Mirrored LCD display | Patent Publication Number 20060202942
US 20060202942 A1A mirrored liquid crystal display (LCD) is provided. One embodiment, among others, comprises a liquid crystal display (LCD); and logic for controlling the LCD to selectively operate in one of two alternative states. The two states include a first state in which the LCD operates in a conventional manner to display visible data to a user, and a second state in which the LCD effectively functions as a mirror.
- 1. A wireless telephone comprising: ncommunication logic configured to send and receive signals from a base station over a wireless channel, the base station in communication with a telephone network; a mirrored liquid crystal display comprising: na liquid crystal module; a half-mirror layer, which is partially reflective and partially transmissive, affixed to one surface of the liquid crystal module; a backlight producing light directed at an opposite surface of the liquid crystal module, wherein the intensity of light produced by the backlight is matched to the reflective and transmissive characteristics of the half-mirror layer such that when the light output is at a minimum, the half-mirror layer is substantially reflective and the liquid crystal module is substantially invisible, and when the light output is at a maximum, the half-mirror layer is substantially transmissive and the liquid crystal module is substantially visible; and input logic configured to receive input from the user to control the communication logic and to control the intensity of the light produced by the backlight.
- 18. A telephone comprising: na liquid crystal display (LCD); and logic for controlling the LCD to selectively function as a mirror.
- 20. A telephone comprising: na liquid crystal display (LCD); and logic for controlling the LCD to selectively function as a mirror.
The present invention relates to a display for a wireless phone or other consumer electronic item.
Wireless phones, also known as cellular phones or mobile phones, have become a common consumer electronics item. While wireless phones were once limited to placing and receiving voice calls, more and more features are being integrated into the wireless phone. Most wireless phones include a contact list, a calculator, an alarm clock, and simplified video games, and many include a digital camera. More advanced models include the features of a personal digital assistant (PDA), such as an address book, a calendar, and a scheduler. Other commonly integrated features include email, web browsing, and instant-messaging. Wireless phones are also getting smaller in size, so that users carry them everywhere. Thus, the wireless phone is fast becoming an indispensable item for both men and women. It is therefore desirable to add even more features to a wireless phone.
A mirrored liquid crystal display (LCD) is provided. One embodiment, among others, comprises: a liquid crystal display (LCD); and logic for controlling the LCD to selectively operate in one of two alternative states. The two states include a first state in which the LCD operates in a conventional manner to display visible data to a user, and a second state in which the LCD effectively functions as a mirror.
Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention.
Mirrored display 102 operates in two modes. In “normal display†mode, the mirrored display 102 functions as the user interface: it allows a user to see his input, and to view status and settings information. In “mirror†mode, the display becomes reflective, so that data normally viewable in “normal display†mode is not visible, and the user sees instead a reflection. Input logic 103 allows a user to switch between the two modes. In this example the mirrored display 102 and input logic 103 are located on the same side of the phone, but in another embodiment mirrored display 102 and input logic 103 are on different sides.
Half-mirror 303 is partially transparent and partially reflective: light incident on transparent side 305 is transmitted, while light incident on the reflective side 306 is reflected. Thus, half-mirror 303 acts as both window and a mirror. Which one dominates depends on the intensity of ambient light 307 incident upon the display front surface compared to the intensity of light produced by backlight 302. Therefore, the intensity of backlight 302 is matched to the reflectance and transmittance characteristics of half-mirror 303.
Backlight 302 is configured so that at full intensity, the transmittance characteristics dominate and half-mirror 303 acts as a window. Through this window, opaque segments 304 are visible against a light background of LCD module 203. When backlight 302 is off, the reflective characteristics of half-mirror 303 are dominant and LCD module 203 is not visible. Instead, the user of the phone 100 can see his reflection mirrored display 102. When the intensity of backlight 302 is between minimum and maximum, LCD module 203 is visible, but reflections off the half-mirror 303 are also visible.
The characteristics of half-mirror 303 can be described by two variables: T, light transmittance through the mirror in either direction; and Rm, reflectance on the reflective side 306. The intensity of the reflected image seen by the viewer is Im×Rm, while the intensity of the LCD image is It×T. Thus, in order for the LCD module 203 to be 13 times brighter than the reflective image, a half-mirror with T=0.8, and Rm=0.7 needs 15 times more light on the transparent side 305 than on the reflective side 306:
Using this information, backlight 302 and half-mirror 303 can be matched appropriately for various viewing scenarios. Because the half-mirror is only partially transmissive, a relatively large value of T is desirable for the half-mirror 303. With a ratio Im:It of at least 5, it appears that the viewer sees the LCD module 203 without being distracted by the reflected image. At a lower ratio, the reflected image begins to interfere. Higher ratios are desirable but require a proportional increase in the amount of light produced by the backlight 302. Note that It is a measure of light exiting LCD module 203 rather than the intensity of the backlight itself, as It takes into account the absorptive and reflective characteristics of the LCD module 203 itself. Nonetheless, for a given LCD module 203 design, there is a direct relationship between the intensity of light produced by backlight 302 and the intensity of light exiting LCD module 203. Thus, it is sometimes convenient to speak of configuring backlight 302, knowing that the characteristics of LCD module 203 must also be taken into account.
Liquid crystal material 401 is in contact with electrodes 404, 405 on the inner surface of transparent layers 402, 403. The electrodes 404 and 405 may take many forms, depending on the type of display. For example, in the segmented display of
In a pixel display, one transparent surface has columns of electrodes and the other transparent surface has rows of electrodes, forming pixels at the intersections of the rows and columns. These pixels are activated and become opaque when an electric current is applied between the electrode 404 on one surface 402 and the electrode 405 on the other surface 403. The pixels are typically implemented in conjunction with a Thin Film Transistor (TFT), which separates control of current through the electrodes to be separate from the electrodes themselves. A variation of TFT LCD called in-plane switching (IPS) mounts both electrodes parallel to each other on the same transparent layer. Pixel displays using TFT are also called active matrix displays. Another type of pixel display called passive matrix is also known. The invention applies to both active and passive matrix, as well as segmented LCD modules.
A polarizer is applied on the other side of each transparent layer, opposite the liquid crystal material 401. Other layers with various optical properties may also be applied between the transparent layer and the polarizer, for example, a retardation layer or a scattering layer. The orientation axis of polarizer 406, on transparent layer 402, is different than the axis of polarizer 407, on transparent layer 403. It is this difference in orientation that causes portions of liquid crystal material 401 to appear opaque when an electric current is applied.
Light enters LCD module 203 from below, passing first through polarizer 407, which polarizes the light in a first direction. When no electric current is applied, the optical properties of liquid crystal material 401 cause the light to be polarized in a second direction. This second direction matches the orientation of polarizer 406, so the light passes through polarizer 406. Thus, the viewer sees LCD module 203 as a light background.
However, when electric current is applied, the optical properties of liquid crystal material 401 do not polarize the light in a second direction. Therefore, the light does not pass through polarizer 406. Those portions of LCD module 203 where the current was applied are seen by a viewer as opaque, with the remaining background portions appearing as the light background.
In she example of
The LCD module 203 of
Other rays 501b produced by backlight 302 pass through regions of liquid crystal material 401 which have an electric current flow. The optical properties of liquid crystal material 401 do not allow these rays to exit LCD module 203, so that these regions of LCD module 203 appear dark to the viewer.
In this scenario, ambient light 307 produces some rays 502. These rays 502 are reflected off the reflective side of half-mirror 303, without entering LCD module 203. Thus, the viewer may see a slight reflection off the display, but the overall effect of half-mirror 303 is as a window into LCD module 203 because the light output from backlight 302 dominates ambient light 503.
Light entering LCD module 203 first passes through linear polarizer 606, and then retarder 607. The result is light that is circularly polarized in a first direction. After passing through liquid crystal material 601, light hits reflective electrode 605, where it becomes circularly polarized in the opposite direction. In areas of LCD module 203 with no current flow, LCD module 203 is substantially transparent, so the light passes through LCD module 203 and enters retarder 607. The second pass through retarder 607 results in linearly polarized light which exits through polarizer 606. In areas of LCD module 203 with current flow, the light does not passes through LCD module 203, so these areas are seen by the viewer as opaque.
The foregoing description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments discussed, however, were chosen, and described to illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variation are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.