Effectiveness and visual performance assessment of anti-peeping films

Some private information inevitably becomes more visible when using wide-angle electronic devices in public places. Thus, some people use anti-peeping films to achieve privacy protection. To examine the effectiveness and its influence on the visual performance of the anti-peeping film, we investigated the color gamut, luminance, contrast ratio, Bhattacharyya coefficient and structural similarity characteristics of a smartphone without-film screen and with two-sided (left and right) of 25°, 30°, and 45° anti-peeping films, respectively, and four-sided (up, down, left, and right) anti-peeping films. The results show that the film reduces the screen luminance and contrast ratio except for the color gamut. At 0° viewing angle, the luminance decreases by 24.8%, 25.2%, 18.6%, and 53.8%, respectively. For the 25°, 30°, 45°, and 360° anti-peeping films, the luminance and contrast ratio decrease to 50% at 24°, 25°, 19°, and 20° horizontal viewing angles. The effectiveness of four-sided anti-peeping film is the best, followed by the two-sided ones, and the smaller the viewing angle, the better the effect. The Bhattacharyya coefficients of the white images' pixel micrographs are 0.887, 0.896, 0.898, and 0.878, respectively, of which the smallest four-sided anti-peeping film has the greatest influence on screen clarity. Under the 0-40° viewing angle, the structural similarity continuously decreases, and the screen becomes blurred due to the anti-peeping film. This work investigates the optical characteristics of anti-peeping film and examines its influence on visual performance, and provides strategy for manufacturers and use guidance for users.