KR20020060764A - Fresnel Lens, Screen, Image Display Device, Lens Mold Manufacturing Method, and Lens Manufacturing Method - Google Patents

Abstract

The refracting prism portion 3A which emits the incident light li1 of the incident angle a as the output light l01 of the exit angle f by two refractions, and the incident light li2 of the incident angle a And a pitch having a hybrid prism portion having a total reflection type prism portion 4A which is emitted as an output ray lo2 parallel to the emission light l01 by refraction, total reflection and refraction.

Description

Fresnel lens, screen, image display device, lens molding frame manufacturing method and lens manufacturing method {Fresnel Lens, Screen, Image Display Device, Lens Mold Manufacturing Method, and Lens Manufacturing Method}

An image display apparatus represented by a rear projection type projection TV is provided with a screen on which image light emitted from an image light source is projected. Generally, the screen of this image display apparatus is comprised by combining the lenticular as a light-diffusion plate which scatters an image light, and forms an image, and the Fresnel lens which refracts the image light from an image light source, and is emitted in substantially parallel to a lenticular. do.

1 is a view showing an overview of a conventional Fresnel lens.

In Fig. 1, 101 is a Fresnel lens viewed from an inclination, 102 is a cross-sectional shape of the Fresnel lens 101, 103 is an optical axis of the Fresnel lens 101, 104 is formed for each pitch of the Fresnel lens 101 Prism part.

The Fresnel lens 101 is completed by pouring a synthetic resin into a mold (lens mold) that has been rotationally molded about the optical axis 103 and removing the mold (lens mold) after the synthetic resin is cured. On one surface of the completed Fresnel lens 101, a plurality of concentric annular bands are formed around the optical axis 103. As can be seen from the cross-sectional shape 102, the concentric annular bands are a plurality of prism portions 104.

That is, in the Fresnel lens 101, the sawtooth prism part 104 of the cross-sectional shape 102 is shape | molded by pitch period, respectively. One pitch width of the actual Fresnel lens 101 is about 0.1 mm, and it is a minute size compared with the minimum size of the image projected through the Fresnel lens 101.

Since the Fresnel lens 101 acts as a single convex lens as a whole, and the prism portion 104 can be made thin, the distance between the incidence point and the exit point of the incoming and outgoing light of the Fresnel lens 101 is almost It is not necessary to change the direction of the light beam.

By the way, in the image display apparatus, it is often performed to project the image light as obliquely as possible to the Fresnel lens 101 of the screen. This is to shorten the depth of the image display apparatus, whereby the image display apparatus can be thinned.

Fig. 2 is a diagram showing the configuration of an image display device in which a conventional Fresnel lens is applied to a screen. Arrows indicate rays.

In FIG. 2, 111 is a light emitter (illumination means) that emits light, 112 is a parabolic mirror (illumination light source means) having the light emitter 111 in focus, and 113 is a condensing light which focuses the light reflected by the parabolic mirror 112 A lens (condensing optical means) and 114 are light valves (light modulating means) such as liquid crystal. The light valve 114 spatially modulates the light condensed by the condenser lens 113 in accordance with the display contents.

115 is a projection optical lens (projection optical means) for imaging the light modulated light modulated light, 116 is a rear projection screen for receiving the image formed by the projection optical lens 115 from the back to display an image to be. The screen 116 forms an image after forming the broadened light beam into substantially parallel light, displays an image, and spreads the light in a wide range to widen the field of view.

In the screen 116, 117 is the Fresnel lens described above, and 118 is a lenticular.

The Fresnel lens 117 receives the light from the projection optical lens 115 to the incident surface 117A, and emits light at a predetermined exit angle through the prism portion 117B for each pitch. In other words, the Fresnel lens 117 is used to substantially parallelize the light widened by the projection optical lens 115. The lenticular 158 diffuses after imaging the light emitted from the Fresnel lens 117.

119 is the optical axis. The optical axis 119 is shared by the parabolic mirror 112, the condenser lens 113, the light valve 114, the projection optical lens 115, the Fresnel lens 117 and the lenticular 118, and the Fresnel lens It is orthogonal to the incident surface 117A of 117.

Next, the operation will be described.

Since the light emitter 111 provided at the focal point of the parabolic mirror 112 can be regarded mostly as a point light source, the light emitted from the light emitter 111 is reflected by the parabolic mirror 112 to be generally parallel to the condensing lens 113. Headed. When the condenser lens 113 collects parallel light by the light valve 114, the light valve 114 spatially modulates light in accordance with the display contents.

The intensity modulated light is projected by the projection optical lens 115 to the screen 116 at a wide angle and imaged. The angle formed by each light ray and the optical axis 119 included in the projection light is a projection angle. As shown in Fig. 2, although the projection angles of the pitches of the Fresnel lens 117 are different from each other, the pitch lengths are minute lengths in view of the size of the projection optical lens 115 or the screen 116. A plurality of light rays incident on the pitch can be generally regarded as parallel light.

The angle formed by the normal line m11 of the incident surface 117A and each incident light beam is an incident angle. Since the angle of incidence and the angle of projection are the same in the relationship of illusion produced by straight lines (angles of light) intersecting two parallel lines (optical axis 119 and normal line m11), the angle of incidence becomes smaller as the light beam closer to the optical axis 119 The light incident from the optical axis 119 is larger. In particular, light rays directed to the shortest pitch of screen 116 are incident at the maximum angle of incidence.

The size of the screen 116 is determined according to this maximum incident angle, that is, the maximum projection angle of the projection optical lens 115 and the projection distance from the projection optical lens 115 to the screen 116. In contrast, when the size of the screen 116 is defined, the larger the maximum projection angle, the shorter the projection distance. Therefore, an optical system with a shorter distance in the direction of the optical axis 119 can be configured, and the image display device can be made thinner.

The Fresnel lens 117 emits a light beam received at the incident angle by the incident surface 117A at a predetermined exit angle to the lenticular 118 through the prism portion 117B of each pitch. The exit angle is an angle formed by a straight line parallel to the optical axis 119 of the Fresnel lens 117 and the outgoing light beam, and is usually a small angle of several degrees at 0 °. In other words, the relationship between the outgoing light beam of the Fresnel lens 117 and the optical axis 119 becomes substantially parallel (outgoing angle 0 ° in FIG. 2). Of course, the higher the light transmittance (incident light power to the emitted light power ratio) of the Fresnel lens 117, the better. The higher the transmittance, the brighter the image can be displayed.

The lenticular 118 receives light from each prism portion 117B of the Fresnel lens 117, and forms the display contents on the light valve 114 by the projection optical lens 115, and then the user's direction (Fig. Diffuses light to the right side of screen 116 of FIG. 2. The user of the image display apparatus visually recognizes the diffused light from the imaging point as an image. Since light is diffused by the lenticular 118, the user can visually recognize an image having a required brightness in a certain field of view.

As described above, the larger the maximum projection angle of the projection optical lens 115, in other words, the larger the maximum incident angle to the Fresnel lens 117, the thinner the image display apparatus with the shorter projection distance can be provided to the user.

If the size of the screen 116 is determined from the specification or the like, the Fresnel lens 117 may receive the light of the maximum projection angle even if a large maximum projection angle is realized by the projection optical lens 115 or another optical configuration. If it cannot, the projection distance cannot be shortened. In conclusion, in the design of the Fresnel lens 117, one of the points is to make it possible to emit incident light of as large an incident angle as possible with a high transmittance.

Next, various principles of the conventional Fresnel lens will be described.

3A and 3B are enlarged cross-sectional shapes in a plurality of pitches of a conventional Fresnel lens, and FIG. 3A shows a case where the incident angle is small, and FIG. 3B shows a case where the incident angle is large. Arrows indicate rays.

In FIGS. 3A and 3B, 121 is a Fresnel lens, and 121A is a refractive prism portion formed for each pitch of the Fresnel lens 121.

121B is an incidence surface of the refractive prism portion 121A, formed into a planar shape, and is orthogonal to the optical axis (not shown) of the Fresnel lens 121. 121C is an exit surface of the refractive prism portion 121A, and 121Z is an ineffective surface for forming the refractive prism portion 121A together with the entrance surface 121B and the exit surface 121C. In this case, the invalid surface 121Z is not related to the light entering and exiting.

In addition, li is incident light on the incident surface 121B, lr is reflected light at the incident surface 121B, lt is transmitted light that is refracted at the incident surface 121B and passes through the inside of the refractive prism portion 121A, lo Is the outgoing ray refracted by the exit surface 121C and emitted into the air. m12 and m13 are normal lines of the entrance face 121B and the exit face 121C, respectively.

Next, the operation will be described.

In FIG. 3A, when the incident ray li reaches the normal line m12 with the normal line m12 with the Fresnel lens 121 having the refractive index n (n> 1) in the air of the refractive index 1, the incident light li reaches is separated from the incident surface 12iB by the transmitted light lt of the refraction angle χ and the reflected light lr of the reflection angle a. The reflected light lr is a loss of the Fresnel lens 121.

The transmitted light lt refracted by the incident surface 121B and passing through the refractive prism portion 121A reaches the emission surface 121C at an angle ψ with the normal line m13. A part of transmitted light lt becomes a reflected light (not shown), and the remainder exits as exit light lo of the exit angle f from exit surface 121C.

As described above, the Fresnel lens 121 is bending the incident light li of the incident angle a in the direction of the exit angle f. Since light is received by the planar entrance face 121B, the Fresnel lens 121 has a feature in that high light receiving efficiency can be realized.

It is well known in optical theory that as the incident angle decreases, the transmittance of the incident surface increases to decrease the reflectance. On the contrary, as the incident angle increases, the transmittance of the incident surface decreases to increase the reflectance. Therefore, as shown in FIG. 3B, when the incident angle a becomes large, the ratio of the transmitted light lt decreases and the ratio of the reflected light lr increases, and the transmittance of the Fresnel lens 121 decreases.

That is, the transmittance of the Fresnel lens 121 has an incident angle dependence, and as the incident angle a increases, the transmittance decreases. In addition, when applied to a screen whose size is defined, the thinning of the image display apparatus is restricted at the limit of the maximum incident angle.

The Fresnel lens provided with the refractive prism portion also has a configuration in which the incidence side and the exit side of the refractive prism portion 121A in FIGS. 3A and 3B are replaced as shown below.

4A and 4B are enlarged cross-sectional shapes in a plurality of pitches of a conventional Fresnel lens. FIG. 4A shows a case where the incident angle is small, and FIG. 4B shows a case where the incident angle is large. Arrows indicate rays.

4A and 4B, 131 is a Fresnel lens, and 131A is a refractive prism portion formed for each pitch of the Fresnel lens 131.

131B is the incidence surface of the refractive prism portion 131A, 131C is the emission surface of the refractive prism portion 131A, and 131Z forms the refractive prism portion 131A together with the entrance surface 131B and the emission surface 131C. Is invalid. The exit surface 131C is shaped into a plane shape and is orthogonal to the optical axis (not shown) of the Fresnel lens 131. The invalid surface 131Z receives light but is not related to the emission of light from the emission surface 131C.

In addition, li is incident light on the incident surface 131B, lr is reflected light on the incident surface 131B, lt is transmitted light which is refracted at the incident surface 131B and passes through the inside of the refractive prism portion 131A, lo Is an outgoing ray refracted by the exit surface 131C and emitted into the air, and le is an invalid ray received at the invalid surface 131Z. m14 and m15 are normals of the emission surface 131C and the incident surface 131B, respectively.

Next, the operation will be described.

In FIG. 4A, when the incident light li reaches the incidence angle a with the normal line m14 to the Fresnel lens 131 having the refractive index n (n> 1) in the air of the refractive index 1, the incident light ( li is incident to the incidence plane 131B by forming an actual incident angle b with the normal line m15, and is separated into a transmission ray lt having a refractive angle χ and a reflection ray lr having a reflection angle b. The reflected light lr is a loss of the Fresnel lens 131.

The transmitted light lt refracted by the incident surface 131B and passing through the refractive prism portion 131A reaches the emission surface 131C at an angle ψ with the normal m14. A part of transmitted light lt becomes a reflected light (not shown), and the remainder is radiated | emitted as the exit light lo of the exit angle f from the exit surface 131C.

In addition, since the invalid light le received at the invalid surface 131Z is emitted from the emission surface 131C at an angle different from the emission angle f, the Fresnel lens 131 is lost.

As described above, the Fresnel lens 131 is bending the incident light li at the incident angle a in the direction of the exit angle f. Since the plane-shaped exit surface 131C is provided, the Fresnel lens 131 has a feature in that the lenticular can be integrally formed on the exit surface 131C when applied to the screen.

However, for the same reason as the Fresnel lens 121, as shown in Fig. 4B, when the incident angle a becomes large, the ratio of the reflected light lr on the incident surface 131B increases, and at the same time the ineffective surface ( The area of the inactive light received at 131Z (the oblique portion in Figs. 4A and 4B) becomes large. As a result, the loss becomes large and the transmittance of the Fresnel lens 131 decreases.

Therefore, like the Fresnel lens 121, the transmittance of the Fresnel lens 131 has an angle of incidence, and the transmittance decreases as the angle of incidence increases.

As described above, in the Fresnel lens having the refractive prism portion, the transmittance decreases as the incident angle increases. In addition, when applied to a screen whose size is prescribed, it becomes a factor of limiting the thinning of the image display apparatus.

A conventional Fresnel lens that solves the above disadvantages of the Fresnel lens having a refractive prism portion and realizes a high transmittance for a large angle of incidence will be described next.

5A and 5B are enlarged cross-sectional shapes in a plurality of pitches of a conventional Fresnel lens. FIG. 5A is a case where the incident angle is large, and FIG. 5B is a case where the incident angle is small. Arrows indicate rays.

5A and 5B, 141 is a Fresnel lens, and 141A is a total reflection prism portion formed for each pitch of the Fresnel lens 141. As shown in FIG.

141B is the incident surface of the total reflection type prism portion 141A, 141C is the total reflection surface of the total reflection type prism portion 141A, and 141D forms the total reflection type prism portion 141A together with the incident surface 141B and the total reflection surface 145C. It is an exit surface. The exit surface 141D is shaped into a plane shape and is orthogonal to the optical axis (not shown) of the Fresnel lens 141. In the total reflection surface 141C, a phenomenon in which light incident from the high refractive index medium to the low refractive index medium is totally reflected at an incident angle larger than the critical angle is used.

Li is incident light on the incident surface 141B, lt1 is transmitted light refracted by the incident surface 141B and transmitted to the total reflection surface 141C, and lt2 is totally reflected at the total reflection surface 141C to the emission surface 141C. The transmitted light, lo, which is transmitted, is an outgoing light that is refracted by the exit surface 141D and is emitted into the air, and le is an invalid light received by the entrance surface 141B. m16, m17, and m18 are normals of the emission surface 141D, the incident surface 141B, and the total reflection surface 141C, respectively.

Next, the operation will be described.

In FIG. 5A, when the incident light li reaches the incidence angle a with the normal line m16 to the Fresnel lens 141 having the refractive index n (n> 1) in the air of the refractive index 1, the incident light ( The li is made into the normal incident angle b with the normal line m17 and is incident on the incident surface 141B, and is separated into the transmitted light lt1 and the reflected light (not shown) having the refractive angle χ. The reflected light of the incident surface 141B becomes a loss of the Fresnel lens 141.

The transmitted light lt1 refracted by the incident surface 141B and passing through the total reflection type prism portion 141A reaches the total reflection surface 141C at an angle at which the angle formed by the normal line m18 is larger than the critical angle, and the total reflection surface ( It totally reflects at 141C and becomes the transmitted light lt2. Since the optical path is bent using the total reflection phenomenon, there is no light emitted from the total reflection surface 141C, and there is almost no loss in the total reflection surface 141C.

The transmitted light lt2 totally reflected at the total reflection surface 141C reaches the exit surface 141D at an angle ψ (0 ° in FIG. 5A) with the normal line m16. A part of the transmitted light lt2 becomes a reflected light (not shown), and the remainder is emitted as an outgoing light lo of the exit angle f (0 ° in FIG. 5A) from the exit surface 141D.

Since the Fresnel lenses 121 and 131 each having the refractive prism portions 121A and 131A bend the optical path due to the refraction phenomenon, in order to bend the optical path largely, the incident light (a and b) has a large incident angle (a, b). li) needs to be received. For this reason, the ratio of the reflected light lr in the incidence surfaces 121B and 131B increases, which causes a decrease in transmittance.

On the other hand, the Fresnel lens 141 provided with the total reflection type prism portion 141A reduces the degree of optical path bending due to refraction since the optical path bending is performed by total reflection. Therefore, incident light li can be made incident on the incident surface 141B at a small actual incident angle b, and the increase in reflectance is suppressed to achieve high transmittance.

As described above, the Fresnel lens 141 provided with the total reflection type prism portion 141A has a feature in that a high transmittance can be realized for a large incident angle, unlike the Fresnel lenses 121 and 131.

However, in the Fresnel lens 141, when the incident angle a becomes smaller as shown in Fig. 5B, the incident light li received at the incident surface 141B decreases and the transmitted light lt2 is totally reflected at the total reflection surface 141C. ) Ratio decreases, and an inactive ray le (the hatched portion in Fig. 5B) is generated.

The ineffective light le is a light beam that does not totally reflect on the total reflection surface 141C even though it passes through the inside of the total reflection type prism portion 141A, resulting in a loss of the Fresnel lens 141. That is, the transmittance of the Fresnel lens 141 also depends on the angle of incidence, and although it is possible to correspond to the large incident angle a, the transmittance decreases in the case of the small incident angle a.

Since the Fresnel lens of the related art is configured as described above, there is a problem that the incident angle dependence of the transmittance is large.

That is, part of the image light projected obliquely above the maximum projection angle could not be deflected in the desired direction in the conventional Fresnel lens, and the transmittance was low.

Here, the conventional Fresnel lens will be briefly described again.

Fig. 6 is a diagram showing a case where image light is projected obliquely with a conventional Fresnel lens, and shows a partial sectional view of a conventional Fresnel lens.

In Fig. 6, 100 is a conventional Fresnel lens having a refractive prism portion at each pitch, 100a is an incident surface on the light incident side of Fresnel lens 100, and 100b is a light incident side of Fresnel lens 100. If the invalid surface, 100c is the output surface on the light exit side of the Fresnel lens 100, R1in is the light beam incident on the incident surface 100a, R2in is the light beam incident on the invalid surface 100b.

The Fresnel lens 100 of FIG. 6 unites the minute refractive index prism portion which deflects the light beam R1in at the inclination incident on the incident surface 100a and is emitted as the light beam R1out from the exit surface 100c. It is provided as a prism part.

However, the light beam R2in incident on the ineffective plane 100b other than the incident surface 100a became stray light without being emitted in a desired direction, so that the light beam R2in could not be effectively used, and the transmittance was low.

A Fresnel lens having a total reflection type prism portion for deflecting light by using total reflection is proposed as a means for solving such a problem.

For example, Japanese Unexamined Patent Application Publication No. 61-52601 proposes a Fresnel lens having alternately arranged a refractive prism portion and a total reflection prism portion. Also, Japanese Patent Laid-Open No. 62-19837 proposes a Fresnel lens in which a portion using refraction and a portion using total reflection are provided in one unit prism portion.

However, in the Fresnel lens disclosed in Japanese Patent Laid-Open No. 65-52601, the refractive prism portion also exists in the region where the refractive prism portion does not function effectively, and conversely, the total reflection prism portion does not function effectively. The total reflection prism part also exists in the area | region. Therefore, there is a problem that there is still a lot of light that is not emitted in a desired direction.

On the other hand, the Fresnel lens disclosed in Japanese Patent Laid-Open No. 62-19837 has a polygonal cross-sectional shape, and requires a specially shaped bite or the like when manufacturing a lens mold for molding Fresnel lenses. It becomes difficult, and manufacture of a lens shaping | molding die becomes difficult. Furthermore, manufacturing of the Fresnel lens itself cannot be performed easily.

In addition, the conventional Fresnel lens has a problem that when applied to a screen of the rear projection type, unevenness occurs in the brightness of the screen image.

In other words, when a Fresnel lens having a refractive prism portion is applied to the screen, it cannot cope with a large projection angle, so that the brightness of the peripheral portion of the screen is lowered and the thickness of the image display device is restricted.

In addition, when a Fresnel lens having a total reflection type prism portion is applied to the screen, it is impossible to cope with a small projection angle, so that the brightness near the optical axis of the screen image is reduced.

This invention is made | formed in order to solve the above subjects, and an object of this invention is to comprise the Fresnel lens which reduced the incident angle dependence of the transmittance | permeability.

Moreover, an object of this invention is to comprise the screen which can suppress unevenness of image brightness, and can respond from a small projection angle to a large projection angle, and the image display apparatus which applied this screen.

Moreover, an object of this invention is to provide the lens shaping | molding die manufacturing method for manufacturing the lens shaping | molding die of said Fresnel lens, and the lens manufacturing method using this lens shaping | molding die manufacturing method.

The present invention relates to a Fresnel lens which has almost the same effect as a convex lens, requiring little distance between the entrance and exit points of light. The present invention also relates to a rear projection screen to which a Fresnel lens is applied, an image display device to which the screen is applied, and a method for manufacturing a lens molding frame and a method for manufacturing a lens.

1 is a view showing an overview of a conventional Fresnel lens.

Fig. 2 is a diagram showing the configuration of an image display device in which a conventional Fresnel lens is applied to a screen.

3A and 3B are enlarged cross-sectional views of a plurality of pitches of a conventional Fresnel lens.

4A and 4B are enlarged cross-sectional views of a plurality of pitches of a conventional Fresnel lens.

5A and 5B are enlarged cross-sectional shapes of a plurality of pitches of a conventional Fresnel lens.

Fig. 6 is a diagram showing a case where image light is projected obliquely with a conventional Fresnel lens.

Fig. 7 is an enlarged view of the cross-sectional shape in one pitch of the Fresnel lens according to the first embodiment of the present invention.

Fig. 8 is a diagram showing the variation of the transmittance with respect to the incident angle of the refractive prism portion, the total reflection prism portion, and the hybrid prism portion.

FIG. 9 is a diagram for explaining the inactive light of the Fresnel lens shown in Embodiment 1. FIG.

Fig. 10 is an enlarged view of the cross-sectional shape in one pitch of the Fresnel lens according to the second embodiment of the present invention.

Fig. 11 is a diagram comparing the transmittance of the hybrid prism portion shown in the first embodiment with that of the refractive prism portion shown in the prior art.

Fig. 12 is an enlarged view of a cross-sectional shape in a plurality of pitches of a Fresnel lens according to Embodiment 3 of the present invention.

Fig. 13 is an enlarged view of the cross-sectional shape in the plural pitches of the Fresnel lens according to the third embodiment of the present invention.

Fig. 14 is an enlarged view of a cross-sectional shape in a plurality of pitches of a Fresnel lens according to Embodiment 3 of the present invention.

Fig. 15 is a diagram showing the transmittances of the hybrid prism portion when the tip angle? Is 45 degrees, 40 degrees, and 35 degrees, respectively.

Fig. 16 is a diagram showing the transmittance of the hybrid prism portion when the emission angle f is set to 0 °, 3 ° and 5 °, respectively.

Fig. 17 is a diagram showing the configuration of an image display device in which a Fresnel lens is applied to a screen.

18 is a diagram for explaining a method of optimizing the emission angle of the emission light beam.

19 is a diagram for explaining a method of optimizing the emission angle of the emission light beam.

20 is a diagram showing the overall configuration of a rear projection type image display device according to a fifth embodiment of the present invention.

21 is a view of the image display device of FIG. 20 seen from the side.

22 is a diagram showing the cross-sectional shape of the Fresnel lens 51. FIG.

23A to 23C are diagrams for explaining the total reflection prism portion U1 and the refractive prism portion U2.

24A to 24C are views for explaining the characteristics of the lens shaping mold used when manufacturing the Fresnel lens 51, respectively.

25A to 25C are views for explaining the characteristics of the lens shaping mold used when manufacturing the Fresnel lens 51, respectively.

Fig. 26 is a flow chart showing a lens forming frame manufacturing method according to the fifth embodiment of the present invention.

27A to 27D are diagrams showing the progress of cutting of the lens forming mold C by the bite B. FIG.

28A to 28D are diagrams showing the progress of cutting the lens shaping mold C by the bite B. FIG.

FIG. 29 shows the ratio from the center of the Fresnel in the Fresnel lens 51 to the ratio of the total reflection type prism portion U1 and the refractive type prism portion U2.

30 is a diagram showing the configuration of a Fresnel lens 110 according to the prior art.

FIG. 31 is a diagram showing the lens ratio of the total reflection prism portion in the Fresnel lens 110 in FIG. 30 by a line L5.

32 is a diagram showing the transmittances of the Fresnel lens 51 of the fifth embodiment and the Fresnel lens 110 according to the prior art, respectively.

33A to 33F are views for explaining the deformation occurring in the manufacturing process of the lens mold.

Fig. 34 is a flow chart showing a lens forming mold manufacturing method according to Embodiment 6 of the present invention.

35A to 35F are views showing the state of the lens shaping mold to be cut according to the lens shaping mold manufacturing method of FIG.

Fig. 36 is a view for explaining the construction and operation of a Fresnel lens without a dummy prism portion.

37 is a diagram for explaining the configuration and operation of a Fresnel lens including a dummy prism portion.

38A and 38B are diagrams for explaining the difference between the Fresnel lens of Fig. 36A and the Fresnel lens of Fig. 37A.

FIG. 39 shows a cross-sectional shape of a Fresnel lens according to the seventh embodiment of the present invention. FIG.

40 is a diagram showing a cross-sectional shape of a Fresnel lens according to the seventh embodiment of the present invention.

41A and 41B are diagrams showing an example of a laminated structure of a light transmitting layer and a light absorbing layer in a stray light absorbing plate.

Fig. 42 is a diagram showing a cross-sectional shape of a Fresnel lens according to the seventh embodiment of the present invention.

A Fresnel lens according to the present invention includes a refractive prism portion for emitting first incident light having a predetermined angle of incidence as a first output ray having a predetermined emission angle by a first refractive phenomenon and a second refractive phenomenon, and a second of a predetermined incident angle. A pitch having a hybrid prism portion having a total reflection type prism portion which emits incident light as a second output light parallel to the first output light by the third refractive phenomenon, the total reflection phenomenon and the fourth refractive phenomenon is provided.

Thereby, the effect of being able to comprise the high transmittance Fresnel lens which reduced the incident angle dependence can be acquired.

The Fresnel lens according to the present invention has a hybrid prism portion in at least two or more pitches, and the ratio of the refractive prism portion to the hybrid prism portion is different for each pitch.

Thereby, the effect that a transmittance | permeability can be improved can be acquired.

The Fresnel lens according to the present invention includes a first incidence plane in which a first incident light incident at a predetermined angle of incidence is a first transmission light by a first refractive phenomenon, and a first incidence light is predetermined by a second refractive phenomenon. A refractive prism portion having a cross-sectional shape consisting of a planar exit face made of the first exit beam of the exit angle, an inclined plane in contact with the first entrance plane and the adjacent pitch, and a second incident ray incident at a predetermined incident angle; A second incidence plane serving as the second transmission ray by the three refraction phenomenon, a total reflection plane in which the second transmission ray is the third transmission ray parallel to the first transmission ray by the total reflection phenomenon, and an exit plane of the refractive prism portion. A part of the second incident light that has a cross-sectional shape and is composed of a total reflection prism portion having the third transmitted light as a second exit light having a predetermined exit angle by the fourth refractive phenomenon at the exit surface, and which does not become the third transmitted light; To 1 will be provided with a pitch having a hybrid type prism integrated with the refraction type prism portion to the total reflection type prism portion to the light receiving section as the incident beam.

Thereby, the effect of being able to comprise the high transmittance Fresnel lens which reduced the incident angle dependence can be acquired.

The Fresnel lens according to the present invention forms a second incident surface in a cross-sectional shape for blocking the invalid surface in the direction of the invalid light incident on the invalid surface of the hybrid prism portion provided in the adjacent pitch, and the second incident surface. The total reflection surface is formed into a second incidence plane compensation shape that compensates for the cross-sectional shape of.

As a result, the effect that the light receiving efficiency of the Fresnel lens can be increased by reducing the invalid region can be obtained.

In the Fresnel lens according to the present invention, the refractive prism portion is provided at each pitch of the small square area determined based on the characteristic change angle that makes the transmittance of the hybrid prism portion equal to the transmittance of the refractive prism portion.

Thereby, the effect that the transmittance | permeability characteristic in a quenching square area | region can be improved can be acquired.

In the Fresnel lens according to the present invention, the refractive prism portion is provided at each pitch of the small square area determined based on the characteristic change angle that makes the transmittance of the hybrid prism portion equal to the transmittance of the refractive prism portion.

Thereby, the effect that the transmittance | permeability characteristic in a quenching square area | region can be improved can be acquired.

The Fresnel lens according to the present invention is such that the mixing ratio of the refractive prism portion to the hybrid prism portion increases as the incident angle decreases at each pitch in the characteristic change region near the characteristic change angle.

Thereby, the effect that the transmittance | permeability characteristic in a quenching angle area | region can be improved and the transmittance | permeability change in the vicinity of a characteristic change angle can be acquired smoothly.

The Fresnel lens according to the present invention is such that the mixing ratio of the refractive prism portion to the hybrid prism portion is increased as the incident angle decreases at each pitch in the characteristic change region near the characteristic change angle.

Thereby, the effect that the transmittance | permeability characteristic in a quenching angle area | region can be improved and the transmittance | permeability change in the vicinity of a characteristic change angle can be acquired smoothly.

In the Fresnel lens according to the present invention, in each pitch of the characteristic change region near the characteristic change angle, the area of the second incidence surface is insignificant and the area of the first incidence surface is insignificant as the incident angle decreases. It is to provide a part.

Thereby, the effect that the transmittance | permeability characteristic in a quenching angle area | region is improved and the transmittance | permeability change in a characteristic change angle can be made smooth can be acquired.

In the Fresnel lens according to the present invention, in each pitch of the characteristic change region near the characteristic change angle, the area of the second incidence surface is insignificant and the area of the first incidence surface is insignificant as the incident angle decreases. It is to provide a part.

Thereby, the effect that the transmittance | permeability characteristic in a quenching angle area | region is improved and the transmittance | permeability change in a characteristic change angle can be made smooth can be acquired.

The Fresnel lens according to the present invention is such that the tip angle formed by the second incidence surface and the total reflection surface is at the sharpest angle in a range in which the angle between the second incidence surface and the exit surface is not obtuse.

Thereby, the effect that a transmittance | permeability can be improved further can be acquired.

In the Fresnel lens according to the present invention, in the incidence angle area smaller than the incidence angle at which the transmittance for the tip angle of the sharpest angle and the transmittance for the tip angle other than the sharp angle is equal, the tip angle is made larger than the sharp angle. It is.

Thereby, the effect that high transmittance | permeability can be implement | achieved with respect to an incidence angle is obtained.

The Fresnel lens according to the present invention is such that the predetermined exit angle is made larger than 0 ° at each pitch of the incident angle at which the transmittance of the hybrid prism portion decreases.

Thereby, the effect that a transmittance | permeability can be improved further can be acquired.

In the Fresnel lens according to the present invention, in the lens outer peripheral side of the boundary ring band that intersects only one side closest to the optical axis among the four sides of the Fresnel lens cut out in a rectangular shape, the emission angle is set in parallel, and On the optical axis side, the exit angle is set larger than the exit angle set in parallel.

Thereby, when it is applied to the screen of the image display apparatus which comprised multiple structures, the effect that brightness uniformity in a screen can be improved can be acquired.

The Fresnel lens according to the present invention is such that the refractive prism portion is provided on the ineffective surface of the thin film for absorbing light.

This makes it possible to absorb ineffective light that is received on the ineffective surface and becomes stray light inside the Fresnel lens, and the effect of reducing ghosts generated on the screen can be obtained.

The Fresnel lens according to the present invention comprises a stray light absorbing plate composed of a plurality of light transmitting layers for transmitting light, and a plurality of light absorbing layers which are stacked between the light transmitting layers substantially in parallel with the optical axis of the Fresnel lens. It is provided on the exit surface.

This makes it possible to absorb stray light generated inside the Fresnel lens and to reduce the ghost generated on the screen.

In the Fresnel lens according to the present invention, the stray light absorbing plate is integrally formed on the exit surface of the Fresnel lens.

Thereby, the effect that a ghost can be reduced with a small number of parts can be acquired.

The Fresnel lens according to the present invention is such that the light transmitting layer and the light absorbing layer are laminated concentrically about the optical axis of the Fresnel lens.

Thereby, the effect that the reduction efficiency of ghost can be made the best can be acquired.

The Fresnel lens according to the present invention is such that the light transmitting layer and the light absorbing layer are laminated substantially parallel to one direction.

Thereby, manufacture of a stray light absorption board becomes easy, and the effect that a manufacturing cost can be reduced can be acquired.

The Fresnel lens according to the present invention has a light absorbing plate for absorbing light on the emission surface.

As a result, the stray light can be absorbed with a simple configuration, and the effect of reducing the ghost generated on the screen can be obtained.

The Fresnel lens according to the present invention is such that the hybrid prism portion is formed with a pitch margin between the pitches, respectively.

Thereby, the effect that the total reflection surface can be made into the shape as designed and the optical performance of a Fresnel lens can be ensured.

The Fresnel lens which concerns on this invention is provided so that the dummy prism part which has a height which does not participate in light reception in an optical axis direction may be continuously provided in at least one pitch group.

Thereby, the effect that the abrupt reduction | decrease and generation | occurrence | production of the manufacturing error resulting from the change of the shape of a prism part can be suppressed, and the sudden change of optical performance, such as transmittance | permeability, can be alleviated.

The screen according to the present invention comprises an image diffusing means for receiving the Fresnel lens according to any one of claims 1 to 22 and the outgoing light to which the display content is added from the Fresnel lens, and for forming the outgoing light to diffuse. It is to be provided.

Thereby, the effect that the unevenness of image brightness can be suppressed and the screen which can respond from a small projection angle to a large projection angle can be comprised can be acquired.

The screen according to the present invention is such that the image forming means is integrally formed on the exit surface of the Fresnel lens.

Thereby, the effect that the screen which reduced the number of parts can be comprised can be acquired.

An image display apparatus according to the present invention includes a screen according to claim 23 or 24, illumination light source means for emitting substantially parallel light, condensing optical means for condensing light from the illumination light source means, and condensing optical means Light modulation means for spatially intensity modulating the collected light according to the display content, and projection optical means for projecting the light modulated by the light modulation means on the screen.

Thereby, the effect that an image display apparatus which improved the brightness of an image can be comprised can be acquired.

The Fresnel lens according to the present invention comprises a subsidiary prism portion on a part of the second incident surface where light that is not totally reflected on the total reflection surface is provided with a total reflection type prism portion, and at the same time refracts incident light to deflect in a desired direction. The refracting prism portion having one incident surface is used as a subunit prism portion.

Thereby, the subunit prism part functions with respect to the light in which the total reflection type prism part does not function effectively, and the effect that the transmittance | permeability of a Fresnel lens can be improved can be acquired.

In the Fresnel lens according to the present invention, the surface on which the first incident surface of the subunit prism portion extends is within the total reflection type prism portion, and is located on the light exit side rather than the total reflection surface.

Thereby, the effect that the Fresnel lens which can be manufactured easily can be comprised.

In the Fresnel lens according to the present invention, the ratio of the subunit prism portion occupying the second incident surface is changed.

Thereby, the effect that an optimal unit prism part shape can be formed according to the incident angle of a light beam, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the ratio of the subunit prism portion occupying the second incident surface is changed.

Thereby, the effect that an optimal unit prism part shape can be formed according to the incident angle of a light beam, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

The Fresnel lens according to the present invention includes a sub-prism portion for receiving light incident on an ineffective surface adjacent to the fresnel peripheral side, the second incidence surface having a refractive prism portion on the first incidence surface, and receiving light; The total reflection type prism portion having a total reflection surface that totally reflects the light received from the second entrance surface and deflects in a desired direction is used as a subunit prism portion.

Thereby, the subunit prism part functions with respect to the light in which the refractive prism part does not function effectively, and the effect that the transmittance of a Fresnel lens can be improved can be acquired.

In the Fresnel lens according to the present invention, the surface on which the second incident surface of the subunit prism portion extends is within the range of the refractive prism portion, and is located on the light exit side rather than the ineffective surface.

Thereby, the effect that the Fresnel lens which can be manufactured easily can be comprised.

In the Fresnel lens according to the present invention, the ratio of the subunit prism portion occupying the first incident surface is changed.

Thereby, the effect that an optimal unit prism part shape can be formed according to the incident angle of a light beam, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the ratio of the subunit prism portion occupying the first incident surface is changed.

Thereby, the effect that an optimal unit prism part shape can be formed according to the incident angle of a light beam, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

The Fresnel lens according to the present invention has a first range of the same form as the Fresnel lens of claim 26 and a second range of the same form as the Fresnel lens of claim 30.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has a first range of the same form as the Fresnel lens of claim 26 and a second range of the same form as the Fresnel lens of claim 31.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has a first range of the same form as the Fresnel lens of claim 26 and a second range of the same form as the Fresnel lens of claim 32.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 26 and the second range of the same form as the Fresnel lens of claim 33.

As a result, the optimum prism portion can be selected and formed in the first range or the second range according to the incident angle of the light beam, and the effect that a Fresnel lens with high transmittance can be obtained can be obtained. .

The Fresnel lens according to the present invention has a first range of the same form as the Fresnel lens of claim 27 and a second range of the same form as the Fresnel lens of claim 30.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has a first range of the same form as the Fresnel lens of claim 27 and a second range of the same form as the Fresnel lens of claim 31.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 27 and the second range of the same form as the Fresnel lens of claim 32.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has a first range of the same form as the Fresnel lens of claim 27 and a second range of the same form as the Fresnel lens of claim 33.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 28 and the second range of the same form as the Fresnel lens of claim 30.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has a first range of the same form as the Fresnel lens of claim 28 and a second range of the same form as the Fresnel lens of claim 31.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 28 and the second range of the same form as the Fresnel lens of claim 32.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 28 and the second range of the same form as the Fresnel lens of claim 33.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention is provided with the first range of the same form as the Fresnel lens of claim 29 and the second range of the same form as the Fresnel lens of claim 30.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 29 and the second range of the same form as the Fresnel lens of claim 31.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 29 and the second range of the same form as the Fresnel lens of claim 32.

This makes it possible to select and form the optimum unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect that a Fresnel lens having a high transmittance can be formed. have.

The Fresnel lens according to the present invention has the first range of the same form as the Fresnel lens of claim 29 and the second range of the same form as the Fresnel lens of claim 33.

This makes it possible to select and form the optimal unit prism portion in the first range or the second range in accordance with the incident angle of the light beam, thereby providing an effect of forming a Fresnel lens having a high transmittance. have.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

In the Fresnel lens according to the present invention, the proportion of the subunit prism portion occupying the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the further away from the boundary. The proportion of the subunit prism portion occupied by the first incident surface in the second range decreases as the number approaches the boundary and decreases as the distance from the boundary increases.

Thereby, the ratio of the subunit prism part increases so that the subunit prism part functions effectively, and the effect that a Fresnel lens with high transmittance | permeability can be comprised can be acquired.

The Fresnel lens according to the present invention is such that a second Fresnel lens different from the Fresnel lens is provided on the light exiting side of the Fresnel lens provided on the light incidence side.

Thereby, the effect that the Fresnel lens of the light incident side and the Fresnel lens of the light exit side raise and act | operate, and can comprise the Fresnel lens which further improved the transmittance | permeability can be acquired.

The Fresnel lens according to the present invention is such that a second Fresnel lens different from the Fresnel lens is provided on the light exiting side of the Fresnel lens provided on the light incidence side.

Thereby, the effect that the Fresnel lens of the light incident side and the Fresnel lens of the light exit side raise and act | operate, and can comprise the Fresnel lens which further improved the transmittance | permeability can be acquired.

The screen according to the present invention is formed on the surface of the Fresnel lens according to any one of claims 26 to 65 and the light exit side of the Fresnel lens, and the light diffusing means for diffusing the light emitted from the Fresnel lens. It is intended to consist of.

Thereby, the effect that the number of parts can be reduced, the image brightness can be suppressed, and the screen which can respond from a small projection angle to a large projection angle can be comprised.

A screen according to the present invention is provided with a Fresnel lens according to claim 66 or 67, and a light diffusing means provided on the light exit side of the Fresnel lens to diffuse light emitted from the Fresnel lens.

Thereby, the effect that the unevenness of image brightness can be suppressed and the screen which can respond from a small projection angle to a large projection angle can be comprised can be acquired.

An image display apparatus according to the present invention is provided with the screen according to claim 68, an image light source for emitting image light, and projection optical means for projecting the image light emitted from the image light source onto the screen.

Thereby, the effect that an image display apparatus which improved the brightness of an image can be comprised can be acquired.

An image display apparatus according to the present invention is provided with the screen according to claim 69, an image light source for emitting image light, and projection optical means for projecting the image light emitted from the image light source onto the screen.

Thereby, the effect that an image display apparatus which improved the brightness of an image can be comprised can be acquired.

In the method for manufacturing a lens forming frame according to the present invention, a main unit prism part cutting step of cutting the inverted shape of the refractive prism part into a bite with respect to the cutting target pitch, and the inverted shape of the total reflection type prism part with a bite with respect to the cutting target pitch At the same time, the part which extends the total reflection surface in the inverted shape of the total reflection type prism part passes the curve which the pitch of a cutting object and the adjacent pitch of the Fresnel center side rather than the cutting object pitch is made to pass or outgo more than a curve. The unit prism portion cutting step is repeated by a predetermined number of pitches.

Thereby, it becomes possible to make manufacture of a lens shaping | molding die easy using a normal cutting tool, and the effect that the manufacturing precision of a lens shaping | molding die can be improved can be acquired.

In the method for manufacturing a lens forming frame according to the present invention, the main unit prism part cutting step of cutting the inverted shape of the total reflection type prism part into a bite with respect to the cutting target pitch, and the inverted shape of the refractive prism part is cut into the bite with respect to the cutting target pitch. At the same time, the surface extending the first incidence surface in the inverted shape of the refracting prism portion passes through the curve formed by the pitch of the cutting target and the adjacent pitch on the peripheral side of the Fresnel rather than the cutting target pitch or becomes the light exiting side than the curve. The subunit prism part cutting step is repeated by a predetermined number of pitches.

As a result, it is possible to easily manufacture the lens forming mold using a normal cutting tool, and the effect of improving the manufacturing precision of the lens forming mold can be obtained.

According to the method for manufacturing a lens forming frame according to the present invention, when cutting is performed for every pitch in the cutting progress direction from the Fresnel center side to the Fresnel peripheral side, in order of total reflection type prism portion, refractive type prism portion, pitch margin for every pitch A pitch margin setting step for setting the step is provided before the subunit prism portion cutting step, and in the subunit prism portion cutting step, the cutting start position is shifted in the cutting direction by the pitch margin, so that the refractive prism portion is cut for each pitch. will be.

As a result, when cutting the refractive prism portion, it is possible to prevent the deformation of the lens forming mold occurring at the curved tip portion between each total reflection prisms for each pitch, so that the lens forming mold can be shaped as designed. Moreover, the effect that the optical performance of the Fresnel lens manufactured with the lens shaping | molding die can be ensured can be acquired.

In the method for manufacturing a lens forming frame according to the present invention, when cutting is performed for every pitch in the order of the cutting progression from the peripheral side of the Fresnel to the center of the Fresnel, the pitch margin is pitch for every pitch. And a pitch margin setting step for setting the? Before the subunit prism portion cutting step, and in the subunit prism portion cutting step, the cutting start position is shifted in the cutting direction by the pitch margin, and the total reflection prism portion is cut for each pitch. It is.

As a result, when cutting the total reflection type prism portion, it is possible to prevent the deformation of the lens forming mold occurring at the curved tip portion between each of the refractive prisms for each pitch, so that the lens forming frame can be shaped as designed. Moreover, the effect that the optical performance of the Fresnel lens manufactured with the lens shaping | molding die can be ensured can be acquired.

In the method for manufacturing a lens mold according to the present invention, the inverted shape of the dummy prism portion having the height not involved in light reception in the optical axis direction is continuously cut to at least part of the pitch group.

Thereby, the effect that the abrupt reduction | decrease and generation | occurrence | production of the manufacturing error resulting from the change of the shape of a prism part can be suppressed, and the sudden change of optical performance, such as transmittance | permeability, can be alleviated.

In the lens manufacturing method according to the present invention, when a resin is poured into a lens forming mold manufactured by the lens forming mold manufacturing method according to any one of claims 72 to 76, and the resin is cured, the lens is formed from the cured resin. The mold was removed to form a lens.

Thereby, the effect that a high precision Fresnel lens can be manufactured easily is acquired.

EMBODIMENT OF THE INVENTION Hereinafter, in order to demonstrate this invention in detail, the best form for implementing this invention is demonstrated according to attached drawing.

Embodiment 1.

Fig. 7 is an enlarged view of the cross-sectional shape in one pitch of the Fresnel lens according to the first embodiment of the present invention. Arrows indicate rays. Here, the cross-sectional shape means the shape of the cut surface of the prism portion when the Fresnel lens is cut along the surface including the optical axis of the Fresnel lens.

In Fig. 7, 1 is a Fresnel lens according to the first embodiment, 2 is a hybrid prism portion molded for each pitch of the Fresnel lens 1, 3A is a refractive prism portion, 4A is a total reflection prism portion, 5 is It is the exit surface of the hybrid prism part 2. The exit surface 5 is shaped in a planar shape and orthogonal to the optical axis (not shown) of the Fresnel lens 1. The refractive prism portion 3A and the total reflection type prism portion 4A share the emission surface 5 to form the hybrid prism portion 2.

In the refractive prism portion 3A, 3B is the incident surface (first incidence surface) of the refractive prism portion 3A, and 3Z is the refractive prism portion 3A together with the incident surface 3B and the exit surface 5. ) Is an invalid surface for molding. The invalid surface 3Z receives light but does not relate to the emission of light from the emission surface 5.

In the total reflection type prism portion 4A, 4B is the total reflection type prism portion 4A together with the incident surface (second incidence surface) of the total reflection type prism portion 4A, and 4C is the entrance surface 4B and the exit surface 5. ) Is a total reflection surface. In the total reflection surface 4C, a phenomenon in which light incident from the high refractive index medium to the low refractive index medium is totally reflected at an incident angle larger than the critical angle is used. In addition, light is blocked by the incident surface 4B and light from the air does not enter the total reflection surface 4C.

li1 is incident light (first incident light) incident on the incident surface 3B in the air, and lt1 is the emission surface 5 due to refraction (first refractive phenomenon) at the incident surface 3B of the incident light li1. The transmitted light (first transmitted light) and lo1 transmitted by the light beams are the outgoing light rays (first outgoing light rays) emitted into the air by the refraction (second refractive phenomenon) at the emission surface 5 of the transmitted light lt1.

li2 is incident light (second incident light) incident on the incident surface 4B in the air, and 1t2 is total reflection surface 4C due to refraction (third refractive phenomenon) at the incident surface 4B of the incident light li2. Transmitted light (second transmitted light) and lt3 transmitted through the light beam transmitted through the exit surface 5 by total reflection (total reflection phenomenon) at the total reflection surface 4C of the transmitted light lt2 (third transmitted light) and lo2 are the outgoing rays (second outgoing rays) emitted into the air by the refraction (fourth refractive phenomenon) on the outgoing surface 5 of the transmitted light lt3.

M1 is a normal of the incident surface 3B, m2 is a normal of the incident surface 4B, m3 is a normal of the total reflection surface 4C, and m4 is a normal of the exit surface 5.

Next, the operation will be described.

In Fig. 7, when the incident rays li1 and li2 reach the incidence angle a, respectively, in the air of the refractive index 1 with the Fresnel lens 1 having the refractive index n (n> 1), the incident ray li1 is By the incident surface 3B of the refractive prism portion 3A, the incident light li2 is received by the incident surface 4B of the total reflection prism portion 4A, respectively.

First, the incident light li1 received at the incident surface 3B is considered.

The incident light li1 is incident to the incidence plane 3B by forming an actual incident angle b1 with the normal line m1, and is a transmission ray lt1 and a reflected ray (not shown) which forms a refractive angle χ1 with the normal line m1. Separated by). The reflected light of the incident surface 3B becomes a loss of the Fresnel lens 1.

The transmitted light lt1 refracted by the incident surface 3B and passing through the refractive prism portion 3A reaches the emission surface 5 at an angle ψ with the normal m4. A part of the transmitted light lt1 becomes a reflected light (not shown), and the rest is emitted as the outgoing light lo1 of the exit angle f from the exit surface 5.

On the other hand, the incident light li2 received at the incident surface 4B forms an actual incident angle b2 with the normal line m2 and is incident on the incident surface 4B, and transmits to form the normal line m2 with the refractive angle χ2. Light rays lt2 and reflected light rays (not shown) are separated. The reflected light of the incident surface 4B becomes a loss of the Fresnel lens 1.

The transmitted light lt2 refracted by the incident surface 4B and transmitted through the total reflection type prism portion 4A reaches the total reflection surface 4C at an angle of 90 ° -d larger than the critical angle formed by the normal line m3. Then, the light is totally reflected by the total reflection surface 4C to become the transmitted light lt3. At this time, the total reflection surface 4C is designed so that the transmitted light lt3 and the transmitted light lt1 have a parallel relationship. Since the optical path is bent using the phenomenon of total reflection, there is no light beam emitted from the total reflection surface 4C, and there is almost no loss in the total reflection surface 4C.

The transmitted light lt3 totally reflected by the total reflection surface 4C reaches the incident surface 5 at an angle ψ with the normal m4. A part of transmitted light lt3 becomes a reflected light (not shown), and the remainder is radiate | emitted from the output surface 5 as the exit light 1o2 of the exit angle f. Since the transmitted light rays lt1 and lt3 are parallel, the outgoing light rays lo1 and lo2 are also emitted in parallel.

As described above, the Fresnel lens 1 is configured to include the hybrid prism portion 2 in which the refractive prism portion 3A and the total reflection prism portion 4A are combined. That is, the hybrid prism portion in which the refractive prism portion 3A is formed on the total reflection prism portion 4A so that the inactive light le (the diagonal portion) described in Fig. 5B is received by the incident surface 3B ( 2) is provided in a plurality of pitches of the Fresnel lens (1). The reactive light le is a part of the incident light li2 on the incident surface 4B which does not become a transmission light lt3 because it is not totally reflected by the total reflection surface 4C, for example, and the total reflection type prism portion is lost. The inactive light le is received by the refractive prism portion 3A.

When the incident angle a and the exit angle f are determined with respect to the plane-shaped exit surface 5, the angle γ formed between the exit surface 5 and the entrance surface 3B is determined according to the law of refraction, and In addition to the incidence angle (a) and the outgoing angle (f), when the tip inclination angle β formed by the total reflection surface 4C and the incidence surface 4B is determined, the angle formed by the emission surface 5 and the total reflection surface 4C is determined. (a) is determined according to the law of refraction and the law of total reflection. The leading angle beta is made optimal with respect to the incident angle so that the hybrid prism portion 2 realizes high transmittance. The angle formed between the exit surface 5 and the ineffective surface 3Z is an angle (90 ° in FIG. 7) at which the mold (lens forming frame) can be taken out when the Fresnel lens 1 is manufactured.

Hybrid prism portion 2 in which a refractive prism portion 3A exhibiting high transmittance in the case of small incident angle a is combined with a total reflection prism portion 4A exhibiting high transmittance in the case of large incident angle a. Since the Fresnel lens 1 is constituted by this, it is possible to have a good transmittance for a wide range of incident angles a.

In order to understand the effect of this Embodiment 1 concretely, the transmittance | permeability is analyzed based on FIG.

When the transmittance | permeability TX of the refractive prism part 3A and the transmittance | permeability TY of the total reflection type prism part 4A are calculated | required, it becomes as (1) and (2) formula, respectively.

<Transmittance TX of Refractive Prism 3A>

[Equation 1]

TX = [tan (α-d) / {tan (α-d) -tan (α + β)}] × {1-tan (γ) × tan (a)} × [1-{(n-1) / (n + 1)} ² ] × [1-0.5 × (PX ² + QX ² )]

only,

PX = tan [a + γ-sin ^-1 {(1 / n) × sin (a + γ)}] ÷ tan [a + γ + sin ^-1 {(1 / n) × sin (a + γ)} ]

QX = sin [a + γ-sin ⁻¹ {(1 / n) × sin (a + γ)}] ÷ sin [a + γ + sin ⁻¹ {(1 / n) × sin (a + γ)} ]to be.

<Transmittance (TY) of the total reflection type prism portion 4A>

[Equation 2]

TY = [tan (α) / {tan (α) -tan (α + β)} -tan (α-d) / {tan (α-d) -tan (α + β)}] × {1-tan (α + β) × tan (a)} × [1-{(n-1) / (n + 1)} ² ] × [1-0.5 × (PY ² + QY ² )]

only,

PY = tan [b-sin ^-1 {(1 / n) × sin (b)}] ÷ tan [b + sin ^-1 {(1 / n) × sin (b)}]

QY = sin [b-sin ^-1 {(1 / n) × sin (b)}] ÷ sin [b + sin ^-1 {(1 / n) × sin (b)}]

to be.

The transmittance (Tall) of the hybrid prism portion (2) is obtained as the sum of the transmittance (TX) and the transmittance (TY), and is expressed by the formula (3).

<Transmittance (Tall) of the hybrid prism portion 2>

[Equation 3]

Tall = TX + TY

Based on the formulas (1) to (3), Fig. 8 shows the state of change of the transmittances TX, TY and Tall with respect to the incident angle a. The calculation conditions are set to the exit angle f = 0 degrees, the tip angle angle beta = 45 degrees, and the refractive index n = 1.5.

In Fig. 8, the horizontal axis represents the incident angle a in degrees, and the vertical axis represents the transmittance in percent. In addition, the transmittance | permeability TX of the refractive prism part 3A is broken line, the transmittance | permeability TY of the total reflection type prism part 4A is broken by 1 point, and the transmittance Tall of the hybrid prism part 2 is solid line. It is indicated by.

In FIG. 8, in the area where the incident angle a is approximately 40 degrees or more, the transmittance TY of the total reflection type prism portion 4A shows a high value of 90% or more. It is to be understood that when the incident angle a becomes smaller at 40 °, the transmittance TY decreases rapidly, indicating the incident angle dependence of the total reflection type prism portion 4A.

On the other hand, in contrast to the characteristic of the transmittance TY, the transmittance TX of the refractive prism portion 3A increases as the incident angle a becomes smaller, and the incident angle dependency of the refractive prism portion 3A is increased. Is shown.

Since the hybrid prism portion 2 is composed of the refractive prism portion 3A and the total reflection prism portion 4A having these two different angles of incidence, the transmittance Tall of FIG. 8 shows, In the region of incidence angle of 40 ° or more, the value is 90% or more, and even in the region of incidence angle of 40 ° or less, since the refractive prism portion 3A compensates for the decrease in the transmittance of the total reflection prism portion 4A, the incidence angle is 0 ° or less. It is possible to realize a total reflectance of at least about 60% over the entire area of 90 degrees.

As described above, according to the first embodiment, the incident surface 4A for receiving the incident light li2 at the incident angle a at the actual incident angle b2 and refracting it as the transmitted light lt2, and the transmitted light lt2. ), The total reflection surface 4C totally reflecting as the transmitted light lt3 by receiving the light at an angle greater than the critical angle, and the emission surface 5 emitting the output light lo2 of the exit angle f by refracting the transmitted light lt3. 4A of cross-sectional total reflection type | molds, the exit surface 5 of the total reflection type prism part 4A, and a part of the invalid light ray of the total reflection type prism part 4A are predetermined predetermined angle b1. An incidence surface 3B that receives light as incident light li1 of light and refracts as transmitted light lt1 parallel to the transmitted light lt3, and an ineffective surface that intersects the exit surface 5 and the incidence surface 3B ( Since the pitch of the hybrid prism portion 2 having the cross-sectional refractive prism portion 3A of 3Z) is provided, the incident angle Effect can be obtained that it is possible to configure the Fresnel lens 1 of the high transmittance which reduce the dependencies.

In addition, it is not necessary to equip the front pitch of the Fresnel lens with the hybrid prism portion 2 shown in the first embodiment, but to be used in combination with the conventional refractive prism portion 131A or the total reflection prism portion 141A. You may also For example, the entire pitch of the Fresnel lens is divided into three pitch groups according to the size of the incident angle, and the refractive prism portion 131A is arranged in the first pitch group, and the hybrid prism portion 2 is formed in the second pitch group. The total reflection type prism portions 141A may be formed in each of the three pitch groups. As such, by constructing a Fresnel lens using the hybrid prism portion 2 and another conventional prism portion, an optimal prism portion can be selected according to the incident angle, and the incident angle dependency of the high transmittance Fresnel lens can be further reduced. The effect of the present invention can be obtained, and the effect of providing an image display device having a bright screen over the entire surface can be obtained.

Embodiment 2.

In the Fresnel lens 1 shown in Embodiment 1, there exists the ineffective light received by the ineffective surface 3Z. Since the invalid light is not emitted from the exit surface 5 at the exit angle f, the Fresnel lens 1 is lost. In the second embodiment, a method of reducing this ineffective light will be described.

FIG. 9 is a diagram for explaining the inactive light of the Fresnel lens 1 shown in Embodiment 1. FIG. Arrows indicate rays. The same or corresponding components as in Fig. 7 are denoted by the same reference numerals.

In Fig. 9, lie is an invalid light received by the invalid surface 3Z or an invalid surface 3Z-1 of the adjacent pitch, and an area E1 with an oblique line is an invalid region through which the luminous flux of the invalid light lie passes. , lte is the transmitted light of the ineffective light (lie) that is refracted at the ineffective surface (3Z) and passes through the Fresnel lens (1), loe is refracted at the emission surface (5) and air at the emission angle (f1) (≠ f) It is the outgoing light of the transmitted light lte emitted in the middle.

As can be seen from Fig. 9, the ineffective light lie is refracted at the ineffective surface 3Z to be transmitted light lte, and is refracted at the emission surface 5 to emit light loe at the exit angle f1. ) That is, the invalid light lie received through the invalid area E1 at the invalid surface 3Z is not emitted at the exit angle f, resulting in loss of the Fresnel lens 1.

Therefore, in the second embodiment, the infra-red rays are reduced by the Fresnel lens having the cross-sectional shape shown in FIG. 10 for each pitch.

Fig. 10 is an enlarged view of the cross-sectional shape in one pitch of the Fresnel lens according to the second embodiment of the present invention. Arrows indicate rays. The same or corresponding components as those in Figs. 7 and 9 are denoted by the same reference numerals.

In Fig. 10, 6 is a Fresnel lens of the second embodiment, 7 is a hybrid prism portion of the Fresnel lens 6, and like the hybrid prism portion 2 of the first embodiment, the refractive prism portion ( 3A) is provided.

8A is a total reflection prism portion for forming the hybrid prism portion 7 together with the refractive prism portion 3A, 8B is an incident surface (second incidence surface) of the total reflection prism portion 8A, and 8C is a total reflection prism The total reflection surface of the portion 8A, 9 is a planar exit surface of the hybrid prism portion 7, 3Z-1 is an invalid surface of the refractive prism portion formed in the adjacent pitch on the side of the total reflection prism portion 8A, 8B- 2 is an incidence surface of the total reflection prism portion formed in the adjacent pitch on the side of the refractive prism portion 3A. E2 is an invalid region through which the luminous flux of the inactive light lie passes, and E3 is an effective region in which the invalid region E2 is removed from the invalid region E1 (that is, a relationship of E1 = E2 + E3 is established).

The incidence surface 8B is shaped into a cross-sectional shape which cuts off a part of the ineffective surface 3Z-1 of the adjacent pitch as viewed in the direction of the ineffective light lie. Therefore, the light rays passing through the effective area E3 among the invalid rays lie passing through the invalid area E1 in FIG. 9 are not received by the invalid surface 3Z-1, and the incident light beams are incident by the incident surface 8B. It is received as (li2). As a result, it can be understood from FIG. 10 that the invalid area E1 is decreasing to the invalid area E2.

Since the cross-sectional shape of the incident surface 8B is curved to block the invalid light lie toward the invalid surface 3Z-1 of the adjacent pitch, the refractive angle at the incident surface 8B is determined by the incident light ( Each light path in li2) is different. Therefore, the total reflection surface 8C totally reflects all the transmission rays lt2 of the different refractive angles to be the transmission rays lt3, and the transmission rays refracted by the incident surface 3B of the refractive prism portion 3A ( It is formed into a curved cross-sectional shape (second incidence plane compensation shape) in which lt1 and transmitted light lt3 are parallel to each other.

Next, the operation will be described.

Since the light ray passing through the refractive prism portion 3A is the same operation as that in the first embodiment, description thereof is omitted.

The transmitted light lt2 refracted at the incident surface 8B is totally reflected at the total reflection surface 8C and directed to the output surface 9 as the transmitted light lt3. Since the shape of the total reflection surface 8C is designed so that the transmission light lt3 totally reflecting the transmission light lt2 is parallel to the transmission light lt1 from the incident surface 3B, the transmission light lt1 Similarly, transmitted light lt3 is refracted at exit surface 9 and exits as exit light lo2 of exit angle f.

In this manner, a part of the invalid light lie (effective area E3), which is to be received by the invalid surface 3Z-1 of the adjacent pitch on the total reflection type prism portion 8A side, is incident by the incident surface 8B. Since light is received as the light beam li2, the invalid region E1 can be reduced to the invalid region E2, so that the light receiving efficiency of the hybrid prism portion 7 can be increased.

The ineffective surface 3Z of the hybrid prism portion 7 is blocked by the incidence surface 8B-2 of the adjacent pitch on the refractive prism portion 3A side in the direction of the ineffective ray. The same applies to other pitches not shown, and the invalid region Ei is reduced as a whole, so that the light receiving efficiency of the entire Fresnel lens 6 can be improved.

As described above, according to the second embodiment, the incidence surface 8B for blocking the invalid surface 3Z-1 of the adjacent pitch on the side of the total reflection type prism portion 8A in the direction of the inactive light lie and incident Since the total reflection surface 8C which totally reflects all the transmitted light lt2 refracted by the surface 8B and becomes the transmitted light 1t3 parallel to the transmitted light lt1, the total reflection type prism part 8A was provided, The effect that the light receiving efficiency of the Fresnel lens 6 can be increased by reducing the invalid region E1 can be obtained.

In addition, since the Fresnel lens 6 is completed by extracting a mold (lens mold) from the cured synthetic resin, the cross-sectional shape of the total reflection type prism portion 8A enables the extraction of the mold.

In addition, the second embodiment is not limited to the Fresnel lens provided with the hybrid prism portion, but can also be applied to the Fresnel lens provided with the conventional total reflection prism portion.

Embodiment 3.

In the first embodiment, the hybrid prism portion 2 including the refractive prism portion 3A and the total reflection prism portion 4A is formed on the Fresnel lens 1, and the transmittance of FIG. Compared to the rectangular area, the characteristics in the hardened square area were slightly lower.

In the third embodiment, a method of improving the transmittance of the small square area will be described.

FIG. 11 is a diagram comparing the transmittance of the hybrid prism portion 2 shown in the first embodiment with that of the refractive prism portion 131A shown in the prior art.

As in Fig. 8, the horizontal and vertical axes in Fig. 11 are the incident angle a [unit: degree] and the transmittance [unit: percentage], respectively. The transmittance of the hybrid prism portion 2 is indicated by a solid line, and the transmittance of the refractive prism portion 131A is indicated by a dashed line.

Since the Fresnel lens 131 described in FIG. 4 has a good transmittance in the small square region, as can be seen from FIG. 11, the refractive type of the Fresnel lens 131 is refractive type compared with the transmittance of the hybrid prism portion 2 The transmittance of the prism portion 131A has a high transmittance in the incident angle region lower than the characteristic change angle a0. The characteristic change angle a0 is an incident angle at the point where the transmittances of both the hybrid prism portion and the refractive prism portion coincide.

Therefore, in the third embodiment, the refractive prism portion 131A is applied to the Fresnel lens 1 having the hybrid prism portion 2 as shown below to improve the transmittance in the small-square area. do.

Fig. 12 is an enlarged view of a cross-sectional shape in a plurality of pitches of a Fresnel lens according to Embodiment 3 of the present invention. Arrows indicate rays.

In Fig. 12, 10 is a Fresnel lens of Embodiment 3, 11A, 11B are hybrid prism portions of Fresnel lens 1 shown in Embodiment 1, and 12A, 12B are Fresnel lens 131 shown in the prior art. Is a planar exit face of the Fresnel lens 10, and m5 is a normal line of the exit face 13.

li3 to li6 are incident light beams to the prism portions 11A, 11B, 12A, and 12B, respectively, and form a normal line m5 and the incident angles a1 to a4, respectively.

The magnitude relationship of each incident angle including the characteristic change angle a0 is a1> a2≥a0> a 3> a4 (or a1> a2> a0≥a3> a4). Therefore, the shortest part of the Fresnel lens 10 exists in the upper direction (upper FIG. 12) of the prism part 11A, and the Fresnel lens 10 in the lower direction (downward in FIG. 12) of the prism part 12B. There is an optical axis.

Each pitch from the shortest end of the Fresnel lens 10 to the hybrid prism portion 11B is formed with a hybrid prism portion, and the angles from the refractive prism portion 12A to the optical axis of the Fresnel lens 10 are respectively formed. Refractive prismatic portions are formed in the pitch, respectively.

That is, in the Fresnel lens 10 of Fig. 12, the hybrid prism portions 11A and 11B are applied to the pitch at which the incident angle a≥a0 (or a> a0), and a0> incidence angle a (or a0≥a). Refractive prismatic portions 12A and 12B are applied to the resulting pitch.

The characteristic change angle a0 is used as the point of change of the cross-sectional shape of the prism portion, and the refractive prism portions 11A and 11B are changed at each pitch of the small-incidence square region smaller than (or less than) the characteristic change angle a0. At each pitch of the large-incidence angle region larger than (or greater than) the angle a0, the hybrid prism portions 12A and 12B are provided, so that the transmittance of the Fresnel lens 10 is lower than the characteristic change angle a0. The characteristic of the Fresnel lens 131 of FIG. 11 in the incident angle region becomes the characteristic of the Fresnel lens 1 of FIG. 11 in the incident angle region lower than the characteristic change angle a0, and the Fresnel lens 1 of Embodiment 1 ), The transmittance in the quenched rectangular region can be made higher.

In addition, in order to smooth the change of the transmittance near the characteristic change angle a0, you may carry out as follows.

Fig. 13 is an enlarged view of the cross-sectional shape at a plurality of pitches of the Fresnel lens according to the third embodiment of the present invention. Arrows indicate rays.

In Fig. 13, 14 is a Fresnel lens of Embodiment 3, 15C to 15H are hybrid prism portions of Fresnel lens 1 shown in Embodiment 1, respectively, and 16C to 16F are Fresnel lens shown in the prior art. The refracting prism portion 131 of 17 is a planar exit face of the Fresnel lens 14, and m6 is a normal line of the exit face 17.

1i7 to li16 are incident rays of the prism portions 15C, 15D, 15E, 16C, 15F, 15G, 16D, 15H, 16E, and 16F, respectively, and form normal lines m6 and incident angles a5 to a14, respectively. .

The magnitude relationship of each incident angle is a5> a6>. a13> a14. Therefore, the shortest part of the Fresnel lens 14 exists in the upper direction (upward in FIG. 13) of the hybrid prism part 15C, and the Fresnel lens in the lower direction (downward in FIG. 13) of the refractive prism part 16F. There is an optical axis of (14).

Hybrid prism portions are respectively formed at the pitches from the shortest end of the Fresnel lens 14 to the hybrid prism portion 15C, and the angles from the refractive prism portion 16F to the optical axis of the Fresnel lens 14 are respectively formed. Refractive prismatic portions are formed in the pitch, respectively.

In the Fresnel lens 14 of Fig. 13, at each pitch corresponding to the incident angle (characteristic change region) near the characteristic change angle a0, the number of refracting prism portions with respect to the hybrid prism portion is reduced together with the decrease of the incident angle. Increasing the ratio of (mixing ratio) to

For example, it is assumed that there is a characteristic change angle a0 between the incident angle a10 and the incident angle a11. At this time, as shown in Fig. 13, the mixing ratio of the prism portions 15C to 15E and the prism portions 16C is 3: 1, the mixing ratio of the mixture to the prism portions 15F to 15G and the prism portions 16D is 2: 1, The prism portion 15H and the prism portion 16E are formed at a mixing ratio of 1: 1 to form a prism portion having an incident angle near the characteristic change angle a0.

In this manner, at each pitch of the characteristic change region corresponding to the incident angle near the characteristic change angle a0, the hybrid prism portions 15C to 15H and the refractive prism portions 16C to 16F are mixed stepwise, and the hybrid type is used. Since the mixing ratio of the refractive prism portion to the prism portion is gradually increased with decreasing the incident angle, the Fresnel lens 14 of FIG. 13 has a characteristic change angle ( a0) It is possible to smoothly change the transmittance in the vicinity.

Of course, the assignment of the characteristic change angle a0 to the magnitude of each incident angle, the number of pitches of the characteristic change region, the mixing ratio, etc. may be determined according to the specifications of the Fresnel lens 14.

Moreover, the transmittance | permeability change of the characteristic change angle a0 vicinity can also be made smooth as follows.

Fig. 14 is an enlarged view of a cross-sectional shape in a plurality of pitches of a Fresnel lens according to Embodiment 3 of the present invention. Arrows indicate rays.

In Fig. 14, 18 is a Fresnel lens of Embodiment 3, 19A is a hybrid prism portion of Fresnel lens 18, 19B to 19D is a hybrid prism portion (mediated prism portion) of Fresnel lens 18, 19E is a refractive prism portion, 19A-1 to 19D-1 is an incident surface of the total reflection prism portion constituting the hybrid prism portions 19A to 19D, and 19A-2 to 19D-2 are hybrid prism portions 19A to 19D. ) Is the incidence surface of the refractive prism portion constituting the ss, 19E-2 is the incidence surface of the refractive prism portion 19E, 20 is the plane exit surface of the Fresnel lens 18, and m7 is the normal of the emission surface 20. .

li17 to li21 are incident light rays on the hybrid prism portions 19A to 19D and the refractive prism portion 19E, respectively, and form a normal line m7 and incident angles a15 to a19, respectively.

21B to 21D are the hybrid prism portions of the first embodiment corresponding to the incident angles a16 to a18, respectively, and have total reflection surfaces 21B-i to 21D-1 and incident surfaces 21B-2 to 21D-2, respectively. . In order to contrast with the hybrid prism parts 19B-19D of this Embodiment 3, it shows with the dashed-dotted line.

The magnitude relationship of each incidence angle is a15> a16> a17> a18> a19. Therefore, the shortest portion of the Fresnel lens 18 is in the upper direction (above in FIG. 14) of the hybrid prism portion 19A, and the Fresnel lens is in the lower direction (down in FIG. 14) of the refractive prism portion 19E. There is an optical axis of (18).

In each pitch from the shortest end of the Fresnel lens 18 to the hybrid prism portion 19A, the hybrid prism portion of the first embodiment is molded, and the refractive prism portion 19E is used to In each pitch up to the optical axis, a conventional refractive prism portion is formed.

In the Fresnel lens 18 of Fig. 14, at each pitch corresponding to the incident angle (characteristic change region) near the characteristic change angle a0, the incident surfaces 19B-1 to 1 are maintained while maintaining a predetermined angle with respect to the incident angle. The area of 19D-1) is reduced, and the area of the incident surfaces 19B-2 to 19D-2 is not maintained while maintaining a predetermined angle with respect to the incident light.

In other words, in Fig. 14, the area relation is represented by the incident surface 19B-1> incident surface 19C-1> incident surface 19D-1 and the incident surface 19B-2 <incident surface 19C-. 2) <incident surface 19D-2, and as a16-a18 and incident angle decrease, the incident surface area of the total reflection prism part is incident surface 19B-1, incident surface 19C-1, and incident surface It is insensitive to (19D-1), and the incident surface area of the refractive prism portion is not known as the incident surface 19B-2, the incident surface 19C-2, and the incident surface 19D-2.

That is, when the characteristic change angle a0 is between a16 and a18 (three pitches corresponding to a16 to a18 is the pitch of the characteristic change region), and as the incident angle decreases from a16 to a18, the incident surfaces 19B-1 to 19D The area of -1) is insignificant, and the area of the incident surfaces 19B-2 to 19D-2 is not increased.

In this manner, the hybrid prism portion 19A is gradually changed into the refractive prism portion 19E through the hybrid prism portions 19B to 19D, thereby smoothly changing the transmittance near the characteristic change angle a0. It can be done.

At this time, the predetermined angles of the incident surfaces 19B-1 to 19D-1 and the incident surfaces 19B-2 to 19D-2 with respect to the incident rays li18 to li20 are determined by the specifications of the Fresnel lens 18. Therefore, you may decide.

For example, the incidence surfaces 19B-1 to 19D-1 are attenuated in parallel with the incidence surfaces 21B-2 to 21B-D of the hybrid prism portions 21B to 21D, respectively (Fig. 14). (White arrow) and the incident surfaces 19B-2 to 19D-2 may use the incident surface of the refractive prism portion of the hybrid prism portions 21B to 21D as they are so as to increase the area.

In addition, although three hybrid prism parts 19B-19D were demonstrated here as an intermediate prism part, the number of intermediate prism parts (namely, the pitch number of a characteristic change area) is not specifically limited.

Furthermore, the area unincreased and the area unincreased of the incident surfaces 19B-1 to 19D-1 and the incident surfaces 19B-2 to 19D-2 are not particularly limited, and may be determined so as to improve the characteristics.

As described above, according to the third embodiment, the hybrid type prism portion is formed at each pitch corresponding to an incident angle greater than (or more than) the characteristic change angle a0 with the characteristic change angle a0 as a boundary. Since the refractive prisms are formed at each pitch corresponding to an angle of incidence smaller than (a0) or less, the transmittance in the incident angle region can be improved.

Further, according to the third embodiment, the mixing ratio of the refractive prism portions 16C to 16F with respect to the hybrid prism portions 15C to 15H in each pitch of the characteristic change region near the characteristic change angle a0 is determined. Since it is made to increase with decreasing incidence angle, the effect that the transmittance | permeability in a quenching angle area | region is improved and the transmittance | permeability change of the characteristic change angle a0 vicinity can be made smooth is obtained.

In addition, according to the third embodiment, in each pitch of the characteristic change region in the vicinity of the characteristic change angle a0, the area of the incident surfaces 19B-1 to 19D-1 is reduced with the decrease of the incident angle. Since the hybrid prism portions 19B to 19D without increasing the area of the surfaces 19B-2 to 19D-2 were provided, the transmittance in the quenched square region was improved, and the transmittance near the characteristic change angle a0. The effect that a change can be made smoothly is acquired.

In addition, the third embodiment may be applied to the second embodiment.

Embodiment 4

In the fourth embodiment, the optimum values of the tip inclination angle β and the emission angle f of the hybrid prism portion 2 described in the first embodiment will be described.

First, the optimum value of the tip inclination angle β formed by the incident surface 4B and the total reflection surface 4C will be described.

Fig. 15 is a diagram showing the transmittances (Tall) of the hybrid prism portion 2 when the tip angle? Is set to 45 ° (solid line), 40 ° (two dashed line), and 35 ° (dashed line), respectively. to be.

Compared to β = 45 ° (in the case of FIG. 8), the transmittance was equal (90% or more) in both β = 40 ° and 35 ° in a large incidence angle region of a = about 40 ° or more.

However, in the case of β = 45 °, the transmittance decreases below a = about 40 °. On the other hand, it can be seen from Fig. 15 that the transmittance Tall of β = 40 ° shows a high transmittance of 90% or more up to the quenched square region of a = about 35 ° as compared with the case of β = 45 °. In the case of β = 35 °, this tendency becomes more remarkable, and the high transmittance region is widened to a = about 30 °.

That is, in the quenching angle region where a = about 40 ° or less, by setting the value of the leading angle beta as small as possible, the incident angle dependence of the transmittance Tall is reduced, and the high transmittance for a wide range of incidence angles is reduced. It can be realized.

In Fig. 15, when the value of the tip angle beta is 40 ° or 35 °, a transmittance of 60% or less is achieved in a region of a = about 15 ° or less, but a = about 15 ° or less In the hybrid-type prism portion 2 having a pitch corresponding to the area of, the decrease in transmittance can be compensated for by increasing the tip angle?

That is, at the incident angle (a) = about 15 °, the transmittance of the tip inclination angle β at 40 ° and the transmittance of the tip inclination angle β at 45 ° are the same, and the incidence angle (a) is about 15 degrees. Since the high and low relations of both transmittances are reversed in the region of more than ° and the angle of incidence (a) = approximately 15 ° or less, the range of β = 40 ° and a = 0 ° to 15 ° in the range of a = 15 ° to 90 °. In the region, by setting β = 45 °, characteristics of β = 40 ° at a = 15 ° to 90 ° (two dashed lines in Fig. 15) and characteristics of β = 45 ° at a = 0 ° to 15 ° (Fig. 15) Can be realized by combining the solid line.

In addition, the decrease in transmittance may be compensated for using the method described in the third embodiment. In this case, the transmittance is obtained by combining the characteristics of the refractive prism portion (broken line in Fig. 15) with the characteristics of the hybrid prism portion having, for example, β = 40 °.

Thus, when designing the Fresnel lens 1 of Embodiment 1, it is preferable to make the tip angle angle (beta) of the hybrid-type prism part 2 as acute angle as much as possible according to the value of an incident angle. However, if the tip inclination angle β is made too small, the angle formed by the incident surface 4B and the exit surface 5 of FIG. 7 becomes obtuse when the value of the incident angle a is large, and the Fresnel lens 1 Since the mold (lens forming die) cannot be extracted at the time of manufacture, in consideration of this point, the leading edge angle β is set to an optimum value in accordance with the value of the incident angle a.

In other words, the transmittance is further improved by setting the leading angle beta of the hybrid prism portion 2 at an acute angle (minimum angle) as far as possible without impairing the manufacturability of the Fresnel lens 1. The effect that it can do is obtained. Further, in the incident angle region in which the transmittance of the tip angle β other than the sharpest angle is larger than the transmittance of the tip angle α of the sharpest angle β, the tip angle of incidence β is made larger than the sharpest angle, thereby increasing the total angle of incidence angle. The effect that high transmittance | permeability can be achieved can be acquired.

Next, the optimum value of the emission angle f of the emission light is described.

Fig. 16 is a diagram showing the transmittances (Tall) of the hybrid prism portion 2 when the emission angle f is set to 0 ° (solid line), 3 ° (two dashed line), and 5 ° (dashed line), respectively. .

From Fig. 16, the transmittance is equivalent (90% or more) in all cases of f = 0 °, 3 °, and 5 ° in a large incidence angle region of a = about 40 ° or more. In the quenched square region of a = about 40 ° or less, the transmittance Tall is improved when f = 3 ° than f = 0 ° and when f = 5 ° than f = 3 °.

Therefore, with respect to the exit angle f, the transmittance Tall can be improved by increasing the exit angle f in the quenching angle region where a = about 40 degrees or less.

Increasing the emission angle f in the small-incidence square region also provides the following effects.

17A and 17B are views showing the configuration of an image display apparatus in which a Fresnel lens 1 is applied to a screen, and FIG. 17A is a configuration view seen from the side, and FIG. Is a front view of the image display apparatus. Arrows indicate rays.

In Fig. 17A, 31 denotes a light emitter (illumination light source) that emits light, 32 a parabolic mirror (illumination light source means) having the light emitter 31 in focus, and 33 is a reflection of the parabolic mirror 32. A condenser lens (condensing optical means) for condensing light, and 34 are light valves (light modulating means) such as liquid crystal. The light valve 34 spatially modulates the light condensed by the condenser lens 33 spatially.

35 is a projection optical lens (projection optical means) for imaging the light modulated light by the light valve 34, 36 is a rear projection screen for receiving the image formed by the projection optical lens 35 from the back to display an image. to be. The screen 36 displays an image by forming an enlarged light beam into a substantially parallel light and then forming an image, and spreading the light in a wide range to widen the field of view.

In the screen 36, 37 is a Fresnel lens shown in each embodiment, and 38 is a lenticular.

The Fresnel lens 37 receives the light from the projection optical lens 36 by the operation described in each embodiment, and emits light at a predetermined emission angle through the hybrid prism portion for each pitch. In other words, the Fresnel lens 37 is used to substantially parallelize the light widened by the projection optical lens 35. The lenticular 38 diffuses after forming outgoing light from the Fresnel lens 37.

39 and 40 are optical axes, respectively. The optical axis 39 is shared by the parabolic mirror 32, the condenser lens 33, and the light valve 34. The optical axis 40 is shared by the projection optical lens 35, the Fresnel lens 37, and the lenticular 38, and is orthogonal to the exit surface of the Fresnel lens 37.

The optical axis 39 and the optical axis 40 do not intersect with each other, but have an independent relationship to achieve an optimum setting angle depending on the light valve 34. That is, the parabolic mirror 32, the condenser lens 33, and the light valve 34 which share the optical axis 39 are eccentrically arranged with respect to the optical axis 40. FIG.

The image display device in which the optical system is configured as shown in FIG. 17A has a front view as shown in FIG. 17B. The same reference numerals as in Fig. 17A denote the same components.

In Fig. 17 (b), 41 is an image display apparatus main body, 42 is an annular band of a hybrid prism portion provided in the Fresnel lens 37, and expresses the relation of the annular band 42 with respect to the screen 36. To show. Reference numeral 43 denotes a support portion of the image display device 41, and contains a parabolic mirror 32, a condenser lens 33, a light valve 34, and the like.

Except for projecting light from the eccentrically arranged light valve 34 to the screen 36, the operation is the same as that of the image display device of FIG. 2, and the operation of the Fresnel lens 37 is also described above, and thus description thereof is omitted.

An even number of image display apparatuses configured in this way is prepared and often used in a multi configuration as shown in FIG.

18 (a) to 18 (c) are diagrams for explaining a method of optimizing the exit angle of the outgoing light rays, and constitute two multi-image display apparatuses. Figure 17 (b) is a cross-sectional view of the Fresnel lens with optimized exit angle, Figure 18 (b) is a front view of the screen with the Fresnel lens of Figure 17 (b), Figure 18 (c) Fig. 18B shows a relationship with the user when the image display device of Fig. 18B is multi-configured.

In Figs. 18A to 18C, 36A and 36B are screens, 37A and 37B are Fresnel lenses, 38A and 38B are lenticulars, 40A and 40B are optical axes of Fresnel lenses 37A and 37B, respectively. And 41B are all the image display apparatuses of FIGS. 17A and 17B, 42A and 42B are ring bands of Fresnel lenses 37A and 37B, and 43A and 43B are respectively the image display apparatuses 41A and 41B. It is a supporting part. The annular bands 42A and 42B intersect only one side closest to the optical axes 40A and 40B at four sides of the Fresnel lenses 37A and 37B cut out in a rectangular shape, respectively (optical axis 40A and 40B). It is a ring (boundary ring) (it does not need to include an optical axis on one side). The annular bands 42A and 42B are determined from the viewing characteristics, the transmittance and the like of the screens 36A and 36B.

In the image display apparatus shown in Figs. 18A to 18C, the support portion 43A is turned upward, and the support portion 43B is turned downward by reversing the top and bottom of one image display apparatus 41A. The upper portion of the screen 36B of the image display device 41B and the upper portion of the screen 36A of the image display device 41A are formed in a multi configuration. In this way, since one image is divided and provided to the image display devices 41A and 41B, respectively, and displayed as one integrated image by the two screens 36A and 36B, a larger image can be displayed. have.

44 denotes a user of the image display devices 41A and 41B, and 45 denotes a viewing angle of the user 44. Further, lo3A to lo7A and 1o3B to 1o7B are the emitted light beams emitted from the respective pitches of the Fresnel lenses 37A and 37B, respectively. The outgoing rays lo3A to lo7A are arranged in an order close to the optical axis 40A, and the outgoing rays lo3B to lo7B are arranged in an order close to the optical axis 40B. The output light closer to the optical axes 40A and 40B, that is, the light emitted from the inner side (the optical axes 40A and 40B side) of the annular bands 42A and 42B, is set to have a larger emission angle.

As shown in Fig. 18C, the user 44 visually recognizes the integrated image of the two image display apparatuses 41A and 41B that are multi-configured at the viewing angle 45. At this time, in the image display apparatus using a normal Fresnel lens, all the outgoing rays of the Fresnel lens become parallel to the optical axis. On the other hand, the lenticulars 38A and 38B have a viewing characteristic, and the direction of the chief ray of each outgoing ray is the brightest, and becomes darker as it is inclined with respect to the chief ray. Therefore, in the vicinity of the supporting portions 43A and 43B where the viewing angle becomes large, since the chief ray emitted in the normal direction with respect to the screen is viewed in the oblique direction along the viewing angle, the brightness usually decreases.

However, in the Fresnel lenses 37A and 37B of the fourth embodiment, the light emitted from the pitch close to the optical axes 40A and 40B, that is, the pitch of which the incident angle is small (the maximum exit angle is the exit light lo3A and lo3B) is obtained. The exit angle is set large. That is, since the chief ray of the outgoing light is directed in the direction of the user 44, the attenuation action according to the viewing characteristics of the lenticulars 38A and 38B can be reduced. In addition, this relatively compensates for the transmittance in the vicinity of the supporting portions 43A and 43B, and at the same time, it is possible to optimize the exit angle so that each of the outgoing rays lo3A to lo7A and lo3B to lo7B faces the viewing angle 45.

In this manner, the Fresnel lenses 37A and 37B can obtain an effect that a bright image can be provided to the user even when applied to an image display apparatus having a multi-configuration.

As shown in Fig. 19, when the four image display devices 41A, 41B, 41C, and 41D are combined and used as an image display device having a multi configuration, each image display device 41A, 41B, 41C, 41D is used. The emission angle f is set larger on the inner side (the optical axes 40A, 40B, 40C, 40D side) than the annular bands 42A, 42B, 42C, 42D. That is, as shown in Figs. 18A to 18C, the main beams of the emitted light are directed in the direction of the user 44A, and the outside of the annular bands 42A, 42B, 42C, 42D (screens 36A, 36B, On the lens outer peripheral side of the Fresnel lens constituting 36C, 36D), the outgoing rays are set to be parallel to the optical axes 40A, 40B, 40C, 40D. As in the case of Figs. 18A to 18C, the annular bands 42A, 42B, 42C, and 42D each have four rectangular shapes of Fresnel lenses constituting the screens 36A, 36B, 36C, and 36D, respectively. It is a ring band (boundary band band) which crosses only one side closest to the optical axis 40A, 40B, 40C, 40D on a side, and can be determined from the visual field characteristic of a screen, transmittance | permeability, etc.

In the vicinity of the boundary between the screens 36A, 36B, 36C, and 36D of each of the image display apparatuses 41A, 41B, 41C, and 41D, which are configured in a multiplicity, it is necessary to set the main rays of the emitted light to be parallel. When the chief rays are in parallel, even if the screen is viewed from an inclination like the user 44B, the attenuation rate due to the lenticular field of view characteristic according to the viewing angle at the inclination of the boundary near the boundary between the screens on both sides across the boundary is shown. Since they all become the same, a uniform image can be obtained even when viewed at an inclination without causing variation in luminance at the screen boundary. In addition, since the exit angle f is set larger inside the annular bands 42A, 42B, 42C, and 42D, the luminance improvement inside the darkened annular bands 42A, 42B, 42C, and 42D becomes possible. Luminance uniformity in the screen can be improved.

As shown above, the outgoing light is set in parallel at the optical axis side pitch of the boundary ring band that intersects only one side closest to the optical axis of the Fresnel lens at four sides of the Fresnel lens cut out in a rectangular shape to fit the screen. In addition, by setting the exit angle of the outgoing light large at the lens outer peripheral side pitch of the boundary ring band, the luminance uniformity in the screen when the Fresnel lens is applied to the screen of the image display device of the multi configuration can be improved. You can get the effect.

Also, as is clear from FIGS. 17A and 17B, 18A to 18C, and 19, the Fresnel lens described in each of the above-described embodiments, and a lenticular to image and diffuse light The screen may be formed by using optical image diffusing means such as a light source. Since the projection light of a wide field of view can be received at a high transmittance without being excessively dependent on the angle of incidence, a large screen image is displayed at a higher brightness under a predetermined depth specification. The effect of being able to construct a screen that can be done can be obtained.

When the Fresnel lens described in each of the above embodiments is applied to the screen, the lenticular may be integrally formed on the exit surface of the Fresnel lens. By doing in this way, the effect that the screen which reduced the number of parts can be comprised can be acquired.

Embodiment 5.

20 is a diagram showing the overall configuration of a rear projection type image display device according to a fifth embodiment of the present invention.

The image display device of FIG. 20 includes a screen 53 having a Fresnel lens 51 and a diffusion plate 52 and an image light source 54, and displays the image light projected from the image light source 54. ) Is a device to display. The screen 53 is a screen having an aspect ratio of 4: 3 and a size of 50 inches.

21 is a view of the image display device of FIG. 20 seen from the side.

The screen 53 is arranged such that the horizontal distance with the image light source 54 is 450 mm, and the distance between the lower end of the screen 53 and the vertical direction of the image light source 54 is 200 mm.

The diffusion plate 52 has a lenticular lens or the like, and is a light diffusion means that serves to diffuse the image light in a predetermined range.

The Fresnel lens 51 is a lens in which minute unit prism portions are arranged side by side, and are circular type Fresnel lenses in which unit prism portions are arranged concentrically. The image light source 54 is disposed on the waterline extending from the center of the concentric circle of the Fresnel lens 51, and the use as the Fresnel lens 51 is a part deviated from the center of the Fresnel lens 51 (Fig. 20).

22 is a diagram showing the cross-sectional shape of the Fresnel lens 51. FIG.

From the Fresnel center side toward the Fresnel circumferential side, the Fresnel lens 51 can be divided into three regions of the regions A1, A2, and A3 according to their cross-sectional shape.

First, the area | region A2 is demonstrated as a basic form.

The unit prism portion (hybrid prism portion) in the area A2 has an incident surface (second incidence surface) 51A and a total reflection surface 51B, and the total reflection type prism portion U1 having a right angle of 40 °. And a refractive prism portion U2 having an incidence surface (first incidence surface) 51C and an ineffective surface 51D. This unit prism part shows between the curve T which is the intersection of the invalid surface 51D of the adjacent unit prism part, and the total reflection surface 51B, and the curve T of the side, and the pitch P of the unit prism part = It is 0.1mm. In addition, this pitch P = 0.1 mm has the same value of the unit prism part of other area | region A2 and A3.

23A to 23C are diagrams for explaining the total reflection prism portion U1 and the refractive prism portion U2.

Fig. 23A shows a Fresnel lens (a conventional Fresnel lens having a refractive prism portion) in which only a unit prism portion having a shape equivalent to that of the refractive prism portion U2 is formed. As described above, the light beam Rlin projected onto the incident surface 51C is refracted by the incident surface 51C and is emitted in a desired direction. However, the light beam R2in projected on the ineffective surface 51D is reflected or refracted by the ineffective surface 51D and becomes stray light.

Fig. 23B shows a Fresnel lens (a conventional Fresnel lens having a total reflection prism portion) in which only a unit prism portion having a shape equivalent to that of the total reflection prism portion U1 is formed. As described above, the light beam R3in is totally reflected by the total reflection surface 51B and is emitted in the desired direction among the light beams projected on the incident surface 51A. However, the remaining light beam R4in cannot reach the total reflection surface 51B and becomes stray light.

Fig. 23C shows a Fresnel lens 51 in the fifth embodiment. In the Fresnel lens 51, the Fresnel lens shown in Figs. 23A and 23B formed only of the total reflection type prism portion U1 and the refractive type prism portion U2 has a desired direction (in the case of the fifth embodiment, the Fresnel lens The shape which combined the total reflection type prism part U1 and the refractive type prism part U2 so that a part of the light beam which cannot be emitted in the direction which is substantially perpendicular to (51) in a desired direction may be used as a unit prism part. Doing.

Specifically, the refracting prism portion U2 is disposed at the portion where the light beam R4in that does not reach the total reflection surface 51B is projected on the total reflection type prism portion U1. Therefore, the Fresnel lens 51 deflects a part of the light beam R4in and deflects the light in the desired direction.

In other respects, the arrangement is a total reflection type prism portion U1 of the adjacent pitch on the Fresnel center side on the optical path of the light beam R2in projected on the ineffective surface 51D in the refractive prism portion U2. It can also be seen that is arranged. Therefore, the Fresnel lens 51 totally reflects a part of the light beam R2in and deflects the light in the desired direction. In other words, each is disposed at a position that can compensate for the disadvantages of each of the total reflection type prism portion U1 and the refractive type prism portion U2.

In addition, in one pitch of the area A2 in Fig. 22, the surface extending the incident surface 51C passes through the curve T on the peripheral side, and the surface extending the incident surface 51A is the Fresnel center side. The total reflection prism portion U1 and the refractive prism portion U2 are disposed so as to pass through the curve T of. The reason for this arrangement is attributable to the manufacturing method of the Fresnel lens 51. Next, the manufacturing method of the Fresnel lens 51 is demonstrated.

Fresnel lens 51 is manufactured by resin molding. Therefore, it is necessary to manufacture the lens shaping | molding die which formed the inverted shape.

24A to 24C and 25A to 25C are views for explaining the characteristics of the lens shaping mold used when manufacturing the Fresnel lens 51, respectively. 24A to 24C show a case of cutting a portion corresponding to the total reflection prism portion U1, and FIGS. 25A to 25C show a case of cutting a portion corresponding to the refractive prism portion U2. .

In FIGS. 24A to 24C and 25A to 25C, reference numeral C denotes a lens molding frame, and reference numeral B denotes a byte for cutting the lens molding frame C such as a diamond bite.

The lens forming frame C is produced by cutting by the bite B, but the lens corresponding to the surface (incident surface 51A, total reflection surface 51B, incident surface 51C) through which image light passes. It is necessary to cut the surface of the mold not with the cutting edge (slope portion), but with the tip (corner) of the bite B (or chip) so that no string, unevenness or the like during cutting occurs. The pitch of the Fresnel lens is about 1 mm (0.1 mm in the Fresnel lens 51), whereas the chip of the bite B has a size of 2 to 3 mm.

Therefore, if the following cutting conditions (A) and (B) are not satisfied, the lens forming mold corresponding to the shape of the unit prism portion cannot be cut.

Cutting condition (A)

The surface extending the incidence surface 51C passes through the curve T (FIG. 25B) or the light exit side than the curve T (FIG. 25C).

Cutting condition (B)

The surface on which the incident surface 51A extends passes through the curve T (FIG. 24B) or the light exit side rather than the curve T (FIG. 24C).

The Fresnel lens 51 according to the fifth embodiment is a portion corresponding to the total reflection prism portion U1 and the refractive prism portion U2 using a bite B (chip) having a right angle of 40 °. Is cutting.

<Manufacture of Lens Molding Mold>

Fig. 26 is a flow chart showing a lens forming frame manufacturing method according to the fifth embodiment of the present invention. 27A to 27D and 28A to 28D are views showing the progress of cutting of the lens forming mold C by the bite B, and FIGS. 27A to 27D are views of the refractive prism portion U2. 28A to 28D show the total reflection prism U1 as the main prism.

In Fig. 26, the pitch number n = 1 is set in step ST1 (the cutting start pitch number setting step). When the process shifts from step ST1 to step ST2 (main unit prism part cutting step), first, the cutting operation of the main unit prism part in the first pitch (cutting target pitch) P1 is performed by the bite B. Lose. The working situation at this time is shown in FIG. 27A or 28A, and the bite B cuts the main unit prism portion with respect to the lens shaping mold C. As shown in FIG.

When the cutting of the main unit prism portion of the first pitch P1 is completed in step ST2, the flow advances to step ST3 (sub-unit prism portion cutting step), and the first pitch (pitch to be cut) P1. The cutting operation of the subunit prism portion of is started. As described with reference to Figs. 25A to 25C and 26A to 26C, when cutting the sub-prism portion into the lens forming mold C by the bite B, the cutting condition A and the cutting condition B are changed. Do so to satisfy. The working situation at this time is shown in Figs. 27B and 28B.

For example, as shown in Fig. 27B, when the total reflection prism portion is cut from the first pitch P1 in which the refractive prism portion is cut as the main unit prism portion, the first pitch ( The extended surface SA1 of the total reflection surface 51A passes through the curve T1 on the Fresnel center side of P1, or the extended surface SA1 of the incident surface 51A than the curve T1 on the Fresnel center side. ) Is cut to the exit side.

Similarly, in Fig. 28B, when cutting the refractive prism portion with respect to the first pitch P1 in which the total reflection type prism portion is cut as the main unit prism portion, the prep of the first pitch P1 is changed according to the cutting condition (A). The extension surface SC1 of the incidence surface 51C passes through the curve T0 on the nel periphery side, or the extension surface SC1 of the incidence surface 51C extends on the emission side than the curve T0 on the fresnel peripheral side. To be cut.

When the cutting operation for the first pitch P1 of steps ST2 and ST3 is completed, the process shifts to step ST4 (pitch number transition step), where the value of the pitch number n is incremented and n = 2. Becomes In the next step ST5 (cutting determination step), the total pitch number Nmax of the lens forming mold C and the pitch number n are compared, and in the case of n ≦ Nmax, that is, the pitch to be cut still remains. In this case (N0 at step ST5), the process returns to step ST2, and the cutting operation (Figs. 27C, 28C) of the main unit prism portion in the second pitch (pitch of the cutting target) P2 is performed.

Subsequently, at step ST3, the cutting operation (Figs. 27D and 28D) of the subunit prism portion in the second pitch (cutting target pitch) P2 is performed. Of course, similarly to the case of the first pitch P1, the cutting operation on the second pitch P2 is performed in step ST3 so as to satisfy the cutting condition A or the cutting condition B. FIG.

For example, in FIG. 27D, when cutting the total reflection type prism portion with respect to the second pitch P2 in which the refractive prism portion is cut as the main prism portion, the second pitch P2 is determined according to the cutting condition (B). The extended surface SA2 of the total reflection surface 51A passes through the curve T2 on the Fresnel center side, or the extended surface SA1 of the incident surface 51A exits from the curve T2 on the Fresnel center side. It is cut to the side.

The same applies to the case of Fig. 28B as well, when cutting the refractive prism portion with respect to the second pitch P2 in which the total reflection prism portion is cut as the main prism portion, according to the cutting condition A. The extension surface SC2 of the incidence surface 51C passes through the curve T1 on the Fresnel circumferential side, or the extension surface SC2 of the incidence surface 51C exits than the curve T1 on the Fresnel circumference side. It is cut to the side.

Thereafter, in step ST4, the pitch number is incremented by one, and the cutting operation is repeated from n = 3 to n = Nmax, and the Fresnel lens is performed by step ST5 at the time when n = Nmax + 1. Cutting of 51 is completed, and manufacture of lens shaping | molding die C is completed. Thus, in Embodiment 5, manufacture of a lens shaping | molding die can be performed easily using a normal cutting tool. In addition, since the cutting of the main prism portion and the sub-prism portion is progressed sequentially by one pitch, the manufacturing precision of the lens forming mold C can be improved, and further, the Fresnel lens 51 is manufactured with high precision, It can provide optical performance as designed.

Incidentally, in Figs. 27A to 27D and 28A to 28D, the advancing direction of the cutting operation is moved from the Fresnel center side to the Fresnel peripheral side, but the advancing direction of the cutting operation is not particularly limited, and the Fresnel peripheral edge is not particularly limited. It may be reversed from the side to the Fresnel center side.

The resin molding mold C is poured into the lens molding mold C thus prepared, and the fresnel lens 51 is completed by removing the lens molding mold C from the cured resin. The Fresnel lens 51 is a large lens sheet of 50 inches, and since the image light is projected in the inclined direction, the difference in the incident angle of the image light increases depending on the incident position. When the total reflection type prism portion U1 has a large incident angle, the luminous flux emitted in a desired direction increases. On the contrary, the refractive type prism portion U2 increases the luminous flux that emits a desired direction when the incident angle is small. Therefore, the total reflection prism portion U1 is suitable for the position of incidence with a large incident angle, and the refractive prism portion U2 is suitable for the position of incidence with a small incident angle.

Thus, as shown in Fig. 22, in the region A1 (the Fresnel center side) which is the side closer to the image light source 54 of the Fresnel lens 51 in the fifth embodiment, the refractive prism portion With U2 as the main unit prism portion and total reflection type prism portion U1 as the subunit prism portion, the ratio occupied by the total reflection type prism portion U1 is smaller than the ratio occupied by the refractive type prism portion U2.

On the other hand, in the area A3 (the Fresnel peripheral side) which is far from the image light source 54, the total reflection prism portion U1 is the main unit prism portion and the refracting prism portion U2 is the subunit prism portion. The ratio occupied by the refractive prism portion U2 is smaller than the proportion occupied by the total reflection prism portion U1.

Here, in order to change the ratio which the total reflection type prism part U1 and the refractive type prism part U2 occupy, the cutting depth of the bite B which cuts the lens shaping | molding die C is changed according to position, The heights of the sand-shaped prism portion U1 and the refractive prism portion U2 were changed.

FIG. 29 shows the ratio from the center of the Fresnel in the Fresnel lens 51 to the ratio of the total reflection type prism portion U1 and the refractive type prism portion U2. 29 also shows a line L1 showing the transmittance when only the total reflection type prism portion U1 is formed, and a line L2 showing the transmittance when only the refractive type prism portion U2 is formed. It is shown. In addition, the measurement of this transmittance | permeability is made into the same arrangement | positioning as the image display apparatus of the rear projection type in Embodiment 5, and is performed using a white light source. In Fig. 29, the horizontal axis represents radius (unit mm), the left vertical axis represents transmittance (unit%), and the right axis vertical axis represents lens ratio.

In Fig. 29, the line L1 and the line L2 intersect at a position of 250 mm in radius, and the refractive prism portion U2 is more than the total reflection prism portion U1 in the area of 250 mm or less with the radius 250 mm as a boundary. It can be seen that the effect of the total reflection type prism portion U1 is high on the contrary, in the region having a high (L1 <L2) radius of 250 mm or more. In the Fresnel lens 51, the ratio which the total reflection type prism part U1 and the refractive type prism part U2 occupies is aimed at this radius of 250 mm.

In Fig. 29, the ratio occupied by the total reflection type prism portion U1 or the refractive type prism portion U2 represents the height of the total reflection type prism portion U1 or the refractive type prism portion U2 in the area A2. It was set to 1 and the ratio with respect to this was shown as a lens ratio. In FIG. 29, the lens ratio of the total reflection prism portion U1 is shown in the diagram L3, and the lens ratio of the refractive prism portion U2 is shown in the curve L4. In addition, although the range of the radius 200-1078mm is actually used as the Fresnel lens 51, in FIG. 29, the range of the radius 100-500mm which shows the difference of each line clearly is shown.

As can be seen from Fig. 29, the total reflection type prism portion U1 does not exist in the portion below the radius of 200 mm, and the ratio occupies at the radius of 200 mm begins to increase, and the lens ratio is 1 (area at 250 mm). The same as the ratio in (A2)) and the lens ratio 1 is maintained at a radius of 250 mm or more.

On the other hand, the refraction-type prism portion U2 has a lens ratio of 1 (the same as the ratio in the area A2) when the radius is 300 mm or less, and gradually decreases the lens ratio when the radius is 300 mm or more.

Since the Fresnel lens 51 changes the ratio which the total reflection type prism part U1 and the refractive type prism part U2 occupy in this way, up to 250 mm radius becomes the shape of area | region A1, and the radius 250- 300 mm is a shape of the area A2, and a radius of 300 mm or more is a shape of the area A3.

In addition, although the lens ratio may be gradually reduced in the refractive prism portion U2 at a radius of 250 mm or more, the area A2 may be omitted, but in the fifth embodiment, the change is smooth and the luminance difference of the displayed image is reduced. In order to reduce, the area | region A2 is provided.

<Comparison of transmittances>

The Fresnel lens 51 which concerns on this Embodiment 5 was produced, and it confirmed that the transmittance | permeability improved compared with the conventional thing.

Here, according to the method described in Japanese Patent Laid-Open No. 61-52601, the Fresnel lens 110 according to the prior art of Fig. 6 and the Fresnel lens 51 of the fifth embodiment can be compared. Both were produced so that the specification other than shape might be the same.

30 is a diagram showing the configuration of a Fresnel lens 110 according to the prior art. The basic shape of the total reflection type prism portion and the refraction type prism portion was the same shape as the Fresnel lens 51, and the pitch P was also the same as 0.1 mm.

FIG. 31 is a diagram showing the lens ratio of the total reflection prism portion in the Fresnel lens 110 in FIG. 30 by a line L5. The Fresnel lens 110 is a form in which the total reflection type prism portion U1 and the refractive type prism portion U2 exist independently, and are the lenses of the total reflection type prism portion U1 and the refractive type prism portion U2. The ratio is shown outside the graph egg on the right side of FIG. In addition, the lines L1 and L2 in FIG. 31 are the same as those in FIG.

32 is a diagram showing the transmittances of the Fresnel lens 51 of the fifth embodiment and the Fresnel lens 110 according to the prior art, respectively. In FIG. 32, the transmittance of the Fresnel lens 51 is shown by the line L6, and the transmittance of the Fresnel lens 110 is shown by the line L7. 29 and 31, diagrams L1 and L2 are also shown. Compared with any of L1, L2, and L7, the line L6 showed a high transmittance in almost all regions, and it was confirmed that the transmittance of the Fresnel lens 51 according to the fifth embodiment was high.

As described above, according to the fifth embodiment, the proportions occupied by the total reflection type prism portion U1 and the refractive type prism portion U2 are changed, and these are combined as one unit prism portion. It is possible to obtain a Fresnel lens 51 having a high overall transmittance.

In addition, according to the fifth embodiment, since the lens forming mold C can be cut using one bite B, the production of the Fresnel lens can be simplified.

Therefore, the screen 53 using the Fresnel lens 51 also has a high transmittance, which makes it possible to make the display of the rear projection type projection display device brighter and at a lower cost.

Not limited to the above description, the fifth embodiment can be variously modified or changed.

<Modification 1>

In the above description, although the Fresnel lens 51 has shown the example provided with three types of area | region A1, A2, and A3, this Embodiment 5 is not limited to this, You may change these combination suitably. . For example, only area | region A1 and area | region A2 may be sufficient, and any area | region of area | region A1, A2, A3 may be sufficient.

<Modification 2>

In the above description, although the surface on the light exit side of the Fresnel lens 51 has shown the flat example, this Embodiment 5 is not limited to this, You may add another Fresnel lens shape, and diffusion means, such as a fine unevenness | corrugation, may be used. You may install it.

<Modification 3>

In the above description, the image light source 54 shows an example in which the image light is directly projected on the Fresnel lens 51. However, the fifth embodiment is not limited to this, for example, from the image light source 54. After changing the optical path by reflecting or refracting the image light, optical means such as a mirror or a prism projected on the Fresnel lens 51 may be provided.

Embodiment 6.

When the lens shaping mold is manufactured by the lens shaping mold manufacturing method shown in the fifth embodiment, deformation occurs in the lens shaping mold due to the malleability of the metal. Naturally, the deformation of the lens shaping mold becomes the deformation of the optical surface of the Fresnel lens, leading to the deterioration of its optical performance.

In the sixth embodiment, the occurrence of deformation of the lens forming mold will be described first, and the lens forming mold manufacturing method capable of ensuring the optical performance of the Fresnel lens by avoiding the occurrence of the deformation will be described. In addition, in the Fresnel lens using the intermediate prism portion (or the method of changing the lens ratio described in the fifth embodiment) near the characteristic change angle described in the third embodiment, even if the deformation of the lens forming frame affects the optical performance, Reference is also made to a method of manufacturing a lens forming mold that can be realized.

33A to 33F are views for explaining the deformation occurring in the manufacturing process of the lens shaping mold, and are based on the method for manufacturing the lens shaping mold described in the fifth embodiment. The same reference numerals as those in FIG. 28 have a corresponding configuration. 33A to 33F, the cutting operation progresses for each pitch from the center of the Fresnel to the Fresnel circumference, and after cutting the forming frame (inverted shape) of the total reflection type prism portion as the main unit prism portion, the refraction as the subunit prism portion is shown. It is a process of cutting the shaping | molding die (inverted shape) of a mold prism part.

First, the total reflection type prism portion forming die of the first pitch P1 is cut into the bite B with respect to the lens forming die C (FIG. 33A), and then the refractive type of the first pitch P1 is continued. The prism portion is cut into the lens forming mold C with a bite B (Fig. 33B). Thereby, the cutting of the hybrid prism portion forming die in the first pitch P1 is completed. The cutting conditions at this time are as described in the fifth embodiment.

Next, the process shifts to the cutting operation of the second pitch P2. The state in which the total reflection type prism portion forming mold of the second pitch P2 is cut into the lens forming mold C is as shown in Fig. 33C. At this time, the total reflection surface of the total reflection type prism portion forming mold of the first pitch P1 is shown. And a sharp end portion of the sharp curve T1 occurs between the incident surface of the total reflection type prism portion forming frame of the second pitch P2.

As shown in Fig. 33D, the bite B is pressed against the tip of the curve T1, and the refracting prism portion forming mold of the second pitch P2 is cut. The deformation | transformation of the lens shaping | molding die C described at the head of this Embodiment 6 arises when cutting the refractive prism part shaping | molding die of this 2nd pitch P2.

That is, since the width | variety of the front-end | tip part of curve T1 becomes narrower at the vertex, the intensity | strength is also weakened accordingly. Accordingly, when the bite B is pressed against the sharp curve T end as shown in Fig. 33E, the pressing force generated in the direction of the first pitch P1 from the second pitch P2 is the apex of the tip of the curve T1. The closer to is, the larger the function becomes, and the malleability of the metal causes deformation of the lens shaping mold C in the dotted circle NG of Fig. 33E.

33F is an enlarged view of the inside of the dotted line NG in FIG. 33E.

In Fig. 33F, the peak of the tip of the curve T1 is pushed in the direction of the first pitch P1 from the second pitch P2 by the bite B, and the cutting of the total reflection surface of the first pitch P1 is performed. Deformation occurs in shape. For example, when the cutting shape of the total reflection surface according to the design is represented by a two-point broken line Real, the deformation of the lens forming mold C is represented by a curved line (curved surface) Err of the one-point broken line.

Hereinafter, since the same cutting operation is repeated even after the third pitch P3 (not shown), when the refractive prism portion of the n + 1 pitch Pn + 1 (n is a natural number) is cut, Deformation occurs at the leading end of the curve Tn between the n pitch Pn and the n + 1th pitch Pn + 1 during cutting. The Fresnel lens according to the lens forming frame (C) manufactured as described above deforms the shape of the total reflection surface as much as the degree of deformation, and the optical performance thereof is deteriorated. If it occurs randomly at, it leads to an unnatural discontinuity in the emitted light intensity.

On the basis of the occurrence of deformation in the lens forming mold C, the manufacturing method of the lens forming mold of the fifth embodiment is improved as follows.

FIG. 34 is a flowchart showing a method for manufacturing a lens molding frame according to Embodiment 6 of the present invention, wherein the same reference numerals as those in FIG. 26 of Embodiment 5 indicate corresponding steps. 35A to 35F are diagrams showing the state of the lens shaping mold C being cut in accordance with the lens shaping mold manufacturing method of FIG. 34, and the same configuration as those in FIG. 28 and FIGS. 33A to 33F. I add a sign. 33A to 33F, in FIGS. 35A to 35F, the cutting operation proceeds from the center of the Fresnel to the Fresnel circumference in the order of the total reflection type prism portion forming mold and the refractive type prism portion forming mold.

34, the pitch number n = 1 is set in step ST1, and the total reflection type prism part shaping of the first pitch P1 is made in step ST2 (primary prism part cutting step). The mold is cut into bites B (FIG. 35A).

The feature of the sixth embodiment is that step ST6 (pitch margin setting step) is set after step ST2. In this step ST6, the pitch margin DELTA P1 in the first pitch P1 is set. Here, the pitch margin ΔPn + 1 in the n + 1th pitch Pn + 1 during the cutting operation is the refracting prism portion forming mold (subunit prism) of the n + 1th pitch Pn + 1. Is a distance in the cutting progress direction from the portion where the vertex of the bite B first contacts the lens shaping mold C to the boundary between the adjacent nth pitches Pn of the cut.

If the pitch margin DELTA P1 is set at step ST6, the process proceeds to step ST7 (subunit prism part cutting step), and the cutting condition A or the cutting condition B and the pitch margin DELTA P1 are set. According to (? 0), the refracting prism portion forming die of the first pitch P1 is cut. The cutting operation state at this step ST7 is as shown in Fig. 35B. As can be seen in comparison with Fig. 33B, the refracting prism portion forming mold is moved and cut from the center of the Fresnel by the pitch margin? P1 in the direction of the Fresnel circumference.

When the pitch number n is 2 in step ST4, and the process moves from step ST5 to step ST2, it moves to the cutting operation of the second pitch P2, and forms the total reflection type prism part of step ST2. Cutting is performed. The state at this time is the same as in Fig. 35C, and similarly to Fig. 33C, a sharp curve T1 tip is formed between the first pitch P1 and the second pitch P2.

In step ST6, the pitch margin DELTA P2 (≥ 0) of the second pitch P2 is set (FIG. 35D), and in step ST7, the refractive prism part forming mold is formed in accordance with the pitch margin DELTA P2. Cutting is performed (Fig. 35E). It is at this time that the reason for setting the pitch margin of step ST6 becomes clear.

That is, as can be seen in Figs. 35D and 35E, the refraction-type prism part forming frame of the second pitch P2 is shifted from the center of the Fresnel to the peripheral edge of the Fresnel by a small pitch pitch? P2. The strength of the tip of the curve T1 in the dotted line OK in Fig. 35E (shown in Fig. 35F) in Fig. 35E is also stronger, and from the second pitch P2 as shown in Figs. 33D and 33E. Even if the pressing force of the bite B acts in the direction of the first pitch P1, the strength enough to oppose the pressing force can be provided at the tip of the curve T1.

Thereafter, the refractive prism portion of each pitch Pn is cut with the pitch margin ΔPn until the completion of the cutting operation is determined in step ST5. As described above, according to the manufacturing method of the lens forming mold of FIG. 34, since no deformation occurs in the lens forming mold C, the total reflection surface of each pitch of the Fresnel lens manufactured by the lens forming mold C is adjusted according to the design. The shape can be maintained and the optical performance of the Fresnel lens can be guaranteed.

To supplement the description, the pitch margin ΔPn in the arbitrary n-th pitch Pn may be a constant minute value or may be set to another minute value.

In each of the above figures, the total reflection type prism portion and the refractive type prism portion are each made of a main prism portion and a subsidiary prism portion, respectively. It is possible to apply also to the case where the refracting prism portion and the total reflection type prism portion are cut into the Fresnel center from the Fresnel circumference, respectively, as the main prism portion and the sub-prismatic portion.

Next, in the Fresnel lens provided with the intermediate prism portion (Embodiment 3), a method of suppressing the influence of deformation by producing a dummy prism portion molding frame in the lens molding frame will be described.

Figures 36 (a) and (b) are views for explaining the configuration and operation of the Fresnel lens without the dummy prism portion, and Figures 37 (a) and (b) show the Fresnel with dummy prism portion It is a figure for demonstrating the structure and operation | movement of a lens.

36 (a) and 37 (a) show enlarged cross-sectional shapes of the Fresnel lens of FIGS. 36 (a) and 37 (a), respectively, and FIGS. 36 (b), In Fig. 37B, the height Rfl (solid line) of the total reflection type prism portion in Figs. 36A and 37A and the height Rfr (one dashed line) of the refracting prism portion are each pitch. Each is shown. The height refers to the cutting depth of the prism portion with respect to the optical axis direction of the Fresnel lens. In Figures 36 (a) and (b), and Figures 37 (a) and (b), the bottom of the page is the Fresnel center, and the top of the page is the Fresnel circumference.

36 (a) and 37 (a), 70 denotes a Fresnel lens, Ph-1, Ph,. , Pi-4 to Pi + 1,... , Pj-1 to Pj + 1 are the respective pitches of the Fresnel lens 70, respectively.

71h-1, 71h,... , 7li-4 to 7li + 1,... , 71j-1 to 71j + 1 are total reflection prism portions provided at respective pitches Phh-1 to Pj + 1, 72h-1, 72h,... , 72i-4 to 72i are refractive prism portions provided at each pitch Ph-1 to Pi, respectively, 73 is an exit surface of the Fresnel lens 70.

Incidentally, only in Fig. 37A, 72i + 1,... , 72j-1, 72j are refractive prism portions (dummy prism portions) provided at each pitch Pi + 1, ..., Pj-1, Pj, respectively. The refractive prism portions 72i + 1 to 72j have a height Rfr as compared to the height Rfl of the total reflection type prism portions 71i + 1 to 71j, as shown in Fig. 37B. Is set low (Rfr = 0) and is not involved in the reception of incident light.

36A and 37A, since the Fresnel lens 70 is manufactured by a lens shaping mold made without a pitch margin, by cutting the refractive prism portions 72h-1 to 72i. It can be seen that the deformation (in the dotted line source NG) is generated on the total reflection surface of the total reflection type prism portions 71h-1 to 7li-1 (in the drawing, the shape of the deformation is linearly displayed for simplicity). have).

In the Fresnel lens 70 of FIG. 37A, since the refractive prism portions 72i + 1 to 72j are also provided, in addition to the total reflection type prism portions 71h-1 to 7li-1, the first half Deformation (in the dotted line source NG) is also generated in the total reflection surfaces of the sand-shaped prism portions 71i to 71j-1. The refractive prism portions 72i + 1 to 72j are provided consciously at each pitch Pi + 1 to Pj. Depending on the presence or absence of the refractive prism portions 72i + 1 to 72j, the difference between the Fresnel lens 70 of FIG. 36A and the Fresnel lens 70 of FIG. 37A is characterized.

In Fig. 36 (a), in the center-side pitch group from the pitch Pi-4 to the center of the Fresnel, since the light is incident at a relatively small angle of incidence, the total reflection type prism portions 71i-4, 71h, 71h- 1,... And a hybrid prism portion including all of the refractive prism portions 72i-4, 72h, 72h-1, ... are formed. Each height Rfl, Rfr in the center side pitch group of the total reflection type prism parts 71i-4, 71h, 71h-1, ..., and the refractive type prism parts 72i-4, 72h, 72h-1, ... ) Is 1: 1 as shown in FIG. 36 (b).

On the other hand, in the peripheral pitch group from the pitch Pi + 1 to the Fresnel periphery in Fig. 36 (a), since the light is incident at a relatively large incidence angle, the refractive index deteriorates due to deterioration of the large incidence angle and hardly functions. The height Rfr of the mold prism portion is 0 (Fig. 36 (b)), and only the total reflection prism portions 71i + i, ..., 71j-1, 71j, 71j + 1, ... are molded.

And in the intermediate pitch group from the pitch Pi-3 which exists in the area | region which moves to the peripheral side pitch group from the center pitch group of FIG. 36 (a) to the pitch Pi, it is shown in FIG. 36 (b). As shown in the figure, the hybrid prism portion (mediated prism portion) gradually decreased by the height Rfr of the refractive prism portions 72i-3, ..., 72i as the pitch from the Fresnel center side to the Fresnel peripheral side. ) Is molded. This is for the purpose of smoothing the transmittance characteristic when the transition from the center side pitch group to the peripheral side pitch group is performed. Principle is provided by providing an intermediate pitch group like the Fresnel lens 70 of Fig. 36A. In general, the transmittance characteristic can be smoothed.

However, since the deformation in the dotted circle NG occurs on the total reflection surface of the total reflection type prism portion, in the Fresnel lens 70 shown in Fig. 36A, the transmittance and pitch of the pitch Pi-1 ( The discontinuity of the transmittance of Pi increases. Therefore, for example, when the Fresnel lens 70 of Fig. 36A is applied to the screen, an unnatural boundary occurs in the brightness of the image on the screen.

On the other hand, in the Fresnel lens 70 of FIG. 37A, it is assumed that the deformation in the dotted circle NG occurs on the total reflection surface of the total reflection type prism portion, and the Fresnel lens 70 of FIG. 36A is shown. In addition to the configuration of the above), as described above, the refractive prism portions 72i + i to 72j are provided on purpose. For this reason, unlike the Fresnel lens 70 of FIG. 36A, the discontinuity of the transmittance | permeability between pitches can be eliminated.

The difference between the Fresnel lens 70 of FIG. 36A and the Fresnel lens 70 of FIG. 37A will be described in more detail.

38A and 38B are views for explaining the difference between the Fresnel lens 70 of FIG. 36A and the Fresnel lens 70 of FIG. 37A. Fig. 38A shows the Fresnel lens 70 of Fig. 36A, Fig. 38B shows the Fresnel lens 70 of Fig. 37A, and enlarges the pitch Pi-1 to the pitch Pj, respectively. There is a limit. 36 (a) and 37 (b), the same reference numerals correspond to the same elements.

In the pitch Pi-1 of FIG. 38A, since the final refractive prism portion 72i is provided at the adjacent pitch Pi on the Fresnel peripheral side, the total reflection surface of the total reflection type prism portion 71i-1. Deformation in the dotted line circle NG occurs at 74i-1. Therefore, the incident light beam 76i-1 received at the incident surface 75i-1 of the total reflection type prism portion 71i-1 is totally reflected at the total reflection surface 74i-1, and is then emitted from the emission surface 73. You cannot exit. That is, some of the light beams 77i-1 are scattered in a direction different from the original total reflection direction due to deformation in the dotted circle NG after being refracted at the incident surface 75i-1, resulting in light loss.

On the other hand, in the pitch Pi of Fig. 38A, since the refracting prism portion does not exist in the pitch Pi + 1 adjacent to the Fresnel circumferential side, the total reflection surface of the total reflection type prism portion 71i of the pitch Pi ( 74i) is not deformed. Therefore, in this pitch Pi, since the light beam 76i received by the incident surface 75i of the total reflection type prism part 71i totally reflects on the front surface of the total reflection surface 74i, and exits from the emission surface 73, the pitch ( Unlike Pi-1), no light loss occurs.

Hereinafter, also in the pitch Pi + 1, ..., since the distortion in the dotted line NG does not generate | occur | produce in the total reflection surface 74i + 1, ..., the pitch Pi-1 which the optical loss by the influence of a deformation generate | occur | produced. ) And the discontinuity of the transmittance is large between the pitch Pi without light loss.

In the case of FIG. 38A, in the Fresnel lens 70 shown in FIG. 38B, it is assumed that the deformation in the dotted circle NG occurs on the total reflection surface 74i, and the fresnel peripheral side of the pitch Pi is assumed. In the adjacent pitch Pi + 1, a refractive prism portion 72i + 1 that does not participate in light reception is deliberately provided. By doing so, even in the pitch Pi, a part of the light beam 77i is refracted at the incident surface 75i and then scattered in a direction different from the original total reflection direction due to deformation in the dotted circle NG. As in Pi-1), light loss is caused and discontinuity in transmittance is eliminated.

Hereinafter, similarly to the pitch of the Fresnel periphery, the refractive prism part which does not participate in light reception is provided to the refractive prism parts 72j-1 and 72j, and the discontinuity of transmittance is eliminated. Then, after the pitch at which the incident light of the incident light to the Fresnel lens 70 becomes large enough and does not totally reflect over the entire surface of the total reflection surface, the dummy refracted prism portion is completely extinguished.

Since the pitch Pj in Fig. 38B corresponds exactly to this, and the incident angle of the incident light is sufficiently large, the part of the total reflection surface 74j in which deformation of the dotted line NG is to be generated is not used for total reflection of the light. The difference in light loss from the adjacent pitch Pj-1 is irrelevant to the presence or absence of deformation of the dotted line NG.

Thus, the dotted line circle NG by providing the refractive prism portions 72i + 1 to 72j which do not participate in light reception until the peripheral side pitch group where the total reflection type prism portions 71j-1 and 71j are provided. All of the discontinuities in transmittance due to the deformation of) can be eliminated.

As described above, according to the sixth embodiment, the step ST6 for setting the pitch margin DELTA Pn is provided after the step ST2, and the cutting start position is cut in the cutting progress direction by the pitch margin DELTA Pn. Since the sub-prism shaping mold is cut at step ST7, the lens shaping mold C generated at the distal end portion of the curve Tn between the main prisms for each pitch when the sub-prism is cut. Deformation can be prevented, and the lens shaping | molding die can be made into the shape as designed, and the optical performance of the Fresnel lens manufactured with the lens shaping | molding die can be ensured.

According to the sixth embodiment, the Fresnel center side pitch group in which the hybrid prism part composed of the total reflection type prism part and the refractive prism part is molded, the Fresnel peripheral side pitch group in which only the total reflection type prism part is molded, As the pitch is shifted from the channel center side pitch group to the Fresnel peripheral side pitch group, when producing a medium pitch group that keeps the height of the total reflection type prism portion constant and reduces only the height of the refractive type prism portion, In the pitch group, a refractive prism portion having a minimum height and not involved in light reception was used as a dummy prism portion to cut at least a part of the pitch of the Fresnel peripheral side pitch group, resulting in deformation of the total reflection surface. The effect of eliminating the discontinuity of the transmittance caused by the loss of light can be obtained.

In addition, although the dummy prism part was cut from the intermediate pitch group to the Fresnel peripheral side pitch group, this Embodiment 6 is not limited to this. For example, a hybrid prism portion (including an individual prism portion), a refractive prism portion, a total reflection prism portion, or the like, and, conversely, a hybrid prism portion (including an individual prism portion) from a refractive prism portion, a total reflection prism portion, or the like. In the case where the shape of the prism portion is changed from pitch to pitch, the manufacturing error caused by the change in the shape of the prism portion is provided by continuously providing the dummy prism portion over at least a part of the pitch group in which the shape of the prism portion is changed. It is possible to suppress the sudden disappearance and generation of the curved tip portion, etc.) and to abruptly change the optical performance such as transmittance.

Embodiment 7.

As described in the first embodiment, the refracting prism portion has an ineffective surface, and the incident light beam (ineffective light group) received at this ineffective surface becomes stray light inside the Fresnel lens, and is emitted from the emission surface, and the image is displayed on the screen. Cause of ghosting. In addition, depending on the size of the incident angle of the incident light, there is also a light beam (commonly referred to as a resonant light that 'wraps' the total reflection surface) even when it enters the total reflection type prism part, which also becomes a ghost and generates ghosts. Let's do it. In the seventh embodiment, a Fresnel lens in which the stray light is absorbed and the ghost is reduced to the incident surface side or the emission surface side will be described.

Fig. 39 is a diagram showing the cross-sectional shape of the Fresnel lens according to the seventh embodiment of the present invention, in which a configuration is provided on the incidence side of the Fresnel lens to reduce the ghost caused by the ineffective light. The same reference numerals as in Fig. 9 correspond to the corresponding structures.

In Fig. 39, 81 is a light absorbing layer provided on the ineffective surfaces 3Z, 3Z-1, ... of the refractive prism portion 3A, respectively.

The light absorbing layer 81 acts to absorb the invalid light lie incident on the invalid surfaces 3Z, 3Z-1, ... of each pitch. By providing the light absorbing layer 81 on the ineffective surfaces 3Z, 3Z-1, ..., it is possible to prevent the generation of stray light inside the Fresnel lens 1 due to the ineffective light, thereby reducing ghosts generated on the screen. You can get the effect that you can.

Fig. 40 is a diagram showing the cross-sectional shape of the Fresnel lens according to the seventh embodiment of the present invention, and shows the configuration of absorbing stray light by the ineffective light or the resonant light at the emission surface side of the Fresnel lens. The same reference numerals as in Fig. 9 correspond to the corresponding structures.

In Fig. 40, 82 is a stray light absorbing plate provided on the exit surface 5 of the Fresnel lens 1. The light absorbing plate 82 is a parallel plate having an incidence plane and an outgoing plane parallel to the exit plane 5 of the Fresnel lens 1, a light transmitting layer 83 that transmits light, and a thin film that absorbs light. The light absorbing layers 84 are alternately stacked so as to be parallel to the optical axis (not shown) of the Fresnel lens 1.

As shown in Fig. 40, in comparison with the light paths b3 and b4 received by the incident surface 3B of the refractive prism portion 3A and the incident surface 4B of the total reflection prism portion 4A, The stray light be1 inside the Fresnel lens 1 incident on the ineffective surfaces 3Z, 3Z-1, ..., or enters the incidence surface 4B of the total reflection type prism portion 4A, and loses the total reflection surface 4C. Since the stray light be2 of the resonant ray travels larger toward the radial direction of the Fresnel lens 1, the light rays be1 'and be2' are emitted from the exit surface 5 of the Fresnel lens 1. As a result, each of the light absorbing layers 84 stacked in parallel with the optical axis of the Fresnel lens 1 is absorbed.

The light rays b3 and b4 received by the incident surface 3B of the refractive prism portion 3A and the incident surface 4B of the total reflection prism portion 4A are also emitted from the emission surface 5 to emit light rays b3 '. , b4 ') is partially absorbed by the light absorbing layer 84, but since these light rays b3' and b4 'are emitted almost parallel to the optical axis of the Fresnel lens 1, the amount of light absorbed is Extremely trivial Most of the light rays b3 'and b4' pass through the light transmitting layer 83 and proceed to, for example, a lenticular (not shown), which is not a big problem.

The laminated structure of the light transmitting layer 83 and the light absorbing layer 84 may be concentric (radial) centering on the optical axis of the Fresnel lens 1 as shown in Fig. 41A, and light transmitting as shown in Fig. 41B. The light transmissive layer 83 and the light absorbing layer 84 may be stacked in the vertical direction of the paper so that the layer 83 and the light absorbing layer 84 are widened in the horizontal direction of the paper. In this case, when applied to a screen having an aspect ratio of 3: 4, the paper vertical direction corresponds to 3 and the paper horizontal direction corresponds to 4.

By adopting the configuration of FIG. 41A, the absorption efficiency of stray light can be optimally achieved. By employing the configuration of FIG. 41B, the stray light absorption plate 82 can be easily manufactured, and manufacturing cost can be reduced.

In addition, the lamination interval (thickness of the light transmitting layer 83) of the light absorbing layer 84 may be matched with the pitch interval of the Fresnel lens 1, and changes according to the distance from the optical axis of the Fresnel lens 1. You may make it possible and can design freely according to a specification. In addition, the laminated structure of the light absorbing layer 84 should be set to a pitch that avoids the generation of moire fringes due to interference with the Fresnel lens 1 and the lenticular periodic structure (not shown).

In addition, a plurality of slits that fill the light absorbing layer 84 are formed on the emission surface 5 side of the Fresnel lens 1 in the lamination pattern of FIG. 41A or 41B, and the light absorbing layer 84 is provided on these slits. Also good. At this time, it is suitable to form the light absorbing layer 84 by filling a light absorbing paint in the plurality of slits. In this manner, by integrally molding the stray light absorbing plate 82 to the exit surface 5 of the Fresnel lens 1, the number of parts can be reduced.

Fig. 42 is a diagram showing the cross-sectional shape of the Fresnel lens according to the seventh embodiment of the present invention, showing the configuration of absorbing stray light generated by receiving light from the ineffective surface at the emission surface side of the Fresnel lens. 9 and 40, the same reference numerals correspond to the same components.

In Fig. 42, 85 is a light absorbing plate provided on the exit face 5 side of the Fresnel lens 1, and has a plane of incidence and an exit plane parallel to the exit plane 5 of the Fresnel lens 1; Reputation.

As described with reference to Fig. 40, the stray light be1 and the stray light be2 proceed larger in the radial direction of the Fresnel lens 1, so that the incident surface 3B or the total reflection type of the refractive prism portion 3A is formed. The light absorbing plate 85 is compared with the optical path lengths B3 'and B4' of the light beams b3 'and b4' received by the light incident surface 4B of the prism portion 4A and emitted from the light emitting surface 5. The optical path lengths BE1 'and BE2' of the stray light be1 'and be2' in the side become larger. The amount of stray light be1 'and be2' is absorbed by the light absorbing plate 85 largely by the optical path difference of both, and the intensity of stray light be1 'and be2' when exiting from the light absorbing plate 85 is obtained. Can be lowered.

In addition, the stray light be3 and be4 that are multiplely reflected inside the light absorbing plate 85 (emission surface) have a longer light path length and are greatly absorbed according to the number of multiple reflections. The strength is lower than that of '), and there is no problem at all.

In addition, since the stray light be5 and be6 reflected from the incident surface side of the light absorbing plate 85 enters the light absorbing plate 85 after being (multiple) refracted and reflected at each part of the Fresnel lens 1, In reflection, the intensity is further reduced by the amount of light that is refracted and reflected at each portion of the Fresnel lens 1 and the light emitted from the Fresnel lens 1 is received at each interface of the refraction and reflection.

Thus, by using the light absorption plate 85, the effect that a stray light can be absorbed with a simple structure and the ghost which generate | occur | produces on a screen can be acquired.

Incidentally, the stray light may be absorbed by arbitrarily combining the respective structures for reducing the ghost in FIGS. 39 to 42. FIG. For example, by applying the combination of the light absorbing layer 81 and the stray light absorbing plate 82 or the combination of the light absorbing layer 81 and the light absorbing plate 85 to the Fresnel lens 1, the stray light can be further absorbed. It is possible to achieve the effect of reducing the ghost on the screen.

As described above, according to the seventh embodiment, the thin film light absorbing layers 81 for absorbing light are provided on the ineffective surfaces 3Z, 3Z-1, ... of the refractive prism portion 3A, respectively. The generation of stray light inside the NEL lens 1 can be prevented, and the effect of reducing the ghost generated on the screen can be obtained.

Further, according to the seventh embodiment, the stray light absorbing plate 82 in which the plurality of light absorbing layers 84 are laminated between the plurality of light transmitting layers 83 so as to be substantially parallel to the optical axis of the Fresnel lens 1 is provided. Since it is provided in the exit surface 5, the stray light which generate | occur | produced in the Fresnel lens 1 can be absorbed, and the effect which can reduce the ghost which generate | occur | produces on a screen can be acquired.

Further, according to the seventh embodiment, the stray light absorbing plate 82 is integrally formed on the exit surface 5 of the Fresnel lens 1, so that stray light can be absorbed with a small number of parts. Can be.

Further, according to the seventh embodiment, the light transmitting layer 83 and the light absorbing layer 84 are laminated concentrically (radially) around the optical axis of the Fresnel lens 1, so that the absorption efficiency of stray light is improved. The effect to be able to do it best is obtained.

In addition, according to the seventh embodiment, since the light transmitting layer 83 and the light absorbing layer 84 are laminated in one direction in parallel, the production of the stray light absorbing plate 82 becomes easy and the manufacturing cost can be reduced. You can get the effect that you can.

In addition, according to the seventh embodiment, since the light absorbing plate 85 is provided on the emission surface 5 of the Fresnel lens 1, stray light can be absorbed with a simple configuration, The effect of being able to reduce ghost can be obtained.

As mentioned above, the Fresnel lens which concerns on this invention is suitable for the back projection type projection system which projects image light from a back surface with respect to a screen.

Claims (77)

A refractive prism portion for emitting the first incident light having a predetermined incident angle as the first emitted light having a predetermined exit angle by a first refractive phenomenon and a second refractive phenomenon; Pitch having a hybrid prism portion having a total reflection type prism portion for emitting the second incident light having the predetermined incident angle as a second output light parallel to the first output light by a third refractive phenomenon, a total reflection phenomenon and a fourth refractive phenomenon Fresnel lens characterized in that it comprises a. 2. A Fresnel lens according to claim 1, wherein a hybrid prism portion is present at at least two or more pitches, and a ratio of the refractive prism portion to the hybrid prism portion is different for each pitch. In a Fresnel lens for emitting the incident light of a predetermined incident angle through each prism portion provided in each pitch as an output light of a predetermined exit angle, A first incident surface which makes the first incident light incident at a predetermined angle of incidence the first transmitted light by the first refractive phenomenon, A plane-shaped exit surface in which the first transmitted beam is a first exit beam having a predetermined exit angle by a second refractive phenomenon; A refractive prism portion having a cross-sectional shape consisting of the first incident surface and an ineffective surface in contact with an adjacent pitch; A second incident surface which makes the second incident light incident at the predetermined incident angle a second transmitted light by a third refractive phenomenon, A total reflection surface comprising the second transmission beam as a third transmission beam parallel to the first transmission beam by total reflection; It has a cross-sectional shape consisting of the exit surface of the refractive prism portion, And a total reflection type prism portion which uses the third transmitted light as the second output light having the predetermined exit angle by the fourth refractive phenomenon at the exit surface, And a pitch having a hybrid prism portion in which the refracting prism portion is integrated with the total reflection prism portion so as to receive a portion of the second incident ray which does not become the third transmitted ray as the first incident ray. Nell lens. The second incidence surface is formed into a cross-sectional shape that cuts off the invalid surface, as viewed from the direction of the invalid light incident on the invalid surface of the hybrid prism portion provided at the adjacent pitch, The total reflection surface is formed into a second incidence plane compensation shape that compensates for the cross-sectional shape of the second incidence plane. The pitch according to claim 3, wherein each of the pitches of the small rectangular region defined on the basis of the characteristic change angle which makes the transmittance of the hybrid prism portion equal to the transmittance of the refractive prism portion is the same. Nell lens. The pitch of each of the small rectangular region defined on the basis of the characteristic change angle which makes the transmittance of the hybrid prism portion equal to the transmittance of the refractive prism portion is provided with each of the refractive prism portions. Nell lens. 6. The Fresnel lens according to claim 5, wherein in each pitch of the characteristic change region near the characteristic change angle, the mixing ratio of the refractive prism portion to the hybrid prism portion increases as the incident angle decreases. 7. The Fresnel lens according to claim 6, wherein the mixing ratio of the refractive prism portion to the hybrid prism portion increases with decreasing angle of incidence in each pitch of the characteristic change region near the characteristic change angle. 6. The median prism portion according to claim 5, wherein in each pitch of the characteristic change region near the characteristic change angle, the area of the second incidence surface is insignificant and the area of the first incidence surface is insignificant according to the decrease in the incident angle. Fresnel lens, characterized in that. 7. The method according to claim 6, wherein in each pitch of the characteristic change region near the characteristic change angle, an area of the second incidence surface is insignificant and an area of the first incidence surface is insignificant in accordance with the decrease in the incident angle. Fresnel lens, characterized in that. 4. The Fresnel lens according to claim 3, wherein the tip angle formed by the second incidence surface and the total reflection surface is set at the sharpest angle in a range in which the angle between the second incidence surface and the emission surface is not obtuse. 12. The angle of incidence angle of claim 11, wherein the tip angle is larger than the angle of incidence in a region where the transmittance with respect to the tip angle at the sharpest angle and the transmittance for the tip angle other than the sharp angle is equal to each other. Fresnel lens, characterized in that. The Fresnel lens according to claim 3, wherein the predetermined exit angle is made larger than 0 degrees at each pitch of the incident angle at which the transmittance of the hybrid prism portion decreases. The lens outer peripheral side of the boundary ring band that intersects only one side closest to the optical axis among the four sides of the Fresnel lens cut out in a rectangular shape, and the emission angle is set in parallel, and on the optical axis side of the boundary ring band. A Fresnel lens, characterized in that the exit angle is set larger than the exit angle set in parallel. The method of claim 3, wherein the refractive prism portion, A Fresnel lens comprising a light absorbing layer of a thin film absorbing light on an ineffective surface. 4. The light emitting surface of claim 3, wherein a light absorbing plate comprising a plurality of light transmitting layers for transmitting light and a plurality of light absorbing layers for stacking the light transmitting layers substantially parallel to the optical axis of the Fresnel lens and absorbing light Fresnel lens characterized in that provided in. The method of claim 16, wherein the stray light absorbing plate, A Fresnel lens, characterized in that integrally molded on the exit surface of the Fresnel lens. The method of claim 16, wherein the light transmitting layer and the light absorbing layer, A Fresnel lens, characterized in that it is laminated concentrically around the optical axis of the Fresnel lens. The method of claim 16, wherein the light transmitting layer and the light absorbing layer, A Fresnel lens, characterized in that laminated substantially parallel to one direction. 4. A Fresnel lens according to claim 3, wherein a light absorbing plate for absorbing light is provided on the exit surface. The Fresnel lens according to claim 3, wherein the hybrid prism portion is formed with a pitch margin between the pitches, respectively. 4. The Fresnel lens according to claim 3, wherein a dummy prism portion having a height not involved in light reception in the optical axis direction is provided continuously in at least part of the pitch group. 23. A fresnel lens according to any one of claims 1 to 22, and an image forming diffusion means for receiving an outgoing light to which display content is added from the fresnel lens, and for forming and diffusing the outgoing light. Screen made. The screen according to claim 23, wherein the image forming diffusion means is integrally formed on the exit surface of the Fresnel lens. The screen according to claim 23 or 24, Lighting source means for emitting substantially parallel light, Condensing optical means for condensing light from said illumination light source means; Light modulating means for spatially modulating the intensity of the light collected by the condensing optical means in accordance with a display content; And projection optical means for projecting the light modulated by the optical modulation means onto the screen. In a Fresnel lens having a plurality of total reflection type prism portion having a second incident surface to which light is incident and a total reflection surface which totally reflects a part of the light incident on the second incident surface and deflects the light in a desired direction, The total reflection type prism portion includes a subunit prism portion on a part of the second incident surface to which light which is not totally reflected on the total reflection surface is incident. And said subunit prism portion is a refracting prism portion having a first incident surface for refracting incident light and deflecting in the desired direction. 27. The Fresnel lens according to claim 26, wherein the surface on which the first incident surface of the subunit prism portion extends is in the outgoing side than the total reflection surface in the range of the total reflection type prism portion. 27. The Fresnel lens according to claim 26, wherein the ratio of the subunit prism portion occupying the second incident surface is varied. The Fresnel lens according to claim 27, wherein the ratio of the subunit prism portion occupying the second incident surface is varied. In a Fresnel lens, a first incidence surface that refracts incident light and is deflected in a desired direction, and a plurality of refracting prism portions having an invalid surface other than the first incidence surface are arranged side by side on the light incident side, The refracting prism portion includes a subunit prism portion on the first incidence surface for receiving light incident on the ineffective surface adjacent to a fresnel peripheral side, The sub-unit prism portion is a Fresnel lens, characterized in that a total reflection type prism portion having a second incident surface for receiving light and a total reflection surface for totally reflecting the light received at the second incident surface and deflected in a desired direction. . 31. The Fresnel lens according to claim 30, wherein the surface on which the second incident surface of the subunit prism portion extends is in the outgoing side than the ineffective surface within the range of the refractive prism portion. 31. The Fresnel lens according to claim 30, wherein the ratio of the subunit prism portion occupying the first incident surface is varied. 32. The Fresnel lens according to claim 31, wherein the ratio of the subunit prism portion occupying the first incident surface is varied. A first range of the same type as the Fresnel lens according to claim 26; A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 30. A first range of the same type as the Fresnel lens according to claim 26; A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 31. A first range of the same type as the Fresnel lens according to claim 26; A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 32. A first range of the same type as the Fresnel lens according to claim 26; A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 33. A first range of the same type as the Fresnel lens according to claim 27, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 30. A first range of the same type as the Fresnel lens according to claim 27, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 31. A first range of the same type as the Fresnel lens according to claim 27, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 32. A first range of the same type as the Fresnel lens according to claim 27, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 33. A first range of the same type as the Fresnel lens according to claim 28, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 30. A first range of the same type as the Fresnel lens according to claim 28, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 31. A first range of the same type as the Fresnel lens according to claim 28, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 32. A first range of the same type as the Fresnel lens according to claim 28, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 33. A first range of the same type as the Fresnel lens according to claim 29, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 30. A first range of the same type as the Fresnel lens according to claim 29, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 31. A first range of the same type as the Fresnel lens according to claim 29, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 32. A first range of the same type as the Fresnel lens according to claim 29, A Fresnel lens comprising a second range of the same type as the Fresnel lens according to claim 33. The ratio of the subunit prism portion to the second incidence surface in the first range is larger as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. 38. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. 40. The ratio of the subunit prism portion to the second incidence surface in the first range is greater as the boundary is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. 41. The ratio of the subunit prism portion to the second incidence surface in the first range is greater as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence plane in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. 43. The ratio of the subunit prism portion to the second incidence surface in the first range is greater as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. 45. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is larger as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion occupying the second incidence plane in the first range is greater as it is closer to the boundary between the first range and the second range, and less as it is farther from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. The ratio of the subunit prism portion to the second incidence surface in the first range is higher as the ratio is closer to the boundary between the first range and the second range, and the smaller the distance is from the boundary. under, The ratio of the said subunit prism part to the 1st incidence surface in a said 2nd range is so large that it is closer to the said boundary, and it becomes smaller as it moves away from the said boundary. 27. The Fresnel lens according to claim 26, wherein a second Fresnel lens different from the Fresnel lens is provided on the outgoing side of the Fresnel lens provided on the incidence side. 32. The Fresnel lens according to claim 30, wherein a second Fresnel lens different from the Fresnel lens is provided on the light exiting side of the Fresnel lens provided on the light incidence side. The fresnel lens according to any one of claims 26 to 65, And a light diffusing means formed on a surface of the Fresnel lens on the light exit side and diffusing light emitted from the Fresnel lens. A fresnel lens according to claim 66 or 67; And a light diffusing means provided at the light exit side of the Fresnel lens to diffuse the light emitted from the Fresnel lens. The screen of claim 68, An image light source emitting image light, And projection optical means for projecting the image light emitted from the image light source onto the screen. The screen of claim 69, An image light source emitting image light, And projection optical means for projecting the image light emitted from the image light source onto the screen. In the method of manufacturing a lens shaping mold for cutting the inverted shape of the refractive prism portion and the total reflection prism portion formed for each pitch of the Fresnel lens with a bite with respect to the lens shaping mold, A main prism portion cutting step of cutting the inverted shape of the refractive prism portion with the bite with respect to the cutting target pitch; While cutting the overall shape of the total reflection prism portion with the bite with respect to the cutting target pitch, The surface extending the total reflection surface in the inverted shape of the total reflection type prism portion passes through a curve formed between the cutting target pitch and the adjacent pitch closer to the Fresnel center than the cutting target pitch or is the light exiting side than the curve. A method of manufacturing a lens shaping die, characterized by repeating a subunit prism portion cutting step by a predetermined number of pitches. In the method of manufacturing a lens shaping mold for cutting the inverted shape of the refractive prism portion and the total reflection prism portion formed for each pitch of the Fresnel lens with a bite with respect to the lens shaping mold, A main prism portion cutting step of cutting the inverted shape of the total reflection prism portion with the bite with respect to the cutting target pitch; While cutting the inverted shape of the refractive prism portion with the bite with respect to the cutting target pitch, A surface extending the first incidence surface in the inverted shape of the refractive prism portion passes a curve formed between the cutting target pitch and the adjacent pitch of the Fresnel circumferential side rather than the cutting target pitch or is outgoing from the curve A method of manufacturing a lens shaping mold, characterized by repeating a subunit prism portion cutting step to be a predetermined number of pitches. 73. The cutting tool according to claim 72, wherein in the cutting progress direction from the Fresnel center side to the Fresnel circumferential side, the cutting is performed for every pitch in the order of total reflection type prism portion and refractive type prism portion. A pitch margin setting step for setting a pitch margin for each pitch is provided before the subunit prism portion cutting step, And in the sub-unit prism portion cutting step, the cutting start position is moved in the cutting progress direction by the pitch margin, and the refractive prism portions are cut for each of the pitches. 74. The method according to claim 73, wherein in the cutting progress direction from the fresnel peripheral side to the fresnel center side, the cutting is performed for each pitch in the order of the refractive prism portion and the total reflection prism portion. A pitch margin setting step for setting a pitch margin for each pitch is provided before the sub-prism subcutting step, The subunit prism portion cutting step, wherein the total reflection-type prism portion is cut for each pitch by shifting the cutting start position in the cutting progress direction by the pitch margin. 74. The method of manufacturing a lens shaping mold according to claim 73, wherein an inverted shape of the dummy prism portion having a height not involved in light reception in the optical axis direction is continuously cut at least in part of the pitch group. 77. A resin is poured into a lens forming mold prepared by the method for manufacturing a lens forming mold according to any one of claims 72 to 76, and when the resin is cured, the lens forming mold is removed from the cured resin. Lens manufacturing method characterized in that to form.