JPH06289387A - Illuminating optical system and projection type display device - Google Patents

Abstract

PURPOSE:To project only polarized light with high efficiency by combining an optical transmission element consisting of two kind of lens plates with a polarized light converting element and converting random polarized light into specific linear polarized light, and superposing and coupling the resulting luminous flux and guiding it to a lighting area. CONSTITUTION:The random polarized light 11 from a light source 10 is split by a polarization beam splitter 16 as a polarized light splitting element into linear polarized lights which are a P polarized light 12 and an S polarized light 13; and the P polarized light passes through a lambda/2 phase plate 14 to become an S polarized light and the S polarized light 13 is projected as it is. Further, the optical transmission element consisting of the 1st lens plate 21 and 2nd lens plate 22 is arranged between the polarized light converting element and lighting area 22, and the split pieces of luminous flux are converted into pieces of luminous flux which are as large as the lighting area 23, and then coupled together one over the other and guided to the lighting area 23. Consequently, even if the intensity of the luminous flux from the polarized light converting element is uneven, the unevenness of the intensity distribution is averaged by the thinning and coupling of the luminous flux, thereby obtaining an excellent light distribution which is free from intensity unevenness and color unevenness in the lighting area 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical system and a projection type display device equipped with the illumination optical system.

[0002]

2. Description of the Related Art Improving the brightness of a display screen is one of the problems to be solved by a projection display device. Most light valves represented by liquid crystal light valves use polarized light to display images, so only one of the polarized components of the light from the light source is used for display, and therefore the light utilization efficiency is improved. It inherently has the drawback of being low.

In order to remedy this drawback, conventional methods, for example, Japanese Patent Laid-Open Nos. 63-121821 and 63-168622 have been used.
An illumination optical system using a polarization conversion element is proposed as shown in FIG. That is, it is intended to improve the brightness of the display image by converting the random polarized light from the light source into one kind of polarized light in advance and then making it enter the light valve.

Specifically, as shown in FIG. 7, a polarized light separating element 71 such as a polarizing beam splitter is used to convert random polarized light (natural light) 11 from a light source 10 into two linearly polarized light (P).
After splitting into polarized light 12 and S polarized light 13), the polarization plane of one polarized light (here, P polarized light 12) is rotated 90 degrees by the λ / 2 retardation plate 14 (referred to as S ′ polarized light 15 for convenience), and the other The polarization plane (here, S-polarized light 13) is made to coincide with the polarization plane, and one kind of polarized light (here, S-polarized light) is made as a whole, and the light valve 51 is illuminated. Reference numeral 62 is a general reflection mirror.

[0005]

In the above-mentioned conventional illumination optical system, 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. Due to occurrences, it is necessary to superimpose S-polarized light and P-polarized light and guide them to the illumination area in actual use. However, since the light emitted from the light source used in a general projection display device has poor parallelism, it is necessary to simply adjust the direction of the light flux emitted from the polarization conversion element and guide it to the illumination area. Light diverges as it reaches the area,
Alternatively, since the illuminance distribution at the time of emission from the polarization conversion element is not preserved, 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.

Therefore, the present invention solves the above problems, and an object thereof is to provide a superposition coupling efficiency of two outgoing light beams after polarization conversion in an illumination optical system having a polarization conversion element. It is intended to provide an illumination optical system having high light utilization efficiency and small unevenness in illuminance. Furthermore,
An object of the present invention is to provide a projection display device that uses an illumination optical system with high light utilization efficiency and small unevenness in illuminance and has excellent display image quality.

[0007]

In order to achieve the above object, the illumination optical system of the present invention is a polarization separating element for separating random polarized light from a light source into two linearly polarized light of P wave and S wave.
And a polarization plane rotation element for rotating the polarization plane of one of the two polarized lights separated by 90 ° and matching the polarization plane of the other linear polarization with the polarization conversion element. In the optical system, the polarization conversion element is a light transmission element for guiding two polarized lights (polarized light having a polarization plane rotation effect and polarized light not having a polarization plane rotation effect) emitted from the polarization conversion element to an illumination region in a substantially superposed state. Between the first lens plate and the illumination region, and the light transmission element is disposed between the first lens plate and the illumination region. The first lens plate and the second lens plate each include a plurality of unit lenses in a plane that is perpendicular to the optical axis of the light emitted from the polarization conversion element. An array of the first array The number of unit lenses constituting the number of unit lenses constituting the's plate and the second lens plate are equal,
A plurality of light source images formed by a plurality of unit lenses forming the first lens plate are formed in the vicinity of the centers of a plurality of corresponding unit lenses forming the second lens plate, and In order to form an image near the plurality of unit lenses forming the first lens plate in the vicinity of the illumination area by the plurality of corresponding unit lenses forming the second lens plate, the first image is formed. The lens plate and the second lens plate are arranged.

Here, at least one lens plate of the first lens plate and the second lens plate comprises one plano-convex lens and a plurality of unit lenses, and the illumination optical system of the present invention is The polarization plane rotating element is a λ / 2 retardation plate, and the polarization plane rotating element is a TN (twisted nematic) type liquid crystal element.

Further, the projection display apparatus of the present invention comprises the illumination optical system of the present invention, a light valve for modulating light from the illumination optical system by an image signal to form an image, and the formed image on a screen. It is characterized by comprising a projection optical system for projecting and displaying on top.

Furthermore, another projection type display device of the present invention is one in which the light from the illumination optical system of the present invention and the light from the light source are three primary color lights (blue,
Color light separating element for separating into green and red), three light valves for forming an image by modulating each primary color light with an image signal, and a color light combining element for combining three kinds of images of each primary color light into one And a projection optical system for projecting and displaying the combined image on the screen.

[0011]

EXAMPLES The present invention will be described in detail below based on examples. However, the present invention is not limited to the following examples.

In the following embodiments, the case where the polarization plane of P-polarized light is rotated to be S-polarized will be described as an example.
Even when polarized, the features of the present invention are not lost. Further, in each embodiment, the same (including the same type) parts are given the same part number.

(Embodiment 1) FIG. 1 is a schematic sectional view showing a first embodiment of the illumination optical system of the present invention. Random polarized light 11 emitted from the light source 10 is separated into two linear polarized lights of P polarized light 12 and S polarized light 13 by a polarization beam splitter 16 which is a polarization separating element. Since the polarization splitting power of the polarization beam splitter has an incident angle dependence,
It is suitable to have a lamp with a short arc length capable of emitting light with excellent parallelism. The separated P-polarized light is transmitted through the λ / 2 phase difference plate 14, which is a polarization plane rotating element, so that the polarization plane is rotated by 90 degrees and becomes S-polarized light. On the other hand, the S-polarized light 13 is emitted as S-polarized light as it is, only by bending the optical path by the prism type reflection mirror 17. Since the reflectance of the S-polarized light is higher than that of the P-polarized light in the reflection mirror made of the vapor-deposited film of aluminum, it is ideal that the optical path of the S-polarized light is bent by the reflection mirror. still,
Although a prism type reflection mirror is used here, a general plane type reflection mirror may be used. With the above configuration, basically only S-polarized light is emitted from the polarization conversion element including the polarization separation element and the polarization plane rotation element.

Next, a light transmitting element composed of the first lens plate 21 and the second lens plate 22 is arranged between the polarization conversion element and the illumination area 23. The first lens plate and the second lens plate, as shown in FIG. 2 as an example of their external appearance, have a large number of unit lenses arranged in a plane perpendicular to the optical axis 26 of the illumination optical system. , The number of unit lenses forming the first lens plate 21 and the number of unit lenses forming 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,
In FIG. 2, the unit lens 24 at the lower left of the first lens plate 21 has an optical correspondence with the unit lens 25 at the lower left of the second lens plate 22.

The optical correspondence between the unit lenses in the first and second lens plates will be described with reference to FIG. Here, for convenience, the unit lens forming the first lens plate is referred to as a lens A, and the unit lens forming the second lens plate is referred to as a lens B. The lens B is arranged between the lens A and the illumination area so that the image 35 near the lens A31 is transmitted to the illumination area 23 by the lens B33. In that case, the position of the lens B is determined by the ratio of the size of the transmitted image in the vicinity of the lens A and the size of the illumination area, in other words, the magnification 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 area is L2, the relationship of the image size in the vicinity of the lens A: the size of the illumination area = L1: L2 is established. Therefore, the position and the focal length of the lens B are determined based on this relationship. On the other hand, the lens A is arranged to enhance the light transmission efficiency of the lens B, and therefore, the light incident on the lens A should be collected in the central portion 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.

As described above, the image 35 in the vicinity of the lens A31 depends on the relationship between the focal lengths of the lens A and the lens B and the positional relationship between the lens A and the lens B and the illumination area.
Are transmitted to the illumination area 23 by the lens B33. At this time, since the focus of the lens A31 is near 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 substantially refracted by the lens, and the lens B The light incident on the peripheral portion of is subjected to the refraction effect to change the optical path and is guided to the illumination area 23 as well, so that there is almost no light loss when the 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 passing through the lens A and entering the lens B is guided to the illumination area. That is, the light emitted from the polarization conversion element is transmitted to the illumination area with almost no light loss.

The relationship of transmitting the image in the vicinity of the lens A to the illumination area by the lens B is also applicable to the unit lenses (lens A32 and lens B34 in FIG. 3) deviated from the optical axis 26 of the illumination optical system. . In that case, either one of the lens A 32 and the lens B 34 or both of them must be a decentered lens (a lens in which the center of curvature forming the spherical shape of the lens is deviated from the lens center). In FIG. 3, the lens B34 deviated from the optical axis 26 of the illumination optical system, and in FIG. 1, all of the unit lenses forming the first lens plate 21 are decentered lenses. As shown in FIG. 1, by constructing the first lens plate with decentered unit lenses, there is an advantage that the size of the second lens plate can be reduced.

Regarding the shape of the lens A, since the image near the lens A is transmitted to the illumination area by the lens B, it is similar to the shape of the illumination area, and
It is necessary to consider that it is possible to form an array so that the light beam from the polarization conversion element can be effectively divided, and in this embodiment, the rectangular shape is used.

Returning to FIG. 1 again. All the unit lenses forming the first lens plate and all the unit lenses forming the second lens plate are optically in the one-to-one correspondence as described above. In FIG. 1, the light flux emitted from the polarization conversion element is divided into fine light fluxes by the unit lenses forming the first lens plate 21, and the same unit area as the illumination area by the corresponding unit lenses of the second lens plate 22. After being converted into a light beam having a size, the light beam is superposed and coupled to one illumination region and guided. As a result, even if the intensity of the light flux emitted from the polarization conversion element has a non-uniform distribution, the non-uniformity of the intensity distribution is averaged due to the subdivision and combination of the light flux, and the intensity unevenness and color in the illumination area are A good light distribution with little unevenness can be obtained.

Therefore, with the above configuration, after the randomly polarized light from the light source is converted into one type of polarized light by the polarization conversion element, there is almost no light loss due to the light transmission element, and at the same time, uneven illuminance and Since the color unevenness is averaged and guided to the illumination area, it becomes 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 or color unevenness is used.

(Embodiment 2) FIG. 4 is a schematic sectional view showing a second embodiment of the illumination optical system of the present invention. The feature of this embodiment is that the second lens plate 2 is different from the first embodiment.
2 is a decentered lens composed of one large plano-convex lens 41 and a large number of unit lenses 42 having the same shape, and a TN type liquid crystal element 44 is used as a polarization plane rotating element.

It is of course possible to form the second lens plate by only unit lenses of the decentering system, but in that case, it is necessary to manufacture many types of unit lenses having slightly different decentering amounts. On the other hand, when one large plano-convex lens 41 and the unit lens 42 are used in combination as in this embodiment, the decentering amounts of the individual unit lenses can be made the same by optimizing the lens design. Therefore, the complexity at the time of manufacturing the lens can be reduced. Of course, the above-mentioned lens configuration including one large plano-convex lens and a large number of unit lenses also applies to the first lens plate 21.

TN (Twisted Nematic)
The type liquid crystal element 44 is one in which nematic liquid crystal is homogeneously aligned while twisting nematic liquid crystal in the gap between the two transparent substrates (total twist angle is 90 degrees). When polarized light is incident in accordance with the alignment direction of the nematic liquid crystal, The polarization plane of light can be rotated according to the twisted state of liquid crystal molecules.
Therefore, this TN type liquid crystal element can be used as a λ / 2 retardation plate.

Furthermore, in the structure of this embodiment, the size of the second lens plate becomes large, so that the light rays that have passed through the second lens plate reach the illumination area at a larger angle than in the case of the first embodiment. Reach Therefore, in order to reduce the irradiation angle of the light applied 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), the irradiation area 23 as shown in FIG. Field lens 43 in front of
Should be installed.

(Embodiment 3) FIG. 5 is a schematic sectional view showing a first embodiment of a projection type display apparatus using the illumination optical system of the present invention. A polarization conversion element including a λ / 2 phase difference plate 14 which is a polarization plane rotation element, a polarization beam splitter 16 which is 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 light transmission element 22 and the illumination optical system composed of both of them are operationally the same as those used in the illumination optical system of the first embodiment.

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 superposed and combined in the vicinity of the field lens 43, and guided to the light valve 51 as illumination light. The field lens is the same as in the second embodiment.
As described above, it is installed to reduce the incident angle of light to the light valve and minimize the light loss due to the projection lens, but it is not always necessary depending on the characteristics of the projection lens. Here, only one liquid crystal light valve is used as a light valve, and two polarizing plates are attached to each of the front and back surfaces of the liquid crystal light valve. The transmission axis of the polarizing plate located on the light incident side is aligned 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. The polarizing plate is arranged. In the case of this embodiment, since S-polarized light is incident on the liquid crystal light valve, a polarizing plate on the incident side is not necessary originally, but it is used to further improve the polarization degree of polarized light incident on the liquid crystal light valve. There is. The liquid crystal light valve changes the amount of transmitted light according to an image signal and forms a display image by the difference in the amount of transmitted light, and generally uses a liquid crystal. However, in addition to the liquid crystal, a light valve can be used as long as it can form an image signal as a change in optical characteristics such as an electro-optic crystal. The display image formed by the light valve is enlarged and projected on the screen 53 surface by the projection lens 52.

Generally, in a projection display device, the display image on the screen surface becomes very dark due to the light loss in the projection lens and the light dispersion caused by the 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 device, the illumination efficiency in the light valve can be increased, and as a result, a bright display image can be obtained.

(Embodiment 4) FIG. 6 is a schematic sectional view showing a second embodiment of the projection type display apparatus using the illumination optical system of the present invention. The feature of this embodiment is that a color light separating element for separating light from a light source into three primary colors in the middle of an illumination optical system, three liquid crystal light valves, and three liquid crystal light valves are formed.
It is possible to enlarge and project a colorized display image by using a color light combining element that combines two display images. However, the basic structure of the illumination optical system that illuminates the liquid crystal light valve is the same as that of the third embodiment.

A first unit composed of a decentered unit lens
A blue reflection dichroic mirror 61 that selectively reflects only blue light is placed after the lens plate 21 of (1) (the side opposite to the light source), and the two luminous fluxes bisected here are respectively reflected by the reflection mirror 62.
(However, the blue light is guided to the two second lens plates 22 by the double-sided reflection mirror 63). The light transmitted through the blue reflection dichroic mirror passes through the second lens plate 22 and then
The green reflection dichroic mirror 64 again divides the light into green light (reflected light) and red light (transmitted light), and the reflection mirror 62 (however, green light is a double-sided reflection mirror 63) bends the optical path, and then the field lens. After 43, the corresponding green light valve 65 and red light valve 66 are reached. On the other hand, blue light is reflected by two reflection mirrors 62.
After the optical path is bent by, it reaches the blue liquid crystal light valve 67 through the field lens 43. Two polarizing plates are attached to each of the three liquid crystal light valves, as shown in the third embodiment. In addition, the field lens 43
The purpose of use is the same as in Example 3.

The three display images (blue image, green image and red image) formed by the three liquid crystal light valves are color combining dichroic prisms 68 which are color light combining elements.
Thus, it is combined into a single colorized display image and enlarged and projected onto the screen 53 surface by the projection lens 52.

The projection type display device using three light valves has become the mainstream of the projection type display device because of its high resolution. The illumination optical system of the present invention can effectively exert its function even when incorporated in such a projection display device, and can be a powerful optical means for obtaining a bright display image.

[0032]

As described above, in the illumination optical system of the present invention, the polarization converting element is combined with the light transmitting element composed of two kinds of lens plates to convert the random polarized light into the specific linearly polarized light, and after the conversion. It is possible to guide the two luminous fluxes to the illumination area while effectively superimposing and coupling them with almost no divergence loss of light, and as a result, it is possible to realize a bright illumination optical system that emits only polarized light with high efficiency. Particularly, the light flux emitted from the light flux conversion element is subdivided into a plurality of light fluxes,
Since the respective luminous fluxes are superposed and combined in the vicinity of the illumination area, the illuminance unevenness and the color unevenness (in the case where the light source has a low point light source property, this kind of unevenness is likely to occur) are averaged. As a result, there is a feature that illumination light with extremely small illuminance 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 a poor point light source property is used.

Furthermore, by using the illumination optical system of the present invention, it is possible to realize a bright projection type display device with extremely little unevenness of illuminance and color unevenness, and the illumination optical system of the present invention is particularly high-definition projection. It is effective for the type display device.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a configuration of a first embodiment of an illumination optical system of the present invention.

FIG. 2 is a schematic external view of a first lens plate and a second lens plate used in Example 1.

FIG. 3 is a diagram for explaining an optical correspondence relationship between unit lenses in the illumination optical system of the present invention.

FIG. 4 is a schematic 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 a projection type liquid crystal display device using the illumination optical system of the present invention.

FIG. 6 is a schematic sectional view showing the 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 a conventional illumination optical system using only polarization conversion elements.

[Explanation of symbols]

 10 light source 11 random polarization (natural light) 12 P polarization 13 S polarization 14 λ / 2 retardation plate 15 S ′ polarization (S polarization converted from P polarization) 16 polarization beam splitter 17 prism type reflection mirror 21 first lens plate 22 Second Lens Plate 23 Illumination Area 24 Unit Lenses Constituting First Lens Plate 25 Unit Lenses Constituting Second Lens Plate 26 Optical Axis of Illumination Optical System 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 near lens A Image 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 of the same shape 43 Field lens 44 TN liquid crystal element 51 light valve 52 projection lens 53 screen 61 blue reflection dichroic mirror 62 reflection mirror 63 double-sided reflection mirror 64 green reflection dichroic mirror 65 green liquid crystal light valve 66 red liquid crystal light valve 67 blue liquid crystal light valve 68 color light combining dichroic prism 71 Polarization separation element

Claims (6)

[Claims] 1. A polarization splitting element for splitting randomly polarized light from a light source into two linearly polarized light of P wave and S wave, and a polarization plane of one of the separated two polarized light is 9
In an illumination optical system having a polarization conversion element that is rotated by 0 ° and has a polarization plane rotation element that matches the polarization plane of the other linearly polarized light, two polarizations emitted from the polarization conversion element (polarization plane rotation action (A polarized light that has been received and a polarized light that has not been received) are arranged between the polarization conversion element and the illumination area for guiding the light transmission element to the illumination area in a substantially overlapping state, and the light transmission element is the polarization conversion element. A first lens plate arranged at an incident part of light from the first lens plate and a second lens plate arranged between the first lens plate and the illumination region, and the first lens plate and the The second lens plate is formed by arranging a plurality of unit lenses in a plane perpendicular to the optical axis of the light emitted from the polarization conversion element, and the number of unit lenses forming the first lens plate. And the second lens plate The number of position lenses is the same, and a plurality of light source images formed by a plurality of unit lenses forming the first lens plate are displayed in the vicinity of the centers of a plurality of corresponding unit lenses forming the second lens plate. Image formed in the vicinity of a plurality of unit lenses that form the first lens plate and is formed in the vicinity of the illumination area by a plurality of corresponding unit lenses that form the second lens plate. The illumination optical system is characterized in that the first lens plate and the second lens plate are arranged so as to perform the above. 2. An illumination optical system, wherein at least one lens plate of the first lens plate and the second lens plate according to claim 1 comprises one plano-convex lens and a plurality of unit lenses. 3. The polarization plane rotating element according to claim 1, wherein the polarization plane rotating element is λ / 2.
An illumination optical system characterized by being a retardation plate. 4. The polarization plane rotating element according to claim 1 is a TN.
An illumination optical system, which is a (twisted nematic) type liquid crystal element. 5. The illumination optical system according to claim 1, a light valve that modulates light from the illumination optical system with an image signal to form an image, and projection optics that projects and displays the formed image on a screen. A projection display device comprising: a system. 6. The illumination optical system according to claim 1, a color light separating element for separating light from a light source into three primary color lights (blue, green, red), and each primary color light modulated by an image signal to form an image. It is composed of three light valves to be formed, a color light combining element for combining three kinds of images of respective primary color lights into one, and a projection optical system for projecting and displaying the combined image on the screen. Characteristic projection display device.