JP2009175637A - Liquid crystal backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal backlight device, securing uniformity of luminance even in a light guide system taking polarized light into consideration, and suitable for a liquid crystal display device taking a laser emitting a laser beam having polarized light, as a light source. <P>SOLUTION: This liquid crystal backlight device 100 includes: a laser light source 10 generating linearly polarized light; polarized light beam splitters 21b-27b, 31b-55b for separating incident light into s-polarized light and p-polarized light; half wavelength plates 21a-27a, 31a-55a for rotating a plane of polarization of incident linearly polarized light around an optical axis by a predetermined amount; and an optional ratio beam splitter, taking a polarized light beam splitter and the half wavelength plate disposed at the incident side of the polarized beam splitter as one set to separate incident linearly polarized light into s-polarized light and p-polarized light at a ratio according to the rotation amount of the plane of polarization by the half wavelength plate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal backlight device used in a liquid crystal display device using a laser as a light source.

  In recent years, the performance of semiconductor lasers has been improved by the progress of optical semiconductor manufacturing technology. For this reason, it is becoming possible to use a semiconductor laser as a highly efficient light source in a liquid crystal display device. One of the characteristics of laser light emitted from a semiconductor laser is polarization.

  On the other hand, in a liquid crystal display device, contrast is created by polarization. Therefore, when a non-polarized light source such as a fluorescent tube or an LED is used in the liquid crystal display device, necessary polarized light is generated using a polarizing filter and is incident on the liquid crystal panel.

  Therefore, if the polarized light of the laser light emitted from the semiconductor laser can be directly incident on the liquid crystal panel, the loss in the polarizing filter can be reduced. That is, a brighter liquid crystal display device can be realized with a light source having the same power. Alternatively, light source power necessary for a liquid crystal display device with the same brightness can be reduced, so that power consumption can be suppressed.

  Since the laser light source is a point light source, when the semiconductor laser is used as the light source of the liquid crystal display device, it is necessary to convert the point light source into a planar light source required by the liquid crystal panel. However, in a general light guide method used for a non-polarized light source such as a fluorescent tube or an LED, it is difficult to maintain the polarization of the light source when converting the shape of the light source into a planar shape. That is, in a general light guide method, polarization is canceled by reflection on a diffuse reflection surface or transmission of a light guide material having birefringence, and polarized light is transformed into non-polarized light. For this reason, when a laser that emits polarized laser light is used as a light source, a general light guide method used for non-polarized light sources such as fluorescent tubes and LEDs cannot be adopted.

Therefore, as a conventional light guide method considering polarization, for example, light from a point light source is separated into P-polarized light and S-polarized light by a polarization separation plate, and the S-polarized light is transmitted through a half-wave plate. There is one that converts to P-polarized light, combines the plurality of P-polarized light into a line light source, and uses the line light source as a surface light source by a light guide plate (see Patent Document 1). In this light guide method, in order to realize a liquid crystal display device having no luminance unevenness, the areas of the polarization separation plate and the reflection plate are gradually increased as the distance from the light source increases.
JP 2003-331626 A

  However, in the conventional light guide method described in Patent Document 1, it is difficult to ensure the uniformity of luminance. The reason is as follows. Since the divergence angle and intensity distribution of the light generated by the light source are not uniform, the intensity of the light incident on the polarization separation plate and the reflection plate is not determined solely by the distance from the light source. Therefore, it is not easy to determine the optimum areas of the polarization separation plate and the reflection plate in this conventional light guide method. Furthermore, since the light divergence angle and intensity distribution change easily due to environmental factors such as temperature and changes over time, even if the area can be determined in the initial state, the polarization separator and reflection It is difficult to maintain the performance of the board.

  The present invention has been made in view of the above points, and even with a light guide system that takes polarization into account, uniformity of luminance can be ensured, and a laser that emits polarized laser light is used as a light source. An object of the present invention is to provide a liquid crystal backlight device suitable for a liquid crystal display device.

  The liquid crystal backlight device of the present invention is a liquid crystal backlight device used in a liquid crystal display device using a laser as a light source, and a laser light source that generates linearly polarized light, and incident light is converted into S wave polarized light and P wave polarized light. A polarizing beam splitter that separates the polarization beam, a half-wave plate that rotates the plane of polarization of incident linearly polarized light by a predetermined amount around the optical axis, and the 1/1 that is disposed on the incident side of the polarizing beam splitter and the polarizing beam splitter. And an arbitrary ratio beam splitter that separates incident linearly polarized light into S wave polarized light and P wave polarized light at a ratio corresponding to the amount of rotation of the polarization plane of the half wave plate. Take the configuration.

  According to the present invention, the uniformity of luminance can be ensured even with a light guide system considering polarized light, and the liquid crystal back is suitable for a liquid crystal display device using a laser that emits polarized laser light as a light source. A light device can be provided.

  That is, according to the present invention, since the laser is used as the light source, the conversion efficiency from electricity to light is good.

  Moreover, since the polarization of the laser light source can be used as it is as the polarization required by the liquid crystal panel, the light utilization efficiency is high. Therefore, a power-saving liquid crystal display device can be realized.

  Furthermore, since the light branching ratio can be accurately determined by the rotation angle of the polarization plane of the half-wave plate, a liquid crystal display device with excellent brightness uniformity can be realized.

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

(Embodiment 1)
FIG. 1 is a schematic diagram showing a configuration of a liquid crystal backlight device according to Embodiment 1 of the present invention. The liquid crystal backlight device 100 shown in FIG. 1 is used for a liquid crystal display device using a laser as a light source, for example.

  In FIG. 1, a laser light source 10 generates collimated linearly polarized laser light as light source light for a liquid crystal backlight. The plane of polarization of the laser light generated by the laser light source 10 is parallel to the substrate 20 as shown in FIG.

  A plurality of half-wave plates and a plurality of polarizing beam splitters are attached to the substrate 20 in order to distribute the light source light generated by the laser light source 10. Each of the plurality of half-wave plates rotates the incident plane of linearly polarized light by a predetermined amount around the optical axis. Each of the plurality of polarization beam splitters separates incident light into S-wave polarized light and P-wave polarized light. Therefore, the polarization beam splitter and the half-wave plate arranged on the incident side of the polarization beam splitter are used as a set, and the incident linearly polarized light is converted into S-wave polarization and P at a ratio according to the rotation amount of the half-wave plate. An arbitrary ratio beam splitter that separates into wave polarization is formed.

  In the present embodiment, the liquid crystal backlight device 100 branches the laser light emitted from the laser light source 10 into a plurality of laser lights parallel to a two-dimensional radiation surface by a plurality of cascaded arbitrary ratio beam splitters. And a secondary branching unit that splits the laser light emitted from the primary branching unit into a plurality of laser beams perpendicular to the radiation surface by a plurality of cascaded arbitrary ratio beam splitters. Here, “connection” means connection by light. In addition, “cascade connection” means that a plurality of arbitrary ratio beam splitters having the same use as a primary branching unit or a secondary branching unit are connected in series.

  Hereinafter, for convenience, polarized light whose polarization plane is parallel to the substrate 20 is expressed as horizontal polarization, and polarized light whose polarization plane is perpendicular to the substrate 20 is expressed as vertical polarization. In FIG. 1, the optical axis of horizontal polarization is indicated by a broken line, and the optical axis of vertical polarization is indicated by a one-dot chain line.

  The laser light emitted from the laser light source 10 enters the half-wave plate 21a, and its polarization plane is rotated by a predetermined amount around the optical axis by the half-wave plate 21a. Incident.

  The light incident on the polarization beam splitter 21b is separated into P wave polarization and S wave polarization by the polarization beam splitter 21b. In FIG. 1, the P-wave polarization in the polarization beam splitter 21b is horizontal polarization, and this P-wave polarization passes right through the polarization beam splitter 21b. On the other hand, the S-wave polarization in the polarization beam splitter 21b is vertical polarization, and this S-wave polarization is reflected by the polarization beam splitter 21b, and its traveling direction is bent 90 degrees and proceeds upward in FIG.

  The horizontally polarized light separated by the polarization beam splitter 21b and traveling in the right direction in FIG. 1 is then incident on the half-wave plate 22a and the polarization beam splitter 22b. And vertically polarized light traveling upward.

  Hereinafter, the half-wave plate 23a and the polarization beam splitter 23b, the half-wave plate 24a and the polarization beam splitter 24b, the half-wave plate 25a and the polarization beam splitter 25b, and the half-wave plate 26a and the polarization beam splitter 26b. In the same manner as described above, the incident light is separated into the horizontally polarized light and the vertically polarized light, and the vertically polarized light travels upward. That is, the primary branching means for branching the laser beam emitted from the laser light source 10 into a plurality of laser beams parallel to the two-dimensional radiation surface by the polarization beam splitters 21b, 22b, 23b, 24b, 25b, 26b, and 27b. Composed.

  In the half-wave plate 27a and the polarization beam splitter 27b, all the incident horizontal polarized light is converted into vertical polarized light and proceeds upward.

  On the other hand, the vertically polarized light emitted upward from the polarizing beam splitter 21b is incident on the half-wave plate 31a and subsequently incident on the polarizing beam splitter 31b. The mounting angle of the polarizing beam splitter 31b is different from the mounting angles of the polarizing beam splitters 21b, 22b, 23b, 24b, 25b, 26b, and 27b. The polarization beam splitter 31b passes vertical polarized light as P-wave polarized light and emits it upward, and reflects horizontal polarized light as S-wave polarized light and emits it vertically to the substrate 20.

  The polarizing beam splitters 32b, 33b, 35b, 36b, 38b, 39b, 40b, 42b, 43b, 45b, 46b, 47b, 49b, 50b, 52b, 53b, 54b are all attached at the mounting angle of the polarizing beam splitter 31b. These polarizing beam splitters pass vertically polarized light as P-wave polarized light and emit it upward, and reflect horizontally polarized light as S-wave polarized light and emit it vertically to the substrate 20. . Further, the polarization beam splitters 34b, 37b, 41b, 44b, 48b, 51b, and 55b convert all incident vertical polarized light into horizontal polarized light and emit it in the vertical direction with respect to the substrate 20. That is, the polarization beam splitters 31b to 55b constitute secondary branching means for branching the laser light emitted from the primary branching means into a plurality of laser beams perpendicular to the two-dimensional radiation surface.

  As described above, the light source light generated by the laser light source 10 is distributed over the entire substrate 20 by the combination of the half-wave plate and the polarization beam splitter, and finally emitted in the direction perpendicular to the substrate 20. The All of the polarized light of the emitted light is horizontal polarized light parallel to the surface of the substrate 20 and parallel to the optical axis of the laser light source 10. Therefore, by making the polarization axis of the emitted light coincide with the polarization axis of the incident side polarization filter of the liquid crystal panel, the amount of light absorbed by the polarization filter can be reduced.

  Further, the branching ratio of the half-wave plate and the polarizing beam splitter is such that the polarizing beam splitter that emits light in a direction perpendicular to the substrate 20 connected to the downstream side of the polarizing beam splitter (hereinafter referred to as “vertical light emitting”). The number of polarization beam splitters).

  For example, when paying attention to the half-wave plate 22a and the polarization beam splitter 22b, there are three polarization beam splitters for emitting light in the vertical direction on the downstream side of the vertical polarization side, and polarized light on the downstream side of the horizontal polarization side. Although there are 23 beam splitters in total, 18 of them are 18 polarization beam splitters for emitting light in the vertical direction that are used as secondary branching means. Therefore, the branching ratio between the half-wave plate 22a and the polarization beam splitter 22b may be 3:18.

  In other words, each branching ratio in the primary branching means is the total number of vertical beam emitting polarization beam splitters connected to the two branch destinations, respectively, n (n is a non-negative integer), m (m is non-negative) (Integer), a laser beam having an intensity corresponding to n / (n + m) of the incident laser beam is sent to a branching destination having n polarization beam splitters for emitting light in the vertical direction, and the remaining m / (n + m It is preferable to set so that the laser beam having the intensity corresponding to () is sent to a branching destination having m pieces of polarization beam splitters for emitting light in the vertical direction.

  Further, for example, when focusing on the half-wave plate 42a and the polarization beam splitter 42b, there are two more polarization beam splitters 43b and 44b on the downstream side thereof, so that the light emitted in the direction perpendicular to the substrate 20 can be obtained. When the amount is 1, the branching ratio of the half-wave plate 42a and the polarization beam splitter 42b may be 1: 2.

  In other words, each branching ratio in the secondary branching means is 1 / (n + 1) of the incident laser beam when the total number of polarization beam splitters cascaded downstream is n (n is a non-negative integer). When the laser beam with the corresponding intensity is radiated from the two-dimensional radiation surface, and the laser beam with the intensity corresponding to the remaining n / (n + 1) is set to be sent to the polarization beam splitter cascaded downstream. Good.

  Similarly, the branching ratios of all polarization beam splitters can be determined.

  FIG. 2 is a schematic diagram showing the operation principle of the arbitrary ratio beam splitter.

  As shown in FIG. 2A, when the angle of the half-wave plate 21a is adjusted to the incident P wave polarization, the emitted polarization becomes P wave polarization.

  Further, as shown in FIG. 2B, when the half-wave plate 21a is tilted 45 degrees and P-wave polarized light is incident, the polarization plane is rotated by 90 degrees, and the emitted polarized light becomes S-wave polarized light. .

  That is, as shown in FIG. 2C, when the angle formed by the incident P-wave polarized light and the half-wave plate 21a is θ, the emitted polarized light is the S-wave polarized light and P shown in FIG. The magnitude of S wave polarization is proportional to the sine of twice the angle θ, and the magnitude of P wave polarization is proportional to the cosine of twice the angle θ.

  Therefore, by determining the angle of the half-wave plate 21a with respect to the incident polarized light, the ratio of the magnitude of the outgoing P-wave polarized light and the magnitude of the outgoing S-wave polarized light is between 0: 1 and 1: 0. You can decide freely.

  On the other hand, as described above, the polarization beam splitter 21b passes the P-wave polarization as it is (see FIG. 2D), reflects the S-wave polarization, and changes the traveling direction of the S-wave polarization to the vertical direction (see FIG. 2). 2 (E)). Therefore, when polarized light in which P wave polarized light and S wave polarized light are mixedly incident on the polarization beam splitter 21b, the polarized light can be separated into S wave polarized light and P wave polarized light (see FIG. 2F).

  Therefore, as shown in FIG. 2 (G), the half-wave plate 21a and the polarizing beam splitter 21b are combined, and the half-wave plate 21a having an angle θ with respect to the incident P-wave polarized light responds to θ. The incident light can be branched at an arbitrary ratio by converting the P-wave polarized light and the S-wave polarized light in the above ratios and separating them by the polarization beam splitter 21b. That is, one arbitrary ratio beam splitter can be configured by combining the half-wave plate 21a and the polarizing beam splitter 21b. Similarly, one arbitrary ratio beam splitter can be configured by combining the half-wave plate 22a and the polarization beam splitter 22b, and the half-wave plate 31a and the polarization beam splitter 31b are combined. One set of arbitrary ratio beam splitters can be configured by combining them. The same applies to other combinations of other half-wave plates and polarizing beam splitters in FIG.

  Since the branching ratio in each polarization beam splitter shown in FIG. 1 depends only on the polarization of incident light, even if the diameter or divergence angle of incident light changes due to temperature change or change with time, it is affected by the change. There is nothing.

  Thus, according to the present embodiment, in a liquid crystal backlight device used in a liquid crystal display device using a laser that emits polarized laser light as a light source, the light branching ratio is changed to the polarization plane of the half-wave plate. Therefore, a liquid crystal display device with excellent brightness uniformity can be realized. In other words, according to the present embodiment, uniformity of luminance can be ensured even with a light guide system that takes polarization into account, and this is suitable for a liquid crystal display device that uses a laser that emits polarized laser light as a light source. A liquid crystal backlight device can be provided.

(Embodiment 2)
FIG. 3 is a schematic diagram showing the configuration of the liquid crystal backlight device according to Embodiment 2 of the present invention. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, the liquid crystal backlight device splits the laser beam emitted from the laser light source 10 into a plurality of laser beams parallel to the two-dimensional radiation surface by a plurality of cascaded arbitrary ratio beam splitters. It has a branching unit and a light guide plate that makes the laser light from the branching unit incident from the end face and emits the light in a direction perpendicular to the radiation surface.

  In the liquid crystal backlight device 200 shown in FIG. 3, the light guide plate 60 emits horizontally polarized light incident from the lower end surface in a direction perpendicular to the substrate 20, that is, a direction perpendicular to the two-dimensional radiation surface. To do.

  When depolarization occurs inside the light guide plate 60, the light emitted from the light guide plate 60 loses its polarization. Therefore, the light guide plate 60 needs to satisfy the condition that the material has little birefringence, does not cause diffuse reflection on the surface, and does not cause light scattering inside.

  In order to suppress birefringence, the manufacture of the light guide plate 60 is not performed by molding processing in which complicated flow conditions that cause material anisotropy are generated, but by cutting from a material having low anisotropy. Is possible. Further, it is possible to prevent diffuse reflection on the surface by making all the surfaces into a mirror finish and performing prism processing to obtain radiation in a direction perpendicular to the substrate 20. In order to suppress light scattering inside the light guide plate 60, a transparent material may be selected.

  In FIG. 3, the laser beam emitted from the laser light source 10 is split into a plurality of laser beams parallel to the two-dimensional radiation surface by the polarization beam splitters 21b, 22b, 23b, 24b, 25b, 26b, and 27b. A branching means is configured.

  Here, for example, when focusing on the half-wave plate 21a and the polarizing beam splitter 21b, since there are further six polarizing beam splitters 22b, 23b, 24b, 25b, 26b, and 27b on the downstream side thereof, the light guide plate 60 When the amount of light emitted to 1 is 1, the branching ratio of the half-wave plate 21a and the polarization beam splitter 21b may be 1: 6.

  In other words, each branching ratio in the branching unit corresponds to 1 / (n + 1) of the incident laser light when the total number of polarization beam splitters cascaded downstream is n (n is a non-negative integer). It is preferable to set so that the laser beam having the intensity is emitted from the two-dimensional radiation surface, and the remaining laser beam having the intensity corresponding to n / (n + 1) is sent to the polarization beam splitter cascaded downstream.

  As described above, according to the present embodiment, since the liquid crystal backlight device is configured using the light guide plate 60, the brightness is improved even with the light guide method considering polarization with a simpler configuration than that of the first embodiment. Therefore, it is possible to provide a liquid crystal backlight device suitable for a liquid crystal display device using a laser that emits polarized laser light as a light source.

(Embodiment 3)
FIG. 4 is a schematic diagram showing a configuration of a liquid crystal backlight device according to Embodiment 3 of the present invention. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, the liquid crystal backlight device divides the laser beam emitted from the laser light source 10 into a plurality of laser beams parallel to the two-dimensional radiation surface by a plurality of cascaded arbitrary ratio beam splitters. Splitting means, primary branching means for splitting the laser light from the splitting means into a plurality of laser beams parallel to the radiation surface by a plurality of cascaded arbitrary ratio beam splitters, and the primary branching means Secondary branching means for branching the laser light into a plurality of laser lights perpendicular to the radiation surface by a plurality of cascaded arbitrary ratio beam splitters.

  In the liquid crystal backlight device 300 shown in FIG. 4, the half-wave plate 73a and the polarization beam splitter 73b divide the light from the laser light source 10 into two.

  The vertically polarized light emitted upward from the half-wave plate 73a and the polarization beam splitter 73b passes through the total reflection prism 71 and enters the half-wave plate 21a and the polarization beam splitter 21b.

  On the other hand, horizontal polarized light emitted in the right direction from the half-wave plate 73a and the polarization beam splitter 73b is incident on the half-wave plate 74a and the polarization beam splitter 74b, and is all converted to vertical polarization. The vertically polarized light passes through the total reflection prism 72 and enters the half-wave plate 25a and the polarization beam splitter 25b.

  Therefore, in the present embodiment, the polarization beam splitters 73b and 74b constitute a splitting unit that splits the laser beam emitted from the laser light source 10 into a plurality of laser beams parallel to the two-dimensional radiation surface.

  The vertically polarized light incident on the half-wave plate 21a and the polarization beam splitter 21b is polarized beam splitters 21b, 22b, 23b, and 24b as primary branching means, and polarization beam splitters 31b, 32b, and 33b as secondary branching means. , 34b, 35b, 36b, 37b, 38b, 39b, 40b, 41b, 42b, 43b, and 44b, the laser beam is branched into a plurality of laser beams that are parallel to the two-dimensional radiation surface and perpendicular to the laser beam. Thus, the light is distributed to a partial region of the substrate 20 and finally emitted in a direction perpendicular to the substrate 20. The basic configuration of this portion is the same as that of the first embodiment using the primary branching means and the secondary branching means.

  The vertically polarized light incident on the half-wave plate 25a and the polarization beam splitter 25b is polarized beam splitters 25b, 26b, 27b as primary branching means and polarization beam splitters 45b, 46b, 47b, 48b as secondary branching means. , 49b, 50b, 51b, 52b, 53b, 54b, and 55b, the remaining region of the substrate 20 is branched into a plurality of laser beams of a laser beam parallel to a two-dimensional radiation surface and a laser beam perpendicular to the two-dimensional radiation surface. And finally emitted in a direction perpendicular to the substrate 20. The basic configuration of this part is the same as that of the first embodiment using the primary branching means and the secondary branching means.

  Therefore, by combining the both, the light source light from the laser light source 10 is distributed over the entire substrate 20 and finally emitted in a direction perpendicular to the substrate 20. This distributes a plurality (two in this case) of laser beams divided by the dividing means by the configuration of the first embodiment, that is, by so-called tree-like connections in which similar configurations are branched appropriately.

  Here, for example, focusing on the half-wave plate 73a and the polarization beam splitter 73b, there are 14 polarization beam splitters for emitting light in the vertical direction on the downstream side of the vertical polarization side, and on the downstream side of the horizontal polarization side. There are 11 polarization beam splitters for emitting light in the vertical direction. Therefore, the branching ratio of the half-wave plate 73a and the polarization beam splitter 73b may be set to 14:11.

  In other words, the branching ratios in the dividing means are the total number of vertical beam emitting polarization beam splitters connected to the two branch destinations, respectively, n (n is a non-negative integer) and m (m is a non-negative integer). ), A laser beam having an intensity corresponding to n / (n + m) of the incident laser beam is sent to a branching destination having n polarization beam splitters for emitting vertical light, and the remaining m / (n + m) It is preferable to set so that the laser beam having the intensity corresponding to is sent to a branch destination where m polarization beam splitters for emitting light in the vertical direction are present.

  As described above, according to the present embodiment, light can be distributed with a tree-like connection in which the same configuration is branched as appropriate, as is distributed from the half-wave plate 73a and the polarization beam splitter 73b. That is, the present invention is not limited to the configuration in the first embodiment shown in FIG. 1, but can be implemented by a configuration in which light is distributed by the tree-like connection in the present embodiment shown in FIG. Thereby, for example, in the case of the present embodiment, the number of half-wave plates and polarizing beam splitters that pass while reaching the polarizing beam splitter 55b is smaller than that of the first embodiment, and during the passage, The loss that occurs can be reduced.

  In each of the above embodiments, the case where a single light source is used has been described. However, the present invention can also be applied to each of the three primary colors of light in order to display natural colors. The present invention can also be applied to white light that is collimated by synthesizing the three primary colors.

  In the present invention, a linear light source light emitted from a high-efficiency laser light source is distributed on a two-dimensional plane while being separated into S-wave polarized light and P-wave polarized light by a polarizing beam splitter. Can be converted into a planar light source.

  Since the laser light can be guided to the liquid crystal panel without losing the inherent polarization property of the laser light source in the process of conversion to the planar light source, the polarizing filter provided on the incident surface side of the liquid crystal panel Light loss can be reduced.

  In addition, since the branching ratio of light can be determined only by the angle of the half-wave plate, the branching ratio can be accurately determined and stabilized regardless of the incident light thickness and beam divergence angle. Can do.

  Therefore, according to the present invention, a highly efficient liquid crystal backlight device having high luminance uniformity can be realized by the above-described operation.

  For example, when the liquid crystal backlight device of the present invention is applied to a portable liquid crystal display device, the required brightness can be obtained with low power consumption, so that the battery life can be extended. For example, if the liquid crystal backlight device of the present invention is applied to a liquid crystal display device used indoors, a brighter and more vivid image can be displayed with the same power consumption. Note that each liquid crystal display device has a light modulation unit illuminated by a liquid crystal backlight device.

1 is a schematic diagram showing a configuration of a liquid crystal backlight device according to Embodiment 1 of the present invention. Schematic diagram showing the principle of operation of an arbitrary ratio beam splitter Schematic diagram showing the configuration of the liquid crystal backlight device according to Embodiment 2 of the present invention. Schematic diagram showing the configuration of a liquid crystal backlight device according to Embodiment 3 of the present invention.

Explanation of symbols

10 Laser light source 20 Substrate 21a, 22a, 23a, 24a, 25a, 26a, 27a, 28a, 29a, 30a, 31a, 32a, 33a, 34a, 35a, 36a, 37a, 38a, 39a, 40a, 41a, 42a, 43a 44a, 45a, 46a, 47a, 48a, 49a, 50a, 51a, 52a, 53a, 54a, 55a, 73a, 74a Half-wave plates 21b, 22b, 23b, 24b, 25b, 26b, 27b, 28b, 29b 30b, 31b, 32b, 33b, 34b, 35b, 36b, 37b, 38b, 39b, 40b, 41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b, 49b, 50b, 51b, 52b, 53b, 54b 55b, 73b, 74b Polarizing beam splitter 60 Light guide plate 71, 7 2 Total reflection prism 100, 200, 300 Liquid crystal backlight device

Claims (11)

A liquid crystal backlight device used in a liquid crystal display device using a laser as a light source,
A laser light source that generates linearly polarized light;
A polarization beam splitter that separates incident light into S-wave polarization and P-wave polarization;
A half-wave plate that rotates the polarization plane of incident linearly polarized light by a predetermined amount around the optical axis;
The polarizing beam splitter and the half-wave plate arranged on the incident side of the polarizing beam splitter are made into one set, and the incident linearly polarized light is S in a ratio corresponding to the rotation amount of the polarization plane by the half-wave plate. An arbitrary ratio beam splitter that separates into wave polarization and P wave polarization;
A liquid crystal backlight device. Primary branching means for branching laser light emitted from the laser light source into a plurality of laser lights parallel to a two-dimensional radiation surface by a plurality of cascaded arbitrary ratio beam splitters;
Secondary branching means for branching laser light emitted from the primary branching means into a plurality of laser lights perpendicular to the radiation surface by a plurality of cascaded arbitrary ratio beam splitters;
The liquid crystal backlight device according to claim 1, further comprising: The branch ratio of the arbitrary ratio beam splitter in the primary branch means is the total number of arbitrary ratio beam splitters of the secondary branch means connected to the two branch destinations of the arbitrary ratio beam splitter, respectively, where n is a non-negative integer. ), M (m is a non-negative integer), a laser beam having an intensity corresponding to n / (n + m) of the incident laser beam is supplied to a branch destination where an arbitrary ratio beam splitter of n secondary branching units is provided. The laser beam having the intensity corresponding to the remaining m / (n + m) is set to be sent to a branch destination having an arbitrary ratio beam splitter of m secondary branching units.
The liquid crystal backlight device according to claim 2. The branching ratio of the arbitrary ratio beam splitter in the secondary branching means is the incident laser when the total number of arbitrary ratio beam splitters cascaded downstream of the arbitrary ratio beam splitter is n (n is a non-negative integer). Arbitrary ratio beam splitter that radiates laser light having intensity corresponding to 1 / (n + 1) of light from the radiation surface and cascades the remaining laser light having intensity corresponding to n / (n + 1) downstream Set to send to
The liquid crystal backlight device according to claim 2. Branching means for branching laser light emitted from the laser light source into a plurality of laser lights parallel to a two-dimensional radiation surface by a plurality of cascaded arbitrary ratio beam splitters;
A light guide plate that makes laser light from the branching unit incident from an end face and emits the laser light in a direction perpendicular to the radiation surface;
The liquid crystal backlight device according to claim 1, further comprising: The branching ratio of the arbitrary ratio beam splitter in the branching means is that the total number of arbitrary ratio beam splitters cascaded downstream of the arbitrary ratio beam splitter is n (n is a non-negative integer). Laser light having an intensity corresponding to 1 / (n + 1) is emitted from the radiation surface, and the remaining laser light having an intensity corresponding to n / (n + 1) is sent to an arbitrary ratio beam splitter cascaded downstream. Set as
The liquid crystal backlight device according to claim 5. Splitting means for splitting the laser beam emitted from the laser light source into a plurality of laser beams parallel to a two-dimensional radiation surface by a plurality of cascaded arbitrary ratio beam splitters;
Primary branching means for splitting the laser light from the splitting means into a plurality of laser lights parallel to the radiation surface by a plurality of cascaded arbitrary ratio beam splitters;
Secondary branching means for branching laser light emitted from the primary branching means into a plurality of laser lights perpendicular to the radiation surface by a plurality of cascaded arbitrary ratio beam splitters;
The liquid crystal backlight device according to claim 1, further comprising: The branching ratio of the arbitrary ratio beam splitter in the splitting means is the total number of arbitrary ratio beam splitters of the secondary branching means respectively connected to the two branch destinations of the arbitrary ratio beam splitter, where n is a non-negative integer. , M (m is a non-negative integer), a laser beam having an intensity corresponding to n / (n + m) of the incident laser beam is sent to a branching destination having an arbitrary ratio beam splitter of n secondary branching units. , The remaining laser beam having an intensity corresponding to m / (n + m) is set to be sent to a branch destination having an arbitrary ratio beam splitter of m secondary branching units.
The liquid crystal backlight device according to claim 7. The branch ratio of the arbitrary ratio beam splitter in the primary branch means is the total number of arbitrary ratio beam splitters of the secondary branch means connected to the two branch destinations of the arbitrary ratio beam splitter, respectively, where n is a non-negative integer. ), M (m is a non-negative integer), a laser beam having an intensity corresponding to n / (n + m) of the incident laser beam is supplied to a branch destination where an arbitrary ratio beam splitter of n secondary branching units is provided. The laser beam having the intensity corresponding to the remaining m / (n + m) is set to be sent to a branch destination having an arbitrary ratio beam splitter of m secondary branching units.
The liquid crystal backlight device according to claim 7. The branching ratio of the arbitrary ratio beam splitter in the secondary branching means is the incident laser when the total number of arbitrary ratio beam splitters cascaded downstream of the arbitrary ratio beam splitter is n (n is a non-negative integer). Arbitrary ratio beam splitter that radiates laser light having intensity corresponding to 1 / (n + 1) of light from the radiation surface and cascades the remaining laser light having intensity corresponding to n / (n + 1) downstream Set to send to
The liquid crystal backlight device according to claim 7. A liquid crystal backlight device according to claim 1,
A light modulator illuminated by the liquid crystal backlight device;
A liquid crystal display device.

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