Optical fiber and portable electronic device

Abstract

Light guide (30) for a portable electronic device (110), which an upper portion (32) formed of an optically transmissive material and a lower section (33) formed from an optically transmissive material, wherein the upper portion (32) has a substantially planar horizontal upper surface (31) and defines first substantially vertical side walls (35) such that the upper portion (32) has the shape of a first rectangle in a cross-sectional view, wherein the lower portion (33) is continuous with and connected to the upper portion (32) such that at least some ambient light (20) incident on the upper surface (31) is transmitted through the upper portion (32) into the lower portion (33), wherein the lower section (33) has a first subsection adjoining the upper section (32), which has the shape of a second rectangle in cross-sectional view, and a second subsection adjoining the first subsection, which has the shape of a non-rectangular, isosceles trapezoid in cross-sectional view, wherein the first subsection defines second substantially vertical side walls (36) extending downwards from the upper section (32), and wherein the second subsection of the lower section (33) has third inclined side walls (37) decreasing downwards to a lowest minimum diameter, wherein the third inclined side walls (37) have an angle with respect to a vertical, which angle is sufficient to cause total internal reflection of ambient light (20) transmitted through the upper portion (32), reflected from the first side walls (35) and subsequently incident on the third inclined side walls (37).

Description

FIELD OF THE INVENTION

[0001] Various embodiments of the inventions described herein relate to the field of optical fibers, portable electronic devices, systems, and methods associated therewith. BACKGROUND

[0002] Ambient light sensors are used in portable electronic devices, such as mobile phones, personal data assistants, PDAs, and portable computers, to sense the intensity of natural ambient light. Since portable electronic devices are often battery-powered, minimizing power consumption and thereby maximizing device operating time on a single battery charge is an important objective. By sensing the intensity of natural ambient light in the environment where a portable electronic device is used, information regarding the intensity of natural ambient light can be used to control the amount or degree of backlighting provided to a backlit display in the portable electronic device. For example, if the ambient light intensity is high, increased backlighting may be required for a user to see the display.When ambient light intensity is low, reduced or no backlighting may be required for a user to view the display. Thus, accurate and reliable ambient light intensity sensing in portable electronic devices has become increasingly important in the bid to extend single-battery operating times of a portable electronic device.

[0003] Examples of prior art ambient light sensors include the Avago Technologies™ APDS-9002 Miniature Surface Mount Ambient Light Photo Diode, the APDS-9003 Miniature Surface Mount Ambient Light Photo Diode, the APDS-9004 Miniature Surface Mount Ambient Light Photo Diode, the ADPS-9005 Miniature Surface Mount Ambient Light Photo Diode, the ADPS-9006 Miniature Surface Mount Ambient Light Photo Diode, the ADPS-9007 Ambient Light Photo Sensor with Logarithmic Current, the ADPS-9008 Miniature Surface Mount Ambient Light Photo Diode, and the APDS-9300 Miniature Ambient Light Photo Sensor with Digital (I1°C) Output. A high-performance light sensor manufactured by Avago Technologies™ is the APDS-9300 sensor, which converts a sampled light intensity into a digital signal output suitable for direct I 2C interface. Each device consists of a broadband photodiode (visible plus infrared) and an infrared photodiode. Two integrating ADCs convert the photodiode currents to a digital output representing the irradiance measured on each channel. This digital output can be input to a microprocessor, where an illuminance (ambient light level) in lux is derived using an empirical formula to approximate the response of the human eye. See, for example, a datasheet describing the Avago Technologies™ APDS-9300 Miniature Ambient Light Photo Sensor with digital (I 2 C) edition, which is hereby incorporated by reference in its entirety.

[0004] DE 12 95 232 A describes a light guide system which is arranged in front of a light-sensitive element built into the housing of a light meter, a camera or a camera accessory, consisting of a lens and a light guide body arranged behind it for limiting the measuring angle and simultaneously mixing the beams of rays, as well as a diaphragm for regulating the luminous flux.

[0005] Unfortunately, reliable, accurate, and cost-effective sensing of ambient light intensity in portable electronic devices remains an elusive goal. What is needed are improved devices, systems, and methods for sensing ambient light intensity, even in dim or low-ambient light conditions, in portable electronic devices that can nevertheless be manufactured and implemented at low cost. SUMMARY

[0006] In some embodiments, a light guide for a portable electronic device is provided, the light guide comprising a first upper portion formed of an optically transmissive material and a second lower portion formed of an optically transmissive material, the first upper portion having a substantially planar horizontal upper surface defining first substantially vertical side walls, such that that the upper section has the shape of a first rectangle in a cross-sectional view, wherein the second lower section is contiguous and connected to the first section such that at least some ambient light incident on the upper surface is transmitted through the first upper section into the second lower section, wherein the second lower section has a first subsection adjoining the upper section, which has the shape of a second rectangle in the cross-sectional view, and a second subsection adjoining the first subsection, which has the shape of a non-rectangular, isosceles trapezoid in the cross-sectional view, wherein the first subsection defines second substantially vertical side walls extending downwardly from the first upper section, and wherein the second subsection of the lower section has third inclined side walls,which decrease downwards to a lowest minimum diameter, wherein the inclined third side walls have an angle with respect to a vertical which is sufficient to cause total internal reflection of ambient light transmitted through the first section, reflected from the first side walls and subsequently incident on the third inclined side walls.

[0007] In other embodiments, a portable electronic device is provided which includes such a light guide.

[0008] Further embodiments are disclosed herein or will become apparent to those skilled in the art after reading and understanding the specification and drawings.

[0009] According to one embodiment, a light guide or a portable electronic device is provided, wherein the second rectangle has a smaller dimension in the horizontal direction than the first rectangle.

[0010] According to one embodiment, a light guide or a portable electronic device is provided, wherein the angle is approximately 10 degrees.

[0011] According to one embodiment, a light guide or a portable electronic device is provided, wherein the angle is approximately 10.6 degrees.

[0012] According to one embodiment, a light guide or a portable electronic device is provided, wherein an angle of incidence on the third inclined side walls of light rays transmitted through the first portion, which are reflected by the first side walls and subsequently incident on the third inclined side walls, exceeds approximately 38 degrees.

[0013] According to one embodiment, a light guide or a portable electronic device is provided, wherein the light guide comprises polycarbonate, polymethyl methacrylate, a polymer, a combination of polymers, plastic, acrylic, acrylic glass or glass.

[0014] According to one embodiment, a light guide or a portable electronic device is provided, wherein the optically transmissive material has a refractive index exceeding approximately 1.4.

[0015] In an optical fiber or a portable electronic device, wherein the optically transmissive material has a refractive index exceeding approximately 1.5.

[0016] According to one embodiment, a light guide or a portable electronic device is provided, wherein a first diameter of the upper portion ranges between approximately 2 mm and approximately 3 mm.

[0017] According to one embodiment, a light guide or a portable electronic device is provided, wherein a second diameter of the first portion ranges between approximately 1 mm and approximately 2 mm.

[0018] According to one embodiment, a light guide or a portable electronic device is provided, wherein a third diameter of the second portion is less than approximately 1.5 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various aspects of the various embodiments of the invention will become apparent from the following specification, drawings and claims, in which: Fig. 1 illustrates the basic principles of Snell's law; Fig. 2 illustrates the basic principles of total internal reflection (“TIR”); Fig. 3 shows a cross-sectional view of a representative prior art light guide; Fig. 4 representative dimensions of the state-of-the-art light guide of Fig. 3 illustrated; Fig. 5 is a perspective bottom view of the prior art light guide of the Fig. 3 and Fig. 4 shows; Fig. 6 Ray tracing results for the state-of-the-art light guide of the Fig. 3, Fig. 4 and Fig. 5 corresponding to Design 1; Fig. Figure 7 shows ray tracing results for a light guide corresponding to a first embodiment (Design 2); Fig. 8 shows total internal reflection results for the light guide according to the first embodiment for vertically incident light rays; Fig. 9 shows total internal reflection results for the light guide according to the first embodiment for non-vertically incident light rays; Fig.10 shows ray tracing results for a light guide corresponding to a second embodiment (Design 3); Fig. 11 shows total internal reflection results for the light guide according to the second embodiment for vertically incident light rays; Fig. 12 shows total internal reflection results for the light guide according to the second embodiment for non-vertically incident light rays; Fig. 13 the variation of an output power in watts against an angle of incidence for the light guide of the prior art, which is shown in Fig. 3 to 5, the first embodiment of a Fig. 7 to 9, and the second embodiment of a light guide shown in Fig. 10 to 12 shown light guide, and Fig. 14 shows an embodiment of a light sensing and backlit display feedback control system.

[0020] The drawings are not necessarily to scale. Similar numbers refer to similar parts or steps throughout the drawings, unless otherwise noted. DETAILED DESCRIPTION

[0021] A light guide for a portable electronic device is an optically transmissive component configured to capture natural ambient light from the exterior of the portable electronic device and direct it toward an ambient light sensor mounted within the portable electronic device, typically on an internal printed circuit board. The light guide serves as a bridge between the surrounding external environment and the light sensor. Most light guides for use in portable electronic devices are constructed of transparent acrylic or a polycarbonate material.

[0022] Now with regard to Fig.1 shows the basic principles behind Snell’s law, which is: ni sin ϕi=nf sin ϕf where n i = refractive index of the overlying incident medium, n f = refractive index of the underlying refractive medium, sin ϕ i = the sine of the angle of incidence in the incident medium, and sin ϕ f = the sine of the angle of incidence in the refracting medium. When light rays are incident on a boundary between two different media with different optical refractive indices, such as a boundary between plastic and air, the light rays are reflected at the boundary in the Fig. 1 illustrated manner. The angle at which the light rays are incident on the boundary is called the angle of incidence ϕ i and the angle at which the light rays leave the boundary is called the angle of refraction ϕ fSnell's law (see equation (1) above) states that the refractive index of the first medium (n i ) multiplied by the sine of the angle of incidence at the boundary (ϕ i ) is equal to the refractive index of the second medium (n r ) multiplied by the sine of the angle of refraction at the boundary (ϕ f ).

[0023] It will be seen that if the angle of refraction ϕ f is equal to 90°, the incident light beam is refracted along the boundary, as in Fig. 2. The sin of 90° = 1.0, and equation 1 for Snell's law reduces to: n i sin ϕ i = n f This expression can be rewritten to give the critical angle of incidence for total internal reflection, ϕ c , which is determined by: sin ϕc=nf / ni

[0024] By setting n f= 1.0 in Equation 2 (the refractive index value for air), the critical angle for a light guide can be determined if the refractive index of the material is known. For most plastics and glass, the refractive index is approximately 1.5. For ray tracing calculation and modulation purposes, a refractive index of 1.58 was selected for a typical polycarbonate material. The resulting calculated critical angle for total internal reflection in a representative polycarbonate material was therefore approximately 39°. Internal specular reflection within a light guide at the guide surface-to-air interface may also be used to help transmit light effectively through the light guide. Thus, light rays internal to a light guide but incident on an internal light guide surface-to-air interface are totally internally reflected if the angle of incidence is 39° or greater.

[0025] Below in Table 1 is a list of some of the materials that may be used to form light guides suitable for use in portable electronic devices and their corresponding refractive indices. Table 1: Refractive indices of some materials material refractive index vacuum 1 (exact) Air 1,000293 Water 1,333 Water ice 1,31 Acrylic glass 1,490 - 1,492 PMMA 1,4893 - 1,4899 Polycarbonate 1,584 - 1,586

[0026] One objective is to provide a light guide capable of capturing light from a wider light collection angle, thereby optimizing light collection from the surrounding environment for subsequent delivery to an ambient light sensor. As explained in more detail below, this objective is partially achieved by selectively employing total internal reflection ("TIR") in a light guide.

[0027] Fig.Figure 3 shows a prior art light guide 30 mounted in a housing or case 80 of a portable electronic device, such as a cellular phone, PDA, or computer. Ambient light 20 incident on a substantially planar horizontal top surface 31 of the light guide 30 is transmitted downward through the first portion 32 of the light guide 30 and then through the second portion 33 of the light guide 30 to emerge from the lowermost portion 34 of the light guide 30 for incidence upon the ambient light sensor 40 mounted on a printed circuit board or other suitable substrate 50. Note that not all of the light incident on the substantially planar horizontal top surface 31 is collected by the light guide 30 for delivery to the ambient light sensor 40.Instead, some light is scattered or diffracted, some light is reflected away from the light guide 30, and some light is otherwise lost for collection and not delivered to the light sensor 40.

[0028] Some typical dimensions of the light guide 30 and the ambient light sensor 40 are shown in Fig.4, wherein the first outer diameter d1 of the first portion 32 is approximately 2.5 mm and defines first substantially vertical sidewalls 35, wherein the second outer diameter d2 of the second portion 33 is approximately 1.5 mm and defines second substantially vertical sidewalls 36, wherein the total height y1 of first and second portions 32 and 33 of the light guide 30 is approximately 2.5 mm, wherein the height y2 of the second portion 33 of the light guide 30 is approximately 1.5 mm, and wherein the width and length x1 of the ambient light sensor 40 are both approximately 1 mm. The distance or gap y3 between the lowermost portion 34 of the light guide 30 and the ambient light sensor 40 was chosen to vary between approximately 0.2 mm and approximately 0.5 mm. Fig. Figure 5 shows a bottom perspective view of a prior art light guide 30, hereinafter referred to as Design 1.

[0029] Using the aforementioned dimensional information and refractive index information for polycarbonate (1.585), ray tracing calculation of the light guide design 1 was undertaken to evaluate the total flux or light power incident on the ambient light sensor 40, assuming that the ambient light sensor 40 has an area of ​​approximately 1 mm 2 An optical fiber model for Design 1 was then calculated using the optical ray tracing software ZEMAX™. See Fig. 6, where incident ambient light rays 20 incident on the light guide 30 are shown, as are the corresponding transmitted and refracted light rays. Using the ZEMAX software, a "universal graphical representation" of the total light flux incident on the detector 40 versus the tilt angle of an external light source was also generated for Design 1 (see Fig.13). Fig. Figure 13 shows that Design 1 exhibits a relatively smooth output power curve with respect to ambient light incidence angles. Predictably, the output power decreases as the incidence angle becomes less vertical.

[0030] With reference to the Fig.7 to 9, a design 2 of a light guide 30 is shown, where it can be seen that the first section 32 of the light guide 30 is substantially the same as that of design 2, where first side walls 35 are substantially vertical and defined by a first outer diameter d1, while the second section 33 has inclined non-vertical second side walls 36 having a varying outer diameter d2. The dimensions of design 2 are similar to those of design 1 with the exception of the diameter d2 of the second side walls 36 of the second section 33, which at the lowermost section 34 is approximately 1.2 mm and which increases in a linear manner upwards towards the first section 32 at an angle of 5.7° with respect to the vertical (as in Fig. 7 to 9 shown).

[0031] Fig. Figure 7 shows ray tracing results from the ZEMAX program for Design 2. Fig.Figure 8 shows that total internal reflection for a vertically incident light beam results in TIR for Design 2. Fig. Figure 9 shows how a non-vertical light beam may result in a non-TIR for Design 2. The angle of the second side walls 36 in Design 2 was calculated based on a refractive index for polycarbonate to give total internal reflection (“TIR”) under certain conditions, with the critical angle (ϕ c ) was calculated as 39°. For a vertically incident ray (with an angle of incidence greater than 84.3°, which is greater than ϕ c , which is 39°) TIR will be done (as in Fig.8). This helps to direct the beam path to the light sensor 40, which in turn increases the output power and sensitivity of the light sensor 40. However, when the angle of incidence of the incident beam becomes less vertical, and in particular when the angle of incidence becomes less than the critical angle (39°), TIR does not occur and the beam is refracted into the adjacent medium, as shown in Fig. 9 to illustrate the disadvantages of Design 2 with regard to the efficient collection of ambient light incident thereon. Referring now to Fig.13, while the light guide of Design 2 does indeed increase the collection of vertically incident light rays for delivery to the ambient light sensor 40, Design 2 also suffers from a rather dramatic drop in light collection at incident angles exceeding approximately 18°. This means that the output of the ambient light sensor 40 decreases significantly as the incident angles of ambient light become increasingly less vertical.

[0032] With reference now to the Fig.10 to 12, a design 3 of a light guide 30 is shown, where it can be seen that the first section 32 of the light guide 30 is substantially the same as that of design 2, with first side walls 35 being substantially vertical and defined by a first outer diameter d1, while the second section 33 has composite side walls 36 and 37 having diameters d2 and d3. Side walls 36 are substantially vertical and defined by the second outer diameter d2, while side walls 37 are inclined, non-vertical, and have a varying outer diameter d3.The dimensions of design 3 are similar to those of designs 1 and 2 with the exception of the diameters d2 and d3 of the second and third side walls 36 and 37 of the second section 33, which at the lowermost section 34 is approximately 1.3 mm and which increases in a linear manner upwards to the second outer diameter d2 at an angle of 10.6° with respect to the vertical (as in . Fig. 10 to 12 shown).

[0033] Fig. Figure 10 shows ray tracing results from the ZEMAX program for Design 3. Fig. Figure 11 shows that total internal reflection for a vertically incident light beam results in TIR for Design 3. Fig. Figure 12 shows how a non-vertical light beam results in TIR for Design 3. The angle of the third side walls 37 in Design 2 was calculated based on a refractive index for polycarbonate to give total internal reflection (“TIR”) under certain circumstances where the critical angle (ϕ c) was calculated to be 39°. For a vertically incident ray (with an angle of incidence greater than 79.4°, which is greater than ϕ c , which is 39°) TIR will be done (as in Fig. 11 and Fig. 12). This helps to direct the beam path to the light sensor, which in turn increases the output and sensitivity of the light sensor 40. Referring now to Fig. 13, it will be seen that the light guide of Design 3 does indeed increase the collection of vertically incident light rays for delivery to the ambient light sensor 40 and also does a good job of collecting non-vertically incident light rays of relatively high amplitude over a wide angular range. This means that Design 3 of the light guide 30, in conjunction with the ambient light sensor 40, provides an output power that does not decrease significantly as the angle of incidence of ambient light becomes increasingly less vertical.

[0034] A preferred material for forming the light guide 30 is LEXAN™ polycarbonate, which is an amorphous engineering thermoplastic that combines high levels of mechanical, optical, electrical, and thermal properties. This combination of physical properties makes it the toughest, most versatile of all available engineering thermoplastics. The refractive index of polycarbonate ranges from approximately 1.584 to approximately 1.586.

[0035] A typical processing range for unreinforced LEXAN™ grades is between approximately 160°F and approximately 200°F (71 to 93°C), which helps give the surface a very smooth, glossy appearance. The aesthetic appeal of surfaces cast in reinforced LEXAN™ resin can be enhanced by using fast fill rates, higher injection pressures, and pour temperatures in the range of 180°F to 240°F (82 to 116°C). Actual injection pressures will depend on variables such as melt temperature, pour temperature, part geometry, wall thickness, flow length, and other pouring and equipment considerations. In general, the lowest pressures that provide the desired properties, appearance, and pour cycle are preferred. Holding pressures of 60 to 80% of the injection pressure (~ 50 to 100 psi (~ 0.345 to 0.689 MPa)) are generally suitable for normal requirements.

[0036] With reference now to Fig.14 shows an embodiment of a light sensing and backlit display control system 100 having a portable electronic device 110 including a light guide 30 and an ambient light sensor 40 operatively associated with and disposed adjacent to the light guide 30. The ambient light sensor 40 is configured to receive the ambient light collimated by the light guide 30 and transmitted through the light guide 30 and to generate an output signal representative of an intensity of the ambient light sensed thereby. The ambient light sensor 40 is, in turn, operatively associated with the backlit display 120 and the computing device 130.Computing device 130 is a microprocessor, processor, CPU, controller, or other type of computing device, as will now become apparent to those skilled in the art, configured to receive the output signal from ambient light sensor 40 and, based on the sensed ambient light intensity, determine whether backlighting for backlit display 120 should be increased or decreased. Computing device 130 is operatively associated with the backlit display and / or backlight feedback light sensor 137.The computing device may be configured to determine whether to activate or not activate backlighting of the display 120 based on the sensed ambient light intensity and / or the amount or degree of backlight illumination generated by a backlight illumination portion of the backlit display 120, and to further substantially continuously adjust an amount of backlighting provided to the display 130 as the sensed ambient light intensity and / or the amount or degree of backlight illumination generated by a backlight illumination portion of the backlit display 120 changes.It is further contemplated that the amount of backlighting provided to the display 130 may be minimized or turned off when the sensed ambient light intensity changes and / or when the amount or degree of backlighting changes if the sensed ambient light intensity is greater than a predetermined amount. It is also contemplated that the amount or degree of backlighting may be adjusted to cause the amount of backlighting provided to the display 120 to be increased or turned on if the sensed ambient light intensity is less than a predetermined amount. Other variations in feedback control of the amount or degree of backlighting provided to the display 120 are also contemplated.

[0037] Included within the scope of the present invention are methods of making and having made the various components, devices and systems described herein.

Claims

[1] Light guide (30) for a portable electronic device (110), which an upper portion (32) formed of an optically transmissive material and a lower section (33) formed from an optically transmissive material, wherein the upper portion (32) has a substantially planar horizontal upper surface (31) and defines first substantially vertical side walls (35) such that the upper portion (32) has the shape of a first rectangle in a cross-sectional view, wherein the lower portion (33) is continuous with and connected to the upper portion (32) such that at least some ambient light (20) incident on the upper surface (31) is transmitted through the upper portion (32) into the lower portion (33), wherein the lower section (33) has a first subsection adjoining the upper section (32), which has the shape of a second rectangle in cross-sectional view, and a second subsection adjoining the first subsection, which has the shape of a non-rectangular, isosceles trapezoid in cross-sectional view, wherein the first subsection defines second substantially vertical side walls (36) extending downwards from the upper section (32), and wherein the second subsection of the lower section (33) has third inclined side walls (37) decreasing downwards to a lowest minimum diameter, wherein the third inclined side walls (37) have an angle with respect to a vertical, which angle is sufficient to cause total internal reflection of ambient light (20) transmitted through the upper portion (32), reflected by the first side walls (35), and subsequently incident on the third inclined side walls (37). [2] The light guide (30) of claim 1, wherein the second rectangle has a smaller dimension in the horizontal direction than the first rectangle. [3] The light guide (30) of claim 1 or 2, wherein the angle exceeds approximately 10 degrees. [4] The light guide (30) of any one of claims 1 to 3, wherein the angle is approximately 10.6 degrees. [5] The light guide (30) of any one of claims 1 to 4, wherein an angle of incidence on the third inclined side walls (37) of vertically incident ambient light (20) transmitted through the upper portion (32), reflected from the first side walls (35) and subsequently incident on the third inclined side walls (37), exceeds approximately 38 degrees. [6] The light guide (30) of any one of claims 1 to 5, wherein the light guide (30) comprises polycarbonate, polymethyl methacrylate, a polymer, a combination of polymers, plastic, acrylic, acrylic glass, or glass. [7] The light guide (30) of any one of claims 1 to 6, wherein the optically transmissive material has a refractive index exceeding approximately 1.

4. [8] The light guide (30) of any one of claims 1 to 7, wherein the optically transmissive material has a refractive index exceeding approximately 1.

5. [9] The light guide (30) of any one of claims 1 to 8, wherein a first diameter (d1) of the upper portion (32) ranges between approximately 2 mm and approximately 3 mm. [10] The optical fiber (30) of any one of claims 1 to 9, wherein a second diameter (d2) of the first portion ranges between approximately 1 mm and approximately 2 mm. [11] The optical fiber (30) of any one of claims 1 to 10, wherein a third diameter (d3) of the second portion is less than approximately 1.5 mm. [12] A portable electronic device (110) comprising a light guide (30) according to any one of the preceding claims.

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