The present application claims the benefit of Swedish patent application No. 1350461-8, filed 11 Apr. 2013.
The present invention relates to a coupling arrangement for injecting light into a panel, and use of the coupling arrangement with a panel and in a touch sensitive system according to the preamble of the independent claims.
Touch sensing systems (“touch systems”) are in widespread use in a variety of applications. Typically, the touch systems are actuated by a touch object such as a finger or stylus, either in direct contact, or through proximity (i.e. without contact), with a touch surface. Touch systems are for example used as touch pads of laptop computers, in control panels, and as overlays to displays on e.g. hand held devices, such as mobile telephones. A touch panel that is overlaid on or integrated in a display is also denoted a “touch screen”. Many other applications are known in the art. To an increasing extent, touch systems are designed to be able to detect two or more touches simultaneously, this capability often being referred to as “multi-touch” in the art.
WO2011/028169 and WO2011/049512 disclose multi-touch systems that are based on frustrated total internal reflection (FTIR). Light sheets are coupled into a panel by emitters to propagate inside the panel by total internal reflection (TIR). When an object comes into contact with a touch surface of the panel, the propagating light is attenuated at the point of touch. The transmitted light is measured at a plurality of outcoupling points by one or more light detectors. The signals from the light detectors are processed for input into an image reconstruction algorithm that generates a 2D representation of interaction across the touch surface. This enables repeated determination of current position/size/shape of touches in the 2D representation while one or more users interact with the touch surface. Examples of such touch systems are found in e.g. U.S. Pat. No. 3,673,327, U.S. Pat. No. 4,254,333 and U.S. Pat. No. 6,972,753.
The emitters and detectors of the system should be connected to external electrical circuitry. These components are typically integrated into and electrically connected to a printed circuit board, a PCB, and placed along the periphery of the touch panel.
Different solutions exist to integrate the components to the PCB. One category of solutions makes use of wire bonding to connect the component to external circuitry. One solution in this category use FR-4, a composite material composed of woven fiberglass cloth. A thin layer of copper foil is laminated to one, or both sides of an FR-4 glass epoxy panel. These are commonly referred to as “copperclad laminates”. A component is connected via bonding wires to a FR-4 panel and forms with a molding a substrate package. The substrate package is in turn connected to the PCB via connections on the package.
Another solution in this category makes use of a lead frame package, where the component is connected via bonding wires to a lead frame. The component and bonding wires are protected by a molding. The lead frame is in turn connected to the PCB.
Another category of solutions for connecting components to external circuitry is to use flip chip, also known as controlled collapse chip connection, or its acronym, C4. The solution makes use of solder bumps that has been deposited to the external circuitry. In order to mount the chip to external circuitry, e.g. a PCB, it is flipped over so that its top side faces down, and aligned so that its pads align with matching pads on the external circuit, and then the solder is flowed to complete the interconnect.
The components and its wire bonding, if used, can be protected by so called glob-top coating. Glob top is a coating consisting of a drop of specially formulated resin deposited over the chip and its wire bonds, to provide mechanical support and exclude contaminations such as fingerprint residues which could disrupt circuit operation.
When having components such as emitters and detectors that shall be used in a touch sensitive system, care must be taken such that light from the emitters is correctly injected into the panel, and such that the detectors can correctly detect light propagating in the panel. To achieve this, the emitters and detectors may be covered by a coating of optically transparent material acting as a filler between the emitters/detectors and the panel. The coating however has to have a certain size to allow correct injection of light into the panel. With a PCB holding the emitters and detectors, the dimensions becomes unpractical. Further, the cost of the coating is relatively expensive.
It is thus an object of the invention to reduce the cost for the system and to provide a manageable assembly with the components. It is a further object to provide an incoupling solution to the system.
According to a first aspect, the object is achieved by a coupling arrangement comprising a printed circuit assembly, PCA, comprising a printed circuit board, PCB; a group of components comprising an emitter, a detector and an integrated circuit, IC, wherein the components are electrically bonded to the PCB, and the emitter and the detector are electrically connected to the integrated circuit via the PCB. The integrated circuit is further configured to control operation of the emitter and the detector in the same group. A first coating covers at least one of the components in the group. The coupling arrangement further comprises a volume element, wherein the first coating and the volume element are made of optically transparent materials, and wherein the volume element is arranged to at least partly cover the first coating.
With such a coupling arrangement, less first coating has to be used as the volume element substitute some of the first coating. Costs can be reduced as the cost for a volume element is lower than having more first coating.
The volume element can act as a guide on a panel for the PCA, and time consuming positioning of the PCA can be removed or at least reduced.
According to one embodiment, the optically transparent materials are configured to be transparent to infra-red light.
According to one embodiment, the optically transparent materials are configured to block visible light.
According to one embodiment, the first coating has a box-shaped form with two longitudinal side surfaces and a top surface, wherein at least one of the side surfaces and top surface is a substantially planar surface.
According to one embodiment, the first coating is a glob-top coating.
According to one embodiment, the volume element has a box-shaped form corresponding to some extent to a shape of the first coating.
According to one embodiment, the PCB has a longitudinal extension.
According to one embodiment, the PCB comprises a plurality of groups of components, wherein the groups of components are positioned at a distance from each other along the longitudinal extension of the PCB.
According to one embodiment, the volume element has a longitudinal extension corresponding to the longitudinal extension of the PCB.
According to one embodiment, the PCA comprises an adhesive layer between the volume element and the first coating.
According to one embodiment, the PCB is a flexible printed circuit board.
According to a second aspect, the object is at least partly achieved by a touch sensitive panel comprises a coupling arrangement as herein explained.
According to a third aspect, the object is at least partly achieved with a touch sensitive system comprising a touch sensitive panel, wherein the printed circuit assembly is attached to the touch sensitive panel along the periphery of said touch surface; the system comprises a control unit connected to at least one integrated circuit in a group, and configured to control operation of the components in each group.
The touch sensitive system is according to one embodiment based on Frustrated Total Internal Reflection, FTIR.
Preferred embodiments are set forth in the dependent claims and in the detailed description.
Below the invention will be described in detail with reference to the appended figures, of which:
The arrangement 1 allows one or several objects 27, 9 that is brought into close vicinity of, or in contact with, the touch surface 3 to interact with the propagating light at the point of touch. In this interaction, part of the light may be scattered by the object 27, 9, part of the light may be absorbed by the object 27, 9 and part of the light may continue to propagate in its original direction across the panel 2. Thus, the touching object 27, 9 causes a local frustration of the total internal reflection, which leads to a decrease in the energy (power/intensity) of the transmitted light, as indicated by the thinned lines downstream of the touching objects 27, 9 in
As illustrated in
In
The PCA 15 further comprises a first coating 16 covering at least one of the components in the group 13. The emitter(s) 4 and the detector(s) 5 in each group 13 are preferably covered with a first coating 16. The first coating 16 is made of an optically transparent material, such that the emitter 4 can emit light into the panel 2 via the first coating 16, and the detector 5 can detect light propagating in the panel 2 via the first coating 16. The optically transparent material is preferably transparent to near infra-red light, thus, it lets through electromagnetic radiation with the wavelengths from 0.74 μm to 1.4 μm. Example of such materials are e.g. a polymer, epoxy, etc. The first coating 16 may additionally comprise a material that is blocking visible light, thus acting as a detector filter to ambient light.
The integrated circuit 12 may be covered with a second coating 22. The second coating 22 may be located between the first coating 16 and the integrated circuit 12 as illustrated in
The first coating 16 may have a box-shaped form with two longitudinal side surfaces 18, 19 and a top surface 20. At least one of the side surfaces 18, 19 and top surface 20 is a substantially planar surface, such that it can act as an optically surface and lie against the panel 2. The first coating 16 here has a height h1 extending from the top of one of the components, e.g. the emitter 4 to the top surface 20.
In
The PCA 15 can be attached to a volume element 23 to form a coupling arrangement 25. The volume element 23 is not shown in
To be able to introduce light into the panel 2 at an angle θ larger than the critical angle, the light from the emitter 4 must be able to travel via an optical medium a certain length before it reaches the panel 2. By having a volume element 23 as an optical medium, the height of the PCA 15 can be kept low, but the light L can still travel in the optical medium such that it can reach the panel 2 in angles θ larger than the critical angle.
In the following text, further alternative coupling arrangements 25 will be explained. The first coating 16 and the volume element 23 are made of optically transparent material. The optically transparent materials are preferably transparent to infra-red light. According to one embodiment, the optically transparent materials are configured to block visible light. The optically transparent materials may thus both be transparent to infra-red light and block visible light. The volume element 23 is here illustrated to have a box-shaped form corresponding to some extent to a shape of the first coating 16 as will be illustrated with reference to
As can be seen from the
The volume element 23 (and when used also the intermediate coating 24), thus extends the optical way the light L can travel from the emitters 4 before it reaches the panel 2 and to the detectors 5. As illustrated in the figures, the panel 2 has a thickness d. The height of the first coating 16 extending from the top of a component, e.g. the emitter 4 or detector 5, to the top surface 20 is h1, and the height of the volume element 23 is h2. To provide an optical path for the light that is great enough, in the embodiment illustrated in
The side surface 18, 19 or top surface 20 that should be aligned to the bottom surface 7 may have a light blocking coating, such that the components, e.g. the detectors 5, can be protected from light introduced mainly along the normal of the panel 2. Care must be taken when providing the surface with a light blocking coating, such that emitted light or light that shall be detected is not blocked. As the height h1 or width w1 of the first coating 16 now is small, the whole surface 18, 19. 20 can be covered with the light blocking coating without any need for precision.
The volume element 23 is in one embodiment attached to the panel 2 before it is attached to the PCA 15. The volume element 23 may then act as a mounting support for the PCA 15.
The volume element 23 may have a longitudinal extension corresponding to the longitudinal extension of the PCB 17. The volume element 23 may alternatively be divided in parts where the parts are placed on the panel 2 or the PCA 15 such that the emitters 4 and the detectors 5 can emit/detect light to/from the panel 2 via the volume element 23. The space between each part will allow the volume element 23 to e.g. expand when exerted to thermal stress.
An adhering means such as an adhesive layer, glue or double coated adhesive tape may be used between the PCA 15 and the volume element 23 (e.g. between the first coating 16 and the volume element 23) and/or between the volume element 23 and the bottom surface 7 of the panel 2 to attach the PCA 15 to the volume element 23 and the volume element 23 to the panel 2. The adhering means may also act as a filler to fill in any irregularities in the surfaces to create a tight attachment.
The coupling arrangement 25 with a plurality of groups 13 of components may thus be located around the periphery of the touch surface 3 or the panel 2, such that light from emitters 4 can be injected into the panel 2 etc. as previously explained. The touch sensitive panel 2 may thus comprise a coupling arrangement 25 according to any of the embodiments as has been previously explained. This is illustrated in
A screen or display may be integrated with the panel 2, e.g. attached to the bottom surface 7 of the panel 2. The coupling arrangement is then preferably placed along the panel 2 outside the extension of the screen or display. If e.g. an 11 inch screen or display is used, the number of emitters 4 may be between 40-80, and the number of detectors 5 may be between 40-80 to cover the total area of the screen or display. Each integrated circuit 12 may be connected to 1-4 emitters 4 each, and 1-4 detectors 5. According to one embodiment, only one emitter 4 and one detector 5 is connected to each integrated circuit 12.
The disclosure also relates to a method for fabricating a printed circuit assembly 15. The method is here explained with reference to the flowchart in
The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. For example, the panel 2 may be formed such that the panel 2 comprises the volume element 23. The panel 2 and the volume element 23 may also be moulded as one unit. The panel 2 and the volume element 23 may then be moulded of a plastic or glass. Alternatively, volume element 23 and the panel 2 may be moulded separately in a first step, and attached to each other in a second step. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.
Number | Date | Country | Kind |
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1350461-8 | Apr 2013 | SE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/SE2014/050438 | 4/9/2014 | WO | 00 |