JPH03110536A - Display device - Google Patents

Abstract

PURPOSE:To prevent moire or a multiple images from occurring by constituting the device so that the non-effective parts of many prisms may be a surface which is nearly along the propagating direction of the main light beam of a luminous flux to the prism excepting a sheet out of the sheets which is the closest to a back surface side. CONSTITUTION:A screen 1 is constituted of two light transmissive sheets 11 and 12 having a Fresnel lens surface consisting of many prisms. The inclination of the non-effective surface 11b of the 1st Fresnel lens part 11b of the sheet 11 on the back surface side, that is, a luminous flux incident side and the inclination of the non-effective surface 12b of the 2nd Fresnel lens part 12b of the sheet 11 are set to be nearly along the propagating direction of the main light beam from a projecting lens out of the luminous fluxes made incident on the respective parts. Thus, a moire phenomenon between the cycle period structures of the prism groups on the plural Fresnel lens sheets 11 and 12 is suppressed to the utmost even when the distribution of power is performed by using the respective sheets 11 and 12. Then, a bright and excellent projected image is observed all over the screen.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a display device, and particularly to a video display device in which an image formed by being projected at an angle by a projection means is observed from a space on the opposite side of the projection means. The present invention relates to a display device suitable for use in a projection device such as a projector.

(Prior Art) Conventionally, in a projection device such as a video projector, an image from a projection means is formed on a screen, and this projected image is observed from the projection side, that is, the space opposite to the rear side. Projection screens are widely used.

FIG. 3(a) schematically shows an example of a projection system using a conventional rear projection screen.

In the figure, 31 is a transmission type screen having a Fresnel lens, 33 is a CRT, and 34 is a projection lens.

For example, the screen 31 has a diagonal length of 50 inches (1100 m
m x 600 mm), and here the projection lens 3
4 is formed. FIG. 3(b) shows an example of a rear projection type display device in which this projection system is housed in a cabinet. 35 and 36 are mirrors, and 37 is a cabinet.

In Figure 3(a), 130 mm from CRT33
.

From screen 31! The angle of incidence of the light beam entering the screen 31 from the pupil center of the projection lens 34 located at a distance of 500 mm to the diagonally most peripheral part of the screen 31 is approximately 23 degrees, and the light beam that has passed through the screen 31 is on the screen 31. With the Fresnel lens, screen 3
It is set so that the light is focused at a distance approximately eight times the height (600 mm) of 1.

As an example of the screen 31 shown in FIGS. 3(a) and 3(b), there is a screen 31 shown in FIGS. 4(a) and 4(b), sectional views of the center thereof. The screen 41 in FIG. 4(a) has a Fresnel lens surface 41a on the light incident side and a lenticular lens surface on the exit side. This screen 4
FIG. 5(a) shows the optical path of a light beam that enters the most peripheral portion of the projection lens 34 at an angle of 23 degrees with respect to the optical axis (indicated by the chain line in FIG. 3(a)) of the projection lens 34. Here screen 4
The refractive index of the material 1 is 1°5, and the exit side of the screen 41 is shown as a plane. In the lower part of the figure, the advancing angle α (the angle with respect to the optical axis of the projection lens 34, that is, the horizontal direction) of the light beam before and after passing through each surface is shown.

If the cross-sectional shape of the arc-shaped prism forming the periphery of the Fresnel lens surface 41a is as shown in FIG. The transmittance at this time is 88%. The angle of incidence on the exit surface is 15 degrees (minus when measured clockwise from the optical axis), and the transmittance at the exit surface is 96%.

Further, the light beam incident on the non-effective surface 41d of the Fresnel lens surface 41a becomes a loss, and the loss ratio Q of the lost light to the amount of incident light is expressed as Q=tan a 11 tan θ. In the example of FIG. 5(a), Q is approximately 38%.

From this, in the case of a vertical incidence projection system using the screen 41 shown in FIG. 4(a, ), the screen 4
The transmittance T1 at the most peripheral part of 1 is TI = 0.88X (
1-0, 38) Xo, 96X100=52(%), resulting in a decrease in light amount of about 43% compared to the transmittance of 92% at the center of the screen.

On the other hand, the screen 42 shown in FIG. 4(b) is provided to prevent the amount of light from decreasing in the peripheral area. In the same figure,
Reference numeral 43 denotes a translucent sheet with a flat surface on the incident side, that is, the rear side, and a Fresnel lens surface 43a on the exit side, that is, the viewing side. Numeral 44 denotes a translucent sheet with a flat surface on the incident side and a lenticular lens surface 44a on the exit side.

FIG. 5(b) shows the optical path of the light beam incident on the outermost periphery of the sheet 43 under the same conditions as FIG. 5(a). If the cross-sectional shape of the prism forming the peripheral part of the Fresnel lens circle 43a is as shown in the figure, the light beam indicated by ■ will be transmitted to the Fresnel lens surface 43 without being lost at the ineffective surface 43b.
In this case, the loss is only due to surface reflection. Therefore, the transmittance at the outermost periphery is approximately 90%, which is approximately equal to that at the center of the screen 42.

The above description relates to a vertical incidence projection system in which the optical axis of the projection lens 34 perpendicularly intersects at the center of the screen surface. On the other hand, in order to reduce the size of the entire system (in particular, to reduce the depth), the image from the CRT 33a is projected at an angle onto the screen 31a via the projection lens 34a, as shown by the broken line in FIG. 3(a). It is desired to realize a projection system of an oblique incidence type in which the optical axis of the projection lens obliquely intersects the screen surface.

This type of rear projection display device is constructed as shown in FIG. 3(C). In the figure, 35a.

36a is a mirror, 37a is a cabinet, and CRT
The image displayed on the tube surface of 33a is projected diagonally onto the screen 31a from the upper right. In addition, in Figure 3 (C),
Although the direction of image projection is different from the system indicated by the broken line in FIG. 3(a), they are optically equivalent.

With this configuration, compared to the vertical incidence method,
It becomes possible to reduce the depth of the cabinet 37a.

[Problem that the invention seeks to solve]

However, in the case of the configuration shown in FIG. 3(C), the projected image light emitted from the screen 31a to the left observation side comes out downward by an angle θ0 from the horizontal direction, so the screen 31a
For an observer observing from the front of a, the image becomes dark. Therefore, it is necessary to construct a screen having an eccentric Fresnel lens as shown in FIG. 3(d), so that the projected image light can be emitted horizontally from the screen 31a.

However, in the oblique incidence method, the angle of incidence of the light beam incident on the outermost periphery of the screen 31a (particularly the lower periphery in FIG. 3(C)) may reach as much as 45 degrees. In this case, even if the screen 42 shown in FIG. 4(b), which worked well in the vertical incidence system, is used, the second surface of the screen 42 at the outermost periphery (particularly the lower part) (i.e., the screen shown in FIG.
Since the angle of incidence of the light beam on the Fresnel lens surface 43a) in b) reaches near the angle of total reflection or exceeds the angle of total reflection,
The amount of ambient light suddenly decreases. In particular, when a color image projector is configured with three red, green, and blue CRTs arranged side by side, the angle of incidence on the screen differs for each color, and a color shift occurs. This increase further amplifies the color shift.

As a means to solve this problem, for example, as shown in FIG.
It is conceivable to use a surface to disperse the power so that even if the incident angle of the light beam to the screen periphery increases, the amount of peripheral light does not drop suddenly. However, with this configuration, moiré and multiple images may occur due to the repeating periodic structure of the plurality of prism groups, which may impede observation of the projected image.

In solving the above problems, it is necessary to consider the following points.

Projection lens 3 of the projector shown in FIG. 3(a)
4 (34a) has a finite pupil diameter. Therefore, the angle of incidence of the light beam incident on a certain point on the screen has a finite spread around the principal ray.

Furthermore, in a configuration in which three projection lenses for red, green, and blue are arranged side by side, each lens has a finite pupil diameter, so the range of incident angles is further expanded.

An object of the present invention is to provide a display device that does not generate moiré or multiple images and can obtain high-resolution images even though it uses a plurality of Fresnel lens surfaces on which a large number of prisms are formed. .

[Means for solving problems]

In order to achieve the above-mentioned object, in the display device of the embodiment described later of the present invention, a plurality of sheets are arranged facing each other, and at least two of these sheets are provided with an observation screen for each sheet. A large number of prisms extending linearly or curved on the side are formed, and further, except for at most one sheet closest to the back side of the at least two sheets, the ineffective portions of the large number of prisms are formed into prisms. The plane is configured to be a plane substantially along the traveling direction of the principal ray of the luminous flux. Here, the principal ray in this specification refers to a ray passing through the center of the pupil of the projection lens.

Here, the surface that roughly parallels the direction in which the principal ray of the luminous flux travels after being refracted at the back surface (incidence surface) of the corresponding sheet, and further refracted at the observation side surface (output surface). The plane should lie within the angle range formed by the two directions with respect to the direction of backward movement.

Furthermore, in a projector, as mentioned above, since the projection lens has a finite pupil diameter, the angle of incidence of the light beam spreads even when viewed at one point on the sheet.

Taking this into consideration, as a more preferable condition for achieving the above purpose, the direction in which the principal ray of the luminous flux travels after being refracted at the back surface (incident surface) of the corresponding sheet, and The ineffective portion can be configured to lie along approximately the middle value of the angular range formed by the two directions with respect to the traveling direction of the principal ray of the luminous flux after being refracted at (the exit surface). Furthermore, in a device having multiple projection lenses, it is sufficient to consider the traveling direction of the principal ray of each pupil and align the surface of the ineffective portion with the average traveling direction of the chief ray of the emitted light flux from each lens. .

[Effect]

In a display device configured as described above, power is dispersed by multiple prism-forming surfaces, so even for light beams that have a large incident angle on the screen surface, it is possible to keep the incident angle relatively small on each prism-forming surface. Therefore, reflection loss on each surface is reduced.

At the same time, with the exception of at most one sheet closest to the projection means, the ineffective portion of the prism forming surface is a surface substantially along the traveling direction of the light beam to each part of the prism forming surface. The unfavorable influence of the repeating periodic structure of the prism group due to vignetting occurs only from at most one sheet, and moiré phenomena and the like hardly occur between a plurality of repeating periodic structures.

FIG. 1(a) shows a schematic structure of main parts when a first embodiment of the display device of the present invention is applied to an oblique incidence type projection system. In the figure, ■ is a screen, and 3 is a CRT, on which a projected image is formed. 4 is a projection lens, the optical axis S of which is inclined by 30 degrees with respect to the horizontal direction. The CRT 3 and the projection lens 4 are elements of a projection means. In the same figure,
Numerical values such as 600 represent dimensions or distances (unit: m)
m).

FIG. 1(b) shows an implementation of a rear projection type display device in which the system of FIG. 1(a) is housed in a cabinet, where 5 and 6 are mirrors and 7 is a cabinet.

FIG. 2(a) is an enlarged view of a part of the screen 1 shown in FIGS. 1(a) and (b), and the peripheral area of the screen (particularly,
The principal rays of the incident light flux are shown in the upper part of FIG. 1(a) and the lower part of FIG. 1(b). At the bottom of the figure, the advancing angle α of the principal ray of the incident light beam on each surface with respect to the horizontal direction is shown. In this embodiment, the screen 1 consists of two translucent sheets (also called Fresnel lenses) 11 and 12 having Fresnel lens surfaces made of a large number of prisms, and the material is made of a material with a refractive index of 1.
．． 5 or so, such as methacrylic resin. The sheet 11 on the back side, that is, on the light flux incident side, has a first surface +1a on the incident side.
is a plane, and the lower part of the observation side, that is, the second surface 11b of the exit surface in FIG. 1(b) has the illustrated inclination angle θ11 + θ1
The first Fresnel lens surface is formed with a large number of prisms each having a shape of . The effective portion 11c of the first Fresnel lens surface has a focal length f1 and a concentric circular shape centered at point la in FIG. In the case of Figure 1(b),
The center of this concentric circle shape is located above the screen I.

The observation side sheet 12 has a first surface 12a on the incident side that is flat, and a second surface 12b on the observation side that has a shape different from the first Fresnel lens surface 11b (inclination angle θ21 +θ22).
) is the second Fresnel lens surface on which a prism is formed. The effective portion 12c of the second Fresnel lens surface has a focal length f2 and a concentric circular shape centered at point 1a in FIG. 4.

By the screen 1 having this configuration, the light beam from the projected image is refracted, and the point 1b (screen 1
The beam moves forward so that the light is focused at a distance approximately 8 times the height of the screen (at a distance from the screen). At this time, as shown in FIG. 2(a), the angle of incidence of the luminous flux incident on the most peripheral part of the screen l (lower part in FIG. 1(b)) on the first surface 11a of the sheet 11 is 45 degrees. The transmittance is approximately 95%, and the incident angle of the second surface 11b to the effective surface 11c is 27 degrees, and the transmittance is approximately 95%. Further, the angle of incidence on the first surface 12a of the sheet 12 is 12 degrees and the transmittance is approximately 96%, and the angle of incidence on the effective surface 11c of the first surface 12a is 26.5 degrees and the transmittance is approximately 95%. . In this way, the light beam is emitted from the second surface 12b of the lens 12 at an advancing angle of -7.5 degrees. Therefore, in this example, the transmittance T2 at the most peripheral part of the screen l is T2=0.95 Xo, 95 Xo, 96 Xo, 9
5×100=82(%).

Therefore, for a transmittance of 85% at the center of the screen I, 82/85=0.97, which means that there is almost no decrease in the amount of light at the periphery of the screen (the lower part of FIG. 1(b)).

Furthermore, in this embodiment, the inclination of the ineffective surface lid of the first Fresnel lens part itb of the sheet 11 and the inclination of the ineffective surface 12d of the second Fresnel lens part 12b of the sheet 11 are used to determine the projection of the light flux incident on each part. It is constructed so as to follow the traveling direction of the chief ray from the lens. That is, in the part shown in FIG. 2(a) of this embodiment, considering only the chief ray from the projection lens, the condition (ineffective part permissible angle range) in which no vignetting occurs at the ineffective surface lid is θ, 2 is 62 degrees (9O-28= since it is parallel to the incident ray to the effective surface 11c)
62) or more, 78 degrees (43+(90-55(θo)) since it is parallel to the emitted ray from the effective surface 11c
= 78), and the conditions under which vignetting does not occur on the non-effective surface 12d are θ4 of 82 degrees or more (9O-8 = 82 since it is parallel to the incident light beam on the effective surface 12c) and 97. 5 degrees (42+ (90-34,5(θz+)=97.
5), so θ, 2= in Figure 5(a)
70 degrees and θ2□=90 degrees satisfy this condition.

In the above explanation, the case where the light beam travels from only one direction to a certain point on the screen has been shown, but in an actual projector, as shown in FIG. 3(a), the projection lens 34 of the projector (34a) has a finite pupil diameter. Therefore, the angle of incidence of the light beam incident on a certain point on the screen has a finite spread around the principal ray. To deal with this, the tolerance range for the orientation of the ineffective portion of the Fresnel lens described above is used. Figure 1(c) shows that the principal ray from the projection lens is 30 degrees from the center of the screen.
This figure shows the optical arrangement of a 30' oblique incidence projection device that enters the image at an angle of .degree., and projects an image from a CRT 33a onto a screen 31a via a projection lens 34a.

Here, the distance between the center of the screen and the tip of the lens is 1500.
m m , the focal length of the projection lens is 130 mm, and the F value (at infinity) of the lens is 1.0, then the effective pupil diameter of this projection system is approximately 120 mm. At this time, the angle Δθ from the center of the screen to the lens pupil diameter is about 5 degrees. At the lower end of the screen 31a, the angle is approximately 5 degrees, considering that the distance between the screen lenses is smaller and the apparent lens pupil diameter is smaller than at the center of the screen. On the other hand, at the upper end of the screen 31a, the screen is lower than the center of the screen.
Since the distance between the lenses is wide (and the apparent lens pupil diameter is small), the angle is less than 5 degrees.

If the angle change of the ineffective part is set to approximately the middle value of the allowable angular range of the ineffective part with respect to the principal ray of the incident light beam with a finite divergence angle, then the divergence angle of the projection lens will be within the allowable angular range of the ineffective part with respect to the principal ray. If it is smaller, the angle of the ineffective portion will be within the permissible range for all possible angles of incidence of the light beam incident on a certain point from the projection lens. Therefore, theoretically, the light from the projection lens does not enter the ineffective area at all, and vignetting does not occur. Even if the divergence angle of the projection lens is somewhat larger than the permissible angle range of the non-effective part, by setting the angle of the non-effective part to approximately the middle value of the permissible angular range of the non-effective part, the light flux incident on a certain point from the projection lens can be reduced. Compared to the incident angle near the center where the light intensity is high, the angle of the ineffective part is within the permissible range. It is possible to reduce vignetting and effectively transmit the light.In this way, it is possible to reduce the incidence of the incident light beam into the ineffective part of the Fresnel lens to zero or to a minimum.The divergence angle is smaller than the above-mentioned allowable angle range. In this case, the direction of the ineffective portion can be freely set within a range that does not cause vignetting of the light beam.

In this embodiment, θ1□=700 for the permissible angle range of the ineffective part of the Fresnel lens 11 (62° or more and 78° or less), and the permissible ineffective part angle range of the Fresnel lens 12 (82° or more and 97°
．． 5° or less), the above configuration is achieved by setting θ2□=906.

In this way, the ineffective portions 11d of both sheets If, 12.

There is almost no vignetting of the light beam in 12d, and almost no moiré phenomenon occurs between the periodic structures.

The permissible range for the direction of the ineffective part of the Fresnel lens shown in the example depends on the difference in the angle of incidence and exit (deflection angle) of the light ray on the effective surface of the Fresnel lens, so even on the screen it has a larger deflection angle. As the position increases, the allowable range of the ineffective portion increases. This shows that the present invention is particularly effective in oblique incidence optical systems in which the incident angle and deflection angle of the light beam onto the screen are larger.

As a modification of this embodiment, if one CRT 33 is provided for each color of R, G, and B, and a projection lens is also provided for each CRT, that is, if a plurality of projection lenses are provided, Since each lens has a finite pupil diameter, consider the traveling direction of the principal ray of each pupil diameter, and calculate the permissible angle range of the ineffective part for the ray whose incident angle is the average value of the angles of the multiple traveling directions. The surface of the ineffective part should be aligned with the angle approximately in the middle of .

FIG. 2(b) shows a partially enlarged view of the screen of the second embodiment of the display device of the present invention and the chief ray of the incident light beam at the periphery of the screen. In the embodiment shown in FIG. 2(b), FIG.
2 having a Fresnel lens surface similar to the embodiment shown in a)
In this embodiment, the second Fresnel lens portion 12b of the sheet 12' is
Only the inclination of the ineffective surface 12d' of ' is configured to be substantially along the traveling direction of the principal ray of the light beam incident on each part.

In this case, among the light fluxes a corresponding to the unit period of the periodic structure of the first Fresnel lens, the light flux a2 incident on the ineffective portion 11b' travels in an abnormal direction. Therefore, the remaining normal light flux a1 after subtracting a2 from the light flux a is emitted from the first Fresnel lens 11'. Here, the normal light flux a has a periodic structure with a period equal to that of the concavo-convex structure of the first Fresnel lens, and when viewed from the second Fresnel lens 12' side, the amount of light decreases by the amount of the abnormal light.

Here, α is the advancing angle of the chief ray of the luminous flux a with respect to the horizontal direction. The second Fresnel lens 12' has an approximately intermediate value (
The angle of the ineffective part is set to 90°). Therefore, as is clear from the above description, vignetting of the light beam from the projection lens having a finite pupil diameter due to the ineffective portion of the second Fresnel lens 12' can be suppressed to zero or to a minimum.

The first Fresnel lens 11' imparts minute alternating bright and dark stripes (periodic structure) corresponding to the concavo-convex structure of the lens to an incident light beam having a substantially --like cross-sectional light intensity, and causes the light to exit to the output side. Here, the intensity amplitude of the periodic structure is generated accompanied by energy loss. In the second Fresnel lens 12', when the incident light is vignetted by the ineffective part, the vignetting in the second Fresnel lens is caused by how the bright part of the stripe of the light beam from the first Fresnel lens overlaps with the ineffective part. The amount of light changes.

Therefore, due to the relationship between the uneven structure of the first Fresnel lens and the second Fresnel lens (periodic unevenness due to period (pitch) difference, manufacturing error, etc. in the case of the same period), large bright and dark areas, that is, moiré, occur on the screen. Resulting in.

In contrast, in this embodiment, as described above, the vignetting due to the ineffective portion of the Fresnel lens 12' is minimized to zero, so no or almost no moiré occurs.

As will be understood from this, the conditions under which moiré does not occur are as follows: excluding the effecting body (here, the first Fresnel lens) that initially imparts periodicity to the acted upon body (here, the luminous flux), and Regarding the effector (here, the second Fresnel lens), there is no or almost no abnormal effect (here, light flux eclipse due to the ineffective area of the second Fresnel lens).

In this embodiment, as described above, in the case where there is a plurality of projection lenses, the allowable angle of the ineffective portion for the light ray whose incident angle is the average value of the angles in the traveling direction of the principal ray from each lens. All you have to do is align the surface of the ineffective part to an angle that is approximately in the middle of the range.

FIG. 2(C) shows an embodiment in which three Fresnel lenses are provided.

In FIG. 2(C), three translucent sheets 14. A Fresnel lens surface is formed on the exit side of 15.degree. Also, in this embodiment, it is possible to make the ineffective surface of the Fresnel lens surface approximately parallel to the intermediate direction of the principal ray of the incident light beam within the lens and the direction of movement after exiting the lens. Sheet 14 of
All you need to do is to apply it to the second and subsequent sheets except for .

The above conditions only relate to the shape of the prism on the Fresnel lens surface, and are not related to the pitch ratio, etc. Also, this moiré suppression method is much more effective than methods such as increasing the distance between the Fresnel lens surfaces. In addition to being effective, it is also excellent in terms of reducing the distance between the Fresnel lens surfaces, suppressing a decrease in resolution, reducing the weight of the screen by reducing its thickness, and simplifying the screen holding mechanism.

As still another embodiment, in FIG. 2(d), the screen of the sheet 19 closest to the viewing side of the screen is a lenticular lens surface having a light diffusion function, and the remaining sheet 19
1.12 is the same as the Fresnel lens of the first embodiment. The second view of this embodiment as seen from above in Figure 1(b) is
It is shown in figure (e).

The double lenticular sea) 19 has a black stripe 19a, which widens the left and right viewing angles and prevents color shift and reflection of external light caused by the arrangement of three CRTs for color images, resulting in better images. and visual field characteristics are obtained. Other points are the same as the embodiment shown in FIG. 2(a).

In FIG. 2(f), the sheets 11 and 12 are similar to those in the first embodiment, and a light diffusing surface having functions such as viewing angle control is formed on the incident side of the sheet 23. The other points are the same as the embodiment shown in FIG. 2(e).

In the embodiment shown above, a plurality of sheets with concentric eccentric circular Fresnel lens surfaces are formed, but it is also possible to combine linear Fresnel lenses, non-powered Fresnel lenses, etc. It is not always necessary to do so.

Further, although it is preferable that the incident side of each sheet be flat as in the above embodiment, this is not essential either.

〔Effect of the invention〕

Since the present invention has the above-described configuration, even if power is distributed using a plurality of Fresnel lens sheets, the moiré phenomenon between the repeating periodic structures of the prism groups on each sheet is suppressed as much as possible, and the entire surface of the screen is covered. It is possible to provide a rear projection screen of an oblique incidence type that allows a bright and good projection image to be observed, and a rear projection display device using the same. Further, if the Fresnel lens surface on at least one sheet is made such that the centers of a large number of concentric prisms are decentered from the center of the screen, the projected image becomes even brighter over the entire surface.

[Brief explanation of drawings]

FIG. 1(a) is a schematic diagram of the main parts when an embodiment of the present invention is applied to an oblique incidence projection system, FIG. 1(b) is a schematic diagram of the overall configuration, and FIG. 1(c) is An explanatory diagram of the same projection lens, FIG. 2(a) is a partial enlarged view of the screen of the embodiment of FIG. 41(a), FIGS. 2(b) to (f) are diagrams showing other embodiments, and FIG. Figure (a) is a schematic diagram of a conventional projection system;
Figure 3(b) is a diagram showing a conventional rear projection type display device corresponding to Figure 3(a), and Figure 3(c) is a diagram showing a conventional oblique incidence type rear projection type display device. (d), (e)
is a diagram showing a conventional decentered Fresnel lens, Fig. 4(a),
5(b) is a diagram showing a conventional rear projection type screen, and FIGS. 5(a) and 5(b) are diagrams illustrating the optical path of an incident light beam on a conventional Fresnel lens surface. l... Screen, 3... CRT, 4... Projection lens, 5゜6... Mirror, 11.
12. 14. 15. 16. 19.
23... Sheet, llb, 12b, llb', 12b
'...Fresnel lens surface, llc, 12c, llc'
, 12c effective part, lld, 12d, lid', 1
2d'...Ineffective part. Tomi 2 Father (e,) 悌 2 Map (-41-) 13 Ward (Shi) % 3 Map (C) Shi-L- Prefecture 3 Map (e) 7 3 Ia

Claims (2)

[Claims] (1) A projection means for projecting an image, which has a projection optical system with a finite pupil diameter, and is arranged at a position where an approximate image is projected by the projection means, and is placed on a surface opposite to the projection means. At least two sheets each forming a large number of prisms extending linearly or curved and having an effective part for emitting the light beam from the projection means in a predetermined direction and an ineffective part that does not contribute to emitting the light in the predetermined direction. and a screen means having an ineffective portion of the plurality of sheets other than the sheet closest to the projection means,
The luminous flux from the projection means is formed to form an angle approximately intermediate between the angle of the chief ray when traveling within the sheet and the exit angle of the chief ray when exiting from the effective surface of the prism of the sheet. A display device characterized by: (2) each has a projection optical system with a finite pupil diameter;
a plurality of projection means for projecting an image; and a plurality of projection means disposed at a position where an approximate image is projected by the projection means, and for emitting a light beam from the projection means in a predetermined direction to a surface opposite to the projection means. a screen means having at least two sheets each forming a large number of prisms extending linearly or curved, each having an effective part and an ineffective part that does not contribute to emission in the predetermined direction; The non-effective portion of one or more sheets other than the sheet closest to the projection means is the average value of the angle of the chief ray when each light beam from the plurality of projection means travels within the sheet. and the average value of the emission angle of the principal ray when emitted from the effective surface of the prism of the sheet.