JPH11160794A - Projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the depth of a rear projector thinner by providing a 1st optical element arranged on either side of a screen and a 2nd optical element arranged on the opposite side of the screen and making projected light move back and forth at least once between both optical elements. SOLUTION: Light emitted from a projection means 1 passes through an optical path 103a an reaches the 1st optical element 101 but is reflected because the light emitted from the projection means 1 is an S wave, and it passes through an optical path 103b and reaches the 2nd optical element 102. Then, it is changed to a P wave and reflected by the 2nd optical element 102. It passes through an optical path 103c and reaches the 1st optical element 101 and is transmitted because it is the P wave, then reaches the lower part of the screen 2. Namely, a distance between the 1st and the 2nd optical elements 101 and 102 and an angle formed by them are reduced by an amount equivalent to a route for moving back and forth, so that the projector is reduced in depth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection device, and more particularly to a so-called rear projector.

[0002]

2. Description of the Related Art As a method for displaying a large image having a diagonal size exceeding 50 cm, an image displayed by a display device such as a liquid crystal display device having a small display CRT or a light source or a DMD (digital mirror device) is used. There has been known a method of projecting an enlarged image on a screen by means for projecting through an optical system such as a projection lens (hereinafter, these are collectively referred to as projection means).

[0003] In particular, an arrangement in which projection means is arranged on the opposite side of the screen from the observer is called a rear projector.
This rear projector can be made very light when displaying images of the same size, as compared with large direct-view type CRTs, liquid crystal display devices, and plasma display devices. It is taking a bath.

Here, FIG. 6 is a diagram showing a schematic configuration of a rear projector, FIG. 6 (a) is a perspective view of the rear projector, and FIG. 6 (b) is a diagram showing a cross section of the rear projector. . In the drawing, reference numeral 1 denotes a projection unit comprising a display device (not shown) such as a liquid crystal display device or a DMD having a small display CRT or light source and an optical system (not shown) such as a projection lens, and 2 is an enlarged view. The screen on which the image is projected. An alternate long and short dash line indicates an optical path at the vertex and the center of the image projected on the screen 2 by the light emitted from the projection unit 1.

The dimension indicated by H in the figure indicates the height of the image enlarged on the screen 2, and the dimension indicated by L 0 indicates the distance between the projection means 1 and the screen 2. However, the projection means 1
The size of is ignored. Φ indicates the angle between the light at the upper end and the light at the lower end of the image projected and enlarged by the projection means 1 on the screen 2, and this angle is hereinafter referred to as the projection angle. In addition,
The rear projector of this configuration is
Called a projector.

Here, if L0 is set to θ0 = 90 ° −φ / 2, L0 is given by L0 = (H / 2) · tan (θ0). Therefore, in order to display an image having a height H on the screen 2, a depth of (H / 2) · tan (θ0) is required even if the size of the projection unit 1 is ignored. That is, a depth depending on the projection angle φ is required. For example, when the projection angle φ is 30 °, the depth is about 1.9 times the height H of the image, and when the projection angle φ is about 53 °, the depth is H.
It becomes 1 time of. That is, the depth of the rear projector becomes considerably large. The depth of the rear projector is preferably as thin as possible in order to reduce the installation place.
Here, it is possible to increase the projection angle by the configuration of the projection lens (not shown) that constitutes the projection unit 1, but when the projection angle is increased, the brightness of the image enlarged on the screen 2 is increased around the periphery. In order to prevent darkening or large aberrations, it is necessary to make the configuration of the projection lens extremely complicated in order to prevent this, and it becomes heavy and expensive.

Here, as a method of reducing the depth of the rear projector without widening the projection angle, a method of projecting the projection light of the projection means 1 on a mirror 2 and then projecting the light on a screen 2 is often used. FIGS. 7A and 7B are cross-sectional views showing a schematic configuration of a rear projector using this mirror.
(b) is a positional relationship that minimizes the depth. In the figure, 1 is a projection means, 2 is a screen, and 3 is a mirror. The dimension indicated by L1 indicates the depth of the rear projector using this mirror. The alternate long and short dash line indicates the optical path.

Here, as shown in FIG. 7B, the upper side of the mirror 3 is in contact with the screen 2 and the angle θ1 formed with the screen 2 is θ
By setting 1 = (90 ° −φ / 2) / 2, L1 takes the minimum value, and L1 = (H / 2) / {1 / tan (θ1) + 1 / tan (θ0)}. However, the size of the projection means 1 is ignored. FIG.
In the case of the arrangement as shown in (b), the projection means 1 needs to be arranged considerably below the screen 2, but the publication number H070
As disclosed in the published patent specification of No. 84313,
This can be avoided by using a plurality of mirrors. FIG. 8 is a cross-sectional view showing a schematic configuration of a rear projector using a plurality of mirrors. In the figure, the configuration other than 4 and 5 is shown in FIG.
As in (b), 4, 5 are additional mirrors. FIG.
The light emitted from the projection means 1 disposed at the rear of the screen 2 is reflected by a mirror 5, reflected by a mirror 4,
And reaches the screen 2.

As a result, it is not necessary to dispose the projection means 1 considerably below the screen 2, and the projection means 1 can be arranged at the rear portion of the screen 2, so that the depth can be reduced. . The rear projector having this configuration is referred to as a conventional reflection type rear projector.

[0010]

However, the depth of the mirror 3, ie, L1 = (H / 2) / {1 / tan (θ1) + 1 / tan (θ0)}.
The depth of the rear projector cannot be made thinner than that.

Therefore, in the case of a large-screen display rear projector, the depth cannot be sufficiently reduced even with the reflection type rear projector using the mirror 3 described above. For example, when an image having a height H = 100 cm is displayed by a projection unit having a projection angle of 53 °, the image cannot be made thinner than about 47 cm.
This depth is not yet satisfactorily thin.

The present invention has been made in view of such a problem, and an object of the present invention is to further reduce the depth of a rear projector.

[0013]

According to a first aspect of the present invention, there is provided a projection apparatus comprising: a projection means for projecting an image; and a screen, wherein a first optical element disposed on one side of the screen is provided. At least a second optical element disposed on the opposite side of the screen with respect to the first optical element, wherein the first optical element is opposite to the screen with respect to the first optical element. Out of the light incident from the side, the first predetermined state of polarized light is transmitted and emitted to the screen side, and the polarized state different from the first predetermined state is changed to the other polarized state. Or an optical element that reflects to the opposite side of the screen without change, wherein the second optical element changes the state of polarization of light incident from the first optical element side to another state of polarization. With or without modification Characterized in that an optical element for reflecting the optical element side of the.

According to such a configuration, the light emitted from the projection means reciprocates at least once between the first optical element and the second optical element, and reaches the screen by the reciprocating distance. The optical path length increases. In other words, since the optical path length increases, the distance between the first optical element and the second optical element can be reduced, and the depth of the projection device can be reduced.

According to a second aspect of the present invention, in the projection apparatus according to the first aspect, the light projected by the projecting means is asked at least once in each of the first optical element and the second optical element. After being reflected without being reflected, the light path reaching the screen.

According to such a configuration, the light emitted from the projection means reciprocates at least once between the first optical element and the second optical element, and reaches the screen by the reciprocating distance. The optical path length increases, and the depth of the projection device can be reduced.

According to a third aspect of the present invention, in the projection apparatus according to the first or second aspect, the first optical element includes:
Among the light incident on the first optical element from the side opposite to the screen, the linearly polarized light in the first predetermined direction is transmitted through the first predetermined direction and is emitted to the screen side, and the linearly polarized light in the first predetermined direction is emitted. An optical element that reflects linearly polarized light in a second predetermined direction orthogonal to the screen to the opposite side of the screen,
The optical element changes at least the linearly polarized light in the second predetermined direction to the linearly polarized light in the first predetermined direction, of the light incident from the first optical element side, and It is an optical element that reflects light toward the optical element.

According to this structure, the light emitted from the projection means makes one round trip between the first optical element and the second optical element, and reaches the screen by the distance of the round trip. The length can be increased, and the depth of the projection device can be reduced.

According to a fourth aspect of the present invention, in the projection apparatus according to the third aspect, the second optical element includes the first optical element.
Of the light incident from the optical element side, the linearly polarized light in the second predetermined direction is changed to the linearly polarized light in the first predetermined direction, reflected on the first optical element side, and Among the light incident from the first optical element side, an optical element that changes the linearly polarized light in the first predetermined direction into the linearly polarized light in the second predetermined direction and reflects the light toward the first optical element side It is characterized by being an element.

According to such a configuration, the light emitted from the projection means reciprocates at least once between the first optical element and the second optical element, and reaches the screen by the reciprocating distance. The optical path length increases, and the depth of the projection device can be reduced.

Here, as the first optical element of the projection apparatus according to the third or fourth aspect, specifically, a cholesteric liquid crystal film and a retardation film are superimposed, or a patent specification (Japanese Patent Application Laid-Open No. Hei 9-1997). It is possible to use the polarization separator (reflection deflector) described in claims 6 to 11 of US Pat.

In addition, as the second optical element of the projection device according to the third and fourth aspects, specifically, a device in which a mirror and a retardation film are overlapped can be used.

According to a fifth aspect of the present invention, in the projection apparatus according to the first or second aspect, the first optical element includes:
Of the light incident on the first optical element from the side opposite to the screen, circularly polarized light in a first predetermined direction is transmitted and emitted to the screen side, and circularly polarized light in the first predetermined direction. And an optical element that reflects circularly polarized light in a second predetermined direction, which is opposite to the screen, to the side opposite to the screen, wherein the second optical element is one of the light incident from the first optical element side. It is an optical element that changes circularly polarized light in the first and second predetermined directions to circularly polarized light in the second and first predetermined directions, respectively, and reflects the light toward the first optical element. I do.

According to such a configuration, the light emitted from the projection means reciprocates at least once between the first optical element and the second optical element, and reaches the screen by the reciprocating distance. The optical path length increases, and the depth of the projection device can be reduced.

Here, as the first optical element, specifically, a cholesteric liquid crystal film or a polarization separator (reflection deflector) according to any one of claims 6 to 11 of Japanese Patent Application Laid-Open No. 9-5006985. It is possible to use a film obtained by superposing a retardation film and a film.

As the second optical element, specifically, a mirror or the like can be used.

According to a sixth aspect of the present invention, in the projection apparatus of the first to fourth aspects, the light projected by the projection means is linearly polarized light in the second predetermined direction, and the polarized light is
Reflected by the first optical element, changed to linearly polarized light in the first predetermined direction by the second optical element, and reflected;
It has an optical path which passes through the first optical element and reaches the screen.

According to such a configuration, the light emitted from the projection means reciprocates once between the first optical element and the second optical element, and reaches the screen by the reciprocating distance. The length can be increased, and the depth of the projection device can be reduced.

According to a seventh aspect of the present invention, in the projection apparatus according to the first to fourth aspects, an optical element for converting light projected by the projection means into linearly polarized light in the second predetermined direction is provided. The light projected by the projection means via an optical element is reflected by the first optical element, and the second optical element converts the linearly polarized light in the second predetermined direction into the first predetermined direction. And has an optical path which is reflected and reaches the screen.

According to such a configuration, the same effect as the projection device according to the sixth aspect can be obtained even with any polarized light emitted by the projection means.

According to an eighth aspect of the present invention, in the projection apparatus according to the first to second or fourth aspects, the light projected by the projection means is linearly polarized light in the first predetermined direction, and the polarized light is the second polarized light. The second optical element changes the light into linearly polarized light in the second predetermined direction, reflects the light, reflects the first optical element, and changes the light into linearly polarized light in the first predetermined direction with the second optical element. And a light path that is reflected and transmitted through the first optical element and reaches the screen.

According to such a configuration, the light emitted by the projection means travels one and a half times between the first optical element and the second optical element. The optical path length of the projection device increases, and the depth of the projection device can be further reduced.

A projection apparatus according to a ninth aspect is the projection apparatus according to any one of the first to second or fourth aspects, further comprising an optical element for converting light projected by the projection means into linearly polarized light in the first predetermined direction. The light projected by the projection means via the optical element is changed into linearly polarized light in the second predetermined direction by the second optical element, reflected, reflected by the first optical element, and reflected by the first optical element. An optical path is changed into linearly polarized light in the first predetermined direction by the second optical element, reflected, transmitted through the first optical element, and reaches the screen.

According to such a configuration, even if the light emitted from the projection means has an arbitrary polarization state, the same effect as that of the projection device according to the eighth aspect can be obtained.

According to a tenth aspect of the present invention, in the projection device of the first to second or fifth aspects, the light projected by the projection means is circularly polarized light in the second predetermined direction, and the polarized light is Having a light path that is reflected by a first optical element, is changed into circularly polarized light in the first predetermined direction by the second optical element, is reflected, passes through the first optical element, and reaches the screen. Features.

According to such a configuration, even if the light emitted from the projection means is circularly polarized light, the same effect as the projection device according to the third aspect can be obtained.

According to an eleventh aspect of the present invention, in the projection device of the first or second or fifth aspect, an optical element for converting light projected by the projection means into circularly polarized light in the second predetermined direction is provided. The light projected by the projection means via the optical element is reflected by the first optical element, changed to circularly polarized light in the first predetermined direction by the second optical element and reflected, It has an optical path that passes through the first optical element and reaches the screen.

According to such a configuration, even if the light emitted from the projection means has an arbitrary polarization state, the same effect as the projection device according to the tenth aspect can be obtained.

According to a twelfth aspect of the present invention, in the projection apparatus according to the first to second or fifth aspects, the light projected by the projection means is circularly polarized light in the first predetermined direction, and the polarized light is The second optical element changes the light into circularly polarized light in the second predetermined direction, reflects the light, reflects the first optical element, and reflects the light into circularly polarized light in the first predetermined direction with the second optical element. It has an optical path that is modified and reflected, passes through the first optical element, and reaches the screen.

According to this configuration, even if the light emitted from the projection means is circularly polarized light, the same effect as that of the projection device according to the eighth aspect can be obtained.

According to a thirteenth aspect of the present invention, in the projection device according to the first or second or fifth aspect, an optical element for converting light projected by the projection means into circularly polarized light in the first predetermined direction is provided. The light projected by the projection means via the optical element is changed to circularly polarized light in the second predetermined direction by the second optical element, reflected, reflected by the first optical element, A light path is changed by the second optical element into circularly polarized light in the first predetermined direction, reflected, transmitted through the first optical element, and reaches the screen.

According to such a configuration, even if the light emitted from the projection means is in an arbitrary polarization state, the same effect as the projection device according to the twelfth aspect can be obtained.

According to a fourteenth aspect of the present invention, in the projection device,
The projection device according to any one of 7, 10 and 11, wherein the projection angle of the light projected by the projection means is approximately 45 ° or more.

In this way, the image projected on the screen does not become uneven. Also, especially about 4
By setting the angle to about 5 °, the size of the screen and the size of the first optical element can be made the same, and waste is reduced.

The projection device according to the fifteenth aspect is characterized in that:
The projection device according to any one of 9, 12, and 13, wherein the projection angle of the light projected by the projection unit is approximately 49 ° or more.

With this arrangement, the image projected on the screen does not become uneven. Also, especially about 4
By setting the angle to about 9 °, the size of the screen and the size of the first optical element can be made the same, and waste is reduced.

According to a sixteenth aspect of the present invention, in the projection device according to the third to fourth or sixth to ninth aspects, a third optical element is provided between the screen and the first optical element. Among the light incident from the first optical element side, the third optical element transmits linearly polarized light in a first predetermined direction and emits it to the screen side, and linearly polarized light in the second predetermined direction. Is an optical element that does not emit light to the screen and the side.

According to such a configuration, the contrast of the image projected on the screen is improved.

The projection device according to the seventeenth aspect is characterized in that:
The projection device according to any one of claims 10 to 13, further comprising a third optical element between the screen and the first optical element, wherein the third optical element receives light incident from the first optical element side. The optical element is characterized by being an optical element that transmits circularly polarized light in a first predetermined direction and emits it to the screen side, and does not emit circularly polarized light in the second predetermined direction to the screen side.

According to such a configuration, the contrast of the image projected on the screen is improved.

The projection device according to claim 18 is the projection device according to any one of claims 1 to 17, wherein the optical device is different from the first and second optical elements and the third optical element provided as necessary. An element is arranged on an optical path until light emitted by the projection means reaches the screen.

According to such a configuration, the size of the projection device can be reduced.

[0053]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a diagram showing a schematic cross section and an optical path of a projection apparatus according to this embodiment.

In the drawing, reference numeral 1 denotes a projection means and 2 denotes a screen. 101 is a first optical element, and 102 is a second optical element. And 103a-c, 104a-c, 10
Reference numerals 5a to 5c denote optical paths. Further, a linearly polarized light in a predetermined first direction is defined as a P-wave, and a linearly polarized light in a second direction orthogonal to the first predetermined direction is defined as an S-wave.
, C, 104a-c, the polarization state of light on each optical path is indicated by the symbol P if it is a P-wave and the symbol S if it is an S-wave. The optical paths 105a to 105c are omitted.

In this embodiment, the first optical element 101 is an optical element that transmits a P wave and reflects an S wave. Such an optical element may be, for example, a combination of a (1/4) wavelength plate and a cholesteric liquid crystal film, or a polarization separator according to claims 6 to 11 of a patent specification (Japanese Patent Application Laid-Open No. 9-5006985). (Hereinafter referred to as reflective deflectors), which have already been commercialized and are readily available.

Next, in this embodiment, the second optical element 102 is an optical element that changes an incident S-wave into a P-wave and reflects it. As a specific configuration of such an optical element, (1.
/ 4) There is a combination of a phase difference plate such as a wave plate and a mirror. That is, by disposing the slow axis of the (1/4) wavelength plate at an angle of approximately 45 ° with respect to the direction of the linearly polarized light of the S wave, (1
The s-wave transmitted through the (/ 4) wavelength plate becomes circularly polarized light, is reflected by the mirror, and the circularly polarized light transmitted through the (1/4) wavelength plate is again emitted as a p-wave.

Although the configuration of the present embodiment is as described above, it is assumed that the projecting means 1 projects an image using S waves. Then, the light emitted by the projection unit 1 is, for example, an optical path 103a.
Through c to reach the lower part of the screen 2. That is,
The light emitted from the projection means 1 first passes through the optical path 103a and reaches the first optical element 101. However, the light emitted from the projection means 1 is reflected because it is an S-wave, and then passes through the optical path 103b and passes through the second optical element 101. Reach 102. Then, the light is changed to a P wave by the second optical element 102 and reflected. Then, the light reaches the first optical element 101 through the optical path 103c.
This time, since the light is a P-wave, it is transmitted and reaches the lower part of the screen 2.

Similarly, some light emitted by the projection means 1 reaches a portion inside the screen 2 through the optical paths 104a to 104c and reaches a portion above the screen 2 through the optical paths 105a to 105c.

As described above, the first optical element 1 is placed on the optical path until the light emitted from the projection unit 1 reaches the screen 2.
A path that makes one round trip between 01 and the second optical element 102 is generated by the configuration of the present embodiment. That is, the distance and the angle between the first optical element 101 and the second optical element 102 can be reduced by the length of the reciprocating path, and the depth can be reduced.

For example, when the projection angle of the projection means 1 is 53 °, the depth is the height H of the image on the screen 2.
On the other hand, the basic type and the reflection type rear projector of the prior art are 1 times and 0.47 times, respectively, whereas in the present embodiment, the thickness can be reduced to about 0.41 times. FIG.
In this embodiment, since the projection means 1 is disposed behind (the right side in the figure) the second optical element, it is not so thin, but it is easy to make it thinner by providing another mirror. Is possible.

FIG. 2 is a diagram showing a schematic cross section and an optical path of another projection apparatus according to this embodiment.

In the figure, except for L2 and 201, the configuration and operation are the same as those in FIG. 1, so the same numbers are assigned and duplicate explanations are omitted.
L2 is a dimension indicating the depth. Reference numeral 201 denotes a mirror that reflects light emitted from the projection unit 1. Then, the projecting means 1 is disposed in front of the second optical element (left side in the figure),
Is reflected by the mirror 201, but the optical path thereafter is the same as the optical path shown in FIG.

With the above configuration, the depth L
2 is about 0.2 with respect to the height H of the image on the screen 2.
It is possible to make it 33 times thinner.

In general, the first optical element 101 and the second
By making the upper sides of the optical elements 102 closer to each other, and making the angle θ2 between them approximately (90 ° −φ / 2) / 3, the depth can be minimized, and the size of the projection means 1 can be reduced. When ignored, the depth L2 is (H / 2) / {1 / tan
(θ2) + 1 / tan (θ0)}.

1 and 2, for example, the optical path 10
Where the light passing through 3a reaches the first optical element and the optical path 10
The position where the light passing through 3c reaches the first optical element is different.

Here, for example, if the light emitted from the projection means 1 has not only the S-wave component but also the P-wave component, the first
Below the intersection with the optical path 103a of the optical element, there is no optical path where the light emitted by the projection means 1 directly reaches the first optical element 101, whereas the optical path 10a of the first optical element does not exist.
Above the intersection with 3a, there is an optical path where the light emitted from the projection means 1 reaches the first optical element 101 directly, and of the light emitted from the projection means 1, the light of the P-wave component passes through to the screen 2 side. It becomes bright. As a result, the image projected on the screen 2 becomes uneven.

In order to prevent this, it is desirable to set the projection angle φ to approximately 45 ° or more. In this manner, in FIGS. 1 and 2, for example, the position at which light passing through the optical path 103a reaches the first optical element is substantially the same as or lower than the position at which light passing through the optical path 103c reaches the first optical element. And the above-mentioned unevenness can be prevented. In particular, when the angle is approximately 45 °, the first optical element 10
The size of the first optical element 101 need not be increased unnecessarily because the size of 1 is approximately the size of the screen 2.

Further, when the first optical element 101 not only completely transmits the P-wave but also slightly transmits the S-wave, the contrast of the image projected on the screen 2 is reduced. Would.

To prevent this, the first optical element 10
An optical element that transmits a P wave and absorbs an S wave, for example, a polarizing plate may be provided between the first optical element 101 and the screen 2. To prevent a decrease in image contrast.

[Embodiment 2] In the embodiment 1, the light emitted from the projection means 1 is reflected by the first optical element, the polarization state is changed and reflected by the second optical element, and the light is transmitted through the first optical element. The depth of the projection device is reduced by a configuration in which the light arrives at the screen through a light path.

Here, the light emitted from the projection means 1 is reflected by changing the polarization state by the second optical element, reflected by the first optical element, and further changed and reflected by the second optical element. ,
With a configuration in which the light reaches the screen through an optical path that passes through the first optical element, the depth of the projection device can be further reduced.

FIG. 3 is a diagram showing a schematic cross section and an optical path of the projection apparatus of this embodiment.

In the figure, reference numeral 1 denotes a projection means and 2 denotes a screen. 101 is a first optical element, and 102 is a second optical element. And 301a-d, 302a-d, 30
4 is an optical path. The symbols S and P on the optical path have the same meaning as those in FIG. L3 is a dimension indicating the depth.

Here, the first optical element 101 is the same as the first optical element 101 of the first embodiment.

Next, in this embodiment, the second optical element 102 is an optical element that changes the incident S-wave into a P-wave and reflects it, and changes the incident P-wave into an S-wave and reflects it. . As a specific configuration of such an optical element, a combination of a retardation plate such as a (1/4) wavelength plate and a mirror may be used similarly to the second optical element 102 of the first embodiment.

The difference between the present embodiment and the first embodiment is only that the light emitted by the projection means 1 is first reflected by the second optical element 102 and that the light emitted by the projection means 1 is a P wave. is there.

With such a configuration, the light emitted from the projection means 1 reaches the lower part of the screen 2 through the optical paths 301a to 301d, for example. That is, the light emitted from the projection unit 1 first passes through the optical path 301a and reaches the second optical element 102. However, since the light emitted from the projection unit 1 is a P-wave, it is changed to an S-wave and reflected, and then passes through the optical path 301b. First
Reaches this optical element 101, but this light is reflected as an S wave. Therefore, the light reaches the second optical element 102 through the optical path 301c. Since this light is an S-wave, the light is changed to a P-wave and reflected, and reaches the first optical element 101 through the optical path 301d at the end. Since the light is a P-wave, it is transmitted and reaches the lower part of the screen 2.

Similarly, some light emitted by the projection means 1 reaches a portion inside the screen 2 through the optical paths 302a to 302d, and reaches a portion above the screen 2 through the optical path 303.

As described above, the first optical element 1 is placed on the optical path until the light emitted from the projection means 1 reaches the screen 2.
A path that reciprocates one and a half times between 01 and the second optical element 102 is generated by the configuration of the present embodiment. That is, the distance and the angle between the first optical element 101 and the second optical element 102 can be further reduced by the length of the reciprocating path, and the depth can be further reduced.

For example, when the projection angle of the projection means 1 is 53 °, the depth is the height H of the image on the screen 2.
In contrast, the basic and reflective rear projectors of the prior art are 1 × and 0.47 ×, respectively, whereas in the present embodiment, the thickness can be reduced to about 0.25 ×.

Generally, the first optical element 101 and the second
By making the upper sides of the optical elements 102 closer to each other and setting the angle θ3 between them to θ3 = (90 ° −φ / 2) / 4, the depth can be minimized. Is ignored, the depth L3 is approximately (H / 2)
It is possible to make the distance close to the value given by / {1 / tan (θ3) + 1 / tan (θ0)}.

In this embodiment shown in FIG. 3, since the projection means 1 is disposed below the lower end of the screen 2, waste occurs in the height direction.
If the arrangement of the mirror and the projection means is appropriately changed, and the light emitted from the projection means 1 is changed in direction by the mirror to reach the second optical element, waste in the height direction can be reduced. Is possible. This is the same as the change of FIG. 2 with respect to FIG. 1 of the first embodiment, and can be easily realized.
The description with reference to the drawings is omitted.

In this embodiment, each of the projections φ
Is preferably about 49 ° or more, more preferably about 49.
Around 1 ° is more preferable. The reason for this is to prevent unevenness in the image projected on the screen 2 as in the first embodiment.

Further, as in the first embodiment, by providing a polarizing plate between the first optical element 101 and the screen 2, a decrease in image contrast can be prevented.

[Third Embodiment] In the first embodiment, the S wave emitted from the projection means 1 is reflected by the first optical element, the polarization state is changed to the P wave by the second optical element, and the first wave is reflected. The depth of the projection device is reduced by a configuration in which the light reaches the screen through an optical path that passes through the optical element.

Here, the light emitted from the projection means 1 is not limited to the S wave, that is, linearly polarized light. For example, the light emitted from the projection means 1 is converted into circularly polarized light (hereinafter, referred to as a first predetermined rotation direction).
It is called an R wave, and circularly polarized light in the opposite direction to the R wave is called an L wave. ).

FIG. 4 is a diagram showing a schematic cross section and an optical path of the projection apparatus of this embodiment.

In the figure, reference numeral 1 denotes a projection means and 2 denotes a screen. 401 is a first optical element, and 402 is a second optical element. And 403a-c, 404a-c, 40
5 is an optical path. R and L on the optical path indicate the polarization state of light passing through the optical path, where R indicates an R wave and L indicates an L wave.

Here, in this embodiment, the first optical element 401 is an optical element that transmits an L wave and reflects an R wave. Examples of such an optical element include a combination of a cholesteric liquid crystal film or a reflective deflector and a (1/4) wavelength plate.

Next, in the present embodiment, the second optical element 402 changes the incident R-wave (L-wave) into an L-wave (R-wave) and reflects it with a mirror.

Although the configuration of the present embodiment is as described above, it is assumed that the projecting means 1 projects an image with an R wave. Then, the light emitted from the projection unit 1 is, for example, an optical path 403a.
Through c to reach the lower part of the screen 2. That is,
The light emitted from the projection unit 1 first passes through the optical path 403a and reaches the first optical element 401. However, since the light emitted from the projection unit 1 is an R-wave, the light is reflected, and then passes through the optical path 403b and passes through the second optical element 401. Reach 402. Then, the light is changed to an L wave by the second optical element 402 and reflected. Then, the light reaches the first optical element 401 through the optical path 403c.
This time, since the light is an L wave, it is transmitted and reaches the lower portion of the screen 2.

Similarly, some light emitted by the projection means 1 reaches a portion inside the screen 2 through the optical paths 404a to 404c, and reaches a portion above the screen 2 through the optical path 405.

As described above, the first optical element 4 is placed on the optical path until the light emitted from the projection unit 1 reaches the screen 2.
A path that makes one round trip between 01 and the second optical element 402 is generated by the configuration of this embodiment. That is, the distance and the angle between the first optical element 401 and the second optical element 402 can be reduced by this reciprocating path. As in the first embodiment, the depth can be reduced.

The difference from the first embodiment is only the polarization state of the light emitted from the projection means 1.

Therefore, the effect of reducing the depth between the first embodiment and the present embodiment is exactly the same. Therefore, either configuration may be adopted. For example, when a small screen display device (not shown) constituting the projection unit 1 is a liquid crystal display device which modulates the amount of linearly polarized light and displays an image, or the like, is used. Since the light emitted from the projection means 1 is linearly polarized light, the first embodiment is more suitable.

However, if the linearly polarized light emitted from the projection means 1 is emitted through a retardation film such as a (1/4) wavelength plate, it can be easily changed to circularly polarized light. Of course, the configuration of can also be used.

Further, even when the light emitted from the projection means 1 is circularly polarized light, if this circularly polarized light is emitted through a retardation film such as a (1/4) wave plate, it can be easily changed to linearly polarized light. The configuration of the first embodiment can of course be used.

Therefore, if necessary, the polarization state of the light emitted by the projection means 1 can be used as it is, or can be easily changed to a predetermined polarization state through an appropriate optical element for use. The light need not be limited to a particular polarization.

The performances of the first optical element and the second optical element of Examples 1 and 3, such as the reflectance, the transmittance, and the conversion efficiency to other polarization states for each polarized light, have been improved over time. Depending on how these performances are improved, one of the first and third embodiments may be selected and used.

Note that, in this embodiment, too, FIG.
It is needless to say that another mirror can be easily made thinner by providing another mirror as in FIG. 2 and arranging the mirror and the projection means 1 appropriately.

In this embodiment, for the same reason as in the first embodiment, similarly, each projection φ of the projection means 1 is approximately 45 °.
The above is preferable, and about 45 ° is more preferable.

Furthermore, when the first optical element 401 has the property of transmitting not only the L-wave completely but also the R-wave slightly, the contrast of the image on the screen 2 is reduced. This is the first optical element 1
By providing an optical element that transmits L-waves and absorbs R-waves, for example, a combination of a retardation plate and a polarizing plate, between the screen 01 and the screen 2, a decrease in image contrast can be prevented.

This is because L from the first optical element 401 side
The wave is changed to, for example, a P wave by the phase difference plate, the R wave is changed to the S wave by the phase difference plate, and the P wave is changed to the L wave by the phase difference plate. Because it becomes.

[Embodiment 4] In Embodiment 2, the P-wave emitted from the projection means 1 is changed in polarization state to S-wave by the second optical element, reflected, reflected by the first optical element, and reflected by the second optical element. The depth of the projection device is reduced by a configuration in which the polarization state is changed to S-wave by the optical element and reflected to reach the screen through the optical path that passes through the first optical element.

Also in this case, the light emitted from the projection means 1 is S
It is not limited to waves, that is, linearly polarized light. For example, light emitted from the projection unit 1 may be circularly polarized light.

FIG. 5 is a diagram showing a schematic cross section and an optical path of the projection apparatus of this embodiment.

In the figure, reference numeral 1 denotes a projection means and 2 denotes a screen. 401 is a first optical element, and 402 is a second optical element. And 503a-d, 504a-d, 50
5 is an optical path. R and L on the optical path indicate the polarization state of light passing through the optical path, where R indicates an R wave and L indicates an L wave.

Here, the first optical element 401 and the second optical element 401 are the first optical element 40 of FIG.
They are the same as the first and second optical elements 401.

With such a configuration, the light emitted from the projection means 1 is converted into an L-wave, so that the light reaches the lower portion of the screen 2 through, for example, the optical paths 501a to 501d. That is, the light emitted from the projection unit 1 first reaches the second optical element 402 through the optical path 501a.
Is emitted is changed to an R wave and reflected, and then the optical path 501b
To the first optical element 401 through the R,
Waves are reflected. Therefore, through the optical path 501c,
The light reaches the second optical element 502, is changed to an L-wave, and is reflected. The light reaches the first optical element 401 through the optical path 501d at the end. Reach the lower part.

Similarly, some light emitted by the projection means 1 reaches a portion inside the screen 2 through the optical paths 502a to 502d, and reaches a portion above the screen 2 through the optical path 503.

As described above, the first optical element 4 is placed on the optical path until the light emitted from the projection means 1 reaches the screen 2.
A path that makes one and a half reciprocation between 01 and the second optical element 402 is generated by the configuration of the present embodiment. That is, the same effect as that of the second embodiment can be obtained.

For the same reason as in the second embodiment, the projection unit 1
Is preferably 49 ° or more, more preferably about 49.1 °. Further, for the same reason as in the third embodiment, an optical element that transmits an L-wave and absorbs an R-wave is provided between the first optical element 101 and the screen 2 in the same manner as the third embodiment. The decline can be prevented.

Further, also in this embodiment, the second embodiment
It is needless to say that the useless space in the downward direction can be reduced by providing another mirror and arranging the mirror and the projecting means 1 as appropriate.

Here, the effect of reducing the depth between the second embodiment and this embodiment is exactly the same.

Further, since the polarization state of the light emitted from the projection means 1 can be used as it is or can be easily changed to a predetermined polarization state through an appropriate optical element for use, the light emitted from the projection means 1 is a specific light. There is no need to specify the polarization.

Therefore, whichever configuration is adopted,
Depending on the performance of the first optical element and the second optical element of Examples 2 and 4 (which have been improved with increasing speed),
Either one of the second and fourth embodiments may be selected.

Further, the configurations of the second and fourth embodiments have a greater effect of reducing the depth of the projection apparatus than the configurations of the first and third embodiments. Therefore, the configurations of the second and fourth embodiments are more preferable. However, the configurations of the second and fourth embodiments increase the number of reflections, and for example, the first optical element and the second optical element of the second and fourth embodiments. If the reflectance is not 100%, it is undeniable that the image projected on the screen 2 in an enlarged manner becomes darker by the number of times of reflection. Therefore, when importance is placed on the brightness of the image projected on the screen 2 in an enlarged manner, the configurations of the first and third embodiments are more preferable.

[0119]

According to the first aspect of the present invention, the light emitted by the projection means makes at least one reciprocation between the first optical element and the second optical element, and the light travels by the reciprocating distance. The optical path length reaching the screen increases, the distance between the first optical element and the second optical element can be reduced, and the depth of the projection device can be reduced.

According to the projection apparatus of the second aspect, the light emitted by the projection means makes at least one reciprocation between the first optical element and the second optical element, and reaches the screen by this reciprocating distance. And the depth of the projection device can be reduced.

According to the third aspect of the present invention, the light emitted from the projection means makes one reciprocation between the first optical element and the second optical element, and the light reciprocates on the screen by the reciprocating distance. The optical path length of the projection device can be increased, and the depth of the projection device can be reduced.

According to the projection apparatus of the fourth aspect, the light emitted by the projection means makes at least one reciprocation between the first optical element and the second optical element, and the light reciprocates on the screen by the reciprocating distance. The optical path length of the projection device can be increased, and the depth of the projection device can be reduced.

According to the projection device of the fifth aspect, the light emitted by the projection means makes at least one reciprocation between the first optical element and the second optical element, and the screen reciprocates by the reciprocating distance. , And the depth of the projection device can be reduced.

According to the projection apparatus of the sixth aspect, the linearly polarized light emitted by the projection means is coupled to the first optical element and the second polarized light.
Makes one reciprocation between the optical elements, and the length of the optical path reaching the screen increases by the reciprocating distance, and the depth of the projection device can be reduced.

According to the projection device of the seventh aspect, the same effect as that of the projection device of the sixth aspect can be obtained even with any polarized light emitted by the projection means.

According to the projection apparatus of the eighth aspect, the light emitted by the projection means travels one and a half times between the first optical element and the second optical element, and travels for a distance of one and a half times. The optical path length reaching the screen is increased, and the depth of the projection device can be further reduced.

According to the projection device of the ninth aspect, the same effect as that of the projection device of the eighth aspect can be obtained even if the light emitted from the projection means has an arbitrary polarization state.

According to the projection device of the tenth aspect, the same effect as that of the projection device of the third aspect can be obtained even if the light emitted by the projection means is circularly polarized light.

According to the projection device of the present invention, even if the light emitted from the projecting means has an arbitrary polarization state,
The same effects as those of the projection device described in No. 0 are obtained.

According to the projection apparatus of the twelfth aspect, the same effect as that of the projection apparatus of the eighth aspect can be obtained even if the light emitted by the projection means is circularly polarized light.

According to the projection device of the thirteenth aspect, even if the light emitted by the projection means has an arbitrary polarization state,
The same effects as those of the projection device described in Item 2 can be obtained.

According to the projection device of the fourteenth aspect, unevenness does not occur in the image projected on the screen.

According to the projection device of the fifteenth aspect, unevenness does not occur in the image projected on the screen.

According to the projection device of the sixteenth aspect, the contrast of the image projected on the screen is improved.

According to the projection device of the seventeenth aspect, the contrast of the image projected on the screen is improved.

According to the projection device of the eighteenth aspect, the size of the projection device can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic cross section and an optical path of a projection device according to a first embodiment.

FIG. 2 is a diagram illustrating a schematic cross section and an optical path of another projection apparatus according to the first embodiment.

FIG. 3 is a diagram showing a schematic cross section and an optical path of a projection device according to a second embodiment.

FIG. 4 is a diagram illustrating a schematic cross section and an optical path of a projection device according to a third embodiment.

FIG. 5 is a diagram illustrating a schematic cross section and an optical path of a projection device according to a third embodiment.

FIG. 6 is a schematic perspective view (a), a schematic cross-sectional view (b), and a view showing an optical path of a conventional basic rear projector.

FIG. 7 is a diagram showing a schematic cross section and an optical path of a reflection type rear projector according to the related art.

FIG. 8 is a diagram showing a schematic cross section and an optical path of another conventional reflection type rear projector.

[Explanation of symbols]

 1 ‥‥‥‥‥ Projection means. 2 ‥‥‥‥‥ screen. 101—first optical element. 102 @ second optical element. 103a-c @ optical path. 104a-c ‥‥ optical path. 105a-c @ optical path. P ‥‥‥‥‥‥‥ linearly polarized light in a first predetermined direction. S ‥‥‥‥‥‥‥ linearly polarized light in a second predetermined direction.

Claims (18)

[Claims] 1. A projection apparatus comprising a projection means for projecting an image and a screen, a first optical element disposed on one side of the screen, and a first optical element opposite to the screen with respect to the first optical element. A second optical element disposed on the first side, wherein the first optical element is
Of the light incident on the optical element from the side opposite to the screen, the first predetermined state of polarized light is transmitted and emitted to the screen side, and the polarized light different from the first predetermined state of polarized light is emitted. An optical element that reflects to the opposite side to the screen without changing or changing the state of polarized light to another state of polarized light, wherein the second optical element is a light element that reflects light incident from the first optical element side. A projection device, wherein the projection device is an optical element that changes the state of polarized light to another state of polarized light or reflects the light toward the first optical element without changing the state. 2. The projection apparatus according to claim 1, wherein the light projected by said projection means is reflected at least once by said first optical element and said second optical element irrespective of their order, respectively. A projection device having an optical path reaching a screen. 3. The projection apparatus according to claim 1, wherein said first optical element is a first optical element of light incident on said first optical element from a side opposite to said screen.
Transmits linearly polarized light in a first predetermined direction as polarized light in a predetermined state and emits it to the screen side, and converts linearly polarized light in a second predetermined direction orthogonal to linearly polarized light in the first predetermined direction to the screen An optical element that reflects to the opposite side of the screen,
The second optical element changes at least the linearly polarized light in the second predetermined direction to the linearly polarized light in the first predetermined direction, of the light incident from the first optical element side, A projection device, which is an optical element that reflects light toward the first optical element. 4. The projection apparatus according to claim 3, wherein the second optical element converts the linearly polarized light in the second predetermined direction out of the light incident from the first optical element side into the first optical element. The linearly polarized light in the first predetermined direction is changed to linearly polarized light in the predetermined direction, and of the light reflected on the first optical element side and incident from the first optical element side, the linearly polarized light in the first predetermined direction is A projection device, wherein the projection device is an optical element that changes to linearly polarized light in a second predetermined direction and reflects toward the first optical element. 5. The projection apparatus according to claim 1, wherein said first optical element is a first optical element out of light incident on said first optical element from a side opposite to said screen.
Transmits circularly polarized light in a first predetermined direction as polarized light in a predetermined state and emits it to the screen side, and converts circularly polarized light in a second predetermined direction opposite to circularly polarized light in the first predetermined direction to the screen. An optical element that reflects light to the opposite side of the screen, wherein the second optical element converts the circularly polarized light in the first and second predetermined directions from the light incident from the first optical element, respectively. A projection device, wherein the projection device is an optical element that changes to circularly polarized light in second and first predetermined directions and reflects the light toward the first optical element. 6. A projection device according to claim 1, wherein the light projected by said projection means is linearly polarized light in said second predetermined direction, and said polarized light is reflected by said first optical element, A projection apparatus, comprising: an optical path that is changed by the second optical element into linearly polarized light in the first predetermined direction, reflected, transmitted through the first optical element, and reaches the screen. 7. A projection apparatus according to claim 1, further comprising an optical element for converting light projected by said projection means into linearly polarized light in said second predetermined direction, wherein said projection is performed via said optical element. The light projected by the means is reflected by the first optical element, and the second optical element changes linearly polarized light in the second predetermined direction to linearly polarized light in the first predetermined direction. A projection device having an optical path that is reflected and reaches the screen. 8. A projection apparatus according to claim 1, wherein the light projected by said projection means is linearly polarized light in said first predetermined direction, and said light is polarized by said second optical element. The light is changed to linearly polarized light in a second predetermined direction, reflected, reflected by the first optical element, changed to linearly polarized light in the first predetermined direction by the second optical element, reflected, and A projection apparatus having an optical path that passes through one optical element and reaches the screen. 9. The projection apparatus according to claim 1, further comprising an optical element for converting light projected by said projection means into linearly polarized light in said first predetermined direction, and via said optical element. The light projected by the projection unit is changed to linearly polarized light in the second predetermined direction by the second optical element, reflected, reflected by the first optical element, and reflected by the second optical element. A projection apparatus having an optical path that is changed into linearly polarized light in a first predetermined direction, reflected, transmitted through the first optical element, and reaches the screen. 10. The projection apparatus according to claim 1, wherein the light projected by said projection means is circularly polarized light in said second predetermined direction, and said polarized light is reflected by said first optical element. A projection device having an optical path that is changed by the second optical element into circularly polarized light in the first predetermined direction, reflected, transmitted through the first optical element, and reaches the screen. 11. A projection apparatus according to claim 1, further comprising an optical element for converting light projected by said projection means into circularly polarized light in said second predetermined direction, and via said optical element. The light projected by the projection means is reflected by the first optical element, changed into circularly polarized light in the first predetermined direction by the second optical element, reflected, and transmitted through the first optical element. A projection device having an optical path reaching the screen. 12. The projection apparatus according to claim 1, wherein the light projected by said projection means is circularly polarized light in said first predetermined direction, and said light is polarized by said second optical element. Changed into circularly polarized light in a second predetermined direction and reflected,
An optical path that is reflected by the first optical element, is changed into circularly polarized light in the first predetermined direction by the second optical element, is reflected, passes through the first optical element, and reaches the screen. A projection device characterized by the above-mentioned. 13. A projection apparatus according to claim 1, further comprising an optical element for converting light projected by said projection means into circularly polarized light in said first predetermined direction, and via said optical element. The light projected by the projection unit is changed into circularly polarized light in the second predetermined direction by the second optical element, reflected, reflected by the first optical element, and reflected by the second optical element. A projection apparatus having an optical path that is changed into circularly polarized light in a first predetermined direction, reflected, transmitted through the first optical element, and reaches the screen. 14. A projection apparatus according to claim 6, wherein the projection angle of the light projected by said projection means is approximately 45 ° or more. 15. A projection apparatus according to claim 8, wherein the projection angle of the light projected by said projection means is approximately 49 ° or more. 16. The projection apparatus according to claim 3, further comprising a third optical element between said screen and said first optical element, wherein said third optical element is provided. Of the light incident from the first optical element side, linearly polarized light in a first predetermined direction is transmitted and emitted to the screen side, and linearly polarized light in the second predetermined direction is emitted to the screen and the side. A projection device, wherein the projection device is not an optical element. 17. The projection apparatus according to claim 5, further comprising a third optical element between said screen and said first optical element, wherein said third optical element is provided with said third optical element. Optical element that transmits circularly polarized light in a first predetermined direction and emits it to the screen side, and does not emit circularly polarized light in the second predetermined direction to the screen side, of light incident from the first optical element side. A projection device, characterized in that: 18. A projection apparatus according to claim 1, wherein said projection means comprises an optical element different from said first and second optical elements and said third optical element provided as necessary. A projection device, which is arranged on an optical path until emitted light reaches the screen.