Virtual image display device and polarization adjustment member
A virtual image display device includes a polarization adjustment member that includes a polarizing plate and a support plate. The polarizing plate has a property of blocking a light which is oscillated in an axial direction of a block axis while the polarizing plate is in a state where a residual stress, a degree of which is maximized in a first residual stress direction along a plane of the polarizing plate, is left in the polarizing plate. The support plate supports the polarizing plate while the support plate is in a state where a residual stress, a degree of which is maximized in a second residual stress direction along a plane of the support plate, is left in the support plate. The polarizing plate and the support plate are bonded together such that the first residual stress direction is along the second residual stress direction.
1. A virtual image display device configured to display a virtual image that is formed by a display light through reflection of the display light at a translucent member and is visually recognizable, the virtual image display device comprising:
a projector that is configured to project the display light; and
a polarization adjustment member that is located along an optical path, which extends from the projector to the translucent member, while the polarization adjustment member is configured to adjust polarization of at least one of the display light and an external light which travel along the optical path, wherein:
the polarization adjustment member includes:
a polarizing plate that is shaped in a thin plate form and has a property of blocking a light which is oscillated in an axial direction of a block axis of the polarizing plate, wherein the polarizing plate is in a state where a residual stress, a degree of which is maximized in a first residual stress direction along a plane of the polarizing plate, is left in the polarizing plate; and
a support plate that is shaped in a plate form and supports the polarizing plate, wherein the support plate is in a state where a residual stress, a degree of which is maximized in a second residual stress direction along a plane of the support plate, is left in the support plate; and
the polarizing plate and the support plate are bonded together such that the first residual stress direction is along the second residual stress direction.
2. The virtual image display device according to claim 1 , wherein the polarization adjustment member is held by a common case, which also holds the projector, so that the polarization adjustment member and the projector are integrated together to form a projector unit.
3. The virtual image display device according to claim 1 , wherein the polarization adjustment member is held through an elongated hold structure that has a contact portion while the contact portion is in contact with the polarization adjustment member and is elongated in a direction which is parallel to or perpendicular to the first residual stress direction and the second residual stress direction.
4. The virtual image display device according to claim 1 , wherein:
the projector includes:
a backlight that is arranged such that an intensity peak direction, in which a degree of an emission intensity of an illuminating light outputted from the backlight is maximized, is along a normal direction that is normal to a light source arrangement surface of the backlight; and
an image display panel that is placed in a tilted posture where the image display panel is rotated from a parallel posture of the image display panel, which is parallel to the light source arrangement surface, by a predetermined tilt angle about a tilt reference axis; and
the polarization adjustment member is arranged such that the first residual stress direction and the second residual stress direction are along a parallel direction, which is parallel to the tilt reference axis, or a perpendicular direction, which is perpendicular to the tilt reference axis.
5. A polarization adjustment member configured to be placed along an optical path of an imaging optical system used for displaying a virtual image, the polarization adjustment member comprising:
a polarizing plate that is shaped in a thin plate form and has a property of blocking a light which is oscillated in an axial direction of a block axis of the polarizing plate, wherein the polarizing plate is in a state where a residual stress, a degree of which is maximized in a first residual stress direction along a plane of the polarizing plate, is left in the polarizing plate; and
a support plate that is shaped in a plate form and supports the polarizing plate, wherein the support plate is in a state where a residual stress, a degree of which is maximized in a second residual stress direction along a plane of the support plate, is left in the support plate wherein:
the polarizing plate and the support plate are bonded together such that the first residual stress direction is along the second residual stress direction.
6. The polarization adjustment member according to claim 5 , wherein:
the support plate is made of a synthetic resin; and
a shape of an outer peripheral contour of the polarization adjustment member is asymmetric about at least one of:
one imaginary reference line which bisects a surface area of the polarization adjustment member in a perpendicular direction that is perpendicular to the first residual stress direction and the second residual stress direction; and
another imaginary reference line which bisects the surface area of the polarization adjustment member in a parallel direction that is parallel to the first residual stress direction and the second residual stress direction.