Virtual image display device
A first lens and a second lens are bonded to each other and configured to be short in an optical axis direction. Further, by providing a half mirror in a bonding portion between a convex surface and a concave surface, power is given when folding an optical path, and additionally, by setting a refractive index of the first lens larger than a refractive index of the second lens, an image with a wide angle of view can be formed.
1. A virtual image display device, comprising:
an image element configured to display an image;
a first lens disposed at a location where image light from the image element is extracted and including a convex surface facing the image element side;
a second lens disposed further toward the image element side than the first lens and including a concave surface to be bonded to the convex surface of the first lens;
a half mirror provided in a bonding portion between the convex surface and the concave surface; and
a transmission/reflection selection member provided at a light emitting side of the first lens and configured to selectively transmit or reflect the light depending on polarization state of the light, wherein
a refractive index of the first lens is larger than a refractive index of the second lens, and
an Abbe's number of the first lens is larger than an Abbe's number of the second lens.
2. The virtual image display device according to claim 1 , wherein
the refractive index of the first lens is equal to or larger than 1.8.
3. The virtual image display device according to claim 1 , wherein
a difference between the refractive index of the first lens and the refractive index of the second lens is equal to or larger than 0.3 and equal to or smaller than 0.5.
4. The virtual image display device according to claim 1 , wherein the first lens and the second lens are glass lenses, and the convex surface and the concave surface are spherical surfaces.
5. The virtual image display device according to claim 1 , wherein
the half mirror is provided on the convex surface by vapor deposition.
6. The virtual image display device according to claim 1 , wherein
a size of an image display area of the image element is smaller than a size of an optical surface of the second lens.
7. The virtual image display device according to claim 6 , wherein
the image element is a micro display having an image display area, and a length of one side of the image display area is equal to or less than 2.5 inches.
8. The virtual image display device according to claim 1 , wherein
the second lens includes a cutout portion.
9. The virtual image display device according to claim 1 , wherein
a surface of the first lens at the light emitting side, on which the transmission/reflection selection member is provided, is a flat surface,
the transmission/reflection selection member includes an emitting side polarization conversion member configured to convert a polarization state of the light passing the polarization conversion member, and a semi-transmissive reflection type polarization plate configured to transmit or reflect the light depending on a polarization state of the light that has passed through the polarization conversion member.