Wearable electronic device adjusting transmittance of visor and brightness of display

A wearable electronic device, comprising:

• a visor configured to adjust an amount of external light entering a user's eyes according to a transmittance of the visor;
• a display configured to output the light that is projected on the user's eyes through at least an optical waveguide;
• a camera configured to capture an image of the user's eyes;
• memory storing instructions that, when executed by a processor, cause the wearable electronic device to:
• select an iris recognition mode and/or a gaze tracking mode,
• identify a size of an iris region of at least one of a user's iris or a user's gaze direction depending on selected mode based on a first image of at least one of the user's eyes captured from the camera, and
• based on the iris recognition mode being selected, determine whether the size of the iris region identified in the first image exceeds a threshold value,
• based on the size of the iris region being determined less than or equal to the threshold value, adjust the visor to increase the amount of the external light entering the user's eyes by increasing the transmittance of the visor and/or the display to increase the light projected on the user's eyes by increasing the intensity of the light output from the display, to induce a response in which the iris region enlarges,
• obtain a second image of at least one of the user's eyes including the enlarged iris region induced by the adjusted visor and/or the adjusted display, and
• recognize the user's iris based on whether the size of the enlarged iris region included in the second image exceeds the threshold value,
• wherein the visor comprises an electrochromic element configured to adjust the transmittance depending on applied power.