JPH09281616A - Video projecting device, adapter device therefor and optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video projecting device which is very compact, and is inexpensive and where a large video and a stereoscopic video having feeling of presence are easily enjoyed by a large number of people. SOLUTION: The video projecting device 1 is constituted of a liquid crystal video projector 10 and an adapter device 20 bisecting projected light from the liquid crystal video projector 10 and shifting the light in mutually orthogonal polarization directions so as to project it to be deviated on a screen 2. The adapter device 20 is constituted of an edge prism 21 having two sufaces (the surfaces of left and right side parts 21L and 21R) whose refractive directions in a horizontal direction are different so as to bisect the projected light from the liquid crystal video projector 10, a pair of hook-shaped attaching parts 22 integrally projectingly formed on both sides of the edge prism 21 and attached at the cylindrical part 15 of the liquid crystal video projector 10 so as to be freely attachable and detachable and a 1/2 wavelength plate 23 stuck to the half (the rear of the right side part 21R) of the rear of the edge prism 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projection device including a liquid crystal video projector, an adapter device for the device, and an optical member.

[0002]

2. Description of the Related Art For example, in order to obtain a pseudo three-dimensional effect, the applicant of the present invention has proposed an image projection apparatus which divides one projection light into two and shifts and projects them as one projection light on the other screen. , Japanese Patent Laid-Open No. 7-333557. A stereoscopic image pickup device capable of observing a stereoscopic image by using prism means (edge prism) is disclosed in JP-A-59-30390.

[0003]

However, in the above-mentioned conventional image projection apparatus, as means for embodying this,
Since an optical system including a plane mirror and a half mirror is used, the size of the entire apparatus may be increased, and assembly and adjustment may be complicated, resulting in an expensive problem.

Therefore, the present invention is very compact,
The present invention also provides an image projection apparatus, an adapter apparatus and an optical member for the apparatus, which are inexpensive and can easily enjoy realistic and large-scale images and stereoscopic images even with a large number of people.

[0005]

A single projection light from a projection means is separated by two separation means, projected on a single screen by shifting, and linearly polarized light of the two projection lights. In a video projector in which the directions are orthogonal to each other or the circular polarization directions are opposite to each other, the separating means for dividing the one projection light into two directions and projecting the projection light into the projection light of the projection means ( It is constituted by two types of edge prisms having different refraction directions in the horizontal direction so that the cross-sectional area of the projected light is approximately half.

For example, since the separating means is constituted by two edge prisms or a combination of the edge prism and the plane plate and the projection light is divided into two directions and projected (projected), the separating means is used. Since it can be molded integrally with a transparent resin or the like, a very compact and inexpensive product that does not require adjustment during manufacturing can be manufactured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[First Embodiment] FIGS. 1 to 8 show a video projection apparatus according to a first embodiment of the present invention. This video projection device 1 is capable of projecting the same image on the screen 2 while shifting the projection lights so that the polarization directions are orthogonal to each other. This image projection device 1 is, as shown in FIGS. 1, 2 and 5,
It is composed of a liquid crystal video projector 10 as a projecting means, and an adapter device 20 which divides the projection light from the liquid crystal video projector 10 into two and shifts them to the screen 2 in the polarization directions orthogonal to each other.

The liquid crystal video projector 10 includes a resin-made cabinet 11 having a light emitting lamp (halogen lamp) 12 as a light source, a reflecting mirror 12a, a first polarizing plate 13a, and a transmissive type from the rear surface side to the front surface side. A liquid crystal display (LCD) 14 and a second polarizing plate 13b are built in, respectively. Further, in the center of the front surface of the cabinet 11 of the housing, the cylindrical portion 1 having both a lens barrel and a focus ring is provided.
5 is projected, and the projection lens 16 is provided in the cylindrical portion 15.
have. Further, a speaker 17 is provided substantially in the center of the right side surface of the cabinet 11 and a ventilation hole 18 and various operation buttons 19 are provided on the upper surface thereof.
Then, light is generated from the light-emitting lamp 12 and the reflecting mirror 12a and passes through the two polarizing plates 13a and 13b and the liquid crystal display plate 14 sandwiched between them, so that the video signal here has a vertical linear polarization. It becomes the light you have and the projection lens 16
Is projected onto the screen 2. Here, the two polarizing plates 13a and 13b are arranged so that the polarization directions thereof are orthogonal to each other. This is because the liquid crystal display plate 14 is a so-called normally white (light passes when no electric field is applied, and a bright state is visually recognized. The liquid crystal display panel 14 is driven in normally black. Therefore, when the liquid crystal display panel 14 is driven in normally black, two polarizing plates 13a,
The polarization directions of 13b are arranged parallel to each other.

As shown in FIGS. 1 to 3, the adapter device 20 has a rhombic shape when viewed from above, and has a horizontal refraction direction so that the projection light from the liquid crystal video projector 10 is divided into two. 2 sides (left, right side 21
Edge prism (separating means) having L and 21R surfaces
21, a pair of hook-shaped mounting portions (mounting means) 22 integrally projectingly formed on both sides of the edge prism 4 and detachably mounted on the cylindrical portion 15 of the liquid crystal video projector 10, and the back surface of the edge prism 21. And a half-wave plate (polarizing means) 23 attached to the half surface (the back surface of the right side portion 21R). This edge prism 21
The pair of mounting portions 22 and 22 are integrally formed of so-called acrylic resin (polymethylmethacrylate).
The half-wave plate 23 is located on the right side 2 of the edge prism 21.
It is fixed to the back surface of 1R with an adhesive or the like.
When the light passes through the wave plate 23, the polarization direction of the light is 90 °.
It can be rotated (ie,
The linearly polarized directions of the projection light split into two by the edge prism 21 are orthogonal to each other).

Next, the optical system of the image projection apparatus 1 shown in FIG. 4 will be described. First, the light emitted by the light emitting lamp 12 in the cabinet 11 of the liquid crystal video projector 10 is reflected by the reflecting mirror 12a or not shown. The light is condensed by a lens and becomes parallel light, and the first polarizing plate 13a and the LCD
14 and the second polarizing plate 13b. Then, normally, the image on the LCD 14 is displayed on the screen 2 by the projection lens 16.
However, in the case of this video projection device 1, the left and right portions 21 of the edge prism 21 are formed.
It is divided into left and right by L and 21R. In addition, as shown in FIG. 4, the second polarizing plate 13b in the cabinet 11 is
Is a vertical linearly polarizing plate, the light emitted from the second polarizing plate 13b becomes vertical linearly polarized light, and the projection lens 16
Is projected on the screen 2.

Then, as shown in FIG. 4, the projection light projected from the projection lens 16 is divided into two by the left and right portions 21L and 21R of the edge prism 21. That is, the projection light incident on the half surface (left side portion 21L) of the edge prism 21 is projected with the optical axis being bent inward by the edge prism 21 while having the vertical linear polarization.
The right side 21R side of the edge prism 21 is 1 /
The polarization direction of the projection light is rotated 90 ° from the vertical direction to the horizontal direction by the two-wave plate 23, and then the optical axis is bent inward by the edge prism 21 and projected. Since the projection light is divided in half here, the image on the screen 2 seems to be in the right or left half.
This is just like when the half of the convex lens is hidden by hand when the candle is imaged on the screen 2 using the convex lens, the image on the screen is half the brightness but the entire image is also reflected here. The image formed by each half surface is half the brightness, but the entire image is visible.

It should be noted that the screen 2 is made of a material which does not scatter the projection light similar to that of the stereoscopic screen but reflects it in the same polarization direction. The half-wave plate 23 is made of a birefringent material such as crystal, retardation film, mica, TN liquid crystal, etc., and can rotate the polarization direction by 90 ° by aligning it with the polarization direction of the incident light. Is something that can be done. Further, D in FIG. 5 is a normal eye distance, and D≈65.
It is set to about mm.

The manner in which the projection light projected from the image projection apparatus 1 of the first embodiment forms an image on the screen 2 and what this looks like to the observer A will be described with reference to FIG. When viewing the image formed on the screen 2 with the liquid crystal video projector 10 of the image projection apparatus 1 facing the screen 2, as shown in FIG. An observer A who is looking at is wearing the polarizing glasses 50 with a horizontal linear polarization filter 51 in the left eye and a vertical linear polarization filter 52 in the right eye, and the image formation 7 is in the horizontal direction. The polarization and the image formation 8 are respectively polarized in the vertical direction.
Then, the horizontal linear polarization filter 5 of the polarizing glasses 50.
Only the virtual image of the image 7 is transmitted to the left eye through the polarizing glasses 50 through 1.
Only the virtual image of the image formation 8 is visible to the right eye through the vertical polarization filter 52 in the vertical direction. If the image formation deviation D between the images 7 and 8 is smaller than the width of the eye, the virtual image 9 is visible at the position of the apex of the triangle L'away from the eye.

That is, from the left side portion 4L of the edge prism 21, it is bent inward as projection light having a vertical polarization direction and is formed on the screen 2 as an image 8 shifted to the right. Further, from the right side portion 21R of the edge prism 21, it is bent inward as projection light having a lateral polarization direction, and is formed as an image 7 shifted to the left side on the screen 2. Here, since the screen 2 is made of a material that does not change or scatter the polarization direction when the image is reflected, for example, a material coated with silver, it reflects the image without changing the polarization direction. Since the observer A is wearing the polarized glasses 50 in FIG. 5, the image 8 is seen by the right eye and the image 7 is seen by the left eye, and the image is seen on the screen 2 at a position separated by D. Then, for the observer A, the position of the image is not far from the position of L where the screen 2 is, but at the position of L ′, farther back from the screen 2. This is because the deviation D is the observer A
However, when the deviation D becomes substantially the same as the pupil distance, the position of the image 9 becomes infinite for the observer A. By shifting this image, it is possible to obtain a pseudo three-dimensional effect. (In addition, according to the experiment, although the effect can be felt even when D is about 10 mm, the pupil distance (about 65 mm))
With a slight distance, a more three-dimensional effect can be felt, and even if the eyes are brought closer to the screen 2, there is no discomfort.

For example, as shown in FIG. 6, when a picture of a landscape K flowing laterally from a train window of a mountain railway in the Alps is photographed with the present video projector 1, as shown in FIG. Anyone can see the vast landscape of nature in the depths in three dimensions. Moreover, as shown in FIG.
Can see the whole screen even if the eyes are brought close to the screen 2. As shown in FIG. 8, this phenomenon is
When the hand is extended and the palm of the hand B is seen, the eyes become crossed eyes, and the palm of the hand B can be clearly seen, but the surrounding ones are blurred. On the contrary, if the lines of sight are parallel as in FIG. 7 (as if the lines of sight are parallel when just looking at a distant scene), a wide range can be seen.

In addition to the natural scenery K shown in FIG. 6, for example, in the software that takes a singer who sings around the stage,
You can get the feeling of being in the best seat near the stage. Also, when you watch a sumo program, you feel like you are wearing sand, and with software that captures tropical fish swimming with an underwater video camera, you feel exactly like you are in the sea.
Thus, the cylindrical portion 1 of the liquid crystal video projector 10
The image having the pseudo three-dimensional effect can be enjoyed easily and at low cost by a simple operation of simply attaching the adapter device 20 to the edge prism 21 through the pair of attaching portions 22, 22 integrally formed with the edge prism 21 (however, , This first
In the embodiment, the angle of deviation is uniquely determined by the edge prism 21, but this is not a problem when implementing it if the screen size is determined and recommended.).

[Second Embodiment] FIGS. 9 to 11 show a second embodiment.
2 shows an image projection device 1'of the embodiment example. This image projection device 1'is composed of a liquid crystal video projector 10 as a projection means and a lens cap type adapter device 20 '. This liquid crystal video projector 10
The configuration of is similar to that of the first embodiment, and the cylindrical portion 1
On the inner peripheral surface of 5, there is formed a screw portion (not shown) to which the adapter device 20 'is detachably screwed.

The adapter device 20 'includes an edge prism (separating means) 21', an inverted conical annular holder 24 incorporating the edge prism 21 ', and the edge prism 2'.
A half-wave plate (polarizing means) 23 attached to the surface of the left side portion 21L of 1 ', a horizontal linear polarizing plate 25L covering the half-wave plate 23, and a right side portion 2 of the edge prism 21'.
A vertical linear polarizing plate 25R covering 1R and a disc-shaped protective glass 26 fitted into the circular opening 24a on the front side of the holder 24 and covering the polarizing plates 25L and 25R are roughly configured. .

Half surface of the edge prism 21 '(left side portion 21
L) is formed in a plate shape having a uniform thickness, and the other half surface (right side portion 21R) is the center (side of the left side portion 21L).
It has the shape of a wedge-shaped prism that becomes thinner as it gets closer to. A ring 22 'is rotatably supported on the rear opening side of the holder 24. A threaded portion (mounting means) 22a is formed on the outer peripheral surface of the ring 22 '.
2a is a cylindrical portion 15 of the liquid crystal video projector 10
It can be freely screwed onto the threaded part of. Also, the holder 24
A knob 24b as a projection angle adjusting means is provided on the outer peripheral portion of the projection. Holding this knob 24b, ring 22 '
By turning the holder 24 against the holder 24
The angles (positions) of the edge prisms 21 'and the like housed inside can be freely determined.

FIG. 11 shows how the image projection apparatus 1'projects. The projection light that has entered the left side portion 21L of the edge prism 21 'proceeds straight because the left side portion 21L of the edge prism 21' is a flat plate, and the polarization direction is changed to 9 by the 1/2 wavelength plate 23.
It is changed by 0 ° and the polarization direction is adjusted by the polarizing plate 25L.
The right side 21R side of the edge prism 21 'is bent outward and projected. The polarization direction of this projection light is properly adjusted by the polarizing plate 25R. Of course, in this case, there is no functional problem even if the two polarizing plates 25L and 25R are not provided. Then, as in the case of the image projection device 1 of the first embodiment, if the screen 2 is viewed through the polarized glasses 50, a stereoscopic image can be enjoyed.

[Third Embodiment] FIG. 12 shows an image projection apparatus 1 ″ according to the third embodiment. This image projection apparatus 1 ″ is a liquid crystal video projector 1 as a projection means.
0 and a hood type adapter device 20 ″,
In each of the above-mentioned embodiments, the one in which the bending angle of the projection light by the edge prisms 21 and 21 'is constant can be adjusted. That is, the adapter device 20 ″ includes a separating means (optical member) 21 ″, a hood-type holder 24 ″ having the separating means 21 ″ built therein, and a half-wavelength affixed to the right front surface of the separating means 21 ″. The plate (polarizing means) 23, a pair of hooks 27, 27 provided on the upper and lower parts of the center of the front surface of the separating means 21 ″, and the pair of hooks 2
7 and 27 have a pair of protrusions 28a, 28a, and a pair of upper and lower pin portions 28b on the left front side in the holder 24 ″.
The arm 28 has a square frame shape and is swingably supported in the front-rear direction via 28b. Since the structure of the liquid crystal video projector 10 is the same as that of the first embodiment, detailed description thereof will be omitted.

As shown in FIGS. 13 and 14, the separating means 2
Reference numeral 1 ″ is an optical member in the form of an angle-variable triangular prism, which has the shape of an isosceles edge prism when viewed from above. That is, the separating means 21 ″ includes the left and right front faces 2
The three surfaces 1L ", 21R" and the back surface 21B "are made of transparent glass plates (transparent thin plates), and a flexible bellows portion 29 is provided between these surfaces. The glass plates 21L ", 21R", and 21B "are hermetically sealed, and colorless and transparent silicon oil (not shown) is sealed therein. If you hold each hook 27 and pull it toward you,
The left and right parts shrink, creating a more acute-angled isosceles triangle. Further, as shown in FIG. 13, the separating means 21 ″ is housed in a holder 24 ″, and the glass plate 21B ″ on the rear side is fixed in the holder 24 ″. Further, the arm 28, which is movable in the front-rear direction (swingable) through the pins 28b in the holder 24 ″, is a knob as a projection angle adjusting means slidable to the outside of the right side surface of the holder 24 ″. 28A moves back and forth. By moving the knob 28A back and forth, it is possible to change the acute angle of the separating means 21 ″ in the form of an edge prism. This angle determines the amount of misalignment between the left and right images on the screen 2. The amount of deviation D can be adjusted by 28A.

A ring 22 'is rotatably supported on the rear opening side of the holder 24 "as in the case of the second embodiment. A screw is attached to the outer peripheral surface of the ring 22'. Portion (attachment means) 22a is formed, and the screw portion 2
2a is a cylindrical portion 15 of the liquid crystal video projector 10
It can be freely screwed onto the threaded part of. Then, as in the case of the image projectors 1 and 1'of the first and second embodiments, the polarized glasses 5
If you see the screen 2 through 0, you can enjoy stereoscopic images.

[Fourth Embodiment] FIG. 15 shows a video projector 1A according to a fourth embodiment. This image projection device 1
A is a slide projector (which may be a projector such as a projector, a film projector, an overhead projector (OHP), a tube-type video projector, etc.) 10A and an adapter device 20A, which have non-polarized emitted light as a projection means. The slide film F is configured to be projected on the screen 2. FIG.
As shown in FIG. 16 and FIG. 16, the adapter device 20A includes an edge prism (separation means) 21A in the shape of an isosceles triangle.
And polarizing plates (polarizing means) 25L attached to the left and right front faces of the edge prism 21A and having orthogonal polarization directions,
25R and a pair of mounting plates (mounting means) 22A, 22A for detachably mounting the edge prism 21A to the slide projector 10A. Then, the projection light emitted from the slide projector 10A is
After being divided into two parts by the edge prism 21A, they are projected on a screen having polarization directions respectively.

In addition, according to each of the above-mentioned embodiments, the separating means composed of the edge prism of the isosceles triangle is used. However, the shape of the separating means is not limited to the isosceles triangle and the like, and FIG. The shape shown in FIG. 17D may be used. That is, FIG. 17A shows a V-shaped edge prism 21B, and the edge prism 21 shown in FIG.
C is one in which wedge-shaped prisms are arranged vertically, and FIG.
The edge prism 21D shown in FIG. 7 (C) is a prism and flat plates arranged in a checkered pattern, and the edge prism 21E shown in FIG. 17 (D) doubles as a concave lens. Although the half-wave plate and the polarizing plate are omitted, they may be appropriately attached by the projection means to be attached.

Although the two projection lights projected on the screen are linearly polarized lights which are orthogonal to each other, they may be circularly polarized lights whose rotation directions are opposite to each other. In the case of this circularly polarized light, there is an advantage that an observer wearing polarized glasses can lick his face (in the case of linearly polarized light, if the face is slanted, the polarization direction does not match),
It is known that the price of polarized glasses can be rather high. Further, although the two prisms or the flat plate have been described as being integrally molded, they may be separately manufactured and later combined. Furthermore, an adapter device as an optical block is attached to the projection lens of the existing projector, but it can be integrated from the beginning or can be configured to be put in and out of the optical path. Good.
Further, a quarter wavelength plate or the like may be used as the polarization means.

Further, in the third embodiment, the separating means (optical member) is formed in the shape of an isosceles triangle so that it can be moved from side to side. However, one side is a right-angled triangle type solid prism and only one side is used. The bellows may be adjusted so that the amount of deviation can be adjusted only on one side.

[0029]

As described above, according to the image projection apparatus of the present invention, since the edge prism is used as the separating means for separating the projection light from the projection means into two, the pseudo stereoscopic effect is compact and inexpensive. It is possible to provide a video projection device that can be enjoyed. In addition, a simple operation of simply attaching an edge prism to the projection means via an adapter device allows a realistic image or a stereoscopic image to be enjoyed at low cost. The projection means is not limited to the liquid crystal video projector, and a slide film projector or the like can be used, so that a versatile video projection device can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing a video projection device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which the liquid crystal projector and the adapter device of the video projection device of the first embodiment are separated.

FIG. 3 is an enlarged perspective view of an adapter device of the video projection device according to the first embodiment.

FIG. 4 is a perspective view of a main part of an optical system of the image projection device according to the first embodiment.

FIG. 5 is a plan view showing a usage state of the video projection device according to the first embodiment.

FIG. 6 is an explanatory view of a view of a car window.

FIG. 7 is an explanatory diagram in which a scene of the car window is pseudo-stereoscopically viewed by the image projection device according to the first embodiment.

FIG. 8 is an explanatory diagram of a phenomenon in the pseudo stereoscopic vision.

FIG. 9 is a perspective view showing a video projection device according to a second embodiment of the present invention.

FIG. 10 is an enlarged perspective view of an adapter device of the video projection device according to the second embodiment.

FIG. 11 is a perspective view of a main part of an optical system of the image projection device according to the second embodiment.

FIG. 12 is a perspective view showing a video projection device according to a third embodiment of the present invention.

FIG. 13 is a perspective view of an adapter device of the video projection device according to the third embodiment.

FIG. 14 is a perspective view of a main part of an adapter device of the video projection device according to the third embodiment.

FIG. 15 is a perspective view showing a video projection device according to a fourth embodiment of the present invention.

FIG. 16 is a perspective view of an adapter device of the video projecting device according to the fourth embodiment.

17 (A) to (D) are perspective views showing various modes of an optical system used in each of the adapter devices.

[Explanation of symbols]

1, 1 ', 1 ", 1A ... Image projection device, 2 ... Screen, 10, 10A ... Projection means, 20, 20', 20",
20A ... Adapter device, 21, 21 '... Separation means, 2
1 ″ ... Separation means (optical member), 22 ... Attachment means, 23 ...
Half-wave plate (polarizing means).

Claims (10)

[Claims] 1. A single projection light from the projection means is separated by two separation means and projected on one screen while being shifted, and the linear polarization directions of the two projection lights are orthogonal to each other. Or in a video projection device in which the directions of circular polarization are opposite to each other, the separating means for dividing the one projection light into two directions and projecting the one projection light is a schematic cross-sectional area of the projection light of the projection means. An image projecting device comprising two types of edge prisms having different horizontal refraction directions so as to be half as much as half. 2. The image projection apparatus according to claim 1, wherein a separating means for dividing the one projection light into two directions and projecting the projection light is provided with an edge prism in approximately half of a sectional area of the projection light of the projection means. The image projection apparatus is characterized in that the remaining approximately half of the cross-sectional area of the projection light is formed by a plane. 3. The image projection apparatus according to claim 1, wherein one polarized light is split into two, or immediately before splitting, one polarization direction is reversed. An image projection apparatus characterized in that the projection is performed in this manner. 4. The image projecting device according to claim 1, wherein one unpolarized projection light is split into two, or just before that, the polarized lights are opposite to each other. Characteristic video projection device. 5. The image projection apparatus according to claim 1, wherein the difference between the central thickness and the peripheral thickness is variable.
An image projection device, characterized in that it is configured so that the amount of displacement of two projection lights can be adjusted and changed. 6. The image projection apparatus according to claim 5, wherein the light entrance side and the light exit side are made of transparent plate-like materials, and the space between them is filled with a transparent liquid. Projection device. 7. The image projection device according to claim 1, wherein the edge prism is configured by using a part of a lens. 8. A single projection light from the projection means is separated by two separation means and projected on a single screen while being shifted, and the linear polarization directions of the two projection lights are orthogonal to each other. Or an adapter device for an image projection device in which the circular polarization directions are opposite to each other, and the horizontal refraction direction is adjusted so that the cross-sectional area of the projection light of the projection means is approximately half the half. Separation means configured to be composed of two different types of edge prisms and projecting the one projection light by dividing it into two directions, and the projection light divided into these two light rays have linear polarization directions orthogonal to each other, or An adapter device comprising at least polarizing means for making circular polarization directions opposite to each other and attachment means detachably attached to the projection means. 9. The adapter device according to claim 8, wherein an edge prism is inserted in approximately half of a cross-sectional area of the projection light of the projection means for the separation means that projects the one projection light in two directions. An adapter device, characterized in that the remaining approximately half of the cross-sectional area of the projection light is constituted by a plane. 10. One of the projection lights from the projection means is separated by two separation means and projected on one screen while being shifted, and the linear polarization directions of the two projection lights are orthogonal to each other. Or an angle-variable triangular prism-shaped optical member of an adapter device in which circular polarization directions are opposite to each other, the triangular prism shape having an approximately isosceles triangular shape when viewed from above, The three sides corresponding to the three sides of this triangle are composed of transparent thin plates, and the triangular portions of these upper and lower surfaces and the portions where the three sides meet are joined and sealed with a flexible material, and a transparent liquid is placed inside them. An optical member characterized in that the angle of the top of the isosceles triangle is made variable by arranging so as to be enclosed.