JP3821758B2 - Illumination optical system and projection display device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an illumination optical system and a projection display device including the illumination optical system.
[0002]
[Prior art]
A problem to be solved by the projection display device is to improve the brightness of the display screen. Many light valves, such as liquid crystal light valves, use polarized light to display images, so only one of the light components from the light source is used for display. It has the inherent disadvantage of being low.
[0003]
In order to remedy this drawback, conventionally, an illumination optical system using a polarization conversion element has been proposed as disclosed in, for example, Japanese Patent Laid-Open Nos. 63-121821 and 63-168622. In other words, the brightness of the display image is improved by converting the random polarized light from the light source into one type of polarized light before entering the light valve.
[0004]
Specifically, as shown in FIG. 7, random polarized light (natural light) 11 from the light source 10 is converted into two linearly polarized light (P-polarized light 12 and S-polarized light 13) using a polarization separation element 71 such as a polarization beam splitter. After the separation, the polarization plane of one polarized light (here, P-polarized light 12) is rotated 90 degrees by the λ / 2 phase difference plate 14 (referred to as S′-polarized light 15 for convenience), and the other polarized light (here, S-polarized light 13). And the polarization plane are made to coincide with each other to form one type of polarized light (here, S-polarized light), and illuminate the light valve 51. Reference numeral 62 denotes a general reflecting mirror.
[0005]
[Problems to be solved by the invention]
In the conventional illumination optical system shown above, the polarization separation efficiency in the polarization separation element differs between the two polarization components, and the amount of transmitted light varies depending on the presence or absence of the phase difference plate. It is necessary to superimpose S-polarized light and P-polarized light and guide them to the illumination area. However, since the parallelism of the light emitted from the light source used in a general projection display device is poor, simply adjusting the direction of the light beam emitted from the polarization conversion element and leading it to the illumination area Light diverges while reaching the area, or the illuminance distribution at the time of emission from the polarization conversion element is not preserved, so that the amount of light available in the illumination area decreases, and at the same time, large illuminance unevenness occurs. As a result, there is a problem that ideal illumination cannot be performed.
[0006]
Therefore, the present invention solves the problems as described above, and the object is to increase the superposition coupling efficiency of two outgoing light beams after polarization conversion in an illumination optical system with a polarization conversion element, An object of the present invention is to provide an illumination optical system with high light utilization efficiency and small illuminance unevenness. It is another object of the present invention to provide a projection display device that uses a lighting optical system with high light utilization efficiency and small illuminance unevenness and has excellent display image quality.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an illumination optical system of the present invention includes a polarization separation element that separates random polarized light from a light source into two linearly polarized light of P wave and S wave, and one of the separated two polarized lights. An illumination optical system comprising a polarization conversion element having a polarization plane rotation element that rotates the polarization plane of the linearly polarized light to coincide with the polarization plane of the other linearly polarized light, and the polarization separation element of the two polarized lights Polarized light that has been subjected to the polarization plane rotation action that is emitted from the polarization conversion element, and includes a reflection mirror that bends the optical axis of the polarized light and emits the polarized light reflected by the light in the same direction as that of the other polarized light. And a light transmission element for guiding the unpolarized polarized light to the illumination area in a substantially superimposed state, the light transmission element is arranged between the polarization conversion element and the illumination area, and the light transmission element transmits light from the polarization conversion element. Located at the entrance A first lens unit, and a second lens unit disposed between the first lens unit and the illumination area, the first lens unit configured to transmit light from the polarization conversion element. A first lens plate in which a plurality of first unit lenses are arranged in a plane perpendicular to the optical axis is provided, and the second lens unit forms a right angle with the optical axis of light emitted from the polarization conversion element. A second lens plate in which a plurality of second unit lenses corresponding to each of the plurality of first unit lenses are arranged in a plane, and a plurality of light source images formed by the plurality of first unit lenses, The first unit lens is formed in the vicinity of the center of each of the plurality of second unit lenses, and an image in the vicinity of the plurality of first unit lenses is superimposed and formed in the vicinity of an illumination region by the second lens unit. Lens plate and the second lens plate, and When the direction parallel to the plane including the separation direction in which the dam-polarized light is separated into the P wave and the S wave is defined as the width direction, the dimensions of the polarization separation element in the width direction and the plurality of first unit lenses The dimension in the width direction of the minute is substantially the same.
[0009]
In the illumination optical system described above, the projected dimension in the width direction when the reflecting mirror is projected in the optical axis direction of the illumination optical system and the dimension in the width direction corresponding to a plurality of the first unit lenses are approximately. It may match.
[0010]
Here, at least one of the first lens unit or the second lens unit may include one plano-convex lens and the lens plate. In the first to second illumination optical systems of the present invention, the polarization plane rotation element may be a λ / 2 phase difference plate or a TN (twisted nematic) type liquid crystal element.
[0011]
The projection display device of the present invention also includes the illumination optical system described above, a light valve that forms an image by modulating light from the illumination optical system with an image signal, and the formed image is projected and displayed on a screen. And a projection optical system.
[0012]
Furthermore, another projection display apparatus of the present invention includes the above-described illumination optical system, a color light separation element that separates light from a light source into three color lights, and three light beams that modulate each color light with an image signal to form an image. It is characterized by comprising a light valve, a color light combining element for combining three types of images of each color light into one, and a projection optical system for projecting and displaying the combined image on a screen.
[0013]
【Example】
Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to the following examples.
[0014]
In the following embodiments, an example is shown in which the polarization plane of P-polarized light is rotated to convert to S-polarized light. However, the characteristics of the present invention are not lost even when S-polarized light is converted to P-polarized light. Moreover, in each Example, the same part number is attached | subjected to the same (including same kind) component.
Example 1
FIG. 1 is a schematic sectional view showing a first embodiment of the illumination optical system of the present invention. The random polarized light 11 emitted from the light source 10 is separated into two linearly polarized light of P-polarized light 12 and S-polarized light 13 by a polarization beam splitter 16 which is a polarization separation element. Since the polarization separation ability of the polarizing beam splitter has an incident angle dependency, a light source provided with a short arc length lamp capable of emitting light with excellent parallelism is suitable. The separated P-polarized light is transmitted through the λ / 2 phase difference plate 14 which is a polarization plane rotation element, so that the polarization plane is rotated by 90 degrees to become S-polarized light. On the other hand, the S-polarized light 13 is emitted as it is as S-polarized light only by bending the optical path by the prism type reflection mirror 17. A reflection mirror made of an aluminum vapor deposition film has an S-polarized light reflectance higher than that of P-polarized light. Therefore, an arrangement configuration in which the optical path of S-polarized light is bent by the reflection mirror is ideal. Although a prism type reflection mirror is used here, a general planar reflection mirror may be used. With the above configuration, basically only the S-polarized light is emitted from the polarization conversion element including the polarization separation element and the polarization plane rotation element.
[0015]
Next, between the polarization conversion element and the illumination area 23, a light transmission element including the first lens plate 21 and the second lens plate 22 is disposed. The first lens plate and the second lens plate are formed by arranging a large number of unit lenses in a plane perpendicular to the optical axis 26 of the illumination optical system, as shown in FIG. The number of unit lenses constituting the first lens plate 21 and the number of unit lenses constituting the second lens plate 22 are equal, and the positional relationship of both unit lenses in the lens plate is also in a corresponding relationship. For example, the unit lens 24 at the lower left of the first lens plate 21 in FIG. 2 has an optical correspondence with the unit lens 25 at the lower left of the second lens plate 22.
[0016]
The optical correspondence between the unit lenses in the first and second lens plates will be described with reference to FIG. Here, for convenience, a unit lens constituting the first lens plate is referred to as a lens A, and a unit lens constituting the second lens plate is referred to as a lens B. The lens B is disposed between the lens A and the illumination area so that the image 35 in the vicinity of the lens A31 is transmitted to the illumination area 23 by the lens B33. In this case, the position of the lens B is determined by the ratio between the size of the aperture cross section of the unit lens constituting the lens A and the size of the illumination area, in other words, the magnification ratio of the lens B. Now, assuming that the distance between the lens A and the lens B is L1, and the distance between the lens B and the illumination region is L2, the size of the aperture cross section of the unit lens constituting the lens A: the size of the illumination region = L1: Since the relationship L2 is established, the position and focal length of the lens B are determined based on this relationship. On the other hand, the lens A is arranged to increase the light transmission efficiency of the lens B. Therefore, in order to collect the light incident on the lens A at the center of the lens B (that is, near the center of the lens B by the lens A). The focal length of the lens A is determined so that a light source image is formed.
[0017]
As described above, the image 35 in the vicinity of the lens A31 is transmitted to the illumination region 23 by the lens B33 due to the relationship between the focal lengths of the lens A and the lens B and the positional relationship between the lens A, the lens B, and the illumination region. Is done. At this time, since the focal point of the lens A31 is in the vicinity of the center of the lens B33, the light incident near the center of the lens B is guided to the illumination region 23 as it is without being refracted by the lens. The light incident on the peripheral part of the light is refracted and changes its optical path, and is also guided to the illumination area 23, so that almost no light loss occurs when light is transmitted from the lens A to the illumination area. Therefore, if the size of the lens B is larger than the size of the light source image formed by the lens A, all the light that has entered the lens B through the lens A is guided to the illumination area. That is, the light emitted from the polarization conversion element is transmitted to the illumination area with little light loss.
[0018]
The relationship that the image in the vicinity of the lens A is transmitted to the illumination area by the lens B is also applicable to unit lenses (lens A32 and B34 in FIG. 3) that are off the optical axis 26 of the illumination optical system. In that case, one or both of the lens A32 and the lens B34 needs to be an eccentric lens (a lens in which the center of curvature forming the spherical shape of the lens deviates from the lens center). In FIG. 3, the lens B34 deviated from the optical axis 26 of the illumination optical system is a decentered lens, and in FIG. 1, all of the unit lenses constituting the first lens plate 21 are decentered lenses. As shown in FIG. 1, the first lens plate is composed of a decentered unit lens, which has the advantage that the size of the second lens plate can be reduced.
[0019]
As for the shape of the lens A, the image in the vicinity of the lens A is transmitted to the illumination area by the lens B, so that it is similar to the shape of the illumination area, and the luminous flux from the polarization conversion element is effective. It is necessary to consider that an array can be formed so as to be divided into a rectangular shape, and in this embodiment, a rectangular shape is used.
[0020]
Returning again to FIG. All the unit lenses constituting the first lens plate and all the unit lenses constituting the second lens plate are optically in a one-to-one correspondence as described above. In FIG. 1, a light beam emitted from the polarization conversion element is divided into fine light beams by a unit lens constituting the first lens plate 21, and is the same as the illumination area by a corresponding unit lens of the second lens plate 22. After being converted into a luminous flux of a size, it is superimposed and coupled to one illumination area. As a result, even if the intensity of the light beam emitted from the polarization conversion element has a non-uniform distribution, the non-uniformity of the intensity distribution is averaged due to the fragmentation and combination of the light beams. A good light distribution with little unevenness can be obtained.
[0021]
Therefore, by adopting the above configuration, after the random polarized light from the light source is converted into one kind of polarized light by the polarization conversion element, there is almost no light loss by the light transmission element, and at the same time, illuminance unevenness and color unevenness are caused. Since the light is guided to the illumination area in an averaged state, it is an ideal illumination device that emits only one type of polarized light. The illumination optical system of the present invention is particularly effective when a light source with large illuminance unevenness and color unevenness is used.
(Example 2)
FIG. 4 is a schematic cross-sectional view showing a second embodiment of the illumination optical system of the present invention. The feature of this embodiment is that, unlike the case of the first embodiment, the second lens plate 22 is a compound lens body comprising a large plano-convex lens 41 and a number of unit lenses 42 having the same shape. TN type liquid crystal element 44 is used as the polarization plane rotation element.
[0022]
Of course, it is possible to construct the second lens plate only by an eccentric unit lens. In this case, however, it is necessary to produce many kinds of unit lenses having slightly different eccentric amounts. On the other hand, when one large plano-convex lens 41 and unit lens 42 are used in combination as in this embodiment, the individual unit lenses can all be made the same by optimizing the lens design. Time complexity can be reduced. Of course, the above-described lens configuration including one large plano-convex lens and a large number of unit lenses also applies to the first lens plate 21.
[0023]
The TN (twisted nematic) type liquid crystal element 44 is obtained by homogeneously aligning the nematic liquid crystal while twisting the nematic liquid crystal in the gap between the two transparent substrates (the overall twist angle is 90 degrees), and in the alignment direction of the nematic liquid crystal. When polarized light is incident together, the polarization plane of light can be rotated according to the twisted state of the liquid crystal molecules. Therefore, this TN type liquid crystal element can be used as a λ / 2 phase difference plate.
[0024]
Furthermore, since the size of the second lens plate is increased in the configuration of the present embodiment, the light beam that has passed through the second lens plate reaches the illumination region at a larger angle than in the case of the first embodiment. Therefore, in order to reduce the irradiation angle of the light irradiated to the illumination area to the same extent as in the case of the first embodiment (in other words, to increase the parallelism of the light), as shown in FIG. A field lens 43 may be installed in front of
Example 3
FIG. 5 is a schematic sectional view showing a first embodiment of a projection display apparatus using the illumination optical system of the present invention. A polarization conversion element comprising a λ / 2 phase difference plate 14 as a polarization plane rotation element, a polarization beam splitter 16 as a polarization separation element, a prism type reflection mirror 17, and the like, and a first lens plate 21 and a second lens plate The illumination optical system composed of the light transmission element 22 and both is functionally the same as that used in the illumination optical system of Example 1.
[0025]
Randomly polarized light 11 from the light source 10 is converted into S-polarized light by the illumination optical system of the present invention, then superimposed and coupled in the vicinity of the field lens 43 and guided to the light valve 51 as illumination light. As described in the second embodiment, the field lens is installed in order to reduce the incident angle of light to the light valve and minimize the light loss due to the projection lens. However, depending on the characteristics of the projection lens, It is not always necessary. Here, only one liquid crystal light valve is used as the light valve, and two polarizing plates are attached to the front and back surfaces of the liquid crystal light valve. The transmission axis of the polarizing plate located on the light incident side coincides with the polarization axis of S-polarized light, while the transmission axis of the polarizing plate located on the light emission side is orthogonal to the polarization axis of S-polarized light. A polarizing plate is arranged. In the case of this embodiment, since the S-polarized light is incident on the liquid crystal light valve, an incident-side polarizing plate is unnecessary, but it is used to further improve the degree of polarization of the polarized light incident on the liquid crystal light valve. Yes. The liquid crystal light valve changes the amount of transmitted light in accordance with an image signal and forms a display image based on the difference in the amount of transmitted light, and generally uses a liquid crystal. However, in addition to the liquid crystal, any material that can form an image signal as a change in optical characteristics, such as an electro-optic crystal, can be used as a light valve. The display image formed by the light valve is enlarged and projected on the screen 53 by the projection lens 52.
[0026]
In general, in a projection display device, a display image on a screen surface becomes very dark due to light loss in a projection lens and dispersion of light accompanying enlarged projection. Therefore, in order to obtain a bright display image, it is essential to increase the amount of illumination light that illuminates the light valve as much as possible. Therefore, as shown in FIG. 5, by incorporating the illumination optical system according to the present invention into such a projection apparatus, it is possible to increase the illumination efficiency in the light valve and to obtain a bright display image as a result.
Example 4
FIG. 6 is a schematic sectional view showing a second embodiment of a projection display apparatus using the illumination optical system of the present invention. A feature of the present embodiment is that a color light separation element that separates light from a light source into three primary colors in the middle of an illumination optical system, three liquid crystal light valves, and three display images formed by the liquid crystal light valves are synthesized. This is in that the projection of a colorized display image using the color light combining element is enabled. However, the basic structure of the illumination optical system that illuminates the liquid crystal light valve is the same as that in the third embodiment.
[0027]
A blue reflecting dichroic mirror 61 that selectively reflects only blue light is placed behind the first lens plate 21 (on the side opposite to the light source) composed of a decentered unit lens. The luminous fluxes are respectively guided to two second lens plates 22 by reflection mirrors 62 (blue light is a double-sided reflection mirror 63). The light that has passed through the blue reflecting dichroic mirror passes through the second lens plate 22, and then is again divided into two by the green reflecting dichroic mirror 64 into green light (reflected light) and red light (transmitted light). However, after the light path of the green light is bent by the double-sided reflection mirror 63), the green light reaches the corresponding green light valve 65 and red light valve 66 through the field lens 43. On the other hand, the blue light has its optical path bent by the two reflecting mirrors 62, and then reaches the blue liquid crystal light valve 67 through the field lens 43. Each of the three liquid crystal light valves has two polarizing plates attached thereto as shown in the third embodiment. The purpose of use of the field lens 43 is the same as that in the third embodiment.
[0028]
Three display images (blue image, green image, red image) formed by three liquid crystal light valves are synthesized into one color display image by a color synthesis dichroic prism 68 which is a color light synthesis element. Then, the projection lens 52 enlarges and projects on the screen 53 surface.
[0029]
Projection-type display devices using three light valves have become the mainstream of projection-type display devices because of higher resolution. Even when the illumination optical system of the present invention is incorporated in such a projection display device, its function can be effectively exhibited, and it can be an effective optical means for obtaining a bright display image.
[0030]
【The invention's effect】
As described above, in the illumination optical system of the present invention, random polarization is converted into specific linearly polarized light by combining the light conversion element composed of two types of lens parts with the polarization conversion element, and the two converted light beams are converted. Since the light can be guided to the illumination region while being effectively superimposed and coupled with almost no light divergence loss, a bright illumination optical system that emits only polarized light with high efficiency can be realized. In particular, the luminous flux emitted from the luminous flux conversion element is subdivided into a plurality of luminous fluxes, and each luminous flux is superimposed and combined in the vicinity of the illumination area. If it is low, this kind of unevenness is likely to occur), and as a result, illumination light with extremely small illumination unevenness and color unevenness can be obtained. From the above, the illumination optical system of the present invention is particularly useful when a light source having poor point light source properties is used.
[0031]
Furthermore, by using the illumination optical system of the present invention, a bright projection display device with extremely little illuminance unevenness and color unevenness can be realized, and the illumination optical system of the present invention is particularly suitable for a high-definition projection display device. It is effective against this.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a configuration of a first embodiment in an illumination optical system of the present invention.
2 is a schematic external view of a first lens plate and a second lens plate used in Example 1. FIG.
FIG. 3 is a view for explaining an optical correspondence between unit lenses in the illumination optical system of the present invention.
FIG. 4 is a schematic cross-sectional view showing the configuration of a second embodiment of the illumination optical system of the present invention.
FIG. 5 is a schematic cross-sectional view showing a configuration of a first embodiment of the projection type liquid crystal display device using the illumination optical system of the present invention.
FIG. 6 is a schematic cross-sectional view showing a configuration of a second embodiment of the projection type liquid crystal display device using the illumination optical system of the present invention.
FIG. 7 is a schematic sectional view showing an outline of an illumination optical system using only a conventional polarization conversion element.
[Explanation of symbols]
10 Light source 11 Random polarization (natural light)
12 P-polarized light 13 S-polarized light 14 λ / 2 retardation plate 15 S′-polarized light (S-polarized light converted from P-polarized light)
16 Polarizing beam splitter 17 Prism-type reflection mirror 21 First lens plate 22 Second lens plate 23 Illumination region 24 Unit lens 25 constituting the first lens plate Unit lens 26 constituting the second lens plate Illumination optical system Optical axis 31 Lens A (on the optical axis of the illumination optical system)
32 Lens A (not on the optical axis of the illumination optical system)
33 Lens B (on the optical axis of the illumination optical system)
34 Lens B (not on the optical axis of the illumination optical system)
35 Image near lens A 36 Light incident near the center of lens B 37 Light incident near the periphery of lens B 41 Plano-convex lens 42 Unit lens 43 having the same shape Field lens 44 TN type liquid crystal element 51 Light valve 52 Projection lens 53 Screen 61 Blue reflective dichroic mirror 62 Reflective mirror 63 Double-sided reflective mirror 64 Green reflective dichroic mirror 65 Green liquid crystal light valve 66 Red liquid crystal light valve 67 Blue liquid crystal light valve 68 Color light composition dichroic prism 71 Polarization separation element

Claims (5)

A polarization separation element that separates random polarized light from a light source into two linearly polarized light of P- polarized light and S- polarized light ; An illumination optical system comprising a polarization conversion element having a polarization plane rotation element matched with
A reflection mirror that reflects one of the two polarized light beams reflected by the polarization separating element and emits the polarized light in a direction substantially the same as the other polarized light direction by bending the optical axis of the polarized light;
A light transmission element is disposed between the polarization conversion element and the illumination area to guide the polarized light emitted from the polarization conversion element to the illumination area in a state of substantially overlapping the polarized light subjected to the rotation of the polarization plane and the unpolarized polarization. And
The light transmission element includes a first lens unit disposed at an incident part of light from the polarization conversion element, and a second lens unit disposed between the first lens unit and the illumination region. Prepared,
The first lens unit includes a first lens plate in which a plurality of first unit lenses are arranged in a plane perpendicular to the optical axis of light emitted from the polarization conversion element,
The second lens section includes a second unit lens in which a plurality of second unit lenses corresponding to each of the plurality of first unit lenses are arranged in a plane perpendicular to the optical axis of the outgoing light from the polarization conversion element. With a lens plate
A plurality of light source images formed by the plurality of first unit lenses are formed in the vicinity of the center of each of the plurality of second unit lenses, and an image in the vicinity of the plurality of first unit lenses is defined by the second The first lens plate and the second lens plate are arranged so as to be superimposed and imaged in the vicinity of the illumination area by the lens unit,
When the random polarized light is in a direction parallel to a plane including a separation direction separated into the P- polarized light and the S- polarized light , and the direction perpendicular to the optical axis of the outgoing light from the polarization converting element is the width direction. The illumination optical system characterized in that the width-direction dimension of the polarization separation element and the width-direction dimensions of the plurality of first unit lenses substantially coincide. The illumination optical system according to claim 1,
The projected dimension in the width direction when the reflecting mirror is projected in the optical axis direction of the illumination optical system and the dimension in the width direction corresponding to a plurality of the first unit lenses substantially coincide with each other. Illumination optical system. The illumination optical system according to claim 1 or 2,
At least one of the first lens unit or the second lens unit includes one plano-convex lens and the lens plate.  4. The illumination optical system according to claim 1, a light valve that forms an image by modulating light from the illumination optical system with an image signal, and a projection that projects and displays the formed image on a screen. And a projection display device comprising an optical system.  The illumination optical system according to any one of claims 1 to 3, a color light separation element that separates light from a light source into three-color light, three light valves that form an image by modulating each color light with an image signal, A projection display device comprising: a color light combining element that combines three types of images of each color light into one; and a projection optical system that projects and displays the combined image on a screen.

Images