Optical systems
By employing a light control body with distinct focal positions and an inclined light guide plate, the optical system addresses light extraction inefficiencies from larger light sources, improving efficiency and mitigating thermal risks.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD
- Filing Date
- 2021-12-13
- Publication Date
- 2026-06-26
AI Technical Summary
Existing optical systems face challenges in efficiently extracting light from larger light sources due to alignment issues between focal positions, leading to reduced light extraction efficiency, especially when the light source size exceeds a certain threshold, and there is a risk of thermal damage to resin-based light guides.
The optical system employs a light control body with distinct focal positions for the first incident and reflecting surfaces, positioned differently from the light source, and a light guide plate with inclined first surfaces to enhance light control and extraction efficiency, using transparent resin materials like polypropylene or polycarbonate.
This configuration improves light extraction efficiency by effectively directing light from the light source edges onto the light guide plate, enhancing the overall light utilization and reducing thermal risks.
Smart Images
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Abstract
Description
Technical Field
[0005]
[0001] The present disclosure relates to an optical system.
Background Art
[0002] Patent Document 1 discloses an image display device that projects a virtual image into a target space. This image display device is a vehicle HUD (Head-Up Display) device. Projection light, which is image light emitted from the vehicle HUD device (optical system) within the dashboard, is reflected by the front glass and directed towards the driver, who is the viewer.
[0003] As a result, the user (driver) can visually recognize an image such as a navigation image as a virtual image, and visually recognize it as if the virtual image is superimposed on a background such as a road surface.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
[0005] One aspect of the present invention comprises a light source that emits light, a light guide plate having an incident surface into which light from the light source enters, and a first surface and a second surface facing each other, the second surface being a light emission surface, and a light control body that focuses light toward the incident surface and emits the focused light toward the incident surface, wherein the first surface is provided with a prism that reflects light passing through the inside of the light guide plate toward the second surface, and the light control body has a first incident surface that focuses a portion of the light emitted from the light source and emits it toward the incident surface, and reflects the light emitted from the light source that does not pass through the first incident surface. The optical system is characterized in that it has an incident surface and a first reflecting surface that emits light from the incident surface, the first focal position of the first incident surface is the position where parallel light converges to a single point when parallel light is incident from the incident surface of the light guide plate to the first incident surface of the light control body, and the second focal position of the first reflecting surface is the position where parallel light converges to a single point when parallel light is incident from the incident surface of the light guide plate to the first reflecting surface of the light control body, and the first focal position and the second focal position are set to be different positions from each other and at positions far from the light-emitting surface of the light source. [Brief explanation of the drawing]
[0006] [Figure 1] This is a cross-sectional view showing an overview of the optical system according to this embodiment. [Figure 2] This is a cross-sectional view showing the positional relationship between the first focal position of the first incident surface and the second focal position of the first reflecting surface. [Figure 3] This is a cross-sectional view showing the positional relationship between the first focal point of the first incident plane and the light source. [Figure 4] This is a cross-sectional view showing the positional relationship between the second focal point of the first reflecting surface and the light source. [Figure 5] This is a cross-sectional view showing the maximum thickness of the light guide plate, the size of the light source, and the distance from the light source to the first incident surface. [Figure 6] This diagram shows the state in which light emitted from the edge of the light source's light-emitting surface is controlled by a light control unit, causing the entire second surface of the light guide plate to emit light from the surface. [Figure 7] This diagram shows a situation where the light emitted from the edge of the light-emitting surface of the light source is not being controlled by the light control unit. [Figure 8]This diagram illustrates the specific dimensions of the light control unit and light guide plate. [Figure 9] This graph shows the relationship between the amount of shift in the first focal point position from the light-emitting surface of the light source and the light extraction efficiency. [Figure 10] This graph shows the relationship between the amount of shift in the second focal point position from the light-emitting surface of the light source and the light extraction efficiency. [Modes for carrying out the invention]
[0007] In the optical system described in Patent Document 1, the focal position of the refractive surface and the focal position of the total reflection surface in the light control body coincide. Therefore, if the size of the light source becomes larger than a certain amount compared to the light guide plate, it may not be possible to effectively control the light emitted from the edge of the light-emitting surface of the light source, and the efficiency of light extraction by the prism may decrease.
[0008] One possible solution is to bring the light source closer to the light guide plate, but if the light guide plate is made of resin, there is a risk that the heat from the light source will melt the light guide plate, making it impossible to bring it closer than a certain distance.
[0009] This invention has been made in view of the above, and its purpose is to provide an optical system that can improve the efficiency of light extraction.
[0010] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments. Furthermore, modifications can be made as appropriate without departing from the scope of achieving the effects of the present invention.
[0011] As shown in Figure 1, the optical system 100 comprises a light source 1, a light guide plate 2, and a light control unit 6.
[0012] Light source 1 is composed of a solid-state light-emitting element such as a light-emitting diode (LED) or an organic electro-luminescence (OEL) element. Although not shown in the illustration, multiple light sources 1 are provided at intervals in the depth direction of the paper in Figure 1.
[0013] The light guide plate 2 is positioned opposite the light-emitting surface of the light source 1. The light guide plate 2 is made of a transparent resin material formed in a flat plate shape. For example, the light guide plate 2 can be made of polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride, ABS resin, acrylic, polyamide, polycarbonate, Teflon (registered trademark), etc.
[0014] The light guide plate 2 has an incident surface 3 into which light is incident, and a first surface 4 and a second surface 5 that are opposite to each other. The incident surface 3 is formed on one of the four sides of the light guide plate 2. The first surface 4 and the second surface 5 are provided on two opposing surfaces of the light guide plate 2 in the thickness direction.
[0015] Multiple prisms 10 are provided on the first surface 4. The prisms 10 reflect the light passing through the inside of the light guide plate 2 toward the second surface 5. The prisms 10 are configured to perform total internal reflection of incident light. However, the prisms 10 are not limited to a configuration in which all incident light is totally internally reflected; a configuration in which some light passes through the inside of the prisms 10 without total internal reflection is also possible.
[0016] The first surface 4 is not perpendicular to the incident surface 3, but is inclined at a predetermined angle. Specifically, the first surface 4 is inclined so that it approaches the second surface 5 as it moves away from the incident surface 3.
[0017] The second surface 5 is the light emission surface. The second surface 5 is perpendicular to the incident surface 3. The light guide plate 2 is configured such that light enters from the incident surface 3 on the side, and the second surface 5, which is the emission surface, emits light from the surface.
[0018] The light control body 6 is disposed on the side of the light source 1 with respect to the incident surface 3 of the light guide plate 2. The light control body 6 is formed integrally with the light guide plate 2. Although illustration is omitted, a plurality of light control bodies 6 are provided at intervals in the depth direction of the paper surface in FIG. 1. The plurality of light control bodies 6 are provided at positions respectively facing the plurality of light sources 1.
[0019] The light control body 6 is, for example, a collimator lens, which condenses the light traveling toward the incident surface 3 and emits the condensed light to the incident surface 3. The light control body 6 has a first incident surface 7, a second incident surface 8, and a first reflection surface 9.
[0020] The first incident surface 7 refracts a part of the light emitted from the light source 1 and emits the refracted light to the incident surface 3. The light that is emitted from the light source 1 and does not pass through the first incident surface 7 is incident on the second incident surface 8. The first reflection surface 9 totally reflects the light that has passed through the second incident surface 8 and guides the totally reflected light to the incident surface 3.
[0021] The light control body 6 controls the divergence angle of the light emitted from the light source 1 by refracting part or all of the light emitted from the light source 1, and emits the light toward the incident surface 3. The light control body 6 controls the divergence angle of the light incident on the light control body 6 so that the optical path of the light emitted to the incident surface 3 approaches an optical path parallel to the second surface 5. In the light guide plate 2, most of the light incident from the incident surface 3 is reflected by the prism 10 and emitted from the second surface 5.
[0022] As described above, in the present embodiment, the light whose divergence angle is controlled through the light control body 6 is directly reflected by the prism 10 provided on the first surface 4 of the light guide plate 2 and emitted from the second surface 5.
[0023] Therefore, in the present embodiment, it is possible to improve the light extraction efficiency as compared with a mode in which light is emitted from the second surface 5 while repeating total reflection at the first surface 4 and the second surface 5 of the light guide plate 2. The "extraction efficiency" in the present embodiment refers to the ratio of the amount of light emitted from the second surface 5 (emission surface) of the light guide plate 2 to the amount of light incident on the incident surface 3 of the light guide plate 2.
[0024] However, if the size of the light source 1 becomes larger than a certain amount compared to the light guide plate 2, it may become difficult to effectively control the light emitted from the edges of the light-emitting surface of the light source 1, potentially reducing the light extraction efficiency of the prism 10.
[0025] Therefore, in this embodiment, the light extraction efficiency is improved by appropriately setting the focal positions of the first incident surface 7 and the first reflecting surface 9 in the light control unit 6, as well as the dimensions of each part.
[0026] Specifically, as shown in Figure 2, the first focal position 11 of the first incident surface 7 and the second focal position 12 of the first reflective surface 9 are set to be at different positions and at positions far from the light-emitting surface of the light source 1.
[0027] The first focal position 11 of the first incident surface 7 is the position where parallel light converges to a single point when parallel light is incident on the first incident surface 7 of the light control unit 6 from the incident surface 3 of the light guide plate 2. The second focal position 12 of the first reflecting surface 9 is the position where parallel light converges to a single point when parallel light is incident on the first reflecting surface 9 of the light control unit 6 from the incident surface 3 of the light guide plate 2.
[0028] In this way, by setting the first focal position 11 and the second focal position 12 to different positions, the light emitted from the edge of the light-emitting surface of the light source 1 can be efficiently emitted onto the first surface 4 of the light guide plate 2. This improves the light utilization efficiency of the light guide plate 2.
[0029] Figure 3 is a cross-sectional view showing the positional relationship between the first focal position of the first incident surface and the light source. As shown in Figure 3, let F be the distance from the part of the light control unit 6 closest to the light source 1 to the first focal position 11 of the first incident surface 7. Also, let D be the distance from the part of the light control unit 6 closest to the light source 1 to the light-emitting surface of the light source 1.
[0030] Here, in order to effectively utilize the light emitted from the edge of the light-emitting surface of light source 1, it is necessary to make distance F greater than distance D to reduce the influence of the size of light source 1. Therefore, distances F and D are set to satisfy the following equation (1).
[0031] D ≤ F ···(1) Figure 4 is a cross-sectional view showing the positional relationship between the second focal position of the first reflective surface and the light source. As shown in Figure 4, F' is the distance from the part of the light control unit 6 closest to the light source 1 to the second focal position 12 of the first reflective surface 9.
[0032] Here, in order to effectively utilize the light emitted from the edge of the light-emitting surface of light source 1, it is necessary to make distance F' larger than distance D to reduce the influence of the size of light source 1. Therefore, distances F' and D are set to satisfy the following equation (2).
[0033] D≦F' ···(2) Furthermore, the first incident surface 7 is closer to the light source 1 than the first reflecting surface 9, and is therefore more susceptible to the influence of the size of the light source 1. For this reason, it is preferable that distance F and distance F' satisfy the following equation (3).
[0034] F'≦F ···(3) Figure 5 is a cross-sectional view showing the maximum thickness of the light guide plate, the size of the light source, and the distance from the light source to the first incident surface. As shown in Figure 5, the maximum thickness of the light guide plate 2 is T, and the size of the light source 1 is A.
[0035] Increasing the thickness of the light guide plate 2 reduces the influence of the size of the light source 1 and allows for more effective use of light, but the overall size of the optical system 100 becomes very large. Therefore, the maximum thickness T of the light guide plate 2 is set to satisfy the following equation (4), preferably the following equation (5), and more preferably the following equation (6).
[0036] T / 20 ≤ A ···(4) T / 10 ≤ A ···(5) T / 5 ≤ A ···(6) As shown in Figure 3, distance H is the difference between distance F and distance D. The first incident surface 7 effectively irradiates the first surface 4 with light by controlling the light emitted from the light source 1. Therefore, if distance H becomes too large, the light cannot be effectively controlled. Accordingly, distance H is set to satisfy the following equation (7), preferably the following equation (8), and even more preferably the following equation (9).
[0037] H ≤ 10A ···(7) H ≤ 5A ···(8) H ≤ A ···(9) As shown in Figure 4, the difference between distance F' and distance D is defined as distance H'. The first reflective surface 9 effectively illuminates the first surface 4 by controlling the light emitted from the light source 1. Therefore, if distance H' becomes too large, the light cannot be effectively controlled. Accordingly, distance H' is set to satisfy the following equation (10), preferably the following equation (11), and even more preferably the following equation (12).
[0038] H'≦10A ···(10) H'≦5A ···(11) H'≦A ···(12) As shown in Figure 5, let G be the distance from the part of the first incident surface 7 closest to the light source 1 to the light source 1. Here, in order to effectively control the light emitted from the edge of the light-emitting surface of the light source 1, it is conceivable to bring the light source 1 closer to the light control unit 6.
[0039] However, if the light source 1 is brought too close to the light guide plate 2, the heat from the light source 1 may melt the light guide plate 2. Therefore, it is preferable that the distance D, the size A of the light source 1, and the distance G satisfy the following equations (13) and (14).
[0040] D≧0 ···(13) A ≤ G ···(14) The light emission principle of the optical system 100 of this embodiment will now be explained. First, as shown in Figure 6, the light emitted from the light source 1 has its divergence angle controlled by passing through the light control unit 6.
[0041] Light with a controlled divergence angle is emitted from the light control unit 6 toward the incident surface 3 of the light guide plate 2. Here, the first surface 4 is inclined to approach the second surface 5 as it moves away from the incident surface 3. As a result, most of the light incident on the incident surface 3 reaches the first surface 4 without reaching the second surface 5 or the side of the light guide plate 2 facing the incident surface 3.
[0042] Then, most of the light incident on the incident surface 3 is totally internalized by one of the multiple prisms 10 provided on the first surface 4, without being reflected by the first surface 4 and the second surface 5.
[0043] The light totally reflected by prism 10 follows an optical path approximately perpendicular to the second surface 5 and is emitted from the second surface 5. As a result, the entire second surface 5 emits light from its surface.
[0044] On the other hand, as shown in the comparative example in Figure 7, in the optical system 200 in which the first focal position 11 of the first incident surface 7 and the second focal position 12 of the first reflecting surface 9 are aligned, there is a problem in that the light emitted from the edge of the light-emitting surface of the light source 1 cannot be effectively controlled.
[0045] Specifically, as shown in Figure 7, some of the light incident on the incident surface 3 does not go toward the first surface 4 and the side surface of the light guide plate 2, but instead goes toward the second surface 5. The light that goes toward the second surface 5 can undergo total internal reflection at the second surface 5. Then, the light that undergoes total internal reflection at the second surface 5 goes toward the first surface 4, and there is a high possibility that the light will leak out from the first surface 4 without being reflected by the prism 10.
[0046] The following explains how the light extraction efficiency changes when the first focal position 11 and the second focal position 12 are shifted relative to the light-emitting surface of light source 1.
[0047] Figure 8 illustrates the specific dimensions of the light control unit and the light guide plate. As shown in Figure 8, the maximum thickness T of the light guide plate 2 is 8 mm, the distance L1 between the part of the light control unit 6 closest to the light source 1 and the first incident surface 7 is 1 mm, the aperture width L2 of the part of the light control unit 6 closest to the light source 1 is 4.3 mm, the distance D is 1 mm, and the size A of the light source 1 is 1 mm.
[0048] In the graph shown in Figure 9, the amount of displacement when the first focal position 11 is located on the light-emitting surface of the light source 1 is set to 0 mm, and the first focal position 11 is shifted in the direction away from the light guide plate 2.
[0049] As shown in Figure 9, when the shift amount of the first focal position 11 is 0 mm, the light extraction efficiency is 49.9%. It can be seen that the efficiency improves as the shift amount of the first focal position 11 increases. In this embodiment, considering the balance with other indicators, the shift amount of the first focal position 11 was set to 0.4 mm. In this case, the efficiency becomes 50.5%.
[0050] In the graph shown in Figure 10, the amount of displacement when the second focal position 12 is located on the light-emitting surface of the light source 1 is set to 0 mm, and the second focal position 12 is shifted in the direction away from the light guide plate 2.
[0051] As shown in Figure 10, when the displacement of the second focal position 12 is 0 mm, the light extraction efficiency is 50.5%. As the displacement of the second focal position 12 is increased, the efficiency improves up to a displacement of 0.3 mm, but then decreases. In this embodiment, the displacement of the second focal position 12 is set to 0.2 mm. In this case, the efficiency is 52.3%.
[0052] In this way, by setting the shift amount of the first focal position 11 to 0.4 mm and the shift amount of the second focal position 12 to 0.2 mm, the light extraction efficiency can be improved from the lowest 49.9% to 52.3%.
[0053] As described above, according to one aspect of the present invention, the efficiency of light extraction can be improved. Specifically, by setting the first focal position of the first incident surface and the second focal position of the first reflecting surface to be at different positions and at positions far from the light-emitting surface of the light source, the light emitted from the edge of the light-emitting surface of the light source can be effectively controlled, thereby improving the efficiency of light extraction by the prism. [Industrial applicability]
[0054] As described above, the present invention is extremely useful and has high industrial applicability because it provides the highly practical effect of improving the efficiency of light extraction. [Explanation of Symbols]
[0055] 1 light source 2 Light guide plate 3 Incidence plane 4 Front page 5 Side 2 6. Light control unit 7 First entrance plane 9 1st reflective surface 10 Prisms 11 1st focus position 12 2nd focal position 100 Optical Systems
Claims
1. A light source that emits light, A light guide plate having an incident surface into which light from the aforementioned light source enters, and a first surface and a second surface facing each other, wherein the second surface is the light emission surface, The system includes a light control unit that focuses light directed toward the incident surface and emits the focused light toward the incident surface, The first surface is provided with a prism that reflects light passing through the inside of the light guide plate toward the second surface. The light control body has a first incident surface that collects a portion of the light emitted from the light source and emits it to the incident surface, and a first reflective surface that reflects the light emitted from the light source that does not pass through the first incident surface and emits it to the incident surface. The first focal position of the first incident surface is the position where parallel light converges to a single point when parallel light is incident from the incident surface of the light guide plate to the first incident surface of the light control body. The second focal position of the first reflective surface is the position where parallel light converges to a single point when parallel light is incident on the first reflective surface of the light control body from the incident surface of the light guide plate. The first focal position and the second focal position are set at different positions from each other and at positions far from the light-emitting surface of the light source. The distance F from the part of the light control body closest to the light source to the first focal position of the first incident surface, the distance D from the part of the light control body closest to the light source to the light-emitting surface of the light source, the distance H which is the difference between distance F and distance D, and the size A of the light source are: H ≤ 5A The conditions are met An optical system characterized by the following features.
2. A light source that emits light, A light guide plate having an incident surface into which light from the aforementioned light source enters, and a first surface and a second surface facing each other, wherein the second surface is the light emission surface, The system includes a light control unit that focuses light directed toward the incident surface and emits the focused light toward the incident surface, The first surface is provided with a prism that reflects light passing through the inside of the light guide plate toward the second surface. The light control body has a first incident surface that collects a portion of the light emitted from the light source and emits it to the incident surface, and a first reflective surface that reflects the light emitted from the light source that does not pass through the first incident surface and emits it to the incident surface. The first focal position of the first incident surface is the position where parallel light converges to a single point when parallel light is incident from the incident surface of the light guide plate to the first incident surface of the light control body. The second focal position of the first reflective surface is the position where parallel light converges to a single point when parallel light is incident on the first reflective surface of the light control body from the incident surface of the light guide plate. The first focal position and the second focal position are set at different positions from each other and at positions far from the light-emitting surface of the light source. The distance F' from the part of the light control body closest to the light source to the second focal position of the first reflecting surface, the distance D from the part of the light control body closest to the light source to the light-emitting surface of the light source, the distance H' which is the difference between distance F' and distance D, and the size A of the light source are: H' ≤ 5A The conditions are met An optical system characterized by the following features.
3. In claim 1 or 2, The distance F from the portion of the light control body closest to the light source to the first focal position of the first incident surface, and the distance D from the portion of the light control body closest to the light source to the light-emitting surface of the light source, D ≤ F The conditions are met An optical system characterized by the following features.
4. In any one of claims 1 to 3, The distance F' from the portion of the light control body closest to the light source to the second focal position of the first reflecting surface, and the distance D from the portion of the light control body closest to the light source to the light-emitting surface of the light source, D ≤ F' The conditions are met An optical system characterized by the following features.
5. In any one of claims 1 to 4, The focal length F from the portion of the light control body closest to the light source to the first focal position of the first incident surface, and the distance F' from the portion of the light control body closest to the light source to the second focal position of the first reflecting surface, F'≦F The conditions are met An optical system characterized by the following features.
6. In any one of claims 1 to 5, The maximum thickness T of the light guide plate and the size A of the light source are, T / 20 ≤ A The conditions are met An optical system characterized by the following features.