Fig. 1. Principle of error diffusion screening

Fig. 2. FM screening image

Fig. 3. FM latent images. (a) Diagram of dot displacement; (b) anti-counterfeiting image; (c) enlarged latent image

Fig. 4. FM latent images extracted by linear grating. (a) Extracted latent image; (b) enlarged extraction area

Fig. 5. Grating type. (a) Linear grating; (b) irregular grating

Fig. 6. Flow chart of experiment

Fig. 7. FM latent images extracted by irregular grating. (a) Extracted latent image; (b) enlarged extraction area

Fig. 8. Extraction effect of latent image in mid-bright tone area. (a) Latent image; (b) enlarged extraction area

Fig. 9. Extraction effect of latent image in dark tone area. (a) Latent image; (b) enlarged extraction area