JP2006128041A - Light emitting device and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device having a condensing body capable of improving utilization efficiency of light and a liquid crystal display device. <P>SOLUTION: The light emitting device 1 has a light source 3 and a condenser 4 on a support body 2 with a light reflecting mirror. The condenser 4 has a nearly circular truncated cone shape and its upper bottom side (lower side in the figure) is an incident side end face 41 and the lower bottom side (upper side in the figure) is an outgoing side end face 42. The shape of the side face 43 is a paraboloid which is a part of parabolas A, B making the end points a, b of the incident side end face 41 as a focus respectively in the cross-section including the center line LC. Light emitted from the light source 3 enters into the condenser 4 from the incident side end face 41 and is condensed mostly at the side face 43 and is emitted from the outgoing side end face 43. Thereby, the utilization efficiency of light at the light emitting device 1 can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device that collects and emits light emitted from a light source and a liquid crystal display device having the light emitting device.

  2. Description of the Related Art Conventionally, in an illumination optical system such as a liquid crystal projector, light (light flux) emitted from a light source is condensed and imaged by a lens or the like and projected onto a screen or the like. However, the amount of light beam that can pass through the lens is limited by the focal point of the lens and the pupil size (F value), and all of the light emitted from the light source cannot pass through. Therefore, the luminance of the final projected image is reduced by limiting the amount of light flux in the illumination optical system.

  In general, the luminance of light emitted from the light source has a spatially non-uniform distribution. Therefore, due to such non-uniformity of the luminance distribution, even in an image that has passed through the illumination optical system and is projected onto a screen or the like, a non-uniform luminance distribution will occur. Therefore, in order to eliminate such non-uniform luminance distribution, a fly-eye lens is generally used. However, when a Fly-eye lens is used, the amount of luminous flux that can pass through the lens is further limited by the F value of the lens group that constitutes the lens. As described above, when the Fly-eye lens is used as the illumination optical system, the luminance distribution of the projection image can be made uniform, but the luminance of the final projection image is further reduced. .

  Therefore, it is conceivable to use a condenser that collects light emitted from the light source instead of the above-described lens or the like as the illumination optical system. Various concentrators have been proposed in the past depending on the application.

  For example, in Patent Document 1, the shape of a reflector having a high light reflectance has a light receiving area that is smaller than that on the light receiving side, and the cross section is formed of a rotating surface of a quadratic curve or a polygonal pyramid. A concentrator having a shape in which a surface where a reflector faces in the direction of a quadratic curve vertex is configured in parallel and a focal point and a focal point plane or a parallel part and a parallel part bottom face are used as a condensing surface is disclosed.

  Further, in Patent Document 2, a condensing part having a highly reflective inner peripheral surface that converges from the rear end side toward the front end side, and a front end part communicate with the rear end part of the condensing part, This is combined with an optical axis aligning portion having an inner peripheral surface whose diameter increases from the front end portion toward the rear end portion and whose diameter expansion rate is larger than the diameter collecting rate at the rear end portion of the light collecting portion. A concentrator of shape is disclosed.

  Patent Document 3 includes a hollow tube having a pair of openings facing each other, and one opening functions as a laser light inlet, and the other opening functions as a laser light exit. A laser concentrator having a shape in which the diameter of the laser light entrance is larger than the diameter of the laser light exit is disclosed.

JP 2003-149586 A JP 2003-98405 A JP 2004-55819 A

  However, in these techniques, when the condenser is directly connected to the light source, depending on the light emission angle of the light source, the Etendue's relational expression (formula (1) shown below), which is the basic principle of the illumination optical system, Some light cannot enter the collector.

Sin · Ωin <Sout · Ωout (1)
(Wherein, Sin is the area of the light incident port in the light collector, Ωin is the divergence angle of light that can enter from the light incident port, Sout is the area of the light output port in the light collector, and Ωout is the light emitted from the light output port. Represents the angle of divergence of

  For these reasons, in the techniques of Patent Documents 1 to 3, for example, as shown in FIG. 1 in Patent Document 1, FIG. 2 in Patent Document 2, and FIG. 1 in Patent Document 3, The incident angle of light with respect to the collector is limited to a certain range. In other words, the light emitted from the light source can be incident on the collector only if the incident angle with respect to the collector is within a certain range. Light utilization efficiency will fall.

  As described above, in the conventional technique in which the incident angle of light with respect to the condenser is limited within a certain range, it is difficult to improve the utilization efficiency of the light emitted from the light source.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a light emitting device and a liquid crystal display device including a light collecting body capable of improving the light utilization efficiency.

  The light-emitting device of the present invention includes an incident-side end surface, an exit-side end surface that is coaxially opposed to the center line of the incident-side end surface and has a larger area than the incident-side end surface, and an end point of the incident-side end surface in a cross section including the center line. Having a parabolic surface including one or more types of parabolas with a focal point, and condensing incident light through the incident side end surface, and emitting the light from the output side end surface within a range of a predetermined emission angle. A light collecting body and a light source that emits light to the light collecting body are provided.

  The liquid crystal display device of the present invention includes the light collector, the light source, and a liquid crystal panel that modulates light emitted from the light collector based on a video signal.

  In the light emitting device and the liquid crystal display device of the present invention, the light emitted from the light source is incident on the light collecting body at an arbitrary angle from the incident side end surface, and is collected on the side surface including a predetermined paraboloid, and the incident side end surface The light is emitted within a certain angle from the emission side end face having a larger area. That is, most of the light emitted from the light source is collected and emitted by the light collector having a predetermined shape.

  According to the light emitting device of the present invention, the light collector is configured in a predetermined shape, and most of the light emitted from the light source is collected and emitted, so that the light use efficiency can be improved. .

  In addition, according to the liquid crystal display device of the present invention, since it is configured using the light emitting device as described above, the luminance of the device can be improved by increasing the light utilization efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional structure of a light emitting device according to an embodiment of the present invention. The light-emitting device 1 includes a light source 3 and a light collector 4 on a support 2 with a light reflecting mirror.

  The support body 2 with the light reflector is a support body for the light source 3 and the light collector 4, and reflects a part of the light emitted from the light source 3 and guides it in the direction of the light collector 4. . The support body 2 with the light reflecting mirror is made of, for example, an aluminum film.

  The light source 3 disposed on the support body 2 with the light reflecting mirror may be constituted by either a point light source or a surface light source. Examples of the former include a cold cathode fluorescent lamp (CCFL), and examples of the latter include a light emitting diode (LED).

  The light collector 4 condenses incident light from the light source 3 and emits the light within a range of a fixed emission angle as will be described later. The light collector 4 is disposed on the light source 3 and is made of, for example, glass (BK7), plastic (PMMA), or quartz.

  Next, with reference to FIG. 2 and FIG. 3, the detail of the structure of the condensing body 4 is demonstrated. FIG. 2 is a perspective view showing an example of the structure of the light collector 4. The light collector 4 has a substantially truncated cone shape, and the upper base side (lower side in the figure) is an incident side end face 41 and the lower base side (upper side in the figure) is an outgoing side end face 42.

  The incident side end face 41 faces the light source 3, and in the example shown in FIG. 2, the shape is a circle centered on the point C1.

  Incident light LI from the incident side end face 41 is condensed on the side face 43 of the condenser 4. The shape of the side surface 43 is a parabola that is a parabola that is focused on the end point of the incident side end surface 41 in the cross section including the center line LC.

  The light condensed on the side surface 43 is emitted from the emission side end face 42 (emitted light LO). In the example shown in FIG. 2, the shape is a circle having a larger area than the incident side end surface 41 with the point C2 on the center line LC including the center C1 as the center.

FIG. 3 shows the light collector 4 shown in FIG. 2 in a cross-sectional view including the center line LC as described above. The condensing body 4 includes an incident side end line ab that is a part of the incident side end face 41, an output side end line a ₀ -b ₀ that is a part of the output side end face 42, and a pair of parabolas ab. ₀ and b−a ₀ .

The pair of parabolas a-b ₀ and b-a ₀ are respectively composed of part of parabolas B and A having focal points b and a on the incident-side end line a-b. Further, the straight lines A1 and B1 in FIG. 3 represent the symmetry axes of the parabolas A and B, respectively, and the angle θ represents the angle formed by the symmetry axes A1 and B1.

Here, this light collector 4, for example, when the emission light L1 from the light source 3 is incident, the light is totally reflected on the parabolic b-a _0, emitted from the emission end lines a ₀ -b ₀ . Also, for example, when the emitted light beam L2 is incident from a direction substantially along the incident side end line ab, the light is totally transmitted near the focal point a or the focal point b on the parabola ab ₀ or ba _0. Reflected (totally reflected in the vicinity of the focal point a in the example of the emitted light beam L2) and emitted from the end point a ₀ or the vicinity of the end point b ₀ on the emission side end line a ₀ -b ₀ (example of the emitted light beam L2) Then, the light is emitted from the vicinity of the end point a ₀ ). At this time, the optical path of the emitted light beam L2 is parallel to the symmetry axis B1 or the symmetry axis A1 (in the example of the emitted light beam L2, it is parallel to the symmetry axis B1), and therefore the relationship of the following expression (2) is established.

  (Angle formed by symmetry axes) = (Maximum emission angle of emitted light from the emission side end face) = θ (2)

  Therefore, if the emission angle of light emitted from the light source 3 is less than 180 °, the light source 3 is disposed below the light collector 4 as shown in FIG. 1 and the light is incident from the incident side end face 41. Thus, most of the light can be collected at the side surface 43 and emitted from the emission side end face 42 within the range of the maximum emission angle θ. In this way, the light use efficiency in the light emitting device 1 can be greatly improved.

  In the example of FIG. 3, assuming that the diameter of the incident-side end face 41 is Rin, the diameter of the outgoing-side end face 42 is Rout, and the maximum outgoing angle of outgoing light is θ, Rin, Rout and θ are expressed by the following equation (3). Satisfy the relationship.

  Rout = Rin / sin θ (3)

  Therefore, as described above, since the emission angle of the emitted light is less than 180 °, the diameter Rout of the emission side end face 42 is larger than the diameter Rin of the incident side end face 41. That is, as described above, the area of the emission side end face 42 is larger than the area of the incident side end face 41.

With such a configuration, in the light emitting device 1 according to the present embodiment, the light emitted from the light source 3 enters the light collector 4 from the incident side end face 41 and is collected on the side surface 43 formed of a predetermined paraboloid. The light is emitted from the emission side end face 43 having a larger area than the incident side end face 41. At that time, the shape of the side surface 43 is a part of the parabolas A and B (parabolas ab ₀ and ba ₀ ) having focal points at the end points a and b of the incident side end surface 41 in the cross section including the center line LC. By being a certain paraboloid, the angle formed between the symmetry axes A1 and B1 of the parabolas A and B is equal to the maximum emission angle of the light emitted from the condenser 4 (angle θ). Therefore, if the emission angle of the light emitted from the light source 3 is less than 180 °, the light source 3 is disposed below the light collector 4 as shown in FIG. 1 and the light is incident from the incident side end face 41. Thus, most of the light is collected on the side surface 43 and emitted from the emission side end face 42 within the range of the maximum emission angle θ.

  Next, the light use efficiency in the light emitting device 1 will be described. The light use efficiency in the light-emitting device 1 is obtained by comparing, for example, the amount of light emitted from the light source 3 and the amount of light emitted from the condenser 4. For example, an integrating sphere is used for measuring the amount of light flux.

  FIG. 4 shows the result of measuring the luminous flux of the light emitting device 1 (using a 3 mm × 3 mm LED as the light source 3) using an integrating sphere as described above. In this figure, the vertical axis represents the amount of light flux per unit wavelength (lm / nm), and the horizontal axis represents the wavelength (nm) of the emitted light from the light emitting device 1. In addition, a waveform P1 in the figure represents the amount of light emitted from the light source 3, and the waveform P2 represents the amount of light emitted from the light emitting device 1, that is, the amount of light collected after condensing in the condenser 4.

  Thus, it can be seen that the waveforms P1 and P2 are almost the same. The difference between the light fluxes in these waveforms is about 2 (lm / nm), and the condenser 4 is about 94% of the light emitted from the light source 3 made of LED, that is, most of the light. It can be seen that the light is condensed. Therefore, it can be seen that the light utilization efficiency in the light emitting device 1 is about 94%, which improves the light utilization efficiency.

  As described above, in the present embodiment, the light collector 4 is configured in a predetermined shape including the side surface 43 formed of a predetermined paraboloid, and most of the light emitted from the light source 3 is collected and emitted. As a result, the light use efficiency in the light emitting device 1 can be improved.

  Further, the condensed light can be emitted within the range of the maximum emission angle θ that is equal to the angle θ formed by the symmetry axes of the parabolas in the cross section including the center line LC of the side surface 43 of the condenser 4. Therefore, it becomes possible to grasp the maximum emission angle of the emitted light in advance at the time of design or the like.

  Further, the shapes of the incident side end face 41 and the emission side end face 42 may be set so as to satisfy the above-described formula (3), and therefore can be easily formed.

  Furthermore, the light source 3 may be composed of, for example, either a point light source or a surface light source, and can have various configurations, so that the degree of design freedom can be improved.

  The light emitting device of the present embodiment described above can be applied to a direct-view type or a projection type liquid crystal display device as shown in FIGS. 5 and 6, for example. In the former case, for example, a liquid crystal panel 6 that modulates the light emitted from the light collector 4 based on the video signal may be disposed on the light emission side of the light emitting device 1 of the present invention (shown in FIG. 5). Liquid crystal display device 5). On the other hand, in the latter case, for example, the liquid crystal panel 6 as described above is disposed on the light emitting side of the light emitting device 1 of the present invention, and the light modulated by the liquid crystal panel 6 is projected onto a screen 72 or the like. For example, a lens 71 in FIG. 6 may be provided (the liquid crystal projector 7 shown in FIG. 6). As described above, when a direct-view or projection-type liquid crystal display device is configured using the light-emitting device 1 of the present invention, the luminance of the liquid crystal display device is increased as the light use efficiency of the light-emitting device 1 increases. Can do. For example, the above-mentioned Fly-eye lens is disposed between the light emitting device 1 and the liquid crystal panel 6 so that the luminance distribution of the light emitted from the light emitting device 1 is uniformized and then incident on the liquid crystal panel 6. May be.

  The present invention is not limited to the embodiment described above, and various modifications can be made.

  For example, as shown in FIG. 7, a matching layer 8 whose refractive index matches the refractive index of the light collector 4 is provided at the junction between the light source 3 and the incident side end face 41 of the light collector 4. It may be. The matching layer 8 is made of, for example, immersion oil or water. For example, when the light collector 4 is made of glass (BK7; refractive index 1.49) or plastic (PMMA; refractive index 1.50) as described above, the matching layer 8 has a refractive index of, for example, 1. An acrylic solution of about 50 can be applied. Further, as shown in FIG. 8, even when the light source of the light emitting device 1 is configured by the LED light source 9 that is a surface light source, the above-described alignment is made at the joint between the light emitting region 91 and the light collector 4. A layer 8 can be provided. By providing such a matching layer 8, for example, even when there is a gap between the light source and the light collector 4, incident light from the light source is reflected at the interface between the matching layer 8 and the light collector 4. The light is incident on the light collector 4 without being refracted or greatly refracted, and the light use efficiency in the light emitting device 1 can be further improved.

  In the above embodiment, the case where the entire light collector 4 is filled with the above-described material has been described. However, for example, as shown in FIG. 9, the inside of the light collector 4 is made hollow. You may comprise. Even in such a case, the same effect as in the case of the above embodiment can be obtained.

  Moreover, although the said embodiment has demonstrated the example in case the shape of the incident side end surface 41 and the output side end surface 42 in the condensing body 4 is a circle centering on intersection C1, C2 with the centerline LC. However, the shape is not necessarily circular, and may be, for example, an ellipse or a polygon centered on the intersections C1 and C2. That is, the shape of the side surface 43 only needs to be configured by a paraboloid that includes one or more parabolas that are focused on the end point of the incident-side end surface 41 in the cross section including the center line LC. Even in this case, the same effect as in the case of the above embodiment can be obtained.

  Note that the material and thickness of each component described in the above embodiment, the film formation method and the film formation conditions are not limited, and other materials and thicknesses may be used. Film forming conditions may be used.

It is sectional drawing showing the structure of the light-emitting device which concerns on one embodiment of this invention. It is a perspective view for demonstrating the structure of the condensing body shown in FIG. It is sectional drawing for demonstrating the structure of the condensing body shown in FIG. It is a characteristic view showing the measurement result of luminous flux. It is a schematic block diagram showing an example of the liquid crystal display device using the light-emitting device of this invention. It is a schematic block diagram showing the other example of the liquid crystal display device using the light-emitting device of this invention. It is sectional drawing showing the other structural example of a light-emitting device. It is sectional drawing showing the other structural example of a light-emitting device. It is a perspective view showing the other structural example of a condensing body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light-emitting device, 2 ... Support body with a light reflecting mirror, 3 ... Light source, 4 ... Condensing body, 41 ... Incident side end surface, 42 ... Output side end surface, 43 ... Side surface, 5 ... Liquid crystal display device, 6 ... Liquid crystal panel 7 ... Liquid crystal projector, 71 ... Lens, 72 ... Screen, 8 ... Matching layer, 9 ... LED light source, 91 ... Light emitting area, LC ... Center line, C1, C3 ... Center of incident side end face, C2, C4 ... Outgoing side Center of end face, LI: incident light, LO: outgoing light, L1, L2: emitted light, A, B ... parabola, A1, B1: symmetry axis, a, b ... focal point, θ: angle formed by symmetry axes (out Maximum emission angle of light).

Claims (15)

An incident-side end face, an exit-side end face that is coaxially opposed to the center line of the incident-side end face and has a larger area than the incident-side end face, and a parabola that focuses on the end point of the incident-side end face in a cross section including the center line A condensing body having a side surface composed of a parabolic surface including one or more kinds, condensing light incident through the incident side end surface, and emitting the light from the output side end surface within a range of a predetermined emission angle; ,
And a light source that emits light to the light collector. 2. The light emitting device according to claim 1, wherein each of the incident side end surface and the emission side end surface has an elliptical shape centering on an intersection with the center line. The light emitting device according to claim 2, wherein each of the incident side end surface and the emission side end surface is circular. The light emitting device according to claim 3, wherein the emission angle is an angle formed by symmetry axes of two parabolas focusing on both end points of the incident side end surface in a cross section including the center line. When the diameter of the incident side end surface is Rin, the diameter of the output side end surface is Rout, and the emission angle is θ,
Rin, Rout, and (theta) satisfy | fill the relationship of following Numerical formula 1. The light-emitting device of Claim 3 characterized by the above-mentioned.
(Equation 1)
Rout = Rin / sinθ The light-emitting device according to claim 1, wherein the light collector is made of glass (BK7), plastic (PMMA), or quartz. The light-emitting device according to claim 1, further comprising: a matching layer having a refractive index matching a refractive index of the light collector at a joint between the light source and the incident-side end surface. The light emitting device according to claim 7, wherein the matching layer is made of an acrylic solution or water. The light-emitting device according to claim 1, wherein the light source is a light-emitting diode. An incident-side end face, an exit-side end face that is coaxially opposed to the center line of the incident-side end face and has a larger area than the incident-side end face, and a parabola that focuses on the end point of the incident-side end face in a cross section including the center line A condensing body having a side surface composed of a parabolic surface including one or more kinds, condensing light incident through the incident side end surface, and emitting the light from the output side end surface within a range of a predetermined emission angle; ,
A light source that emits light to the light collector;
A liquid crystal display device comprising: a liquid crystal panel that modulates light emitted from the light collecting body based on a video signal. The liquid crystal display device according to claim 10, further comprising: a projection unit that projects light modulated by the liquid crystal panel onto a screen. 11. The liquid crystal display device according to claim 10, wherein each of the incident-side end surface and the emission-side end surface has an elliptical shape centering on an intersection with the center line. The liquid crystal display device according to claim 12, wherein each of the incident-side end surface and the emission-side end surface has a circular shape. The liquid crystal display device according to claim 13, wherein the emission angle is an angle formed by symmetry axes of two parabolas focusing on both end points of the incident side end face in a cross section including the center line. . When the diameter of the incident side end surface is Rin, the diameter of the output side end surface is Rout, and the emission angle is θ,
The liquid crystal display device according to claim 13, wherein Rin, Rout, and θ satisfy the following relationship:
(Equation 2)
Rout = Rin / sinθ

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