A method of manufacturing an image array for an optical device, comprising: (a) generating a plurality of different mask images by, for each of at least two different images, the at least two images collectively including parts in at least two different colours: providing a pixelated version of the image comprising a plurality of image pixels, each image pixel exhibiting a uniform colour; for each image pixel of the pixelated image, creating a corresponding mask pixel based on the colour of the respective image pixel, each mask pixel comprising an arrangement of one or more mask regions and/or one or more void regions, different arrangements of the one or more mask regions and/or one or more void regions in different ones of the mask pixels defining different respective colours; arranging the mask pixels in accordance with the positions of their corresponding image pixels in the pixelated image to form a mask image; (b) interlacing the plurality of different mask images, by dividing each mask image into elongate image slices extending along a first direction, selecting a subset of image slices from each mask image, and arranging the selected image slices from all of the mask images to form an interlaced mask image in which the image slices from each respective mask image alternate with one another periodically along a second direction which is substantially orthogonal to the first direction; then, in any order or simultaneously: (c) forming a mask layer comprising a masking material which is patterned in accordance with the interlaced mask image; and characterised by (d) forming a colour layer comprising elongate strips of at least two different colours which alternate with one another periodically in the first direction, the elongate strips extending along the second direction; wherein the mask layer and the colour layer are arranged to overlap one another, whereby the void regions of the mask pixels in the mask layer reveal portions of the colour layer such that, in combination, the mask layer and the colour layer form a multi-coloured image array exhibiting versions of the at least two images interlaced with one another. (a) generating a plurality of different mask images by, for each of at least two different images, the at least two images collectively including parts in at least two different colours: providing a pixelated version of the image comprising a plurality of image pixels, each image pixel exhibiting a uniform colour; for each image pixel of the pixelated image, creating a corresponding mask pixel based on the colour of the respective image pixel, each mask pixel comprising an arrangement of one or more mask regions and/or one or more void regions, different arrangements of the one or more mask regions and/or one or more void regions in different ones of the mask pixels defining different respective colours; arranging the mask pixels in accordance with the positions of their corresponding image pixels in the pixelated image to form a mask image; providing a pixelated version of the image comprising a plurality of image pixels, each image pixel exhibiting a uniform colour; for each image pixel of the pixelated image, creating a corresponding mask pixel based on the colour of the respective image pixel, each mask pixel comprising an arrangement of one or more mask regions and/or one or more void regions, different arrangements of the one or more mask regions and/or one or more void regions in different ones of the mask pixels defining different respective colours; arranging the mask pixels in accordance with the positions of their corresponding image pixels in the pixelated image to form a mask image; (b) interlacing the plurality of different mask images, by dividing each mask image into elongate image slices extending along a first direction, selecting a subset of image slices from each mask image, and arranging the selected image slices from all of the mask images to form an interlaced mask image in which the image slices from each respective mask image alternate with one another periodically along a second direction which is substantially orthogonal to the first direction; (c) forming a mask layer comprising a masking material which is patterned in accordance with the interlaced mask image; and characterised by (d) forming a colour layer comprising elongate strips of at least two different colours which alternate with one another periodically in the first direction, the elongate strips extending along the second direction;