Half-wave plate, optical pickup device, polarization conversion element, and projection display device

Abstract

The invention provides a half-wave plate, an optical pickup device, a polarization conversion element, and a projection display device, which are capable of improving transfer efficiency of a half-wave plate formed by a single crystal plate. The single crystal plate is made of an inorganic material having a birefringent property and rotatory power, wherein a polarization plane of linearly polarized light entering from an entrance surface of the crystal plate is rotated and then output from an exit surface of the crystal plate, the phase difference is disposed as gamma= 180degrees + correcting value gamma alpha, a cutting angle Beta of a quartz plate formed by a normal relative to the entrance surface and an optical axis is disposed as 5 degrees <= Beta <= 30 degrees, the correction value gamma alpha is determined according to a predetermined polynomial, the polynomial uses an optical axis azimuth angle Theta formed by an optical axis projection line formed by projection of the optical axis on the entrance surface and a polarization plane of linearly polarized light entering from the entrance surface, and the cutting angle Beta as variable quantities.

Description

technical field [0001] The present invention relates to a 1 / 2 wavelength plate made of an inorganic crystal material having birefringence and optical activity such as quartz. Furthermore, the present invention relates to an optical pickup device, a polarization conversion element, and a projection display device using the 1 / 2 wavelength plate. Background technique [0002] Conventionally, optical devices such as optical pickup devices, polarization conversion elements, and projection display devices such as liquid crystal projectors used for recording and reproducing optical disc devices have used 1 / 2 wavelength plates that make the lines of incident light The polarization plane of the polarized light is rotated by a predetermined angle, for example, 90°, and then emitted as linearly polarized light. Generally, as the material of the wave plate, a resin film made of an organic material such as polycarbonate that has birefringence by stretching, a retardation plate that sand...

AI Technical Summary

Problems solved by technology

Therefore, there is a problem that when the design retardation of the quartz 1 / 2 wavelength plate is set to 180°, the conversion efficiency thereof does not necessarily become 100% depending on the cutting angle of the quartz plate

Therefore, the strength of the quartz plate is significantly reduced, and it is fragile and easily broken, so it is very difficult to handle in manufacture and practical use

[0016] In addition, when a blue-violet laser expands due to high heat generated during use, there is a problem that the wavelength of the oscillating laser drifts (changes)

Therefore, in the case of a light source used for an optical pickup device, the 1 / 2 wavelength plate has a problem of deterioration in conversion efficiency of linearly polarized light due to wavelength shift of incident laser light.

In particular, the thickness of the 1 / 2 wavelength plate of the high-order mode is large, so as the phase difference becomes larger, the change amount of the phase difference becomes larger, and the conversion efficiency further deteriorates

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