Light source device for image display device

Abstract

The invention discloses a light source device for an image display device, which is characterized in that a single light source module is formed by a surface light-emitting solid light source and an optical element for narrowing the divergence angle of a divergent light beam emitted by the surface light-emitting solid light source, and a plurality of single light source modules are arranged in two dimensions to form a light source unit and an image display device. A light beam from a light source unit is incident on an image display device, and an image is displayed on a screen by adjusting an intensity of the light according to an image signal by the image display device. The reflecting surface of the reflective optical element forming the single light source module is in a paraboloid shape, the surface light-emitting solid element is designed on the end surface of the surface light-emitting solid element, the reflected light beam emergent surface opposite to the surface light-emitting solid element is in a hexahedron shape, and the adjacent single light source modules are tightly arranged and seamlessly butted. The light source device is provided with a light source unit composed of a plurality of two-dimensionally arranged single light source modules, and the inscribed circle diameter of the hexahedron is approximately equal to the maximum diameter of the paraboloid-shaped reflecting surface. According to the invention, the reliability is obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a light source device for an image display device. Background Art

[0002] As image signals become higher in resolution, the resolution of home televisions (TVs) has evolved from 2K (1920×1080 pixels) to 4K (3840×2160 pixels), achieving higher resolution and larger screens. In addition to large-screen televisions, there is a growing demand for compact, lightweight, portable, and outdoor-compatible high-convenience, low-power, high-resolution image information display devices, including projection-type image display devices. Compared to the complex light source devices used in conventional projection-type image display devices, there is a growing demand for highly efficient light source devices that utilize compact, single-panel LCDs with color filters as image display elements. Furthermore, there is a growing demand for highly efficient HUDs (head-up displays) utilizing these devices.

[0003] The specific technical means to achieve high-efficiency HUD image display devices. In traditional technologies, the divergent light from the white individual light source is converted into parallel light by using a light guide tube, and then polarization conversion is performed to convert it into the required polarization wave, thereby greatly improving the utilization efficiency of light, which is more effective than traditional optical components.

[0004] However, existing light sources used in projection-type image display devices have the following problems that need to be solved: (1) The light source structure is complex and large in size. In order to obtain white light, it is necessary to use an individual light source that generates excitation light and a phosphor that mixes green and red light. Therefore, the luminous efficiency of the entire system is the product of the light conversion efficiency of the individual light source and the excitation light conversion efficiency of the phosphor, which makes it difficult to achieve high efficiency in principle. (2) The positional accuracy of the light source and the light guide tube is strictly required. Due to the difference in the incident angle of the polarizing beam splitter (PBS), it is difficult to ensure the assembly accuracy during mass production, making it difficult to stably ensure the polarization conversion efficiency. The structure of the flat reflector is complex, and it is very difficult to correct the mold shape to obtain a high-precision finished product. At the same time, it takes a lot of time to determine the optimal molding conditions and achieve mass production stabilization of the shape.

[0005] Furthermore, conventional projection-type image display devices primarily utilize TN (Twisted Nematic Liquid Crystal Display) or DLP (Digital Light Processing) liquid crystal panels for their display elements. However, to reduce the overall cost of optical components, LCDs with color filters are becoming the mainstream for image display devices. To compete in the image display resolution market, either the panel size needs to be increased or the pixel size needs to be reduced. However, reducing the pixel size requires the introduction of new manufacturing equipment, which is not the optimal strategy. Therefore, currently, high resolution is achieved by increasing the panel size. Consequently, the light source devices required for future image display devices must not only possess high efficiency and brightness uniformity but also be adaptable to larger illuminated surfaces, placing new demands on new light source systems. Summary of the Invention

[0006] To solve the above problems, the present invention provides a light source device for an image display device. By equipping the device with an optical element that controls the diffusion characteristics of the light beam incident on the LCD, the device can achieve a surface light source with uniform brightness distribution when the light sources are arranged.

[0007] To achieve the above-mentioned object, the present invention adopts a technical solution: a light source device for an image display device, comprising a single light source module composed of a surface-emitting solid light source and an optical element for narrowing the divergence angle of a divergent light beam emitted by the surface-emitting solid light source, wherein a plurality of the single light source modules are arranged in a two-dimensional manner to form a light source unit and an image display device; The light beam from the light source unit is incident on an image display device, and the image display device adjusts the intensity of the light according to an image signal to display an image on a screen; The light source unit is constructed as follows: a divergent light beam from a surface-emitting solid light source is reflected on a reflective surface, converted into approximately parallel light, and placed near the focus of a reflective optical element; a cylindrical hole is designed at the focus of an end face of the reflective optical element, and the surface-emitting solid light source is placed in the hole; The reflective surface of the reflective optical element constituting the single light source module is in a parabolic shape, the surface-emitting solid element is designed on its end face, and the reflected light beam exit surface opposite thereto is in a hexahedron shape, and adjacent single light source modules are closely arranged and seamlessly connected; The light source device comprises a light source unit composed of a plurality of two-dimensionally arranged single light source modules, wherein the diameter of the inscribed circle of the hexahedron is substantially equal to the maximum diameter of the parabolic reflecting surface.

[0008] Furthermore, a plurality of individual light source modules are arranged in a two-dimensional manner to form a light source unit, and a hole is provided on the end face of the individual light source module, which is approximately cylindrical along the direction of the optical axis containing the focus of the reflective optical element; these cylindrical side surfaces refract part of the divergent light from the surface-emitting solid light source; and by being reflected at different positions on the reflective surface of the reflective optical element, the divergent light beam from the surface-emitting solid light source can be converted into a light beam with an approximately narrow divergence angle.

[0009] The end face of the single light source module is provided with a hole, which is approximately cylindrical along the optical axis direction including the focus of the reflective optical element, and the side faces of these cylinders refract part of the divergent light from the surface-emitting solid light source; By reflecting at different positions on the reflective surface of the reflective optical element, the divergent light beam from the surface-emitting solid light source can be converted into a divergent light beam with a narrow divergence angle, and the divergent light beam diverges from multiple focal points along the optical axis of the reflective optical element.

[0010] A hole is provided on the end face of the single light source module, which is roughly cylindrical along the optical axis direction including the focus of the reflective optical element. The narrow-angle divergent light beam from the surface-emitting solid-state light source is incident on the front end face of the cylinder and is refracted by the lens shape provided on the front end face, thereby controlling the incident position and incident angle of the light beam incident on the reflective surface of the reflective optical element.

[0011] The single light source module is composed of a surface-emitting solid light source and an optical element that narrows the divergence angle of the divergent light beam emitted from the surface-emitting solid light source; The image display device displays an image on a screen by causing a light beam from a light source unit to be incident on the image display device and adjusting the intensity of the light according to an image signal by the image display device; The light source unit converts a divergent light beam from a surface-emitting solid light source into approximately parallel light by reflecting it on a reflective surface, and places the divergent light beam near the focus of a reflective optical element. A cylindrical hole is also provided at the focus of an end face portion of the reflective optical element, and the surface-emitting solid light source is placed in the hole. The reflective surface of the reflective optical element constituting the aforementioned single light source module is formed by a plurality of regions, and the first region close to the aforementioned surface-emitting solid light source is in a parabolic shape; The second reflective region is located near the end face provided with the surface-emitting solid element and the opposite reflected light beam emission surface, and has different divergence characteristics from the reflected light beam of the first reflective region. The end face provided with the surface-emitting solid element and the opposite reflected light beam emission surface have a hexahedral opening shape, and adjacent single light source modules are seamlessly connected and neatly arranged. The inner diameter of the circumscribed circle of the hexahedron of a single light source module is equal to the maximum diameter of the second reflective region.

[0012] The end face of the single light source module is provided with a hole, which is approximately cylindrical along the optical axis direction including the focus of the reflective optical element. The side faces of these cylinders refract a part of the divergent light from the surface-emitting solid light source. The divergent light beam of the surface-emitting solid light source is converted into a light beam with a divergent angle of approximately narrow angle by reflection through the reflective surfaces at different positions of the reflective optical element.

[0013] A hole is provided on the end face of the single light source module, which is approximately cylindrical along the optical axis direction containing the focus of the reflective optical element. The side surfaces of these cylinders refract a portion of the divergent light from the surface-emitting solid light source, and reflect it at different positions on the reflective surface of the reflective optical element. The divergent light beam from the surface-emitting solid light source can be converted into a divergent light beam with a narrow divergence angle that diverges from multiple focal points along the optical axis of the reflective optical element.

[0014] A hole is designed on the end face of the single light source module, which is approximately cylindrical along the optical axis direction containing the focus of the reflective optical element. After the narrow-angle divergent light beam in the divergent light beam from the surface-emitting solid light source enters the front end face of the cylinder, it is refracted by the lens arranged on the front end face.

[0015] Among the light beams emitted by the single light source module, the reflected light beams from the second reflection area in the side reflection field of the reflective optical element diverge toward the image display device, and the divergent lights from multiple adjacent single light source modules overlap on the light incident surface of the image display device.

[0016] The single light source module is formed of a heat-resistant plastic material.

[0017] The single light source module is made of heat-resistant plastic with a heat-resistant temperature of more than 120 degrees.

[0018] Compared to existing technologies, the present invention offers the following advantages: To achieve a compact, lightweight, portable, and low-power image display device, an LCD with a color filter is used as the image display element. A so-called white LED (Light Emitting Diode) is used, combining a blue LED with a yellow phosphor with high light conversion efficiency, and equipped with an optical element that reflects light of a specific polarization as the light source. By reflecting the specific polarization back toward the phosphor, re-exciting it, a light source device and an image display device employing this light source optical assembly achieve efficient light conversion and display. The amount of light beam incident on a small image display element is typically constant based on the amount of light diffusion, determined by the product of the luminous area and the divergence angle of each individual surface-emitting LED. In an embodiment of the present invention, the LCD is relatively large relative to the light source, so the entire active display area of the LCD cannot be illuminated simultaneously. Instead, the LCD's receiving surface is illuminated in a divided manner, corresponding to each LED. Furthermore, an optical element is provided to control the diffusion characteristics of the light beam incident on the LCD, thereby achieving a surface light source with uniform brightness distribution when the light sources are arranged.

[0019] The present invention returns the aforementioned specific polarized light to the LED side and uses it as excitation light. At the same time, an absorptive polarizer is provided on the incident side of the LCD to significantly reduce the specific polarized light incident on the LCD, thereby significantly improving the reliability of the LCD including the absorptive polarizer and further improving its contrast performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a graph of LED light diffusion characteristics; Figure 2 This is the first luminous characteristic diagram of a common white surface-emitting LED; Figure 3 This is the second luminous characteristic diagram of a common white surface-emitting LED; Figure 4 This is a schematic diagram of the appearance of a common surface-emitting LED; Figure 5 This is a schematic diagram of the internal structure and cross-sectional view of a common surface-emitting LED; Figure 6 is a schematic cross-sectional view of the main components of the light source optical assembly of the image display device of the present invention as a result of ray tracing; Figure 7 This is a characteristic diagram of the intensity variation of the light refractive force along the optical axis of the main components of the light source optical assembly of the image display device of the present invention; Figure 8 is a schematic cross-sectional view of the ray tracing results of the LED light source and main components of the light source optical assembly of the image display device of the present invention; Figure 9It is a schematic cross-sectional view of a portion of the main components of the light source optical assembly of the image display device of the present invention and the light divergence state of the LED light source; Figure 10 It is a schematic structural cross-sectional view of the main components of the light source optical assembly of the image display device of the present invention; Figure 11 is a schematic plan view of the structure of the main components of the light source optical assembly of the image display device of the present invention; Figure 12 is a schematic cross-sectional view of a configuration mode of an image display device of the present invention; Figure 13 is a schematic cross-sectional view of optical components constituting a light source optical assembly of an image display device of the present invention; Figure 14 is a graph showing the transmittance characteristics of a reflective polarizer according to an embodiment of the present invention when the incident angle is around 10 degrees; Figure 15 is a graph showing the transmittance characteristics of a reflective polarizer in an embodiment of the present invention when the incident angle is around 50 degrees; Figure 16 is a characteristic diagram schematically showing the narrow-angle diffusion characteristics obtained by the optical components of the light source device used in the image display device of the present invention; Figure 17 is a schematic characteristic diagram of the narrow-angle diffusion characteristics of LCD image light obtained by the light source optical assembly in an embodiment of the present invention; Figure 18 This is a diagram explaining the invariant of light diffusion amount. DETAILED DESCRIPTION

[0021] The following examples are Figure 2 and Figure 3 The light emitting characteristics shown are explained based on a white LED. Figure 2 The first white LED shown and Figure 3 The second white LED shown differs from the first in that it produces white light by exciting a yellow phosphor containing green and red. The peak wavelength of the blue LED's emission is located at a shorter wavelength in the first embodiment, resulting in white light with a higher color temperature. This embodiment relates to an image display device comprising a light source device including an optical assembly with optical elements capable of controlling the divergence angle and direction of light emitted from the white LED, and an LCD image display element employing a color filter that adjusts the intensity of the light source light according to an image signal.

[0022] The following embodiments primarily describe a light source device and its accompanying light source optical assembly when using a color filter-based LCD panel as an image display element. In these embodiments, the light source optical assembly can efficiently serve as a direct light source for the LCD panel, making it suitable for use in projection-type image displays and head-up displays (HUDs).

[0023] Hereinafter, a light source device and its optical components for realizing the image display device according to the embodiment of the present invention, as well as characteristics of each optical component will be described.

[0024] <Light source optical components> The light source of the present invention adopts a surface emitting solid light source, using a blue LED, mixed with yellow light generated by exciting a yellow phosphor containing green and red to obtain white light from a white LED. Its diffusion characteristics are as follows Figure 1 The figure shows a completely diffuse distribution. To capture and efficiently utilize light from a light source with a large divergence angle, a plano-convex lens with a large aperture receiving surface needs to be configured near the LED light-emitting surface. In the design of the lighting component, the area and divergence angle of the light-emitting surface and the area and collection angle of the receiving surface must satisfy the equal luminance invariant characteristic (such as Figure 18 As shown in Figure 2, conventional light source optical components have the problem of being unable to efficiently utilize the divergent light beams emitted by LEDs. The present invention solves these problems through the following technical means.

[0025] In the embodiment of the present invention, the divergence angle of the light source is as follows: Figure 16 As shown in the figure, it has a narrow-angle divergence characteristic. Compared with the fully diffused characteristics of ordinary surface-emitting LEDs shown in the figure, the divergence angle of the emitting light beam is narrow, thereby increasing the light energy density and improving the brightness of the image displayed on the subsequent LCD. Figure 10 and Figure 11 As shown, a single light source module including a reflective optical element 11 achieves both narrowing the divergent light beam angle and controlling its directivity. Narrowing the divergent light beam angle is controlled by the shape of the reflective surface of the reflective optical element 11, while directivity can be easily adjusted by optimizing the relationship between the reflective surface's focal position and the center of light emission of the surface-emitting white LED in the XY plane.

[0026] As described above, the embodiments of the present invention arrange divergent beams with narrow divergence angles and single light source modules with controllable directivity in a planar direction, so that the divergent beams of surface-emitting LEDs can be precisely controlled like lasers (LASER, Light Amplification by Stimulated Emission of Radiation).

[0027] In the embodiment of the present invention, the surface emitting LED is placed Figure 6At the focal point of the reflective surface shown, the divergent light from the surface light source is converted into a beam approximately parallel to the optical axis (Z axis) of the reflective surface. In this case, since the reflective surface primarily controls the diffusion characteristics of the diffuse light, even a white light source will not produce chromatic aberration. Surface-emitting light source 1 cannot be spatially arranged and cannot capture light from area a, so the corresponding reflective surface needs to be cut off, such as Figure 8 and Figure 9 As shown, the end surface is designed to be approximately flat so that the LED driver substrates can be arranged in close proximity.

[0028] <Multi-focusing of reflective optical elements> The appearance of surface-emitting LED components is as follows Figure 4 As shown, it is wrapped inside a shell with a blue LED inside and a phosphor encapsulated around it with an inorganic encapsulation material. Figure 5 This is a cross-sectional view of a common surface-emitting white LED. The blue LED chip (element) 5 is mounted on a substrate 6, and the blue light emitted from it is used as excitation light by the surrounding green and red yellow phosphors to obtain Figure 2 and Figure 3 The white light shown contains the three primary colors of blue, green and red. In ordinary surface-emitting white LEDs, the surrounding area of the blue LED element light emitting area ( Figure 5 The light intensity in area 2 is the strongest, so the proportion of white light generated is the highest among the packaged phosphors.

[0029] In an embodiment of the present invention, by Figure 12 and Figure 13 The reflective polarizer 19a ( Figure 13 (A) ) can reflect P polarized light. The blue light component of the P polarized light returned by the surface-emitting white LED is used as the excitation light of the phosphor again, thereby emitting light on the surface of the phosphor ( Figure 5 Therefore, the surface-emitting white LED used in this embodiment has high luminous intensity not only in area 2 but also in an area close to the phosphor-coated surface (area 3 in the figure).

[0030] As a result, multiple luminous points with high luminous intensity are formed along the Z axis in the embodiment, thereby increasing the degree of freedom in controlling the topological characteristics of the reflective optical element. This is the first unique advantage of the present invention.

[0031] In the embodiment of the present invention, it is possible to realize that there are multiple focal points along the aforementioned Z-axis direction. Specifically, when optimizing the focal position of the reflective optical element 11, the surface-emitting white LED is arranged at Figure 6The parabola focal position is shown. This results in multiple luminous points along the Z-axis, so a composite focal point reflective surface needs to be designed based on a new design concept.

[0032] In addition, the general method of improving the light utilization efficiency of surface light source white LED is to reduce the light emitting area. Therefore, the light emitting area of surface light emitting white LED with high light output has been rapidly reduced in recent years. In the embodiment of the present invention, it is necessary not only to optimize the optimal shape of the multiple light emitting points formed by the reflective optical element 11 along the Z-axis direction, but also to consider the assembly accuracy of the miniaturized surface light emitting LED. Figure 4 As shown, even if the light-emitting point moves in the XY direction within the light-emitting surface, as long as the light-emitting point is within a specific range, the light receiving efficiency will not drop significantly. In other words, in order to reduce assembly accuracy, it is necessary to design a composite focal reflective optical element 11 with multiple focal planes within the XY plane.

[0033] The following is a description of the design of the reflective surface of the reflective optical element 11 having multiple focal points in the horizontal and vertical directions. Figure 6 FIG is a schematic diagram of a vertical cross section of the reflective optical element 11, showing a vertical cross section of the element along the Z axis. In the region a along the Z axis, since the divergent light of the surface-emitting white LED at the focus cannot be captured, Figure 8 In the cross section of the optical element 11 shown in FIG, a hole is provided in a part of the end surface thereof (such as Figure 9 As shown in the figure, the surface-emitting white LED is placed at the optimal position along the Z axis of the reflective optical element by the refraction effect caused by the shape of the hole. Figure 9 As shown, a roughly cylindrical hole is provided on the end face of the reflective optical element 11 (also referred to as a single light source module) in the area aligned with the optical axis. A surface-light white LED is positioned within this space. Because the reflective optical element and the LED light source are positioned close together, a high-temperature-resistant plastic material (with a heat distortion temperature of 120°C or higher) is recommended for this cylindrical hole. Furthermore, a draft angle of at least 2 degrees is required between the end and tip of the mold to facilitate removal from the mold during molding, significantly improving the release performance of the molded part.

[0034] Figure 9 The divergent light from the surface-emitting white LED shown in the figure is refracted by the cylindrical hole wall and originally diverges in the direction indicated by the dotted line (incident angle θ5 relative to the wall). However, due to refraction at the wall, the divergent direction changes to the direction indicated by the solid line (incident angle θ4 relative to the wall).

[0035] Therefore, relative to Figure 9The first focus of the single light source module at the intersection of the middle dashed lines (ie, the position where the LED light source is placed) generates a second focus slightly further away in space (at a distance L1).

[0036] The position of this second focus can be arbitrarily designed according to the inner diameter of the approximate cylindrical shape, the inclination angle of the wall and the refractive index of the material. These parameters are effective design parameters in the shape design of a single optical module. The light beams refracted by the cylindrical sides and reflected by the reflective surface of the individual optical modules (area b in the figure) are converted into roughly parallel beams because their respective focal points are parabolic surfaces and emitted toward the LED. Area c, farthest from the LED light source, is designed to diverge along the parabola.

[0037] The top surface of the cylindrical shape has a lens shape, and the divergence angle of the surface-emitting white LED is controlled by refraction of the divergence angle in a small range. The design of this shape can be shown in the figure. Since the refractive power of the area a around the optical axis and the surrounding area b is different, the shape design can be used to more accurately control the light distribution. The divergence angle of the light beam incident on these areas is about ±15 degrees. According to Snell's law, the refracted light can be effectively controlled. As described above, the divergent light from the surface-emitting white LED set at the first focus passes through the reflective surface shape of the single optical module in the embodiment of the present invention, as shown in FIG. Figure 8 The dotted line portion shown forms an almost parallel light beam, which then travels to the color filter LED in the lower section.

[0038] On the other hand, due to the lens effect of the cylindrical side wall, a divergent light of the second focus is generated, as shown by the solid line in the figure, and several divergent light beams are emitted from a single optical module. This result makes Figure 11 The individual light source modules shown are arranged to reduce light intensity variations at the boundaries between adjacent optical units, thereby increasing the technical potential.

[0039] Next, if Figure 7 As shown in the embodiment of the present invention, the refractive power variation of each region of the reflective optical element 11 (single light source module) along the optical axis is described. When designing, the refractive power of region c will gradually weaken compared with region b, and the divergence effect will increase. Figure 11 The brightness of the connecting portion of adjacent individual light source modules in the final form is shown. During design, the image light emitted by the LCD panel with color filters is designed to have a uniform light source when the brightness ratio at the connecting portion of the individual light source modules is less than 3%. In this case, in addition to the shape of the individual light source modules, the effect of the optical film for controlling the diffusion angle, described later, can be used to mitigate the effects of design parameters.

[0040] Versatility of a single light source module The final light source unit 12 is as follows Figure 11 As shown, it is composed of multiple individual light source modules 13 arranged in an array. Table 1 shows a representative example of a color filter LCD currently available in the automotive market. To ensure component compatibility, individual light source modules of the same shape (hexagonal circumcircle diameter of 16 mm) were arranged in an array. This result demonstrates that the mold used to mold the light source unit allows the use of identically shaped inserts for the individual light source modules, improving development efficiency.

[0041] When observing from the opening, a single light source module 13 having a parabola symmetrical with respect to the optical axis is formed. Figure 10 As shown in the plan view on the right, it is circular. A light source unit composed of multiple such units is arranged to reduce space loss, such as Figure 11 As shown, the elliptical shape including the reflection area c should be arranged into a hexahedron that appears circular when viewed from above.

[0042] In addition, if Figure 10 As shown in the plan view on the right, the maximum diameter of reflective surface b is aligned with the inscribed circle of the aforementioned hexahedron, and the shape of region c controls the diffusion characteristics of the areas corresponding to the six vertex corners of the hexahedron. This arrangement of individual optical elements creates a light source unit 12 that achieves excellent brightness uniformity, thereby providing new design freedom.

[0043] At the same time, if cheap surface-emitting white LEDs can be obtained, the circumscribed circle diameter of a single light source module can be reduced, and the number of arranged single light source modules can be increased, it will be easier to improve the brightness uniformity of the light source unit.

[0044] In an embodiment of the present invention, Figure 12 The image display device is shown in cross-section. Below a light source unit 12, comprised of a plurality of individual light source modules 13, are surface-emitting white LEDs corresponding to each light source module 13. These LEDs are also connected in series with a metal substrate 16, which is used to optimize heat dissipation.

[0045] To minimize variations in brightness, LED drivers are best connected in series. However, if too many LEDs are connected, the total voltage increases, leading to issues with circuit insulation design. Therefore, it's best to limit the number of LEDs to a maximum of about 10, using a combination of series and parallel connections. When combining in-line and parallel connections, the challenge is variations in drive current between parallel circuits. This can be addressed by providing impedance matching in each branch circuit.

[0046] In this way, the difference in the amount of light emitted by the surface-emitting white LED can be reduced, thereby realizing a high-brightness and uniform brightness image display device.

[0047] Optical films that control diffusion properties Next, the structure and function of the optical film 19 (hereinafter referred to as the light diffusion control film) provided between the light source unit 12 and the LCD panel 20 with a color filter will be described. Figure 13 Shown is the cross-sectional shape of an optical film that controls the light diffusion angle.

[0048] The surface in contact with the light source unit 12 is provided with a reflective polarizing plate 19a that reflects specific polarized light. As mentioned above, the specific polarized light emitted by the light source unit 12 is reflected back to the phosphor of the LED light source 1 in the single light source module 12 and used as excitation light again, thereby increasing the amount of light emitted and improving the luminous efficiency of the input power.

[0049] like Figure 12 As shown, the composite surface of the LCD panel 20 with the light diffusion control film 19 forms a Figure 13 (A) shows the fine pattern 19b used to control light diffusion. In this embodiment, to control the horizontal diffusion angle of the screen, a structure (H-shaped lenticular lens) is used, in which lenticular lenses are arranged horizontally with the LCD display. This controls the diffusion characteristics in the horizontal direction (i.e., the left-right direction in the figure) of the screen, improving the brightness uniformity of the image displayed on the LCD panel.

[0050] As shown in the enlarged view of section A, the cylindrical lens structure has convex surfaces in the direction of light emission. By minimizing the shape variation at the junctions between adjacent convex surfaces, a gentle concave surface is formed, or there is no abrupt change in lens action between the gently concave surface and the flat surface. Furthermore, the light-diffusing film 19 is arranged at an angle θ relative to the shape of the LCD panel 20, as shown in section B, through the cylindrical lens. This not only prevents moiré patterns caused by pixel interference but also controls vertical light diffusion, significantly improving the brightness uniformity of the image light emitted from the LCD panel 20.

[0051] The second technical approach mentioned above to avoid moiré caused by interference with the LCD panel is to choose a lenticular lens pitch that is not an integer multiple of 80μm if the pixel pitch is 80μm. The smaller the pitch, the higher the brightness uniformity of the screen. However, due to manufacturing limitations, refinement has its limits. Choosing a pitch between 100μm and 200μm can achieve good diffusion characteristics without generating moiré.

[0052] The first method for reducing moiré is to tilt the cylindrical lens. The tilt angle θ is preferably between 5 and 15 degrees. According to experimental results, the best effect is achieved within the range of 10 ± 3 degrees. <Reflective polarizing film that reflects specific polarized light> We studied the angular dependence of transmittance of a reflective polarizing film that reflects specific polarized light, an optical film that controls the light diffusion angle and is attached to the side of an LCD. The product used in the study was 3M™ DBEF-QV2, and in addition to studying the wavelength characteristics of the incident light, we also studied how the characteristics change with the incident angle. Figure 14 The characteristics of reflective polarizing films at normal incidence and incident angles close to it are summarized.

[0053] The wavelength transmittance of the other polarized light (P polarized light) varies significantly relative to the transmittance of the specific polarized light (S polarized light). However, the absolute value of the change is small when the change is less than 5%. In this case, reflecting P polarized light is feasible. In addition, there is no significant difference in the characteristics at incident angles of 10 degrees and 20 degrees. A portion of the light from the light source unit 12 with a diffusion angle is also reflected without angle dependence. For the characteristics at an incident angle close to 45 degrees, such as Figure 15 As shown, it also has good characteristics.

[0054] In an embodiment of the present invention, a reflective polarizing film was attached to the light source side of a light diffuser film to test the reflection of S-polarized light (S-polarized light). The results showed that the S-polarized light was reflected back toward the light source, while the P-polarized light (P-polarized light) entered the lenticular lens of the light diffuser film. Because the P-polarized light beam, compared to the S-polarized light beam, has a Brewster angle (0% reflectivity) at an incident angle of approximately 33 degrees, the refractive index is lower in the areas around this angle (±15 degrees). Therefore, even without an anti-reflection coating on the lenticular lens surface, the desired light diffusion angle can be achieved without angular dependence.

[0055] <Image Light Diffusion Characteristics of Image Display Devices> In order to realize a compact and high-brightness image display device, it is necessary to control the directivity of light and obtain image output light having a narrow divergence angle. Figure 17 1a is an explanatory diagram for explaining the diffusion characteristics of image light emitted from the center of the display screen of the image display device, and is also an explanatory diagram for explaining the diffusion characteristics of the display element of the image display device when the liquid crystal panel 20 is used.

[0056] Figure 17 In (a), the liquid crystal panel 20 is an oblique view with the light emitting surface facing upward. To facilitate subsequent explanations, Figure 17 The coordinate axes in (a) are the long side of the screen as the Y axis, the short side as the X axis, and the perpendicular direction to the plane formed by the X and Y axes as the Z axis. In the description of the image light divergence angle in (b), the Z axis is described as the axis representing relative brightness.

[0057] This invention utilizes a liquid crystal display panel as an image display device, while also utilizing the diffusion characteristics of the light source device to narrow the angle of view, thereby controlling image light over a wide range. To this end, design parameters for a new optical component constituting the light source unit 12 were determined, adjusted by the shape of the reflective optical element and the surface shape of a light diffuser sheet as required. In the implementation of this invention, the characteristic design values are as follows: the horizontal diffusion characteristic (long-side direction) of the screen is: ±9 degrees at a relative brightness of 50%; ±16 degrees at a relative brightness of 0%. The vertical diffusion characteristic (short-side direction) of the screen is: ±7.5 degrees at a relative brightness of 50%; ±13 degrees at a relative brightness of 0%.

[0058] In this case, the brightness of the image displayed on the image display device can be approximately 10 times higher using the characteristic C of the present invention compared to the image brightness of a standard diffusion characteristic close to a completely diffuse surface. Characteristic A, with its narrow-angle diffusion characteristic, further enhances the brightness. However, it should be noted that the directional characteristics of the light source device must be adjusted according to the viewer's viewing angle of the image display device, which also introduces new challenges for the light source device.

[0059] Etendue invariants for specifying the brightness of optical components.

[0060] Finally, the description of the equal brightness (Etendue) of the plane aperture (Aperture) applicable to the rotational symmetry of the illumination system, such as Figure 18 As shown. When the refractive index is equal, it is:

[0061] This shows that there is a trade-off between angle and area.

[0062] In other words, reducing the angular distribution to form a collimated beam expands the space, while focusing the light increases the angular distribution but shrinks the space, which remains constant. Therefore, once the image display area S1 of the LCOS panel, which receives light, is determined, the capture angle is also determined.

[0063] Therefore, this invention realizes an optical component based on a new design concept, namely, a single light source unit is realized by overlapping the focal position of the reflective optical element 11 on the optical axis, and the optical component constituted by it is not subject to the invariance of isoluminance (Etendue).

[0064] While various embodiments have been described in detail above, the present invention is not limited to these embodiments and encompasses a variety of variations. For example, the entire system has been described and explained in detail in the above embodiments for easier understanding, but the present invention is not limited to products that necessarily include all of the components described.

[0065] In addition, some parts of the embodiments may be replaced by parts of other embodiments, or parts of one embodiment may be combined with parts of other embodiments. Furthermore, parts of the parts of each embodiment may be added, deleted, or replaced by other parts.

Claims

1. A light source device for an image display device, characterized in that: A single light source module is formed by a surface-emitting solid light source and an optical element for narrowing the divergence angle of a divergent light beam emitted by the surface-emitting solid light source, and a plurality of the single light source modules are arranged in two dimensions to form a light source unit and an image display device; The light beam from the light source unit is incident on an image display device, and the image display device adjusts the intensity of the light according to an image signal to display an image on a screen; The light source unit is constructed as follows: a divergent light beam from a surface-emitting solid light source is reflected on a reflective surface, converted into approximately parallel light, and placed near the focus of a reflective optical element; a cylindrical hole is designed at the focus of an end face of the reflective optical element, and the surface-emitting solid light source is placed in the hole; The reflective surface of the reflective optical element constituting the single light source module is in a parabolic shape, the surface-emitting solid element is designed on its end face, and the reflected light beam exit surface opposite thereto is in a hexahedron shape, and adjacent single light source modules are closely arranged and seamlessly connected; The light source device comprises a light source unit composed of a plurality of two-dimensionally arranged single light source modules, wherein the diameter of the inscribed circle of the hexahedron is substantially equal to the maximum diameter of the parabolic reflecting surface.

2. The light source device for an image display device according to claim 1, wherein A plurality of individual light source modules are arranged in a two-dimensional manner to form a light source unit. Holes are provided on the end faces of the individual light source modules, forming a substantially cylindrical shape along the optical axis direction including the focus of the reflective optical element. The side faces of these cylindrical shapes refract part of the divergent light from the surface-emitting solid light source. By being reflected at different positions on the reflective surface of the reflective optical element, a divergent light beam from a surface-emitting solid light source can be converted into a light beam with an approximately narrow divergence angle.

3. The light source device for an image display device according to claim 2, wherein: The end face of the single light source module is provided with a hole, which is approximately cylindrical along the optical axis direction including the focus of the reflective optical element, and the side faces of these cylinders refract part of the divergent light from the surface-emitting solid light source; By reflecting at different positions on the reflective surface of the reflective optical element, the divergent light beam from the surface-emitting solid light source can be converted into a divergent light beam with a narrow divergence angle, and the divergent light beam diverges from multiple focal points along the optical axis of the reflective optical element.

4. The light source device for an image display device according to claim 1, wherein A hole is provided on the end face of the single light source module, which is roughly cylindrical along the optical axis direction including the focus of the reflective optical element. The narrow-angle divergent light beam from the surface-emitting solid-state light source is incident on the front end face of the cylinder and is refracted by the lens shape provided on the front end face, thereby controlling the incident position and incident angle of the light beam incident on the reflective surface of the reflective optical element.

5. A light source device for an image display device, comprising a light source unit composed of a plurality of individual light source modules arranged in a two-dimensional manner, characterized in that: The single light source module is composed of a surface-emitting solid light source and an optical element that narrows the divergence angle of the divergent light beam emitted from the surface-emitting solid light source; The image display device displays an image on a screen by causing a light beam from a light source unit to be incident on the image display device and adjusting the intensity of the light according to an image signal by the image display device; The light source unit converts a divergent light beam from a surface-emitting solid light source into approximately parallel light by reflecting it on a reflective surface, and places the divergent light beam near the focus of a reflective optical element. A cylindrical hole is also provided at the focus of an end face portion of the reflective optical element, and the surface-emitting solid light source is placed in the hole. The reflective surface of the reflective optical element constituting the aforementioned single light source module is formed by a plurality of regions, and the first region close to the aforementioned surface-emitting solid light source is in a parabolic shape; The second reflective region is located near the end face provided with the surface-emitting solid element and the opposite reflected light beam emission surface, and has different divergence characteristics from the reflected light beam of the first reflective region. The end face provided with the surface-emitting solid element and the opposite reflected light beam emission surface have a hexahedral opening shape, and adjacent single light source modules are seamlessly connected and neatly arranged. The inner diameter of the circumscribed circle of the hexahedron of a single light source module is equal to the maximum diameter of the second reflective region.

6. The light source device for an image display device according to claim 5, wherein: The end face of the single light source module is provided with a hole, which is approximately cylindrical along the optical axis direction including the focus of the reflective optical element. The side faces of these cylinders refract a part of the divergent light from the surface-emitting solid light source. The divergent light beam of the surface-emitting solid light source is converted into a light beam with a divergent angle of approximately narrow angle by reflection through the reflective surfaces at different positions of the reflective optical element.

7. The light source device for an image display device according to claim 5, wherein: A hole is provided on the end face of the single light source module, which is approximately cylindrical along the optical axis direction containing the focus of the reflective optical element. The side surfaces of these cylinders refract a portion of the divergent light from the surface-emitting solid light source, and reflect it at different positions on the reflective surface of the reflective optical element. The divergent light beam from the surface-emitting solid light source can be converted into a divergent light beam with a narrow divergence angle that diverges from multiple focal points along the optical axis of the reflective optical element.

8. The light source device for an image display device according to claim 5, wherein A hole is designed on the end face of the single light source module, which is approximately cylindrical along the optical axis direction containing the focus of the reflective optical element. After the narrow-angle divergent light beam in the divergent light beam from the surface-emitting solid light source enters the front end face of the cylinder, it is refracted by the lens arranged on the front end face.

9. The light source device for an image display device according to claim 5, wherein: Among the light beams emitted by the single light source module, the reflected light beams from the second reflection area in the side reflection field of the reflective optical element diverge toward the image display device, and the divergent lights from multiple adjacent single light source modules overlap on the light incident surface of the image display device.

10. The light source device for an image display device according to any one of claims 1 to 5, wherein: The single light source module is formed of a heat-resistant plastic material.

11. The light source device for an image display device according to claim 10, wherein: The single light source module is made of heat-resistant plastic with a heat-resistant temperature of more than 120 degrees.

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