JP2000305043A - Display optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display optical device that illumination light and projection light can be separately handled by using a normal polarizing beam splitter and an illumination optical system and a projection optical system can be easily constituted in the case of the illumination light widened with a large angle and the projection light obtained based on it and even in the case of a wide wavelength range. SOLUTION: This display optical device is provided with the illumination optical system having a color separation device separation light emitted from a light source 1 arranged in a prescribed polarizing direction in directions being different in every prescribed wavelength area and the polarizing beam splitter guiding the light being as the separated illumination light to a reflection type display panel 16 and guiding the light projected from the panel 16 to the projection optical system 17. Besides, the separated illumination light is made incident on the separation surface of the polarizing beam splitter with the larger incident angle as wavelength becomes shorter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display optical device for projecting an image on a reflective display panel.

[0002]

2. Description of the Related Art Conventionally, as one of the methods for displaying an image, for example, a projection type display optical device is known. In such a display optical device, a so-called reflective display panel such as a reflective liquid crystal display panel is mainly used recently. In order to efficiently and uniformly illuminate an optical image on such a reflective display panel, an illumination optical system is used, and illumination light from the illumination optical system is guided to the reflective display panel. For this purpose, a microlens array or the like arranged immediately before the reflective display panel is used.

[0003] Specifically, for example, a reflection type display panel is used as a so-called single plate in which R, G, and B colors are sequentially arranged for each pixel, and illumination light is divided into RGB in advance. The angle is changed for each RGB, and one picture element (one picture element is a set of three RGB pixels on the display panel) or a plurality of picture elements is incident on each microlens on the microlens array, and each is a reflection type display. Light is condensed on the R, G, and B pixels of the panel.

[0004]

However, in the case of illuminating the reflective display panel by, for example, splitting the illumination light into RGB light, as in the above-described configuration, the angle of the luminous flux in the separation direction of the illumination light is reduced. Spread becomes large. As described above, in order to illuminate the reflective display panel with the illumination light having a wide angle and separate and handle the projection light therefrom,
For example, it is necessary to use a polarizing beam splitter that can handle a light beam spread at a large angle.

However, a polarizing beam splitter capable of dealing with a light beam spread at a large angle cannot be realized by a conventional configuration using a dielectric multilayer film.
Usually, when the angle of incidence on the polarizing beam splitter changes, the characteristics of the transmittance of the incident light in the wavelength region greatly change. Therefore, in the case of the illumination light spread at a large angle and the projection light based thereon, and further in the case of a wide wavelength range, it is difficult to handle the illumination light and the projection light separately.

SUMMARY OF THE INVENTION In view of the above problems, the present invention uses a normal polarizing beam splitter for illumination light spread at a large angle and projection light based on the illumination light, and even in a wide wavelength range. It is an object of the present invention to provide a display optical device that can handle light and projection light separately, and can easily configure an illumination optical system and a projection optical system.

[0007]

In order to achieve the above object, the present invention provides a color separation apparatus for separating light from a light source aligned in a predetermined polarization direction in different directions for each predetermined wavelength region. And a polarizing beam splitter that guides light as the separated illumination light to a reflective display panel and guides projection light from the reflective display panel to a projection optical system. The illuminated light is incident on the separation surface of the polarizing beam splitter at a larger incident angle as the wavelength becomes shorter.

[0008] Further, the illumination optical system has a configuration according to claim 1 provided with a polarization conversion device for aligning light from the light source in the predetermined polarization direction.

Further, the projection light is incident on the separation surface of the polarizing beam splitter at a larger incident angle as the wavelength is shorter, as in the third embodiment of the present invention.

[0010] A microlens array in which one lens corresponds to each picture element of the reflective display panel is provided between the color separation device and the reflective display panel, and a pixel of the reflective display panel is provided. According to a fourth aspect of the present invention, a reflective diffraction grating is provided on the reflecting surface.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram schematically illustrating a display optical device according to an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a light source, and 2 denotes a reflector arranged so as to surround the light source 1. Reference numeral 7 denotes a UVIR cut filter that is disposed so as to cover the light emission port 2 a of the reflector 2 and that cuts ultraviolet light and infrared light included in the light from the light source 1 and the reflector 2.
Behind the UVIR cut filter 7 (right side of the figure)
The birefringent diffraction grating 3, the first lens array 4, the second lens array 6 a little apart, and the superimposing lens 8 immediately after that
Is arranged.

Although not shown here, the first lens array 4 has cells combined in a lattice, and the second lens array 6 has a rectangular shape divided in a direction different from that of the first lens array 4. Have each cell combined in a lattice shape. The birefringent diffraction grating 3 includes a second lens array 6
The light 9 from the light source 1 and the reflector 2 is polarized and separated in the long side direction of each cell. Polarization conversion is performed through the birefringent diffraction grating 3, the first lens array 4, and the second lens array 6, and light 9 from the light source 1 and the reflector 2 emerges with specific polarization. This configuration is called a polarization conversion device. The detailed relationship between them will be described later.

Further, the second lens array 6 and the superimposing lens 8 immediately after the second lens array 6 allow the images of the respective cells of the first lens array 4 to be superimposed in the vicinity of a later-described focal position of the superimposing lens 8. In addition, the superposition lens 8
May be formed integrally with the second lens array 6. Further, instead of the birefringent diffraction grating 3, there is a type in which a birefringent prism array or the like is arranged between the first lens array 4 and the second lens array 6. The above-described first lens array 4 to the superimposing lens 8 are called an integrator optical system, and the optical axis is L. This superimposed lens 8
The display panel 16 is arranged at the focal position of the.

First, R (red), G (green), B (blue) are provided between the superimposing lens 8 and the display panel 16.
Dichroic mirrors R _m , G _m , and B _m as color separation devices that reflect light in the respective wavelength regions are arranged with different inclinations, and a PBS (polarizing beam splitter) is provided behind the dichroic mirror (upper part of the figure). ) A prism 14 is arranged. At this time, the light 9 transmitted through the superimposing lens 8 on the optical axis L is reflected by the respective dichroic mirrors R _m , G _m , and B _m , and the optical axes L _R , L _G , and L _{B at} different angles. With PBS prism 14,
Eventually, it reaches the display panel 16.
Incidentally, the dichroic mirror _Bm may be a total reflection mirror. The light 9 reflected by the dichroic mirror is not shown.

The PBS prism 14 has a property of reflecting S-polarized light and transmitting P-polarized light. On the other hand, the light 9 from the light source 1 and the reflector 2 is incident on the PBS prism 14 while being substantially aligned with S-polarized light by the above-described polarization conversion. Therefore, the PBS prism 14
Most of the light 9 is reflected, and the display panel 16 on the left side of FIG.
Head for.

At this time, specifically, light from the dichroic mirror is applied to the PBS prism 14 which is provided in the diagonal direction of the PBS prism 14 and functions as a PBS separating surface.
The structure is such that the shorter the wavelength becomes in the order of RGB, the larger the incident angle is incident on the dielectric multilayer film 14a as a film. The dielectric multilayer film 14a is set so as to have a characteristic capable of satisfactorily separating the polarized light corresponding to the light of each wavelength region incident at each incident angle. Details will be described later.

Immediately before the display panel 16, a microlens array 15 is arranged. The light 9 color-separated by the dichroic mirror illuminates different pixels of the display panel 16 for each color as illumination light by the microlens array 15. Details will be described later. Due to this illumination, the entire display panel 16 has R, G,
B is sequentially illuminated in stripes by each color of B,
Pixels illuminated by each color display information of each color.

The display panel 16 is a reflection type liquid crystal display panel. The light illuminated on the display panel 16 is rotated (ON) or not (OFF) by rotating the polarization plane according to display information for each pixel. reflect. At this time, the OFF reflected light passes through the microlens array 15 and passes through the PBS prism 1.
Returning to No. 4, since the light remains S-polarized light, it is reflected here and returned to the light source side. On the other hand, since the ON reflected light has been converted into P-polarized light, it returns to the PBS prism 14 via the microlens array 15 and transmits therethrough to reach the next projection optical system 17. The projection optical system 17 projects display information on the display panel 16 onto a screen (not shown).

The display panel 16 has a diffraction effect, and the R, G, and B lights that illuminate the display panel 16 are projected so as to follow the same optical path in the opposite direction. Reflected as light, the PBS prism 14
Return to Thereby, the incident angle of the projection light on the dielectric multilayer film 14a becomes the same as that of the illumination light for each of the R, G, and B colors, so that good polarization separation characteristics can be obtained.
Details will be described later.

FIG. 2 is an exploded perspective view schematically showing the relationship between the birefringent diffraction grating and the first and second lens arrays in the present embodiment. In the figure, some of the cells in the lens array are shown as representatives. As shown in the figure, in the present embodiment, the side direction of each cell indicated by a solid line of the first lens array 4 is different from the side direction of each cell indicated by a broken line of the second lens array 6, and birefringence diffraction is performed. The groove direction of the blaze 3 a of the lattice 3 is set to be along the side direction of each cell of the second lens array 6. Specifically, the diagonal direction of the side direction of each cell of the first lens array 4 is set to be the side direction of each cell of the second lens array 6.

Light 9 from the light source 1 and the reflector 2 (not shown) located diagonally below and to the left of the figure is illuminated by the blaze 3a of the birefringent diffraction grating 3 with light 9a having a predetermined polarization plane indicated by a solid line and perpendicular to the light 9a. The light is polarized and separated into light 9b indicated by a broken line having an appropriate polarization plane. These lights are transmitted through the individual cells A, B, C, and D arranged in the lattice of the first lens array 4 and are arranged in a rectangular lattice divided in a direction different from that of the first lens array 4. On each of the cells Aa, Ba, Ca, and Da of the two-lens array 6, a light source image having a predetermined polarization plane and a light source image having a polarization plane perpendicular thereto are created.

In order to form a light source image from cells A, B, C, and D in cells Aa, Ba, Ca, and Da arranged in different directions, the cells A, B, C, and D of the first lens array 4 Each lens is slightly tilted or the lens apex is decentered. That is, the lens vertex is shifted from the center of the cell. Similarly, the second
Each of the cells Aa, Ba, Ca, and Da of the lens array 6 is also individually inclined or the vertex of the lens is decentered.

These light source images are formed by the birefringent diffraction grating 3
, That is, in the long side direction of each cell of the second lens array 6, and form a correct row. These light source images are projected with a certain size onto individual cells of the second lens array 6 as indicated by solid and broken ellipses (circles when viewed from the front of the lens array). You. By the way,
The coordinate system of the present example has the y-axis above the front of the first lens array 4 and the x-axis to the right as viewed from the light source side, and the side of each cell toward the front of the second lens array 6. The diagonally upper right direction along the direction is the ya axis, and the diagonally lower right direction is the xa axis.

According to such a configuration, light source images in the second lens array 6 are less overlapped with each other, and efficient polarization conversion can be performed. At this time, for example, a half-wave plate 5 in a strip shape may be attached along the row of the light source image indicated by the broken line ellipse, and the polarization planes of the separated light source images may be aligned. Incidentally, the size of the light source of the present embodiment and the area of the cells of the second lens array 6 are equal to those of the conventional system in which the cells of the first and second lens arrays are arranged in the same column direction (side direction is the same).

When the integrator has one stage as in this embodiment, the cells of the first lens array 4 are
Should be approximately equal to the aspect ratio. Even in such a case, by making the side direction of each cell of the first lens array 4 and the side direction of each cell of the second lens array 6 different, efficiency is higher than in the conventional case where the side directions are the same. Good. FIG. 3 is a front view schematically showing the positional relationship between the first and second lens arrays when the integrator has one stage, and shows a case where the aspect ratio is 4: 3. As shown in the drawing, here, one diagonal direction of each cell indicated by a solid line of the first lens array 4 is set to be the long side direction of each cell indicated by a broken line of the second lens array 6.

The light 9 from the light source 1 and the reflector 2 (not shown) is polarized by the birefringent diffraction grating 3 (not shown) into light having a predetermined polarization plane and light having a polarization plane perpendicular thereto. Separated. These lights are the first
The lens array 4 has a rectangular lattice shape that transmits the individual cells A, B, C, D, E, and F arranged in a lattice shape having an aspect ratio of 4: 3 and is divided in a direction different from that of the first lens array 4. , The individual cells Aa, Ba, of the second lens array 6
A light source image having a predetermined polarization plane and a light source image having a polarization plane perpendicular thereto are created on Ca, Da, Ea, and Fa, respectively.

These two light source images are formed by the birefringent diffraction grating 3
In the direction of separation by These light source images are projected with a certain size onto individual cells of the second lens array 6 as indicated by solid and broken circles. Incidentally, the coordinate system of the present example has the y-axis above the front of the first lens array 4 as viewed from the light source side and the x-axis to the right, and each cell toward the front of the second lens array 6. The yaw axis is the diagonally upper right direction along the side direction of
The diagonally lower right direction is the xa axis.

In the present embodiment, as shown in FIG. 2, the birefringence direction of the birefringent diffraction grating 3 is aligned with the ya axis direction which is the groove direction of the blaze 3a. The two types of light 9a and 9b shown, and the two types of light source images shown by the solid line and the broken line ellipse have polarization planes of x respectively.
The directions are the a-axis and the ya-axis. However, for the optical system in which these lights are incident next, the polarization planes must be aligned in the y-axis direction. Therefore, different optical axes that intersect each other at 45 ° are arranged in each of the two light source image columns. The polarization planes are simultaneously aligned by using a band-shaped half-wave plate.

As another method of aligning the polarization planes, first, one of the two types of light source images is arranged in a row of one of the light source images in a band shape.
After using a two-wavelength plate to align the polarization plane with the other light source image, the entire polarization plane is aligned at once in the y-axis direction.
It is also possible to use a two-wave plate on the entire surface of the second lens array 6. Further, the birefringence direction of the birefringent diffraction grating 3 is not set in the groove direction of the blaze 3 a, that is, in the long side or short side direction of each cell of the second lens array 6, but the long side or short side of each cell of the first lens array 4. The direction may be the side direction. Also,
A polarization separation method other than the method using the birefringent diffraction grating may be performed.

FIG. 4 is a diagram schematically showing the relationship between the microlens array of this embodiment and a display panel. FIG.
As described above, the microlens array 15 is disposed immediately before the display panel 16. The R, G, and B colors are sequentially arranged for each pixel of the display panel 16 which is a single plate. The light 9 from the light source 1 is divided into RGB in advance, and the angle is changed for each RGB. Each microlens 15a of the microlens array 15 for one picture element (one picture element is a set of three RGB pixels on the display panel)
To the display panel 16 for R, G, and B, respectively.
To be focused on the pixel for use. The left and right sides of the microlens array 15 and the display panel 16 in FIG.

The display panel 16 has a diffraction effect. Light of each color of R, G, and B illuminating the display panel 16 is indicated by arrows a, b, and b in FIG.
As shown by c, the light is reflected as projection light so as to follow the same optical path in the opposite direction.
Return to 4. Accordingly, the incident angle of the projection light on the dielectric multilayer film 14a of the PBS prism 14 becomes the same as that of the illumination light for each of the R, G, and B colors, so that good polarization separation characteristics can be obtained.

FIG. 5 is a diagram schematically showing a specific configuration of a display panel having the diffraction effect. This is an enlarged view of the vicinity of a portion d surrounded by a circle in FIG. FIG.
As shown in (a), each pixel 16a is arranged at the bottom of a display panel 16 which is a reflection type liquid crystal display panel, and a reflection type diffraction grating 16b is formed on the upper surface (reflection surface) for each pixel. I have. This is made of aluminum and also serves as an electrode. In order to fill irregularities on the surface of the reflective diffraction grating 16b, a transparent member layer 1 made of a resin material or the like is provided on the upper surface thereof.
6c is provided. A ferroelectric liquid crystal layer 16d is formed thereon, and a transparent flat glass 16e is further mounted thereon.

An upper transparent electrode layer 16f is provided between 16d and 16e. This reflection type diffraction grating 1
6b, the display panel 16 has a power that causes a diffraction effect when the illumination light is reflected. By the way, a reflection type liquid crystal display element is formed by stacking layers in the same manner as a normal IC element. Accordingly, the reflection type diffraction grating 16b is also formed by stacking aluminum layers in a stepwise manner as shown in FIG. Here, the number of steps is about 3 to 4 steps, and the height of the grating is constant. The configuration from the light source 1 to the microlens array 15 described above is called an illumination optical system.

FIG. 6 is a graph showing the transmittance characteristics of the PBS prism used in this embodiment. FIG.
(B) and (c) show the incident angles of the PBS prism 14 with respect to the dielectric multilayer film 14a of 40 degrees and 50 degrees, respectively.
The case of 60 degrees is shown. In each graph, the horizontal axis indicates the wavelength of the light used in units of nm, and the vertical axis indicates the transmittance. The transmittance of P-polarized light is indicated by a curve P,
The transmittance of S-polarized light is shown by curve S.

As shown in FIG. 3A, when the incident angle is 40 degrees, the transmittance is generally good for P-polarized light in the R (red) wavelength region of, for example, 580 to 670 nm indicated by an arrow Ra. The reflectance is generally good for S-polarized light (reflectance = 1−transmittance). Further, as shown in FIG. 3B, when the incident angle is 50 degrees, the transmittance is good for P-polarized light in a G (green) wavelength region of, for example, 510 to 580 nm indicated by an arrow Ga. , S-polarized light. Also, as shown in FIG.
When the incident angle is 60 degrees, for example, 450
In the B (blue) wavelength region of ５１０510 nm, the transmittance is generally good for P-polarized light, and the reflectance is good for S-polarized light.

In this manner, light is incident on the dielectric multilayer film at a larger incident angle as the wavelength becomes shorter in the order of RGB. Correspondingly, the dielectric multilayer film is set so as to have a characteristic capable of excellent polarization separation. According to such a configuration, the incident angle of the incident light to the PBS prism fluctuates,
Even if the characteristics of the transmittance of the incident light with respect to the wavelength region greatly change, generally good polarization separation characteristics can be maintained, so that a normal polarization beam splitter is used to separate the illumination light and the projection light respectively. The illumination optical system and the projection optical system can be easily configured.

Incidentally, the incident angle of light of each color with respect to the dielectric multilayer film is generally between R (red) and G (green) and G (green).
(Green) and B (blue) have a difference of 5 to 15 degrees, respectively, and further, the incident angle of G (green) is 45 degrees or more. Is obtained.

Table 1 is a table showing the film configuration of the dielectric multilayer film of the PBS prism used in this embodiment. In the table, Ni means the refractive index of the i-th layer. The optical film thickness is a dimensionless quantity based on a reference wavelength of 650 nm. Here, the 0th and 18th layers indicate the glass blocks constituting the PBS prism,
The seventeenth layer indicates a dielectric multilayer film. In other words, the configuration is such that the dielectric multilayer film is sandwiched between the glass blocks from both sides. The refractive indices of the first and seventeenth layers are the same as those of the glass block in order to improve mutual adhesion and make it easier to conform.

[0039]

[Table 1]

[0040]

As described above, according to the present invention,
In the case of the illumination light spread at a large angle and the projection light based on the illumination light, and even in the case of a wide wavelength range, the illumination light and the projection light can be handled separately by using a normal polarizing beam splitter. It is possible to provide a display optical device that can easily configure an optical system and a projection optical system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a display optical device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view schematically showing a relationship between the birefringent diffraction grating of the present embodiment and first and second lens arrays.

FIG. 3 is a front view schematically showing a positional relationship between first and second lens arrays when the number of integrators is one;

FIG. 4 is a schematic diagram showing the relationship between the microlens array of the embodiment and a display panel.

FIG. 5 is a schematic diagram showing a specific configuration of a display panel having a diffraction effect.

FIG. 6 is a graph showing transmittance characteristics of a PBS prism used in the embodiment.

[Explanation of symbols]

Reference Signs List 1 light source 2 reflector 3 birefringent diffraction grating 4 first lens array 5 1/2 wavelength plate 6 second lens array 7 UVIR cut filter 8 superimposing lens 14 PBS prism 15 micro lens array 16 display panel 17 projection optical system R _m , G _m , B _m dichroic mirror

Claims (4)

[Claims] 1. An illumination optical system including a color separation device that separates light from a light source aligned in a predetermined polarization direction in different directions for each predetermined wavelength region; A polarizing beam splitter that guides light to a reflective display panel and guides projection light from the reflective display panel to a projection optical system, wherein the separated illumination light has a larger incident angle as the wavelength is shorter. A display optical device, which is incident on a separation surface of a polarizing beam splitter. 2. The display optical device according to claim 1, wherein the illumination optical system includes a polarization conversion device for aligning light from the light source with the predetermined polarization direction. 3. The display optical device according to claim 1, wherein the projection light is incident on the separation surface of the polarizing beam splitter at a larger incident angle as the wavelength is shorter. 4. A microlens array in which one lens corresponds to each picture element of the reflection type display panel between the color separation device and the reflection type display panel, and a pixel of the reflection type display panel is provided. 4. The display optical device according to claim 1, wherein a reflection type diffraction grating is provided on the reflection surface.