This application claims the priority benefit of Taiwan application serial no. 100132446, filed on Sep. 8, 2011. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
1. Field of the Invention
The present invention relates to an optical touch sensing technology, and more particularly to an optical touch display panel and a touch sensing method thereof, which are capable of increasing correctness of interpreting a touch position.
2. Description of Related Art
The integration of a touch panel in a liquid crystal display (LCD) may enhance the convenience and quick input of a user and also may provide an interactive access function. Therefore, the touch panel has gradually applied in some portable electronic devices, such as mobile phones, personal digital assistants (PDAs) or laptop computers.
In a conventional touch display, the touch panel is directly attached on the display panel. This assembling method is simple but the touch display panel is thick and the display transmittance is not satisfactory. To overcome the defects, a technique of embedding an optical sensor array in a pixel array structure of an LCD is provided. The embedded in optical sensor when illuminated and not illuminated respectively outputs a different photoelectric signal. Therefore, it may be known if the touch event occurs by interpreting the photoelectric signal output by the optical sensor array.
When the switching transistor Q1 is conducted in response to a scan signal received by the scan line G1, the photoelectric signal SC generated by the photosensing transistor M1 is conducted out via the readout line RO1. When a light intensity varies (i.e. whether fingers or other media shield the photosensing transistor M1), the photoelectric signal SC generated by the photosensing transistor M1 changes. In this manner, by interpreting the photoelectric signal SC generated by the photosensing transistor M1, it is known if the touch event occurs in the area corresponding to the photosensing transistor M1. However, as the photosensing transistor M1 persistently suffers a bias of the common voltage Vcom, a threshold voltage (Vth) of the photosensing transistor M1 may exhibit a shift phenomenon. In this manner, the photoelectric signal SC generated by the photosensing transistor M1 is attenuated, which further influences the correctness of determining the touch position.
However, as the bias of the photosensing transistor M1 is the scan signal received by the scan line G1. Therefore, when the ambient light is bright, the voltage of the scan signal received by the scan line G1 becomes low (which is used for providing the bias of the photosensing transistor M1), and thus the conduction degree of the switching transistor Q1 is reduced, which limits the flow out of the photoelectric signal SC. Obviously, in the situation that the ambient light is bright, the voltage level of the photoelectric signal SC becomes low, and when the ambient light is dim, the voltage level of the photoelectric signal SC becomes high. This manner is in contrast to the common method for interpreting the optical touch. In addition, the voltage of the scan signal received by the scan line G1 becomes low, which also makes the charging capability of the pixel circuit 102 attenuated and further influences the image display quality.
In more details, when applied in a light stylus touch mode, the photoelectric signal SC at the position where the light spot is irradiated on will become small as the conduction degree of the switching transistor Q1 is small. A shadow caused by the handheld light stylus makes the strength of the photoelectric signal SC in the shadow enhanced, which causes the problem in determining the touch position and generates the ghost point. On the other hand, if applied in the shadow mode, the signal difference generated at the touch position becomes more unnoticeable, as the photoelectricity of the touch point is reduced in theory but is enlarged when the conduction degree of the switching transistor Q1 increases, which causes the phenomenon that the strength of the photoelectric signal SC at the touched light shielding position is increased.
The present invention provides an optical touch display panel and a touch sensing method thereof, which may improve a correctness of interpreting a touch position.
The present invention provides an optical touch display panel, which includes a first scan line, a readout line and a photosensing unit. The photosensing unit is coupled to the first scan line and the readout line, is activated in response to a first scan signal received by the first scan line, and reacts a photosensing current on the readout line according to the first scan signal and a reference level.
In an embodiment of the present invention, the photosensing unit includes a switching transistor and a photosensing transistor. A gate of the switching transistor is coupled to the first scan line and a first source/drain is coupled to the readout line. A gate of the photo sensing transistor is coupled to the first scan line, a first source/drain is coupled to a second source/drain of the switching transistor, and a second source/drain receives the reference level.
In an embodiment of the present invention, the optical touch display panel further includes a pixel unit corresponding to the photosensing unit, and the photosensing unit is embedded in the pixel unit.
In an embodiment of the present invention, the reference level is a common voltage applied to the pixel unit.
In an embodiment of the present invention, the optical touch display panel further includes a black matrix located on the photosensing transistor, and the black matrix located on the photosensing transistor has no holes.
In an embodiment of the present invention, the optical touch display panel further includes a second scan line coupled to the second source/drain of the photosensing transistor, and the reference level is a disable level of a second scan signal received by the second scan line.
In an embodiment of the present invention, the optical touch display panel further includes a black matrix located on the photosensing transistor, and the black matrix located on the photosensing transistor has a corresponding hole.
The present invention also provides a touch sensing method of an optical touch display panel, which includes the following steps. A photosensing unit is embedded in a pixel unit of the optical touch display panel, in which the photosensing unit is coupled to a first scan line and a readout line of the optical touch display panel. The photosensing unit is activated in response to a first scan signal received by the first scan line, and reacts a photosensing current on the readout line according to the first scan signal and a reference level. The photosensing current is interpreted to acquire if a touch event occurs.
In an embodiment of the present invention, the reference level is a common voltage applied to the pixel unit.
In an embodiment of the present invention, the photosensing unit is further coupled to a second scan line of the optical touch display panel, and the reference level is a disable level of a second scan signal received by the second scan line.
In view of the above, the present invention activates the photosensing unit by a first scan signal received by the first scan line and reacts a photosensing current on the readout line according to the first scan signal and a reference level. In this manner, the threshold voltage of the photosensing transistor will not be influenced by the bias for a long time and generate the shift. As the voltage corresponding to the first scan signal is greater than the common voltage, the strength of the photosensing current output by the photosensing unit is enhanced, which further enhances the correctness of interpreting the photosensing current by the interpret unit.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
In this embodiment, when the scan line G1 receives the scan signal SS1 from the scan driving unit 304, the TFT M0 is conducted and the liquid crystal capacitor CLC and storage capacitor CST are driven by the data signal SD1 from the source driving unit 306. In addition, the photosensing unit 404 is coupled to the scan line G1 and the readout line RO1, and is activated in response to the scan signal SS1 received by the scan line G1 and reacts a photosensing current IC on the readout line RO1 according to the scan signal SS1 and the reference level (for example, the common voltage Vcom applied to the pixel unit 402). In this manner, the interpret unit 308 may acquire if the touch event occurs just by interpreting the photosensing current IC.
In more details, the photosensing unit 404 includes a switching transistor Q1 and a photosensing transistor M1. A gate of the switching transistor Q1 is coupled to the scan line G1, a first source/drain of the switching transistor Q1 is coupled to the readout line RO1 and a second source/drain of the switching transistor Q1 is coupled to a first source/drain of the photosensing transistor M1. In addition, a gate of the photosensing transistor M1 is coupled to the scan line G1, and a second source/drain of the photosensing transistor M1 is coupled to the common voltage Vcom. The photosensing transistor M1 generates the photosensing current IC accordingly in response to the changes of the light intensity of the optical touch display panel 200.
When the scan signal SS1 is enabled, in addition to that the TFT M0 is conducted to implement the pixel writing, the switching transistor Q1 and the photosensing transistor M1 may be conducted at the same time to implement the touch sensing. At the same time, as the photosensing transistor M1 is biased by the common voltage Vcom, the photosensing transistor M1 outputs the generated photosensing current IC to the readout line RO1 via the switching transistor Q1, thereby providing for the interpret unit 204 to interpret and acquire if the touch event occurs.
Obviously, as the photosensing transistor M1 is conducted only when the scan signal SS1 is enabled, a threshold voltage (Vth) of the photosensing transistor M1 is not influenced by the bias for a long time to generate the shift. In addition, as the corresponding voltage (Vgh) when the scan signal SS1 is enabled usually is greater than the common voltage Vcom, the conduction degree of the switching transistor Q1 and the photosensing transistor M1 is increased, and further the strength of the photosensing current IC output by the photosensing transistor M1 via the readout line RO1 may be enhanced. In this manner, the interpret unit 308 may interpret the photosensing current IC generated by the photosensing transistor M1 easily and accurately.
It should be noted that
Accordingly, in the conventional structure, the black matrix B1 on the photosensing transistor M1 has a hole, and therefore, the photosensing transistor M1 may persistently in an illumination state. In addition, as the photosensing transistor M1 is biased by the common voltage Vcom to generate the photosensing current IC, when the optical touch display panel 302 is illuminated, the photosensing current of the photosensing transistor embedded in the optical touch display panel 302 (regardless whether it is conducted) may possibly influence the stability of the common voltage Vcom, thereby influencing the image display quality.
In view of the above, in the embodiment of
On the other hand, in other embodiments of the present invention, the embodiment of
Likewise, when the scan signal SS1 is enabled, besides the TFT M0 is conducted to implement the pixel writing, the switching transistor Q1 and the photosensing transistor M1 may be conducted at the same time to implement the touch sensing. At this time, as the second source/drain of the photosensing transistor M1 is coupled to the scan line G2 (i.e. the scan signal SS2 received by the scan line G2 is disabled), as compared with the embodiment of
It is worthy of mentioning that the embodiment of
In view of the content disclosed/taught in the above embodiments, at least a touch sensing method of an optical touch display panel is illustrated.
A photosensing unit is embedded in a pixel unit of the optical touch display panel (step S802). The photosensing unit is coupled to a first scan line and a readout line of the optical touch display panel.
The photosensing unit is activated in response to a scan signal received by the first scan line and reacts a photosensing current on the readout line according to the scan signal and a reference level (step S804), in which the reference level may be a common voltage applied to the pixel unit or is a disable level of a scan signal received by a second scan line adjacent to the first scan line.
The photosensing current is interpreted to acquire if the touch event occurs (step S806).
In view of the above, the embodiments of the present invention activate the photosensing unit by the first scan signal received by the first scan line so as to react a photosensing current on the readout line according to the first scan signal and a reference level. In this manner, the threshold voltage of the photosensing transistor will not be influenced by the bias for a long time to generate the shift. As the voltage corresponding to the first scan signal is greater than the common voltage, the strength of the photosensing current output by the photosensing unit is enhanced, which further enhances the correctness of interpreting the photosensing current by the interpret unit. In addition, the photosensing unit may be coupled to the next adjacent scan line, and thus the interpret unit may provide the photosensing current to the next adjacent scan line, so as to pre-charge the display pixel thereon. Furthermore, the photosensing transistor may be further disposed below the black matrix having no holes, thereby preventing the display quality of the optical touch display panel from being influenced by the photoelectricity generated by the ambient light.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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100132446 | Sep 2011 | TW | national |