BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, which are given by way of illustration only and, thus, are not limitative of the present invention. In these drawings, similar elements are referred to using similar reference numbers, wherein:
FIGS. 1A and 1B illustrate the configuration of a typical liquid crystal display (LCD) device;
FIGS. 2A and 2B illustrate different types of backlight sources within typical backlit LCD devices;
FIG. 3 illustrates an exemplary set of touchscreen keys for a particular application;
FIGS. 4A and 4B illustrate an exemplary embodiment of the present invention in which the probe light sensor is disposed within the LCD stack along with the probe light source, while FIGS. 4C and 4D illustrate principles of operation in such an embodiment;
FIGS. 5A-5C illustrate an exemplary embodiment of the present invention utilizing an external probe light sensor in conjunction with a probe light source implemented within the LCD stack, while FIGS. 5D and 5E illustrate principles of operation in such an embodiment;
FIGS. 6A and 6B illustrate the scanning process whereby the touchscreen keys are made active, according to an exemplary embodiment of the present invention;
FIGS. 7A and 7B illustrate scanning patterns whereby touchscreen keys are made active, according to alternative exemplary embodiments of the present invention;
FIGS. 8A and 8B illustrate operation of a backlit LCD device during touchscreen mode and normal display mode, respectively, according to an exemplary embodiment of the present invention; and
FIGS. 9A and 9B illustrate additional elements in the LCD device for processing measurements from the probe light sensor and compensating for the effects of ambient light, according to exemplary embodiments of the present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
In order to integrate a touchscreen interface with a liquid crystal display (LCD) device, the present invention utilizes probe signals transmitted from within the stack of LCD layers to detect user contact with the touchscreen surface (e.g., the front protective sheet of the LCD device). A probe signal sensing device is configured to detect reflections of probe signals from the touchscreen surface, which are caused by a user's touch.
According to an exemplary embodiment, the source of the probe signals is a light source (hereafter “probe light source”), e.g., an LED, implemented behind the liquid crystal (LC) layer within the LCD casing or enclosure. Thus, the probe signal sensing device may comprise a light sensor (hereafter “probe light sensor”) configured to produce intensity measurements of the probe light. To enhance detection properties, the probe light source may be modulated at a particular frequency or range of frequencies, and the probe light sensor may be configured to demodulate and measure such light.
The probe light sensor may be disposed within the LCD stack, or external to the touchscreen surface, according to alternative exemplary embodiments. In either case, the probe light sensor is positioned such that user contact on the touchscreen surface causes some of the probe light to reflect toward the sensor. Since the reflected probe light causes the intensity measurement at the probe light sensor to increase, the probe light sensor may be used for detecting the user contact.
According to a further exemplary embodiment, the touchscreen surface may be partitioned into a plurality of touchscreen keys. It is contemplated that many different types of touchscreen applications could be implemented on the same LCD device. The type of touchscreen keys presented to the user, and configuration (size, shape, etc.) are purely a matter of design choice and the requirements of a given touchscreen application.
FIG. 3 illustrates a particular example of a touchscreen application where the user is presented with touchscreen keys 200 corresponding to traditional numerical keys of a push-button telephone. As shown in FIG. 3, the front protective sheet 10 of an LCD device may be used as the touchscreen surface. Of course, the touchscreen application illustrated in FIG. 3 is purely exemplary, merely providing a point of reference to describe further aspects of the invention.
FIGS. 4A and 4B illustrate a particular exemplary embodiment of the present invention in which both the probe light source and sensor are disposed within the LCD stack. Specifically, FIG. 4A illustrates a side view of the LCD stack in an LCD device 100, including the front surface 10 (or touchscreen surface), polarizers 30A and 30B, LC layer 20, and reflective surface 60. FIG. 4B illustrates a planar view of the device 100 at cross-section CV′ of FIG. 4A.
It should be noted that principles of the present invention may be applied in both backlit (transmissive) and reflective-type LCD devices. However, even though the LCD device 100 illustrated in FIGS. 4A and 4B may be configured as a backlit LCD, these figures do not illustrate the backlight source as part of the LCD stack as a matter of convenience.
As shown in FIGS. 4A and 4B, the probe light source 82 may be a “pinpoint” light source, such as an LED. However, these figures are merely illustrative, and other types of probe light sources 82 may be used as will be contemplated by those of ordinary skill in the art.
According to the embodiment of FIGS. 4A and 4B, the probe light source 82 and probe light sensor 92 are disposed within the LCD stack, behind the LC layer 20 and polarizers 30A and 30B. Thus, as shown in FIG. 4A, the casing 70 and touchscreen surface 10 form an enclosure for the probe light source 82 and sensor 92, as well as other layers of the LCD stack.
A key feature of this particular embodiment is that the probe light source 82 and sensor 92 are implemented behind the LC layer 20. Otherwise, the positioning of probe light source 82 and sensor 92 in these figures are merely illustrative, and may be modified based on various design considerations as will be contemplated by those of ordinary skill in the art. For example, although the probe light source 82 and sensor 92 as being positioned at opposite corners in FIG. 4B, these elements could be positioned on the same side and/or closer to the center of the device 100.
FIGS. 4C and 4D illustrate the principles of operation of this device 100. According to an exemplary embodiment, the touchscreen keys 200 are made “active” one at a time. To do this, the LC layer 20 may be partitioned according to the touchscreen keys 200, similar to the touchscreen surface. By default, each partitioned area of the LC layer 20 may be configured to absorb the probe light transmitted by source 82. When a particular key 200 is made active, the LC layer may be configured to provide an “opening” in the corresponding partition to allow the probe light to pass through to the touchscreen surface, as illustrated in FIG. 4C.
FIG. 4C illustrates a particular situation where the LC layer 20 provides the probe light opening for an active touchscreen key 200ACT, which is not currently touched by the user. As shown in this figure, the probe light sensor 92 will sense some amount of probe light transmitted by the probe light source 82. On the other hand, FIG. 4D illustrates the situation where the same touchscreen key 200ACT is made active, and the active key 200ACT is being touched by a user. In FIG. 4D, the user contact causes a reflection of the probe light back into the LCD stack, thus causing the measured intensity to increase at the probe light sensor 92. Based on this increased intensity measurement, the probe light sensor 92 can detect user contact with the touchscreen surface. Furthermore, since only one touchscreen key 200ACT is active at this particular time, it can be determined which of the plurality of touchscreen keys 200 is touched by the user.
As described above, the probe light sensor 92 is placed within the LCD stack of the LCD device 100, along with the probe light source 82. Accordingly, the probe light sensor 92 must rely on the probe light to be reflected back through the probe light opening in order to detect user contact with the touchscreen surface. Since the probe light passes through the LC layer 20 twice, the signal strength is reduced.
Thus, an alternative exemplary embodiment provides an external probe light sensor in order to increase the strength of the probe signal used for detecting user contact. Particularly, FIGS. 5A-5C illustrate an LCD device 100′, according to this alternative embodiment.
As shown in FIG. 5A, the probe light source 82 is placed within the LCD stack, behind the LC layer 20, similar to the other embodiment described above. However, in FIG. 5A, the probe light sensor 92′ is situated external to the touchscreen surface 10, near the edge of the surface. Thus, the probe light sensor is not disposed within the enclosure formed by casing 70 and touchscreen surface 10.
To further illustrate this, FIG. 5B illustrates a planar view of the device 100′ at cross section CV″ of FIG. 5A, showing that the probe light source 82 is not accompanied by the probe light sensor 92′ within the LCD stack. FIG. 5C illustrates an external planar view of the device 100′, which shows the probe light sensor 92′ being placed at or near the edge of touchscreen surface 10. Although FIGS. 5B and 5C illustrate the probe light source 82 and probe light sensor 92′ at the corners of the device 100′, this is merely exemplary. For instance, the probe light source 82 and sensor 92′ may be disposed closer to the center of any side of the device 100′.
FIGS. 5D and 5E illustrate the principles of operation of the device 100′ according to this alternative embodiment. Similar to the device 100 of FIGS. 4A-4D, the touchscreen keys 200 in device 100′ are made “active” one at a time, based on the operation of the LC layer 20. Particularly, in device 100′, a probe light opening scans through the partitions in the LC layer 20 that correspond to the touchscreen keys 200.
As such, FIG. 5D illustrates the situation where the active key 200ACT is not touched by the user. As such, the probe light passes through the touchscreen surface via key 200ACT. On the other hand, FIG. 5E illustrates the situation where the user is touching the active key 200ACT. As shown in FIG. 5E, some of the probe light passing through the probe light opening will be scattered or reflected by the touch toward the external edges of the touchscreen surface. Thus, the measured intensity of probe light at the probe light sensor 92′ will increase, there by indicating that the user is touchscreen is being touched. Furthermore, given the position of the probe light opening at the time of detection, the device 100′ can determine the particular touchscreen key 200ACT being touched.
The operation of the LC layer 20 in providing the probe light opening to the active key 200ACT will be described below with respect to an exemplary embodiment. It should be noted that, unless specified otherwise, the following description applies to both types of device 100 and 100′ described above in connection with FIGS. 4A-4D and FIGS. 5A-5E, respectively.
During operation, the LCD device 100, 100′ alternates between a normal backlight display mode and touchscreen mode in an interleaved manner. In normal display mode, the LCD device 100, 100′ may display the contents of the touchscreen interface (keys 200, etc.). For instance, if the LCD device 100, 100′ is transmissive (backlit), the backlight sources may be used for displaying such contents.
During touchscreen mode, however, each partitioned area of the LC layer 20 may be, by default, opaque so that it does not transmit or reflect light. However, as each key 200 is made active, the corresponding partition of the LC layer 20 is switched from being opaque to transparent, thereby allowing the corresponding probe light source 82 to transmit through. Thus, as each partition of the LC layer 20 becomes transparent, it creates a probe light opening for the corresponding touchscreen key 200. The probe light opening scans through the LC layer partitions according to the scanning or timesharing process by which the touchscreen keys 200 are to be made active.
FIGS. 6A and 6B illustrate the scanning of the probe light opening through the touchscreen keys 200, according to an exemplary embodiment. For purposes of example, FIGS. 6A and 6B illustrate a situation where touchscreen keys 200A-200D are sequentially made active. In FIG. 6A, the LC layer 20 first provides the probe light opening to the partition corresponding to touchscreen key 200A. This allows the probe light to transmit through key 200A, thus making the key 200A active. FIG. 6B shows the next scanning interval, during which the probe light opening shifts to the partition of LC layer 20 corresponding to touchscreen key 200B. Thus, touchscreen key 200B is made active in FIG. 6B. In the next scanning interval, as illustrated by the arrow in 6B, the probe light opening will shift in order to make key 200C active, and so on.
According to an exemplary embodiment, during touchscreen mode, only one key 200 on the touchscreen surface is active at a given time. For example, in the touchscreen application in FIG. 3, the probe light opening may scan through the touchscreen keys 200 according to the sequence or pattern illustrated in either FIG. 7A or FIG. 7B.
Of course, FIGS. 7A and 7B are provided for illustration only, and other scanning patterns may be implemented. Furthermore, it is not necessary for all the keys 200 to be scanned through during one cycle of the touchscreen mode. Since the interleaving rate between normal display mode and touchscreen mode is assumed to be relatively high, it is possible to allow the probe signal to scan through all of the touchscreen keys 200 over a plurality of touchscreen mode cycles. For example, it is contemplated that an interleaving rate of 60, 90, or 120 Hz could be used.
If the LCD device 100 is backlit, it would be advantageous for the probe light sensor 92, 92′ to be able to discriminate the probe light from the backlight. According to an exemplary embodiment, this can be done by using a different spectrum probe light source 82 than the backlight source(s). For instance, the probe light source 82 may be operated near or at infrared (IR) frequency. In such an embodiment, both the probe light source 82 and the backlight source(s) may remain on during normal display mode and touchscreen mode.
However, alternative embodiments of the invention may make it unnecessary to use a probe light and backlight at different frequencies, based on the interleaving of normal display and touchscreen modes. For example, in one different embodiment, the probe light and backlight may have the same spectrum, but be modulated at different frequencies.
However, another embodiment takes advantage of the fact that the backlight source(s) are unneeded, and thus can be turned off, during touchscreen mode. This embodiment is illustrated in FIGS. 8A and 8B. For purposes of illustration, these figures illustrate an LCD device 100, 100′ utilizing backlight sources described above in connection with FIGS. 2A and 2B.
Specifically, FIG. 8A shows that only the probe light source 82 is operative during touchscreen mode, while backlight sources (LEDs 52 and CCFLs 56) are turned off (as illustrated by dotted lines), during touchscreen mode. Thus, the probe light sensor 92 (not shown) only detects probe light during touchscreen mode. On the other hand, FIG. 8B shows that the backlight sources are operative during normal display mode, while the probe light source 82 is turned off (as illustrated by dotted lines).
Even with the interleaved modes, however, it might be necessary to configure the probe light source 82 so that the probe light is more easily distinguished from other light sources (e.g., ambient light). Thus, in an exemplary embodiment, the probe light source 82 may be modulated at a particular frequency that helps distinguish it from other sources. This may be useful, e.g., for a reflective-type 100, 100′.
As discussed above, user contact with a particular touchscreen key 200 may be detected when the corresponding probe light sensor 92, 92′ measures an intensity level of the probe light (reflected from the touchscreen surface) that exceeds a certain threshold. For instance, the LCD device 100, 100′ may include a contact locating processor 400 designed to receive intensity measurements from the probe light sensor 92, 92′ and compare them to the appropriate threshold. This is illustrated in FIGS. 9A and 9B.
Specifically, FIG. 9A illustrates a contact locating processor 400 for use with an LCD device 100 having an internal probe light sensor 92 (as shown in FIGS. 4A-4D). FIG. 9B illustrates a contact locating processor 400 for use with an LCD device 100′ having an external probe light sensor 92′ (as shown in FIGS. 5A-5E). In FIGS. 9A and 9B, reference is also made to an LCD controller 300, which controls the operation of the LC layer 20.
As each key 200 becomes active during touchscreen mode according to the control of LCD controller 300, the probe light sensor 92, 92′ measures the intensity of probe light and sends the measurement to the contact locating processor 400. The contact locating processor 400 determines whether each measurement exceeds the threshold. The contact locating processor 400 is also notified by the LCD controller 300 as to the current position of the probe light opening in the LC layer 20. Thus, when a measured intensity exceeds the threshold, the contact locating processor 400 may correlate the received measurement to the position of the probe light opening in the LC layer 20, in order to determine which touchscreen key 200 was active at the time of the measurement. Thus, contact locating processor 400 is able to determine which particular key 200 has been touched by the user.
For an LCD device 100 utilizing an internal probe light sensor 92, the performance of the contact locating processor 400 may be improved through the use of “reference key.” An example of a reference key RK in such a device 100 is illustrated in FIG. 9A. As such, the LC layer 20 provides a transparent opening corresponding to the location of the reference key RK. For instance, reference key RK may allow the contact locating processor 400 may adjust the threshold(s) corresponding to the probe light sensors 92, e.g., to compensate for the movement of the bias point of the probe light sensors 92. However, as an alternative to adjusting the threshold, the contact locating processor 400 may be designed to differentially process the intensity measurements to make the necessary compensation. According to the exemplary embodiment, the size and shape of the transparent opening in the LC layer for reference key RK should be of a similar size and shape as the probe light opening for the active touchscreen key 200.
Exemplary embodiments having been described above, it should be noted that such descriptions are provided for illustration only and, thus, are not meant to limit the present invention as defined by the claims below. Any variations or modifications of these embodiments, which do not depart from the spirit and scope of the present invention, are intended to be included within the scope of the claimed invention.
For example, when a large number of touchscreen keys 200 are provided, it may be advantageous to allow multiple active probe signals to simultaneously scan through the keys 200. To do this, the touchscreen interface may be divided into separate partitions, each corresponding to a group or “block” of keys 200. Each partition may have its own probe light source and detector. This would allow touchscreen keys 200 in the respective partitions to simultaneously be made active during touchscreen mode. For instance, each probe light opening may scan through the keys 200 in the corresponding partition according to the pattern illustrated in FIG. 7A or 7B.
Patent Application
20080055495
