Projector

A projector includes a light source; an optical modulator; a projection lens, which has a lens barrel containing plural lenses, for projecting the optical image; as well as a structure showing a substantially L-shaped lateral contour and including an inner horizontal section, to which the optical modulator is attached, and an outer vertical section, to which the projection lens is attached; and a lens shifting mechanism for shifting the projection lens along the outer vertical section. The lens barrel has a flange projecting to the outside of the lens barrel at the base end side of the projection direction so that the lens barrel is fitted to the outer vertical section. The outer vertical section has a lens contacting surface projected and curved in accordance with curvature amount of the image forming surface on the base end side of the projection lens so as to contact the flange.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projector having a light source, an optical modulator for modulating light beam emitted from the light source according to image information and forming an optical image, and a projection lens, which has a plurality of lenses and a lens barrel for containing the plurality of lenses thereinside, for enlarging and projecting the optical image formed by the optical modulator.

2. Description of Related Art

Projectors have been and being popularly used for the purpose of presentation in conferences, academic meetings, exhibitions and so on and also for the purpose of enjoying movies or the like at home. Such projectors include a light source, an optical modulator for modulating light beam emitted from the light source according to image information and forming an optical image and a projection lens for enlarging and projecting the optical image formed by the optical modulator.

While it is ideal for such projectors to project an optical image in a direction perpendicular to the plane of projection such as a screen, they are often made to project an optical image obliquely onto the plane of projection from above or from below in actual applications. Then, there arises a problem of trapezoidal distortion that the projected image is distorted to show an upwardly or downwardly expanding trapezoidal contour. When a trapezoidal distortion occurs, the projected image goes out of focus and becomes blurred partially either in an upper area or in a lower area thereof because the image forming position of the projected image shows a positional discrepancy between the upper area and the lower area.

Projectors adapted to vertically shift the projection lens have been proposed to cope with this problem (see, for example, Japanese Patent Laid-Open Publication No. 2003-315648). Such projectors can dissolve the problem of projecting a partially burred image by vertically translating the projection lens and adjusting image forming position of the projected image relative to the plane of projection. As a result, it is possible to clearly project an optical image.

However, with the technique described in the above-cited patent document, the central axis of the light beam emitted from the optical modulator and entering the projection lens is moved away from the optical axis of the projection lens as the projection lens is translated vertically so that consequently the focal position of the projection lens can be moved out of the image forming region of the optical modulator. More specifically, the focal length of the projection lens that is employed for a projector tends to be decreased as the height of the projected image is increased. Thus, as the projection lens is translated vertically to increase the distance between the central axis of the light beam emitted from the optical modulator and the optical axis of the projection lens, it may be no longer possible to place the focal position of the projection lens in the image forming region of the optical modulator. Then, there arises a problem of degradation of the projected image due to the field curvature of the projection lens.

While it may be conceivable to use a projection lens that is free from field curvature, such a lens is costly and hence the cost of manufacturing a projector having such a projection lens will become prohibitive.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a projector at low cost that can correct the problem of projecting a partially blurred image and at the same time the problem of field curvature of the projection lens.

A projector according to an aspect of the present invention has a light source; an optical modulator for modulating light beam emitted from the light source according to image information and forming an optical image; and a projection lens, which includes a plurality of lenses and a lens barrel for containing the plurality of lenses thereinside, for enlarging and projecting the optical image formed by the optical modulator; the projector including a structure showing a substantially L-shaped lateral contour and including an inner horizontal section, to which the optical modulator is attached, and an outer vertical section, to which the projection lens is attached, each of both sections having an L-shaped lateral contour; and a lens shifting mechanism for shifting the projection lens in a direction orthogonal to the central axis of the light beam emitted from the optical modulator along the outer vertical section; in which the lens barrel has a flange projecting to the outside of the lens barrel at the base end side of the projection direction so as for the lens barrel to be fitted to the outer vertical section; the outer vertical section has a lens contacting surface projected and curved in accordance with curvature amount of the image forming surface on the base end side of the projection lens so as to contact the flange along the shifting direction being shifted by the lens shifting mechanism; and the projection lens moves along the lens contacting surface as the projection lens is shifted by the lens shifting mechanism.

Preferably, in a moving range of the projection lens along the lens contacting surface, the difference of protruding amount of the lens contacting surface is between 0.01 and 0.1 mm from a flat part of the outer vertical section.

Thus, according to the present invention, since the lens contacting surface is curved in accordance with curvature amount of the image forming surface at the base end side of the projection lens, it is possible to place the focal point of the projection lens in the optical image forming region of the optical modulator even when the projection lens is shifted in a direction perpendicular to the central axis of the light beam emitted from the optical modulator. Thus, it is possible to correct the partial blur, if any, of the projected image and correct the curvature of image of the projection lens. Therefore, it is possible to prevent degradation of the projected image and project a clear image.

Additionally, since the lens contacting surface is curved to correct the curvature of image of the projection lens, it is possible to prevent degradation of the projected image and eliminate the need of employing a costly lens or the like hat is free from curvature of image for the projection lens. Therefore, it is possible to broaden the choice of lens for the projector and manufacture the projector at low cost.

Still additionally, in the moving range of the projection lens along the lens contacting surface, when the difference of protruding amount of the lens contacting surface is made between 0.01 and 0.1 mm from a flat part of the outer vertical section, it is possible to produce a curved profile that is satisfactory for correcting the curvature of image of the projection lens employed for the projector.

According to the present invention, preferably, the lens shifting mechanism is adapted to shift the projection lens in the tilting direction of the projector and also in a direction perpendicular to the tilting direction and the lens contacting surface has a curved profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge.

With this arrangement, it is possible to correct, by means of the lens shifting mechanism, the curvature of image of the projection lens not only when the projection lens is shifted in the tiling direction but also when the projection lens is shifted in a direction perpendicular to the tilting direction. Thus, it is possible to correct the curvature of image of the projection lens and prevent degradation of the projected image. Additionally, it is possible to project a clear image and improve the accuracy of the focal point of the projection lens.

In the case where the lens contacting surface has a curved profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge, when the projection lens is shifted to an end of the lens contacting surface, the angle of the optical axis of the projection lens is increased relative to the central axis of the light beam emitted from the optical modulator so that the projected image can be partially blurred to a large extent.

Therefore, it is preferred that the lens contacting surface has a first curved surface section and a second curved surface section being formed along the peripheral edge of the first curved surface section, the protruding amount of the second curved surface section being larger than that of the peripheral edge of the first curved surface section. By letting the lens contacting surface have such a profile, it is possible to make the optical axis of the projection lens run substantially in parallel with the central axis of the light beam emitted from the optical modulator even when the projection lens is shifted to an end of the lens contacting surface. Thus, it is possible to improve the accuracy of correcting the partial blur, if any, of the projected image and also the degree of freedom of the projection lens for projecting an optical image.

According to the present invention, preferably, the lens shifting mechanism is arranged with a gap between itself and the outer vertical section so as to make it correspond to the lens contacting surface and cover the outer vertical section, the flange of the lens barrel is placed in the gap; and a biasing member is arranged between the flange and the lens shifting mechanism so as to bias the flange toward the outer vertical section to force the flange to contact with the lens contacting surface.

With the above-described arrangement, where the lens shifting mechanism is arranged with a gap between itself and the outer vertical section of the structure and the flange of the projection lens is placed in the gap, while a biasing member is arranged to bias the projection lens toward the lens contacting surface, it is possible to make the flange of the projection lens reliably contact the lens contacting surface and hence the projection lens reliably shifts along the lens contacting surface. Additionally, with the above-described arrangement for supporting the projection lens and biasing it by the biasing member, the projection lens can be supported and biased to contact the lens contacting surface in a simple manner. Additionally, the sliding performance of the projection lens on the lens contacting surface can be improved by adjusting the biasing force of the biasing member.

According to the present invention, preferably, contact sections are formed at the end of the flange along the shifting directions so as to project from the surface opposed to the lens contacting surface of the flange and contact the lens contacting surface.

With this arrangement, the projection lens and the lens contacting surface contact with each other by way of the contact sections formed on the surface opposed to the lens contacting surface of the flange so that the sliding performance of the projection lens that is shifted along the lens contacting surface is further improved.

A projector according to another aspect of the present invention has a light source; an optical modulator for modulating a light beam emitted from the light source according to image information; a projection lens, which includes a plurality of lenses and a lens barrel for containing the plurality of lenses thereinside, for enlarging and projecting the optical image formed by the optical modulator; a lens shifting mechanism having an operating section for shifting the projection lens in a direction crossing the central axis of the light beam emitted from the optical modulator; and a curved surface which crosses the central axis of the light beam emitted from the optical modulator at one point, the curved surface having a profile which curves in accordance with curvature amount of an image forming surface on a base end side of the projection lens, and the projection lens sliding along the curved surface by operating the operating section.

Herein, the curved surface is preferably formed in a manner of being protruded from a flat surface perpendicular to the central axis of the light beam emitted from the optical modulator; and, in the moving range of the projection lens along the curved surface, the difference of protruding amount of the curved surface is preferably between 0.01 and 0.1 mm from the flat surface.

According to the present invention, since the projection lens slides along the curved surface which is curved in accordance with curvature amount of the image forming surface at the base end side of the projection lens, it is possible to place the focal point of the projection lens in the optical image forming region of the optical modulator even when the projection lens is shifted. Thus, it is possible to correct the partial blur, if any, of the projected image and correct the image curvature of the projection lens. Therefore, it is possible to prevent degradation of the projected image and project a clear image.

Further, since the curvature of image of the projection lens is corrected by providing the curved surface which crosses the central axis of the light beam emitted from the optical modulator at one point, it is not necessary to employ, for example, an expensive lens which has no image curvature for a projector to prevent degradation of the projected image. Thus, it is possible to widen the range for selecting a lens for a projector and to reduce the manufacturing cost.

Further, in the moving range of the projection lens along the curved surface, when the difference of protruding amount of the curved surface is made between 0.01 and 0.1 mm from the flat surface, it is sufficient to correct the curvature of image of the projection lens being used for a projector.

According to the present invention, the lens shifting mechanism preferably is adapted to shift the projection lens in the tilting direction of the projector and also in a direction perpendicular to the tilting direction; and the curved surface preferably has a profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge.

With this arrangement, it is possible to correct, by means of the lens shifting mechanism, the curvature of image of the projection lens not only when the projection lens is shifted in the tiling direction but also when the projection lens is shifted in a direction perpendicular to the tilting direction. Thus, it is possible to correct the curvature of image of the projection lens and prevent degradation of the projected image. Additionally, it is possible to project a clear image and improve the accuracy of the focal point of the projection lens.

According to the present invention, it is preferred that the projector further has a flange provided on the light incident side of the projection lens and protruding from the lens barrel toward the direction orthogonal to the optical axis of the projection lens; a perpendicular face perpendicular to the central axis of the light beam emitted from the optical modulator and included in the lens shifting mechanism, the flange being disposed between the perpendicular face of the lens shifting mechanism and the curved surface; and a contact section provided on a surface of the flange, the contact section protruding toward the curved surface side to contact the curved surface and sliding along the curved surface as the projection lens is shifted by the lens shifting mechanism.

With this arrangement, the projection lens, which shifts along the curved surface, can slide more smoothly.

In the case where the curved surface has a profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge, when the projection lens is shifted to an end of the curved surface, the angle of the optical axis of the projection lens is increased relative to the central axis of the light bean emitted from the optical modulator, so that the projected image can be partially blurred to a large extent. Therefore, it is preferred that the curved surface has a first curved surface section and a second curved surface section being formed along the peripheral edge of the first curved surface section, the protruding amount of the second curved surface being larger than that of the peripheral edge of the first curved surface section.

By letting the curved surface have such a profile, it is possible to make the optical axis of the projection lens run substantially in parallel with the central axis of the light beam emitted from the optical modulator when the projection lens is shifted to an end of the curved surface. Thus, it is possible to improve the accuracy of correcting the partial blur, if any, of the projected image and also the degree of freedom of the projection lens for projecting an optical image.

According to the present invention, it is preferred that the projector further has a biasing member arranged between the perpendicular face of the lens shifting mechanism and the flange so as to bias the flange toward the curved surface to bring the contact sections of the flange into contact with the curved surface.

With this arrangement, the flange of the projection lens can contact the curved surface securely, and thereby the shift of the projection lens along the curved surface can be performed securely. Further, since the projection lens is supported in the state of being biased by the biasing member, the structure for contacting the projection lens to the curved surface and for supporting the projection lens can be made simple. Furthermore, by adjusting the biasing force with the biasing member, the projection lens can slide along the curved surface more smoothly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. First Embodiment

Now, the first embodiment of the present invention will be described by referring to the related accompanying drawings.

(1) External Configuration

FIG. 1is a schematic perspective view of the first embodiment of a projector1according to the present invention as viewed from above and from the front side thereof.FIG. 2is a schematic perspective view of the projector1as viewed from below and from the front side thereofFIG. 3is a schematic perspective view of the projector1as viewed from above and from the rear side thereof.

The projector1is adapted to modulate a light beam emitted from a light source according to image information and enlarge and project an optical image onto a plane of projection such as a screen. As shown inFIGS. 1 through 3, the projector1has a substantially rectangularly parallelepipedic exterior case2and a projection lens3exposed to the outside through the exterior case2.

Of the above-listed components, the projection lens3has a function of operating as projection optical system for enlarging and projecting the optical image formed as a result of modulation by a later-described liquid crystal panels441(seeFIG. 5) that operate as an optical modulator. It is a combination of a plurality of lenses contained in a lens holding barrel3A, which is a lens barrel.

The exterior case2is a casing made of synthetic resin that shows a substantially rectangular plan view. It contains the main body of the projector1including an optical unit4, which will be described in detail hereinafter. The exterior case2includes an upper case21for covering the top surface of the projector main body, a lower case22for covering the bottom surface of the projector main body, a front case23for covering the front surface of the projector main body, a side case24for covering a part of a lateral side of the projector main body and a rear case25for covering the rear surface of the projector main body (seeFIG. 3).

Note that the corners of the top surface, the front surface, the lateral surfaces, the bottom surface and the rear surface are formed as curved surfaces.

The upper case21by turn includes a substantially rectangular top surface section21A for covering the top surface part of the projector main body, a lateral surface section21B suspended substantially vertically from the edge of one of the long sides of the top surface section21A, another lateral surface section21C suspended substantially vertically from the edge of the other long side of the top surface section21A and a rear surface section21D suspended from the edge of the rear side of the top surface section21A (seeFIG. 3).

As shown inFIGS. 1 and 3, a transversally extending operation panel26to be used for sing and adjusting operations of the projector1is arranged substantially at a middle part of the rear surface side of the top surface section21A. As one of the operation buttons261arranged on the operation panel26is depressed, it is brought into contact with the corresponding one of the tact switches mounted in a circuit board (not shown) that is arranged in the inside of the operation panel26so as to realize a desired operation. An LED (not shown) is fitted to the circuit board so as to emit light in response to a desired operation.

Additionally, the operation panel26is provided with a face plate262that is arranged to surround the operation buttons261so that light emitted from the LED is scattered through the face plate262.

Two dials311,321, which constitute an operating section of a projection lens position adjusting mechanism30as a lens shifting mechanism (seeFIG. 6), are exposed to the outside through the front surface side (the right side inFIG. 1) of the top surface section21A. The projection lens position adjusting mechanism30is adapted to adjust the position of the projection lens3by shifting the projection lens3in the tilting direction of the projector1(the directions of Y3and Y4inFIG. 1) and in the direction perpendicular to the tilting direction. As the left side dial311inFIG. 1of the two dials311,321is moved in Y1direction (downward), the projection lens3is moved in Y3direction (downward). On the other hand, as the dial311is moved in Y2direction (upward), the projection lens3is moved in Y4direction (upward).

As the right side dial321inFIG. 1is moved in X1direction (rightward as viewed from the rear side of the projector1), the projection lens3is moved in X3direction (rightward). On the other hand, as the dial321is moved in X2direction (leftward as viewed from the rear side of the projector1), the projector lens3is moved in X4direction (leftward).

Although not shown, a rib is arranged to surround the outer periphery of the projection lens3at the inner surface side of the top surface section21A.

The lateral surface section21C is provided with a notch21C1for exposing the louver71formed by combining a plurality of vanes711to the outside.

As shown inFIG. 3, the rear surface section21D is provided with a notch21D1to be engaged with the rear case25.

As shown inFIGS. 1 through 3, the lower case22includes a bottom surface section22A, two lateral surface sections22B,22C, a rear surface section22D and a front surface section22E.

The bottom surface section22A shows a substantially rectangular plan view, the bottom surface section22A is provided substantially at the middle of the rear side of the projector1with a fixed leg section22A1and at the opposite ends of the frontal long side thereof with respective adjustable legs27,27.

Each of the adjustable legs27,27has an axial member271(seeFIG. 4) that can be driven to retractably and outwardly project from the bottom surface section22A so that the inclination of the projector1can be adjusted vertically and transversally while it is being driven to project an image.

The bottom surface section22A is also provided with an aperture22A3that holds the outside and the inside of the exterior case2in communication relative to each other. The aperture22A3operates as air intake port for taking cooling air into the exterior case2from the outside of the exterior case2. A cover22A5provided with a plurality of openings is fitted to the aperture22A3.

The lateral surface section22B is made to stand up from the edge of one of the long side edges of the bottom surface section22A. As shown inFIG. 2, the lateral surface section22B is adapted to be engaged with the corresponding lateral surface section21B of the upper case21to form a corresponding lateral surface of the exterior case2.

The lateral surface section22B is provided with a recessed section22B1recessed toward the upper case21. The recessed section22B1serves as holding section when a user holds the projector1by hand.

As shown inFIG. 1, the lateral surface section22C is made to stand up from the edge of the other long side of the bottom surface section22A. The lateral surface section22C is adapted to be engaged with the corresponding lateral surface section21C of the upper case21to form part of a corresponding lateral surface of the exterior case2. The lateral surface section22C is notched to form a notch22C1to a large extent from the top end thereof to produce an aperture through which the louver71is exposed to the outside. To be more accurate, the notch21C1of the lateral surface section21C and the notch22C1of the lateral surface section22C form an aperture through which the louver71is exposed to the outside. Air is expelled from the opening after cooling the inside of the projector1.

As shown inFIG. 3, the rear surface section22D is made to stand up from the end of one of the short sides of the bottom surface section22A. The rear surface section22D is provided with a notch22D1to be engaged with the rear case25. More specifically, in this embodiment, the rear surface sections21D and22D and the rear case25constitute the rear surface of the exterior case2.

The rear surface section22D is provided with a rectangular aperture22D2. An inlet connector22D3is exposed to the outside through the aperture22D2. The inlet connector22D3is a terminal to be used for supplying electric power to the projector1from an external power source. It is electrically connected to a power source unit, which will be described in detail hereinafter.

Referring back toFIG. 1, the front surface section22E is made to stand up from the edge of the other short side of the bottom surface section22A. The front surface section22E is adapted to be engaged with the front case23to produce the front surface of the exterior case2with it.

As shown inFIGS. 1 and 2, the front case23shows a substantially elliptic contour and is provided with, at one of the opposite ends (the right side end inFIG. 1) of the major axis of the ellipse, an aperture231for exposing the projection lens3to the outside.

A remote-controlled light receiving window232is formed substantially at the center of the front case23. A remote-controlled light receiving module (not shown) is arranged at the inside of the remote-controlled light receiving window232to receive operation signals from a remote controller (not shown).

It may be appreciated that the remote controller is provided with a start switch and an adjustment switch equivalent to those of the above-described operation panel26so that, as the remote controller is operated, an infrared signal representing the operation is output from the remote controller and received by a light receiving section by way of the remote-controlled light receiving window232so as to be processed by a control substrate, which will be described in more detail hereinafter.

As shown inFIGS. 1 and 3, the side case24includes a top surface section24A and a lateral surface section24C suspended substantially vertically from the top surface section24A. The top surface section24A is adapted to be engaged with the top surface section21A of the upper case21to form the top surface of the exterior case2.

The lateral surface section24C is adapted to be engaged with the lateral surface section21C of the upper case21and the lateral surface section22C of the lower case22.

As shown inFIG. 3, the rear case25is fitted into the aperture formed by the notch21D1of the rear surface section21D of the upper case21and the notch22D1of the rear surface section22D of the lower case22and rigidly secured there.

The rear case25shows a substantially rectangular plan view and is provided at a position near one of the longitudinal opposite ends thereof with a remote-controlled light receiving window232similar to that of the front case23.

The rear case25is also provided with a recessed section251that is recessed toward the inside of the exterior case2and a plurality of connection terminals252are exposed to the outside at the recessed section251.

The connection terminals252are adapted to receive image signals and audio signals from external electronic appliances. The connection terminals252are connected to an interface substrate arranged in the inside of the rear case25.

The interface substrate is electrically connected to the control substrate, which will be described in more detail hereinafter. The signals processed by the interface substrate are output to the control substrate.

(2) Internal Configuration

FIG. 4shows the internal configuration of the projector1. More specifically,FIG. 4shows the inside of the projector1by removing the upper case21, the front case23, the side case24and the rear case25of the exterior case2, only the lower case22being left inFIG. 4.

The projector main body of the projector1is contained in the inside of the exterior case2. The projector main body includes an optical unit4that extends transversally along the longitudinal direction of the exterior case2, a control substrate5arranged above the optical unit4and a power source unit6.

(2-1) Structure of the Optical Unit4

FIG. 5is a schematic illustration of the optical unit4, showing the configuration thereof.

The optical unit4is adapted to modulate the light beam emitted from a light source device according to image information and project an optical image onto a plane of projection such as a screen through the projection lens3. As shown inFIG. 5, the optical unit4includes an integrator illuminating optical system41, a color separating optical system42, a relay optical system43, an optical device44realized by integrally combining the optical modulator and the color separating optical system and a substantially rectangularly parallelepipedic casing45for containing the optical components41,42,43,44(seeFIG. 6).

The integrator illuminating optical system41is an optical system for uniformizing the illuminance of the light beam emitted from the light source in an orthogonal plane relative to the axis of the illumination light beam. The integrator illuminating optical system41includes a light source device411, a first lens array412, a second lens array413, a polarization converter414and a superimposing lens415.

The light source device411includes a light source lamp411A for irradiating light, a reflector411B and an explosion-proof glass411C for covering the light beam emitting surface of the reflector411B. The radiated light beam emitted from the light source lamp411A is reflected by the reflector411B to become a light beam of substantially collimated rays, which is then emitted to the outside. In this embodiment, a high pressure mercury lamp is adopted for the light source lamp411A and a paraboloidal mirror is adopted for the reflector411B.

The light source lamp411A is, however, not limited to a high pressure mercury lamp and it may alternatively be a metal halide lamp or a halogen lamp. Similarly, while a paraboloidal mirror is adopted for the reflector411B, the present invention is by no means limited to a paraboloidal mirror and, for example, an arrangement using an ellipsoidal mirror and a collimating concave lens arranged at the light emitting surface of the reflector may alternatively be used for the purpose of the present invention.

The first lens array412is formed by arranging small lenses, each having a substantially rectangular contour as viewed in the axial direction of the illumination light beam, in the form of a matrix. The small lenses are adapted to divide the light beam emitted from the light source lamp411A into partial light beams and emit them in the axial direction of the illumination light beam.

The second lens array413have a configuration substantially same as that of the first lens array412. In other words, it is formed by arranging small lenses in the form of a matrix. The second lens array413has a function of cooperating with the superimposing lens415to focus the images of the small lenses of the first lens array412on the liquid crystal panels441R,441G,441B, which will be described in more detail hereinafter, of the optical device44.

The polarization converter414is adapted to convert light from the second lens array413into polarized light of a substantially single type. The efficiency of utilization of light in the optical device44is improved due to the operation of the polarization converter414.

More specifically, the partial light beams converted into polarized beams of light of a substantially single type by the polarization converter414are substantially superimposed one on the other by the superimposing lens415on the liquid crystal panels441R,441G,441B, which will be described in more detail hereinafter, of the optical device44. Since a projector including liquid crystal panels441R,441G,441B that are adapted to modulate polarized light can use polarized light of a single type, it can utilize only about a half of the light beam emitted from the light source lamp411A that is adapted to emit randomly polarized light. Thus, the efficiency of utilization of light of the optical device44is raised as a result of converting the light beam emitted from the light source lamp411A into polarized light of a substantially single type. Such a polarization converter414is described, for example, in Japanese Patent Laid-Open Publication No. Hei. 8-304739.

The color separating optical system42includes two dichroic mirrors421,422and a reflection mirror423. The partial light beams emitted from the integrator illuminating optical system41are separated into light beams of three colors of red (R), green (G) and blue (B) by the two dichroic mirrors421,422.

The relay optical system43includes an incident-side lens431, a pair of relay lenses433and reflection mirrors432,435. The relay optical system43has a function of leading blue light separated by the color separating optical system42down to the liquid crystal panel441B, which will be described in more detail hereinafter, of the optical device44.

At this time, the dichroic mirror421of the color separating optical system42transmits the green light beams and the blue light beams and reflects the red light beams of all the light beams emitted from the integrator illuminating optical system41. Red light reflected by the dichroic mirror421is reflected again by the reflection mirror423to get to the liquid crystal panel441R for red light by way of a corresponding field lens419. The field lens419converts the partial light beams emitted from the second lens array413into light beams that are collimated in a direction parallel to their central axis (main optical axis). The field lenses419arranged at the light incident-sides of the respective liquid crystal panels441G,441B also operate in the same way.

Of blue light and green light transmitted through the dichroic mirror421, green light is reflected by the dichroic mirror422to get to the liquid crystal panel441G for green light by way of the corresponding field lens419. On the other hand, blue light is transmitted through the dichroic mirror422, the relay optical system43and the corresponding field lens419to get to the liquid crystal panel441B for blue light.

The relay optical system43is used for blue light in order to prevent the efficiency of utilization of light from falling due to scattering of light because the optical path of blue light is longer than the optical path of red light and that of green light. In other words, the relay optical system43is provided in order to transmit the partial light beams that enter the incident-side lens431. While the relay optical system43is adapted to transmit blue light out of light beams of the three colors in this embodiment, the present invention is by no means limited thereto and it may alternatively be so adapted as to transmit red light.

The optical device44modulates the incident light beam according to image information and forms a color image. The optical device44includes three incident-side polarization plates442for receiving the color light beams produced by the color separating optical system42as a result of the process of separating the color light beams of the system42, liquid crystal panels441(441R,441G,441B), which constitute an optical modulator, and irradiation-side polarization plates444, the liquid crystal panels441and the irradiation-side polarization plates444being arranged downstream relative to the respective incident-side polarization plates442, and a cross dichroic prism445as a color combining optical device.

The liquid crystal panels441R,441G,441B are typically formed by using a polysilicon TFT as a switching element. Each of the liquid crystal panels441R,441G,441B is formed by putting liquid crystal into the gap between a pair of oppositely disposed transparent sub es so as to be held there in a hermetically sealed state and adapted to modulate the incident light beam entering it by way of the incident-side polarization plate442according to image information and emit the modulated light beam.

Each of the irradiation-side polarization plates442is adapted to transmit only light polarized in a predetermined direction out of the light beam of the corresponding color separated by the color separating optical system42and absorb light polarized in any other directions. It is formed by bonding a polarization film to a substrate that is typically made of sapphire glass.

Each of the irradiation-side polarization plates444has a configuration similar to that of the incident-side polarization plates442and is adapted to transmit only light polarized in a predetermined direction out of the light beam of the corresponding color emitted from the corresponding one of the liquid crystal panels441R,441G,441B. The axis of polarization of polarized light it transmits is arranged orthogonal relative to the axis of polarization of polarized light that the incident-side polarization plate442.

The cross dichroic prism445is designed to synthetically combine the optical images emitted respectively from the irradiation-side polarization plates444and modulated for the different three colors. The cross dichroic prism445contains a dielectric multilayer film adapted to reflect red light and a dielectric multilayer film adapted to reflect blue light that are arranged along the interfaces of four rectangular prisms so as to substantially draw a letter of X. Light of the three colors is synthetically produced by means of the dielectric multilayer films.

The liquid crystal panels441R,441G,441B, the irradiation-side polarization plates444and the cross dichroic prism445described above are arranged integrally to form a unit and mounted in a head body7, which will be described in more detail hereinafter.

FIG. 6is a perspective view of the casing45for containing optical components, illustrating the configuration thereof.

The casing45for containing optical components is typically made of synthetic resin and formed by injection. It includes a components containing member46for containing the above-described optical components41,42,43,44and a closure member47for closing the top opening of the components containing member46.

The components containing member46by turn includes a light source containing section48for containing the light source device411and a components containing section49showing a container-like profile and adapted to contain the optical components other than the light source device411.

The light source containing section48shows a substantially box-like profile and, although not illustrated in detail, has an aperture formed at the side thereof located close to the components containing section49and another aperture formed at the opposite side thereof. The aperture formed at the side of the light source containing section48located close to the components containing section49is adapted to allow the light beam emitted from the light source device411to pass through it. The aperture formed at the opposite side of the light source containing section48is adapted to receive the light source device411so as to put it into it through that lateral side.

The components containing section49show a substantially rectangularly parallelepipedic profile with an open top side. It is connected at a side thereof to the light source containing section48. Although not illustrated in detail, the components containing section49is provided with a plurality of vertical grooves for allowing the optical components412through415,419,421through423,431through435to slide down along them from above and contain them in the inside. The head body7(seeFIG. 12) that constitutes a unit along with the above-described liquid crystal panels441and the cross dichroic prism445is arranged at the opposite side of the components containing section49.

The structure of the projection lens position adjusting mechanism30and that of the head body7will be described in more detail hereinafter.

The closure member47closes the top opening of the components containing section49of the components containing member46except an area thereof located above the optical device44. The closure member47is provided with a plurality of openings47A running through it so as to allow cooling air to be expelled after cooling the inside of the casing45for containing optical components.

(2-2) Structure of the Control Substrate5

As shown inFIG. 4, the control substrate5is arranged above the closure member47of the casing45for containing optical components. The control substrate5is realized as a circuit board where processing devices including a CPU (Central Processing Unit) are mounted and adapted to control the entire projector1. The control substrate5drives the liquid crystal panels441R,441G,441B and controls their operations according to the signals output from the above-described interface substrate. Thus, the liquid crystal panels441R,441G,441B modulate light and produce an optical image under the control of the control substrate5. Additionally, the control substrate5receives the operation signals output from the circuit board of the above-described operation panel26and the above-described remote-controlled light receiving module (not shown) and appropriately outputs control commands to the components of the projector1according to the operation signals.

(2-3) Structure of the Power Source Unit6

The power source unit6supplies electric power to the light source device411, the control substrate5and other components of the projector1. It is arranged in the longitudinal direction of the front case23of the exterior case2. The power source unit6includes a power source block61having a power supply circuit and a lamp drive block (not shown) arranged below the power source block61.

The power source block61is adapted to supply electric power that is supplied from the outside by way of a power supply cable connected to the inlet connector22D3to the lamp drive block and the control substrate5as well as to other related components. The power source block61by turn includes a transformer for converting the AC that is input to it into a low voltage DC, a circuit board that carries a conversion circuit for converting the output of the transformer to a predetermined voltage and is mounted on one of the surfaces thereof and a sleeve member611that operates as shield member for covering the circuit board. The sleeve member611is made of aluminum and shows a substantially box-shaped profile with a pair of open opposite ends.

The lamp drive block is a conversion circuit for supplying electric power to the above-described light source device411with a stabilized voltage. The commercial AC that is input from the power source block61is rectified and converted into a DC and an AC showing a rectangular waveform by this lamp drive block before it is supplied to the light source device411.

An exhaust fan72is arranged at a side of the power source unit6so as to blow out cooling air through the opening where the louver71is fitted after cooling the power source unit6. A duct73is arranged between the power source unit6and the light source containing section48of the casing45for containing optical components so that cooling air is drawn by the exhaust fan72and driven out through the opening by way of the duct73after cooling the light source device411in the light source containing section48.

FIG. 7is a schematic perspective view of the projection lens position adjusting mechanism30.

The projection lens position adjusting mechanism30is adapted to adjust the light projecting position of the projection lens3by shifting the projection lens3in the tilting direction (the directions of Y3and Y4inFIG. 1) and in the direction perpendicular to the tilting direction (the directions of X3and X4inFIG. 1). It is possible to project an optical image shifted upwardly from the reference position (that is located substantially at the center of the movable range of the projection lens3as viewed both along the X-axis and along the Y-axis) of the optical axis of the projection lens3according to the extent of the positional shift of the projection lens3when the projection lens3is shifted in the direction of Y4by means of the projection lens position adjusting mechanism30. Similarly, it is possible to project an optical image shifted downwardly from the reference position of the optical axis of the projection lens3according to the extent of the positional shift of the projection lens3when the projection lens3is shifted in the direction of Y3by means of the projection lens position adjusting mechanism30.

Likewise, it is also possible to project an optical image shifted in the direction of X3or X4from the reference position of the optical axis of the projection lens3according to the extent of the positional shift of the projection lens3when the projection lens3is shifted in the direction of X3or X4, whichever appropriate, by means of the projection lens position adjusting mechanism30.

FIG. 8is an exploded perspective view of the projection lens position adjusting mechanism30.

The projection lens position adjusting mechanism30includes a base section33rigidly secured to the head body7(seeFIG. 12), which will be described in more detail hereinafter, a seat39constituted by a Y-table34and an X-table35adapted to slide on the base section33, a Y-table drive mechanism31for driving the Y-table34of the seat39to slide on the base section33and an X-table drive mechanism32for driving the X-table35of the seat39to side on the base section33.

FIG. 9is a schematic perspective view of the base section33and the Y-table34.

As shown inFIGS. 8 and 9, the base section33includes a plate-like main body section331that is substantially rectangular in plan view and extending sections332extending rectangularly toward the side of the Y-table34from oppositely disposed respective ends of the main body section331.

The main body section331is provided at a substantially central part thereof with a substantially square hole331A for receiving the projection lens3so as to allow the projection lens3to move through it. The movable range of the projection lens3is defined by the hole331A.

The front end sections333of the extending sections332run substantially in parallel with the main body section331. A pair of oppositely disposed ends of the Y-table34that are running along the X-axis are inserted in the respective gaps defined by the front end sections333and the main body section331.

One of the extending sections332, or the extending section332A shows a substantially T-shaped cross section and a pair of bosses333A1are formed at front end section333A of the extending section332A. The paired bosses333A1are introduced into respective oblong holes314B of Y-slider314of the Y-table drive mechanism31, which will be described in more detail hereinafter. Additionally, an oblong hole333A2that extends in the direction of the Y-axis is cut through the front end section333A of the extending section332A.

Still additionally, a fitting piece333A3is formed at the top end of the front end section333A so as to extend substantially rectangularly relative to the front end section333A. Two holes333A4,333A5are bored through the fitting piece333A3in order to rigidly hold a dial311and gear313of the Y-table drive mechanism31, which will be described in more detail hereinafter.

Of the extending section332, the other extending section332B shows a substantially L-shaped cross section and holes333B1are bored through front end section333B thereof in order to securely hold fitting section38to which the X-table drive mechanism32is to be fitted. The X-table drive mechanism32will also be described in more detail hereinafter.

FIG. 10is a schematic perspective view of the base section33and the seat39.

The seat39is constituted by the Y-table34adapted to slide on the base section33in the direction of the Y-axis and an X-table35adapted to slide on the base section33in a direction perpendicular to the Y-axis (in the direction of the X-axis).

As shown inFIGS. 9 and 10, the Y-table34is a plate-shaped member showing a substantially rectangular profile whose outer dimensions are smaller than those of the base section33. The opposite ends of the Y-table34disposed in the direction of the X-axis are placed in the respective gaps formed by the front end sections333and the main body section331of the base section33. Thus, the Y-table34it is adapted to slide in the direction of the Y-axis as it is guided by the main body section331and the front end sections333.

An oblong elliptic hole341is formed substantially at the center of the Y-table34so as to extend in the direction of the X-axis. The length of the minor axis (running in the direction of the Y-axis) of the hole341is substantially equal to the diameter of the projection lens3, while the length of the major axis (running in the direction of the X-axis) of the hole341is substantially equal to the length of the hole331A of the base section33as viewed in the direction of the X-axis. The projection lens3is introduced into the hole341.

A substantially rectangular hole342is formed near the end of the Y-table34in the direction of X3and adjacent to the hole341. The hole342is provided to rigidly secure the Y-slider314to the Y-table34.

A pair of pieces343is fitted to the opposite ends of the Y-table34in the direction of the Y-axis with the hole341interposed between them. Each of the paired pieces343shows a substantially L-shaped cross section and includes a perpendicular section343A that is perpendicular to the Y-table34and a parallel section343B extending from the perpendicular section343A substantially in parallel with the Y-table34. The gap between the parallel section343B and the Y-table34is adapted to receive the corresponding end of the X-table35.

As shown inFIG. 10, the X-table35is a plate-shaped member showing a substantially rectangular profile. The outer dimensions of the X-table35are smaller than those of the Y-table34.

A substantially circular hole351is formed substantially at the center of the X-table35. The diameter of the hole351is substantially equal to the outer diameter of the projection lens3and adapted to receive the projection lens3so as to allow the lens3to pass through it. A pair of projections352is formed on the X-table35and separated from the hole351in the direction of Y4. The opposite ends353of the X-table35that run in the direction of the Y-axis are partly cut so as to make them show a thickness smaller than the remaining part of the X-table35. The narrowed ends353of the X-table35are adapted to be introduced into the respective gaps between the Y-table34and the oppositely disposed pieces343in such a way that they may slide on the respective pieces343. In other words, the X-table35can slide on the base section33by way of the Y-table34.

As shown inFIG. 9, the Y-table drive mechanism31is adapted to linearly drive the Y-table34in the direction of the Y-axis on the base section33. It has a dial311and a transmitting section312for transmitting the rotary motion of the dial311to the Y-table34.

The dial311includes a dial main body311A that shows a substantially cylindrical profile and is exposed to the outside through a dial exposing hole (seeFIG. 1) bored through the top surface section21A of the upper case21of the exterior case2, a gear section311B fitted to the circular surface of the dial main body311A and a shaft section311C fitted to the gear section311B.

The shaft section311C is put into the hole333A4bored through the fitting piece333A3of the base section33and rigidly anchored in position by a substantially C-shaped anchor ring315.

The transmitting section312includes a gear313to be engaged with the gear section311B of the dial311and a Y-slider314to be engaged with the gear313so as to be driven to slide as the gear313is rotated.

The gear313has a shaft that is put into the hole333A5of the fitting piece333A3of the base section33and rigidly anchored in position by another anchor ring315.

The Y-slider314is an oblong member extending in the direction of the Y-axis and has an end part located at one of the short sides thereof that is bent in the direction opposite to the base section33. This part is notched to show a profile like that of saw teeth. It operates as an engaging section314A to be meshed with the gear313. The Y-slider314is provided with a pair of oblong holes314B extending in the longitudinal direction thereof and a recess314C. The oblong holes314B are adapted to receive the respective bosses333A1of the base section33. The recess314C is arranged substantially at the middle of the paired oblong holes314B and shows a V-shaped cross section.

A projection314D is formed substantially at the center of the surface of the Y-slider314that is located vis-à-vis the base section33so as to project away from the surface. This projection314D is adapted to be put into the hole342of the Y-table34and further into the oblong hole333A2of the base section33.

An oblong spring piece36is fitted to the Y-slider314so as to extend in the direction of the Y-axis. The spring piece36biases the Y-slider314toward the base section33and allows the Y-slider314to freely slide.

The longitudinal opposite end sections362of the spring piece36are bent to show a substantially L-shaped profile. Holes362A are bored through the respective end sections362. In the holes362A, screws B1are respectively driven into the bosses333A1by way of the oblong holes314B.

The spring piece36is bent at a substantially longitudinal middle part thereof so as to show a V-shaped profile. In other words, a projection361is formed there to project toward the Y-slider314. The projection361is biased toward the Y-slider314so as to abut the Y-slider314. Thus, as the Y-slider314slides and the optical axis of the projection lens3is driven to move to the reference position, or the substantially central position of its moving range in the direction of the Y-axis, the projection361comes into engagement with the recess314C of the Y-slider314. Then, as a result, the user can recognize that the optical axis of the projection lens3is shifted to the reference position (the substantially central position of the moving range of the Y-slider) in the direction of the Y-axis.

The X-table drive mechanism32is adapted to linearly drive the X-table35in the direction of the X-axis on the base section33. As shown inFIG. 10, it has a dial321and a transmitting section322for transmitting the rotary motion of the dial321to the X-table35.

The dial321has a structure similar to that of the dial311. It includes a dial main body321A that shows a substantially cylindrical profile and is exposed to the outside through a dial exposing hole bored through the top surface section21A of the upper case21, a gear section321B fitted to the circular surface of the dial main body321A and a shaft section321C fitted to the gear section321B.

The dial321is rigidly secured to the base section33by way of a plate-shaped fitting section38. More specifically, the dial321is rigidly secured as the shaft section321C thereof is put into the hole381and the substantially C-shaped anchor ring315is fitted in position. Note that the fitting section38is additionally provided with a hole382that is arranged adjacently relative to the hole381in order to receive the shaft section of the gear323.

The transmitting section322includes a gear323to be engaged with the gear section321B of the dial321and an X-slider324to be engaged with the gear323so as to be driven to slide in the direction of the X-axis as the gear323is rotated.

The X-slider324is a plate-shaped oblong member extending in the direction of the X-axis and has an end part located in the direction of Y4and also in the direction of X4that is notched to show a profile like that of saw teeth. It operates as an engaging section324A to be meshed with the gear313.

The X-slider324is provided with a pair of oblong holes324B extending in the longitudinal direction thereof and a recess324C.

The oblong holes324B are adapted to receive respective bosses383formed in the fitting section38.

The recess324C is arranged substantially at the middle of the X-slider324so as to be interposed between the paired oblong holes324B and shows a V-shaped cross section.

The X-slider324is provided substantially at the middle point thereof as viewed in the direction of the X-axis with an extending section324D extending in the direction of Y3inFIG. 10. The extending section324D is introduced into the space between the paired projections352of the X-table35.

Since the X-table35is adapted to be arranged on the Y-table34, it is moved downward when the Y-table34is driven to move downward. Then, the extending section324D of the X-slider324slides between the projections352. It should be noted that the extending section324D has such a large length that it does not come out of the space between the projections352even when the X-table35is moved to its lowest position. In other words, the length of the extending section324D is greater than the length of the vertical movable range of the X-slider324.

An oblong spring piece37is fitted to the X-slider324so as to extend in the direction of the X-axis. The spring piece37has a profile similar to that of the spring piece36. More specifically, the longitudinal opposite end sections372of the spring piece37are bent to show a substantially L-shaped profile. Holes372A are bored through the respective end sections372. Screws B1are respectively driven into the bosses383formed in the fitting section38by way of the oblong holes324B. Thus, the spring piece37is rigidly secured to the fitting section38that is by turn rigidly fitted to the base section33.

The spring piece37is bent at a substantially longitudinal middle part thereof so as to show a V-shaped profile. In other words, a projection371is formed there to project toward the X-slider324. The projection371is biased toward the X-slider324so as to abut the slider324to the fitting section38side. Thus, as the X-slider324slides and the optical axis of the projection lens3is driven to move to the reference position, or the substantially central position of its moving range in the direction of the X-axis, the projection371comes into engagement with the recess324C of the X-slider324. Then, as a result, the user can recognize that the optical axis of the projection lens3is shifted to the reference position (the substantially central position of the moving range of the X-slider) in the direction of the X-axis.

As pointed out earlier, the projection lens3includes a plurality of lenses and a lens holding barrel3A for containing the plurality of lenses in the inside. As shown inFIG. 8, the lens holding barrel3A is made to pass through the hole351of the X-table35, the hole341of the Y-table34and the hole331A of the base section33so that it is shifted both in the direction of the X-axis and in the direction of the Y-axis as the X-table35and the Y-table34are driven to move in the respective directions. A flange3B for making the head body7support the projection lens3is fitted to the end of the lens holding barrel3A through which an incident light beam enters the lens holding barrel3A.

Now, the operation of adjusting the position of the projection lens3by the projection lens position adjusting mechanism30will be described below.

Firstly, the movement of the projection lens3in the direction of the Y-axis will be described on an assumption that the projection lens3is located at the uppermost position of the movable range thereof in the direction of the Y-axis.

As the user turns the part of the dial311exposed to the outside from the exterior case2downward (in the direction of Y1inFIG. 1), (then the dial311turns in the direction of R1inFIG. 7). As the dial311is turned, the gear313is also turned in the direction of R2inFIG. 7. As the gear313is turned, the Y-slider314is driven to move downward (in the direction of Y3). As a result, the bosses333A1are driven to slide in the respective oblong holes314B of the Y-slider314. Additionally, the projection314D of the Y-slider314is driven to slide in the oblong hole333A2of the base section33.

Since the projection314D is put into the hole342of the Y-table34, the Y-table34also moves downward (in the direction of Y3) as the Y-slider314is driven to move. Since the vertical opposite ends of the X-table35are put into the respective gaps formed by the pieces343of the Y-table34, the X-table35also moves downward as the Y-table34is driven to move. Since the projection lens3is put into the hole351of the X-table35, the projection lens3also moves downward (in the direction of Y3) as a result.

Since the spring piece36is rigidly secured to the base section33, it does not move while the Y-slider314is driven to move. Since the projection361of the spring piece36is biased toward the Y-slider314so as to abut the latter, the Y-slider314receives resistance to a certain extent from the projection361of the spring piece36when it moves in the direction of the Y-axis.

As the dial311is turned further until the projection lens3is moved substantially to the middle point of the hole331A of the base33as viewed in the direction of the Y-axis, the projection361of the spring piece36comes into engagement with the recess314C of the Y-slider314. As a result, the user senses a feeling of a click and hence can recognize that the optical axis of the projection lens3is shifted to the reference position in the direction of the Y-axis.

As the dial311is turned further, the projection361of the spring piece36is disengaged from the recess314C of the Y-slider314so that the projection361and the Y-slider314resist against each other once again.

Now, the movement of the projection lens3in the direction of the X-axis will be described on an assumption that the projection lens3is located at the rightmost position of the movable range thereof in the direction of the X-axis as the projection1is viewed from behind.

As the user turns the part of the dial321exposed to the outside from the exterior case2leftward (in the direction of X2inFIG. 1) as viewed from the rear side of the projector1, (then the dial321turns in the direction of R3inFIG. 7). As the dial321is turned, the gear323is also turned in the direction of R4inFIG. 7. As the gear323is turned, the X-slider324is driven to move leftward (in the direction of X4) as viewed from the rear side of the projector1, As a result, the bosses383are driven to slide in the respective oblong holes324B of the X-slider324.

Since the extending section324D of the X-slider324is put into the space between the paired projections352of the X-table35, the X-table35also slides on the Y-table34, as the X-slider324is driven to move. As a result, the projection lens3is shifted leftward (in the direction of X4).

Sine the spring piece37is rigidly secured to the boss383of the fitting section38, it does not move while the X-slider324is driven to move. Since the projection371of the spring piece37is biased toward the X-slider324so as to abut the latter, the X-slider324receives resistance to a certain extent from the projection371of the spring piece37when it moves in the direction of the X-axis.

As the dial321is turned further until the projection lens3is moved substantially to the middle point of the hole331A of the base section33as viewed in the direction of the X-axis, the projection371of the spring piece37comes into engagement with the recess324C of the X-slider324. As a result, the user senses a feeling of a click and hence can recognize that the optical axis of the projection lens3is shifted to the reference position in the direction of the X-axis.

As the dial321is turned further, the projection371of the spring piece37is disengaged from the recess324C of the X-slider324so that the projection371and the X-slider324resist against each other once again.

While the movement of the projection lens3from the uppermost position to the lowermost position of its vertical moving range and the movement of the projection lens3from the right side to the left side of its horizontal moving range as viewed from the rear side of the projection1are described above, it will be appreciated that the above description is applicable to the movement of the projection lens3from the lowermost position to the uppermost position and the movement of the projection lens3from the left side to the right side.

FIG. 11is a schematic perspective view showing the projection lens3as viewed from the incident-side of the light beam, andFIG. 12is a schematic lateral view of the projection lens3and the head body7.

As pointed out earlier, the projection lens3includes a plurality of lenses and a lens holding barrel3A for containing the plurality of lenses in the inside. Attached to the lens holding barrel3A on its incident-side of the light beam is a flange3B for holding the projection lens3to the head body7. The flange3B protrudes from the lens supporting barrel3A toward the direction perpendicular to the optical axis OA of the projection lens3. Formed to the flange3B on the incident-side of the light beam are four contact sections3B2protruding toward the lens contacting surface7B21, the four contact sections being respectively formed at four corners of the substantially rectangular flange3B. The contact sections3B2are adapted to contact the lens contacting surface7B21provided on the head body7. The head body7is adapted to receive the optical components of the projector1to be mounted on it, including the liquid crystal panels441, the cross dichroic prism445and so on. In addition to the above-listed optical components, the projection lens3and the projection lens position adjusting mechanism30are also fitted to the head body7.

The head body7shows a substantially L-shaped lateral view and includes a horizontal part7A that is the inner horizontal part of the letter L and a head section7B that is the outer vertical part of the letter L. The head section7B rises substantially vertically from a position near the end of the light beam emitting side of the horizontal part7A.

The liquid crystal panels441, the cross dichroic prism445and other optical components are mounted on the horizontal part7A. The projection lens position adjusting mechanism30is arranged at the light beam emitting side of the head section7B at a position separated from the latter. The projection lens position adjusting mechanism30has a face30A perpendicular to the central axis CL of the light beam emitted from the liquid crystal panels441. The flange3B of the projection lens3is arranged between the perpendicular face30A of the projection lens position adjusting mechanism30and the lens contacting surface7B21arranged on the head section7B.

The head section7B is a part to which the projection lens3is fitted. A flat section7B1and a projecting section7B2projecting from the flat section7B1toward the light beam emitting side of the projector1are formed on the surface of the light beam emitting side of the head section7B.

The flat section7B1is a flat surface perpendicular to the central axis CL of the light beam emitted from the liquid crystal panels441.

The light beam emitting side of the projecting section7B2serves as a lens contacting surface7B21for being contacted by the contact sections3B2of the projection lens3. Although not shown in detail, the lens contacting surface7B21is curved surface which crosses the central axis CL of the light beam emitted from the liquid crystal panels441at one point CO. The curved surface has a profile which curves in accordance with curvature amount of the image forming surface on the base end side of the projection lens3. More specifically, the lens contacting surface7B21is so formed as to contain the shifting range of the projection lens3that is shifted by the projection lens position adjusting mechanism30, which is arranged vis-à-vis the lens contacting surface7B21. The largest protruding amount of the lens contacting surface7B21is defined by the reference position of the optical axis OA of the projection lens3(the center CO in the direction of the X-axis and also in the direction of the Y-axis), and the protruding amount becomes smaller gradually from the center toward peripheral edge of the lens contacting surface7B21. The method of defining the curvature of the lens contacting surface7B21will be described hereinafter.

The flange3B of the projection lens3that is held in contact with the lens contacting surface7B21is biased toward the lens contacting surface7B21by a biasing member7C, which may typically be a leaf spring. To be more accurate, the flange3B of the projection lens3is disposed between the head section7B and the projection lens position adjusting mechanism30, and the contact sections3B2of the flange3B are biased toward the lens contacting surface7B21by the biasing member7C that is interposed between the flange3B and the base section33of the projection lens position adjusting mechanism30, while they are held in contact with the lens contacting surface7B21.

FIG. 13is a lateral view of the projection lens3, illustrating how the lens is shifted. Note that the biasing member7C shown inFIG. 12is omitted fromFIG. 13.

As shown inFIG. 12, the projection lens3is biased toward the lens contacting surface7B21by the biasing member7C in a state where the contacting sections3B2of the flange3B of the projection lens3are held in contact with the lens contacting surface7B21. Thus, as shown inFIG. 13, when the projection lens3is shifted in the direction crossing the central axis CL of the light beam emitted from the liquid crystal panels441, more specifically, when the projection lens3is shifted in the tilting direction perpendicular to the central axis CL of the light beam emitted from the liquid crystal panels441(the direction of Y3or that of Y4inFIG. 1) and in the direction perpendicular to the tilting direction of the projector1(the direction of X3or that of X4inFIG. 1) by the projection lens position adjusting mechanism30, the projection lens3is forced to slide along the lens contacting surface7B21. In other words, the projection lens3is slid along the lens contacting surface7B21by operating two dials311,321shown inFIG. 1.

(5) Definition of the Curvature of the Lens Contacting Surface7B21

Now, the method of defining the curvature of the lens contacting surface7B21will be described in detail below.

Firstly, the focal length of the projection lens3is measured relative to the image height. Assume here that the projection lens3has a focal length of 49.7 nm and the flange3B has a vertical dimension (in the direction of the Y-axis) of 110 mm. The focal length, which is a distance between the light beam emitting side of the flange3B and focal point, for each image height is measured using a collimator.

FIG. 14is a graph illustrating the correspondence of the image height and the focal length of the projection lens3having a focal length of 49.7 mm.

It will be appreciated fromFIG. 14that the focal length of such a projection lens3varies as a function of the image height of the projection lens3. In other words, the light beam striking the projection lens3forms an image in such a way that a point separated from the center of the projection lens3is found at a position close to the flange3B because the distance from the end of the flange3B at the light beam emitting side.

More specifically, the light beam striking the projection lens3at a position that makes the image height equal to 0 mm, or the light beam striking the center of the projection lens3, is focused at a position separated from the end of the flange3B by a liner distance of 49.7 mm. On the other hand, the light beam striking the projection lens3at a position that makes the image height equal to 3 mm, or the light beam striking a position separated from the center of the projection lens by 3 mm, is focused at a position separated from the end of the flange3B by a linear distance of 49.6 mm. Additionally, the light beam striking the projection lens3at a position that makes the image height equal to 6 mm, or the light beam striking a position separated from the center of the projection lens by 6 mm, is focused at a position separated from the end of the flange3B by a linear distance of 49.4 mm.

Such divergences of focal position can give rise to a curvature of image of the projection lens3. In other words, when the optical axis of the projection lens3is shifted in one of the tilting directions of the projector1(in the direction of Y3or Y4inFIG. 1) and/or in one of the directions perpendicular to the tilting directions of the projector1(in the direction of X3or X4inFIG. 1) from the reference position (substantially the middle point of the moving range of the projection lens3along the X-axis and also along the Y-axis) by means of the projection lens position adjusting mechanism30, the light beam emitted from the liquid crystal panels441through the cross dichroic prism445strikes the projection lens3at a position separated from the center of the projection lens3by an extent equivalent to the shift of the projection lens3. Then, the focal point of the projection lens3that is defined to agree with the projection surface at the reference position is located in front of the projection surface. Therefore, the curvature of image will become remarkable to degrade the projected image because of the out of focus condition. It will be appreciated that the curvature of image can be corrected by dissolving the divergence of the focal position for each image height.

While the curvature of image of the projection lens3is attributable to the divergence of the focal position for each image height as pointed out above, it is difficult to shift the liquid crystal panels441corresponding to the shift of the projection lens3because the positions of the liquid crystal panels441for forming optical images are fixed in the projector1. Since the focal length of the light beam striking the projection lens3at a position separated from the center thereof tends to become shorter than the focal length of the light beam striking the projection lens3at the center thereof as illustrated inFIG. 14, the focal point of the projection lens3can be made to agree with the liquid crystal panels441when the projection lens3is driven to move close to the liquid crystal panels441as the optical axis of the projection lens3is shifted in the direction of the X-axis or in the direction of the Y-axis from the above-described reference position (substantially the middle point of the moving range of the projection lens3along the X-axis and also along the Y-axis). More specifically, when the projection lens3is shifted, the curvature of image of the projection lens3can be corrected by letting the lens contacting surface7B21have a curved surface so as for the surface of the flange3B of the projection lens3to get close to the liquid crystal panels441corresponding to the extent of the shift of the projection lens3.

Now, the profile of the curved surface of the lens contacting surface7B21, in other words, the protruding amount of the lens contacting surface7B21from the flat section7B1corresponding to the shifting position of the projection lens3will be obtained as below.

First, arranging a spacer having a predetermined size at the side of an end between the lens holding barrel3A of the projection lens3and the flange3B fitted to the corresponding end of the lens holding barrel3A and measuring the size of the spacer for each image height when the focal point of the projection lens3is found on the plane separated from the flange3B by a given constant distance. With this arrangement, it is safe to take the liquid crystal panels441and the image height respectively for the plane where the focal point of the projection lens3is found and for the extent of the shift of the projection lens3.

In the above-measurement, the distance between the plane where the focal point of the projection lens3is found and the light beam emitting side of the flange3B needs to be fixed, and in the present embodiment, it is fixed to 49.2 mm.

FIG. 15is a graph illustrating the correspondence of the image height and the size of a spacer arranged between the lens holding barrel3A and the flange3B.

It is now possible to obtain the size of the spacer with which the focal point of the projection lens3is found on the above-defined plane for each image height by utilizing the results of observation illustrated inFIG. 15. More specifically, when the image height is 0 mm, it is possible to make the focal point of the projection lens3to be found on the plane separated from the flange3B by 49.2 mm by arranging a spacer of 1.0 mm between the lens holding barrel3A and the flange3B. Similarly, when the image height is 2 mm and when the image height is 3 mm, it is possible to make the focal point of the projection lens3to be found on the plane by arranging respectively a spacer of 0.9 mm and a spacer of 0.8 mm between the lens holding barrel3A and the flange3B.

Since the spacer is arranged at the side of an end between the lens holding barrel3A and the flange3B, at the center of the projection lens3(the position at which the face of the flange3B is crossed by the optical axis of the projection lens), the distance obtained by adding a half of the size of the spacer and the distance to the plane where the focal point of the projection lens3is found is the focal length of the projection lens3for each image height. Thus, as shown inFIG. 16, the curved surface of the lens contacting surface7B21can be obtained by determining the image heights first, in other words, by determining the values of half of the spacer size, which correspond to the shift amount of the projection lens3, and then connecting the obtained points into a curved line.

It is possible to adjust the focal length of the projection lens3for each image height and correct the curvature of image of the projection lens3by driving the projection lens3to slide along the lens contacting surface7B21obtained by using the above method. In other words, it is possible to make the focal point of the projection lens3agree with the liquid crystal panels441by causing the lens contacting surface7B21of the projecting section7B2projecting from the head section7B to contact the contact sections3B2formed on the flange3B of the projection lens3and driving the projection lens3to shift along the lens contacting surface7B21by means of the projection lens position adjusting mechanism30. With the above-described arrangement, it is possible to correct the curvature of image of the projection lens3.

Incidentally, the data inFIG. 14toFIG. 16is for a projection lens (as the projection lens3herein) of which the spherical aberration has not been corrected. However, in the case of a general projection lens for a small-sized projector used for company meeting, home theater and the like, since the spherical aberration has already been corrected in some extent, variation in focal length inFIG. 14and the values of the transverse axis inFIG. 15andFIG. 16should respectively be reduced to approximately 1/10. Further, to enable the contact sections3B2formed on the flange3B of the projection lens3to contact the lens contacting surface7B21over the entire curved surface as shown inFIG. 16(the lens contacting surface7B21), the difference of the protruding amount of the curved surface is required to be approximately 0.38 mm. However, in the case of aforesaid general projection lens, within the range in which the contact sections3B2contact the lens contacting surface7B21, it is enough to set the difference of protruding amount of the curved surface between about 0.01 and about 0.1 mm.

(6) Advantages of the First Embodiment

The above-described embodiment of the present invention provides the following advantages.(6-1) A the lens contacting surface7B21is formed on the surface of the light beam emitting side of the head section7B, which is an outer vertical part of the head body7, so as to project its curved surface by a distance that varies as a function of the curvature of image of the image forming plane of the light beam incident-side of the projection lens3and the projection lens3is driven to shift along the lens contacting surface7B21by the projection lens position adjusting mechanism30in the on of the X-axis and also in the direction of the Y-axis. Thus, it is possible to correct the partially blurred image, and to correct the curvature of image of the projection lens3. As a result, it is possible to project clear images.(6-2) Further, since the lens contacting surface7B21is formed to have a curved profile, and the curvature of image of the projection lens3is corrected by shifting the projection lens3along the lens contacting surface7B21, it is not necessary to employ, for example, an expensive lens which has no image curvature for a projector to prevent degradation of the projected image. Also, since the curvature of image of the projection lens3can be corrected with such arrangement, it is possible to widen the range for selecting a lens for a projector and thereby to reduce the manufacturing cost of project1.(6-3) The lens contacting surface7B21has a curved profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge. With this arrangement, it is possible to correct the curvature of image of the projection lens3when the projection lens3is shifted not only in the tilting direction (the direction of the Y-axis) of the projector1but also in the direction perpendicular to the tilting direction (the direction of the X-axis), by the projection lens position adjusting mechanism30. Thus, it is possible to correct the curvature of image of the projection lens3regardless of the shifting direction of the projection lens3. Therefore, it is possible to project clear images.(6-4) The flange3B of the projection lens3is arranged between the lens contacting surface7B21formed on the head section7B of the head body7and the face30A of the projection lens position adjusting mechanism30that is arranged vis-à-vis the light beam emitting side of the head section7B and a biasing member7C, which is typically realized by a leaf spring, is arranged between the projection lens position adjusting mechanism30and the flange3B. With this arrangement, it is possible to hold the projection lens3in a state being biased to the lens contacting surface7B21formed on the light beam emitting side of the head section7B. Thus, it is possible to reliably shift the projection lens3along the lens contacting surface7B21, while the projection lens3is reliably held in contact with the lens contacting surface7B21. As pointed out above, the projection lens3can be held in contact with and supported by the lens contacting surface7B21by means of a simple arrangement. Additionally, it is possible to adjust the friction that arises when the projection lens3is driven to slide along the lens contacting surface7B21by adjusting the biasing force of the biasing member7C. Thus, it is possible to improve the sliding ability of the projection lens3.(6-5) Contact sections3B2that have a semispherical front end are formed at the four corners of the surface of the light beam incident-side of the flange3B of the projection lens3so as to contact the lens contacting surface7B2. With this arrangement, the contact sections3B2of the flange3B contact the lens contacting surface7B21when the projection lens3is driven to shift so that it is possible to further improve the sliding ability of the projection lens3along the lens contacting surface7B21.

2. Second Embodiment

Now, the second embodiment of projector according to the present invention will be described below. While the second embodiment of a projector has a configuration substantially same as that of the above-described first embodiment of the projector1, it differs from the first embodiment in that the lens contacting surface8B13, which contacts the contact sections3B2of the flange3B of the projection lens3, is provided with a first curved section8B11and a second curved section8B12. The components of the second embodiment that are same as or similar to those of the first embodiment are denoted respectively by the same reference symbols and will not be described any further.

FIG. 17is a schematic lateral view of the head body8of the second embodiment of projector according to the present invention.

The head body8of the second embodiment of projector shows a substantially L-shaped lateral view and includes a horizontal part8A that is the inner horizontal part of the letter L and a head section8B that is the outer vertical part of the letter L. The liquid crystal panels441, the cross dichroic prism445and other optical components are mounted on the horizontal part8A.

As shown inFIG. 17, the surface of the light beam emitting side of the head section8B is flatly formed as a flat section8B2, and the flat section8B2is attached with a plate-like body8B1having a curved profile as a separate member of the head body8. The flat section8B2is a flat surface perpendicular to the central axis CL of the light beam emitted from the liquid crystal panels. The surface of the light beam emitting side of the plate-like body8B1is formed as a lens contacting surface8B13having a profile which curves in accordance with curvature amount of the image forming surface of the light beam incident-side of the projection lens3. The contact sections3B2formed on the flange3B of the projection lens3contact and move along the lens contacting surface8B13. The lens contacting surface8B13has a first curved surface section8B11and a second curved surface section8B12being formed along the peripheral edge of the first curved surface section8B11.

Although not shown inFIG. 17, the projection lens position adjusting mechanism30is arranged at the light beam emitting side of the head section8B and the flange3B of the projection lens3is arranged between the projection lens position adjusting mechanism30and the head section8B. Additionally, a biasing member (not shown) such as a leaf spring is arranged between the flange3B and the projection lens position adjusting mechanism30so that the flange3B is biased toward the lens contacting surface8B13by the biasing force of the biasing member.

The first curved surface section8B11is made to show a substantially circular contour as viewed from the light beam emitting side, and protrudes toward the side of the projection lens3.

To describe it in detail, the center CO of the first curved surface section8B11corresponds to the reference position of the optical axis OA of the projection lens3(the middle point in the direction of the X-axis and also in the direction of the Y-axis) and the center CO of the first curved surface section8B11projects to the largest extent. In other words, the protruding amount of the first curved surface section8B11diminishes gradually from the center toward the peripheral edge thereof. Incidentally, the profile of the first curved surface section8B11is set using the method described in the first embodiment. Also, in the case of aforesaid general projection lens, within the range in which the contact sections3B2contact the first curved surface section8B11, it is enough to set the difference of protruding amount of the curved surface between about 0.01 and about 0.1 mm.

The second curved section8B12is formed along the peripheral edge of the first curved surface section8B11so as to project more than the peripheral part P of the curved surface section8B11where the protruding amount is minimal in itself. In other words, the second curved section8B12is formed to the outside of the peripheral part P of the first curved surface section8B11in such a way that it is curved mildly and the protruding amount thereof which is directed to the light beam emitting side, changes continuously. The profile of the second curved section8B12is set in accordance with the profile of the first curved section8B11. In other words, the profile is so set that when the projection lens3slides with the any of the plural contact sections3B2contacting the first curved surface section8B11, the other contact sections3B2are contacting and sliding along the second curved section8B12, and thereby the optical axis OA of the projection lens3is substantially in parallel with the central axis CL of the light beam emitted from the liquid crystal panels441through the cross dichroic prism445.

The second embodiment of projector according to the present invention and having the above-described head body8provides the following advantage in addition to the advantages of the projector1listed above by referring to the first embodiment.

In other words, since the second curved section8B12protrudes in the same direction as the first curved surface section8B11, even when the projection lens3is shifted to the edge of the lens contacting surface8B13, the optical axis of the projection lens3is in parallel with the central axis of the light beam emitted from the liquid crystal panels441through the cross dichroic prism445. Here, if the second curved section8B12is not be formed as in the first embodiment, in other words, as shown inFIG. 13, in a case where the lens contacting surface7B21has a profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge, when the projection lens3is shifted to the edge of the lens contacting surface7B21, the angle defined by the optical axis OA and the central axis CL of the light beam emitted from the liquid crystal panels441will become large, thereby there might be the possibility of causing partially blurred image. Therefore, in the present embodiment, by forming the second curved section8B12which protrudes in the same direction as the first curved surface section8B11and has the protruding amount larger than that of the peripheral edge of the first curved surface section8B11, the optical axis of the projection lens3is in parallel with the central axis of the light beam emitted from the liquid crystal panels441even when the projection lens3is shifted to the edge of the lens contacting surface8B13. Then, it is possible to suppress the partial blur of the projected image and also prevent degradation of the projected image. Thus, it is possible to improve the accuracy of correcting the partial blur of the projected image and increase the degree of freedom of projection of an optical image.

Incidentally, since the partial blur of the projected image caused by inclination of optical axis OA of the projection lens3can be ignored if the curvature of the lens contacting surface7B21is small to a certain level, as the lens contacting surface7B21in the first embodiment, the problem of the present invention still can be solved even with a curved surface having a profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge.

While the present invention is described above in terms of the best mode of carrying out the present invention, the present invention is by no means limited to the above-described mode of carrying out. In other words, while the present invention is illustrated and described above in terms of specific embodiments, it may be obvious to those skilled in the art that the described embodiments can be modified and altered in various different ways without departing from the object and scope of the present invention particularly in terms of the profile and the material of each of the components and the number of each type of component.

Therefore, the above description of profiles and materials are only for the purpose of facilitating understanding of the present invention and do not limit the present invention. In other words, the description using the denominations of members entirely or partly omitting description of profiles and materials is also included in the present invention.

The profile, the protruding amount, and the protruding direction of the lens contacting surface7B21, the first curved surface section8B11, and the second curved section8B12are not limited to the description of the above embodiments, but can be changed in accordance with the properties of the projection lens3.

For example, in the above embodiments, though the lens contacting surface7B21, the first curved surface section8B11, and the second curved section8B12protrude toward the light beam emitting side, they can protrude toward opposite side depending on the properties of the projection lens3.

Further, in the above embodiments, though the lens contacting surface7B21and the first curved surface section8B11show a substantially circular contour as viewed from the light beam emitting side, and have curved profile of which the protruding amount becomes smaller gradually from the center thereof toward peripheral edge, they should not be limited thereto. For example, the lens contacting surface7B21and the first curved surface section8B11can show a rectangular shape as viewed from the light beam emitting side, and the cross section thereof in the Y-axis direction can be substantially a semicircle. With such arrangements, it is still possible to dissolve the partial blur of the projected image and correct the curvature of image if the projection lens3is driven to shift in the tilting direction of the projector1(in the direction of Y3and in the direction of Y4inFIG. 1).

While the flange3B of the projection lens3of each of the above-described embodiments is biased toward the lens contacting surface7B21or8B13by the biasing member7C, which may typically be a leaf spring, the flange3B may be biased by some other arrangement. For example, the flange3B may alternatively be biased toward the lens contacting surface7B21or8B13by means of a spherical resilient member that is typically made of rubber in such a way that the sliding ability of the flange3B is secured. In short, any arrangement may be used for biasing the flange3B toward the lens contacting surface7B21or8B13so long as it is possible to make the flange3B of the projection lens3reliably contact the lens contacting surface7B21or8B13, whichever appropriate, and driven the projection lens3to shift by means of the projection lens position adjusting mechanism30.

While the contact sections3B2are formed respectively at the four corners of the surface of the light beam incident-side of the flange3B so as to project from the surface and contact the lens contacting surface7B21or8B13in each of the above-described embodiments, the present invention is by no means limited thereto. It is not necessary to arrange such contact sections3B2. Alternatively, contact sections different from the above-described shapes may be arranged. For example, the surface of the light beam incident-side of the flange3B may be curved along the edges thereof. However, it should be noted that the above-described contact sections3B2can stably and reliably cause the flange3B to contact the lens contacting surface7B21or8B13and improve the sliding ability of the projection lens3.

Further, in the above embodiments, though the projection lens position adjusting mechanism30moves the projection lens3along two directions of the X-axis direction and Y-axis direction, it should not be limited thereto, but can move the projection lens3along any direction perpendicular to the central axis CL of the light beam emitted from the liquid crystal panels441.

Furthermore, in the above embodiments, though the optical axis OA of the projection lens3corresponds to the central axis CL of the light beam emitted from the liquid crystal panels441in the case when the optical axis OA of the projection lens3is located at the reference position in the direction of the X-axis or in the direction of Y-axis, they are not necessary to correspond to each other.

While each of the above-described embodiments has an optical unit4showing a substantially L-shaped plan view, the present invention is by no means limited thereto and may alternatively have an optical unit showing a substantially U-shaped plan view.

While each of the above-described embodiments exemplifies the projector1using three liquid crystal panels441, the present invention is by no means limited thereto and may alternatively include a projector using a single liquid crystal panel, a projector using two liquid crystal panels, or a projector using four or more than four liquid crystal panels.

While each of the above-described embodiments has transmission type liquid crystal panels whose light beam incident-side surface and light beam emitting side surface are different, the present invention is by no means limited thereto and may alternatively include reflection type liquid crystal panels whose light beam incident-side surface also operates as light beam emitting side surface.

While liquid crystal panels are used as an optical modulator in each of the above-described embodiments, an optical modulator other than liquid crystal panels such as devices realized by using micro-mirrors may alternatively be used for the purpose of the present invention. Then, the polarization plates at the light beam incident-side and at the light beam emitting side can be omitted.

While the above-described embodiments are front type projectors adapted to project an image from the viewing side of the screen, the present invention is also applicable to a rear type projector adapted to project an image from the side opposite to the viewing side of the screen.

The priority application Numbers JP2004-166273 and JP2005-159974 upon which this patent application is based are hereby incorporated by reference.