Patent Publication Number: US-10760955-B2

Title: Optical sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present disclosure is a divisional application of U.S. patent application Ser. No. 15/007,217 filed on Jan. 27, 2016, which claims the benefit of U.S. Provisional Application No. 62/115,648 filed on Feb. 13, 2015, the entirety of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates generally to optical sensors and associated applications to collect and manage the signals. 
     BACKGROUND 
     The reflective optical sensor module emits light and measures the amount of reflected light from an object. An electrical sensor is capable of detecting the electrical properties of an external circuit formed by the contact with an object surface. Multi-parameters measurement including optical and electrical measurement provides acquisition of multiple independent information, or the combination of parameters may infer further parameters. Most inventions make efforts to combine several independent sensors into a single mobile device. When acquiring multi-parameter on a precise location, it is difficult to place multiple probes at exactly the same limited area. Furthermore, the assembly of several sensors increases the form factor of the sensing device tremendously. A compact sensor module capable of measuring both electrical and optical properties is needed for wide applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIGS. 1A and 1B  are schematic diagrams of a cross-sectional view of an optical sensor in accordance with a first and a second embodiments of the present disclosure. 
         FIGS. 2A-2C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor in accordance with an embodiment of the present disclosure. 
         FIGS. 3A-3C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor in accordance with an embodiment of the present disclosure. 
         FIGS. 4A-4C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor in accordance with an embodiment of the present disclosure. 
         FIGS. 5A-5C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor in accordance with an embodiment of the present disclosure. 
         FIGS. 6A-6C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor with an object surface in accordance with an embodiment of the present disclosure. 
         FIGS. 7A-7C  are schematic diagrams of an optical sensor module comprising a cover applied on an object surface. 
         FIG. 8A  is a cross-sectional view of an optical sensor module comprising a cover applied on an object surface;  FIG. 8B  is a partial enlarged view of the double-sided thin film cover. 
         FIG. 9A  is a cross-sectional view of the thin film coated encapsulants;  FIG. 9B  is a partial enlarged view of the first thin film coated encapsulant;  FIG. 9C  is a partial enlarged view of the second thin film coated encapsulant. 
         FIG. 10A  is a cross-sectional view of the optical sensor module comprising a cover and the thin film coated encapsulants;  FIG. 10B  is a partial enlarged view of the first thin film coated encapsulant;  FIG. 10C  is a partial enlarged view of the second thin film coated encapsulant. 
         FIG. 11A  is a cross-sectional view of the optical sensor module comprising a double-sided thin film cover and the thin film coated encapsulants;  FIG. 11B  is a partial enlarged view of the double-sided thin film cover,  FIG. 11C  is a partial enlarged view of the first thin film coated encapsulant, and  FIG. 11D  is a partial enlarged view of the second thin film coated encapsulant. 
         FIGS. 12A-12C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with one embodiment of the present disclosure. 
         FIGS. 13A-13C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 14A-14C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 15A-15C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIG. 16A  is a schematic diagram of a cross-sectional view of an optical sensor in accordance with one embodiment of the present disclosure;  FIG. 16B  is the schematic diagram of a cross-sectional view of one of the encapsulants.  FIG. 16C-16E  are the graphs of the refractive index as a function of the distance from the substrate, wherein the horizontal axis represents the distance and the vertical axis represents the refractive index. 
         FIGS. 17A-17C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 18A-18C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 19A-19C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 20A-20C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 21A-21C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 22A-22C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 23A-23C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 24A-24C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 25A-25C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 26A-26C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 27A-27C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 28A-28C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 29A-29C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 30A-30C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 31A-31C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 32A-32C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 33A-33C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 34A-34C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 35A-35C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 36A-36C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 37A-37C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 38A-38C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIG. 39A  is a cross-sectional view of the optical sensor module comprising a double-sided thin film cover and the thin film coated encapsulants applied on an object surface;  FIG. 39B  is a partial enlarged view of the double-sided thin film cover. 
         FIG. 40A  is a cross-sectional view of the optical sensor module comprising the thin film coated encapsulants applied on an object surface;  FIG. 40B  is a partial enlarged view of the first thin film coated encapsulant;  FIG. 40C  is a partial enlarged view of the second thin film coated encapsulant. 
         FIG. 41A  is a cross-sectional view of the optical sensor module comprising a double-sided thin film cover and the thin film coated encapsulants applied on an object surface;  FIG. 41B  is a partial enlarged view of the first thin film coated encapsulant;  FIG. 41C  is a partial enlarged view of the second thin film coated encapsulant. 
         FIG. 42A  is a cross-sectional view of the optical sensor module comprising a double-sided thin film cover and the thin film coated encapsulants applied on an object surface;  FIG. 42B  is a partial enlarged view of the double-sided thin film cover;  FIG. 42C  is a partial enlarged view of the first thin film coated encapsulant;  FIG. 42D  is a partial enlarged view of the second thin film coated encapsulant. 
         FIGS. 43A-43C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 44A-44C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 45A-45C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 46A-46B  are schematic diagrams of a top view and cross-sectional view of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 47A-47B  are schematic diagrams of a top view and cross-sectional view of an optical sensor module applied to an object surface in accordance with an embodiment of the present disclosure. 
         FIGS. 48A-48B  are schematic diagrams of a top view and cross-sectional view of an optical sensor module comprising a cover applied to an object surface in accordance with an embodiment of the present disclosure. 
         FIGS. 49A-49C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 50A-50C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 51A-51C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 52A-52C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 53A-53C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 54A-54C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 55A-55C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module comprising an analogue front end in accordance with an embodiment of the present disclosure. 
         FIGS. 56A-56B  are schematic diagrams of a top view and oblique view, respectively, of an optical sensor module comprising an analogue front end in accordance with an embodiment of the present disclosure. 
         FIGS. 57A-57B  are schematic diagrams of a top view and oblique view, respectively, of an optical sensor module comprising an analogue front end and a microcontroller in accordance with an embodiment of the present disclosure. 
         FIGS. 58A-58B  are schematic diagrams of a top view and oblique view, respectively, of an optical sensor module comprising an analogue front end and a microcontroller in accordance with an embodiment of the present disclosure. 
         FIGS. 59A-59B  are schematic diagrams of a top view and oblique view, respectively, of an optical sensor module comprising a plurality of analogue front end and a microcontroller in accordance with an embodiment of the present disclosure. 
         FIGS. 60A-60B  are schematic diagrams of a top view and oblique view, respectively, of an optical sensor module comprising an operational amplifier, a light source driver and a microcontroller in accordance with an embodiment of the present disclosure. 
         FIGS. 61A-61C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 62A-62C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensing module in accordance with an embodiment of the present disclosure.  FIG. 62D  is the side view of an optical sensor module from the side of contact surface. 
         FIGS. 63A-63C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensing module in accordance with an embodiment of the present disclosure.  FIG. 63D  is the side view of an optical sensor module from the side of contact surface. 
         FIGS. 64A-64C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 65A-65C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensing module in accordance with an embodiment of the present disclosure.  FIG. 65D  is the side view of an optical sensor module from the side of contact surface. 
         FIGS. 66A-66C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 67A-67C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 68A-68C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensing module in accordance with an embodiment of the present disclosure.  FIG. 68D  is the side view of an optical sensor module from the side of contact surface. 
         FIGS. 69A-69C  are schematic diagrams of a top view, cross-sectional view, and oblique sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 70A-70B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 71A-71B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 72A-72B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 73A-73B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 74A-74B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module in accordance with an embodiment of the present disclosure. 
         FIGS. 75A-75B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 76A-76B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIGS. 77A-77B  are schematic diagrams of a top view and cross-sectional view, respectively, of an optical sensor module comprising a cover in accordance with an embodiment of the present disclosure. 
         FIG. 78A  is a cross-sectional view of the optical sensor module comprising a double-sided thin film cover;  FIG. 78B  is a partial enlarged view of the double-sided thin film cover. 
         FIG. 79A  is a cross-sectional view of the optical sensor module comprising a cover and the thin film coated encapsulants;  FIG. 79B  is a partial enlarged view of the first thin film coated encapsulant;  FIG. 79C  is a partial enlarged view of the second thin film coated encapsulant. 
         FIGS. 80A-80D  are schematic diagrams of the housing of an optical sensing accessory or an optical sensing device.  FIG. 80A  is an example of the housing for a handheld device.  FIGS. 80B and 80C  is an example of the annular shape housing for a wearable device.  FIG. 80D  is an example of the patch shape housing for a wearable device. 
         FIG. 81A  is a block diagram of an optical sensing accessory connected to a computing device;  FIGS. 81B and 81C  are the schematic diagrams of the optical sensing accessory connected to a computing device. 
         FIG. 82A  is a block diagram of a wireless optical sensing accessory connected to a computing device;  FIG. 82B  is a schematic diagram of the wireless optical sensing accessory connected to a computing device. 
         FIG. 83A  is a block diagram of an optical sensing device;  FIGS. 83B and 83C  are the schematic diagrams of the optical sensing device comprising an optical sensor module and a wearable housing. 
         FIG. 84A  is a schematic diagram of the optical sensing device connected to an optical sensing accessory.  FIG. 84B  is a schematic diagram of the optical sensing device connected to another sensing device. 
         FIG. 85A  is a block diagram of a wireless optical sensing device connected to another wireless optical sensing device;  FIG. 85B  is a schematic diagram of the wireless optical sensing device connected to another wireless optical sensing device. 
         FIGS. 86A and 86B  are the schematic diagrams of an application scenario of using an optical sensing device to achieve multi-site measurement. 
         FIGS. 87A and 87B  are the schematic diagrams of the optical sensing device having a bi-directional optical sensor module exposing the two contact surfaces to two different surfaces of an optical sensing device.  FIG. 87C  is a partial cutaway view from side of an optical sensing device having a bi-directional sensing module.  FIG. 87D  is an enlarged view of  FIG. 87C  illustrating a bi-directional sensor module in an optical sensing device having two contact surfaces facing two directions. 
         FIG. 88  is a block diagram of a multi-site sensing accessory. 
         FIG. 89  is a block diagram of a multi-site sensing device. 
         FIG. 90  is a block diagram of a multi-site sensing system. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “outside” refers to a region that is beyond the outermost confines of a physical object. The term “inside” indicates that at least a portion of a region is partially contained within a boundary formed by the object. The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like. 
     The reflective optical sensor module is manufactured to emit light and detect the reflected light from an object surface, and the received reflected light will be proportionally transduced into electrical signal, such as a voltage, a current or a combination thereof. As shown in  FIGS. 1A and 1B , the optical sensor module  10  comprises a light source  110 , a first encapsulant  111  over the light source  110 , a photodetector  120 , a second encapsulant  121  over the photodetector  120 , and a partition  130 . Each of the light source  110 , the photodetector  120 , the first encapsulant  111 , the second encapsulant  121 , and the partition  130  are mounted on a substrate  140 . The optical sensor module  10  may be fabricated in a single compact package. It is also contemplated that the optical sensor module  10  may employ discrete light source  110  and photodetector  120  that are separately packaged and mounted to one or more printed circuit boards (also referred to as “PCB”) depending on various design requirements. The exemplary embodiments of each component are described as below. 
     A substrate  140  is configured to have components installed thereon and provides mechanical or electrical connections between the components. Further, the substrate  140  provides mechanical support to the components of the optical sensor module  10  and interconnectivity between other external electronic components and the optical sensor module  10 . In addition, the first encapsulant  111  and the second encapsulant  121  of the optical sensor module  10  are also formed on the substrate  140 . In implementation, the substrate  140  may be printed circuit board (PCB), metal core PCB (MCPCB), ceramic PCB, or direct bonded copper substrate (DBC). 
     Optoelectronic transducers can convert the signals between optical signals and electrical signals. The light source  110 , which converts electric power into radiant energy in a specific spectrum of wavelengths (for example, ultraviolet, visible, or infrared portions of the spectrum). The light source  110  may have electrical connections to a printed circuit embedded in the substrate to receive triggering signals and applied voltage from a microcontroller, a light source driver, or a gated power source. In implementation, the optical sensor module  10  may employ one or more light emitting diodes (LED), organic light emitting diodes (OLED), laser diodes (LD), or the like as light source  110 . For example, the light source  110  of the optical sensor module  10  may comprise one or more LEDs, each configured to emit light in the specific spectrum of wavelengths. It is contemplated that the light sources  110  may further emit light in different spectrum of wavelengths synchronously or asynchronously depending on various applications. 
     The photodetector  120 , which detects and converts radiant energy in the specific spectrum into electrical current or voltage, is mounted to the substrate  140 . The photodetector should have a spectral response at least active in a part of corresponding wavelengths of the light source  110 . The photodetector  120  may have electrical connections to a printed circuit embedded in the substrate to convey the photocurrent to a microcontroller, an operational amplifier, or an analogue front end. In implementation, the optical sensor module  10  may employ photodiode, phototransistor, photoresistor, photomultiplier, metal oxide semiconductor (MOS), or the like as photodetector  120 . The photodetector  120  may detect the light in the specific spectrum of wavelengths emitted by the light source  110  or the light with a wavelength shift from the light emitted by the light source. Accordingly, the photodetector  120  converts the detected light into electrical signals. The photodetector  120  may also detect light in a spectrum of wavelengths different from the specific spectrum of wavelength of the light source  110 . For example, the fluorescent light emitted from an object surface after receiving the light emitted from the light source  110  may be detected by a photodetector  120 . Furthermore, the photodetector  120  may also detect the infrared light from an object surface, while the light source  110  does not emit infrared light in one example. The photodetector  120  may comprise a single or a plurality of photodiodes to extend the response spectrum or to separately measure different wavelengths of received light. 
     A partition  130  is mounted to the substrate  140  and is formed between the light source  110  and the photodetector  120  for blocking the stray light directly from the light source  110  to the photodetector  120 . In addition, the partition  130  may be formed of opaque material, which reflects and/or absorbs light in a specific spectrum of wavelengths emitted by the light source  110 . Furthermore, an optical sensor module may have packaging walls  131  to prevent the ambient noise. As shown in the  FIGS. 1A and 1B , the packaging walls  131  of the optical sensor module  10  may be formed around the light source  110  and the photodetector  120 . The packaging walls  131  may further provide mechanical support when a cover  150  is applied in an optical sensor module. In some examples, a part of the packaging wall  131  may be disposed between the light source and the photodetector, and replace the function of the partition. The packaging wall may define an area surrounding the light source, the partition, and the photodetector. The partition and the packaging wall may have similar or different material depending on the requirement of the capability of light blocking. Also, the partition and the packaging wall may be formed as a single entity or as multiple separate parts. 
     The encapsulants hermetically seal the optoelectronics for prolonging the durability of the optoelectronics, and improving light extraction efficiency by mediating the high refractive index difference between the optoelectronics and the environmental medium. The encapsulants should be, at least partially, transparent so that it can be an adequate medium of light propagation. In implementation, the material of the encapsulants may have lower refractive index than the optoelectronics have and higher than the environment, such as air, water, or gel. The material can be selected from silicone compound, or selected from clear polymers, which can include polydimethylsiloxane (PDMS), polycarbonate (PC), or poly(methyl methacrylate) (PMMA). 
     The present technology has the features on the construction and the configuration of an encapsulant  111  covering the light source  110  or an encapsulant  121  covering the photodetector  120 . The encapsulants  111 ,  121  can be constructed using a single layer or more than one layer. When a single layer construction manufactured by one kind of material is implemented, the encapsulant may have one refractive index mediating the optoelectronics and the environment. The refractive index difference between an optoelectronic transducer with a great refractive index and the environment with low refractive index leads to poor light extraction or light receiving efficiency. An encapsulant generally has a refractive index between a great refractive index of an optoelectronic transducer and a low refractive index the environment, so that the light extraction or light receiving efficiency can be slightly improved. 
     The multilayer construction may be formed by multiple physical layers with different refractive indices or may be formed as a single entity with non-homogenous refractive index, such as a gradient refractive index. In one example, an encapsulant may be manufactured by stacking multiple layers with different refractive indices. In other example, an encapsulant with one material may be applied with an external electrical field during the manufacturing process, and resulting in the encapsulant with multiple refractive index layers while no physical interfaces presented in the encapsulant. In one example, refractive indices of each of the layers may decrease from proximal portion to distal portion when the encapsulant has a multilayer construction. For ease of understanding, the illustrations of the encapsulants with multilayer construction, including physical layers or a single entity with non-homogenous refractive index, may be depicted with separate line and different hatchings. Without departing from the scope, the drawings are not limited to the encapsulants with multilayer construction in multiple physical layers. It has the advantage of reducing total internal reflection of emitting light by gradually mediating the high refractive index difference between light source  110  and the environmental medium the emitting surface, and, hence, improves the light extraction efficiency. As to the construction styles, presented as various kinds of stacks, are engineered for specific requirements. 
     The surface of an encapsulant may be formed as a specific configuration; especially in the case of multiple layer construction, the interface of any two layers may also be formed as a specific configuration. The specific configuration may be a microstructure or an optical directional component and the detail of the embodied configurations will be described below. An encapsulant may have modifications in configuration and/or construction. A configuration of an encapsulant is a modification of shape, contour, or inclination or any combination thereof. A configuration may be a microstructure or an optical directional component. A microstructure may be a Fresnel lens or a diffractive optical element, while an optical directional component may be an inclined plane or a curvature lens. The configuration can be disposed on any interfaces between two adjacent layers in an encapsulant or on the surface of an encapsulant. The surface of an encapsulant can be defined with medial surface, top surface and lateral surface. The medial surface of an encapsulant is the outline substantially facing to the partition. The top surface of an encapsulant is the surface about parallel to the plane of the substrate. For example, the top surface of the first encapsulant  111  is configured with a first microstructure  112 , and the second encapsulant  121  may have a second microstructure  122 . In addition, the second encapsulant  121 , in order to improve the light receiving efficiency, may have different designs in the construction and configuration from the first encapsulant. 
     The surface of the encapsulants or the interface of any two layers may be formed as a microstructure. For example, the top surface of the uppermost layer of the first encapsulant  111  is configured as a microstructure  112  as illustrated in  FIG. 1A . The encapsulant with microstructure(s) enhances the signal strength because the light is concentrated toward an intended direction while the light passes through the microstructure of the encapsulant. The microstructure may be a refractive microstructure or a diffractive microstructure. A refractive microstructure follows the law of refraction and is engineered to direct the light rays toward an object surface so that most reflected light may reach the photodetector  120 . For example, a Fresnel lens microstructure effectively divides the continuous surface of a standard lens into a set of surfaces resulting in a substantial reduction in thickness. A diffractive microstructure re-distributes the propagating light wave energy on the projection plane. For example, a diffractive optical element (DOE) microstructure may be engineered to achieve a specific light distribution profile. A refractive microstructure or a diffractive microstructure is able to concentrate the emitting light from the light source  110  toward a desired direction so that the effective signals are improved. 
     The optical sensor module  10  is a compact packaged module comprising of a light source  110 , a photodetector  120 , an encapsulant, a partition  130 , and a substrate  140 . The present technology improves the performance of the optical sensor module  10  achieved by enhancing the light extraction efficiency, directing the light path, or reducing the stray light. An optical sensor module can be embodied as a simple composition with one light emitting diode (LED) and one silicon photodiode both mounted on a printed circuit board as a substrate  140 . Each of the LED and the silicon photodiode are hermetically and separately sealed by epoxy encapsulants. In an example for measuring oxygenation of biological tissue, wavelengths in infrared and red regions are required. Therefore, one red LED and one infrared LED may be mounted on the same sensor module  10 . In other examples, a single LED can be implemented that emits light in the infrared and red regions of the spectrum. In the embodiments described later in the text, one light source  110  and one photodetector  120  are used as examples. In other implementations that are within the scope of the present disclosure, the number and the arrangement of the light sources  110  and photodetectors  120  may be modified. 
     As shown in  FIG. 1A , the general construction of the optical sensor module  10  is presented in a schematic cross sectional view. The optical sensor module  10  comprises a light source  110 , a photodetector  120  and a partition  130  located between the light source and the photodetector  120 . Each of the light source  110 , the photodetector  120 , the first encapsulant  111 , the second encapsulant  121 , and the partition  130  are mounted on a substrate  140 . The first encapsulant  111  covers the light source  110 , while the second encapsulant covers the photodetector  120 . The optical sensor module has at least a part of the partition  130  being spaced apart from at least one of the first encapsulant  111  and the second encapsulant  121  by a predetermined distance. Furthermore, a microstructure  112  formed on an outer profile of at least one of the first encapsulant  111  and the second encapsulant  121 . In  FIG. 1B , the medial surface  310  of the first encapsulant  111  may have an inclined plane with an inclined angle  315  between the substrate  140  and the medial surface  310 . In one example, the inclined angle  315  is forty degrees when the partition  130  is 0.6 millimeter height and the first encapsulant is about the same height with the partition  130 . 
     In one embodiment of the present disclosure, as shown in  FIGS. 2-5 , the light source  110  is illustrated as two independent LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a photodiode sealed in a second encapsulant  121 . In addition, a partition  130  is located between the LEDs and the photodiode. An optical sensor module may have the packaging wall  131  extending around the encapsulants to reduce ambient stray light. The surface of both encapsulants have a predetermined surface configuration to enhance SNR. For ease of presentation, the medial surface is the surface facing the partition  130  located between the light source  110  and the photodetector  120 , the lateral surface is the surface facing toward the opposite side, and the top surface is about parallel to the substrate plane. The medial surface of the first encapsulant  111  may have an inclined plane or a curvature lens or the combination thereof. An inclined plane may have an inclined angle  315  between the surface of the encapsulant and the plane of the substrate. The inclined angle may be around ninety degrees to twenty degrees. Therefore, light emitted from the light source is less shed onto the partition  130  to avoid light leakage direct from the light source  110  to the photodetector  120 . 
     As illustrated in  FIG. 2A , the light source  110  is sealed in the first encapsulant  111 , and the top surface of the first encapsulant  111  is formed as a microstructure  112 . Additionally, the photodetector  120  is sealed in the second encapsulant  121 , and the top surface of the second encapsulant  121  is formed as a microstructure  122 . In the cross sectional view ( FIG. 2B ) and oblique view ( FIG. 2C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of a single layer in trapezoid shape. The medial and lateral surfaces of both the first encapsulant  111  and second encapsulant  121  have an angle. It is contemplated that the configuration and the material of the second encapsulant  121  may differ from the ones of the first encapsulant  111 , in order to meet the requirements of the light receiving efficiency for specific applications. 
     As illustrated in  FIG. 3A , the light source  110  is sealed in the first encapsulant  111 , and the top surface of the first encapsulant  111  is formed as a microstructure  112 . Additionally, the photodetector  120  is sealed in the second encapsulant  121 , and the top surface of the second encapsulant  121  is formed as a microstructure  122 . In the cross sectional view ( FIG. 3B ) and oblique view ( FIG. 3C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of a single layer in trapezoid style. The medial and lateral surfaces of both the first  111  and second  121  encapsulants have a predetermined inclined angle  315 . Additionally, the medial surface of the first encapsulant  111  has a tilted at a larger angle, so that the light emitted from the medial surface is mostly allowed to pass toward the upper part of the medial surface. In at least one example, the configuration and the material of the second encapsulant  121  may differ from the ones of the first encapsulant  111 . The inclined angle of an inclined plane or a curvature lens may be larger or smaller than the medial surface of the second encapsulant  121 . 
     As illustrated in  FIG. 4A , the light source  110  is sealed in the first encapsulant  111 , and the top surface of the first encapsulant  111  is formed as a microstructure  112 . Additionally, the photodetector  120  is sealed in the second encapsulant  121 , and the top surface of the second encapsulant  121  is formed as a microstructure  122 . In the cross sectional view ( FIG. 4B ) and oblique view ( FIG. 4C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of a single layer in trapezoid style. The medial and lateral surfaces of both the first  111  and second  121  encapsulants have an inclined angle. 
     As illustrated in  FIG. 5A , the light source  110  is sealed in the first encapsulant  111 , and the top surface of the first encapsulant  111  is formed as a microstructure  112 . Additionally, the photodetector  120  is sealed in the second encapsulant  121 , and the top surface of the second encapsulant  121  is formed as a microstructure  122 . In the cross sectional view ( FIG. 5B ) and oblique view ( FIG. 5C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of a single layer in trapezoid style with a curved medial surface. The lateral surfaces of both the first  111  and second  121  encapsulants have a tilting angle. Specifically, the medial surfaces of both the first encapsulant  111  and the second encapsulant  121  have a curved medial surface, so that the extraction light from the medial surface is enhanced toward the upper part of the medial surface and more reflected light is received from the upper part of the medial surface of the second encapsulant  121 . In at least one example, the configuration and the material of the second encapsulant  121  may differ from the ones of the first encapsulant  111 . The inclined angle of the medial surface of the first encapsulant  111  may be different from the inclined angle of the medial surface of the second encapsulant  121 . Furthermore, the optical sensor module may have an inclined plane on the medial surface of the first encapsulant  111 , while a curvature lens on the medial surface of the second encapsulant  121 . 
     In the embodiments shown in  FIG. 6 , the optical sensor modules  10  may be applied directly on the object surface  190  to have the top surfaces of the encapsulants contact the object surface  190 . The object surface  190  may be the surface of a biological tissue, such as a skin or a mucosa. In  FIGS. 6A  and C, the object surface  190  contacts as much the top surface of the encapsulants as possible to achieve better SNR. In the cross sectional view  FIG. 6B , the object surface  190  directly contacts the top surface of the encapsulants. 
     In one embodiment of the present disclosure, as shown in  FIGS. 7-11 , the light source  110  may include two LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a photodiode sealed in a second encapsulant  121 . Each top surface of the encapsulants is configured as a microstructure. The optical sensor module  10  may further comprise a cover  150  above the first encapsulant  111  and the second encapsulant  121 . The cover  150  may be located, during application, between the encapsulants and the object surface  190 . The cover  150  serves as a contact interface between the object surface  190  (for example, a biological tissue surface or a skin surface) to increase the durability of the optical sensor module  10  and the consistency of measurement. The cover  150  provide a contact surface with the object surface  190  and keep the optical path clear from the water or dust. The cover  150  may be integrated as a part of the optical sensor module  10  or may be a part of the housing of the optical sensor device. As shown in  FIGS. 7A  and C, the optical sensor module  10  may further comprise a cover  150  above the first encapsulant  111  and the second encapsulant  121 . In addition, there may be a slight gap between the cover  150  and the top surface of the encapsulants to reduce light leakage via the cover  150  ( FIG. 7B ). 
     In one embodiment as shown in  FIG. 8A , the optical sensor module  10  comprises a cover  150 . In addition, the internal surface or the external surface of the cover  150  may be coated with a thin film  151 . The thin film  151  may be an anti-reflective thin film (such as index-matching thin film or interference thin film), or an anti-scratch thin film (such as polyethylene terephthalate, or silicon hard coating). As shown in  FIG. 8B , the external surface of cover  150  is covered with an anti-scratch thin film  151  and the internal surface of the cover  150  is covered with an anti-reflective thin film  151 . In at least one example, the two surfaces may be covered with same kind of thin film  151  or one of the surfaces of the cover  150  may have no thin film. It is contemplated that the cover  150  may be coated with a filter thin film to clear out undesired range of lights. 
     In one embodiment, the optical sensor module  10  may comprise a thin film  160  covering an encapsulant. With thin film technology, the SNR of the optical signals may be further improved. The thin film  160  may be an anti-reflective thin film or a filter thin film. The anti-reflective thin film may be an index-matching film (for example, Rayleigh film) or an interference film to improve light extraction efficiency by reducing Fresnel reflection at the interface between the encapsulants and the environmental medium. The filter thin film may be a long-pass filter, a short-pass filter, or a band-pass filter to clear down the full width at half maximum (FWHM) of the emitting light or filter out the noise from undesired wavelengths. The optical sensor module  10  may further comprise a thin film  160  covering the surface of the first encapsulant  111  and/or the second encapsulant  121 . 
     As shown in  FIG. 9 , both the surfaces of the first encapsulant  111  and the second encapsulant  121  are coated with a thin film  160 . The thin film  160  of the first encapsulant  111  is embodied as an anti-reflective thin film ( FIG. 9B ) and the thin film  160  of the second encapsulant  121  is embodied as a band-pass filter thin film ( FIG. 9C ). The anti-reflective thin film improves the light extraction efficiency and the band-pass filter thin film reduces noise. In at least one example, the thin film  160  of the first encapsulant  111  is embodied as a band-pass filter thin film and the thin film  160  of the second encapsulant  121  is embodied as an anti-reflective thin film, so that the FWHM of the emitting light has a clear cut-off wavelength and the photodiode detects the filtered signals within a specific range of wavelengths. In the application of fluorescence detection long-pass filter thin film maybe applied to the second encapsulant  121  to acquire a clear fluorescent signal avoiding the excitation light. Also, the optical sensor module  10  may have a cover  150  as shown in  FIG. 10A  and thin films  160  over the first encapsulant  111  and the second encapsulant  121  ( FIGS. 10  B and C). Furthermore, the optical sensor module  10  may further comprise both a cover  150  coated with thin films  151  and the thin films  160  covering the encapsulants ( FIG. 11A ). The thin film  151  of external surface of the cover  150  may be an anti-scratch thin film and the one  151  of the internal surface may be as an anti-reflective thin film ( FIG. 11B ). The thin film  160  of the first encapsulant  111  may be as an anti-reflective thin film ( FIG. 11  C) and the thin film  160  of the second encapsulant  121  may be as a band-pass filter thin film ( FIG. 11D ). 
     The light source  110  and the photodetector  120  in an optical sensor module  10  may be arranged in a two dimensional pattern in order to increase SNR as shown in  FIGS. 12-15 . In general, the light source  110  may be a set of multiple light emitters with different wavelengths encapsulated in the central region; the photodetector  120  may be a single entity surrounding the light source  110 , or may be multiple photodetectors  120  located around the central light source  110 . The central light source  110  is covered with a first encapsulant  111  and each photodetector  120  is covered with a second encapsulant  121  ( FIG. 12A ). In cross sectional view ( FIG. 12B ) and oblique view ( FIG. 12C ), the photodetector  120  sits beside the light source  110 , and the optical insulating partition  130  separates the light source  110  and photodetector  120 . Furthermore, the top surface of the first encapsulant  111  is configured as a microstructure  112 . The first microstructure  112  is capable of guiding the emitting light outward so that more reflected light reaches the surrounding photodetector  120 . Also, the top surface of the second encapsulant  121  is configured as a microstructure  122  to improve the light receiving efficiency. The microstructure  122  of the second encapsulant  121  may have different designs from the one of the first encapsulant  111  to improve SNR. In at least one example, the configuration of the encapsulants (for example, microstructure), the surface thin film  160  covering the encapsulants, and the cover  150  mentioned in  FIG. 7-11  may be applied to the two dimensional pattern sensor module  10  described in  FIG. 12-15 . 
     In one embodiment of the present disclosure, as shown in  FIG. 13 , the light source  110  is illustrated as two independent LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a single annular photodiode sealed in a second encapsulant  121 . In addition, an annular partition  130  is located between the LEDs and the photodiode to reduce direct light leakage from the light source  110  to the photodetector  120 ; a second annular partition  130  may reside around the second encapsulant  121  to reduce ambient stray light. 
     As illustrated in  FIG. 13A , the optical sensor module  10  can be embodied as a single annular photodiode surrounding the central light source  110 . The central light source  110  may comprise two LEDs having different emitting wavelength(s), and the both of the two LEDs are covered with the first encapsulant  111 . The photodetector  120  may be a single piece of annular silicon photodiode surrounding the central light source  110 , and the annular photodiode is covered with the annular second encapsulant  121 . The top surface of the first encapsulant  111  is configured as a microstructure  112 , and the first microstructure  112  may be in a concentric circular pattern. Additionally, the top surface of the second encapsulant  121  is configured as a second microstructure  122 , which can be a concentric circular pattern. In the cross sectional view ( FIG. 13B ) and oblique view ( FIG. 13C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of in trapezoid shape, which features the narrower upper part of the encapsulant. The arrangement of the first encapsulant and the second encapsulants may be a reflectional symmetric patterns, such as linear, elliptic, hexagonal, or polygonal. The patterns may have some extent of SNR improvement due to the photodetector  120  locating beside the light source  110 . In at least one example, the construction, the microstructure, the material of the second encapsulant  121  may differ from the ones of the first encapsulant  111 , in order to meet the requirements of the light receiving efficiency for specific applications. For example, the second encapsulants have multilayer construction with microstructures on the top surfaces. 
     In one embodiment of the present disclosure, as shown in  FIG. 14 , the light source  110  is illustrated as two independent LEDs sealed in the first encapsulant  111 , and the photodetector  120  may be a group of separate photodiodes, each sealed in a second encapsulant  121 . In addition, a partition  130  is located around the LEDs to reduce direct crosstalk; the photodiodes may have a packaging wall  131  around the second encapsulants  121  to reduce both direct crosstalk and ambient stray light. 
     As illustrated in  FIG. 14A , the optical sensor module  10  may be embodied as multiple photodiodes surrounding the central light source  110 . The central light source  110  may comprise two LEDs of different emitting wavelength, and the LEDs are covered with a first encapsulant  111 . The photodetectors  120  may be a group of square photodiodes annularly arranged around the central light source  110 , and each photodiode is covered with a second encapsulant  121 . Also, a hexagonal partition  130  is located around the LEDs to reduce direct light leakage; photodiodes may have a lateral packaging wall  131  around the second encapsulants  121  to reduce and ambient stray light. In the cross sectional view ( FIG. 14B ) and oblique view ( FIG. 14C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of in trapezoid shape, which features the narrower upper part of the encapsulant. The top surface of the first encapsulant  111  is configured as a microstructure  112 , and the first microstructure  112  may be embodied as a concentric circular pattern. Additionally the top surface of the second encapsulant  121  is configured as a microstructure  122 , and the second microstructure  122  may be embodied as a concentric circular pattern. While the illustrated pattern is a hexagonal pattern, the present disclosure includes other types of polygonal patterns, such as triangular, pentagonal, or octagonal. All other patterns may have some extent of SNR improvement due to the photodetectors  120  locating beside the light source  110 . In at least one example, the construction, the microstructure, the material of the second encapsulants  121  may differ from the ones of the first encapsulant  111 , in order to meet the requirements of the light receiving efficiency for specific applications. 
     As illustrated in  FIG. 15A , the optical sensor module  10  may be embodied as multiple photodiodes surrounding the central light source  110 . The central light source  110  may comprise two LEDs of different emitting wavelength, and the LEDs is covered with a first encapsulant  111 . The photodetectors  120  may be a group of square photodiodes annularly arranged around the central light source  110 , and each photodiode is covered with a second encapsulant  121 . Additionally, a square partition  130  is located around the light source  110  and the photodetectors  120  may have a lateral packaging wall  131  around the second encapsulants  121  to reduce ambient stray light. In the cross sectional view ( FIG. 15B ) and oblique view ( FIG. 15C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed with the feature of the narrower upper part of the encapsulant. The top surface of the first encapsulant  111  is configured as a microstructure  112 , and the first microstructure  112  may be embodied as a concentric circular pattern. Additionally, the top surface of the second encapsulant  121  is configured as a microstructure  122 , and the second microstructure  122  may be embodied as a concentric circular pattern. Without departing from the scope of the disclosure the arrangement pattern of an optical sensor module may be other polygonal patterns, such as triangular, pentagonal, or octagonal. All other patterns may have some extent of SNR improvement due to the photodetectors  120  locating beside the light source  110 . In at least one example, the construction, the microstructure, the material of the second encapsulants  121  may differ from each other or the ones of the first encapsulant  111 . 
     In the present disclosure, the optical sensor module  10  may employ the encapsulant  111  with multiple refractive index layers over the light source  110  for improving the light extraction efficiency or may employ the encapsulant  111  with multiple refractive index layers over the photodetector  120  for improving reflected light receiving efficiency. The optical sensor module  10  enhances the signal strength because the total internal reflection of the emitted light is reduced while the light passes through the encapsulant  111  layer by layer outward from the light source  110 . 
     For example, the first encapsulant  111 , formed on the substrate  140  over the light source  110 , includes multiple refractive index layers. Multiple refractive index layers may be constructed by stacking multiple physical layers with different refractive indices or may be constructed by a single entity of gradient refractive index. The refractive index of each layer of the first encapsulant  111  decreases layer by layer from lower layers to upper layers. As shown in the  FIG. 16A , the first encapsulant  111  includes a plurality of layers (two layers are illustrated) in which each layer is formed of material that allows the emitted light by the light source  110  to pass through. For example, the refractive index (n 1 ) of the lower layer (bottom layer) of the first encapsulant  111 , formed directly over the light source  110 , is higher than the refractive index (n 2 ) of the upper layer (top layer), which abuts the top surface of the bottom layer, of the first encapsulant  111 . With respect to conventional encapsulant with only a single refractive index layer over the light source  110 , the decreasing refractive index of the adjacent layers of the first encapsulant  111 , gradually mediates a drastic refractive index difference between the light source  110  and the environmental medium. Generally, the refractive index of an optoelectronic transducer is greater than three, while the refractive index of ambient air is about one. The critical angle (θc=arc sin(n 2 /n 1 )) occurs at the interface of adjacent layers of the first encapsulant  111  has a significant increase compared to a bare light source  110  alone or a light source  110  merely with a single layer of encapsulant. Also, the critical angle at the interface between the top layer of the first encapsulant  111  and the environmental medium surrounding the optical sensor module  10  is widened. The amount of the total internal reflection is reduced while the light emitted by the light source  110  sequentially passes through the decreasing refractive indices of the multiple layers in the first encapsulant  111 . Consequently, the optical sensor module  10  enhances the signal strength by improving the light extraction efficiency according to the first encapsulant  111  with a plurality of refractive index layers. Similarly, a second encapsulant with multiple refractive index layers may be formed over a photodetector  120  to improve light receiving efficiency for the signal light coming from the light source  110  and reflected by an object surface. 
     As shown in  FIG. 16A , the general construction of the optical sensor module  10  is presented in a schematic cross sectional view. The optical sensor module  10  comprises a LED, a silicon photodiode, and a partition  130  located between the LED and the photodetector  120 , wherein all the above are mounted on a substrate  140 . The first encapsulant  111  covers the light source  110 , while the second encapsulant  121  covers the photodetector  120 . In the embodiments, an encapsulant may have modifications in configuration and construction. For example, the top surface of the first encapsulant  111  is configured as a first microstructure  112 , and the second encapsulant  121  may have a second microstructure  122 . The first encapsulant  111  is constructed with multiple refractive index layers, and a double layer construction is illustrated in  FIG. 16A , while three or more layers may be realized. The interface between any two layers may also have a configuration, such as a microstructure  112  or an optical directional component  113 . Similarly, the second encapsulant  121  may also be constructed with multiple layers and may have a surface microstructure  122  or a configuration (for example, a curvature lens) at the interface between any two layers. In addition, the second encapsulant  121 , in order to improve the light receiving efficiency, may have different designs in the construction and configuration from the first encapsulant  111 . 
       FIG. 16B-E  shows the relation between refractive index within an encapsulant with multiple refractive index layers and distance from the substrate. In  FIG. 16B , a dot line connecting between x 0  and x 1  indicates the corresponding measurements of refractive index, where x 0  represents one of the most proximal portions in an encapsulant and x 1  represents one of the most distal portions in an encapsulant.  FIG. 16C-E  shows the refractive index function of distance from the substrate. In one example as illustrated in  FIG. 16C , the encapsulant with multiple refractive index layers has gradient refractive index. In one example as illustrated in  FIG. 16D , the encapsulant with multiple refractive index layers has discrete refractive indices. In one example as illustrated in  FIG. 16E , the encapsulant with multiple refractive index layers has multiple physical layers with gradient refractive index. In addition, the gradient refractive index may be linear or non-linear to the distance. The refractive index function of distance may be monotonically decreasing. In addition, non-monotonicity of the refractive index function of distance may be tolerable. 
     In one embodiment of the present disclosure, as shown in  FIGS. 17-19 , the light source  110  is illustrated as two independent LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a photodiode sealed in a second encapsulant  121 . The first encapsulant  111  and/or the second encapsulant  121  is constructed with multiple refractive index layers, and the top surface of the first encapsulant  111  or the second encapsulant  121  is configured as a microstructure  112 . 
     As illustrated in  FIG. 17A , the top surface of the upper layer of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode, while a photodiode is sealed in the second encapsulant  121  without a microstructure. In the cross sectional view ( FIG. 17B ) and oblique view ( FIG. 17C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of a stack of multiple layers in Babel Tower style, which features the distal portion of the encapsulant is narrower than the proximal portion. Also, the multiple refractive index layers has different refractive indices arranged in a decreasing fashion from proximal layers to distal layers. 
     As illustrated in  FIG. 18A , the top surface of the distal layer of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode, while a photodiode is sealed in the second encapsulant  121  without a microstructure. In the cross sectional view ( FIG. 18B ) and oblique view ( FIG. 18C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed in multiple refractive index layers in a pancake stack style, which features the circumferential flank sides of the multi-layer encapsulant abutting the partition  130  and the packaging wall  131 . The multiple refractive index layers has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     As illustrated in  FIG. 19A , the top surface of the distal layer of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode, while a photodiode is sealed in the second encapsulant  121  without a microstructure. In the cross sectional view ( FIG. 19B ) and oblique view ( FIG. 19C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed in multiple refractive index layers in a cup-stacking style, which features the upper layer embracing the adjacent lower layer. The multiple refractive index layers has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     It is contemplated that the second encapsulant  121  may be constructed as a single entity (single layer) or a multi-layer stack, and constructed in various stacking styles. The construction and the material of the second encapsulant  121  may differ from the ones of the first encapsulant  111 , in order to meet the requirements of the light receiving efficiency for specific applications. 
     In one embodiment of the present disclosure, as shown in  FIGS. 20-22 , the light source  110  is illustrated as two independent LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a photodiode sealed in a second encapsulant  121 . The first encapsulant  111  is constructed with a multiple refractive index layers, and the top surface of the first encapsulant  111  is configured as a microstructure  112 . Also, the second encapsulant  121  is constructed with multiple refractive index layers, and the top surface of the second encapsulant  121  is configured as a microstructure  122 . 
     As illustrated in  FIG. 20A , the top surface of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode. Additionally, the top surface of the second encapsulant  121  is configured as a microstructure  122 , which is embodied as a set of concentric circles. In the cross sectional view ( FIG. 20B ) and oblique view ( FIG. 20C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of multiple refractive index layers in Babel Tower style. Also, the multiple refractive index layers has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. It is contemplated that the second encapsulant  121  may be constructed as a single entity (single layer) or a multi-layer stack, and constructed in various stacking styles. The construction and the material of the second encapsulant  121  may differ from the ones of the first encapsulant  111 , in order to meet the requirements of the light receiving efficiency for specific applications. 
     As illustrated in  FIG. 21A , the top surface of the upper layer of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode. Additionally, the top surface of the second encapsulant  121  is configured as a microstructure  122 , and the microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 21B ) and oblique view ( FIG. 21C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed in multiple refractive index layers in a pancake stack style, which features the flank sides of the multi-layer encapsulant abutting the packaging wall  131 . Also, the multiple refractive index layers has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     As illustrated in  FIG. 22A , the top surface of the upper layer of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode. Additionally, the top surface of the second encapsulant  121  is configured as a microstructure  122 , and the microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 22B ) and oblique view ( FIG. 22C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed in multiple refractive index layers in a cup-stacking style. Also, the multiple refractive index layers construction has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     In one embodiment of the present disclosure, as shown in  FIGS. 23-25 , the light source  110  is illustrated as two independent LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a photodiode sealed in a second encapsulant  121 . The first encapsulant  111  is constructed with multiple refractive index layers, and one interface of any two adjacent layers of the first encapsulant  111  is configured as a microstructure  112 . Also, one interface of any two adjacent layers of the second encapsulant  121  may be configured as a microstructure  122 . 
     As illustrated in  FIG. 23A , one interface of any two adjacent layers of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode. Additionally, one of the interface of any two adjacent layers of the second encapsulant  121  is configured as a microstructure  122 , and the microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 23B ) and oblique view ( FIG. 23C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed with multiple refractive index layers in Babel Tower style. Also, the multiple refractive index layers construction has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     As illustrated in  FIG. 24A , one interface of any two adjacent layers of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode. Additionally one interface of any two adjacent layers of the second encapsulant  121  is configured as a microstructure  122 , and the microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 24B ) and oblique view ( FIG. 24C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed multiple refractive index layers in a pancake stack style. 
     As illustrated in  FIG. 25A , one interface of any two adjacent layers of the first encapsulant  111  is configured as a microstructure  112 , and the microstructure  112  is embodied as a set of concentric arcs concaved toward the photodiode. Additionally, one interface of any two adjacent layers of the second encapsulant  121  is configured as a microstructure  122 , which is embodied as a set of concentric circles. In the cross sectional view ( FIG. 25B ) and oblique view ( FIG. 25C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed with multiple refractive index layers in a cup-stacking style. Also, the multiple refractive index layers construction has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     In one embodiment of the present disclosure, as shown in  FIGS. 26-28 , the light source  110  is illustrated as two independent LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a photodiode sealed in a second encapsulant  121 . The first encapsulant  111  is constructed with multiple refractive index layers, and multiple interfaces of any two adjacent layers of the first encapsulant  111  is configured as a microstructure  112 . 
     As illustrated in  FIG. 26A , the first encapsulant  111  has multiple microstructures  112  formed as the top surface of the uppermost layer and formed as one interface of the adjacent layers inside, and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodetector  120 , while the second encapsulant  121  may be constructed with multiple refractive index layers without a microstructure. In the cross sectional view ( FIG. 26B ) and oblique view ( FIG. 26C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed with multiple refractive index layers in Babel Tower style. Also, the multiple refractive index layers construction has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. It is contemplated that the second encapsulant  121  may also have microstructures on the top surface and/or at one interface between any layers. 
     As illustrated in  FIG. 27A , the first encapsulant  111  has multiple microstructures  112  formed as the top surface of the uppermost layer and formed as one interface of the adjacent layers inside, and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodetector  120 , while the second encapsulant  121  may be constructed with multiple refractive index layers without a microstructure. In the cross sectional view ( FIG. 27B ) and oblique view ( FIG. 27C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of a stack of multiple layers in a pancake stack style, which features the flank sides of the multi-layer encapsulant abutting the packaging wall  131 . Also, the multi-layer construction has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     As illustrated in  FIG. 28A , the first encapsulant  111  has multiple microstructures  112  formed as the top surface of the uppermost layer and formed as one interface of the adjacent layers inside, and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodetector  120 , while the second encapsulant  121  may be constructed with multiple refractive index layers without a microstructure. In the cross sectional view ( FIG. 28B ) and oblique view ( FIG. 28C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of a stack of multiple layers in a cup-stacking style, which features the upper layer embracing the adjacent lower layer. Also, the multi-layer construction has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     In the examples of the present disclosure, the light source  110  is illustrated as two independent LEDs sealed in a first encapsulant  111 , and the photodetector  120  may be a photodiode sealed in a second encapsulant  121 . The first encapsulant  111  is constructed with multiple refractive index layers, and at least one interface of any two adjacent layers of the first encapsulant  111  is configured as a microstructure  112 . Also, the second encapsulant  121  is constructed with multiple refractive index layers, and at least one interface of any two adjacent layers of the second encapsulant  121  is configured as a microstructure  122 . 
     As illustrated in  FIG. 29A , the first encapsulant  111  has multiple microstructures  112  formed as the top surface of the first encapsulant  111  and formed as one interface of the adjacent layers and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodetector  120 . Additionally, a photodiode is sealed in the second encapsulant  121  with multiple microstructures  122  formed as the top surface of the second encapsulant  121  and formed as one interface of the adjacent layers, and each microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 29B ) and oblique view ( FIG. 29C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed of multiple refractive index layers in Babel Tower style. Also, the multi-layer construction has different refractive indices arranged in a decreasing fashion from lower layers to upper layers. 
     As illustrated in  FIG. 30A , the first encapsulant  111  has multiple microstructures  112  formed as the top surface of the first encapsulant  111  and formed as one interface of the adjacent layers and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodetector  120 . Additionally, a photodiode is sealed in the second encapsulant  121  with multiple microstructures  122  formed as the top surface of the second encapsulant  121  and formed as one interface of the adjacent layers, and each microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 30B ) and oblique view ( FIG. 30C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed with multiple refractive index layers in a pancake stack style. 
     As illustrated in  FIG. 31A , the first encapsulant  111  has multiple microstructures  112  formed as the top surface of the first encapsulant  111  and formed as one interface of the adjacent layers and the microstructure  112  is embodied as a set of concentric arcs concave toward the photodetector  120 . Additionally, a photodiode is sealed in the second encapsulant  121  with multiple microstructures  122  formed as the top surface of the second encapsulant  121  and formed as one interface of the adjacent layers, and each microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 31B ) and oblique view ( FIG. 31C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed with multiple refractive index layers in a cup-stacking style. 
     An optical directional component is a geometric optical component having a distinct refractive index from adjacent substances. Light refraction occurs when incident light travels through the refraction interface at an incident angle other than normal incidence. The refraction interface is a flat or curved plane and the inclined angle and the curvature of the plane is designed to meet the requirements. In one example, the optical directional component may be a curvature lens configured to direct the light path so that the SNR is further improved. The curvature lens may be configured at one interface of any adjacent layers in the encapsulant with multiple refractive index layer or may be configured on the top surface of an encapsulant. The shape of a curvature lens may be a parabolic plane, a spherical plane, or a polygonal plane. 
     As illustrated in  FIG. 32A , the first encapsulant  111  has the configurations as a microstructure  112  formed as the top surface of the uppermost layer. In addition, one interface of the first encapsulant  111  with multiple refractive index layers may be configured as a curvature lens  113 . The microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode and the curvature lens  113  is embodied as a parabolic surface concave to the light source  110 , while a photodiode is sealed in the second encapsulant  121  without a microstructure. In the cross sectional view ( FIG. 32B ) and oblique view ( FIG. 32C ), the first encapsulant  111  is constructed with multiple refractive index layers in cup-stacking style and the second encapsulant  121  is constructed with multiple refractive index layers in Babel Tower style. Also, the multi-layer construction has different refractive indices arranged in a decreasing fashion from proximal layers to distal layers. 
     As illustrated in  FIG. 33A , the first encapsulant  111  has the configurations as microstructure  112  formed as the top surface of the uppermost layer. In addition, one interface of the first encapsulant  111  with multiple refractive index layers may be configured as a curvature lens  113 . The microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode and the curvature lens  113  is embodied as a parabolic surface concave to the light source  110 , while a photodiode is sealed in the second encapsulant  121  without a microstructure. In the cross sectional view ( FIG. 33B ) and oblique view ( FIG. 33C ), the first encapsulant  111  is constructed with multiple refractive index layers in cup-stacking style and the second encapsulant  121  is constructed with multiple refractive index layers in pancake stack style. Also, the multi-layer construction has different refractive indices arranged in a decreasing fashion from proximal layers to distal layers. 
     As illustrated in  FIG. 34A , the first encapsulant  111  has the configurations as microstructure  112  formed as the top surface of the uppermost layer. In addition, one interface of the first encapsulant  111  with multiple refractive index layers may be configured as a curvature lens  113 . The microstructure  112  is embodied as a set of concentric arcs concave toward the photodiode and the curvature lens  113  is embodied as a parabolic surface concave to the light source  110 , while a photodiode is sealed in the second encapsulant  121  without a microstructure. In the cross sectional view ( FIG. 34B ) and oblique view ( FIG. 34C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed with multiple refractive index layers in a cup-stacking style. Also, the multi-layer construction has different refractive indices arranged in a decreasing fashion from proximal layers to distal layers. 
     As illustrated in  FIG. 35A , a photodiode is sealed in the second encapsulant  121  with a microstructure  122  formed as the top surface of the uppermost layer and the microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 35B ) and oblique view ( FIG. 35C ), the second encapsulant  121  is constructed with multiple refractive index layers in Babel Tower style. 
     As illustrated in  FIG. 36A , a photodiode is sealed in the second encapsulant  121  with a microstructure  122  formed as the top surface of the uppermost layer and the microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 36B ) and oblique view ( FIG. 36C ), the second encapsulant  121  is constructed with multiple refractive index layers in pancake stack style. 
     As illustrated in  FIG. 37A , a photodiode is sealed in the second encapsulant  121  with a microstructure  122  formed as the top surface of the uppermost layer and the microstructure  122  is embodied as a set of concentric circles. In the cross sectional view ( FIG. 37B ) and oblique view ( FIG. 37C ), the second encapsulant  121  is constructed with multiple refractive index layers in a cup-stacking style. 
     In one example as shown in  FIG. 38A , a photodiode is sealed in the second encapsulant  121  with a microstructure  122  formed as the top surface of the uppermost layer. In the example, the optical sensor module comprises optical directional components  123  disposed between the two adjacent refractive index layers, wherein the optical directional components are curvature lenses. Further, two curvature lenses  123  are configured in the second encapsulant  121 . In the cross sectional view ( FIG. 38B ) and oblique view ( FIG. 38C ), the first encapsulant  111  is constructed with multiple refractive index layers in cup-stacking style and the second encapsulant  121  is constructed of a stack of multiple layers in Babel Tower style, where the curvature lenses  123  are embodied as parabolic plane concave to the photodiode. 
     In one embodiment of the present disclosure, the optical sensor modules  10  may further comprise a cover  150  distal to the first encapsulant  111  and/or the second encapsulant  121 . The cover  150  serves as a contact interface between the object surface  190 , such as a biological tissue surface or a skin surface, to increase the durability of the optical sensor module  10  and the consistency of measurement. As shown in  FIG. 39A , the optical sensor modules  10  may also comprise a cover  150  in front of the first encapsulant  111  and the second encapsulant  121 , and the cover  150  is located between the encapsulants and the object surface  190 . With a slight press, the cover  150  provide an increased contact area with the object surface  190  to allow better optical reflection and diffusion. The cover  150  may be integrated as a part of the optical sensor module  10  or may be a part of the housing of the optical sensor device. 
     In addition, the internal surface or the external surface of the cover  150  may be coated with a thin film  151 . The thin film  151  may be an anti-reflective or an anti-scratch thin film. As shown in  FIG. 39B , the thin film  151  of external surface of the cover  150  is embodied as an anti-scratch thin film (such as polyethylene terephthalate, or silicon hard coating) and the one of the internal surface is embodied as an anti-reflective thin film. 
     The optical sensor modules  10  may also comprise a thin film  151  covering an encapsulant. With thin film technology, the SNR of the optical sensor module  10  may be further improved. The thin film  151  may be an anti-reflective thin film or a filter thin film. The anti-reflective thin film may be an index-matching film (for example, Rayleigh film) or an interference film to improve light extraction efficiency by reducing Fresnel reflection at the interface between different refractive indices. The filter thin film may be a long-pass filter, a short-pass filter, or a band-pass filter to clear down the full width at half maximum (FWHM) of the emitting light or filter out the noise from undesired wavelengths. Additionally, the anti-scratch thin film may be applied to prevent the signal loss caused by scratches. 
     As shown in  FIG. 40A , both the surfaces of the first encapsulant  111  and the second encapsulant  121  are coated with a thin film  160 . The thin film  160  of the first encapsulant  111  is embodied as an anti-reflective thin film ( FIG. 40B ) and the thin film  160  of the first encapsulant  111  is embodied as a band-pass filter thin film ( FIG. 40C ). The anti-reflective thin film improves the light extraction efficiency and the band-pass filter thin film reduces noise. It is contemplated that the thin film  160  of the first encapsulant  111  is embodied as a band-pass filter thin film and the thin film  160  of the first encapsulant  111  is embodied as an anti-reflective thin film, so that the FWHM of the emitting light has a clear cut-off wavelength and the photodiode detects the filtered signals within a specific window. In the application of the fluorescence detection long-pass filter thin film maybe applied to the second encapsulant  121  to acquire a clear fluorescent signal avoiding the excitation light. Also, the optical sensor module  10  may further comprise a cover  150  in front of the first encapsulant  111  and the second encapsulant  121 . As shown in  FIG. 41A , the optical sensor module  10  further comprises a cover  150  and the thin films  160  covering the encapsulants ( FIGS. 41B and 41C ). 
     Furthermore, the optical sensor module  10  may further comprise both a cover  150  coated with thin film  151  and the thin films  160  covering the encapsulants ( FIG. 42A ). As shown in  FIG. 42B , the thin film  151  of external surface of the cover  150  is embodied as an anti-scratch thin film (such as polyethylene terephthalate, or silicon hard coating) and the one of the internal surface is embodied as an anti-reflective thin film. The thin film  160  of the first encapsulant  111  is embodied as an anti-reflective thin film ( FIG. 42C ) and the thin film  160  of the first encapsulant  111  is embodied as a band-pass filter thin film ( FIG. 42D ). 
     The optical sensor module  10  may have an optical directional component on the medial surface of the first encapsulant  111  or on the medial surface of the second encapsulant  121 . The optical directional component may have an inclined plane or a curvature lens or the combination thereof. An inclined plane may have an inclined angle  315  between the surface of the encapsulant and the plane of the substrate. The inclined angle may be around ninety degrees to twenty degrees. In addition, a curvature lens may be configured in combination of an inclined plane. In one example, the curvature lens may have a radius of curvature with 0.6 millimeter and the inclined angle is about forty degrees when the partition has a height of 0.4 millimeter. Therefore, light emitted from the light source is more concentrated above the partition located between the light source and the photodetector, and less shed onto the partition  130 . 
     As illustrated in  FIG. 43A , the medial surface of the first encapsulant  111  is configured as an optical directional component  113 , and the optical directional component  113  is embodied as an inclined plane, while the photodetector  120  is sealed in the second encapsulant  121  with an inclined plane with a larger inclined angle. In the cross sectional view ( FIG. 43B ) and oblique view ( FIG. 43C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed in trapezoid shape. The optical directional component  113  of the medial surface of the first encapsulant  111  has an inclined angle smaller than the inclined angle of the second optical directional component  123 . 
     As illustrated in  FIG. 44A , the medial surface of the first encapsulant  111  is configured as an optical directional component  113 , and the optical directional component is embodied as an inclined plane. Additionally, the photodetector  120  is sealed in the second encapsulant  121  with an optical directional component  123  as an inclined plane. In the cross sectional view ( FIG. 44B ) and oblique view ( FIG. 44C ), both the first encapsulant  111  and the second encapsulant  121  are separately constructed in trapezoid shape. The first encapsulant  111  and the second encapsulant  121  has an inclined plane with an inclined angle to facilitate light extraction efficiency and light receiving efficiency, respectively. The inclined angle of the first optical directional component  113  may be different from the inclined angle of the second optical directional component  123 . 
     As illustrated in  FIG. 45A-C , the medial surface of the first encapsulant  111  is configured as an optical directional component  113 , and the optical directional component  113  is embodied as a curvature plane. Additionally, the photodetector  120  is sealed in the second encapsulant  121  with an optical directional component  123 , which is embodied as a curvature plane. In the cross sectional view ( FIG. 45B ) and oblique view ( FIG. 45C ), both the first encapsulant  111  and the second encapsulant  121  are separately configured with a curvature plane on the medial surface. It is contemplated that the optical directional component of the second encapsulant  121  may differ from the one of the first encapsulant  111 . For example, the first encapsulant may have a curvature plane on the medial surface, while the second encapsulant has an inclined plane. 
       FIGS. 46-48  shows the situation of measuring the reflected light from an object surface  190  by the optical sensor module  10  with optical directional components, but other optical sensor modules within the present disclosure is also suitable for the application. The object surface  190  may be a surface of a biological tissue, such as skin or mucosa. The optical sensor module  10  is tolerable to various working conditions, such as rough object surface and relative motion between the sensor module and object surface. In  FIGS. 46A and 46B , the top surface of the optical sensor module  10  may directly contact with the object surface  190 . In  FIGS. 47A and 47B , the upper side of the optical sensor module  10  may have a limited distance from the object surface  190  but the optical sensor module  10  is still capable of acquiring sufficient effective signals. In  FIGS. 48A and 48B , a cover  150  may directly attach the object surface  190 , and the optical sensor module  10  have a limited distance from the cover  150 . The cover  150  may be a part of optical sensor module  10  or be integrated with a housing of an optical sensing accessory or an optical sensing device. The material of the cover may be selected from organic glass, such as PMMA or PC, or inorganic glass such as silicate glass or silicone compound. In addition, the internal surface or the external surface of the cover  150  may be coated with a thin film. The thin film may be an anti-reflective (such as index-matching thin film or interference thin film) or an anti-scratch thin film (such as polyethylene terephthalate, or silicon hard coating). Furthermore, the optical sensor module  10  may further comprise a thin film covering an encapsulant. With thin film technology, the SNR of the optical signals may be further improved. The thin film may be an anti-reflective thin film or a filter thin film. The anti-reflective thin film may be an index-matching film (for example, Rayleigh film) or an interference film to improve light extraction efficiency by reducing Fresnel reflection at the interface between the encapsulants and the environmental medium. The filter thin film may be a long-pass filter, a short-pass filter, or a band-pass filter to clear down the full width at half maximum (FWHM) of the emitting light or filter out the noise from undesired wavelengths. 
     Furthermore, a cover  150  may be coupled to the partition  130  and the packaging wall  131  enclosing the first encapsulant  111  and the second encapsulant  121 . The cover may have surface configurations, such as a microstructure, a curvature lens, or the combination thereof. The cover may have tight connection to the packaging wall  131  to have good protection from ambient moisture, water, or dusts. 
     In  FIG. 49A-C , the cover  150  is configured with a planar surface with a microstructure on the inner surface of the cover  150 . In  FIG. 49A , the cover comprises two optical transparent windows  152  and each window is located beyond the first encapsulant  111  or the second encapsulant  121 . In  FIGS. 49B and 49C , the cover comprises two microstructures on the inner surface of the optical transparent windows  152 . 
     In  FIG. 50A-C , the cover  150  is configured with a curvature lens on the surface of the cover  150 . In  FIG. 50A , the cover comprises two semicircular optical transparent windows  152  and each window is located beyond the first encapsulant  111  or the second encapsulant  121 . In  FIGS. 50B and 50C , the cover  150  comprises two plano-convex lens on the surface of the optical transparent windows. 
     In  FIG. 51A-C , the cover  150  is configured with a curvature lens on the outer surface of the cover  150  and a microstructure on the inner surface of the cover  150 . In  FIG. 51A , the cover comprises two semicircular optical transparent windows  152  and each window is located beyond the first encapsulant  111  or the second encapsulant  121 . In  FIGS. 51B and 51C , each optical transparent window has a plano-convex lens on the outer surface and a microstructure on the inner surface. 
     In  FIG. 52A-C , the cover  150  is configured with a curvature lens on the surface of the cover  150 . In  FIG. 52A , the cover comprises two optical transparent windows  152  and each window is located beyond the first encapsulant  111  or the second encapsulant  121 . In  FIGS. 52B and 52C , the optical transparent window on the light source side has a plano-convex lens and the optical transparent window on the light source side has a plano-concave lens. 
     In  FIG. 53A-C , the cover  150  is configured with a curvature lens on the outer surface of the cover  150  and a microstructure on the inner surface of the cover  150 . In  FIG. 53A , the cover comprises two optical transparent windows  152  and each window is located beyond the first encapsulant  111  or the second encapsulant  121 . In  FIGS. 53B and 53C , the optical transparent window on the light source side has a plano-convex lens and the optical transparent window on the light source side has a plano-concave lens. Both the plano-convex lens and the plano-concave lens further comprise microstructures on the inner surface of the cover  150 . 
     In  FIG. 54A-C , the cover  150  is configured with a curvature lens on the surface of the cover  150 . In  FIG. 54A , the cover  150  comprises two optical transparent windows  152  and each window is located beyond the first encapsulant  111  or the second encapsulant  121 . In  FIGS. 54B and 54C , each of the optical transparent windows has a meniscus lens. 
     An optical sensor module may further comprise a microcontroller, an analogue front end, an operational amplifier, a light source driver or the combination thereof. A microcontroller is an integrated circuit chip configured to trigger the emittance of the light sources or to process the signals received from the photodetectors. An analogue front end is configured to receive and process the analogue signals from the photodetectors. The microcontroller and analogue front end may have a function of analogue to digital signal conversion. An operational amplifier is configured to receive and process the analogue signals from the photodetectors. An operational amplifier can amplify at least a part of the signals to achieve signal augmentation, filtering, or noise reduction. A light source driver is configured to control the electrical current flow through the light source, such as LED or laser diode. The electrical connections between an analogue front end, a microcontroller, an operational amplifier, a light source driver, the light source and the photodetectors may be coupled through the circuit printed within the substrate. 
     In  FIG. 55A-C , an optical sensor module has an analogue front end  141  between the encapsulants and the substrate to receive the signals from a photodetector  120 . The analogue front end can be integrated as a part of the substrate  140  and have electrical connection to the photodetector  120 . In  FIGS. 56A and 56B , an optical sensor module has an analogue front end  141  beside the encapsulants separated by the packaging walls. 
     In  FIGS. 57A and 57B , an optical sensor have two light sources  110 , a photodetector  120 , a partition  130 , the packaging walls  131 , a microcontroller  142  and an analogue front end  141  beside the encapsulants separated by the packaging walls  131 . The microcontroller  142  and the analogue front end  141  may have electrical connections to each other and to the photodetectors  120 . 
     In  FIGS. 58A and 58B  an optical sensor module have a light source  110 , four photodetectors  120 , a partition  130 , a microcontroller  142  and an analogue front end  141 . A microcontroller  142  and an analogue front end  141  are separately located between the two second encapsulants  121  and beside the partition  130 . The analogue front end may have electrical connections to the photodetectors  120  and the microcontroller  142  has electrical connections of the analogue front end  141  to receive the signals processed by the analogue front end  141  from the photodetectors  120 . In  FIGS. 59A and 59B  sensor have a light source  110 , four photodetectors  120 , a partition  130 , a microcontroller  142  and three analogue front ends  141 . The microcontroller  142  and the three analogue front ends  141  are separately located between the two second encapsulants  121  and beside the partition  130 . 
     In  FIGS. 60A and 60B  an optical sensor module has a light source  110 , four photodetectors  120 , a partition  130 , a microcontroller  142 , an operational amplifier  143  and a light source driver  144 . The microcontroller  142 , the operational amplifier  143  and the light source driver are separately located between the two second encapsulants  121  and beside the partition  130 . The light source driver  144  is connected to the light source  110  to control the emitting frequency, duration, or intensity. The operational amplifier may have electrical connections to the photodetectors to augment the photocurrent and the microcontroller connects to the operational amplifier to receive the signals processed by the operational amplifier. 
     An optical sensor module  10  may be a multi-directional optical sensor module  5 . In some examples, the multi-directional optical sensor module  5  is a bi-directional sensor module  5 . The bi-directional optical sensor module  5  is manufactured to emit light and detect the reflected light from two directions, and the received reflected light will be proportionally transduced into electrical current. Bi-directional sensor module  5  comprises a light source  110 , a first encapsulant  111  over the light source  110 , two photodetectors  120 , wherein all mentioned above are mounted on a substrate  140 . Each photodetector  120  is covered by a second encapsulant  121  and both second encapsulants  121  are covered by the first encapsulant  111 . The bi-directional optical sensor module  5  may be fabricated in a single compact package. Using the two photodetectors  120 , the bi-directional optical sensor module  5  may detect light from different parts of body for various applications. It is also contemplated that the bi-directional optical sensor module  5  may employ a discrete light source  110  and a photodetector  120  that are separately packaged and mounted to one or more printed circuit boards (also referred to as “PCB”) depending on various design requirements. In addition, the light source may comprise an array of LEDs or a plurality of LEDs, while each photodetector may comprise an array of photodiodes or a plurality of photodiodes. 
     The construction of the encapsulants features a light splitting and light extraction design for the first encapsulant  111  and a light collection design for the second encapsulants  121 . The first encapsulant  111  and the second encapsulants  121  may have the refractive index mediating the optoelectronics and the environment. There are two second encapsulants  121  located on the two sides of the light source  110 . More specifically, the first encapsulant  111  has a predetermined shape for splitting the light from the light source  110  into two beams of light in different directions and for guiding them to the object surface under test; the first encapsulant  111  seals the light source  110  and also covers the two second encapsulants  121  sealing the photodetectors  120 . The first encapsulant  111  may take advantage of total internal reflection of the emitted light by a difference in the refractive index or a predetermined curvature, or the first encapsulant  111  may be covered with the reflective coating  180  confining the emitted light. Each of the second encapsulants  121  may have a predetermined shape for collecting the light reflected from the objects. For example, the second encapsulants are substantially prismatic or quadrispherical. Furthermore, the two second encapsulants  121  may be engineered as a symmetric or an asymmetric shape, and also the first encapsulant  111  may have various shapes for specific requirements. For example, the top surface of the first encapsulant  111  may be two inclined planes intersecting substantially above the light source  110  or may be two curved plane intersecting substantially above the light source  110 . 
     A coating may be disposed on different surfaces of the encapsulants for blocking the stray light directly from the light source  110  to the photodetector  120  or guiding/collecting the light to/from the objects. The coating may be a thin film of metal or a reflective material (for example Ag or TiO2 riched compound). 
     The contact surfaces  191  (one example as shown in  FIG. 61B ) are the openings for the emitted (the first encapsulant  111 ) and reflected (the second encapsulant  121 ) light and are used to attach the objects, while the side surfaces are the surface shown in the cross sectional view and the contralateral surface. At least part of the contact surface of the encapsulants may be formed as a microstructure. For example, the first encapsulant  111  includes a microstructure  112  formed as the contact surface of the first encapsulant  111 . The encapsulant  111  with microstructure(s) enhances the signal strength because the light is concentrated toward intended direction from the light source  110  toward the photodetector  120 , while the light passes through the microstructure  122  of the encapsulant  121 . 
     A wall may be also be disposed on the side surfaces, of the encapsulants for blocking the stray light formed of opaque material, which blocks via reflection and/or absorption in the specific spectrum of wavelengths emitted by the light source  110 , for noise reduction. 
     The bi-directional optical sensor module  5  is a compact packaged module comprising of a light source  110 , a photodetector  120 , a first and two second encapsulants  121 , and a substrate  140 . The primary goal of the present technology is to be capable of measuring two directions of the reflected optical signals by specific shapes of the encapsulants. These shapes also improve the performance of the bi-directional optical sensor module  5  achieved by enhancing the light extraction efficiency, directing the light path, or reducing the stray light. Other modification and further application without departing the scope of disclosure are presented in the embodiments. It may be embodied as the simple composition with one light emitting diode (LED) and two silicon photodiodes all mounted on a printed circuit board as a substrate  140 . Both LED and silicon photodiode are hermetically sealed, separately, with epoxy encapsulants. In the example for measuring oxygenation of biological tissue, both wavelengths in infrared and red regions are required. Therefore, one red LED and one infrared LED may be mounted on the same sensor module  5 . In other implementations that are within the scope of the present disclosure, the number and the arrangement of the light sources  110  and photodetectors  120  may be modified. 
     As shown in  FIG. 61-69 , the general construction of the bi-directional optical sensor module  5  is presented. The bi-directional optical sensor module  5  comprises two LEDs and two silicon photodiodes, wherein both are mounted on a substrate  140 . The first encapsulant  111  covers the light source  110 , while the two second encapsulants  121  cover the two photodiodes  120 . In the embodiments, an encapsulant may have modifications in configuration and construction. For example, the configuration of the first encapsulant  111  may be trapezoid shape or cylindrical shape. In addition, the contact surfaces of the first encapsulant  111  are configured with a first microstructure  112 , and the contact surfaces of the second encapsulants  121  may have a second microstructure  122 . 
     In the examples of the present disclosure, as shown in  FIGS. 61-68 , a second coating  181  is disposed on the top surface of the second encapsulants  121  to reduce light leakage directly from the light source to the photodetector and reduce the effect of ambient stray light. In  FIGS. 61-65 , the first coating  180  is disposed on the surface of the first encapsulant  111  to limit light leakage and thus enhance the light emitting toward the contact surfaces. The surface of both encapsulants have a predetermined surface configuration to enhance SNR. For example in  FIG. 61B , the top surface of the first encapsulant may be formed as two inclined plane  111   a ,  111   b  intersecting at around the above of the light source  110  and formed as an intersected line  111   c  as shown in  FIG. 61A . In the examples, each of the inclined planes is about parallel to the surface plane of the second encapsulant on the same side. In some examples, the inclined planes  111   a ,  111   b  may have asymmetric shape or size, and may have cylindrical shape. For ease of presentation, the first coating  180  is disposed on the top surface of the first encapsulant  111 , and the second coating  181  is the disposed on the top surface of the second encapsulant  121 . Further, the first encapsulant  111  has refractive index, n 1  and the two second  121  encapsulants have refractive indices, n 2 , wherein n 1  and n 2  may be different. 
     The top surfaces of the first encapsulant  111  and the two second encapsulants  121  have a predetermined tilting angle or curvature; therefore, more emitted light is extracted from the LEDs and more reflected light is collected to the photodiodes to enhance effective signal strength. 
     As illustrated in the top view ( FIG. 61A ), the substrate  140  area is divided into three regions by two straight lines; one rectangular area enclosing the LEDs and two rectangular areas, on the two sides of the LEDs, enclosing the two photodiodes. In the cross sectional view ( FIG. 61B ) and the oblique view ( FIG. 61C ), the two second encapsulants  121  are embodied as a shape of a triangle prism, horizontally disposed on two rectangular areas respectively and sealing the two photodiodes. Additionally, the first encapsulant  111  is embodied as a shape of two side-by-side trapezoid prisms, and horizontally disposed on two second encapsulants  121  and sealing the LEDs. In addition, there is the first coating  180  on the first encapsulant  111  and the second coating  181  on the second encapsulants  121 . The two second encapsulants  121  are constructed together or separately with their top surfaces are covered by the second coating  181 ; then the first encapsulant  111  are constructed on top of the two second encapsulants  121  with its top surface is covered by the first coating  180 . 
     In the top view ( FIG. 62A ) and the cross sectional view ( FIG. 62B ), the two second encapsulants  121  are embodied as a shape of a triangle prism, horizontally disposed on two rectangular areas respectively and sealing the two photodiodes. Additionally, the first encapsulant  111  is embodied as a shape of two side-by-side trapezoid prisms, and horizontally disposed on two second encapsulants  121  and sealing the LEDs. It is contemplated that the contact surfaces of the first  111  and second  121  encapsulants may be formed as different microstructures (for example, DOEs or Fresnel patterns as shown in  FIGS. 62C and 62D ) to enhance the light extraction/receiving efficiency. For example, the first microstructures are configured in a set of concentric arcs with wider intervals than the second microstructures. 
     In the top view ( FIG. 63A ) and the cross sectional view ( FIG. 63B ), the two second encapsulants  121  are embodied as a shape of a triangle prism, horizontally disposed on two rectangular areas respectively and sealing the two photodiodes. Additionally, the first encapsulant  111  is embodied as a shape of two asymmetric side-by-side trapezoid prisms, and horizontally disposed on two second encapsulants  121  and sealing the LEDs. It is also contemplated that the configuration (for example the inclined angle of top surfaces) and the material (for example refractive index) of the two second encapsulants  121  and the coatings  181  may differ from each other. In  FIG. 63B , the distance between the light source  110  to the contact surface, d 1 , is shorter than the distance between the light source  110  to the opposite contact surface, d 2 . The two tilting angles, θ 1  and θ 2 , of the top surface of the first encapsulant may be different. For example, asymmetric second encapsulants  121  resulting in an asymmetric first encapsulant  111 . In addition, the contact surfaces of the first  111  and second  121  encapsulants may be formed as different microstructures (for example, DOEs or Fresnel patterns as shown in  FIGS. 63C and 63D ) to enhance the light extraction/receiving efficiency. 
     As illustrated in the top view ( FIG. 64A ), the substrate  140  area may also be divided into three regions in a different way by two curves; the two rectangular areas may be replaced by two semi-circles enclosing the two photodiodes as shown in this embodiment, while the rest area of the substrate  140  enclosing the LEDs. In the cross sectional view ( FIG. 64B ) and the oblique view ( FIG. 64C ), the two second encapsulants  121  are embodied as a shape of a quarter-sphere, disposed on two semi-circular areas respectively and sealing the two photodiodes. Additionally, the first encapsulant  111  is embodied as a shape of two side-by-side trapezoid prisms, horizontally disposed on two second encapsulants  121 , and seals the LEDs. In addition, there is the first coating  180  on the first encapsulant  111  and the second coating  181  on the second encapsulants  121 . The two second encapsulants  121  may also be constructed as a shape of a quarter-ellipsoid, a partial parabolic sphere or the like with their top surfaces covered by the second coating  181 ; the first encapsulant  111  are constructed on top of the two second encapsulants  121  with the top surface covered by the first coating  180 . 
     As illustrated in the top view ( FIG. 65A ), the substrate  140  area may also be divided into three regions in a different way by two curves; the two rectangular areas may be replaced by two semi-circles enclosing the two photodiodes as shown in this embodiment, while the rest area of the substrate  140  enclosing the LEDs. In the cross sectional view ( FIG. 65B ), the two second encapsulants  121  are embodied as a shape of a quarter-sphere, disposed on two semi-circular areas respectively and sealing the two photodiodes. It is contemplated that the contact surfaces of the first  111  and second  121  encapsulants may be formed as different microstructures (for example, DOEs or Fresnel patterns as shown in  FIGS. 65C - and  65 D) to enhance the light extraction/receiving efficiency. 
     In the present disclosure, as shown in  FIGS. 66-68 , the first encapsulant is formed as a shape of side-by-side cylinders to enhance the light extraction efficiency. The top surface of the first encapsulant  111  may be configured as two curvature intersecting beyond the light source  110 . The curvature design of the first encapsulant  111  may follow the rule of the total internal reflection at a critical angle (θ c =arcsin(n 1 /n 0 )), where the refractive index of the first encapsulant, n 1 , is larger than the environment surrounding (for example air) the optical sensor module, no. Further, the first  111  and the two second  121  encapsulants may have different refractive indices, n 1  and n 2 . As a result, the interface between the first encapsulant and one of the second encapsulants follows the rule of the total internal reflection at a critical angle (θ c =arcsin(n 1 /n 2 )) to reduce light leakage directly from the light source to the photodetector. 
     The outer surfaces of the first encapsulant  111  and the two second encapsulants  121  may have modifications of configuration. For example, each top surface of the two second encapsulants may be an inclined plane with a predetermined angle between the top surface and the substrate. In one example, each top surface of the two second encapsulants may be a curvature concaved toward the photodetector on the same side. As a result, more emitted light is extracted from the LEDs and more reflected light is collected to the photodiodes to enhance effective signal strength. 
     As illustrated in the top view ( FIG. 66A ), the substrate area is divided into three regions by two straight lines; one rectangular area enclosing the LEDs and two rectangular areas, on the two sides of the LEDs, enclosing the two photodiodes. In the cross sectional view ( FIG. 66B ) and the oblique view ( FIG. 66C ), the two second encapsulants  121  are embodied as a shape of a triangle prism, horizontally disposed on two rectangular areas respectively and sealing the two photodiodes. Additionally, the first encapsulant  111  is embodied as a shape of two side-by-side quarter-cylinder as shown in this embodiment and horizontally disposed on two second encapsulants  121  and sealing the LEDs. In addition, there is the first coating  180  on the first encapsulant  111  and the second coating  181  on the second encapsulants  121 . The two second encapsulants  121  are constructed together or separately with their top surfaces are covered by the second coating  181 ; then the first encapsulant  111  may also be constructed as two curved surfaces on top of the two second encapsulants  121 . 
     As illustrated in the top view ( FIG. 67A ), the substrate area may also be divided into three regions in a different way by two curves; the two rectangular areas may be replaced by two semi-circles enclosing the two photodiodes as shown in this embodiment, while the rest area of the substrate  140  enclosing the LEDs. In the cross sectional view ( FIG. 67B ) and the oblique view ( FIG. 67C ), the two second encapsulants  121  are embodied as a shape of a triangle prism, horizontally disposed on two rectangular areas respectively and sealing the two photodiodes. Additionally, the first encapsulant  111  is embodied as a shape of two side-by-side quarter-cylinder as shown in this embodiment and horizontally disposed on two second encapsulants  121  and sealing the LEDs. In addition, there is the first coating  180  on the first encapsulant  111  and the second coating  181  on the second encapsulants  121 . The two second encapsulants  121  may also be constructed as a shape of a quadrispherical, a quarter-ellipsoid or a partial parabolic sphere or the like with their top surfaces are covered by the second coating  181 ; then, the first encapsulant  111  may also be constructed as two curved surfaces on top of the two second encapsulants  121 . 
     As illustrated in the top view ( FIG. 68A ), the substrate area may also be divided into three regions in a different way by two curves; the two rectangular areas may be replaced by two semi-circles enclosing the two photodiodes as shown in this embodiment, while the rest area of the substrate  140  enclosing the LEDs. In the cross sectional view ( FIG. 68B ), the two second encapsulants  121  are embodied as a shape of a triangle prism, horizontally disposed on two rectangular areas respectively and sealing the two photodiodes. It is contemplated that the contact surfaces of the first  111  and second encapsulants  121  may be formed as different microstructures (for example, DOEs or Fresnel patterns as shown in  FIGS. 68C and 68D ) to enhance the light extraction/receiving efficiency. In addition, a coating  180  or a wall (nontransparent sealing material) may be disposed on the top surfaces of the second encapsulants to enhance SNR. 
     In one example of the present disclosure, as shown in  FIG. 69 , the first encapsulant  111  and the two second  121  encapsulants may have different refractive indices, where the refractive index of the second encapsulants  121 , n 2 , is larger than the one of the first encapsulant  111 , n 1 , to reduce direct light leakage from the light source to the photodetectors and ambient stray light according to the Fresnel rule. The surface of both encapsulants have a predetermined surface configuration to enhance SNR; in this embodiment, the first encapsulant  111  is formed as a shape of side-by-side cylinders to enhance the light extraction efficiency. The curvature design of the first encapsulant  111  may follow the rule of the total internal reflection at a critical angle (θ c =arcsin(n 1 /n 0 )), where the refractive index of the first encapsulant  111 , n 1 , is larger than the environment surrounding (e.g. air) the optical sensor module, n 0 . 
     The surface planes of the first encapsulant  111  and the two second encapsulants  121  have a predetermined tilting angle or curvature, and hence the second coating  181 ; therefore, more emitted light is extracted from the LEDs and more reflected light is collected to the photodiodes to enhance effective signal strength. 
     As illustrated in the top view ( FIG. 69A ), the substrate  140  area may also be divided into three regions in a different way by two curves; the two rectangular areas may be replaced by two semi-circles enclosing the two photodiodes as shown in this embodiment, while the rest area of the substrate  140  enclosing the LEDs. In the cross sectional view ( FIG. 69B ) and the oblique view ( FIG. 69C ), the two second encapsulants  121  are each embodied as a shape of a triangle prism, horizontally disposed on two rectangular areas respectively and sealing the two photodiodes. Additionally, the first encapsulant  111  is embodied as a shape of two side-by-side quarter-cylinder as shown in this embodiment and horizontally disposed on two second encapsulants  121  and sealing the LEDs. In addition, there is the first coating  180  on the first encapsulant  111  and the second coating  181  on the second encapsulants  121 . The two second encapsulants  121  may also be constructed as a shape of quadrispherical, a quarter-ellipsoid or a partial parabolic sphere or the like; then the first encapsulant  111  may also be constructed as two curved surfaces on top of the two second encapsulants  121 . 
     It is also contemplated that the configuration (for example, inclined angle of top surfaces) and the material (for example, refractive index) of the two second encapsulant  121 /coating  180  may differ from each other. The second encapsulants  121  may be asymmetric resulting an asymmetric first encapsulant  111 , for more specific applications. Further, the side surfaces of the first  111  and second  121  encapsulants may be formed as different microstructures to enhance the light extraction/receiving efficiency. 
     An optical sensor module  10  may be a dual sensor module  6 . The dual sensor module  6  is manufactured to detect the reflected light and electric signals. The dual sensor module comprises a light source, a first encapsulant over the light source, a photodetector, a second encapsulant over the photodetector, a packaging wall, a detector circuit board, and at least one electrode. 
     An electrode is configured to be a transducer or to detect an external circuit formed by the contact with an object surface. An electrode is an electrically conductive material, which connects between the external circuit and the detector circuit board inside the dual sensor module. The material of electrodes are usually metal or alloy with good conductivity, for example, copper or gold. Moreover, a single electrode may serve as a thermocouple, made of two pieces of alloy with a different Seeback coefficient (for example, alumel and chromel). The electrodes are arranged to have an adequate contact interface with the object surface (for example, biological tissue or skin surface). 
     A part of a substrate  140  may be configured as a detector circuit board  175 . A detector circuit board  175  is configured to have an electrical connection to at least an electrode  170  and to provide electrical pin(s) for further signal delivery. The detector circuit board  175  may comprise a logic circuit or an operational amplifier circuit to help the electrodes  170  to obtain the electrical properties, such as electrical current, conductance, impedance, or electrical potential difference. The detector circuit board  175  may be integrated with the substrate having the optoelectronics thereon or may be a separate printed circuit board connected to the substrate. In some examples as shown in  FIG. 73B  and  FIG. 74B , the substrate has the first part  140  of the substrate configured to provide connection to the light source  110  and the photodetector  120  and the second part  175  of the substrate configured as a detector circuit board to provide electrical connection to the electrodes  170 . 
     The dual sensor module  6  is an integrated sensor module comprising an optical sensor part and an electrical sensor part to have multiple function within a single piece of a dual sensor module  6 . The dual sensor module  6  has many advantages, such as volume miniaturization and in situ dual signal acquisition. The single electrode  170  in a dual sensor module may be solely functional as a thermocouple. The single electrode  170  in a dual sensor module may be cooperated with another dual sensor module or an independent electrode to form as a functional pair of electrodes. In  FIG. 70A , the dual sensor module has the light source  110 , the first encapsulant  111  covering the light source  110 , the photodetector  120 , the second encapsulant  121  covering the photodetector  120 , the packaging wall  131 , the substrate  140  and the electrode  170  disposed between the light source  110  and the photodetector  120 . In  FIG. 70B , the light source  110 , the photodetector  120  and the electrode  170  are disposed on the same substrate  140 . 
     As shown in  FIG. 71A , the dual sensor module has the light source  110 , the first encapsulant  111  covering the light source  110 , the photodetector  120 , the second encapsulant  121  covering the photodetector  120 , the packaging wall  131 , the detector circuit board  175  and the electrodes  170 . The packaging wall  131  is disposed between the light source  110  and the photodetector  120 . The two electrodes  170  are disposed on the opposite border of the detector circuit board  175 . One electrode  170  is disposed laterally to the light source  110  and the other electrode  170  is disposed laterally to the photodetector  120 . The packaging wall  131  is configured to reduce the direct light leakage from the light source  110  and the photodetector  120  and may extend bilaterally to further block ambient light. In  FIG. 71B , the light source  110 , the photodetector  120  and the electrode  170  are disposed on the same detector circuit board  175 . 
     As shown in  FIG. 72A , the dual sensor module has the light source  110 , the first encapsulant  111  covering the light source  110 , the photodetector  120 , the second encapsulant  121  covering the photodetector  120 , the packaging wall  131 , the detector circuit board  175  and the electrodes  170 . One electrode is disposed between the light source  110  and the photodetector  120  and the other electrode is disposed on the border of the detector circuit board. The packaging wall  131  is configured to block ambient light and to separate the two electrodes. The packaging wall  131  is electrically insulated, so that the two electrode are capable of detecting the electrical potential difference. In  FIG. 72B , the light source  110 , the photodetector  120  and the electrodes  170  are disposed on the same detector circuit board  175 . It is contemplated that the electrodes  170  may be disposed on other sides of the detector circuit board  175 . For example, one electrode  170  is disposed between the light source  110  and the photodetector  120 , and the other electrode  170  is disposed on the border of the light source side of the detector circuit board  175 . For example, the dual sensor module may have a packaging wall  131  disposed between the light source  110  and the photodetector  120  and the electrodes may be disposed perpendicular to the packaging wall  131 . 
     As shown in  FIGS. 73-74 , the substrate  140  is composed by a first part and a second part. The first part of the substrate may have a light source  110  and the photodetector  120  thereon, while the second part of the substrate may be a detector circuit board  175  to provide connection to the electrode(s)  170 . The light source  110  and the photodetector  120  are disposed on the substrate  140 . The detector circuit board  175  may be mechanical connected to the substrate  140 , or may be electrical connected to the circuit within the substrate  140  for better synchronization between the optical measurement and the electrical measurement. 
     In  FIG. 73A , the detector circuit board  175  is larger than the substrate  140  and the substrate  140  and the two electrodes  170  are disposed on the detector circuit board  175 . The packaging wall  131  is disposed between the light source  110  and the photodetector  120  to reduce light leakage and may extend to enclose the border of the substrate  140  to further block ambient light. In  FIG. 73B , each of the electrodes  170  has electrical connection to the detector circuit board  175 . The electrodes are separated from each other by the substrate  140 . In  FIG. 74A , two electrodes  170  are disposed on the detector circuit board  175  with a limited distance and thus may have a smaller impedance of the external circuit when being applied to an object surface. In  FIG. 74B , each of the electrodes  170  has electrical connection to the detector circuit board  175 . 
     In  FIGS. 75-79 , the dual sensor module  6  may further comprise a cover  150 , and the cover  150  may be located, during application, between the encapsulants and the object surface, while not blocking the contact between the electrodes  170  and the object surface. The cover  150  serves as a contact interface between the object surface (such as a biological tissue surface or a skin surface) to increase the durability of the dual sensor module  6  and the consistency of measurement. 
     In one embodiment as shown in  FIG. 75A , the dual sensor module  6  comprises a cover  150  disposed beyond the light source  110  and the photodetector  120 , while at least a part of the electrode  170  is exposing outward. The cover  150  may be separated by the electrode  170  or may be a single piece with a slot for exposure of the electrode  170 . In  FIG. 75B , the cover  150  may be mechanically connected to the packaging wall  131  to provide mechanical support. 
     In  FIG. 76A , the cover  150  may be disposed beyond the light source  110  and the photodetector  120 , while at least a part of the two electrodes  170  are exposed outward from the cover  150 . In  FIG. 76B , a packaging wall  131  is disposed between the light source  110  and the photodetector  120  and provide mechanical support to the cover  150 . The packaging wall  131  may extend to enclose the border of the detector circuit board  175  to block ambient light and provide better mechanical support for the cover  150 . 
     In  FIG. 77A , the cover  150  may be disposed beyond the light source  110  and the photodetector  120 , while at least a part of the two electrodes  170  are exposed outward from the cover  150 . The cover  150  may be a single piece with one slot for exposure of the electrode  170  between the light source  110  and the photodetector  120 . The cover  150  may be a single piece with two slots each for an electrode  170 . The cover  150  may comprise two separate parts for exposure of the electrodes  170 . In  FIG. 77B , a packaging wall  131  is disposed to provide mechanical support to the cover  150 . The packaging wall  131  may extend to enclose the border of the detector circuit board  175  to block ambient light and provide better mechanical support for the cover  150 . The packaging wall may be separated by the electrodes  170  or may be fabricated as a continuous wall enclosing the border the detector circuit board  175 . 
     In addition, the internal surface or the external surface of the cover  150  may be coated with a thin film  151 . The thin film may be an anti-reflective (such as index-matching thin film or interference thin film) or an anti-scratch thin film (such as polyethylene terephthalate, or silicon hard coating). As shown in  FIG. 78A , both internal surface and the external surface of the cover  150  are coated with thin films. In an enlarged view ( FIG. 78B ), the external surface of cover  150  is covered with an anti-scratch thin film and the internal surface of the cover  150  is covered with an anti-reflective thin film. It is contemplated that the two surfaces may be covered with same kind of thin film or one of the surfaces of the cover  150  may have no thin film. 
     In one example as shown in  FIGS. 79A-C , the dual sensor module  6  may further comprise a thin film  160  covering an encapsulant. With thin film technology, the SNR of the optical signals may be further improved. The thin film  160  may be an anti-reflective thin film or a filter thin film. The anti-reflective thin film may be an index-matching film (for example, Rayleigh film) or an interference film to improve light extraction efficiency by reducing Fresnel reflection at the interface between the encapsulants and the environmental medium. The filter thin film may be a long-pass filter, a short-pass filter, or a band-pass filter to clear down the full width at half maximum (FWHM) of the emitting light or filter out the noise from undesired wavelengths. 
     As shown in  FIG. 79A , both the surfaces of the first encapsulant  111  and the second encapsulant  121  are coated with a thin film  160 . The thin film  160  of the first encapsulant  111  is embodied as an anti-reflective thin film ( FIG. 79B ) and the thin film  160  of the second encapsulant  121  is embodied as a band-pass filter thin film ( FIG. 79C ). The anti-reflective thin film improves the light extraction efficiency and the band-pass filter thin film reduces noise. It is contemplated that the thin film  160  of the first encapsulant  111  may be a band-pass filter thin film and the thin film  160  of the second encapsulant  121  may be an anti-reflective thin film, so that the FWHM of the emitting light has a clear cut-off and the photodiode receive more signal light without unnecessary reflection. In the application of fluorescence detection long-pass filter thin film may be applied to the second encapsulant  121  to acquire a clear fluorescent signal avoiding the excitation light. 
     The integration facilitates acquisition of the optical and electrical signals and computation of acquired signals into meaningful information. The dual sensing device  18  is capable of acquiring optical and electrical signals in situ and computing useful physiological parameters. First, the electric potential difference between two electrodes may be measured by parallel connection to the object circuit. For example, electrocardiogram may be acquired in time series by measuring the potential difference between the electrodes on the body surface with an adequate alignment. Also, the electric impedance of the contact object may be measured by series connection to the object surface  190 . For example, the fat content or hydration status of the biological tissue may be further calculated from the measured impedance. In addition, the electrodes may also serve as a thermocouple to measure the object temperature. For example, body surface temperature may be measured as a reference of core temperature. For example, the pulse wave velocity can be calculated from the pulse phase difference, and some disease status may be inferred from the phase angle of the bioelectrical impedance. 
     In general, an optical sensing device or an optical sensing accessory is an integration of one or more optical sensor modules  10  with other electronic modules in a housing. Other electronic modules are configured to assist the optical sensor module  10  in transmitting, digitizing, processing, or storing the optical signals and to combine the optical signals with other concomitant information; meanwhile, the housing keeps all the electronic modules from external damage and provides a human interface for mobile use. The integration facilitates acquisition of the optical signals and transformation of the acquired optical signals into meaningful information. Specifically, within the range of optical window, incident light can travel in a depth of a biological tissue, and therefore, the information underneath the surface of the biological tissue can be extracted by the reflected light. By studying the spectrum of specific wavelengths, people may further obtain the computed biochemical or physiological parameters. The analysis of optical properties of a biological sample, in vivo, ex vivo, or in vitro, may be accomplished through the operation of the optical sensing device. Accordingly, the acquired optical signals are more accessible and applicable with the present technology of the optical sensing device. 
     With certain purposes of application, the optical sensing device or the optical sensing accessory have, at least, an optical sensor module and a housing. An optical sensor module may be the optical sensor module, the multi-directional optical sensor module, or the dual sensor module defined in the present disclosure. The other electronic modules may be a microprocessor  20 , a communication module  60 , a battery  50 , a memory  40 , a GPS receiver module  70 , or other types of sensors; a wearable housing is configured to carry an optical sensing device and attaching human body for mobile use. 
     A microprocessor  20  may be an ARM based or 8086x microprocessor, most available in mobile device, are capable of processing the large amount of data and have an advantage of energy saving. A microprocessor  20  may have analogue input pins allowing analogue signal processing. 
     The input interface module  31  include keyboard, mouse, or microphone in conventional computing devices, or touch screen, microphone, or camera in mobile devices. The output interface module can output information in visual or audible forms. The visual output module  36  may be a microprojector, LCD, LED, OLED, or E-Paper display, and the audible output module  37  may be a beeper, a speaker, or a piezoelectric buzzer. 
     A memory  40  stores the digital information assigned by the microprocessor  20  of the optical sensing device. The memory  40  may work as a system buffer to deal with abundant data input, and may work as a storage to preserve the structured information for later exporting to the other computing device or a cloud server. The memory  40  may be volatile or non-volatile. Volatile memory is embodied as random access memory (RAM) in most mobile device, and non-volatile memory is embodied as flash memory. 
     A power supply provides the power necessitated for the operation of the device. A power supply may be a battery  50 , a transformer, or a power transmission line connected to a direct current source. Both primary and secondary batteries may be a source of power supply used in the optical sensing device. In at least one example, the primary and secondary batteries can rely upon lithium battery technology. In other examples, the primary and secondary batteries can be made using technology to allow the desired discharge rates, life cycle, and rechargeability. 
     A communication module  60  transmits the electrical signals between an optical sensing device and an external device, where the electrical signals may be control signals or data signals. The communication module  60  may be wired  61  or wireless  66 . Wired communication module  61  may be a serial port such as one wire, USB, I2C, or SPI. Wireless communication module  66  may be Wi-Fi, standard Bluetooth, Bluetooth Low Energy, or cellular mobile network (for example, GSM, 3G, or 4G). In one example, an analogue front end is integrated as a part of Bluetooth module, which enables the analogue signals to be transmitted. 
     A GPS receiver module  70  is configured to gather geographic information, and help to record the location where the optical information is collected. With time series recording, the GPS information provides a dynamic tracing of the user&#39;s displacement and velocity. 
     Other sensors transducing thermal, mechanical, or biopotential signals into electrical signals may be also incorporated into the optical sensing device to provide more environmental and physiological information. For example, electrical thermometer  82  is able to detect the ambient and body temperature; accelerometer  81  detects body motion; electrocardiograph leads detect cardiac electric activity. Besides, the electrical property of biological tissue (for example, electrical impedance, or conductivity) may indicate some physiological information (for example, body fat index, or moisture.) 
     A housing provides suitable container to set up the optical module and electronic modules and may provide adequate connection interface for communication with external devices. It also helps measurement consistency on specific body regions and increases the user compliance to the optical sensing device. A housing may be embodied as a housing for a handheld device or a wearable device. A handheld housing  91  features its compact size, light weight, and robustness for mobile applications ( FIG. 80A ). A wearable housing comprises a body attaching part and a module carrying part. The body attaching part may be an annular shape accessory  96 , which attaches to human body by embracing body parts, and may be embodied as, a wrist band ( FIG. 80B ), a head band, an ankle band, a necklace, a belt, a watch ( FIG. 80C ), or the like. Also, the body attaching part may be a patch shape accessory  97 , which attaches to human body by biocompatible glues or gels, and may be embodied as a tape, a pad ( FIG. 80D ), a patch, or the like. Furthermore, the body attaching part may be a hook shape, and may be embodied as an earplug, an on-ear accessory, or a spectacle frame. In one example as shown in  FIG. 87D , the housing may comprise transparent opening  153  to provide an optical path for the reflective optical sensor module, the optical sensor module, the multi-directional optical sensor module  5 , or the dual sensor module. The transparent opening  153  may have a cover  150  and the cover may be configured with microstructure, curvature lens, or thin film on the surfaces of the cover, or any combinations as mentioned. 
     In the present disclosure, an optical sensing accessory  11  or an optical sensing device  12  may comprise an optical sensor module  10 , a multi-directional optical sensor module  5 , a dual sensor module  6 , or any combinations. For ease of description, an optical sensing accessory or an optical sensing device  12  comprising, but not limited to, an optical sensor module  10  is demonstrated. An optical sensing accessory  11  has a communication module  60  to allow the transmission of acquired signals to a computing device for further signal processing. An optical sensing device  12  has a processor to manage the acquired optical signals. The embodiments of an optical sensing device are exemplified as below. 
     An optical sensing accessory  11  of the present disclosure is configured to transmit the optical signals from one or more optical sensor modules  10  to a computing device. The optical sensing accessory  11  comprises at least one optical sensor module  10 , a communication module  60 , and a housing. The optical signals are obtained by the optical sensor module  10 , and later, the signals may be conveyed to an independent computing device via the communication module  60  ( FIG. 81A ). The computing device  9  may be the optical sensing device  12  or a mobile device (for example, smart phone). As depicted in  FIGS. 81A-C , an optical sensing accessory  11  to transmit the electrical signals to a computing device. In one example, the optical sensing accessory  11  comprises an optical sensor module  10 , a serial cable plug and a wearable housing presented as a wired patch probe. With connection to an external computing device, the optical sensing accessory receives power support and the control signals from the computing device and delivers the converted signals to a computing device via the serial cable ( FIG. 81B ). In addition, the wired patch probe may comprise multiple optical sensor modules  10  as shown in  FIG. 81C . In the case of a wireless optical sensing accessory ( FIG. 82A ), a battery  50  is necessary to power the signal transmission by radiofrequency. The computing device is capable of triggering the operation of the optical sensing accessory  11  and managing the received signals. As shown in  FIG. 82B , multiple wireless optical sensing accessories  11  may be connected and integrated to the computing device. 
     Also, an optical sensing device  12  of the present embodiments is configured to manage the optical signals from an internal optical sensor module  10  or an external sensing devices  8 . An internal optical sensor module  10  is electrically connected to the microprocessor  20 , while an external sensing device is connected through a communication module  60 . The optical sensing device  12  comprises an optical sensor module  10 , a microprocessor  20 , a battery  50 , a memory  40 , and a housing. 
     As depicted in  FIGS. 83A-C , an optical sensing device  12  is configured to receive, process, store and transmit the optical signals. In at least one example, the optical sensing device  12  comprise an optical sensor module  10 , an ARM core microprocessor, a flash memory, and a lithium battery. The optical sensor module  10  may receive and convert the optical signals of a biological tissue to electrical signals and deliver the signals to a microprocessor  20 . The general architecture of an optical sensing device  12  is shown as  FIG. 83A , and the other electronic modules may be integrated into the optical sensing device  12 . The optical signals are obtained by the optical sensor module  10 . Later, the electrical signals may be directly delivered to and processed by the optical sensing device  12 . The optical sensing device  12  comprising electronic modules is presented as an optical sensing watch  12  ( FIGS. 83B and 83C ). The acquired optical signal is transduced into the electrical signal and the electrical signal is processed by the microprocessor  20 , output as physiological parameters, and then stored in the memory. For example, the infrared and red light absorbance of applied biological tissue is detected by the optical sensor module  10 , converted into electrical signals, processed as physiological parameters (for example, oxygen saturation), and stored in a flash memory. In  FIG. 83B , an optical sensing watch comprises one transparent opening  153  on the clock face and one optical sensor module  10  is located in the transparent opening. In  FIG. 83C , the optical sensing watch comprises the other transparent opening  153  on the case back and the other optical sensor module  10  is located in the transparent opening  153 . 
     The optical sensing device  12  may comprise an optical sensor module  10 , an ARM core microprocessor, a flash memory, a lithium battery, and further comprises an input module  31  a visual output module  36 , and an audible output module  37 . The input interface module  31  may be embodied as a touch screen module. The user may input a request by touch screen to have the optical sensing device  12  send out control signal to the sensor module to acquire signals. The acquired signals are then processed by the microprocessor  20  and stored as physiological information in the memory  40  in the optical sensing device  12 . The user may also input a request by touch screen to have the stored physiological information be shown on a display. Additionally, an output module, such as a beeper, may work as a failure-proof reminder or an emergency alerting signal. 
     With further comprising a communication module  60 , the optical sensing device  12  is capable of integrating the information between the optical sensing device  12  and other external devices. As shown in  FIG. 83A , the optical sensing device  12  comprises a microprocessor  20 , a communication module  60 , a memory  40 , and a battery  50 . The communication module  60  is embodied as a Bluetooth module communicating with an external device. The optical sensing device  12  may send out control signal to control an external device or receive the signals acquired from an external device. For example, the external device may be an optical sensing accessory  11  ( FIG. 84A ) so that the optical signals obtained from the optical sensing accessory  11  may be integrated with other health information. Also, the external device may be other accessory sensor devices  8  ( FIG. 84B ), so that the optical sensing device  12  provides more compatibility for various applications. 
     The wearable optical sensing device  12  may also connect to the other optical sensing device  12  to deliver the physiological information for further information management. In at least one example, the other computing device may be a handheld optical sensing device  12  or a smart mobile device (for example, iPhone, Android phone, phablet, or tablets), so that the optical sensing device  12  may have lower power consumption, lower hardware requirement, and better compatibility. 
     In one example as shown in  FIG. 85A , an optical sensing device  12  connected to the other optical sensing device  12 . One of the optical sensing device has basic electronic modules, including an optical sensor module  10 , a microprocessor  20 , and a wireless communication module  66 , to connect with the other optical sensing device with more functional electronic modules. In  FIG. 85B , one of the optical sensing device is a wearable optical sensing watch and the other is an optical sensing smart phone. 
     Multi-site measurement is applicable since the wearable optical sensing device improves measurement accuracy and user compliance to record their physiological condition with the aid of the present technology. With the advance performance of the reflective optical sensor module  10 , measurement of multiple body regions brings extra useful physiological information. Here, blood oxygenation is illustrated to exploit the utility, while other optical signals from multiple body regions may have further applications. The physiological parameters from multiple body regions demonstrates the regional difference of a physiological parameter among the body parts. For example, the blood oxygenation may vary from forehead and wrist. Also, the phase difference demonstrates the conveyance of a physiological parameter between any two body regions. For example, the pulse wave velocity can be calculated from the pulse phase difference. In addition, continuous multiple body region monitoring may provide a temporal-anatomical distribution of the physiological information. The example in  FIGS. 86A and 86B  shows the optical sensing device  12 . The optical sensing device  12  may be applied to measure forehead and wrist ( FIG. 86A ), or a wrist and a finger of the contralateral hand ( FIG. 86B ). Multiple optical measurements may also be acquired through the optical sensing accessory  11  with multiple probes as shown in  FIG. 81C . In addition, the multiple optical measurements may be achieved under the integration of multiple optical sensing accessory  11 . 
     In one example, the optical sensing device  12  comprises a bi-directional optical sensor module  5 . The optical sensing device  12  may be a wearable watch shown in  FIG. 87A-D . In  FIG. 87A , the housing of the optical sensing device  12  have one opening on the internal side of the annular housing, and in  FIG. 87B , the other opening on the external side of the annular housing. The openings are configured to expose the contact surfaces of the bi-directional optical sensor module  5 , so that the light emitted from the light source  110  may be collected by the photodetectors  120  facing different directions. In  FIG. 87C , the perspective view from the lateral side shows that the bi-directional sensor module  5  have one contact surface facing toward the external side of the housing and the other contact surface facing toward the internal side of the housing. In  FIG. 87D , an enlarged view shows a bi-directional sensor module  5  located in the wearable housing. The bi-directional sensor module  5  is located in the transparent opening  153  of the housing. The transparent opening  153  may further have a cover  150  and the cover may be configured with microstructure, curvature lens, or thin film on the surfaces of the cover, or any combinations as mentioned. 
     The optical sensing device  12  may comprise an optical sensor module  10 , an ARM core microprocessor, a flash memory, a lithium battery, and further comprises other sensor modules, or a GPS receiver module  70 , so the other associated information may be stored and processed concomitantly with the physiological information. For example, body temperature may be acquired by an electrical thermometer  82 , or electrocardiogram (ECG) by ECG leads. The optical sensing device  12  may store both blood oxygen saturation level and ECG information and further compute the pulse transit time (PTT) as blood pressure. Furthermore, motion information may be acquired by an accelerometer  81  to evaluate the exercise status and applied for sport medicine. With the integrated GPS receiver module  70 , the optical sensing device  12  can record the user&#39;s physiological information including body temperature, ECG, blood oxygenation, and blood pressure in a time series accompanying the correlated geographic location and exercise status. For example, geographic information obtained by a GPS receiver  70  may be stored with physiological information for geo-medicine applications. 
     With the present technology, personal health information management may bring great benefits to the user in various applications. For example, the optical sensing device  12  may further comprises a communication module  60  in order to connect to Internet and deliver the information to a cloud server to commit big data collection and analysis. Moreover, the optical sensing device  12  may make an alert to the user or other people around when the optical sensing device  12  sensing abnormal physiological conditions. In emergency situations, the optical sensing device  12  may make a phone call or send out an instant message to inform a concerned authority, such as a hospital or an emergency department, to ask an immediate action. By the present technology, the optical sensing device  12  can realize the point of care (POC) service with comprehensive information. Personal, portable, long-term, and continuous health monitoring can be achieved. 
     In general, a multi-site sensing device is the integration of multiple optical sensor modules with other electronic modules in a housing. Other electronic modules are configured to assist the optical sensor modules in transmitting, digitizing, processing, or storing the optical signals and to combine the optical signals with other concomitant information; meanwhile, the housing keeps all the electronic modules from external damage and provides a human interface for mobile use. The integration facilitates acquisition of the optical signals and transformation of the acquired optical signals into meaningful information. Specifically, within the range of optical window, incident light can travel in a depth of a biological tissue, and therefore, the information underneath the surface of the biological tissue can be extracted by the reflected light. By studying the spectrum of specific wavelengths, people may further obtain the computed biochemical or physiological parameters. The analysis of optical properties of a biological sample, in vivo, ex vivo, or in vitro, may be accomplished through the operation of the multi-site sensing device. Accordingly, the acquired optical signals are more accessible and applicable with the present technology of the multi-site sensing device. 
     The multi-site measurement may be acquired by a multi-site sensing accessory  15 , a multi-site sensing device  16 , or a multi-site sensing system  17 . The optical sensing accessory  15 , an optical sensing device  16 , or an optical sensing system  17  comprises at least two reflective optical sensor modules  109 . The reflective optical sensor module  109  is configured to emit light and to measure the reflected light from an object surface. The reflective optical sensor module may be the optical sensor module  10 , the multi-directional optical sensor module  5 , or the dual sensor module  6 . The reflective optical sensor module  109  may also be a sensor module comprising at least the light source  110  and the photodetector  120 . 
     In the present disclosure, the example of a multi-site sensing accessory  15 , an multi-site sensing device  16 , and a multi-site sensing system  17  are illustrated in  FIG. 88-90 . 
     A multi-site sensing accessory  15  is configured to transmit the optical signals from multiple optical sensor modules to a computing device. A multi-site sensing accessory  15  has a communication module  60  to allow the transmission of acquired signals to a computing device for further signal processing. The multi-site sensing accessory  15  comprises plural reflective optical sensor modules, a communication module  60 , and a housing. The optical signals are first transduced into electrical signals by the reflective optical sensor modules. Later, the electrical signals may be conveyed to an independent computing device via the communication module  60  ( FIG. 88 ). The optical sensing accessory  15  transmits the electrical signals from multiple reflective optical sensor modules to a computing device through the communication module  60 . In at least one example, the multi-site sensing accessory  15  comprises three reflective optical sensor modules, a serial cable plug and a wearable housing presented as a wired patch probe. With connection to an external computing device  9 , the multi-site sensing accessory  15  receives power support and the control signals from the computing device and delivers the converted signals to a computing device via the serial cable. In the case of a wireless communication module  66 , a battery  50  is necessary to power the signal transmission by radiofrequency. The coupling external computing device is capable of triggering the operation of the multi-site sensing accessory  15  and managing the received optical signals. The multi-site sensing accessory  15  may have a small volume and be suitable for mobile applications. Most collected physiological information is then transmitted to a mobile device and is further processed. 
     Also, a multi-site sensing device  16  of the present disclosure is configured to manage the optical signals from an internal reflective optical sensor module or an external sensing devices. At least two reflective optical sensor modules  109  are electronically connected to the microprocessor  20 , while an external sensing device is connected through a communication module  60 . The multi-site sensing device  16  comprises at least two reflective optical sensor modules  109 , a microprocessor  20 , a battery  50 , a memory  40 , and a housing. The general architecture is shown as  FIG. 89 , and the other electronic modules may be integrated into the multi-site sensing device  16 . The optical signals are obtained by the optical sensor modules. Later, the electrical signals may be directly delivered to and processed by the microprocessor  20 . 
     The optical sensor module may receive and convert the optical signals of a biological tissue to electrical signals and deliver the signals to a microprocessor  20 . The multi-site sensing device  16  comprising electronic modules is presented as a multi-site sensing watch ( FIGS. 87A-87D ). The acquired optical signals are processed by the microprocessor  20 , output as physiological parameters, and then stored in the memory  40 . For example, the infrared and red light absorbance of applied biological tissue is detected by the optical sensor modules, converted into electrical signals, processed as physiological parameters (for example, oxygen saturation), and stored in a flash memory. 
     In  FIG. 90 , the multi-site sensing system  17  may comprise an optical sensing accessory and an optical sensing device. The optical sensor accessory comprises a first reflective optical sensor module  109 , a first communication module  60  and a first housing, and the optical sensing device comprises a second reflective optical sensor module  109 , a microprocessor  20 , a battery  50 , a memory  40 , a second communication module  60  and a second housing. The communication module  60  may be a wireless communication module  66  which is, for example, a Bluetooth module communicating within the optical sensing system  17 . The optical sensing device may send out control signal to control or receive the signals acquired from the optical sensing accessory. 
     Multi-site measurement is applicable since the multi-site sensing device improves measurement accuracy and user compliance to record their physiological condition with the aid of the present technology. With the advance performance of the multi-site sensing device, measurement of multiple body regions brings extra useful physiological information. Here, blood oxygenation is illustrated to exploit the utility, while other optical signals from multiple body regions may have further applications. First, the physiological parameters from multiple body regions demonstrates the regional difference of a physiological parameter among the body parts. For example, the blood oxygenation may vary from forehead and wrist. Second, the phase difference demonstrates the conveyance of a physiological parameter between any two body regions. For example, the pulse wave velocity can be calculated from the pulse phase difference. Third, continuous multiple body region monitoring may provide a temporal-anatomical distribution of the physiological information. 
     The reflective optical sensor module is used for the measurement of overall optical reflectance of an object surface. The acquired optical signals may be computed as useful information, especially physiological information, such as the blood oxygen saturation level, which is based on the light absorption rate of particular wavelengths. Further physiological information may be derived from the acquired optical information at multiple parts of human body. For example, the blood oxygen saturation levels may be compared between contralateral sides of extremities, which may indicate regional hypoxia, between upper and lower extremities, for example, the Ankle Brachial Pressure Index indicating the condition of peripheral arteries, or between any two distinct parts of human body. 
     The embodiments shown and described above are only examples. Many details are often found in the art such as the other features. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in matters of shape and arrangement of the parts within the principles of the present disclosure up to, and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.