JP2003066531A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the precision of color synthesis of a projector which uses a dichroic prism for color synthesis, and also, to suppress the generation of vertical stripes in the projected image. SOLUTION: In the projector which uses the dichroic prism for color synthesis, the dichroic prism is constituted by joining four triangular prisms whose cross section is formed to almost a right-angled triangle, and in the triangular prism, projections or grooves that have two faces parallel to the two pasted faces are integrally injection-molded on the faces that are substantially perpendicular to the light beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device in which light beams of respective colors modulated by a liquid crystal light valve are combined by a dichroic prism and enlarged and projected on a screen through a projection lens.

[0002]

2. Description of the Related Art A conventional color synthesizing means for a projection type display device,
There is a dichroic prism.

Usually, a dichroic prism is bonded to each other so that the right angles of four right-angled triangular prisms are in contact with each other so as to form an X shape, and the bonding surface has a dielectric property of selective reflection of a predetermined color. A reflective film such as a body film is formed (hereinafter, the reflective film is formed unless otherwise specified).

Glass is currently the mainstream material for such right-angled triangular prisms, but in recent years, as described in Japanese Patent Laid-Open No. 2001-66694, a plastic injection-compression molded product has been used. .

A method of manufacturing such a dichroic prism will be described with reference to FIG.

First, of the two planes sandwiching the right angle of the first triangular prism 19 and the second triangular prism 20, the planes 19a and 20a are used as reference planes and they are bonded on the same plane.

The third triangular prism 21 and the fourth triangular prism 22 are also bonded in the same manner.

Next, the first triangular prism and the second triangular prism are bonded to the third triangular prism and the fourth triangular prism. At this time, since there is no reference surface, it is difficult to align the positions of the apex portions and to bond them accurately.

As a result, for example, when a displacement amount δ occurs on the bonding surface as shown in FIG. 3, the images of the respective colors synthesized through the obtained dichroic prism are not aligned on the screen, and the image quality deteriorates. .

In order to eliminate such a deterioration in image quality, a method for accurately attaching the apex angle positions of the prisms is disclosed in Japanese Patent Laid-Open No.
No. 8-184793. This method is shown in Figure 4.
As shown in FIG. 4, of the four prisms 23, 24, 25 and 26, the pair of prisms 23 and 24 are first attached with a step, and the remaining pair of prisms 25 and 26 are similarly formed.
Steps are attached to each other, and then these step surfaces 23
The prisms of each pair are bonded together by using a and 25a as alignment surfaces.

[0011]

When a right-angled triangular prism made of glass is used, there is a polishing step in the process.
Since it is possible to easily form the surface perpendicular to the surface through which the light flux passes, the dichroic prism can be formed with high accuracy even in the conventional technique.

However, in the above-mentioned right-angled triangular prism formed by injection compression molding of plastic, an inclination of about 2 to 5 degrees occurs due to the injection from the mold.

When an attempt is made to form a dichroic prism by the method described in Japanese Patent Laid-Open No. 8-184793 using such a right-angled triangular prism having an inclination, it is possible to align a stepped surface. Cannot align in the orthogonal direction.

Therefore, since the right-angled ridges of the bonded four prisms cannot be bonded accurately, the luminous fluxes of the respective colors cannot be accurately combined for each pixel, and the desired color cannot be reproduced. Further, the ridgeline itself is displayed as a vertical stripe on the projected image.

An object of the present invention is to improve the accuracy of color combination and to suppress the vertical stripes of a projected image.

[0016]

In order to achieve the above object, the present invention includes the following aspects. (1) A light source, a color separation unit that separates the light flux emitted from the light source into light fluxes for each color, a light valve that modulates the separated light fluxes of each color, and each color modulated through these light valves. In a projection display device having a dichroic prism for synthesizing the modulated light flux of and the projection lens for enlarging and projecting the synthesized modulated light flux on a screen, the dichroic prism has four triangular prisms each having a cross section of a substantially right triangle. As a triangular prism, a projection or a groove having two surfaces forming a plane parallel to the two bonding surfaces is integrally formed on the surface substantially perpendicular to the light flux (the surface where the light flux does not pass). Some use triangular prisms molded in. (2) Light source, color separation means for separating the light flux emitted from the light source into light fluxes of respective colors, a light valve for modulating the separated light fluxes of the respective colors, and respective colors modulated through these light valves In a projection display device having a dichroic prism for synthesizing the modulated light flux of and the projection lens for enlarging and projecting the synthesized modulated light flux on a screen, the dichroic prism includes four triangular prisms whose cross sections are substantially right triangles. It is assumed that the triangular prisms having a positioning mark on the bonding surface are used as the triangular prisms. (3) Light source, color separation means for separating the light flux emitted from the light source into light fluxes of respective colors, a light valve for modulating the separated light fluxes of the respective colors, and respective colors modulated through these light valves In a projection display device having a dichroic prism for synthesizing the modulated light flux of and the projection lens for enlarging and projecting the synthesized modulated light flux on a screen, the dichroic prism includes four triangular prisms whose cross sections are substantially right triangles. Some of them are attached to each other by a protrusion or a groove provided on the attaching surface.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The basic structure of a projection type display device to which the present invention is applied will be described below with reference to FIG.

White light flux 49 from the light source lamp unit 48
Is a uniform white light flux due to the first lens array 50, the cold mirror 51 which is the first reflection mirror, and the second lens array 52, and is separated into a red light flux 54 and a blue-green light flux 55 by the blue-green reflection dichroic mirror 53. To be done.

The red luminous flux 54 is reflected by the first increasing reflection mirror 56, passes through the first condensing lens 57, and enters the first liquid crystal light valve 58. The blue-green light beam 55 is separated into a green light beam 60 and a blue light beam 61 by a green reflection dichroic mirror 59. The green light flux 60 passes through the second condenser lens 62 and enters the second liquid crystal light valve 63.

The blue luminous flux 61 passes through the first relay lens 64, the second increasing reflection mirror 65, the second relay lens 66, the third increasing reflection mirror 67, and the third condensing lens 68 to the third condensing lens 68. Is incident on the liquid crystal light valve 69.

The red light flux containing the image information emitted from the first liquid crystal light valve 58 enters the dichroic prism 70 having the structure shown in FIG. The light enters from the surface 701a, is reflected at 90 degrees on the bonding surface 701c surface and the surface 704d, and exits from the surface 704b. The blue light flux containing the image information emitted from the second liquid crystal light valve 63 is transferred to the dichroic prism 70.
The light enters from the surface 3a, is reflected at 90 degrees on the surfaces 703c and 704c, and is emitted from the surface 704b. The green light flux containing the image information emitted from the third liquid crystal light valve 69 enters the dichroic prism 70 from the surface 702a, and the bonding surface 70
The light is transmitted through the 1c, 703c, 704c, and 704d surfaces and emitted from the 704b surface.

The emitted light 71 containing the color-combined image information is projected by the projection lens unit 72 and imaged on the screen 73.

The embodiment relating to the dichroic prism 70 described below is applied to this basic structure. (Embodiment 1) The dichroic 70 shown in FIG.
The dichroic prism 9 shown in is adopted.

The dichroic prism 9 is composed of four triangular prisms made of plastic and having the same refractive index, that is, the first triangular prism 1, the second triangular prism 2, and the third triangular prism.
3 triangular prism 3 and 4th triangular prism 4 are almost right angle (9
The ridgelines forming 0 ° ± 5 °) are attached to each other by an adhesive so that the ridgelines are in contact with each other to form a quadrangular prism having a rhombus cross-sectional shape. In addition, since a dielectric film is formed on each bonding surface to give desired optical characteristics, there is an interval of about 5 μm or less, but here it is treated as a square pole.

As shown in FIG. 1, the first triangular prism has flat surfaces 5a and 6a parallel to the bonding surface 1a on two surfaces of a right-angled isosceles triangle that does not pass a light beam and is not used for bonding.
And a protrusion having flat surfaces 5b and 6b parallel to the bonding surface 1b
Five and six are provided. This shape is manufactured by injection molding or compression molding of plastic.

As shown in FIG. 1, the third triangular prism has planes 7a and 8a parallel to the bonding surface 3a on two surfaces of a right-angled isosceles triangle that does not pass a light beam and is not used for bonding.
And a protrusion having flat surfaces 7b and 8b parallel to the bonding surface 3b
7 and 8 are provided. This shape is manufactured by injection molding or compression molding of plastic.

Next, a method of manufacturing the dichroic prism 9 in which four triangular prisms are bonded by using these protrusions will be described.

First, the first triangular prism 1 and the second triangular prism 2 are bonded so that the bonding surfaces 1b and 2b are on the same plane. Next, the third triangular prism 3 and the fourth triangular prism 4 are also bonded in the same manner. At this time, the bonding is performed on the surface where the protrusion is a part of the flat surface. A dichroic prism is formed by further bonding the bonded prisms together.

FIG. 13 shows a perspective view of the bonding process.

First, the positioning jig 500 supports one flat surface (flat surface 7b) of the two protrusions of the prism 200 that are bonded together. Although only a part of the jig 500 is illustrated, the flat surface (flat surface 8b) of the projection on the opposite side of the prism 200 is also sandwiched and supported by the same jig. The adhesive 100 is applied to the prism placed on this jig and spread over the entire surface.

Another two prisms 300 that are bonded together
Similarly, for the projections of the jig 400, the flat surfaces (flat surfaces 5b and 6b) of the jig 400
Supported by. The jigs 400 and 500 fix the directions of the prism 200 and the prism 300, and temporarily fix the prisms by matching the surfaces.

Next, the temporarily fixed prism 200 and prism 400 are fitted into the outer frame rough positioning guide shown in FIG. 14 so that the triangular prism having the protrusions face down. Then, the positioning suction plate is used to perform accurate positioning, and the main adhesion is performed.

Since such a projection has a small area even if formed by injection molding, it has little influence on the positioning with the guide, and thus positioning can be performed with high accuracy.

Note that the protrusions have an arbitrary shape such as a cylinder, and even when they are not arranged in a position parallel to the bonding surface, the bonding can be performed by making the assembly jig correspond to the shape of the protrusions. Although it can be performed accurately, a shape having a surface parallel to the bonding surface is preferable from the viewpoint of facilitating the production of the assembly jig. Further, when the triangular prism is injection-molded, if the projection has an inclination θ as shown in FIG. 11, the triangular prism becomes a taper to be released from the prism molding die. It can be easily removed from the mold. Furthermore, if at least one of the light-incident surfaces of the dichroic prism has a lens shape such as a concave surface or a convex surface, chromatic magnification aberration of the dichroic prism can be corrected. (Embodiment 2) FIG. 2 is a perspective view of a dichroic prism 18 according to a second embodiment of the present invention. The dichroic prism 18 has four triangular prisms having the same refractive index, that is, four first prisms 10, a second triangular prism 11, a third triangular prism 12 and a fourth triangular prism 13 are bonded together. As a result, a rectangular cross-section has a prismatic shape, and a dielectric film is formed on each bonding surface to impart desired optical characteristics. In this example, the first triangular prism 10 is a right-angled isosceles triangle that is not used for bonding.
Flat surfaces 14a and 15a parallel to the bonding surface 10a on each of the two surfaces
And a groove 1 having flat surfaces 14b and 15b parallel to the bonding surface 10b.
There are four and fifteen. A method of forming the dichroic prism 18 by adhering the triangular prisms will be described.

First, the first triangular prism 10 and the second triangular prism 11 are bonded so that the bonding surfaces 10b and 11b are on the same plane. Next, the third triangular prism 12 and the fourth triangular prism 13 are also bonded in the same manner. After that, each pair of the triangular prisms is attached in a X shape. In the dichroic prism 18 obtained by bonding in this way, in addition to the alignment surfaces 14a and 16a similar to the conventional one, alignment surfaces 15a and 17a parallel to the alignment surfaces 14a and 16a are formed on the lower end side. Further, in addition to the alignment surfaces 14b and 16b orthogonal to these alignment surfaces, alignment surfaces 15b and 17b parallel to the alignment surfaces 14b and 16b are also formed on the lower end side. Therefore, a jig can be applied to these surfaces to accurately bond the four prisms.

Further, the dichroic prism of this example bonded in this way has the groove formed in the prism.
By using 14, 15, 16 and 17 to attach the optical unit at a predetermined position, the positioning can be accurately performed. Here, even if only the grooves 14 and 15 can be aligned, the bonding can be performed accurately, but the number of the grooves is increased because the more the reference of the alignment is, the more accurate the positioning can be made. Better. Even if the groove has an arbitrary shape such as a cylinder and is not arranged at a position parallel to the bonding surface, the bonding can be accurately performed by making the assembly jig correspond to the groove shape. Yes, but from the perspective of making it easier to make an assembly jig,
A shape having a surface parallel to the bonding surface is preferable. Further, when the prism is injection-molded, if the groove is formed with an inclination θ as shown in FIG. 12, the prism becomes a draw taper when the prism is released from the prism molding die, so that the prism can be easily formed. It can be removed from the mold.
Furthermore, if at least one of the light-incident surfaces of the dichroic prism has a lens shape such as a concave surface or a convex surface, chromatic magnification aberration of the dichroic prism can be corrected. (Embodiment 3) FIG. 5 shows a perspective view of a dichroic prism 27 according to a third embodiment of the present invention. The dichroic prism 27 is formed by bonding four triangular prisms having the same refractive index, that is, four prisms of a first triangular prism 28, a second triangular prism 29, a third triangular prism 30 and a fourth triangular prism 31. As a result, a rectangular cross-section has a prismatic shape, and a dielectric film is formed on each bonding surface to impart desired optical characteristics. In this example, the first triangular prism 28 is provided with the protrusion 33 in advance. A method of forming the dichroic prism 27 by bonding the triangular prisms together will be described.

First, the first triangular prism 28 and the second triangular prism 29 are bonded together. Next, the third triangular prism 30 and the fourth triangular prism 31 are bonded together with the steps 32a and 32b. After that, each pair of the triangular prisms is attached in a X shape. In the dichroic prism 27 obtained by pasting in this way, the alignment surfaces 32a and 33a similar to the conventional one are formed. Furthermore, the alignment surfaces 32b and 33b orthogonal to these alignment surfaces are formed. Therefore, a jig can be applied to these surfaces to accurately bond the four prisms.

Further, the dichroic prism of this example, which is bonded in this manner, can be accurately positioned by using the projection 33 provided on the prism and mounting it at a predetermined position of the optical unit. You can

Here, the protrusion provided in advance on the triangular prism, the groove provided in advance on the triangular prism, and the step provided when the two triangular prisms are bonded together may be used as the alignment reference. Where the protrusion 33
It is possible to perform the alignment even if only by itself, and it is possible to perform the bonding accurately. However, since the more the reference of the alignment is, the more accurate the positioning becomes, it is better to increase the number of the protrusions. Even if the protrusions and grooves have an arbitrary shape such as a cylinder and are not arranged in a position parallel to the bonding surface, the bonding can be performed accurately if the assembly jig is adapted to the shape of the protrusions or grooves. However, the shape having a flat surface parallel to the bonding surface is preferable from the viewpoint of facilitating the production of the assembly jig. Further, when the prism is injection-molded, if the projections and grooves are formed with an inclination θ as shown in FIG. 11 and FIG. 12, it will be a taper when the prism is released from the prism molding die. The prism can be easily taken out of the mold.

Furthermore, if at least one of the light-incident surfaces of the dichroic prism has a lens shape such as a concave surface or a convex surface, chromatic magnification aberration of the dichroic prism can be corrected. (Embodiment 4) FIG. 6 shows a perspective view of a dichroic prism 34 according to a fourth embodiment of the present invention. The dichroic prism 34 is formed by bonding four triangular prisms having a triangular prism shape and having the same refractive index, that is, four prisms of a first triangular prism 35, a second triangular prism 36, a third triangular prism 37 and a fourth triangular prism 38. As a result, a rectangular cross-section has a prismatic shape, and a dielectric film is formed on each bonding surface to impart desired optical characteristics. In this example, the right-angled isosceles triangle 2 used for bonding the first triangular prism 35
Protrusions 40a and 40b and grooves 41a and 41b are provided on portions of the surface that are not used for separating and combining the light fluxes of the three colors. The triangular prisms are attached to each other to form a dichroic prism 34.
A method of creating the will be described. First, the protrusion 40a and the groove 41a of the first triangular prism 35 and the groove 43b of the second triangular prism 36.
And the protrusion 42b is bonded as a positioning. Next, similarly for the third triangular prism 37 and the fourth triangular prism 38,
The protrusion 44b, the protrusion 46a, the groove 45b, and the groove 47b are bonded together for positioning. After this, each pair of triangular prisms is replaced with a protrusion 40b, a protrusion 42a, a protrusion 44a, a protrusion 46b, a groove 41b, a groove 43a, and a groove.
The 45a and the groove 47b are bonded together in an X shape for positioning. Here, the shapes of the protrusions and the grooves in the case where the bonding of the first triangular prism 35 and the second triangular prism 36 is taken as an example are shown in FIG. The height h1 of the protrusions 40a and 42b and the height h2 of the grooves 41a and 43b are
Within the thickness of the adhesive layer. Further, the distance m1 between the protrusion 40a of the first triangular prism 35 and the groove 41a and the groove 43b of the second triangular prism 36.
The distance m2 between the protrusion 42b and the protrusion 42b is within 2 μm, the distance m3 between the groove 41a of the first triangular prism 35 and the center line portion, and the second triangular prism 36.
By accurately setting the difference between the protrusion 42b and the distance m4 between the center line and the protrusion to within 2 μm and the gap between the protrusion 40a and the groove 43b within 1 μm, the positioning can be performed accurately. Since the first triangular prism 35 and the second triangular prism 36 have the same shape, when the triangular prisms made by the same mold are used for combination, the distance m1 between each protrusion and the groove is Since m2 and the distances m3 and m4 between the center line portion and the protrusion or groove are the same, more accurate positioning can be performed. Further, the protrusions and grooves can be bonded accurately even if they have an arbitrary shape such as a square shape. However, in this case, the columnar shape is preferable because there are many restrictions due to the die drawing direction. Here, if at least one light-incident surface of the dichroic prism has a lens shape such as a concave surface or a convex surface, chromatic magnification aberration of the dichroic prism can be corrected.

[0041]

According to the present invention, since the ridge lines of the apex angle of the triangular prism can be made to coincide with each other, it is possible to perform accurate color combination and suppress vertical stripes in the projected image. it can.

[Brief description of drawings]

FIG. 1 is a perspective view of a dichroic prism according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a dichroic prism according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of positional deviation of a prism unit.

FIG. 4 is a diagram for explaining a conventional method of attaching a prism unit.

FIG. 5 is a perspective view of a dichroic prism according to a third embodiment of the present invention.

FIG. 6 is a perspective view of a dichroic prism according to a fourth embodiment of the present invention.

FIG. 7 is a detailed view of a protrusion and a groove according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a positional deviation amount and an illuminance ratio according to the present invention.

FIG. 9 is a top view of a conventional projection display device optical system.

FIG. 10 is a configuration diagram of a conventional color combining prism.

FIG. 11 is a perspective view of a triangular prism showing a modification of the first embodiment.

FIG. 12 is a perspective view of a triangular prism showing a modification of the second embodiment.

FIG. 13 is a diagram showing a manufacturing state of the dichroic prism according to the first embodiment.

FIG. 14 is a diagram showing a manufacturing state of the dichroic prism according to the first embodiment.

[Explanation of symbols]

Dichroic prism ... 9 1st triangular prism ・ ・ ・ 1 Second triangular prism ... 2 Third triangular prism ... 3 4th triangular prism ... 4 Bonding surface ・ ・ ・ 1a, 1b A plane parallel to the bonding surface 1a ... 5a, 6a A plane parallel to the bonding surface 1b ... 5b, 6b Protrusion ... 5, 6, 7, 8 Bonding surface ... 3a, 3b A plane parallel to the bonding surface 3a ... 7a, 8a A plane parallel to the bonding surface 3b ... 7b, 8b

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Aki Nakajo             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Inside the Hitachi, Ltd. production technology laboratory (72) Inventor Hiroki Kuramoto             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Division             Within (72) Inventor Tatsumi Hasebe             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Division             Within (72) Inventor Zenji Kodera             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Division             Within (72) Inventor Sadayuki Nishimura             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Division             Within F-term (reference) 2H042 CA10 CA14 CA17                 2H048 AA07 AA14 AA18 AA25                 2H088 EA15 EA19 HA13                 2K103 AA01 AA05 AA11 AA16 AB06                       AB10 BC01 BC08 CA19 CA29

Claims (8)

[Claims] 1. A light source, a color separating means for separating a light beam emitted from the light source into light beams of respective colors, a light valve for modulating the separated light beams of respective colors, and a light valve which is modulated through these light valves. In a projection display device having a dichroic prism for combining the modulated light fluxes of the respective colors and a projection lens for enlarging and projecting the combined modulated light fluxes on a screen, the dichroic prism includes four triangular prisms each having a cross section of a right angle. As a triangular prism, a protrusion or a groove having two surfaces that form a plane parallel to the two bonding surfaces on a surface that is substantially perpendicular to the light flux (a surface where the light flux does not pass). A projection type display device characterized in that a triangular prism molded integrally with is used. 2. The projection type display device according to claim 1, wherein the two triangular prisms are bonded so that a plane parallel to the bonding surface is substantially the same plane. 3. A light source, a color separating means for separating the light flux emitted from the light source into light fluxes of respective colors, a light valve for modulating the separated light flux of each color, and a light valve which is modulated through these light valves. In a projection display device having a dichroic prism for synthesizing the modulated light flux of each color and a projection lens for enlarging and projecting the synthesized modulated light flux on a screen, the dichroic prism is a triangular prism having a cross section of a right-angled triangle. A projection type display device characterized in that the individual prisms are bonded to each other, and as the triangular prisms, a triangular prism having a positioning mark on the bonding surface is used. 4. The projection display device according to claim 3, wherein the mark is formed on both of the bonding surfaces. 5. The projection display device according to claim 3, wherein the mark is formed by a protrusion or a groove. 6. A light source, a color separation means for separating a light beam emitted from the light source into light beams of respective colors, a light valve for modulating the separated light beam of each color, and a light valve which is modulated through these light valves. In a projection display device having a dichroic prism for synthesizing the modulated light flux of each color and a projection lens for enlarging and projecting the synthesized modulated light flux on a screen, the dichroic prism is a triangular prism having a cross section of a right-angled triangle. A projection-type display device, wherein the projection-type display devices are bonded to each other and are fitted together by projections or grooves provided on the bonding surface. 7. The projection display device according to claim 5, wherein a projection is formed on one surface of the bonding surface and a groove is formed on the other surface. 8. The position according to claim 5, wherein a protrusion and a groove are formed on one surface of the bonding surface, and a protrusion and a groove formed on the one surface can be fitted into the other surface. A projection type display device characterized in that a groove and a protrusion are formed on the surface.