JP2008191172A - Wide incident angle range adaptive lens sheet and rear projection display screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide incident angle range adaptive lens sheet capable of theoretically dealing with projection light from the vicinity of 0 degrees of an incident angle to 90 degrees of an incident angle, and to provide a wide incident angle range adaptive screen capable of displaying high quality images by using it. <P>SOLUTION: Each track refracts the projection light received on an incident face to transmit or refract the projection light received on a refraction type condensing part and the incident face, and next, reflects on the whole reflection face to be composed of composite lenses of an entire reflection type condensing part which includes that a volume ratio of any one is 0%, and that of the other is 100%. The volume ratio of the entire reflection type condensing part of the composite lenses increases as the incident angle of the projection light projected to the composite lenses enlarges, and after it is 100%, the volume ratio is constant in the wide incident angle range adaptive lens sheet. The wide incident angle range adaptive screen using it is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wide incident angle range compatible lens sheet and a screen for a rear projection display using the same.

  As the demand for rear projection displays increases, there is a demand for higher quality display images. In order to cope with a particularly thin and large screen, it is necessary to project projection light from an optical engine at a wide incident angle on the back side of the screen. Therefore, a rear projection display screen (hereinafter also simply referred to as a screen) that has a high-performance optical engine and has a large light deflection function has been proposed.

  For example, screens that require a Fresnel lens that performs the same function as a convex lens and a lenticular lens have been developed (Patent Documents 1 and 2 and Non-Patent Document 1). FIG. 5 shows a rear projection display including such a screen, an optical engine PJ that can display an image on the screen, an aspherical mirror M1, and a flat reflector M2. FIG. 5A shows a state where the screen 1 is viewed from the back side, and FIG. 5B shows the inside of the rear projection display. L indicates an optical path of projection light for displaying an image on the screen 1. Note that in the case of a screen that supports thin and large screens, for example, projection light having an incident angle of 60 degrees or more is substantially perpendicular to the exit surface with respect to the Fresnel lens formed on the outermost track on the back side. A large light deflection function for emitting light in the direction is required.

  As shown in FIG. 6, the screen 1 requiring a lenticular lens has a Fresnel lens sheet 10 having a large light deflecting function and a light condensing function in which unit lenses are arranged with a periodic structure in the horizontal direction on the incident surface side. The lenticular lens 11 and the diffusion plate 12 having scattering characteristics are provided. BM is a black mask layer formed on the exit surface of the lenticular lens sheet 11.

However, as shown in FIG. 7, the Fresnel lens sheet 10 is provided with a hybrid Fresnel lens 10A on the back surface thereof, and the light emitted from the exit surface becomes parallel. For this reason, the lenticular lens 11 having a condensing function, the black mask layer BM and the diffusion plate 12 for measures against external light are essential. Further, the Fresnel lens sheet 10 cannot deflect the light LA _{in the} shaded area shown in FIG. 6 in the normal direction of the screen, and stray light is generated. Therefore, there is a problem that the use efficiency of light is poor and high-quality image display cannot be performed due to a decrease in resolution or the like.

  Therefore, the present inventors have proposed a screen that eliminates the need for a lenticular lens (Patent Document 3). The characteristics of the screen described in Patent Document 3 will be described with reference to FIG. This screen 1 has a function of deflecting large light that is projected from the optical engine PJ in a predetermined incident angle region and received by the incident surface 5 and then deflected and emitted from the exit surface according to the incident angle region. It comprises a deflecting element having a condensing function, and a diffusion plate 3 for diffusing light emitted from its exit surface into a predetermined angle region.

  The deflecting element transmits or refracts the projection light at the incident surface 5 and then reflects off the total reflection surface 6 to collect all the light on the condensing region. Thus, all the tracks are formed. . In FIG. 4, n indicates the exit surface normal direction. The black mask layer BM is formed on the exit surface of the lens sheet and has a function of preventing external light incident from the screen surface from becoming stray light. Hereinafter, this is referred to as a total reflection type lens sheet 30. According to the screen using the total reflection type lens sheet 30, high quality and a bright place contrast ratio can be improved by suppressing the diffuse reflection of external light to the viewer side.

If a lens sheet for a wide incident angle range capable of displaying a high-quality display image corresponding to projection light with a wide incident angle range with an incident angle θ of 0 to 90 degrees can be realized, a thinner and larger screen can be realized. There is also an advantage that the height of the portion called the ridge at the bottom of the screen can be lowered.
Special table 2002-027399 gazette JP2003-114481 Japanese Patent Application 2005-148265 Shikama, S. et al. SID02 DIGEST (May 22-23, Mass. Boston) p.1250-1253

However, when all tracks are configured with only the total reflection type condensing unit, the main function of the total reflection type condensing unit is a light deflection function (prism Therefore, there is a problem that it is difficult to solve the problem that the incident angle θ cannot correspond to the projection light having an angle of 50 degrees or less. In FIG. 4, LA _in indicates the optical path of the projection light that becomes the stray light LA.
That is, the following problems occur due to the deeper groove depth between the total reflection type condensing portions 2B in the region where the incident angle θ is small. (1) The projected light does not reach the total reflection surface 6, but is multiple-reflected on the exit surface to become stray light LA. (2) The utilization efficiency of the projection light is deteriorated. For this reason, it has been found that it is difficult to display a high-quality image in a region where the incident angle θ is small on the screen using the total reflection lens sheet 30.

  On the other hand, a problem in the case where all the tracks are configured by only the refractive condensing part 2A will be described with reference to FIG. As shown in FIG. 3, the refraction type condensing part 2A refracts the projection light of a predetermined incident angle θ projected from the optical engine PJ at the incident surface 4 and condenses it on the condensing region near the exit surface. After that, the microlens is capable of emitting light from the emission surface as an outgoing light beam having a predetermined outgoing angle. The incident surface 4 of the refractive condensing unit 2A has a convex shape toward the optical engine PJ when viewed in a cross section passing through the optical axis PJ0 of the optical engine PJ, and the inclination of the normal line at the center position of the incident surface 4 is inclined. As the distance from the optical axis PJ0 increases, the optical axis PJ0 increases. One of the reasons for this is that the incident angle θ of the projection light from the optical engine PJ increases as the distance from the optical axis PJ0 to the outer track increases. This is because it is necessary to provide a light deflection function (prism action) directed in the normal direction. The other reason is that, in the manufacturing process of the refractive lens sheet 20, when the black mask layer BM is formed on the exit surface of the lens sheet, the condensing region is positioned at the center of the track for each pitch. This is because a black mask layer having a light transmission region is formed at a corresponding position (tracks between concentric circles in FIG. 3B).

  As can be seen from this figure, since it is necessary to provide a light deflection function (prism action) for directing the projection light received by the incident surface 4 in the normal direction of the screen surface, an unnecessary surface 8 (see FIG. 3 (a) circled portion) occurs. This unnecessary surface has a problem that the outer track becomes longer and the circumference of the track becomes longer and the step becomes larger, so that the area increases.

  Due to this unnecessary surface problem, in the refraction type lens sheet 20 composed only of the refraction type condensing part 2A, the projection light is incident from the unnecessary surface in the track region where the incident angle θ of the projection light is large, and stray light is generated. The problem and the problem that the utilization efficiency of projection light falls occur. For this reason, it has been found that it is difficult for the screen using the refractive lens sheet 20 to display a high-quality image in the track area far from the center of the concentric circle.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a lens sheet for a wide incident angle range that can handle projection light whose incident angle is in the vicinity of 0 degrees and in principle up to 90 degrees. . It is another object of the present invention to provide a wide incident angle range compatible screen that can display a high-quality image using it.

  The present inventors diligently studied, and in the case of the refractive lens sheet 20 including only the refractive condensing part 2A, an unnecessary surface connected to the incident surface 4 is generated, and as the track becomes farther from the center of the concentric circle, Since the track circumference is long and the gap is large, the unnecessary surface problem that the area increases (see FIG. 3) is a complex type consisting of a refractive condensing part and a total reflection condensing part in the same track This can be solved by configuring a lens.

Then, when trying to cope with the projection light having a wide incident angle with the total reflection type lens sheet 30 including only the conventional total reflection type condensing unit 2B, a region where the incident angle θ is small, that is, the incident angle θ is 50 degrees or less. The present invention has been made with the knowledge that it is possible to simultaneously solve the difficult-to-solve groove depth problem in which the groove depth between the total reflection type condensing portions becomes deeper in the track region closer to the center of the concentric circle.
The present invention is as follows.

  1. A lens sheet used for a screen for a rear projection display, wherein the lens sheet is composed of a light transmission layer, and the projection light projected from the optical engine within the plane is received by the incident surface and emitted from the emission surface. The track is divided into a plurality of concentric arc-shaped tracks. Each track refracts the projection light received by the incident surface and collects it in a condensing region near the exit surface and receives the light by the incident surface. The total reflection type condensing part that transmits or refracts the projected light that is reflected and then reflected by the total reflection surface and condensed on the condensing region has a volume ratio of 0%, and the other The volume ratio of the total reflection type condensing unit of the composite lens is increased as the incident angle of the projection light projected to the composite lens increases. Or 1 A lens sheet for a wide incident angle range, which becomes constant after reaching 00%.

2. In the compound lens, in the same track, the refraction type condensing part is located on the side near the center of the concentric circle, while the total reflection type condensing part is located on the side far from the center of the concentric circle. 2. The wide incident angle range compatible lens sheet according to 1., which is configured.
3. The height according to 1 or 2 above, wherein the height from the top of the composite lens to the exit surface increases as the incident angle of the projection light projected onto the composite lens increases. Lens sheet for incident angle range.

4. The condensing region of the composite lens is positioned at the center of the track for each pitch, and the lens sheet for wide incident angle range according to any one of 1 to 3.
5. The wide area according to any one of 1 to 4, wherein a black mask layer having a light transmission region is formed on the exit surface at a location corresponding to the light collection region of the composite lens. Lens sheet for incident angle range.

6. The lens sheet for a wide incident angle range according to 5., wherein the ratio of the area of the light transmission region to the area where the other black mask layer is formed is 0.1 or less.
7. A screen for a rear projection display, comprising the lens sheet for a wide incident angle range according to 5. or 6. and a diffusion plate disposed opposite to a black mask layer formed on an exit surface thereof.

  According to the lens sheet corresponding to the wide incident angle range of the present invention, in the case of the refractive lens sheet 20 including only the refractive condensing part 2A, the unnecessary surface that leads to the incident surface 4 as the track becomes farther from the center of the concentric circle. Since the track circumference is long and the gap is large, the area is increased, and the unnecessary surface problem (see FIG. 3) and the conventional total reflection lens sheet 30 (see FIG. 4) have a wide incident angle range. When trying to cope with the projection light, a difficult groove depth problem that the groove depth between the total reflection type condensing portions 2B becomes deeper in the track region near the center of the concentric circle having an incident angle θ of 50 degrees or less. Can be solved simultaneously.

  For this reason, it is possible to realize a wide incident angle range compatible lens sheet that can handle projection light whose incident angle is in the vicinity of 0 degree and in principle up to 90 degrees. In addition, it can be used to realize a wide incident angle range compatible screen capable of displaying a high-quality image.

  First, a wide incident angle range compatible lens sheet according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a configuration when a wide incident angle range compatible lens sheet (hereinafter also simply referred to as a lens sheet 2) according to an embodiment of the present invention is applied to a screen 1 for a rear projection display. The lens sheet 2 is composed of a light transmission layer, and the projection light projected from the optical engine PJ for rear projection display within the plane is received by the incident surface, and is divided into a plurality of concentric arc-shaped tracks that are emitted from the emission surface. Yes. This configuration is the same as the conventional one.

In some cases, it may be divided into a plurality of concentric tracks.
In the lens sheet 2 according to an embodiment of the present invention, each track has a volume ratio of 0% for the refraction type condensing unit 2A and the total reflection type condensing unit 2B, and the other is 100%. It is composed of a compound type lens including the case where In this case, the track including the optical axis PJ0 of the optical engine PJ is composed of only the refractive condensing unit 2A, and the volume ratio in the track is 100%. The volume ratio of the remaining total reflection type condensing unit 2B increases from 0% to 100% as the incident angle θ of the projection light increases, and reaches 100% for a track having a larger incident angle θ of the projection light than a certain value. After that it becomes constant. In this compound type lens, the refraction type condensing part 2A is located on the side close to the center of the concentric circles, and the total reflection type condensing part 2B is located on the side far from the center of the concentric circles. It becomes. Moreover, the height from the top of the compound lens to the exit surface is formed so as to increase as the incident angle θ of the projection light increases.

Here, as shown in FIG. 2, the refraction type condensing unit 2A can refract the first projection light L1 received by the incident surface 4 and condense it on a predetermined condensing region near the exit surface, On the other hand, the total reflection type condensing unit 2B transmits or refracts the second projection light L2 received by the incident surface 5, and then reflects by the total reflection surface 6 to be condensed on the predetermined condensing region. It can be done.
According to the lens sheet 2 according to the embodiment of the present invention configured as described above, in the case of the refractive lens sheet 20 including only the refractive condensing part 2A, the track circumference becomes longer as the track becomes farther from the center of the concentric circle. Since the gap is long and the gap becomes large, the unnecessary surface problem (see FIG. 3) that the area increases can be effectively solved. In addition, when the conventional total reflection type lens sheet 30 (see FIG. 4) is intended to cope with projection light having a wide incident angle range, a track near the center of a concentric circle having a small incident angle θ, that is, an incident angle θ of 50 degrees or less. In the region, it is possible to simultaneously solve the difficult groove depth problem that the groove depth between the total reflection type condensing portions becomes deep. For this reason, it is possible to realize a wide incident angle range compatible lens sheet that can handle projection light whose incident angle is in the vicinity of 0 degree and in principle up to 90 degrees.

Hereinafter, the action of the compound lens formed on each track of the lens sheet corresponding to the wide incident angle range will be described in detail with reference to FIG.
The total reflection type condensing part 2B constituting the compound lens has a top part P formed by the incident surface 5 in the section PR and the total reflection surface 6 in the section PQ, and has a large light deflection function (prism action). Have. On the other hand, the refraction type condensing part 2A has the incident surface 4 of the section RS formed in a convex shape, and the convex incident surface 4 is a cross section passing through the optical axis PJ0 of the optical engine PJ. It is formed so that the inclination of the normal line at the center position becomes larger with respect to the optical axis PJ0 as the distance from the optical axis PJ0 increases. In FIG. 2, L1 indicates the optical path of the first projection light processed by the refraction type condensing unit 2A, and L2 indicates the optical path of the second projection light processed by the projection light total reflection type condensing unit 2B. . The incident angles θ of L1 and L2 are substantially equal.

  When attention is paid to one of the adjacent compound lenses, that is, the compound lens located far from the center of the concentric circle (upper compound lens in the cross-sectional view of FIG. 2), the incident surface 4 of the upper compound lens is S on the surface. The second projection light L2 toward the connecting partition wall surface 7 is received and processed by the total reflection type condensing unit 2B constituting the other composite lens (the lower composite lens in the sectional view of FIG. 2). I understand that. Since the first projection light L1 and the second projection light are also projected from the optical engine PJ to the other adjacent compound lens (see FIG. 1), similarly, the position is far from the center of the concentric circle. The second projection light L2 toward the partition wall surface 7 of the composite lens can be processed by the total reflection type condensing part 2B of the composite lens closer to the center of the adjacent concentric circles.

  Note that the partition wall surface 7 is an unnecessary surface that causes a problem when a plurality of tracks are composed of only the refractive condensing unit 2A, as indicated by broken lines in FIG. That is, the unnecessary surface (the circled portion in FIG. 3A) connected to the incident surface 4 has a longer track circumference and a larger gap as the track becomes an outer track. Due to this unnecessary surface problem, the refraction type lens sheet 20 consisting only of the refraction type condensing part 2A has a problem that the incident light enters from the unnecessary surface and stray light is generated. The problem that the utilization efficiency of projection light falls arises.

In the present invention, such an unnecessary surface problem can be solved, and the problem that the incident light is incident and stray light is generated and the problem that the utilization efficiency of the incident light projected from the optical engine PJ is reduced are effective. Can be solved.
Note that the height of the partition wall surface 7, that is, the height from the groove bottom to the angle S of the incident surface 4 measured in the direction of the exit surface normal n increases as the incident angle θ of the projection light increases. The second projection light L2 directed to the partition surface 7 of the composite lens constituting the track far from the center of the lens is processed by the total reflection type condensing unit 2B of the composite lens closer to the center of the concentric circle adjacent thereto. it can.

As described above, in the same track, the refraction type condensing unit 2A is positioned on the side close to the center of the concentric circle, and the total reflection type condensing unit 2B is positioned on the side far from the center of the concentric circle. This is because the lens is configured, and the height from the top of the composite lens to the exit surface is formed to increase as the incident angle θ of the projection light increases.
Therefore, as shown in FIG. 2, the first projection light L1 projected from the optical engine PJ is processed by the refraction type condensing unit 2A and is condensed on a predetermined condensing region, and as the first outgoing light beam. Light exits from the exit surface. On the other hand, the second projection light L2 projected from the optical engine PJ is processed by the total reflection type condensing unit 2B, and is condensed on the same condensing region as the refraction type condensing unit 2A, and then is second from the exit surface. Light is emitted as an outgoing light beam.

  The lens sheet 2 according to the embodiment in which the compound lens having such an effect is formed on each track is formed in the manufacturing process by forming a black mask layer BM on the exit surface thereof, and for rear projection display. Use for screen 1. At that time, it is preferable to form the black mask layer BM having the light condensing region at the center of the track for each pitch and having the light transmitting region at a position corresponding to the light condensing region. Further, the ratio S1 / S2 of the area S2 between the area S1 of the light transmitting area and the area where the other black mask layer is formed is 0.1 or less, so that the external light incident from the screen surface side becomes stray light. Since the function to prevent is remarkable, it is preferable.

  Then, the rear projection display screen 1 is constituted by the wide incident angle range compatible lens sheet 2 on which the black mask layer BM is formed on the exit surface and the diffusion plate 3 disposed opposite to the black mask layer BM. This diffusing plate 3 has a diffusion characteristic of diffusing the projection light collected in the condensing region near the exit surface from the screen surface toward the front surface where the observer is present, like a top hat type, independent of the incident angle. More preferably, a diffusion plate in which different diffusion films are laminated so that the diffusion characteristics can be controlled independently in the vertical and horizontal directions is preferable because the screen 1 having excellent viewing angle characteristics can be obtained. .

  According to the screen 1 configured as described above, a wide incident angle range compatible screen capable of displaying a high-quality image can be realized.

It is sectional drawing which shows the structure of an example of the screen for rear projection displays to which the lens sheet corresponding to the wide incident angle range of this invention is applied. It is principal part sectional drawing explaining the effect | action of the compound type lens formed in each track | truck of the wide incident angle range corresponding | compatible lens sheet of this invention. It is principal part sectional drawing explaining the problem of the refraction type lens sheet which consists only of a refraction type condensing part. It is principal part sectional drawing explaining the problem of the total reflection type lens sheet which consists only of a total reflection type condensing part. (A) which shows the whole structure of the rear projection display of a nonpatent literature 1 is a front view, (b) is sectional drawing which shows an internal structure. It is principal part sectional drawing explaining the problem of the screen for the conventional rear projection display. It is principal part sectional drawing explaining the problem of the conventional Fresnel lens sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screen 2 Lens sheet 2A corresponding to a wide incident angle range 2A Refraction type condensing part 2B Total reflection type condensing part 3 Diffusion plate 4, 5 Incidence surface 6 Total reflection surface 7 Partition surface 8 Unnecessary surface θ Incident angle of projection light n Output surface Normal direction L Optical path of projection light (L1, L2 first and second projection light)
LA _in optical path of projection light that becomes stray light LA stray light BM black mask layer PJ optical engine PJ0 main axis of optical engine M2 back plane reflector; M1 aspherical mirror
10 Conventional Fresnel lens sheet
10A Hybrid Fresnel lens
20 Refractive lens sheet
30 Total reflection lens sheet

Claims (7)

A lens sheet used for a screen for a rear projection display, wherein the lens sheet is composed of a light transmission layer, and a projection light projected from an optical engine within the surface thereof is received by an incident surface, and a plurality of light beams emitted from an emission surface are emitted. It is divided into concentric arc-shaped tracks,
Each track refracts the projection light received on the incident surface and condenses the light on the condensing region near the exit surface and transmits or refracts the projection light received on the incident surface, A compound lens including a case where the volume ratio of either one of the total reflection type condensing part which is reflected by the total reflection surface and collects in the condensing region is 0% and the other is 100% Consists of
The volume ratio of the total reflection type condensing part of the composite lens increases as the incident angle of the projection light projected onto the composite lens increases or becomes constant after reaching 100%. A lens sheet compatible with a wide incident angle range.   The compound lens forms a one-pitch track by positioning the refraction type condensing part on the side close to the center of the concentric circle and the total reflection type condensing part on the side far from the center of the concentric circle in the same track. The lens sheet for a wide incident angle range according to claim 1, wherein   3. The wide incident angle according to claim 1, wherein the height from the top of the composite lens to the exit surface increases as the incident angle of the projection light projected onto the composite lens increases. 4. Range-compatible condensing lens sheet.   The lens sheet for a wide incident angle range according to any one of claims 1 to 3, wherein the condensing region of the composite lens is positioned at the center of the track for each pitch.   5. The wide incident angle according to claim 1, wherein a black mask layer having a light transmission region at a position corresponding to the light collection region of the composite lens is formed on the emission surface. Range compatible lens sheet.   6. The lens sheet for a wide incident angle range according to claim 5, wherein a ratio of an area of the light transmission region to an area where the other black mask layer is formed is 0.1 or less.   7. A screen for a rear projection display, comprising: the wide incident angle range compatible lens sheet according to claim 5; and a diffuser plate disposed opposite to the black mask layer formed on the exit surface.

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