JP4595441B2 - projector - Google Patents

Description

  The present invention relates to a projector.

Conventionally, a plurality of light modulation devices that form an optical image by modulating a light beam emitted from a light source according to image information, a color combining optical device that combines and emits a light beam modulated by each light modulation device, A projector is known that includes a projection optical device that magnifies and projects a light beam synthesized by a color synthesis optical device.
In such a projector, an exit-side polarizing plate composed of a single polarizing element (optical conversion element) that transmits a light beam having a predetermined polarization axis is disposed on the light beam exit side of the light modulation device. Of the light flux that has passed through the light modulation device, the light flux that does not have a predetermined polarization axis is absorbed by the exit-side polarizing plate, and heat is likely to be generated in the exit-side polarizing plate.
Therefore, a method has been proposed in which the exit-side polarizing plate is composed of two polarizing elements and the heat generated by the exit-side polarizing plate is apportioned (see, for example, Patent Document 1).

JP 2004-102115 A (page 8, FIG. 2)

However, in the conventional projector, since two polarizing elements are installed in a narrow gap between the light modulation device and the color synthesizing optical device, the distance between the light modulation device and one of the polarization elements, a pair of The distance between the polarizing elements and the distance between the other polarizing element and the color synthesizing optical device become very narrow.
Cooling air is used for cooling the exit-side polarizing plate. The cooling air flow path, that is, the gap between the light modulator and one polarizing element, the gap between a pair of polarizing elements, and the other polarizing element In addition, since the gap between the color synthesis optical devices is very narrow, it is difficult to smoothly pass the cooling air. Therefore, even if the heat generated in the exit side polarizing plate is distributed to each polarizing element, it is difficult to dissipate the heat of each polarizing element, and there is a problem that the polarizing elements cannot be sufficiently cooled.

  An object of the present invention is to provide a projector capable of sufficiently cooling an optical conversion element disposed between a light modulation device and a color synthesis optical device.

The projector of the present invention includes a plurality of light modulation devices that modulate light beams emitted from a light source for each color light according to image information, a color combining optical device that combines light beams modulated by the light modulation devices, and the color A projection optical device that enlarges and projects the color light synthesized by the synthesis optical device to form a projection image, while maintaining an optical distance between the projection optical device and the light modulation device at a predetermined distance , A translucent substrate for adjusting a geometric distance between the light modulation device and the color synthesis optical device, the light modulation device, and the color synthesis optical device arranged and incident An optical conversion element that optically converts the luminous flux to be transmitted, the translucent substrate is disposed between the color synthesizing optical device and the projection optical device, and the color synthesizing optical device includes: Modulated by each light modulator A plurality of light flux incident side end surfaces on which the bundle is incident, and a prism having a light beam emission side end surface that emits a light beam obtained by combining the light beams incident on the light flux incident surfaces, It has a refractive index substantially equal to that of a prism .

Here, the translucent substrate according to the present invention is configured so that a geometric distance between the light modulation device and the color synthesis optical device is maintained while maintaining an optical distance between the projection optical device and the light modulation device at a predetermined distance. The target distance is adjusted.
In other words, other conventional projectors that do not have a translucent substrate (including a light modulation device similar to the projector of the present invention, a color synthesis optical device, a projection optical device, and an optical conversion element are provided. The geometric relative positional relationship between the color synthesizing optical device and the projection optical device is the same as that of the projector of the present invention), the optical distance between the projection optical device and the light modulation device, the projection optical device of the present invention, and the The optical distance between the light modulation devices is equal.

Here, in the projector according to the present invention, the light modulation device, the optical conversion element, the color synthesis optical device, the translucent substrate, and the projection optical device are arranged in this order in the light beam emission direction.
In the projector of the present invention, the geometric distance from the projection optical device to the color synthesis optical device is C, and the distance between the color synthesis optical device and the light modulation device is X. Furthermore, the thickness dimension of the translucent substrate is E, the thickness dimension of the color synthesis optical device is H, and the thickness dimension of the optical conversion element is F. Further, the refractive index of the translucent substrate is N ₁ , the refractive index of the optical conversion element is N ₂ , and the refractive index of the color combining optical device is N ₃ .
The optical distance S1 from the projection optical device of the projector of the present invention to the light modulation device as described above is expressed by the following equation (1).
S1 = X−F + F / N ₂ + H / N ₃ + E / N ₁ + CE (1)

On the other hand, in the other projector that is different from the projector of the invention in that it does not have a translucent substrate, if the distance from the color synthesis optical device to the light modulation device is A, the optical from the projection optical device to the light modulation device The target distance S1 ′ is expressed by the following equation (2).
S1 ′ = AF−F / N ₂ + H / N ₃ + C (2)
Since S1 = S1 ′, X = A + E (N ₁ −1) / N ₁ , and in the projector of the present invention, the geometric distance from the color synthesizing optical device to the light modulation device is E compared to other projectors. It can be seen that (N ₁ -1) / N becomes longer by ₁ minute.

According to the present invention, the light transmissive substrate is disposed between the color synthesizing optical device and the projection optical device, so that the light modulation is achieved as compared with the other conventional projectors in which the light transmissive substrate is not installed. The geometric distance between the device and the color synthesis optical device is increased.
As a result, the gap between the optical conversion element and the light modulation device and the gap between the optical conversion element and the color synthesizing optical device are increased, and it becomes possible to smoothly pass cooling air having a sufficient flow rate. Therefore, the optical conversion element can be sufficiently cooled.
The optical conversion element may be a single sheet or a plurality of sheets.
Even when the optical conversion element is a polarizing element and the exit-side polarizing plate is composed of a single polarizing element, in the present invention, the gap between the polarizing element and the light modulation device, the polarizing element and the color composition are combined. A large gap with the optical device can be secured, and cooling air with a sufficient flow rate can be smoothly passed, so that the polarizing element can be sufficiently cooled.
In the present invention, the translucent substrate has a refractive index substantially equal to that of the prism.
According to the present invention as described above, the refractive index of the light-transmitting substrate and the refractive index of the prism are substantially equal to each other, so that when the light beam from the prism enters the light-transmitting substrate, the end surface on the light beam exit side of the prism In addition, the loss due to the interface reflection of the light beam generated between the light beam incident side end faces of the translucent substrate can be minimized.

In the present invention, an optical system for causing a light beam to be incident on the light modulation device is disposed in a front stage of the light modulation device, and the translucent substrate includes the color synthesis optical device and the projection. when placed between the optical device and the optical system, and the color synthesizing optical system, one holding electrolyte geometrical relative positional relationship between the projection optical device in a fixed, before Symbol light modulation device, It is preferable to have a thickness dimension and a refractive index that increase a geometric distance to the color synthesis optical device.
The geometric relative positional relationship among the optical system, the color synthesizing optical device, and the projection optical device in the projector according to the present invention is the same as that of the optical system in the other conventional projector described above. It is equal to the geometric relative positional relationship between the optical device and the projection optical device. In other words, the geometric distance from the optical system to the projection optical apparatus in the projector of the present invention is equal to the geometric distance from the optical system to the projection optical apparatus in another conventional projector.
Therefore, in the present invention, even if a large geometric distance is ensured between the light modulation device and the color synthesizing optical device by arranging the translucent substrate, from the optical system to the projection optical device. Therefore, the projector can be prevented from being enlarged.

In the present invention, it is preferable that a plurality of optical conversion elements are arranged between the light modulation device and the color synthesis optical device.
According to the present invention, as described above, a large gap can be secured between the color synthesizing optical device and the light modulation device. The flow path is not narrowed, and each optical conversion element can be sufficiently cooled.
Here, for example, if a plurality of optical conversion elements are used as a pair of polarizing elements, the generated heat can be divided into two compared to the case where only one polarizing element is arranged. The amount of heat generated can be reduced. Furthermore, the geometric distance between the light modulation device and the color synthesis optical device can be ensured, and the flow path of the cooling air is not narrowed, so that each polarizing element can be efficiently cooled. Thereby, the thermal deterioration of a polarizing element can be prevented reliably.

In the present invention, the plurality of optical conversion elements are a pair of polarizing elements, the thickness dimension of one polarizing element is G, the thickness dimension of the translucent substrate is E, and the refractive index of one polarizing element. Is N ₄ , and the refractive index of the translucent substrate is N ₁ ,
It is preferable that the condition of G (N ₄ −1) / N ₄ <E (N ₁ −1) / N ₁ .

Here, as described above, the geometric distance from the projection optical device to the color synthesis optical device is C, and the distance between the color synthesis optical device and the light modulation device is X. Furthermore, the thickness dimension of the translucent substrate is E, the thickness dimension of the color synthesis optical device is H, the thickness dimension of one polarizing element is G, and the thickness dimension of the other polarizing element is F. Further, the refractive index of the translucent substrate is N ₁ , the refractive index of _one polarizing element is N ₄ , the refractive index of the other is N ₂ , and the refractive index of the color synthesizing optical device is N ₃ .
The optical distance S2 from the projection optical device to the light modulation device is expressed by the following equation (4).
S2 = X−F + F / N ₂ −G + G / N ₄ + H / N ₃ + E / N ₁ + C−E (4)

On the other hand, the optical distance S1 ′ from the projection optical device to the light modulation device in another projector, which is different only in that it does not have the translucent substrate and one of the pair of polarizing elements, is S1 ′ = a _{a-F + F / N 2} + H / N 3 + C.
Therefore, in the projector of the present invention, the geometric distance from the color synthesizing optical device to the light modulation device is G (N ₄ −1) / N ₄ + E (N ₁ −1) / N ₁ compared to the other projectors. It will increase by minutes.
E (N ₁ -1) / N ₁ is an increase in the gap generated between the color synthesizing optical device and the light modulation device due to the arrangement of the translucent substrate, and G (N ₄ -1) / N ₄ is a reduction in the gap generated between the color synthesizing optical device and the light modulation device due to the arrangement of one polarizing element.
That is, in the present invention, a pair of polarizing elements is arranged between the light modulation device and the color synthesis optical device by setting G (N ₄ −1) / N ₄ <E (N ₁ −1) / N _1. Even in this case, a sufficient gap can be ensured between the light modulation device and the color synthesizing optical device, so that each polarizing element can be sufficiently cooled.

Furthermore, in the present invention, it is preferable that the translucent substrate is attached to a light beam emission side end face of the color synthesis optical device.
In general, according to the present invention, in order to prevent the reflection of the light beam, it is necessary to attach an antireflection film to the light beam incident side end surface of the translucent substrate and the light beam emission side end surface of the color synthesis optical device. is there. By attaching the translucent substrate to the color combining optical device, the end surface of the light transmitting side of the light transmitting substrate and the end surface of the light combining side of the color combining optical device are in close contact with each other. There is no need to attach an antireflection film to the side end face and the end face of the color combining optical device on the light beam exit side. Thereby, the number of members can be reduced, and the labor for forming the antireflection film can be simplified, so that the cost can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an optical system of the projector 1.
The projector 1 modulates the light beam emitted from the light source device according to image information to form an optical image, and enlarges and projects the formed optical image. As shown in FIG. 1, the projector 1 includes an integrator illumination optical system 10, a color separation optical system 20 as a color separation optical device, a relay optical system 30, an optical modulation device, and a color synthesis optical device. The apparatus 40 and a projection lens 50 as a projection optical apparatus are configured, and the optical components 10 to 40 are positioned and adjusted and accommodated in an optical component casing 60 in which a predetermined illumination optical axis K is set. ing. The projection lens 50 is installed in the optical component housing 60 at a predetermined position with respect to the optical components 10 to 40.

The integrator illumination optical system 10 is an optical system for making the illuminance of the light beam emitted from the light source uniform in the plane orthogonal to the illumination optical axis, and includes the light source device 11, the collimating concave lens 12, the first lens array 13, and the second lens array 13. A lens array 14, a polarization conversion element 15, and a superimposing lens 16 are provided.
The light source device 11 includes a light source lamp 17 as a radiation light source, a reflector 18, and a windshield 19 that covers an end surface on the light emission side of the reflector 18, and a radial light beam emitted from the light source lamp 17 is reflected by the reflector 18. The collimated concave lens 12 makes a substantially parallel light beam and emits it to the outside. In this example, a high-pressure mercury lamp is used as the light source lamp 17, but a metal halide lamp or a halogen lamp may be used in addition to this. In this example, a configuration in which the collimating concave lens 12 is disposed on the exit surface of the reflector 18 formed of an ellipsoidal mirror is employed, but a parabolic mirror may be employed as the reflector 18.

The first lens array 13 has a configuration in which small lenses having a substantially rectangular outline as viewed from the illumination optical axis direction are arranged in a matrix. Each small lens splits the light beam emitted from the light source lamp 17 into partial light beams and emits them in the direction of the illumination optical axis.
The second lens array 14 has substantially the same configuration as the first lens array 13 and includes a configuration in which small lenses are arranged in a matrix. The second lens array 14 has a function of forming an image of each small lens of the first lens array 13 together with the superimposing lens 16 on a liquid crystal panel as a light modulation device to be described later.

The polarization conversion element 15 converts the light from the second lens array 14 into a single type of polarized light, thereby improving the light use efficiency in the optical device 40.
Specifically, each partial light beam converted into one type of polarized light by the polarization conversion element 15 is finally superimposed on a liquid crystal panel (described later) of the optical device 40 by the superimposing lens 16. In a projector using a liquid crystal panel of a type that modulates polarized light, only one type of polarized light can be used, and therefore approximately half of the light flux from the light source lamp 17 that emits randomly polarized light is not used. For this reason, by using the polarization conversion element 15, the light beam emitted from the light source lamp 17 is converted into substantially one type of polarized light, and the use efficiency of light in the optical device 40 is enhanced. Such a polarization conversion element 15 is introduced in, for example, Japanese Patent Application Laid-Open No. 8-304739. One type of polarized light is polarized light in which the vector directions are aligned in one direction.

The color separation optical system 20 includes a reflection mirror 21 that bends the light beam emitted from the integrator illumination optical system 10, two dichroic mirrors 22 and 23, and a reflection mirror 24. The dichroic mirrors 22 and 23 provide integrator illumination. It has a function of separating a plurality of partial light beams emitted from the optical system 10 into three color lights of red (R), green (G), and blue (B). In this example, the reflection mirror 24 can be adjusted in posture with respect to the optical component casing 60.
The relay optical system 30 includes an incident side lens 31, a relay lens 33, and reflection mirrors 32 and 34, and red light that is color light separated by the color separation optical system 20 up to a liquid crystal panel for red light described later. Has a guiding function.

  At this time, the dichroic mirror 22 of the color separation optical system 20 reflects the red light component and the green light component and transmits the blue light component of the luminous flux emitted from the integrator illumination optical system 10. The blue light transmitted by the dichroic mirror 22 is reflected by the reflection mirror 24, passes through the field lens 25, and reaches a liquid crystal panel for blue light to be described later. The field lens 25 converts each partial light beam emitted from the second lens array 14 into a light beam substantially parallel to the illumination optical axis K. The same applies to the field lens 25 provided on the light incident side of the other liquid crystal panels for green light and red light.

Of the red light and green light reflected from the dichroic mirror 22, the green light is reflected by the dichroic mirror 23, passes through the field lens 25, and reaches a later-described green light liquid crystal panel. On the other hand, the red light passes through the dichroic mirror 23, passes through the relay optical system 30, passes through the field lens 25, and reaches a later-described red light liquid crystal panel.
The relay optical system 30 is used for red light because the optical path length of the red light is longer than the optical path lengths of the other color lights, thereby preventing a decrease in light utilization efficiency due to light divergence or the like. Because. That is, this is to transmit the partial light beam incident on the incident side lens 31 to the field lens 25 as it is. The relay optical system 30 is configured to pass red light of the three color lights, but is not limited thereto, and may be configured to pass blue light, for example.

  The optical device 40 modulates an incident light beam according to image information to form a color image, and includes three incident-side polarizing plates 42 on which the respective color lights separated by the color separation optical system 20 are incident. A liquid crystal panel 41 as a light modulation device disposed downstream of each incident side polarizing plate 42 (41R is a liquid crystal panel for red light, 41G is a liquid crystal panel for green light, and 41B is a liquid crystal panel for blue light) And an exit-side polarizing plate 44 and a cross dichroic prism 45.

The liquid crystal panels 41R, 41G, and 41B include three panel bodies serving as light modulation elements that modulate each color light separated by the color separation optical system 20 according to image information, and three light modulation elements that house these panel bodies. And a holding frame.
Among these, the panel main body uses, for example, a polysilicon TFT as a switching element, and each color light separated by the color separation optical system 20 is incident on the panel main body and the front and rear stages thereof. The side polarizing plate 42 and the emission side polarizing plate 44 are modulated according to image information to form an optical image.

The incident-side polarizing plate 42 transmits only polarized light in a certain direction out of each color light separated by the color separation optical system 20 and absorbs other light beams. A polarizing film is formed on a substrate such as crystal or sapphire. The film is formed. Further, the polarizing film may be attached to the field lens 25 without using the substrate.
The exit side polarizing plate 44 transmits only polarized light in a predetermined direction and absorbs other light beams among the light beams modulated by the liquid crystal panels 41R, 41G, and 41B. In this example, a pair of polarizing elements (optical conversion elements) 44P and 44A are provided. The two exit-side polarizing plates 44 are configured in this way because the incident polarized light is divided and absorbed by each of the polarizing elements 44P and 44A, so that the heat generated by the polarized light is absorbed by both polarizing elements. This is because it is apportioned by 44P and 44A to suppress each overheating.

The cross dichroic prism 45 synthesizes an optical image emitted from the emission side polarizing plate 44 and modulated for each color light to form a color image.
The cross dichroic prism 45 is provided with a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light in a substantially X shape along the interface of four right-angle prisms. Three color lights are synthesized by the multilayer film.

The projection lens 50 has a function as a projection optical device that magnifies and projects an optical image formed by the optical device 40, and is configured as a combined lens in which a plurality of lenses are housed in a cylindrical lens barrel. The
The optical component casing 60 is a synthetic resin product by injection molding or the like, and although not shown, the optical component 10 to 40 described above is housed inside and the projection lens 50 is placed at a predetermined position with respect to the optical component 10 to 40. A lower casing to be installed and an upper casing that closes an opening of the lower casing.

In the optical system as described above, as shown in FIG. 2, a translucent substrate 46 is attached to the end surface of the cross dichroic prism 45 on the light emission side. The translucent substrate 46 is for adjusting the geometric distance between the light beam incident side end surface of the cross dichroic prism 45 and the light beam emission side end surface of the liquid crystal panel 41.
The translucent substrate 46 is a flat rectangular plate-shaped body having substantially the same size and shape as the light beam incident side end surface of the cross dichroic prism 45. The translucent substrate 46 has a refractive index substantially equal to that of the cross dichroic prism 45. For example, when the cross dichroic prism 45 is made of borosilicate glass (for example, BK7: trade name) having a high refractive index, the transparent substrate 46 is also made of the same borosilicate glass (for example, BK7: trade name). ) Is preferable.
In addition, the adhesive for attaching the translucent substrate 46 to the end surface on the light emission side of the cross dichroic prism 45 has a refractive index equivalent to that of the cross dichroic prism 45.
Although not shown, an antireflection film is formed on the end surface of the light transmitting side of the translucent substrate 46.

When the translucent substrate 46 is not attached to the light beam incident side end surface of the cross dichroic prism 45, the light beam incident side end surface of the translucent substrate 46 or the cross dichroic prism 45 is used to prevent reflection of the light beam. It is necessary to form an antireflection film on the light exit end face.
As in the present embodiment, by attaching the translucent substrate 46 to the end surface on the light emission side of the cross dichroic prism 45, the light incident end surface of the translucent substrate 46 and the light exit surface of the cross dichroic prism 45 are in close contact with each other. Therefore, it is not necessary to attach an antireflection film to the light beam incident end surface of the translucent substrate 46 and the light beam emission side end surface of the cross dichroic prism 45. As a result, the number of members can be reduced, the labor for forming the antireflection film can be simplified, and the manufacturing cost can be reduced.
In the present embodiment, the refractive index of the transparent substrate 46 and the refractive index of the cross dichroic prism 45 are made substantially equal, and the refractive index of the adhesive that bonds the transparent substrate 46 and the cross dichroic prism 45 together. Since the rate is substantially equal to that of the translucent substrate 46 and the cross dichroic prism 45, the cross dichroic generated when the light beam emitted from the cross dichroic prism 45 passes through the adhesive and is introduced into the translucent substrate 46. Interface reflection between the prism 45 and the adhesive and interface reflection between the adhesive and the translucent substrate 46 can be reduced. Thereby, the loss of the light beam due to the interface reflection can be minimized.

The optical distance S2 from the projection lens 50 of the projector 1 of the present embodiment as described above to the liquid crystal panel 41 (the liquid crystal panel 41G is illustrated in FIG. 2) is another conventional projector 100 as shown in FIG. Is equal to the optical distance S1 ′ from the projection lens 50 to the liquid crystal panel 41 (the liquid crystal panel 41G is illustrated in FIG. 3). That is, by arranging the translucent substrate 46, the light beam incident side end surface of the cross dichroic prism 45 and the light beam emission side of the liquid crystal panel 41 while maintaining the optical distance between the projection lens 50 and the liquid crystal panel 41 at a predetermined distance. The geometric distance between the end faces can be adjusted.
The other projector 100 differs from the projector 1 of the present embodiment only in that it does not have the translucent substrate 46 and does not have one polarizing element 44P.
Furthermore, the geometric relative positional relationship among the projection lens 50, the cross dichroic prism 45, and the optical system for causing the light beam to enter the liquid crystal panel 41 including the incident side polarizing plate 42 in the other projector 100 is the present embodiment. This is equal to the geometric relative positional relationship between the projection lens 50, the cross dichroic prism 45, and the optical system for causing the light beam to enter the liquid crystal panel 41 including the incident side polarizing plate 42 in the projector 1 of the embodiment. In other words, the geometric distance from the projection lens 50 to the incident side polarizing plate 42 in the other projector 100 is equal to the geometric distance from the projection lens 50 to the incident side polarizing plate 42 in the projector 1.
The liquid crystal panel 41 and the cross dichroic are arranged by arranging the translucent substrate 46 while keeping the geometric relative positional relationship among the incident side polarizing plate 42, the cross dichroic prism 45 and the projection lens 50 constant. The geometric distance to the prism 45 is adjusted.

Here, an optical distance S2 from the projection lens 50 of the projector 1 of the present embodiment to the liquid crystal panel 41 is assumed, and a geometric distance from the projection lens 50 to the cross dichroic prism 45 is assumed to be C. Also, let X be the distance between the cross dichroic prism 45 and the liquid crystal panel 41.
Further, the thickness dimension of the translucent substrate 46 (thickness dimension along the illumination optical axis K) is E, the thickness dimension of the cross dichroic prism 45 (thickness dimension along the illumination optical axis K) is H, The thickness dimension (thickness dimension along the illumination optical axis K) of the polarizing element 44P is G, and the thickness dimension (thickness dimension along the illumination optical axis K) of the other polarization element 44A is F.
Further, the refractive index of the transparent substrate 46 N _1, the refractive index of one of the polarizing element 44P N _4, the refractive index of the other polarizing element 44A and N _2, the refractive index of the cross dichroic prism 45 and N ₃ To do.
The optical distance S2 from the projection lens 50 of the projector 1 of the present embodiment to the liquid crystal panel 41 is expressed by the following equation (5).
S2 = X−F + F / N ₂ −G + G / N ₄ + H / N ₃ + E / N ₁ + CE (5)

On the other hand, if the distance between the cross dichroic prism 45 and the liquid crystal panel 41 in the other projector 100 is A, the optical distance S1 ′ from the projection lens 50 of the other projector 100 to the liquid crystal panel 41 is S1 ′ = A. -F a _{+ F / N 2 + H /} N 3 + C.
As described above, the optical distance S2 from the projection lens 50 of the projector 1 of the present embodiment to the liquid crystal panel 41 and the optical distance S1 ′ from the projection lens 50 of the other projector 100 to the liquid crystal panel 41 are equal. Since S2 = S1 ′, the distance X between the cross dichroic prism 45 and the liquid crystal panel 41 is as follows.
X = A + G (N ₄ −1) / N ₄ + E (N ₁ −1) / N ₁ (6)

In the projector 1 of this embodiment, the distance between the liquid crystal panel 41 and the cross dichroic prism 45 is increased by the amount (α) shown in the following equation (7), compared to the other projectors 100.
X−A = α = G (N ₄ −1) / N ₄ + E (N ₁ −1) / N ₁ (7)
In this way, the translucent substrate 46 is attached to the cross dichroic prism 45 and disposed between the cross dichroic prism 45 and the projection lens 50, so that the translucent substrate 46 is not installed, as compared to other projectors 100. The geometric distance between the liquid crystal panel 41 and the cross dichroic prism 45 is increased.
As a result, the gap between the one polarizing element 44P disposed between the liquid crystal panel 41 and the cross dichroic prism 45 and the liquid crystal panel 41, the gap between the other polarizing element 44A and the cross dichroic prism 45, the polarizing elements 44P, The gap between 44A becomes large, and it becomes possible to let cooling air pass smoothly. Therefore, the one polarizing element 44P and the other polarizing element 44A can be sufficiently cooled.

In the formula (7), E (N ₁ −1) / N ₁ is an increase in the gap generated between the cross dichroic prism 45 and the liquid crystal panel 41 due to the arrangement of the translucent substrate 46. Yes, G (N ₄ −1) / N ₄ is a reduction in the gap generated between the cross dichroic prism 45 and the liquid crystal panel 41 due to the arrangement of one polarizing element 44P.
That is, in this embodiment, a pair of polarizing elements 44P is provided between the liquid crystal panel 41 and the cross dichroic prism 45 by setting G (N ₄ −1) / N ₄ <E (N ₁ −1) / N _1. 44A, a sufficient gap can be secured between the liquid crystal panel 41 and the cross dichroic prism 45, so that each of the polarizing elements 44P and 44A can be sufficiently cooled.

In the present embodiment, since the exit-side polarizing plate 44 includes a pair of polarizing elements 44P and 44A, heat generated by the polarizing element compared to the case where the exit-side polarizing plate is configured by a single polarizing element. Can be divided into two, and the amount of heat generated in each of the polarizing elements 44P and 44A can be reduced. Furthermore, as described above, since the cooling air flow path is not narrowed, the respective polarizing elements 44P and 44A can be efficiently cooled. Thereby, thermal deterioration of the polarizing elements 44P and 44A can be reliably prevented.
Furthermore, even if a large geometric distance between the liquid crystal panel 41 and the cross dichroic prism 45 is ensured by arranging the translucent substrate 46, the optical system, the cross dichroic prism 45, the projection lens in the projector 1 are secured. The geometrical relative positional relationship of 50 is equal to the geometrical relative positional relationship of the optical system, the cross dichroic prism 45, and the projection lens 50 in another conventional projector 100, so that an increase in size of the projector 1 can be prevented. Can do.

In the above description, the green light path is illustrated and described with reference to FIG. 2 and FIG. 3, but the same effect naturally occurs in the other color light paths. The optical distance from the projection lens 50 of the projector 1 to the liquid crystal panels 41R and 41B is equal to the optical distance from the projection lens 50 of another conventional projector 100 to the liquid crystal panels 41R and 41B. By disposing the translucent substrate 46, a large geometric distance between the liquid crystal panels 41R and 41B and the cross dichroic prism 45 can be secured, and the polarizing elements 44P and 44A are sufficiently cooled. can do.
Furthermore, by arranging the translucent substrate 46, even if a large geometric distance between the liquid crystal panels 41R and 41B and the cross dichroic prism 45 is secured, the optical system in the projector 1, the cross dichroic prism 45, Since the geometric relative positional relationship of the projection lens 50 is equal to the geometric relative positional relationship of the optical system, the cross dichroic prism 45, and the projection lens 50 in another conventional projector 100, an increase in the size of the projector 1 is prevented. can do.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the said embodiment, although the exit side polarizing plate 44 shall be provided with a pair of polarizing elements 44P and 44A, the exit side polarizing plate may be one polarizing element. Alternatively, when a plurality of polarizing elements are provided, one of the polarizing elements may be attached to the dichroic prism. By doing in this way, the number of members can be reduced.
In the embodiment, only the exit-side polarizing plate 44 is disposed between the cross dichroic prism 45 and the liquid crystal panel 41. However, the present invention is not limited to this, and for example, in addition to the exit-side polarizing plate, a viewing angle compensation plate May be arranged. That is, the viewing angle compensator is also included in the optical conversion element of the present invention.

Further, in the above embodiment, the translucent substrate 46 is attached to the end surface of the cross dichroic prism 45 on the light emission side. However, the translucent substrate 46 is not attached to the end surface of the cross dichroic prism 45 on the light emission side. Also good.
By doing in this way, the effort which affixes the translucent board | substrate 46 to the light beam emission side end surface of the cross dichroic prism 45 can be saved. In this case, it is preferable to form an antireflection film on the light beam exit side end surface of the cross dichroic prism 45 and the light beam incident end surface of the translucent substrate 46.
Moreover, in the said embodiment, although the refractive index of the cross dichroic prism 45 and the refractive index of the translucent board | substrate 46 were substantially equal, both refractive index may differ.
In the above embodiment, only the example of the projector 1 using three liquid crystal panels has been described, but the present invention can also be applied to a projector using four or more liquid crystal panels.
Furthermore, in the above-described embodiment, only the example of the front type projector 1 that performs projection from the direction of observing the screen has been described. However, the present invention is a rear type projector that performs projection from the side opposite to the direction of observing the screen. It is also applicable to.

  The present invention can be used for a projector.

1 is a schematic diagram showing an optical system of a projector according to an embodiment of the invention. The schematic diagram which shows the principal part of the said optical system. FIG. 6 is a schematic diagram showing a main part of an optical system of a conventional projector.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Projector, 41 ... Liquid crystal panel (light modulation apparatus), 44P, 44A ... Polarizing element (optical conversion element), 44 ... Emission side polarizing plate, 45 ... Cross dichroic prism (color synthesis optical apparatus), 46 ... Translucency Substrate, 50 ... projection lens (projection optical device)

Claims (5)

A plurality of light modulation devices that modulate the light beams emitted from the light source for each color light according to image information, a color combining optical device that combines the light beams modulated by the light modulation devices, and the color combining optical device. A projection optical device that forms a projected image by enlarging and projecting the colored light,
A translucent substrate for adjusting a geometric distance between the light modulation device and the color synthesis optical device while maintaining an optical distance between the projection optical device and the light modulation device at a predetermined distance; ,
An optical conversion element that is disposed between the light modulation device and the color synthesis optical device and optically converts an incident light beam;
The translucent substrate is disposed between the color synthesis optical device and the projection optical device ,
The color synthesizing optical device includes a plurality of light beam incident side end surfaces on which light beams modulated by the light modulation devices are incident, and a light beam emission side that emits light beams synthesized from the light beams incident on the light beam incident surfaces. A prism having an end face;
The light-transmitting substrate has a refractive index substantially equal to that of the prism . The projector according to claim 1, wherein
An optical system for making a light beam incident on the light modulation device is disposed in the front stage of the light modulation device,
When the translucent substrate is disposed between the color synthesis optical device and the projection optical device, a geometric relative position of the optical system, the color synthesis optical device, and the projection optical device. one holding quality relationships constant before and Symbol light modulator, a projector, characterized in that it has a geometrical distance increases thickness and refractive index between the color combining optical device. The projector according to claim 1 or 2,
A projector, wherein a plurality of optical conversion elements are arranged between the light modulation device and the color synthesis optical device. The projector according to claim 3, wherein
The plurality of optical conversion elements are a pair of polarizing elements,
When the thickness dimension of one polarizing element is G, the thickness dimension of the translucent substrate is E, the refractive index of one polarizing element is N ₄ , and the refractive index of the translucent substrate is N ₁ ,
A projector characterized by satisfying a condition of G (N ₄ -1) / N ₄ <E (N ₁ -1) / N ₁ . The projector according to any one of claims 1 to 4,
The projector, wherein the translucent substrate is attached to an end surface on the light beam exit side.

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