Backlight unit with support post and cavity height monitoring

Abstract

This invention is entitled "Backlight unit with support posts and cavity height monitoring." An electronic device can have a display with a backlight. The backlight provides backlight illumination for a pixel array that is displaying an image. The backlight can include an array of cells. Each cell can include a light source having one or more light emitting diodes and a cavity reflector that reflects light from the light source outward through a diffuser for forming the backlight illumination. The light source can be mounted to a printed circuit. Support posts on the printed circuit can be used to hold the diffuser at a fixed distance from the printed circuit. A sensor on the printed circuit can be used to measure the separation distance between the printed circuit and the diffuser. Adjustments to a pixel gain profile can be made based on the measured separation distance.

Description

[0001] This application is a divisional application of the invention patent application filed on May 3, 2018, with application number 201810411876.3 and invention title "Backlight Unit with Support Column and Cavity Height Monitoring". Technical Field

[0002] This invention relates generally to displays, and more particularly to backlit displays. Background Technology

[0003] Electronic devices typically include displays. For example, computers and cellular phones sometimes have backlit liquid crystal displays. Edge-lit backlight units have light-emitting diodes (LEDs) that emit light onto the edge surface of a light guide plate. The light guide plate then distributes the emitted light laterally across the display for backlight illumination. Direct-illuminated backlight units have an array of LEDs that emit light vertically through the display.

[0004] Direct-illumination backlights can feature locally tunable light-emitting diodes (LEDs) that allow for enhanced dynamic range. However, if not carefully managed, the light produced by direct-illumination backlights may not be sufficiently uniform. For example, variations in the distance between the LEDs and the overlapping diffusion layer can lead to undesirable variations in backlight uniformity. Summary of the Invention

[0005] Electronic devices may have a display with a backlight. The backlight provides illumination to the pixel array that is displaying an image. The backlight may include an array of backlight units. Each unit may include a light source having one or more light-emitting diodes and a cavity reflector that reflects light from the light source outward through a diffuser to form the backlight illumination.

[0006] The light source can be mounted to the printed circuit. Support posts can be used to maintain a fixed distance between the diffuser and the printed circuit. The support posts can be formed as integral protrusions of the diffuser, or they can be separate polymer structures formed of polymers such as light-transmitting and white polymers, and can be coupled to the printed circuit and the diffuser using adhesives, screws, or other attachment mechanisms.

[0007] Optical sensors can be mounted on printed circuit boards. Each optical sensor may include a light-emitting device such as a light-emitting diode (LED) and a photodetector. The optical sensor measures light reflected from the LED from the diffuser through a corresponding opening in the cavity reflector. The spacing between the diffuser and the printed circuit boards can be measured by the optical sensor and used by control circuitry to update the pixel gain profile, which corrects the image for changes in backlight intensity across the display. Attached Figure Description

[0008] Figure 1 This is an illustration of an exemplary electronic device with a display according to one embodiment.

[0009] Figure 2 This is a cross-sectional side view of an exemplary display according to an implementation scheme.

[0010] Figure 3 This is a top view of an exemplary backlight unit array having rows and columns of light source units for direct illumination backlight units, according to an embodiment.

[0011] Figure 4 A cross-sectional side view of a light-emitting diode in a cavity reflector of an exemplary light source, such as a backlight unit, according to an embodiment.

[0012] Figure 5 This is a cross-sectional side view of an exemplary transparent support column with backlighting according to the implementation scheme.

[0013] Figure 6 A cross-sectional side view of an exemplary support column according to an embodiment, having white injection-molded plastic that is at least partially covered by light-transmitting injection-molded plastic.

[0014] Figure 7 A cross-sectional side view of a portion of an exemplary support column of white injection-molded plastic, having a rounded tip and at least partially covered by translucent injection-molded plastic, according to an embodiment.

[0015] Figure 8 A cross-sectional side view of a portion of an exemplary diffusion layer according to an embodiment, having a support column of the type that can be formed by an integrated portion of the diffusion layer.

[0016] Figure 9 This is a cross-sectional side view of an exemplary support column with an inverted conical backlight, according to the implementation scheme.

[0017] Figure 10 This is a cross-sectional side view of an exemplary cavity reflector formed above a solid support structure that can be used as a support structure for a diffusion layer, according to an embodiment.

[0018] Figure 11 This is a cross-sectional side view of an exemplary diffuser layer height sensor in a backlight according to an embodiment.

[0019] Figure 12 A top view of an exemplary array of support pillars and diffusion layer height sensors for backlighting, according to an embodiment.

[0020] Figure 13 A graph is provided to illustrate how the backlight intensity varies as a function of lateral position according to the implementation scheme and how the backlight intensity varies when a portion of the backlight is compressed.

[0021] Figure 14It is a graph of an exemplary pixel gain distribution that can be applied to a pixel array in a display according to an implementation scheme to compensate for changes in backlight intensity on the display.

[0022] Figure 15 This is a circuit diagram illustrating an exemplary circuit for an electronic device with an optical diffuser position sensor, according to an embodiment. Detailed Implementation

[0023] Electronic devices may provide backlit displays. Backlit displays may include liquid crystal pixel arrays or other display structures illuminated by light from direct-illuminated backlight units. Figure 1 A perspective view of an exemplary electronic device of the type that may provide a display with a direct-illumination backlight unit is shown. Figure 1 The electronic device 10 may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular phone, a media player, or other handheld or portable electronic device, a smaller device (such as a wristwatch), a hanging device, a headset or handset device, a device embedded in glasses or other devices worn on a user's head, or other wearable or micro-devices, a television, a computer monitor that does not contain an embedded computer, a gaming device, a navigation device, an embedded system (such as a system in which an electronic device with a display is installed in an information kiosk or a car), a device that performs two or more of the functions of these devices, or other electronic devices.

[0024] like Figure 1 As shown, device 10 may have a display such as display 14. Display 14 may be mounted in housing 12. Housing 12, sometimes referred to as enclosure or case, may be formed of plastic, glass, ceramic, fiber composite material, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or any combination of two or more of these materials. Housing 12 may be formed using a one-piece construction in which some or all of the housing 12 is machined or molded into a single structure, or housing may be formed using multiple structures (e.g., an internal frame structure, one or more structures forming the surface of the outer housing, etc.).

[0025] The housing 12 may have a support such as an optional stand 18, may have multiple components (e.g., housing portions that move relative to each other to form a laptop computer or other device with movable parts), may have the shape of a cellular phone or tablet (e.g., in an arrangement where the stand 18 is omitted), and / or may have other suitable configurations. Figure 1 The arrangement of the housing 12 shown is exemplary.

[0026] The display 14 may be a touchscreen display incorporating a conductive capacitive touch sensor electrode layer or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a non-touchscreen display. The capacitive touchscreen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures.

[0027] The display 14 may include an array of pixels 16 formed by a liquid crystal display (LCD) component or may have a pixel array based on other display technologies. Figure 2 The image shows a cross-sectional side view of the display 14.

[0028] like Figure 2 As shown, the display 14 may include a pixel array such as pixel array 24. Pixel array 24 may include, for example, pixel array 24. Figure 1 The pixel array 24 is a pixel array of 16 pixels (e.g., a pixel array with rows and columns of pixels 26). The pixel array 24 may be formed from a liquid crystal display module (sometimes referred to as a liquid crystal display or liquid crystal layer) or other suitable pixel array structure. The liquid crystal display used to form the pixel array 24 may, for example, include upper and lower polarizers, a color filter layer, and a thin-film transistor layer inserted between the upper and lower polarizers, as well as a liquid crystal material layer inserted between the color filter layer and the thin-film transistor layer. Other types of liquid crystal display structures may be used to form the pixel array 24 if desired.

[0029] During operation of 14, an image can be displayed on pixel array 24. Backlight unit 42 (which may sometimes be referred to as backlight, backlight layer, backlight structure, backlight module, backlight system, etc.) can be used to generate backlight illumination 44 through pixel array 24. This illuminates any image on pixel array 24 for viewing by a viewer such as viewer 20 viewing display 14 in direction 22.

[0030] The backlight unit 42 may include an optical film 26, a light diffuser such as a light diffuser (light diffusion layer) 34, and a light source array 36. The light source array 36 may comprise a two-dimensional array of light sources 38. Each light source 38 may include one or more light-emitting diodes and may be associated with a corresponding one of the backlight units 38C. Units 38C may include reflectors for reflecting light through the pixel array 24. Units 38C may be arranged in... Figure 2 In an array with rows and columns in the XY plane.

[0031] The light source 38 in unit 38C can be uniformly controlled by the control circuitry in device 10 or can be individually controlled (e.g., to implement a local dimming scheme that helps improve the dynamic range of the image displayed on pixel array 24). Light generated by each unit 38C can propagate upwards in the Z direction through light diffuser 34 and optical film 26 before passing through pixel array 24. Light diffuser 34 may include a light scattering structure that diffuses light from light-emitting diode array 36 and thus helps provide uniform backlight illumination 44. Optical film 26 may include, for example, films such as dichroic filter 32, phosphor layer 30, and film 28. Film 28 may include a brightness enhancement film and / or other optical films (e.g., compensation film, etc.) that help collimate light 44 and thus enhance the brightness of display 14 for user 20.

[0032] The light-emitting diode (LED) of light source 38 can emit light of any suitable color. With an exemplary configuration, the LED emits blue light. A dichroic color filter layer 32 can be configured such that blue light passes through the LED 38 while simultaneously reflecting other colors of light. The blue light from the LED 38 can be converted into white light by a photoluminescent material such as phosphor layer 30 (e.g., a white phosphor material layer or other photoluminescent material that converts blue light to white light). If desired, other photoluminescent materials can be used to convert blue light into different colors of light (e.g., red, green, white, etc.). For example, layer 30 (which may sometimes be referred to as a photoluminescent layer or color conversion layer) may include quantum dots that convert blue light into red and green light (e.g., to produce white backlighting including red, green, and blue components, etc.). Configurations in which the LED 38 emits white light (e.g., thus omitting layer 30 if desired) and / or in which the LED 38 emits blue light or ultraviolet pump light for pixels containing quantum dots can also be used.

[0033] In a configuration where layer 30 emits white light, such as white light generated by phosphorescent material in layer 30, the white light emitted from layer 30 in the downward (-Z) direction can be reflected back by pixel array 24 via dichroic filter layer 32 as backlight illumination (i.e., layer 32 can help reflect backlight outwards away from array 36). In a configuration where layer 30 includes, for example, red and green quantum dots, dichroic filter 32 can be configured to reflect red and green light from the red and green quantum dots respectively to help reflect backlight outwards away from array 36. By placing the photoluminescent material of backlight 42 (e.g., the material of layer 30) above diffusion layer 34, light-emitting diodes 38 can be configured to emit more light toward the edges of the light-emitting diode cells (sheets) of array 36 than at the center of these cells, thereby helping to enhance the uniformity of backlight illumination.

[0034] Figure 3 This is a top view of an exemplary light source array for backlight 42. Figure 3As shown, array 36 may contain rows and columns of light sources 38. Each light source 38 may be associated with a corresponding unit 38C. The length D of the edge of unit 38C may be 2 mm, 18 mm, 1-10 mm, 1-4 mm, 10-30 mm, greater than 5 mm, greater than 10 mm, greater than 15 mm, greater than 20 mm, less than 25 mm, less than 20 mm, less than 15 mm, less than 10 mm, or other suitable dimensions. If desired, hexagonal tiled arrays and arrays with light sources 38 organized in other suitable array patterns may be used. In an array with rectangular units, each unit may have two sides of equal length (e.g., each unit may have a square outline in which four units of equal length surround a corresponding light-emitting diode) or each unit may have two sides of different length (e.g., a non-square rectangular shape). Array 36 has square light-emitting areas such as rows and columns of units 38. Figure 3 The configuration is merely exemplary.

[0035] If desired, each unit 38C may have a light source formed by an array of light-emitting diode dies (e.g., multiple individual light-emitting diodes 38D arranged in an array, such as a 2x2 cluster of light-emitting diodes for forming four die light sources 38 at the center of each unit 38C). This type of configuration is... Figure 3 The light source 38 in the leftmost and bottommost unit 38C is shown, which has been formed by a 2x2 array of light-emitting diodes 38D (e.g., four individual light-emitting diode dies). Figure 3 The diodes 38D in the light source 38 at the lower left corner of the array 36 can be mounted on a common package substrate, on a printed circuit board substrate extending across the array 36, or in the array 36 using other suitable arrangements. Generally, each unit 38C may include a light source 38 having a single LED 38D, a pair of LEDs 38D, 2-10 LEDs 38D, at least two LEDs 38D, at least four LEDs 38D, at least eight LEDs 38D, fewer than five LEDs 38D, or other suitable number of LEDs.

[0036] Figure 4 This is a cross-sectional side view of an exemplary backlight unit 38C in backlight 42. Figure 4As shown, each cell 38C in array 36 may have a reflector such as cavity reflector 68. Reflector 68 may have a square profile (i.e., a square footprint when viewed from above) or may have other suitable shapes and may be formed of sheet metal (e.g., stamped sheet metal), metallized polymer film, thin film metal on a plastic carrier, a dielectric film stack forming a dielectric mirror (thin film interference mirror) on a polymer film or molded plastic carrier, a white reflective film (e.g., a glossy white polymer sheet formed from a white ink layer or other white layer on a polymer carrier coated with a glossy coating such as a glossy polymer coating), or other suitable reflector structures.

[0037] An opening may be formed in a reflector 68 in each unit 38C to accommodate a corresponding light source 38. The light source 38 in each unit may have an upper portion protruding through the opening in the reflector 68 and a lower portion having contacts with metal traces soldered or otherwise mounted to the printed circuit 60.

[0038] The reflector in unit 38C may have a cross-sectional profile with curved portions to facilitate upward reflection of light from light source 38 as backlight illumination 44. Using an exemplary configuration, a roll-printed polymer film (e.g., a film coated with a dielectric thin-film interference mirror surface or a glossy white reflective surface) may be used (e.g., a film thermoformed using a patterned structure on a heated roller). After the thermoforming operation to form the curved walls of reflector 68 in each unit 38C, a die-cutting tool or other cutting device may cut openings for each of the light source 38.

[0039] like Figure 4 As shown, a transparent structure, such as a transparent dome structure 70, may be formed above each light source 38 to facilitate the lateral distribution of light 80 emitted by that light source. The dome structure 70 may be formed from beads of transparent silicone or other transparent polymers (as an example). During operation, the light source 38 emits light 80, which is refracted away from the Z-axis through the dome structure 70.

[0040] Some rays of light at 80 degrees are relative to Figure 4The light 80 is oriented at a relatively large angle relative to the Z-axis. These off-axis rays of light 80 are reflected upward from reflector 68 in the Z direction. Other rays of light 80 are oriented at a smaller angle relative to the Z-axis (the surface normal of display 14). If desired, backlight 42 may include an optional filter layer such as filter layer 97 having angle-dependent light transmission characteristics. Diffuse layer 34 may include light diffuser layer 34'. Layer 34' may include light scattering particles such as particles 72 in a polymer binder and / or may have other light scattering structures for diffusing light 80 from light source 38. Filter layer 97 may be a thin-film interference filter consisting of multiple dielectric layers 97' or other suitable filters having angle-dependent light transmission characteristics. Filter layer 97 may be formed on a substrate separate from layer 34' or may be formed on layer 34' within diffuser 34, such as... Figure 4 As shown in the exemplary configuration.

[0041] Due to external pressure, expansion and / or contraction due to thermal fluctuations, and / or manufacturing variations, the layers of display 14 may not be perfectly flat. This can cause undesirable fluctuations in the spacing H (sometimes referred to as the optical distance H) between the printed circuitry 60 and the diffuser 34. Using an exemplary configuration, display 14 may include an array of support pillars in the backlight 42 to help maintain an ideal fixed value for the height H across display 14.

[0042] Figure 5 A cross-sectional side view of an exemplary portion of the backlight 42 shows how the backlight 42 may include support pillars. Figure 5 As shown, the support post 90 may extend between the upper surface 60U of the printed circuit 60 and the opposite lower surface (surface 34L) of the diffuser 34 (as an embodiment). The post 90 may be cylindrical (radially symmetrical) or may have other shapes (e.g., a shape in which one or more sides of the post 90 have flat portions). The radially symmetrical arrangement of the post 90 can help reduce shading.

[0043] Support columns such as Figure 5 The presence of the support pillar 90 helps maintain a fixed spacing height H between the diffuser 34 and the printed circuit 60, and thus helps stabilize the vertical spacing between the light source 38 and the diffuser 34 in the array 36. This stabilization will help reduce fluctuations in light intensity that could otherwise cause hot spots and dark areas in the area of ​​the display 14.

[0044] like Figure 5As shown, the support column 90 may have a lower portion such as lower portion 90B and an upper portion such as upper portion 90F. Portion 90B may have a straight edge (e.g., portion 90B may be cylindrical) and portion 90F may taper outwards (e.g., portion 90F may have an inverted conical shape). The reflector 68 may have an array of openings, each opening accommodating a corresponding support column 90. Support columns may be present at each corner of each unit 38C, or the support columns 90 may be arranged more sparsely in the backlight 42 (e.g., to accommodate spaced height measurement sensors, etc.).

[0045] Figure 5 The support pillar 90 can be attached to layer 60 using adhesive 94 and / or screws such as screws 96. Screws 96 may have an axis that passes through an opening in the printed circuit board 60 and engages a threaded opening in a portion 90B of the pillar 90. The upper portion 90F of the pillar 90 can be attached to diffuser 34 using adhesive 92. To prevent dark spots from forming on backlight 42 due to the presence of the pillar 90, the pillar 90 may be formed of a transparent material such as a light-transmitting polymer. Adhesive 92 may also be formed of a light-transmitting material (e.g., a light-transmitting polymer). During operation, light 80 from light source 38 can be incident on portion 90F of the pillar 90 and can be redirected within the pillar 90, as shown by light ray 80-1 (e.g., by refraction). Refraction at the interface between pillar 90 and diffuser 34 can cause light ray 80-2 to form a non-zero angle relative to light ray 80-1, and refraction at the interface between diffuser 34 and the air (or other material) above diffuser 34 can cause light ray 44 (e.g., backlighting exiting diffuser 34) to form a non-zero angle relative to light ray 80-2. Light 80-2 can also be scattered by scattering features in diffuser 34. The horn shape of portion 90F and the transparency of portion 90F can help guide off-axis light rays, such as the exemplary light ray 80 above pillar 90, so that illumination 44 exists above pillar 90. As a result, local dark spots in backlighting 44 caused by the presence of pillar 90 can be reduced or eliminated.

[0046] If needed, other configurations can be used to support the diffuser 34 in the backlight 42. Figure 6In an exemplary configuration, pillar 90 comprises multiple injection-molded plastic. A primary injection-molded plastic, such as a white polymer, is used when forming the lower pillar portion 90W. A secondary injection-molded plastic, at least partially formed on the top of portion 90W, is used when forming the upper pillar portion 90C. Portion 90C may be transparent (e.g., portion 90C may be formed of a light-transmitting polymer). Utilizing this type of configuration, light rays, such as the exemplary off-axis ray 80, can enter the light-transmitting portion 90C and refract to form ray 80A. Ray 80A can be reflected from the reflective white surface 92 of portion 90W to form reflected ray 80B. According to the principle of total internal reflection, ray 80B can be reflected from the inner surface of portion 90C (e.g., the interface between portion 90C and the surrounding air in the space between diffuser 34 and printed circuit 60) to form reflected ray 80C. Ray 80C can enter diffuser 34, then enter a channel through diffuser 34, and exit diffuser 34 as backlight illumination 44 due to possible scattering by diffuser 34. Different rays of light can take different paths as they pass through column 90 and layer 34. However, as... Figure 6 As shown in the exemplary path of the light 80, the presence of the white portion 90W of the pillar 90 helps to reflect light so that it is not absorbed and lost at the pillar 90, and the presence of the light-transmitting portion 90C helps to redirect the light above the pillar 90 to act as illumination 44. As a result, Figure 6 The column structure shown can help reduce dark spots that might be caused by integrating the support into the backlight 42 in another way.

[0047] exist Figure 7 In an exemplary configuration, column 90 includes portion 90WR (e.g., a white polymer portion) and portion 90C (e.g., a light-transmitting polymer portion). Surface 92 of column portion 90WR is circular. This shape facilitates upward redirection of light through diffuser 34 (e.g., less light is reflected laterally and more light is reflected upward). Portion 90C may flare outward (taper) (e.g., making the top of portion 90C adjacent to diffuser 34 wider than the bottom of portion 90C adjacent to column portion 90WR) to facilitate redirection of light passing upward through diffuser 34 via portion 90C. Other shapes may be used for column portions 90WR and 90C if desired. Figure 7 The configuration is merely illustrative.

[0048] like Figure 8 As shown, the support pillar of the backlight 42 can be formed from an integral part of the diffuser 34. Figure 8In one embodiment, a portion 34P of the diffuser 34 serves as a support pillar and extends between the lower surface of the diffuser 34 and the opposing upper surface of the printed circuit 60. The portion 34P may be formed of the same material as the diffuser 34 and may be formed, for example, by molding the diffuser 34 together with the integral support pillars 34P such that these integral support pillars are protrusions from the planar portion of the diffuser 34. Pillars such as... Figure 8 The support column 34P is formed separately from and attached to the diffuser 34 (e.g., using an adhesive or other attachment mechanism). The support column 34P may be formed of a light-transmitting or translucent plastic (e.g., a transparent polymer, a transparent polymer with light-scattering particles or other light-scattering properties, etc.). The lower portion of the support column 34P may be cylindrical, while the upper portion may have a curved, outwardly flared profile. Other shapes may be used for the integral support column such as support column 34P if desired.

[0049] The support post 34P can be attached to the printed circuit 60 using adhesives, screws, or other attachment mechanisms. The printed circuit 60 can overlap with a metal backlight chassis layer such as a metal chassis 61 or other suitable support structure. This type of arrangement can be used in the backlight 42 whenever additional support is required for the backlight 42 layer.

[0050] exist Figure 8 In this embodiment, the support post 34P is configured to receive a screw, such as screw 96 (e.g., the support post 34P may have a threaded opening to receive the threaded shaft portion of the screw 96). An elastic washer 100 (e.g., an annular washer) may be received in an opening 102 in the metal base 61. The shaft of the screw 96 may pass through an opening in the washer 100 and an opening in the layer 60 (e.g., an opening wider than the shaft of the screw 96). The presence of the washer 100 between the head of the screw 96 and the metal base 61 helps to accommodate a lateral mismatch between the position of the post 34P and the position of the opening 102 in the printed circuit 60 (e.g., to meet alignment tolerances to accommodate lateral displacement due to thermal expansion and contraction, etc.).

[0051] like Figure 9 As shown, the support column 90 (e.g., a translucent polymer support column, a white polymer support column, etc.) may have an inverted conical shape or other configurations that minimize the size (diameter W) of the upper portion of the column 90 that contacts the diffuser 34. In configurations where the ratio of the diffuser thickness T to the column top diameter W is sufficient (e.g., at least 1, at least 2, at least 3, less than 100, etc.), the shadows cast by the light from the light source 38 will be minimized and the presence of the column 90 will not significantly disrupt the uniformity of the emitted backlight illumination 44.

[0052] If necessary, molded support structures such as Figure 10A support structure 103 supports the cavity reflector 68. The support structure 103 may have a curved profile, for example, in each unit 38C, allowing the reflector 68 to reflect light upwards to form a backlight illumination 44. The support structure 103 may have an opening for receiving the light source 38. The reflector 68 may be laminated to the surface of the support structure 103, deposited on the surface of the support structure 103, or integrated into the support structure 103 (e.g., by forming the support structure 103 from a reflective material such as white plastic). Figure 10 The molded support structure 103 is strong enough to support the diffuser 34 and can therefore be used to reduce or eliminate the use of the support column 90 in the backlight 42.

[0053] In some configurations, the diffuser height (space) sensor can be integrated into the backlight 42. This type of arrangement is... Figure 11 The backlight 42 is shown in a cross-sectional side view. Figure 11 As shown, reflector 68 may have openings such as openings 106 between corresponding units 38C. Each opening 106 allows light to be reflected from the lower surface 34L of diffuser 34. During operation of device 10, the value of the height H between the lower surface 34L of diffuser and the corresponding upper surface of printed circuit 60 can be dynamically measured and used to provide calibration information (e.g., pixel gain adjustment) to the display driver circuitry in device 10 as the value of the height H changes (e.g., due to external pressure, thermal effects, layer warping, etc.). The calibration information allows for the dynamic removal of any brightness variations that cause changes in H, thereby ensuring that the image on the array of pixels 16 of display 14 does not exhibit unwanted hot spots and dark areas.

[0054] The value of height (distance) H can be measured using any suitable sensor (e.g., capacitive sensor, electromechanical displacement sensor, acoustic sensor, force sensor, etc.). Figure 11 One suitable configuration shown uses an array of optical sensors to monitor the shape of the diffuser 34. For example... Figure 11 As shown, for example, optical sensor 104 may be aligned with opening 106 in reflector 68. Optical sensor 104 may include a light source such as light source 104L and may include a detector such as detector 104D. Light source 104L may be, for example, a light-emitting diode or a laser. Light source 104L may emit light such as infrared light invisible to a user and therefore not affect the image displayed on the pixels of display 14 and / or light source 104L may emit low-power visible light (e.g., pulsed visible light at an intensity that will not interfere with a user viewing the displayed image). Photodetector 104D may be configured to measure light emitted by light source 104, then reflected upward through opening 106, from the lower surface 34 of diffuser, and back to detector 104D through opening 106.

[0055] The distance between the opening 106 and the diffuser 34 varies with height H (e.g., as the diffuser 34 moves relative to the substrate 60, where the sensor 104 is mounted using solder or other conductive material). As the spacing between the opening 106 and the surface 34L changes, the amount of light from the light source that can be reflected from the surface 34L and returned to the detector 104D changes accordingly. For example, if the surface 34L is close to the opening 106, a relatively large amount of light from the source 104L will be reflected from the surface 34L and returned to the detector 104D. If the surface 34L is far from the opening 106, the amount of reflected light from the surface 34L detected by the detector 104D will decrease. As a result, such as Figure 11 The sensor 104 acts as a proximity (distance) sensor, which can dynamically measure the height H of the diffuser 34 at various sensor positions across the backlight 42.

[0056] If needed, sensor 104 can be interposed with support post 90 (e.g., sensor 104 and post 90 can be interposed with each other in an array where the sensor and post are located at the corners of cell 38C). Figure 12 An exemplary pattern of a type that can be used to distribute support pillars 90 and sensors 104 on a backlight 42 is shown. In this arrangement, there are more support pillars 90 than sensors 104. Typically, any suitable number of support pillars 90 and any suitable number of sensors 104 may be present (e.g., one sensor for every 1-5 support pillars, etc.). Figure 12 The arrangement is exemplary.

[0057] Figure 13 and Figure 14 The graph illustrates how sensor measurements can be used to dynamically compensate for changes in display 14 to reduce or eliminate image intensity variations caused by changes in H on display 14. Figure 13 In the graph, the backlight output intensity I (e.g., the intensity of illumination 44) has been plotted as a function of the lateral distance X across the backlight 42. Figure 13 The area of ​​backlight 42 covered by the curve covers two units 38C and two corresponding light sources 38. Due to the presence of the central light source 38 in unit 38C, local peaks in light output may exist at the center of each unit, as indicated by solid lines 108 and 110 (output of each unit 38C) and solid line 112 (the combined output of the two units 38C). To eliminate the intensity variation associated with line 112 in the final image displayed to the user of device 10, the display driver circuitry in device 10 may have features such as pixel gain compensation distribution. Figure 14 The pixel gain distribution 114. By locally reducing the pixel gain at locations where the backlight intensity has a local peak and vice versa, the final image displayed to the user on the display 14 will not exhibit significant intensity fluctuations due to changes in backlight intensity.

[0058] At a distance H Figure 13 and Figure 14 When the intensity of light decreases near the cell (as an example), the light output distribution from each cell will become narrower and more pronounced, as indicated by curves 108' and 110'. This is because a decrease in H will bring the diffuser 34 closer to the light source 38. The resulting intensity distribution of the backlight 42 will therefore change from curve 112 to curve 112'. By measuring the decrease in H with one or more sensors 104, the pixel gain curves can be updated accordingly. For example, the display driver circuit of the display 14 may be configured to correspond to... Figure 14 The pixel gain curve lookup table entry is not curve 114'. By dynamically updating the pixel gain distribution based on sensor data from sensor 104, changes in the transmission of pixel 16 can compensate for changes in backlight intensity, thereby ensuring that the image on display 14 is not affected by hot spots and dark areas.

[0059] Figure 15 This is the circuit diagram for device 10. (For example...) Figure 15 As shown, device 10 may have control circuitry 120. Control circuitry 120 may include storage and processing circuitry for supporting the operation of device 10. This storage and processing circuitry may include storage devices such as hard disk drive storage devices, non-volatile memory (e.g., flash memory configured to form a solid-state drive or other electrically programmable read-only memory), volatile memory (e.g., static or dynamic random access memory), and so on. The processing circuitry in control circuitry 120 can be used to control the operation of device 10. This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application-specific integrated circuits, etc.

[0060] The input-output circuitry in device 10, such as input-output device 122, can be used to allow data to be provided to device 10 and to allow data to be provided from device 10 to external devices. Input-output device 122 may include buttons, joysticks, scroll wheels, touchpads, keypads, keyboards, microphones, speakers, audio generators, vibrators, cameras, sensors (e.g., ambient light sensors, proximity sensors, orientation sensors, magnetic sensors, force sensors, touch sensors, pressure sensors, fingerprint sensors, etc.), LEDs and other status indicators, data ports, etc. Users can control the operation of device 10 by providing commands via input-output device 122 and can use the output resources of input-output device 122 to receive status information and other outputs from device 10.

[0061] Device 10 may include one or more displays, such as display 14. Display 14 may include an array of pixels 16, such as pixel array 24 that displays an image in response to control and data signals from display driver circuitry 124. Control circuitry 16 may be used to run software on device 10, such as operating system code and applications. During operation of device 10, the software running on control circuitry 16 provides image data to pixel array 24 and control signals on path 138 by displaying an image on pixel array 24 using display driver circuitry 124. Display driver circuitry 124 may also issue backlight control commands to light sources 38 in array 36, which is superimposed on pixel array 16, thereby allowing display driver circuitry 124 to adjust both pixel transmission (e.g., by adjusting liquid crystal pixel transmission values) and backlight output (by adjusting the brightness of source 38). Pixel data provided to pixels 16 may be corrected by circuitry 124 for backlight intensity variations 124 by applying pixel gain distributions stored in lookup table 128.

[0062] Sensor data from the array of sensors 104, interspersed in cells 38C of array 36, can be received by control circuitry such as sensor data processing circuitry 130. Circuitry 130 can determine the height H in real time based on measurements received from sensors 104 via path 136. In response, such as in combination... Figure 14 As described in the exemplary pixel gain distribution description, circuit 130 can provide pixel gain distribution updates to pixel gain distribution lookup table 128 in display driver circuit 124. For example, if sensor data from sensor 104 indicates that the value of H decreases in a particular cell 38C, the pixel gain curve for that cell can be obtained from an older pixel gain curve such as... Figure 14 Curve 114 is updated to a new pixel gain curve suitable for reducing H values, such as... Figure 14 The pixel gain distribution 114'. The gain distribution updated in lookup table 128 can be a two-dimensional distribution of pixel gain values ​​covering both the X and Y lateral dimensions of pixel array 24.

[0063] According to the implementation scheme, a display is provided, the display including a pixel array configured to display an image and a backlight configured to generate backlight illumination for the pixel array, the backlight having a two-dimensional cell array, each of the two-dimensional cell arrays including a light source and a reflector, thereon a printed circuit of the light source mounted thereon, a diffuser, and an interlaced support post configured to support the diffuser, the support post including a white polymer portion.

[0064] According to another embodiment, the support column includes a light-transmitting polymer portion.

[0065] According to another embodiment, each of the translucent polymer portions covers at least a portion of a corresponding portion of the white polymer portion.

[0066] According to another embodiment, the light-transmitting polymer portion is tapered.

[0067] According to another embodiment, the white polymer portion has rounded tips, each tip being covered by a corresponding portion of the translucent polymer portion.

[0068] According to another embodiment, the white polymer portion is cylindrical.

[0069] According to another embodiment, the display includes screws for attaching a respective support post of the support posts to the printed circuit.

[0070] According to another embodiment, the display includes a resilient washer, with a corresponding resilient washer inserted between each screw and at least a portion of the printed circuit.

[0071] According to another embodiment, the support column is formed by a protrusion in the diffuser.

[0072] According to another implementation scheme, at least some of the support columns are tapered.

[0073] According to another embodiment, the diameter of the tapered support column at the diffuser is smaller than the diameter at the printed circuit.

[0074] According to another embodiment, the display includes an array of optical sensors on a printed circuit that measures the corresponding spacing distance between the diffuser and the printed circuit.

[0075] According to another implementation, the support pillars are interspersed with optical sensors on the printed circuit board.

[0076] According to another embodiment, the display includes a display driver circuit with a lookup table, the display driver being configured to maintain a pixel gain distribution for a backlight intensity variation compensation image across the pixel array.

[0077] According to another embodiment, the display includes control circuitry configured to update the pixel gain distribution in a lookup table in response to measurements of the spacing distance from an array of optical sensors.

[0078] According to another embodiment, each optical sensor includes a light-emitting diode and a photodetector configured to detect light reflected from the diffuser from the light-emitting diode.

[0079] According to the implementation scheme, a display is provided, the display including a pixel array configured to display an image and a backlight configured to generate backlight illumination for the pixel array, the backlight having a two-dimensional unit array, each of the two-dimensional unit arrays including a light source and a reflector, a printed circuit of the light source mounted thereon, a diffuser, and an array of support pillars, the support pillars being attached to the diffuser with adhesive and configured to space the diffuser from the printed circuit.

[0080] According to another embodiment, the support column includes a light-transmitting polymer portion adjacent to the diffuser.

[0081] According to another embodiment, the display includes an optical sensor on the printed circuit, which is configured to measure a corresponding spacing distance between the diffuser and the printed circuit.

[0082] According to the embodiment, a display is provided, the display including a pixel array configured to display an image and a backlight configured to generate backlight illumination for the pixel array, the backlight having a two-dimensional cell array, each of the two-dimensional cell arrays including a light source and a reflector, a printed circuit of the light source mounted thereon, and a diffuser, and the backlight including a support post configured to space the diffuser from the printed circuit and an optical sensor for measuring the corresponding distance between the printed circuit and the diffuser.

[0083] The foregoing is merely illustrative and various modifications can be made to the described implementation scheme. The aforementioned implementation scheme can be implemented individually or in any combination.

[0084] This patent application claims priority to U.S. Patent Application No. 15 / 687,374, filed August 25, 2017, and Provisional Patent Application No. 62 / 501,002, filed May 3, 2017, the entire contents of which are incorporated herein by reference.

Claims

1. A display comprising: a pixel array configured to display an image; a backlight configured to produce backlight illumination for the pixel array, wherein the backlight has a two-dimensional array of cells each comprising a first light source and a reflector, a printed circuit on which the first light sources are mounted, a diffuser, and support posts configured to support the diffuser, wherein the support posts are selected from the group consisting of posts formed by protrusions in the diffuser, tapered posts where the diameter at the diffuser is less than the diameter at the printed circuit, and posts formed by support structures that support each reflector; and an array of optical sensors on the printed circuit, wherein each optical sensor comprises a second light source and a light detector, each optical sensor is aligned with an opening in the reflector between two respective cells, and each light detector measures a respective separation distance between the diffuser and the printed circuit at the location of the respective optical sensor by measuring an amount of light emitted by the respective second light source, then passing upward through the respective opening, reflecting off a lower surface of the diffuser, and passing back through the respective opening to the light detector.

2. The display of claim 1, wherein the support posts comprise a light-transmissive polymer portion.

3. The display of claim 2, wherein the support posts are formed by the protrusions in the diffuser, the backlight further comprising screws, each screw attaching a respective one of the support posts to the printed circuit.

4. The display of claim 3, further comprising elastomeric washers, wherein a respective one of the elastomeric washers is interposed between the printed circuit and at least a portion of each screw.

5. The display of claim 4, further comprising a chassis on which the backlight is mounted, wherein the chassis has openings through which the heads of each screw pass.

6. The display of claim 5, wherein the chassis is a metal chassis.

7. The display of claim 5, wherein each screw passes through one of the openings in the chassis, an opening in the printed circuit, and is coupled to a respective one of the support posts.

8. The display of claim 1, wherein the support posts are formed by the protrusions in the diffuser, and wherein each support post has an upper portion and a lower portion, the upper portion having a flared profile, and the lower portion being cylindrical.

9. The display of claim 1, wherein, the support posts interspersed with the optical sensors on the printed circuit.

10. The display of claim 9, further comprising a display driver circuit having a lookup table configured to maintain a pixel gain profile that compensates for backlight intensity variations of the image across the pixel array.

11. The display of claim 10, further comprising a control circuit configured to update the pixel gain profile in the lookup table in response to measurements of the separation distances from the array of optical sensors.

12. The display of claim 1, wherein, The optical sensors each include a light emitting diode and a light detector configured to detect light from the light emitting diode that has reflected from the diffuser.

13. The display of claim 1, wherein, The support posts are tapered, and wherein a ratio between a thickness of the diffuser and a diameter of the tapered support posts at the diffuser is at least 2.

14. The display of claim 1, wherein, The support posts are formed from a support structure that supports each of the reflectors, and wherein the support structure has a curved profile in each cell of the two-dimensional array of cells.

15. The display of claim 14, wherein, Each of the reflectors is laminated to the support structure in a given one of the curved profiles.

16. The display of claim 14, wherein, The support structure is formed from a white polymer, and wherein the reflectors are integral with the white polymer support structure.

17. A display comprising: a pixel array configured to display an image; and a backlight configured to produce backlit illumination for the pixel array, wherein the backlight comprises: an array of cells, each cell comprising a first light source and a reflector, a printed circuit on which the first light sources are mounted, a diffuser overlapping the first light sources and the reflectors, wherein the diffuser has a planar portion and integral protrusions extending from the planar portion to the printed circuit to support the diffuser, and an array of optical sensors on the printed circuit, wherein each optical sensor comprises a second light source and a light detector, each optical sensor is aligned with an opening in the reflector between two respective cells, and each light detector measures a respective separation distance between the diffuser and the printed circuit at the location of the respective optical sensor by measuring an amount of light emitted by the respective second light source, then upward through the respective opening, reflected from a lower surface of the diffuser and back through the respective opening to that light detector.

18. The display of claim 17, wherein, The backlight further comprises a metal chassis supporting the printed circuit, and wherein the integral protrusions of the diffuser are attached to the metal chassis with screws.

19. A display comprising: a pixel array configured to display an image; and a backlight configured to produce backlit illumination for the pixel, wherein the backlight comprises: a two-dimensional array of cells, each cell comprising a first light source and a reflector, a printed circuit on which the first light sources are mounted, a diffuser having a planar portion overlapping the first light sources and integral protrusions extending from the planar portion, wherein the integral protrusions extend from the diffuser to the printed circuit to support the diffuser, and wherein each integral protrusion has an upper portion with a flared profile and a lower cylindrical portion, and an array of optical sensors on the printed circuit, wherein each optical sensor comprises a second light source and a light detector, each optical sensor is aligned with an opening in the reflector between two respective cells, and each light detector measures a respective separation distance between the diffuser and the printed circuit at the location of the respective optical sensor by measuring an amount of light emitted by the respective second light source, then upward through the respective opening, reflected from a lower surface of the diffuser and back through the respective opening to that light detector. An optical sensor array on a printed circuit, wherein each optical sensor comprises a second light source and a light detector, each optical sensor is aligned with an opening in a reflector between two respective cells, and each light detector measures a respective separation distance between the diffuser and the printed circuit at the location of the respective optical sensor by measuring an amount of light emitted by the respective second light source, then passing upward through the respective opening, reflecting off a lower surface of the diffuser and passing back through the respective opening to the light detector.

20. The display of claim 19, wherein the pixels are liquid crystal display pixels, and wherein the unitary protrusion comprises a white polymer, a light-transmissive polymer, a translucent plastic, or a transparent polymer portion, wherein each of the optical sensors comprises a light-emitting diode and a light detector configured to detect light from the light-emitting diode that has reflected from the diffuser, and wherein the unitary protrusion is interleaved with the optical sensors on the printed circuit, the display further comprising: a touch sensor layer; an upper polarizer and a lower polarizer; a color filter layer interposed between the upper polarizer and the lower polarizer; a thin-film transistor layer interposed between the upper polarizer and the lower polarizer; a display driver circuit having a lookup table configured to maintain a pixel gain profile that compensates for backlight intensity variations of the image across the array of pixels; and a control circuit configured to update the pixel gain profile in the lookup table in response to measurements of the separation distances from the array of optical sensors.

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