JP2002107663A - Rear projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and thin a rear projector though a high-performance inexpensive projection lens is used. SOLUTION: This rear projector 10 is equipped with a projection optical system 1, a reflection mirror 2 and a housing 4 housing the optical system 1 and the mirror 2. A rear screen 3 is installed on the front of the housing 4. The optical system 1 is equipped with a projection lens 600 incorporating a prism 610 folding an optical path L1 leading to the screen 3 from an electrooptical device by 90 deg.. The optical system 1 is arranged so that an optical path L2 to the prism 61 from the electrooptical device may be inclined by an angle θ to the base 41 of the housing 4. By such constitution, arrangement where the inclination of the mirror 2 is near to a vertical direction is realized, so that the projector 10 is thinned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projector (rear projection display device) for projecting an image on a rear screen.

[0002]

2. Description of the Related Art As a display device having a large screen, a rear projector that enlarges and projects an image on a rear screen and displays the image is often used. As a rear projector that projects an image, there is a rear projector that uses an electro-optical device such as a liquid crystal panel as a light valve, illuminates an image formed on the light valve with a light source such as a discharge lamp, and enlarges and projects the image with a projection lens. Are known. Such a rear projector is a system in which a small electro-optical device is illuminated with a bright light source to obtain a large screen. Therefore, a bright and high-definition image can be easily obtained with a small optical system, while a sufficient magnification ratio is obtained. Since a proper projection distance is required in order to obtain, the miniaturization and thinning of the apparatus have been one of the issues.

In order to solve the above problems, for example, Japanese Patent Laid-Open No.
A technique for reducing the height and depth of the apparatus by turning a projection lens at an acute angle as disclosed in JP-A-187274 is proposed.

[0004]

The above technique is characterized in that a linearly long optical system disposed along the bottom surface of the rear projector is bent at an acute angle in the projection lens, and is therefore folded. Front lens group (lens group before folding) and rear group (lens group after folding) of projection lens
And their optical axes also have an acute angle relationship. On the other hand, if an attempt is made to enlarge the screen while keeping the projection distance (sometimes called the working distance) short in order to keep the rear projector thin, the lens forming the front lens group of the projection lens becomes large, and the projection lens becomes large. The front group and the rear group tend to interfere with each other. Therefore, in order to prevent this interference, it is necessary to take measures such as increasing the distance between the front group and the rear group of the projection lens, or cutting off the lens of the part that interferes.
This causes a reduction in the performance of the projection lens and an increase in cost.

When adjusting the relative position between the projection optical system including the projection lens and the rear screen, it is necessary to move the projection optical system so as to be parallel or perpendicular to the optical axis immediately before reaching the screen. However, in the case of a projection optical system in which the optical axis is bent at an acute angle inside the projection lens as in this technology, a complicated mechanism that obliquely moves the projection optical system body to an angle corresponding to the acute angle is used. Is required, which is also a disadvantage of this optical system.

Further, since the projection optical system is arranged along the bottom surface of the apparatus and there is little gap between the projection optical system and the bottom surface, the projection optical system is required to sufficiently cool the projection optical system. It is also necessary to take care of lifting only.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and has as its object to use a high-performance and inexpensive projection lens to adjust the position of a projection optical system. It is an object of the present invention to provide a technique capable of reducing the size and thickness of a rear projector while simplifying a mechanism.

[0008]

SUMMARY OF THE INVENTION In order to solve at least a part of the problems described above, an apparatus of the present invention includes a light source, an electro-optical device for generating an image using illumination light from the light source,
A projection optical system including a projection lens for enlarging and projecting the image light from the electro-optical device, a housing accommodating the projection optical system, and a rear screen installed on a front surface of the housing. A rear projector, comprising: two optical path changing means for folding an optical path from the electro-optical device to the rear screen in a vertical section including a normal line at a center of the rear screen; One of the optical path conversion means is disposed so as to turn the optical path by 90 degrees inside the projection lens, and the projection optical system is configured such that an optical path from the electro-optical device to the one optical path conversion means is provided in the housing. It is characterized by being arranged to be inclined with respect to the bottom surface. According to such a configuration of the present invention, the optical axis is bent by 90 degrees inside the projection lens, and the projection optical system is inclined with respect to the bottom of the housing, so that the inclination of the reflection surface that constitutes the other optical path changing unit is inclined. Can be arranged closer to the vertical direction, so that the rear projector can be made thinner.

Further, the front group (lens group on the screen side) and the rear group (lens group on the electro-optical device side) of the folded projection lens and their optical axes have a right-angled relationship, and Since the distance can be reduced to a minimum and the lens need not be cut unnecessarily, the degree of freedom in the design and manufacture of the projection lens is improved, and the effect of increasing the performance of the projection lens and reducing the cost is obtained.

Further, since the front group and the rear group of the folded projection lens and their optical axes are in a right angle relationship, the projection optical system is moved horizontally or vertically with respect to those optical axes so that the projection optical system can be connected to the projection optical system. The relative position with respect to the rear screen can be adjusted, and the adjustment mechanism is simplified.

Further, since the projection optical system is arranged inclined with respect to the bottom surface of the housing, air can be easily taken into the projection optical system from a space formed below the projection optical system, and a space for cooling can be provided. Effective cooling can be performed without specially providing a cooling medium.

In the description of the present specification including the claims, "optical path" means a path through which the center of a light beam passes, and "longitudinal section" means a section orthogonal to the bottom surface of the housing. It shall be.

In the above rear projector, it is preferable that the light source includes a lamp, and the lamp is arranged such that an optical axis of the lamp is orthogonal to the longitudinal section.

With this arrangement, the optical axis of the lamp is always kept horizontal (parallel to the bottom surface of the housing), no matter how much the projection optical system is inclined. The life of the lamp can be extended.

Further, since the lamp can be arranged on the rear side (the surface opposite to the rear screen surface) of the rear projector, the lamp can be replaced from the rear side, and the frequency of replacing the lamp is not so high. This is convenient for rear projectors. Further, the space on the screen side of the rear projector can be effectively utilized as a space for arranging speakers and other video equipment.

In the description of the present specification including the claims, the "optical axis of the lamp" means a central axis of a light beam emitted from the lamp.

In the rear projector, the light source may include a lamp, and the lamp may be arranged such that an optical axis of the lamp is parallel to the longitudinal section.

It is desirable that the lamp be in a horizontally lit state (a state in which the optical axis is kept parallel to the bottom surface of the housing) as described above unless the lamp is particularly made for vertical lighting. If so, its effect on life is small. On the other hand, by arranging the lamp so that the optical axis is parallel to the longitudinal section, the lamp is arranged on the screen surface side of the rear projector, and a space is provided on the side surface of the rear projector. Can be empty. Therefore, the lamp can be replaced from the screen surface side (front side) of the rear projector, maintenance is facilitated, and a novel design in which the side surface is cut can be realized.

In the rear projector, it is preferable that the one of the optical path changing means disposed inside the projection lens is a right-angle prism.

In this case, the planar accuracy of the reflection surface of the optical path changing means can be improved, and the optical path length between the front group and the rear group of the projection lens can be extended by filling the space with a glass material.
The arrangement of the front group and the rear group can be facilitated. Also,
Since the turning angle is 90 degrees and a general right-angle prism can be used, positional accuracy with respect to other lens groups can be easily secured, and the performance of the projection lens can be improved.

In the above rear projector, adjustment is made to move the projection optical system in a direction parallel and / or orthogonal to a plane including an optical path from the electro-optical device to the one optical path conversion means and an optical axis of the lamp. It is desirable to have a means.

With this arrangement, it is possible to correct a relative position shift between the projection optical system and the screen, which is caused by a position shift of a mirror or the like constituting the housing of the rear projector or the other optical path changing means. In particular, in the present invention, since the turning angle of the optical path changing means in the projection lens is 90 degrees, effective position adjustment can be performed by adding a simple adjustment mechanism.

In the rear projector, it is preferable that the rear projector further includes a cooling means for passing cooling air from below to the projection optical system.

With this configuration, while effectively utilizing the space below the projection optical system formed by inclining the projection optical system with respect to the bottom surface of the rear projector, it is possible to efficiently use the space without providing a new space for this purpose. Cooling can be performed.

[0025]

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

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
It is a side view which shows schematic structure of the rear projector 10 (rear projection type display apparatus) as embodiment.

In the following, the direction of the optical axis of the light emitted from the rear projector is defined as the x direction, the direction at 9 o'clock as viewed in the + x direction is defined as the y direction, and the direction at 12:00 is defined as the z direction. In FIG. 1, a projection optical system 1 and a mirror 2 serving as a first optical path changing unit are housed in a housing 4, and a rear screen 3 is installed on a front surface of the housing 4. Further, the projection optical system 1 has a base unit 5 that forms an angle θ with respect to the housing bottom surface 41 parallel to the xy plane.
Projection lens 6 held above and being a part of the projection optical system 1
00 has a built-in prism 610 as a second optical path changing means.

FIG. 2 is a plan view showing a main part of the projection optical system 1. The projection optical system 1 includes an illumination optical system 100, a color light separation optical system 200, a relay optical system 300, and three light valves 400R, 400G, and 400 that are electro-optical devices.
B, a cross dichroic prism 500, and a projection lens 600.

The illumination optical system 100 includes a lamp 110 constituting a light source, an integrator optical system 120, and a polarization conversion optical system 130.
The optical axis 140 of 0 is orthogonal to the vertical section 7 (the plane parallel to the xz plane in FIG. 3) including the normal 6 at the center of the rear screen 3. The light emitted from the lamp 110 uniformly illuminates the light valves 400R, 400G, and 400B to be illuminated via the integrator optical system 120. The polarization conversion optical system 130 transmits the non-polarized light to the light valve 40.
It has a function of aligning with polarized light having a polarization direction usable in 0R, 400G, and 400B.

The color light separation optical system 200 includes two dichroic mirrors 210 and 220 and a reflection mirror 230, and has a function of separating illumination light emitted from the illumination optical system 100 into three color lights of different wavelength ranges. have.

The first dichroic mirror 210 reflects red (R) light and emits color light (substantially green (G) light and blue (B) light) on a shorter wavelength side than the reflected color light. To Penetrate. The R light reflected by the first dichroic mirror 210 is reflected by the reflection mirror 230, and enters the R light valve 400R through the field lens 240.

Of the G light and the B light transmitted through the first dichroic mirror 210, the G light is reflected by the second dichroic mirror 220 and is reflected by the field lens 25.
The light enters the light valve 400G for G through 0. On the other hand, the B light is transmitted through the second dichroic mirror 220 and relay optical system 300, that is, the incident side lens 31
0, first relay reflection mirror 320, relay lens 33
0, the light enters the light valve 400B for B via the second relay reflection mirror 340 and the emission side lens 350. Here, the reason that the relay optical system 300 is used for the B light is that the length of the optical path of the B light is longer than the length of the optical paths of the other color lights, so that the reduction of the light use efficiency due to light diffusion or the like occurs. This is to prevent it.

Light valves 400R, 400 for each color
G and 400B modulate the color light incident on them in accordance with the corresponding color signal (image information), and emit the modulated light as transmitted light. As such a transmission type light valve, a transmission type light valve in which a transmission type liquid crystal panel is arranged between a pair of polarizing plates is used.

The R light emitted from the R light valve 400R is applied to the first light of the cross dichroic prism 500.
Are reflected by the dichroic surface 510 and are emitted from the emission surface 530. The B light emitted from the B light valve 400B is reflected by the second dichroic surface 520 and emitted from the emission surface 530. Further, the G light emitted from the G light valve 400G is applied to the first dichroic surface 510 and the second dichroic surface 5G.
The light is emitted from the emission surface 530 through 20. Thereby, the light valves 400R, 400G, 400
The three colors of modulated light modulated in B are combined by the cross dichroic prism 500. The color image represented by the combined modulated light is projected by the projection lens 600.

The configuration and function of each part of the projector as shown in FIG. 2 are described in, for example, JP-A-10-177151 and JP-A-1
Since it is described in detail in Japanese Patent Application Laid-Open No. 0-186548, detailed description is omitted in this specification.

FIG. 4 shows the prism 6 in the projection lens 600.
10 is a schematic diagram for explaining the configuration of FIG. Therefore, the shape and configuration of each lens other than the prism 610 are simplified, and are different from the actual shape and configuration. It should be noted that the number, shape, configuration, and the like of the lenses constituting the simplified portion can be determined by those skilled in the art of the projection lens 600.
Since it is a part whose shape and configuration can be arbitrarily selected according to the characteristics required for the above, the description is omitted here. The prism 610 is a right-angle prism made of glass or optical resin, and an anti-reflection film is formed on the entrance surface 620 and the exit surface 630, and a slope 640 is a total reflection surface or a reflection surface (in this case, a reflection film is formed on the slope). Is necessary). Image light that has entered the projection lens 600 from the cross dichroic prism 500 is converged by a lens group 650 (also referred to as a rear group) on the cross dichroic prism 500 side of the projection lens 600, and is totally reflected or reflected by the inclined surface 640 of the prism 610. The light is turned back by 90 degrees, and is projected toward the rear screen 3 by a lens group 660 (also referred to as a front group) on the rear screen 3 side.

As described above, the following effects can be obtained by using the right-angle prism as the optical path changing means. That is, since the shape of each prism plane hardly changes, the plane accuracy of the reflection surface can be improved, and the reflection angle can be easily maintained. Further, the optical path length between the front group and the rear group of the projection lens can be extended by the medium of the prism, and the arrangement of the front group and the rear group can be facilitated. Further, since the folding angle is 90 degrees, the positional accuracy with respect to other lens groups can be easily secured, and the performance of the projection lens can be improved.

Note that a reflecting mirror may be used instead of the prism 610.

The image light emitted from the projection lens 600 as described above is directed in the direction of the rear screen 3 by the mirror 2 and is imaged on the rear screen 3.

In the rear projector 10 of the present embodiment,
Light valve 400R, 400 corresponding to electro-optical device
The optical path L1 of the projection light from the G, 400B to the rear screen 3 is reflected twice by the prism 610 and the mirror 2 to form a vertical section 7 including the normal 6 at the center of the rear screen 3 (parallel to the xz plane in FIG. 3). Face). Further, the optical path L1 of the projection light is turned 90 degrees inside the projection lens 600 by the prism 610. Further, the projection optical system 1 includes light valves 400R, 400R.
G, the optical path L2 from 400B to the prism 610 is xy
It is arranged so as to be inclined by an angle θ with respect to the housing bottom surface 41 parallel to the surface. With such a configuration, the following effects are newly generated.

That is, when the optical path is bent by 90 degrees inside the projection lens 600 and the projection optical system 1 is inclined by θ with respect to the housing bottom surface 41 as described above, the inclination angle φ of the mirror 2 from the vertical plane becomes , Φ = (90 ° −θ) / 2, and as the angle θ increases, the mirror 2 can be arranged closer to the vertical direction (yz plane).
Can be reduced in thickness.

Further, the front group 660 and the rear group 650 of the folded projection lens 600 and their optical axes are in a right angle relationship, and the distance between the front group 660 and the rear group 650 can be reduced to a minimum. Since there is no need to cut the lens unnecessarily, the degree of freedom in designing and manufacturing the projection lens 600 is improved, and there is an effect that the performance of the projection lens 600 is increased and the cost is reduced.

FIG. 3 is a plan view showing a case where the projection optical system 1 having the structure shown in FIG. In the rear projector 10 of the present embodiment,
The optical axis 140 of the lamp 110 is disposed so as to be orthogonal to the vertical section 7 including the normal 6 at the center of the rear screen and parallel to the xz plane. Therefore, even when the projection optical system 1 is tilted by the angle θ as described above, the lamp 110 can maintain the state of horizontal lighting.

Therefore, no matter how much the projection optical system 1 is tilted, the optical axis 140 of the lamp 110 is always kept horizontal (parallel to the bottom surface 41 of the housing), so that the arc tube forming the lamp 110 is biased by heat. And the life of the lamp 110 can be extended. In addition, since the lamp 110 can be disposed on the rear surface (the surface facing the rear screen 3) of the rear projector 10, the lamp 110 can be replaced from the rear surface, and the lamp replacement frequency is not so high. This is convenient for rear projectors. Further, the space on the screen 3 side of the rear projector 10 can be effectively utilized as a space for arranging speakers and other video equipment.

FIG. 5 shows a specific example of the base means 5 for arranging the projection optical system 1. FIG. 5 (a) is a side view, and FIG.
FIG. 5B is a view of the substrate B53 as viewed from A, and FIG.
FIG. The base means 5 is roughly composed of a base member 51, a substrate A52, and a substrate B53, and the projection optical system 1 is fixed on the substrate B53. Projection optical system 1
Under the cross dichroic prism 500 and the three light valves 400R, 400G, 400B, a cooling fan 800 for cooling the light valve and a polarizing plate (not shown) disposed around the light valve is arranged, and the base member 51, The cooling fan 80 is located at a position corresponding to the position of the cooling fan 800 on the substrate A52 and the substrate B53.
An opening 54 is provided for taking in air into the airbag.

The substrate A52 and the substrate B53 are connected via three height adjusting members 55. When one of the three height adjusting members 55 is rotated, the substrate B53 is moved relative to the substrate A52. Can be close to or separated from The board A52 and the base member 51 are fitted by three positioning pins 56 and guide grooves 57, and the eccentric pin 59 is rotatably held by the base member 51 and fitted into the elliptical hole 58 of the board A52. By rotating, the substrate A52 and the substrate B53 with respect to the base member 51,
That is, the projection optical system 1 is moved in the direction of the arrow E (the light valve 4).
(The direction parallel to the plane including the optical path L2 from 00R, 400G, 400B to the prism 610 and the optical axis 140 of the lamp 110). By providing a similar mechanism in a different direction, the movement can be adjusted in a direction orthogonal to the arrow E. Note that the movement adjustment mechanism may be configured to be adjustable in both directions of arrow E and a direction orthogonal to arrow E.

The front group 660 and the rear group 650 of the projection lens 600 folded by the prism 610 and their optical axes are in a right angle relationship. Therefore, the relative position between the projection optical system 1 and the rear screen 3 can be adjusted by moving the projection optical system 1 horizontally or vertically with respect to the plane of the substrate B53, which is the fixing surface, by the adjustment mechanism. Yes, the adjustment mechanism is simplified.

Further, by arranging the projection optical system 1 at an angle with respect to the housing bottom surface 41, a space is secured on the rear screen 3 side of the projection optical system 1. Therefore, by utilizing the space, as shown in FIG. 6, the wind 810 passed by the cooling fan 800 provided at the lower part of the projection optical system 1 efficiently enters the projection optical system 1 through the opening 54 of the base means 5. It becomes possible to take in. That is, the light valve and the polarizing plate around the light valve can be effectively cooled without specially providing a space for cooling.

(Second Embodiment) FIG. 7 is a plan view showing a main part of a projection optical system 1 'according to a second embodiment of the present invention. FIG. It is a top view of the rear projector 20 stored in 4 '.

FIG. 7 is different from the first embodiment shown in FIG. 2 in that the optical axis 140 of the lamp 110 constituting the illumination optical system 100 ′ is a longitudinal section including the normal 6 at the center of the rear screen 3. 7 (plane parallel to the xz plane in FIG. 8).

That is, the illumination optical system 100 ′ further has a reflection mirror 150, and the lamp 110
The illumination light emitted from the light source enters the reflection mirror 150 while being uniformed and polarized by the integrator optical system 120 and the polarization conversion optical system 130, and the optical path is changed by 90 degrees by the reflection mirror 150. The light enters a first dichroic mirror 210 that separates the B light flux. Other than that, it is the same as the first embodiment. In the description of the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those used in FIGS. 1 to 6, and the detailed description thereof will be omitted.

When the projection optical system 1 'is disposed in the housing 4' at an angle .theta. With respect to the housing bottom similarly to the projection optical system 1 of the first embodiment, the optical axis of the lamp 110 is also changed. The arrangement is inclined at an angle θ with respect to the body bottom. Unless the lamp 110 is particularly designed for vertical lighting, the horizontal lighting shown in the first embodiment is desirable. However, if the lamp 110 is slightly inclined, its influence on the life is small. On the other hand, by arranging the optical axis 140 of the lamp 110 so as to be parallel to the longitudinal section 7 as described above, as shown in FIG.
10 is disposed on the screen 3 side of the rear projector 20, and a space can be made on the side of the rear projector 20. Therefore, the lamp 11 from the screen 3 side (front side) of the rear projector 20
It is possible to replace the zero, maintenance becomes easy, and it is also possible to make a novel design in which the side surface is cut.

In the rear projector according to the present embodiment, the effect of being able to maintain the lamp in the horizontally lit state cannot be obtained, but the other parts have the same effects as those described in the first embodiment. It is possible to get.

The illumination optical system 10 including the lamp 110
The arrangement of 0 'is not limited to the above, and the illumination optical system 100' can be used when the projection optical system 1 'is housed in the housing 4 by rotating the optical system from the lamp 110 to the reflection mirror 150 around the optical axis by an angle θ.
May be arranged so as to be parallel to the bottom surface of the housing.

(Third Embodiment) FIG. 9 is a plan view showing a main part of a projection optical system 1 '' according to a third embodiment of the present invention. In the first and second embodiments described above, the case where a projection optical system in which a transmission type liquid crystal panel is used as a light valve is used as an example, but in the present embodiment, a reflection type liquid crystal panel is used. In that it is a projection optical system 1 ″. In the description of the present embodiment, the same components as those in the first and second embodiments will be described with reference to FIG.
The same reference numerals as those used in Nos. To 8 are used, and the detailed description thereof is omitted.

The projection optical system 1 ″ includes an illumination optical system 100.
, A color light separation optical system 200 ′, and a relay optical system 300 ′.
And polarizing beam splitters 700R, 700G, 700
B and light valves 400R ', 400G', 400
B ′, a cross dichroic prism 500 ′, and a projection lens 600 ′.

The light emitted from the illumination optical system 100 enters the color light separation optical system 200 'and is separated into three color lights. The first dichroic mirror 210 ′ transmits the B light and reflects the color light (G light and R light) on the longer wavelength side than the B light.

Of the G light and the R light reflected by the first dichroic mirror 210 ', the R light passes through the second dichroic mirror 220', passes through the field lens 240 ', and passes through the R polarizing beam splitter. 70
It is incident on 0R. The G light is reflected by the second dichroic mirror 220 ′, and is reflected by the field lens 250 ′.
Through the polarization beam splitter 700G for G.

The B light transmitted through the first dichroic mirror 210 'passes through the relay optical system 300', that is, the entrance side lens 310 ', the relay reflection mirror 320', and the relay lens 330 ', and further, the exit side lens 350'. Through the polarization beam splitter 700B for B.

The polarization beam splitter 700R for each color,
Each color light that has entered 700G and 700B is split into two types of polarized light (s-polarized light and p-polarized light) by the polarization splitting surfaces 710R, 710G and 710B of the corresponding polarizing beam splitters 700R, 700G and 700B. The light valves 400R ', 400G', 400B 'for each color are provided with the corresponding polarizing beam splitters 700R, 700G, 700B.
Are arranged on the optical axis of one of the polarized lights emitted from the light source. In the example of the figure, each polarization beam splitter 700
R, 700G, 700B polarization splitting surfaces 710R, 710
G and 710B reflect the s-polarized light and transmit the p-polarized light, and the light valves 400R 'and 400
G ′ and 400B ′ are arranged on the optical axis of the s-polarized light. Therefore, each color light of the s-polarized light enters the corresponding light valve 400R ', 400G', 400B 'as illumination light.

Light valves 400R ', 400 for each color
G ′ and 400B ′ are reflection-type liquid crystal panels, which modulate the respective color lights incident as illumination light according to the corresponding color signals (image information) and emit the reflected light.

Light valves 400R ', 400 for each color
The light emitted from G ′, 400B ′ re-enters the corresponding color beam splitter 700R, 700G, 700B. The re-entered color lights are mixed lights containing modulated light (p-polarized light) and unmodulated light (s-polarized light). Therefore, of the emission lights of each color, only the modulation light corresponds to the polarization beam splitters 700R and 700R.
G, 700B polarization separation surfaces 710R, 710G, 710
B passes through and enters the cross dichroic prism 500 '.

The respective color lights incident on the cross dichroic prism 500 'are combined and emitted toward the projection lens 600'. As a result, a color image represented by the light synthesized by the cross dichroic prism 500 'is projected by the projection lens 600'.

The projection optical system 1 ″ is housed in a housing in the same manner as the projection optical system 1 of the first embodiment. Therefore, according to the present embodiment, the same effect as that of the first embodiment can be obtained.

As the reflective light valve, a digital micromirror device (trademark of TI) may be used instead of the reflective liquid crystal panel. However, in an electro-optical device that does not use polarization, such as a digital micromirror device, the polarization beam splitter 7
00R, 700G, 700B and the polarization conversion optical system 130 are unnecessary.

The optical system using the reflection type light valve is not limited to the configuration of the present embodiment.
It is also possible to configure the color separation optical system and the color synthesis optical system with a common optical element.

(Other Embodiments) The present invention
The present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are also possible. (1) In the above embodiment, the integrator optical system 120
And the polarization conversion optical system 130, the present invention,
The present invention is also applicable to a rear projector that does not use such an optical system. (2) In the above embodiment, the rear projector using three light valves has been described. However, the number of light valves is not limited to three, and may be one, two, or four or more. . The portion of the color light separation optical system 200 and the cross dichroic prism 500 may be changed to a configuration different from the above embodiment according to the number and type of light valves,
It is also possible to omit it.

[0068]

As described above, the rear projector according to the present invention has a configuration in which the optical path is bent 90 degrees inside the projection lens and the projection optical system is inclined with respect to the bottom of the housing, so that the rear projector is located immediately before the rear screen. It is possible to arrange the mirror so that the tilt angle of the mirror approaches the vertical direction, and it is possible to reduce the thickness of the rear projector. Also, the front and rear groups of the folded projection lens and their optical axes are in a right angle relationship,
The distance between the front group and the rear group can be reduced to a minimum, eliminating the need to cut the lens unnecessarily, improving the freedom of design and manufacture of the projection lens, improving the performance of the projection lens and reducing costs Has the effect of causing Further, the relative position between the projection optical system and the rear screen can be adjusted by moving the projection optical system parallel and / or perpendicular to a plane including the optical path of the projection light and the optical axis of the lamp, and the adjustment mechanism is simplified. Be transformed into Furthermore, since the projection optical system is arranged at an angle to the bottom surface of the housing, air can be easily taken into the projection optical system, and effective cooling can be performed without specially providing a space for cooling. it can.

[Brief description of the drawings]

FIG. 1 is a side view showing a schematic configuration of a rear projector as a first embodiment of the invention.

FIG. 2 is a plan view showing a main part of the projection optical system according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a case where the projection optical system having the configuration shown in FIG. 2 is housed in a housing of a rear projector.

FIG. 4 is a schematic diagram for explaining a configuration of a prism in the projection lens according to the first embodiment of the present invention.

5A and 5B are specific examples of base means for arranging the projection optical system according to the first embodiment of the present invention, wherein FIG. 5A is a side view, FIG. () Is a view of substrate A52 viewed from A. FIG.

FIG. 6 is a diagram for explaining a state of ventilation by a cooling fan according to the first embodiment of the present invention.

FIG. 7 is a plan view illustrating a main part of a projection optical system according to a second embodiment of the present invention.

8 is a plan view of a rear projector in which a projection optical system in FIG. 7 is housed in a housing.

FIG. 9 is a plan view showing a main part of a projection optical system according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Projection optical system 2 ... Mirror 3 ... Rear screen 4 ... Case 5 ... Base means 6 ... Normal line at the center of rear screen 7 ... Longitudinal section including normal line 10 ... Rear projector 20 ... Rear projector 100 ... Illumination optical system Reference Signs List 110 lamp 120 integrator optical system 130 polarization conversion optical system 140 optical axis of lamp 110 200 color light separation optical system 210, 220 dichroic mirror 230 reflection mirror 240, 250 field lens 300 relay optical system 310 Incident side lens 320, 340 Relay relay mirror 330 Relay lens 350 Exit side lens (field lens) 400R, 400G, 400B Light valve 500 Cross dichroic prism 510 First dichroic surface 520 Second dichroic 530 ... exit plane 600 ... projection lens 700R, 700G, 700B ... polarizing beam splitter 710R, 710G, 710B ... polarization separating surface

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/31 H04N 9/31 C

Claims (6)

[Claims] A projection optical system comprising: a light source; an electro-optical device for generating an image using illumination light from the light source; and a projection lens for enlarging and projecting the image light from the electro-optical device; A rear projector including a housing that houses a projection optical system and a rear screen installed on a front surface of the housing, wherein an optical path from the electro-optical device to the rear screen is a center of the rear screen. Has two optical path converting means for folding back in a vertical section including the normal line, and one of the two optical path converting means is arranged so as to fold the optical path by 90 degrees inside the projection lens. Wherein the projection optical system is arranged such that an optical path from the electro-optical device to the one optical path conversion unit is inclined with respect to a bottom surface of the housing. . 2. The rear projector according to claim 1, wherein the light source includes a lamp, and the lamp is arranged such that an optical axis of the lamp is orthogonal to the longitudinal section. Rear projector. 3. The rear projector according to claim 1, wherein the light source includes a lamp, and the lamp is arranged such that an optical axis of the lamp is parallel to the longitudinal section. Rear projector. 4. The rear projector according to claim 1, wherein the one of the optical path changing means disposed inside the projection lens is a right-angle prism. 5. The rear projector according to claim 1, wherein the projection optical system is configured to adjust an optical path from the electro-optical device to the one optical path conversion unit and an optical axis of the lamp. A rear projector having adjusting means for moving in a direction parallel and / or orthogonal to a plane including the rear projector. 6. The rear projector according to claim 1, further comprising a cooling unit that passes cooling air from below to the projection optical system.