Apparatus for display

Abstract

An apparatus includes a display screen and an optical sensor module disposed behind the display screen. The optical sensor module further includes a light emitter operable to generate light having a wavelength that is transmitted through the display screen toward a target object. A light sensor is operable to sense light reflected by the target object and having the wavelength. A reducer is disposed to reduce optical power density by increasing a diameter of a light beam generated by the light emitter on the display screen, wherein the reducer is disposed between the light emitter and the display screen so as to intersect the light beam generated by the light emitter.

Description

Technical Field

[0001] This disclosure relates to an optical sensing system disposed behind a display screen.

[0002] This patent application claims priority to European Patent Application 20181209.6, the disclosure of which is incorporated herein by reference. Background Technology

[0003] Optical sensors, such as proximity sensors, biosensors, and 3D sensors, can cause display distortion when used behind displays such as OLEDs, μLEDs, TFTs, or plasmas. Optical proximity sensing typically relies on emitting infrared (IR) or near-infrared (NIR) light and measuring the energy of the light reflected back from the object being detected. Typically, light, such as IR or NIR light, has an energy exceeding the bandgap of many semiconductors used in displays (e.g., Si-TFTs). Due to the low transmittance of displays, there is a trade-off between the optical power required to achieve the desired sensing distance and the display distortion controlled by optical irradiance.

[0004] The purpose of this disclosure is to provide an apparatus that overcomes the above-mentioned disadvantages.

[0005] This objective is achieved through the subject matter of the independent claims. Further developments and embodiments are described in the dependent claims.

[0006] It should be understood that, unless described as an alternative, any feature described with respect to any embodiment may be used alone or in combination with other features described herein, and may also be used in combination with one or more features of any other embodiment, or in any combination of any other embodiment. Furthermore, the following equivalents and modifications not described may also be used without departing from the scope of the apparatus as defined in the appended claims. Summary of the Invention

[0007] This disclosure describes techniques for helping to reduce or eliminate display distortion caused by the energy emitted by light emitters in optical sensors (e.g., proximity sensor modules, biosensors, 3D sensors, etc.).

[0008] The following relates to an improvement concept in the field of optical sensing systems. It is proposed to reduce the power density on the display while increasing the total emitted light power. Optionally, it is possible to tune the beam divergence. One or more of the following aspects may contribute to the improvement concept:

[0009] • Increasing the package height to increase the beam diameter, for example, by using a crosstalk blocking aperture.

[0010] • Increase the beam diameter, for example, by using beam-shaping optics (with or without increasing the package height), such as light emitters with two or more lenses, microlens arrays, and collimating lenses, and / or light emitters with large field of illumination (FOI) and collimating lenses, such as VCSELs.

[0011] • Adjust the beam divergence, for example, to reduce crosstalk entering the optical sensor.

[0012] In this context, it has been found that to widen the beam diameter on the output side, such as the target-facing aperture of the module or optical package, beam divergence can be increased near the light emitter. While beam divergence can be controlled through emitter design, this can require significant structural changes (often a rather lengthy and complex process, as is the case with epipi). Alternatively, reducers are integrated into the module to increase beam divergence, thereby increasing the beam diameter on the display. Typically, reducers are configured to reduce optical power density by increasing the diameter of the beam generated by the light emitter, for example, on the display.

[0013] For example, in one aspect, this disclosure describes an apparatus including a display screen and an optical proximity sensor module disposed behind the display screen. The optical sensor module further includes a light emitter operable to generate light having a wavelength for transmission through the display screen toward a target object. The light sensor is operable to sense light reflected by the target object and having that wavelength.

[0014] The optical sensor module also includes a reducer for reducing the optical power density by increasing the diameter of the light beam generated by the light emitter on the display screen. The reducer is positioned between the light emitter and the display screen so as to intersect with the light beam generated by the light emitter.

[0015] The improved design allows for the implementation of optical sensors (e.g., optical proximity sensors with detection distances greater than 30mm) behind a display screen, with significantly reduced or virtually no distortion. This improved design can be applied to all types of optical sensors, including light emitters, such as proximity sensor modules, biosensors, and 3D sensors.

[0016] In the following text, "light" refers to electromagnetic radiation within the portion of the electromagnetic spectrum that is perceptible to the human eye. This includes visible light with wavelengths ranging from 400 to 700 nanometers. However, the term "light" also includes infrared radiation, such as near-infrared (longer wavelengths), and ultraviolet radiation (shorter wavelengths).

[0017] An objective lens can be a single lens or a mirror, or a combination of several optical elements. Elements that shape the diameter and / or divergence of a beam are considered beam-shaping optics. This includes lenses, such as collimating lenses, a group of such lenses, and / or one or more optical surfaces that have lens properties.

[0018] The term "located behind the display" means, for example, when viewed from above along the main direction of light emission from the display (e.g., the surface normal of the display), that the display covers the optical sensor module. In any case, the optical sensor module is "located behind the display," meaning that the light beam generated by the light emitter needs to pass through the display, thus becoming a potential source of screen distortion.

[0019] A reducer, in this context, refers to any device that can be positioned between a light emitter and a display screen to intersect with a light beam generated by the light emitter. This can be part of a module of, for example, an optical package or optical element, such as a beam-shaping optics. For instance, a reducer is configured to disperse light energy from the light beam generated by the light emitter, thereby reducing distortion of the display screen.

[0020] Some implementations include one or more of the following features. For example, in some cases, the optical sensor module (e.g., an optical proximity sensor module) is positioned behind the display, with an optical barrier between the light emitter and the light sensor. The distance between the active surface of the light emitter and the top surface of the module (e.g., an optical package) is greater than 2 mm.

[0021] According to another aspect, this disclosure describes a reducer comprising beam-shaping optics between the active surface of an optical emitter and the top surface of a module. The beam-shaping optics are operable to reduce optical power density by increasing the beam diameter to a desired extent, i.e., increasing it to a desired beam diameter at or on a display screen.

[0022] Beam-shaping optics can include various refractive and / or reflective components, such as objectives of lenses or lens groups and / or reflective surfaces such as mirrors. For example, beam-shaping optics include Galilean telescopes, diffusers and collimating lenses, microlens arrays and collimating lenses having at least two reflective surfaces, and optionally one of which is a partially reflective beam shaper.

[0023] The optical sensor module includes a light emitter comprising one of a plurality of light-emitting elements, each operable to generate light transmitted through the display screen toward an external target object. The light emitter and the light-emitting elements can operate together to provide sufficient light energy for proximity sensing.

[0024] Some implementations include a VCSEL laser diode having a large illumination field (i.e., FOI > 30°) on the display screen, and a collimating lens and / or an edge-emitting laser having a beam curvature surface and collimating lens that can produce a wide FOI vertical emission.

[0025] The following description of the accompanying drawings of the exemplary embodiments may further illustrate and explain aspects of the improved concept. Components and parts having the same structure and effect are shown with equivalent reference numerals. Descriptions of components and parts in the following figures need not be repeated, provided that their functional aspects correspond to each other in different figures. Attached Figure Description

[0026] Figure 1A , 1B An example embodiment of the device is shown.

[0027] Figure 2A , 2B Another example embodiment of the device is shown.

[0028] Figure 3 Another example embodiment of the device is shown.

[0029] Figure 4 An example power loss calculation due to lateral offset is shown.

[0030] Figure 5 Another example embodiment of the beam-shaping optics is shown.

[0031] Figure 6 An example simulation is shown, and

[0032] Figure 7 An example embodiment of a beam-shaping optics device with a reflective collimating beam expander is shown. Detailed Implementation

[0033] Figure 1A and Figure 1B An example embodiment of the device is shown. In this embodiment, the device includes an optical package. The optical package includes two chambers 1 and 2, which are optically separated by a light barrier 3 and disposed on a substrate 4. One chamber houses a receiver 5 with a light sensor, and the other chamber houses a light emitter 6. Both chambers are complementary to optics 7 and 8 to alter the beam of light emitted and / or detected. The optical package is positioned relative to a display 9.

[0034] Figure 1A The image shows a standard optical package with a height of 1 mm or less, as indicated by the arrow. Considering a VCSEL with a field of interest (FOI) of 20°, the beam diameter on the display is approximately 200 μm. This may cause distortion in the display when the beam strikes the screen. Figure 1B An example of the proposed optical package with increased height (e.g., 2.5 mm) is shown. Considering a VCSEL as a light emitter with a FOI of 20°, the beam diameter on the display is approximately 750 μm. Therefore, the distortion of the display when the beam strikes the display is significantly reduced. For example, the light power density on the display is reduced by 14 times. The increase in package height can be viewed as a reduction factor. In turn, the reduction factor has the effect of increasing the optical package height.

[0035] Figure 2A and Figure 2B Another example embodiment of the device is shown. This embodiment includes... Figure 1A and Figure 1B Similar to the optical packaging discussed earlier, a beam-shaping optics device 8 is recommended to modify the beam diameter, in addition to setting the package height. The rationale is as follows: To widen the beam diameter at the output end, the beam divergence near the light emitter 6 (e.g., VCSEL) may need to be increased. Beam divergence can be controlled through the emitter design, but this typically requires changing, for example, the epipi, which is a rather lengthy and complex process. Therefore, it is preferable to use a concave lens to increase the divergence; the concave lens is, for example, positioned between the light emitter and the display screen, thereby intersecting the beam generated by the light emitter.

[0036] A simplified model can be assumed to be based on the Galilean telescope. Furthermore, consider a convex lens with focal length f1 and a concave lens with focal length f2, where the two focal points can coincide. Then, the beam radius magnification is m = f1 / f2. Example: f1 = 1 mm, f2 = 0.2 mm, m = 5, total length = 0.8 mm.

[0037] In one implementation option ( Figure 2A In this embodiment, a convex lens is disposed within the cover of the optical package, and a concave lens is replicated onto the light emitter (e.g., a VCSEL). Since the second lens can be considered part of the light emitter (e.g., a VCSEL), this may have little impact on the overall package concept. In another implementation option (… Figure 2B In this optical package, a single optical element with one convex surface and one concave surface is attached to the cover or aperture of the optical package. This improves the centering of the two lenses and reduces pointing errors.

[0038] Figure 3Another example embodiment of the device is shown. The figure illustrates the example with actual figures and explains the effect of the reducer on increasing the beam diameter through the beam-shaping optics. This example assumes a VCSEL emission wavelength of 940 nm and a divergence of ±12.5°. The beam-shaping optics 8, acting as the reducer, has an inner lens radius R1 and an outer lens radius R2. The distance between the emitter 6 and the inner lens of radius R1 is denoted as T1, and the lens height is denoted as T2. The beam diameter at the display screen is assumed to be D = 800 μm. Additional design constraints and tolerances are shown in the figure.

[0039] In this example, the beam diameter is increased by a factor of 3 while maintaining a constant beam divergence. In principle, it is feasible to design a system that extends the VCSEL beam (indicated by upward double arrows in the table). One issue that might be whether the design is stable over a given tolerance range (indicated by downward double arrows in the table).

[0040] Figure 4 An example of power loss calculation due to lateral offset is shown. Figure 3 The embodiments may be prone to power loss due to the lens diameter and its relative offset. The figure shows different lateral offsets of the beam-shaping optics 8 (e.g., the objective lens) and the light emitter 6. The table shows the emission power (in %) as a function of offset (in μm). Within the studied 100 μm offset range, the emission power can decrease by almost 50%.

[0041] Figure 5 Another example embodiment of a beam-shaping optics is shown. Here, a diffuser replaces the first surface. The left figure illustrates how the lens design tends to deflect, as... Figure 4 The first surface of lens 10, i.e., the surface facing the emitter 6, receives light emitted by the emitter. Because the light emitter may have an offset (as shown in the figure), the emitted power may be affected or reduced. In this example, the first surface of the lens does not have a diffuser. The right figure depicts the first surface 10 with a diffuser 11 (e.g., a diffuser at the objective lens entrance), while the rest of the geometry remains unchanged. Despite the offset, the emitted power may increase significantly.

[0042] Figure 6 An example simulation is shown. Figure 5 The diffuser introduced reduces power loss due to lateral offset. This can be simulated as shown in the figure. The graph on the left assumes incoherent irradiance and a spot size of HWHM = 800 μm at the display. On the right, the beam divergence at the display has been determined. Within a lateral offset range of 100 μm and with HWHM = 12°, the power loss in the lateral direction is only 0.5%.

[0043] Figure 7An example embodiment of a beam-shaping optics device with a reflective collimating beam expander is shown. Light is emitted from a light emitter LE (e.g., a VCSEL). The figure shows a chamber with a light emitter disposed on a substrate (e.g., an electronic substrate 4). The light emitter 6 is positioned at the center of a reflector 13 (e.g., a mirror, lens, or a coated lens). Another reflector 12 is disposed within the cover of the optical package.

[0044] The emitted light ultimately strikes the first curved (convex) reflector 12: a larger portion of the light is reflected with high divergence. A smaller portion is transmitted and partially collimated. The reflected light then strikes the second curved (concave) reflector 13: the beam is collimated and directed toward the exit of the package (e.g., an aperture in an optical package). Light from the second reflector passes through the transparent substrate carrying the central reflector. Light passing through the first reflector exits the transparent material through a surface that can be optionally curved (e.g., a lens or lens surface). This lens can be used to fine-tune the divergence of the central portion of the beam. Advantages of this design include a longer focal length at a given z-height, resulting in a larger beam, and optionally better collimation.

[0045] Other aspects, features, and advantages will become apparent from the following detailed description, drawings, and claims.

[0046] Although the description of the improved concept includes many details, these details should not be construed as limiting the scope of the concept or what has been or could be claimed, but rather as a description of specific features of certain embodiments of the invention. Some features described in connection with individual embodiments in this disclosure may also be implemented in combination in a single embodiment. On the other hand, various features described in connection with individual embodiments may also be implemented individually or in any suitable sub-combination in several embodiments. Furthermore, although the foregoing may describe features as functioning in certain combinations, or even initially claimed, in some cases one or more features may be removed from the claimed combination, and the claimed combination may refer to a sub-combination or a variation of a sub-combination.

[0047] Therefore, even though the operations in the accompanying figures are presented in a specific order, this should not be construed as meaning that these operations must be performed in the order shown or sequentially, or that all the operations shown must be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous.

[0048] Many embodiments have been described. However, various modifications can be made without departing from the spirit and scope of the invention. Therefore, other embodiments are also within the scope of the claims.

Claims

1. An apparatus comprising: - Display screen (9), and - An optical sensor module located behind the display screen (9); The optical sensor module also includes: - A light emitter (6), operable to generate light having a wavelength for transmission through the display screen (9) toward a target object. - A light sensor (5), operable to sense light reflected by the target object and having the wavelength, and - A reducer (8) for reducing optical power density by increasing the diameter of the light beam generated by the light emitter on the display screen (9), wherein the reducer is disposed between the light emitter and the display screen to intersect with the light beam generated by the light emitter, wherein the reducer includes a beam-shaping optics configured to increase the diameter of the light beam to a desired extent, wherein, - The beam shaping optics includes an objective lens, which is at least partially disposed on the active surface of the light emitter, and / or - The device further includes an optical package, and the beam-shaping optics are disposed in an aperture of the optical package facing the display screen, and / or - The beam-shaping optics include optical telescopes, and / or - The beam-shaping optics includes a microlens array, and further includes at least one collimating lens and / or collimating optical surface, and / or - The beam-shaping optics includes at least a first reflective optical surface and a second reflective optical surface, the first and second reflective optical surfaces being at least partially operable to reflect light having a wavelength for transmission through the display screen.

2. The apparatus according to claim 1, wherein, The optical package is included in the reducer, and the light emitter and the light sensor are disposed inside the optical package, and the optical package has a height configured to increase the diameter to a desired extent.

3. The apparatus according to claim 2, wherein, The height of the optical package is greater than 1 mm.

4. The apparatus according to claim 2 or 3, wherein, The height of the optical package is limited between a top surface and a bottom surface, wherein the light emitter and the light sensor are disposed on the bottom surface, and the top surface faces the display screen.

5. The apparatus according to claim 1, wherein, The beam-shaping optics include a diffuser.

6. The apparatus according to claim 1, wherein, The central optical axis of the beam-shaping optics is offset relative to the optical axis of the optical package.

7. The apparatus according to any one of claims 1 to 3, wherein, The light emitter includes one or more light-emitting elements, wherein the light-emitting element is of the resonant cavity type.

8. The apparatus according to any one of claims 1 to 3, wherein, The display screen is an OLED, micro-LED, TFT, or plasma display screen.

9. The apparatus according to claim 3, wherein, The height of the optical package is greater than 2 mm.

10. The apparatus according to claim 1, wherein, The optical telescope is a refracting optical telescope and / or a reflecting optical telescope that includes one or more reflecting optical surfaces.

11. The apparatus according to claim 10, wherein, The refracting optical telescope mentioned is the Galilean telescope.

12. The apparatus according to claim 1, wherein, The central optical axis of the beam-shaping optics is offset relative to the optical axis defined by the main emission direction of the light emitter.

13. The apparatus according to claim 7, wherein, The light-emitting element is at least one of the following: -Vertical cavity surface-emitting laser (VCSEL) - Edge-emitting laser with a beam curvature surface - Microdisk laser - Resonant cavity light-emitting diode, and / or - Distributed feedback laser (DFB).

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