CN107884975A - Electronic device and sensor assembly - Google Patents

Abstract

The application provides an electronic device, including: the display screen and the sensor assembly are mounted on the shell, the sensor assembly is arranged below a display area of the display screen, a light shielding layer is arranged on one side, facing the sensor assembly, of the display screen, an opening is formed in the light shielding layer, and the sensor assembly is arranged below the opening; the sensor assembly comprises a signal transmitter and a signal receiver, and a rotatable light guide sleeve is sleeved above the signal transmitter; when the signal emitter needs to emit detection signals, the direction of the rotatable light guide sleeve is adjusted according to the direction of liquid crystal molecules in the display screen, so that the rotatable light guide sleeve corresponds to the gaps among the liquid crystal molecules, and the detection signals emitted by the signal emitter penetrate through the gaps to be emitted to the outside. The invention can realize the full screen to achieve the effect of full screen display and can improve the transmittance of the signal emitted by the signal emitter.

Description

Electronics and sensor components

technical field

The present application relates to the technical field of electronic devices, in particular to an electronic device and a sensor component.

Background technique

With the rapid development of communication technology, electronic devices such as mobile terminals are becoming more and more popular and have become indispensable devices in people's lives. People can learn, entertain and so on through mobile terminals.

At present, the mobile terminal adopts the principle of an infrared proximity sensor to realize the judgment of proximity and distance. Therefore, it is necessary to open a sensor through hole in the non-display area of the display screen, place the infrared proximity sensor under the sensor through hole, and the infrared light signal emitted and received by the infrared proximity sensor is transmitted through the sensor through hole. However, such a design needs to divide the display screen into a non-display area, so that the screen-to-occupancy ratio of the display area is not high, and it is impossible to realize a full screen to achieve a full-screen display effect.

Contents of the invention

An embodiment of the present application provides an electronic device and a sensor component, which can realize a full screen to achieve a full screen display effect, and can improve the transmittance of a signal emitted by a signal transmitter.

An embodiment of the present application provides an electronic device, including: a casing, a display screen and a sensor assembly, the display screen and the sensor assembly are installed on the casing, and the sensor assembly is arranged in the display area of the display screen Below, the side of the display screen facing the sensor assembly is provided with a light-shielding layer, the light-shielding layer is provided with an opening, and the sensor assembly is arranged below the opening;

The sensor assembly includes a signal transmitter and a signal receiver, and a rotatable light guide sleeve is sleeved above the signal transmitter;

When the signal transmitter needs to emit a detection signal, the direction of the rotatable light guide sleeve is adjusted according to the direction of the liquid crystal molecules in the display screen, so that the rotatable light guide sleeve corresponds to the position between the liquid crystal molecules. The gap between them, so that the detection signal emitted by the signal transmitter passes through the gap to be transmitted to the outside.

The embodiment of the present application also provides a sensor assembly, the sensor assembly is arranged below the display area of the display screen, the sensor assembly includes a signal transmitter and a signal receiver, and a Rotating light guide sleeve;

When the signal transmitter needs to emit a detection signal, the direction of the rotatable light guide sleeve is adjusted according to the direction of the liquid crystal molecules in the display screen, so that the rotatable light guide sleeve corresponds to the position between the liquid crystal molecules. The gap between them, so that the detection signal emitted by the signal transmitter passes through the gap to be transmitted to the outside.

In the electronic device and the sensor component provided by the present application, since the sensor component is arranged under the display area of the display screen, the side of the display screen facing the sensor component is provided with a light-shielding layer, and the light-shielding layer is provided with an opening, The sensor assembly is arranged under the opening; therefore, the present application does not need to divide the display screen into a non-display area, thereby realizing a full screen to achieve the effect of a full screen display. In addition, since the rotatable light guide sleeve is set above the signal transmitter of the sensor assembly; when the signal transmitter needs to emit detection signals, the rotatable light guide sleeve is adjusted according to the direction of the liquid crystal molecules in the display Rotate the direction of the light guide sleeve so that the rotatable light guide sleeve corresponds to the gap between the liquid crystal molecules, so that the detection signal emitted by the signal transmitter passes through the gap to be emitted to the outside, effectively improving the signal transmission The transmittance of the signal emitted by the sensor, thereby enhancing the signal strength received by the signal receiver, thereby improving the detection accuracy of the sensor component, thereby improving the accuracy of the electronic device controlling the display screen to turn off or turn on the screen.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings that need to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.

FIG. 2 is a schematic structural diagram of a display screen assembly provided by an embodiment of the present application.

FIG. 3 is another schematic structural diagram of a display screen assembly provided by an embodiment of the present application.

FIG. 4 is a schematic plan view of a display screen in a display screen assembly provided by an embodiment of the present application.

FIG. 5 is another schematic structural diagram of the display screen assembly provided by the embodiment of the present application.

FIG. 6 is another schematic structural diagram of the display screen assembly provided by the embodiment of the present application.

FIG. 7 is a schematic structural diagram of a detection signal passing through gaps between liquid crystal molecules provided by an embodiment of the present application.

Detailed ways

Referring to the drawings in the accompanying drawings, where the same reference numerals represent the same components, the principles of the present application are exemplified by implementing them in an appropriate environment. The following description is based on illustrated specific embodiments of the present application, which should not be construed as limiting other specific embodiments of the present application not described in detail herein.

The word "embodiment" as used in this specification means serving as an example, instance or illustration. Furthermore, the article "a" as used in this specification and the appended claims may generally be construed to mean "one or more" unless specified otherwise or clear from context to refer to a singular form.

In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Orientation indicated by rear, left, right, vertical, horizontal, top, bottom, inside, outside, clockwise, counterclockwise, etc. The positional relationship is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it should not be construed as limiting the application.

In the description of this application, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected, or electrically connected, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation. Those of ordinary skill in the art can understand the specific meanings of the above terms in this application according to specific situations.

In addition, unless otherwise expressly specified and limited, a first feature being "on" or "under" a second feature may include that the first and second features are in direct contact, and may also include that the first and second features are not in direct contact. Rather, through additional characteristic contact between them. Moreover, "above", "above" and "above" the first feature on the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. "Below", "beneath" and "under" the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

The following disclosure provides many different implementations or examples for implementing different structures of the present application. To simplify the disclosure of the present application, components and arrangements of specific examples are described below. Of course, they are examples only and are not intended to limit the application. Furthermore, the present application may repeat reference numerals and/or reference letters in various instances, such repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or arrangements discussed. In addition, various specific process and material examples are provided herein, but one of ordinary skill in the art may recognize the use of other processes and/or the use of other materials.

An embodiment of the present application provides an electronic device. The electronic device may be a smart phone, a tablet computer or other equipment. Referring to FIG. 1 , the electronic device 100 includes a cover plate 10 , a display panel assembly 20 , a circuit board 30 and a casing 40 .

Wherein, the cover plate 10 is installed on the display screen assembly 20 to cover the display screen assembly 20 . The cover plate 10 may be a transparent glass cover plate. In some embodiments, the cover plate 10 may be a glass cover plate made of materials such as sapphire. The cover plate 10 can protect the display screen assembly 20 .

The display screen assembly 20 is mounted on the casing 40 to form a display surface of the electronic device 100 . The display screen assembly 20 serves as the front shell of the electronic device 100 and forms a closed space with the casing 40 for accommodating other electronic components of the electronic device 100 . Meanwhile, the display screen assembly 20 forms a display surface of the electronic device 100 for displaying information such as images and texts.

The circuit board 30 is installed inside the casing 40 to accommodate the circuit board 30 in the above-mentioned closed space. The circuit board 30 may be a main board of the electronic device 100 . A grounding point is provided on the circuit board 30 to realize the grounding of the circuit board 30 . Components such as a camera, a central processing unit, a memory chip, a communication chip, a SIM card socket, and a battery connector can be integrated on the circuit board 30 . Meanwhile, the display screen assembly 20 may be electrically connected to the circuit board 30 .

In some embodiments, a display control circuit is disposed on the circuit board 30 . The display control circuit outputs electrical signals to the display screen assembly 20 to control the display screen assembly 20 to display information.

The casing 40 is used to form the outer contour of the electronic device 100 . The material of the housing 40 can be plastic or metal. The housing 40 can be integrally formed.

In some embodiments, as shown in FIG. 2 , the display screen assembly 20 includes a display screen 21 and a sensor assembly 23 . Wherein, the display screen 21 is a full screen, so as to achieve the effect of full screen display, that is, the display screen 21 does not need to draw a non-display area, but all are display areas. The sensor assembly 23 is disposed below the display area of the display screen 21 .

In some embodiments, the display screen 21 is provided with a light-shielding layer 22 on the side facing the sensor assembly 23, and the light-shielding layer 22 is provided with an opening 220, and the sensor assembly 23 is arranged in the opening 220. below. The opening 220 allows signals such as optical signals and acoustic signals to pass through.

That is, the side of the display screen 21 facing the sensor assembly 23 is an inner surface, and the side of the display screen 21 facing the cover plate 10 is an outer surface. In this embodiment, a light shielding layer 22 is pasted on the inner surface of the display screen 21 , an opening 220 is disposed on the light shielding layer 22 , and the sensor component 23 is disposed below the opening 220 . The light-shielding layer 22 is used to hide the internal structure of the electronic device 100 , preventing the user from observing the internal electronic components of the electronic device 100 through the display screen 21 .

Since the sensor component 23 is arranged below the display area of the display screen 21, the side of the display screen 21 facing the sensor component 23 is provided with a light-shielding layer 22, and the light-shielding layer 22 is provided with an opening 220, and the sensor The component 23 is arranged under the opening 220; therefore, the present application does not need to divide the display screen into a non-display area, thereby realizing a full screen to achieve the effect of a full screen display.

Wherein, the opening 220 provided on the light shielding layer 22 is located in the display area of the display screen 21 . Through the opening 220 , the sensor component 23 can realize the proximity sensing function of the electronic device 100 .

In some embodiments, please refer to FIG. 4 , the opening 220 is a circular hole. The diameter of the opening 220 is 2 to 4 mm. In some other embodiments, the opening 220 may also be a square hole, an elliptical hole or other shaped holes.

The sensor assembly 23 includes a signal transmitter 231 and a signal receiver 232 . Wherein, the signal transmitter 231 is used for transmitting the detection signal A to the outside. The detection signal A is transmitted to the outside through the opening 220 . After the detection signal A touches the external object 200 (for example, the user's face), a reflected signal B is generated. The reflected signal B enters the signal receiver 232 through the opening 220 .

After receiving the reflected signal B, the signal receiver 232 may output the received signal to the central processing unit of the electronic device 100 for processing, thereby controlling the display screen of the electronic device 100 to turn off or turn on.

In some embodiments, please refer to FIG. 5 and FIG. 6 , the sensor assembly 23 includes a signal transmitter 231 and a signal receiver 232 , and a rotatable light guide sleeve 50 is sleeved above the signal transmitter 231 .

Please refer to FIG. 7 , when the signal transmitter 231 needs to emit a detection signal, the direction of the rotatable light guide sleeve 50 is adjusted according to the direction of the liquid crystal molecules in the display screen 21, so that the rotatable light guide sleeve 50 The optical sleeve 50 corresponds to the gap between the liquid crystal molecules, so that the detection signal emitted by the signal transmitter 231 passes through the gap to be emitted to the outside, effectively improving the transmittance of the signal emitted by the signal transmitter 231, so that there is no It will be transmitted to the interior of the electronic device 100, and the signal receiver 232 will not receive the internally diffracted detection signal, thereby enhancing the signal strength received by the signal receiver 232, thereby improving the detection accuracy of the sensor component, effectively avoiding misjudgment or Judging the failure situation, so as to improve the accuracy of the electronic device controlling the display screen to turn off or turn on the screen.

In some embodiments, a control rod is provided inside the housing 40, the control rod is connected to the rotatable light guide sleeve 50, and the control rod is connected to the motor. When the signal transmitter 231 needs to transmit a detection signal, obtain the direction of the liquid crystal molecules in the current display screen 21, and adjust the direction of the rotatable light guide sleeve 50 according to the direction of the liquid crystal molecules in the display screen 21 , that is, the central processing unit calculates the direction of the rotatable light guiding sleeve 50 according to the direction of the liquid crystal molecules in the display screen 21, and the central processing unit outputs to the motor according to the calculated direction of the rotatable light guiding sleeve 50 Direction adjustment signal, the motor drives the control rod, and the control rod drives the rotatable light guide sleeve 50 to move, so that the rotatable light guide sleeve 50 corresponds to the gap between the liquid crystal molecules, so that the signal is emitted The detection signal emitted by the detector 231 passes through the gap to be emitted to the outside, effectively improving the transmittance of the signal emitted by the signal emitter 231, so it will not be emitted into the electronic device 100, and the signal receiver 232 will not receive internal diffraction detection signal, thereby enhancing the signal strength received by the signal receiver 232, thereby improving the detection accuracy of the sensor component, effectively avoiding the situation of judgment error or judgment failure, thereby improving the accuracy of the electronic device to control the display screen to turn off or turn on the screen sex.

In some embodiments, the top end of the rotatable light guide sleeve 50 is arranged in contact with the opening 220 . The advantage of such setting is: the detection signal emitted by the signal transmitter 231 will all pass through the rotatable light guide sleeve 50, will not leak into the electronic device 100, and then pass through the gap between the liquid crystal molecules to be emitted to the outside world. , to effectively improve the transmittance of the signal emitted by the signal transmitter 231.

In some embodiments, the inner surface of the rotatable light guide sleeve 50 is provided with a light guide material, which can well reflect the detection signal emitted by the signal transmitter 231 to the gap between the liquid crystal molecules to Transmitting to the outside, effectively improving the transmittance of the signal transmitted by the signal transmitter 231 .

In some embodiments, the signal transmitter 231 is an infrared transmitter for emitting infrared rays. The signal receiver 232 is an infrared receiver for receiving infrared rays.

In some embodiments, the display screen 21 may be a liquid crystal display (Liquid Crystal Display, LCD) or an organic light-emitting diode display (Organic Light-Emitting Diode, OLED) or other type of display. When the display screen 21 is a liquid crystal display screen, the display screen 21 may include a backlight plate, a lower polarizer, an array substrate, a liquid crystal layer, a color filter substrate, and an upper polarizer that are sequentially stacked. When the display screen 21 is an organic light emitting diode display screen, the display screen 21 may include structures such as a base layer, an anode, an organic layer, a conductive layer, an emission layer, and a cathode stacked in sequence.

In some embodiments, the light-shielding layer 22 may be a thin-layer structure made of materials such as foam or steel sheets.

In some embodiments, as shown in FIG. 3 , when the signal emitted by the signal transmitter 231 is an optical signal, the opening 220 of the light shielding layer 22 may be filled with a light-transmitting material 214 . The light-transmitting material 214 can transmit the signal transmitted by the signal transmitter 231 , and can also hide the internal structure of the electronic device 100 to a certain extent. For example, the light-transmitting material 214 can be infrared ink.

In some embodiments, sensor assembly 23 also includes an ambient light sensor. Wherein, the ambient light sensor is used to detect the ambient light intensity. The electronic device 100 can adjust the brightness of the display screen 21 according to the ambient light intensity detected by the ambient light sensor.

In some embodiments, as shown in FIG. 7 , the sensor assembly 23 includes a signal transmitter 231 and a signal receiver 232 . Wherein, the signal transmitter 231 and the signal receiver 232 are arranged adjacent to each other. The distance d1 between the geometric center of the signal transmitter 231 and the geometric center of the signal receiver 232 is 2 to 14 millimeters.

In some embodiments, the signal transmitter 231 and the signal receiver 232 are packaged into a first chip. Setting the signal transmitter 231 and the signal receiver 232 adjacent to each other can reduce the volume of the first chip.

In some embodiments, the sensor assembly 23 includes a signal transmitter 231 and a signal receiver 232 . Wherein, the signal transmitter 231 and the signal receiver 232 are spaced apart from each other. The distance d2 between the signal transmitter 231 and the signal receiver 232 is 2 to 14 mm. It can be understood that the above distance is the distance between the geometric center of the signal transmitter 231 and the geometric center of the signal receiver 232 . The distance between the signal transmitter 231 and the signal receiver 232 can improve the isolation between the signal transmitter 231 and the signal receiver 232 , and reduce the impact of the signal transmitted by the signal transmitter 231 on the signal receiver 232 .

In some embodiments, the sensor assembly 23 includes a signal transmitter 231 , a signal receiver 232 and an ambient light sensor. Wherein, the ambient light sensor is used to detect the ambient light intensity. The electronic device 100 can adjust the brightness of the display screen 21 according to the ambient light intensity detected by the ambient light sensor.

The signal transmitter 231 , the signal receiver 232 and the ambient light sensor are arranged adjacent to each other. The distance d3 between the geometric center of the signal transmitter 231 and the geometric center of the signal receiver 232 is 2 to 14 millimeters.

In some embodiments, the signal transmitter 231 , the signal receiver 232 and the ambient light sensor are packaged into a second chip.

The signal transmitter 231 , the signal receiver 232 and the ambient light sensor are spaced apart from each other. The distance d4 between the signal transmitter 231 and the signal receiver 232 is 2 to 14 mm. It can be understood that the above distance is the distance between the geometric center of the signal transmitter 231 and the geometric center of the signal receiver 232 . The distance between the signal transmitter 231, the signal receiver 232 and the ambient light sensor can improve the isolation between the signal transmitter 231, the signal receiver 232 and the ambient light sensor, and reduce the signal received by the signal transmitter 231. 232, the impact caused by the ambient light sensor.

The embodiment of the present application also provides a sensor assembly, the sensor assembly is arranged below the display area of the display screen, the sensor assembly includes a signal transmitter and a signal receiver, and a Rotate the light guide sleeve.

When the signal transmitter needs to emit a detection signal, the direction of the rotatable light guide sleeve is adjusted according to the direction of the liquid crystal molecules in the display screen, so that the rotatable light guide sleeve corresponds to the position between the liquid crystal molecules. The gap between them, so that the detection signal emitted by the signal transmitter passes through the gap to be transmitted to the outside.

In some embodiments, the top end of the rotatable light guide sleeve 50 is arranged in contact with the opening 220 . The advantage of such setting is: the detection signal emitted by the signal transmitter 231 will all pass through the rotatable light guide sleeve 50, will not leak into the electronic device 100, and then pass through the gap between the liquid crystal molecules to be emitted to the outside world. , to effectively improve the transmittance of the signal emitted by the signal transmitter 231.

In some embodiments, the inner surface of the rotatable light guide sleeve 50 is provided with a light guide material, which can well reflect the detection signal emitted by the signal transmitter 231 to the gap between the liquid crystal molecules to Transmitting to the outside, effectively improving the transmittance of the signal transmitted by the signal transmitter 231 .

In some embodiments, the sensor component further includes an ambient light sensor for detecting ambient light intensity.

In some embodiments, the distance between the signal transmitter and the signal receiver is 2 to 14 mm. The distance between the signal transmitter and the signal receiver is the distance between the geometric center of the signal transmitter and the geometric center of the signal receiver.

To sum up, in the electronic device and the sensor component provided by the present application, since the sensor component is arranged under the display area of the display screen, the side of the display screen facing the sensor component is provided with a light-shielding layer, and on the light-shielding layer An opening is provided, and the sensor assembly is arranged under the opening; therefore, the present application does not need to divide the display screen into a non-display area, thereby realizing a full screen to achieve a full screen display effect. In addition, since the rotatable light guide sleeve is set above the signal transmitter of the sensor assembly; when the signal transmitter needs to emit detection signals, the rotatable light guide sleeve is adjusted according to the direction of the liquid crystal molecules in the display Rotate the direction of the light guide sleeve so that the rotatable light guide sleeve corresponds to the gap between the liquid crystal molecules, so that the detection signal emitted by the signal transmitter passes through the gap to be emitted to the outside, effectively improving the signal transmission The transmittance of the signal emitted by the sensor, thereby enhancing the signal strength received by the signal receiver, thereby improving the detection accuracy of the sensor component, thereby improving the accuracy of the electronic device controlling the display screen to turn off or turn on the screen.

Although the application has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. This application includes all such modifications and variations and is limited only by the scope of the appended claims. With particular reference to the various functions performed by the components described above, terminology used to describe such components is intended to correspond to any component that performs the specified function (eg, which is functionally equivalent) of the described component (unless otherwise indicated). , even if not structurally equivalent to the disclosed structures that perform the functions shown herein in the exemplary implementations of the specification. Furthermore, although a particular feature of this specification has been disclosed with respect to only one of several implementations, such feature may be combined with one or more other implementations as may be desirable and advantageous for a given or particular application. other feature combinations. Moreover, to the extent the terms "comprises", "has", "comprising" or variations thereof are used in the detailed description or the claims, such terms are intended to be encompassed in a manner similar to the term "comprising".

In summary, although the present application has disclosed the above with preferred embodiments, the above preferred embodiments are not intended to limit the present application, and those of ordinary skill in the art can make various modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application is subject to the scope defined in the claims.

Claims (10)

1. An electronic device, characterized in that it comprises: a housing, a display screen and a sensor assembly, the display screen and the sensor assembly are installed on the housing, and the sensor assembly is arranged on the display area of the display screen Below, the side of the display screen facing the sensor assembly is provided with a light-shielding layer, the light-shielding layer is provided with an opening, and the sensor assembly is arranged below the opening; The sensor assembly includes a signal transmitter and a signal receiver, and a rotatable light guide sleeve is sleeved above the signal transmitter; When the signal transmitter needs to emit a detection signal, the direction of the rotatable light guide sleeve is adjusted according to the direction of the liquid crystal molecules in the display screen, so that the rotatable light guide sleeve corresponds to the position between the liquid crystal molecules. The gap between them, so that the detection signal emitted by the signal transmitter passes through the gap to be transmitted to the outside. 2 . The electronic device according to claim 1 , wherein a top end of the rotatable light guide sleeve is arranged to be in contact with the opening. 3 . 3. The electronic device according to claim 1 or 2, wherein the inner surface of the rotatable light-guiding sleeve is provided with a light-guiding material. 4. The electronic device according to claim 1, wherein the sensor component further comprises an ambient light sensor for detecting ambient light intensity. 5. The electronic device according to claim 1, wherein the distance between the signal transmitter and the signal receiver is 2 to 14 millimeters. 6. The electronic device according to claim 1 or 5, wherein the distance between the signal transmitter and the signal receiver is the geometric center of the signal transmitter and the geometric center of the signal receiver distance between centers. 7. The electronic device according to claim 1, wherein the openings of the light-shielding layer are filled with light-transmitting materials. 8. The electronic device according to claim 7, wherein the light-transmitting material is infrared ink. 9. A sensor assembly, characterized in that, the sensor assembly is arranged below the display area of the display screen, the sensor assembly includes a signal transmitter and a signal receiver, and a rotatable sensor is sleeved above the signal transmitter. Light guide sleeve; When the signal transmitter needs to emit a detection signal, the direction of the rotatable light guide sleeve is adjusted according to the direction of the liquid crystal molecules in the display screen, so that the rotatable light guide sleeve corresponds to the position between the liquid crystal molecules. The gap between them, so that the detection signal emitted by the signal transmitter passes through the gap to be transmitted to the outside. 10. The sensor assembly according to claim 9, characterized in that, the top end of the rotatable light guide sleeve is arranged in contact with the opening, and the inner surface of the rotatable light guide sleeve is provided with a light guide material .