JPH11317918A - Projection optical system and multi-projector using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of uneven luminance because the luminance distribution of an image on a screen differs between a central part and surrounding parts. SOLUTION: Projection lenses comprises a 1st lens 23, a plate 27 with a partly opaque part, a 2nd lens 24, a 3rd lens 25, and a 4th lens 26 from a face plate 22 of a color cathode ray tube sequentially. The plate 27 with a partly opaque part is configured of a material 27-1 not reflecting light and not passing light in the vicinity of an optical axis and of an optical transparent material 27-2 for the other part. The luminance in the middle and its vicinity of an image on a screen is suppressed by providing the plate 27 with a partly opaque part so as to shut part of valid light emitted from the central part 30 of a fluorescent screen and its vicinity among valid lights emitted from the fluorescent screen 28 and passing through the projective lenses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-projector in which a plurality of large-screen rear projector units are arranged in a vertical direction and a horizontal direction so that a larger image can be viewed, and a projection optical system used therefor. .

[0002]

2. Description of the Related Art Conventionally, as a multi-projector, there have been ones described in JP-A-63-88976 and JP-A-62-6733.

In the technology described in Japanese Patent Application Laid-Open No. 63-88976, a projection lens having at least one optical path turning mirror is used, and the optical path of the projection light from the CRT is set to two.
A rear projector unit that folds and projects an image on a transmission screen (hereinafter referred to as a screen)
A plurality of sets were arranged closely in the vertical and horizontal directions to obtain a super-large screen.

In the technique described in Japanese Utility Model Laid-Open Publication No. Sho 62-6733, an image is projected onto each screen from two or more sets of projection optical systems. An optical member that substantially reduces the transmitted light amount of each projection light by about half is provided at a joint portion where the obtained adjacent projected images overlap each other, and the brightness of the projected image overlapping at the joint portion is equal to that of the other projected image portions. I was trying to.

[0005]

SUMMARY OF THE INVENTION Among the above prior arts,
In the technique described in Japanese Patent Application Laid-Open No. 63-88976, the design of a multi-projector can be simplified by arranging a plurality of sets of rear projector units having the same projection optical system. However, there is a problem that there is a lot of wasted space in the cabinet, and the depth cannot be shortened sufficiently.

In the technique described in Japanese Utility Model Laid-Open No. 62-6733, there is a possibility that the brightness of a joint portion between adjacent projected images and the vicinity thereof can be made equal to the brightness of other projected image portions. However, no consideration has been given to the fact that a part of the projection light is scattered by the optical member installed to substantially reduce the amount of transmitted light by half, so that the image of the joint portion and the vicinity thereof is blurred.

In addition, a large screen is indispensable for a multi-projector. For example, obtaining a large screen having a diagonal dimension of 100 inches or more by a single plate requires a large number of screens in terms of manufacturing and cost. It is also very difficult. For this reason, a method for forming such a large screen must be newly devised, but the above-mentioned Japanese Utility Model Application Laid-Open No. 62-6733 does not disclose any method for forming such a screen.

In general, in one set of rear projector units, when the luminance distribution of the screen on the screen is 10 at the center, about 3 at the periphery. The main reason is that, in the projection lens, the amount of light taken in at the peripheral portion is smaller than the amount of light taken in at the central portion.

Therefore, when a multi-projector is constructed by arranging a plurality of sets of such rear projector units, images obtained by the multi-projector have a luminance ratio between the central portion and the peripheral portion of 10: 3. , And even if there is no non-display portion between the projection images, luminance unevenness occurs in a 10: 3 cycle on the entire screen, and a large screen with high image quality is obtained. There was a problem that it was not possible.

[0010] An object of the present invention is to improve the problem that the luminance distribution of the screen on the screen is largely opened between the central portion and the peripheral portion, and the luminance unevenness occurs, among the above-mentioned problems of the prior art. An object of the present invention is to provide a projection optical system capable of providing a high-quality screen with less luminance unevenness, and a multi-projector using the same.

[0011]

In order to achieve the above-mentioned object, the present invention employs the following configuration.

(1) A non-reflective / non-transmissive object is provided on the outer surface or inside of the projection lens constituting the projection optical system, at the optical axis of the projection lens and at a specific portion near the optical axis and in the optical axis direction. Was placed.

(2) In the configuration of (1), the light non-reflective / light non-transmissive object is arranged at the center of the surface of the specific single lens and near the center.

(3) A projection plate is formed by forming a substantially circular plate having a central portion and a central portion near the central portion made of a light non-transmissive / light non-reflective material and a peripheral portion made of a transparent material. Placed on the outside or inside.

[0015]

According to the above-mentioned constitution (1), (2) or (3), a part of the effective light emitted from the vicinity of the center of the fluorescent screen of the cathode ray tube can be partially blocked. On the screen of the rear projector unit, the brightness at the center of the screen and its vicinity can be suppressed, and the difference between the brightness at the center of the screen and the brightness at the periphery can be reduced. Therefore, if a multi-projector is configured by arranging a plurality of such rear projector units, it is possible to obtain a high-quality large screen without causing uneven brightness on the entire screen.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Before that, in order to facilitate understanding of the embodiments of the present invention, a multi-projector based on the premise of the present invention will be described. The configuration will be described first.

FIG. 3 is a side view showing a main part of a multi-projector as a premise of the present invention. As shown in FIG.
The rear projector unit 1 includes a projection optical system including a projection lens 1-1, a cathode ray tube 1-2, and an optical path turning mirror 1-3, and a screen 1-4, and the rear projector unit 2 also includes a projection lens 2- 1, a projection optical system comprising a cathode ray tube 2-2, an optical path turning mirror 2-3, and a screen 2-4. And
The multi-projector in the present configuration example includes the rear projector unit 2 and the rear projector unit 1 described above.
Are stacked in two upper and lower stages.

Each of the rear projector units 2, 1
, The upper and lower projection lenses 2-1 and 1-1, the cathode ray tubes 2-2 and 1-2, the optical path turning mirror 2-3 and
1-3, screens 2-4 and 1-4 basically have the same performance as each other.

In FIG. 3, the projection lenses 2-1 and 1--1
1. Each of the CRTs 2-2 and 1-2 is displayed as a single unit. However, when three color images of red, green and blue are individually projected,
At least three or more projection lenses and cathode ray tubes are arranged in each rear projector unit.

In this embodiment, as shown in FIG. 3, the mirror setting angle θ ₂ of the upper mirror 2-3 with respect to the surfaces of the screens 1-4 and 2-4 is changed to the mirror of the lower mirror 1-3. so that the larger the set angle theta _1, each mirror 1-3 and 2-3, more projection lenses 1-1 and 2-1,
CRTs 1-2 and 2-2 are arranged. Usually, the neck portion 1-21 of the cathode ray tube 1-2 is arranged so as to be as close as possible to the extension of the screen surface of the screens 2-4 and 1-4.

By arranging as described above, the mirror 1-3 of the lower rear projector unit 1 can be brought as close as possible to the rear screen 1-4, so that the depth of the rear projector unit 1 can be made sufficiently short. It is possible to do.

The upper rear projector unit 2
In, by a mirror set angle theta ₂ of the mirror 2-3 and a mirror set angle theta ₁ is greater than an appropriate angle of the mirror 1-3, the upper portion of the projection lens 2-1, a mirror CRT 2-2 1-3 It becomes possible to arrange in space.

With this arrangement, the depth of the rear projector unit 2 may be slightly larger than the depth of the rear projector unit 1, but as a whole the upper and lower units which maximize the space utilization efficiency are used. A multi-projector having a two-stage configuration can be used, and the depth of the entire apparatus can be reduced and the apparatus can be made thin.

In the above structure, the cathode ray tube 2-
It is considered that the depth of the entire device can be reduced to the maximum by bringing the neck portion 2-21 of the second device as close as possible to the mirror 1-3.

In the above description, the mirror setting angles θ ₁ and θ ₂ for thinning the entire apparatus have been described.
Projection rays 1-5, 2 from each projection lens 1-1, 2-1
By defining the incident angles α ₁ and α ₂ when −5 is incident on the mirrors 1-3 and 2-3, it is possible to make the entire apparatus thinner.

That is, the rear projector units 1 and 2 are configured so that α ₁ <α ₂ . Again,
It is necessary to bring the neck portion 1-21 as close as possible to the extension of the screen surface of the screens 2-4 and 1-4 and to bring the neck portion 2-21 as close as possible to the mirror 1-3.

FIG. 4 is a front view schematically showing another example of the multi-projector on which the present invention is based. The multi-projector in this example is configured by arranging four sets of rear projector units vertically and horizontally.

With such a configuration, each of the screens 1-4, 1-4 'of each rear projector unit,
A large screen having a diagonal size twice as large as the diagonal size of 2-4, 2-4 'can be realized with a depth size close to the depth size of each rear projector unit alone.

FIG. 5 is a side view showing a main part of still another example of the multi-projector based on the present invention. FIG.
As shown in the figure, the multi-projector in this example includes three rear projector units 5, 4, and 3 in the vertical direction.
It is constructed by stacking on tiers.

At this time, in each of the rear projector units 3, 4, and 5, each mirror 3-3, 4-
The set angles θ ₃ , θ ₄ , θ ₅ of ₃ , 5-3 are θ ₃ <θ ₄
<A mirror setting angle that satisfies the relationship of θ _5.

As described above, by satisfying the above relationship θ ₃ <θ ₄ <θ ₅ and arranging the projection optical systems in each rear projector unit as close as possible to each other, the entire apparatus can be made as thin as possible. it can.

In the above configuration, each mirror 3-
Light projected on 3,4-3,5-3 3-5,4-5,5-
Even if the angles of incidence α ₃ , α ₄ , and α ₅ are set to satisfy the relationship α ₃ <α ₄ <α ₅ , the entire device can be made thinner.

FIG. 6 is a cross-sectional view showing, as a reference example, a cross section of an example of a screen suitable for the above-mentioned multi-projector, which is a premise of the present invention.

In the present embodiment, a screen for projecting a large screen is in close contact with the respective screen plates 7-1 and 7-2 corresponding to the respective projection optical systems on one large transparent reinforcing plate 6.
It is formed by joining. Here, each of the screen plates 7-1 and 7-2 and the transparent reinforcing plate 6 are bonded by an adhesive (not shown) having substantially the same refractive index as those of the two, or a thin nail. (Not shown) may be joined by a method such as penetrating and fixing them.

In the present embodiment, the projection tubes 8-1 and 8-2 from the respective projection optical systems are prevented from being incident on the screen plates 7-2 and 7-1 adjacent to each other. It is necessary to give sufficient consideration to the size, the angles of the projected light beams 8-1, 8-2, and the like.

When a large-sized transparent reinforcing plate cannot be obtained as the transparent reinforcing plate 6, a plurality of small-sized transparent reinforcing plates are firmly joined to each other to form one large-sized transparent reinforcing plate. It may be formed.

FIG. 7 is a cross-sectional view showing, as a reference example, a cross section of a main part of another screen suitable for a multi-projector as a premise of the present invention.

The difference between the present embodiment and the above-described embodiment of FIG. 6 is that the screen plate 7 is provided on the transparent reinforcing plate 6 '.
The point is that a concave portion 10 is formed in a portion facing the joint portion 9 of -1, 7-2, and a partition plate 11 is fitted into the concave portion 10.

In the present embodiment, the partition plate 11 is a projection light beam effective for projecting a projection image on the screen plates 7-1 and 7-2 among the projection light beams from the respective projection optical systems (not shown). 8'-1, 8'-2 are directly incident on the screen, and unnecessary overscan rays 8'-11, 8 '
-21 is formed and arranged so as to be interrupted by the partition plate 11.

As a result, in this embodiment, the projected light beams from the respective projection optical systems (not shown) can be substantially prevented from being incident on the screens 7-1 and 7-2 adjacent to each other. Joint 9 of screen plates 7-1 and 7-2
In, the joint between adjacent projection images can be reduced.

Here, when the present embodiment is specifically constructed, the depth of the concave portion 10, the thickness of the partition plate 11,
It is necessary to sufficiently consider the surface condition of the partition plate 11, the light blocking performance of the partition plate 11, and the like.

When the overscan rays 8'-11, 8'-21 are blocked by the partition plate 11, if the overscan rays 8'-11, 8 '
When -21 is reflected, flare light is generated, light is scattered, and the contrast of the projected image projected on the screen is reduced, and the projected image is blurred.

Therefore, in the present embodiment, the surface of the partition plate 11 is made black, for example, so that the partition plate 11 has a light absorbing function and the overscan light beam 8'-
Most of 11,8'-21 are not reflected but absorbed. Thus, the projected image projected on the screen is not blurred.

FIG. 8 is a cross-sectional view showing, as a reference example, a cross-section of still another screen suitable for a multi-projector as a premise of the present invention.

The reference example of FIG. 6 and FIG.
The main difference from the reference example is that the screen plates 7'-1, 7'-2 are joined to form a large screen without using the transparent reinforcing plates 6, 6 '. Moreover, in the present embodiment, the outer peripheral portion of the screen is fixed by a strong frame 12 in order to make the strength of the screen sufficient.

In this embodiment, the screen plate 7'-
At the junction 9 'of 1,7'-2, the projection light 13-
1 and 13-2, a concave portion 14 is provided on the incident side.
4, a light-blocking partition plate 15 is fitted. Thereby, similarly to the reference example of FIG.
At the junction 9 'of 7'-2, the joint portion between adjacent projection images can be reduced.

At this time, an appropriate adhesive (not shown) is applied to the concave portion 14, and the partition plate 15 is bonded to the screen plates 7'-1 and 7'-2. Since the bonding area of the screen plates 7'-1 and 7'-2 is larger than that in the case where no 15 is provided, the bonding strength of the screen plates 7'-1 and 7'-2 can be increased.

FIG. 9 is a cross-sectional view showing, as a reference example, a cross section of still another main part of a screen suitable for a multi-projector as a premise of the present invention.

The common point of this embodiment with the embodiment of FIG.
The screen plates 7 "-1,7"-are used without using the transparent reinforcing plates 6,6 'used in the reference example of FIG. 6 and the reference example of FIG.
2 are joined to form a large screen, and the difference is that the screen plates 7 "-1,7"-
The width of the concave portion 14 'provided at the joint portion 9 "of the second embodiment is sufficiently wider than that of the concave portion 14 in the reference example of FIG.
Of the partition plate 15 'fitted into the concave portion 14',
The surface of only the light shielding portion 15'-3 is blackened, for example, and the other fitting portion 15'-1 and its neighboring portion 15'-2 are provided.
Is a transparent point.

In FIG. 9, in order to make the boundary between the fitting portion 15'-1 and the vicinity 15'-2 easy to understand,
For convenience, a broken line is added. In this reference example, the partition plate 15 '
7, the joint portion between the adjacent projection images can be reduced at the joint 9 "of the screen plates 7" -1, 7 "-2, similarly to the reference example of FIG. 7 and the reference example of FIG. it can.

Further, as described above, since the concave portion 14 'is wide, the width of the fitting portion 15'-1 of the partition plate 15' is also larger than the thickness of the light shielding portion 15'-3. Therefore, an appropriate adhesive (not shown) is applied to the concave portion 14 ', and the fitting portion 15'-1 of the partition plate 15' is changed to the screen plate 7 "-1, 7"-. 8 respectively, the bonding area of the screen plates 7 "-1, 7" -2 is further increased as compared with the case of the reference example of FIG. 8, so that the screen plates 7 "-1, 7"-
2 can further increase the bonding strength.

In the partition plate 15 ', the fitting portion 1
When setting the shape and area (that is, the area to be made transparent) of 5′-1 and its neighboring portion 15′-2, the projection angles of the projection rays 13′-1 and 13′-2, It is necessary to calculate and set the projection angles and the like of '-11, 13'-21.

FIG. 10 is a perspective view showing a main part of a screen suitable for a multi-projector as a premise of the present invention, which is cut out and shown as a reference example.

In this embodiment, the screen first
Two front sheets 16-1 and 16-2 each having a black stripe BS on the front surface and a lenticular lens 18 for expanding the horizontal viewing angle on the rear surface are joined to each other,
Next, two rear sheets 17-1 and 17-2 each having a Fresnel lens (not shown) formed on the front surface are joined together, and the joined front sheets 16-1 and 16-2 and rear sheet 17-1 are joined together. , 17-2 are fixed to each other.

At this time, the front seats 16-1 and 16-1
16-2 and the rear seats 17-1, 17-2
Are arranged so that the positions thereof coincide with each other when viewed from the front of the screen and are located at the center of the black stripe BS.

At the joint 20 between the rear sheets 17-1 and 17-2, the recess 19 is fitted with the fitting portion 19 of the partition plate 19.
-1 is fitted, an appropriate adhesive (not shown) is applied to the concave portion, and the fitted portion 19-1 of the partition plate 19 is bonded to the rear sheets 17-1 and 17-2, respectively. 9, the rear seats 17-1 and 17-1
-2 The bonding strength is further increased. The shape and the like of the partition plate 19 conform to the contents described in the reference example of FIG.

In the present embodiment, the provision of the partition plate 19 makes it possible to reduce the joint between adjacent projection images at the joints 20 and 21 to about 1 mm or less.

Moreover, since the joints 20 and 21 are arranged so as to be at the center of the black stripe BS when viewed from the front of the screen, it is possible to make it difficult to visually recognize the above-mentioned joint. Therefore, according to this reference example,
It is possible to obtain image quality equivalent to that of a large screen image having no seams, and to improve the image quality of the screen of the multi-projector.

In the screen of the 100 type class,
When the BS width is set to about 0.5 to 1 mm, a high resolution of 1000 or more horizontal resolutions is possible.

FIG. 11 is a perspective view showing a main portion of another screen suitable for a multi-projector as a premise of the present invention, which is cut out and shown as a reference example.

In the present reference example, the screen first
A plurality of front sheets 38-1, 38-2, 38-3,... Each having a black stripe BS on the front surface and a lenticular lens 18 for expanding the horizontal viewing angle on the back surface.
Are joined together, and then a Fresnel lens (not shown) is formed on the front surface, and four rear sheets 39-1 and 39 provided corresponding to four sets of projection optical systems (not shown), respectively.
-2, 39-3, and 39-4 are joined together, and the joined front and rear seats are fixed to each other.

At this time, the front seats 38-1,
38-2, 38-3,... Joints 40-1, 40-2,.
And the joining portion 41-1 of the rear seats 39-1, 39-2.
The joining portion 41-2 of the rear seats 39-3 and 39-4 is
When viewed from the front of the screen, the positions are arranged so as to be different from each other, and each is arranged so as to be the center of the black stripe BS.

In this embodiment, the rear seat 3
9-1, 39-2, 39-3, 39-4 each joint part 41
In -1, 41-2, 41-3, 41-4, partition plates 42, 42 'are provided on the incident side of the projected light beam (not shown), and further, each of the joint portions 41-1, 41-2, 41-3,
For example, by blackening the joining surface of 41-4, for example, each joining portion 41-1, 41-2, 41-3, 41-.
4 has a light absorbing function.

As described above, in the reference example shown in FIG. 10, the joint 2 of the front sheets 16-1 and 16-2 is formed.
By arranging the joint 21 of the rear sheet 17 and the rear seats 17-1 and 17-2 so as to be at the center of the black stripe BS when viewed from the front of the screen, in many cases, a joint portion between adjacent projected images is provided. Could be hardly visually recognized.

However, since the positions of the joints 20 and 21 coincide with each other when viewed from the front of the screen, the joint state of the joints 20 and 21 is changed.
There is a problem that when the projected image on the screen is viewed, for example, when both of them are incomplete, the joints 20 and 21 are emphasized and visually recognized.

In this embodiment, as described above, the front seats 38-1, 38-2, 38-3,.
And the rear seat 39-
1, 39-2, a joint portion 41-1, a rear seat 39-3,
When viewed from the front of the screen, the bonding portions 41-2 of 39-4 are arranged so that their positions are different from each other.
.. And the joints 41-1, 41-2,... And the joints 41-1, 41-2 when the projected images on the screen are viewed.
-2 became difficult to visually recognize. Therefore, according to the present embodiment, it is possible to view a better image as compared with the embodiment of FIG.

In this embodiment, the partition plate 4
By providing 2, 42 ', of the projection light beams (not shown) from the respective projection optical systems (not shown), unnecessary overscan light beams (not shown) are cut off and do not enter the adjacent rear sheet. You can do so. Moreover, even if,
Even if a part of the overscan light beam (not shown) cannot be blocked by the partition plates 42 and 42 ', in the present embodiment, each of the joints 41-1 to 41-2 and 41- is used.
3 and 41-4 have a light absorbing function, so that each of the joints 41-1, 41-2, 41-3 and 41-4 has
These overscan rays (not shown) can be absorbed, so that unnecessary overscan rays (not shown) can be prevented from completely entering the adjacent rear sheet.

Therefore, according to the present embodiment, each joint 41
-1, 41-2, 41-3, and 41-4 do not have the light absorbing function,
Image quality degradation near -3, 41-4 can be further prevented.

In manufacturing a front sheet, it is generally easier to manufacture a front sheet that is long in the vertical direction than to manufacture a front sheet having a wide width. As shown in FIG. 11, the front seat 38 has no joint in the longitudinal direction.
It is better to use 1, 38-2, 38-3,.

However, a front sheet having a joint in the vertical direction may be used as the front sheet. In this case, the joint in the vertical direction of the front sheet and the joint 41-1 of the rear sheets 39-1 and 39-4 may be used. 3. By arranging the joints 41-4 of the rear seats 39-2 and 39-3 so that the positions thereof are different from each other when viewed from the front of the screen, the joints are formed when the projected image on the screen is viewed. The portions 41-3 and 41-4 can be made hard to visually recognize.

Based on the above, FIG. 1 is a sectional view showing a section of a projection lens of a projection optical system for a multi-projector according to an embodiment of the present invention. That is, the projection lens in the present embodiment is used in a rear projector unit constituting a multi-projector together with a cathode ray tube and the like.

As shown in FIG. 1, the projection lens according to the present embodiment has a large curved first lens 23, a light-impermeable plate 27, and a slightly convex first lens 23 arranged in order from the face plate 22 side of the cathode ray tube. A second lens 24 having a convex shape, a third lens 25 having a convex shape, and a fourth lens 26 disposed on the light exit side.

Here, the light partially opaque plate 27 has its optical axis and its vicinity formed by a light non-reflection / light non-transmission object 27-1, and its other parts formed by a light transmission body 27-2. I have. Further, between the first lens 23 and the face plate 22 of the cathode ray tube, the fluorescent screen 2 of the cathode ray tube is provided.
A liquid 29 is filled to efficiently dissipate the heat generated in 8.

The structural features of this embodiment are as follows.
The point is that the light partially opaque plate 27 is provided inside the projection lens. That is, in the present embodiment, the light partially opaque plate 2
7, the effective light rays emitted from the fluorescent screen 28 of the cathode ray tube and passing through the projection lens
By blocking a part of the effective light rays emitted from the central part 30 of the rear projector 8 and its vicinity, the brightness of the central part of the screen and its vicinity can be suppressed on a screen (not shown) in the rear projector unit.

Here, the effective light means the first to fourth lenses 22 out of the light emitted from the fluorescent screen 28 of the cathode ray tube when the light partially impermeable plate 27 is not provided.
26 through 26, and emitted from the exit surface of the fourth lens 26.

In FIG. 1, the space between the central part 30 of the fluorescent screen 28 and the outer peripheral part 35 of the fluorescent screen 28 is divided into five equal parts, and each of the dividing points is divided into a dividing point 31 and a dividing point 32 in order from the central part 30 side. ,
The division point 33 and the division point 34 are set. Further, among the effective light rays from the central portion 30, the division points 31, 32, 33, and 34, and the outer peripheral portion 35, the central ray is defined as 30-1, 31-1, and 32-.
1, 33-1, 34-1, 35-1, the upper limit ray is 30-
2,31-2,32-2,33-2,34-2,35-
2. Lower limit rays are 30-3, 31-3, 32-3, 33-
3, 34-3 and 35-3.

By arranging the light partially opaque plate 27 as shown in FIG. 1, the central ray 30-1 from the central portion 30 of the fluorescent screen 28 and the vicinity of the central ray 30-1 in the non-reflective / non-transparent object 27-1 Light beam, dividing point 3 of 20% from central part 30 of fluorescent screen 28
A part of the effective ray from 1 and a part of the effective ray from the 40% split point 32 are blocked. Therefore, on the screen of the rear projector unit, about 50% from the central portion of the screen and the peripheral portion toward the peripheral portion.
At the point (2), the luminance is lower than when the light partially impermeable plate 27 is not provided.

Therefore, as described in the prior art, for example, in the projection lens, the amount of light taken in the peripheral portion is smaller than the amount of light taken in in the central portion. Even if the luminance of the part is lower than the luminance of the central part, the luminance of the central part of the screen can be reduced by providing the partially opaque plate 27 in the projection lens, so that the luminance distribution of the screen is reduced. It can be uniform.

Accordingly, if a multi-projector is constructed by arranging a plurality of rear projector units each having such a projection lens and having a cathode-ray tube capable of providing a high-luminance screen, an image obtained by the multi-projector can be obtained. ,
A large screen with high image quality can be obtained without causing uneven brightness on the entire screen.

The degree of luminance reduction at the center of the screen on the screen of the rear projector unit is controlled by the position of the light partially opaque plate 27, the size of the light non-reflection / light non-transmission object, and the like. be able to.

Further, the light non-reflection / light non-transmission object 27-1 is formed on the lens surface of the first lens 23 or the second lens 24 without installing the light partially opaque plate 27 alone.
It may be used instead of the light partially opaque plate 27.
The same effect as when the light partially opaque plate 27 is provided can be sufficiently obtained, and in this case, the structure of the projection lens can be simplified.

FIG. 2 is an explanatory diagram for describing, as a reference example, a luminance distribution of a cathode ray tube suitable for a multi-projector, which is a premise of the present invention. That is, the cathode ray tube in the present reference example is used together with a projection lens and the like in a rear projector unit constituting a multi-projector.

The cathode ray tube according to this embodiment has a thin film made of a low-refractive-index material and a thin film made of a high-refractive-index material alternately laminated between the fluorescent surface 28 and the glass of the face plate 22 shown in FIG. The optical multi-layer film (not shown) having the above configuration has directivity.

For example, the luminance distribution 36 in the peripheral portion 35 of the fluorescent screen 28 is such that the luminance 36-1 in the range of about 20 degrees from the normal direction of the fluorescent screen 28 is lowered, and the luminance 36 in the range of about 20 degrees to about 70 degrees. The distribution has an increased luminance 36-2. In addition, the luminance becomes zero above about 70 degrees.

On the other hand, a substantially circular luminance distribution 37 indicated by a broken line
Is a luminance distribution in a normal CRT without directivity. The absolute values of the luminous flux of a normal CRT and the luminous flux of a directional CRT are basically substantially equal. That is, the area of the portion surrounded by the curve indicating the luminance distribution 36 and the area of the portion surrounded by the substantially circular curve indicating the luminance distribution 37 are basically substantially equal.

The effective rays 35-1, 35-2, 35 shown in FIG.
As can be seen from -3, in the peripheral portion 35 of the fluorescent screen 28, the effective rays 35-1, 35-2, 35-3 fall within a range of 20 to 70 degrees with respect to the normal to the fluorescent screen 28. Therefore,
In the present reference example, the luminance distribution in the peripheral portion 35 of the phosphor screen 28 is represented by the luminance distribution 36 shown in FIG.
The brightness in the range of up to 70 degrees is set to be large. By doing so, it is possible to increase the brightness of the peripheral portion of the screen on the screen of the rear projector unit.

Further, in the present embodiment, the luminance distribution in the central portion and the portion between the peripheral portions 35 of the fluorescent surface 28 as well as the luminance distribution 36 shown in FIG. The luminance in the range of 20 to 70 degrees is large,
The brightness in the range of degrees is reduced. By doing so, it is possible to reduce the luminance at the center of the screen on the screen of the rear projector unit.

Therefore, as described in the prior art, for example, in the projection lens, the amount of light taken in the peripheral portion is smaller than the amount of light taken in the central portion. Even if the luminance of the part is lower than the luminance of the central part, by using the cathode ray tube having the directivity as described above, it is possible to increase the luminance of the peripheral part of the screen and decrease the luminance of the central part, The luminance distribution on the screen can be made uniform.

Therefore, if a multi-projector is constructed by arranging a plurality of sets of rear projector units having such a cathode ray tube, an image obtained by the multi-projector
A large screen with high image quality can be obtained without causing uneven brightness on the entire screen.

As described above, when the brightness in the range of 20 to 70 degrees with respect to the normal line of the fluorescent screen 28 is increased, the brightness in the other range is inevitably reduced. Face 2
In the peripheral portion 35 of FIG.
Light rays emitted in directions other than the range of 0 to 70 degrees are not a problem because they do not become effective light rays necessary for displaying an image.

In the present embodiment, the luminance distribution at the central portion of the fluorescent screen 28 and the area between them is 20 to 20 with respect to the normal line of the fluorescent screen 28, similarly to the luminance section of the peripheral section 35.
Although the brightness distribution is increased in the range of 70 degrees, the brightness distribution of each part of the fluorescent screen 28 may be different.

When setting the range in which the luminance of each part should be increased (ie, setting the directional direction), the angular width should be limited as much as possible in accordance with the projection lens to be used, and the directivity should be increased accordingly. It is better to
For example, at the peripheral portion 35 of the fluorescent screen 28, the angular width of the effective light beam emitted from the peripheral portion 35 (that is, the angle between the upper limit light beam and the lower limit light beam) depends on the projection lens used. It is considered to be about 10 to 30 degrees. Therefore, it is advantageous to make the luminance distribution of the screen uniform by limiting the angle width at which the luminance should be increased to about 10 to 30 degrees and increasing the luminance at that angle.

[0093]

As described above, according to the present invention,
The following effects can be expected.

An object which does not reflect light and does not transmit light at a specific portion in the direction of the optical axis on the outer surface or inside of the projection lens constituting the projection optical system, and on the optical axis of the projection lens and its vicinity. Is arranged, a part of the effective light beams emitted from the central portion of the fluorescent screen of the cathode ray tube and the vicinity thereof can be blocked.

As a result, on the screen in the rear projector unit, the luminance at the center of the screen and the vicinity thereof can be suppressed, and the difference between the luminance at the center of the screen and the luminance at the periphery can be reduced. Therefore,
If a multi-projector is configured by arranging a plurality of sets of rear projector units using such a projection lens, it is possible to obtain a high-quality large screen without causing uneven brightness on the entire screen.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a section of a projection lens of a projection optical system for a multi-projector as one embodiment of the present invention.

FIG. 2 is an explanatory diagram for describing, as a reference example, a luminance distribution of a cathode ray tube suitable for a multi-projector as a premise of the present invention.

FIG. 3 is a side view showing a main part of the multi-projector as a premise of the present invention.

FIG. 4 is a front view schematically showing another example of the multi-projector as a premise of the present invention.

FIG. 5 is a side view showing a main part of still another example of the multi-projector as a premise of the present invention.

FIG. 6 is a cross-sectional view showing, as a reference example, a cross section of an example of a screen suitable for a multi-projector as a premise of the present invention.

FIG. 7 is a cross-sectional view showing, as a reference example, a cross-section of a main part of another screen suitable for a multi-projector as a premise of the present invention.

FIG. 8 is a cross-sectional view showing, as a reference example, a cross section of still another screen suitable for a multi-projector as a premise of the present invention.

FIG. 9 is a cross-sectional view showing, as a reference example, a cross section of a main portion of still another screen suitable for a multi-projector as a premise of the present invention.

FIG. 10 is a perspective view showing a main portion of a screen suitable for a multi-projector as a premise of the present invention, which is cut out and shown as a reference example.

FIG. 11 is a perspective view as a reference example in which a main part of a screen suitable for a multi-projector as a premise of the present invention is cut out and shown.

[Explanation of symbols]

1, 2, 3, 4, 5 ... rear projector unit, 1-
1, 1-2: Projection lens, 1-2, 2-2: CRT, 1-3, 2-3, 3-3, 4-3, 5-3: Optical path turning mirror, 1-4, 2-4 , 1-4 ', 2-4' ...
Screen, θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ ₅ ... mirror setting angle, α ₁ , α ₂ , α ₃ , α ₄ , α ₅ ... incident angle of projected light beam, 6 ... transparent reinforcing plate, 7- 1,7-2,7'-1,
7'-2, 7 "-1, 7" -2: screen plate, 9,
9 ', 9 ", 20, 21, 41-1, 41-2, 41-
3, 41-4 ... joint portion, 10, 14, 14 '... concave portion,
11, 15, 15 ', 19, 42, 42' ... partition plate,
12 ... frame, 16-1, 16-2, 38-1, 38
-2, 38-3: Front seat, 17-1, 17-
2, 39-1, 39-2, 39-3, 39-4: rear sheet, BS: black stripe, 18: lenticular lens, 22: face plate, 27: partially opaque plate, 27-1: non-reflective A light non-transmissive object, 28 a fluorescent screen;

Claims (4)

[Claims] 1. A projection optical system comprising: a projection lens composed of a plurality of single lenses; and a means for preventing reflection and transmission of light provided on an outer surface or inside of the projection lens. 2. The means for blocking reflection and transmission of light has a substantially circular shape, and has a configuration in which a central portion and a first portion in the vicinity thereof block reflection and transmission of light. 2. The projection optical system according to claim 1, wherein the second part around the first periphery is configured to be transparent. 3. In a multi-projector having a plurality of projection optical systems, each projection optical system includes a projection lens composed of a plurality of single lenses, and prevents reflection and transmission of light on the outer surface or inside of the projection lens. A multi-projector, comprising: 4. The means for blocking reflection and transmission of light has a substantially circular shape, and has a configuration in which a central portion and a first portion in the vicinity thereof block reflection and transmission of light. 4. The multi-projector according to claim 3, wherein the second portion around the first periphery is configured to be transparent. 5.