Display device

A display device mounted in a vehicle, the device comprising:

• a presentation unit to producing a light flux including image information and to presenting the light flux to a human viewer;
• a sensor to measure a luminance of external light incident on the vehicle;
• a setting unit configured to receive luminance information to set a luminance of the light flux to be a first luminance, the first luminance being set by the human viewer, the first luminance having a first coefficient being a ratio of the first luminance to the luminance of the external light during the first luminance being set;
• and
• a control unit configured to control the presentation unit to change the luminance of the light flux to a third luminance based on the luminance information received by the setting unit and the luminance of the external light measured by the sensor, a third luminance having a second coefficient being a ratio of the third luminance to a currently measured luminance of the external light,
• the control unit determining the second coefficient being lower than the first coefficient.