Optical scanning device
Provided is an optical scanning device having a stable scanning direction corresponding to a temperature fluctuation of a semiconductor laser by being provided with a predetermined liquid crystal optical element utilizing a characteristic of a linear expansion coefficient of a support of a liquid crystal diffraction element. An optical scanning device includes: a light source; and a light deflection element, in which the light deflection element includes a support and an optically anisotropic layer which is a cured layer of a liquid crystal composition, an optical axis of a liquid crystal compound contained in the liquid crystal composition is parallel to a surface of the optically anisotropic layer, and the optically anisotropic layer has a liquid crystal alignment pattern which is arranged along at least one in-plane direction of the optically anisotropic layer and in which an orientation of the optical axis of the liquid crystal compound changes continuously and rotationally, and the support satisfies Conditional Expression (1): |dλ/(dt×λ0)−α|<2×10 −4 /° C.
1. An optical scanning device comprising:
a light source; and
a light deflection element,
wherein the light deflection element includes a support and an optically anisotropic layer which is a cured layer of a liquid crystal composition,
an optical axis of a liquid crystal compound contained in the liquid crystal composition is parallel to a surface of the optically anisotropic layer, and the optically anisotropic layer has a liquid crystal alignment pattern which is arranged along at least one in-plane direction of the optically anisotropic layer and in which an orientation of the optical axis of the liquid crystal compound changes continuously and rotationally,
the support has anisotropy in a linear expansion coefficient, and a direction in which the linear expansion coefficient of the support is high is parallel to the one direction of the liquid crystal alignment pattern of the optically anisotropic layer, and
the support satisfies Conditional Expression (1),
| d λ/( dt×λ 0)−α|2×10 −4 /° C. (1)
here,
λ0: a central wavelength of the light source at 25° C. (nm),
dλ: an increment in central wavelength of the light source due to a temperature increase (room temperature from 25° C. to 65° C.) (nm),
dt: an increment in temperature (° C.: room temperature from 25° C. to 65° C.), and
α: the linear expansion coefficient of the support (1/° C.).
2. The optical scanning device according to claim 1 ,
wherein, in the optically anisotropic layer, the orientation of the optical axis of the liquid crystal compound rotates by 180° with a period of 0.1 to 5 μm.
3. The optical scanning device according to claim 1 ,
wherein a plurality of the optically anisotropic layers are included in the light deflection element.
4. The optical scanning device according to claim 1 ,
wherein the light deflection element includes a diffraction element having the support and the optically anisotropic layer, and a light deflector.
5. The optical scanning device according to claim 2 ,
wherein a plurality of the optically anisotropic layers are included in the light deflection element.
6. The optical scanning device according to claim 2 ,
wherein the light deflection element includes a diffraction element having the support and the optically anisotropic layer, and a light deflector.
7. The optical scanning device according to claim 3 ,
wherein the light deflection element includes a diffraction element having the support and the optically anisotropic layer, and a light deflector.