JP2004341126A - Light guide body and front light illuminator equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformize light irradiation from a light-emitting surface to emit light from a light guide body. <P>SOLUTION: A plurality of linear protruding parts 11 are formed on the second light-emitting surface 10 of the light guide plate 2 in parallel to one another toward an end face 8 from an incident face 7. The height of each of the protruding parts 11 is made to gradually get higher as going from the incident face 7 to the end face 8. Also arrangement pitches P of each of the protruding parts 11 are made to be fixed. Further, reflection areas of second slopes 13 of the respective protruding parts 11 reflecting internal light L2 inside the light guide plate 2 toward a body 4 to be irradiated are made to gradually increase as going farther away from the incident face 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is, for example, a light guide used in a front light illuminating device or the like that irradiates light to a reflective liquid crystal display device as an auxiliary light source for improving visibility in a dark place of the reflective liquid crystal display device, The present invention relates to a front light illumination device.
[0002]
[Prior art]
The transmissive liquid crystal makes the display almost invisible in a bright outdoor place exposed to direct sunlight, while the reflective liquid crystal looks clear. Reflective liquid crystals have the advantage of low power consumption due to the use of ambient light, and are therefore used in mobile phones and personal digital assistants. However, images cannot be recognized in a dark place because ambient light is not available. For this reason, an auxiliary lighting device is required. However, since the reflective liquid crystal display device has a reflective film on the back surface, a backlight such as a transmissive liquid crystal cannot be used.
[0003]
Therefore, a front light irradiation device that irradiates a reflection type liquid crystal panel is used. For example, there is a front light illuminating device as shown in Patent Document 1.
As shown in FIGS. 19 and 20, the front light illumination device includes a light guide plate 60 having a thickness of 1 to 2 mm and a light source 70. The light source 70 is configured by an LED or a cold cathode tube. The light guide plate 60 has an incident surface 61 on which light from the light source 70 is incident. The surface of the light guide plate 60 has a steep slope 66 that reflects the light in the light guide plate 60 and emits the light toward the liquid crystal panel. And a gentle slope 65 for emitting light from the inside of the light plate 60 to the outside from the surface.
[0004]
In this front light illuminating device, light incident from the incident surface 61 is transmitted through the light guide plate 60 by repeating total reflection on the front and back surfaces of the light guide plate 60. Since a part of the light reflected on the steep slope 66 deviates from the condition of total reflection on the back surface, the light is transmitted through the back surface and emitted to the lower liquid crystal panel side (not shown) as emission light LA. The emitted light LA emitted to the liquid crystal display panel side becomes reflected light of the liquid crystal display pattern, enters the light guide plate 60 from the back surface of the light guide plate 60 again, passes through the surface, and can be recognized by the observer. ing. In this front light irradiation device, the amount of internal light in the light guide plate 60 gradually decreases as the distance from the light source 70 increases.
[0005]
[Patent Document 1]
JP 2001-110223 A
[Problems to be solved by the invention]
In the conventional front light illuminating device, the light amount of the internal light in the light guide plate 60 gradually decreases as the distance from the light source 70 increases, whereas the area of each steep slope 66 is uniform. The emitted light LA1 reflected and emitted from the steep slope 66a close to the light source 70 becomes brighter than the emitted light LA2 reflected and emitted from the steep slope 66b far from the light source 70. Therefore, as shown by the curve a in FIG. 4, the amount of internal light reflected in the light guide plate 60 gradually decreases as the distance from the light source 70 increases, so that light emitted from each position of the light guide plate 60 is not uniform. However, there is a problem of non-uniformity.
[0007]
In view of the above problems, an object of the present invention is to provide a light guide in which light emitted from the light guide is uniform, and to provide a front light illumination device including the light guide. I do.
[0008]
[Means for Solving the Problems]
The invention of claim 1 of the present application is directed to an incident surface on which light from a light source is incident, a terminal surface opposed to the incident surface, and an internal light incident from the incident surface to the object to be illuminated. The light guide having a first exit surface on which reflected light from an illuminated object is incident and a second exit surface facing the first exit surface and emitting reflected light toward an observer. A plurality of linear protrusions are formed on the surface, and each of the protrusions is arranged in parallel from the incident surface toward the terminal surface on the second emission surface, and a second emission surface is formed. The height of each projection with respect to the flat surface of the surface gradually increases as approaching from the incident surface to the terminal surface.
[0009]
The invention according to claim 2 of the present application is the light guide according to claim 1, wherein each of the protrusions is a protrusion having a triangular cross section, the height of the protrusion closest to the incident surface is h0, The distance of the closest protrusion from the incident surface is x0, the height of the protrusion farthest from the incident surface is hm, the distance of the furthest protrusion from the incident surface is xm, and the height h of a certain protrusion is h. Is the distance from the incident surface to the projection, x
h = h0 + (hm−h0) * ((x−x0) / (xm−x0)) ＾ n
(K ＾ j represents k raised to the j-th power), h0 is 0.2 hm to 0.4 hm, and n is 2.5 to 3.5.
[0010]
The invention according to claim 3 of the present application is the light guide according to claim 1 or 2, wherein each of the protrusions is configured to direct the internal light toward the first exit surface side with the first inclined surface transmitting the reflected light. A second inclined surface that reflects light, wherein an inclination angle of the first inclined surface with respect to a flat surface of the second emission surface is set to 4 ° to 10 °.
[0011]
According to a fourth aspect of the present invention, in the light guide according to any one of the first to third aspects, each of the protrusions includes a first inclined surface that transmits the reflected light, and a first inclined surface that transmits the internal light. And a second inclined surface that reflects light toward the second exit surface, and an inclination angle of the second inclined surface with respect to a flat surface of the second exit surface is 35 ° to 45 °.
[0012]
According to a fifth aspect of the present invention, there is provided a first emission surface which emits light to an object to be illuminated and receives reflected light from the object to be illuminated; In a light guide having a pair of left and right entrance surfaces into which light is incident, and a second exit surface facing the first exit surface and emitting reflected light to the observer side, the second exit surface includes: A plurality of linear protrusions are formed, and each of the protrusions is arranged in parallel on the second exit surface from the incident surface toward the terminal surface, and the second exit surface is located on a flat surface of the second exit surface. The height of each projection gradually increases as it approaches the center in the left-right direction from the incident surface.
[0013]
The invention according to claim 6 of the present application is directed to an incident surface on which light from a light source is incident, a terminal surface opposed to the incident surface, and an internal light incident from the incident surface, which is emitted toward an object to be irradiated and is irradiated with light. The light guide having a first exit surface on which reflected light from an illuminated object is incident and a second exit surface facing the first exit surface and emitting reflected light toward an observer. On the surface, a plurality of linear projections having a first inclined surface transmitting the reflected light and a second inclined surface reflecting the internal light toward the first exit surface side are formed, and Each projection is arranged in parallel from the incident surface to the terminal surface on the second exit surface, and the reflection area of the second inclined surface of each projection is such that the amount of reflected light on the second inclined surface is substantially constant. Thus, the distance increases as the distance from the incident surface increases.
[0014]
According to a seventh aspect of the present invention, in the light guide according to any one of the first to sixth aspects, an arrangement pitch of the projections is constant.
[0015]
The invention of claim 8 of the present application is characterized by including the light guide according to any one of claims 1 to 7 and a light source provided on a side of the light guide on the incident surface side.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 18 show an embodiment of the present invention. FIG. 1 is a perspective view of a light guide of the present invention, a front light type illumination device including the same, and an object to be illuminated disposed below the front light illumination device.
As shown in FIG. 1, a front light illuminating device 1 includes a light guide 2 and a light source 3, and emits light of the light source 3 to an object 4 disposed below. Irradiation through. The irradiation object 4 is, for example, a reflection type liquid crystal panel 4a, and as shown in FIG. 1 or 2, light irradiated from the light guide 2 is reflected on the display unit 5 side of the reflection type liquid crystal panel 4a. An image displayed on the display unit 5 of the reflective liquid crystal panel 4a is provided to an observer E facing the liquid crystal panel 4a via the light guide 2.
[0017]
The light guide 2 (light guide plate) of the front light type illuminating device 1 is formed in a thin plate shape, and has a light incident surface 7 on a side end on which light enters, and a terminal surface 8 facing the light incident surface 7. , A first exit surface 9 and a second exit surface 10. The light source 3 of the front light type illuminating device 1 is configured by a cold cathode tube, an LED, or the like, and is disposed on the side of the incident surface 7. The light enters the light guide 2.
[0018]
The first emission surface 9 of the light guide 2 is a flat surface on the back surface side of the light guide 2 and is provided so as to be located above the display unit 5 of the reflective liquid crystal panel 4a. The first exit surface 9 has a function of emitting (transmitting) the internal light L1 incident from the incident surface 7 to the reflective liquid crystal panel 4a side and of entering (transmitting) the reflected light L2 from the reflective liquid crystal panel 4a. Have. The second exit surface 10 of the light guide 2 is a surface on the front side facing the first exit surface 9, and the surface of the second exit surface 10 has a plurality of strip-shaped (linear) protrusions 11. Is formed. The second emission surface 10 emits (transmits) the reflected light L2 reflected from the display unit 5 of the reflective liquid crystal panel 4a to the observer E side, and reflects the internal light L1 to the first emission surface 9 side. Has a function.
[0019]
Each of the protrusions 11 is a protrusion having a triangular cross section. A plurality of protrusions 11 are arranged in parallel from the incident surface 7 toward the terminal surface 8 such that the top ridge line of the protrusion 11 is substantially parallel to the longitudinal direction of the incident surface 7. are doing. The length L of each projection 11 is substantially constant, and the arrangement pitch P of each projection 11 is substantially constant. The height H of each projection 11 (the height H of each projection 11 with respect to the flat surface of the second emission surface 10) gradually increases from the entrance surface 7 to the terminal surface 8. In addition, the protrusion 11 includes a first inclined surface 12 that transmits the reflected light L2 from the display unit 5 of the reflective liquid crystal panel 4a, and a second inclined surface 13. The first inclined surface 12 is inclined from the normal N to the incident surface 7 side, and the second inclined surface 13 is inclined to the end surface 8 side, as viewed from the top ridge line of the protrusion 11.
[0020]
As shown in FIG. 3, in each of the protrusions 11, the first inclined surface 12 has a gentler inclination than the second inclined surface 13, and the first inclined surface 12 with respect to the flat surface of the second emission surface 10. The inclination angle α and the inclination angle β of the second inclined surface 13 with respect to the flat surface of the second emission surface 10 are constant. The second inclined surface 13 reflects the internal light L1 toward the first emission surface 9 and emits the light to the display unit 5 of the reflective liquid crystal panel 4a provided along the first emission surface 9 ( Irradiation).
Therefore, the internal light L1 incident on the light guide 2 from the incident surface 7 by the first and second exit surfaces 9, 10 is as follows.
[0021]
As shown in FIGS. 2 and 3, the internal light L <b> 1 that has entered the inside from the incident surface 7 propagates toward the terminal surface 8 while being reflected by the first exit surface 9 and the second exit surface 10. A part of the internal light L1 is reflected by the second inclined surface 13 of the second exit surface 10 and travels toward the first exit surface 9, and the light is transmitted from the first exit surface 9 to the display of the reflective liquid crystal panel 4a. The reflected light L2 emitted from the first exit surface 9 as the emitted light L3 toward the unit 5 and reflected from the display unit 5 side of the reflective liquid crystal panel 4a enters the interior from the first exit surface 9 and is reflected by the reflected light L2. L2 propagates in the light guide 2 in the thickness direction (the direction of the normal line N) and exits from the first inclined surface 12 of the second exit surface 10 and the flat surface of the second exit surface 10 to the observer E side. .
Here, the light reflected by the second inclined surface 13 and incident on the reflection type liquid crystal panel 4 a is uniform due to the configuration of the projection 11.
[0022]
As shown in FIGS. 2 and 3, part of the internal light L <b> 1 incident from the incident surface 7 is reflected by the second inclined surface 13 of each projection 11 and propagates to the display unit 5 of the reflective liquid crystal panel 4 a. Therefore, the light amount (luminance) of the internal light L1 propagating in the light guide 2 gradually decreases as the distance from the light source 3 increases (from the incident surface 7 side to the terminal surface 8 side).
[0023]
In the case of the present embodiment, since the length L of each projection 11 is constant and the inclination angles α and β of the first and second inclined surfaces 12 and 13 are constant, the height H of the projection 11 is reduced. When the height is gradually increased from the incident surface 7 to the terminal surface 8 (as the distance from the incident surface 7 is increased), the light reflection area of the second inclined surface 13 of each protrusion 11 is changed from the incident surface 7 side to the terminal surface 8 side. It gradually increases as it becomes. Therefore, even if the light amount of the internal light L1 gradually decreases toward the end surface 8 side, the ratio of the internal light L1 impinging on the second inclined surface 13 increases due to the increase in the reflection area of the second inclined surface 13, so that each of the second The amount of reflected light on the inclined surface 13 is substantially constant, so that the emitted light L3 propagating to the reflective liquid crystal panel 4a is entirely uniform.
In other words, at a position where the amount of the internal light L1 is large, the reflection area of the second inclined surface 13 is reduced, and at a position where the amount of the internal light L2 is small, the reflection area of the second inclined surface 13 is increased. The variation in the amount of reflected light reflected by each second inclined surface 13 is eliminated.
[0024]
As shown in FIG. 2, the arrangement pitch P of the projections 11 is constant, and if this arrangement pitch P is smaller than or equal to the pixel pitch of the display unit 5 of the reflection type liquid crystal panel 4a, the reflection type liquid crystal panel In addition to preventing double reflection of the display unit 5a of the display unit 4a, the image quality does not deteriorate.
Here, as shown in FIG. 3, the inclination angle α of the first inclined surface 12 of each projection 11 with respect to the flat surface of the second emission surface 10 is constant, and each projection 11 with respect to the flat surface of the second emission surface 10 is fixed. When the inclination angle β of the second inclined surface 13 is constant, the maximum height of the protrusion 11 that can be formed on the second exit surface 10 is:
H = p · tanα · tanβ / (tanα + tanβ)
It is expressed as For example, if α = 6 ° (constant), β = 40 ° (constant), and P = 100 μm, the maximum height is 9.3 μm.
[0025]
The height of the protrusion 11 closest to the incident surface 7 is h0, the distance of the protrusion 11 closest to the incident surface 7 from the incident surface 7 is x0, and the height of the protrusion 11 farthest from the incident surface 7 is hm. The distance of the projection 11 farthest from the incident surface 7 from the incident surface 7 is xm. The height h of a certain projection 11 is represented by x when the distance from the incident surface 7 is x.
h = h0 + (hm−h0) * ((x−x0) / (xm−x0)) ＾ n (1)
(K ＾ j represents k raised to the j-th power). Here, for example, h0 is 0.2 hm to 0.4 hm.
[0026]
For example, the inclination angle α of the first inclined surface 12 of each projection 11 is 6 ° (constant), the inclination angle β of the second inclined surface 13 of each projection 11 is 40 ° (constant), and each projection 11 The height h of each projection 11 when the arrangement pitch P is 100 μm is calculated, and the amount of reflected light with respect to the distance from the projection 11 closest to the incident surface 7 is n = 2.0 to 4.0. When measured in the range, the result shown in FIG. 4 was obtained. According to FIG. 4, the amount of reflected light is relatively uniform even at a position distant from the protrusion 11 closest to the incident surface 7. According to this graph, n is preferably set to 2.5 to 3.5. In particular, when n = 3.0 in the equation (1), the amount of reflected light is most uniform.
In FIG. 4, a curve a represents the amount of reflected light of the conventional front light device when the pitch and height of the protrusions are constant. The light quantity does not decrease.
[0027]
By the way, as shown in FIG. 3, not all the internal light L1 hitting the second inclined surface 13 of the projection 11 is reflected by the second inclined surface 13, and part of the internal light L1 is stray light L4 toward the observer E. Inject. When the amount of the stray light L4 is large and the exit direction of the stray light L4 substantially coincides with the direction of the normal line N, that is, when the stray light angle i2 between the stray light L4 and the normal line N is near 0 °, the observer E There is a possibility that the display unit 5 of the reflection type liquid crystal panel 4a becomes difficult to see. Further, when the amount of the stray light L4 increases, the reduction rate of the internal light L1 propagating in the light guide 2 increases, so that the luminance of the emission light L3 emitted to the reflective liquid crystal panel 4a decreases, and the contrast decreases. The visibility of the display unit 4a may be deteriorated.
[0028]
Therefore, in the present embodiment, the inclination angle α of the first inclined surface 12 with respect to the flat surface of the first emission surface 9 is set to 4 ° to 10 °, and the angle of the second inclined surface 13 with respect to the flat surface of the second emission surface 10 is set. By setting the inclination angle β to 35 ° to 45 °, the amount of the stray light L4 is suppressed, and the luminance of the emitted light L3 emitted to the reflective liquid crystal panel 4a is improved.
The propagation direction of the emitted light L3 emitted from the light guide 2 to the reflective liquid crystal panel 4a is preferably the normal N direction, and usually the emitted light L3 emitted from the light guide 2 to the reflective liquid crystal panel 4a. The inclination angle α of the first inclined surface 12 and the inclination angle β of the second inclined surface 13 are set so that the emission light angle i1 with respect to the normal N is close to 0 °.
[0029]
For example, when the inclination angle β of the second inclined surface 13 is 40 ° (constant) and the inclination angle α of the first inclined surface 12 is changed from 2 ° to 20 ° in increments of 2 °, the emission light angles i1 and The light intensity of the emitted light L3 (TE, TM) and the light intensity of the stray light L4 (TE, TM) with respect to the stray light angle i2 are as shown in FIGS. As shown in FIGS. 5 to 14, when the inclination angle α of the first inclined surface 12 is 4 ° to 20 °, the light intensity of the emitted light L3 (TE, TM) when the emitted light angle i1 is near 0 ° is 1 2 or more, and the difference due to the change in the inclination angle α is small. When the inclination angle α is 10 ° or more, the amount of stray light L4 (TE, TM) increases as a whole.
Therefore, as shown in FIGS. 6 to 9, the inclination angle α of the first inclined surface 12 is an angle at which the light intensity of the emitted light L3 is high (1.2 or more) and the amount of the stray light L4 is small, that is, It is preferable to set in the range of 4 ° to 10 °.
[0030]
Further, when the inclination angle α of the first inclined surface 12 is 6 ° (constant) and the inclination angle β of the second inclined surface 13 is changed in increments of 5 ° from 30 ° to 50 °, the emission light angle i1 and The light intensity of the emitted light L3 (TE, TM) and the light intensity of the stray light L4 (TE, TM) with respect to the stray light angle i2 are as shown in FIG. 7 and FIGS. As shown in FIG. 15, when the inclination angle β of the second inclined surface 13 is 30 °, the emission light angle i1 when the light intensity of the emission light L3 (TE, TM) reaches a peak is about 30 °. As a result, the emission light angle i1 is deviated more than 0 °. Further, as shown in FIG. 18, when the inclination angle β of the second inclined surface 13 is 50 °, the emission light angle i1 when the light intensity of the emission light L3 (TE, TM) reaches a peak is about −20 °. Thus, the emission light angle i1 is largely shifted from 0 °.
Therefore, as shown in FIG. 7 and FIGS. 16 to 17, the inclination angle β of the second inclined surface 13 is such that the peak of the light intensity of the emitted light L3 (TE, TM) is near the emitted light angle i1 of 0 °. Preferably, the angle is set in the range of 35 ° to 45 °.
[0031]
As described above, according to the configuration of the projection 11 on the second emission surface 10, the height of the projection 11 increases as the distance from the light source 3 (incident surface 7) in the left-right direction increases, so that light is reflected on the projection 11. Since the area is increased, the amount of reflected light at each projection 11 is substantially constant even at a position distant from the light source 2, and the arrangement pitch P of the projections 11 is constant. The luminance of the emitted light L3 is made uniform overall.
[0032]
Further, by setting the inclination angles α and β of the first inclined surface 12 and the second inclined surface 13 as described above, the amount of stray light L4 emitted from the light guide 2 can be reduced. Accordingly, the light efficiency of the light source 3 can be improved, and power saving can be achieved in the front light lighting device 1.
Furthermore, if the arrangement pitch P of the projections 11 is made to correspond to the pixel pitch of the display unit 5 of the reflective liquid crystal panel 4a, the amount of incident light per pixel (per unit area) of the display unit 5 is substantially constant. It is possible to
[0033]
The present invention is not limited to the above-described embodiment, and can be appropriately changed in design. In the above embodiment, the arrangement pitch P of the projections 11 is fixed, but may be irregular according to the form of the irradiation object.
[0034]
Further, in the above-described embodiment, the incident surface 7 and the terminal surface 8 opposed thereto are provided. However, instead of this, the terminal surface 8 is used as another incident surface 7 ′, and the incident surface 7 ′ is provided beside the incident surface 7 ′. The light source 3 may be provided so that light enters the light guide 2 from both right and left end surfaces of the light guide 2. In this case, the height of the protrusion 11 may be increased as the distance from the light source 2 (the incident surface 7 and the incident surface 7 ′) increases. Therefore, the protrusion 11 located at the center in the left-right direction of the light guide 2 is the most. The height of the protrusion 11 may be gradually reduced as the distance from the protrusion 11 approaches the direction of the incident surface 7 and the incident surface 7 ′.
[0035]
The reflection type liquid crystal device including the front light illumination device 1 and the reflection type liquid crystal panel 4a can be mounted on various image display devices and the like. This reflective liquid crystal device can be mounted on, for example, a personal computer (notebook computer), a portable terminal (PDA), a portable television, and the like.
[0036]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, in the light guide and the front light illuminating device provided with the same, it becomes possible to make the emitted light irradiating an irradiation object uniform. Further, the amount of stray light emitted from the light guide can be reduced.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a light guide of the present invention and an object to be illuminated (reflective liquid crystal panel) disposed below a front light illuminating device provided with the light guide.
FIG. 2 is a longitudinal sectional view of FIG.
FIG. 3 is an explanatory diagram of propagation of internal light and a projection.
FIG. 4 is a distribution diagram of the amount of reflected light at a distance x.
FIG. 5 is a characteristic diagram of emission light intensity at a first inclination angle (α = 2 °) and a second inclination angle (β = 40 °).
FIG. 6 is a characteristic diagram of emission light intensity at a first inclination angle (α = 4 °) and a second inclination angle (β = 40 °).
FIG. 7 is a characteristic diagram of emission light intensity at a first inclination angle (α = 6 °) and a second inclination angle (β = 40 °).
FIG. 8 is a characteristic diagram of emission light intensity at a first inclination angle (α = 8 °) and a second inclination angle (β = 40 °).
FIG. 9 is a characteristic diagram of emission light intensity at a first inclination angle (α = 10 °) and a second inclination angle (β = 40 °).
FIG. 10 is a characteristic diagram of emission light intensity at a first inclination angle (α = 12 °) and a second inclination angle (β = 40 °).
FIG. 11 is a characteristic diagram of emission light intensity at a first inclination angle (α = 14 °) and a second inclination angle (β = 40 °).
FIG. 12 is a characteristic diagram of emission light intensity at a first inclination angle (α = 16 °) and a second inclination angle (β = 40 °).
FIG. 13 is a characteristic diagram of emission light intensity at a first inclination angle (α = 18 °) and a second inclination angle (β = 40 °).
FIG. 14 is a characteristic diagram of emission light intensity at a first inclination angle (α = 20 °) and a second inclination angle (β = 40 °).
FIG. 15 is a characteristic diagram of emission light intensity at a first inclination angle (α = 6 °) and a second inclination angle (β = 30 °).
FIG. 16 is a characteristic diagram of emission light intensity at a first inclination angle (α = 6 °) and a second inclination angle (β = 35 °).
FIG. 17 is a characteristic diagram of emission light intensity at a first inclination angle (α = 6 °) and a second inclination angle (β = 45 °).
FIG. 18 is a characteristic diagram of emission light intensity at a first inclination angle (α = 6 °) and a second inclination angle (β = 50 °).
FIG. 19 is a perspective view of a conventional front light illumination device.
FIG. 20 is a side view of a conventional front light lighting device.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 front light illuminating device 2 light guide 3 light source 4 illuminated object 5 display unit 7 incident surface 8 end surface 9 first exit surface 10 second exit surface 11 protrusion 12 first inclined surface 13 second inclined surface E L1 Internal light L2 Reflected light L3 Emitted light L4 Stray light

Claims (8)

An incident surface into which light from a light source is incident, an end surface facing the incident surface, and an internal light incident from the incident surface is emitted toward the irradiated object and reflected light from the irradiated object is incident. In a light guide having a first emission surface and a second emission surface facing the first emission surface and emitting reflected light toward the observer,
A plurality of linear projections are formed on the second emission surface, and each of the projections is arranged in parallel on the second emission surface from the incident surface toward the termination surface. A height of each of the projections with respect to the flat surface of the second exit surface gradually increases from the entrance surface to the terminal surface. Each of the protrusions is a protrusion having a triangular cross section. The height of the protrusion closest to the incident surface is h0, the distance of the protrusion closest to the incident surface from the incident surface is x0, and the distance is farthest from the incident surface. The height of the protrusion is hm, the distance from the incident surface of the protrusion farthest from the incident surface is xm, the height h of a certain protrusion is x the distance from the incident surface to the protrusion,
h = h0 + (hm−h0) * ((x−x0) / (xm−x0)) ＾ n
2. The light guide according to claim 1, wherein h0 is 0.2 hm to 0.4 hm, and n is 2.5 to 3.5. body. Each of the protrusions has a first inclined surface that transmits the reflected light, and a second inclined surface that reflects the internal light toward the first exit surface side, and the second exit surface is flat. The light guide according to claim 1, wherein an inclination angle of the first inclined surface with respect to a plane is set to 4 ° to 10 °. Each of the protrusions has a first inclined surface that transmits the reflected light, and a second inclined surface that reflects the internal light toward the first exit surface side, and the second exit surface is flat. The light guide according to any one of claims 1 to 3, wherein an inclination angle of the second inclined surface with respect to a plane is 35 ° to 45 °. A first exit surface that emits light to the irradiation object side and receives reflected light from the irradiation object; and a pair of left and right entrances located at the left and right ends of the first emission surface and incident light inside. A light guide having a surface and a second exit surface facing the first exit surface and emitting reflected light toward the observer;
A plurality of linear projections are formed on the second emission surface, and each of the projections is arranged in parallel on the second emission surface from the incident surface toward the terminal surface, The height of each projection with respect to the flat surface of the second exit surface gradually increases as approaching the central portion in the left-right direction from the entrance surface. An incident surface into which light from a light source is incident, an end surface facing the incident surface, and an internal light incident from the incident surface is emitted toward the irradiated object and reflected light from the irradiated object is incident. In a light guide having a first emission surface and a second emission surface facing the first emission surface and emitting reflected light toward the observer,
On the second exit surface, a plurality of linear projections having a first inclined surface transmitting the reflected light and a second inclined surface reflecting the internal light toward the first exit surface are formed. And
The projections are arranged in parallel on the second exit surface from the incident surface to the terminal surface, and the reflection area of the second inclined surface of each projection is substantially constant in the amount of light reflected by the second inclined surface. A light guide, which increases as the distance from the entrance surface increases. The light guide according to any one of claims 1 to 6, wherein an arrangement pitch of the projections is constant. A front light type illuminating device comprising: the light guide according to claim 1; and a light source provided on a side of an incident surface of the light guide.

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