A method for forming an icon layer of an optical security device that includes a grayscale in-plane image, wherein the in-plane image has a boundary and an image area within the boundary that visually lies substantially in a plane of the substrate on which the in-plane image is carried, a plurality of control patterns of icons contained within the in-plane image thereby forming an icon layer, and an array of icon focusing elements positioned to form at least one synthetically magnified image of the control patterns of icons, wherein the focusing elements include non-cylindrical refractive, reflective, or hybrid refractive/reflective focusing elements, wherein the synthetically magnified image intersects with the at least one in-plane image, the method comprising: selecting a grayscale in-plane image; and using the grayscale in-plane image to drive placement of the control patterns of icons within the in-plane image to together form the icon layer, the method further comprising: (a) selecting a grayscale in-plane image and scaling the grayscale image to a size suitable for use in the icon layer; (b) superimposing a tiling onto the scaled grayscale in-plane image, the tiling comprising cells that will contain the control patterns of icons, wherein each cell has a preferred size similar to one or several focusing elements; (c) selecting a numerical range to represent the colors black and white and the various levels of gray in between black and white; (d) determining the level of grayscale of the scaled grayscale in-plane image in each cell of the superimposed tiling; (e) assigning to each cell a number which represents the determined level of grayscale and which falls within the selected numerical range, wherein the assigned number is the cell's grayscale value; (f) selecting a number of control patterns of icons for use in a control pattern palette, and for each control pattern of icons, assigning a range of grayscale levels which fall within the selected numerical range; (g) specifying a control pattern probability distribution within the in-plane image and for each possible grayscale value, using the control pattern probability distribution to assign a range of random numbers to each control pattern; (h) providing each cell in the tiling with a random number that falls with the selected numerical range using a Random Number Generator; (i) determining which control pattern will be used to fill each cell using the cell's grayscale value and the cell's random number in conjunction with a mathematical construct which corresponds to the control pattern probability distribution; and (j) filling each cell with its determined control pattern of icons. (a) selecting a grayscale in-plane image and scaling the grayscale image to a size suitable for use in the icon layer; (b) superimposing a tiling onto the scaled grayscale in-plane image, the tiling comprising cells that will contain the control patterns of icons, wherein each cell has a preferred size similar to one or several focusing elements; (c) selecting a numerical range to represent the colors black and white and the various levels of gray in between black and white; (d) determining the level of grayscale of the scaled grayscale in-plane image in each cell of the superimposed tiling; (e) assigning to each cell a number which represents the determined level of grayscale and which falls within the selected numerical range, wherein the assigned number is the cell's grayscale value; (f) selecting a number of control patterns of icons for use in a control pattern palette, and for each control pattern of icons, assigning a range of grayscale levels which fall within the selected numerical range; (g) specifying a control pattern probability distribution within the in-plane image and for each possible grayscale value, using the control pattern probability distribution to assign a range of random numbers to each control pattern; (h) providing each cell in the tiling with a random number that falls with the selected numerical range using a Random Number Generator; (i) determining which control pattern will be used to fill each cell using the cell's grayscale value and the cell's random number in conjunction with a mathematical construct which corresponds to the control pattern probability distribution; and (j) filling each cell with its determined control pattern of icons.