Disclosed are methods and electronic devices for color compensation of a display, and more particularly methods and electronic devices for color compensation of a display having a tinted lens or cover placed over it.
Today, mobile phones have become a necessity and, like an automobile, an extension of a user's personal style. Mobile phones are now considered as a fashion statement of individuality, personality and even a status symbol. Trend conscious people may stress more on the design than features. The color of a phone also may be measured while taking style into consideration. For example, the color black makes a fashion statement that is classically chic and sophisticated. A user can even personalize a phone with different color and pattern schemes by purchasing various phone covers. When shopping for a mobile phone, many customers first observe the look and the design of a mobile.
Another manner in which to differentiate designs of mobile device products in the marketplace is by including a homogeneous color and finish over the complete exterior of the product including over the display viewing areas. Designs of a single color may include a permanent film or a changeable film over the device. In this way, a visually hidden or borderless caller ID (CLI) and main display can give a device a sleek appearance.
Color matching the semi-translucent finishes and material over display viewing areas may be accomplished by applying a tint and/or semi-translucent vacuum metallization (VM) finish to the protective lens/cover located above the display. The tinted VM finish or tinted lens material creates a two way mirror or shadow box effect which visually hides the display from the user. Once the display is activated (via back lighting, front lighting, or an emissive technology) the display is then revealed to the user. This type of display may also be referred to as a morphing display.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
In applying a tinted vacuum metallization (VM) finish or tinted lens material, the color of the display lens/cover translucent finish can offset the intended color of the display image. For example, a red tinted VM finish or red translucent lens will result in a display image that appears to be over saturated in red, a blue finish will result in a bluish looking image, and a yellow finish will result in a yellowish looking image. Therefore, the color of the display image may not be presented to the user as originally intended.
Disclosed are methods and devices for color compensation of a display having a translucent display cover applied to an outside surface of the display. A method may include characterizing a color shift due to the translucent display cover for when there is rendering of an image on the display and compensating for the color shift when rendering an image on the display. The method further includes measuring the color shift induced by the color of the finish, and as described below compensating the red, green, and blue (RGB) levels of the display so that the display image may be presented to the user as originally intended. In this way, the image quality may be substantially optimized for viewing regardless of the lens/cover surface color.
A number of different embodiments are discussed in detail below. For example, an embodiment of an electronic device with a display having a front surface includes a color altering layer adjacent the front surface of the display, a display driver coupled to the display, and a controller coupled to the display driver. The controller may be configured to analyze signals corresponding to an image to be displayed, compensate for a color shift due to the color altering layer, generate color compensated signals and communicate the color compensated signals to the display driver. In this way, the image quality may be substantially optimized for viewing regardless of the lens/cover surface color.
The instant disclosure is provided to explain in an enabling fashion the best modes of making and using various embodiments in accordance with the present invention. The disclosure is further offered to enhance an understanding and appreciation for the invention principles and advantages thereof, rather than to limit in any manner the invention. While the preferred embodiments of the invention are illustrated and described here, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art having the benefit of this disclosure without departing from the spirit and scope of the present invention as defined by the following claims. It is understood that the use of relational terms, if any, such as first and second, up and down, and the like are used solely to distinguish one from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
At least some inventive functionality and inventive principles may be implemented with or in software programs or instructions and integrated circuits (ICs) such as application specific ICs. In the interest of brevity and minimization of any risk of obscuring the principles and concepts according to the present invention, discussion of such software and ICs, if any, is limited to the essentials with respect to the principles and concepts within the preferred embodiments.
The mobile communication device 102 may be implemented as a cellular telephone (also called a mobile phone). The mobile communication device 102 represents a wide variety of devices that have been developed for use within various networks. Such handheld communication devices include, for example, cellular telephones, messaging devices, personal digital assistants (PDAs), notebook or laptop computers incorporating communication modems, mobile data terminals, application specific gaming devices, video gaming devices incorporating wireless modems, and the like. Any of these portable devices may be referred to as a mobile station or user equipment. Herein, wireless communication technologies may include, for example, voice communication, the capability of transferring digital data, SMS messaging, Internet access, multi-media content access and/or voice over internet protocol (VoIP).
The mobile device 102 may include a color sensor 104, a display driver 106 coupled to a controller 108, at least one transceiver 110, a memory 112 that may incorporate modules 114. For example, modules may make up some or all of a color management algorithm that may external to a device 554 (see
As mentioned above, a finish or lens covering that coats one or more displays of the device 102 (see
In this event, the user may optimize the image viewing for a given color of the decorative sheet he or she assembles on the device 802 by, for example, making a selection from list of decorative sheet information provided to the user via a user interface of the device 802. The user may save a color compensation preset in, for example a user profile that may be used to drive the display driver.
Referring to
Characterizing the color shift 970 may be further processed by predetermined optical properties 962 in accordance with a color compensation preset module 162 (see
Once the color shift has been characterized, compensating for the color shift 974 in accordance with a color shift compensating module 174 (see
The step of generating a transformation 976 as discussed above is described in more detail below and may include steps such as calculating Gamma curves from measured display output in a plurality of colors 984 in accordance with gamma curve calculating module 184 (see
When a display is color balanced, the display is perceived by a user to be white when red, green, and blue pixels of the display have perceived luminances in a particular ratio, say rw:gw:bw. A display may be driven by sending an input, denoted R, G, or B according to the pixel color, to each pixel, where the input is a byte value that can range from 0 to 255. The display may be configured so that the RGB brightness settings R=255, G=255, and B=255 result in the display's pixels being driven so that their perceived luminances are in the ratio rw:gw:bw, that is, so that the white may be displayed. However, when a VM finish or film is applied over the display, the perceived color and brightness of each of the pixels is changed, so that the pixels' luminances may no longer be perceived in the ratio rw:gw:bw. Correcting for this requires consideration of both how a pixel of a specific color radiates and how the eye perceives color.
Human eyes have an exponential response to luminance. The exponents of the luminance to the brightness setting are called Gamma. From the luminance curves or Gamma curves, display brightness for each color can be obtained as a function of the R, G, and B values. For example, in an embodiment the pixels may be determined to have a Gamma curves described by
y=0.00006475 x2.28445221 (Red)
y=0.00009669 x2.41969912 (Green)
y=0.00011229 x2.08232755 (Blue)
In these expressions, y is the luminance associated with the pixel and x is the brightness setting, R, G, or B as appropriate and ranging from 0 to 255. The Gamma curves may be determined 984 according to a Gamma curve calculating module 184. In the embodiment described by the Gamma curves above, for example, white corresponds to setting x=255 in all three formulas, so that y=20.364 Cd/m2 for Red, y=64.341 Cd/m2 for Green, and y=11.522 Cd/m2.
Each color pixel radiates according to a spectrum for that color. It is understood that a pixel may radiate by generating light itself, or may, for example, selectively transmit light produced by another element of the display, for example, a backlight. For example, the red, green, and blue pixels may radiate light according to spectra given by Red(λ), Green(λ), and Blue(λ), where λ is wavelength and Red(λ), Green(λ), and Blue(λ) are functions normalized so that
∫dλ Red(λ)=r
∫dλ Green(λ)=g
∫dλ Blue(λ)=b
where the integrations are taken over the standard range of sensitivity of the human eye, 380 nm to 780 nm. The respective luminances are given by r, g, and b. In the example above, r=20.364 Cd/m2, g=64.341 Cd/m2, and b=11.522 Cd/m2.
The human eye has three types of color receptors or cones, those sensitive predominantly to red, those sensitive predominantly to green, and those sensitive predominantly to blue. Their sensitivities as functions of wavelength are depicted in the graph 220 (see
b
r
=∫dλ Blue(λ)
This expression represents the excitation of a red cone due to the luminance of a blue pixel. The integration over wavelength accounts for both the radiation spectrum of the pixel and the spectral sensitivity of the red cone. By repeating this calculation for each type of cone and each color pixel, a color matrix
can be determined for a color balanced display without a VM finish, film, or lens/cover in place. From this color matrix the perceived luminance ratios may be determined. When a color balanced display is driven so as to appear white, the excitation of red cones is given by the sum br+gr+rr. The excitation of cones sensitive to green light is given by the expression bg+gg+rg, and the excitation of cones sensitive to blue light is given by the sum bb+gb+rg. The excitation of the respective cones, for a color balanced display, is thus given by the matrix product
The excitations X, Y, and Z, are the perceived luminances discussed above, which in order that the display be perceived as white, have to have the particular ratio as previously discussed. The required particular ratio may be stored in the device memory 112 as a parameter of the color balanced display.
When a VM finish, film or lens/cover is placed over the display, the display may be corrected to compensate. A color matrix incorporating the effects of the VM finish or film may be calculated 986 according to a color matrix calculating module 186. In this calculating, the spectra Red(λ), Green(λ), and Blue(λ) include the effects of the finish or film. In this way a new color matrix
that includes the effects of the finish is obtained. Inversion of the color matrix (1) and applying the result to the excitation values X, Y, and Z provides pixel luminance values
that would be needed to render white. However, the values Cb, Cg, and Cr may correspond to byte values for R, G, and B in excess of 255. Accordingly, a weight factor α is generated 988 in accordance with weight factor generation module 188, so that when the pixel luminance values are all weighted by the weight factor α, the largest byte value corresponding to Cb, Cg, and Cr has a value of 255. That is to say, the weight factor α is calculated so that inverting each Gamma curve corresponding to each of the colors yields byte values for R, G, and B so that the largest byte value is 255. The weight factor α may be calculated by any known method, for example, by bracketing the solution and/or by successive approximations. The resulting byte values determine the corrected Gamma setting profile 990 that may be sent to the display driver 106 (see
The disclosed methods and devices for color compensation of a display having a translucent display cover applied to an outside surface of the display may substantially optimize image quality for viewing regardless of the lens/cover surface color. The method may include characterizing a color shift due to the translucent display cover for when there is rendering of an image on the display and compensating for the color shift when rendering an image on the display. The method may further include in some way measuring the color shift induced by the color of the finish, and as described above compensating the red, green, and blue (RGB) levels of the display so that the display image may be presented to the user as originally intended. In this way, a visually hidden or borderless caller ID (CLI) and main display can give a device a sleek appearance while not compromising the user experience in viewing one or more displays of the device.
This disclosure is intended to explain how to fashion and use various embodiments in accordance with the technology rather than to limit the true, intended, and fair scope and spirit thereof. The foregoing description is not intended to be exhaustive or to be limited to the precise forms disclosed. Modifications or variations are possible in light of the above teachings. The embodiment(s) was chosen and described to provide the best illustration of the principle of the described technology and its practical application, and to enable one of ordinary skill in the art to utilize the technology in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims, as may be amended during the pendency of this application for patent, and all equivalents thereof, when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.