Optical device

A glass plate for a display surface of a display device,

• wherein the glass plate that is disposed on a side of a display surface of a display device, the glass plate has a first surface having an anti-glare property and a second surface that faces the first surface, the glass plate satisfies a resolution index value T≤0.2, a reflection image diffusiveness index value R≥0.2, and a sparkle index value S≤60, the resolution index value T is calculated by expression, the resolution index value T=(brightness of all transmitted beams−brightness of 0° transmitted light beam)/(brightness of all transmitted light beams), where a first light beam is irradiated from a side of the second surface of the glass plate in a direction of an angle of 0° which is a direction that is parallel to a thickness direction of the glass plate, and the brightness of the 0° transmitted light beam which is a transmitted light beam that is transmitted from the first surface is measured, a light reception angle of receiving a first light beam with respect to the first surface of the glass plate is varied in a range from −90° to +90°, and the brightness of all transmitted beams that are transmitted from a side of the first surface is measured, the reflection image diffusiveness index value R is calculated by expression, the reflection image diffusiveness index value R=(brightness of all reflected beams−brightness of a 45° regular reflected beam)/(brightness of all reflected beams), where a second light beam is irradiated from the side of the first surface of the glass plate in a direction of 45° with respect to the thickness of the glass plate, the brightness of the 45° regular reflected light beam which a light beam that is specularly reflected by the first surface is measured, a light reception angle of receiving the reflected beam that is reflected by the first surface is varied in a range from 0° to +90°, and the brightness of all reflected beams that are reflected by the first surface is measured, and the sparkle index value S is obtained by setting a value output by an analysis software as the sparkle index value S, where the glass plate is positioned at the side of the display surface of the display device such that the second surface is at the side of the display device, a photograph of the glass plate is taken from the side of the first surface to obtain an image, and the image is analyzed by the analysis software.