Detection device

A detection device comprising:

• a light-transmitting light guide plate;
• a plurality of light diffusion structures provided on a surface on one side in a first direction of the light guide plate;
• an optical sensor that is disposed on the one side in the first direction of the light guide plate so as to overlap the light guide plate and comprises a plurality of light detection elements arranged in a plane;
• and
• a light source that is disposed adjacent to the light guide plate in a second direction intersecting the first direction and is configured to emit light to a side surface of the light guide plate, wherein
• as viewed in the first direction,
• the light diffusion structures comprise a first structure, a second structure adjacent to the first structure, a third structure adjacent to the first structure and the second structure, and a fourth structure adjacent to the second structure and the third structure;
• the first structure is positioned opposite the fourth structure with respect to a straight line passing through the second structure and the third structure;
• a first side connecting a first center of the first structure to a second center of the second structure, a second side connecting the first center to a third center of the third structure, and a third side connecting the second center to the third center form a first isosceles triangle that has the first side as a base and the second and third sides as equal sides;
• a fourth side connecting a fourth center of the fourth structure to the second center, a fifth side connecting the fourth center to the third center, and the third side form a second isosceles triangle that has the fifth side as a base and the third and fourth sides as equal sides;
• the first isosceles triangle and the second isosceles triangle form a parallelogram having the first center, the second center, the third center, and the fourth center as vertices;
• in the parallelogram, the first side is parallel to the fifth side, and the second side is parallel to the fourth side;
• and
• four interior angles of the parallelogram are an obtuse angle or an acute angle.