JP2001174756A - Optical device and video display device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance such as the brightness of a display picture or color reproducibility by reducing the light loss in a dichroic prism. SOLUTION: S-polarized white light is mane incident on a dichroic prism 8 along an optical axis 14, and red light and blue light are separated by a red reflection face 9R and a blue reflection face 9B of normals 13R and 13B inclined at an angle A to the optical axis 14, and they are subjected to space modulation by reflection type video display elements 10R and 10B made of liquid crystal elements or the like and are made incident on the prism 8 again. Green light which has passed reflection faces 9R and 9B is also subjected to space modulation by a video display element 10G and is made incident on the prism 8 again. The light beams of these colors are synthesized and are emitted along the optical axis 14. The angle is set to <45 deg. to reduce the difference between wavelengths to be half values of s-polarized light and p-polarized light, that is, the extent of half-value wavelength shift, and the loss on reflection faces 9R and 9B of p-polarized light due to space modulation from video display elements 10R, 10G, and 10B is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device using a polarization technique such as a liquid crystal panel, a polarizing plate, and a polarizing beam splitter, and a liquid crystal projector device, a reflection type video display projector device, and a liquid crystal television using the optical device. The present invention relates to a projection-type image display device such as a projection device and a projection-type display device.

[0002]

2. Description of the Related Art As a conventional example of an optical device used for an image display device, there is known a wavelength separating element combined in a cross shape, such as a dichroic mirror or a dichroic prism, as disclosed in Japanese Patent Application Laid-Open No. 1-157687. A reflection type liquid crystal display element that converts the polarization of blue light, red light, and green light, respectively, is disposed on the three side surfaces. The dichroic prism is formed by combining four triangular prisms into a cube having a square cross section. One of the orthogonal triangular prism joining surfaces in the cube is a dichroic blue reflecting surface, and the other triangular prism joining surface is a dichroic red. It is a reflective surface.

FIG. 11 shows an image display device using a liquid crystal display element using such an optical device (hereinafter referred to as a liquid crystal display device).
1 is a configuration diagram showing a conventional example, wherein 1 is a light source unit,
2 is a light source, 3 is a reflector, 4a and 4b are array lenses, 5 is an illumination optical system, 6 is an incident polarizing plate, 7 is a polarizing beam splitter, 7a is a coating surface, 8 is a dichroic prism, 9R is a red reflecting surface, and 9B. Is blue reflective surface, 10R
Is a reflective image display element for red, 10G is a reflective image display element for green, 10B is a reflective image display element for blue, 7a is a coating surface, 11 is an output polarizing plate, and 12 is a projection lens.

As shown in FIG. 1, this conventional liquid crystal display device includes a light source unit 1 for emitting light, comprising a light source 2, a reflector 3, and array lenses 4a and 4b, an illumination optical system 5, a polarization beam splitter 7, , A projection lens 12,
Video display elements 10R, 10G, 10B for red, green, and blue, each composed of a liquid crystal display element, and a dichroic prism 8
It is composed of

The light from the light source unit 1 enters the illumination optical system 5 and becomes substantially parallel light. The S-polarized light passes through the incident polarizing plate 6 and reaches the polarizing beam splitter 7. The polarization beam splitter 7 has an S
It reflects the polarized light component and allows the P-polarized light component to pass through, and reflects the S-polarized incident light from the incident polarizer 6 and sends it to the dichroic prism 8. In the dichroic prism 8, the S-polarized light incident from the polarizing beam splitter 7 is decomposed into three primary colors of red, green, and blue, and a red reflective image display element 10R, a green reflective image display element 10G,
The light is emitted to the blue reflective image display element 10B. Specifically, the blue light of the incident light from the polarization beam splitter 7 is reflected and separated by the blue reflecting surface 9B of the dichroic prism 8, and the red light is reflected and separated by the red reflecting surface 9R of the dichroic prism 8, The green light is separated by transmitting through these two reflecting surfaces 9R and 9B.

The red, green and blue color lights emitted from the dichroic prism 8 are respectively reflected by the red reflective image display element 1.
0R, the green reflective image display element 10G, and the blue reflective image display element 10B.
Each of R, 10G, and 10B is spatially modulated according to the video signal there, reflected by a not-shown reflecting mirror, and again passes through these video display elements 10R, 10G, and 10B in opposite directions. Since these image display elements 10R, 10G, 10B have birefringence, these image display elements 10R, 10G, 10B
The color light that has reciprocated in G and 10B has its linear polarization plane rotated in proportion to the level of the video signal, and becomes polarized light containing a P-polarized component at a rate corresponding to the magnitude of this rotation.

[0007] These image display elements 10R, 10G, 10
The color light emitted from B enters the dichroic prism 8 again, the red light is reflected by the red reflection surface 9R, the blue light is reflected by the blue reflection surface 8, and the green light passes through as it is, so that these color lights are synthesized. The light is then output to the polarization beam splitter 7. In the polarization beam splitter 7, the S-polarized light component of the light incident from the dichroic prism 8 is reflected by the coating surface 7a toward the light source unit 1,
Only the P-polarized component passes through the coating surface 7a as it is. The P-polarized light that has passed through the polarizing beam splitter 7 is
The light is magnified and projected on a screen (not shown) via an emission polarizer 11 and a projection lens 12 that allow only polarized light to pass therethrough. Thereby, the image display elements 10R, 10G, 10B
Is enlarged and projected on a screen by combining the R, G, and B images formed on the screen.

[0008]

The reflecting surface of the dichroic prism reflects light in the wavelength range λ _{1 to} λ ₂ determined by its characteristics. Therefore, by appropriately setting the wavelength range λ _{1 to} λ ₂ , desired color light can be reflected. Light having a wavelength outside the wavelength range λ _{1 to} λ ₂ is transmitted through the reflecting surface. The wavelengths λ ₁ and λ ₂ that determine this wavelength range
Is the wavelength at which the amount of reflected light (and therefore the amount of transmitted light) is 50%, and such a wavelength is hereinafter referred to as a half-value wavelength.

The half-value wavelength λ of the P-polarized light and the S-polarized light is defined as the angle between the normal to the reflecting surface and the optical axis of the light incident on the reflecting surface (hereinafter, the light incident angle on the reflecting surface). The) θ
And the larger the angle θ, the larger the value of P
Difference in half-value wavelength λ between polarized light and S-polarized light (hereinafter,
Wavelength shift amount). FIG. 12 is a diagram showing an experimental result of a half-value wavelength shift amount between the P-polarized light and the S-polarized light for each of the blue reflection surface and the red reflection surface of the dichroic prism in which the light incident angle θ is in the range of 0 to 50 degrees. As is clear from the experimental results, the half value wavelength shift between the P-polarized light and the S-polarized light increases as the light incident angle θ increases for both the blue reflection surface and the red reflection surface.

Therefore, in the above prior art, the light incident angle θ on the reflecting surfaces 9 R and 9 B of the dichroic prism 8 is 4
Since it is as large as 5 degrees, the half-value wavelength shift amount (the difference between the half-value wavelength λp of the P-polarized light and the half-value wavelength λs of the S-polarized light) between the P-polarized light and the S-polarized light is large, and these half-value wavelengths λp and λs
Is cut by the polarizing beam splitter 7, which causes a decrease in brightness and a deterioration in color reproducibility in the image display device.

More specifically, in FIG. 11, the blue reflecting surface 9B of the dichroic prism 8
At a light incident angle of 5 degrees, white S-polarized light is input from the polarization beam splitter 7, and as shown in FIG. 13, S-polarized blue light having a wavelength equal to or less than the half-value wavelength λs, which is the upper limit wavelength of blue light, is reflected. Are emitted to the blue reflective image display element 10B. Similarly, blue light modulated by a video signal from the blue reflective image display element 10B is incident on the blue reflecting surface 9B of the dichroic prism 8 at a light incident angle of 45 degrees, and the blue light is 13, a P-polarized component up to a wavelength λs indicated by a broken line is included,
In B, P-polarized light is reflected only up to the half-value wavelength λp.
Here, λs> λp, and the P-polarized light reflects only in the wavelength region up to the half-value wavelength λp shown by the solid line in FIG.
The difference between the half-value wavelengths (λs−λp), that is, the amount of P-polarized light in the range of the half-value wavelength shift amount is lost without being reflected by the blue reflection surface 9B. In the above-described prior art, since the half-value wavelength shift amount is as large as 45 degrees, the half-value wavelength shift amount is large, and the amount of P-polarized light lost at the blue reflecting surface 9B is also large.

The blue light from the blue reflective image display device 10B reflected by the blue reflecting surface 9B is sent to the polarizing beam splitter 7, and only the P-polarized component is extracted by the coating surface 7a. Is projected on a screen (not shown) through the LCD and is used for displaying an enlarged color image. However, since the attenuation of the P-polarized light component of the blue light on the blue reflecting surface 9B is large, the blue light The amount of light will be reduced.

The same applies to the red light on the red reflecting surface 9R (in this case, the half-value wavelength which is the lower limit wavelength of the red light wavelength range). The same applies to the transmission characteristics of green light on the reflection surface, and as a result, the red light projected on the screen,
The amount of P-polarized light of blue and green color light is reduced, and the brightness of the displayed enlarged color image is reduced. Further, the ratio of attenuation of the P-polarized light components of the red, green and blue color lights on the reflection surfaces 9R and 9B is slightly different for each color light, and therefore, the light is projected on the screen. The color reproducibility of the displayed color image also deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical device which solves such a problem and which can maintain the brightness and color reproduction performance of a displayed color image, and an image display device using the same.

[0015]

In order to achieve the above object, an optical device according to the present invention is provided with first and second reflecting surfaces for reflecting different kinds of primary color lights arranged crossing each other. A dichroic prism that separates light incident from a side surface perpendicular to the optical axis along a predetermined optical axis into three primary color lights by the first and second reflecting surfaces,
Three reflection-type polarization conversion elements, each of which converts the polarization state of the primary color light separated by the dichroic prism for each of them, and re-enters the dichroic prism.
A is the angle between the normal of the reflecting surface of the
The angle formed by the normal of the reflection surface with respect to the optical axis is −A, and A <45 °. The dichroic prism converts the primary color light re-entered from each of the reflection type polarization conversion elements into the first light. , And are combined on the second reflecting surface and emitted along the optical axis.

As described above, by making the angle A smaller than 45 °, the angle of polarization at the reflecting surface of the dichroic prism depends on the polarization state (ie, the difference between the wavelengths at which the S-polarized light and the P-polarized light have a half value). The half wavelength wavelength shift amount can be reduced, and the loss of the polarized light component converted by the reflection type polarization conversion element can be reduced, so that the three primary color lights are combined in a well-balanced manner.

Further, the optical device according to the present invention reflects different types of primary color lights arranged crosswise to each other and separates light incident along a predetermined optical axis into three primary color lights. The first and second dichroic mirrors, and the three different polarization states of the primary color light separated by the first and second dichroic mirrors, which are re-incident on the first and second dichroic mirrors, respectively. A polarization conversion element, wherein the angle between the normal of the first dichroic mirror and the optical axis is A, and the angle between the normal of the second dichroic mirror and the optical axis is -A. , A <45 °, and the first and second dichroic mirrors are configured to combine the primary color light re-entered from each of the reflection type polarization conversion elements and emit the light along the optical axis. is there.

Thus, similarly to the above-described invention, it is possible to reduce the half-value wavelength shift amount due to the polarization state of the dichroic mirror and reduce the loss of the polarized light component converted by the reflection type polarization conversion element. Are synthesized in a well-balanced manner.

Further, the optical device according to the present invention is provided with first and second reflecting surfaces for reflecting different kinds of primary color lights arranged crossing each other, and the light is incident along a predetermined optical axis. A hexagonal prism that separates the primary light into three primary color lights by the first and second reflection surfaces, and converts the polarization state of the primary color light separated by the hexagonal prism for each,
A first, a second, and a third reflection-type polarization conversion element for re-entering the hexagonal prism;
A first side surface perpendicular to the optical axis is defined as an incident surface of light incident along the optical axis, and a second side surface is defined as an emission surface of the first primary color light separated by the first reflection surface. And an entrance surface for only the first primary color light from the first reflection type polarization conversion element, and a third side surface with an emission surface of the second primary color light separated by the second reflection surface. At the same time, the second primary color light from the second reflection type polarization conversion element was used as an incident surface of the second primary color light, and a fourth side surface opposite to the first side surface passed through the first and second reflection surfaces. As an emission surface of the third primary color light, and as an incidence surface of the third primary color light from the third reflection type polarization conversion element,
The primary color lights from the first, second and third reflection type polarization conversion elements respectively incident from the second, third and fourth side surfaces are combined on the first and second reflection surfaces, and The light is emitted from the first side surface along the optical axis, and the first reflection type polarization conversion device is parallel to the second side surface, and the second reflection type polarization conversion device is parallel to the third side surface. A is an angle between the optical axis perpendicular to the first side surface and the normal of the first reflection surface, and the second angle to the optical axis perpendicular to the first side surface. The angle A formed by the normal to the reflection surface is -A, and A <45 °.

According to this configuration, in contrast to the present invention using the above-described dichroic prism, it is possible to prevent the primary color light separated by the reflection surface of the hexagonal prism from being blurred, and to further reduce the loss of the primary color light. can do.

In the image display apparatus according to the present invention, white light is separated into three primary color lights by an optical device, the polarization states of these primary color lights are converted and combined, and the primary color lights combined by this optical device are polarized. Although a configuration for projecting through a beam splitter is used, the optical device according to the present invention is used as the optical device, and performance such as brightness and color reproduction of a projected image is obtained by using the optical device. Is greatly improved.

Here, the angle formed with respect to the optical axis of the normal to the reflection surface of the dichroic prism will be described.

As described above, FIG. 12 shows the relationship between the angle A formed with respect to the optical axis of the normal to the reflecting surface of the dichroic prism and the half-value wavelength shift between the P-polarized light and the S-polarized light. In this case, it is assumed that the representative ray is incident along the optical axis. Therefore, here, the angle A made with respect to the optical axis of the normal to the reflection surface of the dichroic prism is equal to the incident angle of the light beam.

Here, the reason for using the representative light beam is as follows. That is, in general, light in a certain F value range is incident on a dichroic prism used in a liquid crystal projector, but as an illuminance distribution, the component of light (large F value) substantially parallel to the optical axis is the largest. The light component having a smaller angle with respect to the optical axis (smaller F value) has a smaller component. For this reason, it is possible to determine the optical performance of the dichroic prism using the representative light beam.

In the present invention, the angle A formed with respect to the optical axis of the normal to the reflecting surface of a dichroic prism or the like is set to be smaller than 45 °. This is apparent from FIG. Compared with a conventional optical device having an angle of 45 °, the half-wavelength shift amount is reduced, thereby suppressing light loss.

In the present invention, the angle A is set at 15 ° to 37 °. This is because, as is clear from FIG. The half-value wavelength shift amount can be smaller than that of
This is to suppress an increase in the size of the optical device. As the angle A formed with respect to the optical axis of the normal to the reflection surface of the dichroic prism decreases, the half-wavelength shift amount can be reduced, but the trade-off is to increase the size of the optical device. At present, as a commercial value of a liquid crystal projector, compatibility between brightness and downsizing is an important theme. First, in order to obtain an image with sufficient brightness and color reproducibility, it is desirable that the amount of the half-value wavelength shift be suppressed to a maximum of 20 nm or less, and from FIG. 12, the light normal to the reflection surface of the dichroic prism can be obtained. Angle A to axis
Is 37 °. Also, in order to make the product valuable in business, it is desirable that the size of the optical device be limited to a maximum of three times the size when the angle A is 45 °. , The lower limit of the angle A to the optical axis of the normal to the reflecting surface of the dichroic prism is 15 °.

Further, in the present invention, the angle A is set to 15 ° or less, but this is to suppress the half-value wavelength shift to 5 nm or less at the maximum, with emphasis on optical performance. Accordingly, from FIG. 12, the upper limit of the angle A formed with respect to the optical axis of the normal to the reflection surface of the dichroic prism is set to 1
5 °.

The optical axis is perpendicular to the incident surface of the dichroic prism.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of an optical device according to the present invention, wherein 8a to 8d are side surfaces of a dichroic prism 8, 13R is a normal line of a red reflecting surface 9R, and 13B is a law of a blue reflecting surface 9B. Line, 14 is the optical axis,
Parts corresponding to those in FIG. 11 are denoted by the same reference numerals.

In the drawing, a dichroic prism 8 as a color separating / combining means is formed by combining four triangular prisms (triangular prism-shaped prisms), and has a blue reflecting surface 9B and a blue reflecting surface 9B arranged crosswise to each other. Red reflective surface 9
R. The blue reflecting surface 9B reflects a blue light, and a dichroic film that transmits a longer wavelength region than the blue light is deposited. The red reflecting surface 9R reflects the red light,
A dichroic film that transmits a shorter wavelength band than that is deposited.

The dichroic prism 8 has an optical axis 14 perpendicular to one side 8a.
, S-polarized light is incident, and the red light component of the incident light is reflected and separated by the red reflection surface 9R, and is incident on the red reflective image display element 10R. The blue light component of the incident light is The light is reflected and separated by the blue reflecting surface 9B and is incident on the reflective image display device 10B for blue. Further, the green component of the incident light is separated by transmitting through these reflecting surfaces 9R and 9B, and is reflected by the green. Incident on the image display device 10G. In these image display elements 10R, 10G, and 10B, red, green, and blue color light components are spatially modulated in accordance with an image signal, further reflected by a reflector (not shown), spatially modulated again, and according to the modulation. The light is again incident on the dichroic prism 8 as a color signal containing a P-polarized component. In the dichroic prism 8, the red light component is reflected on the red reflecting surface 9R, the blue light component is reflected on the blue reflecting surface 9B, and the green light component is transmitted through these reflecting surfaces 9R and 9B, so that these color light components are synthesized. Then, the light is emitted from the side surface 8a along the optical axis 14.

Here, one of the reflecting surfaces, ie, the blue reflecting surface 9B
If the angle of the normal 13B to the optical axis 14 is A ゜,
Optical axis 1 of normal 13R to red reflection surface 9R, which is the other reflection surface
The angle with respect to 4 is also assumed to be A ゜, but the blue reflecting surface 9
The normal 13B of B and the normal 13R of the red reflection surface 9R are the optical axis 1
4, the angle between the normal 13R of the red reflecting surface 9R and the optical axis 14 is -A.
゜.

In this embodiment, the angle A ゜ is made smaller than 45 °, and the difference between the half-value wavelengths of the P-polarized light and the S-polarized light at the reflecting surfaces 9R and 9B, that is, the half-value wavelength shift amount is reduced. Things. As described above, the larger the half-value wavelength shift amount, the larger the amount of P-polarized light necessary for projection on the reflecting surfaces 9R and 9B, and, as described in FIG. And normal line 1 of reflection surfaces 9R and 9B
The larger the angle between 3R and 13B, the larger the half-wavelength shift amount. In the conventional optical device, the angle A of the normal to the reflection surface of the dichroic prism with respect to the optical axis is as large as 45 °, but in this embodiment, as described above, this angle A is made smaller than 45 °. Therefore, the amount of P-polarized light lost at the reflecting surfaces 9R and 9B can be reduced.

In the conventional optical device in which the angle A is 45 °, as shown in FIG. 11, the red reflective image display element 10R is connected to the side surface 8 of the dichroic prism 8.
a, the blue reflective image display element 10B faces the side face 8d of the dichroic prism 8,
The green reflective image display element 10G is disposed so as to face the side face 8c of the dichroic prism 8 which faces the side face 8a of the dichroic prism 8, respectively. In the embodiment, the optical axis 14 and the reflecting surface 9
Since the angle A between the normal lines 13R and 13B of R and 9B is smaller than 45 °, the reflective image display element for red 10R
Opposes the two side surfaces 8a and 8d, and the respective surfaces are inclined with respect to the optical axis 14 so that the blue reflective image display element 10B also opposes the two side surfaces 8a and 8b. Will be. The green reflective image display element 10G is arranged to face one side surface 8c, similarly to the conventional optical device.

Here, with reference to FIG. 2, the positional relationship between the video display elements 10R, 10G, and 10B in the first embodiment will be described.

In the figure, the optical axis 14 is the incident optical axis,
Light incident along the incident optical axis 14 is reflected by the blue reflecting surface 9B.
Let the optical axis 15B of the blue term reflected by the optical axis be the reflected optical axis. Further, the width of light along the optical axis 14 is L. Therefore, although the width of the screen of the video display elements 10R, 10G, and 10B is L, the total width thereof is L '.

Now, white light is incident on the side surface 8a of the dichroic prism 8 along the optical axis 14, of which the blue light component is reflected by the blue reflecting surface 9B, and the reflected light axis 15B
, The blue reflective image display element 10B is arranged such that its screen is perpendicular to the reflective optical axis 15B and the center axis of this screen coincides with the reflective optical axis 15B. Here, the width of the screen of the blue reflective image display element 10B is L.

Since the angle of the normal 13B of the blue reflecting surface 9B with respect to the optical axis 14 is A, the reflected optical axis 15B is inclined at an angle 2A with respect to the optical axis 14. Therefore, the screen of the blue reflective image display device 10B whose screen is perpendicular to the reflected optical axis 15B has an angle (90 ° −2) with respect to the optical axis 14.
A) will be arranged at an inclination. In this case, for the blue reflecting surface 9B, the blue reflective image display element 10B
Is tilted by the angle A. Although FIG. 2 shows that the reflection optical axis 15R and the blue reflection surface 9B coincide with each other, and the anti-axle 15B and the red reflection surface 9R coincide with each other, but 90 ° −
They match only when A = 2A, that is, when A = 30 °, and otherwise do not match.

This is because the red reflective image display element 10
The same applies to R, and the inclination directions of the blue reflective image display element 10B and the red reflective image display element 10R viewed from the optical axis 14 are opposite to each other.

For this reason, these video display elements 10R,
If 10B is arranged close to the dichroic prism 8, the space between them will be narrowed, and the optical path incident along the optical axis 14 will be partially obstructed. In order to prevent this, it is necessary to make the shortest interval between the image display elements 10R and 10B larger than the optical path width L of the incident light. For this reason, the center axis is perpendicular to the reflection optical axes 15R and 15B. It is necessary to separate these image display elements 10R, 10B from the dichroic prism 8 under the condition that the light-emitting elements 10R and 15B coincide with the reflection optical axes 15R, 15B.

Further, all the image display elements 10R, 10R
G and 10B need to be arranged at positions equidistant from the intersection of the reflecting surfaces 9R and 9B. This is because, when the optical device of this embodiment is used as an optical device of a video display device as shown in FIG. 11, as will be described later, these video display elements 10R, 10G, 10
This is to focus and project all B on the screen.

As described above, the image display elements 10R, 10R
Since it is necessary to dispose G, 10B at a position equidistant from the intersection of the reflecting surfaces 9R, 9B, these video display elements 10R, 10G, 10B must be separated from the dichroic prism 8 by a predetermined distance. . However, the image display elements 10R, 10G, 1
0B with respect to the dichroic prism 8,
The size of the optical device increases. That is, there is a trade-off relationship between the half-wavelength shift amount and the size of the optical device,
Attempting to improve one will degrade the other.

Hereinafter, the sizes of this embodiment and the conventional optical device when the angle A is 30 ° and 15 ° will be compared with FIG. 3 to FIG. However, in the following description, the reflection-type image display devices 10R, 10G, and 10B are:
Only the screen portion is shown.

FIG. 3 shows the image display elements 10R, 10G, 10
As B, the overall width L ′ is 35 mm, and the width L of the screen is 18.
This shows a conventional optical device using a 4 mm reflective liquid crystal display device (therefore, the minimum required optical path width L is also 18.4 mm), and each side surface of the dichroic prism 8 in this case. Are also shown as L = 35 mm. As such a conventional optical device, as an example, the image display element 10R, 42mm distance L ₂ to the image display element 10G from the end of the 10B, the image display element 10
R, the distance L ₁ between 10B was 49 mm. in this case,
Since the image display elements 10R and 10B are arranged in parallel with both sides of the surface on which the incident light of the dichroic prism 8 is incident, the light does not obstruct the light along the optical axis 14.

FIG. 4 shows the image display elements 10R, 10G, 10
B is the same as the conventional optical device shown in FIG. 3, and the width L of the screen is the same as that of FIG.
Angle A between normal lines 13R and 13B of B with respect to optical axis 14
Is a specific example of the above-described embodiment in which the angle is set to 30 °. In this case, the widths of the two side surfaces 8a and 8c of the dichroic prism 8 are different from those of the image display devices 10R, 10G and 1
L '= 35 mm, which is equal to the width of 0B, but the width of the two side surfaces 8b and 8d is 35 tan30 ゜ ≒ 20.2 mm.

In this case, the video display elements 10R, 10R
Since B must be arranged so as not to obstruct the optical path along the optical axis 14, as shown in FIG.
The angle between the optical axes 14 of the normal lines 13R and 13B of 9B with respect to the optical axis 14 is represented by A, and the reflection type image display devices 10R, 10G and 10B
In FIG. 4, the minimum width of the optical path L along the optical axis 14 is the minimum width of the image display elements 10R and 10B.
In order not to disturb the light of the image display elements 10R, 10B
The maximum distance L ₁ between the,

[0047]

(Equation 1)

In order for the distances from the intersection of the reflecting surfaces 9R and 9B of the dichroic prism 8 to all the reflective image display devices 10R, 10G and 10B to be equal, the image display device 10R , the maximum distance L ₂ from the end of 10B to the image display element 10G is,

[0049]

(Equation 2)

It is necessary that

Then, the image display devices 10R, 10R from the intersection of the reflecting surfaces 9R, 9B of the dichroic prism 8.
G, the distance to 10B is increased by delta, the maximum distance L ₁ between the image display element 10R, 10B delta · 2 sin
(2A) bigger,

[0052]

(Equation 3)

The image display elements 10R, 10R
Maximum distance L ₂ from the end of the B to the image display element 10G is increased by · Δ (1 + cos (2A )),

[0054]

(Equation 4)

Is as follows.

Here, as described above, L ′ = 35 mm,
Assuming that L = 18.4 mm and A = 30 °,
L ₁ ≧ L + L ′ = 53.4 mm L ₂ ≧ (L + L ′) √ {3/2} 46.24 mm As an example, assuming that Δ = 14.54 mm, the image is displayed by the above equations (3) and (4). element 10R, the maximum distance L ₁ between 10B and 78.59Mm, image display device 10
R, and the maximum distance L ₂ to the image display element 10G and 68.06mm from the end of 10B.

As described above, in this specific example, the vertical and horizontal dimensions are larger than those of the conventional optical device shown in FIG. 3, but by setting A = 30 °, as is apparent from FIG. The half-value wavelength shift amount is reduced to approximately 14 nm, which is a half improvement from the half-value wavelength shift amount of approximately 30 nm in the conventional optical device of A = 45 ° shown in FIG.

FIG. 5 shows the image display elements 10R, 10G, 10
As B, the same one as the conventional optical device shown in FIG. 3 is used, and the optical axis 14 of the normal lines 13R and 13B of the reflection surfaces 9R and 9B is used.
This shows a specific example of the above embodiment in which the angle A made with respect to the angle A is 15 °. In this case, the width of the two side surfaces 8a and 8c of the dichroic prism 8 is
It is equal to the width of 0R, 10G, 10B and 35mm,
The width of the two side surfaces 8b and 8d is 35 tan15 ゜ ≒ 9.4.
mm.

In this case, the image display devices 10R, 10R
Since B must be arranged so as not to obstruct the optical path along the optical axis 14, also in this embodiment, the maximum distance L ₁ between the image display elements 10R and 10B, the distance from the ends of the image display elements 10R and 10B. the maximum distance L ₂ are each, the number 1 and number 2 to the image display element _{10G, L 1 ≧ L + L} '· √3 ≒ 79.02mm L 2 ≧ (L + L') · (2 + √3) / 2 ≒ 99・ 64m
m. As an example, a Δ = 24.39mm, by the number 3 and 4, the image display element 10R, the maximum distance L ₁ between 10B and 103.71Mm, image display elements 10R,
Maximum distance L from the end of 10B to the image display element 10G
₂ was 145.16 mm.

As described above, in this specific example, the vertical and horizontal dimensions are larger than those in the specific example shown in FIG.
As is apparent from FIG. 2, the half-value wavelength shift amount is approximately 5n.
m, which is greatly improved.

As described above, the dichroic prism 8
As the angle A between the normals 13R and 13B of the reflecting surfaces 8R and 8B with respect to the optical axis 14 decreases, the half-value wavelength shift amount can be reduced, but as a trade-off, the size of the optical device increases. Therefore, even if the half screen wavelength shift amount is reduced to make the projection screen brighter, it is necessary to consider the size of the optical device.

As is apparent from FIG. 12, the reflection surfaces 9R and 9R of the dichroic prism 8 are different from those of the conventional optical device.
Assuming that the angle A between the 9B normal lines 13R and 13B with respect to the optical axis 14 is 45 °, the half-value wavelength shift amount of the P and S polarized lights is approximately 30 nm, which is large, and the loss amount of the P polarized light is large. Therefore, the brightness of the projected image cannot be sufficiently obtained. In this embodiment, as described above, the angle A formed between the normals 13R and 13B of the reflecting surfaces 9R and 9B with respect to the optical axis 14 is made smaller than 45 °, thereby reducing the half-wavelength wavelength shift amount and projecting. The brightness of the image is increased, or as a specific example, the angle A is set to 15 ° ≦ A ≦ 37 °. The upper limit angle of 37 ° in this range is based on suppressing the half-value wavelength shift amount to 20 nm or less so that sufficient brightness and color reproduction can be obtained in the projected image. According to FIG. 12, it is approximately 37 °. In addition, 15 of the above range
The lower limit angle of ゜ is determined by the size of the optical device, and in order to make the product worthwhile in business, the size of the optical device should be set at a maximum, as shown in FIG.
It is necessary to suppress the size of the optical device to about 3 times the size of 5 °. Therefore, it is necessary to set the size to the configuration shown in FIG.
About と す る.

When importance is placed on the optical performance of the optical device,
The half-wavelength shift amount is suppressed to 15 nm or less. In this case, according to FIG. 12, the normal lines 13R, 1R of the reflection surfaces 9R, 9B are determined.
The angle A with respect to the optical axis of 3B is defined as A ≦ 15 °.

FIG. 6 is a block diagram showing a first embodiment of a projection type image display apparatus according to the present invention using the optical apparatus shown in FIG. 1. In FIG. 6, parts corresponding to FIG. 11 and FIG. The same reference numerals are given.

In the figure, a dichroic prism 8
The reflective image display element 10R for red, the reflective image display element 10G for green, and the reflective image display element 10B for blue constitute the optical device shown in FIG.

The light source unit 1 comprises a light source 2, a reflector 3, and array lenses 4a and 4b. The light source 1 is a white lamp such as an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, a mercury xenon lamp, and a halogen lamp. The reflector 3 has a concave reflecting surface such as an elliptical surface, a parabolic surface, or an aspheric surface. I have. The light source 2 is disposed substantially at the focal point of the concave surface of the reflector 3.

The light radiated from the light source 2 is reflected and collected by the reflector 2 and enters the array lens 4a. The light that has passed through the array lens 4a further passes through the array lens 4b and enters the illumination optical system 5. Illumination optical system 5
Is composed of at least one or more optical lenses and has a positive refractive power.
And has the function of condensing light in a substantially parallel light state.

On the incident side of the polarizing beam splitter 7, S
An incident polarizer 6 that transmits only the polarized light component is disposed,
The S-polarized light component of the light from the illumination optical system 5 is
And is incident on the polarization beam splitter 7. In the polarization beam splitter 7, the incident S-polarized light component is reflected by the coating surface 7 a and is incident on the dichroic prism 8.

The dichroic prism 8 and the reflection type liquid crystal display elements 10R, 10G and 10B constitute the optical device shown in FIGS. 1 to 5, and as described above, the reflection type image display element for red. The combined light of the red light spatially modulated by 10R, the green light spatially modulated by the green reflective image display element 10G, and the blue light spatially modulated by the blue reflective image display element 10B forms a side surface 8a. Are emitted along the optical axis 14.

The combined light emitted from the dichroic prism 8 enters the polarizing beam splitter 7, and its S-polarized light component is reflected by the coating surface 7a toward the reflector 3, and the P-polarized light component passes through this coating surface 7a as it is. Then, the light is projected on a screen (not shown) via the projection lens 12. Thereby, the respective images formed on the reflection type image element liquid crystal display elements 10R, 10G, 10B are synthesized and enlarged and projected on a screen.

The projection-type image display apparatus is characterized in that the brightness and the color reproduction performance of an image magnified and projected on a screen are improved by reducing the half-value wavelength shift amount due to the polarization state in the optical apparatus. Become.

FIG. 7 is a structural view showing a second embodiment of the optical device according to the present invention, wherein 16R and 16B are dichroic mirrors, 17R is a red reflecting surface, 17B is a blue reflecting surface,
18R is the normal to the red reflecting surface 17R, 18B is the blue reflecting surface 17
B is the normal line, and the portions corresponding to FIG. 1 are denoted by the same reference numerals.

In the figure, the second embodiment uses two dichroic mirrors 16R and 16B arranged in a cross, instead of the dichroic prism 8 in the embodiment shown in FIG. Figure 1 shows the other configuration
This is the same as the embodiment shown in FIG. The dichroic mirror 16R has a red reflecting surface 17R, and the dichroic mirror 16B has a blue reflecting surface 17B. On the red reflecting surface 17R, a dichroic film that reflects red light and transmits a shorter wavelength region is deposited, and the blue reflecting surface 17B is deposited.
A dichroic film that reflects blue light and transmits a wavelength longer than that is deposited.

The reflecting surfaces 17R and 17B are respectively shown in FIG.
Reflective surfaces 9R, 9B of dichroic prism 8 at
Therefore, white S-polarized light is generated along the optical axis 14 by the dichroic mirrors 16R and 16R.
When incident on 6B, similar to the embodiment described with reference to FIG.
The spatial light is modulated by the image display elements 10R, 10G, and 10B to obtain a combined light of red light, green light, and blue light including a P-polarized component, and emitted along the optical axis 14.

The optical axis 1 of the normals 17R, 17B of the dichroic mirrors 16R, 16B in the second embodiment
The angle A corresponding to 4 is also set in the same manner as in the embodiment shown in FIG. 1, so that the half-value wavelength shift amount is suppressed to be small. Also in the case of the second embodiment, when the angle A is set so as to suppress the half-value wavelength shift amount to a small value, similarly to the first embodiment shown in FIG. 1 described with reference to FIGS. Since the size increases, it is not possible to set the angle A in consideration of the half-wavelength wavelength shift amount and the size in the same manner as described in the first embodiment shown in FIG. 1 with reference to FIGS. Needless to say.

FIG. 8 is a block diagram showing a second embodiment of the projection type video display apparatus according to the present invention.
The same reference numerals are given to the portions corresponding to and the duplicate description will be omitted.

In the figure, the second embodiment uses the optical device shown in FIG. 7 as the optical device in the embodiment of the video display device shown in FIG. That is, the portion including the dichroic mirrors 16R and 16B and the image display elements 10R, 10G and 10B constitutes the optical device shown in FIG. The S-polarized white light reflected by the coating surface 7a of the polarizing beam splitter 7 is incident on the optical device along the optical axis 14, and is spatially modulated red and red emitted from the optical device along the optical axis 14.
The combined light of green and blue light is incident on the polarization beam splitter 7, only the P-polarized light component is separated by the coating surface 7 a, and is projected on the screen (not shown) via the emission polarizing plate 11 and the projection lens 12.

The video display device according to the second embodiment also operates in the same manner as the video display device according to the first embodiment shown in FIG. 6, and is different from the video display device according to the first embodiment. Similar effects can be obtained.

FIG. 9 is a block diagram showing a third embodiment of the optical device according to the present invention.
9a, 19b, 19c are side surfaces, 20R is a red reflecting surface, 20R.
B is a blue reflective surface, 21R and 21B are normals, 22R and 22B
Denotes a reflection optical axis, and portions corresponding to the above-mentioned drawings are denoted by the same reference numerals.

In the figure, a hexagonal prism 19 as a color separating / combining means is a combination of three triangular prisms (triangular prisms) and one pentagonal prism (pentagonal prisms). There is a red reflecting surface 20R on which a dichroic film that reflects red light and transmits a shorter wavelength region is deposited on the joint surface of these prisms.
And a blue reflection surface 20B on which a dichroic film that reflects blue light and transmits a longer wavelength region than the blue light is crossed. The red reflecting surface 20R has a normal 21
R is inclined with respect to the optical axis 14 so that the angle formed by the optical axis 14 with respect to the optical axis 14 is set to a predetermined angle A. Similarly, the blue reflection surface 20B also Are inclined with respect to the optical axis 14 so that the angle with respect to the
1B are opposite to each other with respect to the optical axis 14.

White light is applied from the outside along the optical axis 14 to the side surface 19 a of the hexagonal prism 19 (the hexagonal prism 19).
, The red light is reflected and separated by the red reflection surface 20R, and the blue light is reflected and separated by the blue reflection surface 20B. The red light separated by the red reflection surface 20R is reflected light axis 2
Along the 2R, the blue light emitted from the other side surface 19c of the hexagonal prism 19 and incident on the red reflective image display device 10R is separated by the blue reflecting surface 20B. The light exits from another side surface 19b of the prism 19 and enters the blue reflective image display element 10B. The green light that has passed through the reflecting surfaces 20R and 20B exits from the side surface 19d of the hexagonal prism 19 and enters the green reflective image display element 10G.

The reflection type image display devices 10R, 10G, 10
B is the image display element 10R, 10G,
Similarly to 10B, the incident color light is spatially modulated. If the incident color light is S-polarized light, polarization conversion is performed in accordance with the degree of the spatial modulation to generate a P-polarized component.

The red light spatially modulated by the image display device 10R is incident on the hexagonal prism 19 from the same side surface 19c as that at the time of its emission along the reflection optical axis 22R, is reflected by the red reflection surface 20R, and is reflected on the optical axis. It becomes light along 14. The blue light spatially modulated by the image display element 10B is incident on the hexagonal prism 19 from the same side surface 19b as that at the time of emission, along the reflection optical axis 22B, is reflected by the blue reflection surface 20B, and is reflected by the optical axis 14B. It becomes light along. Further, the image display element 1
The green light spatially modulated with 0G is incident on the hexagonal prism 19 along the optical axis 14 from the same side surface 19d as when the green light is emitted, and transmits through the reflection surfaces 20R and 20B. As a result, the spatially modulated red light, green light and blue light are combined in the hexagonal prism 19, and the optical axis 1 from the side surface 19a.
The light is emitted to the outside along 4.

In this embodiment, the side surfaces 19a to 19d of the hexagonal prism 19 from which light enters and exits are formed so as to be perpendicular to the optical axis of the light. That is, the side surface 19a is a surface perpendicular to the optical axis 14, and the side surface 19b, 1
9c is a plane perpendicular to the reflection optical axes 22R and 22B, respectively.
The side surface 19d is also a surface perpendicular to the optical axis 14. The red light reflected by the red reflecting surface 20R and the red light from the red reflective image display element 10R are all emitted from the side surface 19c, and are not incident on the other side surface.
c, and similarly, all the blue light reflected by the blue reflecting surface 20B and the blue light from the blue reflective image display element 10B exit from the side surface 19b, enter, and reach the other side surface. This side surface 19b is arranged so as not to be present. Of course, light along the optical axis 14 also enters and exits only at the side surface 19a, and green light separated by the reflection surfaces 20R and 20B also enters and exits only at the side surface 19d.

The above angle A is set in the same manner as in the first embodiment shown in FIG. 1, and the angle A is set so that the image display elements 10R and 10B do not obstruct the optical path along the optical axis 14. Are located, and the reflection surfaces 9R, 9
Equalizing the distance from the intersection of B to the image display elements 10R, 10G, and 10B is the same as in the first embodiment.

In the embodiment shown in FIG. 1, the reflection surfaces 9R,
The red light and the blue light reflected by 9B pass through two side surfaces having different inclination angles of the dichroic prism 8 (that is, the red light passes through the side surfaces 8a and 8d, and the blue light passes through the side surfaces 8a and 8b). In the optical device of the third embodiment, the refraction direction of light is different, and the light is rejected at the corner of the boundary between these two side surfaces. The same effect as that of the first embodiment shown can be obtained, and the respective lights pass through only one side surface and the optical axis thereof is perpendicular to the side surface. It is also possible to prevent refraction at the time of entering and exiting the light beam, and to prevent light from being shaken by corners between adjacent side surfaces, thereby suppressing light loss due to such refraction and damage.

FIG. 10 is a block diagram showing a third embodiment of a projection type video display apparatus according to the present invention. Parts corresponding to those in FIGS. 6 and 9 are denoted by the same reference numerals, and redundant description is omitted. I do.

In the figure, the third embodiment uses the optical device shown in FIG. 9 as the optical device in the embodiment of the video display device shown in FIG. That is, the hexagonal prism 19 and the image display devices 10R, 10R
The portion consisting of G and 10B constitutes the optical device shown in FIG. The S-polarized white light reflected by the coating surface 7a of the polarization beam splitter 7 is incident on the optical device along the optical axis 14, and is also transmitted from the optical device to the optical axis 14a.
The combined light of the spatially modulated red, green, and blue color lights emitted along is incident on the polarizing beam splitter 7, where only the P-polarized component is separated by the coating surface 7a, and the output polarizing plate 11 and the projection lens 12 are separated. Is projected onto a screen (not shown).

The video display device of the second embodiment also operates in the same manner as the video display device of the first embodiment shown in FIG. 6, and is different from the video display device of the first embodiment. The same effect can be obtained, but by using the hexagonal prism 19 as the color separating / combining means of the optical device, the loss of light in the color separating / combining means can be further suppressed, so that the screen can be used. The brightness of the projected image,
Performance such as color reproduction can be further improved.

[0090]

As described above, according to the optical device of the present invention, the angle formed by the normal of the reflection surface of red and blue light with respect to the incident optical axis is made smaller than that of the conventional optical device. Therefore, it is possible to reduce the half-value wavelength shift amount between the P-polarized light and the S-polarized light on the reflecting surface, thereby greatly reducing the loss of the required P-polarized light on the reflecting surface. it can.

Further, according to the image display device of the present invention, since an image is displayed using the optical device of the present invention, the performance of the displayed image such as brightness and color reproduction can be improved.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining an arrangement relationship of video display elements in the embodiment shown in FIG.

FIG. 3 is a diagram illustrating an example of the size of a conventional optical device.

FIG. 4 is a view showing a specific example of the size of the embodiment shown in FIG. 1 when an angle A made with respect to an optical axis of a normal line of a reflection surface of the dichroic prism is 30 °.

FIG. 5 is a diagram showing a specific example of the size of the embodiment shown in FIG. 1 when the angle A formed with respect to the optical axis of the normal to the reflection surface of the dichroic prism is 15 °.

FIG. 6 is a configuration diagram showing a first embodiment of a projection type video display device according to the present invention using the optical device shown in FIG. 1;

FIG. 7 is a configuration diagram showing a second embodiment of the optical device according to the present invention.

8 is a configuration diagram showing a second embodiment of a projection type video display device according to the present invention using the optical device shown in FIG. 7;

FIG. 9 is a configuration diagram showing a third embodiment of the optical device according to the present invention.

FIG. 10 is a configuration diagram showing a third embodiment of a projection type video display device according to the present invention using the optical device shown in FIG. 9;

FIG. 11 is a configuration diagram illustrating an example of a conventional optical device and an image device using the same.

FIG. 12 is a graph showing a relationship between an angle formed with respect to an optical axis of a normal line of a reflection surface of a dichroic prism and a half-value wavelength shift amount between P and S polarized lights.

13 is an explanatory diagram of a light amount loss due to the half-value wavelength shift amount shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 light source unit 2 light source 3 reflector 4a, 4b array lens 5 illumination optical system 6 incident polarizer 7 polarizing beam splitter 7a coating surface 8 dichroic prism 8a to 8d side surface 9R red reflecting surface 9B blue reflecting surface 10R reflective image display element for red 10G Reflective image display element for green 10B Reflective image display element for blue 11 Outgoing polarizer 12 Projection lens 13R, 13B Normal 14 Optical axis 15R, 15B Reflective optical axis 16R, 16B Dichroic mirror 17R Red reflective surface 17B Blue reflective surface 18R, 18B Normal 19 Hexagonal prism 19a-19d Side surface 20R Red reflective surface 20B Blue reflective surface 21R, 21B Normal 22R, 22B Reflected optical axis

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fukubashi Abe 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Digital Media Development Division, Hitachi, Ltd. (72) Tomohiro Miyoshi Inventor Tomohiro Miyoshi 292 F-term (Reference) in Digital Media Development Division, Hitachi, Ltd. JA13 JB06

Claims (8)

[Claims] A first reflection surface for reflecting different types of primary color light arranged crosswise to each other, and a light incident from a side surface perpendicular to the optical axis along a predetermined optical axis; Dichroic prism that separates the separated light into three primary-color lights by the first and second reflecting surfaces; and converts the polarization state of the primary-color light separated by the dichroic prism for each of the dichroic prisms. And three reflection-type polarization conversion elements for incidence, wherein A is an angle between a normal line of the first reflection surface and the optical axis.
The angle between the normal of the second reflecting surface and the optical axis is -A
A <45 °, and the dichroic prism combines the primary color light re-entered from each of the reflection type polarization conversion elements on the first and second reflection surfaces and emits the light along the optical axis. An optical device, characterized in that: 2. A first and a second dichroic mirror for reflecting different types of primary color lights arranged crossing each other and separating light incident along a predetermined optical axis into three primary color lights. And three polarization conversion elements that convert the polarization state of the primary color light separated by the first and second dichroic mirrors, respectively, and re-enter the first and second dichroic mirrors, A <45 [deg.], Where A is an angle formed by the normal of the first dichroic mirror with respect to the optical axis, and -A is an angle formed by the normal of the second dichroic mirror with respect to the optical axis. The optical device, wherein the first and second dichroic mirrors combine the primary color lights re-entered from the reflection type polarization conversion elements and emit the primary color light along the optical axis. 3. A first and a second reflecting surface for reflecting different types of primary color lights arranged crosswise to each other, the light being incident along a predetermined optical axis to the first and second reflecting surfaces. Second
A hexagonal prism that separates the light into three primary colors by the reflection surface, and a polarization state of the primary color light that is separated by the hexagonal prism is converted for each of the prisms, and the first and second light beams are re-entered into the hexagonal prism.
The hexagonal prism includes a first side surface perpendicular to the optical axis as an incident surface of light incident along the optical axis; A side surface is an emission surface of the first primary color light separated by the first reflection surface, and the first reflection type polarization conversion element has a first side.
And a third side surface as an emission surface of the second primary color light separated by the second reflection surface,
A third side, which is an incident surface of the second primary color light from the second reflection type polarization conversion element and has a fourth side facing the first side, passing through the first and second reflection surfaces. The third reflection type polarization conversion element serves as an emission surface for primary color light.
The primary color light from the first, second, and third reflection type polarization conversion elements incident from the second, third, and fourth side surfaces, respectively, is used as the primary color light incident surface. And the light is emitted from the first side surface along the optical axis, and the first reflection type polarization conversion element is provided on the second side surface by the second side surface.
Are arranged in parallel to the third side surface, and the angle between the optical axis perpendicular to the first side surface and the normal of the first reflection surface is A, An optical device, wherein A <45 °, where -A is an angle formed by a normal to the second reflection surface with respect to the optical axis perpendicular to the side surface of the first surface. 4. The optical device according to claim 3, wherein the second side surface of the hexagonal prism through which the first primary color light enters and exits has an optical axis of the first primary color light of the hexagonal prism. And the third side surface of the hexagonal prism through which the second primary color light enters and exits is a plane perpendicular to the optical axis of the second primary color light of the hexagonal prism. An optical device characterized by the above-mentioned. 5. An optical device according to claim 1, wherein 15 ° ≦ A ≦ 37 °. 6. The optical device according to claim 1, wherein A ≦ 15 °. 7. The optical device according to claim 1, wherein the polarization conversion element forms an optical image according to a video signal and modulates light according to the optical image. An optical device characterized in that the optical device is a reflection-type image display element that changes the polarization state of light. 8. A light source unit that emits light, an illumination optical system that converts light emitted from the light source unit to illumination light of a first polarization state, and a first light source that reflects light of a first polarization state. A polarization beam splitter that transmits light in a second polarization state in which a linear polarization plane is rotated with respect to the polarization state, and illumination light in the first polarization state sent from the illumination optical system via the polarization beam splitter. An optical device that combines and emits the primary color light components that have undergone polarization conversion and polarization conversion for each primary color light component, and the second polarization state of the light emitted from the optical device that is separated by the polarization beam splitter. An image display device comprising: a projection unit for projecting light, wherein the optical unit is the optical device according to any one of claims 1 to 7.