A smartphone configured for reading an invisible printed insignia or barcode that comprises a printing ink containing a luminophore that is phosphorescent in the visible spectrum, the smartphone including: a) a camera including an image sensor (7,9) that includes an optical filter that limits the spectral sensitivity of the image sensor (7,9) to the visible range, b) a white-illuminating light emitting diode, or LED (3,103), c) an optional display, and d) a computer including a software application that controls the camera and the LED, characterized in that: i. the LED (3,103) is configured to emit a flash of bright white light, which charges the phosphorescent luminophore contained in the printing ink of an invisible printed insignia or barcode, which becomes visible during afterglow of the phosphorescing luminophore that diminishes within an afterglow time after the bright white light emission from the LED (3,103) is terminated; ii) the camera is configured to set the image sensor (7,9) to a low sensitivity level that precludes the image sensor (7,9) from overexposure during the time when the LED (3,103) is emitting the bright white light; iii) the camera is configured to set the image sensor (7,9), after the terminating of the flash of bright white light of the LED (3,103), to a sensitivity level for acquiring an image at ambient light conditions; and iv) the camera is configured to acquire an image of the phosphorescing luminophore during the afterglow time and within an imaging period of time of less than 100 milliseconds, preferably less than 50 milliseconds, after the terminating of the flash of bright white light of the LED (3,103), wherein the afterglow time is shorter than a sensitivity recovery time of a human eye after the bright white light from the LED (3,103) has terminated to reduce or eliminate the phosphorescence of the luminophore becoming detectable by or visible to an unaided human eye. a) a camera including an image sensor (7,9) that includes an optical filter that limits the spectral sensitivity of the image sensor (7,9) to the visible range, b) a white-illuminating light emitting diode, or LED (3,103), c) an optional display, and d) a computer including a software application that controls the camera and the LED, characterized in that: i. the LED (3,103) is configured to emit a flash of bright white light, which charges the phosphorescent luminophore contained in the printing ink of an invisible printed insignia or barcode, which becomes visible during afterglow of the phosphorescing luminophore that diminishes within an afterglow time after the bright white light emission from the LED (3,103) is terminated; ii) the camera is configured to set the image sensor (7,9) to a low sensitivity level that precludes the image sensor (7,9) from overexposure during the time when the LED (3,103) is emitting the bright white light; iii) the camera is configured to set the image sensor (7,9), after the terminating of the flash of bright white light of the LED (3,103), to a sensitivity level for acquiring an image at ambient light conditions; and iv) the camera is configured to acquire an image of the phosphorescing luminophore during the afterglow time and within an imaging period of time of less than 100 milliseconds, preferably less than 50 milliseconds, after the terminating of the flash of bright white light of the LED (3,103), wherein the afterglow time is shorter than a sensitivity recovery time of a human eye after the bright white light from the LED (3,103) has terminated to reduce or eliminate the phosphorescence of the luminophore becoming detectable by or visible to an unaided human eye. i. the LED (3,103) is configured to emit a flash of bright white light, which charges the phosphorescent luminophore contained in the printing ink of an invisible printed insignia or barcode, which becomes visible during afterglow of the phosphorescing luminophore that diminishes within an afterglow time after the bright white light emission from the LED (3,103) is terminated; ii) the camera is configured to set the image sensor (7,9) to a low sensitivity level that precludes the image sensor (7,9) from overexposure during the time when the LED (3,103) is emitting the bright white light; iii) the camera is configured to set the image sensor (7,9), after the terminating of the flash of bright white light of the LED (3,103), to a sensitivity level for acquiring an image at ambient light conditions; and iv) the camera is configured to acquire an image of the phosphorescing luminophore during the afterglow time and within an imaging period of time of less than 100 milliseconds, preferably less than 50 milliseconds, after the terminating of the flash of bright white light of the LED (3,103), wherein the afterglow time is shorter than a sensitivity recovery time of a human eye after the bright white light from the LED (3,103) has terminated to reduce or eliminate the phosphorescence of the luminophore becoming detectable by or visible to an unaided human eye.