This paper presents an aliasing reduction method for digital still cameras (DSCs) which takes advantage of the colorsignal correlation. The authors have developed a method of reducing aliasing by increasing the resolution of the color signals in DSCs using a single-chip charge-coupled device with a primary-color filter array. The new method interpolates the signals by taking advantage of the fact that color-signal variations are similar to one another in a local region of an image. In addition, it selects the signal that shows the highest correlation, either in the horizontal or vertical direction, for the color-signal positions subject to interpolation, thus improving color resolution. The effectiveness of the new method has been established: tests show that it significantly reduces aliasing. © 1999 SPIE and IS&T. [S1017-9909(99)

SUMMARYThe authors have evaluated a method of expanding the bit depth of image signals called SGRAD, which requires fewer calculations, while degrading the sharpness of images less. Where noise is superimposed on image signals, the conventional method for obtaining high bit depth sometimes incorrectly detects the contours of images, making it unable to sufficiently correct the gradation. Requiring many line memories is also an issue with the conventional method when applying the process to vertical gradation. As a solution to this particular issue, SGRAD improves the method of detecting contours with transiting gradation to effectively correct the gradation of image signals which noise is superimposed on. In addition, the use of a prediction algorithm for detecting gradation reduces the scale of the circuit with less correction of the vertical gradation.