Optical system and method of manufacturing the same

Abstract

This invention provides an optical system and a method for manufacturing an optical system. The optical system includes a carrier, a light emitter, a light receiver, a bulk structure, and an encapsulant. The light emitter is disposed on the carrier. The light receiver is disposed on the carrier and physically spaced apart from the light emitter. The light receiver has a light detection area. The bulk structure is disposed on the carrier. The encapsulant is disposed on the carrier and covers the light emitter, the light receiver, and the bulk structure. The encapsulant has a recess above the bulk structure.

Description

[Technical Field]

[0001] This invention relates to an optical system, and more specifically, to an optical system comprising a photodetector and a bulk structure. [Previous Technology]

[0002] In optical systems (e.g., light scanning sensors, ranging sensors, background light sensing systems), light emitters (e.g., vertical-cavity surface-emitting lasers (VCSELs) or light-emitting diodes (LEDs)) and / or photodetectors are widely used. In some optical systems, an encapsulation can be implemented to protect the light emitter or photodetector. However, some light emitted by the light emitter can be reflected at the boundary between the encapsulation and the air outside the encapsulation (e.g., interface reflection or total internal reflection), and the reflected light can be received by the photodetector, leading to unacceptable crosstalk problems and reducing the signal-to-noise ratio (SNR) of the optical system. [Summary of the Invention]

[0003] According to one aspect of the present invention, an optical system includes a carrier, a light emitter, a light receiver, a bulk structure, and an encapsulant. The light emitter is disposed on the carrier. The light receiver is disposed on the carrier and is physically spaced apart from the light emitter. The light receiver has a light detection area. The bulk structure is disposed on the carrier. The encapsulant is disposed on the carrier and covers the light emitter, the light receiver, and the bulk structure. The encapsulant has a recess above the bulk structure.

[0004] According to another aspect of the present invention, an optical system includes a carrier, a light emitter, a light receiver, a bulk structure, and an encapsulator. The light emitter is disposed on the carrier. The light receiver is disposed on the carrier and is physically spaced apart from the light emitter. The light receiver has a light detection area on one of its top surfaces. The encapsulator is disposed on the carrier and covers at least a portion of the light emitter and the bulk structure. The bulk structure is disposed between the light emitter and the light receiver. The bulk structure has a curved surface. The encapsulator has a recess above the bulk structure. A distance between the bottom surface of the recess and the carrier is less than a distance between the light detection area of ​​the light receiver and the carrier.

[0005] According to another aspect of the present invention, a method of manufacturing an optical system includes: (a) providing a carrier; (b) placing a light emitter on the carrier; (c) placing a light receiver on the carrier, the light receiver being physically spaced apart from the light emitter; (d) forming an encapsulation on the carrier that covers the light emitter and the light receiver; and (e) forming a recess in the bulk structure of the encapsulation.

Implementation Method

[0019] FIG1 shows a cross-sectional view of the optical system 1. The optical system 1 includes a substrate 10, a light emitter 11, a photodetector 12, and a cover 13. As shown in FIG1, the cover 13 has a wall structure disposed between the light emitter 11 and the photodetector 12. In some embodiments, the cover 13 includes an opaque material to prevent unwanted light emitted by the light emitter from being directly transmitted to the photodetector. However, because the thickness of the cover 13 (e.g., thickness d1, d2, or d3) is relatively large (e.g., the total thickness of the cover 13 increases by about 0.5 mm in the x or y direction and by about 0.4 mm in the z direction), the use of the cover 13 hinders the miniaturization of the optical system 1.

[0020] FIG2A shows a cross-sectional view of an optical system 2 in some embodiments of the present invention. The optical system 2 includes a carrier 20, a light emitter 21, a light receiver 22, a bulk structure (e.g., a barrier) 23, and an encapsulation 24.

[0021] The carrier 20 may include, for example, a printed circuit board, such as a paper-based copper foil laminate, a composite copper foil laminate, or a polymer-impregnated (PP) glass fiber-based copper foil laminate. The carrier 20 may include interconnect structures, such as multiple conductive traces, pads, or vias. In some embodiments, the carrier 20 includes a ceramic material or a metal plate. In some embodiments, the carrier 20 may include a substrate, such as an organic substrate or a lead frame. In some embodiments, the carrier 20 may include a bilayer substrate including a core layer and conductive material and / or structures disposed on an upper surface and a bottom surface of the carrier. The conductive material and / or structures may include multiple traces, pads, or vias.

[0022] A light emitter 21 is disposed on a carrier 20. The light emitter 21 may include an emitting die or other optical die. For example, the light emitter 21 may include a light-emitting diode (LED), a laser diode, or another device that may include one or more semiconductor layers. The semiconductor layers may include silicon, silicon carbide, gallium nitride, or any other semiconductor material. The light emitter 21 may be connected to the carrier 20 by means of, for example, flip-chip or wire bonding technology. In some embodiments, the light emitter 21 includes an LED die bonded to the carrier 20 via a die bonding material. The LED die includes at least one wire bonding pad. The LED die is electrically connected to the carrier 20 by a conductive wire, one end of which is bonded to the wire bonding pad of the LED die, and the other end of which is bonded to the wire bonding pad of the carrier 20. The light emitter 21 has an active region (or light-emitting area) facing away from the carrier 20.

[0023] The light receiver 22 is disposed on the carrier 20 and physically spaced apart from the light emitter 21. In some embodiments, the light receiver 22 includes, for example, a PIN diode (a diode including a p-type semiconductor region, a pure semiconductor region, and an n-type semiconductor region), a photodiode, or a phototransistor. In some embodiments, the light receiver 22 not only detects light from the light emitter 21 but also includes several different sensing regions having a filter structure for ambient light sensing (ALS). The light receiver 22 may be connected to the carrier 20, for example, by means of flip-chip or wire bonding technology (e.g., via bonding wire 23w). The light receiver 22 has an active region 22d (or light detection region) facing away from the carrier 20. In some embodiments, the light receiver 22 may include a controller, a processor, memory, an application-specific integrated circuit (ASIC), etc.

[0024] A bulk structure (e.g., a barrier) 23 is mounted on the carrier 20 and spans a portion of the non-photodetection region 22d of the light receiver 22. For example, the bulk structure 23 is positioned across other circuitry integrated within the light receiver 22. In some embodiments, the bulk structure 23 may be positioned across a portion of the bonding line 23w that connects the light receiver 22 to the carrier 20, as shown in FIG2B, which shows a perspective view of the optical system 2 in FIG2A. In some embodiments, the bulk structure 23 may cover a portion of the sidewall of the light receiver 22. In some embodiments, the ratio of the width of the bottom surface of the bulk structure 23 to the height of the bulk structure 23 is approximately 2:1. In some embodiments, the bulk structure 23 may have a curved structure 23c located on or adjacent to the top side of the bulk structure 23.

[0025] In some embodiments, the bulk structure 23 includes an opaque or light-absorbing material to prevent light emitted by the light emitter 21 from being directly transmitted to the light receiver 22. For example, as shown in FIG2A, light L1 detected by the light receiver 22 is reflected by the target object 25, while light L2 reflected at the boundary between the encapsulation 24 and the air outside the encapsulation 24 (e.g., interface reflection) is blocked by the bulk structure 23. Therefore, the crosstalk problem between the light emitter 21 and the light receiver 22 can be eliminated or mitigated, thereby increasing the SNR of the optical system 2.

[0026] In some embodiments, the power of the light reflected at the boundary between the encapsulation 24 and the air outside the encapsulation 24 and received by the light receiver 22 in FIG. 2A or FIG. 2B is about 1% to 5% lower than the power of the light in an optical system without a bulk structure. For example, the power of the light reflected at the boundary between the encapsulation 24 and the air outside the encapsulation 24 and received by the light receiver 22 in FIG. 2A or FIG. 2B can be about 0.063 microwatts (μW) with the bulk structure 23 and about 1.68 μW without the bulk structure 23. Furthermore, since no cover is required in the optical system 2 to prevent crosstalk between the light emitter 21 and the light receiver 22, the area and thickness of the optical system 2 in FIG. 2A or FIG. 2B can be reduced, thereby achieving a compact package size.

[0027] The encapsulant 24 is disposed on the carrier 20 and covers at least a portion of the light emitter 21, the light receiver 22, and the bulk structure 23. In some embodiments, a portion (e.g., the top surface) of the bulk structure 23 is exposed from the encapsulant 24. The top surface of the bulk structure 23 is substantially coplanar with the top surface of the encapsulant 24. In other embodiments, the bulk structure 23 may be completely covered by the encapsulant 24. In some embodiments, the encapsulant 24 comprises a light-transmitting material. For example, the encapsulant 24 is a transparent compound. For example, the encapsulant 24 comprises epoxy resin.

[0028] FIG3A shows a cross-sectional view of an optical system 3A in some embodiments of the present invention. The optical system 3A is similar to the optical system 2 in FIG2A, except that the bulk structure 23 in FIG3A is not disposed across the light receiver 22. For example, the bulk structure 23 is disposed between the light emitter 21 and the light receiver 22 and is spaced apart from the light emitter 21 or the light receiver 22.

[0029] FIG3B shows a cross-sectional view of an optical system 3B in some embodiments of the present invention. Optical system 3A is similar to optical system 3A in FIG3A, and the differences between them are described below.

[0030] As shown in FIG. 3B, the encapsulation 24 has a recess 24r. The recess is disposed between the light emitter 21 and the light receiver 22. The recess 24r is disposed above the bulk structure 23. In some embodiments, the recess 24r exposes the bulk structure 23. In other embodiments, the lower side (e.g., bottom surface or bottom side) of the recess 24r is spaced apart from the bulk structure 23. In some embodiments, the lower side of the recess 24r may be smaller than, equal to or larger than the active region 22d of the light receiver 22, depending on different design requirements.

[0031] In some embodiments, the optical receiver 22 is electrically connected to the carrier 20 via a bonding wire 23w. Since the bonding wire 23w requires space (e.g., a wire loop), the thickness of the encapsulation 24 is subject to minimum constraints. For example, there should be a gap between the top surface of the encapsulation 24 and the optical receiver 22 to accommodate the bonding wire 23w. Furthermore, as mentioned above, the ratio of the width of the bottom surface of the bulk structure 23 to the height of the bulk structure 23 should follow a rule (e.g., 2:1). Therefore, if the height of the bulk structure 23 is designed to be the same as the thickness of the encapsulation 24, the width of the bulk structure 23 will be relatively large, which increases the area occupied by the bulk structure 23 (increasing the package size). However, if the height of the bulk structure 23 is designed to be less than the thickness of the encapsulation 24 (e.g., there is a gap between the top surface of the encapsulation 24 and the top surface of the bulk structure 23), light emitted from the optical emitter 21 can directly enter the optical receiver 22, which can lead to unacceptable crosstalk problems and reduce the SNR.

[0032] According to the embodiment shown in FIG. 3B, the recess 24r is formed above the bulk structure 23. The light emitted by the light emitter 21 (e.g., L33) can be refracted twice by the recess 24r. One refraction occurs when the light is emitted from the encapsulation 24 to the outside of the encapsulation 24, and the other refraction occurs when the light is emitted from the outside of the encapsulation 24 to the encapsulation 24. Therefore, the power of the light emitted by the light emitter 21 and directly entering the active region 22d of the light receiver 22 can be reduced. For example, the power of the light emitted by the light emitter 21 and directly entering the active region 22d of the light receiver 22 (as shown in the structure of FIG. 3B) can be 80% lower than the power of the light without the recess. Therefore, by forming the recess 24r above the bulk structure 23, the power of the light emitted by the light emitter 21 and directly entering the active region 22d of the light receiver 22 can be reduced without increasing the height of the bulk structure 23. In addition, the bulk structure 23 includes opaque or light-absorbing materials to prevent light emitted by the light emitter 21 from being directly transmitted to the light receiver 22 (e.g., via path L34).

[0033] FIG. 3C shows a cross-sectional view of an optical system 3C in some embodiments of the present invention. The optical system 3C is similar to the optical system 3B in FIG. 3B, except that the shape of the recess 24r in FIG. 3C differs from the shape of the recess 24r in FIG. 3B. In some embodiments, the shape of the recess 24r can be designed according to different design requirements. In some embodiments, the bottom surface of the recess 24r is spaced apart from the block structure 23. For example, there is a gap between the recess 24r and the block structure 23.

[0034] FIG. 3D shows a cross-sectional view of an optical system 3D in some embodiments of the present invention. The optical system 3D in FIG. 3D is similar to the optical system 3A in FIG. 3A, except that the encapsulant 24 of the optical system 3D in FIG. 3D has a recess 24r for exposing the top surface of the bulk structure 23. For example, the top surface of the encapsulant 24 is not coplanar with the top surface of the bulk structure 23. In some embodiments, the hardness of the bulk structure 23 in FIG. 3D is greater than the hardness of the bulk structure 23 in FIG. 2A or FIG. 3A. In some embodiments, the bottom surface of the recess 24r is substantially coplanar with the top surface of the bulk structure 23. For example, the top surface of the bulk structure 23 is exposed from the recess 24r. In some embodiments, the width of the recess 24r may be equal to or greater than the width of the bulk structure 23.

[0035] Compared to the optical system 3C in FIG3C, the top surface of the bulk structure 23 in FIG3D is exposed from the recess, which prevents the light emitted by the light emitter 21 from being directly transmitted to the light receiver 22. For example, as shown in FIG3D, the light L31 reflected (e.g., interface reflection) at the boundary between the encapsulation 24 and the air outside the encapsulation 24 is blocked by the bulk structure 23. Therefore, the crosstalk problem between the light emitter 21 and the light receiver 22 can be eliminated or mitigated, thereby increasing the SNR of the optical system 3D.

[0036] FIG3E shows a cross-sectional view of an optical system 3E in some embodiments of the present invention. The optical system 3E in FIG3E is similar to the optical system 3D in FIG3D, and the differences between them are described below.

[0037] In some embodiments, the width of the recess 24r in FIG. 3E is smaller than the width of the bulk structure 23. As shown in FIG. 3E, the bulk structure 23 may have a cut surface 24r1 exposed from the encapsulant 24. The cut surface 24r1 of the bulk structure 23 is recessed from other portions of the bulk structure 23 surrounding the cut surface 24r1. In some embodiments, the recess 24r may be defined by the cut surface 24r1 and at least a portion of the bulk structure 23. As an example, at least a portion of the sidewall of the recess 24r may be defined by a portion of the bulk structure 23. In some embodiments, a portion of the bulk may at least partially surround the cut surface 24r1 and be exposed from the encapsulant 24.

[0038] FIG4 shows a cross-sectional view of an optical system 4 in some embodiments of the present invention. The optical system 4 in FIG4 is similar to the optical system 2 in FIG2A, except that the encapsulant 24 of the optical system 4 in FIG4A has a recess 24r for exposing the top surface of the bulk structure 43. For example, the top surface of the encapsulant 24 is not coplanar with the top surface of the bulk structure 43.

[0039] As shown in FIG. 4, the light L41 reflected (e.g., interface reflection) at the boundary between the encapsulation 24 and the air outside the encapsulation 24 is blocked by the bulk structure 23. Therefore, the crosstalk problem between the light emitter 21 and the light receiver 22 can be eliminated or mitigated, thereby increasing the SNR of the optical system 4. In some embodiments, the power of the light reflected at the boundary between the encapsulation 24 and the air outside the encapsulation 24 and received by the light receiver 22 can be about 0.028 μW.

[0040] Figures 5A and 5B illustrate methods for manufacturing an optical system according to some embodiments of the present invention. In some embodiments, the methods in Figures 5A and 5B are used to manufacture the optical system 2 in Figure 2A.

[0041] Referring to FIG. 5A, a carrier 20 is provided. A light emitter 21 and a light receiver 22 are disposed on the carrier 20 and are physically spaced apart from each other. A bulk structure 23 is formed on the carrier 20 and spans a portion of the non-light-detection region 22d in the light receiver 22. In some embodiments, the bulk structure 23 may be formed by distributing an opaque material on the portion of the non-light-detection region 22d in the carrier 20 and the light receiver 22. In some embodiments, the bulk structure 23 includes silicone, epoxy resin, or any other suitable material (e.g., an opaque material or a light-absorbing material). In some embodiments, the bulk structure 23 is relatively soft or flexible. For example, the bulk structure 23 may be formed of a material having a Shore A50 hardness or greater.

[0042] Next, the mold tool 50 having the film 50f moves toward the carrier 20 to form an encapsulation 24 covering the light emitter 21, the light receiver 22, and the bulk structure 23, thereby forming the optical system 2, as shown in FIG5B. In some embodiments, the encapsulation material 24 is formed by a compression molding process. Because the support structure 23 is relatively soft or flexible, the bulk structure 23 will be compressed when the mold tool 50 is pressed on the bulk structure 23. Therefore, there is no gap between the top surface of the bulk structure 23 and the top surface of the encapsulation 24. In other words, the top surface of the bulk structure 23 and the top surface of the encapsulation 24 are substantially coplanar.

[0043] Figures 6A, 6B, and 6C illustrate, in cross-sectional view, a method for manufacturing an optical system according to some embodiments of the present invention. Figures 7A, 7B, 7C, and 7D illustrate, in perspective view, a method for manufacturing an optical system according to some embodiments of the present invention. In some embodiments, the methods in Figures 6A, 6B, and 6C or Figures 7A, 7B, 7C, and 7D are used to manufacture the optical system 4 in Figure 4.

[0044] Referring to FIG. 6A or FIG. 7A, a carrier 20 is provided. A light emitter 21 and a light receiver 22 are disposed on the carrier 20 and are physically spaced apart from each other. As shown in FIG. 7A, the light receiver 22 is connected to the carrier 20 via a bonding line 22w. A bulk structure 43' is formed on the carrier 20 and is positioned across a portion of the non-light-detecting region 22d in the light receiver 22. In some embodiments, the bulk structure 43' is positioned across a portion of the bonding line 22w, as shown in FIG. 7B. In some embodiments, the bulk structure 43' may cover a portion of the sidewall of the light receiver 22. In some embodiments, the bulk structure 43' may be formed by distributing an opaque material on the portion of the non-light-detecting region 22d in the carrier 20 and the light receiver 22. In some embodiments, the bulk structure 43' includes silicone, epoxy resin, or any other suitable material (e.g., an opaque material or a light-absorbing material). In some embodiments, the bulk structure 43' is relatively rigid. For example, the bulk structure 43' in Figure 6A is harder than the bulk structure 23 in Figure 5A. For example, the bulk structure 43' may be formed of a material with a Shore C hardness or a higher hardness such as Shore D90.

[0045] Next, the mold tool 50 having the membrane 50f moves toward the carrier 20 to form an encapsulation 24 covering a portion of the light emitter 21, the light receiver 22, and the bulk structure 43', thereby forming an optical system, as shown in FIG6B or FIG7C. In some embodiments, the encapsulation 24 is formed by a compression molding process. Because the bulk structure 43' is relatively rigid, the bulk structure 43' does not deform when the mold tool 50 is pressed on the bulk structure 43'. Therefore, as shown in FIG6B, the bulk structure 43' protrudes from the top surface of the encapsulation 24. The membrane 50f is formed of a soft material to provide cushioning for the bulk structure 43' to prevent cracking.

[0046] Referring to FIG. 6C or FIG. 7D, a cutting operation (e.g., half-cut) is performed to remove a portion of the bulk structure 43' and a portion of the encapsulation to form a recess 24r. The top surface of the remaining portion of the bulk structure 43 is exposed from the encapsulation 24. For example, the top surface of the encapsulation 24 is higher than the top surface of the bulk structure 43. For example, the top surface of the bulk structure 43 is recessed from the top surface of the encapsulation 24.

[0047] As used herein, the terms “substantially,” “substantially,” “approximately,” and “about” are used to indicate and explain small variations. For example, when used in conjunction with numerical values, these terms may refer to a range of variation less than or equal to ±10% of that value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. As another example, “substantially homogeneous” thickness of a film or layer may mean that the average thickness of the film or layer has a standard deviation of less than or equal to ±10%, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. The term "substantially coplanar" can refer to two surfaces that are within 50 μm along the same plane, such as within 40 μm, 30 μm, 20 μm, 10 μm, or 1 μm along the same plane. If, for example, two components overlap or are within 200 μm, 150 μm, 100 μm, 50 μm, 40 μm, 30 μm, 20 μm, 10 μm, or 1 μm of overlap, then the two components can be considered "substantially aligned". If the angle between two surfaces or components is, for example, 90° ± 10°, such as ± 5°, ± 4°, ± 3°, ± 2°, ± 1°, ± 0.5°, ± 0.1°, or ± 0.05°, then the two surfaces or components can be considered "substantially perpendicular". When used in conjunction with an event or situation, the terms "substantially," "substantially," "approximately," and "about" can refer to an exact example of the event or situation occurring, or an example of the event or situation occurring very approximately.

[0048] In describing some embodiments, the phrase “on” one component may cover the case where the former component is directly on the latter component (e.g., in physical contact with the latter component), and the case where one or more intermediate components are positioned between the former component and the latter component.

[0049] In addition, quantities, ratios and other values ​​are sometimes presented in range format in this document. It should be understood that such range format is used for convenience and brevity and should be interpreted flexibly to include not only values ​​explicitly specified as the limits of the range, but also all individual values ​​or subranges covered within the range, as if each value and subrange were explicitly specified.

[0050] Although the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not limiting of the invention. Those skilled in the art will readily understand that various changes can be made and equivalent elements can be substituted within the embodiments without departing from the true spirit and scope of the invention as defined by the appended claims. The illustrations may not be drawn to scale. Due to variables such as manufacturing processes, there may be differences between the process reproduction in the invention and actual equipment. Other embodiments of the invention may exist that are not specifically described. This specification and the drawings should be considered illustrative rather than restrictive. Modifications can be made to adapt particular circumstances, materials, compositions, methods, or processes to the objectives, spirit, and scope of the invention. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations can be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations do not limit the invention. [Simplified Explanation of the Diagram]

[0006] FIG1 shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0007] FIG2A shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0008] FIG2B shows a perspective view of an optical system according to some embodiments of the present invention;

[0009] FIG3A shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0010] FIG3B shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0011] FIG3C shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0012] FIG3D shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0013] FIG3E shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0014] FIG4 shows a cross-sectional view of an optical system according to some embodiments of the present invention;

[0015] Figures 5A and 5B illustrate methods for manufacturing an optical system according to some embodiments of the present invention;

[0016] Figures 6A, 6B, and 6C illustrate methods for manufacturing optical systems according to some embodiments of the present invention; and

[0017] Figures 7A, 7B, 7C and 7D illustrate a method for manufacturing an optical system according to some embodiments of the present invention.

[0018] Common reference numerals are used throughout the drawings and detailed description to indicate the same or similar components. The invention can be best understood from the following detailed description taken in conjunction with the accompanying drawings.

Claims

1. An optical system comprising: A light emitter, which is mounted on a carrier; An optical receiver is mounted on the carrier; A light-blocking structure disposed between the light emitter and the light receiver; and an encapsulation disposed on the carrier, the light emitter and the light receiver, wherein the light-blocking structure has a recess and the encapsulation does not overlap with the recess in a first direction substantially perpendicular to one of the top surfaces of the carrier.

2. The optical system of claim 1, wherein the light-blocking structure includes a first portion, a second portion and a third portion, the first portion, the second portion and the third portion being arranged along a second direction substantially parallel to a top surface of the carrier, the second portion being located between the first portion and the third portion and both being lower than the first portion and the third portion, the recess being defined by the first portion, the second portion and the third portion, and the second portion being wider than the first portion and the second portion being wider than the third portion.

3. The optical system of claim 2, wherein at least one of the first portion and the second portion has a curved surface.

4. The optical system of claim 1, wherein the light receiver has an active region and the light-blocking structure is farther from the active region than from the light emitter.

5. The optical system of claim 2, wherein the first portion is closer to the light emitter than the second portion and the third portion, and the first portion contacts the encapsulation.

6. The optical system of claim 2, wherein, relative to the top surface of the carrier, one of the third portions is at a height higher than the height of the second portion and not lower than the height of the first portion, and the third portion is closer to the light receiver than the first portion and the second portion.

7. The optical system of claim 2, wherein, in a cross-section, the first portion is closer to the light emitter than the second portion and the third portion, the first portion having a first side surface exposed from the recess and a second side surface adjacent to the first side surface, and the first side surface and the second side surface of the first portion defining an acute angle.

8. The optical system of claim 2, wherein, in a cross-section, the third portion is closer to the light receiver than the second portion and the first portion, the third portion having a first side surface exposed from the recess and a second side surface adjacent to the first side surface, and the first side surface and the second side surface of the third portion defining an acute angle.

9. An optical system comprising: A light emitter, which is mounted on a carrier; An optical receiver is mounted on the carrier; A light-blocking structure disposed between the light emitter and the light receiver; and an encapsulation structure disposed on the carrier, wherein the encapsulation structure defines a first recess, the light-blocking structure has a second recess, and the first recess is connected to the second recess.

10. The optical system of claim 9, wherein the encapsulation structure includes a first portion and a second portion separated from each other by the first recess.

11. The optical system of claim 9, wherein the encapsulation structure has a first sidewall defining the first recess, the light-blocking structure has a second sidewall defining the second recess, and the transmittance of the first sidewall is greater than the transmittance of the second sidewall.

12. The optical system of claim 9, wherein the width of the first recess is not less than the width of the second recess.

13. A method of manufacturing an optical system, comprising: providing a carrier having a light emitter and a light receiver; forming a light-blocking structure on the carrier and between the light emitter and the light receiver; forming an encapsulation on the carrier, the light emitter, and the light receiver; and forming a recess in the light-blocking structure, wherein the encapsulation and the recess do not overlap in a first direction substantially perpendicular to a top surface of the carrier.

14. The method of claim 13, wherein the light-blocking structure includes a first portion, a second portion and a third portion, the first portion, the second portion and the third portion being arranged along a second direction substantially parallel to a top surface of the carrier, the second portion being located between the first portion and the third portion and both being lower than the first portion and the third portion, the recess being defined by the first portion, the second portion and the third portion, and the second portion being wider than the first portion and the second portion being wider than the third portion.

15. The method of claim 14, wherein at least one of the first portion and the second portion has a curved surface.

16. The method of claim 13, wherein the optical receiver has an active region and the light-blocking structure is farther from the active region than from the optical transmitter.

17. The method of claim 14, wherein the first portion is closer to the light emitter than the second portion and the third portion, and the first portion contacts the encapsulation.

18. The method of claim 14, wherein, relative to the top surface of the carrier, one of the heights of the third portion is higher than the height of the second portion and not lower than the height of the first portion, and the third portion is closer to the light receiver than the first portion and the second portion.

19. The method of claim 14, wherein in a cross-section, the first portion is closer to the light emitter than the second portion and the third portion, the first portion having a first side surface exposed from the recess and a second side surface adjacent to the first side surface, and the first side surface and the second side surface of the first portion defining an acute angle.

20. The method of claim 14, wherein in a cross-section, the third portion is closer to the light receiver than the second portion and the first portion, the third portion having a first side surface exposed from the recess and a second side surface adjacent to the first side surface, and the first side surface and the second side surface of the third portion defining an acute angle.

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