JPH10283816A - Photo-guide plate for back illumination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-guide plate for back illumination which reflects the beams of light led in from a narrow end face of a photo-medium with a high gain inside the photo-medium, which emits the beams upon allowing them to pass through a wide surface uniformly, and directs them to the intended point which a person is watching. SOLUTION: An objective lens 62 with refracting function is installed close to a light source 52 or in a single piece structure, and a group of strip surfaces having reflecting function are installed on, or machined in, the rear surface of a photo-medium 60. Each strip surface is formed from a conically curved surface, wherein the concave of the curve is facing the light incident side. The objective lens 62 constitutes a refractive convergence optical system in which the light source 52 and an information image display surface 70 are in conjugate relationship. The strip surfaces are formed from conical surface in which the lens 62 and the point of watching are in the conjugate relationship so that a convergence optical system is configured. Therei a large quantity of light beams from the light source are introduced to the end face by the lens 62, reflected uniformly by a plurality of strip surfaces, emitted from a wire area of surface, and converged onto the point of watching. Accordingly a light-umemissive image display surface installed on the emitting surface of a photo-guide plate can be viewed at intense lumiannce and uniform illuminance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for guiding a light beam for illuminating an image display surface from behind, and more particularly, to a light introducing end surface having a narrow width for receiving the light beam and a plurality of light reflecting plates for reflecting the light beam in a substantially right angle direction. The present invention relates to a light guide plate having a band-shaped reflective concave surface and a large-area radiation surface for irradiating an information image from behind.

[0002]

2. Description of the Related Art In order to view an information image on a non-luminous (passive) image display surface, for example, a liquid crystal display panel or an electrochromic display surface, it is necessary to illuminate with a light beam from behind. In order to save the space behind, the lighting function member is configured to be thin, and the light beam for lighting is made to enter from the end face of a small area, reflected almost perpendicularly inside the lighting function member, and emitted from the surface of a large area. The information image display surface is illuminated from behind.

[0003] The lighting function member according to the prior art is a means for mixing or laminating a material having a different refractive index or a reflective material into a transparent solid material, or providing an uneven shape on the surface, or applying or sticking a reflective substance. Had been adopted. In these structures, since the illuminating light rays are scattered and projected on the information display surface, they are emitted and dissipated, the amount of light reaching the viewpoint is small, and the luminance for viewing the information display surface is dark. Illumination unevenness on the information display surface was 40% or less in the peripheral light amount ratio, and the light amount utilization rate was 20% or less.

There is a case where the introduction end face is formed as a convex surface for the purpose of improvement, and the light is transmitted and received by guiding the light almost parallel inside the illumination function member. However, the effective area of the introduction end face was reduced, and the amount of incident light from the light source was reduced.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light guide plate for a back illumination capable of uniformly illuminating an information display surface and allowing an image to be viewed with extremely high brightness.

[0006]

That is, the present invention provides:
The objective lens is arranged on the light introduction end face, and the shape of the reflection surface provided in the optical medium is curved and formed in a concave shape in the direction of the light source,
In addition, a plurality of the belt-shaped reflection concave surfaces are provided by gradually changing the intervals and / or widths thereof.

[0007]

FIG. 1 shows an optical system according to the present invention. The light beam from the light source 2 passes through the objective lens 12, enters from the end face 14 of the optical medium 10, is reflected on the plurality of striations 16 in a substantially right angle direction, exits from the surface 18, and illuminates the back of the information screen 20. Light rays transmitted through the information screen 20 are directed to the viewing point 30. The information screen 20 is viewed from the vicinity.

Considering from the viewpoint of geometrical optics, the objective lens 12 focuses light rays from the light source 2 on the information screen 20 with the light source 2 and the information screen 20 in a conjugate relationship. The striation 16 that reflects and directs an incident light ray to the viewpoint 30 is an end face 14.
It is formed by a part of a three-dimensional three-dimensional conical curved surface (general term of a spherical surface, a spheroidal surface, and a paraboloid of revolution) having a conjugate relationship between the image and the viewpoint 30. And the end face 14 corresponds to the entrance pupil,
An exit pupil 32 is formed near the viewing point 30.

For the observer 32 looking at the information screen 20, the size of the surface 18 limits the field of view, and the information screen 2
The size of 0 defines the field of view, and the size of the exit pupil defines the viewing zone 8. Since the information screen 20 is installed close to the surface 18, the size of the field of view is almost equal to the field of view. The size of the viewing zone, ie, the size of the exit pupil, is proportional to the size of the entrance pupil, and the magnification is the ratio of the distance from the end surface 14 to the striation 16 and the distance from the striation 16 to the viewing point 30.

The three-dimensional conical surface is formed innumerably in space with the end surface 14 and the viewpoint 30 in a conjugate relationship.
When the light source 2 is set so as to be included on the surface of the flat optical medium 10, a plurality of striations 16 are set where the three-dimensional conical curved surface intersects the surface of the optical medium 10. If the light source 2 is a point light source, the surface 16 is drawn concentrically around the point light source or elliptical around the point light source. When the light source 2 is a linear light source, the striation surface 16 draws a parabola with the linear light source as the focal point, and a concave surface facing the incident light beam is formed.

The light rays illuminated and reflected on the striations 16 pass through the information screen 20 from the surface 18 and are intensively projected on the viewing point 20. The reflection surface 41 is provided at a goose-running position with respect to the light source 11 so as not to mutually shade the irradiation light beams. Therefore, the strip surface 16 is cut in the back surface of the optical medium 10 stepwise. All the light rays incident on the end face 14 of the optical medium 10 are effectively transmitted and received on the striation face 16.

The brightness when the surface 18 is viewed from the viewing point 30 is proportional to the product of the number of strips installed per unit area of the surface 18 and the effective area of the strip 16. Since the illuminance decreases as the distance from the end surface 14 increases, the product of the number of installation streaks 16 and the effective area is gradually increased, and the luminance of the surface 18 is equalized. When setting the line 16 at equal intervals, the line 1
The height of 6 increases gradually. When the height of the striations 16 is constant, the spacing between the striations 16 is changed from coarse to dense.

[0013]

The light guide plate 60 shown in FIG. 2 transmits a light beam from a tubular light source 52 through a cylindrical lens 62 and a transparent solid body 60 from an end face 64.
V cut into the back of transparent solid body 60
A method of irradiating the group of grooves 66 on the groove is shown. The light rays reflected by the group of striations 66 pass through the surface 68, and
0 is transmitted and is emitted in the direction of the viewing point 30.

The cylindrical lens 62 is arranged with the surface having a weak curvature facing the light source. Since the aperture of the cylindrical lens 62 is large, an increased amount of received light can be obtained. Processing means for integrally molding the cylindrical lens 62 with the transparent solid body 60 is desirable for securing the posture of the member and reducing the manufacturing cost. On the incident surface of the cylindrical lens 62, a minute concave surface 63 is provided as necessary, so that paraxial rays of a light source having high luminance are dispersed around the surface 68, thereby contributing to eliminating uneven illuminance.

The group of striations 66 are arranged at substantially equal intervals along a plurality of concave parabolas. As the distance from the light source increases, the V-shaped groove is cut deeper, and the width of the groove is increased. The angle of inclination of the group of the line surfaces 66 is set to be larger than the critical angle of the light beam, and the light beam incident on the end surface 64 is totally reflected in the direction of the surface 68.

[0016]

According to the light guide plate of the present invention, the objective lens disposed on the end face constitutes a refracting and focusing optical system, and receives and transmits an extremely large number of light rays from a light source to irradiate a group of striations. The group of concave surfaces forms a reflection focusing optical system, and emits most of the incident light rays from the surface and focuses the light rays on the viewpoint. Therefore, an extremely bright visual field can be observed. The exit pupil is formed near the viewpoint, and the viewing area is sufficiently wide.

Further, the minute concave surface provided on the entrance surface of the objective lens constitutes a refraction-divergence optical system, and disperses the light amount that tends to concentrate near the center to the periphery. In addition, the group of striations arranged in a wild goose evenly transmits and receives irradiation light rays and emits the light rays toward the surface. Therefore, uniform brightness is guaranteed on the information image display surface.

Therefore, this light guide plate emits a light beam with extremely strong illuminance from a wide surface and irradiates the information display surface with a uniform light amount, despite the narrow incident end face. It is possible to view the display surface with bright brightness from a viewing zone formed in a wide range near the viewpoint.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical system of a light guide plate.

FIG. 2 is a schematic perspective view showing a light guide plate of the present invention.

[Explanation of symbols]

 2,52 Light source 12,62 Objective lens 10,60 Optical medium 20,70 Information image display surface 30 Viewing point

[Procedure amendment]

[Submission date] April 17, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 2

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

The three-dimensional conical curved surface is formed innumerably in space with the end surface 14 and the viewpoint 30 in a conjugate relationship. When the light source 2 is set so as to be included on the surface of the flat optical medium 10, a plurality of striations 16 are set where the three-dimensional conical curved surface intersects the surface of the optical medium 10. This line 16
Is concentric, or the introduction end face 14 and the viewpoint 30
Off-axis arc shaped like or approximating an ellipse with focus at
It is drawn in a shape.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015] The group of striations 66 are arranged at substantially equal intervals along a plurality of concave conical curves . As the distance from the light source increases, the V-shaped groove is cut deeper, and the width of the groove is increased. The angle of inclination of the group of the line surfaces 66 is set to be larger than the critical angle of the light beam, and the light beam incident on the end surface 64 is totally reflected in the direction of the surface 68. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 3, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Light guide plate for back lighting

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for guiding light rays for illuminating an image display surface from behind, and more particularly, to an introduction end face on which light rays are incident, a back surface for reflecting light rays in a substantially perpendicular direction, and emitting light rays. The present invention relates to a light guide plate formed of a surface having a light guide surface.

[0002]

2. Description of the Related Art In order to view an information image on a non-luminous (passive) image display surface, for example, a liquid crystal display panel or an electrochromic display surface, it is necessary to illuminate the image from behind.
In order to save the space behind, the optical medium as the lighting function member is configured to be thin . Light rays for illumination are incident from a narrow end face, are reflected at almost right angles inside the optical medium , are emitted from a surface having a large area, and illuminate the image display surface from behind.

[0003] Optical media according to the prior art include transparent synthetic trees.
Different materials or reflective material having a refractive index mixed or laminated to solid material fat, or provided or reflective material irregularities had adopted a means for applying or affixed to the bottom. In these structures, the incident light was dissipated until irradiating the image display surface, the amount of light reaching the viewing point was small, and the luminance for viewing the image display surface was dark.

The light guide plate according to the prior art has a light amount utilization rate of 2
0% or less, and uneven illuminance on the image display surface
0% or less. Therefore, both sides of the light guide plate
It is necessary to overlay various sheets for ray correction,
It was difficult to mount it behind the bulky image display surface.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light guide plate for a back illumination capable of uniformly illuminating an image display surface and allowing an image to be viewed with extremely high brightness.

[0006]

That is, the present invention provides:
To induce light to the observer's eye position, to place the objective lens to the introducing end face, and the shape of the reflecting surface provided in the optical medium is curved concavely toward the light source, and the strip
The inclination angle of the reflective concave surface is sequentially changed.
You. Furthermore, evenly distribute the light from the surface of the optical medium
In order to equalize the luminance distribution on the surface of the optical medium, a plurality by graded spacing and or width of the strip-like reflection surface, the arrangement
A functional element that diverges light rays is placed on a part of the introduction end face.
Is to be formed .

[0007]

FIG. 1 shows an optical system according to the present invention. Of the optical medium 10
The direction of the plane including the optical axis is the X axis,
The coordinates are set with the direction perpendicular to the Y axis. Light from the light source 2 is substantially parallel to shaping I through the objective lens 12,
The light enters from the end face 14 of the optical medium 10, is reflected in a substantially perpendicular direction by the plurality of stripes 16, exits from the surface 18, and illuminates the rear of the image display surface 20. The light transmitted through the image display surface 20 goes to the viewing point 30. The image display surface 20 is viewed from the vicinity of the viewing point 30 .

[0008] The refractive index n of the optical medium, from the light source 2 to the striation 16
Distance s and the distance s' from the line surface 16 to the viewpoint 30
Is set, and this optical system is considered from the viewpoint of geometrical optics.

With respect to the light beam directivity along the X axis, the objective lens 12 and the reflecting striation 16 focus the light beam from the light source 2 to the viewing point 30 with the light source 2 and the viewing point 32 in a conjugate relationship. The objective lens 12 has a function of deflecting an incident light beam in parallel. In addition, the inclination angle of the striation 16 gradually increases from the end face 14 to the vicinity of the tip through the vicinity of the center , and the end face 14
Is reflected from the surface 18 at an angle of incidence i
It changes to i ′ = ni and points to the viewpoint 30.

Regarding the directivity of the light ray along the Y axis, the striation 16 that reflects and directs the incident light ray to the viewpoint 30
The light source 2 is formed by a part of a three-dimensional three-dimensional conical curved surface (collectively, a spherical surface, a spheroidal surface, and a paraboloid of revolution) having a conjugate relationship between the light source 2 and the viewpoint 30. Curvature radius of curved line 16
r is a geometrical optics equation: 2n / r = n / s + 1 / s'
Desired. The large amount of experiments performed by the inventor
The validity of the formula was confirmed.

For an observer looking at the image display surface 20, the end surface 14 forms an entrance pupil, the size of the surface 18 limits the field of view, the size of the information screen 20 defines the field of view,
The size of the exit pupil 32 determines the viewing zone 8. Image display surface 2
Since 0 is located close to surface 18, the size of the field of view is approximately equal to the field of view. Light source 2 is located near end face 14
The size of the exit pupil 32 is enlarged by the ratio of the distance from the light source 2 to the striation 16 and the distance from the striation 16 to the viewpoint 30.
It is.

Next, consider the luminance distribution on the X axis.
The striations 16 are installed at the eaves position with respect to the light source 2 so as not to mutually shade the irradiation light. Therefore, the strip surface 16 is cut in the back surface of the optical medium 10 stepwise. All light rays incident on the end face 14 of the optical medium 10 are
It is effectively exchanged on the line 16. From viewpoint 30 to surface 18
Is proportional to the product of the number of strips provided per unit area of the surface 18 and the effective area of the strip 16. The illuminance E of the back surface 16 depends on the distance x away from the light source 2.
Equation: E = ax ^m (a and m are constants)
Since it attenuates , the product of the number of strips installed on the strip 16 and the effective area
The value is gradually increased from the end face 14 to the tip to equalize the brightness of the surface 18. When the stripes 16 are set at equal intervals, the depth z from the reference plane on the back surface to the bottom of the stripe 16 is
Are sequentially deepened according to the formula: dz / dx = E = constant
Settings. When the depth of the line 16 is constant, the line 1
The interval of 6 is processed according to the formula: dx / dz = 1 / E = constant , changing from coarse to dense.

[0013]

The light guide plate 60 shown in FIG. 2 transmits a light beam from a tubular light source 52 through a cylindrical lens 62 and a transparent solid body 60 from an end face 64.
V cut into the back of transparent solid body 60
A method of irradiating the group of grooves 66 on the groove is shown. The light rays reflected by the group of striations 66 pass through the surface 68, pass through the image display surface 70, and are emitted toward the viewing point 30.

The cylindrical lens 62 is arranged with the surface having a weak curvature facing the light source. Since the aperture of the cylindrical lens 62 is large, an increased amount of received light can be obtained. Processing means for integrally molding the cylindrical lens 62 with the transparent solid body 60 is desirable for securing the posture of the member and reducing the manufacturing cost. On the incident surface of the cylindrical lens 62, a minute concave surface 63 or a scattering rough surface is provided as necessary, and the paraxial ray of the light source is dispersed around the surface 68,
It contributes to eliminating uneven illumination.

The group of striations 66 are arranged at substantially equal intervals along a plurality of concave conical curves, concentrically with the vicinity of the light source 52 as the center . The incident light from the end face 64 is
Reflected by the group, emitted from the surface 68, the information image display surface 7
0 is transmitted and converges in the direction of the viewpoint 30.

The further away from the light source, the deeper the V-shaped groove is drilled and the wider the groove. Surface <br/> of Article surface 66 group, the inclination angle is set to about 45 ° is set to be larger than the critical angle of the light beam, each row face the light incident on the end face 64 6
At 6, the light is totally reflected in the direction of the surface 68. And the top of the V-shaped groove
The corner is set at about 130 ° and forms the back. End face 64
The rays that did not directly strike the striation surface 66 while entering from
After multiple reflection at the surface 68, it is reflected at this back surface,
Irradiation on the ridge surface 66 effectively releases from the surface 68.

The surface 68 is provided with a rough surface having fine irregularities so that
Means to eliminate the streak of the striated surface 66
Has the effect of enlarging the area of the exit pupil 32,
The observation work of the person.

[0018]

According to the light guide plate of the present invention, the objective lens disposed on the end surface constitutes a refracting and focusing optical system, and receives and transmits an extremely large number of light rays from a light source to a group of striations. The group of concave surfaces forms a reflection focusing optical system, and emits most of the incident light rays from the surface and focuses the light rays on the viewpoint. Therefore, an extremely bright visual field can be observed. The exit pupil is formed near the viewpoint, and the viewing area is sufficiently wide.

Further, the minute concave surface or the rough scattering surface provided on the entrance surface of the objective lens constitutes a refraction-divergence optical system, and disperses the light amount which tends to concentrate near the center to the periphery. Also,
Increasing the depth placed conditions plane group in is releases in the surface direction by exchanging evenly the incoming Shako line. Therefore, uniform brightness is guaranteed on the information image display surface.

This light guide plate has a uniform light directivity and brightness.
The image allows you to observe the image clearly,
Various types of light correction systems that were conventionally stacked on the front and back sides of a light guide plate
Ports can be reduced or omitted. Image display board spine
It can be designed to be thin as a surface lighting element.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical system of a light guide plate.

FIG. 2 is a schematic perspective view showing a light guide plate of the present invention.

[Description of Signs] 2,52 Light source 12,62 Objective lens 10,60 Optical medium 20,70 Image display surface 30 Viewpoint

Claims (5)

[Claims] 1. An optical medium for reflecting an incident light beam from an introduction end face and emitting the reflected light from a surface, a plurality of three-dimensional conical curved surfaces having a conjugate relationship between a light source and a viewpoint set substantially on a normal line of the surface. A light guide plate for back lighting, wherein a strip-shaped reflection concave surface is formed at a position intersecting with the surface of (1). 2. The light guide plate for back lighting according to claim 1, wherein a linear light source is used, and said strip-shaped reflection concave surface is constituted by a parabolic surface or a surface having an approximate shape thereof. 3. The belt-shaped reflecting concave surface is constituted by a plurality of strips,
The light guide plate for back lighting according to claim 1, wherein the intervals or the widths are different from each other. 4. The light guide plate for back illumination according to claim 1, wherein a converging optical element is provided or formed near the introduction end face. 5. The light guide plate for back illumination according to claim 1, wherein a divergent optical element is provided or formed near the center of the introduction end face.