JPH0720433A - Projection device - Google Patents

Abstract

PURPOSE:To obtain the projection device which can obtain an excellent projection image by reducing the astigmatic aberration of luminous flux at the time of transmission through a dichroic mirror, which demultiplexes incident luminous flux into plural color lights or multiplexes them, when color separation is performed by slantingly arranging the dichroic mirror in the optical path. CONSTITUTION:Color light selecting means 9 and 10 generate the color lights from the luminous flux from a light source means 1, corresponding image forming means 5R, 5G, and 5B are light with the color lights, and images formed on the image forming means 5R, 5G, and 5B are multiplexed through optical path forming means 11 and 12 and projected on a projection surface 16 by a projecting means 16. At this time, the respective elements are so set that the condition (d/p)Xtan(theta)/F<3.5 holds, where theta is the angle of incidence of the luminous flux on the optical axes incident on the optical path forming means 11 and 12, (d) is the thickness of glass mirror constituting the optical path forming means 11 and 12, F is the FNO of the projecting means 15, and (p) is the image pitch in the direction of the plane consisting of the optical axis of the projecting means 15 of the image forming means 5R, 5G, and 5B and the normals of the optical path forming means 11 and 12.

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 projection surface for an image (original image of a projected image) displayed on a liquid crystal panel (liquid crystal display panel) or the like using a color combining optical system using a dichroic mirror. When magnifying and projecting onto a screen surface (for example, the screen surface), the incident angle of the main light beam incident on the dichroic mirror and the thickness of the dichroic mirror are optimized in the projection device, and the astigmatism of the light flux passing through the mirror is reduced and good. The present invention relates to a projection device suitable for use in a device such as a color liquid crystal projector for observing a projected image.

[0002]

2. Description of the Related Art Conventionally, a plurality of images having color information, such as a liquid crystal panel, are illuminated with predetermined color lights respectively, and are optically superposed, and then enlarged by a projection lens at a predetermined magnification. Various projection devices such as a color liquid crystal projector for projection have been proposed.

FIG. 10 is a schematic view of a main part of a conventional projection device that projects (projects) a color image using a plurality of conventional liquid crystal panels.

In the figure, 111G, 111R, 111
B is a liquid crystal panel, which is green (G), red (R),
It is composed of a liquid crystal display element such as a TN type which displays a monochrome image corresponding to each color of blue (B).

Reference numeral 101 denotes a white light source, which is composed of, for example, a metal halide lamp or the like. Reference numeral 102 denotes a reflector, which has a paraboloidal shape or the like, and is a white light source 10.
The liquid crystal panels 111G and 1
It leads to the direction of 11R and 111B. Reference numeral 103 denotes a filter that blocks ultraviolet rays and infrared rays contained in white light.

A first dichroic mirror 104 separates the light beam from the white light source 101 into a first color light (for example, G) and second and third color lights (for example, R and B). 105 is a second dichroic mirror,
Color light (R) and third color light (B). 10
Reference numeral 8 is a total reflection mirror that reflects the third color light (B).
A total reflection mirror 9 reflects the first color light (G).
Reference numeral 106 denotes a third dichroic mirror, which combines the first color light (G) and the second color light (R). 107
Is a fourth dichroic mirror, which combines the first and second color lights (G, R) and the third color light (B).

Reference numeral 110 denotes a projection lens (projection lens) that synthesizes the images (original images of the projected images) of the liquid crystal panels 111G, 111R and 111B and enlarges and projects them on the surface of the screen 126 at a predetermined magnification. Reference numerals 114, 115, and 116 are condenser lenses, and each liquid crystal panel 111.
Projection lens 1 for illuminating luminous flux reaching G, 111R, 111B
It is focused on the panel side pupil of 10.

Each liquid crystal panel 111G, 111R, 111
Before and after B, polarizing filters (not shown) whose polarization directions are orthogonal to each other are provided, and the liquid crystal panels 111G, 111R, 11
The polarization filter on the incident side of 1B has an optical function as a polarizer that polarizes the illumination light beam, and the polarization filter on the emission side cuts and modulates the light beam whose polarization direction does not rotate in the liquid crystal panels 111G, 111R, and 111B. It has an optical function as an analyzer.

In the figure, the image information formed on each of the liquid crystal panels 111G, 111R and 111B is superposed by the above-mentioned structure and the screen 1 is formed by the projection lens 110.
It is enlarged and projected on the 26th plane.

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Each of the dichroic mirrors 104, 105, 106, 107 shown in FIG.
In general, the required optical characteristics are obtained by the dielectric multilayer coating provided on the glass substrate, and the mirror glass is formed with a certain thickness.

When this thick dichroic mirror is arranged in the optical path of the projection optical system with an inclination (45 ° in FIG. 10) with respect to the optical axis of the projection lens, the light beam passing through the dichroic mirror has astigmatism. Occurs, which deteriorates the image (projected image).

As seen in recent years, as the size of the liquid crystal panel becomes smaller, it becomes difficult to reduce the thickness of the dichroic mirror in proportion to the size of the liquid crystal panel.
As a result, it is very difficult to avoid the above-mentioned problems.

The present invention provides a projection device that greatly reduces astigmatism that occurs when a dichroic mirror is arranged as a plate-shaped optical path forming means for combining incident light beams so as to be inclined in a predetermined direction with respect to the optical axis. With the goal.

[0014]

A projection device of the present invention generates color light from a light beam from at least one light source means by color light selection means, and illuminates corresponding image forming means by the generated color light. In a projection device that synthesizes images formed on the image forming means based on the respective color lights through the optical path forming means and projects the images on the projection surface by the projecting means, a light flux on the optical axis that enters the optical path forming means. Is θ, the thickness of the glass mirror forming the optical path forming means is d, the FNO of the projecting means is F, and the plane direction consisting of the optical axis of the projecting means of the image forming means and the normal line of the optical path forming means. Where p is the image pitch of (d / p) × tan (θ) / F <3.5 (1), each element is set so as to satisfy the condition It has a feature.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of the essential portions of a first embodiment when the present invention is applied to a color projection device using a three-plate type liquid crystal panel.

In the figure, reference numeral 1 denotes a white light source, which is composed of, for example, a metal halide lamp. Reference numeral 2 denotes a reflector, which efficiently guides the luminous flux emitted from the white light source 1 toward liquid crystal panels 5G, 5R, 5B described later. Reference numeral 3 is a filter that blocks ultraviolet rays and infrared rays contained in white light.

Reference numeral 4 denotes a polarized light separating means (light flux separating means), which is a stack of a plurality of optical elements such as glass plates utilizing transmission and has an optical characteristic of transmitting a large amount of a predetermined polarized component.

Reference numeral 9 is a first dichroic mirror,
The light flux from the white light source 1 is separated into a first color light (for example, G) and second and third color lights (for example, R and B). 10
Is a second dichroic mirror, which separates the second color light (R) and the third color light (B). 14 is the third
Is a mirror that reflects the colored light (B), and 13 is a mirror that reflects the first colored light (G). Reference numeral 11 denotes a third dichroic mirror, which combines the first color light (G) and the second color light (R). A fourth dichroic mirror 12 combines the first and second color lights (G, R) and the third color light (B). Mirror 13 and mirror 14
May be a normal total reflection mirror or a dichroic mirror.

Dichroic mirrors 9, 10, 11, 1
Reference numeral 2 is made of a plate-shaped mirror glass, and the dichroic mirrors 11 and 12 on the combining side have the incident angle and the mirror thickness set so as to satisfy the conditional expression (1). In the present embodiment, the incident angle is set to 45. By making the thickness smaller than the value, the thickness of the glass can be set to be thicker than in other examples described later.

In this embodiment, the dichroic mirrors 9 and 10 constitute color light selecting means, and the dichroic mirrors 11 and 12 constitute optical path selecting means (optical path forming means).

Reference numerals 6, 7 and 8 denote condenser lenses, respectively, which condense the illumination light flux reaching each of the liquid crystal panels 5G, 5R and 5B on the panel side pupil of the projection lens 15 which will be described later.

Reference numerals 5G, 5R and 5B denote liquid crystal panels as image forming means, which display monochrome images corresponding to respective colors of green (G), red (R) and blue (B).
It is composed of a liquid crystal display element such as N liquid crystal.

The liquid crystal panel 5R in this embodiment has the first
The red light reflected by the second dichroic mirror 9 and reflected by the second dichroic mirror 10 is illuminated. The liquid crystal panel 5G passes through the first dichroic mirror,
It is illuminated by the green light reflected by the reflection mirror 13. The liquid crystal panel 5B is illuminated with blue light that has been transmitted through the second dichroic mirror that is reflected by the first dichroic mirror.

Reference numeral 15 is a projection lens (projection lens) having an FNO (F number) of 3.8 as a projection means, and superimposes the images (original projection images) formed on the respective liquid crystal panels 5G, 5R and 5B. The image is enlarged and projected at a predetermined magnification on the screen 16 that is the projection surface.

In this embodiment, the white light emitted from the white light source 1 is supplied to the dichroic mirrors 9, 10, 11, 12 respectively.
Separates and synthesizes red, green, and blue color lights with the respective color lights, and liquid crystal panels 5G, 5R, and 5B for green, red, and blue, respectively.
And liquid crystal panels 5G and 5 based on these respective color lights
Images of R and 5B are projected onto the screen 16 by the projection lens 15.
A color image is obtained by projecting them on the surface.

Next, the technical meaning of conditional expression (1) will be described.

Conditional expression (1) relates the amount of astigmatism generated to the FNO of the projection lens, the thickness of the glass mirror, and the installation angle of the glass mirror. Astigmatism increases in inverse proportion to FNO, and the dichroic mirror Increases in relation to the increase of the incident angle θ of the light beam on the optical axis incident on the optical axis of the dichroic mirror, and the image pitch in the plane direction consisting of the optical axis of the projection lens in the image forming means and the normal to the dichroic mirror. It indicates that the ratio increases in proportion to the ratio d / p. If the value exceeds the upper limit of conditional expression (1), the astigmatism on the projection screen becomes conspicuous and the image quality deteriorates, which is not good.

Next, a concrete example of the conditional expression (1) will be shown. Assuming that the screen size of the liquid crystal display device used is 3 "diagonally and the aspect ratio is 3: 4, the vertical screen size is (3 x 25.4) / 5 x 3 = 45.7 mm. When projecting an NTSC image, the number of vertical scans is 46
Since the number is 0, the vertical pitch p is 45.7 / 460 = 0.099 mm. When the angle of incidence on the dichroic mirror is 45 degrees and the image of this panel is projected by the projection lens of FNO 3.8, d <3.5 × 0.099 × 3.8 / tan (45 ) =
It is 1.31, which shows that it is desirable to make the thickness of the dichroic mirror thinner than 1.31 mm.

As another example, the panel size is 2 ".
If the FNO of the projection lens is 4 and the thickness of the dichroic mirror is 1 mm, the pitch p is (1.5 × 25.4) /5×3/460=0.050, and the conditional expression ( From 1), tan (θ) <0.924 θ <35, which means that it is desirable to make the incident angle of the dichroic mirror smaller than 35 degrees.

Next, the optical influences when the dichroic mirror is inserted in the optical path between the projection lens and each liquid crystal panel while tilting with respect to the optical axis will be described with reference to FIGS. 3 and 4, respectively.
This will be described with reference to the diagrams (A) to (D) shown in FIG.

In FIG. 3A, the dichroic mirror is arranged so as to be inclined in a predetermined direction with respect to the optical axis so that the incident angle θ of the light beam incident on the dichroic mirror having a thickness of 1 mm on the optical axis is 45 °. Fig. 3 (B), which shows the layout of the main parts
Is a layout drawing of the main parts when the dichroic mirror is tilted in a predetermined direction with respect to the optical axis so that the incident angle θ of the light beam incident on the dichroic mirror having a thickness of 2 mm on the optical axis is 45 °. 3 (C) has an incident angle θ of 3 on the optical axis that is incident on the dichroic mirror having a thickness of 2 mm.
FIG. 3 is a layout view of main parts when the dichroic mirror is tilted in a predetermined direction with respect to the optical axis so as to be 0 °.
(D) shows that the incident angle θ of the light beam on the optical axis entering the dichroic mirror having a thickness of 1.5 mm is 38 °,
It is a principal part layout when the dichroic mirror is tilted in a predetermined direction with respect to the optical axis.

FIGS. 4A to 4D are respectively FIGS. 3A to 3.
5D is an explanatory diagram of an axial luminous flux spot diagram corresponding to FIG. 3D, and FIGS. 5A to 5D are MTF curves on the axes corresponding to FIGS. Cross section of
It is an explanatory view of a cross section in which a dotted line is perpendicular to the paper surface).

Astigmatism also occurs in the state shown in FIG. 3A using a thin dichroic mirror, but the aberration amount at this time is within an allowable range in consideration of the depth of focus. In the state shown in FIG. 3 (B), the peak of the focus in each cross-sectional direction is largely deviated from that in the state of FIG. 3 (A), which is a state in which it is difficult to focus. Here, from the state of FIG. 3 (B) to FIG. 3 (C)
When the state is changed to the above state, that is, when the light flux on the optical axis of the projection lens is configured to enter the dichroic mirror at an incident angle of 30 °, the spot diagram and the MTF are shown.
The curves are as shown in FIG. 4 (C) and FIG. 5 (C), respectively.

This is almost the same as the spot diagram (FIG. 4 (A)) and the MTF curve (FIG. 5 (A)) in the state of FIG. The focus shift can be suppressed, and the thickness can be increased by increasing the thickness of the dichroic mirror while maintaining good resolution. Further, similar optical performance can be obtained even in the case of the configuration intermediate between FIGS. 3A and 3C from FIGS. 4D and 5D.

As described above, in the present embodiment, by setting each element so as to satisfy the above-mentioned conditional expression (1), the astigmatism due to the thickness of the dichroic mirror arranged at an angle with respect to the optical axis is reduced. Therefore, a good projection image is obtained on the screen 16 surface.

The polarized light separating means 4 of the present embodiment is formed by laminating a plurality of thin glass plates (optical elements) (for example, 6 sheets) so as to be substantially parallel to each other with a longer interval than the wavelength. Are configured.

Then, as a whole, a plurality of (12) transmissive surfaces are provided, and the light flux is incident on these transmissive surfaces at the Brewster angle θ to enhance the transmittance of the light flux of the S-polarized component. There is.

FIG. 2 is a schematic view of the essential portions of Embodiment 2 when the present invention is applied to a projection device using a three-plate color liquid crystal panel. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

Reference numeral 29 is a first dichroic mirror, which separates the light flux from the white light source 1 into a first color light (for example, G) and second and third color lights (R, B). Reference numeral 30 denotes a second dichroic mirror, which separates the second color light (R) and the third color light (B). Reference numeral 33 is a reflection mirror that reflects the first color light (G), and 34 is a reflection mirror that reflects the third color light (B). Reference numeral 31 is a third dichroic mirror, which combines the first color light (G) and the second color light (R). A fourth dichroic mirror 32 combines the first and second colored lights (G, R) and the third colored light (B).

Dichroic mirror 2 in this embodiment
Reference numerals 9, 30, 31, 32 are made of plate-shaped mirror glass, and the dichroic mirrors 31, 32 are tilted with respect to the optical axis so as to satisfy the above-mentioned conditional expression (1) and have a predetermined thickness. There is.

In this embodiment, the color light selecting means is constituted by the respective elements of the first and second dichroic mirrors 29 and 30, and the third and fourth dichroic mirrors 31 and 32 are provided.
The respective elements constitute the optical path forming means.

Reference numerals 26, 27 and 28 denote condenser lenses, which collect the illumination light flux reaching the liquid crystal panels 25G, 25R and 25B in the vicinity of the panel side pupil of the projection lens 15. Reference numerals 25G, 25R, and 25B denote liquid crystal panels as image forming means, which display a monochrome image corresponding to each color of green (G), red (R), and blue (B).
It is made up of an N-type liquid crystal display element.

In the present embodiment, the white light from the white light source 1 is separated (or combined) into green, red and blue lights by the dichroic mirrors 29, 30, 31 and 32, and these green lights are
Liquid crystal panel 2 for green, red, and blue, respectively, by red and blue light
5G, 25R, 25B are illuminated, and images (projected image original images) of the liquid crystal panels 25G, 25R, 25B based on the respective color lights are superimposed and projected on the screen 16 surface by the projection lens 15 to obtain a color image. There is.

FIG. 6 is a schematic view of the essential portions of Embodiment 3 when the present invention is applied to a projection device using a reflective color liquid crystal panel. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

In the figure, reference numeral 54 is a polarization beam splitter, which reflects the S-polarized component of the light beam emitted from the white light source 1 and serves as an image forming means of green (G) and red (R).
Reflective liquid crystal panels 55G and 55 for blue and blue (B) colors
R, 55B, and the liquid crystal panels 55G, 55R,
At 55B, the light flux of the P-polarized component whose polarization direction is rotated by 90 ° based on the image information is transmitted and guided to the projection lens 15.

The projection lens 15 is composed of the liquid crystal panels 55G and 5G.
Images of 5R and 55B (original projection images) are superimposed and projected (projected) onto the screen 16 surface. Reference numerals 56, 57, and 58 are condenser lenses, and each liquid crystal panel 55G,
The illumination luminous fluxes reaching 55R and 55B are condensed on the panel side pupil of the projection lens 15.

Reference numeral 59 denotes a first dichroic mirror, which is a first color light (for example, G) and second and third color lights (R, R) of the light flux reflected by the polarization beam splitter 54.
Separated or synthesized in B). A second dichroic mirror 60 separates or combines the second color light (R) and the third color light (B).

Dichroic mirror 5 in this embodiment
Reference numerals 9 and 60 are made of plate-like mirror glass, and the incident angle θ of the light beam on the optical axis incident on the dichroic mirrors 59 and 60 and the thickness of the dichroic mirrors 59 and 60 satisfy the conditional expression (1). Each element is set as follows.

In this embodiment, each element of the first and second dichroic mirrors 59, 60 constitutes an optical path forming means (and color light selecting means).

In this embodiment, of the light beam emitted from the white light source 1, only the S-polarized component is reflected by the polarization beam splitter 54, and then the dichroic mirrors 59 and 6 are used.
At 0, the light is separated into green (G), red (R), and blue (B) color lights, and these green, red, and blue color lights are used to form liquid crystal panels 55G, 55R, and 55B for green, red, and blue, respectively. Illuminates the formed image.

Each liquid crystal panel 55G, 55R, 55
Due to the optical property of B, polarized light (P polarized light) whose polarization plane is rotated based on each pixel of the image is obtained as a reflected light flux. The P-polarized component based on the image at this time passes through the polarization beam splitter 54.

As a result, the liquid crystal panel 55 for green, red and blue
The images formed on the G, 55R, and 55B are overlapped via the dichroic mirrors 59 and 60, and the projection lens 15
Thus, the image is enlarged and projected on the screen 16 at a predetermined magnification.

FIG. 7 is a schematic view of the essential portions of Embodiment 4 when the present invention is applied to a projection device using a three-plate color liquid crystal panel. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

Reference numeral 79 is a first dichroic mirror, which separates the light flux from the white light source 1 into a first color light (for example, R) and second and third color lights (G, B). Reference numeral 80 denotes a second dichroic mirror, which separates the second color light (G) and the third color light (B). Reference numeral 83 is a reflection mirror that reflects the first color light (R), and 84 is a reflection mirror that reflects the third color light (B). Reference numeral 81 denotes a third dichroic mirror, which combines the first color light (R) and the second color light (G). Reference numeral 82 denotes a fourth dichroic mirror, which combines the third colored light (B) with the first and second colored lights (R, G).

Dichroic mirror 7 in this embodiment
Reference numerals 9, 80, 81, and 82 are made of plate-shaped mirror glass, and the dichroic mirrors 81 and 82 are tilted with respect to the optical axis so as to satisfy the conditional expression (1), and have a predetermined thickness. There is.

In the present embodiment, each of the first and second dichroic mirrors 79 and 80 constitutes a color light selecting means, and each of the third and fourth dichroic mirrors 81 and 82 constitutes an optical path forming means. I am configuring.

Reference numerals 76, 77, and 78 are condenser lenses, which collect the illumination light flux reaching the liquid crystal panels 75R, 75G, and 75B near the pupil of the projection lens 15 on the panel side. Reference numerals 75R, 75G, and 75B denote liquid crystal panels as image forming means, which display a monochrome image corresponding to each color of red (R), green (G), and blue (B).
It is composed of an N-type liquid crystal display element or the like.

In the present embodiment, the incident angle of the light beam on the optical axis incident on the third and fourth dichroic mirrors 81, 82 is set to be larger than that of the embodiment 1 of FIG. 1 or the embodiment 2 of FIG. The third and fourth dichroic mirrors 81 and 82
Is arranged so as to be inclined with respect to the optical axis, but if the thickness of the dichroic mirrors 81 and 82 is made sufficiently thin within the range of the conditional expression (1), it does not deviate from the gist of the present invention.

FIG. 8 is a schematic view of the essential portions of Embodiment 5 when the present invention is applied to a projection apparatus using a three-plate color liquid crystal panel. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

A first dichroic mirror 209 separates the light beam from the white light source 1 into a first color light (for example, G) and second and third color lights (R, B). 210 is a second dichroic mirror, which is a second color light (R)
And the third color light (B) is separated. Reference numeral 213 is a reflection mirror that reflects the first color light (G), and 214 is a reflection mirror that reflects the third color light (B). Reference numeral 211 denotes a third dichroic mirror, which combines the first color light (G) and the second color light (R). Reference numeral 212 denotes a fourth dichroic mirror, which combines the third color light (B) with the first and second color lights (G, R).

Dichroic mirror 2 in this embodiment
09, 210, 211, and 212 are made of plate-shaped mirror glass, and the dichroic mirrors 211 and 212 are tilted with respect to the optical axis so as to satisfy the conditional expression (1), and have a predetermined thickness. There is.

In this embodiment, the color light selecting means is constituted by the respective elements of the first and second dichroic mirrors 209 and 210, and the third and fourth dichroic mirrors 211,
Each element 212 constitutes an optical path forming means.

Reference numerals 206, 207 and 208 denote condenser lenses, respectively, and the respective liquid crystal panels 205G, 205R and 2
The illumination light flux reaching 05B is condensed near the panel side pupil of the projection lens 15. Reference numerals 205G, 205R and 205B denote liquid crystal panels as image forming means, each of which includes a TN type liquid crystal display element for displaying a monochrome image corresponding to each color of green (G), red (R) and blue (B). ing.

In the present embodiment, a good projection image can be obtained, and the space around each liquid crystal panel 205G, 205R, 205B can be widened as compared with the other embodiments 1 to 4 described above. The effect can also be obtained. This means that, for example, each liquid crystal panel 205G, 205
This is very advantageous when it is desired to cool R, 205B, especially when air cooling is performed.

FIG. 9 is a schematic view of the essential portions of Embodiment 6 when the present invention is applied to a projection device using a three-plate color liquid crystal panel. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

In the figure, reference numeral 24 denotes a polarized light separating means (light beam dividing means), which is formed by laminating a plurality of optical elements such as a glass plate utilizing reflection, and has optical characteristics for reflecting a large amount of a predetermined polarized component. Have

Reference numeral 309 denotes a first dichroic mirror, which separates the light beam from the white light source 1 into a first color light (for example, R) and second and third color lights (B, G). Reference numeral 310 is a second dichroic mirror, which is a second colored light (B).
And the third color light (G) is separated. Reference numeral 313 is a reflection mirror that reflects the first color light (R), and 314 is a reflection mirror that reflects the third color light (G). Reference numeral 311 is a third dichroic mirror, which combines the first color light (R) and the second color light (B). A fourth dichroic mirror 312 combines the third colored light (G) with the first and second colored lights (R, B).

Dichroic mirror 3 in this embodiment
09, 310, 311 and 312 are also made of plate-shaped mirror glass, and the dichroic mirrors 311 and 312 are tilted with respect to the optical axis so as to satisfy the conditional expression (1), and have a predetermined thickness. There is.

Also in this embodiment, the color light selecting means is constituted by the respective elements of the first and second dichroic mirrors 309 and 310, and the third and fourth dichroic mirrors 311 and 3 are provided.
Each of 12 elements constitutes an optical path forming means.

Reference numerals 305R, 305B, and 305G denote liquid crystal panels as image forming means, which are TN type liquid crystal displays for displaying monochrome images corresponding to respective colors of red (R), blue (B), and green (G). It is made up of elements. Three
Reference numerals 06, 307, and 308 denote condenser lenses, which collect the illumination light flux reaching the liquid crystal panels 305R, 305B, and 305G near the panel side pupil of the projection lens 15.

In the structure of this embodiment, the light flux passing through the dichroic mirror 312 close to the projection lens 15 is RGB.
Since there are two colors of B and R among the three colors, it can be said that the present invention is an embodiment to which the present invention has great significance.

By the way, when the dichroic film is vapor-deposited on a very thin glass plate, the glass plate is warped, which adversely affects the projected image. Even if the warp is the same, this effect becomes larger as the projection lens is closer to the projection lens. Therefore, taking the example 1 of FIG. 1 as an example, it is better to avoid the distortion of the dichroic mirror 12 as much as possible. From such a viewpoint, in Example 1 of FIG. 1, the dichroic mirror 12 is made thicker than the dichroic mirror 11 within a range not exceeding the conditional expression (1) described above.

Further, as described above, in order to gradually reduce the astigmatism, it is preferable to reduce the thickness of the dichroic mirror as the optical path forming means.

In view of the above two points, it is desirable to further reduce the thickness of the dichroic mirror farther from the projection lens among the dichroic mirrors forming the optical path forming means (color combining system), and the dichroic mirror close to the projection lens. the thickness of the mirror d _1, when the thickness of the far dichroic mirror from the projection lens and the d _2, obtained a better projected image by configuring such that d _1> d _2.

As described above, in each embodiment, by setting each element so as to satisfy the above-mentioned conditional expression (1), the astigmatism due to the thickness of the dichroic mirror arranged at an angle with respect to the optical axis is eliminated. Can be reduced.

If the images formed on the three liquid crystal panels can be superposed on each other by the optical path forming means (dichroic mirror), the above-mentioned first to sixth embodiments will be described in particular.
Not limited to the above configuration, any configuration may be used.

Further, the present invention can be applied not only to the color image projecting device but also to a stereo projecting device for synthesizing and projecting two images, for example, similarly to the above-mentioned embodiment.

[0078]

According to the present invention, by appropriately setting each element so as to satisfy the above-mentioned conditional expression, it is possible to adjust the thickness when the dichroic mirror as the optical path forming means is arranged tilted with respect to the optical axis. (EN) A projection device capable of reducing astigmatism and capable of projecting (projecting) an excellent image (original image of a projected image) with a light beam transmitted or reflected by the dichroic mirror onto a projection surface. it can.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment when the present invention is applied to a projection device using a three-plate color liquid crystal panel.

FIG. 2 is a schematic view of a main part of a second embodiment when the present invention is applied to a projection device using a three-plate color liquid crystal panel.

FIG. 3 is an arrangement diagram when a dichroic mirror is arranged between a projection lens and a liquid crystal panel at a predetermined angle.

FIG. 4 is an explanatory diagram showing a spot diagram of an axial luminous flux corresponding to FIG.

5 is an explanatory diagram showing an MTF curve on the axis corresponding to FIG.

FIG. 6 is a schematic view of a main part of a third embodiment when the present invention is applied to a projection device using a three-plate type reflective color liquid crystal panel.

FIG. 7 is a schematic view of a main part of a fourth embodiment when the present invention is applied to a projection device using a three-plate type reflective color liquid crystal panel.

FIG. 8 is a schematic view of a main part of a fifth embodiment when the present invention is applied to a projection device using a three-plate type reflective color liquid crystal panel.

FIG. 9 is a schematic view of the essential portions of Embodiment 6 when the present invention is applied to a projection device using a three-plate type reflective color liquid crystal panel.

FIG. 10 is a schematic view of a main part of a conventional projection device using a three-plate color liquid crystal panel.

[Explanation of symbols]

1 Light Source 2 Reflector 3 Filter 4, 24 Polarization Separation Device 5R, 5G, 5B Image Forming Means (Liquid Crystal Panel) 25R, 25G, 25B Image Forming Means (Liquid Crystal Panel) 55R, 55G, 55B Image Forming Means (Liquid Crystal Panel) 75R, 75G, 75B Image forming means (liquid crystal panel) 205R, 205G, 205B Image forming means (liquid crystal panel) 305R, 305G, 305B Image forming means (liquid crystal panel) 6, 7, 8 Condenser lens 26, 27, 28 Condenser lens 56, 57,58 condenser lens 76,77,78 condenser lens 206,207,208 condenser lens 306,307,308 condenser lens 9,10,29,30 color light selecting means (dichroic mirror) 79,80,209,210 color light Selection means (dichroic mirror) 11, 12, 31, 32 Optical path forming means (dichroic mirror) 59, 60, 81, 82 Optical path forming means (dichroic mirror) 211, 212 Optical path forming means (dichroic mirror) 311, 312 Optical path forming means (Dichroic mirror) 13, 14, 33, 34, 83, 84 Reflecting mirror 213, 214, 313, 314 Reflecting mirror 15 Projecting means (projecting lens) 16 Projected surface (screen) 54 Polarizing beam splitter

Claims (1)

[Claims] 1. A light flux from at least one light source means is generated by a color light selecting means to illuminate corresponding image forming means with the generated color light, and the image forming means is formed based on the respective color light. In a projection device in which the formed images are combined through an optical path forming means and projected onto a projection surface by a projecting means, the incident angle of the light flux on the optical axis entering the optical path forming means is θ, and the optical path forming means is When the thickness of the constituent glass mirror is d, the FNO of the projection means is F, and the image pitch in the plane direction consisting of the optical axis of the projection means of the image forming means and the normal line of the optical path forming means is p, (d /P)×tan(θ)/F<3.5. A projection apparatus in which each element is set so as to satisfy the condition.