Patent Application
20070164943
Display systems may display a viewable image that does not effectively utilize the full dynamic range, fidelity and contrast ratio range of the display system. Improving the utilization of the dynamic range, fidelity and contrast ratio range of a display system may improve the viewable image displayed by the display system.
Input module 12 may be electronically connected to both an image data capture module 18 and to a frame storage buffer module 20 such that input module 12 transmits input data 14, including a set of frame data 16, to both capture module 18 and to frame storage buffer module 20. Such transmission may be simultaneous or sequential, or a mixture thereof. In one embodiment, frame storage buffer module 20 may be utilized whereas in another embodiment, frame storage buffer 20 may not be utilized.
Image data capture module 18 may be electronically connected to an image analysis module 22 such that image data capture module 18 transmits input data 14, including set of frame data 16, to image analysis module 22. Image analysis module 22 may include machine operable instructions 24, such as software code. Instructions 24 may operate to analyze set of frame data 16 to determine a gain setting and a filter setting for set of frame data 16 to increase the dynamic range, fidelity and contrast ratio range of a set of displayed frame data 26 displayed by display system 10 and corresponding to set of frame data 16. In one embodiment, image analysis module 22 may calculate a gain setting as set forth in U.S. Pat. No. 6,463,173, issued on Oct. 8, 2002 to Daniel R. Tretter, assigned to Hewlett-Packard Company, and entitled SYSTEM AND METHOD FOR HISTOGRAM-BASED IMAGE CONTRAST ENHANCEMENT, wherein such patent is hereby incorporated in its entirety by reference herein.
Calculating a gain setting and a corresponding filter setting (see
Determining or calculating a gain setting or settings may be defined as applying a set of gain values to define a tone curve. The actual algorithm or algorithms utilized to calculate the gain setting, wherein many different types of algorithms may be utilized, may involve applying a different gain value to each individual pixel in the image based on the luminance value of the individual pixel. In one simple algorithm this may include applying a single, identical gain value to each pixel. More complex algorithms may involve applying hundreds or more slightly different gain values to the pixels, wherein each individual gain setting value is applied to a corresponding one of the different pixels. In many cases the algorithms attempt to match the average luminance of the frame to the attenuation factor applied by an adjustable filter 30 such that the overall luminance remains approximately constant. The single or multiple gain settings that may be applied to individual pixels of a frame are referred to collectively herein as a “gain” or a “gain setting” for that frame. Accordingly, a “gain setting” as defined herein may include one or more different gain settings applied to pixels of a single frame.
Filter 30, different embodiments of which are shown in
Image analysis module 22 may be electronically connected to a control module 28 that may be operatively connected to a filter 30 and to an image modulator 32. Control module 28 may include a mechanical motor 34 that mechanically moves filter 30 (see
Control module 28 may also include a controller 39 that may electrostatically control individual pixels 40, for example, of image modulator 32. Image modulator 32 may include hundreds, thousands, or more, of individual pixels 40, such as movable micromirrors, which may each be controlled by controller 39 to move between an active or “on” state and an inactive or “off” state. In the “on” state an individual pixel 40 may be positioned to reflect light to an imaging region 42 and in the “off” state, an individual pixel 40 may be positioned to reflect light to a light dump 44.
Control module 28 may further include a controller 46 that may apply the gain setting calculated by image analysis module 22 to a set of frame data 16. In particular, frame storage buffer module 20 may be electronically connected to control module 28 such that frame storage buffer module 20 transmits a set of frame data 16 to control module 28. Controller 46 then applies the gain setting calculated by image analysis module 22 to set of frame data 16 and control module 28 thereafter transmits a second set of frame data 48 to image modulator 32, wherein second set of frame data 48 corresponds to set of frame data 16, having the gain setting applied thereto. In other words, the control module may receive the frame data and the gain data, apply the gain data to the frame data, and then pass the modified or second set of frame data 48 to the modulator 32.
Still referring to
In step 62 data input module 12 transmits set of frame data 16 to both image data capture module 18 and to frame storage buffer module 20. Set of frame data 16 is stored within frame storage buffer module 20 during calculation by image analysis module 22.
In step 64 image data capture module 18 transmits set of frame data 16 to image analysis module 22.
In step 66, image analysis module 22 analyzes set of frame data 16 and calculates a corresponding gain setting and a corresponding filter setting that may increase utilization of the dynamic range, fidelity and contrast ratio of a display to improve the viewable image displayed by the display system 10. The method of calculating the gain setting, in one embodiment, is set forth in U.S. Pat. No. 6,463,173, issued on Oct. 8, 2002 to Daniel R. Tretter, listed above. In one example, the calculated gain setting may be X2, i.e., the value of the data set for one frame of pixels is doubled (X2) such that the human eye can more easily perceive contrast differences between individual pixels, compared to the unmodified data set. A filter setting of 50% may correspond to a gain setting of X2, i.e., fifty percent less light is transmitted through the filter. In such an example, the individual pixels having a higher gain value and a corresponding amount of less light transmitted through the filter result in the overall luminance of the frame remaining approximately the same. In another embodiment wherein individual pixels may each have their own unique gain value, an average of the gain values for all the pixels may be calculated to determine a corresponding filter setting that will result in the overall luminance of the frame remaining approximately the same. In other words, the tone map gain of the image may be averaged in order to calculate a corresponding single filter setting. In still another embodiment, the tone map gain of the image may correspond to individual filter settings within a single filter for a photochromic filter that may change its density according to a level of light incident on individual regions of the filter.
In step 68 image analysis module 22 transmits the calculated gain setting and the calculated filter setting to control module 28.
In step 70 frame storage buffer module 20 transmits set of frame data 16 to control module 28.
In step 72 control module 20 operates mechanical motor 34 to position a region 36 of filter 30 within projection path 38 to correspond to the filter setting calculated in step 66.
In step 74 control module 20 operates controller 46 to apply the calculated gain setting to set of frame data 16 to form second set of frame data 48, wherein second set of frame data 48 is set of frame data 16 having the calculated gain setting applied thereto. As discussed previously, the calculated “gain setting” may include a unique gain value for each pixel of the modulator array for each individual set of frame data. Accordingly, the gain setting calculated in step 66 may be applied to the set of frame data 16 from which the gain setting was calculated, instead of to a subsequent set of frame data. Applying the calculated gain setting to the set of frame data 16 from which the gain setting was calculated may increase the quality of the viewable image projected from display system 10 because there is a direct correlation between the gain setting and the data to which it is applied. Applying a gain setting to a completely different set of data from which the gain setting was calculated may not provide an improved contrast ratio within the image because the gain setting may be inapplicable to the data. In the embodiment shown herein, the gain setting and the filter setting may be applied to the set of frame data 16 from which the settings were calculated, or the settings may be applied to a subsequent set of frame data.
In step 76 control module 20 operates controller 39 to position each of individual pixels 40 of image modulator 32 in a desired “on” or “off” position, based on the information contained with second set of frame data 48, which corresponds to set of frame data 16 having the calculated gain setting applied thereto.
In step 78 light source 50 projects light beam 52 along projection path 38 and toward image modulator 32. Individual activated ones of pixels 40 reflect corresponding portions of light beam 52 as a reflected light beam 52a along projection path 38. An unused portion 52b of light beam 52 that is reflected by unactivated ones of pixels 40 is reflected to light dump 44.
In step 80 reflected light beam 52a is transmitted through transmission region 36 of filter 30 and to imaging region 42 to provide a viewable image 82 having improved utilization of the dynamic range, fidelity and contrast ratio range of display system 10 such that viewable image 82 may have improved contrast when compared to an image projected by a display system that does not utilize a gain setting and a filter setting of the present invention. Moreover, viewable image 82 may be created utilizing a gain setting and a filter setting that are calculated based on the set of frame data that was utilized to create viewable image 82. Accordingly, there may be a direct correlation between the gain and the filter settings and the image itself. In this manner, an improved viewable image is consistently and continuously provided having contrast differences that are more discernable to the human eye than images having gain and filter settings calculated for a previous set of frame data. In other embodiments the gain and filter settings may be calculated for a first set of frame data and then applied to a second set of frame data.
The process may then be repeated, beginning at step 60, for subsequent sets of frame data, in a looping or continuous manner.
A size of each of light transmission regions 36 may be larger than a cone of light or cross-sectional size of light beam 52 such that when light beam 52 is projected toward one of light transmission regions 36, the entirety of light beam 52 impinges on a single of light transmission regions, such as 36a, 36b, or the like. Filter 30 may be controlled by control module 28 to move linearly along an axis of movement 84 so as to position a transmission region 36, or one or more portions of light transmission regions 36, within projection path 38.
Still referring to
In still another embodiment, there may be no interface 88 but instead filter 30 may define a continuous gradient of filtering transmission percentages wherein a lower transmission percentage is positioned in a lower or “ground” region of the filter and a higher transmission percentage is positioned in a higher or “sky” region of the filter. In such an embodiment, the gain value of individual pixels positioned in an upper or “sky” region of an image may be less than the gain value of individual pixels positioned in a lower or “ground” region of an image. Such a gradient of gain values is an example of a spatially varying gain. Another spatially varying gain that may be applied is one based on a retinex-like process, whereby the gain applied to a pixel depends at least partly on the values of the surrounding pixels.
As stated above, filter 30 of the present invention includes filters having a neutral density filter material through which the light directly passes, but does not include mechanical filters such adjustable iris filters wherein the light passes through an aperture defined by the filter material. The advantages of using a neutral density filter are numerous, including reducing image non-uniformity due to interactions between gradients in light density of the light bundle and the shape or position of the aperture. Alignment tolerances may also be increased, thereby reducing non-uniformity resulting from misalignment of mechanical filters. For example, while ideal light bundles are equally uniform, many systems are not ideal, with the result that there may be gradients in the light density at various points in the optical path. Previous methods utilize adjustable mechanical apertures which have been known to introduce image artifacts due to the shape of the aperture and how it interacts with gradients in the light density. These artifacts tend to be non-linear and may result in a decrease of uniformity over the image, which may be worse when the aperture is nearly or completely closed. Conversely, a neutral density filter affects all regions of the image without blocking localized regions that may be high or low intensity and therefore may result in greater image uniformity over the operating range.
Previous implementations using mechanical apertures may be smaller than the light beam and, therefore, may block portions of the light beam from transmitting therethrough. Such previous implementations may require precise alignment of the aperture with the optical beam. Errors in alignment, particularly in systems that have gradients in the light density of the light beam, can result in non-uniform images. Conversely, a neutral density filter can be sized larger than the light beam, which may provide greater alignment tolerances and may reduce non-uniformity of the image resulting from alignment errors.
Moreover, by utilizing a neutral density filter in conjunction with applying a gain factor to the image codes values, the overall dynamic range and contrast ratio of the system can be increased. For example, the overall image quality may be enhanced for scenes that are predominantly dark by increasing the contrast ratio between pixel values to utilize more of the dynamic range available. In other words, the overall black point of an image can be reduced, thus resulting in better image quality as perceived by the human eye.
Furthermore, use of an optical filter that extends throughout a cross section or cone of light beam 52 may reduce distortion of the light beam as it passes therethrough because the filter may equally effect the entire light cone equally or approximately equally. Additionally, the lower the transmission rate of light through the filter, the higher the gain setting that may be applied to the set of frame data. In other words, the light beam 52 is passes through optical filter 30 which may reduce the amount of light beam 52 that is transmitted therethrough. Accordingly, a higher gain is added to the color code values, which the light modulator maybe able to produce more accurately then lower color code values. In this manner, the overall luminance of the viewable image may remain the same as that of a set of frame data in which a gain is not added and which is not passed through a filter. However, the set of frame data in which a gain is added and which is passed through a filter may have the same overall luminance but may be more visibly clear or crisp to the human eye.
The foregoing description of embodiments of the invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variation are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modification as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
