OPTICAL SYSTEM FOR VIRTUAL IMAGE DISPLAY DEVICE, VIRTUAL IMAGE DISPLAY DEVICE AND HEAD-MOUNTED DISPLAY

To improve light utilization efficiency.SOLUTION: An optical system for a virtual image display device comprises: a light guide member that guides image light from an image display element which displays an image; a partial reflection unit that transmits image light in a first direction which is guided within the light guide member from a first side, and reflects image light in a second direction which is guided within the light guide member from a second side different from the first side to be emitted to the outside; a reflection unit that is positioned at the second side different from the first side across the partial reflection unit, and reflects the image light in the first direction which is transmitted through the partial reflection unit, toward the partial reflection unit as the image light in the second direction; and a polarization unit that rotates image light which is in a first polarization direction at the time of transmission of the partial reflection unit to a second polarization direction by rotating polarization of the image light in the first direction which is transmitted through the partial reflection unit, and further rotating polarization of the image light in the second direction which is reflected by the reflection unit. In the partial reflection unit, a reflection rate in the first polarization direction is lower than a reflection rate in the second polarization direction.SELECTED DRAWING: Figure 2 【課題】光利用効率を向上させること。【解決手段】虚像表示装置用光学系は、画像を表示する画像表示素子からの画像光を導光する導光部材と、第１の側から導光部材内を導光される第１方向の画像光を透過させ、かつ第１の側とは異なる第２の側から導光部材内を導光される第２方向の画像光を反射させて外部に射出する、部分反射部と、部分反射部を挟んで第１の側とは異なる第２の側に位置し、部分反射部を透過した第１方向の画像光を第２方向の画像光として部分反射部に向けて反射する反射部と、部分反射部を透過した第１方向の画像光の偏光を回転させ、更に、反射部にて反射された第２方向の画像光の偏光を回転させることにより、部分反射部の透過時に第１の偏光方向にあった画像光を第２の偏光方向に回転させる偏光部と、含む。部分反射部は、第１の偏光方向の反射率が第２の偏光方向の反射率より低い。【選択図】図２