Optical system device

Abstract

The purpose of the present invention is to provide an optical system device that is further miniaturized compared to existing optical system devices and that can suppress buildup of heat generated in light irradiation means and a control unit.　An optical system device 100 includes: light irradiation means 1 that is capable of emitting light; a driver 2 that is electrically connected to the light irradiation means 1 and controls light emission of the light irradiation means, the driver 2 being disposed on the rear surface side of the light irradiation means 1 in the direction of the optical axis, at least the range of the irradiation angle of the light irradiation means 1 being transparent to light; and a heat dissipation unit 3 that is in thermally conductive contact with the light irradiation means 1 and the driver 2. The heat dissipation unit 3 seals the light irradiation means 1 and the driver 2 so as to prevent the surfaces of the light irradiation means 1 and the driver 2 from coming into contact with gas.

Description

optical system equipment

[0001] This invention relates to an optical system.

[0002] Three-dimensional measurement sensors using the time-of-flight (TOF) method are being adopted in portable devices, cars, robots, and other applications. The time-of-flight (TOF) method measures the distance to an object by measuring the time it takes for light emitted from a light source to reflect back onto the object. For example, if light from a light source is uniformly emitted over a predetermined area of ​​the object, the distance at each illuminated point can be measured, making it possible to detect the three-dimensional structure of the object.

[0003] The above sensor system consists of a light-emitting unit that illuminates the object, a light-receiving unit such as a camera that detects the light reflected from each point of the object, and a calculation unit that calculates the distance to the object from the signals received by the light-receiving unit.

[0004] Since the light-receiving unit and the processing unit can use existing CMOS imagers and CPUs, the unique part of the above system is the light-emitting unit. As the light-emitting unit, for example, an optical system device mainly composed of an optical element such as a lens and a light irradiation means such as a VCSEL for irradiating the optical element with light has been considered (for example, Patent Document 1).

[0005] There has been a demand for miniaturization of these devices, and progress has been made in miniaturizing and integrating light irradiation means and optical elements used in the light-emitting section.

[0006] Japanese Patent Application No. 2022-182910

[0007] On the other hand, the light irradiation means includes drivers, such as VCSEL drivers for controlling VCSELs, which are electrically connected to the light irradiation means and control the intensity and irradiation time of the light. Conventionally, the light irradiation means and drivers were arranged on a plane and electrically connected. However, integrating the light irradiation means and drivers in parallel in this way increases the mounting area. Therefore, stacking the light irradiation means and drivers vertically is considered. However, simply stacking them would cause heat generated by the light irradiation means and drivers to accumulate due to the low thermal conductivity of gases, leading to malfunctions.

[0008] Therefore, the present invention aims to provide an optical system that is even smaller than existing optical systems and can suppress the accumulation of heat generated by the light irradiation means and driver.

[0009] To achieve the above objective, the optical system of the present invention is characterized by comprising: a light irradiation means capable of irradiating light; a driver electrically connected to the light irradiation means and controlling the irradiation of the light irradiation means; and a heat dissipation part in which at least the irradiation angle range of the light irradiation means is transparent to the light and which is in heat conduction-conductive contact with the light irradiation means and the driver.

[0010] In this case, it is preferable that the heat dissipation section is sealed so that the surface of the light irradiation means does not come into contact with the gas.

[0011] Furthermore, it is preferable that the heat dissipation section is sealed so that the surface of the driver does not come into contact with gas.

[0012] Furthermore, the heat dissipation portion is preferably made of a resin with a thermal conductivity of 0.2 W / m·K or higher, and more preferably of a resin with a thermal conductivity of 1.0 W / m·K or higher.

[0013] The light irradiation means may also include an optical element having an uneven shape that exhibits optical functionality with respect to the light irradiated by it. In this case, the optical element may be laminated on the surface of the heat dissipation section.

[0014] Furthermore, the optical element consists of lenses that transmit light of wavelength λ arranged periodically, where m and n are natural numbers of 1 or more, and the focal length is determined by the cross-sectional shape of the lens perpendicular to the y-direction. １ The focal length is determined by the cross-sectional shape perpendicular to the x-direction, f ２ The size of the x-direction pitch of the lens is P １ The size of the pitch in the y direction is P ２ Therefore, the distance L between the irradiating portion and the first focal plane of the lens. １ , distance L from the second focal plane ２ However, see equations 1 and 2 below. It may also satisfy the following conditions.

[0015] The optical system of the present invention can reduce the footprint (area occupied) by stacking the light irradiation means and drivers. Furthermore, since the VCSEL and drivers are covered with a solid that has a higher thermal conductivity than gas, the generated heat can be dissipated.

[0016] This is a schematic cross-sectional view showing the optical system of the present invention. This is a schematic cross-sectional view showing another optical system of the present invention. This is a schematic cross-sectional view showing another optical system of the present invention. This is a schematic cross-sectional view showing another optical system of the present invention. This is a schematic plan view showing the optical system of the present invention.

[0017] The optical system 100 of the present invention will be described below. As shown in Figure 1, the optical system 100 of the present invention mainly consists of a light irradiation means 1 capable of irradiating light, a driver 2 that controls the irradiation of the light irradiation means 1, and a heat dissipation unit 3 that dissipates heat from the light irradiation means 1 and the driver 2.

[0018] Light irradiation means 1 is for irradiating light. Any light source capable of irradiating the light required for the purpose may be used. Examples of light irradiation means 1 include LEDs and VCSELs (Vertical Cavity Surface Emitting Lasers) that can be expected to produce high output with low power consumption. VCSELs include single-emitter VCSELs that have one light source capable of irradiating light in a direction perpendicular to the light-emitting surface, and multi-emitter VCSELs that have multiple light sources. Light irradiation means 1 may also consist of multiple LEDs or VCSELs.

[0019] The wavelength of the light emitted by the light source of the light irradiation means 1 can be appropriately determined depending on the purpose. For example, when used to measure blood flow, the light emitted by the light irradiation means 1 should be green light (electromagnetic waves with a wavelength of 500 to 565 nm), which is easily absorbed by red blood. When used to measure blood glucose levels, the light emitted by the light irradiation means 1 should be mid-infrared light (electromagnetic waves with a wavelength of 2.5 to 4 μm), which can measure the concentration of glucose in the blood.

[0020] Driver 2 is electrically connected to the light irradiation means 1 and controls the irradiation of the light irradiation means 1. Driver 2 controls, for example, the ON / OFF state of the irradiation of the light irradiation means 1 and the change in light intensity. Driver 2 is connected to wiring 21 for receiving power from the power supply, wiring 22, 24 for sending current to electrodes such as the anode and cathode of the light irradiation means, and wiring 23 for receiving electrical signals that control the current and voltage supplied to the light irradiation means 1. It receives digital signals such as LVDC (Low Voltage Differential Signaling) and adjusts the current and voltage sent from the power supply to the light irradiation means 1 based on these signals to control the irradiation of the light irradiation means 1. Any driver 2 that can control the irradiation of the light irradiation means 1 is acceptable, but existing semiconductor elements can be used. A specific example of driver 2 is a VCSEL driver that electrically controls the light emission of a VCSEL. Driver 2 is located on the back side of the light irradiation means 1 in the direction of the optical axis. In other words, in a plan view from the optical axis direction of the light irradiation means 1, the light irradiation means 1 and the driver 2 are arranged to overlap in at least part.

[0021] The heat dissipation section 3 is in thermally conductive contact with the light irradiation means 1 and the driver 2. This allows heat generated by the light irradiation means 1 and the driver 2 to be dissipated by thermal conduction, thereby suppressing the accumulation of heat. It is also preferable that the heat dissipation section 3 is in thermally conductive contact with the housing 9 that covers the light irradiation means 1 and the driver 2, and with the optical element 4 described later. This allows heat generated by the light irradiation means 1 and the driver 2 to be dissipated to the outside through the housing 9 and the optical element 4 by thermal conduction. The material of the heat dissipation section 3 is one that has a thermal conductivity at least higher than air, specifically, a thermal conductivity of 0.2 W / m·K or higher is preferable, preferably 0.5 W / m·K or higher, and even more preferably 1.0 W / m·K or higher. Examples of such materials include polydimethylsiloxane (PDMS), polyimide resin, acrylic resin, epoxy resin, and photoresist resin. The heat dissipation section 3 must be transparent to light at least within the irradiation angle range of the light irradiation means 1. Therefore, the material for the heat dissipation section 3 is preferably one that has a transmittance of at least 90% or more to the light irradiated by the light irradiation means 1.

[0022] Furthermore, the form of the heat dissipation section 3 can be any form as long as it can dissipate the heat from the light irradiation means 1 and the driver 2, but it is preferable that the contact area with the light irradiation means 1 and the driver 2 is large in that it can dissipate heat efficiently.Therefore, as shown in Figure 1, it is preferable that the heat dissipation section 3 is sealed so that the surface of the light irradiation means 1 does not come into contact with any gas.It is also preferable that the heat dissipation section 3 is sealed so that the surface of the driver 2 does not come into contact with any gas.In addition, the space between the light irradiation means 1 and the driver 2 is a part where heat generated from them tends to accumulate.Therefore, it is preferable that the heat dissipation section 3 is also formed between the light irradiation means 1 and the driver 2.Preferably, the heat dissipation section 3 should be filled to maintain a gap between the light irradiation means 1 and the driver 2, leaving a sufficient distance.For example, as shown in Figure 1, the light irradiation means 1 and the driver 2 can be stacked without gaps with the heat dissipation section 3.Also, the heat dissipation section 3 may have irregularities formed at the boundary with the light irradiation means 1 and the driver 2, the housing 9, and the optical element 4 to increase the contact area. Furthermore, the heat dissipation section 3 can be formed from different materials for each part. The heat dissipation section 3 can be manufactured in any way, for example, by conventionally known methods such as imprinting or injection molding.

[0023] Furthermore, the optical system 100 of the present invention may include an optical element 4 having an uneven shape 45 that exhibits an optical function with respect to the light emitted by the light irradiation means 1, as shown in Figures 2 and 3. The optical function refers to changing the light emitted by the light irradiation means 1 into a predetermined light distribution. Specific examples of the optical element 4 include, for example, one that transforms the light emitted by the light irradiation means 1 into a dot pattern, a line pattern, or uniform diffused light. The optical element 4 may have an air layer 7 between it and the surface 31 of the heat dissipation section 3, as shown in Figure 2, or it may be laminated on the surface 31 of the heat dissipation section 3, as shown in Figure 3. Here, the surface 31 means the surface from which the light emitted from the light irradiation means 1 is emitted from the heat dissipation section 3. When laminated on the surface 31 of the heat dissipation section 3, the heat generated by the light irradiation means 1 and the driver 2 can be efficiently dissipated to the outside through the optical element 4 by thermal conduction.

[0024] Furthermore, the uneven shape 45 of the optical element 4 can be formed at the boundary with the air layer 7, as shown in Figure 2, or at the boundary of the resin layer, as shown in Figure 3. When the uneven shape 45 is formed at the boundary of the resin layer, the optical element 4 is mainly composed of a first resin layer 41 which is the side into which light from the light irradiation means 1 is incident and has a first refractive index, and a second resin layer 42 which is the side from which light is emitted and has a second refractive index higher than the first refractive index. In this case, as shown in Figure 3, the optical element 4 has the uneven shape 45 at the interface between the first resin layer 41 and the second resin layer 42. On the other hand, the heat dissipation part 3 may also serve as the first resin layer 41. In this case, as shown in Figure 4, the optical element 4 has the uneven shape 45 at the interface (surface 31) between the heat dissipation part 3 and the second resin layer 42. When the heat dissipation section 3 also serves as the first resin layer 41, the refractive index (first refractive index) of the heat dissipation section 3 must be lower than that of the second refractive index of the second resin layer.

[0025] The refractive index difference between the first and second refractive indices can be any value as long as it allows the uneven surface to function optically. Furthermore, in some cases, it is desirable to narrow the angle of light emitted from the lens of the optical element 4. To narrow the emission angle of the lens, one could consider reducing the lens sag. However, there are limits to the processing accuracy, making it difficult to reduce the lens sag beyond a certain point. In such cases, the refractive index difference between the first and second refractive indices may be reduced. This allows, for example, when the uneven surface is a lens shape, to reduce the irradiation angle while maintaining a large lens sag. The refractive index difference should be, for example, 0.4, preferably 0.2 or less. This makes it possible, for example, when the uneven surface is a lens shape, to reduce the irradiation angle to 30 degrees or less while maintaining a lens sag of 10 μm or more.

[0026] As the material of the optical element 4, any material may be used as long as it can transmit light of at least a predetermined wavelength λ. For example, silicone-based resins, epoxy-based resins, acrylic-based resins, etc. can be used. Examples of silicone-based resins include polydimethylsiloxane (PDMS), etc. Also, it is possible to use glass as the material of the optical element 4. Also, the optical element 4 may be fabricated in any manner. For example, conventionally known methods such as imprint method or injection molding may be used.

[0027] As a specific example of the optical element 4, for example, there is one in which lenses that transmit light of wavelength λ are periodically arranged. In this case, let m and n be natural numbers of 1 or more, and let the focal length due to the cross-sectional shape perpendicular to the y direction of the lens be f １ , and the focal length due to the cross-sectional shape perpendicular to the x direction be f ２ , let the size of the pitch in the x direction of the lens be P １ , and the size of the pitch in the y direction be P ２ . Then, if the distance L １ between the irradiation means and the first focal plane of the lens, and the distance L ２ between the second focal plane satisfy the following formulas 1 and 2 , the light of wavelength λ irradiated by the light irradiation means 1 can be made into a dot pattern.

[0028] Note that the first focal plane means a plane that is perpendicular to the optical axis (z direction) of the lens and is at the focal position due to the cross-sectional shape perpendicular to the y direction of the lens. Also, the second focal plane means a plane that is perpendicular to the optical axis (z direction) of the lens and is at the focal position due to the cross-sectional shape perpendicular to the x direction of the lens. Also, the distances L １ , L ２ mean the distance (optical path length) that light travels in vacuum within the same time when it travels in a medium. If the refractive index of the medium is N and the actual distance is L, it is represented by their product NL.

[0029] Furthermore, the optical system 100 of the present invention may include a housing 9 that covers all or part of the light irradiation means 1, driver 2, heat dissipation unit 3, optical element 4, etc., as shown in Figures 1 to 5. As the material of the housing 9, for example, resin materials such as epoxy resin or silicone resin, or glass materials can be used. If wiring is passed through the housing 9, it is preferable that the material of the housing 9 is not a metal material, but metal can also be used if an insulating layer is interposed at the boundary between the wiring and the housing 9. By using metal, improved heat dissipation can be expected. The material of these housings 9 is preferably a light-shielding material such as a colored material (for example, black or white) that blocks the light irradiated from the light irradiation means 1, but transparent materials can also be used for the housing 9 by providing a colored layer or a metal layer on the outermost layer of the housing 9.

[0030] Furthermore, the external shapes of the light irradiation means 1, driver 2, heat dissipation unit 3, optical element 4, housing 9, and the optical system device 100 equipped therewith may be formed in any way. For example, the external shape of the optical system device 100 of the present invention can be (a) a rectangle, (b) a circle, (c) a regular hexagon, etc., as shown in Figure 5, when viewed in a plan view from the optical axis direction of the light irradiation means 1. By making the external shape of the optical system device 100 a rectangle, the handling of the optical system device 100 can be improved, and the degree of freedom in placement when mounting the optical system device 100 on other devices can be increased. Also, by making the external shape of the optical system device 100 circular, the shape of the window portion for light input and output in the device on which the optical system device 100 is mounted can be made circular, which is advantageous in terms of design, processability, and maintainability. Also, by making the external shape of the optical system device 100 a hexagon, the placement density can be increased when mounting many optical system devices 100 on other devices.

[0031] Furthermore, when the light irradiation means 1 is used as a light source for 3D sensing, for example, high current (>1A) and ultra-high-speed operation (>100MHz) are essential. Under these conditions, the parasitic inductance, which is roughly proportional to the distance between the light irradiation means 1 (e.g., VCSEL) and the driver 2 (e.g., VCSEL driver), becomes large. Large parasitic inductance can cause signal delays, noise, and voltage spikes. It also increases the heat and energy loss generated. Therefore, in order to minimize the parasitic inductance generated between the light irradiation means 1 and the driver 2, it is desirable to minimize the distance between the light irradiation means 1 and the driver 2. Accordingly, the wiring 22,24 for connecting the light irradiation means 1 and the driver 2 should be made as short as possible, and preferably formed as a straight line which is the shortest distance between the light irradiation means 1 and the driver 2. In particular, it is preferable that the back surface of the light irradiation means 1 (the surface facing the driver 2) and the front surface of the driver 2 (the surface facing the light irradiation means 1) are connected by wiring that includes a straight line which is the shortest distance between the two surfaces. This type of wiring ensures that the wiring distance can be minimized stably, even if the wiring itself is tilted during manufacturing, or if slopes, steps, or curves are formed on the side walls of the wiring in the cross-sectional view. Furthermore, the width of the sides of the wiring that are in contact with the aforementioned surfaces may be widened independently. Widening the width makes it easier to absorb slight positional misalignments of the light irradiation means and drivers, and also improves connection reliability.

[0032] The connection between the wiring and the driver 2 and the light irradiation means 1 can be achieved, for example, by the following method: (1) Laminate a resin that forms the heat dissipation part on the front surface of the driver 2 up to the height to which the light irradiation means 1 will be installed. If the resin is a thermosetting material, heat curing is performed. (2) Holes are formed in the wiring formation area of ​​the laminated resin using photolithography etching, laser ablation, drilling, etc. Here, holes for wiring to connect to the back surface of the light irradiation means 1 and holes for wiring to connect to the front surface of the light irradiation means 1 are formed. If the resin is a photosensitive material, holes can also be formed by pattern exposure and development processing. (3) Fill the holes formed in the wiring formation area with metal using plating, vapor deposition, sputtering, etc., to form the wiring. At this time, selective filling may be performed using a mask, or excess parts may be removed by CMP or mechanical polishing after filling the entire surface. (4) Place and connect the light irradiation means 1 on the wiring to connect to the back surface of the light irradiation means 1, and laminate the resin up to the front surface of the light irradiation means 1. (5) Using photolithography etching, laser ablation, drilling, etc., holes are formed in the wiring formation area of ​​the laminated resin to expose the wiring for connection to the front surface of the light irradiation means 1. (6) Using plating, vapor deposition, sputtering, etc., metal is filled into the holes formed in the wiring formation area to form the wiring for connection to the front surface of the light irradiation means 1. (7) A lead frame, etc., is formed to connect the front surface of the light irradiation means 1 to the wiring for connection to the front surface of the light irradiation means 1.

[0033] 1 Light irradiation means 2 Driver 3 Heat dissipation part 4 Optical element 9 Housing 31 Surface 41 First resin layer 42 Second resin layer 45 Uneven shape 100 Optical system

Claims

1. An optical system comprising: a light irradiation means capable of irradiating light; and a driver electrically connected to the light irradiation means and controlling the irradiation of the light irradiation means, wherein the driver is arranged on the back side of the light irradiation means in the optical axis direction, and at least the range of the irradiation angle of the light irradiation means is transparent to the light, and the driver is equipped with a heat dissipation part that is in heat conductionable contact with the light irradiation means and the driver.

2. The optical system according to claim 1, characterized in that the heat dissipation section is sealed so that the surface of the light irradiation means does not come into contact with a gas.

3. The optical system according to claim 1, characterized in that the heat dissipation section is sealed so that the surface of the driver does not come into contact with gas.

4. The optical system according to any one of claims 1 to 3, characterized in that the heat dissipation part is made of a resin having a thermal conductivity of 0.2 W / m·K or more.

5. The optical system according to any one of claims 1 to 3, characterized in that the heat dissipation part is made of a resin having a thermal conductivity of 1.0 W / m·K or higher.

6. The optical system according to any one of claims 1 to 3, further comprising an optical element having an uneven shape that exhibits an optical function with respect to the light irradiated by the light irradiation means.

7. The optical system according to claim 6, characterized in that the optical element is laminated on the surface of the heat dissipation section.

8. The optical element consists of lenses that transmit light of wavelength λ arranged periodically, where m and n are natural numbers of 1 or more, and the focal length is determined by the cross-sectional shape of the lens perpendicular to the y-direction. １ The focal length is determined by the cross-sectional shape perpendicular to the x-direction, f ２ The size of the x-direction pitch of the lens is P １ The size of the pitch in the y direction is P ２ Therefore, the distance L between the irradiating portion and the first focal plane of the lens. １ , distance L from the second focal plane ２ However, see equations 1 and 2 below. The optical system according to claim 6, characterized in that it satisfies the following conditions.

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