Light source device

Abstract

To provide a light source device which is small, which can be manufactured at low cost, and which is favorable as a light source for illumination of a display device of an electronic device such as an HUD, a spatially suspended image display device and the like.SOLUTION: A light source device includes: a light source for generating white light by radiating light emitted from a solid light source to a fluorescent body; a collimating optical system for converting a diverged luminous flux of the white light emitted from the light source into parallel light; and a light guide body for allowing the light emitted from the collimating optical system to enter as incident light, and for emitting the incident light in a direction different from the incident direction. The collimating optical system has a filter constituted so as to reflect the light in a blue region of the parallel light and to radiate the fluorescent body.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a light source device that can be used as a planar light source, and more particularly to a planar light source device that is suitable for use in an electronic device that includes an image display device that is intended to be miniaturized. [Background technology]

[0002] 2. Description of the Related Art There is a demand for a compact, highly efficient light source device as a light source for illuminating display devices such as head-up displays (hereinafter referred to as "HUDs") and ultra-compact projectors.

[0003] In order to realize a compact and highly efficient light source device, a light source device that utilizes a light guide having a predetermined texture formed on a transparent resin is already known from the following Patent Document 1. The light guide lighting device described in this Patent Document states that light is incident from the end of the light guide and the incident light is scattered by the texture formed on the surface of the light guide, thereby realizing a thin and highly efficient light source device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-224518 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, with the improvement in the luminous efficiency of LEDs, which are solid-state light sources, it has become effective to use LEDs as the light source of a light source device. However, in an optical system using an LED and an LED collimator that converts the light into approximately parallel light, it has been found that the shape of the optical system disclosed in Patent Document 1 is still insufficient in terms of light utilization efficiency characteristics and uniform illumination characteristics.

[0006] Therefore, specifically, the present invention aims to provide a light source device that achieves miniaturization of the light source device by further improving the light utilization efficiency characteristics and uniform illumination characteristics of laser light from an LED light source, and that can be manufactured at low cost, making it suitable as an illumination light source for display devices of electronic devices such as HUDs and space-floating image displays, and further to provide an electronic device equipped with an image display device that utilizes the same. [Means for solving the problem]

[0007] As one embodiment for achieving the above object, there is provided a light source device comprising: a light source that generates white light by irradiating light emitted from a solid-state light source onto a phosphor; a collimating optical system that converts the divergent light beam of the white light emitted from the light source into parallel light; and a light guide that receives the light emitted from the collimating optical system as incident light and emits the incident light in a direction different from the incident direction, wherein the collimating optical system has a filter configured to reflect light in the blue region of the parallel light to irradiate the phosphor.

[0008] According to the present invention, electronic devices that utilize the light source device as an image display device include HUDs and space-floating image displays. [Effects of the Invention]

[0009] According to the present invention described above, it is possible to realize a light source device that can be manufactured at low cost, and that is compact, highly efficient, and highly reliable. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an exploded perspective view showing an overall overview of a light source device according to a first embodiment of the present invention. [Figure 2] 1 is a perspective view showing an overview of the internal configuration of an optical system in a light source device according to Example 1 of the present invention. [Figure 3] 2A and 2B are perspective views and partially enlarged cross-sectional views for explaining details of a light guide in a light source device according to Example 1 of the present invention. [Figure 4]4 is a side view illustrating the details of the operation of the light guide in the light source device according to Example 1 of the present invention. FIG. [Figure 5] 3A and 3B are top and side views illustrating the details of the operation of the light guide in the light source device according to Example 1 of the present invention. [Figure 6] FIG. 4 is a diagram illustrating a comparative example for explaining the operation of the light guide in the light source device according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a perspective view illustrating details of a collimator and a composite diffusion block in the light source device according to the first embodiment of the present invention. [Figure 8] FIG. 3 is a partially enlarged cross-sectional view illustrating the details of a synthetic diffusion block in the light source device according to the first embodiment of the present invention. [Figure 9] 3A to 3C are diagrams illustrating a method of processing a mold used to form a light guide, which is a component of the optical system of the light source device according to the first embodiment of the present invention. [Figure 10] FIG. 10 is an external perspective view showing an overall overview of a light source device that is a modified example of the light source device according to the first embodiment of the present invention. [Figure 11] FIG. 4 is a perspective view showing an overview of the internal configuration of an optical system of a light source device that is a modified example of the light source device according to the first embodiment of the present invention. [Figure 12] FIG. 10 is an external perspective view showing an overall overview of a light source device that is another modified example of the light source device according to the first embodiment of the present invention. [Figure 13] 10 is a perspective view showing another form of the collimator and the shape of the composite diffusion block in the light source device according to the first embodiment of the present invention. FIG. [Figure 14] 1 is a diagram showing the configuration of an HUD that uses a light source device according to Example 1 of the present invention as a light source for illuminating its display device. [Figure 15] FIG. 10 is a perspective view showing an example of the structure of an optical system of a light source device according to Example 2 of the present invention. [Figure 16] 10 is a side view showing the operation of the optical system of the light source device according to the second embodiment of the present invention. FIG. [Figure 17] 10A and 10B are top and side views illustrating the details of the operation of the light guide in the light source device according to Example 2 of the present invention. [Figure 18] FIG. 10 is a perspective view showing an example of the structure of an LED collimator and a composite diffusion block which are components of the optical system of the light source device according to Example 2 of the present invention. [Figure 19] FIG. 10 is a perspective view showing an example of the structure of a composite diffusion block which is a component of the optical system of the light source device according to Example 2 of the present invention. [Figure 20] 10A and 10B are cross sections and partial enlarged cross sections illustrating details of a synthetic diffusion block in a light source device according to Example 2 of the present invention. [Figure 21] FIG. 2 is a characteristic diagram showing relative radiant energy intensity by wavelength of the high-brightness LED light source according to Example 1. [Figure 22] 1 is a characteristic diagram showing the relative intensity of radiant energy emitted from a high-brightness LED light source according to Example 1. FIG. [Figure 23] FIG. 10 is a characteristic diagram showing relative radiant energy intensity by wavelength according to Example 2 of the high-brightness LED light source. [Figure 24] FIG. 10 is a characteristic diagram showing the relative intensity of radiant energy emitted from a high-brightness LED light source according to Example 2. [Figure 25] This is a characteristic diagram showing the relative radiant energy intensity by wavelength of an LED light source for LCD-TVs. [Figure 26] This is a characteristic diagram showing the relative radiant energy divergence intensity of an LED light source for LCD-TVs. [Figure 27] FIG. 10 is a characteristic diagram showing the spectral transmittance of a filter according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] Example 1 1 is an exploded perspective view showing an overview of a light source device according to a first embodiment of the present invention. As is clear from the figure, light source device (main body) 10 is composed of a light source device case 11 made of, for example, plastic, and accommodating LEDs, a collimator, a composite diffusion block (diffusion block), a light guide, and the like, which will be described in detail later. A liquid crystal display element 50 is attached to the top surface of the case, and an LED substrate 12, on one side of which are mounted LED (Light Emitting Diode) elements, which are semiconductor light sources, and their control circuits, is attached. A heat sink 13 is attached to the outer surface of LED substrate 12 to cool the heat generated by the LED elements and the control circuit.

[0013] Furthermore, the liquid crystal display element 50 attached to the upper surface of the light source device case 11 is composed of a liquid crystal display panel frame 51, a liquid crystal display panel 52 attached to the frame, and an FPC (flexible printed circuit) 53 electrically connected to the panel. That is, the liquid crystal display panel 52 is controlled by a control signal from a control circuit (not shown here) that constitutes the electronic device, as will be described in detail later.

[0014] FIG. 2 shows the interior of the light source device 10, that is, the configuration of the optical system housed in the light source device case 11. As shown in FIG.

[0015] A plurality of (four in this example) LEDs 14a to 14d (only two, LEDs 14a and 14b, are shown in FIG. 2) constituting the light source are attached to the bottom of an LED collimator 15 having a cone-shaped convex outline obtained by rotating a substantially parabolic segment, and a rectangular combining / diffusing block 16 is provided on the light emission side of the LED collimator. That is, the laser light emitted from LED 14a or 14b is reflected by the parabolic boundary surface of LED collimator 15, becomes parallel light, and enters combining / diffusing block 16.

[0016] Furthermore, a rod-shaped light guide 17 with a roughly triangular cross section is provided on the exit surface side of the composite diffusion block 16 via a first diffuser plate 18a, and a second diffuser plate 18b is attached to its upper surface. As a result, the horizontal light from the LED collimator 15 is reflected upward in the figure by the action of the light guide plate 17 and directed to the incident surface of the liquid crystal display element 50. At this time, the intensity of the light is made uniform by the first and second diffusers 18a and 18b.

[0017] <Mastering high-brightness LED light sources> In this example, a high-output LED light source is used. Its basic configuration involves a blue LED exciting a phosphor, which mixes the blue excitation light with fluorescent light (containing green and red components) and radiates it. Figure 21 shows a characteristic diagram of the spectral radiant energy of a high-brightness LED for HUD backlighting (product X, manufactured by company A) as a relative value. With an input current of 1000 mA, it outputs a radiant flux of 224 to 355 lm. A high-brightness blue LED that excites a phosphor containing green and red components as its output light has a peak wavelength of 440 nm, a short-wavelength wavelength of 420 nm (10% of the peak brightness), and a cutoff wavelength of 360 nm. It emits light ranging from the high-energy ultraviolet region to the short-wavelength blue region (labeled the high-energy region in the diagram). Another example of a high-brightness LED for backlighting is product Y, manufactured by company B. Figure 23 shows the characteristics of this product, expressed as a relative value of spectral radiant energy. It outputs a luminous flux of 168 lm with an input current of 650 mA. As a high-brightness blue LED that excites a phosphor containing green and red components as its output light, it has a peak wavelength of 445 nm, a short-wavelength wavelength at 10% of the peak brightness of 423 nm, and a cutoff wavelength of 400 nm. The divergence characteristics of the light source light from the high-brightness LED for HUD backlighting in Figure 21 are shown in Figure 22.

[0018] In contrast, a typical example of an LED used as a backlight source for LCD TVs is Product Z from Company B. Figure 25 shows the characteristics of this product, expressed as relative values for spectral radiant energy. With an input current of 650 mA, it outputs a luminous flux of 168 lm. A high-brightness blue LED that excites a phosphor containing green and red components as its output light has a peak wavelength of 450 nm, a short-wavelength wavelength at 10% of the peak brightness of 430 nm, and a cutoff wavelength of 420 nm; the peak wavelength and cutoff wavelength of a high-brightness LED are shifted to the long-wavelength side.

[0019] For this reason, in light source devices using high-brightness LEDs, it is necessary to limit the amount of high-energy blue light (light in the blue region) entering the LCD panel and polarizer. For this reason, in this embodiment, an optical filter FIL having the transmission characteristics shown in FIG. 27 is configured between the LED light source and the LCD and polarizer. It is recommended to install filters with characteristics A and B, which are formed by sputtering and vapor-depositing a metal multilayer film, respectively, as shown in FIG. 27, on the surface through which the light from the optical element (parallel light) passes. The filter with characteristic A is installed closer to the LED light source, completely blocking light in the high-energy region. It is even better to install a filter with characteristic B on the surface through which the light from the light source passes on other optical elements. To achieve the above filter characteristics, it is essential that the light from the light source be incident perpendicularly to the surface on which the filter is installed.

[0020] However, the divergence characteristics of the source light from an LED are as shown in Figures 22, 24, and 26, respectively. Figures 22, 24, and 26 show the relative brightness, with the direction perpendicular to the LED's emission surface (divergence angle of 0 degrees) set to 100%. At a divergence angle of 40 degrees, the relative brightness is 80%, and at a divergence angle of 60 degrees, the relative brightness is 55% to 50%. If the above LED is used as is, the source light will be incident on the filter installation surface at an angle, as mentioned above. As a result, the cutoff wavelength will shift to the shorter wavelength side, which will affect the reliability of the polarizer and LCD panel.

[0021] To address this issue, in this embodiment, as shown in Figures 4 and 5, the divergent light from the LED is converted into approximately parallel light by the LED collimator 15, and then a filter FIL with the characteristics shown in Figure 27 is provided on the exit surface 152 of the LED collimator 15 or the entrance surface 162 of the composite diffusion block 16, or on both surfaces thereof. This makes it possible to cut out high-energy short-wavelength blue light and ultraviolet light, thereby improving resistance to high-intensity light from a light source.

[0022] In Example 2 described later, as shown in Figures 16 and 17, divergent light from an LED is converted into approximately parallel light by an LED collimator 15, and then a filter having the characteristics shown in Figure 27 is provided on the exit surface 152 or the entrance surface 214 of the polarization conversion element 21, or on both surfaces thereof. This makes it possible to cut high-energy short-wavelength blue light and ultraviolet light, as in Example 1, and significantly improve resistance to high-brightness light source light.

[0023] By providing a filter with characteristic A shown in Figure 27 on the exit surface 152 of the LED collimator, light in the high-energy region (e.g., blue light) reflected by the filter with characteristic A re-excites the phosphor in the high-brightness LED, thereby increasing the light output. When filter characteristic A shown in Figure 27 is used as the standard (cutoff wavelength 435 nm), the light output improved by approximately 15%. Furthermore, when the cutoff wavelength was set to 430 nm, the light output improved by 12%, and at 420 nm, the light output improved by 4%, confirming the effect of improving the light output.

[0024] <Detailed structure of the light guide> Next, the light guide 17 constituting the light source device 10 will be described in detail below with reference to the drawings. Fig. 3(a) is a perspective view showing the entire light guide 17, Fig. 3(b) is a cross-section thereof, and Figs. 3(c) and 3(d) are partially enlarged cross-sectional views showing the cross-section in detail.

[0025] The light guide 17 is a rod-shaped member made of a translucent resin such as acrylic and having a substantially triangular cross section (see FIG. 3(b)). As shown in FIG. 3(a), the light guide 17 includes a light guide light incident portion (surface) 171 that faces the exit surface of the synthetic diffusion block 16 via a first diffuser plate 18a, a light guide light reflecting portion (surface) 172 that forms an inclined surface, and a light guide light exit portion (surface) 173 that faces the liquid crystal display panel 52 of the liquid crystal display element 50 via a second diffuser plate 18b.

[0026] 3(c) and 3(d), which are partially enlarged views, the light guide light reflecting portion (surface) 172 of this light guide 17 is formed with a number of reflecting surfaces 172a and connecting surfaces 172b alternately formed in a sawtooth pattern. The reflecting surfaces 172a (line segments sloping upward to the right in the figures) form angles αn (n: natural number, for example, 1 to 130 in this example) with respect to the horizontal plane indicated by the dashed dotted line in the figures, and as an example, αn is set to 52 degrees or less (but 44 degrees or more).

[0027] On the other hand, the connecting surface 172b (a line segment sloping downward to the right in the drawing) forms an angle βn (n: a natural number, for example, 1 to 130 in this example) with the reflecting surface 172a. That is, the connecting surface 172b of the reflecting section is inclined at an angle with respect to the incident light that casts a shadow within the range of the half-value angle of the scatterer, which will be described later. As will be described in detail later, α1, α2, α3, α4... form the elevation angle of the reflecting surface, and β1, β2, β3, β4... form the relative angle between the reflecting surface and the connecting surface, which is set to, for example, 90 degrees or more (but 180 degrees or less). In this example, β1 = β2 = β3 = β4 = ... = β122 = ... β130.

[0028] 4 and 5 are schematic diagrams showing the reflecting surface 172a and the connecting surface 172b enlarged relative to the light guide 17 for ease of explanation. At the light guide incident surface 171 of the light guide 17, the main light ray is deflected by δ in a direction that increases the angle of incidence with respect to the reflecting surface 172a (see FIG. 5(b)). That is, the light guide incident surface 171 is formed in a curved convex shape that is inclined toward the light source. As a result, the parallel light from the exit surface of the synthetic diffusion block 16 is diffused and incident via the first diffuser plate 18a. As is clear from the figures, the parallel light is slightly bent (deflected) upward by the light guide incident surface 171 before reaching the light guide light reflecting surface 172 (see the comparative example in FIG. 6).

[0029] The light guide light reflecting portion (surface) 172 has a large number of reflecting surfaces 172a and connecting surfaces 172b formed alternately in a sawtooth pattern, and the diffused light is totally reflected by each reflecting surface 172a and directed upward, and then passes through the light guide light emitting portion (surface) 173 and the second diffuser plate 18b to enter the liquid crystal display panel 52 as parallel diffused light. For this reason, the reflecting surface elevation angles α1, α2, α3, α4... are set so that each reflecting surface 172a forms an angle equal to or greater than the critical angle with respect to the diffused light, while the relative angles β1, β2, β3, β4... between the reflecting surface 172a and the connecting surface 172b are set to a certain angle as described above, and more preferably, an angle equal to or greater than 90 degrees (βn≧90°), for the reason to be described later.

[0030] With the above-described configuration, each reflecting surface 172a is always at an angle equal to or greater than the critical angle with respect to the diffused light, so total reflection is possible without forming a reflective film such as a metal film on reflecting portion 172, and a low-cost light source device can be realized. On the other hand, as shown in Fig. 6, which is a comparative example, if there is no bending (polarization) of the main light ray at the light guide entrance portion of light guide 17, part 31b of the diffused light will be at an angle equal to or less than the critical angle with respect to reflecting surface 172a, and sufficient reflectance cannot be ensured, so a light source device with good characteristics (brightness) cannot be realized.

[0031] The reflecting surface elevation angles α1, α2, α3, α4... are values that increase slightly as one moves from the bottom to the top of the light guide light reflecting portion (surface) 172. This is because, since light that has passed through the liquid crystal display panel 52 of the liquid crystal display element 50 has a certain degree of divergence angle, a configuration is realized in which peripheral light rays are slightly deflected toward the central axis, as shown by light ray 30 in Fig. 4, in order to prevent so-called peripheral shading, in which part of the light that has passed through the peripheral portion of the liquid crystal display panel 52 is vignetted by the periphery of a mirror arranged downstream.

[0032] As mentioned above, β1 = β2 = β3 = β4 ... βn ≥ 90°. This is because, as shown in FIG. 9 , when processing mold 40 for manufacturing light guide 17 by injection molding, reflective surface 172a and connecting surface 172b can be simultaneously processed using end mill 35 with a relative angle β between the bottom and side surfaces. Furthermore, since reflective surface 172a and connecting surface 172b can be processed using a relatively thick tool, processing time and processing costs can be significantly reduced. Furthermore, the boundary edge between reflective surface 172a and connecting surface 172b can be accurately processed, thereby improving the light-guiding characteristics of light guide 17.

[0033] In addition, in Figure 4, Lr1, Lr2, Lr3, Lr4... represent the projected lengths of the reflecting surface 172a relative to the horizontal plane, and Lc1, Lc2, Lc3, Lc4... represent the projected lengths of the connecting surface 172b relative to the horizontal plane, respectively. The ratio Lr / Lc, i.e., the ratio between the reflecting surface 172a and the connecting surface 172b, is configured to be variable depending on the location. The intensity distribution of the main light ray 30 incident on the light guide 17 does not necessarily match the desired intensity distribution at the entrance surface of the LCD panel. Therefore, a configuration is adopted in which the ratio Lr / Lc between the reflecting surface 172a and the connecting surface 172b is used to adjust the intensity distribution. Note that the higher this ratio is, the higher the average intensity of the reflected light in that area can be. Generally, the light ray 30 incident on the light guide tends to be stronger in the center. To compensate for this, the ratio Lr / Lc is configured to vary depending on the location, with the intensity being particularly small in the center. Since the ratio Lr / Lc varies depending on the location and the reflecting surface elevation angles α1, α2, α3, α4, etc. vary depending on the location, the envelope 172c representing the general shape of the reflecting portion 172 exhibits a curved shape as shown in FIG.

[0034] Furthermore, Lr1+Lc1=Lr2+Lc2=Lr3+Lc3=Lr4+Lc4...=Lr+Lc≦0.6 mm. By adopting this configuration, the repetition pitch of the reflective surfaces as viewed from the light exit surface 173 of the light guide 17 can be made uniform. Furthermore, because the pitch is 0.6 mm or less, coupled with the action and effect of the diffusers 18a and 18b, when viewed through the liquid crystal display panel 52, the individual exit surfaces do not appear separate but appear as a continuous surface, thereby achieving uniform spatial luminance through the liquid crystal display panel 52 and improving display characteristics. In other words, this configuration makes it possible to uniform the distribution of incident light intensity on the liquid crystal display panel 52. On the other hand, if the value of Lr+Lc is less than 0.2 mm, not only will it take a long time to process, but it will also be difficult to accurately process each reflective surface 172a. Therefore, a value of 0.2 mm or more is desirable.

[0035] Furthermore, although not shown here, the above-mentioned Lr+Lc values (sum of lengths) may be configured as follows, in whole or in part: Lr1+Lc1>Lr2+Lc2>Lr3+Lc3>Lr4+Lc4..., or Lr1+Lc1=Lr2+Lc2=Lr3+Lc3=Lr4+Lc4.....= Lr90+Lc90> Lr91+Lc91= Lr92+Lc92> Lr93+Lc93...> Lr130+Lc130, or Lr1+Lc1≧Lr2+Lc2≧Lr3+Lc3≧ Lr4+Lc4...Lr1+Lc1>Lr130+Lc130. By adopting this configuration, the repetition pitch of the reflective surfaces 172a, as viewed from the exit surface 173 of the light guide 17, becomes finer as one approaches the exit surface 173. Consequently, with this configuration, the repetition pitch of the reflective surfaces 172a, as viewed from the diffuser 18b of the light guide 17, becomes finer as one approaches the diffuser 18b. The repetition structure of the reflective surfaces 172a increases visibility closer to the diffuser 18b, impairing the uniformity of the light intensity. Therefore, a certain degree of diffusivity of the diffuser 18b is necessary. However, by adopting this configuration, the repetition pitch of the reflective surfaces located closer to the diffuser 18b becomes finer, ensuring uniformity of the light intensity even with low diffusivity of the diffuser, thereby improving light utilization efficiency. Furthermore, as described above, it is desirable to set the value of Lr+Lc within the range of 0.2 mm or more and 0.6 mm or less.

[0036] The shape of the light guide light reflecting portion (surface) 172 of the light guide 17 described above satisfies the conditions for total reflection of the main light, eliminating the need to provide a reflective film such as aluminum on the reflecting portion 172, allowing light to be reflected efficiently. This eliminates the need for aluminum thin film deposition, which increases manufacturing costs, and allows for a brighter light source to be realized at lower cost. Furthermore, each relative angle β is set to an angle such that the connecting surface 172b casts a shadow over the main light ray 30 relative to the light diffused by the composite diffusion block 16 and the diffuser plate 18a. This suppresses the incidence of unnecessary light on the connecting surface 172b, thereby reducing the reflection of unnecessary light and enabling the realization of a light source device with excellent characteristics.

[0037] Generally, it is desirable that the inclination of the main light beam incident on the liquid crystal display panel is close to vertical, however, depending on the characteristics of the liquid crystal display panel, it may be possible to incline it by an angle η as shown in Fig. 5(b). That is, among commercially available liquid crystal display panels, some have better characteristics when the incident angle is inclined by about 5 to 10 degrees, and in such cases, it is desirable to set the above η to 5 to 10 degrees depending on the characteristics.

[0038] Also, instead of tilting the panel by η, it is possible to tilt the inclination of the main light beam toward the liquid crystal display panel by adjusting the angle of the reflecting surface 172a. Furthermore, if it is necessary to tilt the light beam toward the side of the light guide, this can be achieved by making the inclination of the slope of the triangular texture 161 formed on the exit surface of the synthesizing / diffusing block 16 asymmetrical, or by changing the formation direction of the texture composed of the reflecting surfaces 172a and 172b.

[0039] Next, the synthetic diffusion block 16, which is another component of the light source device 10, will be described with reference to Figures 7 and 8. Figure 7 shows the synthetic diffusion block 16 integrated with the LED collimator 15, and Figures 8(a) and (b) show enlarged cross sections of a portion of the synthetic diffusion block 16.

[0040] As is clear from FIG. 8( a), a large number of textures 161 each having a substantially triangular cross section are formed on the exit surface of the composite diffusion block 16. The textures 161 diffuse the light emitted from the LED collimators 15 in a direction perpendicular to the plane of the drawing of the incident portion (surface) 171 of the light guide 17. The interaction between the substantially triangular textures 161 and the diffusers 18a and 18b makes it possible to homogenize the intensity distribution of the light emitted from the exit portion 173 of the light guide 17, even if the LED collimators 15 are discretely arranged. In particular, the textures 161 limit the diffusion direction to the lateral direction of the light guide and further enable control of the diffusivity in the lateral direction. This makes it possible to weaken the isotropic diffusion of the first and second diffusers 18a and 18b. As a result, light utilization efficiency is improved, and a light source device with excellent characteristics can be realized. In this example, the texture 161 has a substantially triangular shape with an angle γ of 30 degrees and a formation pitch a of 0.5 mm.

[0041] As described above in detail, the light source device 10 of the present invention further improves the light utilization efficiency of the laser light from the LED light source and its uniform illumination characteristics, while at the same time making the light source device smaller and enabling it to be manufactured at low cost. Therefore, it is possible to provide a light source device that is particularly suitable as an illumination light source for display devices of electronic devices such as HUDs and ultra-compact projectors.

[0042] <Modifications of the Light Source Device> 10 and 11 show a modified example of the light source device according to the first embodiment of the present invention, showing an overall perspective view of the light source device 10b and its internal configuration. In this modified example, a composite diffusion block 16b with a generally trapezoidal cross section is used to mount an LED collimator 15 having multiple conical convex shapes to which LEDs are attached at an inclined position below the device. Reference numeral 13b in the figures denotes a heat sink for cooling the heat generated by the LED elements and the control circuit.

[0043] <Other Modifications of the Light Source Device> 12 shows another modified example of the light source device according to the first embodiment of the present invention, and shows a perspective view of the overall appearance of a light source device 10c. Although not shown in detail, this modified example has a structure in which heat generated by the LED substrate 12 is cooled by a heat sink 13c disposed below the device through a heat transfer plate 13d. This configuration allows for a light source device with a short overall length.

[0044] <Another form of collimator in light source device> Furthermore, Fig. 13 shows another form of collimator 15b in the light source device according to Example 1 of the present invention, and shows an example of a shape that combines the aforementioned composite diffusion block 16. While the collimator shapes shown in Figs. 7 and 8 have an outer shape of a cone convex shape obtained by rotating an approximately parabolic segment, this shape is based on an approximately square pyramid convex shape, with the corners chamfered or curved. Considering the efficiency of light emitted from the LED and emitted from the light guide 17, the paraboloid of revolution shape shown in Figs. 7 and 8 is appropriate, but in this configuration, the boundaries of each approximately square pyramid convex shape are smoothly connected, so a more uniform light intensity distribution can be achieved.

[0045] The light source devices 10b and 10c, which are modifications of the light source device of the present invention, described above, also have the same functions and effects as the light source device 10 shown in Fig. 1. By appropriately selecting these light source devices 10, 10b, and 10c, it is possible to reliably install them in accordance with the internal storage space of electronic devices such as HUDs and micro projectors having various shapes and forms.

[0046] <Application examples of light source devices> In addition, the following describes examples in which the light source device 10 of the present invention described above is mounted on a HUD and a micro projector as typical examples of electronic devices that use the light source device 10 as a light source for their display devices.

[0047] 14(a) shows an example in which the light source device according to the first embodiment of the present invention is applied to a HUD. In this figure, in a head-up display device 100, an image displayed on an image display device 300 including a projector, an LCD (Liquid Crystal Display), or the like is reflected by a mirror 131 or another mirror 132 (for example, a free-form surface mirror or a mirror having an asymmetrical shape about its optical axis) and projected onto a windshield 3 of a vehicle 2. Meanwhile, a driver 105 looks at the image projected onto the windshield 103 and visually recognizes the image as a virtual image ahead through the transparent windshield 103.

[0048] 14(b) shows an example of the internal configuration of the head-up display device 100, particularly the image display device 300. As is clear from this figure, the image display device 300 is a projector, and the image display device 300 has various components such as a light source 301, an illumination optical system 302, and a display element 303. Note that by employing the light source device 10 of the present invention described above as the light source 301, it is possible to generate good illumination light for projection.

[0049] This example further includes an illumination optical system 302 that condenses illumination light generated by the light source 301, makes it more uniform, and irradiates the light onto the display element 303, as well as the display element 303 that generates an image to be projected. However, in the above-described embodiment, these elements are already included in the light source device 10 of the present invention as the combining / diffusing block 16, the first diffuser 18a, the light guide 17, the second diffuser 18b, and the liquid crystal display panel 52. Therefore, the light source device 10 of the present invention can be directly used as the image display device 300 of the head-up display device 100. This makes it possible to realize a head-up display device 100 that can be easily installed in a narrow space, such as a dashboard inside an automobile.

[0050] It will be clear to those skilled in the art that the light emitted from the image display device 300 is further projected onto the windshield 103 of the vehicle 102 via the display distance adjustment mechanism 400 and the mirror drive unit 500.

[0051] As described in detail above, by using the light source device 10 of the present invention as a light source for illuminating a display device, it can be easily installed in a small space and it is possible to realize a smaller and cheaper electronic device.

[0052] Example 2 Next, a second embodiment (embodiment 2) of the present invention will be described in detail below. Unlike embodiment 1, embodiment 2 focuses on the transmittance of polarized waves of the liquid crystal display panel 52 constituting the liquid crystal display element 50 to which the illumination light from the light source device is incident, and further provides a polarization conversion element that aligns the polarization direction of the light emitted from the collimating optical system in one direction, thereby realizing a more compact and efficient light source device.

[0053] 15 to 17 show the configuration of the optical system, which is a feature of a light source device according to Example 2 of the present invention. That is, in Example 2, in the configuration of Example 1 described above, the number of LEDs 14a, 14b constituting the light source is half that of Example 1, that is, two, and a polarization conversion element 21 is provided between each LED collimator 15 and a combining / diffusing block 16. Note that the other components in the figures are the same as those in Example 1 described above, and are indicated by the same reference numerals, and detailed description thereof will be omitted here to avoid duplication.

[0054] 17(a), the polarization conversion element 21 is configured by combining a columnar light-transmitting member having a parallelogram cross section (hereinafter referred to as a parallelogram column) and a columnar light-transmitting member having a triangular cross section (hereinafter referred to as a triangular column), which extend along a direction perpendicular to the paper surface of the drawing, and arranging a plurality of these in an array parallel to a plane (in this example, the vertical direction on the paper surface of the drawing) orthogonal to the optical axis of the collimated light from the LED collimator 15. Furthermore, a polarization beam splitter (hereinafter abbreviated as "PBS") film 211 and a reflective film 212 are alternately provided at the interface between adjacent light-transmitting members arranged in the array, and a ½λ phase plate 213 is provided on the exit surface from which light incident on the polarization conversion element 21 and transmitted through the PBS film 211 exits.

[0055] In this way, the polarization conversion element 21 is configured symmetrically with respect to the plane formed by the optical axis of the collimated light from the LED collimator 15 and the extension direction of the parallelogram prism-shaped light-transmitting member (a vertical plane extending perpendicularly to the paper surface of the drawing), that is, the optical axis plane of the collimated light, and the inclination of the parallelogram prism and triangular prism-shaped light-transmitting member, which are its components, is 45 degrees with respect to the optical axis plane. Then, the polarization conversion element 21 constitutes two sets of polarization conversion elements separated in the vertical direction of the drawing for the collimated light from the two LED collimators 15.

[0056] 17(a), according to the polarization conversion element 21 configured as above, for example, of the incident light emitted from the LED 14a and converted into parallel light by the LED collimator 15, the S-polarized light (see the symbol (x) in the figure) is reflected by the PBS film 211 and then further reflected by the reflective film 212 to reach the incident surface of the combining / diffusing block 16. On the other hand, the P-polarized light (see the up and down arrows in the figure) passes through the PBS film 211, and then becomes an S-polarized light by the 1 / 2λ phase plate 213 to reach the incident surface of the combining / diffusing block 16.

[0057] In this way, with the polarization conversion element 21, all of the light emitted from the (plurality of) LEDs and collimated by the LED collimator 15 becomes S-polarized light and enters the incident surface of the combining / diffusing block 16. Thereafter, the light emitted from the exit surface of the combining / diffusing block 16 passes through the first diffuser plate 18a and enters the light guide 17 already described in detail above, and is further reflected upward in the figure by the action of the light guide 17 and is guided to the incident surface of the liquid crystal display element 50, just as in the first embodiment. That is, the function of the light guide 17 has already been described in detail above, and therefore its description will be omitted here to avoid repetition.

[0058] 18 is a perspective view showing the state in which the two LED collimators 15 described above are attached to the polarization conversion element 21. FIG. 19 is a perspective view showing the external configuration of the synthetic diffusion block 16 attached to the light output surface side of the polarization conversion element, and FIG. 20 is a side view and a partially enlarged cross-sectional view showing the detailed structure of the synthetic diffusion block 16. As is clear from these figures, in Example 2 as well, a large number of textures 161 with a substantially triangular cross section are formed on the light output surface of the synthetic diffusion block 16. However, the details have already been described above and will not be described here.

[0059] That is, according to the light source device of the second embodiment, the light incident on the liquid crystal display panel 52 constituting the liquid crystal display element 50 is converted into S-polarized light by the polarization conversion element 21, and the transmittance of the light through the liquid crystal display panel can be improved, so that a smaller, more efficient light source device can be realized at lower cost using fewer light sources (LEDs). Note that, although the polarization conversion element 21 has been described above as being attached after the LED collimator 15, the present invention is not limited to this, and it will be apparent to those skilled in the art that similar actions and effects can be obtained by providing the polarization conversion element 21 in the optical path leading to the liquid crystal display element.

[0060] Furthermore, although the liquid crystal display panel has been described as having excellent transmittance for S-polarized light, it will be apparent to those skilled in the art that similar actions and effects can be obtained by using a polarization conversion element having a similar configuration as above, even when the liquid crystal display panel has excellent transmittance for P-polarized light. Furthermore, it will be apparent to those skilled in the art that the light source device according to the second embodiment described above can also be used as a light source device in electronic devices such as head-up displays and projectors, just like the light source device according to the first embodiment described above.

[0061] The above describes various embodiments of the present invention, including a surface light source device suitable for use in an electronic device equipped with an image display device. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments describe the entire system in detail to clearly explain the present invention, and the present invention is not necessarily limited to a system including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0062] 10...light source device (main body), 11...case, 50...liquid crystal display element, 12...LED board, 13...heat sink, 14a, 14b...LED, 15...LED collimator, 16...synthetic diffusion block, 17...light guide, 171...light guide light incident portion (surface), 172...light guide light reflecting portion (surface), 172a...reflecting surface, 172b...connecting surface, 173...light guide light exit portion (surface), 21...polarization conversion element, 211...PBS film, 212...reflecting film, 213...½λ phase plate.

Claims

1. A light source device, a light source that generates white light by irradiating a phosphor with light emitted from a solid-state light source; a collimating optical system that converts a divergent light beam of white light emitted from the light source into parallel light; a light guide that receives the light emitted from the collimating optical system as incident light and emits the incident light in a direction different from the incident direction, the collimating optical system has a filter configured to reflect light in a blue region of the parallel light to illuminate the phosphor; a diffusion block for diffusing the parallel light between the collimating optical system and the light guide; The filter is provided on the incident surface of the diffusion block. Light source device.

2. 2. The light source device according to claim 1, The light in the blue region of the parallel light reflected by the filter is light in the short wavelength blue region of the parallel light. Light source device.

3. 2. The light source device according to claim 1, The filters are provided on an exit surface of the collimating optical system and an entrance surface of the diffusion block, respectively. Light source device.

4. 2. The light source device according to claim 1, The divergence angle of the light emitted from the light source that generates white light by irradiating the light emitted from the solid-state light source onto a phosphor is 80 degrees or more. Light source device.

5. 2. The light source device according to claim 1, The filter has a cutoff wavelength of 435 (nm) or less at which the reflectance becomes 50%. Light source device.

6. 2. The light source device according to claim 1, a polarization conversion element for aligning the polarization direction of light in one direction is provided between the collimating optical system and the light guide; Light source device.

7. 2. The light source device according to claim 1, the light guide has an incident portion that receives the incident light, a reflecting portion that reflects the incident light, and an exit portion that emits the light reflected by the reflecting portion, the reflecting portion includes a plurality of reflecting surfaces that reflect the incident light and a plurality of connecting surfaces that connect the plurality of reflecting surfaces, and the incident portion has a structure that deflects light in a direction in which the angle of incidence of the incident light that is incident on the reflecting surface of the reflecting portion increases. Light source device.

8. 8. The light source device according to claim 7, a scatterer is provided between the collimating optical system and the light guide; The connecting surface is inclined with respect to the incident light at an angle at which a shadow is formed within a range of the half-value angle of the scatterer. Light source device.

9. 8. The light source device according to claim 7, The incident surface of the incident portion is an inclined surface disposed obliquely with respect to the incident light. Light source device.

10. 10. The light source device according to claim 9, At least a part of the entrance surface is a curved surface. Light source device.

11. 9. The light source device according to claim 8, The elevation angle of the reflecting surface varies depending on the location, and the relative angle between the reflecting surface and the connecting surface adjacent to each other is 90 degrees or more. Light source device.

12. The light source device according to claim 11, The relative angle is a constant value regardless of location. Light source device.

13. 8. The light source device according to claim 7, a structure for diffusing light is formed on the exit surface of the collimating optical system; Light source device.

Images