Patent Publication Number: US-2021161444-A1

Title: Light Restriction Designs in Optical Sensing Applications Having Shared Windows

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/874,614, filed Jan. 18, 2018, which claims the benefit of U.S. Provisional Patent Application No. 62/458,525, filed Feb. 13, 2017, the entire disclosures of which are herein incorporated by reference in their entirety. 
    
    
     FIELD 
     This relates generally to a device configured for optical sensing having shared windows and including light restriction designs. More particularly, the disclosure relates to reduction or elimination of crosstalk between optical components for enhanced measurement accuracy and signal-to-noise ratio (SNR). 
     BACKGROUND 
     A user&#39;s physiological signals (e.g., pulse rate or arterial oxygen saturation) can be determined by pulse oximetry systems. In a basic form, pulse oximetry systems can utilize one or more point light sources (i.e., light with a defined beam size that exists an aperture 5 mm or less in diameter) to illuminate a user&#39;s tissue and one or more light detectors to receive light that enters and probes a subsurface volume of tissue. The light sources and light detectors can be in contact with the tissue or can be remote (i.e., not in contact) to the tissue surface. 
     SUMMARY 
     This relates to an electronic device configured for optical sensing having shared windows and including light restriction designs. The light restriction designs can include one or more of optical layers, optical films, lenses, and window systems configured to reduce or eliminate crosstalk between optical components. A plurality of accepting sections and a plurality of blocking sections can be employed to selectively allow light having an angle of incidence within one or more acceptance viewing angles and block light with angles of incidence outside of the acceptance viewing angles. In some examples, the light restriction designs can be vary in optical and structural properties. The variations in optical and structural properties can allow the light restriction designs to have spatially varying acceptance angles. For example, one location of an optical film can be allow light with an angle of incidence of a first acceptance angle to pass through (e.g., narrow acceptance viewing angles), whereas another location of the optical film may block light having the same angle of incidence (e.g., wide acceptance viewing angles). Variations in structural properties can include, but are not limited to, differences in widths, heights, and/or tilts of the accepting sections and/or blocking sections. In some examples, the optical film can be bi-directional accepting light incident from multiple directions, but configured with different ranges of acceptance angles for the different directions. Examples of the disclosure can include the optical layer including one or more of a Fresnel lens an infrared transparent material, and multiple types of accepting and/or blocking sections. Methods for manufacturing the optical layers, optical films, lenses, and window systems and operating the device are further disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented. 
         FIG. 2A  illustrates a top view of an exemplary electronic device including light sensors and light emitters for measuring one or more physiological signals according to examples of the disclosure. 
         FIG. 2B  illustrates a cross-sectional view of an exemplary electronic device including light sensors and light emitters for measuring one or more physiological signals according to examples of the disclosure. 
         FIG. 2C  illustrates a top view of an exemplary electronic device including an alternative configuration of light sensors and light emitters for measuring one or more physiological signals according to examples of the disclosure. 
         FIG. 2D  illustrates a cross-sectional view of an exemplary electronic device including light sensors detecting one or more unwanted light rays according to examples of the disclosure. 
         FIG. 2E  illustrates a top view of an exemplary electronic device including an alternative configuration of light sensors and light emitters for measuring one or more physiological signals according to examples of the disclosure. 
         FIG. 3A  illustrates a cross-sectional view of an exemplary device including an optical layer configured to selective control the angles of light that pass through the optical film to the light sensor according to examples of the disclosure. 
         FIG. 3B  illustrates a cross-sectional view of an exemplary device including an optical layer disposed on or located in close proximity to the light sensor according to examples of the disclosure. 
         FIG. 3C  illustrates a cross-sectional view of an exemplary device including an optical layer covering a portion of the reception region of a window according to examples of the disclosure. 
         FIGS. 3D-3E  illustrate cross-sectional and top views of an exemplary device including an optical layer integrated with a Fresnel lens, according to examples of the disclosure. 
         FIGS. 3F-3G  illustrate cross-sectional views of exemplary devices including an optical layer and an opaque mask according to examples of the disclosure. 
         FIG. 4A  illustrates a cross-sectional view of an exemplary optical layer according to examples of the disclosure. 
         FIG. 4B  illustrates a cross-sectional view of an exemplary optical layer including blocking sections of various heights according to examples of the disclosure. 
         FIG. 4C  illustrates a cross-sectional view of an exemplary optical layer including blocking sections of various tilt angles according to examples of the disclosure. 
         FIG. 4D  illustrates a cross-sectional view of an exemplary optical layer and a Fresnel lens disposed on or located in close proximity to the optical layer according to examples of the disclosure. 
         FIG. 4E  illustrates an exemplary optical layer configured with direction-dependent acceptance angles according to examples of the disclosure. 
         FIG. 4F  illustrates an exemplary optical layer configured with triangular accepting sections according to examples of the disclosure. 
         FIGS. 5A-5B  illustrate cross-sectional views of an exemplary optical layer including a plurality of sets of acceptance angles and an exemplary device including the optical layer according to examples of the disclosure. 
         FIG. 5C  illustrates a cross-sectional view of an exemplary optical layer including a section including a section having different optical properties than the accepting sections according to examples of the disclosure. 
         FIGS. 6A-6C  illustrate top views of exemplary optical layers according to examples of the disclosure. 
         FIGS. 6D-6F  illustrate top views of exemplary optical layers including two different types of accepting sections according to examples of the disclosure. 
         FIGS. 6G-6H  illustrate top views of exemplary optical layers including accepting sections of different types having a pre-determined order according to examples of the disclosure. 
         FIGS. 7A-7B  illustrate top views of exemplary optical layers configured for multiple light emitters according to examples of the disclosure. 
         FIGS. 7C-7D  illustrate top views of exemplary optical layers including curved blocking sections according to examples of the disclosure. 
         FIGS. 7E-7L  illustrate top views of exemplary optical layers with various configurations for a device including multiple light emitters according to examples of the disclosure. 
         FIG. 8A  illustrates an exemplary process for manufacturing a device including the optical layers described in this disclosure. 
         FIG. 8B  illustrates an exemplary operation of the device including the optical layer according to examples of the disclosure. 
         FIG. 9  illustrates an exemplary block diagram of a computing system comprising light emitters and light sensors for measuring a signal associated with a user&#39;s physiological state according to examples of the disclosure. 
         FIG. 10  illustrates an exemplary configuration in which an electronic device is connected to a host according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. Numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. It will be apparent, however, to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. In other instances, well-known process steps and/or structures have not been described in detail in order to not obscure some of the aspects and/or features described or referenced herein. 
     A user&#39;s physiological signals (e.g., pulse rate and arterial blood oxygen saturation) can be determined by measurements using pulse oximetry systems. Such pulse oximetry systems can be designed to be sensitive to changes in the red blood cell number, concentration, volume, or blood oxygen state included in the sample or a user&#39;s vasculature. In a basic form, pulse oximetry systems can employ a light source that injects light into the user&#39;s tissue and a light detector to receive light that reflects and/or scatters and exits the tissue. The light source(s) and light detector(s) can be in contact or can be remote to (i.e., not in contact with) the tissue. In some instances, some of the reflected and/or scattered light measured by the light sensor can be include light that has reflected off one or more interfaces of the device and/or one or more superficial layers of the user. In some instances, the unwanted light signal reflected off the one or more interfaces and/or superficial layers may lead to an erroneous signal, a low signal-to-noise ratio (SNR), or both. 
     This relates to an electronic device configured for optical sensing having shared windows and including light restriction designs. The light restriction designs can include one or more of optical layers, optical films, lenses, and window systems configured to reduce or eliminate crosstalk between optical components. A plurality of accepting sections and a plurality of blocking sections can be employed to selectively allow light having an angle of incidence within one or more acceptance viewing angles and block light with angles of incidence outside of the acceptance viewing angles. In some examples, the light restriction designs can be vary in optical and structural properties. The variations in optical and structural properties can allow the light restriction designs to have spatially varying acceptance angles. For example, one location of an optical film can be allow light with an angle of incidence of a first acceptance angle to pass through (e.g., narrow acceptance viewing angles), whereas another location of the optical film may block light having the same angle of incidence (e.g., wide acceptance viewing angles). Variations in structural properties can include, but are not limited to, differences in widths, heights, and/or tilts of the accepting sections and/or blocking sections. In some examples, the optical film can be bi-directional accepting light incident from multiple directions, but configured with different ranges of acceptance angles for the different directions. Examples of the disclosure can include the optical layer including one or more of a Fresnel lens an infrared transparent material, and multiple types of accepting and/or blocking sections. Methods for manufacturing the optical layers, optical films, lenses, and window systems and operating the device are further disclosed. 
     Representative applications of the apparatus and methods according to the present disclosure are described in this section. These examples are being provided solely to add context and aid in the understanding of the described examples. It will thus be apparent to one skilled in the art that the described examples may be practiced without some or all of the specific details. Other applications are possible, such that the following examples should not be taken as limiting. 
       FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented.  FIG. 1A  illustrates an exemplary mobile telephone  136  that can include a touch screen  124 .  FIG. 1B  illustrates an exemplary media player  140  that can include a touch screen  126 .  FIG. 1C  illustrates an exemplary wearable device  144  that can include a touch screen  128  and can be attached to a user using a strap  146 . The systems of  FIGS. 1A-1C  can utilize the optical layers, optical films, lenses, window systems, and/or methods for detecting one or more physiological signals as will be disclosed. 
       FIG. 2A  illustrates a top view and  FIG. 2B  illustrates a cross-sectional view of an exemplary electronic device including light sensors and light emitters for measuring one or more physiological signals according to examples of the disclosure. The top view in  FIG. 2A  can be viewed as the underside of wearable device  144  of  FIG. 1C , for example. A light sensor  204  can be located proximate to a light emitter  206  on a surface (e.g., external surface of the housing opposite the touch screen) of device  200 . In some examples, light sensor  204  and light emitter  206  can be located in the same cavity, which can be covered by window  203 . Device  200  can be situated such that light sensor  204  and light emitter(s)  206  are proximate to a skin  220  of a user. For example, device  200  can be held in a user&#39;s hand or strapped to a user&#39;s wrist, among other possibilities. 
     Light emitter  206  can generate light  222  exiting window  203 . Light  222  can be directed towards and incident upon the user&#39;s skin  220 . A portion of light  222  can be absorbed by skin  220 , vasculature, and/or blood, and a portion of light (i.e., light  223 ) can reflect back for detection by light sensor  204 . Light  224  can also be incident upon skin  220 , a portion of light  224  can be absorbed by skin  220 , vasculature, and/or blood, and a portion of light (i.e., light  225 ) can reflect back towards device  200 . 
     To prevent or reduce optical crosstalk between light sensor  204  and light emitter  206 , device  200  can include isolation  216  located between light sensor  204  and light emitter  206 . Isolation can divide the cavity into a plurality of sub-cavities. In some examples, the light sensors can be located in one or more sub-cavities separate from the light emitters, each sub-cavity can define regions of the window. For example, an emitter region  205  of a window can overlay a sub-cavity having an emitter, and a reception region  207  of a window can overlay a sub-cavity having a detector. The window can further include a boundary region  209  that overlays the isolation  216  and/or an opaque mask  215 . 
     Opaque mask  215  can prevent isolation  216  from being visible to the human eye. In some examples, opaque mask  215  and isolation  216  can include the same materials and/or functions (e.g., act as an optical isolation and/or cosmetic layer). At least one end of opaque mask  215  and/or isolation  216  can located at or in close proximity to the internal surface (i.e., surface furthest from the exterior surface of the housing of device  200 ) of window  203 . 
       FIG. 2C  illustrates a top view of an exemplary electronic device including an alternative configuration of light sensors and light emitters for measuring one or more physiological signals according to examples of the disclosure. Light emitters  206  may be located in one sub-cavity, and light sensor  204  may be located in another sub-cavity. The isolation (not shown) and opaque mask  215  be included in the boundary region of window  203 . Although  FIGS. 2A-2C  illustrate a single window, examples of the disclosure can include a device including multiple windows and multiple cavities. Each window can include any type of configuration of light sensors and light emitters. The configuration of optical components in different cavities can be the same or may differ, as exemplified in  FIG. 2E . For example, the device can include optical components in one cavity and window having the configuration illustrated in  FIG. 2A  and optical components in another cavity and window having the configuration illustrated in  FIG. 2C . 
     In some examples, light detected by the light sensor can include unwanted light, thereby introducing noise in the measurement signal.  FIG. 2D  illustrates a cross-sectional view of an exemplary electronic device including light sensors detecting one or more unwanted light rays according to examples of the disclosure. Unwanted light can include light emitted by light emitter  206  that has not penetrated to one or more intended layers in skin  220 . For example, light  222  can be emitted by light emitter  206 . Instead of exiting window  203 , light  222  may reflect at one or more interfaces of window  203  (and/or material, such as residue or dirt, located on the window  203 ) due to reflecting at the interface(s) and/or total internal reflection. Light  222  may exit window  203  at some point, reaching light sensor  204 . In this manner, light  222  may not have penetrated to skin  220  and thus, may not include any or little relevant physiological information. In some examples, light  222  detected by light sensor  204  can include the same information as light  222  emitted by light emitter  206 . 
     Another way to overcome or prevent the light sensor from detecting unwanted light can be to selectively control the angle(s) of light that reach the light sensor.  FIG. 3A  illustrates a cross-sectional view of an exemplary device including an optical layer configured to selective control the angles of light that pass through the optical layer to the light sensor according to examples of the disclosure. Device  300  can include light sensor  304 , light emitter  306 , opaque mask  315 , isolation  316 , and window  303  each having one or more properties and/or functions as similar components discussed with respect to  FIGS. 2A-2D . In some examples, window  303  can be shared among multiple optical components. For example, window  303  overlay both light sensor and light emitter cavities. Examples of the disclosure are not limited to window sharing among optical components of different types (e.g., a light emitter and light sensor pair). Device  300  can further include optical layer  350 . Optical layer  350  can include an optical film, discussed in further detail blow, configured to selectively control the angle(s) of light that transmit through optical layer  350  to light sensor  304 . For example, the optical film can include a plurality of accepting sections, as will be discussed below. Each accepting section can allow a set of acceptance viewing angles, such as ±30° relative to normal incidence (i.e., 60°-120° relative to the flat surface of the window), to pass through. Viewing angles outside of the acceptance viewing angles may not transmit through to light sensor  304  and may be blocked (e.g., absorbed or reflected back). 
     Optical layer  350  can be placed at various locations. For example, as shown in  FIG. 3A , optical layer  350  can be disposed on (e.g., contacting) or located in close proximity to the reception region of window  303 . In some examples, the optical layer can be disposed on or located in close proximity to the light sensor, as illustrated in  FIG. 3B . In some examples, the optical layer  350  may cover a portion of the reception region of the window, as illustrated in  FIG. 3C . In some examples, a Fresnel lens can be disposed on the optical layer  350  (as illustrated in  FIG. 4D  and discussed below). 
     Examples of the disclosure can further include an optical layer including an optical film and a Fresnel lens, as illustrated in  FIGS. 3D-3E . Optical layer  350  can include optical film  340  and Fresnel lens  352 . Optical film  340  can be at least partially disposed or located in the reception region of window  303 . Fresnel lens  352  can be disposed or located in close proximity to the emitter region of window  303 . In some examples, optical film  340  can be disposed on light sensor  304 , and Fresnel lens  352  can be disposed on light emitter  306 . In some examples, optical film  340  can spatially extend beyond (e.g., outside the field of view of the optical component) the reception region of window  303  into the boundary region. That is, optical film  340  can be disposed on isolation  316  and/or the cavity including light sensor  304 . Fresnel lens  352  can include, for example, clear epoxy. In some examples, the Fresnel lens  352  can be integrated with the optical film  340 , thereby forming a single continuous layer that can be deposited in one processing step. For example, optical layer  350  (including optical film  340  and Fresnel lens  352 ) can be made from a continuous epoxy component. In other examples, optical layer  350  can be formed by adhering or depositing the optical film  340  to Fresnel lens  352 . 
     In some examples, optical layer  350  can include an opaque mask  315 , as illustrated in  FIG. 3F , which can be a continuous layer (e.g., formed in a single processing step). In some examples, device  300  can include an opaque mask  315  separate from, but disposed on (or in close proximity to), optical layer  350 , as illustrated in  FIG. 3G . Although the figures illustrate optical film  340 , optical layer  350 , and/or Fresnel lens  352  as contacting window  303 , examples of the disclosure can include one or more layers, such as an adhesive layer, located between window  303  and one or more of the optical film  340 , optical layer  350 , and Fresnel lens  352 . In some examples, the device can include a Fresnel lens disposed on or adhered to the optical film  340 . In some examples, the device can include a Fresnel lens disposed on (or located in close proximity to) the light sensor  304  and the optical film  340  disposed on (or located in close proximity to) the window  303 , or vice versa. The device can include, for example, multiple Fresnel lenses, at least one optically coupled to a light sensor, and at least one optically coupled to a light emitter. 
     The optical film  440  can be configured to accept one or more acceptance angles and block other angles. The optical film can have variations in both optical and structural properties. That is, one area of the optical film can have different optical and structural properties than another area. Exemplary varied structural properties relate to the widths of the accepting sections, the heights of the blocking sections, and the tilt of the blocking sections.  FIG. 4A  illustrates a cross-sectional view of an exemplary optical film according to examples of the disclosure. Optical film  440  can include a plurality of sections, such as accepting section  442  and blocking section  443 . In some examples, optical film  440  can be located between a plurality of substrate layers (not shown), which can be configured to provide mechanical support to the plurality of sections. Some of the plurality of sections (e.g., accepting section  442 ) can be configured to allow light incident on optical film  440  having an angle of incidence within the acceptance angles  441  to pass through. Other of the plurality of sections (e.g., blocking section  443 ) can be configured to block light incident on optical film  440  having an angle of incidence outside the acceptance angles  441  from passing through optical film  440 . In some examples, each accepting section  442  can include the same acceptance angles  441 . Additionally, the spacing between adjacent sections  443  and/or width w of accepting sections  442  can be the same. In this manner, the number of layers and/or thickness of the optical layer and the device can be reduced. Accepting sections  442  can include clear epoxy, and blocking sections  443  can include opaque (e.g., black) epoxy, for example. 
     In some examples, the height of the blocking sections can vary, as illustrated in  FIG. 4B . For example, blocking section  443 A can have a height H A , and blocking section  443 B can have a height H B . Height H A  can be different from height H B . Due to the differences in height, corresponding accepting sections can be configured with different acceptance angles. For example, accepting section  442 A corresponding to blocking section  443 A can have narrower acceptance angles  441 A than acceptance angles  441 B, corresponding to accepting section  442 B and blocking section  443 B. Light  423  and light  424  can have the same angle of incidence. Due to height H A  of blocking section  443 A being greater than height H B  of blocking section  443 B, light  424  can be blocked, whereas light  423  can be accepted (i.e., allowed to pass through optical film  440 ). In some examples, blocking section  443 A can be located closer to the light emitter (e.g., light emitter  306  illustrated in  FIG. 3A ) than blocking section  443 B. In this manner, the acceptance viewing angles of the optical film  440  can be varied. In some examples, the heights of the blocking sections can vary gradually (e.g., each blocking section  443  can have a height less than an adjacent blocking section  443  and a height greater than the other adjacent blocking section  443 ). In some examples, the optical film can include a plurality of blocking sections  443  with the same height, and each plurality can different heights from other pluralities. Examples of the disclosure can include all of the blocking sections having the same height while one end of all of the blocking sections contact only one substrate layer (and not the other substrate layer). 
     In some examples, the acceptance viewing angles can be adjusted by configuring the tilt (i.e., angle formed between the blocking section and the substrate layer) of the blocking sections, as illustrated in  FIG. 4C . For example, blocking section  443 A can be tilted the least, while blocking section  443 B can have a greater amount of tilt than blocking section  443 A. In this manner, acceptance section  442 A (corresponding to blocking section  443 A) can be configured to accept light with narrower angles of incidence than acceptance section  442 B (corresponding to blocking section  443 B). In some examples, the tilt of the blocking sections can vary gradually (e.g., each blocking section  443  can have a tilt less than an adjacent blocking section  443  and a tilt greater than the other adjacent blocking section  443 ). In some examples, the optical film can include a plurality of blocking sections  443  with the same tilt, and each plurality can have a different tilt from other pluralities (e.g., two adjacent first blocking sections having the same first tilt, followed by two adjacent second blocking sections having the same second tilt). Examples of the disclosure can include all of the blocking sections having the same tilt. 
     The width(s) (e.g., width w illustrated in  FIG. 4A ), height (e.g., height h a  illustrated in  FIG. 4B ), and/or tilt can be configured based on one or more properties of other components included in the device. The one or properties can include the dimensions (e.g., height and width) and material properties (e.g., refractive index) of the window, the amount of light allowed to be incident on the photodiode, the width of the opaque mask, and the separation distance(s) between light emitter(s) and light sensor(s). Examples of the disclosure can further include one or more Fresnel lenses, such as Fresnel lens  452  illustrated in  FIG. 4D  disposed on or in close proximity to optical film  440 . 
     In some examples, the optical film can be configured as a bi-directional optical film with direction-dependent acceptance angles.  FIG. 4E  illustrates an exemplary optical film configured with direction-dependent acceptance angles according to examples of the disclosure. Optical film  440  can include a plurality of blocking sections  443  configured to block light coming from a first direction (e.g., left side). The optical film  440  can include a plurality of angled sections  456  configured to allow light from the first direction having acceptance angles  454  (relative to normal incidence  453 ) to pass through the optical film  440 . Light from the first direction having an angle of incidence outside of the acceptance angles  454  may not pass through the optical film due to total internal reflection occurring at the interface of the angled sections  456 . The optical film can further be configured to allow light from a second direction (e.g., right side) having acceptance angles  455  (relative to normal incidence  453 ) to pass through the optical film  440 . Light from the second direction having an angle of incidence outside of the acceptance angles  455  may not pass through the optical film due to total internal reflection occurring at the interface of the angled sections  456 . The acceptance angles  454  and acceptance angles  455  can be varied by adjusting the angles of angled edges  456  (e.g., accepting sections), where acceptance angles  454  can be different from acceptance angles  455 . For example, acceptance angles  455  can include wider viewing angles than acceptance angles  454 . In this manner, the optical film  440  can be direction-dependent, and the overall range of acceptance angles of the optical film  440  can be tilted (e.g., towards the second direction). That is, the optical film  440  can accept wider viewing angles from the second direction than viewing angles accepted from the first direction. In some examples, an optical film can be configured with direction-dependent acceptance angles by including a plurality of blocking sections  443 , as shown in  FIG. 4F , along with accepting sections  442  having angled edges. The angled (i.e., sloped) edges can be formed by fabricating (e.g., molding, lapping, grinding, polishing, etc.) accepting sections  442  to be triangular in shape, for example. 
     In some examples, the optical film can include a plurality of sets of accepted viewing angles.  FIGS. 5A-5B  illustrate cross-sectional views of an exemplary optical film including a plurality of sets of acceptance angles and an exemplary device including the optical film according to examples of the disclosure. Optical film  540  can include a plurality of accepting sections  542 , each section having one or more acceptance viewing angles. The plurality of sections  542  can have different acceptance viewing angles. For example, at least one accepting section  542 A can have acceptance angles  541 A; at least another accepting section  542 B can have acceptance angles  541 B; and at least another accepting section  542 C can have acceptance angles  541 C. In some examples, the acceptance angles can vary depending on the location of the optical film  540  relative to the intended measurement location on skin  520  and/or other components in device  500 . For example, device  500  can be configured to measure volume  521  in skin  520 . To capture light from volume  521 , optical film  540  can be configured to accept narrower viewing angles for sections located closer to volume  521  (e.g., closer to isolation  516  and/or light emitter  506 ) and wider viewing angles for sections located further away from volume  521 . For example, device  500  can accept both light  522  and light  523 , where the angle of incidence of light  522  is less than the angle of incidence of light  523 . The same section that accepted light  522  may not accept light  524 , which may have the same angle of incidence as light  523 . Light  524  may have originated from an unwanted volume (e.g., a volume outside volume  521 ) of skin  520 . In this configuration, acceptance angles  541 A can be less than acceptance angles  541 B, which can be less than acceptance angles  541 C. In some examples, the acceptance angles can vary gradually (e.g., each accepting section  542  can have acceptance angles less than an adjacent accepting section  542  and acceptance angles greater than the other adjacent accepting section  542 ). In some examples, the optical film can include a plurality of accepting sections  542  with the same acceptance angles, and each plurality can different acceptance angles from other pluralities. 
     In some examples, the width of at least two of the plurality of sections  542  can differ. For examples, accepting section  542 A corresponding to acceptance angles  541 A can have a width w A , which can be different from width w B  corresponding to accepting section  542 B having acceptance angles  541 B and width w e  corresponding to accepting section  542 C having acceptance angles  541 C. In some instances, sections (e.g., accepting section(s)  542 A) of optical film  540  located closer to volume  521  (e.g., closer to isolation  516  and/or light emitter  506 ) can be narrower than sections (e.g., sections  542 C) of optical film  540  located further away. For example, width w A  can be narrower than width w C . Examples of the disclosure can include variations in the widths of the accepting sections that corresponding variations in the acceptance angles (e.g., wider acceptance angles can be achieved by configuring the optical film with wider accepting sections), as discussed above. 
     In some examples, optical film  540  can include one or more sections, such as section  545  illustrated in  FIG. 5C , configured to accept light having optical properties different from the accepting sections. Section  545  can be located a pre-determined distance away from isolation  516  and/or light emitter  506 . Alternatively, section  545  may be excluded from optical film  540  and may instead be an absence of material. In some examples, section  545  can include one or more materials (e.g., an infrared transparent ink) and may be separate and distinct from optical film  540 . Further details with respect to section  545  are provided below. 
     The blocking sections of the optical film can be configured based on the location of the light emitter.  FIGS. 6A-6B  illustrate top views of exemplary optical films according to examples of the disclosure. Optical film  640  can include a plurality of accepting sections  642  and a plurality of blocking sections  643 . The block sections  643  can be straight lines or rectangles, as shown in  FIG. 6A , oriented orthogonal to the direction of light  622  emitted by light emitter  606 . In some examples, as illustrated in  FIG. 6B , the center of the blocking sections  643  can be aligned with the center of the light emitter  606 , as indicated by centerline  607 . As illustrated in the figure, the curvature of the blocking sections  643  can decrease as the separation distance between a respective blocking section  643  and light emitter  606  increases. 
     Examples of the disclosure include various configurations for the sections. For example, as illustrated in  FIG. 6C , optical film  640  can include section  645 . At distances shorter than a pre-determined distance  608 , the optical film  640  can include a plurality of accepting sections  642  and a plurality of blocking sections  643 . At distances longer than distance  608 , the optical film can include section  645 . Section  645  can include one or more functions and/or properties as described above with respect to section  545 . 
     The optical film can also include multiple types of blocking sections and/or accepting sections.  FIG. 6D  illustrates an exemplary optical film including two different types of accepting sections: accepting sections  642  and accepting sections  646 . Accepting sections  642  can have one or more properties different from accepting sections  446 . For example, accepting sections  642  can include a material configured to allow one or more ranges of wavelengths (e.g., visible light) to pass through, while accepting sections  646  can include material configured to allow other ranges of wavelengths (e.g., infrared light) to pass through. In some examples, section  645  can be located on one end (e.g., the end furthest from light emitter  606 ), as illustrated in  FIG. 6D , and in other examples, section  645  can be located between accepting sections, as illustrated in  FIG. 6E . In some examples, section  645  can overlap with at least a portion of the accepting sections, as illustrated in  FIG. 6F . 
     In some examples, the different types of accepting sections can be interleaved (e.g., an accepting section  642 , a blocking section  443 , an accepting sections  646 , a blocking section  443 , an accepting section  642 , etc.). In some examples, blocking sections can be replaced by accepting sections (e.g., an accepting section  642 , an accepting section  646 , an accepting section  642 , an accepting section  646 , etc.), as illustrated in  FIG. 6G . That is, accepting sections can multi-functional configured to both accept light having one or more wavelengths and acceptance viewing angles and block light have other wavelengths and/or other viewing angles. In some examples, optical film  640  can exclude blocking sections. 
     The configuration of the optical film can include any ordering of the accepting section(s) and blocking section(s). The order can depend on several factors, such as the desired amount of light to pass through to the light sensor, the amount of noise and/or crosstalk, the placement of the light emitters, etc. As a non-limiting example,  FIG. 6H  illustrates optical film  640  with the sections ordered as two adjacent accepting sections of differing type next to a block section (e.g., accepting section  646 , accepting section  642 , accepting section  646 , blocking section  643 , accepting section  646 , accepting section  642 , accepting section  646 , blocking section  643 , etc.) Examples of the disclosure including any order and configurations of the sections such that the total area of accepting sections configured for visible transparency is greater than the total area of accepting sections configured for infrared transparency. 
     In some examples, the same optical film can be optically coupled to multiple light emitters.  FIGS. 7A-7B  illustrate top views of exemplary optical films configured for multiple light emitters according to examples of the disclosure. Optical film  740  can restrict acceptance viewing angles for both light emitters  706 . In some examples, as illustrated in  FIG. 7B , optical film  740  can include another section  745 , which can include a material different from accepting sections  742 , can exclude a material, and/or can be separate and distinct from optical film  740 . For example, section  745  can include one or more properties and/or functions as section  545  (illustrated in  FIG. 5D ). For example, section  745  can include an infrared transparent material configured to allow infrared light to pass through to the light sensor for proximity sensing (e.g., off-wrist detection). The infrared transparent ink can be configured to allow infrared light to pass through to the light sensor, while also configured to at least partially block the user&#39;s view (e.g., a material that absorbs or blocks visible light). 
     Although the figure illustrates blocking sections oriented along one direction as straight lines, examples of the disclosure can include any configuration, shape, and/or size of blocking sections and accepting sections as discussed throughout the disclosure.  FIG. 7C  illustrates a top view of an exemplary optical film including curved blocking sections with the center of the blocking sections  743  aligned with the center of its respective light emitter  706 . In some examples, optical film  740  can include section  745 . In some examples, the accepting sections of the different light emitters can overlap, at least partially, as shown in  FIG. 7D . Overlapping the accepting sections may include forming one section on top of another in the stackup, thereby creating multiple layers disposed on the window (not shown). 
     The optical film can be optically coupled to light emitters located on different sizes of the optical film.  FIGS. 7E-7H  illustrate top views of exemplary optical films with various configurations for a device including multiple light emitters according to examples of the disclosure. The blocking sections of the optical film can be configured to be anisotropic to prevent blocking of light from the user&#39;s skin that can include useful physiological information. For example, the accepting sections  742  and blocking sections  743  can be configured as any shape including, but not limited to, circles (as illustrated in  FIG. 7E ), squares/rectangles (as illustrated in  FIG. 7F ), arcs (as illustrated in  FIG. 7G ), or triangles (as illustrated in  FIG. 7H ). The center the blocking sections  743  can be located in the center of the optical film  740  (as illustrated in  FIGS. 7E-7H ) or can be aligned with the center of the optical components (as illustrated in  FIGS. 7I-7K ). Furthermore, optical film  740  can include multiple different types of shapes. Additionally or alternatively, optical film  740  can exclude section  745  (as illustrated in  FIGS. 7I-7J ) or can include section  745  between sections (as illustrated in  FIG. 7K ). In some examples, multiple areas of the optical film can be spatially separated by an absence of material (as illustrated in  FIG. 7I ). In some examples, blocking sections may not form closed shapes and/or may not extend from one side of the optical film to the other, as illustrated in  FIG. 7L . 
     As illustrated in the figures and discussed above and below, the optical film and/or optical layer can have spatially varying asymmetry in its structural and/or optical properties. Additionally, including light emitters configured to emit various wavelengths (e.g., visible and infrared) of light, the device can be a multi-functional device with minimal or reduced crosstalk between the light emitters and light sensors, thereby enhancing the measurement accuracy. The multiple functions can include, but are not limited to, physiological information determination (e.g., heart rate, background heart rate, etc.) and off-wrist detection. Further, although the figures illustrate a single-pixel light sensor, examples of the disclosure can include light sensors having multiple pixels. 
     Although process steps or method steps can be described in a sequential order, such processes and methods can be configured to work in any suitable order. In other words, any sequence or order of steps that can be described in the disclosure does not, in and of itself, indicate a requirement that the steps be performed in that order. Further, some steps may be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Moreover, the illustration of a process by its depiction in a drawing does not imply that the illustrated process is exclusive of other variations and modification thereto, does not imply that the illustrated process or any of its steps are necessary to one or more of the examples, and does not imply that the illustrated process is preferred. 
     The optical layers, optical films, lens, window systems described above can be manufactured using various different fabrication techniques.  FIG. 8A  illustrates an exemplary process for manufacturing a device including the optical layers described in this disclosure. Process  800  can include forming and/or adhering the light emitter(s) (e.g., light emitter  306  illustrated in  FIG. 3A ) and light sensor(s) (e.g., light sensor  304  illustrated in  FIG. 3A ) in one or more cavities included in the device (step  802 ). The isolation (e.g., isolation  316  illustrated in  FIG. 3A ) and/or opaque mask  315  (e.g., isolation  315  illustrated in  FIG. 3A ) can be deposited (step  804 ). Optical layer (e.g., optical layer  350  illustrated in  FIGS. 3A-3B ) can be deposited or mounted to the device (step  806 ). In some examples, the optical layer can be formed on the light sensor. In some examples, the optical layer can be formed on the window. In some examples, forming the optical layer can include forming the accepting sections and blocking sections between substrate layers (not shown). A Fresnel lens (e.g., Fresnel lens  352  illustrated in  FIG. 3D ) can be deposited or mounted to one or more components (e.g., light emitter  306  illustrated in  FIG. 3D ), optical film  440  illustrated in  FIG. 4D , etc.) of the device (step  808 ). In some examples, optical layer can be a single layer including multiple components (e.g., optical film, opaque mask, Fresnel lens, etc.) formed in a single processing step. The window can be adhered/mounted to the device (step  810 ) either before or after the optical layer is deposited. 
       FIG. 8B  illustrates an exemplary operation of the device including the optical layer according to examples of the disclosure. Process  850  includes emitting light from the light emitter (step  852 ). The window can allow the emitted light to transmit through the window (step  854 ). Optionally, the emitted light further transmits through a Fresnel lens. A portion of the emitted light can interact with the skin of the user, and a portion can reflect back towards the device (step  856 ). The window can allow the reflected light to transmit through the window (step  858 ). The optical layer can accept the reflected light if the angle of incidence is within the acceptance angles (step  860 ). Otherwise, the optical layer can prevent (e.g., absorb or reflect back) the reflected light from transmitting through the optical layer (step  862 ). The accepted reflected light can be detected by the light sensor (step  864 ), and the processor can include signals from the detected reflected light in determining the physiological information of the user (step  866 ). Examples of the disclosure can further include the optical layer allowing infrared light to transmit through to the light sensor, the light sensor detecting the infrared light and generating a signal indicative of the infrared light, and the processor executing one or more instructions related to off-wrist detection. 
       FIG. 9  illustrates an exemplary block diagram of a computing system comprising light emitters and light sensors for measuring a signal associated with a user&#39;s physiological state according to examples of the disclosure. Computing system  900  can correspond to any of the computing devices illustrated in  FIGS. 1A-1C . Computing system  900  can include a processor  910  configured to execute instructions and to carry out operations associated with computing system  900 . For example, using instructions retrieved from memory, processor  910  can control the reception and manipulation of input and output data between components of computing system  900 . Processor  910  can be a single-chip processor or can be implemented with multiple components. 
     In some examples, processor  910  together with an operating system can operate to execute computer code and produce and use data. The computer code and data can reside within a program storage block  902  that can be operatively coupled to processor  910 . Program storage block  902  can generally provide a place to hold data that is being used by computing system  900 . Program storage block  902  can be any non-transitory computer-readable storage medium, and can store, for example, history and/or pattern data relating to physiological information measured by one or more light sensors such as light sensors  904 . By way of example, program storage block  902  can include Read-Only Memory (ROM)  918 , Random-Access Memory (RAM)  922 , hard disk drive  908  and/or the like. The computer code and data could also reside on a removable storage medium and loaded or installed onto the computing system  900  when needed. Removable storage mediums include, for example, CD-ROM, DVD-ROM, Universal Serial Bus (USB), Secure Digital (SD), Compact Flash (CF), Memory Stick, Multi-Media Card (MMC) and a network component. 
     Computing system  900  can also include an input/output (I/O) controller  912  that can be operatively coupled to processor  910 , or it can be a separate component as shown. I/O controller  912  can be configured to control interactions with one or more I/O devices. I/O controller  912  can operate by exchanging data between processor  910  and the I/O devices that desire to communicate with processor  910 . The I/O devices and I/O controller  912  can communicate through a data link. The data link can be a one-way link or a two-way link. In some cases, I/O devices can be connected to I/O controller  912  through wireless connections. By way of example, a data link can correspond to PS/2, USB, Firewire, IR, RF, Bluetooth or the like. 
     Computing system  900  can include a display device  924  that can be operatively coupled to processor  910 . Display device  924  can be a separate component (peripheral device) or can be integrated with processor  910  and program storage block  902  to form a desktop computer (e.g., all-in-one machine), a laptop, handheld or tablet computing device of the like. Display device  924  can be configured to display a graphical user interface (GUI) including perhaps a pointer or cursor as well as other information to the user. By way of example, display device  924  can be any type of display including a liquid crystal display (LCD), an electroluminescent display (ELD), a field emission display (FED), a light emitting diode display (LED), an organic light emitting diode display (OLED) or the like. 
     Display device  924  can be coupled to display controller  926  that can be coupled to processor  910 . Processor  910  can send raw data to display controller  926 , and display controller  926  can send signals to display device  924 . Data can include voltage levels for a plurality of pixels in display device  924  to project an image. In some examples, processor  910  can be configured to process the raw data. 
     Computing system  900  can also include a touch screen  930  that can be operatively coupled to processor  910 . Touch screen  930  can be a combination of sensing device  932  and display device  924 , where the sensing device  932  can be a transparent panel that is positioned in front of display device  924  or integrated with display device  924 . In some cases, touch screen  930  can recognize touches and the position and magnitude of touches on its surface. Touch screen  930  can report the touches to processor  910 , and processor  910  can interpret the touches in accordance with its programming. For example, processor  910  can perform tap and event gesture parsing and can initiate a wake of the device or powering on one or more components in accordance with a particular touch. 
     Touch screen  930  can be coupled to a touch controller  940  that can acquire data from touch screen  930  and can supply the acquired data to processor  910 . In some cases, touch controller  940  can be configured to send raw data to processor  910 , and processor  910  can process the raw data. For example, processor  910  can receive data from touch controller  940  and can determine how to interpret the data. The data can include the coordinates of a touch as well as pressure exerted. In some examples, touch controller  940  can be configured to process raw data itself. That is, touch controller  940  can read signals from sensing points  934  located on sensing device  932  and can turn the signals into data that the processor  910  can understand. 
     Touch controller  940  can include one or more microcontrollers such as microcontroller  942 , each of which can monitor one or more sensing points  934 . Microcontroller  942  can, for example, correspond to an application specific integrated circuit (ASIC), which works with firmware to monitor the signals from sensing device  932 , process the monitored signals, and report this information to processor  910 . 
     One or both display controller  926  and touch controller  940  can perform filtering and/or conversion processes. Filtering processes can be implemented to reduce a busy data stream to prevent processor  910  from being overloaded with redundant or non-essential data. The conversion processes can be implemented to adjust the raw data before sending or reporting them to processor  910 . 
     In some examples, sensing device  932  can be based on capacitance. When two electrically conductive members come close to one another without actually touching, their electric fields can interact to form a capacitance. The first electrically conductive member can be one or more of the sensing points  934 , and the second electrically conductive member can be an object  990  such as a finger. As object  990  approaches the surface of touch screen  930 , a capacitance can form between object  990  and one or more sensing points  934  in close proximity to object  990 . By detecting changes in capacitance at each of the sensing points  934  and noting the position of sensing points  934 , touch controller  940  can recognize multiple objects, and determine the location, pressure, direction, speed, and acceleration of object  990  as it moves across the touch screen  930 . For example, touch controller  990  can determine whether the sensed touch is a finger, tap, or an object covering the surface. 
     Sensing device  932  can be based on self-capacitance or mutual capacitance. In self-capacitance, each of the sensing points  934  can be provided by an individually charged electrode. As object  990  approaches the surface of the touch screen  930 , the object can capacitively couple to those electrodes in close proximity to object  990 , thereby stealing charge away from the electrodes. The amount of charge in each of the electrodes can be measured by the touch controller  940  to determine the position of one or more objects when they touch or hover over the touch screen  930 . In mutual capacitance, sensing device  932  can include a two layer grid of spatially separated lines or wires (not shown), although other configurations are possible. The upper layer can include lines in rows, while the lower layer can include lines in columns (e.g., orthogonal). Sensing points  934  can be provided at the intersections of the rows and columns. During operation, the rows can be charged, and the charge can capacitively couple from the rows to the columns. As object  990  approaches the surface of the touch screen  930 , object  990  can capacitively couple to the rows in close proximity to object  990 , thereby reducing the charge coupling between the rows and columns. The amount of charge in each of the columns can be measured by touch controller  940  to determine the position of multiple objects when they touch the touch screen  930 . 
     Computing system  900  can also include one or more light emitters such as light emitters  906  and one or more light sensors such as light sensors  904  proximate to skin  920  of a user. Light emitters  906  can be configured to generate light, and light sensors  904  can be configured to measure a light reflected or absorbed by skin  920 , vasculature, and/or blood of the user. Device  900  can include optical film  940  coupled to light emitters  906 . Light sensor  904  can send measured raw data to processor  910 , and processor  910  can perform noise and/or artifact cancelation to determine the signals. Processor  910  can dynamically activate light emitters and/or light sensors based on an application, user skin type, and usage conditions. In some examples, some light emitters and/or light sensors can be activated, while other light emitters and/or light sensors can be deactivated to conserve power, for example. In some examples, processor  910  can store the raw data and/or processed information in a ROM  918  or RAM  922  for historical tracking or for future diagnostic purposes. 
     In some examples, the light sensors can measure light information and a processor can determine the physiological information from the reflected or absorbed light. Processing of the light information can be performed on the device as well. In some examples, processing of light information need not be performed on the device itself.  FIG. 10  illustrates an exemplary configuration in which an electronic device is connected to a host according to examples of the disclosure. Host  1010  can be any device external to device  1000  including, but not limited to, any of the systems illustrated in  FIGS. 1A-1C  or a server. Device  1000  can be connected to host  1010  through communications link  1020 . Communications link  1020  can be any connection including, but not limited to, a wireless connection and a wired connection. Exemplary wireless connections include Wi-Fi, Bluetooth, Wireless Direct and Infrared. Exemplary wired connections include Universal Serial Bus (USB), FireWire, Thunderbolt, or any connection requiring a physical cable. 
     In operation, instead of processing light information from the light sensors on the device  1000  itself, device  1000  can send raw data  1030  measured from the light sensors over communications link  1020  to host  1010 . Host  1010  can receive raw data  1030 , and host  1010  can process the light information. Processing the light information can include canceling or reducing any noise due to artifacts and determining physiological signals such as a user&#39;s heart rate. Host  1010  can include algorithms or calibration procedures to account for differences in a user&#39;s characteristics affecting the measured signals. Additionally, host  1010  can include storage or memory for tracking physiological information history for diagnostic purposes. Host  1010  can send the processed result  1040  or related information back to device  1000 . Based on the processed result  1040 , device  1000  can notify the user or adjust its operation accordingly. By offloading the processing and/or storage of the light information, device  1000  can conserve space and power-enabling device  1000  to remain small and portable, as space that could otherwise be required for processing logic can be freed up on the device. 
     In some examples, an optical layer is disclosed. The optical layer can comprise: an optical film including a plurality of regions, each region configured to allow light having an angle of incidence within a plurality of viewing angles to pass through, the plurality of viewing angles of each region different from the plurality of viewing angles of other regions, wherein each region is further configured to prevent light having an angle of incidence outside of the plurality of viewing angles from passing through. Additionally or alternatively, in some examples, the optical layer further comprises: a Fresnel lens, wherein the Fresnel lens and the optical film are a continuous layer. Additionally or alternatively, in some examples, the optical layer further comprises: an opaque mask, wherein the Fresnel lens, opaque mask, and optical film are a continuous layer. Additionally or alternatively, in some examples, the optical layer of claim  1 , further comprises: a Fresnel lens disposed on the optical film. Additionally or alternatively, in some examples, the optical film includes: a plurality of accepting sections, each accepting section configured to allow the light to pass through, wherein each of the plurality of accepting sections has the same width as the other of the plurality of accepting sections; and a plurality of blocking sections, each block section configured to prevent light having an angle of incidence outside of the plurality of viewing angles from passing through. Additionally or alternatively, in some examples, the optical film includes: a plurality of accepting sections, each accepting section configured to allow the light to pass through; and a plurality of blocking sections, each block section configured to prevent light having an angle of incidence outside of the plurality of viewing angles from passing through, wherein at least two of the plurality of blocking sections have different heights. Additionally or alternatively, in some examples, the heights of the plurality of blocking sections gradually vary. Additionally or alternatively, in some examples, the optical film includes: a plurality of accepting sections, each accepting section configured to allow the light to pass through; and a plurality of blocking sections, each block section configured to prevent light having an angle of incidence outside of the plurality of viewing angles from passing through, wherein at least two of the plurality of blocking sections have different tilts. Additionally or alternatively, in some examples, the optical layer further comprising: a section configured to accept light having optical properties different from the optical film, wherein the section and the optical film are a continuous layer. Additionally or alternatively, in some examples, the section includes an infrared transparent material. Additionally or alternatively, in some examples, at least two of the regions are configured to allow light having different wavelengths to pass through. Additionally or alternatively, in some examples, one region is configured to allow visible light to pass through, and another region is configured to allow infrared light to pass through. 
     In some examples, an optical layer is disclosed. The optical layer can comprise: an optical film configured to: allow light from a first direction having an angle of incidence within a plurality of first viewing angles to pass through, prevent light from the first direction having an angle of incidence outside of the plurality of first viewing angles from passing through, allow light from a second direction, different from the first direction, having an angle of incidence within a plurality of second viewing angles, different from the first viewing angles, to pass through, and prevent light from the second direction having an angle of incidence outside of the plurality of second viewing angles from passing through. Additionally or alternatively, in some examples, the optical film includes: a plurality of accepting sections, each accepting section configured to allow the light to pass through, wherein each acceptance section includes an angled edge; and a plurality of blocking sections, each block section configured to prevent the light having an angle of incidence outside of the plurality of first and second viewing angles from passing through. Additionally or alternatively, in some examples, the optical layer of claim  13 , further comprises: a Fresnel lens, wherein the Fresnel lens and the optical film are a continuous layer. 
     In some examples, a device is disclosed. The device can comprise: one or more light emitters configured to emit light; one or more light sensors configured to detect at a least a portion of the emitted light; one or more windows configured to allow light from the one or more light emitters, the one or more light sensors, or both to pass through, at least one window including an emitter region, a reception region, and a boundary region; and an optical layer disposed on the one or more windows, the optical layer comprising: an optical film including a plurality of regions, each region configured to allow light having an angle of incidence within a plurality of viewing angles to pass through, the plurality of viewing angles of each region different from the plurality of viewing angles of other regions, wherein each region is further configured to prevent light having an angle of incidence outside of the plurality of viewing angles from passing through, wherein the optical layer covers a portion of the reception region of the at least one window. Additionally or alternatively, in some examples, the device further comprises: an isolation located between at least one of the one or more light emitters and at least one of the one or more light sensors, wherein the isolation is further located in the boundary region of the at least one window, wherein the optical film covers the boundary region of the at least one window. Additionally or alternatively, in some examples, the plurality of accepting sections includes at least one first accepting section and at least one second accepting section, the first accepting section configured with one or more first acceptance angles and the second accepting section configured with one or more second acceptance angles, the one or more second acceptance angles including at least one wider viewing angle than the one or more first acceptance angles, and the at least first accepting section located closer to at least one of the one or more light emitters than the at least second accepting section. 
     In some examples, a method for determining one or more physiological information of a user is disclosed. The method can comprise: emitting light from one or more light emitters; transmitting the emitted light through one or more windows; allowing at least a portion of the emitted light to transmit through an optical layer including: allowing a portion of the emitted light having an angle of incidence within first viewing angles at a first region of the optical layer, allowing a portion of the emitted light having an angle of incidence within second viewing angles, different from the first viewing angles, at a second region, different from the first region, of the optical layer, and blocking a portion of the emitted light having an angle of incidence outside of the first and second viewing angles; detecting the allowed portion of the emitted light by one or more light sensors; and determining the one or more physiological information from the detected allowed portion of the emitted light. 
     In some examples, a method for determining one or more physiological information of a user is disclosed. The method can comprise: emitting light from one or more light emitters; transmitting the emitted light through one or more windows; allowing at least a portion of the emitted light to transmit through an optical layer including: allowing a portion of the emitted light from a first direction and having an angle of incidence within first viewing angles, allowing a portion of the emitted light from a second direction, different from the first direction, having an angle of incidence within second viewing angles, different from the first viewing angles, at a second region, different from the first region, of the optical layer, and blocking a portion of the emitted light having an angle of incidence outside of the first and second viewing angles; detecting the allowed portion of the emitted light by one or more light sensors; and determining the one or more physiological information from the detected allowed portion of the emitted light. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed examples as defined by the appended claims.