1. Field of the Invention
The present invention relates to the correction of non-uniformities in images displayed by an image display apparatus.
2. Description of the Related Art
Various types of image display apparatus have been developed, such as direct-viewing display apparatus and projection-type display apparatus (projectors). Direct-viewing display apparatuses include liquid-crystal panels, plasma display panels (PDPs), CRTs, and other display apparatuses in which the screen of the display device is viewed directly. Projectors are provided with projection lens or optical systems and designed for projecting images formed on display devices, such as liquid-crystal panels, Digital Micromirror Devices (registered trade mark of Texas Instrument), and CRTs, and viewing the images thus projected.
Images displayed by an image display apparatus are preferably uniform images devoid of color non-uniformities or color shift. In reality, however, displayed images sometimes have color non-uniformities due to the variation of input-output characteristics of display devices, electrical characteristics of constituent circuits, and optical characteristics of optical devices.
In conventional practice, image data related to pixels having such color non-uniformities are corrected in order to control these color non-uniformities. Correction data for correcting such image data may, for example, be obtained in the following manner. A uniform middle-tone image such as a uniform gray image is first displayed. The displayed image is photographed with a image camera or measured with a luminance meter, and the distribution of color non-uniformities is measured. Suitable correction data are then obtained while repeated adjustments are made to the image data related to the pixels having the color non-uniformities, and the color non-uniformities are repeatedly measured.
Determining correction data for controlling color non-uniformities in accordance with prior art is disadvantageous, however, in that considerable time is needed to determine the correction data because image data must be repeatedly adjusted and color non-uniformities measured in order to obtain suitable values.
An object of the present invention is to makes it easier to determine correction data for correcting the non-uniformities of displayed images.
In order to attain at least part of the above and other related objects of the present invention, there is provided a method of adjusting operation of an image display apparatus. The image display apparatus comprises: an image correction section configured to correct levels of given image data in accordance with correction data; a data storage device configured to store the correction data; and an image forming section provided with a plurality of pixels each emitting image-forming light responsive to corrected image data supplied from the image correction section, the image-forming light reproducing a displayed image. The adjustment method comprises the steps of: (a) providing input-output characteristic data of the image forming section; (b) supplying uniform image data representing a specific uniform image to the image display apparatus and measuring an output level of light at a plurality of locations on a displayed image; (c) determining data-correction values corresponding to the output levels of measured light, respectively, on the basis of the input-output characteristic data of the image forming section, the data-correction values indicative of correction amounts of image data needed to bring each of the output levels of measured light closer to a predetermined reference level; (d) determining, on the basis of the data-correction values corresponding to the output levels of measured light, the correction data which are to be used in reproducing the data-correction values with respect to the pixels of the image forming section; and (e) storing the correction data thus determined in the data storage device of the image display apparatus.
According to the above-described adjustment method, the correction data can be easily determined on the basis of the input-output characteristics of the image forming section.
The correction data stored in the data storage device may represent the data-correction values with respect to not all but only some of the pixels of the image forming section. In this case, the data-correction values with respect to all of the pixels of the image forming section are determined on the basis of the correction data.
According to this arrangement, the data-correction values pertaining to all the pixels of the image forming section can be easily obtained based on the correction data related to the data-correction values for only part of the image forming section.
The present invention is also directed to an image adjustment system for adjusting operation of the image display apparatus. The image adjustment system comprises: a image signal feeder configured to feed image signals containing the image data to the image display apparatus; a measurement instrument configured to measure an output level of light at a plurality of locations on an image displayed by the image display apparatus; and an adjustment device configured to determine correction data representing data-correction values indicative of correction amounts of image data for each pixel of the image forming section, on the basis of measurements results of the measurement instrument, and storing the correction data into the data storage device. The adjustment device determines the data-correction values on the basis of input-output characteristics of the image forming section, where the data-correction values represent correction amounts of the image data needed to bring, closer to a predetermined reference level, the output levels of measured light measured at the plural locations of the displayed image which is displayed responsive to uniform image data representing a specific uniform image.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.
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