JP2006058535A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector that prevents a cooling structure in a projector from being made complex and a light source device from deteriorating, and to provide a projector capable of reducing visible light loss. <P>SOLUTION: Light having wavelengths beyond the wavelength area of red light is transmitted through a dichroic mirror, passed through a relay optical system, and further passed through a field lens 418. The optical filter 45 provided for the field lens 418 separates this light into light having wavelengths in the wavelength area of the red light and light having wavelengths beyond the wavelength area of the red light. Only the red light enters a polarizing plate 442R and liquid crystal panel 441R disposed on the incident side for red. An optical filter 45 blocks the transmission of light having wavelengths shorter than the wavelength area of the red light and also blocks the transmission of light having wavelengths in an infrared area (approximately 680nm or longer) that is on the long wavelength side relative to the short wavelength area of red light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a projector.

Conventionally, projectors have been used in fields such as presentations and home theaters. In such a projector, a color separation optical device separates a light beam emitted from a light source device into each color light, and a light modulation device modulates each color light according to image information. Thereafter, the modulated color light is synthesized by the color synthesis optical device, and the formed optical image is enlarged and projected by the projection optical device.
An optical filter for blocking infrared light is arranged on the opening side of the reflector of the light source device so as to be adjacent to this opening, preventing deterioration due to overheating of optical components arranged at the rear stage of the light source device. (For example, refer to Patent Document 1).

Japanese Patent Laying-Open No. 2003-287806 (page 4, FIG. 2)

In the conventional method, since the optical filter is disposed adjacent to the opening side of the reflector of the light source device, all the light beams emitted from the light source device are incident on the optical filter. Therefore, the optical filter may be overheated and deteriorated with the incidence of all the light beams emitted from the light source device. In order to prevent this deterioration, it is necessary to cool the optical filter, and there is a problem that the cooling structure in the projector is complicated.
In addition, as an optical filter that blocks infrared light, an infrared light absorption type that blocks infrared light transmission by absorbing infrared light, and an infrared light absorption type that reflects infrared light. There is an infrared light reflection type that blocks transmission, but when an infrared light reflection type optical filter is used, the optical filter is arranged adjacent to the opening side of the reflector of the light source device. The reflected infrared light is directly reflected by the light source device, and the arc tube of the light source device may be heated and deteriorated.
Further, when an infrared light reflection type optical filter is disposed adjacent to the opening side of the reflector of the light source device, not only infrared light but also visible light is lost due to reflection by the interface of the optical filter.

  An object of the present invention is to provide a projector capable of preventing the cooling structure in the projector from becoming complicated, preventing the deterioration of the light source device, and further reducing the loss of visible light.

  A projector according to the present invention includes a light source device, a color separation optical device having a plurality of color separation optical elements that separate light beams emitted from the light source device into a plurality of color lights including red light, and the color separation optical device. A plurality of light modulation devices that modulate each separated color light according to image information, a color synthesis optical device that synthesizes an optical image modulated by each light modulation device, and a projection that enlarges and projects this synthesized optical image An optical conversion element that converts an optical characteristic of a light beam incident on each light modulation device is disposed between each light modulation device and the color separation optical device. A color separation optical element for separating light in the wavelength region of red light or more and light on a shorter wavelength side than the wavelength region of red light, among the color separation optical elements of the color separation optical device; An optical conversion element on which red light is incident; An optical filter is disposed in the optical path between the optical filters, and the optical filter blocks transmission of light on the shorter wavelength side than the wavelength region of red light and infrared on the longer wavelength side of the wavelength region of red light. It is characterized by having the characteristic of blocking the transmission of light in the region.

Here, the optical filter according to the present invention has a characteristic in which the optical filter that blocks transmission of light shorter than the wavelength region of red light and the optical filter for blocking infrared light described above are integrated. It is what has.
According to the present invention as described above, the color separation optical element for separating the light in the wavelength range of the red light or more and the light on the shorter wavelength side than the wavelength range of the red light, and the optical conversion element on which the red light is incident An optical filter is disposed in the optical path between the two. Accordingly, since the light of the wavelength range of the red light separated by the color separation optical element is incident on the optical filter, compared to the case where all the light beams emitted from the light source device are incident as in the prior art. , Hard to overheat. For this reason, it is not necessary to cool the optical filter, and the cooling structure in the projector can be prevented from becoming complicated.
In addition, when an optical filter that reflects infrared light and blocks light in the infrared region is used, the infrared light reflected by the optical filter returns in the reverse direction along the optical path where the infrared light reaches the optical filter. , Will be distributed. Therefore, unlike the prior art, infrared light is not directly reflected by the light source device, so that deterioration of the light source device can be prevented.
Further, in the optical path between the color separation optical element for separating the light having a wavelength longer than the wavelength range of the red light and the light having a shorter wavelength than the wavelength range of the red light, and the optical conversion element on which the red light is incident Since an optical filter is arranged, even if an optical filter that reflects infrared light and blocks light in the infrared region is used, visible light loss due to reflection at the interface of the optical filter is reduced to red light. Therefore, it is possible to prevent loss of light amount of other color lights.

Further, conventionally, a color separation optical element for separating light having a wavelength longer than the wavelength range of red light and light having a shorter wavelength than the wavelength range of red light, and an optical conversion element on which red light is incident. In the optical path, an optical filter that blocks transmission of light having a wavelength shorter than the wavelength region of red light is disposed. With only the color separation optical element, it is difficult to completely separate the light in the wavelength range of the red light and the light shorter than the wavelength range of the red light. An optical filter that blocks transmission of light on the shorter wavelength side than the wavelength region of red light is disposed.
Therefore, the conventional projector is provided with an optical filter for blocking infrared light and an optical filter for blocking light transmission on the shorter wavelength side than the wavelength range of red light, so the number of members is reduced. There are many problems.
On the other hand, the optical filter of the present invention has the characteristic of blocking the transmission of light on the shorter wavelength side than the wavelength region of red light and blocking the transmission of light in the infrared region, and from the wavelength region of red light. Since the optical filter for blocking the transmission of light on the short wavelength side and the optical filter for blocking the infrared light are integrated, the number of members can be reduced.

  In the present invention, the color separation optical device is a first color separation optical device that separates a light beam emitted from the light source device into blue light and light having a wavelength longer than the wavelength region of the blue light. A light having a wavelength longer than the wavelength region of the blue light separated by the element and the first color separation optical element; a light including a green light having a shorter wavelength than the wavelength region of the red light; A second color separation optical element that separates light into a wavelength region or more, and the optical filter is in an optical path between the second color separation optical element and an optical conversion element on which red light is incident. The geometric optical path length of the red light from the first color separation optical element to the optical conversion element on which the red light is incident is the optical conversion on which the green light is incident from the first color separation optical element. From the geometric light path length of green light to the element and the first color separation optical element It is longer than the geometric optical path length of the blue light to the optical conversion element on which the colored light is incident, and the optical filter may block the transmission of the light in the infrared region by reflecting the light in the infrared region. preferable.

  The optical filter disposed between the second separation optical element and the optical conversion element in the optical path of red light reflects infrared light, thereby blocking transmission of infrared light. For this reason, the infrared light reflected by the optical filter returns to the optical path of red light. Since the optical path length of the red light is set longer than the optical path lengths of the other color lights, the infrared light is surely dispersed on the way back along the optical path of the red light. Thereby, return of the reflected infrared light to the light source device can be reliably reduced, and deterioration of the light source device can be reliably prevented.

  Furthermore, in the present invention, the optical conversion element includes a condensing element that is arranged in front of the optical conversion element and collimates a light beam incident on the light modulation device, the condensing element is a plano-convex lens, and the optical filter includes: Optical characteristics that block transmission of light on the shorter wavelength side than the wavelength region of red light, and optical characteristics that block transmission of light in the infrared region on the longer wavelength side than the wavelength region of red light, 2 The film satisfying one optical characteristic is preferably formed on the plane of the light collecting element.

The optical film of the optical filter is generally composed of a dielectric multilayer film and has an incident angle dependency. Therefore, when the light incident on the optical filter is not substantially vertical, it may be difficult to reliably block the transmission of light in the predetermined wavelength region.
On the other hand, in this invention, the optical filter is affixed on the plane of the condensing element. This condensing element collimates the light beam incident on the light modulation device, and its plane is substantially perpendicular to the incident light. By forming the optical film on such a flat surface, it is possible to reliably block transmission of light on the shorter wavelength side than the wavelength region of red light, and to reliably block transmission of light in the infrared region.
Furthermore, when the optical film of the optical filter is not formed on the light condensing element, a glass substrate or the like for forming the optical film is required separately, but in the present invention, the optical film is formed on the light condensing element. Therefore, a glass substrate or the like is not required, and the number of members can be reduced. Further, since a glass substrate or the like is not required, space can be saved.

Furthermore, in the present invention, the optical conversion element includes a condensing element that is arranged in front of the optical conversion element and collimates a light beam incident on the light modulation device, the condensing element is a plano-convex lens, and the optical filter includes: An optical film that blocks transmission of light on a shorter wavelength side than the wavelength region of red light, and an optical film that blocks transmission of light in an infrared region on a longer wavelength side than the wavelength region of red light, An optical film that blocks transmission of light on a shorter wavelength side than the wavelength region of light is formed on a plane of the light condensing element, and transmits light in an infrared region longer than the wavelength region of red light. The optical film that blocks transmission is preferably formed on the convex surface of the light collecting element.
The optical film of the optical filter is generally composed of a dielectric multilayer film and has an incident angle dependency. Therefore, when the light incident on the optical filter is not substantially vertical, it may be difficult to reliably block the transmission of light in the predetermined wavelength region.
Therefore, in the present invention, the optical film that blocks the transmission of light having a shorter wavelength than the wavelength region of red light that affects the color light that forms the image is disposed on the plane of the light condensing element so that the incident light is substantially vertical. By forming in this manner, it is possible to reliably block the transmission of light on the shorter wavelength side than the wavelength region of red light.
In addition, an optical film that blocks transmission of light in the infrared region longer than the wavelength region of red light is intentionally formed on the convex surface of the condensing element, thereby activating infrared light scattering and concentrating heat. Can be prevented.
Furthermore, when the optical film of the optical filter is not formed on the light condensing element, a glass substrate or the like for forming the optical film is required separately, but in the present invention, the optical film is formed on the light condensing element. Therefore, a glass substrate or the like is not required, and the number of members can be reduced. Further, since a glass substrate or the like is not required, space can be saved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Outline of projector optical system]
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 41, a color separation optical device 42, a relay optical system 43, an optical device 44 in which a light modulation device and a color synthesis optical device are integrated, and a projection. The optical components 41 to 44 are positioned and adjusted and accommodated in an optical component casing (not shown) in which a predetermined illumination optical axis X is set. . Moreover, the projection lens 3 is installed in the predetermined position with respect to these optical components 41-44 in the housing | casing for optical components.

  The light source device 411 includes a light source lamp 416 and a reflector 417 as a radiation light source, and the radial light beam emitted from the light source lamp 416 is reflected by the reflector 417 to be a substantially parallel light beam and is emitted to the outside. In this example, a high-pressure mercury lamp is employed as the light source lamp 416, but a metal halide lamp or a halogen lamp may be employed in addition to this. In this example, a parabolic mirror is used as the reflector 417, but a configuration in which a collimating concave lens is arranged on the exit surface of the reflector made of an ellipsoidal mirror can also be used.

The first lens array 412 has a configuration in which small lenses having a substantially rectangular outline when 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 416 into partial light beams and emits them in the direction of the illumination optical axis. The contour shape of each small lens is set so as to be substantially similar to the shape of an image forming area of a liquid crystal panel 441 described later. For example, if the aspect ratio (ratio of horizontal and vertical dimensions) of the image forming area of the liquid crystal panel 441 is 4: 3, the aspect ratio of each small lens is also set to 4: 3.
The second lens array 413 has substantially the same configuration as the first lens array 412, and includes a configuration in which small lenses are arranged in a matrix. The second lens array 413 has a function of forming an image of each small lens of the first lens array 412 on the liquid crystal panel 441 together with the superimposing lens 415.

The polarization conversion element 414 converts the light from the second lens array 413 into one type of linearly polarized light, thereby increasing the light utilization rate in the optical device 44.
Specifically, each partial light beam converted into one type of linearly polarized light by the polarization conversion element 414 is finally substantially superimposed on the liquid crystal panel 441 of the optical device 44 by the superimposing lens 415. In a projector using a liquid crystal panel 441 of a type that modulates linearly polarized light, only one type of linearly polarized light can be used, and therefore approximately half of the light flux from the light source lamp 416 that emits randomly polarized light is not used. For this reason, by using the polarization conversion element 414, all the light beams emitted from the light source lamp 416 are converted into one kind of linearly polarized light, and the use efficiency of light in the optical device 44 is enhanced. Note that. Such a polarization conversion element 414 is introduced in, for example, JP-A-8-304739.

The color separation optical device 42 includes two dichroic mirrors (color separation optical elements) 421 and 422 and a reflection mirror 423, and receives a plurality of partial light beams emitted from the integrator illumination optical system 41 by the dichroic mirrors 421 and 422. It has a function of separating light of three colors, red (R), green (G), and blue (B).
The relay optical system 43 includes an incident side lens 431, a relay lens 433, and reflection mirrors 432 and 434, and has a function of guiding red light, which is color light separated by the color separation optical device 42, to the liquid crystal panel 441R. ing.

Here, the dichroic mirror (first color separation optical element) 421 of the color separation optical device 42 is a transparent substrate such as a glass substrate coated with a dielectric multilayer film. In this dichroic mirror 421, the light emitted from the integrator illumination optical system 41 by the dielectric multilayer film is converted into blue light and light (including red light and green light) on the longer wavelength side than the wavelength region of the blue light. To separate. Note that blue light includes light in a wavelength region (about 435 nm or more and less than about 500 nm) strictly defined as blue light and light in a wavelength region shorter than that (about 435 nm or less).
Blue light is reflected by the dichroic mirror 421, and light on the longer wavelength side than the wavelength region of blue light including red light and green light passes through the dichroic mirror 421.
The blue light reflected by the dichroic mirror 421 is reflected by the reflection mirror 423, passes through the field lens 418 (418B) as a condensing element, and reaches the blue incident side polarizing plate 442B and the liquid crystal panel 441B. The field lens 418 converts each partial light beam emitted from the second lens array 413 into a light beam substantially parallel to the illumination optical axis X. The same applies to the field lenses 418 (418G, 418R) provided on the light incident side of the other liquid crystal panels 441G, 441R.
Here, the field lens 418 (418R, 418G, 418B) is a plano-convex lens having a convex surface on the light incident surface and a flat surface on the light emitting surface.

The dichroic mirror 422 (second color separation optical element) is also a transparent substrate such as a glass substrate coated with a dielectric multilayer film.
In this dichroic mirror 422, light (including green light and red light) longer than the wavelength region of blue light transmitted through the dichroic mirror 421 by the dielectric multilayer film is included in the wavelength region of red light. The light is separated into light on the short wavelength side and light in the wavelength region of red light or higher. In other words, the dichroic mirror 422 separates green light (about 500 nm or more and less than about 590 nm) and light containing red light (about 590 nm or more and less than about 680 nm) longer than the wavelength region of the green light. .
The green light is reflected by the dichroic mirror 422, passes through the field lens 418, and reaches the green incident side polarizing plate 442G and the liquid crystal panel 441G.
A filter that blocks transmission of light longer than the wavelength region of green light is provided between the dichroic mirror 422 and the green incident-side polarizing plate 442G, although not shown. It is difficult for the dichroic mirror 422 to completely separate the green light and the light having a wavelength longer than the wavelength range of the green light, and the light reflected by the dichroic mirror 422 is less than the wavelength range of the green light. Light on the long wavelength side may be included. The filter is arranged to prevent light having a longer wavelength than the wavelength region of green light from reaching the liquid crystal panel 441G.

On the other hand, light in the wavelength region of red light or more passes through the dichroic mirror 422, passes through the relay optical system 43, and further passes through the field lens 418. As will be described in detail later, the optical filter 45 provided in the field lens 418 separates the light in the wavelength region of red light into light having a wavelength longer than the wavelength region of red light, and only red light is red. Incident on the incident-side polarizing plate 442R and the liquid crystal panel 441R.
In this embodiment, the geometrical optical path length of the red light from the dichroic mirror 421 to the incident-side polarizing plate 442R on which the red light is incident is the same as that from the dichroic mirror 421 to the incident-side polarizing plate 442G on which the green light is incident. It is longer than the geometrical optical path length of green light and the geometrical optical path length of blue light from the dichroic mirror 421 to the incident-side polarizing plate 442B on which the blue light is incident.
The relay optical system 43 is used for the red light because the geometric length of the optical path of the red light is longer than the geometric length of the optical path of the other color light, This is to prevent a decrease in usage efficiency. That is, this is to transmit the partial light beam incident on the incident side lens 431 to the field lens 418 as it is.

  The optical device 44 modulates an incident light beam according to image information to form a color image, and includes three incident-side polarizing plates 442 (on which each color light separated by the color separation optical device 42 is incident). 442R, 442G, 442B), a liquid crystal panel 441 (441R, 441G, 441B) as a light modulation device disposed at the subsequent stage of each incident side polarizing plate 442, and disposed at the subsequent stage of each of the liquid crystal panels 441R, 441G, 441B. And a cross dichroic prism 444 as a color synthesizing optical device.

The liquid crystal panels 441R, 441G, and 441B use, for example, polysilicon TFTs as switching elements. Although not shown, a panel body in which liquid crystal is sealed and sealed in a pair of transparent substrates arranged opposite to each other, It is configured to be stored in a holding frame.
In the optical device 44, the respective color lights separated by the color separation optical device 42 are the three liquid crystal panels 441R, 441G, 441B, the incident side polarizing plates 442R, 442G, 442B, and the emission side polarizing plates 443R, 443G, 443B. Is modulated in accordance with the image information to form an optical image.

The incident-side polarizing plate 442 (442R, 442G, 442B) as an optical conversion element transmits only polarized light in a certain direction out of each color light separated by the color separation optical device 42 and absorbs other light beams. In other words, a polarizing film is formed on a substrate such as sapphire glass.
The exit-side polarizing plate 443 is configured in substantially the same manner as the incident-side polarizing plate 442, and transmits only polarized light in a predetermined direction out of the light beams emitted from the liquid crystal panel 441 (441R, 441G, 441B), and transmits the other light beams. Absorb.
The incident side polarizing plate 442 and the exit side polarizing plate 443 are set so that the directions of the polarization axes thereof are orthogonal to each other.

The cross dichroic prism 444 emits from the exit-side polarizing plate 443, and forms a color image by combining optical images modulated for each color light.
The cross dichroic prism 444 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 3 has a function as a projection optical device that enlarges and projects an optical image formed by the optical device 44, and is configured as a combined lens in which a plurality of lenses are housed in a cylindrical lens barrel. The

[Field lenses and optical filters]
As described above, the field lens 418 is a plano-convex lens having a convex surface on the light incident surface and a flat surface on the light emitting surface.
The optical filter 45 is disposed in the optical path from the dichroic mirror 422 to the incident-side polarizing plate 442R. In the present embodiment, the optical filter 45 is formed on the light beam exit side of the field lens 418R on which red light is incident.
The optical filter 45 is a band-pass filter that allows only light in the wavelength region of red light to pass, and has two types of optical films 451 and 452 as shown in FIG. Of these two types of optical films 451 and 452, one optical film 451 is a dielectric multilayer film that blocks transmission of light on a shorter wavelength side than the wavelength region of red light (about 580 nm or more and less than about 680 nm). is there. For example, the optical film 451 blocks transmission of light of less than about 580 nm.

  As described above, the dichroic mirror 422 separates green light and light including red light having a longer wavelength side than the wavelength region of green light, and includes red light having a longer wavelength side than the wavelength region of green light. Transmits light. However, it is difficult for the dichroic mirror 422 to completely separate the green light and the light including the red light having a wavelength longer than the wavelength region of the green light, and the red light is transmitted into the light transmitted through the dichroic mirror 422. Light on the shorter wavelength side than the wavelength region may be included. Light on the shorter wavelength side than the red light wavelength region is blocked by one optical film 451. By providing such an optical film 451, light having a shorter wavelength than the wavelength region of red light is not incident on the liquid crystal panel 441R, and deterioration of the image quality of the projected image can be prevented.

The other optical film 452 blocks the transmission of light having a wavelength longer than the wavelength region of red light, that is, light in the infrared region (about 680 nm or more). The other optical film 452 is also composed of a dielectric multilayer film. The other optical film 452 reflects light in the infrared region, thereby blocking transmission of light in the infrared region.
In the present embodiment, one optical film 451 is formed on the light beam exit side of the field lens 418R, and the other optical film 452 is formed on the one optical film 451.

Since the optical film 452 of the optical filter 45 blocks the transmission of light in the infrared region (about 680 nm or more), the transmission of infrared light longer than the wavelength region of red light is blocked. The infrared light whose transmission is blocked is reflected by the optical film 452 and returns in the optical path of red light. The infrared light reflected by the optical film 452 is gradually dispersed while returning from the optical path.
Therefore, since infrared light is not directly reflected by the light source device 411, deterioration of the light source device 411 can be prevented.
Furthermore, optical components (for example, reflection mirrors 432 and 434, which are disposed in the optical path of red light)
Since the relay lens 433 and the like hardly absorb infrared light, the optical component does not generate heat due to the reflected infrared light. Therefore, a mechanism for cooling a specific optical component is not necessary.

In this embodiment, the relay optical system 43 is employed for red light, and the geometric optical path length of red light is longer than the geometric optical path lengths of other color lights.
By ensuring a long geometric optical path length of red light, it is possible to reliably reduce the return of reflected infrared light to the light source device 411 and to reliably prevent deterioration of the light source device 411 due to infrared light. can do.

  Furthermore, the optical filter 45 of the present embodiment includes an optical film 451 that blocks transmission of light on a shorter wavelength side than the wavelength region of red light, and an optical film 452 that blocks transmission of light in the infrared region, These are laminated, and have the property of blocking the transmission of light on the shorter wavelength side than the wavelength region of red light and blocking the transmission of light in the infrared region. Accordingly, the number of members can be reduced as compared with the conventional case where an optical filter that blocks infrared light and an optical filter that blocks transmission of light shorter than the wavelength range of red light are provided separately. Can be planned.

The optical films 451 and 452 of the optical filter 45 are composed of dielectric multilayer films and have an incident angle dependency. Therefore, when the surface on which the optical filter 45 is attached is inclined with respect to the incident light, it may be difficult to accurately block light in a predetermined wavelength region.
On the other hand, in the present embodiment, the optical filter 45 is formed on the plane of the light emission side surface of the field lens 418. The light exit side surface of the field lens 418 is substantially perpendicular to the incident light. As a result, it is possible to reliably block the transmission of light having a shorter wavelength than the wavelength region of red light and to reliably block the transmission of light in the infrared region.
Furthermore, since the light exit side surface of the field lens 418 is a flat surface, the optical filter 45 can be easily formed.

Further, in the present embodiment, the optical filter 45 is formed on the field lens 418, and the optical filter 45 and the field lens 418 are integrated. Therefore, the optical filter 45 and the field lens 418 are separated from each other. Compared with the case where it does, it does not require time and effort when installing in the optical component casing.
Further, when the optical filter 45 is not formed on the field lens 418, a glass substrate or the like for forming the optical films 451 and 452 is necessary. However, in this embodiment, since the optical filter 45 is formed on the field lens 418, glass is used. The number of members can be reduced without requiring a substrate or the like. Further, since a glass substrate or the like is not required, space can be saved.
Further, since the optical filter 45 is formed in the field lens 418 adjacent to the incident side polarizing plate 442, the infrared light is incident on the incident side polarizing plate 442 and the liquid crystal panel 441R downstream of the incident side polarizing plate 442. Can be reliably prevented. Thereby, deterioration by the infrared light of the incident side polarizing plate 442 and the liquid crystal panel 441R can be prevented.
Further, as shown in the graph of FIG. 3, the transmittance of the red light (wavelength region, about 580 nm or more and less than about 680 nm) of the optical filter 45 of the present embodiment is close to 100%. Therefore, even if the optical filter 45 is disposed in the optical path from the dichroic mirror 422 to the red light incident side polarizing plate 442R, the brightness of the red light is not affected.
Furthermore, since the optical filter 45 of this embodiment is formed in the field lens 418, there is no increase in the interface due to the provision of the optical filter 45, and there is no loss of visible light due to reflection at the interface of the optical filter 45.
Further, since the optical filter 45 of the present embodiment is provided in the optical path of red light, there is no loss of green light and blue light by the optical filter 45.

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.
For example, in the above embodiment, the optical filter 45 is formed on the light beam exit side surface of the field lens 418, but may be formed on the light beam incident side surface.
Furthermore, in the embodiment, the optical filter 45 is formed on the field lens 418. However, the present invention is not limited to this, and the field filter 418 may not be formed. For example, the optical filter 45 is separated from the field lens 418, and as shown in FIG. 4, the optical filter 45 ′ is a transparent substrate 453 made of glass or the like, and an optical film 451 formed on the transparent substrate 453. 452 may be provided.

Further, the optical filter 45 may be formed on the incident side lens 431, the relay lens 433, and the reflection mirrors 432 and 434.
Since the reflecting surfaces of the reflecting mirrors 432 and 434 are inclined by about 45 ° with respect to the illumination optical axis, it may be difficult to accurately block light in a specific wavelength region by the optical filter 45. However, when the accuracy of blocking light in a specific wavelength region is not strictly required, the optical filter 45 can be formed on the reflection surfaces of the reflection mirrors 432 and 434.
In the above embodiment, the red light is passed through the relay optical system 43, and the geometric length of the optical path of the red light is set to be longer than the geometric length of the optical path of the other color light. For example, blue light may be passed through the relay optical system 43. In this case, the optical path of the red light is shorter than the optical path of the red light of the present embodiment, and the infrared light reflected by the optical filter provided in the red light of the present invention is in the middle of returning to the optical path of the red light. Although there is a possibility of not being sufficiently dispersed, loss of visible light due to reflection at the interface of the optical filter or the like can be prevented.

Further, in the above embodiment, the filter disposed between the dichroic mirror 422 and the green incident-side polarizing plate 442 has only the characteristic of blocking the transmission of light on the longer wavelength side than the wavelength region of green light. For example, this filter has an optical film that blocks the transmission of light longer than the wavelength region of green light and the transmission of infrared light longer than the wavelength region of red light. It is good also as a band pass filter provided with the optical film (optical film which has the characteristic similar to the optical film 452) to do. By doing so, it is possible to prevent infrared stray light from entering the liquid crystal panel 441G.
Further, in the previous embodiment, the optical filter 45 has the optical films 451 and 452 and is formed on the light beam emission side surface of the field lens 418 together with the optical films 451 and 452. However, the object of the present invention is achieved. As a method for this, it is also possible to propose a method in which only the optical film 451 is formed on the light emission side that is the plane of the field lens 418 and the optical film 452 is formed on the light incident surface that is the convex surface of the field lens 418.
The optical films 451 and 452 of the optical filter are generally formed of a dielectric multilayer film and have an incident angle dependency. Therefore, when the light incident on the optical filter is not substantially vertical, it may be difficult to reliably block the transmission of light in the predetermined wavelength region.
Therefore, the optical film 451 that blocks the transmission of light having a wavelength shorter than the wavelength region of red light that affects the color light that forms the image is formed on the light beam emission side surface, which is the plane of the field lens 418, so An optical film 452 that blocks the transmission of visible light shorter than the wavelength region of light and blocks the transmission of light in the infrared region longer than the wavelength region of red light is formed on the convex surface of the field lens 418. Infrared light scattering is activated by forming it on a certain light incident surface. As a result, the image quality of the projector can be improved and the influence of heat caused by infrared light can be effectively dispersed, local overheating can be prevented, and the cooling structure in the projector can be simplified.

  Furthermore, in the above-described embodiment, only the example of the front type projector that projects from the direction of observing the screen has been described. However, in the present invention, the rear type projector that projects from the side opposite to the direction of observing the screen is used. Is also applicable.

  The present invention can be used for a projector.

1 is a schematic diagram showing an optical system of a projector according to the present invention. The figure which shows the principal part of the said optical system. The figure which shows the optical characteristic of the optical filter of the said optical system. The schematic diagram which shows the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projector, 3 ... Projection lens (projection optical apparatus), 42 ... Color separation optical apparatus, 45 ... Optical filter, 46 ... Optical filter, 411 ... Light source device, 418 ... Field lens (condensing element), 418R ... Field lens 418G ... Field lens, 418B ... Field lens, 421 ... Dichroic mirror (first color separation optical element), 422 ... Dichroic mirror (second color separation optical element), 441 ... Liquid crystal panel (light modulation device), 441R ... liquid crystal panel, 441B ... liquid crystal panel, 441G ... liquid crystal panel, 442 ... incident side polarizing plate, 442R ... incident side polarizing plate, 442B ... incident side polarizing plate, 442G ... incident side polarizing plate, 444 ... cross dichroic prism (color synthesis) Optical device), 451 ... optical film, 452 ... optical film

Claims (4)

A light source device, a color separation optical device having a plurality of color separation optical elements for separating a light beam emitted from the light source device into a plurality of color lights including red light, and each color light separated by the color separation optical device A plurality of light modulation devices that modulate in accordance with image information, a color combining optical device that combines optical images modulated by the respective light modulation devices, and a projection optical device that enlarges and projects the combined optical image A projector,
Between each of the light modulation devices and the color separation optical device, an optical conversion element that converts an optical characteristic of a light beam incident on each of the light modulation devices is disposed,
Among the color separation optical elements of the color separation optical device, a color separation optical element for separating light having a wavelength longer than the wavelength range of red light and light having a shorter wavelength than the wavelength range of red light, and red light An optical filter is disposed in the optical path between the incident optical conversion element and
The optical filter has a characteristic of blocking transmission of light in a shorter wavelength side than the wavelength region of red light and blocking transmission of light in an infrared region longer than the wavelength region of red light. Characteristic projector. The projector according to claim 1, wherein
The color separation optical device includes a first color separation optical element that separates a light beam emitted from the light source device into blue light and light on a longer wavelength side than the wavelength region of the blue light;
Light that is longer than the wavelength region of the blue light separated by the first color separation optical element, light that includes green light that is shorter than the wavelength region of red light, and the wavelength region of red light or more A second color separation optical element that separates the light into
The optical filter is disposed in an optical path between the second color separation optical element and an optical conversion element on which red light is incident,
The geometrical optical path length of red light from the first color separation optical element to the optical conversion element to which red light is incident is the green light from the first color separation optical element to the optical conversion element to which green light is incident. Longer than the geometric optical path length of the blue light from the first color separation optical element to the optical conversion element on which the blue light is incident,
The projector according to claim 1, wherein the optical filter blocks light in the infrared region by reflecting the light in the infrared region. The projector according to claim 1 or 2,
A condensing element that is arranged in front of the optical conversion element and collimates a light beam incident on the light modulation device;
The condensing element is a plano-convex lens;
The optical filter has an optical characteristic that blocks transmission of light on a shorter wavelength side than the wavelength range of red light, and an optical characteristic that blocks transmission of light in an infrared range longer than the wavelength range of red light. With
The projector satisfying the two optical characteristics is formed on a plane of the light collecting element. The projector according to claim 1 or 2,
A condensing element that is arranged in front of the optical conversion element and collimates a light beam incident on the light modulation device;
The condensing element is a plano-convex lens;
The optical filter includes: an optical film that blocks transmission of light on a shorter wavelength side than the wavelength range of red light; and an optical film that blocks transmission of light in an infrared range longer than the wavelength range of red light; With
An optical film that blocks transmission of light on a shorter wavelength side than the wavelength region of the red light is formed on the plane of the light collecting element,
An optical film that blocks transmission of light in an infrared region longer than the wavelength region of red light is formed on a convex surface of the light collecting element.

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