are fixed in a barrel having a boss pin, respectively, the barrel for holding the third lens group 103 and the barrel for holding the fourth lens group 104 are slidably mounted in a holding cylinder, and the third lens group 103 and the fourth lens group 104 are also rotated in the optical axis direction by rotating a cam cylinder having a cam groove.

In this way, since the stop support cylinder 190 is held by the first barrel 171 via the elastic body 175 in the compressed state, as shown in fig. 10, in the wide-angle end state in which the distance between the lenses of the first lens group 101 and the fourth lens group 104 is increased, the movable stop 70 can be positioned at the position V where the stray light flux R is most intense in the state of being separated from the first lens group 101 and the second lens group 102, and as shown in fig. 15, in the intermediate state in which the distance between the first lens group 101 and the second lens group 102 is decreased, the movable stop 70 can be positioned at the position in the vicinity of the front of the second lens group 102.

Therefore, in the telephoto end state of the projection lens 60 in which the interval between the first lens group 101 and the second lens group 102 becomes smaller as shown in fig. 16, the diaphragm support cylinder 190 comes into contact with the second barrel 181 and compresses the elastic body 175, whereby the interval between the movable diaphragm 70 and the first lens group 101 becomes smaller in a state of being close to the second lens group 102.

In this way, the movable diaphragm 70 having the protruding portion 73 can be moved so as to decrease the blocking ratio of the on-state light flux P with the movement of the movable lens group.

Therefore, the projection 73 is formed in an arc shape having the center of curvature of the stray light beam R as the center, and thus stray light entering the projection-side optical system from the incident side of the projection-side optical system can be effectively blocked, and a desired on-state light beam can be prevented from being blocked as much as possible.

Further, when the diameter of the opening 75 is constant and the stray light is blocked by the projection 73, the stray light beam R can be brought close to the position of the optical axis 69 of the projection lens 60, and it is possible to maintain a clear image and to facilitate downsizing of the projector 10.

Further, the diaphragm support cylinder 190 for fixing the movable diaphragm 70 is not limited to the case where it is supported by the first barrel 171 via the elastic body 175, and the diaphragm support cylinder 190 may be slidably housed in the holding cylinder 151, and a boss pin for penetrating the holding cylinder 151 may be provided on the diaphragm support cylinder 190, a cam groove for moving the movable diaphragm may be formed in the cam cylinder 161, and the cam cylinder 161 may be moved in the direction of the optical axis 69 together with the first barrel 171 and the second barrel 181 by the rotation of the cam cylinder 161.

The projection lens 60 shown in fig. 10 to 16 is a zoom lens in which all of 4 groups are movable, the configuration of the lens group is not limited to 4 groups, the projection lens 60 may be configured by more lens groups, and the projection lens 60 may be configured to have different zoom forms as follows: a mode in which only the plurality of rear lens groups are formed as movable lens groups, a mode in which only the plurality of front lens groups are formed as movable lens groups, a so-called internal zoom mode in which only the plurality of intermediate lens groups are formed as movable lens groups, or the like.

Therefore, in these projection lenses 60, the most dense position V in the zoom state where the most stray light passes through the projection lens 60 is obtained by simulation, and the size, shape, and the like of the region of the stray light beam R in the most dense position V are obtained by simulation.

That is, the movable diaphragm 70 and the diaphragm support cylinder 190 are not limited to the case of being provided between the first lens group 101 and the second lens group 102, and the movable diaphragm 70 having the protruding portion 73 is provided movably at a spatial position between the lens group and the lens group where stray light is most intense and a field shape thereof are determined by simulation in accordance with a lens structure of the zoom lens constituting the projection lens 60.

Further, the present invention is not limited to the above-described respective embodiments, and changes and modifications are possible freely without departing from the scope of the inventive concept.

Claims (14)

1. A projection lens for a projector, comprising a movable diaphragm movable in an optical axis direction in accordance with the movement of a movable lens group, wherein an opening of the movable diaphragm is a circle centered on the optical axis of the projection lens, a protrusion protruding in a curved shape toward the inside of the opening is provided at a part of the periphery of the opening,

the projection is formed in an arc shape with the center of the stray light beam as the center of curvature, and projects inward of the opening of the movable diaphragm.

2. The projection lens for a projector as claimed in claim 1,

the movable stop having the protruding portion is provided in a space between the lens group and the lens group, and a distance between a lens in front of the movable stop and a lens behind the movable stop can be changed.

3. The projection lens for a projector as claimed in claim 1,

the movable diaphragm is fixed to a diaphragm support cylinder, and the diaphragm support cylinder is supported by a movable lens barrel to which a movable lens group is fixed, via an elastic member.

4. The projection lens for a projector as claimed in claim 1,

the above-mentioned movable diaphragm is fixed to a diaphragm support cylinder which is independent of the movable barrel to which the movable lens group is fixed.

5. The projection lens for a projector as claimed in claim 2,

the movable diaphragm is fixed to a diaphragm support cylinder, and the diaphragm support cylinder is supported by a movable lens barrel to which a movable lens group is fixed, via an elastic member.

6. The projection lens for a projector as claimed in claim 2,

the above-mentioned movable diaphragm is fixed to a diaphragm support cylinder which is independent of the movable barrel to which the movable lens group is fixed.

7. The projection lens for a projector according to any one of claims 1 to 6,

the projection lens is a projection lens for a projector using a micromirror display element as a display element, and the projection portion projects toward the opening from a peripheral edge portion in a beam center direction of stray light with respect to an optical axis position of the lens.

8. A projector, having: a light source device, a light source side optical system and an illumination side optical system, a micromirror display element, a projection side optical system having a zoom lens function, and a power supply circuit and a projector control device,

the projection side optical system has a movable diaphragm movable in the optical axis direction in accordance with the movement of the movable lens group in the optical axis direction,

the movable aperture has a circular opening centered on the optical axis position of the projection-side optical system, and has a protruding portion protruding in the central direction of the opening at a peripheral edge portion located in the central direction of the stray light beam away from the center of the opening,

the projection is formed in an arc shape with the center of the stray light beam as the center of curvature, and projects inward of the opening of the movable diaphragm.

9. The projector as claimed in claim 8,

the movable stop having the protruding portion is provided in a space between the lens group and the lens group, and a distance between a lens in front of the movable stop and a lens behind the movable stop can be changed.

10. The projector as claimed in claim 8,

the movable diaphragm is fixed to a diaphragm support cylinder, and the diaphragm support cylinder is supported by a movable lens barrel to which a movable lens group is fixed, via an elastic member.

11. The projector as claimed in claim 8,

the above-mentioned movable diaphragm is fixed to a diaphragm support cylinder which is independent of the movable barrel to which the movable lens group is fixed.

12. The projector as claimed in claim 9,

the movable diaphragm is fixed to a diaphragm support cylinder, and the diaphragm support cylinder is supported by a movable lens barrel to which a movable lens group is fixed, via an elastic member.

13. The projector as claimed in claim 9,

the above-mentioned movable diaphragm is fixed to a diaphragm support cylinder which is independent of the movable barrel to which the movable lens group is fixed.

14. The projector according to any one of claims 8 to 13,

the projector uses a digital micromirror device as the micromirror display element, and the projection portion projects from the peripheral edge portion toward the opening portion in an arc shape.