Patent Application
20140139538
The present invention generally relates to the measurement of light, and more specifically relates to the use of light measurement for optimization of images produced on display devices.
The quality of an image displayed on an image display device is the result of a combination of settings of image processing and/or filtering attributes (e.g., sharpness, brightness, contrast, etc.). Measuring these attributes and identifying their optimal settings can be difficult, particularly for the average user of an image display device. Often, adjusting the settings is a matter of trial and error with little or no quantifiable guidance. As such, many image display devices process and filter images in accordance with settings that are less than optimal.
Although tools exist for assisting users in setting these attributes, such tools need to be able to accurately measure visual changes caused by the image processing and filtering technologies in order to be effective. In addition, the visual (visible) changes in an image must, in general, be assessed at the pixel level by an imaging device (e.g., a camera). However, no known tools are capable of measuring a single quantity of light from a multi-pixel image area and using the measurement of that quantity to guide the user in setting an attribute of the display.
Embodiments of the invention use measurements of light volume (i.e., a measure of the quantity of light entering a detector) to generate adjustments to settings of image display devices. An example of the light volume that is measured may be, for example, luminance. In particular, a light measurement device (e.g., a light meter) takes a single measurement of the light volume of a constant plurality of pixels. This measurement guides the adjustment of a spatial attribute (e.g., sharpness) of the image display device to an optimal value. Conventionally, this optimal value is otherwise inferable only from an imaging device that measures light from individual pixels and subsequently performs image analysis on the measurements of these individual pixels.
A method for accurately and objectively adjusting a spatial and/or temporal attribute of an image display device includes measuring a visual change on a display of the image display device, wherein the visual change is caused by an image processing artifact that is introduced or removed, inferring a correlated effect of the spatial attribute on the display, based on the measuring, and generating an adjustment that adjusts the spatial attribute to a setting that is selected in accordance with the effect.
In another embodiment, a method for adjusting a spatial and/or temporal attribute of an image display device includes measuring a light volume emitted by a display of the image display device at a plurality of settings of the spatial attribute, identifying one of the plurality of settings at which a greatest change in the light volume is produced with a smallest change in the spatial attribute, and outputting an instruction to set the spatial attribute to the one of the plurality of settings.
The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
In one embodiment, the present invention is a method and apparatus for optimizing image quality on an image display device based on measurement of image processing artifacts. Embodiments of the invention exploit common but typically ignored characteristics of displayed image artifacts in order to optimize the quality of an image displayed on an image display device. In particular, spatial and/or temporal attributes of the display device's image processing and filtering functions (e.g., image sharpness, brightness, contrast, etc.) can be deduced based on quantifiable changes in the amount of light energy (e.g., photons) produced on the display device due to the presence of image processing artifacts. These deductions can then be used to adjust the spatial attributes as appropriate in order to optimize the display characteristics.
Within the context of the present invention, an “artifact” or “image artifact” refers to a visible spatial or spatio-chromatic anomaly that appears during visual representation of an image. The artifact may be the result of a malfunction or misuse of hardware or software, or simply a technical limitation of the hardware or software. For instance, the artifact might be introduced as a result of analog or digital image processing, encoding, transcoding, filtering, frame rate conversion, backlight adjustment, backlight zone dimming, ambient light level compensation, ambient light spectra compensation, or the like. The artifact may manifest itself as, for example, an image quality factor (e.g., an anomaly in sharpness, noise, dynamic range, tone reproduction, contrast, color accuracy, distortion, vignetting, exposure accuracy, lateral chromatic aberration, lens flare, or color moiré), a digital artifact resulting from digital image processing (e.g., data compression and transmission loss, oversharpening “halo,” loss of fine, low-contrast detail, texture corruption, T-vertex, pixilation, aliasing, or line scanning), screen door effect or fixed pattern noise, silk screen effect, rainbow effect, screen tearing, purple fringing, or the like.
The image display device 102 comprises any type of electronic device that is used to display still and/or video images. Thus, the image display device may comprise, for example, a television, a computer monitor, or even a mobile device such as a laptop computer, a tablet computer, a portable gaming device, a portable navigation system, or a mobile phone. The image display device 102 may further comprise circuitry for performing image processing and filtering prior to display.
The light measurement device 104 comprises a device that measures the amount of light emitted by an object (in the case of
The computer 106 is a computing device that is coupled to the light measurement device 104. In one embodiment, the computer 106 is integrated with the light measurement device 104 as a single unit; however, in other embodiments, the computer 106 and the light measurement device 104 are separate units. The computer 106 includes a processor that processes measurements taken by the light measurement device 104 and produces instructions for adjusting the image processing and/or image filtering settings of the image display device 102, as described in further detail below. One particular embodiment of the computer 106 is discussed in greater detail in connection with
The method 200 begins in step 202. In step 204, the image display device 102 displays a test pattern. In one embodiment, the test pattern is a pattern that is stored in the image display device. In another embodiment, the test pattern is a pattern that is provided to the image display device 102 by an external device (e.g., the computer 106). In one embodiment, the test pattern is designed to produce measurable visible artifacts. For instance, the test pattern may include a plurality of edges. Depending on what image processing and filtering function is to be measured (e.g., sharpness, brightness, contrast, etc.), the test pattern may be monochromatic or polychromatic. For instance, a monochromatic test pattern may be sufficient to measure the general sharpness settings of the image display device 100, but a polychromatic test pattern may be desirable if a different attribute (e.g., the selection or optimization of red, green, and blue sharpness filter algorithms) is to be measured.
In step 206, the light measurement device 104 measures the light volume (e.g., volume of light power and/or light spectra) emitted by the image display device 102 at a plurality of settings of the attribute of interest (e.g., sharpness, brightness, contrast, etc.). Within the context of the present invention, “light volume” is understood to refer to the total flux of photons captured by a light measurement device from an image display device that is driven by a test pattern. An example of light volume is luminance. The attribute of interest may be adjusted to each of the plurality of settings manually (e.g., by a human user) or automatically (e.g., by a program executing in the image display device 102 or by the image display device 102 under the direction of the computer 106). In one embodiment, step 204 involves measuring the light volume at each of the available settings of the attribute of interest; however, in other embodiments, the light volume may be measured at only a subset of the available settings of the attribute of interest. Measuring the light volume at less than all of the available settings may save processing time; however, the resultant display image quality may be slightly less than optimal.
For instance,
In step 208, the computer 106 identifies the optimal setting, Sb, of the attribute of interest for which the slope of light volume (e.g., luminance) versus attribute setting (e.g., sharpness) is as great as possible. Mathematically, this can be expressed as finding the Sb for which:
|C(S+1)−C(S)| (EQN. 1)
is maximum, where S represents the attribute of interest and C(S) is the luminance of the image display device 102 as a function of the attribute of interest (e.g., in candelas per square meter). In other words, step 208 seeks to identify the setting that produces the greatest change in the light volume (as measured by the light measurement device 104) with the smallest change in the attribute of interest's setting. To avoid data artifacts, it may be necessary to disqualify for Sb values of S for which |C (S+1)−C(S)| is greater than a threshold (e.g., ten cd/m2 in the case where C is luminance).
In step 210, the computer 106 outputs an instruction to adjust the setting of the attribute of interest to the optimal setting Sb. In one embodiment, the instruction is output directly to the image display device 102, so that the image display device 102 can automatically adjust the setting to the optimal setting. In another embodiment, the instruction is output for review by a human user, so that the human user can then manually adjust the setting to the optimal setting. In the latter case, the instruction may be displayed on the computer 106, on the image display device 102, or on another device.
The method 200 ends in step 212.
The method 200 therefore uses the quantifiable and measurable change in light volume or light spectra to infer the visual effects of display image processing and filtering technologies. In turn, this inference facilitates the identification of an optimal setting for a display attribute, such as sharpness. In an alternative embodiment, the same effects could be inferred from measurements of change in the frame rate rather than change in light volume.
Alternatively, the display optimization module 505 can be represented by one or more software applications (or even a combination of software and hardware, e.g., using Application Specific Integrated Circuits (ASIC)), where the software is loaded from a storage medium (e.g., I/O devices 506) and operated by the processor 502 in the memory 504 of the general purpose computing device 500. Thus, in one embodiment, the display optimization module 505 for optimizing image quality on an image display device based on measurement of image processing artifacts, as described herein with reference to the preceding figures, can be stored on a tangible or physical computer readable storage medium (e.g., RAM, magnetic or optical drive or diskette, and the like).
It should be noted that although not explicitly specified, one or more steps of the methods described herein may include a storing, displaying and/or outputting step as required for a particular application. In other words, any data, records, fields, and/or intermediate results discussed in the methods can be stored, displayed, and/or outputted to another device as required for a particular application. Furthermore, steps or blocks in the accompanying figures that recite a determining operation or involve a decision, do not necessarily require that both branches of the determining operation be practiced. In other words, one of the branches of the determining operation can be deemed as an optional step.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. Various embodiments presented herein, or portions thereof, may be combined to create further embodiments. Furthermore, terms such as top, side, bottom, front, back, and the like are relative or positional terms and are used with respect to the exemplary embodiments illustrated in the figures, and as such these terms may be interchangeable.
